Induction of hypoxia in glass versus Permanox petri dishes

The survival of Chinese hamster ovary cells in culture following graded doses of X rays delivered under aerobic and hypoxic conditions, or treatment with the bioreductive drug SR 4233 under hypoxic conditions, was evaluated as a function of whether cells were plated onto glass or Permanox plastic petri dishes. In the case of treatment with SR 4233, the influence of varying the total volume of medium in the dishes was also studied. While the Permanox petri dishes were sufficient to yield "radiobiological" hypoxia, that is, oxygen enhancement ratios of approximately 3.0 were obtained for X irradiation, they were inferior to glass petri dishes with respect to the hypoxia-selective cytotoxicity of SR 4233. For a 90-min hypoxic exposure to 40 microM SR 4233, the surviving fraction of cells plated on plastic dishes averaged about 50-fold higher than that of cells plated on glass dishes. Although varying the total medium volume did affect the extent of SR 4233-induced cytotoxicity for glass dishes--drug toxicity decreased slightly with increasing medium volume--this was not the case for the plastic dishes, in which the cell survival following a fixed SR 4233 exposure was essentially constant as a function of medium volume. These results suggest, at least for SR 4233, and under these experimental conditions, that Permanox petri dishes are not satisfactory for such studies.     

Suggested procedure allowing use of plastic petri dishes in bacteriocin typing.

After bacteria are mechanically removed from solid media, the remaining viable cells can be killed by exposure to chloroform vapors. Until recently, the applicability of this procedure was restricted to glass petri dishes. Here a procedure is described in which plastic petri dishes are used and remain stable in the presence of chloroform vapors.     

Exogenous sphingosine enters Xenopus laevis embryos grown in petri dishes and it is metabolized

Xenopus embryos of different developmental stages were exposed to 0.1 M [1-³H]sphingosine. Labeled sphingosine was quickly absorbed by Xenopus embryos. The amount of radioactivity absorbed increased with embryo age and appeared to be linearly correlated (R=0.97) to the embryo surface area. About 45% of the total radioactivity associated to the embryos was found in the skin, 22% in the intestine, 15% in the heart, 12% in the liver and 6% in the brain.A portion of [1-³H]sphingosine entered very rapidly the biosynthetic pathway of sphingolipids; after 30 min of incubation, in fact, only a small amount of free radioactive sphingosine could be detected. Sphingomyelin was the main radioactive sphingolipid synthesized; radioactive ceramide, galactosylceramide and lactosylceramide could also be recognized and quantified. On the contrary, the amount of radioactive gangliosides was hardly detectable.A portion of [1-³H]sphinogosine absorbed by Xenopus embryos (30 to 60% depending on the developmental stage) entered the catabolic pathway producing radioactive phosphoethanolamine that was recycled for the biosynthesis of radioactive phosphatidylethanolamine. This phospholipid was produced mainly in the intestine and in the skin, while sphingomyelin was the main radioactive lipid in the heart, liver and brain.     

Photograph registration of petri dishes in high quality and image editing of microbiological assays

International Microbiology - Science is based on evidence that can be measured or observed through methodical techniques which are expressed in several ways, either quantitatively or qualitatively....     

A complex of collagenase with low molecular weight inhibitors in the culture medium of embryonic chick skin explants.

Collagenase inhibitors with molecular weights of about 6,000 and 12,000 were isolated from latent chick skin collagenase treated with 3 M NaI and from the culture medium of embryonic skin explants. It is suggested that these inhibitors, which are possibly derived from connective tissue macromolecule metabolites, are candidates for regulating factors of collagenase activity in vivo.     

Effects of irradiated medium on chromatid aberrations in mammalian cells using double mylar dishes.

We examined the potential contribution of irradiated medium on the bystander effect using custom made double-mylar stainless steel rings. Exponentially growing Human-hamster hybrid (AL) cells were plated on either one or both sides of double-mylar dishes 2-4 days before irradiation. One side (with or without cells) was irradiated with alpha particles using the track segment mode of a 4 MeV Van de Graaff accelerator at the Radiological Research Accelerator Facilities of Columbia University. Since alpha particles can only traverse a very limited distance, cells plated on the other side of a medium-filled mylar dish will not be irradiated by the alpha particles. The results of chromosomal aberrations on un-irradiated target cells that were attached to the top mylar layer indicate that the number of chromatid-type aberrations was higher when there was a bottom layer of cells in the medium filled chambers than just medium alone. Furthermore, when transferring the medium from these cell-irradiated dishes to fresh AL cultures, chromatid-type aberrations were produced in the un-irradiated fresh cells. In contrast, medium irradiated in the absence of cells had no effect on chromatid aberrations. These results suggest that certain modulating factors secreted from the irradiated cells on the bottom mylar layer into the medium, induce chromatin damage in the un-irradiated, bystander cells.