一氧化氮合酶抑制剂N-硝基-L-精氨酸甲基酯对大鼠淋巴管运动的影响

目的研究一氧化氮合酶抑制剂N-硝基-L-精氨酸甲基酯对大鼠肠系膜淋巴管作用。方法股静脉注入N-硝基-L-精氨酸甲基酯,活体动态观察其2小时内淋巴管运动的变化;用HE染色、酶组化染色研究其组织学改变。结果发现静注N-硝基-L-精氨酸甲基酯可使淋巴管管径变细,运动频率增加,L-精氨酸可暂时逆转该变化;镜下发现淋巴管内皮细胞及管壁上神经纤维都含有一氧化氮合酶阳性反应产物,注N-硝基-L-精氨酸甲基酯组小肠组织HE切片出现固有层中央乳糜管扩张。说明一氧化氮合酶在淋巴循环中可能具有重要调节作用。     

Vascular endothelial growth factor-A mediates ultraviolet B-induced impairment of lymphatic vessel function

UVB irradiation of the skin induces erythema, epidermal hyperplasia, vascular hyperpermeability, and edema formation. Previous studies have revealed that the cutaneous blood vasculature plays a critical role in the mediation of photodamage. In contrast, the role of lymphatic vessels, which play an essential role in the maintenance of tissue fluid balance, in the response to UVB irradiation has remained unknown. We report here that both acute and chronic UVB irradiation of murine skin results in prominent enlargement of lymphatic vessels. Surprisingly, these enlarged lymphatic vessels were functionally impaired and hyperpermeable, as detected by intravital lymphangiography. The expression levels of vascular endothelial growth factor (VEGF)-A but not of the known lymphangiogenesis factors VEGF-C or VEGF-D, were enhanced in UVB-irradiated epidermis. Targeted overexpression of VEGF-A in the epidermis of transgenic mice led to increased enlargement and leakage of lymphatic vessels after acute UVB irradiation, whereas systemic blockade of VEGF-A signaling largely prevented lymphatic vessel abnormalities and photodamage induced by UVB. Together, these findings identify lymphatic vessels as novel targets for UVB-induced cutaneous photodamage and suggest that VEGF-A mediates impairment of lymphatic vessel function, thereby contributing to the adverse effects of UVB irradiation on the skin.     

小鼠胰腺淋巴管的分布及其与胰岛的关系

目的:探讨小鼠胰腺淋巴管的形态分布及其结构特点。方法:对小鼠胰组织切片进行HE染色,5核苷酸酶(5-Nase)和碱性磷酸酶(ALP)双重染色,光镜、透射电镜、扫描电镜二次电子和背散射电子图像(SEI/BEI)观察。结果:小鼠胰腺的淋巴管结构较典型,在胰腺的小叶间结缔组织内,较大淋巴管与血管和导管相互伴行;毛细淋巴管起自胰腺腺泡周围,并且均匀地分布于整个小叶内;小叶内有单独走行的集合淋巴管,亦存在与血管并行情况;在胰岛内部未发现毛细淋巴管,但胰岛周围可见丰富的毛细淋巴管。结论:小鼠胰腺小叶间和小叶内结缔组织中,均有淋巴管分布;胰岛内部虽无淋巴管,但胰岛与周围毛细淋巴管的关系较密切。     

iNOS抑制剂SMT对内毒素血症大鼠淋巴管动力学的影响

目的 :研究一氧化氮 (NO)在急性内毒素血症中对淋巴管运动的调节作用及诱生型一氧化氮合酶 (iNOS)抑制剂硫酸甲基异硫脲(SMT)对内毒素血症中淋巴微循环的作用。方法 :用倒置显微镜和图像处理系统对肠系膜淋巴管进行动态观测 ,并用硝酸还原酶法测定血清中NO的含量。结果 :LPS组肠系膜淋巴管管径比正常扩大 ,运动频率降低 ,淋巴管运动指数下降。LPS +SMT组则有显著改善。随时间延长LPS组血清NO含量显著升高 ,LPS +SMT组则有明显下降。结论 :内毒素血症中NO过量产生 ,使肠系膜淋巴管扩张 ,收缩减弱。内毒素血症早期应用iNOS抑制剂SMT可维持淋巴微循环于正常水平。     

