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Biomedical subjects

A Arora

Publications and source records attributed to A Arora.

At least 73 records · Page 4Linked to original sources
PubMed1999

Probing the role of C-1 ester group in Naja naja phospholipase A2-phospholipid interactions using butanetriol-containing phosphatidylcholine analogues.

To understand the role of the ester moiety of the sn-1 acyl chain in phospholipase A2-glycerophospholipid interactions, we introduced an additional methylene residue between the glycerol C1 and C2 carbon atoms of phosphatidylcholines, and then studied the kinetics of hydrolysis and the binding of such butanetriol-containing phospholipids with Naja naja phospholipase A2. Hydrolysis was monitored by using phospholipids containing a NBD-labelled sn-2 acyl chain and binding was ascertained by measuring the protein tryptophan fluorescence. The hydrolysis of butanetriol-containing phospholipids was invariably slower than that of the glycerol-containing phospholipids. In addition, the enzyme binding with the substrate was markedly decreased upon replacing the glycerol residue with the 1,3,4-butanetriol moiety in phosphatidylcholines. These results have been interpreted to suggest that the sn-1 ester group in glycerophospholipids could play an important role in phospholipase A2-phospholipid interactions.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1999

Trivial injuries, associated congenital anomaly and medicolegal interpretation of death.

Congenital hypoplasia of the odontoid process is a relatively rare phenomenon. A case is presented of a 12-year-old girl who was admitted to hospital with a history of having sustained trivial external injuries when falling after an alleged push. Later, she developed signs of compression of the spinal cord in the cervical region, resulting in quadriplegia and muscle wasting. A laminectomy was performed to relieve the symptoms but the child died 2 1/2 months later. Autopsy revealed a congenital anomaly of the atlas and axis vertebrae in the form of hypoplasia of the dens. The case being associated with a criminal assault, the post-mortem analysis and autopsy were significant in resolving medicolegal issues pertaining to the assailant, the operating surgeon and the law-enforcement agencies.

Adolescent↗
PubMed1999

A Drosophila Axin homolog, Daxin, inhibits Wnt signaling.

The vertebrate Axin protein, the product of the mouse fused gene, binds to beta-catenin to inhibit Wnt signaling. We have identified a homolog of Axin in Drosophila, Daxin. Using double-stranded RNA interference, we generated loss-of-function phenotypes that are similar to overexpression of the Drosophila Wnt gene wingless (wg). Overexpression of Daxin produces phenotypes similar to loss of wg. In addition, we show that Daxin overexpression can modify phenotypes elicited by wg and another Drosophila Wnt gene, DWnt-2. Using immunoprecipitation of endogenous Daxin protein from embryos we show that Daxin interacts with Armadillo and Zeste-white 3. The loss-of-function and overexpression phenotypes show that Daxin, like its mammalian counterpart, acts as a negative regulator of wg/Wnt signaling.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Primary progressive aphasia : a case report.

Primary progressive aphasia is due to focal left perisylvian degeneration and manifests with progressive decline in language function for two or more years. There is preservation of cognitive functions and activities of daily living continue to be normal. We report a case of progressive aphasia in a 65 year old lady.

Aged↗
PubMed1998

Antioxidant activities of isoflavones and their biological metabolites in a liposomal system.

Genistein and daidzein, the two major soy isoflavones, principally occur in nature as their glycosylated or methoxylated derivatives, which are cleaved in the large intestine to yield the free aglycones and further metabolites. The objective of this study was to compare the antioxidant activities of genistein and daidzein with their glycosylated and methoxylated derivatives and also those of their human metabolites. The abilities of these compounds to inhibit lipid peroxidation in a liposomal system were evaluated using fluorescence spectroscopy, and structural criteria that enhance antioxidant activity were established. The peroxidation initiators employed in the study were Fe(II) and Fe(III) metal ions and aqueous-phase, azo-derived peroxyl radicals. Both the parent isoflavonoids and their metabolites were more effective at suppressing metal-ion-induced peroxidations than the peroxyl-radical-induced peroxidation. Antioxidant activities for the isoflavone metabolites were comparable to or superior to those for the parent compounds. Equol and its 4-hydroxy and 5-hydroxy derivatives were the most potent antioxidants in the study, suggesting that absence of the 2, 3-double bond and the 4-oxo group on the isoflavone nucleus enhances antioxidant activity. Additionally, the number and position of hydroxyl groups were determining factors for isoflavonoid antioxidant activity, with hydroxyl substitution being of utmost importance at the C-4' position, of moderate importance at the C-5 position, and of little significance at the C-7 position.

Amidines↗
PubMed1998

Selectivity of lipid-protein interactions with trypsinized Na, K-ATPase studied by spin-label EPR.

