Solvent effects on the structure,dynamics and activity of lysozyme

Kuntz and Kauzmann have argued that dehydrating a protein results in conformational changes. In contrast, Rupleyet al. have developed a hydration model which involves no significant change in conformation; the onset of enzyme activity in hen egg-white lysozyme at hydration values of about 0.2 g water/g protein they ascribe rather to a solvation effect. Using a direct difference infra-red technique we can follow specific hydration events as water is added to a dry protein. Conformational studies of lysozyme using laser Raman spectroscopy indicate changes in conformation with hydration that are complete just before measurable activity is found. Parallel nuclear magnetic resonance measurements of exchangeability of the main chain amide hydrogens, as a function of hydration from near dryness, suggest a hydration-related increase in conformational flexibility which occurs before-and is probably necessary for-the Raman-detected conformational changes. Very recent inelastic neutron scattering measurements provides direct evidence of a flexibility change induced by hydration, which is apparently necessary before the enzyme can achieve adequate flexibility for it to begin to function.     

Ectoparasite load is linked to ontogeny and cell-mediated immunity in an avian host system with pronounced hatching asynchrony

Several contrasting hypotheses have been proposed to account for host age-biased parasite distribution, with some of them suggesting a key role of ectoparasites in the evolution and maintenance of weight hierarchies within broods. We examined parasite distribution among individual hosts across the whole period of host exposure to the parasite in a host system that shows distinct within-brood differences in age and age-related mortality. By contrast to previous hypotheses, we found that the abundance of a haematophagous, mobile ectoparasite Carnus haemapterus on nestling European rollers ( Coracias garrulus ) was highest approximately during the mid-nestling stage of their host, coinciding with the inflection point of the host growth phase. Parasite load increased neither with absolute resource availability (i.e. body size), nor body condition index. By contrast to previous evidence, higher parasite load under natural conditions was associated with a stronger cell-mediated immune response. However, this association was moderated by low parasite densities, as well as a better brood body condition index. Overall, although we revealed remarkable host ontogenetic effects on parasite distribution, the present study suggests that a highly mobile ectoparasite generally prefers healthier hosts. We propose that, in host systems with a marked asynchrony of hatching and background mortality within the brood, parasites favour persistence rather than nutritional attractiveness of the host.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 463–473.     

How Subchronic and Chronic Health Effects can be Neglected for GMOs, Pesticides or Chemicals

Chronic health effects are increasing in the world such as cancers, hormonal, reproductive, nervous, or immune diseases, even in young people. During regulatory toxicological subchronic tests to prevent these on mammalian health, prior commercialization of chemicals, including pesticides and drugs, or GMOs, some statistically significant findings may be revealed. This discussion is about the need to investigate the relevant criteria to consider those as biologically significant. The sex differences and the non linear dose or time related effects should be considered in contrast to the claims of a Monsanto-supported expert panel about a GMO, the MON 863 Bt maize, but also for pesticides or drugs, in particular to reveal hormone-dependent diseases and first signs of toxicities.     

Seed quality effects in bulb onions (Allium cepa L.)

The nature and persistence of seed quality effects produced by a range of seed production treatments was investigated in the autumn-sown onion crop. Genotypically equivalent seed lots raised in different glasshouses within the same year were found to germinate at significantly different rates. The seed lot which emerged earlier produced larger seedlings and this difference in size persisted throughout the growing period. In a comparison between the effects of hand crossing and self-pollination techniques the hand crossing method produced a much lower total seed yield but heavier seeds and larger plants. The induced effects persisted throughout the year but were not significant in the mature bulb characters. The implications of these results upon the control of seed production for plant breeding and genetical experiments is discussed.     

Embryo survival and smolt to adult survival in second‐generation outbred coho salmon

Outbreeding depression was not detectable in observations of embryonic survival and of survival of smolts to adulthood relative to controls in coho salmon Oncorhynchus kisutch experimentally outbred over two generations by crossing fish from three widely separated populations. Survival in outbred coho salmon was not detectably less than that in second‐generation hybrid controls or second‐generation parental controls. Variation of embryonic survival was affected by the maternal source population and by individual females but not by the paternal source population or by individual males. Survival of smolts to adulthood at sea was greater in one second‐generation control group than in two others, but survival in second‐generation outbred groups was no less than in parental controls or hybrid controls.     

Circamensal Rhythms in Physical Performance

The eumenorrheic menstrual cycle represents a clear inherent biological rhythm that might interact with both physical performance, and/or the physiological response to performance. The predominant hormonal fluctuations throughout the cycle are in the ovarian steroids oestrogen and progesterone. Progesterone has both a thermogenic and ventilatory effect leading to a potential increase in minute ventilation and body temperature during exercise. Oestrogen has been linked to fluctuations in blood flow and heart rate via a vasodilatory mechanism, plus potential variation in muscle strength. If these hormones do indeed influence physical performance, or the physiological response to performance, female athletes might choose to manipulate the cycle through an endogenous hormonal mechanism. Furthermore, researchers utilizing a female population must control for these fluctuations in their research design.     

Exercise training in chronic heart failure: mechanisms and therapies

Decreased exercise capacity negatively affects the individuals’ ability to adequately perform activities required for normal daily life and, therefore, the independence and quality of life. Regular exercise training is associated with improved quality of life and survival in healthy individuals and in cardiovascular disease patients. Also in patients with stable heart failure, exercise training can relieve symptoms, improve exercise capacity and reduce disability, hospitalisation and probably mortality. Physical inactivity can thus be considered a major cardiovascular risk factor, and current treatment guidelines recommend exercise training in patients with heart failure in NYHA functional classes II and III. Exercise training is associated with numerous pulmonary, cardiovascular, and skeletal muscle metabolic adaptations that are beneficial to patients with heart failure. This review discusses current knowledge of mechanisms by which exercise training is beneficial in these patients.