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21.
Volatile anesthetics (VAs) disrupt nervous system function by an ill-defined mechanism with no known specific antagonists. During the course of characterizing the response of the nematode C. elegans to VAs, we discovered that a C. elegans pheromone antagonizes the VA halothane. Acute exposure to pheromone rendered wild-type C. elegans resistant to clinical concentrations of halothane, increasing the EC(50) from 0.43 +/- 0.03 to 0.90 +/- 0.02. C. elegans mutants that disrupt the function of sensory neurons required for the action of the previously characterized dauer pheromone blocked pheromone-induced resistance (Pir) to halothane. Pheromone preparations from loss-of-function mutants of daf-22, a gene required for dauer pheromone production, lacked the halothane-resistance activity, suggesting that dauer and Pir pheromone are identical. However, the pathways for pheromone's effects on dauer formation and VA action were not identical. Not all mutations that alter dauer formation affected the Pir phenotype. Further, mutations in genes not known to be involved in dauer formation completely blocked Pir, including those altering signaling through the G proteins Goalpha and Gqalpha. A model in which sensory neurons transduce the pheromone activity through antagonistic Go and Gq pathways, modulating VA action against neurotransmitter release machinery, is proposed. 相似文献
22.
Nathan A. Crowder Douglas R. Wylie 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2002,188(2):109-119
The accessory optic system and pretectum are highly conserved brainstem visual pathways that process the visual consequences of self-motion (i.e. optic flow) and generate the optokinetic response. Neurons in these nuclei have very large receptive fields in the contalateral eye, and exhibit direction-selectivity to large-field moving stimuli. Previous research on visual motion pathways in the geniculostriate system has employed "plaids" composed of two non-parallel sine-wave gratings to investigate the visual system's ability to detect the global direction of pattern motion as opposed to the direction of motion of the components within the plaids. In this study, using standard extracellular techniques, we recorded the responses of 47 neurons in the nucleus of the basal optic root of the accessory optic system and 49 cells in the pretectal nucleus lentiformis mesencephali of pigeons to large-field gratings and plaids. We found that most neurons were classified as pattern-selective (41-49%) whereas fewer were classified as component-selective (8-17%). There were no striking differences between nucleus of the basal optic root and lentiformis mesencephali neurons in this regard. These data indicate that most of the input to the optokinetic system is orientation-insensitive but a small proportion is orientation-selective. The implications for the connectivity of the motion processing system are discussed. 相似文献
23.
The gene from Enterococcus faecilis encoding the dipeptidase VanX was subcloned into overexpression vectors pET-5b, pET-27b, and IMPACT-T7, and VanX was overexpressed in BL21(DE3) pLysS Escherichia coli. The pET-5b-vanx overexpression plasmid produces VanX at approximately 12 mg/L under optimum conditions. VanX produced from this overexpression system exists primarily as a dimer in solution, binds ca. 1 Zn(II) ion per monomer, and exhibits K(m) and k(cat) values of 500 +/- 40 microM and 0.074 +/- 0.001 s(-1), respectively, when l-alanine-p-nitroanilide is used as substrate. The IMPACT-T7-vanx overexpression plasmid produces a VanX-fusion protein with a chitin-binding domain that allows for purification of the fusion construct with a chitin column. Cleavage of the fusion protein is completed by an on-column chemical cleavage, resulting in approximately 10 mg/L of purified VanX. VanX produced from this system is identical to that produced from the pET-5b system, except the CD spectrum of the IMPACT-T7-produced VanX suggests a small change in secondary structure. This change in secondary structure does not affect any of the kinetic or metal-binding properties of the enzyme. The pET-27b-vanx overexpression plasmid produces and secretes VanX into the growth medium; this system allows for 20 mg of VanX to be isolated per liter of growth medium. The pET-27b-produced VanX is identical to that produced from pET-5b. 相似文献
24.
The use of in vitro gene reporter assays is becoming increasingly widespread in biology and particularly in drug metabolism, where the need for rapid screening of novel compounds is a driving factor. There is, however, little standardization of technique in the control of such assays, nor in the interpretation of results. This leads to confusion in the literature, with the possibility of a single piece of data being interpreted by several different methods, potentially giving vastly differing results. We have developed a reporter gene assay methodology that controls for many biological and experimental variables in the system and allows the application of a mathematical model to determine statistical significance between groups. Use of this methodology, we feel, allows an accurate and reproducible method of analyzing in vitro reporter gene assay data and increases its value as a biological tool. 相似文献
25.
Rod and cone photoreceptors project from the outer retinal surface into a
carbohydrate-rich interphotoreceptor matrix (IPM). Unique IPM
glycoconjugates are distributed around rods and cones. Wheat germ
agglutinin (WGA) strongly decorates the rod matrix domains and weakly
decorates the cone matrix domains. This study characterizes the major
WGA-binding glycoprotein in the human IPM, which we refer to as SPACR
(sialoprotein associated with cones and rods). SPACR, which has a molecular
weight of 147 kDa, was isolated and purified from the IPM by lectin
affinity chromatography. A polyclonal antibody to SPACR was prepared that
colocalizes in tissue preparations with WGA-binding domains in the IPM.
