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H J Granger

Publications and source records attributed to H J Granger.

At least 55 records · Page 3Linked to original sources
PubMed1993

Enhanced myogenic activation in skeletal muscle arterioles from spontaneously hypertensive rats.

The purpose of this study was to determine whether the vascular myogenic response is enhanced in hypertension. Experiments were conducted in the intact cremaster muscle microcirculation as well as in isolated arterioles of hypertensive (SHR) and normotensive (WKY) rats. Increasing venous pressure in vivo by approximately 5 mmHg had no effect on normotensive first- (1A) or third-order arteriolar (3A) diameters; in contrast, hypertensive 1A diameter decreased 4% (89 +/- 2 to 85 +/- 3 microns) with an 8% decrease in 3A (24 +/- 2 to 22 +/- 2 microns). To further examine this enhanced constriction to elevated intravascular pressure in SHR, diameter was monitored in isolated 1A during step increases and decreases in intraluminal pressure. Normotensive arterioles displayed myogenic responses between pressures of 50 and 170 cmH2O; in contrast, hypertensive arterioles demonstrated myogenic responses over an extended pressure range (50-210 cmH2O). In addition, the change in diameter for each step change in pressure was greater in the arterioles from SHR, indicating an increased myogenic responsiveness. The myogenic reactions were unaffected by alpha-receptor blockade with phentolamine (10(-6) M), indicating that adrenergic hypersensitivity was not involved in the enhanced response to stretch. Morphometric analysis of the vascular wall revealed no differences in wall thickness, cross-sectional wall area, or wall-to-lumen ratio between normotensive and hypertensive rats. The length-tension relationships for normotensive and hypertensive rats demonstrated that peak active tension occurred at nearly the same vascular smooth muscle length. In addition, SHR arterioles were capable of maintaining higher levels of active tension that WKY arterioles, indicating an altered length-tension curve in chronic arterial hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Oxygen radicals, enzymes, and fluid transport through pericardial interstitium.

The interstitium is the final link in the transportation of nutrients from the bloodstream to the individual cells of an organism. To assess interstitial fluid transport in normal and inflamed tissue, the hydration (H, ml H2O/g dry wt) and hydraulic conductivity (Kp, 10(-8) cm2.s-1.cmH2O-1) of bovine pericardial stroma were determined. The effect of enzymes and neutrophil-derived products of inflammation on the properties of the interstitial model were determined. Samples of the pericardium were exposed separately to trypsin, elastase, hyaluronidase, collagenase, superoxide radicals, and hydrogen peroxide. After exposure, the tissues were washed repeatedly in physiological saline and equilibrated in transport chambers heated to 37 degrees C and pressurized to 50 cmH2O. Fluid flow across the tissues was monitored. A section of tissue was removed and weighed. The tissue section was subsequently dried and reweighed. Tissue thickness, H, and Kp were calculated. H and Kp of the control tissues were 2.82 +/- 0.04 and 1.71 +/- 0.07, respectively. Hydration was significantly increased (22-38%) by exposure to trypsin, elastase, collagenase, and superoxide radicals. Kp increased significantly (30-1055%) in the groups treated with trypsin, hyaluronidase, collagenase, and superoxide radicals. The inflammatory mediators generally increased the hydration and/or the hydraulic conductivity of the model. These results indicate that neutrophil-derived products could be involved in the development of interstitial edema during the inflammatory process.

Animals↗
PubMed1992

Internalized basic fibroblast growth factor translocates to nuclei of venular endothelial cells.

