Hematopoietic stem cells reversibly switch from dormancy to self-renewal during homeostasis and repair.

Bone marrow hematopoietic stem cells (HSCs) are crucial to maintain lifelong production of all blood cells. Although HSCs divide infrequently, it is thought that the entire HSC pool turns over every few weeks, suggesting that HSCs regularly enter and exit cell cycle. Here, we combine flow cytometry with label-retaining assays (BrdU and histone H2B-GFP) to identify a population of dormant mouse HSCs (d-HSCs) within the lin(-)Sca1+cKit+CD150+CD48(-)CD34(-) population. Computational modeling suggests that d-HSCs divide about every 145 days, or five times per lifetime. d-HSCs harbor the vast majority of multilineage long-term self-renewal activity. While they form a silent reservoir of the most potent HSCs during homeostasis, they are efficiently activated to self-renew in response to bone marrow injury or G-CSF stimulation. After re-establishment of homeostasis, activated HSCs return to dormancy, suggesting that HSCs are not stochastically entering the cell cycle but reversibly switch from dormancy to self-renewal under conditions of hematopoietic stress.

A pipeline approach with spatial information for segmenting multiple sclerosis lesions on brain magnetic resonance imaging

Background: Conventional magnetic resonance imaging (MRI) techniques are highly sensitive to detect multiple sclerosis (MS) plaques, enabling a quantitative assessment of inflammatory activity and lesion load. In quantitative analyses of focal lesions, manual or semi-automated segmentations have been widely used to compute the total number of lesions and the total lesion volume. These techniques, however, are both challenging and time-consuming, being also prone to intra-observer and inter-observer variability.Aim: To develop an automated approach to segment brain tissues and MS lesions from brain MRI images. The goal is to reduce the user interaction and to provide an objective tool that eliminates the inter- and intra-observer variability.Methods: Based on the recent methods developed by Souplet et al. and de Boer et al., we propose a novel pipeline which includes the following steps: bias correction, skull stripping, atlas registration, tissue classification, and lesion segmentation. After the initial pre-processing steps, a MRI scan is automatically segmented into 4 classes: white matter (WM), grey matter (GM), cerebrospinal fluid (CSF) and partial volume. An expectation maximisation method which fits a multivariate Gaussian mixture model to T1-w, T2-w and PD-w images is used for this purpose. Based on the obtained tissue masks and using the estimated GM mean and variance, we apply an intensity threshold to the FLAIR image, which provides the lesion segmentation. With the aim of improving this initial result, spatial information coming from the neighbouring tissue labels is used to refine the final lesion segmentation.Results:The experimental evaluation was performed using real data sets of 1.5T and the corresponding ground truth annotations provided by expert radiologists. The following values were obtained: 64% of true positive (TP) fraction, 80% of false positive (FP) fraction, and an average surface distance of 7.89 mm. The results of our approach were quantitatively compared to our implementations of the works of Souplet et al. and de Boer et al., obtaining higher TP and lower FP values.Conclusion: Promising MS lesion segmentation results have been obtained in terms of TP. However, the high number of FP which is still a well-known problem of all the automated MS lesion segmentation approaches has to be improved in order to use them for the standard clinical practice. Our future work will focus on tackling this issue.

Intrathecal immune responses to EBV in early MS.

EBV has been consistently associated with MS, but its signature in the CNS has rarely been examined. In this study, we assessed EBV-specific humoral and cellular immune responses in the cerebrospinal fluid (CSF) of patients with early MS, other inflammatory neurological diseases (OIND) and non-inflammatory neurological diseases (NIND). The neurotropic herpesvirus CMV served as a control. Virus-specific humoral immune responses were assessed in 123 consecutive patients and the intrathecal recruitment of virus-specific antibodies was expressed as antibody indexes. Cellular immune responses tested in the blood of 55/123 patients were positive in 46/55. The CD8(+) CTL responses of these 46 patients were assessed in the blood and CSF using a CFSE-based CTL assay. We found that viral capsid antigen and EBV-encoded nuclear antigen-1, but not CMV IgG antibody indexes, were increased in early MS as compared with OIND and NIND patients. There was also intrathecal enrichment in EBV-, but not CMV-specific, CD8(+) CTL in early MS patients. By contrast, OIND and NIND patients did not recruit EBV- nor CMV-specific CD8(+) CTL in the CSF. Our data, showing a high EBV-, but not CMV-specific intrathecal immune response, strengthen the association between EBV and MS, in particular at the onset of the disease.

