丙烯酰胺暴露对幼鼠胼胝体PLP和MBP表达的影响

目的:检测断乳期幼鼠胼胝体髓鞘蛋白PLP和MBP的表达,探讨丙烯酰胺(acrylamide,ACR)染毒对幼鼠胼胝体部髓鞘发育的影响。方法:断乳期幼鼠随机分为对照组(0 mg/kg)、低(18 mg/kg)和高(36 mg/kg)剂量组,每组12只,从出生后第22~42 d进行灌胃染毒。观测幼鼠步态的变化,用免疫组化方法和免疫荧光双标记法检测幼鼠胼胝体髓鞘蛋白脂蛋白(myelin PLP,PLP)和髓鞘碱性蛋白(myelin basic protein,MBP)的表达。结果:ACR染毒后幼鼠的步态评分均增加,差异有统计学意义(P0.01),免疫组织化学检测结果显示,与对照组相比较,ACR高剂量组幼鼠大脑PLP和MBP表达减少,差异有统计学意义(P0.05)。免疫荧光双标技术检测结果与免疫组织化学检测结果一致,即ACR染毒后胼胝体PLP和MBP均表达减少。结论:ACR染毒可能会通过减少PLP和MBP的表达,抑制胼胝体髓鞘的形成而影响神经系统发育。     

Draft sequencing and comparative genomics of Xylella fastidiosa strains reveal novel biological insights

Draft sequencing is a rapid and efficient method for determining the near-complete sequence of microbial genomes. Here we report a comparative analysis of one complete and two draft genome sequences of the phytopathogenic bacterium, Xylella fastidiosa, which causes serious disease in plants, including citrus, almond, and oleander. We present highlights of an in silico analysis based on a comparison of reconstructions of core biological subsystems. Cellular pathway reconstructions have been used to identify a small number of genes, which are likely to reside within the draft genomes but are not captured in the draft assembly. These represented only a small fraction of all genes and were predominantly large and small ribosomal subunit protein components. By using this approach, some of the inherent limitations of draft sequence can be significantly reduced. Despite the incomplete nature of the draft genomes, it is possible to identify several phage-related genes, which appear to be absent from the draft genomes and not the result of insufficient sequence sampling. This region may therefore identify potential host-specific functions. Based on this first functional reconstruction of a phytopathogenic microbe, we spotlight an unusual respiration machinery as a potential target for biological control. We also predicted and developed a new defined growth medium for Xylella.     

Immunolocalization of 17 and 21.5 kDa MBP isoforms in compact myelin and radial component

Summary Our previous biochemical analyses revealed that the levels of the minor MBP isoforms 21.5 and 17 kDa are elevated relative to the 14 and 18.5 kDa MBP isoforms in the fraction of isolated myelin of murine CNS that is enriched in interlamellar junctions (or radial component). To substantiate the localization of 21.5 and 17 kDa MBP in the myelin sheath, we used immunoelectron microscopy on thin-sections of mouse optic nerve. Two different polyclonal antibodies were used to distinguish 21.5 and 17 kDa MBP from 14 and 18.5 kDa MBP: Ab-MBP^21.5, which was raised against a synthetic peptide corresponding to the exon II amino acid sequence 61–83 of mouse 21.5 kDa MBP (LKQSRSPLPSHARSRPGLCHMYK), and Ab-MBP¹⁴, which is immunoreactive to all four isoforms of mouse MBP. Our SDS-PAGE/immunoblotting demonstrated that Ab-MBP^21.5, unlike Ab-MBP¹⁴, recognized only the 21.5 and 17 kDa MBP isoforms from isolated mouse CNS myelin. Immunolabelling of tissue sections indicated that Ab-MBP¹⁴ bound tenfold more to junction-free compact myelin than to radial component, whereas Ab-MBP^21.5 bound about equally to the two regions of the myelin sheath. In addition, within the junction-free compact myelin, both antibodies bound nearly three fold more to the major dense line than to the intraperiod line.Deceased.     

