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Biomedical subjects

K Lalitha

Publications and source records attributed to K Lalitha.

At least 19 recordsLinked to original sources
PubMed2006

Selective determination of mimosine and its dihydroxypyridinyl derivative in plant systems.

Our observations on the growth stimulatory nature of mimosine, (beta-(3-hydroxy-4-pyridon-1-yl)-L-alanine), the toxic non-protein plant amino acid, in some model experimental systems, warranted sensitive and selective routine estimations. For the determination of both mimosine and DHP, an indirect spectrophotometric method was developed based on their individual reaction with known excess of DZSAM and by estimating the remaining DZSAM with N-(1-naphthyl)ethylene-diamine (NEDA). The resultant decrease in the secondary coupled product was measured at 540 nm. On equimolar basis, DHP had 40% of the reactivity of mimosine while interference from other relevant compounds was 15-35%. The determination of mimosine and DHP in tissue samples under different physiological conditions was effected after paper chromatographic separation of mimosine and DHP with distinctly differing Rf, from other compounds. The indirect method is superior in terms of absolute selectivity, sensitivity and ease of applicability with linear decreases in absorbance, proportional to increasing concentrations of mimosine from 0.1 to 0.75 microM or DHP from 0.2 to 1.5 microM and with recoveries of 99.2 to 100.5%.

Calibration↗
PubMed2003

Metabolic characteristics of an aerobe isolated from a methylotrophic methanogenic enrichment culture.

An anaerobic methylotrophic methanogenic enrichment culture, with sustained metabolic characteristics, including that of methanation for over a decade, was the choice of the present study on interspecies interactions. Growth and methanation by the enrichment were suppressed in the presence of antibiotics, and no methanogen grown on methanol could be isolated using stringent techniques. The present study confirmed syntrophic metabolic interactions in this enrichment with the isolation of a strain of Pseudomonas sp. The organism had characteristic metabolic versatility in metabolizing a variety of substrates including alcohols, aliphatic acids, amino acids, and sugars. Anaerobic growth was favoured with nitrate in the growth medium. Cells grown anaerobically with methanol, revealed maximal nitrate reductase activity. Constitutive oxidative activity of the membrane system emerged from the high-specific oxygen uptake and nitrate reductase activities of the aerobically and anerobically grown cells respectively. Cells grown anaerobically on various alcohols effectively oxidized methanol in the presence of flavins, cofactor FAD and the methanogenic cofactor F420, suggesting a constitutive alcohol oxidizing capacity. In cells grown anaerobically on methanol, the rate of methanol oxidation with F420 was three times that of FAD. Efficient utilization of alcohols in the presence of F420 is a novel feature of the present study. The results suggest that utilization of methanol by the mixed culture would involve metabolic interactions between the Pseudomonas sp. and the methanogen(s). Methylotrophic, methanogenic partnership involving an aerobe is a novel feature hitherto unreported among anaerobic syntrophic associations and is of ecological significance

Euryarchaeota↗
PubMed2001

Use of DNA markers in prediction of hybrid performance and heterosis for a three-line hybrid system in rice.

Two Cytoplasmic Male Sterile lines were crossed with fourteen restorer lines of rice widely grown in the western regions of Maharashtra, India, to produce 28 F1 hybrids which were evaluated for eight agronomically important traits, contributing to yield potential, in replicated field trials. The hybrid performance was recorded along with heterosis and heterobeltiosis. All the rice lines under investigation were subjected to marker-based variability analysis. An attempt was made to correlate genetic distance based on specific markers for each trait individually, as well as average genetic distance based on all specific markers, with hybrid performance and heterosis, by regression analysis. Specific markers could cluster the parental lines in different groups and showed significant correlation with hybrid performance. The data also supports the proposition that epistasis is the basis of heterosis. The analysis, however, revealed a lack of significant predictive values for field application.

Cluster Analysis↗
PubMed2001

Kinetic analyses of mitochondrial 75selenium uptake in Trigonella foenum-graecum seedlings exposed to selenium and mimosine.

