Determinants of peak muscle power: effects of age and physical conditioning

The relationships between absolute peak muscle power (W _peak), muscle cross sectional area (CSA_tot, i.e. the sum of both thigh and calf CSA) and muscle high energy phosphate concentration (adenosine 5-triphosphate [ATP] and phosphocreatine concentrations [PC]) were studied in 47 subjects classified into five groups: A, 10 sedentary (S) subjects aged 20–35 years; B, 9 S aged 35–50 years; C, 9 S aged more than 50 years; D, 13 children aged 8–13 years; and E, 6 athletes (top level volleyball players) aged 24 (SD 3) years. The W _peak was measured during a maximal vertical high jump off both feet on a force platform. The CSA_tot was measured anthropometrically. The [ATP] and [PC] were determined by ³¹Phosphorus nuclear magnetic resonance spectroscopy. The W _peak decreased with age, was 65% lower in D than in A, and 43% higher in E than in A. The CSA_tot did not vary with age, was 45% smaller in D than in A, and 15% greater in E than in A. The [ATP] and [PC] were essentially the same in all groups. The changes observed in W _peak were only partially accounted for by changes in CSA_tot. Therefore, in addition to the variables investigated, other factors appear to have been involved in the determination of W _peak with increasing age and training. An important role may be played by hormonal, particularly at puberty, and neural factors.     

Choline-Containing Compounds in Human Astrocytomas Studied by 1H NMR Spectroscopy In Vivo and In Vitro

Abstract: We have studied 14 patients with different grades of astrocytomas using ¹H NMR spectroscopy in vivo. Typically, astrocytomas exhibited a low N -acetyl-aspartate peak, a prominent signal from choline group-containing compounds, and lactate in the ¹H NMR spectra in vivo. The uncorrected choline/creatine + phosphocreatine peak area ratios were higher in tumors than in normal brain tissue. Absolute concentration of choline-containing compounds (1.74 ± 0.09 mmol/L) in the normal brain tissue was not different in any grade of astrocytoma, but total creatine concentration in healthy brain (7.49 ± 0.30 mmol/L) was higher than that in grade IV astrocytomas (4.84 ± 0.89 mmol/L). Relaxation constants of choline-containing compounds did not differ in tumors from those determined in normal brain. Perchloric acid extracts of biopsy samples from 35 astrocytomas and 13 samples of normal temporal white matter were analyzed with ¹H NMR. Total concentration of choline-containing compounds did not differ between controls and any grade of astrocytoma when the quantification was done in vitro. It is interesting that phosphorylcholine concentration was about twofold greater in grade IV astrocytomas than in controls or other grades of astrocytomas. We conclude that high phosphorylcholine in grade IV astrocytomas may be an indicator of degree of malignancy. The proportional changes within the group of choline-containing compounds observed in vitro were not reflected in the NMR properties of choline signal in vivo.     

Variable thermal dissipation in a Photosystem I submembrane fraction

Photoacoustic spectroscopy was used to study the thermal deactivation processes in a Photosystem I submembrane fraction isolated from spinach. A large part of the thermal dissipation was variable. The yield of this variable thermal emission depended on the redox state of the Photosystem. It increased with the measuring modulated light intensity coinciding with the gradual closure of the reaction centers. Thermal deactivation was maximal when the reaction centers were closed by a saturating illumination. Extrapolation of the data at zero light intensity indicated that the yield of non-variable thermal emission represented about 37% of the maximal emission. The presence of methylviologen as artificial electron acceptor decreased the yield of variable thermal emission whereas inhibition following heat stress treatments increased it. The significance of the variable and non-variable components of thermal dissipation is discussed and the measured energy storage is suggested to originate from the reduction of the plastoquinone pool during cyclic electron transport around Photosystem I.Abbreviations Chl chlorophyll - DCIP 2,6-dichlorophenolindophenol - MV methylviologen - Pheo pheophytin - PA photoacoustic - PS I Photosystem I - PS II Photosystem II - Tes [N-tris (hydroxymethyl)] methyl-2-aminoethanesulfonic acid     

Probing protein-cofactor interactions in the terminal oxidases by second derivative spectroscopy: study of bacterial enzymes with cofactor substitutions and heme A model compounds.

Second derivative absorption spectra are reported for the aa3-cytochrome c oxidase from bovine cardiac mitochondria, the aa3-600 ubiquinol oxidase from Bacillus subtilis, the ba3-cytochrome c oxidase from Thermus thermophilis, and the aco-cytochrome c oxidase from Bacillus YN-2000. Together these enzymes provide a range of cofactor combinations that allow us to unequivocally identify the origin of the 450-nm absorption band of the terminal oxidases as the 6-coordinate low-spin heme, cytochrome a. The spectrum of the aco-cytochrome c oxidase further establishes that the split Soret band of cytochrome a, with features at 443 and 450 nm, is common to all forms of the enzyme containing ferrocytochrome a and does not depend on ligand occupancy at the other heme cofactor as previously suggested. To test the universality of this Soret band splitting for 6-coordinate low-spin heme A systems, we have reconstituted purified heme A with the apo forms of the heme binding proteins, hemopexin, histidine-proline-rich glycoprotein and the H64V/V68H double mutant of human myoglobin. All 3 proteins bound the heme A as a (bis)histidine complex, as judged by optical and resonance Raman spectroscopy. In the ferroheme A forms, none of these proteins displayed evidence of Soret band splitting. Heme A-(bis)imidazole in aqueous detergent solution likewise failed to display Soret band splitting. When the cyanide-inhibited mixed-valence form of the bovine enzyme was partially denatured by chemical or thermal means, the split Soret transition of cytochrome a collapsed into a single band at 443 nm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mössbauer spectra of the heme peptide (HP) 1–50 and the heme peptide:non-heme peptide (NHP) non-covalent complex 1–50:51–104 derived from cytochrome c: evidence for cytochrome c iron site solvation in aqueous solution

Mössbauer spectroscopic studies on a heme peptide (HP) derived from cytochrome c and on the HP recombined non-covalently with the remaining cleaved section are reported. The results suggest that the environment of the heme site in the known crystal structure of cytochrome c may differ in detail from the environment of the heme in the working protein.     

