Character and OTU stability in five taxonomic groups

The character and OTU stability of classifications based on UPGMA clustering and maximum parsimony (MP) trees were compared for 5 datasets (families of angiosperms, families of orthopteroid insects, species of the fish genusIctalurus, genera of the salamander family Salamandridae, and genera of the frog family Myobatrachidae). Stability was investigated by taking different sized random subsamples of OTUs or characters, computing UPGMA clusters and an MP tree, and then comparing the resulting trees with those based on the entire dataset. Agreement was measured by two consensus indices, that of Colless, computed from strict consensus trees, and Stinebrickner's 0.5-consensus index. Tests of character stability generally showed a monotone decrease in agreement with the standard as smaller sets of characters are considered. The relative success of the two methods depended upon the dataset. Tests of OTU stability showed a monotone decrease in agreement for UPGMA as smaller sets of OTUs are considered. But for MP, agreement decreased and then increased again on the same scale. The apparent superiority of UPGMA relative to MP with respect to OTU stability depended upon the dataset. Considerations other than stability, such as computer efficiency or accuracy, will also determine the method of choice for classifications.     

A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles

Poly(MePEG₂₀₀₀cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems.Received 4 March 2005; accepted 14 April 2005     

Congenital muscular dystrophy: molecular and cellular aspects

The congenital muscular dystrophies are a clinically and genetically heterogeneous group of neuromuscular disorders. Each form has a characteristic phenotype, but there is overlap between some entities and their classification is based on a combination of clinical features and the primary or secondary protein defect. Recent studies have identified the genetic basis of a number of congenital muscular dystrophies (11 genes in total) and have recognised a novel pathological mechanism that highlights the importance of the correct posttranslational processing of proteins, in particular -dystroglycan. Diagnosis of these conditions has been aided by the availability of specific antibodies for each protein and a better understanding of the protein changes that accompany each condition. In this review we present the major molecular, clinical and diagnostic aspects of each group of congenital muscular dystrophy with an emphasis in the more recent developments.Received 11 December 2004; accepted 15 December 2004     

Copper and zinc dismetabolism in the mouse brain upon chronic cuprizone treatment

Recent reports describe successful treatment using copper chelation therapy in neurodegenerative animal models. However, the success claimed for chelation therapy in neurodegenerative diseases is still rather controversial. To acquire new information on copper metabolism/homeostasis, we utilized cuprizone, a very sensitive and selective copper-chelating agent with well-known neurotoxic properties, as a relevant chemical model in mice. Upon cuprizone treatment, mice developed a pronounced astrocytosis, with brain oedema and spongiosis characterised by vacuolisations of the neuropil predominantly in the white matter. In addition, cuprizone treatment severely altered copper and zinc homeostasis in the central nervous system (CNS) as well as in all other tissues examined, with increasing metal ion concentrations particularly in the CNS. Concomitant with this increase in the Cu and Zn concentration in the brain, metallothionein-I and -II were also highly immunoreactive in astrocyte, consistent with the astrocytosis and demyelination observed in our and other laboratories.Received 23 February 2005; received after revision 3 May 2005; accepted 13 May 2005     

A novel pattern of fast calcium oscillations points to calcium and electrical activity cross-talk in rat chromaffin cells

Slow oscillations of cytosolic calcium ion concentration – – typically originate from release by intracellular stores, but in some cell types can be triggered and sustained by Ca²⁺ influx as well. In this study we simultaneously monitored changes in and in the electrical activity of the cell membrane by combining indo-1 and patch-clamp measurements in single rat chromaffin cells. By this approach we observed a novel type of spontaneous oscillations, much faster than those previously described in these cells. These oscillations are triggered and sustained by complex electrical activity (slow action potentials and spike bursts), require Ca²⁺ influx and do not involve release from intracellular stores. The possible physiological implications of this new pathway of intracellular signalling are discussed.Received 30 July 2004; received after revision 14 October 2004; accepted 1 November 2004     

Is chlamydial heat shock protein 60 a risk factor for oncogenesis?

