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Biomedical subjects

N Kumar

Publications and source records attributed to N Kumar.

At least 91 records · Page 5Linked to original sources
PubMed1995

Comparison of fresh and glutaraldehyde-treated autologous stented pericardium as pulmonary valve replacement.

The use of fresh autologous pericardium in valve surgery has shown poor results in the past mainly due to thickening and retraction. Recently, it has been suggested that a short treatment with glutaraldehyde might radically change its behavior. In an attempt to determine whether this disparity in results is due to the glutaraldehyde treatment or to a better present-day surgical technique, fresh and glutaraldehyde-treated autologous pericardium was mounted in a frame and implanted in the pulmonary position of adult sheep. Six survivors obtained in each group were sacrificed between 2 and 8 months in the "fresh" group and between 2 and 6 months in the "glutaraldehyde-treated" group. Macroscopically, the fresh pericardium became thickened and retracted in all specimens, eventually resulting in severe regurgitation, while the glutaraldehyde-treated, although slightly thickened, retained its pliability without significant retraction. Microscopically, viability of the central core of the collagen was more often preserved in the fresh pericardium. Endothelialization was irregular. In conclusion, short glutaraldehyde treatment seems to improve the results of autologous pericardium mounted on a valve stent. Its effect on calcification remains to be ascertained.

Animals↗
PubMed1995

Transmission blockade of Plasmodium falciparum malaria by anti-Pfs230-specific antibodies is isotype dependent.

By use of the parental hybridoma cell line 63F2A2 that produces specific antibodies of immunoglobulin isotype G1 (IgG1; 63F2A2.1) against Pfs230, we attempted to enrich for the synthesis of the downstream switch variant IgG2b and IgG2a monoclonal antibodies (MAbs) of the hybridoma cell line (63F2A2.2b and 63F2A2.2a, respectively). The parental IgG1 did not reduce the Plasmodium falciparum transmission in a bioassay irrespective of the presence of complement. MAbs 63F2A2.2b and 63F2A2.2a were effective in reducing the infectivity of P. falciparum parasites to Anopheles gambiae mosquitoes in membrane-feeding experiments. A transmission reduction of 91% was accomplished by the 63F2A2.2b switch variant, and a reduction of greater than 99% was accomplished by the 63F2A2.2a switch variant, but only in the presence of active human complement. Subsequently, the transmission-reducing effect of MAb 63F2A2.2b or 63F2A2.2a was confirmed in vitro by the rapid lysis of newly formed macrogametes or zygotes in the presence of active complement. MAb 63F2A2.1 did not lyse the newly formed macrogametes or zygotes irrespective of the presence of complement.

Animals↗
PubMed1995

Mechanism of androgen-induced thymolysis in rats.

To investigate the mechanism of androgen-induced thymolysis, the effects of various androgens, including testosterone (T), 19-nortestosterone, and 7 alpha-methyl-19-nortestosterone (MENT), were compared with those of estradiol and dexamethasone (DEX) in intact, castrated, and adrenalectomized male rats. The potency comparisons on thymus regression, based on mass of steroids, showed DEX to be the most potent, followed by estradiol and the androgens. Among the androgens, MENT was the most potent, followed by nortestosterone and T, an order similar to their anabolic potency on muscle. As the thymolytic effects of T and MENT were not altered by the concomitant administration of an aromatase inhibitor or a 5-reductase inhibitor, it was concluded that the effects of androgens were not mediated by their conversion to estrogens or 5 alpha-reduced metabolites. Involvement of glucocorticoid receptors in androgen action was excluded because mifepristone (an antiglucocorticoid) blocked DEX-induced, but not T- or MENT-induced, thymus regression. Flutamide, an antiandrogen, significantly blocked the thymolytic effect of T and MENT, providing further support for this conclusion. This suggested that the thymolytic action of androgens is an intrinsic property mediated via androgen receptors (AR). The occurrence of AR in the thymus was demonstrated by binding assays and the presence of AR messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction. Quantitative reverse transcriptase-polymerase chain reaction for AR mRNA in the thymus showed 6-fold more AR mRNA in the thymic epithelial cells than in the thymocytes. However, epithelial cells represent only a small fraction of the thymus. Hence, it is hypothesized that the androgens produce their thymolytic effects by stimulating the secretion of a factor(s) by the thymic epithelial cells that, in turn, causes regression of the thymus.

