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Biomedical subjects

A Sehgal

Publications and source records attributed to A Sehgal.

At least 109 records · Page 6Linked to original sources
PubMed1990

Aneuploidy in Drosophila. III: Aneuploidogens inhibit in vitro assembly of taxol-purified Drosophila microtubules.

The in vitro effects of aneuploidogens on taxol-purified microtubules from whole Drosophila melanogaster and mouse brain were studied by a spectrophotometric assay and electron microscopy. Colchicine, acetonitrile, propionitrile, acrylonitrile, dimethylsulfoxide (DMSO), griseofulvin, and cadmium chloride inhibit microtubule assembly, whereas methoxyethyl acetate (MEA) does not. Qualitatively similar results were observed with D. melanogaster and mouse brain microtubules. The in vitro results from D. melanogaster correlate well with previously published results from in vivo assays monitoring induced sex chromosome aneuploidy in that effective aneuploidogens are observed to affect microtubule assembly. The inclusion of taxol does not appear to qualitatively affect the assembly assays with the chemicals tested. In contrast with results from assembly assays, the tested aneuploidogens, including colchicine, do not promote disassembly to taxol-purified microtubules. It is possible that taxol has shifted the equilibrium and stabilized the formed microtubules to the extent that they are no longer sensitive to aneuploidogen-induced disassembly.

Acetates↗
PubMed1990

Risk factors related to biological behaviour of precancerous lesions of the uterine cervix.

In a study of factors related to cervical carcinogenesis, a cohort of 1,107 cervical dysplasia along with 1,077 controls matched for age and parity were followed up prospectively. During the follow up 75 dysplasia cases progressed to carcinoma in situ. The overall rate of progression of dysplasia to malignancy was observed to be 15.7% at the end of 108 months of follow-up. The analysis of progression rates in relation to various factors revealed significantly higher progression rates for initially higher grade of dysplastic lesions, and early age at consummation of marriage (ACM). The other factors, such as religion, literacy status of the patient, number of pregnancies, presence of cervical erosion, history of fetal loss and positivity to HSV-II antibodies, did not reveal statistical significance. The case-control comparison for detection of HPV 16/18 by in situ hybridisation revealed the presence of HPV 16/18 sequences in 67.3% of the dysplasia subjects progressed to carcinoma in situ while 27.3% of precancerous cases regressed to normalcy. The difference was found to be statistically significant (P less than 0.001).

Adult↗
PubMed1990

Cancer projection by the turn of century-Indian science.

This is an attempt to understand the magnitude of cancer problem in India. The incidence data generated by the three population based cancer registries at Bangalore, Bombay and Madras and the population projections of country have been utilised for estimating the present and future load of new cancer cases. It is estimated that the total number of incident cases in males increased from 0.29 million to 0.43 million by the turn of the century as a result of change in size and composition of population and when adjusted for tobacco habits the estimates increased to 0.49 million. In females the incident cases of cancer for three registries increased from 0.32 to 0.42 million by 2001, with cancer of uterine cervix and breast being the major problems. The above results show an urgent need for strengthening and augmenting the existing diagnostic/treatment facilities which are vow fully inadequate to tackle even the present load.

Female↗
PubMed1990

Risk for development of cancer in three urban areas of India.

The probability of developing cancer by using life table approach has been computed for the population of three metropolitan cities of India based on data of population based cancer registries located at Bangalore, Bombay and Madras. It was observed that the risk for development of malignancy of all sites from 20 to 64 years ranged from 4.73% to 5.28% in males, whereas it was 6.76% to 9.18% in females. The increased risk in females was mainly due to the high risk of development of cancer of the uterine cervix and breast. The available morbidity indices such as cumulative incidence rate and cumulative risk do not account for the mortality experiences of population. The present exercise will be useful in evaluating the changes in the disease spectrum as a result of change in the mortality experiences and population structure.

Adult↗
PubMed1989

Gene transfer of truncated NGF receptor clones leads to cell surface expression in mouse fibroblasts.

Transfection of recombinant bacteriophage clones encoding human NGF receptor sequences resulted in cell surface expression in mouse fibroblasts. Unexpectedly, receptors were expressed even after transfection with phage clones which lack 5' gene sequences. Stable transformants were purified and analyzed in detail. S1 nuclease protection and primer extension analysis revealed that an initiation site lies within an intron sequence in the middle of the receptor gene. A truncated mRNA transcript was detected that allowed for the expression of NGF receptors capable of binding to NGF. Since the original phage clones lacked the first two exons, these results suggest that the normal N-terminal sequences may not be necessary for cell surface expression and binding to NGF.

Animals↗
PubMed1989

Small family norm and uterine cervical cancer.

