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Biomedical subjects

A E Boyd

Publications and source records attributed to A E Boyd.

At least 73 records · Page 4Linked to original sources
PubMed1983

Pergolide for the treatment of pituitary tumors secreting prolactin or growth hormone.

We gave pergolide mesylate, a new long-acting ergot derivative with dopaminergic properties, to 47 patients with hypersecretion of prolactin or growth hormone. Single doses produced long-lasting reductions of serum prolactin levels; after 24 hours, the values remained depressed at a mean of 28.8 per cent of the base-line value. Among 41 patients (22 women and 19 men) with hyperprolactinemia who took pergolide for three months or more, prolactin levels fell to normal in 37 and remained slightly elevated in 2. In the two patients in whom the levels fell to only 38 to 52 per cent of base line, treatment was regarded as a failure. The level of growth hormone fell to a mean of 52.8 per cent of base line in patients with acromegaly who were taking 100 micrograms of pergolide per day. Among patients for whom adequate CT scans were available, definite tumor shrinkage occurred in 10 of 13 with macroadenomas and definite or probable shrinkage in 5 of 9 with microadenomas. Menses returned in 76 per cent of treated women and testosterone levels rose in 10 of 14 men. We conclude that pergolide reduces hypersecretion and shrinks most prolactin-secreting macroadenomas. In some patients long-term pergolide therapy may be superior to surgery and x-ray treatment.

Acromegaly↗
PubMed1983

Identification of G actin-binding proteins in rat tissues using a gel overlay technique.

Actin-binding proteins were assayed in various tissues using an 125I-actin overlay procedure. Four major G actin-binding proteins of 90000, 65000, 58000 and 40000 Mr have been identified. The 90K protein is present in all tissues and binds labelled actin in a calcium-sensitive manner with binding increasing 3-4-fold in the presence of Ca2+. The distribution of the 58K and 65K protein which are not Ca2+-sensitive was more variable. These proteins were present in different ratios in different tissues. 125I-actin binding to all four actin-binding proteins is specific and can be displaced by preincubation of the gels with unlabelled actin. The interaction of actin with these proteins does not appear to involve ionic forces, since binding is not diminished by varying the salt concentration. Skeletal muscle glycolytic enzymes, the lens crystallins and the histones also bind 125I-actin. This binding cannot be displaced by preincubation with unlabelled actin and is presumably non-specific. The calcium sensitivity of two highly purified actin-binding proteins, the 90K human platelet protein and villin was compared using 125I-actin. The platelet 90K protein binds actin at less than 10(-7) M free calcium, but detectable binding to villin does not occur below 10(-6) M free calcium. The ubiquity of these actin-binding proteins is clear and we conclude that the calcium-sensitive 90K actin-binding protein in all of these tissues is the same as the platelet protein.

Actins↗
PubMed1983

Diabetic retinopathy. The primary care physician's role in evaluation and management.

The primary care physician should educate all diabetics regarding the roles of diet, exercise, and insulin therapy in controlling the course of their disease, as well as the potential complications, including retinopathy. In type I diabetes, blood glucose levels should be controlled as rigidly as possible with multiple insulin injections and self-monitoring of glucose level. Hypertension should be aggressively treated in all diabetics. Yearly eye examination in patients with type I diabetes is important, and ophthalmologic referral should be considered after the disease has been present for five to ten years, with the first evidence of retinopathy, at puberty, during pregnancy, or if ocular symptoms occur. In patients with type II diabetes an ophthalmologist should make an evaluation as soon as the blood glucose level is controlled. Through use of these steps, the risk of blindness in diabetics will be minimized.

Blindness↗
PubMed1983

Calmodulin-binding proteins in a cloned rat insulinoma cell line.

