云南羯布罗香树脂的化学成分

从云南产羯布罗香(Dipterocarpus tubinatus Gaertn. f.)树脂中分离得到6个三萜化合物,鉴定为羟基达玛烯酮—Ⅱ(hydroxydammarenone-Ⅱ,达玛烯二醇—Ⅱ(dammarenediol—Ⅱ),白桦脂酸(betulonk acid),亚细亚酸(asiatic acid),3,23-O-异丙叉亚细亚酸(3,23-O-isopropylidene asiatic acid)和崩大碗酸(madasiatic acid)。其中崩大碗酸系首次从龙脑香科树脂中分离得到。     

国产五种菊属植物的核型研究

本文对国产5种菊属植物的核型进行了研究,结果为:D. indicum 2n=2x=18=16m 2st,2n=4x=36=28m 6sm 2st;D. lavandulifolium 2n=2x=18=14m 4sm,2n=4x=36=28m 6sm 2st;D. lavandulifolium var.seticuspe 2n=2x=18=12m 6sm;D. chanetii 2n=4x=36=20m 14sm 2st,2n=6x=54=38m 14sm 2st;D. potentilloides2n=2x=18=14m 2sm 2st;D. vestitum 2n=6x=54=38m 16sm.核型分析的结果表明,本文所研究类群中出现的多倍体多为异源多倍体;根据对核型资料、形态特征及地理分布特点的综合分析,作者认为多倍化是菊属野生种进行的主要途径。     

Genomic characterization ofCampylobacter jejuni by field inversion gel electrophoresis

The genome ofCampylobacter jejuni was characterized by field inversion gel electrophoresis (FIGE) after digestion with three rare-cutting restriction endonucleases. The restriction enzymesSac II (5-CCGCGG),Sal I (5-GTCGAC), andSma I (5-CCCGGG) were found to produce 13, 5, and 8 fragments respectively from theC. jejuni genome. The fragment sizes ranged from 1.6 kb to 1300 kb, which gaveC. jejuni a genome size of approximately 1900 kb. Furthermore, thegly A and rRNA genes ofC. jejuni were localized to specific fragments by use of Southern analysis, and thegly A gene was shown to be closely linked to one of the three rRNA genes.     

大鼠离体乳头肌收缩末期张力—长度关系的曲线性

大鼠离体左室乳头肌固定于最适初长位,逐步递减“后荷”获得一系列等张收缩的张力、长度缩短程度和速度。结果发现:(1)收缩末期张力-长度关系(ESTLR)为指数曲线,回归方程 T=ar~(-bL)-K 拟合的优度明显高于线性方程拟合的优度(P<0.001),其中 a,k 分别代表总张力和静息张力,b 为曲线的弯曲度;(2)在高钙(4mmol/L)或去甲肾上腺素(NE10~(-6)mol/L)作用下,ESTLR 右上移位,a,b 和无张力缩短速度 L_O 均增大(P均<0.01),尤以高钙时的变化更明显,(3)NE 使张力-速度曲线的右上移位比高钙显著。这提示大鼠离体心肌的 ESTLR 呈非线性特征,参数 a,b 及长度轴截距 L_O 对收缩强度的变化敏感,但对收缩速度改变的敏感性可能比经典的力学指标低。     

刺激大鼠迷走神经向中端对其不同脑区5-HT含量的影响

采用荧光分光光度法,测定脑内5-HT的含量,观察电刺激两侧颈迷走神经向中端对大鼠海马、下丘脑和中-桥脑内5-HT含量的影响,结果如下:(1)刺激迷走神经向中端后,三脑区的5-HT含量均显著增加(P<0.05-0.005);(2)侧脑室内注射新斯的明(10μg/10μl)或烟碱(10μg/10μl)后,刺激迷走神经向中端使三脑区5-HT含量增多的效应显著提高(p<0.01-0.001);(3)侧脑室内注射六烃季胺(250μg/10μl)后,刺激迷走神经向中端使三脑区5-HT含量增多的效应显著下降(p<0.05-0.005);(4)侧脑室内注射阿托品(10μg/10μl)或纳洛酮(10μg/10μl)后,不影响刺激迷走神经向中端引起的三脑区5-HT含量增多的效应(p>0.05)。由此看来,迷走传入冲动很可能先使脑内Ach释放增多,然后,Ach作用于N-胆碱受体而导致海马、下丘脑和中-桥脑内5-HT含量增加。以上结果表明,在脑内,迷走传入纤维和5-HT能神经元之间可能存在着机能联系。     

消炎痛及PGF_(2α)对在体培养人子宫内膜出血的影响

利用甾体激素撤退方法造成移植在地鼠颊囊内人子宫内膜出血的动物模型,研究消炎痛和PGF_(2a)对内膜出血的作用。结果表明,注射三种不同剂量消炎痛并不能完全抑制内膜出血,但对内膜出血时间有延缓作用。用两种不同剂量的PGF_(2a)采取缓慢释放给药方法,虽然地鼠在给药后外周血液中PGF_(2a)水平比给药前显著增高,但内膜出血并不出现在撤退甾体激素之前。结果提示,PGF_(2a)对内膜血管破裂无直接作用,而纤溶活性变化可能是触子宫内膜出血更直接的原因。     

Primary sequence mapping of human apolipoprotein B-100 epitopes. Comparisons of trypsin accessibility and immunoreactivity and implication for apoB conformation

