Biomedical subjects

M P Gupta

Publications and source records attributed to M P Gupta.

At least 37 records · Page 2Linked to original sources

PubMed2000

Sipandinolide: a butenolide including a novel type of carbon skeleton from Siparuna andina.

From a lipophilic extract of leaves of Siparuna andina (Monimiaceae), which exhibited antiplasmodial activity in vitro, two new compounds have been isolated: sipandinolide (1), a compound with a novel type of carbon skeleton and (-)-cis-3-acetoxy-4',5,7-trihydroxyflavanone (2). Their structures were established by spectroscopic methods; 2 showed moderate antiplasmodial activity whereas 1 was inactive.

Animals↗

PubMed1999

New natural sesquiterpenes as modulators of daunomycin resistance in a multidrug-resistant Leishmania tropica line.

The effects produced by nine dihydro-beta-agarofuran sesquiterpenes isolated from Crossopetalum tonduzii (1-8) and Maytenus macrocarpa (9) (Celastraceae) on the reversion of the resistant phenotype on a multidrug-resistant Leishmania line and their binding to recombinant C-terminal nucleotide-binding domain of Leishmania P-glycoprotein-like transporter were studied. The structures of the new compounds (1-5) were elucidated by spectroscopic methods, including (1)H-(13)C heteronuclear correlation (HMQC), long-range correlation spectra with inversal detection (HMBC), ROESY experiments, and chemical correlations. The absolute configuration of one of them (1) was determined by CD studies. The structure-activity relationship is discussed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

A search for anti-viral properties in Panamanian medicinal plants. The effects on HIV and its essential enzymes.

Aqueous and methanolic extracts of 39 Panamanian medicinal plants were tested for anti-human immunodeficiency virus (HIV) effects. The extracts were tested for the inhibition of HIV-induced cytopathic effects in cultured cells, HIV-reverse transcriptase (RT) and HIV-protease (PR) enzymes. The water extract of the branches of Jatropha curcas (Euphorbiaceae) inhibited strongly the HIV-induced cytopathic effects with low cytotoxicity. On the other hand, the water extracts of the whole plant of Chamaesyce hyssopifolia (Euphorbiaceae), the leaves of Cordia spinescens (Boraginaceae) and the aerial parts of Hyptis lantanifolia (Labiatae), and the methanol extract of the aerial parts of Tetrapteris macrocarpa (Malpighiaceae) were potent inhibitors of HIV-RT (IC50: 6-8 microg/ml). Seven out of 39 plants were found to be moderate inhibitors of HIV-PR (IC50: 43-100 microg/ml). Furthermore, we report on the respective inhibitory substances of J. curcas, C. hyssopifolia and C. spinescens, and their possible mechanism of action.

Anti-HIV Agents↗

PubMed1999

1',2',3',4'-tetradehydrotubulosine, a cytotoxic alkaloid from Pogonopus speciosus.

Bioassay-guided phytochemical investigation of the stems of Pogonopus speciosus, using human oral epidermoid carcinoma (KB) cells as a monitor, led to the isolation of a novel alkaloid, 1',2', 3',4'-tetradehydrotubulosine (1), along with tubulosine (2) and psychotrine (3) as bioactive constituents. The structure of the novel compound was elucidated through 1D- and 2D-NMR spectroscopic methods. Alkaloids 1 and 3 showed weak cytotoxic activity against a panel of human cancer cell lines, with the potency of these compounds being markedly less than that of tubulosine (2).

Alkaloids↗

PubMed1999

Manganese superoxide dismutase in rat liver peroxisomes: biochemical and immunochemical evidence.

By using highly purified peroxisomes from rat liver, we have shown that peroxisomes contain manganese superoxide dismutase (MnSOD) activity and a 23 kDa protein immunoreactive with antibodies against purified mitochondrial MnSOD. Immunocytochemical studies have also revealed immunoreaction (immunogold) with MnSOD antibodies in mitochondria and peroxisomes. Studies of the intraperoxisomal localization of MnSOD have shown that in peroxisomes MnSOD is a component of the peroxisomal limiting membranes and dense core. Furthermore, the MnSOD level in peroxisomes was modulated by oxidative stress conditions such as ischemia-reperfusion or the treatment with ciprofibrate, a peroxisomal proliferator. These findings suggest that MnSOD in peroxisomes may play an important role in the dismutation of superoxide generated on the peroxisomal membrane for keeping the delicate balance of the redox state.

