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Biomedical subjects

M R Rao

Publications and source records attributed to M R Rao.

At least 37 records · Page 2Linked to original sources
PubMed1999

Epidemiology of rotavirus diarrhea in Egyptian children and implications for disease control.

Reliable epidemiologic data are essential for formulating effective policy to control rotavirus disease through immunization. The objective of this study was to describe the epidemiology of rotavirus diarrhea in a population-based cohort of children under 3 years of age residing in Abu Homos, Egypt, in 1995-1996. Rotavirus diarrhea incidence rates (episodes per person-year) were 0.13 for infants aged <6 months, 0.61 for those aged 6-11 months, 0.17 for those aged 12-23 months, and 0.15 for those aged 24-35 months. Fifty-six percent of children with rotavirus diarrhea had clinical dehydration; 90% of rotavirus diarrheal episodes occurred between July and November. In infants under 1 year of age, receipt of breast milk was associated with a lower incidence of rotavirus diarrhea. No other sociodemographic or environmental factor was found to be significantly associated with rotavirus diarrhea. Of 46 rotavirus isolates with strains identified, 41 (89%) were G serotypes 1 and 2. Rotavirus diarrhea was a major cause of morbidity in this cohort. Promotion of breastfeeding may exert a protective effect in young infants in this setting, but improvements in water and sanitation are unlikely to be effective preventive measures. The use of effective immunization against rotavirus in early infancy should be considered a public health priority.

Age Distribution↗
PubMed1999

Lamellarin alpha 20-sulfate, an inhibitor of HIV-1 integrase active against HIV-1 virus in cell culture.

HIV-1 integrase is an attractive target for anti-retroviral chemotherapy, but to date no clinically useful inhibitors have been developed. We have screened diverse marine natural products for compounds active against integrase in vitro and found a series of ascidian alkaloids, the lamellarins, that show selective inhibition. A new member of the family named lamellarin alpha 20-sulfate (1), the structure of which was determined from spectroscopic data, displayed the most favorable therapeutic index. The site of action of lamellarin alpha 20-sulfate on the integrase protein was mapped by testing activity against deletion mutants of integrase. Inhibition of isolated catalytic domain was detectable though weaker than inhibition of full length integrase; possibly lamellarin alpha 20-sulfate binds a site composed of multiple integrase domains. Lamellarin alpha 20-sulfate also inhibited integration in vitro by authentic HIV-1 replication intermediates isolated from infected cells. Lamellarin alpha 20-sulfate was tested against wild type HIV using the MAGI indicator cell assay and found to inhibit early steps of HIV replication. To clarify the inhibitor target, we tested inhibition against an HIV-based retroviral vector bearing a different viral envelope. Inhibition was observed, indicating that the HIV envelope cannot be the sole target of lamellarin alpha 20-sulfate in cell culture. In addition, these single round tests rule out action against viral assembly or budding. These findings provide a new class of compounds for potential development of clinically useful integrase inhibitors.

Animals↗
PubMed1999

Characterization of unusual G8 rotavirus strains isolated from Egyptian children.

We report the first detection of P[14], G8 rotaviruses isolated in Egypt from the stool of children participating in a 3 year study of rotavirus epidemiology. Two strains, EGY1850 and EGY2295, were characterized by a serotyping enzyme immunoassay (EIA), virus neutralization, and sequence analysis of the genes encoding VP7 and the VP8* portion of the VP4 gene. These two strains shared a high level of homology of their VP7s (87.8% nucleotide [nt], 97.2% amino acid [aa]) and VP4s (89.6% nt, 97.1% aa) and had the highest VP7 identity to serotype G8 (> 82% nt, > 92% aa) and VP4 identity to genotype P[14] (> or = 81% nt, > 91% aa) strains. Serological results with a VP7 G8-specific and VP4 P[14]-specific neutralizing monoclonal antibodies supported the genetic classification of EGY1850 and EGY2295 as P[14], G8. Genogroup analysis supports earlier findings that human G8 rotaviruses may be genetically related to bovine rotaviruses. These findings demonstrate that our understanding of the geographic distribution of rotavirus strains is incomplete, emphasize the need to monitor rotavirus serotypes, and extend the known distribution of serotype G8 and genotype P[14] strains in Africa.

