A inteligibilidade da palavra em igrejas católicas, através de análises de carácter objectivo e subjectivo
Lencastre, Margarida Maria Mendes de Freitas de Queiroz e
1988-01-01
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18 records were found.
The differences between a thermostable (T) and thermolabile (T) form of tyrosmase from Neurospora crassa have been studied by means of a spectrophotometric technique using ascorbate or ferrocyanide. No significant differences in substrate specificity have been found in a survey of over 30 substances which included mono-, di-, tri-, and conjugated phenols. Catechol was found to be a substrate, in contrast to previous findings. Michaelis-Menten constants for the two forms of enzyme acting on -tyrosine and - and -hydroxyphenylalanine (Dopa) also were found to be similar, as were the pH optima on -Dopa and phenyl-4-catechol, and the response to several inhibitors. On the other hand, the activity of the thermolabile enzyme was lost more rapidly than that of the thermostable one after incubation for 5-15 min. in high concentrations of urea a...
No Abstract.
Results of a cross between a hyperderepressed strain (89601 a) and a normal strain (74A) of Neurospora crassa suggest that there is a single gene difference in this trait. The evidence is clearest with amylase although a similar segregation pattern is suggested for invertase and, perhaps, trehalase. On the other hand, phosphatase activity is not affected by this gene. The gene for hyperderepression does not appear to be widespread in wild-type strains of this organism for, in the seven tested, only 89601 a was hyperderepressed for amylase. The action of the hyperderepression gene probably is not due to diminished sensitivity to catabolite repression because the synthesis of amylase begins at roughly the same point in glucose depletion in both the hyperderepressed and normal strains. Furthermore, growth of these strains on constant but ...
Trehalase has been obtained in crystalline form from the mycelium of Neurospora crassa. During elution from the first pass through a DEAE-cellulose column, two peaks with trehalase activity were obtained. When the first of these was rechromatographed on DEAE-cellulose, two more major peaks were found. The enzymes of these fractions were compared and found to be similar in substrate specificity, response to inhibitors, pH optima, and Michaelis constants. However, small differences in the rate of inactivation of these enzymes at 50 [deg] were detected.
Polymyxin B prevents the germination of ascospores of Neurospora tetrasperma with an LD50 of 3-4 p.p.m. The toxic effect of polymyxin is partially reversed by calcium and magnesium ions. The effect of polymyxin on the respiration of activated ascospores does not become apparent until after 2 hr. The effect upon respiration is reversed by calcium ions. Dormant and activated ascospores remove about the same amount of polymyxin from solution almost immediately upon exposure to the antibiotic. After 90 min. the apparent uptake of activated cells is markedly diminished while that of the dormant spores increases slightly. Polymyxin competes noncompetitively with methylene blue for sites on the surface of the cells when added simultaneously with the dye. However, if the antibiotic is added before methylene blue, dye uptake is almost entirely ...
Cytochrome oxidase activity in the standard type and in four mutants of Glomerella cingulata has been shown to be constant throughout the mycelial development. This enzyme is concentrated on mitochondria-like particles which are extractable in hypertonic solutions of disaccharides. On the other hand, tyrosinase activity is concentrated in the supernatant and changes markedly during the development of the organism. This enzyme is present in the standard type and in two of the mutants, while the other two mutants have only minimal amounts. In the mycelia having such activity, tyrosinase increases precipitously, after the peak of growth has been reached, and then declines almost immediately, although small amounts of tyrosinase remain in the mycelium for as long as it is possible to obtain extracts. The evidence suggests that tyrosinase c...
The metabolism of furfural was studied with regard to possible mechanisms by which the chemical induces germination in ascospores. Incubation of ascospores in furfural resulted in the uptake of a small percent of the furfural, and the conversion of the bulk of it to furoic acid which was in turn converted to furfuryl alcohol. Conversion also occurred in Neurospora mycelium and conidia with the order being furfural to furfuryl alcohol to furoic acid. Conversion appears to be a noninducible enzymatic process localized on the outer surface of the cell. Conversion was completely inhibited without preventing germination indicating that conversion is not involved in the breaking of dormancy in Neurospora ascospores.
Furfural uptake was studied with regard to possible mechanisms of inducing germination in ascospores. Uptake was found to involve a large, weakly bound reversible component and a small tightly bound irreversible component. Localization experiments indicate that almost all of the furfural removed from the media is bound to the spore wall. However, a small amount may penetrate into the cytoplasm. The results so far suggest that furfural induces germination by solubilizing or activating a bound or compartmentalized enzyme(s) on the cell membrane or other diffusion barrier of the cell.
A morphological mutant of Neurospora crassa, snowflake, is shown to contain filaments which are about 70 A in diameter, and up to several microns long, and which usually bunch in groups of a few to several hundred. They may be found longitudinally or transversely arranged with respect to the long axis of the cell and, in many cases, they run up to the plasma membrane, but not through it. The filaments often are arranged in crystalline arrays but may also be found as separate filaments. Sometimes the filaments are closely appressed to nuclei and may be found inside them. It is likely that the filaments are not the result of the dissociation of microtubules and are most likely microfilaments like those found in other organisms. Their relationship to the origin of certain morphological mutants in Neurospora is discussed.
