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S Mathew

Publications and source records attributed to S Mathew.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cytogenetics of gastric and esophageal adenocarcinomas. 3q deletion as a possible primary chromosomal change.

We report clonal chromosome abnormalities in short term cultures of seven gastric or esophageal adenocarcinomas and two squamous carcinomas of the esophagus and EG junction. The most consistent aberration encountered was a del(3) (q13.2q23) seen in six of nine tumors. This finding, together with a survey of published cytogenetic literature, suggested that del(3q) is the most common cytogenetic abnormality, and hence possibly of primary significance, in these tumors. In addition to del(3q), rearrangements affecting 1p13 (two cases), 6q15-q23 (two cases), 7p22 (two cases), 7q22 (two cases), and 11p11.2-p14 (three cases) were seen. Cytogenetic evidence for gene amplification in the form of homogeneously staining region (hsr) was seen at 9q13 in two cases.

Adenocarcinoma↗
PubMed1995

Alternative splicing of a 48-nucleotide exon generates two isoforms of the human calcitonin receptor.

A portion of the human calcitonin receptor (hCTR) gene corresponding to the region of the porcine gene at which alternative splicing generates two CTR isoforms was isolated by polymerase chain reaction amplification of placental DNA. In contrast to the porcine CTR gene, in which two acceptor sites in exon 8 are separated by 48 nucleotides, we found a distinct 48-nucleotide exon in the hCTR gene that is present approximately 6400 basepairs from the up-stream exon, which corresponds to porcine exon 7, and approximately 1100 basepairs from the down-stream exon, which corresponds to porcine exon 8. Splicing of this exon accounts for the two isoforms of hCTR, containing or not containing a 16-amino acid insertion in the first putative intracellular loop. A region similar to the intron 7-exon junction in the porcine CTR gene is present in the human gene, but contains four extra nucleotides that shift the reading frame. Using probes derived from these introns in somatic cell and in situ hybridization analyses, we assigned the CTR gene to human chromosome band 7q21.2-q21.3. Thus, human and porcine species have evolved distinct mechanisms to generate two similar CTR isoforms.

Alternative Splicing↗
PubMed1995

Vancomycin for controlling contamination of selective Kirchner's liquid medium in the culture of gastric lavage for tubercle bacilli.

Gastric lavage (GL) was collected for culture of tubercle bacilli from children too young to expectorate sputum. The selective Kirchner's liquid medium (SKLM), routinely used as one of the media for culture of all extrapulmonary specimens, was found to often get contaminated when cultured with GL. We have shown that vancomycin at a concentration of 10 mg/l successfully reduced the contamination from about 60 to 20 per cent, and enhanced the isolation rate of tubercle bacilli from 3 to 6 per cent. Decontamination of the liquid culture before subculture on solid medium also helped to reduce the contamination rate. Vancomycin was found to be an effective selective drug for use in the Kirchner's liquid medium for culture of tubercle bacilli.

Bacteriological Techniques↗
PubMed1995

A direct rifampicin sensitivity test for tubercle bacilli.

A direct sensitivity test for rifampicin has been standardised for early detection of resistance for the mycobacterium tuberculosis smear positive sputum samples. Indirect sensitivity tests set up from primary cultures of the same samples served as controls. The direct test showed 95 per cent agreement with the standard indirect test and as such 74 per cent and 90 per cent of the resistant strains were detected by the fourth week and fifth week, respectively, with an overall gain of 4-5 wks time. Resistance could be detected earlier for multibacillary specimens. This direct sensitivity test on Lowenstein Jensen (LJ) medium offers a feasible alternative for laboratories which lack facilities to perform drug susceptibility tests by the rapid but sophisticated and costly BACTEC method. The method is simple to perform, economic, reliable and amenable to confirmation by the indirect test, if needed.

Drug Resistance, Microbial↗
PubMed1995

Inversion polymorphism in Drosophila ananassae: persistence of inversions, heterosis and intra- and inter-chromosomal associations in experimental populations of mixed geographic origin.

