Biomedical subjects

Christoph Klein

Publications and source records attributed to Christoph Klein.

At least 19 recordsLinked to original sources

PubMed2007

Regression-based developmental models exemplified for Wisconsin Card Sorting Test parameters: statistics and software for individual predictions.

The prediction of an individual's score is relevant in clinical research and requires normative data and a statistical rationale. In the case of developmental research the latter is typically a set of descriptive statistics (e.g., standard scores) for a set of age groups. Here we illustrate a multiple regression approach with a set of 345 Wisconsin Card Sorting Test (WCST) data obtained from subjects aged 6 to 26 years. We modeled linear and curvilinear age effects for each of the 11 WCST variables and, based on this, determined confidence limits for the expected value (mean) and the prediction of individual scores. In these multiple regression models, which accounted for 2% to 26% of the variance, curvilinear age effects clearly dominated linear ones, suggesting the features under scrutiny to be negatively accelerated functions of age. Finally, we developed a statistics program that can be used to apply multiple regression models for individual predictions that are based on normative data with up to 7 predictor variables. We discuss the conditions of applicability of the approach, compare it with the conventional standard score approach, discuss its cognitive-developmental implications, and outline the applicability in applied research and practising.

Adolescent↗

PubMed2006

A novel human primary immunodeficiency syndrome caused by deficiency of the endosomal adaptor protein p14.

Lysosome-related organelles have versatile functions, including protein and lipid degradation, signal transduction and protein secretion. The molecular elucidation of rare congenital diseases affecting endosomal-lysosomal biogenesis has given insights into physiological functions of the innate and adaptive immune system. Here, we describe a previously unknown human primary immunodeficiency disorder and provide evidence that the endosomal adaptor protein p14, previously characterized as confining mitogen-activated protein kinase (MAPK) signaling to late endosomes, is crucial for the function of neutrophils, B cells, cytotoxic T cells and melanocytes. Combining genetic linkage studies and transcriptional profiling analysis, we identified a homozygous point mutation in the 3' untranslated region (UTR) of p14 (also known as MAPBPIP), resulting in decreased protein expression. In p14-deficient cells, the distribution of late endosomes was severely perturbed, suggesting a previously unknown role for p14 in endosomal biogenesis. These findings have implications for understanding endosomal membrane dynamics, compartmentalization of cell signal cascades, and their role in immunity.

Adaptor Protein Complex 4↗

PubMed2006

HAX1 deficiency causes autosomal recessive severe congenital neutropenia (Kostmann disease).

Autosomal recessive severe congenital neutropenia (SCN) constitutes a primary immunodeficiency syndrome associated with increased apoptosis in myeloid cells, yet the underlying genetic defect remains unknown. Using a positional cloning approach and candidate gene evaluation, we identified a recurrent homozygous germline mutation in HAX1 in three pedigrees. After further molecular screening of individuals with SCN, we identified 19 additional affected individuals with homozygous HAX1 mutations, including three belonging to the original pedigree described by Kostmann. HAX1 encodes the mitochondrial protein HAX1, which has been assigned functions in signal transduction and cytoskeletal control. Here, we show that HAX1 is critical for maintaining the inner mitochondrial membrane potential and protecting against apoptosis in myeloid cells. Our findings suggest that HAX1 is a major regulator of myeloid homeostasis and underline the significance of genetic control of apoptosis in neutrophil development.

Adaptor Proteins, Signal Transducing↗

PubMed2006

p14-MP1-MEK1 signaling regulates endosomal traffic and cellular proliferation during tissue homeostasis.

The extracellular signal-regulated kinase (ERK) cascade regulates proliferation, differentiation, and survival in multicellular organisms. Scaffold proteins regulate intracellular signaling by providing critical spatial and temporal specificity. The scaffold protein MEK1 (mitogen-activated protein kinase and ERK kinase 1) partner (MP1) is localized to late endosomes by the adaptor protein p14. Using conditional gene disruption of p14 in mice, we now demonstrate that the p14-MP1-MEK1 signaling complex regulates late endosomal traffic and cellular proliferation. This function its essential for early embryogenesis and during tissue homeostasis, as revealed by epidermis-specific deletion of p14. These findings show that endosomal p14-MP1-MEK1 signaling has a specific and essential function in vivo and, therefore, indicate that regulation of late endosomal traffic by extracellular signals is required to maintain tissue homeostasis.

