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"Biochemical Processes physiology."
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The chemical reactions of life : from metabolism to photosynthesis
Presents an introduction to the biochemistry, describes the history of the science, and discusses chemical reactions found in plants and animals.
Book
Body Composition in Sport, Exercise and Health
The analysis of body composition (fat, bone and muscle) is an important process throughout the biomedical sciences. This is the first book to offer a clear and detailed introduction to the key methods and techniques in body composition analysis and to explain the importance of body composition data in the context of sport, exercise and health.
With contributions from some of the world's leading body composition specialists, the book goes further than any other in demonstrating the practical and applied value of body composition analysis in areas such as performance sport and weight control in clinical populations. The book pays particular attention to the important concept of change in body composition, and includes discussion of ethical issues in the collection, interpretation and presentation of data, and considerations when working with special populations.
Bridging the gap between research methods and practical application, this book is important reading for advanced students and practitioners working in sport and exercise science, health science, anatomy, nutrition, physical therapy or ergonomics.
eBook
Overexpression of Arabidopsis ECERIFERUM1 promotes wax very-long-chain alkane biosynthesis and influences plant response to biotic and abiotic stresses
Land plant aerial organs are covered by a hydrophobic layer called the cuticle that serves as a waterproof barrier protecting plants against desiccation, ultraviolet radiation, and pathogens. Cuticle consists of a cutin matrix as well as cuticular waxes in which very-long-chain (VLC) alkanes are the major components, representing up to 70% of the total wax content in Arabidopsis (Arabidopsis thaliana) leaves. However, despite its major involvement in cuticle formation, the alkane-forming pathway is still largely unknown. To address this deficiency, we report here the characterization of the Arabidopsis ECERIFERUM1 (CER1) gene predicted to encode an enzyme involved in alkane biosynthesis. Analysis of CER1 expression showed that CER1 is specifically expressed in the epidermis of aerial organs and coexpressed with other genes of the alkane-forming pathway. Modification of CER1 expression in transgenic plants specifically affects VLC alkane biosynthesis: waxes of TDNA insertional mutant alleles are devoid of VLC alkanes and derivatives, whereas CER1 overexpression dramatically increases the production of the odd-carbon-numbered alkanes together with a substantial accumulation of iso-branched alkanes. We also showed that CER1 expression is induced by osmotic stresses and regulated by abscisic acid. Furthermore, CER1-overexpressing plants showed reduced cuticle permeability together with reduced soil water deficit susceptibility. However, CER1 overexpression increased susceptibility to bacterial and fungal pathogens. Taken together, these results demonstrate that CER1 controls alkane biosynthesis and is highly linked to responses to biotic and abiotic stresses.
Journal Article
3D bioprinted silk fibroin hydrogels for tissue engineering
The development of biocompatible and precisely printable bioink addresses the growing demand for three-dimensional (3D) bioprinting applications in the field of tissue engineering. We developed a methacrylated photocurable silk fibroin (SF) bioink for digital light processing 3D bioprinting to generate structures with high mechanical stability and biocompatibility for tissue engineering applications. Procedure 1 describes the synthesis of photocurable methacrylated SF bioink, which takes 2 weeks to complete. Digital light processing is used to fabricate 3D hydrogels using the bioink (1.5 h), which are characterized in terms of methacrylation, printability, mechanical and rheological properties, and biocompatibility. The physicochemical properties of the bioink can be modulated by varying photopolymerization conditions such as the degree of methacrylation, light intensity, and concentration of the photoinitiator and bioink. The versatile bioink can be used broadly in a range of applications, including nerve tissue engineering through co-polymerization of the bioink with graphene oxide, and for wound healing as a sealant. Procedure 2 outlines how to apply 3D-printed SF hydrogels embedded with chondrocytes and turbinate-derived mesenchymal stem cells in one specific in vivo application, trachea tissue engineering, which takes 2–9 weeks.
Park and colleagues describe the synthesis of methacrylated photocurable silk fibroin bioink for digital light processing 3D bioprinting as well as fabrication of biocompatible organ-mimicking hydrogel structures for trachea tissue engineering.
