Search PubMed⌕ Search

Biomedical subjects

K Mehta

Publications and source records attributed to K Mehta.

At least 91 records · Page 5Linked to original sources
PubMed1992

The gelatinous bone marrow (serous atrophy) in patients with acquired immunodeficiency syndrome. Evidence of excess sulfated glycosaminoglycan.

Patients with the acquired immunodeficiency syndrome uniformly exhibit hematologic abnormalities characterized by anemia and/or pancytopenia. In a study of 75 consecutive bone marrow biopsy specimens from patients with acquired immunodeficiency syndrome, 29% exhibited serous atrophy, characterized by marrow hypoplasia, fat atrophy, and deposition of extracellular "gelatinous" material (gelatinous transformation). The latter material was composed exclusively of glycosaminoglycans (alcian blue positive at pHs of 2.5 and 1.0, and sensitive to testicular hyaluronidase digestion). Excess glycosaminoglycan, which significantly alters the bone marrow microenvironment, is detrimental to erythropoiesis. The present findings support the concept that the damaged hematopoietic inductive microenvironment in patients with acquired immunodeficiency syndrome leads to failure of hematopoiesis, and, hence, to peripheral hematologic abnormalities.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Differentiation-associated expression of prostaglandin H and thromboxane A synthases in monocytoid leukemia cell lines.

To elucidate the differentiation-associated expression of enzymes catalyzing arachidonic acid metabolism, we measured arachidonate metabolites by reverse-phase high pressure liquid chromatography in monocytoid leukemia (ML-1, THP-1, and U937) and myeloid leukemia (KG-1) cell lines. Undifferentiated ML-1 or THP-1 cells produced trace amounts of eicosanoids via the cyclooxygenase (COX) and lipoxygenase (LOX) pathways. Upon differentiation induced by phorbol ester (phorbol 12-myristate 13-acetate [PMA]), metabolites via the COX pathway were increased by 100-fold in ML-1 and THP-1 cells, while the LOX products remained barely detectable. All the COX metabolites were elevated, but thromboxane A2 (TXA2) formation was threefold higher in ML-1 cells than in THP-1 cells. Similar time-related increases in COX metabolites were observed in THP-1 cells induced to differentiate with retinoic acid. Undifferentiated U937 cells were capable of generating a much higher quantity of COX products than ML-1 or THP-1 cells, but, upon PMA-induced differentiation, COX products were increased by only two-fold to threefold over the undifferentiated cells and the total COX products in differentiated U937 cells were only one-seventh of those produced by differentiated ML-1 or THP-1 cells. KG-1 cells had an entirely different metabolic profile. They produced a large quantity of a metabolite coeluted with prostaglandin D2, and PMA had no effect on inducing changes in arachidonic acid (AA) metabolism. Increased COX metabolite formation in differentiated THP-1 and ML-1 cells was due to an enhanced level of prostaglandin H synthase enzyme mass, as measured by Western blot analysis. The TXA synthase activity was also increased by approximately 100-fold in PMA-induced ML-1 cells and 10-fold in THP-1 cells. These findings indicate that increased expression of prostaglandin H and TXA synthase enzymes is a feature of differentiated monocytoid leukemia cell lines.

Arachidonic Acid↗
PubMed1991

Brugia malayi and Acanthocheilonema viteae: antifilarial activity of transglutaminase inhibitors in vitro.

The possible involvement of transglutaminase-catalyzed reactions in survival of adult worms, microfilariae (mf), and infective larvae of the filarial parasite Brugia malayi was studied in vitro by using the specific pseudosubstrate monodansylcadaverine (MDC) and the active-site inhibitors cystamine or iodoacetamide. These inhibitors significantly inhibited parasite mobility in a dose-dependent manner. This inhibition was associated with irreversible biochemical lesions followed by filarial death. A structurally related, inactive analog of MDC, dimethyldansylcadaverine, did not affect the mobility or survival of the parasites. Adult worms failed to release mf when they were incubated in the presence of MDC or cystamine, and this inhibitory effect on mf release was concentration dependent. Similar embryostatic and macrofilaricidal effects of MDC were observed in Acanthocheilonema viteae adult worms. These studies suggest that transglutaminase-catalyzed reactions may play an important role in the growth, development, and survival of filarial parasites.

Animals↗
PubMed1991

Bone marrow necrosis in leukemic-phase follicular lymphoma.

Bone marrow necrosis has been regarded as a rare entity in specimens obtained from living patients and has been associated with a poor prognosis. It is most commonly found in patients with neoplastic disorders, severe infections, and sickle cell anemia. We present an unusual case of a small-cleaved type follicular lymphoma associated with bone marrow necrosis and a leukemic phase occurring in a 55-year-old woman. Specimens were studied by morphologic, immunohistochemical, cytogenetic, and DNA hybridization techniques.

Bone Marrow Diseases↗
PubMed1990

Significance of transglutaminase-catalyzed reactions in growth and development of filarial parasite, Brugia malayi.

A novel form of transglutaminase enzyme [EC 2.3.2. 13] was identified in adult worms of Brugia malayi. The molecular size of this enzyme was 22-kilodaltons as determined by Western blot and immunoprecipitation, using a monoclonal (CUB 7401) or polyclonal antibodies against guinea-pig liver tissue transglutaminase. The enzyme was present in female worms only; adult males contained no detectable levels of the enzyme peptide. Possible involvement of transglutaminase-catalyzed reactions in growth and survival of filarial parasites was studied by using various enzyme-specific pseudosubstrates. Presence of these inhibitors resulted into a significant inhibition of microfilariae production and release by gravid female worms in a dose-dependent manner. These results suggest that transglutaminase-catalyzed reactions are essential for development of in utero growing embryos to mature microfilariae.

Animals↗
PubMed1990

Effect of retinoids on the release and gene expression of tumor necrosis factor-alpha in human peripheral blood monocytes.

The effect of retinoic acid (RA) and retinol (ROH) on the release of tumor necrosis factor (TNF) by human peripheral blood monocytes (HPBM) was determined. HPBM were cultured for various periods of time in either 5% complete (cAB) or delipidized (DLS) AB serum. TNF release (L929 cytolytic assay) in the presence of cAB occurred during the first 3 days of in vitro culture. Delipidization of AB serum completely inhibited the lipopolysaccharide (LPS)-induced release of TNF by HPBM. Addition of RA (0.5 microM) to DLS restored LPS-induced TNF release by HPBM, and supplementation with ROH (1.0 microM) resulted in release of TNF-like activity, but only after 3 days of in vitro culture. The maintenance of TNF release by the addition of exogenous RA after 3 days of in vitro culture suggested that depletion of endogenous RA was partially responsible for loss of TNF-like activity. The levels of endogenous TNF protein and mRNA were not influenced by delipidization of serum and were found to be similar to those of HPBM cultured in the presence of AB serum. TNF protein and mRNA were undetectable in HPBM ROH-treated cell lysates, although cytolytic activity was observed in culture supernatants. These results suggest that retinoids are required for the release of cytolytic factors from HPBM and that non-TNF cytolytic factors may be released by these cells at different stages of maturation.

Cells, Cultured↗
PubMed1989

Transglutaminase levels and immunologic functions of BCG-elicited mouse peritoneal macrophages isolated by centrifugal elutriation.

BCG-elicited mouse peritoneal macrophages were separated into three subpopulations by counterflow centrifugal elutriation. The three subpopulations were characterized on the basis of the level of a protein cross-linking enzyme, tissue transglutaminase. Subpopulation-3 consisted of large cells (greater than 95% esterase positive and greater than 90% viable) and had at least a fivefold higher transglutaminase activity (35 +/- 6 nmol/hr/mg) as compared to macrophages in subpopulation-1 (6 +/- 2 nmol/hr/mg) and at least a threefold higher enzyme activity as compared to subpopulation-2 (11 +/- 2 nmol/hr/mg). Subpopulation-3 also showed sevenfold higher phagocytosis of IgG-coated sheep red blood cells. The three subpopulations showed no difference in their ability to kill Listeria monocytogenes as determined by [3H]-thymidine release. Subpopulations-2 and -3 caused 90% inhibition of murine adenocarcinoma (EMT-6) tumor cell growth in the presence or absence of lipopolysaccharide. Subpopulation-1 had a poor ability to inhibit EMT-6 cell growth (29 +/- 12%). However, in the presence of lipopolysaccharide, this activity increased by at least threefold (92 +/- 7%). The three subpopulations showed no significant difference in their cytolytic activity against murine mastocytoma (P815) target cells in the presence or absence of lipopolysaccharide. These results suggest that tissue transglutaminase may have no significant role in bactericidal, tumoricidal, or tumoristatic function of macrophages; however, it might have some role in promoting the Fc-receptor-mediated phagocytic function of the macrophages.

