Coarse-Scale Distribution Surveys and Occurrence Probability Modeling for Wolverine in Interior Alaska

ABSTRACT We determined wolverine (Gulo gulo) distribution and occurrence probabilities using aerial surveys and hierarchical spatial modeling in a 180,000-km² portion of Interior Alaska, USA. During 8 February-12 March 2006, we surveyed 149 of 180 1,000-km² sample units for wolverine tracks. We observed wolverine tracks in 99 (66.4%) sample units. Wolverine detection probability was ≥69% throughout the survey period. Posterior occurrence probabilities of whether a wolverine track occurred in a sample unit was dependent on survey timing, number of transects flown, number of neighboring sample units with detected tracks, percentage of the sample unit with elevation ≤305 m, and human influences. Our model indicated strong evidence of occurrence (>0.80) in 72% of the 180 survey units, strong evidence of absence (<0.20) in 12%, and weak evidence of occurrence or absence (0.20–0.80) in 16%. Wolverine area of occupancy made up 83% of the study area. Simulations illustrated that 2–4 survey routes were necessary for the survey technique to provide strong evidence of wolverine presence or absence in Interior Alaska if a track was not identified along the first route. The necessary number of survey routes depends on the occurrence probability in a sample unit. We provided managers with a map of wolverine distribution in Interior Alaska and an efficient and lower-cost method to detect coarse-scale changes in wolverine distribution. Our technique was effective in both Interior Alaska and Ontario, Canada, suggesting it would be effective throughout most of the boreal forest range of wolverines where tracks can be readily observed from the air. The technique requires a certain skill level in recognizing tracks; it is essential that tracks are identified correctly and training may be necessary depending on surveyor experience.     

Divergence Among an International Population of Trichophyton tonsurans Isolates

Trichophyton tonsurans is a widely distributed pathogen that demonstrates a significant degree of genetic and phenetic heterogeneity. To date, the degree of genetic relatedness among geographically segregated isolates has not been explored. This investigation evaluates the extent of genetic variation among an international population of T. tonsurans isolates and examines the relatedness of isolates within and between countries. Molecular strain typing was performed on 198 isolates obtained from 14 countries. A mixed-marker strategy utilizing 27 sequence variations in 13 gene loci was applied to all isolates and cluster analysis was performed to examine the relationship between strains. Phylogenetic analysis was used to corroborate the findings of the cluster analysis with T. equinum strains serving as an out-group. In total, 47 distinct strain types were identified represented by seven clusters and one singleton. There appeared to be a moderate degree of clustering among isolates obtained from North America, Asia and Australia, although European isolates were uniformly distributed among the majority of clusters. The degree of genetic variation observed in this study coupled with the geographic localization would support the argument for allopatric divergence within this species.     

Effects of Planting Depth,Sediment Grain Size,and Nutrients on Ruppia maritima and Potamogeton perfoliatus Seedling Emergence and Growth

Protocols are now available for seed harvest, storage and germination of several mesohaline and polyhaline species; however, low seedling survival rates point to the need for an increased understanding of factors affecting seedling establishment. Depth of seed burial in sediments and initial seedling growth rates are shown to be limiting factors for photosynthetic competency of Ruppia maritima and Potamogeton perfoliatus. Seedling emergence is inversely proportional to planting depth on sediments ranging in grain size from coarse sands (850 μm) to silt (63 μm). Less than 6% of the seeds of either species emerged when buried to a depth of 3 cm in test sediments. Germination was greatest for seeds placed on the surface of sediments; however, these seedlings were subject to displacement because of the weak and fragile roots produced during early growth. Fine sediments may be more favorable for R. maritima seedling establishment, because seedling emergence and height decreased with increasing sediment grain size. Potamogeton perfoliatus seedlings seem to be more tolerant of a wider range of sediment grain sizes than R. maritima as indicated by the lack of an effect of sediment grain size on P. perfoliatus seed emergence, seedling height, and biomass. Increasing nutrients stimulated seedlings of both species; however, even at the highest concentrations tested, growth, as determined by shoot elongation and leaf and root formation, slowed within 7–10 days. This suggests factors other than mineral nutrients and light limit growth or that growth shifts from aboveground biomass production to belowground vegetative spread.     

