Main Immunogenic Region of Torpedo Electroplax and Human Muscle Acetylcholine Receptor: Localization and Microheterogeneity Revealed by the Use of Synthetic Peptides

Most anti-nicotinic acetylcholine receptor (AChR) antibodies in myasthenia gravis are directed against an immunodominant epitope or epitopes [main immunogenic region (MIR)] on the AChR alpha-subunit. Thirty-two synthetic peptides, corresponding to the complete Torpedo alpha-subunit sequence and to a segment of human muscle alpha-subunit, were used to map the epitopes for 11 monoclonal antibodies (mAbs) directed against the Torpedo and/or the human MIR and for a panel of anti-AChR mAbs directed against epitopes on the alpha-subunit other than the MIR. A main constituent loop of the MIR was localized within residues alpha 67-76. Residues 70 and 75, which are different in the Torpedo and human alpha-subunits, seem to be crucial in determining the binding profile for several mAbs whose binding to the peptides correlated very well with their binding pattern to native Torpedo and human AChRs. This strongly supports the identification of the peptide loop alpha 67-76 as the actual location of the MIR on the intact AChR molecule. Residues 75 and 76 were necessary for binding of some mAbs and irrelevant for others, in agreement with earlier suggestions that the MIR comprises overlapping epitopes. Structural predictions for the sequence segment alpha 67-76 indicate that this segment has a relatively high segmental mobility and a very strong turning potential centered around residues 68-71. The most stable structure predicted for this segment, in both the Torpedo and human alpha-subunits, is a hairpin loop, whose apex is a type I beta-turn and whose arms are beta-strands. This loop is highly hydrophilic, and its apex is negatively charged. All these structural properties have been proposed as characteristic of antibody binding sites. We also localized the epitopes for mAbs against non-MIR regions. Among these, the epitope for a monoclonal antibody (mAb 13) that noncompetitively inhibits channel function was localized within residues alpha 331-351.     

Characterization of the dermatan sulfate proteoglycans, DS-PGI and DS-PGII, from bovine articular cartilage and skin isolated by octyl-sepharose chromatography

Two forms of dermatan sulfate proteoglycans, called DS-PGI and DS-PGII, have been isolated from both bovine fetal skin and calf articular cartilage and characterized. The proteoglycans were isolated using either (a) molecular sieve chromatography under conditions where DS-PGI selectively self-associates or (b) chromatography on octyl-Sepharose, which separates DS-PGI from DS-PGII based on differences in the hydrophobic properties of their core proteins. The NH2-terminal amino acid sequence of DS-PGI from skin and cartilage is identical. The NH2-terminal amino acid sequence of DS-PGII from skin and cartilage is identical. However, the amino acid sequence data and tryptic peptide maps demonstrate that the core proteins of DS-PGI and DS-PGII differ in primary structure. In DS-PGI from bovine fetal skin, 81-84% of the glycosaminoglycan was composed of IdoA-GalNAc(SO4) disaccharide repeating units. In DS-PGI from calf articular cartilage, only 25-29% of the glycosaminoglycan was composed of IdoA-GalNAc(SO4). In DS-PGII from bovine fetal skin, 85-93% of the glycosaminoglycan was IdoA-GalNAc(SO4), whereas in DS-PGII from calf articular cartilage, only 40-44% of the glycosaminoglycan was IdoA-GalNAc(SO4). Thus, analogous proteoglycans from two different tissues, such as DS-PGI from skin and cartilage, possess a core protein with the same primary structure, yet contain glycosaminoglycan chains which differ greatly in iduronic acid content. These differences in the composition of the glycosaminoglycan chains must be determined by tissue-specific mechanisms which regulate the degree of epimerization of GlcA-GalNAc(SO4) into IdoA-GalNAc(SO4) and not by the primary structure of the core protein.     

Spontaneous inflammatory disease in transgenic rats expressing HLA-B27 and human beta 2m: an animal model of HLA-B27-associated human disorders

Humans who have inherited the human class I major histocompatibility allele HLA-B27 have a markedly increased risk of developing the multi-organ system diseases termed spondyloarthropathies. To investigate the role of B27 in these disorders, we introduced the B27 and human beta 2-microglobulin genes into rats, a species known to be quite susceptible to experimentally induced inflammatory disease. Rats from one transgenic line spontaneously developed inflammatory disease involving the gastrointestinal tract, peripheral and vertebral joints, male genital tract, skin, nails, and heart. This pattern of organ system involvement showed a striking resemblance to the B27-associated human disorders. These results establish that B27 plays a central role in the pathogenesis of the multi-organ system processes of the spondyloarthropathies. Elucidation of the role of B27 should be facilitated by this transgenic model.     

Factors influencing erythrocyte choline concentrations

Choline concentrations in human erythrocytes increase after freezing and thawing, during incubation in Krebs-phosphate for 30 min or on storage at 0 degrees C for 3-24 hr. The increase is prevented by protein precipitation by 10% perchloric acid, 10% zinc hydroxide, 10% sodium tungstate or boiling in water. It is not prevented by EDTA (10 mM) and is increased by oleate (5 mM). We suggest that the increase is due to the action of phospholipase D on erythrocyte phospholipids.     

