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Biomedical subjects

N Sinha

Publications and source records attributed to N Sinha.

At least 73 records · Page 4Linked to original sources
PubMed1995

Endosulfan-induced biochemical changes in the testis of rats.

Adult male rats were exposed to 0, 2.5, 5.0 or 10.0 mg endosulfan/kg body weight through oral intubation for 70 d. Decreased sperm counts in the cauda epididymis and reduced intratesticular spermatid counts associated with elevation in the activities of specific testicular marker enzymes (sorbitol dehydrogenase, lactic dehydrogenase, gamma glutamyl transpeptidase, and glucose-6-phosphate dehydrogenase) were seen in all the endosulfan-dosed groups. Endosulfan caused impairment in testicular functions by altering activities of the enzymes responsible for spermatogenesis, thereby influencing intratesticular spermatid count and causing low sperm production and sperm deformity.

Administration, Oral↗
PubMed1993

Effect of metoprolol and diltiazem on the total ischaemic burden in patients with chronic stable angina: a randomized controlled trial.

We conducted a randomised controlled trial to study the effects of metoprolol and diltiazem on the total ischaemic burden--sum of symptomatic and silent myocardial ischaemia, in 146 patients with stable angina pectoris. One-hundred thirty-four completed the study protocol. Sixty-eight patients received metoprolol (100 mg twice daily, n = 52, 50 mg twice daily, n = 16) while 66 received diltiazem (90 mg three times daily, n = 50, 60 mg three times daily, n = 16). The drugs were given for 4 weeks. The primary outcome variables were frequency and duration of total ischaemic burden, silent and symptomatic myocardial ischaemia. These were measured on 48 h of Holter monitoring. The reductions in duration and frequency of total ischaemic burden by metoprolol, 76% and 40%, respectively, were significantly higher than by diltiazem, 43% and 24%, respectively (P < 0.01 and P < 0.02). The frequency and duration of silent myocardial ischaemia, which constituted more than 80% of the total ischaemic burden in the two groups showed similar results. However, the reduction in frequency of symptomatic myocardial ischaemia only was significantly greater by metoprolol (63% than diltiazem (24%) as the difference in reduction of duration of symptomatic ischaemia was insignificant (85% vs. 75%; P > 0.05). Whether a greater reduction of total ischaemic burden by metoprolol as compared to diltiazem has any implications for prognosis in patients with chronic stable angina remains to be established.

Angina Pectoris↗
PubMed1993

Atrio-ventricular regurgitations in constrictive pericarditis: incidence and post-operative outcome.

We studied 33 surgically proven cases of constrictive pericarditis during the period 1989-1991 by color Doppler echocardiography and angiography to look for incidence and postoperative outcome of atrioventricular regurgitation. The mean age was 27.2 + 16.5 years (21 males, 12 females). There was a very high incidence of mitral (79%, trivial in 13, mild in 11 and moderate in 2) and tricuspid (73%, trivial in 7, mild and moderate in 6 each and severe in 5) regurgitation. There was good correlation between 'color Doppler' and angiography for detection and quantification of these regurgitations (r = 0.89 for mitral and 0.76 for tricuspid regurgitation, respectively). There were no preoperative clinical or hemodynamic predictors for the incidence or severity of these regurgitations. Immediate postoperative (7-10 days) evaluation by color Doppler did not show any change in these regurgitations. A follow-up study (by color Doppler and angiography) in 18 patients at a mean period of 229 + 105 days revealed regression of these regurgitations by at least 1 grade in 50% of patients. Patients with persisting regurgitations had persisting hemodynamic abnormality and relatively longer duration of symptoms. The presence of atrio-ventricular regurgitations should not be taken as evidence favoring diagnosis of restrictive cardiomyopathy and against that of constrictive pericarditis. The mechanism of these regurgitations is not clear to us.

Adult↗
PubMed1992

Maize mutants and variants altering developmental time and their heterochronic interactions.

