Simultaneous Dosage Research Articles

LC determination of oxcarbazepine and its active metabolite in human serum

Twenty-five percent of epileptic patients present refractory seizures to current frontline antiepileptic drugs, needing new treatments and leading to the introduction of several new AEDs, among which is oxcarbazepine (Trileptal ®). This 10-ketoanalogue of carbamazepine seems to be a weaker inducer of cytochrome P450 3A4. However, pharmacokinetic interactions with clinical significance have already been reported, before the marketing of Trileptal ® in France. The aim of this study was to develop and validate a HPLC method allowing simultaneous dosage of oxcarbazepine, 10-hydroxycarbamazepine, epoxycarbamazepine, carbamazepine, phenobarbital and phenytoı̈n. After plasma defecation by acetonitrile, dosage was obtained by analysis of the supernatants on a C 18 reversed-phase column coupled with UV detection (240 nm). The statistical validation was performed according to the recommendations of a European technical commission. This method seems to provide a quite good selectivity from the psychotropic therapeutics, which is commonly coprescribed with AEDs. Linearity was established for the whole concentration range, whatever the compound. Quantization limits of oxcarbazepine, 10-hydroxycarbamazepine, epoxycarbamazepine, carbamazepine, phenobarbital and phenytoı̈n are 0.58, 3.5, 2.35, 0.66, 1.02 and 3.13 μg/ml, respectively, and absolute recoveries are 105.15, 84.76, 94.45, 96.52, 98.62 and 95.08%, respectively.

Separation and first structure elucidation of Cremophor EL-components by hyphenated capillary electrophoresis and delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry.

The polyethoxylated heterogeneous components of the so far poorly characterized nonionic emulsifier Cremophor EL (polyoxyl 35 castor oil) (CrEL) were fractionated by cyclodextrin-modified micellar electrokinetic capillary chromatography (CD-MEKC). Due to the low UV absorbance of most of the CrEL-components an indirect UV detection was used with phenobarbital-sodium as background absorber. For a precise assignment of the resulting peaks to the corresponding components capillary electrophoresis (CE) had to be combined with delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry (DE-MALDI-TOF-MS) as detection system. For this purpose, the fractionating robot Probot was employed which enables both the on-line fractionation of the CE eluate on a MALDI target during the electrophoretic separation and the simultaneous dosage of the MALDI matrix solution. The applied CrEL amount was optimized by varying the CE injection parameters time, pressure and concentration of the sample in order to obtain homologue peak series of sufficient intensity without decreasing the separation efficiency. Evaluation of the mass spectra was performed by comparing the residue masses of the homologue peak series with the calculated residue masses of potential CrEL-components. However, the high number of polyethoxylated components leads to overlapping of homologue peak series with isobaric residue masses. These isobaric interferences were detected by a high mass accuracy of the measurements (obtained by internal calibration with polyethylene glycol (PEG) 1000 and by means of the residue mass plot, the newly developed evaluation method. The combination of these techniques allowed the first detailed structure analysis of the CrEL-components showing glycerol polyoxyethylene (POE) monoricinoleate and POE monoricinoleate to be the two main components of the emulsifier. Furthermore, the coupling of CE with DE-MALDI-TOF-MS is generally applicable to the fractionation and identification of polymers.

Separation of recombinant E. coli from culture broths by adsorption to modified carriers and controlled release of an expressed protein

Investigations were carried out concerning the considerate and selective separation of intact, product including recombinant E. coli cells from culture broths by adsorption. Adsorbents were synthesized on basis of porous glass “SIRAN” (Schott, Mainz) by chemical surface modification in order to adapt surface charge density and hydrophobicity to the surface behavior of the hosts. It is possible to accumulate up to 58 mg dry biomass per gram carrier by using the fixed bed circulation technique and by simultaneous dosage of small amounts of polycationic reagent Polyethyleneimine (PEI). The method is especially useful for the separation of shear stress sensible microorganisms.

Test results of electronic control units for field sprayers and future trends1

The BBA has designed and contructed it test stand for thc electronic control units of field sprayers, and drawn up test guidelines. The dynamic and static characteristics of 10 electronic control units on the market have recently been examined. Examples of the results of these examinations are given. Future trends in the field of electronically controlled field sprayers are discussed. The present stand‐alone units will be replaced by the agricultural BUS system (LBS) (DIN 9684 and ISO/TC23/SC19/WGI). Satellite position‐finding systems (c.g. GPS) may be used. Specifications can be developed for site‐specific application of plant protection products, initially including simultaneous dosage of several products and site characteristics. It is doubtful for the moment whether such systems can react to the state of the crop or to indices of pest presence.

Disposition of the Diastereoisomers Quinine and Quinidine in the Ovine Fetus

The disposition of the diastereoisomers quinine and quinidine was investigated in the near-term pregnant ewe. Five sheep were administered quinine and quinidine separately in random order by a combination of bolus and 30-h iv infusion. On a subsequent occasion, four of the five sheep were also administered the two drugs simultaneously. After separate dosage, systemic clearance of quinine tended to be greater than that of quinidine (714 ± 299 versus 422 ± 146 mL/min, p = 0.08). Maternal renal clearance exhibited no stereoselectivity and represented <2% of total clearance. Simultaneous administration did not alter the disposition of either drug in the mother. After separate dosage, fetal total concentrations (C,) of quinine and quinidine were substantially lower than maternal total concentrations, as reflected in C,:Cm ratios of 0.15 ± 0.06 versus 0.10 ± 0.08, respectively. Similarly, fetal unbound concentrations (Ctu) were substantially lower than maternal unbound concentrations (Cmu; CJCmu = 0.46 ± 0.09 for quinine and 0.23 ± 0.09 for quinidine). This indicates the presence of fetal elimination of both isomers. Fetal renal clearances of quinine and quinidine were similar (0.34 ± 0.24 mL/min versus 0.38 ± 0.24 mL/min) and less than that of endogenous creatinine, indicating the absence of net renal tubular secretion. After simultaneous dosage of quinine and quinidine, C,:Cm (0.48 ± 0.24 and 0.31 ±0.19, respectively) and C,u:Cmu (0.73 ± 0.14 and 0.52 ± 0.20, respectively) were greater than for separate dosages. Fetal renal clearance of both drugs was unchanged, suggesting that the higher C(u:Cmu ratios after simultaneous dosage were due to mutual inhibition of the fetal metabolism of these drugs.

