Incidence and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain), 2003-2016.

INTRODUCTION: According to most studies, the incidence of Guillain-Barré syndrome increases with age, with a peak incidence occurring between 70 and 80 years of age. The objective of this study is to describe the incidence (overall and by sex and age group) and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain). METHODS: We performed a retrospective, descriptive, population-based study covering the period 2003 to 2016. RESULTS: The global incidence of Guillain-Barré syndrome is 2.07 cases per 100000 person-years. Incidence increases with age, except for small peaks during childhood and between 40 and 50 years, and reaches a maximum of 6.26 cases per 100000 person-years above the age of 80. The incidences of the different variants were: AIDP, 72.1%; AMAN, 16.3%; ANSAN, 4.7%; and Miller Fisher syndrome, 4.7%. A total of 41.9% of patients had a history of respiratory tract infections, and 20.9% had a history of gastrointestinal infections. Protein in the cerebrospinal fluid was found in 76.7%. EMG findings suggested demyelination in 73.7% of the patients and axonal degeneration in 26.3%. A total of 20.9% of patients needed ventilatory support. Six-month mortality was 9.3%. Variables associated with worse prognosis were age over 80 years, delay in admission, previous gastrointestinal infection, and AMAN variant. CONCLUSIONS: The incidence observed in our study is in the upper range of estimated incidence rates reported in European and North American studies. The syndrome may be underdiagnosed in elderly patients; physicians must be vigilant to the possibility of the disease, which is associated with a high mortality rate if it is not treated early.

Incidencia y características clínicas del síndrome de Guillain-Barré en la comarca de Osona (Barcelona, España) (2003-2016) / Incidence and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain), 2003-2016

Introducción: La mayoría de los estudios muestran que la incidencia del síndrome de Guillain-Barré aumenta con la edad, con un máximo entre los 70 y los 80 años y un descenso posterior. El objetivo del estudio es describir la incidencia global y específica por sexo y grupos de edad y las características clínicas del síndrome de Guillain-Barré en la comarca de Osona (Barcelona, España).MétodosEstudio descriptivo retrospectivo de base poblacional en el periodo 2003-2016.ResultadosLa incidencia global es de 2,07/100.000 habitantes-año. La incidencia aumenta con la edad, salvo un pequeño pico en la infancia y entre los 40 y los 50 años, alcanzando la máxima de 6,26/100.000 habitantes-año pasados los 80 años. Los porcentajes de las variantes fueron: AIDP (72,1%), AMAN (16,3%), ANSAN (4,7%) y síndrome de Miller-Fisher (4,7%). Presentaron infección previa de vías respiratorias el 41,9% e infección gastrointestinal el 20,9%. Se halló proteinorraquia en el 76,7%. El EMG mostraba un predominio desmielinizante en el 73,7% y axonal en el 26,3%. Necesitaron soporte ventilatorio el 20,9%. La mortalidad a los 6 meses fue del 9,3%. Las variables que se asociaron a un peor pronóstico fueron la edad superior a los 80 años, la demora en el ingreso, presentar infección gastrointestinal previa y la variante AMAN.ConclusionesLa incidencia descrita en nuestro estudio se encuentra en el rango más alto de las estimadas en Europa y Estados Unidos. En ancianos pudiera estar infradiagnosticado y se requeriría de una mayor alerta ante una enfermedad con alta mortalidad si no se trata de forma precoz. (AU)