Uptake of (75Se) added in vitro was followed in mitochondria isolated from Trigonella foenum-graecum seedlings grown under different Se status (0.5-1.0 ppm) and with added mimosine (0.1 mM). Uptake of 75Se followed with added Na2 75SeO3 upto 20 microM in the medium was nonlinear in all the groups. Kinetic analyses of the uptake of 75Se for 1 min were carried out for all the groups. The results indicated a cooperative effect during Se transport. Graphical analyses using the Hill plot and Scatchard plot confirmed the existence of negative cooperativity during 75Se uptake. Scatchard plots were biphasic, suggesting the probable presence of two classes of binding sites. The presence of succinate or ATP in the incubation medium inhibited 75Se uptake by 40%. Studies with mitochondrial respiratory inhibitors indicated the uptake to be energy independent. A decrease in the uptake of 75Se by 40% effected by HgCl2, N-ethyl maleimide, and iodoacetate confirmed the interaction of active thiols in the process. The present study confirms the controlled nature of 75Se uptake by plant mitochondria.

Germination↗
PubMed2001

Uptake of 45Ca by mitochondria of Trigonella foenum-graecum as influenced by selenium and mimosine--detailed kinetic analyses.

Mitochondria from Trigonella foenum-graecum seedlings grown independently in the presence of either selenium (0.75 ppm) or mimosine (0.1 mM) exhibited respiration-stimulated energy-dependent uptake of Ca2+. Uptake studies were carried out independently at a series of Ca2+ concentrations at two different levels: (1) 1-20 MM and (2) 25-1,500 microM. Levels of uptake were 50-100% higher in the mitochondria of seedlings of both the Se and mimosine groups. Detailed kinetic analyses revealed negative cooperative effects operative during uptake of Ca2+ at 25-1,500 microM given in the medium. Hill coefficients for Ca2+ uptake by the mitochondria of different groups remained unchanged (nH, 0.75). Biphasic Scatchard plots were concave upward, suggestive of two classes of binding sites. High-affinity binding sites were estimated to be 16 nmol/mg protein with dissociation constant (KCa) of 2.5 x 10(9) L/mol. In contrast, graphical analyses of the uptake of Ca2+ in the range 1-20 microM in the medium revealed cooperative effects of positive nature. The present study demonstrates mixed cooperative effects during Ca2+ uptake by mitochondria from seedlings of T. foenum-graecum.

Biological Transport, Active↗
PubMed1999

Oxidative stress during selenium deficiency in seedlings of Trigonella foenum-graecum and mitigation by mimosine. Part I. Hydroperoxide metabolism.

Oxidative stress during selenium (Se) deficiency in the seedlings of Trigonella foenum-graecum grown for 72 h was investigated and the response to supplemented levels of Se (0.5-1 ppm) and mimosine (0.05-1 mM) was evaluated. Beneficial effects of Se was maximal at 0.75 ppm. Mimosine, a toxic amino acid, was also found to be beneficial to the growth of the seedlings exposed up to 0.2 mM. When compared to the stressed seedlings, mitochondrial oxygen uptake from seedlings of Se (0.75 ppm) group and mimosine (0.2 mM) group exhibited threefold enhancement in state 3 respiration rate and a controlled state 4 rate, with respiratory control ratios of 5-8. Upon supplementation at the optimal levels, superoxide dismutase (SOD) activities were enhanced fourfold with Se and eightfold with mimosine in the mitochondria. The soluble activity in mimosine groups increased twofold, but only by 75% in Se groups. Peroxidase activity registered a significant increase by threefold in mitochondria and fourfold in soluble fraction in both Se and mimosine groups. Exposure to Se or mimosine exhibited a differential response in the mitochondrial catalase and ascorbate peroxidase (Asc-Px) activities. In the Se groups, both catalase and Asc-Px in mitochondria decreased by 50-60%, which was contrasted by 60% increase in Asc-Px activity and 40% in catalase activity in mimosine groups. Supplementation with either Se or mimosine evoked similar responses of increases with respect to soluble catalase by twofold to threefold and Asc-Px by 90%. The results of the present study reveal (1) the prevalence of oxidative stress in T. foenum-graecum during Se deficiency, (2) enhanced mitochondrial functional efficiency mediated by Se and mimosine independently, and (3) an antioxidative role for mimosine during Se deficiency. The study demonstrates for the first time that mimosine, a naturally occurring toxic amino acid, could be a beneficial growth factor in concentrations between 0.1 and 0.2 mM.

