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Biomedical subjects

J Shemer

Publications and source records attributed to J Shemer.

At least 19 recordsLinked to original sources
PubMed1992

[Glucose polymer solutions and prolonged exertion in the heat].

The effect of glucose polymer solutions on physical performance has been extensively investigated, mainly under controlled laboratory conditions. The influence of such beverages on fluid balance and on glycemic state in the field, during prolonged exercise of moderate intensity (a 134 km march) in the heat (32-41 degrees C, 60-14% relative humidity) was therefore studied. 48 endurance-trained men were randomly assigned to drink either a 7.2% glucose polymer (GP) electrolyte beverage or tap water (TW); there were 24 in each group. Each group was then divided into subgroups that either consumed fluid ad libitum, or were instructed to consume 1000 ml/hr. Mean fluid consumption of all subgroups was similar. There was a greater change in plasma volume for the TW than for the GP group (+7.9% vs. +4.8%, respectively; p less than 0.05). However, in neither the GP nor the TP group did dehydration exceed 2% of body weight. Blood glucose concentration increased significantly in subjects ingesting GP (p less than 0.01) while it decreased on each day of march in those drinking TW. It is concluded that the fluid intake recommended at present by the IDF is adequate to maintain hydration within the normal range during physical effort in the heat. The differences between the GP and the TW groups in this study do not justify the substitution of glucose-polymer solutions for water during prolonged, moderate exercise.

Adult↗
PubMed1992

Evolutionary origins of intercellular communication systems: implications for mammalian biology.

Traditionally, the two major systems of intercellular communication (i.e. the nervous and endocrine systems) were considered separate functional and anatomical entities. Recent studies have provided evidence that the biochemical elements of these systems have common early phylogenetic origins and have suggested that, with the exception of their anatomical diversity, all the systems of intercellular communication are biochemically similar. On the basis of these findings, we suggest that the overlaps between the nervous and endocrine systems, the widespread tissue production of hormones, and other phenomena are now more easily understood.

Animals↗
PubMed1992

Tissue-specific transcription start site usage in the leader exons of the rat insulin-like growth factor-I gene: evidence for differential regulation in the developing kidney.

The production of insulin-like growth factor-I (IGF-I) in extrahepatic tissues supports both autocrine and paracrine functions and is regulated differently from that in liver, which supports endocrine function. In rat liver, transcription initiation primarily occurs at four distinct, widely separated sites in exon 1 of the IGF-I gene, whereas in exon 2, transcription initiation occurs at a cluster of sites. To understand the molecular basis for tissue-specific regulation of IGF-I gene expression, we have mapped transcription start site usage in the following extrahepatic tissues: testes, lung, kidney, heart, brain, muscle, and stomach, with liver serving as a control. In adult rats, kidney and brain exhibited a pattern of exon 1 transcription similar to that seen in liver, i.e. roughly equivalent use of start sites 2 and 3. In contrast, testes and lung preferentially used start site 3, while stomach, heart, and muscle predominantly used start site 3. Start sites 1 and 4 were used in all tissues at extremely low levels. In those tissues studied in which exon 2 transcripts are expressed (testes, lung, stomach, and kidney), the pattern of exon 2 transcription initiation was identical to that in adult rat liver. During postnatal development, the use of all transcription start sites in exons 1 and 2 was coordinate in lung and stomach. Selection of transcription start sites in the kidney, on the other hand, was subject to regulation during postnatal development. Specifically, within exon 1, start site 3 was expressed constitutively throughout peri- and postnatal development. In contrast, the usage of start site 2 was not detected at late fetal or early postnatal stages, but appeared and rapidly increased only at the stage of weaning. Exon 2 transcripts in kidney also did not appear until the postnatal period. These data suggest tissue-specific and developmentally regulated transcription factors regulating IGF-I promoter activity or, alternatively, tissue-specific and developmental stage-dependent differences in the stability of IGF-I mRNAs resulting from the use of different transcription start sites. These different mRNAs may be of significance in the differential regulation of IGF-I production for autocrine or paracrine function.

