RESUMO
Yoga is an ancient mind-body practice that is increasingly recognized to have health benefits in a variety of clinical and non-clinical conditions. This systematic review summarizes the findings of randomized controlled trials examining the effects of yoga on immune system functioning which is imperative to justify its application in the clinic. Fifteen RCTs were eligible for the review. Even though the existing evidence is not entirely consistent, a general pattern emerged suggesting that yoga can downregulate pro-inflammatory markers. In particular, the qualitative evaluation of RCTs revealed decreases in IL-1beta, as well as indications for reductions in IL-6 and TNF-alpha. These results imply that yoga may be implemented as a complementary intervention for populations at risk or already suffering from diseases with an inflammatory component. Beyond this, yoga practice may exert further beneficial effects by enhancing cell-mediated and mucosal immunity. It is hypothesized that longer time spans of yoga practice are required to achieve consistent effects especially on circulating inflammatory markers. Overall, this field of investigation is still young, hence the current body of evidence is small and for most immune parameters, more research is required to draw distinct conclusions.
Assuntos
Sistema Imunitário/imunologia , Yoga , Biomarcadores/metabolismo , Humanos , Sistema Imunitário/metabolismo , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
We tested the hypothesis that mother birds counterbalance the negative effects of hatching asynchrony for later-hatched chicks by increasing the yolk androgen concentrations in consecutive eggs of their clutch. In doing so, they may adaptively tune each offspring's competitive ability and, thus, growth and survival. However, evidence in support of this hypothesis is contradictory. The yolk concentrations of maternal androgens in the eggs of black-headed gulls increase significantly with the laying order of the eggs in a clutch. We experimentally tested the functional consequences of this increase on chick development under natural conditions by injecting eggs with either an oil or androgen solution. We created experimental clutches in which androgen levels either stayed constant or increased with laying order while controlling for differences in egg quality by using only first-laid eggs. We then compared development, growth and survival between these broods. Androgen treatment enhanced embryonic development because androgen-treated eggs hatched half a day earlier than controls, while their size at hatching was similar to oil-treated controls. Androgen treatment did not increase chick survival, but it enhanced growth. Androgen-treated, third-hatched chicks had a higher body mass and longer legs than third-hatched chicks that hatched from oil-treated eggs. At the same time, growth of first chicks (which were all oil treated) was reduced by the presence of two androgen-treated siblings, suggesting that yolk androgens enhance the competitive ability of later-hatched chicks. Our results support the hypothesis that transfer of different amounts of androgens to the eggs of a clutch is a mechanism by which mothers maximize their reproductive output.
Assuntos
Androgênios/metabolismo , Aves/crescimento & desenvolvimento , Aves/metabolismo , Óvulo/metabolismo , Androgênios/administração & dosagem , Androstenodiona/administração & dosagem , Androstenodiona/metabolismo , Animais , Constituição Corporal , Peso Corporal/efeitos dos fármacos , Feminino , Masculino , Modelos Biológicos , Óvulo/efeitos dos fármacos , Testosterona/administração & dosagem , Testosterona/metabolismoRESUMO
We investigated in the black-headed gull whether female deposition of antioxidants and immunoglobulins (enhancing early immune function), and testosterone (suppressing immune function and increasing early competitive skills) correlate suggesting that evolution has favoured the mutual adjustment of different pathways for maternal effects. We also took egg mass, the position of the egg in the laying sequence and offspring sex into account, as these affect offspring survival. Yolk antioxidant and immunoglobulin concentrations decreased across the laying order, while yolk testosterone concentrations increased. This may substantially handicap the immune defence of last-hatched chicks. The decrease in antioxidant levels was greater when mothers had a low body mass and when the increase in testosterone concentrations was relatively large. This suggests that female black-headed gulls are constrained in the deposition of antioxidants in last-laid eggs and compensate for this by enhanced testosterone deposition. The latter may be adaptive since it re-allocates the chick's investment from costly immune function to growth and competitive skills, necessary to overcome the consequences of hatching late from an egg of reduced quality.
Assuntos
Adaptação Fisiológica , Aves/fisiologia , Ovos , Impressão Genômica , Animais , Aves/genética , Peso CorporalRESUMO
Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the sexes, particularly in size dimorphic species. Our results show that, within clutches of black-headed gulls (Larus ridibundus) the proportion of males was positively associated with egg mass. This applied for all three laying positions, independently of the absolute egg mass. There was a significant relationship between the distribution of the sexes over the laying sequence and the egg mass change. When egg mass decreased over the sequence, first-laid eggs were male biased and last-laid eggs female biased, and vice versa. The potential adaptive value of this allocation strategy is evaluated with regard to male sensitivity to egg quality and competitive differences between the sexes.