Recommended evaluation of adrenal incidentalomas is costly, has high false-positive rates and confers a risk of fatal cancer that is similar to the risk of the adrenal lesion becoming malignant; time for a rethink?

OBJECTIVE: To assess the performance of current clinical recommendations for the evaluation of an adrenal incidentaloma. DESIGN AND METHODS LITERATURE REVIEW: Electronic databases (Pubmed, Ovid and citation searches from key articles) from 1980 to 2008 were searched. Eligible studies were those deemed most applicable to the clinical scenario of a patient referred to an endocrinologist for assessment of an incidentally detected adrenal mass. Surgical series, histopathological series and oncological series were reviewed and most were excluded. RESULTS: The prevalence of functional and malignant lesions presenting as adrenal incidentaloma was similar to that quoted in most reviews, other than a lower incidence of adrenal carcinoma (1.9 vs 4.7%) and metastases (0.7 vs 2.3%). The development of functionality or malignancy during follow-up was rare (<1% becoming functional and 0.2% becoming malignant). During follow-up, false-positive rates of the recommended investigations are typically 50 times greater than true positive rates. The average recommended computed tomography (CT) scan follow-up exposes each patient to 23 mSv of ionising radiation, equating to a 1 in 430 to 2170 chance of causing fatal cancer. This is similar to the chance of developing adrenal malignancy during 3-year follow-up of adrenal incidentaloma. CONCLUSION: Current recommendations for evaluation of adrenal incidentaloma are likely to result in significant costs, both financial and emotional, due to high false-positive rates. The dose of radiation involved in currently recommended CT scan follow-up confers a risk of fatal cancer that is similar to the risk of the adrenal becoming malignant. This argues for a review of current guidelines.

A genome-wide screen in 1119 relative pairs with autoimmune thyroid disease.

CONTEXT: Autoimmune thyroid diseases (AITD), comprising Graves' disease and autoimmune hypothyroidism, are characterized by loss of immunological self-tolerance to thyroid antigens. These are complex diseases arising from a combination of genetic and environmental factors. An understanding of the genetic susceptibility factors for AITD could help to target treatments more effectively and identify people at risk for these conditions. OBJECTIVE: The objective of this study was to identify regions of genetic linkage to AITD that could potentially harbor genetic susceptibility factors for these conditions. DESIGN: The study design was a genome-wide screen performed on affected relative pairs with AITD. SETTING: Patients were recruited through hospital endocrinology clinics. PARTICIPANTS: Some 1119 Caucasian relative pairs affected with AITD (Graves' disease or autoimmune hypothyroidism) were recruited into the study. INTERVENTION: Blood samples were obtained from each participant for DNA analysis, and clinical questionnaires were completed. MAIN OUTCOME MEASURE: The study aimed to identify regions of genetic linkage to AITD. RESULTS: Three regions of suggestive linkage were obtained on chromosomes 18p11 (maximum LOD score, 2.5), 2q36 (maximum LOD score, 2.2), and 11p15 (maximum LOD score, 2.0). No linkage to human leukocyte antigen was found. CONCLUSIONS: The absence of significant evidence of linkage at any one locus in such a large dataset argues that genetic susceptibility to AITD reflects a number of loci, each with a modest effect. Linkage analysis may be limited in defining such loci, and large-scale association studies may prove to be more useful in identifying genetic susceptibility factors for AITD.

Predicting surgically remedial primary aldosteronism: role of adrenal scanning, posture testing, and adrenal vein sampling.

