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Biomedical subjects

I M Rao

Publications and source records attributed to I M Rao.

At least 37 records · Page 2Linked to original sources
PubMed1990

Limiting Factors in Photosynthesis: VI. Regeneration of Ribulose 1,5-Bisphosphate Limits Photosynthesis at Low Photochemical Capacity.

Earlier work (SE Taylor, N Terry [1984] Plant Physiol 75: 82-86) has shown that the rate of photosynthesis may be colimited by photosynthetic electron transport capacity, even at low intercellular CO(2) concentrations. Here we monitored leaf metabolites diurnally and the activities of key Calvin cycle enzymes in the leaves of three treatment groups of sugar beet (Beta vulgaris L.) plants representing three different in vivo photochemical capacities, i.e. Fe-sufficient (control) plants, moderately Fe-deficient, and severely Fe-deficient plants. The results show that the decrease in photosynthesis with Fe deficiency mediated reduction in photochemical capacity was through a reduction in ribulose 1,5-bisphosphate (RuBP) regeneration and not through a decrease in ribulose 1,5-bisphosphate carboxylase/oxygenase activity. Based on measurements of ATP and NADPH and triose phosphate/3-phosphoglycerate ratios in leaves, there was little evidence that photosynthesis and RuBP regeneration in Fe-deficient leaves were limited directly by the supply of ATP and NADPH. It appeared more likely that photochemical capacity influenced RuBP regeneration through modulation of enzymes in the photosynthetic carbon reduction cycle between fructose-6-phosphate and RuBP; in particular, the initial activity of ribulose-5-phosphate kinase was strongly diminished by Fe deficiency. Starch and sucrose levels changed independently of one another to some extent during the diurnal period (both increasing in the day and decreasing at night) but the average rates of starch or sucrose accumulation over the light period were each proportional to photochemical capacity and photosynthetic rate.

Journal Article↗
PubMed1989

The combination of a left aortic arch, a right-sided descending thoracic aorta with a left-sided arterial duct.

A nine-year-old male child presented with a history of recurrent chest infections and breathlessness. On investigation, he was found to have a left aortic arch with a right-sided descending thoracic aorta along with a left-sided arterial duct. He also had mild aortic stenosis with regurgitation. The duct was successfully ligated under controlled hypotensive anesthesia through a left posterolateral thoracotomy.

Aorta, Thoracic↗
PubMed1989

Surgical experience with diseases of the tricuspid valve. Cross-sectional and Doppler echocardiographic evaluation following DeVega's repair.

Seventy-eight patients undergoing mitral valve surgery with or without replacement of the aortic valve also underwent procedures on the tricuspid valve over a period of 10 years. All patients were in functional class III or IV preoperatively. The procedures were performed in all patients with organic disease of the tricuspid valve (N = 44) and in those with moderate or severe functional tricuspid valvar regurgitation (N = 34). Seventy-one patients underwent DeVega's annuloplasty with or without commissurotomy. The overall mortality was 11.5%. 65 long-term survivors were followed up for a period of 6 months to 10 years (mean 5.3 years). Sixty-three patients were in functional class I or II at the last follow-up. Six patients had clinical evidence of mild to moderate tricuspid regurgitation. Regression of cardiomegaly (as judged by the chest radiograph and right ventricular hypertrophy seen in the electrocardiogram) was evident in most cases. Fifty-one of 54 patients evaluated by cross-sectional echocardiography were reported to have a functionally normal tricuspid valve. Doppler echocardiography in 28 patients showed no significant tricuspid regurgitation or stenosis in 26 patients. Eleven consecutive patients undergoing DeVega's annuloplasty were studied prospectively with pre- and postoperative Doppler echocardiography. Good correlation existed between right ventricular systolic pressures predicted by Doppler with those obtained preoperatively at cardiac catheterization. Postoperative Doppler echocardiography in these 11 patients showed complete restoration of competence of the tricuspid valve as well as normalisation of the right ventricular systolic pressure in 10 patients.

Adult↗
PubMed1989

Influence of Phosphorus Nutrition on Growth and Carbon Partitioning in Glycine max.

