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Biomedical subjects

R Schwartz

Publications and source records attributed to R Schwartz.

At least 307 records · Page 17Linked to original sources
PubMed1982

Factors contributing to the up regulation of dopaminergic receptors by chronic haloperidol.

The relationship of the magnitude and persistence of elevated striatal dopamine receptor binding sites to the dose and duration of haloperidol treatment has been examined in rats. The magnitude of elevation was found to be significantly related both to dose and duration of dose. The persistence of statistically significant receptor binding elevation, after withdrawal, was estimated to be 0.67 days/day on haloperidol. Receptor binding was carried out with 3H-spiroperidol.

Animals↗
PubMed1981

Use of nonabsorbable markers for gastrointestinal contents in in vivo measurement of magnesium bioavailability.

Magnesium absorption from five leafy vegetables was measured in rats using 28Mg as an extrinsic label and polyethylene glycol (PEG) and chromium-mordanted vegetable fibers (cr-mordants) as unabsorbable markers of soluble and particulate gut and fecal contents, respectively. The test meals used in this investigation were identical to those used in a previous test in which we found: a) that stable 26Mg biologically incorporated into the vegetables was freely exchangeable with an extrinsic 28Mg tracer; b) PEG consistently preceded Cr-mordants in transit through the gut; and c) fecal Mg isotope excretion 12 hours after the test meal was inadequate for measurement of Mg absorption. Accordingly, in the present investigation, all measurements in feces and gut contents were made 24 hours after the test meal. By that time an average of greater than 60% of the ingested PEG had been excreted. Magnesium-28 excretions, estimated under these conditions, were 4-5% less than they would have been had fecal PEG excretion been 100%. The discrepancy was due to partial separation of PEG and Mg in the lower gastrointestinal tract (GIT), possibly due to sequestration of Mg by microorganisms. That Mg must have entered an insoluble phase in the lower GIT was born out by the observation that little or no Mg absorption occurred in the cecum or colon. As before, Cr-modants lagged behind PEG and unabsorbed 28Mg, and thus do not seem suitable to monitoring intestinal transit of Mg.

Absorption↗
PubMed1981

Bone pathology and parathyroid gland activity in hypocalcemic magnesium-deficient chicks.

Growing chicks fed magnesium-deficient (150 ppm Mg) diets for 14 or 21 days developed significant hypomagnesemia and hypocalcemia compared to control chicks fed 1,000 ppm Mg. The hypocalcemia was accompanied by significant parathyroid gland hyperactivity, suggesting that magnesium deficiency did not impair parathyroid gland function. Despite parathyroid gland hyperactivity, however, bone resorption was decreased in the magnesium-deficient chicks, although bone formation was not affected by magnesium depletion. The decrease in bone resorption in the magnesium-deficient chicks was correlated with significant bone magnesium depletion and resulted in increased bone calcium content. These findings suggested that the development of hypocalcemia in magnesium-deficient chicks was related to decreased bone resorption, due to impaired osteocytic function rather than parathyroid gland insufficiency. The results also offer an explanation for the decrease in skeletal responsiveness to PTH which has been reported during magnesium depletion.

Animals↗
PubMed1981

Regulation of tropomyosin gene expression during myogenesis.

In skeletal muscle, tropomyosin has a critical role in transduction of calcium-induced contraction. Presently, little is known about the regulation of tropomyosin gene expression during myogenesis. In the present study, qualitative and quantitative changes in the nucleic acid populations of differentiating chicken embryo muscle cells in culture have been examined. Total nucleic acid content per nucleus increased about fivefold in fully developed myotubes as compared to mononucleated myoblasts. The contribution of deoxyribonucleic acid to the total nucleic acid population decreased from 24% in myoblasts to 5% of total nucleic acid in myotubes. Concomitant with the decrement in deoxyribonucleic acid contribution to total nucleic acid was an increase in polyadenylated ribonucleic acid (RNA) content per cell which reached levels in myotubes that were 17-fold higher than those of myoblasts. Specific changes in the RNA population during myogenesis were further investigated by quantitation of the synthetic capacity (messenger RNA levels) per cell for alpha- and beta-tropomyosin. Cell-free translation and immunoprecipitation demonstrated an approximately 40-fold increase in messenger RNA levels per nucleus for alpha- and beta-tropomyosin after fusion in the terminally differentiated myotubes. Indirect immunofluorescence with affinity-purified tropomyosin antibodies demonstrated the presence of tropomyosin-containing filaments in cells throughout myogenesis. Thus, the tropomyosin genes are constitutively expressed during muscle differentiation through the production of tropomyosin messenger RNA and translation into tropomyosin protein.

Animals↗
PubMed1981

Chronic maternal hyperinsulinemia and hypoglycemia. A model for experimental intrauterine growth retardation.