Introduction: According to most studies, the incidence of Guillain-Barré syndrome increases with age, with a peak incidence occurring between 70 and 80 years of age. The objective of this study is to describe the incidence (overall and by sex and age group) and clinical characteristics of Guillain-Barré syndrome in Osona (Barcelona, Spain).MethodsWe performed a retrospective, descriptive, population-based study covering the period 2003 to 2016.ResultsThe global incidence of Guillain-Barré syndrome is 2.07 cases per 100,000 person-years. Incidence increases with age, except for small peaks during childhood and between 40 and 50 years, and reaches a maximum of 6.26 cases per 100,000 person-years above the age of 80. The incidences of the different variants were: AIDP, 72.1%; AMAN, 16.3%; ANSAN, 4.7%; and Miller Fisher syndrome, 4.7%. A total of 41.9% of patients had a history of respiratory tract infections, and 20.9% had a history of gastrointestinal infections. Protein in the cerebrospinal fluid was found in 76.7%. EMG findings suggested demyelination in 73.7% of the patients and axonal degeneration in 26.3%. A total of 20.9% of patients needed ventilatory support. Six-month mortality was 9.3%. Variables associated with worse prognosis were age over 80 years, delay in admission, previous gastrointestinal infection, and AMAN variant.ConclusionsThe incidence observed in our study is in the upper range of estimated incidence rates reported in European and North American studies. The syndrome may be underdiagnosed in elderly patients; physicians must be vigilant to the possibility of the disease, which is associated with a high mortality rate if it is not treated early. (AU)

The Quest for Welfare-Friendly Feeding of Broiler Breeders: Effects of Daily vs. 5:2 Feed Restriction Schedules.

Restricted feeding of broiler breeders is required for improved long-term health and welfare. Because feeding frustration and hunger are major welfare concerns during rearing, many suggestions have been made to decrease the negative feelings of hunger while maintaining suitable growth rates and reproductive health. Non-daily ("skip-a-day") feeding schedules are commonly used around the world to increase portion sizes at meal times while restricting intake but these practices are prohibited in many countries due to welfare concerns on fasting days. We compared birds raised on a non-daily feeding schedule (2 non-consecutive fasting days per week, 5:2), previously suggested as a welfare-friendlier non-daily alternative, to birds raised on daily feed restriction. We found signs of increased physiological stress levels in 5:2 birds, including elevated heterophil to lymphocyte ratios (1.00 for 5:2 vs. 0.75 for daily fed at 12 weeks of age), increased adiposity (0.21% lean body weight [LBW] for 5:2 vs. 0.13% LBW for daily fed), and reduced muscle growth (pectoral muscle 5.94% LBW for 5:2 vs. 6.52% LBW for daily fed). At the same time, 5:2 birds showed signs of lower anxiety before feeding times (activity was reduced from 10.30 in daily fed to 4.85) which may be a result of the lower feed competition associated with larger portion sizes. Although we found no difference in latency to first head movement in tonic immobility between the treatments (136.5 s on average for both groups), 5:2 birds generally showed more interest in a novel object in the home pen which indicated increased risk taking and reduced fear while fasting. The 5:2 birds in this study showed no signs of learning the feeding schedule, and this unpredictability may also increase stress. Taken together, the effects of 5:2 vs. daily feed restriction on the welfare of broiler breeder pullets remain inconclusive and differ between feeding and fasting days. In addition to reducing stress by minimizing the number of fasting days, we suggest that a shift to more predictable schedules may help improve the welfare of broiler breeder pullets.

The physiological and neuroendocrine correlates of hunger in the Red Junglefowl (Gallus gallus).

The ability to regulate food intake is critical to survival. The hypothalamus is central to this regulation, integrating peripheral signals of energy availability. Although our understanding of hunger in rodents is advanced, an equivalent understanding in birds is lacking. In particular, the relationship between peripheral energy indices and hypothalamic 'hunger' peptides, agouti-related protein (AgRP), pro-opiomelanocortin (POMC) and neuropeptide Y (NPY) is poorly understood. Here, we compare AgRP, POMC and NPY RNA levels in the hypothalamus of Red Junglefowl chicks raised under ad libitum, chronic restriction and intermittent feeding regimens. Hypothalamic gene expression differed between chronically and intermittently restricted birds, confirming that different restriction regimens elicit different patterns of hunger. By assessing the relationship between hypothalamic gene expression and carcass traits, we show for the first time in birds that AgRP and POMC are responsive to fat-related measures and therefore represent long-term energy status. Chronically restricted birds, having lower indices of fat, show elevated hunger according to AgRP and POMC. NPY was elevated in intermittently fasted birds during fasting, suggesting a role as a short-term index of hunger. The different physiological and neuroendocrine responses to quantitative versus temporal feed restriction provide novel insights into the divergent roles of avian hunger neuropeptides.