Effects of electrical stimulation of the dorsal skin on systemic and mesenteric microvascular hemodynamics in anesthetized rats

The effects of electrical stimulation of the dorsal skin area on the mesenteric arterioles were investigated in anesthetized rats by the use of an intravital microscope-television system. Changes in the diameter of the mesenteric precapillary arterioles (10-40 microm in diameter) were measured with an image processor. Blood flow velocity in the mesenteric precapillary arterioles was monitored by the dual sensor method developed by the authors. Electrical stimulation was performed through two platinum electrodes placed at the right dorsal Th5-12 level skin area by the use of an electrical stimulator (0.2 ms, 20 Hz). Continuous stimulation lasting for 30 s (1-10 mA) and intermittent stimulation lasting for 10 min (3 mA) were applied. The pressor response following the depressor response was induced by a stimulus current above 8 mA. The decrease in mesenteric blood flow velocity was induced by stimulus current above 10 mA. These responses were abolished by lidocaine injection into the subcutaneous area where the electrodes were attached. No significant change in arteriolar diameter or heart rate were induced by the stimulation for 30 s. Electrical stimulation of the skin for 10 min evoked a decrease in the diameter of arterioles (-3.4 +/- 2%, p < 0.01, n = 12). In the adrenalectomized group, electrical stimulation of the skin for 10 min elicited a slight increase in the diameter (1.1 +/- 0.5%, n = 6). It is therefore suggested that electrical stimulation of the skin for 30 s reflexly evoked decreases in MAP and in blood flow velocity, and that the constriction of the mesenteric precapillary arterioles induced by the stimulation for 10 min was mediated by humoral adrenaline and noradrenaline released by somato-adrenal medullary reflex.     

Organizing pneumonia and pulmonary lymphatic architecture in diffuse alveolar damage

Diffuse alveolar damage represents the pathologic basis of most cases of the acute respiratory distress syndrome. Diffuse alveolar damage reflects injury to the pulmonary alveolar wall and microvasculature, leading to the exudation of water and plasma proteins that can overwhelm the local lymphatic drainage. Organizing pneumonia is a prominent histopathologic feature in some cases of diffuse alveolar damage. We examined whether diffuse alveolar damage-organizing pneumonia and changes in lymphatic architecture might be indicators of clinical outcome in acute respiratory distress syndrome. Formalin-fixed lung sections (n = 26) from thoracoscopic lung biopsies of patients with diffuse alveolar damage in the fibroproliferative phase, with or without organizing pneumonia, were immunostained with anti-CD31 and anti-D240, markers of vascular and lymphatic endothelium, respectively, and examined by morphometric analysis. Positively staining vessels were enumerated and maximal luminal diameters recorded in randomly selected low-power fields. Patients with diffuse alveolar damage-organizing pneumonia showed greater survival than those with diffuse alveolar damage (67% versus 33%, P = .03). The maximal luminal diameter of D240+ lymphatic vessels was larger for diffuse alveolar damage-organizing pneumonia than diffuse alveolar damage (28 +/- 4 versus 59 +/- 16 microm, P = .02). In addition, larger lymphatic luminal diameters (28 +/- 4 versus 47 +/- 11 microm) were associated with increased survival (P = .12). We conclude that lung biopsy histopathology and pulmonary lymphatic morphology may predict survival in acute respiratory distress syndrome.     

