Spatiotemporal variation in home range size of female polar bears and correlations with individual contaminant load

We quantified the effect of multiple environmental and biological determinants on variation in home range size across multiple spatial (total-home range–core-home range areas) and temporal (seasonal and all seasons combined) scales for 22 adult female polar bears (Ursus maritimus) from Svalbard, Norway (2003–2011). We also evaluated if considering spatiotemporal variation in home range size and location is valuable to assess variation in concentrations of persistent organic pollutants (POPs). In general, home range size was negatively related to the proportion of land within the home range and sea ice concentration, but positively to snow depth. However, effects typically differed between seasons and total, and core-home range size, providing evidence that home range size is scale dependent in this large Arctic mammal. Females accompanied by dependent offspring had smaller home ranges during the breeding season and spring compared to solitary females, while age and body mass did not explain variation in home range size. Correlations between POP concentration and space use were marginally significant, but consistently stronger at fine spatiotemporal resolutions (i.e. core-home ranges during the breeding season) compared to coarse resolution (i.e. total-home ranges over the entire year). We also found that the geographic location of the home range is a stronger ecological correlate of POP concentration than home range size. To improve our understanding of the relation between POPs and animal space use, we recommend increasing the temporal frequency of POP measurements to evaluate how POP concentrations vary during a year and across areas.     

Hybrid aspen is not preferred by the large poplar borer (Saperda carcharias)

An industrially valuable tree, aspen, suffers from several fungal diseases and insect pests such as the large poplar borer (Saperda carcharias). The role of the beetle as a pest of aspen and hybrid aspen was investigated in five aspen and three hybrid aspen stands in Finland. Approximately 50% of the trees in the study had signs of the large poplar borer. Of these trees, 5% had insect exit holes. Approximately 70% of the trees with larval galleries had only one or two larval galleries. The trees with larval galleries were on average 2 m shorter than those without larval galleries. No significant difference could be detected in the diameter growth between these two groups. The proportion of decay was greater in hybrid aspen (27%) than in aspen (14%). These results show that the large poplar borer is an important pest of both aspen and hybrid aspen in Finland. No significant difference was observed between the aspen and hybrid aspen stands in the number of trees with larval galleries. Hybrid aspen therefore does not appear to be more sensitive to damage caused by the large poplar borer. Thus, a change from hybrid aspen to regular aspen in aspen cultivation is unnecessary, presuming that healthy saplings and an optimal rotation time are used.     

A Class III PDZ Binding Motif in the Myotilin and FATZ Families Binds Enigma Family Proteins: a Common Link for Z-Disc Myopathies

