Colored Microsphere Technique Research Articles

Organ blood flow in response to infusion of arginine vasopressin in premature fetal sheep.

Arginine vasopressin (AVP) infusion has been shown to be a useful strategy for the management of systemic perfusion failure in premature infants. Our objective was to determine the characteristics of the blood flow redistribution induced by AVP infusion in premature fetal sheep. Nine sheep fetuses at 99 to 113days of gestation were continuously infused with AVP. Measurement of blood flow to individual fetal organs was performed using a colored microsphere technique, with measurements performed at 30min before and 90min after the initiation of AVP infusions. The AVP infusion significantly increased blood flow to the medulla oblongata (P < 0.05), and significantly decreased flow to the adrenal glands (from 492.0 ± 239.6 to 364.9 ± 143.3mL/min/100g, P < 0.05) and heart (from 592.6 ± 184.5 to 435.6 ± 137.4mL/min/100g, P < 0.05). The infusion significantly increased the vascular resistance in adrenal glands, kidneys, ileum, colon, heart, and cerebellum. In the brain, except for the cerebellum, no significant increase in resistance was identified. There was no significant response to AVP infusion in cerebral blood flow in mid-gestation fetal sheep. Our observations suggest that, under AVP stimulation, the blood flow to the adrenal glands and myocardium might be decreased due to an increase in vascular resistance.

Short-Term Western Diet Aggravates Non-Alcoholic Fatty Liver Disease (NAFLD) With Portal Hypertension in TGR(mREN2)27 Rats.

Non-alcoholic fatty liver disease (NAFLD) is gaining in importance and is linked to obesity. Especially, the development of fibrosis and portal hypertension in NAFLD patients requires treatment. Transgenic TGR(mREN2)27 rats overexpressing mouse renin spontaneously develop NAFLD with portal hypertension but without obesity. This study investigated the additional role of obesity in this model on the development of portal hypertension and fibrosis. Obesity was induced in twelve-week old TGR(mREN2)27 rats after receiving Western diet (WD) for two or four weeks. Liver fibrosis was assessed using standard techniques. Hepatic expression of transforming growth factor-β1 (TGF-β1), collagen type Iα1, α-smooth muscle actin, and the macrophage markers Emr1, as well as the chemoattractant Ccl2, interleukin-1β (IL1β) and tumor necrosis factor-α (TNFα) were analyzed. Assessment of portal and systemic hemodynamics was performed using the colored microsphere technique. As expected, WD induced obesity and liver fibrosis as confirmed by Sirius Red and Oil Red O staining. The expression of the monocyte-macrophage markers, Emr1, Ccl2, IL1β and TNFα were increased during feeding of WD, indicating infiltration of macrophages into the liver, even though this increase was statistically not significant for the EGF module-containing mucin-like receptor (Emr1) mRNA expression levels. Of note, portal pressure increased with the duration of WD compared to animals that received a normal chow. Besides obesity, WD feeding increased systemic vascular resistance reflecting systemic endothelial and splanchnic vascular dysfunction. We conclude that transgenic TGR(mREN2)27 rats are a suitable model to investigate NAFLD development with liver fibrosis and portal hypertension. Tendency towards elevated expression of Emr1 is associated with macrophage activity point to a significant role of macrophages in NAFLD pathogenesis, probably due to a shift of the renin–angiotensin system towards a higher activation of the classical pathway. The hepatic injury induced by WD in TGR(mREN2)27 rats is suitable to evaluate different stages of fibrosis and portal hypertension in NAFLD with obesity.

Hepatology Basic Science

Hepatology Basic Science

Detection of Hemodynamically Significant Coronary Artery Stenosis With CT Enhancement Ratio: A Validation Study in a Porcine Model.

