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S Kumar

Publications and source records attributed to S Kumar.

At least 73 records · Page 4Linked to original sources
PubMed1996

Cloning and expression of DiT33 from Dirofilaria immitis: a specific and early marker of heartworm infection.

Dirofilaria immitis is an important filarial parasite of dogs and cats, and a useful model for human filariasis. Current diagnostic tests for heartworm infection in animals rely on the presence of fecund female worms (usually found 6.5 months post-infection or later) and therefore fail to detect pre-patent infections. Putative pepsin inhibitors from 2 filarial parasites of humans namely Onchocerca volvulus (Ov33, Oc3.6, OvD5B) and Brugia malayi (Bm33), have been shown to be useful in diagnosis of onchocerciasis and lymphatic filariasis, respectively. Previous studies have suggested that a homologue exists in D. immitis (DiT33), which may have potential in diagnosis of heartworm infection. In this study, the isolation and characterization of a cDNA clone encoding DiT33 is described. This cDNA contains 12 bases of the nematode-specific 22 nucleotide spliced leader sequence and encodes a 26.4 kDa-protein with a high level of similarity (87-89%) to other filarial members of the family. DiT33 was over-expressed in E. coli as a fusion with the maltose-binding protein and serological analysis was performed using a panel of clinically defined dog sera. The findings of this study indicate that DiT33 is a promising antigen for the early detection of D. immitis and may be a valuable tool in the control and management of heartworm infection.

Amino Acid Sequence↗
PubMed1996

Hippocampal responses to corticosterone and stress, one of which is the 35,000 M(r) protein, glycerol phosphate dehydrogenase.

Previously, the synthesis of a hippocampal 35,000 M(r) protein increased in response to glucocorticoid treatment and a variety of stressors. We now show by immunoprecipitation that this cytosolic protein is glycerol 3-phosphate dehydrogenase (E.C.1.1.1.8; GPDH). In addition, four polypeptides encoded by glucocorticoid-induced mRNAs co-migrated with hippocampal protein synthetic products on two-dimensional polyacrylamide gels, including 35,000 M(r) protein of approximately pl 6.3, that had previously been identified as GPDH by hybrid-selection with a GPDH cDNA clone. The 35,000 M(r) in vitro translation product was also immunoprecipitated with the GPDH antibody. Using radiolabeled hippocampal slices and two-dimensional gel analysis, a 35,000 M(r) polypeptide of approximately pl 6.4 increased five-fold after 30 min of intermittent tail-shock. This protein was found predominantly in the 20,000 x g pellet and did not immunoprecipitate with the GPDH antibody. However, a 35,000 M(r) polypeptide was also found in the cytosol as a minor component after stress, which did immunoprecipitate with the GPDH antibody. Therefore, there are at least two shock-induced 35,000 M(r) proteins, one of which is GPDH. These results establish that increases in GPDH mRNA prevalence and protein synthesis occur in response to both glucocorticoids and stress in the adult rat hippocampus. Based on the increased enzyme activity seen in the nervous system in response to glucocorticoids, dietary restriction, and nerve injury, the induction of GPDH may have functional consequences in cellular adaptation to stress.

Animals↗
PubMed1996

Increased expression of ubiquitin during adenosine 3',5'-cyclic monophosphate-induced differentiation of neuroblastoma cells in culture.

