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PubMed1992

Lymphatic imaging in experimental filariasis using magnetic resonance.

RATIONALE AND OBJECTIVES: To evaluate acquired lymphatic abnormalities caused by filariasis, the authors examined the peripheral lymphatic system in normal ferrets and those chronically infected with Brugia malayi using magnetic resonance imaging (MRI). The findings were compared with previously obtained lymphangioscintigraphic (LAS) images in ferrets both with and without experimental filariasis. METHODS: Fifteen ferrets (11 infected with B. malayi and four noninfected controls) underwent whole body coronal MRI using a quadrature transmission-receive head coil at 0.5 Tesla operating at a resonant frequency of 21.5 mHz for protons with a 25-cm field of view. RESULTS: In contrast to normal animals, infected ferrets showed dilated hindlimb dermal lymphatic collaterals, enlarged high-signal intensity groin lymph nodes with punctate low-signal intensity centers and separate low-signal intensity spots with irregular thin channels, suggestive of nests of viable adult nematodes within tortuous lymphatics and nodes. MRI correlated with the LAS findings, and the interpretations were supported by light, scanning electron, and video microscopy. CONCLUSIONS: T2-weighted MRI in conjunction with LAS accurately depicts the peripheral lymphatic system in filarial-infected ferrets. These two modalities are useful complementary techniques to examine disorders characterized by lymphatic insufficiency.

Animals↗
PubMed1994

Coronary microvascular responses after exposure to iodinated contrast media.

RATIONALE AND OBJECTIVES: Iodinated contrast media can cause a number of well-described acute hemodynamic and vascular effects including vascular spasm, hypotension, and arrhythmias. Coronary microvessels were studied in vitro after high-dose exposure to an ionic, high-osmolar contrast agent diatrizoate meglumine in vivo. The aim of this study was to examine the endothelium-dependent and endothelium-independent vasodilator responses of the microvessels after previous contrast media administration in a clinically relevant setting. METHODS: Left coronary angiography was performed on six pigs using a cumulative dose of 60 mL (5 mL/injection) of diatrizoate meglumine. After 1 hour of reperfusion, epicardial coronary microvessels were studied in vitro in a pressurized, no-flow state with video microscopy. The vasodilators bradykinin, calcium ionophore A23187, and sodium nitroprusside were sequentially applied extraluminally after preconstriction. Serotonin and the thromboxane A2 analog U46619 were studied without preconstriction. RESULTS: Microvessels exposed to diatrizoate meglumine had normal relaxation responses to the endothelium-dependent vasodilators bradykinin and calcium ionophore A23187 when compared to control vessels. The vasoconstrictor responses to U46619 and serotonin were not significantly altered compared to control vessels. Responses to the endothelium-independent vasodilator sodium nitroprusside were not reduced or were slightly enhanced after exposure to contrast media. CONCLUSION: Coronary resistance vessels responses to the endothelium-dependent vasodilators bradykinin and calcium ionophore A23187 are not diminished after previous exposure to diatrizoate meglumine. The vasoconstrictor responses to U46619 and serotonin were similarly unaffected by previous exposure to contrast media. This suggests that, when used in clinically relevant amounts, diatrizoate meglumine does not cause functional endothelium or vascular smooth muscle impairment.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2002

Skin capillary density changes in normal pregnancy and pre-eclampsia.

BACKGROUND: Many abnormalities are known to occur in the microcirculation in essential hypertension, including reduction in capillary density or rarefaction. Peripheral vasodilatation and angiogenesis are critical components of the physiological adaptation in normal pregnancy. OBJECTIVE: To investigate the hypothesis that defective angiogenesis, reflected in capillary rarefaction, may be implicated in the clinical syndrome of pre-eclampsia. METHODS: We used intravital capillary video-microscopy to study functional (baseline) and structural (after maximization with venous congestion) skin capillary density in 22 healthy normotensive pregnant women and compared our findings with those in 22 non-pregnant age-matched healthy controls and 11 women whose pregnancies were complicated by pre-eclampsia. RESULTS: We found that both functional and structural capillary density increased during normal pregnancy. Capillary density in pre-eclamptic women was significantly lower both at baseline and after maximization. Skin capillary density appeared to be inversely correlated with blood pressure during pregnancy and in pre-eclampsia. CONCLUSIONS: A low capillary density may account, in part, for the failure of blood pressure to decrease in pre-eclamptic pregnancies, and may reflect the maladaptive cardiovascular response that is part of the pre-eclampsia syndrome.

