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Biomedical subjects

P Bhargava

Publications and source records attributed to P Bhargava.

At least 37 records · Page 2Linked to original sources

Docetaxel and gemcitabine combinations in non-small cell lung cancer.

Docetaxel and gemcitabine have been shown to be active as single agents in a variety of solid tumors. These two agents have been studied in combination with several different treatment schedules. Two phase I studies used a novel 2-week administration schedule that involved a 1-hour infusion of 35 mg/m2 to 65 mg/m2 docetaxel and gemcitabine administered as either a 30-minute infusion (2,000 to 4,000 mg/m2) or a 10 mg/m2/min infusion (1,000 to 1,200 mg/m2 total dose). Another novel phase I study evaluated the effect of drug sequence on toxicities. Patients received 30 to 40 mg/m2 docetaxel and 800 to 1,250 mg/m2 gemcitabine on days 1 and 8 every 21 days. Two phase I studies of a monthly docetaxel regimen have been conducted. Patients received 800 mg/m2 gemcitabine on days 1, 8, and 15 and 100 mg/m2 docetaxel on day 1 of a 28-day cycle. Finally, in a phase II study, patients received 900 mg/m2 gemcitabine on days 1 and 8 and 100 mg/m2 docetaxel on day 8, with granulocyte colony-stimulating factor administered on days 9 through 15. In these studies, antitumor responses were observed in lung cancer as well as a number of other histologies. Neutropenia was the most frequent dose-limiting toxicity and no difference in clinical toxicity was observed with either sequence of administration. The emerging evidence suggests, therefore, that the combination of gemcitabine and docetaxel is active in a variety of solid tumors and is well tolerated.

Antineoplastic Combined Chemotherapy Protocols↗

Jaipur block in postherpetic neuralgia.

BACKGROUND: Postherpetic neuralgia, a common sequele to herpes zoster infection, is a chronic debilitating problem. The available therapeutic modalities are usually ineffective. METHODS: A total of 3960 patients (1326 women and 2634 men; age group, 21-84 years), with postherpetic neuralgia as the presenting complaint and with pain lasting from 2 months to 5 years, were treated with Jaipur block, consisting of local subcutaneous infiltration of 2% xylocaine, 0.5% bupivacaine, and 4 mg/mL dexamethasone solution. Patients were followed up at six-weekly intervals with subsequent injections given in non-responders. RESULTS: Twenty-eight per cent of patients obtained complete relief from pain after a single injection, another 57% after a second injection, and 11% after a third injection; 4% of patients did not respond to treatment. The non-responders were either old (over 60 years) or had pain lasting for more than 2 years. The response to therapy was similar in both sexes. There were 31 left-handed patients in this study. Pain was less severe in left-handed patients and they obtained complete relief after a single injection. Side-effects including giddiness and sweating were seen, occasionally, in a few patients. CONCLUSIONS: Ninety six per cent of patients obtained complete relief after the block with a follow-up of up to 19 years.

Adult↗

Nucleosome mobility and the maintenance of nucleosome positioning.

To study nucleosome mobility and positioning, the R3 lac repressor was used with an adenosine triphosphate (ATP)-dependent chromatin assembly system to establish the positioning of five nucleosomes, with one nucleosome located between two R3 lac operators. When R3 protein was dissociated from DNA with isopropyl beta-D-thiogalactopyranoside, the R3-induced nucleosome positions remained unchanged for at least 60 minutes in the absence of ATP but rearranged within 15 minutes in the presence of ATP. These results suggest that nucleosomes are dynamic and mobile rather than static and that a DNA binding factor is continuously required for the maintenance of nucleosome positioning.

Adenosine Triphosphate↗

Tuberculoma of the mastoid.

Tuberculoma is a rare but known complication of tuberculosis. It rarely occurs in the mastoid bone. When it occurs in the middle ear cleft, it can lead to intracranial complications if there is a delay in the diagnosis and management. A rare case of tuberculosis of the middle ear cleft which presented as tuberculoma of the mastoid bone with infranuclear facial palsy is described. The tuberculoma was removed and a canal wall down tympanomastoidectomy was performed. Post-operatively the patient was kept on antituberculous therapy. The various problems encountered in the diagnosis and management of this case are discussed.

