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Ana M Briones

Publications and source records attributed to Ana M Briones.

18 recordsLinked to original sources

Guidelines for evaluating endothelial function in vascular tissue.

The endothelium plays a central role in maintaining vascular homeostasis by orchestrating vascular tone, inflammation, healing, permeability, and thrombosis. Assessing endothelial function in vascular tissue is essential for understanding the cellular and molecular mechanisms underlying cardiovascular physiology and pathology. Traditional approaches, such as wire and pressure myography, have been instrumental in defining endothelium-dependent responses and identifying key pharmacological targets. However, the complexity and heterogeneity of endothelial cells across vascular beds and their dynamic phenotypic changes in health and disease necessitate the incorporation of new investigative strategies. Emerging methodologies, including bulk and single-cell transcriptomics, proteomics, and advanced imaging, now provide unprecedented insights into endothelial cell diversity and function. A team of leading experts in the field, who collectively reached a consensus on the most widely used techniques to evaluate endothelial function, developed these guidelines. The document establishes best practices for assessing endothelial function, from endothelial cell cultures to isolated vascular tissues, integrating conventional functional assays with modern molecular approaches. By fostering methodological consistency and embracing innovation, our goal is to enhance rigor, reproducibility, understanding, and discovery in endothelial biology.

Humans↗

The dietary flavonoid quercetin activates BKCa currents in coronary arteries via production of H2O2. Role in vasodilatation.

OBJECTIVE: Large conductance Ca(2+)-activated K(+) channels (BKCa) regulate coronary artery tone in vivo, play a key role in blood pressure regulation, and have been suggested as novel potential drug targets in hypertension. Quercetin exerts systemic and coronary vasodilator effects in vitro and reduces blood pressure in several rat models of hypertension, and its consumption is associated with a lower mortality rate from coronary heart disease in epidemiological studies. We hypothesized that quercetin might activate BKCa channel in isolated myocytes from rat coronary arteries and that this mechanism might be involved in its coronary artery relaxant effects. METHODS: Membrane currents were measured using the whole-cell configuration of the patch-clamp technique. Contractile tension was recorded in rat coronary artery rings mounted in a myograph. RESULTS: Quercetin (>0.1 muM) increased the outward currents in the whole range of test potentials, hyperpolarized cell membranes, and increased the frequency of spontaneous transient outward currents (STOCs) carried by BKCa channels. These effects were abolished by the selective BKCa blocker iberiotoxin and by catalase. Quercetin increased dichlorofluorescein fluorescence in coronary arteries in a polyethylenglycol-catalase-sensitive manner, indicating that it increased cytosolic H(2)O(2). The membrane-permeable analogue of H(2)O(2)t-butylhydroperoxide mimicked the effects of quercetin on outward currents. The vasodilator effect of quercetin in isolated rat coronary arteries was partially inhibited by iberiotoxin. CONCLUSION: Quercetin increased BKCa currents via production of intracellular H(2)O(2). This effect is involved, at least partly, in the coronary vasodilator effects of quercetin.

4-Aminopyridine↗

Postnatal alterations in elastic fiber organization precede resistance artery narrowing in SHR.

Resistance artery narrowing and stiffening are key elements in the pathogenesis of essential hypertension, but their origin is not completely understood. In mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR), we have shown that inward remodeling is associated with abnormal elastic fiber organization, leading to smaller fenestrae in the internal elastic lamina. Our current aim is to determine whether this alteration is an early event that precedes vessel narrowing, or if elastic fiber reorganization in SHR arteries occurs because of the remodeling process itself. Using MRA from 10-day-old, 30-day-old, and 6-mo-old SHR and normotensive Wistar Kyoto rats, we investigated the time course of the development of structural and mechanical alterations (pressure myography), elastic fiber organization (confocal microscopy), and amount of elastin (radioimmunoassay for desmosine) and collagen (picrosirius red). SHR MRA had an impairment of fenestrae enlargement during the first month of life. In 30-day-old SHR, smaller fenestrae and more packed elastic fibers in the internal elastic lamina were paralleled by increased wall stiffness. Collagen and elastin levels were unaltered at this age. MRA from 6-mo-old SHR also had smaller fenestrae and a denser network of adventitial elastic fibers, accompanied by increased collagen content and vessel narrowing. At this age, elastase digestion was less effective in SHR MRA, suggesting a lower susceptibility of elastic fibers to enzymatic degradation. These data suggest that abnormal elastic fiber deposition in SHR increases resistance artery stiffness at an early age, which might participate in vessel narrowing later in life.