Although numerous techniques that are based on CT number analysis have been proposed, the assessment of hemodynamically significant coronary artery stenosis remains a great challenge. The purpose of this study is to validate use of the CT enhancement ratio in the detection of hemodynamically significant coronary artery stenosis in a porcine model. Experiments involving eight closed-chest swine were performed. A balloon catheter was placed into the left anterior descending coronary artery to simulate different degrees of luminal stenosis. The myocardial blood flow (MBF) ratio was measured using the colored microsphere technique. The fractional flow reserve was measured using an invasive pressure wire. CT scans were performed during the first-pass phase, while the pigs were undergoing adenosine stress tests. The CT enhancement ratio and the CT attenuation ratio were calculated using data from the CT images obtained. Results suggested that the CT enhancement ratio had a strong correlation (y = 0.07245 + 0.09963x; r2 = 0.898; p < 0.001) with the MBF ratio measured using the microsphere technique, whereas only moderate correlation (y = -1.5508 + 2.2684x; r2 = 0.498; p < 0.001) was noted between the CT attenuation ratio and the MBF ratio measured using the microsphere technique. In ROC curve analysis, the AUC values of the CT enhancement ratio and the CT attenuation ratio were 0.927 and 0.829, respectively, with regard to the detection of significant ischemia during adenosine stress tests, as defined by the fractional flow reserve. The CT enhancement ratio provides a reliable prediction of the MBF ratio measured using the microsphere technique, indicating that this metric has good diagnostic performance in the detection of hemodynamically significant coronary artery stenosis. The CT enhancement ratio may have potential for use as an imaging biomarker for the relative quantitative assessment of myocardial perfusion.

Effect of quercetin on formation of choroidal neovascularization (CNV) in age-related macular degeneration(AMD).

Age-related macular degeneration (AMD) as a disease entity is "dry" at early stage and made up of two main components at late stage: atrophic AMD and exudative AMD. Quercetin acts as an anti-oxidant to protect retinal pigment epithelial cells (RPE) from damaged by oxidative stress, but its effect on formation of choroidal neovascularization (CNV) in AMD is unclear. The aim of this study is to investigate the effect of quercetin on the formation of CNV in AMD. The development of CNV induced by laser was detected by fluorescein angiography (FA). Colored microsphere technique was used to determine the choroidal blood flow in ocular hypertensive rabbit eyes. In in vitro studies, HUVECs were treated with NaIO3, H2O2 and NaN3 to induce oxidative cell damages. The effect of quercetin on various oxidations-induced injuries in HUVECs was measured by MTT assay. HUVECs migration was assessed using a wound healing assay. Quercetin significantly inhibited the formation of laser-induced CNV. The choroidal blood flow in rabbit eyes was significantly increased after quercetin instillation. In vitro results showed quercetin enhanced various oxidations-induced injuries in HUVECs and inhibited migration of HUVECs during wound healing. Quercetin inhibited the formation of CNV both in vivo and in vitro and increased choroidal blood flow. It could become a promising candidate for the treatment of AMD.

Role of estrogen receptor β selective agonist in ameliorating portal hypertension in rats with CCl4-induced liver cirrhosis.

To investigate the role of diarylpropionitrile (DPN), a selective agonist of estrogen receptor β (ERβ), in liver cirrhosis with portal hypertension (PHT) and isolated hepatic stellate cells (HSCs). Female Sprague-Dawley rats were ovariectomized (OVX), and liver cirrhosis with PHT was induced by CCl4 injection. DPN and PHTPP, the selective ERβ agonist and antagonist, were used as drug interventions. Liver fibrosis was assessed by hematoxylin and eosin (HE) and Masson's trichrome staining and by analyzing smooth muscle actin expression. Hemodynamic parameters were determined in vivo using colored microspheres technique. Protein expression and phosphorylation were determined by immunohistochemical staining and Western blot analysis. Messenger RNA levels were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Collagen gel contraction assay was performed using gel lattices containing HSCs treated with DPN, PHTPP, or Y-27632 prior to ET-1 addition. Treatment with DPN in vivo greatly lowered portal pressure and improved hemodynamic parameters without affecting mean arterial pressure, which was associated with the attenuation of liver fibrosis and intrahepatic vascular resistance (IHVR). In CCl4-treated rat livers, DPN significantly decreased the expression of RhoA and ROCK II, and even suppressed ROCK II activity. Moreover, DPN remarkedly increased the levels of endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS, and promoted the activities of protein kinase G (PKG), which is an NO effector in the liver. Furthermore, DPN reduced the contractility of activated HSCs in the 3-dimensional stress-relaxed collagen lattices, and decreased the ROCK II activity in activated HSCs. Finally, in vivo/in vitro experiments demonstrated that MLC activity was inhibited by DPN. For OVX rats with liver cirrhosis, DPN suppressed liver RhoA/ROCK signal, facilitated NO/PKG pathways, and decreased IHVR, giving rise to reduced portal pressure. Therefore, DPN represents a relevant treatment choice against PHT in cirrhotic patients, especially postmenopausal women.

