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Biomedical subjects

M M Reddy

Publications and source records attributed to M M Reddy.

At least 19 recordsLinked to original sources
PubMed1992

Control of CFTR chloride conductance by ATP levels through non-hydrolytic binding.

Site-specific mutation and membrane reconstitution experiments provide compelling evidence that the product of the gene which is at fault in the disease cystic fibrosis, termed the cystic fibrosis transmembrane conductance regulator (CFTR), is a small-conductance chloride channel activated by phosphorylation. As transport of chloride ions is passive, the predicted presence of two nucleotide-binding domains in CFTR seems as puzzling as a report that ATP hydrolysis is essential to activate the channel. We now find that in the sweat duct, which expresses high levels of CFTR and has a very high Cl- conductance, intracellular concentrations of ATP must be about normal (5 mM) for activation of this conductance, apparently by a non-hydrolytic, perhaps allosteric, mechanism. This passive dependence on ATP should mean that even a modest depletion of cell energy levels will significantly lower the energy demands of electrolyte transport by decreasing chloride conductance. We believe this direct coupling between cellular ATP levels and chloride channel activity is an adaptive mechanism to protect the tissue from damage resulting from excessive energy depletion.

Adenosine Triphosphate↗
PubMed1992

An improved method for monitoring efficacy of anti-retroviral therapy in HIV-infected individuals: a highly sensitive HIV p24 antigen assay.

Circulating human immunodeficiency virus (HIV) p24 antigen levels were measured by a highly sensitive HIV p24 antigen-capture enzyme-linked immunosorbent assay (ELISA) in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) otherwise negative for HIV p24 antigen measured by a commercial antigen-capture ELISA. The assays were performed at baseline and at several intervals during treatment with either zidovudine (ZDV) or dideoxyinosine (ddl). To further enhance the rate of antigen detection, serum was pretreated with hydrochloric acid to denature antibody in immune complexes. Utilizing this assay system, we monitored these patients for drug efficacy. HIV p24 antigen levels obtained by using this sensitive assay decreased in 3 of 8 patients receiving ZDV during 8 weeks of ZDV treatment. Similarly, ddl administration was associated with a decrease of HIV p24 antigen levels in 3 of 5 patients. Thus, the use of the highly sensitive HIV p24 antigen assay permitted the monitoring of surrogate HIV p24 antigen as a measure of efficacy of anti-retroviral therapy in all of these patients who were otherwise HIV p24 antigen-negative at the onset of anti-retroviral therapy.

Biomarkers↗
PubMed1992

cAMP activation of CF-affected Cl- conductance in both cell membranes of an absorptive epithelium.

Cystic fibrosis (CF) is characterized by abnormal epithelial Cl- conductance (GCl). In vitro studies that have shown that cAMP regulation is an intrinsic property of the CF-affected GCl(CF-GCl) have been carried out previously on cultured secretory cells and on nonepithelial cells. Even though GCl in absorption is defective in CF, a clear demonstration of cAMP regulation of CF-GCl in a purely absorptive tissue is lacking. We studied the cAMP regulation of CF-GCl in the microperfused intact human reabsorptive sweat duct. About 40% of the ducts responded to cAMP (responsive) while the remainder of the ducts did not. In responsive ducts, cAMP-elevating agents: beta-adrenergic agonist isoproterenol (IPR), CPT-cAMP, forskolin, theophylline or IBMX increased Gt by about 2.3-fold (n = no. of ducts = 8). Removal of media Cl-, but not amiloride pretreatment (in the lumen), abolished the cAMP response, indicating exclusive activation of GCl. cAMP activated both apical and basolateral GCl. cAMP hyperpolarized gluconate: Cl- (lumen:bath) transepithelial bionic potentials (delta Vt = -20.3 +/- 5.2 mV, mean +/- SE, n = 9) and transepithelial 3: 1 luminal NaCl dilution diffusion potentials (delta Vt = -8.8 +/- 2.9 mV, n = 5). cAMP activated basolateral GCl as indicated by increased bi-ionic (gluconate:Cl-, bath:lumen) diffusion potentials (by about 12 mV). The voltage divider ratio in symmetric NaCl solutions increased by 60%. Compared to responsive ducts, nonresponsive ducts were characterized by smaller spontaneous transepithelial potentials in symmetrical Ringer's solution (Vt = -6.9 +/- 0.8 mV, n = 24, nonresponsive vs. -19.4 +/- 1.8 mV, n = 22, responsive ducts) but larger bi-ionic potentials (-94 +/- 6 mV, n = 35, nonresponsive vs. -65 +/- 5 mV, n = 17, responsive ducts) and dilution diffusion potentials (-40 +/- 5 mV, n = 11, nonresponsive vs. -29 +/- 3 mV, n = 7, responsive ducts). These results are consistent with an inherently (prestimulus) maximal activation of GCl in nonresponsive ducts and submaximal activation of GCl in responsive ducts. We conclude that cAMP activates CF-GCl which is expressed and abnormal in both apical and basal membranes of this absorptive epithelium in CF.

