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71.
ZDENK IKA 《The Journal of eukaryotic microbiology》1978,25(1):50-56
SYNOPSIS. The fine structure of schizonts and free merozoites of the neogregarine Farinocystis tribolii Weiser, and their development in the fat body of larval Tribolium castaneum were studied.
The surface of a multinucleate schizont and that of a uninucleate merozoite is covered by a double-layered membrane. Rhoptries and micronemes are present. The cytoplasm is packed with ribosomes and also contains dark bodies. Mitochondria are of the vesicular type. The spherical nucleus of the schizont and merozoite contains a large nucleolus. The anterior end of the merozoite has a typical conoidal complex composed of a conoid and a polar ring with 22 subpellicular mirotubules projecting from it.
New findings are a membranous septum across the body of the merozoite at 2/3 of its length below the nucleus and a highly osmiophilic spiral structure in the perinuclear space close to the Golgi complex. In addition, we found some "developmental stages" of the latter structure. 相似文献
The surface of a multinucleate schizont and that of a uninucleate merozoite is covered by a double-layered membrane. Rhoptries and micronemes are present. The cytoplasm is packed with ribosomes and also contains dark bodies. Mitochondria are of the vesicular type. The spherical nucleus of the schizont and merozoite contains a large nucleolus. The anterior end of the merozoite has a typical conoidal complex composed of a conoid and a polar ring with 22 subpellicular mirotubules projecting from it.
New findings are a membranous septum across the body of the merozoite at 2/3 of its length below the nucleus and a highly osmiophilic spiral structure in the perinuclear space close to the Golgi complex. In addition, we found some "developmental stages" of the latter structure. 相似文献
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73.
Repeated epilation (Er) is a radiation-induced, autosomal, incomplete dominant mutation in mice which is expressed in heterozygotes but is lethal in the homozygous condition. Many effects of the mutation occur in skin: the epidermis in Er/Er mice is adhesive (oral and nasal orifices fuse, limbs adhere to the body wall), hyperplastic, and fails to undergo terminal differentiation. Skin from fetal +/+, Er/+ and Er/Er mice at ages pre- and postkeratinization examined by light, scanning, and transmission electron microscopy showed marked abnormalities in tissue architecture, differentiation, and cell structure; light and dark basal epidermal cells were separated by wide intercellular spaces, joined by few desmosomes, and contained phagolysomes. The numbers of spinous, granular, and superficial layers were highly variable within any given region and among various regions of the body. In some areas, 2-8 layers of granular cells, containing large or diminutive keratohyalin granules, extended to the epidermal surface; in others, the granular layers were covered by several layers of partially keratinized or nonkeratinized cells. In rare instances, a single or small group of cornified cells was present among the granular layers but was not associated with the epidermal surface. Both the granular and nonkeratinized/partially keratinized upper epidermal layers Er/Er skin gave positive immunofluorescence with antiserum to the histidine-rich, basic protein, filaggrin. Proteins in epidermal extracts from +/+, Er/+ and Er/Er mice were separated and identified by radio- and immunolabeling techniques. The Er/Er extract was missing a 26.5- kdalton protein and had an altered ratio of bands in the keratin region. The 26.5-kdalton band was histidine-rich and cross-reacted with the antiserum to rat filaggrin. Several high molecular weight bands present in both Er/Er and +/+ extracts also reacted with the antiserum. These are presumed to be the precursors of filaggrin and to account for the immunofluorescence om Er/Er epidermis even though the product protein is absent. The morphologic and biochemical data indicated that the genetic defect has a general and profound influence on epidermal differentiation, including alteration of two proteins (filaggrin and keratin) important in normal terminal differentiation, tissue architecture, and cytology. Identification of epidermal abnormalities at early stages of development (prekeratinization) and defective structure of other tissues and gross anatomy suggest that the mutation is responsible for a defect in same regulatory step important in many processes of differentiation and development. 相似文献
74.
The mutation rates of di-, tri- and tetranucleotide repeats in Drosophila melanogaster 总被引:4,自引:1,他引:3
Schug MD; Hutter CM; Wetterstrand KA; Gaudette MS; Mackay TF; Aquadro CF 《Molecular biology and evolution》1998,15(12):1751-1760
In a recent study, we reported that the combined average mutation rate of
10 di-, 6 tri-, and 8 tetranucleotide repeats in Drosophila melanogaster
was 6.3 x 10(-6) mutations per locus per generation, a rate substantially
below that of microsatellite repeat units in mammals studied to date (range
= 10(-2)-10(-5) per locus per generation). To obtain a more precise
estimate of mutation rate for dinucleotide repeat motifs alone, we assayed
39 new dinucleotide repeat microsatellite loci in the mutation accumulation
lines from our earlier study. Our estimate of mutation rate for a total of
49 dinucleotide repeats is 9.3 x 10(-6) per locus per generation, only
slightly higher than the estimate from our earlier study. We also estimated
the relative difference in microsatellite mutation rate among di-, tri-,
and tetranucleotide repeats in the genome of D. melanogaster using a method
based on population variation, and we found that tri- and tetranucleotide
repeats mutate at rates 6.4 and 8.4 times slower than that of dinucleotide
repeats, respectively. The slower mutation rates of tri- and
tetranucleotide repeats appear to be associated with a relatively short
repeat unit length of these repeat motifs in the genome of D. melanogaster.
A positive correlation between repeat unit length and allelic variation
suggests that mutation rate increases as the repeat unit lengths of
microsatellites increase.
相似文献
75.
76.
长春净月潭地区土壤跳虫的生态分布 总被引:9,自引:1,他引:8
土壤动物直接参与土壤形成,它与土壤微生物的相互配合,对植物凋落物的分解起着十分重要的作用。土壤跳虫是土壤动物中最重要的类群之一。关于它的生态分布,目前国内报道不多。东北师范大学和日本九州大学合作,对长春净月潭地区的土壤跳虫进行了初步调查。 相似文献
77.
Background
Poxviruses are important pathogens of humans, livestock and wild animals. These large dsDNA viruses have a set of core orthologs whose gene order is extremely well conserved throughout poxvirus genera. They also contain many genes with sequence and functional similarity to host genes which were probably acquired by horizontal gene transfer. 相似文献78.
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