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Biomedical subjects

M Arumanayagam

Publications and source records attributed to M Arumanayagam.

At least 19 recordsLinked to original sources
PubMed2002

Cervical intraepithelial neoplasia is associated with increased polyamine oxidase and diamine oxidase concentrations in cervical mucus.

OBJECTIVE: The aim of this study was to establish whether reactive oxygen species, generated during oxidation of amines, catalyzed by polyamine oxidase (PAO) and diamine oxidase (DAO) in cervical secretions may play a role in the etiology of cervical cancer. METHODS: Cervical mucus was obtained from women attending the gynecological outpatient department: 139 with and 154 without cytological evidence of cervical intraepithelial neoplasia were recruited. The mucus was freeze dried in liquid nitrogen, weighed, and later resuspended for assay of PAO and DAO concentrations using a chemiluminescence method. The two groups were compared by group sequential analysis using PEST3 software. RESULTS: Patients with a colposcopic diagnosis of a high-grade squamous intraepithelial lesion (SIL) had significantly higher enzyme activities than control cases (L(N)PAO 1.37 (0.37) versus 1.18 (0.35): Student t test: P < 0.001; L(N)DAO 1.37 (0.36) versus 1.15 (0.37): Student t test: P < 0.001). CONCLUSION: It is probable that this rise in enzyme activity precedes cytological changes and plays some part in the etiology of cervical cancer, as the cells that undergo premalignant change are normally squamous in origin, whereas mucus is a product of columnar epithelium. Higher enzyme activity in patients with SIL than in controls may be a reflection of higher risk of exposure to amine substrates in semen through multiple sexual partners.

Amine Oxidase (Copper-Containing)↗
PubMed2001

Antioxidant properties of carvedilol and metoprolol in heart failure: a double-blind randomized controlled trial.

Animal and human studies have shown that carvedilol has significant antioxidant properties compared with other beta-blockers. The objective of this study was to determine if these antioxidant effects are detectable in patients with heart failure and to compare carvedilol with the selective beta-blocker metoprolol. Twenty-four patients with chronic heart failure were randomly assigned to receive either carvedilol or metoprolol in a double-blind control trial for 12 weeks in a University teaching hospital clinic. Blood pressure, heart rate, exercise tolerance, left ventricular ejection fraction, plasma total antioxidant status, erythrocyte superoxide dismutase, and glutathione peroxidase activities were determined at baseline and every 4 weeks up to 12 weeks. The results showed that erythrocyte superoxide dismutase and glutathione peroxidase were significantly reduced in carvedilol treated patients after 12 weeks of therapy, whereas metoprolol had no significant effect, although the clinical improvement over the short-term was similar with both drugs. Thus carvedilol, in addition to improving symptoms in heart failure, also possesses significant antioxidant properties. Whether this additional action influences long-term outcome is at present unknown.

Adrenergic beta-Antagonists↗
PubMed2001

The predictive value of serum 1,5-anhydro-D-glucitol in pregnancies at increased risk of gestational diabetes mellitus and gestational impaired glucose tolerance.

The objective of the study was to determine the efficacy of 1,5-anhydro-D-glucitol (1,5 AG) for the prediction of gestational diabetes and gestational impaired glucose tolerance (GIGT). One hundred and eighty-five pregnant women with epidemiological risk factors of gestational diabetes or GIGT underwent 75 g oral glucose tolerance test and plasma 1,5 AG assay at 26 to 28 weeks of gestation. There was no significant difference in plasma 1,5 AG either before or after an oral glucose load. The area under the receiver operator characteristic curve for 1,5 AG was only 0.485 which implies that 1,5 AG is a poor predictor of GIGT or gestational diabetes.

Adolescent↗
PubMed1999

Influence of gene polymorphisms of the renin-angiotensin system on clinical outcome in heart failure among the Chinese.

