Species-dependent differences in the nature of endothelium-derived vascular relaxing factor

Effluents from perfused acetylcholine-relaxed endothelium segments of rabbit aorta (or canin femoral artery) contained endothelium-derived relaxing factors (EDRF) which dilated the endothelium-free segments of rabbit femoral artery (or side branches of canine femoral artery). The half-life of EDRF was 24 +/- 3 s for the rabbit and 49 +/- 5 s for the canine system. Nordihydroguaiaretic acid was less effective against the formation of canine EDRF than of rabbit EDRF. These findings suggest species differences in the nature of EDRF.

[Blood coagulation changes and pathogenesis of diabetic retinopathy. Recent advances]

In this review the most recent advances in blood coagulation and chronic complications of diabetes mellitus are discussed. Numerous research workers have reported abnormalities in the mechanisms of platelet activation, endothelial cell function, plasma coagulation and fibrinolysis. However, the data available today cannot as yet be interpreted in terms of pathogenesis of retinopathy or any other chronic manifestation of the disease. Consequently, there is at present no rationale for pharmacological prevention or treatment.

Cytofluorometric nuclear DNA determinations on human corneal endothelial cells

In order to investigate polyploidization of human corneal endothelium, nuclear DNA cytofluorometry was performed. Touch smears of 31 human corneal endothelium taken from 21 autopsies and 10 donor eyes were fixed with absolute methanol and subsequently stained by the pararosaniline-Feulgen nuclear reaction. The optimum condition for Feulgen hydrolysis of the specimens was determined, and all smears were hydrolysed in 1 N HCl for 5 min at 60 degrees C. After the Feulgen reaction, the pararosaniline-DNA fluorescence was measured with an epi-illumination cytofluorometer (Olympus AH-QRFL). Polyploid nuclei, which are the result of abortive cell division after DNA synthesis, appeared with DNA contents of tetraploid (19 cases) and octaploid (two cases) classes. All other nuclei had DNA quantities within the range of the diploid class. Nuclei containing DNA between diploid and tetraploid amounts were not found. It was concluded that most human corneal endothelial cells are of post mitotic Gl population but that a few are in the generative G0 phase.

Vascular endothelial cell growth inhibitor of normal and pathologic human vitreous

Normal and pathologic human vitreous have been analyzed for the presence of a low-molecular weight inhibitor of aortic endothelial cell proliferation. Vitreous was subjected to gel chromatography and the material appearing in the retarded volume (less than 13,000 daltons) was tested for its ability to inhibit tritiated thymidine incorporation into DNA by calf aortic endothelial cells. Depending on the sample of vitreous analyzed, one or more fractions showing inhibitory activity were identified in each case.

Adenylate cyclase in the microvessels of the rat brain. A histochemical study with light and electron microscopy

The presence of adenylate cyclase (AC) in the microvessels of the rat brain was studied by a new histochemical method for light and electron microscopy. The method is based on the precipitation of strontium and the subsequent conversion of the formed strontium salt into lead phosphate. Isoproterenol and 5-guanylylimidodiphosphate were used as enzyme activators. In the light microscope, the final reaction product was detected in the choroid plexus as well as in the walls of the microvessels in the brain parenchyma. In the electron microscope, both the luminal and abluminal endothelial membrane as well as the basal lamina of the parenchymal microvessels displayed reaction product. The observations demonstrate that isoproterenol-stimulated AC is located in the endothelium of the rat brain microvessels and suggest that the enzyme may play a role in the receptor-mediated regulation of endothelial functions.

Effect of chlorpropamide and gliclazide on plasminogen activator activity in vascular walls in patients with maturity onset diabetes

The components of the fibrinolytic system were studied in patients with maturity onset diabetes, treated with chlorpropamide for three years or more. Half of the patients (7/15) were shown to have abnormally low plasminogen activator activity of the vascular walls. The patients were then shifted to gliclazide, a new sulfonylurea, and after six months all patients had a normal vascular plasminogen activator activity. At follow up after 24 and 48 months the results remained the same. The normalization of the vascular fibrinolytic defence system could not be explained by improvement of glucose control.

Isolation and characterization of a urokinase-type plasminogen activator (Mr = 54,000) from cultured human endothelial cells indistinguishable from urinary urokinase

A urokinase-type plasminogen activator secreted by subcultured normal human umbilical vein endothelial cells was purified and compared to urinary urokinase (Mr = 54,000). The enzyme was isolated from serum-free conditioned medium in the presence of 0.1% (v/v) Triton X-100 by p-aminobenzamidine-agarose affinity chromatography, followed by Sephacryl S-200 gel filtration, followed by immunoadsorption chromatography on affinity purified specific anti-urokinase IgG-Sepharose CL-4B. This plasminogen activator form was obtained from the culture medium with a yield of about 47% and specific activity of about 93,000 IU/mg of protein, and represented approximately 18% of the total multiple molecular plasminogen activator activity forms present in endothelial cell conditioned medium. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme showed a single band of plasminogen activator activity with an estimated molecular weight of about 54,000 that was completely inhibited by diisopropyl fluorophosphate (DFP) as well as a single band of radioactivity with similar molecular weight for both the isolated L-[4,5-3H]leucine and [3H]DFP-labeled enzyme. The radiolabeled protein focused as a single major band with a pI value of pH 8.5. The endothelial cell activator and urokinase appeared to be identical in terms of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, location of the [3H]DFP-labeled active site in the Mr = 33,000 heavy chain and [3H]DFP-labeled active site tryptic peptide, and two-dimensional 125I-labeled tryptic peptide maps. In quenching experiments of the fibrinolytic activities using affinity purified specific anti-urokinase IgG the endothelial cell-derived activator and urokinase appeared to be immunochemically identical, but unrelated to tissue plasminogen activator. These results indicate that the Mr = 54,000 urokinase-type plasminogen activator from cultured normal human endothelial cells is similar to, or identical with, Mr = 54,000 urinary urokinase.

