Material basis for inhibition of Dragon’s Blood on evoked discharges of wide dynamic range neurons in spinal dorsal horn of rats

In vivo experiments were designed to verify the analgesic effect of Dragon’s Blood and the material basis for this effect. Extracellular microelectrode recordings were used to observe the effects of Dragon’s Blood and various combinations of the three components (cochinchinenin A, cochinchinenin B, and loureirin B) extracted from Dragon’s Blood on the discharge activities of wide dynamic range (WDR) neurons in spinal dorsal horn (SDH) of intact male Wistar rats evoked by electric stimulation at sciatic nerve. When the Hill's coefficients describing the dose-response relations of drugs were dif-ferent, based on the concept of dose equivalence, the equations of additivity surfaces which can be applied to assess the interaction between three drugs were derived. Adopting the equations and Tal-larida's isobole equations used to assess the interaction between two drugs with dissimilar dose-response relations, the effects produced by various combinations of the three components in modulating the evoked discharge activities of WDR neurons were evaluated. Results showed that Dragon’s Blood and its three components could inhibit the evoked discharge frequencies of WDR neurons in a concentration-dependent way. The Hill's coefficients describing dose-response relations of three components were different. Only the combined effect of cochinchinenin A, cochinchinenin B and loureirin B was similar to that of Dragons Blood. Furthermore, the combined effect was synergistic. This investigation demonstrated that through the synergistic interaction of the three components Dragon’s Blood could interfere with the transmission and processing of pain signals in spinal dorsal horn. All these further proved that the combination of cochinchinenin A, cochinchinenin B, and loureirin B was the material basis for the analgesic effect of Dragon’s Blood.     

A rapid and non leaky way for preparation of the sharp intracellular recording microelectrodes

To fill microelectrodes using backfilling method needs excessive time approximately 4–6  h. It is often difficult to fill microelectrodes without damage or leakage. A main problem is bubble formation in microelectrodes which has an impact on the electrical properties of the electrode and thus it influences the quality of the recording. Based on Archimede's principle there is a force within a solution which pushes insoluble material with a lower specific gravity upward and outside of the solution. Centrifugation can increase the force to eliminate the bubbles.

We designed a microelectrode holder to protect microelectrode sensitive tips from mechanical damage due to the gravity tensions; it can help to eliminate the bubbles easily and simultaneously in 10  min or less.

The tests were performed for 2000, 4000, and 8000  rpm centrifugation each one for 3, 6 and 12  min duration respectively, it was found that the bubbles were completely eliminated at 8000  rpm for 6–12  min and there were no significant differences for resistance, and the number of leaky or damaged electrodes between the two methods.

In the new design of devices, the materials used and the design of the holder are simple and the approach is applicable to many laboratories worldwide.     

Gene application with in utero electroporation in mouse embryonic brain

Mouse genetic manipulations, such as the production of gene knock-out, knock-in, and transgenic mice, have provided excellent systems for analysis of numerous genes functioning during development. Nevertheless, the lack of specific promoters and enhancers that control gene expression in specific regions and at specific times, limits usage of these techniques. However, progress in in utero systems of electroporation into mouse embryos has opened a new window, permitting new approaches to answering important questions. Simple injection of plasmid DNA solution and application of electrical current to mouse embryos results in transient area- and time-dependent transfection. Further modification of the technique, arising from variations in types of electrodes used, has made it possible to control the relative size of the region of transfection, which can vary from a few cells to entire tissues. Thus, this technique is a powerful means not only of characterizing gene function in various settings, but also of tracing the migratory routes of cells, due to its high efficiency and the localization of gene expression it yields. We summarize here some of the potential uses and advantages of this technique for developmental neuroscience research.     

Oxygen distribution and movement,respiration and nutrient loading in banana roots (Musa spp. L.) subjected to aerated and oxygen-depleted environments

Excessive soil wetness is a common feature where bananas (Musa spp.) evolved. Under O₂ deficiency, a property of wet soils, root growth and functions will be influenced by the respiratory demand for O₂ in root tissues, the transport of O₂ from the shoot to root and the supply of O₂ from the medium. In laboratory experiments with nodal roots of banana, we examined how these features influenced the longitudinal and radial distributions of O₂ within roots, radial O₂ loss, solute accumulation in the xylem, root hydraulic conductivity, root elongation and root tip survival. In aerated roots, the stele respired about 6 times faster than the cortex on a volume basis. Respiratory O₂ consumption decreased substantially with distance from the root apex and at 300–500 mm it was 80% lower than at the apex. Respiration of lateral roots constituted a sink for O₂ supplied via aerenchyma, and reduced O₂ flow towards the tip of the supporting root. Stelar anoxia could be induced either by lowering the O₂ partial pressure in the bathing medium from 21 to 4 kPa (excised roots) or, in the case of intact roots, by reducing the O₂ concentration around the shoot. The root hair zone sometimes extended to 1.0 mm from the root surface and contributed up to a 60% drop in O₂ concentration from a free-flowing aerated solution to the root surface. There was a steep decline in O₂ concentration across the epidermal-hypodermal cylinder and some evidence of a decline in the O₂ permeability of the epidermal-hypodermal cylinder with increasing distance from the root apex. The differences in O₂ concentration between cortex and stele were smaller than reported for maize and possibly indicated a substantial transfer rate of dissolved O₂ from cortex to stele in banana, mediated by a convective water flow component. An O₂ partial pressure of 4 kPa in the medium reduced net nutrient transfer into the vascular tissue in the stele within 1 or 2 h. Hypoxia also caused a temporary decrease in radial root hydraulic conductivity by an order of magnitude. In O₂ deficient environments, the stele would be among the first tissues to suffer anoxia and O₂ consumption within the root hair zone might be a major contributor to root anoxia/hypoxia in banana growing in temporarily flooded soils.     

