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H G Windmueller

Publications and source records attributed to H G Windmueller.

At least 37 records · Page 2Linked to original sources
PubMed1973

Biosynthesis of lymph and plasma lipoprotein apoproteins by isolated perfused rat liver and intestine.

The ability of rat intestine and liver to synthesize the various apoproteins of plasma lipoproteins was investigated. After the individual isolated organs were perfused with blood containing [(3)H]lysine, chylomicrons plus very low density lipoproteins (VLDL), low density lipoproteins (LDL), and high density lipoproteins (HDL) were isolated from the perfusates and the intestinal lymph. After lipoprotein delipidation, apoproteins were separated by polyacrylamide gel electrophoresis and the (3)H content was determined. Livers incorporated [(3)H]lysine into all apoprotein bands of VLDL and HDL. The (3)H content was greater in large proteins that remained in the stacking gel (group I, predominantly beta-apoprotein) than in proteins with apparent molecular weights near 50,000 (group II) or in the smaller peptides (molecular weights near 10,000, group III). In the intestine, (3)H was incorporated into group I and, in larger amounts, into group II apoproteins of lymph VLDL. No labeled VLDL appeared in the perfusate. (3)H was also incorporated into group II apoproteins of lymph and perfusate HDL. Significantly, no [(3)H]lysine was found in the group III peptides of any lymph or intestinal perfusate lipoproteins. Since these peptides were always present in VLDL from mesenteric lymph collected in vivo, the results suggest that nascent VLDL of gut origin acquires group III peptides from other lipoproteins that penetrate lymph from plasma.

Animals↗
PubMed1973

Metabolic fate of rat and human lipoprotein apoproteins in the rat.

The fate of (125)I-labeled apolipoproteins was studied in vivo in rats that had received intravenous injections of (125)I-labeled rat HDL and (125)I-labeled human HDL, LDL, and VLDL. Plasma decay curves of rat and human HDL were exponential with similar half-lives in the circulation (11-12 hr). After injection, low molecular weight apolipoproteins (apoLP-alanine of human HDL and fraction HS-3 of rat HDL) were found to redistribute to other lipoproteins, predominantly VLDL. Decay curves of individual HDL proteins were constructed after lipoprotein fractionation, delipidation, and polyacrylamide gel electrophoresis. It was found that the half-lives of the different HDL apoproteins were not identical. A major rat HDL protein (52% of total counts) had a circulating half-life (t((1/2))) of 12.5 hr. Two others had a t((1/2)) of 8-9 hr while the t((1/2)) of several others was 11-12 hr. The t((1/2)) of three well-characterized human HDL apoproteins, apoLP-glutamine I, apoLP-glutamine II, and apoLP-alanine, were 13.5, 9.0, and 15.0 hr, respectively. The fate of (125)I-labeled human VLDL and LDL apoproteins in rats was similar to that described previously in humans. After injection of (125)I-labeled human VLDL into rats, apoLP-glutamic acid and apoLP-alanine rapidly transferred to rat HDL and were lost thereafter from the circulation from both VLDL and HDL. The apoLDL moiety of human VLDL moved metabolically to the LDL density range (d = 1.019-1.063) through a lipoprotein of intermediate density (d = 1.006-1.019).

Alanine↗
PubMed1973

Selective measurement of two different triglyceride lipase activities in rat postheparin plasma.

Conclusive evidence has been obtained for the presence of both hepatic and extrahepatic triglyceride lipase activities (TGLA) in rat postheparin plasma, and an assay has been devised for their selective measurement. Heparin-released TGLA in plasma from the intact rat, like TGLA in postheparin hepatic perfusate, was relatively resistant to inactivation by salt and protamine. Postheparin TGLA obtained from the supradiaphragmatic portion of the rat, where any hepatic contribution was eliminated, was nearly completely inactivated by salt and protamine. Utilizing the different sensitivities to protamine inactivation of extrahepatic and hepatic TGLA, assay conditions were selected to achieve simultaneously the maximal reduction of extrahepatic TGLA with preservation of hepatic TGLA. This assay was validated using postheparin plasma from partially hepatectomized rats. The protamine-inactivated activity was independent of the amount of liver removed, whereas protamine-resistant activity was directly proportional to the amount of liver remaining. In the intact rat, liver appeared to be the major source of heparin-released TGLA measured at pH 8.6 with triolein substrate. It was further shown that both hepatic and extrahepatic lipases catalyzed hydrolysis of triglyceride-rich lipoproteins.

Animals↗
PubMed1972

Comparison of the triglyceride lipase of liver, adipose tissue, and postheparin plasma.

Heparin-released triglyceride lipase from three sources, adipose tissue, liver, and postheparin plasma, was compared. Heparin-released triglyceride lipase from liver differed in several major respects from that in adipose tissue. These differences included response to inhibitors and to high density lipoprotein in the incubation media. Heparin-released triglyceride lipase from liver, when compared with that from adipose tissue, was relatively inactive against lipoprotein substrates. The triglyceride lipase from postheparin plasma exhibited properties more like those of liver. These studies raise the possibility that triglyceride lipase in postheparin plasma may be heterogeneous and that levels of the enzyme in postheparin plasma may not accurately reflect the capacity for clearance of triglyceride from the plasma.

Adipose Tissue↗
PubMed1972

Fat transport and lymph and plasma lipoprotein biosynthesis by isolated intestine.

An apparatus and procedure are described for investigating fat transport and lipoprotein biosynthesis in isolated, lymph-cannulated rat intestine perfused with blood under physiological conditions. The small bowel, cecum, proximal half of the colon, and attached mesentery were removed into a tissue bath and perfused vascularly in a recycling system free of blood-air interfaces. Perfusion was continued for 5 hr. Lymph flow, glucose utilization, and oxygen consumption continued unchanged, as did intestinal motility and glucose and water transport from the lumen. No measurable lactate was produced. When 70 micro moles of soybean oil and 9 micro moles of lecithin were infused luminally, more than 50% of the fatty acids were recovered in the lymph, 90% as triglycerides of which 75% appeared in chylomicrons with average diameters estimated to be 100-200 nm, based on their phospholipid content. The preparation incorporated [(3)H]-lysine into the protein moieties of lipoproteins of d < 1.006 g/ml (chylomicrons plus very low density) which appeared in lymph and accounted for more than 30% of all labeled lymph protein. No labeled d < 1.006 lipoproteins appeared in the perfusate. [(3)H]Lysine was also incorporated into the d 1.006-1.21 lipoproteins of both lymph and perfusate, but the specific activity of the former was 500 times as high as the latter, indicating that d 1.006-1.21 as well as d < 1.006 lipoproteins are produced by gut and reach the blood via mesenteric lymph. Most of the labeled d 1.006-1.21 protein appeared to be high density lipoprotein (d 1.063-1.21).

Animals↗
PubMed1970

Identity of very low density lipoprotein apoproteins of plasma and liver Golgi apparatus.

In the rat, very low density lipoproteins isolated from hepatocyte Golgi apparatus, liver perfusates, and whole plasma appear identical in many respects. With specific immunochemical techniques and polyacrylamide-gel electrophoresis it can be demonstrated that the very low density lipoproteins from all three sources contain the same major lipoprotein apoproteins.

Animals↗