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Biomedical subjects

S B Lucas

Publications and source records attributed to S B Lucas.

At least 163 records · Page 9Linked to original sources
PubMed1982

Does Pneumocystis carinii occur in Kenya?

An experiment was carried out exposing immunosuppressed mice to the atmosphere to determine if transmission of Pneumocystis carinii occurred in Kenya. Mice were killed at weekly intervals for four months and the lungs examined histologically for the presence of these parasites. None of the mice contracted even light infections and this, together with the lack of clinical evidence of this disease in immunosuppressed or neonatal cases, suggests that this parasite does not occur in Kenya. Possible reasons for this are discussed.

Animals↗
PubMed1982

Esophageal varices in Nairobi, Kenya: a study of 68 cases.

Sixty-eight patients with proven esophageal varices wer studied at Kenyatta National Hospital, Nairobi, Kenya. Of these patients, 29.4% had schistosomal portal hypertension, 22.1% cirrhosis and only 8.8% extrahepatic portal vein occlusion. One quarter of the patients had a normal liver biopsy and extrahepatic portal vein that was demonstrated to be patent. Problems relating to liver biopsy sampling resulting in underdiagnosis of specific causes of esophageal varices such as schistosomiasis are discussed. We argue that many of these patients were likely to be suffering from idiopathic portal hypertension, a condition apparently not previously recognized in Africa. Of this last group, 70.6% had suffered gastrointestinal bleeding, as had 50% of the patients with schistosomiasis. Together these two groups accounted for three-quarters of all patients who had bled. The detection of eggs of Schistosoma mansoni in stool and/or rectal snip correlated well with liver biopsy findings in both a positive and negative sense. Only 18% of patients with negative stools and snips had evidence of schistosomiasis in the liver, and positive stools or snips were found in only 14.6% of patients without schistosomal liver involvement. Of the patients in the study, 50% were of the Kamba tribe, although only 12.9% of all medical admissions to the hospital were Kamba (P less than 0.01). Luo patients were significantly more frequent within the group with schistosomiasis (P less than 0.02). Esophageal varices were attributed to tropical splenomegaly syndrome in only one patient. The implications of our results are discussed and our findings are compared with previous work from East Africa.

Adolescent↗
PubMed1981

Babesia divergens infections in the Mongolian gerbil: characteristics of a human strain.

A strain of the cattle piroplasm Babesia divergens isolated from a fatal human infection was propagated in the Mongolian gerbil through 150 semi-continuous intraperitoneal passages. The infection was normally fatal; death, accompanied by profuse haemoglobinuria and debilitation, occurred as early as 44 h after intraperitoneal inoculation of heavily parasitized blood with precipitous drops in red blood cell and platelet counts. The average maximum parasitaemia achieved increased on continuous passage reaching 80% by the 150th stage. Twenty-four hours after infection erythrophagocytosis and splenic congestion were apparent by light and electron-microscopical examination and by 48 h hepatic necrosis, renal tubular damage with haemoglobin cast accumulation and ischaemic necrosis of ileal mucosa had developed. Gerbils were highly susceptible to small numbers of parasites when the inoculum was either fresh parasitized blood in high dilution or erythrocytes concentrated from animals showing minimal parasitaemia. Animals inoculated with parasites preserved in dimethyl sulphoxide at low temperatures usually developed fatal infections. However, occasionally animals suffered at most a low grade parasitaemia subsequent to recovery with parasite elimination. These animals were immune to further challenge, and no chronic infections developed. A field strain of B. divergens isolated locally from a case of bovine redwater behaved similarly to the human strain on continuous passage in gerbils.

Animals↗
PubMed1980

Abnormal development of Hymenolepis nana larvae in immunosuppressed mice.

Observations on the course of Hymenolepis nana infection in immunosuppressed mice are presented. Treatment of the host with hydrocortisone acetate caused superinfection of the bowel with worms and the development of normal cysticercoids in the mesenteric lymph node and liver. Natural infection of mice deprived of their T-cells by pre-adult thymectomy and administration of antithymocyte serum resulted in superinfection and widespread metastasis of aberrant cysticercoids that were greatly enlarged and without scolices, causing death after about five months. The significance of these findings and their possible relevance to human infection with H. nana are discussed.

Animals↗
PubMed1980

Opisthorchis viverrini: liver changes in golden hamsters maintained on high and low protein diets.

