Separation of two HMM-S1 species from white muscle myosin

Heavy meromyosin subfragment 1 was resolved by chromatography on DEAE-cellulose into two fractions characterized by the nature of the alkali light chains present. It was shown that even in an HMM-S1 preparation with an extensive fragmentation of the heavy chain a polyacrylamide gel electrophoresis analysis differentiates alkali light chains among the light fragmentation components. A non-fragmented HMM-S1 was obtained from a papain digest of myofibrils and the chromatographic analysis supplied further evidence of the separation of the two species of HMM-S1 present in rabbit white muscle myosin.     

Inhibitory effect of hydroxyurea on [3-H]leucine incorporation in human peripheral lymphocytes.

Hydroxyurea (HU), generally considered to be a specific inhibiter of DNA synthesis, has an inhibitory effect on the incorporation of TCA-precipitable [3-H]leucine in peripheral lymphocytes. This action is not secondary to the inhibition of DNA synthesis since incorporation of [3-H]leucine is unaffected when DNA synthesis is inhibited by 5-fluorodeoxyuridine (FUdR); it does not appear to be directly related to inhibition of RNA synthesis; and it is not mediated at the level of translation since HU has no effect on protein synthesis in rabbit reticulocytes. The relevance of these findings to the use of HU as a DNA inhibitor is discussed.     

Resolution of cyclic AMP stimulated protein kinase from polymerization-purified brain microtubules.

Polymerization-deploymerization purified microtubules from mouse brain contain, in addition to tubulin, several minor proteins, including protein kinase activity. The protein kinase copurifies with microtubules in constant proportion to tubulin through two, three, or four cycles of polymerization; it can be resolved from tubulin by gel filtration chromatography and has an apparent molecular weight of 280,000. Its activity is stimulated 7-fold by cyclic AMP, and resembles the soluble brain protein kinase described by Miyamoto $\text{et al.}$ (1). The microtubule preparation serves as an endogenous substrate for this protein kinase; both 6S and 30S tubulin are substrates for phosphorylation to the extent of about 0.10 ± 0.05 moles/mole.     

Biosynthesis of azetidine-2-carboxylic acid from methionine in Nicotiana tabacum

The administration of dl-methionine-[1¹⁴C] to Nicotia tabacum resulted in the formation of radioactive azetidine-2-carboxylic acid (isolated by dilution) which was specifically labelled on its carboxyl group. This result and other evidence strongly indicates that this imino acid is a normal component of tobacco.     

Molecular weight and amino acid composition of purified spinach beet phenolase

The purification of spinach beet phenolase has been modified to include equilibration of the crude macerate with 0.5% cetyl-trimethylammonium bromide a     

A cutin acid in Pinus sylvestris microspores

Nonacosan-10-ol (0.7%) and the cutin acid, 9,16-dihydroxyhexadecanoic acid (0.3%) are present in Pinus sylvestris microspores. The pollen coat hence has some features in common with leaf cuticles.     

Acetic acid and acidification accelerate chronological and replicative aging in yeast

Comment on: Murakami C, et al. Cell Cycle 2012; 11:3087-96.     

Acid secretion and membrane reorganization in single gastric parietal cell in primary culture

A digitally-enhanced videomicroscopy study of rabbit gastric parietal cells in primary culture was performed using alternate observations with differential interference contrast and fluorescence optics of cells mounted and perfused on a temperature-controlled microscope stage. The effect of histamine, a physiological effector of acid secretion, was followed. Isolated parietal cells possess an internal apical vacuole, which kept the cell in a pseudopolarized state. This apical vacuole is a site of acid secretion. This was demonstrated by the direct visualization of the uptake of the fluorescent weak base 9-amino acridine and of the concomitant enormous swelling of the acid vacuole which reached an estimated size of 3-7 times the normal cell volume. This morphological change of shape and acidification of apical vacuoles was fully reversible and cells could respond to successive stimulations. A quantitative study of these events provided a value of the acid accumulation index for each single cell in response to histamine. Individual cell response varied within a factor of 7. The cellular localization of the proton pump complex responsible for acid secretion and of the major components of the secretory microvilli, actin and ezrin, a histamine-dependent phosphorylation target of protein kinase A, were detected by indirect immunofluorescence microscopy in resting and stimulated cells. Both actin and ezrin colocalized at the apical vacuole membrane in resting and stimulated cells, whereas the proton pump shifted from an intracytoplasmic pool to the apical vacuole membrane upon stimulation.