摘要:

Mosquitoes were collected in Alberta during the spring, summer, and early fall of 1965. Western encephalitis (WE) virus was isolated from pools collected between August 11 and August 25.Two positive pools, one ofAedes vexans(Meigen) and one ofCuliseta inornata(Williston) were collected by sweep nets in irrigated areas of southern Alberta near places where horses were reported sick with WE virus. Seven other positive pools, three ofC.inornataand four ofCulex tarsalisCoquillett, were collected in southern Alberta from mammalian burrows, which are hibernating habitats forC.inornata,C.tarsalis, andAnopheles earleiVargas. This indicates thatC.tarsalisandC.inornatacan enter hibernation infected with WE virus. None of theA.earleipools tested were positive for WE virus.About 50% of theC.inornataand 9% of theC.tarsaliscollected from mammalian burrows were blood-engorged at the time of collection. None of theA.earleicollected from mammalian burrows were blood-fed.

ISSN:0008-4166    

DOI:10.1139/m68-001

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The inhibitory effects of 6-mercaptopurine, Imuran, and chloramphenicol on the in vitro incorporation of radioactive amino acid into antibody have been investigated. Inhibition of antibody synthesis by these drugs was compared to inhibition of protein synthesis within the same tissue cultures. The relative inhibition of antibody synthesis compared to that of protein synthesis provided an index which indicated the specificity and toxicity of the immunosuppressive agent. Imuran, at concentrations of 10–20 μg/ml inhibited antibody synthesis primarily, while at higher concentrations, protein synthesis was similarly affected. 6-Mercaptopurine at 177–250 μg/ml inhibited antibody production to a certain degree, while chloramphenicol at 300 μg/ml showed no preferential inhibition of antibody synthesis.

ISSN:0008-4166    

DOI:10.1139/m68-002

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A simple presence–absence (P–A) test was developed to provide a more economical and more sensitive method for conducting coliform analyses on municipal drinking water samples than the membrane filter (MF) technique. Over ninety percent of these samples routinely gave negative results by the MF method. A modified MacConkey broth, enriched to improve on acid and gas production by coliforms, was the isolation medium for the presumptive part of the P–A test.Parallel analyses of water samples were made by both the P–A and MF methods. Confirmatory tests established the reliability of the respective procedures to detect coliform bacteria. A statistical analysis of the results showed that the P–A test was more sensitive for detecting lower levels of pollution than the MF technique. Many of the confirmed positive P–A results came from P–A bottles that produced presumptive positive tests only after an extended incubation period of two to five days.The P–A test was about five times less expensive than the MF technique and by adding a few simple tests, the P–A procedure could give information on the presence of both fecal coliforms and fecal streptococci. For several samples, fecal streptococci were found by P–A tests in the absence of detectable coliform bacteria by either the MF or P–A methods of analysis.

ISSN:0008-4166    

DOI:10.1139/m68-003

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Transmission of California encephalitis (CE) virus strain R2929 by groups ofAedes vexans(Meigen) mosquitoes to rabbits was accomplished 7 and 9 days after the insects had imbibed an infective blood meal.Aedes aegypti(L.) mosquitoes transmitted virus to newly hatched chickens by biting them 48, 96, and 144 hours after intrathoracic injection.CE vires was found in gut, thorax, legs, and salivary glands of pools ofAedes triseriatus(Say),Aedes canadensis(Theobald), andA.vexansmosquitoes after intrathoracic injection of 101.3mouse LD50per 0.003 ml of virus. Salivary glands contained a maximum virus titer of 105.0mouse LD50per anatomical unit 5 days after injection.A.aegyptimosquitoes also supported virus growth after intrathoracic injection but yielded higher virus titers (106.3mouse LD50) in the salivary glands.The infection threshold ofA.vexansfed CE virus was 102.0LD50per insect. Immediately after ingestion of 102.0LD50of virus only the gut washings contained virus. Detection of virus was not accomplished again until 4 days later. Average maximum titers of 104.5LD50per salivary glands were found after 8 days of extrinsic incubation. The infection threshold ofA.aegyptifed CE virus exceeded 104.5LD50per insect.New Zealand white rabbits and Leghorn chickens circulated CE virus in their blood, which attained peak titers of 102.5mouse LD50per 0.03 ml 48 and 72 hours respectively after subcutaneous inoculation, but weaned mice did not develop viremia. All three animal species produced neutralizing antibodies to CE virus 21 days after inoculation.

ISSN:0008-4166    

DOI:10.1139/m68-004

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The formation and activity of nitrogenase2inAzotobacter vinelandiiOP was examined using a cell-free assay system. A lag period of about 30 min occurred between the exhaustion of the combined nitrogen source and growth on N2. Cells grown on ammonium acetate or potassium nitrate had no detectable nitrogenase activity. Nitrogenase activity appeared in cells, grown under a flowing gas phase of 20% O2– 60% He, about 45 min after the exhaustion of ammonia. Nitrogenase formation was inhibited in a closed system with an atmosphere containing 40% O2but not by one containing 20% O2. Hydrogen did not inhibit enzyme formation. The question of whether N2is required for the formation of the enzyme could not be answered as this gas could not be completely eliminated from the growth system. Chloramphenicol prevented the formation of the enzyme and inhibited nitrogen fixation in whole cells, but had no effect on cell-free enzyme activity. A brief rise in turbidity which occurred during nitrogenase formation appeared to be due to a color change in the cells from reddish brown to dark brown. Spectrophotometric examination of extracts from ammonia- and N2-grown cells did not reveal any components responsible for this color difference, but this result may reflect only the presence of interfering substances in the crude extract.

