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Biomedical subjects

R Shanker

Publications and source records attributed to R Shanker.

At least 19 recordsLinked to original sources
PubMed2006

Doppler effect in fluorine K-Auger line produced in electron-induced core ionization of SF6.

An experimental evidence is reported on the observation of the Doppler effect in fluorine K-Auger line emitted from a core-ionized SF6 molecule under an impact of 16 keV electrons. The emitting source of the Auger line is found to acquire a kinetic energy of 4.7+/-0.3 keV. We propose that such large energy is released from the Coulomb repulsion taking place between F+ and SF5+ fragment ions under influence of an intense focusing field of the incident electrons. In the presence of the Coulomb field of these ions, the Auger line obtains a polarization P = 76%+/-7%.

Journal Article↗
PubMed2002

Modulation of acute cadmium toxicity by Emblica officinalis fruit in rat.

The efficacy of Emblica officinalis in modifying the acute cytotoxicity of cadmium in male rats was evaluated. Oral administration of Emblica fruit juice (500 mg/kg, b.w.) for 8 days followed by a single toxic dose of Cd as CdCl2 (3 mg/kg,b.w. ip), considerably reduced the mortality in rats as well as prevented to some extent the cadmium induced histopathological damage in testis, liver and kidneys. Biochemical investigation also revealed reduced levels of Cd induced serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and gamma glutamyltranspeptidase. The enhanced levels of Cd and lipid peroxidation in liver, kidney, and testes and metallothionein and total sulphydryl in liver and kidney by Cd were significantly reduced by Emblica pretreatment. These results suggest cytoprotective potential of Emblica fruit in acute cadmium toxicity which could be due to its multiple role in biological system.

Animals↗
PubMed2001

Pilot study of expedited HIV-1 testing of women in labor at an inner-city hospital in New York City.

To evaluate the feasibility of offering voluntary counseling and expedited human immunodeficiency virus (HIV) testing to women in labor, and to assess the characteristics of two rapid HIV assays compared with results from an expedited standard enzyme immunoassay (EIA), with Western blot confirmation, as indicated, we undertook a pilot study immediately prior to enactment of New York State regulations (August 1999) requiring expedited testing of laboring women (or newborns) with undocumented HIV status. From June 9, 1999 through July 2, 1999, we offered HIV counseling and testing (C&T) to all medically stable women in active labor, 106 of 125 (85%) of whom accepted. One woman was confirmed HIV-1 seropositive. Rapid assay sensitivity and specificity were: SUDS 100 and 98%, and Multispot 100 and 100%, respectively in comparison with 100 and 99% for the standard EIA. The positive predictive values (PPV) were SUDS 33%; Multispot 100%; and EIA 50%. While our sample size was small, it appears that the accuracy of rapid and expedited HIV assays may be improved by requiring two different reactive assays before informing women of HIV-seropositive results or initiating antiretroviral treatment.

Adolescent↗
PubMed1999

Stress Survival of a Genetically Engineered Pseudomonas in Soil Slurries: Cytochrome P-450cam-Catalyzed Dehalogenation of Chlorinated Hydrocarbons.

Biological treatment of hazardous chemical wastes has potential as an effective, practical, and economically viable process in above the ground treatment systems that consist of both genetically engineered microorganisms (GEMs) and bioreactors with process control instruments to create ideal conditions for biodegradation. A strain of Pseudomonas putida coexpressing cytochrome P-450cam and luciferase (lux) that provides both the reductive detoxification potential of the hemoprotein and a mechanism for its reduction in the absence of "normal" P-450 redox partners was evaluated for its ability to survive and remain metabolically competent under nutrient stress in soil slurry microcosms. More than 74% of the cells of engineered Pseudomonas were culturable after 7 days of multiple nutrient (C,N,P) starvation. The diagnostic luminescence and carbon monoxide-difference spectra for the two engineered traits could be detected in a significant fraction of the surviving population. The GEM could be revived after repeated desiccation and starvation using Luria broth, benzoate, or citrate as nutrients. Soil slurries inoculated with the GEM transformed hexachloroethane (HCE) to tetrachloroethylene (tetraCE) 8-10-fold faster than uninoculated slurries. The GEM also transformed the insecticide, gamma-HCH (gamma-3,4,5,6-hexachlorocyclhexene), to gamma-3,4,5,6-tetrachlorocyclohexene (gammatetraCH) in soil slurries under subatmospheric conditions. These results indicate that GEMs can be constructed with broad substrate range detoxification catalysts such as cytochrome P-450 for remediation.

Journal Article↗
PubMed1998

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation.

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Animals↗
PubMed1998

Prognostic significance of thyroid antibodies in hyperthyroid patients treated with antithyroid drugs.

Lymphocytic infiltration of the thyroid gland in patients with hyperthyroidism is associated with the presence of serum antithyroidal microsomal antibodies (TMA) and serum antithyroglobulin antibodies (TGA). The aim of this study was to evaluate the clinical significance of TMA and TGA during and after treatment of hyperthyroidism with antithyroidal drugs. One hundred and fifty-four hyperthyroid patients were treated for 18 months with methimazole and then followed up for 18 months or more (mean, 24.8 +/- 12.6 months). Patients were classified into three group. group I, patients negative for TGA and TMA before and during 18 months of treatment, group II patients positive for TMA but negative for TGA before and during 18 months treatment and group III patients who were positive for both TGA and TMA before and during treatment. The relapse rates after discontinuation of treatment in these group were 44.7% (17 of 38), 29% (18 of 62) and 11.1% (6 of 54), respectively. The value in group I was significantly higher than that in group III (P < 0.01). These results show that presence of TMA and TGA influence the prognosis of patients with hyperthyroidism treated with methimazole with regard to relapse. Those patients who had both antibodies were least likely to have a relapse and those who had neither antibody before and during treatment were most likely to have a relapse of hyperthyroidism.

