Flattened Endothelial Cells Research Articles

Tumors of the lymphatic vessel of the skin and soft tissue

Tumours of lymphatic vessels comprise only a small group in the heterogeneous spectrum of vascular neoplasms of skin and soft tissues. However, this discrepancy between haemangiomas/angiosarcomas and lymphangiomas/lymphangiosarcomas probably represents the present inability to reliably differentiate between lymphatic and capillary vascular endothelium. Histologically, neoplastic lymphatic vessels tend to be lined by endothelial cells with plumper and more prominent, matchstick-like nuclei (in contrast to vascular spaces in haemangiomas that are lined by flat or epithelioid endothelial cells), often show variations in the thickness of the vessel walls and are not completely surrounded by actin-positive (myo)pericytes. Endothelial cells in lymphatic neoplasms tend to be negative for CD34 or stain only focally positive for this marker and an expression of lymphatic markers as vascular endothelial growth factor-C receptor (VEGRF-3), podoplanin and M2A oncofetal antigen has been reported most recently. In addition to "traditional" lymphatic neoplasms including lymphangioma circumscriptum, cavernous lymphangioma/cystic hygroma, benign lymphangioendothelioma, lymphangiomatosis and the rare lymphangiosarcoma, histological and immunohistochemical features of a group of vascular neoplasms with a hobnail cytomorphology (hobnail haemangioma, retiform haemangioendothelioma, papillary intralymphatic angioendothelioma, benign lymphangiomatous papule following radiotherapy) suggest that these lesions also belong to the spectrum of tumours of lymphatic vessels.

The role of fine-needle aspiration biopsy in the diagnosis and management of juvenile hemangioma of the parotid gland and cheek.

The current recommendation for the management of juvenile hemangiomas (JH) is to delay treatment in the hope of spontaneous regression. However, accurate diagnosis is necessary before considering conservative management. Traditionally, the diagnosis of JH has required excisional biopsy. The cytology literature on this relatively rare neoplasm is sparse. To present our experience with fine-needle aspiration in the diagnosis and management of JH. Three cases with a cytologic diagnosis consistent with JH of the parotid gland and cheek were identified from our cytopathology files. Aspirate smears, immunohistochemical studies, computed tomographic scan findings, and clinical follow-up were reviewed. Patients were female infants ranging in age from 3 to 9 months and presented with an oval firm mass (size range, 2.0-5.0 cm) involving the parotid gland (2 cases) and cheek (1 case). Computed tomographic scan with contrast demonstrated homogeneous enhancement. Aspirate smears revealed spindle-shaped cells in sheets and clusters in a background of blood. The parotid gland aspirates and cell block preparations revealed ductal structures entrapped in sheets of spindle-shaped cells. Immunohistochemical studies revealed prominent vascular spaces lined by CD34 and factor VIII-positive flattened endothelial cells. The diagnosis of JH was rendered on the basis of the cytologic findings in conjunction with the radiologic and clinical findings. On clinical follow-up (8-24 months), none of the patients has shown any progression of the lesion. Fine-needle aspiration, in conjunction with imaging studies, is a useful tool in the diagnosis and management of JH. It eliminates the need for surgical excision for diagnostic purposes and allows for clinical follow-up of patients with JH.

FEMALE URETHRAL HEMANGIOMA

A 59-year-old woman presented elsewhere with genital bleeding, pollakiuria and urgency. The gynecologist noted a raised tumor next to the external meatus and the patient was referred to us. On physical examination the tumor was erythematous, protrusive, inflamed and surrounding the urethral meatus. The lesion was 2.5 cm. in diameter, solid and partly rubbery in consistency. It did not appear to be a urethral caruncle, which is typically a benign, red, raspberrylike, friable tumor involving the posterior lip of the external meatus. There were no lesions on the body surface. The uterus and adnexa were unremarkable. Laboratory values were normal except for urinalysis, which revealed numerous red blood cells. Urinary cytology demonstrated no malignancy. Cystourethroscopy revealed reddish mucosa at the distal urethra but not in the bladder. The lesion was not obstructive. Pelvic magnetic resonance imaging (MRI) in the sagittal plane showed a protrusive mass with low intensity on T1-weighted images, which was clear with high intensity on T2-weighted images (fig. 1). There was clinical suspicion for a malignant tumor. After obtaining informed consent, we performed a biopsy with the patient under lumbar anesthesia. Microscopically, the specimens consisted of clusters of dilated venous-like vessels with thrombi, which were composed of thin endothelial lined spaces. Blood containing spaces were large sinusoids lined by flattened endothelial cells (fig. 2). The specimen was pathologically diagnosed as cavernous hemangioma of the urethra. The tumor was resected completely. The patient was symptom-free at 6-month followup with no evidence of tumor recurrence.

