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31.
The carcinogenicity of several groups of carcinogens is evoked with particular reference to Dibenzo(c,g)carbazole derivatives. The activity of these derivatives is discussed with respect to their species and organ specificity. The enzymatic equipment is decisive as to whether the compounds formed can react with DNA or are simply detoxified and eliminated. All these carcinogens are complete carcinogens, i.e. they have the property of both initiation and promotion. 相似文献
32.
Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance.
For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first
group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic
property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium
in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared
to 0.5–1.5 μg/g). 相似文献
33.
34.
Peter Hechtman Bernard Boulay Marc De Braekeleer Eve Andermann Serge Melançon Jean Larochelle Claude Prevost Feige Kaplan 《Human genetics》1992,90(4):402-406
Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a GA transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7+1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7+1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7+1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada. 相似文献
35.
A minority of 46,XX true hermaphrodites are positive for the Y-DNA sequence including SRY 总被引:4,自引:0,他引:4
Ken McElreavey Raphaël Rappaport Eric Vilain Nacer Abbas François Richaud Stéphen Lortat-Jacob Roland Berger Maryvonne LeConiat Chafika Boucekkine Kiran Kucheria Samia Temtamy Claire Nihoul-Fekete Raja Brauner Marc Fellous 《Human genetics》1992,90(1-2):121-125
Summary A total of 30 cases of 46,XX true hermaphroditism was analysed for Y-DNA sequences including the recently cloned gene for male testis-determination SRY. In 3 cases, a portion of the Y chromosome including SRY was present and, in 2 cases, was localised, to Xp22 by in situ hybridisation. Since previous studies have shown that the majority of XX males are generated by an X-Y chromosomal interchange, the Xp22 position of the Yp material suggests that certain cases of hermaphroditism can arise by the same meiotic event. The phenotype in the 3 SRY-positive cases may be caused by X-inactivation resulting in somatic mosaicism of testis-determining factor expression giving rise to both testicular and ovarian tissues. Autosomal or X-linked mutation(s) elsewhere in the sex-determining pathway may explain the phenotype observed in the remaining 27 SRY-negative cases. 相似文献
36.
Christian Bry Edgar Basset Xavier Rognon François Bonamy 《Environmental Biology of Fishes》1992,35(1):75-84
Synopsis Sibling cannibalism in pike, Esox lucius, larvae and juveniles living in outdoor rearing ponds was studied using stomach contents analysis. For the two initial densities tested (6 and 18 larvae m–2, equivalent to 12 and 36 larvae m–3), cannibalism was non-existent during the larval period (13 to 35 mm total length) and was observed only during the juvenile stages. Initial density of larvae influenced both the date of first detection of cannibalistic individuals and the rate of development of cannibalism in the population. At initial stocking densities of 18 larvae m–2 (36 larvae m–3), cannibalism was observed from 21 days after the start of exogenous feeding (mean total length: 60 mm) onwards. At a mean total length of 100 mm and for initial stocking densities of 6 and 18 larvae m–2, (12 and 36 larvae m–3), the average proportions of cannibals in the populations of juveniles were 7.8% and 41.3% and the cannibals accounted for 15.5% and 65.9% of the total pike biomass, respectively. In stomachs of cannibals, young pike were the dominant prey in terms of weight. Dry weights of invertebrate-prey were lower in cannibals than in non-cannibals of similar size. Cannibalism among pike juveniles was characterized by the prey being swallowed whole and head first in the vast majority of cases. There was a strong positive correlation between predator and prey size and the mouth size of a cannibal was found to be an important constraint determining maximum victim size. The overall mean ratio of pike prey length to pike cannibal length was 66.2% and the average ratio of prey head depth to predator mouth width amounted to 87.6%. Prey size selection could be demonstrated for several length-groups of cannibals. These results are compared with the characteristics of early cannibalism in other fish species. 相似文献
37.
Françoise Farace Anne-Marie Le Ridant Bernard Escudier Thierry Hercend Frédéric Triebel 《Biotherapy》1992,5(1):11-20
We have attempted to improve negative selection procedures for the large scale purification of human CD
in3
–
CD56+ NK cells. In a series of experiments, purifications of NK cells from 108 PBMC were performed by T cell depletion using either direct or indirect anti-CD3 labeling and the Magnetic Activated Cell Separation (MACS) procedure. Contaminating CD3+ cells were still present using either one of these two different T cell depletion protocols as shown by phenotyping IL-2 supplemented cell cultures on day 12. A second cycle of purification was therefore added. When MACS and Dynabeads were compared as complementary procedures to the first MACS cycle starting with 108 cells, the Dynabeads method was found to be superior to the MACS with regard to the elimination of residual T cells. Starting from 109 PBMC, we showed that this MACS+Dynabeads procedure gave similar satisfactory results when compared to the scaling-up of a previously established two steps procedure using Dynabeads. These two approaches (MACS+Dynabeads and 2 cycles of Dynabeads) have been also tested in a clinical setting to purify NK cells from cancer patients prior toin vitro expansion. The results indicate that the two methods are equivalent with respect to purity and recovery rate; a slight advantage in terms of feasibility was found in favor of 2 cycles of Dynabeads. 相似文献
38.
The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed. 相似文献
39.
40.
Vesicular transport of proteins and lipids between distinct subcellular compartments is directly responsible for generating and maintaining the structure of the organelles of the secretory and endocytic pathways in eukaryotic cells. Rapid advances in a variety of experimental systems have resulted in the identification of molecules involved in late steps of the transport process. This article presents a general paradigm for vesicular fusion and reviews the available experimental evidence. 相似文献