Molecular characterization of two host-guest associating hyaluronan derivatives

Molecular characteristics were determined of two high-molecular-weight water-soluble hyaluronan derivatives, namely beta-cyclodextrin (HA-beta-CD) and N-acylurea (EDC-HA). The weight-average molecular weight (M(w)) of HA-beta-CD and of EDC-HA, determined with a multi-angle light scattering detector connected on-line to a size exclusion chromatographic system, was respectively 185.3 and 86.8 kDa. However the M(w) value determined for the equimolar mixture of the two HA derivatives equaled 556.0 kDa. Similarly, the gyration radius of the above equimolar mixture, Rg = 80.6 nm, was significantly greater than the values found for the single HA derivative, i.e. 40.2 nm for HA-beta-CD and 23.8 nm for EDC-HA. These data indicate that the two kinds of substituents, bound to the polymeric chains, form host-guest/inclusion complexes resulting in polymacromolecular associates/aggregates.

Molecular characteristics of some commercial high-molecular-weight hyaluronans

Commercially available hyaluronan (HA) samples were investigated by the method of size exclusion chromatography (SEC). The fractions eluted from the SEC column were on-line molecularly characterized by using a multi-angle laser light scattering (MALLS) photometer. Along with the SEC-MALLS technique, the high-molecular-weight HA biopolymers were (off-line) analyzed by capillary viscometry.

Estimation of drug-protein binding parameters on assuming the validity of thermodynamic equilibrium

This contribution focuses the reader's attention on the pitfalls usually emerging during the phase of evaluation of experimental data of drug-protein binding studies. To overcome the occurrence of problem(s) apparently defying solution, the concept of "affinity spectra" is recommended to be implemented for data evaluation. A (general) "binding study protocol" is also suggested, which can prevent the formation of inadequate conclusions and the generation of unrealistic drug-protein binding parameters.

Neoglycoconjugates of mannan with bovine serum albumin and their interaction with lectin concanavalin A

Neoglycoconjugates were prepared from mannan isolated from yeast Saccharomyces cerevisiae and activated by periodate oxidation to create aldehyde groups. Various degrees of oxidation introduced 11-28 aldehyde groups per mannan molecule and simultaneously resulted in a molar mass decrease from 46 to 44.5-31 kDa. The activated mannans were subsequently conjugated with bovine serum albumin forming neoglycoconjugates. Some parameters of these mannan-bovine serum albumin conjugates were characterized: saccharide content 25-30% w/w, molar mass within the range 169-246 kDa, and polydispersion (M(w)/M(n)) from 2.8 to 3.6. The interaction of these conjugates with lectin concanavalin A was studied using three different methods: (i) quantitative precipitation in solution; (ii) sorption to concanavalin A immobilized on bead cellulose; and (iii) kinetic measurement of the interaction by surface plasmon resonance. Quantitative precipitation assay showed only negligible differences in the precipitation course of original mannan and the corresponding mannan-bovine serum albumin conjugates. Both the sorption method (equilibrium method) and the surface plasmon resonance measurement (kinetic method) demonstrates that the values of dissociation constant K(D) of all synthetic neoglycoconjugates were within the range 10(-7) - 10(-8) mol x L(-1) (close to K(D) = 10(-8) mol x L(-1) determined by the sorption method for the original mannan). In conclusion, characterization of synthetic neoglycoconjugates confirmed that the method used for their preparation retained the ability of mannan moiety to interact with concanavalin A.

Radical degradation of high molecular weight hyaluronan: inhibition of the reaction by ibuprofen enantiomers

The antioxidative and/or free-radical-scavenging activities of R-(-)- and S-(+)-ibuprofen enantiomers, as well as of the drug racemate, were studied in vitro on measuring the kinetics of (uninhibited or drug-inhibited) degradation of high molecular weight hyaluronan by hydroxyl radicals. The continual flux of OH radicals at aerobic conditions was maintained by the H2O2 + Cu2+ system. The kinetics of hyaluronan degradation was monitored indirectly by capillary viscometry. Under experimental conditions, with no drug addition, the relative viscosity ([eta]rel) decreased continuously, reaching 13% of the initial [eta]rel. value in 4 h. Each drug tested exhibited a dose-dependent protective effect against hyaluronan degradation, however R-(-)-ibuprofen demonstrated a slightly greater activity than the drug S-(+)-enantiomer.

Placental transfer of the antioxidant stobadine at different gestational stages in rabbits

The distribution of [3H]-stobadine, a pyridoindole antioxidant, was investigated in New Zealand white rabbits and their fetuses on days 20 and 27 of gestation. The concentrations of [3H]-stobadine were determined in maternal and fetal organs after oral administration in a single dose of 5.0 mg/kg. The results of the study showed that during the late period of gestation the fetal organs, especially the brain and heart, were under the protective action of the antioxidant stobadine.

