PubMed · 7206755
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R J Smith. 1980-11-07. Rethinking allometry.. https://doi.org/10.1016/0022-5193(80)90222-2
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The measurement of ethane and pentane in breath offers a sensitive and noninvasive means to assess in vivo lipid peroxidation in animals and humans. However, numerous technical obstacles inherent in collecting and concentrating air-breath samples have limited the wider application of these measurements for the assessment of in vivo lipid peroxidation. We have developed a relatively simple, inexpensive, rapid, and reliable method to collect, concentrate, and measure breath ethane and total-body pentane from rats. This method, which concentrates alkanes from 4 liters of collected air-breath on adsorbant cooled to -174 degrees C, was found to be superior to similar cryofocusing techniques at -130 degrees C, which fail to effectively trap highly volatile ethane from large volumes of air. We found ethane evolves predominantly through breath, whereas a significant amount of pentane evolves from sources other than breath. Mean evolution rate for ethane was 1.08 pmol/100 g body wt/min. Pentane evolution rates displayed more inter-rat and day-to-day variability with a mean of 0.52 pmol/100 g body wt/min. We also found that excreted rat feces exude large amounts of ethane and pentane.
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A novel classification of planar four-bar linkages is presented based on the systematical variation of one, two or three bar lengths and studying the transmission properties (input-output curves) of the linkages. This classification is better suited to the study of biological systems than the classical Grashof-classification used in engineering as it considers the change of structural elements, in evolution for example, instead of evaluating the possibilities for the rotation of a particular bar. The mechanical features of a wide range of planar linkages in vertebrates, described by various authors, have been included in this classification. Examples are: skull-levation and jaw-protrusion mechanisms in fishes, reptiles and birds, the coral crushing apparatus of parrotfishes, and catapult-mechanisms in feeding pipefishes. Four-bar replacement mechanisms, e.g., crank-slider mechanisms in feeding systems of fishes and cam-mechanisms in mammalian limb-joints, and more complex linkages than four-bar ones, e.g., six-bar linkages and interconnected four-bar linkages in fish feeding mechanisms are also discussed. In this way, an overview is obtained of the applicability of planar linkage theory in animal mechanics to mechanical functioning and the effect of possible variations of bar lengths and working ranges in evolution. Four-bar system analysis often provides a rigorous method of simplifying the study of complex biological mechanisms. The acceptable width-range of necessary and undesired hysteresis ('play') in biological linkages is also discussed.