Scanning electron microscopic studies on blood vessels in cancer of the larynx

Arterial and microvascular supply of cerebral hemispheres in the nude mouse revealed using corrosion casting and scanning electron microscopy

Morphological analyses of cerebral vascularization are not only important for the characterization of the anatomical and physiological relationships between vascular and nervous tissue, but also required to understand structural modifications that occur in many pathological conditions affecting the brain. The aim of this study was to generate a three-dimensional vascular map of the cerebral hemispheres in the nude mouse brain, a widely used animal model for studying tumour biology. We used the corrosion casting (CC) technique to isolate blood vessels from 30 nude mouse brains. All casts were analysed using scanning electron microscopy (SEM), which generated quantitative data regarding vessel length and diameter as well as inter-vascular and inter-branching distances. We identified three different topographical regions: (i) the cortical region, characterized by a superficial wide sheet of vessels giving rise to terminal perforant vessels that penetrate the grey matter; (ii) the inner part of the grey matter, in which dense capillary nets form many flake-like structures extending towards the grey-white matter boundary, where perforant vessels finally change direction and form a well-defined vascular sheet; and (iii) the white matter layer, characterized by a more disorganized vascular architecture. In this study, we demonstrate the accuracy of the CC-SEM method in revealing the 3D-topographical organization of the vascular network of the normal nude mouse brain. These baseline data will serve as a reference for future anatomical investigations of pathological alterations, such as tumour infiltrations, using the nude mouse model.

A Tridimensional Study of Microcirculation in Skeletal Muscle

The authors used a microcorrosion cast technique to study the microvascular bed of skeletal muscles in the rat.

They also tried to clarify the differences, in this respect, between fast twitch and slow twitch muscles. For this purpose they studied as fast twitch muscles, the tibialis anterior muscle and the pectineus muscle and, as a slow twitch mus cle, the soleus muscle.

Thanks to the peculiar technique used, they were able to distinguish differ ent sections of the microvascular bed.

They also found astonishing differences between the capillary networks in the soleus and tibialis anterior muscles, on the original bases of peculiar charac teristics of the capillary network in the soleus.

Early-stage microvascular alterations of a new model of controlled cortical traumatic brain injury: 3D morphological analysis using scanning electron microscopy and corrosion casting

Object

This study was performed to study the microvascular changes that occur during the first 12 hours after traumatic brain injury (TBI) using the corrosion casting technique.

Methods

The authors performed a qualitative and quantitative morphological study of the changes in cerebral vessels at acute (3 hours) and subacute (12 hours) stages after experimental TBI. They used a model of controlled cortical impact (CCI) injury induced by a recently developed electromagnetic device (impactor), focusing their observations mainly on the microvascular alterations responsible for the formation and maintenance of tissue edema and consequent brain swelling during the first hours after TBI. They used corrosion casting, scanning electron microscopy (SEM), light microscopy, and transmission electron microscopy (TEM) to obtain a morphological qualitative map with both 2D and 3D details.

Results

Scanning electron microscopy analysis of vascular casts documented in 3 dimensions the typical injuries occurring after a TBI: subdural, subarachnoid, and intraparenchymal hemorrhages, along with alterations of the morphological characteristics and architecture of both medium-sized and capillary vessels, including ectasia of pial vessels, sphincter constrictions at the origin of the perforating vessels, focal swelling of perforating vessels, widening of intercellular junctions, and some indirect evidence of structural impairment of endothelial cells. All of these vascular alterations were confirmed in 2D analyses using light microscopy and TEM.

Conclusions

The corrosion casting–SEM technique applied to a CCI experimental model proved to be a reliable method for studying the pathophysiology of the vascular alterations occurring at acute and subacute stages after CCI injury. It was also possible to obtain topographical localization of the vascular and cellular events that usually lead to hyperemia, edema, and brain swelling. Moreover, by applying informatic software to anatomical images it was possible to perform quantification and statistical analysis of the observed events.

