Vascular Construction Research Articles

Mesenchymal stem cells-laden self-healing hydrogel microfiber fragments from microfluidic bubbles interrupted spinning for wound healing

Mesenchymal stem cells (MSCs) loaded hydrogels have shown positive therapeutic effects in skin wound treatment, while their application is still impractical on the wound bed. Here, we propose novel MSCs-loaded self-healing hydrogel microfiber fragments from microfluidic bubbles interrupted spinning for wound healing. The hydrogel microfibers are composed of sodium alginate, gelatin, polyvinyl alcohol, and borax, vesting them with good biocompatibility and self-healing ability. Their fragments with adjustable length are generated by introducing bubbles into microfluidic channels. We have demonstrated that the self-healing microfibers can promote the proliferation of MSCs, which are seeded alongside fragments’ surfaces to further facilitate the wound healing process. In addition, these MSCs laden self-healing hydrogel microfibers (MSG-fibers) showed obvious healing effect in rat wound model, which significantly promoted granulation tissue formation, collagen deposition and vascular construction at the wound site. Thus, we believe that our proposed MSC-laden microfiber fragments are valuable in promoting wound healing and have promising prospect in becoming new options for wound management.

SeqSeg: Learning Local Segments for Automatic Vascular Model Construction.

Computational modeling of cardiovascular function has become a critical part of diagnosing, treating and understanding cardiovascular disease. Most strategies involve constructing anatomically accurate computer models of cardiovascular structures, which is a multistep, time-consuming process. To improve the model generation process, we herein present SeqSeg (sequential segmentation): a novel deep learning-based automatic tracing and segmentation algorithm for constructing image-based vascular models. SeqSeg leverages local U-Net-based inference to sequentially segment vascular structures from medical image volumes. We tested SeqSeg on CT and MR images of aortic and aortofemoral models and compared the predictions to those of benchmark 2D and 3D global nnU-Net models, which have previously shown excellent accuracy for medical image segmentation. We demonstrate that SeqSeg is able to segment more complete vasculature and is able to generalize to vascular structures not annotated in the training data.

Research Progress in the Construction and Application of In Vitro Vascular Models

The vascular system maintains cellular homeostasis by transporting oxygen, nutrients, and metabolic waste products. The vascular system is involved in a variety of fundamental physiological phenomena and is closely associated with human vascular diseases. Additionally, the stability of drugs in the vasculature affects their efficacy. Therefore, researchers have used vascular models to study vascular diseases, assess drug stability, and screen drugs. However, there are many shortcomings in the animal models and in vitro two-dimensional vascular models that have been extensively developed. In this paper, we specifically review the construction methods of in vitro vascular models and classify the specific methods into photolithography, soft lithography, self-assembly, template, 3D bioprinting, and laser degradation/cavitation. The first two are microfluidics-based methods and the last three are non-microfluidics-based methods. The vascular model construction methods reviewed in this paper overcome the shortcomings of traditional models—which cannot accurately reproduce the human vascular microenvironment—and can assist in the construction of in vitro 3D vascular models and tissue engineering vascularization. These models can be reused by perfusion devices, and the cells within the channels reside on biocompatible materials that are used to simulate the microenvironment and 3D cellular organization of the vasculature in vivo. In addition, these models are reproducible in shape and length, allowing experiments to be repeated, which is difficult to do with natural vessels. In vitro vascular models are widely used in research and drug screening for diseases associated with endothelial dysfunction, cancer, and other vascular abnormalities.

Three-dimensional vascular graph construction from depth information of blood vessel centerlines in optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) is a noninvasive imaging technique for visualizing high-resolution volumetric vascular networks. Although OCTA has been widely employed in vascular network analysis, most studies have been limited to the analysis of two-dimensional (2D) en-face projection images because leveraging the full potential of OCTA’s three-dimensional (3D) information has been challenging due to projection artifacts beneath blood vessels. In this study, we propose a semi-automatic method for constructing a 3D vascular graph from 3D OCTA images without relying on data-driven learning strategies such as deep learning. The proposed method estimates the depth information of blood vessel centerlines in 2D en-face images and constructs a 3D vascular graph by integrating the depth estimation results for all vessel centerline segments. We demonstrate the effectiveness of the proposed method through experiments conducted on both simulated datasets and real datasets acquired from the dorsal dermis of mice.

