Effect of venlafaxine on scavenging free radicals in vitro

O BJECTIVE: Venlafaxine (VLF) was examined as a potential donor of H atom(s) to scavenge hydroxyl and peroxy-type radicals generated under aerobic conditions by catalytic oxidation of ascorbate with Cu²⁺ ions. Kinetics of the electron-donor property of VLF was investigated by standard ABTS and DPPH assays. Electron paramagnetic resonance measurements were applied to prove/disprove the VLF ability to scavenge superoxide anion radical.

RESULTS

Results indicated that the drug venlafaxine was slightly capable of donating ·H, this way VLF scavenged the in situ generated hydroxyl radicals. Under the experimental conditions VLF was not able to inhibit/retard the propagation of the peroxy-type radicals. Regarding to the drug electron donating property, VLF did not show any ABTS·⁺ or DPPH· radical quenching property. Venlafaxine was not effective in scavenging O2·⁻.

CONCLUSION

Results of ABTS and DPPH assay showed a negligible redox activity of venlafaxine to both DPPH· and ABTS·⁺. Venlafaxine was not capable of scavenging the superoxide anion radical generated in KO₂/DMSO system, which indicates that VLF is not an efficient electron/proton donor molecule.

Radical scavenging activity of Caesalpinia spinosa

OBJECTIVES

To assess protective effects of the tara (Caesalpinia spinosa) extract against hyaluronan (HA) degradation evoked by cupric ions and ascorbate.

METHODS

Uninhibited/inhibited HA degradation was assayed by a decrease in dynamic viscosity of the HA solutions, whereas as a method rotational viscometry was used. To determine radical scavenging capacity of the tara extract, the ABTS and DPPH assays were performed.

RESULTS

The results of rotational viscometry showed remarkable protective effects of the tara extract against the degradation of HA. In the ABTS and DPPH assays the IC50 values of the tara extract 1.59 and 30.8 μg/mL indicated quite high radical scavenging properties.

CONCLUSION

The tara extract is an efficient antioxidant as demonstrated by the methods used.

Free-radical degradation of high-molar-mass hyaluronan induced by ascorbate plus cupric ions: evaluation of antioxidative effect of cysteine-derived compounds

Based on our previous findings, the present study has focused on free-radical-mediated degradation of the synovial biopolymer hyaluronan. The degradation was induced in vitro by the Weissberger's system comprising ascorbate plus cupric ions in the presence of oxygen, representing a model of the early phase of acute synovial joint inflammation. The study presents a novel strategy for hyaluronan protection against oxidative degradation with the use of cysteine-derived compounds. In particular, the work objectives were to evaluate potential protective effects of reduced form of L-glutathione, L-cysteine, N-acetyl-L-cysteine, and cysteamine, against free-oxygen-radical-mediated degradation of high-molar-mass hyaluronan in vitro. The hyaluronan degradation was influenced by variable activity of the tested thiol compounds, also in dependence of their concentration applied. It was found that L-glutathione exhibited the most significant protective and chain-breaking antioxidative effect against the hyaluronan degradation. Thiol antioxidative activity, in general, can be influenced by many factors such as various molecule geometry, type of functional groups, radical attack accessibility, redox potential, thiol concentration and pK(a), pH, ionic strength of solution, as well as different ability to interact with transition metals. Antioxidative activity was found to decrease in the following order: L-glutathione, cysteamine, N-acetyl-L-cysteine, and L-cysteine. These findings might be beneficial in future development of potential drugs in the treatment of synovial hyaluronan depletion-derived diseases.

Aurothiomalate as preventive and chain-breaking antioxidant in radical degradation of high-molar-mass hyaluronan

The potential anti- or pro-oxidative effects of a disease-modifying antirheumatic drug, aurothiomalate, to protect high-molar-mass hyaluronan against radical degradation were investigated along with L-glutathione - tested in similar functions. Hyaluronan degradation was induced by the oxidative system Cu(II) plus ascorbate known as the Weissberger's oxidative system. The time- and dose-dependent changes of the dynamic viscosity of the hyaluronan solutions were studied by the method of rotational viscometry. Additionally, the antioxidative activity of aurothiomalate expressed as a radical-scavenging capacity based on a decolorization 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay was inspected. At the higher concentrations tested, L-glutathione showed excellent scavenging of (.) OH and peroxyl-type radicals, however, at the lowest concentration applied, its pro-oxidative effect was revealed. The effects of aurothiomalate on hyaluronan degradation were similar to that of L-glutathione, however, at the lowest concentration tested, no significant pro-oxidant effect was observed.

