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  • 1995-1999  (308)
  • 1999  (308)
  • Human  (119)
  • Life and Medical Sciences  (96)
  • Apoptosis  (93)
  • Nuclear reactions
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Years
  • 1995-1999  (308)
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Keywords
  • 1
    ISSN: 1432-2307
    Keywords: Key words Peroxisomes ; Hepatocellular tumors ; Immunocytochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A significant reduction of catalase activity, a peroxisomal marker enzyme, occurs in human hepatic neoplasias, but no information is available on other peroxisomal proteins. We have studied by means of immunohistochemistry four specific proteins of peroxisomes (catalase and three enzymes of lipid β-oxidation) in human hepatocellular tumors of various differentiation grades from adenoma to anaplastic carcinoma. In all tumors, except the adenomas, the tumor cells contained fewer peroxisomes than extrafocal hepatocytes and the reduction of antigenic sites in the tumor types generally correlated with the degree of tumor dedifferentiation as assessed by classical histopathological criteria. Two poorly differentiated tumors had no detectable peroxisomes at all. There were no major differences in the intensities of the immunocytochemical staining for all four studied peroxisomal antigens in different tumors, suggesting that the neoplastic transformation affects the biogenesis of the entire organelle and not merely the individual peroxisomal enzyme proteins. Some tumors exhibited a distinct peripheral distribution of peroxisomes. In cases with associated liver cirrhosis, the hepatocytes in the adjacent liver showed marked peroxisome proliferation, forming large perinuclear aggregates, occupying occasionally the entire cytoplasm. Taken together, our observations indicate that peroxisomes are significantly altered in both hepatocellular tumors and liver cirrhosis and, thus, could be responsible for some of the metabolic derangements observed in those disease processes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 185 (1999), S. 297-304 
    ISSN: 1432-1351
    Keywords: Key words Odor coding ; Learning ; Enhanced sensitivity ; Rabbit ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The olfactory system is faced with a particular problem – the high dimensionality and inherent unpredictability of the chemical world. Most natural odorants encountered in everyday life are complex mixtures of many different volatiles. This means that from the outset the olfactory system has to contend with a great and often unpredictable diversity of molecules, making it difficult for stable primary features of the chemical world to be mapped onto the sensory surface. One solution to such unpredictability is provided by learning. Learning confers flexibility, enabling individuals of a given species to acquire and make use of the most appropriate information in a particular environment. Two examples of this are presented: learning of maternal odors in neonatal rabbits, including evidence that the sensory surface itself may be influenced by environmental conditions so as to enhance sensitivity to molecules of particular ecological relevance, and cross-cultural human studies suggesting that experience with everyday odors influences not only the way these are evaluated, but also their perceived intensity. It is concluded that an adequate understanding of odor coding and olfactory function will not be possible without taking such experience-dependent factors into account.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cancer research and clinical oncology 125 (1999), S. 1-8 
    ISSN: 1432-1335
    Keywords: Key words Cell proliferation ; Apoptosis ; Cell death ; Cultured cells ; Hepatocellular carcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There are conflicting results for experiments aimed at determining whether anticancer drug therapy of human hepatocellular carcinoma prolongs the survival rate effectively. The purpose of this study was to assess the effect of low concentrations of doxorubicin, mitomycin C, and ethanol on cell replication (cell number and proliferation), and cell apoptosis of cultured human hepatocellular carcinoma (Hep-G2) cells. After 1 day of exposure doxorubicin inhibited cell replication initially by 72%, but a partial recovery of the cell number was observed. Mitomycin C inhibited to the same extent but without recovery. Ethanol reduced the cell number even further, the maximum inhibition (12 days after exposure) being 96.4%. After 3 days of exposure all three agents stopped cell replication at a level of 2%–4% of the control (P 〈 0.001). Cell apoptosis was activated most strikingly by mitomycin C (5 μg/ml) after 1 day of exposure and by ethanol (150 μl/ml) after 3 days of exposure. Two-way repeated-measures analysis of variance showed statistically significant differences, with ethanol being the most significant followed by mitomycin C doxorubicin, and the control (P 〈 0.01). Thus, a low dose of ethanol combined with an exposure time of up to 3 days appears to be an effective regimen to control growth of human hepatocellular carcinoma cells in vitro. The strong induction of apoptosis by ethanol might be of additional benefit for a local application in vivo.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1335
    Keywords: Key words Basic fibroblast growth factor ; Cisplatinum ; Apoptosis ; Bcl-2 ; MCF-7
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Basic fibroblast growth factor (bFGF) is a classical mitogen in fibroblasts and endothelial cells. Our previous studies have demonstrated that bFGF inhibits the growth of MCF-7 human breast cancer cells. The aim of the present study was to examine the effect of bFGF on cis-diamminedichloroplatinum(cisplatin)-induced cytotoxicity in MCF-7 breast cancer cells as compared to normal endothelial cells. MCF-7/NCF cells transduced with a vector expressing the bFGF gene and overexpressing its product, and MCF-7/N2 cells transduced with the backbone vector were incubated with a combination of bFGF and cisplatin for 5 days; results were compared with those obtained with bovine aortic endothelial cells. Cell proliferation was assessed with the sulforhodamine B colorimetric cytotoxicity assay. Apoptosis was quantitatively determined by flow-cytometric analysis for DNA damage and the apoptotic death assay for DNA fragmentation, and qualitatively by electron microscopy. Reverse transcriptase/polymerase chain reaction analysis and an enzyme immunoassay were used to determine the mRNA and protein level, respectively, of the anti-apoptotic bcl-2 gene product. We found that bFGF enhanced cisplatin-induced cytotoxicity in MCF-7 breast cancer sublines. bFGF enhanced proliferation of normal endothelial cells and did not increase cisplatin-induced cytotoxicity. This effect was accompanied by down-regulation of the anti-apoptotic protooncogene bcl-2 and the enhancement of cisplatin-induced apoptosis. We suggest that the improved understanding of the role of bFGF in the differential modulation of the response of breast cancer and normal endothelial cells to chemotherapy may enable active intervention to alter the therapeutic ratio favorably in breast cancer patients.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1335
    Keywords: Keywords Chemosensitivity ; Human gastric carcinoma ; Micrometastasis ; Apoptosis ; Circulating tumor cells ; Fluoropyrimidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Antimetastatic effects of 5-FU and its derivative, 1-hexylcarbamoyl-5-fluorouracil (HCFU) on human gastric cancer micrometastasis and their mode of action were evaluated, using a spontaneous lung metastasis model (HY-1) in nude mice. Metastases were first detected in the lung from 4 weeks after subcutaneous transplantation, growing intravascularly and forming micrometastases at 100% incidence by 6 weeks after implantation. Lung metastasis in mice bearing subcutaneous tumors was significantly inhibited by HCFU at doses of 100–150 mg kg−1 day−1 without severe toxic side-effects, when orally administered three times per week either from week 4 or week 6 to 9 weeks after implantation. Spontaneous lung metastasis was also inhibited by the administration of 5-FU, but to lesser extent than with HCFU at equimolar low doses. Apoptosis within primary tumors and lung metastatic foci, as detected by the terminal-deoxynucleotidyltransferase-mediated dUTP nick-end labeling method, was found to be significantly enhanced by HCFU as well as 5-FU administration at doses of more than 100 mg kg−1 day−1 and 50 mg kg−1 day−1 respectively. However, proliferating activity of the metastatic foci, as evaluated by MIB-1 immunostaining, was not significantly suppressed by HCFU or 5-FU treatment. Furthermore, polymerase chain reaction analysis using human specific primers for the β-globin gene, which proved to be capable of detecting 10 tumor cells/ml mouse blood, revealed that circulating tumor cells in the peripheral blood of mice bearing primary tumors were reduced by HCFU or 5-FU administration. These results indicate that circulating tumor cells in blood and micrometastases in the lung are sensitive to these chemotherapeutic agents, and suggest that the anti-metastatic effect of these agents is mediated, at least in part, by enhanced apoptosis rather than by inhibition of cell proliferation.
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  • 6
    ISSN: 1432-1335
    Keywords: Key wordsIGF ; Apoptosis ; Transformation ; Chemosensitivity ; Signaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Insulin-like growth factor I (IGF-I) exerts pleiotropic effects on mammalian cells via stimulation of its receptor (IGF-IR), a receptor tyrosine kinase. In vivo, IGF-I acts both as a local tissue growth factor and as a circulating hormone. In oncological research, IGF-I has received increased attention as the activated IGF-I/IGF-IR system displays mitogeneic, transforming, and anti-apoptotic properties in various cell types by stimulating distinct intracellular signaling pathways. Recent data suggest that the anti-apoptotic effect of IGF-I may mediate decreased sensitivity to chemotherapeutic drugs in vitro and in vivo. Thus, targeting the IGF-I/IGF-IR system could serve as an approach to overcome clinical drug resistance in certain tumors.
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  • 7
    ISSN: 1432-1335
    Keywords: Key words Immunohistochemistry ; DNA repair ; Radiation-inducible response ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Immunohistochemical methods were used to determine abundance and subnuclear distribution of DNA topoisomerase I and the Bax protein in normal and excision-repair-deficient xeroderma pigmentosum (XP) fibroblasts after irradiation of cells with γ rays or UV light, or exposure to the topoisomerase I inhibitor topotecan. DNA topoisomerase I and Bax were monitored using antisera raised against the human proteins. In addition, topoisomerases IIα and IIβ were made visible with specific antibodies. In untreated cells, DNA topoisomerase I was found to occur in the cytoplasm and in nucleoli. Irradiation with γ rays (2–12 Gy) or UV light (0.3–1.2 mW/cm2) changed the staining pattern in nuclei such that a multitude of small topoisomerase-I-rich centers occurred, which were evenly distributed over the karyoplasm. Simultaneously nucleoli disintegrated. Treatment of fibroblasts with topotecan (6–100 μM concentrations) resulted in similar alterations although the changes were much more pronounced. Combinations of topotecan and γ irradiation caused additive effects. We conclude that the increase in the number of topoisomerase-I-positive spots and the high fluorescence intensity of the latter may reflect three biological processes: (i) enhanced transcriptional activity (e.g. of DNA damage response genes), (ii) tagging of damaged DNA sites for repair, or (iii) initiation of apoptosis. In separate assays using normal and XP cells, a dose-dependent increase in protein reacting with Bax antibody was observed in nuclei, following treatment with γ rays or topotecan. In addition, topotecan induced a netlike arrangement of this Bax protein in nuclei. The meshes of the net structure resembled vesicles. DNA staining with 4′,6-diamidino-2-phenylindole dihydrochloride revealed that the vesicle-type structures contained DNA. Upon further incubation with topotecan, cells showing the netlike Bax arrangement eventually died. We conclude that topotecan-induced changes made visible by nuclear Bax protein are associated with apoptosis. XP cells, when treated with topotecan, responded more readily than normal cells with both an increase in nuclear Bax protein and rearrangement of Bax, indicating that UV repair functions may be required to process DNA damage inflicted by topotecan. Monitoring of DNA topoisomerases IIα and IIβ in γ-irradiated cells with antibodies revealed a dramatic increase in the IIα form and a redistribution of the IIβ form representing fragmentation of nucleoli.
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  • 8
    ISSN: 1432-1335
    Keywords: Key words Experimental pancreatic cancer ; Hormonal therapy ; Bombesin antagonist ; Somatostatin analog ; LH-RH antagonist ; EGF receptor ; Apoptosis ; AgNOR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Reduction in receptors for epidermal growth factor (EGF) in cancers appears to be one of the principal mechanisms through which peptide hormone analogs can inhibit tumor growth. In this study, hamsters with nitrosamine-induced pancreatic cancers were treated for 8 weeks with bombesin/gastrin-releasing peptide (GRP) antagonist RC-3095, somatostatin analog RC-160 or the luteinizing hormone-releasing hormone antagonist Cetrorelix, using sustained delivery systems releasing 20, 35 and 20 μg analog/ day respectively. To establish the pattern of changes in the number and affinity of EGF receptors on tumors, groups of animals were sacrificed at regular intervals during therapy. Chronic treatment with RC-3095 or Cetrorelix resulted in an early (day 10) and sustained reduction (71% or 69% respectively) in EGF receptors on pancreatic tumors. In contrast, RC-160 decreased receptor concentration by 60% only after 20 days. Among the histological characteristics of proliferation, the decrease in argyrophilic nucleolar organizer regions, but not apoptotic and mitotic indices, showed a correlation with the fall in EGF receptors. The concentration of the receptors returned to the control level 4 days after cessation of chronic treatment with RC-3095. The effect of single injections of RC-3095, RC-160 and Cetrorelix on EGF receptors was also investigated. RC-160 decreased the number of EGF receptors on pancreatic cancers by 31% 3 h after administration, but the receptors had returned to normal level at 6 h. RC-3095 and Cetrorelix caused a 67% and 59% decline, respectively, in EGF receptors only 6 h after injection and the concentration of receptors remained low for 24 h. Thus, the pattern of down-regulation of EGF receptors in pancreatic cancers appears to depend on the peptide used for therapy. Since the antitumor effect may be the result of the fall in EGF receptors in cancers, information on the time course of changes in these receptors during treatment with these analogs may lead to an improvement in therapeutic regimens.
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  • 9
    ISSN: 1432-2307
    Keywords: Key words Proliferation ; Apoptosis ; Ki-67 antigen ; Prognosis ; Retinoblastoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The balance between proliferation and cell death is the major determinant of tumour growth. We analysed the proliferative and apoptotic indices (PI and AI, respectively) of 33 children with retinoblastoma. PI and AI were assessed by immunohistochemistry for Ki-67 antigen and TUNEL staining, respectively. The mean PI was 21.0±21.1%, and higher PI was associated with more advanced tumour stage (P〈0.0001) and poor clinical outcome (P〈0.05). Patients in whom amplified N-myc oncogene was found (n=6) determined by the multiplex polymerase chain reaction tended to have a higher PI (37.6±27.2%) than those without amplified N-myc (n=27; PI=17.3±18.1). A PI value of over 40% was clearly associated with an unfavourable prognosis. The AI, however, did not correlate with any of the other variables analysed. The findings suggest that proliferation, but not apoptosis, is of critical significance in retinoblastoma biology. PI, as determined by the Ki-67 antigen labelling index, seems to be a relevant histopathological parameter that can predict the clinical outcome of retinoblastoma.
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  • 10
    ISSN: 1432-2307
    Keywords: Key words Anencephaly ; Thymic hyperplasia ; CD99 ; Apoptosis ; Aggregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In a significant proportion of cases, anencephaly is associated with thymic enlargement, suggesting a possibility that anencephalic fetuses have a functional disturbance in thymocyte differentiation and development. In this report, we demonstrated that CD99 expression was consistently reduced in cortical thymocytes of all anencephalic fetuses. In addition, the CD99-dependent aggregation of immature cortical thymocytes was almost completely impaired and apoptosis of thymocytes was markedly reduced in several cases. These results are in agreement with previous findings that CD99 regulates the aggregation and apoptosis of various types of cells. These data strongly suggest that functional disturbance of thymocytes and thymic hyperplasia are related to the reduced expression of CD99 molecule in anencephalic fetuses.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 359 (1999), S. 228-234 
    ISSN: 1432-1912
    Keywords: Key words Natural killer ; Pentoxifylline ; Macroangiopathic patients ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The methylxanthine derivative pentoxifylline, widely used in the treatment of vascular diseases, also has numerous immunological effects. In in vitro experiments, the human natural killer cell cytotoxicity was investigated in the presence of pentoxifylline. A clinical trial involved an investigation of the natural killer cell activity in patients to whom pentoxifylline had been administered for different periods. The natural cytotoxicity in macroangiopathic patients treated with pentoxifylline was compared with that in healthy controls and that in patients with vascular diseases who did not receive pentoxifylline therapy. A total of 62 macroangiopathic patients and 20 healthy controls were investigated. The natural killer cell activity in patients receiving pentoxifylline therapy for more than a year proved to be significantly lower (P〈0.005). The presence of vascular disease did not influence the natural killer activity. In the in vitro cytotoxicity reaction, pentoxifylline at a concentration of 100 µg/ml was found to suppress the natural killer cell cytotoxicity at any stage of the reaction. The influence of pentoxifylline on the natural killer cell activity was not due to inhibition of the expression of intercellular adhesion molecule-1. However, this drug significantly decreases (P〈0.05) the apoptosis of target cells. It is presumed that the suppressor effect of pentoxifylline on natural killer cell activity should be taken into consideration in the treatment of clinical diseases where this drug is administered chronically.
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  • 12
    ISSN: 1432-1912
    Keywords: Key words Blood pressure ; Endothelium ; Human ; Mesenteric artery ; Rat ; Smooth muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The majority of the findings concerning arterial physiology and pathophysiology originate from studies with experimental animals, while only limited information exists about the functional characteristics of human arteries. Therefore, the aim of the present work was to compare the control of vascular tone in vitro in mesenteric arterial rings of corresponding size (outer diameter 0.75–1 mm) from humans and Wistar-Kyoto rats. The relaxations to acetylcholine (ACh) were clearly less marked in the mesenteric arteries of humans when compared with rats. How-ever, when calcium ionophore A23187 was used as the vasodilator, the endothelium-mediated relaxations did not significantly differ between these species. The NO synthase inhibitor N G-nitro-l-arginine methyl ester (l-NAME) attenuated the relaxations to ACh and A23187 in both groups. The endothelium-independent relaxations to the β-adrenoceptor agonist isoprenaline and the nitric oxide (NO)-donor nitroprusside were somewhat lower in human arteries, while vasodilation induced by the K+ channel opener cromakalim was similar between humans and rats. Arterial contractile sensitivity to noradrenaline and serotonin was slightly lower in human vessels, whereas contractile sensitivity to KCl was similar between these species. The contractions induced by cumulative addition of Ca2+ with noradrenaline as the agonist were effectively inhibited in both groups by the calcium channel blocker nifedipine, the effect of which was clearly more pronounced in human arteries. In conclusion, the control of vascular tone of isolated arteries of corresponding size from humans and rats appeared to be rather similar. The most marked differences between these species were the impaired endothelium-mediated dilation to ACh and the more pronounced effect of nifedipine on the Ca2+-induced contractions in human arteries.
