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Biomedical subjects

D M McLean

Publications and source records attributed to D M McLean.

At least 19 recordsLinked to original sources
PubMed1994

Reproductive performance in South Australian dairy herds.

Herd breeding records (161) were examined from a random 10% sample of dairy farms (96) in South Australia with more than 40 cows and suitable breeding records for 1988 and/or 1989. Of these farms, 53 (55.2%) had a year-round calving pattern, 42 (43.8%) claimed to be seasonal and one was changing from a year-round to a seasonal pattern. Only 14.6% of farmers observed oestrous behaviour outside milking times and 18.8% used tailpaint. Overall, the average proportion of unobserved heats was estimated to be 32%. Artificial insemination (AI) was carried out on 85.4% of farms (16.7% used AI alone and 68.7% also used bulls) of which 32.9% used commercial technicians and 67.1% were do-it-yourself operators. Overall, the average 30-day submission rate was 59.9% and the average 49-day non-return to service rate was 58.9%. Investigation into the probable causes of suboptimal reproductive performance gave a tentative diagnosis of inefficient oestrous detection, deferral of service, inadequate nutrition, poor AI technique, insufficient bulls, and venereal/other diseases in 69.1, 32.1, 27.2, 28.4, 13.6 and 7.4% of records, respectively.

Animal Nutritional Physiological Phenomena↗
PubMed1992

Genomic and biologic analyses of snowshoe hare virus field and laboratory strains.

Low-passage field strains of snowshoe hare (SSH) virus (Bunyaviridae), the prototype SSH virus (originally isolated in Montana), and La Crosse (LAC) virus were compared serologically by plaque-reduction neutralization (PRNT) and molecularly by oligonucleotide fingerprinting (ONF). The PRNT and ONF results confirmed the identity of the field strains, although some differences in the fingerprints were observed. We have examined the RNA genome variability in the two field and three laboratory strains of SSH virus, using direct sequence analysis of selected RNase T1 oligonucleotides. Few changes were observed among three Montana prototype-derived laboratory isolates, although they have different passage histories. In contrast, the field isolates differed greatly from the laboratory strains. In addition, we have located several of the larger T1 oligonucleotides within the known sequence of the small and large RNA genome segments. We then compared the viruses for their ability to replicate in and be transmitted by Aedes triseriatus mosquitoes. The oral infection rates for LAC, the field isolates, and the SSH prototype, as determined by immunofluorescent examination of midgut tissues, were 100%, 82%, and 47%, respectively. All viruses were also transmissible from mosquitoes to mice.

Aedes↗
PubMed1990

Acute HIV infection presenting with painful swallowing and esophageal ulcers.

We describe an acute human immunodeficiency virus (HIV) infection in 16 homosexual men who presented with painful swallowing (odynophagia). Eleven men had a maculopapular rash and 3 had palatal ulcers. At esophagogastroduodenoscopy (endoscopy), multiple discrete esophageal ulcers measuring 0.3 to 1.5 cm in diameter were observed. Electron microscopy of biopsy specimens taken from the ulcer margins in 8 men revealed viral particles 120 to 160 nm in diameter whose morphologic characteristics were those of retroviruses. Human immunodeficiency virus seroconversion was documented in 15 men by Western blot analysis. In 3 men, HIV-1 was isolated from peripheral blood mononuclear cells, in 2 men HIV-1 was isolated from peripheral blood monocytes, and in 1 man HIV-1 was isolated from tissue taken from the margins of the esophageal ulcers. These observations extend our knowledge of the clinical spectrum of acute HIV infection syndromes and suggest that cells in the esophagus are a target for HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Cloned aerolysin of Aeromonas hydrophila is exported by a wild-type marine Vibrio strain but remains periplasmic in pleiotropic export mutants.

