Timers in Early Development of Sea Urchin Embryos

To elucidate the timing mechanisms in the early development of sea urchin embryos, we measured the times of initiation of the first four cleavages, of ciliary movement, of primary mesenchyme cell ingression, and of gastrulation at four temperatures ranging from 11 to 20°C. The times of cleavage and of initiation of ciliary movement showed similar temperature dependency, indicating that these events may be controlled by a common timer (the first timer). Although batches of eggs often showed variation in the period between fertilization and the first cleavage, their subsequent cleavages were more regular. This indicates that the first timer may not start at fertilization. The ingression of mesenchyme cells and the onset of gastrulation showed similar temperature dependency that was higher than that of other events, suggesting the existence of a second timer. Temperature shift experiments indicate that the second timer starts at the mid-blastula (the 8–9th cleavage) stage when divisions of blastomeres become asynchronous.     

Relative effectiveness and interaction of ultraviolet-B, red and blue light in anthocyanin synthesis of apple fruit

The effect of light on anthocyanin production in apple ( Malus pumila Mill. cv. Jonathan) skin disks was investigated, with prolonged irradiation from different light sources. High fluence rates of white light provided from a xenon lamp were unable to produce large amounts of anthocyanin, and anthocyanin production became saturated at about 30 W m⁻². When UV-B light, provided by a fluorescent lamp which had an emission peak at 312 nm, was combined with the white light, anthocyanin production was synergistically stimulated and increased up to the highest fluence rates of white light tested (44 W m⁻²). This UV-B light was more effective than red and blue light provided from fluorescent lamps, but anthocyanin production became saturated at about 1.7 W m⁻². However, simultaneous irradiation with red and UV-B light had a synergistic effect. UV-B light was also effective in increasing anthocyanin production in whole fruit. Therefore this synergism seemed to have an important role in the development of the desirable red skin color under field light conditions. The results of aminoethoxyvinylglycine treatment suggested that ethylene was not involved in the stimulative effect of UV-B light.     

Tissue- and Stage-Specific Expression of Sericin Genes in the Middle Silk Gland of Bombyx mori

Sericin gene expression in the middle silk glands during Bombyx mori larval development was analyzed using probes from a genomic DNA clone for 10.5 kb sericin mRNA. The 10.5 kb mRNA, the most abundant in the fifth instar, is not detected in the third feeding, fourth feeding and fourth moulting stages. It becomes detectable at 2 days of the fifth instar, and accumulates rapidly. The second major mRNA in the late fifth instar, a 9.0 kb component having a similar sequence to the 10.5 kb mRNA, becomes detectable only at 6 and 7 days of the instar by use of the repetitious coding sequence probe of the sericin clone. Using the same probe about 20 kb RNAs with a fainter intensity than that of the major mRNAs are detected. They are present extremely faintly in the third and fourth feeding stages, disappear in the fourth moulting stage, and increase in the fifth instar. Two other faint poly(A)⁺ RNA components are detected by a DNA probe containing the 5' end sequence of the sericin clone. One is 4.3 kb, and appears in the third, fourth and fifth feeding stages but not in the fourth moulting stage. The other is 3.0 kb, and it becomes detectable after 1 day of the fifth instar.     

FURTHER NOTES ON THE GROWTH AND CHLOROPHYLL FORMATION OF CHLORELLA PROTOTHECOIDES

1. Using area of a fixed concentration as a nitrogen source,cells of Chlorella protothecoides were grown in the presenceof various carbon compounds. Magnitudes of growth of the cellswere widely different depending on the carbon sources used;glucose and fructose being most favourable substrates and galactose,glycerol and acetate coming next. But the amounts of chlorophyllformed in the cells during the experimental period were almost,the same irrespective of the different carbon sources, withsome exceptions. The similarity of the chlorophyll level observedin these experiments seemed to indicate that the formation ofchlorophyll was limited largely by the nitrogen source but notby the carbon source. 2. Strong bleaching effect was recognized with glucose and fructoseat their high concentration, which produced totally chlorophyll-lesscells. On the other hand, a stimulating effect on chlorophyllformation was observed with galactose at the different concentrationsexamined. 3. Effects of glycine and ammonium carbonate as the nitrogensource on the algal growth and pigmentation were studied insome details. The results were similar to those previously obtainedwith urea, confirming our previous conclusion that the algalpigmentation is profoundly affected by the concentration balancebetween glucose and nitrogen source. ¹Present address: Tokyo Research Laboratories, Tanabe SeiyakuCo., Toda-machi, Saitama.     

