Characterization of mixed syngeneic-allogeneic and syngeneic-xenogeneic islet-graft rejections in mice. Evidence of functional impairment of the remaining syngeneic islets in xenograft rejections

Allogeneic mouse islets or xenogeneic rat islets, or fetal porcine islets were implanted under the renal capsule of C57BL/6 mice either alone or carefully mixed with syngeneic islets. With this experimental model the syngeneic islets, although not rejected themselves, are exposed to cytokines and inflammatory mediators released during either allograft or xenograft rejection. No differences in insulin content could be observed between mixed islet grafts and pure syngeneic islet grafts 6 wk after transplantation. Neither was there any morphological evidence of a non-specific destruction of syngeneic islets. These findings suggest that the mechanisms of both allograft and xenograft rejections are highly specific. The hormone release from the mixed syngeneic-allogeneic grafts was similar to that from pure syngeneic islet grafts. In contrast, a pronounced impairment of both the first and second phases of insulin release was observed 2 wk after implantation in mixed syngeneic-xenogeneic islet grafts. When perfusing the mixed islet graft after completed rejection of the concordant xenogeneic rat islets (6 wk after implantation), the insulin release from the remaining syngeneic mouse islets was identical to that of control grafts. However, syngeneic mouse islets exposed to the rejection mechanism of the discordant xenogenic pig islet-like cell clusters did not attain a complete functional recovery.     

Ionic mechanisms mediating the differential effects of methohexital and thiopental on action potential duration in guinea pig and rabbit isolated ventricular myocytes

BACKGROUND: The stress response to injury concept has been proposed as a mechanism of chronic rejection. This hypothesis has been tested with a rat cardiac allograft model in recipients pretreated with donor bone marrow (BM) cells. Chronic rejection is manifested in this BM group by obliterative arteriopathy and the epicardium and endocardium contains lymphocytic infiltrates resembling Quilty lesions. Pretreatment with a liver allograft (the orthotopic liver transplant [OLTx] group) is associated with an absence of chronic rejection in the transplanted heart. METHODS AND RESULTS:. Stress responses in the allograft were assessed by determining heat shock protein (hsp) expression by immunohistology of graft tissues and immunoblot analysis of stromal tissue lysates with monoclonal antibodies (mAb) to mammalian hsp60, the inducible hsp72, the constitutively expressed hsc73, and the grp78 C-terminal sequence KSEKDEL (grp78seq). Immunostaining showed clusters of grp78seq-positive cells in the inflammatory infiltrates of obliterated blood vessels and Quilty lesions in the BM group of cardiac allografts. Such grp78seq-positive cells were not seen in the OLTx group of heart allografts nor in syngrafts. Neither group showed significantly different graft myocyte staining of grp78 or hsp72, whereas hsp60 and hsc73 showed higher expression in the BM group and, to a lesser extent, the OLTx group. The increased expression of hsc73 was seen especially in the obliterated arteries and in myocytes nearby cellular infiltrates. Immunoblot analysis of graft stromal tissue lysates showed additional bands with mAb to hsp60 and hsc73 for the OLTx and especially the BM group. No significant bands were seen for hsp72 and grp78. Lymphocytes isolated from chronically rejecting allografts reacted with irradiated autologous spleen cells in the presence of mycobacterial hsp65 and interleukin-2. Culturing of graft-infiltrating cells with mycobacterial hsp71 and interleukin-2 yielded lymphocyte clones without alloreactivity, but with strong proliferative responsiveness to self-antigen-presenting cells and, only in the presence of mycobacterial hsp71 or murine grp78. This T-cell reactivity seemed to require intact hsp molecules because treatment of hsp71 with proteolytic enzymes, polymyxin, or ATP abrogated this induction of the stimulatory effect of self-antigen-presenting cells. These T cells are similar to the hsp-dependent, autoreactive lymphocytes cloned from acutely rejecting rat allografts. CONCLUSIONS: These findings support the concept that the pathogenesis of chronic rejection involves a stress response and the participation of graft-infiltrating autoreactive T cells that operate under hsp-dependent mechanisms.     