Extraction and chromatographic separation methods in pharmacokinetic studies of Stobadine--an indole-related antioxidant and free-radical scavenger

This overview provides comprehensive information on the most relevant results of Stobadine preclinical disposition studies. In order to investigate pharmacokinetic processes of the drug in rats, dogs and in human volunteers, several bioanalytical assays based on radiometric, spectrofluorometric, as well as chromatographic determination methods were developed and implemented. In small laboratory animals, the drug absorption, distribution, metabolism and elimination were investigated by administering 3H-labeled Stobadine. Spectrofluorometry was used alternatively for the determination of cold/unlabeled Stobadine in extracts of biomaterials sampled from larger animal species. The chromatographic separation methods proved, however, to be the most advantageous for determining details of the drug disposition and fate in the body.

Sonication of chitin-glucan, preparation of water-soluble fractions and characterization by HPLC

A water-insoluble chitin-glucan complex, isolated from the mycelium of Aspergillus niger, was swollen in various aqueous media and treated subsequently by high-energy sonication. The concentration of the resulting water-soluble polysaccharide fractions was dependent on the swelling medium, the amount of the chitin-glucan complex in the suspension, and on the time of sonication. The yields of water-soluble chitin-glucan were within the range 13.6 to 24.4% relative to the mass of the original chitin-glucan. The nitrogen content obtained for the samples of water-soluble chitin-glucan indicated a higher content of chitin (3.45% of nitrogen in high-molecular fraction) than in the original water-insoluble chitin-glucan sample (1.8%). The distribution of the molecular weights of the water-soluble fractions prepared was determined by high-performance liquid chromatography.

Pharmacokinetic study of stobadine

The aim of this paper is to provide a brief overview of most important results of stobadine kinetic studies in rats, dogs, and human volunteers. In these studies, stobadine dihydrochloride and stobadine dipalmitate was used for intravenous and oral administration, respectively. To evaluate kinetic properties of stobadine and its metabolites, TLC, HPLC, GLC, GC-MS, radiometric, and fluorometric methods were developed and used.

Placental transfer of stobadine in rabbits

Stobadine, a pyridoindole antioxidant, was investigated for its placental transfer and distribution in New Zealand white rabbits on the 27th day of gestation. The concentrations of stobadine were determined in maternal and foetal organs (plasma, brain, heart) at 30, 60, 120, and 360 minutes after oral administration of the drug in a dose of 5 mg/kg. The results obtained proved that after oral stobadine intake by rabbits at the stage of advanced pregnancy both maternal and foetal organs were under a certain drug level which could act protectively against oxidative stress--frequently occurring during late organogenesis, foetal stages and delivery, as well as during early postnatal development.

A simple chiral high-performance liquid chromatographic method to study the enantiomer-differentiating action of microorganisms. An assay with DL-tryptophan

To investigate the 'enantiomer-differentiating' action of the microorganisms colonizing a phosphate-buffered DL-tryptophan solution, a novel chiral high-performance liquid chromatographic (HPLC) arrangement was developed and established. As the HPLC stationary phase, bovine serum albumin (BSA) bonded silica gel was used. In the function of the mobile phase, phosphate-buffered DL-tryptophan solution was applied. The composition of the eluate was monitored by an HPLC spectrophotometric detector. After injecting the assayed sample into the eluent stream, the content of each tryptophan enantiomer was evaluated either from the positive or negative responses of the HPLC detector. The validity and the performance of this novel approach were confirmed by applying another chiral HPLC device working with human serum albumin (HSA) bonded silica gel as the stationary phase and with 1-propanol containing phosphate buffer as the eluent.

Aminoglycoside antibiotics--two decades of their HPLC bioanalysis

Several reviews have been published on high-performance liquid chromatographic (HPLC) methods for the determination of aminoglycoside antibiotics (aminoglycosides) in biological fluids [e.g. Nilsson-Ehle, I. (1983). J. Liq. Chromat. 6: 251]. Of these, the paper by Maitra et al. [(1979a). Clin. Chem. 25: 1361.] briefly summarizes the early 2-3 years of experience on HPLC assaying of amikacin, gentamicin, netilmicin and tobramycin in body fluids. The reviews by Nilsson-Ehle, I. [(1983). J. Liq. Chromat. 6: 251] and by Miner, D. J. [(1985). Antibiotics. In Therapeutic Drug Monitoring and Toxicology by Liquid Chromatography, (Wong S. H. Y., ed.), ch. 10, p. 269. Marcel Dekker, New York and Basel.] devoted to the monitoring of antibiotics, also evaluated the first 6-8 years of the application of HPLC assays for the aminoglycosides amikacin, gentamicin, netilmicin, sisomicin and tobramycin. This report presents a great majority of the HPLC assay methods published during the last two decades for determining practically a dozen different aminoglycoside antibiotics in body fluids, particularly in the serum or plasma, and in urine.

