Hyperthermia and maximal oxygen uptake in men and women.

To compare the effect of hyperthermia on maximal oxygen uptake (VO2max) in men and women, VO2max was measured in 11 male and 11 female runners under seven conditions involving various ambient temperatures (Ta at 50% RH) and preheating designed to manipulate the esophageal (Tes) and mean skin (Tsk) temperatures at VO2max. The conditions were: 25 degrees C, no preheating (control); 25, 35, 40, and 45 degrees C, with exercise-induced preheating by a 20-min walk at approximately 33% of control VO2max; 45 degrees C, no preheating; and 45 degrees C, with passive preheating during which Tes and Tsk were increased to the same degree as at the end of the 20-min walk at 45 degrees C. Compared to VO2max (l x min(-1)) in the control condition (4.52+/-0.46 in men, 3.01+/-0.45 in women), VO2max in men and women was reduced with exercise-induced or passive preheating and increased Ta, approximately 4% at 35 degrees C, approximately 9% at 40 degrees C and approximately 18% at 45 degrees C. Percentage reductions (7-36%) in physical performance (treadmill test time to exhaustion) were strongly related to reductions in VO2max (r=0.82-0.84). The effects of hyperthermia on VO2max and physical performance in men and women were almost identical. We conclude that men and women do not differ in their thermal responses to maximal exercise, or in the relationship of hyperthermia to reductions in VO2max and physical performance at high temperature. Data are reported as mean (SD) unless otherwise stated.

Dynamic responses of oxygen uptake at the onset and end of moderate and heavy exercise in trained subjects.

Inconsistencies about dynamic asymmetry between the on- and off-transient responses in VO2 are found in the literature. Therefore the purpose of this study was to examine VO2 on- and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate (<VT) and heavy (>VT) intensities. VO2 kinetics in exercise and recovery were better described by a single exponential model (<VT), or by a double exponential with two time delays (>VT). For moderate exercise, we found a symmetry of VO2 kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed (<VT and >VT). Our results do not support a dynamically linear system model of VO2 during cycling exercise in the heavy-intensity domain.

Reliability of stable carbon and oxygen isotope compositions of pedogenic needle fibre calcite as environmental indicators: examples from Western Europe.

Stable carbon and oxygen isotope analyses were conducted on pedogenic needle fibre calcite (NFC) from seven sites in areas with roughly similar temperate climates in Western Europe, including the Swiss Jura Mountains, eastern and southern France, northern Wales, and north-eastern Spain. The δ(13)C values (-12.5 to-6.8 0/00 Vienna Pee Dee Belemnite (VPDB)) record the predominant C(3) vegetation cover at the sites. A good correlation was found between mean monthly climatic parameters (air temperature, number of frost days, humidity, and precipitation) and δ(18)O values (-7.8 to-3.40/00 VPDB) of all the NFC. Similar seasonal variations of δ(18)O values for monthly NFC samples from the Swiss sites and those of mean monthly δ(18)O values of local precipitation and meteorological data point out precipitation and preferential growth/or recrystallisation of the pedogenic needle calcite during dry seasons. These covariations indicate the potential of stable isotope compositions of preserved NFC in fossil soil horizons as a promising tool for palaeoenvironmental reconstructions.

Right-left digit ratio (2D:4D) and maximal oxygen uptake.

A low digit ratio (2D:4D) and low 2D:4D in the right compared with the left hand (right-left 2D:4D) are thought to be determined by high in utero concentrations of testosterone, and are related to "masculine" traits such as aggression and performance in sports like running and rugby. Low right-left 2D:4D is also related to sensitivity to testosterone as measured by the number of cytosine-adenine-guanine triplet repeats in exon 1 of the androgen receptor gene. Here we show that low right-left 2D:4D is associated with high maximal oxygen uptake (VO2(max)), high velocity at VO2(max), and high maximum lactate concentration in a sample of teenage boys. We suggest that low right-left 2D:4D is linked to performance in some sports because it is a proxy of high sensitivity to prenatal and maybe also circulating testosterone and high VO2(max).