BACKGROUND: An association between the DD allele of the angiotensin-converting enzyme gene and a poorer outcome in patients with heart failure has been found in whites. The DD allele frequency is lower in Chinese, but the M235T variant of the angiotensinogen gene is more common in Chinese than whites; it is not known to what extent polymorphisms of the renin-angiotensin system affect clinical status or prognosis in Chinese patients with heart failure. METHODS: We assessed the relations among polymorphism of the angiotensin-converting enzyme gene, angiotensinogen M235T (AGT) gene, and angiotensin type I receptor A1166C gene with left ventricular systolic function, left and right ventricular diastolic function, serum angiotensin-converting enzyme, plasma aldosterone and atrial natriuretic peptide levels at presentation, and clinical outcome at 1 year (survival, hospital admissions) in a cohort of Chinese patients with typical systolic heart failure (n = 82). RESULTS: We confirmed the low prevalence of the angiotensin-converting DD and the angiotensin type I receptor CC genotypes, and high prevalence of the AGT TT genotype in Chinese subjects compared with whites. There was no relation between the various gene polymorphisms and survival at 1 year assessed by multiple regression or Cox regression survival analysis. The AC variant of the angiotensin type I receptor gene was associated with morbidity over a 1-year period (hospital admissions) and increased baseline aldosterone levels, but none of the other polymorphisms correlated with systolic or diastolic function, aldosterone or atrial natriuretic peptide levels. By multiple regression for effects on mortality rate, only atrial natriuretic peptide and age were significant. CONCLUSIONS: In Chinese patients with heart failure, polymorphisms of the renin-angiotensin system do not appear to be related to survival or severity, probably because of the different prevalence of these genotypes in the Chinese. Thus this study illustrates that large interethnic differences in the frequencies of genotype polymorphisms of the renin-angiotensin system exist and results from one ethnic group cannot be extrapolated to another.

Aldosterone↗
PubMed1999

Diurnal variation in excretion of N-acetyl-beta-glucosaminidase during pregnancy: implications for the prediction of pre-eclampsia.

Significant differences in urinary excretion of N-acetyl-beta-glycosaminidase (NAG) were observed between nulliparous and multiparous patients and between fasted and nonfasted individuals. No significant difference was observed between patients with normal and those with abnormal glucose tolerance. Multiple regression analysis confirmed that the significant independent determinants of NAG/creatinine ratio were age, parity, gestation and fasting state. Significant diurnal variation in urinary NAG/Cr ratio was observed, the highest levels being recorded in early morning fasting specimens, falling in each postprandial specimen and beginning to rise again by midnight. The urinary NAG/Cr ratio is influenced by fasting, parity, gestation and age. More consistent results for prediction of pre-eclampsia are therefore likely to be obtained using fasting (early morning) urine specimens and adjusting cut-off criteria for the other factors.

Acetylglucosaminidase↗
PubMed1999

Platelet sodium pump and sodium potassium cotransport activity in nonpregnant, normotensive, and hypertensive pregnant women.

OBJECTIVE: To determine ouabain-sensitive sodium pump and bumetanide-sensitive sodium potassium cotransport activity in platelets from nonpregnant and normotensive pregnant women and from women with pregnancy-induced hypertension (PIH). METHODS: Blood was collected from 9 normotensive nonpregnant subjects, 24 normotensive pregnant subjects in both second and third trimesters, 9 subjects who developed proteinuric PIH, and 9 subjects who developed moderate nonproteinuric PIH. Platelet sodium pump activity was determined by the difference in the uptake of rubidium-86 in the presence and absence of ouabain; sodium potassium cotransport (SPC) activity is that component that is inhibitable by bumetanide. RESULTS: SPC activity was similar in normotensive subjects in the second [median (range) 78 mmol Rb/h/mg protein (18-140)] and third trimesters [85 (39-134)] but was significantly (p < 0.001) higher than in nonpregnant subjects [22 (4-107)]. In addition, SPC was significantly (p < 0.001) lower in subjects with nonproteinuric [42 (4-67)] or proteinuric PIH [59 (33-102)] compared to those who remained normotensive. Sodium pump activity was significantly higher (p < 0.05) in nonpregnant subjects [263 (188-430)] compared with the other groups of subjects. Total rubidium uptake was significantly higher (p < 0.05) in third-trimester normotensive subjects [471 (243-560)] compared with second-trimester subjects [405 (278-608)]. CONCLUSION: Our results suggest that the lower SPC activity in both nonproteinuric and proteinuric PIH may be an early sign of abnormality in the transport of sodium and potassium across the vascular smooth-muscle cell membrane, which is responsible for the maintenance of blood pressure.

