Physicochemical and microbiological characteristics of groundwater from observation wells of a deep radioactive liquid waste repository

A radioactive liquid waste repository was found to be the habitat of a rich microbial community with a high catabolic potential. Groundwater from a depth of 162–189 m contained aerobic saprotrophic and anaerobic fermentative, sulfate-reducing, and denitrifying bacteria. Nitrate-reducing bacteria residing in this groundwater were isolated in pure cultures. Based on the results of their physiological studies, 16S rRNA sequencing, and phylogenetic analysis, the microorganisms isolated were ascribed to one phylogenetic branch, the γ-subclass of gram-negative bacteria. Among six isolates, four belonged to the genusAcinetobacter, whereas two others belonged to the generaComamonas andAeromonas. The data obtained indicate that the microflora of the repository can exert a certain effect on the chemical composition of the formation fluids and bearing rocks, as well as on the migration of radionuclides     

Effect of creatine supplementation during rapid body mass reduction on metabolism and isokinetic muscle performance capacity

Well-trained subjects (n=6) were studied before and after losing a mean 3.0%–4.3% of body mass to determine whether muscle performance could be maintained or even enhanced by dietary creatine supplementation. During a 5-day period of loss of mass the subjects were randomly assigned to a creatine or placebo supplemented diet. All the subjects were measured before and after loss of mass on both supplements for isokinetic peak torque (PT) and work at peak torque (W _PT) of knee extensors, also for intermittent high intensity working capacity of the same muscle group. The latter test consisted of submaximal isokinetic knee extensions at an angular velocity of 1.57 rad · s⁻¹ for 45 s at the rate of 30 contractions each min (submaximal work, W _{s max} ) followed by 15-s maximal effort (maximal work, W _max ). Total duration of the test was 3 min. Haematocrit was measured and haemoglobin, ammonia, lactate, glucose and urea concentrations were analysed in blood samples obtained at rest and after cessation of muscle performance tests. The results indicated that creatine supplementation in comparison with placebo treatment during rapid body mass reduction may help to maintain muscle PT and W _PT at high angular velocities, not influencing W _max and the rate of fatigue development during W _max , but affecting adversely W _{s max} . Within the limitations of the present study the reasons for the partially detrimental effect of creatine administration remain obscure, but it is suggested that impaired creatine uptake in muscle during body mass loss as well as creatine induced changes in muscle glucose and glycogen metabolism may be involved. Accepted: 18 December 1997     

The uptake of zinc by erythrocytes under near-physiological conditions

The in vitro uptake of zinc by erythrocytes was measured under near-physiological conditions, using⁶⁵Zn as a radioactive tracer. Because of the presence of serum albumin—a strong zinc ligand—a low concentration of medium free zinc was maintained. Under these conditions a high-affinity carrier for zinc transport over the cell membrane was identified. With human erythrocytes, a Michaelis constant (K _m ) of 0.2 nM with respect to free medium zinc was measured and aV _max of 4.5 nmoles Zn transported per h/g dry wt. TheK _m for medium Zn increases when the size of the internal erythrocytic Zn pool is augmented, whereasV _max remains virtually unchanged. A model to explain this phenomenon is proposed. It is suggested that this phenomenon could underlie observations, confirmed here, that the in vitro uptake of Zn by animal erythrocytes depends on the Zn status of the animal.     

Hyaluronic acid depolymerization by ascorbate-redox effects on solid state cultivation of <Emphasis Type="Italic">Streptococcus zooepidemicus</Emphasis> in cashew apple fruit bagasse

The cashew fruit (Anacardium occidentale L.) has been used as a promising agricultural resource for the production of low-molecular weight (M_W) hyaluronic acid (HA) (10⁴–10⁵ Da). The cashew juice is a rich source of vitamin C containing, 1.2–2.0 g L⁻¹. This work explores the effects of the initial concentration of the ascorbate on the solid fermentation of the juice-moisturized bagasse from the cashew apple fruit. The results show that the M_W reduction of HA is proportional to the initial ascorbate concentration. The presence of ascorbate did not influence the Streptococcus zooepidemicus metabolism. However, the HA productivity was increased from 0.18 to 0.28 mg g⁻¹ h⁻¹ when the ascorbate concentration ranged from 1.7 to 10 mg mL⁻¹. These findings contribute to the controlled production of HA in a low M_W range, which is important in cell signalization, angiogenesis and nanoparticles production.     

