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131.
Karl Ekwall Michèle Kermorgant Geneviève Dujardin Olga Groudinsky Piotr P. Slonimski 《Molecular & general genetics : MGG》1992,233(1-2):136-144
Summary We have characterized the nuclear geneNAM8 inSaccharomyces cerevisiae. It acts as a suppressor of mitochondrial splicing deficiencies when present on a multicopy plasmid. The suppressed mutations affect RNA folding and are located in both group I and group II introns. The gene is weakly transcribed in wildtype strains, its overexpression is a prerequisite for the suppressor action. Inactivation of theNAM8 gene does not affect cell viability, mitochondrial function or mitochondrial genome stability. TheNAM8 gene encodes a protein of 523 amino acids which includes two conserved (RNP) motifs common to RNA-binding proteins from widely different organisms. This homology with RNA-binding proteins, together with the intronic location of the suppressed mitochondrial mutations, suggests that the NAM8 protein could be a non-essential component of the mitochondrial splicing machinery and, when present in increased amounts, it could convert a deficient intron RNA folding pattern into a productive one. 相似文献
132.
The effect of high CO2-concentration on photoacoustic signals from tobacco leaves is studied by means of a recently developed pulse modulation method which provides simultaneous information on photothermal and photobaric components in the millisecond time domain. High CO2-concentrations are found to induce large gas-uptake signals. Simultaneous measurements of chlorophyll fluorescence suggest that the uptake signals are correlated with energy-dependent fluorescence quenching. Very similar CO2-concentration dependencies are found in the absence and presence of methylviologen, which is known to catalyze O2-reduction, and in the presence of glyceraldehyde, which blocks Calvin cycle and photorespiration. It is suggested that the CO2-enhanced uptake signal is likely to reflect O2-uptake in the Mehler reaction. However, it is not ruled out that also rapid CO2-solubilisation or CO2-binding caused by light-induced stroma alkalisation are involved. Strong uptake is also induced when the CO2-concentration in the closed photoacoustic chamber increases due to dark-respiration. The consequences of these findings with respect to the interpretation of photoacoustic data (e.g., low-light effect) and to the regulatory role of O2-dependent electron flow are discussed. 相似文献
133.
Ryne A. Palombit 《International journal of primatology》1992,13(2):183-207
This study is a preliminary assessment of the potential of long-tailed macaque (Macaca fascicularis) calls to operate in systems of within-group spacing. Covariation in the rate of occurrence of calls with party spread, size,
and activity among wild individuals of one group suggested that four classes of calls may function in intragroup spacing.
Two of them are “clear” calls of long duration and pronounced frequency modulation. Calling rate increased with party spread
for low- and high-frequency variants of these calls during resting and feeding respectively, suggesting possible utility in
maintenance of spatial relations over moderately long distances. A third “harsh” call was negatively correlated with party
spread during foraging and may thus function to increase dispersion among foraging individuals. Another harsh call with a
tonal onset was unique among all calls in the vocal repertoire in being more frequently performed by lone, isolated individuals
than by macaques accompanied by others, suggesting a possible function in reestablishing contact that has been severed. The
functional significance of these calls with respect to their acoustic structures is discussed. Macaques that use calls to
regulate intragroup spacing can control communication distance and direction by their choice of acoustically different vocalizations.
This choice may be affected not only by varying environmental constraints on sound transmission, but also by social and ecological
factors such as intragroup competition. 相似文献
134.
135.
Adelheid Gauly Alfred Batschauer Albrecht von Arnim Hans Kössel 《Plant molecular biology》1992,19(2):277-287
136.
137.
A biochemical genetic study of the enzyme malate dehydrogenase (MDH) was conducted in the grasshopperOxya j. japonica. Analysis of MDH electrophoretic variation in this species of grasshopper shows that one of the two autosomal loci for MDH in grasshoppers, the Mdh-2 locus, controlling the anodal set of MDH isozymes, is duplicated. Results of breeding studies confirm this and the observed polymorphism at theMdh-2 locus in the two populations ofOxya j. japonica studied can be attributed to three forms of linked alleles at the duplicated locus in equilibrium in both populations. In this respect, all individuals of this species possess heterozygous allelic combinations at the duplicatedMdh-2 locus, which may account for the spread of the duplicated locus in the populations of this species of grasshopper.This research was supported by a grant (Vote F) from the University of Malaya, Kuala Lumpur. 相似文献
138.
C. Stephenson M. Brivet M. Gautier J. Deschatrette R. Gitzelmann P. Karran 《Biochemical genetics》1991,29(3-4):135-144
Expression of the enzymes galactokinase, thymidine kinase, and O6-methylguanine-DNA methyltransferase is occasionally coordinately regulated in human cell lines. We have measured the activities
of these three enzymes in extracts of fibroblasts from individuals with hereditary galactokinase deficiency. These cells do
not express measurable galactokinase activity. The levels of O6-methylguanine-DNA methyltransferase were in the normal range in cells from three galactokinase-deficient individuals. The
activity of thymidine kinase in the affected cells was in the normal range for two of the three individuals. The reduced thymidine
kinase activity in the third individual reflected the extremely poor growth of the cells in culture. Immortalization of one
galactokinase-deficient cell line resulted in loss of O6-methylguanine-DNA methyltransferase activity, but the galactokinase and thymidine kinase levels remained unchanged. The data
indicate that the loss of galactokinase activity in these individuals is the consequence of an alteration of gene expression
which does not involve coordinate silencing with the thymidine kinase and methyltransferase loci. 相似文献
139.
Long-term expression of gene introduction into normal human T-lymphocytes by retroviral-mediated gene transfer 总被引:1,自引:0,他引:1
A A Fauser 《Journal of cellular biochemistry》1991,45(4):353-358
Human T-lymphocytes are long lived, easily accessible, mature, and capable of proliferation. They are theoretically a suitable target for retroviral mediated gene transfer. To test this hypothesis, normal human T-cells obtained from bone marrow and peripheral blood were stimulated with phytohemagglutinin (PHA) and infected 24 h later with the retroviral vector N2 which carries the bacterial neo gene. T-lymphocytes were propagated in culture for up to 14 weeks with interleukin-2 (IL-2). Analysis by whole cell RNA dot/blot using a single stranded RNA probe demonstrated persistent expression of the neo gene. Preliminary functional studies revealed that both helper and suppressor functions were preserved in the infected cells in culture. These results demonstrate that normal T-cells are capable of long-term expression of genes introduced by retroviral mediated gene transfer and are potential target cells for somatic gene therapy. 相似文献
140.