A statistical method for correlating tRNA sequence with amino acid specificity.

A statistical method for finding the nucleotide positions in tRNA sequences that correlate with amino acid specificity has been developed. The procedure involves finding the subset of nucleotide positions and groups of positions where the marginal density of one amino acid tRNA class does not overlap that of any other amino acid class. The procedure is an application of a statistical method known as the Expectation Maximization algorithm.     

Developmental Patterns of Catechol-O-Methyltransferase in Genetically Different Rat Strains: Enzymatic and Immunochemical Studies

Abstract: Catechol- O -methyltransferase (COMT) activity in the liver and kidneys of adult Fischer-344 (F-344) rats is only half of that in the same organs of Wistar-Furth (W-F) rats. The trait of low COMT activity in these animals is inherited in an autosomal recessive fashion. A comprehensive study of patterns of change in COMT activity during growth and development was performed to determine whether "temporal gene" effects might play a role in the inherited differences in enzyme activity present in adult animals. The COMT activity expressed per mg protein in liver and kidneys of newborn F-344 rats is only 50–60% of that in the same organs of W-F animals. The liver and the kidneys of newborn rats of both strains have COMT activity an order of magnitude higher than those in brain, heart, or blood. In addition, in both strains there are much larger increases in liver and kidney COMT activities during growth and development (5–10 fold) than in blood, brain, or heart (one- to twofold). Immunotitration with antibodies against rat COMT demonstrates that differences in immunoreactive COMT parallel differences in COMT activity, both between strains and within strains during growth and development. However, when the temporal patterns of change in enzyme activities in the liver and the kidneys of the two strains of rat are compared at multiple times during growth and development, no differences in the patterns are present. These results make it unlikely that temporal gene effects can explain the inherited differences in COMT activity in liver and kidneys of F-344 and W-F rats.     

Spongelike alginate nanoparticles as a new potential system for the delivery of antisense oligonucleotides.

The aim of this study was to design a new antisense oligonucleotide (ON) carrier system based on alginate nanoparticles and to investigate its ability to protect ON from degradation in the presence of serum. Pharmacokinetics and tissue distribution of ON-loaded nanoparticles have been determined after intravenous administration. An original and dynamic process for ON loading into polymeric nanoparticles has been applied. It is based on the diffusion of ON or ON/polylysine complex into the nanoparticle or the alginate gel, respectively. Indeed, the single coincubation of ON with nanoparticles led, within a few days, to an extremely efficient association. The diffusion kinetic of ON was shown to be dependent on several parameters, incubation temperature, ON concentration, presence or absence of polylysine, polylysine molecular weight, and nanoparticle preparation procedure. This new alginate-based system was found to be able to protect [33P]-radiolabeled ON from degradation in bovine serum medium and to modify their biodistribution, as an important accumulation of radioactivity was observed in the lungs, in the liver, and in the spleen after intravenous administration into mice. ON may be associated efficiently with calcium alginate in a colloidal state. Such nanosponges are promising carriers for specific delivery of ON to lungs, liver, and spleen.     

Ultrastructure of interstitial cells of Cajal at the gastro-oesophageal junction of the monkey (Macaca fascicularis)

The ultrastructure of the interstitial cells of Cajal (ICC) in the oesophagus of the monkey resembled that described in the oesophagus of other mammalian species but differed in their paucity and almost lack of smooth endoplasmic reticulum, caveolae and filaments. The plasmalemma of the ICC was in close contact (20- to 30-nm gaps) with that of smooth muscle cells. This may occasionally take the form of a desmosome, but gap junctions have not been observed. Vesiculated axon profiles, containing large granular or agranular vesicles were in close contact (20- to 30-nm gaps) with the plasmalemma of ICC. In a few vesiculated profiles a presynaptic density could be recognized. The intercalation of the ICC between the vesiculated axon profiles and the smooth muscle cells suggest a role in oesophageal motility. Between 3 and 21 days following bilateral vagotomy some ICC showed regressive changes such as increased electron density and shrinkage of the cytoplasm, crowding of the organelles and dissolution of the nuclear chromatin material. Axon profiles in the vicinity of the affected ICC contained glycogen granules suggesting injury. In late stages, the number of ICC and smooth muscle contacts was reduced. The results suggest that the vagus nerves exert a trophic influence on the ICC and that the intercellular relationships between ICC and smooth muscle cells possess a degree of plasticity. It is tentatively suggested that these vagal effects may be mediated via the oesophageal myenteric ganglia.