**4.2 Rejection**

Hyperacute rejection occurs within 24 hours after anastomosis of the major vessels. It is a complement-mediated response caused by the recipient having pre-existing IgM antibodies to donor antigens (such as ABO, platelet and HLA antigens). Hyperacute rejection of unmatched blood type is mainly mediated by IgG antibodies. In this study, hyperacute rejection caused two deaths. Acute rejection is the most common rejection reaction after transplantation. It is clinically manifested by fever, general malaise, pain, transplant swelling and functional impairment. CD4 Th1 cell-mediated delayed hypersensitivity is the main cause of transplant injury. Transplant HLA stimulates T lymphocyte differentiation and proliferation in the recipient, producing large numbers of sensitized lymphocytes which can damage or kill target cells by releasing lymphokines. In this study, acute rejection caused six deaths in the long-term postoperative period. CD4+T and CD8+T cells may change significantly in acute rejection, followed by worsening of liver function and sometimes death. The pathological characteristics of acute rejection are: (1) inflammatory cell infiltration of the portal area, including activated lymphocytes, neutrophils and eosinophilic granulocytes, (2) endothelial cell inflammation of the portal vein or central vein and (3) bile duct inflammation and injury. Animals with at least two of these characteristics in association with liver dysfunction can be diagnosed with acute rejection. Inflammatory cell infiltration involving > 50% of the bile duct or involving the portal area or central vein are evidence of acute rejection.

### **4.3 Hepatic artery thrombosis**

Studies have reported that hepatic artery anastomosis in a rat model of orthotopic liver transplantation does not influence survival rate or survival time. However, hepatic artery anastomosis is critical in clinical liver transplantation, because hepatic artery thrombosis can cause transplant loss in a short period of time, requiring emergency surgery or even repeat transplantation. Dissection of rhesus monkeys shows that the outer diameter of the proper hepatic artery is 3–4 mm and the inner diameter is 1–2 mm, supplying a large amount of blood to the liver. Liver parenchyma and bile duct necrosis may therefore occur if the hepatic artery is not reconstructed, affecting post-transplant acute rejection and decreasing the survival rate. The cut end of the common hepatic artery can be trimmed into a bellmouth shape to allow full anastomosis. This simplifies the arterial anastomosis for clinical liver transplantation. In this study, the hepatic artery was reconstructed using microsurgical techniques. There were no deaths due to hepatic artery thrombosis or stenosis in the early postoperative period, but hepatic artery thrombosis caused one death in the short-term postoperative period and three deaths in the long-term postoperative period. Hepatic artery thrombosis is mainly caused by the following factors: (1) the artery is very thin and the intima is fragile and easily injured during surgery, which significantly increases the incidence of thrombosis, (2) the rhesus monkey has a relatively low body mass, (3) a hypercoagulable state is common in the rhesus monkey and (4) rejection causes damage to the tunica intima, resulting in degeneration or necrosis and subsequent arterial thrombosis.

### **4.4 Pulmonary infection**

540 A Bird's-Eye View of Veterinary Medicine

modification used direct anastomosis, which is a complex and time-consuming process, increasing the duration of the anhepatic phase and resulting in circulatory and other systemic problems following portal vein opening. Liver transplantation may also lead to coagulation disorders, resulting in wound hematoma. In this study, seven animals (28%) died of abdominal hemorrhage following transplantation; five (71.4%) in the early

Hyperacute rejection occurs within 24 hours after anastomosis of the major vessels. It is a complement-mediated response caused by the recipient having pre-existing IgM antibodies to donor antigens (such as ABO, platelet and HLA antigens). Hyperacute rejection of unmatched blood type is mainly mediated by IgG antibodies. In this study, hyperacute rejection caused two deaths. Acute rejection is the most common rejection reaction after transplantation. It is clinically manifested by fever, general malaise, pain, transplant swelling and functional impairment. CD4 Th1 cell-mediated delayed hypersensitivity is the main cause of transplant injury. Transplant HLA stimulates T lymphocyte differentiation and proliferation in the recipient, producing large numbers of sensitized lymphocytes which can damage or kill target cells by releasing lymphokines. In this study, acute rejection caused six deaths in the long-term postoperative period. CD4+T and CD8+T cells may change significantly in acute rejection, followed by worsening of liver function and sometimes death. The pathological characteristics of acute rejection are: (1) inflammatory cell infiltration of the portal area, including activated lymphocytes, neutrophils and eosinophilic granulocytes, (2) endothelial cell inflammation of the portal vein or central vein and (3) bile duct inflammation and injury. Animals with at least two of these characteristics in association with liver dysfunction can be diagnosed with acute rejection. Inflammatory cell infiltration involving > 50% of the bile duct or involving the portal area or central vein

Studies have reported that hepatic artery anastomosis in a rat model of orthotopic liver transplantation does not influence survival rate or survival time. However, hepatic artery anastomosis is critical in clinical liver transplantation, because hepatic artery thrombosis can cause transplant loss in a short period of time, requiring emergency surgery or even repeat transplantation. Dissection of rhesus monkeys shows that the outer diameter of the proper hepatic artery is 3–4 mm and the inner diameter is 1–2 mm, supplying a large amount of blood to the liver. Liver parenchyma and bile duct necrosis may therefore occur if the hepatic artery is not reconstructed, affecting post-transplant acute rejection and decreasing the survival rate. The cut end of the common hepatic artery can be trimmed into a bellmouth shape to allow full anastomosis. This simplifies the arterial anastomosis for clinical liver transplantation. In this study, the hepatic artery was reconstructed using microsurgical techniques. There were no deaths due to hepatic artery thrombosis or stenosis in the early postoperative period, but hepatic artery thrombosis caused one death in the short-term postoperative period and three deaths in the long-term postoperative period. Hepatic artery thrombosis is mainly caused by the following factors: (1) the artery is very thin and the intima is fragile and easily injured during surgery, which significantly increases the

postoperative period and two (28.6%) in the short-term postoperative period.

