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Biomedical subjects

B Garcia

Publications and source records attributed to B Garcia.

At least 37 records · Page 2Linked to original sources
PubMed2000

Reconstruction of the intestinal lymphatic drainage after small bowel transplantation.

BACKGROUND: The surgical procedure of small bowel transplantation normally results in complete disruption of the graft's lymphatic drainage. The present study was undertaken to determine the impact of lymphatic reconstruction (LR) on the outcome of intestinal grafting, using a microsurgical model that immediately restores lymphatic drainage. MATERIALS: Brown Norway (RT1n) intestinal grafts were orthotopically transplanted into Lewis (RT1(1)) rats either with LR (+LR) or without LR (-LR). Recipients were randomly allocated into the following groups: no treatment or cyclosporine (CsA) at a dose of 2, 5, or 10 mg/kg/day subcutaneously from postoperative day (POD) 0 to 6. RESULTS: There was morphological regeneration of lymphatics in the -LR group between 1-3 weeks as previously reported, whereas normal lymph flow was immediately restored in the +LR group. All untreated and CsA(2 mg)-treated allografts were rapidly rejected in both the +LR and -LR groups. In the groups treated with approximately 5 mg of CsA, five of six -LR animals died of chronic rejection between 38 and 86 days (mean survival time +/- SD: 76.7+/-21 days), while all +LR animals survived until death on POD 100 (P < 0.05). Histological features of mucosal damage found in -LR grafts were absent in the +LR grafts. All of the animals treated with 10 mg of CsA survived indefinitely. Sequential histology revealed mild rejection in -LR and +LR grafts on POD 45, but +LR animals had significantly higher body weight gains (POD 50: -LR: 117+/-12% vs. +LR: 136+/-4%, P < 0.01). LR did not affect donor cell migration and nutritional parameters. CONCLUSION: LR improves the long-term results of small bowel transplantation resulting in better survival rates, less mucosal damage due to chronic graft rejection, and greater weight gain. We conclude that impairment of lymph flow may contribute to poor outcomes when standard surgical techniques are used for small bowel transplantation.

Animals↗
PubMed2000

Sesquiterpene lactones from Centaurea thessala and Centaurea attica. Antifungal activity.

The aerial parts of Centaurea thessala ssp. drakiensis and C. attica ssp. attica afforded, in addition to several known sesquiterpene lactones, two new eudesmanolides, 4-epi-sonchucarpolide and its 8-(3-hydroxy-4-acetoxy-2-methylene-butanoyloxy) derivative and one new eudesmane derivative, named atticin. The in vitro antifungal activity of most compounds was tested against nine fungal species, using the micro-dilution method. All the compounds tested showed great antifungal activity.

Antifungal Agents↗
PubMed2000

Allograft tolerance induced by cyclophosphamide without prior inoculation of donor cells--immune suppression and redirection.

OBJECTIVES: To determine the possibility and cellular mechanism of inducing allograft tolerance by multiple injection of a lower dose of cyclophosphamide without prior infusion of donor cells. METHODS AND RESULTS: Heterotopic heart grafts were performed in MHC mismatched strain combinations (C57/B6 vs. BALB/c). Cyclophosphamide (40 mg/kg) was given intravenously on days 0, 2, 4 and 7 without prior infusion of donor cells. Long-term (> 100 days) allograft survival with normal histology was achieved. The long-term survivors accepted the donor skin grafts, but rejected the third-party skin grafts. Cyclophosphamide treatment initially led to profound lymphocytopenia, inhibition of spontaneous blastogenesis and low levels of lymphocyte proliferation response to both donor and third-party antigens. Ultimately, donor-specific tolerance occurred demonstrated by normal levels of peripheral lymphocytes, spontaneous blastogenesis and lymphocyte proliferation response to third-party antigens, and low levels of lymphocyte proliferation response to donor antigen. A switch of cytokines from IFNgamma dominant to IL-4 dominant, a low level of IgM and a high level of IgG1 were found in tolerant mice. CONCLUSIONS: Allograft tolerance can be induced by a short course of cyclophosphamide without prior donor cell inoculation. Tolerance induced is characterized initially by non-specific immunosuppression, which progresses to donor-specific hyporesponsiveness associated with the development of a Th2 dominant cytokine response.

Animals↗
PubMed2000

High-yield production of a human therapeutic protein in tobacco chloroplasts.

