Seasonal home ranges and fidelity to breeding sites among ringed seals

Population structure and patterns of habitat use among ringed seals (Phoca hispida) are poorly known, in part because seasonal movements have not been adequately documented. We monitored the movements of 98 ringed seals in the Beaufort and Chukchi seas between 1990 and 2006 using three forms of telemetry. In the winter—spring period (when the seals were occupying shorefast ice), we used radio and ultra-sonic tags to track movements above and below the ice, respectively. We used satellite-linked transmitters in summer and fall (when the seals ranged away from their winter sites) to track at-sea movements. In the shorefast ice habitat, the home ranges of 27 adult males ranged from <1 to 13.9 km² (median = 0.628) while the home ranges of 28 adult females ranged from <1 to 27.9 km² (median = 0.652). The 3-dimensional volumes used by 9 seals tracked acoustically under the ice averaged 0.07 (SD = 0.04) km³ for subadults and adult males and 0.13 (SD = 0.04) km³ for adult females. Three of the radio-tracked seals and 9 tracked by satellite ranged up to 1,800 km from their winter/spring home ranges in summer but returned to the same small (1–2 km²) sites during the ice-bound months in the following year. The restricted movements of ringed seals during the ice-bound season—including the breeding season—limits their foraging activities for most of the year and may minimize gene flow within the species.     

Constructions of race: symbolic ethnic capital and the performance of youth identity in multicultural Australia

The relationship between ethnicity and cultural and social capital has been taken up by several scholars in terms of questions of disadvantage. This paper considers the performance of race and ethnicity as positive capital among a group of Sudanese young people with refugee backgrounds in Brisbane, Australia. Based on ethnographic fieldwork, I demonstrate young people's adaptation of cultural associations in their hybridized and essentialized self-representations. In particular, I explore my informants’ use of hip hop music and style as resources in performance. Much of young people's engagement with capital in performance enables their relatively overt and self-conscious process of clarifying who they are in relationship to one another, often with particular reference to race and ethnicity. Their engagement with globally relevant mediums is indicative of young people's agency in defining their own lives in the context of the political and moral framework of Australian multiculturalism.     

Estradiol's beneficial effect on murine muscle function is independent of muscle activity

Estradiol (E?) deficiency decreases muscle strength and wheel running in female mice. It is not known if the muscle weakness results directly from the loss of E? or indirectly from mice becoming relatively inactive with presumably diminished muscle activity. The first aim of this study was to determine if cage activities of ovariectomized mice with and without E? treatment differ. Ovariectomized mice were 19-46% less active than E?-replaced mice in terms of ambulation, jumping, and time spent being active (P ≤ 0.033). After E?-deficient mice were found to have low cage activities, the second aim was to determine if E? is beneficial to muscle contractility, independent of physical activities by the mouse or its hindlimb muscles. Adult, female mice were ovariectomized or sham-operated and randomized to receive E? or placebo and then subjected to conditions that should maintain physical and muscle activity at a constant low level. After 2 wk of hindlimb suspension or unilateral tibial nerve transection, muscle contractile function was assessed. Soleus muscles of hindlimb-suspended ovariectomized mice generated 31% lower normalized (relative to muscle contractile protein content) maximal isometric force than suspended mice with intact ovaries (P ≤ 0.049). Irrespective of whether the soleus muscle was innervated, muscles from ovariectomized mice generated ～20% lower absolute and normalized maximal isometric forces, as well as power, than E?-replaced mice (P ≤ 0.004). In conclusion, E? affects muscle force generation, even when muscle activity is equalized.     