Adult↗
PubMed1998

Flow cytometric assessment of oxidant stress in age-fractionated thalassaemic trait erythrocytes and its relationship to in vitro growth of Plasmodium falciparum.

The role of oxidant stress in mediating the protection against malaria in thalassaemic red blood cells (RBC) has been hypothesized. In this study we have assessed the relationship between oxidant stress, red cell age and malarial parasite activity in thalassaemic RBC. Using a flow cytometric method to assess lipid peroxidation, we have shown that the age-related increase in sensitivity to oxidative stress previously demonstrated in normal RBC also occurs in thalassaemic RBC. Invasion and growth of Plasmodium falciparum was also shown to deteriorate with increasing RBC age. This effect was more pronounced in thalassaemic RBC with associated schizont maturation arrest and abnormal parasite morphology. In addition, there was a slight but consistent inverse correlation between sensitivity to oxidant stress and parasite activity (R = -0.43; P = 0.03 for normal RBC and R = -0.42; P = 0.01 for thalassaemic RBC). Our findings indicate an association between red cell age, oxidant stress and P. falciparum growth, providing further support for the role of oxidant stress in mediating the protective effect against malaria in thalassaemic RBC.

Animals↗
PubMed1998

Development of an enzyme-linked immunosorbent assay with monoclonal antibody for quantification of homovanillic acid [corrected] in human urine samples.

A monoclonal antibody to homovanillic acid (HVA) was prepared by synthesis of a HVA-protein conjugate (HVA-ovalbumin) as an immunogen, immunization of mice, and the subsequent hybridization technique. Monoclonal antibodies were screened on the basis of sensitivity, specificity, and accuracy. An indirect ELISA was developed for quantification of HVA in human urine. The assay was characterized and shown to have high specificity, with cross-reactivities to vanillylmandelic acid and normetanephrine at 0.18% and <0.1%, respectively. The assay coefficients of variation were <10% within the working range of 0.5-40 mg/L. Initial results from testing urine samples of patients with neuroblastoma and other diseases were validated by HPLC, suggesting that this ELISA method is a reliable and convenient system for quantification of HVA in urine and can be used in the mass screening of neuroblastoma in infants.

Adolescent↗
PubMed1996

Platelet angiotensin II receptor status during pregnancy in Chinese women at high-risk of developing pregnancy-induced hypertension.

OBJECTIVES: The aims of this prospective study were to explore the changes in platelet angiotensin II (A-II) binding in pregnancy amongst Chinese women at high risk of developing pregnancy-induced hypertension (PIH) and the effects of low-dose aspirin and calcium supplementation on A-II binding. METHODS: Platelet A-II binding was assayed in 15 non-pregnant women and in 63 pregnant women determined to be at risk of PIH on the basis of 2nd-trimester mean arterial pressure (MAP). The pregnant patients were randomized into three groups: control, low-dose aspirin, and calcium supplementation. A-II binding was assayed again during the 3rd trimester in half the women and 8 weeks after delivery. RESULTS: A-II binding was negatively correlated with MAP measured in the left lateral position (p < 0.05) but not with MAP measured in the supine position. There were no significant differences between A-II binding in non-pregnant and pregnant women. Neither low-dose aspirin nor calcium supplementation caused significant reductions in A-II binding. CONCLUSION: The measurement of platelet A-II binding is unlikely to provide significant information regarding the risk of PIH over and above that obtained from measurement of 2nd-trimester MAP.

Adolescent↗
PubMed1994

Effect of age and disease on two drug binding proteins: albumin and alpha-1- acid glycoprotein.

The influence of age and disease on serum albumin and alpha-1-acid glycoprotein was studied in 126 subjects (69 M, 57 F) presenting with tuberculosis and after recovery. Albumin concentration fell with age in both disease and healthy states, and alpha-1-acid glycoprotein concentration rose with age in the healthy state. Age-related differences were less marked in the disease state. During recovery from illness, serum albumin concentration rose and alpha-1-acid glycoprotein concentration fell. The mean concentration difference in the latter was lower in the older age groups. The clinical consequences of changes in binding protein concentrations as a result of ageing and disease need to be studied further for individual drugs.

