Metabolism of free amino acids, peptides and proteins in early sea urchin development

Abstract

ELEVEN FIGURESThe first study of developmental changes in chemical composition of sea urchin embryos was carried out by Ephrussi and Rapkine in 1928. Relative to the unfertilized eggs of Paracentrotus lividus their figures show that a loss of 4.4% total nitrogen ( N ) , 3470 carbohydrate and 24% lipid occurred in development to the pluteus stage. Hayes ('34) found the total N of Echinometra lucunter to decrease 24% and the free amino N to decrease 11% in development from the 4-hour blastula to the late prism stage. On the other hand, Horowitz ('39) found the total N of the gephyrean worm Urechis caupo to remain practically constant in development to the 24-hour trochophore although an 8.4% decrease occurred by the 30th hour. An important feature of EIorowitz's work is that his assay results were related to one another by counting the number of embryos used, rather than by determinations of dry weight, centrifuged volume or total N (see also Hayes, '38).

The Mitotic Apparatus

“…These eggs have a diameter of 80 tt, as compared with 74 # for A. punctulata, and have a correspondingly larger amount of protein per egg, since the number of eggs in a given volume is smaller. Leitch (28) reported two values from determinations of Kjeldahl nitrogen, which average to 4.3 X 10 -5 nag of protein per egg, and Kavanau's extensive measurements on the free and protein-bound amino acids in this egg (24) can be recalculated to give another measure of protein per egg. Excluding the values for free amino acids and using an average residue weight of 115, his results give a value of 4.7 X 10 -5 mg of protein per egg.…”

Synthesis of Spindle-Associated Proteins in Early Cleavage

“…Some results from these experiments are shown in Table I. Using Kavanau's (1953) data for the valine content of total egg proteins in Strongylocentrotus purpuratus, we compute minimum turnover These values are certainly not in agreement with the observation that the isolated metaphase figure contains 12 per cent of the total protein, if one assumes that the isolated MA is composed entirely of mitotic machinery. But the electron microscope reveals that the fibrous component of the MA accounts for only a small fraction of its volume (Gross et al, 1958;Harris, 1962).…”

“…roy, 1958; Hultin, 1961;Gross and Cousineau, 1963 a). There is, however, no net increase in protein during early development; on the contrary, total protein declines (Kavanau, 1953). The synthesis of some protein or proteins is essential to division, since treatment of the fertilized eggs with Puromycin blocks amino acid incorporation and mitosis in any cleavage cycle (Hultin, 1961).…”

“…This value was obtained from analysis of the isolated MA. It may also be recalled that total protein declines somewhat during early development (Kavanau, 1953;Gustafson and Hjelte, 1951 ).…”

Experimentelle Untersuchungen zur Salzadaptation verschiedener Rassen des Dreistachligen Stichlings (Gasterosteus aculeatus L.)

“…Die allgemeinen Vorstellungen von den Reaktionswegen und den Wechselbeziehungen im intermediaren Stoffwechsel lieljen schon friih auf ein Vorkommen inter-und intrazelluliirer, nicht proteingebundener Aminosauren schlieBen. Die Existenz dieser als ,,freie Aminosauren'' bezeichneten Substanzen konnte inzwischen durch zahlreiche Beobachtungen und Analysen nachgewiesen werden (KAVANAU, 1953;FLORKIN, 1956;FLORKIN etal., 1964;POTTS, 1958;SCHOFFENIELS, 1960;ANDERS et al, 1960ANDERS et al, -1965DUCHATEAU-BOSSON et al, 1961;JEUNIAUX et al, 1961;AWAPARA, 1962;STEITZ, 1963;VIRKAR, 1965;KRISHNAMOORTHI and KRISHNASWAMY, 1965;CLARK 1968 a, b u. a.).…”