Climate Driven Life Histories: The Case of the Mediterranean Storm Petrel

Seabirds are affected by changes in the marine ecosystem. The influence of climatic factors on marine food webs can be reflected in long-term seabird population changes. We modelled the survival and recruitment of the Mediterranean storm petrel (Hydrobates pelagicus melitensis) using a 21-year mark-recapture dataset involving almost 5000 birds. We demonstrated a strong influence of prebreeding climatic conditions on recruitment age and of rainfall and breeding period conditions on juvenile survival. The results suggest that the juvenile survival rate of the Mediterranean subspecies may not be negatively affected by the predicted features of climate change, i.e., warmer summers and lower rainfall. Based on considerations of winter conditions in different parts of the Mediterranean, we were able to draw inferences about the wintering areas of the species for the first time.     

The total burden of rare,non-synonymous exome genetic variants is not associated with childhood or late-life cognitive ability

Human cognitive ability shows consistent, positive associations with fitness components across the life-course. Underlying genetic variation should therefore be depleted by selection, which is not observed. Genetic variation in general cognitive ability (intelligence) could be maintained by a mutation–selection balance, with rare variants contributing to its genetic architecture. This study examines the association between the total number of rare stop-gain/loss, splice and missense exonic variants and cognitive ability in childhood and old age in the same individuals. Exome array data were obtained in the Lothian Birth Cohorts of 1921 and 1936 (combined N = 1596). General cognitive ability was assessed at age 11 years and in late life (79 and 70 years, respectively) and was modelled against the total number of stop-gain/loss, splice, and missense exonic variants, with minor allele frequency less than or equal to 0.01, using linear regression adjusted for age and sex. In both cohorts and in both the childhood and late-life models, there were no significant associations between rare variant burden in the exome and cognitive ability that survived correction for multiple testing. Contrary to our a priori hypothesis, we observed no evidence for an association between the total number of rare exonic variants and either childhood cognitive ability or late-life cognitive ability.     

Oligomeric State and Thermal Stability of Apo- and Holo- Human Ornithine δ-Aminotransferase

Human ornithine δ-aminotransferase (hOAT) (EC 2.6.1.13) is a mitochondrial pyridoxal 5′-phosphate (PLP)-dependent aminotransferase whose deficit is associated with gyrate atrophy, a rare autosomal recessive disorder causing progressive blindness and chorioretinal degeneration. Here, both the apo- and holo-form of recombinant hOAT were characterized by means of spectroscopic, kinetic, chromatographic and computational techniques. The results indicate that apo and holo-hOAT (a) show a similar tertiary structure, even if apo displays a more pronounced exposure of hydrophobic patches, (b) exhibit a tetrameric structure with a tetramer-dimer equilibrium dissociation constant about fivefold higher for the apoform with respect to the holoform, and (c) have apparent T_m values of 46 and 67?°C, respectively. Moreover, unlike holo-hOAT, apo-hOAT is prone to unfolding and aggregation under physiological conditions. We also identified Arg217 as an important hot-spot at the dimer–dimer interface of hOAT and demonstrated that the artificial dimeric variant R217A exhibits spectroscopic properties, T_m values and catalytic features similar to those of the tetrameric species. This finding indicates that the catalytic unit of hOAT is the dimer. However, under physiological conditions the apo-tetramer is slightly less prone to unfolding and aggregation than the apo-dimer. The possible implications of the data for the intracellular stability and regulation of hOAT are discussed.     

Intrinsic vs. extrinsic influences on life history expression: metabolism and parentally induced temperature influences on embryo development rate

Intrinsic processes are assumed to underlie life history expression and trade‐offs, but extrinsic inputs are theorised to shift trait expression and mask trade‐offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass‐specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade‐off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade‐offs across species.     

Effect of auto-oxidized phospholipids on oxidative enzyme assays based on tetrazolium salt reduction

The influence of auto-oxidized phospholipids on the reduction of the tetrazolium salt MTT coupled to the NAD+-dependent lactate dehydrogenase reaction was studied. The following results were obtained: (1) peroxidized phosphatidylcholine interfered in the time-course of the lactate dehydrogenase-mediated MTT reduction; (2) there was a time-dependent decrease in the hydroperoxide content of phosphatidylcholine vesicles during the incubation; (3) the diminution of phosphatidylcholine hydroperoxides required the presence of all the components of the system except MTT; (4) hydroperoxide diminution and MTT reduction were mediated by the superoxide radical O2-, since both processes were inhibited by superoxide dismutase; (5) EDTA inhibited the hydroperoxide decrease and abolished the interference of peroxidized phosphatidylcholine with MTT reduction. It was concluded that hydroperoxides compete with MTT for the electrons coming from substrate oxidation. The superoxide radical O2- and traces of some contaminating metal ion are involved in the process. This is a potential complication in the study of the effect of lipids on enzymatic activities assayed by the tetrazolium salt method.     

Paracentric inversion in a female with multiple miscarriages (7inv)(q2.13;q3.13)

Summary A phenotypically normal woman with a history of multiple miscarriages was found to have a paracentric inversion in the long arm of chromosome, which may be the reason for the miscarriages.     

