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Biomedical subjects

S Ramachandran

Publications and source records attributed to S Ramachandran.

At least 19 recordsLinked to original sources
PubMed1992

Limited proteolysis and active-site labeling studies of soybean lipoxygenase.

Soybean lipoxygenase 1 was studied using limited proteolysis and active-site labeling to begin the structural characterization of the enzyme in solution. The serine proteases trypsin and chymotrypsin cleaved the large monomeric protein (95 kDa) into two large polypeptides, a C-terminal fragment of about 30 kDa and an N-terminal fragment of about 60 kDa. Under conditions that led to complete cleavage of the protein as judged by SDS-polyacrylamide gel electrophoresis, the catalytic activity of the protein was either reduced slightly (chymotrypsin) or enhanced (trypsin). The characteristics of the cleaved enzymes were the same as for native lipoxygenase 1 in all aspects examined: insensitivity to cyanide, fluoride, and EDTA, regiochemical and stereochemical consequences of catalysis, and EPR spectroscopy upon oxidation by product. The two fragments apparently were tightly associated as they could not be resolved under conditions which preserved the catalytic activity. Both native and protease-cleaved lipoxygenase 1 formed covalent adducts when treated with either 14C-phenylhydrazine or 4-nitrophenylhydrazine. The label was found only in the 60-kDa fragment and following complete trypsin digestion was associated with a peptide beginning after Lys-482 in the primary sequence. Therefore labeling occurred in the vicinity of the conserved histidine cluster which has been postulated as the iron-binding site. From these observations it appears that lipoxygenase 1 exists as a pair of tightly associated domains with the iron-binding site located in the larger of the two.

Amino Acid Sequence↗
PubMed1992

Prevention of galactose cataract by pyruvate.

The effect of pyruvate on the progress of galactose cataract has been studied. Pyruvate was administered topically in the form of eye drops. Such treatment was found to delay the onset of the cataractous changes. Cataract formation was studied by visual inspection with pen light, as well as with slit lamp biomicroscopy in the intact animal. The delay in the formation of cataract was associated with the preservation of the levels of lens ATP, soluble proteins and the decreased accumulation of galactitol. In vitro organ culture experiments yielded similar results.

Adenosine Triphosphate↗
PubMed1991

Prevention of selenite cataract by vitamin C.

Studies have been conducted to determine the efficacy of vitamin C in the prevention of cataracts induced by selenite. Administration of the latter to rat pups results in the development of advanced cataracts within 5 days. Treatment with ascorbate had a significant preventive effect. The observations indicate that selenite cataract is due to an oxidative stress to the lens. In addition, the findings are in conformity with our view that ascorbate functions as an anticataractogenic substance.

3,4-Methylenedioxyamphetamine↗
PubMed1991

Radio-isotopic determination of hydrogen peroxide in aqueous humor and urine.

The concentrations of hydrogen peroxide in the aqueous humor and urine of several animal species and humans have been determined. The determinations are based on peroxide-dependent decarboxylation of I-[14C]-alpha-ketoglutaric acid and measurement of the resulting 14CO2 by quantitating the radioactive disintegration. The levels of H2O2 in most animals varied between 5.0 and 41 microM for aqueous, and 115 and 187 microM for urine. The levels of peroxide in the urine of steer, cat and baboon were lower and fell out of the above range. In the aqueous of humans with cataracts, the levels ranged from 33 to 324 microM, the overall average being 189 +/- 88 microM. The source of such high levels in the aqueous of cataract patients is currently being studied.

Aged↗
PubMed1991

Hydrogen peroxide in the eye lens: radioisotopic determination.

Lenses from normal rabbits, mice, rats, cattle, guinea pigs, lambs, chicken, cats, baboons, blue acara (fish) and dogs were examined for the presence of H2O2. No previous reports exist on the presence and levels of H2O2 in normal eye lenses. Freshly isolated lenses of these animals were extracted with trichloroacetic acid and the extract neutralized with Tris. H2O2 was assayed in these extracts by reacting them with 1-14C-alpha-ketoglutarate and measuring the 14CO2 produced by peroxide-dependent decarboxylation. Peroxide of the order of 10(-4)M was detected in most of the lenses except in baboons wherein it exists between 10(-4) and 10(-5)M. Culture experiments with rat lenses demonstrated that GSH may make a major contribution to the formation of H2O2 in the intact lens in vivo.

Animals↗
PubMed1990

Analgesic activity of certain flavone derivatives: a structure-activity study.

Flavone and 10 hydroxy and glucoside flavone derivatives were synthesised. They were tested for their analgesic effect in mice employing acetic acid-induced writhing and tail immersion methods. Subcutaneously all the tested compounds exhibited significant analgesic activity with varying potencies in both assay models. The activity of flavone and its 5-; 7-; 2'-; 5,7- and 7,8-hydroxy derivatives apparently involves an opiate-like mechanism, since their activity was reversed by naloxone pretreatment. It is suggested that flavonoid substances may utilise more than one mechanism in eliciting analgesia.

Analgesics↗
PubMed1990

Prevalence of chlamydial antibody in Malaysians.

