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Biomedical subjects

P Mohanty

Publications and source records attributed to P Mohanty.

At least 19 recordsLinked to original sources
PubMed2006

Kinetics and mechanism of reduction of ferricytochrome c by glutathione and L-cysteine: a comparative study.

The kinetics and mechanism of the reduction of ferricytochrome c [Cyt c(III)] by substrates namely glutathione (GSH) and L-cysteine (L-cys) have been investigated spectrophotometrically employing [substrate]T >> [Cyt c(III)]T. The reaction exhibits first order dependence in [substrate]T and [Cyt c(III)]T. The pseudo-first order rate constant increases with an increase in pH, indicating that the conjugate base form of the HCyt c(III) is a better oxidant than the parent HCyt c(III). The electron transfer rate constants between the oxidants and GSH for both the k1 and k2 paths are found to be greater than that with L-cysteine. Hence, GSH is a better reductant of Cyt c(III) as compared to L-cysteine. A suitable mechanism has been proposed on the basis of experimental findings. The deprotonation constant for HCyt c(III) and the second order rate constants of k1 and k2 paths for the present reaction at 25 degrees C have been determined.

Animals↗
PubMed2004

Novel mode of resistance to Fusarium infection by a mild dose pre-exposure of cadmium in wheat.

Exposure of healthy wheat seeds (Triticum aestivum var Sonalika) to mild dose of cadmium (Cd(2+)) given as 50 microM CdCl(2) for 48 h and then washed off Cd(2+) offered resistance to the subsequent infection by Fusarium oxysporum inoculum. Seven days old seedlings having two primary leaves were aseptically inoculated with fungus, F. oxysporum (1 x 10(6)) spores. The seedlings pre-exposed to low level of Cd(2+) survived the Fusarium infection, while plantlets without Cd(2+) stress wilted and then perished due to Fusarium infection. The stress associated proteins induced by Cd(2+) (50 microM), F. oxysporum and by the co-stress (50 microM Cd(2+) and then with F. oxysporum) treatments were observed to be of same molecular weight (51 kDa). Antibody was raised against the purified Cd(2+)-stress associated protein (CSAP). Immuno-gold labeling of wheat seedling root tissue showed the presence of this CSAP in Cd(2+) pre-exposed and in co-stressed tissues and to be located predominantly on the inner linings of the cell membranes. We also observed that the anti-CSAP-antibody also labeled the root tissue of only Fusarium inoculated seedlings and the gold labeling was intensely located on the membrane. This cross-reaction of anti-CSAP suggests that Fusarium-induced stress protein (FISP) possibly has close homology to CSAP. We thus show for the first time the over expression of a high molecular mass protein by mild dose of Cd(2+) pre-exposure to wheat seeds which subsequently provided protection against Fusarium infection. This mode of resistance developed by an abiotic stress-causing agent against pathogen infection is novel.

Blotting, Western↗
PubMed2003

High-field measurements of electron decoherence time in metallic nanowires: switching off magnetic impurity spins.

We report low-temperature measurements of electron decoherence time in a series of pure gold wires, 18 nm thick and 30 nm wide. At fields up to 15 T, large enough to polarize any concentration of magnetic impurity spins, conductance fluctuation measurements show almost no temperature dependence of the decoherence time below 300 mK, both in the correlation field for interference and the root-mean-square value of the fluctuations. Combined with previous low-field weak localization measurements on samples from similar material, our experiment suggests that the ubiquitous saturation of decoherence time in these samples is not due to any mechanism based on magnetic impurity spins.

Journal Article↗
PubMed2002

Transgenics of an elite indica rice variety Pusa Basmati 1 harbouring the codA gene are highly tolerant to salt stress.

