Evaluation of Maternal Penning to Improve Calf Survival in the Chisana Caribou Herd

Predation is a major limiting factor for most small sedentary caribou (Rangifer tarandus) populations, particularly those that are threatened or endangered across the southern extent of the species’ range. Thus, reducing predation impacts is often a management goal for improving the status of small caribou populations, and lethal predator removal is the primary approach that has been applied. Given that predator control programs are often contentious, other management options that can garner broader public acceptance need to be considered. Substantial calf losses to predation in the few weeks following birth are common for these small caribou populations. Therefore, we employed a novel experimental approach of maternal penning with the goal of reducing early calf mortality in the Chisana Caribou Herd, a declining population in southwest Yukon and adjacent Alaska thought to number around 300 individuals. Maternal penning entailed temporarily holding pregnant females on their native range in a large pen secure from predators from late March through the initial weeks of calf rearing to mid-June. During 2003–2006, we conducted 4 annual penning trials with 17–50 pregnant females each year (n = 146 total), assessed survival of calves born in the pens, and evaluated survival and nutritional effects of penning for females that were held. We also investigated the herd's population dynamics during 2003–2008 to determine effects of maternal penning on calf recruitment and population growth. In addition to information gained during maternal penning, we determined natality and survival patterns via radiotelemetry, conducted autumn age-sex composition surveys each year, and censused the population in mid-October 2003, 2005, and 2007. Based on our penning trials and demographic investigations, we used simulation models to evaluate the effects of maternal penning relative to a population's inherent growth rate (finite rate of increase [λ] without maternal penning) and penning effort (proportion of calves born in penning) to provide perspective on utility of this approach for improving the status of small imperiled caribou populations. Pregnant females held in maternal penning tolerated captivity well in that they exhibited positive nutritional responses to ad libitum feed we provided and higher survival than free-ranging females (0.993 and 0.951 for penned and free-ranging females, respectively). Survival of pen calves from birth to mid-June was substantially higher than that of free-ranging calves ( = 0.950 and 0.376, respectively). This initial period accounted for 76% of the annual calf mortality in the free-ranging population. Pen-born calves maintained their survival advantage over wild-born calves to the end of their first year ( = 0.575 and 0.192, respectively) during years penning occurred. Females in the Chisana Herd were highly productive with 57% producing their first offspring at 2 years of age, and annual natality rates averaging 0.842 calves/female ≥2 years old. Age-specific natality rates exceeded 0.900 for 4–9-year-olds, then exhibited senescent decline to 0.467 by 19 years old. Annual survival of free-ranging adult females and calves averaged 0.892 and 0.184, respectively, over all study years; both were reduced during 2004 because of poor winter survival. We noted reduced nutritional condition of caribou late that winter in that females we captured were lighter than in other years and produced lighter calves. We suspect that the reduced survival during winter 2004 and the observed nutritional characteristics resulted from adverse snow conditions in combination with effects of the extreme drought experienced the previous summer. Age-specific survival of adult females was ≥0.900 through 10 years of age, then declined with age. The Chisana Herd numbered 720 caribou in mid-October 2003, or more than twice that estimated prior to initiating maternal penning, and increased to 766 caribou by mid-October 2007. We calculated that penning added 54.2 yearling recruits, or 40% of calves released from penning. Based on the maternal penning results and the population's vital rates, we determined that the herd would have been stable during 2003–2007 at about 713 caribou without maternal penning; thus, the increase in herd size we observed resulted from maternal penning and was equivalent to the estimate of additional yearling recruits. The improvement in the population trend invoked by maternal penning was limited by the larger than expected population size and resulting low penning effort ( = 11% of calves born in pen). Our simulations corroborated that maternal penning increased population size by the number of additional recruits provided, even at low penning effort, for inherently stable populations. As the inherent rate of increase dropped below λ = 1.000, more of the additional recruits from penning were needed to offset the downward population inertia, thus requiring increased penning effort to reach stability. For populations declining at λ < 0.890, stability could not be achieved with 100% penning effort given the vital rates in our models. Maternal penning in its limited application to date has proven to be broadly popular as a nonlethal management action aimed at reducing initial calf mortality from predation in small caribou populations. However, based on the Chisana program and 3 subsequent efforts elsewhere, improvement in population trends have been modest at best and come at a high financial cost. Given the necessity of maximizing penning effort, maternal penning may have a role in addressing conservation challenges for some small caribou populations that are stable or slowly declining, but its application should be primarily driven by objective assessment of the likelihood of improving population trends rather than popularity relative to other management options.     

