Cortical development associated with conjugation of Paramecium

The cortical cytoskeleton of Paramecium is characterized by a complex, polarized and asymmetrical organization. In order to analyse the cortical development of Paramecium tetraurelia during the sexual process of conjugation, different antibodies have been used to follow the development of five cortical components: basal bodies, ciliary rootlets, outer lattice, epiplasm and cytospindle. This study demonstrates that the cortex of Paramecium undergoes an elaborate development process following conjugation. Some of the cortical structures that are not renewed at any other moment of the cell cycle, are resorbed after conjugation and replaced by other newly formed ones. The reorganization of the cortical components occurs according to different morphogenetic waves that spread over the cell surface. The oral system and the preoral suture line act as morphogenetic epicentres.Junta de Andalucía y Departamento General de Investigación Científica y Técnica (DGICYT) PB91/062

Complex Carbohydrates in the Cyst Wall of Histriculus similis

The ultrastructure of the cyst wall has been studied in severa! hypotrichous ciliates. In Oxytrichafallax (Grimes, 1973),Pleurotricha sp. (Matsusaka, 1976), Stylonychia mytilus (Walker et al., 1975), Gastrostyla steinii (Walker et al., 1980) and Laurentiella acuminata (Gutierrez et al., l 980), the cyst wall is composed of four layers called, from outside to inside :the ectocyst, meso­ cyst, endocyst and granular layers. In these ciliates a resorption of cilia and kinetosomes occurs during encystment, and the mature cyst is termed kinetosome resorbing. Diophrys scutum (Walker & Maugel , 1980) has a three layered cyst wall and the mature cyst is non kinetosome resorbing. In the present work a structural and cytochemical study of the cyst wall in Histriculus similis was carried out by means of light microscopy and transmission electron microscopy

Étude ultrastructurale de la morphogenese corticale. De régénération chez le cilié hypotriche histriculus similis

La régénération chez Histriculus similis a été étudiée en microscopie électronique. Les premiers signes du procesus de régénération s'observenl une heure apres le traitement par l'urée. Pendant la morphogenese corticale de régénération tanl du primordium oral que des primordiums de la ciliature parorale et des cirres, les états premiers sont constitués par des couples de cinétosomes, qui portent des microtubules postciliaires dans le cinétosome postérieur et des microtubules transverses a l'antérieur. L'orientation de ces couples dépend du primordium qu'ils vonl produire. Une fois que les couples de cinétosomes sont alignés, a Iieu une prolifération de nouveaux cinélosomes proches de ces couples. Plus tard il y a une fragmentation transversale de ces primordiums , a l'exception du primordium paroral qui se divise longitudinalement.The cortical morphogenesis of regeneration in Histriculus similis has been studied in this work at level of electronic microscopy. The first signs of the regeneration process become evident one hour after the treatment with urea. During the early steps of the cortical morphogenesis of regeneration, the oral primordium , paroral ciliation primordium and the ciliary streaks, are formed by pairs of kinetosomes. These pairs carry postciliary microtubules in the posterior kinetosome and transverse microtubules in the anterior one. The orientation of these pairs of kinetosomes depends on the type of primordium that is going to be formed. Once the pairs of kinetosomes are aligned, there is a proliferation of new kinetosomes in the vicinity of these pairs of kinetosomes. Afterwards there is a transversal fragmentation of the above mentioned primordia, with the exception of the paroral primordium that is longitudinally divided

A purL mutant of Sinorhizobium fredii HH103 is symbiotically defective and altered in its lipopolysaccharide