It is useful to envision two fundamentally different ways by which the timing of plant development is regulated: developmental stage-transition mechanisms and time-to-flowering mechanisms. The existence of both mechanisms is indicated by the behavior of various mutants. Shoot stage transitions are defined by dominant mutants representing at least four different genes; each mutant retards transitions from juvenile shoot stages to more adult shoot stages. In addition, dominant leaf stage-transition mutants in at least seven different genes have similar phenotypes, but the leaf rather than the shoot is the focus (and at least two of these genes encode homeodomain proteins.) One mutant, Hairy sheath frayed 1-O (Hsf1-O) simultaneously affects shoot and leaf; this mutant's behavior initiated our interest in plant heterochronism. The second type of timekeeping involves time-to-flowering. As with most plant but not animal species, cultivars of the maize species vary greatly for the time-to-flowering quantitative trait: between 6 and 14 weeks is common. It is via the 'slipping time frames' interaction that takes place between stage-transition mutants and time-to-flowering genetic backgrounds that unexpected and radical phenotypes occur. We see a reservoir of previously unsuspected morphological possibilities among the few heterochronic genotypes we have constructed, possibilities that may mimic the sort of variation needed to fuel macroevolution without having to posit (as done by Goldschmidt) any special macromutational mechanisms.

Biological Evolution↗
PubMed1992

Thyroid physiology impairment by malathion in the freshwater catfish Clarias batrachus.

Effects of malathion on serum and glandular thyroxine (T4), triiodothyronine (T3), the T3/T4 ratio, peroxidase activity, and extrathyroidal conversion of T4 to T3 have been studied in the freshwater catfish Clarias batrachus during the prespawning and spawning phases of its annual reproductive cycle. Malathion inhibited T4 secretion in the kidney, but accelerated T4 synthesis in the pharyngeal thyroid. This pesticide also inhibited the extrathyroidal conversion of T4 to T3 in serum during both the studied phases.

Animals↗
PubMed1991

Effect of endosulfan on thyroid physiology in the freshwater catfish, Clarias batrachus.

Effects of endosulfan on thyroid physiology have been studied in the female freshwater catfish. Clarias batrachus during the pre-spawning and spawning phases of its annual reproductive cycle. Effects of endosulfan varied with the length (96 h and 16 days) of exposure, reproductive status of the fish and organ. The 96-h endosulfan exposure significantly increased the level of thyroxine (T4) in serum and pharyngeal thyroid follicles concurrent with induction of peroxidase activity. However, triiodothyronine (T3) level and T3/T4 ratio decreased in serum and pharyngeal thyroid gland. No change was noticed in any of these parameters in the anterior kidney but in the posterior kidney endosulfan reduced T3 and T3/T4 ratio without affecting T4 levels and peroxidase activity. Sixteen days of endosulfan treatment also had a similar impact, except that it did not influence the studied parameters in pharyngeal thyroid.

Animals↗
PubMed1991

The developmental gene Knotted-1 is a member of a maize homeobox gene family.

The Knotted-1 (Kn1) locus is defined by several dominant gain-of-function mutations that alter leaf development. Foci of cells along the lateral veins do not differentiate properly, but continue to divide, forming outpocketings or knots. The ligule, a fringe normally found at the junction of leaf blade and sheath, is often displaced and perpendicular to its normal position. The phenotype is manifested in all cell layers of the leaf blade, but is controlled by a subgroup of cells of the inner layer. Mutations result from the insertion of transposable elements or a tandem duplication. We show that the Kn1 gene encodes a homeodomain-containing protein, the first identified in the plant kingdom. Sequence comparisons strongly suggest that Kn1 acts as a transcription factor. Here we use the Kn1 homeobox to isolate other expressed homeobox genes in maize. The Kn1 homeobox may permit the isolation of genes that, like animal and fungal counterparts, regulate cell fate determination.

Amino Acid Sequence↗