J Pharm Biomed Anal. 1994 May;12(5):675-92.
Chromatographic analysis of selected tetracyclines from dosage forms and bulk drug substance using polymeric columns with acidic mobile phases.

Bryan PD, Stewart JT.

Department of Medicinal Chemistry, College of Pharmacy, University of Georgia, Athens 30602-2352.

The LC analysis of selected tetracyclines from dosage forms and bulk drug substance using polymeric columns has been studied. Mobile phases containing acetonitrile-0.02 M sodium perchlorate (pH 2.0) were used. The tetracyclines were detected by their absorbance at 280 nm. The columns included: a polystyrene-divinylbenzene (PS-DVB) column and a polymethacrylate column with octadecyl ligands (PM-C18). Performance of the two columns was compared and applicability of the described methods for compendial use has been evaluated. The tetracyclines investigated include: minocycline, oxytetracycline, tetracycline, demeclocycline, chlortetracycline, methacycline, doxycycline and meclocycline.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7948189&dopt=Abstract antibiotics, tetracycline




Trop Geogr Med. 1993;45(3):117-20.
Preliminary epidemiological studies on tetracycline resistant plasmids isolated from enteric bacteria in Nigeria.

Olukoya DK, Daini OA, Niemogha MT.

National Institute for Medical Research, Yaba, Lagos, Nigeria.

In an epidemiological investigation on the genetic determinants responsible for tetracycline resistance in Nigeria, 518 isolates of enteric bacteria from hospitals and clinics were screened for susceptibility to antibiotics. 305 (58.8%) were resistant to tetracycline. The commonest resistance pattern that involved tetracycline resistance was tetr ampr sxtr Smr. Of the 305 isolates, 207 (67.8%) transferred resistant plasmids to Escherichia coli K-12. Altogether, 12 types of plasmids were isolated depending on the phenotypes of antibiotics resistant character borne on the plasmids; they ranged in sizes between 3 to 180 kilobases. The plasmids were evenly distributed in the country. Thus R plasmids are a major reason for resistance to tetracycline encountered in Nigeria.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8395740&dopt=Abstract antibiotics, tetracycline




Antimicrob Agents Chemother. 1983 Oct;24(4):544-51.
Susceptible Escherichia coli cells can actively excrete tetracyclines.

McMurry LM, Aronson DA, Levy SB.

Escherichia coli shows severalfold less susceptibility to tetracyclines when grown in enriched medium than in minimal medium. Transport studies with cells harvested from these media showed different handling of the drugs. Whereas an energy-dependent uptake of tetracycline and minocycline was observed in susceptible K-12 and wild-type E. coli strains grown in minimal medium, an active efflux of minocycline and, to a lesser extent, tetracycline was seen in cells grown in L broth and other enriched media. This efflux was replaced by an active uptake system after treatment of cells grown in L broth with EDTA. When assayed at a lower temperature (27 degrees C), even cells grown in minimal medium showed an efflux of minocycline. Everted membrane vesicles prepared from susceptible cells grown in minimal medium or L broth showed an energy-dependent accumulation of minocycline and tetracycline when supplied with certain divalent cations. These results suggest that an active efflux of tetracyclines occurs in susceptible E. coli but is not detected in cells grown in minimal medium because greater permeability of the outer membrane allows a more rapid active uptake. This efflux system is distinct from that specified by tetracycline resistance determinants. Since the active efflux of minocycline in cells grown in L broth disappeared at external antibiotic concentrations of greater than 100 microM, it may be saturable and so mediated by a membrane carrier.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6418064&dopt=Abstract antibiotics, tetracycline




Nucleic Acids Res. 1998 Feb 15;26(4):942-7.
An activator/repressor dual system allows tight tetracycline-regulated gene expression in budding yeast.

Belli G, Gari E, Piedrafita L, Aldea M, Herrero E.

Departament de Ciencies Mediques Basiques, Facultat de Medicina, Universitat de Lleida, Rovira Roure 44, 25198 Lleida, Spain.

We have developed an activator/repressor expression system for budding yeast in which tetracyclines control in opposite ways the ability of tetR-based activator and repressor molecules to bind tetO promoters. This combination allows tight expression of tetO- driven genes, both in a direct (tetracycline-repressible) and reverse (tetracycline-inducible) dual system. Ssn6 and Tup1, that are components of a general repressor complex in yeast, have been tested for their repressing properties in the dual system, using lacZ and CLN2 as reporter genes. Ssn6 gives better results and allows complete switching-off of the regulated genes, although increasing the levels of the Tup1-based repressor by expressing it from a stronger promoter improves repressing efficiency of the latter. Effector-mediated shifts between expression and non-expression conditions are rapid. The dual system here described may be useful for the functional analysis of essential genes whose conditional expression can be tightly controlled by tetracyclines.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9461451&dopt=Abstract antibiotics, tetracycline




J Control Release. 1999 Feb 22;57(3):215-22.
A new intragastric delivery system for the treatment of Helicobacter pylori associated gastric ulcer: in vitro evaluation.

