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Biomedical subjects

A Mehta

Publications and source records attributed to A Mehta.

At least 271 records · Page 15Linked to original sources
PubMed1984

Magnetic resonance studies on the interaction of metal-ion and nucleotide ligands with brain hexokinase.

Our previous studies have shown that one manganous ion binds tightly to bovine hexokinase, with a Kd = 25 +/- 4 microM. The characteristic proton relaxation rate (PRR) enhancement of this binary complex (epsilon b) is 3.5 at 9 MHz and 23 degrees C [Jarori, G.K. Kasturi, S.R., and Kenkare, U.W. (1981) Arch. Biochem. Biophys. 211, 258-268]. On the basis of PRR enhancement patterns, observed on the addition of nucleotides ATP and ADP to this E X Mn binary complex, we now show the formation of a nucleotide-bridge ternary complex, enzyme X nucleotide X Mn. Addition of glucose 6-phosphate to enzyme X ATP X Mn, results in a competitive displacement of ATP Mn from the enzyme. However, a quaternary complex E X ADP X Mn X Glc-6-P appears to be formed when both the products are present. Beta, gamma-Bidentate Cr(III)ATP has been used to elucidate the role of direct binding of Mn(II) in catalysis, and the stoichiometry of metal-ion interaction with the enzyme in the presence of nucleotide. Bidentate Cr(III)ATP serves as a substrate for brain hexokinase without any additional requirement for a divalent cation. However, electron-spin resonance studies on the binding of Mn(II) to the enzyme in the presence of Cr(III)ATP suggest that, in the presence of nucleotide, two metal ions interact with hexokinase, one binding directly to the enzyme and the second interacting via the nucleotide bridge. It is this latter one which participates in catalysis. Experiments carried out with hexokinase spin-labeled with 3-(2-iodo-acetamido)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl clearly showed that the direct-binding Mn site on the enzyme is distinctly located from its ATP Mn binding site.

Adenosine Diphosphate↗
PubMed1984

Comparison of mesna with forced diuresis to prevent cyclophosphamide induced haemorrhagic cystitis in marrow transplantation: a prospective randomised study.

A prospective randomised study was carried out to compare the effect of mesna (2-mercaptoethane sulphonate sodium) with that of forced diuresis in preventing cyclophosphamide induced haemorrhagic cystitis in marrow transplant recipients. Sixty-one consecutive BMT recipients were randomised for treatment with forced diuresis or mesna. The incidence of macroscopic haematuria was significantly lower in the mesna treated group (chi 2 = 4.03, P less than 0.05). No specific side effects of mesna were detected. The lymphopenia induced by cyclophosphamide in the aplastic recipients was similar in the mesna and forced diuresis groups suggesting that mesna has no effect on the lymphocytotoxic activity of cyclophosphamide, although 6 out of 7 episodes of graft failure documented in the study occurred in mesna treated patients. As a result of this study our present policy is to use mesna in all BMT recipients but to continue careful documentation of the incidence of graft failure.

Adolescent↗
PubMed1984

Magnetic resonance of the chest: initial experience with imaging and in vivo T1 and T2 calculations.

Magnetic resonance (MR) imaging of the chest was performed in 33 patients; 28 patients had a variety of malignant tumors and five had benign processes involving the pleura, chest wall, mediastinum, hila , and pulmonary parenchyma. In addition, in vivo T1 and T2 calculations were performed on 17 malignancies and 2 benign processes. Of the 18 patients examined with both MR and computed tomography (CT), 15 MR examinations were considered to be as diagnostic as CT in demonstrating abnormalities. In two cases, CT was superior to MR. In one case without adequate vascular opacification on CT, MR was superior in differentiating a mass from pulmonary artery. It is concluded that, with current technology without respiratory or cardiac gating, MR offers little improvement in diagnosis over contrast-enhanced CT. Furthermore, it does not appear possible to predict tissue type based on T1 and T2 measurements because of a wide overlap in these values.

Carcinoma, Bronchogenic↗
PubMed1983

Antimicrobial properties of some plant extracts against bacteria.

Plant extracts obtained from Feronia limonia (leaves) Xanthium strumarium (flowering twigs) and Glossocardia bosvellia (leaves) were tested for their antimicrobial properties against certain bacterial species. Feronia leaf extract was ineffective on Bacillus pumilus and X. campestris, Vibrio cholerae was found quite sensitive to this extract. The extract of X. strumarium showed an abnormality with V. cholerae, where the inhibition exceeded the control with established antibiotics. Similarly, G. bosvellia caused maximum inhibition in Bacillus mycoides.