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  • 13
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Epitheloides Hämangioendotheliom ; Leber ; Kindesalter ; Proliferation ; Apoptose ; Key words Epithelioid hemangioendothelioma ; Liver ; Childhood ; Proliferation ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We report on a 12-year old boy suffering from malignant epithelioid hemangioendothelioma of the liver, which is a very rare tumor in childhood. The tumor was detected by ultrasound examination at the age of 10 and appeared at that time as a solitary intrahepatic nodular lesion. During the following 2 years multiple nodular lesions developed in both hepatic lobes. There were neither any suspect anamnestic findings nor abnormal clinical or laboratory data. The tumor showed the typical histomorphological, immunohistochemical, and ultrastructural features of this entity, which is usually seen in older patients. We investigated proliferative activity, apoptotic regulation, and expression of VEGF and VEGF-receptor flk-1 by means of immunohistochemical techniques. According to the known slow growth activity of these tumors we found only a few Ki-67 positive tumor cells. We did not detect any apoptotic cells using TUNEL technique. The positive immunoreaction of the tumor cells with antibodies against VEGF and VEGF-receptor flk-1 may indicate the regulation of tumor growth by angiogenetic factors. We present our findings together with a summary of the most important publications of recent years concerning these tumors.
    Notes: Zusammenfassung Bei einem 12 Jahre alten Jungen wurde ein im Kindesalter sehr seltenes malignes epitheloides Hämangioendotheliom der Leber diagnostiziert. Im Alter von 10 Jahren fiel erstmals sonografisch ein solitärer Leberrundherd auf, im Verlauf der nächsten zwei Jahre entwickelten sich multiple Rundherde in beiden Leberlappen. Die Anamnese des Patienten war hinsichtlich möglicher prädisponierender Faktoren unauffällig. Die klinischen und laborchemischen Parameter befanden sich im Normbereich. Der Tumor wies die für diese, üblicherweise bei Erwachsenen auftretenden Entität typischen histomorphologischen, immunhistochemischen und ultrastrukturellen Merkmale auf. Mittels immunhistochemischer Untersuchungen wurde das Tumorgewebe hinsichtlich Proliferationsaktivität, Apoptoseregulation und Expression angiogenetischer Faktoren (VEGF und VEGF-Rezeptor flk-1) untersucht. Bei bekanntermaßen langsamer Wachstumstendenz dieser Tumoren fand sich ein geringer Anteil Ki-67-positiver Tumorzellen. Mittels TUNEL-Technik wurden keine Apoptosen gefunden. Die positive Immunreaktion der Tumorzellen mit Antikörpern gegen VEGF und den VEGF-Rezeptor flk-1 deutet auf eine Regulation des Tumorwachstums durch angiogenetische Faktoren hin. Die Ergebnisse werden in Verbindung mit einer Zusammenstellung der wichtigsten Publikationen der letzten Jahre über diese seltenen Tumoren diskutiert.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Medical microbiology and immunology 187 (1999), S. 221-226 
    ISSN: 1432-1831
    Keywords: Key wordsToxoplasma gondii ; Apoptosis ; Actinomycin D ; HL-60 ; Intracellular survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracellular microorganisms have to rely on the integrity of their host cells to persist. We, therefore, investigated the effect of infections with different Toxoplasma gondii strains on apoptosis of human-derived HL-60 cells at the single cell level. Infection with either mouse-avirulent (NTE strain) or virulent parasites (RH strain) did not induce apoptosis of HL-60 cells as compared to uninfected controls. In contrast, treatment with actinomycin D (act D) led to apoptosis in 15–25% of the cells. However, concomitant infection with T. gondii clearly abrogated act D-induced apoptosis. This was especially apparent in those host cells that were actually infected; in these parasite-positive cells the rate of apoptosis decreased by 82.8±4.3% (mean±SEM, P=0.017, Student's t-test) and 91.7±3.4% (P=0.024) after infection with either the NTE or the RH strain, respectively. Inhibition of host cell apoptosis was similarly observed in cells which had been invaded by UV-irradiated, non-replicating parasites (P=0.001, Student's t-test). However, incubation with heat-killed parasites or T. gondii lysates did not abrogate act D-induced apoptosis. In conclusion, inhibition of apoptosis by living, but not necessarily replicating T. gondii may facilitate parasite survival and persistence within its host cell.
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  • 15
    ISSN: 1432-1831
    Keywords: Key words Verocytotoxin ; Verocytotoxin-producing Escherichia coli ; Hemolytic uremic syndrome ; Renal proximal tubular cell ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Verocytotoxin 1 and 2 (VT1 and 2) produced by verocytotoxin-producing Escherichia coli have been considered to play an important role in the pathogenesis of glomerular and tubular damage in the epidemic form of hemolytic uremic syndrome (HUS). VTs are known to be cytotoxic to culture cells by inhibiting cellular protein synthesis. In this in vitro study, the mechanism(s) of tubular damage in HUS and the ability of VT1 to induce apoptosis in normal human renal proximal tubular epithelial cells (HRPTEC) were examined. VT1 markedly reduced cell viability of HRPTEC and rapidly inhibited overall protein synthesis. VT1 directly induced apoptotic cell death in HRPTEC in a dose- and time-dependent fashion, and co-incubation with tumor necrosis factor-α enhanced the VT1-induced apoptosis. These results suggest that apoptosis induced by VT1, possibly in concert with host cytokines, in renal tubular cells may contribute to the tubular damage in HUS.
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  • 16
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Ataxia teleangiectatica ; Immunfunktionsstörung ; Lymphozytensubpopulationen ; Apoptose ; CD45RO ; CD45RA ; Key words Ataxia teleangiectasia ; Immunodeficiency ; Lymphocyte subset ; Apoptosis ; CD45RO ; CD45RA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background: Can a characterisation of the lymphocyte subset in patients with ataxia teleangiectasia offer an explanation for the cellular defect of their immunfunction? Methods: In ten patients with ataxia teleangiectasia and a corresponding control group of individuals of similar age and sex, immunophenotyping was carried out by means of flow cytometric analysis and the use of monoclonal antibodies. Results: Patients with ataxia teleangiectasia showed a reduction of the number of T-cells with a decrease in the T-helper cell subset (CD3: 990/µl, p〈0.0005 and CD4: 568/µl, p〈0.0005). The number of B-cells was low (CD19: 39/µl, p〈0.005). Moreover, there was an increase in highly activated T-lymphocytes which can be seen from a higher percentage of the HLA-DR- and CD45RO-expression in patients with ataxia teleangiectasia compared to the individuals of the control group (HLA-DR: 57%, p〈0.0005 and CD45RO: 82%, p〈0.001). At the same time, the expression of CD95 (Fas/AP01) was clearly increased (CD95: 74%, p〈0.001). Interpretation: The lymphocyte subset of the patients suffering from ataxia teleangiectasia shows a significant decrease of the B- and T-cell subsets. The reduced number of T-helper cells – caused by a CD45RA-cell loss – leads to a change in the relation „RA/RO”. It is possible that there is a link between the imbalance of „RA/RO”, the increase of highly activated T-lymphocytes and the higher expression of CD95 (Fas/APO1).
    Notes: Zusammenfassung Fragestellung: Können durch eine Charakterisierung der Lymphozytensubpopulationen bei Patienten mit Ataxia teleangiectatica Rückschlüsse auf den zellulären Defekt der Immunfunktionsstörung gezogen werden? Methodik: Mit Hilfe der Durchflußzytometrie und des Einsatzes monoklonaler Antikörper führten wir eine Immunophänotypisierung bei jeweils 10 Patienten mit Ataxia teleangiectatica und eines bezüglich des Alters und des Geschlechts gleichverteilten Kontrollkollektivs durch. Ergebnisse: Die Patienten mit Ataxia teleangiectatica zeigten verminderte T-Zell-Zahlen mit Abnahme der T-Helferzell-Subpopulationen (CD3: 990/µl, p〈0,0005 und CD4: 568/µl, p〈0,0005). Auch die B-Zell-Zahl war erniedrigt (CD19: 39/µl, p〈0,005). Die T-Lymphozyten befanden sich darüber hinaus vermehrt im aktivierten Zustand, erkennbar an einer prozentual erhöhten HLA-DR- und CD45RO-Expression (HLA-DR: 57%, p〈0,0005 und CD45RO: 82%, p〈0,001) sowie an einer Verschiebung der Relation „RA/RO” zugunsten der „RO”-Expression. Gleichzeitig war die Expression von CD95 (Fas/APO1) deutlich gesteigert (CD95: 74%, p〈0,001). Schlußfolgerung: Die Veränderungen der Lymphozytensubpopulationen zeigen bei den Patienten mit Ataxia teleangiectatica eine verminderte B- und T-Zell-Zahl. Die CD4-Lymphopenie – verursacht durch einen CD45RA-Zellverlust – bedingt eine Verschiebung der Relation „RA/RO”. Möglicherweise besteht ein Zusammenhang zwischen der Störung der Homöostase „RA/RO” und dem erhöhten Aktivierungsgrad der Zellen sowie der vermehrten CD95(Fas/APO1)-Expression.
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  • 17
    ISSN: 1432-0843
    Keywords: Key words Baccatin III ; Paclitaxel ; Apoptosis ; Mitotic arrest ; bcl-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Paclitaxel has been demonstrated to possess significant cell-killing activity in a variety of tumor cells by induction of apoptosis, but the mechanism by which paclitaxel leads to cell death and its relationship with mitotic arrest is not entirely clear. In this study, baccatin III, a synthetic precursor of paclitaxel, was used to analyze whether paclitaxel-induced apoptosis can be a separate event from microtubule bundling and G2/M arrest. Methods: Several different methods including DNA fragmentation, flow cytometric analyses, TdT-mediated dUTP nick end labeling (TUNEL) and time-lapse video microscopy were used to analyze apoptotic cell death induced by baccatin III and its possible correlation with cell cycle distribution. Results: Our results demonstrated that baccatin III could also cause apoptotic cell death in both BCap37 (a human breast cancer cell line) and KB cells (derived from human epidermoid carcinoma), but had less effect on microtubule bundling and G2/M arrest. Furthermore, we demonstrated that most apoptotic events induced by baccatin III were not coupled with G2/M arrest. Instead, these apoptotic events occurred predominantly in the cells in other phases of the cell cycle. Conclusion: Baccatin III, which contains the core taxane ring, is the fundamental piece of paclitaxel structure. The finding of baccatin III-induced apoptosis independent of cell cycle arrest, on the one hand, implies that the core taxane ring may play a critical role in inducing cell death and, on the other hand, suggests that paclitaxel might induce apoptosis from other phases of the cell cycle by a similar mechanism.
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  • 18
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    Archives of toxicology 73 (1999), S. 7-14 
    ISSN: 1432-0738
    Keywords: Key words Organophosphates ; Acetylcholinesterase ; Oximes ; Human ; Reactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Human poisoning by organophosphates bearing two methoxy groups, e.g. by malathion, paraoxon-methyl, dimethoate and oxydemeton-methyl, is generally considered to be rather resistant to oxime therapy. Since the oxime effectiveness is influenced not only by its reactivating potential but also by inhibition, aging and spontaneous reactivation kinetics, experiments were performed with human acetyl- (AChE) and butyrylcholinesterase (BChE) to determine the respective kinetic constants. The efficacy of obidoxime in reactivating dimethylphosphoryl-AChE was 40, 9 and 3 times higher than of HI 6, pralidoxime and HLö 7, respectively. Aging (t 1/2 3.7 h) and spontaneous reactivation (t 1/2 0.7 h) occurred concomitantly, with the portion of the aged enzyme being dependent on the presence of excess inhibitor. Calculation of steady-state AChE activity in the presence of inhibitor and oxime revealed that obidoxime was superior to pralidoxime. In addition, organophosphate concentrations up to 10−6 M (paraoxon-methyl) and 10−4 M (oxydemeton-methyl) could be counteracted at clinically relevant oxime concentrations (10 μM). These data indicate that oximes may effectively reactivate human dimethylphosphoryl-AChE. Failure of oximes may be attributed to megadose intoxications and to prolonged time intervals between poison uptake and oxime administration. The potency of the oximes to reactivate dimethylphosphoryl-BChE was much lower and the spontaneous reactivation slower (t 1/2 9 h), while aging proceeded at a comparable rate. Thus, BChE activity determination for diagnosis and therapeutic monitoring may give no reliable information on AChE status.
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  • 19
    ISSN: 1432-0843
    Keywords: Key words Cyclin-dependent kinase ; Cytotoxicity ; Apoptosis ; Multidrug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: To determine the in vitro effects of flavopiridol on bladder cancer cell lines, immortalized urothelial cell lines, and normal urothelial cells well characterized for defects in p53, pRb, and p16. Methods: Growth inhibition was assessed via an MTT assay and apoptosis via DAPI nuclear staining. Cell cycle analysis was performed via propidium iodide staining and fluorescent activated cell sorting (FACS). Multidrug-resistant cells were generated by continuous exposure to doxorubicin. Results: Growth inhibition was not correlated with inactivation of p53, pRb, or p16. All cells experienced G2/M arrest within 24 h of flavopiridol exposure. Modest apoptosis was observed but required 72 h of continuous drug exposure to become evident. There was no obvious synergistic or antagonistic toxicity when flavopiridol was combined with radiotherapy or cisplatin dosed at the IC50 despite the observation that radiotherapy and flavopiridol led to more profound G2/M arrest than either agent alone. Doxorubicin-resistant cells, demonstrated to overexpress the MDR1 multidrug-resistance protein were equally as sensitive to flavopiridol as the parental cells. Conclusions: Flavopiridol is a novel cell cycle inhibitor that may be a useful agent in bladder cancers with tumor suppressor gene alterations and/or multidrug resistance.
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  • 20
    ISSN: 1432-0843
    Keywords: Key words Dolastatin ; Lung cancer ; Apoptosis ; Xenografts ; Experimental therapeutics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: Dolastatin 10 is a natural cytotoxic peptide which acts through the inhibition of microtubule assembly. Studies have suggested that such agents can induce apoptosis in association with bcl-2 phosphorylation. Since bcl-2 overexpression is common in small-cell lung cancer (SCLC), we evaluated the activity of dolastatin 10 in SCLC cell lines and xenografts. Methods: In vitro growth inhibition was evaluated with a standardized MTT assay and apoptosis with fluorescent microscopy and a TUNEL assay. Immunoblot analysis and phosphatase digestion were used to determine bcl-2 modification. In vivo activity was evaluated in subcutaneous and metastatic SCLC xenograft models in SCID mice. Results: Dolastatin 10 had growth inhibitory activity against four SCLC cell lines (NCI-H69, -H82, -H446, -H510) with IC50 values ranging from 0.032 to 0.184 nM. All four cell lines exhibited evidence of apoptosis after 48 h of exposure to 1.3 nM dolastatin 10. Immunoblot analysis revealed that 1.3 nM dolastatin 10 altered the electrophoretic mobility of bcl-2 in NCI-H69 and -H510 cells within 16 h of treatment. Incubation of protein extract from dolastatin 10-treated NCI-H69 and -H510 cells with calcineurin resulted in the disappearance of the altered mobility species, suggesting dolastatin 10-induced bcl-2 phosphorylation. In in vivo studies, 450 μg/kg of dolastatin 10 IV × 2 given after intravenous injection of NCI-H446 cells completely inhibited tumor formation. In established subcutaneous NCI-H446 xenografts, 450 μg/kg of dolastatin 10 IV induced apoptosis in the majority of tumor cells within 96 h, resulting in a log10 cell kill of 5.2 and an increase in median survival from 42 to 91 days. Conclusions: These findings suggest that dolastatin 10 has potent activity against SCLC and that the modulation of apoptotic pathways deserves further evaluation as an anticancer strategy.
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  • 21
    ISSN: 1432-069X
    Keywords: Key words Chronic diabetic wounds ; Human ; fibroblasts ; Wound healing ; Cell culture ; Proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients with diabetes mellitus experience impaired wound healing often resulting in chronic foot ulcers. Hospital discharge data indicate that 6–20% of all diabetic individuals hospitalized (mostly with type 2 diabetes) have a lower extremity ulcer. Maintaining glucose levels at acceptable levels (below 10 mmol/l) is considered to be an important part of the clinical treatment, but the exact mechanism by which diabetes delays wound repair is not yet known. We studied this phenomenon by determining the potential of fibroblasts isolated from the ulcer sites of four patients with non-insulin-dependent diabetes mellitus to proliferate in vitro. Controls were fibroblasts isolated from normal skin of the upper leg of five healthy age-matched volunteers and of six non-insulin-dependent diabetes patients. Proliferative capacity was analysed by evaluation of plates after trypsinization and [3H]thymidine incorporation. Fibroblast morphology was studied by light and transmission electron microscopy. Diabetic ulcer fibroblasts, measured by [3H]thymidine incorporation, proliferated significantly more slowly than the nonlesional control fibroblasts (P 〈 0.00047) and age-matched control fibroblasts (P 〈 0.00003). After culturing the fibroblasts for a prolonged period in high-glucose (27.5 mM) and low-glucose (5.5 mM, i.e. physiological) medium, this difference in proliferation rate between diabetic ulcer fibroblasts and nonlesional diabetic fibroblasts remained (P 〈 0.0001 for high-glucose and P 〈 0.0009 for low-glucose on day 7). Fibroblast proliferation in all three groups was slightly lower in high-glucose than in low-glucose medium, although not significantly at any time-point. Light microscopy showed diabetic ulcer fibroblasts to be large and widely spread. Transmission electron microscopy of cultured diabetic ulcer fibroblasts and nonlesional diabetic skin fibroblasts revealed a large dilated endoplasmic reticulum, a lack of microtubular structures and multiple lamellar and vesicular bodies. These results show a diminished proliferative capacity and abnormal morphology of fibroblasts derived from diabetic ulcers of non-insulin-dependent diabetes patients.
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  • 22
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    Archives of dermatological research 291 (1999), S. 212-216 
    ISSN: 1432-069X
    Keywords: Key words UV irradiation ; Solar-simulated irradiation ; Apoptosis ; bcl-2 ; bax
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recently, the proto-oncogenes bcl-2 and bax have emerged as important regulators of the apoptotic form of cell death. We examined UV irradiation-elicited apoptosis and regulation of bcl-2 and bax expression both in vivo in human skin and in vitro in HeLa cells. Using flow cytometric analysis, HeLa cells were found to undergo apoptosis at the 12-h time-point after exposure to UVB irradiation (100 mJ/cm2). The expression of bcl-2 mRNA was found to decrease after a single dose of UVB radiation (doses 10–200 mJ/ cm2). In contrast, the expression of bax mRNA was not significantly changed. When human skin was irradiated with a single dose of solar-simulated radiation (40 mJ/cm2), Bcl-2-positive cells were significantly reduced in the epidermis at the 3- and 6-h time-points. Our results suggest that UV irradiation downregulates bcl-2 expression both in vitro at the mRNA level and in vivo at the protein level, and that downregulation of bcl-2 constitutes a mechanism of potential importance in UV-induced apoptosis in human epidermis.
