Biomedical subjects

R L Hoover

Publications and source records attributed to R L Hoover.

At least 37 records · Page 2Linked to original sources

PubMed1991

Neutrophil adhesion to endothelium following hyperosmolar insult.

This study examined the effects of hyperglycemic/hyperosmolar conditions on neutrophil adhesion to endothelium. A 2.4-fold increase in neutrophil adhesion was observed following exposure of endothelial cells to 100 mM glucose for 24 hours (n = 9, p less than 0.001), and a 57% increase occurred following pre-incubation in 50 mM glucose for 24 hours (n = 8, p less than 0.01). Phase-contrast microscopy of endothelial monolayers following exposure to 100 mM glucose showed no gross morphological changes, and no differences in membrane permeability were detected. Electron microscopy, however, revealed that cells exposed to 100 mM glucose generally had more pseudopods, an increased density of cytoplasm, and more finely dispersed chromatin throughout the nucleus. Increased neutrophil adhesion to endothelium was also observed following exposure of endothelial cells to 100 mM mannitol, indicating that hyperosmolarity could account for the effect observed with high concentrations of glucose. However, the increase following mannitol treatment was 170% of control (n = 6), while glucose pre-treatment resulted in a 240% increase (n = 9, p = 0.01 for glucose compared to mannitol). The effect of high concentrations of glucose on neutrophil adhesion to endothelial cells was to some degree specific for endothelium, as the same effect was not observed with microvascular pericytes. As neutrophil adhesion to endothelium is an important early step in the acute inflammatory response, these findings may help to explain the increased incidence and severity of infections in diabetic patients.

Animals↗

PubMed1991

Examination of monocyte adherence to endothelium under hyperglycemic conditions.

Increased nonenzymatic glycation of proteins has been implicated in the pathogenesis of diabetic vascular disease. The authors have shown by 3H-NaBH4 reduction of nonenzymatic glycation adducts that endothelial cell membrane proteins undergo increased nonenzymatic glycation in vitro when exposed to elevated concentrations of glucose. Increased nonenzymatic glycation also was found in vivo for microvascular endothelial cells isolated from streptozotocin-induced diabetic rats compared with control rats. Cultured monocytes have previously been reported to express receptors for certain nonenzymatic glycation adducts. The authors have further investigated whether monocyte interactions with endothelium are altered by the presence of nonenzymatic glycation adducts on endothelium. Adherence assays were performed in the presence of elevated concentrations of glucose with decreased NaCl levels to maintain normal osmolarity (as occurs physiologically). Although monocyte adherence to endothelium and levels of early nonenzymatic glycation adducts increased under these conditions, the increased adherence appears to be due to the altered NaCl levels. In fact, freshly isolated monocytes (in contrast to what has been found for macrophages and activated monocytes) were shown not to express appreciable numbers of receptors for nonenzymatic glycation adducts.

Animals↗

PubMed1991

Hyperthermia stimulates plasminogen activator inhibitor type 1 expression in human umbilical vein endothelial cells in vitro.

The effect of exposure to hyperthermia on the fibrinolytic potential of human umbilical vein endothelial cells (HUVEC) in culture was studied. HUVEC responded to exposure to 42 degrees C with a time-dependent increase in plasminogen activator inhibitor type 1 (PAI-1) activity and antigen accompanied by a four- to fivefold increase in PAI-1 specific m-RNA and a decrease in tissue-type plasminogen activator (t-PA) antigen. The effect of 8 hours exposure to hyperthermia on PAI-1 activity and antigen could not be reversed by reexposure of the cells to 37 degrees C for 24 hours as evidenced by continuously increased amounts of PAI-1 released into the conditioned media. t-PA release, however, decreased during the 24-hour period at 37 degrees C after exposure to hyperthermia. No difference in PAI-1 antigen present in the extracellular matrix of heat treated HUVEC as compared to HUVEC kept at 37 degrees C could be found. Our data supports the idea that hyperthermia is one stress factor that influences the fibrinolytic potential of endothelial cells.

