Fc receptors of liver sinusoidal endothelium in normal rats and humans. A histologic study with soluble immune complexes

Fc receptors for immunoglobulin G in the liver sinusoidal wall were studied in the normal rat and in humans by applying peroxidase-antiperoxidase immunoglobulin G complexes to the frozen sections. Fc receptors were found to exist continuously along the sinusoidal lining. The receptors showed no zonal distribution in the rat, and they were generally scarce near the central veins and portal areas in humans. To characterize the sinusoidal cells, carbon or latex was given intravenously and endogenous peroxidase was demonstrated for the rat, whereas factor VIII-related antigen and endogenous peroxidase were demonstrated for the humans. In the rat, Fc receptors were detected on Kupffer cells, which were characterized by an intense endogenous peroxidase activity and ingestion of latex or quantities of carbon. They were also detected on sinusoidal endothelial cells, which were characterized by undetectable peroxidase activity and no ingestion of latex nor of a small quantity of carbon. In humans, Fc receptors were also present on Kupffer cells as well as sinusoidal endothelial cells, as identified by endogenous peroxidase and factor VIII-related antigen, respectively.

Identification of a fibronectin receptor specific for rat liver endothelial cells

Antibodies raised against the fibronectin receptor of rat hepatocytes recognized one protein (Mr 120 and 135 kDa for unreduced and reduced samples, respectively) in immunoblotting of solubilized rat liver endothelial cells (LEC). The antibodies specifically precipitated a 200-kDa protein together with the 135-kDa component from 125I-labeled LEC. Spreading of LEC on fibronectin, but not on laminin or collagen, was inhibited by monovalent Fab fragments of the antibodies, implicating that the 135/200-kDa complex is a specific fibronectin receptor. The results indicate that LEC, hepatocytes, and fibroblasts of rat carry different fibronectin receptors, suggesting that the interaction of fibronectin with these cells may have different functional roles.

Modulation of CD4 antigen on macrophages and microglia in rat brain

Mononuclear phagocytes which express the HIV entry receptor CD4 have been implicated as possible sites of virus replication in brain, but there is still considerable uncertainty as to which cells in the CNS express CD4 Ag. Although it is not susceptible to HIV infection the rat provides a model to define expression of the CD4 Ag on MO in brain. We report that the CD4 epitopes W3/25 and OX35 are found only on monocytes, MO, microglia, and occasional lymphocytes and not on neurons, other glia, or endothelium. CD4 Ag levels are modulated during microglial differentiation, after reactivation after local inflammation, and within the intact blood brain barrier. MO and microglia also express other potential plasma membrane binding and entry sites for HIV viz Fc and complement receptors that are regulated independently of CD4.

cDNA clones reveal differences between human glial and endothelial cell platelet-derived growth factor A-chains

Human platelet-derived growth factor (PDGF) is a potent mitogenic polypeptide which is believed to be a heterodimer of A- and B-chains stabilized by interchain disulphide bonds. The B-chain of PDGF is encoded by the c-sis gene, the normal cellular homologue of the transforming gene of the simian sarcoma virus (SSV). cDNA clones of the B-chain from both normal and transformed cells have mutually consistent DNA sequences. Recently, an A-chain cDNA clone (D-1) was isolated from a transformed human glial cell cDNA library. We report the complete sequence of an A-chain cDNA clone (BT-1) isolated from a normal human umbilical vein endothelial (HUVE) cell cDNA library. BT-1 differs from the sequence of the D-1 clone by a 69 base pair deletion containing the predicted carboxy terminus of the protein. The mRNA levels of the A- and B-chains of PDGF in HUVE cells were analysed and shown to respond differently to the endothelial cell growth factor (ECGF).

Alternative RNA splicing affects function of encoded platelet-derived growth factor A chain

Platelet-derived growth factor (PDGF) is a basic protein of relative molecular mass 30,000 (Mr 30K) composed of two polypeptide chains, designated PDGF A and PDGF B. The B-chain is encoded by the c-sis gene, the cellular counterpart of the simian sarcoma virus transforming gene v-sis. The PDGF A-chain cDNA clones recently isolated and sequenced from a transformed human clonal glioma cell line represent at least two alternatively spliced transcript species differing by 69 base pairs at the C-terminus. Here we demonstrate that the normal human umbilical vein endothelial cell (EC) A chain precursor lacks the 15 carboxy-terminal, highly basic amino acids encoded by the larger tumour cell cDNA. Surprisingly, culture media from monkey kidney cells (COS) transfected with the endothelial cDNA clone contained much less mitogenic activity than media from cells transfected with the longer tumour cell-derived A-chain cDNA. This functional difference appeared to be due to inefficient assembly or secretion of the recombinant endothelial-type growth factor. This suggests that some transformed cells may use alternative RNA splicing to modify normal growth factors and by so doing increase the efficiency of mitogen assembly or secretion.

Biochemical characterization of the soluble form of the junctional plaque protein, plakoglobin, from different cell types

A polypeptide of identical molecular mass (Mr 83,000) and charge to desmosomal plakoglobin from bovine snout epidermis was identified in soluble and pelletable fractions from diverse tissues and cells of different mammalian species, including cells and tissues devoid of desmosomes (e.g. endothelial, retinal, lenticular cells, fibroblasts). The protein, however, was not detected in erythrocytes and platelets and in myeloma cells, nor in smooth muscle tissue. In all cells examined, the plakoglobin soluble upon cell lysis in buffers of near-physiological pH and ionic strength (21-31% of the total plakoglobin in the different cell types) was found to exist in a distinct molecular form. On sucrose gradient centrifugation it appeared at about 7 S and gel filtration chromatography revealed a Stokes radius of about 5.0 nm, from which an Mr of about 170,000 was estimated. By using isoelectric focusing under non-denaturing conditions, soluble approximately equal to 7-S plakoglobin had an isoelectric point at about pH 5.3. The plaque-bound and the soluble form of plakoglobin were indistinguishable by electrical charge and molecular mass, regardless of the source, indicating molecular identity. Cross-linking of soluble proteins with cupric 1,10-phenanthroline resulted in the formaton of a cross-linked product of plakoglobin with similar physical properties as the native approximately equal to 7-S particle, which is compatible with the interpretation that the soluble plakoglobin particle is a dimer. While a major proportion of the plakoglobin in the desmosomal plaque was resistant to various extraction procedures, plakoglobin present in the plaques of non-desmosome-containing cells and tissues was readily extractable under low and high salt conditions. This indicates that differences exist in the binding of plakoglobin to desmosomal plaques and the plaques of non-demosomal junctions.

Tissue plasminogen activator in the trabecular endothelium

By quantitative analysis of tissue plasminogen activator (TPA) in the trabecular endothelium, corneal endothelium, and iris in the eyes of monkeys and dogs, we found significant levels of TPA activity. In a [125I]fibrin-coated well assay, the levels for the dog and monkey were, respectively: trabecular endothelium, 0.2 and 0.5; corneal endothelium, 0.8 and 0.5 IU per mg protein. The iris tissue showed high TPA activity, but its protein content could not be measured with the techniques employed. Activity in the aqueous humor was not detectable. By the ELISA technique, the values (in ng TPA/mg tissue protein) for the dog and monkey were, respectively: trabecular endothelium, 0.16 and 0.44; corneal endothelium, 0.48 and 0.92. Again, iris tissue showed high TPA activity, whereas the aqueous humor showed low activity (0.86 ng/ml). The data obtained with the two methods showed a reasonable consistency, although a direct comparison was not possible because two separate standards were used. The presence of TPA in the trabecular endothelium, corneal endothelium, and iris may be important in modulating the resistance to aqueous outflow under normal conditions as well as those of hyphema.