With a wide host range vector, the structural gene aerA for the hole-forming extracellular protein aerolysin of Aeromonas hydrophila was cloned into the marine Vibrio sp. strain 60 and into three pleiotropic export mutants (epr mutants). The parent strain and all of the mutants were able to express the protein with the aerA promoter in the plasmid. The parent strain exported proaerolysin into the medium, while all of the mutants accumulated the protoxin in their periplasms. Two of the mutants also accumulated protease; however, as we have found earlier with A. hydrophila, the periplasmic form of proaerolysin in the Vibrio sp. must somehow be protected from proteolysis because it was not converted to active toxin until the cells were shocked. Conversion could be prevented by adding o-phenanthroline to the solutions used in shocking. These results show that the export pathway in the marine Vibrio sp. is very similar to the pathway in A. hydrophila.

Aeromonas↗
PubMed1987

Comparison of one- and two-dose regimens of influenza vaccine for elderly men.

In November and December 1984, 102 male residents of a long-term care facility (mean age 74.6 [extremes 59 and 97] years) received 0.5 ml of trivalent inactivated whole-virion influenza vaccine, containing 15 micrograms of the hemagglutinin of each of A/Philippines/2/82 (H3N2), A/Chile/83 (H1N1) and B/USSR/83. A second dose of the vaccine was administered to a subgroup of 55 randomly chosen subjects 8 weeks later. Serum samples were collected from all the subjects before and 4, 8, 12 and 16 weeks after administration of the first dose and were assayed for hemagglutinin-inhibiting (HAI) antibody to each of the three antigens. At 8 weeks there were significant increases (p less than 0.05) in the geometric mean titre of antibody and in the proportion of subjects with HAI antibody titres of 1:40 or more (except to the B/USSR antigen) in both groups. There were no differences between the groups at 8 weeks or at 16 weeks (8 weeks after administration of the second dose of vaccine) in the frequency of seroconversion, the geometric mean titre or the proportion of subjects with HAI antibody titres of 1:40 or more. Overall, 60%, 32% and 13% of the 102 subjects had titres of 1:40 or more to the A/Philippines, A/Chile and B/USSR antigens respectively at 16 weeks. The results suggest that a second dose of influenza vaccine given 8 weeks after the first does not enhance the immune response in elderly men and that a substantial proportion of this population remains unprotected against infection (having HAI antibody titres of less than 1:40) during the influenza season.

Adult↗
PubMed1987

Characterization of the immune response to trivalent influenza vaccine in elderly men.

This study characterizes the time course of the immune response to influenza vaccine in elderly men. Sixty-two men aged 58 to 91 years (mean, 74.3 years) were vaccinated with trivalent inactivated influenza vaccine in the fall of 1983. Serum hemagglutinin-inhibiting (HAI) antibody titers were measured at various times up to 24 weeks postvaccination. Seroconversion frequencies determined at single times after vaccination were 28 to 46% of subjects, whereas cumulative seroconversion frequencies were greater than or equal to 70%. Eighteen to 28% of seroconversions occurred later than four weeks, and greater than or equal to 68% of those who seroconverted experienced greater than four-fold declines in peak HAI antibody titers by 24 weeks after vaccination. Consequently, 31 to 73% of subjects had HAI antibody titers greater than 40 throughout the study period. Measurement of HAI antibody titers at only one time after vaccination may not adequately reflect the immune response of this population or the degree of protection maintained through the influenza season.

Age Factors↗
PubMed1986

Unusual esophageal ulcers containing enveloped viruslike particles in homosexual men.

Eight homosexual men presented with odynophagia. Five had a maculopapular rash and 2 had oral ulcers. Upper panendoscopy revealed the presence of multiple discrete ulcers measuring 3 mm-1.5 cm in diameter in the esophagus of each patient. The intervening mucosa appeared normal. Endoscopic brushings and biopsy specimens taken from the ulcer margins and examined by light microscopy showed no inclusion bodies or giant cells. Fungal stains were negative. Biopsy specimens examined by electron microscopy revealed enveloped virus-like particles 100-140 nm in diameter, exhibiting morphologic features consistent with retroviruses. No virus was isolated after incubation in either rhesus monkey kidney or human foreskin fibroblast culture. Serology for cytomegalovirus and herpes simplex virus was consistent with past infection. In each patient the esophageal ulcers healed completely. In summary, an illness characterized by the presence of esophageal ulcers is described in 8 homosexual men, 5 of whom also had a skin rash and 2 of whom had oral ulcers. The cause of the esophageal ulcers is likely to be the enveloped viruslike particles observed at electron microscopy.

