Flagellate Used In DNA Study

Euglena gracille, a simple, one-celled organism--used in the laboratory to measure the level of vitamin B-12 in the blood of anemic patients--is now being employed in studies to determine the effect of metal deficiencies on nucleic acid and protein metabolism.

Normally found in ponds, the flagellate forms chloroplasts and carries on photosynthesis when exposed to light. It requires vitamin B for growth.

Dr. Warren Wacker, associate in Medicine in the Biophysics Research Laboratory of the Harvard Medical School, recently described his studies on the organism at the 46th annual meeting of the Federation of American Socities for Experimental Biology.

Dr. Wacker reported that the organism--grown either in light or in darkness--develops "profound and complex lesions" when the growth medium is deficient in the trace metal, zinc. Under such conditions, Dr. Walker noted, growth was severely limited and cell division was halted. The cell size increased eight-fold under conditions of extreme zinc deficiency.

"The result," Dr. Wacker said, "was a doubling of the DNA [deoxyribonucleic acid] in the nucleus of the cell [a process that precedes normal cell division] although the RNA [ribonucleic acid] content of the cell was markedly reduced along with protein and zinc."

Mitotic Arrest

"This indicates," Dr. Wacker pointed out, "that there is mitotic arrest and a block in both RNA and protein synthesis resulting from zinc deficiency--a condition that is not reversed when other trace metals [iron, manganese, copper, magnesium and calcium] metabolic precursors or metabolites, are added to the nutrient solution in which the organism is grown.

"Apparently," Dr. Wacker concluded, "zinc may be required to maintain the functional and structural integrity of euglena RNA."

Dr. Warren Wacker, associate in Medicine in the Biophysics Research Laboratory of the Harvard Medical School, recently described his studies on the organism at the 46th annual meeting of the Federation of American Socities for Experimental Biology.

Dr. Wacker reported that the organism--grown either in light or in darkness--develops "profound and complex lesions" when the growth medium is deficient in the trace metal, zinc. Under such conditions, Dr. Walker noted, growth was severely limited and cell division was halted. The cell size increased eight-fold under conditions of extreme zinc deficiency.

"The result," Dr. Wacker said, "was a doubling of the DNA [deoxyribonucleic acid] in the nucleus of the cell [a process that precedes normal cell division] although the RNA [ribonucleic acid] content of the cell was markedly reduced along with protein and zinc."

Mitotic Arrest

"This indicates," Dr. Wacker pointed out, "that there is mitotic arrest and a block in both RNA and protein synthesis resulting from zinc deficiency--a condition that is not reversed when other trace metals [iron, manganese, copper, magnesium and calcium] metabolic precursors or metabolites, are added to the nutrient solution in which the organism is grown.

"Apparently," Dr. Wacker concluded, "zinc may be required to maintain the functional and structural integrity of euglena RNA."