IS THE PREDOMINANT PERIOD OF CELL ARREST AND PRESENCE OF ENDOREDUPLICATED CELLS COINCIDENT WITH PRODUCTION OF SECONDARY VASCULAR TISSUES IN INTACT AND CULTURED ROOTS OF RAPHANUS SATIVUS L.?

Experimental results show that predominant cell arrest in G2 and the presence of endoreduplicated cells are coincident with presence of secondary vascular tissues while preponderant cell arrest in G1 and absence of polyploid cells are coincident with an absence of secondary vascular tissues in mature root tissues of intact and cultured roots of Raphanus sativus L. In mature tissues of intact seedling roots, most cells arrest in G2, and both polyploid cells and secondary vascular tissues are present. If excised roots are grown on simple medium, most mature cells arrest in G1, none undergo endoreduplication, and only primary vascular tissues are present. When bases of these excised roots are later placed in a medium with auxin, cytokinin, and myo-inositol that produces secondary vascular tissues in vitro, preponderant cell arrest occurred in G2 with some polyploid cells. The general relationship of predominant period of cell arrest, presence of polyploid cells, and presence of secondary vascular tissues in mature roots among plants of various taxa is surveyed.     

Change in the Concentration and Tissue localization of Endogenous IAA During the Regeneration of Vascular Tissues After Xylem Removal in Broussonetia papyrifera

Change in the concentration of endogenous IAA was monitored with enzyme-linked immunesorbent assay (ELISA), and IAA localization in the tissues was demonstrated by means of immunogold-silver microscopy, with authors' modification, during the regeneration after removal of xylem in Broussonetia popyrifera (L.) Vent. The stimulation exerted from xylem removal produced a rapid increase of about 70% of the endogenous IAA concentration. However, the concentration decreased during differentiation of the vascular tissues. Although removal of the tree crown inhibited the regeneration of vascular tissues, the change tendency in the concentration of endogenous IAA during the regeneration remained the same as if the tree crown was intact. This suggested that rapid increase of endogenous IAA induced by wounding could be a result from a release of the combined form into free IAA. Tissue-localization showed that there were more silver-grains labelled in the rays, callus and the regenerated differentiating vascular tissue cells than in other tissues. It could suggest that the high concentration of endogenous IAA triggered the dedifferentiation of the vascular tissues after removal of xylem, and the less concentrated IAA flow could promote the initiation and activity of the regenerated cambium.     

Tissue Differentiation of the Regeneration Rind in Jerusalem artichoke Stem

In trees, after removal of the bark, the vascular tissues of the newly-formed bark usually developed as a continuous layer. However, the stem of the herbaceous Jerusalem artichoke, after girdled, gives rise to regeneration of many irregularly arranged vascular bundles. Early July is the best time for girdling as the vascular bundles are well-developed, One week after girdling, some small groups of vascular tissues appeared in callus. Later on the vascular bundles eventually grew close together sooner or later, yet there were some wide pith rays which separated the various sized vascular bundles and exhibited irregularly contours. From these experiments, it is further evidenced that tile stem of herbaceous plants can also be girdled and regenerates a new rind. Furthermore, the girdled portion of this plant regenerates the vascular tissues which in a rather different way from all the plants that previously studied.     

Histological study of nodule morphogenesis fromCichorium intybus L. leaves cultivatedin vitro

Summary Chicory root, stem, and leaf tissues have the propensity to regenerate organogenetic nodules following a wounding treatment. Using histological methods, we described this phenomenon on leaves ofCichorium intybus L. cv. ‘Witloof’ cultivatedin vitro. Nodule morphogenesis and bud regeneration from nodules were characterized with the assistance of light and transmission microscopy techniques. Semithin and ultrathin sections of leaves and nodules were prepared from nodule induction to bud regeneration phases. Starch and inulin in differentiating tissues were histochemically detected in semithin and handmade sections. Our study demonstrates that nodules are formed in direct contact with vascular bundles of the leaves. The nodules consist of organized structures: a vascular center is surrounded by a large parenchyma, which is delimited by a periderm of multiple cork cell layers. Inside the vascular center near phloem tissues, a secretory network of articulated pseudolaticifers develops. From parenchymatous cells, in the vicinity of vascular centers, endogenous buds can be induced. In this region, several cords of vessel initials formed the vascular connection between neoformed buds and vascular centers. Simultaneously, transfer cell specialization occurs near the neoformed vascular strands. Vascular centers play a major role in this kind of organogenesis. Sugar metabolism appears to be closely related to nodule morphogenetic events.     

