中国人ε珠蛋白基因5′侧序列中多态性Hinc Ⅱ位点的进一步研究

本文进一步研究了我国不同民族的正常个体以及β地中海贫血患者θ珠蛋白基因5′侧序列中的多态性HincⅡ位点及其遗传性质。在广西壮族正常个体和β地中海贫血纯合子中,该多态性位点的发生频率均为75％,与正常汉族人测得值相近。家系分析资料表明,该多态性位点完全按照孟德尔规律进行遗传。     

Functional and ultrastructural effects of nontypeable haemophilus influenzae in a hamster trachea organ culture system

Summary A hamster trachea organ culture system was utilized to evaluate quantitatively the effects of a strain of nontypeableHaemophilus influenzae (NTHI) and culture supernatants of the same strain on ciliary activity. Tracheal explants were maintained in organ culture for 96 to 144 h and ciliary activity was observed daily with an inverted microscope. Explants continuously exposed to a strain of NTHI had a progressive decline in ciliary activity which was significantly lower than uninfected controls evaluated concomitantly by 48 h of exposure and thereafter. Histologic studies revealed a progressive degeneration of mucosal cells and exfoliation of ciliated cells. Scanning electron microscopy showed little adherence of NTHI to the mucosal surface. Sterile broth cultures of NTHI and supernatants of organ cultures infected with the same NTHI strain had no adverse effect on ciliary activity. Infected tracheal explants treated with ampicillin 24, 48, or 72 h after continuous bacterial challenge had no significant decline in ciliary activity compared to controls. The lack of adherence and the histologic changes observed when hamster trachea cultures were infected with NTHI suggested a toxin might mediate the damage observed. Broth and organ culture supernatants, however, produced no damage. Therefore, further studies are needed to determine the role, if any, of a toxin in the production of damage to hamster tracheal explants by NTHI. This work was supported by a Merit Review grant from the Veterans Administration and by Grant AI-19641 from the National Institute of Allergy and Infectious Diseases.     

The rabbit C family of short, interspersed repeats. Nucleotide sequence determination and transcriptional analysis

When the entire adeno-associated virus (AAV) genome is inserted into a bacterial plasmid, infectious AAV genomes can be rescued and replicated when the recombinant AAV-plasmid DNA is transfected into human 293 cells together with helper adenovirus particles. We have taken advantage of this experimental system to analyze the effects of several classes of mutations on replication of AAV DNA. We obtained AAV mutants by molecular cloning in bacterial plasmids of naturally occurring AAV variant or defective-interfering genomes. Each of these mutants contains a single internal deletion of AAV coding sequences. Also, some of these mutant-AAV plasmids have additional deletions of one or both AAV terminal palindromes introduced during constructions in vitro. We show here that AAV mutants containing internal deletions were defective for replicative form DNA replication (rep-) but could be complemented by intact wild-type AAV. This indicates that an AAV replication function, Rep, is required for normal AAV replication. Mutants in which both terminal palindromes were deleted (ori-) were also replication defective but were not complementable by wild-type AAV. The cis-dominance of the ori- mutation shows that the replication origin is comprised in part of the terminal palindrome. Deletion of only one terminal palindrome was phenotypically wild-type and allowed rescue and replication of AAV genomes in which the deleted region was regenerated apparently by an intramolecular correction mechanism. One model for this correction mechanism is proposed. An AAV ori- mutant also complemented replication of AAV rep- mutants as efficiently as did wild-type AAV. These studies also revealed an unexpected additional property of the deletion mutants in that monomeric single-stranded single-stranded DNA accumulated very inefficiently even though monomeric single-stranded DNA from the complementing wild-type AAV did accumulate.     

Replication of adenovirus mini-chromosomes

We have isolated adenovirus origins of DNA replication from both the right and left ends of the genome, which are functional on linear autonomously replicating mini-chromosomes. The mini-chromosomes contain two cloned inverted adenovirus termini and require non-defective adenovirus as a helper. Replicated molecules are covalently attached to protein, and DNA synthesis is initiated at the correct nucleotide even when the origins are not located at molecular ends. The activity of embedded origins leads to the generation of linear minichromosomes from circular or linear molecules. These observations therefore suggest that sequences within the adenovirus origin of replication position the protein priming event at the adenovirus terminus. Experiments investigating the regeneration of deleted viral inverted terminal repeat sequences show a sequence-independent requirement for inverted sequences in this process. This result strongly suggests that repair results from the formation of a panhandle structure by a displaced single strand. On the basis of these observations we propose a model for the generation of adenovirus mini-chromosomes from larger molecules.     