Adaptor Proteins, Signal Transducing↗

PubMed2006

An in vitro pyrogen safety test for immune-stimulating components on surfaces.

Due to the discovery of novel surgical techniques and new materials medical devices are increasingly used. Contact of these biomaterials with human tissue or blood commonly leads to inflammation of varying degrees, sometimes resulting in severe health problems. Possible causes are limited biocompatibility or pyrogenic contamination of the material. We adapted the recently validated in vitro pyrogen test (IPT), based on human whole blood cytokine release, to test the safety of biomaterials. Human whole blood is brought into direct contact with the surface of the test material and the release of the pro-inflammatory cytokine IL-1beta is measured. This procedure represents a human-relevant assay allowing the detection of pyrogens of different origins, e.g. Gram-negative (lipopolysaccharide, LPS) or Gram-positive (lipoteichoic acid, LTA), peptidoglycan (cell wall components of most bacteria) and fungal zymosan by direct material contact. The sensitivity of the test system allows a starting concentration of 10 pg/ml for LPS, 10 ng/ml for zymosan and 1 microg/ml for LTA and peptidoglycan from different strains. Furthermore, we have shown that the test for solid materials can be carried out with cryo-preserved blood, which results in an even lower detection limit.

Adjuvants, Immunologic↗

PubMed2006

A phase 1/2 trial of arginine butyrate and ganciclovir in patients with Epstein-Barr virus-associated lymphoid malignancies.

Malignancies associated with latent Epstein-Barr virus (EBV) are resistant to nucleoside-type antiviral agents because the viral enzyme target of these antiviral drugs, thymidine kinase (TK), is not expressed. Short-chain fatty acids, such as butyrate, induce EBV-TK expression in latently infected B cells. As butyrate has been shown to sensitize EBV(+) lymphoma cells in vitro to apoptosis induced by ganciclovir, arginine butyrate in combination with ganciclovir was administered in 15 patients with refractory EBV(+) lymphoid malignancies to evaluate the drug combination for toxicity, pharmacokinetics, and clinical responses. Ganciclovir was administered twice daily at standard doses, and arginine butyrate was administered by continuous infusion in an intrapatient dose escalation, from 500 mg/(kg/day) escalating to 2000 mg/(kg/day), as tolerated, for a 21-day cycle. The MTD for arginine butyrate in combination with ganciclovir was established as 1000 mg/(kg/day). Ten of 15 patients showed significant antitumor responses, with 4 CRs and 6 PRs within one treatment cycle. Complications from rapid tumor lysis occurred in 3 patients. Reversible somnolence or stupor occurred in 3 patients at arginine butyrate doses of greater than 1000 mg/(kg/day). The combination of arginine butyrate and ganciclovir was reasonably well-tolerated and appears to have significant biologic activity in vivo in EBV(+) lymphoid malignancies which are refractory to other regimens.

Adolescent↗

PubMed2006

Strong prognostic value of nodal and bone marrow micro-involvement in patients with pancreatic ductal carcinoma receiving no adjuvant chemotherapy.

AIM: To study the prognostic value of adjuvant chemotherapy in patients with pancreatic, ductal adenocarcinoma. METHODS: Lymph nodes from 106 patients with resectable pancreatic ductal adenocarcinoma were systematically sampled. A total of 318 lymph nodes classified histopathologically as tumor-free were examined using sensitive immunohistochemical assays. Forty-three (41%) of the 106 patients were staged as pT((1/2)), 63 (59%) as pT((3/4)), 51 (48%) as pN(0), and 55 (52%) as pN(1). The study population included 59 (56%) patients exhibiting G((1/2)), and 47 (44%) patients with G(3) tumors. Patients received no adjuvant chemo- or radiation therapy and were followed up for a median of 12 (range: 3.5 to 139) mo. RESULTS: Immunostaining with Ber-EP4 revealed nodal microinvolvement in lymph nodes classified as "tumor free" by conventional histopathology in 73 (69%) out of the 106 patients. Twenty-nine (57%) of 51 patients staged histopathologically as pN(0) had nodal microinvolvement. The five-year survival probability for pN0-patients was 54% for those without nodal microinvolvement and 0% for those with nodal microinvolvement. Cox-regression modeling revealed the independent prognostic effect of nodal microinvolvement on recurrence-free (relative risk 2.92, P=0.005) and overall (relative risk 2.49, P=0.009) survival. CONCLUSION: The study reveals strong and independent prognostic significance of nodal microinvolvement in patients with pancreatic ductal adenocarcinoma who have received no adjuvant therapy. The addition of immunohistochemical findings to histopathology reports may help to improve risk stratification of patients with pancreatic cancer.

