Ventricular performance and Na+-K+ ATPase activity are reduced early and late after myocardial infarction in rats

Myocardial infarction leads to compensatory ventricular remodeling. Disturbances in myocardial contractility depend on the active transport of Ca2+ and Na+, which are regulated by Na+-K+ ATPase. Inappropriate regulation of Na+-K+ ATPase activity leads to excessive loss of K+ and gain of Na+ by the cell. We determined the participation of Na+-K+ ATPase in ventricular performance early and late after myocardial infarction. Wistar rats (8-10 per group) underwent left coronary artery ligation (infarcted, Inf) or sham-operation (Sham). Ventricular performance was measured at 3 and 30 days after surgery using the Langendorff technique. Left ventricular systolic pressure was obtained under different ventricular diastolic pressures and increased extracellular Ca2+ concentrations (Ca2+e) and after low and high ouabain concentrations. The baseline coronary perfusion pressure increased 3 days after myocardial infarction and normalized by 30 days (Sham 3 = 88 ± 6; Inf 3 = 130 ± 9; Inf 30 = 92 ± 7 mmHg; P < 0.05). The inotropic response to Ca2+e and ouabain was reduced at 3 and 30 days after myocardial infarction (Ca2+ = 1.25 mM; Sham 3 = 70 ± 3; Inf 3 = 45 ± 2; Inf 30 = 29 ± 3 mmHg; P < 0.05), while the Frank-Starling mechanism was preserved. At 3 and 30 days after myocardial infarction, ventricular Na+-K+ ATPase activity and contractility were reduced. This Na+-K+ ATPase hypoactivity may modify the Na+, K+ and Ca2+ transport across the sarcolemma resulting in ventricular dysfunction.

Ventricular performance and Na+-K+ ATPase activity are reduced early and late after myocardial infarction in rats.

Myocardial infarction leads to compensatory ventricular remodeling. Disturbances in myocardial contractility depend on the active transport of Ca2+ and Na+, which are regulated by Na+-K+ ATPase. Inappropriate regulation of Na+-K+ ATPase activity leads to excessive loss of K+ and gain of Na+ by the cell. We determined the participation of Na+-K+ ATPase in ventricular performance early and late after myocardial infarction. Wistar rats (8-10 per group) underwent left coronary artery ligation (infarcted, Inf) or sham-operation (Sham). Ventricular performance was measured at 3 and 30 days after surgery using the Langendorff technique. Left ventricular systolic pressure was obtained under different ventricular diastolic pressures and increased extracellular Ca2+ concentrations (Ca2+e) and after low and high ouabain concentrations. The baseline coronary perfusion pressure increased 3 days after myocardial infarction and normalized by 30 days (Sham 3 = 88 +/- 6; Inf 3 = 130 +/- 9; Inf 30 = 92 +/- 7 mmHg; P < 0.05). The inotropic response to Ca2+e and ouabain was reduced at 3 and 30 days after myocardial infarction (Ca2+ = 1.25 mM; Sham 3 = 70 +/- 3; Inf 3 = 45 +/- 2; Inf 30 = 29 +/- 3 mmHg; P < 0.05), while the Frank-Starling mechanism was preserved. At 3 and 30 days after myocardial infarction, ventricular Na+-K+ ATPase activity and contractility were reduced. This Na+-K+ ATPase hypoactivity may modify the Na+, K+ and Ca2+ transport across the sarcolemma resulting in ventricular dysfunction.

Diet and overweight and obesity in populations of African origin: Cameroon, Jamaica and the UK.