An urn model study of variability within a compartment

Formulas are derived for the mean and variance of the number of radioactive atoms present in a compartment (or urn). Initally,n ₁ radioactive atoms andb stable atoms are placed in the urn; and subsequently,r stable atoms are added and an equal number,r, of a random mixture of stable and radioactive atoms is removed per unit time. The expected number of radioactive atoms,E(t), present at timet is, as expected,n ₁ e^−λt where λ=(r/Δt)/(b+r+n ₁). The relative variance, σ²(t)/n ₁ ² , vanishes to zero forr=1, atoms per unit time and for a large number ofn ₁ radioactive atoms; but for a large number of bothr andn ₁ atoms the relative variance is ∼e ^−λt , equal to the fractional retention, fort>1/λ. Thus in studies where radionuclides are injected into animals and a single compartment represents the data, if a large variance is observed it might be due to the fact that large numbers of atoms are transferred out in unit time. When a small variance is observed, this is probably due to the fact that few atoms are transferred in smaller units of time (such that λ is the same in both cases). Research sponsored by the Energy Research and Development Administration under contract with Union Carbide Corporation.     

Outward K+ channels in Brassica chinensis pollen protoplasts are regulated by external and internal pH

Summary.  Patch-clamp whole-cell and single-channel recording techniques were used to investigate the regulation of outward K⁺ channels by external and internal protons in Brassica chinensis pollen protoplasts. Outward K⁺ currents and conductance were insensitive to external pH (pH_o) except at pH 4.5. Maximal conductance (G _max) for the outward K⁺ currents was inhibited at acidic external pH. Half-activation voltage (E _1/2) for the outward K⁺ currents shifted to more positive voltages along with the decrease in pH_o. E _1/2 can be described by a modified Henderson–Hasselbalch equation expected from a single titratable binding site. The activation kinetics of the outward K⁺ channels was largely insensitive to pH_o. An internal pH (pH_i) of 4.5 significantly increased outward K⁺ currents and conductance. G _max for the outward K⁺ currents decreased with elevations in pH_i. In contrast to the effect of pH_o, E _1/2 was shifted to more positive voltages with elevations in pH_i. The outward K⁺ currents, G _max and E _1/2 can be described by the modified Henderson–Hasselbalch equation. Furthermore, acidifying pH_i accelerated the activation of the outward K⁺ currents significantly. The differences in electro-physiological properties among previously reported and currently described plant outward K⁺ channels may reflect differences in the structure of these channels. Received May 7, 2002; accepted July 9, 2002; published online November 29, 2002     

Soil drying and its effect on leaf conductance and CO2 assimilation of Vigna unguiculata (L.) Walp

