Sperm and Egg Jelly Coat from Sea Urchin Lytechinus variegatus Collected in Rio de Janeiro Contain Distinct Sialic Acid-Rich Polysaccharides

This work found the occurrence of a distinct sialic acid-rich polysaccharide in the sperm surface of the sea urchin Lytechinus variegatus, which differed significantly from a similar molecule found in the egg jelly. The sperm polysaccharide extracted by protease digestion was purified using anion exchange chromatography and characterized using agarose gel electrophoresis, gas chromatography/mass spectrometry and NMR spectroscopy. This polysaccharide was highly sulfated and composed almost exclusively of N-acetylneuraminic acid. In contrast, the sialic acid-rich polysaccharide from the egg jelly was composed of N-glycolylneuraminic acid and contains several other hexoses in its structure. This new molecule could help to characterize in further detail the mechanism of fertilization in the sea urchin model system. Sulfated polysaccharides from the jelly coat of sea urchins showed species-specificity in inducing the sperm acrosome reaction, providing an example of a signal transduction event regulated by the sulfated polysaccharide. The new sialic acid-rich polysaccharide found in the sperm head could represent a new molecule involved in the biology of the sea urchin fertilization.

Hepatic alterations in giant bullfrog induced by tordon 2,4-D

Liver fragments of Rana catesbiana, experimentally exposed to 2,4 dichlophenolacetic (tordon 2,4-D) were processed for routine tranmission electron microscopy. Hepatic peroxisomes were visualized after incubation with alkaline 3,3'-diaminobenzidine (DAB) according to the method described by LEHIR et al (1979). Ultrastructural analysis revealed progressive hepatocyte changes induced by this drug. After 2-weeks, the hepatocytes presented evident dilatation and disorder of usual morphology of both smooth abd rough endoplasmic reticulum (SER and RER, respectively). Reduction of glycogen granules associated with an increased frequency of lysosomes was observed. Peroxisomes appeared in clusters with usual morphology. The RER displayed usual appearance but were more often observed in stacks. Lipid droplets were also visualized. After 4-weeks, there was a new increase of glycogen associated with a great number of mitochondia and peroxisomes. Moreover, SER and RER were still dilated. Intracellular lipid inclusions became more abundant. The present study demonstrates that the tordon 2,4-D induces untrastructural changes in the hepatocyte of Rana catesbiana.