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Biomedical subjects

F Khan

Publications and source records attributed to F Khan.

At least 145 records · Page 8Linked to original sources
PubMed1992

Cutaneous vascular responses and thermoregulation in relation to age.

1. Sympathetic vasoconstrictor responses to inspiratory gasp and contralateral arm cold challenge were assessed in fingertip skin in relation to age and were correlated with vasoconstrictor ability during body cooling. The above relationship was also examined in diabetic patients in whom vasoconstrictor responses to inspiratory gasp and contralateral arm cold challenge had been shown previously to be markedly impaired. 2. Vasoconstrictor responses to inspiratory gasp and contralateral arm cold challenge, measured by laser Doppler flowmetry, were significantly reduced in the elderly group, although individual responses varied from normal to absent, and they also had a considerably greater variability as measured on three separate occasions than seen in young subjects. Discriminant analysis showed that, from each of three occasions, 65% of vasoconstrictor responses were abnormal in the elderly group. 3. Body cooling was performed by reducing the environmental temperature from 40 degrees C to 12 degrees C, and the time taken for blood flow to fall to 75%, 50% and 25% of the pre-cooling level (VC75, VC50, VC25, respectively) was calculated. Vasoconstriction was rapid in young subjects and was consistent with good vasoconstrictor responses to inspiratory gasp and contralateral arm cold challenge. In the elderly group, vasoconstriction was slower, but only the VC25 value differed significantly [elderly group, 13.3 (7.9-31.0) min, young group, 5.7 (2.7-15.5) min; median (interquartile range); P less than 0.05].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

A comparison of upper gastrointestinal mucosal damage by standard and delayed-release indomethacin.

Forty-five patients taking long-term indomethacin and with endoscopic erosions or superficial ulcers in the oesophagus, stomach or duodenal bulb were randomized in a double-blind study to continue with standard indomethacin or receive a 'delayed-release' formulation. This consisted of microgranules of indomethacin coated with an acrylic resin, Eudragit L, which releases drug in the small intestine. Endoscopy was repeated after 8 weeks and biopsies taken on both occasions. Changes in endoscopic lesions and histological appearances were similar in both groups, although mucosal erythema was less in those given Eudragit L indomethacin. Systemic, rather than topical, effects of indomethacin may therefore be responsible for persistence of gastro-duodenal mucosal lesions in these patients. There is reason to question the clinical practice of using expensive, delayed-release preparations.

Adult↗
PubMed1992

Risk of ulceration with long-term indomethacin: endoscopic and histological changes in upper gastro-intestinal mucosa.

Twenty patients taking long-term indomethacin were chosen for the study because all had a normal endoscopic examination; biopsies, however, from the oesophagus, gastric antrum and duodenal bulb revealed histological inflammation in all patients in at least one site. After 8 weeks during which indomethacin therapy was continued, a further endoscopy revealed lesions in 5 patients--peptic ulcer in 3 and erosions in 2--but only 1 of these had any change in gastro-intestinal symptoms. Irrespective of whether mucosal lesions are seen on endoscopy in patients established on non-steroidal anti-inflammatory drug therapy, they remain in danger of developing both ulcers and erosions which are likely to be asymptomatic. At no time can one justifiably feel this patient group is not at risk of peptic ulceration.

Arthritis, Rheumatoid↗
PubMed1992

The effects of unilateral and multifocal lesions on the WAIS-R: a factor analytic study of stroke patients.

An exploratory maximum likelihood factor analysis of the inter-correlations among the 11 subtests of the WAIS-R was undertaken for 167 patients who had a primary diagnoses of cerebrovascular accident (right hemisphere, n = 79; left hemisphere, n = 55; diffuse or multifocal, n = 33). On the WAIS-R, this sample performed below normative standards (average scaled score = 7.1), but demonstrated a pattern of variability among subtests similar to the normative groups. Interestingly, VIQ-PIQ discrepancy analyses revealed V > P profiles for patients with lesions in either or both hemispheres. The best fit for the WAIS-R matrix was an oblique two-factor model comprised of the Verbal and Performance subtests. This factor solution, which was moderately correlated (.52), accounted for 58.8% of the total variance. The stability of a two-factor structure in this neurologic impaired population suggests that the WAIS-R is a robust measure, even when used within such a rehabilitation population. Only two of the eleven subtests (i.e., Comprehension and Picture Arrangement), however, were related to lesion site. Rehabilitation settings may need to rely more on neuropsychological procedures that measure the more "fluid" areas of neurocognitive ability, in contrast to the WAIS-R which appears less sensitive to the neurological impairment associated with stroke.

Journal Article↗
PubMed1991

The effects of thromboxane receptor blockade on platelet aggregation and digital skin blood flow in patients with secondary Raynaud's syndrome.