Soybean plants (Glycine max [L.] Merr var Amsoy 71) were grown in growth chambers with high-phosphorus (high-P) and low-phosphorus (low-P) culture solutions. Low-P treatment reduced shoot growth significantly 7 days after treatment began. Root growth was much less affected by low-P, there being no significant reduction in root growth rate until 17 days had elapsed. The results suggest that low-P treatment decreased soybean growth primarily through an effect on the expansion of the leaf surface which was diminished by 85%, the main effect of low-P being on the rate of expansion of individual leaves. Low-P had a lesser effect on photosynthesis; light saturated photosynthetic rates at ambient and saturating CO(2) levels were lowered by 55 and 45%, respectively, after 19 days of low-P treatment. Low-P treatment increased starch concentrations in mature leaves, expanding leaves and fibrous roots; sucrose concentrations, however, were reduced by low-P in leaves and increased in roots. Foliar F-2,6-BP levels were not affected by P treatment in the light but in darkness they increased with high-P and decreased with low-P. The increase in the starch/sucrose ratio in low-P leaves was correlated primarily with changes in the total activities of enzymes of starch and sucrose metabolism.

Journal Article↗
PubMed1989

Leaf phosphate status, photosynthesis, and carbon partitioning in sugar beet: I. Changes in growth, gas exchange, and calvin cycle enzymes.

Sugar beets (Beta vulgaris L. cv F58-554H1) were cultured hydroponically for 2 weeks in growth chambers with two levels of orthophosphate (Pi) supplied in half strength Hoagland solution. Low-P plants were supplied with 1/20th of the Pi supplied to control plants. With low-P treatment, the acid soluble leaf phosphate and total leaf P decreased by about 88%. Low-P treatment had a much greater effect on leaf area than on photosynthesis. Low-P decreased total leaf area by 76%, dry weight per plant by 60%, and the rate of photosynthesis per area at light saturation by 35%. Low-P treatment significantly decreased the total extractable activity of phosphoglycerate kinase (by 18%) and NADP-glyceraldehyde-3-phosphate dehydrogenase (by 16%), but did not decrease the total activities of ribulose-1,5-bisphosphate (RuBP) carboxylase (RuBPCase) and ribulose-5-phosphate kinase. Low-P treatment decreased the initial activities of three rate-limiting Calvin cycle enzymes, but had no effect on the initial activity of RuBPCase. Furthermore, low-P treatment significantly increased the total extractable activities of fructose-1,6-bisphosphatase (by 61%), fructose-1,6-bisphosphate aldolase (by 53%), and transketolase (by 46%). The results suggest that low-P treatment affected photosynthetic rate through an effect on RuBP regeneration rather than through RuBPCase activity and that the changes in Calvin cycle enzymes with low-P resulted in an increased flow of carbon to starch.

Journal Article↗
PubMed1989

Leaf Phosphate Status, Photosynthesis and Carbon Partitioning in Sugar Beet: II. Diurnal Changes in Sugar Phosphates, Adenylates, and Nicotinamide Nucleotides.

Sugar Beets (Beta vulgaris L. cv F58-554H1) were cultured hydroponically in growth chambers. Leaf orthophosphate (Pi) levels were varied nutritionally. The effect of decreased leaf phosphate (low-P) status was determined on the diurnal changes in the pool sizes of leaf ribulose 1,5-bisphosphate (RuBP), 3-phosphoglycerate (PGA), triose phosphate, fructose 1,6-bisphosphate, fructose-6-phosphate, glucose-6-phosphate, adenylates, nicotinamide nucleotides, and Pi. Except for triose phosphate, low-P treatment caused a marked reduction in the levels of leaf sugar phosphates (on a leaf area basis) throughout the diurnal cycle. Low-P treatment decreased the average leaf RuBP levels by 60 to 69% of control values during the light period. Low-P increased NADPH levels and NADPH/NADP(+) ratio but decreased ATP; the ATP/ADP ratio was unaffected. Low P treatment caused a marked reduction in RuBP regeneration (RuBP levels were half the RuBP carboxylase binding site concentration) but did not depress PGA reduction to triose phosphate. These results indicate that photosynthesis in low-P leaves was limited by RuBP regeneration and that RuBP formation in low-P leaves was not limited by the supply of ATP and NADPH. We suggest that RuBP regeneration was limited by the supply of fixed carbon, an increased proportion of which was diverted to starch synthesis.

