家兔面神经后核内侧区在呼吸节律起源中的作用

从腹侧面暴露家兔延髓,脑内微量注射1%普鲁卡因阻滞面神经后核内侧区(mNRF),全部动物(n=20)一次注射(0.3—1.0μl)后即能可逆地消除呼吸节律。区域对照显示此区非常局限,范围约1.0×1.0×1.0mm。组织学检查表明为面神经后核内侧区。本文分析了 mNRF的呼吸相关神经元(RRNs)的放电形式。在 mNRF 有较多的呼气(E)神经元和呼气-吸气跨时相(E-IPS)神经元。在阻滞 mNRF 引起呼吸停止期间,观察到低位延髓背侧呼吸群(DRG)和腹侧呼吸群(VRG)尾端区 RRNs 放电的节律性消失,表现连续放电或停止放电。电刺激DRG,VRG 尾端区,只能诱发短串的膈神经放电,而不能产生节律性发放。说明这些区域的RRNs 无自动节律性活动的能力。结果表明,面神经后核内侧区与呼吸节律发生有关,它可能是呼吸节律发生器的一个重要的所在部位。     

刺激大鼠下丘脑室旁核激活的中脑中央灰质神经元对躯体传入的反应

电刺激大鼠下丘脑室旁核(PVH),在同侧中脑中央灰质(CG)内寻找逆行及顺行反应单位,然后观察它们对躯体感觉刺激的反应。实验结果表明:CG 及邻近网状结构内有10%(32/318)的单位呈逆行反应。逆行传导速度平均为0.37±0.24m/s(均数±标准差);推测这种CG→PVH 投射纤维属于细有髓或无髓神经纤维。这些单位分布于 CG 的腹外侧及背外侧亚核。50%(14/28)的逆行单位对坐骨(胫)神经的强电刺激和夹尾等损伤性刺激起反应,但对触毛或低强度的神经干刺激无明显反应。以上结果表明:外周躯体感觉,特别是损伤性信息传入 PVH 时,CG 是其中枢驿站之一。电刺激 PVH 还能顺行激活7.55(24/318)、抑制0.7%(2/318)的 CG 单位。有69%(18/26)的顺行反应单位对外周躯体神经强电刺激及夹尾起反应。提示 PVH 可能通过影响 CG神经元的活动而参与中枢痛觉的整合。     

Presynaptic regulation of dopaminergic transmission in the striatum

1. In vitro studies have indicated that several transmitters present in the striatum can regulate presynaptically the release of dopamine (DA) from nerve terminals of the nigrostriatal DA neurons. 2. The receptors involved in these local regulatory processes are located or not located on DA nerve terminals. 3. Recent in vivo investigations have demonstrated that the corticostriatal glutamatergic neurons facilitate presynaptically the release of DA and have allowed the analysis of the respective roles of presynaptic events and nerve activity in the control of DA transmission.     

黑质升压和弓状核降压效应及二者间的机能联系

本工作用神经元胞体兴奋剂L-谷氨酸钠(Glu)注入箭毒化、人工呼吸大鼠的下丘脑弓状核(AR),引起血压下降,心率减慢;多巴胺(DA)受体激动剂去水吗啡注入AR和Glu注入黑质(SN)均产生升压和加速心率的效应,Glu(i.SN)效应可被DA受体阻断剂氟哌啶醇注入双侧AR阻断;从而证明:(1)AR具有降压、降心率功能;(2)黑质可通过AR内的DA受体对AR降压、降心率效应起抑制作用,而实现其加压、加速心率效应。     

躯体和内脏传入冲动在大鼠束旁核内的会聚

在麻痹的大鼠上,分别刺激迷走神经、内脏大神经、坐骨神经、腓肠神经、睾丸和副睾,在对侧丘脑束旁核记录到了45个细胞的单位放电。根据诱发反应的潜伏期、时程和放电频谱分布的不同,可将他们分为五种类型,并且认为这些类型和刺激引起的感觉性质有关。在观察到的45单位中,29个的反应具有痛放电的特性,而且对躯体及内脏的传入冲动呈聚合性反应。其中2个单位只对内脏传入冲动产生反应。这项研究的结果表明,束旁核不仅是接受内脏传入的丘脑结构,而且也是一个整合内脏与躯体传入信息的中枢。     

