Identification of Donor Origin and Condition of Transplanted Islets In Situ in the Liver of a Type 1 Diabetic Recipient.

Transplantation of islet allografts into type 1 diabetic recipients usually requires multiple pancreas donors to achieve insulin independence. This adds to the challenges of immunological monitoring of islet transplantation currently relying on surrogate immune markers in peripheral blood. We investigated donor origin and infiltration of islets transplanted in the liver of a T1D patient who died of hemorrhagic stroke 4 months after successful transplantation with two intraportal islet grafts combining six donors. Immunohistological staining for donor HLA using a unique panel of human monoclonal HLA-specific alloantibodies was performed on liver cryosections after validation on cryopreserved kidney, liver, and pancreas and compared with auto- and alloreactive T-cell immunity in peripheral blood. HLA-specific staining intensity and signal-to-noise ratio varied between tissues from very strong on kidney glomeruli, less in liver, kidney tubuli, and endocrine pancreas to least in exocrine pancreas, complicating the staining of inflamed islets in an HLA-disparate liver. Nonetheless, five islets from different liver lobes could be attributed to donors 1, 2, and 5 by staining patterns with multiple HLA types. All islets showed infiltration with CD8+ cytotoxic T cells that was mirrored by progressive alloreactive responses in peripheral blood mononuclear cells (PBMCs) to donors 1, 2, and 5 after transplantation. Stably low rates of peripheral islet autoreactive T-cell responses after islet infusion fit with a complete HLA mismatch between grafts and recipient and exclude the possibility that the islet-infiltrating CD8 T cells were autoreactive. HLA-specific immunohistochemistry can identify donor origin in situ and differentiate graft dysfunction and immunological destruction.

Immunogenicity of human embryonic stem cell-derived beta cells.

AIMS/HYPOTHESIS: To overcome the donor shortage in the treatment of advanced type 1 diabetes by islet transplantation, human embryonic stem cells (hESCs) show great potential as an unlimited alternative source of beta cells. hESCs may have immune privileged properties and it is important to determine whether these properties are preserved in hESC-derived cells. METHODS: We comprehensively investigated interactions of both innate and adaptive auto- and allo-immunity with hESC-derived pancreatic progenitor cells and hESC-derived endocrine cells, retrieved after in-vivo differentiation in capsules in the subcutis of mice. RESULTS: We found that hESC-derived pancreatic endodermal cells expressed relatively low levels of HLA endorsing protection from specific immune responses. HLA was upregulated when exposed to IFNγ, making these endocrine progenitor cells vulnerable to cytotoxic T cells and alloreactive antibodies. In vivo-differentiated endocrine cells were protected from complement, but expressed more HLA and were targets for alloreactive antibody-dependent cellular cytotoxicity and alloreactive cytotoxic T cells. After HLA compatibility was provided by transduction with HLA-A2, preproinsulin-specific T cells killed insulin-producing cells. CONCLUSIONS/INTERPRETATION: hESC-derived pancreatic progenitors are hypoimmunogenic, while in vivo-differentiated endocrine cells represent mature targets for adaptive immune responses. Our data support the need for immune intervention in transplantation of hESC-derived pancreatic progenitors. Cell-impermeable macro-encapsulation may suffice.

Sling Surgery for the Treatment of Urinary Incontinence After Transurethral Resection of the Prostate: New Data on the Virtue Male Sling and an Evaluation of Literature.

