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.     

Fatty acid synthesis in fetal lung

De novo fatty acid synthesis in lung is significant during fetal growth and development. Specific activity and relative rate of synthesis of fatty acid synthetase increase with the days of gestational age and drop significantly after birth. Fetal lungs contain thyroid hormone receptors and binding capacities of this hormone to the fetal lungs also increase with the days of gestational age. Our results suggest that de novo fatty acid synthesis in fetal lungs may make a significant contribution towards surfactant synthesis.     

Structure of the d-galactan isolated from aloe barbadensis miller

Hot-water extraction of the pulp obtained by dehydrating the jelly of the fleshy leaves of Aloe barbadensis furnished a mixture of polysaccharides containing mainly pectic acid, along with a d-galactan, a glucomannan, and an arabinan. The pectic acid was partly removed by treatment with calcium chloride, and the resulting, hexose-enriched, polysaccharide mixture was fractionated through a column of DEAE-cellulose to yield a d-galactan containing d-galactose (92.9% and d-galacturonic acid (3.8%). Hydrolysis of the permethylated d-galactan furnished 2,3,4,6-tetra-, 2,3,6-tri-, and 2,3-di-O-methylgalactose in the molar ratios of 1:26:1. On periodate oxidation, the d-galactan reduced 0.95 molar equivalent of the oxidant per hexosyl residue, and liberated one molar equivalent of formic acid per 26 galactosyl residues. Smith degradation of the d-galactan afforded mainly threitol. From these results, a structure has been assigned to the repeating unit of the d-galactan. The number-average, molecular weight of the peracetylated galactan has been found to be 3.74 x 10⁴.     

Tissue difference in gamma-glutamyl transpeptidase attributed to sialic acid content.

Gamma-glutamyl transpeptidase (GGT) was extracted from the microsomal fraction of various bovine tissues and partially purified. Purified enzymes demonstrated different mobilities toward the anode in polyacrylamide gel electrophoresis in 0.5% Emulphogene BC720, pH 7.5. The ciliary-body GGT migrated fastest, while the brain enzyme was electrophoresed most slowly. The apparent Km values (Km′) of GGT for L-gamma-glutamyl-p-nitroanilide were 1.4–2.0 mM when assayed with glycylglycine as the gamma-glutamyl acceptor. After neuraminidase treatment, electrophoretic mobility was decreased considerably for all enzyme preparations, compatibly with the removal of negatively charged sialic-acid residues. The Km′ values of the enzyme were not affected by the hydrolytic treatment. Electrophoresis of digested enzymes showed essentially identical mobilities. From these results we conclude that tissue differences in GGT are attributable to the varying extent of sialylation of enzyme.     

Membrane-fusions and cytoplasmic bridges in the cells of the developing cerebellum

Summary In the developing cerebellum of the neonate rats membranefusions and cytoplasmic bridges between cells were observed. These membrane-fusions were characterized by the presence of loops of membrane and cytoplasmic bridges between the two limits of the membrane-fusions. They were found between Purkinje cells, Purkinje cells and the migratory cells, mitotically potent cells of the external granular layer, and differentiating granule cells of the internal granular layer. The membrane-fusions were found to be a transient developmental phenomenon. Issues pertaining to the universality of membrane-fusions, their significance in the induction for cell differentiation, and the problem of fixation artifacts are discussed.This research was supported by N.I.H. Research Grants No. NS-08817 and CA-14650. Assistance of Mrs. Kunda Das in various aspects of electron microscopy is gratefully acknowledged     

Protection from nonfreezing cold injury by quinacrine, a phospholipase inhibitor

A recent study from our laboratory indicated additional tissue injury during rewarming of a cooled rabbit leg. Oxygen-derived free radicals were believed to play a role in such "rewarming injury." Since free radicals may attack membrane phospholipids, we analyzed the phospholipid composition in the leg tissue during cooling and rewarming. Our results indicated significant breakdown of membrane phospholipids, particularly phosphatidylcholine and phosphatidylethanolamine, with a corresponding accumulation of lysophosphatidylcholine and nonesterified fatty acids. Quinacrine, a phospholipase inhibitor, was able to preserve membrane phospholipids during rewarming of the cooled leg. Rewarming of cooled tissue was also accompanied by additional tissue injury, as evidenced by the increased release of lactic acid dehydrogenase and creatine kinase, as well as enhanced lipid peroxidation, as evidenced by increased malonaldehyde formation. Quinacrine reduced the release of these intracellular enzymes and decreased lipid peroxidation, suggesting its efficacy as a therapeutic agent against hypothermic injury.     

Antiulcerogenic and anti-inflammatory effects of emodin, isolated from Rhamnus triquerta wall

Emodin, an anthraquinone derivative, isolated from the whole plant of R. triquerta, in 15 mg/kg dose (ip) exhibited anti-inflammatory activity against carrageenin-induced pedal inflammation in rats. In the same dosage it also showed antiulcer activity against 4 hr pylorus-ligated, aspirin and immobilization stress-induced gastric ulcers in rats. It decreased acid and pepsin output and augmented mucus secretion in terms of total carbohydrate: protein ratio in the gastric juice of aspirin treated pylorus-ligated rats, indicating that the antiulcerogenic effect of emodin may be due to its effect on gastric secretion.     

Constitutive mutations of Agrobacterium tumefaciens transcriptional activator virG.

The virulence (vir) genes of Agrobacterium tumefaciens Ti plasmids are positively regulated by virG in conjunction with virA and plant-derived inducing molecules. A procedure that utilizes both genetic selection and a genetic screen was developed to isolate mutations in virG that led to elevated levels of vir gene expression in the absence of virA and plant phenolic inducers. Mutants were isolated at a frequency of 1 in 10(7) to 10(8). Substitution mutations at two positions in the virG coding region were found to result in the desired phenotype. One mutant had an asparagine-to-aspartic acid substitution at residue 54, and the other contained an isoleucine-to-leucine substitution at residue 106. In both cases, the mutant phenotype required the presence of the active-site aspartic acid residue at position 52. Further analysis showed that no other substitution at residue 54 resulted in a constitutive phenotype. In contrast, several substitutions at residue 106 led to a constitutive phenotype. The possible roles of the residues at positions 54 and 106 in VirG function are discussed.     

A 14-kilodalton inner membrane protein of Vibrio cholerae biotype e1 tor confers resistance to group IV choleraphage infection to classical vibrios.

Choleraphage phi 149 differentiates the two biotypes, classical and el tor, of Vibrio cholerae. This phage cannot replicate in V. cholerae biotype el tor cells because the concatemeric DNA intermediates produced are unstable and cannot be chased to mature phage DNA. A V. cholerae biotype el tor gene coding for a 14,000-Da inner membrane protein which destabilizes the concatemeric DNA intermediates by hindering their binding to the cell membrane has been identified. Presumably, a 22,000-Da V. cholerae biotype el tor protein might also have a role in conferring phage phi 149 resistance to cells belonging to the biotype el tor. A nucleotide sequence homologous to the 1.2-kb V. cholerae biotype el tor DNA coding for both the 14,000- and 22,000-Da proteins is present in all strains of classical vibrios but is not transcribed. The nucleotide sequence of the gene coding for the 14,000-Da protein has been determined.     

Mathematical characterization of Chaos Game Representation. New algorithms for nucleotide sequence analysis.

Chaos Game Representation (CGR) can recognize patterns in the nucleotide sequences, obtained from databases, of a class of genes using the techniques of fractal structures and by considering DNA sequences as strings composed of four units, G, A, T and C. Such recognition of patterns relies only on visual identification and no mathematical characterization of CGR is known. The present report describes two algorithms that can predict the presence or absence of a stretch of nucleotides in any gene family. The first algorithm can be used to generate DNA sequences represented by any point in the CGR. The second algorithm can simulate known CGR patterns for different gene families by setting the probabilities of occurrence of different di- or trinucleotides by a trial and error process using some guidelines and approximate rules-of-thumb. The validity of the second algorithm has been tested by simulating sequences that can mimic the CGRs of vertebrate non-oncogenes, proto-oncogenes and oncogenes. These algorithms can provide a mathematical basis of the CGR patterns obtained using nucleotide sequences from databases.