Impact of pore size on the vascularization and osseointegration of ceramic bone substitutes in vivo

The repair of bone defects with biomaterials depends on a sufficient vascularization of the implantation site. We analyzed the effect of pore size on the vascularization and osseointegration of biphasic calcium phosphate particles, which were implanted into critical-sized cranial defects in Balb/c mice. Dense particles and particles with pore sizes in the ranges 40-70, 70-140, 140-210, and 210-280 microm were tested (n = 6 animals per group). Angiogenesis, vascularization, and leukocyte-endothelium interactions were monitored for 28 days by intravital microscopy. The formation of new bone and the bone-interface contact (BIC) were determined histomorphometrically. Twenty-eight days after implantation, the functional capillary density was significantly higher with ceramic particles whose pore sizes exceeded 140 microm [140-210 microm: 6.6 (+/-0.8) mm/mm(2); 210-280 microm: 7.3 (+/-0.6) mm/mm(2)] than with those whose pore sizes were lesser than 140 microm [40-70 microm: 5.3 (+/-0.4) mm/mm(2); 70-140 microm: 5.6 (+/-0.3) mm/mm(2)] or with dense particles [5.7 (+/-0.8) mm/mm(2)]. The volume of newly-formed bone deposited within the implants increased as the pore size increased [40-70 microm: 0.07 (+/-0.02) mm(3); 70-140 microm: 0.10 (+/-0.06) mm(3); 140-210 microm: 0.13 (+/-0.05) mm(3); 210-280 microm: 0.15 (+/-0.06) mm(3)]. Similar results were observed for the BIC. The data demonstrates pore size to be a critical parameter governing the dynamic processes of vascularization and osseointegration of bone substitutes.     

Sequential delivery of dexamethasone and VEGF to control local tissue response for carbon nanotube fluorescence based micro-capillary implantable sensors

In this study, we examined the in vivo pharmacological effects of the sequential delivery of dexamethasone (DX) followed by vascular endothelial growth factor (VEGF) on the immune response and localized vascular network formation around a hydrogel-coated, micro-capillary implant for single-walled carbon nanotube based fluorescence sensors. We demonstrate, for the first time, imaging of an SWNT fluorescence device implanted subcutaneously in a rat. For tissue response studies, the chick embryo chorioallantoic membrane (CAM) was used as a tissue-model for an 8-day implantation period. The average vascular density of the tissue surrounding a hydrogel-coated microdialysis capillary sensor with simultaneous, sequential, or no delivery of DX and VEGF was 1.24+/-0.35x10(-3)vessels/microm(2), 1.15+/-0.30x10(-3)vessels/microm(2) and 0.71+/-0.20x10(-3)vessels/microm(2), respectively. Calculation of the therapeutic index (vasculature/inflammation ratio), which reflects promotion of angiogenesis versus the host immune response, demonstrates that sequential DX/VEGF delivery was 60.3% and 139.3% higher than that of VEGF and DX release alone, respectively, and was also 32.1% higher when compared to simultaneous administration, proving to be a more effective strategy in utilizing the pharmacological impact of DX and VEGF around the biosensor-model implant.     

小鼠空肠缺血再灌注损伤后新生淋巴管内皮细胞的超微结构特征

目的:观察小鼠空肠缺血再灌注损伤后淋巴管再生过程及新生淋巴管内皮细胞的超微结构特征。方法:小鼠深麻醉后,沿上腹正中切开,暴露小肠,用血管钳将肠管两端和营养血管夹闭,15min后松开,恢复血供,将肠管放回腹腔,缝合腹壁。术后0h～7天分别摘取该部分小肠制作光镜和电镜标本,观察新生淋巴管内皮细胞超微结构的变化。结果:小鼠空肠缺血再灌注损伤后,中心淋巴管增殖活跃;残留的淋巴管内皮细胞向生长方向伸出连续细长细胞质突起;新生淋巴管内皮细胞胞质中有丰富的细肌丝和微泡,内皮细胞向管腔内形成较多微突起。内皮细胞周围可以观察到巨噬细胞。结论:小鼠空肠缺血再灌注损伤后,残存的淋巴管内皮细胞显示出明显的增殖特征,提示新生淋巴管内皮细胞可能由残存的淋巴管内皮细胞分裂增殖而来。     

Structure of lymphatics in rat cecum with special reference to submucosal collecting lymphatics endowed with smooth muscle cells and valves. I. A scanning electron microscopic study.

