Regeneration of specific innervation in Xenopus pectoralis muscle

We investigated the motor unit organization and precision of reinnervation in the Xenopus pectoralis muscle following different manipulations, including crush or section of the posterior pectoralis nerve, foreign nerve innervation, and crush coupled with activity modulation or block. Most fibers have two neuromuscular junctions, and multielectrode recordings were used to identify the axonal origin of all inputs to both junctions on most or all fibers covering about 25% of the muscle surface. Following simple nerve crush, a highly organized innervation pattern was restored, indistinguishable from the normal pattern, including selective innervation of fibers of similar input resistance (R_in), compact motor unit organization, and high incidence of exclusive innervation of both end plates on each fiber by the same axon (distributed mononeuronal innervation, or a/a pattern). Initial reinnervation was equally precise when nerve conduction in the regenerating nerve was blocked by tetrodotoxin. More distant or repeated nerve crush or nerve section delayed and reduced the precision of reinnervation, but the majority of fibers still received input to both end plates by the same axon, often in combination with others. A foreign nerve, the pectoralis sternalis, which in its own muscle forms only single end plates, showed less precise reinnervation, but still had an incidence of a/a innervation far above chance. These data imply the expression and recognition of remarkably precise chemospecific cues even in mature animals, superimposed on which is a further refinement by synapse elimination, probably based on an activity-dependent process. © 1996 John Wiley & Sons, Inc.     

广西热带稀有濒危植物迁地保护地域探讨

对广西热带稀有濒危植物在广西及邻近省份植物园的引种保育进行对比研究。结果表明:大部分树种在热带和南亚热带可以正常生长,通过适当的保护措施,部分树种在中亚热带的桂林可以保存。低温和霜冻是广西热带稀有濒危树种能否成功保存的主要限制因素,因此,在引种保存过程中要注意防寒和树种的选择,以提高迁地保护的有效性。     

Technological properties of Oenococcus oeni strains isolated from typical southern Italian wines

Aims: To isolate indigenous Oenococcus oeni strains suitable as starters for malolactic fermentation (MLF), using a reliable polyphasic approach. Methods and Results: Oenococcus oeni strains were isolated from Nero di Troia wines undergoing spontaneous MLF. Samples were taken at the end of alcoholic fermentation and during MLF. Wine samples were diluted in a sterile physiological solution and plated on MRS and on modified FT80. Identification of O. oeni strains was performed by a polymerase chain reaction (PCR) experiment using strain‐specific primers. Strains were further grouped using a multiplex RAPD‐PCR analysis. Then, six strains were inoculated in two wine‐like media with two different ethanol concentrations (11 and 13% vol/vol) with a view to evaluate their capacity to grow and to perform MLF. In addition, a quantitative PCR (qRT‐PCR) approach was adapted to monitor the physiological state of the strains selected. Conclusion: A positive correlation between the malolactic activity performance and the ability to develop and tolerate stress conditions was observed for two selected O. oeni strains. Significance and Impact of the Study: The results reported are useful for the selection of indigenous MLF starter cultures with desired oenological traits from typical regional wines. It should be the base for the improvement in organoleptic quality of typical red wine.     

ED50 G Na Block Predictions for Phenyl Substituted and Unsubstituted n-Alkanols

To study the role the phenyl group plays in producing local anesthetic block, a sequence of n-alkanols and phenyl-substituted alkanols (Φ-alkanols) were characterized in their ability to block Na channels. The sequence of n-alkanols studied possess 3–5 carbons (propanol-pentanol). The action of phenol and 3-Φ-alkanols (benzyl alcohol, phenethyl alcohol, 3-phenyl-1-propanol) were also studied. Na currents (I _Na ) were recorded from single frog skeletal muscle fibers using the Vaseline-gap voltage clamp technique. I _Na s were recorded prior to, during, and following the removal of the solutes in Ringer's solution. All alkanols and phenol acted to block I _Na in a dose-dependent manner. Effective doses to produce half block (ED₅₀) of I _Na or Na conductance (G _Na ) were obtained from dose-response relations for all solutes used. The block of G _Na depended on voltage, and could be separated into voltage-dependent and -independent components. Each solute acted to shift G _Na -V relations in a depolarized direction and reduce the maximum G _Na and slope of the relation. All solutes acted to speed up I _Na kinetics and cause hyperpolarizing shifts in steady-state inactivation. The magnitude of the kinetic changes increased with dose. Size was an important variable in determining the magnitude of the changes in I _Na ; however, size alone was not sufficient to predict the changes in I _Na . ED₅₀s for G _Na and AP block could be predicted as a function of intrinsic molar volume, hydrogen bond acceptor basicity (β) and donor acidity (α), and polarity (P) of the solutes. The equivalency of ED₅₀ predictions for AP and G _Na block can be explained by the fact that AP block arises from channel block and solute-induced changes in I _Na kinetics. Φ-alkanols were more effective at blocking and inactivating Na channels than their unsubstituted counterparts. Phenyl-substituted alkanols are more likely to interact with the channel than their unsubstituted counterparts. Received: 11 August 2000/Revised: 21 December 2000     

