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Biomedical subjects

B Brown

Publications and source records attributed to B Brown.

At least 163 records · Page 9Linked to original sources
PubMed1993

Clinical evaluation of the peritoneal equilibration test: a population-based study.

A total of 143 Peritoneal Equilibration Tests (PETs) were performed in 104 CAPD patients over a period of 18 months. A normal range (95% confidence limits) was constructed from 100 tests (68 consecutive new patients, 32 routine tests on problem-free patients) using a 2-dimensional plot of solute transfer (D/Pcreat) and ultrafiltration volume. These two parameters correlated inversely (r = -0.59, P < 0.0001) allowing calculation of a regression line. In the short term (< 3 months) D/Pcreat was stable across a wide range of values (0.45-0.98) with good correlation between tests indicating reproducibility (r = 0.94, P < 0.001). Repeated tests beyond 3 months were variable, explaining changes in the clinical picture, and in the majority of cases shifts in D/Pcreat and ultrafiltration parallelled the regression line for the whole population. Six of seven (85%) of patients with mechanical problems and 14 of 15 (93%) with poor ultrafiltration had at least one abnormal test, and these two problems could be distinguished in 90% of cases by 2-dimensional plotting. In five with ultrafiltration failure, dialysate volumes were less than predicted by solute clearance, and these patients failed continuous cycling peritoneal dialysis (CCPD). In contrast, a good response to CCPD was predicted correctly in five patients with high solute clearance. In nine patients with plasma creatinine > 1250 mumol/l the PET was normal. The PET is a useful adjunct to understanding and prescribing peritoneal dialysis, particularly when repeated tests are compared to a well-defined normal population.

Adolescent↗
PubMed1993

Intraocular pressure in a selected sample of myopic and nonmyopic Chinese children.

The intraocular pressure (IOP) measurements for 30 myopic and 30 nonmyopic children between 6 and 9 years of age were extracted from eye examination records. The mean IOP of 30 myopic children was 13.69 mm Hg (SD 3.4) and that of 30 nonmyopic children was 11.55 mm Hg (SD 2.06). The difference between the two is significant. These results suggest that IOP may play a role in the determination of refractive error.

Child↗
PubMed1993

Review of the tear break-up time and a closer look at the tear break-up time of Hong Kong Chinese.

The technique of assessing tear stability using the fluorescein instillation technique has been widely used in the clinical diagnosis of "dry eye" and in the screening of potential contact lens wearers. Various inconsistencies in the application of the tear break-up time (TBUT) techniques and the results obtained were noted in the literature and this review summarizes the differences and the conclusions of various investigators. The reliability of this technique using two different methods of observation was examined and the mean TBUT of Hong Kong Chinese subjects (HK-Chinese) was determined. We conclude that the TBUT can be measured reliably using either the scanning or full beam method in most patients. The mean TBUT of HK-Chinese is approximately 8 s and about 70% of HK-Chinese have TBUT's less than 10 s.

Adolescent↗
PubMed1993

Repeated visual acuity measurement: establishing the patient's own criterion for change.

We measured visual acuity in 10 young subjects, 10 times each over a period of approximately 3 weeks, using Bailey-Lovie charts. We used a consistent end-point criterion and scored each letter read on the chart. We derived the mean and standard deviation of visual acuity measures for each subject, and for the group. The standard deviation for the group was about 3 times that of the individuals in the group. We calculated the criterion for reduction of visual acuity for the group, as group mean plus 1.96 group standard deviations; use of this criterion would consistently fail to detect patients with clinically significant reductions in visual acuity. We recommend that visual acuity be measured to threshold for every patient. Measuring visual acuity between three and five times provides an estimate of the patient's variability and allows a criterion for reduction of visual acuity to be established for the individual patient. Use of this criterion will enhance the sensitivity of visual acuity measurement as a diagnostic tool.

Adolescent↗
PubMed1993

Distance visual acuity and monovision.

We have investigated aspects of visual acuity with monovision correction. Binocular distance visual acuity with monovision was approximately equal to monocular visual acuity for addition powers (monocular defocus) of +1.00 to +2.50 D, using both high and low contrast logMAR visual acuity charts. Neither the eye chosen to be defocused (dominant or nondominant) or pupil size (3.5, 5 and 7 mm) affected the binocular visual acuity loss with monovision for high contrast charts. We also investigated the effect of induced residual astigmatism (+0.50, +1.00, and -1.00 D) on binocular distance visual acuity in monovision correction. Residual astigmatism caused a significantly greater reduction of binocular visual acuity in the monovision condition than it did in normal binocular conditions. This effect appears to be related to a process of meridional interocular suppression. It may therefore be of clinical importance to correct low amounts of residual astigmatism in monovision corrections to provide optimum binocular visual acuity.

Adult↗
PubMed1993

Decrease in stereoacuity in the seventh decade of life.