Ascorbate Peroxidases↗
PubMed1999

Oxidative stress during selenium deficiency in seedlings of Trigonella foenum-graecum and mitigation by mimosine Part II. Glutathione metabolism.

Adaptive alterations in glutathione (GSH) metabolism were studied during oxidative stress induced by selenium (Se) deficiency in germinating seedlings of Trigonella foenum-graecum grown for 72 h and the response to supplementation individually of Se or mimosine was explored. Growth enhancement with improved mitochondrial efficiency was elicited by supplementation of Se at 0.5-0.75 ppm or mimosine at 0.1-0.2 mM. Total thiol and protein levels of mitochondrial and soluble fractions, in general, did not vary significantly with supplementation of either Se or mimosine except that the mitochondrial protein levels in mimosine groups (0.1-0.2 mM) decreased by 20-30%. Mitochondrial glutathione peroxidase (GSH-Px) increased by twofold in activity toward H2O2, cumene hydroperoxide (CHP), and t-butyl hydroperoxide (tBHP) in Se groups, and by 50-60% increase toward H2O2 and CHP but by a twofold enhancement in enzyme activity with tBHP in mimosine groups. Soluble GSH-Px activity increased by 30-40% only in mimosine groups and remained unaltered in Se groups. Glutathione S-transferase activity (GST) in the soluble fraction of both Se and mimosine groups increased dramatically by fivefold to sixfold. Distinct differences were noted in the response of the stressed seedlings toward exposure to Se or mimosine and included a decline in glutathione reductase (GR) activity by 50-60% in both mitochondria and soluble fractions of Se groups and an increase in GR activity of the mitochondria by twofold and of the soluble enzyme activity by 30% in the mimosine groups. Mimosine exposure resulted in a dose-dependent decrease in the gamma-glutamyl transpeptidase levels, but, in contrast, a significant enhancement by 50% was noted in the Se group at 0.75 ppm. The results including the differential response of GR activity to Se or mimosine supplementation are reflective of an effective reductive environment in Se groups and increased turnover of GSH in the presence of mimosine.

Glutathione↗
PubMed1999

Enhancement of beta-glucosidase and beta-galactosidase of Trigonella foenum-graecum by exposure to the allelochemical mimosine.

Glycohydrolases assume significance in the metabolism of biological systems and have important industrial applications in the areas of pharmaceuticals, food, and medicine. Glycosidases were screened in germinating seeds, and attempts were made to enhance their levels. Screening of glycosidases in the seedlings during a 72 h germination period revealed higher levels of beta-glucosidase and beta-galactosidase in Trigonella foenum-graecum compared to Cicer arietinum and Vigna radiata. Activity of beta-galactosidase was in general higher than that of beta-glucosidase in all the seedlings tested. During growth, exposure of the seedlings to an allelochemical, mimosine, at 0.1 mM resulted in the enhancement of enzyme levels by 50% in the seedlings of T. foenum-graecum, whereas the addition of mimosine to the assay medium in vitro did not affect the enzyme activities. Hydrolytic activity was enhanced by addition of glycerol in the medium up to 0.1 M in the case of beta-glucosidase and with 0.05 M in the case of beta-galactosidase. In general, the hydrolytic rate was higher by about 30% in the seedlings exposed to mimosine compared to that of the control. Concomitant enhancement in the rates of transgalactosidation by 51% and transglucosidation by 23% was also noted, underscoring the relevance of plant glycohydrolases for appropriate applications.

Fabaceae↗
PubMed1998

Selenium-mediated differential response of beta-glucosidase and beta-galactosidase of germinating Trigonella foenum-graecum.