Two experimental populations of D. ananassae were synthesised by making reciprocal crosses among five geographic strains and mixing the hybrids. Each of the two populations of mixed geographic origin was maintained as mass cultures in food bottles. After five generations chromosomal analysis of these two populations was made by squashing a large number of larvae. The results showed that both experimental populations remained polymorphic due to the persistence of AL, (2L), ZE (2R) and DE (3L) inversions in population A and AL, ZE, DE and ET (3R) inversions in population B. Persistence of inversions in considerable frequency and significant deviation from Hardy-Weinberg equilibrium showed that heterosis is associated with these four inversions in D. ananassae. Further, there is non-random association (linkage disequilibrium) between linked inversions in second (AL-ZE) chromosome. However, the inversions of the different chromosomes are associated randomly indicating no interchromosomal interactions in D. ananassae. The results of these studies on population dynamics of inversion polymorphism in experimental populations are attributable to selection, genetic drift and Founder effect.

Animals↗
PubMed1994

Loss of heterozygosity identifies multiple sites of allelic deletions on chromosome 1 in human male germ cell tumors.

Cytogenetic analysis of human male germ cell tumors (GCTs) and derived cell lines revealed frequent deletions and rearrangements of chromosome 1. However, no detailed molecular analysis of these aberrations has thus far been performed. We undertook loss of heterozygosity (LOH) analysis utilizing a panel of 48 GCTs at 22 subregionally mapped polymorphic loci on both arms of chromosome 1. Eight probes, for which precise mapping data were unavailable, were subregionally mapped to specific regions by fluorescence in situ hybridization. Allelic losses were observed in 46% of cases on 1p and in 23% of cases on 1q. Teratomas showed higher frequency of allelic losses compared to embryonal carcinomas, yolk sac tumors, and seminomas, consistent with the results of our previous allelotype analysis, which showed overall higher genetic loss in teratomas compared to embryonal carcinomas. Our LOH study of chromosome 1 identified 4 sites of frequent deletions, 3 in the short arm (1p13, 1p22, and 1p31.3-32.2) and 1 in the long arm (1q32). Of these, 38.5% LOH at 1p22 (D1S16) identifies the site of a novel candidate tumor suppressor gene (TSG), possibly associated with GCTs. LOH at the remaining sites (1p13, 1p31.3-32.2, and 1q32) has also been reported in breast carcinomas, suggesting the involvement of TSGs common to both tumor types.

Alleles↗
PubMed1994

Characterization of the promoter region of the gene for the rat neutral and basic amino acid transporter and chromosomal localization of the human gene.

The promoter region of the rat kidney neutral and basic amino acid transporter (NBAT) gene has been isolated and sequenced. The major transcription initiation site was mapped by primer extension. The entire promoter region and a set of 5' deletions within it were expressed at a high level in LLC-PK1 cells using the luciferase indicator gene. Positive and negative regulatory elements in the promoter region were observed. A human genomic clone of the transporter was also obtained and was used to localize the NBAT gene at the p21 region of chromosome 2.

Amino Acid Sequence↗
PubMed1994

Replication error-type genetic instability at 1q42-43 in human male germ cell tumors.

The replication error phenotype, recognized as microsatellite sequence alterations, has recently been suggested to be associated with hereditary nonpolyposis colorectal cancer and other types of sporadic tumors. We examined paired tumor-normal DNAs from 69 human male germ cell tumors for somatic instability at the 1q42-43 region. Analysis of a variable number of tandem repeats marker (D1S74) and 3 (CA)n type microsatellite loci (D1S235, D1S180, and angiotensinogen) revealed genetic alterations in tumor DNAs of 26 (38.2%) cases. The changes observed comprised rearrangements with D1S74 detected by Southern blot analysis in 4 of 55 (7%) cases; replication error-type alterations with D1S235, D1S180, and angiotensinogen in 12 of 66 (18.2%) cases; and loss of heterozygosity in 12 of 67 (17.9%) cases with the same probes. The microsatellite sequence alterations were more common in histological subsets other than teratomas, while the loss of heterozygosity was significantly more frequent in teratomas compared to other histologies. These results suggest that microsatellite instability and loss of heterozygosity at 1q42-43 may be unrelated genetic events which may play a role in germ cell tumor development.

Chromosomes, Human, Pair 1↗
PubMed1994

Origin of adult male mediastinal germ-cell tumours.