Calmodulin concentrations were measured in isolated hamster islets or in a cloned rat insulin-secreting cell line RIN-m-5F treated with high glucose. There was no change in the cellular calmodulin content of either islets or RIN-m-5F cells despite increases of insulin concentrations in the media. Treatment of cells with the anti-calmodulin drug W13 inhibited insulin-stimulated glucose release, whereas a small effect on insulin accumulation in the media was observed with W12, the dechlorinated, less active analogue of W13. At the lowest dose tested (30 microM) the effect of W13 on insulin accumulation in the media was completely reversible. To further investigate the possible role of calmodulin in insulin secretion, calmodulin-binding proteins in subcellular fractions of the RIN-m-5F cells were identified using a gel overlay technique. Ca2+-dependent binding of 125I-calmodulin was observed to cytosolic proteins with apparent Mr = 125, 110, 56, 52, and 34 k (kilodalton). This binding was completely displaceable with unlabeled calmodulin, whereas only partial displacement was observed when the homologous Ca2+ binding protein of skeletal muscle, troponin C, was used. Four proteins with Mr similar to the histones bind calmodulin in a Ca2+-independent manner. 125I-calmodulin:calmodulin binding protein interactions were inhibited in a dose-dependent manner by the anti-calmodulin drug, W13. Little effect was observed with the analogue W12.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma, Islet Cell↗
PubMed1982

Plasma acid-base patterns in diabetic ketoacidosis.

In a study of the types of plasma acid-base patterns present at 196 admissions for diabetic ketoacidosis we found no relation between the initial level of serum total carbon dioxide and the plasma anion gap; instead, there was a broad spectrum of acid-base patterns, ranging from pure anion-gap acidosis to pure hyperchloremic acidosis. Although the degree of renal dysfunction on admission, which reflected the magnitude of volume depletion, was independent of the severity of metabolic acidosis, it was responsible for the variable retention of plasma ketones: the more severe the volume depletion on admission, the greater the ketone retention and the less prominent the hyperchloremic acidosis. Recovery from acidosis was significantly slower in patients admitted with pure hyperchloremic acidosis. After therapy, hyperchloremia developed in most patients at four to eight hours after admission, because of the retention of chloride in excess of sodium and the excretion of ketones by the kidney.

Acid-Base Equilibrium↗
PubMed1982

Human pancreatic B cells in vitro: microtubule and insulin immunofluorescence.

Primary monolayer cultures of human B cells established using collagenase digestion, assume a characteristic epithelial morphology which is ideal for indirect immunofluorescence studies. Using double label indirect immunofluorescence, it was possible to identify an extensive cytoplasmic microtubule complex and numerous insulin antigen positive granules within the human B cells. The microtubules are discrete rod-like structures which terminate at, or near, the plasma membrane and are observed sometimes in close association with insulin antigen positive granules. This culture system is well-suited for studying the role of the microtubules in human B cell function.

Antigens↗
PubMed1982

Somatostatin secretion in diabetic rabbits.

Glucose, somatostatin-like immunoreactivity (SLI), and glucagon were measured in the portal vein during a glucose infusion (0.5 mg/kg) in 9 diabetic and 7 normal rabbits. The diabetic animals were from a colony of New Zealand white rabbits which develop spontaneous hyperglycemia characterized by low basal and stimulated serum insulin levels and lack of obesity. SLI and insulin were also extracted from pancreatic islets isolated from the diabetic and normal animals. The concentrations of SLI and glucagon, although quite variable, were similar in the portal and peripheral plasma in diabetic and control animals. The insulin content/islet was moderately decreased in the diabetic rabbits, however the content of insulin/microgram protein was similar to the controls. In contrast, SLI content/islet was no different than controls, but was increased when expressed/microgram of protein. Thus, this rabbit colony develops diabetes characterized by some decrease in beta cell mass. The remaining beta cells appear to have a severe defect in the release of insulin.

Animals↗
PubMed1982

Calmodulin and the cell cycle: involvement in regulation of cell-cycle progression.

Calmodulin levels are elevated twofold at late G1 and/or early S phases during the growth cycle of CHO-K1 cells. These levels are maintained throughout the remainder of the cell cycle unit cytokinesis. The G1 daughter cells then contain half the intracellular calmodulin level found prior to cell division. Elevation of calmodulin at the G1-S boundary is independent of the length of G1, and the increase in calmodulin appears to be related to progression into S phase. The importance of calmodulin for G1-S progression is suggested by the ability of the anticalmodulin drug W13 to elicit specific and reversible progression delays into and through S phase.

Animals↗
PubMed1982

Microtubules and beta cell function: effect of colchicine on microtubules and insulin secretion in vitro by mouse beta cells.

