Architectural alterations in rat cerebral microvessels after hypobaric hypoxia

We performed 3-dimensional studies of vascular casts of the microvasculature of the cerebral cortex of rats that were exposed to three weeks of hypobaric hypoxia and of control rats. Scanning electron microscopy of the casts gave the qualitative impression of increased vascularity of the cerebral cortex, particularly the deeper layers, in hypoxic rats. Quantitative analysis of capillary segment lengths revealed a significant shift in the frequency distribution to longer lengths (from 77 ± 8 to 90 ± 14 μm) in the deep, but not in the superficial, layers of the cerebral cortex of hypoxic rats. These findings agree with previous results reporting increased capillary density in the brain after exposure to prolonged hypobaric hypoxia and suggest that capillary segment elongation plays a role in the increased capillary density in the deeper layers of the cerebral cortex.     

The vascular response to tumor infiltration in malignant gliomas

Summary Neo-vascularization and endothelial hyperplasia have been shown to be very active in malignant gliomas. In this contribution the vascularization of the cortex infiltrated by malignant gliomas is morphometrically studied and the endothelial proliferations are immunohistochemically investigated and reconstructed by a three-dimensional computer-assisted procedure. Vessel density increases after tumor infiltration in some cases only. The diameter of vessels increases and so does the number of nuclei/vessel after the complete invasion of the cortex when vascular glomeruli develop. In completely infiltrated cortex with development of glomeruli and circumscribed necroses, vessel density is very low. No neoformation of vessels takes place before the complete infiltration of the cortex by the tumor. The hyperplastic formations, usually arranged parallel to the deep or outer cortical layers, take origin from the radially penetrating vessels from the meninges and their lateral branching. The hyperplasia deforms the vascular network, making it often inadequate to supply tumor cells. Immunohistochemically, the cells composing the hyperplastic structures are variably positive for factor VIII/RAg and, at a lesser extent, for -smooth muscle actin. The poorness of the vascular network in many instances of completely infiltrated cortex is responsible for the development of circumscribed necroses.Supported by Grant 87.01446.44 CNR, Rome and by A. I. R. C., Milan. Presented in part at the 63rd Annual Meeting of the American Association of Neuropathologists, Seattle, Washington, June 11–14, 1987     

血管生成及其抑制剂在前列腺癌中的研究进展

Angiogenesis plays a key role in progression of prostate cancer. Antigiogenesis becomes a new treament target for prastate cancer. In this review, we focus on the current knowledge of angiogenesis and tumor angiogenesis inhibitor in prastate cancer.     

HESR1基因在血管新生中作用的初步研究

目的研究转录因子HESR1在血管新生中的作用。方法检测内皮细胞激活状态HESR1表达的影响,克隆HESR1基因,转染到HUVEC,绿色荧光和PCR观察HESR1在内皮细胞的表达,流式细胞仪检测它对血管内皮细胞增殖,boyden小室检测对细胞迁移的影响,建体外二维血管模型,观察HESR1对血管形成的影响。结果内皮细胞激活状态HESR1的表达下降,HESR1基因能抑制内皮细胞的增殖和迁移,减少血管新生。结论HESR1基因通过抑制内皮细胞的增殖和迁移,使内皮细胞从激活状态转入安静状态,减少血管的形成,维持血管的稳定状态。     

卵巢癌血管生成的多样性

新血管生成在个体发育、创伤愈合等过程中起着至关重要的作用,也是肿瘤生存、转移、复发的组织基础[1].研究表明,少数极恶性肿瘤存在血管生成(angiogenesis)、血管形成(vasculogenesis)和血管生成拟态(vasculogenic mimicry)等方式,多种血管新生方式与肿瘤的转移、复发等恶性生物行为密切相关.卵巢癌的死亡率在女性生殖道癌瘤中居首位,患者5年生存率长期徘徊在30%左右,最新研究证实,卵巢恶性肿瘤血管生成具有多样性,本文将就卵巢癌不同血管生成方式的研究进展及其与卵巢恶性生物学行为的关系进行综述.     

抗肿瘤血管生成研究的现状与有待解决的问题

 血管生成是指在原有组织血管结构基础上形成新血管结构的过程。1971年Folkman[1]提出了肿瘤血管依赖性生长的概念，并把肿瘤生长分为非血管期和血管期两个生长阶段。固体肿瘤在血管生成前，肿瘤体积一般不超过3 mm3。随着肿瘤细胞的不断增殖，肿瘤组织出现缺氧、代谢产物堆积、pH值改变等，这些因素刺激肿瘤细胞、周围间质细胞和淋巴细胞分泌各种促血管生长刺激因子，通过诱导血管基底膜降解和内皮细胞增殖，启动新生血管的生成。 肿瘤一旦血管化, 不仅生长速度加快，而且容易发生转移，说明血管生成对肿瘤的生长和转移都起到关键作用。因此,在过去30多年中，人们致力于对肿瘤血管生成机制的研究，并试图通过抑制和破坏肿瘤血管生成来建立一种治疗肿瘤的新方法。......     