Surface interactions of gamma-crystallins in the crystal medium in relation to their association in the eye lens

A comparative study of intermolecular interactions in crystals of two homologous low molecular weight proteins, gamma-II and gamma-IIIb crystallins, from calf eye lens was carried out. Crystal packings for these proteins are very different: intermolecular contact areas compose about 33% of the total accessible surface area of gamma-II as compared with 13% in gamma-III. Two key residues seem to be mainly responsible for the differences in protein association in the crystal medium. These are Ser 103 and Leu 155 in gamma-II, which are replaced by Met 103 and His 155 in gamma-IIb. A similar substitution of these residues is observed in different gene products of gamma-crystallins from a number of vertebrates. This is consistent with the existence of a genetically controlled mechanism for determining intermolecular association of gamma-crystallins in the native medium of the lens.     

Freeze-substitution improves the ultrastructural preservation of legume root hairs

The freeze-substitution method was applied toVicia hirsuta root hairs to test its effectiveness in improving preservation of the cell ultrastruture. Freeze-substitution almost certainly represents more faithfully the structure of the hair cell. A previously unreported ‘pyriformis’ vesicle is described. Also unique to freeze-substituted material are coated secretory vesicles; a smooth plasma membrane profile; mitochondrial ribosomes; long microfilament bundles which are associated with vesicles, mitochondria, coated pits and coated vesicles; microtubule-associated filaments; well-preserved coated vesicles and coated pits with enclosing rings; a pliciform nucleus. The results are discussed in context of previous reports using conventional fixation techniques.     

In situ hybridization of corticotropin-releasing factor-encoding messenger RNA in the hypothalamus of the white sucker,Catostomus commersoni

Summary In situ hybridization procedure with a ³²P-labelled synthetic oligonucleotide probe was used to detect corticotropin-releasing factor-encoding messenger RNA (CRF mRNA) in the hypothalamus of the white sucker, Catostomus commersoni. Adjacent sections were immunostained by a sucker CRF-specific antiserum. CRF mRNA-containing neurons were identified by autoradiography in the magnocellular and parvocellular subdivisions of the preoptic nucleus (PON). Many of these neurons were also immunostained by sucker antiserum, showing the same distribution patterns. These results confirm the presence of CRF mRNA and CRF peptide in the white sucker hypothalamus and support the view that the magnocellular and parvocellular neurons of the PON may be involved in the control of adrenocorticotropic hormone secretion from the pituitary in the white sucker.     

Three-dimensional structure of the quinoprotein methylamine dehydrogenase from Paracoccus denitrificans determined by molecular replacement at 2.8 A resolution.

The three-dimensional structure of the quinoprotein methylamine dehydrogenase from Paracoccus dentrificans (PD-MADH) has been determined at 2.8 A resolution by the molecular replacement method combined with map averaging procedures, using data collected from an area detector. The structure of methylamine dehydrogenase from Thio-bacillus versutus, which contains an "X-ray" sequence, was used as the starting search model. MADH consists of 2 heavy (H) and 2 light (L) subunits related by a molecular 2-fold axis. The H subunit is folded into seven four-stranded beta segments, forming a disk-shaped structure, arranged with pseudo-7-fold symmetry. A 31-residue elongated tail exists at the N-terminus of the H subunit in MADH from T. versutus but is partially digested in this crystal form of MADH from P. denitrificans, leaving the H subunit about 18 residues shorter. Each L subunit contains 127 residues arranged into 10 beta-strands connected by turns. The active site of the enzyme is located in the L subunit and is accessible via a hydrophobic channel between the H and L subunits. The redox cofactor of MADH, tryptophan tryptophylquinone is highly unusual. It is formed from two covalently linked tryptophan side chains at positions 57 and 107 of the L subunit, one of which contains an orthoquinone.     

Hidden smectic properties of a chiral side-chain co-oligomer

We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature.