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Biomedical subjects

K Mehta

Publications and source records attributed to K Mehta.

At least 55 records · Page 3Linked to original sources
PubMed1997

Respect redefined: focus group insights from Singapore.

This article re-examines the meaning of the concept of respect within the context of a fast modernizing Asian multicultural society-Singapore. Two key findings emerge. First, the meaning of respect both from the perspective of the aged and the middle-aged generation has shifted from obedience to courteous behavior. Second, in the majority of focus groups members concurred that the degree of respect accorded to elders has in general decreased. The focus group methodology was used in this research. Bearing in mind the limited sample size (88 participants) these findings alert us to the need for social scientists to monitor perceptual shifts in meaning of concepts critical in the sphere of interpersonal relationships. The findings throw light on the subjective views of intergenerational relations within the family as well as the community. As such, they would be valuable to counselors, social workers, and family therapists.

Adult↗
PubMed1997

Minimum criteria for reporting child abuse from health care settings.

We evaluated how consistently clinicians of two hospitals reported child abuse and neglect, and the utility of specific, operational criteria for assessing hospital clinicians' compliance with the child abuse reporting laws. To evaluate clinicians' compliance, we audited the medical records of 85 children who had been reported to a child protective service (CPS) agency by clinicians at either of two hospitals and who had been seen at that hospital at least once before the index report of abuse. The time elapsed from first hospital visit to index abuse report among the 85 children averaged 4.3 years. In the children's records, we identified 28 earlier reports to the CPS agency and four episodes that met criteria we developed but that had not been reported. Thus, application of specific criteria resulted in the finding that 28 (88 percent) of 32 suspected abuse episodes were actually reported to the CPS agency (95 percent confidence interval: 76 to 99 percent). In a second phase of the study, we compared the content of 45 reported episodes of child abuse (4) index reports and four earlier reports) to the criteria in order to evaluate their utility. Thirty-five episodes (78 percent) met one of the criteria. Review of the remaining 10 episodes led to the development of one new criterion. We conclude that, although it has been estimated that hospital personnel nationwide report to CPS agencies only 69 percent of the child abuse cases they identify, clinicians at the hospitals we studied reported 88 percent of documented episodes of suspected abuse. We also conclude that specific, operational criteria can help in the assessment of hospital clinicians' compliance with their obligation to report child abuse and neglect.

Child↗
PubMed1997

Retinoid-mediated inhibition of cell growth with stimulation of apoptosis in aggressive B-cell lymphomas.

Retinoids have been shown to modulate cell growth and differentiation in a variety of human tumor cell types, but their effects on B-cell non-Hodgkin's lymphomas (NHL-B) have not been explored. In this study, all-trans retinoic acid (ATRA) in the free form and liposome-encapsulated form (L-ATRA) were used to determine effects on fresh NHL-B patient cells as well as cell lines recently established from both HIV-negative and -positive NHL-B patient biopsies. Both ATRA and L-ATRA were found to inhibit cell proliferation in NHL-B cells. However, L-ATRA was found to be superior to free ATRA in inhibiting cell proliferation of NHL-B cells and resulted in greater than 90% cell growth inhibition in a dose-dependent manner. In addition, L-ATRA also induced high levels of apoptosis in NHL-B cells in vitro. To delineate the apoptotic pathways involved, the expression of the apoptosis suppressor oncogene bcl-2 was evaluated in different NHL-B cells with and without the t(14;18) chromosomal translocation. After L-ATRA exposure, more than a 50% reduction in the expression of bcl-2 protein was observed. bcl-2 message levels were also down-regulated in the L-ATRA-sensitive NHL-B cells. Bax protein levels were analyzed and found to be up-regulated in L-ATRA-sensitive NHL-B cells. Similar results were observed in sensitive AIDS/lymphoma cell lines. Experiments using an RAR-alpha antagonist (RO 41-5253) showed that both the proliferation inhibition and apoptosis induced by L-ATRA could be blocked in NHL-B cells. The findings of the present study indicate that L-ATRA may possess therapeutic potential in blocking cell proliferation, inducing apoptosis, and

Apoptosis↗
PubMed1996

Post-translational modification of CD38 protein into a high molecular weight form alters its catalytic properties.

