Biomedical subjects
C Clark
Publications and source records attributed to C Clark.
Double-staining artefact observed in certain individuals during dual-colour immunophenotyping of lymphocytes by flow cytometry.
An unusual double-staining artefact has been repeatedly observed in certain individuals (both HIV-positive and healthy laboratory controls) during 2-colour immunophenotyping of lymphocytes by flow cytometry after red cell lysis. This artefact can falsely suggest co-expression of CD4 and CD8, as well as some of the other monoclonal antibody pairs commonly used in the typing of lymphocytes. It is caused by a serum factor associated with the ammonium-sulphate-precipitated and gamma-globulin fractions. It appears to be fairly common in the population (being found in 6 out of 105 of our healthy laboratory controls and in 42 out of 247 of our HIV-1 seropositive subjects); it may be genetically determined, but may be acquired in some. It is a potential source of error in lymphocyte immunophenotyping, which can be avoided by simple adjustments to the recommended techniques.
Experimental investigation of unsteady flow behaviour within a sac-type ventricular assist device (VAD).
The flow behaviour of human blood in a pneumatically driven sac-type ventricular assist device (VAD) has been simulated by a non-Newtonian polymer (Separan) solution, and investigated by both a one-component laser Doppler anemometer (LDA) in back-scattering mode and flow visualisation. The device was driven by a pneumatic driver with a squarewave output pressure, and was operated at a pumping rate of 70 bpm, and a systolic duration of 35% of the pumping cycle. The preload and the average afterload to the device were set at 10 mmHg and 100 mmHg, respectively. The output flowrate was 4.05 l min-1. The wall of the peripheral and the central parts of the blood chamber of the VAD were well 'washed' by a main vortex developed during filling and the flow components perpendicular to the base of the VAD produced by the diaphragm motions, respectively. Flow recirculation regions were found at several locations. Around the junction between the tube sections and the blood chamber, the recirculation with an associated fluid particle deposition indicates an underlying risk of thrombus formation. This risk will be reduced by modifying the device design. The maximum turbulent shear stress estimated from the maximum turbulent normal stress (74 N m-2), is unlikely to cause significant damage to blood for the exposure times found. The maximum particle residence time was found to be closely related to the heart rate and the degree of completion of ejection/filling. At a given flow rate, the operating conditions which produce the highest stroke volume give the shortest residence times.
Use of ambiguous visual stimuli to demonstrate the value of acoustic cues in speech perception.
The purpose of this study was to evaluate a set of English phrases and sentences in a minimal-pairs syllable-test format for assessing use of acoustic cues in the audiovisual perception of speech; in particular, by persons with severe or profound hearing loss. Test items that were not rejected were categorized as "acceptable" or "ideal." An acceptable item was visually confusable but auditorally distinct compared to its foil (analogous to /p/vs/m/). An ideal item was, in addition, tactilely distinct. Forty-eight items, spoken by a male and a female talker, were presented in a videotaped two-alternative force-choice format under three conditions to three young-adult subject groups. In a lipreading-without-sound condition, 39 items were visually confusable; of these, 16 items were reliably identifiable when sound was added (the "acceptable" items). Seven of the 16 acceptable items were also identifiable in a tactile-pattern-alone condition (the "ideal" items). Performance on the 16 acceptable items was analyzed for an additional 27 young adults with moderate, severe, or profound hearing loss. Results obtained with the new protocol were consistent with conventional assessment results (CID Everyday Sentences, with and without sound) in all but 4 cases. Communication characteristics of the exceptions were examined to explain lack of agreement.
Olfactory deficits in neuroleptic naive patients with schizophrenia.
Because previous studies have shown deficits in olfactory identification for male patients with schizophrenia, either withdrawn from or receiving neuroleptic medication, the purpose of the current study was to determine if such deficits occurred in male patients who had never received neuroleptics. A sample of male (n = 30) and female (n = 10) patients as well as age appropriate controls (males, n = 28, females, n = 30) was assessed in terms of olfactory acuity and identification ability. No differences were found in olfactory acuity, but an olfactory identification deficit was present in 31% of the male patients with schizophrenia. As the olfactory pathways project through the limbic system and to the orbitofrontal cortex, odour identification may be a measure of the functional integrity of these structures. Therefore, these results suggest that for a sub-sample of male patients, the functional integrity of these structures is compromised.