Fourier transform infrared (FTIR) spectroscopy for identifying Lactobacillus species

Abstract Fourier Transform infrared (FTIR) spectroscopy can be used to identify microorganisms. This study describes the influence of culture conditions on FTIR spectra and the discrimination of Lactobacillus species found in breweries. Fifty three Lactobacillus strains were analysed by FTIR spectroscopy and identification at the species level was correct for 94% of the strains, and at the strain level for 91% of the strains.     

The early ontogeny of the southern mouthbrooder,Pseudocrenilabrus philander (Pisces,Cichlidae)

Synopsis The early development of the southern mouthbrooder,Pseudocrenilabrus philander, is documented from activation until the early stages of the juvenile period. The duration of the embryonic period is about 14 days at 25°C. Development is direct and there is accelerated exogenous feeding into the embryonic period. The pattern of development and the timing of ontogenetic events and structure formation are a reflection of both internal and external environmental conditions. During mouthbrooding, oxygen uptake is facilitated by embryonic respiratory plexuses and flapping of the pectoral fins. At the time of first release from the buccal cavity, the embryos are in an advanced state of development. The switch-over from the temporary embryonic respiratory system to the adult branchial system has occurred. The yolksac serves as a supplemental source of nutrition as the embryos develop their external food-gathering abilities. The skeletal and sensory systems are sufficiently developed to allow the young to return to the safety of the female's buccal cavity. Pigmentation may provide disruptive colouration. The rate and pattern of development of another mouthbrooding cichlid,Oreochromis mossambicus, is similar to that ofP. philander despite their phylogenetic differences, and may be a consequence of similar life-history styles.     

A comparative study of EPR spin trapping and cytochrome c reduction techniques for the measurement of superoxide anions

Superoxide anions (O₂^.−) generated by the reaction of xanthine with xanthine oxidase were measured by the reduction of cytochrome c and by electron paramagnetic resonance (EPR) spectroscopy using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). Studies were performed to determine the relative sensitivities of these two techniques for the measurement of O₂^.−. Mixtures of xanthine, xanthine oxidase, DMPO generated two adducts, a transient DMPO-OOH and a smaller but longer-lived DMPO-OH. Both adducts were inhibited by superoxide dismutase (SOD), demonstrating they originated from O₂^.−, and were also significantly decreased when the experiments were performed using unchelated buffers, suggesting that metal ion impurities in unchelated buffers alter the formation or degradation of DMPO-adducts. O₂^.−, generated by concentrations of xanthine as low as 0.05 μM, were detectable using EPR spin trapping. In contrast, mixtures of xanthine, xanthine oxidase, and cytochrome c measured spectrophotometrically at 550 nm demonstrated that concentrations of xanthine above 1 μM were required to produce measurable levels of reduced cytochrome c. These studies demonstrate that spin trapping using DMPO was at least 20-fold more sensitive than the reduction of cytochrome c for the measurement of superoxide anions. However, at levels of superoxide generation where cytochrome c provides a linear measurement of production, EPR spin trapping may underestimate radical production, probably due to degradation of DMPO radical adducts.     

Magnesium-deficiency potentiates free radical production associated with postischemic injury to rat hearts: Vitamin E affords protection

Preexisting magnesium deficiency may alter the susceptibility of rat hearts to postischemic oxidative injury (free radicals). This was examined in rats maintained for 3 weeks on a magnesium-deficient (Mg-D) diet with or without concurrent vitamin E treatment (1.2 mg/day, SC). Magnesium-sufficient (Mg-S) rats received the same diet supplemented with 100 mmol Mg/kg feed. Following sacrifice, isolated working hearts were subjected to 30-, 40-, or 60-min global ischemia and 30-min reperfusion. Postischemic production of free radicals was monitored using electron spin resonance (ESR) spectroscopy and spin trapping with -phenyl-N-tert butylnitrone (PBN, 3 mM final); preischemic and postischemic effluent samples were collected and then extracted with toluene. PBN/alkoxyl adduct(s) (PBN/RO·; _H = 1.93 G,_N = 13.63 G) were the dominant signals detected in untreated Mg-S and Mg-D postischemic hearts, with comparably higher signal intensities observed for the Mg-D group following any ischemic duration. Time courses of postischemic PBN/RO· detection were biphasic for both groups (maxima: 2–4 and 8.5–12.5 min), and linear relationships between the extent of PBN/RO· production and the severity of both mechanical dysfunction and tissue injury were determined. Following each duration of ischemia, Mg-D hearts displayed greater levels of total PBN adduct production (1.7 –2.0 times higher) and lower recovery of cardiac function (42–48% less) than Mg-S hearts. Pretreating Mg-D rats with vitamin E prior to imposing 40-min ischemia/reperfusion, led to a 49% reduction in total PBN/RO· production, a 55% lower LDH release and a 2.2-fold improvement in functional recovery, compared to untreated Mg-D hearts. These data suggest that magnesium deficiency predisposes postischemic hearts to enhanced oxidative injury and functional loss, and that antioxidants may offer significant protection against pro-oxidant influence(s) of magnesium deficiency.