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  • 1995-1999  (1,764)
  • 1999  (1,764)
  • Chemistry  (1,469)
  • Industrial Chemistry  (469)
  • Human  (119)
  • Life and Medical Sciences  (96)
  • Children  (81)
  • Nuclear reactions
Material
Years
  • 1995-1999  (1,764)
Year
Keywords
  • 1
    ISSN: 1434-5196
    Keywords: Key words Methadone ; Dihydrocodeine ; Substitution ; Poisoning ; Children ; Schlüsselwörter Methadon ; Dihydrocodein ; Substitution ; Intoxikationen ; Kinder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Es wird über 3 überlebte und 4 tödlich verlaufene akzidentelle Intoxikationen, sechs mit Methadon, eine mit Dihydrocodein, berichtet. Die Intoxikationen betrafen nicht die Substituierten selbst, sondern deren Familienangehörige, Bekannte oder Mit-Patienten. In allen Fällen wurden die Substitutionsmittel weitgehend ungesichert und teilweise vermutlich auch unbeschriftet stehengelassen. Den Substituierten selbst war dabei die Gefahr, die von ihrem Substitutionsmittel ausging, offenbar nicht ausreichend bewußt. Diese Fälle zeigen deutlich, daß qualitätssichernde Maßnahmen bei der immer großzügigeren Substitutionspraxis, insbesondere in Hinblick auf „take-home“-Dosen, notwendig sind.
    Notes: Abstract A total of seven cases of accidental ingestion of methadone or dihydrocodeine by four children and three adults are reported of which four were fatal. In each case, someone in the environment was taking methadone or dihydrocodeine as a substitute drug for heroin addiction who obviously did not realize the dangers of methadone for non-addicts. Possible preventive measures are the usage of child-proof containers with adequate labels for take-home medications. Furthermore substituted addicts have to be thoroughly indoctrinated concerning the toxicity and hazards of methadone.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1248-9204
    Keywords: Contralateral hernia ; Children ; Incidence ; Predisposing disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is impossible to determine whether or not a child will develop a contralateral hernia after inguinal hernia repair. There exists no risk score for the occurrence of a contralateral hernia. This well-known fact prompted us to perform the underlying study. In a retrospective trial, we reviewed the files of all children operated on for inguinal hernias in our department from January 1986 until December 1994. During this period, we performed 1721 hernia repairs on 1708 children aged 0–16 years. In 96 (5.6%) of these patients, the indication to operate was a contralateral hernia following previous unilateral repair. Comparison of the ages at the time of primary inguinal repair of those children who developed a contralateral hernia (n=96) and those who did not (n=1612) showed a significantly increased incidence of contralateral hernias if the primary operation was performed before the age of two months (p〈0.0001). Diseases predisposing to hernias were found in 38% of all children (prematurity, dystrophia, ventriculo-peritoneal shunt, ascites, asthma). The authors recommend a contralateral exploration for children under the age of two months if they have any predisposing disease.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 21 (1999), S. 139-141 
    ISSN: 1279-8517
    Keywords: Anatomy ; Human ; Cross-section ; Computer-assisted instruction ; Education ; Medical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The NPAC visible human viewer (NPAC VHV), graphical interface written in JAVA, freely accessible by the Web, allows the display of anatomic cross-sections of the Visible Human Project developed by the National Library of Medicine. In April 1997, the Medical Media Library of Lyons undertook the construction of a French-language mirror site of the NPAC VHV. The aim of this work is to evaluate first year utilisation of this site. From May 1st, 1997 to April 30th, 1998, the mirror site was consulted 34,752 times. In 45.14% of cases, the request came from France, in 4.42% of cases from Belgium, in 3.98% from Canada and in 2.12% from Switzerland. Other connections came either from a country responsible for fewer than 1% of connections or from unidentified computers. Data analysis showed a peak of connections between 15:00 and 17:00, and an increased number of connections from September to March 1998. The NPAC VHV is housed in 5 sites in the world. It is a software very simple to use. As the figures have no legends, it is more appropriate for group teaching than for self-teaching.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Italian journal of neurological sciences 20 (1999), S. 119-128 
    ISSN: 1126-5442
    Keywords: Key words Learning ; Development ; Memory ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Immediate and 15-min delayed recall of semantically related or unrelated word lists was investigated in 144 normally developing children ranging from 5 to 10 years of age. Immediate recall for the related and unrelated lists increased in a parallel fashion as a function of age. The ability to cluster semantically related items during immediate recall also improved with age. However, in no age class recall scores and clustering indexes were significantly associated. Forgetting rate passing from the last immediate to the delayed recall trial increased for the unrelated list but decreased for the related list of words as a function of age. Results of regression analyses revealed that a developmental increase in forgetting on the unrelated list was actually due to the higher number of words recalled in the last immediate trial by older children. As for the related list, instead, the larger reliance on the clustering strategy of recall by older children was responsible for the progressive reduction of forgetting.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Italian journal of neurological sciences 20 (1999), S. 303-307 
    ISSN: 1126-5442
    Keywords: Key words Lyme disease ; Chronic neuroborreliosis ; Children ; MRI ; Demyelinating disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lyme disease is a polymorphic and multisystemic disease caused by Borrelia burgdorferi. Neurological manifestations are found in 10%–50% of cases. We present 2 cases followed for 5 and 6 years of chronic relapsing-remitting neuroborreliosis. Diagnosis of neuroborreliosis in these cases was based on serum and cerebrospinal fluid findings. We discuss clinical, neurophysiological, laboratory and instrumental aspects regarding the difficulties of reaching a correct diagnosis. Further studies, especially in the field of immunology, should help identify the mechanisms responsible for the disease becoming chronic. With this knowledge, it may be possible to design immunological therapies for relapses, and to prevent the evolution of the disease.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1437-1596
    Keywords: Key words Poisoning ; Benfuracarb ; Carbofuran ; Human ; Blood ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Notes: Abstract We describe here three cases involving acute fatalities due to benfuracarb ingestion and the forensic toxicological implications. Benfuracarb, a carbamate insecticide and its main metabolite carbofuran, were detected using thin layer chromatography (TLC) and gas chromatography/mass spectrophotometry (GC/MS) after extraction with ethyl acetate and then quantified using gas chromatography (GC) equipped with NPD. The blood levels of benfuracarb and carbofuran were in the range of 0.30∼2.32 μg/ml and 1.45∼1.47 μg/ml, respectively. Benfuracarb was not detected in urine, but carbofuran was detected in the range of 0.53∼2.66 μg/ml.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    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.
    Type of Medium: Electronic Resource
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  • 10
    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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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Der Nervenarzt 70 (1999), S. 1-10 
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Tic-Störung ; Zwangsstörung ; Kinder ; Jugendliche ; Neurobiologie ; Psycho- pharmakologie ; Verhaltenstherapie ; Key words Tic-disorder ; Obsessive-compulsive disorder ; Children ; Adolescents ; Neurobiology ; Psychopharmacology ; Behavior therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In children and adolescents motor/vocal tics and obsessive-compulsive behavior are known to be closely related. Thereby, a continuum of symptoms ranging from single tics to a mixed picture of tics/rituals/obsessive-compulsive traits to clinically relevant obsessions and compulsions could be described. As neurobiological substrates dysfunctions in corresponding cortico-striato-thalamo-cortical circuits (sensorimotor circuit in tic symptomatology, orbitofrontal circuit in obsessive-compulsive behavior) were postulated. For both disturbances behavioral therapy can be used to improve control mechanisms to counterregulate tics and obsessive-compulsive behavior, respectively, and psychopharmacological agents can be administerd to compensate dysbalances in neurotransmitter systems. In case of a mixed symptomatologic picture it is necessary to include interventions for both pols of the symptom-continuum in the therapeutic programme to achieve extensive improvement as a basis for a further positive development of the patient.
    Notes: Zusammenfassung Motorische/vokale Tics und zwanghafte Verhaltensweisen kommen bei Kindern und Jugendlichen häufig gemeinsam vor; dabei kann ein Symptomkontinuum von solitär auftretenden Tics über ein Mischbild von Tics und Ritualen/zwanghaften Gedanken und/oder Handlungen bis hin zu eindeutigen Zwangsphänomenen beschrieben werden. Neurobiologisch können diesem Symptomkontinuum unterschiedlich ausgebreitete Dysfunktionen entsprechender kortiko-striato-pallido-thalamo-kortikaler Regulationssysteme zugrunde liegen. Therapeutisch lassen sich bei beiden Verhaltensauffälligkeiten mittels verhaltenstherapeutischer Techniken Steuerungs- und Kontrollmöglichkeiten zur Gegenregulation der Auffälligkeiten verbessern sowie durch Einsatz von Psychopharmaka Dysbalancen von Neurotransmittersystemen ausgleichen. Bei einem Mischbild von Tics und Zwängen sind therapeutische Interventionen für beide Zielbereiche erforderlich. Nur so können umfassende Verbesserungen erreicht und günstige Entwicklungsbedingungen für die betroffenen Kinder und Jugendlichen eröffnet werden.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
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    Springer
    Monatsschrift Kinderheilkunde 147 (1999), S. 328-332 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Asthma bronchiale ; Schulkinder ; Türkische Kinder ; Key words Asthma ; Children ; Turkish children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Objectives: In Germany 4.2% (in Munich 8.6%) of all children under 15 years of age are of Turkish origin, representing the largest ethnic minority in this age group. However, very little is known about the prevalence, severity and management of asthma and other atopic diseases in Turkish children living in Germany. Methods: In a cross-sectional survery the prevalence, severity and treatment of asthma and other atopic diseases was assessed in 7,445 schoolchildren aged 9 to 11 years, living in Munich, southern Germany. Questionnaires were distributed to the parents for self-completion and children underwent skin-prick tests and cold-air hyperventilation challenge. Results: Of those returning the questionnaires (n = 6490/87%), 5,030 (77.5%) were of German and 451 (7%) of Turkish origin. Turkish children showed a significantly lower prevalence of asthma (5.3% versus 9.4%, P 〈 0.05) than their German peers. Furthermore, Turkish children with asthma were less frequently free of symptoms (10.5% versus 34.6%, P 〈 0.05), reported more severe symptoms (41.2% versus 10.9%, P 〈 0.05) and more hospital admissions (55.6% versus 21.6%, P 〈 0.05) due to asthma than German children. Conclusions: The results of this study indicate that despite the lower prevalence of asthma and allergy in the Turkish population living in Germany, asthma is a major health problem for Turkish children. Furthermore, these findings suggest inadequate management of asthma in Turkish children.
    Notes: Zusammenfassung Fragestellung: Türkische Kinder stellen in der Bundesrepublik Deutschland mit 4,2% und in München mit 8,6% den größten Anteil nicht-deutscher Kinder in der Altersgruppe bis 15 Jahren. Wenig ist jedoch bisher über Häufigkeit, Symptome und Behandlung von Asthma bronchiale und anderer atopischer Erkrankungen der türkischen Minderheit in Deutschland bekannt. Methodik: In einer Querschnittstudie wurde bei 7445 Schulkindern im Alter von 9 bis 11 Jahren im Großraum München die Häufigkeit, der Schweregrad und die Behandlung des Asthma bronchiale und anderer atopischer Erkrankungen untersucht. Fragebögen wurden von den Eltern ausgefüllt, Lungenfunktionsuntersuchungen und Hautpricktests wurden bei den Kindern durchgeführt. Ergebnisse: Von denen, die die zugeschickten Fragebögen ausfüllten (n = 6490/87%), waren 5030 (77,5%) deutscher und 451 (7%) türkischer Nationalität. Die türkischen Kinder zeigten eine niedrigere Prävalenz von Asthma bronchiale (5,3% versus 9,4%, p 〈 0,05) und Neurodermitis (1,6% versus 12,9%, p 〈 0,001) im Vergleich zu den deutschen Kindern. Signifikante Unterschiede bestanden zwischen türkischen und deutschen Kindern in Art der Symptome und der Krankheitswahrnehmung. Türkische Kinder mit Asthma bronchiale waren seltener beschwerdefrei (10,5% versus 34,6%, p 〈 0,05) berichteten von schwereren Symptomen (41,2% versus 10,9%, p 〈 0,05) und von einer größeren Anzahl von Krankenhausaufenthalten (55,6% versus 21,6%, p 〈 0,05) aufgrund von Asthma bronchiale. Schlußfolgerung: Die Ergebnisse der Studie legen den Schluß nahe, daß Asthma bronchiale trotz der niedrigeren Prävalenz in der türkischen Bevölkerungsgruppe ein erhebliches Gesundheitsproblem bei türkischen Schulkindern darstellt. Die höhere Anzahl von Fehltagen in der Schule und die deutlich höhere Anzahl von Klinikaufenthalten aufgrund von Asthma bronchiale sprechen für eine mangelhafte präventive Behandlung dieser Erkrankung bei türkischen Kindern.
