Keith Reemtsma

The role of CD4+ helper T cells in the destruction of microencapsulated islet xenografts in nod mice.

Islet transplants for large numbers of patients with diabetes will require xenografts. Microencapsulation is an appealing method for islet xenografting. However, graft function has been limited by a cellular reaction, particularly intense in spontaneously diabetic, NOD mice. The purpose of this study was to elucidate the mechanism of this reaction. Poly-1-lysine-alginate microcapsules containing 4000-12,000 dog or 1800-2000 rat islets were xenografted intraperitoneally into streptozotocin (SZN)-diabetic C57BL/6J and NOD mice, with or without recipient treatment with GK 1.5 (anti-CD4 monoclonal antibody) (20-30 microliters i.p. every 5 days, begun on day -7. Grafts were considered technically successful if random blood glucose (BG) was normalized (less than 150 mg/dl) within 36 hr. Graft failure was defined as BG greater than 250 mg/dl. Dog and rat islets in microcapsules normalized BG in both SZN and NOD mice within 24 hr routinely. Empty microcapsules and GK 1.5 treatments alone did not affect BG. NODs destroyed both microencapsulated dog and rat islets more rapidly than did SZN-diabetic mice (P less than .01). Graft biopsies showed an intense cellular reaction, composed of lymphocytes, macrophages and giant cells, and no viable islets. GK 1.5 treatment significantly prolonged both dog-to-NOD and rat-to-NOD grafts (P less than 0.01). Biopsies of long-term functioning grafts (on days 65-85) demonstrated viable islets and no cellular reaction around microcapsules; 1/4 rat and 1/8 dog islet xenografts continued to function indefinitely in NOD recipients, even after cessation of GK 1.5 therapy. Prediabetic NODs receiving encapsulated dog or rat islets mounted a moderate cellular reaction to grafts. Empty microcapsules excited no cellular reaction in diabetic or prediabetic NODs. We conclude that the NOD reaction to microencapsulated xenogeneic islets is helper T cell-dependent, and that the target of this reaction is not the microcapsule itself, but the donor cells within.

Cost-effectiveness of coronary artery bypass surgery in octogenarians.

OBJECTIVE The objective of this retrospective cohort study was to determine whether coronary artery bypass graft (CABG) surgery is effective and cost-effective relative to medical management of coronary artery disease (CAD) in the elderly. SUMMARY BACKGROUND DATA The aging of the U.S population and the improvements in surgical techniques have resulted in increasing numbers of elderly patients who undergo this surgery. The three randomized, controlled trials (RCTs) that established the efficacy of CABG surgery completed patient enrollment from 19 to 24 years ago excluded patients older than 65 years. Although information regarding outcomes of CABG in this population is mainly available in case series, a major lacuna exists with respect to information on quality of life and cost effectiveness of surgery as compared with medical management. METHODS The authors retrospectively formed surgical and medically managed cohorts of octogenarians with significant multivessel CAD. More than 600 medical records of patients older than 80 years who underwent angiography at our institution were reviewed to identify 48 patients who were considered reasonable surgical candidates but had not undergone surgery. This cohort was compared with 176 patients who underwent surgery. RESULTS The cost per quality-adjusted life year saved was

Effects of open heart surgery on end-diastolic pressure-diameter relations of the human left ventricle.

10,424. At 3 years, survival in the surgical group was 80% as compared with 64% in the entire medical cohort and 50% in a smaller subset of the medical cohort. Quality of life in patients who underwent surgery was measurably better than that of the medical cohort with utility index scores, as measured by the EuroQoL, (a seven-item quality of life questionnaire) of 0.84, 0.61, and 0.74, respectively. CONCLUSIONS Performing CABG surgery in octogenarians is highly cost-effective. The quality of life of the elderly who elect to undergo CABG surgery is greater than that of their cohorts and equal to that of an average 55-year-old person in the general population.