Adrenalectomy↗
PubMed1995

A revised terminology for recording surgical findings of the mitral valve.

The existing terminology for the various structures of the mitral valve are diverse and numerous. With the resurgence of interest in reparative procedures for mitral valve disease, it becomes imperative to have a unified terminology which would convey precise connotations in recording the pathology as well as the corrective procedures applied. In an effort to suggest a commonly acceptable nomenclature, we reviewed the available terminology and propose a simple system which will fulfil the needs of recording the intraoperative observations of the pathology of each valve and the manouveres carried out to correct them by the surgeon. This involves designating all structures anterior to the intercommissural line as "anterior" or "A" and those posterior as "posterior" or "P". The structures, as observed by the surgeon through a standard left atriotomy, to the left of the line dropped perpendicular to the middle of the aortic curtain will be designated by the numeral "1" and those to the right "2". The chords will be termed in groups based on their point of insertion, irrespective of whether they are inserted to the free edge or the ventricular surface of the leaflet. The anterior leaflet chords will further be subdivided based on their relation to the stay chords. We hope that this system of naming the structures would provide a unified method of reporting intraoperative findings of mitral valve disease.

Heart Valve Diseases↗
PubMed1995

Understanding the factors behind the decision to purchase varying coverage amounts of long-term care insurance.

OBJECTIVE: This article examines the factors related to an individual's decision to purchase a given amount of long-term care insurance coverage. DATA SOURCE AND STUDY SETTING: Primary data analyses were conducted on an estimation sample of 6,545 individuals who had purchased long-term care (LTC) insurance policies in late 1990 and early 1991, and 1,248 individuals who had been approached by agents but chose not to buy such insurance. Companies contributing the two samples represented 45 percent of total sales during the study year. STUDY DESIGN: A two-stage logit-OLS (ordinary least squares) choice-based sampling model was used to examine the relationship between the expected value of purchased coverage and explanatory variables that included: demographic traits, attitudes, risk premium, nursing home bed supply, and Medicaid program configurations. DATA COLLECTION: Mail surveys were used to collect information about individuals' reasons for purchase, attitudes about long-term care, and demographic characteristics. Through an identification code, information on the policy designs chosen by these individuals was linked to each of the returned mail surveys. The response rate to the survey was about 60 percent. PRINCIPAL FINDINGS: The model explains about 47 percent of the variance in the dependent variable-expected value of policy coverage. Important variables negatively associated with the dependent variable include advancing age, being married, and having less than a college education. Variables positively related include being male, having more income, and having increasing expected LTC costs. Medicaid program configuration also influences the level of benefits purchased: state reimbursement rates and the presence of comprehensive estate recovery programs are both positively related to the expected value of purchased benefits. Finally, as the difference between the premium charged and the actuarially fair premium increases, individuals buy less coverage. CONCLUSIONS: An important finding with implications for policymakers is that changes in Medicaid policy affect the decisions of consumers regarding the acquisition of private LTC policies as well as the level of protection chosen. This is particularly important to states interested in pursuing public-private partnerships in long-term care financing.

Actuarial Analysis↗
PubMed1995

Ring enhancing CT lesions--a diagnostic dilemma.

