Biomedical subjects
Publications and source records attributed to M Mathai.
Thrombotic veno-occlusion of the upper extremity is infrequent in the absence of external trauma or in the presence of an indwelling catheter. Inadvertent injury to the underlying venous circulation can occur when the upper extremity is subjected to an unaccustomed repetitive action. The resultant intimal damage may become a nidus for thrombus development.
We investigated the contribution of brain angiotensinergic mechanisms to postprandial drinking in sheep. Sheep in fluid balance were given 0.8 kg chaff for 30 min, and water intake was measured for the next hour. Intracerebroventricular infusion of the AT1 type angiotensin II (ANG II) receptor blocker losartan (1 mg/h) reduced postprandial drinking by approximately 70% (n = 7, P < 0.01) but did not affect food intake. The same losartan dose given intravenously had little or no effect on prandial drinking. Feeding increased Na+ concentrations in plasma and cerebrospinal fluid (CSF; n = 5, P < 0.05). Intracerebroventricular losartan (1 mg/h) inhibited the drinking responses to intracarotid infusion of ANG II (0.8 microg/min for 30 min, n = 4, P < 0.01) and to intracerebroventricular infusion of 0.5 M NaCl (1 ml/h for 1 h, n = 5, P < 0.05) but had no effect on drinking responses to intravenous infusion of 4 M NaCl (1.3 ml/min for 30 min). These findings indicate that a brain ANG II-dependent mechanism is involved in postprandial drinking in sheep. They suggest also that the mechanism by which increasing CSF Na+ causes thirst involves brain ANG II and is different from the mechanism subserving the drinking response to changes in blood Na+.
The polypeptide adrenomedullin (ADM) was infused systemically to conscious rabbits to elucidate its actions on overall circulation and especially the renovascular bed and the formation and/or release of hormones important for body fluid homeostasis, including adrenocortical steroids. ADM lowered mean arterial pressure from 71.5 +/- 3.2 to 64.7 +/- 3.2 mmHg only at the highest dose of 25 pmol.min-1.kg-1 infused intravenously for 20 min and concomitantly induced tachycardia, possibly due to both baroreflex activation and direct cardiostimulatory effects. Renal blood flow (RBF) determined in rabbits chronically equipped with a perivascular ultrasonic flow probe increased from 55.4 +/- 2.1 to 67.4 +/- 2.7 and from 58.2 +/- 3.5 to 75.2 +/- 6.0 ml/min at ADM infusions of 5 and 25 pmol.min-1.kg-1, respectively. The elevation in RBF persisted even in the presence of the calcitonin gene-related peptide (CGRP1 receptor antagonist CGRP-(8-37). Of all osmoregulatory hormones tested, only corticosterone (Cort) plasma concentration increased in response to the highest ADM dose from 17.6 +/- 3.1 to 38.9 +/- 6.2 ng/ml, probably due to haroreflex activation. Subdepressor doses of ADM, however, caused a mild reduction in circulating Cort. Expression of functional high-affinity binding sites specific for ADM in vitro could be demonstrated for the renal artery and outer cortical glomeruli using 125I-labeled rat ADM as radioligand and determination of cellular adenosine 3',5'-cyclic monophosphate (cAMP) formation within the glomeruli. The ineffectiveness of CGRP-(8-37) to displace radiolabeled ADM from its binding sites, to inhibit ADM-induced glomerular cAMP formation, and to prevent ADM-induced renal vasodilation supports the hypothesis of ADM altering renal hemodynamics by interacting with ADM- and not CGRP-specific membrane receptors.
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Each year approximately 2 million people are seriously injured in traffic accidents. Injuries to the chest play a major role in the mortality and morbidity of these patients. One-third to one-half of motor vehicle crash victims suffer blunt thoracic trauma. The spectrum of injuries is broad but posttraumatic pulmonary masses are rarely noted. The proper use of radiographic imaging procedures allows documentation of pulmonary hematoma and exclusion of more ominous lesions.
