Characterization of sea urchin yolk glycoproteins

To study the fate of the yolk glycoproteins found in eggs and embryos of the sea urchin, S. purpuratus, a polyclonal antibody to a 90-kDa polymannose glycoprotein was prepared. lmmunoblot analysis of total proteins over the course of development showed that this antibody recognized a family of glycoproteins. Concomitant with the disappearance of the major 160-kDa egg yolk glycoprotein during embryogenesis, glycoproteins with a lower molecular mass appeared. These glycoproteins (115, 108, 90, 83, and 68 kDa) were purified and peptide mapping revealed that they were cleavage products derived from the major yolk glycoprotein. The antibody identified a homologous set of yolk glycoproteins with similar molecular masses in the embryos of three other species in the class Echinoidea: L. pictus, A. punctulata, and D. excentricus. However, eggs from other echinoderm classes and from chicken, frog, fruit fly, and nematode did not contain any cross-reactive molecules. Cross-reactivity within the class Echinoidea was not due to a common carbohydrate epitope, because the antibody recognized the glycoproteins even after the N-linked, polymannose carbohydrate side chains were enzymatically removed. The major yolk glycoprotein (160-170 kDa) from each of the three sea urchin species was purified and analyzed, revealing striking similarities in pI and in amino acid and monosaccharide composition. Peptide mapping showed that the 160-kDa glycoprotein from the four echinoids are structurally homologous. The major yolk glycoprotein appeared to be proteolyzed by a thiol protease, which could be activated in yolk particles prepared from unfertilized eggs by low pH. Immunolocalization by electron microscopy in S. purpuratus showed that the yolk glycoproteins remained within the yolk platelet throughout embryonic development, and that externalization of the glycoproteins was not detectable. The yolk glycoprotein precursor began to be synthesized in premetamorphosis larvae, and continued in adult males and females. Both the yolk glycoproteins and the yolk platelets disappeared during larval development. This disappearance has special significance because there were no yolk proteins in the direct developing sea urchin, H. erthryogramma, which bypasses larval development and metamorphoses directly into an adult. ^

AVIAN ROTAVIRUSES

The prevalence of antirotavirus antibodies in chickens and turkeys in the Gonzales, Texas and Llano, Texas areas was studied. Caged layer chicken flocks were found to have a prevalence of 64% when samples were taken randomly. This compares to 45% in chicken broiler breeder flocks and 92% in turkey breeding flocks. The natural occurrence of turkey rotavirus infection in two separate field studies showed an increase in mortality varying from 9% to 45% above expected death losses. Clinically, pasted vents, lacitude, and general malaise were noted in affected poults. Lesions noted on post mortem examination were; slight ballooning of the small intestine, excessively large ceca, and mild hyperemia of the small and large intestines.^ The use of maternal antibody from simian rotavirus immunized chickens' eggs for preventing murine rotavirus infection in infant mice was investigated. There was a reduction from 91% to 15% incidence when infant mice were treated twice daily with egg yolk immunoglobulin.^ The need for a convenient, easily grown and rapidly reproducing model for avian and mammalian rotaviruses led to the use of coturnix chicks. The turkey rotavirus was adapted to the quail chicks be serial passage. Transmission and scanning electron microscopy as well as micropathological methods were used in the study of the pathogenesis of rotavirus infection in quail and infant mice. ^