Blotting, Northern↗

PubMed1990

Activated human monocytes exhibit receptor-mediated adhesion to a non-enzymatically glycosylated protein substrate.

Non-enzymatic glycosylation of proteins is thought to play an important role in the development of diabetic vascular disease. Advanced glycosylation end products have been shown to accumulate on basement membranes and collagen in diabetes, and receptors for such adducts have recently been found on murine macrophages. We have observed that human monocytes activated by endotoxin express receptors for advanced glycosylation end products of similar affinity and number as has been previously reported for murine macrophages. In addition, there is an increased adherence of activated human monocytes to a non-enzymatically glycosylated albumin substrate, and such adhesion can be competitively inhibited up to 50% by soluble, non-enzymatically glycosylated albumin. We suggest that increased adherence of activated monocytes to non-enzymatically glycosylated proteins in the vessel wall may result in monocyte stimulation and/or local monocyte accumulation and thereby contribute to vascular disease in diabetes.

Cell Adhesion↗

PubMed1990

Role of endothelin in cyclosporine-induced glomerular dysfunction.

Since recent studies indicate that cyclosporine (CsA) disrupts endothelial integrity and that injured endothelial cells release excess endothelin, we examined endothelin's role in acute cyclosporine nephrotoxicity. Following CsA (20 mg/kg i.v.), rabbit anti-porcine endothelin (aE) serum was continuously infused into a first order branch of the main renal artery in Munich-Wistar rats whereupon the hemodynamics of glomeruli not infused with aE as well as those infused with aE within the same kidney were simultaneously assessed by micropuncture techniques. In CsA treated kidneys, in glomeruli not infused with aE, single nephron GFR (SNGFR) and glomerular plasma flow rate (QA) fell profoundly (on average by 42 and 48%, respectively) below the baseline values in association with lower glomerular capillary pressure and elevated afferent arteriolar resistance. By contrast, in glomeruli infused with aE within the same CsA treated kidneys, this vasoconstrictive pattern was markedly attenuated: SNGFR was, on average, only 19% lower than baseline and values for QA as well as other parameters determining glomerular filtration were at or near the levels observed before administration of CsA. In another group of rats (N = 6) an identical dose of CsA was given to measure the circulating level of endothelin. In these CsA treated rats, endothelin level (measured by radioimmunoassay) was elevated at 41.7 +/- 14.7 pg/ml, contrasting the value of less than 2 pg/ml uniformly observed in identically instrumented normal rats not given CsA (N = 5). Thus, cyclosporine is a potential inducer for endothelin release and endothelin appears to have a pivotal role in pathophysiology of cyclosporine-induced acute renal vasoconstriction and glomerular dysfunction.

Animals↗

PubMed1990

Loop diuretic-sensitive potassium flux pathways of rat glomerular mesangial cells.

Glomerular mesangial cells are smooth muscle-like contractile cells that mediate hormonal regulation of glomerular filtration. To gain better understanding of ionic events that accompany contraction/relaxation of these cells, flux pathways of K+ and their regulation by vasoactive agents were investigated in cultured rat mesangial cells using 86Rb+ as a tracer. Of total 86Rb+ influx (16.6 +/- 0.6 nmol x mg protein -1 x min-1), 46% was inhibited by 2 mM ouabain. Loop diuretics inhibited 43% of ouabain-insensitive 86Rb+ influx (3.9 +/- 0.2 nmol x mg protein-1 x min-1). Half-maximum inhibition was observed at 2 and 0.4 microM for furosemide and bumetanide, respectively. Loop diuretic-sensitive 86Rb+ influx was dependent on extracellular Na+ and Cl-; a hyperbolic dependency on extracellular Na+ was noted with apparent Michaels constant of 39 mM while a sigmoidal dependency on extracellular Cl- was present, which, assuming 1:1:2 stoichiometry for Na(+)-K(+)-Cl-, produced an apparent mean affinity constant of 64 mM. Moreover, a fraction of amiloride-insensitive 22Na+ influx was found to be sensitive to furosemide and dependent on extracellular K+ and Cl-, further indicating the presence of Na(+)-K(+)-Cl- cotransport. Efflux of 86Rb+ followed first-order kinetics, of which 60% was inhibitable by furosemide. Manipulations of extracellular osmolarity revealed that these furosemide-sensitive 86Rb+ flux pathways were coordinately regulated in response to osmotic stress. Concentration-dependent stimulation of Na(+)-K(+)-Cl- cotransport-mediated 86Rb+ influx was induced by two vasoconstrictors, angiotensin II (ANG II) and arginine vasopressin (AVP), and by a vasodilator, atrial natriuretic peptide (ANP).(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗

PubMed1990

Bartonella bacilliformis stimulates endothelial cells in vitro and is angiogenic in vivo.

Bartonellosis, a biphasic disease caused by motile intracellular bacteria, produces in its tissue phase a characteristic dermal eruption (Verruga peruana) resulting from a pronounced endothelial cell proliferation. Bacteria are found in the interstitium and within the cytoplasm of endothelial cells (Rocha-Lima inclusion). The aim of this study was to determine if Bartonella bacilliformis produce a substance(s) that might be responsible for the vascular proliferation seen in the Verruga. This was assessed in an in vitro system using human endothelial cells and measuring proliferation as well as production of tissue type plasminogen activator after exposure to the endothelial cultures to B. bacilliformis extracts. Our results indicate that B. bacilliformis possess an activity that stimulates endothelial cell proliferation up to three times that of control. The factor(s) is specific for endothelial cells, heat sensitive, larger than 12 to 14 kd, not enhanced by heparin, has no affinity for heparin, and is precipitated by 45% ammonium sulfate. In addition, the B. bacilliformis extracts stimulate production of t-PA antigen in a concentration-dependent fashion. This activity is also heat sensitive and not lost after dialysis (12 to 14 kd). B. bacilliformis extracts, however, do not increase the production of plasminogen activator inhibitor. It was also determined that B. bacilliformis extracts stimulate the formation of new blood vessels in an in vivo model for angiogenesis. These results describe a bacterial factor(s) that stimulates two important steps in the development of new blood vessels in vitro, as well as the formation of new blood vessels in vivo. Determining the mechanism of action, combined with a complete characterization of this factor(s), may help in understanding the pathogenesis not only of the Verruga and angiogenesis in general but also the recently described Cat-Scratch-associated epithelioid hemangiomas in patients with AIDS and Kaposi sarcoma.

Animals↗

PubMed1990

Prevention of neutrophil-mediated injury to endothelial cells by perfluorochemical.

Myocardial salvage after reperfusion may be limited by neutrophil-mediated microvascular damage. The effect of the perfluorochemical, Fluosol-DA, and its various components on neutrophil adherence, cytotoxicity, and proteolytic enzyme release was examined on sheep large and small vessel endothelial cells in vitro. Cells were studied under normoxic (N) and anoxic conditions (A). Various concentrations of Fluosol (10%, 25%, and 50%) significantly reduced neutrophil adherence under both experimental conditions [mean 22 +/- 3.25% versus 7 +/- 0.8% (N) and 20 +/- 3.2% versus 7.5 +/- 0.9% (A); P less than 0.01]. The perfluorocarbons, perfluorodecalin (PFD), and perfluoro-tripropylamine (PFTP) in a 50 volume/percent concentration exhibited profound effects on adherence, particularly on cells subjected to anoxia (51% and 69% reduction in adherence, respectively; P less than 0.01). No effect on adherence was observed with other components, including the detergent, pluronic F68. A 25% reduction (P less than 0.02) in endothelial cytotoxicity was noted when neutrophils were preincubated with Fluosol. However, pretreatment of endothelial cells with Fluosol did not inhibit neutrophil adherence. Neutrophils stimulated with cytochalasin B and FMLP showed a significant reduction in lysozyme release after incubation with Fluosol (28 +/- 5% versus 17 +/- 4%; P less than 0.01). This study demonstrates that Fluosol significantly attenuates neutrophil adherence, cytotoxicity, and enzyme release in an in vitro model of microvascular injury. It also suggests that prevention of neutrophil-mediated microvascular damage may be an important mechanism whereby Fluosol enhances myocardial salvage after ischemia and reperfusion.