Growth heterogeneity in broiler breeder pullets is settled before the onset of feed restriction but is not predicted by size at hatch.

Uniform growth is a desirable trait in all large-scale animal production systems because it simplifies animal management and increases profitability. In parental broiler flocks, so-called broiler breeders, low growth uniformity is largely attributed to the feed competition that arises from quantitatively restricted feeding. As feed restriction is crucial to maintaining healthy and fertile breeders, several practices for reducing feed competition and the associated growth heterogeneity have been suggested and range from nutrient dilution by increasing fiber content in feed to intermittent fasting with increased portion size ("skip a day"), but no practice appears to be entirely effective. The fact that a large part of the heterogeneity remains even when feed competition is minimized suggests that some growth variation is caused by other factors. We investigated whether this variation arises during embryonic development (as measured by size at hatch) or during posthatch development by following the growth and body composition of birds of varying hatch sizes. Our results support the posthatch alternative, with animals that later grow to be small or large (here defined as >1 SD lighter or heavier than mean BW of the flock) being significantly different in size as early as 1 d after gaining access to feed ( < 0.05). We then investigated 2 possible causes for different postnatal growth: that high growth performance is linked 1) to interindividual variations in metabolism (as measured by cloacal temperature and verified by respirometry) or 2) to higher levels of social motivation (as measured in a social reinstatement T-maze), which should reduce the stress of being reared in large-scale commercial flocks. Neither of these follow-up hypotheses could account for the observed heterogeneity in growth. We suggest that the basis of growth heterogeneity in broiler breeder pullets may already be determined at the time of hatch in the form of qualitatively different maternal investments or immediately thereafter as an indirect result of differences in incubation conditions, hatching time, and resulting fasting time. Although this potential difference in maternal investment is not seen in body mass, tarsometatarsal length, or full body length of day-old chicks arriving at the farm, it may influence the development of differential feed and water intake during the first day of feeding, which in turn has direct effects on growth heterogeneity.

Prevalencia de miastenia gravis en la comarca de Osona (Barcelona, Cataluña) / Prevalence of myasthenia gravis in the Catalan county of Osona

INTRODUCCIÓN: La prevalencia descrita de miastenia gravis (MG) oscila entre 5 y 24 casos por 100.000, representando los mayores de 65 años menos del 50% del total. Se presenta la prevalencia de MG en la comarca de Osona (Barcelona, España). Se describen la prevalencia y las características clínicas por grupos de edad, diferenciando los menores y mayores de 65 años. MÉTODOS: El Servicio de Neurología del Hospital General de Vic puso en marcha en el año 1991 un registro comarcal sobre los casos de MG diagnosticados. RESULTADOS: La prevalencia de MG fue de 32,89 × 105 habitantes (IC 95%, 23,86-41,91). La prevalencia estandarizada (población europea) fue del 35,47×105 habitantes (IC 95%, 26,10-44,84). La razón por sexo, mujeres/hombres, es de 1,3. De forma global, el grupo de más de 65 años representa el 62,75% de los casos. Las prevalencias de MG por grandes grupos de edad presentan un carácter marcadamente ascendente, pasando de ningún caso en el grupo de menos de 25 años, a 21,87 × 105 en el grupo de 25 a 64 años, alcanzando 122,35×105 en el grupo de 65 y más años. Las clínicas pretratamiento y a fecha de corte no presentan diferencias estadísticamente significativas (p > 0,05) entre menores y mayores de 65 años. CONCLUSIONES: Se describe la prevalencia más alta comunicada hasta la actualidad. Esta alta prevalencia es a expensas del grupo de más de 65 años. Estos resultados son una nueva alerta para evitar el infradiagnóstico de la MG en el anciano

INTRODUCTION: The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65 years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65. METHODS: The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991. RESULTS: The prevalence of myasthenia gravis was 32.89 × 105 inhabitants (95% CI, 23.86-41.91). The standardized prevalence (European population) was 35.47 × 105 inhabitants (95% CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25 years old, prevalence was 21.87 × 105 in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35×105. The clinical characteristics prior to treatment and at the cut-off date are similar (P > .05) in patients younger than 65 and those aged 65 and older. CONCLUSIONS: These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly populatio

Prevalence of myasthenia gravis in the Catalan county of Osona. / Prevalencia de miastenia gravis en la comarca de Osona (Barcelona, Cataluña).