Adult↗

PubMed2006

Intra-subject variability in attention-deficit hyperactivity disorder.

BACKGROUND: This study is based on a comprehensive survey of the neuropsychological attention-deficit hyperactivity disorder (ADHD) literature and presents the first psychometric analyses of different parameters of intra-subject variability (ISV) in patients with ADHD compared to healthy controls, using the Continuous Performance Test, a Go-NoGo task, a Stop Signal Task, as well as N-back tasks. METHODS: Data of 57 patients with ADHD and 53 age- and gender-matched controls were available for statistical analysis. Different parameters were used to describe central tendency (arithmetic mean, median), dispersion (standard deviation, coefficient of variation, consecutive variance), and shape (skewness, excess) of reaction time distributions, as well as errors (commissions and omissions). RESULTS: Group comparisons revealed by far the strongest effect sizes for measures of dispersion, followed by measures of central tendency, and by commission errors. Statistical control of ISV reduced group differences in the other measures substantially. One (patients) or two (controls) principal components explained up to 67% of the inter-individual differences in intra-individual variability. CONCLUSIONS: Results suggest that, across a variety of neuropsychological tests, measures of ISV contribute best to group discrimination, with limited incremental validity of measures of central tendency and errors. Furthermore, increased ISV might be a unitary construct in ADHD.

Adolescent↗

PubMed2006

Identification of a homozygous deletion in the AP3B1 gene causing Hermansky-Pudlak syndrome, type 2.

We report on the molecular etiology of an unusual clinical phenotype associating congenital neutropenia, thrombocytopenia, developmental delay, and hypopigmentation. Using genetic linkage analysis and targeted gene sequencing, we defined a homozygous genomic deletion in AP3B1, the gene encoding the beta chain of the adaptor protein-3 (AP-3) complex. The mutation leads to in-frame skipping of exon 15 and thus perturbs proper assembly of the heterotetrameric AP-3 complex. Consequently, trafficking of transmembrane lysosomal proteins is aberrant, as shown for CD63. In basal keratinocytes, the incorporated immature melanosomes were rapidly degraded in large phagolysosomes. Despite distinct ultramorphologic changes suggestive of aberrant vesicular maturation, no functional aberrations were detected in neutrophil granulocytes. However, a comprehensive immunologic assessment revealed that natural killer (NK) and NKT-cell numbers were reduced in AP-3-deficient patients. Our findings extend the clinical and molecular phenotype of human AP-3 deficiency (also known as Hermansky-Pudlak syndrome, type 2) and provide further insights into the role of the AP-3 complex for the innate immune system.

Adaptor Protein Complex 3↗

PubMed2006

Retroviral WASP gene transfer into human hematopoietic stem cells reconstitutes the actin cytoskeleton in myeloid progeny cells differentiated in vitro.

OBJECTIVE: Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency disorder characterized by recurrent infections, autoimmunity, microthrombocytopenia, and susceptibility to malignant tumors. Compared with the conventional treatment using allogeneic bone marrow transplantation, hematopoietic stem cell gene therapy might offer more specific and less toxic therapeutic options. METHODS: We investigated retroviral WAS protein (WASP) gene transfer to assess functional correction and potential toxicities in human CD34(+) cells from WAS patients and healthy individuals, respectively. RESULTS: WASP mRNA and protein levels were restored in CD14(+) cells derived from WASP-transduced hematopoietic stem cells. Functional reconstitution in WASP-transduced myeloid cells was documented by podosome formation and Fc gamma R-mediated phagocytosis. Importantly, overexpression of WASP in CD34(+) cells from healthy donors did not cause any discernible toxic effects. CONCLUSIONS: Our studies document the feasibility of WASP gene transfer into human CD34(+) cells and suggest that the phenotype of WASP-deficient myeloid cells can be restored upon retroviral gene transfer.

Actin Cytoskeleton↗

PubMed2006

Absolute myoglobin quantitation in serum by combining two-dimensional liquid chromatography-electrospray ionization mass spectrometry and novel data analysis algorithms.