Carcinoma of the cervix is known to have a multifactorial etiology and several factors are implicated in increasing the risk of eventual development of cervical malignancy in a woman. This communication attempts to highlight the small family norms in the prevention of uterine cervical cancer. Data on 117,411 cytologically screened women were considered in which 215 women were found to have cervical cancer. Age adjusted rates of malignancy per 100,000 women in three parity groups (0-2, 3-4 and 5+) were 91.1, 174.4 and 393.1 respectively. An increasing trend of malignancy was noticed with increasing parity in women who had their consummation of marriage before 18 years as well as after 18 years. It may be concluded that the small family norm (only two children) being advocated as a part of a national family welfare program would be another primary prevention measure against uterine cervical cancer.

Adolescent↗
PubMed1988

Efficient processing and expression of human nerve growth factor receptors in Xenopus laevis oocytes: effects on maturation.

The nerve growth factor (NGF) receptor is an integral membrane protein that is phosphorylated and heavily glycosylated. Determination of the amino acid sequence by molecular cloning indicates that the receptor is a cysteine-rich protein which contains a signal peptide sequence and spans the lipid bilayer with a single transmembrane sequence. A single mRNA of 3.8 kilobases was observed for the receptor, of which 1.5 kilobases is coding sequence. We have used microinjection of receptor RNA in Xenopus laevis oocytes to obtain cell surface expression of the receptor. The presence of NGF receptors in oocytes was verified by radioimmunoassay, specific binding of [125I]NGF, and metabolic labeling followed by immunoprecipitation. The NGF receptor protein was rapidly processed in oocytes and displayed extensive glycosylation. Furthermore, the presence of NGF receptors in oocytes potentiates the ability of progesterone to induce maturation.

Animals↗
PubMed1988

A constitutive promoter directs expression of the nerve growth factor receptor gene.

Expression of nerve growth factor receptor is normally restricted to cells derived from the neural crest in a developmentally regulated manner. We analyzed promoter sequences for the human nerve growth factor receptor gene and found that the receptor promoter resembles others which are associated with constitutively expressed genes that have housekeeping and growth-related functions. Unlike these other genes, the initiation of transcription occurred at one major site rather than at multiple sites. The constitutive nature of the nerve growth factor receptor promoter may account for the ability of this gene to be transcribed in a diverse number of heterologous cells after gene transfer. The intron-exon structure of the receptor gene indicated that structural features are precisely divided into discrete domains.

Animals↗
PubMed1986

Expression and structure of the human NGF receptor.

The nucleotide sequence for the human nerve growth factor (NGF) receptor has been determined. The 3.8 kb receptor mRNA encodes a 427 amino acid protein containing a 28 amino acid signal peptide, an extracellular domain containing four 40 amino acid repeats with six cysteine residues at conserved positions followed by a serine/threonine-rich region, a single transmembrane domain, and a 155 amino acid cytoplasmic domain. The sequence of the extracellular domain of the NGF receptor predicts a highly ordered structure containing a negatively charged region that may serve as the ligand-binding site. This domain is conserved through evolution. Transfection of a full-length cDNA in mouse fibroblasts results in stable expression of NGF receptors that are recognized by monoclonal antibodies to the human NGF receptor and that bind [125I]NGF.

Amino Acid Sequence↗
PubMed1986

Gene transfer and molecular cloning of the human NGF receptor.

Nerve growth factor (NGF) and its receptor are important in the development of cells derived from the neural crest. Mouse L cell transformants have been generated that stably express the human NGF receptor gene transfer with total human DNA. Affinity cross-linking, metabolic labeling and immunoprecipitation, and equilibrium binding with 125I-labeled NGF revealed that this NGF receptor had the same size and binding characteristics as the receptor from human melanoma cells and rat PC12 cells. The sequences encoding the NGF receptor were molecularly cloned using the human Alu repetitive sequence as a probe. A cosmid clone that contained the human NGF receptor gene allowed efficient transfection and expression of the receptor.

Animals↗
PubMed1986

The nerve growth factor receptor gene is at human chromosome region 17q12-17q22, distal to the chromosome 17 breakpoint in acute leukemias.

Genomic and cDNA clones for the human nerve growth factor receptor have been used in conjunction with somatic cell hybrid analysis and in situ hybridization to localize the nerve growth factor receptor locus to human chromosome region 17q12-q22. Additionally, part, if not all, of the nerve growth factor receptor locus is present on the translocated portion of 17q (17q21-qter) from a poorly differentiated acute leukemia in which the chromosome 17 breakpoint was indistinguishable cytogenetically from the 17 breakpoint observed in the t(15;17)(q22;q21) translocation associated with acute promyelocytic leukemia. Thus the nerve growth factor receptor locus may be closely distal to the acute promyelocytic leukemia-associated chromosome 17 breakpoint at 17q21.

Chromosome Mapping↗