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Biomedical subjects

S K Sharma

Publications and source records attributed to S K Sharma.

At least 379 records · Page 21Linked to original sources
PubMed1991

A recombinant ribonuclease H domain of HIV-1 reverse transcriptase that is enzymatically active.

We report here a human immunodeficiency virus type 1 (HIV-1) recombinant ribonuclease H (RNase H) domain engineered to contain an N-terminal tag for its isolation by affinity chromatography. The purified protein is active in hydrolyzing RNA-DNA hybrids in two separate in vitro assay systems. In light of recent reports of similar HIV-1 RNase H domains which were enzymatically inactive (Becerra, S. P., Clore, G. M., Gronenborn, A. M., Karlstrom, A. R., Stahl, S. J., Wilson, S.M., and Wingfield, P.T. (1990) FEBS Lett. 270, 76-80; Hostomsky, Z., Hostomska, Z., Hudson, G. O., Moomaw, E. W., and Nodes, B. R. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 1148-1152), our results suggest that a stretch of 20-30 residues immediately upstream of the polymerase-RNase H junction (residues 440-441 of HIV-1 reverse transcriptase) may be required for productive binding and alignment of the hybrid RNA-DNA substrate. The active HIV-1 RNase H domain is suitable for structural analysis, thereby providing a unique active molecule to better understand the structural basis for the functional organization of RNase associated with the HIV-1 reverse transcriptase.

Amino Acid Sequence↗
PubMed1991

Could angiotensin I be produced from a renin substrate by the HIV-1 protease?

The standard angiotensin I (Ang I) radioimmunoassay for renin activity determination is a useful clinical tool for the diagnosis of high renin levels in certain cases of hypertension. It depends upon the liberation of Ang I from human plasma angiotensinogen. We considered whether a commercially available synthetic tetradecapeptide (TDP), Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Leu-Val-Tyr-Ser, would produce authentic Ang I upon incubation with protease from human immunodeficiency virus type 1 (HIV-1). This peptide is also known to be cleaved by renin at the Leu-Leu bond to yield the decapeptide Ang I. When the TDP is incubated with the HIV-1 protease, the peptide is readily hydrolyzed. Product formation is linear with respect to time and enzyme concentration. HPLC analysis of reaction products showed two new peaks, as one would expect from the cleavage of a TDP into a decapeptide and a tetrapeptide. Amino acid analysis of HPLC-purified peaks confirmed that the HIV-1 protease cleaves TDP at the Leu10-Leu11 site to produce the desired decapeptide, Ang I. Production of Ang I by the HIV-1 protease, like human renin, is inhibited in the presence of a protease inhibitor. Implications of the discovery of an HIV-1 protease substrate that produces authentic Ang I are discussed in light of a screening assay for soluble HIV-1 protease inhibitors.

Amino Acid Sequence↗
PubMed1991

Domoic acid induced seizure activity in rats.

Domoic acid, in increasing doses (10-300 pmol), was microinjected into the hippocampal CA3 region of rats. All rats consistently exhibited generalized bilateral electrical seizure discharge activity at 100 pmol of domoic acid. Seizure latency varied inversely with the dose of domoic acid in the range tested. Local hippocampal administration of gamma-aminobutyric acid (GABA) resulted in neuronal recovery from domoic acid-induced seizures. The seizure activity of domoic acid might be the result of decreased GABAergic inhibition.

Action Potentials↗
PubMed1991

Protein growth factor(s) from C6 glioma cells that promote the growth of murine hybridomas.

C6 glioma cell conditioned medium (C6CM) has been used as a growth supplement for murine hybridomas. At 10% C6CM has been found to increase cell proliferation by 3-4-fold. This effect is observed in the presence of saturating concentration of FCS. Clonal growth is also enhanced 6.7-fold. No growth promoting effect is seen on murine myelomas or spleen cells. The factor(s) appear to be protein in nature.

Animals↗
PubMed1991

Iodine-125 interstitial implants as salvage therapy for recurrent gynecologic malignancies.

Twenty-one patients with the diagnosis of recurrent gynecologic pelvic malignancy from various primary sites were treated with iodine-125 (I-125) interstitial implants. Eighteen of these patients had been treated with a combination of surgery and radiation therapy for their primary malignancies and 90% had responded. Seventy-five percent had complete local responses. The overall survival time, volume-response relationship, and complications are discussed and the radioresponse of various histologic types is presented.

Brachytherapy↗
PubMed1991

Fine-needle aspiration cytology in azoospermic males.

