Modulatory role of angiotensin-II in the secretion of atrial natriuretic factor in rabbits.

This study was designed to investigate whether the increase in circulating atrial natriuretic factor (ANF) levels produced by angiotensin II (Ang II) is a consequence of the hemodynamic changes or whether it occurs also in the absence of pressor changes. For this purpose in anesthetized and awake rabbits we evaluated the effects of Ang II (0.1 micrograms/kg.min) alone or during the simultaneous infusion of sodium nitroprusside (NP) at a dose titrated to abolish the pressor effects. Systemic blood pressure increased from 76 +/- 4 to 113 +/- 5 mm Hg (P less than 0.001) during Ang II and from 76 +/- 2 to 75 +/- 3 mm Hg (P = NS) during Ang II plus NP. The alpha-adrenergic agonist phenylephrine, used as a control, raised blood pressure from 65 +/- 2 to 101 +/- 8 mm Hg (P less than 0.001), and its pressor effect was abolished by the concomitant infusion of NP (64 +/- 2 to 61 +/- 1 mm Hg; P = NS). The increase in plasma ANF levels produced by Ang II alone (from 36.5 +/- 5 to 237 +/- 57 pg/ml; P less than 0.001) was not different from that observed during Ang II plus NP (from 46 +/- 10 to 207 +/- 88 pg/ml; P less than 0.001). In contrast, the stimulatory effect on ANF release of phenylephrine (from 56.1 +/- 9 to 202 +/- 40 pg/ml; P less than 0.001) was completely abolished when its pressor effects were prevented by the combined infusion of NP (from 58.5 +/- 15 to 42.3 +/- 10 pg/ml; P = NS). These results show that the stimulatory effect of Ang II on ANF release can be clearly dissociated from its pressor effect, whereas the increase in plasma ANF levels caused by phenylephrine is strictly related to its hemodynamic effect. Therefore, Ang II is capable of modulating ANF secretion in a manner that is independent of its pressor actions. In addition, our results suggest that ANF release is not solely linked to myocyte stretch.

Mechanisms of immunologic unresponsiveness induced by ultraviolet-irradiated donor-specific blood transfusions and peritransplant cyclosporine.

Recipient pretreatment with UV-B irradiated donor-specific blood transfusions (UV-DST) combined with peritransplant cyclosporine on days 0, +1, and +2 leads to permanent cardiac allograft survival in the ACI-to-Lewis rat strain combination. This study investigates the mechanisms of immunologic unresponsiveness induced by UV-DST and CsA by examining several in vitro and in vivo parameters in long-term cardiac allograft recipients. The results of the in vitro studies demonstrate that thoracic duct lymphocytes (TDL) of treated and allografted Lewis rats respond less in a mixed lymphocyte reaction to donor splenic lymphocytes (SpL) by 69%, 75%, and 73% (P less than 0.001) at 30, 50, and 100 days after transplantation, respectively, compared with controls, while the response to a third-party (W/F) SpL is unimpaired. In coculture experiments, the TDL from treated recipients specifically suppressed the response of unmodified Lewis TDL to ACI SpL by 59% and 40% (P less than 0.01) at 30 and 50 days after transplantation, respectively, while responses to W/F SpL were suppressed by only 3-6%. The sera obtained from ungrafted rats transfused with UV-DST suppressed the MLR between unmodified Lewis TDL and ACI SpL by 31% (P less than 0.05) while the sera from UV-DST and CsA-treated and allografted rats specifically suppressed the MLR by 75%, 80% (P less than 0.001) and 37% (P less than 0.01) at 10, 30, and 50 days after transplantation, respectively. In vivo adoptive transfer of 10(4) donor-type dendritic cells (DC) into recipients of beating cardiac allografts at 40 or 60 days after transplantation led to rapid and acute allograft rejection, while the adoptive transfer of 10(8) unseparated SpL obtained at 50 days after transplantation from treated Lewis recipients to syngeneic naive hosts led to a modest but significant prolongation of ACI test cardiac allografts. The transfer of serum from treated and allografted recipients at 10, 30, and 50 days after transplantation led to specific and significant prolongation of test grafts in syngeneic naive hosts. These findings suggest that the mechanisms underlying the in vivo immunologic unresponsiveness induced by pretreatment with UV-DST and peritransplant CsA include inactivation without elimination of class II-antigen presenting cells (APC), generation of specific serum suppressor factor(s) and/or antiidiotypic antibody, and induction of donor-specific suppressor cells.

