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  • 1
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Symbiotic filamentous bacteria thrive in the intestinal caecum of the deposit-feeding echinoid Echinocardium cordatum. Specimens of E. cordatum were collected at Wimereux (Nord Pas-de-Calais, France) in 1991. Their symbiotic bacteria build nodules by forming multilayered mats around detrital particles that enter the caecum. The morphological features of the bacteria are those of Thiothrix, a sulfide-oxidizing genus. The filaments, which may form rosettes, are sheathed and made by a succession of hundreds of rod-shaped bacteria which store elemental sulfur in the presence of external sulfide. Live bacteria are restricted to the outer layers of the nodules. Their sulfide-oxidizing activity was investigated, using a Biological Oxygen Monitor, by measuring the O2-consumption when reduced sulfur compounds are provided. They oxidize thiosulfate and sulfide. Optimal sulfide oxidation occurs at intermediary pO2 (100 to 160 μM O2l-1). Spectrophotometry has confirmed that the sulfur content of the filamentous symbiotic sulfideoxidizing bacteria depends on the presence of external sulfide. This is the first report of symbiotic intradigestive Thiothrixspp.-like bacteria; it lengthens the list of symbioses between sulfide-oxidizing bacteria and invertebrates from sulfide-rich habitats.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0738
    Keywords: Lipid peroxidation ; Malondialdehyde ; Ethane ; Glutathione ; Polychlorinated biphenyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ethane exhalation was increased in male Sprague-Dawley rats following a single intraperitoneal (IP) injection of Aroclor 1254 (500 mg/kg). In the first 2 weeks following Aroclor 1254 treatment, the increase in ethane exhalation was due to an inhibition of metabolism of endogenous ethane rather than to an increase in ethane production. In weeks 3 and 4 following Aroclor 1254 administration, metabolic clearance of ethane returned to and exceeded control levels, while ethane production increased to approximately twice the control rates (day 30). The HPLC determination of in situ hepatic malondialdehyde levels revealed a 2-fold increase in malondialdehyde content on day 30 following the Aroclor 1254 injection. Further, parallel increases in in situ malondialdehyde levels and ethane production rates were also found 30 days following a single IP injection of 3,3′,4,4′-tetrachlorobiphenyl, 2,3,4,4′,5-pentachlorobiphenyl and 2,2′,4,4′,5,5′-hexachlorobiphenyl (300 μmol/kg). These effects were not reflected in increased diene conjugation. Redox state of the liver was largely unaffected, as evidenced by the relative concentrations of reduced and oxidized NADPH. However, minor changes in reduced and oxidized glutathione were noted.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0738
    Keywords: cis- and trans-stilbene imine ; cis- and trans-stilbene oxide ; Acenaphthene 1,2-imine ; Drug-metabolizing enzymes ; Mutagenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract trans-Stilbene imine (trans-1,2-diphenylaziridine) is the nitrogen analog of trans-stilbene oxide, a potent inducer of several microsomal and cytosolic xenobiotic-metabolizing enzymes. Although the acute toxicity of cis- and trans-stilbene imines prevents their application at the usual dose for trans-stilbene oxide (400 mg/kg/day), it is apparent that the imines nevertheless potently induce several xenobiotic-metabolizing enzymes in rat liver. The IP administration of trans-stilbene imine resulted in statistically significant increases in the activities of aminopyrine N-demethylase, microsomal epoxide hydrolase, glutathione transferase (toward 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene and Δ5-androstene-3,17-dione) and UDP-glucuronosyltransferase (toward testoster-one). cis-Stilbene imine was less potent in inducing these activities. Although trans-stilbene imine (total dose = 400 mg/kg) was more potent than trans-stilbene oxide (total dose = 1200 mg/kg) in inducing the activities of glutathione transferase (toward 1-chloro-2,4-dinitrobenzene) and UDP-glucuronosyltransferase (toward testosterone), both compounds belong to the class of substances which are more potent inducers of conjugating (phase II) enzymes. Because of their structural similarity with K-region arene imines which are potent mutagens, cis-stilbene imine and trans-stilbene imine were investigated for mutagenicity (reversion of his − strains of Salmonella typhimurium). cis-Stilbene imine and trans-stilbene imine were direct mutagens in the strain TA100. This result, and the finding that acenaphthene 1,2-imine efficiently reverts various strains of Salmonella typhimurium, demonstrates that not only K-region arene imines, but also other aziridines substituted at the two carbons with aromatic moieties, are mutagenic.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-072X
