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H Reinauer

Publications and source records attributed to H Reinauer.

At least 91 records · Page 5Linked to original sources
PubMed1987

[The effect of the small intestine on 3-methylhistidine metabolism in the human].

20 male adult Sprague-Dawley rats were fed exclusively parenterally. After achieving metabolic equilibrium they received a duodenoileostomy and subtotal resection leaving only 8-10% of the small gut. On the 1st postoperative day the urinary 3-MH excretion rose to 1.5-1.7 times the preoperative level, but on the 12th-14th postoperative day it fell again and was equal to the preoperative basal level. A control group of 10 rats undergoing a small gut anastomosis without resection yielded similar results. We conclude that the small gut source does not make a significant contribution to 24h-urinary 3-MH excretion in the adult rat. The transient postoperative increase in urinary 3-MH excretion is probably due to post-injury metabolism. In contrast to these are the measurements in two male patients with a short bowel syndrome because of an occlusion of the superior mesenteric artery. Both patients have a body weight of 60 kg, are aged 44 and 45 years respectively, and have a 24h-urinary 3-MH excretion of 120.7 +/- 28 mumol. More than 1 year after operation they are being nourished parenterally in metabolic equilibrium. The 24h-urinary 3-MH excretion in a similar control group of 8 healthy male volunteers is 229.4 +/- 25 mumol (measurements for 6 days after a 1-week meat-free diet). We conclude that the small gut source makes a significant contribution to 24h-urinary 3-MH excretion in the adult human. There is no evident correlation between the rat model and measurements in human.

Adult↗
PubMed1987

Insulin binding and action in isolated cardiocytes from spontaneously diabetic BB rats.

Isolated cardiac myocytes from control and insulin treated diabetic BB rats were used to study cellular alterations related to partly controlled diabetes. Scatchard analysis of equilibrium binding data showed an unaltered affinity and number of insulin receptors in cardiocytes from both groups of animals. Moreover, insulin internalization was found to be identical under these conditions. Insulin action was determined by measuring the effect of the hormone on initial velocities of 3-0-methylglucose influx. Basal activity of the glucose transporter and maximal transport stimulation by insulin remained unaffected. In contrast, the sensitivity of the carrier towards stimulation by insulin was markedly reduced in cardiocytes from diabetic rats with a half-maximal action occurring at an insulin concentration of 3 X 10(-10) mol/l and 9 X 10(-9) mol/l in control and diabetic animals, respectively. The onset of insulin action was much slower in cells from diabetic BB rats exhibiting an increase in the coupling time by 400% from 5 to 20 min, respectively. The data suggest an association of partly controlled diabetes with myocardial alterations located at the postreceptor level.

Animals↗
PubMed1986

Size and shape of the multicatalytic proteinase from rat skeletal muscle.

The multicatalytic proteinase from rat skeletal muscle, a non-lysosomal high molecular weight enzyme active at neutral to alkaline pH, has been examined in the electron microscope as well as by dynamic laser light scattering. Both methods reveal monodisperse particles. Electron micrographs show a cylinder-shaped complex with a diameter of 11 nm and a length of 16 nm in negatively stained, and a diameter of 9.6 nm and a length of 14.3 nm in freeze-dried, heavy metal replicated specimens. The molecule is composed of four rings or disks.

Animals↗
PubMed1986

Down-regulation of insulin receptors in the heart: studies on primary cultured adult cardiac myocytes.

Primary cultured cardiac myocytes from adult rats have been used to study insulin receptor regulation. Culturing of cells in the presence of insulin induced a dose-dependent down-regulation of insulin binding with a maximal effect of 35% at an insulin concentration of 1.7 X 10(-7) mol/l. The number of high-affinity sites decreased from 110 000 to 70 000 sites per cell in control and down-regulated cells, respectively, with no change in the apparent affinity constant. Down-regulation was found to be rapid (t 1/2 = 3 h) and fully reversible. Culturing of cells in the presence of cycloheximide (0.1 mmol/l) or Tris (35 mmol/l) resulted in a further time-dependent increase in insulin-induced receptor loss with no effect on insulin binding to control cells. The action of both agents was found to be additive reaching a down-regulation of 51% after a culture period of 16 h. Recovery of insulin binding activity after removal of insulin remained unaffected in the presence of cycloheximide, whereas Tris inhibited this process by 74%. In conclusion our results show that the concept of insulin-induced receptor down regulation can be extended to the adult heart muscle. Moreover the data suggest involvement of protein synthesis and receptor recycling in this process.

