Picoeucaryot alga infecting blue mussel Mytilus edulis in southern Norway

During summer 2001, blue mussels Mytilus edulis with abnormal shell growth were collected near Krager?, southern Norway. The mussels had green spots in their mantle tissues, mainly posteriorly and ventrally, and in the adductor muscle. Mussels from 4 sites had a prevalence of green spots varying from 2 to 71% that correlated well with shell deformities. Histological examination revealed the presence of round or ovoid algae, 0.9 to 1.5 x 1.2 to 2.4 microm, free within haemocytes and in the lesions, characterised by an inflammatory response and the presence of cellular debris. The alga contain a relatively large nucleus, 1 chloroplast and 1 mitochondrion. Size and morphology suggest that the alga might be a picoeucaryot green alga. Infection of mussel tissues appears to start in the posterior mantle edge, near the siphons, and spread anterior-ventrally in the mantle connective and storage tissues-occasionally spots were also found in the gonad follicles. Large infected areas were also observed in sinuses within the adductor muscle. Only mussels that were 3 yr old or more were infected. Deformations apparently resulted from years of continuous shell formation by a contracted, partly deformed mantle. Most deformed mussels had eroded shells, allowing some light penetration through the exposed, thin nacre. Young, thin-shelled mussels were not infected. The present work suggests that the alga has, at least partially, a parasitic relationship with the mussels, and is associated with pathological alterations in mussel tissues.     

In vitro research of anti-HSV-1 activity in different extracts from Pacific oysters Crassostrea gigas

Mortalities related to the detection of Ostreid Herpesvirus 1 (OsHV-1) have been previously reported in France among larvae and spat of the Pacific oyster Crassostrea gigas. Adult oysters appear less sensitive to herpesvirus infections, although OsHV-1 has been detected in adults without signs of disease or mortality. This suggests that the virus is able to persist in its host and that adult oysters may be able to control OsHV-1 infection. Little is known about antiviral substances in invertebrates. The present work concerns the research of antiviral substances in adult oyster C. gigas, where putative antiviral activities were monitored using 3 strategies: (1) in metabolites with variable polarity, (2) in peptidic extracts and (3) in crude haemolymph. In vitro antiviral assays were based on inhibition of Herpes simplex virus type 1 (HSV-1) replication in Vero cell monolayers. All extracts presented no cytotoxicity. Antiviral activity was detected in the fresh filtered haemolymph (EC50:425 microg ml(-1)) and seasonal variation of the haemolymph antiviral activity was monitored.     

Phylogenetic relationships and evolutionary traits in Ranunculus s.l. (Ranunculaceae) inferred from ITS sequence analysis

Ranunculus is a large genus with a worldwide distribution. Phylogenetic analyses of c. 200 species of Ranunculus s.l. based on sequences of the nrITS using maximum parsimony and Bayesian inference yielded high congruence with previous cpDNA restriction site analyses, but strongly contradict previous classifications. A large core clade including Ranunculus subg. Ranunculus, subg. Batrachium, subg. Crymodes p.p., Ceratocephala, Myosurus, and Aphanostemma is separated from R. subg. Ficaria, subg. Pallasiantha, subg. Coptidium, subg. Crymodes p.p., Halerpestes, Peltocalathos, Callianthemoides, and Arcteranthis. Within the core clade, 19 clades can be described with morphological and karyological features. Several sections are not monophyletic. Parallel evolution of morphological characters in adaptation to climatic conditions may be a reason for incongruence of molecular data and morphology-based classifications. In some mountainous regions, groups of closely related species may have originated from adaptive radiation and rapid speciation. Split decomposition analysis indicated complex patterns of relationship and suggested hybridization in the apomictic R. auricomus complex, R. subg. Batrachium, and the white-flowering European alpines. The evolutionary success of the genus might be due to a combination of morphological plasticity and adaptations, hybridization and polyploidy as important factors for regional diversification, and a broad range of reproductive strategies.     

The ontogeny of the urogenital system of the spotted hyena (Crocuta crocuta Erxleben)

Studies were conducted to elucidate the importance of androgen-mediated induction of the extreme masculinization of the external genitalia in female spotted hyenas. Phallic size and shape; androgen receptor (AR) and alpha-actin expression; and sex-specific differences in phallic retractor musculature, erectile tissue, tunica albuginea, and urethra/urogenital sinus were examined in male and female fetuses from Day 30 of gestation to term. Similar outcomes were assessed in fetuses from dams treated with an AR blocker and a 5alpha-reductase inhibitor (antiandrogen treatment). Clitoral and penile development were already advanced at Day 30 of gestation and grossly indistinguishable between male and female fetuses throughout pregnancy. Sex-specific differences in internal phallic organization were evident at Gestational Day 45, coincident with AR expression and testicular differentiation. Antiandrogen treatment inhibited prostatic development in males and effectively feminized internal penile anatomy. We conclude that gross masculinization of phallic size and shape of male and female fetuses is androgen-independent, but that sexual dimorphism of internal phallic structure is dependent on fetal testicular androgens acting via AR in the relevant cells/tissues. Androgens secreted by the maternal ovaries and metabolized by the placenta do not appear to be involved in gross masculinization or in most of the sex differences in internal phallic structure.     

