Maximal power and torque-velocity relationship on a cycle ergometer during the acceleration phase of a single all-out exercise

Seven subjects pedalled on a Monark cycle ergometer as fast as possible for approximately 7 s against four different resistances which corresponded to braking torques (T _B) equal to 19, 38, 57 and 76 N · m at the crank level. Exercise periods were separated by 5-min recovery periods. Pedal velocity was recorded every 50 ms by means of a disc with 360 slots fixed on the flywheel, passing in front of a photo-electric cell linked to a microcomputer which processed the data. Every 50 ms, the time necessary to perform half a pedal revolution (t _1/2) was computed by adding the 50-ms periods necessary to reach 669 slots (the number of slots corresponding to half a pedal revolution). To measuret _1/2 to an accuracy better than 50 ms, this time was computed by a linear interpolation of the time-slot number relationship. Power (P) was averaged duringt ₁₂ by adding the power dissipated against braking torque and the power necessary to accelerate the flywheel. The torque-velocity (T-) relationship was studied during the acceleration phase of a sprint against a single TB by computing every 50 ms the relationship between and T (N · m), equal to the sum ofT _B and the torque necessary to accelerate the flywheel at the same time. The T- relationships calculated from the acceleration phase of a single all-out exercise were linear and similar to the previously described relationships between peak velocity and braking force. These relationships can be expressed as follows: = _0,acc (1 –T/T _0,acc) where is pedal velocity,T the torque exerted on the crank andT _0,acc and _0,acc have the dimensions of maximal torque and maximal velocity respectively. Based on this model, maximal power (P _max,acc) is calculated as 0.257_{0, acc} T _{0, acc}. Maximal powerP _max,acc measured with the acceleration method was independent of braking torqueT _B and slightly higher thanP _max calculated from the relationship between peak velocity andT _B.     

A Molecular Method to Discriminate between Mass-Reared Sterile and Wild Tsetse Flies during Eradication Programmes That Have a Sterile Insect Technique Component

Background

The Government of Senegal has embarked several years ago on a project that aims to eradicate Glossina palpalis gambiensis from the Niayes area. The removal of the animal trypanosomosis would allow the development more efficient livestock production systems. The project was implemented using an area-wide integrated pest management strategy including a sterile insect technique (SIT) component. The released sterile male flies originated from a colony from Burkina Faso.

Methodology/Principal Findings

Monitoring the efficacy of the sterile male releases requires the discrimination between wild and sterile male G. p. gambiensis that are sampled in monitoring traps. Before being released, sterile male flies were marked with a fluorescent dye powder. The marking was however not infallible with some sterile flies only slightly marked or some wild flies contaminated with a few dye particles in the monitoring traps. Trapped flies can also be damaged due to predation by ants, making it difficult to discriminate between wild and sterile males using a fluorescence camera and / or a fluorescence microscope. We developed a molecular technique based on the determination of cytochrome oxidase haplotypes of G. p. gambiensis to discriminate between wild and sterile males. DNA was isolated from the head of flies and a portion of the 5’ end of the mitochondrial gene cytochrome oxidase I was amplified to be finally sequenced. Our results indicated that all the sterile males from the Burkina Faso colony displayed the same haplotype and systematically differed from wild male flies trapped in Senegal and Burkina Faso. This allowed 100% discrimination between sterile and wild male G. p. gambiensis.

Conclusions/Significance

This tool might be useful for other tsetse control campaigns with a SIT component in the framework of the Pan-African Tsetse and Trypanosomosis Eradication Campaign (PATTEC) and, more generally, for other vector or insect pest control programs.     

Genomic and resistance gene homolog diversity of the dominant tallgrass prairie species across the U.S. Great Plains precipitation gradient

Background

Environmental variables such as moisture availability are often important in determining species prevalence and intraspecific diversity. The population genetic structure of dominant plant species in response to a cline of these variables has rarely been addressed. We evaluated the spatial genetic structure and diversity of Andropogon gerardii populations across the U.S. Great Plains precipitation gradient, ranging from approximately 48 cm/year to 105 cm/year.