OBJECTIVE: To provide a review of literature regarding the role of male slings in the treatment of stress urinary incontinence (SUI) following a transurethral resection of the prostate (TURP) and to evaluate the effects of the Virtue male sling in patients with post-TURP SUI. MATERIALS AND METHODS: A systematic review of literature was performed to identify all papers on the use of male slings in patients with post-TURP SUI. Second, a prospective cohort study was conducted on 8 patients who received the Virtue as surgical treatment of post-TURP SUI. Questionnaires were collected preoperatively and 1, 3, 6, and 12 months postoperatively. Success and improvement were defined as pad usage (0 pads: success, pad reduction of ≥50%: improvement). Primary end point was the continence rate 1 year postoperatively. Data were analyzed using the paired 2-tailed t test. RESULTS: Sling surgery appears to be significantly less successful in the treatment of SUI post TURP when compared to other types of prostate surgery. The clinical trial on the Virtue sling observed continence in 4 of 8 patients, with another 2 patients with improved continence after 1-year follow-up. No difference in success was observed between patients with mild and patients with severe SUI. CONCLUSIONS: Little is currently known about the effects of sling surgery in patients with mild to severe SUI following a TURP. Although the Virtue male sling seems to be an efficient and safe device in the treatment of this complication, longer follow-up and larger cohorts will be needed to further confirm these results.

Kinetics of HIV-1 Latency Reversal Quantified on the Single-Cell Level Using a Novel Flow-Based Technique.

UNLABELLED: HIV-1 establishes a pool of latently infected cells early following infection. New therapeutic approaches aiming at diminishing this persisting reservoir by reactivation of latently infected cells are currently being developed and tested. However, the reactivation kinetics of viral mRNA and viral protein production, and their respective consequences for phenotypical changes in infected cells that might enable immune recognition, remain poorly understood. We adapted a novel approach to assess the dynamics of HIV-1 mRNA and protein expression in latently and newly infected cells on the single-cell level by flow cytometry. This technique allowed the simultaneous detection of gagpol mRNA, intracellular p24 Gag protein, and cell surface markers. Following stimulation of latently HIV-1-infected J89 cells with human tumor necrosis factor alpha (hTNF-α)/romidepsin (RMD) or HIV-1 infection of primary CD4(+) T cells, four cell populations were detected according to their expression levels of viral mRNA and protein. gagpol mRNA in J89 cells was quantifiable for the first time 3 h after stimulation with hTNF-α and 12 h after stimulation with RMD, while p24 Gag protein was detected for the first time after 18 h poststimulation. HIV-1-infected primary CD4(+) T cells downregulated CD4, BST-2, and HLA class I expression at early stages of infection, proceeding Gag protein detection. In conclusion, here we describe a novel approach allowing quantification of the kinetics of HIV-1 mRNA and protein synthesis on the single-cell level and phenotypic characterization of HIV-1-infected cells at different stages of the viral life cycle. IMPORTANCE: Early after infection, HIV-1 establishes a pool of latently infected cells, which hide from the immune system. Latency reversal and immune-mediated elimination of these latently infected cells are some of the goals of current HIV-1 cure approaches; however, little is known about the HIV-1 reactivation kinetics following stimulation with latency-reversing agents. Here we describe a novel approach allowing for the first time quantification of the kinetics of HIV-1 mRNA and protein synthesis after latency reactivation or de novo infection on the single-cell level using flow cytometry. This new technique furthermore enabled the phenotypic characterization of latently infected and de novo-infected cells dependent on the presence of viral RNA or protein.

Results of collagen sling placement following the partial removal of a synthetic midurethral sling.

OBJECTIVE: To assess results of placement of the Pelvilace collagen sling following partial removal of a primary synthetic sling because of late complications. METHODS: A retrospective study was undertaken of patients with late complications after midurethral sling surgery who underwent placement of a Pelvilace sling at a center in the Netherlands between January 2006 and January 2011. A postoperative questionnaire was used to evaluate the continence status and continence-related quality of life. Patients scoring 0 in the Urogenital Distress Inventory stress symptoms section were considered cured. The subjective improvement or deterioration in symptoms was scored using the Patient Global Impression of Improvement (PGI-I). RESULTS: The questionnaire was completed and returned by 32 (84%) of 38 patients after a mean follow-up of 54.3 months. Nine (28%) patients were deemed cured. Among 29 patients who had not undergone a third surgery, the PGI-I showed a postoperative improvement in 14 (48%). The other 15 patients rated their postoperative situation as little improved, unchanged, or deteriorated. Further subanalysis showed clear differences in postoperative results between the different types of late complications (erosion and/or displacement). CONCLUSION: The concomitant placement of a collagen sling following partial removal of a primary polypropylene sling shows reasonable results for specific complications.