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  • 23
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    Archives of dermatological research 291 (1999), S. 247-252 
    ISSN: 1432-069X
    Keywords: Key words T cell activation ; Nickel ; Human ; Interferon-gamma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Contact hypersensitivity to nickel is the most common form of allergic contact dermatitis. To gain insight into the induction of this frequent disease, T cell reactivity towards nickel was investigated in “nonallergic” individuals defined as those with no skin manifestations and a negative patch test towards NiSO4. Surprisingly, we found that nickel induced proliferation of peripheral blood mononuclear cells (PBMC) from 16 of 18 adult individuals tested. This activation was specific, and no stimulation of PBMC was observed using control stimulants at equimolar concentrations. Furthermore, the NiSO4-induced activation required the presence of professional antigen-presenting cells. To describe the functional capacity of the nickel-inducible T cells, cytokine release was investigated in both nickel-allergic and nonallergic individuals. The T cells from both groups released interferon-γ but no interleukin-4 upon stimulation with nickel, suggesting that the functional capacities of these cell populations were similar in nickel-allergic and nonallergic individuals. Thus, at this level, no qualitative differences could be demonstrated between T cells obtained from nickel-allergic and nonallergic individuals.
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  • 24
    ISSN: 1432-069X
    Keywords: Key words TUNEL ; Apoptosis ; Trichilemmal ; keratinization ; Epidermal appendages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 25
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    Archives of dermatological research 291 (1999), S. 303-305 
    ISSN: 1432-069X
    Keywords: Key words Langerhans cells ; Sunburn cells ; UV ; erythema ; Apoptosis ; Immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 26
    ISSN: 1432-069X
    Keywords: Key words ORS cells ; Melanocytes ; Human ; Organotypic cultures ; Melanosomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Because outer root sheath (ORS) cells are valuable substitutes for interfollicular epidermal keratinocytes, we wanted to determine whether epidermal equivalents generated from ORS cells and containing cultured melanocytes can serve as an in vitro model for skin pigmentation. In such epidermal equivalents prepared with ORS cells and melanocytes from donors of phototypes II, III and VI, a stratified epithelium resembling normal epidermis developed within 14 days, as documented by histological, ultrastructural (e.g. basement membrane-like structure, keratohyalin granules, keratinosomes) and immunohistochemical (e.g. keratins, integrins, gp80, involucrin, filaggrin) criteria. The melanocytes were localized in the basal layer and accounted for 10% of the total cell number. Heavily pigmented melanocytes from black donors contained regular melanosomes in all stages of maturation, whereas melanocytes derived from white donors contained predominantly melanosomes of stages I and II. Melanosome-laden dendrites were readily detected extending from the heavily pigmented melanocytes, while they were less conspicuous in melanocytes from white donors. The extent of melanosome transfer was independent of the racial origin of the ORS cells. Melanosomes could also be transferred “through racial barriers”. Melanosomes, mainly of stages III and IV, were detected in the ORS cells, being distributed either as single or compound melanosomes, again irrespective of the racial origin of the ORS cells. In conclusion, pigmented epidermal equivalents generated from ORS cells offer practical advantages over other in vitro pigmentation models: (1) the ORS cells are easily and repeatedly available from any donor regardless of age; (2) primary cultures of ORS cells are free of contaminating melanocytes, a bias if using interfollicular epidermal keratinocytes; (3) a high degree of epidermal differentiation is maintained for 3 weeks in fully defined medium, enabling labelling and stimulation experiments to be performed and compounds interfering with melanin pigmentation to be tested.
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  • 27
    ISSN: 1432-0533
    Keywords: Key words c-Jun ; Jun B ; Jun D ; Apoptosis ; Colchicine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The expression of members of the Jun family of transcription factors was examined by immunohistochemistry, Western blotting, in situ hybridization and Northern blotting in the developing and adult rat brain following colchicine administration. Apoptotic cells, as revealed by their typical morphology and positive staining with the method of in situ end-labeling of nuclear DNA fragmentation, were restricted to granule cells of the dentate gyrus and olfactory bulb, and a few cells in the upper layers of the entorhinal cortex in adult rats, whereas widespread apoptosis occurred in developing rats after colchicine administration. No modifications in the expression of Jun D and Jun B, except for a generalized and moderate Jun B expression in glial cells, were observed in colchicine-treated rats. Generalized and strong c-jun mRNA induction and c-Jun/AP-1 (Ab-1) protein expression was observed in the cerebral neocortex, entorhinal and piriform cortices, CA1 and CA3 areas of the hippocampus and granule cell layer of the dentate gyrus in adult treated rats, thus indicating a generalized c-Jun response to colchicine administration. In contrast, c-Jun/AP-1 (N) and c-Jun/AP-1 (Ab-2) immunoreactivity was restricted to apoptotic cells in colchicine-treated adult and developing brains. Western blots of hippocampal homogenates and total brain homogenates in adult and developing rats, respectively, demonstrated a band of 39 kDa for the c-Jun/AP-1 (Ab-1) antibody in control animals, the intensity of which increased in colchicine-treated rats. However, a band of 37 kDa, the intensity of which also increased following colchicine administration, was observed for the c-Jun/AP-1 (N) and c-Jun/AP-1 (Ab-2) antibodies. Selective c-Jun/AP-1 (N) and c-Jun/AP-1 (Ab-2) expression was also observed in apoptotic cells of the SH-SY5Y neuroblastoma line after the addition of colchicine to the culture medium. Taken together, the present in vivo and in vitro results indicate a generalized c-Jun response to colchicine in sensitive cells, whereas the antibodies c-Jun/AP-1 (N) and c-Jun/AP-1 (Ab-2) recognize vulnerable cells dying via apoptosis.
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  • 28
    ISSN: 1432-0533
    Keywords: Key words Immediate early gene ; Heat shock protein ; Cerebral ischemia ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neuroprotective role of the expression of heat shock protein (HSP) and immediate early gene remains unclear. Using immunoelectron microscopy, we examined the ultrastructural integrity of the neurons with expression of c-Fos, c-Jun and HSP70 in gerbils after transient cerebral ischemia and repefusion. Induction of c-Fos and c-Jun was observed in the CA3 region resistant to ischemia, while HSP70 was expressed not only in the CA3 but also in the vulnerable CA1 region. With immunoelectron microscopy, the expression of c-Fos/c-Jun and HSP70 was observed in the neurons which retained neuronal integrity except for mitochondrial swelling and polyribosomal disaggregation. In contrast, the CA1 neurons without immunoreaction for HSP70 showed cytoplasmic vacuoles and parallel stacking of rough endoplasmic reticulum, the features associated with the process of delayed neuronal death. These findings suggested that c-Fos and c-Jun were induced selectively in reversibly damaged neurons, whereas HSP70 was up-regulated even in neurons with irreversible damage, but was more preferentially and intensely expressed in neurons with reversible damage.
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  • 29
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    Acta neuropathologica 97 (1999), S. 5-12 
    ISSN: 1432-0533
    Keywords: Key words Creutzfeldt-Jakob disease ; Apoptosis ; Cell death ; Prion protein ; In situ end-labeling of nuclear DNA fragmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The method of in situ end-labeling of nuclear DNA fragmentation was used in the study of ten patients (two biopsies, eight autopsies) with sporadic Creutzfeldt-Jakob disease (CJD). All the patients had the typical morphological lesions including neuron loss, spongiform change and astrocytosis. Four of them also showed prion protein (PrP) deposits in the cerebral cortex, and two of them kuru-like plaques in the cerebellum. A few cells with DNA breaks were found in the two biopsy cases; one of them, suffering from a panencephalopathic form of the disease, showed positive nuclei not only in the cerebral cortex but also in the subcortical white matter. Variable numbers of positive nuclei were observed in the gray and white matter in the eight autopsy cases, in which, although the distribution of positive cells roughly correlated with the distribution of neuron loss, no clear relationship was found as regards the distribution and degree of cell labeling and the degree of neuron loss. Furthermore, large numbers of positive cells were concentrated in a particular area, whereas a few cells were seen in a neighboring equally affected area. Positive glial cells in the plexiform layer of the CA1 area of the hippocampus, and in the frontal white matter were frequently encountered. Staining of the cytoplasm in a minority of cells was interpreted as the result of nuclear DNA leakage. None of the stained cells had the typical morphology of apoptosis; most particularly, peripheral chromatin condensation and formation of apoptotic bodies were not seen in any case. PrP deposits did not result in an increase of nuclear DNA breaks either within the area or in adjacent regions. Although positive cells were also observed in autopsy cases of controls which were processed in the same way, positive labeling as a whole was higher in CJD than in age-matched controls. These results show that brain nuclear DNA is vulnerable in CJD, and suggest that increased DNA vulnerability has a role in cell death and neuron loss. Since nuclear shrinkage and positive nuclear staining with the method of in situ end-labeling of nuclear DNA fragmentation are not exclusive to apoptosis, further information is needed to categorize cell death in CJD as apoptosis. Necrosis or other forms of cell death, as well as increased DNA vulnerability to agonal changes of the individuals, and to postmortem delay in the fixation of the tissues, may account for additional positive staining in cases examined at autopsy.
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  • 30
    ISSN: 1432-0533
    Keywords: Key words Parkinson’s disease ; Apoptosis ; Bcl-2 ; Bax ; Bcl-x
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the substantia nigra of three Parkinson’s disease (PD) patients and three age-matched individuals by in situ DNA-end labeling (ISEL) and immunohistochemistry for the apoptosis regulating proteins Bcl-2, Bax and Bcl-x on 50 consecutive sections per patient. No melanin-containing cell was identified with typical apoptotic changes in either patient or control substantia nigra. With prolonged reaction-time the terminal transferase-mediated DNA-end labeling revealed a signal in 2.0 ± 1.2% melanin-containing cells in PD compared to 1.3 ± 1.1% in control. This difference did nor reach statistical significance and no condensation or margination of the chromatin was evident. No significant changes of any of the apoptosis regulating proteins were apparent in PD substantia nigra. These findings do not support the hypothesis that apoptosis plays a central role in the pathogenesis of PD.
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  • 31
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    Acta neuropathologica 97 (1999), S. 279-287 
    ISSN: 1432-0533
    Keywords: Key words Canine distemper virus ; Oligodendrocytes ; Apoptosis ; Necrosis ; Demyelination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Canine distemper virus (CDV) causes a multifocal demyelinating disease in dogs. It was previously shown that the initial demyelinating lesions are directly virus induced since a correlation between the occurrence of demyelination and CDV replication in white matter cells was observed. During the course of infection oligodendrocytes undergo distinct morphological alterations, partly due to a restricted CDV infection of these cells, and eventually disappear from the lesions. This phenomenon has been described in vivo as well as in vitro. However, the reason for the morphological alterations and the following oligodendroglial depletion remained unclear. Since virus infection can induce cell death, it was investigated whether apoptosis or necrosis plays a role in the pathogenesis of demyelination in canine distemper. In brain tissue sections from dogs with acute distemper apoptotic cells were not detected within the demyelinating lesions using morphological and biochemical cell death criteria. In chronic distemper, apoptotic cells – presumably inflammatory cells – were seen within the perivascular cuffs. These in vivo findings were correlated to the in vitro situation using CDV-infected primary dog brain cell cultures as well as Vero cells. Infection with culture-adapted CDV lead to massive necrosis but not to apoptosis. After infection with virulent CDV neither apoptosis nor necrosis was a predominant feature in either culture system. These findings suggest that virus-induced demyelination in canine distemper is not the direct consequence of apoptosis or necrosis. It is speculated that another mechanism must be responsible for the observed morphological alterations of oligodendrocytes, ultimately leading to demyelination.
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  • 32
    ISSN: 1432-0568
    Keywords: Key words Synaptogenesis ; Primate ; Spinal cord ; Apoptosis ; Neuropeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Development of glomerular synapses in the superficial dorsal horn has been studied in the embryonic macaque spinal cord using light and electron microscopic techniques including Golgi impregnation, 3H-thymidine radioautography and pre-embedding immunohistochemistry of substance P (SP), calcitonin gene related peptide (CGRP), calbindin D-28 K (CB) and parvalbumin (PV). The study revealed that substantia gelatinosa cells of the primate dorsal horn are generated last, but unlike in rodents, synaptogenesis in this region starts at early embryonic (E) stages of the 165-day long gestation. Already by E30, both Type 1 (light) and 2 (dark) dorsal root axons and their growth cones are identifiable within the oval bundle of His, before they form synaptic contact with their final target cells. Subsequently they invade the dorsal horn and enter the bisecting interfaces formed by orderly programmed cell death. Each type of scalloped (sinusoid) central primary afferent terminal (i.e. DSA, RSV and LDCV) have well defined pre- and post-synaptic specializations already by E40. Among the neuropeptides studied, SP appears first at E67 and CGRP at E70 in the lateral position but within a few days both of them are spread to the entire superficial dorsal horn. Both SP and CGRP are present in the thin dorsal root axons and their growth cones, giving rise to scalloped and simple axon terminals. PV is transiently present in the entire length of the thick dorsal root afferents before becoming concentrated in the synaptic boutons. CB is displayed mainly in neurons of the lamina I and III. Dendrites of CB-immunoreactive cells establish synaptic connection with each type of dorsal root afferents, including glomerular synaptic complexes. These data reveal that the superficial dorsal horn in the primate spinal cord develops its characteristic synaptic complexes much earlier in gestation than in any other mammalian species studied. Furthermore, characteristic cytological features of the prospective glomerular complex emerge before establishment of the final synaptic contacts.
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  • 33
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    Acta neuropathologica 97 (1999), S. 192-195 
    ISSN: 1432-0533
    Keywords: Key words Neuronal vacuolation ; Rottweiler dog ; Bcl-2 ; Bax ; c-Jun ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neuronal vacuolation, involving the cerebellar roof nuclei, Purkinje cells, selected nuclei of the brain stem, thalamus, Clarke’s column, anterior and posterior horns of the spinal cord, visceral autonomic ganglia and myenteric plexus, as well as axonal degeneration of the white matter of the brain stem, cerebellar pedunculi, dorsolateral columns of the spinal cord and ventral roots of the spinal cord, were observed in two young Rottweiler dogs which were clinically afflicted with hind limb weakness progressing to paraparesia, ataxia, intention tremor, and difficulty in swallowing and barking. The absence of modifications in Bcl-2 and Bax immunoreactivity, a lack of strong c-Jun/AP-1 (N) immunoreactivity in vacuolated cells, and the absence of DNA breaks, as seen with the method of in situ end-labeling of nuclear DNA fragmentation, all suggest that there is no involvement of the apoptotic pathway in vacuolated cells in this new neurodegenerative disorder.
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  • 34
    ISSN: 1432-0568
    Keywords: Key words Brain ; Cortical parcellation ; Development ; Proteoglycans ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Nitric oxide (NO) regulates several functions both in the developing and the adult central nervous systems (CNS). During development, NO is assumed to contribute to the histogenetic differentiation of the CNS especially through the modulation of programmed neuronal death. The embryonal and postnatal changes in the distribution of the cortical NO producing system were studied in Balb/c mice using immunocytochemistry for nitric oxide synthase-I (NOS-I) and NADPH-diaphorase (NADPH-d) enzyme histochemistry. NOS-I reactive neurons (RN) appeared first at embryonic day 14 (E14) in the spinal cord in the vicinity of the central canal, and later, at E16–18, in the thalamus and striatum. The first cortical region to present NOS-I reactivity was the parietal cortex, which happened at E18–20. After E20 the number of NOS-I RN increased in every cortical area, plateauing at postnatal day 4 (P4). In parietal regions, however, the highest density of NOS-I RN was observed already at P1. The neuronal packing density (PD) of NOS-I RN declined until adulthood, interrupted by a transient increase in some cortical areas at the onset of puberty. The heterochronous appearance of NOS-I during pre- and postnatal development of different brain regions and the sequence of up- and downregulation of expression until adult stages points to an important role of NO in brain development and functional differentiation.
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  • 35
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    Anatomy and embryology 199 (1999), S. 45-56 
    ISSN: 1432-0568
    Keywords: Key words Skin ; Proteoglycan ; Development ; Human ; Fetal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The extracellular matrix of human fetal skin differs substantially from that of adult skin. Fetal skin contains sparse amounts of fibrillar collagen enmeshed in a highly hydrated amorphous matrix composed of hyaluronan and sulfated proteoglycans. Both fetal and adult skin contain two major interstitial proteoglycans that are extracted by chaotrophic agents and detergents. These are the large chondroitin sulfate proteoglycan versican and the small dermatan sulfate proteoglycan decorin. For this study, proteoglycans extracted from fetal and adult skin were compared on Western blots to determine the relative amounts of versican. Decorin present in the same samples provided an internal standard for these studies. Fetal skin differed from adult skin in that it contained a significantly higher proportion of versican than did adult skin. Immunohistochemical studies compared early-fetal with mid-fetal skin and found that versican was a significant component of the interstitial extracellular matrix at both of these stages of skin development. However, by the mid-fetal period, interstitial versican became restricted to the upper half of the dermis, although versican also continued to be highly expressed around hair follicles, glands, and vasculature in the lower half of the dermis. Fetal skin extracts differed from an adult skin extract by the presence of a 66-kDa protein immunologically related to versican and by the absence of a 17-kDa core protein of a proteoglycan related to decorin. Both of these molecular species may represent degradation products of their respective proteoglycans. Monoclonal antibodies which detect epitopes in native chondroitin sulfate glycosaminoglycan chains recognized versican extracted from fetal skin. However, the tissue distribution of these antigens did not entirely conform to that for versican core protein, suggesting that versican in different regions of the skin may be substituted with glycosaminoglycan chains with different microchemistries. The results of these studies indicate that human fetal skin is structurally different from adult skin in terms of both the distribution and the composition of the large, aggregating chondroitin sulfate proteoglycan versican.
