兔出血症病毒核酸的某些理化性质的研究

本文对我国无锡分离的兔出血症病毒A_2R-3毒株核酸的某些理化性质进行了研究。采用孚尔根染色、二苯胺反应和核酸酶解实验证实病毒核酸为DNA类型。吖啶橙染色、甲醛反应、核酸酶S_1消化和核酸热变性实验表明病毒核酸为单链型。核酸电泳呈单一组分。电境观察显示核酸分子链呈线状,平均长度约为2.15μ。计算分子量约为2.1—2.5×10~6d。核酸碱基组盛为A25.34、T29.37、G23.85、C21.43、(G C)克分子百分比值为45.28。结合以前的报道、我们认为:兔出血症病毒可以归类于细小病毒科。     

Xanthine oxidase/hydrogen peroxide generates sulfur trioxide anion radical (SO3.-) from sulfite (SO3(2-)).

In the presence of hydrogen peroxide (H2O2), xanthine oxidase has been found to catalyze sulfur trioxide anion radical (SO3.-) formation from sulfite anion (SO3(2-)). The SO3.- radical was identified by ESR (electron spin resonance) spin trapping, utilizing 5,5-dimethyl-l-pyrroline-l-oxide (DMPO) as the spin trap. Inactivated xanthine oxidase does not catalyze SO3.- radical formation, implying a specific role for this enzyme. The initial rate of SO3.- radical formation increases linearly with xanthine oxidase concentration. Together, these observations indicate that the SO3.- generation occurs enzymatically. These results suggest a new property of xanthine oxidase and perhaps also a significant step in the mechanism of sulfite toxicity in cellular systems.     

Lithium Effects on Inositol Phospholipids and Inositol Phosphates: Evaluation of an In Vivo Model for Assessing Polyphosphoinositide Turnover in Brain

Administration of lithium chloride to rats injected intracerebrally with [3H]inositol led to time- and dose-dependent increases in levels of labeled inositol monophosphates in brain. Quantitative analysis of the inositol phosphates by ion chromatography revealed 37- and 20-fold increases in the mass of myo-inositol 1-phosphate and 4-phosphate, respectively, at 4 h intraperitoneal after injections of 6 mEq/kg of lithium chloride. Albeit to a much lesser extent, lithium administration also resulted in an increase in the level of myo-inositol, 1,4-bisphosphate in brain. The lithium-induced increase in content of labeled inositol monophosphates was marked by a concomitant decrease in content of labeled inositol, and after injections of high doses of lithium, e.g., 10 mEq/kg, this was followed by a general decrease in labeling of the inositol phospholipids. In general, animals injected with [3H]inositol but not lithium did not reveal obvious differences in labeling of inositol monophosphates on stimulation by mecamylamine or pilocarpine. However, when animals were injected with [3H]inositol and then lithium, there were large increases in the levels of labeled inositol monophosphates on administration of these compounds. Administration of atropine to the lithium-treated mice led to a partial reduction in the amount of labeled inositol monophosphates accumulated due to the administration of lithium alone. Furthermore, atropine was able to block the pilocarpine-induced increase in level of labeled inositol monophosphates. These results demonstrate the suitable use of the radiotracer technique together with lithium administration for assessing the effects of drugs and receptor agonists on the signaling system involving polyphosphoinositide turnover in brain.     

Site-specific glycation of lens crystallins by ascorbic acid.

The oxidation of ascorbic acid leads to the formation of several compounds which are capable of reacting with protein amino groups via a Maillard reaction. Radioactivity from [1-14C]ascorbic acid was linearly incorporated into lens crystallins over a 10 day period in the presence of NaCNBH3. This rate of incorporation was 6-7-fold more rapid than that obtained with [14C]glucose under the same conditions. SDS-PAGE showed a linear incorporation into all the crystallin subunits. [1-14C]Ascorbic acid-label led alpha-crystallin was separated into its component A and B subunits, and each was digested with chymotrypsin. HPLC peptide analysis showed a differential labelling of the various lysine residues. Analysis of the peptides by mass spectrometry allowed the identification of the sites and the extent of modification. These values ranged from 6% for Lys-78 to 36% for Lys-11 in the A subunit and from 5% for Lys-82 to an average of 38% for the peptide containing Lys-166, Lys-174 and Lys-175 in the B subunit. Amino acid analysis demonstrated a single modification reaction producing N epsilon-(carboxymethyl)lysine. This agreed with the mass increase of 58 observed for each modified peptide.     

Synthetic peptides representing sequence 39 to 59 of rat V beta 8 TCR fail to elicit regulatory T cells reactive with V beta 8 TCR on rat encephalitogenic T cells.