OBJECTIVES: To determine the relationship of diet to overweight and obesity among populations of African origin. DESIGN AND SETTING: Cross-sectional data were obtained from adults aged 25-74 years in rural Cameroon (n = 686), urban Cameroon (n = 975), Jamaica (n = 924) and Afro-Caribbeans in the UK (n = 257). Dietary data were collected using food-frequency questionnaires specifically designed for each site. Body mass index (BMI) was used as a measure of overweight. RESULTS: The expected gradient in the distribution of overweight across sites was seen in females (rural Cameroon, 9.5%; urban Cameroon, 47.1%; Jamaica, 63.8%; UK, 71.6%); however, among males overweight was less prevalent in Jamaica (22.0%) than urban Cameroon (36.3%). In developing countries increased risks of overweight (BMI > or = 25 kg m(-2) were influenced by higher energy (urban Cameroonian men) and protein (Jamaican women) intakes. No dietary variables were associated with obesity (BMI > or = 30 kg m(-2) in Cameroon or Jamaica. In the UK, energy intakes were inversely related with overweight whereas increased risks of being overweight were associated with higher protein (men) and fat (women) intakes. Similarly, whereas higher protein and fat intakes in UK men and women were associated with obesity, carbohydrate intakes were associated with decreased risks of obesity in men. CONCLUSIONS: Diet and overweight were associated in the UK but few dietary variables were related to overweight in Jamaica and the Cameroon. These findings suggest that associations between diet and overweight/obesity are not generalisable among populations.

Habitual diet in four populations of African origin: a descriptive paper on nutrient intakes in rural and urban Cameroon, Jamaica and Caribbean migrants in Britain.

BACKGROUND: The prevalence of chronic diseases is increasing in West Africa, the Caribbean and its migrants to Britain. This trend may be due to the transition in the habitual diet, with increasing (saturated) fat and decreasing fruit and vegetable intakes, both within and between countries. OBJECTIVE: We have tested this hypothesis by comparing habitual diet in four African-origin populations with a similar genetic background at different stages in this transition. DESIGN: The study populations included subjects from rural Cameroon urban Cameroon Jamaica and African-Caribbeans in Manchester, UK all aged 25-74 years. Habitual diet was assessed by a food-frequency questionnaire, specifically developed for each country separately. RESULTS: Total energy intake was greatest in rural Cameroon and lowest in Manchester for all age/sex groups. A tendency towards the same pattern was seen for carbohydrates, protein and total fat intake. Saturated and polyunsaturated fat intake and alcohol intake were highest in rural Cameroon, and lowest in Jamaica, with the intakes in the UK lower than those in urban Cameroon. The percentage of energy from total fat was higher in rural and urban Cameroon than in Jamaica and the UK for all age/sex groups. The opposite was seen for percentage of energy from carbohydrate intake, the intake being highest in Jamaica and lowest in rural Cameroon. The percentage of energy from protein increased gradually from rural Cameroon to the UK. CONCLUSIONS: These results do not support our hypothesis that carbohydrate intake increased, while (saturated) fat intake decreased, from rural Cameroon to the UK.

Reproducibility and validity of a quantitative food-frequency questionnaire among Jamaicans of African origin.

BACKGROUND: An interviewer-administered quantitative food-frequency questionnaire (FFQ) was developed to determine the energy and nutrient intakes of adult Jamaicans of African origin as part of a study of the epidemiology of diabetes and hypertension. METHODS: Reproducibility of the questionnaire was investigated in 123 participants aged 25-74 years. The relative validity of the FFQ was assessed against twelve 24-hour recalls administered over 12 months in 73 of the participants. In addition, energy intakes (EI) were compared with estimated basal metabolic rates (BMR). RESULTS: Reproducibility correlation coefficients (Pearson and intraclass) varied between 0.42 for retinol and 0.71 for carbohydrate, with most values falling between 0.50 and 0.60. When compared with repeated 24-hour recalls, the FFQ estimated slightly higher energy (mean 6%) and macronutrient intakes (mean 2-14%), and was within 5% when expressed as a percentage of energy intake. Micronutrients were higher by 1.19 (calcium) to 1.61 times (vitamin C). Unadjusted correlations between the FFQ and the reference method ranged from 0.20 for beta-carotene to 0.86 for alcohol. Cross-classification of nutrients into quartiles showed that 46-48% of participants in the lowest and highest quartiles were jointly classified by both methods. Misclassifications were low for most nutrients with one or two persons misclassified at the extreme quartiles. EI/BMR ratios suggested light to moderate activity levels appropriate for an urban population in a developing country. CONCLUSIONS: The FFQ showed reasonable reproducibility and validity and is suitable for estimating the habitual intakes of energy and macronutrients, but was poor for some micronutrients (retinol and beta-carotene).

