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D Behne

Publications and source records attributed to D Behne.

At least 37 records · Page 2Linked to original sources
PubMed1995

A new selenoprotein found in the glandular epithelial cells of the rat prostate.

An inverse relationship between the Se status and the incidence of prostate cancer suggests a significant role of Se in this organ. After labeling of rats with 75Se and sodium dodecyl sulfate-polyacrylamide gel electrophoresis a strongly labeled prostatic 15-kDa protein band was found which was equally distributed among the different lobes. It was localized in the epithelial cells of isolated acini but did not appear in the prostatic secretion. By two-dimensional electrophoresis the band was resolved into three spots with pI-values around 4.5. The most strongly labeled spot stemmed from a cytosolic selenoprotein with an apparent native molecular mass of about 300 kDa which contained Se in the form of selenocysteine. The fact that with insufficient Se intake the element is preferentially incorporated into this compound as compared with glutathione peroxidase implies an important function of this newly found prostatic epithelial selenoprotein (PES).

Animals↗
PubMed1994

Application of nuclear analytical methods in the investigation and identification of new selenoproteins.

Nuclear methods have been applied in the investigation of selenium-containing proteins in rat tissues. Selenium was determined in tissues, cells, and cellular compartments by instrumental neutron activation analysis via 77mSe or 75Se. For tracer studies, the selenium compounds were labeled in vivo by administering 75Se with a high specific activity to rats. Quantitative determination of very small amounts of the element in protein fractions was achieved by measurement of the tracer after replenishment of selenium-depleted animals with the labeled element. The application of the nuclear methods in the detection, characterization, and identification of new selenium-containing proteins is shown with the help of some examples.

Animals↗
PubMed1993

Effects of selenium and iodine deficiency on type I, type II and type III iodothyronine deiodinases and circulating thyroid hormones in the rat.

The effects of nutritional selenium (Se) deficiency over a period of three generations and of a combined selenium and iodine deficiency on hepatic and cerebrocortical iodothyronine deiodinases and on circulating thyroid hormone levels were examined in the rat. Se deficiency strongly decreased hepatic type I iodothyronine 5'- and 5-deiodinase to 6-13% of that in controls. Iodine depletion had only a marginal decreasing effect on the type I activity. Cerebrocortical type II 5'-deiodinase was decreased in Se-deficient, iodine-replete rats. Its 5-6-fold elevation in iodine-deficient rats was not reversed by additional selenium deficiency. Cortex type III 5-deiodinase was modestly decreased in all groups with insufficient trace element supply. Long-term Se deficiency has only limited effects on serum T4 and T3 levels. Two months of iodine deficiency decreased serum T4 to less than 10% of that in controls, but did not significantly affect serum T3 levels. The strong decrease of hepatic outer- and inner-ring deiodination of T4 in Se deficiency obviously reflects the reduced tissue concentration of the type I deiodinase which was recently identified as a selenoenzyme. The maintenance of increased cerebrocortical type II deiodinase in iodine-depleted animals irrespective of adequate or deficient selenium supply suggests that the type II isoenzyme does not contain selenium in its catalytic site. Further studies are necessary to clarify whether the weak, but repeatedly confirmed decrease of cortex type III deiodinase is the direct effect of Se deficiency or the indirect consequence of the multilevel change in thyroid hormone metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of dietary selenium on the tissue concentrations of type I iodothyronine 5'-deiodinase and other selenoproteins.

Since selenium was identified as the essential component of the type I iodothyronine 5'-deiodinase, it has become important to determine the selenium dose necessary for the formation of the deiodinase. In this survey the results of studies of the effects of dosage and chemical form of the element on the concentrations of this enzyme and of other selenoproteins are discussed. They show that the selenium requirement for normal deiodinase activity is lower than it is for adequate glutathione peroxidase activity. Elevated tissue selenium concentrations found after intake of higher doses of the element, especially when given in the form of selenomethionine, are due to nonspecific incorporation into other proteins. The tissue concentrations of the selenonenzymes appear to be homeostatically controlled and cannot be further increased by additional selenium supplementation.

Diet↗
PubMed1992

Speciation of trace elements in biological materials: trends and problems.

