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Biomedical subjects

R Agarwal

Publications and source records attributed to R Agarwal.

At least 127 records · Page 7Linked to original sources
PubMed1999

Inhibition of cell death in human mammary epithelial cells by the cooked meat-derived carcinogen 2-amino-1-methyl-6-phenylimidazo[4, 5-b]pyridine.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary gland carcinogen present in the human diet in cooked meat. To examine if PhIP and its reactive metabolite N-hydroxy-PhIP inhibit apoptosis in human mammary epithelial MCF-10A cells, confluent cultures deprived of serum and growth factors were incubated for 24 h with either compound. The percentages of dead cells (mean +/- SEM, n = 3) as measured by trypan blue exclusion were 5.7 +/- 0.6, 3.4 +/- 0.3, 2.7 +/- 0.3, and 0.2 +/- 0.003%, in control, 1 microM N-hydroxy-PhIP-, 5 microM N-hydroxy-PhIP-, and 100 microM PhIP-treated dishes, respectively. The expression of Bcl-2 and Bcl-x(L) as quantitated by Western blotting was 1.2- to 1.9-fold higher in the treated groups. PhIP-DNA adducts induced by N-hydroxy-PhIP in MCF-10A cells measured by the (32)P-postlabeling assay were low (<1 x 10(7), relative adduct labeling). No adducts were detected after incubation with PhIP. Western blot analysis indicated that PhIP increased ERK2 phosphorylation concomitant with Bcl-2. The results suggest that the inhibition of cell death in mammary epithelial cells by PhIP occurs independently of PhIP-DNA adducts and may involve enhanced signaling through the MAP kinase pathways.

Apoptosis↗
PubMed1999

Inhibition of human carcinoma cell growth and DNA synthesis by silibinin, an active constituent of milk thistle: comparison with silymarin.

Several studies from our laboratory have shown the cancer chemopreventive and anti-carcinogenic effects of silymarin, a flavonoid antioxidant isolated from milk thistle, in long-term tumorigenesis models and in human prostate, breast and cervical carcinoma cells. Since silymarin is composed mainly of silibinin with small amounts of other stereoisomers of silibinin, in the present communication, studies were performed to assess whether the cancer preventive and anti-carcinogenic effects of silymarin are due to its major component silibinin. Treatment of different prostate, breast, and cervical human carcinoma cells with silibinin resulted in a highly significant inhibition of both cell growth and DNA synthesis in a time-dependent manner with large loss of cell viability only in case of cervical carcinoma cells. When compared with silymarin, these effects of silibinin were consistent and comparable in terms of cell growth and DNA synthesis inhibition, and loss of cell viability. Based on the comparable results of silibinin and silymarin, we suggest that the cancer chemopreventive and anti-carcinogenic effects of silymarin reported earlier are due to the main constituent silibinin.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Modulation of mitogen-activated protein kinase activation and cell cycle regulators by the potent skin cancer preventive agent silymarin.

Recently we showed that the skin cancer preventive effect of silymarin involves inhibition of erbB1 activation. Here we assessed the effect of silymarin on cytoplasmic and nuclear signals employing human epidermoid carcinoma A431 cells. Silymarin treatment of cells resulted in a significant inhibition of mitogen-activated protein kinase (MAPK)/ERK1/2 activation only at lower doses, whereas higher doses activated MAPK/JNK1. These differential responses of silymarin were accompanied by its growth inhibitory and apoptotic cell death effects at low and high doses, respectively. Silymarin-caused growth inhibition was via both G2-M and G1 arrests due to a significant decrease in the kinase activity and protein levels of CDKs and cyclins. In other studies, only low doses of silymarin also showed an induction of Cip1/p21 and Kip1/p27. Together, these results identify distinct signaling pathways for the antiproliferative and apoptotic effects of silymarin and form a basis for developing strategies targeted to ERK and JNK pathways for the prevention and intervention of malignancies by silymarin.

Anticarcinogenic Agents↗
PubMed1999

Silibinin decreases prostate-specific antigen with cell growth inhibition via G1 arrest, leading to differentiation of prostate carcinoma cells: implications for prostate cancer intervention.

