Sex,Color, and Mate Choice in Guppies (Monographs in Behavior and Ecology). Anne E. Houde.

Reviews in Fish Biology and Fisheries -     

Changes in the vegetation composition of hay meadows between 1993 and 2009 in the Picos de Europa and implications for nature conservation

The Picos de Europa are a range of predominantly Carboniferous Limestone and Sandstone mountains mainly in the Cantabrian region of northern Spain. The highest peaks are precipitous and reach 2600 m. There are complex gradients between Lusitanian, Alpine and Mediterranean environmental zones, as well as variable soil types. In combination with the long history of traditional agricultural management, a wide range of diverse habitats and species is present. The herb-rich hay meadows have long been recognised as having a high nature conservation value but, as elsewhere in European mountains, such grasslands are threatened by changing agricultural practices. Accordingly, in 1993, 92 quadrats were recorded using a restricted list of indicator species from stratified random samples. The authors repeated the sample in 2009. Changed land use had only occurred in approximately 3% of meadows, however, farmyard manure was no longer used, probably because of shortage of labour. Statistical analysis of the vegetation data showed a range of significant changes consistent with the increased use of slurry, as well as re-seeding of some fields. The grass swards had not only become denser, with fewer species present, but there was also a loss of sensitive indicators especially of calcareous conditions and open vegetation. By contrast, competitors had increased and the vegetation had become simpler, with the balance of vegetation types shifting to more nutrient rich conditions. These changes have mainly occurred in the more fertile meadows used for silage. The core of about 35% of herb-rich meadows, mainly cut for hay, has remained relatively stable but the results show that they are at risk if the current trend continues. If management practices that form the core of traditional agriculture are not maintained, one of the most important resources of herb-rich meadows in Europe will be lost.     

Kinetic models for association of 2,3,7,8-tetrachlorodibenzo-p-dioxin with the Ah receptor

Saturation binding studies of the interaction between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and the Ah receptor obtained from the hepatic cytosol of Wistar rats have been carried out. The conventional Scatchard analysis for determination of the equilibrium constant for ligand-receptor binding has been shown to be inappropriate due to thermal inactivation of the unoccupied receptor. Simulation models of the receptor-ligand binding kinetics which take into account receptor degradation have been developed and the results are consistent with two alternative kinetic models. In Model 1, reversible 2,3,7,8-TCDD-receptor binding occurs in parallel with inactivation of the unbound receptor; analysis of the observed data using this model suggests that the previously determined equilibrium constants (Kass) for association of the ligand with the receptor are orders of magnitude too low and the total initial receptor concentrations are somewhat underestimated. In Model 2, the unbound receptor is converted unimolecularly to an activated state which then undergoes competitive degradation or entrapment by ligand. Experiments have been carried out over the temperature range 4-37 degrees C, enabling activation parameters to be obtained. According to Scheme 1, the activation enthalpies for association of receptor with ligand and for thermal inactivation of the unoccupied receptor are high, and numerically almost identical (delta H++ ca 125 kJ mol-1). These reactions are strongly entropically driven and this is consistent with association being accompanied by a conformational change in the receptor protein, and the previously postulated binding of the ligand to a hydrophobic pocket. According to Scheme 2, there is only one enthalpy of activation because both inactivation and entrapment by 2,3,7,8-TCDD are fast processes which follow the same slow activation step. On the basis of this latter model, a 10(-9) M concentration of 2,3,7,8-TCDD is sufficient to trap roughly two-thirds of the activated receptors.     

Novel Antimicrobial Peptides That Inhibit Gram Positive Bacterial Exotoxin Synthesis

Gram-positive bacteria, such as Staphylococcus aureus, cause serious human illnesses through combinations of surface virulence factors and secretion of exotoxins. Our prior studies using the protein synthesis inhibitor clindamycin and signal transduction inhibitors glycerol monolaurate and α-globin and β-globin chains of hemoglobin indicate that their abilities to inhibit exotoxin production by S. aureus are separable from abilities to inhibit growth of the organism. Additionally, our previous studies suggest that inhibition of exotoxin production, in absence of ability to kill S. aureus and normal flora lactobacilli, will prevent colonization by pathogenic S. aureus, while not interfering with lactobacilli colonization. These disparate activities may be important in development of novel anti-infective agents that do not alter normal flora. We initiated studies to explore the exotoxin-synthesis-inhibition activity of hemoglobin peptides further to develop potential agents to prevent S. aureus infections. We tested synthesized α-globin chain peptides, synthetic variants of α-globin chain peptides, and two human defensins for ability to inhibit exotoxin production without significantly inhibiting S. aureus growth. All of these peptides were weakly or not inhibitory to bacterial growth. However, the peptides were inhibitory to exotoxin production with increasing activity dependent on increasing numbers of positively-charged amino acids. Additionally, the peptides could be immobilized on agarose beads or have amino acid sequences scrambled and still retain exotoxin-synthesis-inhibition. The peptides are not toxic to human vaginal epithelial cells and do not inhibit growth of normal flora L. crispatus. These peptides may interfere with plasma membrane signal transduction in S. aureus due to their positive charges.     

Adventitious bud development and regeneration in Tillandsia eizii

Summary The bromeliad Tillandsia eizii is a stricking species with large, colorful, and persistent inflorescences that can reach 1 m in length. The value of this plant as an ornamental and its importance in cultural and religious activities has led to its overcollection in the wild. Clonal propagation via tissue culture may be a means to repopulate native stands while meeting the demands for this species as an ornamental and ceremonial plant. Adventitious bud proliferation was induced from axenically germinated scedling material. Parameters evaluated were the age of explant material at the time of transfer onto bud-induction medium, the concentration of plant growth regulators, and the period of exposure to induction medium. Light and seanning electron microscopy (SEM) established the origin and development of buds. Twelve-week-old seedling explants rapidly initiated adventitious buds after a 30-d induction period on shoot-initiation medium. Adventitious buds were induced in 40% of the explants placed on media with 2 mg l⁻¹ 6-benzylaminopurine (BA) (8.88 μM) plus 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA) (0.54 μM) with some cultures becoming highly prolific after repeated subeulture. Shoots elongated in proliferating cultures, and plants were successfully acclimatized and planted into the greenhouse. The results indicate that tissue culture may be used as a means to propagate this epiphytic bromeliad species, which is being seriously affected by deforestation and habitat destruction. In addition, adventitious bud proliferation can provide a means to propagate superior genotypes.     

Thienopyrimidine-based dual EGFR/ErbB-2 inhibitors

Two new series of potent and selective dual EGFR/ErbB-2 kinase inhibitors derived from novel thienopyrimidine cores have been identified. Isomeric thienopyrimidine cores were evaluated as isosteres for a 4-anilinoquinazoline core and several analogs containing the thieno[3,2-d]pyrimidine core showed anti-proliferative activity with IC₅₀ values less than 1 μM against human tumor cells in vitro.