Why animals have different muscle fibre types

Animals have different muscle fibre types: slow fibres with a low maximum velocity of shortening (Vmax) and fast fibres with a high Vmax. An advantage conferred by the use of different fibre types during locomotion has been proposed solely on the basis of their in vitro properties. Isolated muscle experiments show that force generation, mechanical power production and efficiency are all functions of V/Vmax, where V is the velocity of muscle shortening. But it is not known whether animals actually use the different fibres at shortening velocities that are optimal for mechanical power production and efficiency. Here we compare the V of muscle fibres during locomotion with their Vmax. This comparison shows that during slow locomotion, the slow fibres shorten at a velocity that gives peak mechanical power and efficiency and the fast fibres shorten at their optimal velocity when powering maximal movements. Our results also show that maximal movements are impossible without fast fibres because the slow ones cannot shorten rapidly enough.     

Locomotory energetics in a marsupial (Antechinomys spenceri) and a rodent (Notomys alexis)

Summary Steady state oxygen consumption was compared in a rodentNotomys alexis and a marsupialAntechinomys spenceri. The marsupial was found to diverge from predicted eutherian energetic patterns.N. alexis appears to use energy storage as a significant part of the step cycle before becoming bipedal. Aerobic scope and heat storage during running are similar in both species.We thankP. Baverstock, C. Watts andH. Aslin for the use of theAntechinomys, Ms.B. Whaite for assistance. Supported by Grants from the Nuffield Foundation, the Ingram Trust and the Flinders University Research Committee to RVB.     

2,4-dinitrophenol inhibition of P32 release from human red cells

Zusammenfassung Inkubiert man P³²-vorbeladene menschliche Erythrozyten unter Zusatz von 5 × 10^–4 M Dinitrophenol, so lässt sich eine Reduktion der Phosphatabgabe feststellen. Mit Erhöhung des extrazellulären Orthophosphatgehalts kann diese Wirkung besser gesehen werden.

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This study was supported by Grant GM-11430 from the U.S. Public Health Service.     

高温高压下Fe-Mn-S体系的性状

硫锰矿与陨硫铁、铁平衡时,压力、温度与硫锰矿组份之间的关系,用实验方法得以确定。实验的压力条件是1bar,2kbar,5kbar和7kbar;温度范围是500℃到900℃。通过实验得出其间的关系,用多元回归的方法整理成下列公式: P_(kbar)=28.1624(T/10~3)-39.8824(N/10~2)-352.3896(T~2/10~6) +912.9442(T·N/10~5)-627.8129(N~2/10~4+18.9960) 硫锰矿和陨硫铁、铁平衡时的最终温度,根据Keil和Shinner等的研究结果,选定为200℃。     

Maternal control of Drosophila segmentation gene expression

Several genes have been identified that are involved in establishing the segmented body pattern during development of the fruit-fly Drosophila melanogaster. These fall into several classes on the basis of the kind of alteration to the wild-type segmentation pattern observed in mutant embryos. For example, mutations of the pair-rule class, such as fushi tarazu (ftz), cause the deletion of pattern elements with a two-segment periodicity; those of the gap class, such as knirps, cause the deletion of contiguous groups of segments. The availability of antibodies against the ftz protein has allowed its spatial pattern of expression to be studied during the development of wild-type and mutant embryos. The aim of the latter kind of experiment is to investigate possible interactions between these important genes. We have recently reported that knirps mutations cause a striking alteration to the pattern of transverse stripes of ftz expression usually seen during embryogenesis. Knirps is a zygotically-expressed gene, but recently a class of maternally-active genes has been identified that causes similar defects in pattern formation. We have now investigated the pattern of ftz expression in mutants of this class and have found that while they do have features seen in knirps mutants, they also exhibit significant differences between the different mutations reflecting the distinct but overlapping domains of gene activity. These observations demonstrate that maternally-active segmentation genes regulate zygotic gene expression, and that some of their effects on ftz may be directed through the knirps gene.