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Biomedical subjects

J B Robinson

Publications and source records attributed to J B Robinson.

At least 73 records · Page 4Linked to original sources
PubMed1986

Heat production of cattle acclimated to cold, thermoneutrality and heat when exposed to thermoneutrality and heat stress.

Four Hereford X Red Angus yearling steers were acclimated to each of the following environments; cold (3 C), thermoneutrality (TNZ; 20 C) and heat (35 C). Intake was equalized for all treatments at 4.9 X kg X head-1 X d-1 (2.9 Mcal metabolizable energy/kg). Heat production, respiration rate and rectal temperature were determined after 3- and (21-h later) 24-h exposures to thermoneutral and heat stress test-temperatures: 25, 30, 32.5, 35, 37.5 and 40 C. Thermoneutral heat production (kcal X kg-.75 X d-1), after 3- and 24-h exposures, was greater (P less than .05) for the cold-acclimated cattle (139.6 +/- 5.0 and 153.0 +/- 5.8) as compared with the TNZ-acclimated cattle (117.7 +/- 5.0 and 121.6 +/- 5.8). Heat production of the heat-acclimated cattle after 3- and 24-h exposures to thermoneutrality was 121.0 +/- 5.1 and 123.5 +/- 3.2 and was not different from the TNZ-acclimated cattle. Heat production of steers acclimated to different temperatures was variable during the 3- and 24-h exposures to test-temperatures ranging from 25 to 40 C. Heat production increased linearly in the TNZ-acclimated cattle (24-h exposure) and in the heat-acclimated cattle (3-h exposure) at the rate of 1.3 and 2.3 kcal X kg-75 X d-1 X C-1 increase in test-temperature, respectively. In the other four comparisons, analysis by regression indicated no significant change in heat production. Rectal temperature and respiration rate increased significantly in either a linear or quadratic manner in all treatment groups exposed to test-temperatures from 25 to 40 C.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1985

Stereoselectivity and isoenzyme selectivity of monoamine oxidase inhibitors. Enantiomers of amphetamine, N-methylamphetamine and deprenyl.

The enantiomers of amphetamine, N-methylamphetamine and deprenyl were studied, using a solubilised rat liver mitochondrial monoamine oxidase (MAO) preparation, as competitive inhibitors of MAO-A and MAO-B (5-hydroxytryptamine and beta-phenylethylamine as substrate respectively). Only in the case of deprenyl enantiomers inhibiting MAO-B was a preference shown towards the [R]-configuration enantiomer justifying the use of [R]-(-)-deprenyl (as compared to the racemate) for the specific inhibition of MAO-B. Recalculation of the observed Ki values in terms of the base form of the inhibitor indicated that the activity of all enantiomers fell within a narrow, approximately 25-fold range when inhibiting MAO-B. The selectivity of inhibition of MAO-B by [R]-(-)-deprenyl cannot therefore be attributed to any specific structural features of the MAO-B isoenzyme form but rather to a lack of affinity of this enantiomer towards MAO-A.

Amphetamine↗
PubMed1985

Organization of Krebs tricarboxylic acid cycle enzymes in mitochondria.

Sonic oscillation of mitochondria usually leads to the release of a number of Krebs tricarboxylic acid cycle enzymes. These enzymes have, therefore, been referred to as soluble matrix enzymes. In the present report, we show that gentle sonic or osmotic disruption can be used to obtain a mitochondrial preparation where these enzymes appear to be organized in a large complex of proteins. Using citrate synthase as a marker for these enzymes, we show that the proposed complex is easily sedimented at 32,000 X g in 30 min. The exposed citrate synthase in these complexes can be inhibited by its antibody, indicating that the enzymes are not merely entrapped in substrate-permeable vesicles. The effects of pH, temperature, ionic strength, and several metabolites on the ability to obtain the sedimentable citrate synthase have been tested. These studies indicate that the complex is stable at conditions presumed to exist in situ. Electron microscopic studies show that gentle sonic oscillation gives rise to an efflux of mitochondrial matrix contents which tend to remain attached to the original membranes. The sedimentable fraction also contained four other presumably soluble Krebs tricarboxylic acid cycle enzymes: aconitase, NAD+-isocitrate dehydrogenase, fumarase, and malate dehydrogenase.

Aconitate Hydratase↗
PubMed1985

The natural-killer-cell-associated HNK-1 (Leu-7) antibody reacts with hypertrophic and malignant prostatic epithelium.