Distinguishing surgically remedial forms from other causes of primary aldosteronism (PA) may be difficult, and it is made more challenging by the earlier detection of milder disease. The technical demands of bilateral adrenal vein sampling (AVS)-increasingly advocated for localizing a unilateral autonomous lesion (UAL)- and lack of agreed criteria for establishing unilateral autonomy, add further to the diagnostic challenge. This retrospective review of 49 hypokalemic patients with unequivocal PA (41 with surgically proven and remedial UAL, eight patients with bilateral adrenal hyperplasia) analyzes the value of computerized tomography adrenal scanning (n = 32), 4 h erect posture testing (n = 42), and AVS (n = 27) in predicting and lateralizing a surgically remedial lesion. A fall in plasma aldosterone during 4 h erect posture (positive test) occurred in 63% of patients with UAL and in none with bilateral adrenal hyperplasia. A positive posture test or computerized tomography adrenal scan (single focal macroadenoma) both had high positive predictive value (100% and 89% respectively), but low sensitivity for diagnosis of UAL. AVS, undertaken during low dose ACTH stimulation, localized the UAL in all cases (positive predictive value 100%) where the aldosterone/cortisol ratio of blood drawn from the uninvolved gland was less than that of peripheral blood (contralateral ratio <1). Biochemical severity, reflected by overnight supine plasma aldosterone, was strongly correlated with the degree of contralateral gland suppression (n = 16, r = 0.79, P < 0.001). Importantly, the AVS findings show that when bilateral access is not possible, UAL can be successfully lateralized when only one adrenal vein (the contralateral) is accessed, or the ipsilateral vein is sampled in subjects whose posture test was positive. In this series of patients with overt (hypokalemic) PA, preoperative testing successfully identified a surgically remedial lesion in 39 of 41 cases. Confirmation of the recommended diagnostic approach must now await larger prospective studies.

Histocompatibility leucocyte antigens and closely linked immunomodulatory genes in autoimmune thyroid disease.

OBJECTIVES: Associations between autoimmune thyroid disease and antigens of the major histocompatibility complex (MHC) have long been recognized. Graves' disease (GD) is associated with the histocompatibility leucocyte antigen (HLA) haplotype A*01-B*0801-DRB1*0301-DQA1*0501-DQB1*0201 (or B8/DR3) whereas autoimmune hypothyroidism (AIH) has been weakly associated with HLA DRB1*03, *04 and *11/*12 alleles (or DR3, DR4 and DR5). However, the presence of important immunoregulatory genes within the HLA Class II and III regions raises the possibility that these genes harbour the primary susceptibility locus. This study examines genetic variation across the MHC in UK Caucasoid subjects with autoimmune thyroid disease. PATIENTS AND METHODS: DNA extracted from venous blood samples from 215 patients with autoimmune thyroid disease (GD 135, AIH 77) and 267 control subjects was analysed. Genotyping was performed using polymerase chain reaction and sequence specific primers for HLA Class I and II alleles and polymorphisms within the TAP1, TAP2, tumour necrosis factor (TNF), lymphotoxin alpha (LTalpha), heat shock protein (HSP)70-1, HSP70-2 and HSP70-Hom genes. RESULTS: For GD, the strongest association was with DRB1*03 [56% patients positive vs. 24% controls, P = 2 x 10(-10), odds ratio (OR) 4.0]. Positive associations were also seen for DRB1*03 linked alleles, B*0801, DRB3*01/02, DQA1*05, DQB1*02 and DPB1*0101 (OR 2.3-3.4). Specific TNF and LTalpha alleles were strongly associated with GD (Pc = 3 x 10(-5) and 0.001) and weak associations were seen for HSP70-1 + 190C and HSP70-2 + 1267G polymorphisms (Pc = 0.05 and 0.01). These associations were not significant when DRB1*03 status was considered. Patients with AIH showed only a weak association with DQB1*03 (P = 0.02). CONCLUSIONS: These results show that, of the polymorphisms tested within the MHC, GD is most strongly associated with DRB1*03, and associations with other immunoregulatory genes previously described in Caucasian subjects most likely reflect linkage disequilibrium. AIH differs from GD, being less influenced by the MHC region.

Cytokine gene polymorphisms in autoimmune thyroid disease.

