高维非自治系统的周期解

本文通过建立并利用齐次线性方程解的估计公式,获得了周期系统（1）的周期解的存在性、唯一性定理,对周期系统（2）给出了一个平稳振荡定理,最后给出了实例。     

EB病毒胸苷激酶基因的扩增

ＥＢ病毒胸苷激酶基因的扩增陈尚武,陈瑞君,黄迪,朱振宇,马涧泉（中山医科大学生化教研室,广州５１００８９）（中山医科大学肿瘤研究所,广州５１００６０）关键词Ｅｐｓｔｅｉｎ－Ｂａｒｒ病毒,胸苷激酶,基因,聚合酶链反应鼻咽癌（ｎａｓｏｐｈａｒｙｎｇｅａｌ...     

人重组GM－CSF／HAS－D3嵌合蛋白（GM－HSA）在大肠杆菌中的表达及其产物稳定性的研究

将人粒细胞－巨噬细胞集落刺激因子（ＧＭ－ＣＳＦ）和人血清白蛋白第三功能区（ＨＡＳ－Ｄ３）的基因串联后,在Ｅ．ｃｏｌｉ中获高效表达,表达量占菌体蛋白的３２．６％．利用ＴＦ－１体外细胞活性测定表明,ＧＭ－ＨＳＡ的活性单位为１．０４×１０~６Ｕ／ｍｇ,虽然其比活性低于ＧＭ－ＣＳＦ,但比后者具有更高的体外热稳定性和储藏稳定性．     

Preferred conformation of peptides rich in Ac8c,a medium-ring alicyclic Cα,α-disubstituted glycine

A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic C^α,α-disubstituted glycine 1-aminocyclooctane-1-carb oxylic acid (Ac₈c), and two Ala/Ac₈c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and ¹H-NMR. The molecular structures of the amino acid derivative Z-Ac₈c-OH, the dipeptide pBrBz- (Ac₈c)₂-OH and the tripeptide pBrBz-(Ac₈c)₃-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac₈c-NHMe. Taken together, the results obtained strongly support the view that the Ac₈c residue is an effective β-turn and helix former. A comparison is also made with the conformational preferences of α-aminoisobutyric acid, the prototype of C^{α, α}-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Ac_nc, with n=3, 5–7) investigated so far. The implications for the use of the Ac₈c residue in peptide conformational design are considered.     

Correction or transfer of immunodeficiency due to TNF-LT alpha deletion by bone marrow transplantation.

BACKGROUND: Mice with inactivated tumor necrosis factor (TNF) and lymphotoxin alpha (LT alpha) genes have profound abnormalities of the immune system including lymphocytosis, lack of lymph nodes, undifferentiated spleen, hypoimmunoglobulinaemia, and defective Ig class switch. Here, we asked whether this phenotype is due to incompetent lymphohemopoietic progenitors or to a defective environment. MATERIALS AND METHODS: Lethally irradiated TNF-LT alpha-deficient and wild-type mice received bone marrow cells from either TNF-LT alpha-deficient or wild-type mice. The reconstitution and transfer of the phenotype was followed by morphological and functional analyses. RESULTS: Bone marrow cells from wild-type mice restored the synthesis of TNF and LT alpha, corrected the splenic microarchitecture, normalized the lymphocyte counts in the circulation, and repopulated the lamina propria with IgA-producing plasma cells of TNF-LT alpha-deficient mice. Furthermore, the formation of germinal centers in the spleen and the defective Ig class switch in response to a T-cell dependent antigen was corrected, while no lymph nodes were formed. Conversely, the TNF-LT alpha phenotype could be transferred to wild-type mice by bone marrow transplantation after lethal irradiation. CONCLUSIONS: These data demonstrate that most TNF- and LT alpha-producing cells are bone marrow derived and radiosensitive, and that the immunodeficiency due to TNF-LT alpha deletion can be corrected to a large extent by normal bone marrow cell transplantation. The genotype of the donor bone marrow cells determines the functional and structural phenotype of the TNF-LT alpha-deficient adult murine host, with the exception of lymph node formation. These findings may have therapeutic implications for the restoration of genetically defined immunodeficiencies in humans.     

Incomplete cerebral ischemia in the rat provokes increase of tissue and plasma malondialdehyde

