Drive-field Frequency Dependent MPI Performance of Single-Core Magnetite Nanoparticle Tracers.

The drive-field frequency of Magnetic Particle Imaging (MPI) systems plays an important role for system design, safety requirements and tracer selection. Because the commonly utilized MPI drive-field frequency of 25 kHz might be increased in future system generations to avoid peripheral nerve stimulation, a performance evaluation of tracers at higher frequencies is desirable. We have studied single-core magnetite nanoparticles that were optimized for MPI applications, utilizing Magnetic Particle Spectrometers (MPS) with drive-field frequencies in the range from 1 kHz up to 100 kHz. The particles have core diameters of 25 nm and a hydrodynamic size of 77 nm. Measurements in the frequency range above 5 kHz were carried out with a newly designed MPS system. In addition, to exclude possible particle interaction, samples of different concentrations were characterized and compared.

Differential effects of chlorpromazine on the in vitro generation and effector function of cytotoxic lymphocytes.

Allograft rejection represents a cytotoxic response mediated to a large degree by thymus-derived T lymphocytes (1). The study of such cell-mediated cytotoxic phenomena has been greatly facilitated by the discovery first noted by Hayry and Defendi (2) and Wunderlich and Cany (3), that a natural consequence of allogeneic stimulation in an unidirectional mixed lymphocyte culture (MLC) was the appearance of cytotoxic lymphocytes specific for antigens present on the stimulator cells. Subsequent studies have shown that such in vitro generation of cytotoxic lymphocytes was dependent on the proliferative response in an MLC (4), was genetically determined (5), and possibly required the interaction of several subpopulations of T cells (6). We now report that the surface active agent chlorpromazine: (a) inhibits allogeneic stimulation of the proliferative response in an MLC; (b) inhibits the MLC generation of cytotoxic lymphocytes, (c) has no effect on the recognition, binding, or lysis of target cells by already sensitized lymphocytes; and (d) blocks a postproliferative membrane-mediated event, independent of proliferation, and necessary for the MLC generation of cytotoxic lymphocytes.

The effect of Pediococcus acidilactici on the gut microbiota and immune status of on-growing red tilapia (Oreochromis niloticus).

AIM: To assess Pediococcus acidilactici as a dietary supplement for on-growing red tilapia (Oreochromis niloticus). METHODS AND RESULTS: Tilapia were fed either a control diet or control diet supplemented with Ped. acidilactici at 10(7) CFU g(-1) for 32 days. Ped. acidilactici colonized the intestinal tract and significantly affected the intestinal microbial communities. PCR-DGGE revealed direct antagonism of gastric Ped. acidilactici with an endogenous uncultured bacterium during a period of reverting to nonsupplemented feeding. Light microscopy revealed that gut integrity and leucocyte levels were unaffected by Ped. acidilactici; however, blood leucocyte levels and serum lysozyme activity were elevated after 14-days' feeding. No significant improvements in growth performance were observed at the end of the trial (day 32), but survival was significantly higher in the probiotic group. CONCLUSIONS: The study demonstrates that oral supplementation of Ped. acidilactici modulates intestinal bacterial communities in on-growing red tilapia and also stimulates some aspects of the nonspecific immune response. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge this is the first study assessing the effects of probiotics on the gut microbiota of tilapia using culture-independent methods. Such methods are crucial to understand the mechanisms which underpin and mediate host benefits.

Evaluation of PEG-coated iron oxide nanoparticles as blood pool tracers for preclinical magnetic particle imaging.