Interactions between Z-disc proteins regulate muscle functions and disruption of these interactions results in muscle disorders. Mutations in Z-disc components myotilin, ZASP/Cypher, and FATZ-2 (calsarcin-1/myozenin-2) are associated with myopathies. We report here that the myotilin and the FATZ (calsarcin/myozenin) families share high homology at their final C-terminal five amino acids. This C-terminal E[ST][DE][DE]L motif is present almost exclusively in these families and is evolutionary conserved. We show by in vitro and in vivo studies that proteins from the myotilin and FATZ (calsarcin/myozenin) families interact via this novel type of class III PDZ binding motif with the PDZ domains of ZASP/Cypher and other Enigma family members: ALP, CLP-36, and RIL. We show that the interactions can be modulated by phosphorylation. Calmodulin-dependent kinase II phosphorylates the C terminus of FATZ-3 (calsarcin-3/myozenin-3) and myotilin, whereas PKA phosphorylates that of FATZ-1 (calsarcin-2/myozenin-1) and FATZ-2 (calsarcin-1/myozenin-1). This is the first report of a binding motif common to both the myotilin and the FATZ (calsarcin/myozenin) families that is specific for interactions with Enigma family members.The sarcomere of striated muscle consists of strictly organized subunits, myosin-containing thick filaments and actin-containing thin filaments. The thin filaments are aligned and cross-linked at the Z-discs by a molecular complex in which α-actinin is one of the core structures. Since the contractile force is transduced via the Z-discs, this structure has special requirements. It must provide extensive stability and yet undergo modulation in response to external signals. The Z-discs also serve as important sensors of extracellular cues and mediators of cellular signals that result in various adaptive responses (37). Muscle cells are able to sense changes in their workload and adapt accordingly via complex signaling pathways, some involving calcium, since its level in muscle cells alters in response to nerve pulses and muscle contraction. Of special importance is calcineurin, a sarcomeric calcium/calmodulin-dependent phosphatase that can act as a sensor of change. It is involved in the regulation of genes affecting muscle differentiation and fiber-type specification (12, 13).The special role of the Z-discs is indicated by the fact that mutations in several Z-disc proteins can result in neuromuscular disorders and cardiomyopathies. For instance, myofibrillar myopathy (desmin-related myopathy), a disease characterized by sarcomere disintegration and accumulation of thin filament material, is caused by dominantly inherited missense mutations in Z-disc proteins: myotilin, filamin-C, and Z-band alternatively spliced PDZ motif-containing protein (ZASP, also named LIM domain-binding factor 3, Cypher, or Oracle) (42, 43, 52). Missense mutations in myotilin can also result in limb-girdle muscular dystrophy 1A and spheroid body myositis (10, 18), while mutations in ZASP/Cypher (8, 57), myopalladin or FATZ-2 (calsarcin-1/myozenin-2) have been found to be associated with dominant familial dilated (7, 50) or hypertrophic cardiomyopathy (33). ZASP/Cypher knockout mice display a severe form of congenital myopathy and die postnatally (58), whereas myotilin knockout mice are virtually normal (31), suggesting redundancy between the myotilin family members and indicating that dysfunctional myotilin is more harmful to muscle cells than loss of the protein.Myotilin (40), palladin (32, 34), and myopalladin (3) are homologous Z-disc proteins that form a novel family of immunoglobulin-domain-containing actin-binding proteins. Biochemical studies on the best-characterized family member, myotilin, have demonstrated an association with important components of the sarcomere: α-actinin (40), which is a core structural component of the Z-disc; filamins (15, 49); the proteins of the FATZ (calsarcin/myozenin) family (15); and actin (51). Myotilin is linked to signaling networks by binding to the ubiquitin ligases Murf-1 and Murf-2 (54) and indirectly via FATZ (calsarcin/myozenin). Experiments using myotilin fragments with dominant-negative effect have shown its critical involvement in sarcomere organization. Myotilin bundles and stabilizes actin effectively, which suggests a role for myotilin in the organization and maintenance of Z-disc integrity.The FATZ (calsarcin/myozenin) proteins form another Z-disc family with structural and signaling functions. The three homologous members—FATZ-1 (calsarcin-2/myozenin-1), FATZ-2 (calsarcin-1/myozenin-2), and FATZ-3 (calsarcin-3/myozenin-3)—are localized in the Z-disc binding not only to myotilin but also to filamins A, B, and C (15), telethonin (T-cap), α-actinin, ZASP/Cypher, and calcineurin (9, 11, 12, 47). The three FATZ (calsarcin/myozenin) proteins share high homology at their N and the C terminals and, in fact, the binding sites for a variety of proteins occur in these regions. It has been suggested that the FATZ (calsarcin/myozenin) family may play a role in contributing to the formation and maintenance of the Z-disc, as well as in cell signaling, since its members bind calcineurin. FATZ-1 (calsarcin-2/myozenin-1) and FATZ-3 (calsarcin-3/myozenin-3) are highly expressed in skeletal muscle fast-twitch fibers, whereas FATZ-2 (calsarcin-1/myozenin-2) is highly expressed in cardiac muscle slow-twitch fibers. Mice lacking FATZ-2 (calsarcin-1/myozenin-2) showed an increase in the level of calcineurin, as well as a concurrent increase in the percentage of slow-twitch fibers (13). A recent report shows that FATZ-1 (calsarcin-2/myozenin-1) knockout mice have reduced body weight and fast-twitch muscle mass without exhibiting muscle atrophy (14). It is noteworthy that they also have the ability to run longer distances than control mice, thus exhibiting endurance to exercise. In fact, thus far only actinin-3 knockout mice have displayed this phenotype of endurance to exercise. FATZ-1 (calsarcin-2/myozenin-1)-deficient mice show an increase in oxidative muscle fibers and a switch from fast-twitch to slow-twitch fibers due to an increase in NFAT activity, as well as the regulator of calcineurin 1-4 (RCAN1-4), resulting in the concomitant increase in calcineurin signaling. Both FATZ-1 (calsarcin-2/myozenin-1) and FATZ-2 (calsarcin-1/myozenin-2) can regulate calcineurin/NFAT activity, thus influencing the fiber type composition of skeletal muscle (14).ZASP/Cypher (Oracle) (8, 35, 57) belongs to the Enigma family of proteins, the members of which all have a N-terminal PDZ domain and one or more LIM domains at the C-terminal (48). To date, there are six isoforms of ZASP/Cypher, all of which contain an N-terminal PDZ domain and none or three C-terminal LIM domains. ZASP/Cypher also contains a third domain known as the ZM motif which can also be found in ALP and CLP-36 (23, 24). It interacts with two different regions of α-actinin-2; its PDZ domain binds to the C-terminal EH-hand region of α-actinin-2, whereas its ZM motif binds to the rod region of α-actinin-2 (2, 23). ZASP/Cypher colocalizes with α-actinin-2 in the Z-disc, whereas the LIM domains interact with and are phosphorylated by all six isoforms of protein kinase C (PKC α, β1, γ, ζ, δ, and ɛ). ZASP/Cypher is important for the stability of the Z-disc; in fact, ZASP/Cypher knockout mice die in the first 24 h after birth as a result of functional failure of striated muscles caused by disruption of the Z-disc during muscle contraction (58). The PDZ of ZASP/Cypher is a classical type I PDZ domain that binds to the C-terminal of α-actinin-2.To better understand the biology of the Z-disc and pathogenesis of muscle disorders, it is important to unravel the dynamic interplay of Z-disc components. In the present study, we demonstrate a novel PDZ domain-binding motif common to the myotilin and FATZ (calsarcin/myozenin) protein families. This domain mediates interaction with ZASP/Cypher in a phosphorylation-dependent manner and is also involved in targeting ZASP/Cypher.     

