Search PubMed⌕ Search

Biomedical subjects

J Hirsch

Publications and source records attributed to J Hirsch.

At least 289 records · Page 16Linked to original sources
PubMed1977

Behavior-genetic analysis of Phormia regina: conditioning, reliable individual differences, and selection.

Using proboscis extension (unconditioned response) to sucrose (unconditioned stimulus), individual blowflies (Phormia regina) were classically conditioned to saline and to water (conditioned stimuli) with sensitization controls, thus providing unique, independently replicated evidence both of learning in Diptera and of reliably measured individual differences. Directional and stabilizing selection have bred high and low performance lines markedly different from an unselected control line as a step in the analysis of behavior-genetic correlates. This replicates and extends previous selection analysis with improved conditioning technique. Also, some unwarranted claims of learning in Diptera are discussed.

Animals↗
PubMed1976

Phosphorylation of rat liver ribonucleic acid polymerase I by nuclear protein kinases.

Phosphorylation of rat liver RNA polymerase I occurred when intact rat liver nuclei were incubated with [gamma32P]ATP and N6,O2' dibutyryl cyclic 3':5'-AMP. In addition, partially purified RNA polymerase I could be phosphorylated in vitro by an endogenous protein kinase. Phosphorylation by either method was followed by extensive purification of the enzyme. This revealed that 32P remained bound to the enzyme throughout purification. Analysis of the homogeneous labeled protein by polyacrylamide gel electrophoresis under nondenaturing conditions followed by autoradiography revealed that only one of the two forms of RNA polymerase I in rat liver nuclei was phosphorylated. RNA polymerase II was not phosphorylated in intact nuclei. Polyacrylamide gel electrophoresis of the phosphorylated RNA polymerase I in the presence of 0.1% sodium dodecyl sulfate followed by autoradiography demonstrated that the 32P was located primarily on enzyme subunits SA1, SA3, and SA5-SA6. High voltage paper electrophoresis of a partial acid hydrolysate of phosphorylated RNA polymerase I revealed that both serine and threonine residues were phosphroylated. N6,O2'-Dibutyryl cyclic 3':5'-AMP stimulated endogenous RNA polymerase I activity and endogenous nuclear protein phosphorylation in intact nuclei. These results suggest that phosphorylation of RNA polymerase I by nuclear protein kinases may play a role in the control of transcription in mammalian cells.

Animals↗
PubMed1976

Adipose tissue cellularity in human obesity.

All human obesity is characterised by adipocyte hypertrophy and when body weight exceeds 170 per cent of ideal, a maximum cell size of roughly twice normal is achieved. With greater severity, hyperplasia becomes increasingly manifest and when body weight exceeds 170 per cent of ideal, the degree of hyperplasia is well correlated with severity. Although severity and hypercellularity are often found in those with early onset of obesity, individuals can be found who are hypercellular but have had a later onset of obesity. Until the details of cellular development in man are more fully understood, the precise timing of 'critical' periods for cellular development must remain speculative.

Adipose Tissue↗
PubMed1976

Effects of hypophysectomy and acute growth hormone treatment upon glucose metabolism in adipose tissues and isolated adipocytes of rats.

Glucose oxidation and incorporation into lipid were measured in epididymal adipose tissues and isolated adipose cells of normal and hypophysectomized rats in an effort to determine whether the acute hypoglycemic effect of a systemic growth hormone (GH) injection was related to alterations in the glucose metabolism of adipose tissue. The rats were fed rat chow or a high sucrose diet and received 100 mug GH intraperitoneally 30 minutes or three and one-half hours before sacrifice. Hypophysectomized rats showed a lower plasma glucose as compared with normal rats on both diets. Thirty minutes after a GH injection there was a further decrease of the plasma glucose which, however, was not present in those rats receiving GH three and one-half hours before sacrifice. Adipose tissues from hypophysectomized rats fed the high sucrose diet showed a blunted insulin sensitivity as compared with normal rats on a similar diet. The insulin sensitivity of these tissues was further decreased 30 minutes after a GH injection. Basal glucose metabolism of isolated adipocytes from hypophysectomized rats, as compared with normal rats, was depressed if they were fed rat chow, was at normal levels if they were fed the high sucrose diet and was increased if they were fed the sucrose diet and received triiodothyronine and cortisone supplements. No manipulations of diet or hormonal treatments made the isolated adipocyte from hypophysectomized rats sensitive to insulin either 30 minutes or three and one-half hours after a GH injection. Since basal glucose utilization is not enhanced by GH injection and both the blunted insulin sensitivity of adipose tissue and the absent insulin sensitivity of adipopocytes would be expected to produce hyperglycemia rather than hypoglycemia, it is concluded that immediate systemic effects of a GH injection on carbohydrate metabolism are not related to changes in glucose metabolism of the peripheral adipose tissues.

Adipose Tissue↗
PubMed1976

Noncompensation of adipose mass in partially lipectomized mice and rats.

