ISSN:0008-4166    

DOI:10.1139/m80-113

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A large number of North American equine samples were tested for the California group of arboviruses (CAL). Of 861 equine sera tested by hemagglutination inhibition using the snowshoe hare virus as an antigen, 106 (12.3%) were positive. Neutralization tests confirmed antibodies to this virus in 72 of the positive sera. This study provides evidence of CAL activity in the domestic animal population of Nova Scotia.

ISSN:0008-4166    

DOI:10.1139/m80-114

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Changes occurring in the cell membrane of nondividing cells ofMicrococcus lysodeikticusdisIIp+grown in the presence of the mucopeptide synthesis inhibitorD-cycloserine include (a) an increase in the relative amount of diphosphatidylglycerol with a concomitant decrease in the relative content of phosphatidylglycerol, (b) a small increase in the relative palmitic acid content of phosphatidylinositol, and (c) leakage of membrane components into the growth medium. Growth of the organism in the presence of bothD-cycloserine andD-alanine (which prevents the effects ofD-cycloserine on cell division and mucopeptide synthesis) prevents the above changes in the cell membrane, demonstrating that secondary damage to the cell membrane can occur as a result of inhibition in mucopeptide synthesis. Growth of the organism in the presence ofD-cycloserine and pantoyl lactone prevents the leakage of membrane components and cell division inhibition. Possible relationships of these changes to cell division are discussed.

ISSN:0008-4166    

DOI:10.1139/m80-115

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A simple and rapid method for microscopical and cultural examination of leaf mycoflora is described. Scotch tape with adhesive on both sides is attached to microscope slides. An impression of the leaf surface is made by pressing the leaf onto the tape. After staining with lactophenol–aniline blue and mounting in AH water-soluble mounting medium the preparation is ready for examination under the microscope. Impressions can also be used for cultural studies by covering them with a thin film of agar medium and incubating them in a moist chamber for 2–3 days. These slide cultures will show both the number and the pattern of distribution of the fungi originally present on the leaf surface.

ISSN:0008-4166    

DOI:10.1139/m80-116

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A comparative study of selenate and selenite assimilation bySalmonella typhimuriumrevealed that selenite was not transported by the sulphate permease. Selenite uptake could be detected both in wild-type cells repressed for sulphate transport and in mutants that lacked a functional sulphate permease. In contrast, selenate was assimilated by the same process as was sulphate; selenate transport was repressed under the same conditions which repressed sulphate uptake and was absent in permeaseless mutants. Selenite transport was absent if cells were glucose starved or treated with either azide orp-chloromercuribenzoate. The pH optimum was between pH 6 and pH 7; transport was most rapid at 36 °C. The double reciprocal plot for selenite transport at different substrate concentrations was biphasic: between 10 and 50 μMSeO32−the apparentKmwas 37.8 μM, and at higher concentrations, 2.87 mM. The transport rate for 0.1 mMSeO32−was significantly stimulated by sulphite concentrations up to 5.0 mM, with a maximum at 3.0 mMSO32−. The results establish a selenite transport process, inS.typhimurium, as the initial step of an assimilatory pathway selective for selenium.

ISSN:0008-4166    

DOI:10.1139/m80-117

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The application of crossed immunoelectrophoresis to the analysis of a reference cytoplasm and cell envelope preparation fromPasteurella multocidaserotype 1 revealed antigenic complexity not previously found. At least 55 cytoplasmic and 19 cell envelope antigens were clearly distinguished. Variation of anticytoplasm immunoglobulin concentration was a major determining factor in resolving the maximum array of cytoplasmic antigens.The use of intermediate gel modification of crossed immunoelectrophoresis permitted the recognition of antibodies in the preimmune rabbit serum against a number of cytoplasmic antigens and a single cell envelope antigen. This technique also demonstrated that reference cytoplasm obtained by 105 000 × gcentrifugation of sonically disrupted pasteurellae and repeatedly washed reference cell envelope preparation contained antigens of either origin in amounts sufficient to elicit antibody responses in the host. Antisera to whole cells in the intermediate gel indicated that formalin killedP.multocidawere capable of eliciting immune responses to both reference systems.

