PubMed Health⌕ Search

Biomedical subjects

H R Chaudhry

Publications and source records attributed to H R Chaudhry.

At least 19 recordsLinked to original sources
PubMed2001

Optimal patterns for suturing wounds of complex shapes to foster healing.

Stress is one of the many biological factors that plays an important role in wound healing. It is therefore essential to analyze stresses around the wound closure theoretically, especially when no invasive/noninvasive technique to measure stress directly is available. The objective of this paper is to determine the regions of high stresses and the optimal pattern of suturing wounds of complex shapes. It is hypothesized that the optimal pattern of suturing wounds is that pattern which will produce minimum principal stresses. The finite element method (FEM) employing the basic equations of elasticity theory for orthotropic materials is utilized to compute the principal stresses and displacements resulting from suturing fusiform, elliptical and triangular wounds in human abdominal skin. The optimal suturing pattern for the triangular wound is determined. The average stress indices for varying suturing density are also determined which can provide useful clinical information for the surgeon. Since regions of high stresses in surgical closures produce adverse affects on healing and scar production, this work of predicting areas of high stresses is useful in indicating regions of slow healing in wounds.

Compressive Strength↗
PubMed2000

Prolactin and beta-endorphin serum elevations after ECT in manic patients.

OBJECTIVE: Alterations in prolactin and beta-endorphin serum levels after ECT are well-established findings in depression. The present study focuses on electroconvulsive therapy (ECT) response patterns of the mentioned parameters in patients suffering from acute mania. METHOD: Following the first three ECTs of a treatment series in 19 patients diagnosed according to DSM-III-R criteria as suffering from mania, blood samples were drawn before, and 20, 30 and 40 minutes after ECT. Serum prolactin and beta-endorphin levels were established in order to gain information about the effects of ECT on different neurotransmitter systems. RESULTS: A significant transient increase in serum prolactin after ECT was found. Furthermore, in females but not males, delta(max)prolactin diminished over the course of treatment as prolactin baseline levels increased. beta-endorphin levels showed a stable transient increase after ECT stimulus regardless from sex or treatment. CONCLUSION: The reported findings reflect those established in depression. This suggests that they are epiphenomenal to ECT.

Acute Disease↗
PubMed1999

Adaptation of passive rat left ventricle in diastolic dysfunction.

This article deals with providing a theoretical explanation for quantitative changes in the geometry, the opening angle and the deformation parameters of the rat ventricular wall during adaptation of the passive left ventricle in diastolic dysfunction. A large deformation theory is applied to analyse transmural stress and strain distribution in the left ventricular wall considering it to be made of homogeneous, incompressible, transversely isotropic, non-linear elastic material. The basic assumptions made for computing stress distributions are that the average circumferential stress and strain for the adaptive ventricle is equal to the average circumferential stress and strain in the normotensive ventricle, respectively. All the relevant parameters, such as opening angle, twist per unit length, axial extension, internal and external radii and others, in the stress-free, unloaded and loaded states of normotensive, hypertensive and adaptive left ventricle are determined. The circumferential stress and strain distribution through the ventricular wall are also computed. Our analysis predicts that during adaptation, wall thickness and wall mass of the ventricle increase. These results are consistent with experimental findings and are the indications of initiation of congestive heart failure.

Adaptation, Physiological↗
PubMed1999

Dopamine D3 receptor gene polymorphism and response to clozapine in schizophrenic Pakastani patients.

The dopamine D3 receptor (DRD3) appears to play an important role in the mediation of antipsychotic drug action. Genetic association of treatment response to the atypical antipsychotic drug clozapine with the DRD3 polymorphism Ser9Gly was investigated in a sample of 32 schizophrenic patients. We found association of treatment response with allele Gly-9 (P=0.0058) and with genotypes consisting of Gly-9 (P=0.033) by this pharmacogenetic approach. A combined analysis with two previous studies (Shaikh et al., Hum. Genet. 97 (1996) 714-719; Malhotra et al., Mol. Psychiatry 3 (1998) 72-75) further substantiates these results (P=0.0041).

Adult↗
PubMed1998

Evaluation of residual stress in rabbit skin and the relevant material constants.

Material constants are needed in order to evaluate stresses. The material constants for orthotropic rabbit skin when residual stresses are eliminated, have been evaluated by Tong & Fung [(1976). J. Biomechanics 9, 649-657]. It is well documented that a circular skin sample taken from the human body becomes elliptical in shape. Thus, it is clear that there are residual stresses in human skin which need to be taken into consideration when evaluating the material constants. In this paper, we therefore evaluate the material constants for rabbit skin taking into account residual stresses.

Animals↗
PubMed1998

Optimal patterns for suturing wounds.

A mathematical model for computing stresses in sutured human skin wounds is presented. The model uses the incremental law of elasticity and elastic constants valid for in vivo orthotropic skin. The model is applied to compute the principal stress and displacements resulting from suturing small elliptical and circular wounds in a large flat sheet of skin, in order to determine the optimal suturing patterns. It is observed that the average stress index for a circular wound sutured toward the center is almost double that of a wound sutured transverse to the diameter. Thus, the latter type of suturing pattern is preferable. Similarly, suturing an elliptical wound transversely produces a lower average stress index than a circular wound of the same area. It is also found that the optimal ratio of semi-major to semi-minor axis of an elliptical wound is near 3 (for abdominal wounds), i.e., this ratio produces the most uniform stresses along the wound edges, where wound healing is slowest. Since high stresses have adverse effects on healing and blood flow, this work, depicting regions of high stresses, may be used along with other biological factors to help predict regions of slower healing in sutured wounds.

