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Biomedical subjects

S Mahadevan

Publications and source records attributed to S Mahadevan.

193 records · Page 11Linked to original sources
PubMedDate not supplied

Facial anthropometry in newborns in Pondicherry.

Two hundred term healthy neonates were examined and 14 anthropometric measurements were taken in the face and ear region. Difference between the sexes was observed in ear length, ear breadth, and philtrum. Significant correlation was found between ear placement and ear length; and outer and inner canthal distances (p less than 0.001). The paper provides baselines data for facial growth measurements and discusses the utility of these measurements in detecting dysmorphogenesis in neonates.

Cephalometry↗
PubMedDate not supplied

Clinical utility of serodiagnosis of tuberculosis.

The use of TB-ELISA tests as a diagnostic tool offer a lot of scope in early diagnosis of serious forms of childhood tuberculosis. The characteristics of these tests have improved with the availability of purified and recombinant antigens and competition assays using monoclonal antibodies. Lower antibody titres to M. tuberculosis specific antigens in children and the presence of 'natural exposure' antibodies make the interpretation of these tests difficult at times. Caution must be exercised in interpreting their results due to problems inherent on currently available methods of TB-immunodiagnosis. The selection of best combination of antigens for serology, prospective clinical trials comparing success rate of serology with the standard different diagnostic procedures are required.

Antibodies, Bacterial↗
PubMedDate not supplied

Advances in diagnosis of tuberculosis.

The diagnosis of childhood tuberculosis is acknowledged to be an imprecise process since bacteriological confirmation is available in only 30-40% of cases. Newer developments in diagnosis of tuberculosis include use of fluorescent stains for smears, newer systems for radiometric detection of mycobacteria, rapid sensitivity testing using firefly bioluminescence, liquid chromatographic analysis of mycolic acids, immunodiagnostics for M. tuberculosis specific antigens and the impact of molecular diagnostics with amplification methods. The search for simple, reliable test for early stages of the disease (in particular TB meningitis) still continues.

Adolescent↗
PubMedDate not supplied

Unnecessary injections and paralytic poliomyelitis in India.

The effect of prior injections on the pattern and severity of paralytic poliomyelitis has been examined by a retrospective analysis of case notes from an outpatient pediatric clinic in South India. Of 262 children with acute polio, 176 had received unnecessary injections < 48 h before paralysis and 12 had received diphtheria-pertussis-tetanus or provocative injections. Two children injected in the right arm had paralysis in that limb only. Children with no injections (controls) had an equal chance of paralysis (0.73) in each left and right leg. Children with injections in the right or left gluteus or in both had a 19% greater chance of paralysis in the injected leg(s), whereas uninjected legs had a 31% lower chance of paralysis. Injected leg muscles were weaker than those of control children. Legs of control children were stronger than those with one leg injected and much stronger than those with both injected. More than 96% of the children had at least one leg paralysed. Age and vaccine status did not affect the results of injections. After injections there was greater likelihood of death or lack of recovery of muscle strength. About three-quarters of the children had received unnecessary injections; of these 60% had more severe paralysis and a non-paralytic attack became paralytic in 40%. If oral medicines for fevers and diarrhoea replaced unnecessary injections, the prevalence and severity of paralytic polio would be reduced.

Arm↗
PubMedDate not supplied

Chiral discrimination in the binding of tris(phenanthroline)ruthenium(II) to calf thymus DNA: an electrochemical study.

The binding of delta-, lambda-, and rac-[Ru(phen)3]2+ (phen = 1,10-phenanthroline) and delta-, lambda-, and rac-[Ru-(bpy)3]2+ (bpy = 2,2'-bipyridyl) with calf thymus DNA has been examined by cyclic and differential pulse voltammetric techniques to obtain structural insight into the noncovalent binding of the enantiomers to DNA. The insignificant shift in RuII/RuIII peak potentials on the addition of DNA suggests that both the oxidized and reduced forms bind to DNA to the same extent. Interestingly, DNA selectively decreases the peak currents of delta-[Ru(phen)3]2+ but not those of the lambda-enantiomer; rac-[Ru(phen)3]2+ exhibits an intermediate behavior, thus suggesting that the delta-form exhibits significant selectivity for B-DNA. The binding constants (K2+) and binding site sizes (s) have been determined from the decrease in the peak currents. The binding constant (K2+) of delta-[Ru(phen)3]2+ is on the order of 10(4) M-1 which is less than that for proven intercalators. In contrast, the electrochemical behavior of all three forms of [Ru(bpy)3]2+ remains almost unaffected in the presence of DNA, suggesting that the complexes might reside on the hydrophilic coat of the DNA helix.

Animals↗
PubMedDate not supplied

Diphenyl ether cleavage of 3-phenoxybenzoic acid by chicken kidney microsomal preparations.