The role of ubiquitin in proliferation and differentiation of nerve cells has not been studied. An elevation of the intracellular level of adenosine 3',5'-cyclic monophosphate (cAMP) in neuroblastoma cells induces terminal differentiation in these cells. Therefore, in this study we investigated the changes in the level and subcellular distribution of ubiquitin during proliferation and differentiation of neuroblastoma cells. Prostaglandin E1, a stimulator of adenylate cyclase, plus beta-carotene, and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 20-1724), an inhibitor of cyclic nucleotide phosphodiesterase, plus beta-carotene were used to induce terminal differentiation in > 90% of neuroblastoma cells. Changes in ubiquitin level were studied by immunofluorescent staining using either a mouse monoclonal antibody or a rabbit polyvalent antibody to ubiquitin. Results showed that the dividing neuroblastoma cells contained very low levels of ubiquitin localized primarily in the cytoplasm. The intensity of cytoplasmic staining for ubiquitin markedly increased during cAMP-induced differentiation of neuroblastoma cells, being the highest at 4 days after treatment. The neurites of these differentiated cells were also stained, but the nuclei were not. We propose a hypothesis that higher levels of cytoplasmic ubiquitin are needed during cAMP-induced differentiation of neuroblastoma cells for the removal of proteins responsible for cell proliferation through rapid degradation and/or inhibition of transcription, later leading to terminal differentiation.

Animals↗
PubMed1996

Taxanes from in vitro cultures of the Himalayan yew Taxus wallichiana.

Culture conditions have been standardized for initiation of callus cultures of Himalayan yew (Taxus wallichiana) using young stem and needle explants from mature trees. Cultures were established on a modified Murashige and Skoog's medium supplemented with various levels of auxins (2.4-D, NAA) and cytokinin (kinetin). A medium containing 0.25 mg/l kinetin and 5.0 mg/l 2.4-D was optimal for stem callus growth whereas the presence of 0.25 mg/l kinetin along with 3.0 mg/l NAA in the medium supported optimal needle callus growth. Growth of stem callus was faster than needle callus growth. Supplementation of ascorbic acid (30 mg/l) amongst various anti-phenolic agents tested significantly reduced browning of initiated callus. Two taxanes (2-deacetoxytaxinine 1 and 2'-deacetoxyaustrospicatine) known to occur in stem bark, have also been isolated from undifferentiated tissue of T. wallichiana in equal or higher yields, for the first time.

Antineoplastic Agents, Phytogenic↗
PubMed1996

bc1-1 rearrangement and cyclin D1 protein expression in multiple lymphomatous polyposis.

Multiple lymphomatous polyposis (MLP), characterized by multiple polyps involving long segments of the gastrointestinal (GI) tract, is believed to represent GI involvement by mantle cell lymphoma (MCL), primarily based on its histologic and immunophenotypic similarities with MCL. However, rearrangement of the bcl-1 locus, the molecular lesion characteristic of MCL, has not been investigated in this group of patients. The authors evaluated the morphologic, immunophenotypic, and molecular features of 18 cases of MLP and 8 B-cell lymphomas involving the GI tract (including 6 MALT lymphomas). All MLP cases presented with GI disease, and were histologically similar to MCL. DNA extracted from formalin-fixed, paraffin-embedded tissue was analyzed for evidence of bcl-1 rearrangement by PCR, using chromosome 11 specific and consensus JH primers. Amplifiable DNA was obtained in 24 of 26 cases (16 of 18 MLP cases and 8 of 8 controls). bcl-1 rearrangement was detected in 6 of 16 cases (38%), subsequently confirmed by sequencing of the breakpoint region, and in 0 of 8 controls. Immunostaining for cyclin D1 was positive in 14 of 18 MLPs, including the 6 bcl-1 rearranged cases and negative in 6 of 6 evaluable controls. The detection of bcl-1 rearrangement and cyclin D1 expression in cases of MLP supports the view that MLP represents primary MCL, of the GI tract. These techniques may also be helpful in differentiating MLP from other GI lymphomas, particularly low grade lymphomas of MALT, when only small routinely fixed endoscopic biopsies are available.

Adult↗
PubMed1996

Evolution of the hedgehog gene family.

