The kinetics of lactate production and removal during whole-body exercise

<p>Abstract</p> <p>Background</p> <p>Based on a literature review, the current study aimed to construct mathematical models of lactate production and removal in both muscles and blood during steady state and at varying intensities during whole-body exercise. In order to experimentally test the models in dynamic situations, a cross-country skier performed laboratory tests while treadmill roller skiing, from where work rate, aerobic power and blood lactate concentration were measured. A two-compartment simulation model for blood lactate production and removal was constructed.</p> <p>Results</p> <p>The simulated and experimental data differed less than 0.5 mmol/L both during steady state and varying sub-maximal intensities. However, the simulation model for lactate removal after high exercise intensities seems to require further examination.</p> <p>Conclusions</p> <p>Overall, the simulation models of lactate production and removal provide useful insight into the parameters that affect blood lactate response, and specifically how blood lactate concentration during practical training and testing in dynamical situations should be interpreted.</p

LL-functions of elliptic curves and binary recurrences

Let $L(s,E)=\sum_{n\ge 1} a_n n^{-s}$ be the $L$-series corresponding to an elliptic curve $E$ defined over \Q and ${\bf u}=\{u_m\}_{m\ge 0}$ be a non degenerate binary recurrence sequence. We prove that if ${\mathcal M}_E$ is the set of $n$ such that $a_n\ne 0$ and ${\mathcal N}_E$ is the subset of $n\in {\mathcal M}_E$ such that $|a_n|=|u_m|$ holds with some integer $m\ge 0$, then ${\mathcal N}_E$ is of density $0$ as a subset of ${\mathcal M}_E$. 10.1017/S000497271300016

L'analyse de cernes : applications aux études de croissance de quelques essences en peuplements naturels de forêt dense africaine

La connaissance de la production ligneuse et en particulier de la croissance en diamètre des individus est fondamentale dans le cadre de l'aménagement d'une forêt. Elle constitue un des paramètres qui permettent de déterminer la rotation des interventions ainsi que le volume maximum exploitable sans risque d'appauvrissement du peuplement. Deux techniques pour l'estimation de la croissance diamétrique des arbres existent : l'analyse de cernes et la mesure périodique de circonférence pendant un laps de temps donné. Les résultats de plusieurs dispositifs d'étude où les arbres sont mesurés périodiquement depuis plus d'une décennie (Mopri, Irobo et La Téné en Côte d'Ivoire, Mbaiki en Centrafrique et Oyane au Gabon), fournissent des accroissements par essences. De même, plusieurs comptages de cernes ont été réalisées pour les essences dont les cernes sont annuels, notamment au Cameroun, en Centrafrique et au Gabon. Ce rapport présente la méthode utilisée pour l'analyse de cernes, l'application de l'analyse de cernes par essence ainsi qu'une synthèse des accroissements obtenus pour les principales essences exploitées en Afrique centrale et de l'Ouest. Les espèces suivantes sont concernées : l'Ayous / Samba (Triplochiton scleroxylon), le Sapelli (Entandrophragma cylindricum), le Limba / Fraké (Terminalia superba), le Sipo (Entandrophragma utile), le Tali (Erythrophleum ivorense), le Tiama (Entandrophragma angolense), le Kosipo (Entandrophragma candollei), l'Okoumé (Aucoumea klaineana) et le Moabi (Baillonella toxisperma

L'analyse de cernes: applications aux études de croissance de quelques essences en peuplements naturels de forét dense africaine