Acute oxygen sensing in heme oxygenase-2 null mice.

Hemeoxygenase-2 (HO-2) is an antioxidant enzyme that can modulate recombinant maxi-K(+) channels and has been proposed to be the acute O(2) sensor in the carotid body (CB). We have tested the physiological contribution of this enzyme to O(2) sensing using HO-2 null mice. HO-2 deficiency leads to a CB phenotype characterized by organ growth and alteration in the expression of stress-dependent genes, including the maxi-K(+) channel alpha-subunit. However, sensitivity to hypoxia of CB is remarkably similar in HO-2 null animals and their control littermates. Moreover, the response to hypoxia in mouse and rat CB cells was maintained after blockade of maxi-K(+) channels with iberiotoxin. Hypoxia responsiveness of the adrenal medulla (AM) (another acutely responding O(2)-sensitive organ) was also unaltered by HO-2 deficiency. Our data suggest that redox disregulation resulting from HO-2 deficiency affects maxi-K(+) channel gene expression but it does not alter the intrinsic O(2) sensitivity of CB or AM cells. Therefore, HO-2 is not a universally used acute O(2) sensor.

Hemilabile phosphine ligands in molybdenum and tungsten octahedral environments

The synthesis of three bidentate, hemilabile phosphine ligands, newly synthesized in the research group (TPOdiphos, DPPrPOdiphos and SODPdiphos), has been up-scaled and optimized. The ligand substitution reaction on Mo(CO)6 and W(CO)6 has been studied and the corresponding complexes fac-[MTPOdiphos(CO)3], fac-[MDPPrPOdiphos(CO)3], and fac-[MSODPdiphos(CO)3], (M= Mo, W) have been isolated in good yields and characterized by NMR, IR and HR MS. In the case of fac- [MoTPOdiphos(CO)3] the XRD crystal structure was resolved. The complexes were found to be octahedral, neutral molecules, with the metal in the zero oxidation state and the ligand adopting a facial P,P,O-coordination. The hard ligand atom (oxygen) is expected to exhibit special features the future applications of these novel ligands.

Effects of dopamine on total oxygen consumption and oxygen delivery in healthy men.

The effect of acute intravenous dopamine (DA) administration at three sequential (but randomized) infusion rates was studied in eight young male volunteers. DA was infused at 2.5, 5, and 10 micrograms.kg-1.min-1. O2 consumption (VO2) and CO2 production (VCO2) were measured continuously by means of a computerized indirect calorimeter (blood system). In response to the 5- and 10-micrograms.kg-1.min-1 DA infusion rates, a significant increase (P less than 0.01) in VO2 corresponding to a 6% (range, 3-10) and 15% (range, 12-23) increase, respectively, of preinfusion values was observed. In contrast, at the low dose (2.5 micrograms.kg-1.min-1), DA induced no significant change in VO2. Cardiac output (Qc) increased significantly after the three DA administration rates [19% (range, 0-42), 34% (range, 17-71), and 25% (range, -3 to +47)] for the doses 2.5, 5, and 10 micrograms.-kg-1.min-1, respectively. The increase in O2 delivery (QO2) outweighed VO2 at all administration rates despite the relative drop in QO2 at the maximal DA administration rate. These results indicate that in humans DA improves net O2 supply to tissues proportionally more than it increases VO2 at all doses used in the present study.

Evaluation of the quantity of Fe3+ in spinels for obtaining the oxygen fugacities in xenoliths.

The analysis by electron microprobe allows the evaluation of the quantity of Fe3+ ih spinels with considerable errors. The use of a correction equation which is based on a the calibration of analyses with an electron microprobe in relation to those carried out with Mossbauer spectroscopy gives more precise evaluations of Fe3+. In fact, it allows a calculation of the oxygen fugacity in peridotitic xenoliths. The obtained results show that peridotites of the French Central Massif crystallised under oxygen fugacities which were higher than those of the Moroccan Anti-Atlas.