Animals↗

PubMed1989

Evaluation of fibrinolytic capacity in plasma during thrombolytic therapy with single (scu-PA) or two-chain urokinase type plasminogen activator (tcu-PA) by a combined assay system for urokinase type plasminogen activator antigen and function.

A combined assay for urokinase type plasminogen activator (u-PA) activity and antigen determination in plasma samples is described. This assay is based on binding of u-PA to an antibody immobilized on a microtiter plate followed by determination of the enzymatic activity of the bound u-PA. Thereafter bound u-PA antigen can be quantified by means of a specific peroxidase labelled monoclonal antibody against u-PA. By use of this assay system u-PA activity and antigen can be determined with lower detection limits of 0.08 IU/ml and 1.0 ng/ml, respectively, and intraassay as well as interassay coefficients of variation of 10% and 12% for activity and 5% and 7% for antigen determinations, respectively. Normal plasma levels of u-PA antigen could be determined to be 1.88 ng/ml +/- 0.61. Furthermore, this assay system allows specific quantification of u-PA antigen and activity during thrombolytic therapy.

Antigens↗

PubMed1989

Vascular origin determines plasminogen activator expression in human endothelial cells. Renal endothelial cells produce large amounts of single chain urokinase type plasminogen activator.

Positioned at the boundary between intra- and extravascular compartments, endothelial cells may influence many processes through their production of plasminogen activators (PA). Available data have shown that tissue-type plasminogen activator (t-PA) is the major form produced by human endothelial cells. We have compared the molecular forms of PA produced by human endothelial cells from different microvascular and large vessel sources including two different sites within the circulation of the kidney. Using combined immunoactivity assays specific for u-PA and t-PA activity and antigen, we found that both human renal microvascular and renal artery endothelial cells produced high levels of u-PA antigen (60.48 ng/10(5) cells/24 h and 50.42 ng/10(5) cells/24 h, respectively) and corresponding levels of u-PA activity after activation with plasmin. Activity was not evident before plasmin activation, showing that the u-PA produced is almost exclusively as single chain form U-PA. In contrast, human omental microvascular endothelial cells and human umbilical vein endothelial cells produced exclusively t-PA (8.80 ng/10(5) cells/24 h and 2.17 ng/10(5) cells/24 h, respectively). Neither endothelial cell type from human kidney produced plasminogen activator inhibitor, as determined by reverse fibrin autography and titration assays. Agents including phorbol ester, thrombin, and dexamethasone were shown to regulate the renal endothelial cell production and mRNA expression of both u-PA and t-PA. Among the macro- and microvascular endothelial cells tested, only those from the renal circulation produced high levels of single chain form U-PA, suggesting the vascular bed of origin determines the expression of plasminogen activators.

Cells, Cultured↗

PubMed1989

Cholesterol-fed heterozygous Watanabe heritable hyperlipidemic rabbits: a new model for atherosclerosis.

Homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits are used widely to study atherosclerosis, but the WHHL heterozygous rabbit has received little attention. To study their potential as a model for atherosclerosis, heterozygous WHHL and New Zealand white (NZW) rabbits were fed diets containing 0%, 0.5% and 1.0% cholesterol. Plasma lipids were analyzed at 0, 4, 8, 12, 16 and 24 weeks, and animals were killed at 12 and 24 weeks. Plasma cholesterol levels were significantly higher in cholesterol-fed WHHL heterozygotes at 8 weeks compared with NZW rabbits, but no differences were apparent at other times. Atherosclerotic plaques in the aortas of cholesterol-fed WHHL heterozygous rabbits differed from those in NZW rabbits, in that the WHHL had complicated lesions with necrosis, cholesterol clefts, fibrous caps and calcification, similar to that found in humans and homozygous WHHL rabbits. In contrast, NZW rabbits had predominantly foam cell lesions. Heterozygous WHHL rabbits also had less extensive extravascular foam cell deposits. Our results suggest that the cholesterol-fed heterozygous WHHL rabbit may provide a promising model for studying the pathogenesis of atherosclerosis.

