Correlation Between Blood Transfusion and Blood Glucose Levels in Adult Living Donor Liver Transplantation.

BACKGROUND: To evaluate the effect of dextrose contained in banked blood products on the changes of blood glucose levels in adult living donor liver transplantation patients retrospectively. METHODS: Four hundred seventy-seven patients were divided into a non-blood transfusion (BT) group (G1) and a BT group (G2). The changes in blood glucose levels during the operation were compared using a Mann-Whitney U test, and a P value less than .05 was regarded as significant. RESULTS: No significant changes were detected in blood glucose levels after anesthesia, during dissection phase, in the anhepatic phase, or after reperfusion between the groups. Estimated blood loss for G1 (n = 89) and G2 (n = 388) were 718 ± 514 and 5804 ± 877 mL respectively, G1 had no blood transfusion but G2 had received 4350 ± 6230 mL leukocyte-poor red blood cell transfusion, the pre- and end operation hemoglobin for G1 and G2 were 13.2 ± 2.0, 10.2 ± 1.9 and 10.1 ± 1.6, 10.2 ± 1.9 mg/dL respectively, indicating that they were not under or over transfused. CONCLUSION: When banked blood products are used to replace ongoing blood loss, the dextrose contained in citrate-phosphate-dextrose-adenine seems to have no effect on the changes in the blood glucose levels of the recipients.

Comparison of Core Temperature Changes Between Pediatric Patients Lying on Regular Operating Room Linen Drapes and Water-Repellent Sheepskin Rug in Living Donor Liver Transplantation.

OBJECTIVES: The aims of this study were to compare the core temperature changes between pediatric patients lying on regular operating room linen drapes and a water-repellent sheepskin rug during living donor liver transplantation (LDLT) and to evaluate the effectiveness of using a water-repellent sheepskin rug in preventing profound hypothermia due to fluid overflow from the abdominal cavity during LDLT. PATIENTS AND METHODS: The operative records of pediatric patients who underwent LDLT from June 1994-September 2003 were reviewed retrospectively. The nasopharyngeal temperature (NT) changes during the LDLT procedure between patients lying on regular operating room drapes (GI) and water-repellent sheepskin rug (GII) were compared and analyzed using the Mann-Whitney U test. A P value <.05 was regarded as significant. RESULTS: Thirty-two patients were included in GI and 56 in GII. Profound hypothermia was not observed in any recipients lying on a water-repellent sheepskin rug (GII). The NT after induction and the following 4 hours into the LT procedure were significantly higher in GII than GI. CONCLUSION: Pediatric patients lying on water-repellent sheepskin preserved their core temperature better in comparison to patients lying on linen drapes. The use of a water-repellent sheepskin rug seems to be effective in preventing profound hypothermia related to physical contact with abdominal fluid overflow during the LDLT.

Eye Protection in Liver Transplantation Patients Under General Anesthesia.

BACKGROUND: Opsite (Smith & Nephew, Hull, UK) is widely used in wound care but its use in eye protection against corneal abrasion during major surgery is rarely reported. The purpose of the current study is to compare the effectiveness of using Opsite in eye protection with either wet gauze alone or with wet gauze following application of eye ointment in patients undergoing living donor liver transplantation (LDLT). METHODS: This is a prospective, double-blinded, randomized controlled trial. Forty-one patients undergoing liver transplantation were enrolled. One eye of each patient was protected with sterile gauze soaked with normal saline solution and covered with Opsite. Duratears (ALCON, Fort Worth, Tex, United States) ointment was applied to the other eye before covering it with sterile wet gauze and Opsite (ointment group). The corneal examination was carried out after fluorescein staining before and at the end of surgery by the same doctor. A Student t-test and a χ2 test were used for the statistical analyses. RESULTS: Forty-one patients with 82 eyes were observed in this study. No corneal epithelial defects were found in either the normal saline group or the ointment group. CONCLUSION: Opsite combined with wet gauze with or without additional eye ointment provided 100% protection against corneal abrasion in patients undergoing LDLT.

Anesthesia Management and Fluid Therapy in Right and Left Lobe Living Donor Hepatectomy.