The pleiotropic phenotype of an auxotrophic purL mutant (SVQ295) of Sinorhizobium fredii HH103 has been investigated. SVQ295 forms colonies that are translucent, produce more slime and absorb less Congo red than those of wild-type strain HH103. SVQ295 did not grow in minimal medium unless the culture was supplemented with thiamin and adenine or with thiamin and AICA-riboside (5-aminoimidazole-4-carboxamide 1-b-D-ribofuranoside), an intermediate of purine biosynthesis. Bacterial cultures supplemented with AICA-riboside or adenine reached the same culture density, although the doubling time of SVQ295 cultures containing AICA-riboside was clearly longer. S. fredii SVQ295 induced pseudonodules on Glycine max and failed to nodulate six different legumes. On Glycyrrhiza uralensis, however, nodules showing nitrogenase activity and containing infected plant cells were formed. SVQ295 showed auto-agglutination when grown in liquid TY medium and its lipopolysaccharide (LPS) electrophoretic profile differed from that of its parental strain HH103-1. In addition, four monoclonal antibodies that recognize the LPS of S. fredii HH103 failed to recognize the LPS produced by SVQ295. In contrast, 1H-NMR spectra of K-antigen capsular polysaccharides (KPS) produced by SVQ295 and the wild-type strain HH103 were similar. Co-inoculation of soybean plants with SVQ295 and SVQ116 (a nodA mutant derivative of HH103) produced nitrogen-fixing nodules that were only occupied by SVQ116

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

El ciclo celular y procesos cariológicos relacionados con la regeneración en laurentia acuminata

La división celular es un proceso complejo, mediante el cual a partir de una célula se originan dos células hijas que, en la mayoría de los casos, son idénticas entre sí e idénticas a la célula de donde proceden. Este proceso, especialmente en las células eucarióticas, implica cambios morfológicos y fisiológicos considerables, que incluyen el cese de la síntesis de ADN, ARN y proteínas, la desaparición de la membrana nuclear y la aparición de los cromosomas cuya estructura, número, fisiología y comportamiento son característicos de cada tipo celular. Pero, como es sabido, la división celular, pese a ser el más estudiado, no es el único proceso importante que llevan a cabo las células en lo que se refiere a la transmisión de la información genética a las células hijas. En efecto, durante el periodo comprendido entre dos divisiones celulares (interfase celular) tiene lugar la duplicación del material celular (ADN, ARN y proteínas) para su ulterior reparto entre las células hijas. Ello ha hecho que se divida la interfase de estas células en distintos periodos que, junto con el de división, constituyen el llamado ciclo celular. Según HOWARD y PELC, el periodo interfásico se puede dividir, a su vez, en los tres periodos siguientes: G1: Es el periodo comprendido entre el final de la división celular y el comienzo de la síntesis de ADN. S: Es el periodo de síntesis de ADN. G2: Es el periodo preparatorio para la división celular y se prolonga desde el final del periodo S hasta el comienzo de la división celular. Esta división de la interfase, aunque puede considerarse norma general, no se da siempre pues se han descrito ciclos celulares en los que falta, o es muy corto alguno de los periodos G. Podemos establecer los siguientes hechos: 1) Aunque son muchos los trabajos realizados sobre el proceso de división de los ciliados, existen relativamente pocos datos sobre las restantes fases del ciclo celular. 2) Entre los ciclos celulares descritos se observan grandes diferencias en cuanto a la duración de los distintos intervalos (algunos pueden faltar), así como en lo que respecta al comportamiento del macro y del micronúcleo. 3) También son escasos y de resultados a veces contradictorios, los estudios sobre el comportamiento del macro y del micronúcleo durante la regeneración cortical. Nosotros hemos creído interesante abordar el problema del estudio del ciclo celular en Laurentia acuminata ya que esta especie, posiblemente muy próxima a Stylonchia, es muy apropiada no sólo para la aplicación de técnicas citofotométricas sino también para la inducción controlada de daños corticales. Ello nos permite, además de establecer el ciclo celular normal de dicha especie, abordar el problema de la interacción entre la regeneración cortical y los fenómenos nucleares concomitantes. De acuerdo con ello, dividiremos la exposición de la parte experimental de este trabajo en dos capítulos. En el primero se hace una descripción el ciclo celular completo, centrando la atención en la cronología de los distintos periodos en el macro y el micronúcleo. En el segundo capítulo, se hace en primer lugar, la descripción del comportamiento del macro y del micronúcleo subsiguiente a la inducción de un daño cortical y luego, mediante el empleo de inhibidores, se estudia la posible interacción entre ambos fenómenos