Endogenous incorporation of nitric oxide from L-arginine into N-nitrosomorpholine sitmulated by Escherichia coli lipopolysaccharide in the rat

The endogenous formation of nitrate in the rat, mouse and human occurs through cellular processes involving the oxidation of the guanido group of arginine. These processes proceed from arginine to nitric oxide with subsequent conversion to electrophilic nitrosating agents capable of forming carcinogenic nitrosamines. We have now demonstrated that endogenous nitrosamine formation can occur via cells stimulated in vivo by bacterial lipopolysaccharide (LPS). The nitrosation of morpholine given to rats by i.p. injection yields N-nitrosomorpholine (NMOR) which is subsequently oxidized in the liver. A major metabolite of NMOR, N-nitroso-(2-hydroxyethyl)glycine, was previously shown by other investigators to be excreted into urine. Treatment of rats with LPS, arginine and morpholine creates a large increase in NMOR urinary metabolites over a 24-h period. This process is not influenced by simultaneous dosage with large amounts of NaNO3. Therefore the endogenous LPS-induced formation of NMOR proceeds directly from nitric oxide prior to incorporation into the nitrate body pool. The proportion of endogenously synthesized nitric oxide incorporated into NMOR is approximately 3 x 10(-6).

Quantitative distribution of DNA and RNA in the bovine ovocyte: a direct ultramicrospectrophotometric method.

An ultramicrospectrophotometric method previously applied to the bull spermatozoon was extended to the bovine ovocyte. Measurements of DNA and RNA content were conducted on thin sections of oocytes examined at two wavelengths to correct for nonspecific background. Further treatment of sections with DNase or RNase provided differential assays of DNA and RNA. Negative controls were carried out after extraction with cold or hot trichloracetic acid. Subsequent analysis of data obtained with this method should allow simultaneous dosage and three -dimensional localization of nucleic acids in both mammalian oocytes and ova.

RNA synthesis in Drosophila melanogaster polytene chromosomes. Indications of simultaneous dosage compensation and dosage effect in X chromosomes.

It is shown that the apparent incompleteness of dosage compensation when RNA synthesis is measured autoradiographically is not due to the existence of contiguous dosage compensated and non-dosage compensated genes. Rather this seems to be the result of peculiarities in the coordination of RNA synthesis between the X chromosomes and autosomes. The slope of the line defined by \([\bar X]_i \) and \([\overline {2R} ]_i \) (number of grains over the X and autosomal segments averaged over the different nuclei assayed in each gland) is indistinguishable in males and females (apparent complete dosage compensation). An average of the slopes obtained for different individual glands (from [X] and [2R], the grain counts over each nucleus belonging to a particular gland), on the other hand, has a value in males which is approximately half of the value attained by females (a value of one half, in males, indicates dosage effect since males have one X and females have two).

Multiple Chemotherapeutic Agents for Hodgkin Disease

Two hundred forty-seven patients with disseminated Hodgkin disease were randomly treated with one of three intensive multiple-agent regimens. Partial or complete response rates of 90% were obtained with each routine. The "MOPP" regimen—mechlorethamine hydrochloride, vincristine sulfate (Oncovin), procarbazine hydrochloride, and prednisone—yielded the longest duration of response but also had the highest toxicity. There was no difference in survival rates among patients on the three routines. Major factors associated with good response were female sex and little or no prior therapy. Minor favorable factors were stage III disease, lack of systemic symptoms, former responsiveness to therapy, and age of less than 60 years. The simultaneous dosage routine was superior in both response rate and lessened toxicity compared to sequential usage of the same drugs with the same total dosage.

The metabolism of hexachlorocyclohexanes and pentachlorocyclohexenes in flies and grass grubs.

1. gamma-Hexachlorocyclohexane, gamma-pentachlorocyclohexene and delta-pentachlorocyclohexene were converted by houseflies and grass grubs into metabolites that had chromatographic properties identical with those of S-2,4-dichlorophenylglutathione. 2. The metabolism of gamma-hexachlorocyclohexane and the pentachlorocyclohexene isomers was negligible in newly emerged blowflies, but increased over the next 10 days. 3. The metabolism of both gamma-hexachlorocyclohexane and the pentachlorocyclohexene isomers was inhibited by simultaneous dosage with tetrabromophenolphthalein ethyl ester or Bromophenol Blue in both grass grubs and flies, but only the metabolism of pentachlorocyclohexenes in blowflies was stopped by simultaneous dosage with bis-(N-dimethylaminophenyl)methane. NN-Di-n-butyl-p-chlorobenzenesulphonamide had no effect on the metabolism of pentachlorocyclohexenes by blowflies. 4. The use of these inhibitors and colorimetric assays leads to the conclusion that a pentachlorocyclohexene is not a major intermediary metabolite of gamma-hexachlorocyclohexane in these insects.