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Biomedical subjects

N Sinha

Publications and source records attributed to N Sinha.

At least 91 records · Page 5Linked to original sources
PubMed1991

Carbaryl-induced thyroid dysfunction in the freshwater catfish Clarias batrachus.

Freshwater female catfish, Clarias batrachus, were exposed to sublethal concentrations of carbaryl (12 mg/liter for 96 hr and 5 mg/liter for 16 days) during the prespawning and spawning phases of their annual reproductive cycle. The effects on the levels of thyroxine (T4) and triiodothyronine (T3), the T3/T4 ratio, and the extrathyroidal conversion of T4 to T3 were studied in serum, pharyngeal thyroid, and anterior and posterior kidney. Carbaryl exposure for 96 hr suppressed T4 but elevated T3 and the T3/T4 ratio in serum during both phases of experimentation. However, 16 days exposure caused a decline in T4 as well as in T3 and in the T3/T4 ratio. In the pharyngeal thyroid, carbaryl increased T4 as well as peroxidase activity and decreased T3 and the T3/T4 ratio. Its treatment for 96 hr did not elicit any change in the parameters studied in the anterior kidney, whereas in the posterior kidney it suppressed the levels of T4 and T3, peroxidase activity, and the T3/T4 ratio. However, carbaryl exposure for 16 days provoked increases in T4 and peroxidase activity but decreases in T3 and the T3/T4 ratio in anterior kidney. In posterior kidney, it did not change T4 and peroxidase activity, but decreased T3 and the T3/T4 ratio. It also stimulated extrathyroidal conversion of T4 to T3.

Animals↗
PubMed1991

Pesticides induced changes in circulating thyroid hormones in the freshwater catfish Clarias batrachus.

1. Effects of endosulfan, malathion and carbaryl on circulating T4, T3 and T3/T4 ratio in the freshwater catfish, C. batrachus have been studied during reproductively active phases, i.e. vitellogenic and post-vitellogenic phases of its annual reproductive cycle. 2. Endosulfan provoked a significant increase in T4 and a decrease in T3 as well as the T3/T4 ratio. 3. Malathion decreased T3 and T3/T4 ratio without altering the level of T4 in circulation. 4. Carbaryl caused a decline in the level of T4 and an elevation in T3 and T3/T4 ratio.

Animals↗
PubMed1990

Chronic toxicity of styrene maleic anhydride, a male contraceptive, in rhesus monkeys (Macaca mulatta).

A newly developed male contraceptive, styrene maleic anhydride (SMA), was injected in the vas deferens of male rhesus monkeys for safety evaluation at the dose of 100 mg (contraceptive dose, CD), 250 mg (CD x 2.5) and 500 mg (CD x 5.0), and the monkeys were kept under observation for one year. The observed behavioural, haematological, biochemical and histopathological parameters in treated monkeys were comparable to controls. The results suggest the polymer SMA to be safe up to 5 times CD in monkeys.

Adrenal Glands↗
PubMed1990

Mutant characters of knotted maize leaves are determined in the innermost tissue layers.

Knotted (Kn1), a dominant mutation in maize, perturbs normal leaf development. Mutant leaves have localized regions of extra growth called knots and, in addition to the normal ligule, ectopic fringes of ligule are found on the leaf blade. Previous clonal analysis showed that the epidermal genotype was immaterial in knot formation. To establish which inner leaf layer was required for formation of knots and ectopic ligule we used a closely linked albino mutation to mark X-ray-induced clonal sectors of wild type (kn) tissue in Kn1 plants. The sectors examined frequently changed in composition of layers in the leaf both transversely and longitudinally. We present results that show that both mutant characters are determined in the middle mesophyll-bundle sheath (MMBS) layer. We show that a lateral vein can produce a knot when only half the MMBS layer around the lateral vein contains the mutant gene. We also show that the ectopic ligule in Kn1 has contributions from both the adaxial epidermal and adaxial mesophyll layer.

In Vitro Techniques↗
PubMed1990

Echocardiographic demonstration of resolving intrapericardial mass in tuberculous pericardial effusion.

A patient with tuberculous pericardial effusion is described who presented with cardiac tamponade. Subsequent to pericardiocentesis, a large echodense intrapericardial mass was observed which disappeared completely with antituberculous chemotherapy. The resolution of the mass suggests that it was a conglomeration of fibrinous exudates deposited in the pericardial cavity. Presence of such exudates should not be considered an indication for surgical intervention.

Echocardiography↗
PubMed1990

RecA protein of Escherichia coli has a third essential role in SOS mutator activity.

The DNA damage-inducible SOS response of Escherichia coli includes an error-prone translesion DNA replication activity responsible for SOS mutagenesis. In certain recA mutant strains, in which the SOS response is expressed constitutively, SOS mutagenesis is manifested as a mutator activity. Like UV mutagenesis, SOS mutator activity requires the products of the umuDC operon and depends on RecA protein for at least two essential activities: facilitating cleavage of LexA repressor to derepress SOS genes and processing UmuD protein to produce a fragment (UmuD') that is active in mutagenesis. To determine whether RecA has an additional role in SOS mutator activity, spontaneous mutability (tryptophan dependence to independence) was measured in a family of nine lexA-defective strains, each having a different recA allele, transformed or not with a plasmid that overproduces either UmuD' alone or both UmuD' and UmuC. The magnitude of SOS mutator activity in these strains, which require neither of the two known roles of RecA protein, was strongly dependent on the particular recA allele that was present. We conclude that UmuD'C does not determine the mutation rate independently of RecA and that RecA has a third essential role in SOS mutator activity.

Alleles↗
PubMed1989

Clinical correlates of acute right ventricular infarction in acute inferior myocardial infarction.