Journal Article↗
PubMed1988

Surgical experience with intracardiac myxomas.

Eighteen patients underwent surgery for intracardiac myxoma (16 left atrial and 2 right atrial) during the last 10 years. Seventeen patients had tumour stalk attached to the oval fossa. The myxoma was excised along with a cuff of the atrial septum, which was reconstructed using a Dacron patch in 15 patients and by direct suture in 2 patients. In the remaining case the myxoma was attached to the left atrial wall and adjacent atrioventricular junction. There was only one early death in a patient who underwent a concomitant lobectomy for lung abscess and one late death due to a noncardiac cause. During the follow-up period of 3-96 months (average 36 months) all the survivors were in New York Heart Association Class I. Scanning electron microscopy of tumour tissue was done in 8 cases. The morphological findings did not help in categorizing the tumours into any pathological subgroups. Postoperative cardiac catheterization done in 3 patients (30-50 months postoperatively) showed return of haemodynamics to normal. Echocardiographic studies done postoperatively have not revealed recurrence of tumour in any patient. Surgical excision of myxomas is possible with very gratifying long-term results.

Adolescent↗
PubMed1988

Antagonism of estrogen-induced prolactin release by progesterone.

Previous work from our laboratory has shown that during the process of nuclear occupancy of the progesterone receptor complex (1-2 h), nuclear estradiol receptors of the anterior pituitary are depleted. The purpose of this study was to determine whether the depletion of nuclear estradiol receptors by progesterone had functional biological significance. The ovariectomized (26 days of age) immature rat was used as the model for analysis of this question. The ability of estradiol to release prolactin from the anterior pituitary was the function chosen to determine the biological significance of the progesterone and estradiol interactions. In response to estradiol exposure (2 micrograms/rat), prolactin release reached peak values from 8 h to 12 h and returned to control levels by 24 h. A second injection of estradiol 13 h after the initial injection stimulated a second increase in serum prolactin at 25 h. This model of two injections of estradiol 13 h apart served to provide adequate levels of anterior pituitary progesterone receptors and elevated serum prolactin levels upon which superimposed progestin modulation could be examined. A single injection of progesterone (0.8 mg/kg BW) 1 h before the second estradiol injection blocked the increase in serum prolactin. This action was a receptor-mediated event because progesterone had no effect without estrogen priming or when the progesterone antagonist RU486 was used. Finally, when the interval between the progesterone and second estradiol injection was extended to 4 h, a time period when progesterone does not deplete pituitary nuclear estrogen receptors, the estrogen-induced increase in serum prolactin was not blocked.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Closed mitral valvotomy during pregnancy. A 20-year experience.

Closed mitral valvotomy for rheumatic mitral stenosis was performed on 126 pregnant women (average duration of pregnancy c. 21 weeks), 91% of whom were in NYHA functional class III or IV. Associated functional tricuspid regurgitation was present in 47 (37%) of the women, and 102 (81%) had critical mitral stenosis (digitally assessed valve area less than 1 cm2). There was no surgical mortality. Postoperatively 84% of the women were in NYHA class I. Clinical evidence of pulmonary artery hypertension and tricuspid regurgitation regressed postoperatively in most patients. Full-term normal delivery was achieved in 82% of the pregnancies, with total fetal mortality 6%. There were no congenital abnormalities and the infants' progress was normal. At 5-year follow-up 86% of the women were in NYHA class I or II and at 10 years the figure was 60%. The restenosis rate was 2%/year and the late mortality 3.3%. Closed mitral valvotomy during pregnancy thus was safe and reliable, giving significant functional and clinical improvement without adversely affecting the fetus.