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  • 36
    ISSN: 1432-0533
    Keywords: Key words Amantadine ; Human ; N-methyl-d-aspartate ; Phencyclidine ; Postmortem brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Low doses of N-methyl-d-aspartate (NMDA)-type glutamate receptor antagonists induce morphological alterations in neurons of the cingulate gyrus and retrosplenial cortex of the rat. Neuronal cell death may result at higher doses. These effects are a major concern with regard to the introduction of new NMDA receptor antagonists into clinical trials. Amantadine is an uncompetitive NMDA receptor antagonist, which has been in clinical use for many years. In the present study we have looked for possible morphological alterations like necrosis in postmortem human brain tissue of patients previously treated with amantadine. Formalin-fixed tissue samples were taken from the hippocampus, cingulate gyrus, and retrosplenial cortex of 8 patients on previous amantadine medication and of 11 controls. Histopathological examination of sections was performed blind. All brains except one revealed either nonspecific age-related or cerebrovascular changes or other neurodegenerative disorders including Alzheimer’s, Parkinson’s or Lewy body disease. In conclusion, histopathological examination of the hippocampus, retrosplenial cortex, and cingulate gyrus of human brain did not reveal changes suggested to be specific for previous amantadine treatment.
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  • 37
    ISSN: 1432-0533
    Keywords: Key words Purkinje cell ; Cerebellum ; Development ; Inositol 1 ; 4 ; 5-triphosphate type 1 receptor ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Immunohistochemical analyses were carried out on the Purkinje cells from 21 autopsied fetal and early postnatal normal cerebella using a monoclonal antibody against the inositol 1, 4, 5-triphosphate type 1 receptor (IP3R1) as a cytochemical marker of Purkinje cells. In normal adult cerebella used as positive controls, the cell bodies, axons, and dendrites, including spiny branchlets of the Purkinje cells, were specifically stained by the antibody. In the fetal cerebella examined, the IP3R1 immunoreactivity was first detected in the soma of multilayered cells just beneath the molecular layer at 16 weeks of gestation. The IP3R1 immunoreactivity gradually increased in area of positive staining from soma to dendrites and spiny branchlets, and the dendritic outgrowth rapidly progressed during 6 months after birth. The Purkinje cell maturation was more advanced in the vermis than in the hemisphere, more in the posterior lobe than in the anterior lobe, and more at the bottom of the folia than at the top. Partial absence of the Purkinje cells in the cerebellar cortex was observed in three cases. Heterotopias including Purkinje cells were often noted in the cerebellar white matter in five cases.
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  • 38
    ISSN: 1432-0533
    Keywords: Key words Glucocorticosteroids ; Apoptosis ; Guillain-Barré syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lipocortin-1 exerts a potent immunosuppressive effect on pathogenic T cells. In multiple sclerosis and experimental autoimmune encephalomyelitis levels of lipocortins are raised, suggesting their involvement in the recovery from an immunological insult or in neural regeneration. To further understand the role of lipocortins in the peripheral nervous system we have characterized lipocortin-1 levels and cellular distribution of lipocortin-1 immunoreactivity in sciatic nerves of rats with experimental autoimmune neuritis (EAN), a model of human Guillain-Barré syndrome. EAN was induced actively by immunization with bovine peripheral myelin (active EAN) or by adoptive-transfer (AT-EAN) of P2-specific T cells. Cellular infiltrates in serial and semithin cryosections were characterized by immunohistochemistry. In parallel, lipocortin-1 levels in tissue extracts were quantified by a sandwich-ELISA. Only weak lipocortin-1 immunoreactivity was found in nerves of control animals injected with non-pathogenic T cells. The majority of macrophages and lymphocytes in EAN lesions exhibited lipocortin-1 immunoreactivity. Some very heavily stained cells showed a distribution and morphology similar to ED-2-positive macrophages which were abundant during early stages of EAN. Lipocortin-1 expression in T cells and macrophages was proven by immunocytochemical studies in semithin serial sections. In tissue extracts, lipocortin-1 levels increased from 0.24 ± 0.14 μg/mg protein in controls receiving non-pathogenic T cells to a maximum of 0.55 ± 0.1 μg/mg protein in AT-EAN at the peak of disease, and then slowly decreased during clinical recovery but still remained elevated. In dose-response studies in AT-EAN, highest values of lipocortin-1 (0.71 ± 0.23 μg/mg protein) were recorded after transfer of 2 × 107 T cells. Increased levels of lipocortin-1 were also measured in active EAN but occurred during the recovery phase (0.65 ± 0.27 μg/mg protein). By analogy with other immune-mediated disorders, increased lipocortin-1 expression in the inflamed sciatic nerve in EAN may exert immunoregulatory functions in-situ and contribute to the termination of the autoimmune response.
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  • 39
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 200 (1999), S. 203-214 
    ISSN: 1432-0568
    Keywords: Key words Extracellular material ; Cell proliferation ; Apoptosis ; Anoikis ; Tenascin ; Laminin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Extracellular material molecules play a key role in the regulation of morphogenesis and differentiation of a large number of organs including the central nervous system. However, the role of the neural basement membrane in the growth of different parts of the neural tube has yet to been delineated. Here, the structural and compositional modifications of the basement membrane (BM) of rhombencephalic tectoria lamina anlage (RTLA) have been examined during the process of RTLA epithelial attenuation. Between stages 10 to 11– the presumptive RTLA epithelium showed a structure, thickness and cell-proliferating capacity similar to those observed in other zones of the rhombencephalic walls. Moreover, the rhombencephalic vesicles were surrounded by a continuous BM that was heterogeneous both ultrastructurally and with regard to ruthenium red, laminin and tenascin distribution. After stage 11, the RTLA epithelium underwent a rapid process of attenuation and change to a stratified flattened epithelium. During this remodelling process, apoptosis and inhibition of both PCNA expression and 3H-thymidine uptake occurred in the RTLA epithelium. The BM of the RTLA underwent a process of degration at the beginning of the remodelling, and apoptosis and cell proliferation inhibition of RTLA epithelium were also observed. The loss of the biochemical signals encoded within the BM could lead to cell shape changes, cell proliferation inhibition and to the anoikis type of cell death. Our findings support the idea that the BM surrounding the neural tube plays a key role in controlling both the structure and growth of the CNS during the early developmental stages.
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  • 40
    ISSN: 1432-0568
    Keywords: Key words Somite explant culture ; Sonic hedgehog protein ; Myogenic induction ; Primary fiber type diversity ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Primary skeletal muscle fibers first form in the segmented portions of paraxial mesoderm called somites. Although the neural tube and notochord are recognized as crucial in patterning myogenic cell lineages during avian and mammalian somitic myogenesis, the source, identities, and actions of the signals governing this process remain controversial. It has been shown that signals emanating from the ventral neural tube and/or notochord alone or Shh alone serve to activate MyoD expression in somites. However, beyond a role in initiating MyoD expression, little is known about the effects of Shh on primary muscle fiber formation in somites of higher vertebrates. The studies reported here investigate how the ventral neural tube promotes myogenesis and compare the effects of the ventral neural tube with those of purified Shh protein on fiber formation in somites. We show that purified Shh protein mimics actions of the ventral neural tube on somites including initiation of muscle fiber formation, enhancement of numbers of primary muscle fibers, and particularly, the formation of primary fibers that express slow myosin. There is a marked increase in slow myosin expression in fibers in response to Shh as somites mature. The effects of ventral neural tube on fiber formation can be blocked by disrupting the Shh signaling pathway by increasing the activity of somitic cyclic AMP-dependent protein kinase A. Furthermore, it was demonstrated that apoptosis is a dominant fate of somite cells, but not somitic muscle fibers, when cultured in the absence of the neural tube, and that application of Shh protein to somites reduced apoptosis. The block to apoptosis by Shh is a manifestation of the maturity of the somite with a progressive increase in the block as somites are displaced rostrally from somite III forward. We conclude that purified Shh protein in mimicking the effects of the ventral neural tube on segmented mesoderm can exert pleiotropic effects during primary myogenesis, including: control of the proliferative expansion of myogenic progenitor cells, antagonism of cell death pathways within the precursors to muscle fibers, and during the crucial process of primary myogenesis, can exert an effect on diversification of muscle fiber types.
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  • 41
    ISSN: 1423-0127
    Keywords: TNFα ; Fas ; FasL ; Apoptosis ; Cytokine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The CD3+/TCRαβ+ T-cell-mediated hepatic inflammation induced byPropionibacterium acnes could be divided into an acute and a chronic phase. The acute phase occurred within 72 h after injection and displayed hepatic apoptosis. Anti-TNFα antibody inhibited both theP. acnes-induced hepatic apoptosis and lymphocyte infiltration seen in this phase, indicating the involvement of this cytokine. Thereafter, a chronic phase was manifested from days 7 to 14 after injection. It was characterized as granulomatous inflammation admixed with apoptosis of infiltrating lymphocytes and some hepatocytes. Immunohistochemical staining showed that the infiltrating lymphocytes displayed TNFα, TNF type I receptor and a variety of cytokines including IL-1β, IL-4, IL-6, IL-10, IFNγ or IL-12. Interestingly, in naive mice, the arteries in the liver constitutively expressed IFNγ. Its expression appeared to be substantially increased at 48 h, decreased at 72 h, and increased again on day 14 afterP. acnes injection. Furthermore, Fas or FasL was only detected on the lymphocytes within the granuloma. We conclude thatP. acnes can induce a TNFα-mediated acute hepatic apoptosis which subsequently progress to a T-cell-mediated granulomatous hepatitis with increased expression of multiple cytokines and Fas/FasL.
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  • 42
    Electronic Resource
    Electronic Resource
    Springer
    Journal of biomedical science 6 (1999), S. 433-438 
    ISSN: 1423-0127
    Keywords: AIDS dementia complex ; Antioxidants ; Apoptosis ; Cerebral atrophy ; gp120 ; HIV-1 protease ; Human neuroblastoma cell ; Neuroprotection ; Protease inhibitor (KNI-272)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A significant number of adult male patients with acquired immunodeficiency syndrome develop cerebral atrophy and progressive brain disorders such as dementia complex and neuropsychiatric problems. Upon entering the brain via activated macrophages or microglias, the human immunodeficiency type 1 virus (HIV-1) may produce cytotoxic factors such as HIV-1 envelope protein (gp 120) and protease. Owing to significant proteolysis of nonviral proteins, the protease derived from HIV-1 may be detrimental to brain cells and neurons. Our results revealed that HIV-1 protease, at nanomolar concentrations, was as potent as gp 120 in causing neurotoxicity in human neuroblastoma neurotypic SH-SY5Y cells. As shown by the Oncor ApopTag staining procedure, HIV-1 protease significantly increased the number of apoptotic cells over the serum-free controls. Moreover, HIV-1 protease-induced neurotoxicity was blocked by a selective protease inhibitor, kynostatin (KNI-272). Antioxidants such as 17β-estradiol, melatonin, andS-nitrosoglutathione also prevented protease-induced neurotoxicity. These findings indicate that oxidative proteolysis may mediate HIV-1 protease-induced apoptosis and the degeneration of neurons and other brain cells. Centrally active protease inhibitors and antioxidants may play an important role in preventing cerebral atrophy and associated dementia complex caused by HIV-1.
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  • 43
    ISSN: 1423-0127
    Keywords: Glioma ; Apoptosis ; Vandate ; Akt ; PKB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The dual signal hypothesis of apoptosis holds that a common signal can activate both apoptotic and proliferative pathways. The fate of a cell is dependent on which of these two pathways predominates. In the MAPK family of kinases, ERK and JNK have been proposed to mediate apoptosis whereas the PI3K-stimulated kinase, Akt/PKB, has been shown to inhibit apoptosis. The object of this study was to determine the role of these kinases in a glioma model of apoptosis. We have previously shown that K252a induces apoptosis and inhibits kinase activity. In this study we confirm these results and shown that the protein tyrosine phosphatase inhibitor sodium vanadate activates ERK, JNK and Akt/PKB, but does not stimulate proliferation. Vanadate did protect T98G cells from K252a-induced apoptosis, an effect that was abolished by addition of the PI3K inhibitor wortmannin. This suggests that PI3K and Akt/PKB may be responsible for mediating vanadate's protective effect on glioma cells. We conclude that the intracellular balance between protein phosphorylation pathways is a critical determinant of both cell proliferation and cell death.
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  • 44
    ISSN: 1423-0127
    Keywords: Autoimmunity ; Apoptosis ; IL-2 ; FasL ; Tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Studies of several gene knockout mice suggest an interesting association of a moderate T cell response with systemic autoimmune diseases. In addition, CD95 ligand (FasL) expression in some strains of these mice is impaired. Because FasL is critically involved in regulating peripheral tolerance, there may be a link between autoimmune diseases and a moderate T cell response that cannot activate the FasL gene. Here, we propose that there are two thresholds of T cell activation. When moderately stimulated, T cells can be activated to the low (1st) threshold, which permits the induction of CD40L, IL-2, IL-4, and other components that help the immune response. The high (2nd) activation threshold can only be achieved by a strong and concurrent stimulation through TCR and IL-2R. Once the high threshold is reached, FasL is produced to induce apoptosis of the activated T and B cells. In the absence of the FasL-mediated downregulation, the activated B cells become efficient antigen-presenting cells for self-antigens and excellent responders for T cell help. Such an exacerbating condition, induced by recurrent and moderate activation, favors the development of autoreactive T cells and autoantibody production. Evidence supporting this hypothesis and some predictions that can be tested are described.
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  • 45
    ISSN: 1432-0851
    Keywords: Key words NK cells ; IL-2 ; Fas ; FasL ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The Fas/Fas-ligand (FasL) system seems to play a key role in regulating immunoresponses. Highly purified CD56+CD3− natural killer (NK) cells were found to be resistant to the apoptosis-inducing Fas mAb CH11 in the absence or in the presence of interleukin-2 (IL-2) for up to 3 days. However, NK cells activated with IL-2 for 3 days became apoptotic following combined treatment with CH11 and actinomycin D, suggesting the presence of an intact apoptotic machinery. In contrast, NK cells cultivated in IL-2 for 6 days became sensitive to CH11-induced apoptosis without addition of actinomycin D. At this time, a pronounced up-regulation of the Fas protein on the NK cell membrane was detected. By using reverse transcription/polymerase chain reaction it was found that the anti-apoptotic gene FLIP was strongly expressed in NK cells for up to 6 days of IL-2 stimulation. After day 6, a time-dependent decrease in the expression of FLIP was observed concomitantly with increased sensitivity for Fas-mediated apoptosis. The amount of apoptotic and necrotic NK cells in the presence of IL-2 increased in a time-dependent manner, reaching 40% at day 6 of culture. The amount of apoptotic and necrotic NK cells was reduced in the presence of Fas-Fc protein. In addition, IL-2 stimulated the NK cells to release soluble FasL in a time-dependent manner, whereas membrane FasL did not seem to increase in a similar manner. These results indicate that Fas/FasL interactions are involved in the down-regulation of IL-2-activated human NK cells.
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  • 46
    ISSN: 1432-0851
    Keywords: Key words CD95L ; FasL ; Renca ; Apoptosis ; Tumor growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The CD95/CD95 ligand (CD95L) system plays an important role in the induction of lymphoid apoptosis and has been implicated in the suppression of immune responses. In this system, two murine CD95L-transfected renca clones and a control renca clone transfected only with the vector were implanted into the subcapsule of the left kidney of Balb/c and Balb/c nude mice. Both CD95L-expressing and control renca clones formed macroscopic tumors in all of the Balb/c and Balb/c nude hosts 14 days after implantation. Growth of tumors of murine CD95L-transfected renca cells was significantly better than that of control renca cells in Balb/c mice, while the growth advantage of CD95L transfectants was not observed in Balb/c nude mice. Lymphocytes underwent apoptosis mainly in the periphery of the CD95L-expressing tumors but not in control tumors grown in Balb/c mice, while lymphocytes undergoing apoptosis were not observed in CD95L-expressing tumors or in control tumors grown in Balb/c nude mice. Neutrophilic recruitment was rarely observed in CD95L-expressing or control tumors. CD95L expressed on renca cells possibly suppressed immune responses against renca tumors by inducing apoptosis of the infiltrating lymphocytes. However, CD95L-expressing renca cells did not form tumors in the renal subcapsule of allogeneic C3H/HeJ mice.
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  • 47
    ISSN: 1432-0851
    Keywords: Key words In vitro immunisation ; MUC1 ; Human ; antibodies ; Phage display ; Carcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have recently described an efficient method to study the human humoral immune response in vitro and to generate isotype-switched, antigen-specific human B cells, which has allowed us to produce high-affinity IgG antibodies against different peptides. In an attempt to study the in vitro immune response against self-antigens, such as tumour-associated antigens, this protocol was used to immunise resting human peripheral blood B cells with a peptide epitope from the human-adenocarcinoma-associated antigen, MUC1. After the two-step in vitro immunisation, the secondary immunised cultures were tested for MUC-1-specific antibodies by enzyme-linked immunosorbent assay (ELISA). Phage molecular libraries were subsequently constructed, using the variable parts of Ig genes derived from cells taken from ELISA-positive wells. The libraries were selected on the MUC1 core peptide. Antigen-specific Fab fragments, specific for the self antigen MUC1, were found in the library of secondary immunised IgG+ B cells and these antibodies were evaluated by BIAcore analysis. The specific Fab fragments exhibited an unusually rapid dissociation rate constant and the overall response frequency was lower, as compared to other antibodies generated by this protocol, which might be explained by the repetitive nature of the core peptide used for immunisation.
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  • 48
    ISSN: 1432-0851
    Keywords: Key words Tumour antigen ; MUC1 ; T cell ; immunosuppression ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The in vitro anti-proliferative properties of various supernatants from MUC1-expressing cell lines and of purified preparations of MUC1 were evaluated. We have observed that supernatants from the MUC1- and MUC3-positive cell line T47D, but not from the MUC1- and MUC4-positive cell line MCF7, were able to inhibit proliferation of cells from various haematopoietic cell lines. Although the activity of T47D supernatants could be abrogated by immunodepletion of MUC1, immunopurified MUC1 from T47D was unable to inhibit cell proliferation. Significantly, supernatants from mouse 3T3 cells transfected with a secreted form of MUC1 or from BHK-21 cells infected with a recombinant vaccinia virus coding for the secreted form of MUC1, as well as preparations of purified MUC1 from bile or urine, were likewise unable to inhibit T cell proliferation. Surprisingly, a crude mixture of bile mucins had a suppressive effect on T cell growth. Our results suggest that other molecules, such as amino sugars or other mucins, which can associate with MUC1, are likely to be responsible for the observed anti-proliferative effects of T47D cells.