High-molecular-weight hyaluronan--a valuable tool in testing the antioxidative activity of amphiphilic drugs stobadine and vinpocetine

The antioxidative activity of stobadine and vinpocetine was studied in vitro by measuring their inhibition effect on the depolymerization of the high-molecular-weight hyaluronan by hydroxyl radicals. The radicals were generated by the Cu(2+)-H2O2 system. Hyaluronan depolymerization was monitored by means of size exclusion chromatography. The antioxidative activity of stobadine and vinpocetine was compared to that of D-mannitol. A 50% inhibition of hyaluronan depolymerization was reached at stobadine and vinpocetine concentrations of 1.7 x 10(-6) and 3.0 x 10(-7) mol l-1, respectively, while a D-mannitol level of 2.6 x 10(-3) mol l-1 was needed to achieve the same inhibitory effect.

Effective one/two step purification of various materials by solid-phase extraction

Simple one/two step purification procedures based on the solid-phase extraction technique were effectively exploited to clean up radiolabelled drugs represented by dihydrochloride of [6-3H]-stobadine and hydrochloride of [4-3H]-pentacaine, derivatization agents such as 4-nitrobenzoyl chloride or 3,5-dinitrobenzoyl chloride, as well as the aqueous phosphate or triethylamine acetate buffer solutions.

Reversible binding interactions between the tryptophan enantiomers and albumins of different animal species as determined by novel high performance liquid chromatographic methods: an attempt to localize the D- and L-tryptophan binding sites on the human serum albumin polypeptide chain by using protein fragments

The stereoselectivity of the reversible binding interactions between the D- and L-tryptophan enantiomers and serum albumins of different animal species and fragments of human serum albumin (HSA) was investigated by applying three novel high performance liquid chromatographic (HPLC) arrangements. The separations were performed by means of 1) an achiral (diol-bond), 2) a chiral (bovine serum albumin-bond) silica gel sorbent, and 3) a column switching technique which uses both the diol- and HSA-bond HPLC stationary phases. A polarimetric detector and/or an ultraviolet (UV) spectrophotometer were used to monitor the separation process. HPLC arrangement 3 allowed the evaluation of enantioselective binding for D- and L-tryptophan to different albumins and albumin fragments. At present, column switching can be considered the technique of the broadest applicability for investigating the reversible binding interactions between a protein and drug enantiomers.

Ethics committees and achievement of good clinical practice

Local ethics committees (institutional review boards, or similar bodies) were established during the last decades at (bio)medical research institutions worldwide to serve as review bodies of the proposed research projects (inclusive protocols of clinical trials), and also to monitor if the ethical principles, including the requirements of good practice (clinical, laboratory, and scientific) are respected and fulfilled during the conduct of research projects. Existing pluralism of the philosophical background on which contemporary bioethics theories are developed is questioning seriously the ancient traditions of Hippocratic, non-utilitarian medical ethics, trying to promote more utilitarian and secular approaches. Individual physicians, or researchers, as well as the ethics committee itself, are faced today with complicated ethical dilemmas, that frequently have to be solved in the atmosphere of considerable social, collegiate, economical, and time pressures, and sometimes without helpful guidance of appropriate legislation. An interesting possibility of how to overcome some of the pitfalls of the ethics review process is to express a common ethical responsibility for the research project or trial protocol in a statement of most (or all) parties involved (such as the principal investigator, sponsor, ethics committee, the patient, "society'). Such an approach has proven helpful in enhancing concrete deliberations of ethics committees-established in Slovakia since 1991 according to the requirements of the national guidelines issued by the Slovak Ministry of Health.

Insight into the distribution of molecular weights and higher-order structure of hyaluronans and some beta-(1 --> 3)-glucans by size exclusion chromatography

The effects of high energy ultrasound and slightly raised temperature combined with the denaturing action of dimethylsulphoxide on the molecular weight and higher-order structure of hyaluronans and some beta-(1 --> 3)-glucans were studied by means of size exclusion chromatography (SEC) technique. Some experimental conditions connected with the (bio-)polymer sample preparation prior to its SEC analysis are overviewed in the light of informational relevance of studies where the action of a physical and/or chemical agent changes the hydrodynamic size of the m omolecule.

Propafenone binding interaction with human alpha 1-acid glycoprotein: assessing experimental design and data evaluation

Binding data on racemic RS-propafenone as well as individual R- and S-drug enantiomers interacting reversibly with human alpha 1-acid glycoprotein, as obtained by a high-performance liquid chromatographic method, are evaluated according to three different approaches introduced, respectively, by Scatchard, Bjerrum, and by Tobler and Engel. A non-linear curve-fitting procedure was applied to compute the binding parameters exclusively for the binary system comprising the examined protein and R- and S-propafenone, individually. The exactness of the study design rather than the numerical values were the focus of attention in the evaluation of the data found.