Animals↗

Alterations in structure and mechanics of resistance arteries from ouabain-induced hypertensive rats.

We have previously described that chronic administration of ouabain induces hypertension and functional alterations in mesenteric resistance arteries. The aim of this study was to analyze whether ouabain treatment also alters the structural and mechanical properties of mesenteric resistance arteries. Wistar rats were treated for 5 wk with ouabain (8.0 microg/day sc). The vascular structure and mechanics of the third-order branches of the mesenteric artery were assessed with pressure myography and confocal microscopy. Total collagen content was determined by picrosirius red staining, collagen I/III was analyzed by Western blot, and elastin was studied by confocal microscopy. Vascular reactivity was analyzed by wire myography. Internal and external diameters and cross-sectional area were diminished, whereas the wall-to-lumen ratio was increased in arteries from ouabain-treated rats compared with controls. In addition, arteries from ouabain-treated rats were stiffer. Ouabain treatment decreased smooth muscle cell number and increased total and I/III collagens in the vascular wall. However, this treatment did not modify adventitia and media thickness, nuclei morphology, elastin structure, and vascular reactivity to norepinephrine and acetylcholine. The present work shows hypotrophic inward remodeling of mesenteric resistance arteries from ouabain-treated rats that seems to be the consequence of a combination of decreased cell number and impaired distension of the artery, possibly due to a higher stiffness associated with collagen deposition. The narrowing of resistance arteries could play a role in the pathogenesis of hypertension in this model.

Adaptation, Physiological↗

Human vascular smooth muscle cells from diabetic patients are resistant to induced apoptosis due to high Bcl-2 expression.

An emerging body of evidence suggests that vascular remodeling in diabetic patients involves a perturbation of the balance between cell proliferation and cell death. Our aim was to study whether arteries and vascular smooth muscle cells (VSMCs) isolated from diabetic patients exhibit resistance to apoptosis induced by several stimuli. Internal mammary arteries (IMAs) were obtained from patients who had undergone coronary artery bypass graft surgery. Arteries from diabetic patients showed increasing levels of Bcl-2 expression in the media layer, measured by immunofluorescence and by Western blotting. Human IMA VSMCs from diabetic patients showed resistance to apoptosis, measured as DNA fragmentation and caspase-3 activation, induced by C-reactive protein (CRP) and other stimuli, such as hydrogen peroxide and 7beta-hydroxycholesterol. The diabetic cells also exhibited overexpression of Bcl-2. Knockdown of Bcl-2 expression with Bcl-2 siRNA in cells from diabetic patients reversed the resistance to induced apoptosis. Consistent with the above, we found that pretreatment of nondiabetic VSMCs with high glucose abolished the degradation of Bcl-2 induced by CRP. Moreover, cell proliferation was increased in diabetic compared with nondiabetic cells. This differential effect was potentiated by glucose. We conclude that the data provide strong evidence that arterial remodeling in diabetic patients results from a combination of decreased apoptosis and increased proliferation.

Aged↗

Increased superoxide anion production by interleukin-1beta impairs nitric oxide-mediated relaxation in resistance arteries.

The present study was designed to analyze the effect of long-term incubation with interleukin-1beta (IL-1beta) on endothelium-dependent relaxation in rat mesenteric resistance arteries. Vessels were incubated in culture medium with or without IL-1beta (10 ng/ml, 14 h). Changes in lumen diameter were recorded in a pressure myograph. Protein expression, nitrite, and superoxide anion (O(2)(.)) production were evaluated by either Western blot or immunofluorescence, Griess reaction, and ethidium fluorescence, respectively. IL-1beta impaired acetylcholine (ACh) and sodium nitroprusside (SNP) vasodilation and increased nitrite and O(2)(.) production and inducible nitric-oxide synthase (iNOS), xanthine oxidase, and p22(phox) expression. However, neither endothelial nitric-oxide synthase (NOS) nor soluble guanylate cyclase protein expression were affected by IL-1beta treatment. Polyethylene glycol superoxide dismutase partially reversed the impairment of ACh relaxation and abolished the O(2)(.) production observed in IL-1beta-treated arteries. The impairment of ACh relaxation induced by IL-1beta was also partially reversed by the xanthine oxidase inhibitor allopurinol (1 mM) but not by either the NADPH oxidase inhibitor apocynin (0.3 mM) or the inducible NOS inhibitor N-3-aminomethylbenzylacetamidine (1 microM). However, all these inhibitors improved the impaired SNP response. The results of the present study demonstrate that long-term incubation with IL-1beta induces an impairment of the nitric oxide-mediated relaxation in mesenteric resistance arteries through the production of O(2)(.), mainly from xanthine oxidase.

