Search PubMed⌕ Search

Biomedical subjects

R Sharma

Publications and source records attributed to R Sharma.

At least 55 records · Page 3Linked to original sources
PubMed1994

The epidermal growth factor mitogenic signal is modulated by protein kinase C in T51B rat liver cells.

The regulation of cell proliferation involves a complex interplay between several signal transduction pathways. The effect of EGF on DNA synthesis in serum starved quiescent, synchronized T51B cells was investigated by [3H]thymidine incorporation and flow cytometry. 1 nM EGF or readdition of serum initiated G1 progression and entry into S phase by 18 h and DNA synthesis reached a maximum by 28 h. Low concentrations of EGF markedly stimulated DNA synthesis, but EGF was not as potent as readdition of serum. The effect of EGF on DNA synthesis was only partially blocked by the tyrosine inhibitors genistein and tyrphostin, suggesting that other signalling pathways play a role in EGF-stimulated mitogenesis. 1 nM EGF caused a rapid, transient increase in the activity of membrane-associated protein kinase C (PKC) followed by a longer sustained increase that continued into S phase. TPA (12-O-tetradecanoyl-phorbol-13-acetate) did not mimic EGF, rather it caused a slight stimulation of membrane-associated PKC activity within 1 h followed by a dramatic downregulation of PKC within 4 h. TPA was without effect on DNA synthesis alone, but when added along with EGF or serum TPA caused a significant enhancement of DNA synthesis. Pretreatment of quiescent, serum-deprived T51B cells with TPA reduced the basal level of DNA synthesis; however, under these conditions EGF became as potent a mitogen as serum. We hypothesize that EGF via activation of PKC regulates the activity of its receptor by switching from high affinity to low affinity states. Downregulation of PKC by long term treatment with TPA removes this regulation thus rendering T15B cells more sensitive to exogenous EGF.

Animals↗
PubMed1994

Plasmapheresis reduces proteinuria and serum capacity to injure glomeruli in patients with recurrent focal glomerulosclerosis.

To test the hypothesis that a circulating mediator is associated with recurrent idiopathic focal glomerulosclerosis (FGS), we studied the effect of plasmapheresis on reducing proteinuria in patients with the disease. An in vitro assay measured the capacity of sera before and after plasmapheresis to cause increased albumin permeability (P(albumin)++) in isolated rat glomeruli. Nine patients (five males aged 2 to 66 years) who underwent plasmapheresis for recurrent FGS were identified. Study variables included age, sex, time from diagnosis of recurrence to first pheresis, glomerular hyalinosis, complications, outcome, and proteinuria before and after plasmapheresis. Rat glomeruli were isolated in medium containing 4 g/dL bovine serum albumin, and P(albumin) was determined from the change in glomerular volume in response to an albumin gradient after incubation of the glomeruli in a 1:50 dilution of patient serum. Plasmapheresis reduced proteinuria from a mean of 12 +/- 7.46 g/24 hr to 5.1 +/- 7.39 g/24 hr (P = 0.03). Six patients in whom the diagnosis was made early in the course of the disease and in whom plasmapheresis was initiated immediately had lasting remissions. Preplasmapheresis biopsies in the patients who did not achieve remissions showed both epithelial foot process effacement and glomerular sclerosis. Serum samples were available from four patients for albumin testing in vitro. P(albumin)++ was reduced from a mean of 0.76 +/- 0.17 before pheresis to 0.18 +/- 0.31 after (P = 0.07). Therefore, the mechanism by which plasmapheresis reduces proteinuria in patients with recurrent FGS involves the decreased capacity of sera from these patients to injure the glomerular permeability barrier.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Modulation of cisplatin cytotoxicity by sulphasalazine.

The efficacy of cisplatin [cis-diamminedichloroplatinum (II); DDP] is hampered by acquired or de novo resistance of malignant cells to its cytotoxic effects. We have previously reported that cisplatin resistance parallels glutathione S-transferase (GST) activity in several human small-cell lung cancer cell lines. In the presently described studies, we used sulphasalazine, an inhibitor of GSTs, to evaluate the relative role of GSTs in mediating cisplatin resistance in two human small-cell lung cancer cell lines, NCI H-69 and H-2496. The H-69 cell line, which contained relatively higher GST activity than the H-2496 cell line (317 +/- 7 vs 9 +/- 1 mU mg-1 protein respectively), also displayed a greater degree of cisplatin resistance (IC50 values of 25.0 +/- 3.9 vs 4.5 +/- 1.0 microM respectively). Western blot and Northern blot analyses of purified GSTs revealed the expression of only the pi-class GST in both cell lines. Sulphasalazine inhibited the purified GSTs (IC50 of 10 microM for H-69 and 12 microM for H-2496) from both lines in a competitive manner with similar Ki values (6.5 and 7.9 microM for the H-69 and H-2496 cell lines respectively). Cytotoxicity studies revealed that sulphasalazine increased the cytotoxicity of cisplatin towards both cell lines. Isobologram analysis showed that sulphasalazine synergistically enhanced the cytotoxicity of cisplatin towards both cell lines, the magnitude of synergy being remarkably higher in H-69 cells than in H-2496 cells. Our studies indicate that clinically achievable concentrations of sulphasalazine may be useful in modulating cisplatin resistance in malignancies with increased GST-pi content.

