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Biomedical subjects

R G McLean

Publications and source records attributed to R G McLean.

At least 55 records · Page 3Linked to original sources
PubMed1990

Colon transit scintigraphy in health and constipation using oral iodine-131-cellulose.

The purpose of the study was to assess if a new scintigraphic method for noninvasive assessment of colonic transit could differentiate between subjects with normal bowel transit and those with constipation. Eleven normal subjects and 29 constipated patients were given 4 MBq iodine-131-cellulose (131I-cellulose) orally and sequential abdominal scans were performed at 6, 24, 48, 72, and 96 hr from which total and segmental percent retentions were calculated. There were clear differences between the normal subjects and the constipated patients for the total percent retention at all time intervals, on a segmental basis in the right colon at 24 hr, and in all segments at 48 and 72 hr. Three-day urinary excretion of radioiodine was minimal; 2.4% +/- 1.2% (mean +/- s.d.) in constipated patients and 3.1% +/- 0.8% in normals, with approximately 75% occurring in the first day. The use of oral radiotracers in the investigation of constipation appears promising.

Administration, Oral↗
PubMed1989

The ecology of Colorado tick fever in Rocky Mountain National Park in 1974. III. Habitats supporting the virus.

Ecologic studies of small mammals in Rocky Mountain National Park (RMNP) were conducted in 1974 in order to identify the specific habitats within the Lower Montane Forest that support Colorado tick fever (CTF) virus. Data was collected on the abundance and distribution of 4 primary rodent species, tick infestation, CTF virus, and neutralizing antibody prevalence. Rodents were captured along transects crossing different habitats. Open stands of ponderosa pine and shrubs on dry, rocky surfaces were found to be important for maintaining CTF virus.

Animals↗
PubMed1989

Co-circulation of multiple Colorado tick fever virus genotypes.

Colorado tick fever (CTF) virus, family Reoviridae, genus Orbivirus, contains 12 genes distinguishable by polyacrylamide gel electrophoresis (PAGE). Multiple genotypes of CTF virus were isolated at 3 field sites in Colorado in 1985. Five genotypes were found at Campos Cabin, 2 at Drake, and 6 at Rocky Mountain National Park. Virus isolations were made in 1985 from 6 patients with CTF. These isolates were distinct from each other and the field isolates. Although the CTF isolates were different by PAGE profile, the majority of the 12 genes were highly conserved among the 1985 isolates and a Florio isolate (FMA). Only genes 4 and 6 were variant among the 1985 CTF isolates and FMA, and no unique genes were identified. In 1986, a follow-up field survey was done at the Campos Cabin site. Of the 3 CTF PAGE genotypes obtained, 2 exhibited PAGE profiles which were different from the 1985 isolates. One isolate may have resulted from the reassortment of genes from 2 of the isolates circulating at Campos Cabin in 1985.

Animals↗
PubMed1989

Western equine encephalitis in avian populations in North Dakota, 1975.

The involvement of wild birds in western equine encephalitis (WEE) and St. Louis encephalitis (SLE) virus activity in the Red River valley area of North Dakota (USA) during a WEE epidemic was investigated in August 1975. Free-ranging birds were captured with mist nets and nestlings by hand. Virologic and serologic results indicated that a similar rate of WEE virus activity occurred throughout Richland County and between permanent and summer resident birds. The rate of SLE virus activity in the birds of Richland County was lower than for WEE virus, but the SLE antibody prevalence was greater in rural areas than within urban locations. Seven of the nine WEE virus isolations were from nestling birds of four different species; the remaining two from adults of two different species. Overall prevalence of neutralizing (N) antibody against WEE virus was 5% in nestling and 14% in adult birds but was the opposite for N antibody against SLE virus, 17% in nestling and 5% in adult birds. Differences between the two viruses in the presence and persistence of maternal N antibody or differential mortality in nestling birds may have caused the disparity in antibody prevalences.

Animals↗
PubMed1989

Characterization of five new phleboviruses recently isolated from sand flies in tropical America.

Five new phlebotomus fever virus serotypes (Bunyaviridae: Phlebovirus) are described. These viruses, designated Ambe, Ixcanal, Mariquita, Armero, and Durania, were isolated from sand flies (Diptera: Psychodidae) collected in Brazil, Colombia, and Guatemala. Two of the agents were recovered from pools of male sand flies. The new viruses are antigenically related to other members of the phlebotomus fever serogroup by immunofluorescence, but are distinct from the other 39 members of this serogroup by plaque reduction neutralization test.

