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M D'Silva

Publications and source records attributed to M D'Silva.

At least 19 recordsLinked to original sources
PubMed2001

Seventy-two hours hypothermic intestinal preservation study using a new perfluorocarbon emulsion.

We investigated the effect of a perfluorocarbon emulsion (FC) added to the University of Wisconsin (UW) solution on hypothermic (4 degrees C, 12-72h) preservation of rat small bowel grafts. The FC was 90%w/v perfluorooctylbromide, 2%w/v egg yolk phospholipids and 1.4%w/v mixed fluorocarbon-hydrocarbon molecular dowels. Four groups were defined: [1] UW flush and UW storage; [2] UW flush and FC storage; [3] flush with FC diluted 2 times with UW (FU) and FU storage; [4] FU flush and storage in oxygenated FU. Preservation was estimated with a histological score based on villus epithelium adhesion, on villus sloughing and on crypt cell adhesion to the basal membrane. Antioxidant potential was estimated by measurement of total thiol functions (SH) and activities of glutathione-peroxidase (GSH-P), superoxide dismutase (SOD) and catalase. FC in flush improved preservation during the first 24h (p<0.01). Storage in FC appeared superior to UW for the first 24h (p<0.01). Oxygenation (100% O2) of the storage medium yielded superior results at 12h and 24h (p<0.01 and p<0.001 versus group [1] respectively). After 72h, SOD and catalase activities increased in groups [3] and [4], and SOD decreased in group [1] (p<0.05). SH progressively decreased in group [1] (p<0.05) and GSH-P increased at 24 and 48h in groups [3] and [4] (p<0.01). The increase of O2 in the perfusion flush or storage medium ameliorated the preservation status and protected the antioxidant potential of the small bowel.

Animals↗
PubMed1999

Long-term fate of heterotopic liver transplants in rats with portal vein inflow only.

Previous studies have suggested that hepatic arterial flow in heterotopic partial liver transplants is necessary to ensure graft survival and regenerative capacity. This report presents findings in a syngeneic rat strain (Lewis) that partial liver transplants can be successfully heterotopically transplanted in the long term with the only inflow coming from the portal vein. When the host liver undergoes a nearly complete resection at 3-4 weeks, the transplanted liver regenerates to maintain the health of the host. Moderate to massive hepatocellular necrosis occurs in the first 3 months postoperatively, with recovery by 4-5 months. Liver transplants 8-10 months postoperatively appear architecturally normal. No host liver tissues were found to be regenerating after subtotal host liver resection. We conclude that portal vein reconstruction without hepatic arterial inflow can sustain a partial liver transplant in the long term, replacing the function of the host liver.

Anastomosis, Surgical↗
PubMed1999

Update on sequential isologous rat organ transplantation: pancreaticoduodenal and kidney transplantations.

This periodic report includes intermittent results of consecutive pancreaticoduodenal (Pd) and kidney (Kt) transplants in inbred rats and results on double kidney transplants that did not follow sequential transplant protocol. Eight 24-month-old Lewis pancreas, kidney, and aorta served histological controls showing normal histological architecture with no atherosclerosis developed in the aorta. Thirty-four month old pancreas and thirty-two month old kidneys, which resided in young hosts for at least three occasions, appeared as youthful Pd and Kt grafts. They show normal histological appearance for more than the expected life span of a Lewis rat. The fact that not only pancreases but also kidneys outlived their host leads to the study of other different organs' viability as aged valuable grafts. Nevertheless, the threats by the development of atherosclerosis in graft-associated aortas resulted in slow progression of the follow-ups.

Animals↗
PubMed1999

Immunosuppressive effect of combination schedules of brequinar with leflunomide or tacrolimus on rat cardiac allotransplantation.

