人参根系发育形态学的研究

人参(Panax qinseng C. A. Meyer)属于直根系植物,有次生构造。一年生苗只具有主根和侧根。二年以上的人参常在根状茎上长出不定根,即人参根系包括主根和不定根及其各级分枝。主根初生木质部为三原型,侧根和不定根及其分枝多为二原型,偶见三原型。根系随参龄的增加而增大。每年末级分枝自基部于休眠前萎缩、脱落,并在萎缩部分的上一级支根内部产生越冬根原基,越冬根原基是翌年形成全部吸收根的基础。一年生人参由中柱鞘产生一圈初生树脂道,由形成层产生一圈(或二圈)次生树脂道,以后次生树脂道的圈数随参龄的增加而每年增加一圈,自第五年开始渐缓。根内淀粉粒含量随发育时期的变化而相应变化,其积累高峰出现在果后期。研究人参根系发育形态学不仅对全面正确认识人参根系具有理论意义,而且对改进人参栽培管理和评价人参质量具有指导意义。     

Physicochemical and structural studies onAcinetobacter calcoaceticus RAG-1 and MR-481—Two standard strains in hydrophobicity tests

Acinetobacter calcoaceticus RAG-1 and MR-481, two standard strains used in microbial adhesion to hydrocarbons (MATH), were characterized by contact angles, pH-dependent zeta potentials, elemental surface composition by X-ray photoelectron spectroscopy (XPS), and molecular composition by infrared spectroscopy (IR). Negatively stained (methylamine tungstate) and ruthenium red-stained cells were studied by transmission electron microscopy to reveal the absence or presence of surface appendages. Despite the fact thatA. calcoaceticus RAG-1 is known to be extremely hydrophobic in MATH, whereas MR-481 is a completely non-hydrophobic mutant, neither XPS nor IR indicated a significant difference in chemical composition of the cell surfaces. Contact angles with polar liquids, water and formamide, were considerably higher on RAG-1 than on MR-481, in accordance with their relative hydrophobicities as measured by MATH. However, no significant differences in contact angles were observed between the two strains with apolar liquids like diiodomethane,-bromonaphthalene, and hexadecane. Fibrous extensions on RAG-1, observed after ruthenium red staining, were absent on the non-hydrophobic mutant MR-481. Tentatively, these extensions could be held responsible for the hydrophobicity ofA. calcoaceticus RAG-1.     

Surface properties of Streptococcus salivarius HB and nonfibrillar mutants: measurement of zeta potential and elemental composition with X-ray photoelectron spectroscopy.

To characterize the functional cell surface, the zeta potentials and elemental surface composition of Streptococcus salivarius HB and a range of mutants with known molecular surface structures were determined. Zeta potentials of fully hydrated cells were measured as a function of pH in dilute potassium phosphate solutions, yielding isoelectric points of the strains. Elemental composition (O, C, N, and P) of the outer 2 to 5 nm of the freeze-dried cell surfaces were measured by X-ray photoelectron spectroscopy. An increasing loss of proteinaceous fibrillar surface antigens of the mutants was found to be accompanied by a progressive decrease in the N/C ratio from 0.104 in the parent strain HB to 0.053 in mutant HBC12. Simultaneously, the value of the isoelectric point shifted from 3.0 to 1.3. In a previous study (A.H. Weerkamp, H.C. van der Mei, and J. W. Slot, Infect. Immun. 55:438-455, 1987) on the cell surfaces of the same strains, it was shown that removal of fibrils led to increased exposure of (lipo)teichoic acid at the surface, which explains the low isoelectric point caused by the low pKa of the phosphate groups.     

Comparison between the adhesion to solid substrata of Streptococcus mitis and that of polystyrene particles.

The adhesion of Streptococcus mitis to solid substrata from phosphate suspensions with various ionic strengths was studied and compared with the adhesion of polystyrene particles. At all ionic strengths, the interfacial free energy of adhesion governed the relative number of bacteria or polystyrene particles adhering at equilibrium, except that in a low-ionic-strength buffer, adhesion occurred less frequently because of increased electrostatic repulsion. Large differences between bacterial and polystyrene particle adhesion were observed, as indicated by the ratio of bacteria to polystyrene particles adhering, which decreased from 30 to 4 with a change from low to high ionic strength.     

Selective destruction by formaldehyde fixation of an H-2Kb serological determinant involving lysine 89 without loss of T-cell reactivity

In preparation for functional analyses, a study of the binding of H-2K^b-specific monoclonal antibodies (mAb) to formaldehyde (FOR)-fixed H-2^b spleen or tumor cells revealed that three of nine mAb tested had lost reactivity with the FOR-fixed cells, whereas the reactivity of the other mAb generally did not diminish. Comparison of the reactivity of these mAb on untreated H-2K ^bm mutant cells and on FOR-treated H-2K^b cells suggests that for three mAb the total loss of reactivity on the latter could be a consequence of the alteration by FOR of lysine 89, which is substituted by alanine in mutant bm3. H-2KP^b-specific alloreactive polyclonal or monoclonal CTL, all of which had retained reactivity with bm3 target cells, had also retained reactivity with FOR-fixed H-2^b cells as indicated by cold target inhibition studies. The H-2K^b-specific CTL were probably reactive with conformational determinants of H-2K^b, which are dependent on the integrity of both the 1 and the 2 domains of the H-2K^b molecule. Results are compatible with FOR treatment selectively affecting a serological determinant in the 1 domain without affecting conformational-type CTL determinants.Abbreviations used in this paper CTL cytotoxic T lymphocyte - FOR formaldehyde - PBS phosphatebuffered saline - FCS fetal calf serum - mAb monoclonal antibody - TNBS trinitrobenzene sulfonate     

