McGill University Thèses et mémoires publiés en 1983

The interaction of a high power laser beam with the lattice of transparent optical materials induces internal strains in the latter. Attention is focused on optical materials of zinc blende structure and excitation at the 10.6-(mu)m wavelength of the laser. A lattice dynamical treatment is presented to obtain the laser induced internal strains in terms of the lattice Green's functions, the transverse effective charge and the Raman coefficient. The transverse effective charge and the Raman coefficient are then thoroughly discussed and discrepancies in previous works concerning these parameters are resolved. The imperfect lattice Green's functions are utilized to calculate the …  Lire la suite

Human leukemia cell K562 in culture displayed an absolute requirement for folate, proliferating at optimal rate only when the total intracellular folate concentration was greater than 1.5 uM. This critical intracellular concentration was maintained by extracellular 5-formyltetrahydrofolic acid or 5-methyltetrahydrofolic acid at a 100-fold lower concentration than folic acid. Growth rate of folate-deficient cells was proportional to intracellular concentration of fully-reduced, non-methylated folate but not to intracellular 5-methyltetrahydrofolate concentration. Growth of folate-deficient cells was stimulated by inosine but not by thymidine, suggesting that the primary cause of growth restriction in these cells was purine deficiency. Serine stimulated, and glycine inhibited, …  Lire la suite

In order to determine the role of biogenic monoamines in the control of pancreatic secretion, the metabolism and disposition of 5-hydroxytryptamine (5-HT) and dopamine in rat exocrine pancreas was studied. Pancreatic acinar cells contained 5-HT which was located exclusively in the zymogen granule fraction. Aromatic amino acid decarboxylase activity was located exclusively in the cytosol of acinar cells and was substrate specific for the L-isomers of hydroxylated aromatic amino acids 3,4-dihydroxyphenylalanine(L-DOPA) and 5-hydroxytryptophan (L-5-HTP). Each substrate competitively inhibited the decarboxylation of the other. When incubated with {('14)C}5-HT dispersed acinar cells took up the amine and concentrated it in zymogen granules. …  Lire la suite

Infection of L cells with reovirus results in a gradual inhibition of host protein synthesis and a concomitant increase in viral specific protein synthesis. Previous in vitro studies using cell-free extracts from uninfected and infected cells suggested that the observed pattern of protein synthesis in infected cells is the consequence of a transition of the host translational apparatus from cap dependence to cap independence. To test this hypothesis, it was necessary to demonstrate that mRNA being translated at late times in infected cells was uncapped. Progeny subviral particles synthesize the bulk of the viral mRNA present in infected cells at …  Lire la suite