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Biomedical subjects

A K Grover

Publications and source records attributed to A K Grover.

144 records · Page 8Linked to original sources
PubMed1979

ESR studies on the orientation of cholesteryl ester in phosphatidylcholine multilayers.

The alignment of cholesteryl esters in multilayer phosphatidylcholine membranes was investigated using two spin-labelled cholesteryl esters: 10 : 3 ester (I) and 1 : 14 ester (II). The nitroxide label of I is aligned in the membrane with a very large angle of tilt (47 degrees +/- 1.5 degrees) with respect to the normal to the membrane surface; II does not show such a tilt. I gives spectra corresponding to immobilized label while II gives nearly isotropic spectra. Ascorbate treatment of the multilayers shows that the labels in I and II are not present at the phosphatidylcholine-water interphase. The data supports a 'horseshoe' configuration for the cholesteryl ester in the bilayer, with both the fatty acid chain and the cholesteryl moiety extending deep into the hydrophobic region of the membrane and with the ester linkage near the surface.

Ascorbic Acid↗
PubMed1979

Cholesteryl ester distribution in lecithin bilayer membranes.

The saturated cholesteryl ester, cholesteryl 16-doxylstearate, is shown to incorporate into hydrated egg yolk lecithin multilayers in two distinct forms as visualized by electron spin resonance (ESR) spectroscopy. At concentrations less than 1 mole%, the ester is uniformly distributed in the membrane while at higher concentrations, patches of solid ester are formed.

Cholesterol Esters↗
PubMed1977

Studies on almond emulsin beta-D-glucosidase. I. Isolation and characterization of a bifunctional isozyme.

A beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) isozyme has been isolated from almond emulsin. The isolated enzyme is a glycoprotein and migrates as a single band on Sephadex G-200 filtration, CM 52 ion exchange chromatography, polyacrylamide gel electrophoresis, sodium dodecyl sulfate polyacrylamide gel electrophoresis and isoelectric focussing. The glucosidase and galactosidase activities traverse together during Sephadex G-200 gel filtration. Polyacrylamide gels stained specifically for the 2 enzymes reveal that the two activities comigrate. The molecular weight of the isozyme has been found to be 135 180 +/- 770, and that of its protomers to be 65 150 +/- 650.

Glucosidases↗
PubMed1977

Studies on almond emulsin beta-D-glucosidase. II. Kinetic evidence for independent glucosidase and galactosidase sites.

A purified beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) isozyme isolated from almond emulsin was found to catalyze hydrolysis of beta-D-glucopyranosides and beta-D-galactopyranosides but not the corresponding alpha-D-derivatives. Hydrolysis of the corresponding beta-D-thioglycopyranosides at rates 10(3)--10(4) times lower than those for the hydrolysis of the beta-D-glycopyranosides was also noted. The enzyme does not exhibit any transferolytic activity using D-glucose or D-galactose as acceptors. D-glucose, p-nitrothiophenyl-beta-D-glucopyranoside, 5-deoxy-5-thio-D-glucose and D-glucono-delta-lactone are shown to exert mainly competitive inhibition on beta-D-galactopyranoside hydrolysis. D-galactose, p-nitrothiophenyl-beta-D-galactopyranside and methylthio-beta-D-galactopyranoside are shown to inhibit the glucopyranoside hydrolysis mainly non-competitively and to exert competitive inhibition of galactopyranoside hydrolysis. The inhibition caused by the antibiotic Nojirimycin (5-amino-5-deoxy-D-glucose) is shown to be more complex. Analysis of the kinetic data indicates that the catalytic site of the enzyme responsible for the beta-D-glucosidase activity is kinetically distinct from the beta-D-galactosidase site.

Binding Sites↗
PubMed1975

Lipid specificity of beta-hydroxybutyrate dehydrogenase activation.

Beef heart mitochondrial beta-hydroxybutyrate dehydrogenase forms a catalytically active complex with lecithin and is inactive in the absence of lecithin. The specificity of the activation process was probed by studying the interaction of the enzyme with phospholipids and other compounds. The compounds were tested for their ability to form active complexes with the enzyme, for the stability of the complex formed, and for the correlation between the activator concentration and the level activation. The phospholipids tested were synthetic lecithins varying in the length (C2 to C18) and degree of unsaturation of the aliphatic chains and in the stereochemistry and type of linkage from the aliphatic chain to the glycerol moiety, synthetic and egg yolk lysolecithins, stearylphosphorylcholine, egg yolk phosphatidylethanolamine, egg yolk phosphatidyl-O-serine, and synthetic cardiolipins. Lecithins, lysolecithins, and stearylphosphoryl-choline form active complexes with the enzyme; the L-alpha-diC4:0 is the smallest lecithin forming an active complex and L-alpha-C12:0 is the smallest lysolecithin. Glycerophosphorycholine, mytistoylcholine, N-trimethyl-n-dodecylamine, decamethonium, sodium dodecyl sulfate, Triton X-100, and Lubrol do not activate the enzyme. A hydrophobic chain followed sequentially by a negative and a positive charge, as in stearylphosphorylcholine, is the minimal structural requirement of an activator. However, the stability of the enzyme-activator complex depends strongly on the aggregation state of the activators, complexes of appreciable stability being formed only with those phospholipids which exist in bilayer membrane-like structures. Thus, lecithins with long aliphatic chains (C9 to C18) form active and stable complexes with the enzyme. The maximal activity and the strength of the lipid-protein interactions depend on the nature of the aliphatic chains of the lipids. Lecithins with saturated and unsaturated fatty acid chains activate the enzyme, but the latter form somewhat more stable complexes. The enzyme-activator interactions in the bilayers can be qualitatively understood in terms of competition between lipid-lipid and lipid-protein interactions: the strength of the interaction between the protein and phosphatidylcholines decreases as the crystalline to amorphous phase transition temperature, which is a measure of the strength of lipid-lipid interactions, increases...