Transgenic lines of indica rice were generated by Agrobacterium-mediated transformation with the choline oxidase ( codA) gene from Arthrobacter globiformis. Choline oxidase catalyses conversion of choline to glycine betaine. Glycine betaine is known to provide tolerance against a variety of stresses. Molecular analyses of seven independent transgenic lines as performed by Southern, Northern and Western hybridization revealed integration and expression of the transgene as well as inheritance in the progeny plants. A good correlation was observed between levels of mRNA and protein accumulation, and a significant amount of choline oxidase product, i.e. glycine betaine, accumulated in R0 as well as R1 plants. Mendelian as well as non-Mendelian segregation patterns were obtained in the progeny plants. Challenge studies performed with R1 plants by exposure to salt stress (0.15 M NaCl) for 1 week, followed by a recovery period, revealed that in some cases more than 50% of the transgenic plants could survive salt stress and set seed whereas wild-type plants failed to recover.

Betaine↗
PubMed2002

Comparative evaluation of adjunctive oral irrigation in diabetics.

AIM: The purpose of this study was to assess the response of diabetics to scaling and root planing treatment and subgingival oral irrigation as adjunctive therapy. METHOD: A total of 52 type 1 and 2 diabetics (mean age 51.3+/-14) with adult periodontitis were randomized to two groups. Treatment included ultrasonic scaling and scaling and root planing in both groups (control and test) plus subgingival water irrigation 2x daily for the test group. Assessments were made prior to and at 6 and 12 weeks after treatment. Parameters measured were modified gingival index (MGI), probing pocket depth (PPD), plaque index (PI), clinical attachment level (CAL), and bleeding on probing (BOP). Systemic measurement of Reactive Oxygen Species (ROS) generation, cytokines (TNF-alpha, IL-1beta, IL-10, and PGE2), and glycated hemoglobin (HbA1C). RESULTS: After treatment, analysis of data showed that both groups had clinical and systemic improvement. The test group had a statistically significant reduction for MGI, PI, and BOP compared to controls (p<0.03) at 12 weeks and for ROS generation at 12 weeks (p<0.012). Unlike controls, systemic analysis of cytokines showed a statistically significant reduction from baseline for IL-1beta at 6 weeks and PGE2 at 6 and 12 weeks (p<0.05) within test group. CONCLUSION: These results suggest that scaling and root planing and adjunctive therapy may be of value in establishing a healthy periodontium in diabetics.

Adolescent↗
PubMed2001

Diamagnetic persistent current in diffusive normal-metal rings.

We have measured a diamagnetic persistent current with flux periodicities of both h/e and h/2e in an array of thirty diffusive mesoscopic gold rings. At the lowest temperatures, the magnitudes of the currents per ring corresponding to the h/e- and h/2e-periodic responses are both comparable to the Thouless energy E(c) identical with Planck's over 2pi/tau(D), where tau(D) is the diffusion time. Taken in conjunction with earlier experiments, our results strongly challenge the conventional theories of persistent current. We consider a new approach associated with the saturation of the phase coherence time tau(phi).

Journal Article↗
PubMed2001

Effect of proline on the production of singlet oxygen.

Molecular oxygen in electronic singlet state is a very powerful oxidant. Its damaging action in a variety of biological processes has been well recognized. Here we report the singlet oxygen quenching action of proline. Singlet oxygen (1O2) was produced photochemically by irradiating a solution of sensitiser and detected by following the formation of stable nitroxide radical yielded in the reaction of 1O2 with the sterically hindered amine (2,2,6,6-tetramethylpiperidine, TEMP). Illumination of a sensitiser, toluidine blue led to a time dependent increase in singlet oxygen production as detected by the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) by EPR spectrometry. Interestingly, the production of TEMPO was completely abolished by the presence of proline at concentration as low as 20mM. These results show that proline is a very effective singlet oxygen quencher. Other singlet oxygen generating photosensitizer like hematopophyrin and fluorescein also produced identical results with proline. Since proline is one of the important solutes which accumulate in many organisms when they are exposed to environmental stresses, it is likely that proline accumulation is related to the protection of these organisms against singlet oxygen production during stress conditions. A possible mechanism of singlet oxygen quenching by proline is discussed.

Antioxidants↗
PubMed2001

Senescence induced structural reorganization of thylakoid membranes in Cucumis sativus cotyledons; LHC II involvement in reorganization of thylakoid membranes.

