Egg shell quality,clutch size and hatching success of the great tit (Parus major) and the pied flycatcher (Ficedula hypoleuca) in an air pollution gradient

Egg shell thickness, egg volume, clutch size and hatching success of Parus major and Ficedula hypoleuca were studied at 14 study sites around a copper smelter complex in Harjavalta, south-west Finland, in 1991–1993. In 1991–1992 unhatched eggs were collected to measure shell quality. F. hypoleuca was more susceptible to pollutants than P. major, the response of which was weaker in all aspects studied. Egg shells of F. hypoleuca were about 17% thinner and eggs were about 8% smaller in volume near the factory than at a distance of 10 km. The clutch size of F. hypoleuca was significantly smaller and hatching success markedly lower at a study site next to the factory complex than at all other sites. In P. major, variation in shell thickness and egg volume was not significantly related to the distance from the pollution source. Clutch size and hatching success of P. major did not significantly differ among study sites, although the trend in hatching success was in the same direction as in F. hypoleuca. Clutches of both species contained less shell material and both species had more nests without eggs near the factory than further away. The surface structure of the eggshells was studied by scanning electron microscope. Especially in F. hypoleuca, the egg shell surface was more rough and porous near the factory. The roles of Ca and heavy metals in shell thinning are discussed.     

Genotypic variation in yellow autumn leaf colours explains aphid load in silver birch

? It has been suggested that autumn-migrating insects drive the evolution of autumn leaf colours. However, evidence of genetic variation in autumn leaf colours in natural tree populations and the link between the genetic variation and herbivore abundances has been lacking. ? Here, we measured the size of the whole aphid community and the development of green-yellow leaf colours in six replicate trees of 19 silver birch (Betula pendula) genotypes at the beginning, in the middle and at the end of autumn colouration. We also calculated the difference between green leaf and leaf litter nitrogen (N) and estimated the changes in phloem sap N loading. ? Autumn leaf colouration had significant genetic variation. During the last survey, genotypes that expressed the strongest leaf reflectance 2-4 wk earlier had an abundance of egg-laying Euceraphis betulae females. Surprisingly, the aphid community size during the first surveys explained N loss by the litter of different birch genotypes. ? Our results are the first evidence at the tree intrapopulation genotypic level that autumn-migrating pests have the potential to drive the evolution of autumn leaf colours. They also stress the importance of recognizing the role of late-season tree-insect interactions in the evolution of herbivory resistance.     

The effects of diet quality and quantity on plumage colour and growth of great tit Parus major nestlings: a food manipulation experiment along a pollution gradient

The yellow carotenoid-based plumage coloration of great tit Parus major nestlings is found to be paler in polluted and urban environments. Because carotenoid pigmentation is often considered to be a condition dependent trait in birds we wanted to find out whether food-limitation and poor nestling condition could explain the pale plumage colour in a polluted area. P. major nestlings were supplemented with variable diets along a well known heavy metal pollution gradient around a copper smelter: two food treatments with carotenoids, one food treatment with little carotenoid and one unsupplemented control. Our field experiment showed that nestlings in the polluted area grew better with carotenoid rich diets, while such effect was not found in the unpolluted area. Nestlings showed higher plasma carotenoid (lutein) levels and higher plumage carotenoid chroma values in the unpolluted area than in the polluted area. However, plasma lutein levels or plumage colour were not associated with heavy metal levels in nestling faeces (a proxy for dietary exposure). Our results provide only weak evidence for carotenoid-based colouration to be condition-dependent in great tit nestlings as we found a positive relationship between body mass and carotenoid chroma in the non-supplemented control group only. The positive relationship between body mass and plumage colour intensity is more likely to be produced by the fact that good availability of caterpillars, an important food source for P. major, also means a good availability of carotenoids to nestlings. Our results suggest that main reason for pale nestling plumage in the polluted area is lower quality invertebrate food, and not nutrition-related oxidative stress.     

Mechanisms of B cell receptor induced apoptosis

B cell receptor (BCR)-mediated apoptosis plays a key role in the negative selection (deletion) of autoreactive B cells. Mechanisms of BCR-mediated apoptosis have been widely studied in cell lines representing both immature (bone marrow) and mature (germinal center) B cells. However, there is much inconsistency and controversy concerning the possible mechanisms of BCR-mediated apoptosis, which may reflect differences in the origin or the maturational stage of the cell line used. Based on recent studies, collapse of mitochondrial membrane potential (Delta Psi m) seems to be an essential event for BCR-mediated apoptosis in both mature and immature cells. The collapse of Delta Psi m is dependent on the synthesis of new proteins, which are involved in the permeability change of mitochondrial membranes. Mitochondrial dysfunction induces activation of caspases, cysteine proteases, which play a central role in apoptosis. However, instead of caspases, other effector proteases, such as cathepsins or calpains, may also be responsible for the organized destruction of cell components seen during BCR-mediated apoptosis.     