Effective intercellular communication is an important feature in the development of multicellular organisms. Secreted hedgehog (hh) protein is essential for both long- and short-range cellular signaling required for body pattern formation in animals. In a molecular evolutionary study, we find that the vertebrate homologs of the Drosophila hh gene arose by two gene duplications: the first gave rise to Desert hh, whereas the second produced the Indian and Sonic hh genes. Both duplications occurred before the emergence of vertebrates and probably before the evolution of chordates. The amino-terminal fragment of the hh precursor, crucial in long- and short-range intercellular communication, evolves two to four times slower than the carboxyl-terminal fragment in both Drosophila hh and its vertebrate homologues, suggesting conservation of mechanism of hh action in animals. A majority of amino acid substitutions in the amino- and carboxyl-terminal fragments are conservative, but the carboxyl-terminal domain has undergone extensive insertion-deletion events while maintaining its autocleavage protease activity. Our results point to similarity of evolutionary constraints among sites of Drosophila and vertebrate hh homologs and suggest some future directions for understanding the role of hh genes in the evolution of developmental complexity in animals.

Amino Acid Sequence↗
PubMed1996

Patterns of nucleotide substitution in mitochondrial protein coding genes of vertebrates.

Maximum likelihood methods were used to study the differences in substitution rates among the four nucleotides and among different nucleotide sites in mitochondrial protein-coding genes of vertebrates. In the 1st + 2nd codon position data, the frequency of nucleotide G is negatively correlated with evolutionary rates of genes, substitution rates vary substantially among sites, and the transition/transversion rate bias (R) is two to five times larger than that expected at random. Generally, largest transition biases and greatest differences in substitution rates among sites are found in the highly conserved genes. The 3rd positions in placental mammal genes exhibit strong nucleotide composition biases and the transitional rates exceed transversional rates by one to two orders of magnitude. Tamura-Nei and Hasegawa-Kishino-Yano models with gamma distributed variable rates among sites (gamma parameter, alpha) adequately describe the nucleotide substitution process in 1st+2nd position data. In these data, ignoring differences in substitution rates among sites leads to largest biases while estimating substitution rates. Kimura's two-parameter model with variable-rates among sites performs satisfactorily in likelihood estimation of R, alpha, and overall amount of evolution for 1st+2nd position data. It can also be used to estimate pairwise distances with appropriate values of alpha for a majority of genes.

Amino Acid Sequence↗
PubMed1996

A stepwise algorithm for finding minimum evolution trees.

A stepwise algorithm for reconstructing minimum evolution (ME) trees from evolutionary distance data is proposed. In each step, a taxon that potentially has a neighbor (another taxon connected to it with a single interior node) is first chosen and then its true neighbor searched iteratively. For m taxa, at most (m-1)!/2 trees are examined and the tree with the minimum sum of branch lengths (S) is chosen as the final tree. This algorithm provides simple strategies for restricting the tree space searched and allows us to implement efficient ways of dynamically computing the ordinary least squares estimates of S for the topologies examined. Using computer simulation, we found that the efficiency of the ME method in recovering the correct tree is similar to that of the neighbor-joining method (Saitou and Nei 1987). A more exhaustive search is unlikely to improve the efficiency of the ME method in finding the correct tree because the correct tree is almost always included in the tree space searched with this stepwise algorithm. The new algorithm finds trees for which S values may not be significantly different from that of the ME tree if the correct tree contains very small interior branches or if the pairwise distance estimates have large sampling errors. These topologies form a set of plausible alternatives to the ME tree and can be compared with each other using statistical tests based on the minimum evolution principle. The new algorithm makes it possible to use the ME method for large data sets.

Algorithms↗
PubMed1996

Approximate methods for estimating the pattern of nucleotide substitution and the variation of substitution rates among sites.

