Recent decrease in chinstrap penguin (<Emphasis Type="Italic">Pygoscelis antarctica</Emphasis>) populations at two of Admiralty Bay’s islets on King George Island,South Shetland Islands,Antarctica

We examined the breeding populations of chinstrap penguins (Pygoscelis antarctica) on Chabrier Rock and Shag Island within Admiralty Bay, King George Island, South Shetland Islands, Antarctica from 2002 to 2004. When comparing our results to historic data from 1979, we found an overall decline of 57% in the last 25 years, mirroring the population trend of this species in other regions of the Antarctic Peninsula. Our results are discussed in relation to factors hypothesized to be driving the declines found at other sites, as well as the importance of consistent annual censuses to accurately determine population trends.     

Versican G3 promotes mouse mammary tumor cell growth, migration, and metastasis by influencing EGF receptor signaling

Increased versican expression in breast tumors is predictive of relapse and has negative impact on survival rates. The C-terminal G3 domain of versican influences local and systemic tumor invasiveness in pre-clinical murine models. However, the mechanism(s) by which G3 influences breast tumor growth and metastasis is not well characterized. Here we evaluated the expression of versican in mouse mammary tumor cell lines observing that 4T1 cells expressed highest levels while 66c14 cells expressed low levels. We exogenously expressed a G3 construct in 66c14 cells and analyzed its effects on cell proliferation, migration, cell cycle progression, and EGFR signaling. Experiments in a syngeneic orthotopic animal model demonstrated that G3 promoted tumor growth and systemic metastasis in vivo. Activation of pERK correlated with high levels of G3 expression. In vitro, G3 enhanced breast cancer cell proliferation and migration by up-regulating EGFR signaling, and enhanced cell motility through chemotactic mechanisms to bone stromal cells, which was prevented by inhibitor AG 1478. G3 expressing cells demonstrated increased CDK2 and GSK-3β (S9P) expression, which were related to cell growth. The activity of G3 on mouse mammary tumor cell growth, migration and its effect on spontaneous metastasis to bone in an orthotopic model was modulated by up-regulating the EGFR-mediated signaling pathway. Taken together, EGFR-signaling appears to be an important pathway in versican G3-mediated breast cancer tumor invasiveness and metastasis.     

Calorimetric study of the order-disorder conformational transition in succinoglycan

Thermally induced order-disorder conformational transition in succinoglycan was studied using the method of high-sensitivity differential scanning microcalorimetry within the range of polysaccharide concentrations from 0.1 to 3.5 mg mL⁻¹ at NaCl concentrations 0, 0.01, and 0.1M. The positions and shapes of the excess heat capacity curves depended substantially on both the NaCl and polysaccharide concentrations. At low polysaccharide concentrations in salt-free solution the experimental curves were closely approximated by the two-state model suggesting the transition mechanism to be of the single helix-coil type. With increasing polysaccharide and/or NaCl concentration, the experimental curves changed significantly in symmetry, which indicated a changing transition mechanism. At high polysaccharide concentrations or in the presence of the salt, the order-disorder transition of succinoglycan was shown to include two stages: the cooperative dissociation of the helix dimer and subsequent two-state melting of the helix monomer. The dependence of thermodynamic parameters for the dissociation and melting of helix structures in succinoglycan on NaCl and polysaccharide concentrations was obtained by fitting the experimental excess heat capacity curves. The cooperativity parameter σ for the single helix-coil transition as well as the average length of the helix segment of succinoglycan were calculated. Some features of succinoglycan ordering in solution are discussed. © 1996 John Wiley & Sons, Inc.     

eIF3j facilitates loading of release factors into the ribosome

eIF3j is one of the eukaryotic translation factors originally reported as the labile subunit of the eukaryotic translation initiation factor eIF3. The yeast homolog of this protein, Hcr1, has been implicated in stringent AUG recognition as well as in controlling translation termination and stop codon readthrough. Using a reconstituted mammalian in vitro translation system, we showed that the human protein eIF3j is also important for translation termination. We showed that eIF3j stimulates peptidyl-tRNA hydrolysis induced by a complex of eukaryotic release factors, eRF1-eRF3. Moreover, in combination with the initiation factor eIF3, which also stimulates peptide release, eIF3j activity in translation termination increases. We found that eIF3j interacts with the pre-termination ribosomal complex, and eRF3 destabilises this interaction. In the solution, these proteins bind to each other and to other participants of translation termination, eRF1 and PABP, in the presence of GTP. Using a toe-printing assay, we determined the stage at which eIF3j functions – binding of release factors to the A-site of the ribosome before GTP hydrolysis. Based on these data, we assumed that human eIF3j is involved in the regulation of translation termination by loading release factors into the ribosome.     

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification

The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.     