Underreporting of energy intake in four populations of African origin.

OBJECTIVE: To investigate the frequency of dietary underreporting in four African populations in different geographic and cultural settings. SUBJECTS: Seven-hundred and forty three men and women from rural Cameroon, 1042 men and women from urban Cameroon, 857 men and women from Jamaica and 243 male and female African Caribbeans from the UK. Subjects who reported dieting or weight control were excluded. MEASUREMENTS: Habitual dietary intake was estimated with a quantitative food frequency questionnaire, developed specifically for each country. Underreporting was defined using three cut-off levels for energy intake/estimated basic metabolic rate (EI/BMRest), based on age, sex and weight, in each site. RESULTS: The EI/BMRest was highest in rural Cameroonian men at 3.07 (95% confidence interval: 2.97, 3.17) and women at 2.84 (2.74, 2.94), intermediate in urban Cameroon and Jamaica and lowest in the UK men and women at 1.44 (1.26, 1.62) and 1.41 (1.21, 1.61). This trend existed even after adjustment for age, BMI and education (P for trend<0.0001). The trend in the frequency of underreporting using the lowest cut-off level for EI/BMRest of 1.15 was 6% and 6% in rural Cameroon for women and men, respectively, 4% and 5% in urban Cameroon, 24% and 19% in Jamaica and 28% and 39% in the UK. With higher cut off levels this trend was similar. CONCLUSION: The results suggest that the frequency of dietary underreporting differs between societies and that Westernization may be one of the factors underlying this phenomenon.

Development of food frequency questionnaires in three population samples of African origin from Cameroon, Jamaica and Caribbean migrants to the UK.

OBJECTIVES: To develop the methods for assessment of food and nutrient intake using standardized food frequency questionnaires (FFQ) in three African origin populations from Cameroon, Jamaica and Caribbean migrants to the United Kingdom. DESIGN: Cross-sectional assessment of diet from a representative sample in each site, using either a 2-day food diary or a 24-h recall method to determine foods for inclusion on the food frequency questionnaire. SETTING: A rural and urban site in Cameroon, Evodoula and Cite Verte in Yaounde, respectively; a district in Kingston Jamaica; African-Caribbeans living in central Manchester, UK. SUBJECTS: Aged 25-79 years, 61 from the Cameroonian urban site, 62 from the village site; 102 subjects from Jamaica (additional analysis on a subsample of 20): 29 subjects from Manchester, UK. MAIN OUTCOME MEASURES: Foods contributing to nutrients in each site to allow the development of a FFQ. RESULTS: A high response rate was obtained in each site. Comparison of macronutrient intakes between the sites showed that carbohydrate was the most important contributor to energy intake in Jamaica (55%) and the least in rural Cameroon. In rural Cameroon, fat (mainly palm oil) was the most important contributor to energy intake (44%). Manchester had the highest contribution of protein to energy (17%). Foods contributing to total energy, protein, fat and carbohydrate were determined. In rural Cameroon, the top 10 food items contributed 66% of the total energy intake compared to 37% for the top 10 foods in Manchester. Foods contributing to energy were similar in Jamaica and Manchester. Cassava contributed 44% of the carbohydrate intake in rural Cameroon and only 6% in urban Cameroon. One FFQ has been developed for use in both sites in Cameroon containing 76 food items. The FFQ for Jamaica contains 69 foods and for Manchester 108 food items. CONCLUSION: Considerable variations exist within sites (Cameroon) and between sites in foods which are important contributors to nutrient intakes. With careful exploration of eating habits it has been possible to develop standardized, but locally appropriate FFQs for use in African populations in different countries.

