Nucleic Acid Profile of the Emt6 Cell Cycle In Vitro

Simultaneous RNA and DNA estimations were carried out during the cell cycle of EMT6/M/CC cells growing in vitro following synchronization by mitotic selection. the determinations were performed with a flow cytofluorimeter on individual cells stained with acridine orange. It was found that the RNA content increased during G₁ then remained virtually constant between early and mid S phase, but a second increase occurred during late S. the rate of uptake of tritiated uridine paralleled these changes in RNA levels, and it was also found that the rate of uptake in metaphase and anaphase was virtually zero, but a rapid increase occurred in telophase. the increase in DNA during S was approximately linear, and the intermitotic phase and cycle durations were very similar to previously reported results.     

Cell surface topography of Candida and Leucosporidium yeasts as revealed by scanning electron microscopy.

The cell surface topography of the following yeast strains was examined by scanning electron microscopy: Candida slooffii, C. lipolytica, Leucosporidium frigidum, and L. nivalis. Multipolar and lateral budding were observed in the Candida yeasts in contrast to bipolar budding in the Leucosporidium species. The cell surface topography and the morphology of the bud and birth scars in these yeasts differed markedly. Apart from the bud and birth scars, the cells of C. slooffii showed a relatively smooth topography. The bud scars were seen as a circular ridge of wall material surrounding a markedly convex scar plug. Birth scars were raised, rounded structures, which appeared to distend upon cell growth. In contrast, bud scars of C. lipolytica were platelike, lacked a distinct annulus of wall material, and were much less protuberent than those of C. slooffii. Birth scars were a more permanent feature of these cells. The topography of Leucosporidium yeasts was characterized by the presence of numerous protrusions on the cell surface. In some cases, the entire cell surface was covered by these protrusions. There appeared to be some correlations between the age of the cell and the extent of surface protrusions and degree of surface convolution...     

Volume regulation by flounder red blood cells in anisotonic media

The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation.     

Possible mitochondrial involvement in mechanism of cytoplasmic male sterility in maize (Zea mays L.)

The mechanism of cytoplasmic male sterility was investigated in maize by isolating mitochondria from seedlings and various anther stages and analyzing cytochrome oxidase and succinic dehydrogenase biochemically and electrophoretically. Sterile anthers exhibited a lack of biochemical activity and fewer isozymatic bands for cytochrome oxidase. No apparent differences were detected biochemically or electrophoretically between fertile and sterile anthers for succinate dehydrogenase.     

Does cyclic GMP mediate amylase release from mouse parotid acini?

In mouse parotid acini both cholinergic and beta-adrenergic agonists increased intracellular levels of cyclic-GMP (c-GMP) as well as amylase release. The derivative of c-GMP, 8-bromo-c-GMP, mimicked the effects of cholinergic and beta-adrenergic stimulation on amylase release. Nitroprusside (NP), hydroxylamine (HA) and sodium azide (NaA) increased c-GMP levels and also enhanced amylase release in a dose-dependent manner; cyclic-AMP (c-AMP) levels were not affected. The phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (MIX) enhanced the effects of carbachol on both c-GMP accumulation and amylase release. These results suggest that c-GMP may mediate the actions of cholinergic agonists and at least partially mediate the actions of beta-adrenergic agonists on mouse parotid enzyme release.     

Taxonomic variation in total leaf protein amino acid compositions of grasses

Leaves of greenhouse grown grasses had free protein amino acid contents of generally less than 5 % total amino acids, while field collected grasses averaged 14.7 % free protein amino acid contents. Taxonomic patterns are detectable in the total leaf amino acid profiles of grasses from both sources, those of pooids being distinguishable from those of chloridoids and panicoids, and those of danthonioids showing an intermediate pattern. Leaf profiles of Oryza, Stipeae, and Ehrharteae resemble one another, and are more like those of pooids than those of panicoids. Variations in Thr and Leu are apparently associated with differences in photosynthetic pathway. Grass leaves are generally low in total amino acid contents (2.2 ? 1.0 g % fr. wt), with Ile, Val and Met + Cys identified as the limiting essential amino acids. However, the nutritional ‘chemical scores’ of grass leaf proteins are high (75 %, based on the WHO scoring pattern).     

Ratio of inferior olivary cells to Purkinje cells in a marsupial (Trichosurus vulpecula)

An indirect estimate of the extent of branching of the olivary axons in the cerebellum in a marsupial (Trichosurus vulpecula) was carried out. The cells in the inferior olivary nuclear complex (IOC) of both sides were estimated (mean = 57,200), as were the cerebellar Purkinje cells (mean = 881,300). Assuming that all climbing fibers arise from IOC cells and that each Purkinje cell receives a climbing fiber input, each IOC cell sends climbing fiber terminals to 15 Purkinje cells.     

Cloning the Tra1 region of RP1

The Tra1 region of RP1 from a derivative with Tn7 inserted into the kanamycin resistance determinant was cloned, using EcoRI, into the multicopy vector plasmid pBR325. For one orientation of the cloned fragment the resultant chimeric plasmid was very frequently lost from the cell, but in the other orientation it was much more stable and also compatible with RP1. Complementation by the stable chimeric plasmid, pED800, of a series of RP1 tra mutants showed that the mutations of all those retaining sensitivity to the P-specific phages PRR1, Pf3, and PR4, or only to PR4, mapped in the Tra1 region, while only 2 out of 20 amber mutations leading to full P-specific phage-resistance did so.