Animals↗
PubMed1999

CpG islands in chromatin organization and gene expression.

CpG islands are stretches of DNA sequence that are enriched in the (CpG)n repeat and are present in close association with all housekeeping genes as well as some tissue-specific genes in the mammalian genome. Methylation of CpG islands strongly influences both structural organization and function of chromatin. The presence of a CpG island in a given chromosomal domain can, by itself, give rise to relatively open and active chromatin. Recently, several histone acetyltransferases, histone deacetylases, and chromatin remodeling factors have been found to be part of the transcription machinery. It is becoming increasingly clear that CpG islands and their methylation status may influence the function or recruitment of these newly discovered chromatin remodeling factors, especially the histone deacetylases. In addition, CpG islands may also play a significant role in the reorganization of chromatin during mammalian spermiogenesis.

Animals↗
PubMed1999

Pesticide induced changes of nitric oxide synthase in rat brain in vitro.

Organic insecticides are well known neurotoxicants. Nitric oxide (NO) is a neurotransmitter formed stoicheometrically with citrulline from L-arqinine through mediation of the enzyme nitric oxide synthase (NOS). We measured NOS activity in rat brain in vitro in the presence of selected organic insecticides such as, 10-200 microM conc carbaryl, kepone and malathion. All these three compounds inhibited NOS activity of rat brain in vitro in a concentration dependent manner. In most cases the changes observed were statistically significant. The order of potency, based on IC50 values of these insecticides, to inhibit NOS activity of rat brain, is carbaryl (105 microM) > Kepone (144 microM) > malathion (170 microM). We further demonstrated that these insecticides inhibit calmodulin (CaM)-stimulated NOS activity without affecting the basal enzyme activity. It is reported that the observed inhibition of NOS by selected insecticides may be due to interaction of these insecticides with Ca2+/CaM on which the NOS activity is well known to be dependent. This ultimately may lead to neurotoxicity of rat brain.

Animals↗
PubMed1999

Fructose-1,6-diphosphate in the treatment of oleander toxicity in dogs.

Oleander, a flowering plant that grows in the Mediterranean and southern US, contains the cardiac glycosides oleandrin, digitoxigenin and nerium, which inhibit Na(+)-K+ ATPase. Clinical manifestations of oleander toxicity include gastrointestinal irritation, marked hyperkalemia, A-V block, ventricular dysrhythmia, and not uncommonly death. Because fructose-1,6-diphosphate (FDP) has been shown to attenuate digoxin toxicity, we determined whether this agent would be effective in the treatment of the toxicity of these similarly-structured cardiac glycosides. Anesthetized dogs (n = 12) were infused i.v. for 5 min with 40 mg oleander extract/kg and then 6 dogs randomly selected from that group received a 50 mg/kg bolus of 10% FDP followed by a constant infusion. The other control animals received the same dosage of 10% dextrose. Within 5 min after oleander administration, all dogs developed dysrhythmias. The FDP-treated animals reverted to sinus rhythm within 1.58 +/- 0.15 h; none in the control group returned to sinus rhythm. One control dog died at 3 h from ventricular fibrillation. Marked hyperkalemia was observed in the control group; plasma K+ remained unchanged in the FDP group. Throughout the 4 h experimental period the FDP group maintained normal arterial pressures; in the control dextrose group, pressures were profoundly depressed. Cardiac output declined in both groups but remained higher in the FDP group. To determine the mechanism whereby FDP attenuates oleander toxicity, we studied the in vitro effect of FDP on oleander poisoned myocardial sarcolemmal membranes. At concentrations of 1 and 2 mg oleander inhibited Na(+)-K+ ATPase activity and addition of 500 microM FDP restored myocardial sarcolemmal Na(+)-K+ ATPase function. FDP effectively prevented hyperkalemia, reversed dysrhythmias and improved hemodynamics in vivo in this canine model of oleander toxicity and also restored sarcolemmal Na(+)-K+ ATPase activity in vitro.

Animals↗
PubMed1998

Treatment and vaccination strategies to control cholera in sub-Saharan refugee settings: a cost-effectiveness analysis.