Animals↗
PubMed1988

A plague epizootic in the white-tailed prairie dogs (Cynomys leucurus) of Meeteetse, Wyoming.

Surveillance for sylvatic plague (Yersinia pestis) was conducted near Meeteetse, Wyoming (USA) from 24 May to 14 June 1985. Ten species of fleas were collected from white-tailed prairie dogs (Cynomys leucurus), and from their burrows and associated rodents. Five of these flea species and two adult prairie dogs were positive for plague. The progression of this plague epizootic appeared to be slower and the intensity was less than in previous epizootics in other prairie dog colonies. The plague epizootic occurred within the only known colony of black-footed ferrets (Mustela nigripes) and was a potential threat to the food source of this endangered species.

Animals↗
PubMed1988

Antibody prevalence of St. Louis encephalitis virus in avian hosts in Los Angeles, California, 1986.

A study was conducted to determine the pattern of St. Louis encephalitis (SLE) virus activity in the avian populations of the Los Angeles metropolitan area in 1986. In total, 679 birds of 42 species were captured at 7 study sites. The overall prevalence of SLE neutralizing (N) antibody of 3% indicated enzootic transmission. Antibody prevalences were higher in birds sampled in the central part of the metropolitan area, which was consistent with other epidemiologic data. The use of specific avian species as sentinels for future surveillance of SLE virus activity was suggested.

Animals↗
PubMed1987

Epizootic vesicular stomatitis in Colorado, 1982: some observations on the possible role of wildlife populations in an enzootic maintenance cycle.

Sera obtained from wild ungulates, carnivores, and rodents in Colorado were tested for neutralizing (N) antibody against vesicular stomatitis, New Jersey serotype (VSNJ), virus to determine their involvement in the 1982 Colorado VSNJ epizootic in domestic animals. Viremic and N antibody responses of two local rodent species to a 1982 Colorado isolate of VSNJ were determined in the laboratory. The rodents produced only weak viremias, but all developed N antibody. N antibody prevalences for VSNJ in sera from wild ungulates was sufficiently high to indicate their involvement during the epizootic. In addition, the demonstration of N antibody in elk (Cervus elaphus) and mule deer (Odocoileus hemionus) prior to the epizootic in cattle and horses suggests that an enzootic cycle may exist in Colorado.

Animals↗
PubMed1987

Isolation of Cache Valley virus and detection of antibody for selected arboviruses in Michigan horses in 1980.

Blood samples collected in September and November 1980 from 87 horses in southwestern Michigan were examined for virus isolation and for plaque-reduction neutralizing antibody against selected arboviruses. Cache Valley virus was isolated from the blood of a clinically normal horse in St Joseph County in September. The age-specific antibody prevalence for Cache Valley virus indicated enzootic transmission in the study area. The high antibody prevalence and the lack of age-specific antibody prevalence indicated sporadic, but intense, exposure to Jamestown Canyon virus. Low prevalences of antibody were detected for Highlands J, snowshoe hare, St Louis encephalitis, and trivittatus viruses.

Animals↗
PubMed1986

Distribution of Bunyamwera serogroup viruses in North America, 1956-1984.

We attempted to tabulate all Bunyamwera serogroup (family Bunyaviridae, genus Bunyavirus) isolates from North America. By summarizing information from the laboratories of the Centers for Disease Control, data generously shared by other laboratories, and the published literature, we were able to accumulate data regarding 1,372 Bunyamwera serogroup viruses. These were: Tensaw (664, including 8 from vertebrates), Cache Valley (396, including 6 from vertebrates), Main Drain (160, including 14 from vertebrates), Lokern (69, including 8 from vertebrates), Northway (13, including 5 from vertebrates), Tlacotalpan (7), Santa Rosa (2), Santa Cruz (1 from a horse), and 60 of undetermined serotype. Virus isolation rates by month of collection were correlated with collection efforts, but associations of viruses and arthropod vectors varied by location, vertebrate host, and arthropod distribution. Tensaw virus was isolated principally from Anopheles crucians mosquitoes (466/656 isolates from arthropods) in the southeastern United States; Cache Valley virus principally from An. quadrimaculatus (94), Coquillettidia perturbans (59), Culiseta inornata (45), Aedes sollicitans (30), Psorophora columbiae (23), An. punctipennis (18), and Ae. vexans and trivittatus (18 each) mosquitoes (total = 305/382 isolates from arthropods from all of the United States and Canada, except the southeastern United States); Main Drain virus from Culicoides variipennis (31), Culicoides (Selfia) sp. (65), and Psorophora (23) and Aedes (21) species mosquitoes in the western United States; Lokern virus from Culicoides species (55/61 isolates from arthropods) in the western United States. Relationships between vector and vertebrate host distributions are discussed briefly in regard to geographic distribution of the Bunyamwera serogroup viruses.