Free-radical degradation of high-molecular-weight hyaluronan induced by ascorbate plus cupric ions. Testing of bucillamine and its SA981-metabolite as antioxidants

High-molecular-weight hyaluronan (HA) samples were exposed to free-radical chain-degradation reactions induced by ascorbate in the presence of Cu(II) ions - the so-called Weissberger's oxidative system. The concentrations of both reactants [ascorbate, Cu(II)] were comparable to those that may occur during an early stage of the acute phase of joint inflammation. The time-dependent changes of the viscosity of the HA solution in the absence of the substance tested were monitored by rotational viscometry. However, when the anti- or pro-oxidative effects of the antioxidants/drugs were investigated, their dose-dependency was also examined. Additionally, the anti-oxidative activities of these substances were screened by the well-established ABTS and DPPH decolorization assays. The actions of the disease-modifying anti-rheumatic drugs, namely bucillamine and D-penicillamine, were compared to those of L-cysteine and of SA981, the oxidized metabolite of bucillamine. The results indicated that bucillamine was the most efficient scavenger of hydroxyl- and/or peroxyl-type radicals, even at the lowest drug concentration. In contrast, SA981 demonstrated no scavenging activity against the aforementioned free radicals. D-Penicillamine and L-cysteine showed a dual effect, i.e. a pronounced anti-oxidative effect was, after a given time period, followed by a significant pro-oxidative effect.

An alternative standard for Trolox-equivalent antioxidant-capacity estimation based on thiol antioxidants. Comparative 2,2'-azinobis[3-ethylbenzothiazoline-6-sulfonic acid] decolorization and rotational viscometry study regarding hyaluronan degradation

Comparison of the effectiveness of antioxidant activity of three thiol compounds, D-penicillamine, reduced L-glutathione, and 1,4-dithioerythritol, expressed as a radical-scavenging capacity based on the two independent methods, namely a decolorization 2,2'-azinobis[3-ethylbenzothiazoline-6-sulfonic acid] assay and a rotational viscometry, is reported. Particular concern was focused on the testing of potential free-radical scavenging effects of thiols against hyaluronan degradation, induced by hydroxyl radicals. A promising, solvent-independent, antioxidative function of 1,4-dithioerythritol, comparable to that of a standard compound, Trolox(®), was confirmed by the 2,2'-azinobis[3-ethylbenzothiazoline-6-sulfonic acid] assay. The new potential antioxidant 1,4-dithioerythritol exhibited very good solubility in a variety of solvents (e.g., H(2)O, EtOH, and DMSO) and could be widely accepted and used as an effective antioxidant standard instead of a routinely used Trolox(®) on 2,2'-azinobis[3-ethylbenzothiazoline-6-sulfonic acid] assay.

Degradation of high-molar-mass hyaluronan by ascorbate plus cupric ions: effects of D-penicillamine addition

Pro- and anti-oxidative effects of an anti-rheumatoid drug, D-penicillamine (D-PN), on the kinetics of high-molar-mass hyaluronan (HA) degradation were monitored using the method of rotational viscometry. The degradation of the dissolved HA macromolecules was attained by applying the Weissberger's system comprising ascorbic acid plus cupric ions. Electron paramagnetic resonance (EPR) spectroscopy was used to identify the generated free radicals. The results obtained indicate that the initial anti-oxidative action of D-PN is followed by induction of pro-oxidative conditions due to the generation of reactive free radicals. It is speculated, however, that the latter situation may be considered as an advantageous property of D-PN. Hydroxyl radicals formed in this way may participate in decomposition of proteinases, which are believed to be responsible for the destruction of joint cartilage under rheumatoid arthritic conditions.

Degradation of high-molar-mass hyaluronan by an oxidative system comprising ascorbate, Cu(II), and hydrogen peroxide: Inhibitory action of antiinflammatory drugs—Naproxen and acetylsalicylic acid

Changes in dynamic viscosity of the solutions of a high-molar-mass hyaluronan (HA) were monitored using a rotational viscometer. The degradative conditions generated in the HA solutions by a system comprising ascorbate plus Cu(II) plus H(2)O(2) were studied either in the presence or absence of a drug--naproxen or acetylsalicylic acid. Continual decrease of the dynamic viscosity of HA solution was indicative of the polymer degradation. Addition of the drug retarded/inhibited the HA degradation in a concentration-dependent manner. The characteristics of the fragmented polymers were investigated by FT-IR spectroscopy and by two different liquid chromatographic techniques, namely by size-exclusion chromatography equipped with a multi-angle light scattering photometric detector and by high-performance liquid chromatography connected on-line to a spectrofluorometer.