Oxygen uptake of isolated toad skin epithelium: micromeasurement and effect of ionic acclimation.

Oxidative metabolism of isolated toad skin epithelium (Bufo viridis) was investigated in vitro under open-circuit conditions using the spectrophotometric oxyhemoglobin micromethod. This highly sensitive technique has been adapted for studying several epithelia in parallel and for detecting possible regional variations of oxygen uptake in individual epithelium. Changes in the proportion of mitochondria-rich cells (MRC) by ionic acclimation affected oxidative metabolism under nontransporting condition. After acclimation of animals to either NaNO3 or NaCl solutions (100 mmol/l, for greater than 2 wk), the number of MRC per square millimeter in epithelia from nonacclimated and NaNO3- and NaCl-acclimated animals was 350 +/- 113, 460 +/- 196, and 107 +/- 52, respectively. O2 uptake of nonacclimated and NaNO3-acclimated epithelia was significantly higher than that of NaCl-acclimated epithelia (i.e., 0.89 and 0.90 vs. 0.57 nmol O2.h-1.mm-2, respectively). The correlation established between O2 uptake and number of MRC allowed evaluation of the respiration rate of one single MRC, i.e., approximately 1 pmol O2/h. The lowest mitochondrial oxidative activity was found in the epithelia from NaCl-acclimated toads where the uncoupler 2,4-dinitrophenol (50 mumols/l) had the highest relative stimulatory effect (+114%). Acetazolamide (50 mumols/l), a potent inhibitor of carbonic anhydrase mainly present in the MRC, reduced selectively by 31% O2 uptake of the MRC-rich epithelia (NaNO3 acclimated). O2 uptake increased significantly by approximately 80% when basolateral pH increased from 5.8 to 7.8, but did not depend on apical pH. These findings indicate that under nontransporting (open-circuit) conditions, aerobic metabolism of the isolated toad skin epithelium is related to the density and/or characteristics of the MRC.(ABSTRACT TRUNCATED AT 250 WORDS)

Bitumens in the late Variscan hydrothermal vein-type uranium deposit of Pribram, Czech Republic: Sources, radiation-induced alteration, and relation to mineralization

