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Results for “Neovascularization, Pathologic”

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PubMed1991

Inhibitors of angiogenesis.

Angiogenesis, the formation of new capillaries, is essential to a number of important physiological events, both normal and pathological. Recently, increased attention has focused on the purification and characterization of inhibitors of this process, because of the potential therapeutic value of angiogenesis inhibitors in controlling such "angiogenic diseases" as proliferative retinopathy, solid tumors, rheumatoid arthritis, and neovascular glaucoma. We review the process of neovascularization and the assays that have been developed to study its inhibition in vivo and in vitro. We also discuss the properties of different angiogenesis inhibitors and examine the mechanisms by which such inhibitors could potentially intervene in the process of neovascularization.

Animals↗

PubMedDate not supplied

Angiogenesis in the uterus: potential regulation and relation to tumor angiogenesis.

Except under certain pathological conditions such as wound healing and solid tumor growth, angiogenesis is a relatively rare event in the adult. One exception, however, is the angiogenesis that occurs during the cyclical changes in the female reproductive tract. Many factors, chemical as well as mechanical, have been shown to be capable of promoting or inhibiting angiogenesis in vivo and in vitro. However, despite intense research efforts, the mechanisms involved in the regulation of angiogenesis in vivo are not fully understood. In this article we briefly review the basic steps involved in angiogenesis and present examples of factors and conditions that may serve as potential regulators of angiogenesis in the nonpregnant uterus. Finally, we discuss some of the architectural, anatomical, and physiological differences between the microcirculatory beds established during normal, self-limited vessel growth and that associated with the uncontrolled, pathological vascular growth that accompanies tumor growth and metastasis.

Cell Transformation, Neoplastic↗

PubMed1986

Doppler ultrasound as an adjunct to the differential diagnosis of pigmented skin lesions.

One hundred and forty-one pigmented skin tumours were examined with a 10 MHz ultrasound Doppler flowmeter to investigate the value of detecting blood flow in the diagnosis of raised pigmented skin lesions. Most of the benign lesions except for those with an angiomatous basis were devoid of blood flow signals while all basal cell carcinomas and 96 per cent of thick melanomas (greater than or equal to 0.9 mm) were associated with detectable Doppler frequency shift signals. While the characteristics of analysed Doppler waveforms are of research interest, the simple detection of blood flow by a hand held instrument gives sufficient information for clinical purposes. In practice this simple test has been sufficiently reliable to prove a useful adjunct in the diagnosis of raised pigmented skin lesions. It has been found particularly helpful in the common clinical problem of differentiation of nodular melanoma from basal cell papilloma and benign intradermal naevus. If such a lesion is thought to be benign, and has detectable flow signals, one should reconsider the diagnosis. Absence of flow signals is strong confirmation of a benign clinical diagnosis. The test should be regarded as an adjunct to clinical diagnosis since, in common with all noninvasive diagnostic techniques, false negative and false positive cases will be encountered. The technique is not appropriate to macular lesions since these are usually flow negative, irrespective of the pathology.

Adolescent↗

PubMed1992

Angiogenesis and angiogenesis inhibitors in paediatric diseases.

Angiogenesis, the generation of new capillaries from existing blood vessels, is rarely observed in the healthy organism, but can present during various paediatric diseases. In this review, we describe recent progress in the understanding of pathological angiogenesis and approaches for an improved therapy of angiogenic childhood diseases.

Angiogenesis Inducing Agents↗

PubMed1992

Mast cells and angiogenesis.

Much data exists in the literature to suggest a correlation between mast cell accumulation and angiogenesis. This correlation exists for normal blood vessel growth as well as pathological vessel growth. The recruitment of mast cells to sites of angiogenesis is not completely understood. However, once at the site, mast cell products may act directly on endothelial cells to stimulate their migration and/or proliferation or may act indirectly by degrading connective tissue matrix to provide space for neovascular sprouts to form. Understanding the role of mast cells in angiogenesis may provide avenues for intervening in and manipulating the neovascularization process.