We measured stereoacuity in 41 subjects with normal Snellen acuity in each eye, and normal ocular health. Patients were measured in each of the age ranges 21-28, 41-49, 51-59 and 60-70 years. Stereoacuity was reduced from about 16 sec arc for the three younger groups to about 27 sec arc for the older subjects. Since stereopsis has a cortical neural substrate, these data suggest that there may be cortical changes affecting the interaction of information from the two eyes with advancing age, but whether these changes result from loss of contrast sensitivity, instability of ocular alignment or binocular stress, all of which have been reported in elderly subjects, is not known.

Adult↗
PubMed1993

Mechanical manipulation of the lids and tear break-up time measurements in Hong Kong Chinese.

We measured tear break-up time (TBUT) after lid-rubbing in a single masked experiment, and found that TBUT was unaltered. A further single masked experiment in which non-invasive tear break-up time (NITBUT) was measured after the lids were raised as if to apply fluorescein also showed no effect of this interference with the lids. An experiment in which fluorescein was applied either with the lid raised or not raised during fluorescein application, again with the experimenter masked with respect to treatment, also produced no significant difference in TBUT. When we measured TBUT with the lid raised so that it was not in contact with the cornea, there was no difference in TBUT for the group between the 'lifted' and 'non-lifted' eye; some subjects showed substantially shorter TBUT values, while others showed substantially longer TBUT values. These findings are surprising in view of the concerns expressed in the literature regarding the sensitivity of the tear film to mechanical interference, and suggest that the tear film is more resistant to disruption than has previously been thought.

Adult↗
PubMed1993

Investigation of parameters influencing intraocular pressure increases during sleep.

In previous studies, we have observed that young normal subjects show an increase in intraocular pressure (IOP) after sleep. Here we describe three experiments which investigated: (i) the effects of sleep in five groups of subjects: glaucoma, suspect glaucoma, young high-normal IOP, old high-normal IOP groups and an elderly control group, (ii) the effect of exposure to bright light (2500 lux) during sleep on associated IOP changes, and (iii) the relationship between changes in IOP and plasma melatonin during sleep. For all experiments IOP was measured before and after sleep. We found that IOP increased significantly after sleep. There was also a significant difference between the five groups with the old high-normal group showing the greatest increase, and the young high-normal group showing the lowest increase in IOP. The increase in IOP after sleep was reduced when the same subjects slept in bright light compared to that recorded when subjects slept in the dark. Plasma melatonin levels, as well as IOP, increased after sleep in the dark although there was no correlation between these changes for individual subjects.

Adult↗
PubMed1993

Risk assessment for aflatoxin: an evaluation based on the multistage model.

Lifetime cancer potency of aflatoxin was assessed based on the Yeh et al. study from China in which both aflatoxin exposure and hepatitis B prevalence were measured. This study provides the best available information for estimating the carcinogenic risk posed by aflatoxin to the U.S. population. Cancer potency of aflatoxin was estimated using a biologically motivated risk assessment model. The best estimate of aflatoxin potency was 9 (mg/kg/day)-1 for individuals negative for hepatitis B and 230 (mg/kg/day)-1 for individuals positive for hepatitis B.

Adult↗
PubMed1993

Long-term reduction in sperm count after chemotherapy with and without radiation therapy for non-Hodgkin's lymphomas.

PURPOSE: Treatment of lymphomas with combination chemotherapy with or without radiation therapy (XRT) can result in long-term or permanent azoospermia. PATIENTS AND METHODS: Semen analyses of lymphoma patients were performed before, during, and after treatment with cyclophosphamide, doxorubicin, vincristine, prednisone, and bleomycin (CHOP-Bleo) chemotherapy. Some of the patients also received other drugs or radiation therapy. RESULTS: Although no patients were azoospermic before treatment, all were rendered azoospermic during treatment. Following the completion of treatment, the fraction of patients whose sperm counts recovered increased gradually over 5 years and plateaued by 7 years, with two thirds of the men achieving normospermic levels. Scattered gonadal radiation dose and cumulative cyclophosphamide dose were found to be independently significant determinants of recovery: the fraction of patients whose sperm counts recovered to 10 x 10(6)/mL were 83%, 47%, and 20% for those who received less than 9.5 g/m2 of cyclophosphamide, greater than 9.5 g/m2 of cyclophosphamide, and pelvic XRT, respectively. The inclusion of additional drugs and interferon alfa did not significantly affect the long-term recovery of spermatogenesis. CONCLUSION: Pelvic XRT and cumulative cyclophosphamide dosages greater than 9.5 g/m2 are associated with a high risk of permanent sterility in lymphoma patients treated with the CHOP-Bleo regimen.

Adolescent↗
PubMed1993

Types of health problems and satisfaction with services in a rural nurse-managed clinic.

The purpose of this study was to investigate the satisfaction of clients with care provided in a rural nurse-managed health center by family nurse practitioners and to describe common health problems for which family nurse practitioner services were sought. The results indicated that of the 2,106 visits from a case load of 1,350 clients, acute health problems were the most common (95.7%), and chronic health problems were the least common (3.9%). Respiratory and ear infections were the most frequent acute illness (55%), and hypertension (29%), respiratory (27%), and musculoskeletal complaints (27%) were the most frequent chronic conditions. Children up to 6 years of age constituted the largest client population (30%), followed by young adults (23%). Older adults were the smallest numbers of clients (3%). Client satisfaction with nurse practitioner-managed care was highly rated by 97% (n = 101) of the subjects in a random sample telephone survey. The results suggested that family nurse practitioners were providing effective and satisfactory healthcare for this rural community. Issues for further investigation are also discussed.