Lapatax: Safety profile of neoadjuvant lapatinib combined with docetaxel in Her 2/neu overexpressing breast cancer - EORTC protocol 10054

Objective: To assess the safety/tolerability of the combination lapatinib (L) and docetaxel (D) in patients with Her 2/neu overexpressing breast cancer (BC). This study is important as it will define how to deliver lapatinib with taxotere, a highly active drug in breast cancer. Patients and Methods: Female patients (pts) with locally advanced, inflammatory or large operable BC were treated with escalating doses of L from 1000 to 1250 mg/day, in combination with D given IV every 21 days at doses ranging from 75 to 100 mg/m2 for 4 cycles. At least 3 pts were treated at each dose level. The definition of dose limiting toxicity (DLT) is based on the toxicity assessed at cycle 1 as follows: any grade 3−4 non hematological toxicity, ANC < 0.5 G/L lasting for 7 days or more, febrile neutropenia or thrombocytopenia <25 G/L. GCSF was not permitted as primary prophylaxis. Core biopsies were mandatory at baseline and after cycle 4. Pharmcokinetic (PK) samples were collected on day 1 of cycles 1 and 2. Results: To date, 18 pts with a median age of 53 years (range 36−65) have been enrolled at 5 Dose Levels (DLs). The toxicity profile for 18 patients (68 documented cycles) is summarized below. At DL5 (1000/100), 2 pts had DLTs (neutropenia grade 4 _7 days and febrile neutropenia), and 3 additional pts were enrolled with primary prophylactic G-CSF. As expected, the safety profile improved and the dose escalation will continue with prophylactic G-CSF to investigate DL6 (1250/100). These findings are consistent with published Phase I data for this combination [1]. N= 18 patients n (%) Grade 1 Grade 2 Grade 3 Grade 4 neutropenia 1 (6) 3 (17) 13 (72) febrile neutropenia 2 (11) fatigue 8 (44) 7 (39) diarrhoea 9 (50) 3 (17) pain: joint/muscle/other 5 (28)/4 (22)/3 (17) 4 (22)/4 (22)/3 (17) 0/0/1 (6) constipation 2 (11) 3 (17) 1 (6) elevated transaminases SGPT/SGOT 7 (39)/5 (28) Conclusions: The main toxicity of the L + D combination is haematological and was reached at DL5 (1000/100), without primary GCSF. An additional DL6 with primary prophylactic GCSF is being investigated (1250/100). PK data will be presented at the meeting plus the recommended dose for phase II studies.

Randomized controlled study demonstrating failure of LPV/r monotherapy in HIV: the role of compartment and CD4-nadir.