Superparamagnetic iron oxide (SPIO) nanoparticles with optimized and well-characterized properties are critical for Magnetic Particle Imaging (MPI). MPI is a novel in vivo imaging modality that promises to integrate the speed of X-ray CT, safety of MRI and sensitivity of PET. Since SPIOs are the source of MPI signal, both the core and surface properties must be optimized to enable efficient in vivo imaging with pharmacokinetics tailored for specific imaging applications. Existing SPIOs like Resovist (ferucarbotran) provide a suboptimal MPI signal, and further limit MPI's in vivo utility due to rapid systemic clearance. An SPIO agent with a long blood half-life (t1/2) would be a versatile MPI tracer with widespread applications. Here we show that a long circulating polyethylene glycol (PEG)-coated SPIO tracer, LS-008, provides excellent colloidal stability and a persistent intravascular MPI signal, showing its potential as the first blood pool tracer optimized for MPI. We evaluated variations of PEG coating and found that colloidal stability of tracers improved with the increasing PEG molecular weight (keeping PEG loading constant). Blood circulation in mice, evaluated using Magnetic Particle Spectrometry (MPS), showed that the t1/2 of SPIO tracers varied with both PEG molecular weight and loading. LS-008, coated with 20 kDa PEG at 18.8% loading capacity, provided the most promising long-term colloidal stability with a t1/2 of about 105 minutes in mice. In vivo MPI imaging with LS-008 using a 7 T/m/µ0 3D x-space MPI mouse scanner revealed a prolonged intravascular signal (3-5 hours) post-injection. Our results show the optimized magnetic properties and long systemic retention of LS-008 making it a promising blood pool MPI tracer, with potential to enable MPI imaging in cardio- and cerebrovascular disease models, and solid tumor quantification and imaging via enhanced permeation and retention.

Physiological and pharmacological stimulation of pancreatic islet hormone secretion in type I diabetic pancreas allograft recipients.

Successful heterotopic and denervated pancreas allograft transplantation (PAT) often results in normoglycemia and peripheral hyperinsulinemia in insulin-dependent (type I) diabetic recipients. The contribution of altered hepatic insulin extraction (HIE) to the resulting hyperinsulinemia in such patients remains uncertain. Furthermore, whether the denervated pancreas allografts exhibit beta-cell hyperresponsiveness to physiological and pharmacological stimulation is controversial. We evaluated beta-cell function and HIE after successful whole cadaveric PAT with systemic venous drainage in 13 type I diabetic patients before and after mixed-meal and intravenous glucose and glucagon administration. The results were compared with those of 5 nondiabetic patients with kidney transplantation only, who had native innervated pancreases with portal insulin delivery and were receiving an equivalent triple immunosuppressive therapy (cyclosporin, azathioprine, and prednisone), and 7 healthy control subjects with no family history of diabetes. After PAT, fasting and poststimulation serum glucose concentrations were normalized. PAT was associated with marked basal hyperinsulinemia (3- to 8-fold) as assessed by immunoreactive insulin (IRI) levels in type I diabetic patients (mean +/- SE 345 +/- 43 pM) compared with control subjects (43 +/- 14 pM) and nondiabetic kidney-transplantation patients (129 +/- 38 pM). After mixed-meal ingestion, the mean incremental integrated insulin area was similar in PAT patients (18 +/- 3 nM.min) compared with kidney-transplantation patients (20 +/- 4 nM.min) and healthy control subjects (21 +/- 3 nM.min). Basal serum C-peptide levels were significantly greater in PAT (1.72 +/- 0.13 nM) and kidney-transplantation (2.15 +/- 0.33 nM) patients than in healthy control subjects (0.50 +/- 0.10 nM; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclosporin A for immunosuppression: observations in rat heart, pancreas, and islet allograft models and in human renal and pancreas transplantation.