The effects of surgical ablation of adipose tissue were studied in normal mice and rats. It was found that: 1) restortation of adipose tissue does not occur locally in epididymal fat pads of young rats. 2) Bilateral epididymal fat pad removal in mice disrupts the testes and causes the other fat depots to accumulate excess lipid, but these effects are not sustained; After a sufficient recovery period, testes appear normal and no excess lipid is found in the remaining depots; 3) Temporary enlargement of remaining depots is probably due specifically to epididymal pad removal. It does not occur in response to inguinal depot removal, nor in response to disruption of the testes alone; 4)The quantity of lipid stored by a rapidly growing mouse depends on the number of intact depots in the mouse. These results suggest that surgical removal of fat does not lead to compensatory growth of fat. Autoregulation of adipose tissue mass, if it occurs, most likely operates through detection of adipocyte size rather than adipocyte number or total fat mass.

Adipose Tissue↗
PubMed1976

Activation of renal erythropoietic factor by phosphorylation.

Renal erythropoietic factor (REF) serves as a substrate for a cyclic nucleotide-dependent protein kinase. The phosphorylation of REF is associated with increased erythropoietic activity. Conversely, REF isolated from hypoxic rats is a poor phosphate acceptor. These findings and the presence of a positive correlation between erythropoietin levels and urinary excretion of adenosine 3',5' monophosphate (cyclic-AMP) in anemic individuals suggest that the cyclic-AMP-protein kinase system plays an important role in the activation of REF.

Anemia↗
PubMed1975

Pancreatic insulin release and peripheral tissue resistance in Zucker obese rats fed high- and low-carbohydrate diets.

An effort was made to determine to what degree the hyperinsulinemia found in the genetically obese Zucker rat is the result of the carbohydrate content of the diet. When Zucker obese rats are fed precisely the same amount of carbohydrate as lean controls and allowed to become obese by drinking vegetable oil, their pancreatic islets still release 59% more insulin than do those from lean controls. When their diet contains even more carbohydrate, fed from weaning, and they become equivalently obese, their islet insulin release is increased by an additional 46%. An obese Zucker rat fed a high-carbohydrate diet possesses muscle sensitivity to insulin and enlarged adipocytes undergoing active lipogenesis. A rat becoming equivalently obese on a high-fat diet has an absence of insulin sensitivity in muscle and diminished lipogenesis in adipocytes. Clearly, the composition of the diet plays an important role in the metabolic consequences of obesity, but neither diet nor changes in peripheral glucose metabolism can completely explain the hyperinsulinemia.

Adipose Tissue↗
PubMed1975

Tracheal mucous transport in experimental canine asthma.

Tracheal mucous velocity (TMV) was measured in experimental canine asthma. All 10 sensitive dogs exposed to an aerosol of Ascaris suum extract showed a decrease in TMV to about one-third of base-line values within 45 min whereas only half of them (reactors) responded with bronchospasm as measured by a significant reduction in specific respiratory system conductance (SGrs). Mean TMV remained decreased at the end of the 2-h observation period when mean SGrs had returned to base-line values in the reactors. Neither TMV nor SGrs changed in nonsensitive animals who inhaled ragweed antigen. Aerosols of acetylcholine and histamine increased TMV thereby excluding these mediators as responsible for the impairment of mucous transport in asthma. Nebulization of A. suum antigen together with a selective antagonist of slow reacting substance of anaphylaxis (srs-a) produced a marked increase of TMV in all dogs regardless of whether or not bronchospasm was elicited. This suggests that the observed decrease in TMV may be related to the release of SRS-A during the immunologic reaction.

Animals↗
PubMed1975

Tracheal mucociliary transport in patients with cystic fibrosis and its stimulation by terbutaline.

Tracheal mucous velocity was measured by observing the motion of teflon discs across the tracheal mucosa through a fiberoptic bronchoscope. The average rate of movement in 14 adult patients with cystic fibrosis was 2.6 mm per min plus or minus 3.3 SD, compared with 20.1 mm per min plus or minus 6.3 in 20 normal subjects of the same age (P less than 0.001). This failure of mucociliary transport may play a role in the pathogenesis of the pulmonary disease in cystic fibrosis. Administration of a beta-adrenergic agent, terbutaline, increased the average mucous velocity in the patients with cystic fibrosis (to 5.5 mm per min plus or minus 3.6 SD, P less than 0.001) but not in control subjects. This observation has potential therapeutic significance.

Adolescent↗
PubMed1975

Effect of cuffed endotracheal tubes on tracheal mucous velocity.

The inflated cuffed endotracheal tube produces a significant depression of tracheal mucous velocity in anesthetized dogs after one hour. This effect occurs with bot low and high compliance cuffs but is not observed with an uncuffed tube. This phenomenon is another factor that must be considered in establishing criteria for the frequency of cuff deflation in patients supported by mechanical ventilators.

Animals↗