Search PubMed⌕ Search

Biomedical subjects

J R Cook

Publications and source records attributed to J R Cook.

154 records · Page 9Linked to original sources
PubMed1966

Photosynthetic activity during the division cycle in synchronized Euglena gracilis.

Axenic populations of the photosynthetic protozoan Euglena gracilis, grown with autotrophic nutrition, were synchronized with respect to cell division by culture on an alternating light-dark cycle. No cell divisions occurred in the light periods; approximately 100% of the cells divided in the dark periods. In such cultures, the synthesis of photosynthetic pigments and accumulation of polysaccharide were confined to the light periods. The capacity for photosynthesis, however, increased continuously over the entire light-dark cycle, and is thus not directly correlated with pigment content. A correlation was seen between photosynthetic capacity and protein content, suggesting that enzymatic mechanisms of the photosynthetic apparatus might be the limiting factor. Estimates of total photosynthetic activity indicate that about 5 x 10(-6) calories are required for the synthesis of a new cell.

Animals↗
PubMedDate not supplied

A double-label technique that monitors sulfur mustard damage to nuclei and mitochondria of normal human epidermal keratinocytes in vitro.

Sulfur mustard and 2-chloro ethyl ethyl sulfide (CEES, a sulfur mustard analog) is known to have immediate (minutes), long-term (hours to days), and toxic effects on human skin. Research was directed toward developing a single in vitro assay that might reflect both these short-term and long-term effects of this vesicating agent on normal human epidermal keratinocytes (NHEK) in vitro. Such an assay system would be useful in identifying and developing sulfur mustard therapeutic agents. NHEK were exposed to the monofunctional sulfur mustard analog 2-chloro ethyl ethyl sulfide for a variety of times. The effects of CEES on NHEK nuclei were assessed using the membrane-permeable SYTO nuclear stains, whereas the effects of CEES on NHEK metabolism were determined by using the nontoxic mitochondria dye Alamar blue. CEES enhanced SYTO binding in a concentration-dependent manner to the nucleus immediately subsequent to a 2-hr exposure, whereas CEES had relatively little effect on metabolic activity at this time. Fifteen to 36 hr subsequent to CEES exposure, however, Alamar blue revealed a robust, sulfur mustard-dependent effect on mitochondrial activity. To determine if both these indicator dyes could be used simultaneously, NHEK were exposed to CEES and stained with the SYTO nuclear stain 2 hr subsequent to exposure. This procedure was followed by assay of the same cell cultures with Alamar blue at 36 hr subsequent to initial CEES exposure. The data indicate that this nuclear/mitochondrial double-label technique can be used to monitor the short- and long-term effects of sulfur mustard on the same culture of NHEK.

Cell Nucleus↗