Nathan H. Hart

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The zebrafish egg provides a useful experimental system to study events of fertilization, including exocytosis. We show by differential interference contrast videomicroscopy that cortical granules are: (1) released nonsynchronously over the egg surface and (2) mobilized to the plasma membrane in two phases, depending upon vesicle size and location.(More)
Morphological studies on the gametes and entry of the spermatozoan into the egg of the zebra danio, Brachydanio rerio, were conducted primarily with scanning electron microscopy. The spermatozoan showed a spherical head, which lacked an acrosome, a midpiece containing several mitochondria, and a flagellum. Observations of the unfertilized egg confirmed and(More)
The structure of the chorion with its associated surface filaments has been examined in Oryzias latipes using several techniques, including scanning and transmission electron microscopy, enzymatic digestion, and sodium dodecylsulfate-polyacrylamide gel electrophoresis. The chorion of the recently fertilized egg was found to be organized into three zones: an(More)
Activation of the teleost (Brachydanio) fish egg includes the exocytosis of cortical granules, the construction of a mosaic surface consisting of the unfertilized egg plasma membrane and the limiting membranes of the cortical granules, and the appearance of coated and smooth vesicles in the cytoplasm (Donovan and Hart, '82). Unfertilized and activated eggs(More)
The sperm entry site (SES) of zebrafish (Brachydanio rerio) eggs was studied before and during fertilization by fluorescence, scanning, and transmission electron microscopy. Rhodamine phalloidin (RhPh), used to detect polymerized filamentous actin, was localized to microvilli of the SES and to cytoplasm subjacent to the plasma membrane in the unfertilized(More)
The ontogeny of glucosephosphate isomerase (GPI; E.C. and triosephosphate isomerase (TPI; E.C. isozymes in Brachydanio rerio, (zebra danio), B. albolineatus (pearl danio) and hybrids formed by their reciprocal crosses were examined by electrophoretic and spectrophotometric methods. The two species showed virtually identical adult,(More)
We have examined the cortex of the teleost (Brachydanio rerio) egg before and during exocytosis of cortical granules by scanning, transmission, and freeze-fracture electron microscopy. In the unactivated egg, the P-face of the plasma membrane exhibits a random distribution of intramembranous particles, showing a density of 959/μm2 and an average diameter of(More)