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111.
112.
Antonio Facchiano 《Journal of molecular evolution》1995,40(6):570-577
Hypothetical Products from Noncoding Frames (i.e., HyPNoFs) are hypothetical, not-coded proteins, translated from alternate reading frames (i.e., coding+1 and coding+2) of cDNAs. HyPNoFs of CD4, PKC, oncostatin, bcl-2 proto-oncogene, tumor suppressor p53, cystic fibrosis transmembrane regulator (CFTR), and tumor necrosis factors a and were searched as query sequences vs the SWISS-PROT data bank. Homology searches carried out revealed that hypothetical products (i.e., HyPNoFs) may share high similarity with real protein products actually coded. Sequence similarity of hypothetical products to real proteins is sometimes very high, suggesting common conformational features, according to the Sander and Schneider cutoff value. This finding supports the hypothesis that eukaryotic DNA, currently considered to be monocistronic, might occasionally have polycistronic regions, carrying different protein messages on overlapping frames. As yet, polycistronic genes have been observed in viral genomes only. The presence of polycistronic regions in eukaryotic genes is likely reminiscent of an ancient strategy, rather than a present feature of the genome in eukaryotes.These data suggest that thorough investigation of HyPNoFs is likely to improve our ability to trace genes' evolution and to investigate structure-function relationships of protein and DNA sequences. 相似文献
113.
Subnucleolar location of fibrillarin and variation in its levels during the cell cycle and during differentiation of plant cells 总被引:5,自引:0,他引:5
The nucleolar protein fibrillarin has been studied in onion cells; it is detected as an Mr 37,000 protein by immunoblotting using a human autoimmune serum. Quantitative immunoelectron microscopy showed that most fibrillarin is localized in the transition zone between the fibrillar center (FC) and the dense fibrillar component (DFC) as well as in the priximal zone of the DFC, where the labeling shows a gradual decrease out-ward until it reaches insignificant levels in the distal zone of the DFC. Thus, fibrillarin is not uniformly distributed throughout the DFC of plant cells. This result supports the hypothesis that the morphologically homogeneous DFC may not be uniform in function; it is also in agreement with the hypothesized vectorial flow of ribosome biogenesis through the same compartments. Data are also presented showing that the amount of fibrillarin increase when nucleolar activity increases in G2, and probably decreases when nucleolar activity decreases during differentiation. 相似文献
114.
During early embryogenesis of the nematode Parascaris univalens (2n=2) the processes of chromatin diminution and segregation of the germ and somatic cell lineages take place simultaneously. In this study we analyzed the nucleolar cycle in early embryos, both in germinal and somatic blastomeres, by means of silver staining and antibodies against the nucleolar protein fibrillarin. We observed an identical nucleolar cycle in both types of blastomeres, hence, the chromatin diminution process has no effect on the nucleolar cycle of somatic blastomeres. We report the existence of outstanding differences between this cycle and those previously reported during early embryogenesis of other species. There is a true nucleolar cycle in early embryos that shows a peculiar nucleolar disorganization at prophase, and a preferential localization of prenucleolar bodies only on the euchromatic regions during nucleologenesis. Moreover, fibrillarin does not form a perichromosomal sheath in metaphase or anaphase holocentric chromosomes, probably owing to their special centromeric organization. The number and location of nucleolus organizer regions (NORs) in the chromosomal complement have been determined using silver impregnation, chromomycin A3/distamycin A staining, and fluorescent in situ hybridization using an rDNA probe. There are only two NORs, one per chromosome, and these are lost in blastomeres after chromatin diminution. Moreover, the constant presence of two nucleoli in somatic blastomeres suggests that NORs are not affected during the fragmentation of euchromatic regions when this process occurs. 相似文献
115.
116.
Annalisa Botta Elizabeth A. Lindsay Vesna Jurecic Antonio Baldini 《Mammalian genome》1997,8(12):890-895
We have constructed a comparative map in mouse of the critical region of human 22q11 deleted in DiGeorge (DGS) and Velocardiofacial
(VCFS) syndromes. The map includes 11 genes potentially haploinsufficient in these deletion syndromes. We have localized all
the conserved genes to mouse Chromosome (Chr) 16, bands B1-B3. The determination of gene order shows the presence of two regions
(distal and proximal), containing two groups of conserved genes. The gene order in the two regions is not completely conserved;
only in the proximal group is the gene order identical to human. In the distal group the gene order is inverted. These two
regions are separated by a DNA segment containing at least one gene which, in the human DGS region, is the most proximal of
the known deleted genes. In addition, the gene order within the distal group of genes is inverted relative to the human gene
order. Furthermore, a clathrin heavy chain-like gene was not found in the mouse genome by DNA hybridization, indicating that
there is an inconsistent level of gene conservation in the region. These and other independent data obtained in our laboratory
clearly show a complex evolutionary history of the DGS-VCFS region. Our data provide a framework for the development of a
mouse model for the 22q11 deletion with chromosome engineering technologies.