We propose two approximate methods (one based on parsimony and one on pairwise sequence comparison) for estimating the pattern of nucleotide substitution and a parsimony-based method for estimating the gamma parameter for variable substitution rates among sites. The matrix of substitution rates that represents the substitution pattern can be recovered through its relationship with the observable matrix of site pattern frequences in pairwise sequence comparisons. In the parsimony approach, the ancestral sequences reconstructed by the parsimony algorithm were used, and the two sequences compared are those at the ends of a branch in the phylogenetic tree. The method for estimating the gamma parameter was based on a reinterpretation of the numbers of changes at sites inferred by parsimony. Three data sets were analyzed to examine the utility of the approximate methods compared with the more reliable likelihood methods. The new methods for estimating the substitution pattern were found to produce estimates quite similar to those obtained from the likelihood analyses. The new method for estimating the gamma parameter was effective in reducing the bias in conventional parsimony estimates, although it also overestimated the parameter. The approximate methods are computationally very fast and appear useful for analyzing large data sets, for which use of the likelihood method requires excessive computation.

Algorithms↗
PubMed1996

Primary cutaneous Hodgkin's disease with evolution to systemic disease. Association with the Epstein-Barr virus.

Hodgkin's disease rarely involves the skin and when it does is an indication of advanced stage disease. Primary cutaneous Hodgkin's disease is exceedingly rare, and only a few cases are reported. We describe a patient who developed multiple cutaneous lesions of Hodgkin's disease 2 years before manifesting nodal disease of mixed cellularity subtype. Reed-Sternberg cells in the skin as well as lymph nodes and bone marrow were positive for Epstein-Barr viral transcripts and expressed viral latent membrane protein. Epstein-Barr virus has not previously been demonstrated in primary cutaneous Hodgkin's disease, and its presence in lesions in all sites in this case supports a diagnosis of primary cutaneous disease with subsequent evolution into systemic disease.

Aged↗
PubMed1996

Cutis laxa.

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Cutis Laxa↗
PubMed1996

Genodermatoses.

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Humans↗
PubMed1996

Arterial complications of pancreatitis and their radiological management.

Arterial haemorrhage from pseudoaneurysm in pancreatitis patients is a formidable complication with a high mortality rate. We encountered six patients in whom a pseudoaneurysm was demonstrated at angiography. Drainage of associated pseudocyst facilitated visualization in one patient. Four patients had pseudoaneurysms arising from the proximal part of the major peripancreatic vessels and were treated by steel coil embolization (n = 3) and surgically (n = 1). There was no episode of rebleeding in these patients during a follow-up period of 10-18 months. Of the two patients with distal small peripancreatic branch vessel involvement hydrogel particle and gelfoam embolization was successful only temporarily in one patient and unsuccessful in the other patient. The literature is reviewed and the efficacy of steel coil embolization is emphasized.

Adolescent↗
PubMed1996

Induction of labour for trial of vaginal birth after caesarean section in a remote district hospital.

In a retrospective review of 79 women with 1 or more previous Caesarean section, 33 (41.8%) women agreed to a trial of vaginal birth. Twenty nine women had labour induced and 26 (89.7%) of them had a successful vaginal delivery. Four women laboured spontaneously and 1 of them needed an emergency Caesarean section for failure to progress. The overall vaginal delivery rate for women selected to undergo a trial of vaginal birth after Caesarean was 87.9%. The overall emergency Caesarean section rate was 4 of 33 (12.1%). During the study period the Caesarean section rate for the hospital fell from 32.2% to 11%. This study suggests that induction of labour in women with a previous Caesarean section is very successful in achieving vaginal delivery and has a role to play in remote and rural hospitals.

Adult↗
PubMed1996

Role of endoscopy in retrieval of misplaced intrauterine device.

We report a series of 45 patients with misplaced intrauterine devices (30 extrauterine and 15 intrauterine). Only those patients with intrauterine misplacements in whom conventional blind removal was not possible were included in the study. All of the 15 misplaced intrauterine devices could be removed hysteroscopically; 22 of the 30 extrauterine misplaced devices (73%) could be removed laparoscopically. One patient required both laparoscopy and hysteroscopy. Only 7 (15.5%) of 45 patients required laparotomy for safe removal of misplaced devices. Considerable comfort and minimal hospital stay associated with endoscopic procedures should offer these as the first line attempt to remove a misplaced intrauterine or extrauterine translocated device.

Adult↗