Animals↗

PubMed1990

Subretinal hemorrhages with or without choroidal neovascularization in the maculas of patients with pathologic myopia.

We examined 20 patients (24 eyes) who had refractive errors of -8 diopters or more and subretinal hemorrhages at the initial visit. They were divided into two groups according to fluorescein angiographic findings: 15 eyes without choroidal neovascularization (CNV) and 9 eyes with CNV. Subretinal hemorrhage without CNV was frequent in patients aged 20-39 years (mean, 36.8 years). CNV was common in patients aged 60-79 years (mean, 61.0 years). No relationship was noted between refractive error and type of hemorrhage. In the eyes without CNV, the subretinal hemorrhages disappeared spontaneously after a few months. The visual acuity of these patients was variable at the initial visit (range, 0.01-0.8), and was unchanged or improved during the follow-up period. In the eyes with CNV, the visual acuity was less than 0.1 at the initial visit and was unchanged or worse during the follow-up period.

Adult↗

PubMed1990

Carcinoma in situ of the cornea.

Carcinoma in situ of the cornea is part of a pathological entity, which covers all conjunctival and corneal epithelial neoplasiae (CIN). The clinicopathological characteristics of this rare ocular tumor will be demonstrated.

Adult↗

PubMed1992

Platelet-derived growth factor is angiogenic in vivo.

PDGF receptors have recently been found to be expressed in microvascular endothelium in vivo under circumstances of endothelial cell activation and angiogenesis suggesting that PDGF may have a direct effect on endothelial cells. We have tested the angiogenic activity of PDGF-AA and -BB homodimers in the chick chorioallantoic membrane in vivo. PDGF-BB was found to consistently induce an angiogenic response whereas PDGF-AA was less active. Morphological analyses revealed that there was little inflammation associated with this response but an increase in vessel density suggested a direct effect of PDGF on embryonic chorioallantoic endothelial cells. In vitro, PDGF-BB was found to be more potent than PDGF-AA in stimulating the chemotaxis of rat brain capillary endothelial cells. This is consistent with a direct effect of PDGF on endothelial cells. Thus, this novel angiogenic activity of PDGF has implications for several developmental and pathological events in which PDGF, particularly the B-chain, is expressed.

Allantois↗

PubMed1990

Comparison of Dolichos biflorus lectin and other lectin-horseradish peroxidase conjugates in staining of cutaneous blood vessels in the hairless mini-pig.

Angiogenesis is necessary for normal growth, wound healing, and plays a key role in many pathologic processes. A variety of endothelial markers have been used to investigate angiogenesis. Unfortunately, excellent markers for vascular endothelium in human tissues exhibit little or no staining of endothelia in tissues of other animal species, including the pig. We are interested in the hairless Yucatan strain of mini-pig as an animal model for studying cutaneous wound healing because its skin is histologically and functionally very similar to that of man. Hoping to find a specific marker to identify vascular endothelium in the mini-pig, we therefore screened a battery of 11 different lectin-horseradish peroxidase conjugates. Based on specificity and staining intensity, Dolichos biflorus agglutinin (DBA) was chosen from this battery to investigate vascular changes in the healing of cutaneous wounds in the mini-pig. When compared with routine histologic sections stained with hematoxylin and eosin, blood vessels were much easier to identify in sections stained histochemically with DBA. Lectin histochemistry was particularly useful in investigations of early events in angiogenesis during wound healing when newly derived capillary buds and minute blood vessels were obscured in normal histologic sections by an inflammatory cell infiltrate associated with the healing wound. Ultrastructural lectin cytochemistry revealed staining along the luminal surface and the basolateral plasmalemma of endothelial cells. Histochemical staining with DBA promises to provide a useful method for further investigation of angiogenesis and other vascular phenomena in a variety of normal and pathologic processes using the hairless Yucatan strain of mini-pig as the animal model.