Animals↗
PubMed1989

Cell-mediated immune responses to sperm antigens: effects on mouse sperm and embryos.

Sperm antigens were assessed for their ability to induce cell-mediated immune (CMI) responses. Purified fertilization antigen (FA-1), protamine, and the lithium diiodosalicylate (LIS)-solubilized sperm preparation activated presensitized lymphocytes to secrete soluble mediators that activated macrophages and significantly inhibited sperm motility and embryonic development. The FA-1, however, was the most potent antigen in inducing proliferative response as well as the release of soluble mediators. LIS-sperm preparation, which contained numerous antigens, showed the least activity. The unsensitized control spleen cells did not secrete any factor(s) when activated with the antigen. In conclusion, these results indicate that sperm antigens can specifically induce (CMI) factors that have detrimental effects on sperm motility and preimplantation embryos. These findings may have potential clinical implications for humans, especially in immunologic and unexplained infertility, recurrent abortions, and development of antisperm contraceptive vaccines.

Animals↗
PubMed1989

A case of acute monocytic leukemia with lysozyme-positive leukemic monocytes and normal serum lysozyme levels.

We report a case of acute monocytic leukemia with normal serum lysozyme but with immunoperoxidase positivity for lysozyme in the leukemic blasts. The diagnosis of acute monocytic leukemia was made on the basis of cellular morphology, immunocytochemistry and cytochemistry. Discrepancy between serum lysozyme and intracytoplasmic lysozyme has not previously been reported in the literature. Levels of serum lysozyme may be misleading in cases of acute monocytic leukemia (FAB classification M5).

Adult↗
PubMed1989

Human immunodeficiency virus-associated large-cell immunoblastic lymphoma presenting as a perianal abscess.

We report a case of perianal non-Hodgkin's lymphoma that presented as a perianal abscess in an otherwise asymptomatic intravenous drug abuser who tested positively for human immunodeficiency virus infection. Extranodal lymphoma of the anal canal is a very rare event, which has recently been described in homosexual men with the acquired immunodeficiency syndrome. This is the first report, to our knowledge, of perianal lymphoma occurring in a nonhomosexual patient with the acquired immunodeficiency syndrome.

Abscess↗
PubMed1989

Treatment of systemic fungal infections with liposomal amphotericin B.

Forty-six patients with systemic fungal infections were treated with liposomal amphotericin B. Twenty-one patients had disseminated candidiasis, 19 had aspergillosis, and the rest had a variety of other fungal infections. Forty patients failed to respond to conventional amphotericin B therapy, and 6 patients were given liposomal amphotericin B because conventional amphotericin B caused severe side effects. Twenty-four patients had a complete response, and 22 patients failed to respond. No short- or long-term toxic reactions were observed. The acute side effects such as fever, chills, and potassium loss were infrequent and milder than those commonly observed with conventional amphotericin B. No chronic renal, hematologic, or central nervous system side effects were observed. Liposomal amphotericin B therapy was effective and less toxic than conventional amphotericin B therapy.

Adolescent↗
PubMed1988

Induction of adenosine deaminase and 5' nucleotidase activity in cultured human blood monocytes and monocytic leukemia (THP-1) cells by differentiating agents.

The in vitro effect of short-term culture as well as the effect of retinol (ROH), retinoic acid (RA), muramyl dipeptide [( Abu']MDP), lipopolysaccharide (LPS), and gamma interferon (IFN-gamma) on the induction of the purine metabolic enzymes, adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), and 5'nucleotidase (5NT) in human peripheral blood monocytes (HPBM) was examined. HPBM isolated by centrifugal elutriation were cultured for up to 96 h. Following an initial time lag of 24 h, mean ADA activity from seven separate experiments as measured in nmoles/10(6) cells/h increased from a baseline of 31.3 +/- 9.3 to 57.8 +/- 16.4 (P less than 0.005) at 72 h and to 72 +/- 21.5 (P less than .025) by 96 h. 5NT activity increased from a baseline of 2.2 +/- 0.9 to a maximum of 44 +/- 10.1 by 72 h and then declined to 29 +/- 18 (P less than 0.005) by 96 h, while no significant change in PNP activity was observed. HPBM incubated for 3 d with optimal concentrations of LPS, RA, and IFN-gamma had increases in ADA and 5NT activity ranging from three- to 10-fold compared to HPBM cultured in media alone, whereas no effect was observed with ROH and [Abu']MDP. RA, but not ROH, significantly enhanced ADA activity in a monocytic leukemia cell (THP-1) line. Addition of RA or the tumor promoter, phorbol 12-myristic 13-acetate (PMA), to HPBM or THP-1 cells resulted in significant increases in 5NT activity with opposite effects on ADA activity. These findings suggest that the biological mechanisms associated with differentiation in normal and malignant monocytes seem to be related and that the sequence and degree to which the various differentiation agents induce the enzyme elevations are also related to the mechanisms of activation/differentiation.