Fc-mediated binding of IgG to vimentin-type intermediate filaments in vascular endothelial cells

Prior studies have shown that vascular endothelial cells bind circulating IgG intracellularly during cell death. We now demonstrate that all endothelial cells have intracellular binding sites for IgG and that these binding sites are exposed to circulating IgG only if the plasma membrane is damaged. The binding sites are located on the cytoskeletal intermediate filaments and can be detected also in other cells containing vimentin-type intermediate filaments. Monoclonal human IgG1 exhibited saturable, high-affinity binding to vimentin-enriched cytoskeletons. Binding was inhibited by Fc fragments but not by Fab, F(ab')2, or pFc' fragments, suggesting that the binding site on IgG is located in the C gamma 2 domain of the Fc fragment. Binding of IgG to intermediate filaments may be important for the destruction and removal of damaged cells.

Sedimentation analysis of von Willebrand and factor VIIIC protein using partition cells in the analytical ultracentrifuge

Sedimentation analysis of factor VIII complex was performed in the analytical ultracentrifuge using partition cells. This method allowed for the calculation of three different sedimentation coefficients from each run: one based on ristocetin agglutination activity for von Willebrand protein, SWF; one based on coagulant activity for factor VIIIC, SVIIIC; and one based on the schlieren or adsorption data for protein concentration, Sconc. In most cases, there was no agreement between the three values calculated from the same run, indicating a heterogeneous system. The calculated functional sedimentation coefficients give values that require the molecules to be highly asymmetric to be consistent with a glycoprotein of high molecular weight, which is in agreement with results observed in electron microscope studies. The dissociation of VIIIC into a smaller form can be demonstrated by this method. Determination of the three sedimentation coefficients in a series of fractions from gel filtration indicates a uniform size for the VIIIC activity but not for the WF activity. These observations are in agreement with the concept of a copolymer between WF and VIIIC and also with the concept of separate polymers for the two activities.

Organization of actin cytoskeleton during early endothelial regeneration in vitro

The pattern of early cell movement after an experimental ‘wound’ and the organization of actin in stationary and moving cultured endothelial cells have been studied by means of: time-lapse photography; indirect immunofluorescence using anti-actin antibodies with and without pretreatment with the actin destabilizing factor present in human plasma; and differential centrifugation and densitometric analysis of stained sodium dodecylsulphate/polyacrylamide gels in order to evaluate the total and relative amounts of G and F-actin. Up to 5 h after a single scratch, movement consists of a coordinate spreading and translocation of a band of about 10 cells from the wound edge. Compared to stationary cells, moving endothelial cells show: no significant changes in the intensity and distribution of immunofluorescent staining with anti-actin antibodies, but an increased sensitivity of cytoplasmic actin, including stress fibres, to the actin-destabilizing factor purified from human plasma; and no significant change in the total amount of actin, but a decreased relative amount of F-actin and a corresponding increased relative amount of G-actin. We conclude that endothelial cell movement in vitro is accompanied by a rapid change in the state of actin organization characterized by an overall decrease in cytoplasmic F-actin.

Estrogen stimulates von Willebrand factor production by cultured endothelial cells

Monolayers of cultured human umbilical vein endothelial cells were exposed to 17 beta-estradiol and compared to control cultures with respect to levels of von Willebrand factor (vWF) released into the media after 3-5 days of incubation. The amount of functional vWF activity was assessed by ristocetin-induced platelet aggregation and by a radioreceptor platelet assay. vWF antigen was quantitated by immunoassay. The DNA content of each monolayer was determined fluorometrically and used as a measure of cell number. By all assays, vWF levels in the media from the estradiol-treated endothelial cells were reproducibly and significantly higher when compared with control values. The amount of vWF produced by the cultured endothelial cells showed a dose-response effect to the estradiol added to the media. The estradiol-treated cells produced approximately 1.3 +/- 0.30 micrograms vWF/ml/micrograms DNA at 2 ng estradiol/ml, compared with control cultures that produced 0.75 +/- 0.16 microgram vWF/ml/micrograms DNA (p less than 0.001). The estradiol-treated monolayers consistently contained slightly greater amounts of DNA than control cultures: 2.0 +/- 0.10 micrograms versus 1.7 +/- 0.12 micrograms DNA (p less than 0.001). By multivariant analysis, however, the differences in cell number could only account for less than or equal to 10% of the elevation in the level of vWF that occurred in response to estradiol. By SDS-agarose electrophoresis and radioimmunoblotting, the vWF within the cytosol of the endothelial cells was found to possess a multimeric pattern similar to that found for either purified plasma vWF or vWF released into media overlying endothelial cell cultures. Our studies indicate that estrogen directly stimulates endothelial cells to increase their rate of production of vWF and, in addition, causes a slight increase in endothelial cell replication. These data may bear on the observation that administration of estrogen to some women with von Willebrand's disease causes an increase in their functional levels of vWF.

