980 resultados para Consumption Rate
Resumo:
In Pseudomonas aeruginosa the extracellular metabolite and siderophore pyochelin is synthesized from two major precursors, chorismate and l-cysteine via salicylate as an intermediate. The regulatory role of isochorismate synthase, the first enzyme in the pyochelin biosynthetic pathway, was studied. This enzyme is encoded by pchA, the last gene in the pchDCBA operon. The PchA protein was purified to apparent electrophoretic homogeneity from a PchA-overexpressing P. aeruginosa strain. The native enzyme was a 52-kDa monomer in solution, and its activity strictly depended on Mg(2+). At pH 7.0, the optimum, a K(m) = 4.5 microm and a k(cat) = 43.1 min(-1) were determined for chorismate. No feedback inhibitors or other allosteric effectors were found. The intracellular PchA concentration critically determined the rate of salicylate formation both in vitro and in vivo. In cultures grown in iron-limiting media to high cell densities, overexpression of the pchA gene resulted in overproduction of salicylate as well as in enhanced pyochelin formation. From this work and earlier studies, it is proposed that one important factor influencing the flux through the pyochelin biosynthetic pathway is the PchA concentration, which is determined at a transcriptional level, with pyochelin acting as a positive signal and iron as a negative signal.
Accounting for Big City Growth in Low Paid Occupations: Immigration and/or Service Class Consumption
Resumo:
Growth of 'global cities' in the 1980s was supposed to have involved an occupational polarisation, including growth of low paid service jobs. Though held to be untrue for European cities, at the time, some such growth did emerge in London a decade later than first reported for New York. The question is whether there was simply a delay before London conformed to the global city model, or whether another distinct cause was at work in both cases. This paper proposes that the critical factor in both cases was actually an upsurge of immigration from poor countries providing an elastic supply of cheap labour. This hypothesis and its counterpart based on growth in elite jobs are tested econometrically for the British case with regional data spanning 1975-2008, finding some support for both effects, but with immigration from poor countries as the crucial influence in late 1990s London. Keywords: regional labour markets; wages; employment; international migration; consumer demand JEL Codes: J21, J23, F22, R12
Resumo:
The relationship between coffee drinking and the risk of digestive tract neoplasms was analyzed in a case-control study of 50 cases of cancer of the mouth or pharynx, 209 of the esophagus, 397 of the stomach, 455 of the colon, 295 of the rectum, 151 of the liver, 214 of the pancreas, and 1944 control subjects admitted for acute, non-digestive tract disorders. There was no significant or consistent association between coffee and cancers of the mouth or pharynx, esophagus, stomach, liver, or pancreas. In particular, for pancreatic cancer, the multivariate relative risks for the intermediate and upper tertiles were 1.05 and 1.01, respectively. There were significant inverse trends in risk with measures of coffee consumption for colon and rectal cancers, the multivariate relative risks according to tertiles of coffee consumption being 0.86 and 0.64 for colon and 0.97 and 0.66 for rectum. This apparent protection is in agreement with some (but not all) previous epidemiological evidence and finds a possible biological interpretation in terms of interference on bile secretion, causing reduced bile acid and neutral sterol concentrations in the bowel. In conclusion, the results of this study, the major interest of which lies in the opportunity of drawing up an overall pattern of risk for various digestive neoplasms, offer further reassurance as regards the effects of coffee on digestive tract carcinogenesis.