We report the formation and appearance of loosely stacked extended grana like structures along with plastoglobuli in the chloroplasts isolated from 27-day old senescing cucumber cotyledons. The origin and the nature of these extended grana structures have not been elucidated earlier. We isolated Photosystem I complexes from 6-day-old control and 27-day-old senescing cotyledons. The chlorophyll a/b ratio of the isolated Photosystem I complex obtained from 6-day cotyledons was 5-5.5 as against a ratio of 2.9 was found in Photosystem I complexes obtained from 27-day-old senescing cotyledons. We also found that the presence of LHC II in the Photosystem I complexes isolated from 27-day cotyledonary chloroplasts. The presence of LHC II in Photosystem I complexes in senescing and not in control samples, clearly suggest the detachment and diffusion of LHC II complexes from stacked grana region to Photosystem I enriched stroma lamellar region thereby, forming loose disorganized extended grana structures seen in the transmission electron microscope. Furthermore, we show that under in vitro condition the senescing cotyledon chloroplasts exhibited lower extent of light induced phosphorylation of LHC II than the control samples suggesting a possible irreversible phosphorylation and diffusion of LHC II in vivo during the progress of senescence in Cucumis cotyledons. From these findings, we suggest that the senescence induced phosphorylation of LHC II and its migration towards Photosystem I may be a programmed one some how causing the destruction of the thylakoid membrane. The released membrane components may be stored in the plastoglobuli prior to their mobilization to the younger plant parts.

Journal Article↗
PubMed2001

Acute suppressive effect of hydrocortisone on p47 subunit of nicotinamide adenine dinucleotide phosphate oxidase.

We have recently demonstrated that reactive oxygen species (ROS) generation by polymorphonuclear leukocytes (PMNL) and mononuclear cells (MNC) is inhibited following the intravenous administration of hydrocortisone. This is associated with a parallel decrease in intranuclear NFkappaB, known to modulate inflammatory responses including ROS generation. We have also shown that the plasma levels of interleukin-10 (IL-10), an anti-inflammatory and immunosuppressive cytokine produced by TH2 cells, are also increased after hydrocortisone administration. In this study, we have investigated the effect of hydrocortisone on p47(phox) subunit, a key component of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, in MNC and the pharmacodynamics of this effect with ROS generation and plasma IL-10 levels. p47(phox) subunit protein levels in MNC showed a progressive decrease after hydrocortisone administration. It reached a nadir at 4 hours and increased thereafter to a baseline level at 24 hours. ROS generation also decreased, reached a nadir between 2 and 4 hours, and returned to a baseline level at 24 hours. IL-10 concentrations increased, peaked at 4 hours, and reverted to the baseline levels at 24 hours. In conclusion, p47(phox) subunit suppression may contribute to the inhibition of ROS generation in MNC after hydrocortisone administration. This suppression occurs in parallel with the suppression of NFkappaB and an increase in IL-10 plasma levels. Therefore, it would appear that the decrease in intranuclear NFkappaB and an increase in IL-10 may cause the inhibitory modulation on p47(phox) subunit and ROS generation by MNC following hydrocortisone and other glucocorticoids.

Adult↗
PubMed2001

The suppressive effect of dietary restriction and weight loss in the obese on the generation of reactive oxygen species by leukocytes, lipid peroxidation, and protein carbonylation.

