The specific amino acid requirements of a human carcinoma cell (Stain HeLa) in tissue culture

Activation of murine leukaemia virus under different physiological conditions

The leukaemic lesions in intact and ovariectomized mice of strain ICRC, induced with 20-methylcholanthrene (20-MCA) in combination with or without hormones were investigated for the presence of mouse leukaemia virus (MuLV) by (i) bioassays and (ii) electron microscopy. The different experimental groups treated with 20-MCA were (i) intact females, (ii) ovariectomized females, (iii) ovariectomized females with pituitary graft, (iv) ovariectomized females with 10 mug oestradiol/day for 30 days and (v) ovariectomized females with 1 mug oestradiol together with 1 mg progesteron/day for 30 days. It was possible to transmit nearly all these experimentally induced leukaemias to syngeneic mice through acellular extracts, compared with very poor transmissibility of spontaneous leukaemias in the ICRC strain, indicating functional activation of viral agents on combined treatment with carcinogen and hormones. Potency of the acellular leukaemic extract from the mice of group (ii) without the ovarian hormones was much weaker than that from mice of the other experimental groups. The leukaemogenic activity of MuLV was enhanced on serial transmission in syngeneic hosts. Leukaemic lesions of ovariectomized mice treated with 20-MCA and oestradiol were also transmissible to the sucklings of allogeneic mice of strain C3H-MTV, C57-BL and Dba-MTV. The cell-free supernatant medium of the cultures of these leukaemic lesions induced leukaemias on back inoculation into syngeneic mice. Electron microscopic studies of lesions induced with carcinogen and oestradiol consistently showed abundant intracytoplasmic type A particles. Numerous intracytoplasmic type A particles as well as some type B particles were found in the leukaemic tissues of ovariectomized females treated with MCA and oestradiol combined with progesterone. Type C particles, characteristic of MuLV were seen in the leukaemic tissues of all other experimental groups. These findings indicate a significant influence of the physiological condition of the host, particularly the hormonal make up, on expression and activity of specific viral agents.

Effect of pH on plating efficiency, serum reguirement, and incorporation of radioactive precursors into human cells

The plating efficiencies of two cell lines (HeLa-AT and WI26 Va) and one cell strain (KL2) appeared to be optimal at pH 7.6 At the optimal pH, ,sing organic buffers, the serum concentration could be reduced by one-half without affecting the initial growth rate or the final population density of the human skin fibroblast strain, KL2. It is suggested that an optimal pH lowers the serum requirement of the cells. The incorporation of [3-H]thymidine, [3-H]uridine, [-3H]fucose and [-14C]amino acids into KL2 was maximal at the pH which normally permits optimal growth of this cell strain. Protein turnover, as measured by loss to the medium of amino acids from prelabeled cells, was pH-independent. Thymidine incorporation did not correlate with culture growth in the cell strain, MS2A.

Atypical pattern of utilization of amino acids for mitochondrial protein synthesis in HeLa cells

The capacity of HeLa cell mitochondria, either isolated or in intact cells, to incorporate different labeled amino acids into proteins was investigated. Eight amino acids (alanine, arginine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, and lysine), which include most of the charged polar ones, showed a very low amount, if any at all, of chloramphenicol-sensitive incorporation, relative to that expected for an "average" HeLa-cell protein. By contrast, the most hydrophobic amino acids (leucine, isoleucine, valine, phenylalanine, and methionine) were the most actively incorporated by HeLa mitochondria. The available evidence suggests that pool effects cannot account for this general pattern of utilization of amino acids; furthermore, this pattern is in good agreement with the known hydrophobic properties of proteins synthesized in mitochondria.