中国人群中微卫星位点DXYS156的多态研究

以中国２个汉族群体和８个少数民族群体的Ｓ２０名个体为研究,采用ＰＣＲ扩增后案丙烯酰胺凝胶电泳分离的方法,分析了Ｙ染色体上ＤＸＹＳ１５６Ｙ和Ｘ染色体上ＸＹＳ１５６Ｘ这两个微卫星位点的遗传多态性。结果表明,在所研究的１０个中国人群中,共观察到１０个不同长度片段的等位基因,在Ｘ染色体上的５个闰基因是：１３０ｂｐ、１３５ｂｐ、１４０ｂｐ、１４５ｂｐ、１５０ｂｐ,在Ｙ染色体上的五个等位基因晃：１６０ｂｐ、１     

Mitochondrial diversity of European pond turtles (Emys orbicularis) in Anatolia and the Ponto-Caspian Region: Multiple old refuges, hotspot of extant diversification and critically endangered endemics

The European pond turtle, Emys orbicularis (Linnaeus, 1758), is one of the world's most widely distributed chelonian species. We investigated its mitochondrial phylogeography and demography using ∼1300 cyt b sequences from the entire range, with a focus on the eastern part, in particular on Turkey, where the species currently suffers massive losses. Coloration data from >1450 turtles were compared with mtDNA differentiation to assess the validity of the currently accepted subspecies from Turkey, the Black Sea Region, the Transcaucasus, and Iran. Our study region harbors considerable part of the mtDNA diversity of Emys, including a newly discovered lineage and 16 new haplotypes. In this area corresponding to approximately one-third of the entire distribution range, six out of the ten mitochondrial lineages and about half of all 72 haplotypes occur. Two mitochondrial lineages (VIII, X) are confined to small ranges along the southern coast of Turkey, another lineage (I) occupies the remainder of Turkey, the entire Black Sea Region, and the north-eastern part of the species’ range. In the south-western corner of the Black Sea and in the Aegean Region, two lineages (II, IV) occur that have their main distribution areas farther west. In the Transcaucasus and northern Iran, another endemic lineage (VII) is found. Lineage I is the largest and most diverse of all lineages and has its greatest diversity in Anatolia. Phylogeographic and demographic data suggest Anatolia as an ancient glacial refuge for turtles harboring mitochondrial lineages I, VIII and X, and that Anatolia and the Black Sea coasts constitute a hotspot for a younger burst of diversification within lineage I. These two regions correspond to the glacial refuge from which lineage I turtles recolonized more northerly parts of the range in the Holocene; lineage II represents an off-shoot of lineage I that became isolated in a westward-located refuge in the south-eastern Balkans during a previous Pleistocene glacial. Our data on coloration indicate that such characters have only limited value for delineating evolutionarily significant units. We propose to reduce the number of subspecies using mtDNA lineages as arbiter, and to recognize three subspecies as valid in Turkey, the Black Sea Region, the Transcaucasus and Iran: Emys orbicularis orbicularis (mtDNA lineage I); E. o. eiselti Fritz et al., 1998 (X); and E. o. persica Eichwald, 1831 (VII). However, the southern Turkish lineage VIII most probably represents an additional undescribed subspecies. Both southern Turkish endemics are critically endangered, with only three surviving populations of fewer than 30 adults each. We recommend establishing sanctuaries for them, and including them in the IUCN Red List.     

Growth and development of the placenta in the capybara (Hydrochaeris hydrochaeris)

Background  

The guinea pig is an attractive model for human pregnancy and placentation, mainly because of its haemomonochorial placental type, but is rather small in size. Therefore, to better understand the impact of body mass, we studied placental development in the capybara which has a body mass around 50 kg and a gestation period of around 150 days. We paid attention to the development of the lobulated arrangement of the placenta, the growth of the labyrinth in the course of gestation, the differentiation of the subplacenta, and the pattern of invasion by extraplacental trophoblast.     

Bax Activates Endophilin B1 Oligomerization and Lipid Membrane Vesiculation

Endophilins participate in membrane scission events that occur during endocytosis and intracellular organelle biogenesis through the combined activity of an N-terminal BAR domain that interacts with membranes and a C-terminal SH3 domain that mediates protein binding. Endophilin B1 (Endo B1) was identified to bind Bax, a Bcl-2 family member that promotes apoptosis, through yeast two-hybrid protein screens. Although Endo B1 does not bind Bax in healthy cells, during apoptosis, Endo B1 interacts transiently with Bax and promotes cytochrome c release from mitochondria. To explore the molecular mechanism of action of Endo B1, we have analyzed its interaction with Bax in cell-free systems. Purified recombinant Endo B1 in solution displays a Stokes radius indicating a tetrameric quarternary structure. However, when incubated with purified Bax, it assembles into oligomers more than 4-fold greater in molecular weight. Although Endo B1 oligomerization is induced by Bax, Bax does not stably associate with the high molecular weight Endo B1 complex. Endo B1 oligomerization requires its C-terminal Src homology 3 domain and is not induced by Bcl-xL. Endo B1 combined with Bax reduces the size and changes the morphology of giant unilamellar vesicles by inducing massive vesiculation of liposomes. This activity of purified Bax protein to induce cell-free assembly of Endo B1 may reflect its activity in cells that regulates apoptosis and/or mitochondrial fusion.