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Biomedical subjects

R B Rao

Publications and source records attributed to R B Rao.

At least 19 recordsLinked to original sources
PubMed2002

Neuropharmacological profile of Barleria lupulina Lindl. Extract in animal models.

Barleria lupulina Lindl. is a popular medicinal plant distributed in mountains of southern and western India. In the present work, the effect of methanolic extract of aerial parts of B. lupulina on CNS activity has been evaluated. The CNS activity was tested in several experimental models, in mice and rats: general behavior, exploratory behavior, muscle relaxant activity, conditioned avoidance response and phenobarbitone sodium-induced sleeping time tests. The aerial parts of the plant B. lupulina was extracted with methanol and the solvent was removed by vacuum distillation. The methanol extract (100, 200 and 300 mg/kg) showed reduction in general behavioral pattern (spontaneous activity, alertness, awareness, pain response and touch response) in a dose dependent manner. The extract was found to produce a significant reduction of the exploratory behavioral profile (Y-maze test, head dip test) and conditioned avoidance response with all the tested doses. The methanolic extract showed significant motor incoordination and muscle relaxant activity. The extract also potentiated phenobarbitone sodium induced sleeping time. Preliminary investigation showed that the methanol extract of B. lupulina has significant psychopharmacological activity.

Acanthaceae↗
PubMed2000

Comparison of helix-stabilizing effects of alpha,alpha-dialkyl glycines with linear and cycloalkyl side chains.

The ability of alpha, alpha-di-n-alkyl glycines with linear and cyclic alkyl side chains to stabilize helical conformations has been compared using a model heptapeptide sequence. The conformations of five synthetic heptapeptides (Boc-Val-Ala-Leu-Xxx-Val-Ala-Leu-OMe, Xxx = Ac8c, Ac7c, Aib, Dpg, and Deg, where Ac8c = 1-aminocyclooctane-1-carboxylic acid, Ac7c = 1-aminocycloheptane-1-carboxylic acid, Aib = alpha-aminoisobutyric acid, Dpg = alpha,alpha-di-n-propyl glycine, Deg = alpha,alpha-di-n-ethyl glycine) have been investigated. In crystals, helical conformations have been demonstrated by x-ray crystallography for the peptides, R-Val-Ala-Leu-Dpg-Val-Ala-Leu-OMe, (R = Boc and acetyl). Solution conformations of the five peptides have been studied by 1H-nmr. In the apolar solvent CDCl3, all five peptides favor helical conformations in which the NH groups of residues 3-7 are shielded from the solvent. Successive NiH<-->Ni + 1H nuclear Overhauser effects over the length of the sequence support a major population of continuous helical conformations. Solvent titration experiments in mixtures of CDCl3/DMSO provide evidence for solvent-dependent conformational transitions that are more pronounced for the Deg and Dpg peptides. Solvent-dependent chemical shift variations and temperature coefficients in DMSO suggest that the conformational distributions in the Deg/Dpg peptides are distinctly different from the Aib/Acnc peptides in a strongly solvating medium. Nuclear Overhauser effects provide additional evidence for the population of extended backbone conformations in the Dpg peptide, while a significant residual population of helical conformations is still detectable in the isomeric Ac7c peptide in DMSO.

Crystallography, X-Ray↗
PubMed2000

Conformational choice at alpha,alpha-di-n-propylglycine residues: helical or fully extended structures?

The conformational analysis of peptides containing a single alpha, alpha-di-n-propylglycine (Dpg) residue incorporated into valine-rich sequences has been undertaken in order to delineate the possible role of sequence effects in stabilizing fully extended (C(5)) or local helical conformations at this residue. The three peptides Boc-Val-Dpg-Val-OMe (3), Boc-Val-Val-Dpg-Val-OMe (4), Boc-Val-Val-Dpg-Val-Val-OMe (5), have been studied by (1)H-nmr methods in chloroform (CDCl(3)) and dimethylsulfoxide (DMSO) solutions. Even in a relatively poorly solvating medium like CDCl(3), all the valine NH groups appear to be solvent-exposed, suggesting an absence of folded beta-turn conformations. However, in both CDCl(3) and DMSO the Dpg NH groups in all the three peptides appear to behave like apparently solvent-inaccessible groups. In fully extended C(5) conformations, the proximity of the NH and CO groups of Dpg may preclude effective solvation due to a combination of stereoelectronic factors. Nuclear Overhauser effects provide support for the largely extended backbones. The crystal structure of peptide 3 reveals an extended conformation at Dpg (2) with straight phi = -176 degrees, psi = 180 degrees. A correlation between the crystallographically observed backbone conformation and solution nmr parameters in DMSO has been attempted using available data. Dpg residues placed in poor helix stabilizing environments may be expected to favor a local C(5) conformation.