Received: 8 July 1997 / Accepted 11 August 1997 相似文献
117.
Differential effects of five types of antipathogenic plant peptides on model membranes 总被引:2,自引:0,他引:2
Jos Manuel M. Caaveiro Antonio Molina Juan M. Gonzlez-Maas Pablo Rodríguez-Palenzuela Francisco García-Olmedo Flix M. Goi 《FEBS letters》1997,410(2-3)
The effects of five antipathogenic plant peptides, wheat α-thionin, potato PTH1 defensin, barley LTP2 lipid transfer protein, and potato tuber DL1 and DL2 defensins, have been tested against phospholipid vesicles (liposomes). Wheat thionin very actively induces aggregation and leakage of negatively charged vesicles. LTP2 displays the same activities, although to a limited extent. Under certain conditions PTH1 and DL2 induce vesicle aggregation, but not leakage. Potato defensin DL1 failed to show any effect on liposomes. The same peptides have been assayed against a plant pathogenic bacterium, both the membrane-active and -inactive compounds having efficient antibacterial action. 相似文献
118.
Neurotrophic Effects of l-DOPA in Postnatal Midbrain Dopamine Neuron/Cortical Astrocyte Cocultures 总被引:4,自引:1,他引:3
Abstract: l -DOPA is toxic to catecholamine neurons in culture, but the toxicity is reduced by exposure to astrocytes. We tested the effect of l -DOPA on dopamine neurons using postnatal ventral midbrain neuron/cortical astrocyte cocultures in serum-free, glia-conditioned medium. l -DOPA (50 µ M ) protected against dopamine neuronal cell death and increased the number and branching of dopamine processes. In contrast to embryonically derived glia-free cultures, where l -DOPA is toxic, postnatal midbrain cultures did not show toxicity at 200 µ M l -DOPA. The stereoisomer d -DOPA (50–400 µ M ) was not neurotrophic. The aromatic amino acid decarboxylase inhibitor carbidopa (25 µ M ) did not block the neurotrophic effect. These data suggest that the neurotrophic effect of l -DOPA is stereospecific but independent of the production of dopamine. However, l -DOPA increased the level of glutathione. Inhibition of glutathione peroxidase by l -buthionine sulfoximine (3 µ M for 24 h) blocked the neurotrophic action of L-DOPA. N -Acetyl- l -cysteine (250 µ M for 48 h), which promotes glutathione synthesis, had a neurotrophic effect similar to that of l -DOPA. These data suggest that the neurotrophic effect of l -DOPA may be mediated, at least in part, by elevation of glutathione content. 相似文献
119.
The role of diet in personal health maintenance is important whether a person is trying to stay healthy or to treat diet-related diseases such as hypercholesterolemia, hypertension, diabetes mellitus or obesity. Dietary recommendations include limiting fat to 30% and protein to 20% of total calories, with the remaining 50% coming from carbohydrate. Maintaining dietary changes for long periods is very difficult for many persons. Specific self-management skills may ease the task. 相似文献
120.
Antonio P. Linares Stuart H. Cohen Elliot Goldstein Alan D. K. Kelley Toby K. Eisenstein 《The Western journal of medicine》1984,141(2):203-205
Salmonella thompson, a common pathogen of poultry, has received scant attention as a cause of human gastroenteritis. At least 45 persons were infected with S thompson in Sacramento, California, after eating at a chicken restaurant and 38 became symptomatic. Ten required admission to hospital, and all were treated with antibiotics and improved. In 19 cases cultures of stool specimens for S thompson over a 60-day period showed slower but statistically insignificant differences in salmonellal elimination in 7 patients who received antibiotics when compared with 12 who were untreated. We report this outbreak to increase awareness of the virulence and prevalence of gastroenteritis due to S thompson. 相似文献