While using the natural killer (NK) cell-associated HNK-1 antibody in a panel of hematopoietic cell markers, the authors found that metastatic tumor cells in the bone marrow of a patient with disseminated prostatic carcinoma stained strongly with this antibody using an indirect immunofluorescence technique. More than 50% of cells from the patient's prostate also reacted with HNK-1. Subsequent study of frozen sections of prostate tissue from patients with benign prostatic hypertrophy (BPH) showed that HNK-1 reacted with prostatic epithelium and the contents of the glandular lumina. Two other markers associated with NK cells (OKM1 and OKT3) were not detected on nonneoplastic or neoplastic prostatic epithelial cells using a two-color immunofluorescence technique. Recent reports have shown that the HNK-1 antibody also detects an antigen on cells of neuroectodermal origin. The authors have concluded that HNK-1 also reacts with prognostic epithelium in patients with BPH and may be useful as another marker for metastatic carcinoma of the prostate.

Antibodies, Monoclonal↗
PubMed1985

Organization of Krebs tricarboxylic acid cycle enzymes.

Binding of enzymes of the Krebs TCA cycle to biological membranes was characterized with respect to intracellular location, susceptibility to various chemical and physical treatments, and extractability as a macromolecular component of the mitochondrial inner membrane. It was shown that citrate synthase and malate dehydrogenase bind to the inner membrane in an ionic strength-sensitive, saturable, and specific manner to a relatively thermostabile component manifested on the inner (matrix) surface of the inner membrane of the mitochondrion. From these data several arguments in support of the physiological applicability of these processes were deduced, and the question of whether these two enzymes bind to the same or different membrane components was considered. Also, experiments preliminary to purification of the citrate synthase binding component were presented.

Animals↗
PubMed1985

Hematopoietic cell surface markers on metastatic small cell carcinoma detected with monoclonal antibodies.

Using a panel of monoclonal antibodies, cells from lymph node biopsies have been examined in three patients with small cell carcinoma presenting with cervical lymphadenopathy. Two patients had small (oat) cell carcinoma of the lung; in the third patient, a primary tumor was not found. Two lymph node biopsies showed typical small (oat) cell carcinoma, and one was an intermediate cell variant; in the last, lung biopsy showed small (oat) cell carcinoma. Electron microscopy demonstrated desmosomes in all three tumors. In each case, lymph node cell suspensions were examined by indirect immunofluorescence with the use of a panel of monoclonal antibodies to antigens usually associated with lymphoid or myeloid cells. In two of the three cases malignant cells were positive with the lymphoid marker BA-2; in two cases malignant cells were positive with OK1a1, a marker for the Ia-like antigen (HLA-DR); and in one case malignant cells were positive with My-1. Caution is needed in the interpretation of cell surface marker studies in the differential diagnosis of small round cell tumors.

Adult↗
PubMed1984

Binding of citrate synthase and malate dehydrogenase to mitochondrial inner membranes: tissue distribution and metabolite effects.

Citrate synthase and malate dehydrogenase bind to mitochondrial membrane preparations obtained from various species of animals and lemon fruit. The amount of enzyme bound per mg mitochondrial protein was comparable in all tissues studied. The effect of various substrates, products, and substrate analogs on citrate synthase binding to rat liver mitochondrial inner membrane was examined. OAA was the most effective inhibitor of binding followed by AcCoA , CoA, citrate, ATP, and MgATP. Neither D- nor L- malate were effective in blocking binding. The wide distribution of binding of citrate synthase and malate dehydrogenase to the inner membrane and specificity of substrate effects on the binding of citrate synthase are discussed in relation to the possible physiologic nature of these phenomena.

Animals↗
PubMed1984

A structure for calmodulin-activated cyclic nucleotide phosphodiesterase deduced from proteolysis studies.

In summary, our studies suggest that unproteolyzed PDE, illustrated as a dimer of identical 63,000-D polypeptide chains in Fig. 5, can exist in two equilibrium conformations. In the absence of calmodulin, the predominant conformational form has a nonfunctional catalytic site, whereas the minor conformational form has a fully functional site. Preferential complexation of calmodulin with the minor conformation shifts the population to that form resulting in a marked activation of catalysis. Alternatively, cleavage of a sizable terminal fragment, termed the calmodulin binding domain, facilitates irreversible acquisition of the functional conformation in the absence of calmodulin activation. By contrast, proteolytic cleavage at the opposite terminus does not significantly alter the conformational equilibrium. This model suggests that a single in vivo cytoplasmic cyclic nucleotide PDE can accommodate many of the variations in the polypeptide chain sizes and in the fold activation observed for enzyme preparations in vitro. The model also places this form of cyclic nucleotide PDE activity in vivo under absolute control by intracellular Ca2+ concentration.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1983

Advantages of preelectrophoretic conjugation of polypeptides with fluorescent dyes.

