摘要:

L-929 cells have been cultivated for more than 6 months in the presence of interferon. These L-cells, referred to as L-int cells, were found to be more susceptible to the lytic properties of vesicular stomatitis virus (VSV) than normal L-929 cells. This phenomenon has been demonstrated by the production of clear plaques as opposed to cloudy plaques as well as the increased release of cell incorporated3H-thymidine after VSV infection. The L-int cells were also signicantly more susceptible than L-929 cells to the cytotoxic properties of DEAE-dextran, protamine sulfate, and methylated albumin.This interferon-induced change to L-cells is not stable. Increased susceptibility to VSV lysis is lost after 4–6 cell generations in the absence of interferon, and increased susceptibility to DEAE-dextran is lost after 16–24 cell generations in the absence of interferon. Moreover, the increased sensitivity to VSV lysis and polycation cytotoxicity can be induced after overnight treatment of L-929 cells with interferon.

ISSN:0008-4166    

DOI:10.1139/m74-169

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Crude extracts prepared from the extremely halophilic bacterium M6catalyzed the conversion of glucose to gluconic acid. The latter compound was dehydrated to 2-keto-3-deoxygluconic acid, which in the presence of ATP, was converted to equimolar amounts of pyruvate and 3-phosphoglyceraldehyde, presumably through the intermediate compound 2-keto-3-deoxy-6-phosphogluconic acid. Additional enzymes catalyzing the conversion of 3-phosphoglyceraldehyde to pyruvic acid were also present. These data are consistent with the operation of a modified Entner-Doudoroff pathway in this organism.

ISSN:0008-4166    

DOI:10.1139/m74-170

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Effects of uranyl acetate (UA) and potassium phosphotungstate (KPT) on dimensions of four tailed bacteriophages have been studied comparatively. All UA stained preparations show positive (UA+) or negative (UA−) staining according to the local, low- or high-particle concentration, and crystals containing swollen, distorted phages. UA causes flattening or shrinking of phage heads, the latter especially after positive staining. Transverse diameters of elongated heads are reduced, and capsids, tails, and tail fibers may be swollen. In addition, isometric heads may show pentagonal outlines and tails may be elongated. Dimensions of phages TP50 and PBP1 have been analyzed by the method of multiple discriminant analysis. Differences between KPT, UA−, and UA+ stained viruses are statistically highly significant (P < 0.001). Dimensions of UA+ stained viruses appear to be unreliable for taxonomic purposes. Dimensions of UA− stained viruses are to be controlled by other staining methods. UA has several advantages but phosphotungstate stains should be preferred, particularly in staining large cubic DNA viruses.

ISSN:0008-4166    

DOI:10.1139/m74-171

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Lysozyme-free antiserum and complement treatment of strain 1885 ofPseudomonas aeruginosawas observed to destroy the penetration barrier of the outer cell wall to lysozyme but not to induce leakage of acid-soluble nucleotides through the cell membrane. The same treatment did not produce a significant increase in uptake of3H-tetracycline or3H-streptomycin by the resistant strain 1885 in spite of the destruction of the penetration barrier to lysozyme. A significant increase in both streptomycin and tetracycline uptake occurred in carbenicillin-treated strains but the increase was similar for both susceptible and resistant (to tetracycline and streptomycin) strains ofP.aeruginosa. These data suggest (1) the outer cell wall is not a significant penetration barrier to these drugs; (2) the peptidoglycan layer does function as a penetration barrier of similar magnitude in resistant and susceptible cells; (3) the resistance of the strains is a property of the cell membrane or materials intimately associated with the cell membrane. The latter conclusion was further supported by the differential uptake of streptomycin in NaCl-lysozyme-induced spheroplasts of strains 1885 and 2379.

ISSN:0008-4166    

DOI:10.1139/m74-172

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The transport systems for all of the amino acids studied, with the exception of isoleucine, obey saturation kinetics. The strong inhibition of the process by cyanide and dinitrophenol provides evidence that energy is required. Additional evidence for the requirement of energy for amino acid transport is the strong temperature dependence (Q10about 2) and the high concentration ratios measured for transported amino acids.Transport parameters (KsandVmax) for several amino acids were determined from data for two different concentration ranges. The results of the kinetic studies indicate the presence of two or more transport systems that become saturated at different substrate concentrations for each of the amino acids. The presence of a high affinity – high capacity transport system for arginine indicates that this amino acid may be utilized efficiently by the diatom when present at low concentrations in the natural environment.Interactions between pairs of amino acids suggest that several transport systems are available. There appears to be one system for ornithine and arginine, one for glutamate and aspartate, and several for neutral amino acids.Restriction of nitrogen in the growth medium produces a marked increase in the rate of amino acid uptake, indicating that amino acids are acquired more rapidly from the medium by nitrogen-limited cells.

