The lower British Columbia mainland waterways are inhabited by two races of the prickly sculpin Cottus asper Richardson. One race lives in the lower part of rivers or in estuaries and spends at least part of its life, particularly during the spawning season, under tidal influence. This race is the "coastal". The other race, called "inland", is confined entirely to fresh water where it is found in scattered, more or less isolated populations. By investigating the effects of ambient salinity on the oxygen consumption and on the utilization of injected radioiodine, it was found that salinity profoundly effects the iodine metabolism and, to a lesser degree, standard metabolic rates of the fish. In fresh water the thyroids of both races appear relatively quiescent but with increasing salinity, particularly in hyperosmotic environment, there is a marked increase in thyroid uptake of tracer iodine and also in the levels of circulating thyroid hormone. The inland fish demonstrate a greater ability than coastal fish to retain iodide in fresh water, and in sea water their thyroids appear more active. The inland fish also have a lower oxygen consumption in fresh water than do coastal fish. Viewed together, the results lead to the conclusion that the inland fish, with respect to their osmoregulating ability, show genetic divergence from the coastal forms. The latter probably more closely resemble the ancestral form. / Science, Faculty of / Zoology, Department of / Graduate

Since 1990, many countries world-wide implemented salt iodisation programs in an effort to<p>tackle iodine deficiency. It was however only during the last few years that an effort was<p>undertaken in order to eliminate iodine deficiency as a public health problem in Belgium. In autumn 1998, a nation-wide study among children clearly showed mild iodine deficiency in<p>Belgium, but no action was taken before 2009. It was only in the framework of the first<p>National Nutrition and Health Plan 2005-2010 that iodine deficiency was formally recognized<p>as a public health problem. An agreement between the Ministry of Health and the bakery<p>sector in April 2009 aimed to encourage and increase the use of iodised salt in the<p>production of bread. A selective and progressive approach was used in order to keep control<p>and to avoid a too rapid increase of iodine intake or an excessive iodine intake among the<p>population. It was calculated that the net yearly savings after installation of such a program<p>amount to at least 14 million Euros a year.<p>A recent national survey among school-aged children in autumn 2010 showed a clear and<p>significant improvement in iodine status compared to more than 10 years ago, suggesting<p>iodine sufficiency among school-aged children. The median urinary iodine concentration was<p>however at the lower end of the optimal range and seasonal effects were not taken into<p>account. The improvement was at least partly linked to the increasing use of iodised salt in<p>the bakery industry. However, some further silent iodine prophylaxis might also have<p>occurred, due to changing dietary habits (milk and fish consumption). Pregnant women and<p>women of child-bearing age in Belgium were found to still suffer from mild iodine deficiency<p>according to the current recommendations. This is at least partly linked to their lower<p>consumption of milk and dairy drinks compared to children and due to the higher iodine<p>requirements during pregnancy. Although the use of iodine-containing supplements among<p>pregnant women was found to be quite high in Belgium compared to other European<p>countries, because of the low iodine status among women of child-bearing age, women<p>became pregnant with a suboptimal iodine status.<p>In view of these findings, a further increase in the use of iodised instead of non-iodised<p>household salt and iodised salt by the bakers is recommended. In addition, one should put<p>efforts in increasing awareness among the public and among health professionals with<p>regard to iodine-rich food sources and with regard to the use of iodine-containing<p>supplements starting before conception and continuing during lactation.<p>In order to further improve iodine status in Belgium and sustain an optimal iodine status<p>over time, a legal framework is necessary. Mandatory fortification of all household salt and<p>bread is recommended, while non-iodised alternatives could still be offered upon specific<p>request. A rigorous monitoring program is indispensable, including vulnerable groups such as<p>pregnant and lactating women and infants. In addition, sustainability is a key issue as iodine<p>deficiency re-emerged in several industrial countries due to lack of interest, regulations and<p>monitoring. Political willing, salt reduction measures, changes in dietary habits among the<p>population and changes in industrial practices all may affect iodine status in Belgium in the<p>future. Therefore the strategy of controlling iodine deficiency needs to be directed and<p>monitored by a Belgian Scientific Committee for the Control of iodine deficiency disorders. / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished