Physiological and nutritional importance of selenium

Summary The essential trace element selenium has recently attracted attention because of its potentialities in the maintenance of human health. Selenium forms part of the active site of the peroxide-destroying enzyme glutathione peroxidase, and it also has other functions, for example in biotransformation, detoxification and the immune response. Functional and clinical consequences of selenium deficiency states have been described, and the selenium requirement, which is influenced by the usual selenium exposure, has been discussed. Wide variations have been found in selenium status in different parts of the world, and populations or groups of patients exposed to marginal deficiency are more numerous than was previously thought.Current research activities in the field of human medicine and nutrition are devoted to the possibilities of using selenium for the prevention or treatment of degenerative or free radical diseases such as neurological disorders, inflammatory diseases or cancer. Pharmacological selenium doses are also recommended as an adjuvant in some treatments.     

Understanding the importance of selenium and selenoproteins in muscle function

Selenium is an essential trace element. In cattle, selenium deficiency causes dysfunction of various organs, including skeletal and cardiac muscles. In humans as well, lack of selenium is associated with many disorders, but despite accumulation of clinical reports, muscle diseases are not generally considered on the list. The goal of this review is to establish the connection between clinical observations and the most recent advances obtained in selenium biology. Recent results about a possible role of selenium-containing proteins in muscle formation and repair have been collected. Selenoprotein N is the first selenoprotein linked to genetic disorders consisting of different forms of congenital muscular dystrophies. Understanding the muscle disorders associated with selenium deficiency or selenoprotein N dysfunction is an essential step in defining the causes of the disease and obtaining a better comprehension of the mechanisms involved in muscle formation and maintenance. Received 13 July 2005; received after revision 9 September 2005; accepted 4 October 2005     

Ursachen der geschlechtsunterschiedlichen MilchdrÜsengewebsentwickiung bei Ratten

Summary Under the same hormonal conditions, mammary gland growth in adult female rats is more pronounced than in males. Since there are no differences in the glandular development of both sexes, either at birth or at 30 days of life, it is assumed that male rats react less sensitively than female rats in response to a hormonal stimulus with regard to mammary gland growth. It is presumed that androgen influence during the differentiation stage is responsible for the fixation of a decreased sensitivity of the positive feedback-mechanism between estrogens and prolactin secretion in males. Thus changes in sensitivity would be the reason for mammary gland growth in males being smaller than in females under the same hormonal conditions.

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Dieser Arbeit liegen zum Teil die Untersuchungsergebnisse einer SchÜler-Facharbeit von U.Rieser zugrunde.     

Effect of progesterone on male and female sex behavior induced by steroid hormones in adult ovariectomized ewes]

Ovariectomized adult Ewes daily treated with I/M injections of testosterone propionate (10 mg/day) or oestradiol benzoate (200 microgram/day) show male-like sexual behaviour and simultaneously a permanent female receptivity. Additional daily treatment with 100 mg of progresterone results in a rapid decrease in male sexual responses both when Ewes are treated with testosterone and with oestradiol. No effect is observed on the female receptivity. Cyproterone acetate (100 mg/day) given to Ewes in addition to daily injection of testosterone propionate (10 mg/day) has effects similar to those of progesterone. These results show that progesterone has antiandrogen and antioestrogen properties and that this hormone administered at high doses is able to inhibit male activity.     

Effect of testosterone on the kinetics of the development of suppressor cells in adjuvant arthritis

Summary The induction of unresponsiveness to mycobacterial adjuvant took a longer time in male DA rats than in female rats. A shift in the induction time of unresponsiveness in males toward the female type was brought about by castration, but could be reverted to the male type by the application of testosterone. The transfer study revealed that cells capable of preventing arthritis required a longer incubation time for their development in males than in females. This suggests that testosterone inhibits the development of suppressor cells in adjuvant arthritis.Acknowledgments. We are grateful to The Naito Foundation Research Grant for 1983.     

Radioimmunoassay of plasma progesterone, testosterone, total estrogen and immunoreactive gonadotropin in the nesting and non-nesting green sea turtle, Chelonia mydas (L.).

Plasma progesterone, testosterone, total estrogens and immunoreactive gonadotropin were measured in nesting and non-nesting sea turtles, Chelonia mydas. Progesterone and gonadotropin concentrations were significantly higher in nesting than in non-nesting turtles, testosterone was not significantly different in either group and total estrogens appeared to be slightly in the nesting group.     

Induction of vitellogenin by estradiol and androgens in a teleostean fish: Gobius niger L]

At any point in the sexual cycle of both males and females, oestradiol benzoate induces synthesis of plasmatic vitellogenin, identifiable by a specific immunserum. Pharmacological doses of purified testosterone and dihydrotestosterone also induce synthesis of this yolk precursor. Although a partial aromatisation of testosterone into oestrogen is possible, our results show that there must also be interaction between the androgens and the oestrogens receptors in the liver.     

