Androgen metabolism in somatic and germinal tissues of the sea star Asterias vulgaris.

1. Cell-free homogenates of male and female pyloric caeca, body wall, testis and ovary were incubated with radiolabeled 3H-androstenedione. 2. Pyloric caeca had highest rates of androstenedione conversion. The predominant metabolites in the pyloric caeca were testosterone, 5 alpha-androstane-3 beta, 17 beta-diol and 5 beta-androstane-3 beta, 17 beta-diol. 3. In body wall, testicular and ovarian homogenates, androstenedione was converted primarily to testosterone and also to 5 alpha-androstanedione and epiandrosterone. 4. Qualitative and quantitative differences in androgen metabolism in somatic and germinal tissues may be related to tissue-specific regulation of cellular metabolism.

Effects of cadmium on metal composition and adenylate energy charge in the sea star Asterias rubens L.

Sea stars, Asterias rubens, were exposed to 200 micrograms Cd/L or fed with mussels which contained about 70 micrograms Cd/g dry wt. After 5 weeks, cadmium in the pyloric caeca of directly and indirectly exposed sea stars had reached levels of 12 and 9 micrograms Cd/g dry wt, respectively. For both types of exposure, a reduction of 30% of the zinc levels in the pyloric caeca was found, which was correlated with a comparable displacement of zinc from the metallothionein-like proteins. Copper levels were increased in the pyloric caeca of directly exposed sea stars. In gonads, stomachs, and body wall of directly exposed sea stars, cadmium concentrations were 4 to 9 times higher than those in animals fed with Cd-contaminated mussels. Cadmium exposure also affected metal composition in these tissues. The ovaries contained relatively large amounts of zinc. Gel filtration chromatography revealed that this zinc and the accumulated cadmium were distributed over a large range of high-molecular-weight proteins. Both direct and indirect cadmium exposure resulted in a small, but significant decrease of the adenylate energy charge (AEC) in the pyloric caeca. In the gonads, no effect of the cadmium exposure could be demonstrated on the AEC, but in the ovaries a reduction of the adenylate pool was found. In semi-field experiments, stars were exposed to 25 micrograms Cd/L or fed with mussels collected from the heavily polluted Dutch Western Scheldt. After 6 months of direct or indirect exposure, cadmium in the pyloric caeca had reached comparable levels of 8 and 7 micrograms/g dry wt, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cadmium and PCBs on reproduction of the sea star Asterias rubens: aberrations in the early development.

In semifield experiments sea stars, Asterias rubens, were exposed to 25 micrograms Cd/liter or fed with mussels containing 0.6 microgram/g wet wt PCBs (Clophen A50). After 5 months of exposure, Cd concentrations in testes and ovaries were respectively 17 and 50 times higher than those in unexposed sea stars. PCB concentrations were respectively 7 and 9 times higher. With spermatozoa obtained from Cd- or PCB-exposed sea stars, normal fertilization could be achieved. However, maturation of oocytes from Cd-exposed animals was delayed and early development of embryos from Cd- or PCB-exposed animals was disturbed. Due to aberrations during the early development only 24 and 30% of the embryos obtained from Cd- or PCB-exposed sea stars, respectively, had developed to normal bipinnaria larvae after 1 week.

Toxicity of heavy metals to early life stages of Daphnia magna.

This study was designed to investigate the susceptibility of the parthenogenetic eggs of Daphnia magna to cadmium, zinc, copper, and lead. Early life stages of D. magna proved to be highly tolerant to heavy metal toxicity in comparison with later stages. This relatively high tolerance might be explained by the structural constitution of the eggs.

Effects of cadmium on consumption, assimilation and biochemical parameters of Daphnia magna: possible implications for reproduction.