CONTEXT: There is significant controversy about how best to control cholera epidemics in refugee settings. Specifically, there is marked disagreement about whether to use oral cholera vaccines in these settings, despite the improved safety and effectiveness profiles of these vaccines. OBJECTIVE: To determine the cost-effectiveness of alternative intervention strategies, including vaccination, to control cholera outbreaks in sub-Saharan refugee camps. DESIGN: A cost-effectiveness analysis based on probabilities of cholera outcomes derived from epidemiologic data compiled for refugee settings in Malawi from 1987 through 1993; data for costs were obtained from a large relief agency that provides medical care in such settings. SETTING AND PARTICIPANTS: A hypothetical refugee camp with 50000 persons in sub-Saharan Africa evaluated for a 2-year period. INTERVENTIONS: We compared the costs and outcomes of alternative strategies in which appropriate rehydration therapy for cholera is introduced preemptively (at the establishment of a camp) or reactively (once an epidemic is recognized) and in which mass immunization with oral B subunit killed whole-cell (BS-WC) cholera vaccine is added to a rehydration program either preemptively or reactively. MAIN OUTCOME MEASURES: Cost per cholera case prevented and cost per cholera death averted. RESULTS: In a situation with no available rehydration therapy suitable for the management of severe cholera, a strategy of preemptive therapy ($320 per death averted) costs less and is more effective than a strategy of reactive therapy ($586 per death averted). Adding vaccination to preemptive therapy is expensive: $1745 per additional death averted for preemptive vaccination and $3833 per additional death averted for reactive vaccination. However, if the cost of vaccine falls below $0.22 per dose, strategies combining vaccination and preemptive therapy become more cost-effective than therapy alone. CONCLUSIONS: Provision for managing cholera outbreaks at the inception of a refugee camp (preemptive therapy) is the most cost-effective strategy for controlling cholera outbreaks in sub-Saharan refugee settings. Should the price of BS-WC cholera vaccine fall below $0.22 per dose, however, supplementation of preemptive therapy with mass vaccination will become a cost-effective option.

Africa South of the Sahara↗
PubMed1998

Expression of rat histone H1d in Escherichia coli and its purification.

Histone H1 is involved in the folding of linear polynucleosomal filament into a 30-nm fiber. In an effort to understand the role of different domains of histone H1 in chromatin folding, we have now expressed rat histone H1d in Escherichia coli using pTrc99A expression vector by providing a 6-His tag at the C-terminus to facilitate its purification. The expressed protein histone H1d was purified from the soluble extract of E. coli by employing Ni2+ NTA-agarose and heparin-agarose chromatography. The recombinant histone H1d was shown to be authentic by its N-terminal amino acid analysis, its secondary structural characteristics, and its ability to (a) condense DNA and (b) bind specifically to synthetic four-way junction DNA.

Amino Acid Sequence↗
PubMed1998

Hyperexpression of rat spermatidal protein TP2 in Escherichia coli by codon optimization and engineering the vector-encoded 5' UTR.

We have recently reported the cDNA cloning of rat spermatidal protein TP2 and its expression in Escherichia coli using pTrc 99A as the expression vector. However, the expression level was very low. We have now improved the expression of TP2 over fivefold by (1) optimizing the codons for lysine, arginine, proline, leucine, glycine, valine, threonine, alanine, and tyrosine and (2) by engineering the vector-encoded 5' UTR. The expressed protein was in the soluble phase and could be purified to homogeneity by successive chromatography on Zinc-NTA-agarose affinity matrix and heparin agarose. Serendipitously, we have also observed a concomitant hyperinduction of vector encoded beta-lactamase gene along with TP2 in the E. coli BL21 (DE3) cells.

Amino Acid Sequence↗
PubMed1998

Effects of taurine on signal transduction steps induced during hypertrophy of rat heart myocytes.

