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P Mishra

Publications and source records attributed to P Mishra.

At least 19 recordsLinked to original sources
PubMed1995

Fourier-transform infrared spectroscopic investigation of protein stability in the lyophilized form.

Upon the removal of water, proteins undergo a major, reversible rearrangement of their secondary structure, as revealed by FTIR spectroscopy. We have found herein that for recombinant human albumin (rHA) the extent of this structural change does not depend significantly either on the composition of the aqueous solution prior to lyophilization (protein concentration, pH, and the presence of excipients such as dextran or NaCl) or on the mode of dehydration (lyophilization, spray drying, or rotary evaporation), even though these factors profoundly affect rHA's solid-state stability against moisture-induced aggregation. In all cases, the alpha-helix content of rHA drops from 58% in solution to 25-35% in the dehydrated state, the beta-sheet content rises from 0 to 10-20%, and unordered structures increase from 40% to 50-60%. We have also investigated another model protein, hen egg-white lysozyme, and confirmed that it too undergoes a significant alteration of the secondary structure upon lyophilization. The extent of this structural reorganization has been found to be insensitive to the pH of the aqueous solution prior to lyophilization from pH 1.9 to 5.1, even though the thermal transition temperature (Tm) in aqueous solution over this range varies by 30 degrees C.

Dextrans↗
PubMed1994

A novel method for labelling human immunoglobulin-G with 99Tcm suitable for inflammation scintigraphy.

An amount of 1.0 mg human immunoglobulin G (hIgG) treated with ascorbic acid at a molar ratio of 1:5000 for 16 h at 4-7 degrees C was mixed with 250 micrograms GHA and 5 micrograms stannous chloride dihydrate in normal saline. Radiolabelling of hIgG (> 98%) was achieved instantly when mixed with 99Tcm-pertechnetate. The preparation was sufficiently stable in serum at 37 degrees C. The competitive binding assay and gel electrophoresis of the native and reduced hIgG did not show any measurable loss in immunoreactivity and intactness due to its reduction. There was no significant decrease in the radiolabel of labelled hIgG when incubated with diethylenetriaminepentaacetate (DTPA) (50-fold), in contrast with about 9% loss of the radiolabel by treating it with a similar concentration of cysteine. Blood clearance of labelled hIgG in rabbits was biphasic with about 78 min and 8 h as T1/2 of the fast and slow phases. Biodistribution of the radiotracer in mice at 4 h showed its uptake by liver (10.2%), kidneys (5.39%), intestines (7.33%) and muscles (3.9%), which altered to 5.63, 3.20, 4.03 and 6.73%, respectively, at 24 h. The radiotracer was excreted through both renal and hepatobiliary routes. High accumulation of the radiolabelled hIgG in inflammatory lesions of the patients confirmed the clinical usefulness of the method developed.

Animals↗
PubMed1994

Differential increase in cytoplasmic pH at bud and germ tube formation in Candida albicans: studies of a nongerminative variant.

The changes in cytoplasmic pH (pHi) accompanying the morphological transition of Candida albicans were studied using a nongerminative variant. A transient cytoplasmic alkalinization at the time of evagination was observed in both the variant and its parent. Under zinc-deficient conditions the wild-type cells that formed buds at pH 4.5 and mycelia at pH 6.5 showed an increase in pHi of 0.58 and 0.12 pH units, respectively. Under similar conditions the pHi of the nongerminative variant that formed buds at both pH 4.5 and 6.5 increased by 0.66 and 0.40 pH units, respectively, suggesting that a greater magnitude of increase in pHi at the time of evagination is probably needed for bud formation. These results provide evidence for a correlation between intracellular alkalinization and time of cell differentiation in C. albicans.

Candida albicans↗
PubMed1992

Emerging role of lipids of Candida albicans, a pathogenic dimorphic yeast.

