Tryptose phosphate broth confers to chick embryo cells resistance to the inhibitory effect of chloramphenicol on growth

Tryptose phosphate broth improves Rickettsia felis replication in mammalian cells

In cell culture, Rickettsia felis grows only at low temperatures (< 31 °C). Therefore, its ability to enter, survive and grow in cell lines has primarily been tested in cells derived from amphibians and arthropods, which naturally grow at low temperatures, and only infrequently in mammalian cells. We subcultured R. felis in mammalian cells for more than 10 passages using media supplemented with tryptose phosphate broth (TPB) and found that TPB is critical for optimal growth of R. felis in mammalian cells.

Mitochondrial DNA--related mitochondrial dysfunction in neurodegenerative diseases

Mitochondrial dysfunction occurs in several late-onset neurodegenerative diseases. Determining its origin and significance may provide insight into the pathogeneses of these disorders. Regarding origin, one hypothesis proposes mitochondrial dysfunction is driven by mitochondrial DNA (mtDNA) aberration. This hypothesis is primarily supported by data from studies of cytoplasmic hybrid (cybrid) cell lines, which facilitate the study of mitochondrial genotype-phenotype relationships. In cybrid cell lines in which mtDNA from persons with certain neurodegenerative diseases is assessed, mitochondrial physiology is altered in ways that are potentially relevant to programmed cell death pathways. Connecting mtDNA-related mitochondrial dysfunction with programmed cell death underscores the crucial if not central role for these organelles in neurodegenerative pathophysiology. This review discusses the cybrid technique and summarizes cybrid data implicating mtDNA-related mitochondrial dysfunction in certain neurodegenerative diseases.

Uroporphyria development in cultured chick embryo fibroblasts long-term treated with chloramphenicol and ethidium bromide

Long-term chloramphenicol- and ethidium bromide-treated chick embryo fibroblasts synthesize large amounts of porphyrins from exogenously added delta-aminolevulinic acid. The porphyrins consist mainly of uro- and heptacarboxyporphyrins and are retained within cells. Uroporphyria development is a time-dependent process which accompanies a step-wise decrease in the capacity of the mitochondrial respiratory chain. Upon removal of chloramphenicol from the medium, the pattern of porphyrin production readily returns to normal (mainly proto- and coproporphyrins found in the medium) while ethidium bromide-treated cells remain uroporphyric. The results suggest that impairment of mitochondrial functions in chicken by xenobiotics leads to uroporphyria development.

On auxotrophy for pyrimidines of respiration-deficient chick embryo cells

Chick embryo cells treated with chloramphenicol are inherently resistant to the growth-inhibitory effect of the drug when cultured in the presence of tryptose phosphate broth. The cells were found to be auxotrophic for pyrimidines and the presence in the broth of compounds of pyrimidine origin is demonstrated by chromatographic procedures and mass spectral analyses. They are in the form of ribonucleosides, ribonucleotides and pyrimidine-containing oligoribonucleotides. To understand the mechanism responsible for pyrimidine auxotrophy, the activity of enzymes involved in the pyrimidine biosynthetic pathway was determined. Measurement of the conversion of dihydroorotic acid to orotic acid in cell-free extracts revealed that chloramphenicol-treated chick embryo cells are deficient in dihydroorotate dehydrogenase activity. The data in vitro are supported by studies on the nutritional requirements of the respiration-deficient cells and by the incorporation in vivo of labelled dihydroorotic acid into the acid-insoluble fraction of the cells. Although the activity of the dehydrogenase in vitro is decreased by 95%, the enzyme is present in chloramphenicol-treated cells and its activity is unmasked by the artificial electron acceptor menadione. A study of the activity of other enzymes of the pyrimidine biosynthetic pathway demonstrated that their activity is comparable to that in control cells. The present results indicate that auxotrophy for pyrimidines results from the inhibition of the flow of electrons along the mitochondrial electron transport chain.

On the effect of inhibitors of mitochondrial macromolecular-synthesizing systems and respiration on the growth of cultured chick embryo cells

We have found that chick embryo fibroblasts (DEF) cultivated in the presence of tryptose phosphate broth (TPB) are inherently resistant to the growth inhibitory effect of ethidium bromide (EB). As demonstrated by cytochrome oxidase activity and oxygen consumption measurements, analyses of reduced-minus-oxidized cytochrome spectra and electron microscopic observations, TPB did not seem to prevent the inhibitory effect of EB on mitochondrial DNA transcription. EB-treated chick cell populations cultivated in the presence of TPB behave essentially the same as populations treated with chloramphenicol (CAM) and grow with mitochondria devoid of a functional respiratory chain. In contrast to CAM-treated CEF populations, however, the respiratory activity of EB-treated cell populations did not reappear when the cells were shifted back to EB-free medium. Attempts to demonstrate that TPB confers resistance to the growth inhibitory effect of carbomycin and mikamycin, inhibitors of the mitochondrial protein-synthesizing system, have failed, the drugs being cytotoxic at doses where protein synthesis on mitoribosomes is not suppressed. On the other hand, the present results demonstrated that chick cell populations proliferate in the presence of the respiratory inhibitors rotenone, antimycin A, amytal and oligomycin whether or not TPB is present in the growth medium.

On the adaptation of cultured chick embryo cells to growth in the presence of chloramphenicol

We have found that tryptose phosphate broth (TPB) prevents the inhibitory effect of chloramphenicol (CAM) on the cell proliferation of chick embryo fibroblasts. Study of growth parameters indicated that no lag or adaptation period appeared necessary for TPB-exposed chick cell populations to grow in the presence of CAM suggesting that a particular cell type was not selected. TPB did not prevent the inhibitory effect of CAM on the mitochondrial protein-synthesizing system. This was supported by cytochrome oxidase activity measurements, studies on the incorporation of 35S-metionine into mitochondrial proteins, electron microscopic observation of alterations in mitochondrial structure. Oxygen consumption was reduced by 95% and cyanide, 2-4-dinitrophenol, and salicylhydroxamic acid do not significantly affect the residual respiration. Analyses of reduced-minus-oxidized-cytochrome spectra of CAM-treated chick cells demonstrate the disappearance of the absorption bands of cytochromes aa3, b559, c1, and c. The presence of a type b cytochrome with maxima at 552 and 557 nm was observed. The results obtained indicate that long-term cultures of CAM-treated chick embryo cells cultivated in the presence of TPB grow with mitochondria devoid of a functional respiratory chain.