Regeneration Around Wounds and the Control of Vascular Differentiation

The question which was the basis of this work was whether (a)vascular regeneration around wounds includes a replacement ofdamaged tissues or (b) only new vascular strands, which arenormally formed from the cambium, are diverted around wounds.It was found that in Coleus and Cucumis no connections are formedto damaged sieve tubes and vessels, so that their continuityaround wounds is not restored. Pisum plants were wounded underconditions in which growth could not be influenced and the areaof the xylem in cross-section was measured 1 month later. Thewounds, which damaged the vascular tissues, significantly increasedvascular differentiation, indicating the replacement of a longnon-functional region of damaged tissues. The results indicatethat in the intact plant vascular differentiation is controllednot only by stimuli from the leaves but also by the capacityof the mature vascular system to transport these stimuli.     

檀香吸器维管组织的个体发育

为了解檀香吸器维管组织的发育过程,采用激光共聚焦显微镜、光学显微镜和透射电镜观察檀香吸器维管组织的个体发育。结果表明,檀香维管组织的分化分为两个时期:入侵前和入侵后。吸器维管组织发育始于盘状吸器时期,起源于吸器基部具有分生能力的细胞,后分为两束。侵入前无向顶的分化,处于吸器基部。侵入后随吸管深入寄主根与寄主根维管束连通,形成具有吸收功能的维管组织。成熟吸器维管组织呈倒烧瓶结构,仅处于吸器烧瓶核心两边,由木质部组成而无韧皮部。檀香的吸器维管组织发育有两个因素诱导,一个是遗传因素,另一个为寄主。这些为檀香半寄生性特性研究提供了形态解剖学基础。     

The vasorelaxant effect of H(2)S as a novel endogenous gaseous K(ATP) channel opener.

Hydrogen sulfide (H(2)S) has been traditionally viewed as a toxic gas. It is also, however, endogenously generated from cysteine metabolism. We attempted to assess the physiological role of H(2)S in the regulation of vascular contractility, the modulation of H(2)S production in vascular tissues, and the underlying mechanisms. Intravenous bolus injection of H(2)S transiently decreased blood pressure of rats by 12- 30 mmHg, which was antagonized by prior blockade of K(ATP) channels. H(2)S relaxed rat aortic tissues in vitro in a K(ATP) channel-dependent manner. In isolated vascular smooth muscle cells (SMCs), H(2)S directly increased K(ATP) channel currents and hyperpolarized membrane. The expression of H(2)S-generating enzyme was identified in vascular SMCs, but not in endothelium. The endogenous production of H(2)S from different vascular tissues was also directly measured with the abundant level in the order of tail artery, aorta and mesenteric artery. Most importantly, H(2)S production from vascular tissues was enhanced by nitric oxide. Our results demonstrate that H(2)S is an important endogenous vasoactive factor and the first identified gaseous opener of K(ATP) channels in vascular SMCs.     

Present status and new perspectives in laser welding of vascular tissues

The laser welding of biological tissues is a particular use of lasers in surgery. The technique has been proposed since the 1970s for surgical applications, such as repairing blood vessels, nerves, tendons, bronchial fistulae, skin and ocular tissues. In vascular surgery, two procedures have been tested and optimized in animal models, both ex vivo and in vivo, in order to design different approaches for blood vessels anastomoses and for the repair of vascular lesions: the laser-assisted vascular anastomosis (LAVA) and the laser-assisted vessel repair (LAVR). Sealing tissues by laser may overcome the problems related to the use of conventional closuring methods that are generally associated with various degrees of vascular wall damage that can ultimately predispose to vessel thrombosis and occlusion. In fact, the use of a laser welding technique provides several advantages such as simplification of the surgical procedure, reduction of the operative time, suppression of bleeding, and may guarantee an optimal healing process of vascular structures, very similar to restitutio ad integrum. Despite the numerous preclinical studies performed by several research groups, the clinical applications of laser-assisted anastomosis or vessel repair are still far off. Substantial breakthrough in the laser welding of biological tissues may come from the advent of nanotechnologies. Herein we describe the present status and the future perspectives in laser welding of vascular structures.     

