运动与营养的健康效应机制研究进展

常规适量运动与合理营养是健康的基石,是健康生活方式与防病治病的核心内容。本文从运动和营养的健康效应机制、线粒体营养素作用与机制等简要综述了相关研究进展。     

Faecal near-IR spectroscopy to determine the nutritional value of diets consumed by beef cattle in east Mediterranean rangelands

Rapid assessment of the nutritional quality of diets ingested by grazing animals is pivotal for successful cow–calf management in east Mediterranean rangelands, which receive unpredictable rainfall and are subject to hot-spells. Clipped vegetation samples are seldom representative of diets consumed, as cows locate and graze selectively. In contrast, faeces are easily sampled and their near-IR spectra contain information about nutrients and their utilization. However, a pre-requisite for successful faecal near-infrared reflectance spectroscopy (FNIRS) is that the calibration database encompass the spectral variability of samples to be analyzed. Using confined beef cows in Northern and Southern Israel, we calibrated prediction equations based on individual pairs of known dietary attributes and the NIR spectra of associated faeces (n=125). Diets were composed of fresh-cut green fodder of monocots (wheat and barley), dicots (safflower and garden pea) and natural pasture collected at various phenological states over 2 consecutive years, and, optionally, supplements of barley grain and dried poultry litter. A total of 48 additional pairs of faeces and diets sourced from cows fed six complete mixed rations covering a wide range of energy and CP concentrations. Precision (linearity of calibration, R²cal, and of cross-validation, R²cv) and accuracy (standard error of cross-validation, SEcv) were criteria for calibration quality. The calibrations for dietary ash, CP, NDF and in vitro dry matter digestibility yielded R²cal values >0.87, R²cv of 0.81 to 0.89 and SEcv values of 16, 13, 39 and 31 g/kg dry matter, respectively. Equations for nutrient intake were of low quality, with the exception of CP. Evaluation of FNIRS predictions was carried out with grazing animals supplemented or not with poultry litter, and implementation of the method in one herd over 2 years is presented. The potential usefulness of equations was also established by calculating the Mahalanobis (H) distance to the spectral centroid of a calibration population of 796 faecal samples collected throughout 2 years in four herds. Seasonal trends in pasture quality and responses to management practices were identified adequately and H<3.0 for 98% of faecal samples collected. We conclude that the development of FNIRS equations with confined animals is not only unexpensive and ethically acceptable, but their predictions are also sufficiently accurate to monitor dietary composition (but not intake) of beef cattle in east Mediterranean rangelands.     

Leishmania donovani: A Chemically Defined Medium Suitable for Cultivation and Cloning of Promastigotes and Transformation of Amastigotes to Promastigotes

A chemically defined medium using commercially available α-MEM supplemented with HEPES, L-glutamine, D-glucose, folic acid, D-biotin and adenine supports the luxuriant growth and propagation of Leishmania donovani promastigotes. A peak parasite population of about 7.0 × 10⁷/ml at stationary phase and a population doubling time of 11.4 h for high-subpassage promastigotes were obtained. The medium was suitable for transformation of isolated amastigotes from infected hamster spleen. Promastigotes could be detected by culturing kala-azar patients’bone-marrow aspirate or spleen puncture material in this medium. Four out of six freshly transformed isolates gradually adapted and grew well in this medium. Macroscopic colonies appeared on agar plates prepared with the medium within 16–20 days after inoculation. The cloning efficiency was increased about five-fold by glycerol supplementation.     

Absence of nitrogen fixation (acetylene reduction) by procaryotes in nectar of Banksias

Summary An earlier hypothesis that blue-green algae in the nectar ofBanksia telmatiaea contribute to the nitrogen economy of the host by fixing N₂ was tested. Field and laboratory experiments failed to demonstrate C₂H₄ production in C₂H₂-treated containers over extended periods. Soil N was not higher at the end of the flowering season and plants in which flower heads were removed prior to nectar production did not contain less N than the controls.     