Whole-body [18F]FDG PET in the management of metastatic brain tumours

BACKGROUND: To determine its roles in the diagnosis and the systemic evaluation of metastatic brain tumours, whole-body positron emission tomography (PET) using [18F]FDG was performed in 20 consecutive patients. METHODS: All patients were thought to be suffering or needing to be differentiated from metastatic brain tumours. Nine patients had multiple brain lesions; six were older and showed a rim-enhancing lesion with surrounding oedema; seven had homogeneously enhancing periventricular lesion(s) on computed tomography (CT) and/or magnetic resonance (MR) imaging, thought to be central nervous system lymphomas. Two patients had skull mass(es) and two patients had a solid mass suspected to be, respectively, a haemorrhagic metastasis and a metastatic malignant melanoma. All of them received whole-body [18F]FDG PET and conventional systemic work-up for metastasis in order to compare the results of the two methods. RESULTS: Metastatic brain tumours were diagnosed on whole-body [18F]FDG PET in eleven patients who had extracranial and intracranial hypermetabolic lesions. In nine of these, a conventional work-up also detected primary lesions which on whole-body [18F]FDG PET were seen to be hypermetabolic foci. Systemic lymph node metastases were detected by whole-body [18F]FDG PET only in two patients and histological diagnosis was possible by biopsy of lymph nodes rather than of brain lesions. In the remaining nine patients who had only intracranial hypermetabolic foci, histological diagnosis was made by craniotomy or stereotactic biopsy. It was confirmed that seven of nine patients were suffering from a primary brain tumour and two from metastatic carcinoma. None of the nine showed evidence of systemic cancer on conventional work-up. Histological diagnoses of the primary brain tumours were four cases of primary central nervous system lymphoma and one each of multifocal glioblastoma, Ewing's sarcoma, and cavernous angioma. Patients felt no discomfort during the whole-body [18F]FDG PET procedure and there were no complications. The false negative rate in [18F]FDG PET and in conventional work-up was 15.4% and 30.7% respectively. There were no false positives on either [18F]FDG PET or conventional work-up. CONCLUSION: It is suggested that whole-body [18F]FDG PET is a safe, reliable, and convenient method for the diagnosis and systemic evaluation of patients thought to be suffering or needing to be differentiated from a metastatic brain tumour.     

Effect of major histocompatibility complex expression on murine intestinal graft survival

BACKGROUND: Clinical intestinal transplantation has been plagued by frequent and severe graft rejection. It has been proposed that the major histocompatibility complex (MHC) antigens might play a critical role in this process owing to their extensive expression on enterocytes and mucosa-associated immune cells. METHODS: The present study examined the role of MHC antigens in intestinal graft rejection using MHC class I-deficient and MHC class II-deficient donors. RESULTS: Grafts with normal MHC expression were rejected by 9 days, whereas survival was prolonged to 14 days in the MHC class II-deficient grafts (P=NS) and to 20 days in the MHC I-deficient grafts (P<0.002). In all groups, early rejection was characterized by (1) increased crypt cell apoptosis, as detected by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique of in situ labeling; and (2) the increased expression of perforin and a CD8 phenotype in the graft-infiltrating cells. CONCLUSIONS: These data suggest that MHC antigens, CD8-positive T cells, and perforin-expressing cells contribute to intestinal graft rejection. Apoptosis of the progenitor epithelial crypt cells during early intestinal rejection may impair the gut's ability to regenerate and repair mucosal damage.     