Hemodynamic Effects of the Non-Peptidic Angiotensin-(1-7) Agonist AVE0991 in Liver Cirrhosis.

Background & AimsAlthough in cirrhosis with portal hypertension levels of the vasoconstrictor angiotensin II are increased, this is accompanied by increased production of angiotensin (Ang)-(1–7), the endogenous ligand of the Mas receptor (MasR), which blunts hepatic fibrosis and decreases hepatic vascular resistance. Therefore, we investigated the effects of the non-peptidic Ang-(1–7) agonist, AVE0991, in experimental cirrhosis.MethodsCirrhosis was induced by bile duct ligation (BDL) or carbon tetrachloride (CCl4) intoxication. The coloured microsphere technique assessed portal and systemic hemodynamic effects of AVE0991 in vivo. Hepatic expression of eNOS, p-eNOS, iNOS, JAK2, ROCK and p-Moesin were analyzed by western blots. Activities of ACE and ACE2 were investigated fluorometrically. Moreover, fibrosis was assessed in BDL rats receiving AVE0991.Results In vivo, AVE0991 decreased portal pressure (PP) in both rat models of cirrhosis. Importantly, systemic effects were not observed. The hepatic effects of AVE0991 were based on upregulation of vasodilating pathways involving p-eNOS and iNOS, as well as by downregulation of the vasoconstrictive pathways (ROCK, p-Moesin). Short-term treatment with AVE0991 decreased the activity of ACE2, long-term treatment did not affect hepatic fibrosis in BDL rats.ConclusionsThe non-peptidic agonist of Ang-(1–7), AVE0991, decreases portal pressure without influencing systemic pressure. Thus, although it does not inhibit fibrosis, AVE0991 may represent a promising new therapeutic strategy for lowering portal pressure.

Inhibition of hydrogen peroxide prevents the development of VEGF‐induced angiogenesis in portal hypertensive rats

AimsTo determine specific effects of inhibiting hydrogen peroxide (H2O2) on splanchnic hemodynamics and angiogenesis in portal hypertension of rats.Methods: Portal hypertensive models were induced by partial portal vein ligation (PPVL). The rats then, received either polyethylene glycol‐catalase (H2O2 inhibitor; PPVL‐PEG) or vehicle (PPVL‐Veh) for 8 days. The hemodynamic studies were performed using colored microsphere technique. Intestinal expressions of VEGF/VEGF‐2 and CD31 (angiogenesis markers) was determined by western blotting, and levels of H2O2 were measured by the Hydrogen Peroxide Assay Kit.Results: Portal pressure was significantly higher, associated with lower splanchnic arteriolar resistance in PPVL group (14.4±0.9 and 11.2±1.1mmHg) than those of normal rats (6.1±0.4 and 35.1±4.0 mmHg). Upregulation of VEGF/VEGF‐2 and CD31 in the intestine/mesentery of PPVL group was indicative of angiogenesis, which consequentially, initiated great collateral vessel formation, leading to the development of splanchnic hyperdynamic circulation. Moreover, levels of H2O2 in the intestine and mesentery of PPVL group of rats were significantly higher than those of normal rats. These alterations were significantly alleviated after treatment of portal hypertensive rats with PEG‐catalase, suggesting a key role of H2O2 in the responses.ConclusionsH2O2 plays an important role in the pathogenesis of portal hypertension, characterized as the potentiation of splanchnic neovascularisation and development of splanchnic hyperdynamic circulation.

