Observed heterospecific clutch size can affect offspring investment decisions

Optimal investment in offspring is important in maximizing lifetime reproductive success. Yet, very little is known how animals gather and integrate information about environmental factors to fine tune investment. Observing the decisions and success of other individuals, particularly when those individuals initiate breeding earlier, may provide a way for animals to quickly arrive at better breeding investment decisions. Here we show, with a field experiment using artificial nests appearing similar to resident tit nests with completed clutches, that a migratory bird can use the observed high and low clutch size of a resident competing bird species to increase and decrease clutch size and egg mass, accordingly. Our results demonstrate that songbirds can discriminate between high and low quantity of heterospecific eggs, and that social information can have long-term physiological consequences affecting reproductive strategies. Such behaviour may help animals to better adapt to changing environments and lead to convergent traits with competitors.     

Patient Parents: Do Offspring Decide on the Timing of Fledging in Zebra Finches?

Parent–offspring conflict over parental care is predicted to become most pronounced during offspring transition to independence when offspring are predicted to attempt to extend care for longer than parents are selected to provide it. However, on the proximate level, it is difficult to determine who plays the most important role in this process, parents or offspring. For several vertebrate taxa, it has been documented that parents end brood care by abandoning offspring after a fixed period or else show high flexibility in the duration of care, but teasing apart the role of offspring and parents underlying this flexibility has been difficult. Here, we studied the decision to fledge in captive zebra finches (Taeniopygia guttata), an altricial songbird. We experimentally delayed the time of fledging to determine who decides about the end of feeding inside the nest, parents or offspring. The experiment indicates that parents do not primarily rely on phenotypic offspring traits in their decision to feed offspring in the nest, but appear to adjust the duration of parental care as long as offspring are in the nest which parents may take as an indicator of offspring need and locomotor abilities. Delayed‐fledging offspring appeared not to suffer a disadvantage in terms of age at the onset of independent feeding. Our study suggests that, in zebra finches, offspring play a major role in determining the time of fledging and leave the nest on their own, possibly to reduce the risk of nest predation, or to evade sibling competition in the nest.     

Requirement of N-glycosylation for the secretion of recombinant extracellular domain of human Fas in HeLa cells

Apoptosis has been shown to be associated with altered glycosylation patterns and biosynthesis of glycoproteins. A major cell surface receptor involved in the induction of apoptosis is Fas that is activated by binding Fas ligand but can also be activated by binding anti-Fas antibody. In order to determine whether the Fas receptor is glycosylated, the extracellular domain of human Fas (shFas) was expressed as a cleavable fusion protein (shFas-Fc) in HeLa cells. These cells were shown to express activities of glycosyltransferases involved in N- and O-glycan biosynthesis. The secreted shFas-Fc was shown to be a glycoprotein with heterogeneous glycan chains. MALDI mass spectrometry revealed a disperse molecular weight of shFas with an average of 23.4kDa. Western blots of shFas-Fc secreted from tunicamycin treated transfected HeLa cells showed that only N-glycosylated glycoforms were secreted, while the unglycosylated shFas-Fc remained intracellular. The results suggest that both N-glycosylation sites of the extracellular domain of Fas are occupied with large N-glycans that play a role in the expression of the glycoprotein.     

The proteoglycan osteoglycin/mimecan is correlated with arteriogenesis

Arteriogenesis or collateral growth is able to compensate for the stenosis of major arteries. Using differential display RT-PCR on growing and quiescent collateral arteries in a rabbit femoral artery ligation model, we cloned the rabbit full-length cDNA of osteoglycin/mimecan. Osteoglycin was present in the adventitia of collateral arteries as a glycosylated protein without keratan sulfate side chains, mainly produced by smooth muscle cells (SMCs) and perivascular fibroblasts. Northern blot, Western blot, and immunohistochemistry confirmed a collateral artery-specific downregulation of osteoglycin from 6 h to 3 weeks after the onset of arteriogenesis. Treatment of primary SMCs with the arteriogenic protein fibroblast growth factor-2 (FGF-2) resulted in a similar reduction of osteoglycin expression as observed in vivo. Application of the FGF-2 inhibitor polyanethole sulfonic acid (PAS) blocked the downregulation of osteoglycin and interfered with arteriogenesis. From our study we conclude that downregulation of osteoglycin is a fundamental requirement for proper arteriogenesis.     

Anthrax toxin targeting of myeloid cells through the CMG2 receptor is essential for establishment of Bacillus anthracis infections in mice

Bacillus anthracis kills through a combination of bacterial infection and toxemia. Anthrax toxin working via the CMG2 receptor mediates lethality late in infection, but its roles early in infection remain unclear. We generated myeloid-lineage specific CMG2-deficient mice to examine the roles of macrophages, neutrophils, and other myeloid cells in anthrax pathogenesis. Macrophages and neutrophils isolated from these mice were resistant to anthrax toxin. However, the myeloid-specific CMG2-deficient mice remained fully sensitive to both anthrax lethal and edema toxins, demonstrating that targeting of myeloid cells is not responsible for anthrax toxin-induced lethality. Surprisingly, the myeloid-specific CMG2-deficient mice were completely resistant to B. anthracis infection. Neutrophil depletion experiments suggest that B. anthracis relies on anthrax toxin secretion to evade the scavenging functions of neutrophils to successfully establish infection. This work demonstrates that anthrax toxin uptake through CMG2 and the resulting impairment of myeloid cells are essential to anthrax infection.     

