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Biomedical subjects

R Tripathi

Publications and source records attributed to R Tripathi.

At least 19 recordsLinked to original sources
PubMed1999

Use of a fluorescence plate reader for measuring kinetic parameters with inner filter effect correction.

A general method is presented here for the determination of the Km, kcat, and kcat/Km of fluorescence resonance energy transfer (FRET) substrates using a fluorescence plate reader. A simple empirical method for correcting for the inner filter effect is shown to enable accurate and undistorted measurements of these very important kinetic parameters. Inner filter effect corrected rates of hydrolysis of a FRET peptide substrate by hepatitis C virus (HCV) NS3 protease at various substrate concentrations enabled measurement of a Km value of 4.4 +/- 0.3 microM and kcat/Km value of 96,500 +/- 5800 M-1 s-1. These values are very close to the HPLC-determined Km value of 4.6 +/- 0.7 microM and kcat/Km value of 92,600 +/- 14,000 M-1 s-1. We demonstrate that the inner filter effect correction of microtiter plate reader velocities enables rapid measurement of Ki and Ki' values and kinetic inhibition mechanisms for HCV NS3 protease inhibitors.

Filtration↗
PubMed1998

[Effect of a positive family history on the prognosis in patient with Bechterew disease].

The objective of the present study was to evaluate whether the patients with a family history of ankylosing spondylitis might have a milder course of the disease than patients with a negative family history. We investigated a group of 197 patients with ankylosing spondylitis who had been suffering from symptoms of the disease for > or = 20 years. After exclusion of the patients with a history, or current evidence of colitis or urethritis, the remaining 148 patients with ankylosing spondylitis (none with psoriasis) were divided into 2 groups on the basis of a positive (25 patients) or a negative (123 patients) family history of ankylosing spondylitis. The variables of mobility were compared. Furthermore, the present height was compared with the former (maximum) height. All variables measured in the present study showed slightly better results in the patients with a positive family history, but the differences were not significant. The decrease of height was slightly larger in patients with a positive family history. Evidently, a positive family history does not appear to give a reliable prediction of the long-term prognosis in Austrian and German patients with ankylosing spondylitis.

Adult↗
PubMed1998

Duplication of insertion element IS50 associated with Tn5 transposition in Azospirillum brasilense.

The characterization of a DNA fragment with a Tn5 insertion in a regulatory nif gene of Azospirillum brasilense is reported. Restriction endonuclease mapping, Southern hybridization with a Tn5 probe, and nucleotide sequencing revealed that IS50 had duplicated in Tn5. The duplication of an IS50 element suggests the occurrence of a replicative mechanism of transposition. A strategy, based on the bacterial ability of homologous recombination that was used to precisely eliminate Tn5 along with the duplicated IS50 element, is presented.

Azospirillum brasilense↗
PubMed1996

Sodium beta-artelinate--a new potential gametocytocide.

The water-soluble artemisinin analogue sodium beta-artelinate, a fast-acting blood schizontocide, was evaluated for gametocytocidal action against simian malaria Plasmodium cynomolgi B, and a single dose of the compound has been found to be an effective gametocytocide by both oral and intravenous routes. The compound was able to sterilize the circulating gametocytes in rhesus monkey, resulting in loss of mosquito infectivity and oocyst development in the Anopheles stephensi. However, no sporontocidal action has been observed with this compound.

Administration, Oral↗
PubMed1996

Gametocytocidal activity of alpha/beta arteether by the oral route of administration.

Arteether (alpha/beta) (a mixture of alpha and beta enantioners) has been reported to possess gametocytocidal activity against Plasmodium cynomolgi B when the drug is given by the intramuscular route, but it would be preferable to use oral route therapy for gametocyte carriers. This is a report of a study of the gametocytocidal action of arteether administered by the oral route. The results indicate high levels of activity at 10 mg/kg in a single dose or in two divided doses when given orally.

Administration, Oral↗
PubMed1995

Effectiveness of apraclonidine and acetazolamide in preventing postoperative intraocular pressure spikes after extracapsular cataract extraction.