The selectivity of the lipid-protein interactions in trypsinised Na, K-ATPase membranes from Squalus acanthias has been determined by using EPR spectroscopy with different lipid probes spin-labelled on the 14-C atom of the fatty acid chain. From measurements at low ionic strength and different pH values, the pattern of selectivity is: (stearic acid)->(phosphatidylserine)->(stearic acid)0>(phosphatidylcholine)+/-, where superscripts indicate the formal electrostatic charge on the lipid headgroup. This is in the same order as that determined with native Na,K-ATPase membranes [M. Esmann, D. Marsh, Biochemistry 24 (1985) 3572-3578]. The selectivity for phosphatidylserine is independent of pH, over the range pH 6.0-9. 0, as found also for native membranes. For membranes trypsinised in the presence of Rb+ ions, and in the presence of Na+ (which allows more extensive proteolysis), the relative association constants, Kr, of all lipids are the same as for control membranes, with the exception of ionised (stearic acid)- that shows the highest specificity. Therefore, both the stoichiometry and the principal determinants of the specificity of lipid-protein interaction are preserved on extensive trypsinisation of Na,K-ATPase membranes. This has implications for the location and arrangement of those amino acid side chains that determine the lipid selectivity of the native Na,K-ATPase.

Animals↗
PubMed1998

Protein-induced vertical lipid dislocation in a model membrane system: spin-label relaxation studies on avidin-biotinylphosphatidylethanolamine interactions.

The change in vertical location of spin-labeled N-biotinyl phosphatidylethanolamine in fluid-phase dimyristoyl phosphatidylcholine bilayer membranes, on binding avidin to the biotinyl headgroup, has been investigated by progressive saturation electron spin resonance measurements. Spin-labeled phospholipids were present at a concentration of 1 mol%, relative to total membrane lipids. For avidin-bound N-biotinyl phosphatidylethanolamine spin-labeled on the 8 C atom of the sn-2 chain, the relaxation enhancement induced by 30 mM Ni2+ ions confined to the aqueous phase was 2.5 times that induced by saturating molecular oxygen, which is preferentially concentrated in the hydrophobic core of the membrane. For phosphatidylcholine also spin-labeled at the 8 position of the sn-2 chain, this ratio was reversed: the relaxation enhancement by Ni2+ ions was half that induced by molecular oxygen. In the absence of avidin, the enhancement by either relaxant was the same for both spin-labeled phospholipids. For a double-labeled system, in which both N-biotinyl phosphatidylethanolamine and phosphatidylcholine were spin-labeled on the 12 C atom of the sn-2 chain, the relaxation rate in the absence of avidin was greater than that predicted from linear additivity of the corresponding singly labeled systems, because of mutual spin-spin interactions between the two labeled lipid species. On binding of avidin to the N-biotinyl phosphatidylethanolamine, this relaxation enhancement by mutual spin-spin interaction was very much decreased. These results indicate that, on binding of avidin to the lipid headgroup, N-biotinyl phosphatidylethanolamine is lifted vertically within the membrane, relative to the phosphatidylcholine host lipids. The specific binding of avidin to N-biotinyl phosphatidylethanolamine parallels the liftase activity proposed for activator proteins associated with the action of certain gangliosidases.

Animals↗
PubMed1998

Structure-activity relationships for antioxidant activities of a series of flavonoids in a liposomal system.

Structurally diverse plant phenolics were examined for their abilities to inhibit lipid peroxidation induced either by Fe(II) and Fe(III) metal ions or by azo-derived peroxyl radicals in a liposomal membrane system. The antioxidant abilities of flavonoids were compared with those of coumarin and tert-butylhydroquinone (TBHQ). The antioxidant efficacies of these compounds were evaluated on the basis of their abilities to inhibit the fluorescence intensity decay of an extrinsic probe, 3-(p-(6-phenyl)-I,3,5-hexatrienyl)phenylpropionic acid (DPH-PA), caused by the free radicals generated during lipid peroxidation. All the flavonoids tested exhibited higher antioxidant efficacies against metal-ion-induced peroxidations than peroxyl-radical-induced peroxidation, suggesting that metal chelation may play a larger role in determining the antioxidant activities of these compounds than has previously been believed. Distinct structure-activity relationships were also revealed for the antioxidant abilities of the flavonoids. Presence of hydroxyl substituents on the flavonoid nucleus enhanced activity, whereas substitution by methoxy groups diminished antioxidant activity. Substitution patterns on the B-ring especially affected antioxidant potencies of the flavonoids. In cases where the B-ring could not contribute to the antioxidant activities of flavonoids, hydroxyl substituents in an catechol structure on the A-ring were able to compensate and become a larger determinant of flavonoid antioxidant activity.

Amidines↗
PubMed1998

Lipaemia retinalis.

PURPOSE: To present a patient with the rare condition of lipaemia retinalis and discuss the clinical features of this condition and its association with elevated triglyceride levels. METHODS: Clinical evaluation of the patient, including fundus photographs before and after the initiation of a low fat diet, was undertaken. RESULTS: Lowering of serum triglyceride and cholesterol levels was associated with complete resolution of the clinical picture of lipaemia retinalis. CONCLUSIONS: Lipaemia retinalis is a rare condition that is related to markedly elevated triglyceride levels. Lowering triglycerides levels leads to resolution of the clinical picture of this disease.

Adult↗
PubMed1998

Airway inflammation in young marijuana and tobacco smokers.