Resumo:
This study aimed to quantitatively describe and compare whole-body fat oxidation kinetics in cycling and running using a sinusoidal mathematical model (SIN). Thirteen moderately trained individuals (7 men and 6 women) performed two graded exercise tests, with 3-min stages and 1 km h(-1) (or 20 W) increment, on a treadmill and on a cycle ergometer. Fat oxidation rates were determined using indirect calorimetry and plotted as a function of exercise intensity. The SIN model, which includes three independent variables (dilatation, symmetry and translation) that account for main quantitative characteristics of kinetics, provided a mathematical description of fat oxidation kinetics and allowed for determination of the intensity (Fat(max)) that elicits maximal fat oxidation (MFO). While the mean fat oxidation kinetics in cycling formed a symmetric parabolic curve, the mean kinetics during running was characterized by a greater dilatation (i.e., widening of the curve, P < 0.001) and a rightward asymmetry (i.e., shift of the peak of the curve to higher intensities, P = 0.01). Fat(max) was significantly higher in running compared with cycling (P < 0.001), whereas MFO was not significantly different between modes of exercise (P = 0.36). This study showed that the whole-body fat oxidation kinetics during running was characterized by a greater dilatation and a rightward asymmetry compared with cycling. The greater dilatation may be mainly related to the larger muscle mass involved in running while the rightward asymmetry may be induced by the specific type of muscle contraction.
Resumo:
In a retrospective study, we examined several determinants of basal fat oxidation in 720 healthy Caucasian volunteers. Adult men (n = 427) and women (n = 293) were characterized for resting energy expenditure and substrate oxidation by indirect calorimetry (after a 12-h overnight fast), peak O2 consumption by a treadmill test to exhaustion, body composition by hydrodensitometry, food intake from a 3-day food diary, and hormonal status by fasting hormone concentrations. Fat oxidation was negatively correlated with fat mass in men (r = -0.11; P < 0.05), but no statistical relationship was found in women. In a stepwise multiple regression analysis, fat oxidation was best predicted by peak O2 consumption and fat-free mass in men (model R2 = 0.142) and by free thyroxine, fat-free mass, and fasting insulin in women (model R2 = 0.153). Relative rates of fat oxidation (fat oxidation adjusted for differences in resting energy expenditure) were not correlated with fat mass in either gender. Women showed a lower rate of basal fat oxidation (both absolute and adjusted) than did men. Our results show that fat oxidation is not greater in individuals with a greater fat mass. Furthermore, our results support a sexual dimorphism in basal rates of fat oxidation.
Resumo:
The magnitude of coffee-induced thermogenesis and the influence of coffee ingestion on substrate oxidation were investigated in 10 lean and 10 obese women, over two 24-h periods in a respiratory chamber. On one occasion the subjects consumed caffeinated coffee and on the other occasion, decaffeinated coffee. The magnitude of thermogenesis was smaller in obese (4.9 +/- 2.0%) than in lean subjects (7.6 +/- 1.3%). The thermogeneic response to caffeine was prolonged during the night in lean women only. The coffee-induced stimulation of energy expenditure was mediated by a concomitant increase in lipid and carbohydrate oxidation. During the next day, in postabsorptive basal conditions, the thermogenic effect of coffee had vanished, but a significant increase in lipid oxidation was observed in both groups. The magnitude of this effect was, however, blunted in obese women (lipid oxidation increased by 29 and 10% in lean and obese women, respectively). Caffeine increased urinary epinephrine excretion. Whereas urinary caffeine excretion was similar in both groups, obese women excreted more theobromine, theophylline, and paraxanthine than lean women. Despite the high levels of urinary methylxanthine excretion, thermogenesis and lipid oxidation were less stimulated in obese than in lean subjects.
Resumo:
The increase in resting energy expenditure (REE) reported in patients with cystic fibrosis (CF) does not necessarily imply an increase in total energy expenditure (TEE). In this study REE was assessed with open-circuit indirect calorimetry, and free-living 24-hour TEE with the heart rate method. Thirteen patients with CF, aged 8 to 24 years, with adequate nutritional status and moderately decreased pulmonary function, were studied. They were compared with 13 healthy control subjects matched for gender, age, height, and nutritional status. Resting energy expenditure was higher in patients with CF (1512 +/- 88 kcal/day) than in control subjects (1339 +/- 76 kcal/day; p less than 0.01), whereas free-living 24-hour TEE (2345 +/- 127 kcal/day and 2358 +/- 256 kcal/day, respectively) and net mechanical work efficiency of walking on a treadmill (20.4 +/- 0.7% and 19.8 +/- 0.6%, respectively) were similar. Respiratory quotient was higher in patients with CF than in control subjects at rest (0.834 +/- 0.009 vs 0.797 +/- 0.008; p less than 0.05), and tended to remain so during physical exercise, indicating a higher contribution of carbohydrate oxidation to energy expenditure. We conclude that in free living conditions, patients with CF can compensate for their increase in REE by a reduction in spontaneous physical activities or other yet undefined mechanisms.
