Constant-parameter capture-recapture models

Jolly (1982, Biometrics 38, 301-321) presented modifications of the Jolly-Seber model for capture-recapture data, which assume constant survival and/or capture rates. Where appropriate, because of the reduced number of parameters, these models lead to more efficient estimators than the Jolly-Seber model. The tests to compare models given by Jolly do not make complete use of the data, and we present here the appropriate modifications, and also indicate how to carry out goodness-of-fit tests which utilize individual capture history information. We also describe analogous models for the case where young and adult animals are tagged. The availability of computer programs to perform the analysis is noted, and examples are given using output from these programs.     

Structure of the mammalian CoA transferase from pig heart

Ketoacidosis affects patients who are deficient in the enzyme activity of succinyl-CoA:3-ketoacid CoA transferase (SCOT), since SCOT catalyses the activation of acetoacetate in the metabolism of ketone bodies. Thus far, structure/function analysis of the mammalian enzyme has been predicted based on the three-dimensional structure of a CoA transferase determined from an anaerobic bacterium that utilizes its enzyme for glutamate fermentation. To better interpret clinical data, we have determined the structure of a mammalian CoA transferase from pig heart by X-ray crystallography to 2.5 A resolution. Instrumental to the structure determination were selenomethionine substitution and the use of argon during purification and crystallization. Although pig heart SCOT adopts an alpha/beta protein fold, resembling the overall fold of the bacterial CoA transferase, several loops near the active site of pig heart SCOT follow different paths than the corresponding loops in the bacterial enzyme, accounting for differences in substrate specificities. Two missense mutations found associated with SCOT of ketoacidosis patients were mapped to a location in the structure that might disrupt the stabilization of the amino-terminal strand and thereby interfere with the proper folding of the protein into a functional enzyme.     

Spatio‐temporal scaling of biodiversity and the species–time relationship in a stream fish assemblage

1. The increase of species richness with the area of the habitat sampled, that is the species–area relationship, and its temporal analogue, the species–time relationship (STR), are among the few general laws in ecology with strong conservation implications. However, these two scale‐dependent phenomena have rarely been considered together in biodiversity assessment, especially in freshwater systems. 2. We examined how the spatial scale of sampling influences STRs for a Central‐European stream fish assemblage (second‐order Bernecei stream, Hungary) using field survey data in two simulation‐based experiments. 3. In experiment one, we examined how increasing the number of channel units, such as riffles and pools (13 altogether), and the number of field surveys involved in the analyses (12 sampling occasions during 3 years), influence species richness. Complete nested curves were constructed to quantify how many species one observes in the community on average for a given number of sampling occasions at a given spatial scale. 4. In experiment two, we examined STRs for the Bernecei fish assemblage from a landscape perspective. Here, we evaluated a 10‐year reach level data set (2000–09) for the Bernecei stream and its recipient watercourse (third‐order Kemence stream) to complement results on experiment one and to explore the mechanisms behind the observed patterns in more detail. 5. Experiment one indicated the strong influence of the spatial scale of sampling on the accumulation of species richness, although time clearly had an additional effect. The simulation methodology advocated here helped to estimate the number of species in a diverse combination of spatial and temporal scale and, therefore, to determine how different scale combinations influence sampling sufficiency. 6. Experiment two revealed differences in STRs between the upstream (Bernecei) and downstream (Kemence) sites, with steeper curves for the downstream site. Equations of STR curves were within the range observed in other studies, predominantly from terrestrial systems. Assemblage composition data suggested that extinction–colonisation dynamics of rare, non‐resident (i.e. satellite) species influenced patterns in STRs. 7. Our results highlight that the determination of species richness can benefit from the joint consideration of spatial and temporal scales in biodiversity inventory surveys. Additionally, we reveal how our randomisation‐based methodology may help to quantify the scale dependency of diversity components (α, β, γ) in both space and time, which have critical importance in the applied context.     

