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Biomedical subjects

R H Johnson

Publications and source records attributed to R H Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1985

In situ localization of T lymphocytes in disseminated coccidioidomycosis.

Immunohistochemical techniques using monoclonal antibodies to T lymphocyte subpopulations were used to characterize further the granulomas of disseminated coccidioidomycosis. Skin biopsy specimens from patients with disseminated coccidioidomycosis were studied and compared with tissues from experimentally infected mice. In human skin biopsy specimens and infected mouse tissues, discrete granulomata were seen in which T lymphocytes formed a peripheral mantle surrounding central aggregates of macrophages. This unusual pattern of granuloma formation may represent an ineffective host response because these individuals are unable to clear their infection. Because of the close similarity of immunopathology in both human and mouse infections, the mouse model should serve as a useful tool in elucidating the factors contributing to ineffective host responses in systemic fungal infections.

Adolescent↗
PubMed1985

No effect of ethanol ingestion on beta-adrenoceptor-mediated circulatory responses to isoprenaline in man.

The acute effects of ethanol on circulatory responses to isoprenaline and atropine were investigated in 21 and 15 normal male subjects respectively. Each subject acted as his own control by participating twice, once after consumption of ethanol (1.0 ml kg-1, 20% v/v in orange juice) and once after orange juice. Ethanol increased baseline heart rate and forearm blood flow, but had no effect on heart rate and forearm blood flow responses to isoprenaline, or on heart rate responses to atropine. Baseline blood pressure and blood pressure responses to isoprenaline were also unaffected by ethanol. It is concluded that acute ethanol ingestion has no physiologically significant effect on beta-adrenoceptor responsiveness as assessed by the cardiovascular responses to bolus doses of isoprenaline.

Adult↗
PubMed1985

Drugs and folate metabolism.

Folates are a group of compounds which are required in the diet and are important in DNA, amino acids and possibly also amine metabolism. The biologically active folates are in the tetrahydro form. Tetrahydrofolates are produced from unreduced dietary folates by the enzyme dihydrofolate reductase. A number of drugs such as aminopterin, methotrexate (amethopterin), pyrimethamine, trimethoprim and triamterene act as folate antagonists and produce folate deficiency by inhibiting this enzyme. With other drugs which produce low serum and tissue concentrations of folate such as anticonvulsants, antituberculosis drugs, alcohol and oral contraceptives, the mechanism of this effect is uncertain. Possible mechanism include reduced absorption, prevention of release of folate from tissue stores, altered plasma protein binding, or increased folate metabolism in the liver. Treatment with folic acid antagonists such as methotrexate readily causes megaloblastic anaemia; this can be prevented by therapy with folinic acid (5-formyltetrahydrofolate). The role of other drugs in producing megaloblastic anaemia is less certain, e.g. it occurs in less than 0.75% of patients receiving anticonvulsants. The possible neurological and psychiatric effects of folate deficiency are also uncertain. However, in patients with folate deficiency who have neuropsychiatric symptoms, neuropathy or myelopathy, and normal vitamin B12 levels, it may be of value to try therapy with folic or folinic acid.

Amines↗
PubMed1985

Pathological and virological studies of experimental parvoviral enteritis in calves.

Calves held in isolation showed a progressive decline in maternally derived antibody titres to bovine parvovirus but low concentrations of inhibitors resistant to heat and kaolin treatment persisted as the animals matured. These inhibitors had both haemagglutination inhibition and plaque neutralising activity and were considered to be of non-specific origin. Following oral challenge with bovine parvovirus, calves developed mild to moderate diarrhoea, with lymphopenia and viraemia. Sequential virological and immunofluorescent studies showed that the virus initially infected tonsils and intestinal tract, subsequently spreading to systemic lymphoid tissues. Histological and scanning electron microscopic examinations revealed moderate small intestinal villus atrophy and fusion due to crypt damage, together with lymphoid necrosis predominantly associated with the intestinal tract and thymus. Although the disease was not very severe, this may have been because the low parasite burden in the animals reduced mitotic activity in susceptible tissues.

Animals↗
PubMed1985

Epidemiological studies of parvovirus infections in calves on endemically infected properties.