Resumo:
The survival and molting incidence in Triatoma infestans, a vector of Chagas disease, were investigated following sequential shocks at 0ºC in fifth instar nymphs under moderate fasting and full nutritional conditions. The shocks were separated by intervals of 8 h and 24 h at 30ºC. The results indicated that in terms of insect survival, T. infestans is tolerant to a single cold shock at 0ºC even for 12 h, or to sequential cold shocks, regardless of the nutritional state of the specimens. In terms of molting rate, fasting enhanced the tolerance to sequential cold shocks, but did not exceed the tolerance acquired by fully-nourished specimens, except when cold shocks were separated by an 8 h interval at 30ºC. The protective action elicited by fasting was assumed to be additive to that induced by a single mild cold shock or sequential cold shocks. The cold-tolerance response of T. infestans may have favoured its survival in areas of South America with low temperatures, even considering that this species is predominantly associated with human habitats.
Resumo:
The prevalence of overweight and obesity has increased with alarming speed over the past twenty years. It has recently been described by the World Health Organisation as a ‘global epidemic’. In the year 2000 more than 300 million people worldwide were obese and it is now projected that by 2025 up to half the population of the United States will be obese if current trends are maintained. The disease is now a major public health problem throughout Europe. In Ireland at the present time 39% of adults are overweight and 18% are obese. Of these, slightly more men than women are obese and there is a higher incidence of the disease in lower socio-economic groups. Most worrying of all is the fact that childhood obesity has reached epidemic proportions in Europe, with body weight now the most prevalent childhood disease. While currently there are no agreed criteria or standards for assessing Irish children for obesity some studies are indicating that the numbers of children who are significantly overweight have trebled over the past decade. Extrapolation from authoritative UK data suggests that these numbers could now amount to more than 300,000 overweight and obese children on the island of Ireland and they are probably rising at a rate of over 10,000 per year. A balance of food intake and physical activity is necessary for a healthy weight. The foods we individually consume and our participation in physical activity are the result of a complex supply and production system. The growing research evidence that energy dense foods promote obesity is impressive and convincing. These are the foods that are high in fat, sugar and starch. Of these potentially the most significant promoter of weight gain is fat and foods from the top shelf of the food pyramid including spreads (butter and margarine), cakes and biscuits, and confectionery, when combined are the greatest contributors to fat intake in the Irish diet. In company with their adult counterparts Irish children are also consuming large amounts of energy dense foods outside the home. A recent survey revealed that slightly over half of these children ate sweets at least once a day and roughly a third of them had fizzy drinks and crisps with the same regularity. Sugar sweetened carbonated drinks are thought to contribute to obesity and for this reason the World Health Organisation has expressed serious concerns at the high and increasing consumption of these drinks by children. Physical activity is an important determinant of body weight. Over recent decades there has been a marked decline in demanding physical work and this has been accompanied by more sedentary lifestyles generally and reduced leisure-time activity. These observable changes, which are supported by data from most European countries and the United States, suggest that physical inactivity has made a significant impact on the increase in overweight and obesity being seen today. It is now widely accepted that adults shoud be involved in 45-60 minutes, and children should be involved in at least 60 minutes per day of moderate physical activity in order to prevent excess weight gain. Being overweight today not only signals increased risk of medical problems but also exposes people to serious psychosocial problems due mainly to widespread prejudice against fat people. Prejudice against obese people seems to border on the socially acceptable in Ireland. It crops up consistently in surveys covering groups such as employers, teachers, medical and healthcare personnel, and the media. It occurs among adolescents and children, even very young children. Because obesity is associated with premature death, excessive morbidity and serious psychosocial problems the damage it causes to the welfare of citizens is extremely serious and for this reason government intervention is necessary and warranted. In economic terms, a figure of approximately â,¬30million has been estimated for in-patient costs alone in 2003 for a number of Irish hospitals. This year about 2,000 premature deaths in Ireland will be attributed to obesity and the numbers are growing relentlessly. Diseases which proportionally more obese