It is clear that C. albicans lipids have gained tremendous importance in recent years. In addition to being a barrier for entrance of various metabolites, it also provides the site of action for the synthesis of enzyme(s) involved in cell wall morphogenesis and antifungal action. While alterations in lipid composition during a yeast to mycelia transition have been observed, in most of the studies, lipid fluctuations reported could have been due to various environmental factors involved in the induction of morphogenesis [4,5]. A clear understanding of lipid biosynthesis and metabolic blocks due to antifungal action is likely to shed further light on selective interactions of antifungals. Despite the multifacet role of lipids in various functions of this pathogenic yeast, their exact involvement is poorly understood. The situation is little better with regard to ergosterol and its metabolism. Ergosterol is, indeed, important for anti-candidal activity and appears to be involved in the morphogenesis of C. albicans. The fluctuation in phospholipid composition have led to altered properties of plasma membrane namely, membrane fluidity, transport activities and drug sensitivity, which suggest that-a critical level of individual phospholipid is important for proper functioning of the plasma membrane. What the exact role is of individual phospholipid is far from clear. Many unanswered questions relating to the role of PI and sphingomyelin in signal transduction, involvement of phospholipases in the maintenance of phospholipid composition, and role of lipid transfer proteins in assembly and asymmetry of lipids are some aspects which merit further work.

Candida albicans↗
PubMed1992

Pharmacological screening of few new 2-(substituted acetyl) amino-5-alkyl-1,3,4-oxadiazoles.

Nine new 2-(substituted acetyl) amino-5-alkyl-1,3,4-oxadiazoles were synthesised and confirmed on the basis of IR and nitrogen analysis. These were screened for spasmolytic, anti-inflammatory and their effects on blood pressure after determining ALD50. Compounds GK-4 i.e. 2-(diethylaminoacetyl)- amino-5-methyl-1,3,4-oxadiazole and GK-8 i.e. 2-(din-propylamino acetyl)-amino-5-ethyl-1,3,4-oxadiazole were found to be spasmolytic. Compound GK-6 i.e. 2-(diethylaminoacetyl)-amino-5-n-propyl-1,3,4-oxadiazole was found to be a potent hypotensive agent with the effect lasting for more than two hours.

Animals↗
PubMed1991

Amino acid uptake as a function of differentiation in Candida albicans: studies of a non-germinative variant.

The transport of four amino acids (L-methionine, L-phenylalanine, L-lysine and L-alanine) was studied during pH-regulated dimorphism in Candida albicans and its stable, non-germinative variant. The permeases responsible for uptake responded differently to differentiation and the transport activities varied during the course of morphogenesis. An increase in uptake around the time of evagination was observed in all four amino acids in both the strains studied. The uptake rates of L-methionine and L-phenylalanine were greater in fully differentiated hyphae, while the rate of L-lysine was higher in fully differentiated buds. Uptake rates of L-alanine, however, did not show any morphotypic related variation. The possible implication of these transport activities in relation to differentiation is discussed.

Alanine↗
PubMed1991

Dimorphism-associated changes in plasma membrane H(+)-ATPase activity of Candida albicans.

In situ plasma membrane H(+)-ATPase activity was monitored during pH-regulated dimorphism of Candida albicans using permeabilized cells. ATPase activity was found to increase in both the bud and germ tube forming populations at 135 min which coincides with the time of evagination. Upon reaching the terminal phenotype the mycelial form exhibited higher H(+)-ATPase activity as compared to the yeast form. At the time of evagination H(+)-efflux exhibited an increase. K+ depletion resulted in attenuated ATPase activity and glucose induced H(+)-efflux. The results demonstrate that ATPase may play a regulatory role in dimorphism of C. albicans and K+ acts as a modulator.

Candida albicans↗
PubMed1990

99mTc-labelled trimethylmonoiodo-IDA: a new radiopharmaceutical for hepatobiliary imaging.

