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Biomedical subjects

R R Schmidt

Publications and source records attributed to R R Schmidt.

At least 127 records · Page 7Linked to original sources
PubMed1973

Purification of Synechococcus lividus by equilibrium centrifugation and its synchronization by differential centrifugation.

A culture of the thermophilic, unicellular, blue-green alga Synechococcus lividus was freed from two thermophilic bacteria by use of equilibrium (isopycnic) centrifugation in Ficoll density gradients. After removal of the bacteria, the alga would grow only on agar plates in a high carbon dioxide atmosphere. Intermittent illumination, equilibrium centrifugation, and differential centrifugation were tested as techniques for obtaining synchronized cultures of the alga. Daughter cells selected by differential centrifugation in Ficoll density gradients yielded the best synchrony, and a cross-wall index of 85% was observed during the period of cell division.

Agar↗
PubMed1968

Continuous-dilution method for the mass culture of synchronized cells.

A new mass-culturing technique for synchronized cells is described. Continuous dilution with fresh culture medium provides the cells with nearly constant environmental conditions (continuous resupply of nutrients, constant adjustment of pH, maintenance of a nearly constant cell mass-to-culture volume ratio, etc.) at high cell densities, thereby resulting in the yield of ample cellular material for most biochemical studies during the cell cycle. The new mass-culturing system, when utilized to culture synchronous Chlorella pyrenoidosa, yielded approximately three times as much cellular material as a previous nondilution method, in the same time period and in less than one-tenth the culture volume. Although the newly developed mass-culture method was tested with a unicellular green alga, the basic method should be readily adaptable to synchronous cultures of other microorganisms and to cells in tissue culture.

Cell Division↗
PubMed1966

Determination of free ammonium and asparagine and glutamine amide-nitrogen in extracts of plant tissue.

A relatively simple and rapid procedure for the measurement of free ammonium and the amides in plant extracts is described. The method was developed by combining a cation-exchange method for blood ammonia with a differential acid-hydrolysis procedure for asparagine and glutamine amide-nitrogen. The recovery of standard samples (100-400 mug of ammonium- or amide-nitrogen) of free ammonium, asparagine, and glutamine after being run through the extraction, column, and analytical procedures ranged between 99 and 102%. The harvest, extraction, and analytical procedures were tested on shoots from 4 to 6-day-old germinating barley seeds. The high levels of the amides and the low level of free ammonium present in the tissue extracts indicated that the extraction and analytical procedures resulted in little if any hydrolysis of the amides.

Amides↗