To begin to understand the molecular mechanisms by which basic fibroblast growth factor (bFGF) stimulates proliferation of coronary venular endothelial cells (CVEC), we have characterized the kinetic interactions of bFGF with various binding sites on CVEC and determined the kinetics of nuclear translocation of bFGF. We report that bFGF rapidly binds to its receptor and is immediately internalized at 37 degrees C with a half-time for receptor binding of 0.9 min. After internalization bFGF is processed by two kinetically and biochemically distinguishable pathways. Up to 40-50% of total internalized bFGF is translocated to the nuclei of serum-starved, quiescent cells at early time points (0-2 h). This proportion declines to less than or equal to 20% by 24 h. Cytoplasmic accumulation continued to increase for up to 24 h. Nuclear-bound 125I-labeled bFGF consisted primarily of the intact 18-kDa species with small amounts of a 16-kDa degradation fragment. Nuclear-bound 125I-labeled bFGF showed little evidence of degradation even after 24 h, whereas cytoplasmic 125I-labeled bFGF showed increased degradation to smaller fragments with time. Nuclear-binding of bFGF reached equilibrium by 8 h, just before initiation of DNA synthesis, which began 9-12 h after growth factor addition. These results suggest that nuclear-bound bFGF may function in triggering division (proliferation) of CVEC subsequent to binding of the growth factor to cell surface receptors.

Animals↗
PubMed1992

Flow modulates coronary venular permeability by a nitric oxide-related mechanism.

This study demonstrates that flow velocity modulates coronary venular permeability to albumin. Apparent permeability coefficients of albumin (Pa) were measured in isolated cannulated coronary venules ranging from 30 to 70 microns in diameter. Hydrostatic and oncotic pressures were controlled while the intraluminal flow velocity was varied. Pa at an intraluminal hydrostatic pressure of 12 cmH2O and a flow velocity of 7 mm/s was 4.01 +/- 0.53 x 10(-6) cm/s. Increasing flow velocity to 10 and 13 mm/s augmented the permeability by 33 +/- 14 and 48 +/- 14%, respectively. The nitric oxide synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA) (10(-5) M), decreased baseline Pa and abolished the flow-induced permeability changes. Administration of L-arginine (3 x 10(-3) M), a physiological precursor of nitric oxide which reverses the effect of L-NMMA, restored the relationship between flow and permeability. From these results we conclude that 1) flow velocity should be considered as a physical force that potentially modulates permeability of venular exchange vessels in the heart and 2) flow modulates coronary venular permeability via the production of nitric oxide.

Animals↗
PubMed1992

[The effect of vasoactive factors on the growth of of coronary endothelial cells].

The aim of this study was to evaluate the effect of adenosine and bradykinin on endothelial cell growth at capillary level. DNA synthesis was measured in subconfluent capillary endothelial cells obtained from coronary venules (CVEC) after exposure to adenosine or bradykinin. Our results indicate that adenosine and bradykinin induced a dose-dependent proliferation of CVEC. Maximal effect was observed at the dose 100 microM concentration for adenosine and 0.1 microM concentration for bradykinin.

Adenosine↗
PubMed1991

Reactive oxygen metabolites inhibit spontaneous lymphatic contractions.

The effects of oxygen-derived free radicals on the contractile activity of the mesenteric collecting lymphatics were evaluated in the anesthetized rat. Lymphatic contractions were monitored before, during and after the application of oxyradicals. Contraction frequency (F), stroke volume (SV), ejection fraction (EF), contraction propagation (PC), and lymph pump flow (LPF) were determined from the lymphatic diameter tracings. Oxyradicals were generated using hypoxanthine and xanthine oxidase. Exposure to oxyradicals inhibited the lymphatic pumping mechanism: 1) F fell from 15.5 +/- 0.8 to 0.8 +/- 0.7 beats/min; 2) EF went from 0.44 +/- 0.02 to 0.08 +/- 0.04; 3) PC dropped from 92 +/- 2 to 56 +/- 8%; and 4) LPF fell precipitously from 41.0 +/- 5.2 to 0.7 +/- 0.4 nl/min. The effects of the oxyradicals were attenuated by superoxide dismutase, implicating superoxide anion as one of the predominant causative agents. We conclude that oxyradicals significantly inhibit the lymph pump and that this inhibition could be a factor contributing to the formation of interstitial edema during inflammation.

Animals↗
PubMed1991

Lymph flow transients following elevation of venous pressure in the dog hindpaw.