Reduction in serum prostate-specific antigen (PSA) levels has been proposed as an endpoint biomarker for hormone-refractory human prostate cancer intervention. We examined whether a flavonoid antioxidant silibinin (an active constituent of milk thistle) decreases PSA levels in hormone-refractory human prostate carcinoma LNCaP cells and whether this effect has biological relevance. Silibinin treatment of cells grown in serum resulted in a significant decrease in both intracellular and secreted forms of PSA concomitant with a highly significant to complete inhibition of cell growth via a G1 arrest in cell cycle progression. Treatment of cells grown in charcoal-stripped serum and 5alpha-dihydrotestosterone showed that the observed effects of silibinin are those involving androgen-stimulated PSA expression and cell growth. Silibinin-induced G1 arrest was associated with a marked decrease in the kinase activity of cyclin-dependent kinases (CDKs) and associated cyclins because of a highly significant decrease in cyclin D1, CDK4, and CDK6 levels and an induction of Cip1/p21 and Kip1/p27 followed by their increased binding with CDK2. Silibinin treatment of cells did not result in apoptosis and changes in p53 and bcl2, suggesting that the observed increase in Cip1/p21 is a p53-independent effect that does not lead to an apoptotic cell death pathway. Conversely, silibinin treatment resulted in a significant neuroendocrine differentiation of LNCaP cells as an alternative pathway after Cip1/p21 induction and G1 arrest. Together, these results suggest that silibinin could be a useful agent for the intervention of hormone-refractory human prostate cancer.

3T3 Cells↗
PubMed1999

Potential role of a membrane-bound NADH oxidoreductase in nitric oxide release and arterial relaxation to nitroprusside.

The site of metabolism in vascular smooth muscle responsible for the release of nitric oxide (NO) from nitroprusside is not well established. In this study we observed that a membrane-bound NADH oxidoreductase in the pulmonary artery activates nitroprusside to release NO, and we examined whether this process could potentially participate in relaxation to nitroprusside. Relaxation to nitroprusside in bovine calf pulmonary artery is inhibited by a scavenger of NO and by an antagonist of NO stimulation of guanylate cyclase. A flavoprotein probe that inhibits pulmonary artery NADH oxidoreductase (1 micromol/L diphenyliodonium) and electron acceptors for NADH oxidoreductase (0.3 mmol/L nitroblue tetrazolium and 0.1 mmol/L ferricyanide) inhibited pulmonary artery relaxation to nitroprusside, but not to nitroglycerin. Pulmonary arteries were observed to promote the release of NO from nitroprusside in vitro, and NO release was inhibited by the presence of nitroblue tetrazolium, ferricyanide, and diphenyliodonium. In homogenates of pulmonary arteries, NADH (0.1 mmol/L) increased the release of NO from nitroprusside by approximately 6-fold, whereas NADPH, mitochondrial substrates, and other redox cofactors had minimal effects on NO release, and the action of NADH on nitroprusside was inhibited by nitroblue tetrazolium, ferricyanide, and diphenyliodonium. A membrane fraction enriched in NADH oxidoreductase activity showed a NADH-dependent release of NO from nitroprusside; nitroprusside caused NADH consumption, and it also inhibited the NADH-dependent reduction of nitroblue tetrazolium. Thus, a membrane-bound NADH oxidoreductase appears to contribute to the release of NO from nitroprusside, but not nitroglycerin, in calf pulmonary artery.

Animals↗
PubMed1999

A flavonoid antioxidant, silymarin, affords exceptionally high protection against tumor promotion in the SENCAR mouse skin tumorigenesis model.