Degradation of High-Molar-Mass Hyaluronan and Characterization of Fragments

A sample of high-molar mass hyaluronan was oxidized by seven oxidative systems involving hydrogen peroxide, cupric chloride, ascorbic acid, and sodium hypochlorite in different concentrations and combinations. The process of the oxidative degradation of hyaluronan was monitored by rotational viscometry, while the fragments produced were investigated by size-exclusion chromatography, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry, and non-isothermal chemiluminometry. The results obtained imply that the degradation of hyaluronan by these oxidative systems, some of which resemble the chemical combinations present in vivo in the inflamed joint, proceeds predominantly via hydroxyl radicals. The hyaluronan fragmentation occurred randomly and produced species with rather narrow and unimodal distribution of molar mass. Oxidative degradation not only reduces the molecular size of hyaluronan but also modifies its component monosaccharides, generating polymer fragments that may have properties substantially different from those of the original macromolecule.

The many ways to cleave hyaluronan

Hyaluronan is being used increasingly as a component of artificial matrices and in bioengineering for tissue scaffolding. The length of hyaluronan polymer chains is now recognized as informational, involving a wide variety of size-specific functions. Inadvertent scission of hyaluronan can occur during the process of preparation. On the other hand, certain size-specific hyaluronan fragments may be desirable, endowing the finished bioengineered product with specific properties. In this review, the vast arrays of reactions that cause scission of hyaluronan polymers is presented, including those on an enzymatic, free radical, and chemical basis.

Solution properties of high-molar-mass hyaluronans: the biopolymer degradation by ascorbate

An accurate molecular characterization, molar mass and size distributions, of 10 hyaluronan (HA) samples was performed by using a multi-angle light scattering detector connected on-line to a size exclusion chromatographic system. The dynamic viscosity eta of the HA solutions was investigated using a rotational viscometer. On monitoring the sample dynamic viscosity for up to 5h, a small however constant increase of the eta value was observed, indicating rheopectic behavior of all 10 HA solutions. Addition of ascorbic acid to the HA solutions caused significant changes in the rheological properties of the samples investigated. The change of eta values in the course of time was explained by the redox reactions (caused by the added ascorbate) that occur during the dynamic viscosity monitoring.

Associating hyaluronan derivatives: a novel horizon in viscosupplementation of osteoarthritic joints

The association of two high-molecular-weight hyaluronan (HA) derivatives, namely a beta-cyclodextrin (HA-beta-CD) and an N-acylurea (EDC-HA), dissolved in aqueous NaCl, was studied. The weight-average of the molecular weights (Mw) of HA-beta-CD and of EDC-HA was 185.3 and 86.8 kDa, respectively. However, the Mw value determined for the equimolar mixture of the two biopolymers equaled 556.0 kDa. Similarly, the radius of gyration (dimension) Rg = 80.6 nm of the above equimolar mixture was significantly greater than the values found for the single macromolecules, 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, borne by the HA polymeric chains, form host-guest inclusion complexes resulting in polymacromolecular associates/aggregates.

Controlling the Association of Adamantyl-Substituted Poly{N-[tris(hydroxymethyl)methyl]acrylamide} and aβ-Cyclodextrin/Epichlorohydrin Polymer by a Small Drug Molecule – Naproxen

Two polymeric substances, a poly{N-[tris(hydroxymethyl)methyl]acrylamide} (THMMA) substituted with adamantyl moieties and a beta-cyclodextrin/epichlorohydrin polycondensate, formed a host-guest type complex, which resulted in the gel formation upon mixing of these two compounds at appropriate conditions. Introduction of a drug molecule, i.e., naproxen, that was able to fill the beta-cyclodextrin cavities, thus expulsing adamantyl moieties, led to disruption of such association and inhibition of gel formation. The conditions required for the association of the two polymeric components and formation of the gel, as well as the dynamics of its inhibition by addition of naproxen was established. The procedure of using solutions of two associating polymers and an appropriate drug competitor can be used at targeted viscosupplementation.