Adrenergic beta-Agonists↗
PubMed1992

A system for the high efficiency replication of HIV-1 in neural cells and its application to anti-viral evaluation.

Stable transfection of H4 neuroglioma cells with the Epstein-Barr virus-based eucaryotic CD4 expression vector pKS286 generated the cell line, H4/CD4, in which greater than 90% of cells express surface CD4 receptors. Optimal conditions for infection of H4/CD4 cells with HIV-1 were determined; these included a cocultivation with growth-arrested, chronically infected T cells. Under these conditions, 3-days after infection up to 50% of H4/CD4 cells expressed HIV-1 antigens as detected by immunofluorescence assay, the number of intracellular HIV-1 RNA copies reached 10(3) molecules per cell as determined by liquid hybridization, and virus production ranged from 0.2 to 1.0 micrograms HIV-1 p24 core antigen per ml of culture supernatant, comparable to that measured under the same conditions in HIV-1 infected T cells. Giant cells and cytolysis were common. Inhibition of HIV-1 infection by nucleoside analogues in H4/CD4 cells was comparable to that in T cells, suggesting that the early stages of HIV-1 infection were similar in both cell systems. Infection in the presence of soluble CD4 reduced HIV-1 expression to the levels determined in CD4-negative H4 cells. This system may be useful for screening of drugs intended to block HIV-1 replication in the brain and for the evaluation of the HIV-1 life cycle in brain cells.

CD4 Antigens↗
PubMed1992

Effect of foscarnet therapy on human immunodeficiency virus p24 antigen levels in AIDS patients with cytomegalovirus retinitis.

Circulating human immunodeficiency virus (HIV) p24 antigen levels were measured in 22 AIDS patients who had detectable serum antigen at baseline after induction and maintenance therapy of foscarnet for cytomegalovirus retinitis in phase I/II multicenter trials. The HIV p24 antigen levels decreased from a baseline value of 199 +/- 236 (mean +/- SD) and 140 pg/mL (median) to 106 +/- 218 and 28 pg/mL after 14 days of foscarnet induction therapy (60 mg/kg every 8 h). During chronic foscarnet maintenance, there was a sustained decrease in mean HIV p24 antigen levels below pre-foscarnet therapy baseline concentrations for a median of 16 weeks after foscarnet induction. These results provide evidence for a sustained clinical antiretroviral effect of chronic foscarnet maintenance therapy, consistent with a recent report that foscarnet-treated AIDS patients live longer than ganciclovir-treated patients.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Reversed anion selectivity in cultured cystic fibrosis sweat duct cells.

