Oleic acid synthesis in the fruit of Persea americana MILL

The tissue slices from the mesocarp of avocado could incorporateradioactive acetate into lipids. Oleic, palmitic and stearicacids were the most labeled fatty acids found to accumulatein triglycerides. The conclusions that oleic acid was formedby way of chain elongation of already unsaturated short-chainfatty acids, and that there was no evidence for the desaturationof stearic acid were based on the following observations: 1)Stearic acid-¹⁴C was incorporated into triglycerides by thetissue slices without formation of oleic acid. 2) The oleicacid synthesized from specifically labeled acetate was not randomlylabeled. The specific radioactivity of azelaic acid moiety ofoleic acid was rapidly increased while that of pelargonic acidmoiety was gradually increased. 3) An unexpected rise of stearicacid was observed among commonly occurring fatty acids in thetissue slices. This was accentuated by anaerobiosis which prevailedduring vacuum infiltration of labeled acetate. ¹Present address: Department of Botany, Faculty of Agriculture,Hokkaido University, Sapporo, Japan. (Received January 13, 1969; )     

AUXIN-INDUCED GROWTH OF TUBER TISSUE OF JERUSALEM ARTICHOKE: II. THE RELATION TO PROTEIN AND NUCLEIC ACID METABOLISM

The following results were obtained using tissue slices excisedfrom cold-stored Jerusalem artichoke tuber. 1. Increase in protein content of the tissue was small duringthe washing (i.e. "aging"), and great in the growth phase, particularlyin washed tissue. 2. RNA content of tissue increased during the growth periodsimilarly in non-growing tissue (in water) and actively growingtissue (in 2,4-D plus KIN). 3. Both RNA and DNA increased during the washing, the increasebeing greater in RNA than in DNA. This RNA increase was enhancedby gibberellic acid. 4. 2-Thiouracil, 8-azaguanine, puromycin, and mitomycin C givenat the washing inhibited the subsequent growth. The effect ofthese inhibitors was not significant when they were given inthe growth period. 5. Mitomycin C reduced the basophilia of nuclei and made themswell, as did deoxyribonuclease. 6. The effect of inhibitors of nucleic acid metabolism was reversedto some extent by gibberellic acid and by kinetin. 7. Chloramphenicol inhibited the growth strongly if given inthe growing period, but not so strongly if given during thewashing. 8. An autoradiographic study using ³H-cytidine suggested thatRNA is synthesized in nucleus during the period of washing andis transferred to cytoplasm via nucleolus. It is conjectured that the RNA synthesized during the agingis responsible for the expansion growth to be caused later byauxin or auxin plus kinetin. (Received September 4, 1965; )     

Morphological Characterization of First Instar Larvae of Asian Horseshoe Crabs and their Hybrids*

The morphological characters of first instar larvae of three Asian horseshoe crabs and their hybrids were examined. For this purpose, the length of six parts on the larvae, the pattern of pigmentation, the structure of the margin of the opisthosoma, and the distribution and shape of spines on the extracardiac region of the prosoma were recorded. In general, the phenotypes of the hybrids were intermediate between those of the parents, suggesting that both male and female genomes contribute to development of the hybrids. However, there were some exceptional characters and phenotypic variations. Some characters were inherited from only one parent. This was suggested to imply that if the maternal species did not have the gene regulating expression of a given paternal character, the paternal gene did not express this character.     

EMBRYO AND ORGAN CULTURES OF THE HORSESHOE CRAB,TACHYPLEUS TRIDENTATUS*

This paper deals with some preliminary technical experiments on cultures of the embryos and organs of Tachypleus tridentatus. In embryo culture, using the embryos at various stages of development, embryonic areas with hardly any yolk remaining in them were cultured in various media and by various methods (Series A); hemispheres of embryos containing the embryonic area (Series B) and whole embryos without egg membranes (Series C) were cultured in sterilized sea water. The suitability of the culture media and methods is described; the medium containing calf serum or 199, and the hanging-drop method were found to be the most appropriate of those used in respective series of experiments. The changes in external and internal structures of the explants from embryos at various developmental stages cultured in various media and by various methods are described; dorsal closure, secretion of inner egg membrane, thickening of the cell layer and the elongation of limb buds were all observed in the Series A experiments. In Series B and C, coelom formation and also normal development of the embryos cultured after the 2nd embryonic moulting were observed. In organ culture, fragments of the embryonic heart were cultured in various media and by various methods. The hanging-drop method resulted in longer survival than the method using agar media.     

