Clupeid Response to Stressors: The Influence of Environmental Factors on Thiaminase Expression

Abstract

Over the past five decades, a reproductive failure related to thiamine deficiency, referred to as thiamine deficiency complex (TDC), has been observed in valuable salmonine fishes in the Great Lakes and Finger Lakes in North America and the Baltic Sea in Europe. The cause of TDC has been linked to the consumption of clupeid fish, which contain high levels of a thiamine-destroying enzyme called thiaminase I (hereafter referred to as “thiaminase”). High activities of thiaminase have been reported from clupeids such as Alewife Alosa pseudoharengus, Gizzard Shad Dorosoma cepedianum and Atlantic (Baltic) Herring Clupea harengus, but no consistent explanation has accounted for the wide range of observed variation in levels of thiaminase in clupeids. Chronic stress can suppress the immune systems of Alewife and other fishes, thereby reducing the number of circulating white blood cells available to suppress bacteria. Because the presence of thiaminase has been associated with thiaminolytic bacteria isolated from Alewife viscera, we hypothesized that stressful conditions, which can potentially limit clupeid immune response or alter internal physiological conditions, could allow for thiaminase to be produced more efficiently by bacteria or thiaminolytic bacteria could proliferate, or both events could occur, resulting in a subsequent increase in thiaminolytic activity. In this study, Alewives and Gizzard Shad were exposed to severe winter temperatures and low food availability, respectively, in replicated pond experiments to evaluate the influence of stressful conditions on clupeid thiaminase activity. Though responses in circulating white blood cell counts and metrics of fish condition indicated that experimental treatments affected these clupeids, these effects were not related to increased thiaminase activity. The only significant treatment effect on clupeid thiaminase was an increase in mean thiaminase activity in Gizzard Shad from ponds where only high quality energy sources were available. These data indicate that variability in clupeid thiaminase may be related to diet composition.

Received June 19, 2012; accepted January 15, 2013     

Occupational per-patient radiation dose from a conservative protocol for veterinary (18) F-fluorodeoxyglucose positron emission tomography

The occupational external radiation dose to human medical personnel from positron emission tomography (PET) radiopharmaceuticals has been documented, but to date no corresponding veterinary staff dose data are available. Electronic personal dosimeters (EPDs) were used in this study to measure the per-patient external radiation doses to veterinary staff using a PET/CT (PET combined with computed tomography) protocol in which the patient radiopharmaceutical dose was injected after anesthetic induction. Radiation doses were recorded for the nuclear medicine technologists, the on-duty anesthesiology technologist, and an occasional observer from 19 veterinary (18) F-fluorodeoxyglucose PET/CT studies. Patient mass range was 2.8 to 61.0 kg (22.3 kg mean) and injected activity averaged 6 MBq kg(-1) . The dose range received by nuclear medicine technologists per procedure was 0-30 μSv (9.1 μSv mean), by anesthetists 1-22 μSv (8.2 μSv mean), and by the observer 0-2 μSv (0.5 μSv mean). In both feline and canine studies, placement of the EPD on staff was a significant predictor of radiation dose. Additional significant predictors of staff radiation dose from canine studies included job position and injected activity. The per-patient occupational radiation doses to veterinary PET/CT technologists were slightly greater than those reported for human nuclear medicine PET/CT technologists, but were comparable to estimated radiation doses for nurses caring for nonambulatory human PET/CT patients. Efforts toward maintaining staff radiation doses as low as reasonably achievable (ALARA) will be important as veterinary PET/CT caseload increases.     

A new collection of wild populations of Capsicum in Mexico and the southern United States

An exploration and collection mission for wild populations of Capsicum was carried out in the fall of 2006 and 2007, in 13 Mexican states and in the U.S. states of Arizona and Texas. The aim of this collection was to expand the number of accessions of wild chile pepper (Capsicum annuum var. glabriusculum and Capsicum frutescens) that are publicly available for research in plant improvement and for subsequent use in an inquiry into the domestication of C. annuum. While Mexico and the United States National Plant Germplasm System both have germplasm repositories INIFAP—Instituto Nacional de Investigaciones Forestales—Agrícolas y Pecuarias and USDA GRIN—United States Department of Agriculture’s Genetic Resources Information Network) with accessions of C. annuum var. glabriusculum, the very limited number available, their age, and/or validity of the information attached to many accessions do not allow for extensive research. Four hundred and sixty-six plants were sampled over two field seasons, of which copies of the collection reside in both UAA and at UC Davis. Given the current environment with the intellectual property of varieties of crop plants and, particularly, the extreme restrictions affecting explorations and the official procuring and sharing of germplasm across national borders, this U.S.—Mexico collaboration is one of the few examples of joint U.S.—Mexico germplasm collection efforts.     

Retrospective Review of 50 Canine Intracranial Tumors Evaluated by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) was performed on 50 dogs with intracranial neoplasia. The following tumor features were assessed: axial origin, location, shape, growth pattern, MRI signal intensity, evidence for edema, and paramagnetic contrast enhancement. Histologic diagnoses included 5 intracranially invading nasal tumors, 7 pituitary tumors, 22 meningiomas, 6 choroid plexus tumors, 7 astrocytomas, 1 ependymoma, and 2 oligodendrogliomas. Axial origin, site, shape, and growth pattern were important diagnostic characteristics for tumor type. Signal intensity and contrast enhancement pattern allowed further differentiation. Characteristic MRI features that facilitate diagnosis and prognosis were identified. Accurate diagnosis of tumor type based on these features was not always possible because of similarities in MRI appearance for some tumors. Tissue biopsy remains necessary for definitive diagnosis of intracranial tumors.     

MR, CT AND CLINICAL FEATURES FROM FOUR DOGS WITH NASAL TUMORS INVOLVING THE ROSTRAL CEREBRUM

The clinical findings and computed tomographic and magnetic resonance images from four dogs with nasal tumors that invaded the central nervous system were revlewed. There were minimal or no clinical signs related to nasal disease. Brain imaging with magnetic resonance or computed tomography demonstrated antemortem involvement of brain and nasal structures. Magnetic resonance imaging was optimal for demonstrating this involvement and showed more detailed anatomic features of the mass and secondary pathologies attributed to the mass.