Changes in Osmotic Pressure and Swelling in Horseshoe Crab Embryos During Development

Water influx accompanying the swelling of embryos during normal development of horseshoe crabs, Limulus polyphemus and Tachypleus tridentatus , following a rupture of the chorion, was analyzed. The increase in volume of perivitelline fluid during deveopment was about 90 percent of the increase in total embryo weight. Considerable water discharge was observed on drying the embryos in air and a reversible water influx occurred with a second immersion in sea water, even though the embryos died as a result of this treatment. Since the osmotic pressure of the perivitelline fluids decreased markedly during development until the end of swelling, a close correlation between swelling and osmotic pressure was recognized. These results indicate that certain osmoactive substances may be produced in the perivitelline fluid at the initial stage of swelling.     

The genus Dugesia in Australia, with its phylogenetic analysis and historical biogeography (Platyhelminthes, Tricladida, Dugesiidae)

The new species Dugesia notogaea Sluys & Kawakatsu, sp. n. is described from Queensland, Australia, representing the first record of the genus Dugesia for that continent. A phylogenetic analysis of the 68 species of Dugesia resulted in the discovery of a new apomorphy for the genus, and a cladogram showing two major phyletic groups. The distributional range of one group has a western accent, whereas that of the other group has an eastern emphasis; the ranges of these two groups overlap in Africa and the Mediterranean region. We attempt to determine the ancestral area for both the Dugesiidae and Dugesia. A scenario for the historical biogeography of the genus Dugesia is discussed. In this scenario it is presumed that the geological history of the Australasian region enabled Dugesia's from southeast Asia to colonize northern Australia. © 1998 The Norwegian Academy of Science and Letters     

A Changing Pattern of the Cell Cycle during the First Two Cleavage Divisions of the Mouse

The cell cycles of the early cleavage stages of the mouse were analyzed by examining Feulgen-stained ova. The period from ovulation to the completion of second cleavage division was investigated. The ova donors were C57BL/6 × DBA/2 female mice, which were hormonally superovulated. To estimate the durations of DNA synthesis and mitotic phases of the cleavage divisions, the ova were pooled into culture medium, and as a function of time, aliquots were removed from the batch of pooled ova. The ova specimens were Feulgen-stained and classified as the ova nuclei in G₁, S, G₂ or mitosis by use of a cytophotometric technique and then the durations of these phases were determined by probit analysis.
The pronuclear stage had a generation time of 11 hr, with a G₁ phase of 6 hr and a short S phase of 1.7 hr. In contrast the two-cell stage had a generation time of 18 hr, with a G₁ phase of 2 hr and an S phase of 3 hr. The duration of cleavage division also changed; the first cleavage division spanned 3 hr while the second spanned 1 hr.     

Ubiquitous distribution of fluorescent protein in muscles of four species and two subspecies of eel (genus <Emphasis Type="Italic">Anguilla</Emphasis>)

In this study, the localization of fluorescent protein (FP) was characterized in the muscles of four species and two subspecies of eels Anguilla anguilla, A. australis, A. bicolor bicolor (b.), A. bicolor pacifica (p.) and A. mossambica in addition to the previously reported A. japonica. The open reading frame of each eel FP was 417 bp encoding 139 amino acid residues. The deduced amino acid sequences among the four species and two subspecies exhibited 91.4–100% identity, and belonged to the fatty-acid-binding protein (FABP) family. The gene structure of eel FPs in A. japonica, A. anguilla, A. australis, A. bicolor b., A. bicolor p. and A. mossambica have four exons and three introns, and were common to that of FABP family. The apo eel FPs expressed by Escherichia coli with recombinant eel FP genes were analysed for the fluorescent properties in the presence of bilirubin. The excitation and emission spectra of holo eel FPs had the maximum wavelengths of 490–496 and 527–530 nm, respectively. The holo eel FPs indicated that the fluorescent intensities were stronger in A. japonica and A. bicolor than in A. mossambica, A. australis and A. anguilla. The comparison of amino acid sequences revealed two common substitutions in A. mossambica, A. australis and A. anguilla with weak fluorescent intensity.     

GROWTH OF CALLUS TISSUE FROM RICE-ROOT IN VIRTO

The callus tissues which had been induced on the roots of riceseedlings by the action of 2,4-D were cultured on a modifiedHELLER medium for more than two years. The tissues were transferredinto new msdium every two to three weeks. Yeast extract and2,4-D were indispensable for maintaining the best growth. Aboutfifty times' increase in tissue mass on a fresh weight basiswas obtained after three weeks' incubation. Glucose, fructose,sucrose and maltose supported equally well the growth of callustissue. The optimum temperature and pH were located between25–30 and 5–6 respectively. Microscopic examinationshowed no sign of organ formation, but some tissue differentiationwas observed at histological level. (Received December 13, 1966; )