RESUMEN
The metabolism of bromhexine [N-cyclohexyl-N-methyl-2-(2-amino-3,5-di-bromo-benzyl)-amine] was studied using pig hepatocyte cultures and LC/MS/MS techniques. Phase I 'single-step' reactions, i.e. hydroxylation and demethylation occurred the fastest whereas the formation of hydroxylated/demethylated and aminal hydroxylated metabolites, which can be considered as multiple-step reactions, occurred more slowly. Phase II conjugates were detected for all hydroxylated metabolites. The glucuronides of the hydroxylated/demethylated components tended to accumulate. In addition to metabolites known to be formed in vivo, three unknown components related to bromhexine were detected. Two of these metabolites accumulated during incubation. Based on the fragmentation patterns, a possible molecular structure is proposed for these components.
Asunto(s)
Bromhexina/metabolismo , Expectorantes/metabolismo , Hepatocitos/metabolismo , Porcinos/metabolismo , Animales , Bromhexina/química , Células Cultivadas , Expectorantes/química , Espectrometría de Masas , Estructura MolecularRESUMEN
The precursor terminal protein pTP is the primer for the initiation of adenovirus (Ad) DNA replication and forms a heterodimer with Ad DNA polymerase (pol). Pol can couple dCTP to pTP directed by the fourth nucleotide of the viral genome template strand in the absence of other replication proteins, which suggests that pTP/pol binding destabilizes the origin or stabilizes an unwound state. We analyzed the contribution of pTP to pTP/pol origin binding using various DNA oligonucleotides. We show that two pTP molecules bind cooperatively to short DNA duplexes, while longer DNA fragments are bound by single pTP molecules as well. Cooperative binding to short duplexes is DNA sequence independent and most likely mediated by protein/protein contacts. Furthermore, we observed that pTP binds single-stranded (ss)DNA with a minimal length of approximately 35 nt and that random ssDNA competed 25-fold more efficiently than random duplex DNA for origin binding by pTP. Remarkably, short DNA fragments with two opposing single strands supported monomeric pTP binding. pTP did not stimulate, but inhibited strand displacement by the Ad DNA binding and unwinding protein DBP. These observations suggest a mechanism in which the ssDNA affinity of pTP stabilizes Ad pol on partially unwound origin DNA.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Fosfoproteínas/metabolismo , Precursores de Proteínas/metabolismo , Sitios de Unión , ADN/química , ADN de Cadena Simple/química , ADN de Cadena Simple/metabolismo , Proteínas de Unión al ADN/química , Dimerización , Ensayo de Cambio de Movilidad Electroforética , Modelos Genéticos , Conformación de Ácido Nucleico , Fosfoproteínas/química , Unión Proteica , Precursores de Proteínas/química , Proteínas Virales/metabolismo , Replicación ViralRESUMEN
The Pharmacokinetics (PK) and distribution into tissue chamber fluid (TCF) of intramuscularly (i.m.) administered ampicillin sodium were examined in horses in order to design adequate dosing strategies. Concentration-time curves of ampicillin in plasma and TCF were determined in six horses following administration of 15 mg/kg ampicillin sodium, before and after the induction of local inflammation with 0.5% carrageenan. The calculated parameters were used to simulate various dosage-dosing interval combinations. Ampicillin was absorbed very rapidly following i.m. administration. Plasma concentrations were maximual between 18 and 21 min after administration. None of the plasma PK parameters were affected significantly by local (TC) inflammation. Penetration of ampicillin into and elimination from the TCF were affected significantly by inflammation and the half-life of elimination from the tissue fluid t1/2(d) was significantly shorter in inflammation. In the simulated dosage-dosing interval scenarios, only a dosage of 15 mg ampicillin/kg four times daily would successfully treat all ampicillin-susceptible bacterial isolates in well vascularized tissues. However a dosage as low as 10 mg/kg twice daily, would, in theory, treat all ampicillin-susceptible isolates in the inflamed poorly vascularized tissues. Decreasing the dosage results in loss of efficacy that cannot be completely compensated for by increasing the frequency of dosing.