Effect of testosterone on the kinetics of the development of suppressor cells in adjuvant arthritis

The induction of unresponsiveness to mycobacterial adjuvant took a longer time in male DA rats than in female rats. A shift in the induction time of unresponsiveness in males toward the female type was brought about by castration, but could be reverted to the male type by the application of testosterone. The transfer study revealed that cells capable of preventing arthritis required a longer incubation time for their development in males than in females. This suggests that testosterone inhibits the development of suppressor cells in adjuvant arthritis.     

Radioimmunoassay of plasma progesterone,testosterone, total estrogens and immunoreactive gonadotropin in the nesting and non-nesting green sea turtle,Chelonia mydas (L.)

Summary Plasma progesterone, testosterone, total estrogens and immunoreactive gonadotropin were measured in nesting and non-nesting sea turtles,Chelonia mydas. Progesterone and gonadotropin concentrations were significantly higher in nesting than in non-nesting turtles, testosterone was not significantly different in either group and total estrogens appeared to be slightly higher in the nesting group.     

Introduction: the selenium conundrum

Selenium was first suspected of being an essential dietary trace element in the 1950s. We now know that indeed it is an essential biological element that serves as an integral component of several enzymes, including those in the families of deiodinases and glutathione peroxidases as well as selenoproteins P and W. The multi-author review that follows this introduction concentrates on the important biological role of selenium in enzymes as well as some of the physiological aspects of selenium as either a potential anticarcinogenic agent or insulin mimetic. What should become clear from these contributed articles is the complex and dynamic role that selenium plays in many biological processes and that the investigations in these areas are at the edge of exciting new frontiers.     

Pituitary-testicular relationships in the rat embryo]

LH given to the Rat embryo at the time of hypophysectomy by decapitation (18 days of intrauterine life) will prevent the drop in androgen synthesis which normally ensues. This is regarded as definite proof that androgen synthesis is under pituitary control in the rat embryo at late gestational stages. On the other hand, the decrease in androgen synthesis following testosterone injection to the pregnant female points to the fact that there is a negative feedback of testosterone on pituitary LH secretion.     

Suppression of annual plasma testosterone and thyroxine cycles in the edible dormouseGlis glis under constant photoperiod at 24°C

Summary Exposure of male ebible dormice all year round to an unwarying photoperiod and warm temperature disrupted their biological cycles; hibernation was almost completely suppressed, and short lived infradian cycles of body weight, and of plasma testosterone and thyroxine were measured instead of the normal annual patten.     

The effect of castration, testosterone and estradiol on 14C-serotonin metabolism by organ cultures of male rat pineal glands

The pineal gland of the male rat does not appear to rely on prior conversion of testosterone to estradiol for the stimulant effect of testosterone on pineal melatonin and 5-methoxytryptophol synthesis.     

Sex difference in polyethylenglycol-induced thirst

Summary The polyethylenglycol-induced thirst in male and female castrated rats has been studied. The polyethylenglycol (PG) increases the water intake more in females than in males. Estradiol benzoate and testosterone P. diminishes the amount of water drunk after PG treatment in the females, but not in the males.     

Maturation of the female Tetrix undulata (Swrb) (Orthoptera, Tetrigidae): influence of the male and copulation:parthenogenetic egg-laying]

The percentage of laying females and laying time, are compared between mature females (diapause break by chilling) and diapause strain females (diapause not broken by chilling) reared with mature male or diapause male or without male. For the same physiological state of the females (mature or diapause) there is no difference in the percentage of females laying, when they are reared with mature male or with diapause one or none; but the laying time is shortest with mature male, longer with male in diapause, even longer without male. Parthenogenetic egg-pods can be obtain. Rearing with mature males does not break the reproductive diapause of females. In parthenogenetic egg-pods the number of eggs is short for low diapause females; greater for mature ones and greatest for females with strong diapause broken by a corpus allatum implant of mature female of Locusta migratoria. Corpus allatum of the low diapause strain of females of Tetrix undulata have less activity than that of mature females. Few parthenogenetic eggs develop, even less hatch. In Tetrix undulata parthenogenesis is accidental.     

Splenic thymidine kinase and DNA during early postnatal development of the androgenized female rat

Administration of a pharmacologic dose of testosterone propionate to neonatal female rats had no effect on either thymidine kinase activity or DNA synthesis in the spleen during the first 3 postnatal weeks.     

Hormonal regulation of a new female-specific serum protein (FP) of the laboratory rat

Summary This paper reports evidence for a hormonal regulation of a new rat serum protein (female specific protein, FP) which is only demonstrable in female rats. Male and female rats were treated with testosterone and estrogen. The FP was assayed with immunological methods. The following results were obtained: 1. In testosterone-treated females the serum level of FP is reduced significantly. 2. In estrogenized males the FP was distinctly demonstrable but not in the control males.     

Effects of castration, estradiol and testosterone on tubulin levels of the medial basal hypothalamus and the adenohypophysis of the rat.

Tubulin levels of the medial basal hypothalamus (MBH) were greater in male than in female rats. Orchidectomy brought about a decrease of MBH tubulin concentration, whereas testosterone injection augmented it in the MBH and adenohypophysis. Estradiol administration augmented MBH tubulin and protein concentration.