Biomedical subjects

R Subramaniam

Publications and source records attributed to R Subramaniam.

At least 19 recordsLinked to original sources

PubMed1995

Brain regional correspondence between Alzheimer's disease histopathology and biomarkers of protein oxidation.

Four biomarkers of neuronal protein oxidation [W/S ratio of MAL-6 spin-labeled synaptosomes, phenylhydrazine-reactive protein carbonyl content, glutamine synthetase (GS) activity, creatine kinase (CK) activity] in three brain regions [cerebellum, inferior parietal lobule (IPL), and hippocampus (HIP)] of Alzheimer's disease (AD)-demented and age-matched control subjects were assessed. These endpoints indicate that AD brain protein may be more oxidized than that of control subjects. The W/S ratios of AD hippocampal and inferior parietal synaptosomes are 30 and 46% lower, respectively, than corresponding values of tissue isolated from control brain; however, the difference between the W/S ratios of AD and control cerebellar synaptosomes is not significant. Protein carbonyl content is increased 42 and 37% in the Alzheimer's HIP and IPL regions, respectively, relative to AD cerebellum, whereas carbonyl content in control HIP and IPL is similar to that of control cerebellum. GS activity decreases an average of 27% in the AD brain; CK activity declines by 80%. The brain regional variation of these oxidation-sensitive biomarkers corresponds to established histopathological features of AD (senile plaque and neurofibrillary tangle densities) and is paralleled by an increase in immunoreactive microglia. These data indicate that senile plaque-dense regions of the AD brain may represent environments of elevated oxidative stress.

Aged↗

PubMed1991

Chlorophyll a/b binding (CAB) polypeptides of CP29, the internal chlorophyll a/b complex of PSII: characterization of the tomato gene encoding the 26 kDa (type I) polypeptide, and evidence for a second CP29 polypeptide.

CP29, the core chlorophyll a/b (CAB) antenna complex of Photosystem II (PSII), has two nuclear-encoded polypeptides of approximately 26 and 28 kDa in tomato (Lycopersicon esculentum). Cab9, the gene for the Type I (26 kDa) CP29 polypeptide was cloned by immunoscreening a tomato leaf cDNA library. Its identity was confirmed by sequencing tryptic peptides from the mature protein. Cab9 is a single-copy gene with five introns, the highest number found in a CAB protein. In vitro transcription-translation gave a 31 kDa precursor which was cleaved to about 26 kDa after import into isolated tomato chloroplasts. The Cab9 polypeptide has the two highly conserved regions common to all CAB polypeptides, which define the members of this extended gene family. Outside of the conserved regions, it is only slightly more closely related to other PSII CABs than to PSI CABs. Sequence analysis of tryptic peptides from the Type II (28 kDa) CP29 polypeptide showed that it is also a member of the CAB family and is very similar or identical to the CP29 polypeptide previously isolated from spinach. All members of the CAB family have absolutely conserved His, Gln and Asn residues which could ligate the Mg atoms of the chlorophylls, and a number of conserved Asp. Glu, Lys and Arg residues which could form H-bonds to the polar groups on the porphyrin rings. The two conserved regions comprise the first and third predicted trans-membrane helices and the stroma-exposed segments preceding them.

Amino Acid Sequence↗

PubMed1991

Trends in selected obstetric complications from University Hospital, Kuala Lumpur, Malaysia.

Trends in selected pregnancy complications from 1969 to 1987 in a tertiary hospital in Malaysia are presented. Complications reviewed were abortion, ectopic pregnancy, anemia, hypertension, hyperemesis, antepartum and postpartum hemorrhage. Possible explanations for the observed trends were discussed, including the role of improved obstetric care and changes in the characteristics of the childbearing population. The data presented give some indication of maternal morbidity in the childbearing population served by this tertiary center and should lead to improvements in provision of services as well as in health data collection in the future.