Neurocognitive and Hormonal Correlates of Voluntary Weight Loss in Humans

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Biochemical characterization of WbpA, a UDP-N-acetyl-D-glucosamine 6-dehydrogenase involved in O-antigen biosynthesis in Pseudomonas aeruginosa PAO1

WbpA (PA3159) is an enzyme involved in the biosynthesis of unusual di-N-acetyl-d-mannosaminuronic acid-derived sugar nucleotides found in the O antigen of Pseudomonas aeruginosa PAO1 (serotype O5). The wbpA gene that encodes this enzyme was cloned into pET-28a, overexpressed as a histidine-tagged fusion protein, and purified by nickel chelation chromatography. Capillary electrophoresis was used to examine substrate conversion by WbpA, and the data revealed that WbpA is a UDP-N-acetyl-D-glucosamine 6-dehydrogenase (EC 1.1.1.136), which uses NAD(+) as a coenzyme. The enzyme reaction product was purified by HPLC and analyzed using NMR spectroscopy. Our results showed unequivocally that the product of the WbpA reaction is UDP-N-acetyl-d-glucosaminuronic acid. WbpA requires either NH(4)(+) or K(+) for activity and the accompanying anions exert secondary effects on activity consistent with their ranking in the Hofmeister series. Kinetic analysis showed positive cooperativity with respect to UDP-N-acetyl-d-glucosamine binding with a K(0.5) of 94 microM, a k(cat) of 86 min(-1), and a Hill coefficient of 1.8. In addition, WbpA has a K(0.5) for NAD(+) of 220 microM, a k(cat) of 86 min(-1), and a Hill coefficient of 1.1. The oligomerization state of WbpA was analyzed by gel filtration, dynamic light scattering, and analytical ultracentrifugation, with all three techniques indicating that WbpA exists as a trimer in solution. However, tertiary structure predictions suggested a tetramer, which was supported by data from transmission electron microscopy. The electron micrograph of negatively stained WbpA samples revealed structures with 4-fold symmetry.     

Constitutive activation of the Saccharomyces cerevislae mating response pathway by a MAP kinase kinase from Candida albicans

The HST7 gene of Candida albicans encodes a protein with structural similarity to MAP kinase kinases. Expression of this gene in Saccharomyces cerevisiae complements disruption of the Ste7 MAP kinase kinase required for both mating in haploid cells and pseudohyphal growth in diploids. However, Hst7 expression does not complement loss of either the Pbs2 (Hog4) MAP kinase kinase required for response to high osmolarity, or loss of the Mkk1 and Mkk2 MAP kinase kinases required for proper cell wall biosynthesis. Intriguingly, HST7 acts as a hyperactive allele of STE7; expression of Hst7 activates the mating pathway even in the absence of upstream signaling components including the Ste7 regulator Ste11, elevates the basal level of the pheromone-inducible FUS1 gene, and amplifies the pseudohyphal growth response in diploid cells. Thus Hst7 appears to be at least partially independent of upstream activators or regulators, but selective in its activity on downstream target MAP kinases. Creation of Hst7/Ste7 hybrid proteins revealed that the C-terminal two-thirds of Hst7, which contains the protein kinase domain, is sufficient to confer this partial independence of upstream activators.     

Burst and coast use, swimming performance and metabolism of Atlantic cod Gadus morhua in sub-lethal hypoxic conditions

Prolonged swimming capacity (critical swimming speed, U _crit, protocol) and metabolism were measured for 14 Atlantic cod Gadus morhua exposed to seven oxygen levels within the non-lethal range normally encountered in the Gulf of St Lawrence (35 to 100% saturation). Burst-and-coast swimming was triggered earlier (at lower speeds) in hypoxia, and burst-and-coast movements were more frequent in hypoxia than in normoxia at low speeds. Furthermore, the metabolic scope beyond the metabolic rate at which Atlantic cod resorted to burst-and-coast movements decreased gradually as ambient oxygen concentration dropped. Overall, fewer burst-and-coast movements were observed in hypoxia while the distance swum in burst-and-coast mode remained c . 1% of the total distance swam in all tests. Oxygen availability had no effect on the rate of increase in metabolic rate with increasing velocity <50 cm s⁻¹_, but limited swimming performances and metabolic rate at higher speeds. The prevailing low oxygen tensions on the bottom in the deep channels may impair the swimming capacity of Atlantic cod in the estuary and northern Gulf of St Lawrence.     

Biological effects of a bifunctional DNA crosslinker. I. Generation of triradial and quadriradial chromosomes.

Interduplex crosslinks by a bifunctional anthramycin DNA crosslinker produced triradial and quadriradial chromosomes. The crosslinker alkylates guanine at N-2. Bovine chromosomes contain GC-rich density satellite DNAs at the centromeric heterochromatin and is the basis for the formation of triradial and quadriradial chromosomes at the centromeres. The in situ crosslinking of interphase chromosomes indicates that the distance between centromeres is 17.5 A. We conclude that the nuclear matrix associated DNA in the centromeric heterochromatin of interphase chromosomes are positioned close enough for crosslinking to occur. We propose a model for the generation of triradial and quadriradial chromosomes based upon the number of interduplex crosslinks between two chromosomes.     