Beta-glucosidase and beta-galactosidase activity profile tested in different seeds during 24 h germination revealed reasonably high levels of activity in Vigna radiata, Cicer arietinum, and Trigonella foenum-graecum. In all seeds tested, beta-galactosidase activity was, in general, higher than that of beta-glucosidase. T. foenum-graecum seedlings exhibited maximal total and specific activities for both the enzymes during 72 h germination. Se supplementation as Na2SeO3 up to 0.75 ppm was found to be beneficial to growth and revealed selective enhancement of beta-galactosidase activity by 40% at 0.5 ppm Se. The activities of both the enzymes drastically decreased at 1.0 ppm level of Se supplementation. On the contrary, addition of Na2SeO3 in vitro up to 1 ppm to the enzyme extracts did not influence these activities. Hydrolytic rates of beta-glucosidase in both control and Se-supplemented groups were enhanced by 20% with 0.05 M glycerol in the medium and 30% at 0.1 M glycerol. The rates were marginally higher in Se-supplemented seedlings than the controls, irrespective of added glycerol in the medium. In contrast, hydrolysis by beta-galactosidase showed a trend of decrease in Se-supplemented seedlings compared to the control, when glycerol was present in the medium. Addition of Se in vitro in the assay medium showed no difference in the hydrolytic rate by beta-galactosidase when compared to control, while the activity of beta-glucosidase declined by 50%. Se-grown seedlings showed an enhancement of transglucosidation rate by 40% in the presence of 0.1 M glycerol. The study reveals a differential response to Se among the beta-galactosidase and beta-glucosidase of T. foenum-graecum with increase in the levels of beta-galactosidase activity.

Catalysis↗
PubMed1996

Evidence for altered structure and impaired mitochondrial electron transport function in selenium deficiency.

Selenium (Se) deficiency in the experimental models, Coturnix coturnix japonica and Corcyra cephalonica, resulted in impaired mitochondrial substrate oxidations and lowered thiol levels. Studies with respiratory inhibitors confirmed reduced mitochondrial electron transport enzyme activities, especially at cytochrome c oxidase (COX), the terminal segment. Enhanced mitochondrial lipid peroxidation in Se deficiency was more pronounced in the heart tissue of the quail compared to other tissues. Glutathione peroxidase (GSH-Px) activity toward H2O2 and cumene hydroperoxide were generally low in the insect muscle tissue and activity toward H2O2 was maximal in the quail heart mitochondria that was not very sensitive to Se status. Lowered COX activity in Se deficiency was more directly correlated with the increased level of lipid peroxidation than with the GSH-Px activity measured, suggestive of Se mediated protective mechanisms independent of GSH-Px. Electron microscopic observations revealed structural changes such as loss of cristae with proliferative and degenerative changes of the mitochondria in Se deficiency. Involvement of Se in maintaining structure and functional efficiency of mitochondria is evident from the present study.

Animals↗
PubMed1995

Mitochondrial selenium-75 uptake and regulation revealed by kinetic analysis.

Uptake of Na2(75)SeO3 by mitochondria of the larvae of the insect C. cephalonica reared at different dietary selenium (Se) levels revealed: 1. A proportional increase in the uptake with externally added Na2(75)SeO3 in concentrations upto 25.32 microM; and 2. At each added selenite concentration, an increase up to 60 min, with linearity up to 15-30 min. A differential affinity for Na2(75)SeO3 was elicited in the mitochondrial protein fractions of different dietary Se groups and correlated well with the pattern and the ratio of distribution of incorporated 75Se in protein to nonprotein fractions. Kinetic studies on 75Se uptake by whole mitochondria negated passive diffusion of selenite and revealed a trend of negative cooperativity, confirmed by Hill and Scatchard plots. Half saturation value was estimated to be approx 13 nmole Se/mg mitochondrial protein. Scatchard plot for 75Se uptake was biphasic and the high affinity binding sites were estimated to be around 5 nmole/mg mitochondrial protein. Calculated dissociation constants revealed maximal affinity for 75Se in the 1.5 ppm group (KSe 0.0034 nM) and minimal in the basal group (KSe 0.007 nM). In the mitochondria of all the three dietary Se groups, the estimated low affinity sites amounted to be 15-19 nmole/mg mitochondrial protein. Inherent Se in the mitochondria of the high Se group positively enhanced the incorporation of 75Se in the mitochondrial protein fraction. About 20-30% of the total uptake was indicated to be energy linked as revealed by studies with respiratory inhibitors. Addition of sulfite and sulfate (5-25 microM) in the medium, inhibited 75Se uptake by 35-55%, suggestive of the involvement of the dicarboxylate port. Thiol interactive 75Se uptake was confirmed by the inhibition mediated by mersalyl and NEM up to 50-70%. The study revealed thiol-selenite interactions of metabolic significance during selenite uptake.