Abortion, Spontaneous↗

PubMed1990

The formation of covalent adducts between benzo[a]pyrenediol epoxide and RNA: structural analysis by mass spectrometry.

Racemic 7-r,8-t-dihydroxy-9-t,10-t-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene was reacted with yeast RNA. Modified nucleosides were isolated and resolved by high-performance liquid chromatography; nine adduct peaks were collected for analysis. The bases in these adducts were identified by comparing their retention times with those of adducts from poly(G), poly(A), and poly(C). These samples gave two major and two minor Guo adducts, four major Ado adducts, and at least four Cyd adducts. The relative efficiencies of adduct formation with the polyribonucleotides were poly(G) greater than yeast RNA greater than poly(A) greater than poly(C). Fluorescence measurements show that emission from Guo adducts is strongly quenched relative to that from Ado adducts. Liquid secondary ion mass spectrometry (LSIMS) of underivatized samples and electron-impact mass spectrometry (EIMS) of permethyl derivatives were used to confirm the base identities and establish the alkylation sites of the RNA adducts. Unique nitrogen-containing hydrocarbon fragments that were observed with all samples by EIMS establish that in each adduct analyzed the C-10 position of the hydrocarbon is linked to the exocyclic amino group of the base. This suggested that the multiple adducts formed with each base are diastereomers derived from cis/trans epoxide ring opening of the (+) and (-) enantiomers of the carcinogen. Several adducts exhibited molecular ions by both LSIMS and EIMS. Large fragments observed by EIMS usually resulted from the loss of CH3OH, CH3O., CH2O, CH3., and H. from the molecular ion. Major fragmentation pathways also resulted in formation of nucleoside, base, ribose, hydrocarbon, and base-hydrocarbon ions. Each of these major ions in turn resulted in further characteristic fragmentation patterns.

Animals↗

PubMed1990

Pattern of rheumatic diseases in south India. IV. Clinical profile of juvenile rheumatoid arthritis.

An analysis of 100 consecutive cases of juvenile rheumatoid arthritis from South India revealed a male preponderance (62%), a lower incidence of the systemic onset variety (10%) and equal incidence of systemic features when compared with the West. Knees and ankles were the joints commonly involved. The incidence of elevated erythrocyte sedimentation rate and C reactive protein, with haemoglobin levels below 10 g/dl was highest in the systemic onset variety. The polyarticular and systemic onset group responded well to aspirin, while the pauciarticular group responded well to indomethacin.

Arthritis, Juvenile↗

PubMed1989

On the inhibition of deoxycytidylate hydroxymethylase by 5-fluoro-2'-deoxycytidine 5'-monophosphate.

Studies were performed to determine whether 5-fluoro-2'-deoxycytidine 5'-monophosphate (FdCMP) is an inhibitor of deoxycytidylate hydroxymethylase and whether it could form an isolable covalent complex with the enzyme and the cofactor, 5,10-methyl-enetetrahydrofolate. The results showed that although FdCMP is a competitive inhibitor of dCMP hydroxymethylase, it does not cause time-dependent inhibition of the enzyme in the presence of cofactor. Further, although uv difference spectral evidence was found for FdCMP-cofactor-enzyme complex, the complex was not sufficiently stable to isolate on nitrocellulose filters. We conclude that FdCMP is not a mechanism-based inhibitor of dCMP hydroxymethylase.

Cytidine Monophosphate↗

PubMed1989

Properties of the immunosuppressive factor induced by murine cytomegalovirus.

Murine cytomegalovirus infection of spleen cultures induced the production of a small (less than 10,000 molecular weight) immunosuppressive factor (VISF), which suppressed concanavalin-A mitogenesis in fresh mouse spleen cells, and in fresh human peripheral blood leukocytes. The factor did not affect the growth of two murine T-cell lines or of mouse fibroblasts. A similar factor was also found in the serum of infected mice, at the time of maximum immune suppression. The properties of VISF indicate that the mechanism of MCMV immune suppression is different from that caused by several other viruses which are important in human and veterinary medicine.