Summary Well watered plants of Vigna unguiculata (L.) Walp cv. California Blackeye No. 5 had maximum photosynthetic rates of 16 mol m^-2 s^-1 (at ambient CO₂ concentration and environmental parameters optimal for high CO₂ uptake). Leaf conductance declined with increasing water vapour concentration difference between leaf and air (w), but it increased with increasing leaf temperature at a constant small w. When light was varied, CO₂ assimilation and leaf conductance were correlated linearly. We tested the hypothesis that g was controlled by photosynthesis via intercellular CO₂ concentration (c _i). No unique relationship between (1) c _i, (2) the difference between ambient CO₂ concentration (c _a) and c _i, namely c _a-c _i, or (3) the c _i/c _a ratio and g was found. g and A appeared to respond to environmental factors fairly independently of each other. The effects of different rates of soil drying on leaf gas exchange were studied. At unchanged air humidity, different rates of soil drying were produced by using (a) different soils, (b) different irrigation schemes and (c) different soil volumes per plant. Although the soil dried to wilting point the relative leaf water content was little affected. Different soil drying rates always resulted in the same response of photosynthetic capacity (A _max) and corresponding leaf conductance (g(_Amax)) when plotted against percent relative plant-extractable soil water content (W _e %) but the relationship with relative soil water content (W _e ) was less clear. Above a range of W _e of 15%–25%, A _max and g(_Amax) were both high and responded little to decreasing W _e . As soon as W _e fell below this range, A _max and g(_Amax) declined. The data suggest root-to-leaf communication not mediated via relative leaf water content. However, g(_Amax) was initially more affected than A _max.List of abbreviations A CO₂ assimilation - A _max photosynthetic capacity at favourable ambient conditions - c _a CO₂ concentration of the air in the leaf chamber - c _i intercellular - CO₂ concentration - E transpiration - g leaf conductance - g(_Amax) leaf conductance corresponding to photosynthetic capacity - I photon flux rate - T _l leaf temperature - W _e relative plant-extractable soil water content - W _e absolute plant-extractable soil water content - W _l relative leaf water content - W _s relative soil water content - w difference in water vapour mole fraction between leaf and air - leaf water potential     

Development and characterization of biofilms on stainless steel and titanium in spent nuclear fuel pools

The aim of the present research was to study the biofilms developed in a Spanish nuclear power plant and their ability to entrap radionuclides. In order to carry this out, a bioreactor, which was then submerged in a spent nuclear fuel pool, was designed. To characterise the biofilm on two different metallic materials (stainless steel and titanium), standard culture microbiological methods and molecular biology tools, as well as epifluorescence and scanning electron microscopy were used. The bacterial composition of the biofilm belongs to several phylogenetic groups (α, β, and γ-Proteobacteria, Actinobacteridae, and Firmicutes). The radioactivity of the biofilms was measured by gamma-ray spectrometry. Biofilms were able to retain radionuclides from radioactive water, especially ⁶⁰Co. The potential use of these biofilms in bioremediation of radioactive water is discussed.     

Bidirectional Transepithelial Water Transport: Chloride-Dependent Mechanisms

We hypothesized that inhibition and activation of basolateral to luminal chloride transport mechanisms were associated with respective decreases and increases in basolateral to luminal water fluxes. The luminal to basolateral (J _W ^L→B ) and basolateral to luminal (J _W ^B→L ) water fluxes across ovine tracheal epithelia were measured simultaneously. The mean J _W ^L→B (6.5 μl/min/cm²) was larger than J _W ^B→L (6.1 μl/min/cm²). Furosemide reduced J _W ^B→L from 6.0 to 5.6 μl/min/cm². Diphenylamine-2-carboxylate (DPC) reduced J _W ^B→L from 7.9 to 7.3 μl/min/cm² and reduced the membrane potential difference by 38%. Furosemide together with DPC decreased J _W ^L→B by 30% and J _W ^B→L by 15%. Norepinephrine increased J _W ^B→L from 4.9 to 6.0 μl/min/cm². Neuropeptide Y in the presence of norepinephrine decreased J _W ^L→B (6.4 to 5.2 μl/min/cm²) and returned J _W ^B→L to its baseline value. Vasopressin increased J _W ^B→L from 4.1 to 5.1 μl/min/cm². Endothelin-1 induced a simultaneous increase in J _W ^B→L (7.0 to 7.7 μl/min/cm²) and decrease in J _W ^L→B (7.4 to 6.4 μl/min/cm²); and decreased the membrane resistance. These data indicate that in tracheal epithelia under homeostatic conditions J _W ^B→L has a ∼15% actively coupled component. Consistent with our hypothesis, inhibition and receptor-induced stimulation of chloride effluxes were associated with decreases and increases in J _W ^B→L , respectively. However, as inhibition of transcellular chloride transport always decreased J _W ^L→B more than J _W ^B→L , reducing transepithelial chloride transport did not result in less water being transported into the airway lumen. Received: 12 October 1999/Revised: 14 March 2000     