Adolescent↗
PubMed1997

Lead-induced changes in ovarian follicular development and maturation in mice.

Lead, a potent reproductive toxicant in humans and experimental animals, was used to detect the morphological basis of ovarian toxicity in mice by counting the various stages of follicular development using different doses of lead acetate (0, 2, 4 or 8 mg/kg/d) for 60 d (5 d/wk) by oral gavage. Our results revealed that while small and medium follicles were significantly affected even at the lowest dose (2 mg), the large follicles were affected mostly at the highest dose. Atresia even in the medium follicles reflected the extent of damage caused by lead. These findings correlated well with increased blood lead levels. Therefore, lead seems to affect the follicular development and maturation, if mice are, exposed to sufficiently high concentrations of metal through the oral route.

Animals↗
PubMed1995

Endosulfan-induced biochemical changes in the testis of rats.

Adult male rats were exposed to 0, 2.5, 5.0 or 10.0 mg endosulfan/kg body weight through oral intubation for 70 d. Decreased sperm counts in the cauda epididymis and reduced intratesticular spermatid counts associated with elevation in the activities of specific testicular marker enzymes (sorbitol dehydrogenase, lactic dehydrogenase, gamma glutamyl transpeptidase, and glucose-6-phosphate dehydrogenase) were seen in all the endosulfan-dosed groups. Endosulfan caused impairment in testicular functions by altering activities of the enzymes responsible for spermatogenesis, thereby influencing intratesticular spermatid count and causing low sperm production and sperm deformity.

Administration, Oral↗
PubMed1994

Dibutyltin dilaurate induced thymic atrophy and modulation of phosphoinositide pathway of cell signalling in thymocytes of rats.

A marked dose dependent reduction in thymus weight and its nucleated cell counts with histological alterations was observed in rats exposed to oral dibutyltin dilaurate (DBTL) for 2 weeks at 2, 4, 8 or 16 mg/kg body weight. The incorporation of [3H]-inositol into all the three major phosphoinositides was drastically reduced in thymocytes in a dose dependent manner. Furthermore, the basal and the mitogen (Con A) stimulated [3H]-inositol phosphates generation was diminished significantly in 8 mg DBTL group. However, in vitro incubation of DBTL with thymocytes failed to evoke any change in phosphoinositide hydrolysis. Similarly, a time and dose dependent inhibition in phosphoinositide synthesis with as high as 80% by 10 microM DBTL was exhibited under in vitro conditions. A 130% and 600% enhancement of protein kinase C (PKC) activity in thymocytes was seen in 4 mg and 8 mg DBTL group, respectively. Addition of DBTL to the cell free assay system of thymocytes resulted in a concentration dependent activation of the enzyme activity. A dose dependent increase in intracellular calcium was also evident when DBTL was added to thymocytes under in vitro conditions. These results are of significance and may bear close relationship to the observed thymic atrophy by DBTL.

Animals↗
PubMed1994

Styrene induced pancreatic changes in rodents.

Subchronic oral exposure to styrene in rodents (25 or 50 mg/kg/day in mice; 160 or 320 mg/kg/day in rats and guinea pigs, 5 days/week) for 4 weeks resulted in moderate congestion of pancreatic lobules, focal inflammatory reactions around islets (in mice) and altered serum insulin level while blood glucose levels remained unaffected. Increased beta cell degranulation together with characteristic neoformation of islets were predominantly seen in pancreas of guinea pigs.

Animals↗
PubMed1993

Immunomodulation due to coexposure to styrene and dioctyl phthalate in mice.

Pathomorphological and immunological alterations caused by a mixture of styrene and dioctyl phthalate were studied in albino mice following oral administration of 0.02, 0.03, 0.05 x LD50 of the mixture. The chemicals were mixed together proportionate to their respective LD50 values and fed in ground nut oil, 5 d/wk for 4 weeks. Histological examination of spleen revealed considerable depletion of cellular population of lymphoid follicles which corresponded to the dose dependent decrease in splenic mononuclear cell population count. The thymic lobules revealed slight atrophy but accompanied by a significant increase in thymocyte population. Correspondingly few significant histological changes were observed in mesenteric and peripheral lymph nodes. The treatment caused impairment of primary humoral immune response to SRBC (IgM) but there was a significant increase in response of splenocytes to B-cell mitogen LPS. There was a suppression of cutaneous delayed type hypersensitivity and increase in splenic lymphocyte response to T-cell mitogen PHA. Simultaneously, indirect immunity represented by decreased phagocytosis and enhanced metabolic function of reducing NBT by peritoneal exudate cells was observed. The in vitro exposure of vero cells to the mixture caused dose dependent protective effect. The results of present study indicate that subchronic exposure to low doses of mixture of styrene and dioctyl phthalate under certain conditions may modulate some of the immune functions as compared to exposure to either chemicals alone.

Adjuvants, Immunologic↗
PubMed1993

Renal toxicity of nickel, sodium lauryl sulphate and their combination after dermal application in guinea pigs.

The guinea pigs were dermally exposed to nickel (Ni), sodium lauryl sulphate (SLS) and in their combination for 7 and 14 days. The exposure to Ni and SLS produced changes in enzymes and lipid peroxidation in kidney. The exposure to Ni or SLS depicted slight changes while combined exposure to Ni plus SLS exhibited more degenerative changes in kidney. The result of the study suggests that industrial workers and/or populations exposed simultaneously to Ni and SLS produces more damage to kidney.

Administration, Cutaneous↗