The Effect of Pumpless Extracorporeal CO2 Removal on Regional Perfusion of the Brain in Experimental Acute Lung Injury

Lung-protective mechanical ventilation with low tidal volumes (V(T)) is often associated with hypercapnia (HC), which may be unacceptable in patients with brain injury. CO2 removal using a percutaneous extracorporeal lung assist (pECLA) enables normocapnia despite low V(T), but its effects on regional cerebral blood flow (rCBF) remain ambiguous. We hypothesized that reversal of HC by pECLA impairs rCBF in a porcine lung injury model. Lung injury was induced in 9 anesthetized pigs by hydrochloric acid aspiration. rCBF and systemic hemodynamics were measured by colored microsphere technique and transpulmonary-thermodilution during a randomized sequence of 4 experimental situations: pECLA shunt-on (1) with HC and (2) without HC, pECLA shunt-off (3) with HC and (4) without HC. HC increased rCBF (P<0.05). CO2 removal with pECLA resulting in normocapnia, decreased rCBF to levels comparable to those without pECLA and normocapnia. HC resulted in increased cardiac output (+25.5%). Cardiac output was highest during HC with pECLA shunt (+44.9%). During pECLA with CO2 removal, cardiac output (+38.1%) decreased compared with pECLA without CO2 removal, but stayed higher than during normocapnia/no pECLA shunt (P<0.05). In this animal model, mechanical ventilation with low V(T) was associated with HC and increased rCBF. CO2 removal by pECLA restored normocapnia, reduced rCBF to levels of normocapnia, but required a higher systemic blood flow for the perfusion of the pECLA device. If these results could be transferred to patients, extracorporeal CO2 removal might be an option for treatment of combined lung and brain injury in condition of a sufficient cardiac flow reserve.

HSC-specific inhibition of Rho-kinase reduces portal pressure in cirrhotic rats without major systemic effects

Rho-kinase activation mediates cell contraction and increases intrahepatic resistance and consequently portal pressure in liver cirrhosis. Systemic Rho-kinase inhibition decreases portal pressure in cirrhosis, but also arterial pressure. Thus, liver-specific Rho-kinase inhibition is needed. The delivery of Rho-kinase inhibitor to activated hepatic stellate cells reduces fibrosis. It might also relax these contractile cells and therewith decrease intrahepatic resistance. We tested this hypothesis by performing acute experiments in cirrhotic rats. Cirrhosis models were CCl(4)-intoxication and bile duct ligation. Three hours after injection of the Rho-kinase inhibitor (Y26732) coupled with a carrier (mannose-6-phosphate modified human serum albumin), which targets activated hepatic stellate cells, hemodynamics were analyzed by the colored microsphere technique and direct pressure measurements. The delivery site and effect of Rho-kinase inhibitor were investigated by immunohistochemical stainings, as well as Western blot. Experiments with Rho-kinase inhibitor coupled with unmodified human serum albumin served as untargeted control. In both models of cirrhosis, the carrier coupled Rho-kinase inhibitor lowered the portal pressure and decreased the hepatic-portal resistance. Immunohistochemical desmin-staining showed the carrier in hepatic stellate cells. The targeted therapy decreased the expression of the phosphorylated substrate of Rho-kinase (moesin) and abolished myosin light chains phosphorylation in fibrotic septae (collagen-staining). The targeted Rho-kinase inhibitor showed no major extrahepatic effects. By contrast, the untargeted Rho-kinase inhibitor elicited severe systemic hypotension. Activated hepatic stellate cells are crucially involved in portal hypertension in cirrhosis. Targeting of Rho-kinase in hepatic stellate cells not only decreased fibrosis, as previously shown, but also lowers portal pressure acutely without major systemic effects as demonstrated in this study.