Multiple Glomus Tumors of the Skin with Male-to-Male Transmission Over Four Generations

To the Editor: Glomus tumors of the skin are benign tumors arising from glomus bodies or neuromyoarterial receptors that are sensitive to variations in temperature and regulate arterial flow. The bluish nodules occur sporadically (mainly as painful solitary tumors on the distal parts of the extremities) or in a familial pattern (multiple and generally asymptomatic tumors scattered over the body or localized in a single area). The inheritance in the few families reported so far has been autosomal dominant, with some instances of male-to-male transmission (Tran et al, 1994; Happle and Konig, 1999Happle R. Konig A. Type 2 segmental manifestation of multiple glomus tumors: a review and reclassification of 5 case reports.Dermatology. 1999; 198: 270-272Crossref PubMed Scopus (34) Google Scholar). In five families, linkage to 1p21-p22, which has been termed "VMGLOM" (Boon et al, 1999), was established. We present a family with a male-to-male transmission over four generations. All males (n = 14) are affected with glomus tumors of the angiomatous type (glomangiomas) and all females (n = 10) remain unaffected (Fig 1). The tumors began to develop at puberty and involve all parts of the skin except the face, neck, genitals, palms, and soles. In the 69-y-old index case new lesions are still developing; in fact, a total of more than 200 have been registered (Fig 2). The tumors were asymptomatic up to the age of 40 y, thereafter they started to cause paroxysmal attacks of pain, aggravated by pressure, trauma, and changes in temperature (Mullikan and Virnelli-Grevelink, 1999Mullikan J.B. Virnelli-Grevelink S. Vascular anomalies.in: Freedberg I.M. Eisen A.Z. Wolff K. Austen K.F. Goldsmith L.A. Katz S.I. Fitzpatrick T.B. Dermatology in General Medicine. 5th edn. McGraw-Hill, New York1999Google Scholar). Histologic examination of three representative lesions revealed widely dilated vascular spaces surrounded by flat endothelial cells, a flat collagen layer, and clusters of glomus cells containing myofibrils, as seen on electron microscopy. The tumor cells stained positive for actin, desmin, and vimentin but negative for pancytokeratin, S100, CD4, CD31, UEA, and factor VIII. Chromosome analyses from peripheral lymphocytes of the index case revealed a structurally abnormal Y- chromosome (paracentric inversion Yq?) and gonosomal aneu- ploidy: 45,X(1)/46,XY(34)/47,XXY(1)/47,XYY(3). In two me- taphases a pericentric inversion (12)(p13.3q13) was present. The breakpoints concern regions of three proto-oncogenes (HST2, HER3, WNT1). Analyses of Y-specific sequences in the genomic DNA of the patient (SY 14, 70, 78, 85, 132, 156, 160) has revealed no Y-deletion thus far. Disruption of a gene by the suspected paracentric inversion Yq cannot be excluded. Further molecular studies are in progress. Conventional chromosome analyses of one tumor revealed, in addition to the structurally abnormal Y- chromosome, a clonal 1; 6 translocation t (1; 6)(q25:q25). Coupling analyses in the family have not been performed thus far because of lack of cooperation.Figure 2Multiple glomus tumors presenting as bluish painful nodules (on the right forearm).View Large Image Figure ViewerDownload (PPT) In summary, the presented pedigree is unique as it shows an exclusive male-to-male transmission of hereditary glomus tumors. Our findings also suggest a causal involvement of a structurally abnormal Y-chromosome. Immunophenotypical characterization of the glomus cells was enabled by Dr. W. Weninger, Univ.-Dept. of Dermatology, Vienna, Austria.

