TDZ-induced high frequency plant regeneration through multiple shoot formation in witloof chicory (<Emphasis Type="Italic">Cichorium intybus</Emphasis> L.)

A very efficient and rapid regeneration system via multiple shoot formation was developed for Cichorium intybus L. when leaf explants excised from sterile seedlings were cultured on medium supplemented with different concentrations and combinations of various plant growth regulators. In a comparison of leaf lamina and petiole explants, lamina explants produced over three times more shoots than petiole explants, with a mean of 7.5 shoots compared to 2.4. Of the combinations of KIN/IAA, KIN/NAA, BAP/IAA, or BAP/NAA, 0.5 mg l⁻¹ KIN combined with 0.3 mg l⁻¹ IAA was the most effective, producing a mean of 19.7 shoots per lamina explant while the control treatment involving no plant growth regulators produced no shoots at all. When either cytokinin was used alone, BAP was found nearly twice more successful than KIN. However, the most effective treatment of all was the combination of 0.01 mg l⁻¹ TDZ and 1.0 mg l⁻¹ IAA, producing as many as 35.8 shoots per lamina explant. This rate of shoot regeneration is remarkably higher than those previously reported for C. intybus, most likely due to the highly inductive effect of TDZ, which was tested for the first time in this species. Rooting of the shoots was readily achieved on medium containing different concentrations of IAA or IBA. IAA was more effective than IBA and resulted in the highest frequency of shoots that rooted (100%) and mean number of roots per shoot (4.2) when used at 0.5 mg l⁻¹. Hardening off process resulted in a production of more than 80% healthy plantlets.     

PtK2细胞的核骨架—核纤层——中间纤维体系

本文用选择性系列抽提的方法结合整装细胞电镜技术和DGD包埋-去包埋超薄切片技术,在电镜下清晰地显示了PtK 2细胞的核骨架-核纤层-中间纤维体系的精细结构。处于分裂中期的细胞经抽提后可以看到,染色体残余与中间纤维仍然保持一定的联系。用免疫荧光技术对抽提后的PtK 2细胞进行分析结果表明:其中间纤维能同时与AE1和AE3反应;能与Lamin B反应的单抗可以特异地定位于其核周,而Lamin A(C)的单抗除了与其核纤层蛋白有很强的反应外还与中间纤维有交叉反应。此外,在分裂期细胞中可以看到Lamin A(C)可能与染色体能特异结合;与HeLa细胞不一样。PtK 2细胞的核骨架成份不能与280kD的核骨架蛋白单抗反应。双向电泳结果显示出PtK 2细胞的核骨架-核纤层-中间纤维体系的组成成份与HeLa细胞相比有较大的差异,而且这种差异主要反映在核骨架组份上,TdR的处理也能导致其组份发生变化。     

核纤层蛋白的研究进展

核纤层普遍存在于高等真核细胞的细胞核中,向外与内层核膜上的蛋白结合,向内与染色质的特定区段结合,其主要成分是核纤层蛋白。核纤层蛋白主要参与细胞核的形状和大小的维持、核膜的组织、DNA的复制及有丝分裂。近年来的研究表明,核纤层蛋白与许多人类疾病密切相关。目前,核纤层蛋白在人类的各种组织和细胞中已有比较系统的研究,并且呈组织特异性及发育时序性表达。本文将就核纤层的最新研究进展做一综述。     

Laminin Network Formation Studied by Reconstitution of Ternary Nodes in Solution

The polymerization of laminins into a cell-associated network is a key process in basement membrane assembly. Network formation is mediated by the homologous short arm tips of the laminin heterotrimer, each consisting of a globular laminin N-terminal (LN) domain followed by a tandem of laminin-type epidermal growth factor-like (LEa) domains. How the short arms interact in the laminin network is unclear. Here, we have addressed this question by reconstituting laminin network nodes in solution and analyzing them by size exclusion chromatography and light scattering. Recombinant LN-LEa1–4 fragments of the laminin α1, α2, α5, β1, and γ1 chains were monomeric in solution. The β1 and γ1 fragments formed the only detectable binary complex and ternary complexes of 1:1:1 stoichiometry with all α chain fragments. Ternary complex formation required calcium and did not occur at 4 °C, like the polymerization of full-length laminins. Experiments with chimeric short arm fragments demonstrated that the LEa2–4 regions of the β1 and γ1 fragments are dispensable for ternary complex formation, and an engineered glycan in the β1 LEa1 domain was also tolerated. In contrast, mutation of Ser-68 in the β1 LN domain (corresponding to a Pierson syndrome mutation in the closely related β2 chain) abolished ternary complex formation. We conclude that authentic ternary nodes of the laminin network can be reconstituted for structure-function studies.     

The number and arrangement of elements in the lamina cartridge of the dragonfly Sympetrum rubicundulum

Summary Five monopolar cells and two long visual fibres are a consistent component of the lamina cartridge of the ventral half of the eye of the dragonfly Sympetrum rubicundulum. They communicate with the chiasm via a cartridge axon bundle comprising a minimum of ten fibres. The arrangement of these elements is documented with respect to the ommatidial photoreceptor axon bundle innervating them. These relationships are described both within the lamina cortex and in the cross-section of the underlying cartridge.     