Susceptibility to the autoimmune thyroid diseases, Graves' disease (GD) and autoimmune hypothyroidism (AIH), depends on a complex interaction between environmental and genetic factors. The human leukocyte antigen and cytotoxic T lymphocyte-associated-4 regions appear to influence susceptibility to disease, but the effect is not major, and the other genes remain unknown. Cytokines are crucial in the regulation of immune and inflammatory responses and therefore are potential candidate genes for autoimmune thyroid disease. In a case-control study, using a unified method of genotyping, we have examined 15 polymorphisms in 9 cytokine genes in 215 patients with autoimmune thyroid disease (GD, 138; AIH, 77) and 101 normal controls. Polymorphisms in the genes for interleukin-1alpha (IL-1alpha), IL-1beta, IL-1 receptor antagonist, IL-1 receptor 1, IL-4, IL-4 receptor, IL-6, IL-10, and transforming growth factor-beta were investigated. Genotyping was performed using the PCR and sequence-specific primers. Analysis showed a reduced frequency of the variant t allele in the IL-4 promoter polymorphism (position 590) in patients with GD and in the entire patient group (GD and AIH) compared with the control group [corrected P (Pc) = 0.00004 and Pc < 0.00001 for GD and all patients, respectively]. This was reflected in a reduction in the heterozygote genotype in the patient groups compared to the controls [c/t heterozygotes GD, 12%; Pc = 0.06, odds ratio, 0.4 (95% confidence interval, 0.2-0.7); all patients, 11%; Pc = 0.008; odds ratio, 0.4 (95% confidence interval, 0.2-0.7); control subjects, 23%]. There were no significant differences between the study groups for the other polymorphisms examined, and subgroup analysis revealed no association with clinical parameters of disease. These results suggest that an IL-4 variant or a closely linked gene has a modest protective effect against the development of autoimmune thyroid disease, particularly GD. This variation in the IL-4 gene may provide further clues to the pathogenesis of autoimmune thyroid disease and other organ-specific autoimmune diseases. Furthermore, these results suggest that subtle variation in immunoregulatory genes may be associated with autoimmune disease states.

Improvement in mood and fatigue after dehydroepiandrosterone replacement in Addison's disease in a randomized, double blind trial.

Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are adrenal precursors of steroid biosynthesis and centrally acting neurosteroids. Glucocorticoid and mineralocorticoid deficiencies in Addison's disease require life-long hormone replacement, but the associated failure of DHEA synthesis is not corrected. We conducted a randomized, double blind study in which 39 patients with Addison's disease received either 50 mg oral DHEA daily for 12 weeks, followed by a 4-week washout period, then 12 weeks of placebo, or vice versa. After DHEA treatment, levels of DHEAS and Delta(4)-androstenedione rose from subnormal to within the adult physiological range. Total testosterone increased from subnormal to low normal with a fall in serum sex hormone-binding globulin in females, but with no change in either parameter in males. In both sexes, psychological assessment showed significant enhancement of self-esteem with a tendency for improved overall well-being. Mood and fatigue also improved significantly, with benefit being evident in the evenings. No effects on cognitive or sexual function, body composition, lipids, or bone mineral density were observed. Our results indicate that DHEA replacement corrects this steroid deficiency effectively and improves some aspects of psychological function. Beneficial effects in males, independent of circulating testosterone levels, suggest that it may act directly on the central nervous system rather than by augmenting peripheral androgen biosynthesis. These positive effects, in the absence of significant adverse events, suggest a role for DHEA replacement therapy in the treatment of Addison's disease.

High-resolution landmark framework for the sequence-ready mapping of Xq23-q26.1.

We have established a landmark framework map over 20-25 Mb of the long arm of the human X chromosome using yeast artificial chromosome (YAC) clones. The map has approximately one landmark per 45 kb of DNA and stretches from DXS7531 in proximal Xq23 to DXS895 in proximal Xq26, connecting to published framework maps on its proximal and distal sides. There are three gaps in the framework map resulting from the failure to obtain clone coverage from the YAC resources available. Estimates of the maximum sizes of these gaps have been obtained. The four YAC contigs have been positioned and oriented using somatic-cell hybrids and fluorescence in situ hybridization, and the largest is estimated to cover approximately 15 Mb of DNA. The framework map is being used to assemble a sequence-ready map in large-insert bacterial clones, as part of an international effort to complete the sequence of the X chromosome. PAC and BAC contigs currently cover 18 Mb of the region, and from these, 12 Mb of finished sequence is available.

Immunoreactive amino-terminal pro-brain natriuretic peptide (NT-PROBNP): a new marker of cardiac impairment.