Bilateral testicular fine-needle aspiration cytology (FNAC) was performed in 100 males, including 10 controls with normal fertility and 90 infertile azoospermic males. The various seminiferous tubular cells were easily identified in smears. It was possible to give a cytological diagnosis in histologic terms by analysis of the combinations of various cell types. The cytohistologic correlation in 25 cases was nearly 100%. FNAC is particularly useful in cases of obstructive azoospermia, where mature spermatozoa are seen in smears.

Biopsy, Needle↗
PubMed1991

Ablation of human choriocarcinoma xenografts in nude mice by antibody-directed enzyme prodrug therapy (ADEPT) with three novel compounds.

Three novel prodrugs have been designed for use as anticancer agents. Each is a bifunctional alkylating agent which has been protected to form a relatively inactive prodrug. They are designed to be activated to their corresponding alkylating agents at a tumour site by prior administration of an antitumour antibody conjugated to the bacterial enzyme carboxypeptidase G2 (CPG2) in a two-phase system called antibody-directed enzyme prodrug therapy (ADEPT). The Km and Vmax values for three different antibody-CPG2 conjugates were determined in relation to each prodrug. The Km values ranged from 4.5-12 mumol/l and the Vmax from 0.5-1.6 mumol/U/min. Athymic Nu/Nu mice with palpable transplanted human choriocarcinoma xenografts, which are resistant to conventional chemotherapy, were treated with anti-human chorionic gonadotropin antibodies conjugated to CPG2. This was followed by each of the three novel prodrugs. Significant increase in survival was obtained in three of the regimens tested using only one course of treatment. This demonstrates the potential of a tumour-localised bacterial enzyme to activate protected alkylating agents in order to eradicate an established human xenograft.

Alkylating Agents↗
PubMed1991

Production of an antibody to arterial fatty acid-binding protein (FABP) using a synthetic peptide as the antigen.

1. A procedure is described for the preparation of an antibody to arterial FABP using a synthetic peptide as an antigen. In order to locate a highly conserved region located on the outer surface of FABP, computer analysis of primary and secondary structures of several proteins from the FABP family was undertaken and a 24 amino acid sequence beginning at the fifth position from the N-terminus of rat heart FABP was chosen. 2. The synthetic peptide consisted of eight replications of the 24 amino acid sequence individually attached to the alpha and epsilon amino groups of each terminal lysine on an octalysine branched peptide. 3. Antibody to the synthetic antigen was raised in New Zealand rabbits. Western analysis was conducted and detection was accomplished by using goat-anti-rabbit second antibody conjugated to alkaline phosphatase. 4. The antibody produced from the previously described peptide, recognized purified rat heart FABP and demonstrated a high positive correlation (r = 0.96) when known concentrations of purified hFABP were plotted against densitometric measurement of the bands. 5. Additionally, the antibody recognized FABP from the 104,000 g supernates of rat atrial and arterial tissue fractionated by a Sephadex G-75 column. 6. Therefore, the antibody produced from this particular protocol employing a synthetic peptide can be utilized qualitatively and quantitatively in the analysis of the heart and arterial FABP content.

Amino Acid Sequence↗
PubMed1991

Percutaneous coronary excimer laser-assisted balloon angioplasty: initial clinical and quantitative angiographic results in 50 patients.

The initial clinical experience and quantitative angiographic results of percutaneous coronary excimer laser-assisted balloon angioplasty are described for 55 lesions in 50 patients. With use of a xenon chloride (308 nm) excimer laser generator and 1.5 to 1.75 mm catheters, excimer laser angioplasty was attempted at 135 ns pulse width, 25 to 40 Hz repetition rate, 2 to 5 s laser delivery time and 30 to 60 mJ/mm2 energy fluence. Laser success (greater than 20% reduction in absolute percent diameter stenosis) was achieved in 41 (75%) of 55 lesions, with 100% subsequent balloon angioplasty success (less than 50% residual stenosis). By quantitative digital caliper technique, the percent diameter stenosis (mean +/- SE) was reduced from 81 +/- 1% to 50 +/- 3% after excimer laser angioplasty (p less than 0.001) and to 20 +/- 1% after balloon angioplasty (p less than 0.001); minimal luminal diameter increased from 0.56 +/- 0.04 to 1.46 +/- 0.08 mm (p less than 0.001) and 2.03 +/- 0.07 mm (p less than 0.001), respectively. By videodensitometric techniques, the percent area stenosis decreased from 86 +/- 2% to 54 +/- 3% after excimer angioplasty (p less than 0.001) and to 26 +/- 3% after balloon angioplasty (p less than 0.001). There were no perforations, need for emergency bypass surgery or deaths. The overall incidence of abrupt closure (3.6%), dissection (1.8%), embolization (1.8%), filling defect (6%), myocardial infarction (5.5%), side branch occlusion (3.6%) or spasm (3.6%) was infrequent and more related to subsequent balloon angioplasty than to the laser procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Laser↗
PubMed1991

Picroliv protects against monocrotaline-induced hepatic damage in rats.

