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Biomedical subjects

A J Tector

Publications and source records attributed to A J Tector.

At least 19 recordsLinked to original sources
PubMed2006

In vitro monitoring of in vivo development of human anti-thymoglobulin antibodies by ELISA.

Thymoglobulin (rATG), polyclonal immunoglobulin, is prepared from rabbits immunized with human thymocytes. It is effective in prevention and treatment of renal allograft rejection. Human antibodies against antilymphocyte preparations can reduce efficacy by accelerating drug clearance or by inducing serum sickness. We developed an enzyme-linked immunosorbent assay (ELISA) to study posttreatment development of anti-rATG. In an Institutional Review Board-approved trial, we tested 101 allograft recipients for anti-rATG antibodies. Patients received rATG intravenously at 1.25 to 2.0 mg/kg/d for 2 to 14 days. Serum samples were obtained pretreatment and at weeks 1, 2, 4, 6, and months 3 and 6 post-rATG. ELISA plates were coated with rATG (10 microg/mL). Samples were diluted 1:100 and tested in quadruplicate. Positive samples were titrated. Horseradish peroxidase-conjugated (HRPO) affinity-purified goat anti-human immunoglobulin G (H&L) antibody reacted with bound human antibody. A chromagenic substrate for HRPO was added and optical density (OD, 490 nm) was read. An OD of twice the negative control was considered positive. Mean ODs of negative and positive controls were 0.113 +/- 0.030 and 1.042 +/- 0.196, respectively. Ten patients had detectable anti-rATG before rATG administration (1:100). Thirty-five of 101 patients (35%) developed anti-rATG antibody. Patients showed an initial positive anti-rATG antibody from days 8 to 59 after infusion and titers from 1:100 to 1:4000. In spite of rATG's postulated anti-B-cell activity, this study confirms that rATG induces sensitization at a frequency and titer seen with other xenogeneic antilymphocyte antibodies. Formation of such antixenoantibodies can have a negative impact on treatment response and hence warrant monitoring.

Animals↗
PubMed2005

Simultaneous liver and pancreas transplantation in patients with cystic fibrosis.

BACKGROUND: Improved survival in patients with cystic fibrosis (CF) has led to an increased incidence of extrapulmonary complications of this disease. Of these, cirrhosis and pancreatic insufficiency, including CF-related diabetes (CFRD) and exocrine insufficiency, are significant causes of morbidity and mortality. Liver transplantation is the treatment of choice for cirrhosis in this setting, but the addition of an isolated simultaneous pancreas transplant in patients with CFRD has not been reported. METHODS: Two female patients with CF underwent simultaneous pancreas and liver transplantation. Both had pancreatic insufficiency, CFRD, cirrhosis, and preserved renal function. In each case, the liver and pancreas were procured from a single cadaveric donor. The liver transplant was performed first. A lower midline extension was added for improved exposure of the iliac vessels. The donor pancreas transplant was performed with systemic venous drainage and enteric exocrine drainage. Immunosuppression included rabbit anti-thymocyte globulin, tacrolimus, mycophenolate mofetil, and early steroid withdrawal. RESULTS: Both patients recovered well with normal liver function, resolution of portal hypertension, and normal blood glucoses independent of insulin. As a result of the enteric exocrine drainage of the pancreas, they are now independent of supplemental pancreatic enzymes. CONCLUSIONS: Simultaneous liver and pancreas transplantation in CF patients provides the advantages of normalization of glucose and improved nutrition for patients requiring liver transplantation and should be considered in CF patients with CFRD who require liver transplants.

Adolescent↗
PubMed2004

HeartMate VE LVAS design enhancements and its impact on device reliability.