Animals↗

PubMed1999

In vitro antiplasmodial activity of Central American medicinal plants.

The in vitro antiplasmodial activities of 14 plant species traditionally used in Central America for the treatment of malaria or fever were evaluated. Lipophilic extracts of Piper hispidum, Siparuna andina, S. pauciflora, S. tonduziana, and Xylopia cf. frutescens, proved to be active against both a chloroquine-sensitive and a resistant strain of Plasmodium falciparum. IC50 values ranged between 3.0 microg/ml and 21.9 microg/ml; however, moderate cytotoxicity of active extracts was observed. Bioactivity-guided fractionation of Piper hispidum yielded 2',4, 6'-trihydroxy-4'-methoxydihydrochalcone (asebogenin) as an active compound.

Animals↗

PubMed1998

Antifungal and larvicidal meroterpenoid naphthoquinones and a naphthoxirene from the roots of Cordia linnaei.

Three new meroterpenoid naphthoquinones, the known cordiaquinone B and a new naphthoxirene have been isolated from the roots of Cordia linnaei. Their structures were established by spectrometric methods including EI, D/CI and FAB mass spectrometry, 1H, 13C and 2D NMR experiments. The naphthoquinones showed activity against Cladosporium cucumerinum, Candida albicans and the larvae of the yellow fever-transmitting mosquito Aedes aegypti, while the naphthoxirene derivative was found to be inactive in the same bioassays.

Aedes↗

PubMed1998

Antiinflammatory activity of Anthurium cerrocampanense Croat in rats and mice.

Aqueous (AE), ethanol (EE) and dichloromethane (DE) extracts from the whole plant of Anthurium cerrocampanense Croat, endemic to Panama, were assayed for antiinflammatory activity by carrageenan-induced rat paw edema and croton oil-induced mouse ear edema tests. The extracts were administered i.p. and topically, respectively. The best antiinflammatory activity in the carrageenan-induced rat paw edema test, was shown by DE (31% inhibition), which did not show any irritant effect in the peritoneal examination 4 h after administration of the extracts. Furthermore, the highest activity in the croton oil-induced mouse ear edema test was also exhibited by DE (93% inhibition). Since DE was the most effective of the extracts in both tests, it's activity was assessed in various inflammation models in rats. At 100 mg/kg, DE markedly inhibited inflammation produced by dextran (66.6% inhibition) and decreased weakly the edema induced by zymosan A, carrageenan and C16-platelet activation factor (C16-PAF) (33.2, 31.6 and 23.8%, respectively). At 50 mg/kg, DE only significantly reduced the swelling caused by dextran (36.2%). No effect was observed at the same doses in arachidonic acid-induced edema. A clear dose-related antiinflammatory activity of DE was seen in the croton oil-induced mouse ear edema test, and ED50 calculated was found to be 25.5 microg/ear. which was much lower than ED50 obtained for indomethacin (56.1 microg/ear).

Animals↗

PubMed1998

Role of 8-epi PGF2alpha, 8-isoprostane, in H2O2-induced derangements of pulmonary artery endothelial cell barrier function.

The non-enzymatic peroxidation product of arachidonic acid, 8-epi-PGF2alpha or 8-isoprostane (8-IP) was measured in H2O2-exposed cultured pulmonary artery endothelial cell (PAEC) monolayers using a commercially-available enzyme immunoassay kit. H2O2 (50 microM for 1-30 min) significantly increased 8-IP production in a time-dependent fashion. Treatment with higher H2O2 concentrations (100 or 250 microM) failed to further increase 8-IP generation. Determinations of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) were not sufficiently sensitive to detect lipid peroxidation in PAEC exposed to 50 microM H2O2 for 15 min. 8-IP (100 pM-500 nM for 2 h) caused PAEC monolayer barrier dysfunction measured as the transmonolayer clearance of albumin without causing significant PAEC cytotoxicity (measured as intracellular lactate dehydrogenase release). This is the first report to provide evidence that 8-IP generated in H2O2-exposed PAEC contributes to oxidant-mediated alterations in monolayer barrier function at non-cytotoxic concentrations.