Animals↗
PubMed1995

Kinetic analysis of 75selenium uptake by mitochondria of germinating Vigna radiata of different selenium status.

Earlier studies in our laboratory demonstrated the beneficial role of Se in Vigna radiata, a Se-deficient legume, during germination, as reflected in growth-related parameters and specific uptake of 75Se. Uptake of Na2(75)SeO3, added in vitro by mitochondria isolated from seedlings germinated in control (without Se), and Se-supplemented groups (0.5, 1.0, and 2.0 ppm Se) indicated a proportional increase in the uptake with added Na2(75)SeO3, in concentrations up to 25 microM. The uptake of 75Se, increased linearly with time up to 15 min and a definite efflux followed at 30 min. The results were indicative of cooperative effects during Se transport. Kinetic analyses of the uptake of 75Se during time intervals of 15 and 30 min were carried out both in the whole mitochondria and the mitochondrial protein fractions. Graphical analyses using Lineweaver-Burk plot, Hill plot, log [v] vs log [A] and Scatchard plot confirmed the existence of negative cooperativity during 75Se uptake. Hill coefficient (nH) values were estimated to be around 0.7-0.8. Scatchard plots for 75Se uptake were biphasic, suggesting the probable presence of two classes of binding sites. The number of high and low affinity binding sites were estimated to be around 4-7 and 26-30 nmol/mg protein, respectively. Studies with mitochondrial respiratory inhibitors indicated about 10-20% of the total 75Se uptake to be energy dependent. Inhibition of 75Se uptake by about 60-70% by sulfate and sulfite (5-25 microM) implies the involvement of dicarboxylate port in Se transport. A decrease in the uptake of 75Se by 40-60% effected by CdCl2, HgCl2, mersalyl, and NEM confirmed the interaction of thiols in the process. Evidence for the regulatory nature of 75Se uptake by mitochondria of V. radiata emerges from the present study.

2,4-Dinitrophenol↗
PubMed1995

Subcellular distribution of selenium during uptake and its influence on mitochondrial oxidations in germinating Vigna radiata L.

The metabolic significance of Se in plants is not well documented, though the presence of many selenoenzymes in bacteria and the essentiality of Se in higher animals is established. Since germination is an active process in plant growth and metabolism, the effect of Se was investigated in germinating Vigna radiata L, a nonaccumulating Se-deficient legume. Growth and protein were enhanced in seedlings supplemented with selenium (Se) as sodium selenite in the medium up to 1 microgram/mL. The pattern of uptake of 75Se in the differentiating tissues and the subcellular distribution were investigated. The percentage of incorporation of 75Se was greater in the mitochondria at the lowest level (0.5 micrograms/mL) of Se supplementation compared to higher levels of Se exposure. Proteins precipitated from the postmitochondrial supernatant fractions, when separated by means of polyacrylamide gel electrophoresis (PAGE), indicated a major selenoprotein in the seedlings germinated at 2.0 micrograms/mL Se. In seedlings grown with supplemented Se, enhanced respiratory control ratio and succinate dehydrogenase activity were observed in the mitochondria of tissues, indicative of a role for Se in mitochondrial membrane functions.

Cotyledon↗
PubMed1995

Return of fertility following discontinuation of Norplant-II subdermal implants. ICMR Task Force on Hormonal Contraception.

A total of 627 women who had discontinued the use of the Norplant-II implants for various reasons and were exposed to the risk of pregnancy were followed-up for two years for return of fertility. The cumulative conception rates in women who had discontinued due to planning pregnancy were 80.3 per 100 women at one year and 88.3 per 100 women at two years. The majority of women who did conceive (90 percent), had full-term normal live births; about 4 percent of women had spontaneous abortions, the remaining 6 percent decided on elective termination of pregnancy (ETP). The cumulative conception rates in women who discontinued due to bleeding irregularities and 'other reasons' were 64.5 and 55.8 per 100 women at one year and 77.9 and 75.1 per 100 women at two years, respectively. These rates were significantly lower as compared to those observed in women who discontinued due to planning pregnancy. A large proportion, about 40 percent, of women who conceived after discontinuation of the method due to bleeding irregularities and "other reasons," opted for ETP indicating that many women in these two groups did not desire another child and that such women need to be counselled for adopting another method of contraception. The spontaneous abortion rates observed in ex-users of Norplant-II implants (1.7 to 4.4% pregnancies) were comparable to the spontaneous abortion rates prior to Norplant-II implant use (3.6% pregnancies) indicating that ex-users of Norplant-II implants were not at a higher risk of spontaneous abortion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Kinetics of biomethanation of solid tannery waste and the concept of interactive metabolic control.