Drug toxicity is one of the major problems in clinical immunosuppression. Combining two immunosuppressants in low or ineffective doses is an attractive strategy if it helps to reduce drug-related toxicity. We examined the immunosuppressive efficacy of brequinar (BQR) in combination with leflunomide (Lef) or tacrolimus (FK) in a heterotopic rat cardiac allotransplantation model. Abdominal heterotopic heart grafts (DA x LEW) were immunosuppressed from the time of transplantation and continued until the ninth posttransplant day (POD) in experiments examining prophylaxis of rejection treatment (PRT). In a separate series of experiments designed to test rescue treatment (RT), immunosuppression was begun on POD 4 and continued for 10 days; transplanted rats were sacrificed the following day intentionally. Cardiac rejection was monitored by palpation and documented by light microscopy. Immunosuppressive drugs (BQR 3 mg/kg and 12 mg/kg; BQR 3 mg/kg + Lef 5 mg/kg; BQR 3 mg/kg + FK 0.5 mg/kg) were given orally by gavage; thrice weekly according to the monotherapy or dual-therapy dosing protocol. Median survival time of the cardiac graft for controls (no treatment) was 5 days. BQR monotherapy 3 mg/kg (low dose) improved graft survival (P = 0.003); graft histology showed moderate acute rejection. BQR monotherapy 12 mg/kg (therapeutic dose) application in the PRT or RT treatment arms of the study design resulted in aortic-graft ruptures and clinical toxicity in each treatment arm due to overimmunosuppression; normal graft morphology was maintained. Successful rescue of rejecting grafts was histologically documented. Combining BQR with Lef or FK in the PRT protocol showed prolonged graft survival in both drug combination groups (median survival time, 14 days; P = 0.009 and 0.014, respectively). Using an identical combination protocol for RT, all grafts achieved a 14-day graft survival; cardiac histology showed reversible moderate acute rejection. BQR given in the presence of Lef or FK not only prevented acute rejection but intercepted it so long as it was administered; grafts were rejected within 4 days of stopping immunosuppression in the PRT study. These combinations using low or subtherapeutic doses may be important for controlling transplant rejection and rescuing ongoing graft rejection. The need for continuing treatment in this strongly allogeneic model is highlighted.

Animals↗
PubMed1998

Effect of peritransplant FTY720 alone or in combination with post-transplant tacrolimus in a rat model of cardiac allotransplantation.

FTY720 is a recently discovered compound that is derived from the fungus Isaria sinclairii. Using a DA donor-to-LEW recipient rat combination, we assessed the efficacy of peritransplant FTY720 alone or in combination with post-transplant tacrolimus on the survival of cardiac allografts. Peritransplant FTY720 given orally at a dose of 5 mg/kg on days-1 and 0 prolonged graft survival from 5 to 13 days (P < 0.05). Combining peritransplant FTY720 with post-transplant tacrolimus resulted in a further prolongation of allograft survival. The lymphocyte count in transplanted rats decreased within 24 h to 46.6%. Analysis of lymphocyte subsets by FACS revealed that FTY720 affected the total population of CD3-bearing T cells while the ratio of CD4 to CD8 cells remained unchanged. Kidney and liver biochemistry remained elevated for 2 weeks. In conclusion, FTY720 is a powerful immunosuppressive agent when used as induction therapy and may have an additive effect--perhaps a synergistic one--with post-transplant tacrolimus.

Animals↗
PubMed1997

Sequential isologous organ transplantation in inbred rats: pancreaticoduodenal transplants.

A total of 847 inbred Lewis rats of mixed sex were used in this pancreaticoduodenal (Pd) donor aging study. Pd grafts were taken from 9- to 12-month-old donors and transplanted into 3-month-old recipients (thus, the first generation Pd graft, or 1 Pd). After 9 to 12 months, the same Pd grafts were again harvested and transplanted into 3-month-old rats (thus the 2 Pd generation). This cycle was repeated to obtain the 3, 4, and 5 Pd series. Sequential transplantation was able to extend the Pd grafts' mean survival time to 32 months for fourteen 4 Pd grafts, and to 39.2 months for four 5 Pd grafts (the longest lived graft survived for 42 months). The pancreas and duodenal sections of the grafts remained normal throughout the entire study. However, the aortic sections of the grafts (which were harvested to include the superior mesenteric and celiac arteries) all exhibited moderate to massive atherosclerotic changes by the 5 Pd mean survival age of 39.2 months. Such histological changes commenced even before 21 months of Pd graft age in some animals, gradually progressing to dilation of the aorta (and subsequent narrowing of aortic tributaries), as well as formation of an eggshell-like inner membrane shielding the aortic intima, by 42 months. Such atherosclerotic changes precluded transplantations beyond the 5 Pd series.

Age Factors↗
PubMed1997

Donor pretreatment with leflunomide has an adverse effect on rat cardiac allograft survival.