Animals↗

PubMed1989

Leukotriene D4 binding and signal transduction in rat glomerular mesangial cells.

We examined the characteristics of [3H]leukotriene D4 (LTD4) binding to mesangial cells in culture. Binding is stereoselective, specific, saturable, and rapidly reversible. Two binding sites are recognized with dissociation constants and binding site densities at equilibrium of 2.2 and 16.8 nM and 1.1 x 10(4) and 3 x 10(4) binding sites per cell. LTD4, LTE4, (5R,6S)LTD4, LTB4, and the LTD4-receptor antagonist, SKF 104353, competitively inhibit radioligand binding in the following rank order of potency: LTD4 greater than LTE4 = SKF 104353 greater than (5R,6S)LTD4 greater than LTB4. LTD4 also induces time- and concentration-dependent phosphoinositide hydrolysis in mesangial cells. Formation of inositol 1,4,5-trisphosphate (IP3) is maximal at 5 s, followed by a time-dependent increase in inositol monophosphate generation, and inhibited by 100-fold excess concentration of SKF 104353. Addition of LTD4 to mesangial cells is associated with an increase in intracellular pH and dose-dependent stimulation of [3H]thymidine incorporation and mitogenesis. Thus rat mesangial cells possess specific binding sites for LTD4, the activation of which stimulates IP3 formation and induces cellular alkalinization and mitogenic responses. These studies provide insight into the cellular basis for LTD4-mesangial cell interactions, which are of potential pathophysiological relevance during acute glomerular inflammatory injury.

Animals↗

PubMed1989

Ceruloplasmin reduces the adhesion and scavenges superoxide during the interaction of activated polymorphonuclear leukocytes with endothelial cells.

The plasma protein, ceruloplasmin, has been implicated as an anti-inflammatory agent, although this property has not been demonstrated unequivocally in vivo. The role of this protein in an in vitro system of cultured endothelial cells and polymorphonuclear leukocytes (PMNs) was investigated. One of the initial steps in an inflammatory response is increased adhesion between PMNs and the endothelial lining of the blood vessels. The results showed that ceruloplasmin interferes with this process and reduces the number of phorbol myristate acetate-activated leukocytes that adhere to endothelium. Preincubation of either the activated PMNs or the endothelium with ceruloplasmin did not produce the same results, suggesting that the continuous presence of ceruloplasmin is required. During attachment PMNs become activated and release a variety of substances, including toxic oxygen species such as superoxide and hydrogen peroxide. In the in vitro system used in this study no injury occurred to the endothelial cells, as measured by 51Cr release, when activated PMNs were added with ceruloplasmin. The data show that ceruloplasmin reduced, in a dose dependent manner, the levels of superoxide produced by the activated PMNs, further supporting ceruloplasmin's previously reported role as a scavenger of superoxide. Ceruloplasmin also reduced the levels of superoxide when activated PMNs were in contact with endothelial cells. Although ceruloplasmin interfered with the copper-dependent scavenger enzyme, superoxide dismutase (SOD), in a cell-free system, ceruloplasmin had no effect on SOD in intact endothelial cells. These results suggest that ceruloplasmin may act as an anti-inflammatory agent by reducing the number of PMNs attaching to endothelium and by acting as an extracellular scavenger of superoxide.

Animals↗

PubMed1988

Effects of hyperthermia on cell survival and patterns of protein synthesis in endothelial cells from different origins.