Comparison of the relative synthesis of the proteins of the 50S ribosomal subunit in growing and valine-deprived HeLa cells

Quantitative studies of the synthesis of the ribosomal proteins of the 50S ribosomal subunit have been made with growing versus valine-deprived HeLa cells. The synthesis of total cell protein and 50S subunits was also compared between the growing and nongrowing cells. It was found that between 12 and 20 hr of valine deprivation the net synthesis of 50S subunits drops to approximately 8% of that in control cells while the over-all synthesis of 50S subunit ribosomal proteins declines to approximately 12% of that in the controls. However, the synthesis rates for each of two particular 50S subunit proteins decline to approximately 8% of the rates in the growing cells, indicating that the synthesis of one of these proteins may be rate limiting for 50S subunit biosynthesis in valine-deprived HeLa cells. Other evidence indicates that the regulation of synthesis of the ribosomal proteins in valine deprivation depends on control at the level of transcription or translation rather than being a function of the relative valine content of these proteins.

pH as a determinant of cellular growth and contact inhibition

1) Both the growth rate and the maximum population density of several normal, virus-transformed, and cancer cells were markedly pH-dependent; the optimum varied from pH 6.9 to 7.8. At the optimum pH, some diploid human cells attained population densities comparable to those of cancer or virus-transformed cells. Contact inhibition of growth is facilitated by repeated fluctuations of pH in nonphysiological ranges, and may not be an intrinsic and necessary attribute of diploid cells in culture. 2) At pH 8.3, at which there was little or no cellular multiplication, the protein content per cell increased 2- to 5-fold over a period of 10-16 days, and was slowly reversed to normal concentrations on restoration of pH to the optimal range. 3) Uridine uptake by contact-inhibited human cell cultures was stimulated by refeeding with salt solution, and to the same extent as by complete (serum-supplemented) growth medium; that immediate increase did not involve the reinitiation of cellular growth and multiplication. Contact inhibition was, however, reversed in 2-4 days by an appropriate increase in the serum concentration of the medium.

Cholesterol requirement of primary diploid human fibroblasts

Primary cultures of fibroblast-like cells were obtained from skin and articular cartilage of human donors in the age bracket of 1 to 15 years. For growth these cultures required 1 mg/liter of cholesterol added to Medium A2 plus acetyl choline, Na pyruvate, and D-galactosamine HCl (APG) containing 10% lipoprotein-free human serum. Established cell lines did not require cholesterol for growth. Eagle's medium could be used in place of Medium A2 plus APG with the same results. Desmosterol could replace cholesterol but lansterol or 7 dehydrocholesterol could not. Other cholesterol precursors were tested and found to be inactive. With the proviso that cholesterol precursors entered the cell and had to be converted to cholesterol to function, it was concluded that the particular primaries studied lacked a functional enzyme system to reduce the double bond at carbon 7.

Specific effect of guanidine in the programming of poliovirus inhibition of deoxyribonucleic acid synthesis

Inhibition of HeLa cell deoxyribonucleic acid (DNA) synthesis, which occurred by the 4th to 5th hr after infection with poliovirus, could be blocked completely by guanidine only when it was present before the 2nd hr. At the 2nd hr, there was no significant ribonucleic acid (RNA)-replicase activity, and addition of guanidine inhibited all production of virus but allowed 57% of maximal DNA inhibition to develop. Maximum DNA inhibition developed in cells infected for 4 hr in the presence of guanidine when the guanidine was removed for a 10-min interval. RNA-replicase activity was not enzymatically detectable and viral multiplication did not develop in these cells unless the interval without guanidine was extended to 60 min. The interpretation of the data was that the effect of guanidine on viral-induced inhibition of DNA synthesis was distinct and not a consequence of the inhibition of RNA-replicase.

Persistence of messenger RNA through mitosis in HeLa cells

The decrease in protein synthesis which occurs in mammalian cells during cell division is associated with significant disaggregation of polyribosomes. For determining whether messenger RNA survives this disaggregation, the reformation of polyribosomes was investigated in synchronized HeLa cells as they progressed from metaphase into interphase in the presence of 2 microg/ml Actinomycin D. The persistence of messenger during cell division was evidenced by: (1) a progressive increase in the rate of protein synthesis in both treated and untreated cells for 45 min after metaphase; (2) reformation of polyribosomes, as determined by both sucrose gradients and electron microscopy, within 30 min after the addition of Actinomycin D to metaphase cells; (3) the persistence of approximately 50% of the rapidly labeled nonribosomal RNA which had associated with polyribosomes just before metaphase; (4) the resumption of synthesis, following cell division, of 6 selected peptides in Actinomycin-treated cells.