OBJECTIVE: The HeartMate VE left ventricular assist system (LVAS) has supported more than 2300 patients and has been shown to be effective for bridge to cardiac transplantation and has demonstrated improved outcomes in survival as a destination therapy. Improvements in device durability are needed as bridge to transplant times increase and as we move into the era of LVAD as destination therapy. The purpose of this study is to determine if design enhancements to the HeartMate LVAS have improved device reliability and durability. METHODS: A retrospective analysis of serious mechanical failures was performed in 1865 devices (1458 VE, 407 XVE). The analysis of data included devices used to support patients from September 1998 for bridge to transplantation and destination therapy. Serious mechanical failures were defined as inflow valve dysfunction, percutaneous lead breaks, diaphragm fractures or punctures, bearing failures, outflow graft erosion and pump disconnects. RESULTS: Median device duration for the VE was 97 days (max 1206 days), and 85 days (max 517 days) for the XVE. A total of 134 serious mechanical failures occurred and included inflow valve dysfunction (5.3% VE, 2.4% XVE) (P = 0.853) percutaneous lead breaks (1.9% VE, 0% XVE) (P < 0.001) diaphragm fractures (0.1% VE, 0% XVE) (P = 0.134) outflow graft erosion (0.2% VE, 0% XVE) (P = 0.1096), pump disconnects (0.1% VE, 0% XVE) (P = 0.1336) and bearing failures (0.6% VE, 0.2% XVE) (P = 0.5538). Of the XVEs 97% were free of serious mechanical failures at 6 months and 82% at 1 year compared to 92 and 73% for the VE, respectively. The 6-month difference between the devices was statistically significant (P = 0.0063) and there was no statistically significant difference at 1 year (P = 0.1492). CONCLUSIONS: Preliminary experience with the HeartMate XVE LVAS demonstrated a significant reduction in percutaneous lead breaks. Early trends indicate positive impact of recent design modifications on XVE performance. These design modifications may improve device durability and reliability, which is crucial as we enter the era of LVADs as an alternative to medical therapy.

Follow-Up Studies↗
PubMed2004

False-positive Histoplasma antigenemia caused by antithymocyte globulin antibodies.

False-positive Histoplasma antigen results were identified in two patients who received rabbit antithymocyte globulin (ATG, Thymoglobulin(R)) to prevent allograft rejection. To determine the prevalence of false-positive results following the administration of Thymoglobulin, sequential specimens were tested from a cohort of transplant recipients. Of 107 such patients, 17 (15.9%) demonstrated false-positive tests for Histoplasma antigenemia. False antigenemia peaked at 2-4 weeks after ATG administration and cleared over the next few months. Physicians should be aware of the potential for false-positive results in specimens from patients who have received ATG.

Animals↗
PubMed2001

Purely internal thoracic artery grafts: outcomes.

BACKGROUND: Most of our patients with coronary artery disease have undergone bypass exclusively with purely internal thoracic artery grafts (PITA). Our goal has been to lengthen the time a patient benefits from coronary bypass operations. The present report describes an 8.5-year study of outcomes including mortality and the need for reintervention in patients who have undergone bypass with PITA. METHODS: We studied 897 patients who underwent PITA with a total of 3,784 internal thoracic artery (ITA) grafts (4.2 grafts per patient). Connecting ITA to ITA along with sequential anastomosis made the procedure possible. RESULTS: Early mortality for the group was 2.3%. Freedom from death was 86% and freedom from reintervention was 94% at 5 years after the operation. CONCLUSIONS: The acceptable early and late mortality and the 94% freedom from reintervention as long as 8.5 years after operation in this group of patients inspire us to continue choosing PITA for patients with three-vessel coronary artery disease.

Adult↗
PubMed2001

Rejection of pig liver xenografts in patients with liver failure: implications for xenotransplantation.

The pathophysiological state of rejection in liver xenotransplantation is poorly understood. Data from clinical pig liver perfusion suggest that pig livers might be rejected less vigorously than pig hearts or kidneys. Pig livers used in clinical xenoperfusions were exposed to blood from patients with liver failure. We have shown in an animal model that transplant recipients with liver failure are less capable of initiating hyperacute rejection of a xenografted liver than a healthy transplant recipient. The goal of this report is to examine the pathological characteristics of pig livers used in 2 clinical pig liver perfusions and combine this information with in vitro studies of pig-to-human liver xenotransplantation to determine whether the findings in the perfused pig livers could be explained in part by the diminished capacity of the patient with liver failure to respond to xenogeneic tissue. Pathological analysis of the perfused pig livers showed immunoglobulin M deposition in the sinusoids with little evidence of complement activation. Our in vitro studies showed that serum from patients with liver failure caused less injury to pig liver endothelium than serum from healthy subjects. Serum from patients with liver failure had similar levels of xenoreactive antibodies as serum from healthy humans. Incubation of serum from patients with liver failure with pig hepatic endothelial cells generated less iC3b, Bb fragment, and C5b-9 than serum from healthy subjects. We conclude that the altered injury in the perfused pig livers can be attributed to the relative complement deficiency that accompanies liver failure.

