Protein-carbohydrate interactions during fertilization

Interaction between gametes during fertilization is at least in part regulated by carbohydrate moieties of the zona pellucida (ZP) and carbohydrate binding proteins of the sperm surface. This review focuses on the protein-carbohydrate interactions during the primary binding of the sperm to the ZP in different species. Synthesis, structure and composition of the ZP an summarized. The functional significance of carbohydrate residues of the ZP as sperm receptor is discussed. Sperm surface proteins known to have specific ZP and carbohydrate-binding sites including the mouse beta 1,4-galactosyltransferase and sp56, the rabbit protein Sp17, a human mannose-binding protein and several members of the sperm-adhesin family are presented

Biosynthesis and expression of zona pellucida glycoproteins in mammals

The zona pellucida (ZP) is an extracellular matrix surrounding the oocyte and the early embryo that exerts several important functions during fertilization and early embryonic development. The ZP of most mammalian species is composed of three glycoproteins (ZPA, ZPB, ZPC), products of the gene families ZPA, ZPB and ZPC that have been found to be highly homologous within mammalian species. Most data on the structure and function of the ZP are obtained from studies in mouse. New data from pig and other domestic animals, however, indicate that the mouse model does not hold for all other species. Whereas in the mouse ZPB is the primary sperm receptor, in the pig ZPA has been shown to possess receptor activity. Contrary to the mouse, where the growing oocyte is the only source of zona glycoproteins, in domestic animals these proteins are expressed in both the oocyte and granulosa cells in a stage-specific pattern and may play also a role in granulosa cell differentiation. In several mammalian species, the epithelial secretory cells of the oviduct synthesize and secrete specific glycoproteins (oviductins) that become closely associated with the ZP of the ovulated oocyte. Once bound to the ZP, oviductin molecules could act as a protective layer around the oocyte and early embryo by virtue of their densely glycosylated mucin-type domains. Copyright (C) 2001 S. Karger AG, Basel

The role of non-uniqueness in the development of vortex breakdown in tubes

Numerical solutions of viscous, swirling flows through circular pipes of constant radius and circular pipes with throats have been obtained. Solutions were computed for several values of vortex circulation, Reynolds number and throat/inlet area ratio, under the assumptions of steady flow, rotational symmetry and frictionless flow at the pipe wall. When the Reynolds number is sufficiently large, vortex breakdown occurs abruptly with increased circulation as a result of the existence of non-unique solutions. Solution paths for Reynolds numbers exceeding approximately 1000 are characterized by an ensemble of three inviscid flow types: columnar (for pipes of constant radius), soliton and wavetrain. Flows that are quasi-cylindrical and which do not exhibit vortex breakdown exist below a critical circulation, dependent on the Reynolds number and the throat/inlet area ratio. Wavetrain solutions are observed over a small range of circulation below the critical circulation, while above the critical value, wave solutions with large regions of reversed flow are found that are primarily solitary in nature. The quasi-cylindrical (QC) equations first fail near the critical value, in support of Hall's theory of vortex breakdown (1967). However, the QC equations are not found to be effective in predicting the spatial position of the breakdown structure

MAXIMUM ECONOMIC YIELD AND RESOURCE ALLOCATION IN THE SPINY LOBSTER INDUSTRY

Resource /Energy Economics and Policy,

Disordered social media use and risky drinking in young adults:Differential associations with addiction-linked traits

Background Excessive or compulsive use of social media has been likened to an addiction, similar to other behavioural addictions such as pathological gambling or Internet addiction. This investigation sought to determine the degree to which personality traits associated with such disordered social media use overlap with those known to predict problematic substance use, with use of the most commonly abused legal substance alcohol as an example of the latter. Method Well‐known indices of disordered social media use, risky or problematic alcohol use, and the personality traits alexithymia, reward sensitivity, narcissism, and impulsivity were administered online to 143 men and women aged 18–35-years who were regular users of social media. The traits examined had previously been linked to substance misuse for a variety of substances, including alcohol, as presumed predisposing factors. Results After controlling for age, gender, and social desirability in hierarchical regressions, disordered social media use was predicted by narcissism, reward sensitivity, and impulsivity, whereas risky alcohol use was predicted by narcissism, alexithymia, and impulsivity. The ability of narcissism to predict disordered social media use was mediated by reward sensitivity, which was not the case for risky drinking. Conclusions Present results point to similarities and differences in addiction‐linked traits when comparing disordered social media use to risky or problematic substance use

Contactless electroreflectance, in the range of 20 K \u3c T \u3c 300 K, of freestanding wurtzite GaN prepared by hydride-vapor-phase epitaxy

We have performed a detailed contactless electroreflectance study of the interband excitonic transitions on both the Ga and N faces of a 200-μm-thick freestanding hydride-vapor-phase-epitaxy grown wurtzite GaN sample with low defect concentration in the temperature range between 20 and 300 K. The transition energies of the A, B, and C excitons and broadening parameters of the A and B excitons have been determined by least-square fits to the first derivative of a Lorentzian line shape. The energy positions and separations of the excitonic transitions in the sample reveal the existence of residual strain. At 20 K the broadening parameter of A exciton deduced for the Ga (5×105 dislocation cm−2) and N (1×107 dislocation cm−2) faces are 3 and 7 meV, respectively, indicating a lower defect concentration on the former face. The parameters that describe the temperature dependence of the interband transition energies of the A, B, and C excitons as well as the broadening function of the A and B features are evaluated. The results from an analysis of the temperature dependence of the broadening function of excitons A and B indicate that GaN exhibits a very large exciton-phonon coupling