A new modified canine model of portal vein thrombosis

Portal vein thrombosis (PVT) is a common complication of liver cirrhosis. Gao et al. [1] reported that the prevalence of PVT in patients with cirrhosis is 8.82%. With the rapid developments in image-based diagnostic technology, the diagnosis rate of PVT is gradually increasing [2]. A follow-up study of 1243 patients with cirrhosis revealed that the cumulative incidences of PVT at 1, 3, and 5 years are 4.6%, 8.2%, and 10.7%, respectively [3]. PVT is a life-threatening factor for patients with cirrhosis, leading to portal hypertension and aggravating gastrointestinal hemorrhage [4]. The prevention of PVT has become a focus of clinical concern nowadays. It is well known that the establishment of animal models is the basis of scientific research. However, it is currently difficult to establish PVT models in large animals. Thereby, the establishment of a stable PVT animal model to study PVT is urgent and significant. We successfully established a new canine model of PVT involving the injection of an autologous thrombus through an indwelling catheter in the portal vein. This model is reliable for further studies of surgical treatment and drug therapy for PVT.     

Effects of the combined administration of propranolol plus sorafenib on portal hypertension in cirrhotic rats

Low doses of sorafenib have been shown to decrease portal pressure (PP), portal-systemic shunts, and liver fibrosis in cirrhotic rats. Nonselective beta blockers (NSBB) are the only drugs recommended for the treatment of portal hypertension. The aim of our study was to explore whether the combination of propranolol and sorafenib might show an additive effect reducing PP in cirrhotic rats. Groups of common bile duct-ligated cirrhotic rats (CBDL) and sham-operated control rats were treated by gavage with vehicle, propranolol (30 mg·kg(-1)·day(-1)), sorafenib (1 mg·kg(-1)·day(-1)), or propranolol+sorafenib. Treatment began 2 wk after the CBDL or sham operation. Hemodynamic evaluation was performed after 2 wk of treatment. In cirrhotic rats, propranolol and sorafenib produced a significant (P < 0.001) and similar reduction in PP (-19 and -15%, respectively). This was achieved through different mechanisms: whereas propranolol decreased PP by reducing portal blood flow (-35%; P = 0.03), sorafenib decreased PP without decreasing portal flow indicating decreased hepatic resistance. After propranolol+sorafenib, the fall in PP was significantly greater (-30%; P < 0.001) than with either drug alone, demonstrating an additive effect. However, the reduction in portal flow (-39%) under combined therapy was not significantly greater than after propranolol alone. Sorafenib, alone or in combination with propranolol, produced significant reduction in portal-systemic shunting (-25 and -33%, respectively), splanchnic vascularization (-37 and -41%, respectively), liver fibrosis (38%), and hepatic neovascularization (-42 and -51%, respectively). These effects were not observed after propranolol alone. In conclusion, the combination of propranolol+sorafenib causes a greater reduction in PP than either drug alone and decreases markedly the extent of portal-systemic shunting, splanchnic and hepatic neovascularization, and liver fibrosis, suggesting that this drug combination is a potentially useful strategy in the treatment of portal hypertension.     

A novel,simplified, and reproducible porcine model of acute ischemic liver failure with portal vein preservation

The current ischemic models of liver failure are difficult and usually time-consuming to produce. The aim of this study was to develop a simplified and reproducible porcine model of acute liver failure for use in preclinical research. Eighteen Bama miniature pigs were randomly divided into Groups A, B, and C. The hepatic artery and common bile duct were ligated in all groups. While the portal vein was completely preserved in Group A, it was narrowed by 1/3 and 1/2 in Groups B and C, respectively. Results of biochemical analyses, encephalopathy scores, and survival times were compared among the groups. Results of hematoxylin-eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, Masson staining, and Ki-67 analyses were recorded. Survival times in Groups B and C were 11.67 ± 1.86 and 2.16 ± 0.75 days, respectively, shorter than that in Group A (>15 days). Following surgery, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, total bilirubin, and direct bilirubin levels significantly increased relative to baseline values in all groups (P<0.05). Groups B and C exhibited a significant decrease in encephalopathy scores and a significant increase in ammonia levels, which were negatively correlated with one another. Pathological analysis revealed obvious necrosis of liver cells, which correlated closely with the degree of portal vein constriction. Our simple, highly reproducible model effectively mimics the clinical characteristics of acute liver failure in humans and provides a foundation for further research on artificial liver support system development.     