Knowledge of wood production, and particularly of diameter increment of trees, is central to forest management. This is one of the parameters contributing to determination of the length of the felling cycle as well as the maximum allowable cut without impoverishment of forest stands. Two techniques can be used to assess diameter increment of trees: analysis of growth rings and periodical measurements of circumference over a given period. The results obtained with several designs, in which trees have been periodically measured for more than ten years (Mopi, Irobo and La Téné in Cote de Ivoire, Mbaiki in Central African Republic and Oyane in Gabon), provide increments for each species. In the same way, several growth ring counts were carried out for species with visible annual growth rings, especially in Cameroon, Central African Republic and Gabon. This report describes the methodology used for growth ring analysis, the application of such analysis for each tree species, as well as a synthesis of the results obtained for the main species exploited in Central and West Africa. The following species are included: Ayous/Samba (Triplochiton sideroxylon), Sapelli (Entandrophragma cylindricum), Limba/Fraké (Terminalia superba), Sipo (Entandrophragma utile), Tali (Erythrophleum ivorense), Tiama (Entandrophragma angolensis), Kosipo (Entandrophragma candollei), Okoumé (Aucoumea klaineana) and Moabi (Baillonella toxisperma). It appears that the mean diameter increment of Meliaceae (Sapelli, Sipo, Kosipo and Tiama - Entandrophragma spp.) and Iroko (Milicia excelsa) is 4-5 mm/year. The increment is 2-3 mm/year for slow-growing species, such as Bossé clair (Guarea cedrata) and Kotibé (Nesogordonia papaverifera), while mean annual increment of Okoumé (Aucoumea klaineana) is slightly under 10 mm/year for trees with diameters from 20 to 100 cm

Oxidative Stress Promotes Doxorubicin-Induced Pgp and BCRP Expression in Colon Cancer Cells Under Hypoxic Conditions

P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) are ATP binding cassette (ABC) transporters that are overexpressed in different drug-resistant cancer cell lines. In this study, we investigated whether doxorubicin promotes Pgp and/or BCRP expression to induce drug resistance in colon cancer cells under hypoxic conditions. We analyzed HIF-1? activity via ELISA, Pgp, and BCRP expression by qRT-PCR and the relationship between doxorubicin uptake and ABC transporter expression via confocal microscopy in HT-29WT and HT-29 doxorubicin-resistant colon cancer cells (HT-29DxR). These cells were treated with doxorubicin and/or CoCl2 (chemical hypoxia), and reactive oxygen species inductors. We found that the combination of chemically induced hypoxia and doxorubicin promoted Pgp mRNA expression within 24 h in HT-29WT and HT-29DxR cells. Both doxorubicin and CoCl2 alone or in combination induced Pgp and BCRP expression, as demonstrated via confocal microscopy in each of the above two cell lines. Thus, we surmised that Pgp and BCRP expression may result from synergistic effects exerted by the combination of doxorubicin-induced ROS production and HIF-1? activity under hypoxic conditions. However, HIF-1? activity disruption via the administration of E3330, an APE-1 inhibitor, downregulated Pgp expression and increased doxorubicin delivery to HT-29 cells, where it served as a substrate for Pgp, indicating the existence of an indirect relationship between Pgp expression and doxorubicin accumulation. Thus, we concluded that Pgp and BCRP expression can be regulated via cross-talk between doxorubicin and hypoxia, promoting drug resistance in HT-29 WT, and HT-29DxR cells and that this process may be ROS dependent. J. Cell. Biochem. 118: 1868–1878, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc

Factor inducible por hipoxia HIF-1? modula la resistencia a drogas en células de cáncer de colon

Introduction: Drug resistance mechanisms may be associated with decreased cell death and its induction may depend on the response to oxidative stress caused by hypoxia. The correlation between hypoxia-inducible factor HIF-1?, the number of reactive oxygen species and their effect on cell survival has not yet been evaluated. Objective: The purpose of this study was to evaluate the effect of HIF-1? activity and reactive oxygen species (ROS) accumulation in apoptosis of colon cancer cells. Materials and methods: HT29 colon cancer cells were treated with Cobalt(II) chloride (CoCl2) or doxorubicin and the activity of HIF-1? was determined by ELISA assay. ROS were determined using fluorescence probe carboxy-H2DFFDA. Apoptosis was assessed by caspase-3 activation analysis, and PUMA and BAX mRNA levels by qRT-PCR. The reduction of the antiapoptotic effect due to hypoxia was attenuated by use of the endonuclease APE-1 (E3330) inhibitor. The endonuclease E3330 APE-1 inhibitor allowed evaluating the effect of ROS generated by doxorubicin and CoCl2 on apoptosis. Results: Chemical hypoxia in combination with doxorubicin is an oxidative stressor in HT29 cells and induces a reduction in the apoptotic process in a time-dependent manner. Conclusion: Resistance to hypoxia and doxorubicin-mediated cell death could be controlled by a mechanism related to the activity of HIF-1? and the amount of reactive oxygen species generated. © 2018, Universidad Nacional de Colombia. All rights reserved