长叶车前花叶病毒(HRV_(sh))外壳蛋白赖氨酸残基的修饰

我们曾报道长叶车前花叶病毒上海分离株(简称HRVsh)的外壳蛋白有二个赖氨酸残基,在PH8.5无变性剂存在的条件下,完整病毒颗粒表面的赖氨酸残基可与三硝基苯磺酸(TNPS)起反应,反应后的TNP-HRVsh病毒颗粒的感染力丧失达90％以上。 本文又进行了甲基乙亚胺甲酯(MEI)对HRVsh赖氨酸残基的修饰反应,修饰后的MEI-HRVsh病毒颗粒的感染力也同样丧失90％以上。 从三硝基苯磺酸修饰的病毒颗粒(TNP-HRVsh)中分离得到的RNA能与天然的HRVsh的外壳蛋白重建病毒颗粒,并具有感染力,说明修饰过程中核酸并不受影响。 进一步用同位素~(35)S,~(32)P双标记病毒,再以TNPS修饰标记的病毒,得到(~(35)S,~(32)P)-HRVsh及TNP-(~(35)S,~(32)P)-HRVsh。将两者分别接种于系统寄主青菜(Brassica chinensis)的一片叶片,一天后在非接种叶片上都可测得~(35)S,~(32)P的放射计数。其中,(~(35)S,~(32)P)-HRVsh的~(35)S/~(32)P比值降低了,而TNP-(~(35)S,~(32)P)-HRVsh的~(35)S/~(32)P比值保持不变。说明HRVsh外壳蛋白赖氨酸残基的修饰并不影响病毒颗粒进入寄主细胞,以及在寄主细胞间的转移。同位素双标记的结果表明,其感染力丧失的原因可能是由于上述修饰作用阻止了病毒在感染中所必须的脱壳过程。     

A Comparison of Internal Standards for Plant Cytophotometry

Plant cell nuclei were compared with chicken erythrocyte nuclei for use as internal standards for microspectrophotometry. The amount of DNA per nucleus and the coefficient of variation for measurement of individual nuclei were determined for cells from dormant embryos of Pinus taeda and Pinus coulteri, from onion root tips and from chicken erythrocytes. The chicken erythrocytes had the least variability and thus were best suited for use as a standard. Onion root tips were least suitable, with a coefficient of variation 2 1/2 times that of erythrocytes. Although onion root tips have been used as an internal standard in other studies, their mitotic activity, in contrast with the nonreplication of DNA of mature erythrocytes, is reflected in a broad distribution of nuclei with values in the 2C-4C range. Coulter pine mature embryos were at the 3C level, whether dry or hydrated, while loblolly pine embryos were in the 2C state. This confirms previous reports. The coefficient of variability for the pine embryo cells was 1 1/2 times that of erythrocytes for nonhydrated seeds and twice the erythrocyte value for hydrated seeds. The larger 2C values for pine (26 pg for P. taeda and 17 pg for P. coulteri) are closer to values expected for many plant species than the 3 pg level of the chicken erythrocytes. Dormant P. taeda embryo cells (2C) are suggested as an alternative where the experimental material has large DNA values and/or chicken erythrocytes are difficult to procure. Large sample size is recommended for the plant materials if they are to be used as internal standards in Feulgen cytophotometry.     

Opposite effects of adrenalectomy on eicosanoid release in rat peritoneal macrophages and spleen

The effect of adrenalectomy on the formation of cyclo-oxygenase and lipoxygenase products by activated peritoneal rat macrophages was determined and compared with that of the spleen. After isolation, the cells and tissues were incubated with [1-¹⁴C] arachidonic acid and the Ca-ionophore A23187 and the metabolites isolated by HPLC chromatography. The main components formed in the macrophages of the controls are 6-keto-PGF_1α, TxB₂ and 12-HETE. One peak represents 5, 12 di HETE. Smaller amounts of PGF_2α, PGE₂, PGD₂, LTB₄ and 15-HETE are also present. After adrenalectomy, a considerable increase occurs in the amounts of LTB₄, 15-HETE and 12-HETE. The increase in the PG is smaller. The compounds formed from endogenous arachidonic acid are also determined. In the cells of the controls, the formation of LTB₄ is considerably increased after adrenalectomy. In the spleen, PGD₂ and 12-HETE are decreased after adrenalectomy.The effect of the macrophages is most probably related to a diminished amount or inactivation of lipocortin, a glucocorticosteroid induced peptide with PlA₂ inhibitory activity in adrenalectomized animals. In the decrease in formation in the spleen, the absence of the permissive effect of glucocorticosteroids on the hormone-induced lipolysis may play a role.     