Adult↗
PubMed1994

Erythrocyte creatine levels in hyperthyroidism.

The mechanism by which erythrocyte mean corpuscular volume (MCV) is decreased in hyperthyroidism is not known. One possible mechanism is premature aging of erythrocytes in the circulation. Since erythrocyte creatine has been shown to be a good marker of cell senescence, we determined this in hyperthyroid patients and control subjects to examine whether the decrease in MCV is related to senescence. Erythrocyte creatine levels were similar in both hyperthyroid patients and controls, suggesting that premature senescence of erythrocytes does not account for the lower MCV in hyperthyroidism.

Adult↗
PubMed1993

Serum ceruloplasmin, plasma copper concentration and copper to ceruloplasmin ratio in cervical carcinoma.

Several studies have shown that plasma/serum copper and ceruloplasmin concentrations are increased in various carcinomas. We determined serum concentrations of ceruloplasmin and plasma copper concentration to evaluate the clinical usefulness of these tests in patients with cervical carcinomas. There was a significantly higher ceruloplasmin concentration in patients with cervical carcinoma compared to healthy controls. Plasma concentrations of copper were not significantly different in the two groups of subjects. The copper to ceruloplasmin ratio was lower in cancer patients than in control subjects. There was a significant increase in the serum concentrations of ceruloplasmin with increasing FIGO stage of cancer. Copper concentration in advanced tumours (FIGO stage 3) were significantly higher compared to control subjects or FIGO 1 and 2. Copper to ceruloplasmin ratio was lower in FIGO stage 2 and 3 patients compared to stage 1 or control subjects. Ceruloplasmin can also discriminate between large tumours which are inoperable and early cervical carcinomas better than copper or copper to ceruloplasmin ratio.

Adult↗
PubMed1993

Serum ultrafiltrable copper, total copper and caeruloplasmin concentrations in gynaecological carcinomas.

Serum copper and caeruloplasmin concentrations are elevated in various carcinomas, but it is not known whether the rise in serum copper is due to elevation of caeruloplasmin alone or whether it is also due to the elevation of 'free' copper. We therefore determined ultrafiltrable copper to answer this question. Serum ultrafiltrate was prepared using the Amicon micropartition system and ultrafiltrable (free) copper was determined by flameless atomic absorption spectrophotometry. Serum total copper was determined by flame atomic absorption spectrometry and caeruloplasmin by rate nephelometry. There was no significant difference in the ultrafiltrable copper concentration between patients with gynaecological tumours and control subjects. However, total copper and caeruloplasmin concentrations were significantly elevated in cancer patients compared with control subjects. In contrast to total copper and caeruloplasmin concentrations, ultrafiltrable copper concentrations showed no significant increase with increase in the stage of the cancer.

Adult↗
PubMed1992

Stimulation of the Na+,K(+)-ATPase activity of K562 human erythroleukemia cells by triiodothyronine.

The effect of triiodothyronine (T3) on Na+,K(+)-ATPase activity of K562 human erythroleukemic cell was studied to understand why the erythrocyte sodium pump activity is decreased in hyperthyroidism. Na+,K(+)-ATPase activity of K562 cell lysates was assayed by measuring the release of inorganic phosphate (Pi) from ATP. Na+,K(+)-ATPase activity of K562 cell grown in the presence of T3 for 48 hours was significantly higher than that of control (0.98 +/- 0.05 mumol Pi h-1 mg protein-1 vs 0.82 +/- 0.10 mumol Pi h-1 mg protein-1, p < 0.05). The Na+,K(+)-ATPase activity could be stimulated in a time- and concentration-dependent manner; maximum stimulatory effect of T3 was seen at a concentration of 10(-7) mol/L. When an inducer [cytosine-beta-D-arabino-furanoside (ARA-C)] was added to the culture medium, the K562 cells showed signs of differentiation and synthesised haemoglobin. At the same time, the Na+,K(+)-ATPase activity remained high. We conclude that T3 stimulates Na+,K(+)-ATPase activity of K562 cells and in the presence of T3 during differentiation, the enzyme activity remains high.