The three-dimensional structure of lymphatic vessels in the rat cecum was studied by KOH-collagenase digestion/scanning electron microscopy (SEM), and corrosion casting/SEM. Abluminal surfaces of the lymphatic vessels show flat elliptical nuclear regions and flat cytoplasmic processes interdigitated with adjacent ones. The lymphatic capillaries closed by interdigitations of flat endothelial processes at their initial portion begin at the various levels of the mucosa. They descend and pass through the muscularis mucosa to connect with the lymphatic vessels in the submucosa. They form polygonal meshwork, the distances between intersections being about 0.2-0.5 mm. They also have valves, the distances between adjacent valves being about 0.1-0.6 mm. Most of the submucosal lymphatic vessels are surrounded by either periendothelial cells or typical smooth muscle cells. The polygonal meshworks made up of stellate periendothelial cells with many irregular processes embrace the initial segment of the collecting lymphatics. As they proceed proximally, the periendothelial cells become elongated and branch out by threes or fours, thus presenting the appearance of smooth muscle cells. These branches are connected side by side and run obliquely along the vessels, thus forming polygonal meshworks around the vessels. The more proximal collecting lymphatic vessels are surrounded by circularly oriented smooth muscle cells. Our results indicate that most of the lymphatic vessels in the submucosa are collecting ones and possess smooth muscle cells as well as valves. This suggests that the lymphatic vessels in the submucosa actively contract and propel the lymph towards the mesenteric lymphatic vessels.     

Vascular endothelial growth factor C is required for sprouting of the first lymphatic vessels from embryonic veins

Lymphatic vessels are essential for immune surveillance, tissue fluid homeostasis and fat absorption. Defects in lymphatic vessel formation or function cause lymphedema. Here we show that the vascular endothelial growth factor C (VEGF-C) is required for the initial steps in lymphatic development. In Vegfc-/- mice, endothelial cells commit to the lymphatic lineage but do not sprout to form lymph vessels. Sprouting was rescued by VEGF-C and VEGF-D but not by VEGF, indicating VEGF receptor 3 specificity. The lack of lymphatic vessels resulted in prenatal death due to fluid accumulation in tissues, and Vegfc+/- mice developed cutaneous lymphatic hypoplasia and lymphedema. Our results indicate that VEGF-C is the paracrine factor essential for lymphangiogenesis, and show that both Vegfc alleles are required for normal lymphatic development.     

A detailed appraisal of mesocolic lymphangiology – an immunohistochemical and stereological analysis

Inadequate resection of the adjoining mesentery is associated with adverse outcome for colon cancer. Disruption of the integrity of the mesenteric lymphatic package has been implicated in this, though not proven. Recent studies have determined mesenteric anatomy and histology and now provide an opportunity to determine accurately the distribution of lymphatic vessels. The aim of this study was to characterise the distribution of the lymphatic vessels (LV) within the small intestinal and colonic mesentery, and in Toldt's fascia, which lies between the mesocolon and underlying retroperitoneum. Mesenteric samples were harvested from 12 human cadavers. Samples were taken from the small bowel mesentery, ascending, transverse, descending mesocolon and from both apposed and non‐apposed portions of the mesosigmoid. Serial sections were stained immunohistochemically with monoclonal antibody D2‐40 (podoplanin), and Masson's Trichrome. Lymphatic vessel (LV) density and radius of diffusion were determined using a stereological approach. A lymphatic network was embedded within the mesenteric connective tissue lattice throughout each mesenteric region. LV were identifiable within the submesothelial connective tissue where they measured 10.2 ± 4.1 μm in diameter and had an average radius of diffusion of 174.72 ± 97.68 μm. Unexpectedly, LV were identified in Toldt's fascia, where they measured 4.3 ± 3.1 μm in diameter and had a radius of diffusion of 165.12 ± 66.26 μm. This is the first study systematically to determine and quantify the distribution of lymphatic vessels within the mesenteric organ and to demonstrate the presence of such vessels within Toldt's fascia. A rich lymphatic network occupies all levels of the mesenteric connective tissue lattice. Within the latter, they are found within 0.1 mm of peritonealised mesenteric surfaces and are separated by an average distance of 0.17 mm and may be particularly vulnerable during surgery.     