Animals↗

Influence of elastin on rat small artery mechanical properties.

We have previously developed a method for estimating elastin content and organization in resistance arteries, where it is a minor component. The aim of the present study was to validate the method against a quantitative assay and to determine the relative importance of elastin content and organization for intrinsic elasticity of small arteries. Mesenteric third order branches (from 10-day-old, 1- and 6-month-old rats) and middle cerebral arteries (from 6-month-old rats) were pressurized. beta-Values were calculated from stress-strain relationships and used as indicators of intrinsic stiffness. The same pressure-fixed arteries were used to estimate elastin content and organization in the internal elastic lamina with confocal microscopy. Collagen and elastin contents were determined by Picrosirius Red staining and radioimmunoassay for desmosine, respectively. Confocal and desmosine assays gave similar results: no difference in elastin content of mesenteric vessels from 1- and 6-month-old rats, and a significant reduction in cerebral compared to mesenteric arteries. For all parameters (elastin and collagen content, fenestrae area and internal elastic lamina thickness) the best correlation was found between beta-values and fenestrae size. These data suggest that in small arteries: (1) confocal microscopy can be used as a method for the simultaneous study of changes in elastin content and organization; and (2) elastin organization might be a key determinant of intrinsic elastic properties.

Aging↗

New aspects of vascular remodelling: the involvement of all vascular cell types.

Conventionally, the architecture of arteries is based around the close-packed smooth muscle cells and extracellular matrix. However, the adventitia and endothelium are now viewed as key players in vascular growth and repair. A new dynamic picture has emerged of blood vessels in a constant state of self-maintenance. Recent work raises fundamental questions about the cellular heterogeneity of arteries and the time course and triggering of normal and pathological remodelling. A common denominator emerging in hypertensive remodelling is an early increase in adventitial cell density suggesting that adventitial cells drive remodelling and may initiate subsequent changes such as re-arrangement of smooth muscle cells and extracellular matrix. The organization of vascular smooth muscle cells follows regular arrangements that can be modelled mathematically. In hypertension, new patterns can be quantified in these terms and give insights to how structure affects function. As with smooth muscle, little is known about the organization of the vascular endothelium, or its role in vascular remodelling. Current observations suggest that there may be a close relationship between the helical organization of smooth muscle cells and the underlying pattern of endothelial cells. The function of myoendothelial connections is a topic of great current interest and may relate to the structure of the internal elastic lamina through which the connections must pass. In hypertensive remodelling this must present an organizational challenge. The objective of this paper is to show how the functions of blood vessels depend on their architecture and a continuous interaction of different cell types and extracellular proteins.

Animals↗

Ageing alters the production of nitric oxide and prostanoids after IL-1beta exposure in mesenteric resistance arteries.

We aimed to analyse age influence on the production of inflammatory mediators from inducible isoforms of nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) in rat mesenteric resistance arteries (MRA). The second and/or third branches of MRA from young (3-month-old) and old (22-month-old) male Sprague-Dawley rats were incubated in culture medium with or without interleukin-1ss (IL-1ss; 10 ng/ml, 14 h). IL-1ss did not modify endothelial NOS (eNOS) expression or endothelial cell distribution. However, IL-1ss increased nitrite production and iNOS expression in endothelial and smooth muscle cells more in arteries from young than from old rats. IL-1ss also increased PGI(2) levels and COX-2 expression in the three layers of the vascular wall. Ageing did not affect COX-2 expression but did increase TXA(2) and PGF(2alpha) levels. The maximum contraction to phenylephrine was increased in arteries from old rats after IL-1ss treatment. Inhibition of iNOS and COX-2 with 1400 W and NS398, respectively, abolished the differences in phenylephrine contraction. In conclusion, IL-1ss induced an inflammatory response in MRA with associated increases in iNOS and COX-2 expression. The lower increase in nitrite production from iNOS together with a greater contractile prostanoid production in the old rats would be responsible for the increase observed in their contraction to phenylephrine after IL-1 ss treatment.

