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Biomedical subjects

B B Singh

Publications and source records attributed to B B Singh.

At least 91 records · Page 5Linked to original sources
PubMed1988

Phorbol ester binding to oral epithelial cells in the presence of retinoic acid or N-nitrosonornicotine.

Although the specific mechanisms by which phorbol ester tumour promoters exert their various effects are not known, their actions are mediated by cell membrane receptors which contain lipids as major components of the receptor complex. Since cell modulators such as retinoic acid (RA) and nitrosonornicotine (NNN) can alter cell lipids, the binding of a phorbol ester to cells was examined at time intervals when lipid changes mediated by these modulators occur. Epithelial cells prepared from hamster cheek pouches were treated with all-trans RA or NNN for varying periods of time, then specific binding of phorbol esters was investigated. Cells treated with RA for intervals up to 24 h showed decreased binding when compared with untreated cells. Those treated with NNN for up to 168 h showed increased specific binding. The results suggest that alterations in the cell lipids may affect the specific binding of phorbol esters to cells.

Animals↗
PubMed1986

[Transcutaneous oxygen tension and apnea during sleep stages in normal infants and infants at risk for sudden infant death syndrome].

The relationship between chronic hypoxemia and sudden infant death syndrome (SIDS) has been reported by several authors. In order to study the influence of the apnea-time during a sleep state on transcutaneous oxygen tension (tcPO2), we have studied polygraphically 30 full-term infants (10 controls, 10 SIDS siblings and 10 near-miss for SIDS), aged from 5 to 13 weeks. No significant difference was observed either for apnea-time or tcPO2 between infant-groups studied in different sleep states. We could not find any correlation between apnea-time and tcPO2 in all groups of infants studied during different states of sleep. It is therefore concluded that in normal and at risk for SIDS infants, tcPO2 levels during sleep states cannot be explained only by the apnea-time.

Blood Gas Monitoring, Transcutaneous↗
PubMed1986

Oral epithelial cell lipid synthesis in the presence of retinoic acid or nitrosonornicotine.

The current study examines the effects of N-nitrosonornicotine (NNN) and all trans-retinoic acid (RA) on the synthesis and composition of lipids of oral epithelial cells grown in culture. Cells were exposed to NNN, RA or methylene chloride (the vehicle for the NNN and RA) and the lipids labelled with [14C]-acetate. Lipids were extracted from the cells, separated by paper chromatography, located by autoradiography, and acetate incorporation determined by liquid scintillation spectrometry. Cholesterol labelling was significantly decreased by the RA between 4 and 48 h when compared to the NNN-treated or control cells. After 48 h the incorporation levels in the presence of the two last compounds decreased. Free fatty acid labelling was also significantly less in cells exposed to RA, while labelling of triglycerides and phospholipids was increased. N-nitrosonornicotine seemed to produce a decreased labelling of cholesterol after 96 h continuous exposure. The results of these studies suggest that retinoid rapidly elevates the cell content of lipid formed from the glycerolipid pathway and membrane mechanisms may be modulated by this effect.

Animals↗
PubMed1985

Significance of histopathology in pulsed NMR studies on cancer.

Characterization of tissue by pulsed nuclear magnetic resonance spectrometry opened a new area of research. The differences in the NMR parameters T1 and T2 of normal and malignant tissues constitute the basis for their distinction by pulsed NMR spectrometry and also by NMR imaging in vivo. The present studies were undertaken to correlate the role of constituent histological elements encountered in various malignancy-associated changes and T1 variations and are based on evaluation of samples taken from surgically resected specimens of carcinoma of the esophagus, comprising the uninvolved portions of the esophagus and the gastric end on gross examination. The uninvolved and involved regions showed low and high T1 values, respectively. High T1 values were also encountered in the zones of samples of uninvolved esophagus which histologically revealed areas with dysplasia. This feature, viz., dysplasia representing malignancy-associated changes, has been found to recur in many samples. Detailed histological studies provided further evidence confirming that areas with dysplasia contribute to an increase in T1 values whereas in zones at the gastric end metaplasia and hyperplasia are more common. The results are of value for demarcation of tumor area by in vivo NMR imaging.

Adenocarcinoma↗
PubMed1985

Temperature dependent modification of radiosensitivity following hypoxic cytocidal action of chlorpromazine.

The hypoxic cytotoxic effect of chlorpromazine towards E. coli B/r was observed to be dependent on temperature of incubation and irradiation. Increasing the temperature of incubation from ambient to 37 degrees C followed by irradiation revealed that the organisms showed radiosensitivity of a magnitude which was two to three times the oxygen effect. The possible mechanisms of this effect are discussed.

Chlorpromazine↗
PubMed1985

Cholinesterase activity in Thysaniezia giardi (Cestoda, Anoplocephalidae).

The activity of cholinesterase was determined separately in the mature and gravid proglottids of Thysaniezia giardi and its significance is discussed. The mean values of the enzyme in mature and gravid proglottids were respectively 225.60 +/- 28.55 and 75.00 +/- 11.64 units per gram of wet weight.

Animals↗
PubMed1985

Non-nitro radiation sensitizers.

A review of the literature on radiosensitization reveals that at least some of the non-nitro compounds, such as metabolic inhibitors and membrane-active drugs, could be considered as potentially valuable radiosensitizers for possible use in future cancer radiotherapy.