INTRODUCTION: The reported prevalence of myasthenia gravis ranges between 5 and 24 cases per 100,000, and people over 65years account for less than 50% of all cases. The prevalence and clinical characteristics of myasthenia gravis in the county of Osona were studied in patients younger and older than 65. METHODS: The study draws from the county-based prospective myasthenia gravis register implemented by the Neurology Department at Hospital General de Vic in 1991. RESULTS: The prevalence of myasthenia gravis was 32.89×105 inhabitants (95%CI, 23.86-41.91). The standardized prevalence (European population) was 35.47×105 inhabitants (95%CI, 26.10-44.84). The ratio of women to men was 1.3. Overall, the group of patients older than 65 accounted for 62.75% of all cases. The prevalence of myasthenia gravis increased considerably in older age groups. No cases were registered among patients under 25years old, prevalence was 21.87×105 in the 25 to 64 age group, and prevalence in patients over 65 years increased to 122.35×105. The clinical characteristics prior to treatment and at the cut-off date are similar (P>.05) in patients younger than 65 and those aged 65 and older. CONCLUSIONS: These figures show the highest prevalence rate reported to date. This high prevalence is due to the rate observed among patients older than 65. These results provide a new warning that myasthenia gravis may be underdiagnosed in the elderly population.

Prenatal hypoxia programs changes in ß-adrenergic signaling and postnatal cardiac contractile dysfunction.

Prenatal hypoxia leads to an increased risk of adult cardiovascular disease. We have previously demonstrated a programming effect of prenatal hypoxia on the cardiac ß-adrenergic (ßAR) response. The aim of this study was to determine 1) whether the decrease in ßAR sensitivity in prenatally hypoxic 5-wk old chicken hearts is linked to changes in ß1AR/ß2ARs, Gαi expression and cAMP accumulation and 2) whether prenatal hypoxia has an effect on heart function in vivo. We incubated eggs in normoxia (N, 21% O2) or hypoxia from day 0 (H, 14% O2) and raised the posthatchlings to 5 wk of age. Cardiac ß1AR/ß2ARs were assessed through competitive binding of [(3)H]CGP-12177 with specific ß1AR or ß2AR blockers. Gαs and Gαi proteins were assessed by Western blot and cAMP accumulation by ELISA. Echocardiograms were recorded in anesthetized birds to evaluate diastolic/systolic diameter and heart rate and tissue sections were stained for collagen. We found an increase in relative heart mass, ß1ARs, and Gαs in prenatally hypoxic hearts. cAMP levels after isoproterenol stimulation and collagen content was not changed in H compared with N, but in vivo echocardiograms showed systolic contractile dysfunction. The changes in ßAR and G protein subtypes may be indicative of an early compensatory stage in the progression of cardiac dysfunction, further supported by the cardiac hypertrophy and systolic contractile dysfunction. We suggest that it is not the changes in the proximal part of the ßAR system that causes the decreased cardiac contractility, but Ca(2+) handling mechanisms further downstream in the ßAR signaling cascade.

Increase in the prevalence of multiple sclerosis over a 17-year period in Osona, Catalonia, Spain.

The prevalence of multiple sclerosis in the south of Europe seems to be higher than previously considered. This study aimed to probe a possible increase in the prevalence of multiple sclerosis (MS) in Osona over the past 17 years. This was a cross-sectional study including MS-confirmed cases from several sources of information. Crude and adjusted prevalence rates were obtained. One hundred and twenty patients fulfilled the study criteria. The crude prevalence of MS was 79.9 (95% CI: 66.3-95.6) per 100,000 inhabitants and 91.2 (95% CI: 75.5-109.2) per 100,000 among Spanish born individuals. The prevalence of multiple sclerosis cases in Osona has increased over the past 17 years to being one of the highest reported in Spain.