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  • 49
    ISSN: 1432-0851
    Keywords: Key words Immunotherapy ; MK-1 antigen ; Chimeric antibody ; ADCC ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Mouse monoclonal antibody FU-MK-1, raised against a human gastric adenocarcinoma, recognizes a glycoprotein antigen (termed MK-1 antigen) present on most carcinomas and seems to be valuable in immunodiagnosis and immunotherapy of various cancers. In a recent study, we constructed a mouse/human chimeric antibody, designated Ch FU-MK-1, by fusing the FU-MK-1 VH and Vκ genes to the human Cγ1 and Cκ genes, respectively. In the present study, we tested combination immunotherapy of Ch FU-MK-1 with human lymphokine-activated killer (LAK) cells in vitro and in mice with severe combined immunodeficiency (SCID) bearing human MK-1-expressing tumors. In in vitro experiments, Ch FU-MK-1 effectively mediated antibody-dependent cell-mediated cytotoxicity (ADCC) against MK-1-expressing MKN-74 cells, which was completely blocked by an anti-FcR antibody. Since the apoptotic pathway as well as the necrotic pathway have been shown to be utilized in various cytotoxic effector mechanisms, we investigated the role of apoptosis in ADCC mediated by LAK cells and Ch FU-MK-1 against MKN-74 cells. The implication of the apoptosis during ADCC was demonstrated by means of both a terminal-deoxynucleotidyltransferase-mediated dUTP-biotin nick-end-labeling assay and a propidium iodide staining method. In vivo antitumor activity of combination treatment with LAK cells and Ch FU-MK-1 was estimated using SCID mice inoculated s.c. with MKN-74 cells. The i.v. administration of LAK cells and i.p. administration of Ch FU-MK-1 and interleukin-2 (IL-2) produced a marked growth inhibition of MKN-74 tumors in SCID mice. When the actual tumor weights were measured 16 days after initiation of treatment, more than 70% reduction was observed in the group receiving LAK cells plus Ch FU-MK-1 plus IL-2 as compared to the control untreated group. Together these results suggest that Ch FU-MK-1 may serve as a potentially useful immunotherapeutic reagent for human MK-1-expressing tumors.
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  • 50
    ISSN: 1432-0983
    Keywords: Key words Fission yeast ; Caspases ; Bcl-2 ; Apoptosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two pro-apoptotic proteases, caspase-1 and caspase-3, have been expressed as full-length proteins in the fission yeast Schizosaccharomyces pombe. Both proteins autoprocess to generate the corresponding active enzyme and both are lethal to the yeast cell. Lethality is due to catalytic activity since the expression of the inactive mutant forms of both caspases does not result in an obvious phenotype. Caspase-expressing yeast can be rescued by co-expression of the baculovirus protein p35, a known inhibitor of the caspase family. Co-expression of Bcl-2, another anti-apoptotic protein, does not prevent the cell death induced by either caspase. However, Bcl-2 is itself cleaved by both caspase-1 and caspase-3 at two adjacent recognition sites, YEWD31′A and DAGD34′V respectively, immediately downstream from the N-terminal BH4 domain, a region of Bcl-2 which is essential for its anti-apoptotic activity; similar cleavage of Bcl-2 by caspases has been demonstrated in mammalian cells. Hence, key elements of the apoptotic pathway can be reliably reconstituted in fission yeast, opening the way to exploit yeast in order to study the control of apoptosis. Furthermore, the activity of caspase-3, although not caspase-1, can be demonstrated in vitro using chromogenic substrates. This offers the possibility of using caspase-producing strains of yeast to screen for chemical inhibitors either in vivo or in vitro.
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  • 51
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 55 (1999), S. 349-352 
    ISSN: 1432-1041
    Keywords: Key words Ischaemic stroke ; Vinpocetine ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objectives: To determine whether vinpocetine decreases short- and long-term case fatality and proportion of dependent survivors if administered within 2 weeks of stroke onset. Methods: All published and unpublished trials were attempted to be identified using the standard search strategy of the Cochrane Collaboration Stroke Review Group, using MEDLINE searches performed with all known manufacturer code names and trade names of vinpocetine and by contacting manufacturers of vinpocetine to give information of all randomised controlled trials on vinpocetine in stroke. Researchers who participated in trials on vinpocetine in Hungary were asked for further information. Only truly randomised, unconfounded clinical trials that compared the effect of vinpocetine to either placebo or another reference treatment for acute stroke where treatment started no later than 14 days after stroke onset were eligible for inclusion. Data synthesis and analysis was performed using the Cochrane Review Manager software (RevMan version 3.0). Results: Among the identified studies on vinpocetine in stroke, only one fulfilled the selection criteria for inclusion in the review. No death occurred in the study groups and no statistically significant difference was found in dependency between the treatment and the placebo groups. No adverse effects were reported. Conclusions: Based on only one small randomised controlled unconfounded study, presently there is not enough evidence to decide whether the administration of vinpocetine does or does not decrease case fatality and dependency in acute stroke.
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  • 52
    ISSN: 1432-0738
    Keywords: Key words Doxorubicin ; Apoptosis ; Testicular toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To clarify whether apoptosis is involved in doxorubicin (DXR)-induced testicular toxicity and to identify the target germ cell type, adult Sprague-Dawley rats were treated with a single intravenous dose of DXR (8 or 12 mg/kg) and euthanized at 3, 6, 12, 24, and 48 h subsequently. Histologically, germ cell degeneration was first found 6 h after dosing in meiotically dividing spermatocytes and early round spermatids of seminiferous tubules at stage I, and subsequently observed in spermatogonia at stages I–VI showing ultrastructural characteristics of apoptosis. Coincident with the appearance of morphological changes, degenerating germ cells were shown to be undergoing apoptosis as revealed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cells increased in a stage- and cell type-specific manner, the peak of frequency gradually progressing from stage I of seminiferous tubules to later stages with time after dosing, suggesting that the damaged germ cells, especially spermatogonia, gradually underwent the processes leading to apoptosis. DNA laddering on gel electrophoresis was apparent 24 and 48 h after dosing. The results demonstrate that apoptosis plays an important role in the induction of testicular toxicity caused by DXR with meiotically dividing spermatocytes and type A and intermediate spermatogonia as highly vulnerable target cells.
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  • 53
    ISSN: 1432-0738
    Keywords: Key words Allylnitrile ; Apoptosis ; Behavioral abnormalities ; Habenula ; Mice brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A single dose of allylnitrile in mice might induce persistent behavioral abnormalities, of which the mechanism is not yet known. The present study was undertaken to explore the relationship between behavioral abnormalities and pathological changes in the brain of mice following exposure to allylnitrile. Exposure to allylnitrile (63, 84, and 112 mg/kg, p.o.) resulted in dose-dependent changes in behavioral abnormalities, including increased locomotor activity, circling, retropulsion, head twitching, and alteration in reflexive behavior, which appeared at day 2 postdosing and were persistent throughout the experimental period (60 days) at the higher dose levels. Allylnitrile produced neuronal retraction including hyperchromasia of the nuclei in the raphe nuclei, cerebral cortex, hypothalamus, hippocampal CA1 and dentate gyrus later than 30 days. No gliosis was observed in these regions. Not all but a significant number of neurons in the hippocampal CA1, medial habenula and raphe nuclei were immunoreactive to CPP32 (Caspase-3) even at day 2. These neurons were also positive to Hoechst 33258 staining, indicating allylnitrile caused apoptotic changes in specific neurons when neuronal behaviors became apparent. These apoptotic changes were persistent even in the area without neuronal contraction such as medial habenula. However, almost all neurons in these areas were also positive to terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL). It is conceivable that allylnitrile caused apoptotic changes in neurons but did not always lead them to cell death immediately. Moreover, even when neuronal contraction resulted in retention of behavioral abnormalities, onset of these abnormalities seems to be associated with the impairment in the habenulo-raphe relay due to activation of apoptotic cascade in neurons.
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  • 54
    ISSN: 1432-069X
    Keywords: Key words Keratinocyte ; UVB ; Apoptosis ; Calcium ; p53
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Normal human keratinocytes are stimulated to proliferate in serum-free medium containing subphysiological concentrations of calcium (0.09 mM, low calcium). In this study, we examined the effect of increased levels of extracellular calcium (2.0 mM, normal calcium) on UVB-induced apoptosis. Apoptosis was assessed by changes in cellular morphology, annexind V-FITC flow cytometry, and the formation of internucleosomal DNA ladders. High doses of UVB induced keratinocytes grown in low calcium medium to undergo apoptosis. In contrast, keratinocytes grown for 72 h in normal calcium medium were completely resistant to UVB-induced apoptosis. No apoptosis was observed even at UVB doses as high as 1200 J/m2. However, despite the lack of UVB-induced cell death, keratinocytes grown in normal calcium medium lost the ability to proliferate following high levels of UVB irradiation. High doses of UVB also increased the expression of the differentiation-specific proteins involucrin and cytokeratin 10 in a dose-dependent manner. In addition, growth in normal calcium medium lowered the UVB-induced stimulation of the p53 protein and altered the normal subcellular localization pattern of p53. UVB irradiation of human keratinocytes grown in normal calcium medium may be inducing further cell differentiation in the absence of overt cell death.
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  • 55
    ISSN: 1432-1106
    Keywords: Key words Spasticity ; Gait ; Spinal cord ; Human ; Clonidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We studied the effect of the intrathecal (i.t.) injection of clonidine (30, 60 and 90 µg) on the polysynaptic spinal reflexes (PSR) elicited by electrical stimulation of flexor reflex afferents (FRA), monosynaptic reflex and gait of 11 subjects with spinal cord injuries. The effect of clonidine administration on gait velocity, stride amplitude and duration was measured in eight subjects who were able to walk. Five subjects were able to walk after intrathecal injection of clonidine and three were not able to stand up. Three subjects improved their gait velocity after clonidine administration; one (S6) increased his stride amplitude; the two others decreased their cycle durations. The tibialis anterior seemed to be more regularly activated during gait. Spasticity was reduced dramatically (P〈0.0001) after i.t. clonidine injection, but there was no statistically significant difference in the soleus H reflex (no effect on Hmax/Mmax). Clonidine administration decreased the amplitude of the early PSR (90–120 ms, N=4) and the threshold and maximal integrated EMG corresponding to the late response (140–450 ms, N=7). This effect was dose dependent (30, 60 and 90 µg). Placebo injection (N=4) caused no change. The changes in spinal reflexes, with a large reduction in spasticity, no change in motoneurone excitability and a large decrease in PSR, suggest that clonidine acts at a premotoneuronal level, possibly by presynaptic inhibition of group II fibres. The increase in gait velocity in three subjects could have been due to reduced spasticity or activation of spinal circuitry.
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  • 56
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    Experimental brain research 124 (1999), S. 241-247 
    ISSN: 1432-1106
    Keywords: Key words Melatonin ; Kainate ; Glutathione ; Apoptosis ; Excitotoxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The anti-excitotoxic efficacy of the pineal hormone melatonin was investigated in kainate-injured brains of rats. Kainate (a glutamate-receptor agonist, 2.5 nmol in 1 µl) was directly injected to unilateral striatum. Melatonin (10 mg/kg) was administrated intraperitoneally 1 h before and 1, 3, and 5 h after intrastriatal kainate injection in adult Sprague-Dawley rats. Three days after kainate injection, a significant neuronal damage was found, as determined by Nissl staining and the TUNEL method, not only in the injected striatum, but also in the ipsilateral neighboring cortex. The kainate-induced cortical apoptotic neuronal death was significantly attenuated by treatment with melatonin compared with the vehicle control group. However, no detectable changes were observed in the contralateral side of the brain in either vehicle- or melatonin-treated rats. Moreover, the biochemical results indicated that kainate can indeed induce oxidative stress, such as a decrease in the content of total glutathione (GSH), oxidized glutathione (GSSG), and an increase in the ratio of GSSG/GSH in the striatum and cortex compared with the contralateral brain regions. In the kainate-injected striatum, melatonin did not reduce the oxidative stress, but in the neighborhood of injected area-cortex, kainate-induced oxidative stress was significantly reduced by melatonin. Enhancement of glutathione-peroxidase activity was induced by intrastriatal kainate injection, not only in the cortical area of control and melatonin-treated rats, but also in striatum of control rats. However, a large elevation was found in the melatonin-treated cortex. Taking the morphological and biochemical data together, the present results suggest that melatonin functions as an antioxidant by upregulating the glutathione antioxidative defense system, thereby reducing neuronal death caused by excitotoxicity and preventing the kainate-induced damage from spreading to adjacent brain regions.
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  • 57
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    Experimental brain research 126 (1999), S. 289-306 
    ISSN: 1432-1106
    Keywords: Key words Motor control ; Trajectory formation ; Coordination ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The degrees of freedom problem is often posed by asking which of the many possible degrees of freedom does the nervous system control? By implication, other degrees of freedom are not controlled. We give an operational meaning to ”controlled” and ”uncontrolled” and describe a method of analysis through which hypotheses about controlled and uncontrolled degrees of freedom can be tested. In this conception, control refers to stabilization, so that lack of control implies reduced stability. The method was used to analyze an experiment on the sit-to-stand transition. By testing different hypotheses about the controlled variables, we systematically approximated the structure of control in joint space. We found that, for the task of sit-to-stand, the position of the center of mass in the sagittal plane was controlled. The horizontal head position and the position of the hand were controlled less stably, while vertical head position appears to be no more controlled than joint motions.
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  • 58
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    Keywords: Key words Optokinetic nystagmus ; Positron emission tomography ; Visual motion ; Area V5 ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Positron emission tomography (PET) was used to address the issue of physiological changes in the cerebral cortex associated to optokinetic nystagmus (OKN) in humans. We studied regional cerebral blood flow in eight volunteers during reflexive induction of OKN by a pattern of dots moving unidirectionally (toward the left side). We used two control conditions, with subjects passively viewing either stationary or incoherently moving dots. This paradigm was designed in order to differentiate the OKN-related activations from blood flow changes related to visual motion. When compared with the stationary condition, OKN activated a set of occipital areas known to be sensitive to visual motion. Bilateral activation was found in the striate cortex (V1) and the parieto-occipital fissure, while area V5, the intraparietal sulcus, and the pulvinar were activated only in the left hemisphere. When compared with incoherent motion, OKN activated the V1 and the parieto-occipital fissure bilaterally and the right lingual gyrus, while a signal decrease was observed in the V5 region in both hemispheres. No significant signal changes were found in areas implicated in saccades or in processing vestibular information. These results indicate that processing of OKN-related information is associated with neural activity in a specific set of visual motion areas and suggest that this network can be asymmetrically activated by a strictly unidirectional stimulation. Results are also discussed in terms of the specific kinds of OKN-related information processing subserved by each area in this network.
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  • 59
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    Experimental brain research 126 (1999), S. 175-186 
    ISSN: 1432-1106
    Keywords: Key words Listing’s plane ; Vergence ; Binocular ; Eye movements ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Earlier studies have reported temporal rotation of Listing’s plane with convergence of the eyes causing torsion, which is dependent on eye elevation. The amount by which the planes rotate differs from study to study. To gain insight into the functional significance of the temporal tilt of Listing’s plane for vision, we examined whether the rotation of the plane depends on the visual conditions, namely on the stimuli driving vergence. In different conditions, accommodative vergence, disparity-vergence, combinations of disparity with accommodation or depth perception were used and the resulting rotation of Listing’s plane was measured. Our findings show, for the first time, that the relationship between convergence and Listing’s-plane temporal rotation depends on the stimuli driving vergence. When the stimulus contains only disparity cues, vergence and Listing’s plane rotate immediately and consistently among subjects. Accommodative vergence, the mutual couplings between vergence and accommodation, can influence the orientation of Listing’s plane, but they do so in a idiosyncratic way. The largest rotation was elicited by stereograms combining disparity-vergence with depth perception. These findings support the idea of a functional role of Listing’s plane rotation for binocular vision, perhaps for depth perception.
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  • 60
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    Keywords: Key words Corpus callosum ; Interhemispheric transfer ; Positron emission tomography ; Split brain ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We studied with PET the intra- and interhemispheric pathways subserving a simple, speeded-up visuomotor task. Six normal subjects and one patient with a complete section of the corpus callosum (M.E.) underwent regional cerebral blood flow (rCBF) measurements under conditions of lateralized tachistoscopic visual presentations in a simple manual reaction time paradigm. Confirming previous behavioural findings, we found that on average crossed hand and/or hemifield conditions, i.e. those requiring an interhemispheric transfer of information, yielded a longer RT than uncrossed conditions. This difference (0.7 ms) was dramatically larger (45.6 ms) in the callosum-sectioned patient M.E. In normal subjects the cortical areas selectively activated in uncrossed and crossed conditions were different. In the former condition, most activation foci were anterior to the ventral anterior commissure (VAC) plane, whereas in the latter there was a prevalent parietal and occipital activation. This shows that a simple model in which the cortical visuo-motor pathways are similar in the intra- and the interhemispheric condition, with an extra callosal route for the latter, is too simplistic. Furthermore, these results suggest that the bulk of visuomotor interhemispheric transfer takes place through the widespread callosal fibres interconnecting the parietal cortices of the two hemispheres. The pattern of activation in the two crossing conditions was markedly different in M.E., in whom interhemispheric transfer might take place via his intact anterior commissure or subcortical commissures.
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  • 61
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    Experimental brain research 127 (1999), S. 355-370 
    ISSN: 1432-1106
    Keywords: Key words Visual cortex ; Motion ; Functional imaging ; Human ; Flicker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Functional magnetic resonance imaging was used to map motion responsive regions of the human brain by contrasting passive viewing of moving and stationary randomly textured patterns. Regions were retained as motion responsive if they reached significance either in the group analysis or in the majority of hemispheres in single-subject analysis. They include well-known regions, such as V1, hMT/V5+, and hV3A, but also several occipito-temporal, occipito-parietal, parietal, and frontal regions. The time course of the activation was similar in most of these regions. Motion responses were nearly identical for binocular and monocular presentations. Flicker-induced-activation introduced a dichotomy amongst these motion responsive regions. Early occipital and occipito-temporal regions responded well to flicker, while flicker responses gradually vanished as one moved to occipito-parietal and then parietal regions. Finally, over a more than four-fold range, stimulus diameter had little effect on the motion activations, except in V1.
