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Biomedical subjects

W R Davidson

Publications and source records attributed to W R Davidson.

At least 91 records · Page 5Linked to original sources
PubMed1980

Applications of a versatile technique for trace analysis: atmospheric pressure negative chemical ionization.

The ability to use ambient air as a carrier and reagent gas in an atmospheric pressure chemical ionization source allows instantaneous air analysis to be combined with hypersensitivity toward a wide variety of compounds. The TAGA (Trace Atmospheric Gas Analyser) is an instrument which is designed to use both positive and negative atmospheric pressure chemical ionization (APCI) for trace gas analysis; this paper describes several applications of negative APCI which demonstrates that the technique is not limited to environmental monitoring. Examples are described which suggest that the TAGA can be used for the detection of illicit drugs and explosives, and for the analysis of breath or skin emissions, as well as for air pollution measurements. The applications are not restricted by the use of ambient air as a reagent gas; addition to the air carrier of various gases allows specific reagent ions such as Cl- or Br- to be generated. Furthermore, in certain situations pure gas carriers can be used to provide even more flexibility in the ion chemistry, with a short term absorber-desorber system used to transfer the sample from the ambient air into the ion source region. The potential uses for APCI are expanding continuously as the understanding of the complex ion-molecule chemistry grows. This paper underlines the complementary relation between the development of new negative chemical ionization (NCI) techniques and practical applications using the TAGA system.

Air↗
PubMed1980

An epornitic of avian pox in wild bobwhite quail.

An outbreak of avian pox, with an estimated 12-fold increase in the incidence of infection, occurred among wild bobwhites (Colinus virginianus) in the southwestern Georgia/northcentral Florida region. The outbreak was first detected in July, 1978, and continued at least until March, 1979. During this period, 26 separate clinical case accessions involving 43 bobwhites from 8 counties in Florida and Georgia were diagnosed as avian pox. A survey of 2,586 bobwhites from 6 southeastern states revealed avian pox infections in 312 bobwhites from Florida, Georgia, North Carolina, and Tennessee. Seventy-seven percent of the infected birds in the survey had only mild lesions on the legs and feet; however, 23% had more extensive lesions on the head. Severely affected birds had lesions around the eyes, nares, and in the mouth which impaired vision, respiration, and/or feeding. Infection rates were not related to age or sex of the birds but varied greatly among locales, even on adjoining properties. A morbidity rate of approximately 2% and a mortality rate between 0.6 and 1.2% were estimated for a 13,000 km2 region in Georgia and Florida.

Animals↗
PubMed1980

Seasonal trends of helminth parasites of bobwhite quail.

Helminthologic examination of 120 adult and 65 juvenile bobwhites (Colinus virginianus) from Leon County, Florida, during a one-year period revealed seven common (> 30% prevalence) species including Raillietina cesticillus, R. colinia, Cheilospirura spinosa, Cyrnea colini, Heterakis bonasae, Tetrameres pattersoni, and Trichostrongylus tenuis. Less frequently found helminths included Hymenolepis sp., Rhabdometra odiosa, Mediorhynchus papillosis, Aproctella stoddardi, Dispharynx nasuta, Gongylonema ingluvicola, Strongyloides avium, and Subulura sp. Juvenile bobwhites had acquired infections of 6 of the 7 common helminths by July and all seven species by August. A shift from a predominance of immature to mature parasites was noted with increasing age of juvenile bobwhites followed both linear and non-linear (plateau effect) trends when compared to age of the host. By mid-winter total helminth burdens of juvenile birds approached levels in adults. Cheilospirura spinosa, C. colini and T. pattersoni showed marked peaks in transmission between June and September. The two cecal nematodes, H. bonasae and T. tenuis, showed seasonal shifts in relative abundance with H. bonasae predominating during the summer and T. tenuis predominating during the winter. Lesions attributable to helminths were rare and involved minimal tissue damage.

Acanthocephala↗
PubMed1980

Endoparasites of selected populations of cottontail rabbits (Sylvilagus floridanus) in the southeastern United States.

