How needle phenology indicates the changes of xylem cell formation during drought stress in Pinus sylvestris L.

Temperature, water availability and photoperiod are the primary drivers of tree phenological processes. However, there is lack of information how the spring temperature and summer drought affect phenology of both cambium and needles. We evaluated the interplay between xylem and needle development of mature Scots pine trees in three consecutive years differing in the spring temperatures and onset and duration of summer drought. Cambial activity began on the day of a year (DOY) 83–87, while the bud break occurred on DOY 113–119, when also the secondary cell wall of tracheids started its formation. While the timing of bud break correlated with the sum of effective temperatures, the beginning of cambial zone activity did not. The needles were fully unfolded around DOY 170, which corresponded to the transition between earlywood and latewood tracheids. Summer drought did not affect needle development, but it changed the rate of production and morphology of latewood tracheids. Latewood tracheids from the year 2015 when the drought was longest (i.e. until the second half of August in 2015 compared to the duration from June until the middle of July in the two other years) were 32% narrower and they had 34% thinner cell walls than in 2014 and 2016. The improvement of tree water status in July resulted in the formation of intra-annual density fluctuations (IADF). The interplay between needle and cambium phenology provided an insight into how the tree allocates the resources with varying temperature and soil water availability.     

Photoacoustic assessment of hemodynamic changes in foot vessels

Monitoring the blood supply in the lower extremities is critical for individuals who are vulnerable to vascular dysfunction. Current clinical approaches are ineffective in observing hemodynamic changes in peripheral vessels. In this paper, we investigate the potential of photoacoustic tomography (PAT) as an alternative way to in vivo monitor hemodynamic changes in foot vessels. High spatial and temporal resolution maps of hemoglobin in major arteries and veins are shown. Results from twelve human subjects are presented here to visualize vascular perfusion of healthy volunteers in two age groups (young vs aged). Significant differences between the two groups are observed and verify the declining in vascular function with aging, highlighting the potential of PAT as a new tool to evaluate vascular function in the lower extremities.      

Differential sectoriality in long-distance transport in temperate tree species: evidence from dye flow, <Superscript>15</Superscript>N transport,and vessel element pitting

The capture of patchily distributed nutrients by tree roots has received extensive research, but the fate of those nutrients has not. We performed experiments to determine if nutrient transport within tree species is preferentially transported from specific roots to specific branches. Saplings of five species with contrasting growth requirements were examined: two Betula species (B. papyrifera and B. lenta), Populus tremuloides, and two Acer species (A. saccharum and A. rubrum). To quantify patterns of long-distance transport, we examined the accumulation of safranin-O dye and ¹⁵N in branches when these tracers were applied to isolated lateral roots (dye and ¹⁵N) and to the main root system (¹⁵N). Because transport of nutrients between sectors requires flow through intervessel pit pairs of adjacent xylem vessel elements, we quantified the area of intervessel pits, the number of pits per unit vessel wall area, and the % vessel wall area as pits in Acer and Betula. We found that the two Betula species were integrated (tracers applied to isolated roots were likely to accumulate in all branches), while P. tremuloides and the two Acer species were sectorial (tracer accumulation was more concentrated in particular branches). Betula had the largest number of intervessel pits per unit vessel wall area and the largest percentage of vessel wall area as pits. The high density of bordered pits may explain the ease of tracer movement throughout the two Betula species. Greater integration may allow certain trees (e.g., Betula) to exploit nutritionally patchy environments such as rocky soils, and may alter plant-herbivore interactions.     

Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees

We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity (k_L) of upper branches was positively correlated with maximum rates of net CO₂ assimilation per unit leaf area (A_area) and stomatal conductance (g_s) across 20 species of canopy trees. Maximum k_L showed stronger correlation with A_area than initial k_L suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch k_L was negatively correlated with A_area/g_s and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics (k_theoretical) was positively related to A_area and k_L, consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, k_L, A_area, net CO₂ assimilation per unit leaf mass (A_mass), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes.     

Neurovascular congruence results from a shared patterning mechanism that utilizes Semaphorin3A and Neuropilin-1