Anaerobic digestion of calf skin collagenous waste was optimized for a batch process based on accelerated maximal methane yield per gram of input volatile solid. A kinetic analysis with respect to changes in the levels of volatile solid, collagen, amino sugars, amino acids, hydroxyproline, ammonium ions, and volatile fatty acid were followed for a period of 80 d. Distinct metabolic phases included an initial high rate collagenolysis for 4d, with 50% degradation and was followed by an acidogenic phase between 4-12 d with volatile fatty acids levels increasing to 215 mmol/L. Subsequently methanogenesis ensued and was maximal between 12-24 d when volatile fatty acids attained steady state levels. During the period of 80 d, the overall decrease in volatile solid level was 65%, whereas the collagen level declined by 85% with 0.45 L of methane yield/g of volatile solid degraded. Based on the levels of various metabolites detected, the concept of interactive metabolic control earlier proposed has been validated.

Anaerobiosis↗
PubMed1994

Metabolic relevance of selenium in the insect Corcyra cephalonica. Uptake of 75Se and subcellular distribution.

Requirement, uptake, and subcellular distribution of Na2(75)SeO3 in the larvae of the insect C. cephalonica was investigated. That Se is well tolerated by C. cephalonica upto an added level of 2 ppm in the diet is suggested by the observed increase in body weight, total protein, and succinate dehydrogenase levels. Significant increases in the State 3 respiration ensued with Se supplementation up to 2 ppm in the mitochondrial oxidation of D-glycerol 1-phosphate, succinate and NADH, along with concomitant unaltered State 4 respiration, leading to enhanced RCR values. Maximal uptake of 75Se was registered in the larvae maintained on basal diet when subjected to short-term exposure to 0.5 ppm 75Se level. When exposure level was further increased up to 20 ppm, the observed decrease in the uptake of 75Se suggested that Se status of larvae itself controlled the tissue uptake. Subcellular distribution pattern revealed maximal incorporation of 75Se (cpm/g tissue) in the supernatant fraction, whereas, maximal specific 75Se activity (cpm/mg protein) was associated with the mitochondrial fraction. Autoradiography of the soluble fractions indicated the presence of single selenoprotein in the larval group with short term 2 ppm 75Se exposure. Inherent Se controls both the extent and the nature of distribution of mitochondrial 75Se incorporation. Uptake of 45Ca by the insect mitochondria was enhanced by dietary Se up to 2 ppm but was unaffected by addition of in vitro 75Se in the medium. A more fundamental role for Se in the mitochondrial energy metabolism emerges from these studies.

Animals↗
PubMed1993

Spectrophotometric determination of mimosine and 3-hydroxy-4-(1H)-pyridone--the toxic principles of Leucaena leucocephala.

A sensitive and selective spectrophotometric method for the estimation of the toxic factors mimosine and 3-hydroxy-4-(1H)-pyridone (DHP) has been developed based on the intense yellow-colored azodye formed with p-nitroaniline which showed a sharp absorption maximum at 400 nm. The method was optimized based on relative sensitivity of the reaction with various aromatic primary amino compounds and under different conditions of pH. Interference from a variety of structurally related compounds and phenols was tested and found insensitive to this method. The molar extinction coefficient at 400 nm for the azodye formed with mimosine was 5.31 x 10(4) M-1 cm-1 and that for DHP was 1.699 x 10(4) M-1 cm-1. The applicability of the method was tested using different plant extracts and recovery was found to be at 100 +/- 0.3%. The method is suitable for accurate estimation of both mimosine and DHP after paper chromatographic separation of extracts of different biological samples.

Azo Compounds↗