摘要:

The hemolysin ofEscherichia colihas been concentrated 23-fold by ethanol and ammonium sulfate precipitation. Further evidence has been presented that the hemolysin is a protein or peptide. Kinetic studies of the hemolytic reaction reveal a complex curve which consists of a lag, an area of accelerated reaction rate, and a plateau. Kinetic studies also show that the hemolytic reaction can be best demonstrated at a pH of 7.9 and a temperature of 30 °C using a 1% suspension of sheep erythrocytes.

ISSN:0008-4166    

DOI:10.1139/m71-118

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Studies were made on the oncogenic properties of a line of polyoma virus transformed hamster cells. Passage of the cells in vivo resulted in an increase in oncogenicity. Thus the latent period for the appearance of a tumor was decreased, and as few as 5 to 10 cells were now sufficient to produce a tumor in a young hamster. Tumors were invariably restricted to the subcutaneous site of injection. In contrast, polyoma virus itself caused widespread production of tumors throughout the animal. Histological examination of tumor tissue revealed marked differences between tumors caused by virus or virus-transformed cells. It was concluded that little or no metastasis of transformed cells could have occurred, and that insignificant rescue of the polyoma virus genome must have been induced in transformed cell tumors.Powassan virus, a group B arbovirus, did not show any oncolytic activity toward tumors induced by the polyoma virus transformed cells.

ISSN:0008-4166    

DOI:10.1139/m71-119

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The site and structure of the viral inclusion can be easily seen in freeze-etched preparations of vaccinia-infected L-cells. It can be recognized not only by its content of virions but also by its granular nature which contrasts with the almost structureless cytoplasm. The granular material (viroplasm) appears to be incorporated into the developing immature virion in a condensed state. The inclusion is surrounded by ribosomes and a fibrous protein structure which appears to contain it, and is interspersed with membrane-bounded vesicles and vacuoles. Both the internal and external surfaces of the virions are visualized and appear similar to those observed in negatively stained preparations of isolated virions.

ISSN:0008-4166    

DOI:10.1139/m71-120

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The heating ofS.aureusMF-31 andS.typhimurium7136 at 52C and 48C respectively, produced a sublethal heat injury. When injured cells were placed in fresh growth medium they recovered. The recovery ofS.aureuswas not inhibited by chloramphenicol. The metabolic activities of tricarboxylic acid (TCA) cycle enzymes, as well as other selected enzymes in crude extracts of normal and heat-injured cells of both microorganisms were assayed. In extracts fromS.typhimuriumthere was some loss of specific activity with fumarate hydratase, glutamate dehydrogenase, fructose diphosphate aldolase, lactate dehydrogenase, and the NAD(P) oxidases as a result of heating. In extracts fromS.aureusoxoglutarate dehydrogenase, malate dehydrogenase and lactate dehydrogenase were severely inactivated after heating. Other enzymes in comparison were only moderately sensitive to heat. No significant increase in enzyme activity was observed in extracts from injured cells of either microorganism. Re-naturation of lactate dehydrogenase and malate dehydrogenase occurred during the recovery ofS.aureusboth in the presence and absence of chloramphenicol. No renaturation of oxoglutarate dehydrogenase was found under the same conditions.

ISSN:0008-4166    

DOI:10.1139/m71-121

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Phages were isolated fromStaphylococcus epidermidisafter exposure of cultures to mitomycin C. Using certain of these phages, genes controlling resistance to novobiocin, streptomycin, and erythromycin and genes involved in the synthesis of adenine and riboflavin were transferred from donor to recipient strains ofS.epidermidis. Interspecific transduction of the Novrmarker was accomplished betweenS.epidermidisandS.aureus. Attempts to transfer penicillin resistance were not successful.

ISSN:0008-4166    

DOI:10.1139/m71-122

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The desire to obtain maximum yields of polyoma virus from infected mouse tissue culture lysates prompted us to examine more closely the interaction between virus and cell fragments. The objective was to find the best and most economical means of alleviating this interaction, and allow quantitative recovery of the virus for further purification. Sonication of polyoma virus infected mouse-kidney cultures sufficed to release the virus in a form amenable to hemagglutinin assay. In contrast infected mouse embryo lysates required neuraminidase to effect maximum release. A variety of other enzymes and treatments were tested and found to be completely ineffective, or less effective than neuraminidase. However, in spite of the ability to effect release of virus at this stage, subsequent centrifugation to pellet the cell fragments always resulted in reattachment of the virus to these fragments. Complete elution of the virus then required several cycles of neuraminidase, trypsin, pH 8.5 treatments. It was shown that full and empty viral capsids behaved similarly.