Mouse parvovirus infection potentiates allogeneic skin graft rejection and induces syngeneic graft rejection

BACKGROUND: The recently identified autonomous mouse parvovirus designated mouse parvovirus-1 (MPV-1) persists in adult BALB/c mice for at least 9 weeks, infects lymphoid tissues, interferes with the ability of cloned T cells to proliferate, and exhibits immunomodulatory properties. As a consequence of these findings, the present studies were undertaken to characterize further the inmunomodulatory effects of MPV-1 on T cell-mediated immune responses in vivo and in vitro. METHODS: To evaluate the effect of MPV-1 infection on CD8+ T cell-mediated responses, BALB/c-H2dm2 mice were infected after transplantation of allogeneic BALB/c skin. RESULTS: MPV-1 potentiated the rejection of allogeneic skin grafts. This potentiation was not a result of virus infecting the cellular or vascular component of the graft as determined by in situ hybridization, but was mediated by T cells. However, the proliferative capacity of alloantigen-reactive lymphocytes from graft-sensitized infected mice was diminished. MPV-1 also induced the rejection of syngeneic skin grafts, and T cells from these infected graft-sensitized mice lysed syngeneic P815 target cells. CONCLUSIONS: These results suggest that MPV-1 infection of skin-grafted mice may disrupt normal mechanisms of peripheral tolerance and provide a unique model to study virus-induced autoimmunity.     

Detection of response to chemotherapy using positron emission tomography in patients with oesophageal and gastric cancer

BACKGROUND: The aim of the study was to determine whether 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) could detect response to chemotherapy in patients with oesophageal and gastric cancer. METHODS: Fourteen patients underwent imaging before and after chemotherapy using FDG-PET. Computed tomography (CT), dysphagia scores and weight changes were used for comparison of evidence of response. Tumour to liver ratios (TLRs) and influx constants for FDG (K) were used for quantification purposes. RESULTS: Thirteen of 14 lesions were successfully imaged before therapy. Changes were seen in all follow-up scans, ranging from a complete response to a 15 per cent increase in tumour FDG uptake. Response was demonstrated by CT in four patients; all four had large reductions in FDG uptake after chemotherapy. Two patients with an increase in FDG uptake reported no improvement in dysphagia and continued to lose weight during therapy. CONCLUSION: Changes in tumour FDG uptake were seen in all tumours after chemotherapy. FDG-PET may have a role to play in the assessment of patients with upper gastrointestinal malignancy receiving chemotherapy.     

PET 2-fluoro-2-deoxyglucose uptake in rat prostate adenocarcinoma during chemotherapy with gemcitabine

This study was performed to investigate the effect of the new chemotherapeutic agent gemcitabine on glucose transport and metabolism in prostate carcinoma in vitro and in vivo. METHODS: After transplantation of rat prostate adenocarcinoma cells, dynamic PET measurements with fluorine-18-labeled 2-fluoro-2-deoxy-D-glucose (18FDG) were performed in 15 animals before and 1 day after therapy with 90 mg/kg of body weight (n = 8) and 180 mg/kg of body weight (n = 7) gemcitabine. In the second examination, the animals received a simultaneous injection of 18FDG and [3H]thymidine. Quantitative evaluation of the PET data was done using the standardized uptake value (SUV) as well as a three-compartment pharmacokinetic model. Furthermore, the incorporation of [3H]thymidine into the DNA was determined. In vitro measurements of the FDG, 3-O-methylglucose and thymidine uptake were performed immediately and 4 hr after a 24-hr incubation period with different doses of gemcitabine. RESULTS: FDG-SUV and the metabolic rate of FD 3 utilization did not change significantly after therapy. However, the values for the transport rate constants K1 and K2 increased significantly. The incorporation of thymidine into the DNA of treated tumors showed an 80% decline as compared with a control group. In the cell culture experiments, a dose-dependent increase of FDG (up to 178%) and 3-O-methylglucose uptake (up to 305%) was demonstrated. The thymidine uptake showed a 96% decline in the nucleic acid fraction and an increase of up to 337% in the cytoplasmic fraction. CONCLUSION: The more global measures of FDG metabolism as SUV and metabolic rate of FDG utilization were unchanged after therapy, while DNA synthesis and cell viability declined. However, in vitro and in vivo evidence of an enhancement of glucose transport is presented, indicating that quantification by modelling may be superior for the evaluation of metabolic effects during chemotherapy.     