Animals↗

PubMed1991

Angiotensin and the regulation of cellular growth. Pathophysiologic implications for cardiovascular and noncardiovascular tissues.

Components of the renin-angiotensin system can be found in the vasculature, although in most cases it is unclear how much, if any, of this renin in the vasculature is locally synthesized. Over recent years, a variety of novel actions of angiotensin II have been delineated which suggest that in appropriate physiologic or pathologic circumstances vascular angiotensin II can play an important role in determining vascular structure. Moreover, angiotensin II may play a role in neoplastic growth of vascular and nonvascular tissues.

Angiotensin II↗

PubMed1990

[Experimental study of an axial vascularized pedicle flap induced in rats].

The authors report an experimental study about induced flaps in rats. The aim of this study is to determine that neoangiogenesis can be formed from surgically introduced pedicle. Two main groups were studied: in the first one the arteriovenous pedicle was be anastomased at its distal end, in the other, an arteriovenous loop was created microsurgically. In both groups we obtained good results and the flaps stayed alive. Neoangiogenesis from the surgically introduced axial pedicle was observed. The prospects in human pathology are interesting to consider, for the surgeon might be liberated from the narrow anatomic limits imposed by vascular territories, by creating a suitable flap anywhere in the body.

Graft Survival↗

PubMed1991

Microsurgical management of neovascularisation secondary to posterior segment ischaemia.

Structural, metabolic and functional rehabilitation of eyes affected by the haemorrhagic and tractional sequelae of neovascularisation secondary to posterior segment ischaemia is discussed. Microsurgical management must pay due attention not only to the mechanical but also to the underlying cell-biological implications of the surgical pathology. The appropriateness of case selection for surgery rests upon the likelihood of successful technical and functional outcomes and also upon the overall visual status of the patient, issues of particular relevance to diabetes.

Diabetic Retinopathy↗

PubMed1990

Developing testicular microvasculature in the golden hamster, Mesocricetus auratus: a model for angiogenesis under physiological conditions.

The ultrastructure of the developing testicular microvasculature in the testes of immature (3, 5, 8, 10, 12, 16, 20, 25, 30 and 35 days old) golden hamsters was examined and compared to the testicular microvasculature of adult (3 months old) hamsters. In addition, in 16- to 35-day-old hamsters vascular permeability was studied after localization of injected horseradish peroxidase (HRP). Angiogenic processes were present in the testes of all examined immature hamsters and were most conspicuous between 8 and 25 days of age. These processes were absent in the testes of 3-month-old hamsters. On days 3 and 5, few undifferentiated blood vessels with activated endothelium were present in the interstitial spaces. Endothelial cell migration started from these 'mother vessels' and led to invasion of intertubular spaces by vascular sprouts, before vascularization of peritubular spaces occurred (after day 12). Sprouting endothelial cells were identified by the presence of a basal lamina and characterized by abundant cytoplasm and cell organelles. HRP-positive slits were seen in developing vessels, which opened to form the vascular lumen. HRP exited the vascular lumen through unspecialized endothelial contacts and micropinocytotic vesicles. By day 16, the blood-testis barrier prevented HRP from entering the seminiferous tubules beyond the basal compartment. By days 30 and 35 most testicular microvessels and at the age of 3 months all testicular microvessels were of the mature type, with narrow inactive endothelium and specialized cell contacts (including tight junctions). These results demonstrate that the postnatal vascularization of the testis in the golden hamster is a timed complex process. Due to high permeability, vascular sprouts are likely to influence the metabolic situation and thus the maturation processes of the testis. Angiogenesis in the golden hamster testis shares typical morphological features with angiogenic processes in other organs and species under various pathological and physiological conditions. We therefore conclude that the postnatal testis can be viewed as a physiological model of angiogenesis.