Cell Differentiation↗
PubMed1991

Induction of the ATP-dependent proteolytic system in guinea pig reticulocyte lysates by triiodothyronine.

The mechanism involved in the decreased numbers of several trans-membrane proteins such as sodium pump sites, sodium-lithium countertransport, sodium potassium cotransport proteins, proteins mediating the passive efflux of sodium and insulin receptors in erythrocytes from patients with hyperthyroidism is not known. The ATP-dependent proteolytic system which is involved in the loss of trans-membrane proteins during the maturation of the reticulocyte may be involved in the accelerated loss of these membrane proteins. Therefore, the effect of thyroid hormones on the ATP-dependent proteolytic activity of reticulocyte lysates was examined in this study. Reticulocytosis was induced in 14 guinea pigs by phenylhydrazine hydrochloride injections for 5 consecutive days followed by 2 days of rest. T3 (10 micrograms/100 g body weight) was injected into 7 animals on day 4 and day 6. Reticulocyte-rich blood was withdrawn on day 8. Oxygen consumption determined 24 hours after injection of T3 was 25% higher (p less than 0.01) and T3 treated animals had a 2.5 fold higher (p less than 0.01) weight loss than control animals. The ATP-dependent proteolytic activity measured in reticulocyte lysates using 125I labelled lysozyme was 3.6 fold higher in the T3 than in the control group of guinea pigs (p less than 0.01). We conclude that thyroid hormones induce the ATP-dependent proteolytic activity of reticulocyte lysates which may be responsible for the reduced number of several trans-membrane proteins found in erythrocytes from patients with hyperthyroidism.

Adenosine Triphosphate↗
PubMed1991

Ouabain-binding sites of reticulocytes from guinea pigs treated with triiodothyronine.

To understand the mechanism of reduced number of sodium pump units (ouabain-binding sites, OBS) of erythrocytes in hyperthyroidism, OBS of reticulocytes from guinea pigs injected with triiodothyronine (T3) were measured. Reticulocytosis was induced in 16 guinea pigs by withdrawing 6 to 10 mL of blood for 5 days followed by 2 days rest. T3 (50 micrograms/100 g body weight) was injected into seven animals on days 4 and 6, and the remainder were injected with solvent for T3. Reticulocyte-rich blood was withdrawn on day 8. Oxygen consumption determined 24 hours after the first injection of T3 was 30% higher in the T3-treated animals (P less than .001). OBS of reticulocytes from control animals were sixfold higher than that of mature erythrocytes. Reticulocytes from T3-treated guinea pigs had significantly lower OBS (P less than .01) compared with controls. We conclude that the loss of OBS induced by thyroid hormones probably occurs during the formation of reticulocytes.

Animals↗
PubMed1990

Erythrocyte sodium fluxes, ouabain binding sites, and Na+,K(+)-ATPase activity in hyperthyroidism.

Erythrocyte sodium pump activity, in contrast to other tissues, is decreased in hyperthyroidism. In order to examine whether the effect of thyroid hormones on erythrocytes is part of a generalized effect on other transport pathways, we measured sodium pump activity, Na+,K(+)-adenosine triphosphatase (ATPase) activity, ouabain binding sites, bumetanide-sensitive sodium potassium cotransport (SPC), sodium lithium countertransport (SLC), and ouabain- and bumetanide-insensitive passive efflux of sodium (sodium "leak") in erythrocytes from 20 healthy subjects and 18 untreated hyperthyroid subjects. Sodium pump activity (ouabain-sensitive sodium efflux rate constant), Na+,K(+)-ATPase activity, and the number of ouabain binding sites were lower and the erythrocyte sodium content was higher in hyperthyroid subjects. The rate constants of erythrocyte SPC (P less than .05), SLC (P less than .001), and sodium "leak" (P less than .05) were also significantly lower in hyperthyroidism. In 11 of the hyperthyroid subjects, sodium flux measurements were repeated after 20 weeks of treatment. Sodium pump activity, the number of ouabain binding sites, and the rate constant for SLC increased. These results suggest that the effect of thyroid hormones on the erythrocyte sodium pump is part of a generalized effect on membrane proteins, rather than a specific effect.

Adult↗