Control of prosthetic bacterial infection: Evaluation of an easily incorporated, tightly bound, silver antibiotic PTFE graft

Curves relating left ventricular end-diastolic pressure (LVEDP) to echocardiographically determined end-diastolic diameter (LVEDD) were obtained before and after ischemic arrest in 15 patients during open heart surgery. LVEDP ranged from 0-20 mm Hg during routine operation of the heart-lung machine. Ischemic arrest ranged from 0-94 minutes.In eight patients averaging 21 ± 7 (SEM) minutes of arrest, we saw no change in LVEDP-LVEDD curves. In five patients averaging 55 ± 15 minutes of arrest, we noted temporary alterations in EDP-EDD curves (p>0.05). The curves returned to normal within 30-60 minutes after ischemia. In two patients with an average of 66 minutes of arrest, we observed changes in the EDP-EDD curves which did not revert to normal. Available data did not allow us to distinguish between impaired ventricular relaxation and a true change in ventricular compliance as a cause of the shift in the EDP-EDD curve, but ischemia appears to be a major factor in the observed changes.Increased LVEDP after ischemic arrest during open heart surgery may reflect a decrease in left ventricular compliance, rather than an increase in heart size. The probability of altered LVEDP-LVEDD relations appears to depend on the duration of ischemic arrest.

Humoral immunity in allograft rejection. The role of cytotoxic alloantibody in hyperacute rejection and enhancement of rat cardiac allografts.

Despite the use of prophylactic antibiotics in vascular surgery, prosthetic infection rate remains 2-5%. Antibiotics bound to vascular prostheses can control experimentally induced infection but prolonged antibacterial activity has not been achieved. This study evaluates the in vivo efficacy and antibiotic retention of an easily prepared silver-antibiotic prosthesis. Prostheses were prepared by combining silver with oxacillin or amikacin using an organic solvent. After evaporation of the solvent, the graft was left impregnated with the antibiotic complex. In vivo retention studies were performed by implanting PTFE 110Ag-oxacillin prostheses in four canine abdominal aortas. When prostheses were explanted at 1 week, mean antibiotic retention was found to be 20% of original activity, higher than the mean inhibitory concentration for Staphylococcus aureus. In three groups of five dogs, 20 X 7-mm prostheses of PTFE alone, PTFE silver-oxacillin, or PTFE silver-amikacin were implanted in the abdominal aorta and the grafts were inoculated with 10(7) S. aureus of a known bacteriophage type, in a closed retroperitoneal pocket. The animals were sacrificed at 1 week and the prostheses were excised for quantitative bacterial culture. PFTE silver-oxacillin, and PTFE silver-amikacin prostheses had 1.7 X 10(2) and 2.0 X 10(2) colonies, respectively, significantly less (P less than 0.05) than controls (1.3 X 10(6) colonies). These data suggest that antibiotic prostheses can be easily prepared without binding agents. They retain the bound antibiotic for a prolonged period and are effective in reducing graft infection in a stringent direct contamination model.

Processes for development of acceptance of transplanted organs and tissues

The role of humoral immunity in graft rejection in the rat model remains controversial. Passive transfer of cytotoxic alloantibody (CAA) has resulted either in hyperacute rejection or in graft enhancement. This study examines the effect of transfer of CAA on cardiac allograft survival in three rat strain combinations that are fully mismatched at the major histocompatibility (MHC) loci. Strain-specific immune responsiveness in donorrecipient pairs varied from low (Lewis-to-ACI) to high (ACI-to-Lewis) as measured by mixed lymphocyte reactions. CAA was obtained from rats sensitized by three successive skin grafts at weekly intervals. Group 1 (high responder recipients), which consisted of Lewis rats presensitized to ACI and had a lymphocytotoxicity titer of 1:512 to 1:2048, rejected ACI cardiac allografts in 10.8±7.2 hr compared with 6.5±0.5 days in naive controls (P<0.001). Injection of 1 ml of high-titer CAA into naive Lewis rats immediately after ACI cardiac grafting led to hyperacute rejection of ACI hearts in 2.1±0.8 hr while 1 ml of CAA followed by 2 ml of guinea pig complement (GPC) resulted in even faster rejection (mean survival time (MST) of 23.8±4.7 min). Injection of 2 ml GPC alone or in combination with 1 ml naive Lewis serum had no effect on graft survival. Multiple pretransplant injections of 1 ml of CAA on days —3, —2, —1, and 0 relative to transplantation resulted in significant prolongation of allograft survival (MST of 10.3± 0.3 days; P <0.01). In group 2 (intermediate responder recipients), where Lewis rats were presensitized to WF