Raynaud's syndrome (RS) is characterized by intense blood vessel spasm resulting in finger blanching. Treatment primarily involves vasodilation. Thromboxane A2 (TXA2) has been shown to be a potent vasoconstrictor and platelet aggregant. It may be possible to produce a vasodilatory and anti-thrombotic effect by blockade of the TXA2 receptors. ICI 192,605 is a potent TXA2 receptor antagonist and we studied its effects on platelet aggregation and digital blood flow in patients with RS. Sixteen patients with RS completed this double-blind, randomized, placebo controlled study. Each patient was seen on three separate occasions and was given ICI 192,605 (100 mg orally) on one occasion and matching placebo tablets on the other two. We measured platelet aggregation using platelet rich plasma (PRP) stimulated by U46619, a thromboxane (TX) mimetic. The concentration of U46619 required to cause just over 50% platelet aggregation before the administration of either ICI 192,605 or placebo (pre-dose) was noted. The same concentration of U46619 was used to stimulate the PRP sample at 1 h after the administration of ICI 192,605 or placebo (post-dose) and the percentage of platelet aggregation was again noted. Fingertip skin blood flow was also measured 1.25 h post-dose using a laser Doppler flowmeter. Patients were seated in a temperature controlled chamber which was initially heated to 40 degrees C to induce centrally mediated vasodilatation. The temperature was then lowered to 12 degrees C followed by rewarming to 40 degrees C. Steady blood flow values at these temperatures were measured and the rates of cooling and rewarming were also noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Optical model description of momentum transfer in relativistic heavy ion collisions.

An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple-scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is shown to be the main contributor to the momentum loss of the projectile. Within the context of the Goldhaber formalism, predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is also discussed.

Ions↗
PubMed1991

Calculations of hadronic dissociation of 28Si projectiles at 14.6A GeV by nucleon emission.

An optical potential abrasion-ablation collision model is used to calculate hadronic dissociation cross sections for one, two, and three nucleon removal for the first time for a 14.6A GeV 28Si beam fragmenting in aluminum, tin, and lead targets. These estimates are compared with recent semi-inclusive measurements. Significant differences between some calculated and measured semi-inclusive cross sections exist which cannot be resolved without measurements of the exclusive channel hadronic cross sections. Calculations for each exclusive reaction channel contributing to the semi-inclusive cross sections are presented and discussed.

Aluminum↗
PubMed1991

Momentum transfer in relativistic heavy ion charge-exchange reactions.

Relativistic heavy ion charge-exchange reactions yield fragments (delta Z = +1) whose longitudinal momentum distributions are downshifted by larger values than those associated with the remaining fragments (delta Z = -1, -2, ...). Kinematics alone cannot account for the observed downshifts; therefore, an additional contribution from collision dynamics must be included. In this work, an optical model description of collision momentum transfer is used to estimate the additional dynamical momentum downshift. Good agreement between theoretical estimates and experimental data is obtained.

Ions↗
PubMed1991

Impairment of vasomotor reflexes in the fingertips of leprosy patients.

A method is described for eliciting fingertip vasomotor reflexes by inspiratory gasp and contralateral hand cold challenge. The results of the two tests are reproducible on replicate testing and, when taken together, have proved reliable for detection of impairment of autonomic reflexes in 10 newly registered leprosy patients who did not have any obvious deformity. Similar, but less severe, impairment of vasomotor reflexes was noted in a group of 10 fully treated, apparently cured ex-leprosy patients, none of whom showed clinically obvious neuropathy. Both the new patients and the ex-patients were significantly different from healthy contacts and from healthy Europeans, who were indistinguishable by this test. Evidence is presented suggesting that impairment of these vasomotor reflexes is mainly due to damage to the efferent pathway in the peripheral nerves. The method might prove valuable for investigation of early nerve damage in new patients or during reversal reactions in leprosy at a stage before irreversible damage is done.

Adult↗
PubMed1991

Pilonidal sinus in an amputee.

A pilonidal sinus developed in the superio-medial aspect of the thigh of an above-knee amputee. This is an unusual site for the condition to develop. We suggest that the same aetiological factors that were responsible for the "Jeep Bottom" of World War II were also responsible for this problem in the amputation stump of a Falklands campaign casualty.

Adult↗
PubMed1991

The effect of oxygen supplementation on post-occlusive reactive hyperaemia in human forearm skin.

