The Stability Constant of the 1:1 Complex of Sodium with Guanosine 5′-Monophosphate

The stability of the 1:1 complex of sodium ion with the dianion of guanosine 5′-monophosphate has been determined by means of a potentiometric titration employing a specific ion electrode. The stability constant for the reaction Na⁺ + 5′-GMP^2- Na(5′-GMP)^- was found to be 2.85 ± 0.36 M^-1 at 5°C and an ionic strength of 1.1 ± 0.1 M. Although 5′-GMP forms ordered self-structures at high concentration in the presence of sodium ions, in dilute solution and at low sodium ion concentrations the Na⁺ binding is weak and typical of that for other nucleotides.     

我国巴拉巴按蚊形态描述

白踝按蚊种团是由很多形态近似的蚊种组成,其中巴拉巴按蚊和白踝按蚊均为东南亚一带的重要传疟媒介。我国过去资料均记载为白踝按蚊,但未从形态上详细鉴定。为了确定该种的分类地位,1963年作者等在海南岛万宁县兴隆附近山林区采集“白踝按蚊”全套标本10批共150多套,1971年后从云南省采集少数标本进行形态鉴定,发现其与Colless(1956,1957)所描述的白踝按蚊Anopheles leucosphyrus leucosphyrus Donitz(1901)有很明显的差别,而与巴拉巴按蚊A.balabacensis balabacensis Balsas(1936)除某些特征略有差异外,余均完全一致。按Colless的分类法,过去我国记载的“白踝按蚊”,应鉴定为巴拉巴按蚊A.balabacensis balabacensis Baisas。     

The General Theory of Mapping Functions for Random Genetic Recombination

The general theory of mapping functions for random genetic recombination is derived without reference to physical models. The results are of particular relevance to asymmetric recombination (preferential recombination of the alleles of either parent) and include the effects of lethal lesions. It is noted that the assumption of randomness determines the mapping functions uniquely so that they are independent of the specifications of any stochastic physical model of recombination. In particular, the functions derived from physical models by Haldane, Wu, Wood and Verhoef and de Haan are special cases of those derived here. A general principle for the testing of genetic linkage is formulated which is valid for both symmetric and asymmetric recombination.     

The oxygen delivery response to acute hypoxia during incremental knee extension exercise differs in active and trained males

Background

It is well known that hypoxic exercise in healthy individuals increases limb blood flow, leg oxygen extraction and limb vascular conductance during knee extension exercise. However, the effect of hypoxia on cardiac output, and total vascular conductance is less clear. Furthermore, the oxygen delivery response to hypoxic exercise in well trained individuals is not well known. Therefore our aim was to determine the cardiac output (Doppler echocardiography), vascular conductance, limb blood flow (Doppler echocardiography) and muscle oxygenation response during hypoxic knee extension in normally active and endurance-trained males.

Methods

Ten normally active and nine endurance-trained males (VO_2max = 46.1 and 65.5 mL/kg/min, respectively) performed 2 leg knee extension at 25, 50, 75 and 100% of their maximum intensity in both normoxic and hypoxic conditions (FIO₂ = 15%; randomized order). Results were analyzed with a 2-way mixed model ANOVA (group × intensity).

Results

The main finding was that in normally active individuals hypoxic sub-maximal exercise (25 – 75% of maximum intensity) brought about a 3 fold increase in limb blood flow but decreased stroke volume compared to normoxia. In the trained group there were no significant changes in stroke volume, cardiac output and limb blood flow at sub-maximal intensities (compared to normoxia). During maximal intensity hypoxic exercise limb blood flow increased approximately 300 mL/min compared to maximal intensity normoxic exercise.

Conclusion

Cardiorespiratory fitness likely influences the oxygen delivery response to hypoxic exercise both at a systemic and limb level. The increase in limb blood flow during maximal exercise in hypoxia (both active and trained individuals) suggests a hypoxic stimulus that is not present in normoxic conditions.