Maximizing modern distribution of complex anatomical spatial information: 3D reconstruction and rapid prototype production of anatomical corrosion casts of human specimens

Anatomical corrosion casts of human specimens are useful teaching aids. However, their use is limited due to ethical dilemmas associated with their production, their lack of perfect reproducibility, and their consumption of original specimens in the process of casting. In this study, new approaches with modern distribution of complex anatomical spatial information were explored to overcome these limitations through the digitalization of anatomical casts of human specimens through three-dimensional (3D) reconstruction, rapid prototype production, and Web-based 3D atlas construction. The corrosion cast of a lung, along with its associated arteries, veins, trachea, and bronchial tree was CT-scanned, and the data was then processed by Mimics software. Data from the lung casts were then reconstructed into 3D models using a hybrid method, utilizing both "image threshold" and "region growing." The fine structures of the bronchial tree, arterial, and venous network of the lung were clearly displayed and demonstrated their distinct relationships. The multiple divisions of bronchi and bronchopulmonary segments were identified. The 3D models were then uploaded into a rapid prototype 3D printer to physically duplicate the cast. The physically duplicated model of the lung was rescanned by CT and reconstructed to detect its production accuracy. Gross observation and accuracy detection were used to evaluate the duplication and few differences were found. Finally, Virtual Reality Modeling Language (VRML) was used to edit the 3D casting models to construct a Web-based 3D atlas accessible through Internet Explorer with 3D display and annotation functions.

The cutaneous microvascular architecture of human diabetic toe studied by corrosion casting and scanning electron microscopy analysis

In this morphological study, we report on the three-dimensional microvascular architecture constituting the toes of a patient affected by diabetic microangiopathy. We applied corrosion casting (CC) technique to the toes of a patient affected by Type 2 diabetes, who underwent surgery for explantation of inferior left limb due to necrotic processes of soft tissues. The toes of a foot traumatically explanted in a motorcycle accident were kept as controls. According to technical protocols, toes were injected with a low-viscosity acrylic resin (Mercox) through the major digital artery, tissues were corroded in KOH solution (8%), and resulting casts processed for SEM observations. Already at low magnification, in diabetic toes, we found an impairment of the linear track-like disposition of the vessels of plantar side, with signs of vascular disruption and obliterations, stopped resin, and leakages. Capillaries under the nail and a lot of vascular villi in eponychium and nail borders were damaged, and vascular regression phenomena acting on them were clearly visible. Resin leakages and impairment of normal vascular architecture were also observed in the root of the nail. This preliminary report represents only the first step for further investigations regarding morphological three-dimensional appearance of diabetic microangiopathy. CC and scanning electron microscopy technique well documented these morphological modifications, highlighting on both structural and ultrastructural features of diabetic toes microvessels. In conclusion, our qualitative data try to better focus on the pathophysiological mechanisms involved in diabetic dermopathy and microangiopathy, proposing CC as useful method to investigate on them.

Angioarchitecture of squamous cell carcinoma from hamster buccal pouch: a scanning electron microscopy study

Tumoral angiogenesis has been widely studied by histochemical analysis but little has been done regarding morphology of these new vessels. The objective of this study was to perform a qualitative analysis of the angiogenic response to chemical induction with dimethylbenzanthracene (DMBA) and carbamide peroxide of squamous cell carcinoma in pouches of Syrian hamsters after different periods of treatment. Twenty-four Syrian golden hamsters, divided into three groups of eight animals each, had their right jugal pouches treated with a 5% DMBA solution three times a week and a 10% carbamide peroxide two times a week for 55, 70 and 90 days. The left pouch was considered the control. After tumor induction, five animals in each group had their pouches prepared for analysis under scanning electron microscopy and three animals for analysis under light microscopy. The control pouches showed a vascular system composed by few main vessels running parallel to the longest axis of the pouch with some branches. In the pouches submitted to tumor induction, a well-differentiated squamous cell carcinoma was present since 55 days induction in all samples. The new vascular system showed the presence of many tortuous vessels and the majority of them were veins and capillaries. Terminal loops were extremely sinuous adopting a glomerular or corkscrew shape. These tumor vessels are different from normal vessels, presenting irregular diameters, outpouchings and constrictions. Angiogenesis of sprouting and intussusceptive kind could be identified in the tumor pouches, and they were more frequent as the tumor developed.