The origin of primary extragonadal germ-cell tumours, especially mediastinal and pineal germ-cell tumours in adult males remains uncertain, although the predominant view is that they originate in misplaced primordial germ cells retained in extra-gonadal sites, in contrast to gonadal germ-cell tumours which are considered to arise in premeiotic spermatocytes. We hypothesised that if mediastinal germ-cell tumours and gonadal germ-cell tumours were derived from precursor cells in different developmental states and in different cellular environments, non-random genetic changes in the two groups would be significantly different. To test this hypothesis, we compared non-random chromosomal abnormalities in mediastinal germ-cell tumours with those in gonadal germ-cell tumours. Our results show that although the two groups differed in the composition of histological subsets, their non-random chromosomal changes were essentially the same. These data suggest gonadal origin of all germ-cell tumours with occasional migration of precursors early in development to extragonadal sites to become established as primary extragonadal germ-cell tumours. Based on a review of cytogenetic data on carcinoma in situ, primary mediastinal and gonadal germ-cell tumours, embryonal migration of primordial germ-cells, and meiotic behaviour of spermatocytes, a model of origin of all germ-cell tumours in males is suggested.

Adult↗
PubMed1994

Transforming growth factor receptor gene TGFBR2 maps to human chromosome band 3p22.

In this study, we map the chromosomal position of the gene that encodes the type II receptor of TGF-beta (HGM symbol TGFBR2), a multifunctional regulator of cell proliferation and differentiation. Using a full-length cDNA and a genomic probe in Southern blot analysis of a human x rodent somatic cell hybrid panel and by direct fluorescence in situ hybridization to normal metaphase chromosomes, we show that the TGFBR2 gene maps to 3p22.

Animals↗
PubMed1994

Pancreatic lesions and modifications of pancreatic juice in tropical chronic pancreatitis (tropical calcific diabetes).

Seventeen Indian patients from Kerala State and 13 Indian controls were submitted to a dietary inquiry. Indian patients and controls had a low fat intake (40.8 g +/- 12.1 and 34.5 g +/- 11.0 per day, respectively) and a moderately low protein intake (52.8 +/- 9.5 and 47.8 +/- 11.3 g per day); 11 patients and 6 controls did not consume cassava. Pure nonactivated pancreatic juice was collected at endoscopy in 10 Indian patients who presented with tropical calcific diabetes, 12 apparently normal controls from the same area, and 23 apparently normal French controls. The only significant differences between Indian and French controls was a decreased pancreatic protein response to cerulein and an increased calcium concentration in the Indian subjects. The pancreatic juice of Indian patients was characterized by decreased volume, normal bicarbonate concentration, increased protein concentration when the acinar cells were not stimulated, with no response to cerulein, increased calcium concentration, and normal citrate concentration. These changes are very similar to the changes observed in French patients with chronic alcoholic pancreatitis. The lesions of 14 surgical resection pancreatic specimens from South Indian patients presenting with tropical pancreatitis were compared to pancreata from French patients presenting with chronic alcoholic pancreatitis. The only difference was that intraductal plugs, lesions of the duct epithelium, and retention cysts or pseudocysts were less frequent in Indians. These results show that the two nutritional forms of pancreatic lithiasis, alcoholic and tropical, have similar histological lesions and biochemical modifications of pancreatic juice.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Stress causes alteration in attachment of rat hepatocytes to matrix protein substratum.

