Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-1106
    Keywords: Environmental modification ; Visual cortex ; Superior colliculus ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cats were reared in a visual environment in which irregularly-shaped patches of luminescent paint moved constantly leftward. The distribution of preferred directions and orientations of cortical neurons in these cats was examined. Most cortical neurons encountered had leftward components in their preferred directions, and although no anisotropy of orientation was present in the rearing environment, most cortical neurons responded optimally to stimuli oriented at or near vertical. Variations in the strength of the induced bias of direction and orientation were noted among the different subclasses of cortical neurons. Preferred velocities of cortical neurons did not appear matched to the velocity of stimuli in the rearing environment. The ocular dominance distribution among cortical neurons in the unidirectional cats was skewed toward the contralateral eye relative to normal cats. The distribution of preferred directions in collicular neurons was largely unaltered by the rearing procedures employed. As in normal cats, units in the left colliculus more frequently responded best to rightward stimulus movement while those in the right colliculus preferred leftward movement. The ocular dominance distribution among collicular units was somewhat skewed toward the contralateral eye.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1106
    Keywords: Environmental modification ; Critical period ; Visual cortex ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Evidence that there is a critical period during which response characteristics of neurons in visual cortex of the cat may be influenced has been provided in several studies, which suggest that the period of influence is restricted to the first few months of life. Using a somewhat different experimental procedure, we have obtained evidence that cortical units retain plasticity long after the end of this period has passed. In our procedure prolonged visual deprivation was followed by exposure in a normal visual environment. The animals were maintained throughout the first year of life either in total darkness or in an enclosure illuminated intermittently by a strobe light. Following the period of deprivation, electrophysiologic recordings were taken from some of these animals. The remaining cats were permitted 6–12 months in a normally-illuminated environment prior to recording. Cats of the same age reared from birth in a normally lit environment were also recorded. Cortical neurons in cats deprived of any normal visual experience rarely show orientation selective responses. In animals allowed subsequent normal visual experience about one-half of the units studied exhibited this property. This level of response specificity is intermediate between that of normally-reared and recently-deprived animals. While most cortical units in normally-reared cats exhibit direction selectivity, this property is rarely observed in the “recovery” cats. A number of unit types which are rarely observed in either normal or totally deprived animals were encountered in cats that had normal exposure following prolonged deprivation. A convergent strabismus was observed, in contrast with the divergent strabismus often shown by cats immediately following prolonged visual deprivation. This shows that ocular alignment as well as cortical unit properties can remain plastic in the adult.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2307
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An 50 makroskopisch unveränderten menschlichen Pankreaten, die von Sektionsfällen stammten, wurden in einer vergleichend röntgenologischen und morphologischen Untersuchung die Gangveränderungen sowie ihre Folgeveränderungen bestimmt und ihr Altersgang verfolgt. Als häufigste Gangveränderungen fanden sich eine Epithelhyperplasie (88%) und eine periduktale Fibrose (74%). Als Folgeveränderungen bestanden an den Gängen cystische Ausweitungen (62%) und intraluminale Eiweißschollen (40%), am Parenchym eine intralobuläre Fibrose bis zur völligen Lobulusfibrosierung (88%). Alle Veränderungen nahmen mit höherem Lebensalter an Häufigkeit und Intensität zu, ließen sich aber auch bereits vor dem 50. Lebensjahr, und gelegentlich auch vor dem 30. Lebensjahr nachweisen. An Serienschnittuntersuchungen und einer Wachsplattenrekonstruktion wurde der formalpathogenetische Zusammenhang zwischen den Gang- und Parenchymveränderungen aufgezeigt. Dabei wurde deutlich, daß den kleinen Seitenästen der größeren Gänge, die kleine periduktal gelegene Lobuli drainieren, eine wesentliche Rolle für die Entstehung der Parenchymveränderungen zukommt. Eine Beziehung der Gang- und Parenchymveränderungen zu Gallenwegserkrankungen war nicht nachweisbar.
    Notes: Summary A postmortem study by ductography and histology was carried out in 50 macroscopically normal human pancreata. The alterations of the pancreatic duct system, their relations to the parenchyma, and their changes depending on age were studied. The most frequent changes of the ducts are epithelial hyperplasia (88%) and periductal fibrosis (74%). In the ducts they produce cystic widening (62% ) and intraluminal protein precipitates (40%), within the parenchyma an intralobulär fibrosis up to total fibrosis of lobules (88%). All these alterations increase with aging both in frequency and intensity. But they are already visible before the age of 50 and sometimes before the age of 30. The pathogenetic connexions between the changes of the duct system and the alterations of parenchyma were studied by serial sections and ceroplasty. This investigation revealed that the small branches of the larger ducts, which drain small periductally situated lobules, play an important role in the development of the parenchymal alterations. No connections were found between the pancreatic alterations and diseases of the bile duct system.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-0711
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung An männlichen, mitEimeria stiedai infizierten Kaninchen (Himalaja-Russen) wurden unter zusätzlicher Berücksichtigung parasitologischer und pathologischer Parameter serumenzymatische Verlaufsuntersuchungen durchgeführt. Die einmalige Infektion erfolgte mit 100000 bzw. 250000 sporulierten Oocysten pro Tier. Der zwischen dem 3. und 10. Tag p.i. beobachtete Aktivitätsanstieg der Sorbit-Dehydrogenase (SDH), Glutamat-Pyruvat-Transaminase (GPT), Glutamat-Oxalacetat-Transaminase (GOT) und Glutamat-Dehydrogenase (GlDH) ließ sich als Beginn der akuten Phase der Gallengangscoccidiose in das Infektionsgeschehen einordnen. Das konjugierte Bilirubin und die γ-Glutamyl-Transpeptidase (γ-GT) zeigten erst nach Ablauf von 10 Tagen Aktivitätszunahmen, die als Ausdruck einer gestörten Exkretionsleistung gedeutet werden können. Die Veränderungen aller serumenzymatischen Parameter erreichten zum Ende der Präpatenz bzw. zu Beginn der Patenz zwischen dem 14. und 21. Tag p.i. ihren Höhepunkt und kennzeichnen die Eignung und Bedeutung der Serumenzyme zum Studium des Infektionsverlaufes bei derEimeria stiedai-Infektion des Kaninchens. Gegen Versuchsende, 42 Tage p.i., lagen die Aktivitäten der Enzyme fast oder bereits wieder im physiologischen Bereich. Zwischen den infizierten Gruppen konnten zu keiner Zeit signifikante Unterschiede ermittelt werden. Die Aktivitäten der übrigen untersuchten Enzyme Lactat-Dehydrogenase (LDH), α-Hydroxybutyrat-Dehydrogenase (α-HBDH), Alkalische Phosphatase (AP), Leucin-Aminopeptidase (LAP) und Cholinesterase (ChE) zeigten im Verlauf der Untersuchungen nur geringfügige Schwankungen, die keine eindeutigen Hinweise auf das Infektionsgeschehen bei der Gallengangscoccidiose gaben.