Aging↗

Direct demonstration of beta1- and evidence against beta2- and beta3-adrenoceptors, in smooth muscle cells of rat small mesenteric arteries.

1 Recent evidence supports additional subtypes of vasodilator beta-adrenoceptor (beta-AR) besides the 'classical' beta(2). The aim of this study was to investigate the distribution of beta-ARs in the wall of rat mesenteric resistance artery (MRA), to establish the relative roles of beta-ARs in smooth muscle and other cell types in mediating vasodilatation and to analyse this in relation to the functional pharmacology. 2 We first examined the vasodilator beta-AR subtype using 'subtype-selective' agonists against the, commonly employed, phenylephrine-induced tone. Concentration-related relaxation was produced by isoprenaline (pEC(50): 7.70+/-0.1) (beta(1) and beta(2)). Salbutamol (beta(2)), BRL 37344 (beta(3)) and CGP 12177 (atypical beta) caused relaxation but were 144, 100 and 263 times less potent than isoprenaline; the 'beta(3)-adrenoceptor agonist' CL 316243 was ineffective. 3 In arteries precontracted with 5-HT or U 46619, isoprenaline produced concentration-related relaxation but salbutamol, BRL 37344, CGP 12177 and CL 316243 did not. SR 59230A, CGP 12177 and BRL 37344 caused a parallel rightward shift in the concentration-response curve to phenylephrine indicating competitive alpha(1)-AR antagonism, explaining the false-positive 'vasodilator' action against phenylephrine-induced tone. Endothelial denudation but not L-NAME slightly attenuated isoprenaline-mediated vasodilatation in phenylephrine and U 46619 precontracted MRA. 4 The beta-AR fluorescent ligand BODIPY TMR-CGP 12177 behaved as an irreversible beta(1)-AR antagonist in MRA and bound to the surface and inside vascular smooth muscle cells in intact vascular wall. Beta-ARs in smooth muscle cells were observed in a perinuclear location, consistent with the location of Golgi and endoplasmic reticulum. 5 Binding of BODIPY TMR-CGP 12177 was inhibited by BAAM (1 microM) in all three vascular tunics, confirming the presence of beta-ARs in adventitia, media and intima. Binding in adventitia was observed in both neuronal and non-neuronal cell types. Lack of co-localisation with a fluorescent ligand for alpha-ARs confirms the selectivity of BODIPY TMR-CGP 12177 for beta-ARs over alpha-ARs. 6 Our results support the presence of functional vasodilator beta(1)-ARs and show that they are mainly located in smooth muscle cells. Furthermore, we have demonstrated, for the first time, the usefulness of BODIPY TMR-CGP 12177 for identifying beta-AR distribution in the 'living' vascular wall.

Adrenergic beta-Agonists↗

Hypertension increases the participation of vasoconstrictor prostanoids from cyclooxygenase-2 in phenylephrine responses.