Anti-Bacterial Agents↗
PubMed1983

Effect of mechanical load in wound healing.

This study was designed to investigate the effect of sequentially increasing mechanical load on healing incisions. Full-thickness incisions were made on the back of a young domestic pig. During the period of fibroplasia, one of the incisions was mechanically loaded with a subcutaneous tissue expander. Mechanical and histological evaluations of mechanically loaded and control incision areas indicated that the mechanical stress encouraged healing and remodeling of dermal tissue.

Animals↗
PubMed1983

The effect of serial dilution of betamethasone-17-valerate on blanching potential and chemical stability.

The effect of serial dilution of betamethasone-17-valerate (Betnovate ointment) in Unguentum Merck was investigated using a single application blanching assay in 10 subjects and high performance liquid chromatography. There was no statistically significant difference between any of the diluted formulations with regard to blanching potential. Chemical stability was maintained following a 1:32 dilution for 2 months and 1:4 dilution for 5 months at least, after storage at room temperature.

Betamethasone↗
PubMed1982

Pituitary responses to a neuroactive tripeptide (TRH) in Friedreich's ataxia families.

Oral glucose tolerance, thyroid function tests, as well as thyrotropin, prolactin and growth hormone release after administration of thyrotropin releasing hormone, were evaluated in patients with Friedreich's ataxia and unaffected family members. Impaired glucose tolerance was found in the majority of family members, affected or not. Thyroid hormone levels and PRL and TSH responses to TRH, were similar in all and normal. However, GH responses to TRH were abnormal in half of the patients, but in none of the unaffected family members. Paradoxical responses to neuropeptides may characterize some Friedreich's ataxia patients, and may predict the possibility of therapeutic maneuvers with such peptides in these patients.

Adolescent↗
PubMed1982

Tumor growth inhibition in patients with prostatic carcinoma treated with luteinizing hormone-releasing hormone agonists.

Ten patients with prostatic carcinoma--six with stage C and four with stage D disease--were treated for 6 weeks to 12 months with agonistic analogues of luteinizing hormone-releasing hormone (LH-RH). [D-Trp6]LH-RH was given subcutaneously once daily at a dose of 100 microgram and [D-Ser(But)6]des-GlyNH2(10)-LH-RH ethylamide (HOE 766) was given subcutaneously (50 microgram once daily) or intranasally (500 microgram twice daily). In all patients, mean plasma testosterone levels showed a 75% suppression by the third week of treatment and remained low thereafter. This was followed by a decrease or normalization of plasma acid phosphatase levels by the second month of treatment and a 47% decrease in serum alkaline phosphatase by the 10th week of treatment in all but one patient. In patients with stage C disease presenting with prostatism or urinary outflow obstruction, there was a noticeable clinical improvement. In two such patients, a decrease in the size of the prostate was confirmed by ultrasonography. In patients with stage D disease manifested by diffuse bone metastases, there was relief of bone pain, and in one patient treated for greater than 12 months the improvement was documented by radioisotope bone imaging. It is concluded that superactive agonistic LH-RH analogues hold promise as therapeutic agents in patients with androgen-sensitive prostatic adenocarcinoma. Furthermore, the analogous of LH-RH may be used to assess the responsiveness of patients to surgical castration. Long-term administration of LH-RH analogues could become an alternative to surgical castration and estrogen therapy for the treatment of hormone-dependent prostatic carcinoma.

Buserelin↗
PubMed1982

The stability and blanching efficacy of betamethasone-17-valerate in emulsifying ointment.

The bio-availability of betamethasone-17-valerate (Betnovate ointment) in emulsifying ointment (1 in 4 dilution) was investigated in ten subjects using a single-application vasoconstrictor assay; the blanching induced was measured using a skin reflectance spectrophotometer. The vasoconstrictor activity of the diluted preparations decreased with age. There was no significant difference between the vasoconstrictor activity of freshly made Betnovate 1 in 4 in emulsifying ointment and undiluted Betnovate ointment, and between 3-4 week old diluted Betnovate and emulsifying ointment base. Blanching induced by freshly prepared 4, 8 and 16-fold dilutions was not significantly different but a large reduction in blanching occurred on diluting 32-fold with emulsifying ointment. The degradation of betamethasone -17-valerate in emulsifying ointment was quantified by high performance liquid chromatography. More than 60% of the betamethasone -17-valerate underwent degradation within 6 h. There was a simultaneous increase in the concentration of betamethasone-21-valerate which peaked within 2 days and was followed by a slow degradation (half-life 8 days) to betamethasone free alcohol.