OBJECTIVE: Human brain natriuretic peptide-32 (BNP) (i.e. proBNP(77-108)), the mature form of BNP and secreted predominantly by the cardiac ventricle, is formed from a high molecular weight precursor, proBNP(1-108). We have recently identified the aminoterminal form proBNP(1-76) (NT-proBNP) in human plasma but its source, metabolism and production in circulatory disorders are unknown. We have investigated the relationship between immunoreactive (IR) NT-proBNP and BNP-32 in normal and hypertensive subjects and in patients with cardiac impairment, as well as the regional plasma concentrations in patients undergoing routine cardiac catheterization. DESIGN AND PATIENTS: Plasma hormone measurements were made in 26 normal subjects, 20 subjects with untreated mild hypertension and 111 treated patients with a history of coronary heart disease and documented cardiac impairment (left ventricular election fraction (LVEF) < 45% (mean 29%); 25 NYHA Class I, 65 Class II and 21 Class III). Regional blood sampling from the femoral artery, femoral vein, renal vein and coronary sinus was undertaken in 14 patients presenting for left and right cardiac catheterization studies in the course of standard investigation for a range of cardiac disorders. MEASUREMENTS: Plasma samples were assayed for IR NT-proBNP and IR BNP-32 (and atrial natriuretic peptide (ANP) in the regional blood samples). In the patients with cardiac impairment, LVEF was determined by gated radionuclide ventriculography, exercise capacity was measured using a modified Naughton multistage protocol and creatinine clearance was calculated from plasma creatinine, age and weight. In the regional study, extraction ratios across the kidney and lower limb (and step-ups across the heart) were calculated from plasma peptide concentrations. RESULTS: In normal subjects mean IR NT-proBNP levels (10.8 +/- 1.3 pmol/L) were similar to levels of IR BNP-32 (9.7 +/- 0.5 pmol/L). In hypertensive patients the levels of IR NT-proBNP and IR BNP-32 tended to be higher than but were not significantly different from normal subjects. Both IR NT-proBNP and IR BNP-32 were raised in NYHA Classes I, II and III compared with normals (P < 0.001 for all) with higher levels of both BNP forms seen with increasing cardiac impairment. The levels of IR NT-proBNP were greater than IR BNP-32 in all NYHA Classes (P < 0.001) for all). Overall, the levels of IR NT-proBNP (129 +/- 12 pmol/L) were 4-fold higher than concomitant BNP-32 levels (29 +/- 2 pmol/L). Multivariate analysis showed that LVEF, exercise test time and creatinine clearance were independent predictors of IR NT-proBNP. In all study groups, the levels of IR NT-proBNP and IR BNP-32 levels were highly correlated. Regional plasma sampling showed similar step-ups in IR NT-proBNP and IR BNP-32 levels across the heart, together with similar extraction of both BNP forms across the kidney and lower limb. For both BNP forms, these changes across tissues were significantly less than for ANP. CONCLUSIONS: Plasma levels of immunoreactive amino terminal-proBNP are raised in cardiac impairment, including NYHA Class I, and rise with increasing cardiac decompensation. Metabolism and tissue uptake of immunoreactive amino terminal-proBNP and immunoreactive BNP-32 appear similar. In cardiac impairment the proportional and absolute increment above normal levels of the aminoterminal BNP peptide exceeds that for BNP-32 and suggest that amino terminal-proBNP may be a more discerning marker of early cardiac dysfunction than BNP-32.

The effects of pathophysiological increments in brain natriuretic peptide in left ventricular systolic dysfunction.

Plasma levels of brain natriuretic peptide (BNP) are raised in patients with left ventricular impairment and may play a role in the adaptation to left ventricular impairment. Manipulation of BNP levels may have therapeutic potential. The effects of BNP have not been well studied in patients with left ventricular impairment. We studied the effects of low-dose BNP infusion, reproducing the increment in plasma BNP seen with progression from mild to severe heart failure in patients with impaired left ventricular systolic function. BNP was infused in a placebo-controlled, single-blind, crossover design at a rate of 3.3 pmol x kg(-1) x min(-1) over 4 hours to 8 patients with a history of congestive heart failure and persistent impairment of left ventricular systolic function (left ventricular ejection fraction <35%). Endocrine, renal, and hemodynamic effects were measured. Compared with time-matched placebo-control, BNP infusion decreased mean systemic arterial pressure (peak decrease, 17.1 mm Hg; P=.04), mean pulmonary artery pressure (peak decrease, 6.1 mm Hg; P=.007), mean pulmonary capillary wedge pressure (peak decrease, 5.5 mm Hg; P=.04), and systemic vascular resistance (peak decrease, 1400 dyne s(-1) cm(-5); P=.015), but cardiac output and heart rate were unchanged. Urinary volume and urinary excretion of sodium and potassium were not altered. BNP infusion increased plasma cGMP (2.3-fold change, P=.002). Plasma atrial natriuretic peptide levels were increased for the first hour of BNP infusion (peak increase, 11.5 pmol/L; P=.005). Plasma aldosterone levels were unchanged during but increased over time-matched control levels after the end of the BNP infusion (peak increase, 90 pmol/L; P=.02). Plasma renin activity and cortisol and catecholamine levels were unchanged. Low-dose infusion of BNP causes favorable hemodynamic changes and relative neurohormonal suppression but has attenuated renal effects in patients with impaired left ventricular systolic function.