Bioinspired polymers that control intracellular drug delivery

One of the important characteristics of biological systems is their ability to change important properties in response to small environmental signals. The molecular mechanisms that biological molecules utilize to sense and respond provide interesting models for the development of “smart” polymeric biomaterials with biomimetic properties. An important example of this is the protein coat of viruses, which contains peptide units that facilitate the trafficking of the virus into the cell via endocytosis, then out of the endosome into the cytoplasm, and from there into the nucleus. We have designed a family of synthetic polymers whose compositions have been designed to mimic specific peptides on viral coats that facilitate endosomal escape. Our biomimetic polymers are responsive to the lowered pH within endosomes, leading to disruption of the endosomal membrane and release of important biomolecular drugs such as DNA, RNA, peptides and proteins to the cytoplasm before they are trafficked to lysosomes and degraded by lysosomal enzymes. In this article, we review our work on the design, synthesis and action of such smart, pH-sensitive polymers.     

pH track of expanding bacterial populations

A method of pH distribution measurements in agar nutrient media containing expanding bacterial populations is described. It is based on measuring pH microsamples taken at different points of the media. The sample volume was 10 microliters. A pH sensitive field effect transistor was used as a measuring electrode. Acidification was found to occur in glucose media, while alkalization occurred in the media containing peptone.     

Photosynthesis and respiration of a diatom biofilm cultured in a new gradient growth chamber

Abstract A diatom biofilm was grown in a chamber developed for culture of biofilms in chemical gradients. The diatoms grew on a polycarbonate membrane filter which separated a sterile reservoir, with added phosphate, from a reservoir without phosphate. Within 3 weeks of inoculation, a thick biofilm developed on the surface of the filter. The biofilms were homogeneous and therefore suitable for calculations of O₂ diffusion fluxes from concentration profiles of O₂. Profiles of O₂, pH, and gross photosynthesis at different light intensities and liquid medium concentrations of dissolved inorganic carbon and O₂ were measured with microelectrodes. Respiratory activity in a layer of the biofilm was determined as the difference between gross photosynthesis and outflux of O₂ from that layer. The photosynthetic activity in a well-developed biofilm grown at 360 μEinst m⁻² s⁻¹ and 2.4 mM HCO₃⁻ was limited by the supply of inorganic carbon. Exposure to light above 360 μEinst m⁻² s⁻¹ stimulated gross photosynthesis as well as respiratory processes without affecting net outflux of O₂. Higher concentrations of inorganic carbon, on the other hand, enhanced gross photosynthesis without concurrent increase in respiratory rate, resulting in an increased outflux of O₂. High concentrations of O₂ in the liquid medium decreased the net outflux of O₂ with little effect on the gross photosynthesis. The effects of inorganic carbon and O₂ on the metabolic activities of the biofilm were consistent with the presence of photorespiratory activity.     

Influence of the nature of the sterol on the behavior of palmitic acid/sterol mixtures and their derived liposomes

The phase behavior of mixtures formed with palmitic acid (PA) and one of the following sterols (dihydrocholesterol, ergosterol, 7-dehydrocholesterol, stigmasterol and stigmastanol), in a PA/sterol molar ratio of 3/7, has been characterized by IR and ²H NMR spectroscopy at different pH. Our study shows that it is possible to form liquid-ordered (lo) lamellar phases with these binary non-phospholipid mixtures. The characterization of alkyl chain dynamics of PA in these systems revealed the large ordering effect of the sterols. It was possible to extrude these systems, using standard extrusion techniques, to form large unilamellar vesicles (LUVs), except in the case of ergosterol-containing mixture. The resulting LUVs displayed a very limited passive permeability consistent with the high sterol concentration. In addition, the stability of these PA/sterol self-assembled bilayers was also found to be pH-sensitive, therefore, potentially useful as nanovectors. By examining different sterols, we could establish some correlations between the structure of these bilayers and their permeability properties. The structure of the side chain at C17 of the sterol appears to play a prime role in the mixing properties with fatty acid.     

应用线性硅电极阵列检测海马场电位和单细胞动作电位

近年来,硅材料微电极阵列发展迅速,μ为研究大脑神经细胞活动的时空特性提供了理想的手段.考察了线性硅材料微电极阵列在神经细胞电位检测中的稳定性,以及对于单细胞动作电位检测的有效性.实验结果表明,在麻醉大鼠海马CA1区场电位记录中,上下移动记录微电极200μm,对于正向和反向诱发电位的记录几乎没有影响,说明,线性微电极阵列对于神经细胞的损伤很小,检测性能稳定.电极阵列上处于细胞胞体层的测量点可以有效地记录到CA1神经细胞的动作电位发放,同一记录点上可以清楚地分辨出数个不同神经细胞的发放电位.实验结果显示了硅电极阵列操作简便、检测信号稳定和获取信息多等特点,对于开展微电极阵列应用研究的工作人员具有借鉴作用.