Lymph flow transients were studied in a dog paw preparation when venous pressure was elevated by 15 and 25 mmHg. The lymph flow transients showed a very rapid initial increase which then declined to a steady-state value that was one-half the peak lymph flow response for both pressure changes. Lymph flow increased in the initial 5.3 minutes following venous pressure elevation to 10.4 +/- 2.0 and 18.1 +/- 4.5 times the normal lymph flow (mean +/- standard deviation) for the 15 and 25 mmHg increases in venous pressure, respectively. However, approximately 9 minutes after attaining the maximal flow rate, the lymph flow declined to only 5.5 +/- 0.7 and 9.8 +/- 1.8 times the control values. These data demonstrate another condition in which lymph flow is not maintained at the maximal capability. Possible mechanisms causing the observed biphasic lymph flow response to capillary pressure elevation are: 1) changes in Starling forces oppose an increase in capillary pressure; 2) the rate of change in tissue fluid pressure affects lymph flow to a greater extent than does the absolute change in tissue fluid pressure; or, 3) the lymphatics empty upon elevation and refill as the capillaries filter.

Animals↗
PubMed1990

An in vitro model of ischemia/reperfusion-induced microvascular injury.

The major objective of this study was to develop an in vitro model of ischemia/reperfusion (I/R)-induced microvascular injury. Cultured venular endothelial cells were grown to confluency, labeled with 51Cr, and exposed to different durations of anoxia (0.5, 1, 2, 3, and 4 h). 51Cr release and cell detachment (indexes of cell injury) were determined at different times after reoxygenation (1, 2, 4, 6, 8, and 18 h). Because in vivo studies have implicated neutrophils in I/R injury, in some experiments human neutrophils were added to the endothelial cells upon reoxygenation. Periods of anoxia greater than or equal to 2 h resulted in 70-80% 51Cr release and 80-95% cell detachment upon reoxygenation. Under these conditions (near maximal injury), the addition of neutrophils produced negligible effects. Periods of anoxia less than or equal to 1 h resulted in 30-40% 51Cr release and 50-60% cell detachment. Under these conditions (moderate cell injury), addition of neutrophils enhanced endothelial cell injury. Using a 30-min period of anoxia, we also assessed the effects of superoxide dismutase (SOD; 300 U/ml) and allopurinol (20 microM) on anoxia/reoxygenation (A/R)-induced injury in the presence or absence of neutrophils. In the absence of neutrophils, SOD or allopurinol did not protect against A/R-induced injury. However, in the presence of neutrophils, both SOD and allopurinol attenuated the increases in 51Cr release. The results derived using this in vitro model of I/R injury are largely consistent with published in vivo studies. Thus this in vitro model may provide further insights regarding the mechanisms involved in I/R injury.

Allopurinol↗
PubMed1990

Mechanisms leading to adenosine-stimulated proliferation of microvascular endothelial cells.

This study investigated the mechanisms by which adenosine stimulates proliferation of microvascular endothelial cells. The metabolic byproducts of adenosine, inosine and hypoxanthine were unable to stimulate proliferation. When adenosine uptake was prevented, the stimulation of proliferation was unchanged, suggesting that uptake of adenosine with subsequent incorporation into the nucleotide pool is not the mechanism for increasing proliferation. Treatment of endothelial cells with adenosine analogues, presumably selective for either the A1 or A2 receptor, stimulated proliferation equally. This suggested that adenosine 3', 5'-cyclic monophosphate (cAMP) might not mediate the proliferative response to adenosine. However, radioimmunoassay of cell extracts after treatment with either analogue showed an increase in cAMP. In addition, adenylate cyclase blockade with 2', 5'-dideoxyadenosine prevented the proliferative response brought about by these analogues. These data suggest that the proliferative response to adenosine depends on an increase in cAMP. A 2-h pulse of cholera toxin stimulated endothelial cell proliferation, further supporting a role for cAMP. Pretreatment of endothelial cells with pertussis toxin blocked the stimulation of proliferation, indicating that a Gi or similar G protein is also involved in proliferation. We conclude that the proliferative response to adenosine involves a pertussis toxin-sensitive substrate as well as an increase in cAMP.

Adenosine↗
PubMed1990

Anoxia-reoxygenation-induced, neutrophil-mediated endothelial cell injury: role of elastase.

The aim of this study was to assess the role of neutrophilic elastase in anoxia-reoxygenation-induced, neutrophil-mediated injury to microvascular endothelium. Cultured bovine microvascular endothelial cells were grown to confluence and labeled with 51Cr. The endothelial cells were exposed to a 30-min period of anoxia and subsequently reoxygenated. Endothelial cell injury, quantitated as 51Cr release and cell detachment, was determined 8 h after reoxygenation. Addition of neutrophils upon reoxygenation enhanced the anoxia-reoxygenation-induced increase in 51Cr release and cell detachment. The neutrophil-mediated injury was associated with elastase release from the neutrophils. Four agents were used to inhibit neutrophilic elastase activity: Eglin C, methoxysuccunyl-Ala2-Pro-Val-CH2Cl, L658,758, and a monoclonal antibody against neutrophilic elastase. All elastase inhibitors attenuated the neutrophil-mediated endothelial cell detachment but not 51Cr release. Addition of purified human neutrophilic elastase, at a level that mimicked the release from neutrophils, increased cell detachment in endothelial cells exposed to anoxia-reoxygenation but did not affect 51Cr release. Our results indicate that elastase plays an important role in anoxia-reoxygenation-induced, neutrophil-mediated endothelial cell dysfunction.

Animals↗
PubMed1990

Atriopeptin does not augment the transvascular flux of macromolecules in the hamster cheek pouch.

Natriuretic peptides elaborated by atrial myocytes promote marked renal sodium and water excretion as a mechanism for fluid and electrolyte balance. Recent evidence suggests that atriopeptin (ANP) also targets the non-renal vasculature as a site for enhanced fluid exchange. It remains unclear whether ANP alters microvascular integrity to facilitate the efflux of both plasma and proteins across the endothelial barrier, or if fluid exchange is selectively enhanced. This study evaluated the influence of ANP on macromolecular transport through the direct observation of microvessels in the hamster cheek pouch using fluorescent intravital microscopy. Fluorescein isothiocyanate conjugated to either bovine serum albumin or dextran 150,000 Mw was utilized as a permeability probe. Macromolecular efflux was quantified as fluorochrome clearance. The clearance of fluorescein-conjugated bovine serum albumin (57.94 +/- 7.03) or fluorescein-conjugated dextran 150 (4.09 +/- 1.35) remained unaltered by intravascular injection of 1 microgram/kg ANP. Topical application of 40 ng to cheek pouch microvessels produced similar results. All pouches demonstrated positive leakage response to histamine 2.5 x 10(-6) M, increasing fluorochrome clearance approximately 2- to 11-fold. Bolus injection of 1 microgram/kg ANP reduced mean arterial pressure, increased urine flow from 6.63 +/- 2.59 microliters/min to 8.20 +/- 6.13 microliters/min, and elevated sodium excretion from 1.37 +/- 0.49 microEq/min to 2.54 +/- 0.99 microEq/min. These results suggest that ANP fails to significantly alter the integrity of the protein-transporting channels in the microvascular exchange barrier.

Animals↗
PubMed1989

Leukocyte phagocytosis and alterations in microvascular integrity elicited by FITC-dextran 150 and epi-illumination in the microcirculation of the hamster cheek pouch.

