Evaluation of physical fitness from field tests at high altitude in circumpubertal boys: comparison with laboratory data

Field tests of running and laboratory tests were performed in La Paz [high altitude (HA), 3700 m] and in Clermont-Ferrand [low altitude (LA), 300 m] to investigate their validity at HA. Prepubertal boys of mean ages 10.6 years (HA1,n = 16; LA1,n = 28) and pubertal boys of 13.7 years (HA2,n = 12; LA2,n = 41) took part in the study. All the boys performed a 30-m sprint (v _30m), a 30-s shuttle run (v _3os) and a progressive shuttle run test until their maximal aerobic velocity (v _maxsRT). Maximal oxygen consumption was extrapolated from the last test. . In the laboratory, the boys performed a force-velocity test (P _max), a Wingate test (P _Wing) and a graded test to measure maximal oxygen consumption ; direct method) on a cycle ergometer. At similar ages, there was no significant difference between HA and LA boys forv _30m andP _max. Thev _30s of HA boys was 3%–4% lower than those of LA boys (P<0.05); there was no significant difference forP _Wing. Significant relationships were observed at both altitudes betweenP _max (watts per kilogram) andv _30m (HA:r=0.76; LA:r=0.84) and betweenP _Wing andv _30s (HA:r=0.67; LA:r = 0.77); the slopes and the origins were the same at HA and LA. The ,v _maxSRT and were lower by 9%, 12% and 20%, respectively, at HA than at LA (P<0.05). However, the relationships between and (litres per minute) at HA (r=0.88) and at LA (r=0.93) were identical. In conclusion, chronic hypoxia did not modify performance in very short dash exercises. The influence of HA appeared when the exercise duration increased and, during a maximal shuttle run test, performance was reduced by 10% at HA. Moreover, it was possible to assessP _max,P _Wing and at HA as well as at LA from field tests.     

A major difference between the divergence patterns within the lines-1 families in mice and voles

L1 retroposons are represented in mice by subfamilies of interspersed sequences of varied abundance. Previous analyses have indicated that subfamilies are generated by duplicative transposition of a small number of members of the L1 family, the progeny of which then become a major component of the murine L1 population, and are not due to any active processes generating homology within preexisting groups of elements in a particular species. In mice, more than a third of the L1 elements belong to a clade that became active approximately 5 Mya and whose elements are > or = 95% identical. We have collected sequence information from 13 L1 elements isolated from two species of voles (Rodentia: Microtinae: Microtus and Arvicola) and have found that divergence within the vole L1 population is quite different from that in mice, in that there is no abundant subfamily of homologous elements. Individual L1 elements from voles are very divergent from one another and belong to a clade that began a period of elevated duplicative transposition approximately 13 Mya. Sequence analyses of portions of these divergent L1 elements (approximately 250 bp each) gave no evidence for concerted evolution having acted on the vole L1 elements since the split of the two vole lineages approximately 3.5 Mya; that is, the observed interspecific divergence (6.7%-24.7%) is not larger than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses showed no clustering into Arvicola and Microtus clades.      

Induction of accelerated feline immunodeficiency virus disease by acute-phase virus passage.

Development of feline immunodeficiency virus (FIV) infection in cats as a small animal model for lentiviral immunodeficiency disease has been hampered by the prolonged and variable disease course following experimental infection. To address this issue, we generated high-titer, unselected FIV stocks by pooling plasma from cats acutely infected with a subgroup C FIV isolate designated CABCpadyOOC (FIV-C-PGammer). Subsequent infection with this virus pool resulted in rapidly progressive, fatal disease in greater than 50% of infected cats. Accelerated FIV disease was characterized by rapid and progressive CD4+ T-cell loss, lymphadenopathy, weight loss, lymphoid depletion, and severe thymic atrophy. Mortality and rate of disease progression were affected by the age of each cat at infection and whether the virus source animal was in the acute or chronic stage of infection. The rapid FIV disease syndrome was consistently associated with systemic lymphoid depletion, clinical disease, and susceptibility to opportunistic infections, analogous to accelerated and/or terminal HIV-1 infection. The results of this study demonstrate that FIV infection is a valid small animal model for lentiviral immunodeficiency disease.     

Molecular phylogeny and divergence times of drosophilid species

The phylogenetic relationships and divergence times of 39 drosophilid species were studied by using the coding region of the Adh gene. Four genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and Sophophora--were included. After conducting statistical analyses of the nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila as the outgroup. The phylogenetic tree obtained showed that the first major division of drosophilid species occurs between subgenus Sophophora (genus Drosophila) and the group including subgenera Drosophila and Engiscaptomyza plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then divided into D. willistoni and the clade of D. obscura and D. melanogaster species groups. In the other major drosophilid group, Zaprionus first separates from the other species, and then D. immigrans leaves the remaining group of species. This remaining group then splits into the D. repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila, Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups is monophyletic. The splitting of subgenera Drosophila and Sophophora apparently occurred about 40 Mya, whereas the D. repleta group and the Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya, suggesting that Scaptomyza experienced a rapid morphological evolution. The D. obscura and D. melanogaster groups apparently diverged about 25 Mya. Many of the D. repleta group species studied here have two functional Adh genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two duplication events.      

Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

An enzymatic model for rat liver alcohol dehydrogenase in the presence of low-Km aldehyde dehydrogenase

Four isoenzymes of aldehyde dehydrogenase were partially purified from rat liver mitochondria by hydroxylapatite chromatography and gel filtration. While three forms display low affinity for acetaldehyde, the fourth is active at extremely low aldehyde concentrations (Km less than or equal to 2 microM) and allows the oxidation of the acetaldehyde formed by catalysis of alcohol dehydrogenase at pH 7.4. Different models of alcohol dehydrogenase have been examined by analysis of progress curves of ethanol oxidation obtained in the presence of low-km aldehyde dehydrogenase. According to the only acceptable model, when the acetaldehyde concentration is kept low by the action of aldehyde dehydrogenase, NADH no longer binds to alcohol dehydrogenase, but acetaldehyde still competes with ethanol for the active site of the enzyme. The seven kinetic parameters of the two enzymes (four for alcohol dehydrogenase and three for aldehyde dehydrogenase) and the equilibrium constant of the reaction catalyzed by alcohol dehydrogenase have been determined by applying a new fitting procedure here described.     

Ant versus bird exclusion effects on the arthropod assemblage of an organic citrus grove

1. Predation‐exclusion experiments have highlighted that top‐down control is pervasive in terrestrial communities, but most of these experiments are simplistic in that they only excluded a single group of predators and the effect of removal was evaluated on a few species from the community. The main goal of our study was to experimentally establish the relative effects of ants and birds on the same arthropod assemblage of canopy trees. 2. We conducted 1‐year long manipulative experiments in an organic citrus grove intended to quantify the independent effects of bird and ant predators on the abundance of arthropods. Birds were excluded with plastic nets whereas ants were excluded with sticky barriers on the trunks. The sticky barrier also excluded other ground dwelling insects, like the European earwig Forficula auricularia L. 3. Both the exclusion of ants and birds affected the arthropod community of the citrus canopies, but the exclusion of ants was far more important than the exclusion of birds. Indeed, almost all groups of arthropods had higher abundance in ant‐excluded than in control trees, whereas only dermapterans were more abundant in bird‐excluded than in control trees. A more detailed analysis conducted on spiders also showed that the effect of ant exclusion was limited to a few families rather than being widespread over the entire diverse spectrum of spiders. 4. Our results suggest that the relative importance of vertebrate and invertebrate predators in regulating arthropod populations largely depends on the nature of the predator–prey system.