In cancer chemoprevention studies, the identification of better antitumor-promoting agents is highly desired because they may have a wider applicability against the development of clinical cancers. Both epidemiological and animal studies have suggested that microchemicals present in the diet and several herbs and plants with diversified pharmacological properties are useful agents for the prevention of a wide variety of human cancers. Silymarin, a flavonoid isolated from milk thistle, is used clinically in Europe and Asia as an antihepatotoxic agent, largely due to its strong antioxidant activity. Because most antioxidants afford protection against tumor promotion, in this study, we assessed the protective effect of silymarin on tumor promotion in the SENCAR mouse skin tumorigenesis model. Application of silymarin prior to each 12-O-tetradecanoylphorbol 13-acetate (TPA) application resulted in a highly significant protection against tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated mouse skin. The protective effect of silymarin was evident in terms of reduction in tumor incidence (25, 40, and 75% protection, P < 0.001, X2 test), tumor multiplicity (76, 84, and 97% protection, P < 0.001, Wilcoxon rank sum test), and tumor volume (76, 94, and 96% protection, P < 0.001, Student's t test) at the doses of 3, 6, and 12 mg per application, respectively. To dissect out the stage specificity of silymarin against tumor promotion, we next assessed its effect against both stage I and stage II of tumor promotion. Application of silymarin prior to that of TPA in stage I or mezerein in stage II tumor promotion in dimethylbenz(a)anthracene-initiated SENCAR mouse skin resulted in an exceptionally high protective effect during stage I tumor promotion, showing 74% protection against tumor incidence (P < 0.001, X2 test), 92% protection against tumor multiplicity (P < 0.001, Wilcoxon rank sum test), and 96% protection against tumor volume (P < 0.001, Student's t test). With regard to stage II tumor promotion, silymarin showed 26, 63, and 54% protection in tumor incidence, multiplicity, and volume, respectively. Similar effect of silymarin to that in anti-stage I studies, were also observed when applied during both stage I and stage II protocols. In other studies, silymarin significantly inhibited: (a) TPA-induced skin edema, epidermal hyperplasia, and proliferating cell nuclear antigen-positive cells; (b) DNA synthesis; and (c) epidermal lipid peroxidation, the early markers of TPA-caused changes that are associated with tumor promotion. Taken together, these results suggest that silymarin possesses exceptionally high protective effects against tumor promotion, primarily targeted against stage I tumors, and that the mechanism of such effects may involve inhibition of promoter-induced edema, hyperplasia, proliferation index, and oxidant state.

Animals↗
PubMed1999

Sequential production of cytokines by dengue virus-infected human peripheral blood leukocyte cultures.

The study was undertaken to elucidate the sequence of appearance of T helper (Th)1- and Th2-type cytokines in human peripheral blood leucocyte cultures infected in vitro with dengue type 2 virus. Commercial sandwich enzyme-linked immunosorbent assay kits were used to assay the levels of tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, IL-6, and IL-10 in culture supernatants. Culture supernatants were also screened for the cytotoxic factor and the dengue virus titres determined. The cytokines that appeared in the culture supernatants on the first day post-infection (p.i.) were cytotoxic factor, TNF-alpha, IL-2, and IL-6; their levels were highest on the second day p.i. IFN-gamma appeared on the second day with a peak on the third day p.i. The levels of these cytokines declined quickly, except for human cytotoxic factor (hCF) and IL-2. The cytokines that appeared later were IL-10 and IL-5 on the fourth day and IL-4 on the sixth day p.i. Dengue virus replicated in the peripheral blood leucocyte (PBL) cultures and was present throughout the course of the study. The findings of the present study show that dengue virus induced a predominant Th1-type cytokine response during the first 3 days of infection of PBL cultures that was replaced by a Th2-type response later.

Animals↗
PubMed1999

Fas-activated apoptosis and apoptosis mediators in human trabecular meshwork cells.

A gradual loss of cells occurs within the human trabecular meshwork during normal aging and appears to be increased in patients with primary open-angle glaucoma. The exact mechanism by which cells are lost in either condition is not known, however phagocytosis, cell migration and cell death have been suggested. Apoptosis is one method by which cell death can occur. We have examined the modulators for apoptosis within the human trabecular meshwork using both cell lines and ex-vivo dissected trabecular meshwork tissues obtained from normal donors. Using RT-PCR it was shown that mRNA for several modulators of apoptosis (Fas, Bcl-2, Bcl-xl, Bax, and ICE) are expressed by both cell lines and ex-vivo tissues. Apoptosis was stimulated to occur by treating cell lines with a monoclonal antibody (IgM) to Fas. Apoptosis was verified via morphological changes to the cells, transferase-mediated dUTP nick-end labeling TUNEL Immunofluorescence, and DNA laddering. Control cells exposed to IgM did not undergo apoptosis. These results represent the first report of apoptosis modulators within the human trabecular meshwork and demonstrate that human trabecular meshwork cells can be stimulated to undergo apoptosis via the Fas/FasL pathway.

