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Biomedical subjects

B V Kumar

Publications and source records attributed to B V Kumar.

33 records · Page 2Linked to original sources
PubMed1985

Fast and efficient method for detection and estimation of proteins.

A quick, simple, inexpensive and sensitive method is described to stain and quantitate proteins on nitrocellulose papers. The proteins may be spotted or transferred from polyacrylamide gels by Western blotting. The procedure involves non-radioactive iodination of the polypeptides by chloramine T and potassium iodide followed by detection of bound iodine with starch. The method is more sensitive and much quicker than Coomassie brilliant blue staining and may be used for quantitation or detection of proteins in unknown samples. Another major advantage of this procedure is that ionic or nonionic detergents, although at higher concentrations causing the sample to disperse more broadly in the membranes, do not affect the staining procedure. Further, this method may be used for detection of proteins bound to papers that have high affinity for proteins such as the Zeta probe membranes.

Candida albicans↗
PubMed1985

Cross-reacting human and rabbit antibodies to antigens of Histoplasma capsulatum, Candida albicans, and Saccharomyces cerevisiae.

Using Western blots of electrophoretically separated antigens, we show that human antibodies react most frequently to antigens shared by three fungi (Histoplasma capsulatum, Candida albicans, and Saccharomyces cerevisiae). Reactivity to antigens specific for individual fungi was relatively uncommon. The pattern of reactivity could not distinguish infected patients from uninfected controls. Rabbits immunized with extracts of each fungus also produced antibodies to cross-reactive or shared antigens of the other two fungi. Furthermore, preimmune sera showed similar but lower reactivity with the same fungal antigens. We believe that the preimmunization antibodies, which probably resulted from earlier fungal colonization or inapparent infections, predisposed the immune responses elicited by the vaccinations. A similar mechanism likely explains the results with human sera.

Animals↗
PubMed1983

Sulfhydryl induced respiratory "shunt" pathways and their role in morphogenesis in the fungus, Histoplasma capsulatum.

When the mycelial to yeast transition of the dimorphic fungus Histoplasma capsulatum is induced by a temperature shift from 25 to 37 degrees C, the activities of the cytochrome system and the alternate oxidase decrease in parallel over the first 24 to 40 h (stage 1 of the transition). The decrease in activity of the cytochrome system is correlated with extensive decreases in the amounts of cytochromes b, c, and aa3, assayed spectrophotometrically. After 40 h, the cells enter a dormant phase (stage 2 of the transition) and cysteine or other sulfhydryl-containing compounds are required to reactivate mitochondrial respiration. This reactivation is due to the establishment of shunt pathways which bypass blocked segments of the electron transport system. The "shunt" pathways operate normally in mycelia grown at 25 degrees C, but are shut down during the transition, possibly because of depletion of intracellular cysteine. The longstanding observation that cysteine is required to progress beyond the initial stages of the morphological transition may be due, at least in part, to the reactivation of these "shunt" pathways.

Cytochromes↗
PubMed1981

Temperature- and cyclic nucleotide-induced phase transitions of Histoplasma capsulatum.

The transition from yeast to mycelia of Histoplasma capsulatum could be accomplished by shifting the temperature of incubation from 37 to 25 degrees C. It was accompanied by many changes in cellular metabolism, including changes in respiration, intracellular cyclic adenosine 3',5'-monophosphate (cAMP) levels, and activities of two enzymes specific for the yeast phase, cystine reductase (EC 1.6.4.1) and cysteine oxidase (EC 1.13.11.20). Even at 37 degrees C, the yeast to mycelial transition could be induced by cAMP and agents which raise the intracellular levels of cAMP (theophylline, acetylsalicylic acid, prostaglandin E1, and nerve growth factor). During this morphogenesis the same pattern of changes occurred as in the temperature-induced transition. Therefore, these changes were not simply dependent on a shift in temperature, but rather were part of the process of the phase transition.

Aspirin↗
PubMed1980

Comparison of the ribonucleic acid polymerases from both phases of Histoplasma capsulatum.

The three ribonucleic acid (RNA) polymerases (ribonucleoside triphosphate RNA nucleotidyltransferases, EC 2.7.7.6) of the two phases (yeast and mycelial) of the dimorphic fungus Histoplasma capsulatum have been purified and characterized. The corresponding enzymes from the two phases differ in sensitivity to alpha-amanitin, ion and salt requirements, temperature sensitivity, and subunit structure. This is the first case in which such qualitative differences in RNA polymerases have been demonstrated in two growth states of the same organism.