A new radiopharmaceutical, 99mTc-3-iodo-2,4,6-trimethylphenylcarbamoylmethyl iminodiacetic acid (99mTc-trimethylmonoiodo-IDA) was prepared and evaluated for hepatobiliary scintigraphy. The new agent has less plasma protein binding capacity and greater lipophilicity as compared to that of di-isopropyl-IDA. Hepatobiliary specificity, a short transit time and a high gall bladder-to-liver ratio of the new agent were evident from tissue distribution data in mice. Blood tmax and clearance t1/2 of the radiopharmaceutical were observed at 2 and 3.5 min respectively. The hepatic peak-time tmax (5 min) and release time t1/2 (12.75 min) and release t1/2 (25.00 min) suggest the suitability of this agent for hepatobiliary imaging. Results of hepatobiliary scintigraphy in rabbits have further confirmed the above view.

Animals↗
PubMed1989

99mTc(Cu)-mannitol complex: a new agent for dynamic renal function studies.

Mannitol has been labeled with 99mTc by using cuprous chloride as a reducing agent. Blood and kidney clearance of 99mTc(Cu)-mannitol was slightly faster than that of 99mTc(Sn)-DPTA in rat and maximum radioactivity ratio of kidneys to blood was 84.6 at 5 min. A comparative study of 99mTc(Cu)-mannitol, 99mTc(Sn)-DTPA was made in rabbits by taking serial images of kidneys and bladder with a gamma camera. Results show superiority of 99mTc(Cu)-mannitol over other agents for dynamic renal function studies.

Animals↗
PubMed1989

Relationship between fluidity and L-alanine transport in a fatty acid auxotroph of Saccharomyces cerevisiae.

The influence of the physical state of membrane on L-alanine uptake has been investigated in Saccharomyces cerevisiae KD115, an unsaturated fatty acid auxotrophic mutant. By monitoring the unsaturation index and steady state fluorescence polarization of 1,6 diphenyl hexatriene (DPH), it was observed that at mid log phase the membrane fluidity increased with an increase in the number of double bonds of supplemented fatty acid. Arrhenius plots of the velocities for L-alanine transport in cells grown on palmitoleate, oleate, linoleate and linolenate were biphasic and dependent on supplemented unsaturated fatty acid. Results illustrate a correlation between membrane fluidity and shift in transition points. Further, results confirm the role of fatty acyl milieu in regulation of transport activity of S. cerevisiae.

Alanine↗
PubMed1988

Dimorphism-associated changes in intracellular pH of Candida albicans.

Intracellular pH (pHi) was monitored during pH-regulated dimorphism of Candida albicans using two different methods: (1) by steady-state distribution of propionic acid and (2) by use of polyene antibiotic, nystatin. There was no significant change in pHi during the first 120 min in either bud- or germ tube-forming populations. However, there was a rapid increase around 135 min which also coincided with the time of evagination. The magnitude of increase in pHi was different in the two populations; being 0.44 and 0.14 pH units in bud- and germ tube-forming populations, respectively. In the two diverging populations, the transient increase in pHi was followed by a rapid drop. The sharp rise in pHi of the population destined to form buds was sensitive to orthovanadate and to the depletion of K+ from the medium while this was not the case with germ tube-forming cells. The results suggest that pHi may play an important role in the phenotypic divergence of C. albicans.

Candida albicans↗
PubMed1988

A novel method for labelling of leukocytes with technetium-99m and its comparative evaluation for abscess scintigraphy.

A new method, based on the pretreatment of leukocytes with glucoheptonate prior to treating with reduced 99mTc, has been developed for the preparation of 99mTc labelled leukocytes. The leukocytes labelled with a 99mTc concentration (5.59%/g tissue) similar to that of 111In-leukocytes (6.27%/g tissue), in the experimental abscess were in rat thigh. Concentration of 99mTc-leukocytes in blood at 24 h was only about 35% as compared to that of 111In-leukocytes. Biodistribution in the rat organs was similar in both cases, except in the liver where 99mTc-leukocytes exhibited about 4-fold greater concentration. Images of experimental abscess in rat by using 99mTc-leukocytes were comparable to those obtained with 111In-leukocytes.

Abscess↗