Chronic hypoglycemia was produced in pregnant rats during the last third of gestation through the constant infusion of insulin by a subcutaneously implanted, osmotically driven minipump. The offspring, delivered by cesarean section on day 20 of gestation, demonstrated intrauterine growth retardation compared to control fetuses. This effect was associated with fetal hypoglycemia and hypoinsulinemia. Fetal total and branch-chain amino acid concentrations were not affected. Increases in maternal to fetal glucose ratio and fetal insulin to glucose ratio in the experimental group were interpreted to indicate that limitation in the availability of glucose, a major fetal nutrient, was the basis for these effects.

Amino Acids↗
PubMed1981

Increased erythropoiesis and elevated erythropoietin in infants born to diabetic mothers and in hyperinsulinemic rhesus fetuses.

The pathogenesis of the increased erythrocytosis and extramedullary erythropoiesis observed in infants of diabetic mothers (IDM) has been obscure. In the present studies, IDM were found to have elevated umbilical plasma erythropoietin (Ep) concentrations by radioimmunoassay. 22 of 61 IDM (36%) had levels above the range of 28 nonasphyxiated, appropriately grown normal infants. In 16 controls and 20 IDM, plasma Ep correlated directly with plasma insulin (P less than 0.001, r = 0.73). To investigate this relationship further, a chronic rhesus model was studied with continuous fetal hyperinsulinemia for 21 d in utero in the last third of pregnancy. In five experimental fetuses, plasma insulin levels averaged 4,210 microU/ml at delivery, whereas plasma Ep was above the range of six controls. In addition, the experimental fetuses had elevated reticulocyte counts in umbilical cord blood. The mechanism for the increased plasma Ep associated with hyperinsulinemia in the fetus is unexplained but may be mediated by fetal hypoxia.

Animals↗
PubMed1981

Tartrazine-containing drugs.

Although the incidence of tartrazine sensitivity in the general population is low, serious adverse reactions have occurred. To prevent unnecessary exposure of sensitive patients, physicians should avoid prescribing tartrazine-containing drugs. Because of new FDA requirements that manufacturers list tartrazine dye in both over-the-counter and prescription drugs, many manufacturers have reformulated their products to remove this colorant. Therefore, previously published lists of tartrazine-containing drugs are outdated. We conducted a survey of American manufacturers to derive a current list of tartrazine-containing drugs. This list is intended for use as a guide for health professionals who wish to avoid products containing tartrazine in prescribing for patients sensitive to it.

Azo Compounds↗
PubMed1981

Experimental-induced hyperinsulinemia in a fetus and newborn rhesus monkey (Macaca mulatta).

An osmotically driven minipump continuously delivering 19 microU of pork insulin daily (6 microliter/day) was implanted subcutaneously into the upper thigh of a rhesus monkey fetus in utero at 122 days of gestation. A female infant weighing 408 g was delivered spontaneously and prematurely at 141 days of gestation. Within 6-12 hours of birth, she was in shock with signs of hypoglycemia. A radiograph of the chest showed normal lung aeration. Her blood glucose was undetectable (less than 1 mg/dl) and plasma insulin was 130 microU/ml at 12 hours. The minipump was removed, and the monkey was treated with 50% dextrose orally (2.5 g/kg body weight). The infant recovered and had a normal rate of growth thereafter. There was no neurological impairment consistent with hypoxia or hypoglycemia. Subsequent plasma glucose and insulin levels determined at various intervals were within normal limits.

Animals↗
PubMed1981

Glycohemoglobin in postpartum women.

As women giving birth to large for gestational age (LGA) infants are at risk for glucose intolerance during pregnancy, fasting plasma glucose (FPG) and glycohemoglobin levels (Hb AIc) were studied in the immediate postpartum period (less than 10 days). These laboratory tests, in addition to infant birth weights and perinatal histories in a group of 146 women whose infants were above the 95th percentile for gestational age, were compared with those of a group of women whose infants were appropriate for gestational age (AGA: above the 25th percentile but below the mothers 75th percentile) as well as with those of a group of control mothers without diabetic risk factors. Mean Hb AIc and FPG were elevated in the mothers of the LGA infants. When either the LGA group alone or all 3 groups together were analyzed by linear regression, significant relationships were observed for maternal Hb AIc versus FPG (P less than .001); maternal Hb AIc versus birth weight corrected for gestational age (P less than .001); and maternal FPG versus birth weight corrected for gestational age (P less than .001). In addition, infant weight correlated with maternal prepregnancy weight (r = .36), maternal weight gain in pregnancy (r = .23), and maternal height (r = .17), but not with any of the paternal anthropometric features studied. Twenty-six women with LGA infants underwent postpartum oral glucose tolerance tests before discharge. Four had abnormal results and all had Hb AIc values above SD of the nonrisk control values (5.8% total Hb). Of the 16 mothers of LGA infants with FPG levels greater than 85 mg/dl (above SD of the nonrisk control values), 7 (44%) also had Hb AIc levels of more than 5.8%. Moreover, on retrospective analysis, the LGA infants manifested increased perinatal morbidity (P less than .05) compared to the combined control groups.

Birth Weight↗