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Biomedical subjects

K Nath

Publications and source records attributed to K Nath.

At least 19 recordsLinked to original sources
PubMed1992

Heterogeneity in restriction patterns of Gardnerella vaginalis isolates from individuals with bacterial vaginosis.

This study was undertaken to resolve the genetic make up of Gardnerella vaginalis present in bacterial vaginosis (BV). DNA from several G. vaginalis isolates from within and between individual BV patients were compared by BamHI, ClaI and EcoRI restriction endonuclease analysis (REA) followed by a restriction fragment length polymorphism (RFLP) study, utilizing a 5.7-kb BamHI G. vaginalis ATCC14018 DNA probe. Four G. vaginalis isolates from one patient (GVP-062) were composed of 3 different biotypes (biotypes 3, 5 and 8), and while the REA mirrored the biotype, in RFLP studies at least 3 isolates had DNA fragments in common. All of the isolates from 2 other patients (GVP-063 and GVP-072) represented a single biotype (biotype 2), but under REA and in RFLP studies, the isolates GVP-063 differed from GVP-072. An opposite case existed with the isolates GVP-072 (biotype 2) and GVP-065 (biotype 5), which appeared similar under REA and in RFLP studies. Finally, reisolates after 8 weeks (GVP-080) from a BV patient (isolates GVP-065) representing the same biotype (biotype 5) differed under REA and in RFLP studies. Thus, lacking any unique DNA fingerprint, G. vaginalis occurring in BV represents a (genetically) mixed population.

Bacterial Typing Techniques↗
PubMed1992

Endothelial cell heme oxygenase and ferritin induction by heme proteins: a possible mechanism limiting shock damage.

Acutely, hemin sensitizes endothelial cells to oxidants but chronically protects the endothelium through the induction of ferritin. By releasing its heme, methemoglobin can sensitize endothelial cells in a fashion similar to free hemin. Furthermore, prolonged incubation with the endothelium allows methemoglobin to induce heme oxygenase and ferritin and concomitantly to modulate oxidant-mediated cytotoxicity. Methemoglobin but not hemoglobin, metmyoglobin or cytochrome c induces heme oxygenase and ferritin. Heme needs to be released from methemoglobin, since sodium cyanide, haptoglobin, and hemopexin inhibit the induction of these proteins. Neutrophils can oxidize hemoglobin to methemoglobin, which can subsequently induce both heme oxygenase and ferritin. We speculate that in shock with disseminated intravascular coagulation, marginated PMNs oxidize hemoglobin to heme-releasing methemoglobin. If critical defenses such as haptoglobin and hemopexin are overwhelmed, heme enters the endothelin cells, sensitizing them to oxidant damage. Endothelial cell adaptation via heme-induced heme oxygenase and ferritin production might limit ultimate progression to pulmonary and other vascular leak syndromes.

Animals↗
PubMed1979

Ring prosthesis.

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Eye Burns↗
PubMed1978

Effect of dibutyryl cyclic AMP and analogs on the rate of contractions of myocytes in culture.

2O, 6N-butyryl, 3', 5'-cyclic monophosphate (dibu cAMP) when added to fetal rat heart cells in culture inhibits myocyte contraction. This inhibition is 100, 84 and 51% complete when the dibu cAMP concentration used is 2, 0.2 and 0.02 mM, respectively. The potency of dibu cAMP derivatives in myocyte contraction inhibition follows the order, dibu cAMP greater than 6N-bu cAMP greater than 2O-bu cAMP = AMP greater than butyrate. The inhibition caused by the first three chemicals is greater than 70%.

Animals↗
PubMed1978

Relationship between dibutyryl cyclic AMP and microtubule organization in contracting heart muscle cells.

Rhythmic and synchronous contractions of interconnecting myocyte cultures prepared from fetal rat hearts are arrested upon the addition of 0.2--2.0 mM N6, O2'-dibuturyladenosine 3':5'-cyclic monophosphate (Bt2cAMP). The contractions arrested by Bt2cAMP are restored either by diluting the Bt2cAMP from the media or by adding colchicine. While colchicine restores Bt2cAMP-arrested myocyte contractions at concentrations as low as 1.0 micron, the inactive isomer lumicolchicine shows no effect. Morphologically, Bt2cAMP treatment of myocyte cultures results in the appearance of numerous elongated cellular processes not present in control cultures. Ultrastructural examination indicates that in Bt2cAMP-treated cells the intracellular distribution of microtubules is altered such that these organelles appear to accumulate in parallel arrays. In cells not treated with Bt2cAMP, the microtubules appear randomly oriented, while in cells treated with only colchicine, intact microtubules are not observed. The relationship between microtubules an heart cell contraction is discussed.

Animals↗
PubMed1977

Organization of the yeast ribosomal RNA gene cluster via cloning and restriction analysis.

The restriction endonuclease EcoR1 cleaves Saccharomyces cerevisiae DNA, which codes for ribosomal RNA (rRNA), into seven fragments, A second restriction endonuclease, HindIII, cleaves the same yeast ribosomal DNA into two fragments. These two restriction enzymes each yield DNA segments that total about 5.9 megadaltons. The "repeat unit" of the yeast genes coding for rRNA is thus about 5.9 megadaltons or about 9000 base pairs long. The two HindIII-cleaved DNA fragments as well as one of the EcoR1-cleaved DNA fragments were purified and amplified by cloning in Escherichia coli. Three of the seven EcoR1-generated DNA fragments could then be ordered by treating the two cloned HindIII DNA fragments with EcoR1. This led the assignment of the two HindIII restriction sites. The various restriction DNA fragments were hybridized directly from the gel utilizing 32P-labeled 5 S, 5.8 S, 18 S, and 25 S rRNA. Identification of the various DNA restriction segments then led to the final ordering of the DNA fragments. The gene coding for the 5 S RNA is adjacent to the gene coding for the 35 S precursor rRNA. These two groups of genes thus occur as a cluster in the following sequence: [5 S-spacer]-[spacer-18 S-5.8 S-25 S-spacer]-[spacer-5 S]. The actual map of the DNA restriction fragments is presented.

DNA↗
PubMed1977

Effects of temperature, metabolic and cytoskeletal inhibitors on the rate of BHK cell adhesion to polystyrene.

Adhesion of baby hamster kidney fibroblasts (BHK cells) to a Falcon tissue culture flask was measured under various physiological conditions. While 75-80% of the fibroblasts adhere at temperatures from 19-50 degrees, cellular adhesion decreased dramatically below 19 degrees. Less than 10% of the cells adhere to the substratum even after prolonged incubations at temperatures of 8 degrees or below. This lack of adhesion at low temperatures cannot be overcome by the application of increased gravitational force to the cells. No correlation exists between cellular ATP concentrations or respiration rates and the rate of cell adhesion to the substratum. One millimolar Na F and 1 mM 2,4 dinitrophenol together lower cellular ATP concentration by 95% but adhesion is reduced by only 50%. NaN3 and KCN greatly lower cellular ATP concentrations without a corresponding inhibition of adhesion. Inhibition of cellular respiration by these compounds occurs at lower concentrations than does the inhibition of adhesion. Two micrograms/milliliters of cytochalasin B inhibits adhesion by 90%, 0.1 mM vinblastine sulphate or colchicine by less than 50% and 50 microgram/ml colcemid by less than 30%. Fixing the cells with formaldehyde, hardening their membranes with ZnCl2 or treating the cells with toluene, all cause an inhibition in adhesion. Again, application of increased gravitational force cannot overcome these latter inhibitions of BHK cell adhesion to the surface of the flasks.

Adenosine Triphosphate↗