Characterization of a candidate Borrelia burgdorferi beta3-chain integrin ligand identified using a phage display library

The spirochaetal agents of Lyme disease, Borrelia burgdorferi (sensu lato) bind to integrins alphaIIbbeta3, alphavbeta3 and alpha5beta1 in purified form and on the surfaces of human cells. Using a phage display library of B. burgdorferi (sensu stricto) DNA, a candidate ligand for beta3-chain integrins was identified. The native B. burgdorferi protein, termed p66, is known to be recognized by human Lyme disease patient sera and to be expressed on the surface of the spirochaete. We show here that recombinant p66 binds specifically to beta3-chain integrins and inhibits attachment of intact B. burgdorferi to the same integrins. When expressed on the surface of Escherichia coli, this protein increases the attachment of E. coli to a transfected cell line that expresses alphavbeta3, but not to the parental cell line, which expresses no beta3-chain integrins. Localization of p66 on the surface of B. burgdorferi, the ability of recombinant forms of the protein to bind to beta3-chain integrins and the fact that p66 and B. burgdorferi bind to beta3-chain integrins in a mutually exclusive manner make p66 an attractive candidate bacterial ligand for integrins alphaIIbbeta3 and alphavbeta3.     

Multiple glucose 6-phosphate pools or channelling of flux in diverse pathways?

Glucose 6-phosphate is an intermediate of pathways of glucose utilization and production as well as a regulator of enzyme activity and gene expression. Studies on the latter functions are in part based on measurement of the glucose 6-phosphate content in a whole-cell extract. Several studies have suggested that there are multiple subcellular pools of glucose 6-phosphate. It is proposed that this data can be interpreted in terms of channelling of metabolic intermediates through multiple pathways of glucose metabolism with leakage of glucose 6-phosphate from the channels into a single free pool. It is also proposed that measurement of total tissue content of glucose 6-phosphate approximates the free pool.     

Response to transforming growth factor α (TGFα) and epidermal growth factor (EGF) in hepatocytes: Lower EGF receptor affinity of TGFα is associated with more sustained activation of p42/p44 mitogen-activated protein kinase and greater efficacy in stimulation of DNA synthesis

The epidermal growth factor (EGF) receptor mediates the effects of both EGF and transforming growth factor α (TGFα). Recent data suggested that EGF acts as a partial agonist/antagonist in hepatocytes, TGFα exerting a larger maximal stimulation of DNA synthesis than EGF. To further study the mechanisms involved in mediating the different effects of EGF and TGFα, we have examined receptor binding of the two growth factors and their action on the p42/p44 mitogen-activated protein (MAP) kinase activity in hepatocytes. Single-ligand concentration curves and competition experiments showed that the binding affinity to a common population of surface binding sites was about 20-fold lower for TGFα than for EGF. MAP kinase activity responded to EGF and TGFα with different kinetics. While the two agents produced almost identical acute (5 min) stimulation (peak about fivefold), TGFα produced a more sustained MAP kinase activity than EGF. The difference between EGF and TGFα was still detectable 24 h after growth factor addition. The results show that in hepatocytes a lower receptor affinity of TGFα, as compared to EGF, is associated with a more sustained activation of the MAP kinase and a greater efficacy in the stimulation of DNA synthesis. This suggests that differential interaction of these two agents with the EGF receptor results in differences in the downstream events elicited at a given level of receptor occupancy. The data also are compatible with a role of a prolonged MAP kinase activity in the mitogenic effects of EGF and TGFα. J. Cell. Physiol. 175:10–18, 1998. © 1998 Wiley-Liss, Inc.     

Acetylcholine exerts additive and permissive but not synergistic effects with insulin on glycogen synthesis in hepatocytes

Parasympathetic (cholinergic) innervation is implicated in the stimulation of hepatic glucose uptake by portal vein hyperglycaemia. We determined the direct effects of acetylcholine on hepatocytes. Acute exposure to acetylcholine mimicked insulin action on inactivation of phosphorylase, stimulation of glycogen synthesis and suppression of phosphoenolpyruvate carboxykinase mRNA levels but with lower efficacy and without synergy. Pre-exposure to acetylcholine had a permissive effect on insulin action similar to glucocorticoids and associated with increased glucokinase activity. It is concluded that acetylcholine has a permissive effect on insulin action but cannot fully account for the rapid stimulation of glucose uptake by the portal signal.     

Amino acid metabolism in hepatocytes isolated from lactating rats

Parenchymal hepatocytes isolated from lactating rats had similar rates of amino acid incorporation into protein, but increased rates of urea formation compared to hepatocytes from non-lactating rats. The increased urea formation may be due to increased amino acid transport and degradation. The liver contributes to the increased utilization of amino acids during lactation.