Animals↗
PubMedDate not supplied

Target size analysis of neurotensin receptors.

The neurotensin receptors from rat brain synaptosomal membranes differed in subunit structure from those in rat gastric fundus smooth muscle plasma membranes when studied following photoaffinity labelling or after exposure to cross-linking reagents. However, these two receptors were similar in their recognition properties. In this study we compared the target size of the two receptors by radiation inactivation and observed that the receptors in both tissues had similar target sizes (mean values 103,000 and 108,000 daltons). This suggests that the differences in size observed in biochemical studies may reflect changes occurring during the isolation procedures, or, on the other hand, there might be inherent difference in the subunit structure of these receptors.

Animals↗
PubMedDate not supplied

Ascorbate transport in pig coronary artery smooth muscle: Na(+) removal and oxidative stress increase loss of accumulated cellular ascorbate.

Pig deendothelialized coronary artery rings and smooth muscle cells cultured from them accumulated ascorbate from medium containing Na(+). The accumulated material was determined to be ascorbate using high-performance liquid chromatography. We further characterized ascorbate uptake in the cultured cells. The data fitted best with a Hill coefficient of 1 for ascorbate (K(asc) = 22 +/- 2 microM) and 2 for Na(+) (K(Na) = 84 +/- 10 mM). The anion transport inhibitors sulfinpyrazone and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS) inhibited the uptake. Transferring cultured cells loaded with (14)C-ascorbate into an ascorbate-free solution resulted in a biphasic loss of radioactivity - an initial sulfinpyrazone-insensitive faster phase and a late sulfinpyrazone-sensitive slower phase. Transferring loaded cells into a Na(+)-free medium increased the loss in the initial phase in a sulfinpyrazone-sensitive manner, suggesting that the ascorbate transporter is bidirectional. Including peroxide or superoxide in the solution increased the loss of radioactivity. Thus, ascorbate accumulated in coronary artery smooth muscle cells by a Na(+)-dependent transporter was lost in an ascorbate-free solution, and the loss was increased by removing Na(+) from the medium or by oxidative stress.

Actins↗
PubMedDate not supplied

Thallium uptake by canine iliac arteries.

Most of the thallium uptake by canine iliac arteries (70%) was inhibited by ouabain. The component sensitive to ouabain was significantly increased by incubating tissues in K+-free solution and reduced by low temperatures, metabolic inhibitors, and loading with lithium. The apparent Km for thallium for the ouabain-sensitive uptake was 0.47 +/- 0.046 mM. External K+ inhibited thallium uptake and the apparent Ki was estimated to be 6.5 mM. Thallium thus appears to have a greater affinity for the ouabain-sensitive components. The residual component of thallium uptake was unaffected by maneuvers that affected the ouabain-sensitive uptake, which thus appears to be a suitable indicator of Na+ pump activity in vascular smooth muscle.

Animals↗
PubMedDate not supplied

Traumatic cataract surgery with intraocular lens implantation in children.

We evaluated our experience of intraocular lens implantation in 22 children with uniocular traumatic cataract. Good visual acuity was achieved in a large proportion of the children despite associated corneal opacities and several intraoperative and postoperative complications. Our study suggests that intraocular lens implantation may have a major role in management of monocular cataracts in children.

Cataract Extraction↗
PubMedDate not supplied

Relaxation of coronary artery smooth muscle cells.

The effect of adenosine and nitroglycerine on single smooth muscle cells isolated from the right coronary artery of the pig is reported. Trypan Blue exclusion and electron microscopy revealed that the cells used in this study were structurally intact. These cells were 79.2 +/- 1.6 microns long. Within 1 min of exposure to solutions containing norepinephrine, carbachol and high KCl, the cells contracted by 20-30%. The concentrations required for half maximal contraction for norepinephrine, carbachol and KCl were 0.1 to 1 nM, 0.01 to 0.1 nM and 15 to 25 mM, respectively. Adenosine and nitroglycerine inhibited the contractions caused by high (30 mM) K+ and also relaxed the cells previously contracted by high K+. Thus adenosine and nitroglycerine relax by acting directly on the smooth muscle cells.

2-Chloroadenosine↗
PubMedDate not supplied

Modified canaliculo-dacryocystorhinostomy.

The management of cases with common canalicular obstruction poses a difficult problem. Nineteen patients presenting with common canalicular obstruction of unknown cause or in association with trauma, encysted mucocoele and previous sac surgery, were operated on by the modified canaliculodacryocystorhinostomy technique. The surgery involves a microsurgical dissection at the site of the common canalicular obstruction followed by anastomosis to the sac or nasal mucosa with silicone tube intubation of the passage using an improvised metallic introducer. The procedure was successful in 13 of the cases in a follow-up period varying from 4 months to 15 months. The complications included extrusion of the tube and nasal bleeding. The indications of the procedure, the precise technique and precautions to avoid intra and post operative complications have been elaborated in the paper.

Adolescent↗