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Biomedical subjects

J Tepperman

Publications and source records attributed to J Tepperman.

At least 55 records · Page 3Linked to original sources
PubMed1976

Insulin binding and insulin response of adipocytes from rats adapted to fat feeding.

The effect of fat feeding on adipocyte insulin binding was examined to expand a study of adaptive changes in plasma membrane functions. Cells from rats fed a high fat (L) diet for five to seven days bound less insulin and showed a decreased response to insulin (glucose oxidation) compared to those from rats fed a high glucose (G) diet. Both high and low affinity sites were influenced; the extent of the binding difference increased as increasing concentrations of insulin were present in the assay medium. Diet did not change hormone degradation on the capacity of phospholipase C to increase binding. Concanavalin A effects on fat cells were also decreased by L diet both in inhibition of insulin binding and its insulin-like effect on glucose oxidation. Spermine, which had no effect on insulin binding, also had a smaller insulin-like effect on glucose oxidation by L cells than by G cells. Serum insulin was significantly lower (30 +/- 3.7 muU/ml) in L than in G (43 +/- 3.1 muU/ml) groups. Dietary fat produces alterations in fat cells that decrease insulin binding as a part of a complex overall adaptation to the diet.

Adipose Tissue↗
PubMed1975

Nicotinamide adenine dinucleotide phosphate-malic enzyme of rat liver. Purification, properties, and immunochemical studies.

Rat liver malic enzyme (EC 1.1.1.40) was purified from livers of rats fasted and refed a high sucrose diet containing 1% desiccated thyroid powder. The purification was accomplished by a six-step procedure. The specific activity of the purified enzyme was increased 181-fold above that of the initial high speed supernatant of liver extracts. Slight additional purification of malic enzyme was achieved with preparative disc electrophoresis. The specific activities of the purified rat liver malic enzyme from the least two steps were between 28.0 and 30.5 units per mg of protein. Homogeneity of the purified enzyme was determined by disc and starch gel electrophoresis as well as sedimentation velocity and sedimentation equilibrium studies. The molecular weight and S20, w values of rat liver malic enzyme are 268,000 and 10.2, respectively. Amino acid analysis based on milligram of protein hydrolyzed yielded higher amounts of leucine and glutamic acid but lower quantities of alanine and voline per subunit than the corresponding Escherichia coli enzyme...

Amino Acids↗
PubMed1975

Effects of high carbohydrate, high fat, or high protein diets on glucose oxidation by isolated intestinal epithelial cells of the chick.

A parallel study of 3-O-methyl glucose transport by everted intestinal sacs and [U-14C]glucose oxidation by isolated, dispersed intestinal cells was done in chicks (1) adapted to a high carbohydrate (HC), high fat (HF), or high protein (HP) diet for 2 weeks or (2) fasted up to 5 days. HF and HP diets significantly decreased both serosal : mucosal (S : M) distribution ratios of 3-O-methyl glucose by everted sacs and glucose oxidation by dispersed cells. The effects were more pronounced in HF diet-fed chicks. Fasting signficiantly increased the S : M ratio throughout a 5-day fasting period, whereas glucose oxidation was increased after a 1-day fast and was decreased after a 5-day fast. Feeding HC diet for 1 week to chicks adapted to HF diet restored both functions to control levels. Refeeding fasted chicks for 3 days also restored S : M ratio to control levels. Histological examination of tissues from various treatment groups revealed no obvious morphological differences. The results suggest that the functional changes described represent adaptive changes at the cellular level and that these changes are readily reversible.

Adaptation, Physiological↗
PubMed1973

Epinephrine binding and the selective restoration of adenylate cyclase activity in fat-fed rats.

Fat feeding results in a progressive loss of epineph-rine- and glucagon-stimulated adenylate cyclase activity in adipocyte plasma membrane sacs (ghosts). Basal and NaF-stimulated adenylate cyclase activities in fat-fed animals are not significantly different from those in preparations obtained from chow-fed rats. The high fat diet increases the mean adipocyte diameter rapidly, but increased cell size, at least in the case of epinephrine stimulation, is not responsible for the decreased hormone-stimulated adenylate cyclase activity. Diet shifts to high carbohydrate or high protein regimens result in the restoration of the epinephrine-stimulated, but not the glucagon-stimulated, activity without a significant reduction in mean cell diameter. Both hormone-resistant adipocyte ghosts from fat-fed animals and ghosts obtained from hormone-sensitive adipocytes bind the same amount of [(3)H]epinephrine per milligram of membrane protein. These data indicate that the fat diet inhibits epinephrine-stimulated adenylate cyclase activity at a point between the hormone receptor and the catalytic unit of adenylate cyclase.

Adenylyl Cyclases↗
PubMed1972

Effects of starvation, refeeding, and fat feeding on adipocyte ghost adenyl cyclase activity.

Basal adenyl cyclase activity and its response to epinephrine and glucagon were studied in isolated adipocyte ghosts obtained from fed, starved, refed, and fat-diet-adapted rats. Epinephrine stimulation of adenyl cyclase was significantly increased in fasted rats, but the glucagon response did not change. Rats fasted for 48 hr and refed a high carbohydrate, low fat diet for 48 or 96 hr showed no differences from chow-fed animals in either basal or hormone-stimulated adenyl cyclase activity. Rats adapted to a high fat, low carbohydrate diet showed an initial and transitory increase in basal activity but a progressive loss of epinephrine- and glucagon-stimulated enzyme activities. The loss in hormone responsiveness correlated well with a decrease in hormone-stimulated lipolysis of fat pads and was associated with a significant increase in fat cell diameter.

Adenosine Triphosphate↗