Adult↗
PubMed1995

Positive end-expiratory pressure decreases mesenteric blood flow despite normalization of cardiac output.

Positive end-expiratory pressure (PEEP) is a commonly used adjunct to mechanical ventilation and is known to have deleterious effects on cardiac output (CO). Its effects on regional blood flow are not well known. We evaluated the effect of PEEP on the mesenteric microcirculation and CO. Sprague-Dawley rats were treated with mechanical ventilation and either no PEEP (Control) or increasing levels of PEEP (PEEP). Using in vivo video-microscopy, mesenteric A1 arteriolar optical Doppler velocities and A1 and A3 (the first- and third-order arterioles branching off the feeding mesenteric arcade) intraluminal diameters were measured (n = 6/group). In a separate set of experimental animals, CO was determined by thermodilution technique (n = 5/group). Additionally, after the PEEP group attained a PEEP level of 20-cm H2O PEEP, two boluses of 2 mL 0.9 normal saline (NS) were given intravenously. The Control groups had the same determinations performed over the same time course as the PEEP group but were not exposed to any PEEP. Mesenteric blood flow (MBF) was calculated from vessel diameter and red blood cell velocity. The MBF and CO fell progressively as PEEP was increased from 10- to 15- to 20-cm H2O pressure. MBF was reduced 75% (p < 0.05) and the CO was reduced 31% (p < 0.05) from baseline at 20-cm H2O pressure PEEP. After 4 mL normal saline, the MBF was still 45% below baseline (p < 0.05) while the CO had returned to baseline. In conclusion, both MBF and CO are decreased significantly with increasing PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Dalteparin sodium treatment during resuscitation inhibits hemorrhagic shock-induced leukocyte rolling and adhesion in the mesenteric microcirculation.

BACKGROUND: Ischemia/reperfusion-induced polymorphonuclear neutrophil leukocyte (PMN) adhesion and extravasation are pivotal for the development of postinjury multiple organ failure. We hypothesized that the deleterious microcirculatory consequences of hemorrhagic shock (HS) could be altered by low-molecular-weight heparin (LMWH) therapy. Our aim was to investigate the effects of dalteparin sodium on leukocyte-endothelial cell interactions when LMWH treatment was initiated before HS or during resuscitation. METHODS: Anesthetized dogs underwent HS (40 mm Hg mean arterial pressure for 60 minutes) and resuscitation either with shed blood or with lactated Ringer's (LR) solution. LMWH or conventional heparin sodium pretreatment was administered subcutaneously before hemorrhage; or LMWH was given intravenously during resuscitation. Mesenteric postcapillary venules were observed by intravital video microscopy before and after HS, and 60 minutes, 120 minutes, and 180 minutes after resuscitation, and leukocyte rolling and firm adherence were determined. RESULTS: HS significantly increased PMN rolling and adhesion in the mesenteric microcirculation. LMWH, but not heparin sodium pretreatment, significantly inhibited both primary and secondary interactions. LMWH treatment was also effective when initiated during resuscitation. LMWH exerted the same inhibitory effect regardless of the type of resuscitation. CONCLUSION: LMWH treatment during resuscitation effectively inhibits PMN rolling and adhesion.

Animals↗
PubMed2001

Continuous intravenous infusion of CGS 26303, an endothelin-converting enzyme inhibitor, prevents and reverses cerebral vasospasm after experimental subarachnoid hemorrhage.

