Pulmonary function of a firemen-diver population: a longitudinal study

Non smoking, male professional firemen-divers (n = 20) underwent two pulmonary function tests (PFT) separated by 8–9 years. Measured data were compared to European Coal Steel Community recommended reference values to permit cross-sectional and then longitudinal studies. Higher vital capacity (VC) and forced expiratory volume in 1 s (FEV₁; bothP<0.001), and lower residual volume (P<0.01) were observed in both PFT. Longitudinal analysis showed a smaller VC reduction than FEV₁ reduction, leading to a FEV₁/VC percentage decrease with time. Maximal mid expiratory flow (MMEF) and MMEF/VC changes during this 9-year period showed an unusually pronounced decrease, suggesting possible chronic effects of diving on small airways. Thus, it is suggested from our observations that a hyperbaric stimulus compensates in part for the effects of aging on VC and that obstructive disease could occur in subjects with long diving experience.     

Habitual physical activity and peak anaerobic power in elderly women

The aim of this study was to investigate the relationship between maximal anaerobic power (P _max) and corresponding optimal velocity (V _opt) and habitual physical activity (PA) on the one hand and with maximal oxygen consumption (V˙O_2max) on the other hand, in elderly women. Twenty-nine community dwelling, healthy women aged 66–82 years participated in the study. PA was evaluated using the Questionnaire d'Activite Physique Saint-Etienne (QAPSE) and expressed using two QAPSE activity indices: mean habitual daily energy expenditure (MHDEE) and daily energy expenditure corresponding to leisure time sports activities (sports activity). The subjects' P _max and V _opt were measured while they cycled on a friction-loaded non-isokinetic cycle ergometer. P _max was expressed relative to body mass [P _max/kg(W · kg⁻¹)], and relative to the mass of two quadriceps muscles [P _{max /Quadr}(W·kg_Quadr ⁻¹)]. A negative relationship between P _max/kg (Spearman's r = −0.56; P < 0.01), P _max/Quadr (r = −0.53; P < 0.01) and V _opt (r = −0.45; P < 0.05) and age was found. P _max/kg was positively associated with MHDEE (r = 0.51; P < 0.01) and sports activity (r = 0.58; P < 0.01), as were P _max/Quadr and V _opt (r = 0.55; P < 0.01 and r = 0.54; P < 0.01, respectively). P _max/kg, P _max/Quadr and V _opt correlated positively with V˙O_2max. The positive relationship between ergometer measurements and PA indices was similar to that between V˙O_2max and PA. P _max/kg was, moreover, closely related to V _opt (r = 0.77; P < 0.001). When a multiple stepwise regression analysis was used to select the variables influencing ergometer measurements, MHDEE contributed significantly to P _max/kg variance, whereas sports activity contributed to P _max/Quadr and V _opt variances. In conclusion, the data from this cross-sectional study suggest that in healthy elderly women habitual PA, and especially leisure time PA, alleviates the decline of the P _max of the quadriceps muscles. Accepted: 30 January 1997     

Loss of alveolar membrane diffusing capacity and pulmonary capillary blood volume in pulmonary arterial hypertension

Background

Reduced gas transfer in patients with pulmonary arterial hypertension (PAH) is traditionally attributed to remodeling and progressive loss of pulmonary arterial vasculature that results in decreased capillary blood volume available for gas exchange.

Methods

We tested this hypothesis by determination of lung diffusing capacity (DL) and its components, the alveolar capillary membrane diffusing capacity (D_m) and lung capillary blood volume (V_c) in 28 individuals with PAH in comparison to 41 healthy individuals, and in 19 PAH patients over time. Using single breath simultaneous measure of diffusion of carbon monoxide (DL_CO) and nitric oxide (DL_NO), DL and D_m were respectively determined, and V_c calculated. D_m and V_c were evaluated over time in relation to standard clinical indicators of disease severity, including brain natriuretic peptide (BNP), 6-minute walk distance (6MWD) and right ventricular systolic pressure (RVSP) by echocardiography.