ISSN:0008-4166    

DOI:10.1139/m80-118

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Comparisons of slowly growingBacillus subtiliscultures grown in batch culture, a chemostat, and a turbidostat were made. Cultures in a turbidostat were found to grow optimally and to be in balanced growth. The duration of deoxyribonucleic acid (DNA) replication, orCperiod, was estimated by means of an autoradiographic analysis, a genetic analysis, and determinations of DNA per cell. These measurements were performed on cells growing at different slow rates. The results showed that theCperiod increased with increasing generation times, but the increase in duration of theCperiod was not proportional to the increase in generation time.

ISSN:0008-4166    

DOI:10.1139/m80-119

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The photosensitizing action of 7-phenylhepta-2,4,6-triyne (PHT), a polyacetylenic compound isolated fromBidens pilosaL. (Asteraceae), has been studied usingEscherichia coliandSaccharomyces cerevisiaeas the test organisms. The survival curves forE.colitreated with PHT and ultraviolet (UV) radiation were obtained and have been interpreted quantitatively on the basis of a target theory model. The number of "targets" in the cell that must be destroyed before cell death occurs was estimated at six, whereas the dose,D0, that reduced the surviving fraction of the population to 1/e of its value was estimated to be 280 J/m2.Survival was enhanced in aerobic conditions as compared with anaerobic conditions, which is strong evidence that PHT does not behave as a photodynamic sensitizer in vivo. This view was confirmed by work with azide (a quencher of singlet oxygen), D2O (which increases the lifetime of singlet oxygen), and superoxide dismutase (which scavenges superoxide radicals). None of these treatments modified the survival curves significantly, indicating that activated species of O2are probably not involved in photosensitizations with PHT in vivo.Cell respiration was found to be rapidly inhibited by mild treatments of PHT and UV radiation, suggesting that nuclear metabolism is not the primary target of photosensitization as is the case with another group of photosensitizers, the furanocoumarins. The available evidence indicates that PHT is a representative of a new class of phototoxic compounds. A mechanism of action involving production of free radicals is proposed.

ISSN:0008-4166    

DOI:10.1139/m80-120

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A scanning electron microscopic examination of the surface ornamentation of haploid, heterokaryotic, and diploid conidiospores ofAspergillus parasiticusis presented. Previous studies on the parasexual cycle in this aflatoxin-producing species have shown that heterozygous diploids may be isolated with ease. However, rational genetic analysis of diploids has been hampered by the nonrandom recovery of auxotrophic markers from heterozygous diploids. In this study, a double transfer method involving only brief exposure top-fluorophenylalanine (FPA) allowed increased recovery of auxotrophic markers from heterozygous diploids. Extensive sampling of green-spored types from FPA-treated diploids provided an estimate of auxotrophic segregants not visually identifiable. We examined seven heterozygous diploids involving three spore color markers and eight auxotrophic markers. In addition, two mutants blocked in aflatoxin production which accumulated visually detectable aflatoxin precursors were analyzed. One linkage between an auxotrophic marker and a spore color marker was detected; however, no evidence for linkage was found between the blocked aflatoxin mutants and the other markers studied.

ISSN:0008-4166    

DOI:10.1139/m80-121

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Free-living, dinitrogen-fixing bacteria associated with roots of grasses were isolated from several locations in Israel. Bacteria with characteristics similar to those ofAzospirillumwere isolated fromCynodon dactylonroots and were compared withAzospirillum brasilensefrom Brasil (Sp-7) and from California (Cd). Colonies of the Israeli isolates were yellow and consisted of curved rods, 0.5–0.6 μm in diameter with polar flagella, whereas colonies ofA.brasilensewere pink (Sp-7) and red (Cd) and the cells were 1.0–1.1 μm in diameter with polar flagella. Ultraviolet absorption spectra of solublecand membrane-boundcandbcytochromes were similar in all isolates. When grown in semisolid agar medium with or without ammonium chloride all isolates formed a growth zone below the surface. However, they grew best under aerobic conditions in liquid medium containing NH4Cl. All isolates could use salts of malate and lactate, arabinose, and galactose, but not mannitol, as sole carbon sources; they did not need biotin to shorten their lag phase. One Israeli isolate was capable of growing and fixing nitrogen with glucose as a sole carbon source. The Israeli isolates formed aggregates above pH7.6 in liquid or semisolid medium and were capable of reducing nitrate to nitrogen gas under anaerobic conditions.

ISSN:0008-4166    

DOI:10.1139/m80-122

出版商:NRC Research Press    

年代:1980

数据来源: NRC