Respiration in Eggs of the Echiuroid, Urechis unicinctus, Before and After Fertilization

In eggs of the echiuroid Urechis unicinctus the respiration rate, which is not altered by fertilization, is inhibited by rotenone, antimycin A and cyanide. The respiration in echiuroid eggs is probably mediated by the mitochondrial respiratory chain. In fertilized eggs, the respiration was inhibited by oligomycin and stimulated by the uncouplers of oxidative phosphorylation 2,4-dinitrophenol and carbonylcyanide p-trifluoromethoxyphenylhydrazone, whereas respiration in unfertilized eggs was insensitive to these compounds. Insemination increased the respiratory rate in eggs in the presence of uncouplers and reduced it in the presence of oligomycin. These findings suggest that the capacity of electron transport in mitochondira is elevated by fertilization but becomes latent on fertilization-induced coupling of respiration with oxidative phosphorylation. Strong stimulation of the respiration in unfertilized eggs was induced by dichlorophenol indophenol, phenazine methosulfate and tetramethyl p-phenylenediamine, suggesting possible sites at which electron transport is regulated in unfertilized eggs. The resulting stimulation of respiration in unfertilized eggs was insensitive to uncouplers and oligomycin, but became sensitive to them after fertilization simultaneously with considerable decrease in its rate. Fertilization-induced coupling of the respiration seemed to reduce the respiratory rate enhanced artificially by these redox compounds.     

PRODUCTION AND UTILIZATION OF GLUCOSE 1-PHOSPHATE IN THE EGGS OF THE SEA URCHIN ANTHOCIDARIS CRASSISPINA

Concentrations of G1P, G6P, UDPG, UTP and PPi were measured in the eggs of the sea urchin, Anthocidaris crassispina. Activities of phosphorylase a (EC 2.4.1.1), phosphoglucomutase (EC 2.7.5.1), UDPG pyrophosphorylase (EC 2.7.7.9) and pyrophosphatase (EC 3.6.1.1) were also estimated. Levels of G1P and G6P increase following fertilization, but concentrations of UDPG and UTP in unfertilized eggs are very similar to those in fertilized eggs. PPi is undetectable. In unfertilized and fertilized eggs, the G1P level is very low as compared with the G6P level and is far less than that expected from the equilibrium constant in a reaction catalyzed by phosphoglucomutase. Since the phosphoglucomutase activity is higher by about 20 times than the phosphorylase a activity, G1P is probably produced in the reverse reaction, catalyzed by phosphoglucomutase, rather than in the reaction catalyzed by phosphorylase. The G1P thus produced seems to be utilized thoroughly in the reaction catalyzed by UDPG pyrophosphorylase. The reaction seems to be irreversible and tends to go to UDPG production in sea urchin eggs, since the PPi level is negligible due to high pyrophosphatase activity. The utilization of G1P in the reaction catalyzed by UDPG pyrophosphorylase seems to keep the G1P level low.     

INHIBITION OF RESPIRATION IN SEA URCHIN SPERMATOZOA FOLLOWING INTERACTION WITH FIXED UNFERTILIZED EGGS

The respiration of spermatozoa of the sea urchin, Hemicentrotus pulcherrimus , was found to be sensitive to rotenone, antimycin A, and cyanide. This suggests that sperm respiration results from electron transport which spans the whole mitochondrial respiratory chain. The sperm respiration was inhibited by oligomycin and this inhibition was released by 2, 4-dinitrophenol (DNP). DNP did not stimulate the respiration of spermatozoa in a diluted suspension (2 × 10⁸/ml), where they were swimming vigorously. The ADP level of spermatozoa in the diluted suspension was markedly higher than that in dry sperm. The spermatozoa, which had reacted with unfertilized eggs fixed with glutaraldehyde, were immotile with a quite low respiratory rate. The respiratory rate of the immotile spermatozoa was enhanced by DNP. In the immotile spermatozoa, ADP level was markedly low and the ATP level was as high as that in dry sperm. From these findings, it is concluded that in the swimming spermatozoa respiration coupled with oxidative phosphorylation occurs at the maximum rate. State 3 respiration probably occurs in the swimming spermatozoa. The low respiratory rate of the immotile spermatozoa is assumed to be due to a shortage of ADP and is practically regarded as state 4 respiration.     

Change in the Triglyceride Level in Sea Urchin Eggs and Embryos During Early Development

Triglycerides in the embryos of the sea urchin, Anthocidaris crassispina , analyzed by gas-liquid chromatography, distributed in a range of carbon numbers between 42 and 58 in the sum of three fatty acid residues. During the development until gastrulation, the levels of triglycerides with 48, 56 and 58 carbon numbers decreased at constant rates and the levels of the others decreased at specific stages different with one another, respectively. Thereafter, the amounts of all triglycerides decreased simultaneously. The amount of oxygen consumed in the embryos is enough for the oxidation of mobilized triglycerides during post-hatching period but is not during pre-hatching period. The levels of neutral glycerides increased gradually during pre-hatching period and thereafter decreased. The fatty acid level also increased during pre-hatching and post-hatching period. These suggest that the cleavage of triglycerides and the oxidation of their cleavage-products occur during whole span of early development. During pre-hatching period, the break down of triglycerides is probably higher in its rate than the rate of their oxidation, resulting in the increase in the levels of neutral glycerides, as well as fatty acids.     