To measure myoglobin, a marker for myocardial infarction, directly in human serum, two-dimensional liquid chromatography in combination with electrospray ionization mass spectrometry was applied as an analytical method. High-abundant serum proteins were depleted by strong anion-exchange chromatography. The myoglobin fraction was digested and injected onto a 60 mm x 0.2 mm i.d. monolithic capillary column for quantitation of selected peptides upon mass spectrometric detection. The addition of known amounts of myoglobin to the serum sample was utilized for calibration, and horse myoglobin was added as an internal standard to improve reproducibility. Calibration graphs were linear and facilitated the reproducible and accurate determination of the myoglobin amount present in serum. Manual data evaluation using integrated peak areas and an automated multistage algorithm fitting two-dimensional models of peptide elution profiles and isotope patterns to the mass spectrometric raw data were compared. When the automated method was applied, a myoglobin concentration of 460 pg/microL serum was determined with a maximum relative deviation from the theoretical value of 10.1% and a maximum relative standard deviation of 13.4%.

Algorithms↗

PubMed2006

Development of hematopoietic stem cell gene therapy for Wiskott-Aldrich syndrome.

Wiskott-Aldrich syndrome (WAS) is a complex primary immunodeficiency disorder associated with microthrombocytopenia, autoinnmunity and susceptibility to malignant lymphoma. At the molecular level, this rare disorder is caused by mutations in the gene encoding the Wiskott-Aldrich syndrome protein (WASP). WASP is a cytosolic adaptor protein mediating the rearrangement of the actin cytoskeleton upon surface receptor signaling. Allogenic hematopoietic stem cell (HSC) transplantation represents a curative approach but remains problematic in light of severe risks and side effects. Recently, HSC gene therapy has emerged as an alternative treatment option. Cumulative preclinical data obtained from WASP-deficient murine models and human cells indicate a marked improvement of the impaired cellular and immunological phenotypes associated with WASP deficiency. The first clinical trial is currently being conducted to assess the feasibility, toxicity, and potential therapeutic benefit of transplanting autologous WASP-reconstituted hematopoietic stem cells.

Animals↗

PubMed2005

Lifespan development of pro- and anti-saccades: multiple regression models for point estimates.

The comparative study of anti- and pro-saccade task performance contributes to our functional understanding of the frontal lobes, their alterations in psychiatric or neurological populations, and their changes during the life span. In the present study, we apply regression analysis to model life span developmental effects on various pro- and anti-saccade task parameters, using data of a non-representative sample of 327 participants aged 9 to 88 years. Development up to the age of about 27 years was dominated by curvilinear rather than linear effects of age. Furthermore, the largest developmental differences were found for intra-subject variability measures and the anti-saccade task parameters. Ageing, by contrast, had the shape of a global linear decline of the investigated saccade functions, lacking the differential effects of age observed during development. While these results do support the assumption that frontal lobe functions can be distinguished from other functions by their strong and protracted development, they do not confirm the assumption of disproportionate deterioration of frontal lobe functions with ageing. We finally show that the regression models applied here to quantify life span developmental effects can also be used for individual predictions in applied research contexts or clinical practice.

Adolescent↗

PubMed2005

Developmental fractionation and differential discrimination of the anti-saccadic direction error.

This partial re-analysis of the data of a total of 433 experimental sessions transfers the distinction of "express" and "regular" latency ranges from the pro-saccade task to the latencies of the anti-saccadic direction errors. Express errors and express saccades (ES) loaded on one and the same PCA factor, and both variables were subject to only minor developmental changes from childhood to young adulthood. Regular direction errors loaded, with opposite signs, on the same factor as pro-saccadic reaction times and were unrelated to express errors; these direction errors showed substantial developmental changes. Our data contribute with new evidence from the anti-saccade task to the long standing debate on whether ES should be considered as a separate type of saccade. Anti-saccadic direction errors with express latencies can be distinguished from those with regular latencies. Future anti-saccade task research should therefore analyse these error types separately in order to look for further evidence in favour of their conceptual and statistical distinction.

Adolescent↗

PubMed2005

WASP deficiency leads to global defects of directed leukocyte migration in vitro and in vivo.