Carcinoma, Small Cell↗
PubMed1994

Polymorphonuclear leukocytes increase glomerular albumin permeability via hypohalous acid.

Acute glomerulonephritis is characterized by the presence of neutrophils within glomeruli and the generation of reactive oxygen species (ROS) by activated polymorphonuclear leukocytes (PMNs). Hydrogen peroxide (H2O2) and other ROS including hypothalous acids have been implicated in PMN mediated injury. To determine the role of specific ROS in PMN mediated glomerular injury, isolated rat glomeruli were incubated for 30 minutes at 37 degrees C with H2O2, with H2O2 and myeloperoxidase, or with activated PMNs. Scavengers of ROS were included in some experiments. PMNs were harvested from rat peritoneal cavity and activated with phorbol myristate acetate (PMA). Glomerular albumin permeability (Palbumin) was calculated from the volume response to an oncotic gradient. Palbumin of glomeruli incubated with H2O2 (10(-3) or 10(-1) M) was not increased, while Palbumin after incubation with H2O2 and MPO was markedly increased (0.94 +/- 0.004). Palbumin after incubation with PMA, or with non-activated PMNs was not different from that of control glomeruli, Palbumin of the glomeruli incubated with activated PMNs increased (0.85 +/- 0.01, P < 0.001). This increase in Palbumin was inhibited by superoxide dismutase, catalase, or taurine (Palbumin = 0.035 +/- 0.06, -0.39 +/- 0.10, 0.028 +/- 0.06, respectively) and ameliorated by sodium azide (Palbumin = 0.21 +/- 0.03). In contrast, dimethyl sulfoxide did not prevent the increase in Palbumin (Palbumin = 0.92 +/- 0.01). Our results show that the hypohalous acid derived from that of H2O2-MPO-halide system is capable of increasing Palbumin. We conclude that hypohalous acid may be the primary mediator of the immediate increase in glomerular protein permeability induced by PMNs.

Albumins↗
PubMed1994

Influence of certain essential oils on carcinogen-metabolizing enzymes and acid-soluble sulfhydryls in mouse liver.

The influence of essential oils from naturally occurring plant dietary items such as cardamom, celery seed, cumin seed, coriander, ginger, nutmeg, and zanthoxylum on the activities of hepatic carcinogen-metabolizing enzymes (cytochrome P450, aryl hydrocarbon hydroxylase, and glutathione S-transferase) and acid-soluble sulfhydryl level was investigated in Swiss albino mice. Each oil was fed by gavage at 10 microliters/day for 14 days, and then the animals were sacrificed and their hepatic enzyme activities and sulfhydryl levels were evaluated. Only nutmeg and zanthoxylum oils induced cytochrome P450 level significantly (p < 0.05), whereas cardamom oil caused a significant reduction in its activity (p < 0.05). Furthermore, aryl hydrocarbon hydroxylase activity was significantly elevated only by treatment with ginger oil (p < 0.01), whereas nutmeg oil caused a significant reduction in its activity (p < 0.01). The remaining oils did not significantly alter the level of cytochrome P450 and aryl hydrocarbon hydroxylase activity. Glutathione S-transferase activity was significantly elevated in all experimental groups (p < 0.1-p < 0.001) compared with controls. The acid-soluble sulfhydryl was significantly elevated only by the essential oils of cardamom (p < 0.05), nutmeg (p < 0.05), and zanthoxylum (p < 0.01). Our observations suggest that intake of essential oils affects the host enzymes associated with activation and detoxication of xenobiotic compounds, including chemical carcinogens and mutagens.

Animals↗
PubMed1994

Modulation of phenobarbitone-induced loss of gap junctional intercellular communication in hepatocyte couplets.