Characterization of a new human glioblastoma cell line that expresses mutant P53 and lacks activation of the PDGF pathway

Summary We have established and characterized a new glioblastoma cell line, termed GT9, from a biopsy sample of a female adult patient with glioblastoma multiforme. The line has now undergone over 60 passages and has been successfully cultured after cryopreservation. Immunofluorescence analyses with a panel of monoclonal antibodies were positive for glial fibrillary acidic protein and vimentin, and negative for neurofilament, galactocerebroside, and fibronectin, a pattern typical of glial cells. Based on a tetraploid, the composite karyotype of GT9 cells included the loss of chromosome 10, gain of chromosome 7, and the presence of double minute chromosomes, three of the most common karyotypic abnormalities in glioblastoma. Sequence analysis of p53 cDNA revealed a homozygous double mutation at codon 249 (commonly mutated in aflatoxin-associated hepatocellular carcinoma) and codon 250. Moreover, there was a complete absence of wild-type p53. However, unlike the majority of human glioblastomas previously described, the expression of platelet-derived growth factor-B (PDGF-B), a potent mitogenic autocrine factor, was low in GT9 cells. The expression and phosphorylation of c-Jun and Jun-B, downstream mediators of the PDGF pathway, were also low. Thus, deregulation of the PDGF pathway does not appear to be involved in the pathogenesis of the GT9 glioblastoma. Conversely, Jun-D, a negative regulator of cell growth, was also low. In addition, Phosphorylated Egr-1, a recently reported suppressor of PDGF-B/v-sis-transformed cells, was also low, suggesting that the lack of activation of the PDGF pathway was not due to these suppressive mechanisms. The circumstance of a weak or inactive PDGF-B autocrine mechanism in human glioblastoma paired with a homozygously altered p53 suggests that the loss of suppressor function of p53 may be a major contribution to the transformed phenotype of these cells.     