During the fall of 1966 and spring of 1967, 260 cottontail rabbits (Sylvilagus floridanus) were collected from 13 sites in 8 southeastern states and examined for endoparasites. In order of prevalence, the endoparasites found were: Obeliscoides cuniculi, Trichostrongylus calcaratus, Trichostrongylus affinis, Taenia pisiformis (cysticerci), Raillietina salmoni, Eimeria spp., Longistriata noviberiae, Cittotaenia variabilis, Hasstilesia tricolor, Trichuris leporis, Dermatoxys veligera, Passalurus ambiguus, Dirofilaria scapiceps, Sarcocystis sp., Linguatula serrata, Nematodirus leporis, and Gongylonema pulchrum. Data are presented on prevalance and intensity of infection with each parasite along with information on geographic distribution. Cottontail rabbits in the southeastern United States show a higher level of parasitism than has been reported from other regions, although these higher parasite burdens were not necessarily associated with increased host morbidity.

Animals↗
PubMed1980

Haemonchosis in white-tailed deer in the southeastern United States.

Haemonchosis concomitant with malnutrition has been a frequent parasitic disease observed in white-tailed deer (odocoileus virginianus) in the southeastern United States. Typically, afflicted deer were fawns from the southeastern coastal plain, and most cases were submitted between October and March. A survey of deer from 14 areas along the Atlantic coast revealed that fawns had significantly higher numbers of Haemonchus contortus than adults and in some areas fawns harbored H. contortus burdens that were considered pathogenic. The lower H. contortus burdens in adult deer suggested a naturally-acquired immunity. This hypothesis was supported by a trial in which challenge of small groups of Haemonchus-naive and previously exposed penned deer resulted in poorer performance of H. contortus in previously exposed deer. This study indicated that during their first winter fawns are particularly vulnerable to a haemonchosis/malnutrition syndrome.

Age Factors↗
PubMed1979

Apteragia pursglovei sp. n. (Trichostrongyloidea: trichostrongylidae) from the white-tailed deer, Odocoileus virginianus.

Two species of Apteragia were found in white-tailed deer (Odocoileus virginianus) from 152 counties in 13 southeastern states. Specimens previously reported as Skrjabinagia odocoilei were reidentified as belonging to 2 similar species of the genus Apteragia, A. odocoilei, and A. pursglovei sp. n. Apteragia pursglovei sp. n. is differentiated primarily by the length, conformation, and degree of sclerotization of the spicules. Of the 824 deer, A. odocoilei occurred in 76.5%, A. pursglovei in 13.8%, both species in 5.0%, and neither in 4.7%. Reassessment of distribution data revealed that only A. odocoilei was present in deer from 99 counties, only A. pursglovei in deer from 25 counties, and both species in deer from 28 counties. Both A. odocoilei and A. pursglovei were found in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, and Virginia. Apteragia odocoilei also occurred in Maryland, Tennessee, West Virginia, Texas, Oklahoma, New Jersey, and the Virgin Islands.

Animals↗
PubMed1978

Hematotropic parasites of translocated raccoons in the southeast.

Ninety-four raccoons (Procyon lotor) from 6 southeastern states were examined for hematotropic parasites, to evaluate the carrier potential of these animals as they relate to translocation and release for hunting purposes. Four species of hematotropic parasites were identified, viz, Babesia procyonis, Haemobartonella procyoni, Hepatozoon procyonis, and Trypanosoma cruzi. Lesions in infected raccoons were associated only with H procyonis. Babesia procyonis was enzootic in populations of raccoons used as sources for exportation and in raccoons resident in typical release areas. Haemobartonella procyoni, H procyonis, and T cruzi were prevalent only in locales of raccoon origin. Due to the potential pathogenicity of H procyonis and T cruzi in raccoons or other hosts, the practice of translocating raccoons from enzootic to nonenzootic areas was considered biologically hazardous.

Anaplasmataceae↗
PubMed1978

Studies on endoparasites of the black bear (Ursus americanus) in the southeastern United States.