Thermotolerance, transient resistance to heat induced by heat itself, is generally thought to be linked to the accumulation of heat-shock proteins in eukaryotic cells. The induction of thermotolerance and the synthesis of heat-shock proteins in primary and passage cultures of bovine aortic endothelium, passage cultures of bovine brain capillaries, and passage cultures of rat epididymal capillaries were examined. Primary and passage cultures of bovine aortic endothelial cells readily acquired thermotolerance; however, passage cultures of rat epididymal capillary cells and bovine brain capillary cells were very heat sensitive. In all endothelial cell types examined except rat epididymal capillary cells, the levels of HSP71, the most inducible of the HSP70 family, correlated well with thermotolerance. With prolonged passage, rat epididymal capillary cells and bovine brain capillary cells lost their ability to acquire heat resistance. Endothelial cells from different origins (aortic endothelium versus capillary endothelium) but from the same species and about the same passage number had a notably different response in terms of thermotolerance and synthesis of proteins after exposure to hyperthermia. The results of this study suggest that, while the expression of HSP71 may be a good indicator of heat resistance, the reverse is not necessarily true. Furthermore, the data show that endothelial cells from different origins are dissimilar in their response to hyperthermia.

Animals↗

PubMed1988

Effects of heat shock on the expression of thrombospondin by endothelial cells in culture.

Heat-shock proteins from confluent primary cultures of bovine aortic endothelial cells were analyzed by SDS-polyacrylamide gels. In addition to the increased synthesis of the classical heat-shock proteins, there is an increase of a 180,000-mol wt polypeptide in the growth media of heat-shocked cells. Immunoprecipitation with specific antiserum indicates that the 180,000-mol wt polypeptide is thrombospondin. Assay of mRNA levels coding for thrombospondin after brief hyperthermic treatment (45 degrees C, 10 min), followed by a recovery of 2 h at 37 degrees C, results in a twofold increase in mRNA abundance. In contrast, the activation level of the 71,000-mol wt heat-shock protein mRNA occurs at an earlier time than for thrombospondin mRNA. Immunofluorescence microscopy was used to study the intracellular and extracellular distribution of thrombospondin. Thrombospondin is localized to a prominent pattern of granules of intracellular fluorescence in a perinuclear distribution in cells not exposed to heat. Upon heat treatment, the pattern of granules of intracellular fluorescence appears more pronounced, and the fluorescence appears to be clustered more about the nucleus. There are at least three pools of extracellular forms of thrombospondin: (a) the fine fibrillar extracellular matrix thrombospondin; (b) the punctate granular thrombospondin; and (c) the thrombospondin found in the conditioned medium not associated with the extracellular matrix. When bovine aortic endothelial cells are exposed to heat, the extracellular matrix staining of a fibrillar nature is noticeably decreased, with an increase in the number and degree of fluorescence of focal areas where the punctate granule thrombospondin structures are highly localized. No gross morphological changes in extracellular matrix staining of fibronectin was noted. However, the intermediate filament network was very sensitive and collapsed around the nucleus after heat shock. We conclude that the expression of thrombospondin is heat-shock stimulated.

Animals↗

PubMed1988

Evidence for glomerular actions of epidermal growth factor in the rat.