OBJECTIVE: To obtain birthweight standards for south Indian babies. DESIGN: Prospective cohort study. SETTING: A tertiary care hospital in south India. PATIENTS AND METHODS: Data from 11, 641 singleton live births between 1991 and 1994 were used to calculate smoothed gestation specific birthweight centiles for four categories based on sex of the infant and birth order. Smoothed gestation specific birthweight centiles were also calculated for all births between 37-41 weeks without adjustments for sex of infant or birth order. Data for births between 37 and 41 weeks were reanalysed using non-adjusted birthweight centiles and birthweight centiles adjusted for sex and birth order to determine misclassification of data. Multiple regression analysis was used to determine the influence of various variables on birthweight. RESULTS: Factors influencing birthweight were gestation at birth, sex of infant, birth order and maternal height. A quadratic equation including these variables and the square of the gestational age explained 18% of variation in birthweight. Female infants were on the average 113 g (95% CI 26-200 g) lighter than male infants. Later born babies were on the average 130 g (95% CI 40-220 g) heavier than first born babies. Therefore significant misclassification of infants occurred when non-adjusted birthweight centiles were used. Babies born to women whose heights were outside the interquartile range (150-158 cm) were 81 g lighter or heavier than those born to women within this range. CONCLUSIONS: Birthweight centiles for gestation when used should be adjusted for birth order, sex of infant and maternal height.
Because of the frequent use of central venous catheters, deep venous thrombosis of the upper extremity is more common than previously reported. A significant number of patients suffer pulmonary embolization from catheter-associated thrombosis. This observation should be considered as a major factor in the risk benefit analysis of the utility of deep venous catheters.
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OBJECTIVES: To determine the pattern of intrauterine growth and the gestation at birth of Indian fetuses. METHOD: One hundred twenty consecutive women who had reliable menstrual histories, low-risk pregnancies and who were booked for delivery at the Christian Medical College Hospital, Vellore, before 20 weeks' gestation were recruited to the study. Ultrasound fetal biometry was carried out at 4-weekly intervals from 20 weeks and at weekly intervals after 36 weeks until delivery. RESULTS: Growth patterns of fetal biparietal diameter and femur length were comparable to those reported in Western populations. However there was a lag in growth of abdominal circumference (AC) after 28 weeks in comparison with that reported in Western populations. The median gestation at delivery following spontaneous labor was 39 weeks. No association was observed between rate of growth of AC and gestation at birth. CONCLUSION: Slowing of growth of the fetal AC after 28 weeks and a shorter length of gestation result in the birth of smaller babies in this ethnic group. The implications of these findings are discussed.
A longitudinal study was carried out on 38 women with low risk pregnancies. These women had cardiotocography at 27-28 wk initially, at fortnightly intervals thereafter until 36 wk and at weekly intervals thereafter until delivery. All cardiotocographs were analyzed by one investigator who was not aware of the individual clinical situation. Of the 232 cardiotocographs, 12 (0.5%) of poor quality were excluded from analyses. The mean base-line heart rate decreased from 142.5 (SD 6.03) beats per min at 27-30 wk to 138.2 (SD 7.4) at term. Analysis of variance for repeated measures showed that the decrease in foetal heart rate with gestation was statistically significant (P < 0.001). The number of accelerations increased with gestation (P = 0.002). There were no significant changes in variability and decelerations with increasing gestation.