1. The effects of cadmium on consumption, assimilation rates and biochemical parameters of Daphnia magna were determined. 2. The consumption and assimilation rates of 14 days 1.0 ppb Cd treated animals tended to decrease slightly, the decline of these rates at 5.0 ppb Cd (14 days), however, was highly significant (P less than 0.001). 3. The assimilation efficiencies of daphnids exposed to cadmium did not significantly differ from control. 4. No notable changes in the biochemical composition of daphnids could be noticed after 7, 14 and 21 days of cadmium exposure. 5. It seems as if not one metabolic process in particular was depressed due to cadmium, but metabolic activities seemed to be inhibited on the whole. 6. Results are discussed in relation with data of a previous study on the reproduction of D. magna under cadmium stress.

Effects of cadmium and zinc on steroid metabolism and steroid level in the sea star Asterias rubens L.

Steroid metabolism was studied in gonads and pyloric caeca of male and female sea stars which had been exposed to cadmium or zinc for 3 weeks. Steroid metabolism had increased in animals exposed to heavy metals. Significant increase of the enzyme activity was observed for 17 alpha-hydroxylase in the pyloric caeca of female animals exposed to zinc (pregnenolone----17 alpha-hydroxypregnenolone) or cadmium (progesterone----17 alpha-hydroxyprogesterone), for 17 beta-hydroxysteroiddehydrogenase in the gonads of female animals (dehydroepiandrosterone----androstenediol) and in pyloric caeca of male animals (androstenedione----testosterone) after exposure to cadmium, and for 5 alpha-reductase (progesterone----5 alpha-pregnane-3,20-dione) in ovaries of cadmium exposed sea star. There is some evidence that pregnenolone metabolism in male and female animals is affected by zinc in a different way. The effect of cadmium on the esterification of androstenedione differed highly significantly among male and female animals. It was concluded that the main way of entrance of cadmium into sea stars is via the surrounding medium and not via the food consumed. Testosterone and progesterone levels in, respectively, gonads of female and pyloric caeca of male sea stars which had been exposed to cadmium were significantly higher than the corresponding values in control animals. The effect of zinc exposure on testosterone level in pyloric caeca is significantly different for both sexes. Cadmium interacts directly with the esterification of testosterone, strongly stimulating this process. Cadmium stimulates the production of testosterone by action at the level of the biosynthesis of 17 beta-hydroxysteroiddehydrogenase.

An ultrastructural study of relationships between the ovarian haemal system, follicle cells, and primary oocytes in the sea star, Asterias rubens. Implications for oocyte nutrition.

The genital haemal sinus, present throughout the gonad wall of sea stars, is supposed to be the site of ultimate accumulation of nutrients for the germinal epithelium. Early vitellogenic pear-shaped oocytes are attached to this sinus by stalk-like processes. The ultrastructure of this association and of the oocyte-follicle cell complex is described with emphasis on mechanisms involved in oocyte nutrition. The genital haemal sinus, and sometimes portions of the surrounding genital coelomic sinus, contain a fine granular ground substance and amoeboid cells. Material similar to the haemal ground substance also fills vacuities in the inner basal laminae of the haemal sinus and intervenes between this layer and adjacent germinal and follicle cells in the ovarian lumen. Vitellogenesis is first detectable as numerous vacuoles accumulate within the oocyte-stalk near the haemal sinus; they contain flocculent material and often fuse with adjacent lysosome-like vacuoles. As vitellogenesis proceeds, oocytes develop complex and tenuous connections with the haemal sinus. These consist of a network of pseudopodia that interdigitate with thin sheet-like extensions of follicle cells. These cells are attached to the oolemma by microfilamentous processes and contain regularly arranged concentrations of glycogen granules and well developed rough endoplasmic reticulum. It is concluded, that follicle cells provide each oocyte with a compartmentalized microenvironment within the ovarian lumen, that such compartments are intimately associated with the nutrient laden haemal sinus, and that nutritive and vitellogenic substances, derived extragonadally and stored temporarily in the ovarian wall, can pass through the oocyte-stalk.

NUTRIENT TRANSLOCATION IN THE SEA STAR: WHOLE-BODY AND MICROAUTORADIOGRAPHY AFTER INGESTION OF RADIOLABELED LEUCINE AND PALMITIC ACID.