贵州凯里生物群中的宏观藻类化石丘尔藻(Chuaria)及其意义

丘尔藻Chuaria Walcott,1899是宏观藻类中研究最早、延续时限最长的一类宏观藻类化石,它是新元古代赵家山生物群、淮南生物群及西陵峡动物群的代表分子之一.寒武纪第3世凯里生物群中Chuaria化石的产出,不仅是其最年青的代表,也是凯里生物群中宏观藻类组合中较为重要的分子之一.凯里生物群中Chuaria化石呈...     

Direct Synthesis of Lamin A,Bypassing Prelamin A Processing,Causes Misshapen Nuclei in Fibroblasts but No Detectable Pathology in Mice

Lamin A, a key component of the nuclear lamina, is generated from prelamin A by four post-translational processing steps: farnesylation, endoproteolytic release of the last three amino acids of the protein, methylation of the C-terminal farnesylcysteine, and finally, endoproteolytic release of the last 15 amino acids of the protein (including the farnesylcysteine methyl ester). The last cleavage step, mediated by ZMPSTE24, releases mature lamin A. This processing scheme has been conserved through vertebrate evolution and is widely assumed to be crucial for targeting lamin A to the nuclear envelope. However, its physiologic importance has never been tested. To address this issue, we created mice with a “mature lamin A-only” allele (Lmna^LAO), which contains a stop codon immediately after the last codon of mature lamin A. Thus, Lmna^LAO/LAO mice synthesize mature lamin A directly, bypassing prelamin A synthesis and processing. The levels of mature lamin A in Lmna^LAO/LAO mice were indistinguishable from those in “prelamin A-only” mice (Lmna^PLAO/PLAO), where all of the lamin A is produced from prelamin A. Lmna^LAO/LAO exhibited normal body weights and had no detectable disease phenotypes. A higher frequency of nuclear blebs was observed in Lmna^LAO/LAO embryonic fibroblasts; however, the mature lamin A in the tissues of Lmna^LAO/LAO mice was positioned normally at the nuclear rim. We conclude that prelamin A processing is dispensable in mice and that direct synthesis of mature lamin A has little if any effect on the targeting of lamin A to the nuclear rim in mouse tissues.     

Sur la vascularisation de la lame terminale humaine

Résumé La lame terminale de l'homme, comme celle de nombreuses classes de vertébrés, est occupée par un système vasculaire remarquable.A partir de sources artérielles constituées dans les cas les plus typiques de quatre pédicules, un réseau capillaire superficiel tapisse la face pie-mérienne ou antérieure de la lame terminale; le sang de ce réseau est drainé dans un réseau profond formé de capillaires sinusoides groupés en anses ou en boucles dans la partie haute de l'organe, tandis que sa partie basse est occupée par un vaste plexus. Le sang du réseau profond gagne ensuite des veines communes à d'autres régions hypothalamiques qui se déversent dans le système des veines cérébrales antérieures.L'aspect des vaisseaux de la lame terminale et leur organisation particulière permet de penser qu'ils interviennent dans la fonction encore inconnue de l'organe vasculaire de la lame terminale.

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On the vascularisation of the lamina terminalis in the human

Summary The human supra-optic crest like that of numerous classes of vertebrates, has a highly differentiated vascular system.From the arterial supply usually consisting of four pedicles, a superficial capillary network covers the pia-mater or anterior side of the supra-optic crest. The blood in this superficial network is drained into a deep network made up of sinusoidal capillaries in loops or whirls, situated in the upper part of the organ, whereas in the lower part a vast plexus is to be found. The blood from the deep network then flows into veins which also drain other hypothalamic regions and then flow into the anterior cerebral veinous system.The appearance of the vessels of the supra-optic crest and their special arrangement seems to indicate that they play a part in the as yet unknown function of the vascular organ of the supra-optic crest.

     

Peripheral sympathetic innervation and serotonin cells in the habenular region of the rat brain

Summary The pineal gland of the rat is located near the brain surface and is via a slender stalk connected to lamina intercalaris which constitutes a cell formation between the habenular and posterior commissures, continuing to the subcommissural organ. The stalk and lamina intercalaris, like the pineal proper, exhibited a yellow, formaldehyde-induced fluorescence which showed the histochemical and pharmacological properties of 5-HT. All these structures were richly supplied with catecholamine-fluorescent nerves which could be further followed rostrally from lamina intercalaris, mixing with the non-fluorescent commissural fibres and stria terminalis, into the medial habenular nucleus in which they extensively supplied both blood vessels and non-fluorescent nerve cells. Cytospectrofluorometric and chemical analysis suggested that the fluorescent nerves stored noradrenaline. This was supported by the finding that they disappeared after bilateral cervical sympathectomy (as did the fluorescent nerves in the pineal complex). In the medial habenular nucleus also catecholamine-containing and 5-HT-containing nerves of central origin were present.The occurrence of a rich, peripheral sympathetic innervation in the medial habenular nucleus of the brain offers possibilities for a previously not observed sympathetic influence on this nucleus. Also the arrangement, and the apparent continuity of the sympathetic innervation in the pineal gland, the lamina intercalaris, and the medial habenular nucleus, suggests some functional interconnection or coordination between these structures.