Biomedical subjects
Publications and source records attributed to M K Jain.
A 6 1/2 year old female child with congenital lipodystrophy is being presented. The noteworthy feature in this case was the defective leucocyte function and its association with tuberculous pericardial effusion.
Eighty nine children were studied for retinol (vitamin A) estimation and its transport protein--retinol-Binding Protein (RBP). Serum levels of retinol, RBP and serum protein and albumin were found to be low in children with signs of vit. A deficiency irrespective of their nutritional status. Serum levels of retinol and RBP were risen significantly almost double, after the oral and parenteral administration of vitamin A. PEM interferes with hepatic synthesis of RBP and the release of RBP from the liver depends on vitamin A. Vitamin A is a limiting factor, the presence of which is required for the release of apo-RBP from the liver.
The purpose of the present study was to re-evaluate the effects of cocaine on cardiac responses elicited by sympathetic nerve stimulation. Cats anesthetized with pentobarbital and subjected to spinal cord transection were used. Control heart rate increases were obtained to submaximal stimulation of postganglionic accelerator nerves, before and after i.v. bolus doses of cocaine ranging from 0.0625 to 2.0 mg/kg. Maximal potentiation of heart rate increases elicited by nerve stimulation were observed with 0.25 mg/kg. In precocaine controls, stimulation increased sinus rate by 31 +/- beats/min; 30 sec to 1 min after cocaine (0.25 mg/kg), stimulation increased sinus rate by 55 +/- beats/min. Maximal potentiation (80 +/- 10%) was observed at 30 sec to 1 min after cocaine administration, and was usually over by 45 to 60 min later. Cocaine was repeated twice (0.25 mg/kg i.v.) at hourly intervals and the magnitude of potentiation was only 19 +/- 6 and 24 +/- 4%, respectively, indicating that tachyphylaxis had developed toward cocaine's potentiating effect. Dose-response studies indicated that as little as 0.0625 mg/kg of cocaine can potentiate heart rate increases elicited by sympathetic nerve stimulation. Doubling the dose to 0.125 mg/kg, and again to 0.25 mg/kg, resulted in a linear dose-related increase in the magnitude of potentiation. However, doubling the dose again to 0.5 mg/kg and increasing this dose by 4-fold to 2 mg/kg did not result in additional potentiation. Indeed, there was a significant drop-off in the magnitude of potentiation to nerve stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Biological evaluation of methyl 5(6)-(4-methylpiperidin-1-yl) carbonylbenzimidazole-2-carbamate against Ancylostoma ceylanicum, Nippostrongylus brasiliensis, Syphacia obvelata, Hymenolepis nana, H. diminuta and Cysticercus fasciolaris in experimental animals is reported. The compound (mg/kg) causes 100% elimination of A. ceylanicum (25 x 1), N. brasiliensis (100 x 1), S. obvelata (50 x 1), H. nana (250 x 3) and C. fasciolaris (50 x 10). It was also effective against the developing larvae (L3, L4 and L5) of A. ceylanicum at a single oral dose of 100 mg/kg. Another study indicated that the compound elicits 100% response within 32 hr of drug administration. The drug is well tolerated and LD50 is greater than 4500 mg/kg.
Human gastric lipase (HGL) is a sulfhydryl enzyme which has been shown by Gargouri et al. (Gargouri, Y., Moreau, H., Piéroni, G. and Verger, R. (1988) J. Biol. Chem. 263, 2159-2162) to be inhibited by hydrophobic disulfides. Since HGL is involved in the digestion and absorption of dietary fats we have investigated in vitro the ability of ajoene, a natural disulfide to inactivate HGL. Ajoene is derived from ethanolic garlic extracts. The finding that ajoene inactivates HGL is consistent with the fact that it is reactive towards sulfhydryl compounds and also corroborates previous reports on the ability of garlic to lower triacylglycerol blood levels. These data may explain the age-old Mediterranean and Oriental belief in the 'blood-thinning' effects of garlic on a molecular and physiological basis.
Kinetic studies with phospholipase A2 are complicated by the fact that binding of the enzyme to the interface precedes catalytic turnover. This difficulty can be overcome by monitoring interfacial catalysis in the scooting mode where the enzyme does not leave the interface. The kinetics of inhibition by transition-state analogues shows that specific competitive inhibition is the result of competition between inhibitor and substrate for the binding to the active site of the enzyme in the interface. Several lipophilic compounds, including alkanols, substituted butyrophenones, aristolochic acid, and mepacrine apparently reduce the rate of lipolysis by promoting the desorption of phospholipase A2 from the interface.