people suffer from than the general population include hypertension, type 2 diabetes, angina, heart attack and osteoarthritis. There are indirect costs also such as days lost to the workplace due to illness arising from obesity and output foregone as a result of premature death. Using the accepted EU environmental cost benefit method, these deaths alone may be costing the state as much as â,¬4bn per year. The social determinants of physical activity include factors such as socio-economic status, education level, gender, family and peer group influences as well as individual perceptions of the benefits of physical activity. The environmental determinants include geographic location, time of year, and proximity of facilities such as open spaces, parks and safe recreational areas generally. The environmental factors have not yet been as well studied as the social ones and this research gap needs to be addressed. Clearly there is a public health imperative to ensure that relevant environmental policies maximise opportunities for active transport, recreational physical activity and total physical activity. It is clear that concerted policy initiatives must be put in place if the predominantly negative findings of research regarding the determinants of food consumption and physical activity are to be accepted, and they must surely be accepted by government if the rapid increase in the incidence of obesity with all its negative consequences for citizens is to be reversed. So far actions surrounding nutrition policies have concentrated mostly on actions that are within the remit of the Department of Health and Children such as implementing the dietary guidelines. These are important but government must now look at the totality of policies that influence the type and supply of food that its citizens eat and the range and quality of opportunities that are available to citizens to engage in physical activity. This implies a fundamental examination of existing agricultural, industrial, economic and other policies and a determination to change them if they do not enable people to eat healthily and partake in physical activity. The current crisis in obesity prevalence requires a population health approach for adults and children in addition to effective weight-reduction management for individuals who are severely overweight. This entails addressing the obesogenic environment where people live, creating conditions over time which lead to healthier eating and more active living, and protecting people from the widespread availability of unhealthy food and beverage options in addition to sedentary activities that take up all of their leisure time. People of course have a fundamental right to choose to eat what they want and to be as active as they wish. That is not the issue. What the National Taskforce on Obesity has had to take account of is that many forces are actively impeding change for those well aware of the potential health and well-being consequences to themselves of overweight and obesity. The Taskforce’s social change strategy is to give people meaningful choice. Choice, or the capacity to change (because the strategy is all about change), is facilitated through the development of personal skills and preferences, through supportive and participative environments at work, at school and in the local community, and through a dedicated and clearly communicated public health strategy. High-level cabinet support will be necessary to implement the Taskforce’s recommendations. The approach to implementation must be characterised by joined-up thinking, real practical engagement by the public and private sectors, the avoidance of duplication of effort or crosspurpose approaches, and the harnessing of existing strategies and agencies. The range of government departments with roles to play is considerable. The Taskforce outlines the different contributions that each relevant department can make in driving its strategy forward. It also emphasises its requirement that all phases of the national strategy for healthy eating and physical activity are closely monitored, analysed and evaluated. The vision of the Taskforce is expressed as: An Irish society that enables people through health promotion, prevention and care to achieve and maintain healthy eating and active living throughout their lifespan. Its high-level goals are expressed as follows: Its recommendations, over eighty in all, relate to actions across six broad sectors: high-level government; education; social and community; health; food, commodities, production and supply; and the physical environment. In developing its recommendations the Taskforce has taken account of the complex, multisectoral and multi-faceted determinants of diet and physical activity. This strategy poses challenges for government, within individual departments, inter-departmentally and in developing partnerships with the commercial sector. Equally it challenges the commercial sector to work in partnership with government. The framework required for such initiative has at its core the rights and benefits of the individual. Health promotion is fundamentally about empowerment, whether at the individual, the community or the policy level.
