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Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 307 records · Page 17Linked to original sources
PubMed1989

Observations on Indian node-negative breast cancer patients: a multivariate analysis.

The modern treatment of breast cancer has evolved over the past 100 years based on clinical observations. Therapeutic principles, from the choice of surgical procedure to the management of disseminated disease, have also changed. The axillary tumour burden, that is, the number of histologically positive nodes (N+) plays an important role as a prognostic factor. However, in histologically Negative nodes (N-), it is necessary to discriminate individuals at high risk despite negative nodes. This presentation analyses retrospectively the prognostic factors for long-term failures in N- patients. These prognostic factors need to be studied in detail, and controlled clinical trials should be carried out to detect high risk N- patients and consider them for adjuvant chemotherapy.

Antineoplastic Agents↗
PubMed1989

Cloning of the gene for the capsid protein of potato leafroll virus.

DNA complementary to the RNA of purified potato leafroll virus (PLRV) was synthesized and cloned into the lambda insertion vector NM1149. Overlapping PLRV-specific cDNA clones were isolated that represent some 80% of the viral genome. Sequences coding for the capsid protein were identified by subcloning size-selected cDNAs into the lambda expression vector gt11 and screening with PLRV-specific antisera. The gene for the viral capsid protein was shown to reside in the 3' terminal half of the genomic RNA. Sequence comparisons with the recently published genomes of the beet western yellows virus (BWYV) and the barely yellow dwarf virus (BYDV) reveal some 65% protein sequence homology between the capsid proteins of BWYV and PLRV and some 45% homology between BYDV and PLRV. Furthermore, it is evident that the structural organization of the PLRV genome in the CP gene region is similar to that of BWYV and BYDV.

Amino Acid Sequence↗
PubMed1989

Myosin light chain 3 synthesis during chick pectoralis muscle development in ovo.

The level of myosin light chain 3 (LC3) in vertebrate skeletal muscle is developmentally regulated in a tissue-specific manner. We have used the RNA-cDNA hybridization assay to quantitate LC3 mRNA levels at various stages of chick pectoralis muscle development in ovo. The LC3 mRNA was found significantly in breast muscle only on Day 16 in ovo and later, the level of mRNA ranging from about 30 to 32% of that present in adult tissue. These values are in good agreement with the corresponding levels of LC3 in embryonic muscle. These results do not support the earlier reports that the protein and mRNA for LC3 accumulate in a noncoordinate manner in embryonic pectoralis muscle and they suggest that LC3 synthesis in ovo is regulated primarily at the transcriptional level.

Animals↗
PubMed1989

Differential diagnosis and management of renovascular hypertension through nuclear medicine techniques.

Identification of patients with renovascular hypertension (RVH) among the larger group of patients with essential hypertension has been aided by a wide variety of in vitro and in vivo nuclear medicine procedures. The most valuable in vitro procedure remains the radioimmunoassay (RIA) for renin activity obtained from individual renal vein catheterization studies. Lateralizing renin activity provides valuable prognostic information about the likelihood for surgical cure of RVH. Older in vivo procedures for the diagnosis of RVH included rectilinear scanning and probe renography, which suffered from poor resolution and specificity, respectively. These tests have been replaced by computer-interfaced gamma camera scintirenography using 131I- or 123I-labeled orthoiodohippurate (OIH), or scintiangiography using 99mTc-DTPA. False-positive (FP) results for RVH persist due to a wide variety of relatively common conditions that can cause asymmetric renal size and function, including outflow obstruction and parenchymal renal disease. Newer approaches promise to improve the specificity of nuclear medicine procedures for identification of RVH. In particular, the number of FP exams appears to improve when scintirenography is performed before and after the administration of oral angiotensin converting enzyme (ACE) inhibitors, using either 99mTc-DTPA or OIH. The incentive for improved diagnostic testing has increased with the availability of percutaneous transluminal angioplasty (PCTA) for treatment of renal artery stenosis (RAS). Follow up of PCTA with scintirenography is of great value in assessing its effect on renal function and in evaluating the subsequent clinical course of the patient.

Diagnosis, Differential↗
PubMed1989

Determining proportions of human X and Y sperm with a recombinant deoxyribonucleic acid probe carrying a homologous sequence of sex chromosomes.

A molecular sexing assay method for human sperm DNA has been described, which is particularly suitable for estimating proportions of X and Y sperm in a large number of sample points. The method should have general applicability for testing any mammalian sperm species, since it is based on probing the homologous DNA sequences that are known to be present probably in all mammalian sex chromosomes.

DNA Probes↗
PubMed1989

Mutagenicity and carcinogenicity of smoked meat from Nagaland, a region of India prone to a high incidence of nasopharyngeal cancer.

The incidence of nasopharyngeal cancer (NPC) in the northeastern part of India is reported to be high. A possible correlation between consumption of smoked meat by the tribal people and high suceptibility to NPC has been postulated. The charred portion of smoked beef and meat of other animals was collected from this area, extracted with acetone and the extract (SME) was tested using the Ames test as well as for chromosomal aberration in mouse bone marrow cells and carcinogenicity using Swiss bare mice. It was observed that SME was mutagenic in all five strains of Salmonella typhimurium (TA98, TA1538, TA100, TA1535 and TA1537), with or without S9 mix, and was clastogenic in a mammalian test system. SME also has the potential to induce skin papilloma as well as systemic tumours in Swiss bare mice. Chemical analysis of SME revealed the presence of low concentrations of volatile nitrosamines.

