Role of sialyloligosaccharide binding in Theiler's virus persistence.

Theiler's murine encephalomyelitis viruses (TMEVs) belong to the Picornaviridae family and are divided into two groups, typified by strain GDVII virus and members of the TO (Theiler's original) group. The highly virulent GDVII group causes acute encephalitis in mice, while the TO group is less virulent and causes a chronic demyelinating disease which is associated with viral persistence in mice. This persistent central nervous system infection with demyelination resembles multiple sclerosis (MS) in humans and has thus become an important model for studying MS. It has been shown that some of the determinants associated with viral persistence are located on the capsid proteins of the TO group. Structural comparisons of two persistent strains (BeAn and DA) and a highly virulent strain (GDVII) showed that the most significant structural variations between these two groups of viruses are located on the sites that may influence virus binding to cellular receptors. Most animal viruses attach to specific cellular receptors that, in part, determine host range and tissue tropism. In this study, atomic models of TMEV chimeras were built with the known structures of GDVII, BeAn, and DA viruses. Comparisons among the known GDVII, BeAn, and DA structures as well as the predicted models for the TMEV chimeras suggested that a gap on the capsid surface next to the putative receptor binding site, composed of residues from VP1 and VP2, may be important in determining viral persistence by influencing virus attachment to cellular receptors, such as sialyloligosaccharides. Our results showed that sialyllactose, the first three sugar molecules of common oligosaccharides on the surface of mammalian cells, inhibits virus binding to the host cell and infection with the persistent BeAn virus but not the nonpersistent GDVII and chimera 39 viruses.     

Recombinant adeno-associated virus mediates a high level of gene transfer but less efficient integration in the K562 human hematopoietic cell line.

We tested the ability of a recombinant adeno-associated virus (rAAV) vector to express and integrate exogenous DNA into human hematopoietic cells in the absence of selection. We developed an rAAV vector, AAV-tNGFR, carrying a truncated rat nerve growth factor receptor (tNGFR) cDNA as a cell surface reporter under the control of the Moloney murine leukemia virus (MoMuLV) long terminal repeat. An analogous MoMuLV-based retroviral vector (L-tNGFR) was used in parallel, and gene transfer and expression in human hematopoietic cells were assessed by flow cytometry and DNA analyses. Following gene transfer into K562 cells with AAV-tNGFR at a multiplicity of infection (MOI) of 13 infectious units (IU), 26 to 38% of cells expressed tNGFR on the surface early after transduction, but the proportion of tNGFR expressing cells steadily declined to 3.0 to 3.5% over 1 month of culture. At an MOI of 130 IU, nearly all cells expressed tNGFR immediately posttransduction, but the proportion of cells expressing tNGFR declined to 62% over 2 months of culture. The decline in the proportion of AAV-tNGFR-expressing cells was associated with ongoing losses of vector genomes. In contrast, K562 cells transduced with the retroviral vector L-tNGFR expressed tNGFR in a constant fraction. Integration analyses on clones showed that integration occurred at different sites. Integration frequencies were estimated at about 49% at an MOI of 130 and 2% at an MOI of 1.3. Transduction of primary human CD34+ progenitor cells by AAV-tNGFR was less efficient than with K562 cells and showed a declining percentage of cells expressing tNGFR over 2 weeks of culture. Thus, purified rAAV caused very high gene transfer and expression in human hematopoietic cells early after transduction, which steadily declined during cell passage in the absence of selection. Although the efficiency of integration was low, overall integration was markedly improved at a high MOI. While prolonged episomal persistence may be adequate for gene therapy of nondividing cells, a very high MOI or improvements in basic aspects of AAV-based vectors may be necessary to improve integration frequency in the rapidly dividing hematopoietic cell population.     

Preadipocyte Recruitment in Stromal Vascular Cultures After Depletion of Committed Preadipocytes by Immunocytotoxicity

Glucocorticoids or the glucocorticoid analog dexamethasone (DEX) enhances the differentiation of preadipocytes in the presence of insulin and influences preadipocyte proliferation. The purpose of the present study was to determine if DEX can induce the recruitment of preadipocytes. Using monoclonal antibodies for complement-mediated cytotoxicity, preadipocytes were removed from porcine stromal vascular (S-V) cell cultures. Our experiments demonstrated for the first time that after removal of preadipocytes by cytotoxicity, preadipocytes or fat cells could be induced by DEX or DEX plus insulin but not by insulin alone. However, many more fat cells were induced (258 ± 15/unit area) when DEX was added with fetal bovine serum (FBS) followed with insulin treatment, compared to DEX with insulin (21.3 ± 5.1/ unit area) after removal of preadipocytes. Immunocyto-chemistry with AD-3, a preadipocyte marker, showed that DEX with FBS for 3 days after seeding (i.e., the proliferation phase) produced many more preadipocytes (AD-3 positive, 223 ± 45/unit area) than FBS alone (10.5 ± 1.4/unit area). Bromodeoxyuridine (BrdU) incorporation assays demonstrated that the efficiency of DEX with FBS (i.e., during proliferation) was mitosis dependent. Accordingly, we conclude that: porcine S-V cultures contain preadipocytes at different stages of differentiation and that DEX induced early preadipocyte differentiation depends on mitosis.     