INTER AND INTRATISSUE COMMUNICATION DURING AMPHIBIAN DEVELOPMENT*

The changes of electrical communication between various tissues of the newt (Cynops pyrrhogaster) embryo during development have been investigated by measuring electrotonic potentials at various interelectrode distances. In general, cells of the same tissue are electrically coupled from gastrulation up to closure of the neural tube. Notochordal cells, however, are an exception in that cell coupling decreases during stages 22–23 in comparison to earlier stages. Neuroectoderm cells are coupled to adjacent chorda-mesoderm cells during the initial stages of gastrulation (st. 12c). Subsequently coupling of these tissues diminishes (st. 15–16) and finally disappears (st. 22–23). The similar decrease of coupling was observed in inter-tissues of the chorda-mesoderm cells and the somitic mesoderm cells during the mesodermal differentiation. In contrast, coupling values of less than 0.1 recorded between somite cells and cells of the neural tube or epidermis still remain at st. 22–23. The neural plate cells remain coupled to the lateral ectoderm cells at st. 18 and then become insulated from the epidermis by st. 22–23, even though a coupling ratio of 0.1 remains between these tissues. These developmental patterns of coupling are discussed with respect to cellular movements of neuroectoderm and mesoderm during gastrulation, and with special reference to neural competence.     

Rapid stimulation of RNA biosynthesis by auxin

Auxin stimulated the synthesis of RNA (incorporation of uracil-2-¹⁴Cinto the RNA fraction) in oat coleoptile cells in 10 min. Mitomycin C inhibited the auxin-induced elongation of segmentsof oat coleoptile and pea internode. Auxin did not affect the process of heat denaturation of isolatedpea stem DNA. Based on these experimental results the mode of action of auxinon the template activity of DNA is discussed. (Received September 10, 1968; )     

Auxin-induced growth of tuber tissue of Jerusalem artichoke VI. Biochemical changes in chromatin during aging and cell expansion

Possible mechanisms by which auxin and gibberellic acid stimulateRNA synthesis were examined, using slices excised from cold-storedtubers of Jerusalem artichoke. The ratio of DNA in nucleo non-histone to the total DNA in chromatinincreased during the aging process. On the other hand, cellexpansion did not involve this kind of change in chromosomalcomponents. Gibberellic acid and 2,4-D showed no significanteffects on the ratio of DNA in nucleo non-histone to the totalDNA in chromatin. Melting points of DNA and nucleohistone did not differ significantlyaccording to their sources, i.e. unaged, aged and growing tissues. (Received November 13, 1970; )     

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.     

Role of the pentose phosphate pathway during callus development in explants from potato tuber

Metabolic change during callus formation in explants from potatotuber (Solarium tuberosum L.) was investigated. Under the presentculture conditions, callus starts exponential growth (estimatedby the fresh weight increase) with a 5-day lag period, at whichtime marked production of DNA occurs. In the lag period, respirationis very much resistant to malonate, and the value of the C6/C1ratio and activities of both G6PDH 6PGDH pass their peaks. Onthe basis of these and relevant findings, glucose metabolismthrough the PP pathway is surmised to play a significant rolein the initial DNA multiplication phase of callus development. (Received October 15, 1969; )     

Metabolism of glucose in relation to the lipid synthesis in the fruit of Persea americana MILL.

Studies on the lipogenesis in the fruit of avocado were undertakento elucidate the metabolism of glucose relative to the lipidsynthesis as an important process. The relative participationof the pentose phosphate pathway was determined. Approximately30% of the glucose metabolized by catabolic pathways was directlyoxidized to release carbon dioxide and to provide about 50%of the total reducing power responsible for the fatty acid synthesis.Whereas carbon number 1 of glucose was incorporated into theglyceryl moiety, carbon number 6 was incorporated into the fattyacyl moiety of glycerolipids in the tissue slices of the developingfruit. From the experiments in vitro, it may be concluded that,besides glucose-6-phosphate dehydrogenase, malic enzyme andisocitrate dehydrogenase participate in the provision of NADPH₂for the fatty acid synthesis in the mesocarp of avocado fruit. ¹Present address: Department of Botany, Faculty of Agriculture,Hokkaido University, Sapporo 060, Japan (Received January 13, 1969; )