Regional muscle oxygenation differences in vastus lateralis during different modes of incremental exercise

Background

Near infrared spectroscopy (NIRS) is used to assess muscle oxygenation (MO) within skeletal muscle at rest and during aerobic exercise. Previous investigations have used a single probe placement to measure MO during various forms of exercise. However, regional MO differences have been shown to exist within the same muscle which suggests that different areas of the same muscle may have divergent MO. Thus, the aim of this study was to examine whether regional differences in MO exist within the same muscle during different types of incremental (rest, 25, 50, 75, 100 % of maximum) exercise (1 leg knee extension (KE), 2 leg KE, or cycling).

Methods

Nineteen healthy active males (Mean ± SD: Age 27 ± 4 yrs; VO_2max: 55 ± 11 mL/kg/min) performed incremental exercise to fatigue using each mode of exercise. NIRS probes were placed on the distal and proximal portion of right leg vastus lateralis (VL). Results were analyzed with a 3-way mixed model ANOVA (probe × intensity × mode).

Results

Differences in MO exist within the VL for each mode of exercise, however these differences were not consistent for each level of intensity. Comparison of MO revealed that the distal region of VL was significantly lower throughout KE exercise (1 leg KE proximal MO – distal MO = 9.9 %; 2 leg KE proximal MO – distal MO = 13 %). In contrast, the difference in MO between proximal and distal regions of VL was smaller in cycling and was not significantly different at heavy workloads (75 and 100 % of maximum).

Conclusion

MO is different within the same muscle and the pattern of the difference will change depending on the mode and intensity of exercise. Future investigations should limit conclusions on MO to the area under assessment as well as the type and intensity of exercise employed.

     

Association of FCGR2A and FCGR2A-FCGR3A haplotypes with susceptibility to giant cell arteritis

The Fc gamma receptors have been shown to play important roles in the initiation and regulation of many immunological and inflammatory processes and to amplify and refine the immune response to an infection. We have investigated the hypothesis that polymorphism within the FCGR genetic locus is associated with giant cell arteritis (GCA). Biallelic polymorphisms in FCGR2A, FCGR3A, FCGR3B and FCGR2B were examined for association with biopsy-proven GCA (n = 85) and healthy ethnically matched controls (n = 132) in a well-characterised cohort from Lugo, Spain. Haplotype frequencies and linkage disequilibrium (D') were estimated across the FCGR locus and a model-free analysis performed to determine association with GCA. There was a significant association between FCGR2A-131RR homozygosity (odds ratio (OR) 2.10, 95% confidence interval (CI) 1.12 to 3.77, P = 0.02, compared with all others) and carriage of FCGR3A-158F (OR 3.09, 95% CI 1.10 to 8.64, P = 0.03, compared with non-carriers) with susceptibility to GCA. FCGR haplotypes were examined to refine the extent of the association. The haplotype showing the strongest association with GCA susceptibility was the FCGR2A-FCGR3A 131R-158F haplotype (OR 2.84, P = 0.01 for homozygotes compared with all others). There was evidence of a multiplicative joint effect between homozygosity for FCGR2A-131R and HLA-DRB1*04 positivity, consistent with both of these two genetic factors contributing to the risk of disease. The risk of GCA in HLA-DRB1*04 positive individuals homozygous for the FCGR2A-131R allele is increased almost six-fold compared with those with other FCGR2A genotypes who are HLA-DRB1*04 negative. We have demonstrated that FCGR2A may contribute to the 'susceptibility' of GCA in this Spanish population. The increased association observed with a FCGR2A-FCGR3A haplotype suggests the presence of additional genetic polymorphisms in linkage disequilibrium with this haplotype that may contribute to disease susceptibility. These findings may ultimately provide new insights into disease pathogenesis.     

The in vivo effect of indomethacin and prostaglandin E2 on ACTH and DBCAMP-induced steroidogenesis in hypophysectomized rats

The level of plasma corticosterone attained in hypophysectomized rats stimulated with ACTH was significantly reduced by pretreatment with indomethacin, an inhibitor of prostaglandin synthesis. This effect was not seen in animals stimulated with dibutyryl cyclic AMP. Intraperitoneal injection of prostaglandin E₂ to indomethacin treated rats restored the normal response to ACTH stimulation. However, PGE₂ itself did not have any significant effect on plasma corticosterone levels. These findings suggest that prostaglandins are involved, perhaps in an allosteric fashion, in the mechanism of action of ACTH.