Glycosphingolipids of human umbilical vein endothelial cells and smooth muscle cells

Glycosphingolipids (GSLs) represent an important class of immunogens and receptors. Although cell surface antigens and receptors of endothelial cells (ECs) have been the subject of extensive biochemical investigation, no information is available about their GSLs. We report here the characterization by chromatographic and immunological techniques of GSLs of cultured human umbilical vein ECs and, for comparison, umbilical vein smooth muscle cells (SMCs). The most abundant neutral GSLs of both cell types were lactosylceramide, Gb3, and Gb4, and both cells contained complex lacto and globo series compounds. Immunostaining revealed that ECs, but not SMCs, contained long chain GSLs bearing a type 2 blood group H determinant. ECs also contained more long chain GSLs bearing an unsubstituted terminal lactosamine structure than SMCs. Labeling with galactose oxidase/NaB3H4 demonstrated that neutral glycolipids that contained three or more sugars were accessible on the cell surface. The major gangliosides of both cell types were GM3 and IV3NeuAcnLc4. Immunostaining following neuraminidase treatment revealed that most of the long chain gangliosides in both types of cells contained a lacto core structure, and that ganglio series compounds were more abundant in SMCs than ECs. Gangliosides that contain a polyfucosyllactosamine core and a globo core were also present in both cell types. These results demonstrate that endothelial and smooth muscle cells contain a large diversity of GSL structures, and provide the basis for investigation of the role of these GSLs as cell surface antigens and receptors for blood components.

Co-distribution of von Willebrand factor and fibronectin in cultured rhesus endothelial cells

The synthesis and secretion of von Willebrand factor (VWF, or Factor VIII-related antigen) and fibronectin by cultured endothelial cells from rhesus monkey choroid retina were demonstrated by immunofluorescence, immunoperoxidase and single radial immunodiffusion techniques. Both VWF and fibronectin are localized in intracellular granules and extracellular fibrils. The results of double immunofluorescence staining and post-embedding immunoelectron microscopy showed that there was a co-distribution of VWF and fibronectin not only in pericellular fibrils where they co-aligned with each other to be the components of extracellular matrix, but also in intracellular granules, suggesting they were synthesized or translocated in the same compartment.

Aortic endothelial cell proteoheparan sulfate. I. Isolation and characterization of plasmamembrane-associated and extracellular species

Proteoheparan sulfate biosynthesis was studied in cultured bovine aortic endothelial cells by means of pulse and pulse-chase experiments and subcellular fractionations. Three proteoheparan sulfate species were found in the medium. The major species, which the authors have called HS I, appeared in the medium only after an initial lag period and was also found associated with the plasma membrane. The other two (HS II and HS III) appeared in small amounts in the medium at early time points. At later times these were not readily observed because the large amounts of HS I present in the medium. The major medium species, HS I, appeared to be composed of approximately four heparan sulfate chains of approximately 35,000 daltons and a core protein of approximately 55,000 daltons apparent molecular weight. HS I appeared to be homogeneous by gel filtration on Sepharose CL 2B and 6B and elution from DEAE Sephacel, electrophoresis on Nu-Sieve agarose, and CsCl density centrifugation. After digestion with heparinase the core protein appeared to be homogeneous by S-200 Sephacel chromatography. HS I was also found associated with plasma membrane fractions of the cultured bovine aortic endothelial cells, and antisera raised against it stained epithelial and endothelial cells in patterns consistent with a cell surface localization. Of the other two species found in the medium, one (HS II) also appeared to be a component of the cell layer. This species appeared to contain approximately four heparan sulfate chains of approximately 20,000 daltons apparent molecular weight. Antisera raised against a similar molecule produced by HR 9 cell cultures stained basement membranes intensely, supporting the subcellular matrix localization of this molecule. The third species (HS III) was detected in culture medium only and apparently contained two heparan sulfate chains of approximately 20,000 daltons apparent molecular weight. These results support the concept of multiple endothelial cell proteoheparan sulfate species which exhibit differences in structure and localization and possibly diverse specialized functions.

Characterization of the blood-brain barrier: glycoconjugate receptors of 14 lectins in canine brain, cultured endothelial cells, and blotted membrane proteins

The avidin-biotinylated peroxidase complex (ABC) method was used to detect binding of 14 lectins in tissue, cultured cells, and nitrocellulose blots. When applied to frozen sections of canine cerebral cortex and pituitary and evaluated by light microscopy, these lectins produced distinct staining patterns as determined by their individual carbohydrate specificities. Major saccharide residues detected in the endothelium of these cerebral tissues include alpha- and beta-galactose, alpha-mannose and/or alpha-glucose, and N-acetylglucosamine. Application to cells cultured from the canine cerebral endothelium gave staining results similar to those of microvessels in tissue. Thus, these characteristics of intact capillaries are retained in cultured cells and define fundamental properties of the blood-brain interface. Visual comparison of these staining patterns to those obtained for electrophoretic blots of solubilized membrane proteins identified multiple glycoprotein receptors and illustrated the vast quantity and variety of surface carbohydrate residues and the complexity of the cerebral endothelial cell glycocalyx. This carbohydrate-rich layer, which extends into the capillary lumen, may be of significant importance to the unique function of the blood-brain barrier.

Molecular sieving characteristics of the cultured endothelial monolayer

We examined the selectivity of the bovine pulmonary artery endothelial monolayer in vitro to molecules of different sizes. The cultured bovine pulmonary endothelial monolayer was grown on a gelatinized filter and the transendothelial transport was studied by determining the permeability of molecules ranging from 182 to 340,000 daltons under diffusion conditions. The permeabilities across the cultured bovine endothelium were modeled according to cylindrical pore theory. The data were best fit by a two-pore model with radii 65 A and 304 A and a ratio of small to large pores of 160:1. The results indicate that the cultured endothelial monolayer is a selective barrier to molecules of different sizes and that the molecular selectivity is consistent with a diffusional pathway through endothelial pore equivalents. The cultured endothelial monolayer is a useful system for studying the permeability characteristics of the endothelial barrier.

Coronary disease prediction using a new atherogenic index

This report demonstrates the utilization of a new serum factor, Toxicity Preventing Activity (TxPA) in the diagnosis of coronary disease prone individuals. Our laboratory has recently identified TxPA, which offsets the toxicity of very low density lipoproteins (VLDL) upon arterial cells in vitro. In the present study, we measured TxPA activity and serum lipoprotein levels in 73 individuals undergoing coronary angiography. Serum from control subjects demonstrated 270% more TxPA than aged matched individuals with angiographically demonstrable coronary disease (CHD). When TxPA was combined with serum lipoprotein values, a new atherogenic index was generated which further distinguished these individuals with CHD from non-angiographed controls. These results demonstrate that TxPA is a new protective factor in coronary artery disease, and that the new atherogenic index provides for the first time an accurate classification of individuals with coronary artery disease.

