. Chemical embryology. Embryology. I050 CARBOHYDRATE METABOLISM [PT. Ill From this they concluded that lactic acid was formed normally by the developing sea-urchin's egg, and that if its oxidation was in- hibited it accumulated as in all other cells. There was a hint of more rapid formation after fertilisation. It will be recalled that Meyerhof in 1911 (see the Section on Respiration) did not succeed in demon- strating any glycogen or free glucose in unfertiHsed Strongylocentrotus eggs, but that Matthews in 1913 (see the Section on Constitution) had found a Hpoid in Arbacia eggs which containe
. Chemical embryology. Embryology. I050 CARBOHYDRATE METABOLISM [PT. Ill From this they concluded that lactic acid was formed normally by the developing sea-urchin's egg, and that if its oxidation was in- hibited it accumulated as in all other cells. There was a hint of more rapid formation after fertilisation. It will be recalled that Meyerhof in 1911 (see the Section on Respiration) did not succeed in demon- strating any glycogen or free glucose in unfertiHsed Strongylocentrotus eggs, but that Matthews in 1913 (see the Section on Constitution) had found a Hpoid in Arbacia eggs which contained sugar. In 1927 by improved methods Blanchard did demonstrate the presence of traces of glycogen in Arbacia eggs, though not the minutest amount of free glucose. Perlzweig & Barron determined to estimate the total carbohydrate in the eggs before fertilisation, and, using much the same technique as in Needham's studies on the frog, they found about 50 mgm. of glucose per gram of egg protein. It is probable, there- fore, that the major part of the carbohydrate in Arbacia eggs is present as a mucoid. As has already been indicated in the Section on Energetics, re- spiratory quotients closely ap- proaching unity have frequently been obtained during the cleavage stages of echinoderm eggs. Barron has recently been able to fertilise Arbacia, Asterias and Nereis eggs in strictly anaerobic conditions, a finding which suggests carbohydrate metabolism (see p. 758), the cells piling up an oxygen debt. More- over, direct measurements of glycolysis rate have been made by Ashbel on Paracentrotus eggs: revealing an augmentation of on fertilisation. One mgm. of tgg nitrogen produced 0-845 rngm- of carbon dioxide per hour from the glucose mixture before fertilisation and 2-32 afterwards. It would be still more interesting to compare this with that of later stages up to the free-swimming pluteus (cf Section 4-20).. Fig. Please note that these images are extracted from scan
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Keywords: ., bookcentury1900, bookpublishernewyorkthem, booksubjectembryology