Novel threadlike structures (Bonghan ducts) inside lymphatic vessels of rabbits visualized with a Janus Green B staining method

A staining method has been developed for in situ and in vivo observation of a threadlike tissue afloat inside the lymphatic vessels of rabbits without adherence to the vessel wall. The existence of this novel structure was not noticed previously because it is extremely difficult to detect it by microscopic inspection of lymphatic vessels. We have found a method that utilizes Janus Green B (JGB), which stained heavily the novel structure. The tissue was studied by confocal laser scanning microscopy (CLSM), light microscopy, and cryoscanning electron microscopy (cryo-SEM). The CLSM image obtained by acridine orange staining of the novel tissue revealed its characteristic nuclei distribution: rod-shaped nuclei of 10-20 microm length aligned in a broken-line/striped fashion. Hematoxylin and eosin staining revealed the threadlike structure passing through a lymphatic valve as histologically distinct from lymphatic vessels and valves. The cryo-SEM image showed the threadlike structure inside a collapsed lymphatic vessel. There were spherical globular structures observable inside sinuses in a rapidly frozen sample, which suggests liquid flowing through the longitudinal ductules in the threadlike structure. The specific staining of the JGB suggests that these threadlike structures inside lymphatic vessels have a high density of mitochondria in their cells and/or nerve-like properties, either of which may provide important clues to their physiological function.     

Effects of S-nitrosation on hemoglobin-induced microvascular damage

Blood substitutes, such as diaspirin cross-linked hemoglobin (Hb), cause microvascular leakiness to macromolecules. Because of the potentially stabilizing effects of nitric acid (NO) on endothelium, experiments were performed to determine whether S-nitrosohemoglobin (SNO-Hb), a potential NO-donor Hb-based blood substitute, would not cause microvascular damage. Release of NO, or its metabolites, from the SNO-Hb was facilitated by addition of glutathione, which aids in the decomposition of S-nitrosothiols. In anesthetized rats, the mesenteric microvasculature was perfused with SNO-Hb with glutathione (six rats), SNO-Hb alone (six rats), or saline (eight rats) for 10 min, followed by fluorescein isothiocyanate (FITC)-albumin for 1 min, and finally fixed for epifluorescence microscopic examination. When comparing the SNO-Hb group with saline, both the numbers and areas of leaks were significantly increased [0.019 +/- 0.003 (SEM) microm vs. 0.0030 +/- 0.0004 and 7.36 +/- 1.50 vs. 0.156 +/- 0.035 (p < 0.005)]. With the addition of glutathione, leakage was still high (0.005 +/- 0.00005 microm and 5.086 +/- 0.064 microm) but decreased compared with SNO-Hb alone (p < 0.005). In conclusion, NO, or a related vasodilator, when released from SNO-Hb, significantly reduces but does not eliminate microvascular damage. Further improvements may result by S-nitrosating a more stable form of modified hemoglobin.     

Intravital insights in skin wound healing using the mouse dorsal skin fold chamber

The skin fold chamber is one of the most accepted animal models for studying the microcirculation both in health and disease. Here we describe for the first time the alternative use of the skin fold chamber in mice for intravital microscopic investigation of skin regeneration after creating a full dermal thickness wound. The dorsal skin fold chamber was implanted in hairless SKH1-hr mice and a full dermal thickness wound (area approximately 4 mm2) was created. By means of intravital fluorescence microscopy, the kinetics of wound healing were analyzed for 12 days post wounding with assessment of epithelialization and nutritive perfusion. The morphology of the regenerating skin was characterized by hematoxylin-eosin histology and immunohistochemistry for proliferation and microvessel density. The model allows the continuous visualization of wound closure with complete epithelialization at day 12. Furthermore, a sola cutis se reficientis could be described by an inner circular ring of vessels at the wound margin surrounded by outer radial passing vessels. Inner circular vessels presented initially with large diameters and matured towards diameters of less than 15 microm for conversion into radial spreading outer vessels. Furthermore, wound healing showed all diverse core issues of skin repair. In summary, we were able to establish a model for the analysis of microcirculation in the healing skin of the mouse. This versatile model allows distinct analysis of new vessel formation and maturation in regenerating skin as well as evaluation of skin healing under different pathologic conditions.     