Animals↗
PubMed1986

Effect of starvation or treatment with corticosterone on the amount of easily releasable myofilaments in rat skeletal muscles.

Treatment of isolated myofibrils with an ATP-containing relaxing solution results in the dissociation of a preformed quantity of myofilaments called 'easily releasable myofilaments'. Van der Westhuyzen, Matsumoto & Etlinger [(1981) J. Biol. Chem. 256, 11791-11797] presented experimental evidence that these myofilaments represent intermediate products in the turnover of myofibrillar proteins. To investigate further this question, we measured the size of the fraction of easily releasable myofilaments in three different species of skeletal muscles from rats subjected to well-defined catabolic conditions, namely starvation or chronic glucocorticoid administration. The results were as follows: (1) The amount of easily releasable myofilaments was transiently increased about 2-3-fold during both experiments, and thus paralleled the known alterations in the rate of overall muscle protein breakdown rather than in those of synthesis. (2) These changes were observed in muscles containing predominantly fast-twitch fibres, but not in slow-twitch soleus muscle, a muscle that is known to be more resistant to catabolic conditions. (3) The starvation-induced increase of the size of the fraction of easily releasable myofilaments could be significantly reduced by treatment of the starving animals with the proteinase inhibitor E-64. These results are compatible with the idea that easily releasable myofilaments are intermediates in the degradative pathway of myofibrillar proteins and that a proteolytic step may be involved in the conversion of myofilaments into easily releasable myofilaments.

Actin Cytoskeleton↗
PubMed1986

Different types of postinsulin receptor defects contribute to insulin resistance in hearts of obese Zucker rats.

The influence of obesity on myocardial function and metabolism was studied in obese (fa/fa) and thin (Fa/Fa) Zucker rats using the isolated perfused heart as model. Cardiac performance of obese Zucker rats was not impaired. Instead, left ventricular pressure and contractility were increased as compared to controls. In agreement with these findings, creatine phosphate and the ratios of ATP/ADP and creatine phosphate creatine were elevated. The uptake and the conversion of glucose by hearts of obese Zucker rats were impaired. Insulin stimulated the uptake and oxidation of glucose. However, the responsiveness of these processes to insulin was diminished. Lipolysis of endogenous lipids was accelerated severalfold in obesity. Inhibition of fatty acid oxidation by a specific carnitine palmitoyl-transferase inhibitor, phenylalkyloxirane carboxylic acid (POCA), led to a slow rate of lipolysis, and to an acceleration of glucose oxidation and of the basal, noninsulin-dependent uptake of glucose. In the presence of POCA, insulin had, however, no additional stimulatory effect on the glucose uptake by hearts of obese rats. In contrast to hearts of ketotic, acutely diabetic rats where POCA fully restored myocardial responsiveness of glucose uptake and conversion to insulin, in hearts of obese rats only a shift in the glucose pathway from glycolytic formation of lactate and pyruvate to oxidation to CO2 was observed. Thus, POCA can be used as a tool to distinguish different forms of insulin resistance in obesity: 1) a lipid metabolism-dependent defect--presumably an inhibition of phosphofructokinase and pyruvate dehydrogenase by metabolites of fatty acid oxidation, influenced by inhibition of carnitine palmitoyltransferasei, and 2) a lipid metabolism-independent defect in the activation of uptake of glucose and glycogen synthesis by insulin not affected by POCA.

Adenine Nucleotides↗
PubMed1986

Immunofluorescent localization of an alkaline proteinase in skeletal muscles from diabetic rats.

Alkaline proteinase (chymase) was localized in skeletal muscle tissues from seven day streptozotocin-diabetic rats. Extruded mast cell granules containing proteinase were visible in the extracellular space and inside certain myofibers from both extensor digitorum longus (EDL) and soleus muscles. Additional diffuse staining was present in the cytoplasm of many EDL fibers. This evidence provides support for a possible role of muscle cells in the endocytosis of mast cell granules.

Animals↗
PubMed1986

Studies on the multicatalytic proteinase from rat skeletal muscle.

The multicatalytic proteinase purified from rat skeletal muscle was shown by electron microscopy to be a uniform cylinder-shaped protein particle. As the enzyme activities are enhanced by free fatty acids in vitro, we tested, by in vivo perfusion, whether high concentrations of free fatty acids increased the multicatalytic proteinase activities in skeletal muscle tissue. Perfusion of rat hindquarters with plasma containing 1.5 mM oleic acid bound to albumin led to a 30-40% increase of the proteinase activities in gastrocnemius muscle. This increase was statistically not significant when compared to control rats perfused with plasma containing fatty acid free albumin. These results are discussed under the following aspects: 1. the in vivo concentration of non-esterified fatty acids within the muscle cell is not known; 2. the uptake of free fatty acids by the muscle cell is too low, or the metabolism of free fatty acids taken up by the cell is too fast to allow activation of the multicatalytic proteinase; 3. the free fatty acids are bound to other proteins (e.g. fatty acid binding protein), which abolish their ability to activate the proteinase.

Animals↗
PubMed1986

[The influence of the small intestine on the metabolism of 3-methylhistidine in the rat].

20 male adult Sprague-Dawley rats were fed exclusively parenterally. After achieving metabolic equilibrium they received a duodenoileostomy and subtotal resection leaving only 8-10% of the small gut. On the 1st pop. day the urinary 3-MH excretion rose to 1.5-1.7 of the preoperative level, but on the 12th-14th pop. day it fell again and was equal to the preoperative basal level. A control group of 10 rats undergoing a small gut anastomosis without resection yielded similar results. We conclude that the small gut source does not make a significant contribution to 24 h-urinary 3-MH excretion in the adult rat. The transient postoperative increase in urinary 3-MH excretion is probably due to post-injury metabolism.

Animals↗
PubMed1985

Purification and characterization of a multicatalytic high-molecular-mass proteinase from rat skeletal muscle.

A proteolytic enzyme was purified from the post-myofibrillar fraction of rat skeletal muscle. The purification procedure consisted of fractionation of the muscle extract by (NH4)2SO4, chromatography on DEAE-Sephacel, fast protein liquid chromatography on Mono Q and gel filtration on Sepharose 6B. The enzyme preparation appeared to be homogeneous as judged by disc electrophoresis in polyacrylamide gels and by immunoelectrophoresis. The isoelectric point of the proteinase is at 5.1-5.2. The enzyme has an Mr of about 650 000 and dissociates into eight subunits of Mr 25 000-32 000 when subjected to electrophoresis in sodium dodecyl sulphate/polyacrylamide gels. The proteinase contains hydrolytic activity against N-blocked tripeptide 4-methyl-7-coumarylamide substrates with an arginine or phenylalanine residue adjacent to the leaving group. Maximum activity with the first group of substrates was at pH 10.5, and this activity was inhibited by leupeptin, chymostatin and Ca2+. Maximum activity with the latter group of substrates was at pH 7.5, and was also inhibited by the two microbial inhibitors, but was activated by Ca2+ ions. By using [14C]methylcasein as a substrate, maximum activity was observed at pH9.0, and this proteolytic activity was not affected by leupeptin, was enhanced by chymostatin and inhibited by Ca2+. Similar effects were observed when benzyloxycarbonyl-Leu-Leu-Glu 2-naphthylamide was used as a substrate. These enzymic activities were abolished by p-hydroxymercuribenzenesulphonic acid or mersalyl acid, whereas a small activation was observed with cysteine or dithiothreitol.

Animals↗
PubMed1985

Activation of the multicatalytic proteinase from rat skeletal muscle by fatty acids or sodium dodecyl sulphate.

A multicatalytic proteinase from rat skeletal muscle contains active site(s) catalysing the degradation of benzoyl-Val-Gly-Arg 4-methyl-7-coumarylamide, succinyl-Ala-Ala-Phe 4-methylcoumarylamide and [14C]methylcasein as well as benzyloxy-carbonyl-Leu-Leu-Glu 2-naphthylamide. These activities are 7-14-fold activated by 1 mM-sodium dodecyl sulphate. The activation leads to a higher susceptibility to the proteinase inhibitor chymostatin and to a lower ability to be inhibited and precipitated by antibodies raised against the non-activated enzyme. Since no changes in Mr or subunit composition were observed in the SDS-activated form, some conformational changes seem to occur during the activation step. More pronounced activation was observed in the presence of physiological concentrations of fatty acids; oleic acid at 100 microM concentrations stimulated the proteinase about 50-fold. In contrast with the non-activated proteinase, the activated enzyme considerably degrades muscle cytoplasmic proteins in vitro. Thus it is not unlikely that, in vivo, potential activators such as fatty acids can induce the multicatalytic proteinase to participate in muscle protein breakdown.

Animals↗
PubMed1985

The insulin receptor of adult heart muscle cells.

Isolated cardiac myocytes possess specific receptors for insulin which consist of high- and low-affinity sites and are randomly distributed at the cell surface at 37 degrees C. Low-affinity sites can mediate a biological response comparable to that of high-affinity sites. Calcium appears to modulate the high-affinity site and thus may be involved in the regulation of cardiac sensitivity towards insulin. The data suggest involvement of the insulin receptor in insulin degradation, which includes internalization and lysosomal processing of insulin.

