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Biomedical subjects

S N Tiwari

Publications and source records attributed to S N Tiwari.

18 recordsLinked to original sources
PubMed2005

Larvivorous fish in wells target the malaria vector sibling species of the Anopheles culicifacies complex in villages in Karnataka, India.

Malaria was a major problem in a sericulture area of Karnataka, south India, where Anopheles culicifacies s.l. and A. fluviatilis s.l. were considered to be the main vectors. Sibling species complexes of these two species were analysed in three ecologically different villages. Among A. culicifacies, only sibling species A and B were found. In Puram, a village with 22 wells, species A predominated; species B predominated in a village with four wells and a stream, and in a village with a stream and no wells. Poecilia reticulata fish were introduced into all wells and streams in the villages, and after one year no vectors were found in Puram, and all, or nearly all, A. culicifacies were species B in the other two villages. All A. fluviatilis belonged to the sibling species T. Blood meal analysis indicated that a few of the A. culicifacies collected had fed on humans while all the A. fluviatilis had fed on bovines. Before the introduction of fish, the annual parasite incidence for malaria was high in Puram, but much lower in the other two villages. From 1998 (over one year after release of fish) until 2003, no malaria cases were detected in the three villages.

Animals↗
PubMed2004

Widespread occurrence of the Plasmodium falciparum chloroquine resistance transporter (Pfcrt) gene haplotype SVMNT in P. falciparum malaria in India.

The Plasmodium falciparum chloroquine resistance transporter (Pfcrt) K76T mutation and haplotype (amino acids 72-76) and the P. falciparum multidrug resistance 1 (Pfmdr1) mutation (N86Y) were analyzed as markers of chloroquine resistance in the DNAs of 73 blood samples from patients with P. falciparum malaria in India. Seventy of the 73 DNAs had the Pfcrt K76T mutation. Of these, 66 had the SVMNT haplotype and four had CVIET, the African/Southeast Asian haplotype. Only 20 of 69 DNAs had the Pfmdr1 N86Y mutation. It is surprising that the Pfcrt haplotype in India is predominantly SVMNT, rather than that seen in Southeast Asia. The widespread prevalence of the Pfcrt K76T mutation is a cause for concern.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Entropy generation method to quantify thermal comfort.

The present paper presents a thermodynamic approach to assess the quality of human-thermal environment interaction and quantify thermal comfort. The approach involves development of entropy generation term by applying second law of thermodynamics to the combined human-environment system. The entropy generation term combines both human thermal physiological responses and thermal environmental variables to provide an objective measure of thermal comfort. The original concepts and definitions form the basis for establishing the mathematical relationship between thermal comfort and entropy generation term. As a result of logic and deterministic approach, an Objective Thermal Comfort Index (OTCI) is defined and established as a function of entropy generation. In order to verify the entropy-based thermal comfort model, human thermal physiological responses due to changes in ambient conditions are simulated using a well established and validated human thermal model developed at the Institute of Environmental Research of Kansas State University (KSU). The finite element based KSU human thermal computer model is being utilized as a "Computational Environmental Chamber" to conduct series of simulations to examine the human thermal responses to different environmental conditions. The output from the simulation, which include human thermal responses and input data consisting of environmental conditions are fed into the thermal comfort model. Continuous monitoring of thermal comfort in comfortable and extreme environmental conditions is demonstrated. The Objective Thermal Comfort values obtained from the entropy-based model are validated against regression based Predicted Mean Vote (PMV) values. Using the corresponding air temperatures and vapor pressures that were used in the computer simulation in the regression equation generates the PMV values. The preliminary results indicate that the OTCI and PMV values correlate well under ideal conditions. However, an experimental study is needed in the future to fully establish the validity of the OTCI formula and the model. One of the practical applications of this index is that could it be integrated in thermal control systems to develop human-centered environmental control systems for potential use in aircraft, mass transit vehicles, intelligent building systems, and space vehicles.

Algorithms↗
PubMed2000

Effects of volatile anesthetics on the direct and indirect protein kinase C-mediated enhancement of alpha1E-type Ca(2+) current in Xenopus oocytes.

The effect of the volatile anesthetics (VAs) halothane (0.59 mM) and isoflurane (0.70 mM) on protein kinase C (PKC)-mediated modulation of alpha1E type of high-voltage-gated Ca(2+) channels was examined in Xenopus oocytes coexpressing m1 muscarinic acetylcholine receptors. Phorbol-12-myristate-13-acetate (PMA) or 1, 2-dioctanoyl-sn-glycerol (DOG) was used to activate PKC directly, whereas indirect activation was induced with acetyl-beta-methylcholine (MCh). The interaction between PKC activators and VAs was examined by perfusing either VA before, during, or after the administration of PMA, DOG, or MCh. In addition, the effect of VAs was studied after the down-regulation of PKC. The application of VAs inhibited Ba(2+) current (I(Ba)), whereas PMA (500 nM), DOG (100 microM), or MCh (1 and 10 microM) markedly potentiated I(Ba). VAs inhibited PMA- or DOG-enhanced I(Ba) to the same extent as seen in controls. The inhibition of I(Ba) induced by VAs was not reversed by PMA or DOG. The administration of VAs in combination with PMA, DOG, or MCh (1 microM) led to the inhibition of I(Ba). MCh (10 microM) counteracted the inhibitory effect of VAs when administered together and reversed the inhibition of I(Ba) produced by VAs. These differences in the responses between PMA and MCh (10 microM) may be based on the involvement of various pools of PKC. It is suggested that VAs act directly at the membrane, because they blocked the membrane-based action of PMA, whereas the receptor-based action of MCh was only partially blocked. It is possible that some PKC isoforms may not be a direct target of VAs.

Anesthetics, Inhalation↗
PubMed1997

Analysis and quantification of mental stress and fatigue using Maxwell relations from thermodynamics.

Several experimental and theoretical techniques have been developed to analyze both physical and psychological stresses. These techniques have relied mainly on certain parameters based on physiological, behavioral, and performance related data. This study is based on a thought experiment which describes the technique to quantify mental stress based on physiological responses using the entropy concept. It relates different physiological parameters using the Maxwell relations of thermodynamics with a systems approach. Data for testing this analytical approach were obtained from an experimental study which was conducted to determine the effects of a mentally stressful situation (final examination) on the common physiological responses (blood pressure, pulse rate, and oral body temperature) of students. The results indicated that the imposed mental stress causes significant changes in physiological responses. The Maxwell relations of thermodynamics were used to quantify the level of stress under different conditions. The results obtained from these relations validated the principles of thermodynamics as applied to the human system.

Adolescent↗
PubMed1997

Seasonality of indoor resting anophelines in stone quarry area of District Allahabad, U.P.

Alongitudinal study was conducted in four indicator villages of PHC Shankargarh, District Allahabad, U.P. from July 1991 to June 1992 to have information on seasonality of indoor resting anopheline species in silica sand/hard stone quarry area. Fourteen anopheline species namely, An. aconitus (0.35%), An. annularis (17.03%), An. barbirostris (0.09%), An. culicifacies (36.74%), An. fluviatilis (0.13%), An. nigerrimus (0.01%), An. pallidus (4.40%), An. splendidus (0.02%), An. stephensi (0.01%), An. subpictus (40.84%), An. tessellatus (0.15%), An. turkhudi (0.004%), An. vagus (0.20%) and An. varuna (0.02%) were collected. An. culicifacies, An. subpictus and An. annularis were found throughout the year. An. fluviatilis, An. pallidus, An. vagus and An. aconitus were also observed in all the seasons except extreme summer. However, An. barbirostris and An. splendidus were collected only in monsoon/post-monsoon and winter seasons. An. tessellatus and An. stephensi were recorded in winter and spring seasons. An. nigerrimus and An. varuna were recorded in winter, while An. turkhudi in spring. Prolonged high vector density may be attributed to the extended malaria transmission in this area.

Animals↗
PubMed1994

Correlation of malaria endemicity with An. culicifacies sibling species composition and malaria antibody profile in district Allahabad (U.P.).

Entomological, parasitological and serological surveys were conducted between October 1989 and November 1990 in 27 villages (population 33,250) belonging to three topographically different areas of district Allahabad, viz. Gangapar, Doaba and Yamunapar. A good correlation existed in all the three areas between malaria incidence vis-a-vis An. culicifacies sibling species composition and malaria antibodies titre in the populations. In Gangapar and Doaba villages, An. culicifacies densities were low and the proportions of vector species A and C were much less than that of species B, the non-vector species. Low endemicity of malaria was supported by low antibody titres observed in the population. In contrast, in Yamunapar villages An. culicifacies densities were high, species A and C together were almost equal to species B, and malaria incidence as well as antibody titre were high. Based on these observations, district Allahabad, Uttar Pradesh, could be divided into two zones, low malaria transmission zone--Gangapar and Doaba areas and high malaria transmission zone--Yamunapar area.

Adolescent↗
PubMed1993

Malaria in Shankargarh PHC, Allahabad District (U.P.): a clinical report.

A longitudinal study of malaria incidence recorded at malaria clinic of MRC, Shankargarh, during 1988-1991 showed the immense popularity of the clinic in quarry area. In clinical cases, SPR and SfR gradually increased from 45.6 and 18.2 in 1988 to 52.5 and 34.5 respectively in 1991. Increase in malaria cases during the reporting period was mainly contributed by P. falciparum cases. Peaks of vivax and falciparum malaria were recorded in September and October respectively. Extended transmission in Shankargarh region might be attributed to the influx of quarry labourers after post-monsoon season. SfR for 0 to 1-year age group malaria cases was found to be relatively low as compared to the higher age groups. Only 56 per cent of malaria-positive patients reported in the clinic had fever.

Adolescent↗
PubMed1990

Chloroquine sensitivity of Plasmodium falciparum in Shankargarh block of Allahabad district (U.P.).

Chloroquine sensitivity of Plasmodium falciparum was carried out in Shankargarh block of Allahabad district, U.P. to confirm the presence of resistant strain in the area. A total of 47 cases were subjected to in vivo extended test, of which resistance was detected in 11 cases at R-II/R-III level and in 9 cases at R-I level. One case out of 18 subjected to standard 7-day in vivo test showed resistance at R-III level. Micro in vitro test was done for 24 cases, of which growth was seen in 21 control samples. Out of these 7 cases were found to be resistant. The significance of the findings are discussed.

Adolescent↗
PubMed1990

A theoretical study of acriflavin-DNA binding.

A theoretical study of binding behaviour of acriflavin, a well-known mutagen, with DNA base pairs such as AT, GC, TA and CG has been performed using CNDO/2 method to compute net atomic charges and dipoles located at various centres in acriflavine as well as base pairs. Acriflavine-DNA base pair interactions have been evaluated using second order perturbation method with multicentered multipole approximation. Only minimum energy configurations have been reported. Results have been discussed with a view to obtain a comparative behaviour of other similar dyes like proflavine and acridine orange.

Acriflavine↗
PubMed1990

Stacking interactions between demethylated ellipticines and DNA base pairs--a quantum mechanical study.

A study of the binding behaviour of ellipticine compounds, derivatives of pyrido (4-3b) carbazole, has been carried out to elucidate the relationship between the drug-activity and demethylation of ellipticine. An all valence electron method (CNDO/2) has been employed to compute molecular charge distribution corresponding to various atomic centres of ellipticines and DNA base pairs. Using these atomic charges and dipoles, intermolecular interaction energy has been calculated with the help of second order perturbation theory and multicentered-multipole expansion technique. A comparative analysis of the binding patterns for nor-5,11-dimethyl-ellipticine and nor-11-methyl-ellipticine has been presented vis-a-vis ellipticine. Attempt has been made to correlate interaction energy studies with demethylation of ellipticine and the possible binding patterns.