Journal Article
Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids
Responding to the expansion of scientific knowledge about the roles of nutrients in human health, the Institute of Medicine has developed a new approach to establish Recommended Dietary Allowances (RDAs) and other nutrient reference values. The new title for these values Dietary Reference Intakes (DRIs), is the inclusive name being given to this new approach. These are quantitative estimates of nutrient intakes applicable to healthy individuals in the United States and Canada. This new book is part of a series of books presenting dietary reference values for the intakes of nutrients. It establishes recommendations for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. This book presents new approaches and findings which include the following:
The establishment of Estimated Energy Requirements at four levels of energy expenditure
Recommendations for levels of physical activity to decrease risk of chronic disease
The establishment of RDAs for dietary carbohydrate and protein
The development of the definitions of Dietary Fiber, Functional Fiber, and Total Fiber
The establishment of Adequate Intakes (AI) for Total Fiber
The establishment of AIs for linolenic and a-linolenic acids
Acceptable Macronutrient Distribution Ranges as a percent of energy intake for fat, carbohydrate, linolenic and a-linolenic acids, and protein
Research recommendations for information needed to advance understanding of macronutrient requirements and the adverse effects associated with intake of higher amounts
Also detailed are recommendations for both physical activity and energy expenditure to maintain health and decrease the risk of disease.
eBook
Identifying sources of variation and the flow of information in biochemical networks
To understand how cells control and exploit biochemical fluctuations, we must identify the sources of stochasticity, quantify their effects, and distinguish informative variation from confounding \"noise.\" We present an analysis that allows fluctuations of biochemical networks to be decomposed into multiple components, gives conditions for the design of experimental reporters to measure all components, and provides a technique to predict the magnitude of these components from models. Further, we identify a particular component of variation that can be used to quantify the efficacy of information flow through a biochemical network. By applying our approach to osmosensing in yeast, we can predict the probability of the different osmotic conditions experienced by wild-type yeast and show that the majority of variation can be informational if we include variation generated in response to the cellular environment. Our results are fundamental to quantifying sources of variation and thus are a means to understand biological \"design.\"
Journal Article
Effects of sensorimotor delays and muscle force capacity limits on the performance of feedforward and feedback control in animals of different sizes
Animals rely on feedforward and feedback control for perturbation responses. When comparing terrestrial mammals of different sizes, we generally find that several features that affect perturbation responses change—larger animals have longer sensorimotor time delays, heavier body segments, and proportionally weaker muscles. We used simple computational models to study how control of fast perturbation responses is constrained by two limitations—sensorimotor delays and muscle force capacity—as a function of animal size. We developed two tasks representing common perturbation response scenarios in animal locomotion: a distributed mass pendulum approximating swing limb repositioning (swing task), and an inverted pendulum approximating whole body posture recovery (posture task). First, we used a normalized feedback control system to show how feedback response times can either be limited by the force generation capacity of muscles (force-limited), or by sensorimotor delays which constrain the maximum feedback gains that can be used to produce stable responses (delay-limited). Next, we used more detailed scaled models which represent the full size range of terrestrial mammals and parameterized the sensorimotor delays, maximum muscle forces, and inertial properties using scaling relationships from literature. Across animal size and in both tasks, we found that feedback control was primarily delay-limited—the fastest responses used a fraction of the available muscle force capacity. We compared feedback control to the fastest feedforward control strategy, and found that feedforward control response times were about four times faster than feedback control in the smallest animals, and around two times faster in the largest animals. For rapid perturbation responses, feedback control appears ineffective for terrestrial mammals of all sizes, as our simulated fastest response times exceeded available movement times. Thus, feedforward control strategies—including anticipatory adjustments, ballistic motor programs, and exploitation of intrinsic musculoskeletal dynamics—may be essential for reacting quickly to sudden and large perturbations in terrestrial mammals.