Animals↗

PubMed1998

Tissue-restricted expression of the cardiac alpha-myosin heavy chain gene is controlled by a downstream repressor element containing a palindrome of two ets-binding sites.

The expression of the alpha-myosin heavy chain (MHC) gene is restricted primarily to cardiac myocytes. To date, several positive regulatory elements and their binding factors involved in alpha-MHC gene regulation have been identified; however, the mechanism restricting the expression of this gene to cardiac myocytes has yet to be elucidated. In this study, we have identified by using sequential deletion mutants of the rat cardiac alpha-MHC gene a 30-bp purine-rich negative regulatory (PNR) element located in the first intronic region that appeared to be essential for the tissue-specific expression of the alpha-MHC gene. Removal of this element alone elevated (20- to 30-fold) the expression of the alpha-MHC gene in cardiac myocyte cultures and in heart muscle directly injected with plasmid DNA. Surprisingly, this deletion also allowed a significant expression of the alpha-MHC gene in HeLa and other nonmuscle cells, where it is normally inactive. The PNR element required upstream sequences of the alpha-MHC gene for negative gene regulation. By DNase I footprint analysis of the PNR element, a palindrome of two high-affinity Ets-binding sites (CTTCCCTGGAAG) was identified. Furthermore, by analyses of site-specific base-pair mutation, mobility gel shift competition, and UV cross-linking, two different Ets-like proteins from cardiac and HeLa cell nuclear extracts were found to bind to the PNR motif. Moreover, the activity of the PNR-binding factor was found to be increased two- to threefold in adult rat hearts subjected to pressure overload hypertrophy, where the alpha-MHC gene is usually suppressed. These data demonstrate that the PNR element plays a dual role, both downregulating the expression of the alpha-MHC gene in cardiac myocytes and silencing the muscle gene activity in nonmuscle cells. Similar palindromic Ets-binding motifs are found conserved in the alpha-MHC genes from different species and in other cardiac myocyte-restricted genes. These results are the first to reveal a role of the Ets class of proteins in controlling the tissue-specific expression of a cardiac muscle gene.

Animals↗

PubMed1998

H2O2 causes endothelial barrier dysfunction without disrupting the arginine-nitric oxide pathway.

We have previously demonstrated that nitric oxide (.NO) donors attenuate and that inhibition of endogenous nitric oxide synthase (NOS) enhances hydrogen peroxide (H2O2)-mediated porcine pulmonary artery endothelial cell (PAEC) injury. The current study investigates the hypothesis that oxidant-mediated inhibition of NOS contributes to PAEC injury. PAEC barrier function, measured as the transmonolayer clearance of albumin, was significantly impaired by H2O2 (10-100 microM) in the absence of cytotoxicity. Treatment with H2O2 did not alter NOS activity, measured as the conversion of [3H]arginine to [3H]citrulline in PAEC lysates, either immediately after treatment with 0-250 microM H2O2 for 30 min or for up to 120 min after treatment with 100 microM H2O2. H2O2 had little effect on NOS activity in intact PAECs, measured as 1) the formation of [3H]citrulline in [3H]arginine-loaded PAECs, 2) PAEC guanosine 3',5'-cyclic monophosphate content, and 3) PAEC.NO release to the culture media. These results indicate that the arginine-.NO pathway remains intact after exposure to oxidant conditions sufficient to promote functional derangements of vascular endothelial cells.

Animals↗

PubMed1997

Exogenous fatty acids modulate the functional and cytotoxic responses of cultured pulmonary artery endothelial cells to oxidant stress.