Action of pig pancreatic phospholipase A2 on vesicles and micelles of homologous anionic phospholipids is examined in the absence of additives. As shown elsewhere (Jain et al. (1986) Biochim. Biophys. Acta 860, 435-447), hydrolysis of anionic vesicles occurs by interfacial catalysis in the scooting mode, i.e., the catalytic turnover is fast relative to the off-rate of the enzyme from the interface. When the rate of intervesicle exchange of the enzyme is negligibly slow, it hydrolyses only the substrate molecules in the outer monolayer of the vesicle to which it is bound. Interfacial catalysis in the scooting mode with a high processivity occurs on vesicles of anionic phospholipids, and under these conditions the dynamics and order of the substrate in the interface influences the catalytic turnover only moderately, i.e., about 2- to 10-fold. Similarly, anomalous kinetic effects of the thermotropic gel-fluid phase transition or of a change in the general disorder of the bilayer organization (fluidity) has a minor effect on the kinetics of hydrolysis in the scooting mode. Similarly, higher unsaturation and shorter acyl chains in the substrate modestly increase the rate of catalytic turnover by the low-calcium form of the enzyme without noticeably influencing the affinity of the enzyme for the interface. On the other hand, perturbation of the charge distribution in the substrate interface can shift the proportion of the bound enzyme by several orders of magnitude. For example, the membrane perturbing amphiphiles (e.g., mepacrine, indomethacin, compound 48/80, aristolochic acid, local anesthetics, and the products of hydrolysis) do not influence the catalytic turnover of the bound enzyme but the proportion of the bound enzyme. Short-chain anionic phospholipids are readily hydrolyzed by phospholipase A2. Now no anomalous increase in the rate of hydrolysis is observed at the critical micelle as is the case with the zwitterionic analogs. This is because with anionic (but not with zwitterionic) substrates the enzyme forms an aggregated complex below the cmc of the monomer. The stability of these micellar complexes does not appear to change noticeably with the acyl chain length of the monomers. These observations show that the factors regulating the quality of interface substantially influence the binding of the enzyme, but not the catalytic turnover in the interface.
Ajoene (E,Z-4,5,9-trithiadodeca-1,6,11-triene 9-oxide), a product of the rearrangement of allicin (a major component of raw garlic), has been shown to be a potent inhibitor of platelet aggregation in vitro through inhibition of granule release and fibrinogen binding. Our present study further elaborates on this inhibitory action, through studies of the effect of ajoene on the earliest steps of platelet activation. The transducing mechanism involved in thrombin-induced platelet activation was not modified by the drug as indicated by a normal breakdown of phosphatidylinositol 4,5,bisphosphate and normal production of phosphatidic acid. Likewise, the agonist-induced phosphorylation of myosin light chain (P20) and of the 43 kD protein (P43) were not impaired by ajoene. Under the same conditions, however, ajoene (100 microM) produced a strong inhibition of the thrombin-induced release of dense body and alpha-granule constituents. Electron spin resonance studies of the effect of ajoene on some physico-chemical properties of the platelet plasma membrane (intact platelets), as well as on artificial lipid membranes, indicated that ajoene increased mobility of the fatty acid spin label 16 nitroxide stearate. This suggests the existence of a decreased microviscosity of the most internal region within the lipid bilayer membrane, without affecting the outer hydrophilic moieties of the bilayer. As a whole, these results suggest that the effect of ajoene on the release reaction must be, in part, due to physical modification of the bilayer, which impairs the fusion of the granules and plasma membrane, a prerequisite for exocytosis.
Explore the source record for details and available documents.
