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Biomedical subjects

F Khan

Publications and source records attributed to F Khan.

At least 127 records · Page 7Linked to original sources
PubMed1995

Digital blood flow response to body warming, cooling, and rewarming in patients with Raynaud's phenomenon.

Although the diagnosis of Raynaud's phenomenon (RP) is usually made easily from a careful history, the assessment of RP severity is difficult, for the vasopastic attacks are not easily induced under experimental conditions. In this study, the laser Doppler flowmetry (LDF) technique was used to quantify digital blood flow, which was standardized by body cooling and warming in patients with RP. Twenty-one healthy subjects and 56 RP patients were studied: 7 had primary RP, 22 had suspected secondary Raynaud's syndrome (susp RS), and 27 had systemic sclerosis (SSc)-associated secondary Raynaud's syndrome (SSc RS). The inherent variability in the acral cutaneous circulation was minimized by whole-body warming and cooling. Digital blood flow values at environmental temperatures of 40 degrees C, 12 degrees C, and after rewarming, to 40 degrees C were recorded, as was the time taken for blood flow to reach 25%, 50%, and 75% of the full effects of whole-body cooling and rewarming. Patients with primary RP and susp RS had normal blood flow values at ambient temperatures of 40 degrees C, 12 degrees C, and after rewarming to 40 degrees C when compared with controls, but they had significantly faster vasoconstrictor responses to whole-body cooling, suggesting a heightened sympathetic activity. Additionally, they had slower vasodilator responses with longer 25%max response time to whole-body rewarming. Patients with SSc RS had significantly lower blood flow values at 40 degrees C after initial warming and following subsequent rewarming, and despite a normal vasoconstrictor response to cooling, it took longer for them to vasodilate during rewarming, suggesting that poor digital blood flow in these patients may be more related to digital vasculature abnormalities and not an increase in sympathetic activity. In conclusion, our assessment technique can be used to quantify digital blood flow in patients with RP and may be potentially useful in the investigation of the etiologic role of the sympathetic nervous system in RP.

Adult↗
PubMed1994

Quality assurance in radiation oncology.

Quality assurance in radiation oncology attempts to prescribe consistent, safe, and optimal delivery of radiation to treat disease. It encompasses three major areas of treatment: clinical, physical, and technical. Although national approaches and guidelines of quality assurance in radiation oncology are available, they usually are not adequate to deal with the particular needs of individual institutions, nor are they adequate to ensure uniform standards of diagnosis and treatment among institutions. Therefore, it is important for individual institutions to develop and implement strict quality assurance standards, based on national guidelines as well as their own strengths and needs, to ensure that patients receive the highest quality of radiotherapy and that the successes and failures of treatment are statistically reliable. This paper addresses the importance of quality assurance in radiation oncology and examines the quality assurance program in the Department of Therapeutic Radiology-Radiation Oncology at the University of Minnesota as an example of a program tailored to the needs of an individual institution.

Breast Neoplasms↗
PubMed1994

Refinement of the DNA marker maps of mouse chromosome 12.

To refine the linkage map of mouse Chromosome (Chr) 12 and to define better the homology relationships between it and human chrs 2p and 14q, nine new anonymous DNA markers of Chr 12 were identified, and mouse loci homologous to the human D14S17, CHGA, HSPA2, RRM2, TPO, and ZFP50 ("KUP") genes were defined. The inheritance of DNA variants associated with these markers was followed in progeny of a reciprocal backcross between the C57BL/6J and SWR/J laboratory mouse strains and in recombinant inbred (RI) strains of mice. These data, combined with results of previous analyses of the backcross, allowed the construction of a 22-marker multilocus linkage map that spanned 58 cM. Use of this map to anchor the RI typing data collected in this and previous studies allowed the construction of a 79-marker map that spanned 66 cM and the identification of a framework of unambiguously ordered, extensively typed markers that should facilitate the use of RI mice in testing new markers for possible linkage to Chr 12.

Animals↗
PubMed1994

Acute myeloid leukemia in patients treated for rhabdomyosarcoma with cyclophosphamide and low-dose etoposide on Intergroup Rhabdomyosarcoma Study III: an interim report.

