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Biomedical subjects

C J Mitchell

Publications and source records attributed to C J Mitchell.

At least 109 records · Page 6Linked to original sources
PubMed1985

Detection, identification, and classification of mosquito larval habitats using remote sensing scanners in earth-orbiting satellites.

A method of identifying mosquito larval habitats associated with fresh-water plant communities, wetlands, and other aquatic locations at Lewis and Clark Lake in the states of Nebraska and South Dakota, USA, using remote sensing imagery obtained by multispectral scanners aboard earth-orbiting satellites (Landsat 1 and 2) is described. The advantages and limitations of this method are discussed.

Animals↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. II. Arthropod collections and virus isolations from Argentine mosquitoes.

Prospective surveys for arboviruses were carried out in Santa Fe, Corrientes, and Chaco provinces, Argentina, aperiodically during 1977-1980. A total of 313,233 mosquitoes and 598 biting flies other than mosquitoes were collected and tested for virus in 5,197 and 45 pools, respectively. Forty virus strains were isolated, all from mosquitoes, as follows: Santa Fe Province: 4 Gamboa group viruses from Aedeomyia squamipennis, 1 strain each of St. Louis encephalitis virus from Culex pipiens quinquefasciatus and Culex (Culex) spp.; Corrientes Province: a single strain of a newly discovered Anopheles A serogroup virus, Las Maloyas, from Anopheles albitarsis; and Chaco Province: 4 Gamboa group viruses from Ad. squamipennis, 6 strains of new Bunyaviridae (1 Antequera, 1 Barranqueras, and 4 Resistencia) from Culex (Melanoconion) delpontei, 3 strains of a new subtype of western equine encephalitis virus and 1 strain of Para virus from the Cx. (Mel.) ocossa group, 12 strains of a newly discovered subtype (VI) of the Venezuelan equine encephalitis complex from Cx. (Mel.) delpontei, and 1 strain each from Ad. squamipennis, Aedes scapularis, Ae. spp., Cx. (Cux.) spp., Cx. (Mel.) ocossa group, Mansonia spp., and Psorophora spp. Bloodmeals from 265 engorged mosquitoes were identified by precipitin test. These data, coupled with data on engorgement rates for 25,995 mosquitoes from bait collections, provide information on the host feeding patterns of several mosquito species. This information is discussed, along with data on relative abundance of mosquito species, within the context of the vector relationships of the species from which viruses were isolated. The association of Cx. (Mel.) delpontei with 18 strains of 4 different viruses in Chaco Province, plus its catholic feeding habits, clearly indicate for the first time the importance of this species as an arbovirus vector.

Aedes↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. III. Identification and characterization of viruses isolated, including new subtypes of western and Venezuelan equine encephalitis viruses and four new bunyaviruses (Las Maloyas, Resistencia, Barranqueras, and Antequera).

Forty viruses isolated from mosquitoes between 1977 and 1980 in Argentina have been identified and characterized. Nineteen strains of VEE virus, identical by neutralization (N) tests, were shown by hemagglutination-inhibition tests with anti-E2 glycoprotein sera to represent a new subtype VI of the VEE complex. RNA oligonucleotide fingerprints of this virus were distinct from subtype I viruses. The virus was not lethal for English short-haired guinea pigs, indicating that it is probably not equine-virulent. Three strains of a member of the WEE virus complex were shown to differ by N tests in 1 direction from prototype WEE virus. The new WEE subtype was also found to be distinct by RNA oligonucleotide mapping. Its vector relationships indicate that it is an enzootic virus, and it has not been associated with equine disease. A new member of the Anopheles A serogroup was identified, shown to be most closely related to Lukuni and Col An 57389 viruses, and given the name Las Maloyas virus. A strain of Para virus (Bunyaviridae, Bunyavirus) was identified. Six isolates, representing 3 new viruses morphologically resembling bunyaviruses are described; the names Antequera, Barranqueras, and Resistencia are proposed for these agents, which were all isolated from Culex (Melanoconion) delpontei in Chaco Province. No serologic relationships between these viruses and other bunyaviruses were found. Since they are antigenically interrelated, they form a new (Antequera) serogroup. Eight Gamboa serogroup viruses and 2 strains of St. Louis encephalitis virus were also identified.

Aedes↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. IV. Serologic surveys and sentinel equine program.

Serologic surveys of wild and domestic birds, wild mammals, and horses were conducted during arbovirus field studies in Argentina from 1977 through 1980, a non-epizootic interval. The prevalence of neutralizing antibodies to eastern equine encephalitis (EEE) was consistently higher than to western equine encephalitis (WEE) virus in all species and all areas. The presence of antibodies in short-lived avian species and in young unvaccinated horses and the demonstration of seroconversions in horses during the period, indicated that these viruses are either enzootic in, or annually reintroduced into, Argentina. Antibodies to AG80-646, a new subtype of WEE virus isolated in the subtropical north (Chaco Province) from Culex (Melanoconion) mosquitoes, were found in horses and rodents in that region. Antibodies to the TC-83 strain of Venezuelan equine encephalitis (VEE) virus were found in all areas studied. The presence of antibodies in some horses was probably related to vaccination, but the demonstration of seroconversions in sentinel horses and of antibodies in birds and wild mammals indicates active transmission of VEE virus. In 1980 a new enzootic subtype of VEE virus (AG80-663) was isolated from mosquitoes in Chaco; neutralizing antibodies to this virus were prevalent in horses and rodents in this area. Infections with Aura and Una viruses were most common in the subtropical northern provinces. Infection with St. Louis encephalitis was prevalent and widespread, and birds, principally passerine and columbiform species, appear to be the principal hosts. An interesting and unexplained finding was the absence of arbovirus antibodies, in particular SLE antibodies in house sparrows (Passer domesticus). Antibody prevalences in horses exceeded 50% in all areas, and 12% of horses surveyed in Santa Fe Province developed antibody in a 17-month period. Antibodies to other flaviviruses were rare. A high prevalence of immunity to Maguari virus was found in horses; this agent is considered to be a potential equine pathogen. Antibodies to 2 new viruses, Barranqueras and Resistencia, which had been isolated from Cx. (Melanoconion) in Chaco Province, were found in rodents there. Immunity to Gamboa group viruses was prevalent, and birds were implicated as principal hosts.

Alphavirus↗
PubMed1985

The use of an animal-baited net trap for collecting mosquitoes during western equine encephalitis investigations in Argentina.

A large net trap was used to sample mosquito populations attracted to horses at three sites each in Santa Fe and Rio Negro Provinces, Argentina, during the austral summer of 1984. These provinces, as well as others in Argentina, were affected by a severe epizootic of western equine encephalitis (WEE) during 1982-83. Totals of 2,752 and 6,929 mosquitoes were collected in Santa Fe and Rio Negro Provinces during five and three trap nights, respectively. Culex mosquitoes of the subgenus Culex were predominant (45.8% of total) in the Santa Fe collections, although Aedes albifasciatus also was prevalent (21.7%). The latter species was predominant (95.7% of total) in the Rio Negro collections. The mosquito fauna was less complex (minimum of 6 species) in Rio Negro Province as compared to Santa Fe Province (minimum of 18 species). The advantages of the net trap indicate that this trap can become a useful tool in arbovirus ecology studies in other areas.

Animals↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. I. Historical aspects and description of study sites.

This is the introductory paper to a series on the ecology of arboviruses in Argentina. Epizootics of equine encephalitis have occurred since at least 1908, principally in the Pampa and Espinal biogeographic zones, with significant economic losses; human cases of encephalitis have been rare or absent. Both western equine and eastern equine encephalitis viruses have been isolated from horses during these epizootics, but the mosquitoes responsible for transmission have not been identified. A number of isolations of Venezuelan equine encephalitis (VEE) virus were reported between 1936 and 1958 in Argentina, but the validity of these findings has been seriously questioned. Nevertheless, serological evidence exists for human infections with a member of the VEE virus complex. Serological surveys conducted in the 1960s indicate a high prevalence of infection of humans and domestic animals with St. Louis encephalitis (SLE), and 2 SLE virus strains have been isolated from rodents. Human disease, however, has rarely been associated with SLE infection. Only 7 isolations of other arboviruses have been described (3 of Maguari, 1 of Aura, 2 of Una, and 1 of an untyped Bunyamwera group virus). In 1977, we began longitudinal field studies in Santa Fe Province, the epicenter of previous equine epizootics, and in 1980 we extended these studies to Chaco and Corrientes provinces. The study sites are described in this paper.

Animals↗
PubMed1984

Prospective comparison of three non-invasive tests for pancreatic disease.