Bovine parvovirus serology and virus excretion were monitored in calves located on three endemically infected North Queensland properties. Maternally derived serum antibody to bovine parvovirus was found to have a half-life of 19 days. On all three properties, calves developed intestinal bovine parvovirus infection with seroconversion soon after weaning. This occurred more promptly where the environment was subject to heavier bovine parvovirus contamination due to management practices. The concurrent presence of moderate levels of residual serum antibody had only minor influence on the onset of the infection. On one beef cattle property, onset of intestinal bovine parvovirus infection was associated with an outbreak of post-weaning diarrhoea. Anthelmintic treatment trials indicated that this syndrome was unrelated to helminth burdens, though coccidiosis appeared responsible for occasional subsequent cases of dysentery. It was considered that bovine parvovirus may have significantly contributed to the development of the diarrhoea syndrome, in conjunction with substantial weaning stresses.

Animals↗
PubMed1985

Exacerbation of experimental parvoviral enteritis in calves by coccidia and weaning stress.

The disease induced in calves following oral dosing with bovine parvovirus (BPV) was found to be substantially exacerbated when the animals had subclinical coccidiosis. Low levels of passive serum antibody appeared to have little influence on the response to BPV. Imposition of weaning stress on coccidia-infected calves which had apparently recovered from prior infection with BPV, was found to induce severe diarrhoea with recrudescence of BPV excretion in faeces. This was in marked contrast to the relatively mild diarrhoea which was found following weaning of control animals and animals infected with either agent alone. It was concluded that BPV activity and damage in the intestinal tract was probably enhanced as a consequence of the extra mitotic activity induced in the region by coccidial infection and the local effects of weaning. On the basis of these and previous findings in the field, it is suggested that BPV may play a significant role in the aetiology of post-weaning diarrhoea in calves.

Animals↗
PubMed1984

Radiation retinopathy after orbital irradiation for Graves' ophthalmopathy.

Recent reports indicate that orbital irradiation for Graves' ophthalmopathy is sometimes beneficial, particularly for dysthyroid optic neuropathy, and is not associated with serious complications. We are aware, however, of four patients who were found to have radiation retinopathy after orbital irradiation for Grave's ophthalmopathy. All four patients have decreased central acuity, and three of the four are legally blind in one or both eyes. Computer reconstruction of the dosimetry, based on computed tomography and beam profiles, shows that errors in dosage calculations and radiotherapy technique probably account for the radiation retinopathy in three of the four patients. Radiotherapy for Graves' ophthalmopathy should be administered only by competent radiotherapists who are experienced in the treatment of this disease. Similar errors in dosage calculations and treatment techniques may account for other reports of radiation retinopathy after reportedly safe dosages.

Adult↗
PubMed1984

Plaque titration and inhibition tests for bovine parvovirus.

Bovine parvovirus readily produced plaques when inoculated into 60% confluent, actively growing bovine embryonic lung cells. Incorporation of DEAE-dextran, MgCl2 and DMSO in the agarose overlay medium was found to improve plaque production, especially with the latter chemical. In contrast, protamine sulphate inhibited plaque development. It was found that plaque titration and plaque inhibition tests could be conveniently carried out in 24-well cell culture plates, using an agarose overlay containing DMSO, DEAE-dextran and foetal calf serum. The procedures were highly sensitive, when compared with other established techniques.

Animals↗
PubMed1984

Effects of ethanol ingestion on alpha-adrenoceptor-mediated circulatory responses in man.

The acute effects of ethanol on pressor responses to graded intravenous infusions of noradrenaline (24, 48, 90 ng kg-1 min-1) and methoxamine (0.2, 0.4, 0.8, 1.6, 2.0 mg/min, 1 min each) were each investigated in eight normal male subjects. The effects of ethanol on blood pressure, heart rate and plasma catecholamine responses to lower body negative pressure were also examined in six normal male subjects. Each subject acted as his own control by participating twice, once after consumption of ethanol (1.0 ml/kg, 20% v/v, in orange juice) and once after an equivalent volume of orange juice. Ethanol consumption significantly reduced the diastolic blood pressure response to infusion of noradrenaline. This occurred despite a significantly greater increase in plasma noradrenaline concentrations during infusion after ethanol. The systolic and diastolic blood pressure responses to infusion of methoxamine were both significantly reduced after ethanol. During lower body negative pressure, prior consumption of ethanol resulted in a greater fall in systolic blood pressure and a smaller rise in diastolic blood pressure. Plasma noradrenaline responses to lower body negative pressure were significantly increased after ethanol. It is concluded that acute ethanol ingestion depresses alpha-adrenoceptor-mediated vasoconstriction, with resulting impairment of blood pressure control.