Results

Both DL_CO and DL_NO were reduced in PAH as compared to controls and the lower DL in PAH was due to loss of both D_m and V_c (all p < 0.01). While DL_CO of PAH patients did not change over time, DL_NO decreased by 24 ml/min/mmHg/year (p = 0.01). Consequently, D_m decreased and V_c tended to increase over time, which led to deterioration of the D_m/V_c ratio, a measure of alveolar-capillary membrane functional efficiency without changes in clinical markers.

Conclusions

The findings indicate that lower than normal gas transfer in PAH is due to loss of both D_m and V_c, but that deterioration of D_m/V_c over time is related to worsening membrane diffusion.     

Additive and testcross genetic variances in crosses among recombinant inbreds

 Breeders desire populations with a high mean performance and a large genetic variance. Theory and methods are lacking for predicting additive variance (V _A ) and testcross variance (V _T ) in biparental populations. Breeders have unsuccessfully attempted to predict V _A based on the coefficient of coancestry ( f ) or molecular-marker similarity between parents. In this paper, we derive the expected values of V _A and V _T in biparental populations, examine the variability of V _A among biparental crosses, and discuss how V _A and V _T may be predicted in applied breeding programs. Suppose i is a recombinant inbred derived from the cross between inbreds P ₁ and P ₂, and inbred j is not a direct descendant of i. Let V _A(i,j) be the additive variance in the F₂ of the (i×j) biparental cross. Let V _T(i, j) be the variance among testcrosses of F₂ individuals with a specific unrelated inbred or population. Assuming linkage equilibrium and the absence of epistasis, V _A(i, j) =λV _A(P1, j) +(1−λ) V _A(P2, j) , where λ= parental contribution of P ₁ to i. Similarly, V _T(i, j) = λV _T(P1, j) +(1−λ) V _T(P2, j) . Additive variance in crosses between recombinant inbreds cannot be modelled as a function of  f if, as indicated in the literature, V _A differs among crosses of founder inbreds. If molecular-marker similarity between parents is used as an estimate of f, then a strong linear relationship is likewise not expected between V _A and marker similarity. Differences between the actual and expected λ led to variation in V _A . In applied breeding programs, modelling V _A or V _T in biparental crosses may be feasible with estimates of V _A or V _T in prior crosses and information on λ obtained from molecular-marker data. Received: 23 September 1997 / Accepted: 30 December 1997     

A field study of the effects of elevated CO2 on plant biomass and community structure in a calcareous grassland

The effects of elevated CO₂ on plant biomass and community structure have been studied for four seasons in a calcareous grassland in northwest Switzerland. This highly diverse, semi-natural plant community is dominated by the perennial grass Bromus erectus and is mown twice a year to maintain species composition. Plots of 1.3 m² were exposed to ambient or elevated CO₂ concentrations (n = 8) using a novel CO₂ exposure technique, screen-aided CO₂ control (SACC) starting in March 1994. In the 1st year of treatment, the annual harvested biomass (sum of aboveground biomass from mowings in June and October) was not significantly affected by elevated CO₂. However, biomass increased significantly at elevated CO₂ in the 2nd (+20%, P = 0.05), 3rd (+21%, P = 0.02) and 4th years (+29%, P = 0.02). There were no detectable differences in root biomass in the top 8 cm of soil between CO₂ treatments on eight out of nine sampling dates. There were significant differences in CO₂ responsiveness between functional groups (legumes, non-leguminous forbs, graminoids) in the 2nd (P = 0.07) and 3rd (P < 0.001) years of the study. The order of CO₂ responsiveness among functional groups changed substantially from the 2nd to the 3rd year; for example, non-leguminous forbs had the smallest relative response in the 2nd year and the largest in the 3rd year. By the 3rd year of CO₂ exposure, large species-specific differences in CO₂ response had developed. For five important species or genera the order of responsiveness was Lotus corniculatus (+271%), Carex flacca (+249%), Bromus erectus (+33%), Sanguisorba minor (no significant CO₂ effect), and six Trifolium species (a negative response that was not significant). The positive CO₂ responses in Bromus and Carex were most closely related to increases in tiller number. Species richness was not affected by CO₂ treatment, but species evenness increased under elevated CO₂ (modified Hill ratio; P = 0.03) in June of the 3rd year, resulting in a marginally significant increase in species diversity (Simpson's index; P = 0.09). This and other experiments with calcareous grassland plants show that elevated atmospheric CO₂ concentrations can substantially alter the structure of calcareous grassland communities and may increase plant community biomass. Received: 12 July 1997 / Accepted: 14 September 1998     