Transgenic plants have become attractive systems for production of human therapeutic proteins because of the reduced risk of mammalian viral contaminants, the ability to do large scale-up at low cost, and the low maintenance requirements. Here we report a feasibility study for production of a human therapeutic protein through transplastomic transformation technology, which has the additional advantage of increased biological containment by apparent elimination of the transmission of transgenes through pollen. We show that chloroplasts can express a secretory protein, human somatotropin, in a soluble, biologically active, disulfide-bonded form. High concentrations of recombinant protein accumulation are observed (>7% total soluble protein), more than 300-fold higher than a similar gene expressed using a nuclear transgenic approach. The plastid-expressed somatotropin is nearly devoid of complex post-translational modifications, effectively increasing the amount of usable recombinant protein. We also describe approaches to obtain a somatotropin with a non-methionine N terminus, similar to the native human protein. The results indicate that chloroplasts are a highly efficient vehicle for the potential production of pharmaceutical proteins in plants.

Blotting, Western↗
PubMed2000

The axis of interleukin 12 and gamma interferon regulates acute vascular xenogeneic rejection.

Recent advances using transgenic animals or exogenous complement inhibitors have demonstrated prevention of hyperacute rejection of vascularized organs, but not graft loss due to acute vascular rejection. Using various wild-type and cytokine-deficient mice strains, we have examined the mechanisms of acute vascular rejection. C57BL/6 mice deficient in interleukin12 or gamma interferon showed faster acute vascular rejection than did wild-type mice. Furthermore, mice defective in B-cell development showed no acute vascular rejection. These results demonstrate that the axis of interleukin 12 and gamma interferon provides a survival advantage in vascularized xenografts by delaying or preventing acute vascular rejection caused by a B cell-dependent mechanism.

Acute Disease↗
PubMed2000

Endothelin-1, endothelin-3 and their receptors (endothelin(A) and endothelin(B)) in chronic renal transplant rejection in rats.

Endothelins (ET) are a family of vasoactive peptides that play an important role in several disorders affecting kidneys. In this study we investigated the expressions of ET-1, ET-3, and their receptors, ET(A) and ET(B), in a rat chronic renal transplant rejection model. Renal allografts were performed (F344 --> Lewis) with bilateral nephrectomy in recipients. For isograft control, lewis --> lewis transplantations were performed. All recipients were sacrificed 140 days after transplantation and the grafts were analyzed histologically. ET-1 and ET-3 protein expression in grafts was measured by immunohistochemistry and ELISA. Semiquantitative RT-PCR methods were used for mRNA levels of ET-1, ET-3, ET(A) and ET(B). No evidence of chronical rejection was manifested in isografts. The allografted rats showed proteinuria and increased serum creatinine levels. Histologically, renal allografts showed atrophy and sclerosis of the glomeruli, cortical scarring and vascular intimal thickening. Immunohistochemically, ET-1 and ET-3 were localized in the convoluted tubules, collecting ducts, endothelium and smooth muscle cells of the large blood vessels. Significantly increased staining for ET-1 and ET-3 were found in allografts compared to isografts. Simultaneously, ELISA for ET-1 and ET-3 showed elevated protein concentrations in allografts compared to isografts. Allografts showed significantly increased ET-1- and ET-3 mRNA compared to isografts. On the other hand, a significant down regulation of the ET(A) mRNA was noted, and the ET(B) mRNA remained unchanged. The data from the present study suggest that alteration of ET system may be of importance in the pathogenesis of chronic renal transplant rejection.

Animals↗
PubMed1999

Complement inhibition with an anti-C5 monoclonal antibody prevents hyperacute rejection in a xenograft heart transplantation model.

BACKGROUND: The present study was undertaken to determine whether anti-complement 5 (C5) monoclonal antibodies (mAb) prevent hyperacute rejection (HAR) in a rat-to-presensitized mouse heart transplantation model and whether these mAb, combined with cyclosporine (CsA) and cyclophosphamide (CyP), can achieve long-term graft survival. METHODS: BALB/c mice were presensitized with 2x10(7) splenocytes from Lewis rats 14 days before grafting. Heart grafts from Lewis rats were heterotopically transplanted into BALB/c mice. Presensitized mice were treated with either anti-C5 mAb or a combination of anti-C5 mAb, CsA, and CyP. Controls included: presensitized mice with no treatment, presensitized mice treated with either CsA + CyP or IgG, and nonpresensitized mice with either no treatment or with CsA + CyP treatment. RESULTS: Although typical features of HAR were evident in the presensitized grafts, the mAb completely inhibited complement activation and successfully prevented HAR. Despite complement inactivation, the graft was rejected on postoperative day 6 with acute vascular rejection (AVR) also known as delayed xenograft rejection (DXR). Notably, this type of rejection cannot be effectively overcome by CsA and CyP. CONCLUSIONS: We conclude that (1) anti-C5 mAb prevents HAR, (2) AVR/DXR still occurs when HAR is prevented by complement inactivation, and (3) AVR/DXR cannot be overcome by conventional immunosuppression. These data suggest that anti-C5 mAb may be valuable for preventing HAR in future clinical xenotransplantation and that additional interventions may be required to address AVR/DXR.