Evaluation of compartmental and spectral analysis models of [18F]FDG kinetics for heart and brain studies with PET

Various models have been proposed to quantitate from [18F]-Fluoro-Deoxy-Glucose ([18F]FDG) positron emission tomography (PET) data glucose regional metabolic rate. We evaluate here four models, a three-rate constants (3K) model, a four-rate constants (4K) model, an heterogeneous model (TH) and a spectral analysis (SA) model. The data base consists of [18F]FDG dynamic data obtained in the myocardium and brain gray and white matter. All models were identified by nonlinear weighted least squares with weights chosen optimally. We show that: 1) 3K and 4K models are indistinguishable in terms of parsimony criteria and choice should be made on parameter precision and physiological plausibility; in the gray matter a more complex model than the 3K one is resolvable; 2) the TH model is resolvable in the gray but not in the white matter; 3) the classic SA approach has some unnecessary hypotheses built in and can be in principle misleading; we propose here a new SA model which is more theoretically sound; 4) this new SA approach supports the use of a 3K model in the heart with a 60 min experimental period; it also indicates that heterogeneity in the brain is modest in the white matter; 5) [18F]FDG fractional uptake estimates of the four models are very close in the heart, but not in the brain; 6) a higher than 60 min experimental time is preferable for brain studies.     

Blockade of the CD40-CD40 ligand pathway potentiates the capacity of donor-derived dendritic cell progenitors to induce long-term cardiac allograft survival

BACKGROUND: Failure of costimulatory molecule-deficient donor dendritic cells (DCs) to induce indefinite allograft acceptance may be a result of the 'late" up-regulation of these molecules on the DCs after interaction with host T cells. Ligation of CD40 on antigen-presenting cells by its cognate ligand CD40L is thought to induce expression of CD80 (B7-1) and CD86 (B7-2). We examined the influence of anti-CD40L monoclonal antibody (mAb) on the capacity of donor-derived DC progenitors to induce long-term allograft survival. METHODS: High purity DC progenitors were grown from B10 (H2b) mouse bone marrow in granulocyte-macrophage colony-stimulating factor and transforming growth factor beta1 (TGFbeta1). Mature DC were propagated in granulocyte-macrophage colony-stimulating factor and interleukin-4. Their phenotype was characterized by flow cytometric analysis and their function by mixed leukocyte reactivity. Anti-donor cytotoxic T lymphocyte activity in grafts and spleens of vascularized heart allograft recipients was also assessed. RESULTS: The TGFbeta3-cultured cells were (1) DEC 205-positive, MHC class II-positive, CD80dim, CD86dim, and CD40dim, (2) poor stimulators of naive allogeneic T-cell proliferation, and (3) able to prolong significantly B10 cardiac allograft survival in C3H (H2k) recipients when given (2 x 10[6] i.v.) 7 days before organ transplantation (median survival time [MST] 26 days vs. 12 days in controls, and 5 days in interleukin-4 DC-treated animals). Their allostimulatory activity was further diminished by addition of anti-CD40L mAb at the start of the mixed leukocyte cultures. Anti-CD40L mAb alone (250 microg/mouse, i.p.; day -7) did not prolong cardiac graft survival (MST 12 days). In contrast, TGFbeta-cultured DCs + anti-CD40L mAb extended graft survival to a MST of 77 days, and inhibited substantially the anti-donor cytotoxic T lymphocyte activity of graft-infiltrating cells and host spleen cells assessed 8 days after transplant. CONCLUSIONS: The CD40-CD40L pathway appears important in regulation of allogeneic DC-T-cell functional interaction in vivo; its blockade increases markedly the potential of costimulatory molecule-deficient DCs of donor origin to induce long-lasting allograft survival.     