374 HSC-DIRECTED RHO-KINASE INHIBITION IS AN EFFECTIVE AND SAVE APPROACH FOR TREATMENT OF PORTAL HYPERTENSION

Background: In liver cirrhosis Rho-kinase expression and activation is increased and mediates contraction of activated hepatic stellate cells (HSC) and therefore portal hypertension. Rho-kinase inhibition decreases myosin light chain phosphorylation and contraction of HSC. Consequently inhibition of Rho-kinase decreased portal pressure (PP). However, this was associated with serious side effects on systemic circulation. Mannose-6-phosphate-humanserum- albumin (M6P-HSA) modified compounds bind specifically to activated HSC. The Rho-kinase inhibitor (Y-27632) was coupled to this compound, and was tested with respect to its effect on portal pressure. Methods: CCl4 intoxication and bile-duct ligation (BDL) were used as models of cirrhosis in rats. Injections of an undirected compound or HSA served as controls. Rho-kinase inhibitor was injected i.v. 3 h later invasive measurements of PP and mean arterial pressure (MAP) were performed. Coloured microsphere technique analyzed portal and systemic hemodynamics. Organs were taken for further analyses. Double staining for HSA-carrier and desmin investigated the HSC specifity of the HSC-directed carrier. Rho-kinase activity was measured as the phosphorylation of its substrate moesin using phospho- and site-specific antibodies. Phospho-myosin light chain and collagen was immunohistologically stained in cirrhotic CCl4 rat liver sections to detect the Rho-kinase activity in HSC. Results: The HSC-directed carrier coupled to Rho-kinase inhibitor was localized within the HSC of cirrhotic livers. In contrast to the undirected Rho-kinase inhibition HSC-directed Rho-kinase inhibition decreased the Rho-kinase expression and activity. HSCdirected inhibition of Rho-kinase abolished phosphorylation of myosin light chains in fibrotic septae of cirrhotic rat livers as shown by immunohistology. HSC-directed Rho-kinase inhibitor decreased intrahepatic resistance and PP in vivo in CCL4 and BDL cirrhosis. In other tissues (kidney, heart, femoral muscle) the Rho-kinase expression and activity were not influenced by the HSC-directed Rho-kinase inhibitor. Discussion: The coupling of Rho-kinase inhibitor to M6P-HSA carriers is a save approach to lower portal pressure in portal hypertension. HSC-directed Rho-kinase inhibition should be further considered for a therapy of portal hypertension in cirrhosis.

Clarology for Conjugated Carbon Nano-Structures: Molecules, Polymers, Graphene, Defected Graphene, Fractal Benzenoids, Fullerenes, Nano- Tubes, Nano-Cones, Nano-Tori, etc.

Aim: The effects of Guanabenz, an agonist of α2-adrenergic receptors routinely used in human medicine as an antihypertensive drug, were studied on NaIO3-induced retinal pigment epithelium (RPE) degeneration, laser-induced choroidal neovascularization (CNV) and choroidal blood flow, in animal models.Methods: The 35mg/kg NaIO3-induced RPE degeneration rat eyes were instilled with 1% Guanabenz eye drops 3 times a day for 7 days before NaIO3 injection, and then 2 to 4 weeks thereafter. RPE function was measured with c-wave of electroretinogram (ERG). Male Brown Norway rats were anesthetized to receive Nd:YAG laser to break the Bruch’s membrane. One percent Guanabenz eye drops were given likewise. The development of CNV was determined by fluorescein angiography performed on week 2 and week 4 using sodium fluorescein (FA) or fluorescein isothiocyanatedextran (FD70-FA). Colored microsphere technique was used for in vivo experiments to determine the choroidal blood flow in ocular hypertensive (40 mmHg) rabbit eyes.Results: The RPE function was protected significantly by Guanabenz according to the c-wave of ERG. Four weeks after NaIO3 injection, the amplitude of ERG c-wave was 0.422±0.092 millivolts in the control group, 0.103±0.04 millivolts in the NaIO3 group, and 0.254±0.061 millivolts in the Guanabenz+NaIO3 group. There was a significant protection of the ERG c-wave by Guanabenz as compared to NaIO3 group (P<0.01). The angiograms of FD70-FA showed decreased lesion size in the Guanabenz group. Four weeks after laser treatment, the size of the CNV lesion was 2.99±0.18 mm2 in the control group, and 1.24±0.16 mm2 in the Guanabenz group (P<0.01). The choroidal blood flow was significantly increased at 30 and 60 minutes after Guanabenz instillation as compared to corresponding controls. Conclusions: Guanabenz significantly protected RPE from NaIO3-induced degeneration, inhibited the development of CNV in laser-induced rat AMD model and increased choroidal blood flow markedly in vivo.