TFEB safeguards trophoblast syncytialization in humans and mice

Nutrient sensing and adaptation in the placenta are essential for pregnancy viability and proper fetal growth. Our recent study demonstrated that the placenta adapts to nutrient insufficiency through mechanistic target of rapamycin (mTOR) inhibition-mediated trophoblast differentiation toward syncytiotrophoblasts (STBs), a highly specialized multinucleated trophoblast subtype mediating extensive maternal-fetal interactions. However, the underlying mechanism remains elusive. Here, we unravel the indispensable role of the mTORC1 downstream transcriptional factor TFEB in STB formation both in vitro and in vivo. TFEB deficiency significantly impaired STB differentiation in human trophoblasts and placenta organoids. Consistently, systemic or trophoblast-specific deletion of Tfeb compromised STB formation and placental vascular construction, leading to severe embryonic lethality. Mechanistically, TFEB conferred direct transcriptional activation of the fusogen ERVFRD-1 in human trophoblasts and thereby promoted STB formation, independent of its canonical function as a master regulator of the autophagy-lysosomal pathway. Moreover, we demonstrated that TFEB directed the trophoblast syncytialization response driven by mTOR complex 1 (mTORC1) signaling. TFEB expression positively correlated with the reinforced trophoblast syncytialization in human fetal growth-restricted placentas exhibiting suppressed mTORC1 activity. Our findings substantiate that the TFEB-fusogen axis ensures proper STB formation during placenta development and under nutrient stress, shedding light on TFEB as a mechanistic link between nutrient-sensing machinery and trophoblast differentiation.

Constructing liver-like tissue in situ based on plant-derived cellulose scaffolds alleviating acute liver injury

Despite the promise of tissue engineering for treating acute liver injury (ALI), functional vascular system construction is still not fully achieved in liver tissue engineering. Multilayered space materials similar to liver lobules and high-precision vasculature are necessary for liver regeneration. In the present study, we found that apple-derived cellulose scaffolds prepared via decellularization possessed the aforementioned properties and could serve as a three-dimensional scaffold for proliferation of adipose-derived stem cells (ADSCs). In vitro, we successfully induced ADSCs into hepatocyte-like cells in apple-derived cellulose scaffolds. Then, we implanted apple-derived cellulose scaffolds loaded with ADSCs in mice with ALI. Interestingly, we found that liver function recovered in ALI mice and the implants developed vasculature and bile duct structures. Further transcriptomic analysis indicated that apple-derived cellulose scaffolds could activate metabolism and promote vascular regeneration pathways while inhibiting immune and inflammatory pathways. Our study demonstrated that apple-derived cellulose scaffolds combined with stem cells can treat ALI.

Combination of neuroendoscopic hematoma evacuation and endovascular coil embolization for a ruptured anterior choroidal artery aneurysm in patients with moyamoya disease: illustrative cases.

The treatment strategy for hemorrhagic moyamoya disease (MMD) due to a ruptured aneurysm at the distal portion of the anterior choroidal artery remains controversial. The authors successfully treated the ruptured aneurysm with neuroendoscopic hematoma evacuation, followed by endovascular coil embolization. The authors encountered two patients with massive hemorrhagic MMD whose MMD had already been diagnosed and who had a periventricular anastomosis due to a ruptured aneurysm of the distal portion of the anterior choroidal artery involving the periventricular anastomosis. In both cases, neuroendoscopic hematoma evacuation was performed for hemorrhagic MMD in the acute phase, followed by endovascular coil embolization of the ruptured aneurysm in the chronic phase. In both endovascular treatments, the patient's condition was stabilized by hematoma evacuation, allowing a detailed preoperative evaluation of the anatomical findings of the vessel and functional findings of intraoperative neurophysiological monitoring using continuous monitoring of motor evoked potentials to preserve motor function. Combination therapy can be useful for hemorrhagic MMD in patients with diagnosed MMD with a periventricular anastomosis. Additionally, a preoperative understanding of the vascular construction and intraoperative neurophysiological monitoring will aid in the successful coil embolization of aneurysms at the distal portion of the anterior choroidal artery with hemorrhagic MMD.

The "Bad Father": Paternal Role in Biology of Pregnancy and in Birth Outcome.

