Die Aktivität des Glykogen-synthetisierenden Enzyms(UDPGGT) in der Leber unter normalen und experimentellen Bedingungen

Zusammenfassung Unter Normalbedingungen ist die Aktivität des Glykogen-synthetisierenden Enzyms UDPGGT stets in den periportalen Bereichen des Leberläppchens nachzuweisen, die dadurch als wichtige Funktionseinheiten gekennzeichnet sind. Die UDPGGT-Aktivität unterliegt starken individuellen Schwankungen, dennoch kann in den Abendstunden eine allgemeine Aktivitätszunahme erkannt werden. Insulin und Glucosezufuhr führen unter den gewählten Versuchsbedingungen zu keiner Veränderung der UDPGGT-Aktivität; es wird angenommen, daß die jeweilige Glykogenkonzentration in der Leberzelle der entscheidende Faktor für die Aktivität der UDPGGT ist.

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The activity of glycogen-synthetase (UDPGGT) in the liver under normal and experimental conditions

Summary Under normal conditions the enzymatic activity of glycogen-synthetase (UDPGGT) can be demonstrated only in the periportal areas of the liver lobules. So the periportal areas are characterized as important functional units. The UDPGGT-activity shows strong individual variations, however there is a general increase of activity during the evening hours. Under the chosen experimental conditions neither the application of insulin nor of glucose causes a change of liver-UDPGGT-activity; it is supposed, that the concentration of glycogen in the liver cell is the crucial factor for the synthetase-activity.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Histochemical studies on carbohydrate metabolism in rat liver after galactosamine administration.

The development of hepatitis, induced in 48 rats by the administration of galactosamine (GalN) in varying doses, was studied with the use of substrate and enzyme histochemical techniques. The so-called atypical glycogen, which is at first highly resistant to diastase, was shown to be digestible after deamination. The increasing accumulation of atypical glycogen during the course of GalN-hepatitis conceals the loss of normal glycogen when the PAS-reaction is used. Nevertheless glycogenolysis could also be demonstrated by the increasing activity of phosphorylase. The acid phosphatase activity was progressively diminished, which was interpreted as signifying early lysosomal damage. G6Pase activity remained nearly constant but SDH showed a decrease in activity after 12 h. These histochemical results are considered to provide deeper insight into the pathological mechanism of GalN-hepatitis.     

A cartilage-derived growth factor enhances hyaluronate synthesis and diminishes sulfated glycosaminoglycan synthesis in chondrocytes

Cartilage-derived growth factor purified to homogeneity by affinity chromatography on columns of heparin-Sepharose was mitogenic for early passage bovine fetal chondrocytes. Hyaluronate and sulfated glycosaminoglycan synthesis in these cells was analyzed by differential enzymatic digestion of the glycosaminoglycans labeled with [14C] glucosamine or [35S]. It was found that chondrocyte proliferation was accompanied by about a four-fold increase in hyaluronate synthesis over a two-day period, while the synthesis of sulfated glycosaminoglycans decreased by about 2-fold. Chromatographic analysis of the sulfated glycosaminoglycans showed decreases in chondroitin 4 and 6 sulfates. It was concluded from these results that cartilage-derived growth factor was a proliferative factor for chondrocytes and differed from the somatomedins.     

Proliferating hair cell precursors in the ear of a postembryonic fish are replaced after elimination by cytosine arabinoside

Identified, proliferating S-phase cells in the postembryonic fish ear are known to be the precursors to new hair cells. It is not known, however, whether the ability to proliferate is restricted to a small population of cells. The ability of cells that are not normally in the cell cycle to enter S-phase was examined using the antimitotic drug cytosine arabinoside (ara-C). The normal population of S-phase cells in the saccule was destroyed by a single large dose of ara-C. Two weeks later, the prsence of S-phase cells was evaluated using the S-phase marker bromodeoxyuridine. The results strikingly demonstrate that S-phase cells are replaced, since S-phase cells returned to the saccule in the same number as found in normal fish. The data are interpreted to suggest that a large number of nonsensory support cells are capable of entering the cell cycle and that some mechanism must regulate which of these are actually cycling at any given time. © 1995 John Wiley & Sons, Inc.