摘要:

Long-term euglycemia by intraperitoneal transplantation of microencapsulated islets has not been described in the diabetic large animal model. In this study, we report the successful long-term reversal of diabetes by this method in spontaneous diabetic dogs. We have identified fundamental mechanism (s) associated with alginate-based microcapsule fibrosis, and have devised methods to ameliorate this problem. These include the use of purified alginate of low mannuronic acid content and cytokine suppression. Ten insulin-dependent, spontaneous diabetic dogs (insulin requirement 1–4 units/kg/day; absence of circulating C-peptide and diabetic K-values of 0.6±0.4) were entered into the study. Islets from mongrel donor pancreata were isolated and transplanted intraperitoneally either as free islet controls (n=3) or as microencapsulated islet allografts (n=7). In all seven encapsulated islet recipients, euglycemia was achieved within 24 hr (serum glucose falling from 304±117 to 116±72 mg/dl). IVGTT performed 14 days after islet transplant demonstrated normalization of K-values changing from a pretransplant level of 0.6±0.4 to 2.6±0.6. All animals receiving encapsulated islets remained euglycemic, free of the need for exogenous insulin, for a period of 63–172 days, with a median insulin-independence for 105 days. In contrast, recipients receiving free islets rejected their graft within seven days of implantation. In conclusion, this is the first report of long-term successful reversal of spontaneous diabetes in the large animal model by an intraperitoneal injection of encapsulated islets. The potential exists for this form of therapy to be explored in the treatment of type I diabetes in man.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

We have previously documented that cyclosporine exerts a direct cytotoxic effect on endothelial cells and causes an increase in renal vascular resistance (RVR) in the rat. In the present study we investigated whether FK506, a novel immunosuppressive agent thought to be less nephrotoxic than CsA, impairs endothelial cell function in vitro and affects RVR in vivo. In vitro eicosanoid release and endothelin release were measured in bovine aortic endothelial cells in culture exposed for 1, 6, and 24 hr to increasing concentrations of FK506 (1 nM to 10 μM) or CsA (0.5, 10 μM). No significant changes in TxB2and 6-keto-PGF1α(the stable breakdown products of TxA2and PGI2, respectively) and endothelin release were found after 1 and 6 hr of incubation with all the concentrations of FK506 and CsA considered. FK506 did not affect endothelin release even after 24 hr of incubation. In contrast, cell exposure to CsA was associated with a dose-dependent increase in TxB2, 6-keto-PGF1α, and endothelin release that reached statistical significance after incubation with 10 μM CsA. FK506 did not induce cell detachment or lysis at any concentration and time considered, while 10 μM CsA induced a significant reduction in cell count accompanied by cell lysis. In vivo studies showed that a single i.v. injection of FK506 to rats within a broad range of doses (28 ng/kg to 2.8 μg/kg) did not modify RVR. This was true even for a dose as high as 20 mg/kg, while 20 mg/kg CsA caused a dramatic increase in RVR. We conclude that FK506, unlike CsA, does not induce endothelial cell injury in vitro. Whether this explains the differences in renovascular resistance observed in vivo after acute injection of FK506 and CsA is an attractive possibility that needs to be further explored.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Maximum preservation times of 4–6 hr continue to plague lung transplantation. The high-potassium colloid University of Wisconsin solution (UWS) has proved superior to the crystalloid modified Eurocollins' solution (ECS) for preservation of the liver, kidney, and pancreas. The purpose of this study was to compare UWS and ECS for extended lung preservation using a technique of combined pulmonary and bronchial artery perfusion. Simultaneous pulmonary artery and bronchial artery (via a closed aortic segment) perfusion was employed to harvest the lungs of ten mongrel dogs (wt 25–35 kg) using either UWS (n=5) or ECS (n=5) preservation solutions. Following 17 hr of cold (4°C) pulmoplegic storage, the lungs were placed in an isolated perfused working lung (IPWL) apparatus. Seven freshly harvested lungs served as a control group (CON). Lung aerodynamics and gas exchange were evaluated at standard intervals until failure of the lung on the IPWL apparatus. Time until failure (mean ± SEM) for each group was: CON = 209±14 min; UWS = 227±26 min; and ECS = 123±29 min. Only one of the ECS lungs lasted longer than 90 min. UWS-preserved lungs displayed a gas exchange efficiency equal to the CON group and better than that in the ECS-preserved lungs (lower A-aDO2, lower intrapulmonary shunt), suggesting better protection of the alveolar capillary membrane. Although the UWS lungs were initially less compliant than the ECS lungs, at no time was there a significant difference in the total work of respiration between the two groups. We conclude that UWS provides superior protection of the alveolar capillary membrane. The aerodynamic disadvantages of UWS preservation did not effect lung survival or total work of respiration.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The pancreatic parenchyma was evaluated as a potential recipient site for hepatic fragment autotransplantation. Histologic and functional studies of hepatic autografts in the pancreas were performed in 15 mongrel dogs. Approximately 10 g of liver parenchyma was resected from each left lateral lobe. The remnant liver remained in situ. Bile secretion from the hepatic tissues implanted into the pancreas was estimated by measuring the indocyanine green (ICG)*concentration in pancreatic juice following intravenous ICG injection. One month following implantation, the hepatocytes in the pancreatic parenchyma were histologically colorless and did not have sinusoids. However, by the second month following implantation, hepatic nodules had grown extensively to become normal liver tissue, with sinusoids and a single liver cell-plate structure. At 4 months following intrapancreatic implantation the transplanted hepatic masses consisted of several hepatic lobules. Furthermore, ICG could be detected in the pancreatic juice of dogs surviving more than 2 months after implantation but no ICG could be detected in the pancreatic juice of normal controls. The present study provides direct evidence that hepatic grafts transplanted into the pancreas that has a ductal drainage system for bile secretion can reconstitute histologically normal liver tissue capable of secreting bile. This model can be used to understand the early steps of hepatic regeneration.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