Complete nucleotide sequences of all three poliovirus serotype genomes. Implication for genetic relationship, gene function and antigenic determinants

The complete nucleotide sequences of the genomes of the type 2 ( P712 , Ch, 2ab ) and type 3 (Leon 12a1b ) poliovirus vaccine strains were determined. Comparison of the sequences with the previously established genome sequence of type 1 (LS-c, 2ab ) poliovirus vaccine strain revealed that 71% of the nucleotides in the genome RNAs were common, that the 5' and 3' termini of the genomes were highly homologous, and that more than 80% of the nucleotide differences in the coding region occurred in the third letter position of in-phase codons, resulting in a low frequency of amino acid difference. These results strongly suggested that the serotypes of poliovirus derived from a common prototype. A comparison of the amino acid sequences predicted from the genome sequences showed highest variation in the capsid protein region, whereas non-structural proteins are highly conserved. Initiation of polyprotein synthesis occurs in all three strains more than 740 nucleotides downstream from the 5' end. An analysis of the non-coding region suggests that small peptides that could potentially originate from this region are conserved. The amino acid sequences immediately surrounding the cleavage signals, however, show a higher than average degree of variation. The analysis of the amino acid sequences of the capsid protein VP1 of all serotypes has led to the prediction of potential antigenic sites on the virion involved in neutralization.     

正常及白血病小鼠白细胞染色质和DNA的酶切分析

 本文应用的核酸酶为DNaseⅡ、微球菌核酸酶与限制性内切核酸酶BstNI、EcoRⅡ、HpaⅡ和MspⅠ,将它们作用于正常小鼠615和可移植性白血病小鼠L7712脾脏白细胞染包质及其DNA,根据酶切电泳谱及水解动力学分析表明:1.白血病小鼠染色质相对正常小鼠染色质易被DNaseⅡ微球菌核酸酶水解;2.白血病小鼠染色质比正常小鼠者易被MspⅠ水解,但其DNA的MspⅠ酶切电泳谱无明显差别;3.白血病小鼠染色质及其DNA较正常小鼠染色质及其DNA易被EcoRⅡ水解。这些观察说明,白血病小鼠脾脏白细胞染色质有较活跃的构象状态;其染色质DNA的CCATGC区段内有较低的甲基化程度。     

pH dependence of the in situ formation of an organicN-chloramine water disinfectant

Summary Staphylococcus aureus was used to assess the bactericidal efficacy of aqueous solutions of the organicN-chloramine compound 3-chloro-4,4-dimethyl-2-oxazolidinone (agent I) formed in situ. The rate of in situ formation, accomplished by reacting free chlorine with the amine precursor, was a function of pH. When the reagents were combined under acidic conditions (pH5.5) and allowed to react for 22 h, sufficient residual free chlorine was present to inactivate the bacteria in less than 5 min. When combined under less acidic conditions (pH6.0), comparable bacterial inactivation required 30–60 min due to the extensive reaction of the free chlorine to form agent I. The kill rates present under less acidic and neutral conditions are equivalent to those for pre-formed agent I. In water disinfection applications for pH6.0, in situ formation of agent I would provide a combination of rapid initial and slower long-term disinfection.     

水分胁迫下露花光合型的转变

CAM植物按其对环境的反应可分为两种类型:即专一CAM植物和兼性CAM植物。前者不易受外界环境的变化而改变其CAM性质;后者的光合型可随季节和水分胁迫等而发生变化,也可因人工诱导作用而使其由C_3型转变为CAM型。     

Effect of oxygen limitation on the formation of the electron transport system of the phytopathogenic fluorescent bacteriumPseudomonas cichorii

The composition of the membrane-bound electron transport system of the phytopathogenic bacteriumPseudomonas cichorii underwent modification in response to oxygen supply. Growth adaptation to low oxygen concentrations was characterized by repression of cytochromes involved in ubiquinol-cyt.c oxidoreductase and cyt.c oxidase activities. By contrast, cyto.o, i.e., the alternative cyanide-insensitive oxidase ofP. cichorii, was unaffected by low oxygen tension. Noa-type cytochromes could be detected at any stage of growth.