We previously reported that supplementation with exogenous fatty acids modulated the susceptibility of cultured pulmonary artery endothelial cells (PAEC) to oxidant-mediated cytotoxicity. The current study investigates the effects of fatty acids with increasing degrees of unsaturation on oxidant-mediated dysfunction and cytotoxicity in cultured porcine pulmonary artery and aortic endothelial cells (AEC). Monolayers supplemented with 0.1 mmol/L oleic (18:1), linoleic (18:2), or gamma-linolenic (18:3) acids were exposed to oxidant stress (100 mumol/L hydrogen peroxide (H2O2)) or to control conditions for 30 minutes. Gas chromatographic analysis of the PAEC fatty acids confirmed incorporation of supplemental fatty acids into PAEC lipids. Cytotoxicity, measured as the release of intracellular lactate dehydrogenase (LDH), and PAEC monolayer barrier function, assessed by measuring the monolayer clearance of Evans blue dye bound to albumin, were determined for 1 to 3 hours after oxidant stress. The PAEC and AEC demonstrated comparable responses to H2O2. Hydrogen peroxide caused increases in monolayer permeability and detachment of cells from the monolayer that were most attenuated by supplementation with 18:2 or 18:3, and to a lesser degree with 18:1. In contrast, H2O2-mediated LDH release was attenuated by supplementation with 18:1, whereas 18:2 and 18:3 potentiated cytotoxicity after exposure to H2O2. These results indicate that the relationship between PAEC lipid composition and oxidant susceptibility is complex and that the extent of fatty acid unsaturation does not predict the functional or cytotoxic responses of PAEC to oxidant stress. Furthermore, these results suggest that functional derangements may not correlate with traditional assays of cytotoxicity induced by oxidant injury in cultured endothelium.

Animals↗

PubMed1997

Transcription enhancer factor 1 interacts with a basic helix-loop-helix zipper protein, Max, for positive regulation of cardiac alpha-myosin heavy-chain gene expression.

The M-CAT binding factor transcription enhancer factor 1 (TEF-1) has been implicated in the regulation of several cardiac and skeletal muscle genes. Previously, we identified an E-box-M-CAT hybrid (EM) motif that is responsible for the basal and cyclic AMP-inducible expression of the rat cardiac alpha-myosin heavy chain (alpha-MHC) gene in cardiac myocytes. In this study, we report that two factors, TEF-1 and a basic helix-loop-helix leucine zipper protein, Max, bind to the alpha-MHC EM motif. We also found that Max was a part of the cardiac troponin T M-CAT-TEF-1 complex even when the DNA template did not contain an apparent E-box binding site. In the protein-protein interaction assay, a stable association of Max with TEF-1 was observed when glutathione S-transferase (GST)-TEF-1 or GST-Max was used to pull down in vitro-translated Max or TEF-1, respectively. In addition, Max was coimmunoprecipitated with TEF-1, thus documenting an in vivo TEF-1-Max interaction. In the transient transcription assay, overexpression of either Max or TEF-1 resulted a mild activation of the alpha-MHC-chloramphenicol acetyltransferase (CAT) reporter gene at lower concentrations and repression of this gene at higher concentrations. However, when Max and TEF-1 expression plasmids were transfected together, the repression mediated by a single expression plasmid was alleviated and a three- to fourfold transactivation of the alpha-MHC-CAT reporter gene was observed. This effect was abolished once the EM motif in the promoter-reporter construct was mutated, thus suggesting that the synergistic transactivation function of the TEF-1-Max heterotypic complex is mediated through binding of the complex to the EM motif. These results demonstrate a novel association between Max and TEF-1 and indicate a positive cooperation between these two factors in alpha-MHC gene regulation.

Animals↗

PubMed1997

Nitric oxide attenuates hydrogen peroxide-mediated injury to porcine pulmonary artery endothelial cells.

To examine the role of nitric oxide (.NO) in vascular endothelial cell injury, cultured porcine pulmonary artery endothelial cells (PAEC) were treated with H2O2 (100-500 microM) for 30 min in the presence or absence of the .NO donors (+/-)S-nitroso-N-acetylpenicillamine (SNAP) or diethylamine nitric oxide (DEANO). H2O2 caused dose-dependent PAEC cytotoxicity detected 2 h after H2O2 treatment as the release of lactate dehydrogenase. SNAP (100 microM) and DEANO (100 microM) attenuated H2O2-induced cytotoxicity if present during H2O2 treatment. In contrast, restricting treatment with .NO donors to periods before (30 min) or after (2 h) incubation with H2O2 did not prevent PAEC injury. Furthermore, the .NO synthase inhibitor NG-nitro-L-arginine methyl ester (1 mM) sensitized PAEC to H2O2-induced injury. SNAP also attenuated H2O2-induced PAEC lipid peroxidation even if restricted to periods before or after exposure to H2O2. Thus, although .NO effectively attenuated H2O2-mediated PAEC lipid peroxidation and cytotoxicity, these effects were clearly dissociated, suggesting that the antiperoxidative effects of .NO are not sufficient to account for its cytoprotective properties.