Forty healthy young subjects, ages 20 to 49 yr, underwent videobronchoscopy, mucosal biopsy, and bronchial lavage to evaluate the airway inflammation produced by habitual smoking of marijuana and/or tobacco. Videotapes were graded in a blinded manner for central airway erythema, edema, and airway secretions using a modified visual bronchitis index. The bronchitis index scores were significantly higher in marijuana smokers (MS), tobacco smokers (TS), and in combined marijuana/tobacco smokers (MTS), than in nonsmokers (NS). As a pathologic correlate, mucosal biopsies were evaluated for the presence of vascular hyperplasia, submucosal edema, inflammatory cell infiltrates, and goblet cell hyperplasia. Biopsies were positive for two of these criteria in 97% of all smokers and for three criteria in 72%. By contrast, none of the biopsies from NS exhibited greater than one positive finding. Finally, as a measure of distal airway inflammation, neutrophil counts and interleukin-8 (IL-8) concentrations were determined in bronchial lavage fluid. The percentage of neutrophils correlated with IL-8 levels and exceeded 20% in 0 of 10 NS, 1 of 9 MS, 2 of 9 TS, and 5 of 10 MTS. We conclude that regular smoking of marijuana by young adults is associated with significant airway inflammation that is similar in frequency, type, and magnitude to that observed in the lungs of tobacco smokers.

Adult↗
PubMed1997

Novel thermal phase transition behavior of phosphatidylcholine analogs containing 1,2,4-butanetriol as their backbone.

The sn-glycerol moiety in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) was replaced by the rac-1,2,4-butanetriol residue, and the aqueous dispersions of the resulting DPPC analogs, viz. 1,2-dihexadecanoyloxy-rac-but-4-yl-[2-(trimethyl-ammonium)ethyl]ph osphate (1,2-bPC) and 1,3-dihexadecanoyloxy-rac-but-4-yl-[2-(trimethylammonium)ethyl]pho sphate (1,3-bPC), were characterized by differential scanning calorimetry (DSC) and fluorescence polarization technique. Also, the corresponding (3R)-isomer of 1,3-bPC (1,3-(3R)bPC) was prepared and characterized by DSC. While the thermal phase transition properties of 1.2-bPC were similar to that of racemic DPPC, 1.3-bPC in identical conditions showed an abnormal property by exhibiting a metastable phase behavior at about 15 degrees C. This abnormal property was associated only with the racemic mixture and was completely absent in its 3R-isomer. 1,3-(3R)bPC, unlike DPPC, showed only two high enthalpy transitions at about 29.7 degrees C (delta H, 7.45 kcal/mol) and 35.3 degrees C (delta H, 6.93 kcal/mol). These results clearly demonstrate that an insertion of one additional methylene residue between the glycerol C1 and C2 carbons in DPPC markedly alters its thermal phase transitional properties, whereas these properties remain virtually unchanged if a similar chemical change is introduced between the glycerol C2 and C3 carbon atoms.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Glycerol backbone conformation in phosphatidylcholines is primarily determined by the intramolecular stacking of the vicinally arranged acyl chains.

To analyse the effect of the altered glycerol backbone structure on the glycerophospholipid conformation, we have replaced the glycerol moiety by the rac-1,2,4-butanetriol residue in 1,2-diacyl-sn-glycero-3-phosphocholines (PC), and then analysed the resulting 1,2-dialkanoyloxy-rac-but-4-yl-[2-(trimethylammonium)ethyl] phosphates (1,2-bPC) and 1,3-dial-kanoyloxy-rac-but-4-yl-[2-(trimethylammonium)ethyl] phosphates (1,3-bPC) by high-resolution 1H- and 13C-NMR spectroscopy in both CDCI3 and D2O. The preferred conformation about the C1-C2 glycerol bond in PC was almost completely preserved in 1,2-bPC, but it was completely random in case of 1,3-bPC. Out of the three C-C bonds present in the butanetriol backbone of 1,3-bPC, only the C2-C3 bond experienced a restricted rotation. However, the conformational preference about this bond was virtually similar to that observed for the C1-C2 bond in PC. These results clearly demonstrate that the preferred conformation of the glycerol backbone is determined primarily by the intramolecular acyl chain stacking which essentially requires a vicinal arrangement of the acyl chains in glycerophospholipids.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Subsyndromes of chronic schizophrenia: a phenomenological study.

Statistical grouping of clinical symptoms and signs is one method of classifying schizophrenia. This study attempted to find factors of symptoms generated through clinical ratings on three scales, namely the Scale for the Assessment of Positive Symptoms (SAPS), the Scale for the Assessment of Negative Symptoms (SANS) and the Comprehensive Psychopathological Rating Scale (CPRS) in a sample of 80 stable chronic schizophrenics diagnosed by DSM-III-R. It was found that the positive-negative dichotomy could not be replicated. Inappropriate affect was found to be a clear misfit in the cluster of negative symptoms. Inclusion of CPRS led to the generation of a factor loading high on depressive and asthenic items, and this could be clearly distinguished from the factor of negative symptoms. This factor had not hitherto been identified.

Activities of Daily Living↗