Cyclosporin A (CsA) is a unique immunosuppressive cyclic polypeptide that is currently being used, either alone or in combination with low-dose prednisone, to treat recipients of renal or pancreas allografts in clinical trials. CsA is very effective in preventing rejection of heart and renal allografts in rodents, but in nontoxic doses does not consistently prevent rejection of pancreas and islet allografts. Therefore, we tested low-dose CsA in various combinations with low-dose prednisone, azathioprine, or total lymphoid irradiation in rat heart, pancreas, and islet allograft models. Several combinations are synergistic and when administered continuously can indefinitely prevent rejection of heart allografts, but only delay rejection of pancreatic allografts, transplanted across a major histocompatibility barrier, CsA by itself prolonged the survival of islet allografts transplanted across a minor, but not a major, histocompatibility barrier. CsA and azathioprine had a synergistic effect in the minor histocompatibility barrier islet transplant model, but, in the nontoxic combinations tested, could not prevent rejection indefinitely. A randomized prospective trial comparing standard immunosuppressive therapy (ALG, prednisone, and azathioprine), with CsA and low-dose prednisone for clinical renal allotransplantation is ongoing at the University of Minnesota. Current actuarial 1-yr graft survival is 93% for CsA-treated patients (N = 48) and 81% for conventionally treated patients (N = 52). Patient survival is 98% for CsA and 100% for conventionally treated patients. A pilot trial of CsA in the clinical pancreas transplant program at the University of Minnesota is also underway. Since 1978, 46 pancreas transplants have been performed in 43 patients. Of 30 technically successful pancreatic allografts, 5 of 12 recipients treated with conventional immunosuppression and 6 of 18 recipients treated with CsA currently have functioning grafts and are insulin independent between 1 and 44 months after transplantation. The results of metabolic studies are similar in conventional and CsA-treated patients with functioning pancreas grafts. Since pancreas grafts may fail for reasons other than rejection, further observations are needed to ascertain the role of CsA in clinical pancreas transplantation.

Fever in renal transplant recipients: causes, prognostic significance and changing patterns at the University of Minnesota Hospital.

During a three year period in which 433 renal transplants were performed, 194 episodes of fever were documented in allograft recipients hospitalized at the University of Minnesota. Viral infections were responsible for over half of the febrile episodes, and 98 (51 percent) of the fevers were associated with cytomegalovirus (CMV), either occurring alone or in conjunction with allograft rejection or another systemic infection. Bacterial infections, fungal infections and rejection were other important causes of fever, accounting for 14 percent, 5 percent and 13 percent of the febrile episodes, respectively. Most fevers occurred in the first four months after transplantation; although about two thirds of these fevers were due to CMV, only 17 percent of fevers that occurred more than one year after the renal transplant were due to CMV. Bacterial and fungal infections and malignancy were important causes of these fevers. Of the febrile illnesses associated with transplant nephrectomy or death, a majority occurred in patients with CMV disease. Secondary bacterial and/or fungal infections were observed in a large majority of patients with lethal CMV disease. During the third year of this study there was a significant decrease in the proportion of febrile episodes due to CMV.

Fatal central nervous system infection with varicella-zoster virus in renal transplant recipients.

Three renal transplant patients with culture-positive central nervous system infections resulting from varicella-zoster virus died of the virus infection. No finding predicting a poor outcome in these patients could be identified. Varicella-zoster infection in transplant recipients is a potentially fatal disease, and upon diagnosis should it be treated by (1) reduction in immunosuppression, and (2) initiation of either vidarabine or acyclovir as specific antiviral therapy.

Suppression of in vitro cell-mediated lympholysis generation by alloactivated lymphocytes. Examination of radioresistant suppressive activity.

We investigated the radioresistant (1000 rads) suppression of CML generation mediated by alloactivated murine splenocytes. Suppressive cells were generated in MLCs by stimulation of (A X 6R)F1 splenocytes with irradiated C57BL/10 splenocytes. Suppressive cells could lyse targets bearing H-2b alloantigens, but would not lyse parental B10.T(6R) or B10.A targets. Suppressive activity was detected by including the alloactivated (A X 6R)F1 cells in B10.T(6R) anti-B10.A(1R) MLCs. Relative to the suppressive (A X 6R)F1 cells, the B10.A(1R) lymphocytes display both parental and suppressor-inducing alloantigens. In the absence of a suppressive population, B10.A(1R) stimulators cause B10.T(6R) splenocytes to generate cytolytic activity specific for both H-2Db (suppressor-inducing) and H-2Kk (suppressor-borne) target determinants. The irradiated, alloactivated (A X 6R)F1 cells decrease the H-2Db-specific CML generated in this system, thus mediating apparent antigen-specific suppression. However, cytolytic activity concomitantly generated in the same culture against the unrelated H-2Kk target determinants is similarly reduced by the (A X 6R)F1 cells. Thus, radioresistant suppression by alloactivated splenocytes is not necessarily antigen-specific. The irradiated (A X 6R)F1 cells would not suppress the generation of H-2Kk-specific CTL in B10.T(6R) anti-B10.A MLCs. Hence, the irradiated (A X 6R)F1 cells can impede CML generation against third-party alloantigens if, and only if, those alloantigens are coexpressed with suppressor-inducing alloantigens on the stimulator cells in suppressed MLCs. Similar results were also obtained using a different histoincompatible lymphocyte combination. Since the pattern of suppressor specificity and the pattern of CTL specificity were identical and concomitant under these experimental conditions, these data are consistent with the hypothesis that radioresistant suppression by alloactivated lymphocytes can reflect coincidental in vitro cytolytic T cell function in vitro.