Animals↗
PubMed1992

Normal renin-aldosterone-insulin and potassium interrelationship in FMF patients and amyloid nephropathy.

The renin-aldosterone system and plasma insulin were studied in 19 patients with familial Mediterranean fever (FMF). Their relationships to serum potassium level at rest and before and after oral glucose loading are described. An interesting finding is the occurrence of hyperkalemia in the absence of oliguria, in the advanced stages of renal failure. No differences were found in the activity of the renin-angiotensin-aldosterone system to explain these variations in serum potassium found in some of the patients. The response of the renin-aldosterone system to glucose loading showed no abnormality, and the regular relationship between serum potassium, plasma renin activity (PRA), aldosterone, insulin, and plasma pH is maintained. Levels of insulin, potassium, and bicarbonate in serum or plasma pH were found similar in FMF patients with normal renal function with and without proteinuria. Further decrease in renal function due to the progression of the underlying disease is manifested by an increase in FENa+ and FEK+ and a hyperchloremic metabolic acidosis, as is the case in other patients with chronic renal failure.

Adult↗
PubMed1992

Medical limitations of gas masks for civilian populations: the 1991 experience.

Using a gas mask (GM) may involve considerable inconvenience, impairment of respiration and communication, and serious psychological reactions. The medical literature is primarily focused on the occupational aspects of using the GM by young and healthy workers. In contrast, there is hardly any information concerning the use of GMs by large, unselected populations, including children, the elderly, and the sick. Issuing GMs to all residents of Israel prior to Operation Desert Storm created an urgent need to define the populations whose health might be jeopardized by using the standard GM. Adding an active air supply system (AASS) to a standard GM may ease the burden on this high-risk group. We evaluated the physiological aspects of breathing with a GM, with and without AASS, in respect to pathophysiology of diseases, and reached a set of criteria for identifying those who may be endangered by a GM and are expected to benefit from the AASS. The method used to sort and identify those entitled to the AASS is described.

Chronic Disease↗
PubMed1991

The Ural train-gas pipeline catastrophe: the report of the IDF medical corps assistance.

Following the destruction of two trains in the Urals 2000 km east of Moscow, as a consequence of the conflagration caused by an explosion from a leaking natural gas pipeline, 3000 people were injured;* most of them (2200) died* immediately and the others (about 800) were badly burned. At the request of the Soviet Union Government a medical military delegation was sent to give assistance to the injured people. This report describes the treatment given by the delegation to 40 patients with burns of between 40 and 90 per cent TBSA during a period of 10 days. An insight into a Soviet Union Trauma Center is given and the good treatment given by the Soviet colleagues is emphasized.

Blast Injuries↗
PubMed1989

Insulin and IGF-I stimulate phosphorylation of their respective receptors in intact neuronal and glial cells in primary culture.

Previous studies have shown that insulin and IGF-I bind to their respective receptors and stimulate autophosphorylation of the receptor beta subunits in detergent extracts of neuronal and glial cells. In the present study, intact neuronal and glial cells in primary culture have been utilized to characterize insulin- and IGF-I-stimulated phosphorylation of their receptors. Following [32P]orthophosphate labelling and stimulation by insulin or IGF-I, the cells were solubilized and the phosphorylated receptors were partially purified on wheat germ agglutinin--agarose columns, and immunoprecipitated using anti-phosphotyrosine or anti-insulin receptor antibodies. Insulin stimulated the phosphorylation of its receptor beta subunit (95 kD phosphoprotein) in a dose-dependent manner, within at least 20 seconds in both neuronal and glial cells. Additionally, a 102-kD phosphoprotein was observed in insulin-stimulated neuronal cells. Maximal stimulation of receptor phosphorylation occurred at 1 minute for the glial cells, and 10 minutes for the neuronal cells. IGF-I stimulated the phosphorylation of two phosphoproteins in intact neuronal and glial cells; a 95-kD protein and a 102-kD protein, in a dose-dependent manner. These observations demonstrate that both insulin and IGF-I stimulate the phosphorylation of the beta subunits of their respective receptors in brain cells in a similar fashion to their effects on receptors from nonneural tissues.