The late Variscan (275-278 Ma) Pribram uranium deposit is one of the largest known accumulations of uraniferous bitumens in hydrothermal veins. The deposit extends along the northwestern boundary of the Central Bohemian pluton (345-335 Ma) with low-grade metamorphosed Late Proterozoic and unmetamorphosed Cambrian rocks. From a net uranium production of 41,742 metric tons (t), more than 6,000 t were extracted from bitumen-uraninite ores during 43 years of exploration and mining. Three morphological varieties of solid bitumen are recognized: globular, asphaltlike, and cokelike. While the globular bitumen is uranium free, the other two types are uraniferous. The amount of bitumen in ore veins gradually decreases toward the contact with the plutonic body and increases with depth. Two types of bitumen microtextures are recognized using high-resolution transmission electron microscopy: amorphous and microporous, the former being less common in uraniferous samples. A lower Raman peak area ratio (1,360/1,575 cm(-1)) in mineralized bitumens (0.9) compared with uranium-free samples (2.0) indicates a lower degree of microtextural organization in the latter The H/C and O/C atomic ratios in uranium-free bitumens (0.9-1.1 and 0.09, respectively) are higher than those in mineralized samples (H/C = 0.3-0.8, O/C = 0.03-0.09). The chloroform extractable matter yield is Very low in uranium-free bitumens (0.30-0.35% of the total organic carbon,TOC) and decreases with uranium content increase. The extracted solid uraniferous bitumen infrared spectra show depletion in aliphatic CH2 and CH3 groups compared to uranium-free samples. The concentration of oxygen-bearing functional groups relative to aromatic bonds in the IR spectra of uranium-free and mineralized bitumen, however, do not differ significantly. C-13 NMR confirmed than the aromaticity of a uraniferous sample is higher (F-ar = 0.61) than in the uranium-free bitumen (F-ar = 0.51). Pyrolysates from uraniferous and nonuraniferous bitumens do not differ significantly, being predominantly cresol, alkylphenols, alkylbenzenes, and alkylnaphthalenes. The liquid pyrolysate yield decreases significantly with increasing uranium content. The delta(13)C Values of bulk uranium-free bitumens and low-grade uraniferous, asphaltlike bitumens range from -43.6 to 52.3 per mil. High-grade, cokelike, uraniferous bitumens are more C-13 depleted (54.5 to -58.4 parts per thousand). In contrast to the very light isotopic ratios of the high-grade uraniferous cokelike bitumen bulk carbon, the individual n-alkanes and isoprenoids (pristane and phytane) extracted from the same sample are significantly C-13 enriched. The isotopic composition of the C13-24 n-alkanes extracted from the high-grade uraniferous sample (delta(13)C = -28.0 to 32.6 parts per thousand) are heavier compared with the same compounds in a uranium-free sample (delta(13)C = 31.9 to 33.8 parts per thousand). It is proposed that the bitumen source was the isotopically light (delta(13)C = 35.8 to 30.2 parts per thousand) organic matter of the Upper Proterozoic host rocks that were pyrolyzed during intrusion of the Central Bohemian pluton. The C-13- depleted pyrolysates were mobilized from the innermost part of the contact-metamorphic aureole, accumulated in structural traps in less thermally influenced parts of the sedimentary complex and were later extracted by hydrothermal fluids. Bitumens at the Pribram deposit are younger than the main part of the uranium mineralization and were formed through water-washing and radiation-induced polymerization of both the gaseous and liquid pyrolysates. Direct evidence for pyrolysate reduction of uranium in the hydrothermal system is difficult to obtain as the chemical composition of the original organic fluid phase was modified during water-washing and radiolytic alteration. However, indirect evidence-e.g., higher O/C atomic ratios in uranium-free bitumens (0.1) relative to the Upper Proterozoic source rocks (0.02-0.05), isotopically very light carbon in associated whewellite (delta(13)C = 31.7 to -28.4 parts per thousand), and the striking absence of bitumens in the pre-uranium, hematite stage of the mineralization-indicates that oxidation of organic fluids may have contributed to lowering of aO(2) and uraninite precipitation.

Oxygen isotope compositions of iron oxides from high-grade BIF-hosted iron ore deposits of the Central Hamersley Province, Western Australia: Constraints on the evolution of hydrothermal fluids

The Hamersley province of northwest Australia is one of the world's premier iron ore regions with high-grade martite-microplaty hematite iron ore deposits mostly hosted within banded iron formation (BIF) sequences of the Brockman Iron Formations of the Hamersley Group. These high-grade iron ores contain between 60 and 68 wt percent Fe, and formed by the multistage interaction of hydrothermal fluids with the host BIF formation. The oxygen isotope compositions of magnetite and hematite from BIF, hydrothermal alteration assemblages, and high-grade iron Ore were analyzed from the Mount Tom Price, Paraburdoo, and Charmar iron ore deposits. The delta(18)O values of magnetite and hematite from hydrothermal alteration assemblages and high-grade iron ore range from -9.0 to -2.9 per mil, a depletion of 5 to 15 per mil relative to the host BIF. The delta(18)O values are spatially controlled by faults within the deposits, a response to higher fluid flux and larger influence the isotopic compositions by the hydrothermal fluids. The oxygen isotope composition of hydrothermal fluids (delta(18)O(fluid)) indicates that the decrease in the (18)O content of iron oxides was due to the interaction of both basinal brines and meteoric fluids with the original BIF. Late-stage talc-bearing ore at the Mount Tom Price deposit formed in the presence of a pulse of delta(18)O-enriched basinal brine, indicating that hydrothermal fluids may have repeatedly interacted with the BIFs during the Paleoproterozoic.