Sequential digestion of SPACR with N- and O- glycosidases results in a
systematic increase in electrophorectic mobility, indicating the presence
of both N- and O-linked glycoconjugates. Complete deglycosylation results
in a reduction in the relative molecular mass of SPACR by about 30%.
Analysis of lectin binding allowed us to identify some of the structural
characteristics of SPACR glycoconjugates. Treatment with neuraminidase
exposes Galbeta1- 3GalNAc disaccharide as indicated by positive peanut
agglutinin (PNA) staining, accompanied by the loss of WGA staining. Maackia
amurensis agglutinins (MAA-1 and MAA-2), specific for sialic acid in
alpha2-3 linkage to Gal, bind SPACR, while Sambucus nigra agglutinin (SNA),
specific for alpha2-6 linked sialic acid, does not, indicating that the
dominant glycoconjugate determinant on SPACR is the O-linked carbohydrate,
NeuAcalpha2-3Galbeta1-3GalNAc. The abundance of sialic acid in SPACR
suggests that this glycoprotein may contribute substantially to the
polyanionic nature of the IPM. The carbohydrate chains present on SPACR
could also provide sites for extensive crosslinking and participate in the
formation of the ordered IPM lattice that surrounds the elongate
photoreceptors projecting from the outer retinal surface.
相似文献
26.
Stacy E. Aguilera Jennifer Cole Elena M. Finkbeiner Elodie Le Cornu Natalie C. Ban Mark H. Carr Joshua E. Cinner Larry B. Crowder Stefan Gelcich Christina C. Hicks John N. Kittinger Rebecca Martone Daniel Malone Carrie Pomeroy Richard M. Starr Sanah Seram Rachel Zuercher Kenneth Broad 《PloS one》2015,10(3)
Globally, small-scale fisheries are influenced by dynamic climate, governance, and market drivers, which present social and ecological challenges and opportunities. It is difficult to manage fisheries adaptively for fluctuating drivers, except to allow participants to shift effort among multiple fisheries. Adapting to changing conditions allows small-scale fishery participants to survive economic and environmental disturbances and benefit from optimal conditions. This study explores the relative influence of large-scale drivers on shifts in effort and outcomes among three closely linked fisheries in Monterey Bay since the Magnuson-Stevens Fisheries Conservation and Management Act of 1976. In this region, Pacific sardine (Sardinops sagax), northern anchovy (Engraulis mordax), and market squid (Loligo opalescens) fisheries comprise a tightly linked system where shifting focus among fisheries is a key element to adaptive capacity and reduced social and ecological vulnerability. Using a cluster analysis of landings, we identify four modes from 1974 to 2012 that are dominated (i.e., a given species accounting for the plurality of landings) by squid, sardine, anchovy, or lack any dominance, and seven points of transition among these periods. This approach enables us to determine which drivers are associated with each mode and each transition. Overall, we show that market and climate drivers are predominantly attributed to dominance transitions. Model selection of external drivers indicates that governance phases, reflected as perceived abundance, dictate long-term outcomes. Our findings suggest that globally, small-scale fishery managers should consider enabling shifts in effort among fisheries and retaining existing flexibility, as adaptive capacity is a critical determinant for social and ecological resilience. 相似文献
27.
28.
每搏量变异度是动态的容量监测指标.机械通气患者心肺的相互作用是每搏量变异度的产生基础,通过动脉压力波形分析技术可以进行连续监测.每搏量变异度能够准确预测容量治疗反应,与静态的血流动力学参数相比,对于优化心输出量和组织氧供更有优势,但也存在一定的局限性.每搏量变异度受多种因素影响且不能用于自主呼吸和心律失常的患者.临床应用时应该综合考虑其影响因素,结合其他的指标和方法指导容量治疗. 相似文献
29.
Beehler Angela Markowski Daniel Crowder Michael Iaquinto Kate E. Kinley Jason 《Wetlands Ecology and Management》2022,30(5):975-985
Wetlands Ecology and Management - When developing a plan to restore or modify a wetland within the Pacific Northwest of the United States (PNW), land managers must consider all of the potential... 相似文献
30.
Donald E. Mitchell Nathan A. Crowder Kaitlyn Holman Matthew Smithen Kevin R. Duffy 《Proceedings. Biological sciences / The Royal Society》2015,282(1803)
Extended periods of darkness have long been used to study how the mammalian visual system develops in the absence of any instruction from vision. Because of the relative ease of implementation of darkness as a means to eliminate visually driven neural activity, it has usually been imposed earlier in life and for much longer periods than was the case for other manipulations of the early visual input used for study of their influences on visual system development. Recently, it was shown that following a very brief (10 days) period of darkness imposed at five weeks of age, kittens emerged blind. Although vision as assessed by measurements of visual acuity eventually recovered, the time course was very slow as it took seven weeks for visual acuity to attain normal levels. Here, we document the critical period of this remarkable vulnerability to the effects of short periods of darkness by imposing 10 days of darkness on nine normal kittens at progressively later ages. Results indicate that the period of susceptibility to darkness extends only to about 10 weeks of age, which is substantially shorter than the critical period for the effects of monocular deprivation in the primary visual cortex, which extends beyond six months of age. 相似文献