Aged↗
PubMed1999

Transmyocardial laser revascularization: early results and 1-year follow-up.

BACKGROUND: Transmyocardial revascularization using a high-energy CO2 laser has emerged as a new therapeutic option for patients with severe diffuse coronary artery disease refractory to conventional modes of therapy. METHODS: From December 1994 to September 1997, 102 patients underwent isolated transmyocardial revascularization. The mean age was 56.7 +/- 9.2 years and 92.15% were men. Mean preoperative angina class and ejection fraction were 2.6 +/- 0.7 and 44.7% +/- 10.5%, respectively. Diabetes was present in 49.01% of patients, 32.3% had history of previous myocardial infarction, and 12.7% had undergone a previous coronary artery bypass graft procedure. An average number of 23 +/- 8 channels were created in each patient using an 800-W CO2 laser. RESULTS: The early mortality was 14.7% and univariate predictors of mortality were age more than 55 years, female sex, creatine kinase more than 1,600 IU, absence of intercoronary collaterals, and mean pulmonary artery pressure greater than 21 mm Hg. At 1-year follow-up there was significant improvement in angina class and effort tolerance but no significant change in left ventricular ejection fraction. CONCLUSIONS: We conclude that transmyocardial revascularization provides symptomatic benefit and improves exercise tolerance in a group of patients suffering from disabling angina not amenable to other modes of treatment. The high early mortality can be brought down with strict patient selection criteria. The mechanism of beneficial effects is uncertain and patency of laser channels is controversial, but laser-induced neoangiogenesis is being looked on as a possible explanation.

Adult↗
PubMed1999

Role of limited posterior thoracotomy for open-heart surgery in the current era.

BACKGROUND: The earliest open-heart operations were performed employing the thoracotomy approach. Over the years, median sternotomy has become the routine way of approaching the heart. However, lately there has been progressive enthusiasm in minimally invasive techniques for accessing the heart. We present our technique of correction of congenital heart defects employing the limited posterior thoracotomy approach. METHODS: From June 1997 to April 1998, 27 patients underwent correction for various intracardiac defects without any mortality. There were 19 ostium secundum defects, with or without other associated anomalies. There were six sinus venosus defects with partial anomalous pulmonary venous connections. Two patients had perimembranous ventricular septal defects, while 2 patients had partial atrioventricular defects. In 2 other patients, pulmonary stenosis was repaired, using pulmonary valvotomy in 1 patient, whereas the other patient required short transannular patch. RESULTS: The median age was 7 years and the median weight was 20 kg. The median skin-to-skin time was 260 minutes. The median bypass time was 63.25 minutes and the median cross-clamp time was 35.0 minutes. All the patients were extubated within 12 hours following surgery and the median ICU stay was 24 hours. Three patients required blood transfusions in the ICU for significant blood loss and the mean chest drainage was 85 cc per 24 hours. None of the patients had phrenic nerve palsies. None of the patients required additional analgesics other than routine ibuprofen or ketorolac tromethamine. Short-term follow-up revealed no functional or physical disability of the thoracic wall and the right arm. All who underwent surgery with this approach were happy with the limited visibility of their scars. CONCLUSIONS: Limited posterior thoracotomy offers a viable alternative for midsternotomy and submammary thoracotomy. It has the advantage of a scar in the back that does not impede the future growth of the breast tissue and the pectoralis major. Our approach does not need any new instruments and hence no contraptions are necessary to perform the operation with this approach. Our results have shown satisfactory short-term results and better cosmesis.

Adolescent↗
PubMed1999

Role of home blood pressure monitoring in hemodialysis patients.

