Ds transposition mediated by transient transposase expression in Heiracium aurantiacum

The feasibility of using transient transposase expression to mobilize Ds elements for gene tagging in Hieracium aurantiacum was evaluated. A T-DNA construct carrying the Ac transposase gene and either a visible marker gene (uidA) or the conditionally-lethal marker gene (codA) was transferred to H. aurantiacum leaf discs (previously transformed with a Ds element) by co-cultivation with Agrobacterium tumefaciens. Shoots were regenerated directly from the co-cultivated leaf discs under selection for antibiotic resistance resulting from Ds excision. Most regenerants carried unique transposition events. Of 84 regenerated plants, twenty one (25%) did not express the marker gene and the DNA coding sequence of the transposase could not be detected in seven (8.3%). Potential advantages of this method over conventional gene-tagging methods are: rapid recovery of individual transposition events; regenerated plants are isogenic; and the transient nature of transposase expression should facilitate the stabilisation of the transposed element.     

Na/K-ATPase as an oligomeric ensemble

Differences in the kinetic behavior and properties of monomeric and oligomeric forms of membrane-bound Na/K-ATPase are analyzed. It is concluded that enzyme molecules within oligomeric complexes are affected by extrinsic signals that result in change of enzyme activity, whereas the individual (protomeric) state is insensitive to these signals. Some of the major factors of such regulation are microviscosity of the lipid environment, reactive oxygen species, and intracellular protein kinases.     

粘、易型1B/1R小麦雄性不育系产生单倍体的遗传机理及育性恢复性能的研究

调查了ms(Ae.kotschyi)-77(2)和ms(Ae.variabilis)-77(2)低、高世代和在转育、组配中单倍体频率的变化趋势及在不同胞质间、核型间存在的变异。结果表明:(1)粘、易型1B/1R小麦雄性不育系产生单倍体的遗传机理是由于1B/1R卵细胞与粘、易胞质的专一互作,并在花粉蒙导下而导致孤雌生殖的结果;(2)1B·1B/1R杂合核型比1B/1R·1B/1R纯合核型产生的单倍体频率高,1B/1R·1B/1R纯合核型世代间单倍体诱导频率相对稳定;(3)在同一核背景下,诱导单倍体频率粘质高于易质;(4)用不同来源的1B/1R易位系来转育粘、易型不育系及用不同核型的父本与其组配杂种,诱导单倍体频率明显不同;依此差异进行亲本选择,分别可选出与组配出不产生或很少产生单倍体的粘、易型1B/1R不育系和F_1杂种。此外,分析了粘、易型1B/1R不育系一般恢复度不高的内在原由,认为与1B·1B/1R杂合核型中的易位染色体在减数分裂中能否正常联会配对直接相关。     

Diethyldithiocarbamate Potentiates the Neurotoxicity of In Vivo l-Methyl-4-Phenyl-1, 2, 3, 6-Tetrahydropyridine and of In Vitro 1-Methyl-4-Phenylpyridinium

Diethyldithiocarbamic acid (DDC) potentiates in vivo neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and in vitro neurotoxicity of 1-methyl-4-phenylpyridinium (MPP+). Male C57B1/6 mice were given two or five injections of MPTP (30 mg/kg i.p.) preceded 0.5 h by DDC (400 mg/kg i.p.). The mice were tested for catalepsy, akinesia, or motor activity during and after the period of dosing. Striatal and hippocampal tissues were obtained at 2 and 7 days following the last injection and evaluated for dopamine and norepinephrine levels, respectively. These same tissues were also analyzed for the levels of glial fibrillary acidic protein (GFAP), an astrocyte-localized protein known to increase in response to neural injury. Pretreatment with DDC potentiated the effect of MPTP in striatum and resulted in substantially greater dopamine depletion, as well as a more pronounced elevation in GFAP. In hippocampus, the levels of norepinephrine and GFAP were not different from controls in mice receiving only MPTP, but pretreatment with DDC resulted in a sustained depletion of norepinephrine and an elevation of GFAP, suggesting that damage was extended to this brain area by the combined treatment. Mice receiving MPTP preceded by DDC also demonstrated a more profound, but reversible, catalepsy and akinesia compared to those receiving MPTP alone. Systemically administered MPP+ decreased heart norepinephrine, but did not alter the striatal levels of dopamine or GFAP, and pretreatment with DDC did not alter these effects, but did increase lethality. DDC is known to increase brain levels of MPP+ after MPTP, but our data indicate that this is not due to a movement of peripherally generated MPP+ into CNS.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of the Antifungal Ability of Bacillus subtilis Strain PY-1 in Vitro and Identification of its Antifungal Substance （Iturin A）

