第三脑室注射组胺及其受体激动剂对五肽促胃液素诱导的大鼠胃酸分泌的影响

本文报道第三脑室注射组胺(0.25—2.0μg/5μl)对五肽促胃液素诱导的胃酸分泌的双重影响。雄性Wistar大鼠,重200—300g,戊巴比妥钠腹腔麻醉。用37℃生理盐水通过恒流泵进行连续胃灌流。在静脉恒速灌注五肽促胃液素(7.5μg/kg·h)的基础上,第三脑室注射组胺(0.25μg/5μl)或H_1受体激动剂2-Pyridylethylamine(PEA,10μg/5μl),10min后总酸排出量即开始减少,90min仍未恢复。组胺剂量增至1.0μg或2.0μg时,出现双重效应。部份动物(分别占73％或50％)胃酸分泌减少,另一部分动物(27％或50％)胃酸分泌增多。H_2受体激动剂dimaprit(10μg/5μl)或impromidine(0.1μg/5μl)对胃酸分泌无明显影响。苯海拉明(16μg/0.2ml或32μg/0.2ml,i.m.)预处理可分别取消组胺和PEA的抑胃酸效应。这些结果提示:脑内组胺可能参与胃酸分泌中枢调节。其抑制效应似通过H_1受体介导;双重效应的机制有待进一步研究。     

鹅掌楸种子和胚胎发育的研究

应用控制授粉、软 X-射线法、常规石蜡制片法和荧光检测等手段,研究了鹅掌楸(Lirio-dendron chinense(Hemsl.)Sarg.胚胎发育和控制授粉与结籽率的相关性。控制授粉后2小时花粉萌发,6小时萌发率最高,柱头可授期持续30小时左右。花粉管借助于柱头毛之间的分泌物进入柱头沟,经花柱沟、珠孔塞和珠心冠原进入胚囊,行珠孔受精。授粉后2周,胚乳为2至3细胞厚的狭组织;第6周,胚乳充满胚囊腔,珠心随之解体殆尽;第7到8周,球形胚、心形胚发生;第14到16周,子叶形成;第22周种子或熟,胚乳丰富。单株自然授粉结籽率不足1%。控制授粉后,单个聚合果的最高结籽率可达39%,9个聚合果的平均结籽率为17.7%。     

若干种枝角类卵鞍表面亚显微结构的比较研究

以扫描电镜对发头裸腹溞、蚤状溞、隆线溞指名亚种以及隆线溞东湖一亚种的卵鞍分别进行了比较研究,发现卵鞍表面的亚显微结构有明显的差异,但亚种之间差异较小。隆线溞指名亚种与隆线溞东湖一亚种二者的卵鞍在光学显微镜下看不出有什么差异,然而亚显微结构却互不相同。这就为东湖一新亚种的确定提供了一项可靠的依据,同时也进一步证实卵鞍的超微结构确可作为枝角类分类的表征。     

Use of an organic buffer for the selection of acid tolerantRhizobium meliloti strains

Summary Nine media used to grow rhizobia were examined for their ability to maintain a stable low pH during the growth ofR. meliloti Large fluctuations in the pH of all media were recorded within 72 h, indicating their unsuitability for use in the selection of acid tolerant rhizobia. Morpholino-ethanesulphonic acid (MES) was assessed for its ability to buffer the pH of the media whilst still permitting rapid growth ofR. meliloti, R. trifolii, andBr. lupini. With 30.7 mM MES, the pH of a defined medium containing galactose, arabinose, and glutamate did not change from the initial value of 5.5 even though rhizobial numbers increased from 10⁴ to 10⁹ cells.ml^–1. Even at a buffer concentration of 15.3 mM, pH only increased from 5.5 to 5.6. There was no effect of the buffer on rhizobial growth.     

Personal reflections on the nature of intelligence in humans and machines

Computers, the human mind, and social systems have common problems of inadequate memory and insufficient data manipulation speed. In each of these domains, information compression techniques have evolved to reduce storage and processing needs. Among the techniques for information compression, coding of information in procedures stands out as exceptionally powerful. Procedural information coding also gives rise to behavior that may be defined as intelligent. It is found in the human mind, in machines and in social systems. Its use in human thought is aided by language development which promotes regular review of abstract procedures. A practical consequence of better understanding of procedural information coding is the possibility of training people to exhibit greater mental capacity, a controversial possibility. This paper explores the impact of data processing resource limitations, data compression and procedural thinking in men and machines.     