Ventilatory efficiency and exercise tolerance in 101 healthy volunteers

The ventilatory equivalent for CO₂ defines ventilatory efficiency largely independent of metabolism. An impairment of ventilatory efficiency may be caused by an increase in either anatomical or physiological dead space, the latter being the most important mechanism in the hyperpnoea of heart failure, pulmonary embolism, pulmonary hypertension and the former in restrictive lung disease. However, normal values for ventilatory efficiency have not yet been established. We investigated 101 (56 men) healthy volunteers, aged 16–75 years, measuring ventilation and gas exchange at rest (n = 64) and on exercise (modified Naughton protocol, n = 101). Age and sex dependent normal values for ventilatory efficiency at rest defined as the ratio ventilation:carbon dioxide output (V˙ _E:V˙CO₂), exercise ventilatory efficiency during exercise, defined as the slope of the linear relationship between ventilation and carbon dioxide output (V˙ _E vs V˙CO₂ slope), oxygen uptake at the anaerobic threshold and at maximum (V˙O_2AT,V˙O_2max, respectively) and breathing reserve were established. Ventilatory efficiency at rest was largely independent of age, but was smaller in the men than in the women [V˙ _E:V˙CO₂ 50.5 (SD 8.8) vs 57.6 (SD 12.6) P<0.05]. Ventilatory efficiency during exercise declined significantly with age and was smaller in the men than in the women (men: (V˙ _E vs V˙CO₂ slope = 0.13 × age + 19.9; women: V˙ _E vs V˙CO₂ slope = 0.12 × age + 24.4). The V˙O_2AT and V˙O_2max were 23 (SD 5) and 39 (SD 7) ml O₂ · kg · min⁻¹ in the men and 18 (SD 4) and 32 (SD 7) in the women, respectively, and declined significantly with age. The V˙O_2AT was reached at 58 (SD 9)% V˙O_2max. Breathing reserve at the end of exercise was 41% and was independent of sex and age. It was concluded from this study that ventilatory efficiency as well as peak oxygen uptake are age and sex dependent in adults. Accepted: 11 June 1997     

Changes in performance, muscle metabolites, enzymes and fibre types after short sprint training

In contrast to endurance training, little research has been carried out to investigate the effects of short (<10 s) sprint training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running training sessions over 6 weeks. Distances sprinted were 30–80 m at 90–100% maximum speed and between 20 and 40 sprints were performed in each session. Endurance (maximal oxygen consumption; V˙O_{2 max}), sprint (10 m and 40 m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6 × 40 m sprints, 24 s recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis) were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements were seen in 40 m time (P < 0.01), supramaximal treadmill run time (P < 0.05), repeated sprint performance (P < 0.05) and V˙O_{2 max} (P < 0.01). Resting muscle concentrations of ATP and phosphocreatine did not change. Phosphorylase activity increased (P < 0.025), citrate synthase activity decreased (P < 0.01), but no significant changes were recorded in myokinase and phosphofructokinase activities. The proportion of type II muscle fibres increased significantly (P < 0.05). These results demonstrate that 6 weeks of short sprint training can improve endurance, sprint and repeated sprint ability in fit subjects. Increases in the proportion of type II muscle fibres are also possible with this type of training. Accepted: 5 January 1998     

Insights into ET<Subscript>A</Subscript> subtype selectivity of benzodiazepine endothelin receptor antagonists by 3D-QSAR approaches