Examination of 53 black bears (Ursus americanus) from six states in the southeastern United States revealed at least 17 species of endoparasites, including Sarcocystis sp., Spirometra mansonoides (spargana), Macracanthorhynchus ingens, Ancylostoma caninum, Arthrocephalus lotoris, Baylisascaris transfuga, Capillaria aerophila, Capillaria putorii, Crenosoma sp., Cyathospirura sp., Dirofilaria immitis, Gnathostoma sp., Gongylonema pulchrum, microfilariae, Molineus barbatus, Physaloptera sp. and Strongyloides sp. Twelve of these represent new host records for black bear, and two are considered to be new species. Data are presented on prevalence, intensity and geographic distribution of each species. Pathologic effects were associated with infections of spargana of S. mansonoides and adults of C. aerophilia.

Animals↗
PubMed1977

Status of the genus Cyrnea (Nematoda: Spiruroidea) in wild turkeys from the southeastern United States.

Two species of Cyrnea are reported from 706 wild turkeys (Meleagris gallopavo) from 25 localities in 9 southeastern states. Cyrnea (Cyrnea) neeli sp. n. in birds from Alabama and Florida is differentiated primarily by distal processes of the left spicule and spicule lengths. Specimens from wild turkeys previously reported as C. eurycerca are identified as C. coloni. The configuration of caudal papillae of C. colini is redescribed. Neither species occurred in birds from montainous regions, and C. neeli sp. n. was restricted to Florida and southern Alabama. Poults less than 1-month old were not infected. Infections peaked in early fall and then declined rapidly.

Animals↗
PubMed1976

Hepatozoon griseisciuri infection in gray squirrels of the southeastern United States.

Blood films and selected tissue sections from 270 gray squirrels (Sciurus carolinensis) from 18 sites in 11 southeastern states were examined for Hepatozoan griseisciuri. This parasite was found in 110 (41%) squirrels from 17 of the 18 sites. Data suggested transmission of the parasite apparently occurs throughout the year and increases from spring to late summer. The infection was more prevalent in subadults and adults than in juveniles. Schizogonic stages were found only in the lungs, suggesting this organ is a major site of schizogony. Pathologic changes associated with H. griseisciuri infection were thickening of alveolar walls, eosinophil infiltration, pulmonary congestion and atelectasis.

Animals↗
PubMed1976

Epizootiology of an outbreak of cerebrospinal nematodiasis in cottontail rabbits and woodchucks.

An epizootic of cerebrospinal nematodiasis in cottontail rabbits (Sylvilagus floridanus) and woodchucks (Marmota monax) caused by Baylisascaris procyonis larvae followed the establishment of an ascarid-infected raccoon (Procyon lotor) population in a woodlot. Five of seven raccoons examined from the woodlot harbored ascarids, with one heavily infected animal shedding approximately 27,500 eggs per gram of feces. A laboratory-reared cottontail rabbit developed neurologic disease due to larval migration 80 days after infection with B. procyonis eggs from the raccoons.

Animals↗
PubMed1975

An epizootic of cerebrospinal nematodiasis in cottontail rabbits.

A progressively debilitating neurologic syndrome characterized by torticollis, ataxia, circling, and abnormal posture was observed in 16 of approximately 60 cottontail rabbits (Sylvilagus floridanus) captured in a 12-hectare portion of a woodlot in southwestern Virginia. Inflammatory and degenerative alterations in cerebellum and midbrain regions were characterized principally by malacia, perivascular cuffing, and gliosis. Single Ascaris columnaris larvae were found in the cerebellum of 2 rabbits and the spinal cord of 1 rabbit.

Animals↗
PubMed1975

Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa.

In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control.

Ammonia↗
PubMed1975

Severe parasitism in an opossum.

Chronic debilitation and anemia were observed in a free-living opossum (Didelphis marsupialis) heavily parasitized by Physaloptera turgida, Brachylaima virginianum, and Cruzia americana. Chronic interstitial pneumonia associated with Capillaria aerophila and a metastrongyloid nematode also was present.

Animals↗