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Physiological Relationships (physiological + relationships)
Selected AbstractsNitrogen fertilization effects on Myzus persicae aphid dynamics on peach: vegetative growth allocation or chemical defence?ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2010Marie-Hélène Sauge Abstract Plant nitrogen (N) fertilization is a common cropping practice that is expected to serve as a pest management tool. Its effects on the dynamics of the aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) were examined on young peach [Prunus persica (L.) Batsch (Rosaceae)] trees grown under five N treatments, ranging from N shortage to supra-optimal supply for growth. Aphid population increased over time at the three intermediate N levels. It remained stable at the lowest N level and decreased at the highest N level. Four weeks after the start of infestation, the number of aphids displayed a parabolic response to N level. The relationships between N status and parameters of plant vegetative growth (stem diameter) or biomass allocation (lateral-total leaf area and root-shoot ratio) were consistent with responses proposed by models of adaptive plasticity in resource allocation patterns. However, the variation in plant growth predicted aphid population dynamics only partially. Whereas aphid number was positively correlated with plant N status and vegetative growth up to the intermediate N level, it was negatively correlated with plant N status above this level, but not with vegetative growth. The concentrations of primary and secondary (plant defence-related) metabolites in the plant shoots were modified by N treatments: amino acids (main nutritional resource of aphids) and prunasin increased, whereas chlorogenic acid decreased with increasing N availability. Constitutive changes in plant chemistry in response to N fertilization could not directly explain the reduced aphid performance for the highest N level. Nevertheless, the indirect effect of N on the induction of plant defence compounds by aphid feeding warrants further investigation. The study focuses on the feasibility of handling N fertilization to control M. persicae in orchards, but findings may also be relevant for our understanding of the physiological relationships between the host's nutritional status and the requirements of the insect. [source] The Influence of Gonadal Hormones on Neuronal Excitability, Seizures, and Epilepsy in the FemaleEPILEPSIA, Issue 9 2006Helen E. Scharfman Summary:, It is clear from both clinical observations of women, and research in laboratory animals, that gonadal hormones exert a profound influence on neuronal excitability, seizures, and epilepsy. These studies have led to a focus on two of the primary ovarian steroid hormones, estrogen and progesterone, to clarify how gonadal hormones influence seizures in women with epilepsy. The prevailing view is that estrogen is proconvulsant, whereas progesterone is anticonvulsant. However, estrogen and progesterone may not be the only reproductive hormones to consider in evaluating excitability, seizures, or epilepsy in the female. It seems unlikely that estrogen and progesterone would exert single, uniform actions given our current understanding of their complex pharmacological and physiological relationships. Their modulatory effects are likely to depend on endocrine state, relative concentration, metabolism, and many other factors. Despite the challenges these issues raise to future research, some recent advances have helped clarify past confusion in the literature. In addition, testable hypotheses have developed for complex clinical problems such as "catamenial epilepsy." Clinical and animal research, designed with the relevant endocrinological and neurobiological issues in mind, will help advance this field in the future. [source] A sympathetic view of the sympathetic nervous system and human blood pressure regulationEXPERIMENTAL PHYSIOLOGY, Issue 6 2008Michael J. Joyner New ideas about the relative importance of the autonomic nervous system (and especially its sympathetic arm) in long-term blood pressure regulation are emerging. It is well known that mean arterial blood pressure is normally regulated in a fairly narrow range at rest and that blood pressure is also able to rise and fall ,appropriately' to meet the demands of various forms of mental, emotional and physical stress. By contrast, blood pressure varies widely when the autonomic nervous system is absent or when key mechanisms that govern it are destroyed. However, 24 h mean arterial pressure is still surprisingly normal under these conditions. Thus, the dominant idea has been that the kidney is the main long-term regulator of blood pressure and the autonomic nervous system is important in short-term regulation. However, this ,renocentric' scheme can be challenged by observations in humans showing that there is a high degree of individual variability in elements of the autonomic nervous system. Along these lines, the level of sympathetic outflow, the adrenergic responsiveness of blood vessels