Pregnancy is generally studied as a biological interaction between a mother and a fetus; however, the father, with his characteristics, lifestyle, genetics, and living environment, is by no means unrelated to the outcome of pregnancy. The half of the fetal genetic heritage of paternal derivation can be decisive in cases of inherited chromosomal disorders, and can be the result of de novo genetic alterations. In addition to the strictly pathological aspects, paternal genetics may transmit thrombophilic traits that affect the implantation and vascular construction of the feto-placental unit, lead to placenta-mediated diseases such as pre-eclampsia and fetal growth retardation, and contribute to the multifactorial genesis of preterm delivery. Biological aspects of immunological tolerance to paternal antigens also appear to be crucial for these pathologies. Finally, this review describes the biological findings by which the environment, exposure to pathogens, lifestyle, and nutritional style of the father affect fetal pathophysiological and epigenetic definition.

A 4D printed nanoengineered super bioactive hydrogel scaffold with programmable deformation for potential bifurcated vascular channel construction.

Four-dimensional (4D) printing of hydrogels enabled the fabrication of complex scaffold geometries out of static parts. Although current 4D fabrication strategies are promising for creating vascular parts such as tubes, developing branched networks or tubular junctions is still challenging. Here, for the first time, a 4D printing approach is employed to fabricate T-shaped perfusable bifurcation using an extrusion-based multi-material 3D printing process. An alginate/methylcellulose-based dual-component hydrogel system (with defined swelling behavior) is nanoengineered with carbonized alginate (∼100 nm) to introduce anti-oxidative, anti-inflammatory, and anti-thrombotic properties and shape-shifting properties. A computational model to predict shape deformations in the printed hydrogels with defined infill angles was designed and further validated experimentally. Shape deformations of the 3D-printed flat sheets were achieved by ionic cross-linking. An undisrupted perfusion of a dye solution through a T-junction with minimal leakage mimicking blood flow through vessels is also demonstrated. Moreover, human umbilical vein endothelial and fibroblast cells seeded with printed constructs show intact morphology and excellent cell viability. Overall, the developed strategy paves the way for manufacturing self-actuated vascular bifurcations with remarkable anti-thrombotic properties to potentially treat coronary artery diseases.

#6345 HIGH BRACHIAL ARTERY BIFURCATION AND CLINICAL IMPLICATIONS UPON HEMODIALYSIS VASCULAR ACCESS PLANNING

Abstract Background and Aims Preoperative ultrasound mapping provides information about overall vessel, caliber, flow and anatomic variations, useful for hemodialysis (HD) vascular access planning. High bifurcation of the brachial artery (HBBA) is one of such variations, established early upon fetal development. Its implications in arteriovenous HD access creation are fairly unknown. The present work aims to characterize the prevalence and demographic characteristics of patients presenting with HBBA and study its impact upon HD vascular access planning, construction and patency. Method We developed a retrospective study focusing on 457 patients accessed from 2018 to 2021. Demographic data and presence of HBBA were registered as well as vessel diameter and peak systolic velocities (PSV) for brachial and radial arteries. Theoretical feasibility for each specific access (i.e., radiocephalic, brachiocephalic, brachiobasilic and prosthetic fistulae, according to ultrasound evaluation), final choice of access and 30-day patency were also gathered. Categorical variables are presented as frequencies and percentages and continuous variables as means and standard deviations or medians and interquartile ranges, as appropriate. Logistic regressions were adjusted considering sex, race, arm dominance and HBBA as independent variables. Results From a total of 457 patients, 193 (42,2%) were women and 264 (57,8%) were men. Mean age was 65,4 ±15,3 years. 383 (83,8%) were caucasian and 427 (93,4%) were right-handed. High bifurcation of the brachial artery was present on both arms of 6 (1,3%) patients, only one arm on 62 (13,6%) and on none of the remaining 389 (85,1%) patients. We found an association between being non-caucasian and presenting with HBBA (27% vs 12,5%, p-value = 0,01) but not with sex or arm dominance. Considering all patients, female sex was associated with smaller radial artery diameter, (2,0 ± 0,7 mm vs 2,2 ± 0,6 mm, p < 0,01). HBBA was not associated with a significant difference on arterial diameters (adjusted for sex and race) and there were also no significant differences when comparing dominant vs non-dominant arms. We found no association between HBBA and the theoretical feasibility of a raciocephalic fistula but rather with the choice of arteriovenous graft as the only possible access (26,5% vs 19,5%, p-value = 0,044). A total of 379 (77,0%) patients proceeded to vascular access construction: 59 (15,6%) radiocephalic fistulas, 229 (60,4%) brachiocephalic fistulas, 31 (8,2%) brachiobasilic fistulas and 60 (15,8%) arteriovenous grafts were created, with no differences between HBBA and non-HBBA groups. There was, however, an association between non-caucasian patients and the choice for a more proximal access (p = 0,001) as well as the need for surgical or angiographic reintervention within 45 days after access creation (11 (5%) vs 6 (17,6%), p-value = 0,002). Conclusion Our study suggests that presenting with HBBA is not necessarily associated with lower quality vessels and less distal access construction. However, this variation seems to be more frequent among non-caucasians, who appear to receive more proximal accesses, in greater need for early intervention than their counterparts. Further investigation is necessary to understand if apart from diameter or PSV, HBBA could influence other determinants of access placement choice, such as distance from brachial artery to cephalic or basilic vein or risk of distal hypoperfusion syndrome.