ET_A subtype selective antagonists constitute a novel and potentially important class of agents for the treatment of pulmonary hypertension, heart failure, and other pathological conditions. In this paper, 60 benzodiazepine derivatives displaying potent activities against ET_A and ET_B subtypes of endothelin receptor were selected to establish the 3D-QSAR models using CoMFA and CoMSIA approaches. These models show excellent internal predictability and consistency, external validation using test-set 19 compounds yields a good predictive power for antagonistic potency. Statistical parameters of models were obtained with CoMFA-ET_A (q ² = 0.787, r ² = 0.935, r ² _pred  = 0.901), CoMFA-ET_B (q ² = 0.842, r ² = 0.984, r ² _pred  = 0.941), CoMSIA-ET_A (q ² = 0.762, r ² = 0.971, r ² _pred  = 0.958) and CoMSIA-ET_B (q ² = 0.771, r ² = 0.974, r ² _pred  = 0.953) respectively. Field contour maps (CoMFA and CoMSIA) corresponding to the ET_A and ET_B subtypes reflects the characteristic similarities and differences between these types. The results of this paper provide valuable information to facilitate structural modifications of the title compounds to increase the inhibitory potency and subtype selectivity of endothelin receptor.     

Oral Iron Treatment Has a Positive Effect on Iron Metabolism in Elite Soccer Players

The purpose of this study was to assess the effects of oral iron supplementation on hematological and iron metabolism in elite soccer players. Thirty-five members of the Real Zaragoza SAD soccer team took part in this study: group A (GA, n = 24; Spanish Premier League) took an oral iron supplement of 80 mg day⁻¹ for 3 weeks, and group B (GB, n = 11; Spanish Third Division League) did not receive any supplementation. In GA, the parameters were measured before and after giving the iron supplements, while in GB, measurements were only made at the time of collecting the second set of data from GA. After supplementation, GA showed an increase in serum iron (SI) (P < 0.05), serum ferritin (Ftn) (P < 0.01), and transferrin saturation (Sat) (P < 0.01) with respect to the basal values. In addition, GA showed higher values of hematocrit (P < 0.01), mean corpuscular volume (P < 0.01), Ftn (P < 0.01), and Sat (P < 0.01) than GB. No significant differences were found in any other parameters. More specifically, a higher percentage of players had Ftn levels above upper limits in GA vs. GB (P < 0.05), and GB had a higher incidence of Ftn below lower limits with respect to subjects in GA (P < 0.01). Further, after treatment, 58.3% of GA had >800 mg of SI, while all players in GB presented levels below the lower limits. In conclusion, iron supplementation with 80 mg·day⁻¹ for 3 weeks, before the start of the soccer season, can be recommended for elite soccer players.     

Pulvinus activity,leaf movement and leaf water-use efficiency of bush bean (<Emphasis Type="Italic">Phaseplus vulgaris</Emphasis> L.) in a hot environment

Pulvinus activity of Phaseolus species in response to environmental stimuli plays an essential role in heliotropic leaf movement. The aims of this study were to monitor the continuous daily pulvinus movement and pulvinus temperature, and to evaluate the effects of leaf movements, on a hot day, on instantaneous leaf water-use efficiency (WUE_i), leaf gas exchange, and leaf temperature. Potted plants of Phaseolus vulgaris L. var. Provider were grown in Chicot sandy loam soil under well-watered conditions in a greenhouse. When the second trifoliate leaf was completely extended, one plant was selected to measure pulvinus movement using a beta-ray gauging (BRG) meter with a point source of thallium-204 (²⁰⁴Tl). Leaf gas exchange measurements took place on similar leaflets of three plants at an air temperature interval of 33–42°C by a steady-state LI-6200 photosynthesis system. A copper-constantan thermocouple was used to monitor pulvinus temperature. Pulvinus bending followed the daily diurnal rhythm. Significant correlations were found between the leaf-incident angle and the stomatal conductance (R ² = 0.54; P < 0.01), and photosynthesis rate (R ² = 0.84; P < 0.01). With a reduction in leaf-incidence angle and increase in air temperature, WUE_i was reduced. During the measurements, leaf temperature remained below air temperature and was a significant function of air temperature (r = 0.92; P < 0.01). In conclusion, pulvinus bending followed both light intensity and air temperature and influenced leaf gas exchange.     