Profound underestimation of glucose uptake by [18F]2-deoxy-2-fluoroglucose in reperfused rat heart muscle

BACKGROUND: [18F]2-deoxy-2-fluoroglucose (FDG) is widely used as a tracer for glucose uptake in ischemic heart muscle. We tested the effects of low-flow ischemia and reperfusion on the ratio of tracer/tracee (lumped constant, LC). METHODS AND RESULTS: Isolated working rat hearts were perfused with Krebs-Henseleit buffer containing only glucose 5 mmol/L (group 1) or glucose 5 mmol/L plus oleate 0.4 mmol/L (group 2, fed; group 3, fasted). Dynamic glucose uptake was measured simultaneously with [2-3H]glucose and with FDG. After 20 minutes, coronary flow was reduced by 75% for 30 minutes before it was returned to control conditions for the final 20 minutes. Hexokinase activity in the cytosolic and mitochondrial fractions and tissue metabolites were determined. Rates of glucose uptake were highest when glucose was the only substrate. Glucose uptake, FDG uptake, and the LC increased during ischemia only in group 3. There was no change of these parameters during ischemia in groups 1 and 2. FDG uptake decreased significantly with reperfusion in groups 2 and 3, and there was a striking fall in the LC (from >1.0 to <0.2, P<.001). The fall in the LC was associated with a significant increase in intracellular free glucose. Neither ischemia nor reperfusion affected the kinetic properties of hexokinase. CONCLUSIONS: FDG profoundly underestimates glucose uptake during reperfusion in the presence of fatty acids. In the fasted state, however, FDG overestimates glucose uptake during ischemia. The results indicate limitations in the use of FDG to quantify myocardial glucose uptake in human heart.     

Pulmonary fibrosis correlates with duration of tissue neutrophil activation

The role of inflammatory cells such as neutrophil granulocytes in the pathogenesis of pulmonary scarring is unclear. We determined the metabolic activity of neutrophils with positron emission tomography (PET) to measure regional uptake of (18F)-2-fluoro-2-deoxy-D-glucose (18FDG) following its intravenous injection. Fibrogenic or nonfibrogenic substances were instilled into the right upper lobe of rabbit lungs. Time course and intensity of the 18FDG signal in the affected region varied markedly, depending on the stimulus. Time to peak signal (Tmax) and rate constant for its decline (k) for the test substances were, respectively: C5a 10 h (Tmax), 0.045 +/- 0.030 h-1 (k); Streptococcus pneumoniae 15 h, 0.068 +/- 0.012 h-1; bleomycin 28 h, 0.002 +/- 0.001 h-1; microcrystalline silica (microXSiO2), 90 h, 0.0012 +/- 0.0007 h-1; amorphous silica (aSiO2), no response. Response to the nonfibrogenic agents C5a, S. pneumoniae and aSiO2 was brief or nonexistent, falling to baseline values within 3 d, whereas that to the fibrogenic agents bleomycin and microXSiO2 persisted for up to 4 wk. Neutrophil numbers in the lung were proportional to the 18FDG signal following C5a and S. pneumoniae, but not bleomycin and microXSiO2. Autoradiography of lungs following administration of (3H)-deoxyglucose [(3H)-DG] showed specific localization to neutrophils in all models. Thus, 18FDG uptake provides a remarkably specific measure of neutrophil activity in situ, and the development of pulmonary fibrosis may be related to persistence of this activity.     

Untreated primary lung and breast cancers: correlation between F-18 FDG kinetic rate constants and findings of in vitro studies

PURPOSE: To compare kinetic modeling of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (F-18 FDG) between untreated primary lung and untreated primary breast cancers by using positron emission tomographic (PET) findings and to correlate these findings with findings of in vitro studies. MATERIALS AND METHODS: Nineteen patients (12 men, seven women; age range, 49-82 years) with untreated primary lung cancer and 17 women with untreated primary breast cancer (age range, 26-65 years) underwent 1-hour dynamic F-18 FDG PET. A three-compartment model was applied to F-18 FDG kinetics in tumors. The standard uptake value normalized for lean body mass (SUVlean) in tumors was measured 50-60 minutes after tracer injection. In vitro, thin-layer chromatography was performed to evaluate the intracellular phosphorylation of tritiated F-18 FDG in human lung cancer and breast cancer cell lines. RESULTS: At PET, lung cancer had a significantly (P < .003) higher rate constant for F-18 FDG phosphorylation (k3) and SUVlean than did breast cancer (0.164 +/- 0.150 [standard deviation] vs 0.043 +/- 0.018 and 8.25 +/- 3.28 vs 3.17 +/- 1.08, respectively). Breast cancer showed a significant correlation between k3 and SUVlean (r = .607, P < .01), although no such correlation was observed in lung cancer. In vitro studies showed phosphorylation of F-18 FDG in breast cancer cells was less complete in hyperglycemia than it was in lung cancer cells. CONCLUSION: A much lower k3 appears to be a rate-limiting factor for F-18 FDG accumulation in breast cancer, while the higher k3 in lung cancer is probably not rate limiting for F-18 FDG accumulation.     