Base Composition↗
PubMed1984

Vasovasostomy in rabbits after vasectomy or vas occlusion by tantalum clip.

Vasovasostomy was performed in rabbits that had been vasectomized or had the vas occluded by a tantalum clip for 6 or 15 months. Vasovasostomy restored fertility to 40-50% in vasectomized rabbits and 60-70% in the tantalum clip-occluded animals. Any changes that occurred due to vasectomy and tantalum clip occlusion (e.g. testicular weight, enzyme concentrations in the testis) returned to normal within 3-6 months of vasovasostomy. We suggest that vas occlusion with tantalum clips is a good method of surgical male sterilization and has a high success rate for restoration of fertility.

Alkaline Phosphatase↗
PubMed1983

Vasectomy in langur monkeys (Presbytis entellus entellus dufresne).

The sex accessory gland functions were studied in 1-12 months vasectomized langur monkeys. Seminal plasma fructose did not change. Semen volume, magnesium, and citric acid decreased transitionally up to 6 months. A significant decrease in LDH and transaminases (GOT, GPT) following vasectomy indicated an altered secretory activity of the accessory sex organs.

Animals↗
PubMedDate not supplied

Ultrastructural changes in the rabbit epididymis following vasectomy and clip occlusion.

Adult male rabbits were subjected to vasectomy, tantalum clip occlusion and sham operations. Caput and cauda regions of epididymis were studied with electron microscope at intervals of 15 days and 15 months after operation. Vasectomized and clip occluded subjects revealed similar changes when compared with sham operated animals. The epithelium remained functionally active even after vasectomy and clip occlusion as indicated by the presence of all characteristic complements of cellular organelles. Increased number of vacuoles and electron dense bodies indicated enhanced absorptive and digestive mechanisms at 15 months of vasectomy and clip occlusion. Disposal of continuously producing spermatozoa following vas occlusion may take place by intraluminal disintegration of sperm and subsequent phagocytosis by epididymal epithelium as evidenced by presence of identifiable parts of spermatozoa and flocculent material in caput and cauda regions.

Animals↗
PubMedDate not supplied

Ultrastructural changes in rabbit testis and epididymis following vasectomy: a long term study.

The Ultrastructural changes in testis and epididymis were studied in rabbits following 18 months of bilateral vasectomy. No fine structural changes were observed in seminiferous tubules and all stages of spermatogenesis appeared normal in most of the sample studied. Intracellular spaces in the spermatogonia cytoplasm may denote ionic deficiency. Digestion of sperms to some extent in the lumen of seminiferous tubules was denoted by the presence of round membrane bound bodies which may be remnants of digested cytoplasmic organelles and sperm parts. Cells of the epididymal epithelium showed normal characteristics. Electron dense bodies (lysosomes) were more prevalent in the supranuclear region of principal cells suggesting increased resorption capacity of caput epididymis after vasectomy. Presence of large oval bodies in the lumen needs further investigation.

Animals↗
PubMedDate not supplied

Effect of vasectomy on biochemical constituents of the blood in langur monkey--a 2 1/2 years follow up.

Bilaterally vasectomized langur monkeys were compared with age matched sham operated controls for biochemical constituents of the blood following 1.5, 2.0 and 2.5 years of surgery. No appreciable changes were observed in blood glucose and blood urea and serum total protein, total lipid, phospholipid, total cholesterol, sialic acid, electrolytes (chloride, phosphorus, magnesium, sodium, potassium, copper and zinc) and enzymes (LDH, alkaline phosphatase SGOT and SGPT) suggesting that long-term vasectomy does not cause adverse effects on general body metabolism including atherosclerosis.

Animals↗