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  • 62
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    Experimental brain research 129 (1999), S. 241-246 
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    Keywords: Key words Selective attention ; Visual attention ; Putamen ; Orienting ; Positron emission tomography ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We used positron emission tomography (PET) in ten subjects to study the brain regions involved in voluntary shifts of attention. For six scans, subjects performed a visual target detection task in which the location of the target was indicated in advance on some proportion of trials by the appearance of an arrow cue at fixation. The informative cues were successful in speeding reaction time to the target. Blood flow in the left putamen was correlated with the proportion of informative cues provided within a scan. We discuss this finding in terms of three possible interpretations: attentional shifts, response inhibition, and motor preparation related to the use of the right hand to respond. Blood flow in cortical regions commonly associated with attention was not related to cue ratio, a finding that may reflect automatization of the processes involved in interpreting and using the cues.
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  • 63
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    Experimental brain research 125 (1999), S. 109-114 
    ISSN: 1432-1106
    Keywords: Key words Motor control ; Visual pathways ; Illusions ; Prehension ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Visual size illusions have been shown to affect perceived object size but not the aperture of the hand when reaching to those same objects. Thus, vision for perception is said to be dissociated from vision for action. The present study examines the effect of visual-position and visual-shape illusions on both the visually perceived center of an object and the position of a grasp on that object when a balanced lift is required. The results for both experiments show that although the illusions influence both the perceived and the grasped estimates of the center position, the grasp position is more veridical. This partial dissociation is discussed in terms of its implications for streams of visual processing.
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  • 64
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    Experimental brain research 125 (1999), S. 43-49 
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    Keywords: Key words Proprioception ; Visual localization ; Visual context ; Multisensory integration ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In a previous study we investigated how the CNS combines simultaneous visual and proprioceptive information about the position of the finger. We found that localization of the index finger of a seen hand was more precise (a smaller variance) than could reasonably be expected from the precision of localization on the basis of vision only and proprioception only. This suggests that, in localizing the tip of the index finger of a seen hand, the CNS may make use of more information than proprioceptive information and visual information about the fingertip. In the present study we investigate whether this additional information stems from additional sources of sensory information. In experiment 1 we tested whether seeing an entire arm instead of only the fingertip gives rise to a more precise proprioceptive and/or visual localization of that fingertip. In experiment 2 we checked whether the presence of a structured visual environment leads to a more precise proprioceptive localization of the index finger of an unseen hand. In experiment 3 we investigated whether looking in the direction of the index finger of an unseen hand improves proprioceptive localization of that finger. We found no significant effect in any of the experiments. The results refute the hypothesis that the investigated effects can explain the previously reported very precise localization of a seen hand. This suggests that localization of a seen finger is based exclusively on proprioception and on vision of the finger. The results suggest that these sensory signals may contain more information than is described by the magnitude of their variances.
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  • 65
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    Experimental brain research 125 (1999), S. 302-312 
    ISSN: 1432-1106
    Keywords: Key words Overarm throwing ; Finger opening ; Proprioceptive feedback ; Perturbations ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Accuracy in an overarm throw requires great precision in the timing of finger opening. We tested the hypothesis that finger opening in an overarm throw is triggered by proprioceptive feedback from elbow extension or wrist flexion. The hypothesis was tested in two ways: first, by unexpectedly perturbing elbow extension or slowing wrist flexion and determining whether changes occurred in finger opening, and second, by measuring the latency from the start of these joint rotations to the start of finger opening. Subjects threw balls fast and accurately from a sitting or standing position while joint rotations were recorded with the search-coil technique. Elbow extension was unexpectedly blocked near the start of forward motion of the hand by a rope attached to the wrist that passed through a catch mechanism located behind the subject. In spite of a slowing or complete block of elbow extension, and in some cases a replacement of elbow extension by elbow flexion, finger opening always occurred and at the same latency as for normal throws. Wrist flexion was slowed in seven of eight subjects when subjects changed from throwing with a light ball (14 g, 70 mm diam.) to a heavy ball (210 g, 65 mm diam.). For the first throw with the heavy ball, this slowing was neither fully anticipated by the subject nor compensated for by the changed proprioceptive feedback associated with the slowing. Consequently, the timing of finger opening was unchanged and (to the surprise of the thrower) the ball went high. Furthermore, in unperturbed throws with tennis balls, the latency from onset of wrist flexion or elbow extension to onset of finger opening was too short for either to have triggered finger opening (across subjects means were 4 ms for wrist flexion and 21 ms for elbow extension). In additional analysis, no relation was found between the time of onset of earlier occurring rotations at the shoulder and the time of onset of finger opening. We concluded that, although a role for all proprioceptive feedback in triggering finger opening cannot be disproved by these experiments, it can be ruled out for feedback arising from elbow extension and wrist flexion, and it seems unlikely for feedback arising from events occurring very early in the throw. The more likely possibility is that finger opening in an overarm throw is triggered by a central command based on an internal model of hand trajectory.
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  • 66
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    Keywords: Key words Corticospinal tract ; Handedness ; Spinal premotoneurones ; Voluntary movement ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The possibility was investigated that human handedness is associated with an asymmetrical cortical and/or peripheral control of the cervical premotoneurones (PreMNs) that have been shown to mediate part of the descending command to motoneurones of forearm muscles . Heteronymous facilitation evoked in the ongoing voluntary extensor carpi radialis (ECR) electromyographic activity (EMG) by weak (0.8 times motor threshold) stimulation of the musculo-cutaneous (MC) nerve was assessed during tonic co-contraction of biceps and ECR. Suppression evoked by stimulation of a cutaneous nerve (superficial radial, SR) at 4 times perception threshold in both the voluntary EMG and in the motor evoked potential (MEP) elicited in ECR by transcranial magnetic stimulation (TMS) was investigated during isolated ECR contraction. Measurements were performed within time windows or at interstimulus intervals where peripheral and cortical inputs may interact at the level of PreMNs. Results obtained on both sides were compared in consistent right- and left-handers. MC-induced facilitation of the voluntary ECR EMG was significantly larger on the preferred side, whereas there was no asymmetry in the SR-evoked depression of the ongoing ECR EMG. In addition, the suppression of the ECR MEP by the same SR stimulation was more pronounced on the dominant side during unilateral, but not during bilateral, ECR contraction. It is argued that (1) asymmetry in MC-induced facilitation of the voluntary EMG reflects a greater efficiency of the peripheral heteronymous volley in facilitating PreMNs on the dominant side; (2) asymmetry in SR-induced suppression of the MEP during unilateral ECR contraction, which is not paralleled by a similar asymmetry of voluntary EMG suppression, reflects a higher excitability of cortical neurones controlling inhibitory spinal pathways to cervical PreMNs on the preferred side.
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  • 67
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    Keywords: Key words Hyperventilation ; Magnetoencephalography ; Somatosensory cortex ; Auditory cortex ; Somatosensory evoked response ; Auditory evoked response ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It is well established that voluntary hyperventilation (HV) slows down electroencephalographic (EEG) rhythms. Little information is available, however, on the effects of HV on cortical responses elicited by sensory stimulation. In the present study, we recorded auditory evoked potentials (AEPs) and magnetic fields (AEFs), and somatosensory evoked magnetic fields (SEFs) from healthy subjects before, during, and after a 3- to 5-min period of voluntary HV. The effectiveness of HV was verified by measuring the end-tidal CO2 levels. Long-latency (100–200 ms) AEPs and long-latency AEFs originating at the supratemporal auditory cortex, as well as long-latency SEFs from the primary somatosensory cortex (SI) and from the opercular somatosensory cortex (OC), were all reduced during HV. The short-latency SEFs from SI were clearly less modified, there being, however, a slight reduction of the earliest cortical excitatory response, the N20m deflection. A middle-latency SEF deflection from SI at about 60 ms (P60 m) was slightly increased. For AEFs and SEFs, the center-of-gravity locations of the activated neuronal populations were not changed during HV. All amplitude changes returned to baseline levels within 10 min after the end of HV. The AEPs were not altered when the subjects breathed 5% CO2 in air in a hyperventilation-like manner, which prevented the development of hypocapnia. We conclude that moderate HV suppresses long-latency evoked responses from the primary projection cortices, while the early responses are less reduced. The reduction of long-latency responses is probably mediated by hypocapnia rather than by other nonspecific effects of HV. It is suggested that increased neuronal excitability caused by HV-induced hypocapnia leads to spontaneous and/or asynchronous firing of cortical neurones, which in turn reduces stimulus-locked synaptic events.
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  • 68
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    Experimental brain research 125 (1999), S. 389-396 
    ISSN: 1432-1106
    Keywords: Key words Neck muscles ; Vibration ; Proprioception ; Sound localization ; Space perception ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of transcutaneous vibration of the posterior neck muscles on the lateralization of dichotic sound was investigated in human subjects. Two-alternative forced-choice (left/right) judgements were made on acoustic stimuli presented with different interaural level differences via headphones during neck-muscle vibration. A shift of the subjective auditory median plane toward the side contralateral of vibration was found, indicating that the sound was perceived as shifted toward the side of vibration. The mean magnitude of the vibration-induced intracranial shift was 1.5 dB. The results demonstrate a neck-proprioceptive influence on sound lateralization and suggest that this proprioceptive input is used for a central-nervous transformation of auditory spatial coordinates onto a body-centered frame of reference.
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  • 69
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    Experimental brain research 125 (1999), S. 435-439 
    ISSN: 1432-1106
    Keywords: Key words Transcranial magnetic stimulation ; Plasticity ; Synchronization ; Motor system ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We used focal transcranial magnetic stimulation to examine the effects of 120 synchronized thumb and foot movements on the motor output map of the right abductor pollicis brevis muscle (APB) (experiment 1). To evaluate the performance, the latencies between the onset of the electromyographic activity (EMG) of the two muscles were measured. As control, 120 asynchronous thumb and foot movements were performed (experiment 2). Exclusively in experiment 1, the center of gravity (CoG) of the output map moved medially in the direction of the foot representation area (mean 7 mm, P〈0.05) and returned into its original location within 1 h. In experiment 2, the CoG remained unchanged (mean displacement, 0.68 mm into a lateral direction; not significant). The effect in experiment 1 was independent of an improvement in performance. We conclude that a short-lasting training of synchronous movements induces modulations of motor output maps which probably occur due to interactions between hand and foot representation areas in the motor cortex.
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  • 70
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    Keywords: Key words Reach to grasp ; Human ; Perturbation ; Kinematics ; Motor control ; Parkinson’s disease ; Elderly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study assessed the adaptive response of the reach-to-grasp movement of 12 Parkinson’s disease (PD) and 12 control subjects to a simultaneous perturbation of target object location and size. The main aim was to test further the reported dysfunction of PD subjects in the simultaneous activation of movement components. Participants were required to reach 30 cm to grasp a central illuminated cylinder of either small (0.7 cm) or large (8 cm) diameter. For a small percentage of trials (20/100) a visual perturbation was introduced unexpectedly at the onset of the reaching action. This consisted of a shift of illumination from the central cylinder to a cylinder of differing diameter, which was positioned 20° to the left (n=10) or to the right (n=10). The subject was required to grasp the newly illuminated cylinder. For the Parkinson’s disease subject group, the earliest response to this ’double’ perturbation was in the parameter of peak reaching acceleration, which was on average 50 ms earlier for ’double’ perturbed than for non-perturbed trials. The grasp component response followed more than 500 ms after the earliest transport response. For the control subjects initial signs of a response to the ’double’ perturbation were seen almost simultaneously in the transport parameter of peak arm deceleration, and in the manipulation parameter of maximum grip aperture, but these changes were not evident until more than 400 ms after movement onset. These results indicate that the basal ganglia can be identified as part of a circuit which is involved in the integration of parallel neutral pathways, and which exercise flexibility in the degree to which these components are ’coupled’ functionally. With basal ganglia dysfunction the activation of integration centres that at first gate the flow of information to the parallel channels of reach and grasp seems inefficient.
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    Experimental brain research 128 (1999), S. 353-368 
    ISSN: 1432-1106
    Keywords: Key words Multijoint arm ; Simulations ; Muscle torques ; Kinetics ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Adults are able to reach for an object for the first time with appropriate direction, speed, and accuracy. The rules by which the nervous system is able to set muscle activities to accomplish these outcomes are still debated and, indeed, the sensitivity of kinematics to variations in muscle torques is unknown for complex arm movements. As a result, this study used computer simulations to characterize the effects of change in muscle torque on initial hand path. The same change was applied to movements towards 12 directions in the horizontal plane, and changes were systematically manipulated such that: (1) torque amplitude was changed at one joint, (2) timing of torque was changed at one joint, and (3) amplitude and/or timing was changed at two joints. Results showed that simultaneous changes in torque amplitude at shoulder and elbow joints affected initial speed uniformly across direction. These results add to conclusions from previous experimental and modeling work that the simplest rule to produce a desired change in speed for any direction is to scale torque amplitude at both joints. In contrast, all simulations showed nonuniform effects on initial path direction. For some regions of the workspace, initial path direction was little affected by either a ±30% change in amplitude or a ±100-ms change in timing, whereas for other regions the same changes produced large effects on initial path direction. These findings suggest that the range of possible torque solutions to achieve a particular initial path direction varies within the workspace and, consequently, the requirements for an accurate initial path will vary within the workspace.
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    Experimental brain research 124 (1999), S. 287-294 
    ISSN: 1432-1106
    Keywords: Key words Magnetoencephalography ; V1 cortex ; V2 cortex ; V6 complex ; Horizontal meridian ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We recorded whole-scalp magnetoencephalographic (MEG) responses to black-and-white checkerboards to study whether the human cortical responses are quantitatively similar to stimulation of the lower and upper visual field at small, 0–6°, eccentricities. All stimuli evoked strongoccipital responses peaking at 50–100 ms (mean 75 ms). The activation was modeled with a single equivalent current dipole in the contralateral occipital cortex, close to the calcarine fissure, agreeing with an activation of the V1/V2 cortex. The dipole was, on average, twice as strong to lower than to upper field stimuli. Responses to hemifield stimuli that extended to both lower and upper fields resembled the responses to lower field stimuli in source current direction and strength. These results agree with psychophysical data, which indicate lower visual field advantage in complex visual processing. Parieto-occipital responses in the putative V6 complex were similar to lower and upper field stimuli.
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  • 73
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    Keywords: Key words Vibration-induced kinesthetic illusions ; Antagonist vibratory response ; Motor units ; Wrist extensor muscles ; Human ; Microelectromyography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In humans, vibration applied to muscle tendons evokes illusory sensations of movement that are usually associated with an excitatory tonic response in muscles antagonistic to those vibrated (antagonist vibratory response or AVR). The aim of the present study was to investigate the neurophysiological mechanisms underlying such a motor response. For that purpose, we analyzed the relationships between the parameters of the tendon vibration (anatomical site and frequency) and those of the illusory movement perceived (direction and velocity), as well as the temporal, spatial, and quantitative characteristics of the corresponding AVRs (i.e., surface EMG, motor unit firing rates and activation latencies). Analogies were supposed between the characteristics of AVRs and voluntary contractions. The parameters of the AVR were thus compared with those of a voluntary contraction with similar temporal and mechanical characteristics, involving the same muscle groups as those activated by vibration. Wrist flexor muscles were vibrated either separately or simultaneously with wrist extensor muscles at frequencies between 30 and 80 Hz. The illusory movement sensations were quantified through contralateral hand-tracking movements. Electromyographic activity from the extensor carpi radialis muscles was recorded with surface and intramuscular microelectrodes. The results showed that vibration of the wrist flexor muscle group induced both a kinesthetic illusion of wrist extension and a motor response in the extensor carpi radialis muscles. Combined vibration of the two antagonistic muscle groups at the same frequency evoked neither kinesthetic illusion nor motor activity. In addition, vibrating the same two antagonistic muscle groups at different frequencies induced both a kinesthetic illusion and a motor response in the muscle vibrated at the lowest frequency. The surface EMG amplitude of the extensor carpi radialis as well as the motor unit activation latency and discharge frequency were clearly correlated to the parameters of the illusory movement evoked by the vibration. Indeed, the faster the illusory sensation of movement, the greater the surface EMG in these muscles during the AVRs and the sooner and the more intense the activation of the motor units of the wrist extensor muscles. Moreover, comparison of the AVR with voluntary contraction showed that all parameters were highly similar. Mainly slow motor units were recruited during the AVR and during its voluntary reproduction. That the AVR is observed only when a kinesthetic illusion is evoked, together with the similarities between voluntary contractions and AVRs, suggests that this vibration-induced motor response may result from a perceptual-to-motor transformation of proprioceptive information, rather than from spinal reflex mechanisms.
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    Experimental brain research 124 (1999), S. 351-362 
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    Keywords: Key words Saccadic adaptation ; Gaze ; Short term adaptation ; Transfer to hand movements ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We investigated whether and how adaptive changes in saccadic amplitudes (short-term saccadic adaptation) modify hand movements when subjects are involved in a pointing task to visual targets without vision of the hand. An experiment consisted of the pre-adaptation test of hand pointing (placing the finger tip on a LED position), a period of adaptation, and a post-adaptation test of hand pointing. In a basic task (transfer paradigm A), the pre- and post-adaptation trials were performed without accompanying eye and head movements: in the double-step gaze adaptation task, subjects had to fixate a single, suddenly displaced visual target by moving eyes and head in a natural way. Two experimental sessions were run with the visual target jumping during the saccades, either backwards (from 30 to 20°, gaze saccade shortening) or onwards (30 to 40°, gaze saccade lengthening). Following gaze-shortening adaptation (level of adaptation 79±10%, mean and s.d.), we found a statistically significant shift (t-test, error level P〈0.05) in the final hand-movement points, possibly due to adaptation transfer, representing 15.2% of the respective gaze adaptation. After gaze-lengthening adaptation (level of adaptation 92±17%), a non-significant shift occurred in the opposite direction to that expected from adaptation transfer. The applied computations were also performed on some data of an earlier transfer paradigm (B, three target displacements at a time) with gain shortening. They revealed a significant transfer relative to the amount of adaptation of 18.5±17.5% (P〈0.05). In the coupling paradigm (C), we studied the influence of gaze saccade adaptation of hand-pointing movements with concomitant orienting gaze shifts. The adaptation levels achieved were 59±20% (shortening) and 61±27% (lengthening). Shifts in the final fingertip positions were congruent with internal coupling between gaze and hand, representing 53% of the respective gaze-amplitude changes in the shortening session and 6% in the lengthening session. With an adaptation transfer of less than 20% (paradigm A and B), we concluded that saccadic adaptation does not ”automatically” produce a functionally meaningful change in the skeleto-motor system controlling hand-pointing movements. In tasks with concomitant gaze saccades (coupling paradigm C), the modification of hand pointing by the adapted gaze comes out more clearly, but only in the shortening session.