Ultrastructural localization of lectin receptors on the bone-marrow sinusoidal endothelium of the rat

The bone-marrow sinusoidal endothelium is a cellular barrier that separates developing blood cells in the extravascular space from the peripheral circulation. Mature blood elements enter the circulation via transendothelial migration pores. In the present study, monosaccharide constituents on the bone marrow endothelium were examined using lectin-affinity cytochemistry. With lectin-horseradish and lectin-ferritin conjugates, mannosyl, N-acetylglucosaminyl, galactosyl, N-acetylgalactosaminyl, and sialic acid were localized to the luminal plasmalemma, bristle-coated pits and diaphragmed fenestrae. These were conspicuously reduced on the abluminal plasmalemma. When the tissue was treated with biotinylated lectins followed by avidin-ferritin, only a localization with wheat-germ agglutinin (sialic acid; N-acetylglucosaminyl) was observed. Pretreatment of the bone marrow with neuraminidase enabled the localization of the other monosaccharide components by the biotin-avidin method. Accumulations of carbohydrate residues were identified near the endothelium subjacent to migrating cells. Fucosyl moieties marked by Ulex europaeus agglutinin ( UEA ) reagents on the endothelium were not present. All binding was abolished by incubation of tissue and lectin conjugates with specific hapten sugars. labeling was also not present after Pronase E treatment, indicating that the identified monosaccharides are components of glycoproteins rather than glycolipids. The possible function of endothelial-surface glycoproteins as receptors for the surfaces of mature blood cells and their role in transmural migration are discussed.

Reverse fibrin autography: a method to detect and partially characterize protease inhibitors after sodium dodecyl sulfate--polyacrylamide gel electrophoresis

A new technique, reverse fibrin autography, was developed to detect protease inhibitors previously fractionated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Exogenous proteases were incorporated into fibrin-agar indicator films, eventually causing the fibrin to lyse. When an acrylamide gel containing inhibitors was placed on top of such an indicator, the positions of the inhibitors were revealed by the formation of opaque, lysis-resistant zones in the otherwise cleared fibrin film. The technique was versatile in that a variety of inhibitors were revealed, and semiquantitative since the size of the lysis-resistant zone in the indicator increased in proportion to the amount of inhibitor subjected to electrophoresis. This approach could be used not only to detect inhibitors having different protease specificities, but also to distinguish between the inhibitor activities of antibodies directed against urokinase or tissue-type plasminogen activator. Thus, reverse fibrin autography offers a convenient new approach to rapidly screen and partially characterize inhibitors present in complex biological samples.

Fatty acid composition in native and cultured human endothelial cells

Endothelial cells from human umbilical veins were isolated by collagenase treatment. Cells were cultured in the presence of either 20% fetal bovine serum (FBS) or 20% human serum (HS). At confluency, endothelial cell lipids were labeled with tracer concentrations of tritiated arachidonic acid, then extracted and separated into lipid subclasses by thin layer chromatography. The fatty acid composition of each lipid class was determined by glass capillary gas-liquid chromatography analysis and compared to that of cells freshly isolated from the cord (NC cells). The fatty acid compositions differed only in phospholipids. Polyunsaturated fatty acids (PFAs), arachidonic, and linoleic acids were depleted in FBS cell phospholipids and replaced by both stearic and oleic acids. No significant difference could be observed between NC cell and HS cell phospholipids. We conclude that PFAs might be decreased in FBS cells because of the relative paucity of PFAs in FBS as compared to HS. It seems therefore more convenient to cultivate endothelial cells in the presence of HS, especially in respect to their phospholipid content of arachidonic acid, which is the physiological reservoir for prostacyclin synthesis.

Cellular distribution of the asialoglycoprotein receptor in rat liver. Implications for hepatic accumulation of desialylated lymphocytes

It has been postulated that the selective accumulation of circulating desialylated cells in the mammalian liver results from the binding of desialylated glycoproteins on surfaces of the cells to asialoglycoprotein receptors in the liver. Since circulating cells in the liver are in contact predominantly with sinusoidal lining cells (Kupffer cells and endothelial cells), this postulate requires the presence of asialoglycoprotein receptors on the luminal surface of the sinusoidal lining cells. Whether the receptor is present on these cells, however, remains controversial. To clarify this issue, we used an indirect immunoelectron microscopic method to determine the distribution of the receptor on the surfaces of hepatic cells accessible to the circulation. F(ab')2 fragments of antireceptor antibodies were perfused in situ via the portal vein prior to tissue fixation. After perfusion fixation, sections were reacted with peroxidase-labeled antibodies to the antireceptor F(ab')2. The plasma membranes of Kupffer cells, endothelial cells, and fat-storing cells were devoid of the asialoglycoprotein receptor. In contrast, the receptor was associated with hepatocytes, where it was present diffusely on the sinusoidal plasma membranes and concentrated within coated pits. We conclude that it is unlikely that circulating desialylated cells bind to the asialoglycoprotein receptor in the liver unless a breach in the continuity of sinusoidal lining cells exists.

Regulation of factor Xa in vitro in human and mouse plasma and in vivo in mouse. Role of the endothelium and plasma proteinase inhibitors

The regulation of human Factor Xa was studied in vitro in human and mouse plasma, and in vivo in mouse. In human plasma, 125I-Factor Xa bound to alpha 1-proteinase inhibitor, antithrombin III, and alpha 2-macroglobulin in a ratio of 4.9:1.9:1 as determined by gel electrophoresis and by adsorption to IgG-(antiproteinase inhibitor)-Sepharose beads. The distribution of Factor Xa in mouse plasma was similar. The clearance of Factor Xa in mice was rapid (50% clearance in 3 min) and biphasic. alpha 1-Proteinase inhibitor-trypsin, even at a 2,000-fold molar excess, failed to inhibit the clearance of Factor Xa, while alpha 2-macroglobulin-trypsin inhibited only the later phase of clearance. The plasma clearance of diisopropylphosphoryl-Factor Xa was more rapid than native Factor Xa (50% clearance in 2.5 min), and the clearance was blocked by diisopropylphosphoryl-thrombin. Electrophoresis experiments confirmed that by 2 min after injection into the murine circulation, 90% of the bound Factor Xa was on alpha 2-macroglobulin, in marked contrast to the in vitro results. Organ distribution studies at 3 and 15 min with 125I-Factor Xa demonstrated that the majority of radioactivity was in the liver, with significant radioactivity also present in lung and kidney. Autopsies performed 30 s after injection of 125I-Factor Xa also demonstrated significant binding to the aorta and vena cava. These studies indicate that Factor Xa binds to specific thrombin-binding sites on endothelial cells, and that this binding alters its proteinase inhibitor specificity. Factor Xa binds to alpha 2-macroglobulin in vivo, whereas the predominant in vitro inhibitor of Factor Xa is alpha 1-proteinase inhibitor.