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Because intracerebroventricular (ICV) infusion of hypertonic saline or angiotensin II (Ang II) both induce water drinking, vasopressin secretion, natriuresis and increased arterial pressure, the possibility that common neural pathways mediate responses to ICV Ang II and hypertonic saline has been investigated. This was done by testing the effect of ICV infusion of the Ang II antagonist losartan on the natriuretic and pressor responses to ICV hypertonic NaCl in sheep. The effect of ICV losartan on plasma renin concentration (PRC) was also investigated. Infusion of losartan (1 mg/hr) into a lateral ventricle prevented both natriuretic and pressor responses to infusion of 0.6 mol/liter NaCl into a lateral ventricle at 1 ml/hr. In another experiment, ICV losartan at 1 mg/hr caused a pronounced increase in the PRC of Na-depleted sheep, while ICV Ang II at 3 micrograms/hr decreased PRC. The results suggest that: (i) a central angiotensinergic pathway may mediate osmoregulatory responses to centrally administered hypertonic saline, and (ii) a central angiotensinergic pathway may have a tonic inhibitory influence on renin secretion in Na-depleted animals.
A cohort of 200 women with singleton pregnancies attending the antenatal clinic, were studied to determine the prevalence of genital mycoplasma and ureaplasma infections in pregnant women and the effect of infection on pregnancy outcome. Vaginal and endocervical swabs were taken at 26-30 wk and again at 36-38 wk of pregnancy and cultured for mycoplasma and ureaplasma. Forty (20%, 95% CI 14.5-25.6%) women were found to be infected with arginine metabolising mycoplasmas and 79 (39.5%, 95% CI 32.7-46.3%) with ureaplasma at either site or either time. The mean +/- SD birth weight of infants born to women infected with mycoplasma alone was 2879 +/- 471 g while that of infants born to women infected with ureaplasma alone was 2964 +/- 412 g. Mean +/- SD birthweight of infants born to women infected with both organisms was 2969 +/- 389 g while that of infants born to uninfected women was 2919 +/- 432 g. These differences were not statistically significant. The median gestation at delivery was 39 wk in the cohort; the differences among the groups were minor and statistically not significant. Thus, although genital mycoplasma/ureaplasma infections were frequent, no association was observed between infection and pregnancy outcome.
OBJECTIVE: To measure inter- and intra-observer reliability in the amniotic fluid index (AFI). METHODS: To measure inter-observer reliability, three observers measured the AFI at random in 32 patients without knowing each other's results. To determine intra-observer reliability, each investigator made repeated measurements on ten other patients. Patients at 26-41 weeks' gestation who were referred for an antenatal ultrasound examination were asked to participate. Intra-observer reliability and inter-observer reliability were expressed as intra-class correlation coefficients. Inter-observer agreement was also expressed as the kappa statistic after dichotomizing the AFI (less than 8 cm, 8 cm or more). RESULTS: The intra-class correlation coefficient for intra-observer reliability exceeded 0.8, and for inter-observer reliability it was 0.67 (95% confidence interval [CI] 0.52-0.79), with an overall kappa of 0.44 (95% CI 0.22-0.65). The percentage disagreement between pairs of observers reached 22-28%. CONCLUSION: Measurements of AFI have good intra-observer and moderate inter-observer agreement. In clinical use, an AFI level near a cutoff value should be interpreted with caution.
A randomized controlled study of valethamate bromide administered by intramuscular injection in acceleration of labor was done in 60 consecutive primigravidae and 60 consecutive multigravidae admitted in labor at 2-4 cm cervical dilatation. There was no difference observed in the rate of cervical dilatation between those who received valethamate bromide and those who received normal saline. However, maternal tachycardia was observed in significantly more women primigravida RR 1.97, 95% CI 1.3-3.0; multigravida RR 2.16, 95% CI 1.3-3.6) who had received valethamate bromide.
OBJECTIVE: To determine the effects of passive maternal smoking on birthweight. DESIGN: Cohort of consecutive singleton live births. SETTING: Teaching hospital in South India. SUBJECTS: 994 infants and their mothers. MAIN OUTCOME MEASURE: Birthweight. RESULTS: All the women were themselves non-smokers; 520 (52%) were passive smokers while the remainder were not exposed to tobacco smoke. Infants born to passive smokers were on the average 55 g lighter than those born to non-smokers. Passive smoking was associated with a decrease in birthweight of 63 g (95% CI 12-114 g) even after adjusting for other variables known to affect birthweight.