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Biomedical subjects

R J Davidson

Publications and source records attributed to R J Davidson.

At least 145 records · Page 8Linked to original sources
PubMed1985

Immunosuppressive activity and toxicity of cyclosporin A in rats pretreated with high dose cyclophosphamide.

Cyclophosphamide (Cy; 150 mg/kg) was administered (i.p.) to groups of Sprague-Dawley rats, followed two days later by immunization with ovalbumin (OVA). From that time, cyclosporin A (CsA; 25 mg/kg) or its vehicle was given (p.o.) for a further 13 days. Control animals tested 14 days after immunization, showed strong Arthus-like and modest delayed-type skin reactions to OVA, in contrast to almost total inhibition in animals tested with Cy, CsA or both. Similar effects were observed with respect to serum anti-OVA antibody levels. Despite itself producing lymphopenia, CsA had no additional effect on the lymphocyte depletion caused by Cy. Both drugs, either alone or in combination, caused neutrophilia and monocytosis. An additional eosinophilia due to Cy was prevented by CsA. Cy induced splenomegaly, nodal extramedullary haemopoiesis and increases in both tissue eosinophils and marrow neutrophils. There was also lymphoid depletion in both spleen and lymph nodes which was enhanced by CsA. Thymic lymphoid atrophy was found only when CsA was given. Despite the powerful immunosuppressive properties of both drugs, detailed biochemical and structural analyses showed no other synergistic toxicity, apart from modest hepatic abnormalities. In particular, there was no enhancement of the nephrotoxicity of CsA.

Animals↗
PubMed1985

Cross-cultural differences in hemisphericity: EEG asymmetry discriminates between Japanese and Westerners.

This study was designed to test the hypothesis that Japanese subjects exhibit different patterns of resting EEG asymmetry compared with Westerners. EEG was recorded from the left and right temporal and parietal scalp regions in bilingual Japanese and Western subjects during eyes-open and eyes-closed rest periods before and after the performance of a series of cognitive tasks. Alpha activity was integrated and digitized. Japanese subjects were found to exhibit greater relative right-sided parietal activation during the eyes closed condition. This difference was found to be a function of greater left hemisphere activation among the Westerners. Various possible contributors to this cross-cultural differences are discussed.

Adult↗
PubMed1985

Purdue pegboard performance of disabled and normal readers: unimanual versus bimanual differences.

Differences between dyslexics and controls in the unimanual and bimanual conditions of the peg placement section of the Purdue Pegboard Test were examined. Twenty-three disabled and twenty-three normal readers were studied. The groups were carefully screened on a neuropsychological battery. The disabled readers were comprised of a relatively homogeneous language-disordered subgroup exhibiting deficits in naming. Significant Group X Condition interactions were obtained for both raw and percentile scores and indicated that disabled readers performed worse than controls in the unimanual compared to bimanual conditions. The dyslexics performed particularly poorly compared with controls on the left hand condition. The implications of these data for hypotheses which argue for left hemisphere dysfunction, as well as those which posit interhemispheric transfer deficits in reading disabled children, are discussed.

Adolescent↗
PubMed1985

Inhibition by cyclosporin A of IgE production and cyclophosphamide-induced eosinophilia in rats immunized with non-parasite antigens.

Administration of cyclosporin A (CS-A; 25 mg/kg daily) to rats from the time of immunization with ovalbumin (OVA) in complete Freund's adjuvant abolished the production of anti-OVA antibodies, including IgE. Cyclophosphamide (Cy; 150 mg/kg) given 2 days before immunization also inhibited specific antibody production but at the same time induced a striking eosinophilia. Combined administration of both drugs resulted in the inhibition by CS-A of the Cy-induced eosinophilia. The results suggest that IgE synthesis and eosinophil proliferation may be under the control of separate T cell subsets. This rat model may prove useful in studies on the regulation of eosinophil production and the role of these cells in disease processes.