Sequential antilymphoblast globulin and cyclosporine for renal transplantation.

The nephrotoxic effects of cyclosporine (CsA) seem to be augmented by co-existing renal injury. A high rate of prolonged delayed function (acute tubular necrosis [ATN]) and non-function (NF) has been associated with the use of CsA prior to and following renal transplantation. Cyclosporine has also been associated with a slower recovery of allograft function and poor baseline renal function even in allografts that function immediately compared with conventionally treated recipients. In 1983 we hypothesized that the rate of ATN and NF following renal transplantation could be decreased and more normal kidney function achieved if renal injury was resolved before adding the nephrotoxic effects of CsA. A group of 300 nonsplenectomized, uremic recipients have received 304 renal transplants and have been initially immunosuppressed with azathioprine, prednisone, and Minnesota antilymphoblast globulin (ALG) prior to starting maintenance CsA and prednisone. The incidence of NF has been 1.9% and the development of ATN has been 7.6% following transplantation with sequential use of ALG and CsA. Other benefits to the renal recipient have also occurred with use of this immunotherapy protocol. Renal allograft survival for recipients of first, second, and third renal allografts has been higher than that generally reported with cyclosporine and prednisone alone. Rejection episodes have been infrequent during the first six months posttransplant, as 75% and 62% of first and second renal allograft recipients have remained rejection-free. Clinically significant infectious complications were infrequent. No cadaver recipient has developed a lymphoma. Moreover, the initial hospitalization following transplantation with sequential ALG/CsA has been short and generally uncomplicated. We conclude that sequential ALG/CsA following renal transplantation provides excellent early posttransplant immunosuppression while avoiding the nephrotoxic effects of CsA and also provides the steroid and infection-sparing benefits derived from maintenance CsA therapy.

Frequency of human alloantigen-reactive T lymphocytes. III. Evidence that cyclosporine has an inhibitory effect on human CTL and CTL precursors, independent of CsA-mediated helper T cell dysfunction.

We have used limiting dilution analysis to study the behavior of alloantigen-reactive cytolytic T lymphocytes derived from human peripheral blood. During these studies, we found that the presence of cyclosporine in limiting dilution microcultures significantly impairs the subsequent development of alloantigen-reactive cytolytic T cell activity. As a result, CsA reduces the estimate of CTL precursor frequency by limiting dilution analysis. CTL frequency estimates are reduced by CsA in a dose-dependent manner, and concentrations of CsA that are readily achieved in human peripheral blood (100-1000 ng/ml) are capable of reducing estimates of CTL frequency by 90% to 100%. Further studies revealed that (1) human CTL derived either from fresh peripheral blood or from primary mixed lymphocyte cultures are sensitive to the suppressive effects of cyclosporine in limiting dilution microcultures, indicating that CsA influences both alloantigen-primed CTL and CTL precursors; (2) CsA impairs an immunologic event or events, that occurs for at least the first four days of limiting dilution microculture incubation; (3) CsA-mediated suppression is eliminated by separation of CTL from cyclosporine; (4) CsA blocks development of CTL generation, but not cell proliferation in limiting dilution microcultures; and (5) the CsA-mediated suppression is not reversed by supraoptimal concentrations of IL-2, high concentrations of gamma-IFN, or supplementation with the multiple lymphokines present in MLC supernatants. These data suggest that CsA may have a direct inhibitory influence on the differentiation of human CTL precursors that is independent of helper T cell dysfunction.

Improved immediate function of renal allografts with Belzer perfusate.

The characteristics of 254 cadaveric kidneys were evaluated and the incidence of immediate function identified. The Belzer perfusate was used primarily (n = 140) and secondarily (n = 14) in combination with pulsatile machine perfusion. These two groups were compared with a previous group of kidneys machine-perfused with silica gel (cryoprecipitated human plasma). The incidence of immediate function of the group primarily perfused with Belzer perfusate was statistically significantly improved over that of the silica gel. The secondarily perfused Belzer group, "imported" kidneys previously preserved with simple cold storage, had notably longer periods of preservation and higher resistances on the machine. However, 100% of this group functioned immediately. Other findings in this study show that the Belzer perfusate allows for improved parenchymal function posttransplant, as noted by a more rapid clearance of serum creatinine posttransplant. When comparing the immediate function group with those suffering early dysfunction, there is a statistically significant increased resistance on the machine in the latter group. This allows for prediction of immediate function based on perfusion characteristics of the kidney. The Belzer perfusate, composed of metabolic substrates for high-energy phosphate production, improves the incidence of immediate function in machine-perfused kidneys, as well as improved qualitative function posttransplant. It also is effective as a "rescue" mechanism in previously simple cold-stored (ATP-depleted) kidneys.

Differential susceptibility of human peripheral blood lymphocyte subpopulations to mitogenic activation. Influence of methylprednisolone.

The inhibition of the mitogenic activation of human peripheral blood lymphocyte (PBL) subpopulations by methylprednisolone (MP) was dependent on the mitogen used. Purified human T cells were more sensitive to the effects of MP than were B cells or PBLs, especially when these cells were activated by pokeweed mitogen (PWM). MP did not function by inhibiting binding of mitogen to the cell surface. After being mitogenically activated, human lymphocytes were resistant to the effects of MP. These effects of MP were shown to be reversible. Monocytes did not provide a significant degree of protection to mitogenically activated human T cells incubated with MP. These data suggest that MP-induced inhibition of the mitogenic activation of human PBLs may be a reflection of lymphocyte heterogeneity, and that the differential sensitivity of PBLs to MP may be used to isolate functionally different subpopulations of these cells.

Partial characterization of cytotoxic cells infiltrating sponge matrix allografts.

Adapting the Roberts and Hayry sponge allograft model, we have demonstrated the presence of an enriched, specifically cytotoxic population of cells which infiltrate rejecting sponge allografts. The number of cells infiltrating a rejecting sponge allograft peaks on day 14 after transplantation. Utilizing a short-term 51chromium cytotoxicity assay, peak antiallogeneic killing was demonstrable on day 14 also. Only T cell killing was apparent for the first 15 days after transplantation. After day 20, specific cytolysis was present which was not sensitive to anti-theta serum and complement. The infiltrating cytotoxic cells are large, specifically cytotoxic, do not proliferate in culture, do not respond to mitogen, and do not respond in mixed lymphocyte culture even to the same alloantigen to which the animal had been sensitized. In contrast, spleens from sponge-bearing animals kill poorly, respond to mitogen, and respond vigorously in mixed lymphocyte culture to specific and nonspecific alloantigens. The following hypotheses are set forth with regard to the cytotoxic lymphocytes (1) Such cells may be end stage and cannot proliferate. (2) The cytotoxic cells may kill the stimulator cells more rapidly than they can be stimulated to proliferate. (3) The sponge cell population may be enriched for nonspecific supressor cells. (4) The sponge cells may be devoid of helper T cells.

Frequency of human alloantigen-reactive T lymphocytes. II. Method for limiting dilution analysis of alloantigen-reactive helper T cells in human peripheral blood.

Quantitative immunologic techniques for analysis of human alloreactivity are currently lacking in transplantation immunology. We report a rapid, sensitive, and quantitative limiting dilution analysis technique that provides a minimal estimate of the number of peripheral blood mononuclear cells (PBMC) capable of secreting interleukin-2 (operationally defined as helpter T lymphocytes) when cultured in vitro with allogeneic PBMC bearing serologically identified MHC disparities. Using this LDA technique, we have estimated that approximately 1/500 to 1/2000 (0.2% to 0.05%) of the PBMC from various individuals can secrete IL-2 after in vitro contact with completely major-histocompatibility-complex-disparate PBMC. Under normal conditions the HTL frequency in human peripheral blood appears quite stable, based on serial analysis of HTL frequency in a healthy human donor. This LDA technique is more rapid and informative than the MLR, and may be useful for pretransplant evaluation and posttransplant monitoring of donor reactivity in transplant recipients.