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  • 13
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    Springer
    HNO 47 (1999), S. 535-540 
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Hörschäden ; Knalltrauma ; Kinder ; Tinnitus ; Erweiterte Hochtonaudiometrie ; Key words Hearing loss ; Acoustic trauma ; Children ; Tinnitus ; High-frequency audiometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The study presents an analysis of 20 cases of acute acoustic trauma caused by toy pistols. The problem generally involves boys within the age range from 6 to 11 years. Half of the incidents involved attacks with toy pistols used as weapons. Auditory damage appeared in two types, each of which had a notch in the audiogram at the frequency range between 10 and 14 kHz. In children, a shot close to one ear can damage both ears. Great differences in the severity of tinnitus were apparent. The most severe cases of tinnitus were observed in the children with no or minor premanent auditory damage. Children experiencing long periods of uninterrupted tinnitus suffer significantly. This is not only detrimental to family-life but also to the performance of the children at school. The total expenses of treatment for these 20 cases were estimated to be approximately 80,000 DM (40.000 Euro).
    Notes: Zusammenfassung Im Rahmen einer Studie wurden 20 Fälle von Knalltraumata durch Kinderpistolen erfaßt und ausgewertet. Die Problematik betrifft fast nur männliche Personen und schwerpunktmäßig den Altersbereich von 6–11 Jahren. Die Hälfte der Vorfälle waren Angriffe, bei denen die Kinderpistole als Waffe eingesetzt wurde, 2 Typen von Hörschäden sind festzustellen, die jedoch beide durch eine Senke im Bereich von 10–14 kHz charakterisiert sind. Bei Kindern kann der Schuß in eines der Ohren auch das andere Ohr schädigen. Sehr große Unterschiede bestehen im Auftreten von Tinnitus. Die Fälle mit starkem Tinnitus haben keine oder nur geringe bleibende Hörschäden. Die von Knalltraumata betroffenen Kinder leiden oft sehr stark unter langanhaltendem Tinnitus. Dabei wird nicht nur das Leben der Familien beeinträchtigt, sondern auch die schulischen Leistungen der Kinder leiden teilweise sehr stark darunter. Für die Therapie dieser 20 Fälle entstanden Gesamtkosten von ca. 80.000,- DM
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  • 14
    ISSN: 1433-0458
    Keywords: Schlüsselwörter Laryngotracheale Stenose ; Cricotracheale Resektion ; Kinder ; Tracheotomie ; Key words Laryngotracheal stenosis ; Cricotracheal resection ; Tracheostomy ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Approximately 90% of infants and children with severe acquired laryngotracheal stenoses are tracheotomy dependent and therefore impaired in their physical and speech developments. In addition, tracheotomized infants can be endangered by the cannula due to the possible crusting of secretions or its dislocation. Thus, early repair of a stenosis is mandatory. Within the last 10 years, we successfully operated on 18 children with severe laryngotracheal stenoses. Ten children were treated with a modified Cotton technique. This paper reports our results of cricotracheal resection performed in 8 children since 1994 (age distribution: 7 months through age 15 years). Four children had Cotton grade II stenoses, three had grade III stenoses and one grade IV stenoses. In 3 patients a tracheotomy had been performed at another institution. Since their tracheostomas were too far caudal, they could not be included in the primary resection. All 8 children have been successfully decannulated. Five children without tracheotomies could be extubated uneventfully on the 5th postoperative day. All three primarily tracheotomized children needed further endotracheal stenting with T-tubes because of stomal and suprastomal collapse. Two of these latter children additionally required a tracheoplasty with rib cartilage grafts in order to stabilize the suprastomal trachea prior to decannulation. No patient experienced injuries to the recurrent laryngeal nerves or insufficiencies of the anastomosis. All children’s voices were not impaired. This is the third report in literature of cricotracheal resections in infants and children, indicating that this effective, one-stage procedure is superior to laryngotracheal reconstruction with rib cartilage.
    Notes: Zusammenfassung Kinder mit schweren, erworbenen subglottischen laryngotrachealen Stenosen sind zu 90% tracheotomiert und daher in ihrer körperlichen und sprachlichen Entwicklung beeinträchtigt. Zusätzlich sind mit einer Trachealkanüle versorgte Kinder, insbesondere Kleinkinder, gefährdet, so daß die chirurgische Beseitigung der Stenose dringend geboten ist. Wir haben innerhalb der vergangenen 10 Jahre 18 Kinder mit einer schweren subglottischen laryngotrachealen Stenose operiert; 10 Kinder, über die kürzlich berichtet wurde, konnten mit der modifizierten Cotton-Technik erfolgreich dekanüliert werden. Über 8 Kinder (Alter 7 Monate bis 15 Jahre, 4mal Stenose II. Grades, 3mal Stenose III. Grades, einmal Stenose IV. Grades), die wir mit cricotrachealer Resektion (CTR) und thyrotrachealer Anastomose operierten, wird in der vorliegenden Arbeit berichtet. 3 Kinder waren anderenorts bereits tracheotomiert. Da die Stomata zu weit kaudal lagen, konnten sie nicht in die Resektion einbezogen werden. Alle 8 Kinder konnten inzwischen dekanüliert werden und sind beschwerdefrei: Die 5 nicht tracheotomierten Kinder konnten problemlos am 5. postoperativen Tag extubiert werden. Die zuvor tracheotomierten Kinder konnten erst nach endotrachealer Schienung (2mal nach zusätzlicher Trachealplastik mit Rippenknorpel bei suprastomaler Tracheomalazie) dekanüliert werden. Bei keinem der Kinder trat eine Recurrensparese auf. Die Stimme bei allen Kindern ist unbeeinträchtigt. Die CTR, über die bei kindlichen laryngotrachealen Stenosen mit dieser Arbeit in der Literatur zum 3. Mal berichtet wird, ist eine sehr effektive, einzeitige, komplikationsarme Operationsmethode, deren Resultate für Atmung und Stimme günstiger sind, als mit der Erweiterungsplastik nach Cotton.
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  • 15
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    Monatsschrift Kinderheilkunde 147 (1999), S. 122-127 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Körperliche Beschwerden ; CBCL/4 ; 18 ; Kultur-vergleichend ; Kinder ; Jugendliche ; Key words Somatic complaints ; CBCL/4 ; 18 ; Cross-cultural ; Children ; Adolescents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Question: What is the frequency of parent-reported somatic complaints of children in Germany and the Netherlands dependent on their age, sex and the education of their parents. Methods: 4876 CBCL (Child Behaviour Checklist) of children aged 4 through 17 years from the general population were analysed. Results: Dutch children were scored higher by their parents than German children. Moreover somatic complaints increased with age and girls were scored higher. The frequencies of somatic complaints varied from 2% for ’problems with eyes’ to 15% for ’headaches’. The presence of one somatic complaint increased the likelihood of concomitant somatic complaints. Conclusion: Somatic complaints of children without any known cause are often seen. Some symptoms are often reported together. More, especially causal studies on the somatic symptoms of children are recommended.
    Notes: Zusammenfassung Fragestellung: Wie verhält sich die Häufigkeit körperlicher Beschwerden bei Kindern in Deutschland und den Niederlanden nach Laieneinschätzung, gibt es Unterschiede abhängig vom Alter und Geschlecht der Kinder und des Ausbildungsniveaus der Eltern? Methode: 2757 deutsche und 2119 niederländische CBCL (child behavior checklist) über Kinder und Jugendliche im Alter zwischen 4 und 17 Jahren aus repräsentativen Studien wurden mit Hilfe von Varianzanalysen ausgewertet. Ergebnisse: Niederländische Eltern beschrieben mehr körperliche Beschwerden als deutsche. Die Ausprägung auf der Symptomskala stieg mit zunehmendem Alter und zeigte höhere Werte für Mädchen. Die Häufigkeit der Beschwerden variiert von 2% für „Augenbeschwerden” bis zu 15% für „Kopfschmerzen”. Bei Anwesenheit eines körperlichen Symptoms stieg die Frequenz zusätzlicher Beschwerden. Schlußfolgerung: Körperliche Beschwerden bei Kindern treten häufig ohne bekannte Ursache auf, bestimmte Beschwerden werden häufig gleichzeitig beschrieben, wobei die Koinzidenz nicht umkehrbar ist. Weitere, besonders ursächliche Studien auf dem Gebiet der körperlichen Beschwerden bei Kindern sind auch hinsichtlich steigender Kosten im Gesundheitswesen empfehlenswert.
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  • 16
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    Monatsschrift Kinderheilkunde 147 (1999), S. 351-355 
    ISSN: 1433-0474
    Keywords: Schlüsselwörter Latexallergie ; Neuogene Blasenentleerungsstörung ; Kinder ; Key words Latex allergy ; Neurogenic bladder dysfunction ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Objectives: The risk to suffer from natural latex allergy is increased in children with congenital neurogenic bladder dysfunction. We, therefore, evaluated whether or not a serologic screening for detection of sensitization to latex is reasonable in these children. Patients and Methods: 40 children aged from 6 months to 17 years were examined by specific questionnaire-based patient histories, and by determination of total serum immunoglobuline E (total IgE) and natural latex-specific serum immunoglobulin E (latex-IgE) by solid-phase immunoassays. Results: 5 children had a history of allergic reaction to rubber containing materials. In 10 children, latex-IgE was elevated 〉 0.35 kU/l, 6 out of these 10 children without a history of allergic reactions to rubber containing materials. There was a positive correlation of elevated latex-IgE values and the number of former surgical procedures (p 〈 0.006), while no correlation was found between elevated latex-IgE values and clean intermittent catheterization (p = 0.408). Conclusion: Compared to questionnaire-based patient histories, serologic screening examination including determination of latex-IgE values may better identify children at risk to suffer from sensitization to natural latex.
    Notes: Zusammenfassung Fragestellung: Naturlatexallergien kommen bei Kindern mit angeborener neurogener Blasenentleerungsstörung gehäuft vor. Es wurde deshalb untersucht, ob bei dieser Patientengruppe ein serologisches Screening zur Erfassung einer Sensibilisierung gegenüber Naturlatex sinnvoll ist. Patienten und Methode: Untersucht wurden 40 Kinder im Alter von 6 Monaten bis 17 Jahren. Die Untersuchung umfaßte eine gezielte Anamneseerhebung durch Fragebogen sowie die Bestimmung des Gesamtimmunglobulin E (Gesamt-IgE) und des naturlatexspezifischen Immunglobulin E (Latex-IgE) im Serum durch Festphasenimmunoassays. Ergebnisse: 5 Kinder hatten anamnestisch Zeichen einer allergischen Reaktion nach Gummikontakt. 10 Kinder wiesen im Serum erhöhte Werte des Latex-IgE auf, wobei 6 dieser Kinder bisher noch keine Zeichen einer Latexallergie hatten. Pathologische Werte für das Latex-IgE korrelierten statistisch signifikant mit der Anzahl operativer Eingriffe (p 〈 0,0006), nicht aber mit einem durchgeführten sauber intermittierenden Einmalkatheterismus (p = 0,408). Schlußfolgerung: Im Vergleich zur alleinigen fragebogengestützen Anamneseerhebung können durch ein serologisches Screening mit Bestimmung des Latex-IgE mehr Kinder entdeckt werden, die durch eine Sensibilisierung gegenüber Naturlatex gefährdet sind.