Inhibition of protein synthesis in Krebs 2 ascites cells and cell-free systems by phenylalanine and its effect on leucine and lysine in the amino acid pool

1. The inhibition of incorporation of (14)C-labelled amino acids into protein of whole cells by phenylalanine has been reproduced in a cell-free system. In both cases only the l-isomer was inhibitory. 2. The effect of phenylalanine on incorporation of [(14)C]leucine and [(14)C]lysine into protein was different in both whole cells and cell-free systems. 3. In whole cells inhibition of incorporation of leucine at 2.5mug./ml. was very rapid, but when the concentration was increased to 100mug./ml. the inhibition was not apparent for about 1hr. The kinetics of inhibition of lysine was the same at both these concentrations and was similar to that found with leucine at 100mug./ml. 4. Neither a lower specific radioactivity of the two amino acids in the pool nor a decrease in their pool size could be consistently related with inhibition of protein synthesis. 5. In the cell-free system l-phenylalanine inhibited the incorporation of leucine but not of lysine. 6. Charging of transfer RNA by leucine was markedly decreased in the presence of phenylalanine, whereas charging of transfer RNA by lysine was not.

Programming of poliovirus inhibition of deoxyribonucleic acid synthesis in HeLa cells

Ackermann, W. W. (The University of Michigan, Ann Arbor), and D. Wahl. Programming of poliovirus inhibition of deoxyribonucleic acid synthesis in HeLa cells. J. Bacteriol. 92:1051-1054. 1966.-Deletion of arginine from a culture medium reduced the rate of deoxyribonucleic acid (DNA) synthesis in uninfected HeLa cells. The normal rate was promptly restored by addition of arginine. Deletion of arginine also prevented poliovirus from inhibiting DNA synthesis in HeLa cells. However, the inhibitory potential of the infection and the capacity of the host cell for stimulation with regard to DNA synthesis were both retained in arginine-depleted cells which were infected. Upon addition of arginine late in the infection, DNA synthesis was first stimulated and then inhibited.

Differentiation in vitro: effects of Sephadex fractions of chick embryo extract

Chicken embryo extract has been fractionated into high-and low-molecular-weight components on Sephadex G-25. Media supplemented with the low-molecular-weight fraction (L) support full differentiation in clones of cartilage and of pigmented retina cells from chicken embryos. Growth rates of such cultures in L-supplemented media are greater than in media without embryo extract, and plating efficiencies are higher than in media with or without whole embryo extract. The high-molecular-weight fraction (H) in low concentrations also stimulates growth and plating efficiency, but inhibits the expression of differentiation.

Amino acid metabolism of different mammalian cell lines

After long-term storage under liquid nitrogen, 16 different mammalian cell lines from normal and malignant origins were cultured in the presence of14C-glucose for 3 and 7 days without a change in growth medium.All cell lines synthesized from glucose at least six amino acids: aspartate, glutamate, serine, alanine, glycine, and threonine. In addition, HeLa S, human heart (HH), and L-929 synthesized cystine after 7 days of incubation without change of growth medium. The most highly labeled compounds were alanine, glycine, and glutamic acid in all cell media. The incorporation of14C into aspartic acid, serine, and threonine was for the most part detected in small amounts.Citrulline appeared in large quantities in the growth medium of HeLa F, HeLa Q, and HeLa Clone S-3, whereas arginine was greatly reduced after the 3-day growth period. At the same time, the ammonia content greatly increased in all three cases. Proline disappeared in the medium of HeLa S, HEp II, human amnion (HA-FL), canine kidney (MD-CK), human appendix (HA-A1), human liver (HL-CW), and human embryonic adrenal (W-AD62). Glutamic acid increased in the medium of monkey kidney (MK-MS) and canine kidney (MD-CK). In the HeLa Clone S-3 medium, lysine decreased and histidine increased.Each cell line in this investigation may be distinguished on the basis of the degree of14C incorporation into glutamic acid, serine, glycine, and alanine, except three pairs of cell lines: HEp II and HA-A1, MD-CK and MK-MS, and rat embryo and HeLa F.