Targeting the Vascular Endothelial Growth Factor Pathway in the Treatment of Human Malignancy

Over 30 years ago, it was proposed that blocking new blood vessel formation would significantly inhibit solid tumor growth and hence, limit cancer progression. Efforts guided by this philosophy have resulted in a better understanding of the molecular basis of tumor angiogenesis. The first successful therapeutic to emerge from this work, an antibody (bevacizumab) targeting the vascular endothelial growth factor (VEGF), was recently approved for the treatment of colorectal cancer. Additional positive clinical data with bevacizumab in the treatment of breast and lung carcinoma have also been reported. These clinical achievements have validated the approach of anti-angiogenesis therapy for cancer and provided further confirmation for antibodies as a therapeutic class in this disease. Nevertheless, important unanswered questions with regard to preclinical and clinical results of VEGF pathway inhibitors remain. For example, preclinical models with a number of VEGF pathway inhibitors suggest that these agents would have significant clinical activity on their own; yet, clinical activity in patients with bevacizumab or other VEGF pathway inhibitors as monotherapy have been disappointing. Moreover, while bevacizumab is approved for the treatment of colorectal cancer in combination with cytotoxics, the mechanism for the benefits of this combination are still poorly understood, with a number of viable mechanisms under active experimental evaluation. The 3-8-month survival benefit in colorectal cancer patients treated with bevacizumab is a positive step forward. However, improving our understanding of the mechanism for these effects, as well as the mechanism underlying the inability as yet to achieve greater effects, is needed in order to follow up on the positive clinical results with improved strategies. This review discusses the experimental results surrounding the current status of our understanding of the mechanism of action of VEGF signaling inhibitors, and the potential for utilizing these agents in the future so that clinical benefits will be measured in years rather than months.

Microvascular growth of 7,12-dimethylbenz(alpha)anthracene-induced adenocarcinomas in rats: histology and scanning electron microscopy of resin casts

Vascular changes at various stages of growth of 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced mammary adenocarcinomas in 22 female Sprague-Dawley rats were investigated using histology, immunohistochemistry and scanning electron microscopy (SEM) of corrosion casts. In the early stage of tumour growth, capillaries within the neoplasms were thin, with 8-10 microm diameter, and characterized by rows of vascular sprouts representing extensive neovascularization and formation of a high-density capillary plexus. In the intermediate stage of tumour growth, the growing tumour was multi-nodular and tumour cells were arranged in a tubulopapillary pattern. Capillaries formed spheroid vascular capsules and were characterized by dilation, to a diameter of 10-80 mum, and blind ends. In the late stage of tumour growth, a remarkable reduction in the number of vascular endothelial growth factor-positive cells and Ki-67-stained nuclei was demonstrated. The tunica media of nutritive arteries displayed a tendency to atrophy. Many arteriovenous anastomoses between the major arteries and the veins were found in regions just before their entry into the tumour. The central regions of the tumour were degenerative and necrotic, and vasculature was confined to surface regions of the tumour, forming a basket-like configuration around the avascular central regions. Resin leakages representing haemorrhage or oedema and distortions such as flattening, break-off and strangulations of capillaries were frequently observed, all of which are known as late tumour signs. We concluded that these microvascular alterations might change the homogeneity of tumour perfusion and contribute to necrosis in central portions of the tumour.

The three-dimensional microvascular architecture of the human Kaposi sarcoma implanted in nude mice: a SEM corrosion casting study

The human Kaposi sarcoma represents one of the most common skin lesions associated with AIDS. Its clinical presentation and anatomopathological structure seem to demonstrate a particularly rich vascularity. The latest therapies aim to limit its intrinsic angiogenic activity in an attempt to reduce vascular density and the formation of new vessels. For these reasons, we decided to study the microvascular architecture of Kaposi sarcoma in three dimensions. We used a corrosion casting technique applied to nude mice previously transplanted subcutaneously with human modified neoplastic Kaposi sarcoma cells. The cooption of host vessels made by the tumor was demonstrated by three-dimensional scanning electron microscopy (SEM) images. At high magnification several angiogenic patterns were observed in the form of potato-shaped vessels, sprouts, intussusceptions and mouse tailed end tipped capillaries along with some ultrastructural features such as intercellular extravasations and endothelial cell modifications. Our investigation allowed us to build a detailed map of tumor vasculature in human Kaposi sarcoma. Furthermore, this study want to shed light on the sharp morphological three-dimensional conformation of angiogenic sprouts so to be able to better understand their modifications occurred during time and after antiangiogenic experimental therapies, by now observed only by immunohistochemical or immunofluorescent assays.