Amanitins↗
PubMed1977

Mechanism of the inhibition by RNA of the RNA polymerases of Histoplasma capsulatum.

4 S RNA isolated from the dimorphic fungus Histoplasma capsulatum inhibited the DNA-dependent RNA polymerase activity of the yeast phase of this fungus. Inhibition was specific for initiation, and resulted from binding of the RNA to the enzyme. Among a variety of synthetic polynucleotides tested, only poly(G) and oligo(dG) were effective inhibitors, suggesting a role for guanines or guanine-rich sequences of RNA in the inhibition reaction.

DNA-Directed RNA Polymerases↗
PubMed1976

Protective effects of amphotericin B against spontaneous and transplantable murine tumors.

Two tumor systems were used to test prophylactic effects of amphotericin B (AmB). When 0.5 mg AmB was given ip every 2 weeks to AKR mice beginning at 8 weeks of age, the 50% tumor incidence for spontaneous lymphoma development was delayed 2-3 months. In the second tumor system, BALB/c mice received injections of either 20 or 50 mug AmB before receiving MOPC-315-C cells sc. The mice given the low dose of AmB demonstrated a decreased tumor incidence and a reduced tumor growth rate, when compared with controls. Opposite effects were found for the group administered the high dose; tumor incidence and rate of growth were increased.

Adjuvants, Immunologic↗
PubMed1974

Rifampin: inhibition of ribonucleic acid synthesis after potentiation by amphotericin B in Saccharomyces cerevisiae.

The inhibition of Saccharomyces cerevisiae growth by amphotericin B and rifampin was studied. Rifampin alone had no effect on growth or macromolecular syntheses. Lethal amounts of amphotericin B produced a late inhibition of ribonucleic acid (RNA) synthesis simultaneous with the arrest of growth and protein synthesis. In contrast, low doses of amphotericin B along with rifampin caused an early arrest of RNA synthesis, followed by a later arrest of growth and protein synthesis. Used with rifampin, amphotericin B thus appears to increase cell permeability for rifampin, which in turn inhibits RNA synthesis; such results are consistent with some reports of inhibition of yeast RNA polymerase function by rifampin. Experiments with petite mutants ruled out any special effect of the antibiotics on mitochondrial RNA synthesis, so that nuclear RNA synthesis is affected. Acrylamide gel analyses of RNA pulse-labeled after addition of the two antibiotics in synergy showed that synthesis of all major classes of RNA was progressively and uniformly inhibited.

Amphotericin B↗
PubMedDate not supplied

Histology of the epididymis in men with obstructive infertility.

The histology of different regions of human epididymis in men undergoing vasoepididymostomy to correct epididymal obstruction was studied. The data indicate major degenerative changes in intertubular connective tissue and in the epididymal epithelium. These include increase in connective tissue thickness and its infiltration by leucocytes in some cases, decrease in tubular diameter, degeneration and/or vacuolation of cytoplasm of nonciliated cells of efferent duct and principal cells of epididymis and presence of multinucleate giant cells in the epididymal lumen. These histological abnormalities are discussed in relation to the role such epididymis can play in sperm maturation following vasoepididymostomy.

Epididymis↗
PubMedDate not supplied

Effect of vasectomy on the ultrastructure of epididymal epithelium in rhesus monkey.

Ultrastructural changes in the epididymal epithelium and the fate of accumulating spermatozoa were examined in the vasectomized rhesus monkey (Macaca mulatta). Accumulation of spermatozoa resulted in an increase in the diameter of the tubule and its lumen. Ultrastructure of principal cells revealed that they continue to perform both secretory and absorptive functions after vasectomy. The rough endoplasmic reticulum, Golgi complex, and mitochondria were well developed in the principal cell. Bulging of the apical portion of principal cells and membrane-bound structures in the lumen suggests an increase in apocrine secretion. An increase in the number of vesicles, vacuoles, and multivesicular bodies in the principal cells indicates an increased absorptive activity. Increased absorptive function was also evident in the apical cells. Macrophages with sperm remnants were seen in the lumen, and occasionally in the connective tissue. The principal or only mechanism of sperm disposal after vasectomy appeared to be intraluminal endocytosis by macrophages.

Animals↗