肝细胞生长因子刺激大鼠离体肝细胞DNA合成的剂量—与时间—效应

本工作采用３ＨＴｄＲ掺入ＤＮＡ法观察重组人肝细胞生长因子（ｒｈＨＧＦ）刺激大鼠离体肝细胞ＤＮＡ合成的剂量与时间效应。实验结果表明：ｒｈＨＧＦ是最强的促肝细胞分裂剂,在一定剂量范围内,ｒｈＨＧＦ与肝细胞ＤＮＡ合成有明显的量效关系。１ｎｇ／ｍｌｒｈＨＧＦ即可引起３ＨＴｄＲ掺入显著增加（Ｐ＜０．０１）,随剂量增加,刺激ＤＮＡ合成的效应也随之增强;１０ｎｇ／ｍｌ时３ＨＴｄＲ掺入量最大,较对照组高７倍（Ｐ＜０．００１）,剂量再增加即出现抑制效应;ｒｈＨＧＦ刺激肝细胞ＤＮＡ合成存在时间效应关系,表现为ｒｈＨＧＦ作用２４ｈ,ＤＮＡ合成量明显高于对照组（Ｐ＜０．０１）,４８ｈ作用达最高（Ｐ＜０．００１）,随后开始下降,至９６ｈ下降到相当于２４ｈ的水平。     

肝细胞生长因子对四氯化碳损伤原代培养大鼠肝细胞的保护…

本工作采用无血清原供培养大鼠肝细胞法,观察了重组人肝细胞生长因子对四氯化碳致大鼠肝细胞损伤的保护作用。结果表明,ｒ－ｈＨＧＦ对ＣＣｌ４染毒肝细胞有明显的保护作用。ｒ－ｈＨＧＦ保护组较ＣＣｌ４染毒组细胞存活率显著升高,细胞内丙氨酸转氨酶,钾离子漏出明显降低。     

黑莓汁的理化特性及贮藏期营养成分的变化

对黑莓浓缩汁的理化特性及其营养成分变化进行研究,结果表明：ｐＨ３～４,波长５１１～５１４ｎｍ时,果汁色泽最佳;果汁抗氧化还原能力很弱,但具有很强的光和热的稳定性。０～４℃低温贮藏１年后,６种维生素的损失率都超过５０％;含糖量损失４０７％;ＳＯＤ活性和氨基酸含量分别损失１０％和１２４％;含酸量略有增加     

热休克反应中小鼠心脏HSP70表达的免疫组织化学研究

用免疫组织化学方法研究了小鼠心脏在不同温度（40、42、44、46℃）热休克处理后，各恢复期（2、4、8、12、24小时）HSP70 的表达。结果表明，（1）44、46℃热处理能诱导心肌细胞合成 HSP70，以46℃为多（P＜0.01），且于恢复期4～8小时为合成高峰（P＜0.01）；（2）阳性免疫反应定位于心肌细胞质中，核呈阴性反应。提示了心脏有较强的耐热能力。     

Cytochrome c reconstituted from two peptide fragments displays native-like redox properties.

Recombination of two fragments of horse cytochrome c (the heme-containing N-fragment, residues 1-56, and the C-fragment, residues 57-104), which are substantially unstructured at neutral pH, gives rise to a 1:1 fragment complex with a compact conformation, in which the alpha helical structure and the native Met80-Fe(III) axial bond are recovered. With respect to the native protein, the ferric complex shows a less rigid atomic packing and a decreased stability [Delta(DeltaG(o))D = 14.7 kJ.mol(-1)], ascribed to perturbations involving the Trp59 microenvironment and, to a lower extent, the heme pocket region. The redox potential, E1/2 = 234 +/- 5 mV vs. normal hydrogen electrode at 25 degrees C, is close to that of the intact protein, consistent with recovery of the native Met80-heme Fe(III) axial bond. Furthermore, the fragment complex shows reactivity similar to intact cytochrome c, in the reaction with cytochrome c oxidase. We conclude that the absence in the complex of some native cross-links and interlocked packing important for protein rigidity and stability is not as relevant for maintaining the native redox properties of the protein, provided that some structural requirements (i.e. recovering of the native-like alpha helical structure) are fulfilled and coordination of Met80 to the heme-iron is restored.     

Electric field induced desorption of bacteria from a conditioning film covered substratum.

Desorption of three oral bacterial strains from a salivary conditioning film on an indium tin oxide electrode during application of a positive (bacterial adhesion to the anode) or a negative electric current was studied in a parallel plate flow chamber. Bacterial adhesion was from a flowing suspension of high ionic strength, after which the bacterial suspension was replaced by a low ionic strength solution without bacteria and currents ranging from -800 to +800 microA were applied. Streptococcus oralis J22 desorbed during application of a positive and negative electric current with a desorption probability that increased with increasing electric current. Two actinomyces strains, however, could not be stimulated to desorb by the electric currents applied. The desorption forces acting on adhering bacteria are electroosmotic in origin and working parallel to the electrode surface in case of a positive current, whereas they are electrophoretic and electrostatic in origin and working perpendicular to the surface in case of a negative current. By comparison of the effect of positive and negative electric currents, it can be concluded that parallel forces are more effective in stimulating bacterial desorption than perpendicular forces. The results of this study point to a new pathway of cleaning industrial and biomedical surfaces without the use of detergents or biocides.     

