No abstract

A direct comparison of the photochemical interconversions between red (Pr‐) and far‐red (Pfr‐) absorbing forms of highly‐purified 124 kDa oat and rye phytochromes under identical experimental conditions was performed. In two different buffer systems at 5°C, the quantum yields for the Pr to Ptr and Pfr to Pr phototransformations under constant red and far‐red illumination, φr and φfr respectively, were determined to be 0.152‐0.154 and 0.060‐0.065 for oat preparations and 0.172‐0.174 and 0.074‐0.078 for rye preparations. These values as well as the wavelength dependence of the photoequilibrium produced under continuous illumination throughout the visible and near‐ultraviolet spectrum were based on the absorption spectra of the two phytochrome preparations and revised molar absorption coefficients. The molar absorption coefficients were estimated by quantitative amino acid analysis and shown to be identical for the two monocot phytochromes (i.e. 132 mM−1 cm−1 at the red absorption maximum for the Pr form). Because these measurements were performed under identical experimental conditions, including buffer, temperature, light fluence rate, and instrumentation, the differences observed must reflect structural features inherent to the two different monocotyledonous phytochromes.

Desmogleins and desmocollins are transported to the plasma membrane by different kinesin motors, providing a potential mechanism to tailor desmosome structure and function during development and epithelial remodeling.

Although clinical magnesium deficiency is now recognized frequently in chronic alcoholics, its cause or causes are not clear. A poor dietary intake is undoubtedly important, but it is unlikely that magnesium deficiency results from dietary depletion alone, since it has been quite difficult to produce experimental dietary magnesium deficiency in man (2). Earlier workers have shown that the kidneys are reasonably efficient in conserving magnesium (2, 3). Thus, it is likely that some additional mechanism may be responsible for magnesium deficiency associated with chronic alcoholism. Recent studies have indicated that ethanol may induce increased urinary excretion of magnesium (4, 5). The purpose of the present study was to determine the effect of an acute ethanol load on urinary excretion of magnesium and other electrolytes, and to make preliminary observations on the mechanism responsible for an observed increase in urinary excretion of magnesium. METHODSFifteen studies were performed on nine normal and four alcoholic subj ects. Two of the alcoholic subj ects had significant hypomagnesemia at the time of study, while the other two had been repleted before study. One alcoholic subject was restudied several weeks later when he was readmitted to the hospital with acute alcoholic intoxication. All subjects were on a normal hospital diet and were fasted overnight before the experiments, which began at 8:00 a.m. Water-loading was achieved with 20 ml of water per kg of body weight and was maintained for the duration of the stu(ly by replacing the fluid vol- (7), and PAH by that of Smith and associates (8). Lactate was measured by the Marcus modification of Barker's and Summerson's procedure (9), and the method of Beutler and Yeh (10) was used for citrate. Total organic acids were determined by a modification of the method of Palmer (11). The methods for calculating correlation coefficient and probability are described by Snedecor (12). RESULTS

The binding of phytochrome to Cibacron Blue 3GA was utilized to develop a new affinity purification procedure for phytochrome. Brushitepurified phytochrome from rye (Secale cereak c.v. Cougar) was bound to agarose-immobilized blue dye in 0.1 molar potassium phosphate (pH 7.8), contaminating proteins washed out with 0.5 molar KCI, and homogeneous phytochrome eluted with 10 millimolar flavin mononucleate. Ninety-five per cent of the phytochrome applied bound, and 60 to 65% was eluted, giving a 25 to 30% yield for the complete one-day procedure. Affinitypurified rye phytochrome was identical to conventionally purified phytochrome in its behavior on sodium dodecyl sulfate gels, in gel exclusion chromatography, in sedimentation in sucrose density gradients and in its spectral properties.