In vivo mechanisms of alloreactivity. I. Frequency of donor-reactive cytotoxic T lymphocytes in sponge matrix allografts.

To study the development of alloreactive cytolytic T cells in vivo, C57BL/6 mice were implanted s.c. with polyurethane sponges bearing allogeneic (DBA/2) splenocytes. On various days thereafter, cells that had accumulated in these sponge grafts were tested for cytolytic activity against DBA/2 target cells in 51Cr-release assays, and for frequency of DBA/2-reactive CTL as determined by limiting dilution analysis (LDA). During these studies we found that LDA was consistently more efficient at detecting alloreactive CTL than the traditional 51Cr-release assays. As determined by LDA, sponge grafts initially infused with DBA/2 splenocytes acquired high levels of DBA/2-reactive CTL, while sponge grafts infused only with saline acquired few DBA/2-reactive CTL. DBA/2-reactive CTL first became detectable in sponge allografts approximately four days after implantation, and reached a maximal frequency by the 10th day after implantation. This frequency was maintained for at least the next seven days. In contrast, the ability of cellular infiltrates from sponge allografts to lyse DBA/2 target cells in 51Cr-release assays was not detectable until the 7th day after implantation, was optimal by the tenth day, but declined thereafter to lower levels, as observed on the 13th and 17th day after implantation. Since the frequency of CTL remains stable through the 17th day after implantation, this decline in cytolytic activity may indicate that donor-reactive CTL remain in sponge allografts, but they continue to differentiate to a noncytolytic status. We further observed that previous allosensitization with skin grafts markedly accelerates the accumulation of alloreactive CTL in sponge allografts. The mechanism that promotes more rapid accumulation of CTL in allosensitized sponge graft recipients remains to be established. Throughout these studies, we observed that even at peak development, donor reactive CTL are, at most, 0.2% of the cells recovered from sponge allografts. This raises some questions regarding not only the fundamental role of the CTL in allograft rejection, but also the role of the remaining 99.8% of the allograft-infiltrating cells.

In vivo mechanisms of alloreactivity. VI. Evidence that alloantigen deposition initiates both local and systemic mechanisms that influence CTL accumulation at a graft site.

We have used sponge matrix allografts to investigate how alloantigen influences the pattern of CTL accumulation at a graft site. These studies employed two limiting dilution analysis techniques to monitor CTL accumulation. One technique quantitates the subpopulation of CTL that show evidence of in vivo contact with graft alloantigens (alloantigen-conditioned CTL or cCTL). The other quantitates all CTL with specificity for graft alloantigens, regardless of their differentiative status. Using these techniques, we have demonstrated that sponge allografts acquire three types of CTL: (a) donor-reactive CTL precursors (pCTL), (b) donor-reactive cCTL, and (c) pCTL with irrelevant antigen specificity. Sponge isografts rarely acquire LDA-detectable CTL, unless they receive a concurrent allogeneic stimulus at a distant anatomic site. In that instance, sponge isografts acquired pCTL, but not cCTL. This indicates that an ongoing immune response to alloantigens can influence the immunologic characteristics of an unrelated inflammatory response occurring elsewhere. We further observed that sponge isografts can be made to acquire alloreactive cCTL only when specific alloantigens are placed in the isograft. This indicates that specific grant alloantigen present at the graft site plays a necessary but undefined role in the acquisition or development of cCTL in sponge allografts. Collectively, these data demonstrate that alloantigen deposition initiates both local and systemic mechanisms that influence alloreactive CTL accumulation at a graft site.

Combined nephrotoxic effects of cyclosporine and endotoxin.