Fluorescein-labeled dextran MW 150K (FITC-Dx 150) is commonly utilized as a macromolecular fluorochrome in inflammatory studies. We examined the influence of FITC-Dx 150 on leukocyte activity as assessed by adherence to cheek pouch microvessels. Transcapillary exchange was evaluated as fluorochrome clearance (Cl). Few leukocytes adhered to the microvascular wall in venous segments prior to and immediately following administration of the dextran fluorochrome. Spontaneous leukocyte adhesion to venous endothelium ensued within 30 min in epi-illuminated, FITC-Dx 150-loaded vessels. However, the Cl of FITC-Dx 150 (1.75 +/- 0.68 nl/min) remained unaltered (2.21 +/- 1.83 nl/min). Hamsters pretreated with FITC-Dx 150 (a minimum of 7 hr prior to experimentation) and subsequently exposed to epi-illumination showed marked leukocyte adhesion in small venules and an impressive pool of marginating leukocytes in large venules. Leukocyte aggregation, thrombus formation, lymphatic distension, and leukocyte adherence to arteriolar endothelium also ensued as a consequence of epi-illumination. Uptake of FITC-Dx 150 by extravascular phagocytes was evident. Some hamsters pretreated with FITC-Dx 150 developed spontaneous leaky sites upon epifluorescent stimulation. Focal accumulation of interstitial phagocytes was suggestive of fluorochrome uptake and elicitation by FITC-Dx 150. These effects were not observed in control animals treated with FITC-albumin. The results of this study suggest caution in employing FITC-Dx 150 as a permeability probe for studies involving inflammatory processes, especially those dependent on neutrophil/endothelial interactions and prolonged circulation time of fluorochrome.

Animals↗
PubMed1989

Acute microvascular effects of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine: comparisons with leukotriene B4.

Acute effects of the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) on microvessels of the hamster cheek pouch were studied using intravital and electron microscopy. FMLP (1.0 microM) applied topically to the pouch microvasculature produced transient vasoconstriction of second- and third-order arterioles, which was accompanied by modest narrowing of pericytic venules, leukocyte adherence, diapedesis, and macromolecular extravasation. Contrary to observations of leukotriene B4 (LTB4)-exposed venules in the same animal model, electron micrographs of fMLP-treated venules supported junctional, vesicular, and potential transcellular modes of transendothelial protein transport. Endothelial junctions were not characterized by large gaps, but failure of endothelial processes to effectively bridge diapedesing cells and reestablish junctional contact resulted in substantial deposition of subendothelial reaction product. Venous microvessels 18-21 micron in diameter were particularly susceptible to the deleterious effects of fMLP and revealed the highest percentage of total junctions or endothelial cells labeled by reaction product. Implied barrier dysfunction was more prevalent in fMLP-treated vessels exhibiting adherence and/or diapedesis; however, the presence of barrier defects was not correlated with leukocyte margination and/or emigration (Marg/Emig). The absence of simple correlation, without persuasive evidence for direct vasopermeability effects, recognizes that some Marg/Emig events may not have been present at the time of fixation and suggests the potential for neutrophil-mediated endothelial dysfunction, governed by multiple determinants, is often unrealized.

Animals↗
PubMed1989

Superoxide mediates reperfusion-induced leukocyte-endothelial cell interactions.

The objective of this study was to determine whether superoxide mediates the leukocyte-endothelial cell interactions elicited by reperfusion (reoxygenation) of ischemic (hypoxic) tissues. Mesenteric and intestinal blood flows were reduced to 20% of control for 1 h, followed by 1 h of reperfusion. Sixty minutes after reperfusion, red blood cell velocity (Vr), leukocyte rolling velocity (Vw), and the number of adherent leukocytes were measured in mesenteric venules. Then, either human superoxide dismutase (hSOD), hydrogen peroxide-inactivated hSOD, or MoAb IB4 (a monoclonal antibody against the leukocyte adhesion molecule CD18) was injected intravenously. Ten minutes later, repeat measurements were obtained and compared with pretreatment values. hSOD attenuated reperfusion-induced neutrophil adherence and increased Vw/Vr, an index of the fracture stress between leukocytes and endothelium. Peroxide-inactivated hSOD did not alter any parameter. MoAb IB4 attenuated reperfusion-induced adherence but did not alter Vw/Vr. In a correlate study, cultured bovine microvascular endothelium was exposed to 30 min of anoxia, followed by 60 min of reoxygenation. Cat neutrophils were added during reoxygenation. Reoxygenation-induced leukocyte adherence was attenuated by either hSOD or MoAb IB4 but not by inactivated hSOD. Adherence of phorbol 12-myristate 13-acetate-activated cat neutrophils to plastic was unaffected by hSOD or inactive hSOD, yet MoAb IB4 virtually abolished the response. These results indicate that superoxide mediates reperfusion-induced leukocyte adherence and that endothelial cells are required for this superoxide-mediated adherence.

