具有植物特征的动物

一般说来 ,人们很容易把动物和植物区别开来 ,因为动物会动 ,如虫鱼鸟兽 ;植物有叶绿素 ,能进行光合作用 ,如花草树木。可是 ,有一类生活在水体中的微小生物 ,就很难说出它们是动物还是植物。因为它们既有动物的特征 ,又具有植物的特征 ,如有鞭毛 ,能运动 ,动物学家把它们归入动物 ;同时 ,它们具叶绿素 ,能进行光合作用 ,制造有机物 ,植物学家把它们归入植物。这就是原生动物门、鞭毛纲、植鞭亚纲的动物。植鞭类原生动物全身只有 1个细胞 ,这个细胞在生理上是 1个完全独立的动物体。它要担负起运动、营养、呼吸、排泄、生殖等各种生理机能 ,…     

椰子的胚在哪里?

植物的种子在形状、大小、色泽、硬度等方面常因植物种类不同而有很大的差别。自然界里的种子植物约有2 5万种左右 ,种子的大小相差悬殊 ,大种子莫过于椰子的种子 ,直径可达 2 0 cm,复椰子的种子更大 ,果实可达1 5～ 2 0 kg。说到椰子 ,你会想起熟悉的天然饮料——椰子汁及其椰果中的椰肉 (胚乳或椰仁 ) ,然而 ,你见过椰子的胚吗 ?椰子属核果 ,但与桃、李、杏等核果不同 ,桃、李、杏等的中果皮是发达的肉质食用部分 ,而椰子的中果皮干燥无汁 ,纤维状 ,俗称“椰棕”,椰棕外面薄而光滑的一层为革质的外果皮 ,椰棕里面的硬壳为内果皮。有的教科…     

Exploring chromophore--protein interactions in fluorescent protein cmFP512 from Cerianthus membranaceus: X-ray structure analysis and optical spectroscopy

Autofluorescent proteins of the GFP family all share the same three-dimensional beta-can fold; yet they exhibit widely different optical properties, arising either from chemical modification of the chromophore itself or from specific interactions of the chromophore with the surrounding protein moiety. Here we present a structural and spectroscopic characterization of the green fluorescent protein cmFP512 from Cerianthus membranaceus, a nonbioluminescent, azooxanthellate cnidarian, which has only approximately 22% sequence identity with Aequorea victoria GFP. The X-ray structure, obtained by molecular replacement at a resolution of 1. 35 A, shows the chromophore, formed from the tripeptide Gln-Tyr-Gly, in a hydrogen-bonded cage in the center of an 11-stranded beta-barrel, tightly restrained by adjacent residues and structural water molecules. It exists in a neutral (A) and an anionic (B) species, with absorption/emission maxima at 392/460 (pH 5) and 503/512 nm (pH 7). Their fractional populations and peak positions depend sensitively on pH, reflecting protonation of groups adjacent to the chromophore. The pH dependence of the spectra is explained by a protonation mechanism involving a hydrogen-bonded cluster of charged/polar groups. Cryospectroscopy at 12 K was also performed to analyze the vibronic coupling of the electronic transitions.     

Live-cell imaging with EosFP and other photoactivatable marker proteins of the GFP family

Fluorescent proteins from the green fluorescent protein family have become indispensable imaging tools for cell biology. A wide variety of these proteins were discovered in nonbioluminescent anthozoa in recent years. Some of them feature exciting new properties, with the possibility to alter their intensity and/or fluorescence color by irradiation with light of specific wavelengths. Fluorescent highlighter proteins enable many interesting applications based on regional optical marking in live cells and tissues. This review provides an overview of photoactivatable marker proteins, with a focus on EosFP, a protein that can be switched from green to red fluorescence by approximately 400-nm light. A variety of applications are presented to illustrate the versatility of EosFP in live-cell imaging.     

