The light-dependent incorporation of NaH(14)CO3 into low molecular weight compounds, polysaccharide, or protein was determined in cultures of the cyanobacteriumMerismopedia tenuissima incubated at a series of light intensities. There was an inverse relationship between incorporation into polysaccharide and protein. At light intensities of 90 μE/m(2)/sec or above, relative incorporation of radioisotope into polysaccharide was greatest and relative incorporation into protein was lowest. Optimal relative protein accumulation occurred in samples incubated at 20 μE/m(2)/sec. A broader optimum of light intensity for maximal protein accumulation was found if ammonia rather than nitrate was the nitrogen source. Physiological adaptation of cultures to growth at a particular light intensity did not alter the pattern of macromolecular incorporation when those cultures were tested over the series of light intensities. The response of cultures ofOscillatoria rubescens to light intensity was similar to that ofM. tenuissima, although incorporation into low molecular weight compounds was significantly greater.The effect of light intensity on macromolecular synthesis in a natural population ofOscillatoria rubescens was also determined. A pattern similar to that observed in batch cultures ofO. rubescens was occasionally found, but in other experiments there was no increase in relative protein incorporation when light intensity was decreased.
Continuous cultures of Merismopedia tenuissima Lemmerman, limited by phosphorus, nitrogen, sulfur, or carbon, were compared to non limited batch cultures by two methods. The cellular content of photosynthetic pigments (chlorophyll and phycocyanin) was found to decrease in all nutrient limited cultures, except for the carbon limited culture. The ratio of carbohydrate to protein was 4‐ to 7‐fold higher in P, N or S limited cultures than in non‐limited or C limited cultures. The macromolecular products of photosynthesis were determined in samples to which NaH14CO3 was added. Relative incorporation into protein decreased in P or N limited cultures, increased accumulation of low molecular weight compounds was found in S and P limited cultures, and little change was noted in C limited cultures as compared to non‐limited cultures. Although relative incorporation into protein was significantly greater at 20μEin·m−2·s−1 light intensity than at 180 μEin·m−2.s−1 in non‐limited cultures, this effect was abolished in all nutrient limited cultures. These results suggest that measurement of the cellular carbohydrate to protein ratio and the products of photosynthesis would be useful in the analysis of algal population dynamics in nature.
Previous studies demonstrated that the formamidine pesticide chlordimeform (CDM) reversibly inhibited prostaglandin biosynthesis and prevented the late (PG-mediated) phase of carrageenin-induced hind paw edema. This study emphasizes antagonism by CDM of the early (5HT and histamine-mediated) phase of carrageenin edema. CDM and cyproheptadine both antagonized paw edema induced by albumin (5HT and histamine-mediated) and by the direct injection of 5HT and histamine, whereas aspirin and the PG antagonist, SC-19220, were ineffective. As expected, cyproheptadine selectively reduced the early phase, whereas aspirin and SC-19220 selectively reduced the late phase of carrageenin-induced edema. These results are thus consistent with earlier studies demonstrating PG mediation of the late phase of carrageenin edema, and 5HT and histamine mediation of albumin edema and the early phase of carrageenin edema. In addition, they indicate that CDM possesses multiple acute anti-inflammatory actions not exhibited by aspirin, by SC-19220 or by cyproheptadine alone.
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