Biomedical subjects
Publications and source records attributed to M M Hammond.
Measurements of radioactive noble gases are routinely made with gamma-ray spectrometers. This work describes the calibration of high purity germanium detectors provided by the full-energy-peak efficiency as a function of the gamma-ray energy. A comparison of measured efficiency values with a new, simplified method based on a direct mathematical method is given here.
Efficiency calibrations of multiple high-purity germanium (HPGe) detectors are being maintained at the National Institute of Standards and Technology (NIST). Four generally available software packages for HPGe detector gamma-ray spectrum analysis, including the one currently used at NIST, were tested on spectra collected from two HPGe detectors at different source-to-detector distances and using point sources and ampoules as calibration geometries. The resulting efficiency curves were inter-compared.
The aerotolerant, anaerobic parasite Giardia lamblia, which depends solely upon salvage pathways for its pyrimidine requirements, was found to transport uridine, cytidine, and thymidine by a carrier mediated mechanism. Support for this conclusion comes from the facts that uptake of radiolabeled uridine, cytidine, and thymidine exhibited saturation kinetics, and uptake of these same radiolabeled nucleosides was inhibited by unlabeled homologs, certain pyrimidine analogs, iodoacetate, and N-ethylmaleimide. Uridine and cytidine (perhaps uracil and cytosine also) are postulated to be transported at a common site which is distinct from the site for thymidine transport. Thymidine does appear to bind nonproductively to the uridine/cytidine transport site, but the reverse of this does not appear to occur.
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An electron microscopic study was carried out on specimens of feces and intestinal contents from cases of canine gastroenteritis submitted to the Diagnostic Laboratory, New York State College of Veterinary Medicine, during 1979-1981. The majority of samples came from New York State and the Northeast with no marked shift in distribution over the three year period. Canine parvovirus was the major virus identified. In August and September 1980 there was an epidemic of canine gastroenteritis, with 247 samples received during this two month period alone, of which 48 percent were positive for canine parvovirus. Almost half of the total number of specimens examined were from dogs less than 6 months of age and well over 50 percent of these were parvovirus positive. In addition to canine parvovirus, three cases of coronavirus, two cases of rota-like virus and one case of astro-like virus were detected. Three dual infections with canine parvovirus and rota or astro-like virus were also confirmed. An unidentified virus-like particle with cubic symmetry was found in two specimens. The adoption of immunoelectron microscopy for the detection of canine parvovirus in March 1980 facilitated identification of this virus and greatly increased the sensitivity of the technique.