Intact cellular migration is critically important for the induction and regulation of the immune response. The Wiskott-Aldrich syndrome protein (WASP) regulates surface receptor signaling to the actin cytoskeleton in hematopoietic cells and thus plays a pivotal role in cellular locomotion. WASP deficiency causes the Wiskott-Aldrich syndrome (WAS), characterized by immunodeficiency, thrombocytopenia, and eczema. Cell migration defects may contribute to the pathophysiology of WAS. In this study, we used a variety of in vitro and in vivo assays to comprehensively analyze migration properties of lymphocytes, dendritic cells (DC), and neutrophils from WASP-deficient mice. We provide evidence that WASP-deficient lymphocytes show a marked reduction in tethering in an in vitro flow chamber assay as well as decreased migration of T cells in response to the CC chemokine ligand 19 (CCL19). In vivo, compared with wild-type lymphocytes, WASP-deficient lymphocytes showed significantly impaired homing to Peyer's patches upon adoptive transfer into recipient mice. In addition, bone marrow-derived DC migrated less efficiently in response to CCL19. In vivo studies showed decreased migration of DC from skin to draining lymph nodes in WASP-deficient animals. Finally, we also document decreased neutrophil migration in vitro and in vivo. In summary, our studies suggest that WASP plays an important role in the locomotion of lymphocytes, DC, and granulocytes in vitro and in vivo and thus, reveal a crucial role of WASP in physiological trafficking of various hematopoietic cell lineages. These results further delineate immunological abnormalities in WASP-deficient mice, which will be useful to assess preclinical gene therapy studies.

Animals↗

PubMed2005

An independent components analysis (ICA) approach to the study of developmental differences in the saccadic contingent negative variation.

This study investigated the development of the saccadic CNV in 74 subjects aged 7-18 years, using pro- and anti-saccade tasks, and independent components analysis (ICA) for data analysis. Within the 2-stimulus paradigm, a central fixation point (S1) was followed 2.5s later by a peripheral cue (S2) presented at 4 degrees to the left or right of S1 in random order. The EEG was recorded from 40 electrodes applied over both hemispheres using a DC amplifier. With increasing age, pro- and anti-saccadic reaction times became faster, this effect being slightly more pronounced during childhood for the anti-saccade task. ICA revealed a lateral-posterior sCNV in younger children, and the known anterior-central sCNV in late adolescents. By contrast, the gaze maintenance negativity (GMNb), an anterior-central negativity accompanying the excursion of the eye, was present in all age groups. Our results underline the importance of topographical approaches in developmental ERP research and the usefulness of ICA. They suggest major task-dependent developmental differences in the spatial modulation of frontal-lobe sensitive ERP components.

Adolescent↗

PubMed2005

Instrumental and test-retest reliability of saccadic measures.

Little is known about the reliabilities of the various measures of saccade control that can be derived from pro- and anti-saccade tasks. This paper presents correlational results of 2 different studies comprising altogether 446 psychiatrically and neurologically healthy participants in the range of 6-88 years. Saccades were elicited under different stimulation conditions and during task blocks of 100 or 200 trials. Odd-even and split-half correlations determined for study 1 (N = 327, age 9-88 years) were found to be good to excellent (.60 < or = r < or = .97) for most measures and generalisable over the entire life-span. The 19-month test-retest correlations obtained in study 2 (N = 117, age 6-18 years) ranged between .43 and .66 after controlling for age, and suggest moderate stability of individual differences over time during childhood and adolescence. Hence, these parameters are very useful for concurrent validity studies at every age, but less so for predictive validity studies with children and adolescents.

Adolescent↗

PubMed2005

Cytogenetic characterization of a BCR-ABL transduced mouse cell line.

Most patients with Philadelphia (Ph)-positive acute lymphoblastic leukemia (ALL) show evidence of secondary chromosome aberrations that may influence the course of disease and response to treatment. To better understand how these secondary chromosomal aberrations occur and to investigate whether the p185/p190 BCR-ABL fusion protein may directly induce an increased chromosomal instability and subsequently the appearance of clonal chromosome aberrations, three BRC-ABL (p185/ p190)-transduced mouse pre-B cell lines were analyzed by spectral karyotyping and fluorescence in situ hybridization. The human wild-type BCR-ABL gene was expressed at a level comparable with that in human Ph-positive leukemias at diagnosis. All BCR-ABL-transduced cell lines acquired similar clonal chromosomal aberrations. Trisomy 5 was always present, followed by loss of the Y chromosome, trisomy of chromosomes 12 and 18, and an unbalanced translocation between chromosomes X and 12. Thus, ectopic p185/p190 BCR-ABL expression, such as p210 BCR-ABL, PML-RARA, or C-MYC transduction, may induce an increased chromosomal instability leading to clonal karyotypic evolution, which may mimic secondary chromosome aberrations in human Ph-positive ALL.

Animals↗