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SYNOPSIS. A sequence of developmental stages of Plistophora hyphessobryconis Schaperclaus, a microsporidian protozoan parasite of the muscular tissue of several species of freshwater fishes, was studied with the electron microscope. The youngest stages observed, ca. 4 × 2 μ, have a single nucleus and their plasm contains only ergastoplasmic lamellae and ribosomes. They are surrounded by a halo of lysed host tissue. They increase in volume to become large sporonts with a great number of nuclei and a thick, 2-layered membrane. Thru schizogony, a corresponding number of sporoblasts is produced within this pansporoblast membrane. Sporoblasts start to develop a thick spore membrane, and a number of smooth-membraned vesicles appear in the plasm. These vesicles fuse to make the outer membrane of the filament. Later, its inner structures originate—the axial electron-dense substance, filling the hollow lumen of the filament, and a middle, electron-transparent layer. The structure of the filament is discussed in relation to its function and with regard to the findings of other authors. The polaroplast is a laminated structure, originating possibly by transformation of endoplasmic reticulum; the polar cap forms its apical part. The cap is also lamellar; its substance reaches into the lumen of the filament for a certain distance. No micropyle was discovered in the shell; the filament is fastened to the polar cap. These observations on microsporidian development and on the structure of their spores are compared with similar data on myxosporidian species. Such a comparison speaks clearly in favor of the complete taxonomic separation of the Microsporidea from the Myxosporidea, the latter being quite different also from other sporozoa sensu lato. 相似文献
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By the help of this method the morphological -variability ofScenedesmus quadricauda during its ontogenesis was studied.During the life cycle the size and shape of the cells vary simultaneously.Some species described on the bases of these features are onlydifferent states of the same species. Genera of the subfamily Crucigenioideae (Scened-esmaceae) havebeen distinguished by very subjective and indistinct features.Examination of the course of their life cycles in the synchronizedcultures showed that only valuable feature for distinguishingthese genera is the mode of reproduction; the mode of orientationof autocoenobia in the mother coenobium. Two basic modes offormation of daughter coenobia were discovered. Based on thesecriteria it is possible to deduce all other types of this wholetaxonomical group. (Received November 24, 1962; ) 相似文献
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PAVEL OSTASOV LENKA BOUROVA LUCIE HEJNOVA JIRI NOVOTNY PETR SVOBODA 《Journal of receptor and signal transduction research》2013,33(5-6):335-352
We monitored the radioligand-binding characteristics of thyrotropin-releasing hormone (TRH) receptors, functional activity of Gq/11α proteins, and functional status of the whole signaling cascade in HEK293 expressing high levels of TRH receptors and G11α. Our analyses indicated that disruption of plasma membrane microdomains by cholesterol depletion did not markedly influence the binding parameters of TRH receptors, but it altered efficacy of signal transduction. The functional coupling between TRH receptor and Gq/11α was assessed by agonist-stimulated [35S]GTPγS binding, and results of these measurements pointed out to significantly lower potency of TRH to mediate G protein activation in the plasma membrane fraction isolated from cholesterol-depleted cells; there was a shift in sensitivity by one order of magnitude to the higher concentrations. A markedly lower sensitivity to stimulation with TRH was also observed in our experiments dealing with determination of hormone-induced Ca2+ response. These data suggest that the intact structure of plasma membranes is an important optimum signal transduction initiated by TRH receptors and mediated by Gq/11α proteins. 相似文献
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JES JOHANNESEN REAS KIEFER MICHAEL VEITH JIRI KRAL 《Biological journal of the Linnean Society. Linnean Society of London》2005,86(1):1-9
The eresid spider genus Eresus is morphologically and ecologically conservative. At least three species occur in Europe. However, deep genetic divergence among geographical samples within two species, E. cinnaberinus and E. sandaliatus , may suggest more cryptic species. In the present study we investigate the genetic cohesion of the third species, Eresus walckenaeri , throughout its eastern Mediterranean distribution range, relative to the E. cinnaberinus–E. sandaliatus species complex. Eresus walckenaeri specimens were monophyletic. Genetic discreteness of E. walckenaeri in a region of sympatry with its sister species in Greece provides evidence for species integrity of E. walckenaeri within the European Eresus species complex. Eresus walckenaeri exhibited high concordance between geographical location and mtDNA genealogy. Two major phylogeographical clades were found in the Greek–Turkish and Syrian–Israel parts of the investigated area, respectively (∼6.5% sequence divergence). Concordance between geography and genetic divergence was further observed between Aegean island samples and their corresponding Greek and Turkish mainland samples, suggesting regional subdivision with gradual but potentially high dispersal propensity. Monophyly and limited regional distribution indicate Mediterranean endemic origin. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 1–9. 相似文献