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  • 17
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    Pediatric surgery international 15 (1999), S. 32-35 
    ISSN: 1437-9813
    Keywords: Key words Appendicitis ; Ultrasonography ; Children ; Graded compression ultrasonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The diagnosis of acute appendicitis in childhood is frequently difficult. In some situations the need to operate is clear, but in others the decisions may be much “tougher” because the clinical findings are equivocal. This is a retrospective study of a consecutive series of 253 children presenting with “acute abdominal pain? appendicitis” who had graded compression ultrasonography (GCUS) because the clinical scenario did not warrant immediate laparotomy. This represents 30% of all cases seen in the study period. The aim of the study was to examine the role of GCUS and a clinical scoring system (the Alvarado score) in patients in whom the diagnosis is uncertain.
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  • 18
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    Pediatric surgery international 15 (1999), S. 50-55 
    ISSN: 1437-9813
    Keywords: Key words Burns ; Inhalation injury ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Survival from serious burns in children has improved substantially in recent years. Mortality is predominantly determined by the total body surface area burned and the often unrecognised inhalation injury. A retrospective review of 4,451 consecutive children with thermal injuries over a 10-year period was undertaken to determine the incidence, clinical presentation, and pathology of inhalation injury and its contribution to morbidity and mortality. Inhalation burns were diagnosed clinically and confirmed endoscopically and post-mortem in 97 (2.2%) children; 77 sustained fire burns (mean age 4 years) and 20 hot-water burns (mean age 18 months). The Moylan classification stratified them into upper-airway burns in 59 children, major–airway burns in 29, and parenchymal burns in 44. Major-airway burns were always seen in conjunction with either upper-airway or parenchymal injury. Stridor and acute progressive respiratory distress were the two main symptoms, the onset of which was occasionally delayed for up to 72 h. Endoscopy was most helpful in confirming the diagnosis and determining airway management. Endotracheal intubation was needed in more than 50% of children, usually for less than 5 days, and was converted to tracheostomy in only 6. Persistent laryngeal and tracheal damage was identified in 4. Secondary pneumonia occurred in 41.5% of children with fire burns and 55% with hot-water burns. Extensive surface burns, parenchymal injury, and secondary pneumonia all contributed to the significant mortality. Post-mortem findings corroborated clinical and endoscopic evidence. This study suggests that inhalation burns were often not recognised, could present late, and usually had significant consequences. Early clinical diagnosis, supported by endoscopic findings and appropriate management, is essential if the high morbidity and mortality amongst these children is to be improved.
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  • 19
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    Pediatric surgery international 15 (1999), S. 63-65 
    ISSN: 1437-9813
    Keywords: Key words Actinomycosis ; Antibiotic treatment ; Appendicitis ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Abdominal actinomycosis (AMC) is a rare infection in children. The appendix is the most common intra-abdominal organ involved. It presents as an undifferentiated mass, forming abscesses and fistulas in the right lower quadrant. The case of a 15-year-old girl with a AMC of the appendix detected by the pathologist after routine appendectomy is discussed. Long-term antibiotic treatment and follow-up by ultrasound and laboratory controls are necessary.
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  • 20
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    Pediatric surgery international 15 (1999), S. 121-122 
    ISSN: 1437-9813
    Keywords: Key words Ingrowing nails ; Conservative treatment ; Children ; Adolescents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ingrowing nails are not uncommon in children, and even so receive little attention in the pediatric surgery literature. The purpose of the present study was to demonstrate our modification of the conservative treatment of ingrowing nails. Our technique of local treatment combined with patient education for better foot and toe care was successfully used and well tolerated by 19 out of 20 young patients with ingrown toenails.
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  • 21
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    Pediatric surgery international 15 (1999), S. 353-357 
    ISSN: 1437-9813
    Keywords: Key words Testis torsion ; Scrotum ; Appendage ; Cremasteric reflex ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A total of 543 boys suffering from acute scrotal pain underwent emergency surgery between 1986 and 1996. Of these, 91 had a testicular torsion (TT) (16.8%) and 250 had an appendage torsion (AT) (46%). The cause varied with patient age, with most TTs in newborns and boys of 15 years and most ATs in 10–11-year-olds; 21.5% were operated upon within 6 h of the onset of pain and 69.2% within 24 h. Most stayed in hospital for less than 24 h. Pre-surgical examination identified no criterion for excluding TT. We therefore believe that all children complaining of acute scrotal pain should undergo surgery. As release of an inflamed AT reduces pain, three-fourths of the children benefited directly from surgery.
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  • 22
    ISSN: 1437-9813
    Keywords: Key words Ovarian tumor ; Children ; Hypercalcemia ; Small-Cell carcinoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Tumors of the ovary in girls represent about 80% of pediatric genital tumors; approximately 30% of these tumors are malignant. The risk of malignancy increases with decreasing age. The most frequent finding is a teratoma; other tumors are rare. Small-cell carcinoma (SCCO) of the ovary is extremely rare, occurring mostly in young women. We present an 8-year-old girl with a SCCO of the hypercalcemic type. The findings and treatment are discussed with emphasis on the poor prognosis in these patients, even in stage 1 disease. The current literature is reviewed.
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  • 23
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    Pediatric surgery international 15 (1999), S. 579-581 
    ISSN: 1437-9813
    Keywords: Key words Hydatid disease ; Pancreas ; Children ; Echinococcosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Primary hydatid disease of the pancreas is rare. The authors report a 3-year-old girl who had a cystic mass in the head of the pancreas with no other viscera involved. At laparatomy the entire endocyst was totally extracted from the surrounding pancreatic parenchyma. The postoperative course was uneventful. She is currently disease-free with a follow-up of 5 years. Only four other pediatric cases have been reported in the English literature.
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  • 24
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    Pediatric surgery international 15 (1999), S. 525-526 
    ISSN: 1437-9813
    Keywords: Key words Central venous catheters ; Children ; Complications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The insertion of central venous catheters has become an established practice in the management of children with different types of malignancies for the administration of chemotherapeutic agents, antibiotics, blood and blood products, as well as drawing blood for various investigations. A commonly encountered problem is that despite the catheter being patent it may be impossible to draw blood from it. We believe this is related to the cut of the catheter tip. To overcome this problem, a technique for cutting the tip of the catheter is described.
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  • 25
    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.
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  • 26
    ISSN: 1432-2307
    Keywords: Key words p21 ; p53 ; Colon ; Immunohistochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The WAF1/CIP1 gene product, p21, an inhibitor of cyclin-dependent kinases, is a critical downstream effector in the p53 pathway. The expression of p21 in human neoplasms is heterogeneous, and may be related to p53 functional status. We evaluated p21 immunoreactivity in 103 colorectal carcinomas (CC) in relation to the p53 gene and protein alterations and clinico-pathologic parameters. High p21 expression (more than 10% reactive cells) was seen in 39% of cases. p21 staining was heterogeneous and often detected in clusters of tumour cells; in some tumours p21 staining was more pronounced in superficial areas. No relation was seen between p21 immunoreactivity and site of the tumours (right vs left), TNM stage and grade. p21 expression was related to p53 status as evaluated with IHC or with SSCP analyses, low p21 expression usually being associated with p53 protein overexpression (P=0.048) and p53 gene alteration (P=0.005). The strongest associations were seen when the combined p53/p21 immunophenotype was compared with p53 gene alterations (P=0.0002). These data support the hypothesis that p21 expression in CC is mainly related to p53 functional status, suggesting that p21 expression could be an interesting adjunct in the evaluation of the functional status of the p53 pathway in CC.
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  • 27
    ISSN: 1434-0879
    Keywords: Key words Alpha-1-microglobulin ; Calcium oxalate ; Crystallization ; ELISA ; Human ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the past few years, alpha-1-microglobulin (α1m) has been copurified from human urine with bikunin, a potent inhibitor of calcium oxalate (CaOx) crystallization in vitro. In this study, we have purified α1m without bikunin contamination and investigated its possible role in CaOx crystallization by in vitro and in vivo studies. Alpha-1m was purified with an anti-α1m antibodies CNBr-activated sepharose column. Two molecular species of α1m of respectively 30 and 60 kDa were purified. For each protein, two blots of 30 and 60 kDa cross-reacted with anti-α1m antibodies, suggesting that these two forms were derived one from the other. Both protein species inhibited CaOx crystallization in a dose-dependent manner in two in vitro tests. In the first test, the presence of α1m of 30 kDa (8 μg/ml) in a medium containing 0.76 mM CaCl2 (with 45Ca) and 0.76 mM Ox(NH4)2 inhibited CaOx crystallization by 38% as estimated by supernatant radioactivity after 1 h of agitation. In the second test, CaOx kinetics were examined for 3 to 10 min in a turbidimetric model at 620 nm. The presence of α1m of 30 kDa in a medium containing 4 mM CaCl2 and 0.5 mM Na2Ox inhibited CaOx crystallization by 41.5%, as estimated by the slope modification of turbidimetric curve. Alpha-1m can be considered as another inhibitor of urinary CaOx crystal formation, as shown by the present in vitro studies. Using an ELISA assay, we found that urinary α1m concentration was significantly lower in 31 CaOx stone formers than in 18 healthy subjects (2.95 ± 0.29 vs 5.34 ± 1.08 mg/l respectively, P = 0.01). The decreased concentration of α1m in CaOx stone formers could be responsible in these patients, at least in part, for an increased risk of CaOx crystalluria.
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  • 28
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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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  • 29
    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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  • 30
    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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  • 31
    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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  • 32
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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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  • 33
    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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  • 34
    ISSN: 1432-0584
    Keywords: Key words Hypergammaglobulinemia ; Polyclonal ; Acute myeloid leukemia ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Polyclonal hypergammaglobulinemia (PHG) associated with hematological malignancies is a rare occurrence. We reviewed our series of 47 children with AML in order to define the prevalence of PHG and its prognostic value in achieving complete remission (CR) after induction treatment. Patients were stratified by immunoglobulin levels into two groups: with PHG and without PHG. CR reached after induction chemotherapy was considered a positive response. Conditional exact tests were used for the statistical analysis; conditional maximum likelihood estimates of the odds ratio (OR) were obtained. Significance levels (p) were determined from two-tailed tests. Twenty-two of 38 (57.9%) evaluable children showed PHG. Children with PHG and AML were more likely to be in CR after first induction treatment (OR=6.25, p=0.021), independent of sex, age at diagnosis, white blood cell count, percentage of blasts in the bone marrow, FAB phenotype, and treatment protocol. Infections seemed to positively influence early treatment response (p=0.038). PHG and infections were not statistically associated (p=0.16). PHG may result from the uncontrolled stimulation of B lymphocytes by cytokines. Infections or transfusions may act as triggers for the immune system, leading to the antileukemic effect seen in patients with AML and PHG going into spontaneous remission. It could be that this activation caused the larger number of CRs observed in our series. Clarification of why PHG exerts a positive influence on children with AML could help us to understand the ways by which the organism is able to control a malignant disease.