Preferred conformations and dynamics of five core structures of mucin typeO-glycans determined by NMR spectroscopy and force field calculations

Glycosyltransferases acting onO-glycans have been shown to exhibit distinct specificity for the carbohydrate and the peptide moiety of their substrates. As an approach to study the 3-dimensional interactions between enzymes andO-glycan substrates, we determined the preferred conformations of five oligosaccharide-core structures of mucin type glycoproteins by NMR spectroscopy and by static and dynamic force field calculations. Seven oligosaccharides, representing five basic core structures, were investigated: Gal(1–3)GalNAcBzl (1, core 1), GlcNAc(1–6)[Gal(1–3)]GalNAcBzl (2, core 2), GlcNAc(1–3)GalNacBzl (3, core 3), GlcNAc(1–6)[GlcNAc(1–3)]GalNAcBzl (4, core 4), GlcNAc(1–6)GalNAcBzl (5, core 6), the elongated core 2, Gal(1–4)GlcNAc(1–6)[Gal(1–3)]GalNAcpNp (6) and GalNAc-Bzl (7). The dynamic behaviour of the molecules was studied by Metropolis Monte Carlo (MMC) simulations. Experimental coupling constants, chemical shift changes, and NOEs were compared with results from static energy minimizations and dynamic MMC simulations and show a good agreement. MMC simulations show that the (1–6) linkage is much more flexible than the (1–3) or the (1–4) linkages. The preferred conformations of the disaccharides (1) and (3) show only slight differences due to the additionalN-acetyl group in (3). The conformational equilibrium of (1–3) glycosidic bonds of1 and3 was not affected by attaching a (1–6) linked GlcNAc unit to the GalNAc residue in2 and4. However, experimental and theoretical data show that the (1–6) linkages of the trisaccharides2 and4, which carry an additional (1–3) linked glycosyl residue, change their preferred conformations when compared with (5). The 6-branch also shows significant interactions with the benzyl aglycon altering the preferred conformation of the hydroxymethyl group of the GalNAc to a higher proportion of the gt conformer. The (1–6) linkage of2, 4, and6 can have two different families of conformations of which the lower energy state is populated only to about 20% of the time whereas the other state with a relative enthalpy of 4 kcal mol^–1 is populated to 80%. This fact demonstrates that the two conformational states have different entropy contents. Entropy is implicitly included in MMC simulations but cannot be derived from energy minimizations.Abbreviations Bzl benzyl - COSY correlation spectroscopy - Gal d-galactose - GalNAc N-acetyl-d-galactosamine - GalNAc-ol N-acetylgalactosaminitol - GlcNAc N-acetyl-d-glucosamine - HOHAHA homonuclear Hartmann-Hahn-spectroscopy - MMC metropolis Monte Carlo - NOE nuclear Overhauser enhancement - pNp p-nitrophenyl - ROESY rotating frame Overhauser enhancement spectroscopy - TOCSY totally correlated spectroscopy     

Mucin glycoproteins in neoplasia

Mucins are high molecular weight glycoproteins that are heavily glycosylated with many oligosaccharide side chains linked O-glycosidically to the protein backbone. With the recent application of molecular biological methods, the structures of apomucins and regulation of mucin genes are beginning to be understood. At least nine human mucin genes have been identified to date. Although a complete protein sequence is known for only three human mucins (MUC1, MUC2, and MUC7), common motifs have been identified in many mucins. The pattern of tissue and cell-specific expression of these mucin genes are emerging, suggesting a distinct role for each member of this diverse mucin gene family. In epithelial cancers, many of the phenotypic markers for pre-malignant and malignant cells have been found on the carbohydrate and peptide moieties of mucin glycoproteins. The expression of carbohydrate antigens appears to be due to modification of peripheral carbohydrate structures and the exposure of inner core region carbohydrates. The expression of some of the sialylated carbohydrate antigens appears to correlate with poor prognosis and increased metastatic potential in some cancers. The exposure of peptide backbone structures of mucin glycoproteins in malignancies appears to be due to abnormal glycosylation during biosynthesis. Dysregulation of tissue and cell-specific expression of mucin genes also occurs in epithelial cancers. At present, the role of mucin glycoproteins in various stages of epithelial cell carcinogenesis (including the preneoplastic state and metastasis), in cancer diagnosis and immunotherapy is under investigation.     

Inferring pH from diatoms: a comparison of old and new calibration methods

Two new methods for inferring pH from diatoms are presented. Both are based on the observation that the relationships between diatom taxa and pH are often unimodal. The first method is maximum likelihood calibration based on Gaussian logit response curves of taxa against pH. The second is weighted averaging. In a lake with a particular pH, taxa with an optimum close to the lake pH will be most abundant, so an intuitively reasonable estimate of the lake pH is to take a weighted average of the pH optima of the species present.Optima and tolerances of diatom taxa were estimated from contemporary pH and proportional diatom counts in littoral zone samples from 97 pristine soft water lakes and pools in Western Europe. The optima showed a strong relation with Hustedt's pH preference groups. The two new methods were then compared with existing calibration methods on the basis of differences between inferred and observed pH in a test set of 62 additional samples taken between 1918 and 1983. The methods were ranked in order of performance as follows (between brackets the standard error of inferred pH in pH units); maximum likelihood (0.63) > weighted averaging (0.71) = multiple regression using pH groups (0.71) = the Gasse & Tekaia method (0.71) > Renberg & Hellberg's Index B (0.83) » multiple regression using taxa (2.2). The standard errors are larger than those usually obtained from surface sediment samples. The relatively large standard may be due to seasonal variation and to the effects of other factors such as humus content. The maximum likelihood method is statistically rigorous and can in principle be extended to allow for additional environmental factors. It is computer intensive however. The weighted averaging approach is a good approximation to the maximum likelihood method and is recommended as a practical and robust alternative.