This study presents experimental evidence that cyclosporine (CsA) potentiates the nephrotoxicity of endotoxin. This study was motivated by clinical observations in 4 cyclosporine (CsA)-treated renal allograft recipients who developed severe, and sometimes irreversible, nephrotoxicity after infections. CsA or vehicle was administered intramuscularly to rabbits for 5 days, and subsequently both groups of animals received one dose of endotoxin intravenously. Compared with controls, CsA-treated animals demonstrated significantly higher elevations of blood urea nitrogen and serum creatinine 24 hr after endotoxin. By contrast, both groups of animals developed similar degrees of thrombocytopenia. Histologic evaluation of kidney tissues 24 hr after endotoxin revealed significantly greater tubular toxicity and a higher glomerular polymorphonuclear leukocyte (PMN) infiltration in CsA-treated animals. Semiquantitative scores of tubular damage correlated directly with the mean number of PMN/glomeruli in both groups of animals. Immunofluorescent microscopy of kidney tissues was negative for fibrinogen and for complement deposition in both CsA and control groups. We conclude that CsA enhances endotoxin nephrotoxicity in rabbits. This effect does not appear to be mediated by activation of coagulation factors. However, a role for PMN is suggested. CsA should be used with caution in patients with deteriorating renal function who are suspected of having severe bacterial infections.

Cyclosporine nephrotoxicity in spontaneously hypertensive rats.

In the present study, we investigated the combined, nephrotoxic effects of cyclosporine (CsA) and hypertension in young, spontaneously hypertensive rats (SHR). After 4 weeks of CsA therapy, SHR, compared with oil-treated SHR, showed an acceleration in the development of hypertension, mild renal insufficiency, and the accumulation of periodic-acid-Schiff-positive (PAS [+]) material in periglomerular arterioles. By electron microscopy, PAS(+) material was composed of intracytoplasmic inclusion bodies consistent with the accumulation of renin granules. This finding was demonstrated in SHR after 4 weeks of CsA therapy but not after 8 weeks of therapy. By contrast, CsA had no significant effect on blood pressure in Wistar-Kyoto rats, a normo-tensive control. To investigate the effect of unilateral nephrectomy (UNx) on the development of renal histopathologic changes in this model, SHR were subjected to uninephrectomy and CsA or oil therapy. UNx accelerated the development of hypertension in all SHR groups. SHR subjected to UNx demonstrated no renal histopathologic changes after CsA or oil treatment. In conclusion, CsA accelerates the development of hypertension in SHR, and this effect is probably renin-mediated. The combination of UNx and CsA therapy in the SHR does not result in significant renal histologic damage.

Serum cyclosporine kinetic profile. Failure to correlate with nephrotoxicity or rejection episodes following sequential immunotherapy for renal transplantation.

Cyclosporine (CsA) level monitoring in renal transplant recipients has been thought to aid in separating clinical episodes of nephrotoxicity from rejection. Twenty-four-hour CsA pharmacodynamic profiles were obtained from 85 consecutive primary renal transplant recipients in the immediate peritransplant period in order to determine the value of this test in predicting subsequent episodes of nephrotoxicity or rejection. All patients were treated with sequential antilymphoblast globulin/CsA following transplantation. Serum samples from each recipient were analyzed for CsA levels estimated by radioimmunoassay (RIA) four days after initiation of a daily single oral CsA dose (10 mg/kg/day). A total of 52 episodes of rejection and 303 episodes of nephrotoxicity occurring within the first six months posttransplant were correlated with selected parameters from the immediate posttransplant CsA kinetic profile. For each profile these parameters were maximum CsA level, time to maximum CsA level, minimum CsA level, 95% clearance time of CsA, and total CsA accumulation and clearance during the 24 hr following ingestion of CsA. No significant correlation was found between any of these parameters and either the incidence or frequency of rejection or nephrotoxic episodes, as determined by least-squares linear regression analysis. Furthermore, following a single oral dose of CsA (10 mg/kg/day), no correlation could be found between the dose and the absorption, accumulation, metabolism, and clearance of the drug. In conclusion, maximum CsA level, time to maximum CsA level, minimum CsA level, 95% clearance time of CsA, and total CsA accumulation and clearance measured from CsA kinetic profiles cannot be correlated with or predict the incidence of rejection or nephrotoxic episodes that subsequently occur during the first six months following renal transplantation.