Fluorescence emission properties of a cationic indodicarbocyanine dye, NK-529, bound to anionic and zwitterionic vesicles, are examined under a variety of conditions to monitor lateral distribution of anionic amphiphiles in bilayers as a function of their phase properties. The change in the fluorescence properties of NK-529 arises from the binding of the dye to the bilayer that is dominated by ionic interactions when possible, as well as from the self-quenching of the dye bound to bilayers when the surface density of the dye is high. The binding affinity of the dye to anionic interfaces is more than 100-fold higher compared to that in zwitterionic bilayers. The limiting phospholipid/dye ratio in anionic bilayers at low vesicle concentrations is about 3. Thus the density of the bound dye in anionic bilayers can be more than 40-fold higher than that in zwitterionic bilayers, and therefore under such conditions the bound dye is completely self-quenched in vesicles or micelles of anionic phospholipids. The change in the fluorescence emission intensity on incorporation of anionic amphiphiles in zwitterionic bilayers is used to monitor segregation of the anionic amphiphiles. The organizational features of bilayers that cause a change in the fluorescence properties of bound NK-529 show that the lateral distribution of anionic amphiphiles is appreciably influenced not only by the mole fraction of the amphiphile but also in the presence of other additives, and by the gel-fluid thermotropic transition. As shown in the following paper, the fluorescence changes related to self-quenching in anionic bilayers containing NK-529 can be used to understand the organizational changes that occur during the course of interfacial catalysis by phospholipase A2 on zwitterionic bilayers.
Catalytic action of phospholipase A2 is appreciably influenced by the organization and dynamics of bilayers of glycerophosphocholines (Apitz-Castro et al. (1988) Biochim. Biophys. Acta 688, 341-348). However, such effects of the quality of the interface are not observed with bilayers of glycerophosphoryl methanol and other anionic phospholipids (Jain et al. (1986) Biochim. Biophys. Acta 860, 435-447). Such differences between the catalytic susceptibility of zwitterionic versus anionic bilayers are due to a large difference in the affinity of the enzyme for these interfaces. Binding to phospholipase A2 to zwitterionic interfaces can be promoted in the presence of certain anionic additives. For example in the pre-steady-state phase of hydrolysis, segregation of the nacently produced products of hydrolysis could promote binding of phospholipase A2 to regions of higher anionic charge density in the zwitterionic interface. In this paper we show that the dynamics of segregation of the nacently produced products of hydrolysis in zwitterionic bilayers can be readily followed by monitoring the fluorescence intensity of the cationic dye NK-529 (Yu and Jain (1989) Biochim. Biophys. Acta 980, 15-22). The fluorescence emission characteristics of NK-529 change appreciably due to self-quenching of the bound dye molecules as the fatty acid molecules segregate in the bilayer. The kinetics of segregation of fatty acids during the course of hydrolysis of bilayers of zwitterionic phospholipids by phospholipase A2 exhibits an unequivocal correlation with a variety of phenomena that are observed during the transition from the pre-steady-state phase to the steady-state phase of hydrolysis in the reaction progress curves as a function of temperature and in the presence of lipophilic additives.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
During the past 3 years, we have seen a changing pattern of cutaneous tuberculosis, in which its incidence was recorded to show an upward trend affecting predominantly the adult men. The latter was true in reinfection--lupus vulgaris and tuberculosis verrucosa cutis, whereas a substantial number of children were victims of reactivation--scrofuloderma. The duration of the disease was usually short in reactivation tuberculosis. Its clinical expression, however, conformed largely to the ritual text except that apple-jelly nodules were infrequently demonstrated. Similarly, the morbidity was low. The affliction of the extremities in lupus vulgaris, in particular, was a contrasting feature. The histopathology invariably either confirmed or supplemented the clinical impression. The ultimate confirmation of cutaneous tuberculosis was done only by the demonstration of Mycobacterium tuberculosis in smears, or its recovery in vitro. In view of the limitations of the preceding parameters, the diagnosis may reasonably be made based on the history and evolution of the disease, cardinal morphologic features of reinfection and reactivation tuberculosis, and histopathologic characteristics. A response to antitubercular drugs may be of assistance.
A simple, stable, and transferable coculture of Clostridium collagenovorans and Methanosarcina barkeri that readily degraded gelatin into methane and carbon dioxide was developed. In monoculture, C. collagenovorans fermented all of the amino acids in gelatin except proline into acetate and carbon dioxide as the main products, with hydrogen, isovalerate, and isobutyrate detected in trace amounts (<1 mM). In coculture with M. barkeri, gelatin was transformed into methane and carbon dioxide, with varying levels of intermediary acetate formed as a function of incubation time. Various complex proteinaceous polymers could be readily transformed into methane and carbon dioxide at 30 to 40 degrees C by a stable coculture which did not require exogenous growth factor additions. In addition, the coculture was readily transferable and preserved in the viable state for long periods, and methanogenesis could be initiated rapidly without the need for exogenous pH control.
