Effect of infusing branched-chain amino acid during incremental exercise with reduced muscle glycogen content

The aim of this study was to investigate whether, when muscle glycogen is reduced, a pre-exercise infusion of branched-chain amino acids (BCAA) modifies exercise performance or the metabolic and respiratory responses to incremental exercise. Six moderately trained volunteers took part in the following protocol on two occasions. On day 1, at 9 a.m. in the postabsorptive state, they performed a graded incremental exercise (increases of 35 W every 4 min) to exhaustion (Ex-1). A meal of 1,000 kcal (4,200 kJ; 60% protein, 40% fat) was consumed at 12 p.m. No food was then allowed until the end of the experiment (20–21 h later). A 90-min period of exercise at alternating high and moderate intensities, designed to deplete muscle glycogen, was performed between 6 p.m. and 7.30 p.m. The morning after (day 2), the subjects randomly received either a mixed solution of BCAA (260 mg × kg^–1 × h^–1 for 70 min), or saline. They then repeated the graded incremental exercise to exhaustion (Ex-2). Metabolic and respiratory measurements suggested a muscle glycogen-depleted state had been achieved. No significant differences were observed in total work performed, maximal oxygen uptake or plasma ammonia, alanine, and blood pyruvate concentrations in the two treatments. After BCAA infusion, higher blood lactate concentrations were observed at maximal power output in comparison with those during saline [BCAA 4.97 (SEM 0.41) mmol × l^–1, Saline 3.88 (SEM 0.47) mmol × l^–1,P < 0.05]. In summary, in conditions of reduced muscle glycogen content, after a short period of fasting, BCAA infusion had no significant effect on the total work that could be performed during a graded incremental exercise.     

Atypical Chordoid Structures in the Aristotle's Lantern of Regular Echinoids

Regular sea–urchins, as a rule, prepare and process their food as pellets in their buccal cavity before ingesting them. This is obtained through the synergistic interaction of the five teeth with five fleshy protuberances (paradental tongues) which extend into the oral cavity and work like tongues. Each of these structures consists of two anatomically distinct parts: the outer component is a deep pouch of the terminal tract of the pharynx and shows a histological organization similar to that usually shown by the pharyngeal wall itself. The deeper component (paradental axis) is represented by a supporting rod and shows a peculiar histological structure, which consists of glycogen containing vesiculate cells mixed to slim muscle fibres and held together by a thin fibrillar stroma. The paradental axes are very problematic structures in terms of comparative anatomy and phylogenetic aspects. Their microscopic and submicroscopic organization is unusual for an echinoderm and recalls that of different types of chordoid organs commonly found in other invertebrates (Protostomata and Deuterostomata).     

Protein Phosphorylation Is Induced in Tobacco Cells by the Elicitor Cryptogein

Changes in plasmalemma ion fluxes were observed when tobacco (Nicotiana tabacum) cells were treated with cryptogein, a proteinaceous elicitor from Phytophthora cryptogea. A strong alkalization of the culture medium, accompanied by a leakage of potassium, was induced within a few minutes of treatment. These effects reached a maximum after 30 to 40 min and lasted for several hours. This treatment also resulted in a rapid, but transient, production of activated oxygen species. All these physiological responses were fully sensitive to staurosporine, a known protein kinase inhibitor. Furthermore, a study of protein phosphorylation showed that cryptogein induced a staurosporine-sensitive phosphorylation of several polypeptides. These data suggest that phosphorylated proteins may be essential for the transduction of elicitor signals.     

Identification of Tuber magnatum Pico DNA markers by RAPD analysis

Summary Different species of truffle were studied in order to identify species-specific markers. The isolation of two Tuber magnatum Pico markers is reported. One of these could be used as a probe in dot blot hybridization, allowing the development of a rapid test able to identify Tuber magnatum species.     

Electrotransformation of Streptococcus agalactiae with plasmid DNA

Abstract A protocol for efficient electrotransformation of Streptococcus agalactiae (group B streptococcus) Lancefield's strain O90R (NTCT 9993) (an unencapsulated derivative of type Ia strain O90) was developed. The Escherichia coli - Streptococcus shuttle vector pDP28 (7.8 kb) carrying the ermB gene for resistance to erythromycin was used as donor DNA. Frozen 'electrocompetent' cells were prepared by repeated washes in 10% glycerol. A 50-μl aliquot containing about 5×10⁹ colony forming units of bacteria was subjected to the electric pulse. Optimal conditions for electrotransformation were determined using different media, harvesting cells at different points of the growth curve, and using different field strengths. The dose-response curve for transformation of S. agalactiae with pDP28 showed one-hit kinetics as donor DNA varied between 0.01 and 3 μg. The efficiency of electrotransformation for this range of amounts of donor DNA was 1.2×10⁴ cfu μg⁻¹. The transformation frequencies obtained with this electroporation protocol are high enough to allow both subcloning and shotgun cloning of streptococcal DNA in S. agalactiae .     