We studied the effectiveness of two prophylactic agents in controlling early postoperative intraocular pressure (IOP) increases after cataract surgery. Fifty-four nonglaucomatous patients received either topical 1% apraclonidine, one drop before and after surgery, or sustained-release acetazolamide, 500 mg, or no medication at the completion of planned extracapsular cataract extraction (ECCE). Mean baseline IOPs were similar among patients randomized to the apraclonidine, acetazolamide, and control groups: 15.29 mm Hg, 15.33 mm Hg, and 14.26 mm Hg, respectively. At 3 hours postoperatively, IOPs were significantly lower in the apraclonidine group (11.13 mm Hg, P = .035), nonsignificantly lower in the acetazolamide group (13.3 mm Hg, P = .17), and significantly increased in the control group (21.32 mm Hg, P = .003). One eye in the apraclonidine group and six in the control group had IOPs greater than 30 mm Hg. At 24 hours, the only statistically significant difference was in the control group, whose mean IOPs remained elevated (21.83 mm Hg, P = .0008). One eye in the apraclonidine group, two in the acetazolamide group, and five in the control group had IOPs greater than 30 mm Hg. We found a significant early IOP reduction with apraclonidine given topically preoperatively and at the completion of planned ECCE.

Acetazolamide↗
PubMed1992

MR observations on the effects of praziquantel in neurocysticercosis.

Eight patients with neurocysticercosis treated with praziquantel (PZQ) were studied with serial MR imaging to demonstrate the early effects of the drug in brain lesions. Increase in cyst size and appearance of pericystic edema were observed as early as 24 hr, followed by gradual degeneration of the scolex and cyst contents. Cysts showed varied degree of response to the drug and in their rate of disappearance. MRI was found to be a sensitive technique to objectively document early changes in the parasite and patterns of response to the cysticidal drug in brain cysticercosis.

Adult↗
PubMed1991

Comparison of antimalarial efficacy of alpha, beta, and alpha/beta arteether against Plasmodium cynomolgi B infection in monkeys.

The blood schizontocidal activity of alpha and beta arteether has been compared with that of alpha/beta arteether (a 30:70 mixture of alpha and beta isomers), which is a fast-acting blood schizontocide undergoing phase I clinical trials at the Central Drug Research Institute. Both beta and alpha/beta arteether have comparable activity and are curative at a dose of 5 mg/kg for 3 days against blood-induced Plasmodium cynomolgi B infection in the rhesus monkey; alpha arteether alone is slightly less active, with a 50% cure rate at the above dose.

Animals↗
PubMed1990

Gametocytocidal activity of the antimalarial alpha/beta arteether against Plasmodium cynomolgi B.

A new sesquiterpene lactone alpha/beta arteether (a 30:70 mixture of enantiomers), which possesses very high blood schizontocidal activity, has been evaluated for gametocytocidal/sporontocidal action against Plasmodium cynomolgi B infection in the rhesus monkey. This paper reports gametocytocidal action of this new antimalarial drug at 2.5-5 mg/kg (single im dose) against P. cynomologi B as shown by the complete absence of mosquito infectivity. No sporontocidal action was demonstrable in the vector at a dose of up to 20-50 mg/kg im.

Animals↗
PubMed1975

Perivascular and intervascular reticular fibers of the retina.

We demonstrated the existence in the retina of an argyrophilic perivascular membrane comparable in all respects to that which exists throughout the vascular system. We compared our findings by light microscopy with those previously reported. We identified, by electron microscopy, the normal general location of the network between the basal laminae of the glial and vessel cells and demonstrated its selective staining with silver methenamine. These perivascular fibers, intercapillary strands, and bridges develop in relation to the process of retinal vascularization and the potential for forming these fibers is reactivated in senility and disease, as in diabetes. We summarized the evidence by concluding that these fibers are most likely composed of reticulin; it appears provable that in the past there may have been some confusion with neural fibers.

Age Factors↗