Increased reactive oxygen species generation by the leukocytes of the obese may be responsible for increased oxidative injury to lipids and proteins and, hence, atherosclerosis. We have investigated whether reactive oxygen species generation by leukocytes and other indexes of oxidative damage in the body fall with short-term dietary restriction and weight loss. Nine nondiabetic obese subjects (body mass index, 32.5-64.4 kg/m(2)), not taking any antioxidants, were put on a 1000-Cal diet. Fasting blood samples were taken at 0, 1, 2, 3, and 4 weeks and at 12 weeks after the cessation of dietary restriction. Blood samples were also obtained at 1 and 2 h after administration of 75 g oral glucose at 0 and 4 weeks. Mononuclear cells (MNC) and polymorphonuclear leukocytes (PMN) were isolated, and reactive oxygen species generation was measured. Plasma concentrations of thiobarbituric acid-reactive species (TBARS), 13-hydroxyoctadecadienoic acid (13-HODE), 9-hydroxyoctadecadienoic acid (9-HODE), carbonylated proteins, o-tyrosine, and m-tyrosine as indexes of oxidative damage to lipids, proteins and amino acids, respectively, were measured. Antioxidant vitamins were measured as indexes of antioxidant reserves. Plasma tumor necrosis factor-alpha concentrations were also measured. Mean weight loss was 2.4 +/- 0.6 kg at week 1, 2.5 +/- 1.7 kg at week 2, 3.9 +/- 0.8 kg at week 3, and 4.5 +/- 2.8 kg at week 4 (P < 0.05). Reactive oxygen species generation by PMN fell from 236.4 +/- 95.8 to 150.9 +/- 69.0, 125.9 +/- 24.3, 96.0 +/- 39.9, and 103.1 +/- 35.7 mV at weeks 1, 2, 3, and 4, respectively (P < 0.001). It increased 3 months after the cessation of dietary restriction to 270.0 +/- 274.3 mV. Reactive oxygen species generation by MNC fell from 187.8 +/- 75.0 to 101.7 +/- 64.5, 86.9 +/- 42.8, 63.8 +/- 14.3, and 75.1 +/- 32.2 mV and increased thereafter to 302.0 +/- 175.5 mV at 1, 2, 3, 4, and 16 weeks, respectively (P < 0.005). Reactive oxygen species generation by PMN and MNC increased in response to glucose; the relative increase was greater at 4 weeks than that at week 0 due to a fall in the basal levels of reactive oxygen species generation. Consistent with the fall in reactive oxygen species generation, there was a reduction in plasma TBARS from 1.68 +/- 0.17 micromol/L at week 0 to 1.47 micromol/L at 4 weeks (P < 0.05). The 13-HODE to linoleic acid ratio fell from a baseline of 100% to 56.4 +/- 36.1% at 4 weeks (P < 0.05), and the 9-HODE to linoleic acid ratio fell from a baseline of 100% to 60.5 +/- 37.7% at 4 weeks (P < 0.05). Carbonylated proteins fell from 1.39 +/- 0.27 microgram/mg protein at week 0 to 1.17 +/- 0.12 microgram/mg protein at week 4 (P < 0.05); o-tyrosine fell from 0.42 +/- 0.03 mmol/mol phenylalanine at week 0 to 0.36 +/- 0.02 mmol/mol phenylalanine at 4 weeks (P < 0.005), and m-tyrosine fell from 0.45 +/- 0.04 mmol/mol phenylalanine at week 0 to 0.40 +/- 0.03 mmol/mol phenylalanine at 4 weeks (P < 0.05). The basal concentrations of TBARS, 9-HODE, 13-HODE, carbonylated proteins, o-tyrosine, and m-tyrosine in the obese were significantly greater than those in normal subjects. On the other hand, tumor necrosis factor-alpha concentrations did not change during this 4-week period, nor was there any change in antioxidant vitamins. This is the first demonstration of 1) an increase in reactive oxygen species-induced damage in lipids, proteins, and amino acids in the obese compared with normal subjects; and 2) a decrease in reactive oxygen species generation by leukocytes and oxidative damage to lipids, proteins, and amino acids after dietary restriction and weight loss in the obese over a short period.

Adult↗
PubMed2001

Hydrocortisone suppresses intranuclear activator-protein-1 (AP-1) binding activity in mononuclear cells and plasma matrix metalloproteinase 2 and 9 (MMP-2 and MMP-9).

