Carbohydrate nutrition before, during, and after exercise

The role of dietary carbohydrates (CHO) in the resynthesis of muscle and liver glycogen after prolonged, exhaustive exercise has been clearly demonstrated. The mechanisms responsible for optimal glycogen storage are linked to the activation of glycogen synthetase by depletion of glycogen and the subsequent intake of CHO. Although diets rich in CHO may increase the muscle glycogen stores and enhance endurance exercise performance when consumed in the days before the activity, they also increase the rate of CHO oxidation and the use of muscle glycogen. When consumed in the last hour before exercise, the insulin stimulated-uptake of glucose from blood often results in hypoglycemia, greater dependence on muscle glycogen, and an earlier onset of exhaustion than when no CHO is fed. Ingesting CHO during exercise appears to be of minimal value to performance except in events lasting 2 h or longer. The form of CHO (i.e., glucose, fructose, sucrose) ingested may produce different blood glucose and insulin responses, but the rate of muscle glycogen resynthesis is about the same regardless of the structure.     

Transmembrane helices before, during, and after insertion

The transmembrane (TM) helix is the fundamental structural unit of helix-bundle membrane proteins. Recent biophysical studies provide new insights into the interactions of TM helices with each other and with membrane lipid bilayers. The biological process of helix insertion is carried out by translocon complexes acting in concert with ribosomes. An electron cryo-microscopic reconstruction of these complexes reveals their architecture in new detail, and shows that the complex is constructed from four SecY/Sec61 heterotrimers and two TRAP complexes. A disulfide bridge study shows that elongating polypeptide chains pass through the pore previously identified in the X-ray structure of an archaeal SecY heterotrimer. The fundamental code used by the translocon to select polypeptide segments for insertion as TM helices has been broken. A detailed analysis of the TM amino acid distributions of helix-bundle membrane proteins of known structure recapitulates this code.     

Emotions before, during, and after dreaming sleep.

The aim of this study was to provide a preliminary overview of the emotions before, during, and after dreaming sleep in Chinese people. One hundred Chinese participants were included in the study. Cheerful emotions, including interest, exhilaration, and enjoyment, were pervasive in the collected dreams, although anxiety was also a common type of emotion. Positive correlations were found between the intensities of dream, presleep, and postsleep emotions. Significant reductions in intensity were noted in the analyses of emotions preceding dreaming sleep versus emotions following dreaming sleep. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evolution after gene duplication: models, mechanisms, sequences, systems, and organisms

Gene duplication is postulated to have played a major role in the evolution of biological novelty. Here, gene duplication is examined across levels of biological organization in an attempt to create a unified picture of the mechanistic process by which gene duplication can have played a role in generating biodiversity. Neofunctionalization and subfunctionalization have been proposed as important processes driving the retention of duplicate genes. These models have foundations in population genetic theory, which is now being refined by explicit consideration of the structural constraints placed upon genes encoding proteins through physical chemistry. Further, such models can be examined in the context of comparative genomics, where an integration of gene-level evolution and species-level evolution allows an assessment of the frequency of duplication and the fate of duplicate genes. This process, of course, is dependent upon the biochemical role that duplicated genes play in biological systems, which is in turn dependent upon the mechanism of duplication: whole genome duplication involving a co-duplication of interacting partners vs. single gene duplication. Lastly, the role that these processes may have played in driving speciation is examined.     

Detection and prevention of protein aggregation before,during, and after purification

The use of proteins for in vitro studies or as therapeutic agents is frequently hampered by protein aggregation during expression, purification, storage, or transfer into requisite assay buffers. A large number of potential protein stabilizers are available, but determining which are appropriate can take days or weeks. We developed a solubility assay to determine the best cosolvent for a given protein that requires very little protein and only a few hours to complete. This technique separates native protein from soluble and insoluble aggregates by filtration and detects both forms of protein by SDS-PAGE or Western blotting. Multiple buffers can be simultaneously screened to determine conditions that enhance protein solubility. The behavior of a single protein in mixtures and crude lysates can be analyzed with this technique, allowing testing prior to and throughout protein purification. Aggregated proteins can also be assayed for conditions that will stabilize native protein, which can then be used to improve subsequent purifications. This solubility assay was tested using both prokaryotic and eukaryotic proteins that range in size from 17 to 150 kDa and include monomeric and multimeric proteins. From the results presented, this technique can be applied to a variety of proteins.     

Vasopressinergic,Oxytocinergic, and Somatostatinergic Neuronal Activity after Adrenalectomy and Immobilization Stress

Twenty days after bilateral adrenalectomy (ADX) or immediately after the last of three 6-h long immobilization periods, the levels of hypothalamic and neurohypophyseal L-[³⁵S]Cys-labeled arginine vasopressin (AVP), oxytocin (OT), and somatostatin-14 (SRIF) (only stressed animals) were measured simultaneously in male Wistar rats, after third ventricular administration of the labeled precursor, via guide-cannulae. The acetic acid-extracted labeled peptide fractions were purified by two sequential HPLC steps. After a 4 h period of labeling, only L-[³⁵S]Cys-AVP was selectively increased in the hypothalami of ADX-ized rats, compared to the sham-operated animals, possibly reflecting a significant activation of the paraventricular parvocellular (PVC) AVP/corticotropin-releasing factor (CRF) neurons. The increased accumulation of neurohypophyseal L-[³⁵S]Cys-labeled AVP and OT in these animals, without changes in the endogenous levels of these peptides, as measured by UV absorbance, also suggests a moderate activation of the magnocellular (MGC) AVP and OT neurons, as a consequence of adrenal insufficiency. In response to immobilization stress, levels of L-[³⁵S]Cys-OT were selectively increased in the hypothalami and corresponding neurohypophyses, 2 h and 4 h after receiving the label, concomitantly with a statistically significant reduction in the stores of OT in the neural lobes. AVP and SRJF biosynthesis remained unaffected by immobilization; the neurohypophyseal AVP stores likewise remained unchanged. These observations suggest the selective activation of MGC-OT neurons in response to chronic immobilization stress. Selective increases in hypothalamic L-[³⁵S]Cys-AVP in ADX-ized rats, and in hypothalamic L-[³⁵S]Cys-OT in chronically stress-immobilized rats, are presented as a measure of PVC-AVP/CRF and MGC-OT neuronal activation, respectively.     

Myogenin, MyoD, and myosin expression after pharmacologically and surgically induced hypertrophy

The relationshipbetween myogenin or MyoD expression and hypertrophy of the rat soleusproduced either by clenbuterol and 3,3',5-triiodo-L-thyronine(CT) treatment or by surgical overload was examined. Mature female ratswere subjected to surgical overload of the right soleus with the leftsoleus serving as a control. Another group received the same surgicaltreatment but were administered CT. Soleus muscles were harvested 4 wkafter surgical overload and weighed. Myosin heavy chain isoforms wereseparated by using polyacrylamide gel electrophoresis while myogeninand MyoD expression were evaluated by Northern analysis.CT and functional overload increased soleus muscle weight. CT treatmentinduced the appearance of the fast type IIX myosin heavy chain isoform,depressed myogenin expression, and induced MyoD expression. However,functional overload did not alter myogenin or MyoD expression inCT-treated or non-CT-treated rats. Thus pharmacologically andsurgically induced hypertrophy have differing effects on myogenin andMyoD expression, because their levels were associated with changes inmyosin heavy chain composition (especially type IIX) rather thanchanges in muscle mass.