Asunto(s)
Ampicilina/farmacocinética , Antibacterianos/farmacocinética , Caballos/metabolismo , Ampicilina/administración & dosificación , Ampicilina/sangre , Animales , Antibacterianos/administración & dosificación , Antibacterianos/sangre , Área Bajo la Curva , Espacio Extracelular/metabolismo , Femenino , Inyecciones Intramusculares , Masculino , Distribución TisularRESUMEN
The distribution of trimethoprim (TMP) and sulfadiazine (SDZ) into subcutaneously implanted noninfected tissue chambers was studied in healthy adult ponies. Six ponies were given an oral TMP/SDZ paste formulation at a dose of 5 mg/kg TMP and 25 mg/kg SDZ at 12 h intervals for 2 days in order to reach steady-state concentrations. Plasma concentrations and tissue chamber fluid (TCF) concentrations of both drugs were measured at regular intervals during a period commencing 24 h after the last oral administration. The peak concentration of TMP (mean +/- SD) was 2.92 +/- 0.86 microg/mL for plasma and 1.09 +/- 0.25 microg/mL for TCF. For SDZ, the mean peak concentration was 40.20 +/- 14.74 microg/mL for plasma and 23.48 +/- 5.84 microg/mL for TCF. TMP peak concentrations in plasma were reached at 3.17 +/- 03.48 h and those in TCF at 7.33 +/- 03.72 h. SDZ peak concentrations in plasma were reached at 1.83 +/- 02.04 h and those in TCF at 8.00 +/- 03.10 h. Concentrations of TMP and SDZ in TCF remained above the generally accepted breakpoint for susceptibility (0.5/9.5 for the TMP/SDZ combination) for 12 h. Therefore, in ponies oral administration of TMP/SDZ at a dose rate of 30 mg/kg given twice daily in the form of a paste should be appropriate for effective treatment of infections caused by susceptible bacteria.
Asunto(s)
Antiinfecciosos Urinarios/farmacocinética , Sulfadiazina/farmacocinética , Trimetoprim/farmacocinética , Administración Oral , Animales , Antiinfecciosos Urinarios/administración & dosificación , Antiinfecciosos Urinarios/sangre , Área Bajo la Curva , Cromatografía Líquida de Alta Presión , Combinación de Medicamentos , Femenino , Semivida , Caballos , Masculino , Sulfadiazina/administración & dosificación , Sulfadiazina/sangre , Distribución Tisular , Trimetoprim/administración & dosificación , Trimetoprim/sangreRESUMEN
The human transcription factor Oct-1 can stimulate transcription from a variety of promoters by interacting with the coactivators OBF-1/OCA-B/BOB-1, SNAP190 and VP16. These proteins contact Oct-1 regions different from the DNA binding surface. Oct-1 also stimulates the DNA replication of adenovirus through its DNA binding site in the origin. The Oct-1 POU homeodomain (POUhd) binds the adenovirus precursor terminal protein pTP, which serves as the protein primer of DNA replication and recruits pTP to the origin. To map the interaction with pTP at the POUhd surface, we screened a library of randomly mutated POU domains and identified mutations that interfered with pTP interaction and DNA replication stimulation. These mutants clustered at a surface different from those recognized by OBF-1, SNAP190 and VP16. Unexpectedly, the pTP binding region largely overlapped with the DNA binding surface of POUhd. In agreement with this, pTP binding and DNA binding were mutually exclusive. We propose a model to reconcile pTP recruitment and DNA binding by Oct-1.