A single antigen indirect immunofluorescence test was used to screen for chlamydial antibody among Malaysian infants, children, sexually active adults and prostitutes. Of 794 serum samples tested, 361 (45.5%) were positive. Seropositivity increased with age and sexual activity and ranged from 10 to 16% among children under 10 years old to 94.4% among prostitutes. Pregnant women and female adolescents showed a higher antibody prevalence than nonpregnant and older women. Six (13%) infants under 6 months of age were positive for chlamydial IgM.

Adolescent↗
PubMed1990

The prevalence of sexually transmitted diseases among prostitutes in Malaysia.

The prevalence of sexually transmitted diseases was determined among 370 prostitutes in Kuala Lumpur, Malaysia. Chlamydial cervicitis (26.5%) was detected more frequently than gonorrhoea (14.25%) and was associated more often with pelvic inflammatory disease. Concurrent infections and asymptomatic infections were common. Seropositivity to hepatitis B and syphilis were 66.3% and 13.6% respectively. Women under 20 years of age had significantly higher rates of infection with Chlamydia trachomatis and hepatitis B virus than older women.

Adolescent↗
PubMed1990

Allergic bronchopulmonary aspergillosis and Candida albicans colonization of the respiratory tract in corticosteroid-dependent asthma.

Fungal studies were conducted on 35 patients with corticosteroid-dependent asthma (CSDA) and 20 asthmatics who had never received prednisolone. Candida albicans was repeatedly cultured from the sputa of 12 patients with CSDA. Isolation was more frequent in those patients who were receiving more than 10 mg prednisolone for more than six months. Nearly half of these patients demonstrated a positive immediate cutaneous reaction and precipitating antibodies against C. albicans. Although no pathological significance, beside colonization, could be attributed to this finding, it was felt that it would be prudent to restrict the daily dose of prednisolone to less than 10 mg, when administered for more than six moths. Two patients with allergic bronchopulmonary aspergillosis (ABPA), were identified, one from each group. The possibility of ABPA, however, remained open in two other patients with CSDA. It is probable that some patients with CSDA may be suffering from ABPA but characteristic features of the disease are masked by costicosteroid therapy, making it difficult to diagnose.

Adolescent↗
PubMed1988

Involvement of calcium in flavonoid analgesia.

Calcium has been reported to play a key role in opioid analgesia. Several flavonoids also elicit an analgesic effect through the opioid system. The involvement of calcium in the analgesic activity of these flavonoid compounds was now investigated. Calcium antagonised the analgesic action of flavonoids while nifedipine, a calcium channel blocker, potentiated it. This suggests a possible role for calcium in the analgesic action of flavonoids as with that of morphine.

Analgesics↗
PubMed1986

Recent aspects of alcoholism in Sri Lanka--an increasing health hazard.

Eighty-five patients (81 males and 4 females) with significant alcoholic histories were studied. Alcohol misuse was directly or indirectly responsible for about 5-10% of hospital admissions in Sri Lanka. Prevalence of alcoholism in patients below 40 years (43% of cases) or with a strong family history (56% of cases) were demographic features simulating trends in developed nations. Although rarely an occupational hazard, the majority in this lower socio-economic group drank illicitly-manufactured brews with high alcohol content while many consumed a mixture of beverages. Lone drinkers were predominant (86%); features of psychological interest were sleep disturbance (64%), emotional problems (42%) and loneliness (34%); domestic problems (36%), social problems (24%) and financial problems (34%) were also noted. Many such factors, either singly or in combination, initiated or perpetuated the drinking habits of the patients. Drug misuse and suicidal tendencies were not observed. Severe hepatic damage was noted in 63% of 42 patients where the histology was demonstrated, and who usually presented with significant hepatomegaly; about 50% of patients below the age of 40 had hepatic damage of a serious or irreversible nature. Direct toxicity of ethanol, toxic contamination during the preparation of illicit brews and nutritional factors appear pertinent to hepatic damage in developing nations. Nutritional factors may cause variations in relation to abnormalities in liver function tests and also liver size among the population studied when compared to findings from the western world.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Zinc and vitamin A status of alcoholics in a medical unit in Sri Lanka.

Zinc and vitamin A concentrations in the serum were measured in 40 alcoholics (33 males and 7 females) and 35 healthy, age-matched subjects (31 males, 4 females). Liver zinc concentrations were measured in 15 alcoholics from specimens collected by liver biopsy and compared with the zinc concentrations in liver specimens taken at autopsy from victims of road-traffic accidents. Alcoholics had significantly lower serum concentrations of both zinc and vitamin A compared to the control group of healthy subjects. The depression of zinc and vitamin A levels was related to the severity of the hepatic lesions, the lowest levels being observed among cirrhotics. Liver zinc concentrations were similar in alcoholics and healthy subjects and were not related to plasma zinc concentrations. Serum zinc and vitamin A levels were positively correlated among cirrhotics, but not in other alcoholics or controls. Thus low levels of vitamin A in cirrhotics may have arisen as a result of impaired mobilisation from the liver due to zinc deficiency, or to non-availability of hepatic zinc. Female alcoholics were more severely affected than males with respect to their zinc and vitamin A levels, although they consumed lesser amounts of alcohol and had a shorter duration of alcohol intake. A strong positive relationship existed between zinc and albumin levels in all alcoholics but not in controls. It is possible that the decreased serum albumin levels may have limited the availability of albumin for the transport of zinc in the plasma and this in turn may have resulted in increased urinary excretion of zinc.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