The human genetic disease cystic fibrosis (CF) is characterized by defective epithelial Cl- conductance (GCl). To distinguish the CF-affected GCl from other Cl- channels, we have studied the properties of GCl in normal and CF cells grown from explanted reabsorptive sweat ducts (RD). The cultured cells from normal subjects retained some of the typical duct cell properties. The Na+ conductance inhibitor amiloride hyperpolarized intracellular potentials (Vm) by 10.4 +/- 1.6 mV (n = 12). Substitution of gluconate for Cl- depolarized Vm by 15.5 +/- 1.1 mV (n = 33). The apparent GCl (G'Cl) of normal cells was sensitive to adenosine 3',5'-cyclic monophosphate (forskolin, 10(-6) M), as evidenced by a significant increase (63%, n = 9) in the Cl- gradient induced depolarization, and more selective for Cl- than I- (substitution of Cl- by I- depolarized Vm by 6.3 +/- 0.3 mV, n = 49). Although the cells from CF subjects were statistically indistinguishable from normal cells based on Vm (-18.5 +/- 1.2 mV, n = 49 vs. -20.1 +/- 1.8 mV, n = 28), CF cells expressed differences in G'Cl, responses to forskolin, and anion selectivity. CF cells had a significantly reduced G'Cl as indicated by blunted responses to imposed Cl- gradients (26% of normal, n = 28). In contrast to our observations in normal cells, the G'Cl of CF cells was insensitive to forskolin.(ABSTRACT TRUNCATED AT 250 WORDS)

Anions↗
PubMed1992

Electrophysiologically distinct cell types in human sweat gland secretory coil.

The human sweat gland secretory coil consists of three histologically distinct cell types: myoepithelial (ME), light (or clear), and dark cells. The electrophysiological properties of all these cells are poorly defined. Employing electrophysiological techniques, we report distinct pharmacological responses of three different cell types from freshly isolated human sweat gland secretory coil. The superficial ME cells are characterized by 1) spontaneous depolarizing spikes (2 to 50 mV), 2) high cell membrane potentials [Vm = -68.6 +/- 3.9 (SE) mV; n = 21], 3) a K(+)-selective cell membrane (slope response = 54.2 +/- 6.7 mV per decade K+ concentration; n = 4), 4) depolarizing responses to cholinergic agonist mecholyl (delta Vm = 29.1 +/- 3.1 mV, n = 21), and 5) insensitivity to beta-adrenergic stimulation (n = 12). Two other types of cells, presumably secretory, were also observed. We arbitrarily labeled these cells as beta-adrenergic sensitive (beta-S) and beta-adrenergic insensitive (beta-I) cells based on their respective sensitivity to isoproterenol (IPR), a beta-adrenomimetic. Properties of the beta-S cells include 1) relatively higher basolateral membrane potentials (Vm = -57.3 +/- 3.1 mV; n = 13), 2) depolarizing responses to IPR (delta Vm = 16.8 +/- 2.6 mV; n = 9) inhibitable by the beta-adrenergic antagonist propranolol, and 3) hyperpolarizing responses to mecholyl (delta Vm = -21.8 +/- 2.0 mV; n = 13). The beta-I cells are characterized by 1) low basolateral membrane potentials (Vm = -23.6 +/- 2.1 mV; n = 16), 2) insensitivity to beta-adrenergic stimulation, and 3) hyperpolarizating responses to mecholyl (delta Vm = -16.1 +/- 2.1 mV; n = 16).

Electrophysiology↗
PubMed1992

Evidence of two distinct epithelial cell types in primary cultures from human sweat gland secretory coil.

