Syncope: Assessment of risk and an approach to evaluation in the emergency department and urgent care clinic

Syncope is among the most frequent forms of transient loss of consciousness (TLOC), and is characterized by a relatively brief and self-limited loss of consciousness that by definition is triggered by transient cerebral hypoperfusion. Most often, syncope is caused by a temporary drop of systemic arterial pressure below that required to maintain cerebral function, but brief enough not to cause permanent structural brain injury. Currently, approximately one-third of syncope/collapse patients seen in the emergency department (ED) or urgent care clinic are admitted to hospital for evaluation. The primary objective of developing syncope/TLOC risk stratification schemes is to provide guidance regarding the immediate prognostic risk of syncope patients presenting to the ED or clinic; thereafter, based on that risk assessment physicians may be better equipped to determine which patients can be safely evaluated as outpatients, and which require hospital care. In general, the need for hospitalization is determined by several key issues: i) the patient''s immediate (usually considered 1 week to 1 month) mortality risk and risk for physical injury (e.g., falls risk), ii) the patient''s ability to care for him/herself, and iii) whether certain treatments inherently require in-hospital initiation (e.g., pacemaker implantation). However, at present no single risk assessment protocol appears to be satisfactory for universal application, and development of a consensus recommendation is an essential next step.     

Survival costs of reproduction vary with age in North American red squirrels

The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits.     

Factors that contribute to the ecological risks of salmon and steelhead hatchery programs and some mitigating strategies

State and federal agencies in the United States annually release millions of hatchery salmon and steelhead into public waters. Many of the hatchery programs are located in areas where the wild populations are now listed under the U.S. Endangered Species Act (ESA) (16 U.S.C. §§ 1531–1544). These hatchery programs pose genetic and ecological risks to wild fish populations. Genetic risks occur when hatchery and wild fish interbreed and usually occur within a taxonomic species. Ecological risks occur when the presence of hatchery fish affects how wild fish interact with their environment or with other species and may affect whole species assemblages. This paper reviews some of the factors that contribute to ecological risks. Important contributing factors include the relative abundance of hatchery and wild fish in natural production areas, hatchery programs that increase density-dependant mortality, residual hatchery fish, some physical advantages that hatchery fish can have over wild fish, and life history characteristics that may make some species especially vulnerable to the effects of ecological risks. Many of these risk factors can be mitigated by management activities that reduce the level of interactions between hatchery and wild fish. This paper concludes by recommending twelve mitigation strategies that may be useful when agencies need to bring hatchery programs into compliance with the take provisions of the ESA.     

Developmental costs of rapid growth in a damselfly

Abstract.  1. Developmental costs of rapid growth in terms of increased fluctuating asymmetry are expected to contribute to the widespread occurrence of growth rates below the physiological maximum, but have rarely been demonstrated. Here, these costs are studied for the first time in an invertebrate, the damselfly Lestes viridis , using a rearing experiment where early- and late-hatched larvae of both sexes were reared at decreasing or permanent water levels.
2. Late-hatched animals were more asymmetrical than early-hatched animals except for males in the drying treatment. Also, females were more asymmetrical than males except in early-hatched animals in the drying treatment.
3. The data presented suggest that in females but not in males treatment groups with higher growth rates have more asymmetrical wings. However, at the individual level no relationship between growth rate and asymmetry was present.
4. Possible reasons why the suggested trade-off between growth and developmental instability was not present at the individual level, and at the group level only in females, are discussed.     

Enhanced consumption of an aversively conditioned taste following the presentation of a “medicine” taste

Rats given presentations of a citric acid solution while recovering from LiCl-induced illness (i.e., a “medicine effect” treatment) subsequently drank more of an aversively conditioned NaCl solution at test, when the NaCl presentation was immediately preceded by citric acid. That is, citric acid passed a summation test of conditioned inhibition. Such an effect was not observed in a group given explicitly unpaired presentations of LiCl and citric acid. It is proposed that enhanced consumption of an aversive taste due to the previous presentation of a “medicine” taste can provide an animal model of human maladaptive behavior in regards to food consumption.     

Adaptive Shifts in the Regulation System of Seed Yield in Japanese Species of Epimedium (Berberidaceae)

Abstract Total seed yield per plant in one season was differentiated neither between Epimedium diphyllum and the E. grandiflorum complex ( E. grandiflorum and E. sempervirens ), nor between these two groups and one of their hybrid derived species, E. trifoliatobinatum . Total ovules per plant and seed-set rate per capsule ( SR ) did not vary greatly between these species, and seed weight ( SW ) was almost the same between them. The number of flowers per inflorescence ( F ) was also constant. However, the remaining reproductive component characters, ovule number per ovary ( O ) and inflorescence number per plant ( I ), were differentiated between the three taxa. These two characters were negatively correlated and a trade-off relationship occurred under the constant total seed yield (= O × F × I × SR × SW ). Ovule number per ovary was highly correlated with spur length of the flower. During the course of the hybrid speciation of E. trifoliatobinatum , selection pressure by pollinators on intermediate spur length seems to have favored plants with an intermediate ovule number. On the other hand, this selection pressure counteracted the increase of the inflorescence number under the trade-off. The resultant seed yield of E. trifoliatobinatum did not differ from that of the parental species, but the pattern of ovule allocation to ovaries (capsules) was altered.     

An inducible morphological defence is a passive by-product of behaviour in a marine snail

Many organisms have evolved inducible defences in response to spatial and temporal variability in predation risk. These defences are assumed to incur large costs to prey; however, few studies have investigated the mechanisms and costs underlying these adaptive responses. I examined the proximate cause of predator-induced shell thickening in a marine snail (Nucella lamellosa) and tested whether induced thickening leads to an increase in structural strength. Results indicate that although predators (crabs) induce thicker shells, the response is a passive by-product of reduced feeding and somatic growth rather than an active physiological response to predation risk. Physical tests indicate that although the shells of predator-induced snails are significantly stronger, the increase in performance is no different than that of snails with limited access to food. Increased shell strength is attributable to an increase in the energetically inexpensive microstructural layer rather than to material property changes in the shell. This mechanism suggests that predator-induced shell defences may be neither energetically nor developmentally costly. Positive correlations between antipredator behaviour and morphological defences may explain commonly observed associations between growth reduction and defence production in other systems and could have implications for the evolutionary potential of these plastic traits.