OBJECTIVE: Endothelin-mediated vasoconstriction has been implicated in the pathophysiology of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). Endothelin-1, the most potent vasoconstrictor peptide of the endothelin family, is synthesized initially as a large prepropeptide that requires multiple steps of post-translational processing for activation. The final step of this processing involves the proteolytic cleavage of a relatively inactive precursor, big endothelin-1, by the metalloprotease endothelin-converting enzyme. Previous findings have demonstrated that intravenous bolus injections of an endothelin-converting enzyme inhibitor (CGS 26303) administered twice daily can prevent and reverse arterial narrowing in a rabbit model of SAH. However, attenuation of vasospastic response was incomplete and required relatively high doses to be effective in reversing vasospasm. Therefore, the present study evaluated an alternative protocol for administration of CGS 26303 to optimize the antispastic influence of this compound. METHODS: Continuous intravenous infusion of CGS 26303 at doses of 2.4, 8.0, or 24.0 mg/kg/d was initiated either 1 hour (prevention paradigm) or 24 hours (reversal paradigm) after experimental SAH in New Zealand White rabbits. All animals were killed by perfusion-fixation 48 hours after SAH. Basilar arteries were then removed and sectioned, and their cross-sectional areas were measured by use of computer-assisted video microscopy. RESULTS: Continuous intravenous infusion of CGS 26303 attenuated SAH-induced cerebral vasospasm in a dose-dependent manner in both the prevention and the reversal groups. These effects achieved statistical significance at all doses as compared with the SAH-only or SAH-plus-vehicle groups. Furthermore, the attenuation of vasospasm after continuous infusion of CGS 26303 was more efficacious than that obtained with bolus injections. CONCLUSION: These findings provide further support for the use of endothelin-converting enzyme inhibition as a therapeutic strategy for reduction of cerebral vasospasm, and they also support the effectiveness of this strategy even when initiated after arterial narrowing has been established. The findings also indicate that continuous intravenous infusion of CGS 26303 is a more effective approach for attenuation of vasospasm than bolus intravenous administration.

Animals↗
PubMed1994

Visualization of nutritive perfusion following tourniquet ischemia in arterial pattern skin flaps: effect of vasoactive medication.

We present an experimental model that makes it possible to investigate the effects of global ischemia and reperfusion on microvascular perfusion and viability of ill-proportioned (poorly designed) arterial pattern skin flaps in hairless mice. Skin flaps were created on the ears of hairless mice by dissecting two of three nutritional vessel bundles at the ear base. Under these nonischemic conditions, 19 percent of the total flap area went on to necrose (as a result of poor flap design). Global ischemia was induced to the flap tissue for 6 hours with a tourniquet clamp directly after flap incision. The extension of perfused tissue area and flap viability were assessed at the microcirculatory level by intravital video microscopy at 1, 3, 6, and 18 hours and 7 days after reperfusion in animals treated with either normal saline (control) or the vasoactive drug buflomedil hydrochloride (3 mg/kg of body weight per day, i.v., starting 4 hours prior to flap creation and continued at daily intervals until the end of the experiments). In untreated animals (n = 18), 1 hour after clamp release we observed reperfusion of 39.55 percent (38.5/44.9) of total flap area. Reperfusion remained unchanged within the following 5 hours. Within the next 12 hours, reperfused flap area was dramatically reduced to 21.9 percent (15.1/58.4). Seven days thereafter, only 18.8 percent (10.9/42.2) of total flap area remained viable. In contrast, we found in buflomedil-treated animals (n = 18) that 57.3 percent (53.5/62.9) of the total flap tissue was reperfused within the first hour after clamp release (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Lazaroids prevent acute cyclosporine-induced renal vasoconstriction.