Subpathogenic doses of syngeneic autoreactive T cells protect experimental animals against associated autoimmune disease. Preferential use of the TCR of encephalitogenic T cells suggests that this molecule serves as the target for immunoregulation in experimental autoimmune encephalomyelitis (EAE). Whether peptides derived from the V beta 8 of the rat TCR elicit regulatory T cells and produce the same vaccinating effect against EAE as do whole T cells remains unknown. Here we show that immunization of Lewis rats with V beta 8(39-59), a peptide representing residues 39 to 59 of the rat V beta 8 TCR, does not induce the production of regulatory T cells reactive to the intact TCR V beta 8 containing this sequence. Moreover, animals that had recovered from both actively induced EAE and transferred EAE did not generate regulatory T cells that recognized the V beta 8(39-59) peptide. Further, transfusion of large doses of peptide-specific T cells did not protect the animals from EAE. Our results suggest that the V beta 8(39-59) peptide may comprise so-called cryptic epitopes, which function as immunogens only when dissociated from large protein complexes.     

Clinical significance of adrenal computed tomography in Addison's disease.

Adrenal computed tomographic (CT) scanning was conducted in twelve patients with Addison's disease during the clinical course. In tuberculous Addison's disease (n = 8), three of four patients examined during the first two years after disease onset had bilaterally enlarged adrenals, while one of four had a unilaterally enlarged one. At least one adrenal gland was enlarged after onset in all six patients examined during the first four years. Thereafter, the adrenal glands may atrophy bilaterally, in contrast to adrenal glands in idiopathic Addison's disease, which atrophy bilaterally from disease onset (n = 2). Adrenal calcification was a less sensitive clue in tracing pathogenesis, i.e., adrenal calcification was observed in five of eight patients with tuberculous Addison's disease, but not in idiopathic patients. Thus, adrenal CT scanning could show the etiology of Addison's disease (infection or autoimmunity) and the phase of Addison's disease secondary to tuberculosis, which may be clinically important for initiating antituberculous treatment.     

Characterization of a keratinocyte-specific extracellular epitope of desmoglein. Implications for desmoglein heterogeneity and function.

Despite the presumed importance of desmoglein, a 160-kDa glycoprotein, in desmosome formation and its possible involvement in certain blistering skin diseases, the precise location and function of this protein have not yet been firmly established. We describe here the characterization of a new monoclonal antibody, AE23, against an extracellular epitope of desmoglein. Both the AE23 epitope and another epitope, defined by the previously characterized DG3.4 antibody, reside on a 160-kDa human epidermal desmoglein as evidenced by their identical solubility profile, their coexistence in a 130-kDa desmoglein degradative product, their coadsorption by an AE23 immunoaffinity column, and the identical changes in the two antigens' electrophoretic mobility after air oxidation and deglycosylation. The AE23 epitope is resistant to various endoglycosidases, suggesting that sugar moieties are not involved. Characterization of several proteolytic fragments of this epidermal desmoglein enabled us to map the DG3.4 epitope to a 96-kDa intracellular domain and the AE23 epitope to an extracellular domain flanked by the plasma membrane and the distal N-glycosylation site(s). However, these two epitopes do not always coexist on the same desmoglein molecule. For example, tissue surveys showed that although the DG3.4 epitope is present in the desmogleins of all epithelial cell types, the AE23 epitope is limited to normal keratinocytes. Moreover, electron microscopic localization data indicate that whereas the DG3.4 epitope is detected in the submembranous plaques of desmosomes, the AE23 epitope is present in the intercellular space of both desmosomal and nondesmosomal areas. These results raise the possibility that there exist several biochemically closely related isoforms of desmoglein, one (AE23+/DG3.4+) restricted to epidermal desmosomes, one (AE23+/DG3.4-) uniformly distributed along the keratinocyte cell surface, and another (AE23-/DG3.4+) present in desmosomes of simple epithelia and basal cells of cultured keratinocytes. The uniform distribution of at least one desmoglein-related antigen in the intercellular space of keratinocytes coupled with the realization that different isoforms of desmogleins form a subfamily of cadherins suggest that desmoglein(s) may play a more general role in keratinocyte adhesion than previously appreciated.     

A monoclonal anti-idiotype specific for human polyclonal IgM rheumatoid factor.

One of the hallmarks of rheumatoid arthritis (RA) is the production of high titers of rheumatoid factor (RF) antibody directed against the Fc portion of IgG. Anti-Id that recognize the majority of monoclonal RF from patients with B cell dyscrasias are reactive with only 1 to 2% of these polyclonal RF from RA patients. We describe a new monoclonal anti-Id, 4C9, that recognizes a L chain determinant on polyclonal IgM RF from patients with RA but does not recognize a panel of monoclonal RF from patients with B cell malignancies. 4C9 reactivity is found in the serum of 34/43 RF-positive RA patients and in 12/12 RF-positive synovial fluids, but in only 1/14 RF-negative sera from RA patients and 1/22 sera containing monoclonal IgM RF. 4C9 reactivity is highly enriched in purified IgM RF from nine RA patients and represents a variable percentage of total IgM RF up to a maximum of 23%. Furthermore, 4C9 reactivity is enriched in the synovial fluid of three of five RA patients compared with serum, suggesting that 4C9-reactive IgM RF are synthesized within the joint. IgG RF from RA synovial fluids are not 4C9 reactive, indicating either that different genes are used to encode IgM and IgG RF in RA patients, or that IgG RF have somatically mutated away from idiotypic reactivity.