Ultrasonography, computed tomography (CT), and an oral pancreatic function test were evaluated prospectively in 107 consecutive patients suspected of having pancreatic disease, the final diagnosis being made independently of these tests. Seventeen patients proved to have either chronic pancreatitis or a pancreatic neoplasm. Five had an unfused ventral pancreas and 10 had "minimal change" pancreatograms. Seventy five patients did not have pancreatic disease. Among the 17 patients with pancreatic disease the sensitivities of ultrasound, CT, and the pancreatic function test were 70%, 71%, and 76% respectively; among those without disease values of specificity of the three tests were 75%, 87%, and 72%. All three tests failed to detect most of the patients with unfused ventral pancreases or minimal change pancreatograms. The predictive values of a positive result for the three tests were 43%, 67%, and 34%. The predictive value of a negative result was greater than 90% for all the tests. Results improved when CT was combined with either of the two other tests. These findings show that CT is the most accurate of the three tests in diagnosing pancreatic disease but that a combination of ultrasound and the oral pancreatic function test offers a more widely applicable and almost as accurate alternative.

4-Aminobenzoic Acid↗
PubMed1983

Functional recovery of the exocrine pancreas after acute pancreatitis.

A tubeless pancreatic function test (BTP test) using N-benzoyl-l-tyrosyl-p-aminobenzoic acid was used to assess exocrine function from urinary recovery of p-aminobenzoic acid produced by hydrolysis of the peptide by chymotrypsin. Patients with acute pancreatitis were studied at various time intervals after the acute attack and compared with controls with abdominal pain that was not pancreatic in origin. The initial BTP test carried out in the convalescent period was abnormal in all of 30 patients with acute pancreatitis but normal in 10 patients with non-pancreatic abdominal pain and also in 8 patients who had recovered from an attack of acute pancreatitis 2-6 years previously. Results were improved or normal in 12 of 15 patients re-tested 1 year after the attack of pancreatitis, but 4 out of 6 still had abnormal results 2-6 months after the attack. The data suggest that an attack of acute pancreatitis may impair exocrine pancreatic function for several months.

4-Aminobenzoic Acid↗
PubMed1983

Assessment of a rapid pancreatic isoamylase assay as a screening test for chronic pancreatic disease.

A new, rapid assay for pancreatic isoamylase (PIA) has been evaluated in normal subjects and patients with either proven chronic pancreatic disease or diseases in which chronic pancreatitis commonly enters the differential diagnosis. A wide normal range limited the diagnostic usefulness of the test. In non-pancreatic disease the serum levels of PIA were normal in 107 of 109 patients with non-pancreatic disease, but only 3 of 16 patients with chronic pancreatitis and proven exocrine insufficiency had a low PIA level, and variable levels occurred in pancreatic carcinoma. These results suggest that measurement of serum PIA is of limited value as a screening test for chronic pancreatic disease.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1983

Experimental infections of birds with Turlock virus.

Two experiments were conducted with five gallinaceous and one passerine bird species to determine their responses to Turlock (TUR) virus inoculations. Inoculation of TUR strain 847-32 into bobwhites, chukars, ring-necked pheasants, chickens, and Japanese quail did not product detectable viremias. The first four species, however, did respond with neutralizing antibody. Inoculation of chickens with strain 69V-1095 resulted in a viremia which lasted 5 days and had a peak mean titer of 2.0 log 10 PFU per 0.2 ml of blood on the third day after infection. The observation that viremic birds exhibited no noticeable virus-associated morbidity or mortality suggested that TUR virus does not have a detrimental effect on free-ranging populations of the avian hosts studied during this investigation.

Animals↗
PubMed1982

Endoscopic retrograde cholangiograms of the normal and post-cholecystectomy biliary tree.

The diameter of extrahepatic and intrahepatic bile ducts was measured on 50 normal retrograde cholangiograms and on the cholangiograms of 109 post-cholecystectomy patients undergoing endoscopic retrograde cholangiopancreatography: 70 of the post-cholecystectomy patients had a normal cholangiogram and 39 had retained stone or biliary stricture, of whom 17 were jaundiced. Biliary diameter at all points measured was greater in the post-cholecystectomy patients with no biliary lesion than in normals, and further increased in the presence of pathology (e.g. retained stone). The extent of overlap in biliary diameter between all these three groups is so great that measurement of bile duct calibre cannot separate patients with retained stone from post-cholecystectomy patients without retained stone, or from patients with an entirely normal biliary tree, even in the presence of obstructive jaundice. Methods of evaluating the biliary tract which rely on the measurement of bile duct diameter (e.g. ultrasound) are therefore of limited value in the investigation of post-cholecystectomy patients.

Adolescent↗