Hyaluronan degradation by copper(II) chloride and ascorbate: rotational viscometric, EPR spin-trapping, and MALDI–TOF mass spectrometric investigations

The degradation of high-molar-mass hyaluronan (HA) by copper(II) chloride and ascorbate was studied by means of rotational viscometry. It was found that even small amounts of CuCl(2) present in the oxidative system led to the pronounced degradation of HA, reflected in a rapid decrease of the dynamic viscosity of the biopolymer solution. Such degradation was induced by free radicals generated in elevated amounts in the presence of copper ions. Electron paramagnetic resonance investigations performed on a model oxidative system containing Cu(II) and ascorbic acid proved the formation of relatively stable ascorbate anion radicals resulting from the reaction of ascorbic acid with hydroxyl radicals. In this way, by scavenging the hydroxyl radicals, ascorbic acid protected HA from their degradative action. Matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry was applied to analyze the degraded HA. The results showed that only regular fragmentation of hyaluronan occurred using the mentioned oxidative system that led to the formation of HA oligomers with unaffected primary chemical structure.

The degradative action of peroxynitrite on high-molecular-weight hyaluronan

OBJECTIVES

This contribution presents the results of the kinetics of HA degradation by peroxynitrite, which represents one of the main reactive oxygen species degrading various biomacromolecules under inflammatory conditions.

METHODS

Two simple procedures have been adapted to prepare sodium peroxynitrite: the first containing an excess of H(2)O(2), and the second in which the H(2)O(2) excess had been decomposed by MnO(2) treatment. The kinetics of hyaluronan degradation by action of peroxynitrite was monitored by rotational viscometry.

RESULTS

High-molecular-weight hyaluronan was degraded by peroxynitrite. The degradation was increased in the presence of ONOO(-) previously treated by MnO(2) in order to remove residual hydrogen peroxide. One of the reasons of this finding could be that by the action of the residual metal the pathway of ONOO(-) decomposition starts to be manifested immediately on mixing traces of metals originally present in the HA sample with the ions of manganese.

CONCLUSIONS

Trace amounts of transition metal(s) should be taken into consideration on evaluating the experimental results. Purchase of the marketed peroxynitrite product appears to be the appropriate approach to simplify and standardize the quality of ONOONa.

Hyaluronic acid: a natural biopolymer with a broad range of biomedical and industrial applications

Hyaluronic acid (hyaluronan, HA) is a linear polysaccharide formed from disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. It has a high molecular mass, usually in the order of millions of Daltons, and interesting viscoelastic properties influenced by its polymeric and polyelectrolyte characteristics. HA is present in almost all biological fluids and tissues. In clinical medicine, it is used as a diagnostic marker for many diseases including cancer, rheumatoid arthritis and liver pathologies, as well as for supplementation of impaired synovial fluid in arthritic patients by means of intra-articular injections. It is also used in certain ophthalmological and otological surgeries and cosmetic regeneration and reconstruction of soft tissue. Herein we present an overview of the occurrence and physiological properties of HA, as well as of the recent advances in production biotechnology and preparation of the HA-based materials for medical application.

Degradative action of reactive oxygen species on hyaluronan

Many human diseases are associated with harmful action of reactive oxygen species (ROS). These species are involved in the degradation of essential tissue or related components. One of such components is synovial fluid that contains a high-molecular-weight polymer--hyaluronan (HA). Uninhibited and/or inhibited hyaluronan degradation by the action of various ROS has been studied in many in vitro models. In these studies, the change of the molecular weight of HA or a related parameter, such as HA solution viscosity, has been used as a marker of inflicted damage. The aim of the presented review is to briefly summarize the available data. Their correct interpretation could contribute to the implementation of modern methods of evaluation of the antioxidative capacity of natural and synthetic substances and prospective drugs--potential inflammatory disease modifying agents. Another focus of this review is to evaluate briefly the impact of different available analytical techniques currently used to investigate the structure of native high-molecular-weight hyaluronan and/or of its fragments.

Degradation of high-molecular-weight hyaluronan by hydrogen peroxide in the presence of cupric ions

Dynamic viscosity (eta) of the high-molecular-weight hyaluronan (HA) solution was measured by a Brookfield rotational viscometer equipped with a Teflon cup and spindle of coaxial cylindrical geometry. The decrease of eta of the HA solution, indicating degradation of the biopolymer, was induced by a system containing H2O2 alone or H2O2 plus CuCl2. The reaction system H2O2 plus CuCl2 as investigated by EPR spin-trapping technique revealed the formation of a four-line EPR signal characteristic of a *DMPO-OH spin adduct. Thus, hydroxyl radicals are implicated in degradation of high-molecular-weight HA by the system containing H2O2 and CuCl2.