OBJECTIVE: The present study was designed to analyse whether hypertension alters the involvement of cyclooxygenase-2-derived mediators in phenylephrine-induced vasoconstrictor responses. METHODS: Vascular reactivity experiments were performed in aortic segments from normotensive, Wistar-Kyoto, and spontaneously hypertensive rats (SHR); protein expression was measured by western blot and/or immunohistochemistry, and prostaglandin F2alpha (PGF2alpha), 8-isoprostane and prostacyclin release were determined by enzyme immunoassay commercial kits. RESULTS: The protein synthesis inhibitor dexamethasone (1 micromol/l), the non-selective cyclooxygenase inhibitor indomethacin (10 micromol/l), the selective cyclooxygenase-2 inhibitor NS 398 (1 micromol/l), and the thromboxane A2/prostaglandin H2 (TP) receptor antagonist SQ 29,548 (1 micromol/l), reduced the concentration-response curves to phenylephrine more in segments from hypertensive than from normotensive rats; however, the thromboxane A2 (TxA2) synthase inhibitors furegrelate (10 micromol/l) and OKY 046 (1 and 10 micromol/l) had no effect in either strain. Removing endothelium or adding dexamethasone almost abolished the NS 398 effect. Cyclooxygenase-2 protein expression, which was reduced by dexamethasone, was higher in aorta from hypertensive animals. In both strains cyclooxygenase-2 was localized mainly in endothelial cells and adventitial fibroblasts. 13,14-Dihydro-15-keto-PGF2alpha, 6-keto-PGF1alpha and 8-isoprostane levels were greater in the medium from hypertensive than from normotensive rats; NS 398 decreased levels of the three metabolites studied only in the medium from SHR. CONCLUSIONS: PGF2alpha and 8-isoprostane seem to be involved in the response to phenylephrine in rat aorta; this involvement is greater in hypertensive rats, probably due to a higher endothelial induction of cyclooxygenase-2.

Animals↗

Hypertension alters role of iNOS, COX-2, and oxidative stress in bradykinin relaxation impairment after LPS in rat cerebral arteries.

This study was performed to investigate the role of reactive oxygen species and inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) metabolites in the lipopolysaccharide effect on bradykinin-induced relaxation in middle cerebral arteries from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). LPS exposure (10 microg/ml for 1-5 h) reduced bradykinin relaxation; this effect appeared earlier and was greater in arteries from SHR than WKY rats. LPS also reduced the relaxation to the NO donor diethylamine (DEA)-NO; however, LPS modified neither the bradykinin relaxation after inhibiting NO synthesis with N(G)-monomethyl-L-arginine (0.1 mM) nor endothelial NOS expression. In arteries from WKY rats, the respective iNOS and COX-2 inhibitors aminoguanidine (0.1 mM) and NS-398 (10 microM) and the superoxide anion scavenger SOD (100 U/ml) reduced the LPS effect on bradykinin relaxation; however, the thromboxane A(2) (TxA(2))PGH(2) receptor antagonist SQ-29548 (1 microM) and the H(2)O(2) scavenger catalase (1,000 U/ml) did not modify the LPS effect. In arteries from SHR, all of these drugs reduced the LPS effect. LPS exposure (5 h) increased superoxide anion levels in arteries from both strains and TxA(2) levels only in SHR. COX-2 expression rose to a similar level in arteries from both strains after 1 and 5 h of LPS incubation, whereas expression of Cu/Zn- and Mn-SOD only increased after 5 h. In conclusion, in segments from WKY rats, LPS reduced bradykinin-induced relaxation through increased production of NO (from iNOS) and superoxide anion. The greater LPS effect observed in arteries from SHR seems to be related to higher participation of reactive oxygen species and contractile prostanoids (probably TxA(2)).

Animals↗

Role of elastin in spontaneously hypertensive rat small mesenteric artery remodelling.

Chronic hypertension is associated with resistance artery remodelling and mechanical alterations. However, the contribution of elastin has not been thoroughly studied. Our objective was to evaluate the role of elastin in vascular remodelling of mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR). MRA segments from Wistar Kyoto rats (WKY) and SHR were pressurised under passive conditions at a range of physiological pressures with pressure myography. Confocal microscopy was used to determine differences in the quantity and organisation of elastin in intact pressure-fixed arteries. To assess the contribution of elastin to MRA structure and mechanics, myograph-mounted vessels were studied before and after elastase incubation. When compared with WKY, MRA from SHR showed: (1) a smaller lumen, (2) decreased distensibility at low pressures, (3) a leftward shift of the stress-strain relationship, (4) redistribution of elastin within the internal elastic lamina (IEL) leading to smaller fenestrae but no change in fenestrae number or elastin amount. Elastase incubation (1) fragmented the structure of IEL in a concentration-dependent fashion, (2) abolished all the structural and mechanical differences between strains, and (3) decreased distensibility at low pressures. The study shows the overriding role of elastin in determining vascular dimensions and mechanical properties in a resistance artery. In addition, it informs hypertensive remodelling. MRA remodelling and increased stiffness are accompanied by elastin restructuring within the IEL and elastin degradation reverses structural and mechanical alterations of SHR MRA. Differences in elastin organisation are, therefore, a central element in small artery remodelling in hypertension.