The effect of different types of stress on the attachment of rat hepatocytes to various matrix protein substrata, such as collagen IV, fibronectin and laminin, was investigated. Study of the kinetics of attachment of adult hepatocytes subjected to heat-shock at 45 degrees C for 30 min showed significantly lower attachment to collagen IV, fibronectin and laminin substrata when compared to untreated controls. The alteration in attachment was observed after heat-treatment for 10 min and the extent of alteration appeared to increase with duration of the heat-treatment, as well as with increase in temperature. Foetal rat hepatocytes, which appeared to attach much more readily than adult rat hepatocytes to these substrata, particularly to laminin, also showed significantly lower attachment to all three substrata after heat-treatment at 45 degrees C for 30 min. This alteration in attachment appeared to be specific for matrix proteins as there was no significant effect on interaction of cells with non-matrix proteins, such as Con A and asialoglycoproteins. While the attachment of adult hepatocytes appeared to attain near control levels in about 4 h, the foetal cells recovered in about 2 h after heat-shock, indicating that the heat-shock effect is reversible and the recovery is faster in foetal hepatocytes. Other stress-causing agents, such as heavy metals, also caused an alteration in attachment of hepatocytes to these matrix proteins. Attachment of adult and foetal hepatocytes to collagen substratum was reduced by 100-microM concentrations of heavy metals in the order Zn > Cd > La > As > Cu for adult cells and La > Zn > As/Cu > Cd for foetal cells. These heavy metals also caused significant reduction in attachment of adult hepatocytes to fibronectin and laminin, although the extent of inhibition was less than that for collagen substrata. However, these heavy metals did not significantly affect the attachment of foetal hepatocytes to laminin substratum indicating that the effect of heavy metals appeared to vary with the nature of the matrix protein substratum. On heat-shock, incorporation of [3H]leucine into cytoskeletal proteins such as cytokeratins CK8 and CK18 was reduced and significant amounts of two new proteins having an average molecular mass of 80 kDa and 90 kDa were found to be tightly associated with cytoskeletal proteins.

Aging↗
PubMed1993

Interphase cytogenetics of gastric and esophageal adenocarcinomas.

Numerical changes affecting chromosomes 1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 16, 17, 18, and the X and Y chromosomes have been analyzed using chromosome-specific centromeric alpha-satellite repeat DNA probes in a panel of biopsies of six gastric and three esophageal adenocarcinoma and one epidermoid carcinoma of esophagus obtained at surgery. For each case, with each probe, the number of hybridization signals were determined in 200 nuclei. Hybridization of each probe to phytohemagglutinin-stimulated normal peripheral blood lymphocytes served as controls. Monosomy was defined by loss of one signal in 15% or more cells and trisomy or tetrasomy was defined by the presence of 3 or 4 signals in 7% or more cells, respectively. The Y chromosome was lost in 6 of 8 cases and monosomy 10 was seen in 5 of 10 cases. Trisomy for chromosomes 17, 8, 7, 12, 11, and 1 was seen in 4 of 10, 4 of 10, 4 of 10, 2 of 10, 2 of 8, and 2 of 10 cases, respectively, and tetrasomy for chromosome 7 was seen in 1 of 10 cases. These data show that the Y chromosome and chromosomes 10, 8, 7, 17, and 12 are most frequently involved in nondisjunctional changes in these tumors. They also document the feasibility and utility of interphase cytogenetics of gastric adenocarcinomas.

Adenocarcinoma↗
PubMed1993

Chromosomal localization and nucleoside diphosphate kinase activity of human metastasis-suppressor genes NM23-1 and NM23-2.

Human metastasis-suppressor genes nm23-1 (NME1) and nm23-2 (NME2) are implicated in control of the metastatic potential of malignant cells. Using somatic cell hybrid analysis and fluorescence in situ hybridization we co-localized both genes to 17q21.3. The 17q21 region carries the locus responsible for early-onset familial breast-ovarian cancer and several other genes that are involved in tumorigenesis and differentiation and undergo frequent rearrangements during neoplastic development. Thus, our mapping places the NME genes in a region that may be subjected to multiple selection pressures. NME1 and NME2 genes were expressed as soluble proteins in a T7 bacterial expression system. Both proteins are independently active nucleotide diphosphate kinases and readily form intra- and intermolecular disulfide bonds. The biochemical properties of these proteins may explain the diversity of mature eucaryotic nucleoside diphosphate kinases.

Animals↗
PubMed1993

Chromosomal localization of genes encoding the transcription factors, c-rel, NF-kappa Bp50, NF-kappa Bp65, and lyt-10 by fluorescence in situ hybridization.

We have used fluorescence in situ hybridization (FISH) to perform precise chromosomal mapping of the genes encoding the transcription factors c-rel, NF-kappa Bp50, NF-kappa Bp65, and lyt-10. The previously published assignments of c-rel and NF-kappa Bp50 have been refined to specific bands. The map position of lyt-10, inferred from its isolation from a t(10;14)(q24;q32) translocation, has been confirmed. NF-kappa Bp65 has now been mapped to 11q13, a site of frequent involvement in aberration in multiple tumor types.

Chromosome Mapping↗