Human CD38 is a 45-kDa transmembrane protein that acts as a bifunctional ectoenzyme, catalyzing the synthesis of cyclic ADP-ribose (cADPR) from NAD+ and the hydrolysis of cADPR to ADP-ribose. All-trans-retinoic acid (RA) is a potent and specific inducer of CD38 in myeloid cells. In this report, we demonstrate that RA-induced CD38 protein from human myeloid (HL-60) leukemia cells coimmunoprecipitates with another protein of molecular mass approximately190 kDa (p190). The p190 protein is localized exclusively in the membranes and is a consequence of post-translational cross-linking of CD38 protein. This conclusion was based on the observations that purified CD38 effectively competes with p190, its accumulation is preceded by the accumulation of CD38, it immunoreacted with three different monospecific anti-CD38 antibodies on immunoblots, and its peptide map revealed several peptides in common with CD38. Furthermore, CD38 could serve as a suitable substrate for transglutaminase (TGase)-catalyzed cross-linking reactions in vitro, and the accumulation of p190 in RA-treated HL-60 cells is effectively blocked by the presence of TGase-specific inhibitor. The purified p190 showed at least three times more cyclase activity than CD38. Conversely, p190 was at least 2.5-fold less active than CD38 in hydrolyzing cADPR to ADPR. These results suggest that post-translational modification of CD38 may represent an important mechanism for regulating the two catalytic activities of this bifunctional enzyme.

ADP-ribosyl Cyclase↗
PubMed1996

Long-term outcome in patients with four or more positive lymph nodes treated with conservative surgery and radiation therapy.

PURPOSE: The purpose of this study was to review management strategies with respect to systemic therapy, radiation therapy treatment techniques, and patient outcome (local regional control, distant metastases, and overall survival) in patients undergoing conservative surgery and radiation therapy (CS + RT) who had four or more lymph nodes involved at the time of original diagnosis. METHODS AND MATERIALS: Of 1040 patients undergoing CS + RT at our institution prior to December 1989, 579 patients underwent axillary lymph node dissection. Of those patients undergoing axillary lymph node dissection, 167 had positive nodes and 51 of these patients had four or more positive lymph nodes involved and serve as the patient population base for this study. All patients received radiation therapy to the intact breast using tangential fields with subsequent electron beam boost to the tumor bed to a total median dose of 64 Gy. The majority of patients received regional nodal irradiation as follows: 40 patients received RT to the supraclavicular region without axilla to a median dose of 46 Gy, 10 patients received radiation to the supraclavicular region and axilla to a median dose of 46 Gy. Thirty of the 51 patients received a separate internal mammary port with a mixed beam of photons and electrons. One patient received radiation to the tangents alone without regional nodal irradiation. Adjuvant systemic therapy was used in 49 of the 51 patients (96%) with 27 patients receiving chemotherapy alone, 14 patients receiving cytotoxic chemotherapy and tamoxifen, and 8 patients receiving tamoxifen alone. RESULTS: As of December 1994, with a minimum evaluable follow-up of 5 years and a median follow-up of 9.29 years, there have been 18 distant relapses, 2 nodal relapses, and 5 breast relapses. Actuarial statistics reveal a 10-year distant metastases-free rate of 65%, 10-year nodal recurrence-free rate of 96%, and a 10-year breast recurrence-free rate of 82%. All five patients who sustained a breast relapse were successfully salvaged with mastectomy. Both patients with nodal relapses (one supraclavicular and one axillary/supraclavicular) failed within the irradiated volume. Of the 40 patients treated to the supraclavicular fossa (omitting complete axillary radiation), none failed in the dissected axilla. With a median follow-up of nearly 10 years, 29 of the 51 patients (57%) remain alive without evidence of disease, 15 (29%) have died with disease, 2 (4%) remain alive with disease, and 5 (10%) have died without evidence of disease. Overall actuarial 10-year survival for these 51 patients is 58%. CONCLUSIONS: We conclude that in patients found to have four or more positive lymph nodes at the time of axillary lymph node dissection, conservative surgery followed by radiation therapy to the intact breast with appropriate adjuvant systemic therapy results in a reasonable long-term survival with a high rate of local regional control. Omission of axillary radiation in this subset of patients appears appropriate because there were no axillary failures among the 41 dissected but unirradiated axillae.