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  • 35
    ISSN: 1432-0584
    Keywords: Key words Thrombopoietin ; Interleukin-11 ; Interleukin-6 ; Thrombocytopenia ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We measured serum levels of thrombopoietin (TPO), interleukin (IL)-11, and IL-6 in 90 different samples from 67 pediatric patients with thrombocytopenia (TP). The cytokine levels were determined by enzyme-linked immunosorbent assays (ELISA), and the biological activity of TPO was measured using a cell line transfected with human c-mpl. In patients with impaired megakaryocytopoiesis, as found in diseases such as aplastic anemia, amegakaryocytic TP, or TP with absent radii, we found TPO levels which were highly elevated compared with normal values (mean=261 AU/ml, n=52, vs. 22 AU/ml in healthy controls). In contrast, patients suffering from idiopathic thrombocytopenic purpura (mean=16 AU/ml, n=31) or platelet function defects (mean=23 AU/ml, n=7) demonstrated normal TPO levels. The biological activity tested in the bioassay correlated well with the ELISA data. However, sera of some patients with amegakaryocytic TP demonstrated a remarkably higher biological activity of TPO than expected from the ELISA data. Within the different groups there was no correlation between platelet counts and TPO levels. Only 27% of all samples had elevated levels of IL-11 (mean=450 pg/ml, n=20). Elevated IL-6 serum levels were detected in only 13% of all samples analyzed (mean=42 pg/ml, n=12). We conclude that megakaryocytopoiesis is regulated mainly by TPO, that it is dependent on the platelet and the megakaryocytic mass, and that IL-11 plays an additional role in supporting the platelet production. IL-6 does not appear to be up-regulated in children with thrombocytopenia.
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  • 36
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    Cancer chemotherapy and pharmacology 44 (1999), S. 203-209 
    ISSN: 1432-0843
    Keywords: Key words Vincristine ; Pharmacokinetics ; Repetitive dosing ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: We studied vincristine disposition after 169 weekly i.v. bolus injections in 32 children with acute lymphoblastic leukemia, non-Hodgkin lymphoma, or Wilms' tumor. The aim of the study was to determine intrapatient and interpatient variability in vincristine disposition and demographic, clinical, and biochemical characteristics influencing this variability. Methods: Vincristine plasma concentrations were measured by a high-performance liquid chromatography assay with electrochemical detection. A limited sampling strategy was used based on a bayesian parameter estimation algorithm that is part of the ADAPT II software package. A two-compartment, first-order model was fitted to the data, and pharmacokinetic parameters were calculated from the model using the ADAPT II software. For statistical analysis, analysis of variance (ANOVA), t test, simple and multiple regression analysis, and non-parametric or robust equivalents were used. Results: Results showed a large intrapatient and interpatient variability in distribution half-life, elimination half-life, total body clearance, apparent volume of distribution at steady state, and area under the concentration–time curve. Intrapatient variability was significantly smaller than interpatient variability for all these parameters except distribution half-life. The diagnosis or treatment protocol turned out to be the most predictive characteristic; leukemia and non-Hodgkin lymphoma patients had a significantly higher total body clearance than Wilms' tumor patients. Conclusions: We conclude that both intrapatient and interpatient variability in vincristine pharmacokinetics is large in pediatric cancer patients and that variability, although significantly influenced by diagnosis, largely remains unpredictable.
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  • 37
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    Immunogenetics 49 (1999), S. 438-445 
    ISSN: 1432-1211
    Keywords: Key words PA28 ; Proteasome ; Gene structure ; Evolution ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Two proteasome activators PA28α and β, which have been implicated in antigen processing for loading class I MHC molecules, are synthesized in response to Ifn-γ. The human genes encoding these activators (PSME1 and PSME2, respectively) were analyzed by sequencing. Each gene comprised 11 exons, consistent with gene duplication during vertebrate evolution. The intron/exon organization of both genes was highly conserved, the major difference being the absence of the exon encoding the lysine and glutamic acid-rich 'KEKE' motif in PA28β. Two other genes of relevance to the immune system were located close to those for PA28 at 14q11.2 including ISGF3G, a protein involved in transcription after IFNα signalling. These sequences were also characterized.
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  • 38
    ISSN: 1432-1211
    Keywords: Key words NK cells ; Human ; Surface molecule ; Lectin superfamily ; NK gene complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Natural killer (NK) cells constitute the third major population of lymphocytes. They possess the inherent capacity to kill various tumor and virally infected cells and mediate the rejection of bone-marrow grafts in lethally irradiated animals. A large family of NK cell receptors belong to the C-type lectin superfamily and are localized to the NK gene complex on Chromosome (Chr) 6 in the mouse and Chr 12 in the human. Genes in the NK gene complex encode type II receptors and examples include the families of NKR-P1, Ly-49, and NKG2 receptors. Examples of other C-type lectin-like NK cell receptors that occur as individual genes are CD94, CD69, and AICL. Here we report the molecular characterization and chromosomal mapping of a human lectin-like transcript (LLT1) expressed on NK, T, and B cells and localized to the NK gene complex within 100 kilobases of CD69. The cDNA encodes a predicted protein of 191 amino acid residues with a transmembrane domain near the N-terminus and an extracellular domain of 132 amino acid residues with similarity to the carbohydrate recognition domain of C-type lectins. The predicted protein of LLT1 shows 59 and 56% similarity to AICL and CD69, respectively. The predicted protein does not contain any intracellular ITIM motifs, suggesting that LLT1 may be involved in mediating activation signals.
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  • 39
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    European journal of pediatrics 158 (1999), S. 519-522 
    ISSN: 1432-1076
    Keywords: Key words Pulmonary function test ; Adjustment ; Children ; Prediction equations ; Population specific
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fitting adequate prediction equations for pulmonary function test (PFT) parameters is crucial in the analysis of lung function tests and their interpretation. Our work aimed at studying the necessity of building population specific prediction equations, rather than using prediction equations built-in in commercial equipment. We used as an example results of studies carried out among Israeli schoolchildren. Second to sixth grade children (7–13 years old), 1064 boys and 1211 girls, were studied in Tel-Aviv. PFT (forced vital capacity, forced expiratory volume in 1st second, peak expiratory flow, forced expiratory flow in 50% volume, forced expiratory flow in 75% volume) performed by these children were adjusted for height, weight and age, for each sex separately, by a multiple regression procedure. Predicted PFT parameters of 300 boys and 301 girls aged 7–13 years, living along the southern shore of Israel, were calculated using the equations built for the same aged Tel-Aviv children as well as the prediction equations built-in in the spirometer used. The ratios between the observed PFT parameters in the southern children and their expected values, using the Israeli population specific equations, were around 1.00. Using the built-in equations resulted in ratios around 0.90. Conclusion The development of population specific prediction equations for PFT parameters is necessary. Such equations should be used both in clinical assessment to minimize misclassification (healthy/sick child) and in epidemiological studies.
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  • 40
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    European journal of pediatrics 158 (1999), S. 550-552 
    ISSN: 1432-1076
    Keywords: Key wordsShigella ; Toxic encephalopathy ; Children ; Brain oedema ; Shiga toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A 6-year-old girl is described who died following rapid neurological deterioration, ending in lethal cerebral oedema. Despite the absence of severe intestinal and metabolic derangement, Shigella was cultured from the stool. Toxic encephalopathy is responsible for death following this rare complication of childhood shigellosis in developed countries. The pathophysiology is unknown. Conclusion Lethal toxic encephalopathy can be caused by Shigella despite the absence of severe intestinal and metabolic derangement. If shigelllosis is suspected, headache may be a first significant sign for the development of toxic encephalopathy. Early recognition and rapid measures to prevent brain oedema may improve outcome.
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  • 41
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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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  • 42
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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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  • 43
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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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  • 44
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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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  • 45
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    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.
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  • 46
    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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  • 47
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    Experimental brain research 126 (1999), S. 235-251 
    ISSN: 1432-1106
    Keywords: Key words Motor learning and memory ; Perseveration ; Prefrontal cortex ; Reversal learning ; Basal ganglia ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The ability to inhibit previously learned visuomotor associations is essential for efficient learning of novel behaviors. While the neural basis of the system that might control interactions between competing motor memories is not known, it has been demonstrated that animals with ventral and orbital prefrontal cortex (PFC) deficits have particular difficulties in learning to withhold responses to previously conditioned sensory stimuli. Here we measured regional cerebral blood flow (rCBF), using positron emission tomography, during learning of a novel motor task that required inhibition of a previously learned motor memory. Subjects (n=24) learned reaching movements in a force field (field A). After a variable time interval, some subjects (n=15) learned to reach in a field with a reversed pattern of forces (field B). When the time interval was short (10 min), learning in field B was coincident with a reactivation of regions that had become initially activated during learning in field A: the left putamen and bilaterally in the dorsolateral PFC. Behaviorally, this was accompanied with perseveration that lasted for hundreds of movements, suggesting an instantiation of the internal model for field A during learning in field B. Neither the reactivation nor the perseveration were observed in a different group of subjects that learned field B at 5.5 h. We found that the regions which significantly differentiated the two groups during learning of B were in the ventrolateral PFC (bilaterally): there were sharp decreases in rCBF here in the 5.5 group but not in the 10-min group. At 5.5 h motor learning again involved the striatum, but this time in the left caudate. Neither the caudate nor the ventral PFC had exhibited learning-related activity in field A. Instead, they showed changes in rCBF during the reversal of the learning problem when the previously acquired motor memory was successfully gated. The results demonstrate that: (1) perseveration of a competing motor memory may be linked to reactivation of the neural circuit that participated in acquiring that memory, and (2) the ventral PFC may play an important role in the inhibitory control of the competing motor memory.
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  • 48
    ISSN: 1432-1106
    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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  • 49
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    Experimental brain research 125 (1999), S. 43-49 
    ISSN: 1432-1106
    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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  • 50
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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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  • 51
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    Keywords: Key words Three-dimensional pointing ; Human ; Remembered targets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The accuracy of visually guided pointing movements decreases with speed. We have shown that for movements to a visually defined remembered target, the variability of the final arm endpoint position does not depend on movement speed. We put forward a hypothesis that this observation can be explained by suggesting that movements directed at remembered targets are produced without ongoing corrections. In the present study, this hypothesis was tested for pointing movements in 3D space to kinesthetically defined remembered targets. Passive versus active acquisition of kinesthetic information was contrasted. Pointing errors, movement kinematics, and joint-angle coordination were analyzed. The movements were performed at a slow speed (average peak tangential velocity of about 1.2 m/s) and at a fast speed (2.7 m/s). No visual feedback was allowed during the target presentation or the movement. Variability in the final position of the arm endpoint did not increase with speed in either the active or the passive condition. Variability in the final values of the arm-orientation angles determining the position of the forearm and of the upper arm in space was also speed invariant. This invariance occurred despite the fact that angular velocities increased by a factor of two for all the angles involved. The speed-invariant variability supports the hypothesis that there is an absence of ongoing corrections for movements to remembered targets: in the case of a slower movement, where there is more time for movement correction, the final arm endpoint variability did not decrease. In contrast to variability in the final endpoint position, the variability in the peak tangential acceleration increased significantly with movement speed. This may imply that the nervous system adopts one of two strategies: either the final endpoint position is not encoded in terms of muscle torques or there is a special on-line mechanism that adjusts movement deceleration according to the muscle-torque variability at the initial stage of the movement. The final endpoint position was on average farther from the shoulder than the target. Constant radial-distance errors were speed dependent in both the active and the passive conditions. In the fast speed conditions, the radial distance overshoots of the targets increased. This increase in radial-distance overshoot with movement speed can be explained by the hypothesis that the final arm position is not predetermined in these experimental conditions, but is defined during the movement by a feedforward or feedback mechanism with an internal delay.