    Keywords: Key wordsThiobacillus sp. W5 ; Sulfide oxidation ; Sulfur formation ; Flavocytochrome c ; Chlorobium ; limicola ; Chromatium vinosum ; Thiobacilli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel membrane-bound sulfide-oxidizing enzyme was purified 102-fold from the neutrophilic, obligately chemolithoautotrophic Thiobacillus sp. W5 by means of a six-step procedure. Spectral analysis revealed that the enzyme contains haem c and flavin. SDS-PAGE showed the presence of two types of subunit with molecular masses of 40 and 11 kDa. The smaller subunit contains covalently bound haem c, as was shown by haem staining. A combination of spectral analysis and the pyridine haemochrome test indicated that the sulfide-oxidizing heterodimer contains one molecule of haem c and one molecule of flavin. It appeared that the sulfide-oxidizing enzyme is a member of a small class of redox proteins, the flavocytochromes c, and is structurally most related to the flavocytochrome c sulfide dehydrogenase of the green sulfur bacterium Chlorobium limicola. The pH optimum of the enzyme is 8.6. At pH 9, the V max was 2.1 ± 0.1 μmol cytochrome c (mg protein)–1 min–1, and the K m values for sulfide and cytochrome c were 1.7 ± 0.4 μM and 3.8 ± 0.8 μM, respectively. Cyanide inhibited the enzyme by the formation of an N-5 adduct with the flavin moiety of the protein. On the basis of electron transfer stoichiometry, it seems likely that sulfur is the oxidation product.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-072X
    Keywords: Key wordsThiobacilli ; Chemolithoautotrophy ; Thiosulfate dehydrogenase ; Thiosulfate ; Tetrathionate ; Cytochrome c ; Respiratory chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A periplasmic thiosulfate dehydrogenase (EC 1.8.2.2) was purified to homogeneity from the neutrophilic, obligately chemolithoautotrophic Thiobacillus sp. W5. A five-step procedure resulted in an approximately 2,300-fold purification. The purified protein had a molecular mass of 120 ± 3 kDa, as determined by gel filtration. It is probably a tetramer containing two different subunits with molecular masses of 33 ± 1 kDa and 27 ± 0.5 kDa, as determined by SDS-PAGE. UV/visible spectroscopy revealed that the enzyme contained haem c; haem staining showed that both subunits contained haem c. A haem c content of 4 mol per mol of enzyme was calculated using the pyridine haemochrome test. The pH optimum of the enzyme was 5.5. At pH 7.5, the Km and Vmax were 120 ± 10 μM and 1,160 ± 30 U mg–1, respectively. The absence of 2-heptyl-4-hydroquinoline-N-oxide (HQNO) inhibition for the oxidation of thiosulfate by whole cells suggested that the electrons enter the respiratory chain at the level of cytochrome c. Comparison with thiosulfate dehydrogenases from other Thiobacillus species showed that the enzyme was structurally similar to the thiosulfate dehydrogenase of the acidophilic, facultatively chemolithoautotrophic Thiobacillus acidophilus, but not to the thiosulfate dehydrogenases published for the obligately chemolithoautotrophic Thiobacillus tepidarius and Thiobacillus thioparus.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 55 (1984), S. 445-454 
    ISSN: 1432-1106
    Keywords: Cerebellum ; Climbing fiber responses ; Olivocerebellar projection ; Somatotopic organization ; Mechanoreceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The topographic organization of the climbing fiber (CF) responses was mapped in the rostral vermal cortex (lobules III, IV, and Va) of the cerebellum. Extracellular, single-unit recordings were obtained from 699 Purkinje cells in cats anesthetized with sodium pentobarbitol. Approximately 72% of the CF responses were elicited by low-threshold or deep tactile stimulation, whereas the remaining units were unresponsive to any peripheral stimulation. On the basis of response characteristics, the vermal cortex was separated into an approximately 1-mm-wide medial zone and a 1 to 1.5-mm-wide lateral zone. The medial zone contained many unresponsive cells, except along the midline, where about 35% of the CF responses were elicited by deep stimulation at the base of the tail. The majority (78%) of the CF responses within the lateral vermal cortex represented various areas of the hindpaw, although representations of the forepaw (8%), tail (4%), and chin (0.6%), as well as unresponsive units (10%), were evident. The lateral vermal cortex contained a mediolateral topography of different receptive fields, although the topography was not sharply defined or equally displayed in all animals. The medial part of the lateral zone contained a representation of the ipsilateral forelimb in lobules IV and Va; the middle part had a representation of the medial or the lateral half of the hindpaw; and the lateral portion of the zone had an extensive representation of the distal hindpaw. The CF responses with similar receptive fields were often found in patches, which in some areas were arranged in layers from the inner to the outer areas of the sublobules. A particular body surface may be represented in multiple patches and in different lobules. Activation of the majority of CF responses within a sublobule may occur only during selected behaviors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 61 (1985), S. 73-86 
    ISSN: 1432-1106