Aedes↗
PubMed1986

Viremic enhancement due to transovarially acquired antibodies to St. Louis encephalitis virus in birds.

Adult house sparrows (Passer domesticus) were captured and experimentally inoculated with St. Louis encephalitis (SLE) virus to produce high concentrations of circulating antiviral antibody. Nestlings, 5-7 and 14-16 days of age, from SLE immune adult females and challenged with SLE virus, exhibited viremic enhancement by producing viremias of greater duration and magnitude than did controls. Nestlings possessing maternal antibody and challenged with SLE virus between 8 and 13 days of age did not produce viremias differing significantly from controls in magnitude, duration, or temporal appearance. Experimental nestling sparrows possessed detectable amounts of maternally derived passive antibody to SLE virus prior to challenge with this virus. Passive geometric mean antibody titers ranged from a high of 1:34.5 in nestlings tested 5-7 days posthatching, to a low of 1:11.2 in 14-16-day-old birds. Results presented imply that enhancement of SLE virus infections could lead to increased viral amplification and dissemination rates during natural disease cycles.

Animals↗
PubMed1986

Prognostic value of axillary lymphoscintigraphy in breast carcinoma patients.

Axillary lymphoscintigraphy (AxLS) with bilateral interdigital injection of [99mTc]antimony sulfide colloid carried out concurrently with internal mammary lymphoscintigraphy in 488 patients with breast carcinoma was evaluated. Patterns of radiocolloid distribution within the ipsilateral axilla and supraclavicular fossa were compared with similar features on the contralateral side to determine whether image characteristics are significantly disrupted by prior surgery, reflect the presence of metastases, and can predict treatment failure. Interpretive criteria for AxLS were refined after correlation of the identified image components with clinical parameters including axillary surgery, lymph node histology and relapse within a follow-up period of 2 years from the study. Results indicate that AxLS is at least as accurate as clinical assessment and provides data predictive of relapse to complement axillary lymph node status although the technique cannot presently replace lymph node sampling for patient staging.

Adolescent↗
PubMed1985

Role of radionuclide imaging in the diagnosis of chondrosarcoma.

The diagnosis of chondrosarcoma may be difficult if there is an atypical radiographic appearance or an inconclusive biopsy. Radionuclide bone scans of 13 patients with chondrosarcoma were reviewed to assess if a pattern of scan features could be recognised in association with this tumour. A combination, including increased blood pool activity, moderate intensity of uptake, patchy uptake with cortical predominance of activity, minimal distortion of bony outline, and a well-defined scintigraphic margin, occurred regularly in the series. Recognition of this characteristic pattern of scintigraphic features in cases of suspected chondrosarcoma may assist in the diagnostic assessment.

Adolescent↗
PubMed1985

Late cardiac, thyroid, and pulmonary sequelae of mantle radiotherapy for Hodgkin's disease.

Cardiac, thyroid and pulmonary function were evaluated in 25 patients aged 35 years or under, treated for Hodgkin's disease by mantle radiotherapy 5-16 years previously. No patient had symptoms of heart disease. Although thallium myocardial perfusion scintigraphy was normal in all patients, abnormalities of myocardial function were detected in 6 (24%) patients using gated equilibrium rest and exercise radionuclide ventriculography. Resting left ventricular ejection fraction (LVEF) was abnormal in 1 patient, and in 3 patients there was an abnormal LVEF response to exercise. All 6 patients had right ventricular dilatation. Apical hypokinesia was present in 4 of these patients. A small asymptomatic pericardial effusion was detected by M-Mode echocardiography in only 2 (8%) patients. Twenty-three (92%) patients had evidence of abnormal thyroid function. Two (8%) patients had become clinically hypothyroid. Serum TSH was elevated in 13 (52%) patients and TRH stimulation test was abnormal in a further 10 (40%) patients in whom TSH was normal. Pulmonary function studies showed a moderate decrease in diffusing capacity (72% of predicted) and a minor reduction in lung volume. Although a high incidence of cardiac, thyroid and pulmonary abnormalities was detected, only the 2 patients who had become hypothyroid were symptomatic. Modification of the irradiation technique may reduce the incidence of cardiac abnormalities, but is unlikely to alter significantly the thyroid or pulmonary sequelae.

Adult↗