Effect of Tetramethylpyrazine on RPE degeneration, choroidal blood flow and oxidative stress of RPE cells.

To study the effects of Tetramethylpyrazine (TMP) on retinal pigment epithelium (RPE) degeneration, choroidal blood flow and oxidative stress of RPE cells. The 35mg/kg NaIO(3)-induced RPE degeneration rat eyes was given 25µg 1% TMP eye drops 3 times a day for 7 days before NaIO(3) injection, and then 2 to 4 weeks after NaIO(3) injection. RPE function was measured with c-wave of electroretinogram (ERG). Colored microsphere technique was used for in vivo experiments to determine the choroidal blood flow in ocular hypertensive (40mmHg) rabbit eyes. Methylthiazoltetrazolium (MTT) assay was used to study in vitro effect of TMP on various oxidants induced injury in the hRPE (ARPE-19 (ATCC, Manassas, VA, USA)). Two weeks after NaIO(3) injection, the amplitude of ERG c-wave fell markedly in NaIO(3) group to 36% of control group(P<0.01). No apparent difference was observed in TMP+NaIO(3) group. Four weeks later, the NaIO(3) group fell to 46% of control group (P<0.01), while the TMP+NaIO(3) group fell to only 77% of control group (P<0.01). There was a 67% reversal of the ERG c-wave by TMP as compared to NaIO(3) group(P<0.01). The choroidal blood flow was significantly increased at all time points (at 30, 60 and 120 minutes after TMP instillation) as compared with corresponding controls. TMP had no effect on hypoxia-(1% O(2)), t-BHP- and H(2)O(2)-induced damage in RPE cells. 10(g/mL TMP could reverse 1 and 3mM NaN(3)-induced loss of viability of RPE by 18.5% (P<0.01) and 23% (P<0.01), respectively. 30µg/mL TMP could reverse 30 and 100mM NaIO(3) induced loss of viability of RPE by 18.1% (P<0.05) and 16.8% (P<0.01), respectively. TMP can significantly protect RPE from NaIO(3) induced degeneration in vivo and oxidative stress in vitro and can increase choroidal blood flow markedly in vivo.

Effect of flavone on the ocular blood flow and formation of choroidal neovascularization.

To investigate the effect of flavone on ocular blood flow in rabbit eyes and the formation of choroidal neovascularization (CNV) in rat model of age-related macular degeneration (AMD). In in vivo studies, colored microsphere technique was used to determine the ocular blood flow in ocular hypertensive rabbit eyes. The rat eyes were treated with 0.5% flavone eye drops 3 times a day for 1 week before and 4 weeks after laser-induced injury of Bruch's membrane. The development of CNV was determined by fluorescein angiography (FA) performed on the 2nd and 4th after injury. In in vitro studies, the effect of flavone on the viability of human umbilical vein endothelial cells HUVECs was measured by MTT assay. The ocular blood flow in rabbit eyes was significantly increased after flavone instillation. Flavone significantly inhibited the formation of laser induced CNV. In vitro results showed that flavone inhibited the proliferation of HUVECs. Flavone could increase ocular blood flow and inhibit the formation of CNV.

Abstract 5050: Wnt11 Enhances Mesenchymal Stem Cells Mediated Angiogenesis via Paracrine Signaling

Neovascularization is essential for an organ repair. It has been previously reported that MSC transfected with Wnt11 (MSC Wnt11 ) promotes ischemic heart repair through protecting native cardiomyocytes. However, the mechanism of cardioprotection of MSC Wnt11 remains unknown. Here, it is hypothesized that Wnt11 may enhance MSC mediated angiogenesis via the paracrine effects. Methods: MSCs were isolated from bone marrow of rats and transfected with Wnt11 using Clontech pMSCV retroviral expression system. MSCs transfected with GFP (MSC GFP ) were used as control. MSC (2×10 6 /50 μ l) were transplanted into the border area of ischemic rat hearts which have already underwent left anterior descending coronary artery (LAD) ligation. Four weeks post LAD ligation, regional myocardial blood flow in the ischemic and border zone was evaluated with a colored microsphere technique. The blood vessels were stained with von Willebrand factor (vWF) and counted in peri-infarct regions. Spontaneous capillary-like structure formation was monitored with Gelatin-coated Cytodex 3 microcarrier beads. The expression of growth factors was assayed by microarray and ELISA. Results: The blood flow was significantly increased and the density of blood vessel was higher in MSC Wnt11 transplanted heart than that in MSC GFP transplanted hearts (Fig. A, B ). Microcarrier beads were completely covered by MSC Wnt11 and formed a confluent monolayer and sprouts than MSC GFP (Fig. C ). Growth factors were highly expressed in MSC Wnt11 (Table and Fig. D ). Conclusions: Wnt11 promotes MSC mediated angiogenesis via up-regulating paracrine factors.