ISSN:0008-4166    

DOI:10.1139/m68-005

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A cell-free system which permits nitrogen fixation by extracts ofKlebsiella pneumoniaeM5al(formerlyAerobacter aerogenes) has been developed. It is, essentially, that system described by Bulen and associates forAzotobacter vinelandii, utilizing ATP as a source of energy and dithionite as a source of electrons. The Michaelis constant for fixation has been estimated to be 0.12 atm. The extracts possessed an ATP-dependent hydrogen evolving system. Hydrogen evolution from these extracts was less under nitrogen than under helium in the presence of ATP. Nitrogen gas appears to be the inducer of nitrogen fixation. In the absence of N2, no induction of nitrogenase occurs. Nitrogenase is absent in cells grown on NH4+-N. There is a lag of about 13 h after the introduction of N2gas into a culture which has depleted its supply of NH4+-N before nitrogenase can be detected. For reasons discussed in the text, this conclusion must be regarded as tentative at this time. Ammonium ion appears to prevent the synthesis of new molecules of nitrogenase without affecting the activity of those already formed.

ISSN:0008-4166    

DOI:10.1139/m68-006

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Growth inhibition by adenine or adenosine and its reversal by other purines were quantitatively different in the fourStaphylococcus aureusstrains we have studied. After 11 hours, 0.25 μmole/ml adenine or adenosine reduced growth by 6 and 4%, respectively, in the coagulase-negative SA-13 strain, by 35 and 35% in the tryptophan-dependent Smith strain, by 68 and 98% in a Wood 46 thymineless mutant strain, and by 40 and 37% in the parent Wood 46 strain. Normal growth in the presence of adenine or adenosine was restored in most cases by guanine, guanosine, hypoxanthine, inosine, and inosinic acid. However, for the thymineless mutant strain, guanine and inosine were much less effective in this respect in the presence of adenine, and none of these purines could reverse the inhibitory effect of adenosine. Purine analogs were mostly ineffective in inhibiting or in restoring growth. Our observations indicate that some patterns of purine biosynthesis and utilization inStaphylococcus aureusare different from those already known in other bacterial species. Adenine or adenosine had a greater inhibitory effect on the growth of coagulase-positive strains than on that of the coagulase-negative strain.

ISSN:0008-4166    

DOI:10.1139/m68-007

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Three hemagglutinins were separated by equilibrium density centrifugation in CsCl of Sindbis concentrates obtained from infected chick-embryo cultures. They were designated heavy fraction (HF, density 1.240 g/ml), intermediate fraction (IF, density 1.212 g/ml), and light fraction (LF, density 1.191 g/ml). On the basis of work published by other authors, HF is considered to consist of Sindbis virions and LF to consist of non-infectious coreless particles and other membranous structures. The third hemagglutinin fraction, IF, appeared in the culture fluid at about the same time as the virions (HF) and before the non-infectious LF. In a series of rebanding experiments in CsCl gradients the relationshipwas demonstrated. The constant buoyant density of IF and results of the reconstitution experiments described suggest that IF consists of virions surrounded by LF material in a fixed and constant proportion. It is not established whether IF plays any role in the intracellular replication of the virus.

ISSN:0008-4166    

DOI:10.1139/m68-008

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Precipitins against influenza A/PR8 were detected in the serum of normal rabbits with a highly sensitive cellulose acetate micro-immunodiffusion technique which allows the diffusion of whole virus particles. Rabbits were susceptible to subclinical artificially induced influenza A/PR8 infection. These natural antibodies might be indicative of natural infection in animal populations with influenza A/PR8 or a closely related influenza A strain. Similar immunodiffusion reactions were observed with normal serum from a sheep, a goat, guinea pigs, and roosters.

ISSN:0008-4166    

DOI:10.1139/m68-009

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Previous studies demonstrated that acriflavine treatment of early log phase cells ofBacillus subtilisproduced both stable oligosporogenic and asporogenic mutants in high yield. More recently it has been demonstrated that high numbers of oligosporogenic mutants, believed to be defective for a regulatory gene, were found consistently after acriflavine addition. The asporogenic mutants were found on only a few occasions at approximately 19 hours after the addition of acriflavine. Results did not imply that acriflavine selected out either type of mutant. Exposure of late log and stationary phase cells to acriflavine was not effective in producing sporulation mutants. However, if these cells grown to the late growth phase are irradiated with specific doses of ultraviolet light and then treated with acriflavine, high numbers of oligosporogenic mutants appeared. The acriflavine-induced Sp−mutants were not found to be auxotrophic for amino acids or resistant to acriflavine. They had no detectable respiratory deficiencies and produced the protease and bacteriocin associated with the early stages of sporogenesis.

ISSN:0008-4166    

DOI:10.1139/m68-010

出版商:NRC Research Press    

年代:1968

数据来源: NRC