The role of the circulation in processing pro-brain natriuretic peptide (proBNP) to amino-terminal BNP and BNP-32.

Human proBNP (purified from cardiac tissue) was incubated at 37 degrees C in whole blood, serum and plasma and the products analyzed by size exclusion high pressure liquid chromatography and radioimmunoassay (RIA). In addition to RIAs for BNP-32 and NT-proBNP(1-13), a newly developed RIA for proBNP(62-76) was also used to identify the peptides. Incubation with serum resulted in the formation of a 9 kDa and a 3 kDa peptide, consistent with the N-terminal and the C-terminal peptides of the propeptide. Minimal processing of proBNP was seen in blood or plasma, suggesting that the circulation does not play a major role in the activation of proBNP. Analysis of degradation products of human proBNP using site directed specific antisera indicates that removal of N-terminal amino acids from proBNP occurs in serum. These findings support the view that the "high molecular weight BNP-32" previously identified in human plasma comprises amino-terminal deleted forms, and is unlikely to be intact proBNP(1-108).

Differing biological effects of equimolar atrial and brain natriuretic peptide infusions in normal man.

Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP) are cardiac hormones with similar actions and potency in humans yet with distinctly different effects on plasma cyclic guanosine monophosphate (cGMP). Because most biological actions of natriuretic peptides are thought to be mediated by the guanylate cyclase (G-C) receptors via cGMP, we have compared the biological and G-C-stimulating effects of equimolar infusions of ANP and BNP (2 pmol/kg.min), or vehicle control, on renal, hormonal and hemodynamic function in 8 normal subjects. In addition, the modulating effects of ANP and BNP on the biological actions of infused angiotension II (AngII) were studied. During ANP infusions, plasma ANP concentration increased from 8.8 +/- 0.7 pmol/L to 34 +/- 3 pmol/L at 120 min. Similar increments in plasma BNP occurred during BNP infusions (7.3 +/- 0.6 pmol/L preinfusion, 37 +/- 1 pmol/L at 120 min). Increase in plasma cGMP during ANP infusions was 4-fold that observed during BNP infusions yet natriuresis, contraction in plasma volume, and inhibition of plasma aldosterone were comparable. By contrast, ANP (but not BNP) significantly inhibited the plasma aldosterone response to AngII (P < 0.001). The pressor response to AngII was unaltered by ANP or BNP. Thus, at plasma ANP/BNP levels observed in mild heart failure, ANP is more potent than BNP in inhibiting the aldosterone response to AngII. Comparable natriuresis and inhibition of basal aldosterone is seen, despite much less stimulation of plasma cGMP by BNP, suggesting a different mechanism of hormone action-possibly via non-G-C receptor pathways.

Regional anesthesia in foot and ankle surgery.

A method of regional anesthesia use in forefoot and midfoot surgery is described. Careful identification of the peripheral sensory nerves allows for effective anesthesia using bupivacaine and lidocaine in addition to sedation for comfort. A review of 355 patients showed that 98% received an effective surgical block of the sensory nerves. Complications were found to be minimal and patient satisfaction was high. This method provides a safe and effective anesthesia alternative for foot and ankle surgery.