BACKGROUND: Cyclosporine (CsA)-induced nephrotoxicity may be due to intrarenal vasoconstriction and glomerular hypoperfusion. Several factors, including endothelin and prostanoids, are suggested mediators of this response. Recent evidence suggests that CsA leads to increased oxygen-derived free radical (ODFR) production and lipid peroxidation in renal tissue. Whether this leads to alterations in renal vessel reactivity is unclear. Lazaroids, such as U74389G, are radical-quenching antioxidants that inhibit ODFR-induced lipid peroxidation and may improve renal function after ischemia and reperfusion. We hypothesized that ODFRs contribute to CsA-induced alterations of the renal microcirculation. METHODS: Rat hydronephrotic kidneys were studied by video microscopy. Interlobular arteriolar diameter and flow, afferent and efferent arteriolar diameters, and cardiac output were measured at 15-min intervals for 120 min. U74389G or its vehicle was infused 15 min before topical application of CsA to the kidney. The results were compared with U74389G alone and normal saline. RESULTS: CsA administration caused renal microvascular vasoconstriction (10-25% below baseline) and hypoperfusion (35% below baseline). Both vasoconstriction and hypoperfusion were significantly attenuated by U74389G (5-8% and 20% below baseline, respectively). CONCLUSIONS: Inhibition of lipid peroxidation by U74389G maintained renal blood flow during acute CsA administration. These data suggest that ODFRs are involved in the renal microvascular response to CsA. Inhibition of ODFR-induced lipid peroxidation may help prevent CsA-induced glomerular hypoperfusion. Lazaroids may prove an effective adjunct in reducing CsA-induced nephrotoxicity.

Animals↗
PubMed1994

Escherichia coli endotoxemia alters coronary and pulmonary arteriolar responses to platelet products.

In order to examine the effects of Escherichia coli endotoxemia on coronary and pulmonary microvascular responses to serotonin (5-HT) and ADP, arterioles (80-190 micros diameter) were isolated from pigs 3 h after administration of E. coli endotoxin (150 micrograms/kg, intravenously over 1 h, n = 8) or Ringer's lactate (control, n = 8). Arterioles were studied in vitro in a pressurized, partially contracted, no-flow state with video-microscopy. Precontracted (30-50% of baseline diameter) control coronary arterioles dilated in responses to either 5-HT (24 +/- 2%) or ADP (89 +/- 2%). These relaxations were partially inhibited by indomethacin, but were markedly reduced with nitric oxide synthase inhibition. After 3 h of endotoxemia, 5-HT caused contraction of coronary arterioles which was inhibited with indomethacin. In the presence of indomethacin, coronary vessels from endotoxic pigs relaxed slightly, but significantly, more to 5-HT than did control vessels exposed to indomethacin. In contrast, the relaxation response to ADP was unchanged following endotoxemia. Precontracted (15-30% of baseline diameter) pulmonary arterioles dilated in response to 5-HT (13 +/- 1%) or ADP (67 +/- 3%). Following 3 h of endotoxemia, the pulmonary arteriolar relaxation induced by 5-HT was reduced, whereas the response to ADP was not altered. In both coronary and pulmonary arterioles, relaxation induced by the endothelium-independent vasodilator, sodium nitroprusside, was unaffected by endotoxemia. Thus, coronary and pulmonary microvascular relaxation response to ADP are minimally affected by 3 h of endotoxemia, but relaxation responses to 5-HT are significantly reduced or converted to contractile responses.

Adenosine Diphosphate↗
PubMed1998

Interleukin-1 and interleukin-6 mediated skeletal muscle arteriolar vasodilation: in vitro versus in vivo studies.