Verticillium dahliae Asp1 regulates the transition from vegetative growth to asexual reproduction by modulating microtubule dynamic organization

Verticillium dahliae is a devastating pathogenic fungus that causes severe vascular wilts in more than 400 dicotyledonous plants. The conidiation of V. dahliae in plant vascular tissues is the key strategy for its adaptation to the nutrient-poor environment and is required for its pathogenicity. However, it remains unclear about the regulatory mechanism of conidium production of V. dahliae in vascular tissues. Here, we found that VdAsp1, encoding an inositol polyphosphate kinase, is indispensable for the pathogenicity of V. dahliae. Loss of VdAsp1 function does not affect the invasion of the host, but it impairs the colonization and proliferation in vascular tissues. The ΔVdAsp1 mutant shows defective initiation of conidiophore formation and reduced expression of genes associated with the central developmental pathway. By live-cell imaging, we observed that some of ΔVdAsp1 mutant hyphae are swollen, and microtubule arrangements at the apical region of these hyphae are disorganized. These results indicate that VdAsp1 regulates the transition from vegetative growth to asexual reproduction by modulating microtubule dynamic organization, which is essential for V. dahliae to colonize and proliferate in vascular tissues. These findings provided a potential new direction in the control of vascular wilt pathogen by targeting conidium production in vascular tissues.     

Sucrose-metabolizing enzymes in transport tissues and adjacent sink structures in developing citrus fruit

Juice tissues of citrus lack phloem; therefore, photosynthates enroute to juice sacs exit the vascular system on the surface of each segment. Areas of extensive phloem unloading and transport (vascular bundles + segment epidermis) can thus be separated from those of assimilate storage (juice sacs) and adjacent tissues where both processes occur (peel). Sugar composition, dry weight accumulation, and activities of four sucrose-metabolizing enzymes (soluble and cell-wall-bound acid invertase, alkaline invertase, sucrose synthase, and sucrose phosphate synthase) were measured in these transport and sink tissues of grapefruit (Citrus paradisi Macf.) to determine more clearly whether a given enzyme appeared to be more directly associated with assimilate transport versus deposition or utilization. Results were compared at three developmental stages. Activity of sucrose (per gram fresh weight and per milligram protein) extracted from zones of extensive phloem unloading and transport was significantly greater than from adjacent sink tissues during the stages (II and III) when juice sacs grow most rapidly. In stage II fruit, activity of sucrose synthase also significantly surpassed that of all other sucrose-metabolizing enzymes in extracts from the transport tissues (vascular bundles + segment epidermis). In contrast, sucrose phosphate synthase and alkaline invertase at this stage of growth were the most active enzymes from adjacent, rapidly growing, phloem-free sink tissues (juice sacs). Activity of these two enzymes in extracts from juice sacs was significantly greater than that form the transport tissues (vascular bundles + segment epidermis). Soluble acid invertase was the most active enzyme in extracts from all tissues of very young fruit (stage I), including nonvascular regions, but nearly disappeared prior to the onset of juice sac sugar accumulation. The physiological function of high sucrose synthase activity in the transport tissues during rapid sucrose import remains to be determined.     

The vasculature of xenotransplanted human melanomas and sarcomas on nude mice. I. Vascular corrosion casting studies

The vascular system of xenotransplanted human melanomas and sarcomas on nude mice was studied by means of microorrosion casting. In summary, the vascular system of xenotransplants can be described in termes of a simply structured system, lacking not only a hierarchy with respect to wall formation but also to vascular distribution. Thus, the vasculature clearly differs from that in normal tissues.     