Nutritional influences on the emergence of diabetes mellitus and high blood pressure in Afro-origin populations in Cameroon, Jamaica, and Caribbean migrants to Europe - abstract

Our four nation study is establishing the role of nutrition in evolving diabetes mellitus (DM) and high blood pressure (BP) in these Afro-origin populations. Using highly standardized methods, we are testing whether increasing energy (particularly fat) and Na+ intakes, and decreased K+, Ca+ and antioxidant intakes, are associated with decreasing glucose tolerance (GT) and increasing BP within and between centres. Random community samples, aged 25 - 74 years, are stratified by sex up to 1,500/centre to generate sufficient index cases of impaired (I) GT and `high' BP (> 140 and/or 90 mm Hg but < 160 to 95 mm Hg) for an intervention trial and incident phase. During a 2-hr 759 glucose tolerance test (GTT), a food frequency questionnaire (FQQ), built up from food dairies and 24-hr recalls, and repeat 24-hr urines are supplying mean energy, fat, carbohydrate, fibre, protein and cation intakes. To date, 894 Jamaicans have been seen at the Spanish Town site, some 780 people (360 Afro-Caribbean) in Manchester, with 180 GT tested, 416 Cameroonians (246 urban) and a pilot study completed in Paris. Rates of IGT and DM run at approximately 8 percent and 14 percent in Jamaica, 15 percent of each in Manchester, and 4-8 percent in Cameroon through Jamaica to Manchester. Those at risk of hypertension (> 140 and/or 90 mm Hg) are similarly distributed. As baseline prevalence rates are established, the nutritionally-based intervention programme will be piloted as a randomized trial. Such efforts offer the chance for primary prevention of high BP, diabetes mellitus and their complications in these populations, before or as they face an epidemic from them (AU)

Blood pressure and renal prostaglandin E2-like content in unilateral kidney radiation

Se estudiaron los efectos de la irradiación renal con rayos X sobre la concentración de prostaglandina medular y la tensión arterial en la rata. A tales fines, 26 ratas fueron divididas en los siguientes grupos: 6 controles (operados pero no irradiadas) fueron sacrificadas a las 12 semanas; a 20 se les irradió un riñón expuesto a través de una incisión en el flanco recibiendo una dosis de 3000r. Estas ratas fueron sacrificadas en grupos de cinco a 1, 4, 8 y 12 semanas después de la irradiación. Se determinó tensión arterial sistólica, concentración de sustancia tipo PGE2 y tamaño renal. La tensión arterial promedio aumentó progresiva y significativamente (p<0,005). El riñon irradiado disminuyó en tamaño y la diferencia con el riñon opuesto fue estadísticamente significativa a 8 y 12 semanas post-irradiación (p<0,05). Al mismo tiempo el contenido de PGE2 tanto en el riñon irradiado como en el opuesto disminuyó significativamente (p<0,005 y 0,001, respectivamente). Hubo una correlación negativa estadísticamente significativa entre la tensión arterial y el contenido de sustancia tipo PGE2 en ambos riñones (r=-0,50), así como también entre los valores tensionales y el promedio y la suma del contenido de PGE2 de ambos riñones (r=0,53). Los resultados sugieren un rol de las prostaglandinas renales en el desarrollo de la hipertensión en este modelo experimental

Unilateral renal radiation blood pressure and PGE2-Like renal substance: a one-kidney model

