Culex erythrothorax (Diptera: Culicidae): Activity periods, insecticide susceptibility and control in California (USA).

The mosquito Culex erythrothorax Dyar is a West Nile virus (WNV) vector that breeds in wetlands with emergent vegetation. Urbanization and recreational activities near wetlands place humans, birds and mosquitoes in close proximity, increasing the risk of WNV transmission. Adult Cx. erythrothorax abundance peaked in a wetland bordering the San Francisco Bay of California (USA) during the first 3 hours after sunset (5527 ± 4070 mosquitoes / trap night) while peak adult Culex tarsalis Coquillett abundance occurred during the subsequent 3 h period (83 ± 30 Cx. tarsalis). When insecticide resistance was assessed using bottle bioassay, Cx. erythrothorax was highly sensitive to permethrin, naled, and etofenprox insecticides compared to a strain of Culex pipiens that is susceptible to insecticides (LC50 = 0.35, 0.71, and 4.1 µg/bottle, respectively). The Cx. erythrothorax were 2.8-fold more resistant to resmethrin, however, the LC50 value was low (0.68 µg/bottle). Piperonyl butoxide increased the toxicity of permethrin (0.5 µg/bottle) and reduced knock down time, but a higher permethrin concentration (2.0 µg/bottle) did not have similar effects. Bulk mixed-function oxidase, alpha-esterase, or beta-esterase activities in mosquito homogenates were higher in Cx. erythrothorax relative to the Cx. pipiens susceptible strain. There was no difference in the activity of glutathione S-transferase between the two mosquito species and insensitive acetylcholine esterase was not detected. Larvicides that were applied to the site had limited impact on reducing mosquito abundance. Subsequent removal of emergent vegetation in concert with larvicide applications and reduced daily environmental temperature substantially reduced mosquito abundance. To control Cx. erythrothorax in wetlands, land managers should consider vegetation removal so that larvicide can efficiently enter the water. Vector control agencies may more successfully control adult viremic Cx. erythrothorax that enter nearby neighborhoods by applying adulticides during the 3 h that follow sunset.

A rapid approach for quantitative magnetization transfer imaging in thigh muscles using the pulsed saturation method.

Quantitative magnetization transfer (qMT) imaging in skeletal muscle may be confounded by intramuscular adipose components, low signal-to-noise ratios (SNRs), and voluntary and involuntary motion artifacts. Collectively, these issues could create bias and error in parameter fitting. In this study, technical considerations related to these factors were systematically investigated, and solutions were proposed. First, numerical simulations indicate that the presence of an additional fat component significantly underestimates the pool size ratio (F). Therefore, fat-signal suppression (or water-selective excitation) is recommended for qMT imaging of skeletal muscle. Second, to minimize the effect of motion and muscle contraction artifacts in datasets collected with a conventional 14-point sampling scheme, a rapid two-parameter model was adapted from previous studies in the brain and spinal cord. The consecutive pair of sampling points with highest accuracy and precision for estimating F was determined with numerical simulations. Its performance with respect to SNR and incorrect parameter assumptions was systematically evaluated. QMT data fitting was performed in healthy control subjects and polymyositis patients, using both the two- and five-parameter models. The experimental results were consistent with the predictions from the numerical simulations. These data support the use of the two-parameter modeling approach for qMT imaging of skeletal muscle as a means to reduce total imaging time and/or permit additional signal averaging.

Increased sensitivity to apoptosis induced by methotrexate is mediated by JNK.

OBJECTIVE: Low-dose methotrexate (MTX) is an effective therapy for rheumatoid arthritis (RA), yet its mechanism of action is incompletely understood. The aim of this study was to explore the induction of apoptosis by MTX. METHODS: Flow cytometry was performed to assess changes in the levels of intracellular proteins, reactive oxygen species (ROS), and apoptosis. Quantitative polymerase chain reaction was performed to assess changes in the transcript levels of select target genes in response to MTX. RESULTS: MTX did not directly induce apoptosis but rather "primed" cells for markedly increased sensitivity to apoptosis via either mitochondrial or death receptor pathways, by a JNK-dependent mechanism. Increased sensitivity to apoptosis was mediated, at least in part, by MTX-dependent production of ROS, JNK activation, and JNK-dependent induction of genes whose protein products promote apoptosis. Supplementation with tetrahydrobiopterin blocked these MTX-induced effects. Patients with RA who were receiving low-dose MTX therapy expressed elevated levels of the JNK target gene, jun. CONCLUSION: Our results support a model whereby MTX inhibits reduction of dihydrobiopterin to tetrahydrobiopterin, resulting in increased production of ROS, increased JNK activity, and increased sensitivity to apoptosis. The finding of increased jun levels in patients with RA receiving low-dose MTX supports the notion that this pathway is activated by MTX in vivo and may contribute to the efficacy of MTX in inflammatory disease.