Interleukin (IL) 1 and IL-6 have been implicated in the decreased systemic vascular resistance of septic shock; however, their sites of action and underlying mechanisms remain unclear. This study determined the effects of IL-1 and IL-6 on rat skeletal muscle arterioles using both in vitro and in vivo preparations. In the in vitro preparation, first order cremasteric arterioles were isolated from rats, cannulated with micropipettes, pressurized to 70 mmHg, superfused with physiologic saline solution, and allowed to achieve spontaneous basal tone in the absence of intraluminal flow. In the in vivo preparation, the cremaster muscle of anesthetized rats was surgically opened, secured as a flat sheet over an optical pedestal, and superfused with physiologic saline solution. Responses of third order arterioles were studied using transillumination video microscopy. In both arteriolar preparations, vessel diameter and phenylephrine (PE) responsiveness were assessed before and after cytokine exposure and washout. In vitro exposure of IL-1 (20 ng/mL (n=8) or 60 ng/mL (n=4)) or IL-6 (500 U/mL (n=2) or 1,000 U/mL (n=4)) for 1 h did not cause arteriolar vasodilation or change in PE responsiveness. However, during a 1 h in vivo exposure of IL-1 (.01, .1, 1.0, or 20 ng/mL), arteriolar diameter increased from 47+/-2 to 58+/-2% of maximum diameter (Dmax) (n=14, p < .0001), from 45+/-2 to 69+/-3% of Dmax (n=14, p < .0001), from 45+/-3 to 96+/-2% of Dmax (n=8, p < .0001), and from 47+/-4 to 96+/-1% of Dmax (n=14, p < .0001), respectively. Cytokine washout resulted in arteriolar return to basal diameter. Cytokine exposure and washout did not affect arteriolar PE responsiveness. In vivo exposure of IL-6 (10, 50, or 250 U/mL) for 1 h increased diameter from 47+/-2 to 57+/-2% of Dmax (n=14, p < .0001), from 46+/-2 to 75+/-3% of Dmax (n=14, p < .0001), and from 46+/-2 to 68+/-4% of Dmax (n=15, p < .0001), respectively. After washout of IL-6 (10, 50, or 250 U/mL), arteriolar dilation persisted, from 16.3+/-.5 to 20.1+/-1.4 microm (n=14, p < .003), from 16.1+/-.4 to 20.1+/-.6 microm (n=14, p < .0001), and from 17.7+/-.4 to 22.5+/-.8 microm (n=15, p < .0001), respectively. There was no change in PE responsiveness. These data indicate that the cytokines IL-1 and IL-6 are potent dilating agents for skeletal muscle resistance vessels under in vivo conditions. However, given that IL-1 and IL-6 are ineffective in causing relaxation of similar arterioles under isolated in vitro conditions, it is suggested that IL-1 and IL-6 interact with parenchymal or intravascular factors to elicit arteriolar relaxation.

Administration, Topical↗
PubMed1999

P-selectin contributes to the initial recruitment of rolling and adherent leukocytes in hepatic venules after ischemia/reperfusion.

We have recently reported that hepatic ischemia/reperfusion (I/R) is associated with a biphasic increase in the expression of P-selectin in the liver microvasculature, with peak expression levels observed at 20 min and 5 h after reperfusion. This I/R-induced upregulation of P-selectin expression is accompanied by leukocyte-endothelial cell adhesion in terminal hepatic venules (THV). The objective of this study was to determine whether the early expression of P-selectin contributes to the initial recruitment of rolling and adherent leukocytes in THV after liver I/R. Left hepatic lobe ischemia was induced for 30 min in anesthetized C57B1/6 and P-selectin knockout (KO) mice. The number of rolling, saltating, and adherent leukocytes in THV was measured at 0, 15, 30, 60, and 120 min after reperfusion using intravital video microscopy. Hepatic I/R elicited significant increases in the number of rolling, saltating, and adherent leukocytes, with peak values observed at 30 min after reperfusion. All of these responses were absent in P-selectin KO mice and in C57B1/6 mice treated with a blocking antibody to P-selectin. Our findings suggest that P-selectin is the primary determinant of leukocyte-endothelial cell adhesion observed in hepatic venules in the initial period after I/R. Hence, this adhesion molecule may represent a target for therapeutic intervention in liver transplantation and other conditions associated with hepatic I/R.

Animals↗
PubMed2002

Cardiac response to nitric oxide synthase inhibition using aminoguanidine in a rat model of endotoxemia.

