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Biomedical subjects

J MacDonald

Publications and source records attributed to J MacDonald.

At least 109 records · Page 6Linked to original sources
PubMed1983

Cluster analysis of the WAIS on brain-damaged patients.

In recognition of increased usage of cluster analytic techniques, the current study attempted to examine sampling bounds for tests and subjects on one cluster-analytic procedure. Specifically, the WAIS subtest scores from a heterogeneous group of subjects with CNS involvement were first, factor analyzed and then clustered by means of Ward's hierarchical procedure. This methodology had been previously applied to two different samples of aphasics and aphasia batteries. In both these aphasic studies, an underlying severity dimension of language dysfunction was found. In contrast, in the current study, salient feature groups were found. Moreover, these groups were distributed in a sequential or hierarchical model in terms of specific cognitive deficits. From these data, it is argued that two major parameters in determining the resulting cluster structures are the homogeneity/heterogeneity of the sample and test battery employed. Although such a statement is obvious, the theoretical ramifications are large, in that the cluster structure may be a function of test weighting or sample diversity, not the phenomenon of interest. However, the cluster structures found in the current study were consistent with historical models of cognitive dysfunction and also lend support to hierarchical models of sequential cognitive impairment. These findings are discussed in terms of their clinical and experimental ramifications with respect to grouping subjects in terms of WAIS profiles.

Adult↗
PubMed1983

An application of the background interference procedure to the Benton Visual Retention Test.

This study involved applying Canter's Background Interference Procedure to the Benton Visual Retention Test. In a heterogeneous sample of psychiatric and brain-damaged patients, it was found that brain-damaged patients reproduced fewer designs and made more errors in reproducing those designs than did psychiatric patients. Right-hemisphere and diffusely brain-damaged patients reproduced fewer designs correctly and made more errors than did left-hemisphere damaged patients. This pattern was maintained when the effects of level of intellectual functioning and age were statistically controlled. These results suggest that the Background Interference Procedure in conjunction with the Benton Visual Retention Test may make a contribution to the assessment of brain-injured patients.

Adult↗
PubMed1982

Potassium conservation with amiloride/hydrochlorothiazide ("Moduret') in thiazide-induced hypokalaemia in hypertension.

A double-blind study was carried out in 24 hypertensive patients with thiazide-induced hypokalaemia (serum potassium less than 3.2 mmol/l) to compare the effects of treatment with an amiloride/hydrochlorothiazide combination or hydrochlorothiazide alone. The study was divided into three phases: (i) potassium repletion (Weeks 0 to 4) with oral potassium chloride (40 mmol/day), (ii) stabilization (Weeks 4 to 6) of normokalaemia, and (iii) active drug treatment (Weeks 6 to 14), patients being allocated at random to receive one or other of the two treatments. Dosage was 2 tablets per day of the 5 mg amiloride plus 50 mg hydrochlorothiazide combination or of 50 mg hydrochlorothiazide alone. The results showed that blood pressure control was comparable in both treatment groups but hydrochlorothiazide alone caused a statistically significant reduction in serum potassium levels compared to the drug combination. Apart from 1 patient who developed hypokalaemia on hydrochlorothiazide alone, no other side-effects of treatment were reported.

Amiloride↗
PubMed1981

Epidemic measles in Shetland during 1977 and 1978.

During 1977 and 1978 an unusual epidemic of measles occurred in Shetland, affecting 1032 (5%) of the population. All age groups were represented, and 309 cases occurred in people over 15. Geographical distribution of notified cases ranged from 1% to over one-third of the population aged under 65. All the recognised complications occurred, with a significant excess of respiratory troubles (p less than 0 . 05). Complications were much less common in female patients (p less than 0 . 05). Only about 30% of children under 5 had been vaccinated against the disease, and, based on a sample population, vaccination was found to have had a protective effect of 92%. On cost effectiveness alone, uptake of vaccination by a community as susceptible as that of Shetland should clearly be encouraged and probably given high priority.

Adolescent↗
PubMed1978

Cerebral metastasis from a malignant thymoma.

A 14-year-old girl was found to have a solitary metastatic thymoma in the occipital lobe of the brain eight years following thoracotomy for removal of a malignant thymoma. Histologically, the lesions appear identical. Initial neurological examination was normal. The metastatic lesion was surgically removed followed by radiation therapy. No neurologic deficits related to the metastasis to the brain were evident nine months postoperatively.

Adolescent↗
PubMed1967

Influence of urea on the growth of T-strain mycoplasmas.

T-strain mycoplasmas require urea for propagation, but urea metabolism also occurs in nonpropagating viable cultures. Ammonia results from this metabolism and alkalinizes the medium. Ammonium ions and an alkaline pH both inhibit the multiplication of T strains and reduce the viability of T strains in broth. These toxic effects of urea metabolism currently limit the growth of T strains in broth. Stock T-strain cultures are optimally maintained in continuous culture if the routine medium at pH 6.0 is supplemented with 0.05% urea and 0.002% phenol red, but an incubation temperature of 30 C is preferable to 37 C for subculture at 24-hr intervals.

Ammonia↗
PubMedDate not supplied

Rapid identification of Candida albicans using 4-methylumbelliferyl N-acetyl-beta-galactosaminide.

Rapid identification of Candida albicans is performed mainly by the germ-tube test. However, recent reports have suggested that up to 5% of C. albicans species can give false negative results. We describe the use of 4-Methylumbelliferyl N-acetyl-beta-D-galactosaminide (4-MAG) conjugate as an alternative to the germ-tube test. Our results indicate that, in comparison to the germ-tube test, the 4-MAG test has a sensitivity of 100% and a specificity of 92%. Candida tropicalis can give false-positive results, and that a further screening test is required to identify this species. Problems reading end-points were not encountered.

Candida albicans↗
PubMedDate not supplied

Aluminum output fluxes from forest ecosystems in Europe: a regional assessment.

Data from 89 forested catchments and plots across Europe were used to define empirical relationships between aluminum leaching and input fluxes of major ions, output fluxes of major ions, ecosystem parameters such as soil pH, and combinations of these. Forests that release dissolved Al to seepage or surface waters are located primarily in areas receiving the highest loading of acid rain, and the output flux of Al shows the highest correlations to the throughfall flux of inorganic nitrogen, the output fluxes of NO3-, H+, and SO4(2-), and the mineral soil pH. If the speciation of Al is taken to be Al3+ (an overestimate), Al is released in a nearly 1:1 molar charge ratio with the sum of NO3- and SO4(2-) in runoff or seepage water over a wide range of basepoor bedrock types and acid deposition across Europe. The empirical data point to a threshold range of N deposition of 80 to 150 mmolc N m(-2) yr(-1) and a (less clearly defined) range of S deposition of 100 to 200 mmolc SO4(-2) m(-2) yr(-1) above which Al released from forests exceeds 100 mmolc Al m(-2) yr(-1). Within this threshold range, the sites that release little or no dissolved Al are those that continue to assimilate input N and/or have high soil pH (>4.5).

Acid Rain↗