Amino Acid Sequence↗
PubMed2000

Predicting cesarean delivery with decision tree models.

OBJECTIVE: The purpose of this study was to determine whether decision tree-based methods can be used to predict cesarean delivery. STUDY DESIGN: This was a historical cohort study of women delivered of live-born singleton neonates in 1995 through 1997 (22,157). The frequency of cesarean delivery was 17%; 78 variables were used for analysis. Decision tree rule-based methods and logistic regression models were each applied to the same 50% of the sample to develop the predictive training models and these models were tested on the remaining 50%. RESULTS: Decision tree receiver operating characteristic curve areas were as follows: nulliparous, 0.82; parous, 0.93. Logistic receiver operating characteristic curve areas were as follows: nulliparous, 0.86; parous, 0.93. Decision tree methods and logistic regression methods used similar predictive variables; however, logistic methods required more variables and yielded less intelligible models. Among the 6 decision tree building methods tested, the strict minimum message length criterion yielded decision trees that were small yet accurate. Risk factor variables were identified in 676 nulliparous cesarean deliveries (69%) and 419 parous cesarean deliveries (47.6%). CONCLUSION: Decision tree models can be used to predict cesarean delivery. Models built with strict minimum message length decision trees have the following attributes: Their performance is comparable to that of logistic regression; they are small enough to be intelligible to physicians; they reveal causal dependencies among variables not detected by logistic regression; they can handle missing values more easily than can logistic methods; they predict cesarean deliveries that lack a categorized risk factor variable.

Adolescent↗
PubMed1999

Deaths related to liposuction.

BACKGROUND: The technique of tumescent liposuction involves the subcutaneous infusion of a solution containing lidocaine, followed by the aspiration of fat through microcannulas. Although the recommended doses of lidocaine are as high as 55 mg per kilogram of body weight, few safety data are available. Since reporting of adverse events associated with tumescent liposuction is not mandatory, the incidence of complications and deaths is unknown. METHODS: We identified 5 deaths after tumescent liposuction among 48,527 deaths referred to the Office of Chief Medical Examiner of New York City between 1993 and 1998. The patients' records and postmortem examination results were reviewed to identify common contributory factors. RESULTS: The five patients had received lidocaine in doses ranging from 10 to 40 mg per kilogram. Other drugs, such as midazolam, were also administered. Three patients died as a result of precipitous intraoperative hypotension and bradycardia with no definitively identified cause. Postmortem blood lidocaine concentrations in two of the patients were 5.2 and 2 mg per liter. One patient died of fluid overload, and one died of deep venous thrombosis of calf veins with pulmonary thromboembolism after tumescent liposuction of the legs. CONCLUSIONS: Tumescent liposuction can be fatal, perhaps in part because of lidocaine toxicity or lidocaine-related drug interactions.

Adult↗
PubMed1996

Peptide design: crystal structure of a helical peptide module attached to a potentially nonhelical amino terminal segment.

The peptide Boc-Gly-Dpg-Gly-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe has been designed to examine the structural consequences of placing a short segment with a low helix propensity at the amino terminus of a helical heptapeptide module. The Gly-Dpg-Gly segment is a potential connecting element in the synthetic construction of a helix-linker-helix motif. Crystal parameters for the peptide are P21, a = 8.651 (3) A, b = 46.826 (13) A, c = 16.245 A, beta = 90.13 (3) degrees, Z = 4; 2 independent molecules/asymmetric unit. The structure reveals almost identical conformations for the two independent molecules. The backbone is completely helical for residues 2-9, with on 4 --> 1 hydrogen bond and six 5 --> 1 hydrogen bonds. The alpha, alpha-di-n-propylglycine residue adopts a helica conformation. Gly (1) adopts an extended conformation resulting in a nonhelical N-terminus, with the Boc group swinging away from the helix. the lateral association of helices in the beta axis direction is unusual in that the helix axes are directed up or down (parallel or antiparallel) by pairs: decrease decrease increase increase decrease decrease, etc.

Amino Acid Sequence↗
PubMed1996

Ehretianone, a novel quinonoid xanthene from Ehretia buxifolia with antisnake venom activity.

Ehretianone (1), a new quinonoid xanthene, together with known sterols, was isolated from a MeOH extract of the root bark of Ehretia buxifolia. The structure of ehretianone was elucidated as 7-hydroxy-9a alpha-(3-methylbut-2-enyl)-4a alpha,9 alpha-(2-methylprop-2-enyl)-4a, 9a-dihydro-1,4-dioxoxanthene on the basis of spectroscopic data and X-ray crystallographic analysis. The antisnake venom activity of ehretianone against Echis carinatus venom in mice is also reported.