Adolescent↗
PubMed1993

Anthropometric measurements and estimating body composition in ballet dancers.

The purpose of this study was to develop and cross-validate an equation for estimating fat-free mass (FFM) in female ballet dancers. One hundred twelve, 11- to 25-yr old, female dancers had FFM measured by total body electrical conductivity (TOBEC) and anthropometrics, including skinfold and circumference measurements. The regression equation that best estimated FFM in the dancers was FFM = 0.73 x body weight (kg) + 3.0, (R2 = 88%, SEE = 1.5 kg, P < 0.001). This equation was then cross-validated on a separate group of 23 female dancers who also had FFM measured by TOBEC. FFM estimated by this equation correlated with FFM measured by TOBEC (r = 0.94, SEE = 0.9 kg), and the difference in the FFM values using the two methods (the equation and TOBEC) did not change with the size of the FFM of the dancers. FFM in accomplished female ballet dancers can be best estimated from body weight alone. This is related to the homogeneity of body size and body composition in female ballet dancers at this level.

Adolescent↗
PubMed1993

Measuring the psychological construct of control. Discriminant, divergent, and incremental validity of the Shapiro Control Inventory and Rotter's and Wallstons' Locus of Control Scales.

The psychological construct of control is increasingly thought to be an important variable in psychosomatic medicine, but there are limitations with how it has been measured by previous instruments. The current study details four limitations of previous instruments as a rationale for developing a new multi-faceted, multi-dimensional instrument to measure control, the Shapiro Control Inventory (SCI). Discriminant, divergent, and incremental validity of the SCI is compared with the Rotter's Internal/External Locus of Control Scale and Wallstons' Multidimensional Health Locus of Control Scales on five groups, one normal and four clinical groups (depression, generalized anxiety disorder, borderline personality, and panic disorder). Analysis of variance showed significant differences among populations on each of the nine SCI scales. The majority of these results were highly significant, whereas for Rotter's scale the results were barely significant, and for Wallstons' three scales, not at all significant. Correlations of the SCI scales with Rotter's and Wallstons' scales were small to moderate, but in no case explained more than 15% of the variance. The SCI also provided incremental validity over Rotter's and Wallstons' scales both for sensitivity (clinical versus normal) and specificity (between clinical groups). The discussion section provides suggestions for future research.

Adolescent↗
PubMed1993

The admissions process of a bachelor of science in nursing program: initial reliability and validity of the personal interview.

The undergraduate nursing degree program (B.Sc.N.) at McMaster University School of Nursing uses small groups, and is learner-centered and problem-based. A study was conducted during the 1991 admissions cycle to determine the initial reliability and validity of the semi-structured personal interview which constitutes the final component of candidate selection for this program. During the interview, three-member teams assess applicant suitability to the program based on six dimensions: applicant motivation, awareness of the program, problem-solving abilities, ability to relate to others, self-appraisal skills, and career goals. Each interviewer assigns the applicant a global rating using a seven-point scale. For the purposes of this study four interviewer teams were randomly selected from the pool of 31 teams to interview four simulated (preprogrammed) applicants. Using two-factor repeated-measures ANOVA to analyze interview ratings, inter-rater and inter-team intraclass correlation coefficients (ICC) were calculated. Inter-team reliability ranged from .64 to .97 for the individual dimensions, and .66 to .89 on global ratings. Inter-rater ICC for the six dimensions ranged from .81 to .99, and .96 to .99 for the global ratings. The item-to-total correlation coefficients between individual dimensions and global ratings ranged from .8 to 1.0. Pearson correlations between items ranged from .77 to 1.0. The ICC were then calculated for the interview scores of 108 actual applicants to the program. Inter-rater reliability based on global ratings was .79 for the single (1 rater) observation, and .91 for the multiple (3 rater) observation. These findings support the continued use of the interview as a reliable instrument with face validity. Studies of predictive validity will be undertaken.

Analysis of Variance↗
PubMed1992

Detection of coronavirus RNA and antigen in multiple sclerosis brain.

Epidemiological studies of patients with multiple sclerosis (MS) and animal model data support the hypothesis that viruses initiate the immunopathogenic events leading to demyelination in MS. There have been no reports, however, of consistent detection of viruses in MS central nervous system tissue. We probed MS and control brain with cDNA probes specific for human, murine, porcine, and bovine coronaviruses. We report the in situ hybridization detection of coronavirus RNA in 12 of 22 MS brain samples using cloned coronavirus cDNA probes. In addition, tissue was screened for coronavirus antigen by immunohistochemical methods; antigen was detected in two patients with rapidly progressive MS. Significant amounts of coronavirus antigen and RNA were observed in active demyelinating plaques from these two patients. These findings show that coronaviruses can infect the human central nervous system and raise the possibility that these viruses may contribute to the pathogenesis of MS in some patients.

Antigens, Viral↗