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Biomedical subjects

V N Singh

Publications and source records attributed to V N Singh.

At least 19 recordsLinked to original sources
PubMed2005

Nanoparticle size-dependent lowering of temperature for phase transition from In(OH)3 to In2O3.

Phase transformation of In(OH)3 to In2O3 has been studied as a function of nanoparticle size without any alteration of nanoparticle size during transformation. Chemically capped In(OH)3 nanoparticles having sizes of 15, 11, and 8 nm transform to In2O3 at temperatures of 285, 272, and 255 degrees C, respectively. This first-time unambiguous observation of size-dependent lowering of transformation temperature represents a thermodynamic characteristic of the nanoparticle system. The results have been explained in terms of a lower cohesive energy of surface atoms and an increase in surface-to-volume ratio with a decrease in nanoparticle size.

Hydroxides↗
PubMed2001

The role of gas analysis with exercise testing.

Evaluation of exercise performance is an integral component of every medical history. Currently, it is accomplished by means of subjective history taking. Routine exercise testing adds very little information; however, the addition of gas analysis (or cardio pulmonary exercise [CPX] testing) provides the crucial objective assessment by analyzing breath-by-breath oxygen uptake, carbon dioxide production, and anaerobic threshold (AT). Cardiac and pulmonary causes can be reliably differentiated, e.g., cardiac patients cross AT and attain VO2max, use less than 50% of maximal voluntary ventilation (MVV) at peak exercise, and do not develop desaturation. Pulmonary patients, on the contrary, fail to cross AT or achieve VO2max, utilize more than 70% of MVV at peak exercise, and develop arterial desaturation. In the current cost-conscious health care system, CPX proves to be a better cost-effective test because it is objective and more directly targeted to the issues than the conventional exercise test. CPX provides an important link between the disease process and its effect on exercise performance, which is crucial to a comprehensive clinical evaluation, diagnosis, prognosis, exercise prescription, and follow-up after medical or surgical intervention in patients with various diseases causing cardiopulmonary dysfunction.

Carbon Dioxide↗
PubMed2000

Effects of a 6-month vitamin intervention on DNA damage in heavy smokers.

Because their formation is associated with tumor development in specific tissues, DNA adducts have potential usefulness as intermediate end points in chemoprevention studies. To determine the efficacy of a combination of antioxidant vitamins (vitamins C and E and beta-carotene), a randomized clinical trial was conducted among heavy smokers using DNA damage as the end point. Immunological methods were used to measure polycyclic aromatic hydrocarbon-DNA adducts and oxidative DNA damage (8-oxo or hydroxydeoxyguanosine) in mononuclear and oral cells. A total of 121 subjects were randomized to the 6-month intervention and received either vitamins or placebo. Dropout rates were higher in the placebo than in the vitamin group; 65% of subjects in the vitamin group, but only 47% in the placebo group, provided specimens at 6 months. Plasma levels of all three antioxidants rose significantly in the vitamin group but not in the placebo group. All four measures of DNA damage decreased in both groups; the between-group differences were not statistically significant. These data do not provide clear evidence that antioxidant vitamin intake prevents DNA damage. However, the study demonstrates that DNA damage is a useful end point in chemoprevention trials.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1997

Changes in LDH isozyme pattern in uterine fluid of mice during early pregnancy.

The total LDH activity in the uterine fluid of mice shows a rising trend from the first day after mating (DAM-1) to the seventh day after mating (DAM-7). This suggests that LDH activity increases as gestation progresses. During early pregnancy, M-isozymes of LDH show a predominance from DAM-1 to DAM-3 in the uterine luminal fluid of mice, while H-isozyme shows a rising level from DAM-5 (implantation day) and attains a maximum level at DAM-7 (the post-implantation period). Such shift of M-isozymes into H-isozymes of LDH (lactate dehydrogenase) during pre-implantation (DAM-3) to post-implantation (DAM-7) period changes the uterine luminal environment from anaerobic to aerobic condition which is more conducive for the normal development, implantation and survival of the growing blastocyst.

Animals↗
PubMed1996

Use of antioxidant supplements in the treatment of human oral leukoplakia.

