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S Hauser

Publications and source records attributed to S Hauser.

25 records · Page 2Linked to original sources
PubMed1970

Biochemical site of regulation of bile acid biosynthesis in the rat.

The production of bile salts by rat liver is regulated by a feedback mechanism, but it is not known which enzyme controls endogenous bile acid synthesis. In order to demonstrate the biochemical site of this control mechanism, bile fistula rats were infused intravenously with (14)C-labeled bile acid precursors, and bile acid biosynthesis was inhibited as required by intraduodenal infusion of sodium taurocholate. The infusion of taurocholate (11-14 mg/100 g of rat per hr) inhibited the incorporation of acetate-1-(14)C, mevalonolactone-2-(14)C, and cholesterol-4-(14)C into bile acids by approximately 90%. In contrast, the incorporation of 7alpha-hydroxycholesterol-4-(14)C into bile acids was reduced by less than 10% during taurocholate infusion. These results indicate that the regulation of bile acid biosynthesis is exerted via cholesterol 7alpha-hydroxylase provided that hepatic cholesterol synthesis is adequate.

Acetates↗
PubMed1969

Feedback regulation of bile acid biosynthesis in the rat.

The hepatic biosynthesis of bile salts in the rat has been shown to be controlled homeostatically by the quantity of bile salt returning to the liver via the portal circulation. The feedback mechanism was demonstrated in two kinds of experiments. In the first, rats with bile fistulas were infused intraduodenally with sodium taurocholate 12 hr after surgery. If the rate of infusion was greater than 10 mg per 100 g rat per hr, the increase in bile acid output normally observed in bile fistula rats was prevented. In the second type of experiment, the rats were infused with taurocholate 48-72 hr after biliary diversion, when bile acid output had reached a maximal value. Provided the rate of infusion exceeded 10 mg per 100 g rat per hr, bile acid secretion returned to the low levels observed in intact rats. Previous attempts to demonstrate the feedback control have been unsuccessful because too little bile salt was infused. The taurocholate pool of the experimental animals was measured as approximately 15 mg per 100 g rat; it was calculated from this and the above results that this pool circulated 10-13 times daily.

Acetates↗
PubMed1968

7-alpha-hydroxylation of cholestanol by rat liver microsomes.

In a study of the mechanism whereby 5alpha-bile acids are formed from cholestanol, the 7alpha-hydroxylation of cholestanol was investigated in rat liver preparations in vitro. It was found that in the presence of NADPH and oxygen, rat liver microsomes catalyzed the 7alpha-hydroxylation of cholestanol to the same extent as that of cholesterol. The rate of the hydroxylation was enhanced by prior treatment of the experimental rats with cholestyramine (a bile acid sequestrant) or by establishment of bile fistulas-i.e., by partial or complete removal of bile acids from the enterohepatic circulation. The 7-hydroxylation reaction was further stimulated by pretreatment of the animals with phenobarbital, a drug known to produce increased biosynthesis of hepatic endoplasmic membranes. The 7alpha-hydroxylase was inhibited by the reaction product, by sterols with 7-keto or 7beta-hydroxyl groups, and also by mono- and dihydroxy bile acids of the 5beta-series, although cholic acid or taurocholate produced no inhibition unless added in high concentrations. The results of these studies are in accord with the concept that the presence of a Delta(5)-double bond is not required for the enzymatic formation of the 7alpha-hydroxy derivative. The rate of this hydroxylation reaction in vitro appears to depend on the concentration of bile salts in the enterohepatic circulation of the experimental animals from whom the microsomes were obtained.

Animals↗
PubMed1966

Biosynthesis of cholestanol: 5-alpha-cholestan-3-one reductase of rat liver.

The 3-beta-hydroxysteroid dehydrogenase of rat liver which catalyzes the conversion of 5alpha-cholestan-3-one to 5alpha-cholestan-3beta-ol is localized mainly in the microsomal fraction. The enzyme required NADPH as hydrogen donor and differed from the known 3-beta-hydroxysteroid dehydrogenases of the C(19) series in being inactive in the presence of NADH. The microsomal preparations did not reduce the 3-keto groups of cholest-4-en-3-one, cholest-5-en-3-one, or 5beta-cholestan-3-one to the corresponding 3beta-hydroxy compounds. The conversion of 5alpha-cholestan-3-one to 5alpha-cholestan-3beta-ol was only slightly inhibited by the reaction product or by other monohydroxy steroids, but a strong inhibitory effect was noted with cholest-5-en-3-one, 5alpha-cholestane-3beta, 7alpha-diol and 5alpha-cholestan-7-on-3beta-ol. The microsomes, but not high speed supernatant solution, catalyzed the reverse of the cholestanone reductase reaction, namely the conversion of 5alpha-cholestan-3beta-ol to 5alpha-cholestan-3-one in the presence of oxygen and an NADP-generating system. The action of the microsomal preparations upon 5alpha-cholestan-3-one produced 5alpha-cholestan-3alpha-ol in addition to the 3beta-epimer. The 3-alpha-hydroxysteroid dehydrogenase involved functioned with either NADH or NADPH as hydrogen donor. The ratio of 5alpha-cholestan-3beta-ol to 5alpha-cholestan-3alpha-ol formed from 5alpha-cholestan-3-one was approximately 10:1 and was independent of the sex of the animal from which the microsomes were prepared.

Animals↗
PubMedDate not supplied

[Retrospective marker analyses performed with blood and bone marrow smears using an immunoenzyme procedure (alkaline phosphatase-anti-alkaline phosphatase technic)].

In the present study the possibility of immunophenotyping of routinely prepared (air dried) peripheral blood and bone marrow smears is described after storage. The immunoenzymatical alkaline-phosphatase-anti-alkaline-phosphatase (APAAP)-method was carried out in differently stored blood smears (+4 degrees C and -80 degrees C). Last results were compared with originals made from freshly prepared mononuclear cells at time of diagnosis. The results showed no remarkable decrease of antigenicity, neither under the procedure refrigeration and thawing of the frozen smears (-80 degrees C), nor under storage conditions of more than 22 months. In our opinion this highly sensitive method enables us to get additional results from unexplained haematological disorders using retrospective analysis.

Antibodies, Monoclonal↗
PubMedDate not supplied

[Use of a new silicon chamber system for carrying out immunologic technics with blood and bone marrow samples and histologic specimens].

We are reporting for the first time on the successful application of the newly developed method of Silicon-Chamber-System (SCS). For this purpose we are utilizing a commonly manufactured silicon sealant by which we are able to obtain reaction fields of any size and number. We are applying the sealant on cell- and on tissue-slides without any special preparation. These reaction fields on the slides allow us to immunohistochemically analyse cells with multiple different monoclonal antibodies without running great risk of a cross-reaction between the different immunoreagents. It is a simple inexpensive and convenient method, giving us the opportunity to analyze elaborate cell material.

Antibodies, Monoclonal↗