Serum Cytokines as Biomarkers in Islet Cell Transplantation for Type 1 Diabetes.

BACKGROUND: Islet cell transplantation holds a potential cure for type 1 diabetes, but many islet recipients do not reach long-lasting insulin independence. In this exploratory study, we investigated whether serum cytokines, chemokines and adipokines are associated with the clinical outcome of islet transplantation. METHODS: Thirteen islet transplant patients were selected on basis of good graft function (reaching insulin independence) or insufficient engraftment (insulin requiring) from our cohort receiving standardized grafts and immune suppressive therapy. Patients reaching insulin independence were divided in those with continued (>12 months) versus transient (<6 months) insulin independence. A panel of 94 proteins including cytokines and adipokines was measured in sera taken before and at one year after transplantation using a validated multiplex immunoassay platform. RESULTS: Ninety serum proteins were detectable in concentrations varying markedly among patients at either time point. Thirteen markers changed after transplantation, while another seven markers changed in a clinical subpopulation. All other markers remained unaffected after transplantation under generalized immunosuppression. Patterns of cytokines could distinguish good graft function from insufficient function including IFN-α, LIF, SCF and IL-1RII before and after transplantation, by IL-16, CCL3, BDNF and M-CSF only before and by IL-22, IL-33, KIM-1, S100A12 and sCD14 after transplantation. Three other proteins (Leptin, Cathepsin L and S100A12) associated with loss of temporary graft function before or after transplantation. CONCLUSIONS: Distinct cytokine signatures could be identified in serum that predict or associate with clinical outcome. These serum markers may help guiding patient selection and choice of immunotherapy, or act as novel drug targets in islet transplantation.

Innate and adaptive immunity to human beta cell lines: implications for beta cell therapy.

AIMS/HYPOTHESIS: Genetically engineered human beta cell lines provide a novel source of human beta cells to study metabolism, pharmacology and beta cell replacement therapy. Since the immune system is essentially involved in beta cell destruction in type 1 diabetes and after beta cell transplantation, we investigated the interaction of human beta cell lineswith the immune system to resolve their potential for immune intervention protocol studies. METHODS: Human pancreatic beta cell lines (EndoC-ßH1 and ECi50) generated by targeted oncogenesis in fetal pancreas were assessed for viability after innate and adaptive immune challenges. Beta cell lines were pre-conditioned with T helper type 1 (Th1) cytokines or high glucose to mimic inflammatory and hyperglycaemia-stressed conditions. Beta cells were then co-cultured with auto- and alloreactive cytotoxic T cells (CTL), natural killer (NK) cells, supernatant fraction from activated autoreactive Th1 cells, or alloantibodies in the presence of complement or effector cells. RESULTS: Low HLA expression protected human beta cell lines from adaptive immune destruction, but it was associated with direct killing by activated NK cells. Autoreactive Th1 cell inflammation, rather than glucose stress, induced increased beta cell apoptosis and upregulation of HLA, increasing beta cell vulnerability to killing by auto- and alloreactive CTL and alloreactive antibodies. CONCLUSIONS/INTERPRETATION: We demonstrate that genetically engineered human beta cell lines can be used in vitro to assess diverse immune responses that may be involved in the pathogenesis of type 1 diabetes in humans and beta cell transplantation, enabling preclinical evaluation of novel immune intervention strategies protecting beta cells from immune destruction.

Results of sling surgery in a non-selected population.