An increasing public awareness of antioxidants may prompt a patient's request to be treated without surgery if a leukoplakic lesion is discovered. However, surgical excision remains the treatment of choice for oral leukoplakia. The use of antioxidant supplements has shown some promise, but the predictability of success remains uncertain and long-term results are unavailable. Before the decision to use any antioxidant is made, it is critical to obtain a histopathologic diagnosis of the lesion. When dealing with a lesion diagnosed as hyperkeratosis, it may be appropriate to choose an antioxidant that may take some time for clinical improvement to occur. However, as the grade of epithelial dysplasia becomes more severe, consideration must be given to the possibility of malignant transformation during antioxidant treatment. We do not recommend the use of antioxidant supplements in the treatment of any carcinoma. The therapeutic use of antioxidant supplements outside of clinical trials conducted at academic medical centers should be done with considerable caution by practitioners in private practice. It should be emphasized that in these clinical trial patients were seen at frequent intervals to monitor their progress and to intervene if there was a noticeable deterioration in the clinical appearance of the lesion. In spite of the uncertainty with respect to antioxidant treatment, there are circumstances in which it should be considered. Recurrence after surgical excision when there is little reason to believe that a second surgical excision would be any more successful is an ideal candidate. Also, patients with widespread leukoplakia that involves a large area of the oral mucosa might be suitable for treatment with antioxidants, as well as patients who have extensive medical problems that make them surgical risks. The choice of which antioxidant(s) to use is complex because thus far there is no combination that is superior to the others. Beta-carotene with ascorbic acid or alpha-tocopherol is attractive because of a lack of side effects, but the range in reported values for lesion improvement has been broad and the clinical improvement typically takes several months. Clinical response with 13-cRA is faster but requires baseline and periodic serologic testing, as well as close monitoring for side effects. In those circumstances in which time is an important consideration, 13-cRA might be useful because clinical improvement can be evaluated within a matter of weeks as compared with beta-carotene. The group from M.D. Anderson Hospital has shown the value of an induction dose of 13-cRA that is followed by a lower maintenance dose. Unfortunately, the problem of recurrence after discontinuation of 13-cRA is quite common. One aspect that has not been evaluated is the combination of conventional surgical excision and the administration of postoperative antioxidants. This would have the obvious advantage of conventional treatment of surgery together with the possible protective effect of the antioxidants. Although this is an attractive hypothesis, we do not know of any studies that have proven this to be beneficial.

Animals↗
PubMed1995

Human uterine amylase in relation to infertility.

In the uterine fluid of infertile women the amylase activity is significantly lower (90.00 to 357.75 mg/hr/100 ml) than that in parous women (172.14 to 536.99/hr/100 ml) during the different phases of menstrual cycle. Possibly the low enzyme activity in infertile women can impair the sperm capacitation and thus adversely affect the fertility of these infertile women.

Adult↗
PubMed1995

Estrogen dependent LDH-Y, a new LDH isozyme and fertility factor in mice uterus during early pregnancy.

In estrogen treated ovariectomized and pregnant mice on the first day after mating a sixth LDH isozyme appeared at Relative mobility (Rm) 0.08 to 0.15 and for convenience this isozyme is provisionally designated as LDH-Y. The appearance of a sixth LDH isozyme (LDH-Y) in mice uterus after ovariectomy and estrogen treatment favours the idea that this isozyme is estrogen dependent. Presence of this LDH-Y in mice uterus during preimplantation and finally its sudden disappearance during implantation and post implantation periods further suggest that LDH-Y is estrogen dependent and responsible for restoring fertility in mice.

Animals↗
PubMed1994

A clinical trial of antioxidant supplements in the treatment of oral leukoplakia.

Seventy-nine patients with oral leukoplakia that was histologically verified as either hyperkeratosis or epithelial dysplasia with hyperkeratosis were enrolled in an antioxidant supplementation program for the treatment of the oral lesions. The patients received 30 mg of beta-carotene, 1000 mg of ascorbic acid, and 800 IU of alpha-tocopherol per day for 9 months. Clinical improvement of the oral lesion was noted in 55.7% of the patients and was more likely to occur in patients who reduced their use of alcohol or tobacco (p = 0.0056). Although risk-factor reduction was important, approximately half of the patients who did not alter their exposure to either alcohol or tobacco showed clinical improvement. The antioxidant supplementation significantly increased serum and tissue levels of beta-carotene, ascorbic acid, and alpha-tocopherol, but these changes did not correlate strongly with clinical improvement.

Adult↗
PubMed1994

Lactate dehydrogenase isozymes in uterine fluid of infertile women.

Electrophoretic studies revealed predominance of LDH isozymes (LDH4 and LDH5: M-isozymes) throughout the menstrual cycle in the uterine luminal fluid of both parous and infertile women. Parous women M-isozymes maintain higher activity during phase I to phase III (early follicular phase to ovulatory phase) than infertile women. During the post-ovulatory phase (phase IV) the M-isozyme shows lowest level in parous women. In contrast, during this phase (phase IV) to late-luteal phase (phase VI) the M-isozymes show high activity in the fluid milieu of infertile women.

