Biomedical subjects

M R Rao

Publications and source records attributed to M R Rao.

At least 109 records · Page 6Linked to original sources

PubMed1992

Evolutionary conservation of a germ cell-specific lamin persisting through mammalian spermiogenesis.

We had identified earlier a germ cell-specific lamin of 60 kDa in rat which is related to somatic lamin B. This polypeptide was shown to be the only major component organizing the lamina structure of round spermatids. In the present study, we find that this 60-kDa polypeptide persists in the testicular and epididymal sperms of rat. We also show, by indirect immunofluorescence studies, that the 60-kDa protein is antigenically conserved in the germ cells of grasshopper, rooster, and frog and in plant meiocytes. The distribution of fluorescence among the various germ cell populations shows that the antigen is located around the nuclear cortex of pre- and postmeiotic germ cells, while it is distributed all over the pachytene nuclei. The anti-60-kDa polyclonal antibodies also reacted with a 60-kDa polypeptide in the Western blot analysis of nuclear matrix proteins of grasshopper germ cells. The similar fluorescent localization pattern of the antigen observed in various eukaryotic species strongly suggests that this germ cell-specific lamin may play a very crucial role during meiotic prophase, particularly during homologous chromosome pairing and recombination.

Animals↗

PubMed1992

Seroepidemiologic evaluation of antibodies to rotavirus as correlates of the risk of clinically significant rotavirus diarrhea in rural Bangladesh.

A case-control study was conducted among children and adult women in rural Bangladesh to evaluate whether serologic immunity to rotavirus was associated with a lower risk of rotavirus diarrhea of sufficient severity to cause patients to seek medical care. Acute-phase sera from 219 cases of rotavirus diarrhea, detected among patients treated in three diarrheal treatment centers, were compared with sera from 477 contemporaneously selected community controls. Overall, serum IgG antirotavirus antibody titers were nearly one-fourth as high in cases as in controls (107 vs. 417 units/ml; P less than .001). Among persons aged greater than or equal to 8 months, in whom titers of maternal antirotavirus antibodies should have been negligible, even the lowest range of detectable titers (100-200 units/ml) was associated with a substantial (75%, P less than .05) reduction of the risk of rotavirus diarrhea. We conclude that titers of serum IgG antirotavirus antibodies induced by earlier infection were inversely related to the risk of clinically significant rotavirus diarrhea.

Adult↗

PubMed1992

Evidence that inactivated oral cholera vaccines both prevent and mitigate Vibrio cholerae O1 infections in a cholera-endemic area.

In a randomized, placebo-controlled field trial of B subunit-killed whole cell (BS-WC) and killed whole cell only (WC) inactivated oral cholera vaccines in rural Bangladesh, active surveillance of selected neighborhoods during the first year after vaccination identified 127 Vibrio cholerae O1 infections among 3285 three-dose recipients. For each vaccine, protective efficacy was greater against symptomatic (57%, P < .05 for BS-WC; 58%, P < .05 for WC) than against asymptomatic infections (46%, P < .05 for BS-WC; 32%, P = .09 for WC), and protection against each grade of infection was demonstrable for both the classical and El Tor biotypes. Although vaccine protection against symptomatic infections was evident in both young children and older persons, only persons vaccinated at age > 5 years were protected against asymptomatic infections. These results suggest that the inactivated oral vaccines acted both to protect against intestinal colonization by V. cholerae O1 and to interrupt the pathogenic sequence of established infections.

Adolescent↗

PubMed1992

Evidence that protection against rotavirus diarrhea after natural infection is not dependent on serotype-specific neutralizing antibody.

This case-control study sought to determine whether protection against clinically significant rotavirus diarrhea in children aged 4-35 months correlated with titers of serum neutralizing antibody and, if so, whether this protection was serotype-specific. Titers of acute-phase sera from 156 cases of treated rotavirus diarrhea in rural Bangladesh were contrasted with titers from 312 contemporaneously selected, age-matched controls. Analyses of the culture-adapted rotaviruses from the cases revealed that 24%, 15%, 43%, and 17% belonged to serotypes 1-4, respectively. Titers of both homologous and heterologous neutralizing antibody in acute blood specimens of cases were significantly lower than those of matched controls. However, multivariate logistic regression models demonstrated that only antibody titers to heterotypic rotaviruses were independently associated with protection against rotavirus disease. These data, which indicate that the correlation of protection with neutralizing antibody titers is not serotype-specific, suggest that immunity to rotavirus disease may be mediated by other factors.