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  • 52
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    Experimental brain research 125 (1999), S. 265-270 
    ISSN: 1432-1106
    Keywords: Key words Tendon reflexes ; Biceps femoris ; Gait ; Ia afferents ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  During gait it is generally accepted that there is a reduction in amplitude of H-reflexes as compared to standing. For short-latency stretch reflexes, however, it is less clear whether a similar reduction in reflex gain is present during locomotion. Stretches of constant amplitude are hard to produce under these circumstances and for this reason some previous studies on the biceps femoris (BF) have used ”reduced gait” in which the stimulated leg is stepping on the spot while the contralateral leg is walking on a treadmill. With this method it was possible to show that BF tendon jerk reflexes are larger at end swing and therefore are likely to contribute to the EMG burst normally occurring in that part of the step cycle when the BF is rapidly stretched. In the present study two questions were addressed: first, whether the reflex is different in size during gait compared to standing and, second, whether it is modulated in size during the gait cycle not only during reduced but also during normal gait. It was found that during both types of gait there was a general reflex depression with regard to the respective control values obtained during standing at similar EMG activity levels. In previous studies on soleus and quadriceps, discrepancies between EMG activity and reflex amplitude have been ascribed to changes in presynaptic inhibition of Ia terminals mediating the afferent volley of the reflex. Based on the data presented, this may also be true for the BF. In both normal and reduced gait the reflex was similarly modulated in size, showing a maximum at the end of swing. This similarity implies that reduced gait may be useful as an acceptable alternative for normal gait in studies on phase-dependent reflex modulation during locomotion.
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  • 53
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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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  • 54
    ISSN: 1432-1076
    Keywords: Key words HIV-1 ; T-cells ; CD69 ; Activation ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We evaluated the use of a whole-blood assay that measures spontaneous and activation-induced CD69 expression on peripheral blood T-cells in vitro for assessment of T-cell function in HIV-1-infected paediatric patients. Heparinized venous blood from 28 HIV-1 positive children and adolescents and 23 healthy controls was incubated for 4 h with or without 5 μg/ml phytohaemagglutinin (PHA). Thereafter, analysis of CD69 expression on CD4+ and CD8+ T-cells was done by flow cytometry; simultaneously we determined CD4+ T-cell counts and plasma HIV-1 viral load. Neither spontaneous nor PHA-induced CD69 expression differed significantly between HIV-1 positive patients and healthy controls. However, T-cells from HIV-1 positive patients with plasma HIV-1 viral load levels above 70 × 103 copies/ml showed a higher spontaneous CD69 expression than T-cells from patients with lower plasma viral load levels in different stages of the disease. Antiretroviral treatment in four patients reduced spontaneous CD69 expression in CD4+ T-cells and PHA-induced CD69 expression in CD4+ and CD8+ T-cells significantly after 8 weeks of therapy. Conclusion Spontaneous and activation-induced expression of the early (activation) antigen CD69 on peripheral blood T-cells does not distinguish HIV-1 positive patients from HIV-1 negative healthy controls and is not correlated with peripheral blood CD4+ T-cell counts. This test may not be a reliable marker for functional T-cell deficiency during early stages of HIV disease. Increased spontaneous as well as PHA-induced CD69 expression on T-cells from HIV-1-infected children and adolescents in vitro may rather reflect HIV-induced pre-activation of T-cells in vivo.
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  • 55
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    European journal of pediatrics 158 (1999), S. 662-667 
    ISSN: 1432-1076
    Keywords: Key words Somatosensory evoked potentials ; Far-field potentials ; Achondroplasia ; Foramen magnum stenosis ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Children with achondroplasia may have high cervical myelopathy due to stenosis of the cranio-cervical junction resulting in neurological disability and an increased rate of sudden death. To detect myelopathy we recorded somatosensory evoked potentials (SEPs) after median nerve stimulation in 30 patients with achondroplasia aged 13 months to 18 years (mean 6 years). In addition to the conventional technique of recording the cortical N20 and the central conduction time (CCT), we employed a noncephalic reference electrode recording the subcortical waveforms N13b and P13, generated near the cranio-cervical junction. The findings were related to the clinical status and MRI results. Eighteen patients had MRI evidence of spinal cord compression with indentation or narrowing of the upper cervical cord, and 13 showed signs of myelomalacia. Seven patients had neurological abnormalities. The sensitivities of the SEPs were 0.89 for cervical cord compression, 0.92 for myelomalacia and 1.0 for the clinically symptomatic patients. There were no false-positive results. The subcortical SEPs were more sensitive than the conventional recordings. However, the conventional SEPs were highly specific in the most severely affected patients; here the specificity was 1.0 for patients with myelomalacia and 0.96 for symptomatic patients. Postoperative SEPs improved after occipital decompression in two children. Conclusion The analysis of somatosensory evoked potentials, in particular of subcortical tracings, is useful in the detection of early cervical myelopathy in children with achondroplasia. Early neurosurgical decompression may prevent irreversible damage.
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  • 56
    ISSN: 1432-1076
    Keywords: Key words Antithrombin concentrate ; Children ; Septicaemia ; Acquired antithrombin deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Consumption coagulopathy is a serious problem in childhood. In addition to treatment of the underlying disease, consumption coagulopathy was previously treated with heparin. Nowadays it is treated by substitution of coagulation factors, especially antithrombin (AT) concentrate, alone or in combination with heparin. In this pilot study we administered AT concentrate (dosage 80 U/kgbw/d), without additional heparin treatment, to 29 children beyond infancy with acquired AT deficiency. Antithrombin, platelet count, fibrinogen, PT, and APTT were assayed before and during the course of AT substitution. These coagulation parameters returned to normal 48 hours after normalisation of the plasma AT level. AT levels normalised within 24 h of initial substitution in all children. Lethal outcome due to the underlying disease was observed in only two children. Conclusion Data of this pilot study suggest that, concomitantly with the treatment of the underlying disease, consumption coagulopathy in childhood can be managed successfully with early substitution of AT concentrate.
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  • 57
    ISSN: 1432-1076
    Keywords: Key words Coagulation ; Fibrinolysis ; Head injury ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was designed to evaluate the post-trauma haemostatic changes in 27 children with severe cranio-cerebral trauma defined by a modified Glasgow Coma Score (GCS) 〈10. Blood samples for coagulation studies (fibrinogen, von Willebrand factor (vWf), factor VIII:C, antithrombin, protein C, plasminogen, tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI), D-dimer) were obtained within two hours of admission, 24 h later, and on days 3–5, 7–9, 21 and 35. Data of this study indicate that alterations of coagulation in paediatric patients are similar to those in adults: On hospitalisation, activated haemostasis was found with decreased fibrinogen, antithrombin and protein C along with enhanced t-PA and PAI. Twenty-four hours later, hypercoagulability with significantly increased vWF and fibrinogen started, with a peak level within the second week. Within 24 h of admission, 17 children developed disseminated intravascular coagulation (DIC) with a clear-cut decrease of antithrombin and fibrinogen together with platelet consumption and enhanced D-dimer. The outcome of children with DIC was significantly poorer than in those without DIC. Complete recovery was seen in five patients; sequelae no handicap and moderate disability were each found in six patients. Severe disability was diagnosed in two children, and fulminant DIC with lethal outcome occurred in eight patients. The GCS (P 〈 0.01) and the occurrence of DIC (P 〈 0.005) showed the strongest association with the patients' clinical outcome. Conclusion Our data underline the significance of post-trauma disturbances of the haemostatic system for the clinical course and outcome in children with severe cranio-cerebral injuries.
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  • 58
    ISSN: 1432-1084
    Keywords: Key words: Lung disease ; Pneumoconiosis ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We report two cases of children with malignancies and subpleural nodules found on computed tomography (CT) scan. In both cases the diagnosis was anthracosis. This pathologic condition has never been reported in children. Causes of anthracosis include a smoking environment, living in urban areas and air pollution.
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  • 59
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    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.
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  • 60
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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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  • 61
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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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  • 62
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    Experimental brain research 124 (1999), S. 469-473 
    ISSN: 1432-1106
    Keywords: Key words Form from motion ; Visual development ; Visual acuity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The development of dynamic vision was investigated in 400 healthy subjects (200 females and 200 males) aged between 4 and 24 years. The test consisted of a computer-generated random-dot kinematogram in which a Landolt ring was briefly presented as a form-from-motion stimulus. Motion contrast between the ring and background was varied in terms of the percentage of dots moving coherently within the ring in four levels (100%, 50%, 30%, and 20%). The subject’s task was to indicate the position of a gap in the ring (left, right, top, bottom). Results show a clear increase in performance with age for all motion contrast levels, with the greatest changes for the lowest levels. Adult performance was reached at the age of 15 years. Luminance-based static acuity measured with the Landolt test was poorly correlated with acuity for its form-from-motion analogue.
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  • 63
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    Experimental brain research 124 (1999), S. 503-512 
    ISSN: 1432-1106
    Keywords: Key words Reaching movements ; Memory for positions ; Laterality ; Posture copying ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Many recent studies indicate that memory for final position is superior to memory for movement. There is ambiguity about what is meant by the term final position, however. Is it final spatial location or final posture? According to a recently proposed theory by Rosenbaum et al., which maintains that stored postures form the basis for movement planning, when people try to return to recently reached positions, they should try to adopt the postures they just occupied. An alternative view, which holds that movements are primarily planned with respect to spatial locations, predicts that subjects should tend to return to places in external space. We describe an experiment that tested these opposing predictions. The experiment relied on the notion that if people store and use postures, they should ”copy” the posture adopted with one arm to the other arm when possible. The results support this hypothesis.
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  • 64
    ISSN: 1432-1106
    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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  • 65
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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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  • 66
    ISSN: 1432-1106
    Keywords: Key words Grip force ; Force control ; Parabolic flight ; Microgravity ; Hypergravity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In the present study, grip forces exerted against a stationary held object were recorded during parabolic flights. Such flight maneuvers induce changes of gravity with two periods of hypergravity, associated with a doubling of normal terrestrial gravity, and a 20 s period of microgravity. Accordingly, the object’s weight changed from being twice as heavy as normally experienced and weightless. Grip-force recordings demonstrated that force control was seriously disturbed only during the first experience of hyper- and microgravity, with the grip forces being exceedingly high and yielding irregular fluctuations. Thereafter, however, grip force traces were smooth, the force level was scaled to the object’s weight under normal and high-G conditions, and the grip force changed in parallel with the weight during the transitions between hyper- and microgravity. In addition, during weightlessness, when virtually no force was necessary to stabilize the object, a low force was established, which obviously represented a reasonable safety margin for preventing possible perturbations. Thus, all relevant aspects of grip-force control observed under normal gravity conditions were preserved during gravity changes induced by parabolic flights. Hence, grip-force control mechanisms were able to cope with hyper- and microgravity, either by incorporating relevant receptor signals, such as those originating from cutaneous mechanoreceptors, or by adequately including perceived gravity signals into control programs. However, the adaptation to the uncommon gravity conditions was not complete following the first experience; finer tuning of the control system to both hyper- and microgravity continued over the measurement interval, presumably with a longer observation period being necessary before a stable performance can be reached.
