UTILITY OF SYNCHRONIZED ALGAL CULTURES IN EXPERIMENTAL TAXONOMY

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; )     

Disruption of the Plasma Membrane Integrity by Cholesterol Depletion Impairs Effectiveness of TRH Receptor-Mediated Signal Transduction via Gq/G11α Proteins

We monitored the radioligand-binding characteristics of thyrotropin-releasing hormone (TRH) receptors, functional activity of G_q/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 G_q/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 G_q/11α proteins.     

Ultrastructural Observations on the Development of the Microsporidian Protozoon Plistophora hyphessobryconis Schaperclaus*

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.     

Genetic cohesion of Eresus walckenaeri (Araneae, Eresidae) in the eastern Mediterranean

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.     

Functional and Structural Chromosome Analyses in Autotetraploid Silene latifolia

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 ).     

Nosema algerae n. sp. (Cnidospora, Microsporida) a Pathogen in a Laboratory Colony of Anopheles stephensi Liston (Diptera, Culicidae)

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.     

A Newly Revised Classification of the Protozoa*

SYNOPSIS The subkingdom Protozoa now includes over 65,000 named species, of which over half are fossil and ～ 10,000 are parasitic. Among living species, this includes ～ 250 parasitic and 11,300 free-living sarcodines (of which ～ 4,600 are foraminiferids); 1.800 parasitic and 5,100 free-living flagellates: ～ 5,600 parasitic “Sporozoa” (including Apicomplexa, Microspora, Myxospora, and Aseetospora); and ～ 2,500 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unmamed. Seven phyla of PROTOZOA are accepted in this classification—SARCOMASTIGOPHORA. LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and representative genera of each are named. the present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of new taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporates most of the major changes that will be made for some time. and that it will be used for many years by both protozoologists and non-protozoologists.