Exp Cell Res. 2001 Nov 1;270(2):138-50.
A model system for studying postnatal myogenesis with tetracycline-responsive, genetically engineered clonal myoblasts in vitro and in vivo.

Link D, Irintchev A, Knauf U, Wernig A, Starzinski-Powitz A.

Xantos Biomedicine AG, Fraunhoferstrasse 22, Martinsried, D-82152, Germany.

The aim of this work was to introduce a tetracycline-responsive (Tet-off) gene expression system into myoblasts in order to regulate a reporter gene not only in vitro but also particularly in muscles implanted with these engineered myoblasts. Mouse myoblasts from a long-term culture (i28 cells) were transfected initially to generate and characterize two stable master clones expressing tetracycline-responsive transactivator protein tTA. Like parental i28 myoblasts, these clones differentiated well in vitro. The second step introduced the firefly (Photinus pyralis) luciferase gene into one of the stable tTA clones producing double transfectants expressing luciferase in the absence of tetracycline. Addition of tetracycline (1 microg ml(-1)) resulted in at least 100-fold decreases in luciferase activity within 8 h in both growing and differentiating myoblast cultures. Enzyme activity was rapidly restored after tetracycline was removed (8 h). After successful implantation of these myoblasts into damaged mouse muscles, luciferase expression in the matured progeny cells could be regulated by oral application of doxycycline for at least 1 month. The tetracycline-responsive master clones are potentially powerful tools for studying the function of various genes in postnatal myogenesis. Copyright 2001 Academic Press.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11640878&dopt=Abstract antibiotics, tetracycline

ualberta.ca

Tet(o) is an elongation factor-like protein found in clinical isolates of Campylobacter jejuni that confers resistance to the protein-synthesis inhibitor tetracycline. Tet(o) interacts with the 70S ribosome and promotes the release of bound tetracycline, however, as shown here, it does not form the same functional interaction with the 30S subunit. Chemical probing demonstrates that Tet(o) changes the reactivity of the 16S rRNA to dimethyl sulphate (DMS). These changes cluster within the decoding site, where C1214 is protected and A1408 is enhanced to DMS reactivity. C1214 is close to, but does not overlap, the primary tetracycline-binding site, whereas A1408 is in a region distinct from the Tet(o) binding site visualized by cryo-EM, indicating that Tet(o) induces long-range rearrangements that may mediate tetracycline resistance. Tetracycline enhances C1054 to DMS modification but this enhancement is inhibited in the presence of Tet(o) unlike the tetracycline-dependent protection of A892 which is unaffected by Tet(o). C1054 is part of the primary binding site of tetracycline and A892 is part of the secondary binding site. Therefore, the results for the first time demonstrate that the primary tetracycline binding site is correlated with tetracycline's inhibitory effect on protein synthesis.

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J Pharm Sci. 1976 Mar;65(3):400-4.
Analysis of tetracycline in pharmaceutical preparations by improved high-performance liquid chromatographic method.

Tsuji K, Robertson JH.

The analysis of tetracycline in pharmaceutical preparations by an improved high-performance liquid chromatographic (HPLC) method is described. The improved method uses a 30-cm long stainless steel column packed with octadecylsilane bonded on 10-mum silica gel, with a linear gradient from 10 to 60% acetonitrile in pH 2.5, 0.02 M phosphate buffer in 11 min at a flow rate of 1.0 ml/min (68 atm). The resolution functions obtained between 4-epitetracycline and tetracycline and between 4-epianhydrotetracycline and anhydrotetracycline were improved 150 and 250%, respectively. The analysis of a tetracycline sample takes approximately 16 min; the original method required more tan 25 min. The relative standard deviation for the analysis of tetracycline powder was 0.66%, and the recovery of 4-epianhydrotetracycline added in tetracycline was linear over the 0.3-100% range. Recovery of tetracycline from products was better than 99.6% at label concentration. The drug content of products as calculated from the HPLC data agreed well with those of the microbiological assay methods.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1263088&dopt=Abstract antibiotics, tetracycline




Hokkaido Igaku Zasshi. 1986 May;61(3):379-87.
[Effect of tetracyclines on protein metabolism in cultured hepatocytes]

[Article in Japanese]

Yokoyama K.

The purpose of the present study was to investigate the effect of Tetracyclines (TCs); Minocycline (MINO), Tetracycline (TC), Demethylchlortetracycline (DMTC), Pyrrolidinomethyltetracycline (PMTC), on amino acid transport and incorporation in hepatocytes. By the use of liver cell culture, this study was done without complex interactions taking place in whole animals. MINO inhibited most strongly both uptake and incorporation into cellular protein of 3H-L-leucine in cultures of a clonal strain of rat hepatoma cells. This inhibitory effect of MINO was proved to be dose-dependent and reversible. The order of the inhibitory effect of TCs was follows; MINO, DMTC, TC, PMTC. But this inhibitory effect showed no significant correlation with the intracellular content of TCs. Almost the same degree as the inhibition by TCs of 3H-L-leucine incorporation into protein was noted when measuring total intracellular 3H-L-leucine reduction by TCs. These results suggest that the TCs-induced liver dysfunction is probably due to the inhibitory effect of TCs on amino acids uptake followed by inhibition of protein synthesis.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3091471&dopt=Abstract antibiotics, tetracycline




Tierarztl Prax. 1990 Feb;18(1):27-32.
[The effect of feed preparation on the pharmacokinetics of peroral administration of chlortetracycline in weaned piglets]

[Article in German]

Sutter HM, Wanner M.