Effect of selection for commercially productive traits on the plasticity of cardiovascular regulation in chicken breeds during embryonic development.

Domesticated animal breeds have experienced profound anatomical and physiological changes as a result of human-driven genetic selection. In poultry, this selection process has resulted in many distinct phenotypes from the ancestral bird, the Red Junglefowl. Growth rate and egg-laying capacity are 2 traits that have been commercially prioritized, and this has resulted in a fast-growth breed, the broiler, and a prolific egg layer, the White Leghorn. In this study, we investigated basic cardiovascular physiology in these 3 breeds at 90% of incubation. We aimed to identify breed-specific features of arterial blood pressure and heart rate as well as the physiological mechanisms regulating them. Specifically, we investigated mechanisms mediated by the autonomic nervous system by means of cholinergic and adrenergic receptors. Our overriding hypothesis was that selection for rapid growth would require an acceleration of heart rate and arterial pressure development in broilers compared with White Leghorns and the ancestral breed. The embryonic broiler is characterized by resting relative hypertensive bradycardia, whereas the White Leghorn is hypotensive. All 3 breeds maintained resting arterial pressure and heart rate via a similar ß- and α-adrenergic receptor tone; however, cholinergic tone on heart rate was absent in the embryonic White Leghorn. Each breed responded differently to incubation in chronic hypoxic conditions (14% O(2)). White Leghorn relied on augmenting cholinergic heart rate tone, and broilers relied on reducing ß-adrenergic tone on pressure. We concluded that selection for rapid growth shifts cardiovascular regulatory plasticity to emphasize mechanisms that modulate pressure, and that selection for egg-laying capacity emphasizes mechanisms that modulate heart rate.

Physiological variability in yearling alligators: clutch differences at rest and during activity.

The adult phenotype of an organism is the result of its genotype, the environment, and the interaction between the two. Assessing the relative contribution of these factors to the final adult phenotype continues to occupy researchers. Studies have shown clutch effects early in development but few have investigated the persistence of clutch effects on a longer time scale. Five clutches of American alligators were reared for 1 year in a common environment then assessed for the presence of clutch effects as they related to morphological and physiological characteristics. After 1 year, significant clutch effects were evident in all size related variables despite open access to food. Additionally, lung and liver masses remained different between clutches after animal mass was taken into account. Although clutch had no effect on resting heart rate, it significantly contributed to mean arterial pressure. During swimming and exhaustive exercise, the resulting respiratory and metabolic acidoses were strongly dependent on clutch. Therefore, while the environment can have significant influences on the American alligator from hatching to death, the measureable contribution of genetics to the morphology and physiology of the organism remains evident, even after 1 year of common rearing conditions. It behooves researchers to acknowledge and control for clutch effects when designing experiments.

Sensitivity of organ growth to chronically low oxygen levels during incubation in Red Junglefowl and domesticated chicken breeds.

Genetic selection programs have imposed large phenotypic changes in domesticated chicken breeds that are also apparent during embryonic development. Broilers, for example, have a faster growth rate before hatching in comparison with White Leghorns, indicating that the allocation of resources toward different functions already begins before hatching. Therefore, we hypothesized that embryonic organ growth would follow different developmental trajectories and would be differentially affected by an oxygen shortage during incubation. Heart, brain, and liver growth were studied in broiler, White Leghorn, and Red Junglefowl embryos at embryonic (E) ages E11, E13, E15, E18, and E20, and the results were fitted to growth allometric equations to determine the degree of organ stunting or sparing caused by low oxygen during incubation. Hypoxia caused a 3-fold larger mortality in Red Junglefowl than in the domesticated breeds, with a similar impairment of embryonic growth of 18%, coupled with a reduction in yolk utilization of 56%. Relative brain size was not affected by hypoxia in any breed, but a substantial stunting effect was observed for the liver and heart at late embryonic ages, with marked differences between breeds. In Red Junglefowl, only the heart was stunted. In White Leghorns, only the liver was stunted, and in broilers, both organs were stunted. These results can be explained in terms of the selection pressure on long-term production traits (reproductive effort) in White Leghorns, requiring a more efficient lipid metabolism, compared with the selection pressure on shorter-term production traits (growth) in broilers, requiring overall metabolic turnover and convective nutrient delivery to all tissues. At the same time, a remarkable sparing of the heart was observed in broilers and Red Junglefowl between E11 and E15, which suggests that cardiac growth can be manipulated during embryonic development. This result could be relevant for manipulating the phenotype of the heart for management purposes at a developmental stage when the bird is most versatile and phenotypically malleable.