In the determination of trace elements in biological materials, speciation is of particular importance as the essential effects or toxicity of an element and its metabolic behaviour depend to a large extent on the chemical forms in which it is present in the organism. Speciation is relatively easy if a property of a particular compound can be measured directly in the sample without interference from the other components of the material, e.g., the enzymic activities of the metallo-enzymes. Another possibility for speciation is immunoassay, which likewise allows direct determination of a particular trace element. At present, however, with most trace elements both fractionation methods and analytical procedures have to be combined and speciation has to be carried out by determining the elemental content in the separated fractions. The methods and apparatus used in taking, storing and preparing the samples can, therefore, not be selected solely according to the requirements of trace element determination, but it is also essential to ensure that the biological structures of the components to be separated remain intact. In this work the need for speciation in the investigation of the toxic and essential effects of trace elements is shown with the help of some examples, and the problems that can occur in the various steps of sampling, storage and sample preparation are discussed.

Animals↗
PubMed1992

Type I iodothyronine deiodinase activity after high selenium intake, and relations between selenium and iodine metabolism in rats.

Type I iodothyronine deiodinase (I-D), which catalyzes the production of the thyroid hormone 3,3',5-triiodothyronine from thyroxine, has recently been identified as a selenoenzyme. It is therefore of interest to investigate the relationships between selenium and iodine metabolism. In the livers of Se-deficient rats I-D activity was inhibited; the production of 3,3',5-triiodothyronine and 3,3'-diiodothyronine from added thyroxine was decreased by greater than 95% relative to Se-adequate controls. The hepatic I-D activity was also reduced in rats fed a diet with a low iodine concentration. Unaltered glutathione peroxidase activities in liver and plasma of these rats suggest, however, that with normal Se intake this metabolic pathway of Se is not affected by iodine depletion. When rats were administered 75Se-labeled selenium at levels equal to the amounts ingested from diets with Se concentrations of 0.3 or 2 mg Se/kg, greater Se concentrations were found in the thyroid and liver of the animals receiving the higher dosage. The thyroidal 3,3',5-triiodothyronine and thyroxine concentrations, however, were comparable in rats fed diets with 0.3 mg Se/kg diet as selenite and 2 mg Se/kg as selenite or L-selenomethionine. The measurement of the hepatic I-D and glutathione peroxidase activities in these animals showed that excessive Se supply does not elevate the activities of the two enzymes but might even have the opposite effect. At high Se intake tissue Se concentration cannot therefore be used as indicator of the selenoenzyme activities.

Administration, Oral↗
PubMed1992

Effects of selenium and iodine deficiency on iodothyronine deiodinases in brain, thyroid and peripheral tissue.

Long term nutritional selenium (Se) deficiency had only marginal effects on the thyroid T4 and T3 content and on the activity of the selenoenzyme type I deiodinase (5'D-I) in the thyroid gland. These findings reveal a remarkable resistance of the thyroid to Se-deficiency which may substantially contribute to the observed maintenance of T4 and T3 levels in circulating blood. In contrast to its maintained thyroidal activity, 5'D-I in peripheral tissues like liver and kidney was strongly decreased by Se-deficiency. The observed decrease of type II deiodinase (5'D-II) in the cerebral cortex of Se-deficient rats was obviously caused by the suppressing regulatory effect of elevated cortex T4 concentrations. The severalfold 5'D-II enhancement in iodine depleted animals was not abolished by additional Se-deficiency, suggesting that brain type II deiodinase is not a selenoenzyme. The role of selenium for cortex type III 5-deiodinase, which was moderately decreased in selenium as well as iodine-deficient rats, awaits definite evaluation by further studies. The different responsiveness to thyroidal and hepatic 5'D-I to Se restriction is further evidence for priorities in the selenium supply to different tissues.

Animals↗
PubMed1992

Sex-related effects of zinc deficiency on the selenium metabolism in rats.

The effects of a low zinc status on selenium metabolism were investigated in female and male rats which were fed diets with low and adequate zinc contents and a suboptimal selenium content. For the selenium content and glutathione peroxidase activity in the liver and plasma of the female animals no differences were found between the low zinc group and the pair-fed zinc-adequate control group. In the male rats zinc depletion resulted in testis atrophy and decreased testicular contents of selenium and glutathione peroxidase. In the pair-fed and ad libitum-fed control groups the levels of hepatic selenium and glutathione peroxidase and plasma glutathione peroxidase in the males were lower than those in the females. In the low zinc group, however, they rose to the levels of the females. The results indicate that these effects of zinc deficiency on selenium metabolism are sex-specific and suggest that they are related to changes in the sex hormone status of the male animals.