Moisture adsorption capacity and surface area as deduced from vapour pressure isotherms in relation to hygroscopic water of soils

Six calcareous and alluvial soil profiles differing in their texture, CaCO₃ and salinity were chosen from west and middle Nile Delta for the present study. The 1^st and 2^nd profiles from Borg El-Arab area were sandy loam in texture and > 30% CaCO₃, while the 3^rd and 4^th profiles (from Nubaria area) were sandy clay loam and < 30% CaCO₃. The 2^nd and 4^th profiles were taken from cultivated area with maize. The 5^th profile from Epshan area was non-saline clay alluvial soil and the 6^th from El-Khamsen was saline clay alluvial soil. The relation between soil moisture content (W%) and water vapour pressure (P/P _o) was established for the mentioned soils. Data showed that the specific surface area (S) values were 34–53 and 44–60 m²/g for calcareous soils of Borg El-Arab and Nubaria areas, 206–219 and 206–249 m²/g for non-saline and saline clay alluvial soils of Epshan and El-Khamsen areas, respectively. The corresponding values of the external specific surface area (S _e) were 16–21, 14–22, 72–86 and 92–112 m²/g. Submitting W _m+W _me as an adsorption boundary of moisture films (W _c) (where W _m is mono-adsorbed layer of water vapour on soil particles and W _me is the external mono-adsorbed layer), the maximum water adsorption capacity (W _a) was found to be W _c + W _me or W _m + 2W _me. It was ranged from 1.88 to 2.70%, 1.97 to 2.95%, 9.70–10.70% and 10.80 to 13.12% while the maximum hygroscopic water (M _H) values were 2.43–3.78%, 2.91–4.65%, 16–17% and 18.30–21.9% for the studied soil profiles respectively. The residual moisture content (θ _r) at pF 7 and P/P _o = 0 was ranged from 0.0005–0.0010%, 0.0007–0.0019% and 0.0043–0.0048% in Borg El-Arab, Nubaria and Epshan soil profiles, respectively. The inter-relations between the surface area and the hygroscopic moisture parameters of the soils under investigation were as follows Calcareous soils; W _m = 0.40 M _H, W _c = 0.55 M _H, W _a = 0.70 M _H, S = 14 M _H Non-saline soil; W _m = 0.35 M _H, W _c = 0.49 M _H, W _a = 0.63 M _H, S = 13 M _H Saline soil; W _m = 031 M _H, W _c = 0.45 M _H, W _a = 0.59 M _H, S = 12 M _H These relations give possibility to deduce the soil moisture adsorption capacities and specific surface area via maximum hygroscopic water, which can be obtained through the experimental determination of water vapor adsorption isotherms.     

Genetic analysis of the position of meiosis in <Emphasis Type="Italic">Porphyra haitanensis</Emphasis> Chang et Zheng (Bangiales,Rhodophyta)