Reactivity of chicken chorioallantoic arteries, avian homologue of human fetoplacental arteries.

The reactivity of human fetoplacental arteries is regulated by humoral and local factors of maternal and fetal origin. The chorioallantoic (CA) arteries of bird embryos are homologous to fetoplacental arteries and fulfill the same gas-exchange purpose without maternal influences, but their reactivity has not been studied in detail. In the present study we hypothesized that CA arteries would respond to vasoactive factors similarly to fetoplacental arteries and the response would change during development between maximal vascular CA expansion (15 of the 21 days incubation period) and prior to hatching. Therefore, we analyzed the reactivity of third order arteries (≈200 µm) from the CA membrane of 15 and 19 day chicken embryos. CA arteries contracted in response to K(+), the thromboxane A(2) mimetic U46619, endothelin-1, acetylcholine and acute hypoxia, but showed no reaction to α-adrenergic stimulation (phenylephrine). The nitric oxide donor sodium nitroprusside, the adenylyl cyclase agonist forskolin, and the ß-adrenergic agonist isoproterenol relaxed CA arteries pre-contracted with K(+) or U46619. The contraction evoked by acetylcholine and the relaxations evoked by sodium nitroprusside and isoproterenol decreased with incubation age. In conclusion, CA arteries share many characteristics with human fetoplacental arteries, such as pronounced relaxation to ß-adrenergic stimuli and hypoxic vasoconstriction. Our study will be the foundation for future studies to explain disparate and common responses of the CA and fetoplacental vasculature.

Optimal dosing of bemiparin as prophylaxis against venous thromboembolism in surgery for cancer: an audit of practice.

AIMS: Low-molecular-weight heparins are drugs of first choice for thromboprophylaxis in cancer surgery. We sought to determine the optimal use of bemiparin in cancer surgery in standard clinical practice. PATIENTS AND METHODS: A retrospective, multicentre audit on the use of bemiparin in patients undergoing cancer surgery and given prophylaxis with bemiparin was undertaken. Surgeons' assessment of venous thromboembolic (VTE) risk (moderate or high) was compared to the criteria of current Consensus Guidelines for VTE management. We assessed the incidence of documented symptomatic VTE, bleeding events, thrombocytopenia, deaths and total events related to VTE or bemiparin prophylaxis (i.e. bleeding, thrombocytopenia). The potential economic impact of postoperative vs. preoperative bemiparin was also analysed. RESULTS: Clinical records from 197 patients from 5 Spanish centres were checked. Prophylaxis was started postoperatively in 45 patients (22.8%). According to the surgeons' criteria, 73 (37.1%) patients were at high VTE risk and received bemiparin 3500 IU/d. However, according to the criteria of current Guidelines, 189 (95.9%) patients were at high risk of VTE (heterogeneity P-value<0.0001). Three (1.5%) patients, all of them receiving bemiparin 2500 IU/d, developed a symptomatic confirmed VTE. There were 4 major and 5 minor bleeding events during bemiparin prophylaxis. A lower incidence of bleeding (2.2% vs. 5.3%; P=0.48) and total events (2.2% vs. 9.9%; P=0.11) was seen with bemiparin started postoperatively as compared to preoperative bemiparin. Bleeding rates did not significantly differ between patients given low or high bemiparin prophylactic doses (4.0% vs. 5.5%; P=0.72). Two patients died due to cardio-respiratory failure and sepsis, respectively. Postoperative bemiparin provided net cost savings of 909 euro per patient compared to preoperative start of prophylaxis due to shorter hospital stays (9 vs. 11 days) and lower incidence of complications in the postoperative bemiparin group. CONCLUSIONS: Many cancer patients are still poorly assessed for risk of VTE. Bemiparin 3500 IU/d is associated with a lower incidence of VTE without significant increase in complications as compared with bemiparin 2500 IU/d. Postoperative bemiparin prophylaxis seems to be as effective and safer than preoperative start of prophylaxis. Further prospective clinical studies are needed to fully address this issue.