Characterization of the blood-brain barrier: protein composition of the capillary endothelial cell membrane

Microvessels were isolated from canine cerebral cortex, and the composition of the endothelial cell membrane was investigated. Endothelial cell membranes were separated from the surrounding basement membrane, solubilized, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis in 12% gels. Staining with Coomassie Blue revealed a characteristic banding pattern of at least 12 major proteins with apparent molecular weights between 14,000 and 250,000. When proteins from red blood cell ghosts were run simultaneously, no similarities were observed, except for proteins at apparent molecular weights of 43,000 (band 3) and 35,000 (band 4). These two proteins migrated exactly to the positions of the erythrocyte proteins actin and glyceraldehyde 3-phosphate dehydrogenase, respectively. Membrane glycoproteins in gels were also examined by the use of fluorescent lectins. Of the fluorescein isothiocyanate-conjugated (FITC) lectins tested, only FITC-concanavalin A had an affinity for any membrane components. Diazotized [125I]iodosulfanilic acid, a membrane-impermeable reagent, was used to label the internal (lumen) cell surface and the external (antilumen) cell surface. Autoradiography and determination of radioactivity levels in gel slices showed that several proteins were specifically labeled, and that major differences in radioactivity of proteins existed in internal and external labeling experiments. It is concluded that the protein composition of the luminal membrane is different from that of the antiluminal membrane.

The presence of EC collagen and type IV collagen in bovine Descemet's membranes

When bovine Descemet's membranes (DMs) were characterized after limited pepsinization the major component in DM was found to be endothelial cell (EC) collagen. Phenol extractions of the undigested pepsin residue recovered only type IV collagen. This study provides evidence that EC collagen may be produced by corneal endothelial cells in vivo.

The susceptibility of renal arterial forks in rabbits to dietary-induced lipid deposition

The major forks of the renal arteries from 21 rabbits fed a cholesterol-supplemented diet for periods of 1-90 d were examined electron-microscopically to compare the changes in the stem of the renal arteries with those at the first main fork. Lipid accumulated preferentially in the intimal pads or cushions at the fork. Matrix vesicles diminished in number and appeared to be transformed into enlarged membrane-bound vacuoles with electron-translucent contents. Foam cells were observed particularly beneath the endothelium. The lipid in endothelial and smooth muscle cells differed from that in the foam cells, indicating the likelihood of a different metabolic response. Interstitial lipid resembled an infiltration of the matrix with separation of the mural constituents but was not associated with the increased cellular degeneration, the progressive accumulation of matrix vesicles or the augmentation of the dystrophic basement membrane changes prominent in spontaneous atherosclerosis. In the arterial stems of 2 rabbits fed cholesterol for 62 and 90 d respectively, interstitial lipid deposition occurred without intimal proliferation.

A rapid, isocratic method for phospholipid separation by high-performance liquid chromatography

A rapid, isocratic method for separating the most prevalent phospholipids by high-performance liquid chromatography is described. Baseline resolution of phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, lysophosphatidylcholine, and sphingomyelin is achieved in less than 40 min on a silica column. Lipids are injected in 10 microliter of chloroform-diethyl ether 1:2 (v/v) and eluted with a solvent mixture of acetonitrile-methanol-sulfuric acid 100:3:0.05 (v/v/v) at a flow rate of 1 ml/min. Neutral lipids and cardiolipin elute with the solvent front. Chromatography of a radioactive cell lipid extract indicates a recovery of better than 97%. The procedure is sensitive enough to permit the analysis of the main phospholipids present in a monolayer culture containing about 100 micrograms of cell protein.

Components of subendothelial aorta basement membrane. Immunohistochemical localization and role in cell attachment

Cryosections of fetal and adult bovine aorta were stained with purified, cross-absorbed antibodies against various connective tissue components. The antibodies to the basement membrane components, laminin, heparan sulfate proteoglycan, and type IV collagen, gave a sharp reaction in the subendothelial layer. Antibodies against type III procollagen showed a broad endothelial staining, and staining was also seen in the media layer. A similar staining reaction was seen with antibodies against fibronectin. Bovine fetal aortic endothelial (BAE) cells were isolated and cultured in vitro. The cells became stained by the indirect immunofluorescence method with antibodies against laminin and heparan sulfate proteoglycan and also with antibodies against types III and IV collagen and type I procollagen, as in previously reported experiments. The attachment properties of endothelial cells to the same extracellular matrix components were also studied. BAE cells became attached most readily to surfaces coated with fibronectin or type III or type IV collagen. Laminin and collagen types I and V served as less effective substrates. Attachment to heparan sulfate proteoglycan was slowest of the tested components. The results of the study demonstrate that the BAE cells are associated with basement membranes in vivo. The BAE cells in culture produced interstitial connective tissue components in addition to basement membrane components and showed no clear specific preference in their attachment to any of these.