Journal Article
Pleiotropic Phenotypes of the sticky peel Mutant Provide New Insight into the Role of CUTIN DEFICIENT2 in Epidermal Cell Function in Tomato
Plant epidermal cells have evolved specialist functions associated with adaptation to stress. These include the synthesis and deposition of specialized metabolites such as waxes and cutin together with flavonoids and anthocyanins, which have important roles in providing a barrier to water loss and protection against UV radiation, respectively. Characterization of the sticky peel (pe) mutant of tomato (Solanum lycopersicum) revealed several phenotypes indicative of a defect in epidermal cell function, including reduced anthocyanin accumulation, a lower density of glandular trichomes, and an associated reduction in trichome-derived terpenes. In addition, pe mutant fruit are glossy and peels have increased elasticity due to a severe reduction in cutin biosynthesis and altered wax deposition. Leaves of the pe mutant are also cutin deficient and the epicuticular waxes contain a lower proportion of long-chain alkanes. Direct measurements of transpiration, together with chlorophyll-leaching assays, indicate increased cuticular permeability of pe leaves. Genetic mapping revealed that the pe locus represents a new allele of CUTIN DEFICIENT2 (CD2), a member of the class IV homeodomain-leucine zipper gene family, previously only associated with cutin deficiency in tomato fruit. CD2 is preferentially expressed in epidermal cells of tomato stems and is a homolog of Arabidopsis (Arabidopsis thaliana) ANTHOCYANINLESS2 (ANL2). Analysis of cuticle composition in leaves of anl2 revealed that cutin accumulates to approximately 60% of the levels observed in wild-type Arabidopsis. Together, these data provide new insight into the role of CD2 and ANL2 in regulating diverse metabolic pathways and in particular, those associated with epidermal cells.
Journal Article
Transitions in information processing dynamics at the whole-brain network level are driven by alterations in neural gain
A key component of the flexibility and complexity of the brain is its ability to dynamically adapt its functional network structure between integrated and segregated brain states depending on the demands of different cognitive tasks. Integrated states are prevalent when performing tasks of high complexity, such as maintaining items in working memory, consistent with models of a global workspace architecture. Recent work has suggested that the balance between integration and segregation is under the control of ascending neuromodulatory systems, such as the noradrenergic system, via changes in neural gain (in terms of the amplification and non-linearity in stimulus-response transfer function of brain regions). In a previous large-scale nonlinear oscillator model of neuronal network dynamics, we showed that manipulating neural gain parameters led to a 'critical' transition in phase synchrony that was associated with a shift from segregated to integrated topology, thus confirming our original prediction. In this study, we advance these results by demonstrating that the gain-mediated phase transition is characterized by a shift in the underlying dynamics of neural information processing. Specifically, the dynamics of the subcritical (segregated) regime are dominated by information storage, whereas the supercritical (integrated) regime is associated with increased information transfer (measured via transfer entropy). Operating near to the critical regime with respect to modulating neural gain parameters would thus appear to provide computational advantages, offering flexibility in the information processing that can be performed with only subtle changes in gain control. Our results thus link studies of whole-brain network topology and the ascending arousal system with information processing dynamics, and suggest that the constraints imposed by the ascending arousal system constrain low-dimensional modes of information processing within the brain.
Journal Article
Anticipatory coadaptation of ankle stiffness and sensorimotor gain for standing balance
External perturbation forces may compromise standing balance. The nervous system can intervene only after a delay greater than 100 ms, during which the body falls freely. With ageing, sensorimotor delays are prolonged, posing a critical threat to balance. We study a generic model of stabilisation with neural delays to understand how the organism should adapt to challenging balance conditions. The model suggests that ankle stiffness should be increased in anticipation of perturbations, for example by muscle co-contraction, so as to slow down body fall during the neural response delay. Increased ankle muscle co-contraction is indeed observed in young adults when standing in challenging balance conditions, and in older relative to young adults during normal stance. In parallel, the analysis of the model shows that increases in either stiffness or neural delay must be coordinated with decreases in spinal sensorimotor gains, otherwise the feedback itself becomes destabilizing. Accordingly, a decrease in spinal feedback is observed in challenging conditions, and with age-related increases in neural delay. These observations have been previously interpreted as indicating an increased reliance on cortical rather than spinal control of balance, despite the fact that cortical responses have a longer latency. Our analysis challenges this interpretation by showing that these observations are consistent with a functional coadaptation of spinal feedback gains to functional changes in stiffness and neural delay.
Journal Article