This study investigated the influence of hepatic arterialization on early graft function, microcirculation, and leukocyte-endothelial interaction after syngeneic orthotopic liver transplantation in Lewis rats. Livers were preserved for 17 hr in UW solution and transplanted without rearterialization (group 1: n = 10) or with immediate arterial reconstruction (group 2: n = 10). Graft function was analyzed by bile flow; microcirculation was assessed by laser Doppler flowmetry (LDF) and intravital microscopy (IVM). In addition, flow behavior of leukocytes was quantified by IVM after i.v. injection of the WBC marker acridine orange. Improved graft function in group 2 was indicated by increased bile production during the observation period of 90 min after reperfusion (7.18±0.62 vs. 3.63±0.63 ml/100 g liver [mean ± SEM]P<0.001). In arterialized grafts LDF values increased by 22.9±3.8% upon reperfusion of the hepatic artery (P=0.004). Arterialization increased WBC velocities in sinusoids (group 1: 0.29±0.02 mm/sec, group 2: 0.34±0.01 mm/sec,P<0.001) and postsinusoidal venules (0.43±0.05 vs. 0.64±0.05 mm/sec,P=0.029). In addition, the number of nonperfused midzonal sinusoids decreased significantly (8.5±2.2% of all sinusoids analyzed vs. 4.2±1.3%,P=0.048). However, the marked sinusoidal and venular WBC adherence observed 1 hr after reperfusion was not altered by arterialization. It is concluded that arterial reconstruction in rat liver transplantation improves microvascular perfusion and graft function but this improvement does not relate to WBC accumulation within the graft. We propose that studies on hepatic preservation and postischemic reperfusion in the rat should be based on the physiological model of dual vascularization.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Parallel in vivo, histological, and ultrastructural studies were carried out and markers of lipid peroxidation (Schiff's bases [SB] and thiobarbituric-acid-reactive material [TEAR]) were measured in rat adipomusculocutaneous flap isotransplants that had been stored for 0, 2, 4, 6, and 8 hr under normothermic (37°C) conditions and reperfused for specific periods. Flaps stored for 4 hr and treated with intravenous desferrioxamine (DFX) or hypertonic citrate flush (HCA) were also evaluated. In vivo assessment was made after 7 days of reperfusion. Flaps stored for 4 hr eventually exhibited partial necrosis in vivo, and neither DFX or HCA flush increased the area of surviving skin. Electron microscopy revealed extensive storage damage in epidermal, follicle, fat, and smooth muscle cells and in endothelium. HCA significantly preserved fat cells (P=0.0035) and DFX diminished smooth muscle damage. Reperfusion injury was seen in endothelial cells in the form of swelling that was not prevented by HCA or DFX. Ultrastructural alterations correlated with changes in susceptibility to lipid peroxidation in fat but not in skin. The results of these parallel studies indicate that both free radical-dependent and independent mechanisms operate in ischemia and reperfusion injury in flap tissue and that fat has a greater predisposition to free radical damage than skin.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