Factor VIII as a marker of endothelial cells in follicular carcinoma of the thyroid

Factor VIII-related antigen is a recognised marker of endothelial cells. A brief immunocytochemical study of its distribution in follicular carcinoma of the thyroid and its value in the recognition of vascular invasion by this tumour has been carried out. Ten cases of follicular carcinoma of the thyroid were studied. In each strong endothelial staining was found in the majority of vessels in the adjacent normal thyroid. Lymphatic endothelium was negative. In eight of the 10 cases the staining of vessels within the tumour was absent or very weak. Staining was also absent in the majority of vessels completely occluded by tumour, but was present in the endothelium of vessels only partly occluded by tumour. It is concluded that factor VIII-related antigen staining has only limited value in the recognition of vascular invasion in follicular carcinoma. The absence of vascular staining in the tumour leads us to suggest that inhibition of factor VIII production by the tumour could be a possible mechanism which facilitates vascular invasion and metastasis.

Uneven distribution of sialic acids on the luminal surface of aortic endothelium

Lectins which bind sialic acid (aprotinin, wheat germ) were used to measure sialic acid density on the luminal surface of aortic endothelium of rabbit. The bound fluorescein-labelled lectin was released from the sialic acids by the competing ligand N-acetyl-D-glucosamine and measured fluorimetrically. The specificity of the technique was shown by an 80% decrease of bound fluorescence after neuraminidase treatment of the endothelium. Endothelial sialic acid density was the same in the thoracic and abdominal parts of the aorta but significantly less in the arch. Around the orifices of the branches of the intercostal arteries, less surface fluorescence was observed. Ultrastructural studies have shown much less staining of the surface membranes with peroxidase-conjugated wheat germ lectin at these places than elsewhere. These areas, where less sialic acid density was found, coincide with the sites where the atherosclerotic process is known to develop.

The formation of capillary-like tubes by calf aortic endothelial cells grown in vitro

Cloned, large vessel endothelial cells derived from fetal bovine and bovine calf aortas formed three-dimensional structures in vitro without tumor-conditioned medium or special substrata. Transmission electron microscopy showed the structures to be hollow tubes composed of typical endothelial cells with overlapping and interdigitating cytoplasmic processes typical of those seen in in vivo capillaries. The putative lumen of these tubes generally contained abundant electron-dense fibrous material, which by ruthenium red and indirect immunofluorescent staining appeared to be extracellular matrix. This suggests that the endothelial cell orientation in the tubes is the reverse of that normally found in in vivo vessels.

Transformation of rat cerebral endothelial cells by Rous sarcoma virus

Rat cerebral microvascular endothelial cells were infected with Schmidt-Ruppin Rous sarcoma virus-strain D (SR-RSV-D), an avian retrovirus. A single focus of transformed cells was isolated and the resultant cell line designated RCE-T1. The specificity for SR-RSV-D transformation was determined by virus rescue assay and demonstration of virus-specific antigens. RCE-T1 cells are virogenic when fused with chicken embryo fibroblasts (CEF) and do not produce infectious virus as demonstrated by the absence of detectable virus in culture fluid from these cells alone. Studies using an enzyme-linked immunosorbent assay (ELISA) for avian retrovirus-coded internal proteins show that RSV-transformed endothelial cells contain mainly p27 and react to some extent to p19 and p15 viral antigens. These data demonstrate conclusively that the transformation event was indeed due to SR-RSV-D. In addition, chromosome analysis confirmed these cells to be of rat origin. RSV-transformed endothelial cells express the typical array of transformation-related properties such as anchorage-independent cell growth in soft agar, decreased cell adhesiveness, ability to grow in low serum, and capability of producing tumors in newborn rats. Demonstration of differentiated endothelial characteristics included positive immunofluorescent staining for factor VIII antigen and angiotensin-converting enzyme and histochemical localization of gamma-glutamyl transpeptidase activity. This cell line should provide a useful model to study not only specialized biochemical and other functional characteristics of cerebrovascular endothelium but also the cellular mechanisms that involve the transition from normal to neoplastic expression.

Cultured endothelial cells produce a platelet-derived growth factor-like protein

The platelet-derived growth factor (PDGF) binds specifically to high-affinity receptors on the surface of bovine aortic smooth muscle cells and 3T3 cells. Conditioned medium from cultured bovine aortic endothelial cells (EC) prevents PDGF binding to these receptors in a dose-dependent manner at 4 degrees C. The (125)I-labeled PDGF that is displaced by the conditioned medium shows no increase in trichloroacetic acid solubility or decrease in binding capability to fresh cells. The competitor activity was identified as a protein by ammonium sulfate precipitability and sensitivity to trypsin. The competitor protein also is found in the serum-free conditioned media from porcine aortic EC and human umbilical vein EC but not in media from bovine aortic smooth muscle cells, human neonatal foreskin fibroblasts, or the interleukin-producing thyoma cell line EL-4. The competitor protein, like PDGF, has no effect on the specific 4 degrees C binding of either (125)I-labeled insulin to 3T3 cells or (125)I-labeled epidermal growth factor to human epidermoid A431 cells. Saturation curves of PDGF binding to smooth muscle cells that had been preincubated in the presence and absence of competitor indicate that the concentration for half-maximal binding of (125)I-labeled PDGF to its receptor ( approximately 30 pM) is unchanged by the competitor, whereas the apparent number of available receptor sites or maximal level of binding is greatly diminished. The competitor activity produced by cultured human umbilical vein EC is completely inhibited by antiserum against pure human PDGF, whereas the same PDGF antiserum only partially inhibits the mitogenic activity of the conditioned media. In addition, approximately 7-fold more crude endothelium-derived growth factor is required for half-maximal inhibition of (125)I-labeled PDGF binding as is required for half-maximal stimulation of DNA synthesis. These results suggest that EC secrete a PDGF-like protein that is biochemically distinct from the majority of EC-derived mitogenic activity.