Populus tremuloides photosynthesis and crown architecture in response to elevated CO2 and soil N availability

We tested the hypothesis that elevated CO₂ would stimulate proportionally higher photosynthesis in the lower crown of Populus trees due to less N retranslocation, compared to tree crowns in ambient CO₂. Such a response could increase belowground C allocation, particularly in trees with an indeterminate growth pattern such as Populus tremuloides. Rooted cuttings of P. tremuloides were grown in ambient and twice ambient (elevated) CO₂ and in low and high soil N availability (89 ± 7 and 333 ± 16 ng N g⁻¹ day⁻¹ net mineralization, respectively) for 95 days using open-top chambers and open-bottom root boxes. Elevated CO₂ resulted in significantly higher maximum leaf photosynthesis (A _max) at both soil N levels. A _max was higher at high N than at low N soil in elevated, but not ambient CO₂. Photosynthetic N use efficiency was higher at elevated than ambient CO₂ in both soil types. Elevated CO₂ resulted in proportionally higher whole leaf A in the lower three-quarters to one-half of the crown for both soil types. At elevated CO₂ and high N availability, lower crown leaves had significantly lower ratios of carboxylation capacity to electron transport capacity (V _cmax/J _max) than at ambient CO₂ and/or low N availability. From the top to the bottom of the tree crowns, V _cmax/J _max increased in ambient CO₂, but it decreased in elevated CO₂ indicating a greater relative investment of N into light harvesting for the lower crown. Only the mid-crown leaves at both N levels exhibited photosynthetic down regulation to elevated CO₂. Stem biomass segments (consisting of three nodes and internodes) were compared to the total A _leaf for each segment. This analysis indicated that increased A _leaf at elevated CO₂ did not result in a proportional increase in local stem segment mass, suggesting that C allocation to sinks other than the local stem segment increased disproportionally. Since C allocated to roots in young Populus trees is primarily assimilated by leaves in the lower crown, the results of this study suggest a mechanism by which C allocation to roots in young trees may increase in elevated CO₂. Received: 12 August 1996 / Accepted: 12 November 1996     

The effect of a thiamin derivative on exercise performance

The purpose of this study was to investigate the effect of a thiamin derivative, thiamin tetrahydrofurfuryl disulfide (TTFD), on oxygen uptake (˙VO₂), lactate accumulation and cycling performance during exercise to exhaustion. Using a randomized, double-blind, cross-over design with a 10-day washout between trials, 14 subjects ingested either 1 g · day⁻¹ of TTFD or a placebo (PL) for 4 days. On day 3, subjects performed a progressive exercise test to exhaustion on a cycle ergometer for the determination of ˙VO_2submax, ˙VO_2peak, lactate concentration ([La⁻ ]), lactate threshold (Th_La) and heart rate ( f _c). On day 4, subjects performed a maximal 2000-m time trial on a cycle ergometer. A one-way analysis of variance (ANOVA) with repeated measures was used to determine significant differences between trials. There were no significant differences detected between trials for serial measures of ˙VO_2submax, [La⁻] or f _c. Likewise, ˙VO_2peak [PL 4.06 (0.19) TTFD 4.12 (0.19) l · min⁻¹, P = 0.83], Th_La [PL 2.47 (0.17), TTFD 2.43 (0.16) l · min⁻¹, P = 0.86] and 2000-m performance time [PL 204.5 (5.5), TTFD 200.9 (4.3) s, P = 0.61] were not significantly different between trials. The results of this study suggest that thiamin derivative supplementation does not influence high-intensity exercise performance. Accepted: 19 December 1996     

Aerobic Fitness in Children and Young Adults with Primary Ciliary Dyskinesia

Background

Although aerobic fitness is regarded as an overall prognostic measure of morbidity and mortality, its evaluation in the chronic progressive sinopulmonary disease primary ciliary dyskinesia (PCD) has been infrequently and inconsistently reported. Here we assessed peak oxygen uptake (VO_2peak) in a large well-characterized cohort of PCD patients, and explored whether VO_2peak was associated with parameters of pulmonary function, self-reported physical limitations, and physical activity level.

