The energetic savings of sleep versus temperature in the Desert Iguana (Dipsosaurus dorsalis) at three ecologically relevant temperatures

One of the proposed ecological functions of sleep is to conserve energy. The majority of studies that support this theory have been done on endothermic animals whose body temperatures drop during sleep due to the reduced neurological control of thermoregulation. In the present study, we examined typical temperatures to which the Desert Iguana, Dipsosaurus dorsalis, is exposed to in the field and found that mean high temperatures ranged from 24-58 degrees C throughout the active portion of the year. We also examined the ecological savings that sleep could provide for this ectothermic iguana using a closed system respirometer. We found that laboratory-acclimated iguanas are able to save significantly more (27.6%) energy by sleeping than by being awake and that field iguanas also had significant savings of energy (69.1%) while asleep. However, iguanas could save more energy by remaining awake at cooler temperatures than by sleeping at warmer temperatures. In addition, we found no correlation for time of night with metabolic rate. Our study supports the hypothesis that one potential function of sleep is to conserve energy.     

Intrapleural activation, processing, efficacy, and duration of protection of single-chain urokinase in evolving tetracycline-induced pleural injury in rabbits

High levels of adenosine can be measured from the lungs of asthmatics, and it is well recognized that aerosolized 5'AMP, the precursor of adenosine, elicits robust bronchoconstriction in patients with this disease. Characterization of mice with elevated adenosine levels secondary to the loss of adenosine deaminase (ADA) expression, the primary metabolic enzyme for adenosine, further support a role for this ubiquitous mediator in the pathogenesis of asthma. To begin to identify pathways by which adenosine can alter airway tone, we examined adenosine-induced bronchoconstriction in four mouse lines, each lacking one of the receptors for this nucleoside. We show, using direct measures of airway mechanics, that adenosine can increase airway resistance and that this increase in resistance is mediated by binding the A(1) receptor. Further examination of this response using pharmacologically, surgically, and genetically manipulated mice supports a model in which adenosine-induced bronchoconstriction occurs indirectly through the activation of sensory neurons.     

Function and stability of abscisic acid acyl hydrazone conjugates by LC-MS2 of ex vivo samples

We prepare a biotinylated conjugate of the ubiquitous plant hormone (S)-(+)-abscisic acid via an acyl hydrazone linkage at the C4' position and demonstrate in vivo cleavage of the otherwise stable acyl hydrazone linkage using LC-MS2. As part of a wider chemical genomic study, biological activity of the conjugate was assessed using standard epidermal peel and gravimetric transpiration assays, showing significant activity but at a level lower than the unconjugated hormone. When deuterated samples of the conjugate were fed to the plant, however, it was apparent by LC-MS2 experiments that significant levels of hydrolysis of the acyl hydrazone had taken place, contrary to in vitro stability assays in artificial sap. We conclude that abscisic acid is liberated in sufficient quantities to account for the observed physiological response and that LC-MS2 monitoring of conjugates is a simple and practical method by which such events may be assessed, whether in plants or other organisms.     

Ab initio random model method facilitates 3D reconstruction of icosahedral particles

Model-based, three-dimensional (3D) image reconstruction procedures require a starting model to initiate data analysis. We have designed an ab initio method, which we call the random model (RM) method, that automatically generates models to initiate structural analysis of icosahedral viruses imaged by cryo-electron microscopy. The robustness of the RM procedure was demonstrated on experimental sets of images for five representative viruses. The RM method also provides a straightforward way to generate unbiased starting models to derive independent 3D reconstructions and obtain a more reliable assessment of resolution. The fundamental scheme embodied in the RM method should be relatively easy to integrate into other icosahedral software packages.     

A Mutation in the SH2 domain of STAT2 prolongs tyrosine phosphorylation of STAT1 and promotes type I IFN-induced apoptosis

Type I interferons (IFN-alpha/beta) induce apoptosis in certain tumor cell lines but not others. Here we describe a mutation in STAT2 that confers an apoptotic effect in tumor cells in response to type I IFNs. This mutation was introduced in a conserved motif, PYTK, located in the STAT SH2 domain, which is shared by STAT1, STAT2, and STAT3. To test whether the tyrosine in this motif might be phosphorylated and affect signaling, Y631 of STAT2 was mutated to phenylalanine (Y631F). Although it was determined that Y631 was not phosphorylated, the Y631F mutation conferred sustained signaling and induction of IFN-stimulated genes. This prolonged IFN response was associated with sustained tyrosine phosphorylation of STAT1 and STAT2 and their mutual association as heterodimers, which resulted from resistance to dephosphorylation by the nuclear tyrosine phosphatase TcPTP. Finally, cells bearing the Y631F mutation in STAT2 underwent apoptosis after IFN-alpha stimulation compared with wild-type STAT2. Therefore, this mutation reveals that a prolonged response to IFN-alpha could account for one difference between tumor cell lines that undergo IFN-alpha-induced apoptosis compared with those that display an antiproliferative response but do not die.