A monolayer culture system was developed to study the role of microtubules in insulin secretion. Cultured cells were obtained to study the role of microtubules in insulin secretion. Cultured cells were obtained by enzymatic digestion of pancreases from C57BL-KsJ mice 6-12 wk of age. On day 4 of culture, the medium was changed, control or treatment medium added, and frequent samples were removed for insulin assay. Microtubules and beta cells were identified by indirect immunofluorescence with monospecific antibodies to tubulin and insulin. An extensive microtubule network radiates from the perinuclear region of the beta cell to the plasma membrane. Although alterations in the calcium concentration of the medium did not affect the microtubule pattern, the absence of calcium or glucose in the medium inhibited insulin secretion (P less than 0.001). Optimum insulin release occurred at a calcium concentration of 2.5 mM. Colchicine, in concentrations of 10(-10) M, did not affect the microtubule immunofluorescent pattern, whereas concentrations of 1 and 5 x 10(-7) M decreased the number of microtubules, and microtubules could not be identified in cultures treated with 10(-6) M colchicine for 2 h. After a 2-h preincubation, the prolonged release of insulin at either 2.0 or 4.5 mg/ml of glucose was decreased by 10(-6) M colchicine (P less than 0.02). The immediate release of insulin was similar to that in control plates and occurred in cultures with no identifiable microtubules. Microtubules and insulin secretion were not altered by 10(-6) M lumicolchicine and prolonged insulin secretion recovered 24 h after removal of colchicine. These studies show that the microtubules facilitate sustained secretion of insulin but are not required for the immediate release of the hormone. Alterations in the extracellular calcium concentration which play an essential role in insulin secretion do not alter the microtubule pattern in the beta cell.

Animals↗
PubMed1982

Human insulinoma hybrids produce proinsulin-like material.

We have established somatic cell hybrids by fusing cells from two human insulinomas with an established murine cell line LMTK- Cl1D. After selection of the hybrids, the media were analyzed and found to contain insulin and human C-peptide immunoreactive material. The newly synthesized material was further characterized by pulse labeling and immunoprecipitation, and shown in five hybrid lines on Sephadex G-50 chromatography to have a size similar to proinsulin. The hybrids produced the apparent proinsulin-like material for up to 7 mo. Chromosome composition of the hybrids was determined by isozyme analysis and banding techniques. Chromosome 11, which previously has been assigned the insulin gene using cDNA probes, was identified in the hybrids producing proinsulin-like material. However, the retention of this chromosome did not always assure the production of hormone. This independent technique has confirmed the localization of the insulin gene to chromosome 11 and offers the opportunity of studying insulin processing and developing continuous insulin-producing cell lines.

Adenoma, Islet Cell↗
PubMed1982

Phosphate therapy in diabetic ketoacidosis.

To determine the efficacy of phosphate replacement in the therapy for diabetic ketoacidosis (DKA), 44 patients were randomly assigned to three treatment groups: those who received no phosphate replacement, those who received 15 mmole of sodium phosphate at the fourth hour, or those who received 15 mmole of sodium phosphate at 2, 6, and 10 hours. All patients were treated with intravenous insulin injection (0.1 units/kg/hr), fluids, and potassium. Four hours after a 15-mmole sodium phosphate infusion, the serum phosphate level was 2.8 +/- 0.8 mg/dL vs 2.1 +/- 0.8 mg/dL in the control patients; however, this dose was insufficient to maintain the serum phosphate level at 16 and 24 hours. Forty-five millimoles of phosphate prevented severe hypophosphatemia in all but one patient and produced substantially higher phosphate levels at 8, 16, and 24 hours. Phosphate therapy did not affect the duration of DKA, dose of insulin required to correct the acidosis, abnormal muscle enzyme levels, glucose disappearance, or morbidity and mortality. Although theoretically appealing, phosphate therapy is not an essential part of the therapy for DKA in most patients.

Adolescent↗
PubMed1981

A DNase I binding/immunoprecipitation assay for actin.

An actin assay which employs the competition between labeled and unlabeled rabbit skeletal muscle actin for DNase I has been developed. Iodination of actin by the method of Bolton and Hunter results in the incorporation of approximately 0.5 mol of 125-iodine/incorporation of approximately 0.5 mol of 125-iodine/mol of actin. This 125I-actin retained the ability to bind to DNase I and inhibit enzymatic activity. The 125I-actin-DNase complex can be precipitated by the addition of a monospecific rabbit antibody to DNase I. The efficiency of this immunoprecipitation step is improved by the use of a second sheep anti-rabbit gamma-globulin. Using this immunoprecipitation assay, there is a linear displacement of the DNase I-bound 125I-actin by rabbit skeletal muscle actin standards or by the actin present in tissue and cell extracts. Using 17.5 ng of DNase I and approximately 500 pg of 125I-actin, 50% inhibition of binding was obtained with 23 ng of unlabeled actin. Reducing the amount of DNase I to 2 ng results in 50% inhibition of binding with 4 ng of unlabeled actin and an increase in the estimated sensitivity of the assay from 1.7 to 0.24 ng. The slopes of the displacement curves generated with both vertebrate and invertebrate non-muscle actins are parallel to rabbit skeletal muscle actin. This observation indicates approximately equal actin-DNase I binding affinities and suggests a high degree of conservation of the actin-DNase I binding site. The assay is useful for measuring the pools of F- and G-actin in a wide range of cells.

