22 research outputs found
Methodology of peening intensity evaluation basing on the Almen tests
Abstract Surfaces of casting products as well as cores and moulds require thorough cleaning and treatment. Several cleaning methods are available, depending on the type of the material, the surface's geometry and condition, and the type of contamination. Shot peening treatment using rotor machines is a widely adopted solution and the peening performance is chiefly associated with shot peening intensity. A methodology of evaluating the peening intensity is outlined. The method uses the Almen test, widely employed when analysing the efficiency of dynamic, surface treatment methods. The evaluation method is illustrated by experimental data, process parameters and operational parameters of a shot peening machine manufactured in Poland
Evidence for bystander signalling between human trophoblast cells and human embryonic stem cells
Maternal exposure during pregnancy to toxins can occasionally lead to miscarriage and
malformation. It is currently thought that toxins pass through the placental barrier, albeit bilayered
in the first trimester, and damage the fetus directly, albeit at low concentration. Here we
examined the responses of human embryonic stem (hES) cells in tissue culture to two metals at low
concentration. We compared direct exposures with indirect exposures across a bi-layered model
of the placenta cell barrier. Direct exposure caused increased DNA damage without apoptosis or
a loss of cell number but with some evidence of altered differentiation. Indirect exposure caused
increased DNA damage and apoptosis but without loss of pluripotency. This was not caused by
metal ions passing through the barrier. Instead the hES cells responded to signalling molecules
(including TNF-α) secreted by the barrier cells. This mechanism was dependent on connexin 43
mediated intercellular ‘bystander signalling’ both within and between the trophoblast barrier and
the hES colonies. These results highlight key differences between direct and indirect exposure of hES
cells across a trophoblast barrier to metal toxins. It offers a theoretical possibility that an indirectly
mediated toxicity of hES cells might have biological relevance to fetal development
Effects of Maternal Thyroid Status on Thyroid Hormones and Growth in Congenitally Hypothyroid Goat Fetuses during the Second Half of Gestation
RC3/neurogranin structure and expression in the caprine brain in relation to congenital hypothyroidism
In view of the profound effects of thyroid hormone deficiency on the central nervous system (CNS), neuronal genes regulated by thyroid hormone could potentially be involved in the development of the CNS. Expression of the neuronal gene RC3/neurogranin was shown to be induced by thyroid hormone in the rat. No data are available on RC3 expression in mammals with prenatal brain development, like humans. To study RC3 mRNA expression in a genetic in vivo model of congenital hypothyroidism, which also resembles the human situation in the timing of brain development relative to birth, we used an inbred strain of congenitally hypothyroid goats. We isolated a cDNA for the caprine RC3 homolog. The deduced amino acid sequence had 99% similarity with the rat and bovine protein sequence. An analysis of the developmental expression of RC3 mRNA levels showed a 3-fold increase between E90 and P0. In situ hybridization analysis showed that in euthyroid goats, the RC3 expression pattern was region-specific and resembled that in rats. However, in contrast to rats, hypothyroid goats showed only a reduced RC3 mRNA expression in the striatum. Hypothyroidism had no effect on RC3 mRNA expression in all other brain regions. T4-treatment of the hypothyroid fetus increased RC3 mRNA expression in the striatum to euthyroid control levels. These data suggest that thyroid hormone is a regulator of RC3 gene expression in the caprine brain, and that the striatum is highly sensitive to thyroid hormone deficienc
Effects of maternal thyroid status on thyroid hormones and growth in congenitally hypothyroid goat fetuses during the second half of gestation
Congenital hypothyroidism in Dutch goats is due to a thyroglobulin (TG) synthesis defect that is inherited in an autosomal recessive manner. Minute amounts of mutated TG messenger RNA are translated into glycosylated TG fragments that contain the N-terminal hormonogenic site and are able to form T4, albeit less efficiently. We analyzed the effects of maternal thyroid status on fetal plasma thyroid hormones and growth during the second half of gestation (E90-E150). Maternal hypothyroidism, present from midgestation, resulted in decreased brain and cerebellum weights of affected goitrous fetuses, most evident at term gestation (E150). Brain and cerebellum weights of affected fetuses from unaffected mothers were not decreased. T4 and FT4 levels in affected fetuses were dependent on the maternal phenotype, as was the degree of enlargement of the goiter at E150. Newborn unaffected lambs from affected mothers had plasma T4 levels within the normal range. The present data show that in late gestation, fetal goats have to rely on their own thyroidal T4 production. The results suggest that affected fetuses are able to maintain sufficiently high T4 and T3 levels to prevent severe adverse effects of thyroid hormone deficiency on the brain if maternal iodide supply is adequate, although a possible increased transfer of maternal T4 to affected fetuses cannot be excluded. Under normal conditions, sufficient amounts of iodine are provided by the efficient iodine metabolism in euthyroid mothers. In affected mothers, much iodine is wasted because the thyroid also iodinates proteins other than the aberrant TG, resulting in insufficient iodine provision of the fetus and, consequently, in severe hypothyroidis
Caffeine and Other Methylxanthines as Interceptors of Food-Borne Aromatic Mutagens: Inhibition of Trp-P-1 and Trp-P-2 Mutagenic Activity
Complexation of Biologically Active Aromatic Compounds with DNA in the Presence of Theophylline
1H NMR measurements (500Â MHz) have been used to determine the equilibrium hetero-association constants of theophylline (THP) with various biologically active aromatic compounds (daunomycin, novantrone, ethidium bromide, proflavine, norfloxacin) and the complexation constants of THP with both single- and double-stranded oligonucleotides in solution. The results provide a quantitative estimation of the effect of THP on the binding of aromatic ligands with DNA, and a determination of the fraction of aromatic ligand removed from DNA on addition of THP