Biomedical subjects
Publications and source records attributed to G S Edwards.
Airborne N-nitrosomorpholine (0 to 27 micrograms per cubic meter) was found in two of four rubber industry factories. N-Nitrosodimethylamine was also found in two factories, but at lower levels. These findings may be relevant to the reported increased risk of certain types of cancer in rubber workers in some of the same areas where the N-nitrosomorpholine levels were highest.
In vivo nitrosation of dimethylamine by nitrite was measured with an intrahepatic host-mediated mutagenicity assay using Salmonella typhimurium as the detecting organism. It was possible to detect the product, N-nitrosodimethylamine, at much lower doses with this system than with previously reported in vivo systems. This and other improvements made it possible to detect the formation of nitrosodimethylamine from relatively low levels of gavaged precursors.
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Fish liver postmitochondrial supernatant preparations in the presence of carbon monoxide were used to prepare purified aflatoxicol from aflatoxin B1 in high yield (23-38%). Such fish liver postmitochondrial and postmicrosomal supernatant preparations were five to ten times more active in making aflatoxicol than rat or human liver preparations under the same conditions.
1. Using dog liver microsomal preparations, we have isolated and identified a new metabolite of aflatoxicol, aflatoxicol M1; this metabolic transformation is analogous to the conversion of aflatoxin B1 to aflatoxin M1. 2. Aflatoxicol M1 can also be produced from aflatoxin M1 by a reductase present in rabbit liver cytosol, a reaction analogous to the reduction of aflatoxin B1 to aflatoxicol. 3. In addition, aflatoxicol M1 can be oxidized to aflatoxin M1 by a carbon monoxide-insensitive dehydrogenase activity associated with human liver microsomes, a reaction analogous to the production of aflatoxin B1 from aflatoxicol by this fraction. 4. Ultra-violet, fluorescence, and mass spectral characteristics of aflatoxicol M1 are described. 5. The significance of this new aflatoxin metabolite and the possibility that it may be biologically active are discussed.
The metabolism of [14C]aflatoxicol by liver postmitochondrial and microsomal fractions from humans and eight other species was compared. A major metabolic pathway involves the dehydrogenation of aflatoxicol yielding aflatoxin B1. Human liver preparations were more active in this regard than preparations from any of the other species tested. The aflatoxicol dehydrogenase activity was mainly associated with the microsomal fraction and required a hydrogen acceptor (e.g., nicotinamide adenine dinucleotide phosphate), but was not inhibited by carbon monoxide, which implies that it was not dependent on the heme-containing microsomal drug-metabolizing system. It had a pH optimum of 8.0. Postmitochondrial liver fractions also oxidized aflatoxicol (and/or the aflatoxin B1 made from it) to at least five other metabolites that comigrated on thin-layer chromatography plates with authentic standards of aflatoxins Q1,P1,H1,M1, and B2a. None of these oxidative metabolites were formed in the presence of carbon monoxide. We also report on the in vitro reduction of aflatoxin B1 to aflatoxicol by the cytosol fractions from eight species. Most active in this regard were rabbit and trout preparations, while this activity was almost absent in the guinea pig. Preparations from humans and four other species were intermediate between these extremes.
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Ankle diastasis without associated fracture occurs in a latent form in which the diastasis is detected only by stress radiographs, and in a frank form with the diastasis visible on routine, unstressed radiographs. Whereas latent ankle diastasis requires no reduction and can be treated by cast immobilization, frank diastasis requires anatomical reduction of the ankle mortise. The method of reduction depends upon the particular type of frank diastasis. We have identified four types of frank ankle diastasis without fracture. Type I injuries demonstrate straight lateral fibular subluxation without plastic deformation of the fibula and are best treated by open reduction, removal of any interposed soft tissue, and stabilization with a tibiofibular screw. Type II injuries present with straight lateral subluxation of the fibula due to plastic deformation of the distal fibula and may require a fibular osteotomy for reduction prior to internal fixation. Plastic deformation of the fibula as a cause of ankle diastasis has not been previously reported. The uncommon type III injury consists of posterior rotatory subluxation of the fibula. In type IV injuries the talus is dislocated superiorly, resulting in divergence of the tibia and fibula. Type III and IV injuries can usually be treated by closed manipulation and plaster immobilization. The authors treated four type I and two type II patients by open reduction and internal fixation. Both type II injuries required fibular osteotomy to restore the normal tibiofibular relationship. Good results were obtained in four patients. Fair results secondary to stiffness and pain on activity were present in two patients. All patients maintained anatomical reduction of the ankle mortise following removal of the tibiofibular screw.
Free-Electron Lasers (FELs) collectively operate from the terahertz through the ultraviolet range and via intracavity Compton backscattering into the X-ray and gamma-ray regimes. FELs are continuously tunable and can provide optical powers, pulse structures and polarizations that are not matched by conventional lasers. Representative research in the biological and biomedical sciences and condensed matter and material research are described to illustrate the breadth and impact of FEL applications. These include terahertz dynamics in materials far from equilibrium, infrared nonlinear vibrational spectroscopy to investigate dynamical processes in condensed-phase systems, infrared resonant-enhanced multiphoton ionization for gas-phase spectroscopy and spectrometry, infrared matrix-assisted laser-desorption-ionization and infrared matrix-assisted pulsed laser evaporation for analysis and processing of organic materials, human neurosurgery and ophthalmic surgery using a medical infrared FEL and ultraviolet photoemission electron microscopy for nanoscale characterization of materials and nanoscale phenomena. The ongoing development of ultraviolet and X-ray FELs are discussed in terms of future opportunities for applications research.