OBJECTIVE: To evaluate sling surgery in terms of effectiveness and quality of life, and describe the effects of confounding variables on outcomes. METHODS: A retrospective cohort study using multiple validated questionnaires was conducted in a specialized pelvic floor center in the Netherlands. Women were enrolled after undergoing sling surgery between January 1, 2010, and January 31, 2012. In addition to the preoperative questionnaire, participants completed a questionnaire a minimum of 6weeks after surgery to assess outcomes. RESULTS: Of 255 eligible participants, 228 (89.4%) returned the postoperative questionnaire after a mean follow-up of 14.9months (range 2-32). At the time of follow-up, 158 (69.3%) patients considered themselves cured, and an improvement was observed in 155 (68.9%) patients; 70 (31.1%) patients rated their postoperative situation as little improved, unchanged, or deteriorated. Compared with patients who had no history of previous related surgery, patients with prior sling surgery benefited significantly less from surgery, whereas those with concomitant vaginal surgery showed similar scores in all outcome parameters. A high body mass index was found to have a negative effect on the results of surgery. CONCLUSION: midurethral sling surgery is both efficient and effective in curing stress urinary incontinence. However, patient characteristics and confounding variables can influence the outcome of surgery and should therefore always be discussed with the patient.

Risk of Damage to the Somatic Innervation of the Penis during the AdVanceProcedure: An Anatomical Study.

INTRODUCTION: One of the methods to treat post radical prostatectomy stress urinary incontinence is the AdVance (American Medical Systems, Minnetonka, MN, USA) male sling procedure. During this procedure, the somatic innervation of the penis may be at risk for injury. Six AdVance procedures were performed in six donated bodies at the Anatomy and Embryology Department of the Leiden University Medical Centre. The pelves were dissected and the shortest distance between the sling and the dorsal nerve of the penis (DNP) was documented. AIM: The aim of this study was to describe the anatomical relation between the AdVance male sling and penile nerves based on the dissection of six adult male pelves. METHODS: The AdVance male sling procedure was conducted in six donated male bodies. After placement, the pelves were dissected and the shortest distance between sling and the DNP was documented. MAIN OUTCOME MEASURE: The main outcome measure was the distance between the AdVance male sling and the DNP. RESULTS: The mean distance of the sling to the DNP was 4.1 mm and was found situated directly next to the nerve (distance 0 mm) in 4 out of 12 (33%) hemipelves. The distance of the sling to the obturator neurovascular bundle was 30 mm or more in all six bodies. CONCLUSIONS: Damage to the DNP caused by the AdVance male sling procedure appears to be an extremely rare complication, which has not been described in current literature. The proximity of the AdVance to the DNP could, however, pose a risk that should be taken into consideration by physicians and patients when opting for surgery.

Possible role of minor h antigens in the persistence of donor chimerism after stem cell transplantation; relevance for sustained leukemia remission.

Persistent complete donor chimerism is an important clinical indicator for remissions of hematological malignancies after HLA-matched allogeneic stem cell transplantation (SCT). However, the mechanisms mediating the persistence of complete donor chimerism are poorly understood. The frequent coincidence of complete donor chimerism with graft-versus-leukemia effects and graft-versus-host disease suggests that immune responses against minor histocompatibility antigens (mHags) are playing an important role in suppressing the host hematopoiesis after allogeneic SCT. Here, we investigated a possible relationship between donor immune responses against the hematopoiesis-restricted mHag HA-1 and the long-term kinetics of host hematopoietic chimerism in a cohort of 10 patients after allogeneic HLA-matched, HA-1 mismatched SCT. Functional HA-1 specific CTLs (HA-1 CTLs) were detectable in 6/10 patients lysing host-type hematopoietic cells in vitro. Presence of HA-1 CTLs in the peripheral blood coincided with low host hematopoiesis levels quantified by highly sensitive mHag specific PCR. Additionally, co-incubation of host type CD34+ cells with HA-1 CTLs isolated after allogeneic SCT prevented progenitor and cobblestone area forming cell growth in vitro and human hematopoietic engraftment in immunodeficient mice. Conversely, absence or loss of HA-1 CTLs mostly coincided with high host hematopoiesis levels and/or relapse. In summary, in this first study, presence of HA-1 CTLs paralleled low host hematopoiesis levels. This coincidence might be supported by the capacity of HA-1 CTLs isolated after allogeneic SCT to specifically eliminate host type hematopoietic stem/progenitor cells. Additional studies involving multiple mismatched mHags in more patients are required to confirm this novel characteristic of mHag CTLs as factor for the persistence of complete donor chimerism and leukemia remission after allogeneic SCT.