Animals↗
PubMed1985

A simplified method for culture of oral epithelial cells.

In order to facilitate studies on oral mucosa a simplified method for the culture of oral epithelial cells from adult hamsters was developed. Cheek pouches were excised and epithelial cells isolated by collagenase digestion. These were grown in CM-V medium containing spermine in order to inhibit overgrowth of the epithelial cells by fibroblasts. The epithelial cells were subcultured by routine tissue culture procedures. The cells isolated were examined by light microscopy and scanning and transmission electron microscopy. Morphologically the cells were typical of epithelial cells. Ultrastructural examination showed structures typical of epithelia including filaments, keratohyalin granules and desmosomal junctions. The culture system provides epithelial cells that can be used for a variety of biochemical and morphological studies.

Animals↗
PubMed1984

Radioprotection of euoxic bacteria by phenothiazine drugs.

Survival studies on irradiated euoxic E. coli B/r cells in presence of various concentrations of four radioprotecting phenothiazine drugs have been carried out. Maximum radioprotection was obtained at a optimal concentration for each drug and it decreased on either side of it. The DNA strand break studies at the maximum protective and non-protective concentrations of chlorpromazine and promethazine revealed that the number of ssbs in DNA were less at the protective concentration which were efficiently repaired by the type-III repair process. On the other hand, at the non-protective concentrations, inhibition of DNA repair was noticed and a higher number of DNA ssbs were detected. We suggest that the membrane is fluidized to a greater extent at the protective concentrations allowing the chemical restitution of damaged sites by NPSH compounds. At the non-protective high concentrations of the drugs, the membrane may be too grossly disorganised to allow any repair and at the same time high concentrations of the drugs or their radicals may also react with radioprotective intracellular sulphhydryls.

Cell Survival↗
PubMed1984

The effects of retinoic acid on [14C]acetate incorporation into lipids of normal and transformed hamster fibroblasts.

This study examined the effects of retinoic acid (RA) on [14C]acetate incorporation and fatty acid composition of hamster embryo fibroblasts (HEF) and two cell lines derived from the same inbred strain but transformed by herpes simplex-2 virus (HSV) or polyoma virus (HFT). Cells were exposed to all trans RA, or dimethylsulfoxide (DMSO), the vehicle for RA, and the lipids labeled with [14C]acetate. Lipids were extracted from the cells, separated by paper chromatography, located by autoradiography, and acetate incorporation determined by liquid scintillation spectrometry. The distribution of fatty acids in total cell lipids was examined by gas chromatography. HEF cells incorporated more acetate into cholesterol than either transformed cell type. The HFT line incorporated more acetate into triglycerides and less into total phospholipids than either the HSV line or the HEF line. RA caused a significant decrease in incorporation of acetate into cholesterol and sphingomyelin in all three cell lines. HEF and HSV cells had decreased incorporation into phosphatidyl inositol-phosphatidyl serine and increased incorporation into triglycerides, changes not evident in the HFT cell. The control fatty acid profiles of the HEF and HSV cells were similar, while the HFT cells had a larger proportion of C16:0 and 18:1 fatty acids. Following treatment with RA all three cell types showed an increase in palmitic and a decrease in oleic acids. The three related cell types showed different [14C]acetate labeling patterns which did not respond uniformly to RA. On the other hand, exposure elicited some like responses in all cell types.

Acetates↗
PubMed1984

Effects of 12-0-tetradecanoyl-phorbol-13-acetate on oral epithelium in vitro.

TPA, a tumor promotor whose initial site of action is the cell membrane, was examined for its actions on hamster oral mucosa using light and scanning electron-microscopic procedures. Hamster cheek-pouch explants were cultured in vitro, then treated for 72 h with 1.6 X 10(-8) M TPA. Treated cultures showed a higher mitotic index and more extensive growth than control cultures. Epithelial cells in the control cultures appeared polygonal, with thin, small to medium microvilli. The cells in the treated cultures showed variable shape and surface morphology. Some were interconnected by broad cytoplasmic extensions while others demonstrated long, thin processes that traversed great distances. The unusual surface morphology may be a manifestation of altered phospholipid metabolism that produces a more "fluid" cytoplasmic membrane.

Animals↗
PubMed1984

The biomaterial-tissue interface: a morphological study utilizing conventional and alternative ultrastructural modalities.

The interface between oral tissues and ceramic endosteal dental implants was investigated in 36 experimental cases in dog jaws. Conventional electron microscopic modalities showed those tissues adjacent to the implants to be viable with no adverse cellular response to the biomaterial. A procedure to retrieve additional ultrastructural data from previously processed biological material was developed to expand upon these data. This included surface-etching with oxygen plasma of routinely processed electron microscopy specimens and formalin fixed histological specimens for scanning electron microscopy (SEM) study; and, cryofracturing of similar histological specimens for additional transmission electron microscopic (TEM) analysis. Results from these alternative protocols supported our observations from conventional studies of the direct association of bone and epithelia to the implant. In addition, they demonstrated a unique portrayal of the epithelial maturation patterns. Further, this alternative TEM method showed excellent retention of cellular integrity and demonstrated a hemidesmosomal-external basal lamina attachment apparatus at the junctional epithelial-implant interface. This latter composite attachment structure was not retained in our previous conventional microdissection procedures. Thus, the interface between oral tissues and the single crystal sapphire endosteal dental implant could be elucidated by these protocols.

Animals↗