Algorithms↗

PubMed1992

[Protective effects of praeruptorin C and nifedipine on ischemia-reperfused injury in working rat hearts].

The effects of praeruptorin C (Pra-C, 15 mg/kg, bid x 3 d, ip) on global myocardial ischemia and reperfusion were investigated in the isolated working rat hearts. The results at 35 min after reperfusion showed that as compared with the values before ischemia, AP, LVSP, +dP/dtmax, -dP/dtmax, LVEDP and T were recovered up to 80 +/- 19%, 82 +/- 16%, 78 +/- 21%, 85 +/- 11%, 136 +/- 77% and 133 +/- 21%, respectively. The corresponding parameters of Nifedipine (Nif, 60 micrograms/kg, bid x 3 d, ip) were 80 +/- 16%, 97 +/- 30%, 102 +/- 24%, 106 +/- 32%, 129 +/- 41% and 145 +/- 46%, respectively. The CF, SV and HR were recovered by 81 +/- 11%, 104 +/- 20% and 78 +/- 7% when using Pra-C and 86 +/- 11%, 106 +/- 25% and 82 +/- 11%, respectively, when using Nif. Additionally, in comparison of Pra-C and Nif with the ischemia group, the levels of creatine kinase released from cardiac cells decreased by 30% and 40%; while calcium accumulation in myocardial mitochondria were 41% and 46%, respectively. The study suggests that the protective effects of Pra-C on myocardial cells in the isolated working rat heart during myocardial ischemia are similar to those Nif.

Animals↗

PubMed1992

[Effects of m-nifedipine on experimental myocardial metabolism and infarct size in rabbits].

The protective effects of m-Nif 15, 30 and 50 micrograms.kg-1 and of Nif 30 micrograms.kg-1 on experimental myocardial infarction and metabolism in rabbits were evaluated. Blood samples were collected simultaneously from the femoral artery and the coronary sinus for examining lactate and potassium balance. In the normal group (n = 8) and the sham ligated group (n = 5), the lactate balance were +17 +/- 1.0 and + 13 +/- 1.1% respectively and the potassium balance were +2.1 +/- 0.08 and +2.4 +/- 0.08%, respectively. After occlusion of the LAD, the lactate and K+ balance reduced to -196 +/- 60.2 and -83.0 +/- 8.2% respectively, and m-Nif produced a dose dependent improvement of both balance. After giving m-Nif 15, 30 and 50 micrograms.kg-1 i.v., the lactate balance improved to -60 +/- 9, -48 +/- 6.7 and -24 +/- 1.8% and the K+ balance went up to -32.2 +/- 2.1, -17.6 +/- 0.1, -3.3 +/- 0.06, respectively. In the mean time, Nif 30 micrograms.kg-1 i.v. improved the lactate and K+ balances to -52 +/- 8.6% and -36.4 +/- 3.1%. In another experiment, propranolol 1 mg.kg-1 i.v. improved the lactate balance to -18 +/- 1.2% while the K+ balance increased to +2.0 +/- 0.05%. The area of the myocardial infarct was measured by nitroblue tetrazolium (N-BT) technique 24 h after LAD occlusion.2+ angina pectoris.

Animals↗

PubMed1992

Community-based evaluation of the effect of breast-feeding on the risk of microbiologically confirmed or clinically presumptive shigellosis in Bangladeshi children.

