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At least 19 recordsLinked to original sources
PubMed1979

Potentiation by p-fluorophenylalanine of the division-delaying effects of high hydrostatic pressure in synchronized Tetrahymena pyriformis.

Cultures of heat-synchronized Tetrahymena pyriformis, growing in a proteose peptone medium, were subjected to short pulses of the amino acid analogue, p-fluorophenylalanine, and high hydrostatic pressure. The pulses of these agents were chosen so that, when applied individually, they did not appreciably delay cell division. However, combined treatments, analogue pulse followed by pressure pulse, produced a pronounced synergism. The results are interpreted as further evidence to support the inclusion of analogue division proteins in pressure labile assemblies during the progression of Tetrahymena into division.

Animals↗
PubMed1979

Synergistic effects of p-fluorophenylalanine and supra-optimal temperatures on cell division in Tetrahymena pyriformis.

The combined effects of sub-optimal (20 degrees) or supra-optimal (31 degrees C and 34 degrees C) temperatures and the amino acid analogue p-fluorophenylalanine on preparations for cell division in Tetrahymena pyriformis were analysed. A supra-optimal temperature of 31 degrees produced a marked exaggeration of the division-delaying capacity of the analogue. The analogue also sensitises cells when combined with the normal heat shock temperature of 34 degrees, which indicates that division proteins continue to be synthesized at this temperature but cannot be effectively utilized by the cell. These results support the model that preparations involve interactions between and formation of assemblies of proteins on a strict time schedule shortly before division.

Animals↗
PubMedDate not supplied

Effects of alpha-aminooxy-beta-phenylpropionic acid on phenylalanine metabolism in p-fluorophenylalanine sensitive and resistant tobacco cells.

A p-fluorophenylalanine (PFP) resistant cell line with high phenylalanine ammonia lyase (PAL) activity and wild type cells with low PAL activity were compared in their responses to PAL inhibition by alpha-aminooxy-beta-phenylpropionic acid (AOP). Inhibition of PAL reduced the levels of the main phenolic compounds to 30% of the controls. Free phenylalanine pools increased 17 fold in the resistant line and 6 fold in the sensitive line, respectively. The accumulation of phenylalanine did not reduce the flow of labeled shikimic acid into the aromatic amino acids tyrosine and phenylalanine. The results are discussed with respect to the feedback inhibition of chorismate mutase activity by phenylalanine and tyrosine in both cell lines.

Ammonia-Lyases↗
PubMed1979

Analysis of the time of utilization of proteins for the initiation and completion of division in synchronized Tetrahymena pyriformis.

We exposed division-synchronized Tetrahymena pyriformis to pulse treatments with the structural amino acid analogue p-fluorophenylalanine. We related the timing of the treatments to the delays in onset or completion of division, or both. The results enable us to distinguish between early and late phases in cell division in which the cells bring into action proteins which contribute to initiate and complete division, respectively. Normally, these events are separated by 25-30 min.

Animals↗
PubMed1979

Effect of N-trifluoroacetyl derivatives of amino acids and amino acid analogs on microbial antitumor screen.

Eighteen trifluoroacetyl derivatives of amino acids and of amino acid analogs were prepared and tested for growth-inhibitory activity using a Lactobacillus casei system as a prescreen for antitumor activity. Of the compounds tested, the trifluoroacetyl derivatives of o-, m-, and p-fluorophenylalanine and of beta-3-thienylalanine showed modest activity; trifluoroacetyl derivatives of phenylalanine and of beta-2-thienylalanine showed marginal activity. The activity exhibited by the active trifluoroacetyl compounds was equal to that noted for most active chloroacetyl derivatives reported previously, as judged by comparison of their activity with that of chloroacetyl-m-fluorophenylalanine. No reversal of inhibition was noted when a representative of these inhibitors was challenged with a corresponding natural metabolite, both as a free amino acid and as a noninhibitory acylated compound.

Amino Acids↗
PubMedDate not supplied

Amino acid uptake by amino acid analog resistant tobacco cell lines.

Two tobacco cell lines resistant to p-fluorophenylalanine (PFP) and one resistant to 5-methyltryptophan (5-MT) are compared with wild type cells in their ability to absorb amino acids from the medium. One p-fluorophenylalanine-resistant cell line shows greatly reduced uptake of all amino acids so is resistant to growth inhibition by other amino acid analogs. The impaired absorption is noted with amino acids, amino acid analogs and shikimate, but not with cinnamate, salicylate, nicotine, glucose, 3-O-methylglucose and palmitate. The phenylalanine transport system of the PFP-resistant cell line and the wild type both have Km values of 90 micrograms, but have different Vmax values. Several analogs of phenylalanine and several neutral L-amino acids inihibt the phenylalanine transport system, while L-aspartic acid, L-arginine, D-phenylalanine or chlorogenic acid do not interfere with the L-phenylalanine uptake. The results indicate the presence of more than one transport system for amino acid uptake. The lessened uptake of all amino acids, the specificity of the uptake systems and the unchanged binding let us conclude that a pleiotropic mutation or that some inhibitor causes the reduced uptake of all amino acids by the PFP-resistant cell line.

