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Uptake of methionine, alpha-aminoisobutyric acid, and alpha-(methyl-amino)-isobutyric acid has been shown to occur by at least two transport systems, one sensitive and the other insensitive to the Na(+) concentration. For alpha-aminoisobutyric acid and its N-methyl derivative, the Na(+)-insensitive uptake is not concentrative and its rate increases almost linearly with concentration within the range examined. In contrast, the Na(+)-insensitive uptake of methionine is concentrative and subject to inhibition by such amino acids as phenylalanine, leucine, and valine, although not in a manner to indicate that the uptake is mediated by a single agency. This component is not produced by a residual operation of the Na(+)-requiring transport system, handicapped by the absence of Na(+) or by its having combined with alpha-aminoisobutyric acid. The increase in the rate of methionine uptake is linear with concentration only above about 16 mM methionine. The Na(+)-sensitive uptakes of methionine, alpha-aminoisobutyric, and alpha-(methylamino)-isobutyric acid appear to occur by the same population of transport-mediating sites. Both K(m) and V(max) of the Na(+)-sensitive uptake of these three amino acids change with changes in the concentration of Na(+), an effect which is shown to have a theoretical basis. A similarity in the values of Vmax for ten amino acids entering principally by the Na(+)-sensitive agency indicates that differences in their K(m) values probably measure differences in their affinities for that transport-mediating system.

Purified mammalian plasma membrane vesicles are shown for the first time to transport amino acids. The transport system shows time and temperature dependence. The transport of the nonmetabolizable amino acid, 2-aminoisobutyric acid (AIB) was shown to require sodium ions, potassium and choline ions being, unable to substitute. The Na-dependent AIB transport was saturable with an apparent Michaelis constant of 3.7 mm. Several observations indicate that AIB is actively accumulated despite and apparent lack of sensitivity to agents which abolish cation gradients or reduce ATP production such as gramicidin A, cyanide and dinitrophenol. Several observations, particularly the sensitivity to increased osmotic strength indicate that the phenomenon under investigation is transport rather than binding of AIB. Evidence that the system is also capable of catalyzing exhange diffusion is demonstrated by the fact that methionine and ethionine in the medium stimulate the efflux of previously accumulated methionine whereas no such effect is seen with AIB. [ABSTRACT FROM AUTHOR]

The role played by transmembrane K gradients in providing an energy input for Na-dependent monosaccharide transport systems was evaluated with the use of isolated intestinal epithelial cells. Experimentally imposing a K gradient in a sense reversed from normal did not lead to extrusion of sugar from cells which had been pre-equilibrated withC-3-OMG, even in situations where a reversed Na gradient was also imposed. Furthermore, cells preloaded with K have no better ability to accumulate 3-OMG than do cells depleted of K, when the two populations are compared under identical incubation conditions. Fluxes of K associated with the sugar carrier could not be detected in terms of suspected sensitivity to agents which immobilize the sugar carrier. In addition, fluxes of sugar in response to imposed K gradients were not demonstrable in cells de-energized by preincubation with DNP, no matter in which direction the K gradient was imposed. Finally, the severe inhibitory effects of K on Na-dependent sugar transport by the cells disappears in de-energized cells, despite the fact that Na-dependent carrier-mediated sugar entry still occurs. All of these facts are difficult to reconcile with a significant role for cellular K gradients in supporting active sugar transport as envisioned by the ion gradient hypothesis. We have suggested instead a fundamental Na-dependent energy transductive event which depends on ATP, and which can generate a membrane-bound energized intermediate which serves to support a variety of active transport events. An analogy is drawn between this concept for animal cell plasma membranes and the better documented phosphotransferase system for sugar transport described for certain microorganisms. [ABSTRACT FROM AUTHOR]

Gibberellins A, A and A and (−)-kaurene delay floral-bud initiation and flowering and decrease the number of floral-buds and flowers in Impatiens balsamina under 4-hr photoperiods. They do not have any marked effect under 8-hr photoperiods. Under 16- and 24-hr photoperiods they hasten floral-bud initiation and flowering and increase the number of flowers, the effect being greater under 16- than under 24-hr days and the order of effectiveness being GA>GA>GA>(−)-kaurene. While GA and GA promote extension growth, the effect being greater with the former, GA and (−)-kaurene do not promote it under any photoperiod. The magnitude of stem elongation in different treatments prior to floral-bud initiation increases from 4- to 8-hr photoperiods but decreases under 16- and 24-hr periods, the effect being more under 24-hr although both 16-and 24-hr photoperiods are noninductive for flowering. [ABSTRACT FROM AUTHOR]

The effect of starvation on glycogen, lipid, water content and muscle proteins of red and white muscles in the plaice Pleuronectes platessa L. has been investigated. The two muscle systems behave differently in their response to food shortage, glycogen and protein depletion being more marked in the white muscle. Little change occurred in the constituents of the red muscle, except lipid. Starvation resulted in an increase in water content in the white, but not in the red muscle. The differential response of these two musole systems to starvation is discussed. It is suggested that the small amount of red muscle in the body is spared from the effects of starvation because it is needed for continuous activity during swimming at all speeds. [ABSTRACT FROM AUTHOR]

The Subject categories are those in by Nathan W. Shock, published by Stanford University Press. Stanford, California (1951). Only major headings are used and the Roman numerals correspond to those given in the bibliography. In so far as possible, references are classified according to organ systems. Thus, most of the material on Geriatrics will be found under the organ system involved in the disease. Cross references are indicated by number at the end of each section. When available, abstract references are given (B. A.—, P. A.—, and P. I.—). Abbreviations for journals are those used in . For journals not listed, abbreviations were devised to the general rules used in the above source. It is impossible to cover all journals and list all papers concerned with aging and the aged. Authors and publishers are requested to call attention to publications or to send reprints to the Gerontology Branch, Baltimore City Hospitals, Baltimore 24, Maryland. The assistance of the Forest Park Foundation, Peoria, Illinois, in the preparation of these materials is gratefully acknowledged. [ABSTRACT FROM PUBLISHER]