Transmural Peak Systolic Strain and Strain Rate Predict Transmural Myocardial Blood Flow in a Pig Myocardial Infarction Model

Objective: To test the hypothesis that the transmural variation of the longitudinal myocardial peak systolic strain (Sp) and strain rate (SRp) can predict the transmural distribution of myocardial blood flow (MBF) in a pig model of acute myocardial infarction. Methods: The longitudinal Sp and SRp were measured by echocardiography in both subendocardium (Sp-endo, SRp-endo) and subepicardium (Sp-epi, SRp-epi) in the normal, ischemic and infarct segments, respectively. The MBF in corresponding sites was measured by colored microspheres technique. The subendocardial to subepicardial ratio of Sp (Sp-EER), SRp (SRp-EER) and MBF (MBF-EER) were calculated. Results: In the normal segments, Sp-endo and SRp-endo were significantly higher than Sp-epi and SRp-ep, respectively. In the ischemic segments, Sp-endo and SRp-endo decreased to a greater extent than Sp-epi and SRp-epi, respectively. In the infarct segments, Sp-endo, SRp-endo Sp-epi and SRp-epi were all remarkably reduced. High correlations were found between Sp and SRp measurements and MBF in both subendocardium and subepicardium (r = –0.75 to –0.84, p < 0.001). Conclusion: Strain and strain rate imaging provides a reliable approach to the noninvasive estimation of the transmural blood distribution across the normal, ischemic and infarct segments.

Hemodynamic and tissue blood flow responses to long-term pneumoperitoneum and hypercapnia in the pig

Increased peritoneal blood flow may influence the ability of cancer cells to adhere to and survive on the peritoneal surface during and after laparoscopic cancer surgery. Carbon dioxide (CO2) pneumoperitoneum is associated with a marked blood flow increase in the peritoneum. However, it is not clear whether the vasodilatory effect in the peritoneum is related to a local or systemic effect of CO2. In this study, 21 pigs were exposed to pneumoperitoneum produced with either CO2 (n = 7) or helium (He) (n = 7) insufflation at 10 mmHg for 4 h, or to two consecutive levels of hypercapnia (7 and 11 kPa) (n = 7) produced by the addition of CO2 to the inhalational gas mixture. Tissue blood flow measurements were performed using the colored microsphere technique. Blood flow in peritoneal tissue increased during CO2, but not He, pneumoperitoneum, whereas it did not change at any level of hypercapnia alone. There was no change in blood flow in most organs at the partial pressure of CO2 (PaCO2) level of 7 kPa. However, at a PaCO2 of 11 kPa, blood flow was increased in the central nervous system, myocardium, and some gastrointestinal organs. The blood flow decreased markedly in all striated muscular tissues during both levels of hypercapnia. The effect of CO2 on peritoneal blood flow during laparoscopic surgery is a local effect, and not attributable to central hemodynamic effects of CO2 pneumoperitoneum or high systemic levels of CO2.