Production of second generation triploid and tetraploid rainbow trout by mating tetraploid males and diploid females — Potential of tetraploid fish

Summary First generation tetraploids were produced by hydrostatic pressure treatment before the first cleavage and raised until the adult stage. Their survival and growth were severely depressed when compared to the diploid control: after two years, no ovulated females were found although males produced sperm at 1 and 2 years of age and were mated individually with diploid females. The progenies were consistently normal with high survival rates. They were found to be almost all triploids by karyology, which failed to detect a significant rate of aneuploidies. However, the fertilizing ability of tetraploid males was always low (0 to 97% of the control; average 40%). Several arguments presented here support the hypothesis that diploid spermatozoas, which are wider than haploid ones, would be frequently blocked during their penetration through the micropyle canal. Second generation tetraploids were produced after such matings by heat shocks, causing the retention of the second polar body. Their survival and growth were much more satisfactory than in the first generation, although still lower than in diploid and triploid controls issuing from diploid parents. Performances of second generation triploids were comparable to those of diploids, and slightly better than those of conventional triploids issuing from diploid parents. 94.5% of the second generation tetraploids were male.     

Predation on artificial,solitary and aggregated wader nests on farmland

Predation rates on artificial wader nests, solitary curlew (Numenius arquata) and lapwing (Vanellus vanellus) nests and lapwing nests in colonies were studied on a farmland site in central Sweden. Predation rates were highest on artificial wader nests, intermediate on solitary curlew and lapwing nests and lowest on lapwing nests in colonies, probably because of active defence of adults at real nests and/or because of selection of nest sites with lower predation risk by breeding birds. A comparison of nests close to (50 m) and far away from (200 m) forest edges revealed no increased predation risk close to edges for any of the studied nest types. Predation risk changed during the season for artificial nests (highest in the middle of May), while predation rates on lapwing and curlew nests were more stable. Artificial nests seem to be inappropriate for measuring actual predation rates and temporal differences in predation rates on real nests, but they might be suitable for use as an index of spatial differences.     

芸苔属脱外壁花粉的分离与人工萌发

芸苔属青菜（Ｂｒａｓｓｉｃａ ｃｈｉｎｅｎｓｉｓ）与紫菜苔（Ｂ． ｃａｍ ｐｅｓｔｒｉｓｖａｒ． ｐｕｒｐｕｒｅａ）的花粉经低温水合、热激、渗激三步程序,分离出大量具萌发能力的脱外壁花粉,脱外壁率可高达６０％ 以上。在含有碳源与氮源及Ｒｏｂｅｒｔｓ培养基盐成分的碱性ＰＥＧ 培养基中,首次使芸苔属脱外壁花粉萌发,萌发率可达３３％ ～４１％ 。在扫描电镜下观察了花粉脱外壁与萌发的过程。讨论了不同植物花粉脱外壁的方法与花粉壁生物学特点的对应关系,以及外壁对花粉萌发的可能作用     

Transmembrane movements of artificial redox mediators in relation to electron transport and ionic currents in chloroplasts

Electrochemical data obtained with TMPD⁺-sensitive electrodes indicate that ammonium-uncoupled chloroplasts retain TMPD (N,N,N',N'-tetramethyl- p -phenylenediamine) mainly in the reduced form during illumination, whereas uncoupled DCMU-treated chloroplasts accumulate TMPD in the oxidized form (TMPD⁺). This observation indicates that the reduced plastoquinol is the preferred electron donor for photosystem I (PSI) and TMPD can only compete efficiently when plastoquinone reduction is blocked. After adding DCMU the formation of a transmembrane gradient for TMPD⁺ is reflected by a slow-down of the electrogenic electron transport and by the emerging of the overshoot of the membrane current in the light-off response. A light-dependent increase in photoelectric current generated by chloroplasts in the presence of NH₄Cl and TMPD is observed and considered to be caused by a reversible release of current limitation in the interfacial conductance barriers in the lumen.     

病毒基因组启动子识别的人工神经网络方法

本文运用神经网络方法,并结合病毒基因分子生物学有关理论与统计事实,对病毒基因启动子区域进行了识别,文中选择了共35个基因组,作为研究对象．学习组选择了28个基因组,预测组选择了7个基因组,结果表明,将神经网络模型与病毒基因有关理论相结合,能够运用计算方法,以大量的可能启动子组合中排列出唯一的启动子区域．