口腔粘膜に症状を呈したＲｅｎｄｕ‐Ｏｓｌｅｒ‐Ｗｅｂｅｒ病の１例

Rendu-Osler-Weber disease (hereditary hemorrhagic telangiectasia) is a rare autosomal dominant disorder characterized by abnormal subepithelial vessels in the skin or the respiratory or gastrointestinal mucosa. We report a case of Rendu-Osler-Weber disease with manifestations in the oral mucosa. A 56-year-old woman visited Hokkaido University Dental Hospital because of blood oozing from the maxillary gingiva. Frequent epistaxis was included in her medical history. The patient's father and brother had died of cerebral hemorrhage, and her father and grandmother had suffered from freqent epistaxis. Telangiectases were observed on the skin of the neck. Many angiomatoid lesions were observed on the lower lip, tongue, and buccal mucosa. Histologically, a number of blood vessels were seen in the subepithelial layer of a biopsy specimen of a gingival lesion. The vessels were dilated and were covered with flattened endothelial cells. The clinical and histologic findings were consistent with the diagnosis of Rendu-Osler-Weber disease.

Expression profile of active genes in mouse lymph node high endothelial cells.

High endothelial venules (HEV) allow rapid and selective lymphocyte trafficking from the blood into secondary lymphoid tissues. Here we report the expression profile of active genes in mouse high endothelial cells (HEC). HEC were first purified from mouse lymph nodes (LN) by magnetic cell sorting with MECA-79 mAb and a 3'-directed cDNA library that faithfully represents the composition of mRNA was constructed. A total of 1495 cDNA sequences were obtained from randomly selected clones. Based on their sequence identity, they were grouped into 754 different species [gene signatures (GS)] of which 335 GS were identified in GenBank. Among the previously identified genes, expression of several endothelial cell surface molecules including endoglin and ICAM-1 was detected in HEC. Comparison of the gene expression profile with that of purified CD31(+) flat endothelial cells identified several molecules, such as KC chemokine and Duffy antigen/receptor for chemokines, that are known to be selectively expressed in activated endothelial cells or post-capillary venules. Interestingly, mac25/TAF, which is known to be expressed specifically in tumor vessels and implicated in the regulation of cell adhesion, was highly and selectively expressed in HEC in mouse LN, suggesting that it may participate in regulating HEC-specific functions. Comparison with the expression profiles obtained from 35 different cell types showed at least 22 GS that were apparently specific to HEC. Our results illustrate the expression differences between HEC and CD31(+) flat endothelial cells, and will be useful for the identification and characterization of genes specific for HEC.

Microvascular and tumor cell alterations during continuous hyperfractionated irradiation: an electron microscopic investigation on the rat R1H rhabdomyosarcoma

Purpose: Conventionally fractionated γ-irradiation results in severe damage of tumor capillaries associated with decreasing oxygen partial pressure within the tumor. The present study was undertaken to assess whether vasculo-connective changes are less pronounced after continuous hyperfractionated irradiation, implying better tumor oxygenation and improved radiosensitivity. Materials and Methods: Twenty rats with an isotransplanted R1H rhabdomyosarcoma were irradiated for 12 days with 2 daily fractions of 2.5 Gy (Δt = 6 h). After 0, 15, 30, 45, and 60 Gy, tumor tissue of 4 rats each was analyzed histologically and electron-microscopically. Results: Untreated rhabdomyosarcomas were composed of spindle-shaped tumor cells with numerous mitoses. There were many apoptotic nuclei and a large central necrosis. Tumor capillaries showed a continuous lining of flattened endothelial cells with broad overlapping cell contacts overlying a delicate continuous basal lamina. During irradiation, mean tumor volume declined from 1.9 cm 3 to 1.2 cm 3. The number of atypical mitoses and apoptoses increased and numerous giant tumor cells appeared. The proportion occupied by necrotic tumor tissue rose from 30% to 60%. After 15 Gy (3 days), a marked vasodilatation was apparent accompanied by an interstitial edema. Occasionally, endothelial cells were rounded up and showed indented nuclei, with the underlying basal lamina disintegrated. These changes progressed with increasing radiation doses. After 30 Gy (6 days), leukocytes started to adhere to the endothelial wall. Electron-dense fine fibrillar and basal lamina-like deposits appeared in the perivascular space. Endothelial cell edema was only observed after 60 Gy (12 days). Cell contact areas were shortened, however, the endothelial lining was not interrupted. No signs of radiation fibrosis were observed. Conclusion: Continuous hyperfractionated irradiation induces relatively discrete alterations of the vasculo-connective tumor tissue as compared to conventional irradiation. This may be an advantage with respect to tumor blood flow, oxygenation, and thus, radiosensitivity.