福建省肖叶甲科物种垂直分布与区域分化的比较研究(鞘翅目:肖叶甲科)

研究福建省肖叶甲科物种的垂直分布和区域分化,通过对闽西北武夷山垂直分布的调查分析,认为肖叶甲科垂直分布呈现３个基本分带;海拔３５０ｍ以下,３５０－１２００ｍ和海拔１２００ｍ以上,其中以中间带种类最丰富,与闽中戴云山对比,发现物种的垂直分布范围（上限和下限）在戴云山比在武夷山高,有明显的上移趋势,主要影响因素是南北不同气流的作用和植被垂直分布变化,综合平面分布与垂直分布结果,福建省肖甲科区系以适应于     

Stereospecific synthesis of "para-hydroxymexiletine" and sodium channel blocking activity evaluation

Both enantiomers of "para-hydroxymexiletine" (PHM), one of the main metabolites of mexiletine, were synthesized and fully characterized. Properties of (R)- and (S)-PHM, in terms of blocking potency and stereoselectivity on frog skeletal muscle Na(+) channels, were evaluated. The presence of a hydroxy group on the aryloxy moiety in the 4-position, as in PHM, reduced potency with respect to mexiletine in reducing I(Na max). However, PHM showed clear use-dependent behavior similar to that of mexiletine and, in contrast with what is observed with the parent compound, maintained its stereoselectivity during the use-dependent block. Chirality 16:72-78, 2004.     

Elongated mouse chromosomes suitable for enhanced molecular cytogenetics

Characterization of genetic disorders in humans and animal models requires identification of chromosomal aberrations. However, identifying fine deletions or insertion in metaphase chromosomes has been always a challenge due to limitations of resolution. In this study we developed a rapid method for chromosome elongation using two different intercalating agents: ethidium bromide and 5-bromo-2′-deoxyuridine (BrdU), together with a short-term mitotic block using colcemid. About 70% of the chromosomes from cells that underwent this elongation procedure reached three times longer than those prepared from control cells. FISH experiments using elongated chromosomes revealed a duplicated region of chromosome 11 that was not visible in cells prepared with conventional methods.     

Regional hydrodynamic gene delivery to the rat liver with physiological volumes of DNA solution

BACKGROUND: The major barrier to the clinical application of hydrodynamic gene delivery to the liver is the large volume of fluid required using standard protocols. Regional hydrodynamic gene delivery via branches of the portal vein has not previously been reported, and we have evaluated this approach in a rat model. METHODS: The pGL3 plasmid with the luciferase reporter gene was used at 50 micro g/ml in isotonic solutions, and was administered with a syringe pump for precise control of the hydrodynamic conditions evaluated. Gene expression was individually measured in six anatomically distinct liver lobes. The effect of systemic chloroquine to promote endocytic escape and a (Lys)(16)-containing peptide to condense the DNA into approximately 100-nm nanoparticles was also evaluated. RESULTS: Hydrodynamic conditions for excellent gene delivery were obtained by using 3-ml volumes ( approximately 12 ml/kg) of isotonic DNA solution delivered at 24 ml/min to the right lateral lobe ( approximately 20% of the liver mass). Under these conditions, >95% of gene delivery usually occurred in the targeted right lateral lobe. Outflow obstruction was essential for gene delivery, both at optimal and at very low levels of hydrodynamic gene delivery. The use of systemic chloroquine to promote endocytic escape did not augment hydrodynamic gene delivery, while condensation of DNA in non-ionic isotonic solutions (5% dextrose) to nanoparticles of approximately 100 nm completely abolished gene delivery. CONCLUSIONS: Regional hydrodynamic gene delivery via a branch of the portal vein offers a physiological model of liver gene therapy, for experimental and clinical application.     