The human sweat gland secretory coil (SC) is comprised of myoepithelial (ME) and two types of secretory epithelial cells. The secretory cells include beta-adrenergic-sensitive (beta-S) cells [responsive to the beta-adrenergic agonist isoproterenol (IPR)] and beta-adrenergic insensitive (beta-I) cells. We have grown segments of SC in primary culture and found that under the conditions described here, only epithelial cells form outgrowths as indicated by morphological and physiological properties. As in the native SC epithelium, the secretory cells in primary culture were comprised of polygonal epithelial cells with a characteristic hyperpolarization of cell potentials (Vm) to cholinergic stimulation by mecholyl (magnitude of change of Vm = delta Vm = 21.5 +/- 1.3 mV, mean +/- SE, n = number of cells = 44). We have found both beta-S and beta-I cells as determined by unstimulated membrane potentials, sensitivity to IPR, and K+ conductance (GK+). The frequency distribution of unstimulated cells indicated two distinct populations of cells, one with high membrane potentials (Vm = -63 +/- 2.6 mV), which correlated with beta-S cells, and a second with low membrane potentials (Vm = -22 +/- 1.5 mV), which correlated with the beta-I cells. IPR depolarized the Vm of beta-S cells (delta Vm = 11.0 +/- 0.8 mV, n = 25) without affecting the Vm of beta-I cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1992

Circulating elevated levels of soluble CD23, interleukin-4, and CD20+CD23+ lymphocytes in atopic subjects with elevated serum IgE concentrations.

Circulating IgE protein levels, leukocyte counts, lymphocyte subsets, IL-4, and soluble CD23 levels were quantitated in 43 atopic and 19 nonatopic subjects. Mean values of IgE protein levels, total eosinophil counts, CD20+CD23+ cells (B cells with low-affinity IgE receptor), IL-4 and sCD23 levels were elevated in atopic patients compared with nonatopic controls. The results suggest that sCD23, IL-4, and CD20+CD23+ lymphocytes may play a role in the increased production of IgE in atopic subjects in a manner similar to that observed by other investigators in prior in vitro studies.

Adult↗
PubMed1991

Quantitative changes in T helper inducer (CD4+ CD45RA-), T suppressor inducer (CD4+ CD45RA+), T suppressor (CD8+ CD11b+), and T cytotoxic (CD8+ CD11b-) subsets in human immunodeficiency virus infection.

To determine changes in subsets of CD4 and CD8 in relation to HIV infection and progression to AIDS, we quantitated peripheral blood lymphocytes obtained from 17 heterosexual controls, 22 asymptomatic HIV-seronegative and 18 HIV-seropositive intravenous drug users. 50 patients with AIDS-related complex (ARC), and 9 patients with AIDS using an EPICS "C" flow cytometer by two-color analysis. Both T helper inducer (CD4+ CD45RA-) and suppressor inducer (CD4+ CD45RA+) lymphocytes were decreased significantly in patients with ARC or AIDS. In contrast, T cytotoxic (CD8+ CD11b-) cells were significantly increased and accompanied by a significant decrease in the T suppressor (CD8+ CD11b+) subset in patients with ARC or AIDS. These results suggest that both T helper inducer and T suppressor inducer subsets of the CD4+ population and the T suppressor subset of CD8+ are depleted after HIV infection, while the T cytotoxic subset of CD8+ was increased after HIV infection.

AIDS-Related Complex↗
PubMed1991

Evaluation of HIV P24 antigen, beta 2-microglobulin, neopterin, soluble CD4, soluble CD8, and soluble interleukin-2 receptor levels in patients with AIDS or AIDS-related complex treated with 2',3'-dideoxyinosine (ddI).

Circulating HIV P24 antigen, beta 2-microglobulin, neopterin, soluble CD4, soluble CD8, and soluble interleukin-2 receptor were measured in 13 zidovudine-intolerant patients (8 with ARC and 5 with AIDS) treated with dideoxyinosine (ddI). Measurements were made at baseline and at several intervals during therapy. Mean levels of HIV P24 antigen decreased early and significantly (P less than 0.01) after 2 weeks of ddI administration and remained low at weeks 8 and 12. In addition, mean SCD8 levels decreased late and significantly (P less than 0.02) after 16 weeks of ddI treatment and remained low at 24 weeks. In contrast, ddI administration had no substantial effect on mean levels of beta 2-microglobulin, neopterin, soluble CD4, and soluble interleukin-2 receptor. ddI administration appears to have been associated with early reduction of HIV P24 antigen levels and later reduction of SCD8 mean levels in these patients.