Single-molecule FRET study of denaturant induced unfolding of RNase H

Single-molecule fluorescence (F?rster) resonance energy transfer (FRET) experiments were performed on surface-immobilized RNase H molecules as a function of the concentration of the chemical denaturant guanidinium chloride (GdmCl). For comparison, we measured ensemble FRET on RNase H solutions. The single-molecule approach allowed us to study FRET distributions of the subpopulation of unfolded molecules without interference from the folded population. The unfolded ensemble experienced a continuous shift of the FRET efficiency distribution with increasing concentration of GdmCl, indicating a heterogeneous population of expanding, unfolded polypeptide chains. We have analyzed the behavior of the unfolded state quantitatively with a model in which the unfolded state is described by a continuum of substates, with the free energy of each substate linearly coupled to its m-value, the proportionality coefficient between free energy and denaturant activity. By fitting this model to the data, we have derived energetic and structural parameters that describe the unfolded state ensemble. Specifically, we have found that the average size of the unfolded state increases from 23-38 A between 0 and 6 M denaturant. Excellent agreement was achieved between the fitted model and our FRET measurements, and with previously published nuclear magnetic resonance and small-angle X-ray scattering data.     

Single-molecule force spectroscopy of the aplysia cell adhesion molecule reveals two homophilic bonds

Aplysia californica neurons comprise a powerful model system for quantitative analysis of cellular and biophysical properties that are essential for neuronal development and function. The Aplysia cell adhesion molecule (apCAM), a member of the immunoglobulin superfamily of cell adhesion molecules, is present in the growth cone plasma membrane and involved in neurite growth, synapse formation, and synaptic plasticity. apCAM has been considered to be the Aplysia homolog of the vertebrate neural cell adhesion molecule (NCAM); however, whether apCAM exhibits similar binding properties and neuronal functions has not been fully established because of the lack of detailed binding data for the extracellular portion of apCAM. In this work, we used the atomic force microscope to perform single-molecule force spectroscopy of the extracellular region of apCAM and show for the first time (to our knowledge) that apCAM, like NCAM, is indeed a homophilic cell adhesion molecule. Furthermore, like NCAM, apCAM exhibits two distinct bonds in the trans configuration, although the kinetic and structural parameters of the apCAM bonds are quite different from those of NCAM. In summary, these single-molecule analyses further indicate that apCAM and NCAM are species homologs likely performing similar functions.     

乳杆菌制剂在不同阴道炎治疗中的作用分析

目的探讨微生态疗法在女性不同阴道炎症治疗中的临床价值,为临床使用微生态制剂治疗阴道炎症,提供新的方法和理论基础。方法以2013年3月至2013年8月在沈阳医学院附属第二医院妇科门诊就诊的阴道炎患者共计892例,作为研究对象,在治疗上采取抗（真）菌药＋乳杆菌制剂,比较各组的治疗效果（7d及14d治愈率）。结果治疗效果比较（7d和14d治愈率）：单纯外阴阴道假丝酵母菌病（VVC）：分别为91．34％和99．10％,P〈0．01,差异有统计学意义;单纯细菌性阴道病（BV）：分别为98．50％和100％,P〉0．05,差异无统计学意义;单纯滴虫性阴道炎（TV）：分别为98．41％和100％,P〉0．05,差异无统计学意义;混合感染：分别为88．12％和99．01％,P〈0．01,差异有统计学意义。结论乳杆菌制剂配合抗（真）菌药在治疗不同阴道炎中的效果不同,疗程不同。     

Systemic administration of neuregulin-1β1 protects dopaminergic neurons in a mouse model of Parkinson's disease

Neuregulin-1 (Nrg1) is genetically linked to schizophrenia, a disease caused by neurodevelopmental imbalance in dopaminergic function. The Nrg1 receptor ErbB4 is abundantly expressed on midbrain dopaminergic neurons. Nrg1 has been shown to penetrate blood-brain barrier, and peripherally administered Nrg1 activates ErbB4 and leads to a persistent hyperdopaminergic state in neonatal mice. These data prompted us to study the effect of peripheral administration of Nrg1 in the context of Parkinson's disease, a neurodegenerative disorder affecting the dopaminergic system in the adult brain. We observed that systemic injections of the extracellular domain of Nrg1β(1) (Nrg1β(1)-ECD) increased dopamine levels in the substantia nigra and striatum of adult mice. Nrg1β(1)-ECD injections also significantly protected the mouse nigrostriatal dopaminergic system morphologically and functionally against 6-hydroxydopamine-induced toxicity in vivo. Moreover, Nrg1β(1)-ECD also protected human dopaminergic neurons in vitro against 6-hydroxydopamine. In conclusion, we have identified Nrg1β(1)-ECD as a neurotrophic factor for adult mouse and human midbrain dopaminergic neurons with peripheral administratability, warranting further investigation as therapeutic option for Parkinson's disease patients.