Animals↗
PubMed1989

Characterization of intact mesenteric lymphatic pump and its responsiveness to acute edemagenic stress.

The contractile properties of the mesenteric collecting lymphatics of the rat were analyzed under control conditions and during periods of enhanced lymph formation using in vivo microscopic techniques. Pressure and diameter were simultaneously monitored in microscopic collecting lymphatics, and lymphatic pump function was analyzed in accordance with basic principles of cardiac mechanics. The lymphatic contractile cycle was divided into two phases of systole and four phases of diastole. Under control conditions, lymphatics contracted with a frequency of 6.4 +/- 0.61 beats/min and ejected approximately 67% of their end-diastolic volume. Ten minutes after the rate of lymph formation was elevated by plasma dilution, end-diastolic diameter, contraction frequency, ejection fraction, and stroke volume increased. Pressure in the lymphatic network became less pulsatile in high lymph flow states. Contractility, an index of inotropic changes in lymphatic pump, was unaltered when lymph flow was increased by plasma dilution. Furthermore, the maximal shortening velocity of lymphatic smooth muscle did not change during periods of enhanced lymph flow. Thus it appears that passive increases in the rate of lymph formation exert few, if any, inotropic effects on the lymphatic pump. The augmented stroke volume and contraction frequency appear to result mainly from intrinsic stretch-dependent mechanisms set in motion by elevated preload. These data represent the first comprehensive characterization of both the flow-generating and muscle characteristics of intact collecting lymphatics and provide a basis for future studies on the physiological regulation of lymphatic contraction.

Animals↗
PubMed1988

Diapedesis and the permeability of venous microvessels to protein macromolecules: the impact of leukotriene B4 (LTB4).

The cellular basis of the reported neutrophil-dependent increase in microvascular permeability evoked by leukotriene B4 (LTB4) was probed using protein intravascular fluorescent and electron dense tracers in conjunction with intravital, light and electron microscopy. LTB4 (1 microM) applied topically to the hamster cheek pouch promoted neutrophil (PMN) adherence to endothelial cells (ECs) and resulted in limited, diffuse leakage of fluorescein-labeled albumin from pericytic venules. ECs to which PMNs adhered displayed many vesicles and a prominent cytoskeletal reorganization of microfilaments. During emigration, microfilament-rich luminal extensions of ECs effectively resealed the endothelial barrier prior to or in conjunction with PMN penetration of the basal lamina. Intimate associations between PMNs and ECs, coupled with efficient bridging of the lumen by EC processes, argued against significant transendothelial escape of macromolecules concomitant with PMN egress. Studies employing horseradish peroxidase as an intravascular tracer suggested minimal enhancement of junctional permeability in small venules and refuted a role for vesicular transport. The primary apparent barrier defect was a selective alteration in the membrane integrity of a proportion of ECs.

Animals↗
PubMed1988

Venular endothelial cells from bovine heart.

Coronary venular endothelial cells were isolated by a bead-perfusion technique that allowed the selection of endothelial cells from venules of a specific size. Culture conditions for the microvascular cells were established. Cells grew well in supplemented Dulbecco's modified Eagle's medium. The effect of various substrata on the proliferation of the venular endothelial cells was determined. Matrigel, gelatin, and fibronectin supported high levels of proliferation. Cell shape was correlated with ability of the substratum to support cell proliferation. Cells exhibiting a broad, flattened morphology achieved high levels of proliferation. The formation of vessel meshworks by the coronary venular endothelial cells provides an in vitro model for the study of coronary angiogenesis. Confluent monolayers of these cells can be utilized to examine mechanisms of water and protein transport across coronary venules.

Animals↗