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SYNOPSIS. A new microsporidan, Nosema algerae n. sp., was found in a laboratory colony of Anopheles stephensi. The microsporidan infects a variety of tissues of both larvae and adults and is highly pathogenic for its host. The structure and life cycle of the microsporidan under the light and electron microscope is described and its relationship to other Nosema species infecting mosquitoes is discussed. 相似文献
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Recent immunocytological and molecular data show that heterochromaticnuclear regions, both constitutive and facultative, are modifieddifferently (cytosine hypermethylation and histone hypoacetylation)and late replicating, when compared to euchromatin. Intrusiveand/or additive (supernumerary) DNA sequences are often functionallysilenced; this is accompanied by their heterochromatinization.In this work we present a number of karyological studies onautotetraploid female cells of Silene latifolia (syn. Melandriumalbum). Immunofluorescence analyses do not indicate any globaldifferences in DNA methylation, histone H4 acetylation, andchromosome replication patterns which could arise as a consequenceof the duplication of the whole chromosome set of the originaldiploid genome. Similarly, the number of silver-positive nucleoliroughly correlates to the ploidy level. Early replication andH4 hyperacetylation have been detected at all subterminal chromosomeregions. This, together with cDNA in situ hybridization patterns,indicates the localization of gene-rich regions. DNA methylationand chromosome replication patterns, but not histone H4 acetylation,show differences among the four X chromosomes present: one tothree X chromosomes were observed as hypermethylated and/orlate replicating. Taken together, the data demonstrate thatthere is no overall silencing of the additional two sets ofautosomes in the tetraploid cells, but the X chromosomes couldbe subject to an irregular dosage compensation. Copyright 1999Annals of Botany Company DNA methylation, histone acetylation, polyploidy, replication patterns, sex chromosomes, Silene latifolia (syn.Melandrium album ). 相似文献
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Scanning Electron Microscopy of Gregarines (Protozoa, Sporozoa) and Its Contribution to the Theory of Gregarine Movement 总被引:2,自引:0,他引:2
SYNOPSIS. Scanning electron microscopy was used to reveal detailed surface structure of 4 septate ( Gregarina cuneata, G. steini, G. rhyparobiae, Pileocephalus blaberae ) and one aseptate species ( Nematocystis elmassiani ) of eugregarines. The epicyte of all these gregarines is differentiated into a system of regular longitudinal folds. In the septate species these folds undulate so that these organisms glide along. The undulatory pattern is absent from Nematocystis , which does not glide. The theories and the mechanism of gregarine gliding are discussed. 相似文献
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JIRI HULCR STEPHANIE A. DOLE ROGER A. BEAVER ANTHONY I. COGNATO 《Systematic Entomology》2007,32(3):568-584
Abstract A cladistic analysis of morphological characters of the subtribe Xyleborina (Curculionidae, Scolytinae) is presented. An examination of individual characters revealed little phylogenetic information in many characters currently used for delimiting genera. Phylogenetically stable characters were used for the evaluation of the contemporary generic concept. The following genera have been recovered as monophyletic: Cnestus, Dryocoetoides, Eccoptopterus, Xylosandrus, Schedlia, Sampsonius and Taurodemus. The following genera have been found to be polyphyletic: Amasa, Ambrosiodmus, Arixyleborus, Coptoborus, Coptodryas, Cryptoxyleborus, Cyclorhipidion, Euwallacea, Leptoxyleborus, Taphrodasus, Theoborus, Webbia, Xyleborinus and Xyleborus. The analysis permitted the resurrection of four genera: Anisandrus, Microperus, Pseudowebbia and Streptocranus. A number of new combinations at specific level are given: Anisandrus cornutus (Schaufuss, 1891), A. dispar (Fabricius, 1792), A. eggersi (Beeson, 1930), A. improbus (Sampson, 1913), A. longidens (Eggers, 1930), A. maiche Stark, 1936, A. obesus (LeConte, 1868), A. sayi Hopkins, 1915, A. apicalis (Blandford, 1894), A. hirtus (Hagedorn, 1904), Microperus myristicae (Schedl, 1939), M. eucalypticus (Schedl, 1938), M. huangi (Browne, 1983), M. intermedius (Eggers, 1923), M. kadoyamaensis (Murayama, 1934), Pseudowebbia armifer (Schedl, 1942), P. seriata Browne, 1963, P. squamatilis (Schedl, 1955), P. trepanicauda (Eggers, 1923), P. curvatus (Browne, 1986), Streptocranus bicolor Browne, 1949, S. bicuspis (Eggers, 1940), S. capucinulus (Schedl, 1942), S. forficatus (Schedl, 1957), S. fragilis Browne, 1949, S. longicauda Browne, 1960, S. longispinis Browne, 1986, S. mirabilis Schedl, 1939, S. usagaricus (Eggers, 1922), S. sexdentatus (Eggers, 1940). The characters most useful for generic‐level taxonomy of Xyleborina were identified and their states refined and illustrated. An accompanying illustrated multiple‐entry electronic key for the updated xyleborine classification has been published on‐line at www.scolytid.msu.edu . 相似文献