The effect of leflunomide (Lef) donor pretreatment (DPT) on rat cardiac allograft survival was investigated. In untreated Lewis recipients of untreated DA hearts, median graft survival was 5 days. DPT (Lef 5 or 10 mg/kg per day for 30 days) reduced median graft survival to 4.0 and 4.5 days, respectively. In immunosuppressed (Lef 5 mg/kg for 10 or 30 days) Lewis recipients of untreated DA hearts, median graft survival was 21 and 33 days, respectively. DPT with Lef 5 mg/kg per day for 5 days or 30 days reduced median graft survival to 12 and 23.5 days, respectively (p < 0.05). DPT with Lef resulted in earlier graft rejection but the histological appearance at the time of rejection was the same as in untreated controls. DPT with Lef resulted in a 40% reduction in MHC class II-positive cells in the heart. Histological examination of rejecting hearts showed no obvious difference in the nature of the rejection process between DPT and untreated control hearts. The paradox between class II reduction but earlier rejection indicates that DPT is exerting a deleterious effect through some unrecognized property of the graft.

Animals↗
PubMed1997

Glycogen content of the donor liver and its relation to postreperfusion hepatic energy metabolism.

OBJECTIVES: Many studies have suggested that glycogen in donor livers is an important fuel during cold ischemic time and at reperfusion. However, it remains unclear as to whether the depression of glycogen content in the graft results in a critical derangement of energy metabolism after reperfusion. The purpose of this study was to assess the possible implications of the glycogen concentration of donor livers for the hepatic energy metabolism after reperfusion. METHODS: The glycogen content of 28 donor livers and the plasma concentrations of metabolic substrates were measured during liver transplantation. RESULTS: Gluconeogenesis was maintained even in the glycogen-depleted graft at reperfusion. However, glycogen-depleted grafts produced more ketone bodies until 24 h after reperfusion. Free carnitine concentrations in these patients were significantly higher than those in the patients with glycogen-nondepleated grafts until 48 h after reperfusion. CONCLUSIONS: A glycogen-depleted liver graft may restore essential metabolic function by producing energy substrates through enhanced ketogenesis in the postreperfusion period. The enhanced production of carnitine by the graft provides a substrate for the production of ketone bodies and thus may be relevant to the enhanced ketogenesis.

Energy Metabolism↗
PubMed1996

Effect of RS61443 in combination with leflunomide or FK506 on rat heart allograft survival.

Mycophenolate Mofetil (RS61443) is a potent inhibitor of de novo purine synthesis and lymphocyte proliferation. It is known to prevent ongoing rejection and even reverse established rejection, alone and in combination with, cyclosporin. We investigated whether RS61443 in combination with leflunomide (Lef) or FK506 (FK) could prolong allograft survival in a rat heart model, since combination therapy might help to overcome drug toxicity. Abdominal heart grafting was performed from DA to LEW rats (250 g) and RS61443, 10 mg/kg or 30 mg/kg monotherapy or combination treatment (RS 10 mg/kg with Lef 5 mg/kg or FK 0.5 mg/kg) was begun orally at transplantation and continued daily until the ninth posttransplant (post-Tx) day. Ventricular motion was graded daily and rejection was defined as lack of contractions, confirmed by histology. Results were analysed using non-parametric tests. A two-tail P value < 0.05 was considered significant. RS at 10 mg/kg was ineffective and all grafts were rejected under immunosuppression between 5 and 6 post-Tx day, whereas RS at 30 mg/kg was immunosuppressive for as long as it was given. The combinations of RS at 10 mg/kg with either Lef at 5 mg/kg or FK at 0.5 mg/kg were immunosuppressive in the majority of cases, for as long as they were given. However, the combination of RS at 10 mg/kg with FK at 0.5 mg/kg was attendant with graft vein anastomosis rupture (3/5). The combination of RS with Lef was clinically therapeutic for as long as it was given; grafts were rejected 3-4 days after withdrawing immunosuppression. The combination of RS with FK resulted in over-immunosuppression, leading to graft vein anastomosis non-healing and rupture within 5 days of grafting; histology demonstrated evidence of bacterial infection with complete destruction of the vein wall. These data suggest that the combination of RS with Lef or FK in subtherapeutic doses might be a potentially promising strategy for combination therapy in solid organ transplantation.

Animals↗