Animals↗

Mechanisms involved in the early increase of serotonin contraction evoked by endotoxin in rat middle cerebral arteries.

The present study investigated the mechanisms involved in the increased 5-hydroxytryptamine (5-HT) vasoconstriction observed in rat middle cerebral arteries exposed in vitro to lipopolysaccharide (LPS, 10 microg x ml-1) for 1-5 h. Functional, immunohistochemical and Western blot analysis and superoxide anion measurements by ethidium fluorescence were performed. LPS exposure increased 5-HT (10 microm) vasoconstriction only during the first 4 h. In contrast to control tissue, indomethacin (10 microm), the COX-2 inhibitor NS 398 (10 microm), the TXA2/PGH2 receptor antagonist SQ 29548 (1 microm) and the TXA2 synthase inhibitor furegrelate (1 microm) reduced 5-HT contraction of LPS-treated arteries from hour one. The iNOS inhibitor aminoguanidine (0.1 mm) increased 5-HT contraction from hour three of LPS incubation. The superoxide anion scavenger superoxide dismutase (SOD, 100 U ml-1) and the H2O2 scavenger catalase (1000 U ml-1), as well as the respective inhibitors of NAD(P)H oxidase and xanthine oxidase, apocynin (0.3 mm) and allopurinol (0.3 mm), reduced 5-HT contraction after LPS incubation. LPS induced an increase in superoxide anion levels that was abolished by PEG-SOD. Subthreshold concentrations of the TXA2 analogue U 46619, xanthine/xanthine oxidase and H2O2 potentiated, whereas those of sodium nitroprusside inhibited, the 5-HT contraction. COX-2 expression was increased at 1 and 5 h of LPS incubation, while that of iNOS, Cu/Zn-SOD and Mn-SOD was only increased after 5 h. All the three vascular layers expressed COX-2 and Cu/Zn-SOD. iNOS expression was detected in the endothelium and adventitia after LPS. In conclusion, increased production of TXA2 from COX-2, superoxide anion and H2O2 enhanced vasoconstriction to 5-HT during the first few hours of LPS exposure; iNOS and SOD expression counteracted that increase at 5 h. These changes can contribute to the disturbance of cerebral blood flow in endotoxic shock.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Hypertension alters the participation of contractile prostanoids and superoxide anions in lipopolysaccharide effects on small mesenteric arteries.

The involvement of cyclooxygenase-2 (COX-2)-derived products and superoxide anion in the effect of lipopolysaccharide in noradrenaline (NA)-induced contraction was investigated in small mesenteric arteries (SMA) from normotensive, Wistar Kyoto (WKY), and spontaneously hypertensive (SHR) rats. In WKY, lipopolysaccharide (10 microg/ml, 1 and 5 h) only inhibited the NA response (0.1-30 microM) in the presence of dexamethasone (1 microM), indomethacin (10 microM), the selective COX-2 inhibitor, NS 398 (10 microM), and the TXA(2)/PGH(2) receptor antagonist, SQ 29,548 (10 microM) but not of superoxide dismutase (SOD, 100 U/ml). In SHR, lipopolysaccharide inhibited the NA response by itself; this inhibition was potentiated by dexamethasone, indomethacin, NS 398, SQ 29,548 and SOD. The effect of lipopolysaccharide plus indomethacin, NS 398 or SQ 29,548 was higher in SMA from WKY than SHR only after 1 h lipopolysaccharide incubation. N(G)-nitro-L-arginine methyl ester (100 microM) and endothelium removal abolished the indomethacin-induced potentiatory effect of lipopolysaccharide in both strains. Endothelium removal also abolished the SOD potentiatory effect in SMA from SHR. Lipopolysaccharide increases COX-2 expression to a similar level in both strains and iNOS expression in a greater extent in SHR; these increases were reduced by dexamethasone. These results indicate: 1) lipopolysaccharide induces the endothelial production of contractile prostanoids from COX-2 in SMA, probably to compensate the increase in NO from iNOS; 2) the production of prostanoids in the presence of lipopolysaccharide seems to be greater in normotensive than hypertensive rats only after lipopolysaccharide short incubation times; 3) endothelial production of O(2)(.-) contributes to counteract depression of NA contraction caused by lipopolysaccharide only in SHR.