Nonuniform spatial patterns of respiratory activity within biofilms during disinfection.

Fluorescent stains in conjunction with cryoembedding and image analysis were applied to demonstrate spatial gradients in respiratory activity within bacterial biofilms during disinfection with monochloramine. Biofilms of Klebsiella pneumoniae and Pseudomonas aeruginosa grown together on stainless steel surfaces in continuous-flow annular reactors were treated with 2 mg of monochloramine per liter (influent concentration) for 2 h. Relatively little biofilm removal occurred as evidenced by total cell direct counts. Plate counts (of both species summed) indicated an average 1.3-log decrease after exposure to 2 mg of monochloramine per liter. The fluorogenic redox indicator 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and the DNA stain 4',6-diamidino-2-phenylindole (DAPI) were used to differentiate respiring and nonrespiring cells in biofilms. Epifluorescence micrographs of frozen biofilm cross sections clearly revealed gradients of respiratory activity within biofilms in response to monochloramine treatment. These gradients in specific respiratory activity were quantified by calculating the ratio of CTC and DAPI intensities measured by image analysis. Cells near the biofilm-bulk fluid interface lost respiratory activity first. After 2 h of biocide treatment, greater respiratory activity persisted deep in the biofilm than near the biofilm-bulk fluid interface.     

Optimal Staining and Sample Storage Time for Direct Microscopic Enumeration of Total and Active Bacteria in Soil with Two Fluorescent Dyes

Direct counting techniques, first developed for aquatic samples, can be used to enumerate bacteria in soil and groundwater sediments. Two fluorescent dyes, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) for actively respiring bacteria and 4(prm1),6-diamidino-2-phenylindole (DAPI) for total bacteria, were tested for their usefulness in epifluorescent direct bacterial enumeration in soil. Both dyes can be used for the same soil sample without affecting enumeration results. Staining for 8 h with CTC and for 40 min with DAPI resulted in maximum numbers of stained cells. The optimal DAPI staining concentration is 10 mg liter(sup-1). After preparation, slides should be stored at 4(deg)C and counted within 2 days for CTC and within 24 h for DAPI. Sodium PP(infi) or sodium chloride solutions were used to desorb bacteria from soil prior to counting. Counts were significantly higher when sodium chloride was used.     

标志技术在研究小皱蝽成虫种群特征中的应用

应用标志－释放－回收技术研究小皱蝽成虫的主要种群特征,结果如下：（１）成虫扩散的偏离度Ｋｕ＝２．４,为一阶峻开曲线;（２）分别用Ｐｅｔｅｒｓｏｎ和Ｊａｃｋｓｏｎ方法对种群蜜度进行了估计,结果表明,Ｊａｃｋｓｏｎ的方法较好;（３）雄虫平均寿命４０－４５,虫平均寿命１２０－１３０。天。     

Three Antigenic Regions in p17 of Human Immunodeficiency Virus Type 1 (HIV-1) Revealed by Mouse Monoclonal Antibodies and Human Antibodies in HIV-1 Carrier Sera

We investigated the murine antibody response to recombinant p17 (rp17) of human immunodeficiency virus type 1 (HIV-1) and the human antibody response directed to p17 in HIV-1 infection. Three large peptides covering residues 12-29, 53-87 and 87-115 of p17 were synthesized. The cysteine residues 57 and 87 of peptide 53-87 were reoxidized to form a disulfide bridge. Eighteen out of 19 murine monoclonal anti-rp17 antibodies had relatively high affinities (K_A = 1.9 × 10⁵?1.4 × 10⁸ M^?1) with one of the 3 p17 peptides in the liquid phase. Each monoclonal antibody reacted only with one particular peptide and had no reactivity with the other 2 p17 peptides. All the monoclonal antibodies reacted with rp17 in the liquid phase with a reasonable degree of affinity (K_A = 2.0 × 10⁵?1.8 × 10⁷ M^?1). Four HIV-1 carrier sera, which were positive in ELISA using rp17 as the antigen, reacted positively in an ELISA using 3 p17 peptides which were used to titrate murine monoclonal antibodies. Murine monoclonal antibodies having specificity for the 3 p17 peptides stained live HIV-1-infected cells by means of indirect membrane immunofluorescence, irrespective of their specificity. This suggests that the various portions of p17 (at least 3 regions of p17) were exposed on the surface of live infected cells, probably as short polypeptide chains.     