Adult↗
PubMed1994

High plasma vitamin C associated with high plasma HDL- and HDL2 cholesterol.

High plasma vitamin C may lower risk of cardiovascular disease as indicated by direct association with plasma high-density-lipoprotein (HDL) cholesterol and HDL2 cholesterol. Plasma lipids and vitamin C were determined in 316 women and 511 men (aged 19-95 y). After adjustment for age, sex, obesity, and smoking, plasma vitamin C was directly associated with HDL- (P = 0.01) and HDL2 cholesterol (P = 0.0002). When men and women with diseases that might affect lipids were excluded, associations between plasma vitamin C and HDL- and HDL2 cholesterol persisted, though the relationships were strongest in older men. Comparisons of diets in a subset (n = 485) who completed 7-d diet records were made. Total fat, saturated fatty acids, energy from fat, and cholesterol intakes were not associated with plasma vitamin C. Mean intakes of vitamin C were well above recommended dietary allowances. These findings suggest that high plasma concentrations of vitamin C may lower atherogenic risk.

Adult↗
PubMed1994

Vitamin A and E intakes and plasma concentrations of retinol, beta-carotene, and alpha-tocopherol in men and women of the Baltimore Longitudinal Study of Aging.

Antioxidants have been linked to protection against degenerative diseases associated with aging. Plasma concentrations were determined for and 7-d diet records collected from 200 women and 231 men aged 20-95 y who took part in the Baltimore Longitudinal Study of Aging. Men consumed more vitamin A from animal and less from vegetable sources than did women. These sex differences are reflected in plasma concentrations of retinol and beta-carotene. About 20% of subjects had vitamin A intakes less than recommended dietary allowances; however, no men and only two women had marginal plasma retinol (< 0.35 mumol/L) concentrations. Older people had higher plasma alpha-tocopherol, which correlated with total intake. Forty-two men and 35 women had plasma alpha-tocopherol concentrations that were considered marginal. Sex differences in sources of dietary and plasma vitamin A may have consequences in relation to aging and longevity. Apparent marginal intakes and plasma concentrations of vitamin E need to be further examined to determine effects on health status.

Adult↗
PubMed1994

Polycyclic aromatic hydrocarbon-DNA adducts in smokers and their relationship to micronutrient levels and the glutathione-S-transferase M1 genotype.

Sixty-three male cigarette smokers were entered into a cross-sectional study to determine whether inverse associations existed between polycyclic aromatic hydrocarbon (PAH)-DNA adduct levels and intake/serum levels of vitamin A, vitamin C and vitamin E. Associations between PAH-DNA adducts and intakes of carotene, as well as serum levels of beta-carotene, were also determined. Fasting blood samples were collected for assays of PAH-DNA adducts in circulating mononuclear cells, plasma cotinine and serum levels of vitamin A, beta-carotene, vitamin C and vitamin E. Since genetic deficiency in the detoxifying enzyme glutathione S-transferase M1 (GSTM1) has been associated with increased risk of lung cancer, GSTM1 genotype was also determined. Analysis of PAH-DNA adducts by competitive enzyme-linked immunosorbent assay (ELISA) indicated that 70% of the subjects had detectable adducts, with a mean of 4.38 adducts/10(8) nucleotides (range 1.00-24.1/10(8)). Pearson's method was utilized to determine whether any associations existed between the various host variables and PAH-DNA adducts. Previously, no significant associations were found between PAH-DNA adducts and cigarettes smoked/day, pack-years, daily/life-time tar exposures or plasma cotinine levels (Santella et al., Carcinogenesis, 13, 2041-2045, 1992). PAH-DNA adducts were inversely associated with serum cholesterol-adjusted vitamin E levels (r = -0.25, P < or = 0.05) and with smoking-adjusted vitamin C serum levels (r = -0.22, P < or = 0.09). Stratification by GSTM1 genotype indicated that these associations were limited to subjects with the null genotype. The relationship between adducts and serum cholesterol-adjusted vitamin E was significant in those of the null genotype (r = -0.38, P < or = 0.04), but not in those with the gene present (r = -0.12, P = 0.5). Similarly, for smoking-adjusted vitamin C, the relationship with adducts was stronger in subjects with the null genotype (r = -0.35, P < or = 0.06) than in those with GSTM1 present (r = -0.05, P = 0.77). These results are consistent with findings of prior epidemiological studies identifying significant inverse associations between anti-oxidant micronutrient status or GSTM1 genotype and the incidence of lung cancer. Additional studies should be conducted to confirm a possible role for vitamin E in PAH-DNA adduct formation and to explore further the possible roles of vitamin A, beta-carotene and vitamin C in modulating adduct formation and lung cancer risk.