Animals↗
PubMed1989

Liver insulin receptor tyrosine kinase activity in a rat model of type II diabetes mellitus and obesity.

Spontaneous hypertensive-corpulent rats (SHR/N-corpulent), homozygous for the corpulent gene (cp/cp), are obese, hyperinsulinemic and exhibit abnormal glucose tolerance and thus represent a model for type II diabetes and obesity. In view of their overall insulin resistance, we examined liver insulin receptor binding and tyrosine kinase activity from corpulent rats and lean littermates fed purified diets containing 54% sucrose or starch for about 12 wk. Specific 125I-insulin binding to crude liver membranes from female corpulent rats fed either starch or sucrose was reduced to approximately 50% of that seen in lean rats (14 vs. 7%). Affinity of insulin receptors was similar in all groups, suggesting that hyperinsulinemic corpulent rats possess fewer hepatic insulin receptors than do lean rats. Using similar numbers of wheat germ agglutinin-agarose (WGA)-purified insulin receptors with similar affinities for insulin, it was found that basal and insulin-stimulated phosphorylation of the synthetic tyrosine-specific kinase substrate poly(Glu, Tyr)4:1 was similar in lean and obese rats fed sucrose or starch. It is suggested that the contribution of the liver to the insulin resistance in obese SHR/N-cp rats probably lies distal to the insulin receptor tyrosine kinase.

Animals↗
PubMed1988

Characterization of the altered oligosaccharide composition of the insulin receptor on neural-derived cells.

Typical insulin receptors are present on neuroblastoma cell lines. High affinity binding for insulin was present in membrane preparations from NG108 (a hybrid mouse neuroblastoma-rat glioma) as well as in membranes from SK-N-MC and SK-N-SH, two human neuroblastoma cell lines. Specific [125I]insulin binding was 24.4% for NG108, 16.9% for SK-N-MC and 5.2% for SK-N-SH at membrane protein concentrations of 0.4 mg/ml. IC50 for [125I]insulin binding was 3.4 nM in NG108 membrane preparations and 0.9 nM for SK-N-SH and 1.8 nM in SK-N-MC membranes. Apparent mol. wt. for the alpha subunits (identified by specific immunoprecipitation using the anti-insulin receptor antiserum B10) on SDS PAGE was 134 kDa for NG108; 124 kDa for SK-N-MC and 120 kDa for SK-N-SH. Neuraminidase digestion increased the mobility of the alpha subunit from both NG108 and SK-N-MC receptors to 120 kDa, whereas that from SK-N-SH were unaffected. Endoglycosidase H and endoglycosidase F digestions increased the mobility of the alpha subunits of all 3 cell lines to varying degrees, suggesting the presence of N-linked glycosylation. Insulin induced autophosphorylation of the insulin receptor beta subunit in WGA-purified membranes from all 3 cell lines. In addition, phosphorylation of a protein with an apparent mol. wt. 105 kDa was stimulated by insulin in WGA purified membranes from NG108. Tyrosine-specific kinase activity was present in the membranes from each cell line and was stimulated by insulin in a dose-dependent manner from 10(-9) to 10(-6) M. Proinsulin was about 100 times less potent in stimulating phosphorylation of the artificial substrate poly (Glu, Tyr)4:1 when compared to insulin in accordance with its lower binding affinity to the insulin receptor. Hexose transport was stimulated by insulin in all 3 cell lines. These results indicate that neuroblastoma cells contain specific insulin receptors and that they may be useful as models for studying the role of insulin in nervous tissue.

Binding, Competitive↗
PubMed1988

Insulin receptors in the brain: structural and physiological characterization.