To investigate the use of manual home blood pressure (BP) monitoring in chronic hemodialysis patients, daily home BPs in 20 patients undergoing chronic hemodialysis were compared with the 44-hour interdialytic ambulatory BPs (ABPs). Each patient recorded home BPs for 2 consecutive weeks with a digital BP monitor three times daily. Prehemodialysis and posthemodialysis BPs were recorded by an oscillometric device in the hemodialysis unit during the same 2 weeks. ABPs were recorded either after the first or second hemodialysis session of the second week during a 44-hour interdialytic period using a Spacelab 90207 ABP monitor. ABP monitoring showed that BP decreased progressively after dialysis, decreased during the first night, and rapidly reached predialysis levels by the next morning. There was no decrease in BP during the second night. There was an excellent correlation between average systolic and diastolic ABP and respective home BPs. Prehemodialysis diastolic BPs were a good reflection of diastolic ABP, but there was more variability in predialysis systolic BP. Posthemodialysis BPs did not correlate with ABP. In patients undergoing chronic hemodialysis, home BPs more reliably reflected the overall BP than incenter BP readings. Predialysis, but not postdialysis, BP should be used as a screening tool to detect hypertension in the hemodialysis unit. Home BP monitoring should be used as a cost-effective means to diagnose occult hypertension in chronic hemodialysis patients.

Adolescent↗
PubMed1999

Monitoring interposition graft venous pressures at higher blood-flow rates improves sensitivity in predicting graft failure.

Monitoring the patency of hemodialysis interposition grafts is recommended to improve graft survival. Which blood flows best predict graft survival is not known. We monitored venous pressures in 32 dialysis patients over a median of 252 days at variable flow rates of the blood pump (Qb). Venous pressure trends (VPTs), maximum venous pressure (MVP), and the variability of venous pressure (percent coefficient of variation) were calculated. Kaplan-Meier curves were constructed from the time of the end of VPT monitoring to time to failure, defined as angioplasty, clotting, or surgical revision. Risk for graft failure for each 10-mm Hg increase in venous pressure was calculated by the Cox proportional hazards model. There were 12 graft failures, but no failures in 12 fistulas over the course of the study. The variability in venous pressure was less at greater Qbs. For grafts, VPTs were predictive of event only when calculated for Qbs greater than 100 mL/min. At Qbs of 400 mL/min, there was a 70% risk for graft failure with each 10-mm Hg increase in VPT. The risk for graft failure increased between 28% and 44% for each 10-mm Hg increase in MVP at all Qbs. MVP of 230 mm Hg at a Qb of 400 mL/min provided the best efficiency of test performance. Dialysis venous chamber pressure monitoring is a useful test to predict graft stenosis or thrombosis. There is a substantial variability in venous pressures in the same patient that reduces with increasing Qbs. Venous pressure monitoring at greater Qbs provides a more sensitive method for predicting access failure.

Arteriovenous Shunt, Surgical↗
PubMed1999

Studies on immunomodulatory activity of Withania somnifera (Ashwagandha) extracts in experimental immune inflammation.

The immunomodulatory activities of an Indian Ayurvedic medicinal preparation, i.e. extracts from Ashwagandha, Withania somnifera (L.) Dunal (Solanaceae), namely WST and WS2, were studied in mice for immune inflammation: active paw anaphylaxis and delayed type hypersensitivity (DTH). Immunomodulatory effect was assessed in If IgE-mediated anaphylaxis as reduction of ovalbumin-induced paw edema, in animals treated with WS2 at doses of 150 and 300 mg/kg, and the results were compared with the standard drug disodium chromoglycate. In the DTH model, the modulatory effect was assessed as potentiation or suppression of the reaction, revealing an increase or decrease in mean foot pad thickness, respectively. Potentiation of the DTH reaction was observed in animals treated with cyclophosphamide at a dose of 20 mg/kg, WST at a dose of 1000 mg/kg and WS2 at a dose of 300 mg/kg. On the other hand, cyclophosphamide-induced potentiation of DTH reaction was suppressed in animals treated with WST and WS2. A significant increase in white blood cell counts and platelet counts was observed in animals treated with WST. A protective effect in cyclophosphamide-induced myelosuppression was observed in animals treated with WST and WS2, revealing a significant increase in white blood cell counts and platelet counts. Cyclophosphamide-induced immunosuppression was counteracted by treatment with WS2, revealing significant increase in hemagglutinating antibody responses and hemolytic antibody responses towards sheep red blood cells.

