Endocardium-to-coronary artery differentiation during heart development and regeneration involves sequential roles of Bmp2 and Cxcl12/Cxcr4

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Inhibition of Endosteal Vascular Niche Remodeling Rescues Hematopoietic Stem Cell Loss in AML

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New aspects of the intrafilamental vascular system in gills of a euryhaline teleost,Tilapia mossambica

Summary The non-respiratory vascular system of T. mossambica gill filaments was studied in serial longitudinal and cross sections. Comparatively few scattered vascular communications occur between the afferent filament artery and the central venous sinus (AVA_aff). The efferent filament artery, however, is connected by regularly arranged anastomoses (AVA_eff), directly, and sometimes indirectly via nutritive vessels, to the central sinus. These AVA_eff are about as numerous as lamellae counted on one side of each filament, although they diminish slightly in number towards the filament base. The relation AVA_eff to AVA_aff was 17.6:1 in the distal and 17.8:1 in the basal filamental region, while in the tip region of 7 filaments 126 AVA_eff but only 1 AVA_aff were encountered. No direct connection between the lamellar lacunae and the central sinus was detected. According to these results, non-respiratory intrafilamental blood shunting appears unlikely. AVA_eff are assumed to be the main route for blood entering the central venous sinus which would consequently flow into the branchial veins.The authors wish to express their sincere thanks to Miss Angelika Krauß for her valuable technical assistance and to Miss Erna Finger for making the photographs. Thanks are also due to Mr. W. Zeltmann for drawing Figs. 2, 5, and 8 and to Mr. K. Herzog for Fig. 7.     

周期性土壤干旱和叶片水势对气孔响应木质部ABA灵敏度的影响

研究了周期性土壤干旱期间气孔对木质部ＡＢＡ响应的灵敏度的变化以及叶片水势对灵敏度的影响。实验结果证明了木质部ＡＢＡ浓度是反映根系周围土壤水分状况的一个指标的结论。土壤周期性干旱不影响木质部ＡＢＡ浓度对土壤水分状况的依赖关系,但显著地提高了气孔对木质部ＡＢＡ 响应的灵敏度。根据对实测数据的数学模拟结果显示,引起气孔导度下降５０％ 所需的木质部ＡＢＡ浓度从第一轮土壤干旱的７５０ ｎｍｏｌ／Ｌ降至第二轮土壤干旱的５５０ ｎｍｏｌ／Ｌ。分根实验的结果表明,叶片水分亏缺显著提高了气孔对木质部ＡＢＡ 的响应的灵敏程度,全根干旱中引起气孔导度下降５０ ％ 所需的木质部ＡＢＡ 浓度比半根干旱的小２ ～４ 倍。这表明,气孔对木质部ＡＢＡ响应的灵敏度不是一个固定的特性,可随植物生长环境及许多其他因素的变化而表现出很大的差异     

The embryonic epicardium: an essential element of cardiac development

The epicardium has recently been identified as an active and essential element of cardiac development. Recent reports have unveiled a variety of functions performed by the embryonic epicardium, as well as the cellular and molecular mechanisms regulating them. However, despite its developmental importance, a number of unsolved issues related to embryonic epicardial biology persist. In this review, we will summarize our current knowledge about (i) the ontogeny and evolution of the epicardium, including a discussion on the evolutionary origins of the proepicardium (the epicardial primordium), (ii) the nature of epicardial–myocardial interactions during development, known to be essential for myocardial growth and maturation, and (iii) the contribution of epicardially derived cells to the vascular and connective tissue of the heart. We will finish with a note on the relationships existing between the primordia of the viscera and their coelomic epithelial lining. We would like to suggest that at least a part of the properties of the embryonic epicardium are shared by many other coelomic cell types, such that the role of epicardium in cardiac development is a particular example of a more general mechanism for the contribution of coelomic and coelomic-derived cells to the morphogenesis of organs such as the liver, kidneys, gonads or spleen.     

Change of supercooling capability in solutions containing different kinds of ice nucleators by flavonol glycosides from deep supercooling xylem parenchyma cells in trees

Deep supercooling xylem parenchyma cells (XPCs) in Katsura tree contain flavonol glycosides with high supercooling-facilitating capability in solutions containing the ice nucleation bacterium (INB) Erwinia ananas, which is thought to have an important role in deep supercooling of XPCs. The present study, in order to further clarify the roles of these flavonol glycosides in deep supercooling of XPCs, the effects of these supercooling-facilitating (anti-ice nucleating) flavonol glycosides, kaempferol 3-O-β-d-glucopyranoside (K3Glc), kaempferol 7-O-β-d-glucopyranoside (K7Glc) and quercetin 3-O-β-d-glucopyranoside (Q3Glc), in buffered Milli-Q water (BMQW) containing different kinds of ice nucleators, including INB Xanthomonas campestris, silver iodide and phloroglucinol, were examined by a droplet freezing assay. The results showed that all of the flavonol glycosides promoted supercooling in all solutions containing different kinds of ice nucleators, although the magnitudes of supercooling capability of each flavonol glycoside changed in solutions containing different kinds of ice nucleators. On the other hand, these flavonol glycosides exhibited complicated nucleating reactions in BMQW, which did not contain identified ice nucleators but contained only unidentified airborne impurities. Q3Glc exhibited both supercooling-facilitating and ice nucleating capabilities depending on the concentrations in such water. Both K3Glc and K7Glc exhibited only ice nucleation capability in such water. It was also shown by an emulsion freezing assay in BMQW that K3Glc and Q3Glc had no effect on homogeneous ice nucleation temperature, whereas K7Glc increased ice nucleation temperature. The results indicated that each flavonol glycoside affected ice nucleation by very complicated and varied reactions. More studies are necessary to determine the exact roles of these flavonol glycosides in deep supercooling of XPCs in which unidentified heterogeneous ice nucleators may exist.     