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  • 67
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    Experimental brain research 129 (1999), S. 156-160 
    ISSN: 1432-1106
    Keywords: Key words Optokinetic nystagmus ; Depth-from-motion ; Transparent motion ; Ambiguous ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  When two visual patterns moving in opposite directions are superimposed, they appear to be at different depths and to slide over each other. Because the stimulus does not specify the depth-order between the surfaces, this transparent motion perception is essentially ambiguous. With prolonged observation, the perceived depth-order of the two moving surfaces reverses spontaneously. In the present study, the correlation between the perceived direction of transparent motion and optokinetic nystagmus (OKN) was examined. While viewing superimposed random-dot patterns moving in opposite horizontal or vertical directions, subjects attempted to fixate the center of the stimulus, while paying attention to either the near or far depth plane, and reported any changes of the direction of surface-motion at the attended depth. Even with attention focused on a particular depth, the spontaneous reversal of transparent motion perception still occurred. This indicates that the perceptual reversal may reflect a preattentive mechanism for depth-from-motion. Furthermore, the OKN slow-phase tended to be in the same direction as the perceived motion of the surface at the attended depth. These results support the idea that the mechanisms for OKN maintenance are sensitive to perception of depth-from-motion and, therefore, cortically mediated.
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  • 68
    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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  • 69
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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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    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.
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  • 71
    ISSN: 1432-1106
    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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    Neuroradiology 41 (1999), S. 512-516 
    ISSN: 1432-1920
    Keywords: Key words Meninges ; Tumours ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Childhood meningeal tumours are uncommon and mostly meningiomas. We reviewed the histological and radiological findings in meningeal tumours in six children aged 12 years or less (four benign meningiomas, one malignant meningioma and one haemangiopericytoma). Compared to the adult counterpart, childhood meningiomas showed atypical features: cysts, haemorrhage, aggressiveness and unusual location. MRI features varied according to the site of the tumour, histology, haemorrhage, and presence of intra- or peritumoral cysts. Diagnosis of the extra-axial tumour was relatively easy in two patients with meningiomas, one malignant meningioma and one haemangiopericytoma. MRI findings strongly suggested an intra-axial tumour in two patients with benign meningiomas, because of severe adjacent edema. Awareness of the variable findings of childhood meningiomas and similar tumours may help in differentiation from brain tumours.
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  • 73
    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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    Neuroradiology 41 (1999), S. 929-934 
    ISSN: 1432-1920
    Keywords: Key words Magnetic resonance imaging ; diffusion weighted ; Myelination ; Children
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the changes in brain water diffusion in childhood as seen on diffusion-weighted MRI in 30 children from 1 day of life to 17 years to provide a data base and to investigate the correlation of diffusion changes with known patterns of white matter maturation. The apparent diffusion coefficient (ADC) and apparent anisotropy (AA) were calculated in numerous regions of the brain to include major white matter tracts and gray matter. ADC and AA values were directly related to the structural maturity and compactness of the white matter tracts and changed with aging in a way that predated early myelination markers such as signal change on T1- or T2-weighted images. Diffusion of water is sensitive to structural changes in the brain such as white matter maturation and may be useful in investigating white matter disorders.
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  • 75
    ISSN: 1432-2099
    Keywords: Key words Case-control study ; Children ; CNS tumour ; Environmental exposure ; Indoor radon ; Leukaemia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract  A population-based case-control study on risk factors for childhood malignancies was used to investigate a previously reported association between elevated indoor radon concentrations and childhood cancer, with special regard to leukaemia. The patients were all children suffering from leukaemia and common solid tumours (nephroblastoma, neuroblastoma, rhabdomyosarcoma, central nervous system (CNS) tumours) diagnosed between July 1988 and June 1993 in Lower Saxony (Germany) and aged less than 15 years. Two population-based control groups were matched by age and gender to the leukaemia patients. Long-term (1 year) radon measurements were performed in those homes where the children had been living for at least 1 year, with particular attention being paid to those rooms where they had stayed most of the time. Due to the sequential study design, radon measurements in these rooms could only be done for 36% (82 leukaemias, 82 solid tumours and 209 controls) of the 1038 families initially contacted. Overall mean indoor radon concentrations (27 Bq m–3) were low compared with the measured levels in other studies. Using a prespecified cutpoint of 70 Bq m–3, no association with indoor radon concentrations was seen for the leukaemias (odds ratio (OR): 1.30; 95% confidence interval (95% CI): 0.32–5.33); however, the risk estimates were elevated for the solid tumours (OR: 2.61; 95% CI: 0.96–7.13), mainly based on 6 CNS tumours. We did not find any evidence for an association between indoor radon and childhood leukaemia, which is in line with a recently published American case-control study. There is little support for an association with CNS tumours in the literature.
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  • 76
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    Der Radiologe 39 (1999), S. 472-477 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Fremdkörper ; Ingestion ; Kinder ; Diagnostik ; Key words Foreign body ; Ingestion ; Children ; Diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Foreign body ingestion is not infrequent in infants and children. The diagnosis of radiopaque foreign body ingestion does not pose a major problem. It is crucial to take an X-ray from the pharynx to the level of the pylorus. If a foreign body that might get stuck at the ileocoecal valve is ingested, it is necessary to perform a radiograph of the whole abdomen. Foreign bodies that do not pass the cardia must be extracted endoscopically. In the case of foreign bodies with a smooth contour that have passed the pylorus, parents are advised to check the child’s stool or collect it and bring it for X-raying. If after a week there is no definite evidence that the foreign body has been excreted a follow-up radiograph is carried out. If the foreign body is still in the stomach or duodenum, endoscopy is necessary. The detection of nonopaque foreign bodies can be facilitated by giving oral contrast medium, making the depiction of the foreign body as a filling defect possible. As a complication, perforation can occur, the diagnosis of which may entail the use of sonography, conventional radiography and, to a lesser extent, CT.
    Notes: Zusammenfassung Fremdkörperingestion ist im späten Säuglings- und frühen Kleinkindalter kein seltenes Ereignis. Die Diagnose röntgendichter Fremdkörper bereitet keine Schwierigkeiten. Hierbei ist jedoch zu beachten, daß die Region vom Pharynx bis zum Pylorus abgebildet sein sollte. Wurden Fremdkörper verschluckt, bei denen die Gefahr der Einklemmung in der Bauhin’schen Klappe besteht, sollte das komplette Abdomen bis zum Anus dargestellt werden. Fremdkörper, welche die Kardia nicht passieren, müssen endoskopisch extrahiert werden. Haben glatt begrenzte Fremdkörper den Pylorus passiert, werden die Eltern aufgefordert, den Stuhl zu untersuchen oder zu sammeln und ihn zur röntgenologischen Untersuchung mitzubringen. Sollte der Fremdkörper innerhalb einer Woche nicht auffindbar sein, wird eine Kontrolluntersuchung durchgeführt. Ist der Fremdkörper dann noch im Magen oder im Duodenum, sollte er ebenfalls extrahiert werden. Der Nachweis nicht röntgendichter Fremdkörper kann mittels Gabe von positivem Kontrastmittel als Aussparungsfigur gelingen. Als Komplikation kann eine Perforation auftreten. Hierbei dienen Sonographie, konventionelles Röntgen und gegebenenfalls CT zur Diagnosefindung.
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  • 77
    ISSN: 1432-2072
    Keywords: Key words Marijuana ; Human ; THC ; Withdrawal ; Dependence ; Tolerance ; Subjective effect ; Performance ; Food intake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Symptoms of dependence and withdrawal after the frequent administration of high doses (210 mg/day) of oral Δ9-tetrahydrocannabinol (THC) have been reported, yet little is known about dependence on lower oral THC doses, more relevant to levels attained by smoking marijuana. In a 20-day residential study, male (n = 6) and female (n = 6) marijuana smokers worked on five psychomotor tasks during the day (0915–1700 hours), and in the evening engaged in private or social recreational activities (1700–2330 hours); subjective-effects measures were completed 10 times/day, and a sleep questionnaire was completed each morning. Food and beverages were available ad libitum from 0830 to 2330 hours. Capsules were administered at 1000, 1400, 1800, and 2200 hours. Placebo THC was administered on days 1–3, 8–11, and 16–19. Active THC was administered on days 4–7 (20 mg qid) and on days 12–15 (30 mg qid). Both active doses of THC increased ratings of “High,”“Good Drug Effect,” and “Willingness to Take Dose Again” compared to baseline (days 1–3). THC also increased food intake by 35–45%, and decreased verbal interaction among participants compared to placebo baseline. Tolerance developed to the subjective effects of THC but not to its effects on food intake or social behavior. Abstinence from THC increased ratings of “Anxious,”“Depressed,” and “Irritable,” decreased the reported quantity and quality of sleep, and decreased food intake by 20–30% compared to baseline. These behavioral changes indicate that dependence develops following exposure to lower daily doses of THC than have been previously studied, suggesting that the alleviation of abstinence symptoms may contribute to the maintenance of daily marijuana use.
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  • 78
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    Psychopharmacology 141 (1999), S. 395-404 
    ISSN: 1432-2072
    Keywords: Key words Marijuana ; Dependence ; Withdrawal ; Human ; Tolerance ; Subjective effect ; Performance ; Residential laboratory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Symptoms of withdrawal after oral Δ9-tetrahydrocannabinol (THC) administration have been reported, yet little is known about the development of dependence on smoked marijuana in humans. In a 21-day residential study, marijuana smokers (n = 12) worked on five psychomotor tasks during the day (0915–1700 hours), and in the evening engaged in recreational activities (1700–2330 hours); subjective-effects measures were completed 10 times/day. Food and beverages were available ad libitum from 0830 to 2330 hours. Marijuana cigarettes (0.0, 1.8, 3.1% THC) were smoked at 1000, 1400, 1800, and 2200 hours. Placebo marijuana was administered on days 1–4 . One of the active marijuana doses was administered on days 5–8, followed by 4 days of placebo marijuana (days 9–12). The other concentration of active marijuana cigarettes was administered on days 13–16, followed by 4 days of placebo marijuana (days 17–20); the order in which the high and low THC-concentration marijuana cigarettes were administered was counter-balanced between groups. Both active doses of marijuana increased ratings of “High,” and “Good Drug Effect,” and increased food intake, while decreasing verbal interaction compared to the placebo baseline (days 1–4). Abstinence from active marijuana increased ratings such as “Anxious,”“Irritable,” and “Stomach pain,” and significantly decreased food intake compared to baseline. This empirical demonstration of withdrawal from smoked marijuana may suggest that daily marijuana use may be maintained, at least in part, by the alleviation of abstinence symptoms.
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  • 79
    ISSN: 1432-2072
    Keywords: Key words Aggression ; Tryptophan ; Serotonin ; Human ; Diet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Some studies have shown that sharp reduction of L-tryptophan (Trp) concentration in plasma results in increases in laboratory-measured aggression. Conversely, raising plasma Trp has blunted aggression. These effects are presumably due to impaired or enhanced serotonin synthesis and neurotransmission in the brain. In this study, the laboratory-measured aggressive behavior of eight men under both Trp depletion (T-) and Trp loading (T+) conditions was compared to their aggressive behavior under food-restricted control conditions (overnight fast without an amino acid beverage). Subjects were provoked by periodic subtraction of money which was attributed to a fictitious other participant, and aggression was defined as the number of retaliatory responses the subject made ostensibly to reduce the earnings of the (fictitious) other participant. Following ingestion of the T- beverage, aggressive responding was significantly elevated relative to the food-restricted control condition, and this increased aggressive behavior became more pronounced across behavioral testing sessions on a time-course which paralleled previously documented decreases in plasma Trp concentrations. In contrast, no changes were observed in aggressive responding under T+ conditions relative to food-restricted conditions. These within-subject behavioral changes under depleted plasma Trp conditions support earlier indications of a role of serotonin in regulating aggression.