The introduction of mid-urethral slings: an evaluation of literature.

INTRODUCTION AND HYPOTHESIS: The objective of this study was to evaluate the degree and reliability of evidence used by manufacturers before the introduction of mid-urethral slings (MUS) onto the commercial market. Furthermore, minimum standards for marketed slings are recommended by evaluating recent suggestions for the introduction of gynecological meshes. METHODS: A systematic literature search was conducted using PubMed and commercial internet search engines in order to identify slings introduced by the industry over the last decade. Moreover, manufacturers were contacted by email, mail, and phone to provide data from before the introduction of the slings onto the commercial market. Once contact had been initiated, a 6-month deadline was set for data collection. RESULTS: Forty-one slings introduced between 1996 and 2012 were identified. Ten slings were described in a total of 20 studies with sample sizes varying from 10 to 368. The 41 MUS were produced by a total of 19 different companies. Seven companies never responded to recurrent emails, phone calls or other means of attempted contact. Thirty-one slings (76%) remained without any comparative pre-launch data. CONCLUSIONS: Mid-urethral slings were often introduced without any scientifically proven basis or pre-launch research. The US Food and Drug Administration and the European authorities should undertake immediate action by imposing strict rules before the launch of new MUS comparable with those recently suggested for meshes used in vaginal prolapse surgery.

Pretransplantation GAD-autoantibody status to guide prophylactic antibody induction therapy in simultaneous pancreas and kidney transplantation.

BACKGROUND: Daclizumab and antithymocyte globulin (ATG) have been shown to reduce allograft rejection. We assessed the safety and efficacy of daclizumab or ATG prophylaxis in combination with triple immunotherapy in simultaneous pancreas-kidney transplant (SPKT) recipients. METHODS: Thirty-nine type 1 diabetic patients scheduled for primary SPKT were randomized to receive prophylactic therapy with either daclizumab or ATG. A group of 27 patients without prophylactic antibodies was used for retrospective comparison. All patients received cyclosporine and mycophenolate mofetil and gradually tapered prednisone. Autoantibodies and cellular autoreactivity were measured to assess recurrent autoreactive responses. RESULTS: Baseline and transplant characteristics were comparable among groups. Both daclizumab and ATG therapy resulted in a significant reduction in acute rejection episodes. The incidence of rejection episodes was significantly higher in pretransplantation GAD autoantibody-positive daclizumab-treated recipients compared with GAD autoantibody-negative or ATG-treated recipients. IA-2 islet autoantibodies showed no association with rejection. There were no significant differences between the groups for in vitro autoreactivity, clinical outcome, or functional parameters. CONCLUSIONS: Daclizumab or ATG combined with a maintenance immunosuppressive regime consisting of cyclosporine, mycophenolate mofetil, and prednisolone were well tolerated and equally effective in reducing the incidence of acute rejection episodes in SPKT recipients. Up to 3 years, no adverse sequelae of the immunoprophylaxis or clinical and ex vivo recurrent autoimmunity were observed. We propose that the pretransplantation existence of GAD65 autoantibodies serves as a marker guiding the choice for prophylactic therapy in pancreas transplantation.

Predictive factors of allosensitization after immunosuppressant withdrawal in recipients of long-term cultured islet cell grafts.