Animals↗
PubMed2000

A native soluble form of CTLA-4.

CTLA-4 is an immunoregulatory receptor expressed on the surface of activated T and B lymphocytes. The counterreceptors for CTLA-4 are the B7 family molecules. We describe alternatively spliced mRNAs expressed in hematolymphoid tissues of humans, mice, and rats that lack the transmembrane domain coded by exon 3 of the CTLA-4 gene. These alternate transcripts were detected by RT-PCR in B cells and resting T cells of both the CD4 and the CD8 phenotype. Activation of human blood mononuclear cells with PHA or anti-CD3 + anti-CD28 monoclonal antibodies appears to effect a decrease in the amount of the alternative transcript relative to the full-length transcript. Recombinant sCTLA-4 is a B7-binding protein and has immunomodulatory effects as measured by inhibition of the mixed leukocyte response. Human serum contains immunoreactive material consistent with a native soluble form of CTLA-4.

Abatacept↗
PubMed2000

Experimental discordant hepatic xenotransplantation in the recipient with liver failure: implications for clinical bridging trials.

BACKGROUND: Clinical xenotransplantation might start with bridge-to-bridge trials. Situations where hyperacute rejection is avoided would provide opportunities for the initiation of bridging trials. Patients with liver failure have a diminished capacity to initiate antibody and complement-induced injury of xenogeneic endothelium. Hyperacute rejection of a liver xenograft manifests as a coagulopathy. We examined the ability of a recipient with liver failure to hyperacutely reject a liver xenograft in the dog-to-pig model in the immediate postoperative period. STUDY DESIGN: Liver failure in pigs was induced with galactosamine. Canine livers were transplanted into pigs with liver failure and into healthy pigs. The postoperative course was monitored for 1 hour for histologic changes in the xenograft, changes in platelet counts, and whole blood clotting with Sonoclot analysis. In vitro assays with pig serum and canine hepatic sinusoidal endothelial cells were used to assess the effect of liver failure on serum cytotoxicity and xenoreactive antibody levels. RESULTS: All untreated pig recipients of liver xenografts died from a coagulopathy. Recipients with liver failure manifested no signs of coagulopathy, and had minimal change in platelet counts or Sonoclot (Sienco Inc., Morrison, CO) tracings. Liver xenograft biopsies from recipients with liver failure showed no evidence of the tissue injury that characterized the biopsies of control recipients. Serum from pigs was less cytotoxic to the canine hepatic sinusoidal endothelium after induction of liver failure. The xenoreactive antibody levels and repertoire were similar in the pig serum before and after liver failure was induced. CH50 (total complement) levels were diminished in pigs after the induction of liver failure. CONCLUSIONS: Liver xenotransplantation used in bridging trials in recipients with liver failure might not face the barrier of hyperacute rejection.

Animals↗
PubMed1998

Transition from cardiopulmonary bypass to the HeartMate left ventricular assist device.

BACKGROUND: Safe transition from cardiopulmonary bypass to the HeartMate left ventricular assist device without periods of low output, air emboli, or injury to the right ventricle is vital to its successful implantation. A right atrial-to-left ventricular shunt has been developed to purge quickly and completely all air from the system and prevent its reentry, as well as to assist the right ventricle during the transition from cardiopulmonary bypass to the HeartMate. METHODS: From January 1994 through July 1996, we used an extracorporeal membrane oxygenation right atrial-to-left ventricular shunt during 17 HeartMate implantations in 16 patients. The shunt consists of the existing right atrial two-stage cannula, the bypass circuit, and a separate aortic line that fills the left ventricle using a 21F cannula in the lateral ventricular wall. Air is monitored in the heart and aorta using transesophageal echocardiography. RESULTS: Ten of the 16 patients are living and 8 have undergone transplantation. Two patients are still using the device and are awaiting transplantation. None of the patients have experienced postoperative neurologic events suggestive of air emboli. CONCLUSIONS: The extracorporeal membrane oxygenation right atrial-to-left ventricular shunt is simple and inexpensive to construct. It provides for a smoother and safer transition from cardiopulmonary bypass to the HeartMate left ventricular assist device.

Cardiopulmonary Bypass↗
PubMed1998

Pulmonary injury in recipients of discordant hepatic and renal xenografts in the dog-to-pig model.