Adult↗
PubMed1984

Effects of milk protein genetic variants on milk yield and composition.

Effects of genetic variants of the milk proteins, alpha S1-casein, beta-casein, kappa-casein and beta-lactoglobulin (beta-lg), on milk yield and composition, particularly the protein composition, were investigated in milk samples from 289 Jersey and 249 Friesian cows in eight commercial herds. Milk protein genotypes had no significant effect on yields over a complete lactation of milk and fat, but significant differences in fat content were detected for beta-casein (B, A1B, A2 greater than A1A2) and beta-lg (B, AB greater than A) variants. Significant differences between beta-lg variants were also found with total solids (B, AB greater than A), casein (B, AB greater than A), whey protein (A greater than AB greater than B) and beta-lg (A greater than AB, AC greater than B greater than BC) concentrations. Casein genotypes were not significantly different in total protein and casein concentrations but many differences were found in casein composition. alpha S1-Casein variants significantly affected alpha S1-casein (BC greater than B) and kappa-casein (B greater than BC) concentrations. beta-Casein variants affected concentration and proportion of beta-casein (A1B, A2B greater than A1, A1A2, A2, B), alpha S1-casein (A1, A2 greater than B) and kappa-casein (B greater than A2) and concentration of whey protein (A1 greater than most other beta-casein variants). kappa-Casein variants affected concentration and proportion of kappa-casein (B greater than AB greater than A), proportion of alpha S1-casein (A greater than AB greater than B) and concentrations of beta-lg (A greater than AB, B) and alpha-lactalbumin (A, AB greater than B). Differences in milk composition were found between breeds, herds and ages, and with stage of lactation. The potential use of milk protein genotypes as an aid in dairy cattle breeding is discussed.

Age Factors↗
PubMed1983

Yukon isolates of snowshoe hare virus, 1972-1982.

Bunyaviruses including 53 strains of snowshoe hare (SSH) and 4 of Northway (NOR) were isolated from 132,428 unengorged adult female mosquitoes of 7 species collected throughout the boreal forest of the Yukon Territory and open woodland terrain in the Mackenzie Valley, Northwest Territories, Canada during 8 of 11 arctic summers from 1972 through 1982. Isolations of SSH virus were also achieved from mosquito larvae during 1974 and 1975. Percentage virus infection rates of important vectors were Aedes communis (0.038) and Culiseta inornata (0.124). Isolations of NOR virus were achieved during 1976 and 1978 only. Infection thresholds of SSH virus for Ae. communis were 0.1 mouse LD50, when virus transmission occurred both after virus feeding and after intrathoracic injection and Cs. inornata transmitted SSH virus after intrathoracic injection. Both Ae. communis and Cs. inornata were infected after injection of 3 plaque-forming units (PFU) NOR virus, and transmitted after injection of 300 PFU, but they also became infected after feeding on 30 PFU virus.

Aedes↗
PubMed1983

Effect of lymphoblastoid interferon on lymphocyte subsets in cancer patients.

The effect of interferon dose on lymphocyte subsets is unclear for humans, especially with prolonged intermittent administration. Enumeration of T4 and T8 cells and natural killer (NK) cell activity against K562 cells were examined as part of our ongoing randomized clinical study comparing low- and high-dose treatment strategies. Fifty-four patients have been entered into study, of which 46 are now evaluable. High-dose patients showed no significant changes during actual interferon infusion. However, over the entire period on study, there was a significant increase in NK cell activity (p = 0.001), a concurrent decrease in T8 (p = 0.004), and an increase in T4/T8 (p = 0.02). By contrast, for low-dose patients there was a trend of increasing NK activity during interferon administration, but no change during the total time on study, with a concurrent trend of decreasing T4/T8 and a significant increase in T8 (p = 0.01). Although there is as yet no significant response difference between high- and low-dose treatments, a favourable response was associated with an overall increase in NK activity (p = 0.005), a decrease in T8 (p = 0.02), and an increase in T4/T8 (p = 0.03). In a preliminary study of immune complexes in selected patients, an inverse relationship between NK cell activity and immune complex concentration was suggested. This was supported by in vitro addition of autologous immune complex-containing sera during NK cell assay.