Myocardial glucose uptake in patients with NIDDM and stable coronary artery disease

Whole body insulin resistance characterizes patients with NIDDM, but it is not known whether insulin also has impaired ability to stimulate myocardial glucose uptake (MGU) in these patients. This study was designed to evaluate MGU as measured by 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) in patients with NIDDM and stable coronary artery disease (CAD) under standardized metabolic conditions. Eight patients with NIDDM, 11 nondiabetic patients with CAD, and 9 healthy control subjects were enrolled in the study. MGU was quantitated in the normal myocardial regions with [18F]FDG and PET and the whole body glucose disposal by glucose-insulin clamp technique (serum insulin, -430 pmol/l). Plasma glucose and serum insulin concentrations were comparable in all groups during PET studies. The whole body glucose uptake was 45% lower in NIDDM patients (22 +/- 9 micromol x min(-1) X kg(-1) body wt [mean +/- SD]), compared with healthy control subjects (40 +/- 17 micromol x min(-1) x kg(-1) body wt, P < 0.05). In CAD patients, whole body glucose uptake was 30 +/- 9 micromol x min(-1) x kg(-1) body wt (NS between the other groups). MGU was similar in the normal segments in all three groups (69 +/- 28 micromol x min(-1) x 100 g(-1) in NIDDM patients, 72 +/- 17 micromol x min(-1) x 100 g(-1) in CAD patients, and 76 +/- 10 micromol x min(-1) x 100 g(-1) in healthy control subjects, NS). No correlation was found between whole body glucose uptake and MGU. As studied by [18F]FDG PET under stable normoglycemic hyperinsulinemic conditions, MGU is not reduced in patients with NIDDM and CAD in spite of peripheral insulin resistance. These findings suggest that there is no significant defect in MGU in patients with NIDDM.     

2-[C-11]thymidine imaging of malignant brain tumors

Malignant brain tumors pose diagnostic and therapeutic problems. Despite the advent of new brain imaging modalities, including magnetic resonance imaging (MRI) and [F-18]fluorodeoxyglucose (FDG) positron emission tomography (PET), determination of tumor viability and response to treatment is often difficult. Blood-brain barrier disruption can be caused by tumor or nonspecific reactions to treatment, making MRI interpretation ambiguous. The high metabolic background of the normal brain and its regional variability makes it difficult to identify small or less active tumors by FDG imaging of cellular energetics. We have investigated 2-[C-11]thymidine (dThd) and PET to image the rate of brain tumor cellular proliferation. A series of 13 patients underwent closely spaced dThd PET, FDG PET, and MRI procedures, and the image results were compared by standardized visual analysis. The resulting dThd scans were qualitatively different from the other two scans in approximately 50% of the cases, which suggests that dThd provided information distinct from FDG PET and MRI. In two cases, recurrent tumor was more apparent on the dThd study than on FDG; in two other patients, tumor dThd uptake was less than FDG uptake, and these patients had slower tumor progression than the three patients with both high dThd and FDG uptake. To better characterize tumor proliferation, kinetic modeling was applied to dynamic dThd PET uptake data and metabolite-analyzed blood data in a subset of patients. Kinetic analysis was able to remove the confounding influence of [C-11]CO2, the principal labeled metabolite of 2-[C-11]dThd, and to estimate the flux of dThd incorporation into DNA. Sequential, same-day [C-11]CO2 and [C-11]dThd imaging demonstrated the ability of kinetic analysis to model both dThd and CO2 simultaneously. Images of dThd flux obtained using the model along with the mixture analysis method for pixel-by-pixel parametric imaging significantly enhanced the contrast of tumor compared with normal brain. Comparison of model estimates of dThd transport versus dThd flux was able to discern increased dThd uptake simply on the basis of blood-brain barrier disruption retention on the basis of increased cellular proliferation. This preliminary study demonstrates the potential for imaging brain tumor cellular proliferation to provide unique information for guiding patient treatment.     