BACKGROUND: Long-term side-effects and cost of HIV treatment motivate the development of simplified maintenance. Monotherapy with ritonavir-boosted lopinavir (LPV/r-MT) is the most widely studied strategy. However, efficacy of LPV/r-MT in compartments remains to be shown. METHODS: Randomized controlled open-label trial comparing LPV/r-MT with continued treatment for 48 weeks in treated patients with fully suppressed viral load. The primary endpoint was treatment failure in the central nervous system [cerebrospinal fluid (CSF)] and/or genital tract. Treatment failure in blood was defined as two consecutive HIV RNA levels more than 400 copies/ml. RESULTS: The trial was prematurely stopped when six patients on monotherapy (none in continued treatment-arm) demonstrated a viral failure in blood. At study termination, 60 patients were included, 29 randomized to monotherapy and 13 additional patients switched from continued treatment to monotherapy after 48 weeks. All failures occurred in patients with a nadir CD4 cell count below 200/microl and within the first 24 weeks of monotherapy. Among failing patients, all five patients with a lumbar puncture had an elevated HIV RNA load in CSF and four of six had neurological symptoms. Viral load was fully resuppressed in all failing patients after resumption of the original combination therapy. No drug resistant virus was found. The only predictor of failure was low nadir CD4 cell count (P < 0.02). CONCLUSION: Maintenance of HIV therapy with LPV/r alone should not be recommended as a standard strategy; particularly not in patients with a CD4 cell count nadir less than 200/microl. Further studies are warranted to elucidate the role of the central nervous system compartment in monotherapy-failure.

Cerebrospinal fluid soluble amyloid-β protein precursor as a potential novel biomarkers of Alzheimer's disease.

In this report, we confirm our previous findings of increased concentrations of soluble amyloid-β protein precursor (sAβPP) in cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) in a large cohort of patients (n = 314), not overlapping with those of our previous study, and we extend our observations by including a control group of participants with normal cognition. In addition, we investigate the effects of age, the APOEε4 genotype, and the blood-CSF barrier function on the concentrations of sAβPPα and sAβPPβ. The study participants were categorized according to clinical-neuropsychological criteria, supported by CSF neurochemical dementia diagnostics (NDD) analyses. sAβPPα concentrations in the AD group (132.0 ± 44.8) were significantly higher than in the control group (105.3 ± 37.3, p < 0.0005) but did not differ from the MCI-AD group (138.5 ± 39.5, p = 0.91). The MCI-AD group differed significantly from the MCI-O (97.3 ± 34.3, p < 0.05) group. There was no difference between the control and the MCI-O groups (p = 0.94). Similarly, sAβPPβ concentrations in the AD group (160.2 ± 54.3) were significantly higher than in the control group (129.9 ± 44.6, p < 0.005) but did not differ from the MCI-AD group (184.0 ± 56.4, p = 0.20). The MCI-AD group differed significantly from the MCI-O (127.8 ± 46.2, p < 0.05) group. There was no difference between the control and the MCI-O groups (p > 0.99). We observed highly significant correlation of the two sAβPP forms. Age and the CSF-serum albumin ratio were significant albeit weak predictors of the sAβPPα and sAβPPβ concentrations, while carrying the APOEε4 allele did not influenced the levels of the sAβPP forms. Taken together, the results strongly suggest that CSF sAβPP concentrations may be considered as an extension of already available NDD tools.

Determinants of the essential one-carbon metabolism metabolites, homocysteine, S-adenosylmethionine, S-adenosylhomocysteine and folate, in cerebrospinal fluid.

BACKGROUND: Disturbances in the levels of one-carbon (1C) metabolism metabolites have been associated with a wide variety of neuropsychiatric diseases. Cerebrospinal fluid (CSF) levels of homocysteine (Hcy) and the other 1C metabolites, nor their interrelatedness and putative determinants, have been studied extensively in a healthy population. METHODS: Plasma and CSF samples from 100 individuals free from neuropsychiatric diseases were analyzed (55 male, 45 female; age 50±17 years). In blood, we measured plasma Hcy, serum folate and serum vitamin B12. In CSF, we measured total Hcy, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and 5-methyltetrahydrofolate (5-methylTHF). Highly selective analytical methods like liquid chromatography combined with either mass spectrometry or fluorescence detection were used. RESULTS: CSF Hcy was inversely correlated with CSF 5-methylTHF and positively with plasma Hcy, independent of serum folate status. CSF SAH correlated with age, lower CSF 5-methylTHF and higher CSF Hcy. CSF 5-methylTHF showed independent negative correlations with age and positive correlations with serum folate. CSF SAM did not correlate with any of the 1C metabolites. CONCLUSIONS: Aging is characterized by a reduction in CSF 5-methylTHF levels and increased CSF levels of the potentially neurotoxic transmethylation inhibitor SAH. CSF 5-methylTHF, which is itself determined in part by systemic folate status, is a powerful independent determinant of CSF levels of Hcy and SAH.

Mobilization of hemopoietic stem cells with high-dose methotrexate plus granulocyte-colony-stimulating factor in patients with primary central nervous system lymphoma.

BACKGROUND: High-dose therapy with autologous stem cell support after standard dose induction is a promising approach for therapy of primary central nervous system lymphoma (PCNSL). High-dose methotrexate (HD-MTX) is a standard drug for induction of PCNSL; however, data about the capacity of HD-MTX plus granulocyte-colony-stimulating factor (G-CSF) to mobilize hemopoietic progenitors are lacking. STUDY DESIGN AND METHODS: This investigation describes the data from stem cell mobilization and apheresis procedures after one or two cycles of HD-MTX for induction of PCNSL within the East German Study Group for Haematology and Oncology 053 trial. Eligible patients proceeded to high-dose busulfan/thiotepa after induction therapy and mobilization. RESULTS: Data were available from nine patients with a median age of 58 years. The maximal CD34+ cell count per microL of blood after the first course of HD-MTX was 13.89 (median). Determination was repeated in six patients after the second course with a significantly higher median CD34+ cell count of 33.69 per microL. Five patients required two apheresis procedures and in four patients a single procedure was sufficient. The total yield of CD34+ cells per kg of body weight harvested by one or two leukapheresis procedures was 6.60 x 10(6) (median; range, 2.68 x 10(6)-15.80 x 10(6)). The yield of CD34+ cells exceeded the commonly accepted lower threshold of 3 x 10(6) cells per kg of body weight in eight of nine cases. Even in the ninth, hemopoietic recovery after stem cell reinfusion was rapid and safe. CONCLUSION: HD-MTX plus G-CSF is a powerful combination for stem cell mobilization in patients with PCNSL and permits safe conduction of time-condensed and dose-intense protocols with high-dose therapy followed by stem cell reinfusion after HD-MTX induction.

ECIL recommendations for the use of biological markers for the diagnosis of invasive fungal diseases in leukemic patients and hematopoietic SCT recipients.

As culture-based methods for the diagnosis of invasive fungal diseases (IFD) in leukemia and hematopoietic SCT patients have limited performance, non-culture methods are increasingly being used. The third European Conference on Infections in Leukemia (ECIL-3) meeting aimed at establishing evidence-based recommendations for the use of biological tests in adult patients, based on the grading system of the Infectious Diseases Society of America. The following biomarkers were investigated as screening tests: galactomannan (GM) for invasive aspergillosis (IA); β-glucan (BG) for invasive candidiasis (IC) and IA; Cryptococcus Ag for cryptococcosis; mannan (Mn) Ag/anti-mannan (A-Mn) Ab for IC, and PCR for IA. Testing for GM, Cryptococcus Ag and BG are included in the revised EORTC/MSG (European Organization for Research and Treatment of Cancer/Mycoses Study Group) consensus definitions for IFD. Strong evidence supports the use of GM in serum (A II), and Cryptococcus Ag in serum and cerebrospinal fluid (CSF) (A II). Evidence is moderate for BG detection in serum (B II), and the combined Mn/A-Mn testing in serum for hepatosplenic candidiasis (B III) and candidemia (C II). No recommendations were formulated for the use of PCR owing to a lack of standardization and clinical validation. Clinical utility of these markers for the early management of IFD should be further assessed in prospective randomized interventional studies.