Plasminogen activator inhibitor from human endothelial cells. Purification and partial characterization

An inhibitor of plasminogen activator was purified to apparent homogeneity from human umbilical vein endothelial cell conditioned medium. The purification was achieved by a speedy and simple two-step procedure, without the use of denaturants. The purified protein was a single-chain glycoprotein with apparent molecular mass of 48 kDa. The purified inhibitor had a specific activity of 8500 U/mg protein and the activity could be stimulated about fourteenfold by treatment with denaturants. An antiserum to the purified inhibitor was raised in rabbits. It recognised plasminogen activator inhibitor from platelets and plasma as well as from cultured endothelial cells. The immunoglobulin fraction of the antiserum neutralised the functional activity of the inhibitor from all these sources.

Distribution of von Willebrand factor in porcine intima varies with blood vessel type and location

The von Willebrand factor (vWF) has been generally accepted as a marker for endothelial cells. In a systematic immunolocalization study of porcine blood vessels that used indirect immunofluorescence with a monospecific polyclonal anti-vWF and two monoclonal anti-vWFs, we observed that vWF is not universally distributed in intact, fresh endothelia. vWF is consistently localized in veins, with the exception of the pulmonic vein. In arteries, vWF is generally absent except for areas of the distal abdominal aorta, the vaso vasorum of the thoracic aorta, and the pulmonic artery. We conclude that there are regional differences in the distribution of vWF in the various endothelial beds of pigs.

Methodological approaches for the study of the aortic endothelium of the rat

This report describes a new method for obtaining whole mount preparations of rat thoracic aorta which allows the study en face of the complete surface of the endothelium. A comparative study of the different techniques utilized for silver staining of endothelium has been performed. Included is the description of an apparatus for perfusion fixation of rat aorta which allows sequential perfusion of several fluids at a constant pressure. Conditions for perfusion fixation at physiological pressure and flow and for optimal nuclear staining and silver staining of the interendothelial junctions have been studied. The method is rapid and easy to perform and, in the same preparation, allows by optical microscopy the study of the most commonly described parameters for the characterization of normal and injured endothelium. Qualitative aspects of the endothelial lesions found in rats with antibodies to Mycoplasma pulmonis are presented.

Immunochemical and amino-terminal sequence comparison of two cytoadhesins indicates they contain similar or identical beta subunits and distinct alpha subunits

Platelet membrane glycoprotein (GP) IIb-IIIa is functionally and antigenically related to proteins present on many cell types, suggesting that it is a member of the proposed cytoadhesin family of membrane proteins. We have compared the purified tissue vitronectin receptor (VnR) with GP IIb-IIIa. Anti-VnR immunoprecipitated GP IIb-IIIa and a related endothelial cell protein. In immunoblots, GP IIIa reacted with anti-VnR and the beta subunit of the VnR reacted with poly and monoclonal anti-GP IIIa. In contrast, the alpha subunit of the VnR failed to react either with a polyclonal anti-GP IIb or with monoclonal anti-GP IIb. Furthermore, the amino-terminal sequence of GP IIIa and the beta subunit of VnR were identical at determined residues while the alpha subunit and the GP IIb were different, but showed 33% identity. These data indicate the identity or close homology of GP IIIa and the beta subunit of the VnR. In contrast, the alpha subunit and GP IIb are distinct polypeptides which may be homologous. Since GP IIb-IIIa and the VnR differ in ligand recognition specificity, the data also suggest that this specificity may be governed by the alpha subunit of cytoadhesins.

Lack of cytochemically detectable cholesterol in rabbit vena cava endothelial plasma membrane

The response of rabbit vascular endothelial plasma membranes to the cholesterol-binding agents filipin and tomatin was investigated by freeze-fracture electron microscopy. In both single and double labelling experiments, the endothelial plasma membranes of the posterior vena cava were remarkably resistant to the agents compared with the endothelial plasma membranes of other vessels (aorta, pulmonary artery, and pulmonary and cardiac capillaries). This suggests that vena cava endothelium differs markedly from other endothelia, either by having exceptionally low cholesterol levels in its plasma membranes, or with respect to other membrane properties that influence the reaction to filipin and tomatin.

Cell surface chemistry of arterial endothelium and blood monocytes in the normolipidemic rabbit

Chemical mapping of the luminal surface of normal rabbit aortic and coronary endothelium was investigated cytochemically to establish a baseline for further comparison with the biochemical changes possibly induced by the experimental hypercholesterolemia. Morphometric analysis showed that in the aortic endothelium the plasma membrane exposes a large number of uniformly-distributed positively-charged groups of high pKa, and a heterogeneous pattern of dense anionic groups of low pKa. Among the latter, only a third was represented by neuraminidase-cleavable sialic acids. These are constituted by various classes of N-, and O-substituted sialyl residues in glycoconjugates, most frequent being those non-O-acetylated at C8 or C9. Among the oligosaccharides detected with lectins, very abundant were the glycoconjugates containing mannosyl and subterminal galactosyl, whereas N-acetyl-glucosamine, terminal galactosyl and N-acetyl-galactosaminyl moieties were rather poorly represented. The density of the latter two markedly increased after its unmasking by neuraminidase treatment. Coated pits contained both anionic and cationic sites, but only few sialic acids and saccharide residues in significantly lower amounts than plasma membrane. The membrane of plasmalemmal vesicles displayed a high number of cationic sites and mannosyl residues, but very few anionic groups, sialyl residues, and galactosyl and N-acetyl-galactosaminyl moieties. Coronary endothelium displayed a chemical pattern similar to aorta, with some differences, especially in the frequency of some oligosaccharides. Vena cava was low in acidic groups but rather rich in galactose. Plasmalemmal vesicles were only occasionally labeled by the probes used. Monocyte surface exhibited a high density of anionic sites, and binding sites for wheat germ agglutinin and Ricinus communis agglutinin. No mononuclear cells were observed adhering to endothelial surface.

Prelesional events in atherogenesis. Changes induced by hypercholesterolemia in the cell surface chemistry of arterial endothelium and blood monocytes, in rabbit

We investigated the modifications that diet-induced hypercholesterolemia, in rabbit, can produce in the cell surface charge and chemistry of arterial endothelium (E) and blood monocytes (M). Weekly, up to 8 weeks, after blood samples were taken for lipid analysis and blood cell preparation, the vasculature was washed free of blood and the endothelial luminal surface (ES) exposed to cytochemical probes for detecting charged groups, sialoconjugates and oligosaccharides. After fixation in situ, specimens collected from lesion-prone regions (aortic arch and coronary artery) and vena cava, were processed for electron microscopy. Morphometric analysis of tracer distribution on endothelium of nonlesional and lesional areas occurring in various stages of structural alterations, showed a remarkable resistance of the cell coat to very high level of serum cholesterol. In nonlesional zones the E surface charge and glycoconjugates were not significantly changed. In lesional areas, including those with forming fatty streaks, while cationic sites, galactosyl-, and N-acetyl-galactosaminyl residues were not altered whereas mannosyl moieties increased in density. A reduction in anionic groups and sialoconjugates appeared only after advanced extracellular and intracellular accumulation of lipoprotein-derived material and stromal proliferation developed in the intima. Moreover, these ES changes were usually restricted to the relatively rare E cells heavily loaded with lipid inclusions. The modulations were generally paralleled by comparable variations in the M surface. Regardless the extent of surface charge reduction, monocytes continued to migrate and foam cells to egress from the vessel wall. The results suggest that the onset and progression of early intimal lesions are not preceded but followed by significant restricted alterations in cell surface charge and glycoconjugates of arterial endothelium and monocytes.