Circular Vessels and the Control of Vascular Differentiation in Plants

The occurrence of vessels in the form of rings is used as a critical example for a hypothesis about the control of the pattern of cells in vascular tissues. These vessels, rare in intact plants, are common in the basal or root side of tissues close to transverse wounds of bean seedlings, radish storage tissues, and other plant material. Their formation is promoted, as are normal vascular tissues, by developing parts of the shoot or by a source of the hormone auxin. They are also found in grafts where cells of opposite polarities are close together, and in cut plants where vascular induction occurs from the direction of the roots and is therefore opposite to the original polarity of the tissue. Circular vessels are found, therefore, where the flux of auxin and possibly other signals controlling vascular differentiation is expected to follow a circular route. They show that differentiation is a response of individual cells to the flux rather than the gradient or concentration of the hormonal signals and suggest a hormonal interpretation of differences between apical and basal callus growth.     

Monoamine oxidase and semicarbazide-sensitive amine oxidase kinetic analysis in mesenteric arteries of patients with type 2 diabetes

Monoamine oxidase (MAO, type A and B) and semicarbazide-sensitive amine oxidase (SSAO) metabolize biogenic amines, however, the impact of these enzymes in arteries from patients with type 2 diabetes remains poorly understood. We investigated the kinetic parameters of the enzymes to establish putative correlations with noradrenaline (NA) content and patient age in human mesenteric arteries from type 2 diabetic patients. The kinetic parameters were evaluated by radiochemical assay and NA content by high-performance liquid chromatography (HPLC). The activity of MAO-A and SSAO in type 2 diabetic vascular tissues was significantly lower compared to the activity obtained in non-diabetic tissues. In the correlation between MAO-A (K(m)) and NA content, we found a positive correlation for both the diabetic and non-diabetic group, but no correlation was established for patient age. In both groups, MAO-B (V(max)) showed a negative correlation with age. The results show that MAO-A and SSAO activities and NA content of type 2 diabetic tissues are lower compared to the non-diabetic tissues, while MAO-B activity remained unchanged. These remarks suggest that MAO-A and SSAO may play an important role in vascular tissue as well as in the vascular pathophysiology of type 2 diabetes.     

A comparative karyological and cytophotometric study of normal and wounded stem tissues ofLathyrus odoratus L.

Wounding of stems ofLathyrus odoratus induced increased mitoses with polyploid in vascular and pith tissues, but not in cortex. Cell division area extended 200 μm from the wound edge. These facts confirm the previous observations inPisum sativum. DNA content of normal stem nuclei was high in vascular and pith tissues, but not in cortex.     

刺槐幼苗根茎过渡区初生维管组织的观察

对不同苗龄(1-12d)的刺槐(Robinia pseudoacacia L.)幼苗进行观察,比较了其初生维管组织的发育变化。结果表明:根中的初生维管组织借助下胚轴过渡到子叶中,而茎中的初生维管组织与下胚轴中的维管组织仅是简单的连接。这与Esau等认为幼苗的外部形态可以分为根-下胚轴-子叶和上胚轴苗两个系统的观点是一致的。本研究亦证实了可以将刺槐幼苗的外部形态描述为这两个系统,二者的维管组织只是简单的连接,不存在过渡。     

海桑和无瓣海桑叶片结构的比较研究

为了探讨外来植物无瓣海桑的潜在危害,采用石蜡切片法对海桑(Sonneratia caseolaris Engl.)、无瓣海桑(S.apetala B.Ham)叶片进行了解剖学研究。实验结果显示,两种植物的叶片均为等面叶;中脉维管束为周韧维管束;具4级侧脉,第1级侧脉为半周韧维管束;成熟叶片叶肉组织具发达的贮水薄壁细胞,具含单宁成分的薄壁细胞,具晶体细胞和石细胞;盐腺由表皮细胞发育而成,可分为3个发育阶段。作为外来植物的无瓣海桑,其中脉维管束具微弱形成层,叶脉维管组织比海桑更发达;贮藏组织中含单宁细胞、晶体细胞较多;栅栏组织含叶绿体多于海桑等特点,使其比海桑对环境具有更大的适应性。因此,无瓣海桑有可能成为入侵植物。