Inositol 1,4,5-trisphosphate is not effective in releasing calcium from skeletal sarcoplasmic reticulum microsomes

Regulation of many cell systems has been shown to be mediated by Inositol 1,4,5-trisphosphate which causes a release of calcium from intracellular sites. We have shown that release of Ca2+ from sarcoplasmic reticulum microsomes was not stimulated by IP3. The phorbol ester, TPA, also had no effect on Ca2+ release or Ca2+ ATPase activity. Thus, it is unlikely that the breakdown of polyphosphatidylinositides serves as a second messenger to mediate release of Ca2+ in skeletal muscle.     

Protein Kinase PKR Mediates the Apoptosis Induction and Growth Restriction Phenotypes of C Protein-Deficient Measles Virus

The measles virus (MV) accessory proteins V and C play important roles in MV replication and pathogenesis. Infection with recombinant MV lacking either V or C causes more cell death than infection with the parental vaccine-equivalent virus (MVvac), and C-deficient virus grows poorly relative to the parental virus. Here, we show that a major effector of the C phenotype is the RNA-dependent protein kinase PKR. Using human HeLa cells stably deficient in PKR as a result of RNA interference-mediated knockdown (PKR^kd cells), we demonstrated that a reduction in PKR partially rescued the growth defect of C knockout (C^ko) virus but had no effect on the growth of either wild-type (WT) or V knockout (V^ko) virus. Increased growth of the C^ko virus in PKR^kd cells correlated with increased viral protein expression, while defective growth and decreased protein expression in PKR-sufficient cells correlated with increased phosphorylation of PKR and the α subunit of eukaryotic initiation factor 2. Furthermore, infection with WT, V^ko, or especially C^ko virus caused significantly less apoptosis in PKR^kd cells than in PKR-sufficient cells. Although apoptosis induced by C^ko virus infection in PKR-sufficient cells was blocked by a caspase antagonist, the growth of C^ko virus was not restored to the WT level by treatment with this pharmacologic inhibitor. Taken together, these results indicate that PKR plays an important antiviral role during MV infection but that the virus growth restriction by PKR is not dependent upon the induction of apoptosis. Furthermore, the results establish that a principal function of the MV C protein is to antagonize the proapoptotic and antiviral activities of PKR.     

Epsilonematidae (Nematoda) from a cold-water coral environment in the Porcupine Seabight, with a discussion on the status of the genus Metaglochinema Gourbault & Decraemer, 1986

Thirteen species of nematodes from the family Epsilonematidae Steiner, 1927 were found to be associated with a cold-water coral reef in the Porcupine Seabight. Among them, four species were already known from various locations such as Chile and Papua New Guinea. Three new species are described here: Glochinema trispinatumsp. n. is recognized by three dorsal thorns in the pharyngeal region. This species was also recovered from the Antarctic shelf. Epsilonema multispiralumsp. n. is characterised by a multispiral amphid consisting of 3.25 coils. Bathyepsilonema lopheliaesp. n. is characterised by its body length, the position and relative width of the amphids and the nature of the cuticular ornamentation. Within the subfamily Glochinematinae Lorenzen, 1974, the number and arrangement of ambulatory setae is considered not to be of diagnostic importance. The former species Metaglochinema strigosumGourbault & Decraemer, 1993 is therefore classified under the genus GlochinemaLorenzen, 1974. The original genus diagnosis of Metaglochinema, now a monotypic genus, is adjusted. The geographic distribution of epsilonematid nematodes is briefly discussed.     

Severe and rapid population declines in exotic birds

A particularly vexing phenomenon within invasion ecology is the occurrence of spontaneous collapses within seemingly well-established exotic populations. Here, we assess the frequency of collapses among 68 exotic bird populations established in Hawaii, Puerto Rico, Los Angeles and Miami. Following other published definitions, we define a ‘collapse’ as a decline in abundance of ≥90 % within ≤10 years that lasts for at least 3 years. We show that 44 of the 68 exotic bird populations have exhibited declines at some point within their time series. Sixteen of the populations declined sufficiently to be defined as collapsed. It took on average 3.8 ± 1.8 years for populations to decline into a collapsed state, and this state persisted on average for 7.1 ± 6.3 years across (collapsed) populations. We compared the severity and duration of declines across all 44 declining populations according to taxonomic Order and geographic region. Neither variable explained substantial variation in the metrics of collapse. Our results indicate that severe, rapid, and persistent population declines may be common among exotic populations. We suggest that incorporating the probability and persistence of collapses into management decisions can inform efforts to enact control or eradication measures. We also suggest that applying our approach to other taxa and locations is crucial for improving our understanding of when and where collapses are likely to occur.     

Evolution of Sickness and Healing

Evolution of Sickness and Healing. Horacio Fábrega Jr. Berkeley: University of California Press, 1997 (cloth), xv. 364pp.     

