Microanalysis of gene expression in cultured cells

In this thesis two aspects of gene expression in cultured cells have been studied: the heterogeneity in gene expression in relation with the development and application of microchemical techniques for the prenatal diagnosis of inborn errors of metabolism and the possibility of inducing gene expression in cultured cells using somatic cell hybridization. The (prenatal) diagnosis of genetic metabolic diseases is based on a comparison of data after biochemical analysis of cultured amniotic fluid cells and fibroblasts from normal individuals, heterozygotes and affected patients or fetuses. For a reliable prenatal diagnosis the effect of cell cultivation conditions and various morphological cell types within one culture on the biochemical parameters to be studied must be known. In this thesis the activity of three lysosomal enzymes, acid a-glucosidase, S-galactosidase and S-N-acetylhexosaminidase were investigated in relation to different cell types in primary amniotic fluid cell cultures. This was possible by microchemical analysis on small groups (10- 100) of morphologically different clones isolated from freeze-dried amniotic fluid cell cultures. The activities of the three lysosomal enzymes when expressed per cell appeared to be about the same in the small epithelioid cell types 1 and 2 and the fibroblast-! ike cells. In the large, often multinuclear cells however, the enzyme activity per cell was 5 to 10 fold higher than this in the other cell types. By performing combined microinterferometric determinations of the dry mass and enzyme assays on single cells we were able to show that no differences in lysosomal enzyme activities exist between the various amniotic fluid cell types if the activity is expressed per unit dry mass (appendix paper 1)

The effect of three years of TNF alpha blocking therapy on markers of bone turnover and their predictive value for treatment discontinuation in patients with ankylosing spondylitis: a prospective longitudinal observational cohort study

INTRODUCTION: The aim of this study was to investigate the effect of three years of tumor necrosis factor-alpha (TNF-alpha) blocking therapy on bone turnover as well as to analyze the predictive value of early changes in bone turnover markers (BTM) for treatment discontinuation in patients with ankylosing spondylitis (AS). METHODS: This is a prospective cohort study of 111 consecutive AS outpatients who started TNF-alpha blocking therapy. Clinical assessments and BTM were assessed at baseline, three and six months, as well as at one, two, and three years. Z-scores of BTM were calculated to correct for age and gender. Bone mineral density (BMD) was assessed yearly. RESULTS: After three years, 72 patients (65%) were still using their first TNF-alpha blocking agent. In these patients, TNF-alpha blocking therapy resulted in significantly increased bone-specific alkaline phosphatase, a marker of bone formation; decreased serum collagen-telopeptide (sCTX), a marker of bone resorption; and increased lumbar spine and hip BMD compared to baseline. Baseline to three months decrease in sCTX Z-score (HR: 0.394, 95% CI: 0.263 to 0.591), AS disease activity score (ASDAS; HR: 0.488, 95% CI: 0.317 to 0.752), and physician's global disease activity (HR: 0.739, 95% CI: 0.600 to 0.909) were independent inversely related predictors of time to treatment discontinuation because of inefficacy or intolerance. Early decrease in sCTX Z-score correlated significantly with good long-term response regarding disease activity, physical function and quality of life. CONCLUSIONS: Three years of TNF-alpha blocking therapy results in a bone turnover balance that favors bone formation, especially mineralization, in combination with continuous improvement of lumbar spine BMD. Early change in sCTX can serve as an objective measure in the evaluation of TNF-alpha blocking therapy in AS, in addition to the currently used more subjective measures

Vygotsky in English: What Still Needs to Be Done

At present readers of English have still limited access to Vygotsky’s writings. Existing translations are marred by mistakes and outright falsifications. Analyses of Vygotsky’s work tend to downplay the collaborative and experimental nature of his research. Several suggestions are made to improve this situation. New translations are certainly needed and new analyses should pay attention to the contextual nature of Vygotsky’s thinking and research practice

A method for sensitivity analysis to assess the effects of measurement error in multiple exposure variables using external validation data

Measurement error in self-reported dietary intakes is known to bias the association between dietary intake and a health outcome of interest such as risk of a disease. The association can be distorted further by mismeasured confounders, leading to invalid results and conclusions. It is, however, difficult to adjust for the bias in the association when there is no internal validation data

Comparison of the stable carbon and nitrogen isotopic values of gill and white muscle tissue of fish

The potential use of stable carbon and nitrogen isotope ratios (d13C, d15N) of fish gills for studies on fish feeding ecology was evaluated by comparing the d13C and d15N of gill tissue with the more commonly used white muscle tissue. To account for the effect of lipid content on the d13C signatures, a study-specific lipid correction model based on C:N ratios was developed and applied to the bulk d13C data. For the majority of species in the study, we found no significant difference in d13C values between gill and muscle tissue after correction, but several species showed a small (0.3–1.4‰) depletion of 13C in white muscle compared to gill tissue. The average species difference in d15N between muscle and gill tissue ranged from - 0.2 to 1.6‰ for the different fish species with muscle tissue generally more enriched in 15N. The d13C values of muscle and gill were strongly linearly correlated (R2 = 0.85) over a large isotopic range (13‰), suggesting that both tissues can be used to determine long-term feeding or migratory habits of fish. Muscle and gill tissue bulk d15N values were also strongly positively correlated (R2 = 0.76) but with a small difference between muscle and gill tissue. This difference indicates that the bulk d15N of the two tissue types may be influenced by different isotopic turnover rates or a different composition of amino acids