To assess the association between breast-feeding and the risk of microbiologically confirmed or clinically presumptive shigellosis, the authors performed a case-control analysis of Bangladeshi children younger than 3 years of age who were followed up for 1 month after exposure to Shigella in their residential neighborhoods. Two hundred sixty-nine cases with culture-confirmed shigellosis (n = 119) or clinically presumptive shigellosis (culture-negative dysentery, n = 150) were compared with 819 controls without Shigella diarrhea or other invasive diarrheal illnesses. The odds ratio relating breast-feeding to confirmed or presumptive shigellosis, adjusted for potentially confounding variables, was 0.48 (95% confidence interval = 0.32 to 0.72; P less than .001), suggesting a substantial protective effect. The protective association decreased with age but was still significant during the third year of life; appeared to be directly related to the degree of stunting; and was equivalent for confirmed and presumptive shigellosis. Notably, the protective association remained substantial against episodes due to Shigella which were resistant to at least one of the antibiotics customarily used for treatment of Shigella diarrhea (age-adjusted odds ratio = 0.40; 95% confidence interval = 0.22 to 0.74; P less than .01). These data suggest that breast-feeding confers a high level of protection against shigellosis throughout the first 3 years of life, especially among nutritionally compromised children, and thereby underscore the importance of promotion of breast-feeding as a central component of Shigella control programs in less developed settings.

Age Factors↗

PubMed1991

Mammalian spermatid specific protein, TP2, is a zinc metalloprotein with two finger motifs.

An analysis of the recently reported cDNA derived amino acid sequences of mouse (Kleene and Flynn, J. Biol. Chem. 262, 17272-17277, 1987) and rat (Luersson et al., Nucl. Acids Res. 17, 3585, 1989). TP2 has revealed the presence of two potential zinc finger motifs involving cysteine and histidine residues. TP2, as purified from rat elongating spermatids, is shown here to contain 0.2 atoms of zinc bound per molecule of the protein by atomic absorption spectroscopy. On incubation with 10 microM ZnCl2, in vitro, and subsequent exhaustive dialysis, TP2 had 2 atoms of zinc bound per molecule. The involvement of cysteine residues of TP2 in coordination with zinc was also suggested by the observation that TP2 could be labeled, in situ, with iodoacetamidofluorescein only after preincubation of spermatid nuclei with EDTA. The zinc finger domains of TP2 may play an important role in initiation of chromatin condensation and/or cessation of transcriptional activity during mammalian spermiogenesis.

Amino Acid Sequence↗

PubMed1991

Biotype as determinant of natural immunising effect of cholera.

To test the hypothesis that clinical Vibrio cholerae O1 infections protect against recurrent cholera, treated cholera episodes in a rural Bangladesh population of 188,153 people who were followed between 1985 and 1988 were analysed. Of the 2214 people with initial episodes of cholera, 7 had a second episode. The incidence of cholera was 61% lower in subjects who had had an earlier episode than in those without such an episode. Whereas initial episodes of classical cholera were associated with complete protection against subsequent cholera, initial episodes of El Tor cholera were associated with negligible protection.

Adolescent↗

PubMed1991

Tetrandrine: a novel calcium channel antagonist inhibits type I calcium channels in neuroblastoma cells.

Tetrandrine, an alkaloid isolated from the Chinese herb, Radix stephaniae tetrandrae, has been used clinically as a hypotensive agent for a long time. Recently, several studies have demonstrated that tetrandrine behaves like a calcium entry blocker. In the present investigation, the whole cell version of the patch clamp technique was used to study the effect of tetrandrine on the type I (transient inward) calcium current in neuroblastoma cells. These results showed that tetrandrine inhibited the transient inward current, without affecting the channel kinetics. The effects of tetrandrine were dose-dependent and reversible but did not depend on the frequency of stimulation (use-dependence) or the membrane potential. These data clearly demonstrate that tetrandrine is a novel and potent antagonist of the transient inward current in neuroblastoma cells.

Alkaloids↗

PubMed1991

Field trial of oral cholera vaccines in Bangladesh: serum vibriocidal and antitoxic antibodies as markers of the risk of cholera.

The relationship of serum vibriocidal (VC) and IgG anti-cholera toxin (CT) antibodies to the risk of cholera was evaluated during the first year of follow-up of recipients of three oral doses of B subunit (BS)-whole-cell vaccine, whole-cell vaccine, or Escherichia coli K12 strain placebo in Bangladesh. Acute sera from 121 cholera patients were compared with sera from 2592 contemporaneous community controls. Each doubling of VC titer was associated, on average, with a 22%-47% reduction of cholera risk in the three groups. In contrast, in the two groups that did not receive BS, anti-CT titers were directly associated with cholera and thus served as markers of higher cholera risk. Each vaccine conferred approximately 65% protective efficacy against cholera, but antibody titers did not correlate with vaccine efficacy, indicating that serum VC and anti-CT antibodies are poor markers of the longitudinal pattern of vaccine efficacy.