Two groups of hamsters maintained on eight high (25.6%) or low (5.3%) content protein diets were infected with 50 Opisthorchis viverrini metacercariae by intragastric inoculation. Three animals from each group were sacrificed at 14-day intervals over a 32-week period. Two groups of non-infected control animals maintained on identical diets were killed at similar intervals. Histological examination revealed qualitatively similar pathological responses to the parasite in both diet groups, but overall the low protein diet group had the more severe lesions. Two weeks after infection, second order bile ducts showed epithelial focal necrosis, reactive hyperplasia and folding of the bile duct epithelium with some periductal fibrosis. Periductal inflammatory cells were predominantly eosinophils and lymphocytes at this time, changing after six weeks to predominantly lymphoblast and plasma cell infiltrates. Central bile ducts showed maximal concentric fibrosis at 12 weeks and this was considerably more pronounced in high protein fed animals. The small peripheral bile ductules proliferated and by four weeks post-infection, adjacent portal tracts appeared linked together, until at eight weeks some of the livers were nodular. The degree of bile ductule proliferation was markedly more pronounced in the low protein fed animals such that by 12 weeks parts of the peripheral liver substance was obliterated by proliferating ductules. No tumours or evidence of premalignant lesions were detected in livers from any of the infected animals, but it is likely that the infection period was rather too short for malignant transformation to ensue. The possible pathogenetic mechanisms operating in this animal model of opisthorchiasis are discussed with particular reference to the disease in man.

Animals↗
PubMed1979

Leucocyte ascorbate levels and postoperative deep venous thrombosis.

Forty-four general surgical patients were included in a prospective, randomized double-blind controlled trial of ascorbic acid (500 mg b.d.) or placebo for 7 days before operation. This was to test the hypothesis that vitamin C may reduce the instance of deep venous thrombosis postoperatively. Venous blood samples were taken before entering the trial, just immediately before surgery, on the day of operation and on three further occasions at 3-day intervals postoperatively for leucocyte ascorbic acid concentration (LAC). Venous thrombosis was diagnosed using the 125I-fibrinogen test and the leg scans interpreted by Roberts' criteria. There was no significant difference in the incidence of DVT between the treatment and placebo groups. In those with DVT (n = 23) the mean LAC on the day of operation was not significantly different from that in those without DVT. However, on the sixth and ninth postoperative days LAC levels were significantly lower in the DVT group. These results suggest that the administration of ascorbic acid preoperatively does not reduce the incidence of DVT, but a striking decrease in the LAC levels in the DVT patients is in keeping with the hypothesis that the initial event in the pathogenesis of DVT is adherence of leucocytes to the venous endothelium.

Ascorbic Acid↗
PubMed1979

An analysis of the spatial distribution of attenuation values in computed tomographic scans of liver and spleen.

An autocorrelation analysis of the attenuation values in computed tomographic scans has been performed for a total of 35 normal and eighteen cirrhotic patients. The results confirm preliminary observations on a smaller sample which suggested that this technique may be used to separate normal and cirrhotic livers. The noise structure in a region within the spleen was also examined and found to change in the presence of cirrhosis.

Humans↗
PubMed1977

Peripheral retinal ablation in the treatment of proliferative diabetic retinopathy: a three-year interim report of a randomised, controlled study using the argon laser.

A randomised controlled trial is reported of 94 patients with a symmetrical proliferative diabetic retinopathy involving the optic disc, who were treated by a peripheral retinal ablation technique using the argon laser. A highly significant difference in mean cumulative deterioration of visual acuity and blindness was shown in all but the late stages of the disease process between treated and untreated eyes. The untreated eyes exhibited far worse results. The earlier photocoagulation is initiated in the course of the proliferative process in this disease to control or preferably eliminate optic disc neovascularisation, the better the visual prognosis.

Blindness↗
PubMed1976

Can digoxin dose requirements be predicted?

A search for patient variables relevant to digoxin dose requirements was made in fourty-three patients with a wide range of renal and hepatic function. The daily dose of digoxin to achieve a mean serum concentration of 1.5 ng/ml, the standardized dose, was calculated for each patient. The standardized dose correlated significantly with the following variables, in descending order of correlation coefficient; creatinine clearance, serum creatinine concentration, body weight and serum albumin concentration. An equation containing the two independent variables, creatinine clearance and serum albumin concentration, had a significantly stronger correlation with standardized dose than creatinine clearance alone. Attempts were made in each patient to predict the standardized dose using both empirical prescribing methods and the published nomograms. Although a maximum of 70% of the variance of the standardized dose was explained, this corresponded approximately to one patient in three having a predicted dose outside the 95% confidnece limits for the standardized dose. There remain important sources of individual variation in digoxin dose requirements yet to be identified. Future application of empirical prescribing methods, such as multiple linear regression and Bayes' theorem, to prescription for large, defined patient groups may improve dose prediction for individual patients.

Digoxin↗