Not Looking a Gift Horse in the Mouth: Exploring the Merits of a Student–Teacher–Scientist Partnership

One major emphasis of reform initiatives in science education is the importance of extended inquiry experiences for students through authentic collaborations with scientists. As such, unique partnerships have started to emerge between science and education in an ongoing effort to capture the interest and imaginations of students as they make sense of the world around them. One such partnership is called the student–teacher–scientist partnership, in which teachers and their students participate in and contribute to the research of scientists. This article explores a partnership between a 10th-grade biology teacher, her students, and practicing scientists who collaborated in the design, implementation and evaluation of a horse evolution unit. The primary goal of the collaborative activity was to involve teachers and students in a process of conceptual change as a means of eliminating common misconceptions implicit in horse evolution displays in museums in various parts of the country. The evidence-based lessons developed enhanced students’ understanding of concepts in macroevolution but also connected the science classroom with a community of scientists whose personalization of the horse evolution unit situated biological concepts and the learning experience within the context of real-world issues.     

Proteins containing an uncleaved signal for glycophosphatidylinositol membrane anchor attachment are retained in a post-ER compartment

Glycophosphatidylinositol (GPI)-anchored membrane proteins are initially synthesized with a cleavable COOH-terminal extension that signals anchor attachment. Overexpression in COS cells of hGH-DAF fusion proteins containing the GPI signal of decay accelerating factor (DAF) fused to the COOH-terminus of human growth hormone (hGH), produces both GPI-anchored hGH-DAF and uncleaved precursors that retain the GPI signal. Using hGH-DAF fusion proteins containing a mutated, noncleavable GPI signal, we show that uncleaved polypeptides are retained inside the cell and accumulate in a brefeldin A-sensitive, Golgi-like juxtanuclear structure. Retention requires the presence of either a functional or a noncleavable GPI signal; hGH-DAF fusion proteins containing only the COOH-terminal hydrophobic domain (a component of the GPI signal) are secreted. Immunofluorescence analysis shows colocalization of the retained, uncleaved fusion proteins with both a Golgi marker and with p53, a marker of the ER-Golgi intermediate compartment. Since N-linked glycosylation is postulated to facilitate the transport of proteins to the cell surface, we engineered a glycosylation site into hGH-DAF. Glycosylation failed to completely override the transport block, but allowed some uncleaved hGH-DAF to pass through the secretory pathway and acquire endoglycosidase H resistance. The retained molecules remained endoglycosidase H sensitive. We suggest that the uncleaved fusion protein is retained in a sorting compartment between the ER and the medial Golgi complex. We speculate that a mechanism exists to retain proteins containing an uncleaved GPI signal as part of a system for quality control.     

Three loci on mouse chromosome 5 and 10 modulate sex determination in XX Ods/+ mice

In mouse, XY embryos are committed to the male sex determination pathway after the transient expression of the Y-linked Sry gene in the Sertoli cell lineage between 10.5 and 12.5 dpc. In the C57BL/6J strain, male sex determination program can be modulated by some autosomal genes. The C57BL/6J alleles at these autosomal loci can antagonize male sex determination in combination with specific Sry alleles. In this report, the authors have identified an effect of these C57BL/6J specific alleles in combination with a mutated Sox9 allele, Sox9(Ods). Authors report the mapping of three of these genetic loci on mouse chromosome 5 and 10 in a backcross of the Ods mutation to the C57BL/6J background. Our study confirms the importance of the strain C57BL/6J for the investigation of the genetic mechanisms that control sex determination.     

Preface

Reviews in Environmental Science and Bio/Technology -     

Assembly and interactions of cotJ-encoded proteins, constituents of the inner layers of the Bacillus subtilis spore coat

During Bacillus subtilis endospore formation, a complex protein coat is assembled around the maturing spore. The coat is made up of more than two dozen proteins that form an outer layer, which provides chemical resistance, and an inner layer, which may play a role in the activation of germination. A third, amorphous layer of the coat occupies the space between the inner coat and the cortex, and is referred to as the undercoat. Although several coat proteins have been characterized, little is known about their interactions during assembly of the coat. We show here that at least two open reading frames of the cotJ operon ( cotJA and cotJC ) encode spore coat proteins. We suggest that CotJC is a component of the undercoat, since we found that its assembly onto the forespore is not prevented by mutations that block both inner and outer coat assembly, and because CotJC is more accessible to antibody staining in spores lacking both of these coat layers. Assembly of CotJC into the coat is dependent upon expression of cotJA . Conversely, CotJA is not detected in the coats of a cotJC insertional mutant. Co-immunoprecipitation was used to demonstrate the formation of complexes containing CotJA and CotJC 6 h after the onset of sporulation. Experiments with the yeast two-hybrid system indicate that CotJC may interact with itself and with CotJA. We suggest that interaction of CotJA with CotJC is required for the assembly of both CotJA and CotJC into the spore coat.     