Adult↗
PubMed1988

Pregnancy in patients with prosthetic cardiac valve. A 10-year experience.

Pregnancy after valve replacement has been considered hazardous because of maternal and fetal complications secondary to anticoagulant medication, in addition to basic myocardial problems. Of 229 females aged 15-45 years with prosthetic valve replacement, 37 (including 34 with Björk-Shiley valve and anticoagulants) subsequently had a total of 47 pregnancies. Fullterm delivery of a normal infant was achieved in 40 cases. There were three premature births, two spontaneous abortions, one stillbirth and one ectopic pregnancy. The fetal mortality was 8.5%. Valve thrombosis developed in two cases, but surgical treatment was successful. Oral anticoagulants (acenocoumarin and dipyridamole) were continued throughout pregnancy. Heparin was substituted before labour began, but discontinued after delivery, when effective oral anticoagulation was resumed. Our experience showed that pregnancy in women with mechanical heart valve prosthesis and continued oral intake of anticoagulants is safe and successful in most cases.

Acenocoumarol↗
PubMed1988

Chest injuries: a clinical and autopsy profile.

The clinical profiles and management of 236 consecutive chest injury patients treated and followed up at All India Institute of Medical Sciences between January 1983 and July 1985 were analyzed prospectively. There were 149 blunt and 87 penetrating injuries; 21 patients (9%) required thoracotomy. Single- or multiple-tube thoracostomy was performed in 141 patients (60%). The remaining 74 patients (31%) required only observation for a period of 24-48 hours. Fifteen patients (6.3%) died, the mortality being related to head injury in four, irreversible hypovolemic shock in four, pulmonary embolism in three, septicemia in two, and respiratory failure in two. Nonfatal complications included residual hemothorax in 18 cases, persistent air leak in 13, pulmonary infection in eight, pulmonary embolism in one, and empyema in one. The average hospital stay was 6.9 days. Evidence of chest injury of various magnitudes was found in 756 of 2,286 autopsies conducted for trauma-deaths during the same study period analyzed retrospectively; however, it was the major cause of death in only 147 (19%). Cardiac injuries accounted for 41% of the deaths resulting primarily from chest trauma. Only 10% of the patients who sustained cardiac injury reached hospital alive.

Adolescent↗
PubMed1987

Leaf magnesium alters photosynthetic response to low water potentials in sunflower.

We grew sunflower (Helianthus annuus L.) plants in nutrient solutions having nutritionally adequate but low or high Mg(2+) concentrations and determined whether photosynthesis was effected as leaf water potentials (psi(w)) decreased. Leaf Mg contents were 3- to 4-fold higher in the plants grown in high Mg(2+) concentrations (10 millimolar) than in those grown in low concentrations (0.25 millimolar). These contents were sufficient to support maximum growth, plant dry weight, and photosynthesis, and the plants appeared normal. As low psi(w) developed, photosynthesis was inhibited but moreso in high Mg leaves than in low Mg leaves. The effect was particularly apparent under conditions of light- and CO(2)-saturation, indicating that the chloroplast capacity to fix CO(2) was altered. The differential inhibition observed in leaves of differing Mg contents was not observed in leaves having differing K contents, suggesting that the effect may have been specific for Mg. Because Mg(2+) inhibits photophosphorylation and coupling factor activities at concentrations likely to occur as leaves dehydrate, Mg may play a role in the inhibition of chloroplast reactions at low psi(w), especially in leaves such as sunflower that markedly decrease in water content as psi(w) decreases.

Journal Article↗
PubMed1986

Role of progesterone in the modulation of the preovulatory surge of gonadotropins and ovulation in the pregnant mare's serum gonadotropin-primed immature rat and the adult rat.