Resumo:
Click here to download PDF The prevalence of overweight and obesity has increased with alarming speed over the past twenty years. It has recently been described by the World Health Organisation as a ‘global epidemic’. In the year 2000 more than 300 million people worldwide were obese and it is now projected that by 2025 up to half the population of the United States will be obese if current trends are maintained. The disease is now a major public health problem throughout Europe. In Ireland at the present time 39% of adults are overweight and 18% are obese. Of these, slightly more men than women are obese and there is a higher incidence of the disease in lower socio-economic groups. Most worrying of all is the fact that childhood obesity has reached epidemic proportions in Europe, with body weight now the most prevalent childhood disease. While currently there are no agreed criteria or standards for assessing Irish children for obesity some studies are indicating that the numbers of children who are significantly overweight have trebled over the past decade. Extrapolation from authoritative UK data suggests that these numbers could now amount to more than 300,000 overweight and obese children on the island of Ireland and they are probably rising at a rate of over 10,000 per year. A balance of food intake and physical activity is necessary for a healthy weight. The foods we individually consume and our participation in physical activity are the result of a complex supply and production system. The growing research evidence that energy dense foods promote obesity is impressive and convincing. These are the foods that are high in fat, sugar and starch. Of these potentially the most significant promoter of weight gain is fat and foods from the top shelf of the food pyramid including spreads (butter and margarine), cakes and biscuits, and confectionery, when combined are the greatest contributors to fat intake in the Irish diet. In company with their adult counterparts Irish children are also consuming large amounts of energy dense foods outside the home. A recent survey revealed that slightly over half of these children ate sweets at least once a day and roughly a third of them had fizzy drinks and crisps with the same regularity. Sugar sweetened carbonated drinks are thought to contribute to obesity and for this reason the World Health Organisation has expressed serious concerns at the high and increasing consumption of these drinks by children. Physical activity is an important determinant of body weight. Over recent decades there has been a marked decline in demanding physical work and this has been accompanied by more sedentary lifestyles generally and reduced leisure-time activity. These observable changes, which are supported by data from most European countries and the United States, suggest that physical inactivity has made a significant impact on the increase in overweight and obesity being seen today. It is now widely accepted that adults shoud be involved in 45-60 minutes, and children should be involved in at least 60 minutes per day of moderate physical activity in order to prevent excess weight gain. Being overweight today not only signals increased risk of medical problems but also exposes people to serious psychosocial problems due mainly to widespread prejudice against fat people. Prejudice against obese people seems to border on the socially acceptable in Ireland. It crops up consistently in surveys covering groups such as employers, teachers, medical and healthcare personnel, and the media. It occurs among adolescents and children, even very young children. Because obesity is associated with premature death, excessive morbidity and serious psychosocial problems the damage it causes to the welfare of citizens is extremely serious and for this reason government intervention is necessary and warranted. In economic terms, a figure of approximately â,¬30million has been estimated for in-patient costs alone in 2003 for a number of Irish hospitals. This year about 2,000 premature deaths in Ireland will be attributed to obesity and the numbers are growing relentlessly. Diseases which proportionally more obese people suffer from than the general population include hypertension, type 2 diabetes, angina, heart attack and osteoarthritis. There are indirect costs also such as days lost to the workplace due to illness arising from obesity and output foregone as a result of premature death. Using the accepted EU environmental cost benefit method, these deaths alone may be costing the state as much as â,¬4bn per year. The social determinants of physical activity include factors such as socio-economic status, education level, gender, family and peer group influences as well as individual perceptions of the benefits of physical activity. The environmental determinants include geographic location, time of year, and proximity of facilities such as open spaces, parks and safe recreational areas generally. The environmental factors have not yet been as well studied as the social ones and this research gap needs to be addressed. Clearly there is a public health imperative to ensure that relevant environmental policies maximise opportunities for active transport, recreational physical activity and total physical activity. It is clear that concerted policy initiatives must