Right ventricular infarction was diagnosed on the basis of ST-segment elevation greater than or equal to 1 mm in at least one right precordial lead (V3R-V6R) in 20 of 50 patients with first acute inferior myocardial infarction. Seventy five percent of these had ST elevation in 2 or more right precordial leads. Giddiness and hiccups were more common amongst such patients (P less than 0.05). Signs of right ventricular dysfunction-raised jugular venous pressure (65%), Kussmaull's sign (45%), hypotension (without cardiogenic shock, 40%) and right-sided third sound (25%) in the absence of clinical left ventricular failure, were noted in 65% of such patients. Eleven patients had 2 or more of the above signs. ST elevation in 2 or more right precordial leads was found in 10 of these 11 patients. A more complicated course in the hospital characterised by bradyarrhythmias, hypotension and cardiogenic shock, combined with a greater mortality was seen in such patients. We conclude that the bedside diagnosis of haemodynamically significant right ventricular infarction can be made on the basis of a combination of clinical signs and ST elevation in 2 or more right precordial leads, even in units not equipped for bedside haemodynamic monitoring, echocardiography and radionuclide studies. This should lead to a better identification and management of such patients.

Acute Disease↗
PubMed1989

Digoxin or verapamil or metoprolol for heart rate control in patients with mitral stenosis--a randomised cross-over study.

The effect and choice of a drug to control heart rate for symptomatic improvement in patients with isolated mitral stenosis with normal sinus rhythm (n = 10) or atrial fibrillation (n = 10) were studied. Digoxin (0.25-0.5 mg daily), metoprolol (50-100 mg twice a day) and verapamil (40-80 mg three times a day) were evaluated for this purpose. An open randomised cross-over design was followed. The efficacy of a drug was evaluated by: (1) subjective improvement on a visual analog scale, and (2) objective improvement on repeated multi-stage symptom-limited treadmill exercise. In patients with sinus rhythm greater than or equal to 50% subjective improvement was seen in 90%, 40% and nil with metoprolol, verapamil and digoxin, respectively. The total work done by these patients was 1008 +/- 541 kpm (control), 2869 +/- 1418 kpm on metoprolol, 2369 +/- 884 kpm on verapamil and 1654 +/- 918 kpm on digoxin. In patients with atrial fibrillation greater than or equal to 50% subjective improvement was seen in 80%, 40% and 30% with verapamil, metoprolol and digoxin, respectively. The total work done by these patients was 555 +/- 232 kpm (control), 1379 +/- 553 kpm on verapamil, 1251 +/- 575 kpm on metoprolol and 716 +/- 340 kpm on digoxin. The degree of improvement on a drug appeared to be a function of its ability to control resting and exercise heart rates in two different rhythms in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

A dumbbell-shaped, double-hairpin structure of DNA: a thermodynamic investigation.

We report the first calorimetric and spectroscopic investigation on a member of a new class of nucleic acid secondary structures in which both ends of a duplex core are closed by single-stranded loops. Such structures can be formed intramolecularly from appropriately designed base sequences. We have synthesized the 24-mer sequence shown, and we present calorimetric, spectroscopic, and electrophoretic (formula; see text) evidence that it adopts a dumbbell-shaped, double-hairpin structure. Our data allow us to reach the following conclusions: (1) The phosphodiester gap in the center of the core duplex of the dumbbell does not reduce the transition enthalpy relative to that measured for the corresponding octameric duplex d(GGAATTCC)2. (2) Incorporation of a 5'-phosphate group into the gap decreases the thermal stability of the dumbbell relative to its unphosphorylated sequence. On the basis of the salt dependence of this effect, we propose that the phosphorylation--induced decrease in thermal stability is electrostatic in origin. From the changes in the transition enthalpy and entropy, we suggest that the phosphorylation-induced decrease in thermal stability of the double hairpin arises from electrostatically induced based unstacking at the nick. (3) The thymine residues in the loop behave both electrostatically and enthalpically like denatured single strands. Published nuclear magnetic resonance studies reveal partial stacking of thymine residues in the loops of linear hairpin structures. If this feature persists in the double-hairpin structure, then the spatial overlap of thymine residues in the loops does not necessarily produce a favorable enthalpic contribution. (4) When both ends of the nicked octameric core duplex are constrained by loops of only four thymine residues, the dumbbell structure may adopt conformations in which the 5' and 3' ends at the nick are twisted relative to the helical axis and therefore are not in phase. Such conformations would account for the observed resistance of the double-hairpin structure to ligation, since the 3'OH and 5'P would no longer be collinear.

Base Sequence↗
PubMed1987

Facilitation of allogeneic bone marrow transplantation by a T cell-specific immunotoxin containing daunomycin.

Daunomycin coupled via an acid-sensitive spacer to monoclonal Thy-1.2-specific antibody was used to purge T lymphocytes from a 1:1 mixture of murine C57BL/6J bone marrow and spleen cells prior to engraftment in fully allogeneic, irradiated BALB/c recipients. Treatment of bone marrow with the immunotoxin at a concentration used for purging had no effect on the viability of committed hematopoietic progenitor or multipotent stem cells. All of the recipients of purged bone marrow were at least 80% chimeric for donor peripheral blood cells and none developed graft-versus-host disease. Out of 50 chimeras, 49 were still alive more than 200 days posttransplantation. The chimeras were shown to be tolerant to donor tissue as tested by mixed lymphocyte reactivity, cell-mediated cytotoxicity, and skin grafting. The same tests revealed full immunocompetence of chimeras to third-party alloantigens. In vivo IgM and IgG antibody responses to sheep red blood cells were similar in magnitude in allogeneically and syngeneically reconstituted mice.

Animals↗