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Biomedical subjects

D W Mackenzie

Publications and source records attributed to D W Mackenzie.

At least 73 records · Page 4Linked to original sources
PubMed1980

The preparation of protoplasts from Aspergillus fumigatus mycelium.

Protoplasts have been prepared from the mycelium of Aspergillus funigatus, using a lytic enzyme mixture from Trichoderma harzianum. A variety of experimental conditions were investigated in order to achieve optimal conditions for protoplast production. Electron micrographs showed the preparations to be free of cell-wall. Material obtained by this procedure can be used as a source of cytoplasmic antigens for further analysis.

Aspergillus fumigatus↗
PubMed1979

The preparation and chemical composition of fractions from Aspergillus fumigatus wall and protoplasts possessing antigenic activity.

A detergent-soluble fraction was prepared from the fragmented wall of Aspergillus fumigatus mycelium using the non-ionic detergent Triton X-100, and a wall-free extract was prepared from the same source in the form of protoplasts, released by a lytic enzyme system from Trichoderma harzianum. These extracts were examined by polyacrylamide gel electrophoresis and their detailed chemical composition was established. They were compared with the water-soluble fraction prepared from total mycelium, which is used routinely in this laboratory for serological tests. All fractions had immunological reactivity towards an antiserum prepared in rabbits against this water-soluble fraction of the mycelium, as shown by double diffusion. Both protein and carbohydrate moieties appear to be involved in the antigenic sites, with carbohydrate reactivity predominantly associated with the protoplast fraction. The fact that all preparations contained at least one common antigenic determinant, as judged by lines of identity to a single antiserum, is discussed in relation to antigen location.

Antigens, Fungal↗
PubMed1979

Imported fungal infections.

Data on mycoses known to be imported into the United Kingdom are sparse. Estimates on the prevalence of fungal infections have to be based on indirect and incomplete figures, obtained from isolation figures and reports of individual cases to co-ordinating centres such as the Mycological Reference Laboratory and the Communicable Disease Surveillance Centre of the Public Health Laboratory Service. Imported species of dermatophytes account for less than 1% of the total number of isolations made annually at mycological laboratories throughout the U.K. A suggested prevalence of dermatophytosis in this country is c. 250 000 cases per annum. Trichophyton rubrum may now be the most common species of dermatophyte. Other estimates of the frequencies with which infections are recorded each year include mycetoma (7-10), histoplasmosis (2-5), aspergilloma (50-80), invasive aspergillosis (10-30), Candida vaginitis (greater than or equal to 1 000 000), invasive candidiasis (10-80), Candida endocarditis (1-2) and cryptococcosis (6-10).

Aspergillosis↗
PubMed1977

Genetic damage induced by ethyl alcohol in Aspergillus nidulans.

Heterozygous diploid conidia of Aspergillus nidulans were treated during germination with ethyl alcohol in concentrations ranging from 0.25% to 20% (v/v). The diploid strain carried three recessive conidial color mutations, in addition to genetic markers on all eight pairs of linkage groups. It was thereby possible to detect events of crossing over, non-disjunction, and mutation. An increase in the dose of ethanol was associated with a decrease in conidial viability and an increase in the relative and absolute frequencies of formation of (a) normal colonies which produced colored sectors and (b) phenotypically abnormal colonies, the majority of which (83.1%) produced normal sectors. At a concentration of 5% (v/v) ethanol, the survivors included 17.59% of the former and 44.7% of the latter colonies. Genetic analysis of the various segregants suggested that the frequencies of both mitotic crossing over and non-disjunction or the misdistribution of chromosomes were increased by ethanol. Among 133 abnormal colonies which segregated normal clones, 79 (59.4%) were associated with one of these genetic events. A total of 297 haploids and 130 diploids arose as normal segregants from the abnormal colonies. There were 31 recognizable events of non-disjunction and 14 crossing over in linkage groups I and II, where these events could be distinguished. These data suggested that the predominant effect of ethanol was a disruption of chromosome distribution. A cytological examination of ethanol-treated, germinating conidia revealed an interference with the mitotic spindle apparatus. The frequency of detectable spindles decreased more than 3-fold after 8 h exposure to 5% (v/v) ethanol. This finding supported the conclusion that ethanol disrupted chromosome distribution, and suggested the mechanism by which it does so. Human clinical data on alcohol consumption were examined in light of these findings.

Aspergillus nidulans↗
PubMed1977

Laboratory evaluation of serological tests for systemic candidiasis: a cooperative study.