Adult↗
PubMed1996

Alterations in tretinoin pharmacokinetics following administration of liposomal all-trans retinoic acid.

We administered liposome-encapsulated all-trans retinoic acid (L-ATRA) to 48 patients with refractory hematologic malignancies using an every-other-day schedule for 28 days and doses of 15 to 175 mg/m2. In 19 patients, pharmacology studies were conducted after the first (day 1) and seventh (day 15) doses. In contrast to the decline in tretinoin concentration seen within 3 to 4 days of administration of daily oral ATRA, there were no differences between the area under the curve (AUC) of tretinoin concentration versus time on day 1 and day 15 (P = .98, Wilcoxon signed-rank test). Peak day 1 concentrations after 15 mg/m2 were higher than those reported after 45 mg/m2 oral ATRA. Six patients with relapsed acute promyelocytic leukemia (APL) were treated. Three, each in first relapse and at least year from the last exposure to oral ATRA, achieved a complete response (CR). Disease recurred in two (one at 3 months despite maintenance L-ATRA and similarity in tretinoin AUC on days 1 and 85, and the other at 5 months, 2 months after discontinuation of L-ATRA) and the third was transplanted 1 month into CR. The three nonresponders were in at least a second relapse and failed to respond to oral ATRA before or immediately after receiving L-ATRA. Severe toxicity developed in three of eight patients treated at 175 mg/m2 (joint pains in two, skin in one). The maximum tolerated dose (MTD) was determined to be 140 mg/m2, at which dose grade 2 toxicity (primarily headache and skin) occurred in eight of eight patients, but grade 3 to 4 toxicity in none. Compared with oral ATRA, L-ATRA apparently results in greater exposure to tretinoin and for a longer time.

Drug Carriers↗
PubMed1996

Human CD38, a cell-surface protein with multiple functions.

Human CD38 is a nonlineage-restricted type II transmembrane glycoprotein that has emerged as a multifunctional protein in recent years. It can serve as an ectoenzyme that catalyzes the synthesis and hydrolysis of cyclic ADP-ribose, a recently identified Ca2+ mobilizing agent that acts independently of inositol triphosphate. The enzymatic functions of CD38 probably contribute to an array of its immunoregulatory functions. The release of soluble CD38 and the ability of membrane-bound CD38 to become internalized in response to appropriate stimuli suggest that extracellular and intracellular roles for this protein are equally plausible. Ligation of CD38 with agonistic antibodies induces diverse effects in hematopoietic cells that range from growth stimulation to induction and prevention from apoptosis, induction of cytokines, activation of kinases, and phosphorylation of certain proteins. These observations suggest that CD38 may serve as receptor for an as yet unidentified ligand. Other molecules that share significant structural and functional homology to CD38 have been identified in humans and mice, suggesting that these molecules may represent a new family of proteins. Understanding the role of CD38 in certain pathological conditions such as myeloma, X-linked agammaglobulinemia, and HIV infection may provide insight into its physiological functions.

ADP-ribosyl Cyclase↗
PubMed1996

Leukemic phase of mantle cell lymphoma two case reports and review of the literature.

Two cases of mantle cell lymphoma are presented. Both patients were women, aged 68 and 56 years, who presented with lymph node enlargement. Each case was initially interpreted as a follicular small cleaved cell lymphoma. Both patients later presented with splenomegaly and recurrent lymphadenopathy. Morphologic and immunologic studies on a parotid swelling in one case and a splenectomy specimen in the other indicated a diagnosis of mantle cell lymphoma. Both women subsequently presented in leukemic phase associated with a poor prognosis, and both patients succumbed soon after. The characteristics, differential diagnosis, and leukemic phase of mantle cell lymphoma are discussed. The importance of appropriate immunohistochemical and flow cytometry analysis in distinguishing mantle cell lymphoma from morphologically similar follicular center cell lymphomas is demonstrated.