The Role of HIF-1α in Bone Regeneration: A New Direction and Challenge in Bone Tissue Engineering.

The process of repairing significant bone defects requires the recruitment of a considerable number of cells for osteogenesis-related activities, which implies the consumption of a substantial amount of oxygen and nutrients. Therefore, the limited supply of nutrients and oxygen at the defect site is a vital constraint that affects the regenerative effect, which is closely related to the degree of a well-established vascular network. Hypoxia-inducible factor (HIF-1α), which is an essential transcription factor activated in hypoxic environments, plays a vital role in vascular network construction. HIF-1α, which plays a central role in regulating cartilage and bone formation, induces vascular invasion and differentiation of osteoprogenitor cells to promote and maintain extracellular matrix production by mediating the adaptive response of cells to changes in oxygen levels. However, the application of HIF-1α in bone tissue engineering is still controversial. As such, clarifying the function of HIF-1α in regulating the bone regeneration process is one of the urgent issues that need to be addressed. This review provides insight into the mechanisms of HIF-1α action in bone regeneration and related recent advances. It also describes current strategies for applying hypoxia induction and hypoxia mimicry in bone tissue engineering, providing theoretical support for the use of HIF-1α in establishing a novel and feasible bone repair strategy in clinical settings.

ASPSCR1::TFE3 orchestrates the angiogenic program of alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a soft part malignancy affecting adolescents and young adults. ASPS is characterized by a highly integrated vascular network, and its high metastatic potential indicates the importance of ASPS’s prominent angiogenic activity. Here, we find that the expression of ASPSCR1::TFE3, the fusion transcription factor causatively associated with ASPS, is dispensable for in vitro tumor maintenance; however, it is required for in vivo tumor development via angiogenesis. ASPSCR1::TFE3 is frequently associated with super-enhancers (SEs) upon its DNA binding, and the loss of its expression induces SE-distribution dynamic modification related to genes belonging to the angiogenesis pathway. Using epigenomic CRISPR/dCas9 screening, we identify Pdgfb, Rab27a, Sytl2, and Vwf as critical targets associated with reduced enhancer activities due to the ASPSCR1::TFE3 loss. Upregulation of Rab27a and Sytl2 promotes angiogenic factor-trafficking to facilitate ASPS vascular network construction. ASPSCR1::TFE3 thus orchestrates higher ordered angiogenesis via modulating the SE activity.

Design and implementation of diabetic retinopathy detections on retinal images

A retinal picture gives a depiction of what's going on inside the human body. Specifically, the condition of the retinal vessels has been appeared to mirror the cardiovascular state of the body. Retinal pictures give impressive data on neurotic changes brought about by neighbourhood visual illness which uncovers diabetes, hypertension, arteriosclerosis, cardiovascular infection and stroke. PC supported examination of retinal picture assumes a focal part in indicative methodology. Nonetheless, programmed retinal division is muddled by the way that retinal pictures are frequently uproarious, inadequately differentiated, and the vessel widths can shift from enormous to exceptionally little. So in this venture, we can carry out robotize division approach dependent on diagram hypothetical strategy to give local data utilizing measure. We address the portioned vascular construction as a vessel fragment diagram and make the issue of recognize vessels as one of discovering the veins in the chart given a bunch of requirements like CRAE and CRVE. These estimations are found to have great connection with hypertension, coronary illness, and stroke. Be that as it may, they require the precise extraction of particular vessels from a retinal picture. We plan a strategy to tackle this improvement issue and assess it on an enormous genuine world dataset of retinal pictures.

A bump in the node: The hydraulic implications of rhizomatous growth.