Adjuvants, Immunologic↗
PubMed1999

Developmental pattern of reactive oxygen species generation and antioxidative defense machinery in rat cerebral microvessels.

The developmental profile of certain enzymatic antioxidants as well as the generation of reactive oxygen species was studied in the rat cerebral microvessels during first three weeks of life and the levels were compared to those present in adults. The data showed a higher generation of superoxide anion (+67%) and H2O2 (+200%) at postnatal day (PND) 21. Superoxide anion production was significantly lower (-24%) at PND 14 and almost comparable to adult values at PND 7. The activity of superoxide dismutase increased with development and attained an adult level at PND 21. Catalase was higher in neonates with a maximum activity at PND 7 and 14 (+68, 69%). The measurement of microvessel glutathione and glutathione-related antioxidant enzymes showed that glutathione level was higher at PND 7, which declined to an adult level at PND 14. Se-dependent GPx showed a marked increase between PND 14 and 21, however, it declined in adults. The activity of Se-independent glutathione peroxidase was very low in cerebral microvessels. Glutathione reductase activity in 7-day-old, that was comparable to adult level, declined at PND 14 and 21. The level of glutathione S-transferase was higher (+43%) at PND 21. The activity of microvessel marker enzyme gamma-glutatmyl transpeptidase increased with age, whereas, alkaline phosphatase showed a slight increase up to PND 14 and thereafter it declined. Lipid peroxidation was found to be significantly lower (-18%) at PND 21 as compared to adults. It may be concluded that developing cerebral microvessels contain high levels of several antioxidant enzymes that are more or equal to those present in adult brain microvessels.

Aging↗
PubMed1999

Metabolic activation of 4H-cyclopenta[def]chrysene in human mammary carcinoma MCF-7 cell cultures.

The tumor initiating activities of 4H-cyclopenta[def]chrysene (C[def]C) and its two putative reactive metabolites, trans-1, 2-dihydroxy-anti-3,3a-epoxy-1,2,3, 3a-tetrahydro-4H-cyclopenta[def]chrysene (C[def]C-3,3a-DE) and trans-6,7-dihydroxy-anti-8,9-epoxy-6,7,8, 9-tetrahydro-4H-cyclopenta[def]chrysene (C[def]C-8,9-DE), were evaluated previously in mice [Amin, S., et al. (1995) Carcinogenesis 16, 2813-2817]. C[def]C-3,3a-DE was the more active inducer of lung tumors and elicited twice as many tumors as C[def]C-8,9-DE. In this study, the route of metabolism of C[def]C to DNA-reactive metabolites in the human mammary carcinoma cell line (MCF-7) was investigated using the 32P-postlabeling assay. The results show that metabolic activation to DNA-binding species proceeds through the formation of both trans-1,2-dihydrodiol and trans-6,7-dihydrodiol metabolites of C[def]C. At a 1 microM dose, adducts from the methylene-bridged (C[def]C-3,3a-DE) and bay region (C[def]C-8,9-DE) dihydrodiol epoxides were detected in comparable amounts. In contrast, the majority of the postlabeled adducts recovered from cells exposed to a 10 microM dose were derived from the bay region dihydrodiol epoxide, C[def]C-8,9-DE. Using markers from reactions of the dihydrodiol epoxides with deoxyguanosine 3'-phosphate and deoxyadenosine 3'-phosphate, it was shown that the major radioactive spots formed with both anti-C[def]C-3,3a-DE and anti-C[def]C-8,9-DE chromatographed with deoxyguanosine adduct markers. Thus, the human cells used in these studies can activate C[def]C to carcinogenic metabolites.

Animals↗
PubMed1999

Primary subcutaneous Nocardia asteroides infection in a renal allograft recipient.

Nocardia asteroides is an important opportunistic pathogen in immunocompromised hosts. The primary infection is usually in the lungs and is followed by dissemination to other parts of the body. Primary subcutaneous infection with Nocardia asteroides has been reported rarely (three reports) and no such case has been reported in a renal transplant recipient. We describe here a case of renal transplant recipient who developed primary subcutaneous infection with Nocardia asteroides within one and half years of the transplantation.

Dermatomycoses↗