Animals↗
PubMed1991

Effects of chemical form and dosage on the incorporation of selenium into tissue proteins in rats.

We investigated the incorporation of Se into the proteins of liver and muscle, the two main Se pools, during replenishment of Se-deficient rats with normal or large doses of 75Se-labeled selenite and selenomethionine, doses equivalent to the amounts ingested from a diet with 0.2 or 2 mg Se/kg. With the higher intake, Se levels were elevated. More Se was retained from selenomethionine than from selenite. After separation of the labeled proteins, it was apparent that the higher tissue Se contents were mainly due to nonspecific incorporation into a large number of proteins. We observed no differences between the two chemical forms with regard to the formation of the specific selenoproteins. The 10-fold increase in the Se supply led to a relatively small rise in the levels of these compounds. The results indicate that after ingestion of normal amounts of selenite nearly all of the element is present in the specific selenoproteins. With increasing doses a part is also incorporated nonspecifically into numerous other proteins. In the case of selenomethionine, a part of the element follows the same metabolic pathways, but a percentage is also deposited directly and nonspecifically into proteins in place of methionine.

Animals↗
PubMed1990

Identification of type I iodothyronine 5'-deiodinase as a selenoenzyme.

A 27.8 kDa membrane selenoprotein was previously identified in rat thyroid, liver and kidney, the tissues with the highest activities of type I iodothyronine 5'-deiodinase. This membrane enzyme catalyzes the deiodination of L-thyroxine to the biologically active thyroid hormone 3,3',5-triiodothyronine. A decrease in the activity of this enzyme, observed here in the liver of selenium-deficient rats, was found to be due to the absence of a selenium-dependent membrane-bound component. By chemical and enzymatic fragmentation of the 75Se-labeled selenoprotein and of the 27 kDa substrate binding type I 5'-deiodinase subunit, affinity-labeled with N-bromoacetyl-[125I]L-thyroxine, and comparison of the tracer distribution in the peptide fragments the identity of the two proteins was shown. The data indicate that the deiodinase subunit contains one selenium atom per molecule and suggest that a highly reactive selenocysteine is the residue essential for the catalysis of 5'-deiodination. From the results it can be concluded that type I iodothyronine 5'-deiodinase is a selenoenzyme.

Animals↗
PubMed1990

Subcellular distribution of selenoproteins in the liver of the rat.

After in vivo labeling with [75Se]selenite, the intracellular distribution of selenoproteins in the liver was investigated in selenium-adequate and selenium-deficient rats. In the subcellular fractions, which were obtained by differential centrifugation, the proteins were separated by means of SDS-PAGE and the selenium compounds were identified via their 75Se activity. In this way twelve selenium-containing proteins or protein subunits with molecular weights between 12,100 and 75,400 were found. Glutathione peroxidase was concentrated in the cytosol and in the mitochondria. With the newly detected selenoproteins, some were enriched in the cytosol, one was mainly found in the nuclear fraction and some, which were present mainly in the mitochondrial and microsomal fractions, are most probably membrane-bound. In the liver of selenium-depleted rats the selenium administered was used predominantly to restore the levels of some of the newly found selenoproteins, while in the liver of selenium-adequate animals most of the selenium retained was incorporated into the glutathione peroxidase. The differences in the distribution among the subcellular fractions and the specific incorporation of the element in selenium deficiency into certain compounds suggest that there are several metabolic pathways for selenium and that the selenoproteins are involved in several different processes of intracellular metabolism.

Animals↗
PubMed1989

The influence of renal insufficiency on caesium metabolism in man and rat (with a note on the Cs content of some biological standard materials).