向日葵未受精胚珠培养时胚状体发生的显微观察

由开花前1—4天的向日葵子房中取出胚珠,在液体培养基上进行漂浮培养,诱导了未受精的卵细胞发育为单倍体的胚状体.亦诱导了珠被绒毡层产生胚状体。对两种胚状体的发生和发育过程及其形态发生特点作了显微观察与描述。     

Mg~(2+)影响嵌有线粒体H~+-ATP酶脂酶体的表面电荷密度和流动性

<正> 我们实验室曾报道,用胆酸盐透析法将猪心线粒体H~+-ATP酶嵌入大豆磷脂脂质体形成脂酶体时,透析液中Mg~(2+)的存在会降低脂酶体的膜脂流动性,并明显提高重建H~+-ATP酶的活性以及对寡霉素或DCCD的敏感性,因而推论Mg~(2+)的作用很可能是通过改变膜脂的物理状态,形成了维持H~+-ATP酶较高活性的合适构象。但共确切的作用机制仍     

MSI2通过下调circRNA_001214促进急性髓系白血病细胞HL60生长

Musashi-2（MSI2）是一种RNA结合蛋白质,对维持造血干细胞功能具有重要作用。研究表明,MSI2高表达能促进急性髓系白血病（acute myelocytic leukemia, AML）进展,但其作用机制尚不明确。本研究稳定沉默HL60细胞MSI2后,第1、2、3、4 d对照组的相对细胞生长率分别为1.931 ± 0.027、3.070 ± 0.073、4.017 ± 0.092和4.215 ± 0.246;敲减组分别为1.927 ± 0.035、2.564 ± 0.090、2.825 ± 0.097和3.223 ± 0.182,两组相比具有统计学差异,P<0.001;细胞凋亡明显增加(7.967% ± 0.698% vs 3.400% ± 0.322%., P<0.01);G₀/G₁期细胞比例明显增高（67.430% ± 4.390% vs. 50.360% ± 2.160%, P<0.01）;NUMB蛋白明显上调,LEF1明显下降。环状RNA（circular RNA, circRNA）芯片筛选和荧光定量PCR验证显示,MSI2沉默组circRNA_001214表达水平是对照组3.48倍。这一结果也在NALM6细胞得到证实。进一步用生物信息学分析,显示circRNA_001214最可能与miR-1273a、miR-1273e和miR 5095结合,进而影响参与细胞凋亡相关基因（CYCS、AKT1、BAX、TNFRSF10A、TNFRSF10D）、Wnt信号基因（WNT4、WNT2B、WNT7B、 DKK2、SFRP1、CSNKE1和LEF1）以及参与细胞代谢相关基因（RPE, PGAM4, PGAM1, TAT, CBS、RPE、SUCLG2、PGAM4、PGAM1和 IDNK）。总而言之,MSI2可能通过干扰circRNA_001214生成,减少靶miRNA对凋亡、Wnt信号及细胞代谢相关基因表达的影响,促进细胞生长。     

ATF4在内质网应激调控成骨分化中的作用

为避免内质网中未折叠蛋白质的过度累积,真核细胞能激活一系列信号通路来维持内质网稳态,这个过程称为内质网应激。在骨生长发育中,适宜的内质网应激有助于成骨细胞、破骨细胞和软骨细胞的生长,可以促进骨髓间充质干细胞向成骨细胞分化。而过度的内质网应激会抑制成骨分化,严重的甚至导致骨质疏松、成骨不全等相关骨病的发生。内质网应激时可激活未折叠蛋白质反应,其主要是通过PERK/eIF2α/ATF4信号通路,上调转录激活因子4(ATF4)的表达。ATF4位于许多成骨分化调节因子的下游,是促进成骨分化的关键因子,在内质网应激对成骨分化的调节中发挥重要作用。在成骨分化过程中,适宜的内质网应激能通过激活PERK信号通路,诱导ATF4表达增加,进而上调骨钙素、骨涎蛋白等成骨所必需基因的表达,促进成骨分化。过度的内质网应激会激活ATF4/CHOP促凋亡途径,并导致Bax、胱天蛋白酶等凋亡信号分子的大量产生,进而导致细胞凋亡,抑制成骨分化。由于ATF4在ERS和成骨分化中的重要作用,ATF4在骨质疏松、成骨不全等骨相关疾病的治疗中具有重要意义。本文通过综述ATF4在内质网应激调控成骨分化中的作用机制,为相关骨性疾病治疗提供理论依据。     

Role of actin binding protein phosphorylation in platelet cytoskeleton assembly

Actin binding protein from human blood platelets is shown to exist in the resting platelet as a phosphorylated protein and contains two residues of phosphate per 260,000 kd. Removal of one-half of these residues with E. coli alkaline phosphatase results in the loss of its ability to crosslink F-actin into a low speed sedimentable complex (its cytoskeleton) and to bind to an F-actin affinity column. Thus, phosphorylation-dephosphorylation of ABP may be an important regulatory mechanism by which the platelet regulates its shape via its cytoskeletal structure.