OBJECTIVE: Right lobe living donor hepatectomy poses a greater risk for the donor in relation to blood loss. The aims of this study were to compare anesthetic and intraoperative fluid management in right and left lateral segment living donor hepatectomy. PATIENTS AND METHODS: The anesthesia records of living donor hepatectomy patients were retrospectively reviewed. Donor age and weight, anesthesia time, central venous pressure, blood loss, blood product transfusion, intravenous fluids used, doses of furosemide, and urine output were compared and analyzed between groups using the Mann Whitney U test. RESULTS: Forty-six patients underwent living donor left lateral segment hepatectomy (Group I); while 31 patients underwent right lobe hepatectomy (Group II). The mean blood loss in Group II was significantly higher compared to Group I (118 ± 81 mL vs 68 ± 64 mL), but clinically such amount of blood loss was not high enough to affect the hemodynamics. The fluid management was therefore not meaningfully different between the two groups. No blood transfusions or colloid infusions were required for either group. Urine output, hemoglobin changes, blood urea nitrogen, and serum creatinine pre- and postoperatively were not significantly different between groups. CONCLUSIONS: As long as blood loss is minimal, we found no difference in the anesthetic management and fluid replacements between right and left lateral segment living donor hepatectomy.

The Correlation Between CVP and SVV and Intraoperative Minimal Blood Loss in Living Donor Hepatectomy.

BACKGROUND: Blood loss during liver surgery is found to be correlated with central venous pressure (CVP). The aim of the current retrospective study is to find out the cutoff value of CVP and stroke volume variation (SVV), which may increase the risk of having intraoperative blood loss of more than 100 mL during living liver donor hepatectomies. METHOD AND PATIENTS: Twenty-seven adult living liver donors were divided into 2 groups according to whether they had intraoperative blood loss of less (G1) or more than 100 mL (G2). The mean values of the patients' CVP and SVV at the beginning of the transaction of the liver parenchyma was used as the cutoff point. Its correlation to intraoperative blood loss was evaluated using the χ2 test; P < .001 was regarded as significant. RESULTS: The cutoff points of CVP and SVV were 8 mm Hg and 13% respectively. The odds ratio of having blood loss exceeding 100 mL was 91.25 (P < .001) and 0.36 (P < .001) for CVP and SVV, respectively. CONCLUSION: CVP less than 5 mm Hg, as suggested by most authors, is not always clinical achievable. Our results show that a value of less than 8 mm Hg or SVV 13% is able to achieve a minimal blood loss of 100 mL during parenchyma transaction during a living donor hepatectomy. Measurements used to lower the CVP or increased SVV in our serial were intravenous fluids restriction and the use of a diuretic.

The impact of hepatitis B virus infection and vaccination on the development of non-Hodgkin lymphoma.

Hepatitis B virus (HBV) infection has been documented as a risk factor for non-Hodgkin lymphoma (NHL). However, there are few large cohort studies, and there is no report about the impact of HBV vaccination. We conducted this study to evaluate these issues. We used the nationwide cohort of the Taiwan National Health Insurance Research Database for 1997-2013. We compared the incidence and the risk of developing NHL and CD20+ aggressive lymphoma between HBV and non-HBV cohorts. The hazard ratios (HRs) were computed using Cox proportional hazards models. We matched these two large cohorts to reconfirm the data. We also compared the incidence of NHL between cohorts born before and after the inception of universal HBV vaccination. We found that HBV infection increased the risk for developing NHL and CD20+ aggressive lymphoma, with HRs of 4.14 and 5.52, with a higher incidence of 17.07 and 13.9 per 100 000 person-years, respectively, compared to the non-HBV cohort. The incidence of NHL in the cohort born in the era before universal HBV vaccination was higher with 1.85 per 100 000 person-years compared to 0.74 in the cohort born later aged younger than 20. Our study confirms that HBV confers a greater risk for developing NHL, especially CD20+ aggressive lymphoma. The impact of HBV vaccination is protective against lymphoma development in the teenagers in an endemic area, but longer follow-up is needed for older age.

Predictive Risk Factors in the Development of Intraoperative Hyperkalemia in Adult Living Donor Liver Transplantation.