Neoplastic angioendotheliomatosis. Histologic, immunohistochemical, and ultrastructural findings in two cases

Two cases of neoplastic angioendotheliomatosis are described. Both patients presented with subacute development of dementia punctuated by focal neurologic signs. Postmortem examination in both cases disclosed a vasculocentric distribution of neoplastic cells in many organs. Two characteristic histologic patterns were seen: (1) distension of vascular spaces by free-floating, intraluminal cells and (2) asymmetric, subendothelial tumor growth. Intravascular tumor and secondary vascular changes were associated with microinfarcts in involved organs. Immunohistochemical localization of factor VIII-related antigen in the neoplastic cells of one case provides evidence for their endothelial origin. The neoplastic cells in both cases exhibited similar but nonspecific ultrastructural features. In addition, dramatic fine structural changes including the acquisition of numerous pinocytotic vesicles and bundles of fine filaments with periodic densities were found in the non-neoplastic endothelial cells.

Immunolocalization of a novel, cytoskeleton-associated polypeptide of Mr 230,000 daltons (p230)

Antibodies were raised against a cytoskeleton-associated, nonphosphorylated, 230,000-dalton bovine lens polypeptide (designated p230), and rendered monospecific by using a novel immunoaffinity technique. In immunofluorescence and electron microscopy of cultured fibroblasts, as well as of various other cells (endothelial, epithelial, lenticular, monocytes, neuroblastoma cells) and tissues (human kidney and liver), p230 was localized as a distinct subplasmalemmal layer in the peripheral cytoplasm of the cells. It constituted less than 0.3% of the total cellular protein in cultured fibroblasts and was not extractable with Triton X-100. In detergent-extracted cytoskeletal preparations of cultured fibroblasts, p230 remained as an elaborate peripheral network that showed a distribution distinctly different from that of the major cytoskeletal structures, stress fibers, cortical myosin, vinculin, and intermediate filaments (IF). The distribution was not dependent on the presence of intact stress fibers or microtubules, as shown by double-fluorescence microscopy of cells exposed to cytochalasin B or cultured in the presence of monensin and of cold-treated cells. Upon demecolcine-induced reorganization of intermediate filaments, however, the localization of p230 was rapidly altered to a dense plaque underneath the perinuclear aggregate of intermediate filaments. On the other hand, p230 seemed to colocalize with the detergent-resistant cell surface lamina, visualized in fluorescence microscopy with fluorochrome-coupled wheat germ agglutinin-lectin. The results suggest that p230 is part of a cell surface- and cytoskeleton-associated subplasmalemmal structure that may play an important role in cell surface-cytoskeleton interaction in various cells both in vitro and in vivo.

Intracellular pH and glutathione levels in rabbit corneal endothelium following storage in moist chamber and MK medium

Rabbit corneas were stored for up to 14 days at 4 C either as the whole eye in a moist chamber or as the isolated cornea in MK medium with HEPES buffer. The intracellular pH, the glutathione content, and its oxidation state were determined in the endothelial cells of fresh and stored tissue. The endothelial pH was found to be unchanged following storage of up to 7 days by either method, but after 14 days the pH rose slightly but statistically significantly in corneas stored by both techniques. The intracellular pH was similar in endothelia of those corneas stored in MK medium and of those stored as the whole eye in a moist chamber, for all time periods studied. The intracellular total and percent oxidized glutathione of the endothelium were increased by 50 and 180%, respectively, following 7 days of moist chamber storage. Over this time period there was a 50-fold increase in total glutathione content of the aqueous humor in the stored eyes. In contrast, corneas stored in MK medium for 7 days maintained intracellular total glutathione at levels similar to those of fresh corneas. A gradual but constant decrease in percent oxidized glutathione was observed with increasing length of storage. In terms of pH and glutathione content, the MK medium provided a much more stable environment for the stored cornea than did the aqueous humor in the stored eye.

Differential localisation and synthesis of porcine factor VIII related antigen (VIIIR:AG) in vascular endothelium and in endothelial cells in culture

Porcine and human umbilical vein and adult blood vessels were studied for the presence and synthesis of factor VIII related antigen (VIIIR:Ag) and fibronectin (Fn) by immunofluorescence histology and immunoautoradiography. Investigation of human tissue confirmed the widespread distribution of VIIIR:Ag on the endothelium of all blood vessels examined but observations on porcine tissue gave different results. Porcine umbilical vein and porcine adult veins were positively stained for VIIIR:Ag whilst porcine aorta and other pig arteries appeared to be negative or only weakly positive. Some blood vessels (?venous) in the adventitia of porcine aorta were positively stained whilst adjacent ones (?arterial) were negative. Radiolabelled methionine was added to culture medium and proteins synthesised by cultured EC were examined by two dimensional crossed immunoelectrophoresis and autoradiography. Identification of radiolabelled precipitin arcs provided a highly sensitive method for confirming the specificity of antisera and for detecting VIIIR:Ag and Fn. Examination of cultured human umbilical vein EC confirmed the synthesis of VIIIR:Ag and distinguished between VIIIR:Ag and Fn. Studies of porcine umbilical vein EC in culture gave similar results to those observed with corresponding human EC. However, cultures derived from porcine aorta did not demonstrate synthesis of VIIIR:Ag and microscopy failed to locate VIIIR:Ag in these cells with certainty. The results confirmed the synthesis of VIIIR:Ag by human and porcine umbilical vein EC but differences in staining reactions and the apparent inability to synthesise VIIIR:Ag by cells derived from porcine aorta suggested that porcine EC at different anatomical sites may subserve different functions.