Angiogenesis of glioma: evaluation of ultrastructural characteristics of microvessels and tubular bodies (Weibel–Palade) in endothelial cells and immunohistochemical findings with VEGF and p53 protein

Capillary endothelial proliferation is often a prominent feature of malignant gliomas. The understanding of structural and functional characteristics of the vascular microenvironment in gliomas is essential for the design of future therapeutic strategies against this tumor. Electron microscopic analysis of the capillary endothelial proliferation in malignant gliomas indicated that the complex vascular structures within the tumor were composed essentially of immature capillaries. Immature capillaries had a narrow slitlike lumen composed of endothelial cells with their high nuclear:cytoplasmic ratio and the relative paucity of organelles. They resembled capillary buds seen in normal repair tissue. Immature microvessels caused by angiogenesis were found more frequently in marginal zone of the tumors with increased microvessels. The tubular body was an organelle observed in vascular endothelial cells and was used frequently as a marker of the endothelial cell. Tubular bodies were evaluated by quantitative measurement of the mean percent (%) ratio of the number of endothelial cells with tubular bodies to all endothelial cells in microvessels of tumors. In glioblastomas it yielded a value of 32.4% in the margin, about two times as high as that in the center of the tumors. However, it was lower in all locations of astrocytomas. Tubular bodies in endothelial cells could be increased in proportion to neovascularization, and they might serve as a marker for increasing microvessels in astrocytic tumors. Tumor angiogenesis may be regulated by growth factors with angiogenic activities that are secreted by tumor cells. Vascular endothelial growth factor (VEGF) may play a critical role in the regulation of vascular endothelial proliferation. We found that 86% of 29 glioblastomas and 79% of 14 anaplastic astrocytomas demonstrated immunoreactivity for VEGF in their tumor cells. There tended to be a correlation between VEGF and vascularity. A correlation existed between the grade of immunoreactivity for VEGF and the grade of p53 protein expression in the malignant gliomas. However, the MIB-1 indices did not increase in correlation with increase in the extent of immunoreactivity for VEGF.     

Changes in VEGF expression and in the vasculature during the growth of early-stage ethylnitrosourea-induced malignant astrocytomas in rats

 Vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, may be important as a mediator of brain tumour progression. However, it is still not clear whether VEGF plays a causative role in the early stage of glioma development. We investigated the relationship between VEGF protein expression (as assayed by immunohistochemistry) and different morphological parameters reflecting tumour progression (tumour diameter, vascular density and vascular diameter) in tumours at various stages. As a tumour model, ethylnitrosourea (ENU)-induced rat malignant astrocytoma was used. Tumours were classified by size and level of vascularity estimated by the von Willebrand factor (vWF) staining. Tumours less than 10 mm in diameter were designated early stage neoplastic lesions. All 34 early astroglial tumours were found to be VEGF positive. Increase in the VEGF immunopositive rate of tumour cells correlated significantly with increase in vascular density and vascular diameter. We suggest that VEGF induces angiogenesis and growth of microvessels, promoting growth of the early stage malignant astrocytoma. Received: 7 October 1997 / Accepted: 9 June 1998     

Model for Intravital Microscopic Evaluation of the Effects of Arterial Occlusion-caused Ischemia in Bone

An in vivo model has been developed for chronic observation of the effects of ischemia on cortical bone remodeling and perfused vascularity. Diaphragm occluders were implanted around the right common iliac artery of four rabbits and inflated to produce 10 h of ischemia to the limb. Microcirculation was monitored with intravital microscopy of injected fluorescent microspheres and FITC-Dextran 70 through a bone window, the tibial bone chamber implant (BCI). Bone resorption and apposition in the BCI were indicated with mineralization dyes. Between 2 and 12 h following release of the occluder, secondary ischemia/no-reflow and other evidence of reperfusion injury were observed. Vessel damage was suggested by abnormally high leakage of FITC-D70 from the few vessels perfused during secondary ischemia. In the weeks following occluder release perfused vasculature increased beyond pre-occlusion levels. Net bone resorption reached a maximum when vascularity passed normal levels. In order to further validate the arterial occlusion model for osteonecrosis, techniques for (1) confirming bone death and (2) detecting increased leukocyte adherence to endothelial cells were added. The dead cell stain Ethidium homodimer-1 was used to tag dead osteocytes immediately after occlusion and produced a measure designated osteonecrosis index. To detect leukocytes adhering to vessel walls, carboxyfluorescein diacetate, succinimidyl ester was injected at occluder release. An increase in the number of adherent leukocytes was detected. © 1999 Biomedical Engineering Society. PAC99: 8764Rr, 8717-d, 8719Tt     

A modified chorioallantoic membrane (CAM) assay for qualitative and quantitative study of growth factors

Summary The application of Thermanox tissue culture coverslips to the day 9 CAM of the chick causes constant effects beneath the carrier after 3 days, and these are associated with a change in the blood vessel pattern. Histological sections show enormous thickening of the CAM in the reactive areas. The stroma of the CAM shows fibrocyte proliferation, leucocyte infiltration, and clusters of dispersed ectodermal epithelial cells exhibiting signs of necrosis. The latter obviously cause a strong vascular response. The same effects are seen when the Thermanox discs are applied at day 11. Following application on day 12 a positive or negative response to the carrier is observed, whereas on day 13 no such carrier effects are seen. The only remaining effect is compression of the intra-ectodermal capillary plexus of the CAM. This can macroscopically be seen after peroxidase staining of the blood vessels. The effect of 5 l PBS dried on the Thermanox disc and applied to the day 13 CAM is to cause, after 3 days, hyperosmotic damage to the ectodermal epithelium, which becomes overgrown by fibrocytes. We found dose-dependent effects of salt-free human bFGF applied to the day 13 CAM. The first and main effect is fibrocyte proliferation (0.5 g). New capillaries appear with higher doses, but are not as frequent as would be expected for an angiogenic substance (1.25–2.5 g). Also with higher doses additional hyperplasia of the endodermal (3.75 g) and ectodermal (5 g) epithelium can be seen. The latter might be a non-specific hyperosmotic effect. Leucocytes are regularly present within the reactive areas. When salt-free angiogenin is applied to the day 13 CAM, some effects appear with doses of 4.6 g and more. The ectodermal epithelium of the reactive areas is discontinuous, exhibiting signs of necrosis. It is overgrown by parallel fibrocytes. Whether this is a non-specific hyperosmotic effect, or indicates enhancement of invasive growth, calls for further investigation.