Angiotensin II plays an important role in the development of cardiac hypertrophy. One factor thought to contribute to the trophic activity of angiotensin II in fibroblasts is the elevation in [Ca2+]i. Although this theory has received considerable support in cardiac fibroblasts, it is much more controversial in cardiac myocytes. Therefore, the aim of this report was to examine the effect of several Ca2+ modulators on protein synthesis in neonatal cardiac myocytes. We found that angiotensin II increased both [Ca2+]i and the rate of protein synthesis in isolated myocytes. Both effects were blocked by nifedipine, but only the angiotensin II-mediated increase in [Ca2+]i was inhibited by taurine in a dose-dependent manner. These data support the notion that Ca2+ plays only a permissive role in angiotensin II-mediated stimulation of protein synthesis. By contrast, the ability of taurine to attenuate the positive chronotropic effect, the prolongation of the action potential and the proarrhythmic activity of angiotensin II appear to be linked directly to changes in [Ca2+]i. We conclude that taurine reverses these actions of angiotensin II by altering Ca2+ flux across the cell membrane.

Angiotensin II↗
PubMed1998

In vitro induction of nitric oxide by fructose-1,6-diphosphate in the cardiovascular system of rats.

Nitric oxide (NO) functions as a cellular messenger in a number of organs and cell systems in the cardiovascular system (CVS); it is a significant determinant of basal vascular tone and regulates myocardial contractility and platelet aggregation. The present study focused upon understanding the in vitro effects of fructose-1,6-diphosphate (FDP) on the rat cellular NO pathway. The iNOS activity was measured by monitoring the formation of (3H)-citrulline in 50,000 g soluble fractions of crude homogenates of endothelial (ET) and smooth muscle cells (SMC) from the arteries of rats, and macrophages (MAC) and lymphocytes (LYM) from rat blood. FDP in concentrations of 10-1000 microM stimulated rat cellular iNOS activity in a concentration-dependent manner. FDP-stimulated rat cellular iNOS was found to be completely reversed by 5 microM concentration of NG-monomethyl-L-arginine (L-NMMA), the potent mammalian NOS inhibitor. These studies demonstrated that FDP may induce the formation of NO by stimulating rat cardiovascular iNOS activity.

Animals↗
PubMed1998

Changes in the cardiovascular nitric oxide pathway in cyclosporin-A treated rats.

Cyclosporin A (CsA), an immunosuppressive agent is known to induce cellular toxic effects by alerting calcium homeostasis. Nitric oxide (NO) has been implicated in a number of physiologic roles in the mammalian cardiovascular system (CVS). The aim of our present study is to investigate the effects of CsA on the rat CV NO pathway. We measured iNOS and cNOS activities in the 100,000 g soluble fraction of ventricles and serum nitrite (NO2-) and nitrite (NO3-) levels in rats treated with 25 mg/kg or 50 mg/kg body weight of CsA/24 hr in olive oil. CsA inhibited cNOS activity of rat ventricles and failed to bring about changes in their iNOS activity. Serum NO2-/NO3- levels were elevated in CsA treated tars. Most of these changes were found to be statistically significant (P < 0.01) at 50 mg/kg body wt of CsA. It is likely that elevation of serum NO2-/NO3- levels may cause myocardial toxicity by alerting rat CV NO pathway.

Animals↗
PubMed1997

Condensation of DNA and chromatin by an SPKK-containing octapeptide repeat motif present in the C-terminus of histone H1.

Several DNA binding motifs have been described in the C-terminus of histone H1 (Churchill & Travers, 1991), of these the S/TPKK repeat (Suzuki, 1989) often occurs as a part of an octapeptide repeat of the type XTPKKXKK. We have studied in detail the DNA and chromatin condensing properties of a consensus octapeptide KSPKKAKK (8 mer) present in many histone H1 subtypes and its imperfect repeat ATPKKSTKKTPKKAKK (16 mer TPKK) as it occurs in the C-terminus of rat histone H1d. The 16 mer TPKK peptide containing two S/TPKK motifs was able to condense both rat oligonucleosomal (2-5 kbp) DNA and histone H1-depleted chromatin as revealed by circular dichroism spectroscopy. The 8 mer peptide, however, was unable to condense either the DNA or the histone H1-depleted chromatin. Both the 8 mer peptide and the 16 mer TPKK peptide displaced distamycin A from the drug-DNA complex, although with different efficiency, indicating that while these two peptides could bind DNA, only the 16 mer (TPKK) peptide could bring about condensation of DNA and histone H1-depleted chromatin. A mutant 16 mer (TAKK) peptide wherein two proline residues are replaced by alanine, was ineffective in bringing about condensation of both DNA and histone H1-depleted chromatin. These results suggest that the two beta-turn structures present in the 16 mer (TPKK) peptide could be important in facilitating binding to different regions of duplex DNA thereby bringing about close packing and condensation. The condensation property of the 16 mer (TPKK) peptide was very similar to that of histone H1 in terms of (a) its preference for AT rich DNA, (b) cooperativity of condensation, and (c) salt dependence of condensation. The 16 mer (TPKK) peptide, but not the 8 mer peptide or the 16 mer (TAKK) peptide, could form complexes with a polynucleosomal 5S DNA core resulting in retarded mobility similar to the complexes formed with histone H1 on agarose gel electrophoresis.