Acute Disease↗
PubMed1999

Cyclosporine inhibits long-term survival in cardiac allografts treated with monoclonal antibody against CD45RB.

BACKGROUND: We have previously reported that a monoclonal antibody to CD45RB is a novel immunosuppressive agent; however, the optimal regimen in cardiac allografts remains unknown. The present study was undertaken to determine the optimal protocol of this therapy and its interaction with cyclosporine. METHODS: A heterotopic heart allograft model was used in C57BL/6 to BALB/c mice. The following studies were conducted: 1) dose response study (low, intermediate, and high doses at 1, 3, and 9 mg/kg/day respectively), 2) short course (2 days) therapy vs. long course (9 days) therapy, 3) pretreatment (starting on day -1) vs no pretreatment, 4) daily therapy vs. alternative day therapy, and 5) monoclonal antibody treatment with and without cyclosporine. RESULTS: The efficacy of the CD45RB monoclonal antibody was dose and duration dependent (p<0.01). Pretreatment significantly improved the efficacy of this therapy (74.5+/-13.4 days vs. 30.6+/-1.5 days, p<0.01). Daily therapy was superior to alternate day therapy (74.5+/-13.4 days vs. 30.4+/-1.5 days, p<0.03). Interestingly, we found that administration of cyclosporine prior to, at the same time as, or after administration of the CD45RB monoclonal antibody had a detrimental effect on graft survival compared to mAb treated alone (16.6+/-0.4 days, 25+/-2.3 days, and 35.3+/-0.9 days respectively vs. 74.5 days, p<0.01). CONCLUSIONS: Immunosuppression with CD45RB monoclonal antibody is dose and duration dependent. Pretreatment and daily therapy improves results. Addition of cyclosporine inhibits long-term graft survival achieved by the monoclonal antibody alone.

Animals↗
PubMed1999

Adoptively transferable tolerance induced by CD45RB monoclonal antibody.

The phenomenon of rejection remains the most serious problem in transplantation. The ultimate goal in transplant immunology is to develop therapeutic strategies that lead to tolerance. It has been shown that two injections of a monoclonal antibody to CD45RB leads to indefinite acceptance of renal allografts in mice. Moreover, the CD45RB monoclonal antibody reverses acute rejection and still induces tolerance. The purpose of this study was to assess mechanisms that could underlie this therapeutic benefit. It was shown that splenic lymphocytes from tolerant animals augmented proliferation in allogeneic mixed lymphocyte reactions against donor alloantigens, and the serum of tolerant mice contained donor-specific antibodies, mainly of the IgG1 isotype, suggesting the presence of TH2 cytokines. Tolerance could not be broken by interleukin-2 infusion, but tolerance could be adoptively transferred by transfusion of tolerant mouse CD4+ splenic lymphocytes into naive allografted animals. These data suggest that an active immunoregulatory mechanism is partly responsible for the therapeutic effect. CD45RB-directed therapy may find clinical application in organ transplantation in human patients.

Adoptive Transfer↗
PubMed1998

Treatment of cardiac allografts with established leukocyte infiltration by modulation of alpha4 (CD49d) and leukocyte function-associated antigen-1 (CD11a/CD18) integrin function.

BACKGROUND: Leukocyte infiltration is a landmark feature of organ rejection. The present study was undertaken to determine whether monoclonal antibodies (mAb) against alpha4 (CD49d) and/or leukocyte function-associated antigen-1 (LFA-1; CD11a/CD18) would reverse ongoing rejection in a mouse C57BL/6-to-BALB/c heart transplant model. METHODS: Control animals had rejection on postoperative day (POD) 8. Treatment with mAb started on POD 4 when leukocyte infiltration was well established. The recipients were treated with (1) mAb LFA-1, (2) mAb alpha4, and (3) mAbs LFA-1 + alpha4 at a dose of 6 mg/kg/day i.v. on PODs 4, 5, and 7. Untreated and rat IgG-treated animals were used as controls. RESULTS: Control animals experienced rejection on POD 8. Treatment with mAb against LFA-1 or alpha4 alone prolonged allograft survival to 17.0+/-3.2 and 24.3+/-4.6 days, respectively (P < 0.01 vs. controls). Combination therapy with both mAb increased allograft survival to 28.2+/-3.7 days (P < 0.01 vs. controls). Sequential pathological studies showed the mAb to alpha4, but not LFA-1, markedly reduced the degree of lymphocytic infiltration in cardiac allografts. In contrast, a different pattern was observed using in vitro studies: mAb to LFA-1, not alpha4, significantly reduced proliferative responses in mixed lymphocyte culture and interleukin-2 production from recipient splenocytes on POD 8. CONCLUSION: These data indicate that integrins play an important role in rejection. Although the effect of mAb against alpha4 and LFA-1 may involve different mechanisms, treatment with mAbs to integrins may be valuable in future clinical transplantation by averting ongoing rejection and prolonging graft survival.