Animals↗

PubMed1990

Increased angiogenesis in diabetes.

Rats with streptozotocin-induced diabetes mellitus showed a 3.4-4.5 times increased angiogenic response following mast-cell activation in situ as compared with age-matched normal controls. The test tissue used was the mesenteric window, which we have previously exploited as a quantitative angiogenesis assay. In the present study two independent techniques for quantifying the angiogenic response showed essentially the same result. The finding of a pathologically increased angiogenic reaction in the diabetic animals is noteworthy since some of the most harmful complications of diabetes in man relate to proliferative vascular lesions.

Animals↗

PubMed1989

Fibroblast growth factors.

The existence of fibroblast growth factors (FGFs) was proposed over 40 years ago to account for the ability of tissue extracts to stimulate fibroblast proliferation. In the 1970s it became clear that preparations containing FGF activity were in fact pleiotropic, affecting the growth and function of a wide variety of mesenchymal, endocrine and neural cells. Their angiogenic effects have promoted research in cardiology and neurology because of their proposed role in stimulating collateral vascularisation and recovery from ischemia. Their identity with a component of tumour angiogenesis factor activity has stimulated research in oncology and their capacity to enhance wound healing, nerve regeneration and cartilage repair has affected research in neurology, orthopaedic medicine and pathology. The potential therapeutic value of FGFs is just beginning to be realized and will be dependent on a concerted effort to establish their function in the regulation of normal cell homeostasis and the pathophysiology of disease.

Animals↗

PubMed1991

Angiogenesis in arteries: review.

The inner parts of the walls of large blood vessels do not normally contain intrinsic vasculature. In pathologic conditions such as arteriosclerosis or thrombosis, angiogenesis occurs, and may have significant clinical consequences. This review attempts to relate the little that is known about the factors specific to vascular walls which regulate angiogenesis to more general knowledge of the phenomenon.

Animals↗

PubMed1992

Quantitative image analysis of angiogenesis in rats implanted with a fibrin gel chamber.

Angiogenesis, a fundamental process in various physiological and pathological events, is generally studied using in vivo models, such as the chick chorioallantoic membrane or the rabbit cornea, which are difficult to quantitate. We developed the quantitation of angiogenesis in an in vivo model previously described by Dvorak et al [6]. Perforated plexiglass chambers filled with human or rat fibrin were implanted into the dorsal subcutaneous space of a Wistar rat. After four days of implantation, a sequentially organized invasion of the fibrin gel by various blood cell types occurred through the holes and neovascularized granulation tissue buds appeared. These buds presented mature neovessels and a new collagen matrix. Three dimensional computer image analysis of the chambers was performed using macroscopic and microscopic parameters: total vascularized area, bud height and equivalent diameter, number of vessels per bud and percentage of central vessels. The time course of the angiogenic response to rat or human fibrin gel was studied and 14 days was found to be the optimum period of implantation. The bud height and number of neovessels were not found to be significantly different when rat or human fibrin gels were used. This quantitative study was a prerequisite for further investigations of the effects of biological and pharmacological agents on angiogenesis.

Animals↗

PubMed1987

Vascular response of the cornea to contact lens wear.

The subject of contact lens-induced corneal vascularization has attracted considerable interest in recent times in view of the relatively high prevalence of this condition with the use of extended wear soft lenses. This paper reviews clinical features and underlying mechanisms of the vascular response to lens wear. The concept of a "normal" vascular response to contact lens wear is proposed; the limits of this response are defined and incorporated into a simple grading system. The clinical presentation of vessel growth in the cornea is described together with appropriate methods of slit lamp evaluation. Current theories of the pathology and etiology of lens-induced vascularization are reviewed, and a dual-etiology model of stromal vessel formation is described. It is concluded that the prognosis for halting the progression of vascularization is excellent; however, little information is available concerning the long-term regression of "ghost" vessels.

Contact Lenses, Extended-Wear↗