Having demonstrated recently that hydrocortisone (HC) suppresses intranuclear and total cellular nuclear factor-kappa B (NF-kappa B) and increases inhibitor kappa B (I kappa B) in mononuclear cells (MNC), in vivo, we have now investigated the effect of hydrocortisone on the other major pro-inflammatory transcription factor, AP-1 and the two proteins, MMP-2 and MMP-9, whose transcription is modulated by it. MMP's hydrolyze extracellular matrix proteins and thus, allow the spread of inflammation. HC (100 mg) was given intravenously to eight normal subjects following an overnight fast. Blood samples were obtained at 0, 1, 2, 4, 8 and 24 h. MNC were separated and the nuclear fractions and cellular homogenates were prepared by standard techniques. AP-1 binding activity was measured by electrophoretic mobility shift assay (EMSA). Plasma MMP-2 and MMP-9 were measured by ELISA. AP-1 binding activity fell significantly at 1, 2, 4 and 8 h. Plasma MMP-2 concentration also decreased significantly at 1, 2, 4 and 8 h while MMP-9 decreased at 1 and 2 h. These data demonstrate that the acute anti-inflammatory effect of HC, in vivo, is, in part, due to AP-1 suppression and a reduction in MMP-2 and MMP-9. Thus, HC may reduce the extracellular spread of inflammation through the inhibition of matrix metalloproteinases.

Adult↗
PubMed2001

Suppression of nuclear factor-kappaB and stimulation of inhibitor kappaB by troglitazone: evidence for an anti-inflammatory effect and a potential antiatherosclerotic effect in the obese.

To elucidate whether troglitazone exerts an antiinflammatory effect in humans, in vivo, we investigated the suppression of nuclear factor kappaB (NFkappaB) in mononuclear cells (MNC) by this drug. We measured intranuclear NFkappaB, total cellular NFkappaB, inhibitor kappaB (IkappaB)alpha, reactive oxygen species (ROS) generation, and p47(phox) subunit (a key component protein of nicotinamide adenine dinucleotide phosphate oxidase) in MNC. Plasma tumor necrosis factor (TNF)-alpha, soluble intercellular adhesion molecule-1 (sICAM-1), monocyte chemoattractant protein-1 (MCP-1), plasminogen activator inhibitor type 1 (PAI-1), C-reactive protein (CRP), and interleukin (IL)-10 (antiinflammatory cytokine) concentrations were also measured as mediators of inflammatory activity that are regulated by the proinflammatory transcription factor NFkappaB. Seven nondiabetic obese patients were given 400 mg troglitazone daily for 4 weeks. Blood samples were collected before and at weekly intervals thereafter. MNC were separated; and the levels of intranuclear NFkappaB, total cellular NFkappaB, IkappaBalpha, and p47 (phox) subunit and ROS generation were determined. Plasma was used to measure insulin glucose, TNFalpha, sICAM, MCP-1, PAI-1, CRP, and IL-10. Plasma insulin concentrations fell significantly at week 1, from 31.2 +/- 29.1 to 14.2 +/- 11.4 mU/L (P < 0.01) and remained low throughout 4 weeks. Plasma glucose concentrations did not alter significantly. There was a fall in intranuclear NFkappaB, total cellular NFkappaB, and p47 (phox) subunit, with an increase in cellular IkappaBalpha at week 2, which persisted until week 4. There was a parallel fall in ROS generation by MNC at week 1; this progressed and persisted until week 4 (P < 0.001). Plasma TNF-alpha, sICAM-1, MCP-1, and PAI-1 concentrations fell significantly at week 4. Plasma IL-10 concentration increased significantly, whereas plasma CRP concentrations decreased. We conclude that troglitazone has an antiinflammatory action that may contribute to its putative antiatherosclerotic effects.

Adult↗
PubMed2001

Inhibitory effect of a two day fast on reactive oxygen species (ROS) generation by leucocytes and plasma ortho-tyrosine and meta-tyrosine concentrations.

