5 research outputs found
Teachers of mother-tongue education in action
No full textIn this paper we report on the first year of a two year action-research project in the Netherlands. Fourteen teachers of mother-tongue education worked together to design concept-contextenriched education. Three teachers of higher vocational education with knowledge of action research facilitated the project and an academic researcher from the university (first author of this paper) researched the implementation of this action-research project as the teachers were experiencing it. This paper reports on the knowledge the teachers developed, the materials they produced, and the mothertongue (or L1 concepts and contexts) they applied during the first ten months of the project. With this paper we wish to contribute to the knowledge on how in-service action-research projects develop and elaborate on what lessons may be learned from the first year of an action-research project in which teachers design concept-context enriched education. Teaching and Teacher Learning (ICLON
Ethanolamines permeate slowly across human skin ex vivo, but cause severe skin irritation at low concentrations.
No full textSkin exposures are common during cleaning activities, and may contribute to the overall body burden. Cleaning products may contain irritants such as monoethanolamine (MEA) and diethanol amine (DEA). The significance of the skin exposure route is unknown, as no estimates for MEA skin permeation are available. We used in vitro flow-through diffusion cells with excised fresh human skin to measure skin permeation, and assessed skin damage with histological methods. MEA(aq) by itself (2%) or as a constituent in cleaning products (0.25% working solution) did not permeate after 1 h or 24 h of exposure. MEA(aq) (10%) did not permeate skin after 1 h but after 24 h with a delay (T lag ; 7 h) and a moderate permeation rate (J; 26.6 μg/cm 2 /h). MEA permeation rate was 20-fold greater (544 μg/cm 2 /h) and ¼ of the time lag (1.5 h) when applied as undiluted cleaning product (13% MEA) compared to 10% MEA(aq). DEA in cleaning products did not permeate skin after 24 h. MEA and DEA produced skin irritations at low concentrations (1% MEA) and severe skin irritations when tested as a constituent in cleaning products. Absorption increased from 0 to 3% after 24 h to 14-29% after 88 h of MEA exposure, and is likely explained by the increased damage of the skin barrier. Limitations of this study are the low number of skin donors (N = 5) available. Our results demonstrate that topically applied MEA permeates across human skin relatively slowly and not below 5% while relatively extensively as a constituent of a commercial cleaning product
Impact of physical activity on ethoxy- and propoxypropanol human toxicokinetics in vivo
No full textOrganic solvents such as propylene glycol ethers (PGEs) represents more than 20 different substances and are incorporated in thousands of commercial and professional products. Two PGEs commonly used in Europe and found mainly in cleaning and water-based paint products are propylene glycol ethyl ether (PGEE) and propylene glycol propyl ether (PGPE). Given their volatile properties, inhalation is the most common route of exposure. The aim of this study was to characterize human toxicokinetics following PGEE and PGPE inhalation exposure. The participants were exposed (4 h) at rest to a single PGE (between 15 and 35 ppm) under controlled conditions and blood, urine, and exhaled breath were collected. Our study shows that both PGEs were rapidly detected in blood (absorption rate: 0.01 µg/mL/h*ppm) and elimination was more important through urine (half-life: 1 h) than exhaled breath (half-life: 2 min). We also evaluated the impact of a moderate physical activity (30 min, 100 W) during exposure. A significant increase of blood absorption (absorption rate: 0.03 µg/mL/h*ppm) and internal dose (increase of 48%) was observed. Our results confirm that both PGEs are easily absorbed at rest and even faster with a moderate physical activity. The biomonitoring approach we have developed here allow the measurement of the "real" internal dose in workers handling these solvents. The existing occupational exposure limits do not consider workload, which may lead to their underestimation. Therefore, we recommend the use of biomonitoring for future studies and the consideration of physical workload for future exposure limits settings as an important parameter for risk assessment.