Synchronization of Mating Reactivity Rhythms in Populations of Paramecium bursaria

Cell populations of Paramecium bursaria show arhythmic mating reactivity after exposure to constant light (LL) for more than 2 wk. After this arhythmic population is exposed to darkness for 9 h, the mating reactivity rhythm of the cell population reappears. The phases of rhythms in individual cells are synchronized to each other. When the arhythmic population in constant light is exposed to dark pulses of various durations, the first peak of the recovered mating reactivity rhythm appears 6 h after the end of the dark pulse. Thus, in the case of dark pulses to cells in LL, the transition from dark to light sets the phase of the subsequent mating reactivity rhythm. When an arhythmic population in LL is transferred to constant darkness (DD), a rhythm of mating reactivity also appears and, in this case, the first peak of the rhythm occurs 18 h after the LL to DD transition. Therefore, arhythmic populations of cells in LL can be synchronized by either a dark pulse or by transition to continuous darkness. When the arhythmic populations in LL were transferred to various light/dark (LD) cycles, the mating reactivity rhythms entrained to LD cycles of 18 to 30 h in duration. Finally, mating rhythms can also be synchronized by treatment with puromycin (400 μg/ml for 6–18 h).     

The second phantom aquatic leaf beetle in Japan: Macroplea mutica rediscovery in the wetlands (Coleoptera: Chrysomelidae)

Wetland biodiversity is currently declining on a global scale. Wetland biodiversity understanding is critical for determining the wetlands' conservation value. In this study, Macroplea Samouelle, 1819 (Coleoptera: Chrysomelidae) was discovered in Aomori Prefecture, Honshu Island, Japan. Only two Macroplea species have been recorded in Japan, M. japana (Jacoby, 1885) and M. mutica (Fabricius, 1792). Macroplea japana had been unrecorded for 60 years before being rediscovered in Honshu Island in 2022, and a single adult M. mutica female was discovered in Hokkaido Prefecture in 2003. The discovered individuals were concluded to be M. mutica based on morphological and molecular analyses. Although morphological differences were observed with the Eurasian M. mutica individuals, the male genitalia was nearly identical to M. mutica. For the molecular phylogenetic analysis based on COI and 28S sequences, Macroplea individuals in Japan were clustered with M. mutica on the Eurasian Continent. This is the first record of this species on Honshu Island (and the second in Japan), as well as the first record of adult males. This species would require conservation policies and additional distributional surveys.     

蜥臀目霸王龙及有鳞目沧龙牙齿组织的微细结构

本文是利用扫描电子显微镜对陆栖恐龙tvrannosaurid与海栖渐增mosasaurid”牙齿结构进行的比较解剖学研究。化石采自加拿大RedDeerhiverValley上白里统Horse－shoeCanyon组。通过研究地层中出现的生物化石,特别是动物牙齿的组织结构,可以了解动物为了适应生活环境而发生的进化过程,也可以推测它们的系统发育关系。tyrannosaund与mosas。id都拥有锥状的同形齿,牙齿侧向扁平,且略向后弯曲。研究结果确认了tyrannosaurid的牙齿由于薄层的无柱釉质bPrismaticenamel）向齿质的侵人而造成许多的凹凸构造,此锯齿状构造沿着牙齿的前后缘,由牙齿的顶端分布至基部。因此tyrannosaurid的牙齿呈现着锐利的切缘;在这些凹凸状切缘的沟与小窝的深部可观察到有机物的沉积。但是类似的锯齿状构造只能在齿冠呈钝圆状的mosasaurid牙齿的基部附近观察到。我们以扫描电子显微镜（SEM）检索,确认两爬行类的齿质皆是属于中间型的真性齿质（intermediatetypeorthodentine）;所谓orthodentine即是细管齿质（tubulardentine）。tyrannosaurid的真性齿质的齿质小管只在齿质一釉质相接处Uentino—enamaljunction）附近放散出规则性的分歧与末枝。但mosasaurid的真性齿质的齿质J。管,在齿质的中间层与表层中,呈现着由复杂     

Control of Late Development of Dictyostelium discoideum by Proteins Functioning at Early Stages

We examined two mutants of D. discoideum which are temperature-sensitive for development. At the nonpermissive temperature one mutant becomes arrested in development during the transition from the finger to the migrating slug. Temperature-shift experiment indicates that the temperature-sensitive period begins at considerably earlier tip-forming stage. The other mutant becomes arrested at the Mexican hat stage and the temperature-sensitive period coinsided with this stage. The analysis of protein synthesis by two-dimensional gels, however, showed specific changes at the nonpermissive temperature at an earlier finger-forming stage.
These results indicate the presence of a control of late development by proteins at early stages.