Asunto(s)
ADN Viral/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de Homeodominio/metabolismo , Fosfoproteínas/metabolismo , Precursores de Proteínas/metabolismo , Factores de Transcripción/metabolismo , Proteínas Virales , Adenoviridae/genética , Secuencia de Aminoácidos , Secuencia de Bases , Replicación del ADN , Factor C1 de la Célula Huésped , Humanos , Datos de Secuencia Molecular , Factor 1 de Transcripción de Unión a Octámeros , Mutación Puntual , Unión ProteicaRESUMEN
Tibial quantitative ultrasonometry is a relatively novel technique in the field of bone sonometry, an emerging alternative to bone densitometry. The implementation of this technique in a pediatric population could prove valuable from a clinical as well as a research viewpoint. In clinical practice it is necessary to know the precision of this technique and the possible influence on measurements before implementation. This study presents the precision in a Caucasian pediatric population and the influence of measurement site, dexterity, brand of coupling gel, and temperature of coupling gel. To assess intra- and interobserver variance duplicate measurements, with repositioning, ultrasonometry was performed in 10 children over a short period of time. The observers were blinded for the results of the other observer and after each measurement the skin markings were removed. Intraobserver variance for operator one (MHL) and for observer two (SFGR) was CV 0.43%. The interobserver variance was CV 0.61%. Left midtibial and right midtibial speed of sound (SOS) measurements showed no significant differences. There were, however, significant differences in both boys and girls between right proximal versus right midtibial, right midtibial versus right distal, and right proximal versus right distal (for all P < 0.001). One-way analysis of variance (ANOVA) showed that neither the use of different coupling gels nor an increase in gel temperature had a significant influence on measurements. The results of our study show that tibial quantitative ultrasonography (QUS) is a highly reproducible technique in a Caucasian pediatric population.
Asunto(s)
Tibia/diagnóstico por imagen , Adolescente , Adulto , Análisis de Varianza , Niño , Femenino , Humanos , Masculino , Sensibilidad y Especificidad , Factores Sexuales , Ultrasonografía , Población BlancaRESUMEN
Mercer et al. (1977) proposed a three-phase experimental design to establish withdrawal times, based on plasma pharmacokinetics. This approach was the premise of a study in which plasma pharmacokinetics and tissue depletion data of oxytetracycline after intramuscular administration were correlated. Correlations between estimated and measured concentrations were shown to be significant for kidney tissue (r = .9236, p < .001), liver tissue (r = .9302, p < .01) as well as for muscle tissue (r = .9045, p < .001). The data presented support the pharmacokinetic approach as proposed by Mercer et al. (1977) and demonstrate that tissue elimination rates correlate highly with elimination rates in plasma. Although generalizations must be applied with caution, this article shows that when certain criteria are fulfilled, plasma pharmacokinetics can reliably predict tissue withdrawal times.
Asunto(s)
Bovinos/metabolismo , Residuos de Medicamentos/farmacocinética , Oxitetraciclina/farmacocinética , Absorción , Animales , Inyecciones Intramusculares , Masculino , Carne/análisis , Modelos Biológicos , Oxitetraciclina/administración & dosificación , Oxitetraciclina/sangre , Distribución TisularRESUMEN
The pharmacokinetics of oxytetracycline were studied after both intravenous (i.v.) and intramuscular (i.m.) administration to a group of five veal calves. Blood samples were taken frequently during the terminal elimination phase in order to calculate a reliable elimination rate constant. Because of the low limit of quantification of the method of analysis used, oxytetracycline plasma concentrations could be monitored over a 12-day period of time. After the intravenous administration of oxytetracycline, data were fitted according a three-compartment model. After i.m. administration, plasma-concentration-time curves could best be described by a two-compartment model. It was demonstrated that a very slow terminal elimination phase was present both after i.v. and i.m. administration with a half-life of approximately 95 h. The data show that this phase cannot be explained by slow absorption from the injection site and that release of oxytetracycline incorporated into bone is not a likely explanation.
Asunto(s)
Bovinos/metabolismo , Oxitetraciclina/farmacocinética , Absorción , Animales , Semivida , Inyecciones Intramusculares , Inyecciones Intravenosas , MasculinoRESUMEN
The bioavailability and pharmacokinetics of doxycycline hyclate were determined in calves with immature rumen function. The bioavailability of doxycycline after oral administration in a milk replacer was approximately 70%. The elimination half-life of doxycycline was found to be 9.5 +/- 3.0 h. after intravenous administration, and 12.6 +/- 5.0 h. after single oral administration. Plasma concentrations were determined after repeated oral administration of doxycycline dissolved in a milk replacer, at a dose of 5 mg per kg body weight, twice daily. During the period of administration, the plasma concentrations varied between Cmin of 1.0 +/- 0.19 mg/L and Cmax of 2.3 +/- 0.19 mg/L.