Epidermal growth factor (EGF), an endogenous mitogenic peptide, has recently been shown to be a potent vasoconstrictor of vascular smooth muscle. In view of its potential role in proliferative and inflammatory renal glomerular diseases, we examined the effects of EGF both on cultured rat mesangial cells and on in vivo glomerular hemodynamics. Mesangial cells possess specific, saturable EGF receptors of differing affinities, with Kd's of 0.1 and 1.7 nM, respectively. EGF produced a rapid increase in intracellular pH of 0.12 +/- 0.01 pH U, which was sodium dependent and amiloride inhibitable. The addition of EGF to mesangial cells cultured on either glass or dimethylpolysiloxane substratum induced reproducible cell contraction. Intrarenal EGF infusion did not affect systemic blood pressure or hematocrit but reversibly decreased GFR and renal blood flow from 4.19 +/- 0.33 to 3.33 +/- 0.26 and from 1.17 +/- 0.09 to 0.69 +/- 0.07 ml/min, respectively. Glomerular micropuncture confirmed decreases in single nephron plasma flow and in single nephron GFR (from 142 +/- 9 to 98 +/- 8 and from 51.6 +/- 11.7 to 28.5 +/- 3.5 nl/min, respectively) which were due to significant increases in both pre- and postglomerular arteriolar resistances (from 1.97 +/- 0.31 to 2.65 +/- 0.36 and from 1.19 +/- 0.11 to 2.00 +/- 0.15 10(10) dyn.s.cm-5 respectively) and to a significant decrease in the ultrafiltration coefficient, Kf, which fell from 0.100 +/- 0.019 to 0.031 +/- 0.007 nl/(s.mmHg). These studies demonstrate that mesangial cells possess specific receptors for EGF, and exposure of these cells to physiologic concentrations of EGF results in an in vitro functional response characterized by activation of Na+/H+ exchange and by resultant intracellular alkalinization, as well as by cell contraction. EGF administration in vivo significantly reduces the glomerular capillary ultrafiltration coefficient, Kf, which, in combination with EGF-induced constriction of both preglomerular and postglomerular arterioles, results in acute major reductions in the rates of glomerular filtration and perfusion.

Animals↗

PubMed1988

Reduction in pO2 decreases the fibrinolytic potential of cultured bovine endothelial cells derived from pulmonary arteries and lung microvasculature.

The effect of anoxia on the fibrinolytic potential of cultured endothelial cells derived from bovine pulmonary artery and bovine lung microvasculature was studied. Both cell types reacted with an increase in plasminogen activator inhibitor (PAI) activity and a decrease in the plasminogen activator (PA) activity in the media after incubation under anoxic conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by fibrin autography and reverse fibrin autography indicated that the change in fibrinolytic potential was due to an impaired release of PA and not an increase in the production of PAI. Although anoxia did not affect the viability of the cells as judged by 51Cr release, their metabolism was influenced, which is reflected by increases in the levels of lactate in cell lysates and media. Furthermore, the effect of short-term anoxia on PA and PAI could not be reversed by reoxygenation for 24 hours. The results are discussed in terms of helping to explain the tendency of reocclusion after successful thrombolytic therapy, the development of pulmonary hypertension, and the thrombotic tendency of areas with an impaired circulatory supply.

Animals↗

PubMed1987

Electrical resistance and macromolecular permeability of brain endothelial monolayer cultures.

Electrophysiological measurements were made on endothelial cells initially isolated as individual clones from bovine brain microvessels, and then grown as monolayers on a permeable support of glutaraldehyde-treated collagen gel. When transendothelial cell resistance (R) of the clones was measured, there was a range of values from a low of 157.4 +/- 4.5 omega.cm2 (n = 6) to a high of 783.2 +/- 7.0 omega.cm2 (n = 34). With the high-resistance cells, there was also a small potential difference of -0.46 +/- 0.03 mV luminal-side negative (n = 34). In comparison, endothelial cells from bovine aortas and rat epididymal fat pads cultured on the collagen gels had transendothelial R values of 13.5 +/- 0.2 (n = 62) and 0.45 +/- 0.03 (n = 10) omega.cm2, respectively. Exposure of the high-resistance brain endothelial cell monolayers to a Ca2+-free medium for 10 min decreased the R to 75% of the control values. Addition of Ca2+ back to the medium caused a return of the transendothelial R to control values within 1 h. Endothelial cells were also grown to confluency on microcarrier beads for permeability measurements to Evans blue dye-bovine serum albumin. Microcarriers with no cells (control) and microcarriers with bovine and epididymal endothelial cell monolayers showed no difference in the amount of adsorbed dye. Microcarriers with brain endothelial monolayers excluded up to 80% of the dye. This mammalian brain endothelial culture system will be a useful model for studies of the electrophysiological and permeability properties of the blood-brain barrier.

Animals↗