Identification and localisation of chitinases induced in the roots of potato plants infected with the potato cyst nematode Globodera pallida

L'analyse par électro-transfert d'extraits provenant de racines de pomme de terre infestées par le nématode à kyste #Globodera pallida$ et leur marquage par un anticorps polyclonal contre les chitinases a révélé l'induction et l'augmentation de l'intensité de plusieurs bandes correspondant aux chitinases et ayant une masse moléculaire s'étageant de 18 à 80 kDa. L'immuno-marquage par l'anticorps de sections de racines infestées a démontré la localisation extracellulaire des chitinases et leur concentration dans le cortex, l'endoderme et le péricycle. Le rôle de ces chitinases dans le contexte de défense de la plante contre les attaques d'agents pathogènes est discuté. (Résumé d'auteur

The lipid content and fatty acid composition of hatched second stage juveniles of Globodera rostochiensis and G. pallida

Les juvéniles de deuxième stade (J2) de #Globodera rostochiensis$âgés d'un jour (éclos dans les diffusats de racines de pomme de terre) contiennent en moyenne 29,2$ en contiennent en moyenne 27,2%. Les lipides des J2 de #G. rostochiensis$J2 sont composés de 72,8$ J2 sont composés de 73,0% de lipides neutres, 13,2% d'acides gras libres et 13,8% de phospholipides. 77,4% des acides gras totaux de #G. rostochiensis$et 80,6$ sont insaturés. Les deux espèces présentent un profil d'acides gras similaire. Vingt acides gras ont été identifiés, allant de C14 à C22 ; les principales classes de lipides sont surtout composées d'acides gras en C20 (50-60%) et C18 (30-35%). Les trois acides gras les plus abondants caractérisés chez les deux espèces sont C20:4, C20:1 et C18:1, représentant à eux seuls plus de 60% du total. Les J2 de #G. rostochiensis$ récoltés toutes les 24 heures au cours des première et seconde semaines après l'exposition aux PRD, présentent la même composition en acides gras que les J2 récoltés toutes les 96 heures pendant les troisième et quatrième semaines. (Résumé d'auteur

Immunocytochemical studies on the occurence of gamma-aminobutyric acid in the nervous system of the nematodes Panagrellus redivivus, Meloidogyne incognita and Globodera rostochiensis

Un antisérum polyclonal a été utilisé en immunofluorescence indirecte pour démontrer la présence d'acide gamma-aminobutyrique - un inhibiteur possible de la transmission de l'influx nerveux aux muscles - chez #Panagrellus redevivus et chez les juvéniles de deuxième stade (J2) de #Meloidogyne incognita. Chez #P. redivivus, il a été observé une immunoréactivité, présumée GABA, dans la corde nerveuse dorsale, dans la corde ventrale ainsi que dans certaines cellules nerveuses et les commissures qui ceinturent le nématode entre les cordes nerveuses. Une immunoréactivité a été également observée autour du pharynx et dans l'anneau nerveux. Chez les J2 de #M. incognita, on a détecté cette immunoréactivité dans les nerfs et les cellules de la corde nerveuse ventrale. La coloration à l'immunogold après inclusion de J2 de #Globodera rostochiensis$ traités à l'osmium a montré une immunoréactivité, présumée GABA, dans les procès de neurones des cordes nerveuses ventrale et dorsale, et dans le cytoplasme et le noyau de certaines cellules de la corde ventrale. La position de ces neurones dans les cordes nerveuses indique qu'ils sont probablement des neurones moteur inhibiteurs. Dans l'anneau nerveux, l'immunoréactivité a été observée dans les procès neuronaux et dans un corps cellulaire, probablement le neurone moteur de l'anneau ventral. (Résumé d'auteur

Calcium regulation of androgen receptor expression in the human prostate cancer cell line LNCaP

Elevation of intracellular calcium levels in the presence of normal androgen levels has been implicated in apoptotic prostate cell death. Since the androgen receptor (AR) plays a critical role in the regulation of growth and differentiation of the prostate, it was of interest to determine whether Ca2+ would affect the expression of androgen receptor messenger RNA (mRNA) and protein, thus affecting the ability of androgens to control prostate function. AR-positive human prostate cancer cells, LNCaP, were incubated with either the calcium ionophore A23187 or the intracellular endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin. Subsequently, AR mRNA and protein levels were assessed by Northern and Western blot analysis. Both A23187 and thapsigargin were found to down-regulate steady state AR mRNA levels in a time- and dose-dependent manner. AR mRNA began to decrease after 6-8 h of incubation with 10(-6) M A23187 or 10(-7) M thapsigargin, reaching a nadir at 16 and 10 h of incubation, respectively. In contrast, control mRNA (glyceraldehyde 3-phosphate dehydrogenase) did not change significantly during the treatments with either A23187 or thapsigargin. AR protein levels were found to be decreased after 12 h of incubation with either 10(-6) M A23187 or 10(-7) M thapsigargin. The decrease in AR mRNA and protein seemed to precede apoptosis, since neither A23187 (24 h) nor thapsigargin (30 h) was found to alter cell morphology within the treatment time. Cycloheximide and actinomycin D were unable to change the calcium-mediated decrease in AR mRNA, ruling out the necessity for de novo protein synthesis or a change in mRNA stability. Moreover, the decrease in AR mRNA induced by calcium does not seem to involve protein kinase C- or calmodulin-dependent pathways, since inhibitors of these cellular components had no effect. Nuclear run-on assays demonstrated little or no effects of either A23187 or thapsigargin treatment on AR gene transcription (8 h and 10 h). In conclusion, these studies show that intracellular calcium seems to be a potent regulator of AR gene expression in LNCaP cells

Fostering Preservice Teacher Identity in Science through a Student-Selected Project

This article addresses the problem of authentic student engagement in the science classroom by incorporating a semester long research and writing assignment that enables students to investigate scientific topics related to strong personal, career, or health interests

Thinking about growth : a cognitive mapping approach to understanding small business development

School of Managemen

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

The {approx}80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching {approx}800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to a few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to {approx}20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km{sup 3}, scoria cone--0.02 km{sup 3}, and lavas--0.03 km{sup 3}. Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of {approx}21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of volcanic surfaces, and failure to account for this resulted in previous erroneous interpretation that the volcano is polycyclic (eruptions separated by 1,000s-10,000s of years). Lathrop Wells volcano provides an example of the wide range of eruptive processes that can occur with little change in major element composition; the variation in explosive and effusive processes, including their simultaneous occurrence, must result entirely from fluid dynamic, crystallization, and degassing processes in the ascending multiphase magma. The volcano also provides key analog information regarding processes that are important for volcanic risk assessment at the proposed Yucca Mountain radioactive waste repository, {approx}18 km north of the volcano

Investigation of the ferromagnetic transition in the correlated 4d perovskites SrRu1−x_{1-x}Rhx_xO3_3

The solid-solution SrRu$_{1-x}$Rh$_x$O$_3$ ($0\le x \le1$) is a variable-electron-configuration system forming in the nearly-cubic-perovskite basis, ranging from the ferromagnetic 4$d^4$ to the enhanced paramagnetic 4$d^5$. Polycrystalline single-phase samples were obtained over the whole composition range by a high-pressure-heating technique, followed by measurements of magnetic susceptibility, magnetization, specific heat, thermopower, and electrical resistivity. The ferromagnetic order in long range is gradually suppressed by the Rh substitution and vanishes at $x \sim 0.6$. The electronic term of specific-heat shows unusual behavior near the critical Rh concentration; the feature does not match even qualitatively with what was reported for the related perovskites (Sr,Ca)RuO$_3$. Furthermore, another anomaly in the specific heat was observed at $x \sim 0.9$.Comment: Accepted for publication in PR