Untangling ecological complexity on different scales of space and time

Ecological systems are complex and essentially unpredictable, because of the multitude of interactions among their constituents. However, there are general statistical patterns emerging on particular spatial and temporal scales, which indicate the existence of some universal principles behind many ecological phenomena, and which can even be used for the prediction of phenomena occurring on finer scales of resolution. These generalities comprise regular frequency distributions of particular macroscopic variables within higher taxa (body size, abundance, range size), relationships between such variables, and general patterns in species richness. All the patterns are closely related to each other and although there are only a few major explanatory principles, there are plenty of alternative explanations. Reconciliation of different approaches cannot be obtained without careful formulation of testable hypotheses and rigorous quantitative empirical research. Two especially promising ways of untangling ecological complexity comprise: (1) analysis of invariances, i.e. universal quantitative relationships observed within many different systems, and (2) detailed analysis of the anatomy of macroecological phenomena, i.e. explorations of how emergent multispecies patterns are related to regular patterns concerning individual species.

Zusammenfassung

Ökologische Systeme sind komplex und im Wesentlichen aufgrund der Vielzahl von Interaktionen zwischen ihren Bestandteilen nicht vorhersagbar. Dennoch gibt es allgemeine statistische Muster, die in bestimmten räumlichen und zeitlichen Skalen auftreten. Dies weist auf die Existenz von einigen universellen Prinzipien hinter diesen ökologischen Phänomenen hin, die sogar für die Vorhersage von Phänomenen genutzt werden können, die auf kleineren Skalen auftreten. Diese Allgemeingültigkeiten bestehen aus Häufigkeitsverteilungen von bestimmten makroskopischen Variablen innerhalb höherer Taxa (Körpergröße, Abundanz, Arealgröße), den Beziehungen zwischen diesen Variablen und allgemeinen Mustern des Artenreichtums. Alle Muster stehen in enger Beziehung zueinander und obwohl es nur wenige bedeutende Erklärungsprinzipien gibt, existieren viele alternative Erklärungen. Die Abstimmung zwischen verschiedenen Ansätzen kann ohne eine sorgfältige Formulierung von testbaren Hypothesen und rigorose quantitative empirische Forschung nicht erreicht werden. Zwei besonders vielversprechende Wege ökologische Komplexität zu entwirren beinhalten (1) die Analyse von Invarianten, d.h. universellen quantitativen Beziehungen, die innerhalb verschiedener Systeme beobachtet werden, und (2) detaillierte Analysen der Anatomie von makroökologischen Phänomenen, d.h. Untersuchungen darüber, in welcher Beziehung die auftauchenden Muster von Multi-Arten-Systemen zu regulären Mustern individueller Arten stehen.     

In silico protein design by combinatorial assembly of protein building blocks

Utilizing concepts of protein building blocks, we propose a de novo computational algorithm that is similar to combinatorial shuffling experiments. Our goal is to engineer new naturally occurring folds with low homology to existing proteins. A selected protein is first partitioned into its building blocks based on their compactness, degree of isolation from the rest of the structure, and hydrophobicity. Next, the protein building blocks are substituted by fragments taken from other proteins with overall low sequence identity, but with a similar hydrophobic/hydrophilic pattern and a high structural similarity. These criteria ensure that the designed protein has a similar fold, low sequence identity, and a good hydrophobic core compared with its native counterpart. Here, we have selected two proteins for engineering, protein G B1 domain and ubiquitin. The two engineered proteins share approximately 20% and approximately 25% amino acid sequence identities with their native counterparts, respectively. The stabilities of the engineered proteins are tested by explicit water molecular dynamics simulations. The algorithm implements a strategy of designing a protein using relatively stable fragments, with a high population time. Here, we have selected the fragments by searching for local minima along the polypeptide chain using the protein building block model. Such an approach provides a new method for engineering new proteins with similar folds and low homology.