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Biomedical subjects

R Srivastava

Publications and source records attributed to R Srivastava.

At least 73 records · Page 4Linked to original sources
PubMed1997

On the mechanism of isomerization of ocular retinoids by the crayfish Procambarus clarkii.

The eyes of some crustaceans store substantial amounts of retinyl esters, with most of the retinol in the 11-cis configuration. Earlier work in this laboratory suggested that in lobster and crayfish the mechanism of isomerization of retinol to the 11-cis form involves the hydrolysis of all-trans retinyl esters. Although this is the same process as that occurring in the vertebrate eye, it is different from the retinal photoisomerase reaction known in other arthropods, specifically diurnal insects (Hymenoptera and probably Diptera). Using homogenates of crayfish, we have tested this proposed mechanism by inhibiting retinyl ester synthetase activity in the presence of exogenous all-trans retinol. Inhibition of lecithin:retinol acyl transferase with 5 mumol l-1 retinyl bromoacetate or 2 mmol l-1 phenylmethylsulfonyl fluoride blocks the formation of both all-trans and 11-cis retinyl esters as well as 11-cis retinol, as shown by direct assay and by the decrease in counts derived from tritiated all-trans retinol. The similarity of this isomerization to the mechanism in vertebrate pigment epithelium is thus an interesting example of convergent evolution in the biochemistry of visual pigments, in which the pigments themselves (the opsins) are largely conserved across phyla.

Animals↗
PubMed1997

Perceived level and sources of stress in university professional schools.

The purpose of this study was to investigate the perception of level and sources of stress in students of two baccalaureate nursing programs, to compare these groups in their perceived stress and to compare the nursing groups to those enrolled in other health-related disciplines: Medicine, Pharmacy and Social Work. The study was descriptive correlational in design. The sample consisted of 552 full-time university students enrolled in years 2, 3 and 4 of their programs in selected disciplines. Data were collected by means of a questionnaire consisting of three main instruments: the Beck-Srivastava Stress Inventory (BSSI), the General Health Questionnaire 30-item version (GHQ-30) and a demographic profile. Data were analyzed using the SPSSx Statistical Package and included analysis of variance, frequency distribution, measures of correlation, item analysis and factor analysis. The results revealed that baccalaureate nursing students, regardless of year in program or university of attendance, experienced higher levels of stress and higher levels of physiological and psychological symptoms than students in other health-related disciplines. Identified stressors among the disciplines are also reported in the article.

Adult↗
PubMed1997

Glutamine synthetase from N2-fixing cyanobacterium Nostoc muscorum--purification, biochemical and immunological characteristics.

A modified procedure for purification of glutamine synthetase [L-glutamate: ammonia ligase (ADP-forming)] from N2-fixing cyanobacterium N. muscorum, to homogeneity is described using DEAE-Sephadex and Blue-Sepharose affinity chromatography. Specific activities of the purified enzyme in biosynthetic and transferase assays were 8.5 and 28 mumole product formed min-1 mg-1 protein. Apparent molecular mass of native GS enzyme was about 610 kDa as estimated by gel filtration. On SDS-PAGE the enzyme protein migrated as single band with molecular weight of 51 kDa. Apparent Michaelis Menten constant (Km) for glutamate, glutamine, ATP and ammonium were 2.8, 4.0, 0.35 and 0.82 mM respectively. Ammonium and structural analogues of glutamine and ammonium viz, methionine sulfone (MSO), methionine-DL-sulfoximine (MSX), ethylenediamine (EDA) and glyphosine significantly inactivated the enzyme activity while azaserine showed partial inhibition. Polyclonal antibodies raised against purified GS protein of N. muscorum showed high specificity to both crude and pure GS preparations in different immunological assays like double diffusion, rocket immunoelectrophoresis, ELISA and western blotting. With serological procedure a microquantity of GS-antigen upto 2 ng in vivo and immunological relationship of the protein with different strains have been documented.

Cyanobacteria↗
PubMed1996

Variability in physicians' reported ordering and perceived reassurance value of diagnostic tests in children with 'growing pains'.

