Biomedical subjects
Publications and source records attributed to L Cummins.
A theoretical model is presented that simulates the thermal effects of laser radiation incident on biological tissue. The multiple scattering and absorption of the laser beam and the thermal diffusion process in the tissue are evaluated by a numerical technique that is well suited for microcomputers. Results are compared with recent empirical observations.
Sorbitol dehydrogenase was characterized as a homogeneous protein on affinity chromatography and ion-exchange chromatography. Tests of stability, sensitivity to inhibitors, and protection by coenzyme suggest that the enzyme has essential cysteine, metal, and probably histidine. The native enzyme has a molecular weight around 140 000 and a subunit around 35 000--40 000, suggesting a tetrameric quaternary structure. Subunits are highly similar if not identical as judged by characterization of one unique 45-residue sequence containing a single reactive cysteine residue. Properties resemble those of mammalian and yeast alcohol dehydrogenases, and the sequence determined for the region around the reactive cysteine residue is homologous to that around one of the zinc-liganding cysteine residues at the active site of horse liver alcohol dehydrogenase. Sorbitol dehydrogenase thus reveals an unexpected relationship to alcohol dehydrogenases, from which ancestral connections and functional mechanisms in this group of enzymes may be further elucidated.
A strain of cytomegalovirus (CMV) was isolated during the third subcultivation of explants from the left frontal lobe of a chimpanzee that developed paralysis more than 3 years after intracerebral inoculation at birth with brain cell cultures derived from a patient with multiple sclerosis. Another strain of CMV was also isolated from a lymph node culture taken from the same chimp. The isolates, designated MZM-13 and MZM-14, produced a cytopathic effect characteristic for CMV when inoculated into brain, ganglion, or fibroblast cultures of human or simian origin. Infected cells contained characteristic Cowdry A intranuclear as well as intracytoplasmic inclusion bodies, and 100-nm spherical herpes-like virus particles were detected by electron microscopy in the nucleus and cytoplasm of infected cells. Virus was further identified as CMV with convalescent human anti-CMV serum. Complement-fixing antibody to CMV was present at a titer of 1:32 when the acutely ill chimpanzee was sacrificed. No antibody was detected at birth or at 1 or 2 years of age. A newborn chimpanzee inoculated intracerebrally with MZM-13 developed clinically asymptomatic lesions in the central nervous system characterized by acute and chronic inflammation and degeneration of myelin in cranial and spinal nerve roots. Restriction endonuclease analysis of viral deoxyribonucleic acid isolated from these two viruses indicated that MZM-13 and MZM-14 are identical and are closely related to chimpanzee CMV. No similarity in restriction endonuclease fragment patterns was found between MZM virus and the Towne and Clegg strains of human CMV.
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