Chromatin interactions in differentiating keratinocytes reveal novel atopic dermatitis– and psoriasis-associated genes

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The pathobiology of the osteoclast.

This article reviews recent information concerning the origin of osteoclasts and the local and systemic regulation of their activity. It appears that much of the environmental responsiveness of osteoclasts is mediated by cells of the osteoblastic lineage, which exert a major influence on the localisation, induction, stimulation, and inhibition of osteoclastic bone resorption. Some of the mechanisms by which osteoclast function may be disturbed by inflammatory and neoplastic diseases are discussed, and it is suggested that many pathological disturbances of osteoclastic bone resorption may be explicable as mimicry of physiological regulatory mechanisms by local hormones introduced into bone as the local regulators of the diseased tissue.     

The use of behavioral mutants in biological control

Flies of the genusDrosophila fall into three classes with respect to the effect of light on their mating behavior. Class I species mate freely in both light and darkness, while class II species are inhibited in darkness. Class III represents those species with an absolute requirement for light, which will not mate in darkness. The breadth of geographic distribution and the extent of light dependency are correlated; endemic species have the greatest light dependency and cosmopolitan species demonstrate the least dependency. Class II species are intermediate in both respects. These classes of light dependency reflect the degree to which the courtship behavior of the various species is locked in on unique visual stimuli. Species which mate freely in darkness can use sensory modalities other than vision in their courtship. This indicates the relative flexibility of the underlying genetic architecture subserving mating behavior and suggests that widely distributed species possess greater behavioral plasticity than specialized forms. The existence of genetic control elements as well as morphological and neurological mutants provides several modes by which the reproductive activities of species uniquely dependent on visual stimuli can be interrupted. Some insects in orders other than Diptera also rely on visual stimuli for reproductive activities. There are several points in the course of a mating sequence where such stimuli can be used: (1) as a trigger for activity, (2) as a signal to initiate courtship, and (3) as a releaser of a specific motor pattern during courtship itself. The use of mutants affecting behavior is potentially feasible for biological control of insects relying on information received via other sensory systems as well. The basic requirements for the practical use of behavioral mutants are (1) species uniquely dependent on a particular sensory input, (2) a means of generating mutants which interfere with this path of information flow and (3) techniques for delivering and/or maintaining behavioral mutants in populations. Rearing and release of behavioral mutants could be an effective means of reducing fertility of pest populations by rendering translocationhomozygotes sterile in an overall program using the semisterility of translocation heterozygotes to effect population control. Alternately, behavioral mutants could be used at the point in a program where further reduction of population density with multiple heterozygous translocations alone was not practicable.This work was supported in part by GB-8140 (NSF) to W. L. Pak and by a Health Sciences Advancement Award to Purdue University.     

The possible biological and reproductive functions of ubiquitin

The protein ubiquitin (Ub) appears to be present in all eukaryotic cells. Its widespread presence and extremely conserved structure indicate that it may play a vital role in cell metabolism. The roles of Ub are mediated by its covalent attachment to target proteins, a process known as ubiquitylation, a form of protein modification which may lead to degradation of the modified protein. A number of proteins with similar structure to Ub but varying in function have been isolated. Recently, there has been much interest in the role of Ub and its related proteins in reproductive processes. Ub and Ub-related proteins may be involved in gametogenesis, modulation of steroid receptor concentrations, placental development and endometrial modification at the beginning of pregnancy. These wide-ranging effects have led to extensive research which will be reviewed in this article.     