The early occurrence of five cases of acute myeloid leukemia (AML) in children treated for primary rhabdomyosarcoma on the Intergroup Rhabdomyosarcoma Study III (IRS III) has prompted this report. These patients received cyclophosphamide and four received etoposide in addition to other agents. There were 1,062 eligible patients entered on IRS III between 1984 and 1991. Following surgery, treatment consisted of multiagent chemotherapy and radiotherapy in select clinical groups. Median follow-up time is 3.7 years (range 0-7.4 years). Incidence densities and odds ratios for AML were calculated for various treatment groups. Five cases of secondary AML have been reported through August 1992. A single case of osteogenic sarcoma was reported in the same period and a patient with myelodysplastic syndrome has occurred since that time. Median time to development of AML was 39 months. Incidence density of AML for patients receiving neither cyclophosphamide nor etoposide was 0, for those receiving cyclophosphamide but no etoposide it was 7.6, and when both agents were given, it was 51.6. The odds ratios of AML for the latter two groups indicated a risk of AML which was seven times higher in the patients who received both agents. A history of breast cancer was present in all five families of patients with AML and several other cancers had occurred in three families. Preliminary analysis suggests a possible causal role for low-dose etoposide in addition to that assumed for cyclophosphamide in the early development of AML among pediatric patients treated for rhabdomyosarcoma.

Adolescent↗
PubMed1994

Role of intrinsic width in fragment momentum distributions in heavy ion collisions.

It is demonstrated that the intrinsic widths incorporating correlations in conjunction with dynamical contributions give better agreement with experiments for collisions in the energy range of 200A MeV to 2A GeV than using only intrinsic widths without correlations. The sensitivity of the intrinsic width decreases with increasing projectile mass. A simple recipe for calculating intrinsic width with correlations is presented.

Argon↗
PubMed1994

Molecular analysis of rRNA and cholera toxin genes carried by the new epidemic strain of toxigenic Vibrio cholerae O139 synonym Bengal.

Vibrio cholerae O139 synonym Bengal recently caused large epidemics of cholera-like disease in Bangladesh and India. We compared the restriction fragment length polymorphisms of ctxA and rRNA genes (ribotypes) in 27 isolates of V. cholerae O139 from patients in Bangladesh and India with those of 48 isolates of V. cholerae O1 from patients and 21 V. cholerae isolates from surface waters in Bangladesh, which included 2 O139 and 19 other non-O1 isolates. Ribotyping of the isolates with BglI revealed that all 29 isolates of O139 vibrios belonged to a single ribotype, suggesting a clonal nature of the infection. However, the O139 vibrios comprised two ctxA genotypes and carried three or more copies of the ctxA gene, and the chromosomal locations of these copies were unlike those of the El Tor or classical vibrios. Analysis of the restriction fragment length polymorphisms of the rRNA genes suggested that V. cholerae O139 isolates are more closely related to El Tor strains of V. cholerae O1 than were 19 other non-O1 vibrios and 33 classical V. cholerae O1 isolates that were studied. However, further studies are needed to determine whether V. cholerae O139 originated from mutations and genetic changes in a V. cholerae O1 strain or was due to the acquisition of virulence genes by a previously unknown V. cholerae non-O1 strain.

Bacterial Typing Techniques↗
PubMed1994

Enhanced cholinergic cutaneous vasodilation in Raynaud's phenomenon.

BACKGROUND: Vasodilator function was determined in patients with Raynaud's phenomenon during intra-arterial infusions of the endothelium-dependent and -independent vasodilators, methacholine and sodium nitroprusside, respectively. Reactive hyperemia, induced by 5 minutes of arterial occlusion with exercise, was also measured. METHODS AND RESULTS: Total blood flow was measured in the fingertip and forearm by venous occlusion plethysmography, and blood flow in the forearm skin was determined with laser Doppler flowmetry. Basal fingertip blood flow was not significantly different between control subjects and patients with Raynaud's phenomenon. Infusions of methacholine had no significant effect on fingertip blood flow in control subjects, whereas patients with Raynaud's phenomenon showed a significant increase in fingertip blood flow. Basal total forearm blood flow was significantly lower in patients with Raynaud's phenomenon than in control subjects. Infusions of methacholine and sodium nitroprusside produced dose-related increases in total forearm blood flow that were of similar magnitudes in the two groups, as were the reactive hyperemic responses. Laser Doppler measurements of forearm skin blood flow, however, showed a significantly greater vasodilator response to methacholine in patients with Raynaud's phenomenon than in control subjects. Infusions of sodium nitroprusside produced a relatively small vasodilator response in the skin of the forearm that was smaller than that to methacholine and not significantly different between the two groups. CONCLUSIONS: In Raynaud's phenomenon, a greater vasodilator response to infusions of methacholine in the fingertip, where changes in blood flow mainly reflect those of skin, and in the skin of the forearm may reflect increased responsiveness of cutaneous blood vessels to stimulation of the endothelium. The mechanism involved is unclear but may result from a general abnormality of blood vessels in the skin, which is related to the pathophysiology of cutaneous vasospasm.