广西九万山藓类植物区系分析及其对划分热带,亚热带分界线的意义

九万山位于广西北部的中央(25°10’～25°25’N,108°27’E),界于泛北极植物区和古热带植物区的交汇处。其主要植被为亚热带常绿阔叶林。最高海拔为1693m,最低处仅170m。经对1850号标本的鉴定,共计有藓类植物35科、101属和189种。本文分析了九万山的藓类植物区系成分,将其划分为 10种类型。其中东亚成分最为丰富(39.33％),热带、亚热带成分次之(38.20％),而温带成分居第三位(18.54％)。本文选择了九万山临近的五个地区加以比较。其中,金佛山与九万山藓类植物的属和种的相似性系数分别为60.68％和36.87％,神农架为57.29％和33.13％。尖峰岭为48.83％和22.29％,西双版纳为57.29％和29.63％。而我国东部的武夷山则为69.86％和39.57％,其相似性系数在相比较的五个山区中为最高。九万山区有4个特有属并明显受喜马拉雅的影响。特别值得注意的是,在九万山区藓类区系中约有7％的种类是典型的热带成分。根据定量和定性的分析,笔者认为九万山的藓类区系表现出由热带向亚热带过渡的特性,其分界线可能位于九万山的南侧。     

A de novo satellited short arm of the Y chromosome possibly resulting from an unstable translocation

A satellited long arm of the Y chromosome (Yqs) is considered a normal variation, whereas the presence of a satellite on the short arm of the Y (Yps) has never been described in the literature. A Yps chromosome could be clinically significant if the translocation resulting in Yps has relocated the testis-determining gene, SRY, to another chromosome. A carrier of such a translocation would therefore be at increased risk for having XX male and XY female offspring. Here we describe the first reported case of de novo Yps present in a phenotypically normal male. This Yps chromosome was positive for C-banding and nucleolus organizer region (NOR) staining and showed a hybridization signal for the -satellite sequence. Fluorescence in situ hybridization (FISH) analysis indicated that SRY was retained on the Yps and the translocation breakpoint on Yps was distal to the pseudoautosomal region. At prenatal diagnosis, a normal appearing Y chromosome was found in his son, and thus the satellite on Yps was lost during meiotic Xp-Yp pairing. This Yps chromosome was likely the product of an unstable translocation.     

Pharmacokinetics of anti-ganglioside GD2 mAb 14G2a in a phase I trial in pediatric cancer patients

A phase I trial of a murine anti-ganglioside (GD2) monoclonal antibody (mAb) 14G2a was conducted in 14 neuroblastoma patients and 1 osteosarcoma patient to assess its safety, toxicity and pharmacokinetics in pediatric patients. The pharmacokinetics of mAb 14G2a were biphasic with at ₁ ^2/ of 2.8±2.8 h and at ₁ ^2/ of 18.3±11.8 h. In general,t ₁ ^2/ was dose-dependent with a level of significance ofP=0.036, and it reached a plateau at doses of 250 mg/m² or more. Overall the peak serum levels were dose-dependent atP<0.001. However, they demonstrated an abrupt increase between doses of 100 mg/m² and 250 mg/m². The latter two suggest a saturable mechanism for mAb elimination. In addition, peak serum concentrations were observed earlier at higher mAb doses, which indicates the achievement of a steady state. Thet ₁ ^2/ of mAb 14G2a in children appears to be shorter than in adults. Furthermore, 2 patients demonstrated a considerable decrease int ₁ ^2/ following retreatment with 14G2a. This was paralleled by high human anti-(mouse Ig) antibody levels. This study represents the first comprehensive analysis of murine mAb pharmacokinetics in children and will be useful in the future design of mAb therapy.This work was supported by grants from FDA, FD-R-000377 and NIH U10 CA 28439 and in part by a grant from the general Clinical Research Center program, MOI RR00827, of the National Center for Research Resources, National Institutes of Health. M. M. U.-F. and C.-S. H. were supported in part by a grant from the Children's Cancer Research Foundation, and R. A. R. was supported in part by NIH grant CA 42508