我国东喜马拉雅及其邻区牛肝菌目的研究（续）

本属与多种树种有菌根关系：如Pinus,Larix,Abies和Pseudotsuga,但在Larix林下,本菌往往与土壤中的鞣料相聚集,对周围某些植物根系不利。本属现知15种,本区6种。     

Genomic DNA sequence for human C-reactive protein

The gene for the prototype acute phase reactant, C-reactive protein, has been isolated from two lambda phage libraries containing inserted human DNA fragments using synthetic oligonucleotide probes. Nucleotide sequence analysis indicates that after coding for a signal peptide of 18 amino acids and the first two amino acids of the mature protein, there is an intron of 278 base pairs followed by the nucleotide sequence for the remaining 204 amino acids. The intron is unusual in that it contains on the positive strand a poly(A) stretch 16 nucleotides long and a poly(GT) region 30 nucleotides long which could adopt the Z-form of DNA. The nucleotide sequence reported here confirms the amino acid sequence of mature C-reactive protein as originally reported except that it codes for an additional 19 amino acids beginning at position 62. Thus DNA sequence analysis predicts that the mature protein consists of 206 amino acids rather than 187 as originally reported. The mRNA cap site is located 104 nucleotides from the start of the signal peptide and there is a 3' noncoding region 1.2 kilobase pairs in length. The gene has a typical promoter containing the sequences TATAAAT and CAAT 29 and 81 base pairs upstream, respectively, of the cap site.     

An improved DNA sequencing strategy

A modification of Hong's systematic DNA sequencing strategy is described. The original procedure has been simplified and transfectant yield increased. After DNase I limited cleavage in the presence of Mn2+, the single-cut linear DNA does not have to be separated from supercoiled or open circular DNA on an agarose gel. After ligation, the DNA is digested with a second restriction endonuclease for which a unique cleavage site resides between the insert and the first restriction endonuclease cutting site. The original intact DNA is linearized whereas the deleted subclone is not. The background is decreased to an undetectable level. This DNA sequencing strategy was tested on a 1.4-kb DNA fragment containing the araC regulatory gene from Erwinia carotovora. A set of subclones sufficient to sequence the fragment on both strands was produced in 2 days and the yield was at least 60-fold higher than in the original protocol.     

Murine polyspecific antibodies. I. Monoclonal and serum anti-DNA antibodies cross-reactive with 2,4,6-trinitrophenyl derivatives

Six anti-DNA hybridoma autoantibodies were prepared by fusing spleen cells from unimmunized MRL/MpJ/lpr/lpr female mice with BALB/c myeloma cells. The monoclonal antibodies were analyzed by solid-phase ELISA for antigen-binding specificities. Three antibodies (62A2, 85A5, and 43B2) bound ssDNA, TNP-KLH, and recognized an epitope(s) present on insolubilized proteins such as BSA, KLH, ferritin, and insulin. The antibodies bound, with a marked preference, TNP-KLH, either soluble or insoluble. The other three antibodies (35A1, 32C5, and 39D2) bound only ssDNA. However, this binding was inhibited by free flavinic acid. None of the six antibodies bound either cardiolipin or proteoglycans, indicating that they do not recognize the repeating negatively charge units common to cardiolipin, proteoglycans, and DNA. All six monoclonal antibodies were purified by affinity chromatography with TNP-Sepharose. Moreover, both anti-DNA and anti-TNP antibodies from sera of nonautoimmune and autoimmune mice were purified easily on TNP-Sepharose.     

Cell-cell interaction can influence drug-induced differentiation of murine embryonal carcinoma cells

When cultured in the presence of either retinoic acid (RA) or dimethyl sulfoxide (DMSO), aggregates of the P19 line of mouse embryonal carcinoma (EC) cells differentiate and the spectrum of cell types formed depends on the drug dose. It is shown here the EC cells rapidly lose their colony-forming ability when cultured as aggregates in the presence of DMSO. This loss of plating efficiency (PE) also occurs rapidly following RA treatment. Loss of PE has been used as a quantitative procedure for assessing the rate of drug-induced differentiation. The relationship between drug dose and loss of PE is much steeper for DMSO than for RA, suggesting that these two drugs affect different stages of the differentiation decision-making apparatus. Mutant EC cell lines (D3 and RAC65) do not differentiate in the presence of drug-inducers (DMSO and RA, respectively). Neither differentiation-deficient mutant has an altered ability to form gap junctions. When D3 and P19 cells were mixed within the same DMSO-treated aggregates, the D3 cells remained undifferentiated and the P19 cells differentiated much less efficiently than if they were cultured in the absence of the D3 cells. When RAC65 and P19 cells were mixed in RA-treated aggregates, each cell responded to the drug as though the other were absent. Thus RA behaves as a cell-autonomous inducer of differentiation, whereas DMSO-induced differentiation seems to be mediated by interactions between neighboring cells.     

Three types of transmitter release from embryonic neurons

Prior to the contact with their target muscle cells in culture, growth cones of many isolated Xenopus embryonic neurons release acetylcholine (ACh) spontaneously. Using patch clamp techniques, this release can be detected by an outside-out patch of muscle membrane placed near the growth cone. Intracellular recording from innervated muscle cells showed spontaneous miniature endplate potentials (MEPPs) of varying amplitudes. Amplitude histograms showed a skewed distribution with multiple peaks, suggesting the existence of subunits in either the quantal packages of ACh released by the nerve terminal or in the postsynaptic muscle response. In addition to the quantal ACh release reflected by MEPPs, nerve terminal also release a large amount of ACh in a non-quantal fashion. This non-quantal ACh release is revealed by the hyperpolarization of the muscle membrane following extracellular application of curare or alpha-bungarotoxin, as well as by denervation of the muscle cell.