Molecular cloning and sequencing of human palmitoyl-CoA ligase and its tissue specific expression

A complimentary DNA clone encoding the entire human palmitoyl-CoA ligase has been isolated from a liver cDNA library and sequenced in it's entirety. The predicted product is a 699 amino acid protein. Southern analysis utilizing the human palmitoyl-CoA ligase gene as a probe revealed varying degrees of similarity amongst various mammalian species. The palmitoyl-CoA ligase gene is highly expressed in liver, heart, skeletal muscle and kidney, and to a lesser extent in brain, lung, placenta and pancreas. The expression of palmitoyl-CoA ligase in various tissue parallels the function of this enzyme in the metabolism of fatty acids in these tissues.     

Cell cultures derived from early zebrafish embryos differentiate in vitro into neurons and astrocytes

The zebrafish is a polular nonmammalian model for studies of neural development. We have derived cell cultures, initiated from blastula-stage zebrafish embryos, that differentiate in vitro into neurons and astrocytes. Cultures were initiated in basal nutrient medium supplemented with bovine insulin, trout serum, trout embryo extract and fetal bovine serum. After two weeks in culture the cells exhibited extensive neurite outgrowth and possessed elevated levels of acetylcholinesterase enzyme activity. Ultrastructural analysis revealed that the neurites possessed microtubules, synaptic vessicles and areas exhibiting growth cone morphology. The cultures expressed proteins recognized by antibodies to the neuronal and astrocyte-specific markers, neurofilament and glial fibrillary acidic protein (GFAP). Poly-D-lysine substrate stimulated neurite outgrowth in the cultures and inhibited the growth of nonneuronal cells. Medium conditioned by the buffalo rat liver line, BRL, promoted the growth and survival of the cells in culture. Mitotically active cells were identified in cultures that had undergone extensive differentiation. The embryo cell cultures provide an in vitro system for investigations of biochemical parameters influencing zebrafish neuronal cell growth and differentiation.     

Comparison of aldolase isozymes in placenta, HeLa cells, and human fibroblast cultures

The aldolase specific activity of the human carcinoma cell line, HeLa, against fructose 1,6-diphosphate as substrate is 4- to 5-fold greater than the specific activity of diploid human fibroblast cultures derived from skin and lung. HeLa aldolase is isozyme is predominantly the A type and its substrate preferences resemble human placenta. These findings provide further support for the oncofetal enzyme consitution of HeLa cells.     

Lack of repair of ultraviolet light damage in Mycoplasma gallisepticum

Molecules with single-stranded tails (rolling circles) were isolated as replicating intermediates in G4 progeny single-stranded DNA synthesis. Lysates from infected cells harvested late in infection during single-stranded DNA synthesis were not deproteinised but analysed directly in caesium chloride and propidium diiodide gradients. The gradient fractionated them on the basis of tail length. If the lysates were first deproteinised however, the tailed replicative intermediates banded as a peak at a density just greater than that of replicative form II DNA (RFII) and did not spread down the gradient. The origin of synthesis of the viral strand tail was mapped by electron microscopy as 55 to 60% away from the single EcoRI cleavage site. Termination molecules finishing a round of viral strand DNA synthesis have been identified as molecules consisting of a closed single-stranded DNA circle attached by a very small region to the parent double-stranded DNA circle.