We studied 68 such cases of RECTL with follow up ranging from 3 months to 3 years. Patients were divided into 3 groups depending on the size of ring ie. Group I (less than 5 mm), Group II (5-10 mm), Group III (10-20 mm). Maximum cases were in Group II (42), in the age group 20-40 years. 60 cases presented with seizures. Single ring was seen in 46 cases and multiple rings in remaining 22 cases. There were 22 cases of tuberculoma, 15 neurocysticercosis, 15 disappearing lesions, 4 malignancy, 2 abscess, 1 each showing infarction and gliosis and 8 of unknown etiology. Partial or total excision biopsy was done in 18 cases of which 3 were due to tuberculoma, 7 neurocysticercosis, 4 tumours, 2 abscess and 1 each due to infarction and gliosis. We found that RECTL could be a real diagnostic problem, which could be solved only be repeated clinical examination and CT Scan with excision biopsy in some selected cases.

Diagnosis, Differential↗
PubMed1994

Thrombotic obstruction of bileaflet valves: surgical management and fiberoptic thrombectomy.

Three patients underwent emergency operation for thrombotic obstruction of a bileaflet mechanical prosthesis (two St. Jude and one Duromedics) in the mitral position. The three valves were successfully thromboectomized with return to normal function. In 2 patients removal of the thrombus at the valve hinges was assisted by the use of a flexible fiberoptic choledochoscope. All 3 patients remain well 2 years after the procedure, maintained on a regimen of warfarin and dipyridamole.

Dipyridamole↗
PubMed1994

Aromatization of 7 alpha-methyl-19-nortestosterone by human placental microsomes in vitro.

Part of the biological effects of testosterone (T) are mediated by its enzymatic reduction to 5 alpha-dihydrotestosterone (DHT) or aromatization to estradiol (E2). 7 alpha-Methyl-19-nortestosterone (MENT) is a synthetic androgen that is considerably more potent than T. Previous studies have shown that MENT is not 5 alpha-reduced. The studies reported here were undertaken to determine whether MENT undergoes enzymatic aromatization in vitro. Human placental microsomes were used as the source of the aromatase. Radioactive or nonradioactive T or MENT was incubated with the microsomes in the presence of NADPH and the metabolites extracted out with ethyl ether. Following evaporation of ether, the residue was dissolved in benzene-petroleum ether and extracted with 0.4 N NaOH which selectively removes phenolic metabolites of the androgens. When either radioactive T or MENT was incubated with the aromatase in the presence of NADPH, there was a 20-fold increase in the amount of radioactivity extracted with NaOH. In contrast, if the incubation was carried out in the absence of NADPH or in the presence of R76713, an aromatase inhibitor, most of the radioactivity remained in the benzene-petroleum ether phase. To further identify the enzymatic reaction products, thin layer chromatography (TLC) was performed. The Rf value for MENT was 0.22 while that of the major reaction product was 0.34, which corresponded with the RF value of the estrogen, 7 alpha-methyl-estradiol (MeE2). This was further verified by using a second solvent system for the chromatographic separation. In an effort to ascertain whether the metabolites bind to estrogen receptors (ER), rat uterine cytosol was used. NaOH extracts of medium following incubation of nonradioactive MENT with microsomes showed competitive inhibition of [3H]E2 binding to rat uterine ER. Furthermore, after [3H]MENT was incubated with microsomes, the radioactive metabolite extracted in NaOH showed specific binding to the ER which could readily be displaced with E2 or MeE2. These results indicate that like T, MENT undergoes enzymatic aromatization.

Aromatase↗
PubMed1994

7 alpha-Methyl-19-nortestosterone: an ideal androgen for replacement therapy.

MENT is a synthetic androgen which cannot be 5 alpha-reduced. Therefore, relative to T, its stimulatory action on the prostate is lower than that on the muscle and pituitary. Like T, MENT undergoes enzymatic aromatization to an estrogen. We conclude that the use of MENT instead of T for androgen replacement therapy could have health-promoting effects by reducing the occurrence of prostate disease.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1994

Post lumbar puncture discitis and vertebral collapse.