Tubular invaginations in cerebral endothelium and their relation to smooth-surfaced cisternae in hagfish (Myxine glutinosa)

Summary The organization of vesicular profiles in the endothelium of cerebral capillaries of the hagfish, Myxine glutinosa, has been reinvestigated. Judged from random thin sections the endothelial cells contain numerous vesicles and tubules, in contrast to brain endothelia of most other vertebrates. However, three-dimensional reconstructions based on ultrathin serial sections (thickness 18 nm) showed that the profiles represent a system of irregular tubular invaginations of the cell membrane, comparable to the vesicular invaginations demonstrated in extracerebral capillary endothelia of frogs and rats. In addition, smooth-surfaced cisternae were present in close relation to the invaginations. The function of endothelial invaginations is unknown. They do not transport macromolecules, because the blood-brain barrier is practically impermeable to proteins. However, since the system of the invaginations and smooth-surfaced cisternae is structurally similar to the system of caveolae and sarcoplasmic reticulum in smooth muscle cells, a common function seems likely. It is proposed that endothelial invaginations and smooth-surfaced cisternae are involved in regulation of cytosolic Ca⁺⁺-concentration.     

Comparison of the effects of canopy and understory nitrogen addition on xylem growth of two dominant species in a warm temperate forest,China

Understanding the effect of increasing atmospheric nitrogen (N) deposition on xylem growth of trees is critical to predict tree growth and carbon sequestration under global change. Canopy N addition (CAN) is generally believed to realistically simulate atmospheric N deposition on terrestrial ecosystems given it takes all processes of N deposition from forest canopy to belowground into account. However, whether CAN is more effective in reflecting the effect of atmospheric N deposition on xylem growth of trees than understory N addition (UAN) has been rarely reported. To address the question, we conducted a CAN vs. UAN experimental study to weekly monitor xylem growth of two dominant broadleaf species (Quercus acutissima Carruth. and Quercus variabilis Blume) in a warm temperate forest of China during 2014–2015. Weekly xylem increment during the two years was measured. Mixed-effects models were used to quantify the effects of N addition on xylem growth and detect the differences among treatments. We found that CAN of 50 kg N ha⁻¹ yr⁻¹ plays a more significant role in promoting xylem growth of Q. acutissima than UAN of 50 kg N ha⁻¹ yr⁻¹, and significantly enhanced the formation of differentiating xylem (zones of radial enlarging and wall-thickening cells) of Q. acutissima in the early growing season (April-June) and the rate of xylem increment, but no significant difference in xylem increment of Q. variabilis was detected between CAN50 and UAN50. This is the first study to quantitatively demonstrate that previous UAN studies may have underestimated the effects of atmospheric N deposition on tree growth by ignoring the N interception through forest canopy. Furthermore, our study also suggested a species-specific response of xylem growth to N addition. Under a certain amount of atmospheric N deposition in the future, the xylem increment of Q. acutissima may be superior to that of Q. variabilis.     

Dynamic changes in endoglin expression in the developing mouse heart

Endoglin (ENG) is essential for cardiovascular development and is expressed in the heart from its earliest developmental stages. ENG expression has been reported in the cardiac crescent, endocardium, valve mesenchyme and coronary vascular endothelial cells. However, its expression in these cell types is non-uniform and the dynamic changes in ENG expression during heart development have not been systematically studied.Using immunofluorescent staining we tracked ENG protein expression in mouse embryonic hearts aged from 11.5 to 17.5 days, and in postnatal and adult hearts. ENG is expressed in the endocardium and in venous endothelial cells throughout these developmental stages. ENG protein is down-regulated by approximately two-fold as a subset of early coronary veins reprogram to form arteries within the developing myocardium from E13.5. This two-fold higher ratio of ENG protein in veins versus arteries is maintained throughout cardiac development and in the adult heart.ENG is also down-regulated two-fold following mesenchymal transition of endocardial cells to form cardiac valve mesenchyme, whilst expression of the pan-endothelial marker CD31 is completely lost. A subset of epicardial cells (which do not express ENG protein) delaminate and undergo a similar mesenchymal transition to form epicardially derived cells (EPDCs). This transient intra-myocardial mesenchymal cell population expresses low levels of ENG protein, similar to valve mesenchyme.In conclusion, ENG shows dynamic changes of expression in vascular endothelial cells, endocardial cells and mesenchymal cells in the developing heart that vary according to cardiovascular cell type.