Adult↗
PubMed1993

Prevention of myocardial reinfarction. Recommendations based on results of drug trials.

Therapy after acute myocardial infarction offers the prospect of increased survival in carefully selected patients. Current recommendations favor the use of beta blockers and antiplatelet agents, but some positive effects have been seen with use of anticoagulants, angiotensin-converting enzyme inhibitors, and calcium channel blockers. Further studies are needed to evaluate these drug classes in reinfarction prophylaxis and to define differences among the agents in each class.

Adrenergic beta-Antagonists↗
PubMed1993

A review of the use of antioxidant supplements in the treatment of human oral leukoplakia.

Over the past twenty years, research into the role of antioxidants in the prevention of cancer has increased dramatically. The use of antioxidant supplements to treat oral leukoplakia has gained acceptance due to the success demonstrated in several clinical trials. This review discusses the role of antioxidants in the development of cancer and their possible use in the treatment of oral leukoplakia.

Animals↗
PubMed1993

Human uterine protein in relation to infertility.

The concentration of electrophoretic protein in the uterine fluid of infertile women is significantly higher at all the phases of the menstrual cycle, except at phase I where it is significantly (p < 0.01) lower than parous women. At phase III (ovulatory phase) the concentration of electrophoretic protein (2812.00 micrograms/ml) is maximum in infertiles, and shows a highly significant (p < 0.001) increase over that of parous women (954.85 micrograms/ml). The highest level of electrophoretic protein at phase III in infertile women is due to maximum increase in anodic (electronegative) protein at this stage. This suggests that significant (p < 0.001) increase in concentration of anodic protein in the uterine fluid of infertile women at the ovulatory phase adds negative charge on sperm membrane that may possibly affect the capacitation of spermatozoa, thus causing infertility in women.

Adult↗
PubMed1992

Cigarette smoking related polycyclic aromatic hydrocarbon-DNA adducts in peripheral mononuclear cells.

Studies on cigarette smoking related polycyclic aromatic hydrocarbon-DNA adducts in blood have produced conflicting results. To determine whether a subset of specific white blood cells is a useful marker for monitoring exposure to cigarette smoke, blood was obtained from 63 heavy smokers and 27 non-smokers. Adduct levels were determined by competitive enzyme-linked immunosorbent assay with a polyclonal antiserum recognizing benzo[a]pyrene and structurally related diolepoxide-DNA adducts. Analysis of the lymphocyte plus monocyte fraction from smokers indicated 70% had detectable adducts with a mean of 4.38 +/- 4.29 adducts/10(8) nucleotides, while in non-smokers the corresponding values were 22% and 1.35 +/- 0.78/10(8) (P < 0.001). Plasma cotinine levels differed significantly in smokers (286 +/- 90 micrograms/l) compared to non-smokers (4.4 +/- 3.3 micrograms/l) (P < 0.001). However, cotinine was not correlated with self-reported smoking history in these heavy smokers. Nor were DNA adducts in smokers correlated with cigarettes per day, pack-years and plasma cotinine, indicating large interindividual variation in DNA adduct formation. These data demonstrate lymphocytes plus monocytes from smokers have elevated levels of polycyclic aromatic hydrocarbon diolepoxide-DNA adduct levels compared to non-smokers.

Adult↗
PubMed1992

A current perspective on nutrition and exercise.

Nutrition has always been a subject of great interest to athletes. In recent years use of exercise has, however, expanded from competitive sports to prevention/management of chronic diseases and maintenance of optimal health. Exercise is recommended in the prevention/management of noninsulin-dependent diabetes, hypertension, coronary heart disease, osteoporosis, obesity, mental health, colon cancer, stroke and back injury. Similarly, there is evidence that certain nutrients (e.g., vitamins C and E, beta-carotene and calcium) may reduce the risk of certain cancers, coronary heart disease, osteoporosis, hypertension and cataract. Thus, there seems to be concordance between the health benefits of exercise and certain nutrients. However, several human and animal studies suggest that strenuous exercise may promote free radical production, leading to lipid peroxidation and tissue damage. On the other hand, there is evidence that vitamins C and E and beta-carotene may protect against such damage. Thus, concordance between the health benefits of exercise and nutrition and a compensatory role of antioxidant nutrients against the potentially harmful effects of exercise suggests that nutrition and exercise should form important components of any regimen for prevention of chronic diseases and/or promotion of optimal health.

Animals↗