Aged↗
PubMed1996

Activation of retinoid receptors RAR alpha and RXR alpha induces differentiation and apoptosis, respectively, in HL-60 cells.

Induction of granulocytic differentiation in HL-60 myeloid leukemia cells by retinoids is followed by their death via apoptosis. Retinoids are known to mediate their biological effects through at least two distinct types of nuclear receptors, the retinoic acid receptors and retinoid X receptors. We undertook to characterize the potential role of these receptors in inducing differentiation and apoptosis by retinoids. For this, we used a previously described variant of an HL-60 cell line (HL-60R) in which retinoid receptor function has been abrogated due to a trans-dominant negative mutation. Retroviral vector-mediated gene transfer was used to introduce the normal retinoic acid receptor (RAR alpha) or retinoid X receptor (RXR alpha) into HL-60R cells. Our results suggest that ligand-induced activation of RAR alpha is sufficient to induce differentiation in HL-60 cells, whereas activation of RXR alpha can induce direct apoptosis of these cells without their prior commitment to differentiate.

ADP-ribosyl Cyclase↗
PubMed1995

Human immunodeficiency virus 1 reservoir in CD4+ T cells is restricted to certain V beta subsets.

The human immunodeficiency virus 1 (HIV-1) replicates more efficiently in T-cell lines expressing T-cell receptors derived from certain V beta genes, V beta 12 in particular, suggesting the effects of a superantigen. The targeted V beta 12 subset was not deleted in HIV-1-infected patients. It was therefore possible that it might represent an in vivo viral reservoir. Viral load was assessed by quantitative PCR with gag primers and with an infectivity assay to measure competent virus. It was shown that the tiny V beta 12 subset (1-2% of T cells) often has a higher viral load than other V beta subsets in infected patients. Selective HIV-1 replication in V beta 12 cells was also observed 6-8 days after in vitro infection of peripheral blood lymphocytes from normal, HIV-1 negative donors. Viral replication in targeted V beta subsets may serve to promote a biologically relevant viral reservoir.

Adult↗
PubMed1995

Administration of subtoxic doses of t-butyl alcohol and trichloroacetic acid to male Wistar rats to study the interactive toxicity.

Tertiary butyl alcohol and trichloroacetic acid (TCA) are known to be contaminants in drinking water. In order to evaluate the interactive toxicity of t-butyl alcohol (TBA) with TCA, young male Wistar rats were dosed through water at a dose level of TBA (0.5% v/v), 25 ppm TCA and a combined dose of TBA+TCA (0.5% v/v TBA, 25 ppm TCA) for a period of 10 weeks ad libitum and were maintained on normal diet. The control animals received plain water and normal diet. There was remarkable loss of body weight and significantly decreased liver triglycerides in the treatment groups in the order of TBA+TCA, TCA, TBA and increased liver weights were observed. Serum succinate dehydrogenase (SDH) levels were significantly increased in TCA- and TBA+TCA-treated groups. There was no significant change in serum alanine (GPT), aspartate (GOT) aminotransferase, serum alkaline (ALP) and acid (ACP) phosphatase levels as well as liver glutathione (GSH) and liver and serum cholesterol levels in the treated groups. But serum triglycerides, liver glycogen, serum glucose (only in TBA- and TCA-treated animals) were significantly high in the treated groups. Lipid peroxidation measured by diene conjugation was significant in TBA+TCA-treated group and kidney GSH levels were significantly low in the treated groups. These results show that interaction of TBA+TCA does bring about alteration in biochemical parameters which may play a pivotal role in toxic responses on long-term exposure.

Alanine Transaminase↗
PubMed1995

Transglutaminase-catalyzed reaction is important for molting of Onchocerca volvulus third-stage larvae.