The biological effect and medical functions of the Infrared Rays

Do you know whether the infrared rays have the biological effect?Could youbelieve in medical effort of the infrared rays to the living things including humanbeings and animals?The replies to the quetionsare determinate.Asa matterof fact,at present,a variety of infrared medical-instruments and health-protection-equipments and materials containing infrared lamps,underwear,trousers and beltsand alotof thermal-radiatorshaveextensively been sold in stores and used forcuringsickness and protecting h…     

Schwann cell invasion of the central nervous system of the myelin mutants

Schwann cells are excluded from the CNS during development by the glial limiting membrane, an area of astrocytic specialisation present at the nerve root transitional zone, and at blood vessels in the neuropil. This barrier, however, can be disrupted and, with the highly migratory nature of Schwann cells, can result in their invasion and myelination of the CNS in many pathological situations. In this paper we demonstrate that this occurs in a number of myelin mutants, including the myelin deficient ( md ) and taiep rats and the canine shaking ( sh ) pup. While it is still relatively uncommon in the rodent mutants, the sh pup shows extensive Schwann cell invasion along the neuraxis. This invasion involves the spinal cord, brain stem, and cerebellum and increases in amount and distribution with age. In situ hybridisation studies using a P₀ riboprobe suggest that the likely origin of these cells in the sh pup is the nerve roots, primarily the dorsal roots. Paradoxically, Schwann cell myelination of the CNS increases with time in the sh pup despite a marked, progressive gliosis involving the glia limitans and neuropil. Thus the mechanism by which these cells migrate into the CNS through the gliosed nerve root transitional zone or from vasa nervorum remains unknown. Extensive Schwann cell CNS myelination may have therapeutic significance in human myelin disease.     

Functional analyses of two newly identified PITX2 mutants reveal a novel molecular mechanism for Axenfeld-Rieger syndrome

The specific role of PITX2 in the pathogenesis of anterior segment dysgenesis has yet to be clearly defined. We provide here new insight into PITX2 pathogenesis through mutational and functional analyses. Three PITX2 mutations were found in a screen of 38 unrelated individuals affected with anterior segment anomalies (8%). All three mutations were found among the 21 individuals affected with Axenfeld-Rieger syndrome (ARS). We have identified two novel mutations, a valine-->leucine (V45L) missense mutation at position 45 within the PITX2 homeodomain, and a seven amino acid duplication (7aaDup) of residues 6-12 of the homeodomain. DNA-binding studies of the two mutant PITX2 proteins demonstrated a <10-fold reduction in the DNA-binding activity of the V45L mutant, and a >100-fold reduction in activity of the 7aaDup mutant. Luciferase reporter assays showed a >200% increase in PITX2 transactivation activity of the V45L mutant, while the 7aaDup mutant was unable to transactivate at detectable levels. Our analyses of the V45L PITX2 mutant reveal that the DNA-binding domain of PITX2 can influence transactivation activity independently of DNA binding. Furthermore, our findings expand the hypothesis that the amount of residual PITX2 activity underlies the variable severity of ocular phenotypes that result from PITX2 mutation. For the first time, we present evidence that increased PITX2 activity may underlie the severe ARS ocular phenotype. We conclude that increased activity of one PITX2 allele may be as physiologically disruptive as a mutation that nullifies a PITX2 allele, with either condition resulting in ARS.     

The pathobiology of the septin gene family

Septins are an evolutionarily conserved group of GTP-binding and filament-forming proteins that belong to the large superclass of P-loop GTPases. While originally discovered in yeast as cell division cycle mutants with cytokinesis defects, they are now known to have diverse cellular roles which include polarity determination, cytoskeletal reorganization, membrane dynamics, vesicle trafficking, and exocytosis. Septin proteins form homo- and hetero-oligomeric polymers which can assemble into higher-order filaments. They are also known to interact with components of the cytoskeleton, ie actin and tubulin. The precise role of GTP binding is not clear but a current model suggests that it is associated with conformational changes which alter binding to other proteins. There are at least 12 human septin genes, and although information on expression patterns is limited, most undergo complex alternative splicing with some degree of tissue specificity. Nevertheless, an increasing body of data implicates the septin family in the pathogenesis of diverse disease states including neoplasia, neurodegenerative conditions, and infections. Here the known biochemical properties of mammalian septins are reviewed in the light of the data from yeast and other model organisms. The data implicating septins in human disease are considered and a model linking these data is proposed. It is posited that septins can act as regulatable scaffolds where the stoichiometry of septin associations, modifications, GTP status, and the interactions with other proteins allow the regulation of key cellular processes including polarity determination. Derangements of such septin scaffolds thus explain the role of septins in disease states.     