Adult↗
PubMed1994

Renal toxicity of ifosfamide in pilot regimens of the intergroup rhabdomyosarcoma study for patients with gross residual tumor.

PURPOSE: The purpose of this review is to characterize the nephrotoxicity noted in newly diagnosed patients under 21 years of age after treatment with ifosfamide-containing chemotherapy regimens and local irradiation for localized gross residual rhabdomyosarcoma or undifferentiated sarcoma. PATIENTS AND METHODS: From 1987 to 1991, 194 previously untreated patients received vincristine and ifosfamide plus dactinomycin or etoposide for 1-2 years. Ifosfamide was given at 1.8 g/m2/day for 5 days with sodium mercaptoethane sulfonate, or 9 g/m2 of ifosfamide per course. The three-drug regimen was repeated every 3-4 weeks. RESULTS: Twenty-eight patients (14%) developed renal toxicity: 19 had renal tubular dysfunction (RTD) characterized by low serum phosphate (< or = 3 mg/dl) or bicarbonate (< 20 or = mEq/L) levels, five had decreased glomerular function (DGF), and four had both RTD and DGF. When nine or more courses of ifosfamide (> 72 g/m2) were given, children < 3 years of age had a higher incidence of RTD than did children > or = 3 years of age (34% versus 6%; p < 0.001). A similar age difference was observed even when eight or fewer courses (< or = 72 g/m2) were given (p = 0.03). A matched case-control comparison showed that renal abnormalities at diagnosis, chiefly hydronephrosis, also increased the risk of renal tubular injury by ifosfamide by a factor of 13 (p < 0.001). Patients with DGF tended to be older than those with RTD, and all but one received > 72 g/m2 of ifosfamide. CONCLUSIONS: Patients who are < 3 years of age who receive more than eight courses (> 72 g/m2) of ifosfamide and who have a preexisting renal abnormality have an increased risk of RTD and DGF. The renal function of patients being considered for ifosfamide treatment must be carefully monitored. Ifosfamide should be avoided in patients with renal abnormalities at diagnosis unless the potential benefit clearly exceeds the risk of further renal impairment.

Acute Kidney Injury↗
PubMed1993

Vasomotor reflexes in the fingertip skin of patients with type 1 diabetes mellitus and leprosy.

Fingertip skin blood flow was measured by laser Doppler flowmetry (as LDflux) under environmental conditions promoting vasodilation in Scottish patients with diabetes mellitus and Indian patients with leprosy. The reflex control of fingertip blood flow was assessed by measuring the reduction in LDflux induced by deep inspiratory gasp (IG) and cold challenge (CC) of immersing the contralateral hand in cold water. The uncomplicated diabetic patients showed normal vasomotor reflexes and an increased, though non significant, LDflux level (p < 0.06). The patients with diabetic neuropathy had resting LDflux levels significantly less than the uncomplicated group and also had substantial impairment of both IG and CC reflexes. Those with retinopathy (but no clinically apparent neuropathy) had LDflux within the normal range, but they showed minor evidence of impairment of the vasomotor reflexes. The uncomplicated newly registered leprosy patients had reduced LDflux and substantial impairment of CC reflexes. These changes were more marked in newly registered leprosy patients with clinical evidence of neuropathy. Leprosy patients with long-standing neuropathy requiring orthopaedic treatment had LDfluxes so greatly reduced that measurement of vasomotor reflexes was not practicable. The CC reflex was more severely affected than the IG reflex and more frequently absent in leprosy patients, possibly because of associated sensory neuropathy affecting the afferent limb of this response. Thus laser Doppler flowmetry can detect impairment of reflex control of fingertip blood flow in both diabetes mellitus and leprosy, but there are functional differences in the pattern of autonomic impairment between the diseases, suggesting differences in the pathogenesis of nerve damage.