Animals↗
PubMed1985

Adult cardiac myocytes in primary culture: cell characteristics and insulin-receptor interaction.

Calcium-tolerant adult cardiac myocytes were kept in culture under serum-free conditions in the presence of physiological concentrations of insulin. Up to 4 days, 70% of cells retained their in vivo rodshaped morphology without gross structural alterations. During that period a constant ATP-to-ADP ratio was observed with a mean value of 10.6 +/- 0.5 (n = 4). The rate of [14C]phenylalanine incorporation remained unaltered up to 63 h in culture. Insulin binding to cultured cells was found to be time-and temperature-dependent, reversible, and highly specific. Scatchard analysis of equilibrium binding data showed a curvilinear plot with a high-affinity segment yielding an apparent dissociation constant of 4.5 X 10(-10) mol/l and a receptor number of 125,000 sites/cell. Both affinity and receptor number remained unaltered between 18 and 66 h in culture. [14C]phenylalanine incorporation was stimulated by 108% in cardiocytes cultured in the presence of high concentrations of insulin (1.7 X 10(-7) mol/l) for 63 h, when compared with control cells cultured in the absence of insulin. These data demonstrate the retention of structural integrity, insulin receptors, and insulin responsiveness in primary cultured adult cardiac myocytes and provide a useful model for long-term studies on the regulation of insulin action on the heart.

Animals↗
PubMed1985

Insulin resistance in the heart: studies on isolated cardiocytes of genetically obese Zucker rats.

Isolated cardiac myocytes from lean and genetically obese (fa/fa) Zucker rats were used to study cellular alterations related to the obesity syndrome in this tissue. Scatchard analysis of insulin binding data suggested a reduction in the number of low affinity sites in cells from obese rats; in contrast, an unaltered high affinity segment with Kd values of 5.7 +/- 0.6 and 4.5 +/- 0.7 X 10(-10) mol/liter (n = 4) in lean and obese rats, respectively, has been observed. Insulin internalization, as estimated from the amount of increased cell-associated radioactivity in chloroquine-treated cells, was decreased by 70% from 12.8 fmol insulin/10(6) cells X 120 min in lean rats to 3.8 fmol/10(6) cells X 120 min in obese rats. Determinations of initial velocities of 3-O-methylglucose influx were used for assessing glucose transport activity. Basal activity of the glucose transport system was reduced in cells from obese animals. This was found to be due to a decreased maximum velocity of the carrier with corresponding values of 69.8 +/- 5.2 and 38.3 +/- 3.2 nmol/10 sec X 10(6) cells (n = 3) in cardiocytes from lean and obese rats, respectively. Glucose transport exhibited an unaltered sensitivity toward stimulation by insulin, but an impaired responsiveness in cardiocytes from obese rats. The data suggest involvement of both receptor and postreceptor defects in the development of an insulin-resistant state in cardiac muscle.

3-O-Methylglucose↗
PubMed1985

Insulin receptor protein rendered visible in triton X-114 membranes.

Insulin receptor protein has been visualized by electron microscopy. This was rendered possible after the molecules had been extensively purified and had been reinserted into Triton X-114 membranes in a situation similar to that found in biological membranes. Freeze fracturing then revealed the insulin receptor molecules as particles randomly distributed in the fracture plane of the artificial membranes. The sizes of the particles are in the range expected from biochemical data.

Animals↗
PubMed1985

Insulin action on cardiac glucose transport. Studies on the role of the sodium pump.

Isolated muscle cells from adult rat heart have been used to study the relationship between myocardial glucose transport and the activity of the Na+, K+ pump. 86Rb+ uptake by cardiac cells was found to be linear up to 2 min, with a steady state reached by 40-60 min, and was used to monitor the activity of the sodium pump. Both the ouabain-sensitive and ouabain-insensitive 86Rb+ uptake by cardiac cells were found to be unaffected by insulin treatment under conditions in which a significant stimulation of 3-O-methylglucose transport occurred. 86Rb+ uptake was markedly reduced by the presence of calcium or magnesium or both, but remained unresponsive toward insulin treatment. Inhibition of the sodium-pump activity by ouabain and a concomitant shift in the intracellular Na+/K+ ratio did not affect basal or insulin-stimulated rates of 3-O-methylglucose transport in cardiac myocytes. The data argue against a functional relationship between the myocardial Na+, K+ pump and the glucose-transport system.

3-O-Methylglucose↗