Metabolism of semisynthetic single-chain GM1 derivatives in cerebellar granule cells in culture

Semisynthetic single-chain GM1 derivatives containing N-acetyl-sphingosine (LIGA4) or N-dichloroacetyl-sphingosine (LIGA20) were recently reported to exert strong protection against glutamate-induced neuronal death in primary cultures of cerebellar granule cells. Elucidation of the molecular mechanism underlying the evoked effect requires knowledge of the metabolic fate of such molecules in the same cultured cells. For this, LIGA4 and LIGA20 were made radioactive on the long chain base moiety and added to cerebellar granule cells in culture in parallel with GM1 ganglioside. The metabolic fate was then investigated. It was found that both these molecules were easily taken up by the cells and promptly metabolized in a fashion qualitatively similar to that of control GM1. The highest amount processed was attributed to the different aggregation properties of LIGAs in solution. Among metabolites, higher accumulation of the single-chain ceramide residues was found after LIGA administration. Interestingly, sphingomyelin was generated, regardless the added compound, suggesting a recycling of the free long chain base.     

Electrical characteristics of ascidian egg fragments

Fragments of ascidian eggs, but at random in any plane and ranging in size from 10 to 90% of the total egg volume, displayed the electrical characteristics of the intact egg, having a resting potential of -86 mV and giving rise to an action potential upon stimulation by electrical current injection. Following insemination, the fragments generated fertilization potentials, comparable to those of intact eggs, although the repolarization phase was shorter. Our data show that there are sufficient ion channels throughout the egg surface to generate action potentials and fertilization potentials in excised egg fragments, irrespective of their global origin. Furthermore, the fertilizing spermatozoon is capable of activating fertilization channels in areas of the egg plasma membrane not destined for sperm entry.     

Involvement of the globular domain of histone H1 in the higher order structures of chromatin

We have attacked H1-containing soluble chromatin by α-chymotrypsin under conditions where chromatin adopts different structures.Soluble rat liver chromatin fragments depleted of non-histone components were digested with α-chymotrypsin in NaCl concentrations between 0 mm and 500 mm. at pH 7, or at pH 10, or at pH 7 in the presence of 4 m-urea. α-Chymotrypsin cleaves purified rat liver histone H1 at a specific initial site (CT) located in the globular domain and produces an N-terminal half (CT-N) which contains most of the globular domain and the N-terminal tail, and a C-terminal half (CT-C) which contains the C-terminal tail and a small part of the globular domain. Since in sodium dodecyl sulfate/polyacrylamide-gel electrophoresis CT-C migrates between the core histones and H1, cleavage of chromatin-bound H1 by α-chymotrypsin can be easily monitored.The CT-C fragment was detected under conditions where chromatin fibers were unfolded or distorted: (1) under conditions of H1 dissociation at 400 mm and 500 mm-NaCl (pH 7 and 10); (2) at very low ionic strength where chromatin is unfolded into a filament with well-separated nucleosomes; (3) at pH 10 independent of the ionic strength where chromatin never assumes higher order structures; (4) in the presence of 4 m-urea (pH 7), again independent of the ionic strength. However, hardly any CT-C fragment was detected under conditions where fibers are observed in the electron microscope at pH 7 between 20 mm and 300 mm-NaCl. Under these conditions H1 is degraded by α-chymotrypsin into unstable fragments with a molecular weight higher than that of CT-C. Thus, the data show that there are at least two different modes of interaction of H1 in chromatin which correlate with the physical state of the chromatin.Since the condensation of chromatin into structurally organized fibers upon raising the ionic strength starts by internucleosomal contacts in the fiber axis (zig-zag-shaped fiber), where H1 appears to be localized, it is likely that in chromatin fibers the preferential cleavage site for α-chymotrypsin is protected because of H1-H1 contacts. The data suggest that the globular part of H1 is involved in these contacts close to the fiber axis. They appear to be hydrophobic and to be essential for the structural organization of the chromatin fibers. Based on the present and earlier observations we propose a model for H1 in which the globular domains eventually together with the N-terminal tails form a backbone in the fiber axis, and the nucleosomes are mainly attached to this polymer by the C-terminal tails.     

Salmonella typhimurium infection in high and low antibody responder mice: inverse correlation between antibody responsiveness and resistance to infection

Susceptibility to Salmonella typhimurium infection was compared in H (high Ab responder) and L (low Ab responder) mice obtained by several selective breeding experiments (Selections I, II, III, IV and IV A). H mice were always much more susceptible to infection than their L mice counterparts within a continuous LD 50 variation range. In three of the selections (I, II and IV A) the low responsiveness character is known to result mainly from rapid Ag degradation in L mice macrophages. It was hypothesized that resistance to multiplication of intracellular pathogens could be related to an increased catabolic activity towards Ag. This was actually demonstrated, in F2 segregant hybrids of selection IV A, by the significant inverse correlation between capacity for Ab production and resistance to infection.