Absence of atherosclerosis evolution in the coronary arterial segment covered by myocardial tissue in cholesterol-fed rabbits.

The evolution of atherosclerotic lesions is suppressed in the intima of the human coronary artery, beneath myocardial bridges. To elucidate the mechanism of the protective effect, we investigated morphological changes using the rabbit coronary artery as a model. Rabbit fed a 1%-cholesterol diet were killed at intervals up to 20 weeks. Two short segments of the left coronary arteries running in the epicardial adipose tissue (EpiLAD) and subsequently running in the myocardium (MyoLAD) were compared morphologically. The intima of the EpiLAD had flat endothelial cells with a polygonal shape, and demonstrated raised atherosclerotic lesions with increase in serum cholesterol level. In contrast, the intima of the MyoLAD was free of atherosclerotic lesions throughout the study, and the endothelial cells were spindle-shaped and engorged. While ferritin particles reached only the surroundings of the internal elastic lamina in the MyoLAD, they permeated into the media of the EpiLAD. We suggest that myocardial bridges suppress coronary atherosclerosis by an alteration of endothelial permeability, which may be due to changes in haemodynamic force tending towards a higher shear stress. The data provide an insight into the relationship between haemodynamics and the development of coronary atherosclerosis.

Analysis of the capillary architecture in the precursors of prostate cancer: recent findings and new concepts.

To report on recent findings and new concepts in the remodeling of the capillary architecture in the precursors of prostate cancer. Immunohistochemical methods have been adopted in prostate cancer and in its precursors (prostatic intra-epithelial neoplasia) to investigate capillary pattern changes-which were mainly analyzed as capillary frequency- and the degree of endothelial cell proliferation. Several features related to the capillary architecture have been considered. Manual, semiautomatic, and automatic (machine vision) types of evaluation have been used to quantify the features. The data available indicate that: (1) Going from normal prostate through prostatic intra-epithelial neoplasia up to invasive adenocarcinoma, an increasing proportion of capillaries becomes shorter, with open lumen and undulated external contour and with greater proliferation of the endothelial cells and greater expression of type IV collagenase. The highest proportion of touching capillaries is seen in normal prostate, while the lowest is found in invasive adenocarcinoma, being intermediate in prostatic intra-epithelial neoplasia. (2) When total androgen ablation is induced, there is no proliferation of the endothelium, whereas the capillaries are reduced in frequency and represented by small vessels lined by flat endothelial cells and with an open lumen. (3) Automation in the evaluation of the capillary architecture is feasible with a machine vision system. The progression in prostate carcinogenesis is associated with changes in the capillary architecture. There are some preliminary data indicating that total androgen ablation can inhibit the angiogenesis in precursors of prostate cancer.

Blood and serous cysts in the atrioventricular valves of the bovine heart.

A survey of 30,907 slaughterhouse cattle (5,984 calves, 15,937 young adult, 8,986 cows) was carried out to determine the incidence of blood and serous cysts on atrioventricular valves. The cysts were classified by their content (blood/serous fluid), location (mitral/tricuspid valve), and size. Cyst wall samples were processed for histology, immunohistochemistry for factor VIII-related antigen, and transmission electron microscopy. The content of some cysts was studied by electrophoresis and biochemical and microbiologic methods. Older cows had a higher incidence (16.2%) than younger animals (11.5% in calves, 7.9% in steers, 6.4% in heifers), suggesting that the lesions may be acquired. Blood cysts were often present on both atrioventricular valves; serous cysts prevailed on the mitral valve. Cysts of both types were larger in older animals; serous cysts were larger than the blood cysts. Histologically, blood cysts contained fresh blood, and serous cysts were filled with a hyaline fluid devoid of cells, sterile, and biochemically similar to lymph. All the cysts were lined with endothelium, but a positive immunostaining for the factor VIII-related antigen was appreciable only in blood cysts. Ultrastructurally, the endothelium was composed of flat endothelial cells holding several cytoplasmic filaments, lying in blood cysts on a continuous and often laminated basal lamina with many cytoplasmic projections. The results support the hypothesis that cysts of the atrioventricular valves derive from the dilation of blood and lymphatic valvular vessels, do not regress with age, and are mainly the result of mechanical effects.