Methodology/Principal Findings

Genomic diversity was evaluated with AFLP markers and diversity of a disease resistance gene homolog was evaluated by PCR-amplification and digestion with restriction enzymes. We determined the degree of spatial genetic structure using Mantel tests. Genomic and resistance gene homolog diversity were evaluated across prairies using Shannon''s index and by averaging haplotype dissimilarity. Trends in diversity across prairies were determined using linear regression of diversity on average precipitation for each prairie. We identified significant spatial genetic structure, with genomic similarity decreasing as a function of distance between samples. However, our data indicated that genome-wide diversity did not vary consistently across the precipitation gradient. In contrast, we found that disease resistance gene homolog diversity was positively correlated with precipitation.

Significance

Prairie remnants differ in the genetic resources they maintain. Selection and evolution in this disease resistance homolog is environmentally dependent. Overall, we found that, though this environmental gradient may not predict genomic diversity, individual traits such as disease resistance genes may vary significantly.     

First Record of Culicoides oxystoma Kieffer and Diversity of Species within the Schultzei Group of Culicoides Latreille (Diptera: Ceratopogonidae) Biting Midges in Senegal

The Schultzei group of Culicoides Latreille (Diptera: Ceratopogonidae) is distributed throughout Africa to northern Asia and Australasia and includes several potential vector species of livestock pathogens. The taxonomy of the species belonging to this species group is confounded by the wide geographical distribution and morphological variation exhibited by many species. In this work, morphological and molecular approaches were combined to assess the taxonomic validity of the species and morphological variants of the Schultzei group found in Senegal by comparing their genetic diversity with that of specimens from other geographical regions. The species list for Senegal was updated with four species: Culicoides kingi, C. oxystoma, C. enderleini and C. nevilli being recorded. This is the first record of C. oxystoma from Africa south of Sahara, and its genetic relationship with samples from Israel, Japan and Australia is presented. This work provides a basis for ecological studies of the seasonal and spatial dynamics of species of this species group that will contribute to better understanding of the epidemiology of the viruses they transmit.     

Trypanosoma vivax GM6 Antigen: A Candidate Antigen for Diagnosis of African Animal Trypanosomosis in Cattle

Background

Diagnosis of African animal trypanosomosis is vital to controlling this severe disease which hampers development across 10 million km² of Africa endemic to tsetse flies. Diagnosis at the point of treatment is currently dependent on parasite detection which is unreliable, and on clinical signs, which are common to several other prevalent bovine diseases.

Methodology/Principle Findings

the repeat sequence of the GM6 antigen of Trypanosoma vivax (TvGM6), a flagellar-associated protein, was analysed from several isolates of T. vivax and found to be almost identical despite the fact that T. vivax is known to have high genetic variation. The TvGM6 repeat was recombinantly expressed in E. coli and purified. An indirect ELISA for bovine sera based on this antigen was developed. The TvGM6 indirect ELISA had a sensitivity of 91.4% (95% CI: 91.3 to 91.6) in the period following 10 days post experimental infection with T. vivax, which decreased ten-fold to 9.1% (95% CI: 7.3 to 10.9) one month post treatment. With field sera from cattle infected with T. vivax from two locations in East and West Africa, 91.5% (95% CI: 83.2 to 99.5) sensitivity and 91.3% (95% CI: 78.9 to 93.1) specificity was obtained for the TvGM6 ELISA using the whole trypanosome lysate ELISA as a reference. For heterologous T. congolense field infections, the TvGM6 ELISA had a sensitivity of 85.1% (95% CI: 76.8 to 94.4).

Conclusion/Significance

this study is the first to analyse the GM6 antigen of T. vivax and the first to test the GM6 antigen on a large collection of sera from experimentally and naturally infected cattle. This study demonstrates that the TvGM6 is an excellent candidate antigen for the development of a point-of-treatment test for diagnosis of T. vivax, and to a lesser extent T. congolense, African animal trypanosomosis in cattle.     

