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Biomedical subjects

P M Atkinson

Publications and source records attributed to P M Atkinson.

At least 19 recordsLinked to original sources
PubMed2006

Issues of scale and uncertainty in the global remote sensing of disease.

Scale and uncertainty are important issues for the global prediction of disease. Disease mapping over the entire surface of the Earth usually involves the use of remotely sensed imagery to provide environmental covariates of disease risk or disease vector density. It further implies that the spatial resolution of such imagery is relatively coarse (e.g., 8 or 1km). Use of a coarse spatial resolution limits the information that can be extracted from imagery and has important effects on the results of epidemiological analyses. This paper discusses geostatistical models for (i) characterizing the scale(s) of spatial variation in data and (ii) changing the scale of measurement of both the data and the geostatistical model. Uncertainty is introduced, highlighting the fact that most epidemiologists are interested in accuracy, aspects of which can be estimated with measurable quantities. This paper emphasizes the distinction between data- and model-based methods of accuracy assessment and gives examples of both. The key problem of validating global maps is considered.

Animals↗
PubMed2004

Spatial analysis for epidemiology.

Remote sensing, geographical information systems (GIS) and spatial analysis provide important tools that are as yet under-exploited in the fight against disease. As the use of such tools becomes more accepted and prevalent in epidemiological studies, so our understanding of the mechanisms of disease systems has the potential to increase. This paper introduces a range of techniques used in remote sensing, GIS and spatial analysis that are relevant to epidemiology. Possible future directions for the application of remote sensing, GIS and spatial analysis are also suggested.

Animals↗
PubMed2000

Linking remote sensing, land cover and disease.

Land cover is a critical variable in epidemiology and can be characterized remotely. A framework is used to describe both the links between land cover and radiation recorded in a remotely sensed image, and the links between land cover and the disease carried by vectors. The framework is then used to explore the issues involved when moving from remotely sensed imagery to land cover and then to vector density/disease risk. This exploration highlights the role of land cover; the need to develop a sound knowledge of each link in the predictive sequence; the problematic mismatch between the spatial units of the remotely sensed and epidemiological data and the challenges and opportunities posed by adding a temporal mismatch between the remotely sensed and epidemiological data. The paper concludes with a call for both greater understanding of the physical components of the proposed framework and the utilization of optimized statistical tools as prerequisites to progress in this field.

Animals↗
PubMed1991

Case report: splenic-gonadal fusion--the ultrasound appearances.

We report the ultrasound appearances, with pathological correlation, of splenic-gonadal fusion in a patient who presented with an asymptomatic scrotal swelling. Ultrasound examination showed an echo-poor 2 cm diameter lesion in the upper pole of the left testicle. Histologically the lesion was normal spleen. Splenic-gonadal fusion should be considered in the differential diagnosis of scrotal swellings.

Female↗
PubMed1989

Biochemical characterisation of the haemophilias on the Witwatersrand.

Blood samples obtained from patients on the Witwatersrand with haemophilia A, haemophilia B and von Willebrand disease were analysed. Factor activities were assayed by conventional methods. Immunoradiometric assay using labelled monoclonal anti-VIIIC:Ag was developed to assay factor VIIIC:Ag in haemophilia A. Factor IX:Ag levels were determined by a commercial ELISA kit. Multimer pattern analysis of von Willebrand factor was performed by agarose gel electrophoresis and Western blotting. In 43 patients haemophilia A was severe, in 8 it was moderate and in 2 it was mild. Factor VIIIC:Ag was undetected in 36 haemophiliacs (CRM-) while VIIIC:Ag was detected in levels exceeding or correlating with those of VIII:C in 17 cases (CRM+). Four severe, CRM- haemophiliacs were found to have inhibitors. An assay of IX:Ag in 6 severely and 2 moderately affected patients with haemophilia B revealed 6 to be CRM- while 2 were CRM+. Multimer pattern analysis was performed on 11 von Willebrand disease patients, of which 5 were type I, 5 were type II and 1 was type III. More informative techniques for the diagnosis and classification of haemophilia are now available. In addition, these results will assist in further molecular studies of these disorders.

Electrophoresis, Agar Gel↗
PubMed1989

Fatty acid composition of some South African fresh-water fish.

Because of the antithrombotic and anti-inflammatory properties of the n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in large quantities in marine fish, the fatty acid composition of the flesh of 18 different species of fresh-water fish found in South Africa was analysed by capillary gas chromatography. In general all the fish studied had low percentages of EPA and DHA and fairly high percentages of arachidonic acid and linoleic acid when compared with some marine fish. The saturated fats constituted 33% of total fatty acids and the mono-enes averaged 35%. The fish studied are therefore not as good a source of n-3 fatty acids as marine fish.