Kaposi's sarcoma-associated herpesvirus infects endothelial and spindle cells.

Kaposi's sarcoma (KS), a vascular tumour that contains characteristic spindle cells forming slit-like spaces, may have an infectious aetiology. Recently, sequences of a new human herpesvirus, KSHV/HHV-8, have been identified in both HIV-associated and classical KS. We sought to identify the target cell of this virus in KS tumour tissue. Using PCR in situ hybridization (PCR-ISH) we show that KSHV/HHV-8 is present in the flat endothelial cells lining vascular spaces of KS lesions as well as in typical KS spindle cells. These findings show that KSHV/HHV-8 is present in the cell types thought to represent neoplastic cells in these lesions.

Complexus adhaerentes, a new group of desmoplakin-containing junctions in endothelial cells: II. Different types of lymphatic vessels

Abstract In diverse mammalian species, including (man, cow and rat) the very flat endothelial cells of lymphatic vessels of various organs, including the retothelial meshwork of sinus of lymph nodes, are connected by zonula-like plaque-bearing junctions which differ from the similarly structured junctions of blood vessel endothelia by the presence of desmoplakin or an as yet unknown but closely related plaque protein. These extended junctions, which also contain plakoglobin but none of the presently known desmogleins and desmocollins, are therefore different from the spot-like desmosomes ( maculae adhaerentes) present in epithelia, myocardium and dendritic reticulum cells of lymphatic follicles, and are collectively subsumed under the new category of complexus adhaerentes, including the ‘syndesmos’ connecting the processes of the retothelial cells. The lymphatic endothelial cells possessing these special desmoplakin-containing junctions also contain the calcium-dependent transmembrane glycoproteins, V-cadherin and cadherin 5, of which the latter has also been partly localized to regions with desmoplakin-positive junctions. Possible functional reasons for the formation and maintenance of complexus adhaerentes are discussed as well as the potential value of reagents which allow their identification in relation to physiology and pathology.

Multiple Blue Papules

REPORT OF A CASE Over the past 20 years, a 75-year-old white man noted gradually progressive blue-to-black papules scattered over his cheeks, nipples, and upper chest. The number of papules increased and darkened but otherwise remained asymptomatic. Of interest, his father had similar lesions located in the same areas. Findings from the physical examination revealed multiple 1- to 4-mm nonblanchable blue-to-black papules over both cheeks, the nipples, and the upper chest. Telangiectasia was noted sporadically (Fig 1). A biopsy specimen was obtained from the upper chest and was stained with hematoxylin-eosin (Fig 2). What is your diagnosis? DIAGNOSIS: Hereditary glomangiomas. HISTOPATHOLOGIC FINDINGS The biopsy specimen of the papillary dermis revealed large, irregularly shaped vascular spaces. The vascular spaces were lined by a single layer of flat endothelial cells. The glomus cells were peripheral to the endothelial cells. DISCUSSION Glomus tumors are either solitary or multiple.1-3The solitary form is more common.

Immunohistochemical characterization of vascular endothelial cells in cutaneous T-cell malignancies with special references to heterogenous expression of surface antigens associated with monocytes and macrophages.

The immunologic characteristics of vascular endothelial cells (EC) in cutaneous T-cell malignancies were studied immunocytochemically at light and electron microscopic levels. In cutaneous lesion of adult T-cell lymphoma, a large number of small vessels with flat EC was distributed, whereas another types of cutaneous T-cell malignancies were rich in high endothelial venules (HEV). They were HLA-DR+, OKM5+, IL-1+ and von Willebrand factor antigen (FVIII RAg/vWF)+. The upper dermis of normal and inflammatory skin disease was rich in HEV, which were HLA-DR+, OKM5-, IL-1+ and FVIII RAg/vWF+. Lymphoma cells, regardless of the histologic type, were CD3+, HLA-DR+ and predominantly CD4+. About one third of CD3+ cells displayed IL-2 receptor. We discussed the possibility that the EC in cutaneous T-cell lymphoma may allow the proliferation of T lymphoma cells, which also have been known to induce angiogenesis.