Evaluation of Laser Doppler Flowmetry for Measurement of Capillary Blood Flow in the Stomach Wall of Dogs During Gastric Dilatation‐Volvulus

To validate laser doppler flowmetry (LDF) for measurement of blood flow in the stomach wall of dogs with gastric dilatation-volvulus (GDV). Six purpose-bred dogs and 24 dogs with naturally occurring GDV. Experimental and clinical. Capillary blood flow in the body of the stomach and pyloric antrum was measured with LDF (tissue perfusion unit (TPU) before and after induction of portal hypertension (PH) and after PH plus gastric ischemia (GI; PH + GI) and compared with flow measured by colored microsphere technique. Capillary flow was measured by LDF in the stomach wall of dogs with GDV. PH and PH+GI induced a significant reduction in blood flow in the body of the stomach (P = .019). A significant positive correlation was present between percent changes in capillary blood flow measured by LDF and colored microspheres after induction of PH + GI in the body of the stomach (r = 0.94, P = .014) and in the pyloric antrum (r = 0.95, P = .049). Capillary blood flow measured in the body of the stomach of 6 dogs that required partial gastrectomy (5.00+/-3.30 TPU) was significantly lower than in dogs that did not (28.00+/-14.40 TPU, P = .013). LDF can detect variations in blood flow in the stomach wall of dogs. LDF may have application for evaluation of stomach wall viability during surgery in dogs with GDV.

Effects of Exogenous Big Endothelin-1 on Regional Blood Flow in Fetal Lambs

Endothelin-1, a 21 amino acid polypeptide produced by vascular endothelial cells, has potent vasoactive properties. The purpose of this study was to estimate the effects of exogenous big endothelin-1 on fetal lamb circulation. Regional blood flow was measured by the colored microsphere technique during continuous infusion (60 minutes) of big endothelin-1, or saline (control), in 12 chronically instrumented sheep fetuses. After 60 minutes of big endothelin-1 administration, the fetal plasma endothelin-1 concentration increased significantly from 24.0 +/- 6.7 to 49.7 +/- 31.4 pg/mL (P = .018) without significant changes in fetal arterial blood gases. Continuous infusion of big endothelin-1 decreased blood flow in most organs except the brain and the heart. After the big endothelin-1 infusion, the blood flow to the brain significantly increased from 158 +/- 51 to 174 +/- 71 mL/min/100 g (P = .002); the blood flow to the heart also increased significantly from 171 +/- 95 to 200 +/- 112 mL/min/100 g (P = .001), respectively. Continuous infusion of endothelin-1 decreases blood flow in most of organs except the brain and the heart. It is likely that endothelin-1 plays an important role in fetal redistribution of blood flow.

The Effect of Mild Hypothermia on Plasma Fentanyl Concentration and Biotransformation in Juvenile Pigs

Therapeutic hypothermia may alter the required dosage of analgesics and sedatives, but no data are available on the effects of mild hypothermia on plasma fentanyl concentration during continuous, long-term administration. We therefore assessed in a porcine model the effect of prolonged hypothermia on plasma fentanyl concentration during 33 h of continuous fentanyl administration. Seven female piglets (weight: 11.8 +/- 1.1 kg) were anesthetized by IV fentanyl (15 microg . kg(-1) . h(-1)) and midazolam (1.0 mg . kg(-1) . h(-1)). After preparation and stabilization (12 h), the animals were cooled to a core temperature of 31.6 degrees +/- 0.2 degrees C for 6 h and were then rewarmed and kept normothermic at 37.7 degrees +/- 0.3 degrees C for 6 more hours. Plasma fentanyl concentrations were measured by radioimmunoassay, cardiac index by thermodilution, and blood flows of the kidney, spleen, pancreas, stomach, gut, and hepatic artery by a colored microspheres technique. Furthermore, in an additional 4 pigs, temperature dependency of hepatic microsomal cytochrome P450 3A4 (CYP3A4) was determined in vitro by ethylmorphine N-demethylation. Plasma fentanyl concentration increased by 25% +/- 11% (P < 0.05) during hypothermia and remained increased for at least 6 h after rewarming. Hypothermia reduced the cardiac index (41% +/- 15%, P < 0.05), as well as all organ blood flows except the hepatic artery. A strong temperature dependency of CYP3A4 was found (P < 0.01). Mild hypothermia induced a distribution and/or elimination-dependent increase in plasma fentanyl concentration which remained increased for several hours after rewarming. Consequently, a prolonged increase of the plasma fentanyl concentration should be anticipated for appropriate control of the analgesia/sedatives during and early after therapeutic hypothermia.