Liposome retention in size exclusion chromatography

Background  

Size exclusion chromatography is the method of choice for separating free from liposome-encapsulated molecules. However, if the column is not presaturated with lipids this type of chromatography causes a significant loss of lipid material. To date, the mechanism of lipid retention is poorly understood. It has been speculated that lipid binds to the column material or the entire liposome is entrapped inside the void.     

Calcium as an extracellular signalling molecule: perspectives on the Calcium Sensing Receptor in the brain

Calcium acts as a universal signal that is responsible for controlling a spectrum of cellular processes ranging from fertilization to apoptosis. For a long time, calcium was regarded solely as an intracellular second messenger. However, the discovery that calcium can also act as an external ligand together with the molecular cloning of its cell surface receptor, the Calcium Sensing Receptor (CaSR), demonstrated that calcium also acts as an important extracellular or first messenger. Here, we give an overview of the main structural, pharmacological and physiological features of the CaSR and provide an assessment of its functions and cellular and molecular mechanisms of action. In addition, we propose possible avenues for future research into the trafficking of CaSR and the role(s) of this receptor in the central nervous system.     

AMP-activated protein kinase beta subunit tethers alpha and gamma subunits via its C-terminal sequence (186-270)

AMP-activated protein kinase (AMPK) is an important metabolic stress-sensing protein kinase responsible for regulating metabolism in response to changing energy demand and nutrient supply. Mammalian AMPK is a stable alphabetagamma heterotrimer comprising a catalytic alpha and two non-catalytic subunits, beta and gamma. The beta subunit targets AMPK to membranes via an N-terminal myristoyl group and to glycogen via a mid-molecule glycogen-binding domain. Here we find that the conserved C-terminal 85-residue sequence of the beta subunit, beta1-(186-270), is sufficient to form an active AMP-dependent heterotrimer alpha1beta1-(186-270)-gamma1, whereas the 25-residue beta1 C-terminal (246-270) sequence is sufficient to bind gamma1, gamma2, or gamma3 but not the alpha subunit. Deletion of the beta C-terminal Ile-270 precludes betagamma association in the absence of the alpha subunit, but the presence of the alpha subunit or substitution of Ile-270 with Ala or Glu restores betagamma binding. Truncation of the alpha subunit reveals that beta1 binding requires the alpha1-(313-473) sequence. The conserved C-terminal 85-residue sequence of the beta subunit (90% between beta1 and beta2) is the primary alphagamma binding sequence responsible for the formation of the AMPK alphabetagamma heterotrimer.     

Homo- and hetero-oligomerization of beta-arrestins in living cells

Arrestins are important proteins, which regulate the function of serpentine heptahelical receptors and contribute to multiple signaling pathways downstream of receptors. The ubiquitous beta-arrestins are believed to function exclusively as monomers, although self-association is assumed to control the activity of visual arrestin in the retina, where this isoform is particularly abundant. Here the oligomerization status of beta-arrestins was investigated using different approaches, including co-immunoprecipitation of epitope-tagged beta-arrestins and resonance energy transfer (BRET and FRET) in living cells. At steady state and at physiological concentrations, beta-arrestins constitutively form both homo- and hetero-oligomers. Co-expression of beta-arrestin2 and beta-arrestin1 prevented beta-arrestin1 accumulation into the nucleus, suggesting that hetero-oligomerization may have functional consequences. Our data clearly indicate that beta-arrestins can exist as homo- and hetero-oligomers in living cells and raise the hypothesis that the oligomeric state may regulate their subcellular distribution and functions.     

Identification of zebrafish insertional mutants with defects in visual system development and function

Genetic analysis in zebrafish has been instrumental in identifying genes necessary for visual system development and function. Recently, a large-scale retroviral insertional mutagenesis screen, in which 315 different genes were mutated, that resulted in obvious phenotypic defects by 5 days postfertilization was completed. That the disrupted gene has been identified in each of these mutants provides unique resource through which the formation, function, or physiology of individual organ systems can be studied. To that end, a screen for visual system mutants was performed on 250 of the mutants in this collection, examining each of them histologically for morphological defects in the eye and behaviorally for overall visual system function. Forty loci whose disruption resulted in defects in eye development and/or visual function were identified. The mutants have been divided into the following phenotypic classes that show defects in: (1) morphogenesis, (2) growth and central retinal development, (3) the peripheral marginal zone, (4) retinal lamination, (5) the photoreceptor cell layer, (6) the retinal pigment epithelium, (7) the lens, (8) retinal containment, and (9) behavior. The affected genes in these mutants highlight a diverse set of proteins necessary for the development, maintenance, and function of the vertebrate visual system.