A rapid simple procedure is described for the conjugation of proteins, glycoproteins, and peptides with the fluorescent dye fluorescein isothiocyanate during the time required to polymerize a polyacrylamide gel. Such conjugation does not perturb the electrophoretic mobility of the polypeptides in detergent containing gels. The location of polypeptide . dye conjugate is evident by inspection immediately upon removal of a gel from an electrophoresis cabinet avoiding the time required for postelectrophoretic staining and destaining procedures. The sensitivity of detection of polypeptide . fluorescein conjugates is at least equivalent to that obtained using Coomassie blue.

Animals↗
PubMed1983

A globular high spin form of ferricytochrome c.

Acidification of a salt-free solution of native low spin globular horse heart ferricytochrome c with HCl causes a single cooperative transition centered at pH 2.5 at 23 degrees C resulting in the formation of denatured high spin ferricytochrome c. By contrast, acidification with HCIO4 uncouples denaturation from the spin-state transition, resulting in the formation of a globular high spin form of ferricytochrome c at pH 0.0 exhibiting only modest conformational differences from native cytochrome c as judged by far ultraviolet circular dichoroic, tryptophan fluorescence, and reduced viscosity measurements. This uncoupling is consistent with the preferential binding of two perchlorate anions to the globular form(s) cytochrome c. The acid spin-state transition of the perchlorate complex is biphasic, having midpoint values at pH 0.7 and 3.6 involving 1.0 and 1.6 protons, respectively, when measured in the presence of 1 M perchlorate.

Animals↗
PubMed1982

Ascorbic acid absorption in humans: a comparison among several dosage forms.

There have been few studies conducted to determine the efficiency of ascorbic acid absorption in humans. Differences in the extent of its absorption among individuals may contribute to the outcome of clinical trials. Ascorbic acid absorption in four subjects was investigated from several oral dosage forms containing 1 g of the vitamin (solution, tablet, chewable tablet, and timed-release capsule. Approximately 85% of an intravenous dose was recovered in the urine as ascorbic acid and its major metabolites. In contrast, only approximately 30% of the dose was recovered from the solution and tablet forms. A considerably smaller fraction of the dose (approximately 14%) was recovered from the timed-release capsule. There was considerable intersubject variation in ascorbic acid absorption and there appeared to be good and poor absorbers of the vitamin. Consideration should be given to the influence of the extent of ascorbic acid absorption on the results of clinical trails.

Adult↗
PubMed1981

A monoisozymic nucleoside diphosphate kinase capable of complete phosphorylation.

Nucleoside diphosphate kinase (EC 2.7.4.6) has been purified nearly 2000-fold from beef brain particulate material in 65% yield. The purification procedure described here takes advantage of the relatively unique complexation of the enzyme with blue dextran-Sepharose in the presence of a nonionic detergent. Unlike preparations of the enzyme previously described, the bovine brain enzyme is monoisozymic and each polypeptide chain can be phosphorylated by a nucleoside triphosphate substrate. Catalytically functional forms of the enzyme having lower pI values can be generated by proteolysis.

Animals↗
PubMed1981

The effect of proteolysis on the calmodulin activation of cyclic nucleotide phosphodiesterase.

A high Km cytoplasmic cyclic nucleotide phosphodiesterase (EC 3.4.1.17) has been obtained from bovine brain. The unproteolyzed enzyme contains (63 +/- 1) X 10(3) molecular weight polypeptide chains which exhibit little if any basal catalytic activity. Complexation with calmodulin stimulates the catalytic activity nearly 2 orders of magnitude, presumably, by causing a conformational change in the enzyme which either creates or exposes the catalytic sites. Removal of about 120 amino acids from the terminal portion(s) of each polypeptide chain either by an endogenous protease or by exogenous trypsin prevents calmodulin complexation and generates a basal catalytic activity equivalent to that of the unproteolyzed enzyme-calmodulin complex. In contrast to affinity chromatography using immobilized calmodulin, blue dextran-Sepharose chromatography can be used to select for enzyme containing only unproteolyzed polypeptide chains.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1981

Prediction of neutral salt elution profiles for affinity chromatography.

Neutral salts exhibit very marked differences as eluants of proteins from affinity columns. We observe: (i) that the relative potencies of neutral salts as eluants are independent of the protein or the affinity ligand in the systems studied, (ii) that the absolute salt concentration necessary to elute any given protein bound to the affinity matrix is proportional to the algebraic sum of a set of elution coefficients defined herein for the separate ions present in the solution, and (iii) that the proportionality between elution potency and elution coefficient is a function of the affinity of the protein for the immobilized ligand. Given the concentration of one neutral salt required for elution of a protein of interest from an affinity column, the elution capability of any neutral salt at any temperature can be quantitatively predicted for that protein. Accordingly, application and elution protocols for affinity chromatography can be designed to optimize the yield and fold purification of proteins.

Adenosine Triphosphate↗