Microvascularization of the human digit as studied by corrosion casting

The aim of this study was to describe microcirculation in the human digit, focusing on the vascular patterns of its cutaneous and subcutaneous areas. We injected a functional supranumerary human thumb (Wassel type IV) with a low-viscosity acrylic resin through its digital artery. The tissues around the vessels were then digested in hot alkali and the resulting casts treated for scanning electron microscopy. We concentrated on six different areas: the palmar and dorsal side of the skin, the eponychium, the perionychium, the nail bed and the nail root. On the palmar side, many vascular villi were evident: these capillaries followed the arrangement of the fingerprint lines, whereas on the dorsal side they were scattered irregularly inside the dermal papillae. In the hypodermal layer of the palmar area, vascular supports of sweat glands and many arteriovenous anastomoses were visible, along with glomerular-shaped vessels involved in thermic regulation and tactile function. In the eponychium and perionychium, the vascular villi followed the direction of nail growth. In the face of the eponychium in contact with the nail, a wide-mesh net of capillaries was evident. In the nail bed, the vessels were arranged in many longitudinal trabeculae parallel to the major axis of the digit. In the root of the nail, we found many columnar vessels characterized by multiple angiogenic buttons on their surface.

Angioarchitecture of tumors induced by two different cloned cell lines established from a transplantable rat malignant fibrous histiocytoma

Angiogenesis, a biologic process whereby endothelial cells divide and migrate to form new blood vessels, is a key step in tumor growth, invasion, and metastasis. In the present study, we investigated the differences in angioarchitecture between two different tumors induced by cloned cell lines (MT-8 and MT-9), derived from a transplantable rat malignant fibrous histiocytoma, by scanning electron microscopy of vascular corrosion casts. During a 3-week observation period after implantation, the growth of MT-8 tumors appeared to be faster than that of MT-9 tumors. Histologically, MT-8 tumors were of the uniformly undifferentiated sarcoma type arranged in characteristic organoid structures, and MT-9 tumors showed a storiform growth pattern. In MT-8 tumors, neovascularization occurred by sprouting at postimplantation (PI) week 1, and the newly formed capillaries gradually became more tortuous. In MT-9 tumors, at PI week 1, the corrosion casts of newly formed capillaries mainly showed a wavy course but no finger-like outgrowths of capillaries were seen. At PI weeks 2 and 3, the sprouting was seen specifically in MT-9 tumors, forming basket-like structures and glomeruloid structures of capillaries. These results indicate that angiogenesis or angioarchitecture of MT-8 tumors is different from that of MT-9 tumors, depending on the differences in their tumor histology and by the features like absence or presence of basket-like structures and glomeruloid structures of capillaries.

Relation between lymphatic vessel diameter and clinicopathologic parameters in squamous cell carcinomas of the oral region

BACKGROUND

In an attempt to determine the mechanism of cervical lymph node metastases, the authors studied the relation between lymphatic vessels in or around tumor tissue and lymph node metastases in patients with primary squamous cell carcinoma (SCC) of the oral region by enzyme histochemistry using 5'nucleotidase-alkaline phosphatase.

METHODS

The subjects were 23 patients who had biopsy proven oral SCC. After enzyme histochemical staining, the cross-sectional dimension (referred to as diameter) of the lymphatic vessels were measured and analyzed in relation to the T classification of the tumor, degree of tumor differentiation, and mode of invasion.

RESULTS

The average diameter of the lymphatic vessels in or around tumor tissue was significantly greater than that in tumor free tissue (P < 0.01). The mode of invasion correlated significantly with the lymphatic vessel diameter (P < 0.01). The diameter did not correlate significantly with the T classification (P range, 0.135-0.254) or tumor differentiation (P = 0.274). The following relation was found between the incidence of cervical lymph node metastases and the mode of invasion: 40.0% of Grade 2 tumors were positive for metastases, 71.4% of Grade 3 tumors were positive, and 75.0% of Grade 4 tumors were positive (grading was according to Jakobsson's classification).

