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Biomedical subjects

S Jacobs

Publications and source records attributed to S Jacobs.

At least 199 records · Page 11Linked to original sources
PubMed1981

Structural similarities between human receptors for somatomedin C and insulin: analysis by affinity labeling.

Human placental receptors for insulin and somatomedin C (Sm-C) were affinity labeled with [125I]insulin and [125I]Sm-C by using the bifunctional cross-linking agent disuccinimidyl suberate. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that both labeled hormones were specifically cross-linked to three protein species with apparent molecular weights of 240 000, 310 000, and 330 000. Following disulfide bond reduction, subunits of approximately 140 000 daltons were evident. Partial reduction of disulfide bonds yielded intermediate-sized species with apparent molecular weights of 180 000, suggesting the existence of an additional, smaller subunit attached to the 140 000-dalton subunit. Limited proteolysis of the hormone-receptor complexes with chymotrypsin, trypsin, and Staphylococcus aureus V-8 protease gave similar but not identical results for each labeled receptor. The distinction between the two receptors was further documented by inhibition of affinity labeling with graded amounts of the native hormones. These data demonstrate a substantial structural similarity between the human Sm-C and insulin receptors paralleling the homology of the native hormones and their actions.

Affinity Labels↗
PubMed1981

Purification and properties of the human placental insulin receptor.

Human placenta insulin receptor was purified 11,000-fold to near homogeneity using DEAE-cellulose chromatography and affinity chromatography on insulin-Sepharose. Approximately 200 to 300 micrograms of purified receptor were obtained from a single placenta. In solution, the native receptor is a complex (Mr = 440,000) of an acidic, multi-subunit protein with a Mr of 350,000 and bound detergent accounting for the remainder of the mass. The receptor protein is asymmetric (f/f0 = 1.4) and consists of a single Coomassie blue staining polypeptide of Mr = 135,000. In addition to the 135,000-dalton polypeptide, two smaller polypeptides of Mr = 45,000 and 90,000 were observed upon autoradiography of 125I-labeled receptor subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These two smaller polypeptides did not stain with Coomassie blue but migrated with native receptor activity on isoelectric focusing gels and were coimmunoprecipitated with the 135,000-dalton polypeptide by anti-insulin receptor antibody. The 135,000-dalton subunit was specifically labeled by 125I-insulin using the bifunctional cross-linking reagent disuccinimidyl suberate (P. F. Pilch, and M. P. Czech, (1979) J. Biol. Chem. 254, 3375-3381), suggesting that this component contains the insulin binding domain.

Binding, Competitive↗
PubMed1981

Minor products from the reaction of (+) and (-) benzo[a]-pyrene-anti-diolepoxide with DNA.

The reaction of trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BP-diolepoxide) with deoxyguanosine has been studied. In addition to the expected N2-guanine derivative minor products resulting from reaction at the O6 and 7-positions have been identified. Reaction of racemic, (+) or (-) BP-diolepoxide with [14C] and [3H]purine labelled DNA allowed these same products to be identified and their yields estimated. It was found that the O6 and 7-guanine products were derived mainly from reaction of the (-)isomer. The 7-substituted guanine derivative in DNA was unstable, undergoing either spontaneous release of the substituted guanine or imidazole ring opening.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1980

The clinical management of grief.

The clinical management of grief involves issues that demonstrate the integration of psychosocial risk factors into clinical practice. Recommendations for the clinical management of grief are based on a review of the pattern of morbidity and mortality of bereavement, of the emotional response to conjugal loss, and of several postulated pathogenetic mechanisms.

Adaptation, Psychological↗
PubMed1980

Disulfide reduction converts the insulin receptor of human placenta to a low affinity form.

Treatment of human placenta membranes with dithiothrietol (DTT) followed by N-ethylmaleimide results in a 60% reduction in insulin binding. Treatment with N-ethylmaleimide alone has little effect. The decrease in insulin binding that results from DTT treatment is due to a decrease in affinity for insulin, with little change in total receptor number. DTT has similar effects on receptor solubilized from placenta membranes with Triton X-100, indicating that its effects are not attributable to changes in the arrangement of receptors in the membrane. In contrast to placenta membranes, treatment of liver membranes with DTT does not decrease insulin binding. These results suggest that reduction of a critical disulfide bond in insulin receptors from human placenta converts the receptor to a low affinity form.