© 2025. The Author(s)
'Herbal' but potentially hazardous: an analysis of the constituents and smoke emissions of tobacco-free waterpipe products and the air quality in the cafes where they are served
No full textBACKGROUND: There are limited data on the composition and smoke emissions of 'herbal' shisha products and the air quality of establishments where they are smoked. METHODS: Three studies of 'herbal' shisha were conducted: (1) samples of 'herbal' shisha products were chemically analysed; (2) 'herbal' and tobacco shisha were burned in a waterpipe smoking machine and main and sidestream smoke analysed by standard methods and (3) the air quality of six waterpipe cafes was assessed by measurement of CO, particulate and nicotine vapour content. RESULTS: We found considerable variation in heavy metal content between the three products sampled, one being particularly high in lead, chromium, nickel and arsenic. A similar pattern emerged for polycyclic aromatic hydrocarbons. Smoke emission analyses indicated that toxic byproducts produced by the combustion of 'herbal' shisha were equivalent or greater than those produced by tobacco shisha. The results of our air quality assessment demonstrated that mean PM2.5 levels and CO content were significantly higher in waterpipe establishments compared to a casino where cigarette smoking was permitted. Nicotine vapour was detected in one of the waterpipe cafes. CONCLUSIONS: 'Herbal' shisha products tested contained toxic trace metals and PAHs levels equivalent to, or in excess of, that found in cigarettes. Their mainstream and sidestream smoke emissions contained carcinogens equivalent to, or in excess of, those of tobacco products. The content of the air in the waterpipe cafes tested was potentially hazardous. These data, in aggregate, suggest that smoking 'herbal' shisha may well be dangerous to health
Cortical organotypic slice cultures as a tool to analyze the neurovascular unit in hypoxia/ischemia and hypothermia-induced neuroprotection
No full textNeurons and glial cells of the central nervous system (CNS) communicate and work together to function and execute an array of complex tasks. In addition to them a third cell type which also works to keep the brain alive are the cerebral endothelial cells that create the vascular system which supply and deliver oxygen and nutrients. The cerebral endothelium is also specialized with a blood-brain barrier (BBB) that is important for protecting the CNS from harmful substances and for regulating access only to certain ions and nutrients for optimal maintenance and support of CNS activities. A complex of tight junction proteins which include occludin, Claudin-1/3, Claudin-5, and ZO1-3 are thought to keep the endothelium impermeable, while a system of transporters, such as GLUT1 and P-gp are involved in regulating the molecular trafficking across the BBB. The endothelium is also characterized by a low pinocytotic activity compared to vessels in peripheral organs. A lot is known on the formation and composition of the BBB, but less is understood on the maintenance. This is probably due to the heterogeneity of the cerebral endothelium, which makes it difficult to study. However, the cerebrovascular function is supported by a combination of interactions with glia, pericytes, and nerve cells, known together as the neurovascular unit (NVU). A number of in vitro studies show that co-culturing endothelial cells with astrocytes and pericytes, as well as nerve tissue is capable of expressing tight junction proteins and a tight endothelial barrier, suggesting that cell-cell interactions and production of essential factors such as FGF and TGF-beta are involved in BBB maintenance.
Disruption of the BBB is often associated with brain injury and considered to be detrimental to the recovery process. Although the mechanisms are poorly understood, breakdown of the BBB has been suggested to be due to production of matrix-metalloproteinases, growth factors and cytokines. Inflammatory mediators have been well known to modulate BBB permeability. Since inflammation typically follows excitotoxicity in the ischemic cascade to cell death, BBB disruption may be secondary in the injury process. Whether the vascular damage is precipitated by neurodegeneration is unclear. Understanding how the neurovasculature might be affected is important for prevention and treatment of neurovascular diseases, such as stroke or neonatal asphyxia since neuroprotectants, except for therapeutic mild-hypothermia, have failed in the clinics.
Cooling of the head or body down to about 33°C for up to 3 days has so far been the most effective neuroprotective strategy for treating cerebral ischemia observed in stroke or perinatal asphyxia. Along with reducing energy demand and energy consumption, mild hypothermia seems to affect many aspects of cellular injury but overall is very efficient at stopping cell death. A small group of proteins are expressed during mild-hypothermia. One of them is the RNA binding motif protein 3 (RBM3) and based on in vitro studies it is involved in cell proliferation and survival. Whether RBM3 is involved in hypothermia-induced neuroprotection deserves investigation as it may provide some hints into the mechanisms of how hypothermia prevents cell death.
A useful in vitro system to study aspects of neurodegeneration that is close to the in vivo situation is the organotypic slice culture system, which has been very well established for cortical, hippocampal, and cerebellar tissue. Previously our lab has established an in vitro BBB model utilizing the cortical organotypic slice culture system, which preserves tight junction proteins for more than a week under the presence of FGF2. The main objective of my PhD thesis was to analyze the expression of the neuronal and vascular elements of the blood-brain barrier (BBB) under normal and stressed conditions and to study the cell-cell interaction at the biochemical and cellular level utilizing the organotypic slice culture system established in our laboratory. In the first project we have studied the expression of transporter proteins in cortical organotypic slice cultures (COSCs). We could show that transporters such as glucose transporter 1 (GLUT-1) and the ATP-binding cassette (ABC) transporter, P-glycoprotein (P-gp) were present and functional in the blood vessels of COSCs. In the second project we used entorhino-hippocampal organotypic slice cultures (EHOSCs) derived from newborn mice to study the effect of oxygen-glucose deprivation (OGD) as well as excitotoxicity on neurodegeneration and accompanying neurovascular changes. We could show that changes in BBB integrity and vascular remodeling were linked to neurodegeneration. Selective loss of the neurovasculature in CA1 of the hippocampus was preceded by neuronal death indicating that not OGD by itself, but the OGD-induced neurodegeneration was responsible for the loss of local blood vessels. Finally, in the third project we have explored a potential function of the cold-inducible RNA binding motif protein 3 as a neuroprotectant in response to mild hypothermia that is employed after neonatal asphyxia. We could show that RBM3 expression was strongly induced in COSCs upon hypothermia and was required and sufficient for neuroprotection of dissociated PC12 cells from induced apoptosis