Breast Neoplasms↗
PubMed1979

Bunyavirus development in arctic and Aedes aegypti mosquitoes as revealed by glucose oxidase staining and immunofluorescence.

Northway virus replication has been detected in salivary glands of wild-caught Culiseta inornata and Aedes communis mosquitoes from the western Canadian Arctic after incubation at 4 degrees C for 9 to 11 months, and after incubation at 13 degrees C for 3 to 4 months after they received virus by oral ingestion or intrathoracic injection. Aedes hexodontus supported Northway virus replication after incubation at 13 degrees C for one month after intrathoracic injection. Aedes aegypti supported Northway virus replication after incubation at 13 degrees C or 23 degrees C for 6 to 28 days following intrathoracic injection. A larval isolate of California encephalitis virus (snowshoe hare subtype) multiplied in all 3 species of arctic mosquito after incubation at 13 degrees C for 1 to 3 months after virus was administered by oral ingestion or intrathoracic injection. Virus was detected in salivary glands of Cs. inornata after 329 days incubation at 4 degrees C after intrathoracic injection. Bunyavirus antigens in salivary glands of arctic and domestic mosquitoes were detected by the glucose oxidase immunoenzyme technique somewhat less frequently than by assay for virus infectivity.

Aedes↗
PubMed1978

Transmission of Northway and St. Louis encephalitis viruses by arctic mosquitoes.

Transmission of a Canadian arctic isolate of Northway virus has been demonstrated after incubation of arctic Aedes communis mosquitoes at 13 degrees C for 27 days after intrathoracic injection of 300 plaque forming units of virus. Replication has also been demonstrated after intrathoracic injection of domestic A. aegypti mosquitoes of this virus. Virions of Northway virus, 84--92 nm diameter were morphologically typical of a bunyavirus after propagation in salivary glands of A. communis or in tissue cultures of baby hamster kidney (BHK-21) cells. An Ontario isolate of St. Louis encephalitis was transmitted by bites of A. communis after 27 days incubation at 13 degrees C after oral ingestion of 3 or 30 mouse LD50 virus. This mosquito species transmitted virus after 13 to 76 days incubation at 13 degrees C following intrathoracic injection of 3 mouse LD50 or higher virus doses.

Aedes↗
PubMed1977

Virions associated with acute gastroenteritis in Vancouver, 1976.

Virions were identified by electron microscopic observation of unconcentrated extracts of feces obtained from 55 (33%) of 167 children aged 3 weeks to 5 years who were hospitalized with acute gastroenteritis at Children's Hospital, Vancouver between January and December 1976. Morphologic types included 30 rotavirus, 15 adenovirus, 5 astrovirus and 5 picornavirus-like particles.

Acute Disease↗
PubMed1977

Methisazone therapy in pediatric vaccinia complications.

Methisazone 40 mg/kg/day was administered orally to six pediatric and one adult patient who contracted vesicular complications affecting the skin or mucocutaneous junctions 3 to 9 days after antismallpox vaccination, and to one elderly man with myeloid leukemia who developed vaccinia necrosum. Therapy was commenced 2 to 10 days after onset of complications and was administered for 3 days. All patients with skin or mucocutaneous complications showed dramatic clinical responses within one day after commencement of antiviral chemotherapy, and complete recovery occurred within one week. Clinical improvement was noted 4 days after therapy was begun in the case of vaccinia necrosum, and recovery occurred after 3 weeks.

Adult↗