The present study was conducted to characterize insulin receptors and to determine the effects of insulin in synaptosomes prepared from adult rat brains. Binding of 125I-insulin to synaptosome insulin receptors was highly specific and time dependent: equilibrium binding was obtained within 60 minutes, and a t1/2 of dissociation of 26 minutes. Cross-linking of 125I-insulin to its receptor followed by SDS-PAGE demonstrated that the apparent molecular weight of the alpha subunit of the receptor was 122,000 compared with 134,000 for the liver insulin receptor. In addition, insulin stimulated the dose-dependent phosphorylation of exogenous tyrosine containing substrate and a 95,000 MW plasma membrane associated protein, in a lectin-purified insulin receptor preparation. The membrane associated protein was determined to be the beta subunit of the insulin receptor. Incubation of synaptosomes with insulin caused a dose-dependent inhibition of specific sodium-sensitive [3H]norepinephrine uptake. Insulin inhibition of [3H]norepinephrine uptake was mediated by a decrease in active uptake sites without any effects in the Km, and was specific for insulin since related and unrelated peptides influenced the uptake in proportion to their structural similarity with insulin. These observations indicate that synaptosomes prepared from the adult rat brain possess specific insulin receptors and insulin has inhibitory effects on norepinephrine uptake in the preparation.

Animals↗
PubMed1988

Insulin-related materials in the nervous system of vertebrates and non-vertebrates: possible extrapancreatic production.

Studies from multiple laboratories with a range of methods raised the possibility that insulin production occurs naturally at extrapancreatic sites. Part A covers the presence of insulin-related materials in organisms that do not have an endocrine pancreas, including unicellular prokaryotes and eukaryotes as well as multicellular non-vertebrate animals (insects et al.) and plants. Part B covers possible production of insulin by extrapancreatic tissues of vertebrates that are remote from a source of pancreatic insulin e.g. early chick embryos and mammalian cells in culture. Part C covers possible extrapancreatic insulin production in mammals in vivo. Each section ends with an outline summary with evidence in favor of and against the hypothesis.

Amino Acid Sequence↗
PubMed1988

Insulin-sensitive tyrosine kinase is increased in livers of adult obese Zucker rats: correction with prolonged fasting.

Adult obese Zucker rats (fa,fa) are hyperinsulinemic and insulin resistant. Specific insulin binding to crude membranes prepared from livers was 2.8% (per mg protein) in fatty animals compared with 7.9% in homozygous lean (Fa,Fa) and 9.0% in heterozygous lean (Fa,fa) animals. Insulin binding increased in liver membranes from fatty animals after a 72-h fast to 6.4%. The reduced insulin binding in livers from fatty rats was associated with elevated insulin-sensitive tyrosine kinase activity, which fell towards control values after the fast. The elevated tyrosine kinase activity was associated with an increased maximum velocity (Vmax) without a change in Michaelis-Menten constant (Km) for its substrates, ATP and poly(Glu,Tyr)4:1. These findings suggest that, in adult fatty rats, insulin-sensitive tyrosine kinase has increased intrinsic activity. Further, the effect of the prolonged fast on both insulin binding and kinase activity, suggest that in this model environmental factors, and not necessarily a genetic abnormality, may regulate liver insulin receptors and their kinase. Whether the inverse relationship of the kinase and insulin receptor number is the result of a compensatory mechanism remains to be elucidated.

Animals↗
PubMed1987

Insulin and insulin-like growth factor-I stimulate a common endogenous phosphoprotein substrate (pp185) in intact neuroblastoma cells.

Mouse neuroblastoma N18 cells contain specific high affinity insulin and insulin-like growth factor-I (IGF-I) receptors. Insulin and IGF-I induce phosphorylation, in intact cells, of their respective receptor beta subunits. The insulin receptor beta subunit is represented by a 95-kDa phosphoprotein that is recognized by a specific antiserum (B10). The IGF-I receptor beta subunit is represented by two phosphoproteins of molecular mass 95 and 105 kDa. The hormone-induced phosphorylation was rapid and dose-dependent occurring on both phosphoserine and phosphotyrosine residues. In addition, both insulin and IGF-I induced phosphorylation of an endogenous protein of molecular mass 185 kDa (pp185). The rapidity and dose dependency of the phosphorylation of pp185 suggested that it may represent a common endogenous substrate for the insulin and IGF-I receptors in these neural-derived cells. Phosphorylation was primarily on phosphoserine and phosphotyrosine residues. pp185 did not absorb to wheat germ agglutinin-agarose and was not stimulated by either epidermal growth factor or platelet-derived growth factor. The finding of pp185 in these neural-related cells as well as in non-neural tissues suggests that it may represent a ubiquitous endogenous substrate for both the insulin and IGF-I receptor kinases.