ABSTRACT Since glucose intake acutely increases reactive oxygen species (ROS) generation by polymorphonuclear leucocytes (PMN) and mononuclear cells (MNC), we have now investigated whether a fast over a period of 48h reduces ROS generation by these cells. Eight normal subjects were fasted for 48h. Blood samples were obtained at 0, 24h and 48h. ROS generation by PMN fell significantly at 24h (66.1 +/- 19.5% of basal) and further at 48h (45.9 +/- 23.0 % of basal; p < 0.001). ROS generation by MNC fell to 62.4 +/- 16.5% at 24h and by 48.4 +/- 16.5% (p < 0.001) by 48h. The level of p47(phox) subunit, an index of NADPH oxidase, the enzyme converting molecular oxygen to superoxide (O(.)(2)(-)) radical, also fell in parallel. Plasma o-tyrosine/phenylalanine ratio fell significantly from 0.326 +/- 0.053 mmol/mol to 0.303 +/- 0.055 mmol/mol at 48h and m-tyrosine/phenylalanine ratio fell from 0.363 +/- 0.063 mmol/mol to 0.340 +/- 0.064 mmol/mol (p < 0.05). Thus, a 48h fast may reduce ROS generation, total oxidative load and oxidative damage to amino acids.

Adult↗
PubMed2001

Nuclear factor-kappaB suppressive and inhibitor-kappaB stimulatory effects of troglitazone in obese patients with type 2 diabetes: evidence of an antiinflammatory action?

It has been shown recently that troglitazone exerts an anti-inflammatory effect, in vitro, and in experimental animals. To test these properties in humans, we investigated the effect of troglitazone on the proinflammatory transcription factor nuclear factor-kappaB and its inhibitory protein IkappaB in mononuclear cells (MNC) and plasma soluble intracellular adhesion molecule-1, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, and C-reactive protein. We also examined the effect of troglitazone on reactive oxygen species generation, p47(phox) subunit expression, 9-hydroxyoctadecadienoic acid (9-HODE), 13-HODE, o-tyrosine, and m-tyrosine in obese patients with type 2 diabetes. Seven obese patients with type 2 diabetes were treated with troglitazone (400 mg/day) for 4 weeks. Blood samples were obtained at weekly intervals. Nuclear factor-kappaB binding activity in MNC nuclear extracts was significantly inhibited after troglitazone treatment at week 1 and continued to be inhibited up to week 4. On the other hand, IkappaB protein levels increased significantly after troglitazone treatment at week 1, and this increase persisted throughout the study. Plasma monocyte chemoattractant protein-1 and soluble intracellular adhesion molecule-1 concentrations did not decrease significantly after troglitazone treatment, although there was a trend toward inhibition. Reactive oxygen species generation by polymorphonuclear cells and MNC, p47(phox) subunit protein quantities, plasminogen activator inhibitor-1, and C-reactive protein levels decreased significantly after troglitazone intake. 13-HODE/linoleic acid and 9-HODE/linoleic acid ratios also decreased after troglitazone intake. However, o-tyrosine/phenylalanine and m-tyrosine/phenylalanine ratios did not change significantly. These data show that troglitazone has profound antiinflammatory effects in addition to antioxidant effects in obese type 2 diabetics; these effects may be relevant to the recently described beneficial antiatherosclerotic effects of troglitazone at the vascular level.

Adult↗
PubMed2001

Insulin inhibits intranuclear nuclear factor kappaB and stimulates IkappaB in mononuclear cells in obese subjects: evidence for an anti-inflammatory effect?

In view of the fact that insulin resistance is associated with atherogenesis and that troglitazone, an insulin sensitizer, has anti-inflammatory effects, which may be potentially antiatherogenic in the long term, we have now investigated whether insulin has potential anti-inflammatory effects. We infused 2.0 to 2.5 IU/h in 5% dextrose (100 mL/h) iv into 10 obese subjects for 4 h followed by 5% dextrose alone for 2 h. The rate of insulin infusion was varied to maintain glucose concentrations as close to the baseline as possible. Blood samples were obtained before and at 2, 4, and 6 h. Subjects were also infused with 5% dextrose without insulin and with saline on separate occasions. Intranuclear nuclear factor kappaB (NFkappaB) in mononuclear cells fell at 2 and further at 4 h, reverting toward the baseline at 6 h (P < 0.05). IkappaB increased significantly at 2 h, increasing further at 4 h and remaining elevated at 6 h (P < 0.001). Reactive oxygen species (ROS) generation by mononuclear cells fell significantly at 2 h and fell further at 4 h; it partially reverted to baseline at 6 h (P < 0.005). p47(phox) subunit, the key protein of nicotinamide adenine dinucleotide phosphate oxidase also fell at 2 h and 4 h, reverting toward the baseline at 6 h (P < 0.05). In addition, soluble intercellular adhesion molecule-1 (sICAM-1), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1) fell significantly following insulin infusion. Glucose or saline infusions without insulin caused no alteration in NFkappaB, IkappaB, ROS generation, p47(phox) subunit, sICAM-1, MCP-1, or PAI-1. We conclude that insulin has a potent acute anti-inflammatory effect including a reduction in intranuclear NFkappaB, an increase in IkappaB, and decreases in ROS generation, p47(phox) subunit, plasma soluble intercellular adhesion molecule-1 (sICAM-1), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1. This acute anti-inflammatory effect, if demonstrated in the long term, may have implications for atherosclerosis and its complications.