Algorithms↗
PubMed1997

Residual stresses in oscillating thoracic arteries reduce circumferential stresses and stress gradients.

The purpose of this paper is to examine the effects of residual stresses and strains in the oscillating arteries on the stress distribution in the vascular wall. We employ a static theory of large elastic deformations for orthotropic material (Chuong and Fung, 1986, J. biomech. Engng 108, 189-192) with the acceleration term added to make the theory dynamic. We use the static elastic parameters of residual stresses in our analysis because the dynamic parameters are not available in the literature. Our analysis reveals that the effect of considering the residual stresses is to decrease the very large circumferential stresses at the inner wall by 62% and reduces the stress gradient through the arterial wall by 94% compared to the case when residual stresses are ignored. Thus, because the arteries do contain residual stresses, the consequent lower stresses at the inner wall and the reduced stress gradient may reduce the progression of atheroma. Our computations show that the stress gradients do not depend on the heart rate.

Animals↗
PubMed1994

Risk factors for drug misuse in Pakistan.

While a number of risk factors have been identified for drug misuse in the United States, little evidence is available about such factors in other societies. This study attempted to identify risk factors in Pakistan. Ten of 11 sociodemographic variables which had previously been identified as predictors in the United States successfully differentiated groups of addicts and controls in Pakistan. About 97% of the 60 addicts studied were at risk on four or more factors; 100% of controls were at risk on four or fewer factors. It appears that the precursors for misuse cut across cultural lines.

Adolescent↗
PubMed1994

Nasal administration of naloxone is as effective as the intravenous route in opiate addicts.

Naloxone is used intravenously in opiate addiction in emergency cases, in rapid opiate detoxification, and as a diagnostic tool. This is a study comparing the efficacy of intranasal naloxone to other routes (intravenous/intramuscular) in 17 opiate-dependent patients. The nasal drug administration of naloxone was found to be as effective as the intravenous route. The nasal drug application offers a wide margin of safety for patients and medical staff, especially in emergency situations in regard to infection risks associated with vessel puncture.

Administration, Intranasal↗
PubMed1992

Midazolam shortens seizure duration following electroconvulsive therapy.

In an open, prospective clinical trial, midazolam anaesthesia was compared with thiopental (plus suxamethonium chloride as a muscle relaxant) to clinically evaluate the former as an anaesthetic and a muscle relaxant during electroconvulsive therapy (ECT). Twelve depressed patients underwent a course of ECT, receiving midazolam or thiopental anaesthesia alternatively. Significant differences were found in seizure duration between the two anaesthetics. Midazolam shortened the seizures to a duration that was not therapeutically desirable. There were no differences in stimulus parameters between the two groups. The muscle relaxant effect of midazolam failed to provide optimal paralysis. Thus, midazolam anaesthesia offers no advantage over standard anaesthetic agents for ECT.

Adult↗
PubMed1992

Nasal administration of naloxone for detection of opiate dependence.

In clinical trials, nasally applied naloxone was used to identify opiate dependence in humans for the first time. Withdrawal distress was recorded, and pupillary response, pulse rate and blood pressure measured. A significant increase in withdrawal distress and pupillary dilation was observed after nasal administration of 1mg (1mg/400 microliters) naloxone in all subjects who also showed opiate-positive urine samples. In control subjects, no reaction to naloxone was observed. It may be concluded that the nasal route for naloxone administration is as effective as the parenteral route. This test is sensitive enough to identify the physically-dependent opiate user and might have a role in emergency medicine and withdrawal treatment.

Administration, Intranasal↗
PubMed1992

Diagnostic value of electroencephalography in arteriovenous malformations.

Arteriovenous malformations (AVM) are usually located superficially in the subcortical white matter, and seizures are one of the frequently seen presenting features of AVM. The diagnosis of AVM is confirmed with various neuroimaging techniques. The present study comprised six patients presenting with seizures and headaches, referred to the neurodiagnostic unit to rule out/confirm epilepsy. All patients showed epileptiform activity on electroencephalography (EEG). Further investigations, such as angiography supplemented with computed tomography (CT) showed AVM. EEG is usually not considered a valuable diagnostic tool in AVM, but our results support the finding that EEG is an extremely reliable investigative tool, and should be supplemented with angiography and CT scan for better localization of AVM.

Adult↗
PubMed1991

Familial history of opium use and reported problems among opium addicts in Pakistan.

One-hundred and twenty-nine opiate addicts on a monthly maintenance regimen were studied. Subjects with a positive family history of opium use had an earlier age of onset than the subjects without a family history of opium use. Self-reported psychosocial problems resulting from opium use were documented in only seven subjects. Individuals who began opium use after 1979, when it became illegal to use the drug, had a significantly later age of onset than subjects who began before 1979, suggesting that negative legal sanctions can delay initiation of opium consumption.

Adult↗