Administration, Oral↗

PubMed1991

ABO blood groups and the risk of diarrhea due to enterotoxigenic Escherichia coli.

To determine whether blood group O persons are at higher risk for enterotoxigenic Escherichia coli (ETEC) diarrhea, a case-control study was done for 17 months among rural Bangladeshis who were under systematic surveillance for diarrhea. Cases were children less than 3 years old who presented between 1 January 1985 and 1 June 1986 for care of heat labile (LT) or heat stabile toxin-producing ETEC diarrhea. Controls were of similar ages and were randomly selected from three community-based serosurveys between July 1985 and May 1986. No association between blood group O and ETEC diarrhea was found for the 510 cases and 641 controls, nor was an association evident for cases of each toxin phenotype. Further refinement of the case definition to include only patients with LT-ETEC diarrhea, without enteric copathogens, also failed to reveal a substantial association with blood group O. These data suggest that a strong association with ABO groups, analogous to that for cholera, does not exist for ETEC diarrhea.

ABO Blood-Group System↗

PubMed1991

Rotavirus-associated diarrhea in rural Bangladesh: two-year study of incidence and serotype distribution.

Stools were evaluated from 5,811 patient visits for treatment of diarrhea in Matlab, Bangladesh, between June 1987 and May 1989. The stools were analyzed to determine the distribution of serotypes of group A rotaviruses (RV). A total of 898 stool samples (15.5%) contained RV, as determined by using an enzyme-linked immunosorbent assay. RV isolates from 855 of these samples were serotyped by using serotype-specific synthetic oligonucleotide probes. A total of 558 (65.3%) could be assigned to specific serotypes: 166 (19.4%), 228 (26.7%), 39 (4.6%), and 125 (14.6%) belonged to serotypes 1 through 4, respectively; 12 (1.4%) hybridized with more than one serotype; and 285 (33.3%) failed to hybridize. RV diarrhea was evident throughout the year, with peaks in the dry winter months and in September 1988, coinciding with a major flood. RV was isolated from 46.6% of patients between 7 and 12 months old. Among children under 24 months of age with RV diarrhea, 1.2% (10 of 828) died. The corresponding percentage for children with diarrhea from all causes is 0.9% (29 of 3,301).

Bangladesh↗

PubMed1991

[Effect of M-nifedipine and metoprolol in combination on the hemodynamics in rabbits].

Hemodynamic effects of m--nifedipine (m--Nif) combined with metoprolol (Met) were studied in conscious rabbits with impedance cardiography. Administration of m--Nif by intravenous injection (20 micrograms/kg) or by intraduodenal route (0.25 mg/kg) increased cardiac index (CI) and reduced total peripheral resistance (TPR) and arterial pressure. Intravenous injection of Met significantly slowed heart rate without great change in other hemodynamic parameters in conscious rabbits. Combination of m--Nif with Met gained the advantages of both m--Nif and Met. The negative effects of Met on CI and TPR were balanced by the vasodilatory effect of m--Nif. The difference between the results of m--Nif combined with equal dose of Met or with five times the dose of Met was just that further decrease of heart rate was observed. These results suggest that combined administration of m--Nif with Met may be more beneficial than giving each drug alone. It may be more suitable to use m--Nif combined with low doses of Met in order to avoid the danger of depressing myocardium.

Animals↗

PubMed1990

Stage-dependent changes in localization of a germ cell-specific lamin during mammalian spermatogenesis.

We had earlier identified a 110/120-kDa protein specific to nuclear matrix of rat pachytene spermatocytes (Behal, A., Prakash, K., and Rao, M.R.S. (1987) J. Biol. Chem. 262, 10898-10902). This protein is now shown to be a disulfide-linked homodimer of a 60-kDa polypeptide. Indirect immunofluorescence and Western blot analyses using anti-120-kDa polyclonal antibodies have shown that this protein is a component of the pore-complex lamina structure of spermatogonia. As germ cells enter meiotic prophase and the lamina structure disassembles, this polypeptide is redistributed in the nucleus and can be isolated as a component of synaptonemal complexes. Following meiotic division, this 60-kDa protein is relocalized in the lamina, then representing the sole major component of the lamina structure of round spermatids. The identity of the 60-kDa protein in the pore-complex lamina fraction and synaptonemal complexes was further confirmed by two-dimensional analysis of iodinated tryptic peptides. Such an analysis has also shown that the germ cell-specific 60-kDa protein is related but not identical to somatic lamin B.