Peripheral nerves and blood vessels have similar patterns in quail forelimb development. Usually, nerves extend adjacent to existing blood vessels, but in a few cases, vessels follow nerves. Nerves have been proposed to follow vascular smooth muscle, endothelium, or their basal laminae. Focusing on the major axial blood vessels and nerves, we found that when nerves grow into forelimbs at E3.5-E5, vascular smooth muscle was not detectable by smooth muscle actin immunoreactivity. Additionally, transmission electron microscopy at E5.5 confirmed that early blood vessels lacked smooth muscle and showed that the endothelial cell layer lacks a basal lamina, and we did not observe physical contact between peripheral nerves and these endothelial cells. To test more generally whether lack of nerves affected blood vessel patterns, forelimb-level neural tube ablations were performed at E2 to produce aneural limbs; these had completely normal vascular patterns up to at least E10. To test more generally whether vascular perturbation affected nerve patterns, VEGF(165), VEGF(121), Ang-1, and soluble Flt-1/Fc proteins singly and in combination were focally introduced via beads implanted into E4.5 forelimbs. These produced significant alterations to the vascular patterns, which included the formation of neo-vessels and the creation of ectopic avascular spaces at E6, but in both under- and overvascularized forelimbs, the peripheral nerve pattern was normal. The spatial distribution of semaphorin3A protein immunoreactivity was consistent with a negative regulation of neural and/or vascular patterning. Semaphorin3A bead implantations into E4.5 forelimbs caused failure of nerves and blood vessels to form and to deviate away from the bead. Conversely, semaphorin3A antibody bead implantation was associated with a local increase in capillary formation. Furthermore, neural tube electroporation at E2 with a construct for the soluble form of neuropilin-1 caused vascular malformations and hemorrhage as well as altered nerve trajectories and peripheral nerve defasciculation at E5-E6. These results suggest that neurovascular congruency does not arise from interdependence between peripheral nerves and blood vessels, but supports the hypothesis that it arises by a shared patterning mechanism that utilizes semaphorin3A.     

自发性高血压大鼠心肌和血管组织牛磺酸的转运障碍

在自发性高血压大鼠（SHR）的心肌和主动脉血管组织上观察牛磺酸（taurine)转运和牛磺酸转运体（taurine transporter,TAUT) mRNA 的改变,结果显示,与对照组WKY大鼠相比,SHR组血浆牛磺酸水平和牛磺酸释放量增加,而心肌和血管组织牛磺酸水平和TAUT mRNA含量均降低,牛磺酸最大转运速率（Vmax)分别低24％和35％（P＜0．05）,米氏常数（Km)值分别高16％和39％（P＜0．05）,这些结果提示,SHR的心肌和血管组织牛磺酸转运障碍可能与TAUT活性和亲和力降低及TAUT基因水平的下调有关。     

Identification of a hydroxy substituted calamenene--a sesquiterpene associated with wound reactions in non-infected xylem of Tilia spp

Xylem of lime trees (Tilia spp.) with wound reactions was structurally investigated by scanning (SEM) and transmission electron microscopy (TEM) as well as chemically analyzed by direct thermal desorption-gas chromatography-mass spectrometry (DTD-GC-MS). Wound reactions in the outer xylem lead to distinct discolorations around the wound. Within a 4-week response no fungal infection occurred in discoloured xylem. At the fine structural level, wound reactions become primarily visible as the secretion of dark-staining substances from parenchyma cells into lumens of vessels and fibres. With increasing reaction time vessels aggregate large amounts of secretion products, whereas in fibres wall-associated linings are formed and the inner secondary wall appears incrusted. After 2-3 months a narrow, greenish-brown boundary developed at the transition between the discoloured outer and the unchanged inner xylem. This green-brown boundary layer remained non-infected also in older wounds. DTD-GC-MS analyses revealed that the sesquiterpene Hydroxycalamenene represents a key substance of wound reactions in non-infected lime trees. Other substances such as fatty acids or their esters and coniferyl aldehydes or their derivatives were also found. TEM investigations of the samples after DTD-GC-MS showed less pronounced cell wall-attached linings in fibres as well as reduced incrustation of inner secondary walls. The massive deposits in the vessel lumens remained unchanged. The role of these wound reaction products and their ways of synthesis are discussed.     

αvβ3 expression on blood vessels and melanoma cells in primary lesions; differential association with tumor progression and clinical prognosis

The α_vβ₃ integrin has emerged as a key mediator in angiogenesis. Its role in tumor-induced angiogenesis is supported by its up-regulation in vivo in the vasculature of a number of different types of carcinoma. The potential clinical significance of α_vβ₃ expression on blood vessels in carcinomas is suggested by its association with tumor progression. Currently no information is available about the clinical significance of α_vβ₃ expression on the vasculature of lesions of melanocytic origin. Since we have previously found that α_vβ₃ expression on melanoma cells in primary lesions is associated with a poor prognosis, in the present study we have compared α_vβ₃ expression on blood vessels and on cells of melanocytic origin in nevi and in malignant melanoma lesions. In addition we have examined the lesions for expression of the α_v subunit to gain information on the regulation of α_vβ₃ expression on endothelial cells and on cells of the melanocyte lineage. α_vβ₃ expression on endothelial cells and on melanocytic cells was a relatively sensitive and specific marker for malignant lesions. However, α_vβ₃ expression on endothelial cells in primary melanoma lesions was not associated with the prognosis of the disease. The α_v subunit and the α_vβ₃ complex were differentially expressed on endothelial cells and on melanocytic cells, implying that different regulatory pathways control their expression. This finding may account for the differential clinical significance of α_vβ₃ expression on tumor vasculature and on melanoma cells we observed in our patient cohort. Lastly, α_vβ₃ may be a useful target for immunotherapeutic approaches in melanoma because of its high expression on the vasculature of all metastatic lesions tested and its restricted distribution in normal tissues. Received: 18 February 2000 / Accepted: 12 April 2000