BACKGROUND: Islet transplantation has been reported to induce allosensitization in the majority of type 1 diabetic recipients of fresh or shortly incubated islet grafts prepared from one to three donors. METHODS: We examined the appearance of human leukocyte antigen (HLA) antibodies after withdrawal of immunosuppressants in 35 type 1 diabetic recipients of islet cell grafts prepared from a median of 6 donors (range, 2-11), cultured for longer periods, and characterized for their cellular composition. Immunosuppression consisted of antithymocyte globulin induction followed by mycophenolate mofetil plus calcineurin inhibitors (n=28, with 7 also receiving steroids) or sirolimus with (n=3) or without calcineurin inhibitors (n=4). Both the complement-dependent cytotoxicity (CDC) assay (class I) and the solid-phase flow-based Luminex method (class I and II) were used to identify HLA antibodies. RESULTS: Immunosuppressant withdrawal resulted in CDC positivity for class I antibodies in only 6% of patients. However, the majority became positive for class I antibodies (72%) or class II antibodies (72%) in the Luminex assay; positivity was not correlated to a higher number of donors or HLA mismatches, but with a lower ß-cell purity; use of steroids reduced de novo positivity for Luminex class I antibodies. CONCLUSION: Allosensitization to cultured human islet cell grafts was low when assessed by CDC assay but high in Luminex. No correlation was found with the number of donors but risk was higher for grafts with lower ß-cell purity.

[Immunotherapy for type 1 diabetes mellitus (DM1)]. / Immunotherapie voor diabetes mellitus type 1.

Treatment of type 1 diabetes mellitus (DM1) has greatly improved but remains limited to combating the consequences of the disease. Target values for glucose regulation are achieved in only 20% of patients. Immunosuppression can slow disease progression, but does not cure DM1. Immunotherapy attempts to protect remaining insulin-producing ß cells and ß cell function. Promising results of immunotherapy in phase 2 studies in patients with DM1 could not be reproduced in phase 3 studies. These studies showed heterogeneity played a role in patient populations and between ethnic groups. In future studies better endpoints of efficacy, biomarkers of disease progression and response to therapy are essential. Vaccination with ß-cell specific antigens to stimulate tolerance and vaccination combined with immunotherapy (biologicals) are options for future therapy. Discussion on the acceptability of the side effects of immunotherapy is desirable.

The somatic and autonomic innervation of the clitoris; preliminary evidence of sexual dysfunction after minimally invasive slings.

INTRODUCTION: Vaginal sling procedures may have a negative effect on sexual function due to damage to vascular and/or neural genital structures. Even though autonomic innervation of the clitoris plays an important role in female sexual function, most studies on the neuroanatomy of the clitoris focus on the sensory function of the dorsal nerve of the clitoris (DNC). The autonomic and somatic pathways in relationship to sling surgery have up to the present not been described in detail. AIM: The aim of this study is to reinvestigate and describe the neuroanatomy of the clitoris, both somatic and autonomic, in relation to vaginal sling procedures for stress urinary incontinence. METHOD: Serially sectioned and histochemically stained pelves from 11 female fetuses (10-27 weeks of gestation) were studied, and three-dimensional reconstructions of the neuroanatomy of the clitoris were prepared. Fourteen adult female hemipelves were dissected, after a tension-free vaginal tape (TVT) (7) or tension-free vaginal tape-obturator (TVT-O) (7) procedure had been performed. MAIN OUTCOME MEASURES: Three-dimensional (3-D) reconstruction and measured distance between the clitoral nerve systems and TVT/TVT-O. RESULTS: The DNC originates from the pudendal nerve in the Alcock's canal and ascends to the clitoral bodies. In the dissected adult pelves, the distance of the TVT-O to the DNC had a mean of 9 mm. The cavernous nerves originate from the vaginal nervous plexus and travel the 5 and 7 o'clock positions along the urethra. There, the autonomic nerves were found to be pierced by the TVT needle. At the hilum of the clitoral bodies, the branches of the cavernous nerves medially pass/cross the DNC and travel further alongside it. Just before hooking over the glans of the clitoris, they merge with DNC. CONCLUSION: The DNC is located inferior of the pubic ramus and was not disturbed during the placement of the TVT-O. However, the autonomic innervation of the vaginal wall was disrupted by the TVT procedure, which could lead to altered lubrication-swelling response.