A ferredoxin and a rubredoxin from Butyribacterium methylotrophicum, which displays a carbonyl-dependent acetyl-coenzyme A synthesis, were purified to electrophoretic homogeneity. The two electron carriers showed absorption spectra similar to those in Clostridium species. The ferredoxin displayed absorption peaks at 280 and 391 nm, while rubredoxin displayed absorption peaks at 279, 382, and 482 nm. Minimum molecular weights calculated from the respective amino acid compositions were 5,727 for ferredoxin and 5,488 for rubredoxin, excluding iron and inorganic sulfur atoms. Both electron carriers were isolated as monomers, according to gel-filtration data. Electron spin resonance analysis revealed that the ferredoxin was a 2[4Fe-4S]-type and that both clusters had a midpoint redox potential value of -410 mV, whereas rubredoxin contained one acid-stable iron and had a redox value of -40 mV. The coupling of these electron carriers to hydrogenase and carbon monoxide dehydrogenase activities was investigated. Rubredoxin showed higher activity towards carbon monoxide dehydrogenase, whereas ferredoxin showed higher activity towards hydrogenase.
Methyl 5(6)-(alpha-hydroxyphenyl methyl) benzimidazole-2-carbamate, a major metabolite of mebendazole was evaluated against Cysticercus fasciolaria (larval form of Taenia taeniaeformis) in rats. The metabolite was assessed in various doses. A regimen of 50 mg/kg x 10 (ip), given one day apart, was found to be most effective and killed all the mature cysticerci. On developing cysts, the treatment was initiated in two schedules; 5 days prior to (d-5 to d-1) and 5 days after (d + 6 to d + 10) administration of T. taeniaeformis eggs to rats. The later protocol with 100 mg/kg x 5 dose (ip) resulted in 95% inhibition in the establishment of cysticerci. Activity of mebendazole against mature cysts was parallel to metabolite whereas against developing cysts, it was inferior. The time related topographical changes that occurred in mature C. fasciolaris after treatment with metabolite (50 mg/kg x 10, ip, one day apart) were observed by scanning electron microscopy. There was loss of contractivity, gradual disappearance of microtriches and progressive degeneration of tegument. Similar changes were noticed with mebendazole. The possession of better efficacy and higher safety range [Indian J Exp. Biol, 25 (1987) 871], suggests that the metabolite can be a potential anthelmintic for man and animals.
The time-course of binding of phospholipase A2 and prophospholipase A2 to vesicles and micelles of a variety of substrate and nonhydrolyzable phospholipid analogs is obtained by monitoring the change in the fluorescence intensity of Trp-3 on the protein or of the 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) chromophore on the surface of the vesicles. The time-dependent increase in the fluorescence intensity of phospholipase A2 is observed only under conditions where catalysis and equilibrium binding are also observed. The overall kinetics of binding is described by two rate constants. A rapid second-order rate constant (ka) for binding of both the proteins is 2.10(7) per s per mol expressed in terms of phospholipids as monomers, and 10(10) per s per mol expressed in terms of vesicles. This is probably a diffusion-limited encounter of the protein with vesicles as the first step in binding. An additional first-order rate constant (kb = 4 per s) was also discerned for the binding of phospholipase A2 but not for prophospholipase A2. The rate of desorption of the bound iphospholipase A2 in the presence of EGTA is very slow (less than 0.0002 per s), whereas the rate of desorption of the bound prophospholipase A2 is much more rapid (2.9 per s). The mechanistic significance of these rate constants is elaborated in terms of the differences in the rates of interfacial catalytic turnover of phospholipase A2 and prophospholipase A2. As shown elsewhere (Jain et al. Biochim. Biophys. Acta 860, 435-447) the hydrolysis of anionic vesicles by phospholipase A2 occurs in the scooting mode such that the bound enzyme remains on the target vesicles for several thousand catalytic turnover cycles. On the other hand, as shown in this paper, the kinetics of hydrolysis by prophospholipase A2 is dominated by its intervesicle exchange. Therefore, interfacial catalysis by prophospholipase A2 in the hopping mode would involve an on- and an off-step in each cycle, resulting in a catalytic turnover number of about 1.2 per s. A change from the hopping to the scooting mode of catalysis thus provides the kinetic basis for activation of interfacial catalysis by phospholipase A2 compared to that for prophospholipase A2.