介绍拍摄几种植物运动的方法

介绍用显微摄影装置定格拍摄气孔开闭、颖花开闭、浆片膨大、花粉萌发,用扫描仪录入稻穗开花以及用相机拍摄稻根负向光性生长等植物运动的技术和方法,并展示所摄植物运动的照片。     

Controlled Gating of Lysenin Pores

Lysenin forms unitary large conductance pores in artificial bilayer membranes containing sphingomyelin. A population of lysenin pores inserted into such a bilayer membrane exhibited a dynamic negative conductance region, as predicted by a simple two-state model for voltage-gated channels. The recorded I-V curves demonstrated that lysenin pores inserted into the bilayer are uniformly oriented. Additionally, the transition between the two-states was affected by changes in the monovalent ion concentration and pH, pointing towards an electrostatic interaction governing the gating mechanism.     

Operant generalization in quail neonates after intradimensional training: Distinguishing positive and negative reinforcement

Operant generalization has been demonstrated in neonates only recently. To investigate the development of intradimensional stimulus control immediately after hatching, northern bobwhite chicks (Colinus virginianus) pecked for brief heat presentations while hearing a high-pitched sound repeated at two constant rates: an S+ tempo signaling a rich reinforcement schedule, alternating with an S− tempo signaling a leaner schedule. Tempo generalization was then assessed in extinction. The expected excitatory gradients were produced after a threshold number of training sessions; unexpectedly, below that threshold, gradients were inhibitory. The chicks’ rapidly developing thermoregulatory capability may have resulted in a change from perceived negative reinforcement initially to positive reinforcement later. Given past research showing excitatory gradients after negative reinforcement, we suggest that these results demonstrate that all negative reinforcement is not equivalent, and, further, that classical conditioning effects require consideration.     

Mechanical behaviour analyses of sap ascent in vascular plants

A pure mechanical anisotropic model of a tree trunk has been developed based on the 3D finite element method. It simulates the microscopic structure of vessels in the trunk of a European beech (Fagus sylvatica) in order to study and analyse its mechanical behaviour with different configurations of pressures in the conduits of xylem and phloem. The dependence of the strains at the inner bark was studied when sap pressure changed. The comparison with previously published experimental data leads to the conclusion that a great tensile stress—or ‘negative pressure’—must exist in the water column in order to achieve the measured strains if only the mechanical point of view is taken into account. Moreover, the model can help to design experiments where qualitatively knowing the strains and the purely mechanical behaviour of the tree is required.     

The role of the glycine triad in human glutathione synthetase

Experimental kinetics and computational modeling of human glutathione synthetase (hGS) support the significant role of the G-loop glycine triad (G369, G370, G371) for activity of this ATP-grasp enzyme. Enzyme kinetic experiments indicate that G369V and G370V mutant hGS have little activity (<0.7 and 0.3%, respectively, versus wild-type hGS). However, G371V retains ∼13% of the activity of wild-type hGS. With respect to G-loop:A-loop interaction in hGS, mutations at Gly369 and Gly370 decrease ligand binding and prevent active site closure and protection. This research indicates that Gly369 and Gly370 have essential roles in hGS, while Gly371 has a lesser involvement. Implications for glycine-rich ensembles in other phosphate-binding enzymes are discussed.     

Enhanced cell viability and cell adhesion using low conductivity medium for negative dielectrophoretic cell patterning

Negative dielectrophoretic (n-DEP) cell manipulation is an efficient way to pattern human liver cells on micro-electrode arrays. Maintaining cell viability is an important objective for this approach. This study investigates the effect of low conductivity medium and the optimally designed microchip on cell viability and cell adhesion. To explore the influence of conductivity on cell viability and cell adhesion, we have used earlier reported dielectrophoresis (DEP) buffer with a conductivity of 10.2 mS/m and three formulated media with conductivity of 9.02 (M1), 8.14 (M2), 9.55 (M3) mS/m. The earlier reported isotonic sucrose/dextrose buffer (DEP buffer) used for DEP manipulation has the drawback of poor cell adhesion and cell viability. A microchip prototype with well-defined positioning of titanium electrode arrays was designed and fabricated on a glass substrate. The gap between the radial electrodes was accurately determined to achieve good cell patterning performance. Parameters such as dimension of positioning electrode, amplitude, and frequency of voltage signal were investigated to optimize the performance of the microchip.     

Algorithm-assisted elucidation of disulfide structure: application of the negative signature mass algorithm to mass-mapping the disulfide structure of the 12-cysteine transforming growth factor beta type II receptor extracellular domain

The power of an algorithm-driven method for interpreting disulfide mass-mapping data is demonstrated in the context of determining the disulfide structure of the extracellular domain of the transforming growth factor beta type II receptor, a 14-kDa cystinyl protein containing 12 cysteines in the form of six disulfide bonds. The disulfide mass-mapping methodology is based on partial reduction and cyanylation-induced cleavage of the cystinyl protein. Because the multiplicity of possible disulfide structures that must be considered grows rapidly with the number of cysteines, as does the difficulty in physically isolating each of the partially reduced and cyanylated isoforms of the analyte, manual data interpretation for disulfide mapping a cystinyl protein containing more than eight cysteines becomes unmanageable. Recently, we introduced the concept of a "negative signature mass algorithm" (NSMA) to determine the disulfide structure of a cystinyl protein by processing an input of its amino acid sequence and mass spectral data from analysis of its associated cyanylation-induced cleavage products. Here, we present experimental results to validate the NSMA concept. A key advantage of the NSMA, in addition to convenience and automation, is its capacity to interpret mass spectra from mixtures of cyanylation-induced cleavage fragments without separating the partially reduced isoforms of the cystinyl protein and without knowledge of the extent of partial reduction.     

Facilitation of hypothalamic-pituitary-adrenal responses to novel stress following repeated social stress using the resident/intruder paradigm

Our goal in these studies was to characterize some specific aspects of hypothalamic-pituitary-adrenal (HPA) activity in rats exposed to repeated social stress. We used a modification of the resident/intruder paradigm in which male intruder rats were subjected to defeat and then separated from the resident by an enclosure for a total of 30 min on Day 1. On Days 2-7, intruder rats were exposed to different resident rats every day through a wire mesh enclosure for 30 min in order to minimize injurious physical contact between the two rats. The intruder rats gained significantly less weight than controls over the 7-day period of stress though basal corticosterone levels and adrenal and thymus weights were not significantly different between the two groups. On Day 8, repeatedly stressed rats exhibited facilitation of HPA responses to novel restraint compared to controls but no differences in negative feedback sensitivity to dexamethasone (0.05 or 0.2 mg/kg) were observed. Thus, the HPA axis of socially stressed rats remains responsive to a stimulus that has never been encountered. Using this type of repeated presentation to an aggressive resident allows us to examine the neuroendocrine and behavioral consequences, and their underlying neural mechanisms, of exposure to a stressor that is social in nature and naturalistic for rodents.