Incubation of 3-phenoxybenzoic acid[carbonyl-14C] with chicken kidney microsomal fraction produced two major radioactive compounds identified as 3-hydroxybenzoic acid and 4'-hydroxy-3-phenoxybenzoic acid. It was found that 4'-hydroxy-3-phenoxybenzoic acid was transitory in nature and was rapidly converted into 3-hydroxybenzoic acid. The conversion of 3-phenoxybenzoic acid to the products was NADPH dependent. This is a first example of metabolism of 4'-hydroxy-3-phenoxybenzoic acid to 3-hydroxybenzoic acid. Cytosol did not promote any cleavage. Similar activities were present in liver microsomes, but the activity was lower than in kidney. Intestinal contents, homogenates, or microsomal fractions did not metabolize 3-phenoxybenzoic acid.

Animals↗
PubMedDate not supplied

The polymorphic cytochrome P-4502D6 is involved in the metabolism of both 5-hydroxytryptamine antagonists, tropisetron and ondansetron.

Tropisetron and ondansetron, which are potent and selective 5-hydroxytryptamine (5-HT3) receptor antagonists, were both metabolized by human liver microsomes to several metabolites. These metabolites include the major metabolites found in humans, which are the 5-, 6-, and 7-hydroxy tropisetron and the 7- and 8-hydroxy ondansetron. The cytochrome P-450 (CYP) 2D6 inhibitor quinidine (1 microM) reduced the hydroxylation of tropisetron (67%) and ondansetron (18%). Confirmation of CYP2D6 involvement in the hydroxylation of tropisetron and ondansetron was obtained by the formation of these metabolites in recombinant V79 cells expressing human CYP2D6. The CYP3A substrate/inhibitor, cyclosporine A (CsA) had little effect on tropisetron hydroxylation (< 10%), whereas CsA and triacetyloleandomycin reduced ondansetron 7- and 8-hydroxylation up to 27%. Substrates for CYP1A (phenacetin and acetanilide), CYP2C (mephenytoin), and CYP2E (chlorzoxazone) had negligible inhibitory effects on the hydroxylation of either tropisetron or ondansetron. For the CYP2D6-dependent O-demethylation of dextromethorphan, tropisetron and ondansetron were competitive inhibitors with Ki values of 14 and 29 microM, respectively. The CYP3A specific metabolism of CsA was also competitively inhibited by tropisetron (Ki = 2.1 mM) and ondansetron (Ki = 31 microM). Other metabolites, which are only minor in vivo were also inhibited by CsA, 47-60% for tropisetron metabolism and 43% for ondansetron metabolism. To summarize, this study has identified the involvement of CYP2D6 in the formation of the hydroxylated metabolites of tropisetron and ondansetron and in addition of CYP3A in ondansetron hydroxylation. Because these are the major pathways in vivo, coadministration of drugs competing for CYP2D6 and possibly CYP3A4 could influence the human kinetics of tropisetron and ondansetron.

Animals↗
PubMedDate not supplied

Determination of formaldehyde in fresh and retail milk by liquid column chromatography.

A quantitative method is described for the determination of formaldehyde (CH2O) in milk by liquid chromatography. Aldehyde derivatization-extraction was carried out in situ with 2,4-dinitrophenylhydrazine in 2-phase reaction medium. Average recovery of added CH2O (0.1 microgram/mL) was 89.9 +/- 3.9% with an estimated detection limit of 0.009 mg/kg. The technique was used for the determination of CH2O in commercial 2% milk and in fresh milk of cows fed on a typical North American dairy diet. The average concentrations of CH2O in fresh and commercial milk were 0.027 and 0.164 mg/kg, respectively. Several methods for CH2O determination in milk are compared.

Animals↗
PubMedDate not supplied

Electrophysiological studies in children with paralytic poliomyelitis.

Ten healthy children (Group I), twenty children with acute spinal poliomyelitis (Group II and III) and twenty children of post-polio residual paralysis (Group IV) between the age group of 9 months to 4 years were the study subjects. The motor nerve conduction velocity (MNCV), standardized distal motor latency (SDML) and motor latency (M-RL) were similar in all the groups studied No H-reflex could be elicited in children with acute spinal poliomyelitis seen within one week of onset of paralysis (Group II). The H-max from 4-6 week group (III) improved with time in 9-12 month (Group IV) but did not attain the control (Group I) value. The H-reflex latency (H-RL) which was prolonged in Group III children returned back to normal value in children with residual paralysis (Group IV). The M-max which was significantly reduced in Group II children further decreased in Group III children before showing a significant rise in children with residual paralysis (Group IV). The M-max showed a significant correlation to duration of paralysis during the first week of onset of the disease process and with the muscle power assessed clinically in children with residual paralysis (Group IV). The H/M ratio of children with acute paralysis (Group III) was similar to control while that of residual paralysis was significantly lower in comparison to controls. However, the corrected H/M ratio of children with acute paralysis (Group III) and residual paralysis (Group IV) was significantly lower than the controls. There was significant increase in corrected H/M ratio in group IV children compared to group III.

Child, Preschool↗