OBJECTIVES: To determine the variability in the reported ordering of tests and treatment and to determine physicians' perceptions of the reassurance value to families of diagnostic tests in children with "growing pains." DESIGN: Cross-sectional survey using a mailed questionnaire. SETTINGS: Primary care and referral practices in Toronto, Ontario. PARTICIPANTS: University-affiliated primary care pediatricians and family physicians were surveyed, as well as all pediatric orthopedic surgeons and pediatric rheumatologists in Ontario. Pediatric orthopedic surgeons and pediatric rheumatologists were combined into a single group. MAIN OUTCOME MEASURES: Frequency of office visits because of growing pains, frequency of diagnostic testing, management strategies for these children, and physicians' perceptions of the reassurance value of diagnostic tests. RESULTS: Of 205 eligible physicians, 181 (88.3%) responded. The median reported frequency of office visits because of growing pains was 1%. Compared with the other physician groups, family physicians were significantly more likely to order a determination of the hemoglobin level (P = .003), erythrocyte sedimentation rate (P = .01), white blood cell count (P = .01), and differential blood cell count (P = .003), but not imaging tests. Family physicians were also more likely to order diagnostic tests when they were under parental pressure to do so (P = .001) or for the child with repeated visits (P = .02). In total, 86% of pediatric orthopedic surgeons and pediatric rheumatologists, 95% of pediatricians, and 100% of family physicians perceived normal test results to be reassuring to parents. Treatment strategies were similar across the 3 physician groups. CONCLUSIONS: The frequency of diagnostic testing varied among physician groups. Virtually all physicians perceived normal test results to be reassuring to families.

Adult↗
PubMed1996

Study of mercury-selenium (Hg-Se) interactions and their impact on Hg uptake by the radish (Raphanus sativus) plant.

Pot culture experiments were conducted to study the effects of selenite and selenate treatment (0.5-6.0 microg/ml) on the uptake and translocation of root-absorbed mercury (Hg) in radish plants irrigated with 2 and 5 microg/ml Hg in sand and soil culture. Statistically significant reductions in mercury uptake with increasing concentrations of selenium (Se) were observed. Both forms of selenium (selenite and selenate) were equally effective in reducing the mercury burden of the plant. The observed reduction in plant uptake of mercury is explained by the formation of an HgSe insoluble complex in the soil-root environment. No significant difference (P > 0.05) in dry matter yields with the various selenium treatments was found, suggesting that no selenium toxicity or salt injury occurred in the plants.

Drug Interactions↗
PubMed1996

Identification of a 25-kilodalton protein of Mycobacterium bovis BCG to distinguish BCG strains from Mycobacterium tuberculosis.

Mycobacterium bovis BCG vaccine strains were compared with Mycobacterium tuberculosis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 25-kDa protein observed in the BCG strains was absent in M. tuberculosis. Rabbit antibodies specific to the 25-kDa protein uniquely identified this protein in BCG strains but not in M. tuberculosis. It is suggested that the 25-kDa protein and polyclonal antibodies directed against this antigen can be exploited to distinguish BCG strains from M. tuberculosis.

Antibodies, Bacterial↗
PubMed1995

Human CD8 transgene regulation of HLA recognition by murine T cells.

A series of human CD8 transgenic (hCD8 Tg) mice with differential expression in the thymus and periphery were produced to investigate CD8 coreceptor regulation of repertoire selection and T cell responses. Expression of hCD8 markedly enhanced responses to both HLA class I molecules and hybrid A2/Kb molecules providing functional evidence for a second interaction site, outside of the alpha 3 domain, which is essential for optimal coreceptor function. Peripheral T cell expression of hCD8 was sufficient to augment responsiveness to HLA class I, as hCD8 Tg mice which lacked thymic expression responded as well as mice expressing hCD8 in the thymus and periphery. Both murine CD8+ and CD4+ T cells expressing hCD8 transgenes exhibited markedly enhanced responses to foreign HLA class I, revealing the ability of T cell receptor repertoires selected on either murine class I or class II to recognize human class I major histocompatibility complex (MHC). In contrast to recognition of foreign class I, thymic expression of hCD8 transgenes was absolutely required to enhance recognition of antigenic peptide restricted by self-HLA class I. Thus, our studies revealed disparate requirements for CD8 coreceptor expression in the thymus for selection of a T cell repertoire responsive to foreign MHC and to antigenic peptides bound to self-MHC, providing a novel demonstration of positive selection that is dependent on human CD8.