Liver parenchymal cells differ from the fat-storing cells in their lipid composition

The neutral lipid and phospholipid compositions of purified sinusoidal (fat-storing, endothelial and Kupffer) cells, parenchymal cells and liver homogenates were determined by thin layer chromatography. In addition, the retinoid content of the same purified cell populations was determined by high performance liquid chromatography. From each cell type, both a lipid droplet fraction and a pellet fraction (containing the majority of the remaining cell organelles) were prepared by differential centrifugation. Electron microscopic analysis showed that lipid droplets isolated from fat-storing cells were larger (up to 8 microns) than those isolated from parenchymal cells (up to 2.5 microns). Moreover, the parenchymal lipid droplets seemed to be surrounded by a membranous structure, while the fat-storing lipid droplets seemed not to be. Both fat-storing and parenchymal cells contained high concentrations of neutral lipids, 57.9 micrograms and 71.0 micrograms/10(6) cells, respectively, while endothelial and Kupffer cells contained only 8.6 micrograms and 13.8 micrograms/10(6) cells of neutral lipids, respectively. Sixty-five percent of fat-storing cell lipid droplet fractions comprised esters of retinol and cholesterol. This combined ester fraction contained mainly retinyl esters. In addition, considerable quantities (20%) of triglycerides were present. Parenchymal cell lipid droplet fractions comprised triglycerides (62%) and cholesteryl esters (up to 30%). The pellet fractions prepared from all four cell types consisted mainly of cholesterol (41-67%) and free fatty acids (20-28%). The phospholipid content was much higher in parenchymal cells than in the sinusoidal liver cell types. The relative proportions of the four major phospholipid classes were comparable in all liver cell types analyzed.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein sequence of endothelial glycoprotein IIIa derived from a cDNA clone. Identity with platelet glycoprotein IIIa and similarity to "integrin"

Platelet membrane glycoprotein (GP) IIIa forms a Ca2+-dependent heterodimer complex with GP IIb. The GP IIb-IIIa complex constitutes the fibrinogen and fibronectin receptor on stimulated platelets. A biochemically and immunologically similar membrane glycoprotein complex is present on endothelial cells. A human umbilical vein endothelial cell cDNA library was screened using oligonucleotide probes designed from peptide sequences obtained from platelet GP IIIa. A cDNA clone was sequenced and found to encode a protein of 84.5 kDa. The translated endothelial cDNA contained five sequences that corresponded to peptide sequences in platelet GP IIIa, including the amino-terminal 19 residues. Thus, the endothelial and platelet forms of GP IIIa are apparently identical. Glycoprotein IIIa consists of a long amino-terminal extracellular domain with several potential N-linked glycosylation sites and four cysteine-rich tandem repeats, a 29-residue hydrophobic transmembrane segment, and a short carboxyl-terminal cytoplasmic domain. Glycoprotein IIIa has a 47% amino acid sequence homology to "integrin," a fibronectin receptor from chicken embryo fibroblasts. This homology suggests that GP IIIa is a member of a family of cell-surface adhesion receptors.

Ploidy of endothelium in high-grade astrocytomas

To determine the ploidy and proliferative activity of the endothelium in high-grade astrocytomas, the nuclear DNA content of 11 high-grade astrocytomas, including two gliosarcomas, was measured by cytophotometry. This technique allowed comparison of the endothelial population with the astrocytic population. In all cases, the endothelium was diploid, with an average of 24.6% of cells in the S + G2M phases of the cell cycle. In contrast, the astrocytic population displayed marked DNA abnormalities. The two gliosarcomas had a marked difference in proliferative activity of the endothelium with 4% and 40% of cells, respectively, in the S + G2M phases. These data indicate that the vast majority of endothelial cells compromising the vascular hypercellularity observed in high-grade astrocytomas are in the normal cell cycle whereas in many cases the malignant astrocytes are not. The nuclear DNA content of gliosarcomas appears to be similar to other high-grade astrocytomas.

Thomsen-Friedenreich-related antigen in non-neoplastic ureter urothelium and transitional cell tumours of the urinary bladder. An immunohistochemical study employing the monoclonal antibody 49H.8

This study, which is part of a larger immunohistochemical investigation of blood-group antigens in non-neoplastic urothelium and bladder cancer, reports our findings on the expression of an antigen related to the cryptic Thomsen-Friedenreich antigen (beta Gal 1-3 GalNAc) of erythrocytes. De-waxed sections of 19 ureters and of 93 transitional cell tumours, either untreated or pretreated with neuraminidase, were subjected to an indirect immunoperoxidase staining, employing the monoclonal antibody 49H.8. Staining results were compared to Lewis-secretor types, morphology, and in tumours to the clinical course as regards recurrence rate and the development of either stroma invasive recurrence or papillomatosis as well. Ureters not subjected to neuraminidase were unstained, whereas urothelium in 12 of 19 ureters subjected to neuraminidase showed staining. Serial dilution of antibody disclosed quantitative differences related to the Lewis-secretor types. Lea+b- urothelium, i.e., non-secretor urothelium, had the highest end-point titers. Endothelium was unstained. Thirty-six of the 93 tumours showed staining without prior neuraminidase treatment, 31 showed staining after neuraminidase treatment only, while 26 were unstained. Staining correlated with the pathological stage and grade (p less than 0.05), but not with the clinical course (p greater than 0.05). The results do not support previous observations on the prognostic value of Thomsen-Friedenreich antigen determination in superficial bladder cancer.

Characterization of vascular relaxant factor released from cultured endothelial cells

Cultured bovine endothelial cells were grown on microcarrier beads. Columns (0.2 ml) packed with microcarriers were perfused with oxygenated (20% O2) Tyrode's solution containing indomethacin (10 microM), and the effluent was passed through precontracted, endothelium-denuded detector arteries. When the endothelial cells were stimulated with bradykinin (3-100 nM), adenosine 5'-triphosphate (0.3-30 microM), or calcium ionophore A23187 (10-300 nM), they released dose-dependently a nonprostanoid compound that dilated the detector vessel. The factor, probably identical to the endothelium-derived relaxing factor of native endothelium, evoked dilations of the same magnitude in different types of detector vessels (rabbit thoracic aorta, rabbit femoral artery, canine coronary artery). However, this relaxant factor was significantly more effective in arteries precontracted by norepinephrine or serotonin than in arteries precontracted by potassium depolarization. Thus, its dilator action resembles that of the nitrovasodilators. The factor is labile, with an apparent half-life in the range of 20 to 30 seconds. Its dilator potency was inhibited by dithiothreitol (0.2 mM), metyrapone (0.2 mM), nordihydroguaiaretic acid (20 microM), and hemoglobin (1 microM), all of which apparently inactivated the factor. Synthesis or release (or both) of the relaxant factor was abolished by methylene blue (1 microM). High PO2 levels (greater than 400 mm Hg) in the perfusate markedly reduced the release of the relaxant factor from the cultured cells. This study demonstrates that a vascular relaxant factor is released from endothelial cells in monoculture by adenosine 5'-triphosphate, bradykinin, and A23187 and establishes such a culture as a useful tool for analyzing the mechanisms of endothelium-dependent vasomotion.