A Pulsatile Assist Device (PAD) for Use During Cardiopulmonary Bypass

A patients acceptance of transplanted organs and tissues may be enhanced by treating donor specific blood with a suitable dose of ultraviolet radiation for an appropriate period of time, transfusing the irradiated blood into the patient during a suitable pretransplantation time period and then transplanting the organ or tissue into the subject. Acceptance of transplanted organs and tissues can also be enhanced by treating the organs or tissues to be transplanted with a suitable dose of ultraviolet radiation for an appropriate period of time and then transplanting the organ or tissue. Suitably irradiated donor specific blood, organs and tissues are preferred for use in transplantation.

Pancreatic islet transplantation in cynomolgus monkeys: initial studies and evidence that cyclosporine impairs glucose tolerance in normal monkeys

A pulsatile assist device (PAD) has been developed to convert roller pump flow to pulsatile flow in a simple fashion. The device can also be used as an arterial counterpulsator before and after cardiopulmonary bypass. The PAD has been used in 125 adult patients undergoing open-heart operations for coronary artery or valvular heart disease or the combination. Ninety-two patients were in New York Heart Association Functional Class III or IV or had ejection fractions of less than 0.3. The PAD functioned as a hemodynamically effective arterial counterpulsator before and after perfusion. All patients were successfully weaned from bypass with the PAD. There has been 1 intraoperative death and 2 late deaths. Only 1 patient had a perioperative myocardial infarction, and this person was successfully treated with intraaortic balloon pumping. We believe the PAD is a simple and reliable device for intraoperative counterpulsation and for the creation of pulsatile cardiopulmonary bypass. More important, use of the PAD may decrease both the incidence of perioperative myocardial infarction and the need for postoperative intraaortic balloon pumping.

Pancreatitis after renal transplantation

Using a model of streptozotocin-induced, ketosis-prone, insulin-dependent diabetes mellitus (IDDM) in the cynomolgus monkey, we performed 11 intraportal transplants of collagenase-digested, Ficoll-purified pancreatic islets (9 ABO-compatible allografts and 2 concordant baboon xenografts). Islets were pretreated with ultraviolet-B irradiation and recipients received cyclosporine A immunosuppression. Two grafts never functioned, five grafts showed evidence of partial function, and four grafts (three allografts and one xenograft) showed evidence of good function, with the animals independent of exogenous insulin with morning fasting blood glucose levels less than 200 mg/dl. Because two grafts functioned only after CsA was either tapered or discontinued, we performed a related study that showed that therapeutic doses of CsA (morning trough serum level 150-250 ng/ml) impaired intravenous glucose tolerance tests (IVGTT) of normal monkeys and may contributed to graft dysfunction in our islet transplantation model. The results show that there is a decrease in release of serum insulin during an IVGTT leading to impairment of glucose utilization, while serum glucagon remains unaffected. After cessation of CsA, the IVGTT did not return to normal for 28 days. Oral glucose tolerance tests were unaffected in CsA-treated monkeys. These initial studies show that the streptozotocin-diabetic monkey is a valuable model to study IDDM and islet transplantation in nonhuman primates. We also confirm studies in rodents, dogs, and sheep by showing that CsA partially inhibits beta cell function in normal monkeys.

Prolongation of primate cardiac xenograft survival with cyclosporine.

Abstract Five cases of fatal pancreatitis in a series of eighty-six renal allotransplants illustrate the difficulties of diagnosis and treatment of this complication. Pancreatitis after renal transplantation may be caused by steroid medication, hyperparathyroidism, surgical trauma to the pancreas, autorejection, or viral pancreatitis. We suggest alert early detection, appropriate standard treatment, and reduction of steroids as the best steps now available to improve survival of the patient.