Amino Acid Sequence↗
PubMed1995

Construction of a recombinant cellulolytic Escherichia coli.

A 1.2-kb DNA fragment from Bacillus subtilis CD4 encoding endo-beta-1,4-glucanase and cellobiase activities was cloned and expressed in Escherichia coli. Carboxymethylcellulase (CMCase) and cellobiase activities were detected in a cell-free lysate of recombinant (re-) E. coli (Ec). The re-enzymes were functional in Ec, as it utilized carboxymethylcellulose, soluble cellulose and cellobiose as sole carbon sources for growth.

Bacillus subtilis↗
PubMed1995

Studies on uptake of trivalent and hexavalent chromium by maize (Zea mays).

Pot culture experiments were carried out to study the uptake and translocation of chromium from irrigation water when supplied in its trivalent and hexavalent states to maize plants grown in soil and sand culture. The uptake of chromium was observed to increase with increase in the concentration for both oxidation states of chromium. For the root, the observed order of uptake was CrIII sand > CrVI sand > CrIII soil > CrVI soil, whereas in the lower shoot, upper shoot and fruit the order was CrVI sand > CrVI soil > CrIII sand > CrIII soil. Significantly high uptake of chromium by roots in the sand culture (CrIII treatment) is attributed to the effect of root exudates and degradation products on the mobilization of CrIII. In aerial parts of the plants a higher uptake was observed when the initial supply was CrVI. The trends observed are explained on the basis of the redox behaviour of chromium.

Chromium↗
PubMed1995

Plant uptake of fluoride in irrigation water by ladyfinger (Abelmorchus esculentus).

Because of suggestions that food is a rich source of fluoride to humans and the absence of permissible and upper limits of fluoride for irrigation water, plant uptake studies were conducted using fluoride-rich irrigation water. Ladyfinger was grown in sand and soil cultures for 18 wk and the accumulation of fluoride in various plant parts was studied. The potential for ingestion of fluoride by humans through this route was also considered. The percentage uptake was greater in sand-cultured plants than in soil-cultured plants. The root accumulates most of the fluoride supplied through irrigation water and the fruit accumulates the least. Up to 120 mg fluoride/litre of irrigation water did not harm the plants. The ingestion of fluoride by humans from plants irrigated with water containing 10 mg fluoride/litre would be 0.20 mg per 100 g ladyfinger.

Fluorides↗
PubMed1995

Purification and characterization of an acid phosphatase from Arachis hypogaea.

An acid phosphatase from Arachis hypogaea (peanuts) has been purified. The electrophoretically homogeneous enzyme preparation is free of any phophodiesterase activity. The enzyme has a molecular weight of 120,000. Among the various phosphomonoesters tested, p-nitrophenylphosphate was found to be its most effective substrate. The Km for p-nitrophenylphosphate was 1.21 mM at pH 5.0 and 25 degrees C. The enzyme was thermostable and did not loose activity after 1 hr at 50 degrees C.

Acid Phosphatase↗
PubMed1995

Evaluation of resistant-reversal, CDRI compound 87/209 and its possible mode of action in rodent experimental malaria.

The resurgence of malaria in form of resistance against chloroquine (CQ) has decreased the importance of the drug as a chemotherapeutic agent. If an agent in combination with CQ can make CQ resistant plasmodia susceptible to CQ, the problem of drug resistance may then be solved. Use of conventional drugs like verapamil, desipramine along with CQ suggested the feasibility of this approach. This report is concerned with a new class of compound, CDRI compound 87/209 (15 mg/kg b. wt.) which is given in combination with chloroquine (10 mg/kg b. wt.) for 10 consecutive days to chloroquine resistant P. berghei/P. yoelii nigeriensis (multidrug resistant) infected Mastomys coucha/Swiss albino mice respectively, displayed a potential in curing the animals. A tentative mode of action of the CDRI compound 87/209 based upon its unique property of inhibiting heme-oxygenase (a heme degrading enzyme) has been presented. It is likely that CDRI compound 87/209 in combination with chloroquine may reverse the resistance acquired by the malarial parasites and in combination with CQ is capable of clearing the parasite from the animals.