Estimation of endothelial receptor sites with the mean transit time approach

A new procedure for quantitating endothelial receptor sites is described. The mean transit time of the passage of an appropriate radio-labeled ligand from the artery to vein of an organ is compared to the mean transit times of a vascular indicator and a water label. The concentration of the unlabeled ligand is progressively increased to define that concentration at which half of the enzyme sites are occupied. Values are calculated for the number of receptor sites accessible during a single circulation in each ml of exchangeable tissue water. This approach is illustrated by estimating the sites of carbonic anhydrase present on the pulmonary endothelium, utilizing labeled acetazolamide as a ligand. Preliminary studies of the receptor sites on isolated endothelial cells suspended in an elutriator are also presented.

Characterization of the C3 receptor induced by herpes simplex virus type 1 infection of human epidermal, endothelial, and A431 cells

Herpes simplex virus type 1 (HSV-1) infection induces the appearance of viral analogues of human Fc IgG and C3 receptors on the surface of human cells. The virally induced C3 receptor(s) has been broadly defined as a C3b receptor, but its ligand binding characteristics have not been rigorously defined. In this study, human epidermal cells, A431 cells, and human umbilical vein endothelial cells infected with HSV-1 demonstrated rosetting with sheep erythrocytes (E) coated with IgG (E-IgG) or the complement components C3b (EAC3b) or iC3b (EAC3bi), but not with E-IgM, C4 (EAC14), C3d (EAC3d), or E alone. Rosetting was markedly enhanced by pretreatment of HSV-1-infected cells with neuraminidase. Unlike human C3 receptors, the HSV-1-induced C3 receptor was found to be trypsin resistant. To determine whether HSV-1 induced CR1-like receptors or CR3-like receptors, infected cells were pretreated with EDTA, which is known to inhibit native CR3 function. EDTA failed to prevent rosetting with EAC3bi. Furthermore, blocking studies using monoclonal antibodies against CR1 and CR3 revealed that the anti-CR1 antibody 5C11 consistently blocked EAC3b and EAC3bi rosetting with HSV-1-infected cells in a dose dependent manner, but monoclonal antibodies against CR3 did not. This study indicates that the HSV-1-induced C3 receptor is an analogue of CR1.

Disulfide-bonded heparan sulfate proteoglycans associated with the surfaces of cultured bovine vascular endothelial cells

A predominant species of heparan sulfate proteoglycan that consisted of at least two subunits linked by disulfide bonding was isolated from cell layers of normal ('cobblestone') bovine vascular endothelial cells in culture. Treatment of the parent molecules with dithiothreitol caused their complete cleavage and permitted the subsequent separation of the larger and smaller subunits on Sepharose CL-4B columns. Removal of dithiothreitol by dialysis resulted in the reformation of large disulfide-bonded molecules but such recombination of the subunits was prevented by prior reductive alkylation using iodoacetamide. Buoyant density gradient analysis as well as gel chromatography on Sepharose CL-6B columns, following alkaline borohydride and nitrous acid treatment of individual carbohydrate-rich subunits, showed that the latter consisted of core proteins associated solely with heparan sulfate glycosaminoglycans. The sizes of the latter were estimated by chromatographic techniques to be approximately 50 kDa in the case of the larger and 14 kDa for the smaller subunit. This is the first description of disulfide-bonded proteoheparan sulfates in endothelial cells.

The elastic fibre system in the veins of the human lower oesophagus

The elastic, elaunin and oxytalan fibres in the tunica mucosa and tela submucosa of veins of the human lower oesophagus were studied in 30 necropsy and biopsy specimens using appropriate histological and ultrastructural methodologies. Elaunin fibres predominate in the veins endowed with muscle cells. Scattered oxytalan and elastic fibres were also observed, the latter being more numerous at the vein periphery. No noteworthy fibre arrangement was encountered in veins lacking muscle cells. Those fibres disposed around the veins were considered to belong to the connective tissue of the tunica mucosa and tela submucosa in which they are embedded. The veins of the lower oesophagus seem to be of low elasticity, which may be related to a blockage mechanism described for the gastro-oesophageal blood stream in cases of portal hypertension.

Differential distribution of von Willebrand factor in endothelial cells. Comparison between normal pigs and pigs with von Willebrand disease

Endothelial cells were cultured from the thoracic aorta, inferior vena cava, and pulmonary artery of normal adult and young pigs as well as from pigs with von Willebrand disease (vWD). The von Willebrand factor (vWF) was estimated by ELISA in endothelial cell supernatants and lysates as well as by immunofluorescence of cells by use of either a polyclonal or a monoclonal antibody to vWF. In normal adult pigs, the content of vWF in supernatants and cell lysates was the highest in the pulmonary artery, lower in the inferior vena cava, and almost nil in the thoracic aorta. In the normal young pigs, vWF was higher in the inferior vena cava endothelial cell supernatants and lysates than in the pulmonary artery. Thus the synthesis of vWF by endothelial cells varies along the vascular tree and appears to be modulated by the age of the animals. In pigs with vWD, levels of vWF were slightly detectable in endothelial cells from the pulmonary artery (contrasting with levels of plasmatic vWF below 0.01 U/ml), but were undetectable in the thoracic aorta and inferior vena cava. Thus, if vWF plays a role in atherogenesis, this involves circulating, not its intracellular, form.

Factor V in human vascular endothelium and in endothelial cells in culture

Human blood vessels and human umbilical vein endothelial cells in culture were examined for the presence and synthesis of factor V. Factor V antigen was detected on the luminal surface of blood vessels washed with buffers containing calcium but was absent from segments of the same vessels perfused with buffers containing EDTA. Very low levels of endogenous factor V antigen were found in endothelial cells in culture but these cells did not synthesise factor V in sufficient quantities to be detected by the present methods. Factor V activity was not detected in any of the present cell preparations.

Stabilization and partial characterization of endothelium-derived relaxing factor from cultured bovine aortic endothelial cells

The extreme lability of the chemically undefined vasoregulatory mediator, endothelium-derived relaxing factor (EDRF), has been overcome. The activity of EDRF, from cultured bovine aortic endothelial cells stimulated with A23187, was stabilized by acidification. An additional action of EDRF, platelet disaggregation was used as a sensitive and convenient bioassay to monitor purification. EDRF appears to be a hydrophilic molecule, rapidly inactivated under alkaline conditions. However, activity is restored upon reacidification suggesting that this instability results from a readily reversible chemical process. The stabilization and partial purification of EDRF sets the stage for its further biochemical and chemical characterization.