The glycerol channel Fps1p mediates the uptake of arsenite and antimonite in Saccharomyces cerevisiae.

The Saccharomyces cerevisiae FPS1 gene encodes a glycerol channel protein involved in osmoregulation. We present evidence that Fps1p mediates influx of the trivalent metalloids arsenite and antimonite in yeast. Deletion of FPS1 improves tolerance to arsenite and potassium antimonyl tartrate. Under high osmolarity conditions, when the Fps1p channel is closed, wild-type cells show the same degree of As(III) and Sb(III) tolerance as the fps1Delta mutant. Additional deletion of FPS1 in mutants defective in arsenite and antimonite detoxification partially suppresses their hypersensitivity to metalloid salts. Cells expressing a constitutively open form of the Fps1p channel are highly sensitive to both arsenite and antimonite. We also show by direct transport assays that arsenite uptake is mediated by Fps1p. Yeast cells appear to control the Fps1p-mediated pathway of metalloid uptake, as expression of the FPS1 gene is repressed upon As(III) and Sb(III) addition. To our knowledge, this is the first report describing a eukaryotic uptake mechanism for arsenite and antimonite and its involvement in metalloid tolerance.

Trends in certified reference materials for the speciation of trace elements.

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.

Non-ideal behaviour of free vanadate on a Superose 12 size-exclusion column. Application to in vivo 48V-labelled rat spleen homogenate.

Seven chromatographic columns were evaluated for the recovery of 48V-radiolabelled vanadate. Further, the behaviour of vanadate (H2VO4-) was studied on a size-exclusion column Superose 12 as a function of (a) buffer salt molarity, (b) different buffer salts, (c) different buffers and (d) organic solvents added to the buffer. As opposed to the unsatisfactory recovery of V-compounds on other columns, we recovered the vanadium quantitatively. We observed that in most cases vanadate eluted after the total volume of the Superose 12 column. This indicates a non-ideal behaviour of vanadate. However, through this non-ideal behaviour it was possible to separate low-molecular-mass bound (Mr<5000) and unbound vanadium which would not be possible under normal behaviour. A possible explanation for this non-ideal behaviour of vanadium is put forward. The method has been successfully applied for the fractionation of different vanadium species in rat spleen homogenate.

In vivo distribution and speciation of [114mIn]InCl3 in the Wistar rat.

Five Wistar rats were given an intraperitoneal injection of [114mIn]InCl3 during four consecutive days. One hour after the last injection the rats were sacrificed. The in vivo distribution of 114mIn was studied in the blood and in different organs. Differential centrifugation was used to study the distribution in liver, kidney and spleen homogenate. Rat serum, packed cell lysate, urine and the cytosol of liver, kidney and spleen homogenate were examined by size exclusion fast protein liquid chromatography. The results showed that serum accounts for 90% of the indium activity in whole blood. Indium is preferentially accumulated within the liver, spleen and kidney, the highest amount of 114mIn being localised in the cytosolic fraction followed by the mitochondria. Size exclusion experiments showed that, in rat serum, indium is exclusively bound to transferrin. These results differed from earlier in vitro incubation experiments of human serum with 114mIn. It was not possible, from the experiments described herein, to conclude unequivocally whether indium is bound to haemoglobin of packed cell lysate or to another high molecular mass compound. Indium is associated with the high molecular mass fraction in liver, kidney and spleen cytosol; only in kidney are small amounts of 114mIn found in the low molecular mass fraction. The in vivo inhibitory effect of indium on the delta-aminolaevulinic acid dehydratase (ALAD) enzymatic activity in red blood cells and kidney tissue, well documented by other researchers, could not be attributed to direct binding of indium with this enzyme.