The effects of raised tissue oxygen levels on reactive hyperaemia (RH) in the skin following arterial occlusion of short duration were investigated. Oxygen levels were increased by breathing 100% oxygen at 1 and 2 atmospheres absolute (ATA) in a hyperbaric chamber. Superficial skin blood flow and oxygen tension were measured throughout using a laser Doppler flowmeter and a transcutaneous oxygen monitor. The basal pre-occlusion and the maximum post-occlusion blood flows (Flb and Flmax), the time taken for flow to fall to half maximum (TR1/2), and the time for flow to return to its basal level (TR) were measured. Pre- and end-occlusion transcutaneous oxygen levels were also recorded. Oxygen breathing at 1 ATA significantly reduced TR1/2 (p less than 0.05) and at 2 ATA significantly reduced TR1/2 and TR (p less than 0.005 and p less than 0.0001) compared with control measurements during air breathing at 1 ATA. Flmax was not significantly reduced breathing oxygen at 1 or 2 ATA. These findings support the view that maximum post-occlusion blood flow in superficial skin is determined mainly by myogenic mechanisms, whereas the recovery of blood flow to basal levels is influenced largely by oxygen tension. We conclude that the direct vasoconstrictor effect of high oxygen levels is small and that the faster recovery at high tissue oxygen tensions may result from a decrease in vasodilators formed during hypoxia.

Adult↗
PubMed1991

Quantification of sympathetic vascular responses in skin by laser Doppler flowmetry.

An improved physiological test of focal sympathetic nervous function using a laser Doppler flowmeter is presented. The test evaluates rapid reflex changes in skin blood flow at the finger tip where there are abundant arteriovenous anastomoses with dense sympathetic innervation. Indirect body heating was employed in all subjects to induce central vasodilation and to obtain stable comparable finger tip blood flows prior to stimulus. The reflex vasoconstriction which occurs following inspiratory gasp and contralateral hand cold challenge was quantified and its reproducibility investigated on three separate occasions in 20 young subjects. The variability in responses both within and between young subjects was small. The test was applied to 10 diabetic patients with autonomic neuropathy and to 10 age-matched control subjects. Vasoconstrictor reflexes were significantly lower in the diabetic group (p less than 0.005) with responses lower than 2 SD from the mean for age-matched controls. In conclusion, the test provides an assessment of focal autonomic damage which can be applied to other regions of the body rich in arteriovenous anastomoses and may have application in clinical studies investigating autonomic activity.

Adult↗
PubMed1990

Moments of dipole oscillator-strength distribution for the helium sequence.

The moments S(mu) for -6 < or = mu < or = 2 and L(mu) for mu = 0, 1 and 2 are calculated for the helium sequence for atomic numbers Z up to 30 under a screened hydrogenic model. In this model, one describes the atom by single-particle hydrogenic wavefunctions and treats the initial and the final state as characterised by two different effective charge parameters Zi and Zf, respectively. An asymptotic expansion is made of the differential oscillator strength of the screened hydrogenic model. Assuming the value 287.6 for the coefficient of the term epsilon -7/2 for helium atom as given by Salpeter and Zaidi, the parameter Zf is determined for the helium sequence. This approach has resulted in values which are in reasonable agreement with the various moment values of other authors.

Helium↗
PubMed1990

Pattern of acute myocardial infarction in a district hospital in Brunei Darussalam--a pilot study.

The objective of the authors was to study the pattern of presentation, risk factors, and natural course of acute myocardial infarction in the general population of Belait District in Brunei Darussalam. A prospective study was done of 100 consecutive cases of acute myocardial infarction admitted to the coronary care beds of a District General Hospital. The patients were followed up to 12 weeks after admission to hospital. There were three times more males than females (75 males, 25 females). Nine cases out of 75 males were below the age of 40 years, 3 being below 30 years. The mean age of the male denominator was 57.4 years while that of the female counterpart was 67.48 years showing a mean difference of 10.08 years. There were significant association with hypertension (31%), smoking (30%) and diabetes mellitus (27%). The majority of the patients had prodromal symptoms, the most common presenting symptoms were chest pain (63%) and shortness of breath (27%). Only 4% of the patients had silent infarction. Acute myocardial infarction is common in Brunei forming 2.6% of all the patients admitted to the medical wards and the relative rate is 3 times higher in males than in females. There is significant association of IHD with 3 main risk factors namely hypertension, smoking and diabetes mellitus.

Adult↗
PubMed1989

Screened hydrogenic radial integrals.

The screened hydrogenic radial integral both for discrete-discrete and discrete-continuum transitions is expressed in forms suitable for obtaining closed-form expressions for specific transitions. Two effective charge parameters Zi and Zf, respectively, for the initial state and for the final state are retained in these formulas. As examples, explicit expressions for a few transitions are derived and a method for obtaining a series for a discrete-discrete radial integral, suitable for large final-state principal quantum numbers, is indicated.

Electrons↗