Using the sea star, Asterias rubens, whole-body autoradiography has been employed to follow the distribution and the pathways of translocation of both soluble and tissue-incorporated label derived from orally administered 14C-labeled leucine or palmitic acid. Radioactivity remains localized predominantly in the stomach and pyloric caeca until sixteen days after ingestion. Labeling of the perivisceral coelomic cavity in regions close to the stomach shortly after ingestion points to initial displacement of ingested nutrients through the coelomic fluid and coelomocytes. After oral administration of labeled palmitic acid, distinct labeling of the gastric hemal tufts, axial organ, and aboral ring prior to labeling of the gonads also suggests the involvement of hemal tissue and surrounding perihemal coelomic sinuses in storage and translocation of substances needed for gamete nutrition. Microautoradiography of gonad tissue reveals a rapid labeling of the walls of the genital coelomic sinus, the ground substance of the genital hemal sinus, and, after prolonged incubation, the germinal epithelium. Little or no label is incorporated into the outer sac of the gonad wall. The results are discussed in terms of current knowledge on nutrient translocation in the sea star.

An autoradiographic investigation of the proliferative activity of pyloric caeca and gondas of Asterias rubens.

The proliferative activity of the pyloric caeca of Asterias rubens was investigated. Autoradiographic experiments using intracoelomically injected (methyl-3 H)-thymidine were performed throughout the year and incorporation into pyloric caeca and into gonads was studied. Tritiated thymidine was found to be incorporated mainly in the coelomic lining of both organs. Cell divisions in the coelomic lining may be necessary for the growth of these organs, for the production of coelomocytes or, in the case of the pyloric caeca, for growth of the digestive epithelium. Proliferative activity of the digestive epithelium of the pyloric caeca was only observed in the median duct. It is hypothesized that new cells, arising from mitosis, grow from the median duct to the side lobes and differentiate into storage cells, for example. The existence of a mitosis-inducing or mitosis-stimulating substance is discussed. In the ovaries follicle cells were found to incorporate (methyl-3 H)-thymidine; in the testis, proliferation of the germinal epithelium occurred simultaneously in all spermatogenic columns. First, the spermatogonia and then later the spermatocytes became labeled. Absorption of substances from the coelomic fluid is discussed.

Histochemical observations on the pyloric caeca of Asterias rubens (Echinodermata, asteroidea) in relation to the reproductive cycle.

The pyloric caeca of the starfish Asterias rubens were investigated histochemically during the reproductive cycle. The median duct and the side lobes reacted differently. The median duct reacted positively for acid phosphatases and glucose-6-phosphate dehydrogenase, whereas the side lobes reacted positively for alkaline phosphatases, neutral lipids, and fatty acids. In the transition zone between the median duct and the side lobes, the reaction for alkaline phosphatases and neutral lipids increased toward the side lobes. The function of the enzymes and the histochemical results are discussed in relation to the function of the pyloric caeca and to the reproductive cycle.

Effects of oestradiol-17 beta on the synthesis of RNA, proteins and lipids in the pyloric caeca of the female starfish Asterias rubens.

1. The effects of oestradiol-17 beta on processes of synthesis in the pyloric caeca of female Asterias rubens were studied. 2. In vitro treatment with 2.5 X 10(-7) M oestradiol-17 beta resulted in significantly higher RNA levels. 3. In vivo treatment with oestradiol-17 beta resulted in higher lipid levels in the pyloric caeca, but RNA levels, protein levels and the incorporation of 6-[14C]orotic acid, L-leucine-[14C] and sodium 1-[14C] acetate into RNA, proteins and lipids, respectively were not affected, neither were the indices of the gonads and pyloric caeca.

On the sterols of some ascidians.

The lipid content of sea squirts is low, namely less than a half percent of the fresh weight. Lipids consist of about seventy percent of saponifiable lipids and of about twenty percent of non-saponifiable lipids. Both types of these lipids, including sterols, can be synthesized from acetate by these animals. Small amounts of C30 sterols were observed only in Microcosmus sulcatus and Halocynthia papillosa, the species with a low content of C27 sterols and a high content of C28 sterols. In addition these species contained considerable higher amounts of sterols with a double bond at the C22 position than Ciona intestinalis and Styela plicata did.