Ocular Adnexal Kaposi's Sarcoma in Acquired Immunodeficiency Syndrome

We examined histopathologically 18 ocular adnexal Kaposi's sarcoma lesions related to acquired immunodeficiency syndrome. These lesions were classified into three types. Type I consisted of thin, dilated vascular channels lined by flat endothelial cells with lumen-containing erythrocytes. Type II featured plump, fusiform, endothelial cells, often with a hyperchromatic nucleus and foci of immature spindle cells and occasional slit vessels. Type III was characterized by large aggregates of densely packed spindle cells with hyperchromatic nuclei, occasional mitotic figures, and abundant slit spaces often containing erythrocytes in between. Clinically, type I and type II tumors were patchy and flat (less than 3 mm in height) and of less than four months' duration. Type III tumors were nodular and elevated (greater than 3 mm in height). We describe the clinical and histopathologic types of Kaposi's sarcoma that may help in diagnosis.

Rapid cellular luminal coverage of Dacron inferior vena cava prostheses in dogs by immediate seeding of autogenous endothelial cells derived from omental tissue: Results of a preliminary trial

Endothelial cell seeding methods might reduce the high failure rates of venous vascular prostheses, but low flow rates in venous vascular prostheses impose a need to protect early patency and to attain early endothelial cell coverage without waiting several weeks for relatively small endothelial cell innocula from autologous veins to form confluent linings. To obtain large number of autologous endothelial cells for high-density seeding, canine omental microvascular endothelial cells were harvested by collagenase digestion and density gradient centrifugation, with yields of 1.34 ± 0.24 (SD) × 106 cells/gm of omentum (N = 8 harvests). Primary culture of a subfraction from each harvest showed the cell population to be dominated by factor VIII—related antigen-positive endothelial cells with only a few nonstaining cells (estimated to be 10% or less of total cell number) visible. Freshly harvested omental cells were seeded onto double velour knitted Dacron prostheses at densities of 5 × 105 cells/cm2 of graft luminal surface in an autologous plasma suspension by use of prior preclotting with cell-free autologous plasma, followed by endothelial cell seeding in autologous plasma, with plasma recalcification during endothelial cell instillation. Six seeded and two control (sham-seeded) vascular prostheses 5 cm long with 10 mm inner diameter were used as inferior vena cava interposition grafts. A distal arteriovenous fistula and aspirin (300 mg) and dipyridamole (50 mg orally every day) starting 3 days before surgery were used to protect early patency of all grafts. Seeded venous vascular prostheses were explanted for study at intervals of 1, 5 and 10 days after surgery (N = 2 prostheses at each time); the two control venous vascular prostheses were explanted at 10 days. All venous vascular prostheses were patent at time of removal. In seeded venous vascular prostheses, light, scanning, and transmission electron microscopy showed emergence of numerous flattened endothelial cell-like cells on the luminal surface 24 hours after surgery, followed by formation of a confluent cellular lining without adherent platelets by 5 to 10 days after surgery. Control venous vascular prostheses, in contrast, remained covered by an irregularly thickened fibrin and red cell thrombus, which sometimes encroached on the lumen. Our results suggest that (1) omental tissue can furnish endothelial cells for high-density immediate seeding of venous vascular prostheses, and (2) that the method we used to combine features of both so-called high density “seeding” and “sodding” techniques offers both more rapid prosthesis coverage than the former and shorter intraoperative times for cell attachment to prostheses than the latter. The relatively rapid coverage by endothelial cell-like cells we observed at 5 to 10 days with this method may be of particular value for low-flow venous vascular prostheses.

Ca2+-ATPase cytochemistry in the spinal cord microvasculature of prenatal rats

Membrane-bound Ca2(+)-ATPase activity was localized cytochemically in the blood vessels of the spinal cord of rat embryos to obtain a better understanding of the membrane activities of vascular cells. The cytochemical method revealed a growth of the parenchymal vasculature. In the parenchyma, reaction product was dense over the entire plasma membrane of voluminous endothelial cells provided with large nuclei and enriched cytoplasmic organelles, suggesting that the endothelial cells may be of a vascular sprout. The parenchymal vessels with a wide lumen were frequently associated with pericytes, and the Ca2(+)-ATPase activity was diminished in intensity on the luminal surface of the flattened endothelial cells. On the other hand, the endothelium of extraparenchymal capillaries exhibited Ca2(+)-ATPase activity primarily on the luminal surface of the plasma membrane. Quercetin, a Ca2(+)-transporting ATPase inhibitor, considerably decreased the abluminal activity in the voluminous endothelial cells with slit-like vascular lumen and the luminal activity of functioning capillary endothelium as well. Thus, a dual activity of Ca2(+)-ATPase, postulating for the activities of Ca2(+)-transporting ATPase and ecto-ATPase, was closely correlated with the maturation processes of the capillary endothelium.