Adult↗
PubMed1984

Disability in multiple sclerosis and the provision of social and medical services: findings in Wellington, New Zealand.

A study of the incapacity and socioeconomic scales in 120 patients with multiple sclerosis (MS) living in Wellington, New Zealand, is described. The questionnaire has been compared by different health professionals. There was good correlation between the observations of different professionals on incapacity analysis and this may be improved by reducing the questions to six. The findings on the socioeconomic scale, however, cannot be predicted accurately from the incapacity scale. The socioeconomic survey revealed major improvement in patient support in New Zealand during the last decade. We consider that our New Zealand findings indicate the value of field officers concerned with co-ordination of services and provision of information for patients with MS. Future research should be directed towards assessment of support systems.

Activities of Daily Living↗
PubMed1984

Parasympathetic denervation of the iris in alcoholics with vagal neuropathy.

Parasympathetic innervation of the pupil was studied in 30 alcoholics. Twelve alcoholics had cardiac vagal neuropathy. The resting pupillary diameters in this group were larger, and pupil responses to methacholine were greater, than in control subjects or alcoholics without vagal neuropathy. These observations imply that lesions in the parasympathetic supply to the pupil may occur in alcoholics with other evidence of autonomic neuropathy involving the parasympathetic system.

Adult↗
PubMed1984

Alcoholic vagal neuropathy: recovery following prolonged abstinence.

Cardiac vagal reflexes were studied in 11 alcoholic subjects, 1 to 6 weeks after withdrawal and again after up to 27 months of continued abstinence. On initial investigation six subjects had vagal neuropathy. On the second occasion only two subjects had vagal neuropathy and significant improvement was seen in the total patient group with regard to heart rate responses to standing, Valsalva's manoeuvre and atropine infusion. Vagal neuropathy in alcoholics may be reversible with abstinence and/or improved nutrition.

Adult↗
PubMed1984

Clinical assessment of sympathetic function in man.

Investigations are reviewed which are suitable for use in clinical situations in which lesions of the sympathetic nervous system are suspected. Particular attention is given to the problems of cardiovascular regulation as orthostatic hypotension is one of the commoner manifestations of sympathetic failure. Tests of the autonomic innervation of the eyes are also discussed. Tests of parasympathetic function are briefly described, as both parts of the autonomic nervous system may be affected by the same disease process.

Heart↗
PubMed1983

Improving health care team work by education.

The place of team work in health care is emphasised. Reasons for caution among members of the medical profession are defined. The importance of medical students being aware of the input of other health care professionals together with association with them in their training years and integration in activities where possible has been proposed previously, but largely neglected. A number of schemes for improving the education of other professional groups in association with the Wellington Clinical School of Medicine are described. Better teamwork in health care depends upon people learning to work together by association during their training years.

Biomedical Engineering↗
PubMed1983

Epilepsy and driving.

A survey was made of driving habits of 103 epileptic patients who, having suffered a seizure, were picked up by the Wellington Free Ambulance Service. It was found that 21 (20%) subjects were driving a motor vehicle--for nine this was necessary for their employment; 57% of drivers with epilepsy reported that the Ministry of Transport had not been informed of their epilepsy. For three subjects a driving accident was a direct result of their seizure. Forty-three percent of subjects in this study claimed never to have had any professional advice about driving. Of the 21 subjects who continued to drive, 13 were receiving inadequate drug therapy at the time of seizure. Advice and drug therapy for epileptic patients therefore required regular review. We consider that the Ministry of Transport should issue a simple statement about epilepsy and driving which should explain the law, risks, precipitating factors for epilepsy, and the need for good drug control. This should be issued to doctors and also be available for those applying for a driving licence.

Accidents, Traffic↗