Crossing experiments were carried out between artificial pigmentation mutants and the wild type in Porphyra haitanensis Chang et Zheng to ascertain where meiosis occurs in its life history by confirming whether the color segregation and the color-sectored blades appear in F₁ gametophytic blades developed from conchospores which are released from heterozygous conchocelis. Two red-type pigmentation mutants (R-10 and SPY-1) were used as the female parent. Their blades are red or red orange in color, thinner than the wild type and weak in elasticity, and have no denticles on their margins. The wild type (W) was used as the male parent; its blades are light brown in color, thick and good in elasticity, and have many marginal denticles. The F₁ gametophytic blades developed from conchospores which were released from heterozygous conchocelis produced in the crosses of R-10(♀)×W(♂) and SPY-1(♀)×W(♂) showed two parental colors (R and W) and two new colors (R', lighter in color than R; W', wild-type-like color and redder than W). Linear segregation of colors occurred in the F₁ blades, forming color-sectored blades with 2–4 sectors. In the color-sectored blades, R and R' sectors were thinner than W and W' sectors, and had weak elasticity and no denticles on their margins, whereas W and W' sectors were thick and had good elasticity and many marginal denticles. Of the F₁ gametophytic blades, 95.2–96.7% were color-sectored and only 3.3–4.8% were unsectored. These results indicate that meiosis of P. haitanensis occurs during the first two cell divisions of a germinating conchospore, and thus it is considered that the initial four cells of a developing conchosporeling constitute a linear genetic tetrad leading to the formation of a color-sectored blade. The new colors of R' and W' were recombinant colors due to the chromosome recombination during the first cell division in meiosis. It is considered that color phenotypes of the two mutants used in this paper were result of two (or more) recessive mutations in different genes, and that they also have mutations concerned with blade thickness and formation of marginal denticles, which are linked with the color mutations.     

Relationships between dynamics of nitrogen uptake and dry matter accumulation in maize crops. Determination of critical N concentration

The concept of critical nitrogen concentration(%N _c) has been proposed as the minimum%N in shoots required to produce the maximum aerial biomassat a given time. Several authors have shown that%N _c declines as a function of aerial biomassaccumulation (W) and the %N _c –W relationship has been proposed as a diagnostic tool of N statusin different crops, excluding maize. From data obtained in five nitrogenfertilisation experiments in irrigated maize crops, 26 critical data-pointswere selected with a precise statistical procedure. An allometric relationwas fitted and a critical %N−W relationshipmodel is proposed in maize as: If W < 1 t ha^-1%N _c = 3.40 If 1 t ha^-1≤ W ≤ 22 t ha^-1%N _c = 3.40(W)^−0.37 The model is applicable to maize crop development between emergenceand silking + 25 days. The model was tested and validated with dataobtained in a network of 17 N fertilisation experiments conducted inFrance under contrasting pedoclimatic conditions. In only nineout of 280 data-points (3.2%), the plant N status was mispredictedwhen ±5% error around %N _c wasallowed. A critical N uptake model (Nu_c, kg Nha^-1) is proposed as Nu_c = 34 (W)^0.63 A comparison between Nu_c and N uptake observedin N treatments giving the maximal grain yields has shown that maizecrops assimilate at least 30 kg N ha^-1 in a storage N poolat the silking stage. The significance of the critical%N−W and Nu−W relationships is discussed in relation to theoretical models proposed inwhole plant ecophysiology. Different relationships calculated betweenleaf area index and aerial biomass accumulation, and between N uptakeand leaf area were consistent with previous results for other crops.This strengthens the interest of the critical%N−W relationship for use as diagnostictool of nitrogen status in maize crops. This revised version was published online in June 2006 with corrections to the Cover Date.     

The influence of maximal aerobic power on recovery of skeletal muscle following anaerobic exercise