Animals↗
PubMed1980

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to MHC region antigens.

The maturation sequences of thymocytes is known to some extent: A generative layer of subcapsular large lymphoblasts gives rise to a major population of small cortical thymocytes and a minor population of midsize medullary thymocytes. The relative contribution of these three populations to the peripheral T cell populations is not yet known. In this study, subcapsular lymphoblasts, cortical small cells, medullary cells, and thymic emigrant cells have all been analyzed by immunofluorescence for expression of the antigens H-2D, I-A, H-2K, and TL. H-2D is expressed brightly on all subcapsular large cells, dimly on cortical small cells, and brightly on all migrants, cortisone-resistant thymocytes (CRT), and peripheral T cells. I-A can be detected at low levels on 30 to 50% of cells in all the thymic subpopulations, and on 30 to 50% of migrants and peripheral T cells. Fifty to 80% of small cortical cells do not express detectable H-2K, but all the other subpopulations, both inside and outside the thymus, stain uniformly quite brightly. TL3 is expressed on 70 to 80% of subcapsular and cortical thymocytes, 30 to 40% of CRT, is undetectable on migrants but can be seen at low levels on 10 to 20% of spleen and lymph node T cells. The possibility that some or all of these antigens represent stable markers of separate lineages rather than unstable, stage-specific markers is discussed.

Animals↗
PubMed1979

Effect of marihuana on cardiorespiratory responses to submaximal exercise.

Six male chronic marihuana (MH) users exercised on a bicycle ergometer for 15 min at approximately 50% VO2max under 3 conditions: (1) not smoking (control), (2) after smoking MH containing 7.5 mg (-) delta-9-tetrahydrocannabinol, and (3) after smoking placebo marihuana (PL). The MH was administered double-blind in a counterbalanced repeated-measures design. Heart rates (HRs), arterial blood pressures (BPs), pulmonary ventilation (VE), and oxygen uptake (VO2) were measured during exercise and 15 min recovery. PL had no effect on any of the physiologic variables. Smoking MH had no effect on systolic blood pressure (SBP), diastolic blood pressure (DBP), VE, or VO2, but did induce a marked increase in heart rate which persisted throughout exercise and recovery periods, averaging 34% higher than control values at rest, 18% higher during exercise, and up to 50% higher during recovery. MH smoking increased the product of HR x SBP in all circumstances.

Adult↗
PubMed1979

Outpatient evaluation of patients with calcium urolithiasis.

Eighty patients with proved calcium urolithiasis participated in an outpatient study designed to define the most likely metabolic problem related to the cause of the stone disease. Diagnostic categories included absorptive hypercalciuria (33 patients), renal leak hypercalciuria (20 patients), hypomagnesiumuria (27 patients), hyperuricemia and hyperuricuria (16 patients), hyperoxaluria (15 patients), normal stone-former (4 patients), renal tubular acidosis (2 patients) and suspicion of hyperparathyroidism (7 patients). Of the 80 patients 40 had more than 1 defect. Patients with a high suspicion of hyperparathyroidism were excluded from the study. Based on these criteria treatment plans incorporating medications, diet or both were instituted. Of 21 patients observed for greater than 2 years 90 per cent have shown no new stone disease.

Acidosis, Renal Tubular↗
PubMed1979

Insulin receptor: covalent labeling and identification of subunits.

Two methods were used to label insulin receptors covalently with 125I. In the first, an aryl azide derivative of insulin, 125I-labeled 4-azido-2-nitrophenyl-insulin, was synthesized and used to photolabel the binding region of the insulin receptor in rat liver membranes and human placenta membranes. In the second, insulin receptors were purified from rat liver membranes and labeled with 125I by use of chloramine-T; this method presumably has no specificity for the binding region of the receptor. The proteins labeled by both methods were analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis after or without reduction by dithiothreitol. The photoaffinity label specifically labeled a single band in both liver and placenta that had an apparent molecular weight of 135,000 after reduction. A band with similar mobility was present in the chloramine-T-labeled preparation, which also contained a second major band with an apparent molecular weight of 45,000. Without reduction, both methods resulted in a single labeled band with an apparent molecular weight of about 310,000. These results indicate that the insulin receptor of both liver and placenta has a subunit of molecular weight 135,000 that binds insulin and that the receptor may be composed of at least two different subunits that are linked together or greatly stabilized by disulfide bonds.

Affinity Labels↗