Verapamil as a co-mutagen in the Salmonella/mammalian microsome mutagenicity test

Verapamil is a calcium-channel blocking agent, commonly used for chronic treatment of heart conditions. We have previously demonstrated that verapamil acts as a co-mutagen in a bacterial mutagenicity test for some experimental anilinoacridine antitumour drugs. Within the anilinoacridines series there are several compounds which are apparently non-mutagenic (or very weak mutagens) in the absence of verapamil, but strong mutagens in its presence. We have now tested a wider range of materials for verapamil enhancement of mutagenicity, to include some of those to which persons on verapamil therapy might be exposed through life-style or occupation. Some verapamil enhancement of mutagenicity was seen with most mutagenic compounds including anticancer drugs, antiparasitic agents, one biological stain and one hair dye. A number of tricyclic antidepressants and biological stains were tested and found to be non-mutagenic. If these results extrapolate to mammalian cells, long-term verapamil therapy could potentially increase the effects of certain environmental mutagens.     

Sequence Determinants of GLUT1 Oligomerization: ANALYSIS BY HOMOLOGY-SCANNING MUTAGENESIS*

The human blood-brain barrier glucose transport protein (GLUT1) forms homodimers and homotetramers in detergent micelles and in cell membranes, where the GLUT1 oligomeric state determines GLUT1 transport behavior. GLUT1 and the neuronal glucose transporter GLUT3 do not form heterocomplexes in human embryonic kidney 293 (HEK293) cells as judged by co-immunoprecipitation assays. Using homology-scanning mutagenesis in which GLUT1 domains are substituted with equivalent GLUT3 domains and vice versa, we show that GLUT1 transmembrane helix 9 (TM9) is necessary for optimal association of GLUT1-GLUT3 chimeras with parental GLUT1 in HEK cells. GLUT1 TMs 2, 5, 8, and 11 also contribute to a less abundant heterocomplex. Cell surface GLUT1 and GLUT3 containing GLUT1 TM9 are 4-fold more catalytically active than GLUT3 and GLUT1 containing GLUT3 TM9. GLUT1 and GLUT3 display allosteric transport behavior. Size exclusion chromatography of detergent solubilized, purified GLUT1 resolves GLUT1/lipid/detergent micelles as 6- and 10-nm Stokes radius particles, which correspond to GLUT1 dimers and tetramers, respectively. Studies with GLUTs expressed in and solubilized from HEK cells show that HEK cell GLUT1 resolves as 6- and 10-nm Stokes radius particles, whereas GLUT3 resolves as a 6-nm particle. Substitution of GLUT3 TM9 with GLUT1 TM9 causes chimeric GLUT3 to resolve as 6- and 10-nm Stokes radius particles. Substitution of GLUT1 TM9 with GLUT3 TM9 causes chimeric GLUT1 to resolve as a mixture of 6- and 4-nm particles. We discuss these findings in the context of determinants of GLUT oligomeric structure and transport function.     

Mutagenic and clastogenic activity of nitracrine analogues in cultured V79 Chinese hamster cells

Nitracrine is used clinically as an antitumour agent, and analogues are actively being developed in some laboratories. The mutagenic activity of 9-[(3-dimethylaminopropyl)amino]-acridine and its 1-nitro (nitracrine), 2-, 3- and 4-nitro derivatives was evaluated at the 6-thioguanine and ouabain resistance loci in cultured Chinese hamster fibroblasts (V79-171b cell line). The des-nitro, 2- and 3-nitro caused no statistically significant mutagenic activity at either locus. Each of these 3 compounds weakly increased (approximately 2-fold) the incidence of micronuclei in the same cell line when tested at cytotoxic doses. Both the 1- and 4-nitro compounds increased the incidence of 6-thioguanine resistant cells from around 1 in 10(-6) to approximately 1 in 10(-4). The former compound significantly increased the frequency of ouabain-resistant cells. Both of these compounds were potent inducers of micronuclei in V79-171b cells, indicating high clastogenic activity. It would appear prudent to regard both of these compounds as potential human carcinogens.     

The assessment game in sand fiddler crab contests for breeding burrows

The single enlarged claw of male sand fiddler crabs, Uca pugilator, is used in contests for control of breeding burrows. The larger of the two contestants has the larger claw and usually wins. Males use one or more of 10 agonistic elements that vary in intensity from a no-contact extension of the claw to the flip of an opponent. We used the sequence of elements employed and the duration of unstaged, naturally occurring contests in a South Carolina salt marsh to evaluate three models of extended contests: (1) energetic war of attrition, (2) cumulative assessment and (3) sequential assessment. Contests usually began with elements of low action intensity and often proceeded to elements of high intensity. Elements of higher intensity were correlated with both contest duration and the number of contest elements. Contest duration increased as opponents became more evenly matched in size, a result consistent with both cumulative and sequential assessment models. Variation in duration increased as the relative sizes of opponents increased, also in accordance with sequential assessment. The absolute size of the smaller contestant had no effect on contest duration, in contrast to predictions based on cumulative assessment or energetic war of attrition models. Contestants that lost a fight were more likely to engage immediately in another fight without loss of contest intensity, if their previous fight had been long and intense. This result is inconsistent with contests of endurance, such as the energetic war of attrition or the cumulative assessment game, but it is consistent with the ritualized display of strength and fighting skill. Thus, sequential assessment appears to best explain ritualized fiddler crab contests. Cumulative assessment, however, may be the appropriate model for extended, nonritualized, all-out fights. Cumulative assessment may also explain the tenure of individuals on breeding grounds where multiple engagements are likely to test endurance and tolerance to damage over a period of days. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.