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  • 75
    ISSN: 1432-1106
    Keywords: Key words Locomotion ; Load ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Prior work from mammals suggests that load experienced by extensor muscles of the hindlimbs (i.e. Duysens and Pearson 1980; Pearson and Collins 1993; Fouad and Pearson 1997) or cutaneous afferents from the plantar surface of the foot (Duysens and Pearson 1976; Guertin et al. 1995) enhances activity in extensor muscles during the stance phase, and delays the onset of flexor activity associated with the swing phase. The presumed functional significance of this phenomenon is that extensor activity of the supporting limb during walking can: (a) reinforce the supporting function in proportion to the load experienced, and (b) prolong the stance phase until unloading of the limb has occurred. Whether a similar functional role exists for load-sensitive afferents during walking in the human is unknown. In this study, the effect of adding or removing a substantial load (30% of body weight) at the centre of mass was studied in healthy adult human subjects. Loads were applied near the centre of mass to avoid the need for postural adjustments which might confound the interpretation of the results. Subjects walked on a treadmill with either: (a) a sustained increase or decrease in load, or (b) a sudden unexpected increase or decrease in load. In general, subjects responded to the changes in load by changing the amplitude of the extensor electromyographic (EMG) bursts. For example, with sudden unexpected additions in load, the average increase in amplitude was 40% for the soleus across the stance phase, and 134% for the quadriceps during the early part of the stance phase. Extensor EMGs increased with both sustained and sudden increases in load. Extensor EMG durations also increased (average increase in duration of 4% for soleus with sudden loading, and 7% for sustained loading). Cycle duration hardly changed (average increase of 0.5% with both sudden and sustained loading). These results differ from those of infants subjected to a similar perturbation during supported walking. A large change in timing (i.e. an increase in the duration of the stance phase by 30% and the step cycle by 28%) was seen in the infants, with no change in the amplitude of the EMG burst (Yang et al. 1998). These results suggest that the central nervous system can control the timing and amplitude of extensor EMG activity in response to loading independently. Maturation of the two components most likely occurs independently. In the adult, independent control of the two components may provide greater flexibility of the response.
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  • 76
    ISSN: 1432-1106
    Keywords: Key words Motor development ; Reaching ; Anticipatory postural control ; EMG ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The present study focused on the developmental changes of postural adjustments accompanying reaching movements in healthy infants. We made a longitudinal study of ten infants between 6 and 18 months of age. During each session multiple surface electromyograms of arm, neck, trunk and leg muscles at the right side of the body were recorded during right-handed reaching movements in two positions (”upright sitting” in an infant chair and ”long-leg” sitting without support). Simultaneously the whole session was recorded on video. Comparable data were present from the same infants at 3–5 months. Additionally, 18 infants (8–15 months) were assessed once during similar reaching tasks, but in these infants electromyographic activity of the trunk and neck muscles at both sides of the body were recorded. Our data revealed two transitions in the development of postural adjustments. The first transition was present around 6 months of age. At this age the postural muscles were infrequently activated during reaching movements. At 8 months ample postural activity reappeared and the infants developed the ability to adapt the postural adjustments to task-specific constraints such as arm movement velocity or the sitting position at the onset of the reaching movement. The second transition occurred between 12 and 15 months. Before 15 months the infants did not show consistent anticipatory postural activity, but from 15 months onwards they did, particularly in the neck muscles.
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  • 77
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    Experimental brain research 126 (1999), S. 536-544 
    ISSN: 1432-1106
    Keywords: Key words Magnetic brain stimulation ; Afferent input ; Motor cortex ; Plasticity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previously, we had described a technique for investigating probable GABAergic cortical inhibitory circuits in conscious man using transcranial magnetic stimulation. This type of inhibition has been termed intracortical inhibition. During voluntary contraction, activity in the circuits responsible for this inhibition is reduced. The mechanism by which this reduction in activity is brought about is unknown. However, evidence exists to suggest that afferent input may be, at least in part, responsible for the reduction in inhibition. The experiments described here were designed to investigate this possibility further. The results of these experiments showed that afferent input, produced by electrical peri- pheral-nerve stimulation, reduced the level of intracortical inhibition. Also, motor imagery, which activates similar brain regions as overt movement, but does not result in afferent input, failed to produce significant changes in intracortical inhibition. We conclude from these results that afferent input is capable of altering activity in cortical inhibitory circuits. The relevance of these findings to the mechanisms involved in cortical reorganisation is discussed.
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  • 78
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    Experimental brain research 126 (1999), S. 556-562 
    ISSN: 1432-1106
    Keywords: Key words Acceleration ; Ocular microtremor ; Eye movements ; Partial coherence ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A novel technique for the study of human eye movements was used to investigate the frequency components of ocular drift and microtremor in both eyes simultaneously. The tangential components of horizontal eye accelerations were recorded in seven healthy subjects using light-weight accelerometers mounted on scleral contact lenses during smooth pursuit movements, vestibulo-ocular reflexes and eccentric gaze with and without fixation. Spectral peaks were observed at low (up to 25 Hz) and high (60–90 Hz) frequencies. A multivariate analysis based on partial coherence analysis was used to correct for head movement. After correction, the signals were found to be coherent between the eyes over both low- and high-frequency ranges, irrespective of task, convergence or fixation. It is concluded that the frequency content of ocular drift and microtremor reflects the patterning of low-level drives to the extra-ocular muscle motor units.
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  • 79
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    Experimental brain research 127 (1999), S. 83-94 
    ISSN: 1432-1106
    Keywords: Key words Target interception ; Reaching ; Grasping ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The goal of the present study was to understand which characteristics (movement time or velocity) of target motion are important in the control and coordination of the transport and grasp-preshape components of prehensile movements during an interception task. Subjects were required to reach toward, grasp and lift an object as it entered a target area. Targets approached along a track at four velocities (500, 750, 1000 and 1250 mm/s) which were presented in two conditions. In the distance-controlled condition, targets moving at all velocities traveled the same distance. In the viewing-time-controlled condition, combinations of velocity and starting distances were performed such that the moving target was visible for 1000 ms for all trials. Analyses of kinematic data revealed that when, target distance was controlled, velocity affected all transport-dependent measures; however, when viewing time was controlled, these dependent measures were no longer affected by target velocity. Thus, the use of velocity information was limited in the viewing-time-controlled condition, and subjects used other information, such as target movement time, when generating the transport component of the prehensile movement. For the grasp-preshape component, both peak aperture and peak-aperture velocity increased as target velocity increased, regardless of condition, indicating that target velocity was used to control the spatial aspects of aperture formation. However, the timing of peak aperture was affected by target velocity in the distance-controlled condition, but not in the viewing-time-controlled condition. These results provide evidence for the autonomous generation of the spatial and temporal aspects of grasp preshape. Thus, an independence between the transport and grasp-preshape phases was found, whereby the use of target velocity as a source of information for generating the transport component was limited; however, target velocity was an important source of information in the grasp-preshape phase.
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  • 80
    ISSN: 1432-1106
    Keywords: Key words Frontal eye field ; Saccade ; Efference copy ; Spatial short-term memory ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Physiological studies in monkeys have shown that the frontal eye field (FEF) is involved in the preparation and triggering of purposive saccades. However, several questions of FEF function remain unclear: the role of the FEF in visual short-term memory, its ability to update its spatial map and its role in reflexive saccade inhibition. We have addressed these issues in a patient with a small acute ischemic lesion whose location corresponded very accurately to the region of the left FEF according to the most recent cerebral blood flow studies. An initial study was conducted on days 7 and 8 after the stroke, i.e., before substantial recovery. A first group of paradigms (smooth pursuit, simple saccade tasks) was performed to assess FEF dysfunction. In a second group of paradigms, (1) visual short-term memory was tested by means of memory-guided saccade paradigms with short and long delays (1 and 7 s), (2) spatial updating abilities were tested by a double-step saccade task and two memory-guided saccade tasks in which the central fixation point was displaced during the memorization delay, and (3) reflexive saccade inhibition was tested by the antisaccade task. Results show that the FEF is involved in short-term memorization of the parameters of the forthcoming memory-guided saccade encoded in oculocentric coordinates. Normal results in the antisaccade task suggest that the FEF is not involved in reflexive saccade inhibition.
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  • 81
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    Experimental brain research 129 (1999), S. 378-390 
    ISSN: 1432-1106
    Keywords: Key words Manual tracking ; Microgravity ; Visuomotor transformation ; Adaptation ; Human ; Spaceflight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A series of step-tracking experiments was conducted before, during, and after a 3-week space mission to assess the effects of prolonged microgravity on a non-postural motor-control task. In- and post-flight accuracy was affected only marginally. However, kinematic analyses revealed a considerable change in the underlying movement dynamics: too-small force and, thus, too-low velocity in the first part of the movements was mainly compensated by lengthening the deceleration phase of the primary movement, so that accuracy was regained at its end. The observed in-flight decrements in peak velocity and peak acceleration point to an underestimation of mass, in agreement with the re-interpretation hypothesis of Bock et. al. Post-flight no reversals of the in-flight changes (negative aftereffects) were found. Instead, there was a general slowing down, which could be due to post-flight physical exhaustion.
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  • 82
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    Experimental brain research 125 (1999), S. 50-60 
    ISSN: 1432-1106
    Keywords: Key words Pointing errors ; Remembered target Navigation ; Active self-movements ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We studied pointing movements to remembered visual targets in a completely darkened room with and without self-made step movements in order to investigate in which coordinate system and to what extent target representations relative to the body are updated for self-induced egomotion. A small red-light-emitting diode on the fingertip provided visual feedback about fingertip position at all times. We asked subjects to make pointing movements that started 2 s after disappearance of a visual target. In this interval of 2 s the subject did or did not make a step. The pointing errors without a step showed that subjects undershot faraway targets in a systematic way, whereas they sometimes overshot nearby targets. We found that the step causes larger pointing errors both in amplitude and direction with a bias in the direction of the step. We explored three different versions of a descriptive model in which polar coordinates were used to describe the pointing movement, and in which either Cartesian or polar coordinates were used to update target position relative to the shoulder for the step. The results suggest that incorporation of the step displacement in the new target position relative to the subject is done in a Cartesian frame of reference. Moreover, the amplitude of the step displacement tends to be underestimated by subjects.
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  • 83
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    Experimental brain research 125 (1999), S. 139-152 
    ISSN: 1432-1106
    Keywords: Key words Reaching movements ; Direction ; Amplitude ; Initial kinematics ; Spatial variability ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The accuracy of reaching movements to memorized visual target locations is presumed to be determined largely by central planning processes before movement onset. If so, then the initial kinematics of a pointing movement should predict its endpoint. Our study examined this hypothesis by testing the correlation between peak acceleration, peak velocity, and movement amplitude and the correspondence between the respective spatial positions of these kinematic landmarks. Subjects made planar horizontal reaching movements to targets located at five different distances and along five radially arrayed directions without visual feedback during the movements.The spatial dispersion of the positions of peak acceleration, peak velocity, and endpoint all tended to form ellipses oriented along the movement trajectory. However, whereas the peaks of acceleration and velocity scaled strongly with movement amplitude for all of the movements made at the five target distances in any one direction, the correlations with movement amplitude were more modest for trajectories aimed at each target separately. Furthermore, the spatial variability in direction and extent of the distribution of positions of peak acceleration and peak velocity did not scale differently with target distance, whereas they did for endpoint distributions. Therefore, certain features of the final kinematics are evident in the early kinematics of the movements as predicted by the hypothesis that they reflect planning processes. However, endpoint distributions were not completely predetermined by the Initial kinematics. In contrast, multivariate analysis suggests that adjustments to movement duration help compensate for the variability of the initial kinematics to achieve desired movement amplitude. These compensatory adjustments do not contradict the general conclusion that the systematic patterns in the spatial variability observed in this study reflect planning processes. On the contrary, and consistent with that conclusion, our results provide further evidence that direction and extent of reaching movements are planned and determined in parallel over time.
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  • 84
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    Journal of cancer research and clinical oncology 125 (1999), S. 357-360 
    ISSN: 1432-1335
    Keywords: Key words Colorectal neoplasms ; Apoptosis ; Chemosensitivity ; p53 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose : The p53 gene is considered one of the most important in the control of apoptosis, and its mutations have a close relationship with chemosensitivity. The aim of this work was to investigate the role of p53 in the apoptosis of colorectal cancer cells in vitro, induced by 5-fluorouracil (5-FU) and hydroxy-camptothecin (HCPT). Methods : A total of 39 colorectal cancer samples from patients were treated in vitro with 5-FU (10 μg/ml), 5-FU (10 μg/ml) + leucovorin (5 μg/ml), HCPT (0.1 μg/ml) and HCPT (0.1 μg/ml) + Salvia mitorrhiza (6 μl), using an in situ terminal deoxynucleotidyltransferase assay to detect chemosensitivity. p53 gene mutations from tumor DNA were detected, after amplification by the polymerase chain reaction of exons 5–8, by non-radioactive single-strand conformation polymorphism. Results : p53 gene mutations were observed in 43.6% (17/39) of colorectal carcinomas, when the terminal deoxynucleotidyltransferase assay was used to detect the tumor apoptotic rate. Cells with mutated p53 had lower chemosensitivity than those without (p 〈 0.01). Conclusion : Routine assessment of p53 status may be helpful in selecting patients with the wild-type p53 gene, who have a predictably better response to chemotherapy.
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  • 85
    ISSN: 1432-1335
    Keywords: Key words EGF receptor signalling ; Tyrphostin ; Apoptosis ; Colon cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Growth effects of tyrphostins A25 and AG1478 on colorectal tumor cells were studied to explore therapeutic potential. Cell number, DNA synthesis and apoptotic index were measured as growth parameters and cell-death-associated proteins Bcl-2 and Bak and protein phosphorylation were analyzed. Both tyrphostins inhibited DNA synthesis and induced apoptosis in tumor cell cultures with different patterns of activity. A25 displayed strong selectivity for the cell lines expressing high levels of epidermal growth factor (EGF), HT29/HI1 and SW480. Inhibition of DNA synthesis was efficient in all cells except T84, and the apoptotic index increased two- to fivefold. By contrast, AG1478 was highly effective in all cell lines. In addition, it caused cell loss in VACO235 adenoma cells at concentrations lower than those necessary to inhibit BrdU incorporation, reflecting preferential retention of cells actively synthesizing DNA. Induction of apoptosis was more efficient with AG1478 than with A25 (tenfold in VACO235). Insulin-like growth factor (IGF1) did not rescue cells exposed to A25 or to high concentrations of AG1478, but was effective with suboptimal amounts of AG1478. Both compounds inhibited phosphorylation of the EGF receptor as well as additional proteins. AG1478 induced expression of Bak and down-regulated Bcl-2. In summary, tyrphostins may provide alternatives for colorectal tumor treatment. Their broader range of activities and the lower susceptibility to interactions with IGF1 can be an advantage over receptor antibodies.
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  • 86
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    Experimental brain research 128 (1999), S. 539-542 
    ISSN: 1432-1106
    Keywords: Key words Silent period ; Transcranial magnetic stimulation ; Motor cortex ; Epidural recordings ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We investigated the nature of the silent period (SP) following transcranial magnetic stimulation by recording corticospinal volleys in a patient with implanted cervical epidural electrodes. Single suprathreshold test stimuli and paired stimuli at interstimulus intervals (ISIs) of 50–200 ms were delivered while the subject maintained a constant background contraction. The silent period duration from a single test stimulus was 357±62 ms. The test motor-evoked potentials were markedly reduced at all the ISIs tested. The I (indirect) waves induced by the test stimulus were largely unchanged at an ISI of 50 ms, suggesting that there was little change in motor cortex excitability. However, the corticospinal volleys, especially the late I waves, were substantially reduced at ISIs of 100 ms, 150 ms, and 200 ms. Our findings suggest that the early part of the SP is mainly due to spinal mechanisms, while the late part of the SP is related to reduced motor cortex excitability.
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  • 87
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    Experimental brain research 128 (1999), S. 550-556 
    ISSN: 1432-1106
    Keywords: Key words Selective attention ; Kinematics ; Human ; Visual pathways
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In solving the selection-for-action problem, it is believed that attentional mechanisms enable dominance of target over non-target objects. However, under some conditions, information from non-target objects ”interferes” with the action to a relevant target. We investigated the possibility that this interference may result when the irrelevant object activates a specific subset of visuomotor pathways. Participants reached to grasp three-dimensional stimuli while actively attending to a nearby flanker object. The means by which the flanker was presented was manipulated. This relevant object was illuminated either abruptly or gradually. The parvocellular pathway in early visual processing is equally activated in both conditions. The magnocellular pathway is strongly activated by abrupt presentation and weakly activated with gradual presentation of the flanker object. Kinematics of the reach-to-grasp action to the target showed signs of interference only in the sudden illumination condition. This suggests a dissociation between dorsal and ventral cortical streams in terms of relevance for action. Our data suggests that this effect is not due to early visual-pathway differences, but instead reveals a property of a transient object-based visual attention mechanism.
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  • 88
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    Experimental brain research 128 (1999), S. 578-582 
    ISSN: 1432-1106
    Keywords: Key words Prehension ; Binocular ; Vergence ; Distance perception ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Human prehension requires accurate information on the properties of an object and on the position of the object relative to the body. In principle, prehension might be more accurate with binocular rather than monocular vision. Previous studies have shown that the kinematics of prehension are altered when one eye is covered. Unfortunately, the source of the useful binocular information cannot be established using this approach. In the current study, we used a perturbation technique to explore whether the human nervous system uses a signal from vergence in prehension. Perturbing vergence caused predictable changes in the kinematics of prehension. Our results thus provide clear evidence that the nervous system uses vergence information in the programming of prehensile movement.