The role of MIC-1/GDF15 cytokine in glioblastoma

AbstractDespite advances in diagnosis and treatment made over the past two decades, high-gradeprimary brain tumors remain incurable neoplasms. Glioblastoma (GBM) represents the mostmalignant stage of astrocytic brain tumors. Identification of diagnostic and prognostic markers ineasily accessible biological material, such as plasma or cerebro-spinal fluid (CSF), would greatlyfacilitate the management of GBM patients. Elucidation of the molecular mechanisms that underlie thefunction of the factors implicated in GBM development would pave the way towards their potentialutility in cancer-targeting therapy.MIC-1/GDF15 (Macrophage Inhibitory Cytokine-1/ Growth Differentiation Factor 15), asecreted protein of the TGF-β superfamily, emerged as a candidate marker exhibiting increasingmRNA expression during astrocytoma malignant progression. However, injection of MIC-1/GDF15over-expressing GBM cell lines into nude mice has been previously shown to completely abolish theinherent tumorigenicity.In this study, determination of MIC-1/GDF15 protein levels in the CSF of a cohort of 94patients with intracranial tumors including astrocytomas (grades II, III and IV), meningioma, andmetastasis revealed significantly increased concentrations in GBM patients as compared to controlcohort of patients treated for non-neoplastic diseases. However, MIC-1/GDF15 levels were notelevated in the matching plasma samples from these patients. Most interestingly, GBM patients withthe increased concentrations of MIC-1/GDF15 in the CSF had worse outcome.In GBM tissue, it was found that the expression of MIC-1/GDF15 gene is low. Promotermethylation of the gene may partially explain the overall low expression levels. Investigation of thecellular origin of MIC-1/GDF15 expression in GBM tissue led to the MIC-1/GDF15 protein detectionin a subpopulation of the tumor infiltrating macrophages. These findings substantiated the workinghypothesis of MIC-1/GDF15 as harboring tumor-suppressive properties in GBM. Analysis of thesignaling pathway mediated by MIC-1/GDF15 in GBM highlighted the potential role of TGF-β signaltransduction. However, the lack of the functional response to the presence of MIC-1/GDF15 in-vitrosuggested operation of a paracrine loop for suppression of tumor formation which is evident solely invivo.In conclusion, MIC-1/GDF15 protein measured in the CSF may have diagnostic andprognostic values in patients with intracranial tumors. Molecular studies collectively proposeimplication of the tumor-host interactions in mediating the MIC-1/GDF15 tumor-suppressing activityduring GBM development.RésuméMalgré les progrès durant ces deux dernières décennies dans le diagnostique et le traitementdes tumeurs du cerveau primaires, ces néoplasmes restent incurables. Le glioblastome représente laforme la plus maligne des tumeurs astrocytiques du cerveau (astrocytomes). Pour le diagnostic et lepronostic, l'identification de marqueurs présents dans des substances facilement accessibles comme leplasma où le liquide céphalorachidien (LCR) faciliterait beaucoup la prise en charge des patients. Lacompréhension des mécanismes moléculaires de facteurs impliqués dans le développement du GBMpourrait ouvrir la voie vers l'utilisation de ces mécanismes dans des thérapies ciblées.MIC-1/GDF15 (Macrophage Inhibitory Cytokine-1/ Growth Differentiation Factor 15), uneprotéine secrétée qui appartient à la superfamille TGF-β, s'est révélé être un marqueur candidat, dontl'expression d'ARN messager augmente pendant la progression des astrocytomes malins. Cependant,une précedente étude montre que l'injection des lignées cellulaires de GBM fortement productrices deMIC-1/GDF15 dans des souris immunodéprimées abolit la tumorigénicité.Dans cette étude, les mesures dans une cohorte de 94 patients atteints de tumeursintracrâniennes comprenant des astrocytomes (grades II, III et IV), méningiomes et métastases,présentent des augmentations significatives des niveaux protéiques de MIC-1/GDF15 dans le LCRdes patients atteints de GBM par rapport aux patients traités pour des maladies non cancéreuses.Cependant, les niveaux de MIC-1/GDF15 n'étaient pas spécialement élevés dans le plasma. De plus,les patients atteints d'un GBM avec des niveaux élevés de MIC-1/GDF15 dans le LCR ont survécumoins longtemps. Dans les tissus de glioblastome, on observe que le gène MIC-1/GDF15 est peuexprimé. La méthylation du promoteur explique partiellement le faible niveau d'expression du gène.La recherche l'origine cellulaire de l'expression de MIC-1/GDF15, a permis de découvrir la présencede protéines MIC-1/GDF15 dans une sous-population de macrophages qui infiltrent les tumeurs. Cetteobservation supporte l'hypothèse que MIC-1/GDF15 présentait des propriétés de suppression destumeurs de type GBM. Des études sur les voies de signalisation régulées par MIC-1/GDF15 dans lesGBMs ont souligné l'importance de la voie de transduction du signal TGF-β. Cependant, l'absence deréponse fonctionnelle à MIC-1/GDF15 in vitro suggère fortement l'activité d'une boucle paracrinepour la répression de la formation de tumeur, qui n'est observé que in vivo.En conclusion, la protéine MIC-1/GDF15 mesurée dans le LCR pourrait avoir une valeur pourle diagnostic et le pronostic chez les patients atteints de GBM. Les études moléculaires suggèrent unepossible implication de l'interaction hôte-tumeur dans l'activité anti-tumorale de MIC-1/GDF15 sur leGBM.