    Notes: Summary In experimental investigations onEimeria stiedai infected rabbits, serum enzymatic studies have been carried out in correlation with the examination of parasitological and pathological parameters. The rabbits were orally infected with a single dose of either 100,000 or 250,000 sporulated oocysts. Increase of the activity of the sorbit dehydrogenase (SDH), glutamate oxalate transaminase (GOT), glutamate pyruvate transaminase (GPT) and glutamate dehydrogenase (GlDH) could be found first between 3 and 10 days after infection indicating the beginning of the acute phase of liver coccidiosis. The increase of the conjugated bilirubin and of the γ-glutamyl-transferase (γ-GT) could be found not earlier than 10 days after infection and is to be explained as sign of disturbed efficiency of excretion. The various investigated parameters reached their peak of alteration about the end of the prepatent period and at the beginning of patency between 14 and 21 days after infection. The results emphasize the value and usefulness of serum enzymes, particularly the glutamate dehydrogenase (GlDH) and the γ-glutamyl-transferase (γ-GT) with about 30fold activity, as indicators in the course ofEimeria stiedai infection of rabbits. The enzymes returned to physiological values at the end of the experiment, 42 days after infection. Significant differences could not be detected within the infected groups. The activities of the alkaline phosphatase (AP), leucine aminopeptidase (LAP), choline esterase (ChE), lactate dehydrogenase (LDH) and isoenzym 1 (α-HBDH) showed only slight alterations and proved to be no significant parameters for the pathophysiological evaluation of the liver coccidiosis.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Cirolana borealis utilises glycogen during anaerobiosis and shows a marked Pasteur effect. In 18h, 20–30 mg/g dry weight were converted, about half of the initial total glycogen content (Table 1). 2. Lactate is the major end product, while succinate and alanine are minor end products. 27–52% of the lactate produced was excreted into the incubation water (Tables 2 and 3). A good stoichiometric relationship was obtained between the glycogen consumed and the accumulation of these end products. 3. Small amounts of glutamate and aspartate contribute to the carbon flow, which could be of significance for obtaining redox balance (Table 3). 4. ATP production during anoxia was 75% of that during the standard aerobic state. 5. It is concluded that anaerobic fermentative metabolism ofC. borealis is adapted to maintain a high ATP output per unit time, which suits the high energy demand under natural anaerobic conditions. 6. WhenC. borealis are subjected to experimental anoxia they expel their gut contents and the incubation water becomes enriched with acetate, propionate, and amino acids. Most of these compounds probably stem directly from the gut content, while some, like acetate, may be produced by microbial activity. Starvation and anaerobic preincubation resulted in a marked lowering of the amounts of these compounds in the incubation water.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 257 (1975), S. 584-586 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Humans show considerable ability to compensate for prism-induced displacement3, partial rotation4 and even complete inversion5 of the retinal image. The physiological mechanisms underlying this capacity are not understood. On the other hand, amphibians never adjust their orienting behaviour to ...
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Subambient temperatures ; Cryogenic unit, inexpensive ; Temp. programming from ca. -50°C ; Automobile exhaust analysis, improved separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The quantitative plant species composition of the rumen contents of a large number of individuals from eight East African herbivores was determined by direct visual analysis. All plant species were classified as either C3 or C4, and an estimated δ13C for the rumen sample was calculated. This estimated value was compared to a measured value determined directly from rumen subsample. The two methods of determining quantitative C3 and C4 composition differed by less than 1%, and the isotopic analysis has the advantage of being rapid and totally objective. The isotopic analysis allowed us to differentiate between grazers and browsers and to determine the quantitative dependence of each animal on C3 and C4 photosynthetic types. Kongoni, wildebeest, cattle, and sheep were nearly pure grazers on the Athi Kapiti Plains; and the Grant's gazelle were predominantly browsers. Thompson's gazelle, goast and impala were intermediate. The species most dependent upon browse showed a marked and rapid shift to grass within a few days following rain. This isotopic method may have general utility in the study of East African ecology.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...