CONCLUSIONS

Of the factors evaluated in this study, only the mode of invasion correlated significantly with the diameter of the lymphatic vessels. Although other studies have shown that tumor thickness and perhaps even perineural and blood vessel invasion may be equally important, the findings of the current study suggest that both lymphatic vessel diameter and the mode of invasion may be important factors in the prediction of cervical lymph node metastases.

The role of hyaluronan in tumour neovascularization (review)

Tumour growth and metastasis are totally dependant upon neovascularization. The target cell for tumour neovascularization is the blood-vessel endothelial cell, and specific angiogenic molecules produced or induced by the tumour are believed to initiate the process. In this report, we review one of these angiogenic molecules, the glycosaminoglycan hyaluronan (HA), which appears to have differing roles in neovascularization depending on its molecular mass. High-molecular-mass HA is anti-angiogenic whereas oligosaccharides of HA, of specific size, actively stimulate endothelial-cell proliferation and migration, 2 of the key events associated with neovascularization, and induce angiogenesis in vivo. We provide details of the action of HA oligosaccharides on endothelial cells, from binding to cell-surface receptors, through activation of signal transduction pathways and gene expression to protein synthesis, cell proliferation and cell migration. We also suggest a model to account for HA of differing molecular mass being present, at different locations, within a single tumour and how this HA aids both general tumour growth and tumour metastasis.

Pulmonary venous sphincter constriction is attenuated by alpha-adrenergic antagonism

Pulmonary veins of rats have regular thin bands of constriction (sphincters) that deepen when the animals are given a blow to the head that is sufficient to cause pulmonary edema. Pulmonary edema caused by a stimulus to the brain is attenuated by alpha-adrenergic blockade. This study tested the hypothesis that alpha-adrenergic antagonism decreases this contraction in pulmonary veins. Male and female Sprague-Dawley rats were given prazosin, an alpha 1-specific antagonist, phentolamine, a combined alpha 1- and alpha 2-antagonist, or saline 10 min before their lungs were cast and they were given a blow on the head. The casts were fractured, causing the veins to break at the site of the constriction. Depth of contraction expressed as a percentage was 1 minus the ratio of the inner (constricted) and outer (total) diameters of the vein at the fracture. Resin that escaped the vascular space to cast alveoli and lymphatics was also measured. The average contraction of the veins at the site of the sphincters was 7.9 +/- 1.1% in the saline group, 5.4 +/- 0.7% in the phentolamine group, and 4.8 +/- 0.7% in the prazosin group (p < 0.05), although about a third of the constrictions were less than 2% in all groups. Arteries had no contraction. Contraction was greater in heavier and male animals, which were variables that interacted with the agent the animals were given in a multivariate analysis. Contrary to the hypothesis, lymphatic casts were greater in the animals receiving alpha-blockers (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Electron microscopic study of vascular regeneration in rat tracheal mucosa following physical curettage

Transmission and scanning electron microscopic studies were made of regeneration of the vascular network of rat tracheal mucosa on 30 min to 8 hr after the mechanical curettage. The vascular network casts were made by infusion of Mercox resin through the aortic arch for scanning electron microscopy. At 30 min after curettage, vascular thromboses were observed, and terminal blind branches were formed in the injured blood vessels areas through SEM observation. Diapedesis of leukocytes appeared at 30 min after curettage from intact venules at the wound margins. Recovery from the loss of endothelial cells began at 30 min after curettage. At 3 hr after curettage, vascular indentation (protrusion) and vascular process (bud-like process) were developed from intact venules at the wound margins. It is concluded that the formation of thrombus and terminal blind branch vessels constitute the initial reparative reactions of the injured vascular network and that new vessels then begin to form by outgrowth of protrusions and bud-like processes from intact venules at the wound margins.