Phenobarbitone (PB) produced a dose- and time-dependent decrease in gap junctional intercellular communication (GJIC) (up to 25.0 +/- 5.3% inhibition) in rat hepatocyte couplets (4 h cultures). The effect was reversible and independent of protein synthesis. This inhibition was exacerbated (to 53.3 +/- 5.4% inhibition) by depletion of intracellular glutathione following pretreatment with diethylmaleate (0.5 microM, 15 min). Inhibition was also significantly enhanced by addition of the cytochrome P450 inhibitors SKF 525A (25 microM) and metyrapone (20 nM). In contrast, hepatocyte couplets derived from rats pretreated with PB (0.1% w/v in drinking water) for up to 28 days were fully functional regarding GJIC and were found to be refractory to the effects of PB added in vitro. This, coupled with the lack of effect of p-hydroxy-PB, suggests that an active metabolite of PB is not involved in the inhibition of GJIC which may, instead, be through an oxidative stress, which is prevented by glutathione.

Animals↗
PubMed1994

Topoisomerase II-dependent novel antitumor compounds merocil and merodantoin induce apoptosis in Daudi cells.

Three photoproducts of merocyanine 540 have been isolated, chemically characterized and synthesized. Two of these photoproducts, merocil and merodantoin, show significant antitumor activity in vitro and in vivo while demonstrating minimal toxicity to normal cells and tissues. Treatment of lymphoma cells with these compounds resulted in a rapid decline in macromolecular synthesis, DNA fragmentation inhibitable by actinomycin D and cycloheximide, and a marked rise in intracellular calcium. In vitro analysis revealed that activity of these compounds is dependent on topoisomerase II. These results are discussed in terms of the novel class of topoisomerase II-dependent compounds for potential use in chemotherapy.

Antineoplastic Agents↗
PubMed1994

Evaluation of the healing process in fractures using early and delayed bone scanning.

Fifty-two fracture sites were evaluated by bone scintigraphy after acquiring similar views of the lesions at 4 and 24 h following technetium-99m methylene diphosphonate administration. After calculating 24/4 h radio-uptake ratio (RUR) and using 1.15 as the critical point of separation, fresh healing lesions could be separated from old healed fractures persisting as 'hot spots' with a sensitivity of 100% and specificity of 82%. The 24/4 h RUR technique is a new approach in measuring the osteoblastic activity at the lesion site. The technique appears to have clinical significance in the detection and follow up of the healing status of occult fractures where radiological procedures are of limited value.

Adolescent↗
PubMed1994

Adenosine triphosphate-dependent transport of doxorubicin, daunomycin, and vinblastine in human tissues by a mechanism distinct from the P-glycoprotein.

Previous studies have demonstrated that a human glutathione conjugate transporter, designated as dinitrophenyl-S-glutathione ATPase (DNP-SG ATPase), catalyzed ATP hydrolysis in the presence of several amphiphilic compounds other than glutathione conjugates (Singhal, S. S., R. Sharma, S. Gupta, H. Ahmad, P. Zimniak, A. Radominska, R. Lester, and Y. C. Awasthi. 1991. FEBS [Fed. Eur. Biochem. Soc.] Lett. 281:255-257). We now demonstrate that DNP-SG ATPase purified from human lung and erythrocyte membranes catalyzed the hydrolysis of ATP in the presence of doxorubicin and its metabolites. Doxorubicin-stimulated ATP hydrolysis by DNP-SG ATPase was saturable with respect to doxorubicin (Km 1.2 and 2.8 microM for the lung and erythrocyte enzymes, respectively). Antibodies against DNP-SG ATPase immunoprecipitated the ATP hydrolyzing activity stimulated by doxorubicin, its metabolites, and glutathione conjugates. Inside our vesicles prepared from erythrocyte membranes took up doxorubicin, daunomycin, and vinblastine in an ATP-dependent manner. The uptake was linear with respect to time and vesicle protein, was dependent on ATP and magnesium, was inhibited by heavy metal salts or by heating the vesicles, and was sensitive to both osmolarity and orientation of the vesicles. The transport had an activation energy of 13 kcal/mol, was saturable with respect to both doxorubicin and ATP (Km values of 1.8 microM and 1.9 mM, respectively), and was competitively inhibited by glutathione conjugates as well as by a number of amphiphiles such as daunomycin or vinblastine. Transport was diminished upon coating the vesicles with antibodies against DNP-SG ATPase. Incorporation of increasing amounts of purified DNP-SG ATPase into the vesicles resulted in a linear increase in transport of doxorubicin. These studies demonstrated for the first time that a membrane protein that catalyzed the transport of anionic amphiphilic molecules such as glutathione conjugates could also mediate the transport of weakly cationic antitumor antibiotic, doxorubicin. Notably, the Km of transport was in the range of doxorubicin concentration achievable in human serum after intravenous dosing of doxorubicin.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Choroid plexus papillomas.