UVB pretreatment of rat bone marrow allografts. Prevention of GVHD and induction of allochimerism and donor-specific unresponsiveness.

Ultraviolet B irradiation has been used to pretreat blood and islets to prevent subsequent graft rejection. In this study the optimal dose of UVB irradiation of bone marrow was determined in syngeneic recipients and was subsequently applied to in-vitro treatment of bone marrow allografts. UVB pretreatment of donor bone marrow inoculum led to complete prevention of GVHD in allogeneic rat recipients without major marrow or other toxicity. Long-standing recipients of allogeneic UVB-BM became stable adult chimeras. The recipients of allogeneic BM were populated by donor-type peripheral blood lymphocytes and did not reject host or donor-type heart grafts. The BM allograft recipients were immunocompetent as measured by their ability to normally reject third-party cardiac allografts. We suggest that the prevention of GVHD and induction of stable chimerism in adult recipients of allogeneic UVB-BM may be mediated by suppressor mechanisms.

Beta-adrenergic receptor sensitivity and guanine nucleotide regulatory proteins in transplanted human hearts and autotransplanted baboons.

This study was conducted in human subjects and in baboons to assess elements of the beta-adrenergic receptor complex in vivo and in vitro following cardiac transplantation. In human subjects, the concentration at which administered isoproterenol increased heart rate by 25 beats per min was within the normal range (mean, 3.2 +/- 0.4 micrograms). Myocardial biopsies and lymphocytes were obtained from 14 transplant recipients undergoing routine right heart catheterization. The stimulatory guanine nucleotide regulatory protein, Gs, was significantly greater in the lymphocyte than in right ventricular myocardium (5.8 +/- 1.7 vs. 2.0 +/- 0.5 relative to standard rat heart membrane preparation, P less than 0.05). In contrast, Gi was significantly greater in the myocardium than in the lymphocyte (4.2 +/- 1.3 vs. 1.1 +/- 0.3, P less than 0.025). There was no correlation between lymphocyte and cardiac G protein determinations. In the autotransplanted baboon heart, beta-receptors were increased (73 +/- 4 vs. 36 +/- 10 fmol/mg, P less than 0.05). Gs was not significantly different in denervated myocardial tissue vs. control cardiac tissue (1.1 +/- 0.2 vs. 0.8 +/- 0.2, P greater than 0.05). However, the inhibitory G protein, Gi, was significantly greater in transplanted animals (0.4 +/- 0.1 vs. 0.2 +/- 0.04, P less than 0.05). Relative enrichment of a Gi-like protein in the autotransplanted baboon heart was associated with a non-statistically significant trend towards a uniform reduction in basal and Gs-mediated adrenergic effects on adenylate cyclase activity. Despite the lack of biochemical evidence of enhanced beta-adrenergic receptor-mediated adenylate cyclase coupling, denervation in the autotransplanted baboon was associated with in vitro evidence of chronotropic and inotropic supersensitivity to isoproterenol. The results call into question the notion of adrenergic hypersensitivity in human subjects following cardiac transplantation, indicate the potential role for guanine nucleotide regulatory proteins in mediating responses of the denervated heart, and distinguish between several characteristics of the chronically denervated, transplanted human heart compared with the acutely auto-denervated of the baboon heart.

Prosthetic abdominal fascial closure after ventricular assist device insertion.

The requirement for adequate abdominal domain does not allow placement of left ventricular assist devices into patients with body surface areas less than 1.5 m2. We describe a technique for prosthetic abdominal wall closure that may allow placement of devices into smaller recipients, primarily children and women.

Relation of HLA antibodies and graft atherosclerosis in human cardiac allograft recipients.