Dimethylsulfoniopropionate Turnover Is Linked to the Composition and Dynamics of the Bacterioplankton Assemblage during a Microcosm Phytoplankton Bloom

Processing of the phytoplankton-derived organic sulfur compound dimethylsulfoniopropionate (DMSP) by bacteria was studied in seawater microcosms in the coastal Gulf of Mexico (Alabama). Modest phytoplankton blooms (peak chlorophyll a [Chl a] concentrations of ~2.5 μg liter⁻¹) were induced in nutrient-enriched microcosms, while phytoplankton biomass remained low in unamended controls (Chl a concentrations of ~0.34 μg liter⁻¹). Particulate DMSP concentrations reached 96 nM in the enriched microcosms but remained approximately 14 nM in the controls. Bacterial biomass production increased in parallel with the increase in particulate DMSP, and nutrient limitation bioassays in the initial water showed that enrichment with DMSP or glucose caused a similar stimulation of bacterial growth. Concomitantly, increased bacterial consumption rate constants of dissolved DMSP (up to 20 day⁻¹) and dimethylsulfide (DMS) (up to 6.5 day⁻¹) were observed. Nevertheless, higher DMSP S assimilation efficiencies and higher contribution of DMSP to bacterial S demand were found in the controls compared to the enriched microcosms. This indicated that marine bacterioplankton may rely more on DMSP as a source of S under oligotrophic conditions than under the senescence phase of phytoplankton blooms. Phylogenetic analysis of the bacterial assemblages in all microcosms showed that the DMSP-rich algal bloom favored the occurrence of various Roseobacter members, flavobacteria (Bacteroidetes phylum), and oligotrophic marine Gammaproteobacteria. Our observations suggest that the composition of the bacterial assemblage and the relative contribution of DMSP to the overall dissolved organic sulfur/organic matter pool control how efficiently bacteria assimilate DMSP S and thereby potentially divert it from DMS production.     

External Protons Enhance the Activity of the Hyperpolarization-activated K Channels in Guard Cell Protoplasts of Vicia faba

Hyperpolarization-activated K channels (K _H channels) in the plasmalemma of guard cells operate at apoplastic pH range of 5 to over 7. Using patch clamp in a whole-cell mode, we characterized the effect of varying the external pH between 4.4–8.1 on the activity of the K _H channels in isolated guard cell protoplasts from Vicia faba leaves. Acidification from pH 5.5 to 4.4 increased the macroscopic conductance of the K _H channels by 30–150% while alkalinization from pH 5.5 to 8.1 decreased it only by roughly 15%. The voltage-independent maximum cell conductance, increased by ∼60% between pH 8.1 and 4.4 with an apparent pK _a of 5.3, most likely owing to the increased availability of channels. Voltage-dependent gating was affected only between pH 5.5 and 4.4. Acidification in this range shifted the voltage-dependent open probability by over 10 mV. We interpret this shift as an increase of the electrical field sensed by the gating subunits caused by the protonation of external negative surface charges. Within the framework of a surface charge model the mean spacing of these charges was ∼30 ? and their apparent dissociation constant was 10^−4.6. The overall voltage sensitivity of gating was not altered by pH changes. In a subgroup of protoplasts analyzed within the framework of a Closed-Closed-Open model, the effect of protons on gating was limited to shifting of the voltage-dependence of all four transition rate constants. Received: 26 April 1996/Revised: 29 June 1996