Actins↗
PubMed1981

Detection of actin-binding proteins in human platelets by 125I-actin overlay of polyacrylamide gels.

Actin-binding proteins have been identified in human platelets with a gel-overlay technique that uses 125I-G-actin. Platelet proteins were separated on SDS polyacrylamide gels using the buffer system of Laemmli (1970, Nature [Lond.] 227:680-685). The proteins were fixed in the gels with methanol-acetic acid, the SDS was washed out, and the proteins were renatured. The gels were incubated with 125I-G-actin from rabbit skeletal muscle that was radiolabeled with 125I according to the method of Bolton and Hunter (1973, Biochem. J. 133:529-538) and has been shown to retain biological activity. After nonspecifically bound radioactivity was washed out, gels were dried and processed for autoradiography. The 125I-G-actin binds to several proteins in human platelets, platelet extracts, and the particulate fraction. Control experiments demonstrate that the 125I-G-actin can be displaced by use of increasing amounts of unlabeled actin, that the binding is stable to 0.6 M NaCl, and that preheating the 125I-G-actin to 90 degrees C for 3 min eliminates all binding. Prominent 125I-G-actin-binding activities were present at Mr 90,000 and 40,000. The binding to the 90,000 Mr protein appears to be at least partially Ca++ sensitive, whereas the binding to the 40,000 Mr protein does not. 125I-G-actin bound to proteins in the SDS gels can be fixed in situ and compared directly with the stained gel. This technique should prove generally useful in identification and purification of some actin-binding proteins from cells and tissues.

Actins↗
PubMed1980

Evaluation of growth hormone production from GH1 cells in vitro: effect of culture media and time in culture.

Growth hormone production by a rat pituitary tumor cell line (GH1) was measured during lag, exponential, and plateau phases of growth in different culture media. Growth hormone secretion was low during lag and early exponential phase; it increased late in the exponential phase and continued to increase during the plateau phase. This biphasic pattern of growth hormone production was observed in all media and sera utilized. Both the doubling time and growth hormone production were influenced by the choice of media and sera. In addition, the length of time in culture affected the growth fraction with passage level 40 GH1 cells having a 79% growth fraction, whereas the growth fraction of passage level 100 cells was 95%. Using the population doubling time as a criterion for a choice of medium, F-10 medium supplemented with 20% fetal bovine serum consistently yielded the most rapid doubling time (32 hr), whereas Dulbecco's MEM supplemented with 15% horse serum and 2.5% fetal bovine serum yielded the greatest plateau cell density. Growth hormone secretion and the population doubling times were directly related to culture conditions including length of time in culture, choice of tissue culture media, choice of sera, and the phase of cell growth (lag, exponential or plateau).

Animals↗
PubMed1980

Spontaneous diabetes mellitus in the New Zealand white rabbit: preliminary morphologic characterization.

Electron microscopic studies on a closed colony of rabbits with an 18.5 per cent incidence of spontaneous onset insulin-dependent diabetes mellitus revealed that the beta-cells of the islets of Langerhans of the diabetic animals were hypergranulated. This finding contrasts with most other animal models of spontaneous diabetes mellitus which show degranulation of the beta-cells. There was no evidence of hyperplasia, insulitis, amyloid, or fibrosis of the islets by either light or electron microscopy. Correlation of our morphologic findings with physiologic data suggests a defect in insulin secretion. Rabbits with normal glucose metabolism showed a normal degree of granulation of their beta-cells. The alpha and delta cells were within normal limits in all animals. No other abnormalities associated with diabetes in humans or other animals were noted except for minimal fusion of the glomerular epithelial foot processes and mineralization of the proximal tubules and Bowman's capsules.

Animals↗