ISSN:0008-4166    

DOI:10.1139/m74-173

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Several amino acids supplied at 0.1 mM allow good growth ofCyclotella cryptica. The cells can grow as well on arginine and glutamine as on nitrate. Glutamate, proline, ornithine, and asparagine also allow good growth, while glycine, alanine, and aspartate support relatively low initial growth rates. Isoleucine appears not be utilized at all. Ammonium and urea are excellent nitrogen sources for growth.There is good correlation between chlorophyll and protein content in cells grown on different nitrogen sources. Cells grown in nitrate, arginine, and glutamine media contain the highest amount of protein and the best pigmentation. Although both glutamate and proline allowed good growth, cells grown in these media have low levels of protein and chlorophyll, indicating nitrogen limitation. No growth inhibition was observed for any of the amino acids tested at 0.1 mM in the presence of nitrate. It is estimated that amino acids at naturally occurring concentrations may contribute significantly to the nitrogen economy of this diatom when more common nitrogen supplies such as nitrate and ammonia are scarce.Nitrate reductase inC.crypticaappears to be found only in the presence of nitrate, and is repressed by other nitrogen compounds. The extent of repression by amino acids, urea, and ammonium is related to their ability to promote growth when supplied as sole sources of nitrogen.

ISSN:0008-4166    

DOI:10.1139/m74-174

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Six rough mutants ofSalmonella typhimuriumLT2 with defects in the heptose region of the lipopolysaccharide were isolated and analyzed for phage sensitivity, for sugar composition and serological specificity of the lipopolysaccharide, and for genetic properties. Three of the mutants were of chemotype Rd2, with mutations presumably in therfaFgene. Three mutants of chemotype Re represent mutants in at least two separate genes, one perhapsrfaEand the other a previously undescribed generfaC, which maps in the cluster ofrfagenes at 116 min on the linkage map.

ISSN:0008-4166    

DOI:10.1139/m74-175

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Six mutants ofSalmonella typhimuriumLT2 with defects in the heptose region of the lipopolysaccharide (LPS) ("rough" mutants) were more sensitive to the growth-inhibitory effects of erythromycin, bacitracin, vancomycin, novobiocin, kanamycin, and cloxacillin and of deoxycholate than smooth strains, but less sensitive to tetracycline and ampicillin. In general, growth of the three rough mutants of chemotype Rd2, which lack the distal but not the proximal heptose unit in the LPS, was less inhibited than the three mutants of chemotype Re, which are heptose-deficient. In addition, inhibition of uracil-1-14C incorporation in the presence of actinomycin D and spheroplast formation in the presence of lysozyme occurred in the rough mutants without ethylenediaminetetraacetate (EDTA) treatment of the cells, while actinomycin D and lysozyme were effective on smooth strains only after EDTA treatment. Since the major part of the LPS is in the outer membrane of the cell envelope, and since the target of the toxic agents used is located inside this layer, these data indicate that the carbohydrate part of the LPS component of the outer membrane is an essential part of a barrier layer preventing penetration of large molecules.

ISSN:0008-4166    

DOI:10.1139/m74-176

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The synthesis of alternative adsorbents and their attempted use for the purification of urease from jack bean extracts and from several strains ofProteus morganiiby affinity chromatography is described. The nature of the ligand and the length of the side chain joining the ligand to the agarose backbone of the matrix were critical factors in determining the suitability of these adsorbents for urease purification. Adsorbent capacities continued to be the only factor limiting the purification of urease by this method from any of the sources so far used.

ISSN:0008-4166    

DOI:10.1139/m74-177

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The effect of sublethal heating onStaphylococcus aureuswas followed by plate counting on trypticase soy agar and by calculating decimal reduction times (D52C). Pseudodecimal reduction times (D′52C) were obtained from plate counts on trypticase soy agar containing 7.5% NaCl.D52Cwas a measure of lethality and the ratioD′52C/D52Cwas used as a measure of injury. Sublethal heating was carried out in various 100 mM (pH 7.2) solutions.Orthophosphates of potassium, ammonium, and sodium were more lethal than the corresponding chlorides (averageD52values of 18.2 and 29.6 min respectively). Orthophosphates also appeared to be more injurious than chlorides (averageD′52C/D52Cvalues of 0.43 and 0.62 respectively). 'Phosphate'-heated cells lost 28.4% of their cellular Mg while 'chloride'-heated cells lost 11% of their Mg. Good correlation exists betweenD′52C/D52Cvalues and the magnesium lost. Kinetic studies in potassium buffer also showed good correlation between loss of salt tolerance and loss of cellular Mg. This, and other evidence, suggests that loss of Mg is one of the primary events in the sublethal heat injury ofS.aureus.

ISSN:0008-4166    

DOI:10.1139/m74-178

出版商:NRC Research Press    

年代:1974

数据来源: NRC