The role of progesterone in the regulation of the preovulatory surge in gonadotropins and ovulation was examined in this study by use of a potent antagonist of progesterone, RU 486 (17 beta-hydroxy-11 beta-[4-dimethyl-aminophenyl]-17 alpha- [prop-1-ynyl]estra-4,9-diene-3-one). The immature rat primed with pregnant mare's serum gonadotropin (PMSG) and the cycling adult animal were the models used to verify the role of progesterone. When RU 486 (200 micrograms/rat) was given as a single dose on the morning of proestrus, there was a significant reduction in the preovulatory surge levels of gonadotropins and ovulation in both animal models. Serum progesterone levels in both models at the time of death on the evening of proestrus were unaltered upon treatment with RU 486. RU 486 did not have any effect on gonadotropin levels in immature rats 7 days after castration. These results show that the actin of RU 486 on the preovulatory gonadotropin surge is due to an antagonism of the action of progesterone on the hypothalamic-pituitary axis. Thus, a role for progesterone in modulating the preovulatory surge of gonadotropins and, consequently, ovulation is strongly suggested.

Animals↗
PubMed1986

Fate of thrombectomized Björk-Shiley valves. A long-term cinefluoroscopic, echocardiographic, and hemodynamic evaluation.

Fourteen patients underwent thrombectomy for thrombosis of implanted Björk-Shiley valves (13 in the mitral and one in the aortic position) between January, 1975, and July, 1984. There was no operative mortality or perioperative embolism. Over a follow-up period of 1 to 96 months (average 23.5 months), there was no late mortality. Serial evaluation of valve function by cinefluoroscopy and echocardiography has shown no evidence of rethrombosis or valve dysfunction in any of the patients. Cardiac catheterization and angiocardiography done in 10 patients at various intervals (1 month to 6 years) postoperatively have shown normal valve function in all and normalization of elevated preoperative intracardiac pressures in the majority. Our experience suggests that thrombectomy of thrombosed Björk-Shiley valves provides excellent early and long-term results in terms of patient survival and valve function.

Adult↗
PubMed1985

Direct inhibitory actions of GnRH on accessory reproductive organs of rat.

Recently gonadotropin releasing hormone (GnRH) and its agonistic analogs were demonstrated to have some direct actions in accessory reproductive organs. In our study the effects of GnRH and its analogs on some steroid hormone induced responses were investigated. GnRH and its analogs inhibited estradiol induced ornithine decarboxylase (ODC) and glucosamine-6-phosphate synthase activities in the uterus of rat. These enzymes which are markers for cell proliferation are regulatory enzymes in the biosynthetic pathways of polyamines and glycoproteins, respectively. Similarly, GnRH and its analogs also inhibited testosterone stimulated ODC activity in ventral prostate of rat. In addition, GnRH analog inhibited incorporation of radioactive precursors into RNA and protein induced by estradiol in uterus or dihydrotestosterone (DHT) in ventral prostate. In an effort to elucidate the mechanism of action of GnRH in uterus, it was found that GnRH analog treatment does not alter the estradiol receptor content in vivo. Also, GnRH does not show any effect on radioactive estradiol binding to its receptor in vitro. Hence, the inhibitory actions of GnRH in uterus may not involve estradiol receptors. However, GnRH analogs were found to have post-transcriptional effects. It was observed that DHT induced poly(A) polymerase activity in ventral prostate and estradiol induced poly(A) polymerase activity in uterus were inhibited by GnRH analog treatment. It was further observed that GnRH inhibited incorporation of [3H]uridine into poly(A)+ RNA of ventral prostate. This indicates that the inhibitory effects of GnRH involve post-transcriptional mechanisms.

Animals↗
PubMed1984

Direct inhibitory effect of gonadotropin releasing hormone in the uterus of rat.

Estradiol induced increase in ornithine decarboxylase (ODC) and glucosamine-6-phosphate synthase activities of rat uterus were inhibited by simultaneous treatment with gonadotropin releasing hormone (GnRH) or its agonists. The direct inhibitory effect of GnRH analogs was found to be dose dependent. It was observed that a higher dose of GnRH analog was needed to cause inhibition of glucosamine-6-phosphate synthase when compared to ODC activity. The inhibitory effect of GnRH was not observed if its injection was delayed following estradiol treatment. These results show that the extra-pituitary inhibitory effects of GnRH involves enzymes associated with cell proliferation.

Animals↗