Abteilung fur Tierernahrung, Vet. Med. Fakultat, Universitat Zurich.

The influence of different modes of feeding on the bioavailability of orally administered chlortetracycline was studied in weaned pigs. The animals were divided into three groups receiving a dry, a moist or a soup diet, respectively. CTC was applied at a concentration of 6000 ppm and 2500 ppm to each diet and the oral dosage of CTC was 40 mg chlortetracycline/kg bodyweight. The results of the experiments show that the pharmacokinetics of orally applied chlortetracycline are significantly influenced by the mode of feeding. A significantly higher bioavailability was observed with soup feeding compared with moist or dry food. To achieve a therapeutic blood level of 0.5-1.5 micrograms chlortetracycline/ml blood, 20-30 mg chlortetracycline/kg bodyweight/12 h and 30-40 mg chlortetracycline/kg bodyweight/12 h should be applied to soup and dry or moist feed, respectively.

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J Assoc Off Anal Chem. 1978 Sep;61(5):1222-7.
Effect of storage and processing on tetracycline residues in meat and bones.

Honikel KO, Schmidt U, Woltersdorf W, Leistner L.

A semiquantitative microbiological screening test for antibiotics, a sensitive and quantitative microbiological assay, and a fluorometric method specific for tetracyclines are described. Using these procedures, tetracycline residues in animals derived from feed can be detected in tissues like organs, muscles, and bones. Meat contaminated with chlortetracycline (CTC) and oxytetracycline (OTC) and stored at +8 degrees C and -22 degrees C showed very little decrease in antibiotic concentration; however, heating above 65 degrees C reduced the tetracycline content in meat. Temperatures above 130 degrees C were necessary to destroy CTC in bones, CTC in bones was insoluble above pH 4. Manufacturing products with contaminated meat reduced the tetracycline content only if heating was involved.

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Hum Gene Ther. 1995 Sep;6(9):1203-13.
Inducible, high-level production of infectious murine leukemia retroviral vector particles pseudotyped with vesicular stomatitis virus G envelope protein.

Yang Y, Vanin EF, Whitt MA, Fornerod M, Zwart R, Schneiderman RD, Grosveld G, Nienhuis AW.

Department of Hem/Onc, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.

Murine leukemia viruses (MuLV) have been adapted for use as gene transfer vectors for experimental and human gene therapy applications. Their utility for these purposes has been circumscribed by the limited host range and relatively low titer of available producer clones. Pseudotyping of MuLV particles with the vesicular stomatitis virus envelope protein (VSV-G), expressed transiently in cells producing MuLV Gag and Pol proteins, has yielded vector preparations with a broader host range that can be concentrated by ultracentrifugation. We have explored the use of steroid-inducible and tetracycline-modulated promoter systems (necessary because the VSV-G protein is toxic to cells when constitutively expressed) to derive stable producer cell lines capable of substantial production of VSV-G pseudotyped MuLV particles. A packaging cell line and producer clones capable of expressing a chimeric transcription factor, composed of the tetracycline repressor (tetR) and the VP16 trans-activating sequences of herpes simplex virus VP16 gene and containing the VSV-G coding sequences linked to a minimal promoter having seven tandem copies of the tetracycline responsive operator (tetO), exhibited high levels of VSV-G protein expression when cultured in the absence of tetracycline. Vector particles, produced at titers of 10(5)-10(6) infectious colony forming units per ml (cfu/ml), could be concentrated effectively by ultracentrifugation yielding vector preparations having a titer of 10(9) cfu/ml. These cell lines grew normally when VSV-G protein expression was repressed by tetracycline. Such producer clones hold promise for future human gene therapy applications.

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J Antimicrob Chemother. 1990 Jul;26(1):61-70.
Modulation of the proliferative response of murine thymocytes stimulated by IL-1, and enhancement of IL-1 beta secretion from mononuclear phagocytes by tetracyclines.

Ingham E.

University Department of Immunology, General Infirmary, Leeds, UK.

The capacity of minocycline and tetracycline for modulation of IL-1 secretion by LPS-stimulated human monocytes was investigated in vitro. Both minocycline and tetracycline suppressed the murine thymocyte co-mitogenic bioassay of IL-1 at 2 and 4 mg/l respectively. IL-1 beta secretion by LPS-stimulated human monocytes cultured for 24h at 1 x 10(6)/ml with 0, 5, 10 and 50 mg/l minocycline or tetracycline was therefore determined by ELISA. Monocytes from five different individuals served as replicates. LPS-stimulated monocytes secreted significantly more IL-1 beta in the presence of minocycline (P less than 0.01, 2-way analysis of variance). There was no difference in the enhanced levels of IL-1 beta secreted with 5 mg/l minocycline compared with 50 mg/l minocycline. Loss of viability could only be associated with enhanced IL-1 beta release by monocytes with 50 mg/l minocycline. Although tetracycline enhanced IL-1 beta secretion in four of the five replicate experiments, this did not prove significant owing to the large error variance between individual monocyte cultures. Thus, therapeutic levels of tetracyclines, especially minocycline, modulate mononuclear cell activities in vitro.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1698759&dopt=Abstract antibiotics, tetracycline