and individual haemodynamic patterns appear to exist in a complex, but appropriate, balance in normotension. Furthermore, evidence from animals and humans has now clearly shown that the sympathetic nervous system can play an important role in longer term blood pressure regulation in both normotension and hypertension. Finally, humans with high baseline sympathetic traffic might be at increased risk for hypertension if the ,balance' among factors deteriorates or is lost. In this context, the goal of this review is to encourage a comprehensive rethinking of the complexities related to long-term blood pressure regulation in humans and promote finer appreciation of physiological relationships among the autonomic nervous system, vascular function, ageing, metabolism and blood pressure. [source] Seasonal patterns of sucrose concentration in relation to other quality parameters of sugar beet (Beta vulgaris L.)JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2006Christine Kenter Abstract The chemical composition of sugar beet is the most important parameter affecting its processing. Sugar factories require beet with high concentrations of sucrose and low concentrations of melassigenic substances to maximise the amount of extractable sugar. In order to plan the processing campaign, forecasts of root and sugar yield by prediction models are possible but there are no means to predict the technical quality of the beet. In the present study, the seasonal development and physiological relationships of different parameters of sugar beet quality were analysed. In order to estimate possibilities for quality forecasts, the concentrations of beet quality variables in October were correlated with corresponding quality measurements in late summer and to weather variables during the growing season by linear regressions. In 2000 and 2001, 27 field trials were conducted on commercial farm fields in all sugar beet growing areas in Germany. From June to October, sequential samples were taken every 4 weeks and the concentrations of sucrose, potassium, sodium, total soluble nitrogen, ,-amino nitrogen, nitrate, betaine, reducing sugars and marc in the beet were determined. The sucrose concentration increased progressively until the final harvest date in autumn, whereas the concentrations of the melassigenic substances decreased markedly until late summer and remained fairly constant as the season progressed. Marc concentration was the most stable of the parameters analysed. The sucrose concentration was positively correlated with the concentrations of dry matter, betaine and marc, but negatively with nitrate concentration and leaf yield throughout the season. The correlation between the concentrations of sucrose and nitrogenous compounds measured in summer and their final concentrations in autumn was rather weak. However, it was close for potassium, sodium and marc and a satisfactory prediction of their final concentrations was possible by the end of August. Based on weather data, beet quality was not predictable. Therefore, it seems to be difficult to integrate beet quality parameters into prediction models. Copyright © 2005 Society of Chemical Industry [source] Proteomic investigation of the effects of weight loss in the gastrocnemius muscle of wild and NZW rabbits via 2D-electrophoresis and MALDI-TOF MSANIMAL GENETICS, Issue 3 2010A. M. Almeida Summary The study of changes within the key agents regulating metabolism during genetic upgrading because of selection can contribute to an improved understanding of genomic and physiological relationships. This may lead to increased efficiencies in animal production. These changes, regarding energy and protein metabolic saving mechanisms, can be highlighted during food restriction periods. In this study, a 20% weight reduction was induced in two rabbit breeds: New Zealand white, a selected meat producer (Oryctolagus cuniculus cuniculus), and Iberian wild rabbit (Oryctolagus cuniculus algirus), with the aim of determining differential protein expression in the gastrocnemius muscle within control (ad libitum) and restricted diet experimental animal groups, using techniques of two-dimensional gel electrophoresis and peptide mass fingerprinting. Results show that l -lactate dehydrogenase, adenylate kinase, , enolase and , enolase, fructose bisphosphate aldolase A and glyceraldehyde 3-phosphate dehydrogenase, which are enzymes involved in energy metabolism, are differentially expressed in restricted diet experimental animal groups. These enzymes are available to be further tested as relevant biomarkers of weight loss and putative objects of manipulation as a selection tool towards increasing tolerance to weight loss. Similar reasoning could be applied to 2D gel electrophoresis spots corresponding to the important structural proteins tropomyosin , chain and troponin I. Finally, a spot identified as mitochondrial import stimulation factor seems of special interest as a marker of undernutrition, and it may be the object of further studies aiming to better understand its physiological role. [source] | ||||||||||