Fine Structural Changes in the Acrosome Reaction of the Japanese Abalone, Haliotis disus

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.     

Larval ecology of prosobranch gastropods and its bearing on biogeography and paleontology

The larval ecology of prosobranch gastropods, which ranges from long pelagic plankto-trophic life histories to directly developing lecithotrophic ones, has a strong influence on larval dispersion. Because of low migrative ability in the post-larval stage, gastropod distribution must depend fundamentally on larval dispersion. It is probable that the modes of larval dispersion relate importantly to the mechanism by which prosobranch populations become isolated, and consequently to their modes of speciation. This idea is applicable for analysis of fossil material, for both biological and oceanographical information.     

Distribution of Intramembrane Particles and Its Changes during the Acrosome Reaction in Spermatozoa of the Japanese Abalone

The distribution of intramembrane particles in the plasma and acrosomal membranes of sperm of the Japanese abalone, Haliotis discus , and its changes during the acrosome reaction were studied by the freeze-fracture replica technique. The P face of the plasma membrane covering the acrosome has sparse membrane particles except in the apical region, which includes the trigger and 'truncated cone' regions. Large particles with an average diameter of 10 nm are located in this apical region. The E face of the plasma membrane has only a few particles. On the outer acrosomal membrane, many particles are randomly distributed throughout the P face, but only a small number of particles are found on the E face. Numerous particles on the P face of the inner acrosomal membrane show a regular arrangement as a dense lattice or with a concentric circular pattern. The initial change in the acrosome reaction is clearance of membrane particles from both the P and E faces of the plasma and outer acrosomal membranes around the apical region, where fusion of the two membranes occurs. As the acrosomal process elongates, the dense arrangement of particles on the inner acrosomal membrane changes via a loose lattice arrangement to a patchy distribution with particle-free areas. Then the arrangement is further disorganized becoming a sparse, random distribution.     

The sugars in the seeds and seedlings of Pinus Thunbergii

The yerba santa plant, Eriodictyon californicum, contains a substance antagonistic chiefly to gram-positive and acid-fast organisms.The active principle, named eriodin, has been prepared in partially purified form by adsorption on activated bone charcoal.Further work on the active principle is still in progress.     

Ultrastructural Changes of the "Truncated Cone" during the Acrosome Reaction in Japanese Abalone Spermatozoa

An electron-dense structure termed the "truncated cone" covers the apical surface of the acrosomal contents except for the trigger region in Haliotis discus spermatozoa. The truncated cone, having a slant height of 0.3 μm and diameters of circular top and base of 0.3 and 0.6 μm, shows striations with a periodicity of 6.6 to 8.0 nm. During the acrosome reaction, the truncated cone elongates simultaneously with the protrusion of the acrosomal process through the truncated cone. As the growth of the acrosomal process further proceeds, the truncated cone transforms into a cylindrical shape and eventually reaches 1 μm in length and 0.2 μm in diameter. The elongated truncated cone is characterized by regularlly helical striations with a periodicity of 19 to 21 nm with an inclination of 40° to 46°. These results may suggest that the truncated cone is composed of coiled filaments, which coil up further during the acrosome reaction causing the truncated cone to slenderize and elongate. The elongation is also achieved by stretching of the coil. In H. discus hannai Ino, structural changes in the truncated cone show close homology to those in H. discus. No such morphologically unique organelle has been found in other species thus far.     

Purification of Acetylcholinesterase from Sea Urchin (Hemicentrotus pulcherrimus) Embryos by Affinity Chromatography

Only one form of acetylcholinesterase (AchE) was detected in Hemicentrotus pulcherrimus embryos. In H. pulcherrimus embryos as well as in the other sea urchin embryos, AchE activity begins to increase rapidly after gastrula stage.
Purification of AchE from plutei has been carried out by the procedure including affinity chromatography. Purified AchE had the activity 14,600 times higher than that of homogenate, and the final yield of AchE was 8%. The enzyme seems to be electrophoretically homogeneous, and has a molecular weight of 3 × 10⁵ as determined by Sepharose CL–6B column chromatography.     

Seasonal Changes in Respiration, Photosynthesis, and Translocation of the 14C Labelled Products of Photosynthesis in Young Pinus strobus L. Plants

Three-year-old Pinus strobus plants, grown under conditionsof either high or low light intensities, were brought from thenursery to the laboratory every three to four weeks from themiddle of April 1961 until January 1962. Translocation, measuredas the amount of ¹⁴C recovered from the roots at the end ofseven hours of illumination following exposure of the shootto ¹⁴CO₂, was found to be high in the spring, dropping to negligibleamounts during June and July, increasing again in the autumnand declining after October. Seasonal variation in root respirationwas found to parallel that of translocation. Rates of apparentphotosynthesis were low during the spring, rising to a maximumduring September, and then declining over the winter. The respiration,photosynthesis, and translocation of the low-light grown plantsfollowed a similar pattern to those grown in high-light, exceptthat in general rates were of a lower order. In the high-light grown plants more than 90 per cent of theabsorbed carbon was present in the ethanol-soluble form, ofwhich sugars formed at least 90 per cent. This was even morepronounced in the case of low-light grown plants. The main sugarwas always sucrose. The raffinose content was found to decreaseduring the warmer months. The new needles, during their period of maximum growth, fixedcarbon dioxide photosynthetically at a rate comparable to thatof the old needles. The new stems also possessed a relativelyhigh carbon dioxide fixing ability. Shoot growth, as measured by the increase in length of the newleader stem and new needles, showed the typical patterns forpine species.