Granulocyte macrophage colony stimulating factor improves mucosal repair in a mouse model of acute colitis (P278)

Background and Aims: Granulocyte-macrophage colonystimulating factor (GM-CSF), a cytokine modulating the number and function of innate immune cells, has been shown to provide symptomatic benefit in some patients with Crohn's disease (CD). Since, it becomes widely appreciated that a timely and spatially regulated action of innate immune cells is critical for tissue regeneration, we tested whether GM-CSF therapy may favours intestinal mucosal repair in the acute mouse model of dextran sulfate sodium (DSS)-induced colitis. Methods: Mice treated with GM-CSF or saline were exposed for 7 days to DSS to induce colitis. On day 5, 7 and 10, mice were subjected to colonoscopy or sacrificed for evaluation of inflammatory reaction and mucosal healing. Results: GM-CSF therapy prevented body weight loss, diarrhea, dampened inflammatory reactions and ameliorated mucosal damages. Mucosal repair improvement in GM-CSF-treated mice was observed from day 7 on both by colonoscopy (ulceration score 1.2}0.3 (GM-CSF-treated) vs 3.1}0.5 (untreated), p = 0.01) and histological analysis (percentage of reepithelialized ulcers 55%}4% (GM-CSF-treated) vs 18%}13% (untreated), p = 0.01). GM-CSF therapy can still improve the colitis when hematopoietic, but not non-hematopoietic cells, are responsive to GM-CSF, as shown in WT→GM-CSFRKO chimeras. Lastly, we observed that GM-CSF-induced promotion of wound healing is associated with a modification of the cellular composition of DSS-induced colonic inflammatory infiltrate, characterized by the reduction of neutrophil numbers and early accumulation of CD11b+Gr1lo myeloid cells. Conclusion: Our study shows that GM-CSF therapy accelerates the complex program leading to tissue repair during acute colitis and suggests that GM-CSF promotion of mucosal repair might contribute to the symptomatic benefits of GM-CSF therapy observed in some CD patients.