This study evaluates the effect of aminoguanidine, a preferential inhibitor of inducible nitric oxide synthase (iNOS), on the prevention of cardiac depression in acute endotoxemia. Cardiac performance was evaluated after 4 h of exposure to endotoxin. Rats (n = 5) were selected randomly to receive, by intraperitoneal injection, one of four treatments: saline, LPS (lipopolysaccharide, E. coli, 4 mg/kg, AG (aminoguanidine 100 mg/kg), and LPS + AG at various times. AG and saline treatments were administered 30 min before LPS and at 1 and 3 h after LPS injection. Hearts were perfused using the Langendorff isolated perfusion system and a balloon-tipped catheter was placed into the left ventricle to measure left ventricular developed pressure (LVDP). Myocyte contractile function was assessed with electrical field stimulation and video microscopy. Tissue was immunostained for the expression of iNOS and for nitrotyrosine, a byproduct of protein nitration by peroxynitrite. Perfused hearts from LPS-treated rats exhibited a 57% decrease (P < 0.05) in LVDP compared to saline-treated animals. No improvement in ventricular function was observed with the administration of AG. Similarly, cardiac myocytes prepared from LPS-treated animals demonstrated a significant (P < 0.05) reduction in percent and velocity of shortening and this effect was unaltered with the same dose of AG. AG administration significantly reduced serum nitrite/nitrate levels (P < 0.05) in endotoxemic rats to control levels. Localized expression of iNOS in the myocardium was lessened with AG treatment and was not associated with peroxynitrite formation in this model of endotoxemia. The results indicate that AG given in vivo before and after endotoxin (at a concentration sufficient to decrease NO production) did not reduce cardiac depression. We conclude that selective inhibition of iNOS and the reduction of NO production do not prevent cardiac dysfunction at an early stage in an acute model of endotoxemia.

Animals↗
PubMed2002

Resuscitation regimens for hemorrhagic shock must contain blood.

Endothelial cell dysfunction occurs during hemorrhagic shock (HS) and persists despite adequate resuscitation (RES) that restores and maintains hemodynamics. We hypothesize that RES from HS with crystalloid solutions alone aggravate the endothelial cell dysfunction. To test this hypothesis, anesthetized nonheparinized rats were monitored for hemodynamics, and the terminal ileum was studied with intravital video microscopy. HS was 50% of mean arterial pressure (MAP) for 60 min. Four hemorrhaged groups (10 animals in each group) were randomized for RES: group I with shed blood returned + equal volume of normal saline (NS); group II with shed blood returned + 2x NS; group III with 2x NS only; and group IV with 4x NS only. Two hours post-RES, endothelial cell function was assessed with the endothelial-dependent agonist acetylcholine (ACh, 10(-9)-10(-4) M). Maximum arteriolar diameter was elicited by the endothelial-independent agonist sodium nitroprusside (NTP, 10(-4) M). HS caused a selective vasoconstriction associated with low blood flow in inflow A1 arterioles in all hemorrhaged groups. Post-RES vasoconstriction developed in A1 and premucosal arterioles (pA3 and dA3) In all hemorrhaged groups regardless of the RES regimen. However, A1 vasoconstriction and flow were significantly worst in the animals RES with NS alone (-43% and -75%, respectively) compared with those resuscitated with blood and NS (-27% and -57%). Impaired dilation response to ACh was noted in all hemorrhaged animals. However, a significant shift to the right of the dose-response curve (decreased sensitivity) was observed in the animals resuscitated with NS alone irrespective of the RES volume. These animals required at least two orders of magnitude greater ACh concentration to produce a 20% dilation response. For all vessel types, Group II had the best preservation of endothelial cell function. In conclusion, HS causes a selective vasoconstriction of A1 arterioles, which was not observed in A3 vessels. RES from HS results in progressive vasoconstriction in all intestinal arterioles irrespective of the RES regimen. Crystalloid RES after HS does not restore hemodynamics to baseline and is associated with a marked endothelial cell dysfunction. Blood-containing RES regimens preserve and maintain hemodynamics and are associated with the least microvascular dysfunction. Therefore, regimens for RES from HS must contain blood. Endothelial cell dysfunction is not the sole etiologic factor of post-RES microvascular impairment.

Animals↗
PubMed2003

Supplementation and inhibition of nitric oxide synthesis influences bacterial transit time during bacterial translocation in rats.