Adult↗
PubMed1993

Chronic inhibition of nitric oxide production augments skin vasoconstriction in the rabbit ear.

The effect of chronic inhibition of nitric oxide (NO) synthesis by NG-nitro-L-arginine methyl ester (L-NAME) on cutaneous ear blood flow (EBF) in the rabbit was examined in vivo with use of laser Doppler flowmetry. Additionally, the efficacy of inhibition of NO by L-NAME was studied ex vivo in isolated preparations of aortic rings from these rabbits. Before surgical implantation of osmotic pumps loaded with L-NAME, resting EBF was not significantly different in rabbits selected for control or L-NAME treatment. Although chronic L-NAME treatment had no significant effect on resting core temperature, resting EBF was reduced significantly in L-NAME-treated rabbits as compared with EBF in control rabbits. Short-term body warming for 10-20 min caused a significant increase in EBF, but not in body temperature, to levels that were not significantly different between groups at 0, 1 and 2 weeks. Prolonged body warming for a further 30-40 min produced a rise in body temperature and a further increase in EBF of 22% to levels that were not significantly different in control and L-NAME-treated groups. Acetylcholine-induced relaxations of aortic rings and levels of cyclic GMP were significantly reduced in L-NAME-treated rabbits as compared with control rabbits, whereas relaxations to sodium nitroprusside were enhanced significantly. These findings demonstrate that the synthesis of NO can be inhibited chronically in the rabbit and are consistent with the concept that NO participates in the control of skin blood flow by counteracting vasoconstrictor tone but not in the vasodilation induced by body warming.

Acetylcholine↗
PubMed1993

Optical model analyses of 1.65 A GeV argon fragmentation: cross sections and momentum distributions.

An optical potential fragmentation model capable of predicting fragmentation cross sections and fragment momentum distributions is used to analyze recent measurements of 1.65 A GeV argon projectiles fragmenting in carbon and potassium-chloride targets obtained with the Heavy Ion Spectrometer System (HISS) at the Lawrence Berkeley Laboratory Bevalac. The theoretical model uses an abrasion-ablation-FSI (frictional spectator interaction) collision formalism to estimate elemental and isotopic production cross sections for comparison with the measured values. The collision momentum transfer model is incorporated into a Goldhaber formalism to analyze measured transverse and longitudinal distributions of the projectile fragments. Good agreement between theory and experiment is obtained for all observables.

Argon↗
PubMed1993

Universal characteristics of transverse momentum transfer in intermediate energy heavy ion collisions.

A microscopic optical model formalism for estimating momentum transfer in intermediate energy heavy ion collisions predicts universal behavior of the transverse component. In particular, for symmetric systems (Ap = AT) heavier than niobium, it appears that values of P perpendicular/A are independent of the mass and charge of the colliding nuclei and vary only with impact parameter and incident beam energy. This suggests that momentum transfer per nucleon saturates to some limiting value with increasing mass.

Calcium↗
PubMed1993

Widths of transverse momentum distributions in intermediate-energy heavy-ion collisions.

The need to include dynamical collision momentum transfer contributions, arising from interacting nuclear and Coulomb fields, to estimates of fragment momentum distributions is discussed. Methods based upon an optical potential model are presented. Comparisons with recent experimental data of the Siegen group for variances of transverse momentum distributions for gold nuclei at 980 A MeV fragmenting on silver foil and plastic nuclear track detector targets are made. The agreement between theory and experiment is good.

Gold↗
PubMed1993

Phenomenology of flow disappearance in intermediate-energy heavy ion collisions.

The disappearance of collective flow effects in heavy ion collisions is investigated using a microscopic optical model formalism for estimating collision momentum transfers. Phenomenological expressions for the balance energy are obtained which agree very well with measurements for various experimental collision pairs and with results obtained from Boltzmann-Uehling-Uhlenbeck simulations.

Elementary Particles↗