Charles T. Gregg

Substantial replacement of mammalian body carbon with carbon-13

Abstract Administration to weanling mice of a diet in which the digestible carbon fraction averaged 80 atom % carbon-13 led to an average tissue content of 60 atom % carbon-13 with little change in overall enrichment between 127 and 234 days of feeding. Urine and feces rapidly attained an isotopic steady state (in 7 days or less). The mice appeared to be in normal health throughout the experiment, and subsequently necropsy and microscopic examination of tissues revealed no abnormalities clearly attributable to the high isotopic enrichment.

Large-scale photosynthetic production of carbon-13 labeled sugars: The tobacco leaf system

Abstract A system is described for the production of carbon-13 uniformly labeled starch, glucose, fructose, and sucrose from kilogram quantities of tobacco leaves. Nearly 60% of the CO 2 administered (at 80 atom % carbon-13 or above) was found in these four compounds; the loss of enrichment between carbon-13 administered and isolated sugars was 3% or less. About 25 g 13 C-glucose can be produced in a 40-hr incubation from 1.2 kg of leaves. Label uniformity in the products was established by 13 C-nmr spectroscopy.

The effects of carbon-13 incorporation into preimplantation mouse embryos on development before and after implantation

Abstract Preimplantation mouse embryos were cultured in vitro for 48 hours from the 8-cell to the blastocyst stage in media containing uniformly labelled 13 C-glucose. The 13 C content of the blastocysts was 20 atom % according to incorporation studies with 14 C-glucose. No embryotoxic effects of carbon-13 incorporation could be detected on the basis of these criteria of normal development: the percentage of embryos reaching the blastocyst stage during the culture period; the number of cells in these blastocysts; and the development after transplantation to pseudopregnant foster mothers.

Effects of uncouplers of oxidative phosphorylation on the infection of Escherichia coli K12 by phage-λ DNA☆

Abstract Some effects of two uncouplers of oxidative phosphorylation on infection of Escherichia coli K12 by bacteriophage λ deoxyribonucleic acid (DNA) are described. Dinitrophenol did not interfere with the initial interaction of the cells with free DNA, and neither dinitrophenol nor carbonyl cyanide m -chlorophenylhydrazone affected the linear portion of the infection reaction. However, the process by which λ-DNA bound to the bacterial cell became insensitive to deoxyribonuclease was strongly inhibited by both uncoupling agents. These results support the conclusion that successful infection of E. coli with phage λ-DNA is coupled to cellular energy metabolism and localize a portion of the infection reaction which is sensitive to the uncoupling of oxidative phosphorylation. Possible energy-requiring steps in the infection process are discussed.

Multiparameter Light Scattering for Rapid Virus Identification

Multiparameter light scattering (MLS) is a term we have used to describe the simultaneous measurement of multiple elements of the Mueller matrix at specific wavelengths and scattering angles. This 4 Χ 4 matrix describes the polarization sensitive transformation of an incident beam of light into a scattered beam of light by a scattering object such as a virus or suspension of virus particles. The Mueller matrix contains a great deal of information about the internal structure and shape of the virus particle. This information is sufficient in many cases to enable discrimination among a wide variety of different viruses of clinical significance.