Animals↗

PubMed1997

Cardiac hypertrophy: old concepts, new perspectives.

Growth of the heart in hypertrophy is accompanied by changes in the phenotypic expression of cardiac genes. To explore the molecular basis of cardiac hypertrophy, we have analyzed the regulation of myosin heavy chain gene (MHC) expression. In one set of experiments, pressure overload on the rat heart was produced by constriction of the abdominal aorta. Changes in the alpha and beta-MHC mRNA were then studied in overloaded hearts and following load removal. Pressure overload resulted in down-regulation of the alpha-MHC with corresponding up-regulation of the steady state level of beta-MHC mRNA. Load removal (debanding) resulted in regression of cardiac hypertrophy and a rapid return of alpha-MHC mRNA to normal values. In contrast, the recovery in beta-MHC mRNA was much slower to the extent that it remained substantially elevated compared to respective sham controls even after 7 weeks of post-debanding. These results suggest that putative load-related signals independently regulate two genes. Several lines of evidence indicate that adrenergic nervous system plays an important role in the induction and maintenance of cardiac hypertrophy and in the redistribution of myosin isoforms. We have analyzed the effect of cAMP inducing agents on the regulation of alpha-MHC gene in primary cultures of the fetal (18 day) rat cardiac myocyte. Inclusion of 8 Br-cAMP in the culture media increased the expression of alpha-MHC promoter/reporter construct comprising of 2.9 kb upstream sequence of the alpha-MHC gene. Several deletion mutations in the alpha-MHC gene promoter defined the cAMP responsive boundaries to be a 32 bp region comprising of -71 to -40 bp sequences. Deletion of this region resulted in loss of cAMP response as well as in basal expression of alpha-MHC promoter/reporter construct. These data suggest a role of beta-adrenergic pathway in the modulation of alpha-MHC gene expression.

Animals↗

PubMed1995

Bioactive anthraquinone glycosides from Picramnia antidesma spp. fessonia.

A bioactivity guided fractionation, using KB cells and brine shrimp assays, of the methanolic extract from the leaves of Picramnia antidesma yielded two known anthraquinones, aloe-emodin and aloe-emodin anthrone, and three new aloe-emodin C-glycosides, named picramnioside A, picramnioside B and picramnioside C. Structures were established by spectroscopic methods (UV, IR, mass spectrometry, 1H and 13C and 2D NMR including COSY 45, HMQC, HMBC and ROESY). CD was used to establish the absolute configuration of the picramniosides.

Animals↗

PubMed1995

Cytotoxic biflavonoids from Selaginella willdenowii.

Bioactivity-guided fractionation of the leaves of Selaginella willdenowii afforded three known biflavones, 4',7"-di-O-methylamentoflavone, isocryptomerin and 7"-O-methylrobustaflavone, that were significantly cytotoxic against a panel of human cancer cell lines. Non-cytotoxic isolates were also obtained, namely, amentoflavone, bilobetin, robustaflavone and 2",3"-dihydroisocryptomerin, a new dihydrobiflavone. The structure for the new biflavonoid was unambiguously assigned by a combination of spectroscopic methods.

Antineoplastic Agents↗

PubMed1995

Xanthine oxidase inhibitory activity of some Panamanian plants from Celastraceae and Lamiaceae.

Thirty four crude extracts of Panamanian plants, from nine species of Celastraceae and Lamiaceae, were assayed for xanthine oxidase (XO) inhibitory activity. The enzymatic activity was estimated by measuring the increase in absorbance at 290 nm due to uric acid formation. Eighty five percent of the crude extracts were found to possess XO inhibitory activity at 50 micrograms/ml and all the extracts of the species from Lamiaceae were active even at 1 micrograms/ml. The ethanol extracts of Hyptis obtusiflora Presl ex Benth. (Lamiaceae) and H. lantanaefolia Poit. (Lamiaceae) exhibited the highest activity with an inhibition of approximately 40% at 1 micrograms/ml.

Ethanol↗