Amino Acids↗
PubMed1976

Degradation of abnormal proteins in HeLa cells.

The experiments show that abnoramal proteins are degraded faster than normal ones in HeLa cells. Among the fragmentary proteins made in the presence of puromycin, those with low molecular weight are least stable. Proteins made after incubation with 5-fluorouracil or in the presence of some amino acid analogues are also unstable. Breakdown of proteins made in the presence or absence of puromycin is nearly unaffected by cycloheximide and is independent of pH between 7 and 8.

Amino Acids↗
PubMed1975

The enhancing effect of copper, nickel, and cobalt ions on plaque formation by Semliki Forest virus (SFV) in chicken embryo fibroblasts.

In cultured chicken embryo fibroblasts treated with copper-(copper cation 10-minus 3.5-10-minus 5 M), nickel and cobalt salts an enhancement of the plating efficiency of Semliki Forest virus could be observed. This augmented plaque formation was most probably due to a higher adsorption rate of virions to the cell surface under the influence of the transition metal ions. The plating efficiency of West Nile virus in chicken-embryo fibroblasts and, to a lesser degree, of poliovius type 1 and 2 in KB-cells was also enhanced by copper sulfate.

Adsorption↗
PubMed1975

Isolation and characterization of a mutant of Neurospora crassa deficient in general amino acid permease activity.

A mutant of Neurospora crassa (pm-nbg27) was isolated on the basis of its resistance of p-fluoro-phenylalanine on ammonium-deficient Vogel's medium. This mutant was found to be devoid of both conidial and post-conidial (after 180 min of preincubation) transport activity of all amino acids. Genetic analysis of pm-nbg27 by crossing it to wild-type (74A) resulted in the predicted segregants exhibiting transport characteristics of pm-n, pm-b, pm-g, pm-nb, pm-ng, pm-bg and parental types. The above observations confirm the postulated general amino acid permease system as well as a single genetic locus control of that activity.

Arginine↗
PubMedDate not supplied

Ageing of Neurospora crassa. IV. Induction of senescence in wild type by dietary amino acid analogs and reversal by antioxidants and membrane stabilizers.

The extensional growth rate of wild-type 74A8 N. crassa in the presence of various concentrations of 19 amino acid analogs was measured. Seven analogs were not inhibitory at concentrations in the range of one to 10mM. Of the remaining 12 analogs, nine inhibited growth in a novel way. The kinetics of growth in the presence of these analogs at 30 degrees were characterized by seven sequential phases: (1)lag; (2) acceleration of growth rate; (3) steady-state growth rate; (4) exponential rate of decline of growth rate; (5) no growth or growth rate less than or equal to 0.1 mm h-1; (6) accleration of growth rate; and (7) steady state. At 33 degrees, phases 6 and 7 did not occur and irreparable death of the clones occurred. The mechanism by which the clones acquired resistance at 30 degrees appeared to involve a combination of physiological adaptation and cellular selection. Dietary application of either free radical scavengers or surface-active membrane 'stabilizers' alleviated or prevented the inhibition and deterioration of growth rate which occurred in the presence of the nine amino acid analogs. Culture with either 4-fluorophenylalanine or ethionine led to an increase of the activities of antioxygenic enzymes glutathione peroxidase, glutathione reductase and superoxide dismutase. The amino acid analogs that cause senescence and death of growing cells are known to be incorporated into proteins and such proteins are generally abnormal. Because a substantial fraction of cellular protein occurs in membranes and the proteins synthesized by mitochondria are exclusively intrinsic membrane proteins, we suggest that a primary consequence of errors in protein synthesis is the production of faulty membranes. The deterioration of such membranes with associated lipid autoxidation and free radical production proceeding as a chain reaction at an exponential rate may in itself contribute to the exponential rate of cellular deterioration which is characteristic of the ageing process. According to this hypothesis, dietary membrane stabilizers, free radical scavengers and antioxygenic enzymes protect cells from error catastrophy arising from the chain of events leading from membrane deterioration.

Adrenal Cortex Hormones↗
PubMed1979

The influence of fluoro-phenyl-alanine on the synthesis of simian virus 40 DNA and T antigens.

Treatment of Simian Virus 40 (SV40) infected monkey cells with fluorophenylalanine (FPA) resulted in increased uptake of thymidine by the cells, and progressive inhibition of both viral and cellular DNA synthesis. Viral DNA synthesis was more sensitive to inhibition by FPA than cell DNA synthesis. Synthesis of SV40 T antigens was however unaffected by FPA, as judged from immunofluorescence assays. The M.W. of the major polypetides immunoprecipitated from cell extracts by antibodies from tumor bearing hamster sera was similarly unaffected. It is suggested that T antigen synthesized in the presence of FPA is non functional.

Animals↗
PubMed1977

A functioning complex between tryptic fragments of cytochrome c. A route to the production of semisynthetic analogues.

We report the discovery of a functioning non-covalent complex between two peptides obtained from a limited tryptic digest of horse heart cytochrome c. We have used the phenomenon to produce three modified versions of the complex. We have replaced lysine-39 semisynthetically with ornithine in the first analogue, with p-fluorophenyl-alanine in the second, and removed it entirely in the third.

Animals↗