Rac Activation: P-Rex1 — A Convergence Point for PIP3 and Gβγ?

AbstractP-Rex1, a novel Rac activator, has been identified in the first biochemical purification of a guanine nucleotide exchange factor for GTPases of the Rho family. P-Rex1 is synergistically activated by PIP3 and Gβγ and may act as a coincidence detector for these signaling molecules

A pharmacological cocktail for arresting actin dynamics in living cells.

The actin cytoskeleton is regulated by factors that influence polymer assembly, disassembly, and network rearrangement. Drugs that inhibit these events have been used to test the role of actin dynamics in a wide range of cellular processes. Previous methods of arresting actin rearrangements take minutes to act and work well in some contexts, but can lead to significant actin reorganization in cells with rapid actin dynamics, such as neutrophils. In this paper, we report a pharmacological cocktail that not only arrests actin dynamics but also preserves the structure of the existing actin network in neutrophil-like HL-60 cells, human fibrosarcoma HT1080 cells, and mouse NIH 3T3 fibroblast cells. Our cocktail induces an arrest of actin dynamics that initiates within seconds and persists for longer than 10 min, during which time cells maintain their responsivity to external stimuli. With this cocktail, we demonstrate that actin dynamics, and not simply morphological polarity or actin accumulation at the leading edge, are required for the spatial persistence of Rac activation in HL-60 cells. Our drug combination preserves the structure of the existing cytoskeleton while blocking actin assembly, disassembly, and rearrangement, and should prove useful for investigating the role of actin dynamics in a wide range of cellular signaling contexts

The Effects of Seated Position on Occupant Kinematics in Low-speed Rear-end Impacts

Copyright © 2005 SAE International Seventeen rear-end impacts with a nominal 8 km/hr change in velocity to five human subjects in four positions were conducted. The four seated positions consisted of the Normal position, with the torso against the seat back, looking straight ahead, hands on the steering wheel, and feet on the floor; the Torso Lean position, with the torso leaned forward approximately 10 degrees away from the seat back; the Head Flex position, with the head flexed forward approximately 20 degrees from normal; and the Head Flex / Torso Lean position, with the head flexed forward approximately 20 degrees from normal and the torso leaned forward approximately 10 degrees from normal position. Relative to the Normal position, it was found that in both positions involving the torso lean, the peak head acceleration for the subject’s head was reduced during the head-restraint impact. Further, the inertial acceleration of the head due to the forces on the neck, prior to the head rest impact, was somewhat higher for the two positions involving torso lean. Minor, transient, whiplash associated disorder (WAD) symptoms were noted. The nominal change in velocity used in this study appears to be of a reasonable magnitude to continue human subject out of position (OOP) testing

Longidorus israelensis sp. n. (Nematoda : Dorylaimoidea), a parasite of carrot in Israel

#Longidorus israelensis sp. n., espèce parthénogénétique associée à des dégâts sur carotte en Israël, est décrite. Cette espèce est caractérisée par une grande longueur du corps (7,1-9,1 mm), une région labiale légèrement en relief et aplatie frontalement, des poches amphidiennes non bilobées, un long odontostyle (125-135 micromètres) et une queue courte, sub-hémisphérique (36-46 micromètres). Elle présente également une disposition inhabituelle des noyaux des glandes oesophagiennes. Les carottes attaquées par #L. israelensis sp. n. voient la croissance de leurs racines stoppée, le départ de racines secondaires et l'apparition de renflements à l'extrémité des racines. Il en résulte des carottes déformées et divisées en pluseiurs parties. Le nématode est généralement rencontré à des profondeurs du sol variant de 20 à 40 cm mais il peut migrer jusqu'à 40-100 cm de profondeur de façon à survivre pendant la période estivale chaude et sèche. (Résumé d'auteur