A Bacillus strain,denoted as PY-1,was isolated from the vascular bundle of cotton.Biochemical,physiological and 16S rDNA sequence analysis proved that it should belong to Bacillus subtilis.The PY-1strain showed strong ability against many common plant fungal pathogens in vitro.The antibiotics producedby this strain were stable in neutral and basic conditions,and not sensitive to high temperature.From theculture broth of PY-1 strain,five antifungal compounds were isolated by acidic precipitation,methanolextraction,gel filtration and reverse-phase HPLC.Advanced identification was performed by mass spec-trometry and nuclear magnetic resonance spectroscopy.These five antifungal compounds were proved to bethe isomers of iturin A:A2,A3,A4,A6 and A7.In fast atom bombardment mass spectrometry/mass spec-trometry collision-induced dissociation spectra,fragmentation ions from two prior linear acylium ions wereobserved,and the prior ion,Tyr-Asn-Gln-Pro-Asn-Ser-βAA-Asn-CO~ ,was first reported.     

Mechanotransduction of keratinocytes in culture and in the epidermis

The epidermis, like many other tissues, reacts to mechanical stress by increasing cell proliferation. Mechanically stressed skin regions often develop thicker skin and hyperkeratosis. Interestingly, a large number of skin diseases are accompanied by epidermal proliferation and hyperkeratosis even under normal mechanical stress conditions. Although, some of the molecular pathways of mechanical signaling involving integrins, the epidermal growth factor receptor and mitogen-activated protein kinases are known it is still unclear, how mechanical force is sensed and transformed into the molecular signals that induce cell proliferation. This review focuses on the molecules and pathways known to play a role in mechanotransduction in epidermal keratinocytes and discusses the pathways identified in other well-studied cell types.     

提高重组TRAIL表达产率的优化策略

肿瘤坏死因子相关凋亡诱导配体（Apo2L/TRAIL）是一种新型的抗肿瘤蛋白。针对缩短发酵周期,提高生产效率这一目标,首先在摇瓶中利用响应面设计优化发酵表达条件,总TRAIL蛋白的表达量提高到25.7%。在此基础上研究了发酵条件对可溶性TRAIL蛋白表达量的影响。于3.7L发酵罐放大进行补料-分批发酵实验时,单位菌体可溶性TRAIL蛋白的表达量提高了67%,实现了在大肠杆菌高密度培养过程中单位细胞重组TRAIL蛋白的可溶性表达和体积生产率的提高。     

CHANGES IN PHOTOSYNTHESIS IN RESPONSE TO COMBINED IRRADIANCE AND TEMPERATURE STRESS IN CYANOBACTERIAL SURFACE WATERBLOOMS1

Buoyant cyanobacteria, previously mixed throughout the water column, float to the lake surface and form a surface waterbloom when mixing subsides. At the surface, the cells are exposed to full sunlight, and this abrupt change in photon irradiance may induce photoinhibition; at the same time, temperature rises as well. This study investigated the damaging effects of this increase in temperature as well as the ecologically more relevant combination of both an increased temperature and a high photon irradiance. Analysis of surface blooms with oxygen microelectrodes showed that integrated oxygen contents that are dependent on the balance of photosynthetic oxygen evolution and respiratory oxygen uptake decreased when temperature was raised above the lake temperature. Gross rates of photosynthesis were unaffected by temperatures up to of 35°C; hence, a moderate increase in temperature mainly stimulated oxygen uptake. Preincubation of cells of the cyanobacterium Anabaena flos-aquae (Lyngb.) de Brébisson at temperatures up to 35°C did not affect the subsequent measurement of rates of net photosynthesis. Another 5°C rise in temperature severely damaged the photosynthetic apparatus. Failure to restore net rates of photosynthesis was coupled to a strong quenching of the ratio of variable to maximum fluorescence, F_v/F_m, that was the result of a rise in F_o. A combination of high temperature and high photon irradiance was more damaging than high temperature alone. In contrast, low photon irradiances offered substantial protection against heat injury of the photosynthetic apparatus. I conclude from this study that because cyanobacteria usually are acclimated to low average irradiance prior to bloom formation, there is a reasonable risk of chronic photoinhibition. The increase in temperature will enhance the photodamage of cells in the top layer of the bloom. Low photon irradiances in subsurface layers will offer protection against heat injury. If the high temperatures extend to the deepest, dark layers of the bloom, damage in those layers is likely to occur.