Mechanical efficiency of the trout heart during volume and pressure-loading: metabolic implications of the stiffness of the ventricular tissue.

In the mammalian heart the metabolic costs of pressure loading exceed those of volume loading. As evidence suggests that the opposite may be true in fish, we evaluated the metabolic costs of volume and pressure loading in the isolated trout heart and compared the results with the mammalian heart based on the biomechanical properties of cardiac muscle. The highest power output (2.33+/-0.32 mW g(-1), n=5) appeared at the highest preload pressure tested (0.3 kPa) and at an afterload of 5 kPa. At a higher afterload, power did not increase because stroke volume fell. The highest mechanical efficiency (20.7+/-2.0%, n=5) was obtained at a preload of 0.15 kPa and an afterload of 5 kPa. Further increases in preload or afterload did not increase mechanical efficiency, probably because of increases in ventricular wall stress which increased the oxygen consumed disproportionately more than the stroke work. Under pressure unloading (25% decrease in power output), mechanical efficiency was significantly higher in comparison with volume unloading. Given that stiffness of the ventricular tissue is larger in trout than in rat papillary muscles, it is suggested that the increased strain during volume loading is energetically disadvantageous for stiff muscles like those of trout, but it is advantageous when muscle stiffness is lower as it occurs in the rat papillary muscle.

Morphometry and estimated bulk oxygen diffusion in larvae of Xenopus laevis under chronic carbon monoxide exposure.

To understand the mechanisms that allow tadpoles of the African clawed frog Xenopus laevis to develop under conditions of impaired convective transport (hemoglobin poisoning with carbon monoxide), whole animal surface area and volume were measured and bulk oxygen diffusion was modeled at four developmental stages (from initiation of heartbeat to pre-metamorphic climax). Surface area [8.5 mm2 at stages Nieuwkoop-Faber (NF) 33-34 to 70.2 mm2 at stages NF 50-51] and volume (1.8 mm3 at stages NF 33-34 to 35.7 mm3 at stages NF 50-51) measured from volumetric analysis from dual plane images of each animal were not significantly different between treatments. Bulk oxygen radial diffusion was estimated by modeling the larvae as a set of adjacent cylinders with different radii. The model was used to predict the oxygen tension at the water-skin interface at which the oxygen tension in the center of the animal is nil (0.7 kPa at stage NF 33-34 and 14.0 kPa at stage NF 50-51), suggesting that bulk oxygen diffusion is sufficient to meet the metabolic demand up to stages NF 46-47 irrespective of the oxygen tension at the water-skin interface. At NF 50-51 an anoxic core in the animal would appear if bulk oxygen diffusion were the only means of oxygen transport at oxygen tensions below 15 kPa. However, the relative volume of the anoxic core would only exceed 10% of the total volume of the animal only at oxygen tensions below 5 kPa. Therefore, the ten-fold increase in mass between NF 50-51 and metamorphosis would prove insufficient for embryonic oxygen requirements via simple diffusion, and therefore would require additional transport mechanisms.

Ontogeny of cholinergic and adrenergic cardiovascular regulation in the domestic chicken (Gallus gallus).

Adrenergic and cholinergic tone on the cardiovascular system of embryonic chickens was determined during days 12, 15, 19, 20, and 21 of development. Administration of the muscarinic antagonist atropine (1 mg/kg) resulted in no significant change in heart rate or arterial pressure at any developmental age. In addition, the general cardiovascular depressive effects of hypoxia were unaltered by pretreatment with atropine. In addition, the ganglionic blocking agent hexamethonium (25 mg/kg) did not induce changes in heart rate. The beta-adrenergic antagonist propranolol (3 mg/kg) induced a bradycardia of similar magnitude on all days studied, with a transient hypertensive action on days 19-20, indicating the existence of an important cardiac and vascular beta-adrenergic tone. Injections of the alpha-adrenergic antagonists prazosin or phentolamine (1 mg/kg) reduced arterial pressure significantly on all days of incubation studied. Collectively, the data indicate that embryonic chickens rely primarily on adrenergic control of cardiovascular function, with no contribution from the parasympathetic nervous system.

