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M Vobecký

Publications and source records attributed to M Vobecký.

10 recordsLinked to original sources
PubMed1998

Long-term action of potassium bromide on the rat thyroid gland.

Male rats fed by a standard diet with determined of bromine and iodine content were exposed to a 133-day oral administration of KBr (100, 200, 400 mg Br-/l drinking water). Their thyroid glands showed increased growth of the epithelial cells reflected by a microfollicular rearrangement of the parenchyma due to proliferation of very small follicles with a low or zero content of colloid. Morphometric analysis of thyroids of Br(-)-exposed animals revealed a significant decrease in the volume of intrafollicular colloid and marked increase in the number of the smallest follicles (areas up to 100 and 100-300 micron 2). In addition, the nuclei of thyrocytes showed an increased number of mitoses. The vascularization was increased as well. In the blood plasma of the Br(-)-exposed animals the T4 concentration was significantly decreased in dependence on the bromine concentrations. Thyroglobulin immunoreactivity in the colloid of Br(-)-exposed animals decreased after administration of 400 mg Br-/l drinking water. Increasing concentrations of Br- in the drinking water caused an increased bromine concentration in the thyroid, a decreased iodine content and a decreased I/Br molar ratio. The changes in the rat thyroid caused by long-term administration of 100 mg Br-/l were similar to hyperplastic parenchymal goitre and were comparable to those induced in previous experiments by the same bromine concentration administered over a 16- and 66-day period respectively.

Administration, Oral↗
PubMed1997

Expression of the proliferating cell nuclear antigen (PCNA) in the rat thyroid gland after exposure to bromide.

Analysis of expression of the proliferating cell nuclear antigen (PCNA) was used to determine the presumed hyperplastic character of morphological changes in the rat thyroid evoked by bromide administration. Male rats fed by a standard diet with determined iodine and bromine content were given potassium bromide. Control animals received no bromide. Experimental animals were given 10, 50 or 100 mg Br- per 11 drinking water for 16 and 66 days, or 100, 200, 400 mg Br-/l drinking water for 133 days. The thyroids of treated animals showed activation of growth of the epithelial follicular component as well as diffuse and focal microfollicular rearrangement of the parenchyma with higher follicular cells accompanied by a decrease of the amount of colloid even at low bromine concentrations (10-100 mg Br-/l drinking water). Using the PCNA-LI index (PCNA-positive nuclei.100/total number of follicular cell nuclei in the section), immunohistochemical analysis of PCNA in the nuclei of the follicular cells was carried out in parrafin sections. The index was significantly higher in bromide exposed animals (P < 0.01) and correlated well with the histological changes, with bromide concentration and with a increased mitotic activity of the follicular cells. PCNA analysis showed that morphological changes resembling a parenchymatic goitre reflect a microfollicular rearrangement of the thyroid of rats exposed to bromide and have the character of hyperplasia owing to the increased mitotic activity of the follicular epithelium.

Animals↗
PubMed1997

Potassium bromide and the thyroid gland of the rat: morphology and immunohistochemistry, RIA and INAA analysis.

The increasing environmental concentration of bromine has resulted in attempts to obtain information on its possibly deleterious effect on humans, particularly on a major target organ of this halogen i.e. the thyroid gland. In order to establish the morphological and functional effects of bromine on the thyroid, we have performed experiments on male rats which, in addition to a standard diet with an estimated iodine/bromine content, were fed for periods of 16 and 66 days with the small quantities of bromide expected to be encountered in the environment (10, 50 and 100 mg of Br-/l in drinking water). This treatment induced growth of the follicular epithelial component and microfollicular tissue rearrangement, a reduction of intrafollicular colloid, an increase in the height of the follicular cells and the number of mitoses, and it enhanced vascularization. Image analysis revealed a significant reduction in the volume of colloid, despite the accompanying rise in the number of minute follicles. The immunohistochemical positivity of the thyroglobulin fell in the microfollicular colloid of the exposed animals, although this was affected to a lesser extent in the larger follicles. The concentration of bromine in the thyroid increased with the amount of bromine intake, while at the same time the molar ratio of iodine/bromine decreased. The plasma level of T4 was lowered after both 16 and 66 days of treatment, but the T3 level only after 66 days treatment. The level of TSH did not exhibit any significant change. The observed changes, which have a parenchymatous goitre-like character, may have a direct relevance for human medicine, since the concentrations of bromide chosen in these experiments are readily encountered in the environment.

Animals↗
PubMed1997

Biological half-life of bromine in the rat thyroid.

The biological half-life of bromine in the rat thyroid was determined by measuring the radioactivity of thyroids of animals which continuously received 82Br labelled bromide in their food. The value of this half-life (110 h) is practically the same as the biological half-life of iodine. The rate of establishing the I/Br concentration ratio in the thyroid depends on the biological half-life of bromine. The mechanism of this process depends on the state of iodine supply. When the supply is sufficient, the iodine concentration in the thyroid remains constant, while during iodine deficiency the iodine atoms are replaced by atoms of bromine.

Animals↗
PubMed1996

Interaction of bromine with iodine in the rat thyroid gland at enhanced bromide intake.

In experiments with rats, we have found that at enhanced intake of bromide, bromine does not replace chlorine in the thyroid; it replaces iodine. Under our experimental conditions, more than one-third of the iodine content in the thyroid was replaced by bromine. In the thyroid, bromine probably remained in the form of bromide and, in proportional to its increased concentration, the production of iodinated thyronines decreased, with the sum of the iodine and bromine concentrations being constant at the value of 20.51 +/- 1.16 mumol/g dry wt of the thyroid. In contrast to other organs, the biological behavior of bromine in the thyroid is not similar to the biological behavior of chlorine but resembles more that of iodine.

Animals↗
PubMed1996

Effect of increased bromide intake on iodine excretion in rats.

The time course of iodine excretion in adult male rats substantially differs from bromine excretion. Bromine is excreted at a single rate, whereas iodine evinces two excretion rates. Even a strong increase in bromide intake in experimental animals failed to affect the rate of iodine excretion but it lowered the fraction of iodine accumulated in the thyroid gland by 20% probably by affecting the transport of iodide into the thyroid gland.

Animals↗
PubMed1995

Marcus Marci.

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Czechoslovakia↗
PubMed1994

Effect of enhanced bromide intake on the concentration ratio I/Br in the rat thyroid gland.

Interaction of bromine with iodine was studied in the rat thyroid gland under the conditions of different bromide intake. Bromine and iodine in the thyroid dry weight were determined by instrumental neutron activation analysis (INAA). It was found that with increased bromide intake the bromine concentration in the thyroid gland increased with simultaneous decrease in the iodine concentration. The change in the I/Br concentration ratio depends on a number of halogen binding positions and on the bromide supply. The I/Br parameter reacts sensitively to the changes of bromide intake already in the region of low bromine concentration levels.

Animals↗
PubMed1984

Effects of the withdrawal of solid food on maternal milk intake and the development of young rats.

Young rats deprived of solid food will survive on mother's milk only for about seven weeks but their development will become arrested completely. As soon as they receive solid food their development recommences immediately at the same rate as that of control infant rats. However, young rats still continue to take maternal milk for about one more week, which is the result of the gradual extinction of the sucking reflex depending the maturity of the young rats.

Animal Population Groups↗