Macronuclear division of the ciliate laurentiella-acuminata

The distribution of DNA in the macronuclear division of the Hypotrich ciliate Laurentiella acuminata has been studied by cytophotometric techniques. The mean degree of inequality found in the distribution of DNA between sister cells is 10.05 %. Differences in DNA contents in randomly-paired cells is greater than in sister cells, this result could be due to accumulation of small differences over many divisions.La distribution de PADN lors de la division macronucléaire du cilié hypotriche Laurentiella acuminata a été étudiée par cytophotométrie. Le degré moyen d'inégalité de la répartition de PADN entre cellules sceurs est 10,05 p. cent. Les différences de teneur en ADN sont plus grandes entre deux cellules tirées au sort qu'entre deux cellules sceurs: ce résultat peut étre expliqué par l'accumulation des petites différences qui apparaissent á chaque division

The cyst of urostyla grandis (hypotrichida : Urostylidae) : ultrastructure and evolutionary implications

L'examen , en microscopie électronique, du kyste d'Uros1y la grandis a révélé que sa paroi se compose de trois couches : un exokyste fibrillaire, un endokyste a structure homogéne et une couche granulaire avec une structure granulaire ou fibrillaire. Le maintien de quelques cinétosomes, microtubules subpellicula ires et d'autres particularités permettent de distinguer ces kystes des kystes KR et NKR. On propose d'ajouter un nouveau groupe a la classification de WALKER et MAUG EL. On commente quelques relations phylogéniques reposan! sur des caractéristiques comparatives.U ltrastructural study of Urostyla grandis cysts shows that the cyst wall is constitued of three layers :a fibrous ectocyst, a structurally homogeneous endocyst and a granular layer that exhibits a dispersed granular or fibrillar structure. The maintenance of only a few kinetosomes and scattered bundles of subpellicular microtubules, and other particular ities distinguish the Urostyla grandis cyst, both KR and NKR cysts. It is proposed to amplify the WALKER and MAUGEL classification by an additional group. Based on comparative features, sorne of the phylogenetic relations are discussed

Unusual characteristics of ciliate actins

Actin is a cytoskeletal protein that is ubiquitous in eukaryotes, hence the corresponding genes and proteins have been isolated from numerous organisms as different as animals, plants, fungi and protozoa. Several atomic models are available for the monomeric as well as the filamentous form, and more than 70 proteins that bind actin and control filament dynamics have been isolated from diverse eukaryotes. Moreover, the function and dynamics of the actin cytoskeleton in several eukaryotic systems have been depicted in depth. Unlike other protozoa, such as amoeba, actin is not an abundant protein in ciliates, whose cytoskeleton is mainly composed of microtubular arrays. Ciliate actin has been studied in several species, and it was established early on that this ciliate protein is very different from that of other eukaryotes. Similarly, the actin-binding proteins studied in ciliates display great differences with those of other eukaryotes. Consequently, ciliate actin has been considered as "unconventional," and this review focuses on molecular data leading to this conclusion.Dirección General de Investigación Científica y Técnica (DGICYT) PB97-0710-C02-0

α-Tubulin of Histriculus cavicola (Ciliophora; Hypotrichea)

Se ha secuenciado un fragmento de un gen de la a-tubulina, amplificado por PCR, del cil iado hipotrico Histriculus cavicola. Este fragmento, de 1182 pb, contiene un codón de terminación (UAA) en la fase de lectura, que en otros ciliados hipotricos codifica la glutamina. La comparación de los genes de la cx-tubulina de varias clases de ciliados ha mostrado que algunas posiciones de aminoácidos pueden servir para distingu i r estos grupos taxonóm icos.An α-tubulin gene fragment amplified by PCR from the hypotrichous ciliate Histriculus cavicola has been sequenced. This fragment, 1182 bp long, contains an in-frame "stop" codon (UAA), which i n other hypotrichous species codes for a glutamine residue. The comparison of the a-tubu li n genes from severa!ciliates classes have revealed amino acid positions which could serve to distinguish these taxonomic groups