A longitudinal genetic survey identifies temporal shifts in the population structure of Dutch house sparrows.

Dutch house sparrow (Passer domesticus) densities dropped by nearly 50% since the early 1980s, and similar collapses in population sizes have been reported across Europe. Whether, and to what extent, such relatively recent demographic changes are accompanied by concomitant shifts in the genetic population structure of this species needs further investigation. Therefore, we here explore temporal shifts in genetic diversity, genetic structure and effective sizes of seven Dutch house sparrow populations. To allow the most powerful statistical inference, historical populations were resampled at identical locations and each individual bird was genotyped using nine polymorphic microsatellites. Although the demographic history was not reflected by a reduction in genetic diversity, levels of genetic differentiation increased over time, and the original, panmictic population (inferred from the museum samples) diverged into two distinct genetic clusters. Reductions in census size were supported by a substantial reduction in effective population size, although to a smaller extent. As most studies of contemporary house sparrow populations have been unable to identify genetic signatures of recent population declines, results of this study underpin the importance of longitudinal genetic surveys to unravel cryptic genetic patterns.

Post-fragmentation population structure in a cooperative breeding Afrotropical cloud forest bird: emergence of a source-sink population network.

The impact of demographic parameters on the genetic population structure and viability of organisms is a long-standing issue in the study of fragmented populations. Demographic and genetic tools are now readily available to estimate census and effective population sizes and migration and gene flow rates with increasing precision. Here we analysed the demography and genetic population structure over a recent 15-year time span in five remnant populations of Cabanis's greenbul (Phyllastrephus cabanisi), a cooperative breeding bird in a severely fragmented cloud forest habitat. Contrary to our expectation, genetic admixture and effective population sizes slightly increased, rather than decreased between our two sampling periods. In spite of small effective population sizes in tiny forest remnants, none of the populations showed evidence of a recent population bottleneck. Approximate Bayesian modelling, however, suggested that differentiation of the populations coincided at least partially with an episode of habitat fragmentation. The ratio of meta-Ne to meta-Nc was relatively low for birds, which is expected for cooperative breeding species, while Ne /Nc ratios strongly varied among local populations. While the overall trend of increasing population sizes and genetic admixture may suggest that Cabanis's greenbuls increasingly cope with fragmentation, the time period over which these trends were documented is rather short relative to the average longevity of tropical species. Furthermore, the critically low Nc in the small forest remnants keep the species prone to demographic and environmental stochasticity, and it remains open if, and to what extent, its cooperative breeding behaviour helps to buffer such effects.

Genetic diversity and population structure in contemporary house sparrow populations along an urbanization gradient.

House sparrow (Passer domesticus) populations have suffered major declines in urban as well as rural areas, while remaining relatively stable in suburban ones. Yet, to date no exhaustive attempt has been made to examine how, and to what extent, spatial variation in population demography is reflected in genetic population structuring along contemporary urbanization gradients. Here we use putatively neutral microsatellite loci to study if and how genetic variation can be partitioned in a hierarchical way among different urbanization classes. Principal coordinate analyses did not support the hypothesis that urban/suburban and rural populations comprise two distinct genetic clusters. Comparison of FST values at different hierarchical scales revealed drift as an important force of population differentiation. Redundancy analyses revealed that genetic structure was strongly affected by both spatial variation and level of urbanization. The results shown here can be used as baseline information for future genetic monitoring programmes and provide additional insights into contemporary house sparrow dynamics along urbanization gradients.

Metabolic correlates of tumour hypoxia in malignant canine mammary carcinoma.

Given its importance in human and canine tumour biology, a profound understanding of tumour hypoxia is of paramount importance. Therefore, the aim of this work was to investigate the relationship between tumour hypoxia and the expression of a number of hypoxia-induced proteins that play a role in tumour metabolism. The hypoxia marker pimonidazole was administered to dogs affected by spontaneous mammary carcinoma and compared with immunohistochemical staining for GLUT1 and 3, HK 2 and CA IX. A statistically significant correlation was found between pimonidazole staining and GLUT1-expression (R=0.607; p=0.001). These results indicate a strong interaction between tumour hypoxia and tumour metabolism by the induction of proteins essential to maintain a stable tumour microenvironment.

FDG uptake in primary squamous cell carcinoma of the head and neck. The relationship between overexpression of glucose transporters and hexokinases, tumour proliferation and apoptosis.

AIM: This study aimed at assessing the relationship between over-expression of glucose transporters and hexokinases, tumour proliferation and apoptosis corrected for cellularity and partial volume corrected (pvc) FDG SUV values in primary squamous cell carcinoma of the head and neck (pSCCHN). PATIENTS, METHODS: In 27 consecutive patients suffering from pSCCHN, FDG SUVmax and mean pvc values of the primary tumour were derived from a pre-surgical routine staging FDG PET/CT examination. GLUT-1, GLUT-3, HK-1, HK-3 expression, tumour proliferation (Ki-67 staining) and the number of apoptotic cells (cleaved caspase-3 staining), corrected for tumour cellularity, were subsequently assessed on the corresponding post-surgically obtained biopsies and tumour specimens. FDG SUVmax and mean pvc values of pSCCHN were correlated with the corresponding histological findings. RESULTS: FDG SUV max and mean pvc values correlated significantly: with GLUT-1 scores r = 0.408 (p = 0.04) and r = 0.439 (p = 0.03) as well as with the number of apoptotic cells r = 0.529 (p = 0.008) and r = 0.484 (p = 0.017). The number of apoptotic cells also correlated to GLUT-3 scores: r = 0.62 (p = 0.001) and GLUT-1 scores r = 0.528 (p = 0.008). CONCLUSION: FDG SUV pvc proved significantly related to GLUT-1 expression by tumour cells and to the absolute number of apoptotic cells. The latter finding warrants further exploration and confirmation by additional studies.

Identification and validation of housekeeping genes as internal control for gene expression in an intravenous LPS inflammation model in chickens.

Real-time PCR has become a powerful tool for the detection of inflammatory parameters, including cytokines. Reference or housekeeping genes are used for the normalization of real-time RT-PCR results. In order to obtain reliable results, the stability of these housekeeping genes needs to be determined. In this study the stability of five genes, including beta-actin, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), hypoxanthine phophoribosyl-transferase (HPRT), ubiquitin (UB) and glucose-6-phosphate dehydrogenase (G6PDH), was determined in a lipopolysaccharide inflammation model in chickens. beta-Actin appeared to be the most stable single gene in our model. Because the use of a single gene for normalization can lead to relatively large errors, the use of the geometric mean of multiple reference genes or normalization factor is preferred. The most stable combination for gene expression analysis in this lipopolysaccharide inflammation model in chickens is G6PDH and UB, since their correlation coefficients were 0.953 and 0.969, respectively (BestKeeper) and an M value of 0.34 and a low V(2/3) value of 0.155 (geNorm) were obtained. The use of HPRT and GAPDH should be avoided. The stable housekeeping genes, G6PDH and UB together, can be used to normalize the expression of pro-inflammatory cytokines in a lipopolysaccharide inflammation model in chickens.