肝硬化门脉高压症食道胃底静脉破裂出血的治疗

目的：探讨Child C级肝硬化门脉高压症食道胃底静脉破裂出血病人的安全有效的治疗方案。方法：对89例急性大出血入院的Child C级肝硬化门脉高压症病人的治疗结果进行回顾性分析,对外科手术（19例）、内科治疗（51例）和TIPSS（颈内静脉肝内门体分流术）（19例）三种治疗方法的疗效、并发症和死亡率进行对比。结果：急诊手术、内科治疗、TIPSS的住院死亡率分别为65．5％。36．1％和26．3％;住院期间再出血率分别为24．1％,36．1％％15．8％。随访期的再出血率分别为33．0％,36．1％和21．4％。住院死亡率手术组显著高于另外两组（P〈0.01）。TIPSS组的住院再出血率及随访期再出血率显著低于内科组（P〈0．05和P〈0.01）。三组病人的生存率无显著性差异（Kaplan—Meier分析,P=0．07〉0．05）。结论：TIPSS作为一种微创介入技术是一种挽救Child C级门脉高压症食管静脉破裂出血病人生命的有效方法。其止血效果不亚于手术治疗,死亡率低于手术治疗,而再出血率低于内科治疗。更长期的疗效尚待进一步研究。     

A novel vein graft model: adaptation to differential flow environments

Accelerated intimal hyperplasia in response to altered flow environment is critical to the process of vein bypass graft failure. Lack of a reproducible animal model for dissecting the mechanisms of vein graft (VG) remodeling has limited progress toward solving this clinically significant problem. Combining a cuffed anastomotic technique with other surgical manipulations, we developed a well-defined, more robust method for studying hemodynamic factors in VG arterialization. VG with fistula placement, complete occlusion, or partial distal branch ligation (DBL) was performed in the carotid artery of 56 rabbits. Extensive hemodynamic and physiological analyses were performed to define the hemodynamic forces and histological adaptations of the wall at 1-28 days. Anastomotic time averaged 12 min, with 100% patency of bilateral grafts and unilateral grafts plus no adjunct or delayed fistula. Bilateral VG-DBL resulted in an immediate disparity in wall shear (0.8 +/- 0.1 vs. 12.4 +/- 1.1 dyn/cm2, ligated vs. contralateral graft). Grafts exposed to low shear stress responded primarily through enhanced intimal thickening (231 +/- 35 vs. 36 +/- 18 microm, low vs. high shear). High-shear-stress grafts adapted through enhanced outward remodeling, with a 24% increase in lumen diameter at 28 days (3.0 +/- 0.1 vs. 3.7 +/- 0.2 mm, low vs. high shear). We have taken advantage of the cuffed anastomotic technique and combined it with a bilateral VG-DBL model to dissect the impact of hemodynamic forces on VG arterialization. This novel model offers a robust, clinically relevant, statistically powerful small animal model for evaluation of high- and low-shear-regulated VG remodeling.     

急诊断流术在门静脉高压症并食道胃底静脉出血的疗效观察

目的观察急诊断流术在门静脉高压症并食道胃底静脉出血的临床疗效。方法选取我院收治的门静脉高压症并食道胃底静脉出血患者103例,随机分为两组。对照组52例,在患者入院后先采取保守止血治疗,再择期进行断流术;观察组51例,在患者入院后立即采取急诊断流术治疗。观察比较两组的临床疗效。结果观察组患者术后死亡率为11.76%,对照组为25.00%,两组比较差异有统计学意义(P0.05)。观察组患者住院时间短于对照组,差异有统计学意义(P0.05)。经随访3~4年,观察组再次出血发生率为12.76%,对照组再次出血发生率为13.46%,两组比较差异无统计学意义(P0.05)。结论急诊断流术在门静脉高压症并食道胃底静脉出血的临床疗效显著,可降低患者死亡率,缩短住院时间,值得临床应用。     

Effects of somatostatin in patients with portal hypertension

Portal hypertension is a common complication of chronic liver disease. Conventional therapy consists of surgery and palliative measures for the hemodynamic problem. It has been recently reported that somatostatin may reduce portal pressure without altering the systemic circulation and so reducing hepatic blood flow. This peptide also causes a significant fall in azygos circulation in patients with esophageal varices. The mechanism of this effect is unclear although suppression of intestinal vasodilating hormones and of glucagon have been claimed to play a role. Comparative clinical studies have shown somatostatin to be superior to the standard vasopressin treatment. Recent findings suggest that the efficacy of somatostatin can be increased by administering this peptide in repeated intravenous bolus injections. New derivatives, specially long-acting peptides, may eventually prove beneficial in the chronic treatment of this complication.     