Animals↗
PubMed1998

Apoptosis in thyroid neoplasms: relationship with p53 and bcl-2 expression.

AIM: Cell gain and loss occurs concurrently in tumours. Apoptosis may play a major role in determining the growth and aggressiveness of the tumours. The aim of this study was to investigate whether apoptosis is related to the degree of differentiation and expression of mutated p53 and bcl-2 in thyroid neoplasms. METHODS AND RESULTS: Fifty-three thyroid tumours of various histological types and 10 multinodular goitres were investigated semiquantitatively for the presence of apoptosis using a DNA end ligase method. Simultaneously, quantitative immunostaining was performed for bcl-2 and p53, two known regulators of apoptosis. No apoptosis was detected in normal thyroid tissues, multinodular goitres and in four follicular adenomas, all of which were positive for bcl-2. On the other hand, two anaplastic and one insular carcinomas showed marked increase in apoptosis along with intense p53 positivity and bcl-2 negativity. The majority of the follicular carcinomas showed results similar to that of follicular adenomas. No apoptosis was detected in 41% of papillary carcinomas, the majority of these being p53 negative and bcl-2 positive. Forty-four per cent of the papillary carcinomas demonstrated low apoptosis rate, with variable bcl-2 positivity and mostly negative for p53. Fifteen per cent of papillary carcinomas showed a high apoptosis rate. They were p53 negative and mostly negative for bcl-2. The differences of staining in various tumours with respect to p53, bcl-2 and apoptosis were statistically significant. Correlation analysis demonstrated a significant relationship between apoptosis and bcl-2 expression in thyroid tumours (P < 0.001), whereas no relationship was seen with p53. CONCLUSION: These data suggest that bcl-2 expression in thyroid neoplasms is related to apoptosis, p53 expression is associated with high grade thyroid tumours, but may not be important in the apoptotic pathways in all thyroid tumours.

Apoptosis↗
PubMed1998

Characterization of Plesiomonas shigelloides from diarrheic children.

Infrastructure of 29 P. shigelloides strains isolated as the only positive finding from children with diarrhea (biochemical properties, antigenic structure, antigenic relationship to shigellae, ATB susceptibility and plasmids) were described. A big variety of 22 serovars in a relatively small number of strains was found, inclusive four new 0 (093, 094, 095 and 096) and one new H (H46) antigen. Some strains belonged to the so-called "Schubert antigenic scheme" the serovars of which come of surface water of small ponds in Germany.

Child↗
PubMed1997

Budesonide, a locally acting steroid, prevents graft rejection in a rat model of intestinal transplantation.

BACKGROUND: The requirement for potent systemic immunosuppression to prevent intestinal graft rejection has resulted in high rates of infection and post-transplant lymphoproliferative disease. Budesonide (BUD) is a locally acting steroid that is almost completely metabolized during its first pass through the intestinal wall and liver. The present study examined whether BUD could prevent small bowel allograft rejection without causing the adverse systemic effects associated with prednisolone. METHODS: Orthotopic Brown Norway to Lewis rat small bowel allotransplants were randomly assigned to treatment with low-dose BUD (0.1 mg/kg/day, p.o.) and high-dose BUD (1.0 mg/kg/day, p.o.) with and without cyclosporine (CsA; 2 mg/kg/day s.c.). The following parameters were assessed: allograft survival, recipient plasma adrenocorticotrophic hormone (ACTH) levels, recipient adrenal, splenic and thymic weights, recipient CsA levels, and graft histopathology. RESULTS: Low- and high-dose BUD alone did not prolong graft survival compared with the untreated group (9.1+/-0.4 days vs. 11+/-0.8 days vs. 9.7+/-0.4 days, respectively). However, when low-dose BUD and high-dose BUD were given in combination with CsA, the mean graft survival times were prolonged to 27.6+/-5.3 and 36.6+/-8.0 days, respectively (P<0.01). ACTH levels, adrenal weights, and thymic weights were not significantly different in the treatment and control groups receiving intestinal transplants. CONCLUSIONS: BUD enhances the immunosuppressive effects of CsA and prolongs small bowel allograft survival in rats without inhibiting normal ACTH release. These data suggest that BUD may be a useful immunosuppressive agent for clinical intestinal transplantation.

Adrenocorticotropic Hormone↗