Effect of poliovirus on deoxyribonucleic acid synthesis in HeLa cells

Ackermann, W. W. (University of Michigan, Ann Arbor), D. C. Cox, H. Kurtz, C. D. Powers, and S. J. Davies. Effect of poliovirus on deoxyribonucleic acid synthesis in HeLa cells. J. Bacteriol. 91:1943-1952. 1966.-Both poliovirus and arginine stimulated deoxyribonucleic acid (DNA) synthesis in cultures of HeLa cells which were preconditioned by incubation in a medium deficient in arginine. However, the number of cells producing DNA was unaffected. DNA synthesis in such preconditioned cells was 10 to 20% of the maximal value obtained with a full complement of amino acids. Inhibition of DNA synthesis was produced in these cultures either by increasing the multiplicity of exposure above 40 plaque-forming units of virus per cell or by increasing the concentration of the deficient amino acid at the time of virus addition. Inhibition of DNA synthesis resulted from a reduction in the fraction of cells producing DNA. The concentration of arginine required for viral inhibition of DNA synthesis is greater than that for viral multiplication.

Interaction of diphtheria toxin with cell cultures from susceptibile and resistant animals

The cytotoxicity (TD) level of diphtheria toxin for human Chang liver strain was 0.1 guinea pig MLD per ml; for mouse liver NCTC 1469 strain, the TD was 500 MLD per ml. The results of cell culture toxicity correlated well with relative susceptibility of both man and mouse. The initial effects of toxin on the susceptible Chang liver cells were studied at one half the TD level (0.05 MLD per ml). At this low concentration of toxin, the number of cells per culture was reduced slightly below the "0" hr values, whereas the amounts of cell protein, RNA, and DNA were increased. Analysis of the toxin-treated cells indicated an enlargement of the cells. The individual cells contained significantly more protein, RNA, and DNA than the control cells and the cell volume was increased 1.9 times. When purified diphtheria toxin was incubated with the susceptible Chang liver cells and then tested for its biological activity, the results showed an increased diffusion rate in parabiotic culture chambers and definite cytotoxicity to the normally resistant mouse liver cells. The cytotoxicity was neutralizable with antitoxin. The results suggest that the toxin-susceptible cells transform the toxin molecule to a more active derivative which affects the highly resistant mouse liver cell.

The role of methionine deficiency in poliovirus replication in tissue cultures

The role of methionine in poliovirus infection in HeLa and monkey kidney cells was investigated by using the methionine analogue l-ethionine. In the presence of 2.0 x 10(-3) and 4.0 x 10(-3) moles ethionine, the growth of HeLa and monkey kidney cells was significantly inhibited. Under the same experimental conditions, ethionine had no significant effect on the biosynthesis of two strains of poliovirus (Mahoney and Lansing) in HeLa cells, whereas in primary monkey kidney cells, it markedly inhibited the biosynthesis of the Lansing strain of poliovirus. HeLa cells partly depleted of their intracellular amino acids did not change the rate of viral biosynthesis. The inhibitory effect of ethionine on cell growth and viral biosynthesis was reversed by addition of an excess of l-methionine.

Effects of arginine deprivation, ultraviolet radiation, and x-radiation on cultured KB cells. A cytochemical and ultrastructural study

CULTURED KB CELLS (DERIVED FROM A HUMAN ORAL CARCINOMA) GROWN IN MONOLAYERS WERE INJURED BY ONE OF THREE AGENTS: starvation by arginine deprivation or treatment with high doses of either ultraviolet radiation or x-radiation. The different agents produced changes in nucleolar structure and varying accumulations of triglyceride and glycogen. All three agents produced an increase in number and size of lysosomes. These were studied in acid phosphatase preparations, viewed by both light and electron microscopy, and, occasionally, in vital dye, esterase, and aryl sulfatase preparations. Ultrastructurally, alterations in lysosomes suggested that "residual bodies" developed in a variety of ways, i.e., from the endoplasmic reticulum, multivesicular bodies, or autophagic vacuoles. Following all three agents the endoplasmic reticulum assumed the form of "rough" or "smooth" whorls, and, after two of the agents, arginine deprivation or ultraviolet radiation, it acquired cytochemically demonstrable acid phosphatase activity. Near connections between the endoplasmic reticulum and lysosomes raise the possibility that in KB cells, at least when injured, the endoplasmic reticulum is involved in the formation of lysosomes and the transport of acid phosphatase to them.