La nefritis por irradiación puede producir hipertensión arterial. Se estudiaron los efectos que la irradiación, producía sobre un modelo uninefrectomizado en la rata. Se evaluó tensión arterial sistólica, tamaño renal y concentración en médula renal de sustancia tipo PGE2. A cuarenta y una ratas se les practicó nefrectomía de un riñon. Tres semanas después a cinco ratas se les aplicaron las técnicas quirúrgicas previamente descriptas pero sin irradiarlas. Estas ratas fueron sacrificadas doce semanas después y sirvieron de control. A 20 ratas se les irradió el riñon remanente con una dosis de 3000r y luego fueron sacrificadas en grupos de cinco a 1, 4, 8 y 12 semanas después de la irradiación. A 16 ratas se les aplicó una dosis de 1000r sobre el riñon y se las sacrificó en grupos de cuatro en iguales períodos. Hubo un aumento significativo aunque desigual de la tensión arterial sistólica en los dos grupos (p<0,05 para la dosis de 1000r y p<0,0005 para las ratas que recibieran 3000r). En ambos grupos hubo una disminución progresiva y significativa del contenido de sustancia tipo PGE2 (p<0,001 para ambos). El tamaño renal no cambió. El grupo que recibiera 3000r sufrió hipertensiones sistólicas más severas y presentó concentraciones medulares de PGE2 más bajas. Ambas grupos demostraron valores tensionales más altos que aquellos observados previamente en el modelo de dos riñones. Los resultados sugieren que en este modelo experimental la hipertensión puede estar relacionada a la disminución de la concentración renal de prostaglandinas

Blood pressure and renal prostaglandin E2-like content in unilateral kidney radiation

Se estudiaron los efectos de la irradiación renal con rayos X sobre la concentración de prostaglandina medular y la tensión arterial en la rata. A tales fines, 26 ratas fueron divididas en los siguientes grupos: 6 controles (operados pero no irradiadas) fueron sacrificadas a las 12 semanas; a 20 se les irradió un riñón expuesto a través de una incisión en el flanco recibiendo una dosis de 3000r. Estas ratas fueron sacrificadas en grupos de cinco a 1, 4, 8 y 12 semanas después de la irradiación. Se determinó tensión arterial sistólica, concentración de sustancia tipo PGE2 y tamaño renal. La tensión arterial promedio aumentó progresiva y significativamente (p<0,005). El riñon irradiado disminuyó en tamaño y la diferencia con el riñon opuesto fue estadísticamente significativa a 8 y 12 semanas post-irradiación (p<0,05). Al mismo tiempo el contenido de PGE2 tanto en el riñon irradiado como en el opuesto disminuyó significativamente (p<0,005 y 0,001, respectivamente). Hubo una correlación negativa estadísticamente significativa entre la tensión arterial y el contenido de sustancia tipo PGE2 en ambos riñones (r=-0,50), así como también entre los valores tensionales y el promedio y la suma del contenido de PGE2 de ambos riñones (r=0,53). Los resultados sugieren un rol de las prostaglandinas renales en el desarrollo de la hipertensión en este modelo experimental (AU)

Unilateral renal radiation blood pressure and PGE2-Like renal substance: a one-kidney model

La nefritis por irradiación puede producir hipertensión arterial. Se estudiaron los efectos que la irradiación, producía sobre un modelo uninefrectomizado en la rata. Se evaluó tensión arterial sistólica, tamaño renal y concentración en médula renal de sustancia tipo PGE2. A cuarenta y una ratas se les practicó nefrectomía de un riñon. Tres semanas después a cinco ratas se les aplicaron las técnicas quirúrgicas previamente descriptas pero sin irradiarlas. Estas ratas fueron sacrificadas doce semanas después y sirvieron de control. A 20 ratas se les irradió el riñon remanente con una dosis de 3000r y luego fueron sacrificadas en grupos de cinco a 1, 4, 8 y 12 semanas después de la irradiación. A 16 ratas se les aplicó una dosis de 1000r sobre el riñon y se las sacrificó en grupos de cuatro en iguales períodos. Hubo un aumento significativo aunque desigual de la tensión arterial sistólica en los dos grupos (p<0,05 para la dosis de 1000r y p<0,0005 para las ratas que recibieran 3000r). En ambos grupos hubo una disminución progresiva y significativa del contenido de sustancia tipo PGE2 (p<0,001 para ambos). El tamaño renal no cambió. El grupo que recibiera 3000r sufrió hipertensiones sistólicas más severas y presentó concentraciones medulares de PGE2 más bajas. Ambas grupos demostraron valores tensionales más altos que aquellos observados previamente en el modelo de dos riñones. Los resultados sugieren que en este modelo experimental la hipertensión puede estar relacionada a la disminución de la concentración renal de prostaglandinas (AU)