Cloning and characterization of SK2 channel from chicken short hair cells

In the inner ear of birds, as in mammals, reptiles and amphibians, acetylcholine released from efferent neurons inhibits hair cells via activation of an apamin-sensitive, calcium-dependent potassium current. The particular potassium channel involved in avian hair cell inhibition is unknown. In this study, we cloned a small-conductance, calcium-sensitive potassium channel (gSK2) from a chicken cochlear library. Using RT-PCR, we demonstrated the presence of gSK2 mRNA in cochlear hair cells. Electrophysiological studies on transfected HEK293 cells showed that gSK2 channels have a conductance of approximately 16 pS and a half-maximal calcium activation concentration of 0.74±0.17 M. The expressed channels were blocked by apamin (IC₅₀=73.3±5.0 pM) and d-tubocurarine (IC₅₀=7.6±1.0 M), but were insensitive to charybdotoxin. These characteristics are consistent with those reported for acetylcholine-induced potassium currents of isolated chicken hair cells, suggesting that gSK2 is involved in efferent inhibition of chicken inner ear. These findings imply that the molecular mechanisms of inhibition are conserved in hair cells of all vertebrates.     

Development of experimental designs for atherosclerosis studies in mice

The mouse has become the de facto model for the majority of atherosclerosis studies. Studies involving the quantification of lesions in mouse models of the disease represent the basis of our evolving concepts on the biochemical and cellular mechanisms underlying the atherogenic process. Many issues of experimental design, including specific model, strain, gender, atherogenic stimulus, duration of study, group size, and statistical analysis may influence the outcome and interpretation of atherosclerosis studies. The selection of vascular bed in which to quantify atherosclerotic lesion size could also impact the interpretation of results. Early studies quantified atherosclerotic lesion size in either specific regions or all of the aortic sinus. Measurement of atherosclerosis throughout the aortic intimal surface has become a common mode for defining lesion size. It is likely that other vascular regions will be increasingly used. In addition to size, there is an increased emphasis on identifying and quantifying the cellular and chemical composition of atherosclerotic lesions.     

Conditioning reduces metabolic rate and time to steady-state in the lizard Naultinus manukanus (Reptilia: Gekkonidae)

The rate of oxygen consumption (VO2) is commonly used as a measure of whole organism metabolic rate, but requires the animal to be motionless and at rest. Few studies have measured whether animals that appear motionless are truly at rest, or whether being in a novel environment elevates metabolic rate. We investigated whether conditioning of the gecko Naultinus manukanus to experimental procedures influenced the VO2 and probability of achieving a constant rate of oxygen consumption. Metabolic rate was measured at 24 degrees C in 22 individuals until a steady-state was achieved, or for 80 min if no steady-state was reached, once a day on 5 consecutive days (five trials). Geckos in the first trial, when compared with subsequent trials, had a significantly higher mass-adjusted VO2 (0.89+/-0.06 vs. 0.67+/-0.05 ml O2 h(-1), respectively), and time to reach a steady-state VO2 (66+/-8 vs. 47+/-3 min, respectively), as well as a significantly lower probability of reaching a steady-state VO2 (24% vs. 74%, respectively). We conclude that there may be hidden inaccuracies in studies that do not condition animals and that at least one conditioning trial should be used to obtain a metabolic rate at rest for small lizards.     

Relative Susceptibility of Vitis vinifera Cultivars to Vector-Borne Xylella fastidiosa through Time

Understanding the interactions between pathogen, crop and vector are necessary for the development of disease control practices of vector-borne pathogens. For instance, resistant plant genotypes can help constrain disease symptoms due to infections and limit pathogen spread by vectors. On the other hand, genotypes susceptible to infection may increase pathogen spread owing to their greater pathogen quantity, regardless of their symptom status. In this study, we evaluated under greenhouse conditions the relative levels of resistance (i.e. relatively lower pathogen quantity) versus tolerance (i.e. less symptom severity) of 10 commercial grapevine (Vitis vinifera) cultivars to Pierce’s disease etiological agent, the bacterium Xylella fastidiosa. Overall, no correlation was detected between pathogen quantity and disease severity, indicating the existence of among-cultivar variation in plant response to infection. Thompson Seedless and Barbera were the two most susceptible among 10 evaluated cultivars. Rubired showed the least severe disease symptoms and was categorized as one of the most resistant genotypes in this study. However, within each cultivar the degree of resistance/tolerance was not consistent across sampling dates. These cultivar and temporal differences in susceptibility to infection may have important consequences for disease epidemiology and the effectiveness of management protocols.