AIDS-Related Complex↗
PubMed1991

Intracellular potassium activity and the role of potassium in transepithelial salt transport in the human reabsorptive sweat duct.

We have measured the intracellular potassium activity, [K+]i and the mechanisms of transcellular K+ transport in reabsorptive sweat duct (RSD) using intracellular ion-sensitive microelectrodes (ISMEs). The mean value of [K+]i in RSD is 79.8 +/- 4.1 mM (n = 39). Under conditions of microperfusion, the [K+]i is above equilibrium across both the basolateral membrane, BLM (5.5 times) and the apical membrane, APM (7.8 times). The Na+/K+ pump inhibitor ouabain reduced [K+]i is insensitive to the Na+/K+/2 Cl- cotransport inhibitor bumetanide in the bath. Cl- substitution in the lumen had no effect on [K+]i. In contrast, Cl- substitution in the bath (basolateral side) depolarized BLM from -26.0 +/- 2.6 mV to -4.7* +/- 2.4 mV (n = 3; *indicates significant difference) and decreased [K+]i from 76.0 +/- 15.2 mM to 57.7* +/- 12.7 mM (n = 3). Removal of K+ in the bath decreased [K+]i from 76.3 +/- 15.0 mM to 32.3 +/- 7.6 mM (n = 4) while depolarizing the BLM from -32.5 +/- 4.1 mV to -28.3* +/- 3.0 mV (n = 4). Raising the [K+] in the bath by 10-fold increased [K+]i from 81.7 +/- 9.0 mM to 95.0* +/- 13.5 mM and depolarized the BLM from -25.7 +/- 2.4 mV to -21.3* +/- 2.9 mV (n = 4). The K+ conductance inhibitor, Ba2+, in the bath also increased [K+]i from 85.8 +/- 6.7 mM to 107.0* +/- 11.5 mM (n = 4) and depolarized BLM from -25.8 +/- 2.2 mV to -17.0* +/- 3.1 mV (n = 4). Amiloride at 10(-6) M increased [K+]i from 77.5 +/- 18.8 mM to 98.8* +/- 21.6 mM (n = 4) and hyperpolarized both the BLM (from -27.5 +/- 1.4 mV to -46.0* +/- 3.5 mV, n = 4). However, amiloride at 10(-4) M decreased [K+]i from 64.5 +/- 0.9 mM to 36.0* +/- 9.9 mM and hyperpolarized both the BLM (from -24.7 +/- 1.4 mV to -43.5* +/- 4.2 mV) and APM (from -18.3 +/- 0.9 mV to -43.5* +/- 4.2 mV, n = 6). In contrast to the observations at the BLM, substitution of K+ or application of Ba2+ in the lumen had no effect on the [K+]i or the electrical properties of RSD, indicating the absence of a K+ conductance in the APM.(ABSTRACT TRUNCATED AT 400 WORDS)

Amiloride↗
PubMed1991

Human immunodeficiency virus type-1 infection of homosexual men is accompanied by a decrease in circulating B cells.

As part of the multidisciplinary effort to characterize the natural history of human immunodeficiency virus type 1 (HIV-1) infection, the cell-surface phenotypes of lymphocytes from a cohort of homosexual men were analyzed in detail and related to clinical and laboratory parameters associated with HIV-1 infection. The present study represents a cross-sectional analysis of coded specimens from 153 homosexual men, of whom 74 were seronegative and 79 seropositive for HIV-1. Fewer circulating B lymphocytes (CD19+) were found in HIV-1-seropositive subjects relative to a seronegative reference group. HIV seropositivity was not associated with decreased numbers of CD8+ T cells or activated T cells, which suggests that the number of circulating B cells specifically decreased. In addition to CD19, B cells were measured by CD20 and CD21 in a subset of subjects, and decreases in circulating CD20+ and CD21+ B cells were also apparent in HIV-1-seropositive subjects. The decrease in B-cell numbers was present at the earliest stages of HIV-1 infection (asymptomatic, clinically silent) and became more pronounced at more advanced stages of HIV-1 infection. The absolute B-cell numbers correlated with absolute CD4+ cell numbers (r = 0.59, p less than 0.001). These data suggest that HIV-1 infection is associated with progressive, selective decreases in the numbers of circulating CD4+ T cells and B cells.