Animals↗
PubMed1988

Cloning, sequencing and expression of a full-length rabbit fast skeletal troponin-C cDNA.

A full-length cDNA coding for troponin-C isolated from an adult rabbit fast skeletal muscle library has been sequenced and expressed in an E. coli host. The amino acid sequence derived from the coding region agrees with the published protein sequence except that the first two residues are reversed. The expressed protein was found to be identical to purified rabbit skeletal troponin-C based on electrophoretic mobilities in polyacrylamide gels containing either SDS or urea, and on immunoblotting. These results establish that our troponin-C cDNA clone is suitable for site-directed mutagenesis studies on the structure and function of troponin-C.

Animals↗
PubMed1988

Differential distribution of beta-tubulin isotypes in cerebellum.

We describe the structure and expression of a mammalian beta-tubulin isotype (M beta 6) that is weakly expressed in testis but is abundant in developing brain, with transcripts declining to lower levels in the adult brain. The expression of M beta 6 was undetectable in any other mouse tissue examined. A serum specific for this isotype was prepared using a cloned fusion protein as immunogen. M beta 6 is one of five known beta-tubulin isotypes expressed in brain, and using the anti-M beta 6 serum along with sera, anti-M beta 2, anti-M beta 3/4 and anti-M beta 5, previously characterized, we have examined the pattern of expression of beta-tubulin isotypes in rat cerebellum. The isotypes each have characteristic cell-type specific patterns of localization in cerebellum. M beta 2, M beta 3/4 and M beta 5 are present in both neuronal and non-neuronal cells, but in contrast M beta 6 was only detectable in neurons in tissue sections and in dissociated cerebellar cell culture. The majority of sequence differences among the beta-tubulin isotypes lie at the carboxy terminus, the region of beta-tubulin involved in MAP binding. In the case of M beta 2 and M beta 6, the patterns of expression are similar or identical to the patterns of expression of MAP3 and MAP1A respectively. These results suggest that beta-tubulin isotypes may contribute to the determination of the specific association of MAPs with microtubules of diverse function. However, the strict subcellular segregation of other MAPs in brain may be determined by other factors.

Amino Acid Sequence↗
PubMed1988

Molecular genetics in basic myology: a rapidly evolving perspective.

Myology has greatly benefited from the recent unification of concepts in molecular, cellular, and developmental biology. The interplay between intrinsic and extrinsic factors in determining the physiologic characteristics of individual myofibers has emerged as an important theme. Of special note is the manner in which the study of contractile protein gene structure and expression has contributed to our understanding of the development and ultimate plasticity of the contractile apparatus. As mechanistic models of normal myogenesis achieve increasing sophistication, the opportunities for understanding the pathogenesis of progressive muscle disfunction improve. In this article we review recent progress in basic myology which will be of interest to clinicians studying the heritable neuromuscular disorders.

Gene Expression Regulation↗
PubMed1988

Molecular genetics in muscular dystrophy research: revolutionary progress.

The contribution of "reverse genetic" strategies to neuromuscular disease research is evident in the progression of breakthroughs that have recently culminated in the cloning of the Duchenne muscular dystrophy (DMD) cDNA. The resultant improvements in our understanding of the genetic basis of Becker muscular dystrophy (BMD) and DMD serve as models for similar investigation of other heritable disorders. These genetic advances have outpaced concurrent work on the molecular pathogenesis of the dystrophic process, with the curious result that inferences about the DMD protein's amino acid sequence have preceded any information about its function or intracellular localization. In recognition that this foundation sets the stage for the rapid elucidation of the disease's pathogenesis, we review the experimental basis of such advances, with reference to relevant progress in basic myology, pathology, and molecular biology. We conclude with a view towards the ultimate clinical implications of these experimental breakthroughs.

Animals↗
PubMed1988

Carcinogenicity of Indian bidi and cigarette smoke condensate in Swiss albino mice.

The carcinogenicity of Indian bidi and cigarette smoke condensate given by gavage was studied in Swiss mice. Bidi smoke condensate induced liver haemangiomas in four animals, forestomach papilloma in one animal and carcinomas in two animals, in one of them was in the oesophagus and in the other in the forestomach. At the same dose level cigarette smoke condensate failed to produce any tumour. Similarly, none of the untreated and solvent-treated control mice developed tumour. Chemical analysis of the smoke concensate of bidis and cigarettes showed that condensate from bidis had a higher benzo[a]pyrene level than was observed in cigarette smoke condensate, when compared on the basis of the mass (mg) burnt.

Animals↗
PubMed1988

Nebulin cDNAs detect a 25-kilobase transcript in skeletal muscle and localize to human chromosome 2.

By virtue of the protein's size, myofibrillar localization, and proposed functional role, the gene encoding the giant sarcomere matrix protein nebulin represents a possible site for myopathic mutations. Using polyclonal anti-nebulin antisera to screen a cDNA expression library, we have isolated and characterized two separate human fetal muscle cDNA clones. By recovering fusion polypeptide-bound portions of our polyclonal antiserum and reutilizing them to probe Western blots, we further demonstrate that the expressed cDNAs encode polypeptide epitopes unique to the protein nebulin. Both cDNAs detect a 25-kb skeletal muscle RNA transcript and localize to human chromosome 2. The identification of nebulin cDNA clones enables the complete analysis of this enormous mRNA by transcript walking through muscle cDNA libraries. Here we report a restriction map of the 3' end of the human nebulin transcript, with reference to the genomic fragments identified by the cDNA.

Chromosome Mapping↗