Synthesis of 4-[2-aminoethyl(nitrosamino)]-1-pyridin-3-yl-butan-1-one, a new NNK hapten for the induction of N-nitrosamine-specific antibodies

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the most abundant and potent procarcinogens in tobacco smoke. In order to induce a strong and substained antibody response against NNK, we developed a functionalized derivative that closely mimicked its structural features, in particular, the pyridyloxobutyl moiety, the adjacent ketone, and the N-nitrosamino group. This hapten was conjugated via a C 2 linker to the highly immunogenic diphteria toxoid licensed as a vaccine in humans to induce polyclonal and monoclonal antibodies. Two monoclonal antibodies were obtained with Kd values of 45.8 nM (P9D5) and 37.6 nM (P7H3), respectively, for NNK-C 2. Both the monoclonal (P9D5 and P7H3) and polyclonal antibodies reacted strongly with NNK (IC 50 = 80 microM or 160 microM) and NNAL (IC 50 = 29 microM or 93 microM) and to a lesser extent with some of the metabolites of NNK. Interestingly, the mAbs did not react with the metabolites of the detoxification pathways such as NNK-N-Oxide and NNAL-N-Oxide (IC 50 > 512 microM). Therefore, such antibodies detect NNK and NNAL and may have the potential to modulate their redistribution in vivo, perhaps reducing some detrimental effects of smoking.     

Population Genetic Structure and Isolation by Distance of Helicobacter pylori in Senegal and Madagascar

Helicobacter pylori has probably infected the human stomach since our origins and subsequently diversified in parallel with their human hosts. The genetic population history of H. pylori can therefore be used as a marker for human migration. We analysed seven housekeeping gene sequences of H. pylori strains isolated from 78 Senegalese and 24 Malagasy patients and compared them with the sequences of strains from other geographical locations. H. pylori from Senegal and Madagascar can be placed in the previously described HpAfrica1 genetic population, subpopulations hspWAfrica and hspSAfrica, respectively. These 2 subpopulations correspond to the distribution of Niger-Congo speakers in West and most of subequatorial Africa (due to Bantu migrations), respectively. H. pylori appears as a single population in Senegal, indicating a long common history between ethnicities as well as frequent local admixtures. The lack of differentiation between these isolates and an increasing genetic differentiation with geographical distance between sampling locations in Africa was evidence for genetic isolation by distance. The Austronesian expansion that started from Taiwan 5000 years ago dispersed one of the 10 subgroups of the Austronesian language family via insular Southeast Asia into the Pacific and Madagascar, and hspMaori is a marker for the entire Austronesian expansion. Strain competition and replacement of hspMaori by hpAfrica1 strains from Bantu migrants are the probable reasons for the presence of hspSAfrica strains in Malagasy of Southeast Asian descent. hpAfrica1 strains appear to be generalist strains that have the necessary genetic diversity to efficiently colonise a wide host spectrum.     

Transferable amikacin and cefamandole resistance: Pseudomonas maltophilia and Acinetobacter strains as possible reservoirs of R plasmids

Three strains belonging to gramnegative non-fermenting rods, i.e. a Pseudomonas maltophilia strain and two strains of Acinetobacter, were tested, as representatives of different types of nosocomial strains, for transferability of their multiple drug resistance. As all of them posed difficulties in demonstrating the transferability of their resistance by conventional methods, a three-step procedure was developed that includes a transfer to rifampicin-resistant P. aeruginosa recipients, then to susceptible P. aeruginosa intermediate strains, and, finally, from these strains to rifampicin-resistant Enterobacteriaceae. In three strains studied three genetically different types of R plasmids have been demonstrated. P. maltophilia transferred Amikacin resistance, as well as resistance to other antibiotics, to P. aeruginosa and then to Enterobacteria. In contrast, an Amikacin-resistant Acinetobacter with quite identical multiple drug resistance spectrum transferred its resistance to P. aeruginosa only, but not to Enterobacteria. Finally, another Acinetobacter strain, resistant to Gentamicin but susceptible to Amikacin transferred this resistance directly to Enterobacteria (and, separately, to P. aeruginosa, too). All three strains transferred Cefamandole resistance together with other resistances. Non-fermenting rods, thus, might be a source of transmissible resistance to reserve antibiotics as Amikacin, and advanced-type Cephalosporins.