BACKGROUND: Hyperkalemia, defined as a serum potassium level higher than 5 mEq/L, is common in the liver transplantation setting. Severe hyperkalemia may induce fatal cardiac arrhythmias; therefore, it should be monitored and treated accordingly. The aim of the current retrospective study is to evaluate and indentify the predictive risk factors of hyperkalemia during living-donor liver transplantation (LDLT). METHODS AND PATIENTS: Four hundred eighty-seven adult LDLT patients were included in the study. Intraoperative serum potassium levels were monitored at least five times during LDLT; patients with a potassium level higher than 5 mEq/L were included in group 1, and the others with normokalemia in group 2. Patients' categorical characteristics and intraoperative numeric variables with a P value <.1 were selected into a multiple binary logistic regression model. In multivariate analysis, a P value of <.05 is regarded as a risk factor in the development of hyperkalemia. RESULTS: Fifty-one of 487 (10.4%) patients had hyperkalemia with a serum potassium level higher than 5.0 mEq/L during LDLT. Predictive factors with P < .1 in univariate analysis (Table 1), such as anesthesia time, preoperative albumin level, Model for End-stage Liver Disease score, preoperative bilirubin level, amount of blood loss, red blood cell (RBC) and fresh frozen plasma transfused, 5% albumin administered, hemoglobin at the end of surgery, and the amount of furosemide used, were further analyzed by multivariate binary regression. Results show that the anesthesia time, preoperative serum albumin level, and RBC count are determinant risk factors in the development of the hyperkalemia in our LDLT serials. CONCLUSION: Prolonged anesthesia time, preoperative serum albumin level, and intraoperative RBC transfusion are three determinant factors in the development of intraoperative hyperkalemia, and close monitoring of serum potassium levels in patients with abovementioned risk factors are recommended.

Relationship Between Patients With or Without a History of Esophageal Varices Bleeding and the Changes in Hemodynamics During Inferior Vena Cava Clamping in Living Donor Liver Transplantation.

BACKGROUND: Whether the history of esophageal variceal bleeding (EVB) can be used clinically to predict the tolerability or hemodynamic instability during clamping of the inferior vena cava (IVC) and portal vein in liver transplantation is unknown and, therefore, needs to be elucidated. PATIENTS AND METHODS: A total of 50 anesthesia charts of patients who underwent living donor liver transplantation were reviewed, analyzed and compared retrospectively. Patients without a history of EVB were classified as group 1 and patients with a history of EVB were classified as group 2. The numbers of patients with a decrease in cardiac index (CI) of ≥20%, ≥30%, or ≥40% from their preclamping values after IVC clamping were compared with a χ(2), and a P value of .05 was regarded as statistically significant. RESULTS: The measured hemodynamic parameters before and 5 minutes after clamping of the IVC and portal vein were all significantly different in comparison with the patient's preclamping values. The incidence of a decrease in CI of ≥20%, ≥30%, or ≥40% 5 minutes after clamping of the IVC and portal vein were not significantly different between groups. CONCLUSIONS: Clamping of the portal vein and IVC without performing veno-venous bypass in living donor liver transplantation had a significant negative impact on CI in both groups due to the drastic reduction in the venous return. Statistical analysis revealed that a history of EVB affects hemodynamics in a manner similar to that in patients without history of EVB during IVC clamping.

Preoperative Portal Vein Velocity/Size and Effect on Living Donor Liver Transplantation Recipient Hemodynamics During Inferior Vena Cava Clamping.

BACKGROUND: The aim of this study is to determine whether preoperative portal vein flow velocity or size has any correlative effect on hemodynamic changes during clamping of the inferior vena cava in liver transplantation. PATIENTS AND METHODS: A total of 42 anesthesia charts of adult patients who underwent living donor liver transplantation (LDLT) were analyzed and compared retrospectively. Preoperative portal vein (PV) flow velocity and sizes were obtained using Doppler ultrasound. All changes in the hemodynamic data before and after clamping of the portal vein (PV) and inferior vena cava (IVC) were recorded and analyzed by linear regression. A P value of <.05 was considered significant. RESULTS: Heart rate (HR), mean arterial blood pressure (MAP), central venous pressure (CVP), cardiac output (CO), cardiac index (CI), and stroke volume (SV) before and after clamping of the PV and IVC were significantly different for as long as the PV and IVC were clamped. Linear regression analysis indicated that R2 of HR, MAP, CVP, CO, and CI in correlation with the PV velocity were 0.002, 0.035, 0.024, and 0.001; R2 of the PV diameter for HR, MAP, CVP, CO, and CI were 0.028, 0.01, 0.034, and 0.004. The changes in the percentages of cardiac output at 1- and 5-minute intervals after IVC clamping were not correlated significantly with either the preoperative flow velocity or the size of the PV. CONCLUSION: Preoperative PV flow velocity and size are not correlated or associated with hemodynamic changes during IVC clamping in liver transplantation.

Effects of Pre-Existing Liver Disease on Acute Pain Management Using Patient-Controlled Analgesia Fentanyl With Parecoxib After Major Liver Resection: A Retrospective, Pragmatic Study.