Animals↗
PubMed1996

Conformation-activity correlations for chemotactic tripeptide analogs incorporating dialkyl residues with linear and cyclic alkyl sidechains at position 2.

Five stereochemically constrained analogs of the chemotactic tripeptide incorporating 1-aminocycloalkane-1-carboxylic acid (Ac(n)c) and alpha,alpha-dialkylglycines (Deg, diethylglycine; Dpg, n,n-dipropylglycine and Dbg, n,n-dibutylglycine) at position 2 have been synthesized. NMR studies of peptides For-Met-Xxx-Phe-OMe (Xxx=Ac(7)c, I; Ac(8)c, II; Deg, III; Dpg, IV and Dbg, V; For, formyl) establish that peptides with cycloalkyl residues, I and II, adopt folded beta-turn conformations in CDCl3 and (CD3)2SO. In contrast, analogs with linear alkyl sidechains, III-V, favour fully extended (C5) conformations in solution. Peptides I-V exhibit high activity in inducing beta-glucosaminidase release from rabbit neutrophils, with ED50 values ranging from 1.4-8.0 x 10(-11) M. In human neutrophils the Dxg peptides III-V have ED50 values ranging from 2.3 x 10(-8) to 5.9 x 10(-10) M, with the activity order being V > IV > III. While peptides I-IV are less active than the parent, For-Met-Leu-Phe-OH, in stimulating histamine release from human basophils, the Dbg peptide V is appreciably more potent, suggesting its potential utility as a probe for formyl peptide receptors.

Amino Acid Sequence↗
PubMed1996

Crystal structures of a nonapeptide helix containing alpha, alpha-di-n-butylglycine (Dbg), Boc-Gly-Dbg-Ala-Val-Ala-Leu-Aib-Val-Leu-OMe.

Two crystal structures of a nonapeptide (anhydrous and hydrated) containing the amino acid residue alpha, alpha-di-n-butylglycyl, reveal a mixed 3(10)-/alpha-helical conformation. Residues 1-7 adopt phi, psi values in the helical region, with Val(8) being appreciably distorted. The Dbg residue has phi, psi values of -40, -37 degrees and -46, -40 degrees in the two crystals with the two butyl side chains mostly extended in each. Peptide molecules in the crystals pack into helical columns. The crystal parameters are: C50H91N9O12, space group P2(1), with a = 9.789(1) A, b = 20.240(2) A, c = 15.998(3) A, beta = 103.27(1); Z = 2, R = 10.3% for 1945 data observed > 3 sigma (F) and C50H91N9O12.3H2O, space group P2(1), with a = 9.747(3) A, b = 21.002(8) A, c = 15.885(6) A, beta = 102.22(3) degrees, Z = 2, R = 13.6% for 2535 data observed > 3 sigma (F). The observation of a helical conformation at Dbg suggests that the higher homologs in the alpha, alpha-dialkylated glycine series also have a tendency to stabilize peptide helices.

Norleucine↗
PubMed1995

beta-turn conformations in crystal structures of model peptides containing alpha,alpha-di-n-propylglycine and alpha,alpha-di-n-butylglycine.

The crystal state conformations of three peptides containing the alpha,alpha-dialkylated residues, alpha,alpha-di-n-propylglycine (Dpg) and alpha,alpha-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Ala-OMe (I) and Boc-Ala-Dbg-Ala-OMe (II) adopt distorted type II beta-turn conformations with Ala (1) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: phi = 66.2 degrees, psi = 19.3 degrees; III: phi = 66.5 degrees, psi = 21.1 degrees) deviate appreciably from ideal values for the i + 2 residue in a type II beta-turn. In both peptides the observed (N...O) distances between the Boc CO and Ala (3) NH groups are far too long (I: 3.44 A; III: 3.63 A) for an intramolecular 4-->1 hydrogen bond. Boc-Ala-Dpg-Ala-NHMe (II) crystallizes with two independent molecules in the asymmetric unit. Both molecules IIA and IIB adopt consecutive beta-turn (type III-III in IIA and type III-I in IIB) or incipient 3(10)-helical structures, stabilized by two intramolecular 4-->1 hydrogen bonds. In all four molecules the bond angle N-C alpha-C' (tau) at the Dxg residues are > or = 110 degrees. The observation of conformational angles in the helical region of phi,psi space at these residues is consistent with theoretical predictions.

Amino Acid Sequence↗