肝硬化门脉高压症大鼠模型制作方法的探讨

目的：建立稳定可靠的肝硬化门脉高压大鼠动物模型。材料与方法：50只雄性sD大鼠,随机分为3组。正常对照组10只,行假手术,给予正常饮食。肝硬化A组20只,先行左肾上腺静脉结扎,然后给予初始浓度为0．03％的硫代乙酰胺（thioacetamide,TAA）溶液作为饮用水并根据大鼠体重变化调节给药浓度。肝硬化B组20只,行假手术,给予固定浓度为0．03％TAA溶液。给药时间为14周。结果：肝硬化A组大鼠死亡率为0,肝硬化形成率达到100％。肝硬化B组大鼠死亡率15％,肝硬化形成率75％。肝硬化A组大鼠的门静脉压力明显高于肝硬化B组和对照组。结论：采用左肾上腺静脉结扎并根据体重变化调节TAA给药浓度可建立稳定可靠的肝硬化门脉高压大鼠动物模型。     

Increased plasma volume in two models of portal hypertension in the rat: cirrhosis of the liver and partial portal vein ligation

Portal hypertension has been studied in the rat to see if it is associated to altered blood volume composition, as it has been shown in other species. Plasma volume was measured by isotope dilution using 99mTc labelled albumin in three groups of male Sprague-Dawley rats: normal rats (controls), partially ligated portal vein rats and rats with Cl4C induced cirrhosis. Plasma volume was significantly higher in rats with portal hypertension due to partially ligated portal vein and cirrhosis than in control animals. Similarly, the calculated blood volume was also significantly higher in the portal hypertensive animals than in control group. Portal hypertension in the rat, therefore, has been demonstrated to be associated to a marked hypervolemia and this finding should be taken into consideration in haemodynamic and pharmacokinetic studies in portal hypertensive rat models.     

Spaceflight regulates ryanodine receptor subtype 1 in portal vein myocytes in the opposite way of hypertension

Gravity has a structural role for living systems. Tissue development, architecture, and organization are modified when the gravity vector is changed. In particular, microgravity induces a redistribution of blood volume and thus pressure in the astronaut body, abolishing an upright blood pressure gradient, inducing orthostatic hypotension. The present study was designed to investigate whether isolated vascular smooth muscle cells are directly sensitive to altered gravitational forces and, second, whether sustained blood pressure changes act on the same molecular target. Exposure to microgravity during 8 days in the International Space Station induced the decrease of ryanodine receptor subtype 1 expression in primary cultured myocytes from rat hepatic portal vein. Identical results were found in portal vein from mice exposed to microgravity during an 8-day shuttle spaceflight. To evaluate the functional consequences of this physiological adaptation, we have compared evoked calcium signals obtained in myocytes from hindlimb unloaded rats, in which the shift of blood pressure mimics the one produced by the microgravity, with those obtained in myocytes from rats injected with antisense oligonucleotide directed against ryanodine receptor subtype 1. In both conditions, calcium signals implicating calcium-induced calcium release were significantly decreased. In contrast, in spontaneous hypertensive rat, an increase in ryanodine receptor subtype 1 expression was observed as well as the calcium-induced calcium release mechanism. Taken together, our results shown that myocytes were directly sensitive to gravity level and that they adapt their calcium signaling pathways to pressure by the regulation of the ryanodine receptor subtype 1 expression.     

A mathematical model of canine granulocytopoiesis

Summary The granulocyte cell renewal system of the dog is represented by a mathematical model consisting of the following compartments: The pool of pluripotential stem cells, the committed stem cell pool, divided into a blood and a bone marrow compartment, the proliferation pool, the maturation pool, the reserve pool and the blood pool of functional granulocytes. This chain of compartments is described by a system of non-linear differential equations. Cell losses anyplace in the system provoke increased production in all pools containing cells capable to divide. A reduced number of granulocytes in the blood pool stimulates production of a granulocyte releasing factor which mobilizes a rising number of cells to transit from the marrow reserve into the blood pool.The model was simulated on a digital computer. It was found to be capable to reproduce the steady state conditions and it also fits the data of two distinct experimental perturbations of the system both equally well. These perturbations are a loss of proliferating cells as it occurs after the administration of cytostatic drugs and losses of functional cells as they are induced by leukapheresis experiments of differing leukapheresis rates.This study was supported by the Deutsche Forschungsgemeinschaft (SFB 112)     

Hepatic neovascularization after partial portal vein ligation: novel mechanism of chronic regulation of blood flow