Environmental factors explaining the vegetation patterns in a temperate peatland

Although ombrotrophic temperate peatlands are important ecosystems for maintaining biodiversity in eastern North America, the environmental factors influencing their flora are only partly understood. The relationships between plant species distribution and environmental factors were thus studied within the oldest temperate peatland of Québec. Plant assemblages were identified by cluster analysis while CCA was used to related vegetation gradients to environmental factors. Five assemblages were identified; three typical of open bog and two characterized by more minerotrophic vegetation. Thicker peat deposit was encounter underlying the bog assemblages while higher water table level and percentage of free surface water distinguished the minerotrophic assemblages. Overall, the floristic patterns observed were spatially structured along the margins and the expanse. The most important environmental factors explaining this spatial gradient were the percentage of free surface water and the highest water-table level. To cite this article: S. Pellerin et al., C. R. Biologies 332 (2009).     

High depth, whole-genome sequencing of cholera isolates from Haiti and the Dominican Republic

ABSTRACT: BACKGROUND: Whole-genome sequencing is an important tool for understanding microbial evolution and identifying the emergence of functionally important variants over the course of epidemics. In October 2010, a severe cholera epidemic began in Haiti, with additional cases identified in the neighboring Dominican Republic. We used whole-genome approaches to sequence four Vibrio cholerae isolates from Haiti and the Dominican Republic and three additional V. cholerae isolates to a high depth of coverage (>2000x); four of the seven isolates were previously sequenced. RESULTS: Using these sequence data, we examined the effect of depth of coverage and sequencing platform on genome assembly and identification of sequence variants. We found that 50x coverage is sufficient to construct a whole-genome assembly and to accurately call most variants from 100 base pair paired-end sequencing reads. Phylogenetic analysis between the newly sequenced and thirty-three previously sequenced V. cholerae isolates indicates that the Haitian and Dominican Republic isolates are closest to strains from South Asia. The Haitian and Dominican Republic isolates form a tight cluster, with only four variants unique to individual isolates. These variants are located in the CTX region, the SXT region, and the core genome. Of the 126 mutations identified that separate the Haiti-Dominican Republic cluster from the V. cholerae reference strain (N16961), 73 are non-synonymous changes, and a number of these changes cluster in specific genes and pathways. CONCLUSIONS: Sequence variant analyses of V. cholerae isolates, including multiple isolates from the Haitian outbreak, identify coverage-specific and technology-specific effects on variant detection, and provide insight into genomic change and functional evolution during an epidemic.     

Effect of sodium bicarbonate as a pharmaceutical formulation excipient on the interaction of fluvastatin with membrane phospholipids

Excipients in the pharmaceutical formulation of oral drugs are notably employed to improve drug stability. However, they can affect drug absorption and bioavailability. Passive transport through intestinal cell walls is the main absorption mechanism of drugs and, thus, involves an interaction with the membrane lipids. Therefore in this work, the effect of the excipient NaHCO₃ on the interaction of the anticholesterolemic drug fluvastatin sodium (FS) with membrane phospholipids was investigated by ¹H NMR and FTIR spectroscopy. Sodium bicarbonate is often combined with fluvastatin for oral delivery to prevent its degradation. We have used model DMPC/DMPS membranes to mimic the phospholipid content of gut cell membranes. The results presented in this work show a 100% affinity of FS for the membrane phospholipids that is not modified by the presence of the excipient. However, NaHCO₃ is shown to change the interaction mechanism of the drug. According to our data, FS enters the DMPC/DMPS bilayer interface by interacting with the lipids’ polar headgroups and burying its aromatic moieties into the apolar core. Moreover, lipid segregation takes place between the anionic and zwitterionic lipids in the membranes due to a preferential interaction of FS with phosphatidylserines. The excipient counteracts this favored interaction without affecting the drug affinity and location in the bilayer. This work illustrates that preferential interactions with lipids can be involved in passive drug permeation mechanisms and gives evidence of a possible nonpassive role of certain excipients in the interaction of drugs with membrane lipids.     

Nuclear FAK promotes cell proliferation and survival through FERM-enhanced p53 degradation

FAK is known as an integrin- and growth factor-associated tyrosine kinase promoting cell motility. Here we show that, during mouse development, FAK inactivation results in p53- and p21-dependent mesodermal cell growth arrest. Reconstitution of primary FAK-/-p21-/- fibroblasts revealed that FAK, in a kinase-independent manner, facilitates p53 turnover via enhanced Mdm2-dependent p53 ubiquitination. p53 inactivation by FAK required FAK FERM F1 lobe binding to p53, FERM F2 lobe-mediated nuclear localization, and FERM F3 lobe for connections to Mdm2 and proteasomal degradation. Staurosporine or loss of cell adhesion enhanced FERM-dependent FAK nuclear accumulation. In primary human cells, FAK knockdown raised p53-p21 levels and slowed cell proliferation but did not cause apoptosis. Notably, FAK knockdown plus cisplatin triggered p53-dependent cell apoptosis, which was rescued by either full-length FAK or FAK FERM re-expression. These studies define a scaffolding role for nuclear FAK in facilitating cell survival through enhanced p53 degradation under conditions of cellular stress.