Light-dependent oxygen uptake by non-living, chlorophyll-containing particles obtained from oceanic environments

Chlorophyll-containing, non-living particles obtained from oceanicenvironments showed a light-dependent oxygen uptake reaction.Activity was found in marine samples rich in diatom cells andcell fragments, though particles originating from dinoflagellatesshowed only insignificant activity. The same reaction was seenin sonic-disrupted and washed cell fragments of cultured Phaeodactylumtricomutum. The reaction did not require extra electron donors or electroncarriers, even in particles washed thoroughly with buffer. Add-backof the soluble fraction had no effect. The action spectrum ofthe reaction indicated that only light absorbed by chlorophyllswas effective though the sample also contained carotenoids. Based on the data obtained we inferred that the O₂ uptake reactionis the same as that caused by the action of isolated chlorophyllsand, that a water-insoluble compound(s) contained in the samplesserved as electron donor. A possible contribution of this reactionto the O₂ economy in oceanic environments is discussed. (Received January 30, 1971; )     

DNA CONTENTS IN PURKINJE CELLS AND INNER GRANULE NEURONS IN THE DEVELOPING RAT CEREBELLUM

Cytophotometric studies revealed that the content of Feulgen DNA in Purkinje cells in the developing rat cerebellum remains at the diploid level throughout the postnatal life. No evidence was found to suggest resumption of DNA synthesis in the neurons. This finding is in accord with autoradiographic observations that neuroblasts once differentiated from matrix cells do not synthesize DNA nor divide again.     

Growth of Notochord and Formation of Cranial and Mesencephalic Flexures in Chicken Embryo

The proliferative activity of notochordal cells, neuroepithelial cells and endodermal cells in the chicken embryo is examined during flexure formation along its long axis by using bromodeoxyuridine (BrdU)-immunohistochemistry.
White Leghorn chicken embryos, Hamburger and Hamilton stages from 9 to 15 are cumulatively labled with BrdU for 120 min and fixed with Carnoy's fluid. Serial transverse and sagittal sections are immunostained with a monoclonal anti-BrdU antibody. The distribution of labeled and unlabeled cells is determined on various regions of the embryos.
Before and during the external flexure development from state 10 to 14, the labeled cells are virtually absent at two regions; The cranial region including the floor of the prosencephalon and pharynx close to the pre-chordal plate and the mesencephalic region comprising the mesencephalic notochord and mid-ventral side of the mesencephalon. At stages 10 and 11, the cranial and mesencephalic flexure become apparent at the respective unlabeled regions. It is concluded that the regional differences in proliferative activity between the notochord, neural tube and endoderm play a causal role in the flexure formation of early morphogenesis in the embryo.