Work in our lab demonstrated that the early post-operative course of discordant hepatic and renal xenotransplantation is complicated by a pulmonary injury. The aim of this study was to characterize the nature of this injury, as well as to determine whether endothelin-1 (ET-1) and inducible-nitric oxide synthase (iNOS) are present in this form of pulmonary injury. Dog-to-pig orthotopic liver and kidney xenografts were performed. Pulmonary artery pressures were monitored throughout all procedures. The lungs were stained with monoclonal antibodies for ET-1, endothelin converting enzyme-1, and iNOS. The lungs from pig recipients of hepatic or renal xenografts were compared to lungs from untreated pigs. Pulmonary artery pressures were elevated in recipients of liver xenografts when the suprahepatic caval cross clamp was placed and continued to rise to systolic levels following unclamping. The mean pulmonary artery pressures in recipients of renal and hepatic xenografts rose significantly following revascularization. Pathology in lungs from kidney and liver recipients was similar, showing congestion with peribronchial and septal edema, with diffuse adhesion of PMN to alveolar endothelium. ET-1, endothelin converting enzyme-1 (ECE-1), and iNOS staining was widespread and intense in alveolar and pulmonary arterial endothelium. Discordant xenotransplantation of livers and kidneys is associated with a significant early pulmonary injury that is associated with early PMN infiltration and expression of ET-1 and iNOS.

Animals↗
PubMed1998

Complement activation in discordant hepatic xenotransplantation.

Little is known about hyperacute rejection in hepatic xenotransplantation. Information from clinical xenoperfusions suggests that the liver may be rejected by a mechanism less vigorous than either kidney or heart xenografts. We used the in vitro model of porcine hepatic sinusoidal endothelial cells (PHEC) incubated with either complement replete or deficient human serum to determine the relative roles of the classical and alternate pathways of complement in the immediate response to hepatic xenotransplantation. Our results suggest that either the classical or alternate pathways are capable of independently activating the complement cascade upon exposure to the porcine hepatic sinusoidal endothelium. Our results also imply that either pathway alone is capable of initiating similar degrees of injury as the entire cascade.

Acute Disease↗
PubMed1997

Recurrence-free long-term survival after liver transplantation for hepatitis B using interferon-alpha pretransplant and hepatitis B immune globulin posttransplant.

OBJECTIVE: The authors determined whether pretransplant reduction of hepatitis B virus (HBV) load using alpha-interferon-2b (IFN) and passive immunoprophylaxis using hepatitis B immunoglobulin (HBIg) posttransplantation can prevent HBV recurrence in patients undergoing liver transplantation (LT) for HBV cirrhosis. SUMMARY BACKGROUND DATA: Liver transplantation in patients with HBV cirrhosis is associated with a high rate of recurrence and reduced survival. In patients with evidence of replicating virus (HBV-DNA or hepatitis B e antigen [HBeAg]-positive serum or both), recurrence is nearly universal. Passive immunoprophylaxis with HBIg alone is not effective in preventing HBV recurrence posttransplant, especially in patients with evidence of active viral replication pretransplant. Higher doses of HBIg posttransplant has reduced recurrence rates to 30% to 50%. Lamivudine, a nucleoside analogue that has shown early promise, also is associated with significant HBV recurrence. The authors report a reliable method of preventing viral recurrence in patients even with evidence for active HBV replication pretransplant. METHODS: Pretransplant patients with evidence of replicating HBV were given IFN starting at 1 million IU 3 times per week subcutaneously. This dose was increased to 2 and then 3 million IU 3 times per week when patient's side effects permitted and was maintained until the patient underwent a LT. All patients were tested every 4 weeks for hepatitis B surface antigen (HBsAg), HBeAg, and HBV-DNA. When patients became negative for HBeAg and HBV-DNA, they were listed for LT. Patients that were only HBsAg positive were listed immediately and received a LT without prior IFN treatment. Post-LT, all patients began receiving HBIg 2000 IU (10 mL) daily from days 1 to 20 and then weekly for the first 2 years. After 2 years, all patients received 2000 IU (10 mL) monthly. Additional HBIg immunoprophylaxis was given during intense immunosuppression for rejection. Posttransplant serum was tested for HBsAg, HBeAg, and HBV-DNA in all patients 1 week, 1 month, and every 3 months thereafter. Liver biopsies were done at least yearly and when liver enzymes were abnormal and were always tested for HBsAg and HBcAg by immunoperoxidase. RESULTS: Thirteen patients with decompensated HBV cirrhosis were transplanted. Pretransplant, eight patients had evidence of active viral replication at the initial assessment (HBeAg or HBV-DNA-positive serum or both). All eight were successfully treated with IFN (median duration, 24 weeks; range, 8-53) and converted to a negative status before transplantation. Side effects from IFN were minimal and well tolerated, except in one patient who required 6 million IU to convert to a nonreplicating status. The five patients that were only HBsAg positive were not treated with IFN pretransplant. After surgery, HBIg given as described achieved consistently serum levels greater than 1000 IU/L. Twelve of the 13 patients are alive with normal liver function and without serologic evidence of HBV recurrence at a median follow-up of 32 months (range, 9-56 months). None have evidence of HBV recurrence as measured by serum HBsAg/HBeAg/HBV-DNA at recent follow-up. The sera of the seven longest survivors has tested negative for HBV-DNA using the polymerase chain reaction method. In addition, a liver biopsy was obtained in six of these patients, the results of which also tested negative for HBV-DNA using polymerase chain reaction. Liver biopsy specimens have been negative for the presence of HBsAg and HBcAg by immunoperoxidase staining in all 12 patients. CONCLUSION: A reduction of viral load pretransplant with IFN and posttransplant HBIg prevents recurrence of hepatitis B and permits LT for HBV cirrhosis, even in patients with evidence of replicating virus. The IFN pretransplant was well tolerated, and the small frequent dosing of HBIg posttransplant did not cause side effects while achieving serum levels > 1000 IU/L.