Phosphorus magnetic resonance spectroscopy (³¹P-MRS) was used to investigate the influence of maximal aerobic power (˙VO _2max) on the recovery of human calf muscle from high-intensity exercise. The (˙VOO_2max) of 21 males was measured during treadmill exercise and subjects were assigned to either a low-aerobic-power (LAP) group (n = 10) or a high-aerobic-power (HAP) group (n = 11). Mean (SE) ˙VO _2max of the groups were 46.6 (1.1) and 64.4 (1.4) ml · kg⁻¹ · min⁻¹, respectively. A calf ergometry work capacity test was used to assign the same relative exercise intensity to each subject for the MRS protocol. At least 48 h later, subjects performed the rest (4 min), exercise (2 min) and recovery (10 min) protocol in a 1.5 T MRS scanner. The relative concentration of phosphocreatine (PCr) was measured throughout the protocol and intracellular pH (pH_i) was determined from the chemical shift between inorganic phospate (P_i) and PCr. End-exercise PCr levels were 27 (3.4) and 25 (3.5)% of resting levels for LAP and HAP respectively. Mean resting pH_i was 7.07 for both groups, and following exercise it fell to 6.45 (0.04) for HAP and 6.38 (0.04) for LAP. Analysis of data using non-linear regression models showed no differences in the rate of either PCr or pH_i recovery. The results suggest that ˙VO_2max is a poor predictor of metabolic recovery rate from high-intensity exercise. Differences in recovery rate observed between individuals with similar ˙VO_2max imply that other factors influence recovery. Accepted: 17 December 1996     

Efficient method of gas laser pumping by an electron beam in the SIGE-1 experimental setup

Lasers, sources of coherent UV and vacuum UV radiation, plasmachemical reactors, reactors for cleaning fouled gases, etc., can be classified as devices the working medium of which is plasma formed as a result of the interaction of a high-current relativistic electronic beam with gas. Efficiency of such devices which are united under the common name “systems of injection gas electronics” (SIGE) depends mainly on the efficiency of energy transfer from a beam to gas (ηg = W _g /W _b ) and that of the transform of the energy transferred to gas into the energy of the ultimate product W _in (η_in = W _in/W _g ). As a special case of SIGE, an experimental bench laser is considered. The new efficient method of pumping is supposed to be implemented on this laser to optimize the energy contribution η _g and useful output η_in.     

Do trace elements modify the activity of erythrocyte sodium-proton exchanger in hemodialyzed patients?

The kinetics (V _max and K _m ) of the erythrocyte Na⁺−H⁺ exchanger was studied in a group of 21 patients undergoing regular hemodialysis (HD) and in 21 control subjects. The activity of antioxidative enzymes—superoxide dismutase and glutathione peroxidase—as well as the concentrations of their cofactors—zinc, copper, and selenium—in plasma and in erythrocytes were determined. The thiobarbituric acid-reactive substances (TBARS) concentration served as an indicator of oxidative stress intensity in plasma and erythrocytes. It was found that in the control group the concentration of copper in erythrocytes was positively correlated with K _m and V _max. When the concentration of copper increased, the shape of the kinetic curve changed from sigmoidal to hyperbolic. In the control group, the concentration of zinc in erythrocytes also correlated with K _m . However, the results obtained for the group of hemodialyzed patients were the opposite: when the erythrocyte concentration of copper increased, a K _m decline was observed and the shape of the curve changed from hyperbolic to sigmoidal. In the group of hemodialyzed patients, we also found a positive correlation between K _m and the concentration of selenium in erythrocytes, and a negative correlation between K _m and erythrocyte TBARS.     

Low dose of dopamine may stimulate prolactin secretion by increasing fast potassium currents

Dopamine (DA) released from the hypothalamus tonically inhibits pituitary lactotrophs. DA (at micromolar concentration) opens potassium channels, hyperpolarizing the lactotrophs and thus preventing the calcium influx that triggers prolactin hormone release. Surprisingly, at concentrations ∼1000 lower, DA can stimulate prolactin secretion. Here, we investigated whether an increase in a K⁺ current could mediate this stimulatory effect. We considered the fast K⁺ currents flowing through large-conductance BK channels and through A-type channels. We developed a minimal lactotroph model to investigate the effects of these two currents. Both I _BK and I _A could transform the electrical pattern of activity from spiking to bursting, but through distinct mechanisms. I _BK always increased the intracellular Ca²⁺ concentration, while I _A could either increase or decrease it. Thus, the stimulatory effects of DA could be mediated by a fast K⁺ conductance which converts tonically spiking cells to bursters. In addition, the study illustrates that a heterogeneous distribution of fast K⁺ conductances could cause heterogeneous lactotroph firing patterns. Action Editor: Christiane Linster     

