Most species of birds have a uropygial gland, also known as a preen gland, which produces oil that birds spread through their plumage when preening. The plumage of waterfowl deprived of uropygial oil becomes brittle and is subject to breakage. For other groups of birds, however, the importance of preen oil remains unclear. Previous workers have argued that preen oil may serve little or no function in Columbiforms (pigeons and doves). We tested that assertion by removing uropygial glands from Rock Doves (Columba livia) and assessing their plumage condition after several months. The results of that experiment showed significant degradation of plumage in the absence of oil. Our results are the first rigorous demonstration that preen oil is important for plumage condition in nonwaterfowl. We tested one possible function of preen oil—that it has insecticidal properties and that reduction in plumage condition on birds without glands is due to an increase in ectoparasites. We tested that hypothesis for feather-feeding lice (Phthiraptera:Ischnocera) using both in vitro and in vivo experiments. Lice raised in an incubator died more rapidly on feathers with preen oil than on feathers without oil, which suggests that preen oil may help combat lice. However, removal of the preen gland from captive birds had no significant effect on louse loads over the course of a four-month experiment. Although the results of our in vivo experiments suggest that preen oil may not be an important defense against lice, further experiments are needed. We also consider the possibility that preen oil may protect birds against other plumage-degrading organisms, such as bacteria and fungi.
Ca2+ transients were activated in rabbit ventricular cells by a sequence of action potential shaped voltage clamps. After activating a series of control transients, Na + currents (I Na ) were inactivated with a ramp from −80 to −40 mV (1.5 s) prior to the action potential clamp. The transients were detected with the calcium indicator Fluo-4 and an epifluorescence system. With zero Na + in the pipette I Na inactivation produced a decline in the SR Ca 2+ release flux (measured as the maximum rate of rise of the transient) of 27 ± 4% (n = 9, P < 0.001) and a peak amplitude reduction of 10 ± 3% (n = 9, P < 0.05). With 5 mm Na + in the pipette the reduction in release flux was greater (34 ± 4%, n = 4, P < 0.05). The ramp effectively inactivates I Na without changing I Ca , and there was no significant change in the transmembrane Ca 2+ flux after the inactivation of I Na . We next evoked action potentials under current clamp. TTX at 100 nm, which selectively blocks neuronal isoforms of Na + channels, produced a decline in SR Ca 2+ release flux of 35 ± 3% (n = 6, P < 0.001) and transient amplitude of 12 ± 2% (n = 6, P < 0.05). This effect was similar to the effect of I Na inactivation on release flux. We conclude that a TTX-sensitive I Na is essential for efficient triggering of SR Ca 2+ release. We propose that neuronal Na + channels residing within couplons activate sufficient reverse Na + -Ca 2+ exchanger (NCX) to prime the junctional cleft with Ca 2+ . The results can be explained if non-linearities in excitation-contraction coupling mechanisms modify the coupling fidelity of I Ca , which is known to be low at positive potentials. IntroductionThe microscopic theory of excitation-contraction coupling (ECC) in cardiomyocytes is organized around the concept of the couplon (Stern et al. 1997;Franzini-Armstrong et al. 1999) cisternae of the SR. Although it is widely held that I Ca is the principal trigger for SR Ca 2+ release in cardiac cells, there are studies suggesting that the Na + -Ca 2+ exchanger (NCX) may also be involved in this process (Haworth et al. 1991;Nuss & Houser, 1992;Kohomoto et al. 1994;Levi et al. 1994b; Vites & Wasserstrom, 1996a,b;Wasserstrom & Vites, 1996;Litwin et al. 1998).Recently Inoue & Bridge (2003) established in patch clamped rabbit ventricular myocytes that when action potentials (APs) are used to repetitively stimulate a cell, in those locations where sparks are present, they occur with a probability approaching 100%. This, despite (1) the inherent low open probability (P o ) of LCCs, which is less than spark probability (P s ), and (2) their low coupling fidelity (P Cpl ) (Zhou et al. 1999;Polakova et al. 2008;Sobie & Ramay, 2009). Preliminary data show that when the magnitude of the trigger is increased spikes are not induced at new locations (Tsujii et al. 2005). This suggests that, at least in rabbit, APs activate all couplons. However SR Ca 2+ release is graded with voltage clamp pulses from −40 to +50 mV by voltage-dependent local recruitment of Ca 2+ sparks which are under local ...
Human head lice (Pediculus humanus capitis De Geer) occur worldwide and infest millions of children and adults every year. Head lice infestations, which are known as pediculosis capitis, are psychologically stressful, physically irritating, and are one of the leading causes of K-6 school absence. The prevalence of head lice in many countries is increasing rapidly because of resistance to chemicals used in many head lice treatments. We tested the efficacy of an alternative method for controlling head lice, the LouseBuster, a custom-built medical device designed to kill head lice and their eggs using controlled, heated air. A total of 56 infested subjects was treated with the LouseBuster, and the efficacy of the treatment was evaluated by comparing the viability of lice and eggs on randomly assigned pre- and posttreatment sides of each subject's scalp. We evaluate treatment efficacy in the hands of novice versus experienced operators. We also evaluate treatment efficacy on different hair types and at different ambient humidities. Overall mortality of lice and eggs was 94.8% after treatment by experienced operators. Novice operators also achieved good results after a short training session; their results did not differ significantly from those of experienced operators. No adverse events were associated with the LouseBuster treatment. The LouseBuster is efficacious for killing head lice and their eggs. The use of heated air is appealing because it is a fast, safe, nonchemical treatment. Head lice are also unlikely to evolve resistance to desiccation, which is the apparent mode of action.
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