In the obstructed gut, nitric oxide (NO) may influence intestinal barrier function and translocation of bacteria. By using a novel experimental approach, we investigated the effect of supplementation and inhibition of NO synthesis on the time interval necessary for translocation of green fluorescent protein-transfected Escherichia coli (GFP-uv E. coli) in a rat model of small bowel obstruction. In anesthetized Wistar rats, 4 x 10(8) GFP-uv E. coli were administered into a reservoir of terminal ileum formed by ligature. Animals were randomized to receive either i.v. arginine (10 mg/kg), aminoguanidine (300 mg/kg), L-NAME (25 mg/kg), or saline (control). Translocation of GFP-uv E. coli was assessed using intravital video microscopy. Minimal transit time of translocation was measured as time from injection of GFP-uv E. coli into the gut lumen until bacteria were observed in the lamina submucosa and as time from injection of bacteria into the gut lumen until bacteria were observed in the lamina muscularis propria. Minimal transit times were expressed as mean +/- SD. Bacterial translocation into the submucosa and muscularis propria took 36 +/- 7 min and 81 +/- 9 min, respectively in control animals receiving saline. Aminoguanidine and L-NAME caused a marked delay of minimal transit time into the submucosa (63 +/- 5 min and 61 +/- 7 min, respectively; P < 0.05). Arginine significantly accelerated bacterial translocation into the muscularis propria (61 +/- 9 min, P < 0.05). GFP-uv E. coli were detected on frozen sections of small bowel, mesentery, liver, and spleen 2 h after GFP-uv E. coli administration in all animals. A marked upregulation of inducible NO synthase (NOS) in the obstructed bowel segment was demonstrated on immunohistochemistry. The assessment of a newly defined parameter, minimal bacterial transit time, may serve as an additional functional aspect of intestinal barrier function for pathophysiological and pharmacological studies. Aminoguanidine, L-NAME, and arginine were effective in influencing minimal transit time of E. coli during small bowel obstruction.

Animals↗
PubMed2004

Differential interplay between protein kinase C and Rho-kinase in the endothelin-1-induced and pressure-induced contractions of rat posterior cerebral artery.

To clarify the involvement of protein kinase C and Rho-kinase in the contractile activation of cerebral artery in response to endothelin-1 and pressurization, rat posterior cerebral artery (outer diameter, 100-200 microm) was mounted in arteriograph, and the changes in cytosolic Ca2+ and vessel diameter were measured by video-microscopy in connection with an Argus 50 system. Endothelin-1 (10 nM) induced a tonic contraction with a slight increase in cytosolic Ca2+, which was mostly dependent on protein kinase C (chelerythrine sensitive). Intraluminal pressurization (60 mmHg) also produced contraction with a low cytosolic Ca2+, which was myogenic in nature and dependent on both protein kinase C and Rho-kinase (Y-27632 sensitive). The results suggest differential interplay between protein kinase C and Rho-kinase in the endothelin-1-induced and pressure-induced tonic phase of contractions in the rat posterior cerebral artery.

Amides↗
PubMed2003

Low dose carboplatin combined with angiostatic agents prevents metastasis in human testicular germ cell tumor xenografts.

PURPOSE: Low dose chemotherapy combined with angiogenesis inhibitors has been shown to be more effective for experimental tumor treatment than chemotherapy alone. To our knowledge whether germ cell tumors could benefit from this treatment strategy remains to be evaluated. We examined the efficacy of angiostatic thrombospondin-1 (TSP-1), endostatin and combined angiostatic/low dose carboplatin in mice xenografted with human nonseminomatous germ cell tumor. MATERIALS AND METHODS: We monitored tumor progression and angiogenesis in the established model of human nonseminomatous germ cell tumor xenograft in 120 SCID mice using intravital video microscopy, immunocytochemistry and real-time polymerase chain reaction. Mice received TSP-1 (20 mg/kg daily) or endostatin (10 mg/kg daily) subcutaneously (via osmotic mini pumps) for 2 weeks starting 15 days after cancer cell grafting, carboplatin cycled twice (30 mg/kg intraperitoneally days 14 and 21 after cancer cell grafting), or a combination of carboplatin with TSP-1 or endostatin. Untreated, sham and tumor bearing mice treated with Ringer's solution served as controls. RESULTS: Primary tumor development was not affected in mice treated with TSP-1, endostatin or carboplatin alone. All animals had metastases at 6 months, while metastasis did not develop following the combination of carboplatin with TSP-1 or endostatin. This combined therapy suppressed tumor angiogenesis, enhanced apoptosis in tumor cells and decreased vascular endothelial growth factor-A tissue mRNA expression vs controls (p <0.05). CONCLUSIONS: These data indicate that angiostatic agents added to low dose carboplatin have the ability to suppress the progression of human germ cell tumor xenografts toward a metastatic phenotype. Therefore, this treatment strategy might be beneficial to prevent metastasis in germ cell tumors.