Physiological responses to nitrogen and sulphur addition and raised temperature in <Emphasis Type="Italic">Sphagnum balticum</Emphasis>

Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NP_max), maximum efficiency of photosystem II [variable fluorescence (F _v)/maximum fluorescence yield (F _m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NP_max did not differ between control (0.2 g N m⁻² year⁻¹) and high N (3.0 g N m⁻² year⁻¹), but was higher in the mid N treatment (1.5 g N m⁻² year⁻¹). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F _v/F _m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had no significant effect on NP_max or F _v/F _m. Addition of 2 g S m⁻² year⁻¹ showed a weak negative effect on NP_max and F _v/F _m. Our results suggest a unimodal response of NP_max to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g⁻¹. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes.     

Increase in water-use efficiency and underlying processes in pine forests across a precipitation gradient in the dry Mediterranean region over the past 30 years

Motivated by persistent predictions of warming and drying in the entire Mediterranean and other regions, we have examined the interactions of intrinsic water-use efficiency (W _i) with environmental conditions in Pinus halepensis. We used 30-year (1974–2003) tree-ring records of basal area increment (BAI) and cellulose ¹³C and ¹⁸O composition, complemented by short-term physiological measurements, from three sites across a precipitation (P) gradient (280–700 mm) in Israel. The results show a clear trend of increasing W _i in both the earlywood (EW) and latewood (LW) that varied in magnitude depending on site and season, with the increase ranging from ca. 5 to 20% over the study period. These W _i trends were better correlated with the increase in atmospheric CO₂ concentration, C _a, than with the local increase in temperature (~0.04°C year⁻¹), whereas age, height and density variations had minor effects on the long-term isotope record. There were no trends in P over time, but W _i from EW and BAI were dependent on the interannual variations in P. From reconstructed C _i values, we demonstrate that contrasting gas-exchange responses at opposing ends of the hydrologic gradient underlie the variation in W _i sensitivity to C _a between sites and seasons. Under the mild water limitations typical of the main seasonal growth period, regulation was directed at increasing C _i/C _a towards a homeostatic set-point observed at the most mesic site, with a decrease in the W _i response to C _i with increasing aridity. With more extreme drought stress, as seen in the late season at the drier sites, the response was W _i driven, and there was an increase in the W _i sensitivity to C _a with aridity and a decreasing sensitivity of C _i to C _a. The apparent C _a-driven increases in W _i can help to identify the adjustments to drying conditions that forest ecosystems can make in the face of predicted atmospheric change.     

Lactate and catecholamine responses in male and female sprinters during a Wingate test

A total of six male and six female sprinters at the same national competition level and aged 18–20 years performed a force/velocity test and a 30-s supramaximal exercise test (Wingate test) on 2 different days, separated by a maximal interval of 15 days. The maximal anaerobic power (W _max) was determined from the force/velocity test, and the mean anaerobic power (W) from the Wingate test. Immediately after the Wingate test, a 5-ml venous blood sample was drawn via a heparinized catheter in an antebrachial vein for subsequent catecholamine (adrenaline and noradrenaline) analysis. After 5 min recovery a few microlitres of capillary blood were also taken for an immediate lactate determination. Even expressed per kilogram lean body mass,W _max andW were significantly lower in women. The lactate and adrenaline responses induced by the Wingate test were also less pronounced in this group whereas the noradrenaline levels were not significantly different in men and women. Above all, very different relationships appeared between lactate, adrenaline, noradenaline and W according to sex. Thus, as reported by other authors, the adrenergic response to a supramaximal exercise seemed to be lower in women than in men. Nevertheless a different training status between the two groups, even at same national competition level, could not be excluded and might contribute, at least in part, to the gender differences observed in the present study.