The human choriocapillaris in organ culture.

4 x 4 mm pieces of human eye walls consisting of the sclera, the choroid and the pigment epithelium were kept in organ culture for 1 month and studied with light and transmission electron microscopy comparing the findings with normal tissue. After 1 month the choriocapillaris still had open vessel lumina lined with flattened endothelial cells containing organelles and vesicles on both inner and outer cell membranes. The endothelial cells lost their fenestrations and polarity in regard to the location of cell nuclei. Otherwise the ultrastructure was similar to that of the choriocapillaris in vitro. This study has shown that choriocapillaris can survive in organ culture for 1 month, and it permits further studies on the behaviour of the choroid under controlled conditions, and on the long-term effects of different types of trauma to the choroid in vitro.

High endothelial venule morphology and function are inducible in germ-free mice: A possible role for interferon-γ

Cytokines may facilitate lymphocyte traffic by modulating HEV structure and lymphocyte binding function in accordance with local tissue requirements. This study investigated whether the morphology of HEVs and their lymphocyte binding ligand are altered following antigenic challenge and evaluated the role of IFN-γ in the induction of such changes. The morphology and lymphocyte binding function of mesenteric LN HEVs of GFM exposed to environmental pathogens were compared to those from GFM and conventional mice. Lymph nodes from all mice had microscopically identifiable HEVs. The morphology of HEVs from GFM was not uniform; many HEVs contained flat endothelial cells with sparse cytoplasm and prominent interendothelial gaps. The number of lymphocytes within the lumen and the HEV wall was low. In contrast, HEVs from GFME and conventional mice were characterized by cuboidal endothelial cells with plentiful cytoplasm and large numbers of lymphocytes in the vessel wall and lumen. There was no delineation of interendothelial cell borders. Lymphocyte binding to HEVs of lymph node sections from GFM was reduced (mean ± SEM: 1.08 ± 0.15) compared to that of conventional mice (1.91 ± 0.20), P < 0.003. GFME had augmented lymphocyte binding (2.23 ± 0.26) to levels comparable with those of conventional mice. GFM injected intraperitoneally with IFN-γ, IFN-αβ, or diluent resulted in minor changes in HEV morphology. By contrast, lymphocyte binding to HEV of GFM was more than doubled by the injection of IFN-γ (1.95 ± 0.25), P < 0.01, but not IFN-αβ (0.54 ± 0.07) or the relevant diluent controls (0.89 ± 0.11, 0.56 ± 0.06, respectively). It appears that the HEV binding ligand is inducible, and its expression is regulated by at least one immunomodulator, IFN-γ. Although short-term exposure of HEVs to IFN-γ influenced HEV function it caused only minor changes in morphology.

Reconstitution of the vascular wall in vitro: A novel model to study interactions between endothelial and smooth muscle cells

To study the biology of the endothelium under conditions that mimic the architecture of the vessel wall, endothelial cells were grown on a collagen lattice containing a multilayer of smooth muscle cells. Light and electron microscopy of such cultures revealed a confluent monolayer of flattened endothelial cells. In co-culture, endothelial cells tend to elongate, whereas in the absence of smooth muscle cells, the endothelial cells show the polygonal morphology typical for cultures of endothelial cells grown on polystyrene substrates. As conditioned culture media of endothelial cells contain substances that may both promote or inhibit the growth of smooth muscle cells, the availability of this vessel wall model prompted us to examine to what extent endothelial cells regulate the proliferation of smooth muscle cells when these cells are maintained in co-culture. Here we show that endothelial cells suppress the proliferation of co-existing smooth muscle cells. This finding suggests that under physiological conditions the balance of the action of growth-promoting and growth-inhibiting substances produced by endothelial cells is in favour of the latter.