Quantitative morphometry analysis of the fetal brain using clinical MR imaging

In vivo fetal magnetic resonance imaging provides aunique approach for the study of early human braindevelopment [1]. In utero cerebral morphometry couldpotentially be used as a marker of the cerebralmaturation and help to distinguish between normal andabnormal development in ambiguous situations. However,this quantitative approach is a major challenge becauseof the movement of the fetus inside the amniotic cavity,the poor spatial resolution provided by very fast MRIsequences and the partial volume effect. Extensiveefforts are made to deal with the reconstruction ofhigh-resolution 3D fetal volumes based on severalacquisitions with lower resolution [2,3,4]. Frameworkswere developed for the segmentation of specific regionsof the fetal brain such as posterior fossa, brainstem orgerminal matrix [5,6], or for the entire brain tissue[7,8], applying the Expectation-Maximization MarkovRandom Field (EM-MRF) framework. However, many of theseprevious works focused on the young fetus (i.e. before 24weeks) and use anatomical atlas priors to segment thedifferent tissue or regions. As most of the gyraldevelopment takes place after the 24th week, acomprehensive and clinically meaningful study of thefetal brain should not dismiss the third trimester ofgestation. To cope with the rapidly changing appearanceof the developing brain, some authors proposed a dynamicatlas [8]. To our opinion, this approach however faces arisk of circularity: each brain will be analyzed /deformed using the template of its biological age,potentially biasing the effective developmental delay.Here, we expand our previous work [9] to proposepost-processing pipeline without prior that allow acomprehensive set of morphometric measurement devoted toclinical application. Data set & Methods: Prenatal MRimaging was performed with a 1-T system (GE MedicalSystems, Milwaukee) using single shot fast spin echo(ssFSE) sequences (TR 7000 ms, TE 180 ms, FOV 40 x 40 cm,slice thickness 5.4mm, in plane spatial resolution1.09mm). For each fetus, 6 axial volumes shifted by 1 mmwere acquired under motherâeuro?s sedation (about 1min pervolume). First, each volume is segmentedsemi-automatically using region-growing algorithms toextract fetal brain from surrounding maternal tissues.Inhomogeneity intensity correction [10] and linearintensity normalization are then performed. Brain tissues(CSF, GM and WM) are then segmented based on thelow-resolution volumes as presented in [9]. Ahigh-resolution image with isotropic voxel size of 1.09mm is created as proposed in [2] and using B-splines forthe scattered data interpolation [11]. Basal gangliasegmentation is performed using a levet setimplementation on the high-resolution volume [12]. Theresulting white matter image is then binarized and givenas an input in FreeSurfer software(http://surfer.nmr.mgh.harvard.edu) to providetopologically accurate three-dimensional reconstructionsof the fetal brain according to the local intensitygradient. References: [1] Guibaud, Prenatal Diagnosis29(4) (2009). [2] Rousseau, Acad. Rad. 13(9), 2006. [3]Jiang, IEEE TMI 2007. [4] Warfield IADB, MICCAI 2009. [5]Claude, IEEE Trans. Bio. Eng. 51(4) 2004. [6] Habas,MICCAI 2008. [7] Bertelsen, ISMRM 2009. [8] Habas,Neuroimage 53(2) 2010. [9] Bach Cuadra, IADB, MICCAI2009. [10] Styner, IEEE TMI 19(39 (2000). [11] Lee, IEEETrans. Visual. And Comp. Graph. 3(3), 1997. [12] BachCuadra, ISMRM 2010.

Use of anisotropic modelling in electrical impedance tomography: description of method and preliminary assessment of utility in imaging brain function in the adult human head.

Electrical Impedance Tomography (EIT) is an imaging method which enables a volume conductivity map of a subject to be produced from multiple impedance measurements. It has the potential to become a portable non-invasive imaging technique of particular use in imaging brain function. Accurate numerical forward models may be used to improve image reconstruction but, until now, have employed an assumption of isotropic tissue conductivity. This may be expected to introduce inaccuracy, as body tissues, especially those such as white matter and the skull in head imaging, are highly anisotropic. The purpose of this study was, for the first time, to develop a method for incorporating anisotropy in a forward numerical model for EIT of the head and assess the resulting improvement in image quality in the case of linear reconstruction of one example of the human head. A realistic Finite Element Model (FEM) of an adult human head with segments for the scalp, skull, CSF, and brain was produced from a structural MRI. Anisotropy of the brain was estimated from a diffusion tensor-MRI of the same subject and anisotropy of the skull was approximated from the structural information. A method for incorporation of anisotropy in the forward model and its use in image reconstruction was produced. The improvement in reconstructed image quality was assessed in computer simulation by producing forward data, and then linear reconstruction using a sensitivity matrix approach. The mean boundary data difference between anisotropic and isotropic forward models for a reference conductivity was 50%. Use of the correct anisotropic FEM in image reconstruction, as opposed to an isotropic one, corrected an error of 24 mm in imaging a 10% conductivity decrease located in the hippocampus, improved localisation for conductivity changes deep in the brain and due to epilepsy by 4-17 mm, and, overall, led to a substantial improvement on image quality. This suggests that incorporation of anisotropy in numerical models used for image reconstruction is likely to improve EIT image quality.