Interactions of atrial and brain natriuretic peptides at pathophysiological levels in normal men.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are both circulating plasma hormones that are secreted by the heart and have similar physiological effects. We have shown previously that abrupt increases in plasma BNP in normal humans impair the clearance of ANP from plasma and result in additive physiological effects. Because large increases in plasma ANP are reported to have no effect on plasma BNP levels in patients with heart failure, we have studied ANP-BNP interactions in eight normal male subjects receiving background infusions of BNP (2 pmol.kg-1.min-1 for 5 h). Each subject also received a coinfusion of ANP ("active" day, 2 pmol.kg-1.min-1 for 2 h) or vehicle ("placebo" day) using a balanced random order, single-blind design. Metabolic clearance rate of ANP (mean 4.1 +/- 0.6 l/min) and disappearance rate from the plasma (t1/2 3.4 +/- 0.3 min) were similar to values measured previously in the absence of exogenous BNP. In contrast, steady-state plasma BNP levels were reversibly increased (mean BNP increment 10 pmol/l) during the administration of ANP (P = 0.038). Associated with these changes were significant (additive) physiological effects. Thus the addition of ANP increased plasma and urine guanosine 3',5'-cyclic monophosphate (P < 0.001 for both) and lowered systolic blood pressure (P = 0.049). When ANP was coinfused, significant differences were also observed in urine volume (P = 0.001) and sodium excretion (P = 0.043) between the infusion period (when urine volume and sodium excretion were enhanced) and postinfusion period (when values decreased). Taken together, our findings of similar interactions between ANP-BNP and BNP-ANP infusions occurring at pathophysiological concentrations of these two peptides, suggest that the interactions result from dissociation of prebound hormone, presumably from biological or clearance receptors.

The amino-terminal portion of pro-brain natriuretic peptide (Pro-BNP) circulates in human plasma.

Using an antiserum raised in rabbits to a synthetic human brain natriuretic peptide (BNP) N-terminal fragment [ProBNP(1-13)], a single large molecular weight (MW) N-terminal form of ProBNP has been identified in human plasma. Sep-pak extracts of plasma, drawn from patients with congestive heart failure and subjected to size exclusion and reverse phase high pressure liquid chromatography (HPLC) coupled to radioimmunoassay (RIA) revealed a single large immunoreactive (ir-) peak which was not detected in assays of BNP-32 [ProBNP(77-108)]. This material has a MW of 8600--similar to that expected for the complete N-terminal portion of ProBNP(1-76). Previously reported high MW BNP forms, cross reacting with BNP-32 antisera, were not detected using the N-terminal antisera, indicating that this material is unlikely to be intact ProBNP(1-108). In patients with congestive heart failure plasma ir-levels of N-terminal ProBNP were greatly raised compared to normal subjects and were up to ninefold higher than ir-BNP-32 values.

Carboxyfluorescein (CFSE) labelling of hepatocytes for short-term localization following intraportal transplantation.

Renewed interest in the transplantation of isolated hepatocytes into the liver as a potential therapy for liver disease has stimulated the development of methods for the identification of donor cells within the recipient organ. We describe a method for cellular tagging and in vivo identification of intraportally transplanted hepatocytes using an intracellular fluorescent dye, 5(6)-carboxyfluorescein diacetate, succinimidyl-ester (CFSE). Rat and porcine hepatocytes were isolated and labelled with CFSE. The optimal conditions for labelling consisted of a buffered saline suspension of hepatocytes (5 x 10(6) cells/mL) in 20.0 microM CFSE incubated for 15 min at 37 degrees C. In vitro, labelled hepatocytes were cultured either on fibronectin-coated chamber slides or in culture flasks. Cultures were evaluated in situ by fluorescence photomicrography or by fluorescence-activated cell sorting (FACS) after cell detachment. Cell viability was assessed serially and cultured, labelled hepatocytes retained the dye for up to 3 wk (last day of study). CFSE did not effect hepatocyte viability and there was no evidence of intercellular diffusion of the dye. In vivo, syngeneic Lewis rats underwent selective portal vein infusion of freshly isolated, labelled hepatocytes (2.0 x 10(7) cells/2.0 mL saline/animal) into the posterior liver lobes. All recipients were sacrificed 48 h and 96 h later and their livers examined. Transplanted hepatocytes were identified by fluorescence microscopy in tissue sections and by FACS following collagenase digestion of the liver tissue. CFSE persisted in a population of viable, engrafted hepatocytes. FACS analysis demonstrated that 9 +/- 3% of the hepatocytes in the posterior liver lobes were labelled 48 and 96 h after transplantation. At 96 h following transplantation, multiple engrafted hepatocytes could be observed by fluorescence microscopy around the central veins. CFSE labelling allows for both in vitro identification and in vivo localization of donor hepatocytes. Furthermore, it appears to be more stable and specific for labelling hepatocytes than other tested dyes (especially DiI).