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排序方式: 共有313条查询结果,搜索用时 15 毫秒
1.
A González-Fernández J Sans P Aller C de la Torre 《Cell biology international reports》1985,9(3):237-243
Bromosubstitution for most of the S period in synchronous populations of Allium cepa L. meristematic cells resulted in a delay in the late S-G2 transition point where protein synthesis is needed for later mitotic entrance to occur. This retardation in the position of the transition point was not accompanied by the expected delay in the entrance into mitosis, suggesting that such protein synthesis is a requisite, but not a timer for prophase triggering. 相似文献
2.
The events that characterize egg formation and maturation inPteris cretica were investigated using transmission electronmicroscopy and electron microscope microprobe analysis. Theydid not differ significantly from those described for sexuallyreproducing ferns. The significance of these findings is discussedin relation to current theories concerning phase change in ferns. Pteris cretica, fern, apogamy, agamospory, transmission electron microscopy, oogenesis 相似文献
3.
Direct measurements of net production rates and pore water profiles of solutes in the fine-grained sediments of Saginaw Bay, imply corresponding steady-state fluxes to the overlying water of 1.1–1.3 (I), 450–1010 (NH4
+), 1250–2650 (Si(OH)4), 3000–3400 (Ca2+), 440–1330 (Mg2+), 1.5–728 (Fe2+), and 179–281 (Mn2+) moles/m2/day and 11.0–11.8 (alkalinity) meq/m2/day at 17.5 °C. Silica production rates in sediments apparently follow first order kinetics with a rate coefficient of 0.09/day and a steady-state silica concentration of 1.2 mM at 23.5°C. The remaining solutes follow kinetics approximately independent of solute concentration over the range of concentrations observed. Measured solute production rates are consistent with observed solute profiles only if lateral diffusion gradients are maintained in the sediments by the burrowing and irrigation activity of benthic organisms such asChironomous, the dominant burrower in Saginaw Bay. Assuming that solute fluxes from Saginaw Bay are representative of all of the post-glacial sediments of Lake Huron, the iodine flux from sediments is comparable to the total fluvial input of iodine. The extrapolated silica fluxes from Lake Huron sediments balance the estimated biogenic silica flux to the sediments. 相似文献
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Genotype and phenotype associations with drought tolerance in barley tested in North Africa 总被引:8,自引:0,他引:8
B P FORSTER R P ELLIS J MOIR V TALAMÈ M C SANGUINETI R TUBEROSA D THIS B TEULAT-MERAH I AHMED S A E E MARIY H BAHRI M EL OUAHABI N ZOUMAROU-WALLIS M EL-FELLAH M BEN SALEM 《The Annals of applied biology》2004,144(2):157-168
A review is presented of genetic strategies deployed in a 3-yr project on drought tolerance in barley. Data were collected on genetic, physiological and agronomic traits in non-irrigated and irrigated field trials in Egypt, Morocco and Tunisia. A wide range of barley germplasm (developed from African and European cultivars, adapted landraces and wild barleys) was tested, and positive traits were found in each gene pool. The contrasting environments of the three North African countries had major effects on plant/genotype performance. Genetic effects were also detected, as were genotype × environment interactions. A range of strategies were deployed to investigate the physiology and genetics of quantitative traits associated with field performance. Quantitative trait locus (QTL) analysis was performed using backcross lines, recombinant inbred lines and doubled haploid mapping populations. A detailed genetic map was generated in the Tadmor × (ER/Apm) recombinant inbred lines, an important mapping population specifically developed by ICARDA (Centre for Agricultural Research in Dry Areas) and CIMMYT (International Maize and Wheat Improvement Center) to study drought. Quantitative trait loci (QTLs) for grain yield and other important morphological and physiological traits were also identified in a population of doubled haploids derived from F2BCj plants from a cross between a cultivar and a wild barley accession. Significantly, the wild parental line was found to contribute a number of positive alleles for yield. Effects of major developmental genes could explain many of the responses observed. QTLs were found to cluster around major genes controlling flowering time (sghI), plant stature (sdwI and arie.GP) and ear type (vrsl), and it is highly likely that the associations represent pleiotropic effects. Some QTLs were associated with candidate genes such as dehydrins and rubisco activase. One of the most significant results was the identification and generation of material that out performed the best local standards in the three participating North African countries; the selected lines have now entered local breeding programmes. The strategies adopted provided information on physiological traits, genotypes and genetic markers that could be used for marker-assisted selection. Target QTLs and their associated genetic markers may be deployed in marker assisted selection programmes to match crop phenology to the field environment. 相似文献
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J. del Mazo J. A. Abrisqueta Amalia Pérez-Castillo V. Aller M. Angeles Martín Lucas M. Luisa de Torres M. José Martín 《Human genetics》1978,44(1):105-108
Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports. 相似文献
8.
Modifications of anionic-lipid domains preceding membrane fusion in guinea pig sperm 总被引:19,自引:15,他引:4
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The relationship between anionic-lipid concentration and the functional properties of plasma-membrane domains was explored using the guinea-pig sperm membrane as a model, with polymyxin B (PXB) as a probe. Areas of plasmalemma specialized for fusion during the acrosome reaction had a higher affinity for the probe than adjacent nonfusigenic regions. In addition, capacitation--a process preceding acrosome:plasma-membrane fusion--markedly enlarged the area susceptible to PXB binding over the acrosomal cap. Protease treatment mimicked capacitation by increasing the acrosome-reaction incidence as well as PXB binding, at enzyme concentrations not affecting the surface coat nor altering filipin/sterol localization. Both proteolytic digestion and capacitation failed to augment PXB- or filipin-affinity in nonfusigenic zones, such as the post-acrosomal segment, including its particle-free maculae. Incubation of sperm in capacitating medium supplemented with 32P-labeled phosphate, followed by lipid extraction, thin-layer chromatography, and autoradiography, revealed a radioactive band comigrating with cardiolipin and phosphatidic acid. Vermiform protrusions elicited by PXB in the outer lamellae of cardiolipin- phosphatidylcholine liposomes resembled those seen in fusional regions of sperm membrane. We conclude that (a) differing concentrations of anionic lipids are found in adjacent domains of the sperm plasma membrane; (b) these domains mirror the functional regions of the membrane, with higher anionic-lipid concentrations localized over fusional zones; (c) the surface coat does not participate in the maintenance of such domains; (d) anionic-lipid synthesis may contribute to their formation; and (e) anionic-lipid concentrations increase as the membrane becomes fusionally competent, indicating that cellular modulation of lipid domains accompanies regulation of membrane function. 相似文献
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10.
P Aller 《Revista Espanola de Fisiología》1987,43(4):415-420
The effect of mitomycin C on the accumulation of specific mRNAs was studied in asynchronously growing Swiss 3T3 cells, as well as in synchronously growing serum stimulated ts13 cells (a temperature-sensitive mutant from the BHK cell line). It was observed that the steady-state level of p53 RNA experienced some increase in 3T3 cells treated for 24 h with the drug. In addition, mitomycin when applied to serum stimulated ts13 cells increased the level of p2F1 RNA. Mitomycin diminished the level of core histone H3 RNA, a finding consistent with the inhibitory action of this compound on DNA replication. 相似文献