Adult↗
PubMed1996

Complete revascularization with internal thoracic artery grafts.

Saphenous vein graft atherosclerosis continues to be the major cause of late failures of coronary artery bypass operations (CABG). The internal thoracic artery (ITA) is an ideal bypass graft because it remains free of atherosclerosis at late follow-up in most patients. Myocardial revascularization with only ITA grafts has developed in an incremental manner from single grafts of the left ITA to the left anterior descending coronary artery (LAD), to use of bilateral, free and sequential ITAs, and now recently to the use of preconstructed grafts that attach the free right ITA to the left ITA. The microanatomy and vascular reactivity of the ITA have been recently defined, and they explain why the ITA remains free of obstruction. Our techniques and results of ITA grafting developed over the past 25 years are presented.

Anastomosis, Surgical↗
PubMed1995

Reoperation in patients with closed SVG and patient LITA-LAD graft: T-graft approach.

Selection of the bypass graft that the patient has demonstrated will remain patent and free from critical atherosclerosis is a most important part of coronary artery bypass reoperations. Sixteen patients in whom a patent left internal thoracic artery-left anterior descending coronary artery bypass graft and obstructed or closed saphenous vein grafts to other coronary arteries were visualized underwent reoperation. To reach the inadequately perfused circumflex and right coronary arteries, the right internal thoracic artery was anastomosed to the left internal thoracic artery as a T graft and then was attached to the circumflex and right coronary artery branches. All patients survived the procedure and are free from angina. There were no perioperative myocardial infarctions, and there was no suggestion of hypoperfusion by the grafts. We believe this technique may reduce the incidence of graft failure in patients undergoing reoperative coronary artery bypass grafting.

Adult↗
PubMed1995

Polymerase chain reaction cloning and expression of the rat granulocyte-macrophage colony-stimulating factor.

We used reverse transcription-polymerase chain reaction (RT-PCR) to clone a rat complementary DNA that encoded the PVG rat granulocyte-macrophage colony-stimulating factor (GM-CSF). PCR products were cloned into a eukaryotic expression vector and transfected into the mouse myeloma cell line Sp2/0-Ag14. Cell culture supernatants of two of these transfectants supported proliferation of the growth factor-dependent cell line, DA-3, and promoted myeloid colony formation in rat and mouse bone marrow cell (BMC) cultures. The GM-CSF activity in these supernatants was neutralized by a polyclonal antibody to mouse GM-CSF. The cloning and expression of rat GM-CSF provides a valuable reagent for the study of the biology and clinical applications of the GM-CSFs.

Amino Acid Sequence↗