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  • 80
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Human ; Self-administration ; D1 agonist ; Subjective effect ; Craving ; Cardiovascular effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rationale: Data in laboratory animals suggest that D1 receptor agonists may have potential utility for the treatment of cocaine abuse. Objective: The effects of ABT-431, a selective agonist at the dopamine D1 receptor, on the reinforcing, cardiovascular and subjective effects of cocaine were investigated in humans. Method: Nine experienced cocaine smokers (8M, 1F), participated in nine self-administration sessions while residing on an inpatient research unit: three doses of ABT-431 (0, 2, 4 mg IV) were each given in combination with three doses of smoked cocaine (0, 12, 50 mg). ABT-431 was intravenously administered over a 1-h period immediately prior to cocaine self-administration sessions. A six-trial choice procedure (cocaine versus $5 merchandise vouchers) was utilized, with sessions consisting of: (a) one sample trial, where participants received the cocaine dose available that day, and (b) five choice trials, where participants chose between the available cocaine dose and one merchandise voucher. Results: ABT-431 did not affect the number of times participants chose to smoke each dose of cocaine, but produced significant dose-dependent decreases in the subjective effects of cocaine, including ratings of “High,”“Stimulated,” dose liking, estimates of dose value, “Quality,” and “Potency.” Furthermore, there was a trend for ABT-431 (4 mg) to decrease cocaine craving. ABT-431 also increased heart rate, while decreasing systolic and diastolic pressure at each dose of cocaine. Conclusions: These data suggest that D1 agonists may have potential utility for the treatment of cocaine abuse.
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  • 81
    ISSN: 1432-2072
    Keywords: Key words Methadone maintenance treatment ; Chiral analysis ; Methadone ; Plasma ; Urine ; Abused drug ; Daily variation ; Rating scales ; Dose-adjustment ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rationale: One of the major problems in methadone maintenance treatment is to find optimal individual doses for the patients. Objective: The present study investigated whether the use of rating scales together with enantioselective analysis of l-methadone might facilitate dose adjustments in a clinical situation. Methods: Rating scales were used to evaluate subjective and objective signs of well-being in relation to plasma methadone concentrations in two groups of patients receiving methadone maintenance treatment. The first group (n = 25) was well-adjusted according to clinical observations and were satisfied with their methadone doses (86.2 ± 4.3 mg). The second group (n = 25) was in need of the methadone dose adjustment; they complained of low dosing, despite a dose level of 69.2 ± 4.0 mg/day. Results: Results indicated a significant correlation between dose and methadone concentration among dissatisfied patients only. The trough levels of d,l-methadone and l-methadone, as well as their elimination rates, were similar in the two groups of patients. There was a variable predominance of l- over d-methadone in plasma (ratio ≈1.2; range 0.7–3.6). Illicit use of drugs by the patients was related to the methadone dose and to satisfaction with the dose received. Increased illicit drug use among dissatisfied patients was successfully eliminated by raising the methadone dose. Subjective and objective ratings of the satisfied patients were quite stable throughout the evaluation period, whereas the ratings of the dissatisfied patients were unstable. These patients seemed to be more sensitive to low trough levels of methadone than the satisfied patients. Associations between the subjective and objective ratings and plasma methadone, along with background characteristics, were characterized by multiple regression analyses. The plasma concentrations of l-methadone were one of the most important explanatory variables in these analyses. Associations between well-being and methadone concentrations in plasma were stronger for l-methadone than for d,l-methadone. Conclusions: Selective measurements of the active isomer and the use of rating scales should be of clinical value when monitoring methadone maintenance treatment patients.
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  • 82
    ISSN: 1432-2072
    Keywords: Key words MDMA ; Ecstasy ; Human ; EEG ; Power ; Coherence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rationale: Despite animal studies implicating 3,4-methylenedioxymethamphetamine (MDMA or Ecstasy) in serotonergic neurotoxicity, there is little direct evidence of changes in neural function in humans who use MDMA as a recreational drug. Objective: The present study investigated whether there is a correlation between quantitative EEG variables (spectral power and coherence) and cognitive/mood variables, and level of prior use of MDMA. Methods: Twenty-three recreational MDMA users were studied. Resting EEG was recorded with eyes closed, using a 128-electrode geodesic net system, from which spectral power, peak frequency and coherence levels were calculated. Tests of intelligence (NART), immediate and delayed memory, frontal function (card sort task), and mood (BDI and PANAS scales) were also administered. Pearson correlation analyses were used to examine the relationship between these measures and the subject’s consumption of MDMA during the previous 12-month period. Partial correlation was used to control for the use of other recreational drugs. Results: MDMA use was positively correlated with absolute power in the alpha (8–12 Hz) and beta (12–20 Hz) frequency bands, but not with the delta (1–3 Hz) or theta (4–7 Hz) bands. MDMA use was negatively correlated with EEG coherence, a measure of synchrony between paired cortical locations, in posterior brain sites thought to overly the main visual association pathways of the occipito-parietal region. MDMA use did not correlate significantly with any of the mood/cognitive measures except the card sort task, with which it was weakly negatively correlated. Conclusions: Alpha power has been shown to be inversely related to mental function and has been used as an indirect measure of brain activation in both normal and abnormal states. Reduced coherence levels have been associated with dysfunctional connectivity in the brain in disorders such as dementia, white-matter disease and normal aging. Our results may indicate altered brain function correlated with prior MDMA use, and show that electroencephalography may be a cheap and effective tool for examining neurotoxic effects of MDMA and other drugs.
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  • 83
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    Psychopharmacology 145 (1999), S. 162-174 
    ISSN: 1432-2072
    Keywords: Key words Opioid blockade ; Buprenorphine ; Naltrexone ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rationale: One therapeutic benefit of mu opioid agonist or antagonist maintenance is the resultant attenuation of the effects of illicit opioids. It is important to characterize the development and duration of opioid blockade produced by buprenorphine, a novel opioid dependence pharmacotherapy. Objective: This study characterized the ability of buprenorphine to attenuate opioid effects during treatment initiation and discontinuation compared to naltrexone and placebo. Methods: Opioid-experienced volunteers (n = 8) participated in this 10-week, inpatient, double-blind, within-subject, crossover study. Five randomized conditions [buprenorphine (2 and 8 mg, sublingually), naltrexone (25 and 100 mg, PO) and placebo] were each examined during a 2-week period; the test drug was given for 7 days followed by a 7-day placebo wash-out. Cumulative doses of hydromorphone (0, 2 and 4 mg, IM, 45 min apart) were administered thrice-weekly corresponding with treatment and wash-out days 1, 3, and 5; behavioral, physiological and pharmacokinetic measures were collected. Results: Buprenorphine alone produced dose-related prototypic agonist effects during induction (i.e., positive mood, respiratory depression, miosis); tolerance developed only to the subjective effects. Buprenorphine 2 mg partially attenuated the effects of hydromorphone, while nearly complete attenuation was observed with 8 mg that lasted up to 72 h after discontinuation. Both naltrexone doses produced complete hydromorphone blockade after a single dose; blockade of the behavioral, but not physiological, effects persisted for 5 days after discontinuation of 100 mg. Conclusions: These data suggest that 2 mg buprenorphine is a sub-therapeutic maintenance dose, both buprenorphine 8 mg and naltrexone produce immediate and efficacious opioid blockade, and adequate protection against illicit opioids may be achieved with less-than-daily dosing.
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  • 84
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    Psychopharmacology 145 (1999), S. 39-51 
    ISSN: 1432-2072
    Keywords: Key words Zaleplon ; Triazolam ; Benzodiazepine ; Hypnotics ; Learning ; Memory ; Abuse potential ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Zaleplon, a pyrazolopyrimidine that is under development as a hypnotic, produces its pharmacological effects at the benzodiazepine-recognition site on the GABAA benzodiazepine-receptor complex. Unlike most benzodiazepines, zaleplon binds selectively to the BZ1 (ω1) subtype of the benzodiazepine receptor. The present study compared the acute subject-rated effects, performance-impairing effects, and abuse potential of zaleplon and triazolam, a triazolobenzodiazepine hypnotic, in 14 healthy volunteers with histories of drug abuse. Zaleplon (25, 50, and 75 mg), triazolam (0.25, 0.5, and 0.75 mg) and placebo were administered orally in this double-blind, crossover study. Zaleplon and triazolam produced comparable dose-related effects on several subject-rated drug-effect questionnaires. Zaleplon and triazolam also produced comparable dose-dependent decrements on several performance tasks including balance, circular lights, digit-enter and recall, DSST, picture recall/recognition and repeated acquisition. Same-day and next-day subject-rated measures reflecting abuse potential (e.g., drug liking, good effects, and monetary street value) also suggest that zaleplon and triazolam were comparable. The only notable between-drug difference observed in the present study was that the time-action function of zaleplon differed from that of triazolam. The onset time, time to maximum drug effect, and duration of action were shorter with zaleplon than triazolam. Thus, despite its non-benzodiazepine structure and unique benzodiazepine-receptor binding profile, the behavioral pharmacological profile of zaleplon is similar to that of triazolam.
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  • 85
    ISSN: 1432-2072
    Keywords: Key words Nicotine ; Drug discrimination ; Training conditions ; Testing conditions ; Three-choice procedure ; Subjective effect ; Human ; Smoking status
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Discrimination of a drug’s interoceptive stimulus effects often depends substantially on training and testing conditions. Objectives: We examined changes in nicotine discrimination behavior in humans as a function of lowering the training dose and of varying the discrimination testing procedure. Methods: Smokers and never-smokers (n=10 each) were initially trained to discriminate 20 µg/kg nicotine by nasal spray from placebo (0) and tested on generalization of discrimination responding across a range of doses from 0 to 20 µg/kg. Each subsequently learned to reliably discriminate progressively smaller doses of nicotine from placebo until his or her threshold dose for discrimination was identified (mean=2.7 µg/kg). A repeat testing of generalization responding across 0–20 µg/kg was then conducted, using placebo and the subject’s threshold dose as training doses. Generalization testing involved both two-choice and three-choice (novel response option) quantitative procedures. Results: A significant shift to the left was seen in nicotine-appropriate responding in the two-choice procedure when the nicotine training dose was lowered (i.e. from the first to the second test of generalization). In the three-choice procedure, however, there was no such leftward shift. Instead, in never-smokers, a flattening of nicotine-appropriate responding occurred with a lowering of the training dose, while novel-appropriate responding significantly increased. The subjective effects of ”head rush” and, in never-smokers only, ”jittery” also showed a shift to the left in their relationship with nicotine generalization dose when the training dose was lowered. Conclusions: These results confirm the importance of training and testing conditions on discrimination behavior and subjective drug responses within subjects and demonstrate the utility of the novel-response, three-choice procedure for assessing qualitatively different stimulus effects of novel drug doses.
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  • 86
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    Psychopharmacology 146 (1999), S. 111-118 
    ISSN: 1432-2072
    Keywords: Key words Buprenorphine ; Heroin dependence ; Opioid dependence ; Human ; Opioid withdrawal ; Treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Administration of double the maintenance dose of buprenorphine has been shown to permit every-other-day dosing. Whether longer periods between dosing can be achieved is unknown. Objectives: To examine whether triple the maintenance dose can be administered every 72 h without opioid withdrawal or intoxication. Methods: Sixteen opioid-dependent outpatients each received three conditions (1) the maintenance dose of buprenorphine every 24 h, (2) double the maintenance dose every 48 h, and (3) triple the maintenance dose every 72 h under double-blind placebo-controlled conditions. Each conditions was imposed in a random sequence for 21–22 days. Self report and observer measures were taken at 24-h intervals. Results: No significant differences were observed on measures of opioid agonist and withdrawal effects between the dosing conditions. However, averaging effects across conditions may obscure important within-condition effects. When conditions were analyzed by individual days within a condition, several significant effects were observed. For example, 24 h after administration of triple the maintenance dose, significant effects were observed in eight opioid agonist measures. Also, 72 h after administration of triple the maintenance dose, significant effects were observed on four measures of withdrawal. Neither adverse medical reactions nor excessive opioid intoxication were observed. Conclusions: These results suggest that buprenorphine may be administered safely every 72 h by tripling the maintenance dose, with only minimal withdrawal complaints. Importantly, this 72-h dosing may permit patients to attend clinic thrice weekly without the use of take-home doses.