Analysis of covariance in statistical parametric mapping.
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No major differences in energy metabolism between matched and unmatched groups of 'large-eating' and 'small-eating' men.
Rates of energy expenditure (J/kg fat-free mass (FFM) per min) in normal weight, 'small-eating' men were compared with those obtained for normal weight (n 8) and underweight (n 5) 'large-eating' men. For the matched groups of 'large-' and 'small-eaters' there were no differences in resting metabolic rate (RMR) measurements but during controlled daily activities there was a small but significant increase (P < 0.05) in energy expenditure in the 'large-eaters'. These results contrast with those obtained for the unmatched groups where energy requirements were about 10% (P < 0.01) higher in the underweight 'large-eaters' at rest but were not different during the more energetic (walking) activities. However, after adjustment for differences in FFM between these two groups, the resting energy expenditures of the 'large-eaters' (82.54 (SE 1.51) J/kg FFM per min) were similar to those of the 'small-eaters' (81.87 (SE 1.51) J/kg FFM per min). Oral temperatures were significantly higher in the matched (0.35-0.65 degrees) and unmatched (0.7-0.9 degrees) 'large-eaters' both at rest and during the different activities, but the thermic effect of food (50 kJ/kg FFM) was one fifth lower (not significant) in both groups of 'large-eaters'. These results provide little evidence for any major metabolic differences between groups of 'large-eating' and 'small-eating' men.
Long-term outcome of head injuries: a 23 year follow up study of children with head injuries.
The purpose of the 23 year follow up study was to determine the relationship between trauma variables including measures of head injury and very long-term sequelae. The study included 159 individuals with a mean age 31.40 years, of whom approximately 90% were admitted to hospital with a mild head injury during childhood (mean age 7.96). Extent of head injury was determined by unconsciousness, neurological status, skull fracture, EEG, post-traumatic seizures and a composite measure. The composite measure of neurological variables was the best predictor of long-term outcome. In addition, IQ recorded in the post-acute phase was a reliable predictor of long-term outcome. Of the sample, 32.7% reported physical complaints and 17.6% reported current psychological/psychiatric problems unrelated to the head injury. Subjective sequelae (physical, intellectual and emotional) specified as due to the head injury were reported by 31% of the sample, and the sequelae were found to be related to the extent of the head injury and initial IQ. There were no discernible relationships between attribute variables including premorbid status and age with subjective sequelae. There were, however, significant relationships between subjective sequelae and objective, psychosocial measures of adaptation including educational lag, unemployment, current psychological/psychiatric problems and relationships with family members. Finally, there appeared to be continuity of complaints elicited during the five year follow up of the original project and current sequelae. The severity of the head injury was identified as the primary contributory factor in the reconstitution process and in the prediction of long term outcomes.
Vascular complications after balloon and new device angioplasty.
BACKGROUND: Despite their potential advantages, new coronary angioplasty devices may be associated with more frequent vascular complications than noted after standard balloon angioplasty, theoretically due to the larger sheaths and prolonged periods of anticoagulation required by some of these devices. This study sought to identify the incidence, predictors, and clinical outcome of vascular complications after new device angioplasty. METHODS AND RESULTS: The clinical course of 1413 patients was reviewed after balloon or new device angioplasty. Vascular complications were defined as formation of a pseudoaneurysm, arteriovenous fistula, retroperitoneal hematoma, or groin hematoma associated with a > 15-point hematocrit drop or the need for surgical repair. Stepwise logistic regression was used to identify independent predictors for vascular complications. Vascular complications developed after 84 (5.9%) procedures; they occurred more frequently after intracoronary stenting (14.0%) and extraction atherectomy (12.5%) than after balloon angioplasty (3.2%) (odds ratios, 4.86; P < .001, and 4.26, P < .05, respectively). Independent predictors of vascular complications included the use of intraprocedural thrombolytic agents (P < .01), intracoronary stenting (P < .005), or extraction atherectomy (P < .05); high maximum creatinine level (P < .005); low nadir platelet count (P < .001); longer periods of excess anticoagulation (P < .05); and the need for repeat coronary angioplasty (P < .005). Vascular complications were not related to the size of the arterial sheath used. CONCLUSIONS: Vascular complications developed more frequently after new device angioplasty than after balloon angioplasty, with the risk for vascular complications directly related to the degree of periprocedural anticoagulation.