Highly insoluble proteins, which are probably cross-linked, are common in the cuticle and epicuticle of filarial parasites and other nematode species. We have investigated the possible involvement of transglutaminase (TGase)-catalyzed reactions in the development of Onchocerca volvulus fourth-stage larvae (L4) by testing the effects of TGase inhibitors on the survival of third-stage larvae (L3) and the molting of L3 to L4 in vitro. The larvae were cultured in the presence of three specific TGase inhibitors: monodansylcadaverine, cystamine, and N-benzyloxycarbonyl-D,L-beta-(3-bromo-4,5-dihydroisoxazol-5-yl)-al anine benzylamide. None of the inhibitors reduced the viability of either L3 or L4. However, the inhibitors reduced, in a time- and dose-dependent manner, the number of L3 that molted to L4 in vitro. Molting was completely inhibited in the presence of 100 to 200 microM inhibitors. Ultrastructural examination of L3 that did not molt in the presence of monodansylcadaverine or cystamine indicated that the new L4 cuticle was synthesized, but there was an incomplete separation between the L3 cuticle and the L4 epicuticle. The product of the TGase-catalyzed reaction was localized in molting L3 to cuticle regions where the separation between the old and new cuticles occurs and in the amphids of L3 by a monoclonal antibody that reacts specifically with the isopeptide epsilon-(gamma-glutamyl)lysine. These studies suggest that molting and successful development of L4 also depends on TGase-catalyzed reactions.

Animals↗
PubMed1994

GDP-ribosyl cyclase activity as a measure of CD38 induction by retinoic acid in HL-60 cells.

Retinoic acid (RA) treatment of HL-60 cells induces surface expression of CD38. This lymphocytic antigen is also a novel bifunctional enzyme catalyzing the synthesis and hydrolysis of cyclic ADP-ribose (cADPR), a Ca2+ mobilizing metabolite of NAD+. The synthetic activity of CD38 is very difficult to detect because of the concurrent hydrolytic activity. In this study, a Ca2+ release assay capable of detecting submicromolar concentrations of cADPR was used to demonstrate the induction of ADP-ribosyl cyclase activity in HL-60 cells by RA. Concomitantly, cADPR hydrolase activity was also increased. The results were further substantiated by using a newly developed assay for GDP-ribosyl cyclase activity. This assay uses NGD+ as substrate instead of NAD+. The resulting fluorescent product, cyclic GDP-ribose, is resistant to hydrolysis and accumulates, making it a highly sensitive and convenient assay for CD38-like enzymes.

ADP-ribosyl Cyclase↗
PubMed1994

Purification and characterization of a novel transglutaminase from filarial nematode Brugia malayi.

A transglutaminase (pTGase) was purified from filarial nematode, Brugia malayi. The steps used for purification were thermoprecipitation, ammonium sulfate precipitation, gel filtration on Superose 12 HR 10/30, ion-exchange chromatography on a Mono-Q column and further gel filtration on Superose 12 HR 10/30. The last step yielded an electrophoretically homogenous enzyme protein with 2200-fold purification and a reproducible yield of approximately 20%. The purified enzyme had a molecular mass of 56 kDa, specific activity of 2.25 U/mg protein and an isoelectric point of 7.2. The enzyme was active in the basic pH range with an optimum activity at pH 8.5. The pTGase activity was Ca(2+)-dependent and was inhibited by ammonia, primary amines, EDTA, and -SH group blocking reagents. The enzyme activity was also inhibited by high salt (NaCl and KCl) concentrations, detergents, metal ions, and organic solvents. Ampholine (pH 6-8) at 1% (by vol.) caused about 20% inhibition of pTGase activity but at 3% (by vol.) the inhibition increased up to 80%. Similarly, the micromolar concentrations of GTP inhibited the enzyme activity only moderately but at millimolar concentration a significant inhibition was observed. The stability of the pTGase was not affected by 0.1% SDS or other physical parameters such as freezing and thawing. Further, the pTGase was found to be highly thermostable (stable at 60 degrees C for several hours) with optimum activity observed at 55 degrees C. The distinct substrate specificity, unique N-terminal sequence along with the other physico-chemical properties studied, suggested that pTGase is a novel member of transglutaminase family.

Animals↗