BACKGROUND: The aim of this study was to compare the outcomes of pain management with the use of patient-controlled analgesia (PCA) fentanyl with IV parecoxib between patients with healthy liver with patients with diseased liver undergoing major liver resection. METHODS: Patients with healthy liver undergoing partial hepatectomy as liver donors for liver transplantation (group 1) and patients with liver cirrhosis (Child's criteria A) undergoing major liver resection for hepatoma (group 2) were identified retrospectively. Both groups routinely received post-operative IV PCA fentanyl and a single dose of parecoxib 40 mg. They were followed up for 3 days or until PCA fentanyl was discontinued post-operatively. Daily Visual Analog Scale, PCA fentanyl usage, rescue attempts, and common drug side effects were collected and analyzed with the use of SPSS version 20. RESULTS: One hundred one patients were included in the study: 54 in group 1, and 47 in group 2. There were no statistical differences between the two groups in terms of the daily and total fentanyl usage, VAS resting, and incidence of itchiness. The rate of rescue analgesia on post-operative day (POD) 1 was lower in group 2, with a value of P = .045. VAS dynamics were better on POD 1 and 2 for group 2, with P = .05 and P = .012, respectively. CONCLUSIONS: We found that combining a single dose of IV parecoxib 40 mg with PCA fentanyl is an easy and effective method of acute pain control after major liver resection. We propose the careful usage of post-operative fentanyl and parecoxib in patients with diseased liver, given the difference in effect as compared with healthy liver.

Retrospective Cohort Study to Compare Anesthesia in Living Donor Liver Transplantation Recipients Who Received Single and Dual Liver Grafts.

OBJECTIVE: Dual graft living donor liver transplantation (LDLT) is an alternative way to overcome small-for-size syndrome in LDLT. Surgical technique and outcome of using dual grafts have been reported, but there are no reports regarding anesthetic management. The aim of the current study is to compare the anesthetic management of single graft and dual graft liver transplantation. METHODS AND PATIENTS: Anesthesia records of 24 single graft liver transplantation recipients (GI) and 6 dual graft recipients (GII) were reviewed, analyzed, and compared retrospectively. Patient characteristics and intraoperative data between groups were compared with Mann-Whitney t test and Fisher's exact test where appropriate. P value less than .05 was regarded as significant. RESULTS: Patient characteristics and most of the intraoperative data were similar between groups. Significant difference was noted in the total anesthesia time and the anhepatic time. Both times were significantly longer in GII compared to GI. CONCLUSION: Dual graft living donor liver transplantation is surely a technically more challenging and demanding procedure. Therefore the total anesthesia time is longer, especially the anhepatic phase, because there are more graft vessels to be reconstructed before reperfusion. Overall the anesthetic management in terms of blood transfusion, fluid administration, sodium bicarbonate, calcium supplement, and the number of patients requiring fractional diluted noradrenaline support for maintenance of acceptable hemodynamic were not much different between the 2 groups.

Correlation Between Changes in End-Tidal Carbon Dioxide Concentration and Cardiac Output During Inferior Vena Cava Clamping and Unclamping in Living-donor Liver Transplantation.

BACKGROUND: To test the hypothesis that low end-tidal carbon dioxide tension encountered during anhepatic phase in liver transplantation is related to hemodynamic status rather than ventilatory status, and can be used to predict the change in cardiac output during anhepatic phase. METHODS: We retrospectively analyzed and compared data, included end-tidal carbon dioxide tension (ETCO2), arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index, and stroke volume, before and after inferior vena cava clamping, and 0, 5, 10, 30 minutes during the anhepatic, and 5 minutes after the release of IVC cross clamp during the reperfusion phase, with paired Student t test, repeated measurement, and linear regression. P < .05 was regarded as significant. RESULTS: The cardiac output and ETCO2 decrease significantly after clamping the inferior vena cava and increase concomitantly after unclamping. There is a positive correlation between the changes in % in cardiac output and ETCO2 (Pearson coefficient r = 0.741). CONCLUSION: The changes in ETCO2 can be used to predict the changes of the cardiac output in % when cardiac output monitoring is not available. Before unclamping of the IVC, mild hyperventilation is suggested to prevent excessive increase in PaCO2.

The impact of joint range of motion limitations on health-related quality of life in patients with haemophilia A: a prospective study.