Morphological analysis of neovascularization at early stages of rat splenic autografts in comparison with tumor angiogenesis

This study was undertaken to reveal the neovascularization at early stages of splenic autografts three-dimensionally, to illustrate the differences between it and tumor angiogenesis, and to establish its origin. Early vascular formation after transplantation of the rat spleen or Walker tumor into the major omentum was examined by using a video macroscope, vascular casting methods and the organ culture technique. A complex vascular network layer (vascular cortex) was first formed beneath the capsule of an autograft; later, vascular buds grew from this network toward the necrotic center. They anastomosed and changed into a form resembling withered twigs (vascular medulla). Tumor angiogenesis did not present such morphological features and was characterized by capillary loop formation with a columnar vertex resembling an "inverted V". This fundamental structure did not change throughout angiogenesis except for dilation and irregularity of vascular diameter. The organ culture technique demonstrated that the preliminary vasculature was formed in splenic autografts by regeneration of preexisting vessels in the graft and not by invading capillaries. Transmission electron microscopy showed that the cells present had characteristics of sinus endothelial cells. These results suggest that preexisting sinus endothelial cells rearrange themselves after devascularization and reconstruct a new vasculature that anastomoses with the penetrating capillaries. This mechanism establishes vascular circulation at an early stage, and accelerates regeneration of the splenic autograft before complete necrosis.

Tumor-related angiogenesis

In recent years, tumor-related angiogenesis has become an important field of research in oncology. It could be stated that growth of solid tumors is completely dependent on neovascularization to provide the tumor with all required nutrients. Special compounds (tumor angiogenesis factor[s]) are released by tumor cells into the environment to stimulate different types of normal cells to become active for the tumor. In particular, endothelial cells of neighboring capillaries are induced to react. They disintegrate their own basal lamina, detach from their neighbors, enter the extracellular matrix, and migrate toward the tumor mass. Cell divisions occur within such sprouts, thereby increasing the number of migrating endothelial cells. Strands of such cells are formed, and inter- and intracellular lumina develop. Loops of these hollow strands anastomose to form a network of new vessels which become connected with the blood circulation. The tumor mass thus becomes vascularized and can continue to grow. The prevention of neoangiogenesis has an enormous impact on cancer treatment by inhibiting the growth of the tumor. In this review, all important aspects of tumor-related angiogenesis are presented.

The vascular pattern of basal cell tumors: light microscopy and scanning electron microscopic study on vascular corrosion casts

Light microscopy of hematoxylin-eosin stained tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts were used to study the blood vascular system of human basal cell tumors. Concerning the gross angioarchitecture there is a very close correlation between the histological appearance and the findings obtained from vascular corrosion casts, when evaluated in a SEM. The tumor cell beds are enveloped by basket-like capillary plexus. The tumors are traversed over long distances by superficially running, teleangiectatic, but flattened capillaries. These compressed vessels are squeezed between tumor cell cords and epidermis. In vascular corrosion casts of human basal cell tumors the vascular system exhibits three different features. Blind-ending vascular casts; Four different causes for blind-ending cast structures are pointed out and discussed. Incomplete filling of the vascular system; compression of tumor vessels; new proliferating capillary sprouts; broken cast endings. Variations in vessel caliber and extravasation of the injection resin. Most of the variation in vessel calibers are thought to be caused by dilation of the weakened endothelial walls, but some of them presumably represent new projecting vascular swellings. Circumscribed leakage of the injected resin could be attributed to regions of advanced connective tissue degeneration and endothelial lysis. Flattened cast structures; The addition of tissues during tumor growth results in an increase of tissue pressure. Thus many tumor vessels get displaced, compressed, and flattened and vascular occlusions will occur. However, it must be stressed that much caution is needed in assessing the nature of the vascular cast structures of basal cell tumors.

Morphology of arteries, veins, and capillaries in cancer of the larynx: scanning electron-microscopical study on microcorrosion casts

Morphology of blood vessels in cancer of the larynx, which as other solid tumors has great neoangiogenic abilities, was studied on microcorrosion casts in SEM. Most evident changes of the endothelial patterns were seen on the casts of capillaries, venules, and veins. Capillaries, especially the newly formed, are the most numerous constituent of the vascular bed in all zones of cancer of the larynx. These vessels exhibit great morphological differentiation varying from the single, blind-ended pipes via relatively long hairpin loops spirally twisted in the long axis, to strongly spiralled and convoluted loops, resembling pseudoglomeruli. The newly formed capillaries deriving predominantly from the host's capillaries, venules, and veins have a embryonal character. It seems reasonable to presume that the neoangiogenesis process triggered by active influence of the tumor angiogenesis factor, is in principle, a repetition of the mechanism of the embryonal angiogenesis.