Actin filament localization and distribution in the young adult mouse cornea: a correlative immunofluorescent and cytochemical study

The localization and distribution of actin filaments was determined in the corneal epithelium and endothelium of the young adult Swiss Webster mouse by correlative indirect immunofluorescence using rabbit anti-skeletal muscle actin antiserum and by in situ labelling with heavy meromyosin subfragment-1 (HMM-S1). A diffuse fluorescent staining was observed in the cytoplasm of epithelial and endothelial cells and in stromal keratocytes. In addition, a highly fluorescent punctate cytoplasmic staining was seen only in the corneal epithelium. Ultrastructurally, HMM-S1 decorated actin filament bundles were generally distributed within the cytoplasm of glycerinated superficial, wing and basal epithelial cells and within pedicle-like processes on the posterior surface of superficial and wing cells. Actin filament bundles also were seen in close association with intermediate filament bundles in the epithelium. HMM-S1 labelled filaments were observed in the endothelial cytoplasm anteriorly near Descemet's membrane, posteriorly near the anterior chamber and adjacent to lateral cell borders. Actin filaments in epithelial and endothelial cells appeared to insert into the plasma membrane.

Cytofluorescence localization of adriamycin in the nervous system. IV. cellular uptake of the drug in peripheral nerve following various modes of injection to bypass the blood-nerve and the perifascicular barriers

Adriamycin (Doxorubicin) is a powerful anthracyclic compound, which is widely used in the treatment of malignant diseases. In the rat a single systemic injection of the drug can induce pronounced lesions in peripheral ganglia, whereas in other parts of the peripheral nervous system (PNS) no changes have been reported. Since adriamycin can be directly traced in tissue sections by fluorescence microscopy it is very well suited for experimental studies on the relation between cytotoxic effects and distribution of the drug following various modes of administration. We have previously shown that after an intravenous (i.v.) injection there is an absence of adriamycin-induced nuclear fluorescence in the endoneurium of mouse sciatic nerve (Bigotte et al. 1982 b). This could either be due to barrier effects in endoneurial vessels and the perineurium or to a lacking capacity of the endoneurial cell population to take up and retain adriamycin. In the present study the blood-nerve and the perifascicular diffusion barriers were therefore bypassed by endoneurial microinjections of adriamycin. After this mode of administration, Schwann cells, endoneurial mast cells, endothelial cells, and pericytes became labeled. Experimental damage of these barriers induced by ligation of the nerve also resulted in a diffusion of the drug into the endoneurial area and labeling of the same cells. The absence of nuclear binding in the endoneurium of mouse sciatic nerves after i.v. injection of adriamycin is therefore most probably due to a low or absent passage of the drug from the blood into the endoneurium, i.e., a combined barrier action of endoneurial vessels and the perineurium. Other experiments with epineurial application of the drug showed that thin intramuscular (i.m.) nerve branches differ from the sciatic nerve fascicles in allowing small amounts of adriamycin to enter the endoneurium. The present observations are of interest since it can be assumed that patients receiving adriamycin as a cytostatic drug may suffer nerve lesions whenever defects of nerve barriers are present.

Distribution of endothelial and basement membrane markers in angiogenic tumors of the nervous system

The distribution of two endothelial cell markers Factor-VIII-related antigen and Ulex europaeus agglutinin was examined by immunoperoxidase and immunofluorescence techniques in paraffin-embedded specimens representing the three main types of angiogenic neoplasms of the nervous system, hemangioblastoma, hemangioendothelioma and hemangiopericytoma. In addition, the distribution of the basement membrane (BM) marker, laminin, was studied in the same tumors. It was found that Ulex europaeus agglutinin was a more sensitive marker of neoplastic endothelial cells than Factor-VIII-related antigen. Both markers only stained endothelial cells, while the tumor cells of hemangiopericytomas and the stromal cells of hemangioblastomas remained unstained. These findings do not support the view that the stromal cells of hemangioblastomas are derived from endothelial cells. With antiserum to laminin a typical staining pattern could be noticed in each tumor, showing the architectural relationships of the cells very clearly. In all three tumor types laminin was only found in the BM of the vessels, not in the interstices of the neoplastic cells outside vessel lumina. Therefore, the reticulin network previously found between the individual cells of hemangiopericytomas does not correspond to BM. It is concluded that both Ulex europaeus agglutinin and laminin antisera could be valuable new aids for the diagnosis of the three tumor types.

Pathogenesis of viral encephalitis: demonstration of viral antigen(s) in the brain endothelium

One of the enigmas in the pathogenesis of inflammation is why the white cells adhere to the endothelium. In trying to define the pathogenic mechanism, we carried out experiments on ferrets infected with an SSPE strain of measles virus. Using immunoperoxidase labeling techniques, viral antigens were demonstrated on the luminal surface and in the cytoplasm of endothelial cells, irrespective of the presence or absence of inflammatory changes. The degree of inflammation corresponded well with antibody titer. These data suggest that the viral antigen in the endothelial cells is the site of interaction between these cells and sensitized lymphoid cells.

