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Loss of body weight and fat during exercise in a cold chamber (1977)

O'Hara, W. J. ; Allen, C. ; Shephard, R. J.

Springer

European journal of applied physiology 37 (1977), S. 205-218

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ISSN: 1439-6327

Keywords: Arctic exercise ; Energy balance ; Fat loss ; Cold dehydration ; Ketosis

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Summary Ten men spent one week in a cold climatic facility performing a simulated arctic military exercise demanding an energy expenditure of 13–16 MJ·day−1. Although the ration pack was adequate, extensive plate wastage led to a negative energy balance of 2.2 MJ·day−1. Fluid intake was also insufficient, with a 3.25% decrease of body weight, and a 9.7% decrease in skin thickness over the cold exposure. Extensive fat mobilization was indicated by a decrease of skinfold thicknesses, an increase of body density, and associated ketonuria and glycosuria. The fat breakdown far exceeded the calculated energy deficit, and it is postulated that much of the “surplus” energy was required for synthesis of additional muscle protein. In the arctic environment, both energy and fluid balances are better maintained because there are few distractions from the simple pleasure of preparing and eating meals.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00421776

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Microtubule assembly: Some possible regulatory mechanisms (1974)

Olmsted, J. B. ; Marcum, J. M. ; Johnson, K. A. ; [et al.]

New York, N.Y. : Wiley-Blackwell

Journal of Supramolecular Structure 2 (1974), S. 429-450

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ISSN: 0091-7419

Keywords: Life Sciences ; Molecular Cell Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Microtubule polymerization in vitro was examined using material purified from porcine brain tissue by a reversible temperature dependent assembly procedure, and was characterized by electron microscopy, viscometry, and sedimentation. The reaction was endothermic, colchicine sensitive, and occurred at neutral pH and moderate ionic strength. Divalent cations (calcium, magnesium) were inhibitory at millimolar concentrations, but stimulated polymerization at the micromolar level. Nucleoside triphosphates were required for assembly of purified subunits. As determined by quantitative sedimentation analyses, the reaction was an equilibrium process. Below a critical concentration of tubulin no assembly occurred. Analytical ultracentrifugation studies indicated that tubulin species with sO20, w of 6S and 30S were in equilibrium with each other, and that both were incorporated into microtubules. Electron microscopic analyses suggested that disc (or ring) structures might be intermediates in assembly, and that they were primarily utilized early in the polymerization process. Assembly could be seeded by mixing microtubular fragments from brain or flagella with brain microtubule subunits; depending on conditions of temperature and protein concentration, addition of subunits occurred either with unipolar or biased polar directionality. The possible significance of these properties of the polymerization reaction for control of assembly is discussed.

Additional Material: 12 Ill.