Child↗

Time-resolved emission spectroscopy as a tool to follow nucleic acid-protein interaction.

Fluorescence spectroscopy is undoubtedly a useful tool to study the structural and functional aspects of nucleic acids-protein interactions as well as the catalytic functions of particular residues of multi-subunit enzyme complexes. The dynamic interaction of nucleic acids and proteins occurring at nanosecond time scale can now be monitored by making life-time measurements or by time-resolved emission spectroscopy. These measurements are made by exploiting the intrinsic fluorescent residues in proteins i.e. W or by the use of extrinsic fluorophores which are tagged on to particular residues and that are sensitive to the microenvironment changes. In this study we describe the use of time resolved emission spectroscopy to (a) analyse the transient binding between sigma 70 and DNA by monitoring the quenching of W residues and (b) monitor the various states which nucleosomes of active, inducible or inactive chromatin may adopt in vivo.

Animals↗

Dynamics of interaction of RNA polymerase II with nucleosomes. I. Effect of salts.

Mononucleosomes were labeled with the sulfhydryl-specific fluorescence probe 1,5-IAEDANS (5-(2-((iodoacetyl)amino)ethyl)amino-naphthalene-1-sulfonic acid) by attaching the dye to the single cysteine of H3 through a covalent linkage. The enzyme RNA polymerase II (pol II) utilized the native and the reconstituted fluorescent nucleosomes as templates with greatest efficiency when 0.2 M potassium acetate (AcOK) was used as the supporting salt; 0.2 M NaCl was found to be very much inhibitory. Measurement of polarity of the microenvironment of the dye at its binding site in the nucleosome showed the conformation to be more open in the presence of AcOK, compared to that in 0.1 or 0.2 M NaCl. The binding of pol II to the nucleosome resulted in a relatively more compact structure when measured in terms of the polarity of the microenvironment of the dye in various salt-dependent conformations of the nucleosomes. Time-resolved fluorescence spectroscopy showed that the probe molecule at its binding site undergoes certain excited-state processes, and the presence/absence or rate of these excited-state processes depends on the conformation of nucleosomes, which in turn depends on the type and concentration of the ion present in the medium. Time-resolved emission spectra showed that binding of nucleosomes by pol II established some new contacts that resulted in inaccessibility of the dye to the bulk solvent, reflecting a more hydrophobic environment for the dye in the steady-state spectra. Thus, binding or transcription of nucleosomes by pol II did not break open their structure. Rather, some transient internal adjustments within the histone octamer may take place to accommodate the bulky pol II molecule.

Acetates↗

Dynamics of interaction of RNA polymerase II with nucleosomes. II. During read-through and elongation.

The sulfhydryl-specific fluorescence probe 1,5-IAEDANS (5-(2-((iodoacetyl)amino)ethyl)amino-naphthalene-1-sulfonic acid) was attached to the single cysteine of H3, and reconstituted fluorescent mononucleosomes were used as the template for in vitro transcription by the yeast RNA polymerase II (pol II). DNase I digestion analysis revealed that transcription of nucleosomes by pol II resulted in an overall loosening of the structure. Monitoring the transcription event by steady-state fluorescence analysis showed that nucleosomes only partially open during transcription. This opening is transient in nature, and nucleosomes close back as soon as the pol II falls off the template. Thus, using the technique of fluorescence spectroscopy, partial opening of nucleosome structure could be differentiated from complete dissociation into free DNA and histone octamer, a distinction that may not be possible by techniques like gel electrophoresis. Time-resolved fluorescence emission spectroscopy suggested that during read-through of the template by the pol II, histone octamers do not fall off the DNA. Only minor conformational changes within the histone octamer take place to accommodate the transcribing polymerase.

Animals↗