Three serological tests for candidiasis, agar gel diffusion (AGD-1), whole cell agglutination (AGGL-1), and latex agglutination (LAT), were evaluated by six laboratories with 100 coded sera. In addition, each of six laboratories performed a test of its choice, either the AGD-2, the AGD-3, the AGGL-2, or one of three counterimmunoelectrophoresis (CEP) methods (CEP-1, CEP-2, and CEP-3). Results are presented by laboratory for a group of 53 "candida-involved" cases (33 proven, 14 presumptive, and 6 probable) and 47 negative controls (41 normal and 6 other disease states). The AGD-1 test produced an overall average of 85.1% positive results in the candida-involved group and 5.0% positives in the control group. The LAT produced an overall average of 89.0% positives in the candida-involved group and 17.4% positives in the controls. The AGGL-1 test produced an overall average of 63.8% positives in the candida-involved group, with 12.3% positives in the controls. In the individual tests, the best performance was shown by the CEP-3 test (92.5% positives in the candida-involved group and 2.1% positives in controls) and the CEP-1 test (88.7% positive in the candida-involved group and no positives in the controls). The tests with the highest sensitivity were the AGGL-2 and CEP-2 (94.3 and 96.2%, respectively). These tests were also the least specific (80.9 and 76.6%, respectively). In the three common tests, the AGD-1 was the most reproducible, whereas the AGGL-1 produced considerable laboratory-to-laboratory variation. Since cell-free extracts of mechanically disrupted C. albicans were used for the LAT and all the AGD and CEP tests, the difference in performance was considered to be mainly due to antigenic composition and the conditions of the test. The results of this study confirm the value of serological tests for the diagnosis of systemic candidiasis, but point out the need for standardized reagents.

Agglutination Tests↗
PubMed1976

A comparison of Aspergillus fumigatus antigens by counterimmunoelectrophoresis.

Counterimmunoelectrophoresis (CIE) has been evaluated for routine diagnostic work, using antigens prepared from 2 different isolates of Aspergillus fumigatus, at 2 different concentrations. Additional antigens prepared in a variety of ways and 2 commercially available antigens (Bencard, London; Institut Pasteur, Paris, France) have been compared with the routine antigens. It has been shown that the use of the routine antigens will detect the majority of positive reactions. At optimal reacting concentrations antibodies were detected in 75% of asthmatic patients. In sera from patients with a presumptive diagnosis of allergic aspergillosis, CIE will detect twice as many positive reactions as a conventional agar gel diffusion test.

Antibodies, Fungal↗
PubMed1975

Counterimmunoelectrophoresis as a routine mycoserological procedure.

Counterimmunoelectrophoresis (CIE) has been compared in a diangostic laboratory with agar gel double diffusion (DD) as a routine procedure for detection of antibodies to pathogenic and allergenic fungi and actinomycetes. It was shown to be of particular value in detecting antibodies to Aspergillus fumigatus. Thus 72 of 106 sera in which precipitins were detected were positive by CIE alone. Some sera were positive only by CIE to antigens prepared from Histoplasma capsulatum, Allescheria boydii, Candida albicans and C. parapsilosis.

Actinomycetales↗
PubMed1974

Proteinaceous virus-like particles from an isolate of Aspergillus flavus.

Virus-like particles were purified from a single nonaflatoxin-producing isolate of Aspergillus flavus. The virus-like particles were spherical, measuring 27 to 30 nm in diameter, were electrophoretically homogeneous, and sedimented at approximately 49S. The particles had a buoyant density of 1.28 g/cm(3) in CsCl and contained no detectable nucleic acid.

Aflatoxins↗
PubMed1971

Effect of relative humidity on survival of Candida albicans and other yeasts.

Individual blastospores of Candida albicans were deposited on the surface of 50-mm membranes (Millipore Corp.) and placed within sealed glass chambers at various relative humidities (RH). After 48 hr, virtually all cells maintained at 100 and 10% RH had survived, but 84% of the cells maintained at 60% RH failed to develop into colonies when transferred to Sabouraud medium. No morphological abnormalities could be observed in cells surviving low RH values, but their initial rate of multiplication after transfer to Sabouraud medium was greatly reduced, compared to that demonstrated by cells maintained at 100% RH. At 60% RH, the exposure time required to kill 50% of the blastospores was 2 to 3.5 days. The inimical effect of 60% RH was confirmed in a total of 21 isolates of C. albicans. No deleterious effect was noted when 12 other species of yeasts were subjected to 10, 60, and 100% RH. The single isolate of Candida brumptii and 1 out of the 20 isolates of Cryptococcus neoformans tested also failed to grow after blastospores had been exposed to 60% RH for 4 days.

Agar↗