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1.
GUNTER WEBER 《The Journal of eukaryotic microbiology》1980,27(1):59-71
SYNOPSIS The term kinete is used in this paper for the cigar-shaped, motile development stages (“vermicule”) of Babesia occurring intra- and extracellularly in hemolymph and ovary (including oocytes) of vectors, hard ticks (Ixodoidea). The structure of, and cyto-chemical activities of hydrolases (acid phosphatase, nonspecific esterase) in the pellicle and the apical complex were studied at the fine-structural level in kinetes of Babesia bigemina Smith & Kilborne, in hemolymph of female Boophilus microplus Canestrini. The cytochemistry of acid hydrolases was studied also in kinetes of Babesia ovis (Babes) Starcovici, in hemolymph and ovary of Rhipi-cephultis bursa Canestrini & Fanzago. The pellicle of the B. bigemina kinetes is composed of 3 membranes (pellicular complex): an outer membrane, ?8 nm thick (the plasmalemma) and 2 inner ones, each ?6 nm thick, lying closely together. The outer membrane appears to be covered by a structureless coat, 3 nm thick. The space between the inner double membrane and the plasmalemma is 7.5 nm. The whole pellicular complex is 30 nm in diameter. The 2 inner pellicular membranes appear to be derived from the endoplasmic reticulum (ER) for the following reasons: (a) a layer of hydrolase-active material is enclosed by these membranes; (b) in the spheroid parasite stages which transform from kinetes inside hemocytes, the inner double membrane is apparently replaced by an ER cisterna; (c) the thickness of each of the inner pellicular membranes is approximately the same as that of the ER membrane. There are circular openings in the pellicular double membrane with average diameters of 100 nm; despite some similarity to micropores, they have a specific structure. The term Intrapellikularfenster (IPF) (intrapellicular windows) or pseudomicropores is proposed for these pellicular differentiations. The margin of an FPF is formed by the 2 inner membranes folding into each other; cytoplasmic, electron-dense material is accumulated alongside this edge. Unlike that of micropores, the plasmalemma of the IPF is not invaginated. The IPF appears as a single, dark ring in tangential sections. At times, rhoptry-like bodies are associated with the openings. The function of the IPF is not known. An intrapellicular opening similar to the IPF, although wider, is present at the apex of the parasite. Its margin coincides with the inner edge of the apical ring. Typical subpellicular microtubuli were not observed in the Babesia kinetes. The apical complex of the B. bigemina kinetes consists of an Apikalschirm (apical umbrella), a crown of microtubuli beneath it, and rhoptries: micronemes are also present in large numbers. The Apikalschirm is located beneath the pellicle of the apical pole of the parasite. It is a wheel-like structure composed of spokes radiating from a wide, hub-like central ring (apical ring). It should be stressed that the apical ring is not identical with the polar ring described as an integral part of the pellicular complex in other Apicomplexa. Beneath each “rib” of the Apikalschirm there is one microtubule (subcostal microtubule). In kinetes of B. ovis the “ribs” are less well developed. In addition, the Apikalschirm is more pointed in kinetes of this species in tick oocytes and ova. The rhoptries of the kinetes are spindle-shaped and largely located directly beneath the Apikalschirm. They are arranged radially, each row being associated with a “rib”. A conoid was not observed. Occasionally, low hydrolytic activity could be detected in micronemes. The rhoptries and the Apikalschirm were always negative for phosphatase and esterase activity. With regard to the number and arrangement of its membranes and to its hydrolase activity, the pellicle of the kinetes of Babesia closely resembles the pellicular complex of the Coccidia. It differs from the latter by the presence of the IFF and by the lack of micropores and of true subpellicular microtubules. In the complexity of their pellicle and in some details of the organization of their apical complex (lack of a conoid; umbrella-like structure), the kinetes of Babesia resemble the ookinetes of the Haemosporidia. 相似文献
2.
Cooperation within Actin Filament in Vertebrate Skeletal Muscle 总被引:56,自引:0,他引:56
When actin molecules form “rigor complexes” with nucleotide-free myosin, tropomn binds calcium with greater affinity and in a cooperative response the remaining actin molecules not cornplexed with myosin are “turned on” even though calcium is absent. 相似文献
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ROLAND K. EBERWEIN ANTON WEBER 《Botanical journal of the Linnean Society. Linnean Society of London》2004,146(4):513-517
Exorhopala ruficeps is a rare parasitic plant of the family Balanophoraceae, endemic to the north-western part of Peninsular Malaysia. It was originally described in Rhopalocnemis and later placed in a new monotypic genus on the basis of the exogenous origin of its inflorescences. A new collection of material enabled a detailed morphological study, the results of which are presented here. Inter alia, it is documented that the inflorescences originate endogenously as in all other Balanophoraceae. However, no volva is formed and the tuber-tissue covering the emerging inflorescence crumbles into pieces. The inflorescence and flower characters established here are neither in full accordance with Rhopalocnemis nor do they justify a genus of its own, but instead place the species in Helosis , which thus becomes a genus of transpacific distribution. The new combination is Helosis ruficeps (Ridl.) R. K. Eberwein. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 513–517. 相似文献
5.
MARY OSBORN JÖRG CASELITZ KLAUS WEBER 《Differentiation; research in biological diversity》1981,20(1-3):196-202
The display of the two distinct intermediate filament proteins, desmin and vimentin, in rat vascular smooth muscle tissue was studied by immunofluorescence microscopy on frozen sections of aorta and other blood vessels. Vascular smooth muscle cells present in these vessels always appeared rich in vimentin. However, staining of sections covering six distinct but contiguous parts of the aorta showed that the number of desmin containing cells was low distal to the truncus brachiocephalicus, but increases until in distal parts of the aorta and in the arteria iliaca communis almost all cells appear positive for desmin. Thus blood vessels show heterogeneity of intermediate filament expression not only in cross-section but can also display heterogeneity along their length. Muscular arteries such as the renal artery and the arteria femoralis, as well as arterioles and veins including the vena jugularis and the vena cava also contain desmin. Thus it may be that low numbers of desmin-positive cells are typical of elastic arteries, while muscular arteries and other blood vessels are characterized by large numbers of desmin-positive cells. We discuss whether desmin-positive and desmin-negative vascular smooth muscle cells may perform different functions and raise the possibility that desmin expression may coincide with the turn on of a specially regulated contractility program. 相似文献
6.
The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press. 相似文献
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WEBER G 《The Biochemical journal》1950,47(1):114-121