The HLA-DP2 protein binds the immunodominant epitope from myelin basic protein, MBP85-99, with high affinity

Myelin basic protein (MBP) is a candidate autoantigen in multiple sclerosis (MS). The immunodominant epitope for T-cell responses is assigned to the amino acid sequence MBP84-102, which binds to human leukocyte antigen (HLA)-DR2a (DRB5*0101) and HLA-DR2b (DRB1*1501) of the HLA-DR2 haplotype carrying the strongest genetic association with MS. In contrast with HLA-DR and -DQ molecules, HLA-DP molecules are poorly characterized with respect to the binding of self-peptides. We show here that HLA-DP2 binds MBP85-99 with high affinity, and that the amino acid residues in position MBP91, MBP92 and MBP93 are influencing the binding, as shown by alanine scans. We further used a series of truncated peptides to identify the core of the binding. Moving the frame along the peptide from residues 87-97 to 89-99 progressively decreased the binding affinity for HLA-DP2, while moving further towards the C-terminal completely abrogated the binding of peptides to HLA-DP2. The data suggest that the docking of the MBP85-99 peptide into the HLA-DP2 groove is dependent on MBP88V and MBP89V and may use either of them as primary anchor for the p1 position. HLA-DP2 might thus present the MBP85-99 peptide in the same register as the HLA-DRB1*1501, where the MBP89V is preferred as the p1 anchor. Notably, full-length MBP was able to compete for peptide binding with an affinity similar to that seen for the high-affinity binding peptides, DRα170-83 and IIP53-65. In summary, the HLA-DP2 molecule binds the immunodominant epitope in MS, MBP85-99, possibly in more than one register.     

TMS can reveal contrasting functions of the dorsal and ventral visual processing streams

In order to investigate the functional specificity of the dorsal and ventral visual processing steams we used transcranial magnetic stimulation (TMS) to briefly disrupt one or the other while subjects performed three tasks, involving discrimination of colour or shape or relative position. TMS was delivered over right posterior parietal cortex (PPC) or right lateral occipital (LO) cortex, regions known to have visuo-spatial and object processing properties respectively. LO but not PPC stimulation had a significant effect on reaction time when subjects were asked to make a discrimination of relative shape. PPC stimulation had a significant effect when subjects were asked to discriminate relative position of the same shapes. Stimulation of LO also lengthened reaction times on the position task. There were no effects of stimulation at either site on colour discrimination. Results are discussed within the framework of how the dorsal stream and ventral stream are dissociated following their damage in neurological patients and possible ways in which they may interact in the normal brain.     

Intracerebral injection of myelin basic protein (MBP) induces inflammation in brain and causes paraplegia in MBP-sensitized B6 mice

Brain inflammation and paraplegia can be induced by an additional intraperitoneal (i.p.) and intracerebral (i.c.) restimulation in B6 mice after standard immunization with MBP in Freund's complete adjuvant (FCA) and Bordetella pertussis coadjuvant. Only the combination of i.p. MBP/FCA and i.c. MBP injection could induce clinical paraplegia; either one alone was not effective. Clinical symptoms would develop 2 days after the i.c. injection. The induction of paraplegia was MBP-specific, as irrelevant bovine serum albumin with the same protocol could not induce it. The i.p. restimulation was requisite and needed the MBP in FCA, as MBP in PBS was ineffective. Histopathological observation manifested cellular infiltration by leucocytes in perivascular spaces and cerebral cortex. Neutrophils were prominent at 12 h after i.c. injection, then were replaced by mononuclear cells 24 h later. There were dynamic changes in cell number and immunophenotype of VLA-4⁺ expression in cervical lymph node cells after i.c. injection. The cells derived from cervical lymph nodes had higher MBP-stimulated proliferation than that of distal lymph nodes. This additional i.p. and i.c. stimulation provides a new manipulation to study brain inflammation.