Animals↗
PubMed1989

Alcohol intakes and deficiencies in thiamine and vitamin B6 in black patients with cardiac failure.

Thiamine and vitamin B6 status was evaluated in 73 consecutive black patients with cardiac failure at Baragwanath Hospital. They consumed moderate to large amounts of traditional as well as Western-type beer and liquor. Thirty per cent had erythrocyte thiamine concentrations below the reference range. The transketolase response to thiamine pyrophosphate (TPP effect) suggested thiamine deficiency in 32.4%, of whom 13.2% were classified as severely deficient. Vitamin B6 deficiency was present in 21.4%, with a further 42.9% in the very low normal range. Only one patient had beriberi heart disease. Idiopathic dilated cardiomyopathy was the main cause of cardiac failure. It is suggested that excessive alcohol consumption is an important factor contributing to cardiac morbidity in urban blacks.

Adult↗
PubMed1989

Hypothesis: a central role for platelet activating factor in the pathogenesis of pre-eclampsia.

The pathophysiology of pre-eclampsia is uncertain, though many mechanisms have been postulated. These include an immune response to fetal or placental antigens, a thromboxane-prostacyclin system imbalance and an increase in levels of or responsiveness to angiotensin. We propose the hypothesis that platelet activating factor (PAF), a mediator of inflammatory and allergic responses, may be an important link between these pathophysiological events.

Angiotensin II↗
PubMed1988

Disturbances of blood coagulation associated with Salmonella typhi infections.

Disturbances of blood coagulation were studied in 32 consecutive patients with typhoid fever on their admission to hospital. Estimations of prothrombin time, activated partial thromboplastin time, fibrinogen, fibrin degradation products (FDPs), factors VII, VIII and XII, alpha I antitrypsin, plasminogen, CI esterase inhibitor, and platelet counts were performed as well as liver function tests and blood counts. Five patients had laboratory evidence of disseminated intravascular coagulation (DIC) and two had a generalised bleeding disorder which in the other three was inapparent. The platelet count in the group as a whole was low (P less than 0.05) and the FDPs in most cases were mildly elevated. The pre-kallikrein values were depressed in three of the five with DIC, whereas factor XII was not reduced. These results indicate that bleeding disorders in typhoid fever are uncommon. The depression of pre-kallikrein indicates that the DIC is probably triggered by activation of the intrinsic coagulation pathway. Most patients had lymphopenia and monocytopenia but only two had neutropenia.

Adolescent↗
PubMed1988

Platelet aggregations, fatty acids, clotting factors and serum lipids in rural and urban blacks, and urban whites in South Africa.

Platelet fatty acids, platelet aggregations, and coagulation factors were measured in 27 rural blacks, 27 urban blacks and 39 urban whites. Platelets were significantly less aggregable to collagen and arachidonic acid in in both black groups as compared to whites (p less than 0.01), but there were no significant differences in ADP or epinephrine aggregation between these groups. Factor VIII coagulant activity was much higher in rural and urban blacks than whites (p less than 0.001), and the partial thromboplastin times were shorter (p less than 0.005). Platelet arachidonic acid showed a marked difference between the groups, being 16.4 +/- 5.4% of total platelet fatty acids in the rural blacks, 19.9 +/- 4.2% in the urban blacks and 22.6 +/- 3.3% in the whites (p less than 0.001). Whites had higher LDL and lower HDL cholesterol than blacks (p less than 0.005). These findings suggest that in addition to the well known association of raised LDL cholesterol and acute myocardial infarction, platelet aggregation patterns and platelet arachidonic acid levels may be associated risk factors in coronary thrombosis.

Adult↗
PubMed1988

Fatty acid composition of human milk from South African black mothers consuming a traditional maize diet.

Fatty acid composition of mature human milk of rural and urban black South African mothers was determined by gas-liquid chromatography. Rural mothers consumed traditional diets low in animal protein and fat, and high in carbohydrate and fibre. Urban mothers consumed more varied, partially westernized diets, and two-thirds were overweight. Plasma cholesterol concentrations were significantly lower in the rural group (3.64 vs 4.75 mmol/l, P less than 0.01). Milk of rural mothers contained significantly higher percentages of C10:0, C12:0, and total saturated fatty acids. Fatty acids C8:0-C14:0 synthesized de novo in the mammary gland were substantially higher in the milk of the rural mothers (24.7 vs 15.9 per cent). Conversely, the milk of the urban group contained higher percentages of monounsaturated fatty acids, 18:3 omega 3 and 20:2 omega 6. The ratio of polyunsaturated to saturated fatty acids in rural samples was 0.36 +/- 0.13 compared to 0.41 +/- 0.15 in urban samples (P greater than 0.1). It is concluded that maternal dietary intake significantly affects milk composition, as demonstrated by the high percentages of fatty acids synthesized de novo in the mammary gland of rural mothers habituated to low-fat, high-carbohydrate intakes.