ISSN:0008-4166    

DOI:10.1139/m71-123

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

These investigations provide evidence that theN.crassacolonial mutants col-2 and col-3 are defective for two of the HMP shunt enzymes, G6PD and 6PGD respectively. Nutritional studies indicate that both mutants will revert to a more nearly wild-type morphology when they are grown on carbon sources capable of generating NADPH by alternative metabolic pathways. The HMP dehydrogenases are repressed when the organism is grown on acetate or low levels of glutamate. It appears that the lowered steady-state level of NADPH in the colonial mutants is the limiting factor in growth. The principal function of the shunt, apparently, is to supply the reduced NADP required by the cell for its major biosynthetic pathways. The genes coding for the two apparently coordinately controlled dehydrogenases are linked and may be part of a functional region regulating the HMP shunt.

ISSN:0008-4166    

DOI:10.1139/m71-124

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The two dehydrogenases of the hexose monophosphate shunt, glucose-6-phosphate dehydrogenase and 6-phosphogluconic acid dehydrogenase, were examined in two morphology mutants ofNeurospora crassa. Glucose-6-phosphate dehydrogenase extracted from the mutant colonial-2 was found in an altered form as compared to the wild-type enzyme. The second enzyme of the pathway was observed to be abnormal in the mutant colonial-3. In addition, 6-phosphogluconic acid dehydrogenase was found to exhibit non-classical kinetics. The data indicate that the altered morphology exhibited by both colonial-2 and colonial-3 is due to the suboptimal capacity of the hexose monophosphate shunt to function normally. This physiological impairment of the pathway is reflected in a lowered cellular steady-state level of NADP.

ISSN:0008-4166    

DOI:10.1139/m71-125

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Six isolates ofC.albicanswere tested for their capacities to form methionine via S-adenosyl-L-methionine (or S-methyl-L-methionine): homocysteine methyltransferase (EC. 2.1.1.e). Cell-free extracts from all organisms were obtained from cultures containing predominantly (greater than 85%) yeast-like cells. Assay conditions with respect to pH, time of incubation, substrate, and protein concentrations for the methyltransferase reaction were determined.Extracts from all six strains formed methionine when eitherL-homocysteine,L-homocysteine thiolactone, orL-homocystine was used as the methyl acceptor, and more methionine was synthesized when S-methyl-L-methionine was the methyl donor than when S-adenosyl-L-methionine was used. The methyltransferase reaction was inhibited by methionine,L-methionine-ethyl-ester, andDL-N-hydroxy-methyl-methionine. Substantially less inhibition was observed withL-ethionine and S-methyl-L-cysteine, while no inhibition occurred when six other methionine analogs were tested.

ISSN:0008-4166    

DOI:10.1139/m71-126

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Several characteristics of antigenic competition were studied in mice using various pairs of antigens administered in sequence. Enhanced immunosuppression of the response to the second antigen was obtained by increasing the dose of the initial antigen relative to the dose of the test antigen. Diminished immunosuppression was elicited when the dose of the second antigen was increased to near maximum levels, corresponding to the plateau of immune responsiveness to this antigen when it was administered in equivalent dosage to normal control groups of animals. Induction of a primary immune response to the initial antigen was a more effective immunosuppressant than was induction of a secondary immune response to an equivalent dose of the same antigen. Antigenic competition was manifested when antigen was administered in differing sites in the animal such as in separate footpads. Administration of the antigens in the same site did not invariably result in antigenic competition, since a combination of two intraperitoneal injections of unrelated antigens in sequence was not associated with immunosuppression of response to the test antigen. Immunosuppression by antigenic competition did not alter the affinity of the antibody product to the test antigen.

ISSN:0008-4166    

DOI:10.1139/m71-127

出版商:NRC Research Press    

年代:1971

数据来源: NRC