High resolution ultrasound elastomicroscopy imaging of soft tissues: system development and feasibility

Research in elasticity imaging typically relies on 1-10 MHz ultrasound. Elasticity imaging at these frequencies can provide strain maps with a resolution in the order of millimetres, but this is not sufficient for applications to skin, articular cartilage or other fine structures. We developed a prototype high resolution elastomicroscopy system consisting of a 50 MHz ultrasound backscatter microscope system and a calibrated compression device using a load cell to measure the pressure applied to the specimen, which was installed between a rigidly fixed face-plate and a specimen platform. Radiofrequency data were acquired in a B-scan format (10 mm wide x 3 mm deep) in specimens of mouse skin and bovine patellar cartilage. The scanning resolution along the B-scan plane direction was 50 microm, and the ultrasound signals were digitized at 500 MHz to achieve a sensitivity better than 1 microm for the axial displacement measurement. Because of elevated attenuation of ultrasound at high frequencies, special consideration was necessary to design a face-plate permitting efficient ultrasound transmission into the specimen and relative uniformity of the compression. Best results were obtained using a thin plastic film to cover a specially shaped slit in the face-plate. Local tissue strain maps were constructed by applying a cross-correlation tracking method to signals obtained at the same site at different compression levels. The speed of sound in the tissue specimen (1589.8+/-7.8 m s(-1) for cartilage and 1532.4+/-4.4 m s(-1) for skin) was simultaneously measured during the compression test. Preliminary results demonstrated that this ultrasound elastomicroscopy technique was able to map deformations of the skin and articular cartilage specimens to high resolution, in the order of 50 microm. This system can also be potentially used for the assessment of other biological tissues, bioengineered tissues or biomaterials with fine structures.     

Optical imaging analysis of microscopic radiation dose gradients in Gafchromic EBT film using a digital microscope

By providing superior localization and immobilization, stereotactic radiosurgery (SRS) is capable of delivering millimeter spheres of dose to intracranial targets with submillimeter precision. Several authors have proposed new SRS solutions to dramatically reduce beam penumbra to hundreds of microns. These solutions require new quality assurance methods capable of penumbra measurement at the micron scale. This article examines the capability of a digital microscope, with translation stage and associated software, to resolve dose gradients in Gafchromic EBT film at this level. To produce very steep penumbra, films were irradiated in phantom beneath pinhole collimators using lower energy x rays (100 kVp, 300 kVp, and Iridium-192) and minimal geometric penumbra contribution. For film analysis, a method was developed which improved the signal to noise ratio by finding the center of the irradiation spot, generating several radial dose profiles and averaging these to obtain the final off-axis dose profile. Optical density was converted to dose using a calibration curve. The experimentally determined off-axis dose profiles were compared with MCNP Monte Carlo simulations which replicated the irradiation geometry and served to validate our measured data. The measured 80%-20% penumbral widths were 46 microm +/- 26 microm (100 kVp, 2 mm field size), 69 microm +/- m 27 microm (300 kVp, 2 mm field size), and 241 microm +/-31 microm (Ir-192, 1 mm field size). These penumbral widths agreed with Monte Carlo simulations within experimental uncertainty. Our findings suggest that reading Gafchromic EBT films using a digital microscope with translation stage is suitable for the quality assurance of very sharp penumbra able to resolve gradients to within at least 30 microm.     