Yang L, Eshraghi J, Fassihi R.

Temple University School of Pharmacy, 3307 N. Broad St., Philadelphia, PA 19140, USA.

A new strategy is proposed for the triple drug treatment (tetracycline, metronidazole and bismuth salt) of Helicobacter pylori associated peptic ulcers. The design of the delivery system was based on the swellable asymmetric triple layer tablet approach, with floating feature in order to prolong the gastric retention time of the delivery system. Hydroxypropylmethylcellulose and poly(ethylene oxide) were the major rate-controlling polymeric excipients. Tetracycline and metronidazole were incorporated into the core layer of the triple-layer matrix for controlled delivery, while bismuth salt could be included in one of the outer layers for instant release. The concentration of tetracycline and metronidazole released over time was determined simultaneously on a gradient high-performance liquid chromatography system. Results demonstrated that sustained delivery of tetracycline and metronidazole over 6-8 h can be easily achieved while the tablet remained afloat. The floating aspect was envisaged to extend the gastric retention time of the designed system to maintain effective localized concentration of tetracycline and metronidazole. Additionally, the developed HPLC method for the concurrent determination of tetracycline and metronidazole was proved to be rapid and accurate. The developed delivery system has potential to increase the efficacy of the therapy and improve patient compliance.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9895409&dopt=Abstract antibiotics, tetracycline




J Assoc Off Anal Chem. 1984 May-Jun;67(3):576-9.
Rapid assay for tetracycline in premixes and mixed feeds.

Katz JM, Katz SE.

A rapid assay for tetracyclines in premixes and mixed feeds is described, which uses the extraction and dilution systems of AOAC methods, and a strain of Bacillus stearothermophilus ATCC 12980 selected to grow at 40 degrees C. The incubation period is 4.5 h. The rapid assay yields results similar to those obtained using the AOAC methods. For a 50 g chlortetracycline (CTC)/lb commercial premix, the rapid procedure averaged 109.2% of label vs 104.4% obtained using the AOAC method; for a 20 g CTC/lb premix, the rapid procedure averaged 89.2% vs 89.3% obtained with the AOAC method. In 2 commercial premixes containing 50 g oxytetracycline/lb, the rapid assay averaged 127.1 and 110.5% vs 134.7 and 113.5% obtained using the AOAC method. In feed extracts supplemented with CTC equivalent to 25-200 g/ton, rapid assay recoveries averaged 101.9%; recoveries using the AOAC method averaged 110.6%. For feed extracts supplemented with oxytetracycline at the same levels, recoveries by the rapid assay averaged 95.4%, and by the AOAC method, 106.0%.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6430864&dopt=Abstract antibiotics, tetracycline




Antibiotiki. 1983 Sep;28(9):682-6.
[Content of SH- and --S--S-groups in the blood and liver homogenates in acute poisoning with tetracycline antibiotics]

[Article in Russian]

Skakun NP, Vysotskii IIu.

It was shown in experiments with albino rats that intoxication with tetracyclines and especially with chlortetracycline and tetracycline lowered the levels of sulfhydryl groups in the blood and liver homogenates of the animals, while the levels of the --S--S-groups increased. Tetracycline is characterized by a lower hepatotoxic action and did not affect the levels of sulfhydryl groups. It is suggested that impairment of lipid metabolism, inhibition of bile production and suppression of tissue respiration and oxidative phosphorylation due to oxidation or binding of SH-groups of enzymes and low molecular substances were the main links in the pathogenesis of liver fatty degeneration induced by tetracycline antibiotics.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6638982&dopt=Abstract antibiotics, tetracycline




Acta Anat (Basel). 1986;127(2):133-6.
Incorporation and stabilization of 3H-tetracycline in embryonic chick bone: an autoradiographic study.

Sandhu HS, Tonna EA.

Tibiae from 11-day-old chick embryos, injected with 3H-tetracycline, were autoradiographically analyzed at different stages to localize and study the dynamics of the initial phases of bone mineralization. 3H-tetracycline was localized within newly formed trabeculae, but only at the surfaces of older trabeculae, indicating that the incorporation of tetracycline into bone occurs at active sites of calcification. It takes between 24 and 36 h for injected tetracycline to become stabilized and incorporated into the mineralized matrix. Absence of 3H-tetracycline grains over the osteoblasts suggests a paracellular pathway for incorporation of tetracycline into the mineralizing bone matrix.

Source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3788455&dopt=Abstract antibiotics, tetracycline