Effect of ionizing irradiation on susceptibility of McCoy cell cultures to Chlamydia trachomatis.
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The effect of graded doses of irradiation (cobalt-60) on the morphology of McCoy cells was analyzed, and 4,000 to 5,000 r was selected as a satisfactory dose for production of giant cells. The susceptibility of radiation-induced giant cells to chlamydial infection was compared with that of nonirradiated cells by using three strains of Chlamydia trachomatis and one of C. psittaci. Monolayers of giant cells were more susceptible than normal McCoy cells as indicated by (i) greater numbers of inclusions (four- to eightfold) per unit area of monolayer, (ii) larger inclusions (fourfold greater in area), (iii) higher infective titers (1 log or more greater) of harvested cells, and (iv) greater ease of promoting a second cycle of growth. Graded doses of irradiation were applied also to mouse fibroblast (L) cells, and a similar increase in susceptibility to chlamydial infection was noted. It is concluded that giant cells produced by irradiation possess advantages over nonirradiated cells in culture for growth of Chlamydia. (+info)
Production of types A and B spores of Clostridium botulinum by the biphasic method: effect on spore population, radiation resistance, and toxigenicity.
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Spores of three strains each of type A and type B Clostridium botulinum were produced both by a biphasic (solid medium overlaid with an aqueous phase) and by a "conventional" (deep broth culture) procedure. Sporogenesis by the biphasic system was more rapid, convenient, and economical, and yielded as many or more heat-resistant (80 C, 10 min) spores per milliliter as by the conventional technique. Of several aqueous phases [thiamine-hydrochloride, yeast extract, (NH(4))(2)SO(4)] tested with strain 62A, the highest spore colony counts were obtained with 2.0% (NH(4))(2)SO(4). The six strains formed maximum spore numbers in 5 to 6 days of incubation. Spores produced by the two methods had essentially equal radiation resistances (D and lag values), and their subcultures gave similar toxin titers (LD(50) values). (+info)
Thymus-independence of slowly metabolized immunogens.
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The role of thymus in antibody responses to a series of four synthetic polypeptide immunogens of the general formula multi-copoly(Tyr,Glu)-poly(Pro)-poly(Lys) was investigated as a function of the optical activity of the amino acids composing their structure. Irradiated nonthymectomized and thymectomized SJL mice were injected with thymocytes, marrow cells, or a mixture of both. Each group of recipients was immunized with the following copolymer enantiomorphs: all L-amino acids; L-amino acids outside and D inside; D-amino acids outside and L inside; or all D-amino acids. The antibody response to the immunogen composed of all L-amino acids was thymus-dependent, whereas the responses to the other three copolymers were all independent of the thymus. Similar cell transfers were performed in DBA/1 mice immunized with multi-copoly(L-Phe,L-Glu)-poly(D-Pro)-poly(D-Lys). This mouse strain produces specific antibodies against the (Phe,Glu) region and against the poly(D-prolyl) region. The immune response to the determinant with only L-amino acids on the outside was thymusdependent, whereas the response to the inside immunopotent region with only D-amino acids was thymusindependent. Since earlier studies have demonstrated that synthetic polypeptide antigens that contain D-amino acids are poorly metabolized, the thymus-independence of the antibody responses to these multichain synthetic polypeptides that possess repeating antigenic determinants was correlated with the metabolizability of the immunogens or their component determinants. (+info)
The effect of the replacement of calcium by strontium on excitation-contraction coupling in frog skeletal muscle.
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1. In frog skeletal muscle strontium can replace calcium in potassium contractures for 5 hr, though it is less effective than Ca. Sr can restore the responsiveness to K after it had been lost in the presence of Mn.2. Muscles refractory to caffeine following repeated exposure to it in the absence of Ca, recover in part following addition of Sr.3. The uptake of (85)Sr was increased during mechanical activity, whereas the uptake of (58)Co was not changed. Resting uptake of (58)Co was 3-4 times greater than that of (85)Sr.4. Sr fully activated the myofibrillar adenosine triphosphatase (ATP-ase), though its affinity was about 30 times less than Ca.5. The sarcoplasmic reticulum took up Sr, though less effectively than Ca. (+info)
Electron spin resonance of irradiated single crystals of L-phenylalanine-HCl.
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Single crystals of L-phenylalanine-HCl have been observed with electron spin resonance after irradiation with a cobalt 60 gamma-ray source. The predominant signals observed are from long-lived benzyl radicals. The results indicate that one form of radiation damage to proteins containing this amino acid is breakage of the carbon-carbon bond to release the benzyl radical from the polypeptide chain. Hyperfine structure due to proton couplings of the two methylene hydrogens and of the hydrogens on the ring of the benzyl radical is observed and analyzed to give the electron spin density on the various carbons. The spin density on the methylene carbon is found to be 0.71; that on carbon C((2)), C((4)), or C((6)) is 0.17. The sum of the spin densities on C((1)), C((3)), and C((5)) is -0.22. (+info)
Radical transformation in irradiated DNA and its constituents.
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Electron spin resonance spectroscopy has been used to study transformation of radicals in DNA and a number of its constituents. It was found that in all the bases irradiated at 77 degrees K, hydrogen-addition radicals were formed on warming. The following mechanism of radical transformation has been proposed: damaged species, probably ion-radicals, release hydrogen atoms on warming, which then add to the undamaged bases, preferentially thymine. Thymine need not be the place of the primary damage. (+info)
Unusual Sphaerophorus species from the large intestine of man.
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An obligately anaerobic, gram-negative microorganism identified as a Sphaerophorus species was recovered from the fecal material of two cancer (chronic myelogenous leukemia and idiopathic thrombocythemia) patients receiving cobalt radiation therapy. The organism, isolated on sheep blood-agar, exhibited extreme pleomorphism (rods, filaments, and spheroids) and was a major component of the anaerobic fecal microflora. In one patient the numbers of Sphaerophorus species (designated as isolate 6-13-68), Bacteroides species, and Clostridium perfringens declined after irradiation; however, they were stable in this same patient after a second therapeutic dose of radiation. The numbers of anaerobes in the other patient remained fairly consistent after radiation. The biochemical and morphological characteristics and carbohydrate fermentation reactions of isolate 6-13-68 most closely resembled those of Sphaerophorus ridiculosis. (+info)