Quantification of water diffusion and relaxation times of human U87 tumors in a mouse model

Assessing the potential of anti-cancer agents can be greatly facilitated by applying MRI methods to investigations with animal models. Quantitative diffusion imaging, T1, and T2 measurements may offer valuable information for understanding properties of the tumor and for evaluating new therapeutic approaches. The human U87 high-grade glial tumor is widely used for cancer investigations in orthotopic murine models. The physiological features of this model at the cellular and sub-cellular level have not, however, been well characterized by MRI. In this study, we measured the diffusion, T1 and T2 characteristics of water in the human U87 tumor at 8.5 T in an orthotopic murine model in vivo and analyzed their detailed changes in the transition from the tumor core through the tumor periphery, and out to surrounding tissue using custom developed radial profile analysis software. For the tumor bearing mice (n = 10), the mean average apparent diffusion coefficient (ADC) of the tumor core was 1.03 +/- 0.02 ( x 10(-3) mm2/s), while in the contralateral normal brain it was 0.73 +/- 0.03 ( x 10(-3) mm2/s). The mean T1 in tumor was 2.03 +/- 0.08 s and in normal brain tissue was 1.64 +/- 0.06 s. The mean T(2) in tumor was 0.062 +/- 0.002 s and in normal brain tissue was 0.048 +/- 0.001 s. The mean ADC, T1 and T2 of the tumor compared to normal tissue were significantly different (p < 0.005).     

Regulatory mechanisms in lymphatic vessel contraction under normal and inflammatory conditions

The lymphatic system is composed of a dense network of lymphatic vessels, which are critical components of physiological interstitial fluid transport. These vessels possess intrinsic contractile properties providing the driving force for the fluid to be drained away from the tissues and propelled, as lymph, back into the bloodstream. Lymphatic pumping is also important to carry immune cells, bacteria, macromolecules, viruses and their products to and through lymph nodes, the other component of the lymphatic system, to initiate the adaptive immune response. In addition, among the many circulating mediators known to modulate lymphatic contractile activity and thus lymph flow, mediators of inflammation have potent excitatory or inhibitory actions. The involvement of lymphatic vessels in edema resolution, immune cell trafficking and their sensitivity to inflammatory mediators make them pivotal players of the inflammation process. The ability of lymphatic vessels to generate and regulate lymph flow is provided by the lymphatic muscle present in the vessels’ wall. Although molecular studies investigating the mechanisms of lymphatic vessel contraction are still very limited, recent findings suggest that lymphatic pumping requires complicated muscle activities that have similarities to those seen in both the heart (striated muscle) and blood vessels (smooth muscle). This review article focuses on presenting and discussing the mechanisms that regulate lymphatic vessel contraction under normal and pathophysiological states, specifically pertaining to inflammatory conditions.     

Angiogenesis occurs by vessel elongation in proliferative phase human endometrium

BACKGROUND: Angiogenesis occurs by at least three mechanisms: sprouting, intussusception and elongation. Studies to date have failed to identify the mechanisms or timing of endometrial angiogenesis during the menstrual cycle. The aim of this study was to determine if vessel elongation plays a role in human endometrial angiogenesis. METHODS: Forty-nine full thickness endometrial sections from 27 hysterectomy samples were immunostained for CD34 to identify blood vessels, and analysed using an interactive computerized stereological program. Based on counts from 9746 individual microscope fields, blood vessel length density (L(v)), branch point density (N(v)) and mean vessel length per branch point (L(v)/N(v)) were calculated for three endometrial zones during five phases of the menstrual cycle. RESULTS: There was an increase in L(v)/N(v) in the mid-late proliferative compared with early proliferative, early-mid secretory and late secretory phases of the menstrual cycle in the functionalis (mean +/- SEM: 174.5 +/- 20.1 versus 76.6 +/- 8.4, 118.6 +/- 9.4 and 104.2 +/- 4.1 microm respectively, P < 0.001) and between the mid-late proliferative and the menstrual phases in the basalis (158.0 +/- 18.2 versus 95.4 +/- 10.0 microm, P = 0.025). An increase in L(v) occurred in the subepithelial capillary plexus in the mid-late proliferative and early-mid secretory phases compared with the early proliferative phase (316.7 +/- 32.4 and 338.8 +/- 45.3 versus 178.5 +/- 8.9 mm/mm(3), P = 0.027). CONCLUSIONS: These data are the first evidence that vessel elongation is a major angiogenic mechanism in mid-late proliferative phase human endometrium.