Macronutrients mediate the functional relationship between Drosophila and Wolbachia

Wolbachia are maternally inherited bacterial endosymbionts that naturally infect a diverse array of arthropods. They are primarily known for their manipulation of host reproductive biology, and recently, infections with Wolbachia have been proposed as a new strategy for controlling insect vectors and subsequent human-transmissible diseases. Yet, Wolbachia abundance has been shown to vary greatly between individuals and the magnitude of the effects of infection on host life-history traits and protection against infection is correlated to within-host Wolbachia abundance. It is therefore essential to better understand the factors that modulate Wolbachia abundance and effects on host fitness. Nutrition is known to be one of the most important mediators of host–symbiont interactions. Here, we used nutritional geometry to quantify the role of macronutrients on insect–Wolbachia relationships in Drosophila melanogaster. Our results show fundamental interactions between diet composition, host diet selection, Wolbachia abundance and effects on host lifespan and fecundity. The results and methods described here open a new avenue in the study of insect–Wolbachia relationships and are of general interest to numerous research disciplines, ranging from nutrition and life-history theory to public health.     

Review: Are we using probiotics correctly in post-weaning piglets?

Intensive farming may involve the use of diets, environments or management practices that impose physiological and psychological stressors on the animals. In particular, early weaning is nowadays a common practice to increase the productive yield of pig farms. Still, it is considered one of the most critical periods in swine production, where piglet performance can be seriously affected and where they are predisposed to the overgrowth of opportunistic pathogens. Pig producers nowadays face the challenge to overcome this situation in a context of increasing restrictions on the use of antibiotics in animal production. Great efforts are being made to find strategies to help piglets overcome the challenges of early weaning. Among them, a nutritional strategy that has received increasing attention in the last few years is the use of probiotics. It has been extensively documented that probiotics can reduce digestive disorders and improve productive parameters. Still, research in probiotics so far has also been characterized as being inconsistent and with low reproducibility from farm to farm. Scientific literature related to probiotic effects against gastrointestinal pathogens will be critically examined in this review. Moreover, the actual practical approach when using probiotics in these animals, and potential strategies to increase consistency in probiotic effects, will be discussed. Thus, considering the boost in probiotic research observed in recent years, this paper aims to provide a much-needed, in-depth review of the scientific data published to-date. Furthermore, it aims to be useful to swine nutritionists, researchers and the additive industry to critically consider their approach when developing or using probiotic strategies in weaning piglets.     

Reproductive Ecology of American Black Bears in the Alleghany Mountains of Virginia,USA

We studied reproduction of American black bears (Ursus americanus) in western Virginia from 1994 to 2003. We handled 326 ≥2-year-old female black bears 672 times during summer trapping and followed 176 of these individuals through 424 winter den seasons. We examined 183 litters consisting of 455 cubs. Primiparity occurred at mean and modal ages of 3.8 and 3 years, respectively. Composite mean litter size was 2.49 (SE = 0.06) cubs/litter; 3- and 4-year-olds had smaller litters than older bears. We tracked reproductive synchrony using 5 indices and documented a resetting of this synchrony, likely in response to hard-mast failure. The amplitude of oscillations in synchrony indices dampened through time after the synchronizing events. Documentation and quantification of relationships between nutrient availability, reproduction and population dynamics can be used to inform population modeling efforts and more accurately forecast harvest. © 2011 The Wildlife Society.     

Significance of magnetic resonance image and blood manganese measurement for the assessment of brain manganese during total parenteral nutrition in rats

In this study, we report on the influence of trace elements (TE) on signal intensities of nuclear magnetic resonance images (MRI), both in vivo and in vitro. Optimal parameters for the assessment of Mn concentration in the brain of rats on total parenteral nutrition were established. For the in vitro study, Mn and trace element solutions, one containing Zn, Cu, Fe, and I (TE-4) and another containing the above elements plus Mn (TE-5), were diluted with physiological saline or with rat brain homogenate and used to measure signal intensities in MRI. Concentration-dependent signal hyperintensity was observed in both cases in the Mn and the TE-5 solutions, but no effect was observed with the TE-4 solution. The signal increase was greater for brain tissue homogenates. In the in vivo study, the experimental animals were maintained under total parenteral nutrition (TPN) with a standard clinical dose of TE-5 and/or with 10-fold the clinical dose of TE-4 and TE-5 for 1 wk. Only rats that were receiving the increased TE-5 dose showed signal hyperintensity on MRI. Positive correlations were observed among the signal hyperintensity, the blood Mn concentrations, and that of the rat brain. Our results suggest that Mn in TE preparations may be the cause of signal hyperintensity on MRI in a concentration-dependent fashion, and that MRI and measurement of blood Mn may be used to estimate Mn accumulation in brain tissue.