Animals↗
PubMed1985

Hemorrheology of marathon running.

The hemorheological effects of severe exertion were evaluated in eight males and six females before and after a marathon. A highly significant fall in red cell filterability (RCF) was accompanied by a significant rise in plasma osmolality. This correlation was further studied by a series of in vitro experiments to establish a cause-effect relationship. As plasma osmolality increased, RCF progressively diminished. These observations demonstrate that plasma hyperosmolality is an important etiological factor in reducing RCF during strenuous exercise.

Adult↗
PubMed1985

Estimation of plasma volume changes during marathon running.

Indices of fluid loss have been compared in 47 male runners who completed a competitive marathon (42.2 km) race in times varying from 2 hr 37 min to 4 hr 51 min. Body weight was recorded before and after the race; venous blood samples were collected shortly before and immediately after the race and used for the estimation of haemoglobin concentration, packed cell volume and serum concentration of albumin and total protein. All runners drank a total of 1.4 L of water during the race. The mean decrease in body weight was 2.1 +/- 0.8 kg (mean +/- SD), corresponding to 3.0 +/- 1.1% of initial weight. The decrease in plasma volume (PV), calculated from the haematological parameters, was 6.5 +/- 7.8% (P less than 0.001). Serum total protein concentration increased (P less than 0.001) by 10.4 +/- 4.8% and serum albumin (P less than 0.001) by 9.6 +/- 5.6%. The increase in serum protein concentration was correlated (r = 0.64, P less than 0.001) with the calculated decrease in PV, but was greater (P less than 0.001) than could be accounted for by the loss of plasma water. The change in PV varied widely between individuals and was unrelated to running speed. The estimated decrease in total body water (5%) was not different from the decrease in PV (6.5%), suggesting that water losses were evenly distributed between the intracellular and extracellular compartments.

Adult↗
PubMed1985

Haematological and haemorheological changes associated with cigarette smoking.

A prospective study was undertaken to establish the haematological and haemorheological changes associated with long standing cigarette smoking in 20 heavy smokers and to assess whether any such changes were reversible after smoking was stopped. Highly significant differences were observed in whole blood viscosity, plasma viscosity, plasma fibrinogen concentrations, packed cell volume, and carboxyhaemoglobin concentrations between smokers and non-smokers. Ten of the subjects were followed up for two weeks after stopping smoking by which time whole blood viscosity and carboxyhaemoglobin concentrations had improved significantly and indications of improvement could be seen in all other measurements. Two of these subjects were further followed up for two months when all the measured variables were comparable with those in non-smokers. No correlation could be established between carboxyhaemoglobin concentration and any of the other variables. Although patients' compliance may be difficult to obtain, further prospective studies would be required to confirm our findings.

Adult↗
PubMed1984

Human parvovirus infection and aplastic crisis in hereditary spherocytosis.

This report records an episode of parvovirus-induced bone-marrow aplasia in a child with hereditary spherocytosis and arising during a local outbreak of erythema infectiosum (fifth disease or 'slapped-cheek syndrome'). Inapparent infection was found in two haematologically normal family contacts.

Anemia, Aplastic↗
PubMed1984

A search for the mechanism underlying the altered MCV in thyroid dysfunction: a study of serum and red cell membrane lipids.

The mean red cell volume (MCV) is increased in hypo- and decreased in hyperthyroidism but the underlying cause(s) is unknown. In view of the well recognised alterations in serum lipids in thyroid dysfunction, we have examined the possibility that a corresponding alteration in the amount or distribution of lipids in the red cell membrane may account for the red cell volume changes. Our findings however do not support this hypothesis.

Adult↗
PubMed1984

Whole blood and red cell ATP content in patients with peripheral vascular disease: the effect of cigarette smoking and oxpentifylline.