Caesium was measured by instrumental neutron activation analysis in blood plasma and erythrocytes of persons suffering from renal disorders and in age-and sex-matched controls. The disease was at an early stage of development, the patients having creatinine plasma values below 1000 mumol/l. None of them had been dialysed. In a group of 5 patients with plasma creatinine below 250 mumol/l no changes in the blood caesium contents could be observed, but in a group of 17 with plasma creatinine between 250 and 1000 mumol/l the caesium level in the plasma was increased by 70% and in the erythrocytes by 50%, compared to the controls. An effect of renal insufficiency on the caesium metabolism was also observed in rats, in which 5/6-nephrectomy led to increases in the caesium tissue levels (muscle 30%; spleen 25%; pancreas 100%). However, as in the animals the element content in blood plasma and erythrocytes remained unchanged, it is not clear to what extent the nephrectomized rat can be used as a model in the investigation of relations between chronic uraemia and caesium metabolism. It can therefore not yet be decided whether the changes in the blood caesium levels in the patients are due to a decrease in renal excretion or are only a secondary effect of unnoticed changes in dietary habits. The increase in caesium levels suggests, however, that in the first stages of the disease the patients may receive higher radiation doses from the radioisotopes of caesium than the normal population does in the case of environmental or industrial exposure.

Animals↗
PubMed1988

Evidence for specific selenium target tissues and new biologically important selenoproteins.

After in-vivo labeling with [75Se]selenite the Se-containing proteins present in rat tissues were investigated by means of SDS-polyacrylamide gel electrophoresis. Thirteen Se-containing proteins or protein subunits with relative molecular weights of 12,100, 15,600, 18,000, 19,700, 22,200, 23,700, 27,800, 33,300, 55,500, 59,900, 64,900, 70,100 and 75,400 were detected in the tissue homogenates. The protein with the molecular weight of 23,700 was the subunit of glutathione peroxidase, which is the only selenoprotein so far known to have biological functions in animals. Most of these proteins were found in all tissues investigated but one was only detected in the testes and the spermatozoa and one was present mainly in the thyroid. With inadequate selenium intake there was a priority supply of the element to the brain, the reproductive and the endocrine organs, and at a molecular level to Se-containing proteins other than glutathione peroxidase. The results suggest important biological functions of these selenoproteins, especially in the specific target tissues.

Animals↗
PubMed1988

Selenium, rubidium and zinc in human semen and semen fractions.

The levels of selenium, rubidium and zinc were determined in samples of semen, seminal plasma and spermatozoa from men with suspected infertility, together with several parameters of semen quality. The proportion of whole semen selenium present in sperm increased with increasing sperm count from 0 to 40%. For rubidium 98 +/- 4% and for zinc 95 +/- 8% of the total amount in semen was contained in seminal plasma. In seminal plasma a positive correlation was found between the levels of zinc and selenium, and between the levels of zinc and rubidium, indicating that, like zinc, selenium and rubidium in seminal plasma also derive mainly from the prostate gland. Semen quality parameters, such as sperm motility, vitality, speed and morphology, were not correlated with the contents of the three elements in either whole semen or seminal plasma. As the seminal content of selenium is dependent on the proportion of prostatic secretion in seminal plasma and on the sperm count, and both factors can vary considerably, the selenium level of whole semen does not appear to be a suitable parameter for investigation of the relationship between selenium and semen quality. Provisional measurements suggest lower sperm selenium levels at abnormally low or high sperm counts.

Humans↗
PubMed1986

Selenium content and glutathione peroxidase activity in the testis of the maturing rat.

In rats fed a diet with 0.25 mg Se/kg the testis selenium content rose during maturation. The value in 4-mo-old animals (7.0 mg Se/kg dry mass; 0.9 mg Se/kg wet mass) was six times higher than that in 20-d-old weanling rats. By comparison, the selenium content in the main selenium pools, muscle and liver, remained unchanged and rose by half, respectively. Due to the increased selenium requirement of the testis during its pubertal maturation the amount of selenium taken up by the male gonads was 50% of the amount deposited in muscle and liver, whereas before and after that period it was about 10%. Feeding animals a low vitamin E diet had no effect on the rise in testis selenium. Glutathione peroxidase activity was twice as high in 4-mo-old animals as in weanling rats. Because only a small percentage of the element in the male gonads was bound to the enzyme, the rise in testis selenium must have been due to other selenium compounds. The selenium content of the spermatozoa was about 21 mg Se/kg dry mass, which by far exceeded the level of this element in other compartments of the rat. The increase in testis selenium content coincided with the beginning of spermatogenesis, and it may therefore ensure the supply of adequate amounts of the element for the spermatozoa.

Animals↗