Aspects Regarding the Action of CCC in Hollyhock Plants

CCC [(2-chloroethyl) tnmethyl ammonium chloride] retarded shootelongation and increased leaf thickness and size (or volume)of leaf mesophyll cells in hollyhock plants. Photosyntheticactivities were stimulated by CCC, whereas post-illuminationCO₂ outburst-1 [PIB-1], PIB-2 and dark respiration were depressedby CCC. Chlorophyll and protein content of leaves treated withCCC also increased as compared with those of control leaves.CCC enabled the plant to bear flowers at the nodes from lowerto upper positions of the hollyhock shoots without flower (bud)abortion. Key words: Photosynthesis, CCC, mesophyll cell     

Herbivory in canopy gaps created by a typhoon varies by understory plant leaf phenology

1. Availabilities of light and soil nitrogen for understory plants vary by extent of canopy gap formation through typhoon disturbance. We predicted that variation in resource availability and herbivore abundance in canopy gaps would affect herbivory through variation in leaf traits among plant species. We studied six understory species that expand their leaves before or after canopy closure in deciduous forests. We measured the availabilities of light, soil nitrogen, soil water content, and herbivore abundance in 20 canopy gaps (28.3–607.6 m²) formed by a typhoon and in four undisturbed stands. We also measured leaf traits and herbivory on understory plants. 2. The availabilities of light and soil nitrogen increased with increasing gap size. However, soil water content did not. The abundance of herbivorous insects (such as Lepidoptera and Orthoptera) increased with increasing gap size. 3. Concentrations of condensed tannins, total phenolics, and nitrogen in leaves and the leaf mass per area increased in late leaf expansion species with increasing gap size, whereas none of the leaf traits varied by gap size in early leaf expansion species. 4. Herbivory increased on early leaf expansion species with increasing gap size, but decreased on late leaf expansion species. In these late leaf expansion species, total phenolics and C : N ratio had negative relationships with herbivory. 5. These results suggested that after typhoon disturbance, increased herbivory on early leaf expansion species can be explained by increased herbivore abundance, whereas decreased herbivory on late leaf expansion species can be explained by variation in leaf traits.     

Inhibition of Respiration in Sea Urchin Spermatozoa Following Interaction with Fixed Unfertilized Eggs V. Inhibition of Electron Transport in a Span of Mitochondrial Respiratory Chain between Cytochrome b and Cytochrome c in Sea Urchin Spermatozoa, Induced by the Interaction with Glutaraldehyde Fixed Eggs

In the sea urchin, Anthocidaris crassispina , α and γ peaks of reduced cytochrome b were distinctly observed but no peaks of cytochrome a and cytochrome c were found in the difference spectra between H₂O₂ oxidized and the aerobic suspensions of the immotile spermatozoa, which were obtained by an incubation of the suspension of spermatozoa and the glutaraldehyde-fixed eggs for 15 min at 20°C. A similar profile of difference spectrum was also obtained between the aerobic sperm suspension containing antimycin A and the H₂O₂ oxidized one. In Hemicentrorus pulcherrimus , faint peaks of reduced cytochrome a and cytochrome c , as well as evident peaks of cytochrome b , were also found in the difference spectra between aerobic suspension of the fixed-egg-reacted spermatozoa and the H₂O₂ oxidized one. In intact swimming spermatozoa of A. crassispina as well as H. pulcherrimus , no peaks of reduced cytochromes were found under aerobic condition. These results suggest that the inhibition of sperm respiration by the fixed eggs is due, at least in part, to the blockage of electron transport in a span between cytochrome b and cytochrome c.     

CHANGE IN THE GLYCOGEN CONTENT OF SEA URCHIN EGGS DURING EARLY DEVELOPMENT

During development of eggs of the sea urchins, Pseudocenrotus depressus and Anthocidaris crassispina , the glycogen level is maintained from the time of fertilization to the swimming blastula stage and then decreases rapidly in the early gastrula stage. During development of eggs of Clypeaster japonicus. Hemicentrotus pulcherrimus and Mespilia globulus the glycogen content decreases slowly from the time of fertilization to the mesenchyme blastula stage, and then more rapidly during gastrulation. The amounts of glycogen mobilized in the embryos from the time of fertilization to the morula stage correspond to 67% of the amount of O₂ consumed in Mespilia eggs, 62% in Clypeaster eggs, 30% in Hemicentrotus eggs and 0–4% in Anthocidaris and Pseudocentrotus eggs. The main energy source in early development seems to differ in different species. When eggs and embryos were incubated with [¹⁴C]glucose for 10min, considarable ¹⁴C-radioactivity accumulated in the glycogen fraction. The rate of [¹⁴C]glucose incorporation into glycogen increased gradually during the first 6 hr after fertilization (up to the morula stage), decreases during the next 4 hr (up to the early blastula stage), and then increased again.