Animals↗
PubMed1995

Prevalence of malaria among pregnant and non-pregnant women of district Jabalpur, Madhya Pradesh.

In the study period of two years 145 pregnant and 79 non-pregnant women with malarial infection were recorded. Plasmodium falciparum was the most prevalent species accounting for 72% of the total malaria infection in pregnant women while, in non-pregnant women it accounted for 58%. Results were analysed according to the species to which the parasite belonged, period of gestation and parity. While cerebral malaria, abortions, intrauterine foetal death, maternal anaemia were common in pregnant patients, only one neonatal death was recorded. Malaria parasites were not found in infants born to mothers with very heavy parasitaemia at the time of delivery. Even though pregnant women of all age groups and parity remain highly susceptible to malaria throughout pregnancy and puerperium from this area, some striking differences like malaria infection more prevalent in primigravidas than multigravidas and in second trimester than in third trimester were noticed in comparison to northern India. Results emphasize the need to target malaria control for this group of women. Failure to clear parasitaemia after chloroquine administration in P. falciparum was common in both pregnant and non-pregnant women. This is an area, where there is a great need to introduce effective malaria interventions. As chloroquine resistant parasites spread a better understanding of the problem is needed leading to a few chemotherapeutic options for pregnant women.

Adult↗
PubMed1994

Sequence of the gene encoding the N-terminal portion of the Plasmodium yoelii yoelii 17XL merozoite surface protein-1 (MSP-1).

The nucleotide (nt) sequence of the 5' portion of the gene encoding the Plasmodium yoelii yoelii (Pyy) 17XL merozite surface protein-1 (MSP-1) was determined by direct sequencing of both strands of the polymerase chain reaction (PCR) product. This report completes the entire coding region of the Pyy 17XL MSP-1 gene which we have found to be identical to the nt sequence of the Pyy YM MSP-1 [Lewis, Mol. Biochem. Parasitol. 36 (1989) 271-282], despite independent selection of parasite clones, passages and replications in mice over many years.

Amino Acid Sequence↗
PubMed1994

A 53 kDa protein of Vibrio cholerae classical strain 0395 involved in intestinal colonization.

Mutants of Vibrio cholerae 01 strain 0395 (classical) mutated in genes encoding secretory or cell surface proteins were induced by TnphoA mutagenesis and were selected as blue colonies on L-agar plates containing 5-bromo-4-chloro-3-indolyl phosphate. Southern analysis of the total DNA from blue colonies showed that all mutants had TnphoA insertion in genomic DNA. These mutants were analysed for adherence, colonization and protein profile. Adherence to freshly isolated rabbit intestinal discs was affected in some mutants. The less adhesive mutants were examined for colonization of the intestine of infant mice. One mutant, designated T-87, was extremely poor at colonization and less diarrhaegenic than the parent strain. Analysis of T-87 by SDS-PAGE revealed that two proteins of 53 and 38 kDa were lacking. The 38 kDa protein was identified as OmpU. The 53 kDa protein was extracellular and cells treated with anti-53-kDa antibodies could not colonize the gut of infant mice. The expression of the 53 and 38 kDa proteins in T-87 was dependent of the growth medium. The data suggest that T-87 is mutated in a regulatory gene which regulates the expression of proteins involved in intestinal colonization.

Animals↗
PubMed1994

recA mutations reduce adherence and colonization by classical and El Tor strains of Vibrio cholerae.

Two recA mutants of Vibrio cholerae (classical and El Tor biotypes) were constructed by disruption of the wild-type recA gene with mutated recA sequences of V. cholerae cloned in the suicide vector pGP704. Mutants defective in the recA gene were compared with their respective RecA+ parent strains with regard to their adherence to isolated rabbit intestine and colonization of intestine of infant mice. The recA mutation in V. cholerae was found to diminish adherence and markedly affected colonization.

Animals↗