Brain induces the expression of an early cell surface marker for blood-brain barrier-specific endothelium

Capillaries derived from the perineural vascular plexus invade brain tissue early in embryonic development. Considerably later they differentiate into blood-brain barrier (BBB)-forming blood vessels. In the chick, the BBB as defined by impermeability for the protein horseradish peroxidase develops around embryonic day 13. We have previously found that brain endothelial cells start to express a number of proteins at around the same time, suggesting that these proteins play a role in BBB function. Here we describe a 74 kd protein defined by the monoclonal antibody HT7 that is expressed on the surface of chick embryonic blood cells and brain endothelial but on no other endothelial cells. This protein is not detectable on early embryonic brain endothelium, but is expressed by these cells on embryonic day 10. It is absent in choroid plexus endothelial cells which represent permeable fenestrated endothelial cells. The antigen is expressed on choroid plexus epithelium which is the site of the blood-cerebrospinal fluid barrier. Since it is also found in basolateral membranes of kidney tubules, it may be involved in specific carrier mechanisms. Embryonic mouse brain tissue transplanted on the chick chorio-allantoic membrane induces the expression of this antigen on endothelial cells derived from the chorio-allantois. Brain tissue can therefore induce in endothelial cells in vivo the expression of a molecule characteristic of brain endothelium.

cDNA cloning of human plasminogen activator-inhibitor from endothelial cells

Full-length cDNA for plasminogen activator inhibitor (PAI-1) was isolated from a human umbilical vein endothelial cell (HUVEC) lambda gt11 cDNA library. Three overlapping clones were identified by immunologic screening of 10(6) recombinant phage using a rabbit anti-human fibrosarcoma PAI-1 antiserum. The fusion proteins encoded by these three clones also react strongly with a monoclonal mouse anti-human fibrosarcoma PAI-1 antibody. By nucleotide sequence analysis, PAI-1 cDNA encodes a protein containing 402 amino acids with a predicted, nonglycosylated molecular mass of 45 kD. Identity of this material as authentic PAI-1 was confirmed by the presence of high level homology with the primary amino acid sequence of an internal peptide prepared from purified rat hepatoma PAI-1. The predicted amino acid sequence also reveals extensive homology with other members of the serine protease inhibitor gene family. Cultured HUVECs contain two PAI-1 mRNA species, both encoded by a single gene, differing by 1 kb in the 3' untranslated region. The PAI-1 gene is located on human chromosome 7.

Method for the determination of fast acting plasminogen activator inhibitor capacity (PAI-cap) in plasma, platelets and endothelial cells

A titration assay for the determination of the fast acting plasminogen activator inhibitor capacity (PAI-cap) was developed. Most of the hitherto published assays for fast acting PAI are reported to have the disadvantage of non-parallel titration curves of tissue plasminogen activator (t-PA) in buffer and plasma. In the assay reported here, this problem has been overcome by adequate predilution of the samples, thus achieving parallel titration curves regardless of the individual PAI-cap of a sample. Provided that values are calculated from parallel titration curves, reproducible PAI-cap values at different dilutions of a sample are obtained. This assay can be applied for the determination of PAI-cap in plasma, serum and other biological fluids as platelet releasates and endothelial cell conditioned medium. PAI-cap of plasma of 10 healthy male volunteers ranged from 15.3 to 32.3 arbitrary inhibitor units AU/ml (24.5 +/- 5.2, mean +/- SD). The alternative use of three different anticoagulants (citrate, EDTA, heparin) had no influence on PAI-cap determinations. Serum generated from blood contained a mean of PAI-cap of 129% in comparison to the plasma of the same donor indicating the release of PAI from cells during clotting. Plasma PAI-cap changed during the day with a constant decrease from the highest levels in the morning (100%) to low levels in the evening (62.9%). Platelets aggregated by thrombin released plasminogen activator inhibitor amounting to a mean PAI-cap of 4.33 +/- 2.98 AU per 2.5 X 10(8) cells.

Extraction of adenine nucleotides from cultured endothelial cells

The goal of this work was to find a method suitable for the extraction of adenine nucleotides from cultured vascular endothelial cells. Extraction of cell monolayers with 80% methanol in water yielded extracts with a higher content of ATP than did extraction of cells with perchloric acid, trichloroacetic acid, or boiling water. The optimal extraction solution was 80% methanol with 0.5 mM ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA) or EDTA, heated to 70 degrees C immediately before use. Extraction of nucleotides by this solution was rapid and the recovery of exogenous ATP added during the extraction process was generally greater than 90%. An aqueous methanol or ethanol solution may be applicable for the extraction of nucleotides and other metabolites from cultured animal cells, dispersed cells, and frozen, powdered tissues.

The relationship between von Willebrand factor antigen and fibronectin in human plasma, endothelial cells and fibroblasts in culture

The distribution of von Willebrand factor antigen (vWFAg) and fibronectin (Fn) in endothelial cells and in fibroblasts in culture was examined using immunohistological methods. Extracellular matrices were studied after removal of cells by mild hypotonic lysis. Co-distribution of these antigens was also examined after culture of fibroblasts in the presence of endothelial cell conditioned medium or of exogenous vWFAg. The presence of intracellular vWFAg and its association with extracellular Fn in confluent endothelial cells was confirmed. Furthermore, both antigens were detected in matrices from fibroblasts grown in the presence of human plasma and endothelial cell medium. vWFAg was not found, however, in the absence of endothelial cell conditioned medium or in experiments using human serum in place of plasma. Cross-linking of vWFAg was examined using quantitative and qualitative electrophoretic methods. Levels of vWFAg in serum from patients with severe Haemophilia A were approximately 50% of those found in the corresponding plasma. Furthermore, vWFAg was reduced to similar levels in serum from normal blood to which heparin was added. The lowest levels of vWFAg were found in the presence of sufficient heparin to totally inhibit the formation of fibrin. In contrast, levels of Fn remained unchanged in these circumstances. The results did not support the view that vWFAg was cross-linked to Fn in plasma by thrombin-activated factor XIII. In addition, immunoelectrophoresis of cultured endothelial cell products did not demonstrate cross-linking of vWFAg to Fn. The data are consistent with the concept that deposition of vWFAg on the subendothelium is dependent on viable endothelial cells or on another product of these cells.

In situ detection of class I and II major histocompatibility complex antigens in the rat central nervous system during experimental allergic encephalomyelitis. An immunohistochemical study

To determine in situ localization of cells bearing major histocompatibility complex (MHC) class I or II antigens in the central nervous system (CNS), immunohistochemical examination was performed on CNS sections of Lewis rats sensitized for experimental allergic encephalomyelitis (EAE). Class I antigens identified by OX18 were detected on endothelial cells (EC) and cells with dendritic morphology (DC) of normal rats. OX18+ DC increased in number as the clinical signs of EAE became more severe, while the number of OX18+ EC in clinical EAE rats was not different from that of normal control rats. Infiltrating lymphocytes were always observed around OX18+ vessels. Double staining showed that OX18+ DC was negative for glial fibrillary acidic protein (GFAP). Cells with morphological features of oligodendroglia were not detected with OX18 in both normal control and EAE rats. MHC class II antigens (Ia antigens) were detected using three MAbs: OX3, OX6 and OX17. These three different MAbs essentially showed the same staining pattern. In normal controls, mononuclear cells in the subarachnoid space were stained positively, but no Ia+ parenchymal cells were detected. In EAE rats, Ia+ DC were first detectable in the white matter of the spinal cord at the preclinical stage, and increased in number as the disease progressed. On the other hand, double-staining with OX6 and anti-factor VIII-related antigen antiserum, or with OX3 and anti-vimentin antiserum demonstrated that endothelial cells even with lymphocyte cuffing were negative for Ia antigens. Based on the data obtained in the present study, the possible role of MHC class I and II antigens in the development of EAE is discussed.