The involvement of mitochondria and the caspase-9 activation pathway in rituximab-induced apoptosis in FL cells

Despite the wide use of anti-CD20 antibody rituximab in the cancer treatment of B cell malignancies, the signalling pathways of CD20-induced apoptosis are still not understood. By using dominant negative (DN)-caspase-9 overexpressing follicular lymphoma cells we demonstrated that the activation of caspase-9 was essential for rituximab-mediated apoptosis. The death receptor pathway mediated by caspase-8 activation was not involved in rituximab-mediated apoptosis since overexpression of FLIP_short or FLIP_long proteins, inhibitors of caspase-8 activation, could not inhibit rituximab-induced apoptosis. However, the death receptor pathway activation by anti-Fas antibodies showed an additive effect on rituximab-induced apoptosis. The stabilisation of the mitochondrial outer membrane by Bcl-x_L overexpression inhibited cell death, showing the important role of mitochondria in rituximab-induced apoptosis. Interestingly, the rituximab-induced release of cytochrome c and collapse of mitochondrial membrane potential were regulated by caspase-9. We suggest that caspase-9 and downstream caspases may feed back to mitochondria to amplify mitochondrial disruption during intrinsic apoptosis.     

Proteolytic Function of GPI-Anchored Plasma Membrane Protease Yps1p in the Yeast Vacuole and Golgi

Yps1p is a member of the GPI-anchored aspartic proteases which reside at the plasma membrane of Saccharomyces cerevisiae. Here we show that in Δerg6 cells, where a late biosynthetic step of the membrane lipid ergosterol is blocked, part of Yps1p was targeted to the vacuole. There it overtook proteolytic functions of the Pep4p protease, resulting in processing of pro-CPY to CPY in cells lacking the PEP4 gene. Yps1p was enriched in membrane microdomains, as it could be isolated in detergent-insoluble complexes from both normal and Δerg6 cells. Vacuolar Yps1 caused degradation of a mammalian sialyltransferase ectodomain fusion protein (ST6Ne), which was directed from the Golgi to the vacuole in both normal and Δerg6 cells. Unexpectedly, ST6Ne was degraded also when arrested in the Golgi in a temperature-sensitive sec7–1 mutant. Newly synthesized Yps1p, in transit to the plasma membrane, was also involved in the Golgi-associated degradation. These data show that GPI-anchored proteases, whose biological roles are unknown, may reside and function in different subcellular locations.     

Loss of Occludin and Functional Tight Junctions, but Not ZO-1, during Neural Tube Closure—Remodeling of the Neuroepithelium Prior to Neurogenesis

Neuroepithelial cells can generate nonepithelial cells, the neurons. Here we have investigated, for chick and mouse embryos, the epithelial character of neuroepithelial cells in the context of neurogenesis by examining the presence of molecular components of tight junctions during the transition from the neural plate to the neural tube. Immunoreactivity for occludin, a transmembrane protein specific to tight junctions, was detected at the apical end of the lateral membrane of neuroepithelial cells throughout the chick neural plate. During neural tube closure, occludin disappeared from all neuroepithelial cells. Correspondingly, the addition of horseradish peroxidase to the apical side of the neuroepithelium by injection into the amniotic cavity of mouse embryos revealed the presence of functional tight junctions in the neural plate (Embryonic Day 8), but not the neural tube (Embryonic Day 9). In contrast to occludin, expression of ZO-1, a peripheral membrane protein of tight junctions, increased from the neural plate to the neural tube stage, also being confined to the apical end of the lateral neuroepithelial cell membrane. This localization coincided with that of N-cadherin, whose expression increased concomitantly with the disappearance of occludin. We propose that the loss of tight junctions from neuroepithelial cells reflects an overall decrease in their epithelial nature, which precedes the generation of neurons.     

Activation of Plasmin in Mastitic Milk

Milk and whey samples from healthy and inflamed udder quarters of 10 Ayrshire cows were analyzed for proteolytic activity using radial caseolysis procedures, a fluorogenic coumaryl peptide substrate, and casein agarose zymography. Free lysosomal enzyme activity (N–acetyl–beta–D–glucosaminidase) was used as the criterion for inflammation. All mastitic milk samples had proteolytic activity, tentatively identified as plasmin (comigration at Mr 83 000 and characteristic fragmentation). The plasmin activities in mastitic milk were on average 2.9 μg/ml (range 0.5–12.5) as measured by radial caseolysis. Milk or whey specimens from healthy quarters were all negative except 1 in which an activity of 0.1 μg/ml was found in both specimens. The caseolytic activities were totally inhibited by 50 KITJ/ml of aprotinin, a serine proteinase inhibitor from bovine lung. No free plasminogen activator (PA) activity was found in any of the samples. Howewer, according to zymographic analyses PA molecules corresponding to urokinase were found in healthy and especially in mastitic specimens. Analysis of plasmin may provide an alternative means of screening for mastitic milk samples.