The present study was undertaken to investigate hepatic microcirculatory response following partial portal vein ligation (PPVL) in rats. Portal pressure was markedly increased 2-6 wk after PPVL, but no significant reduction in sinusoidal perfusion and hepatocellular injury were detected. However, marked neovascularization was observed in PPVL rats using intravital microscopy and scanning electron microscopy (SEM). Extremely high red blood cell velocity (2,000-4,900 microm/s) was seen in these vessels. Injection of fluorescein sodium via the carotid artery revealed that the neovessels originated from the hepatic arterial vasculature. This was further confirmed by clamping the common hepatic artery and phenylephrine injection from the carotid artery. These vessels maintained sufficient flow after massive sinusoidal shutdown elicited by the portal infusion of endothelin receptor B agonist IRL-1620. SEM also showed extensive neovascularization at the hilum. Additionally, clamping the portal vein decreased sinusoidal perfusion only by 9.5% in PPVL, whereas a 71.2% decrease was observed in sham. These results strongly suggest that the liver maintains its microcirculatory flow by vascular remodeling from the hepatic arterial vasculature following PPVL.     

Role of thromboxane A2 in early BDL-induced portal hypertension

Although the mechanisms of cirrhosis-induced portal hypertension have been studied extensively, the role of thromboxane A(2) (TXA(2)) in the development of portal hypertension has never been explicitly explored. In the present study, we sought to determine the role of TXA(2) in bile duct ligation (BDL)-induced portal hypertension in Sprague-Dawley rats. After 1 wk of BDL or sham operation, the liver was isolated and perfused with Krebs-Henseleit bicarbonate buffer at a constant flow rate. After 30 min of nonrecirculating perfusion, the buffer was recirculated in a total volume of 100 ml. The perfusate was sampled for the enzyme immunoassay of thromboxane B(2) (TXB(2)), the stable metabolite of TXA(2). Although recirculation of the buffer caused no significant change in sham-operated rats, it resulted in a marked increase in portal pressure in BDL rats. The increase in portal pressure was found concomitantly with a significant increase of TXB(2) in the perfusate (sham vs. BDL after 30 min of recirculating perfusion: 1,420 +/- 803 vs. 10,210 +/- 2,950 pg/ml; P < 0.05). Perfusion with a buffer containing indomethacin or gadolinium chloride for inhibition of cyclooxygenase (COX) or Kupffer cells, respectively, substantially blocked the recirculation-induced increases in both portal pressure and TXB(2) release in BDL group. Hepatic detection of COX gene expression by RT-PCR revealed that COX-2 but not COX-1 was upregulated following BDL, and this upregulation was confirmed at the protein level by Western blot analysis. In conclusion, these results clearly demonstrate that increased hepatic TXA(2) release into the portal circulation contributes to the increased portal resistance in BDL-induced liver injury, suggesting a role of TXA(2) in liver fibrosis-induced portal hypertension. Furthermore, the Kupffer cell is likely the source of increased TXA(2), which is associated with upregulation of the COX-2 enzyme.     

Insulin secretion-independent effects of GLP-1 on canine liver glucose metabolism do not involve portal vein GLP-1 receptors

Whether glucagon-like peptide (GLP)-1 requires the hepatic portal vein to elicit its insulin secretion-independent effects on glucose disposal in vivo was assessed in conscious dogs using tracer and arteriovenous difference techniques. In study 1, six conscious overnight-fasted dogs underwent oral glucose tolerance testing (OGTT) to determine target GLP-1 concentrations during clamp studies. Peak arterial and portal values during OGTT ranged from 23 to 65 pM and from 46 to 113 pM, respectively. In study 2, we conducted hyperinsulinemic-hyperglycemic clamp experiments consisting of three periods (P1, P2, and P3) during which somatostatin, glucagon, insulin and glucose were infused. The control group received saline, the PePe group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally, the PePo group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally (P2) and then intraportally (P3), and the PeHa group received GLP-1 (1 pmol.kg(-1).min(-1)) peripherally (P2) and then through the hepatic artery (P3) to increase the hepatic GLP-1 load to the same extent as in P3 in the PePo group (n = 8 dogs/group). Arterial GLP-1 levels increased similarly in all groups during P2 ( approximately 50 pM), whereas portal GLP-1 levels were significantly increased (2-fold) in the PePo vs. PePe and PeHa groups during P3. During P2, net hepatic glucose uptake (NHGU) increased slightly but not significantly (vs. P1) in all groups. During P3, GLP-1 increased NHGU in the PePo and PeHa groups more than in the control and PePe groups (change of 10.8 +/- 1.3 and 10.6 +/- 1.0 vs. 5.7 +/- 1.0 and 5.4 +/- 0.8 micromol.kg(-1).min(-1), respectively, P < 0.05). In conclusion, physiological GLP-1 levels increase glucose disposal in the liver, and this effect does not involve GLP-1 receptors located in the portal vein.