Methods

VO_2peak, spirometry, diffusing capacity, whole-body plethysmography, and nitrogen multiple breath inert gas washout (N₂ MBW) were assessed in a cross-sectional, single-occasion study of clinically stable children and young adults with PCD. We used a questionnaire including self-reported physical limitations in everyday life or in vigorous activities, and estimation of weekly hours of strenuous physical activity. VO_2peak in PCD patients was compared with that in matched, healthy control subjects and a national reference.

Results

Forty-four PCD patients aged 6–29 years exhibited reduced VO_2peak compared to healthy controls (P<0.001) and the national reference. VO_2peak was abnormal (z-score <–1.96) in 34% of PCD patients. Spirometric values, RV/TLC, and indices of N₂ MBW were significantly abnormal, but VO_2peak only correlated with FEV₁ and DL_CO/V_A. VO_2peak correlated with complaints of moderate or significant limitations in vigorous activities (P = 0.0001), exhibited by 39% of PCD patients.

Conclusion

One-third of PCD patients exhibited substantially lower aerobic fitness than healthy subjects. Aerobic fitness correlated with FEV₁, DL_CO/V_A and self-reported complaints of limitations in vigorous physical activity. These findings are most likely explained by PCD pulmonary disease and its impact on pulmonary function and physical ability. Considering fitness as an important outcome and including regular strenuous physical activity in PCD treatment would probably altogether increase pulmonary clearance, lung function, aerobic fitness, and quality of life, and prevent lifestyle-related diseases.     

Reversal of Osteoporotic Changes of Mineral Composition in Femurs of Diabetic Rats by Insulin

Insulin plays an important role in bone prevention of diabetic osteoporosis, but little is known about the relation between the bone mineral density (BMD) increase and the change of mineral element content after treated with insulin. To address this problem, male Wistar rats were randomly divided into three groups: normal group (n = 6), streptozotocin-induced diabetic group (n = 5), and streptozotocin-induced diabetic group with insulin treatment (n = 5). The femoral BMD was measured by dual energy X-ray absorptiometry, and the element content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results showed that the femoral BMD in diabetic group was significantly lower than that in normal group (P < 0.01) but restored by insulin treatment (P < 0.01 vs diabetic group). ICP-AES analysis revealed that the element content of calcium (Ca), phosphorous (P), magnesium (Mg), strontium (Sr), and potassium (K) in diabetic group were remarkably lower than those in normal group (P < 0.01) but only Ca, P, and Mg content were significantly increased compared with diabetic group (P < 0.05) after insulin treatment. However, no significant differences were observed in element zinc (Zn) content among three groups. Our findings suggested that the loss of Ca, P, Mg, Sr, and K content accounted for the lower BMD in streptozotocin-induced diabetes rats, insulin treatment could restore BMD by increasing the content of Ca, P, and Mg.     

The effect of exercise intensity on hematuria in healthy male runners

The purpose of this study were: (1) to establish the prevalence of exercise-induced hematuria in a group of otherwise healthy male runners (n = 70), and (2) to investigate the role of exercise intensity in those runners who exhibited exercise-related hematuria (n = 10) by evaluating the effect of running and cycling at high and low intensities. The identified and recruited subjects participated in four different exercise protocols: (1) a 60-min treadmill run (RUN) at 90% of anaerobic threshold (Th_ae), (2) a 60-min leg cycle ergometer ride (BIKE) at 90% of Th_ae, (3) a 3×400-m sprint (SPRINT), each followed by 4 min of rest or light walking, and (4) 3×60-Wingate leg cycle ergometry tests, each followed by 4 min of rest or light cycling. The study employed a 3×4 (time by protocol) within-subjects design and dependent variables were measured before exercise, 4 min after, and 1 h after exercise, and included measurements of hematuria, proteinuria, urinary pH, serum haptoglobin concentration, serum creatine phosphokinase activity, plasma lactate concentration, and hemoglobin. The 400-m sprint at maximal effort significantly increased both hematuria and proteinuria (P < 0.01). Post-exercise hematuria for the SPRINT protocol was significantly different than that for the BIKE (P < 0.01) and RUN (P < 0.01) protocols. Due to the significant increase in hematuria and proteinuria following the SPRINT protocol, it was concluded that exercise-related changes in renal function were associated with weight-bearing exercise intensity rather than non-weight-bearing exercise duration. Accepted: 30 April 1998     