In patients with haemophilia A, repeated occurrences of haemarthrosis and synovitis lead to limitations in range of motion (ROM) of major joints. However, the effect of limitations in joint ROM on health-related quality of life (HRQOL) in these patients has not been studied previously. The aim of this study was to assess the impact of ROM limitations of 10 major joints (bilateral shoulders, elbows, hips, knees and ankles), combined with other possibly influential factors, on HRQOL in patients with haemophilia A. The ROM limitations in 13 movements and pain intensity of the 10 major joints were measured. The socio-demographic and clinical data were recorded. Short-Form 36 was used as the HRQOL measurement. Eighteen patients (mean age: 36.9 years) were included. Hip ROM limitations, knee ROM limitations and hip pain intensity predicted physical functioning scale (P < 0.001; adjusted R2 = 0.553). Shoulder ROM limitations and age predicted role limitation were due to emotional problems scale (P < 0.001; adjusted R2 = 0.373). Elbow ROM limitations and haemophilia severity predicted mental health scale (P = 0.001; adjusted R2 = 0.320). Hip ROM limitations predicted social functioning scale (P = 0.041; adjusted R2 = 0.091). Educational level and elbow ROM limitations predicted vitality scale (P < 0.001; adjusted R2 = 0.416). The ROM limitations of hip, knee, shoulder and elbow could be predictors for HRQOL in patients with haemophilia A. Improving ROM of major joints could be an appropriate treatment strategy to enhance HRQOL in these patients.

Detection of human papillomavirus in the oral cavities of persons with Fanconi anemia.

OBJECTIVE: We conducted a cross-sectional study to describe the prevalence and correlates of type-specific human papillomavirus (HPV) DNA in the oral cavities of persons with Fanconi anemia. MATERIALS AND METHODS: Oral swabs were collected from 67 participants with Fanconi anemia and tested for 27 HPV genotypes using polymerase chain reaction-based methods. RESULTS: Participants were a mean of 18.6 (standard deviation, 10.0) years of age (range 4-47 years). The prevalence of oral HPV infection was 7.5%, and the prevalence of high-risk HPV infection was 6.0%. HPV type 16 was not detected in any samples. Prevalence was higher in adults than in children (13.3% vs 2.7% in those ≥18 vs <18 years of age). Among adults, prevalence was higher in males than in females (25.0% vs 9.1%, respectively). CONCLUSIONS: Prevalence of oral HPV infection in persons with Fanconi anemia was comparable to estimates from other studies in the general population. However, in contrast to previous studies, we did not identify HPV type 16 (the type found in most HPV-related head and neck cancers) in any participants.

Favorable clinical outcome and unique characteristics in association with Twist1 overexpression in de novo acute myeloid leukemia.

Epithelial-mesenchymal transition (EMT) is a critical process for inducing stem-like properties of epithelial cancer cells. However, the role of EMT inducers in hematological malignancies is unknown. Twist1, an EMT inducer necessary for cell migration, has recently been found to have transcriptionally regulatory activity on the expression of Bmi1, and these two are capable of promoting tumorigenesis in a synergized manner. Knowing that Bmi1 expression is essential for maintenance of leukemic stem cells, we speculate that Twist1 might govern the pathogenesis of acute myeloid leukemia (AML) development as well. We found that upregulated Twist1 increased Bmi1 expression in AML and endued leukemic cells a higher proliferative potential and increased resistance to apoptosis. In primary AML samples, there was strong positive correlation between the expression levels of Twist1 and Bmi1. AML patients whose leukemic blasts harbored overexpressed Twist1 had a more aggressive clinical phenotype, but they were more likely to have a better clinical outcome after standard therapy. In vitro studies confirmed that Twist1-overexpressing leukemic cells were more susceptible to cytarabine, but not daunorubicin, cytotoxicity. Our findings suggest that, in a subset of AML patients, Twist1 has a prominent role in the pathogenesis of the disease that leads to unique clinical phenotypes.

Can coronary vein size predict hemodynamic instability during inferior vena cava clamping in liver transplantation?

OBJECTIVE: This study aimed to determine whether coronary vein size can serve as a predictor of hemodynamic instability during inferior vena cava clamping in living-donor liver transplantations. METHODS: Fifty-two patients' hemodynamic data before and after clamping were retrospectively analyzed and compared with the use of linear regression and repeated measurement. Data included arterial blood pressure, heart rate, central venous pressure, cardiac output, cardiac index, stroke volume, stroke volume variation, and systemic vascular resistance. RESULTS: The values of hemodynamic parameters at 1, 3, 10, and 30 minutes after clamping were compared with baseline data. All changes were found to be significant when the presence of the coronary vein was not considered. When the coronary vein was taken into consideration, linear regression analysis showed that only the percentage changes of cardiac index; stroke volume at 1, 3, and 10 minutes; and systemic vascular resistance at 1 minute after portal and inferior vena cava clamping were significantly correlated with the presence of the coronary vein. CONCLUSIONS: Coronary vein size is a weak predictor of hemodynamic tolerability and instability during portal vein and inferior vena cava clamping in this kind of surgery.