Evaluation of benign vs malignant hepatic lesions with positron emission tomography

BACKGROUND: In most malignant cells, the relatively low level of glucose-6-phosphatase leads to accumulation and trapping of [18F]fluorodeoxyglucose (FDG) intracellularly, allowing the visualization of increased uptake compared with normal cells. OBJECTIVES: To assess the value of FDG positron emission tomography (PET) to differentiate benign from malignant hepatic lesions and to determine in which types of hepatic tumors PET can help evaluate stage, monitor response to therapy, and detect recurrence. DESIGN: Prospective blinded-comparison clinical cohort study. SETTING: Tertiary care university hospital and clinic. PATIENTS: One hundred ten consecutive referred patients with hepatic lesions 1 cm or larger on screening computed tomographic (CT) images who were seen for evaluation and potential resection underwent PET imaging. There were 60 men and 50 women with a mean (+/-SD) age of 59 +/- 14 years. Follow-up was 100%. INTERVENTIONS: A PET scan using static imaging was performed on all patients. The PET scan imaging and biopsy, surgery, or both were performed, providing pathological samples within 2 months of PET imaging. All PET images were correlated with CT scan to localize the lesion. However, PET investigators were unaware of any previous interpretation of the CT scan. MAIN OUTCOME MEASURES: Visual interpretation, lesion-to-normal liver background (L/B) ratio of radioactivity, and standard uptake value (SUV) were correlated with pathological diagnosis. RESULTS: All (100%) liver metastases from adenocarcinoma and sarcoma primaries in 66 patients and all cholangiocarcinomas in 8 patients had increased uptake values, L/B ratios greater than 2, and an SUV greater than 3.5. Hepatocellular carcinoma had increased FDG uptake in 16 of 23 patients and poor uptake in 7 patients. All benign hepatic lesions (n = 23), including adenoma and fibronodular hyperplasia, had poor uptake, an L/B ratio of less than 2, and an SUV less than 3.5, except for 1 of 3 abscesses that had definite uptake. CONCLUSIONS: The PET technique using FDG static imaging was useful to differentiate malignant from benign lesions in the liver. Limitations include false-positive results in a minority of abscesses and false-negative results in a minority of hepatocellular carcinoma. The PET technique was useful in tumor staging and detection of recurrence, as well as monitoring response to therapy for all adenocarcinomas and sarcomas and most hepatocellular carcinomas. Therefore, pretherapy PET imaging is recommended to help assess new hepatic lesions.     

Usefulness of FDG-PET in diagnosing primary lymphoma of the liver

This case report shows for the first time the usefulness of positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in the diagnosis of primary non Hodgkin's lymphoma of the liver. Results of FDG-PET, which in contrast to other imaging techniques offers the advantage of screening the whole body, demonstrated a high glycolytic activity of a solitary mass in the liver with central necrosis (loss of glycolytic activity), but no spread of lymphoma to the body. These results were confirmed by ultrasound, computed tomography, magnetic resonance imaging and were biopsy proven. From our findings we conclude that in patients with liver masses with high uptake of FDG, lack of liver dysfunction and absence of signs indicating other malignancies, a primary lymphoma of the liver should be considered as a possible diagnosis.     