试论云阳县人口激增与土地锐减的矛盾及对策

土地是人们赖以生存的物质基础,是其它任何东西不可代替的生产资料。离开了土地,人就不能生存下去,这是众所周知的真理。但是,目前人口的激增与土地锐减的矛盾越来越尖锐。据有关统计资料表明,1978—1988年全国耕地面积减少3.66×10~6ha,与此同时全国人口又猛增1.33亿,给农业粮食生产、     

多聚酶链反应技术鉴别肾综合征出血热病毒血清型的初步研究

肾综合征出血热(HFRS)为一组抗原性密切相关的布尼亚科汉坦病毒引起的急性传染病。在我国存在至少两种临床表现、动物宿主及流行特征截然不同的血清型别,即血清Ⅰ型(汉坦型)和血清Ⅱ型(汉城型)。这两型病毒间的血清学定型已有报道。近年来,除啮齿类动物外,从临床病人以及非啮齿类动物体内也分离到了HFRS病毒。同时出现两类型别毒株共存,以及从家鼠体内分离到野鼠型毒株或从野鼠体内分离到家鼠型毒株的复杂情形。为此,准确检定并鉴别不同来源毒株型别,将为深入了解其病原学、流行病学以及制定疫苗生产策略提供重要信息。     

PHA激活的脐血T细胞条件培养液对人骨髓CFU-c的抑制

本文研究了PHA刺激18小时收获的脐血T细胞条件培养液(PHA-TCM)对正常人骨髓CFU-c的影响。结果显示PHA-TCM能够显著抑制CFU-c的生长,这种抑制与PHA-TCM浓度有关。并发现经PHA-TCM作用后M型集落比例明显降低。PHA-TCM中未检出IFN和IL-2活性。进一步研究证实,PHA-TCM中CFU-c抑制活性是一种对酸碱敏感对热相对不敏感的蛋白质,其分子量大于10,000道尔顿。     

Inflammatory infiltration of the trigeminal ganglion after herpes simplex virus type 1 corneal infection.

Following herpes simplex virus type 1 (HSV-1) infection of the cornea, the virus is transmitted to the trigeminal ganglion, where a brief period of virus replication is followed by establishment of a latent infection in neurons. A possible role of the immune system in regulating virus replication and maintaining latency in the sensory neurons has been suggested. We have investigated the phenotype and cytokine pattern of cells that infiltrate the A/J mouse trigeminal ganglion at various times after HSV-1 corneal infection. HSV antigen expression in the trigeminal ganglion (indicative of the viral lytic cycle) increased until day 3 postinfection (p.i.) and then diminished to undetectable levels by day 7 p.i. The period of declining HSV antigen expression. was associated with a marked increase in Mac-1+ cells. These cells did not appear to coexpress the F4/80+ (macrophage) or the CD8+ (T cell) markers, and none showed polymorphonuclear leukocyte morphology, suggesting a possible early infiltration of natural killer cells. There was also a significant increase in the trigeminal ganglion of cells expressing the gamma delta T-cell receptor, and these cells were found almost exclusively in very close association with neurons. This period was also characterized by a rapid and equivalent increase in cells expressing gamma interferon and interleukin-4. The density of the inflammatory infiltrate in the trigeminal ganglion increased until days 12 to 21 p.i., when it was predominated by CD8+, Mac-1+, and tumor necrosis factor-expressing cells, which surrounded many neurons. By day 92 p.i., the inflammatory infiltrate diminished but was heaviest in mice with active periocular skin disease. Our data are consistent with the notion that gamma interferon produced by natural killer cells and/or gamma delta T cells may play an important role in limiting HSV-1 replication in the trigeminal ganglion during the acute stage of infection. In addition, tumor necrosis factor produced by CD8+ T cells and macrophages may function to maintain the virus in a latent state.     

Torque generation in the flagellar motor of Escherichia coli: evidence of a direct role for FliG but not for FliM or FliN.

Among the many proteins needed for assembly and function of bacterial flagella, FliG, FliM, and FliN have attracted special attention because mutant phenotypes suggest that they are needed not only for flagellar assembly but also for torque generation and for controlling the direction of motor rotation. A role for these proteins in torque generation is suggested by the existence of mutations in each of them that produce the Mot- (or paralyzed) phenotype, in which flagella are assembled and appear normal but do not rotate. The presumption is that Mot- defects cause paralysis by specifically disrupting functions essential for torque generation, while preserving the features of a protein needed for flagellar assembly. Here, we present evidence that the reported mot mutations in fliM and fliN do not disrupt torque-generating functions specifically but, instead, affect the incorporation of proteins into the flagellum. The fliM and fliN mutants are immotile at normal expression levels but become motile when the mutant proteins and/or other, evidently interacting flagellar proteins are overexpressed. In contrast, many of the reported fliG mot mutations abolish motility at all expression levels, while permitting flagellar assembly, and thus appear to disrupt torque generation specifically. These mutations are clustered in a segment of about 100 residues at the carboxyl terminus of FliG. A slightly larger carboxyl-terminal segment of 126 residues accumulates in the cells when expressed alone and thus probably constitutes a stable, independently folded domain. We suggest that the carboxyl-terminal domain of FliG functions specifically in torque generation, forming the rotor portion of the site of energy transduction in the flagellar motor.