Animals↗

Alterations of the nitric oxide pathway in cerebral arteries from spontaneously hypertensive rats.

Hypertension-associated alterations of the nitric oxide (NO) pathway were analyzed in middle cerebral arteries (MCA) from normotensive (WKY) and hypertensive (SHR) rats. The vasoconstrictor response to prostaglandin F2alpha (PGF(2 alpha), 30 and 100 microM) was smaller in MCA from SHR than from WKY. Endothelium-dependent relaxations to bradykinin (1 nM-10 microM) or acetylcholine (10 microM) were similar in MCA from both strains, whereas the endothelium-independent response to sodium nitroprusside (1 nM-0.1 mM) was smaller in MCA from SHR. L-arginine (L-Arg, 10 microM) similarly inhibited the vasoconstrictor responses in both strains; however, the inhibitory effect of 100 microM of L-Arg was greater in MCA from SHR. N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM), but not aminoguanidine (100 microM) or 7-nitroindazole (10 microM), increased basal tone, potentiated the PGF(2 alpha)-induced vasoconstrictor responses and reduced the bradykinin-elicited relaxation in a similar way in MCA from WKY and SHR. N(omega)-nitro-L-arginine methyl ester also antagonized the inhibitory effect of 10 microM of L-Arg. Incubation for 5 h with lipopolysaccharide (10 microg/ml) similarly reduced the response to PGF(2 alpha) in MCA from WKY and SHR; this reduction was antagonized by dexamethasone (1 microM). Cerebral arteries expressed endothelial (eNOS) and neuronal (nNOS) NO synthase similarly in both strains, but inducible NOS (iNOS) expression was more evident in SHR. Lipopolysaccharide increased iNOS expression in both strains to a similar level. The basal constitutive NOS (cNOS) and iNOS activities were similar in arteries from WKY and SHR. Lipopolysaccharide increased iNOS activity only in arteries from SHR. These results indicate that hypertension did not impair endothelial NO production by NOS activation but induced an up-regulation of basal iNOS expression.

Animals↗

Ouabain-induced hypertension is accompanied by increases in endothelial vasodilator factors.

The involvement of nitric oxide (NO), prostaglandins, and calcium-dependent potassium channel (K(Ca)) activators on the negative modulation of phenylephrine-induced contractions was evaluated on the isolated aorta and caudal (CAU) artery obtained from rats treated with ouabain for 5 wk to induce hypertension. In ouabain-treated rats, the reactivity to phenylephrine was reduced in the endothelium-intact aorta but not the CAU segments. Endothelial modulation of phenylephrine contraction, as demonstrated by endothelium removal, NO synthase (NOS) inhibition with N(omega)-nitro-L-arginine methyl ester and aminoguanidine, as well as K(Ca) inhibition with tetraethylammonium, was more pronounced in segments from ouabain-treated animals, and here greater effects were seen in the aorta than in CAU. An increased expression of endothelial NOS and neuronal NOS was seen in the aorta after ouabain treatment. In CAU, only endothelial NOS was detected and ouabain treatment did not alter its expression. These results suggest that ouabain-induced hypertension is accompanied by increased NO release derived from endothelial NOS and neuronal NOS and increased release of an endothelial hyperpolarizing factor that presumably opens K(Ca), all of which contribute to the increased negative modulation of the phenylephrine contraction.

Animals↗

Confocal microscopic image sequence compression using vector quantization and three-dimensional pyramid.

The three-dimensional (3-D) pyramid compressor project at the University of Glasgow has developed a compressor for images obtained from confocal laser scanning microscopy (CLSM) device. The proposed method using a combination of image pyramid coder and vector quantization techniques has good performance at compressing confocal volume image data. An experiment was conducted on several kinds of CLSM data using the presented compressor compared with other well-known volume data compressors, such as MPEG-1. The results showed that the 3-D pyramid compressor gave a higher subjective and objective image quality of reconstructed images at the same compression ratio, and presented more acceptable results when applying image processing filters on reconstructed images.

Animals↗