Efficacy and safety of dose-modified docetaxel plus cisplatin-based induction chemotherapy in Asian patients with locally advanced head and neck cancer.

WHAT IS KNOWN AND OBJECTIVE: The beneficial effects of docetaxel plus cisplatin-based induction chemotherapy for patients with unresectable, advanced head and neck cancer (HNC) have been documented in Western countries. However, the efficacy of such treatment has not been confirmed in Asian patients. We aimed to determine whether incorporation of dose-modified docetaxel into a cisplatin-based induction regimen would be both effective and tolerable in our Asian population of patients. METHODS: Thirty-six patients with stage III or IV HNC who had undergone cisplatin-based induction chemotherapy were included in the current analysis. Fifty-three percentage of the patients had received induction chemotherapy with bolus cisplatin and continuous 5-fluorouracil (PF group), while the remaining 47% had additionally received dose-modified docetaxel (TPF group). We assessed the relative impact of the two treatments on clinical outcomes and treatment-related toxicities. RESULTS AND DISCUSSION: The disease control rate was higher in the TPF group (92·9% vs. 76·5%), although the difference did not reach statistical significance (P = 0·217). Addition of docetaxel increased the median progression-free survival to 435 days, which was 2·3 times longer than that (188 days) of patients not receiving docetaxel (P = 0·019). Non-haematological toxicity profile was similar and acceptable in both treatment groups. Higher incidence of grade 3/4 neutropenia and more episodes of neutropenic fever-related hospitalization occurred in the docetaxel-treated patients, but most of them were managed uneventfully. WHAT IS NEW AND CONCLUSION: Addition of dose-modified docetaxel to cisplatin-based induction chemotherapy was both efficacious and generally safe. Docetaxel addition significantly prolonged progression-free survival and had an acceptable safety profile in our Asian population of patients with locoregionally advanced HNC.

Roles for ligases in the RNA editing complex of Trypanosoma brucei: band IV is needed for U-deletion and RNA repair.

Trypanosome RNA editing utilizes a seven polypeptide complex that includes two RNA ligases, band IV and band V. We now find that band IV protein contributes to the structural stability of the editing complex, so its lethal genetic knock-out could reflect structural or catalytic requirements. To assess the catalytic role in editing, we generated cell lines which inducibly replaced band IV protein with an enzymatically inactive but structurally conserved version. This induction halts cell growth, showing that catalytic activity is essential. These induced cells have impaired in vivo editing, specifically of RNAs requiring uridylate (U) deletion; unligated RNAs cleaved at U-deletion sites accumulated. Additionally, mitochondrial extracts of cells with reduced band IV activity were deficient in catalyzing U-deletion, specifically at its ligation step, but were not deficient in U-insertion. Thus band IV ligase is needed to seal RNAs in U-deletion. U-insertion does not appear to require band IV, so it might use the other ligase of the editing complex. Furthermore, band IV ligase was also found to serve an RNA repair function, both in vitro and in vivo.

The two RNA ligases of the Trypanosoma brucei RNA editing complex: cloning the essential band IV gene and identifying the band V gene.

Kinetoplastid RNA editing is a posttranscriptional insertion and deletion of U residues in mitochondrial transcripts that involves RNA ligase. A complex of seven different polypeptides purified from Trypanosoma brucei mitochondria that catalyzes accurate RNA editing contains RNA ligases of approximately 57 kDa (band IV) and approximately 50 kDa (band V). From a partial amino acid sequence, cDNA and genomic clones of band IV were isolated, making it the first cloned component of the minimal RNA editing complex. It is indeed an RNA ligase, for when expressed in Escherichia coli, the protein autoadenylylates and catalyzes RNA joining. Overexpression studies revealed that T. brucei can regulate of total band IV protein at the level of translation or protein stability, even upon massively increased mRNA levels. The protein's mitochondrial targeting was confirmed by its location, size when expressed in T. brucei and E. coli, and N-terminal sequence. Importantly, genetic knockout studies demonstrated that the gene for band IV is essential in procyclic trypanosomes. The band IV and band V RNA ligases of the RNA editing complex therefore serve different functions. We also identified the gene for band V RNA ligase, a protein much more homologous to band IV than to other known ligases.