Monocrotaline, a pyrrolizidine alkaloid, caused changes in most of the biochemical parameters in rats 12 days after a single dose of 120 mg/kg. These included significantly increased activities of hepatic succinate dehydrogenase, acid ribonuclease, acid phosphatase, gammaglutamyl transpeptidase and 5'-nucleotidase and decreased in the activities of glucose-6-phosphatase and cytochrome P450. The levels of DNA, RNA and glycogen in liver and albumin and protein in serum decreased while serum bilirubin increased. The histopathological changes in liver were characterized by diffused hepatocyte alterations in the form of ballooning, granular cytoplasm, indistinct cell outlines, nuclear changes, focal necrosis, and vascular damage. When picroliv, a standardized iridoid glycoside fraction of Picrorhiza kurroa, was administered orally in a dose of 25 mg/kg simultaneously with monocrotaline, alterations in most of the biochemical parameters along with the histopathological changes in liver caused by monocrotaline were prevented.

Animals↗
PubMed1991

Picroliv affords protection against thioacetamide-induced hepatic damage in rats.

Thioacetamide (100 mg/kg), when administered to normal rats, caused a significant increase in the activities of 5'-nucleotidase and gamma-glutamyl transpeptidase and a decrease in the activities of glucose 6-phosphatase and succinate dehydrogenase enzymes in the liver. DNA, RNA, and proteins were increased while the cytochrome P450 in the microsomal fraction and the glycogen content in the liver were decreased significantly. Elevations in the activities of GOT, GPT, and alkaline phosphatase and bilirubin content in serum were also observed. Picroliv, a standardised glycoside fraction of Picrorhiza kurroa, in doses of 12.5 and 25 mg/kg prevented most of the biochemical changes induced by thioacetamide in liver and serum. The hepatoprotective activity of Picroliv was comparable with that of silymarin, a known hepatoprotective agent obtained from seeds of Silybum marianum.

Animals↗
PubMed1991

Incomplete penoscrotal transposition associated with hemivertebrae.

Penoscrotal transposition is a rare anomaly of external genitalia, often associated with a variety of defects usually related to the urinary and the gastrointestinal tracts and the vertebral column. We report such a patient with hemivertebrae at L4-5, who had no other urological anomaly. To our knowledge this anomaly as an isolated urological entity with hemivertebrae has not been reported before. A brief mention is made of the embryology, incidence and various surgical techniques of correction.

Abnormalities, Multiple↗
PubMed1991

Tear lysozyme levels in bacterial, fungal and viral corneal ulcers.

Low levels of tear lysozyme were observed in patients with infective corneal ulcers, when compared with controls. Lowest levels were seen in patients with bacterial corneal ulcers. The levels of tear lysozyme showed a corresponding decrease with the increase in Schirmer test values; meaning thereby, that in ocular conditions associated with increased rate of tear flow, the lysozyme content in tears tends to be low.

Adult↗
PubMed1991

Atrial septal defect presenting as recurrent primary amoebic lung abscess.

A middle-aged female with an atrial septal defect (secundum type) presented with a primary pulmonary amoebic abscess. She was successfully treated with antiamoebic therapy. One year later she presented with a similar lung abscess which again responded to antiamboebic treatment. Attention is drawn to the fact that a patient with a left to right shunt can present with a recurrent rare primary parasitic infection of the lung.

Amebicides↗
PubMed1991

Urethrorectal fistulas complicated by posterior urethral stricture: an appraisal of management by transpubic approach.

Seven cases of difficult urethrorectal fistulas complicated by posterior urethral stricture following accidental trauma were repaired successfully by a transpubic approach. This method makes urethroplasty of complex posterior urethral stricture, closure of urethrorectal fistulas and an omental interposition possible. This approach was considered after a review of all techniques described to treat the urethrorectal fistulas.

Accidents, Traffic↗
PubMed1991

Male urethral calculi.

Male urethral stone is a rare clinical entity in western parts of the world, but continues to be common in developing countries. We report 26 cases of male urethral calculi, treated over a 6-year period. The age of the patients ranged from 12 to 67 years. The calculi were encountered all along the urethra, but predominantly in the posterior urethral region. We found multiple stones in 6 cases and large giant calculi in 5. Presentation, etiology, treatment, and prevention of these calculi are discussed.

Adolescent↗