Angiogenesis Inhibitors↗
PubMed2003

A role for caspase-1 in serum withdrawal-induced apoptosis of endothelial cells.

Mouse lung endothelial cells (MLEC) and HUVEC were used under serum withdrawal (SW) conditions as a model of endothelial cell (EC) apoptosis. Apoptosis was quantified by time-lapse video microscopy. Mouse lung ECs from caspase-1(-/-) mice had significantly reduced rates of SW-induced apoptosis compared with wild-type mice, specifically implicating caspase-1 in proapoptotic signaling in ECs. SW conditions induced HUVEC apoptosis with concomitant activation of caspase-1. Further studies demonstrated that the caspase-1 inhibitors z-VAD and z-YVAD significantly reduced the rate of SW-induced HUVEC apoptosis. HUVEC, when transfected with caspase-1, showed a highly significant increase in apoptosis. SW was associated with increases in reactive oxygen species production that were significantly inhibited by the antioxidant N-acetyl-L-cysteine, although rates of apoptosis and caspase-1 activation were unaffected. These results demonstrate the involvement of caspase-1 in SW-induced EC apoptosis, independently of reactive oxygen species production.

Amino Acid Chloromethyl Ketones↗
PubMed2006

Altered cerebrovascular responses after exposure to venoarterial extracorporeal membrane oxygenation: role of the nitric oxide pathway.

BACKGROUND: Previous studies in our laboratory on newborn lambs have shown cerebral autoregulation impairment after exposure to venoarterial extracorporeal membrane oxygenation (VA ECMO), with additional studies showing an altered cerebrovascular response to NG-nitro-L-arginine methyl ester in lamb cerebral vessels in this same model. OBJECTIVE: To further study the mechanisms involved in altered cerebrovascular responses in vessels exposed to VA ECMO. DESIGN: Prospective study. SETTING: Research Animal Facility at Children's National Medical Center, Washington, DC. SUBJECT: Newborn lambs, 1-7 days of age, 4.76 +/- 0.8 kg (n = 10). METHODS: Animals randomly assigned two groups, control and VA ECMO, were anesthetized, ventilated, heparinized, and kept in a normal physiologic condition. Control animals were continued on ventilatory support, whereas animals in the VA ECMO groups were placed on VA ECMO, with bypass flows maintained between 120 and 200 mL x kg x min(-1) for 2.5 hrs. Isolated third-order branches of the middle cerebral arteries were studied for myotonic reactivity to increasing intraluminal pressure changes, response to acetylcholine, an endothelium-dependent vasodilator, 3-morpholinyl-sydnoneimine chloride, an endothelium-independent vasodilator, and serotonin, a direct vascular vasoconstrictor. Arterial caliber was monitored using video microscopy. RESULTS: Myogenic constriction response was significantly decreased in the VA ECMO group compared with the control group (p = .03). Intraluminal acetylcholine caused concentration-dependent arterial dilation in the control group, whereas it resulted in vasoconstriction in the VA ECMO group (p = .008). There were no significant differences in dilation responses to 3-morpholinyl-sydnoneimine chloride and contractile responses to serotonin among the groups. CONCLUSION: Cerebral arteries exposed to VA ECMO had impaired myogenic responses combined with altered endothelial function. The endothelial alteration seems to be mediated through the nitric oxide pathway, with recovery noted after addition of a nitric oxide donor. It can be postulated that these changes may reflect the mechanisms for the impairment of cerebral autoregulation previously reported in this lamb model.

Animals↗