Rhizomatous growth characterizes numerous taxa among vascular plants. While abundant information exists on nutrient sharing and demography, the question of how these metameric organisms move water through their bodies remains largely unstudied. Moreover, we lack an understanding of the evolutionary implications of rhizomatous growth across vascular plants. Here, we examined these questions by investigating how rhizomatous growth and vascular construction affect whole-plant hydraulic function. In five terrestrial fern species with diverse vascular construction, we used microcomputed tomography and bright-field microscopy to examine vascular construction across nodes along the rhizome. These data were integrated with measurements of leaf stomatal conductance under rooted and uprooted conditions to relate vascular patterning and hydraulic architecture to leaf water status. Similar to phytomers of woody seed plants, nodal regions in rhizomatous ferns are areas of hydraulic resistance. While water is sharedalong the rhizomes of these investigated species, hydraulic conductivity drops at nodes and stomatal conductance declines when nodes were locally uprooted. Together, our data suggest that nodes are chokepoints in axial water movement along the rhizome. Nodal chokepoints decrease hydraulic integration between phytomers. At the same time, chokepoints may act as "safety valves", hydraulically localizing each phytomer-potentially decreasing embolism and pathogen spread. This suggests a potential trade-off in the principal construction of the fern rhizome. Moreover, we propose that shoot-borne roots (homorhizy) and the prostrate habit of rhizomatous ferns decrease the hydraulic and structural burdens that upright plants typically incur. The absence of these hydraulic and structural demands may be one reason ferns (and many rhizomatous plants) lack, or have minimally developed, secondary xylem.

Effects of Chemical Composition on the Shape Memory Property of Poly(dl-lactide-co-trimethylene carbonate) as Self-Morphing Small-Diameter Vascular Scaffolds.

Smart materials have great potential in many biomedical applications, in which biodegradable shape memory polymers (SMPs) can be used as surgical sutures, implants, and stents. Poly(dl-lactide-co-trimethylene carbonate) (PDLLTC) represents one of the promising SMPs and is widely used in biomedical applications. However, the relationship between its shape memory property and chemical structure has not been fully studied and needs further elaboration. In this work, PDLLTC copolymers in different compositions have been synthesized, and their shape memory properties have been investigated. It has been found that the shape memory property is related to the chemical composition and polymeric chain segments. The copolymer with a DLLA/TMC ratio of 75:25 (PDLLTC7525) has been demonstrated with great shape fixation and recovery ratio at human body temperature. Furthermore, PDLLTC7525-based self-morphing small-diameter vascular scaffolds adhered with inner electrospun aligned gelatin/hyaluronic acid (Gel/HA) nanofibers have been constructed, as a merit of its shape memory property. The scaffolds have been demonstrated to facilitate the proliferation and adhesion of endothelial cells on the inner layer. Therefore, PDLLTC with tailorable shape memory properties represents a promising candidate for the development of SMPs, as well as for small-diameter vascular scaffolds construction.

Case report: Vascular graft infection due to Aspergillus species presenting with recurrent vascular occlusion

BackgroundAn aortic graft implantation is an effective therapeutic method for various aortic diseases. However, it is known that sometimes these implanted grafts can be the foci of infections. Here we report a rare case of graft infection that presented multiple embolisms of aortic branches and peripheral organs.Case presentationA 63-year-old Japanese woman with a history of aortic graft implantation presented with occlusions of large arteries in different loci and time points, with elevation of non-specific inflammatory markers. Thoracic contrast-computed tomography (CT) captured vegetation in the descending aortic graft and the [18F]fluorodeoxyglucose positron emission tomography/computed tomography ([18F]FDG PET/CT) showed accumulation of FDG in the same site, suggesting a graft infection. Despite all these suspicious findings, repeated blood culture examinations never detected any microorganisms. A diagnosis of Aspergillus graft infection was made based on an elevated serum β-D glucan (βDG) and a positive Aspergillus galactomannan (GM) antigen test. The patient subsequently had surgery with replacement of the descending aortic graft and anti-fungal drugs were instituted with significant improvement noted.ConclusionIn the present case, the patient’s specific feature in the anatomical vascular construction, past operation, and basal fundamental diseases collaboratively contributed to the pathogenesis of the present infection. It is important to recognize the risk of graft infection and conduct imaging studies when indicative symptoms emerge. The negativity in blood culture studies often makes detection of pathogenic microbes extremely difficult. This case suggests that non-cultural tests such as bDG and GM can be useful for diagnosis and starting appropriate anti-fungal drugs in the early stages.

Human embryonic development: from peri-implantation to gastrulation.