5'-Nucleotidase↗
PubMed1988

Pharmacological nature of newer imidazoli(di)nes on rat anococcygeus muscle.

The Pharmacological nature of newer imidazoli(di)nes (clonidine analogs) on rat anococcygeus muscle (RA) was investigated. Clonidine analogs produced dose-dependent (1 X 10(-3) to 1 X 10(-5) M) contractions on RA. The relative affinity (pD2) values were in the rank order of ST 375 greater than ST 567 greater than ST 608 greater than CLO greater than ST 600 greater than ST 363 greater than noradrenaline (NA) greater than ST 91 greater than ST 93. The intrinsic activity (alpha E) values of ST 93, ST 91, ST 600 and clonidine were comparable to alpha E of NA while the other analogs showed lower values. The responses of the clonidine analogs and NA on RA were antagonised in the presence of phentolamine and prazosin but were unaffected by yohimbine. Propranolol, atropine, cyproheptidine, mepyramine and metiamide had no effect on the responses. Reserpine pretreatment did not inhibit the responses of clonidine analogs on RA. The data suggests that newer clonidine analogs exhibited differences for their receptor occupation and receptor activation. The excitatory effects of newer clonidine analogs on RA are mediated through the stimulation of postsynaptic alpha (alpha 1) adrenoceptors.

Animals↗
PubMed1987

Suppression of macrophage cytostatic activation by serum retinoids: a possible role for transglutaminase.

Mouse resident peritoneal macrophages, activated in vitro with murine recombinant interferon-gamma and lipopolysaccharide in the presence of sera from different sources, showed marked differences in their abilities to inhibit murine adenocarcinoma cell growth, and in induced activity of the enzyme, tissue transglutaminase. The extraction of lipids from the serum abolished its ability to induce tissue TGase activity and to inhibit cytostatic activity, but these capabilities were fully restored by readdition of all trans-retinol or all trans-retinoic acid at physiological concentrations. Addition of dansylcadaverine, a competitive inhibitor of TGase, resulted in complete recovery of macrophages from retinoid-induced suppression of cytostatic activity. These results suggest that endogenous retinoids play an important role in the regulation of macrophage-mediated cytostatic activity in a process that is independent of prostaglandin secretion but seems to involve the protein cross-linking enzyme, tissue transglutaminase.

Adenocarcinoma↗
PubMed1987

Treatment of hepatosplenic candidiasis with liposomal-amphotericin B.

Nine patients with hematologic malignancies developed fungal infections, predominantly involving the liver and spleen. Eight patients had biopsy-documented progressive candidiasis and one had an unclassified fungus. The patients were treated with liposomal-amphotericin B (L-AmpB) after their fungal infection progressed during treatment with standard intravenous (IV) AmpB (Fungizone; E. R. Squibb & Son, Princeton, NJ) and/or other antifungals. Eight patients (88.8%) were cured of their fungal infection, and one showed improvement after treatment. Minor acute toxicity and no chronic toxicity were associated with the administration of L-AmpB. L-AmpB is a safe and effective therapeutic method for treating fungal infections that have invaded the liver and spleen even when they are refractory to conventional anti-fungal therapy.

Adolescent↗
PubMed1987

Expression of c-fos, c-myb, and c-myc in human monocytes: correlation with monocytic differentiation.

Terminal differentiation of human monocytic leukemia cells (THP-1 cells) was associated with the induction of c-fos, the down regulation of c-myb, and no significant change in the level of c-myc expression. Gamma interferon, which resulted in a slight decrease in c-myb but no change in c-fos or c-myc expression, had a transient antiproliferative effect without a morphological or functional differentiation of THP-1 cells. Resting human peripheral blood monocytes have a high c-fos, a low c-myc, and no detectable c-myb expression. These findings suggest that a switch in c-fos/c-myb expression is associated with the terminal differentiation of cells of the monocytic lineage.

Cell Differentiation↗