Structural and immunological comparison of human thrombospondins isolated from platelets and from culture supernatants of endothelial cells and fibroblasts. Evidence for a thrombospondin polymorphism

Thrombospondin is a 450-kDa glycoprotein secreted by a variety of cells including endothelial cells, fibroblasts and platelets. The aim of this study was to compare the structural and immunological properties of human endothelial, fibroblast and platelet thrombospondins. All three thrombospondins were purified, digested with thermolysin, and the subsequent thermolysin-generated fragments isolated on a Superose 12 gel-permeation column using non-denaturating conditions. Each isolated proteolytic fragment of thrombospondins was then detected using either a radioimmunoassay with a polyclonal antibody or an enzyme-linked immunosorbent assay with three monoclonal antibodies (P10, MA-I, MA-II) directed against different epitopes of whole platelet thrombospondin. The fragmentation pattern of human endothelial thrombospondin consists of six major thermolysin-generated fragments (135-110, 98-82, 54-47, 25-20, 18-15 and 10 kDa) having molecular masses very similar to those observed with human fibroblast thrombospondin (115-100, 92-80, 54-49, 27-21, 17-13 and 12-10 kDa). Treatment of platelet thrombospondin with thermolysin only generated four proteolytic fragments having molecular masses of 110, 50, 25 and 12/10 kDa respectively. All these proteolytic fragments of endothelial, fibroblast and platelet thrombospondins were recognized by a polyclonal antibody. Monoclonal antibodies MA-I and P10 essentially recognized two proteolytic fragments (135-110, 98-82 kDa) of endothelial and fibroblast (115-100, 92-80 kDa) thrombospondins, and the 110-kDa fragment of platelet thrombospondin. Monoclonal antibody MA-II recognized three proteolytic fragments (54-47, 25-20, 18-15 kDa) of endothelial and fibroblast (54-49, 27-21, 17-13 kDa) thrombospondins, and two fragments (50, 25 kDa) of platelet thrombospondin, different from those detected by P10 an MA-I. The results clearly demonstrate that, under non-denaturating conditions, endothelial and fibroblast thrombospondins are structurally different from platelet thrombospondin since two fragments of endothelial thrombospondin (98-82, 18-15 kDa), equivalent to those of fibroblast thrombospondin (92-80, 17-13 kDa), are not released from platelet thrombospondin after thermolysin treatment. These three forms of thrombospondin are, however, immunologically indistinguishable. To investigate further the structural differences observed between platelet and the two other forms of thrombospondin, their degree of polymerization was compared. Prior to thermolysin treatment, the three forms of thrombospondin were separated into several oligomers ranging from 450 kDa to 3300 kDa when injected onto a Superose 6 gel-permeation column.(ABSTRACT TRUNCATED AT 400 WORDS)

The active and the inactive plasminogen activator inhibitor from human endothelial cell conditioned medium are immunologically and functionally related to each other

In human endothelial cell conditioned medium a fast-acting inhibitor of tissue-type plasminogen activator and urokinase has been detected. Moreover, an inactive inhibitor of these plasminogen activators is present, that can be activated by denaturing agents such as sodium dodecyl sulphate (SDS). The mutual relationship between these inhibitors was studied. The fast-acting plasminogen activator inhibitor from human endothelial cell conditioned medium was purified in a complex with tissue-type plasminogen activator by immune adsorption, using an immobilized anti-tissue-type plasminogen activator antibody. With the complex as an antigen, specific antibodies were raised against this inhibitor in rabbits. The antiserum immunoreacted with both the inactive and the fast-acting plasminogen activator inhibitor. Endothelial cell conditioned medium (containing the inactive plasminogen activator inhibitor) was treated with SDS and the inhibitory activity that emerged was purified. The SDS-generated product formed complexes with tissue-type plasminogen activator with the same molecular mass as those formed with the fast-acting inhibitor. Moreover, the inhibitory activity generated by SDS treatment showed the same kinetic behaviour with tissue-type plasminogen activator as did the fast-acting inhibitor. These data show that the fast-acting and the inactive plasminogen activator inhibitor are immunologically and functionally related to each other, and probably represent different molecular forms of the same protein.

Isolation and partial characterization of endothelial cell extracellular complexes

Human endothelial cells release components into the growth medium that stimulate cell-substratum adhesion. Several macromolecular components were isolated by ultracentrifugation of the endothelial cell conditioned medium. The components were heterogeneous, consisting of several sizes when examined by sedimentation velocity and gel filtration. When the extracellular components were evaluated by electron microscopy, structurally discrete particles were observed. The extracellular components and the complexes mediated cell-substratum adhesion to both human umbilical and arterial endothelial cells. The majority of the extracellular components that promote endothelial cell adhesion were pelleted by ultracentrifugation. Although the complexes contained fibronectin, antibodies to fibronectin did not inhibit cell adhesion to the complexes. Significant inhibition of endothelial cell adhesion was observed in the presence of heparin and heparan sulfate. The supernatant fraction following ultracentrifugation of the growth medium contained a component that suppressed endothelial cell adhesion to culture dishes coated with fibronectin, type I collagen, and endothelial cell complexes. SDS-polyacrylamide gel electrophoresis indicated that the complexes contained several components, and the majority of the large-molecular-weight components were pelleted by ultracentrifugation. The conditioned medium from human endothelial cells contains specific complexes that promote cell-substratum adhesion and components that suppress cell-substratum adhesion.

Distribution of anionic sites and glycoconjugates on the endothelial surfaces of the developing blood-brain barrier

The distribution of anionic sites detected in vitro with cationized ferritin and lectin-binding sites on the endothelial cell (EC) surface of brain micro-blood vessels was studied by electron microscopy. Gold-labeled lectins and glycoproteins and Lowicryl K4M-embedded brain samples obtained from mouse embryos (19th day), and from 1-, 5-, 12-, 24- and 48-day-old and adult mice were used. It was shown that the functional maturation of the blood-brain barrier (BBB) occurring in the mouse after birth between the 12th and 24th day of life is accompanied by a disappearance of vesicular transport in capillaries and by the formation of a uniform, thin, negatively charged layer on the surface of the EC. Concomitantly the binding of lectins specific for beta-D-galactosyl (RCA) and sialyl (LFA and WGA) residues become progressively more intense and uniform on both luminal and abluminal fronts of the EC. The concentration of HPA-binding sites on the abluminal side of the EC and in the basement membrane increases. Similarly the binding of Con A becomes more intense on abluminal than on luminal front of the EC. These observations suggest that extensive remodeling of anionic sites and surface glycoprotein layer and also the elaboration of ECs polarity occur during BBB maturation.

Fucosterol decreases angiotensin converting enzyme levels with reduction of glucocorticoid receptors in endothelial cells

The modulation of angiotensin converting enzyme (ACE) levels was studied using fucosterol, one of phytosterols, in cultured bovine carotid endothelial cells. Addition of fucosterol to the culture medium resulted in the decrease of ACE activity of endothelial cells; however, fucosterol did not directly inhibit ACE activity. Dexamethasone elevated the levels of ACE in normal cells, but this effect was not seen in the fucosterol-treated cells. Receptor assays showed that the amount of glucocorticoid receptors in fucosterol-treated cells decreased to an undetectable level. These results indicate that fucosterol lowers the ACE levels on the endothelial cells by inhibiting the synthesis of glucocorticoid receptors involved in the regulation of ACE levels.