Nitric oxide production by mouse sponge matrix allograft-infiltrating cells. Comparison with the rat species

We have recently demonstrated in the rat species that sponge matrix allograft infiltrating cells spontaneously produce nitric oxide (.N = 0) and this .N = 0 production precedes the development of CTL. Compared with our experience in the mouse species, the CTL activity recovered from rat sponge grafts is of shorter duration and less intense. Assessment of the spontaneous .N = 0 production by mouse allograft infiltrating cells reveals a more delayed time course of production, paralleling the recovery of CTL activity from the graft. The in vitro spontaneous .N = 0 production by mouse allograft-infiltrating cells was greater than the production by syngeneic graft-infiltrating cells on all days tested. Exposure of allogeneic but not syngeneic graft infiltrating cells to the sensitizing alloantigen in vitro resulted in enhanced .N = 0 synthesis. In contrast, LPS stimulated .N = 0 production by both syngeneic and allogeneic graft cells on all days postgrafting. Culture of day-14 allograft infiltrating cells with alloantigen in the absence of NG-monomethyl-L-arginine (NMA), the competitive inhibitor of .N = 0 synthesis, resulted in elevated supernatant NO2- levels and decreased 3H-TdR uptake and CTL activity compared with cultures carried out in the presence of NMA. The supernatant NO2- levels, as well as the CTL activity and 3H-TdR incorporation of the cultured cells, was dependent on the concentration of NMA present, and these effects could be reversed by excess L-arginine. Thus, the species difference in .N = 0 synthesis (rat > mouse), observed by others, is evident in the sponge allograft model and may explain why CTL activity recovered from rat allografts is of shorter duration and less intense than that from the mouse allografts.     

Ethical hazards of the substituted judgement test in decision making concerning the end of life of dementia patients

Previously we reported that the South American gray short-tailed opossum, Monodelphis domestica, had an MHC class-I locus similar to that of eutherian species. In addition to the detection of lymphocyte antigens by cytotoxic antisera, we concluded that this marsupial rejected allogeneic skin grafts, as would be expected of animals with MHC class-I polymorphism. However, this conclusion was based on a limited number of skin transplants that were assayed for only a short period. Here we report the results of 22 reciprocal skin grafts made between individuals of known genetic relationships. On the basis of gross inspection of the grafts and histologic examination, we found that the average time of the onset of graft rejection was about 19 days and that the average time for complete graft rejection was about 31 days. In general, it took longer for the onset of graft rejection among pairs of genetically related animals than among less related animals. These results indicate unequivocally that this marsupial species has a high degree of class-I polymorphism and rejects allogeneic skin transplants in a manner similar to but more slowly than eutherian mammals.     

NOS2 mediates opposing effects in models of acute and chronic cardiac rejection: insights from NOS2-knockout mice

To compare regulatory effects of NOS2 in acute and chronic cardiac allograft rejection, we used NOS2 knockout mice as recipients in a cardiac transplant model. To study acute and chronic rejection separately but within the same genetic strain combination, we compared allografts placed into recipients without or with immunosuppression (anti-CD4/8 for 28 days). NOS2 mRNA and protein expression were compared using 32P-RT-PCR and immunohistochemistry. In our acute rejection model, NOS2 was predominately localized to graft-infiltrating immune cells. At day 7, grafts in NOS2-deficient recipients (n = 7) showed reduced inflammatory infiltrates and myocyte damage resulting in significantly lower rejection scores (1.6 +/- 0.4) compared to wild-type controls (n = 18; 2.8 +/- 0.2, P = 0.002). In contrast, in our chronic rejection model, additional NOS2 expression was localized to graft-parenchymal cells. At day 55, grafts in NOS2-deficient recipients (n = 12) showed more parenchymal infiltration and parenchymal destruction (rejection score 3.8 +/- 0.1) than wild-type controls (n = 15; 1.6 +/- 0.2, P < 0.0001). This was associated with a significant decrease in ventricular contractility (palpation score 0.3 +/- 0.1 compared to 2.3 +/- 0.3 in wild-type, P < 0.0001). Hence, NOS2 promotes acute but prevents chronic rejection. These opposing effects during acute and chronic cardiac allograft rejection are dependent on the temporal and spatial expression pattern of NOS2 during both forms of rejection.