be put in place if the predominantly negative findings of research regarding the determinants of food consumption and physical activity are to be accepted, and they must surely be accepted by government if the rapid increase in the incidence of obesity with all its negative consequences for citizens is to be reversed. So far actions surrounding nutrition policies have concentrated mostly on actions that are within the remit of the Department of Health and Children such as implementing the dietary guidelines. These are important but government must now look at the totality of policies that influence the type and supply of food that its citizens eat and the range and quality of opportunities that are available to citizens to engage in physical activity. This implies a fundamental examination of existing agricultural, industrial, economic and other policies and a determination to change them if they do not enable people to eat healthily and partake in physical activity. The current crisis in obesity prevalence requires a population health approach for adults and children in addition to effective weight-reduction management for individuals who are severely overweight. This entails addressing the obesogenic environment where people live, creating conditions over time which lead to healthier eating and more active living, and protecting people from the widespread availability of unhealthy food and beverage options in addition to sedentary activities that take up all of their leisure time. People of course have a fundamental right to choose to eat what they want and to be as active as they wish. That is not the issue. What the National Taskforce on Obesity has had to take account of is that many forces are actively impeding change for those well aware of the potential health and well-being consequences to themselves of overweight and obesity. The Taskforce’s social change strategy is to give people meaningful choice. Choice, or the capacity to change (because the strategy is all about change), is facilitated through the development of personal skills and preferences, through supportive and participative environments at work, at school and in the local community, and through a dedicated and clearly communicated public health strategy. High-level cabinet support will be necessary to implement the Taskforce’s recommendations. The approach to implementation must be characterised by joined-up thinking, real practical engagement by the public and private sectors, the avoidance of duplication of effort or crosspurpose approaches, and the harnessing of existing strategies and agencies. The range of government departments with roles to play is considerable. The Taskforce outlines the different contributions that each relevant department can make in driving its strategy forward. It also emphasises its requirement that all phases of the national strategy for healthy eating and physical activity are closely monitored, analysed and evaluated. The vision of the Taskforce is expressed as: An Irish society that enables people through health promotion, prevention and care to achieve and maintain healthy eating and active living throughout their lifespan. Its high-level goals are expressed as follows: Its recommendations, over eighty in all, relate to actions across six broad sectors: high-level government; education; social and community; health; food, commodities, production and supply; and the physical environment. In developing its recommendations the Taskforce has taken account of the complex, multisectoral and multi-faceted determinants of diet and physical activity. This strategy poses challenges for government, within individual departments, inter-departmentally and in developing partnerships with the commercial sector. Equally it challenges the commercial sector to work in partnership with government. The framework required for such initiative has at its core the rights and benefits of the individual. Health promotion is fundamentally about empowerment, whether at the individual, the community or the policy level.
Resumo:
A five-year domiciliary collection in the 22 departments of Guatemala showed that out of 4,128 triatomines collected, 1,675 were Triatoma dimidiata (Latreille, 1811), 2,344 were Rhodnius prolixus Stal 1859, and only 109 were T. nitida Usinger 1939. The Chagas disease parasite, Trypanosoma cruzi, was found in all three species. Their natural infection rates were similar in the first two species (20.6%; 19.1%) and slightly lower in T. nitida(13.8%). However there was no significant difference in the infection rates in the three species (p = 0.131). T. dimidiata males have higher infection rates than females (p = 0.030), whereas for R. prolixus there is no difference in infection rates between males and females (p = 0.114). The sex ratios for all three species were significantly skewed. More males than females were found inside houses for T. dimidiata (p < 0.0001) and T. nitida (p = 0.011); a different pattern was seen for R. prolixus (p = 0.037) where more females were found. Sex ratio is proposed as an index to show the mobility of T. dimidiata in different populations. T. dimidiata is widely distributed in the country, and is also the main vector in at least ten departments, but R. prolixus with higher vectorial capacity is an important vector in at least two departments.