Cronobiologic analysis of abortions in two related populations of teenager girls during two decades

STUDY OBJECTIVE

To identify and compare the time dynamics of artificial abortions in two (Czech and Slovak) ethnically, historically and socially closely related populations.

DESIGN

Data have been taken separately for 12-15 and 16-18 year age girls from official exhaustive statistical sources and processed by advanced procedures of time series analysis.

SETTING

Czech and Slovak Republics.

PARTICIPANTS

All girls of the given age.

INTERVENTIONS

Legislative liberalization of abortions 1987.

MAIN OUTCOME MEASURES

Estimated starting values of relative numbers of abortions by 1971, increasing linear trends, period lengths of fluctuation, coefficients of determination and those of cross-correlation. Level of significance alpha = 0.05.

RESULTS

The Czech figures are significantly higher than the Slovak. Thus, estimated abortion percentage (from pregnancies) for 1971 was for younger Czech girls 53%, and for those from Slovakia 29%. All estimated trends were increasing significantly in all cases for the Czech population (by 1.5% per year in the younger group) and in one case for Slovakia. The estimated period lengths were usually 10-12 years. Czech and Slovak data display significant positive mutual cross-correlation, the delay being 1-3 years in Slovak girls. Surprisingly, all data significantly cross-correlate with the geomagnetic index value Ap, acting as lead-lag, with 3-6-year delay for abortions.

CONCLUSIONS

Despite living in the same federal state--the former Czechoslovak Republic, both Czech and Slovak populations do differ in starting values and general trends of abortions in teenagers. This can be due to historical, racial and religious peculiarities as well as a more advanced process of industrialization in the western part--the Czech Republic. The latter hypothesis is corroborated by strong dynamism of changes and by the time delay in Slovakia. The periodicity exhibits a frequency resembling that known for solar motion round barycenter of solar system, for sunspots and geomagnetism.

Multimodal liquid chromatographic separation methods in the study of ethimizol metabolism in man

The metabolism of ethimizol in the human body has been investigated. Focus was on the detection and demonstration of the regioselective pathway of metabolic demethylation of ethimizol by determining the presence of the corresponding metabolites in blood, saliva and urine. Isolation, purification and identification of the metabolites present in the biological samples was achieved by applying a combination of the following methods: solid phase extraction, high performance liquid chromatography, high performance thin layer chromatography, nuclear magnetic resonance and mass spectrometry. The suggested chemical structures were definitely established by comparing the physicochemical characteristics of the ethimizol metabolites obtained from the individual biological fluids with the characteristics of synthetized authentic derivatives.

Enhanced selectivity of the isolation of basic drugs from body fluids by means of extraction minicolumns and sophisticated elution schemes

The paper presents results and experience obtained in the isolation of a number of basic polar/non-polar solutes (drugs, their metabolites and structural derivatives) from biological samples by using the separation minicolumns Separcol SI and Separcol SI C18 L/T. The aim was to provide insight into some simple procedures yielding optimal selectivity/specificity of the isolation of the studied solutes either by proper selection of the sorbent or by applying sophisticated elution schemes which use to advantage different properties of the eluents/solvents.

High-performance liquid chromatographic determination of bilirubin distribution on serum proteins

We describe a high-performance liquid chromatographic method for the determination of bilirubin distribution on serum proteins. The procedure is based on both size-exclusion and adsorptive properties of the column packing material LiChrosorb Diol. The elution of all sample constituents is accomplished by means of an aqueous mobile phase containing phosphate buffered solution of adult serum, supplemented by a small amount of bilirubin. The different distribution of bilirubin on albumin, beta-lipoprotein, and as free (loosely bound) pigment fraction is exemplified by assaying normal adult and infant sera.

Pharmacokinetics of stobadin and of the sum of its metabolites in rats during repeated administration

Stobadin dihydrochloride was administered p.o. to rats at a dose of 1 mg kg-1 once daily for 25 consecutive days. The peak and trough concentrations of the sum of stobadin metabolites, determined from Days 6-16 of treatment, demonstrated a steady-state. The mean daily excretion of 3H-radioactivity during this period was 43 per cent and 52 per cent of the administered dose into urine and faeces, respectively. The terminal half-life of stobadin in plasma following a 25-day chronic treatment was 78.3 min, which was shorter than the value of 95.3 min, determined in a single dose experiment. The data indicate that no accumulation of stobadin and of its labelled metabolites occurs in the course of repeated administration of 3H-stobadin.