Adult↗
PubMed1987

Normal haematological reference values in the adult black population of the Witwatersrand.

Normal haematological reference values for healthy adult blacks residing on the Witwatersrand are given. The haemoglobin concentration was 13.95 +/- 0.8 g/dl for women and 15.82 +/- 1.05 g/dl for men. Leucocyte counts were lower than those found in whites, being 5.60 +/- 1.51 X 10(9)/l for both sexes. Platelet counts were 280 +/- 59.4 X 10(9)/l for men and 317 +/- 64.0 X 10(9)/l for women. The differential counts and other parameters are given in the text.

Adult↗
PubMed1987

Effects of a 4-week freshwater fish (trout) diet on platelet aggregation, platelet fatty acids, serum lipids, and coagulation factors.

Eight healthy subjects consumed a diet in which all animal products were replaced by 750 g/day of freshwater trout. Platelet eicosapentaenoic acid (EPA) as a percentage of total platelet fatty acids rose from a prediet level of 0.2 +/- 0.4% to 3.4 +/- 1.6% after 4 weeks on the diet. Platelet arachidonic acid remained unchanged. Platelets became more hyperaggregable to collagen (p less than .025) but became hypoaggregable to arachidonic acid (p less than .05). The Ivy bleeding time became prolonged rising from a mean of 148 seconds before the diet to 168 seconds at 2 weeks and 202 seconds at 4 weeks. Serum lipids, coagulation profiles, and blood pressure remained unchanged. The changes induced by this diet were much less marked than changes induced by marine fish diets and diets supplemented by marine fish oil extracts, despite the fact that an equivalent amount of EPA was consumed and incorporated into platelets. These findings suggest that other substances, in addition to n-3 unsaturated fatty acids, may be responsible for the antithrombotic properties of marine fish.

Adult↗
PubMed1987

Pregnancy induced hypertension: will treatment with dietary eicosapentaenoic acid be effective?

The current understanding of endothelial membrane prostaglandin metabolism is presented together with an explanation of how this may be altered in pregnancy induced hypertension (PIH). A hypothesis is proposed to explain why dietary supplementation with eicosapentaenoic acid (EPA) may reverse abnormal prostaglandin metabolism, increase membrane fluidity and lower blood pressure in PIH.

Eicosapentaenoic Acid↗
PubMed1985

Inhibition of platelet aggregation by ketamine hydrochloride.

Ketamine hydrochloride, 10 mg/kg by intramuscular injection, inhibited aggregation of platelets from three out of three baboons. Aggregation to ADP, arachidonic acid, epinephrine, and collagen was inhibited but aggregation to ristocetin was normal. Two baboons anaesthetised with the related drug phencyclidine, 1.0 mg/kg intramuscularly, had delayed aggregation. Ketamine inhibition of human platelets was irreversible in that aggregation could not be restored by either gel filtration of inhibited platelets and the re-addition of normal plasma, or by increasing the concentrations of agonists. Mixtures of human ketamine inhibited and aspirinised platelets failed to aggregated. Thromboxane B2 production was reduced to 3% of the amount produced by non inhibited platelets but the oxygen burst was not inhibited.

Adenosine Diphosphate↗
PubMed1985

Long-term ultra-low-dose aspirin therapy and platelet function.

The effect of ultra-low-dose aspirin on platelet aggregation and thromboxane B2 (TXB2) production was studied in two groups of normal subjects. Group 1 received 162 mg/d and group 2 received 20 mg/d for 4 weeks. For the first 2 weeks the effects were similar in the two groups, namely inhibition of aggregation and inhibition of TXB2 production. However, after 4 weeks there was significantly less inhibition of platelet aggregation in those receiving 20 mg/d. Inhibition of TXB2 production in the two groups was not significantly different. Two of 9 individuals receiving 20 mg/d showed an escape from the aspirin effect by the 4th week. When 40 mg/d was given to these 2 individuals they again responded. A daily dose of 20 mg aspirin is therefore too small to maintain adequate inhibition of platelet function in normal subjects.

Adenosine Diphosphate↗