Respiratory responses to short term hypoxia in the snapping turtle, Chelydra serpentina.

Among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. We have investigated the compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short exposure to hypoxia. Snapping turtles started to hyperventilate when oxygen levels dropped below 10% O(2). Total ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. During normoxia, respiration occurred in bouts of four to five breaths, whereas at 5% O(2), the ventilation pattern was more regular with breathing bouts consisting of a single breath. The increase in the heart rate between breaths during hypoxia suggests that a high pulmonary blood flow may be maintained during non-ventilatory periods to improve arterial blood oxygenation. After 4 days of hypoxia at 5% O(2), hematocrit, hemoglobin concentration and multiplicity and intraerythrocytic organic phosphate concentration remained unaltered. Accordingly, oxygen binding curves at constant P(CO(2)) showed no changes in oxygen affinity and cooperativity. However, blood pH increased significantly from 7.50+/-0.05 under normoxia to 7.72+/-0.03 under hypoxia. The respiratory alkalosis will produce a pronounced in vivo left-shift of the blood oxygen dissociation curve due to the large Bohr effect and this is shown to be critical for arterial oxygen saturation.

Role of nitric oxide in the systemic and pulmonary circulation of anesthetized turtles (Trachemys scripta).

In reptiles the influence of local vascular factors on blood flow regulation is vaguely understood. The aim of this study was to investigate the role of nitric oxide (NO) on vascular function in anesthetized Trachemys scripta. The experimental protocol consisted of serial injections of sodium nitroprusside (SNP; 25 microg. kg(-1)), L-arginine (185 mg. kg(-1)) and L-NAME (50 mg. kg(-1)). SNP induced a systemic vasodilation (0.05 to 0.02 kPa. min. kg. mL(-1), P = 0.015), with no change in pulmonary vascular resistance (0.07 versus 0.08 kPa. min. kg. mL(-1), P > 0.05). L-Arg had no effect on resistances but increased cardiac output by 17%. L-NAME increased systemic resistance (33% increase; P = 0.01) while pulmonary resistance was unchanged. These effects are consistent with in vivo and in vitro studies on the systemic vasculature of different reptilian species, suggesting that NO has an important role in maintaining systemic vascular tone. The pulmonary vasculature did not respond to NO due to either a lack of an endogenous NO tone or a relaxed state of the pulmonary vasculature. The importance of NO-based mechanisms versus other neuro-humoral modulators in the reptilian circulation remains uncertain. However, as established in prior studies, cholinergic control of the proximal pulmonary artery is the main regulator of pulmonary resistance while systemic resistance depends on a more complex suite of neural, humoral and local effectors that include NO.

Control of blood pressure mediated by baroreflex changes of heart rate in the chicken embryo (Gallus gallus).

Pharmacological manipulation of peripheral resistance via sodium nitroprusside and phenylephrine was used to study baroreflex function over the latter two-thirds of incubation in embryonic chickens. From day 9 to day 19 of incubation, there is a positive linear relation between heart rate and blood pressure, indicating the feedforward action of arterial pressure on heart rate. A reciprocal relationship between blood pressure and heart rate became pronounced during the last 3 days of incubation. For the purpose of the study, gain of the baroreflex was calculated as maximal gain (only those embryos that demonstrated the response) or average gain (all embryos). Maximal gain increased progressively from 13 +/- 7 beats. min(-1). kPa(-1) at 18 days to 105 +/- 83 beats. min(-1). kPa(-1) in 2-day-old hatchlings. The percentage of embryos older than 18 days with baroreflex responses increased from 33% on day 19 to 56% on day 21, indicating that baroreflex regulation begins late in incubation ( approximately 90% incubation time), and the gain of this reflex exhibits a maturation over the final 3 days of incubation.