Dimethylarginines, homocysteine metabolism, and cerebrospinal fluid markers for Alzheimer's disease.

Dimethylarginine and homocysteine metabolism are closely linked and alterations of both were observed in plasma and cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD). CSF parameters of homocysteine metabolism have recently been found to be associated with the CSF level of the AD biomarker phosphorylated tau (ptau) in AD patients. To investigate possible relationships between homocysteine and dimethylarginine metabolism and the AD CSF biomarkers ptau181 and amyloid-β 1-42 (Aβ42), we assessed parameters of homocysteine metabolism (CSF homocysteine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), 5-methyltetrahydrofolate (5-MTHF)) and dimethylarginine metabolism (plasma and CSF asymmetric dimethylarginine (ADMA), symmetric dimethylarginine, L-arginine) as well as CSF Aβ42 and ptau181 in 98 controls and 51 AD patients. Multivariate linear regression analyses were performed to assess associations between the considered parameters. SAH concentrations show significant associations to CSF ADMA levels, and CSF ADMA and L-arginine to ptau181, but not to Aβ42 concentrations in AD patients. When including concentrations of homocysteine, 5-MTHF, SAM, and SAH into the analysis, CSF ADMA concentrations independently predicted ptau181 levels in AD patients but homocysteine-related metabolites were associated with ptau181 only when ADMA was removed from the analysis model. These results suggest that CSF ADMA may interact with CNS homocysteine metabolism and may contribute to neurodegeneration and accumulation of phosphorylated tau in AD. Functional and interventional studies are needed to further proof this hypothesis.

Partial protection and intrathecal invasion of CD8(+) T cells in acute canine distemper virus infection.

Initial non-inflammatory demyelination in canine distemper virus infection (CDV) develops against a background of severe immunosuppression and is therefore, thought to be virus-induced. However, recently we found a marked invasion of T cells throughout the central nervous system (CNS) in dogs with acute distemper despite drastic damage to the immune system. In the present study, this apparent paradox was further investigated by immunophenotyping of lymphocytes, following experimental CDV challenge in vaccinated and non-vaccinated dogs. In contrast to CDV infected, unprotected dogs, vaccinated dogs did not become immunosuppressed and exhibited a strong antiviral immune response following challenge with virulent CDV. In unprotected dogs rapid and drastic lymphopenia was initially due to depletion of T cells. In peripheral blood, CD4(+) T cells were more sensitive and depleted earlier and for a longer time than CD8(+) cells which recovered soon. In the cerebrospinal fluid (CSF) we could observe an increase in the T cell to B cell and CD8(+) to CD4(+) ratios. Thus, partial protection of the CD8(+) cell population could explain why part of the immune function in acute distemper is preserved. As found earlier, T cells invaded the CNS parenchyma in these dogs but also in the protected challenged dogs, which did not develop any CNS disease at all. Since markers of T cell activation were upregulated in both groups of animals, this phenomenon could in part be related to non-specific penetration of activated T cells through the blood brain barrier. However, in diseased animals much larger numbers of T cells were found in the CNS than in the protected dogs, suggesting that massive invasion of T cells in the brain requires CDV expression in the CNS.