Contribution of Oxidative-Reductive Reactions to High-Molecular-Weight Hyaluronan Catabolism

Since the content of hyaluronan (HA)-degrading enzymes in synovial fluid (SF), if any, is extremely low, the high rate of HA turnover in SF is to result from a cause different from enzymatic catabolism. An alternative and plausible mechanism is that of oxidative-reductive degradation of HA chains by a combined action of oxygen and transition metal cations maintained in a reduced oxidation state by ascorbate.

Electrophoretic analysis of oxidatively modified eye lens proteins in vitro: implications for diabetic cataract

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of eye lens proteins showed that both progression of diabetic cataract in rats in vivo and precipitation of soluble eye lens proteins stressed by free radicals in vitro were accompanied by significant protein cross-linking. There was a noticeable contribution of disulfide bridges to protein cross-linking in diabetic eye lens in vivo. In contrast, under conditions in vitro, when eye lens proteins were exposed to hydroxyl or peroxyl radicals, we showed that the participation of reducible disulfide linkages in the formation of high molecular mass products was markedly lower. These in vivo--in vitro differences indicate that the generally accepted role of reactive oxygen species in diabetic cataractogenesis may be overestimated in connection with the processes of protein cross-linking.

The Hummel-Dreyer method: impact in pharmacology

Reviews devoted to drug-protein binding present mostly a variety of analytical methods applied to studying the unique process when the protein reversibly binds a low-molecular-weight substance-the drug. This report, however, reviews the great majority of papers presenting the application of one particular method introduced by Hummel and Dreyer in 1962: Measurement of protein-binding phenomena by gel filtration. The main criterion in reviewing published papers was the application of the Hummel-Dreyer method when the counterpart substances were the drug and the human plasma protein.

Effect of melatonin on neurobehavioral dysfunctions induced by intrauterine hypoxia in rats

Intrauterine hypoxia associated with oxidative stress represents an important risk factor for development of neurobehavioral dysfunctions. In the present study, we investigated the potential protective effect of melatonin (MEL) on neurobehavioral dysfunctions induced by chronic intrauterine hypoxia in rats by the anticonvulsant drug phenytoin (PHT), which is known by its teratogenic potential. Pregnant female rats (Wistar/DV) were orally treated by PHT (150 mg/kg) from day 7 to 18 of gestation. MEL was dissolved in drinking water (40 microg/ml) and administered from day 0 to 19 of gestation. Neurobehavioral development of offspring was evaluated from birth up to day 90 of postnatal life. The results of the study confirmed the high behavior-teratogenic potential of PHT. Prenatal administration of PHT resulted in delayed neuromotor and reflex development, decreased exploration in the open field, abnormal "circling" and impaired performaces in water maze. Co-administration of MEL failed to have any effect on neurobehavioral dysfunctions induced by PHT treatment. Even administration of MEL alone caused developmental alterations in offspring manifested by accelerated testes descent and delayed onset of negative geotaxia and startle reflex. The results suggest to pay increased attention to MEL concerning its exogenous use during pregnancy.

Effect of melatonin and stobadine on maternal and embryofoetal toxicity in rats due to intrauterine hypoxia induced by phenytoin administration

The aim of the present study was to test the hypothesis that the natural antioxidant melatonin (MEL) and the synthetic antioxidant stobadine (STO) could reduce the incidence of maternal and embryofoetal toxicity in rats due to intrauterine hypoxia. Chronic hypoxia was induced pharmacologically by the administration of the anticonvulsant phenytoin (PHT) during the entire period of pregnancy. PHT disturbed the normal course of pregnancy, affected reproductive parameters and increased the incidence of skeletal anomalies. MEL did not protect the PHT-induced development toxicity in rat. On the other hand, STO partially prevented PHT-induced reduction of foetal and placental weights. Administration of STO also decreased the frequency of pre- and post-implantation loss and resorptions in the PHT group. We concluded that pretreatment of pregnant rats with STO prevented to a certain extent reproductive and foetal development alterations caused by chronic intrauterine hypoxia.

Evaluation of Radius of Gyration and Intrinsic Viscosity Molar Mass Dependence and Stiffness of Hyaluronan

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (Rg), and intrinsic viscosity ([eta]) were measured in 0.15 M NaCl at 37 degrees C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the Rg and [eta] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 x 10(4) to 5.5 x 10(6) g/mol. The Rg and the [eta] molar mass dependence found for HA showed a meaningful difference. The Rg = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [eta] = f(M) power law (Mark-Houwink-Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from Rg vs M data) and the Bohdanecky's plot (6.8 nm from [eta] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.

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.