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  • 89
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    Experimental brain research 124 (1999), S. 1-7 
    ISSN: 1432-1106
    Keywords: Key words Temporal cortex ; Connectivity ; Human ; Interhemispheric transfer ; Talairach coordinates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The human anterior commissure is believed, by extrapolation from data obtained in macaque monkeys, to convey axons from the temporal and orbitofrontal cortex. Reports of interhemispheric transfer and sexual dimorphism related to the anterior commissure, however, make more precise data on the human anterior commissure desirable. We investigated the connectivity of the human anterior commissure in six adults (male and female) that had circumscribed hemispheric lesions in temporal, frontal, parietal or occipital cortices or in infrapallidal white matter using the Nauta for anterogradely degenerating axons. Axons originating in the inferior part of temporal or occipital lobes, occipital convexity and possibly central fissure and prefrontal convexity were found to cross the midsagittal plane in the anterior commissure. The largest contigent of commissural axons originated in the inferior part of the temporal lobe; it displayed a roughly topographic organization, preferentially running through the inferior part of the commissure. The inferior temporal contigent seemed to reach homotopic and heterotopic targets in the opposite hemisphere. Among the latter were the amygdala and possibly the orbitofrontal cortex. The present data suggest that the human anterior commissure conveys axons from much larger territories than expected from work on non-human primates. Similarly to the human and non-human primate corpus callosum, the anterior commissure is roughly topographically organized and participates in heterotopic connectivity.
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  • 90
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    Experimental brain research 126 (1999), S. 200-204 
    ISSN: 1432-1106
    Keywords: Key words Motor development ; Anticipatory postural adjustments ; Bimanual coordination ; Children ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Anticipatory postural adjustments (APA) are needed to perform a movement without perturbing posture. We investigated the development of APA in 3- to 4-year-old children during a bimanual load-lifting task. The task required maintaining a stable elbow position despite imposed or voluntary unloading of the forearm. Although children can compensate the consequences of unloading by using APA, their performance did not reach an adults’ level. In addition, children showed high intra-individual variability in the voluntary situation, revealed by the coexistence of both adult-like and immature patterns in kinematic and electromyographic data. In conclusion, the present study reports that APA, associated with a bimanual load-lifting task, are still being set up in 3- to 4-year-old-children. The intra-individual variability should decrease with age and be associated with a progressive mastering of the timing parameters characterizing APA.
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  • 91
    ISSN: 1432-1106
    Keywords: Key words Transcranial magnetic stimulation ; Silent period ; Voluntary motor drive ; Motor threshold ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To evaluate changes in the motor system during the silent period (SP) induced by transcranial magnetic stimulation (TMS) of the motor cortex, we investigated motor thresholds as parameters of the excitability of the cortico-muscular pathway after a suprathreshold conditioning stimulus in the abductor digiti minimi muscle (ADM) of normal humans. Since the unconditioned motor threshold was lower during voluntary tonic contraction than at rest (31.9±5.4% vs. 45.6±7.5%), it is suggested that the difference between active and resting motor threshold indicates the magnitude of the voluntary drive on the cortico-muscular pathway. Therefore, we compared conditioned resting and active motor threshold (cRMT and cAMT) during the SP. cRMT showed an intensity-dependent period of elevation of more than 200 ms in duration and approximately 17% of the maximum stimulator output above the unconditioned threshold, due to decreased excitability of the cortico-muscular pathway after the conditioning stimulus. Some 30–40 ms after the conditioning stimulus, cAMT approximated cRMT, indicating complete suppression of the voluntary motor drive. This suppression did not start directly after the conditioning stimulus since cAMT was still significantly lower than the cRMT within the first 30–40 ms. Threshold elevation was significantly longer than the SP (220±41 vs. 151±28 ms). Recovery of the voluntary motor drive started late in the SP and was nearly complete at the end of the SP, although thresholds were still significantly elevated. We conclude that the SP is largely due to a suppression of voluntary motor drive, while the threshold elevation is a different inhibitory phenomenon that is of less importance for the generation of the SP, at least in its late part. It is argued that the pathway of fast cortico-spinal fibers activated by TMS is partially different from the pathway involved in the maintenance of tonic voluntary muscle activation.
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  • 92
    ISSN: 1432-1106
    Keywords: Key words Motor control ; Multijoint movement ; Movement synergy ; Stroke ; Laterality ; Redundancy ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previous studies have shown that in neurologically normal subjects the addition of trunk motion during a reaching task does not affect the trajectory of the arm endpoint. Typically, the trunk begins to move before the onset and continues to move after the offset of the arm endpoint displacement. This observation shows that the potential contribution of the trunk to the motion of the arm endpoint toward a target is neutralized by appropriate compensatory movements of the shoulder and elbow. We tested the hypothesis that cortical and subcortical brain lesions may disrupt the timing of trunk and arm endpoint motion in hemiparetic subjects. Eight hemiparetic and six age-matched healthy subjects were seated on a stool with the right (dominant) arm in front of them on a table. The tip of the index finger (the arm endpoint) was initially at a distance of 20 cm from the midline of the chest. Wrist, elbow, and upper body positions as well as the coordinates of the arm endpoint were recorded with a three-dimensional motion analysis system (Optotrak) by infrared light-emitting diodes placed on the tip of the finger, the styloid process of the ulna, the lateral epicondyle of the humerus, the acromion processes bilaterally, and the sternal notch. In response to a preparatory signal, subjects lifted their arm 1–2 cm above the table and in response to a ”go” signal moved their endpoint as fast as possible from a near to a far target located at a distance of 35 cm and at a 45° angle to the right or left of the sagittal midline of the trunk. After a pause (200– 500 ms) they moved the endpoint back to the near target. Pointing movements were made without trunk motion (control trials) or with a sagittal motion of the trunk produced by means of a hip flexion or extension (test trials). In one set of test trials, subjects were required to move the trunk forward while moving the arm to the target (”in-phase movements”). In the other set, subjects were required to move the trunk backward when the arm moved to the far target (”out-of-phase movements”). Compared with healthy subjects, movements in hemiparetic subjects were segmented, slower, and characterized by a greater variability and by deflection of the trajectory from a straight line. In addition, there was a moderate increase in the errors in movement direction and extent. These deficits were similar in magnitude whether or not the trunk was involved. Although hemiparetic subjects were able to compensate the influence of the trunk motion on the movement of the arm endpoint, they accomplished this by making more segmented movements than healthy subjects. In addition, they were unable to stabilize the sequence of trunk and arm endpoint movements in a set of trials. It is concluded that recruitment and sequencing of different degrees of freedom may be impaired in this population of patients. This inability may partly be responsible for other deficits observed in hemiparetic subjects, including an increase in movement segmentation and duration. The lack of stereotypic movement sequencing may imply that these subjects had deficits in learning associated with short-term memory.
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    Experimental brain research 126 (1999), S. 134-138 
    ISSN: 1432-1106
    Keywords: Key words Upper limb ; Posture ; Geometric constraints ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Significant debate exists regarding the neural strategies underlying the positioning and orienting of the hand during voluntary reaching movements of the human upper extremity. Some authors have suggested that positioning and orienting are controlled independently, while others have argued that a strong interdependence exists. In an effort to address this uncertainty, our study employed computer simulations to examine the impact of physiological limitations of joint rotation on the proposed independence of hand position and orientation. Specifically, we analyzed the effects of geometric constraints on final arm postures using a 7 degree-of-freedom model of the human arm. For 20 different hand configurations within the attainable workspace, we computed sets of achievable joint angles by applying inverse kinematics. From each set, we then calculated the locus of possible elbow positions for the particular final hand posture. When the joints were allowed 360° of rotation, the loci formed complete circles; however, when joint ranges were limited to physiological values, the extent of the loci decreased to an average arc angle of 54.6° (±27.9°). Imposition of joint limits also led to practically linear relationships between joint angles within a solution set. These theoretical results suggest a requirement for coordinated interaction between control of the joints associated with hand position and those involved with hand orientation in order to ensure attainable joint trajectories. Furthermore, it is conceivable that some of the correlations observed between joint angles in the course of natural reaching movements result from geometric constraints.
    Type of Medium: Electronic Resource
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  • 94
    ISSN: 1432-1106
    Keywords: Key words Suprathreshold heat pain ; Adapting temperature ; Temporal parameters ; Spinal dorsal horn neuron ; Descending control ; Rat ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The influence of stimulus temperature rise rate (2.5ºC/s, 5.0ºC/s, and 10.0ºC/s), adapting (baseline) temperature (25ºC, 30ºC, and 35ºC), and duration of peak stimulus temperature (1.0 s, 2.5 s, 5.0 s, and 10.0 s) on responses evoked by noxious heat stimuli of suprathreshold intensity was studied in wide dynamic range (WDR) neurons of the rat spinal dorsal horn. The spinal neuronal responses were compared with human psychophysical data obtained using the same stimuli. Noxious heat stimuli with a peak temperature of 54ºC were applied with a contact thermostimulator to the glabrous skin of the hindfoot in rats or to the palmar skin in humans. With the highest ramp rate and the highest adapting temperature, the sensory and spinal neuronal response latencies were decreased more than expected on the basis of the change in physical parameters of the stimulus. The magnitudes of sensory and spinal neuronal response were independent of the stimulus ramp rate, whereas pain magnitude estimates and spinal neuronal impulse counts evoked by the same peak stimulus temperature were increased with an increase in the adapting stimulus temperature. The onset latencies of pain reactions and spinal neuronal responses were independent of the peak stimulus duration, whereas the latency of the maximum discharge in spinal neurons increased with prolongation of the peak stimulus. The sensory magnitude estimate of pain and the neuronal impulse count were increased with increase in stimulus duration. Following spinalization, the spinal neuronal responses were stronger and the stimulus duration-dependent increase in the impulse count developed faster. Moreover, the peak frequency of spinal neuronal response increased significantly with prolongation of the heat stimuli after spinalization, but not in animals with an intact spinal cord. The results indicate that stimulus rise rate, stimulus duration, and the adapting temperature are important factors in determining the sensory and spinal neuronal responses to high-intensity heat stimuli. The changes in the total impulse counts evoked by varying supraliminal heat stimuli in spinal dorsal horn WDR neurons corresponded well with the changes in pain magnitude estimates in humans. Also, the changes in spinal neuronal response onset latencies were accompanied by corresponding changes in onset latencies of human pain reactions but not with pain magnitude estimates. The effect of spinalization indicated that descending pathways control not only the response magnitude in the spinal dorsal horn WDR neurons but also the temporal characteristics of the spinal neuronal response.
    Type of Medium: Electronic Resource
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  • 95
    ISSN: 1432-1106
    Keywords: Key words Reaching movements ; Grasping movements ; Prehension ; Manual control ; Computational model ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Reaching and grasping an object can be viewed as the solution of a multiple-constraint satisfaction problem. The constraints include contact with the object with the appropriate effectors in the correct positions as well as generation of a collision-free trajectory. We have developed a computational model that simulates reaching and grasping based on these notions. The model, rendered as an animation program, reproduces many basic features of the kinematics of human reaching and grasping behavior. The core assumptions of the model are: (1) tasks are defined by flexibly organized constraint hierarchies; (2) manual positioning acts, including prehension acts, are first specified with respect to goal postures and then are specified with respect to movements towards those goal postures; (3) goal postures are found by identifying the stored posture that is most promising for the task, as determined by the constraint hierarchy, and then by generating postures that are more and more dissimilar to the most-promising stored posture until a deadline is reached, at which time the best posture that was found during the search is defined as the goal posture; (4) depending on when the best posture was encountered in the search, the deadline for the search in the next trial is either increased or decreased; (5) specification of a movement to the goal posture begins with straight-line interpolation in joint space between the starting posture and goal posture; (6) if an internal simulation of this default movement suggests that it will result in collision with an obstacle, the movement can be reshaped until an acceptable movement is found or until time runs out; (7) movement reshaping occurs by identifying a via posture that serves as a body position to which the actor moves from the starting posture and then back to the starting posture, while simultaneously making the main movement from the starting posture to the goal posture; (8) the via posture is identified using the same posture-generating algorithm as used to identify the goal posture. These processes are used both for arm positioning and, with some elaboration, for prehension. The model solves a number of problems with an earlier model, although it leaves some other problems unresolved.
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  • 96
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 127 (1999), S. 207-212 
    ISSN: 1432-1106
    Keywords: Key words Attention ; Distractor interference ; Path deviation ; Horse race model ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It has been suggested that, when movements are planned within cluttered environments, competing responses programmed to distracting stimuli are inhibited based on their relation to the action being performed. Further, as a result of this inhibition, the path of the movement made to the target object deviates away from the distractor. In contrast to the object avoidance hypothesis, the results of the present study show that, for aiming movements made in environments in which distractors are present, the path of the movement veers toward the distractor. Moreover, the effects of the distractors on the movement trajectory were independent of the direction of limb movement. These findings suggest that, when a distractor is not a potential physical barrier, a response to the distractor may be activated along with the target response and, owing to temporal advantages, cause a deviation of the movement trajectory toward the distractor.
    Type of Medium: Electronic Resource
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  • 97
    ISSN: 1432-1106
    Keywords: Key words Coordination ; Posture ; Movement ; Anticipatory postural adjustments ; Axial synergy ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The whole-body center of mass (CoM) has been classically regarded as the stabilized reference value for human voluntary movements executed upon a fixed base of support. Axial synergies (opposing displacements of head and trunk with hip segments) are believed to minimize antero-posterior (A/P) CoM displacements during forward trunk movements. It is also widely accepted that anticipatory postural adjustments (APAs) create forces of inertia that counteract disturbances arising from the moving segment(s). In the present study, we investigated CoM stabilization by axial synergies and APAs during a whole-body reaching task. Subjects reached towards an object placed on the ground in front of them in their sagittal plane using a strategy of coordinated trunk, knee, and hip flexion. The reaching task imposed constraints on arm-trajectory formation and equilibrium maintenance. To manipulate equilibrium constraints, differing conditions of distance and speed were imposed. The comparison of distance conditions suggested that axial synergies were not entirely devoted to CoM stabilization: backward A/P hip displacements reduced as head and trunk forward A/P displacements increased. Analysis of upper- and lower-body centers of mass in relation to the CoM also showed no strict minimization of A/P CoM displacements. Mechanical analysis of the effects of APAs revealed that, rather than acting to stabilize the CoM, APAs created necessary conditions for forward CoM displacement within the base of support in each condition. The results have implications for the CoM as the primary stabilized reference for posture and movement coordination during whole-body reaching and for the central control of posture and voluntary movement.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 124 (1999), S. 42-52 
    ISSN: 1432-1106
    Keywords: Key words Ocular tracking ; Oculomanual coordination ; Electromyography ; Internal model ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  When the eyes and arm are involved in a tracking task, the characteristics of each system differ from those observed when they act alone: smooth pursuit (SP) latency decreases from 130 ms in external target tracking tasks to 0 ms in self-moved target tracking tasks. Two models have been proposed to explain this coordination. The common command model suggests that the same command be addressed to the two sensorimotor systems, which are otherwise organized in parallel, while the coordination control model proposes that coordination is due to a mutual exchange of information between the motor systems. In both cases, the interaction should take into account the dynamic differences between the two systems. However, the nature of the adaptation depends on the model. During self-moved target tracking a perturbation was applied to the arm through the use of an electromagnetic brake. A randomized perturbation of the arm increased the arm motor reaction time without affecting SP. In contrast, a constant perturbation produced an adaptation of the coordination control characterized by a decrease in arm latency and an increase in SP latency relative to motor command. This brought the arm-to-SP latency back to 0 ms. These results support the coordination control model.
    Type of Medium: Electronic Resource
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  • 99
    ISSN: 1432-1106
    Keywords: Key words Aiming movements ; Target size ; Inertial load ; Strategies ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Two experiments are reported that investigated the effects of target size and inertial load on the control of rapid aiming movements. Based on kinematic profiles, movements were partitioned into their preprogrammed initial impulse- and feedback-based error correction phases. Electromyographic (EMG) rise rates were examined to investigate whether participants used a speed-sensitive or speed-insensitive control strategy. The results from both experiments showed that initial impulse velocity and EMG rise rates varied as a function of target size, i.e., a speed-sensitive strategy. This was the case whether participants were allowed to make error corrections to their movements (experiment 1) or were instructed to produce initial impulses that hit the target (experiment 2). Both experiments also showed that initial impulse velocity and endpoint variability were inversely related to inertial load. The results from experiment 2 indicated that, while the manipulation of inertial load had no effect on EMG rise rates for movements to a large target, EMG slopes were modulated between inertial load conditions when the target was small.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 124 (1999), S. 273-280 
    ISSN: 1432-1106
    Keywords: Key words Vestibular system ; Posture control ; Balance ; Cross-spectral analysis ; Coherency ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Galvanic vestibular stimulation serves to modulate the continuous firing level of the peripheral vestibular afferents. It has been shown that the application of sinusoidally varying, bipolar galvanic currents to the vestibular system can lead to sinusoidally varying postural sway. Our objective was to test the hypothesis that stochastic galvanic vestibular stimulation can lead to coherent stochastic postural sway. Bipolar binaural stochastic galvanic vestibular stimulation was applied to nine healthy young subjects. Three different stochastic vestibular stimulation signals, each with a different frequency content (0–1 Hz, 1–2 Hz, and 0–2 Hz), were used. The stimulation level (range 0.4–1.5 mA, peak to peak) was determined on an individual basis. Twenty 60-s trials were conducted on each subject – 15 stimulation trials (5 trials with each stimulation signal) and 5 control (no stimulation) trials. During the trials, subjects stood in a relaxed, upright position with their head facing forward. Postural sway was evaluated by using a force platform to measure the displacements of the center of pressure (COP) under each subject’s feet. Cross-spectral measures were used to quantify the relationship between the applied stimulus and the resulting COP time series. We found significant coherency between the stochastic vestibular stimulation signal and the resulting mediolateral COP time series in the majority of trials in 8 of the 9 subjects tested. The coherency results for each stimulation signal were reproducible from trial to trial, and the highest degree of coherency was found for the 1- to 2-Hz stochastic vestibular stimulation signal. In general, for the nine subjects tested, we did not find consistent significant coherency between the stochastic vestibular stimulation signals and the anteroposterior COP time series. This work demonstrates that, in subjects who are facing forward, bipolar binaural stochastic galvanic stimulation of the vestibular system leads to coherent stochastic mediolateral postural sway, but it does not lead to coherent stochastic anteroposterior postural sway. Our finding that the coherency was highest for the 1- to 2-Hz stochastic vestibular stimulation signal may be due to the intrinsic dynamics of the quasi-static postural control system. In particular, it may result from the effects of the vestibular stimulus simply being superimposed upon the quiet-standing COP displacements. By utilizing stochastic stimulation signals, we ensured that the subjects could not predict a change in the vestibular stimulus. Thus, our findings indicate that subjects can act as ”responders” to galvanic vestibular stimulation.
    Type of Medium: Electronic Resource
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