Although cyclosporine has helped make heart transplantation a clinical reality, long-term survival remains limited by rejection and graft atherosclerosis. We have previously demonstrated the development of alloreactive lymphocytotoxic antibodies in baboon recipients of heterotopic heart transplants despite cyclosporine administration. The hypothesis of the present study is that cyclosporine-treated human heart transplant recipients are also capable of generating strong humoral immune responses that might adversely affect clinical outcome. Serial serum specimens from 240 heart transplant recipients were tested against a reference panel of 70 cells for anti-HLA lymphocytotoxic antibodies. Patients with serum panel reactive antibody levels greater than 10% were considered antibody producers, whereas those with serum panel reactive antibody levels less than 10% were considered nonproducers. To establish the time course of post-transplantation sensitization, we have tested anti-HLA antibodies in sequential sera at 3-month intervals after transplantation. The 4-year actuarial survival rate of those patients whose panel reactive antibody levels were greater than 10% during the first 6 months after transplantation was 70%, whereas the survival rate of patients whose levels were less than 10% during this time was 93%. The results were significantly different (p less than 0.01). Further heterogeneity among the patients was demonstrated by differential analysis of survival in patients who showed (1) panel reactive antibody levels less than 10% in any of the sera obtained during the first year after transplantation, (2) panel reactive antibody levels greater than 10% in sera obtained during the first 6 months but not thereafter, and (3) panel reactive antibody levels greater than 10% throughout the first year after transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Photochemotherapy in human heart transplant recipients at high risk for fatal rejection.

Heart transplant recipients in whom high levels of lymphocytotoxic antibodies directed towards a spectrum of histocompatibility antigens develop frequently represent difficult management problems. Recipients of multiple transplants and multiparous females generally form higher levels of panel reactive antibodies, which have been associated with fatal rejection episodes and accelerated graft atherosclerosis. In this study, two multiple transplant patients with preexistent high levels of panel reactive antibodies and two multiparous women who were considered at risk of sensitization were treated with a new form of immunotherapy termed photochemotherapy in addition to conventional immunosuppression. High levels of panel reactive antibodies have been reduced, and patients have suffered few rejection episodes and no infectious complications. This preliminary experience shows that the addition of photochemotherapy to conventional regimens may improve the clinical course of hypersensitized transplant patients without additional immunosuppressive risk.

Right ventricular obstruction in aortic dissection: a mechanism of hemodynamic collapse.

The main and right pulmonary arteries may be compressed by the false lumen of a type I aortic dissection. We report a 73-year-old women with a dissection of the aorta in whom echocardiographic examination revealed acute pulmonary arterial compression causing right ventricular failure and hemodynamic collapse.

Low dose aprotinin as blood saver in open heart surgery.

Bleeding after open heart surgery is still a great concern for the surgeon, especially when the surgical field has been revised accurately and hemostatic stitches and electrical cauterization have been used extensively. Among non-surgical adjuncts, aprotinin has been reported as very effective in reducing complications. At the time we started using this drug, we intended to test two different dosages lower than those reported in the literature. We evaluated three groups of 18 patients: the first (A) received about 350 mg of aprotinin from the start of anesthesia up to the end of operation (140 mg in the priming of cardio-pulmonary bypass and 70 mg/h i.v. during the procedure; the second (A/2) received half that dose (i.e. 70 mg and 35 mg, respectively), and the third (C) did not receive aprotinin. We compared in these groups: postoperative bleeding, blood transfusions, red blood cells, hemoglobin, hematocrit, platelets. The results were good only in the A group: bleeding was reduced and few transfusions were required. The patients in the A/2 and C groups did not show significant differences. From our observations we conclude that aprotinin is a useful adjunct, but has to be given in the proper dose.

Morphological and molecular characterization of healthy human ascending aorta.

Knowledge of the characteristics of the normal human aorta has been constrained by lack of data on fresh aortic tissue, especially from healthy individuals. In this study, the gene expression and morphological characteristics of the thoracic ascending aorta (AA) of healthy organ donors have been evaluated, with the aim of providing reference data for the analysis of pathological AAs. We analysed by RT-PCR the differential expression of mRNAs coding for myocardin, smoothelin, alpha-smooth muscle actin (alpha-SMA) and the ED-A isoform of fibronectin (ED-A FN) in AA specimens from donors, integrating the results with immunohistochemical analysis of the same targets. Morphological and morphometric characteristics of the AAs were also evaluated. In order to account for possible regional variations in wall structure, the convexity of the aortic profile was compared to the concavity. No differences in gene expression occurred for any of the target genes between the concavity and the convexity of AAs. Immunohistochemistry revealed a different distribution of total FN and of its ED-A isoform in the media and in the intima. Smoothelin is expressed by the majority of cells in the media, with some positive cells also in the intima. Alpha-SMA is expressed in all the tunicae. Immunohistochemistry also revealed in the convexity of 50% of AAs the presence of discrete areas in the subadventital media with altered structure and cell morphology and with altered gene expression, resulting positive for ED-A FN and alpha-SMA, but not for smoothelin, indicating the occurrence of early lesions also in macroscopically healthy AAs.