The basic body plan of the mammalian embryo is established through gastrulation, a pivotal early postimplantation event during which the three major germ layers (endoderm, ectoderm, and mesoderm) are specified with cellular and spatial diversity. Despite its basic and clinical importance, human embryo development from peri-implantation to gastrulation remains shrouded in mystery. Recent advances in the elongated in vitro culture of rodent and non-primate embryos and the construction of embryo-like structures have helped to improve understanding of the mechanisms of human early embryonic development. Here, we review the recent advances and possible future directions in the development of in vitro models to better understand human embryogenesis from peri-implantation to gastrulation.

Arteriovenous fistula formation with adjuvant endovascular maturation

BackgroundThe clinical utility of the native arteriovenous fistula (AVF) has been limited by the prolonged time required for maturation, the low overall maturation rate, and subsequent abandonment. Endovascular intervention has been increasingly accepted as the first-line therapy for AVF stenosis. The objective of the present study was to evaluate the AVF formation outcomes when early endovascular intervention was selectively performed to bring about timely AVF maturation. MethodsWe performed a retrospective study (February 2014 to February 2020) of 82 AVF consecutive patients (mean age, 62.5 ± 13.5 years; range, 17-83; 58 men [70.7%]) with end-stage renal failure who had undergone vascular access construction at a single institution. The 4-year AVF patency, vascular diameters, hemodialysis parameters, reintervention rate, and mortality were analyzed. ResultsRadiocephalic AVF was the most common fistula constructed (71 patients; 88.6%). The evaluation at a mean of 46.2 ± 56.0 days (range, 5-343 days) after AVF formation revealed 33 immature AVFs (40.2%). Subsequently, 19 patients had undergone endovascular procedures, including angioplasty and/or stenting of the juxta-anastomosis, cannulation zones, and/or outflow segments to bring about timely maturation of the AVF. Hence, 93.9% of the AVFs had reached functional patency (maturation) by 6 months after formation, with a mean time to maturation of 67.8 ± 65.9 days (range, 5-320 days). After reaching maturation, the primary access functional patency was 82% ± 4.3% at 6 months, 58% ± 5.5% at 12 months, and 34% ± 6.8% at 48 months. The primary assisted access functional patency was 95% ± 2.4% at 6 months, 90% ± 3.3% at 12 months, and 83% ± 4.7% at 48 months. A total of 121 endovascular interventions were performed to maintain patency, equating to an endovascular reintervention rate of 0.37 procedure/patient year. The mean arterial, venous, and brachial flow rates did not change significantly after maturation with a mean AVF (primary assisted functional patency) survival time of 5.9 ± 0.26 years (range, 5.33-6.36 years) from maturation. Only 12 thromboses had occurred after the first follow-up review after AVF formation. These were all salvaged using endovascular techniques, leading to 100% total secondary functional patency at 4 years. The 5-year estimated all-cause mortality was 45.6% ± 12.7%. ConclusionsThe AVF maturation rate and interval to maturation were improved when early endovascular intervention was selectively performed after AVF formation. This allowed for near universal maturation. In addition, once matured, the use of ongoing endovascular reinterventions allowed for a low reintervention rate and long-term patency, providing reliable long-term renal vascular access.

From cells to stems: the effects of primary vascular construction on drought-induced embolism in fern rhizomes.

While a considerable amount of data exists on the link between xylem construction and hydraulic function, few studies have focused on resistance to drought-induced embolism of primary vasculature in herbaceous plants. Ferns rely entirely on primary xylem and display a remarkable diversity of vascular construction in their rhizomes, making them an ideal group in which to examine hydraulic structure-function relationships. New optical methods allowed us to measure vulnerability to embolism in rhizomes, which are notoriously difficult to work with. We investigated five fern species based on their diverse xylem traits at the cellular, histological, and architectural levels. To link below- and above-ground hydraulics, we then measured leaf-stem vulnerability segmentation. Overall, rhizome vulnerability to embolism was correlated most strongly with cellular but not histological or architectural traits. Interestingly, at P6-12 , species with increased architectural dissection were actually more vulnerable to embolism, suggesting different hydraulic dynamics at low compared to high percent embolism. Importantly, leaves fully embolize before stems reach P88 , suggesting strong vulnerability segmentation. This is the first study to explore the functional implications of primary vascular construction in fern rhizomes and leaf-stem vulnerability segmentation. Strong segmentation suggests that leaves protect perennial rhizomes against severe drought stress and hydraulically induced mortality.

Brachial Arterial Transposition: Another Option for Vascular Access?

Brachial Arterial Transposition: Another Option for Vascular Access?