    Keywords: Cerebellum ; Climbing fiber responses ; Olivocerebellar projection ; Somatotopic organization ; Receptive fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The fine grain organization of the climbing fiber (CF) representation for the intermediate cortex of lobules III, IV, and Va was examined. Data were obtained from cats anesthetized with sodium pentobarbital. Through extracellular recording techniques, CF responses were identified in 814 Purkinje cells; 74% were elicited by mechanical stimulation of various body surfaces. Of the CF responses elicited by stimulation, 60% involved the ipsilateral hindlimb, 36% represented parts of the forelimb, and only 4% represented areas of the face, tail, or abdomen. Hindlimb representation predominated in lobules III and IV, and forelimb representation was mainly confined to lobule Va. No distinct parasagittal zones that involved all three lobules were identified. In general, the organization for most sublobules could be best described as a mixture of patches of forelimb or hindlimb representations. Within the patches there was considerable diversity of receptive field types, particularly for the extremities. The receptive fields involving the distal phalanges were generally smaller than those for the proximal areas, but a range in field sizes was evident for both distal and proximal regions. More than half of either the forelimb or the hindlimb representation was limited to the distal paw areas; the two middle toes received the most frequent representation. Representations of the proximal limb areas were generally centered around either the wrist or the heel, or around the elbow or knee, but many of these receptive fields also extended to the phalanges. The multiple representation of various areas of forelimb and hindlimb throughout the rostral intermediate cortex was consistent with the type of organization that had been identified in other regions of the anterior lobe, although each cortical area contained a unique proportional CF representation of various body areas.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 23 (1975), S. 447-462 
    ISSN: 1432-1106
    Keywords: Dentate nucleus ; Cerebellum ; Motor systems ; Skilled movements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The activity of neurons in the dentate nucleus of the squirrel monkey was studied during the execution of a controlled, sequential movement that required different trajectories of the forelimb. Examination of 207 dentate neurons ipsilateral to the performing limb revealed that over 80% of the neurons isolated were distinctly correlated with performance. The majority of these neurons had a tonic discharge pattern that usually increased coincident with the start of the movement and was maintained throughout most of the performance. A smaller group of cells had a burst of activity that was restricted only to a narrow part of the performance. About 30% of the tonic neurons altered their pattern of discharge whenever different limb trajectories were required, but burst cells showed essentially no change. Detailed analysis of spike patterns revealed that no dentate neurons were phasically correlated with individual flexionextension cycles of the performance sequence. Dentate neurons appear to be related to some general function of motor performance rather than the actions of joints or muscles used to execute the task.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 46 (1982), S. 281-291 
    ISSN: 1432-1106
    Keywords: Cerebellum ; Vermis ; Climbing fibers ; Somatotopic organization ; Spino-olivocerebellar projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The somatotopic organization of the climbing fiber (CF) projections to the vermal cortex of lobule V of the cat was revealed by low threshold natural stimulation of mechanoreceptors. Extracellular single-unit recordings were made from 554 Purkinje cells in cats anesthetized with sodium pentobarbital. Forty-nine percent of the CF responses were elicited by cutaneous stimulation of the forelimb (62%), hindlimb (25%), or upper back and neck (13%). The topographical arrangement consisted of a 1 mm wide medial zone and a 1–1.5 mm wide lateral zone. In the medial zone, the CF responses were mainly nonresponsive to any cutaneous stimulation except in the caudomedial portion of the lobule where the upper back, neck or ears were represented in a narrow parasagittally oriented strip. The lateral zone contained a mixture of CF responses representing projections from different portions of the ipsilateral forelimb and hindlimb. Although CF responses connected with the forepaw or hindpaw predominated throughout all parts of the lateral zone, the more medial portions of this zone contained larger receptive fields involving the more proximal areas of the limb whereas the lateral part of the zone had smaller receptive fields representing the distal regions, particularly the ventral forepaw surface. Cells with similar receptive fields were often grouped together, but adjacent skin areas were not necessarily represented in adjacent cortical patches. Thus, the cutaneous projections to this lobule terminated in a patchy or mosaic fashion.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Animal Reproduction Science 15 (1987), S. 177-187 
    ISSN: 0378-4320
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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