To study the effects of donor T lymphocytes on engraftment and graft-versus-host disease in relation to recipient total-body irradiation, we have returned small numbers of T cells to T-cell-depleted bone marrow transplanted across a minor histocompatibility barrier in mice (B10.BR°CBA). T-cell-depleted B10.BR marrow (107cells) was transplanted into CBA recipients prepared with TBI doses ranging from 4 to 14 Gy. Selected animals also received 104(0.1%) and 105(1.0%) measured B10.BR T lymphocytes. The extent of donor marrow engraftment was determined from hemoglobin and carbonic anhydrase phenotyping of peripheral blood at 3 months posttransplant. Toxicity was assessed from breathing-rate measurements, histopathology, and animal survival. Addition of T cells had a profound effect on survival related to radiation dose. The TBI doses resulting in an LD50at 12 weeks were 6.9 Gy, 9.3 Gy, and 13.0 Gy for animals receiving 105, 104, and no T cells, respectively. Mortality was associated with pulmonary dysfunction as measured by an elevation of breathing rates. Autopsy and histological analysis revealed extensive damage to the lung parenchyma. In contrast to the toxicity data, addition of T cells to the donor marrow had no effect on the TBI dose required for equivalent erythroid engraftment. These results demonstrate that in combination with TBI small numbers of T cells in the transplanted marrow do not aid engraftment but do significantly increase the risk of pulmonary toxicity.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Airway disease after lung or heart-lung transplantation is one of late major complications, affecting the prognosis of the transplants. Little is known about the causes of airway changes. We performed rat lung transplantation and investigated the late airway changes of the long-term surviving lung grafts: allografts, BN to Lewis; isografts, BN to BN rat. All recipients were treated with CsA. We found airway changes, i.e., mucosal ulceration, granulation, submucosal fibrosis, which was located in the large airways, in four of five allografted lungs. The lung isografts showed no pathological abnormalities.Immunopathological studies disclosed the localized expression of MHC class II antigens on the bronchial epithelium of the large airways where recipient type dendritic cells accumulated in the submucosa and CD4 positive predominant lymphocytes infiltrated.These findings support the idea that the late airway changes in lung transplants are caused by immunologically mediated chronic rejection.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

A novel immunosuppressant, succinyl acetone (4,6-dioxoheptanoic acid), was studied in dogs. Results with bolus intravenous injections at doses ranging from 50 to 1600 mg/kg showed dose-dependent α and β half-lives, ranging from 30 to 80 min and 7 to 27 hr, respectively. Results suggested that continuous i.v. infusion was necessary to maintain constant plasma levels. Four dogs were given 9.2 Gy total-body irradiation and autologous marrow transplants along with continuous i.v. infusion of succinyl acetone at 50, 100, 200, or 400 mg/kg/day for 21 days, and all four had rapid, sustained hematopoietic engraftment. However, two of the four dogs receiving 200 and 400 mg succinyl acetone/kg/day, respectively, developed bilateral hind-limb ataxia, with histologically confirmed cerebellar lesions in the dog given the higher dose, thus establishing a potential doselimiting neurotoxicity.Prevention of graft-versus-host disease was studied in recipients of allogeneic marrow. Dogs were given 9.2 Gy TBI, followed by hematopoietic grafts from unrelated DLA-nonidentical or DLA-haploidentical littermate dogs. Succinyl acetone was given as continuous infusion for 21 days after transplant at doses of 100–300 mg/kg/day. Starting succinyl acetone on the day of marrow infusion in four dogs failed to prevent rapid onset of acute GVHD, and dogs survived no longer than controls. Starting succinyl acetone 3 days before transplant delayed the onset of acute GVHD and prolonged survival significantly compared with that of dogs not given postgrafting immunosuppression (P=0.008); survival was comparable to that in previously reported dogs given either methotrexate or cyclosporine as postgrafting immunosuppression (P=0.88 and 0.99, respectively). Seven of the sixteen allogeneic recipients developed evidence of neurotoxicity during succinyl-acetone infusion. Neurological dysfunctions were manifested by hind-limb ataxia and posterior paresis.In conclusion, succinyl acetone significantly delayed the onset of GVHD and prolonged survival of DLA-nonidentical marrow graft recipients but did not induce graft-host tolerance and was associated with dose-limiting neurotoxicity.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

A retrospective review of 375 consecutive orthotopic liver transplants was performed to determine the incidence and outcome of late rejection episodes ([LR] rejection occurring more than 6 months following transplant). A total of 31 episodes in 26 patients were identified. Eighteen of these episodes were associated with subtherapeutic levels of cyclosporine. Of these, 7 were due to noncompliance, 2 were due to biliary strictures, and 1 was due to malabsorption in a cystic fibrosis patient. All 31 episodes were treated initially with steroids, and 22 had a complete response, although one progressed to chronic rejection over a year later. Of the remaining 9, 1 received FK506 with a complete response, and 8 received OKT3. Of the 8 patients who received OKT3, 5 had a complete response, 1 received RS61443 following OKT3 and progressed to chronic rejection, and the remaining 2 received further steroids. Of these 2, 1 had a complete response following the steroids while the second was converted to FK506 with a complete response. Compared with 315 acute rejection episodes ([AR] occurring less than 6 months posttransplant), patients with late rejection episodes had an equivalent response to steroids (63.2% AR reversed vs. 71% LR reversed) but a lower response rate to OKT3 (91.5% AR reversed vs. 62.5% LR reversed). There was, therefore, a higher rate of persistent rejection (61% AR episodes vs. 15.4% LR episodes) but no increase in the incidence of chronic rejection (7% AR episodes vs. 7.7% LR episodes). We conclude that LR is a relatively common occurrence following liver transplant, which is most often associated with low cyclosporine levels. Many of these episodes are due to noncompliance, but biliary problems must also be investigated. The incidence of resistant rejection is higher in this group of patients but is not associated with a concurrent increase in chronic rejection.

ISSN:0041-1337    

出版商:OVID    

年代:1992

数据来源: OVID