Development, Growth & DifferentiationVolume 42, Issue 6 p. 539-539 Free Access Ikuo Yasumasu Masukichi Okada, Masukichi OkadaSearch for more papers by this author Masukichi Okada, Masukichi OkadaSearch for more papers by this author First published: 25 December 2001 https://doi.org/10.1046/j.1440-169x.2000.00538.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume42, Issue6December 2000Pages 539-539 RelatedInformation

The spermatozoon of the Japanese abalone, Haliotis discus, and its structural changes during the acrosome reaction were observed by electron microscopy. The spermatozoon has a huge acrosome in the shape of a hanging bell or a forefinger with a deep fossa at the posterior end being filled with a bundle of microfilaments. The membranes of the acrosomal apex, the so-called trigger region, are structurally discernible from those of other acrosomal regions. Following the trigger region, a unique structure under the acrosomal membrane covers the surface of the acrosomal content in the form of a truncated cone. The acrosome reaction occurs in the jelly layer very close to the egg envelope. First, the membranes at the apex of the acrosome are vesiculated, followed by the formation of a narrow gap between the outer acrosomal membrane and the acrosomal content. Next, the bundle of micro-filaments elongates, running through the center of the acrosome, reaching the trigger region and protruding out of the acrosomal top. Then release of the acrosomal content occurs in two steps, disclosing the "membrane undercoating structure" that comprises globular particles with a fuzzy material connecting them. This resembles the undercoat network found in erythrocytes.

The effects of potent carcinogens, 20-methylcholanthrene (MC) and benzo(α)pyrene (BP), on limb regeneration were studied in adult newts. A microcrystal of these carcinogens was administered directly to the blastema of forelmibs on day 7 after amputation. The formation of the regeneration cone was delayed and the cone was shifted in abnormal polarity depending upon the site of micro-crystal administration. These carcinogens affected morphogenesis of skeletal structures of regenerating limbs. Subregeneration and superregeneration of either or both carpals and digits, absence of either or both ulna and radius, and accessory limb formation have been recorded as abnormalities caused by these carcinogens. Non-carcinogenic benzocompounds did not show such effects as those of MC and BP. The regeneration blastema of the limb appears to be resistant to carcinogenic effects of the carcinogens used since tumor formation has never been observed in our study so far.

The types of actin present during development of skeletal muscle in chick embryos were investigated by various electrophoretic methods. The proportions of the actin types in the tissue were estimated by a novel method involving separation of actin bands by electrophoresis, staining of the bands with Coomassie Brilliant Blue R-250, extraction of dye and measurement of its absorbance. Results showed that α-, β- and γ-actins were all present in embryonic skeletal muscle and were assembled into myofibrils. However, β- and γ-actins disappeared from myofibrils as muscle development proceeded. In embryonic muscle, the proportions of the three actin types in the soluble and myofibril fractions were different: their amounts were in the order β>γ>α in the soluble fraction, and α>β>γ in the myofibril fraction.

A modification of silver nitrate staining, when applied to embryos of Oryzias latipes, was found to make clear not only the boundary of enveloping layer during epiboly, but also the outline of individual cells of the layer. The linear speed of advance of the enveloping layer was constant at fixed temperatures (20°, 25° or 30°C), except for the start and the end of the epibloy. Observation of the shape and arrangement of cells in the layer stained at successive stages of epiboly revealed that the enveloping layer expands uniformly over the yolk until late gastrula (3/4 epiboly). No cytokinetic figure was observed during epiboly until the blastopore was going to close. Total cell number of the layer remained constant during epiboly. Thus the expansion of the enveloping layer is accomplished without an accompanying increase in the number of constituent cells. In the last phase of epiboly, the surface area occupied by individual cells reduced locally at the region above the embryonic body, which suggests the occurrence in teleost of the convergence of cell sheets commonly observed in amphibian embryos.

Cytoplasmic ATPase of sea urchin eggs was partially purified by ammonium sulfate fractionation, DEAE-cellulose chromatography, gel-filtration chromatography and sucrose density gradient centrifugation. The specific activity increased to 0.7 μmole/min/mg protein indicating 100 fold purification. The ATPase had a sedimentation constant of 12S and was highly specific for ATP. The enzyme fraction contained neither (Na, K)-ATPase, Ca-ATPase, oligomycin-sensitive ATPase, phosphatases, nor myosin. This cytoplasmic ATPase was inhibited by a low concentration of vanadate (V). Half-maximal inhibition was observed at a vanadate concentration of 1 μM at low ionic strength. The inhibition was almost totally reversed by addition of norepinephrine. The vanadate-sensitivity of cytoplasmic ATPase decreased with increasing KCl concentration. The activation by Mg2+ or Ca2+ , and dependence of the activity on KCl concentration characteristic of dyneins from sea urchin sperm flagella and the embryonic cilia were observed with cytoplasmic ATPase. These results allowed the cytoplasmic ATPase to be classified as a dynein. In addition, this designation was reinforced by the fact that an oligomeric 23S form of cytoplasmic dynein was identified in the cytoplasm as well as in the isolated mitotic apparatus.

Previous work from this laboratory has shown that the β-amino acid taurine can support and stimulate hamster sperm motility during in vitro capacitation in the presence or absence of epinephrine. The present report describes in vitro results which demonstrate that hypotaurine, a precursor of taurine, can also support and stimulate motility under these conditions and that a higher number of acrosome reactions occur in the presence of taurine as compared to hypotaurine (both in the presence and absence of epinephrine). In all cases, the greates percentage of acrosome reactions occurs in the presence of epinephrine. Whether these β-amino acids act independently of epinephrine of in a synergistic manner with it remains to be determined. In addition to these in vitro studies, we report that hypotaurine and taurine are present at high levels in bovine follicular fluid, rabbit uterine and ampullar oviductal fluid (11 hr after mating, i.e., 1 hr after ovulation), monkey oviductal fluid, bovine adrenal cortex "motility factor" preparation and human, guinea pig and hamster sperm preparations. Based on these results, we suggest the possibility that taurine and hypotaurine may have roles in vivo in the maintenance and stimulation of sperm motility and stimulation of capacitation and/or acrosome reactions.