Heat shock protein 60 (HSP60) plays an important role in the protein folding of prokaryotic and eukaryotic cells. Most of the papers published on chlamydial HSP60 concern its role in immune response during infection. In the last decade, exposure to Chlamydia trachomatis has been consistently associated with the development of cervical and ovarian cancer. Moreover, it has been suggested that chlamydial HSP60 may have an anti-apoptotic effect during persistent infection. We hypothesize that the accumulation of exogenous chlamydial HSP60 in the cytoplasm of actively replicating eukaryotic cells may interfere with the regulation of the apoptotic pathway. The concomitant expression of viral oncoproteins and/or the presence of mutations may lead to the ability to survive apoptotic stimuli, loss of replicative senescence, uncontrolled proliferation and, finally neoplastic transformation.Received 15 August 2004; received after revision 1 October 2004; accepted 7 October 2004     

Compensatory caspase activation in MPP+-induced cell death in dopaminergic neurons

Many have hypothesized that cell death in Parkinsons disease is via apoptosis and, specifically, by the mitochondrial-mediated apoptotic pathway. We tested this hypothesis using a mouse dopaminergic cell line of mesencephalic origin, MN9D, challenged with the Parkinsonism-causing neurotoxin MPP⁺ (1-methyl-4-phenylpyridinium ion). Apoptosis was the main mode of cell death when the cells were subjected to MPP⁺ treatment under serum-free conditions for 24 h. Caspase-3 and caspase-9, however, were not activated, thus indicating the existence of alternate or compensatory cell death pathway(s) in dopaminergic neuronal cells. Using caspase inhibitors, we demonstrated that these pathways involve caspase-2, –8, –6 and –7. A time-course study indicated that activation of caspase-2 and –8 occurred upstream of caspase-6 and caspase-7. Upon MPP⁺ challenge, the apoptosis-inducing factor was translocated from the mitochondria into the MN9D cytosol and nucleus. These results suggest the existence of alternative apoptotic pathways in dopaminergic neurons.Received 20 September 2004; received after revision 5 November 2004; accepted 22 November 2004     

Molecular cloning and polymorphism of major histocompatibility complex class I genes from grass carp (Ctenophayngodon idellus)

In order to clarify the molecular sequences,allelic polymorphism and the tertiary structure of grass carp (Ctenophayngodon idellus) MHC class I,and to further study their relationship with disease resistances,grass carp MHC class I gene (Ctid-MHC I) was cloned from a cDNA library and the allelic polymorphism in the population was investigated.The results showed that most of the variations exist in the peptide-binding domain (PBD) and high polymorphism was identified in the Ctid-MHC I allelic genes from 12 individuals.Based on the genetic distance,Ctid-MHC class I can be classified into 6 types (from Ctid-MHC I-UA to Ctid-MHC I-UF) which were subdivided into 9 lineages (from A to I).Comparison of the Ctid-MHC I among animals and humans showed that the key amino acids of the peptide binding sites are conserved.Analysis of the tertiary structure of the PBD between Grass carp and human crystallographic data of HLA-A2,the variation with insertion or deletion was found in eight regions (A～H).The phylogenetic tree of MHC class I indicates the evolution of MHC class I among grass carp,fish,amphibian,birds,higher vertebrates and humans.     

混凝土板梁的有限条法简化分析

桥梁结构在各种荷载作用下产生的内力和弯矩影响着桥梁的性能.桥梁弯曲、扭转和挠度等过大时会导致结构的破坏,这在结构设计阶段就应加以分析.本文提出一种有限条简化分析方法,可以较好地分析桥梁的挠度、弯曲和扭转变形.通过对一座简支板梁桥模型的分析,与现行有限元方法的分析结果进行了比较.结果表明,本方法能够较好地处理边界条件,只需要很少的输入工作就可以得到正确的分析结果,从而为结构工程师提供了一种用于分析板梁桥在交通荷载作用下行为的有效工具.