Animals↗

PubMed1988

On the mechanism of DNA-adenine methylase.

Experiments were performed to determine whether EcoRI methylase catalyzes the transfer of the methyl group of S-adenosylmethionine (a) directly to the N6 of adenine in DNA or (b) initially to N1 to give N1-methyladenine followed by isomerization of the N1-methylamino and 6-NH2 to give N6-methyladenine (Dimroth rearrangement). A facile synthesis of highly enriched [6-15N]deoxyadenosine and a dodecamer substrate of EcoRI methylase with [6-15N]adenine in the methylation site are reported. In the product of EcoRI enzymatic methylation, all of the isotope remains at the N6 position of the N6-methyladenine product. It is concluded that, contrary to existing chemical precedent, the methylation occurs by direct transfer from S-adenosylmethionine to the N6 of adenine in DNA.

Adenine↗

PubMed1987

Characterization of a murine cytomegalovirus-induced immunosuppressive factor.

Murine cytomegalovirus infection in spleen cultures resulted in the production of a soluble factor, VISF (virus-induced suppressive factor), which inhibited concanavalin A mitogenesis in fresh spleen cells. Its production was specific for MCMV, since infection of spleen cultures by Sindbis virus, or bacteriophages PM 2 and T 4, and the phagocytosis of latex beads, all failed to elicit VISF. Maximum appearance of the factor occurred within 24 hours p.i. in spleen cultures, and its source was identified as the population of spleen cells which adhered to a plastic culture dish within two hours at 37 degrees C. Non-adherent cells did not produce the factor. Its production was not inhibited by indomethacin. VISF could be concentrated by ultrafiltration on a YM 2 membrane filter, and it was readily fractionated by chromatography on sephadex G-25. In relation to peptides of known molecular weight it appeared to be smaller than 1,400 daltons. Its ability to suppress concanavalin A mitogenesis was largely removed by digestion with proteinase K. Thus VISF appears to be a relatively small peptide or peptide-containing substance. It was purified further by HPLC.

Animals↗

PubMed1987

Clinical significance of virulence-related assay of Yersinia species.

During the 42-month period from June 1982 through December 1985, 215 fecal specimens from 171 patients were found to be positive for yersiniae by using a combination of CIN agar and cold enrichment. Isolates were tested for markers of virulence including carriage of a plasmid 42 megadaltons in size, calcium dependence, autoagglutination, Congo red uptake, pyrazinamidase activity, fermentation of salicin, and hydrolysis of esculin. The results were correlated to symptoms in patients. A total of 80 Yersinia enterocolitica and 52 Y. enterocolitica-like strains (42 Y. frederiksenii, 8 Y. intermedia, and 2 Y. kristensenii) were examined. Positive virulence-related tests were as follows (for Y. enterocolitica, Y. frederiksenii, Y. intermedia, and Y. kristensenii, respectively): pyrazinamidase negativity, 12.5, 0, 0, and 50%; Congo red positivity, 5, 7.1, 87.5 and 0%; calcium dependence, 3.8, 0, 0, and 0%; autoagglutination positivity, 8.8, 0, 0, and 0%; carriage of the 42-megadalton plasmid, 28.6, 73.2, 5.7, and 0; salicin and esculin negativity, 12.5, 0, 0, and 50%. The isolates recovered from symptomatic patients were characterized in relation to the presenting symptoms. Isolates from 12 of 32 (37.5%) patients with acute-onset diarrhea and 9 of 30 (30.0%) patients with chronic symptoms expressed at least one virulence feature. No individual test or group of tests was consistently associated with onset or either type of symptoms. Routine testing of plasmid carriage, uptake of Congo red, calcium dependence, autoagglutination, and pyrazinamidase activity did not appear to provide information that would link the presence of symptoms with the virulence potential of fecal isolates of yersiniae.

Acute Disease↗

PubMed1987