Partial molecular characterization of endothelial cell mitogens from human brain: acidic and basic fibroblast growth factors

Two endothelial cell growth factors have been isolated from human brain extracts by a procedure involving heparin-Sepharose affinity chromatography and reverse-phase HPLC. On the basis of molecular size, amino acid composition and extended amino-terminal sequences, the two proteins are structurally closely related to bovine acidic and basic fibroblast growth factors (aFGF, bFGF). The N-terminal sequences of human and bovine aFGF differ in two positions while those for bFGF are indistinguishable. Human aFGF is microheterogenous: in addition to aFGF two N-terminally truncated forms lacking the first and the seven first amino acids, respectively, were characterized. Human and bovine mitogens possess similar mitogenic activities.

A monoclonal antibody to the endothelium of rat brain microvessels

A rat brain fraction enriched with microvessels was used as the immunogen to produce mouse hybridoma cell lines secreting monoclonal antibodies. One of these antibodies, selected from 156 supernatants by enzyme-linked immunosorbent and immunofluorescent assays, reacted only with the endothelium of microvessels in the brain. The endothelium-specific antibody labelled the cytoplasm of microvascular endothelial cells, their luminal membranes, and an extracellular layer, the endocapillary coat, which covered the luminal surface of these cells. In the kidney, the antibody specifically stained the brush border of the proximal tubuli, and in the liver, the antibody specifically stained bile canaliculi. This demonstrates that 3 morphological structures with important transport functions, cerebral microvascular endothelium, brush border of kidney proximal tubuli, and liver bile canaliculi, express the same epitope.

Platelet surface glycoproteins. Studies on resting and activated platelets and platelet membrane microparticles in normal subjects, and observations in patients during adult respiratory distress syndrome and cardiac surgery

The accurate definition of surface glycoprotein abnormalities in circulating platelets may provide better understanding of bleeding and thrombotic disorders. Platelet surface glycoproteins were measured on intact platelets in whole blood and platelet membrane microparticles were assayed in cell-free plasma using 125I-monoclonal antibodies. The glycoproteins (GP) studied were: GP Ib and GP IIb-IIIa, two of the major intrinsic plasma membrane glycoproteins; GMP-140, an alpha-granule membrane glycoprotein that becomes exposed on the platelet surface following secretion; and thrombospondin (TSP), an alpha-granule secreted glycoprotein that rebinds to the platelet surface. Thrombin-induced secretion in normal platelets caused the appearance of GMP-140 and TSP on the platelet surface, increased exposure of GP IIb-IIIa, and decreased antibody binding to GP Ib. Patients with adult respiratory distress syndrome had an increased concentration of GMP-140 and TSP on the surface of their platelets, demonstrating in vivo platelet secretion, but had no increase of platelet microparticles in their plasma. In contrast, patients after cardiac surgery with cardiopulmonary bypass demonstrated changes consistent with membrane fragmentation without secretion: a decreased platelet surface concentration of GP Ib and GP IIb with no increase of GMP-140 and TSP, and an increased plasma concentration of platelet membrane microparticles. These methods will help to define acquired abnormalities of platelet surface glycoproteins.

Isolation of bovine aortic endothelial cell plasma membranes: identification of membrane-associated cytoskeletal proteins

The plasma membrane of bovine aortic endothelium was isolated, characterized, and found to contain at least four membrane-associated cytoskeletal proteins. Exposure of the plasma membranes to salt media (up to 1M KCl) resulted in the release of 30% of the total plasma membrane-associated proteins and extraction with 1% Triton X-100, 60%. At least four heavily glycosylated bands (185-, 165-, 150-, and 130,000 mol-wt) were evident. The Triton-insoluble pellet fraction contained several major polypeptides (30-, 43-, 58-, and 240,000 mol-wt), two of which were identified by immunoblotting as cytoplasmic actin (43,000 mol-st) and vimentin (58,000 mol-wt). Strikingly, vimentin and a 240,000 mol-wt polypeptide were routinely present in approximately a mole ratio of 4:1 in more than 60% of the plasma membrane preparations. We also report the presence of a 2.1-like and a 4.1-like protein associated with plasma membranes. The 2.1-like protein demonstrated similar solubilities and apparent molecular weight (210,000) as erythroid protein 2.1. Likewise, the endothelial 4.1-like protein exhibited similar solubilities and apparent molecular weight as erythroid protein 4.1. Immunofluorescence staining of fixed and permeabilized cultures with anti-2.1 antibodies showed a fibrillar pattern. In contrast, cells stained with anti-protein 4.1 were brightly fluorescent, bearing both a diffuse and punctate pattern. This paper presents several novel observations pertaining to the composition of bovine aortic endothelial cell plasma membranes, namely: the presence of two erythroid-like cytoskeletal polypeptides; the presence of vimentin and a 240,000 mol-wt polypeptide in a 4:1 mole ratio in more than 60% of the plasma membrane preparations and the co-elution in a 4:1 mol ratio with a protein perturbant; and the inability to release actin from the plasma membrane preparations, suggesting the association of actin with other molecules in the plasma membrane preparation.

Isolation and sequencing of a cDNA clone homologous to the v-sis oncogene from human endothelial cells

A clone containing the 3' end of the mRNA for the human c-sis gene (homologous to the B chain of platelet-derived growth factor) was isolated from a cDNA library derived from human umbilical vein endothelial cells and then sequenced. The analysis of possible translation products in all three reading frames indicated that the A chain of platelet-derived growth factor was not coded for within the 3' end of the c-sis mRNA. The 3' end of the mRNA for c-sis is contained in or adjacent to exon 6.

Dual peroxidase and colloidal gold-labeling study of angiotensin converting enzyme and angiotensin-like immunoreactivity in the rat subfornical organ

The cellular relationships between angiotensin converting enzyme (ACE) (EC 3.4.14.1) and angiotensin-like immunoreactivity (AGLI) were examined in the subfornical organ (SFO). Brains from adult rats were fixed by vascular perfusion with 3.75% acrolein and 2% paraformaldehyde. The region containing the SFO was then sectioned on a vibrating microtome. Partially permeabilized sections were immunocytochemically labeled using the peroxidase-antiperoxidase (PAP) or combined PAP and immunogold methods. Goat antiserum to ACE was localized to both non-neuronal and neuronal cells within the SFO. Intense peroxidase immunoreactivity for ACE was associated with the ventricular and basal surface of ependymal cells, the luminal surface of the vascular endothelium, portions of glial membranes exposed to extracellular spaces, and membranous organelles within neuronal processes. Two antisera raised in rabbits against angiotensin II showed peroxidase immunoreactivity within the extracellular spaces and throughout the cytoplasm of numerous axon terminals and a few perikarya and dendrites in the SFO. Axon terminals and dendrites also showed aggregates of AGLI in smooth membranes and vesicles near the plasmalemma. Gold labeling for AGLI was evident in only 6% of the axon terminals and in a smaller number of dendrites containing peroxidase immunoreactivity for ACE. The low incidence of terminals containing both markers appeared to at least partially reflect limited penetration of the 10 nm gold particles. These results provide the first ultrastructural evidence that ACE is associated with the plasmalemma and membranous organelles strategically located for interaction with precursors of angiotensin II or other peptides within the cerebrospinal fluid, extracellular spaces and neurons of the SFO.