Animals↗
PubMed1987

Insulin receptors and insulin action in dissociated brain cells.

The present study was conducted to characterize insulin receptors and insulin action in rat brain cells. Binding of [125I]insulin to cells obtained by mechanically dissociating rat brains was 86% specific, time-dependent and reached equilibrium within 90 min. The t1/2 of association was 14 min and t1/2 of dissociation was 8 min. Scatchard analysis demonstrated the typical curvilinear plot providing high affinity (0.03 nM) and low affinity (6.6 nM) binding sites. The total number of binding sites were 0.15 pmol/mg protein. Crosslinking of [125I]insulin to its receptors on dissociated brain cells followed by SDS-PAGE and autoradiography showed that the alpha-subunit of the receptor had a molecular weight of 122,000. This was in contrast with a molecular weight of 134,000 for the liver alpha-subunit. Incubation of dissociated brain cells with insulin resulted in a concentration-dependent inhibition of total [3H]norepinephrine (NE) uptake. This inhibitory effect of insulin on [3H]NE uptake was sodium ion-dependent suggesting that 80-90% of the sodium ion-dependent uptake was insulin-sensitive. Incubation of lectin-purified insulin receptors with insulin resulted in a time- and concentration-dependent stimulation of phosphorylation of the tyrosine residue of an exogenous substrate poly (Glu, Tyr) (4:1). In addition, insulin also stimulated the autophosphorylation of the beta-subunit of the insulin receptors. These observations corroborate our contention that insulin exerts neuromodulatory effects mediated by the specific insulin receptors in the brain.

Animals↗
PubMed1987

Insulin-like growth factor I receptors in neuronal and glial cells. Characterization and biological effects in primary culture.

Primary cultures of neuronal and glial cells from 1-day-old neonatal rats contain high affinity receptors for insulin-like growth factor I (IGF-I). The IC50 for displacement of 125I-IGF-I binding by unlabeled IGF-I was 3 nM for neuronal cells and 4 nM for glial cells. Unlabeled insulin was 20-50 times less potent. Apparent molecular mass of the alpha subunits of the IGF-I receptor was 125 kDa in neuronal and 135 kDa in glial cells. IGF-I induced autophosphorylation of the IGF-I receptor beta subunit in lectin-purified membrane preparations in a dose-dependent manner. The major phosphoamino acid of the beta subunit in both cell types was tyrosine in the IGF-I-stimulated state and serine in the basal state. Apparent molecular mass of the beta subunits of the IGF-I receptors was 91 kDa for neuronal and 95 kDa for glial cells. Tyrosine kinase activity of the IGF-I receptors was demonstrated by IGF-I-induced phosphorylation of the exogenous substrate poly(Glu, Tyr) 4:1 in both cell types. IGF-I had no effect on 2-deoxyglucose uptake in neuronal cells. In contrast, in glial cells, IGF-I stimulated 2-deoxyglucose uptake at very high doses, presumably acting via the insulin receptor. The effect of IGF-I as a neurotrophic growth factor in both neuronal and glial cells was demonstrated by its stimulation of [3H]thymidine incorporation. These findings suggest the IGF-I is an important growth factor in nervous tissue-derived cells.

Animals↗
PubMed1987

Characterization of an endogenous substrate related to insulin and insulin-like growth factor-I receptors in lizard brain.

Lizard insulin receptors are evolutionarily highly conserved. Wheat germ agglutinin-purified brain membranes demonstrate the presence of an endogenous substrate (pp 105) for both the insulin and insulin-like growth factor-I receptors. Both insulin and I-insulin-like growth factor-I stimulate the phosphorylation of this endogenous substrate in a dose-dependent manner. Following insulin-stimulated autophosphorylation of the beta subunit, there is a lag period of about 5 min prior to observable phosphorylation of the endogenous substrate. Phosphoamino acid analysis of both the beta subunit as well as pp 105 reveal primarily phosphotyrosine in both the basal as well as the stimulated state.

Amino Acids↗