Amino Acid Sequence↗
PubMed1997

Cloning of the cDNA encoding rat homologue of the mismatch repair gene MSH2 and its expression during spermatogenesis.

A rat cDNA clone encoding the mismatch repair protein MSH2 has been isolated and characterized. The cDNA has an open reading frame of 2802 nucleotides in length coding for a protein of 933 amino acids (100 kDa). It shows significant homology to human and mouse MSH2. Northern blot analysis of rat MSH2 in the testes of rats of different ages showed maximum expression at 20 days, at which time the germ cells are undergoing premeiotic DNA replication. We observed down-regulation in the expression of rat MSH2 beyond 25 days by which time the germ cells have entered meiotic prophase.

Amino Acid Sequence↗
PubMed1997

Field trial of a locally produced, killed, oral cholera vaccine in Vietnam.

BACKGROUND: Several studies have shown that orally administered killed cholera vaccines are safe and protective in populations at risk of cholera in developing countries. However, these vaccines have not been adopted for use in developing countries because of their expense and limited efficacy in young children. We have tested an inexpensive, killed whole-cell cholera vaccine developed and produced in Vietnam. METHODS: The efficacy of the vaccine was assessed in a large-scale, open field trial in people at least 1 year old residing in 22,653 households in the central coastal city of Hue. Alternate households were assigned vaccine (67,395 people; two doses per person) or no vaccine (67,058 people). Surveillance for cholera was conducted in all Ministry of Health facilities serving this population. Analysis was by intention to treat. FINDINGS: During an outbreak of El Tor cholera 8-10 months after vaccination, 37 cases of cholera requiring inpatient care occurred among age-eligible people allocated to the vaccine group, and 92 cases among age-eligible people allocated to the no-vaccine group (protective impact 60% [95% CI 40-73]). Among the 51,975 people who received the complete two-dose vaccine regimen, the protective efficacy was 66% (46-79): in this subset, the protective efficacy was similar for children aged 1-5 years (68%) and for older people (66%). INTERPRETATION: These findings suggest that oral killed whole-cell vaccines can confer substantial protection against El Tor cholera in young children, who are at highest risk of cholera in endemic settings. An inexpensive, locally produced, and effective oral cholera vaccine may be within reach of the limited health-care budgets of poor countries with endemic cholera, if our findings can be replicated in a randomised double-blind trial.

Administration, Oral↗
PubMed1997

Preferential condensation of SAR-DNA by histone H1 and its SPKK containing octapeptide repeat motif.

Linker histone H1 binds preferentially the scaffold associated region (SAR) DNA elements that contain characteristic oligo dA x dT tracts. In the present study, we have compared the condensation brought about by histone H1 of a SAR DNA fragment in the histone spacer region of Drosophila melanogaster with that of a random DNA (pBR322 EcoRI-SalI) fragment by circular dichroism spectroscopy. The condensation of the SAR DNA fragment by histone H1 is 3-4-fold higher than that of the random DNA fragment. A 16-mer peptide, ATPKKSTKKTPKKAKK, the sequence that is present in the C-terminus of histone Hld, which has recently been shown to possess DNA and chromatin condensing properties, also condenses the SAR DNA fragment preferentially in a highly cooperative manner. We have proposed a model for the dynamics of chromatin structure involving histone H1-SAR DNA interaction through SPKK containing peptide motifs and its competition by AT-hook peptides present in the nonhistone chromosomal proteins like HMG-I and HMG-Y.

Amino Acid Sequence↗