Mitochondrial DNA reveals low population differentiation in elongate loach, <Emphasis Type="Italic">Leptobotia elongata</Emphasis> (Bleeker): implications for conservation

Elongate loach (Leptobotia elongata (Bleeker)), an endemic fish species to China, is a famous ornamental freshwater fish. Here, a comparative study of mtDNA control region (D-loop) (835 bp) sequences was performed to analyze its wild population structure and evaluate the genetic diversity for 110 individuals from five locations in the upper reaches of the Yangtze River, China. A total of 49 polymorphic sites and 45 haplotypes yielded high haplotype diversity (h = 0.952), but low nucleotide diversity (π = 0.00454) as that of many fish species. Sequence divergences between haplotypes ranged from 0.0033 ± 0.0011 to 0.0050 ± 0.0012 in intra-groups, and from 0.0037 ± 0.0.0011 to 0.0050 ± 0.0012 between groups. Significant values of Tajima’s D (−1.86383, P < 0.01) and Fu’s F _S (−25.93, P < 0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of the species. Analysis of molecular variance (AMOVA) indicated a small amount of differentiation among groups (1.7%); most of the total variation occurred within groups (98.3%). Also, there was no significant population structure (F _ST = 0.017, P > 0.05), and estimates of gene flows among groups were extremely high (Nm = 28.88), suggesting low genetic divergence between populations in the species. The lack of genetic differentiation among groups is most likely due to the combined gene flow from the downstream movement of eggs and larvae with currents and the upstream or downstream migration of adults throughout the distribution. These groups of L. elongata distributed in upper reaches of the Yangtze River should be considered as a single management unit.     

Noninvasive skeletal muscle lactate detection between periods of intense exercise in humans

We investigated whether localized ¹H nuclear magnetic resonance spectroscopy (NMRS) using stimulated echoes (STEAM) with a long mixing time (t _m) allowed the suppression of the fat signal and detection of lactate in skeletal muscle. The ¹H NMRS sequence was first validated in three isolated and perfused rabbit biceps brachii muscles. Spectra were obtained on a wide-bore spectrometer using a dual-tuned probe (¹H and ³¹P). Death was simulated by ceasing the muscle perfusion, which allowed post-mortem changes to be followed. During and after the simulated death, changes in levels of pH and in content of energy-rich compounds were observed with ³¹P NMRS. Our results showed an inverse linear relationship between pH and lactate in each of the three rabbits (r = 0.93, P < 0.001; r = 0.92, P < 0.01; r = 0.89, P < 0.01) and a decrease in phosphocreatine and concomitant increase in lactate. We then investigated whether this sequence allowed repeated detection of lactate in human soleus muscle during the recovery between periods of intense exercise (force-velocity test, F-v test). Seven subjects mean age 25.1 (SEM 0.8) years participated in this study. Soleus muscle lactate was detected at rest and for 3 min 30 s of the 5-min recovery between periods using a 2.35-T 40-cm bore magnet spectrometer. Arm venous plasma lactate concentration was measured at rest, during the F-v test when the subject stopped pedalling (S₁), and at the end of each 5-min recovery between periods (S₂). Results showed that the venous plasma lactate concentration at S₁ and S₂ increased significantly from the beginning of the F-v test to peak anaerobic power (W _an,peak) (P < 0.001). The spectra showed that muscle lactate resonance intensity rose markedly when W _an,peak was achieved. The muscle lactate resonance intensity plotted as a percentage of the resting value increased significantly at W _an,peak compared with submaximal braking forces (P < 0.05). We concluded from these results that localized ¹H NMRS using STEAM with a long t _m allows suppression of the fat signal and repeated detection of lactate on isolated perfused skeletal muscle in animals and between periods of intense exercise in humans. Accepted: 19 January 1998     