Differential trypsin-accessibility and monoclonal antibodies (Mabs) to human apolipoprotein (apo) B-100 are both important tools for probing apoB structure and conformation on low-density lipoproteins (LDL). In this study, we have mapped greater than 80% of the C-terminal region (720 residues) of LDL apoB-100 using trypsin digestion. Our results extend our previous data [Yang et al. (1986) Nature (Lond.) 323, 738-742] confirming that the C-terminal region of about 420 residues of apoB-100 is largely inaccessible to trypsin, whereas the part just preceding this region has interspersed trypsin-accessible and inaccessible peptides. We have determined the amino acid sequence of specific apoB-100 peptides containing epitopes recognized by four separate Mabs: two epitopes have been mapped to within 20 residues, one has been mapped to 36 residues, and the last to 80 residues. We used polyclonal antisera to identify 16 overlapping clones of varying lengths of apoB-100 cDNAs extending from the C-terminus of apoB-100 cloned in the expression vector, lambda gt11. These clones were then tested against individual Mabs. By nucleotide sequence analysis of overlapping clones that show differential reactivities to different Mabs, we have mapped the individual epitopes of each Mab to within about 50-150 amino acid residues predicted from the DNA sequences. Confirmation and further fine mapping were accomplished by competition for LDL binding using partially purified fusion proteins and chemically synthesized oligopeptides. Two epitopes (Mabs 7 and 22) were mapped to the C-terminal 20 amino acids of apoB-100, one (Mab 16) to residues 4154-4189, and another (Mab 20) to residues 3926-4005. Mab 16 precipitates more than 80% of LDL particles. Mab 20 precipitates only denatured apoB but not native LDL apoB [Milne et al. (1987) Mol. Immunol. 24, 435]. Mabs 7 and 22 are unique in that they precipitate LDL apoB modified by storage much better than freshly isolated LDL-apoB. Although epitope expression and trypsin-accessibility represent two useful probes for the study of protein conformation, there was no obvious correlation between these two parameters when applied to LDL apoB for the antibodies we have examined.     

The effect of repetitive haemorrhage on plasma cortisol, beta-endorphin and N-terminal pro-opiomelanocortin in conscious sheep

We measured the effect of repeated haemorrhagic stress, performed on four consecutive days in conscious adult sheep, on the plasma concentrations of cortisol and ACTH-related peptides to determine whether the pituitary-adrenal response was altered by stress repetition. Peptides from the C-terminus of the ACTH pro-hormone was measured by beta-endorphin RIA. Glycopeptides derived from the N-terminus of the ACTH pro-hormone were measured by tau 3-MSH RIA. The immunoreactive tau 3-MSH in sheep plasma was found to have an apparent molecular weight of approximately 10,000 by gel chromatography through Sephadex G-75, which is similar to the size of the major circulating form of pro-tau-MSH found in human and rat plasma. Daily haemorrhage consistently elevated plasma concentrations of cortisol and pro-tau-MSH. There was no significant difference in the daily responses of either cortisol or pro-tau-MSH when considered individually. However, there was a significant change over the four days in the relationship between the cortisol and pro-tau-MSH responses, as judged by analysis of variance of the difference in daily z-scores of cortisol and pro-tau-MSH. This trend indicated a relative increase in the secretion of pro-tau-MSH from the pituitary compared to the cortisol response, and suggested that repeated exposure to stressful stimuli may alter the pituitary-adrenal-axis.     

pH dependence of the tryptophan fluorescence in cytochrome c oxidase: further evidence for a redox-linked conformational change associated with CuA

When the low-potential metal centers of cytochrome c oxidase are reduced, the enzyme undergoes a conformational transition that shifts the fluorescence maximum of the emitting tryptophan residues from 329 to 345 nm. At pH 7.4, the change in this tryptophan fluorescence intensity is a nonlinear function of the electron equivalents added to the cyanide-inhibited enzyme. This nonlinear behavior is a result of the difference in redox potential between cytochrome a and CuA, which, at equilibrium, favors electron occupancy at cytochrome a. Studies on the cyanide-inhibited enzyme suggest that the conformational change is associated with reduction of CuA [Copeland, R. A., Smith, P. A., & Chan, S. I. (1987) Biochemistry 26, 7311-7316]. In this work we present tryptophan fluorescence data for the cyanide-inhibited enzyme at pH 8.9. Because of the pH dependence of the midpoint potential of cytochrome a in this form of the enzyme, the two low-potential centers become virtually isopotential at pH 8.9. The results obtained confirm our earlier conclusion that the observed conformational change is linked to the reduction of CuA only, rather than to the redox activity of both low-potential metal centers. We find that, in partially reduced cyanide-inhibited oxidase, raising the pH from 7.4 to 8.9 results in an intensification and red shift of the enzyme's tryptophan emission as the electron occupancy redistributes from cytochrome a to CuA. Moreover, when the fluorescence change is plotted as a function of the number of electrons added to the enzyme at pH 8.9, the data fit the nearly linear function expected for a conformational change triggered by reduction of CuA exclusively.     

Locomotory characteristics of Treponema denticola

Locomotion of pathogenic spirochetes has been suggested as a virulence factor in their pathogenesis. Little is known of the locomotory characteristics of oral anaerobic spirochetes. We have determined the optimal conditions for motility of seven strains of Treponema denticola in menstrua of different viscosities. The viscosity for optimum motility for all strains was found to be 9.57 centipoises at 25 degrees C. Under these conditions the average speeds for each strain was computed from the motility tracks as recorded by timed exposures under dark-field microscopy. Differences in speeds were found between the various strains. In addition, we have determined the "persistence" (direct distance/actual pathlength travelled) of cell movement of each strain. Interstrain differences were also noted. These locomotory characteristics contribute to the locomotory phenotypes of the various strains and therefore may aid in their characterization and provide an insight into locomotion as a virulence factor in periodontitis.