Choroid plexus papillomas (CPPs) are rare neoplasms accounting for less than 1% of all intracranial tumours. We present our experience with 13 consecutive cases managed by us between 1981 and 1991. There were eight children and five adults. Five patients had tumours in the 4th ventricle, four in lateral ventricle, one in the 3rd ventricle, two in the cerebellomedullary cistern and one in the cerebellopontine angle. The cerebellomedullary cistern is a rare site for CPPs. Although the 4th ventricle remains the common site for adult CPPs, in our series there was a higher incidence of posterior fossa papillomas even in children. Only six patients out of 13 underwent precraniotomy shunts. All patients had their tumours operated upon and verified histologically. Total excision of the tumour could be achieved in nine patients; only a sub total excision was possible in the remaining four. There were two surgical mortalities in the earlier part of this series. Two patients with subtotal excisions underwent radiation therapy; one of these had regrowth of the tumour and another was lost to follow up. The other nine patients are doing well with a follow-up ranging from 9 to 90 months. Surgical resection with the objective of achieving total excision should be attempted in these tumours.

Adolescent↗
PubMed1994

Effect of orpiment (As2S3) on cytochrome P-450, glutathione and lipid peroxide levels of rat liver.

Oral administration of orpiment (50 mg/kg b. wt.) caused significant decreases of cytochrome P-450 (44%) and glutathione levels (47%) of rat liver microsomes. Concomitantly, there was an increase in the lipid peroxidation (78%). Orpiment caused significant decreases in the activities of antioxidant enzymes. The glutathione-S-transferase activity was, however, lowered by 42%. The cytochrome P-450-dependent mixed function oxygenase system was also affected. The results show the hepatotoxic nature of orpiment.

Animals↗
PubMed1994

Intermediate variables as determinants of adverse pregnancy outcome in high-risk inner-city populations.

A probability sample survey of high-risk inner-city women with a live birth in the last 3 years shows that maternal medical risks and health behaviors during pregnancy are important intermediate variables influencing preterm delivery and birthweight. Women who developed two or more medical risks had about three-and-a-half times the risk of preterm delivery and two-and-a-half times the risk of low birthweight compared to those without such risks. Women with prior fetal loss had twofold increase in the risk of preterm delivery and low birthweight. Unintended pregnancy resulted in one-and-a-half to twofold increase in preterm delivery and low birthweight, respectively. Inadequate gestational weight increased the risk of preterm delivery by about 50%. Smoking during pregnancy raised the risk of low birthweight slightly more than one-and-a-half times.

Adolescent↗
PubMed1994

Zinc levels in maternal and cord blood and in amniotic fluid--a possible marker for foetal malformation.

Zinc levels were estimated from the maternal and cord blood drawn at delivery and in the amniotic fluid drawn before delivery in 9 pregnancies resulting in congenitally abnormal foetuses and 21 pregnancies resulting in normal healthy babies. Zinc levels were significantly lower (P < 0.01) in maternal and cord blood serum in congenitally malformed babies as compared to healthy normal controls. Amniotic fluid zinc levels were significantly higher (P < 0.01) in pregnancies with malformed babies. The use of zinc levels as marker for foetal malformation has been suggested.

Amniotic Fluid↗
PubMed1994

Surface epithelial tumours of the ovary.

Surface epithelial tumours (SET) constituted 65.7% of all the ovarian tumours. Benign tumours were 182 (71.9%), of low malignant potential (LMP) 11 (4.4%) and frank malignant 60 (23.7%). Maximum number of cases, 102 (40.3%) belonged to 3rd decade. Mean age for serous cystoma was 31.5% years as compared to 30.8 years for mucinous cystoma. The commonest presenting feature was the abdominal lump observed in 182 cases (71.9%) and pain in abdomen in 120 (47.4%). Serous cystomas were t he most frequent tumours and comprised of 32.21% of all the ovarian tumours or 46.01% of all the SET or 65.56% of all the cystic SET. Seventeen (11.7%) of serous tumours were bilateral. Mucinous cystomas constituted 14.55% of all the ovarian tumours or 30.8% of all the SET. These tumours were bulky (78.6%; 15 cm diameter) and multilocular (83.9%). Mucinous cystadenocarcinoma was the commonest malignant epithelial tum our (36.6%). Endometroid carcinoma comprised 3.65% of all the SET or 8.4% of all the ovarian malignancy. Squamous metaplasia was seen in one case whereas 2 cases were of mesodermal mixed tumour with heterologous element as rhabdomyosarcoma. Clear cell carcinoma, Brenner tumour and unclassified group constituted 0.79%, 1.18% and 1.58% of all SET respectively.

Adenocarcinoma, Clear Cell↗