Betamethasone↗
PubMed1982

Pseudocyesis: pituitary function before and after resolution of symptoms.

Pseudocyesis was clinically established in a 39-year-old woman. Pituitary function was assessed with the use of hypothalamic peptides and dopamine receptor agonists. Basal serum concentrations of anterior pituitary and ovarian hormones were normal. An exaggerated rise in luteinizing hormone (LH) and prolactin levels was seen following the administration of luteinizing hormone-release hormone and thyrotropin-releasing hormone (TRH), respectively. A paradoxic rise in growth hormone (GH) levels followed TRH administration, whereas the response to dopamine receptor agonists was normal. Pituitary hormone secretion after deflation remained similar to that before deflation, although a normal response of GH to apomorphine was reestablished. These data indicate that the amenorrhea of pseudocyesis is associated with normoprolactinemia and a readily releasable pituitary LH pool, which suggests a suprahypophyseal etiology of the amenorrhea. The abnormalities in GH secretion may also support this contention.

Adult↗
PubMed1981

His-Purkinje responses and refractory periods during atrial extrastimulation in children with heart defects.

During atrial extrastimulation, split His potentials, prolonged His-to-ventricular (H2V2) intervals and block distal to the His bundle deflection were observed in both preoperative and postoperative children with heart defects. His-Purkinje responses and refractoriness were identified in 31 of 78 (40%) pediatric patients (20 of 51 preoperative and 11 of 27 postoperative) during atrial extrastimulation coupled to sinus and/or paced cycle lengths. Split His potentials were found in 14 patients (eight preoperative and six postoperative) and His bundle relative refractory periods ranged from 250--490 msec. Prolonged H2V2 intervals were found in these and in an additional 16 patients (11 preoperative and five postoperative) and the relative refractory period of the His-Purkinje system ranged from 230--500 msec. Block distal to the His deflection occurred in seven patients (five preoperative and two postoperative) and the effective refractory period ranged from 230--510 msec. Split His potentials, long H2V2 intervals and block distal to the His bundle deflection produced by atrial extrastimulation were found in peroperative as well as postoperative children. These responses probably represent functional electrophysiologic characteristics of the pediatric cardiac conduction system.

Adolescent↗
PubMed1981

Suppression of androgen production by D-tryptophan-6-luteinizing hormone-releasing hormone in man.

Four male transsexual subjects were given a superactive luteinizing hormone-releasing hormone (LHRH) analogue, D-tryptophan-6-LHRH at daily doses of 100 micrograms for 3--6 mo. A decrease in beard growth, acne, and erectile potency was noted; the latter was documented objectively with the recordings of nocturnal penile tumescence episodes. Plasma testosterone and dihydrotestosterone levels fell to castrate values; basal prolactin and luteinizing hormone levels showed a small decline, whereas the acutely releasable luteinizing hormone was significantly suppressed. A rise of plasma testosterone from castrate to normal levels was demonstrable with the use of human chorionic gonadotropin. Discontinuation of treatment led to a normalization of erectile potency and plasma testosterone. The suppression of Leydig cell function by D-tryptophan-6-LHRH might have wide application in reproductive biology and in endocrine-dependent neoplasia (where it could replace surgical castration).

Adult↗
PubMed1980

Friedreich's ataxia and oral glucose tolerance: I. The effect of ingested glucose on serum glucose and insulin values in homozygotes, obligate heterozygotes and potential carriers of the Friedreich's ataxia gene.

Glucose tolerance and insulin release were evaluated in 16 families with Friedrich's ataxia. Impaired glucose tolerance differed in incidence according to the method of evaluation, but was increased in number in parents and siblings of Friedreich's cases. Insulin output was not quantitatively different from normal, although the insulin peak was often delayed. This finding, in association with impaired glucose tolerance, suggest a defect in glucose entry into cells.

Adolescent↗