BIOSYNTHESIS OF COLLAGEN AND NON-COLLAGEN PROTEIN DURING DEVELOPMENT OF THE CHICK CORNEA

The relationship between the rates of increase of corneal protein fractions and incorporation of labeled precursors has been examined during embryonic and early posthatching development of the chick corneal stroma. Non-collagen protein increased gradually from 9 through 20 days of incubation. Collagen accumulated approximately logarithmically through the 19th day, the most rapid rate occurring between 13 and 20 days of incubation. The rates at which labeled amino acids are incorporated into collagen in vivo and in vitro undergo marked changes during the last week of embryonic development, corresponding closely to the rate of collagen accumulation in vivo; whereas incorporation into non-collagen protein changes much less markedly. Changes in the rate of incorporation of precursors into collagen are not due to changes in the rate of conversion of collagen from the soluble to insoluble form, or to changes in the endogenous amino acid pool size. Chick embryo corneal stroma collagen turns over very slowly, if at all. Non-collagen protein turns over more rapidly. An increase in cell number, as indicated by DNA content, does not account for the increased rate of collagen synthesis between the 9th and 16th day of incubation. It is concluded that the observed changes in collagen synthesis reflect changing activities in the individual cornea fibroblasts. These activities are comparable in the intact tissue in vivo and in isolated corneas in vitro.     

Untersuchungen über die regionalen Potenzen der Neuralleiste zur Bildung von Melanoblasten bei der Hausente (Anas domestica)

Ohne ZusammenfassungDie Untersuchungen wurden während des Aufenthaltes am Hubrecht-Laboratorium in Utrecht (Holland) anläßlich des Second International Teamwork begonnen und am Zoologischen Institut der Universität Köln fortgesetzt. — Zur Durchführung der Untersuchungen standen Mittel der Deutschen Forschungsgemeinschaft zur Verfügung. — Teil der von der Math.-Naturwissenschaftlichen Fakultät der Universität zu Köln angenommenen Habilitationsschrift.     

Ein Beitrag zur Biosynthese und Physiologie von Kaffein und Trigonellin beiCoffea arabica

Summary Whole young plants were allowed to fix photosynthetically C¹⁴O₂ for 12 hours. The absolute amount and the specific activity of trigonelline, caffeine and glucose in developing and adult leaves were subsequently determined during up to five weeks. There is a rapid incorporation of photosynthetically fixed carbon into trigonelline in both developing and adult leaves. The specific activity of caffeine however increases to any extent only in young developing leaves. It can be concluded that both trigonelline and caffeine are synthesized in leaves ofCoffea arabica. Other problems of the metabolism and translocation of the two substances are discussed.

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