Discitis and vertebral collapse are rare but serious complications of lumbar puncture. Clinical profile, management and course of post lumbar puncture discitis in five patients is presented. Such a complication should be kept in mind whenever any invasive procedure is carried out on the spine.

Adult↗
PubMed1994

Lipoprotein lipids and the prevalence of hyperlipidaemia in rural India.

BACKGROUND: The prevalence of hyperlipidaemias has been inadequately studied in rural populations of developing countries. No significant data exist on the population levels of serum cholesterol, cholesterol subclasses or triglycerides in these countries. METHODS: We studied fasting blood samples of 300 apparently healthy adults (202 men and 98 women, age range 20-73 years) randomly selected from a larger sample of 3148 individuals during a comprehensive cardiovascular risk-factor survey in Rajasthan, India. Levels of serum total cholesterol, its subfractions [low-density-lipoprotein (LDL) cholesterol, very-low-density-lipoprotein cholesterol and high-density-lipoprotein (HDL) cholesterol] and triglycerides were measured and correlated with age and anthropometric data. RESULTS: The mean +/- SD serum total-cholesterol levels were 4.39 +/- 1.0 mmol/l in men and 4.37 +/- 1.0 mmol/l in women, the mean LDL-cholesterol levels 2.51 +/- 1.0 mmol/l in men and 2.62 +/- 0.9 mmol/l in women, the mean HDL-cholesterol levels 1.15 +/- 0.4 mmol/l in both mean and women and the mean fasting serum triglyceride levels 1.63 +/- 0.6 mmol/l in men and 1.48 +/- 0.7 mmol/l in women. Age correlated positively with total-cholesterol, LDL-cholesterol, HDL-cholesterol and triglyceride levels in both men and women. Levels of the cholesterol subtypes did not differ between the sexes (P > 0.01), although triglyceride levels were significantly higher in men (P < 0.01). Lipoprotein lipids did not correlate significantly with height, weight, body-mass index or waist:hip ratio. When classified according to the recommendations of the US National Cholesterol Education Program for the determination of the prevalence of hyperlipidaemia, 43 individuals (14.3%; men 14.4% and women 14.3%) had borderline high cholesterol levels (5.20-6.18 mmol/l) and 24 (8%; men 7.9% and women 8.2%) had high cholesterol levels (> or = 6.21 mmol/l). Forty-five participants (15%) had borderline high LDL-cholesterol levels (3.36-4.11 mmol/l) and 20 (6.7%) had high LDL-cholesterol levels (> or = 4.14 mmol/l); low HDL-cholesterol levels (< 0.9 mmol/L) were found in 89 (29.7%). Eighteen participants (6%) had mild hypertriglyceridaemia (2.82-5.64 mmol/l) and two (0.7%) had severe hypertriglyceridaemia (> 5.64 mmol/l). CONCLUSION: Total-cholesterol and LDL-cholesterol levels are low in a rural Indian population, although an atherogenic lipid profile is present in a significant proportion.

Adult↗
PubMed1994

Long-term care insurance and Medicaid.

Depending on length-of-stay, somewhere between 29 percent and 38 percent of long-term care insurance purchasers who use nursing homes would qualify for Medicaid payments if they did not own a policy. This is equivalent to between 13 percent and 17 percent of all policyholders. Owning such a policy would, however, reduce spend-down rates among policyholders by 39 percent. Thus, in the presence of long-term care insurance, only 8 to 10 percent of all policyholders would receive Medicaid. Medicaid would spend between $6,492 and $14,179 (in 1990 dollars) on nursing home entrants with long-term care insurance policies--$14,437 to $29,698 if entrants did not have insurance. The ultimate impact on Medicaid expenditures is reduced, however, because many policyholders voluntarily let their policies lapse before entering nursing homes. If policies paid reduced benefits for voluntary lapses, then Medicaid could reap more significant fiscal savings.

Aged↗