Influence of Selenium on Body Weights and Immune Organ Indexes in Ducklings Intoxicated with Aflatoxin B<Subscript>1</Subscript>

To investigate the influence of selenium on body weights and the immune organ indexes in ducklings administrated with aflatoxin B₁ (AFB₁), 90 7-day-old ducklings were randomly divided into three groups (groups I–III). Group I was used as a blank control. Group II was administered with AFB₁ (0.1 mg/kg body weight). Group III was administered with AFB₁ (0.1 mg/kg body weight) plus sodium selenite (1 mg/kg body weight). All treatments were given once daily for 21 days. It showed that the ducklings’ bursa of fabricius, thymus indexes, and body weights in group II significantly decreased when compared with group I (P < 0.01). Furthermore, the spleen indexes significantly decreased (P < 0.01). However, the ducklings’ bursa of fabricius and thymus indexes, body weights in group III ducklings significantly increased when compared with group II (P < 0.01). In addition, the spleen indexes significantly decreased (P < 0.01). These results revealed that AFB₁ significantly affect ducklings’ growth and immune organs development. However, selenium significantly ameliorated the negative effects induced by AFB₁.     

Ventilation response to CO2 and exercise-induced hypoxaemia in master athletes

Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyper- pnoea. The aim of this study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation of the central chemoreceptors. The ventilation response to CO₂ was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7 (SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, V˙O_2max), and during strenuous exercise (70% V˙O_2max) using the rebreathing method. Our results showed that the ventilation response to CO₂ did not differ with endurance training and/or exercise, that the threshold of the CO₂ response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [ΔTh_0–40: 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that ΔTh_0–40 and Th during moderate exercise were negatively correlated with arterial O₂ saturation during maximal exercise (r = 0.50, P<0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response to CO₂, but may be partly related to a greater increase in Th during moderate exercise. Accepted: 18 August 1997     

Nutrient relations in calcareous grassland under elevated CO2

Plant nutrient responses to 4 years of CO₂ enrichment were investigated in situ in calcareous grassland. Beginning in year 2, plant aboveground C:N ratios were increased by 9% to 22% at elevated CO₂ (P < 0.01), depending on year. Total amounts of N removed in biomass harvests during the first 4 years were not affected by elevated CO₂ (19.9 ± 1.3 and 21.1 ± 1.3 g N m⁻² at ambient and elevated CO₂), indicating that the observed plant biomass increases were solely attained by dilution of nutrients. Total aboveground P and tissue N:P ratios also were not altered by CO₂ enrichment (12.5 ± 2 g N g⁻¹ P in both treatments). In contrast to non-legumes (>98% of community aboveground biomass), legume C/N was not reduced at elevated CO₂ and legume N:P was slightly increased. We attribute the less reduced N concentration in legumes at elevated CO₂ to the fact that virtually all legume N originated from symbiotic N₂ fixation (%N_dfa ≈ 90%), and thus legume growth was not limited by soil N. While total plant N was not affected by elevated CO₂, microbial N pools increased by +18% under CO₂ enrichment (P = 0.04) and plant available soil N decreased. Hence, there was a net increase in the overall biotic N pool, largely due increases in the microbial N pool. In order to assess the effects of legumes for ecosystem CO₂ responses and to estimate the degree to which plant growth was P-limited, two greenhouse experiments were conducted, using firstly undisturbed grassland monoliths from the field site, and secondly designed `microcosm' communities on natural soil. Half the microcosms were planted with legumes and half were planted without. Both monoliths and microcosms were exposed to elevated CO₂ and P fertilization in a factored design. After two seasons, plant N pools in both unfertilized monoliths and microcosm communities were unaffected by CO₂ enrichment, similar to what was found in the field. However, when P was added total plant N pools increased at elevated CO₂. This community-level effect originated almost solely from legume stimulation. The results suggest a complex interaction between atmospheric CO₂ concentrations, N and P supply. Overall ecosystem productivity is N-limited, whereas CO₂ effects on legume growth and their N₂ fixation are limited by P. Received: 12 July 1997 / Accepted: 15 April 1998