Resumo:
Aim and purpose: Moderate alcohol consumption has been associated with lower risk of diabetes mellitus, but few data exist on the metabolic syndrome and on the metabolic impact of heavy drinking. The aim of our study was to investigate the complex relationship between alcohol and the metabolic syndrome and diabetes mellitus in a population-based study in Switzerland with high mean alcohol consumption. Design and methods: In 6188 adults aged 35 to 75, alcohol consumption was categorized as 0, 1-6, 7-13, 14-20, 21-27, 28-34 and >= 35 drinks/week or as nondrinkers, moderate (1-13 drinks), high (14-34 drinks) and very high (>= 35 drinks) alcohol consumption. The metabolic syndrome was defined according to the ATP-III criteria and diabetes mellitus as fasting glycemia >= 7 mmol/l or self-reported medication.We used multivariate analysis adjusted for age, gender, smoking status, physical activity and education level to determine the prevalence of the conditions according to drinking categories. Results: 73% (n = 4502) of the participants consumed alcohol, 16% (n = 993) were high drinkers and 2% (n = 126) very high drinkers. In multivariate analysis, alcohol consumption had a U-shaped relationship with the metabolic syndrome and diabetes mellitus. The prevalence of the metabolic syndrome significantly differed between nondrinkers (24%), moderate (19%), high (20%) and very high drinkers (29%) (P<= 0.005). The prevalence of diabetes mellitus also significantly differed between nondrinkers (6.0%), moderate (3.6%), high (3.8%) and very high drinkers (6.7%) (P<= 0.05). These relationships did not differ according to beverage types. Conclusions: The prevalence of the metabolic syndrome and diabetes mellitus decrease with moderate alcohol consumption and increase with heavy drinking, without differences according to beverage types. Recommending to limit alcohol consumption to 1-2 drinks/day might help prevent these conditions in primary care Metabolic Syndrome and Diabetes Mellitus.
Resumo:
Oxidative metabolism of the isolated embryonic heart of the chick has been determined using a spectrophotometric technique allowing global as well as localized micromeasurements of the O2 uptake. Entire hearts, excised from embryos of 10 somites (primordia fused, stage 10 HH) and 40 somites (S shaped, stage 20 HH) were placed in a special chamber under controlled metabolic conditions where they continued to beat spontaneously and regularly. During the 32 h of development, the O2 consumption of the whole heart increased from 0.9 +/- 0.1 to 5.3 +/- 0.8 nmol O2/h. These values corrected for protein content were, however, comparable (0.45 nmol O2.h-1.micrograms-1). At stage 10-12, the O2 uptake varied along the cardiac tube (from 0.74 to 1.0 nmol O2.h-1.mm-2). From stage 10 to 20, the O2 uptake per unit area of ventricle wall increased from 0.7 +/- 0.2 to 1.8 +/- 0.2 nmol O2.h-1.mm-2, and the O2 uptake per myocardial volume during one cardiac cycle varied from 7 to 2.5 nmol O2/cm3. These results indicate that, despite an intense morphogenesis, the cardiac tissue has a rather low and stable oxidative metabolism, although the O2 requirement of the whole heart increases significantly. Moreover, the normalized suprabasal aerobic energy expenditure decreases throughout early cardiogenesis. The functional integrity of the isolated embryonic heart combined with the experimental possibilities of the microtechnique make the preparation appropriate for studying the changes in cardiac metabolism during development.
Resumo:
The infection rates of Babesia sporokinetes in engorged Boophilus microplus were evaluated during a 2-year period in a dairy farm located in an area of enzootic stability. Every 14 days engorged females were collected from calves and from adult animals. Ticks were incubated at 27 ± 0.5ºC and 80-90% relative humidity and Babesia infection rates were determined by microscopic examination of Giemsa-stained hemolymph smears. After 52 collections, 2105 ticks were obtained, from which 982 were collected from calves and 1123 from cows. The total Babesia infection rate was 10%, however the incidence was higher (p < 0.05) in ticks collected from calves (17.5%) than in those collected from cows (3.6%). Females collected from cows showed the highest infection rates in January, March, and August, and absence of infection in April and May. Ticks feeding on calves were infected throughout the experimental period. The infection rates of engorged females collected from naturally infected calves that were artificially infested with Babesia-free-larvae of B. microplus gradually decreased until the calves were four months old. No differences were observed among infection rates of ticks collected from calves maintained under natural conditions.