Antigens, CD↗
PubMed1990

Elevated levels of circulating immune complexes in human immunodeficiency virus infection.

Circulating immune complexes were quantitated in asymptomatic intravenous drug abusers (IVDA), male homosexuals, and patients with lymphadenopathy or acquired immunodeficiency syndrome (AIDS) by two different methods. Circulating immune complexes were elevated in HIV-seronegative IVDAs and male homosexuals, probably reflecting viral infections such as cytomegalovirus (CMV). Circulating immune complexes were also elevated in HIV-seropositive IVDAs and male homosexuals and in patients with lymphadenopathy or AIDS, reflecting infections such as CMV and HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Effect of azidothymidine on soluble CD4 levels in patients with AIDS or AIDS-related complex.

Circulating soluble CD4 (sCD4) levels were measured in 20 patients (11 with the acquired immunodeficiency syndrome [AIDS] and 9 with AIDS-related complex [ARC]) treated with azidothymidine (AZT) and in 12 patients (nine with AIDS and three with ARC) who were in the placebo group. The mean CD4 level in the AZT treatment group at baseline was 41 +/- 12 (SEM) U/ml. After 4 wk of treatment, the mean level decreased to 23 +/- 5; it was 29 +/- 10, 31 +/- 14, and 21 +/- 5 at 8, 12, and 16 wk of therapy, respectively. No significant changes were observed in the placebo group. These results suggest that AZT administration may be associated with reduced sCD4 levels in these patients.

AIDS-Related Complex↗
PubMed1990

Natural killer cell activity in a longitudinal dietary fat intervention trial.

It has been hypothesized that dietary fat may affect natural killer (NK) cell activity, a factor of potential importance in early tumor surveillance. Fourteen men successfully completed an intervention trial designed to test the effect of dietary fat on NK activity in humans. Study subjects lowered their fat intake to an average of 22% of calories as fat and consumed two dietary supplements (of coconut and safflower oils), in a cross-over design. These supplements resulted in large changes in the ratio of polyunsaturated to saturated fatty acids (1.73 to 0.34, on average). Results of a general linear model in which we fitted covariates on exercise, body mass, intervention sequence, and various dietary predictors revealed a significant effect of decreased total dietary fat intake on increased NK activity at an E/T ratio of 100:1 (about 0.79% increase for each absolute percent of calories as fat, P = 0.04). Similar results were obtained at E/T ratios of 50:1 and 25:1. No other nutritional predictor was significantly associated with NK activity at any E/T ratio.

Adult↗
PubMed1990

Effect of azidothymidine (AZT) on HIV P24 antigen, beta 2-microglobulin, neopterin, soluble CD8, soluble interleukin-2 receptor and tumor necrosis factor alpha levels in patients with AIDS-related complex or AIDS.

Circulating HIV P24 antigen, beta 2-microglobulin, neopterin, soluble CD8, soluble interleukin-2 receptor and TNF alpha levels were measured in 20 patients (9 with ARC and 11 with AIDS) treated with azidothymidine (AZT) and in 12 patients (3 with ARC and 9 with AIDS) who were in a placebo group. Mean levels of HIV P24 antigen, beta 2-microglobulin, neopterin and SCD8 decreased significantly (P less than 0.05) after 12 to 16 weeks of AZT administration. SIL-2R and TNF alpha serum levels did not appear to change in association with AZT therapy. No changes were observed in the placebo group except that TNF alpha levels appeared to increase after 12 to 16 weeks. These results suggest that AZT administration may have led to reduced HIV P24 antigen, beta 2-microglobulin, neopterin and SCD8 mean levels in these patients.

AIDS-Related Complex↗