The consortium to establish a registry for Alzheimer's disease (CERAD). Part IV. Rates of cognitive change in the longitudinal assessment of probable Alzheimer's disease.
Reliable information on rate of progression of cognitive impairment in probable Alzheimer's disease (AD) is important for evaluating possible beneficial effects of therapeutic agents and in planning long-term care for patients with this chronic illness. However, wide variability exists in published rates of change for psychometric measures of the dementing process, and there is need for an accurate analysis of large numbers of persons with the disorder studied over long periods. Utilizing the large, well-characterized sample of the Consortium to Establish a Registry for Alzheimer's Disease and employing a least squares regression method to adjust for different levels of impairment and periods of observation, we report rates of change on the Short Blessed Test, Mini-Mental State Examination, Blessed Dementia Scale, Clinical Dementia Rating, and other cognitive measures in 430 patients with probable AD (mean age at entry = 70.9 +/- 8.0 SD years) studied for up to 4 years. We found that rate-of-change determinations are less reliable when the observation period is 1 year or less, that dementia progression may be nonlinear when described by certain measures, and that simple change scores do not accurately characterize the rate of decline. We also found that rate of progression in AD is determined by the severity of cognitive impairment: the less severe the dementia, the slower the rate of decline.
Acne--general practice management.
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Andy and David ... a personal look at two special needs' children. Andy.
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Health hucksters continue preying on Iowans.
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Clinical issues in social network therapy for clients with schizophrenia.
Social networks are viable foci for therapeutic interventions. A social network therapy program for clients with schizophrenia was developed by a community-based mental health agency. This paper presents four of the most common clinical issues encountered and illustrates each with a case example.
Chronic pain management training for senior registrars in anaesthesia.
In 1985 and 1990 postal questionnaires were sent to anaesthetic senior registrars in training in the United Kingdom to determine the extent of higher specialist training in chronic pain management. There were wide variations in training and experience amongst senior registrars. Overall there was little change between 1985 and 1990. In particular the number of anaesthetic senior registrars who felt equipped to undertake a consultant post with an interest in chronic pain management had not increased.
Cortical glucose metabolism in Huntington's disease.
We measured cortical glucose metabolism with positron emission tomography in 39 patients with Huntington's disease (HD) and in 34 controls. In the 23 patients with symptoms for less than 5 years, there was a 15% decrease in metabolism in frontal and inferior parietal cortex. In 16 patients with symptoms for more than 5 years, all cortical areas (except temporal) were significantly involved, with metabolic rates 25 to 30% below those of controls. These data indicate the presence of a diffuse abnormality of cortical function with early involvement of frontal lobes in HD, suggesting that the clinical manifestations may not be related solely to basal ganglia pathology, even in early disease.
High hemoglobin A2 beta 0-thalassemia due to a 532-basepair deletion of the 5' beta-globin gene region.
We identify and characterize a novel beta 0-thalassemia mutation that is associated with an unusually high level of hemoglobin (Hb) A2 in the heterozygote. This newly discovered mutation is caused by a 532-basepair deletion that extends from positions -454 to + 78 relative to the mRNA cap site of the beta-globin gene. The propositi are 9-month-old fraternal twins. One of the twins is a compound heterozygote for the deletion and Hb S, the other is a compound heterozygote for the deletion and Hb C.
Estimated prevalence of dementia among elderly black and white community residents.
A stratified random sample of 83 black and 81 white community residents aged 65 years and older in a five-county area in the Piedmont region of North Carolina was evaluated for dementia, using the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, and the National Institute of Neurological Disorders and Stroke--Alzheimer's Disease and Related Disorders Association criteria. Of 164 subjects, 26 were found to be demented, resulting in an estimated prevalence rate of dementia in the five-county area of 16% (95% confidence interval, 7.92 to 24.08) for blacks and 3.05% (95% confidence interval, 0 to 6.91) for whites. The estimated prevalence of dementia for white women (2.9%) was similar to that for white men (3.3%), but the rate for black women was distinctly higher than for black men (19.9% and 8.9%, respectively). Blacks were more likely than whites to have a history of stroke, hypertension, and other chronic disorders that might have contributed to the development of dementia. Apart from differences in rates of institutionalization, no other relevant factors were identified that might explain the difference in the prevalence of dementia in these black and white community residents.