Cerebrospinal fluid gamma aminobutyric acid levels in migraine.

Gamma-Aminobutyric acid (GABA) levels in cerebrospinal fluid were measured in seven patients with tension headache and 12 patients with migraine. GABA was detected only during the migraine attack. The results suggest disordered GABA metabolism in migraine.     

The Wiskott-Aldrich syndrome protein directs actin-based motility by stimulating actin nucleation with the Arp2/3 complex.

Actin polymerization at the cell cortex is thought to provide the driving force for aspects of cell-shape change and locomotion. To coordinate cellular movements, the initiation of actin polymerization is tightly regulated, both spatially and temporally. The Wiskott-Aldrich syndrome protein (WASP), encoded by the gene that is mutated in the immunodeficiency disorder Wiskott-Aldrich syndrome [1], has been implicated in the control of actin polymerization in cells [2] [3] [4] [5]. The Arp2/3 complex, an actin-nucleating factor that consists of seven polypeptide subunits [6] [7] [8], was recently shown to physically interact with WASP [9]. We sought to determine whether WASP is a cellular activator of the Arp2/3 complex and found that WASP stimulates the actin nucleation activity of the Arp2/3 complex in vitro. Moreover, WASP-coated microspheres polymerized actin, formed actin tails and exhibited actin-based motility in cell extracts, similar to those behaviors displayed by the pathogenic bacterium Listeria monocytogenes. In extracts depleted of the Arp2/3 complex, WASP-coated microspheres and L. monocytogenes were non-motile and exhibited only residual actin polymerization. These results demonstrate that WASP is sufficient to direct actin-based motility in cell extracts and that this function is mediated by the Arp2/3 complex. WASP interacts with diverse signaling proteins and may therefore function to couple signal transduction pathways to Arp2/3-complex activation and actin polymerization.     

Characterization and purification of the 94-kDa glucose-regulated protein

Increased synthesis of so-called glucose-regulated proteins (grp) of 78 and 94 kDa occurs in mammalian cells exposed to a variety of agents, including 2-mercaptoethanol, tunicamycin, agents which perturb calcium homeostasis, and amino acid analogs. Herein we describe a number of properties of 94-kDa grp (grp 94) and present a method for its purification to homogeneity. The protein, within the endoplasmic reticulum (ER), is modified by the addition of high mannose-containing oligosaccharides. The predicted amino acid sequence of grp 94, as determined by others, has revealed the protein to contain a putative transmembrane domain near its amino terminus, but in addition, a potential endoplasmic reticulum retention sequence (KDEL) at its COOH terminus. Consequently, the question of whether grp 94 exists as a transmembrane or luminal protein of the ER remains controversial. Results using isolated microsomes subjected to either limited proteolysis or lactoperoxidase-mediated iodination were consistent with the idea that the grp is a transmembrane protein. On the other hand, using the method of sodium carbonate extraction, grp 94 exhibited properties of both a luminal and integral membrane protein. These results raise the question of whether there exist two different forms of grp 94 within the ER.     

Baculovirus Actin-Based Motility Drives Nuclear Envelope Disruption and Nuclear Egress

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Seasonal distribution of sympagic amphipods near Chesterfield Inlet, N.W.T., Canada

The seasonal distribution of sympagic amphipods was investigated in the Chesterfield Inlet area of northwestern Hudson Bay (63°30′N). Amphipod abundance was measured by photographic samples and species composition was determined by sweep net samples. Twelve species of amphipods were collected, the most common being Ischyrocerus anguipes, Pontogeneia inermis, Apherusa megalops and Weyprechtia pinguis. The major environmental variable affecting amphipod distribution was water depth. Amphipod abundance was highest near 20 m and near zero past 50 m. The maximum recorded abundance was 1367 m⁻². A minor factor affecting the distribution of amphipods was snow depth, through its modifying effect on light and thereby the growth of ice algae. Amphipods began to inhabit the sea ice shortly after its formation. From the beginning of March, the number of amphipods on the ice increased steadily to about the 3rd week of April, after which numbers declined. This pattern coincided with the seasonal ice algae abundance. Amphipods reduced ice algal biomass over 20-m depth by 63%. No evidence of diurnal changes in abundance was observed. Received: 15 May 1996 / Accepted: 4 November 1996