Adult↗
PubMed2001

Troglitazone reduces the expression of PPARgamma while stimulating that of PPARalpha in mononuclear cells in obese subjects.

We have recently demonstrated that troglitazone exerts an anti-inflammatory effect in the insulin resistant obese in vivo in parallel with its insulin-sensitizing effect. Because these effects are thought to be mediated through peroxisome proliferator-activated receptors alpha and gamma (PPARalpha and PPARgamma), we have now examined the possibility that troglitazone may modulate the expression of PPARalpha and PPARgamma. Seven obese hyperinsulinemic subjects were administered 400 mg troglitazone daily for 4 weeks. Fasting blood samples were obtained before and during troglitazone therapy at 1, 2, and 4 weeks. Fasting insulin concentrations fell at week 1 and persisted at lower levels till 4 weeks. PPARgamma expression fell significantly at week 1 and fell further at weeks 2 and 4. In contrast, PPARalpha expression increased significantly at week 2 and further at week 4. 9- and 13-hydroxyoctadecanoic acid, products of linoleic acid peroxidation and agonists of PPARgamma, decreased during troglitazone therapy. We conclude that troglitazone, an agonist for both PPARalpha and PPARgamma, has significant but dramatically opposite effects on PPARalpha and PPARgamma. These effects may be relevant to its insulin sensitizing and anti-inflammatory effects.

Adult↗
PubMed2001

Characterization of high temperature induced stress impairments in thylakoids of rice seedlings.

Exposure of isolated thylakoids or intact plants to elevated temperature is known to inhibit photosynthesis at multiple sites. We have investigated the effect of elevated temperature (40 degrees C) for 24 hr in dark on rice seedlings to characterize the extent of damage by in vivo heat stress on photofunctions of photosystem II (PSII). Chl a fluorescence transient analysis in the intact rice leaves indicated a loss in PSII photochemistry (Fv) and an associated loss in the number of functional PSII units. Thylakoids isolated from rice seedlings exposed to mild heat stress exhibited >50% reduction in PSII catalyzed oxygen evolution activity compared to the corresponding control thylakoids. The ability of thylakoid membranes from heat exposed seedlings to photooxidize artificial PSII electron donor, DPC, subsequent to washing the thylakoids with alkaline Tris or NH2OH was also reduced by approximately 40% compared to control Tris or NH2OH washed thylakoids. This clearly indicated that besides the disruption of oxygen evolving complex (OEC) by 40 degrees C heat exposure for 24 hr, the PSII reaction centers were impaired by in vivo heat stress. The analysis of Mn and manganese stabilizing protein (MSP) contents showed no breakdown of 33 kDa extrinsic MSP and only a marginal loss in Mn. Thus, we suggest that the extent of heat induced loss of OEC must be due to disorganization of the OEC complex by in vivo heat stress. Studies with inhibitors like DCMU and atrazine clearly indicated that in vivo heat stress altered the acceptor side significantly. [14C] Atrazine binding studies clearly demonstrated that there is a significant alteration in the QB binding site on D1 as well as altered QA to QB equilibrium. Thus, our results show that the loss in PSII photochemistry by in vivo heat exposure not only alters the donor side but significantly alters the acceptor side of PSII.

Atrazine↗