Evolutionary ecology of periodical insects

To be periodical, a species must have a fixed life cycle length and adults must appear synchronously, reproduce only once, and die. The consequence of this life history is that, at a given location, adults of a periodical species will be absent or rare in some years and abundant in others. The relative scarcity of periodical Insect species suggests that periodicity does not evolve easily. The major obstacle to its evolution is selection favoring life cycles In which the offspring of any given female appear over a two- or three-year period. Chance events which disrupt this 'bet-hedging' strategy set the stage for periodicity. Mathematical models predict that, given certain initial conditions, intraspecific competition and predation favor its development. Recent studies suggest that periodicity is rarely perfect but that it can persist in the face of limited gene flow through time.     

Coupling of Astroglial α2-Adrenoreceptors to Second Messenger Pathways

Abstract: We have investigated which α₂-receptor subtypes are expressed in cultured cortical astroglia, and their coupling to second messengers. Binding assays using [³H]rauwolscine showed a very low number of α₂ receptors in the astrocytic cultures. Treatment of cultures with dibutyryl cyclic AMP (dBcAMP) increased significantly the number of receptors. The RNase protection assay was used to investigate which receptor subtype the cells express. The α_2B message was expressed at a low level in both treated and untreated cells, the levels of mRNA for the α_2A/D subtype were up-regulated significantly in cells treated with dBcAMP and no expression of mRNA for the α_2C subtype was detected. The α₂ agonist dexmedetomidine inhibited forskolin-induced increases in cyclic AMP both in treated and untreated cultures in a pertussis toxin-dependent manner. This effect was abolished by the α₂-receptor antagonist rauwolscine. Selective α₂-receptor agonists dexmedetomidine, clonidine, and UK14,304 all increased intracellular calcium only in dBcAMP-treated cells. The antagonist rauwolscine abolished this effect. Ca²⁺ responses were also seen in the absence of extracellular Ca²⁺ and they were inhibited by the phospholipase C inhibitor U-73122, suggesting that astroglial α₂ receptors are coupled to the inositol phospholipid pathway. We therefore also tested the effect of dexmedetomidine directly on inositol 1,4,5-trisphosphate accumulation. A significant increase was seen that was blocked by the antagonist rauwolscine and, as expected, by U-73122. In short, the results demonstrate that the α₂ receptors in astroglia are coupled to multiple second messenger pathways. They are up-regulated in cells treated with dBcAMP, which simultaneously assume a process-bearing morphology. If this morphological change reflects some in vivo process such as reactive gliosis, the up-regulation of α₂-receptor expression could mean an adaptive change in astrocytic responses to a common neurotransmitter, noradrenaline.     

Larval mortality of pine sawflies [Hymenoptera: Diprionidae] in relation to pollution level: A field experiment

Larval mortality ofNeodiprion sertifer (Geoffroy),Diprion pini (L.) andGilpinia pallida (Klug) were studied in field experiments around a factory complex in southwestern Finland. Larval colonies were transferred on the shoots of Scots pines growing at different distances from the emission source. Larval mortality was highest near the factories. InN. sertifer, larval mortality caused by the nuclear polyhedrosis virus was higher and cocoon mortality caused by parasitoids was lower near the pollutant source. The most abundant parasitoid species wereSynomelix scutulata (Hartig) andLamachus eques (Hartig). 16–67% of theN. sertifer, 0–5% of theD. pini and the 73–100% ofG. pallida cocoons contained parasitoids oviposited during the larval period of the sawflies.