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  • 87
    ISSN: 1432-2072
    Keywords: Key words Alcohol effect ; Impulsivity ; Working memory ; Executive function ; High-risk ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Impulsivity is associated with increased risk for alcoholism. Alcohol also may increase impulsive behavior, although little is known about the processes underlying this effect. Objectives: This study tested a model proposing that the executive processes of working memory (WM) and conditional associative learning (CAL) modulate behavioral inhibition. Subjects had either a positive (FHP) or a negative (FHN) family history of alcoholism. Hypotheses were that alcohol would increase Go/No-Go impulsive responding but only in subjects with low working memory capacity (low-WM), low-CAL ability, or FHP for alcoholism. The model also predicted that WM and CAL modulate inhibitory responses to contingency reversal on a Go/No-Go task. Methods: A Go/No-Go learning task with a midway contingency reversal was administered to 71 FHP and 78 FHN subjects when sober and after drinking one of two moderate doses of alcohol. WM (digits backward) and CAL (conditional spatial association task) were also assessed when sober. Results: Alcohol resulted in more false alarms but only in low-WM subjects. Both WM and CAL modulated learning to inhibit behavior after contingency reversal, suggesting separate modulation mechanisms for WM and CAL. Subjects with low- capacity WM and subjects with low-capacity CAL ability had more difficulty learning response inhibition after contingency reversal. FHPs and FHNs did not differ in their response to alcohol. Conclusions: The results support our model of the modulatory role of WM and CAL in the ongoing regulation of behavioral inhibitory systems. The results also suggest that individuals with low capacity WM are more susceptible to alcohol’s effect of increasing impulsive behavior, suggesting that alcohol reduces the capacity of working memory to modulate response inhibition.
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  • 88
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    Psychopharmacology 147 (1999), S. 200-209 
    ISSN: 1432-2072
    Keywords: Key words Benzodiazepine ; Flumazenil ; Precipitated withdrawal ; Antagonist ; Physical dependence ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Preclinical studies of the benzodiazepine antagonist flumazenil (Romazicon®) have contributed to the understanding of the physical dependence associated with chronic benzodiazepine use; when administered to animals chronically pretreated with benzodiazepines, flumazenil precipitates a withdrawal syndrome. However, few controlled clinical studies have been conducted. Objectives: The objective was to characterize the effects of flumazenil in long-term users of therapeutic doses of benzodiazepines. Methods: The acute physiological, participant-rated, and observer-rated effects of intravenously administered flumazenil (1 mg/70 kg) and caffeine (300 mg/70 kg; active drug control) were evaluated in an experimental group of 13 long-term users (mean 4.6 years) of low therapeutic doses (mean 11.2 mg/day diazepam equivalent) relative to a matched group of 13 volunteers without prior exposure to benzodiazepines in a double-blind, placebo-controlled, mixed design. Results: Whereas the experimental group did not differ from the control group with respect to the effects of placebo, and both groups showed some changes in response to caffeine (e.g., increased blood pressure and anxiety scores), only the experimental group showed considerable changes in physiological measures, participant ratings (e.g., increased ratings of dizziness, blurred vision, heart pounding, feelings of unreality, pins and needles, nausea, sweatiness, noises louder than usual, jitteriness, things moving, sensitivity to touch), and observer ratings in response to flumazenil; in addition, four participants developed panic attacks. Conclusions: This study clearly demonstrates that flumazenil can precipitate symptoms commonly associated with benzodiazepine withdrawal in chronic low-dose benzodiazepine users.
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  • 89
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    Psychopharmacology 147 (1999), S. 266-273 
    ISSN: 1432-2072
    Keywords: Key words Benzodiazepine ; Lorazepam ; Human ; Memory ; Auditory priming ; Visual priming ; Explicit memory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: Lorazepam has been repeatedly shown to impair both explicit memory and perceptual priming, a form of implicit memory, in the visual domain. However, the effects of this benzodiazepine on priming in other perceptual domains, such as auditory priming, have never been explored. Objective:The present study investigated whether the deleterious effects of lorazepam on perceptual priming are restricted to the visual domain, or if they could be extended to the auditory domain. Methods: Thirty-two healthy volunteers were randomly assigned to two parallel groups, placebo and lorazepam 0.038 mg/kg. The drug was administered orally, following a double-blind procedure. In the same subjects, perceptual priming was assessed in the auditory and visual domains using similar word-stem completion tasks, and explicit memory was explored using a free- recall task. Results: Lorazepam markedly reduced free-recall performance for visually and auditorily presented words. Lorazepam equally impaired visual and auditory priming. In the auditory word-stem completion task, prior presentation of a word facilitated perception of its stem in the placebo group. This facilitation effect was not observed in the lorazepam group. The lorazepam-induced impairment of priming was not due to sedation or explicit contamination. Conclusion: These results indicate that the deleterious effects of lorazepam on priming are not restricted to the visual modality, but extend to the auditory modality.
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  • 90
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    European journal of pediatrics 158 (1999), S. S154 
    ISSN: 1432-1076
    Keywords: Key words Veno-occlusive disease ; Antithrombin ; Children ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hepatic veno-occlusive disease (VOD) is a well-known complication of chemotherapy in Wilms tumor patients, particularly young children. Although this complication resolves uneventfully in most patients, fatal cases have been reported. Severe VOD after transplantation has a high mortality rate ranging from 45% to 98%. New hemostatic therapeutic strategies have significantly improved the prognosis of VOD. Chemotherapy-related VOD in Wilms tumor usually has a good prognosis. We describe two patients with Wilms tumor and one with acute lymphoblastic leukemia, who developed severe veno-occlusive disease of the liver according to the Baltimore criteria while undergoing chemotherapy; the symptoms were hepatomegaly, ascites, hyperbilirubinemia, weight gain and, in one patient, short-term lethargy. Elevated LDH levels of 872 to 12,000 U/l were observed in our patients. All patients had thrombocytopenia between 29,000 and 40,000/μl and decreased antithrombin (AT) and protein C levels; two patients had gastrointestinal bleeding. All patients developed a coagulopathy because of severe hepatic dysfunction. Two patients received low-dose heparin at the onset of VOD. The thrombolytic therapy was rapidly changed to AT supplementation (20–80 IU/kg bw 2× per day) without heparin when thrombocytes were very low or gastrointestinal bleeding occurred. Resolution of VOD was observed in all patients receiving AT alone. The chemotherapy was discontinued in a patient with accidental actinomycin D overdosage in view of the severity of symptoms. The remaining two patients received chemotherapy according to the therapy protocol after restitution. All patients survived without sequelae with a median follow-up of 28 months (range 8–48 months). Conclusion Hepatic veno-occlusive disease is a rare but increasingly recognized complication in pediatric cancer patients receiving conventional chemotherapy. AT supplementation constitutes a good alternative treatment of severe VOD in comparison with other thrombolytic therapies, particularly in patients at high risk of bleeding.
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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.
    Type of Medium: Electronic Resource
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  • 92
    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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  • 93
    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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  • 94
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    Experimental brain research 124 (1999), S. 422-428 
    ISSN: 1432-1106
    Keywords: Key words Lifting forces ; Size-weight illusion ; Microgravity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Individuals usually report for two objects of equal mass but different volume that the larger object feels lighter. This so-called size-weight illusion has been investigated for more than a century. The illusion is accompanied by increased forces, used to lift the larger object, resulting in a higher initial lifting speed and acceleration. The illusion holds when subjects know that the mass of the two objects is equal and it is likely that this also counts for the enlarged initial effort in lifting a larger box. Why should this happen? Under microgravity, subjects might be able to eliminate largely the weight-related component of the lifting force. Then, if persistent upward scaling of the weight-related force component had been the main cause of the elevated initial lifting force under normal gravity, this elevated force might disappear under microgravity. On the other hand, the elevated initial lifting effort in the large box would be preserved if it had been caused mainly by a persistent upward scaling of the force component, necessary to accelerate the object. To test whether the elevated initial lifting effort either persists or disappears under microgravity, a lifting experiment was carried out during brief periods of microgravity in parabolic flights. Subjects performed whole-body lifting movements with their feet strapped to the floor of the aircraft, using two 8-kg boxes of different volume. The subjects were aware of the equality of the box masses. The peak lifting forces declined almost instantaneously with approx. a factor 9 in the first lifting movements under microgravity compared with normal gravity, suggesting a rapid adaptation to the loss of weight. Though the overall speed of the lifting movement decreased under microgravity, the mean initial acceleration of the box over the first 200 ms of the lifting movement remained higher (P=0.030) in the large box (1.87±0.127 m/s2) compared with the small box (1.47±0.122 m/s2). Under normal gravity these accelerations were 3.30±0.159 m/s2 and 2.67±0.159 m/s2, respectively (P=0.008). A comparable trend was found in the initial lifting forces, being significant in the pooled gravity conditions (P=0.036) but not in separate tests on the normal gravity (P=0.109) and microgravity (P=0.169) condition. It is concluded that the elevated initial lifting effort with larger objects holds during short-term exposure to microgravity. This suggests that upward scaling of the force component, required to accelerate the larger box, is an important factor in the elevated initial lifting effort (and the associated size-weight illusion) under normal gravity.
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  • 95
    ISSN: 1432-1106
    Keywords: Key words Microneurography ; Peripheral nerve ; Pacinian afferent ; Cutaneous mechanoreceptor ; Vibrotactile stimuli ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To further study the functional organisation of human peripheral nerves, the intrafascicular arrangement of afferent fibres supplying Pacinian corpuscles (PCs) was explored by percutaneous microneurography using thin-calibre, concentric needle electrodes. In normal adults, 20 PC afferents were identified in 13 recording sites. Low-amplitude (less than 30 µm) vibratory stimuli to the skin were applied with tuning forks oscillating at 128 Hz or 256 Hz and response patterns of individual PC units were studied. In many recording sites, two, sometimes even three, PC afferents with adjacent or overlapping receptive fields in the hand were clustered in the nerve. The observed incidence in the records containing a certain number of PC units was compared with the expected probability calculated according to the hypothesis that all nerve fibres are randomly organised in peripheral nerves. The results suggested that PC afferents are partially segregated in the nerve. In addition, PC afferents were neighbouring on slowly adapting type II (SAII) units and skin sympathetic activity in individual fascicles. SAII units often innervated the same skin area as PC units, but did not respond to vibration. The data provided additional information regarding the functional organisation of the human peripheral nerve and the mechanisms underlying the sense of vibration in man with special regard to population behaviour of neighbouring PC mechanoreceptors.
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  • 96
    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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  • 97
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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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  • 98
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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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  • 99
    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.
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  • 100
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    Experimental brain research 125 (1999), S. 521-524 
    ISSN: 1432-1106
    Keywords: Key words Light touch ; Sway ; Centre of pressure ; Hand force ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  It has previously been shown that light contact with the finger tip on a fixed surface reduces centre of pressure (CoP) fluctuations in the frontal plane when standing in an unstable posture with the feet in line (tandem Romberg stance). Positive cross-correlations between horizontal finger forces and CoP fluctuations with finger forces exhibiting a phase lead suggest the hand provides sensory input for postural stability. The present study investigates whether this is the case for normal posture. We report reduced CoP fluctuations in the sagittal plane when light touch is permitted during normal bipedal stance. Moreover, we find positive crosscorrelations between finger tip forces and CoP fluctuations which are of similar magnitude and phase lag to those observed in tandem Romberg stance. This shows the utility of hand touch input for regulation of normal upright posture as well as inherently unstable postures such as tandem Romberg.
    Type of Medium: Electronic Resource
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