**4.2 Rejection** 

are evidence of acute rejection.

**4.3 Hepatic artery thrombosis** 

Pulmonary infection is one of the causes of early death following reduced-size liver transplantation in rats, and may be due to an infection focus prior to surgery or to aspiration during surgery. Kamada et al proposed that an anhepatic phase of 26 minutes was safe. Shortening of the anhepatic phase to restore organ perfusion and maintain hemodynamic function is one method to reduce the rate of pulmonary infection following reduced-size liver transplantation, as pulmonary infection is associated with prolonged blood vessels clamping. Prolonged clamping of the portal vein causes prolonged intestinal tract congestion, increasing the likelihood of enteric bacteria entering the circulation and of inflammation-induced lung injury. Preoperative intramuscular atropine to reduce respiratory secretions, small tidal volume anesthesia to reduce aspiration and comfortable living environment and surgical conditions can help to prevent pulmonary infection in rats. In this study, pulmonary infection caused one death in the short-term postoperative period and two deaths in the long-term postoperative period.

#### **4.5 Other causes of death following liver transplantation**

One animal in this study died due to primary nonfunction and one due to pneumothoraxinduced respiratory failure. Both these animals underwent transplantation using our original surgical model. The primary nonfunction may have been due to the significant fatty degeneration (> 50%) of the donor liver and the differences in weight between donor and recipient causing microhepatia. This animal underwent an anhepatic phase of approximately 1 hour with significant blood loss after portal vein opening, and deteriorated postoperatively with high bilirubin levels, hypoventilation, mydriasis, respiratory arrest and cardiac arrest. Autopsy showed no bleeding, a large amount of ascites in the abdominal cavity and gaseous distension of the gastrointestinal tract. In one animal, the diaphragm was damaged during surgery, resulting in pneumothorax. This animal died due to respiratory failure despite attempted treatment. Autopsy showed a normal liver, no abdominal bleeding or ascites, a bulging diaphragm, gas in the abdominal cavity and collapse of both lungs.

Compared with the rat model, establishment of an orthotopic liver transplantation model in large animal such as the monkey is more difficult. There are some important issues to consider to improve animal survival rate following liver transplantation. The quality of the donor liver is a key factor, and donation of an unhealthy liver is not appropriate. The weight of recipient and donor livers should be similar for the donor liver to function well. Intraoperative blood loss and injury to tissues and organs should be minimized. The modified cuff technique can minimize the duration of the anhepatic phase and of anesthesia, reducing circulatory and other systemic problems. Care should also be taken in perioperative management. This study analyzes the causes of death of rhesus monkeys at different stages following liver transplantation, which can help to modify models of liver transplantation to improve survival rate and to increase the quality of future experimental studies.

Causes of Death of Rhesus Monkeys Undergoing Liver Transplantation 543

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10


**27** 

*China* 

Ningying Xu and Xiaoling Jiang

*Zhejiang University,* 

**Molecular Characterization of Hypothalamo–**

Almost all the body functions of vertebrate animals including swine are regulated by the nervous system and endocrine system. Especially the hormones released from the endocrine system have effective biological amplifying effects. Minor changes in the hormone level

Hypothalamus, extensively connected with other brain regions, is the vital bridge between nervous system and endocrine system. It exerts its regulating function on endocrine system mainly via the pituitary, which is the central endocrine organ in vertebrate animals. Except the growth hormone, most of the hormones secreted by pituitary have their specific target organs. For example, thyrotropin target thyroid. The hypothalamus, pituitary and target organs are always described together as "axis", e.g. hypothalamo-pituitary-gonadal axis, hypothalamo-pituitary-adrenal gland axis, and hypothalamo-pituitary-thyroid (HPT) axis.

Hypothalamus synthesizes and secrets thyrotropin-releasing-hormone (TRH) to send regulating information to pituitary (see Figure 1). TRH binds to the thyrotropin-releasinghormone receptors (TRHR) on the thyrotroph cells of pituitary to activate the intracellular signal pathways and induce the secretion and synthesis of thyrotropin (TSH). Circulating TSH in blood then binds to the thyrotropin receptors (TSHR) on the follicular cells of

TH secreted by thyroid is important to growth, development, and protein, fat, and carbohydrate metabolisms (Porterfield and White, 2007). It acts on almost all the organs and tissues. Each individual has a unique thyroid function set-point, and this set-point was suggested to be genetically determined (Hansen et al., 2004). Genetic variations of the hormones of HPT axis and their respective receptors could be the excellent candidates as the

Thyrotropin releasing hormone, produced in the paraventricular nucleus of the hypothalamus, is fully conserved in all species from human to bony fish that have been

thyroid to activate the synthesis and secretion of thyroid hormone (TH).

**1. Introduction** 

could cause huge alternations in physiology.

**2. The axis of hypothalamo-pituitary-thyroid** 

causing of related phenotype variations.

**2.1 Thyrotropin releasing hormone gene (***TRH***)** 

**Pituitary-Thyroid Genes in Pig (Sus Scrofa)** 