The relationship between erythrocyte ATP content and the presence of atherosclerotic peripheral occlusive vascular disease was investigated. In 20 elderly patients with severe peripheral vascular insufficiency (10 male, 10 female; age 68.8 +/- 12.5 years; Mean +/- SD) the mean erythrocyte ATP content was 1.57 +/- 0.16 mmol/litre. In a sex and age matched group (69.1 +/- 9.6 years) with no signs or symptoms of peripheral or myocardial ischaemia, erythrocyte ATP content did not differ significantly (1.49 +/- 0.29 mmol/litre). In young healthy volunteers, there was no difference in erythrocyte ATP content between males and females or between cigarette smokers and non-smokers, nor were the values for the young group different from those obtained from the elderly patients. The effect of oxpentifylline administration on erythrocyte ATP levels in patients with peripheral vascular disease was also studied. Administration of oxpentifylline (1.6 g per day in divided doses) over 7 days had no effect on erythrocyte ATP content in 10 patients (5 male, 5 female) with ischaemic lower limbs. These results suggest that measurement of erythrocyte ATP content is unlikely to be a useful index in the assessment of peripheral vascular disease.

Adenosine Triphosphate↗
PubMed1983

The heterogeneity of the 5q--chromosome marker in refractory anemia.

A patient presenting with an unusual case of refactory anemia is described in whom acquired markers originating from chromosomes No. 5 and 8 are identified by G- and sequential C-banding. Comparison with various published illustrations of chromosome No. 5 deletions in this general broad category of disease raises the possibility that karyotypic misclassification in cases of absent or substandard banding (typical of bone marrow) may help to explain the considerable variation in size and morphology of the 5q--marker.

Adenocarcinoma↗
PubMed1983

Raised Coulter mean corpuscular volume in diabetic ketoacidosis, and its underlying association with marked plasma hyperosmolarity.

An abnormal and transient increase of the Coulter mean red cell volume (MCV) was observed in four of 10 patients with diabetic decompensation. A sequential study of haematological and biochemical measurements in these patients revealed that this phenomenon was associated with the hyperosmolar state. The proposed mechanism and the clinical implications of this change are briefly discussed.

Adolescent↗
PubMed1983

Pathological changes in rats receiving cyclosporin A at immunotherapeutic dosage for 7 weeks.

In rats given an immunotherapeutic dose (25 mg/kg orally each day for 7 weeks) of cyclosporin A (Cy A) characteristic drug-induced pathological changes were observed, including impaired liver function, renal proximal tubular cell damage, progressive lymphopenia, lymphocyte depletion in lymphoid organs and marrow hypoplasia. Several additional and previously unreported features of Cy A toxicity were also demonstrated. The changes in renal and hepatic function were biphasic with temporary improvement during the course of the study. The most striking liver damage was in the form of a granulomatous hepatitis and a hypochromic microcytic anaemia developed in all experimental animals.

Anemia, Hypochromic↗
PubMed1983

Frontal and parietal electroencephalogram asymmetry in depressed and nondepressed subjects.

High vs. low scorers on the Beck Depression Inventory (BDI) were compared on measures of resting EEG activation asymmetry from frontal and parietal brain regions. Depressed subjects showed greater relative right frontal activation compared with nondepressed subjects. Parietal asymmetry did not distinguish between the groups. These data support the hypothesis of right hemisphere hyperactivation in the frontal region of depressed individuals and are consistent with the growing body of literature which suggests that the left and right frontal regions may be differentially specialized for particular positive and negative affects.

Adult↗
PubMed1982

Asymmetrical brain activity discriminates between positive and negative affective stimuli in human infants.

Ten-month-old infants viewed videotape segments of an actress spontaneously generating a happy or sad facial expression. Brain activity was recorded from the left and right frontal and parietal scalp regions. In two studies, infants showed greater activation of the left frontal than of the right frontal area in response to the happy segments. Parietal asymmetry failed to discriminate between the conditions. Differential lateralization of the hemispheres for affective processes seems to be established by 10 months of age.

Affect↗