Water stress,temperature, and light effects on the capacity for isoprene emission and photosynthesis of kudzu leaves

Kudzu (Pueraria lobata (Willd) Ohwi.) is a vine which forms large, monospecific stands in disturbed areas of the southeastern United States. Kudzu also emits isoprene, a hydrocarbon which can significantly affect atmospheric chemistry including reactions leading to tropospheric ozone. We have studied physiological aspects of isoprene emission from kudzu so the ecological consequences of isoprene emission can be better understood. We examined: (a) the development of isoprene emission as leaves developed, (b) the interaction between photon flux density and temperature effects on isoprene emission, (c) isoprene emission during and after water stress, and (d) the induction of isoprene emission from leaves grown at low temperature by water stress or elevated temperature. Isoprene emission under standard conditions of 1000 mol photons·m^-2·s^-1 and 30°C developed only after the leaf had reached full expansion, and was not complete until up to two weeks past the point of full expansion of the leaf. The effect of temperature on isoprene emission was much greater than found for other species, with a 10°C increase in temperature causing a eight-fold increase in the rate of isoprene emission. Isoprene emission from kudzu was stimulated by increases in photon flux density up to 3000 mol photons·m^-2·s^-1. In contrast, photosynthesis of kudzu was saturated at less than 1000 mol·m^-2·s^-1 photon flux density and was reduced at high temperature, so that up to 20% of the carbon fixed in photosynthesis was reemitted as isoprene gas at 1000 mol photons·m^-2·s^-1 and 35°C. Withholding water caused photosynthesis to decline nearly to zero after several days but had a much smaller effect on isoprene emission. Following the relief of water stress, photosynthesis recovered to the prestress level but isoprene emission increased to about five times the prestress rate. At 1000 mol photons·m^-2·s^-1 and 35°C as much as 67% of the carbon fixed in photosynthesis was reemitted as isoprene eight days after water stress. Leaves grown at less than 20°C did not make isoprene until an inductive treatment was given. Inductive treatments included growth at 24°C, leaf temperature of 30°C for 5 h, or witholding water from plants. With the new information on temperature and water stress effects on isoprene emission, we speculate that isoprene emission may help plants cope with stressful conditions.     

Phenylacetaldehyde by acetic acid bacteria oxidation of 2-phenylethanol

Summary This paper reports the production of 2-phenylacetaldehyde from 2-phenylethanol by acetic bacteria. Several strains of acetic bacteria were investigated and three were found to be effective for this bioconversion. Different conditions (different C source for the microorganisms, pH, substrate concentration, cell immobilization) were tested with yields ranging from 30 to 52.6%.     

Release of cholecystokinin in the central nervous system

The octapeptide cholecystokinin (CCK) is one of the most abundant neuropeptides of the central nervous system. A number of features (for instance heterogeneity of the regional distribution, subcellular localization at the nerve terminal level, calcium-dependent release upon nervous tissue depolarization) support the candidacy of CCK as a neurotransmitter. The reported co-existence of CCK and dopamine in some meso-limbic neurons has led to speculation that the neuropeptide may interact with the catecholamine in neuropsychopathologies linked to dopamine dysfunctions, like schizophrenia. Data from the experimental animals have so far generated conflicting results. It should be noted that the interactions between CCK and dopamine, and, in particular, the effects of CCK and dopamine on each other release, both in vitro and in vivo, have been poorly investigated and would require special attention. Evidence is accumulating that CCK may participate in the expression of anxiety. Indeed antagonists at the central CCK receptors exhibit anxiolytic activity in the laboratory animal. An interesting linkage appears to exist in the brain between 5-hydroxytryptamine (5-HT) and CCK. Activation of 5-HT₃ receptors was found to increase CCK release from rat cortical or nucleus accumbens synaptosomes. Interestingly, antagonists at 5-HT₃ receptors appear to possess anxiolytic activity. Recent studies carried out in conscious unrestrained rats show that the calcium-dependent, tetrodotoxin-sensitive release of CCK-like immunoreactivity evoked in the rat frontal cortex by veratrine infusion can be inhibited by submicromolar concentrations of 5-HT₃ receptor antagonists. It seems legitimate to conclude that 5-HT and CCK interact in the living brain, the former increasing the release of the latter through activation of receptors of the 5-HT₃ type. On the basis of this interaction both 5-HT₃ and CCK receptor antagonists may become novel anxiolytics.     

Reversible and irreversible modifications ofβ-lactoglobulin upon exposure to heat

Modifications in the exposure to the solvent of hydrophobic residues, changes in their organization into surface hydrophobic patches, and alterations in the dimerization equilibrium ofβ-lactoglobulin upon thermal treatment at neutralpH were studied. Exposure of tryptophan residues was temperature dependent and was essentially completed on the time scale of seconds. Reorganization of generic hydrophobic protein patches on the protein surface was monitored through binding of 1,8-anilinonaphthalenesulfonate, and was much slower than changes in tryptophan exposure. Different phases in surface hydrophobicity changes were related to the swelling and the subsequent collapse of the protein, which formed a metastable swollen intermediate. Heat treatment ofβ-lactoglobulin also resulted in the formation of soluble oligomeric aggregates. The aggregation process was studied as a function of temperature, demonstrating that (i) dimer dissociation was a necessary step in a sequential polymerization mechanism and (ii) cohesion of hydrophobic patches was the major driving force for aggregation.