Short-term incomplete cerebral ischemia was induced in the rat by bilaterally clamping for 5 min the common carotid arteries; subsequent reperfusion of 10 min was obtained by removing carotid occlusion. At the end of ischemia or reperfusion, animals were sacrificed by decapitation. A control group was represented by sham-operated rats. Peripheral venous blood samples were withdrawn from the femoral vein from rats subjected to cerebral reperfusion 5 min before ischemia, at the end of ischemia, and 10 min after reperfusion. A highly sensitive HPLC method for the direct determination of malondialdehyde, oxypurines, and nucleosides was used on 200 μL of brain tissue and plasma extracts. Incomplete cerebral ischemia induced the, appearance of a significant amout of tissue malondialdehyde (undetectable in control animals) and a decrease of ascorbic acid. A further 6.6-fold increase of malondialdehyde and a 18.5% decrease of ascorbic acid occurred after 10 min of reperfusion. Plasma malondialdehyde, which was present in minimal amount before ischemia, significantly increased after 5 min of ischemia, being strikingly augmented after 10 min of reperfusion. A similar trend was observed for oxypurines and nucleosides. From these data, it can be affirmed that tissue concentrations of malondialdehyde and ascorbic acid, and plasma levels of malondialdehyde, oxypurines, and nucleosides, reflect both the oxygen radical-mediated tissue injury and the depression of energy metabolism thus representing early biochemical markers of short-term incomplete brain ischemia, and reperfusion in the rat.     

HSP70 Translocates into a cytoplasmic aggregate during lymphocyte activation

The percentage of T and B lymphocytes expressing a distinct cytoplasmic aggregate enriched in spectrin, ankyrin, and in several other proteins including protein kinase C greatly increases following various activation protocols. Members of the 70 kDa family of heat shock proteins (hsp70) temporarily bind to and stabilize unfolded segments of other proteins, a function apparently required for proper protein folding and assembly. Considering the multiprotein and dynamic nature of the lymphocyte aggregate, the possibility that hsp70 also might be associated with componets of this structure is considered here. Double immunofluorescence analysis indicates that hsp70 is a component of the lymphocyte aggregate and is coincident with spectrin in a subpopulation of freshly isolated, untreated lymphocytes from various murine tissues and in a T-lymphocyte hybridoma. When cell lysates of lymph node T cells are immunoprecipitated using an antibody against hsp70 or spectrin and then analyzed by Western blot utilizing the alternate antibody, it was found that hsp70 and spectrin coprecipitated with one another. Moreover, this coprecipitation could be abolished by addition of ATP. This latter observation was extended to lymphoid cells using a transient permeabilization procedure, and it was shown that addition of exogenous ATP results in the dissipation of the aggregate structure itself. Finally, conditions that result in T-cell activation and aggregate formation, i.e., treatment with the phorbol ester PMA or T-cell receptor cross-linking, also lead to the repositioning of hsp70 into the aggregate from a membrane/cytosolic locale in congruence with spectrin. These data suggest that hsp70 is an active component of the aggregate and that it may function in the interactions believed to occur in this unique activation-associated organelle. © 1995 Wiley-Liss, Inc.     

Analysis of wheat resistance to the cereal aphidSitobion avenae using electrical penetration graphs and flow charts combined with correspondence analysis

The behaviour ofSitobion avenae (F.), was compared on resistant wheat lines ofTriticum monococcum (L.) and a susceptible variety ofTriticum aestivum (L.). Firstly, stylet penetration activities were monitored with the Electrical Penetration Graph (EPG) technique and subsequently analysed using flow charts combined with correspondence analysis. Plant resistance was shown to be associated with repeated penetrations without access to either the xylem or the phloem, and with numerous failures in starting a sustained sap ingestion (as represented by pattern E2). Access to sieve elements of the phloem did not seem to be much affected on resistant plants but it took the aphid three times as long to produce a sap ingestion pattern when maintained on the resistant lineT. monococcum n^o 44 (Tm44) as compared with aphids maintained on susceptible plants. As a result the total time spent in ingesting from sieve elements was reduced by 72% on Tm44. Secondly, direct observations of freely-moving apterous adults were performed. Aphids did not discriminate between resistant and susceptible wheat during the first 30 min of access to test leaves, but only 4 out of 25 aphids were still probing after eight hours on resistant Tm44. The relevance of these results to possible location of the resistance factor(s) are discussed. Although detection of plant resistance before sieve elements are reached can not be rigorously excluded, the factors involved inT. monococcum resistance toS. avenae undoubtedly occur within the phloem vessels.     

Modulated red blood cell survival by membrane protein clustering

Human and murine blood cells treated with ZnCl₂ and bis(sulfosuccinimidyl)suberate (BS³) (a cross linking agent) undergo band 3 clustering and binding of hemoglobin to red blood cell membrane proteins. These clusters induce autologous IgG binding and complement fixation, thus favouring the phagocytosis of ZnCl₂/BS³ treated cells by macrophages. The extension of red blood cell opsonization can be easily modulated by changing the ZnCl₂ concentration in the 0.1–1.0 mM range thus providing an effective way to affect blood cell recognition by macrophages. In fact, murine erythrocytes treated with increasing ZnCl₂ concentrations have proportionally reduced survivals when reinjected into the animal. Furthermore, the organ sequestration of ZnCl₂/BS³ treated cells strongly resembles the typical distribution of the senescent cells. Since the ZnCl₂/BS³ treatment can also be performed on red blood cells loaded with drugs or other substances, this procedure is an effective drug-targeting system to be used for the delivery of molecules to peritoneal, liver and spleen macrophages.