Demonstration of fibronectin in normal and injured aorta by an indirect immunoperoxidase technique

The presence and localization of fibronectin in normal and mechanically injured aorta in rabbits was studied using an indirect immunoperoxidase technique on tissue specimens fixed in formaldehyde, embedded in paraffin and pretreated with pepsin. The effect on staining quality of treatment with testicular hyaluronidase prior to immunoperoxidase staining was also examined. In the intima from normal aorta fibronectin was present in the subendothelial basal layer, along the internal and external elastic laminae, around and between the smooth muscle cells of the media and along the collagen and elastic fibres in the adventitia. Sixteen days after a single mechanical dilatation of the descending thoracic aorta all animals developed gross atherosclerotic-like changes. Microscopic examination revealed prominent neo-intimal hyperplasia with subendothelial, cushion-like thickenings but no medial or adventitial alterations. Fibronectin, in increased amounts, was found between and around the endothelial cells and in the subendothelial thickenings between the proliferating smooth muscle cells in relation to the fine, thin elastic and argyrophilic fibres. In the media and adventitia the amount and distribution of fibronectin was indistinguishable from uninjured control aortas. Treatment with testicular hyaluronidase before immunoperoxidase staining resulted in a higher staining resolution in normal and injured aorta. The conspicuous observation in the present study is that fibronectin exclusively accumulates in areas of tissue repair. The origins and functions of fibronectin during tissue injury and repair are discussed.

Arteriosclerosis in normal and von Willebrand pigs: long-term prospective study and aortic transplantation study

In a long-term prospective study, five normal control pigs and five pigs with homozygous von Willebrand's disease received a nonfatty diet from age 3 months to 4 years; then the aortas were analyzed. The fibrous arteriosclerotic plaques in the distal abdominal aortic region involved an average of 28% of the surface area in control pigs and only 7% of the surface area in pigs with von Willebrand's disease (P less than 0.01). In a subsequent study of 3-month-old pigs, the distal abdominal aortic segments from nine normal pigs were cross-transplanted with segments from nine other normal pigs (control study), and aortic segments from four normal pigs were transplanted into four host pigs with von Willebrand's disease (exchange study). All pigs received a 2% cholesterol diet for up to 6 months; then the transplanted aortic segments were analyzed. The donor normal aortic segments in the host normal pigs developed arteriosclerosis that involved an average of 20% of the surface; the endothelial fluorescent pattern of von Willebrand factor was identified. In contrast, the donor normal aortic segments in the host pigs with von Willebrand's disease had arteriosclerosis that involved an average of only 4% of the surface (P less than 0.01); the endothelial cell von Willebrand factor was not identified. The long-term prospective study indicates that pigs with von Willebrand's disease are resistant to the development of spontaneous arteriosclerosis. The aortic transplantation data are compatible with the hypothesis that the absence of von Willebrand factor in pigs with von Willebrand's disease may cause impairment of platelet-arterial wall interaction and resistance to arteriosclerosis.

Carbohydrate cytochemistry on hypodermic lymphatic endothelium of the green lizard, Lacerta hispanica

A cytochemical study on the endothelium of the hypodermic lymphatic capillaries of the green lizard, Lacerta hispanica, has been carried out. The dialysed iron method produced a homogeneous precipitate on the surface of the endothelial cells and on the inside of the endocytic vesicles. The periodic acid-thiocarbohydrazide-silver proteinate, low pH phosphotungstic acid and high iron diamine techniques gave negative results. The carbohydrates in the capillaries thus seem to be glycosaminoglycans with carboxyl groups. The possible role of these glycosaminoglycans in the formation of the endocytic vesicles is discussed.

Domain and basement membrane specificity of a monoclonal antibody against chicken type IV collagen

A monoclonal antibody, IV-IA8, generated against chicken type IV collagen has been characterized and shown to bind specifically to a conformational-dependent site within a major, triple helical domain of the type IV molecule. Immunohistochemical localization of the antigenic determinant with IV-IA8 revealed that the basement membranes of a variety of chick tissues were stained but that the basement membrane of the corneal epithelium showed little, if any, staining. Thus, basement membranes may differ in their content of type IV collagen, or in the way in which it is assembled. The specificity of the antibody was determined by inhibition ELISA using purified collagen types I-V and three purified molecular domains of chick type IV collagen ([F1]2F2, F3, and 7S) as inhibitors. Only unfractionated type IV collagen and the (F1)2F2 domain bound the antibody. Antibody binding was destroyed by thermal denaturation of the collagen, the loss occurring at a temperature similar to that at which previous optical rotatory dispersion studies had shown melting of the triple helical structure of (F1)2F2. Such domain-specific monoclonal antibodies should prove to be useful probes in studies involving immunological dissection of the type IV collagen molecule, its assembly within basement membranes, and changes in its distribution during normal development and in disease.

Surface topography of mitral valve endothelium from diet-induced, hypercholesterolemic rabbits

Mammalian, cardiac endothelium has a surface topography that is characterized by plasmalemmal microappendages, nuclear bulges and ruffled cellular margins. SEM of the endothelial population over the two surfaces of the anterior cusp (leaflet) of the rabbit mitral valve revealed a very pleomorphic topography. The atrial and ventricular surfaces of the cusp displayed differences in microappendage population, cell density, nuclear contour and surface reactivity to Ruthenium Red and Concanavalin A. Comparative studies of similar populations from diet-induced hypercholesterolemic rabbits suggested an enhanced endothelial permeability as observed by an increase in cytoplasmic vesicles containing RR or Con A and by their intercellular passage into the subendothelium. Concomitant with these changes were disproportionate responses in the surface reaction of the carbohydrate cell coat (glycocalyx). The endothelial cells over the ventricular surface of the anterior cusp displayed the most dramatic changes with the appearance of numerous microappendages and intercellular fenestrations, the loss of RR and Con A surface reaction and the engorgement of the adjacent intima with foam-like cells containing the surface markers. Such surface responses appeared to precede or accompany alterations in endothelial integrity which suggests the importance of the blood-endothelial interface in the maintenance of the vascular wall.