丁草胺对水稻土甲烷释放和厌氧细菌的影响

近年来,我国水稻田的化除面积增加很快,除草剂的使用已成为一种必不可少的手段。因而除草剂大量使用的环境污染问题日益突出,对生态系统的平衡产生威胁性影响,引起农产品农药含量超标,或者即使不超标也由于食物链的生物富集最终进入人体危害健康。除草剂致癌、致突变和致畸胎的事实不胜枚举。除草剂在水稻田使用,至少有70％进入土壤,直接影响土壤微生物的生长和代谢。     

Isolation of transcription factors binding auxin response elements using a yeast one-hybrid system

Plant hormones play an important role during higher plant embryogenesis. Auxin is central to the development of vascular tissues, formation of lateral and adventitious roots, control of apical dominance, and tropic responses. Auxin response element (AuxRE), present in the promoters of many auxin-induced genes, can confer auxin responsiveness. Using carrot somatic embryo under specific developmental phase, a cDNA expression library was constructed. Several plasmids were recombined containing the tetramer of AuxRE as a bait. After screening by a yeast one-hy-brid system, one positive clone was confirmed and characterized. Electrophoretic mobility shift assay showed that AxRF1 protein expressed in yeast cell could bind AuxRE in vitro. It suggests that AxRF1 participates in regulation of the expression of auxin responsive gene during carrot somatic embryogenesis.     

Stimulation of regional lymphatic and blood flow by epicutaneous oxazolone.

The application of the epicutaneous antigen oxazolone results in persistent induration and erythema; however, the relative changes in lymph and blood flow in the inflammatory skin are largely unknown. To define the contribution of lymph and blood flow to the clinical appearance of cutaneous inflammation, we studied the sheep ear after the application of oxazolone. As a model for the study of these changes, the sheep ear had several experimental advantages: 1) a simplified superficial vascular network, 2) defined lymphatic drainage, and 3) an avascular and alymphatic cartilaginous barrier. Lymph flow was continuously monitored by cannulation of the prescapular efferent lymph duct. Blood flow, as reflected by cutaneous erythema, was noninvasively measured by use of a visible-spectrum spectrophotometer. The application of the epicutaneous oxazolone resulted in increased ear thickness for >7 days. The lymph flow from the oxazolone-stimulated ear peaked between 24 and 48 h after oxazolone stimulation. Spectrophotometric evaluation indicated that the cutaneous erythema peaked 72-96 h after application of oxazolone. Corrosion casting and scanning electron microscopy of the microcirculation at 96 h after antigen stimulation demonstrated significant dilatation of the superficial vascular network. These results suggest a biphasic response to oxazolone stimulation: 1) an early increase in vascular permeability associated with increased lymph flow and 2) a subsequent increase in relative blood flow associated with a dilated inflammatory microcirculation.     

SYSTEMATICS OF THE CALCIFIED GENERA OF THE GALAXAURACEAE (NEMALIALES,RHODOPHYTA) WITH AN EMPHASIS ON TAIWAN SPECIES1

The current separation of the calcified genera Actinotrichia Decaisne, Galaxaura Lamouroux, and Tricleocarpa Huisman et Borowitzka in the Galaxauraceae is largely based on type of life history (whether the gametophytes and tetrasporophytes are isomorphic or heteromorphic with respect to gross morphology or cortical‐cell features) and on features of postfertilization development (such as the composition of the pericarp). We reexamined the phylogenetic relationships of these genera based on comparative rbcL sequence analysis, types of life cycle, and cystocarp development. Four distinct assemblages have been identified: an Actinotrichia clade, a Tricleocarpa clade, a Galaxaura clade (containing the type species), and a Dichotomaria clade made of a number of formerly Galaxaura species (D. obtusata [Ellis et Solander] Lamarck, D. marginata [Ellis et Solander] Lamarck, and D. diesingiana [Zanardini] Huisman, Harper and Saunders). Key differences between Dichotomaria and Galaxaura include the habit of the gametophytic and tetrasporophytic generations (isomorphic in Dichotomaria and dimorphic in Galaxaura) as well as the presence or absence of a persistent pericarp in the cystocarp (present in Dichotomaria and absent in Galaxaura). Molecular data do not support monophyly for the putatively pantropical species Galaxaura rugosa, Dichotomaria obtusata, and D. marginata, all of which we conclude are in need of taxonomic revision.