Animals↗

PubMed1990

Interaction of spermatid-specific protein TP2 with nucleic acids, in vitro. A comparative study with TP1.

TP2 was purified from rat testes employing a gentle method involving differential salt extraction of the sonication-resistant spermatid nuclei. The nucleic acid binding properties of TP2 were studied by fluorescence quenching, thermal denaturation, circular dichroism techniques and compared with those of TP1 (Singh, J., and Rao, M. R. S. (1987) J. Biol. Chem. 262, 734-740). The tyrosine fluorescence of TP2 was quenched upon binding to double-stranded and denatured DNA and poly(rA). The apparent association constants for binding of TP2 to these nucleic acids were calculated from the fluorescence quenching data, obtained at 50 mM NaCl, and found to be 1.63 x 10(5) M-1, 6.5 x 10(5) M-1, and 7.3 x 10(5) M-1, respectively. Thermal denaturation studies of calf thymus DNA and its complexes with TP2 showed that at 1 mM NaCl, TP2 shifted the Tm from 53 degrees C to 62-67 degrees C, while at 50 mM NaCl, the Tm was shifted from 72 to 78 degrees C suggesting that TP2 is a DNA stabilizing protein. Circular dichroism studies of TP1.DNA and TP2.DNA complexes have revealed that TP2 has a better DNA condensing property than TP1. Furthermore, in contrast to TP1, TP2 does not destabilize in vitro the compactness of liver nucleosome core particles. The DNA binding properties of TP1 and TP2 have been discussed in relation to the significance of their transient appearance during mammalian spermiogenesis.

Amino Acid Sequence↗

PubMed1990

Field trial of oral cholera vaccines in Bangladesh: results from three-year follow-up.

The protective efficacy (PE) of B subunit killed whole-cell (BS-WC) and killed whole-cell-only (WC) oral cholera vaccines was assessed in a randomised double-blind field trial among children aged 2-15 years and women over 15 years in rural Bangladesh. Among the 62 285 subjects who received three doses of BS-WC, WC, or Escherichia coli K12 strain placebo, cumulative PE at 3 years of follow-up was 50% for BS-WC and 52% for WC. PE was similar against severe and non-severe cholera, but was significantly lower in children who were vaccinated at 2-5 years (26% for BS-WC; 23% for WC) than in older persons (63% for BS-WC; 68% for WC). Among persons vaccinated at 2-5 years, protection at 4-6 months of follow-up was similar to that for older persons, but rapidly waned thereafter and was not evident during the third year of follow-up. In contrast, persons vaccinated at older ages were protected even in the third year of follow-up (PE 40% for BS-WC; 62% for WC). PE was substantially higher against classical cholera (58% for BS-WC; 60% for WC) than against El Tor cholera (39% and 40%).

Administration, Oral↗

PubMed1990

An essential Saccharomyces cerevisiae single-stranded DNA binding protein is homologous to the large subunit of human RP-A.

Single-stranded DNA binding proteins (SSBs) are known to play a role in DNA replication and recombination in prokaryotes. An SSB was previously purified from the yeast Saccharomyces cerevisiae. This SSB stimulated the activity of a cognate strand exchange protein (SEP1) in vitro suggesting a role in recombination. We have cloned and functionally analyzed the gene encoding this protein. DNA sequencing of the cloned DNA revealed a 621 amino acid open reading frame with a coding potential for a Mr 70,269 polypeptide. Highly significant amino acid homology was detected between this S.cerevisiae gene and the Mr 70,000 subunit polypeptide of human RP-A, a cellular protein essential for SV40 DNA replication in vitro. Therefore, we named the S.cerevisiae gene RPA1. RPA1 encodes an essential function in this organism as shown by tetrad analysis of heterozygous insertion mutants and is continuously required for mitotic growth. Cells lacking RPA1 accumulate as multiply budded cells with a single nucleus suggesting a defect in DNA replication.

Amino Acid Sequence↗