RNA regulation and cancer development

Cancer is viewed as a genetic disease. According to the currently accepted model of carcinogenesis, several consequential mutations in oncogenes or tumor suppressor genes are necessary for cancer development. In this model, mutated DNA sequence is transcribed to mRNA that is finally translated into functionally aberrant protein. mRNA is viewed solely as an intermediate between DNA (with 'coding' potential) and protein (with 'executive' function). However, recent findings suggest that (m)RNA is actively regulated by a variety of processes including nonsense-mediated decay, alternative splicing, RNA editing or RNA interference. Moreover, RNA molecules can regulate a variety of cellular functions through interactions with RNA, DNA as well as protein molecules. Although, the precise contribution of RNA molecules by themselves and RNA-regulated processes on cancer development is currently unknown, recent data suggest their important role in carcinogenesis. Here, we summarize recent knowledge on RNA-related processes and discuss their potential role in cancer development.

Structures and pathways of the central nervous system are potentially involved in the serotonergic modulation of gastrointestinal activity

The supposed involvement of rat brain regions in the modulation of rat small intestine serotonergic activity was investigated. Small electrolytic lesions were placed in the areas of medulla oblongata and pons Varoli; one week later, changes in the serotonergic response of the intestine were detected. The contractions mediated by the activation of 5-HT2 receptors in the proximal ileum were investigated. The whole ileum segments were cut and placed into the bath. The preparations were contracted by adding increasing concentrations of 5-hydroxytryptamine (5-HT) (10 nM-1 microM) and noncumulative concentration-response curves (CRCs) were established. The differences between 5-HT responses of preparations from either sham-operated or experimental rats suggest the existence of brainstem regions (dorsal vagal and solitary nuclei, parvocellular reticular nuclei and serotonergic A1,2,5 groups) that either stimulate or inhibit 5-HT modulatory action in the rat gastrointestinal tract.

Muramyl dipeptide (MDP) and 5-HT receptors. Neuroimmunomodulatory effects of MDP are probably not mediated through 5-HT4 or 5-HT1A receptors

A possible interaction of immunomodulator muramyl dipeptide (MDP) with 5-HT4 and 5-HT1A receptors was investigated. The activation of 5-HT4 receptors releases acetylcholine from nerve terminals, thereby contracting the guinea-pig distal ileum. The whole ileum segments were therefore cut and placed into the bath. The preparations were contracted by 5-HT (10 nM-3.2 microM); these contractions were totally abolished in the presence of atropine (1 microM) and significantly attenuated in the presence of SDZ-205,557 (320 nM). The 5-HT evoked contractions remained unchanged in the presence of MDP (5, 50 or 500 nM). MDP (l0 nM-3.2 microM) could not directly contract the preparations. In further experiments, the possible interaction of MDP with 5-HT1A receptors was investigated. The activation of 5-HT1A receptors inhibits the release of acetylcholine from nerve terminals, thereby decreasing the height of electrically evoked neurogenic twitches of guinea-pig ileum. The whole ileum segments were cut, placed into the bath and stimulated electrically. Selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) decreased the height of twitches and this effect was significantly attenuated in the presence of 5-HT antagonist metergoline (1 microM). The effect of 8-OH-DPAT remained unchanged in the presence of MDP (5, 50 or 500 nM). MDP (10 nM-3.2 microM) did not exert any direct effect on the preparations. These results suggest that MDP interacts with neither 5-HT4 nor 5-HT1A receptors.

Determination of anthracycline antibiotics doxorubicin and daunorubicin by capillary electrophoresis with UV absorption detection

Sweeping preconcentration and electrokinetic injection was used for the capillary electrophoretic analysis of trace amounts of biologically active anthracyclines with UV absorption detection. Phosphate buffer (100 mM), pH 2.5, with addition of 40% v/v methanol was used as background electrolyte (BGE). Sodium dodecyl sulfate (150 mM) was added to BGE in the inlet vial as the sweeping agent. The system enables effective separation of anthracyclines as well as cleanup from matrix impurities. Sweeping preconcentration of sample provides an excellent detection limit (1 x 10(-9) mol L(-1)). The method was applied for the determination of therapeutic levels of doxorubicin in real plasma samples.

Fast analysis of antibacterial isothiazolones by capillary electrophoresis

Some technical aspects influencing the total time of CE analysis are discussed. A high throughput electrophoretic system based on micellar electrokinetic chromatography (MEKC) is demonstrated as an example. A short capillary, strong electric field, alkaline buffer (pH 9.5) generating strong electroosmotic flow, and parallel hydrodynamic pressure allow the separation of two uncharged isothiazolone derivatives within 45 s.

Capillary electrophoresis of methylderivatives of quinolines. I

Migration behavior of quinoline, isoquinoline and related methylderivatives has been investigated with respect to the influence of running buffer acidity and to the presence of polyethylene glycol (PEG) 2000 as additive. Dissociation constants and ionic mobilities were determined by capillary electrophoresis (CE). Mobility and viscosity measurements in PEG containing buffers show that analyte transport is not in accordance with Walden's rule and microviscosity plays the role in analyte retardation. Variation of pH and PEG concentration provides the optimal conditions for the CE separation of methylquinolines (0.0176 M acetate-Tris buffer, pH 5.5, 10% PEG 2000). Analysis of industrial mixture (isoquinoline fraction from distillation of coal tar) was performed and good agreement with gas chromatographic results was found.

Purification, crystallization and preliminary X-ray analysis of two crystal forms of ribonuclease Sa3

RNase Sa3 produced by Streptomyces aureofaciens strain CCM 3239 belongs to the T1 family of microbial ribonucleases. It is closely related both to RNase Sa, studied in detail earlier, and to RNase Sa2 produced by the same microorganism. The most important property of RNase Sa3 is the relatively high cytotoxic activity, which was not observed for RNase Sa and Sa2. Recombinant RNase Sa3 was overexpressed in Escherichia coli and purified to high homogeneity. The hanging-drop vapour-diffusion method was used for crystallization. The two crystal forms are trigonal P3(1)21 and tetragonal P4(1)2(1)2, with unit-cell parameters a = b = 64.7, c = 69.6 A, gamma = 120 degrees and a = b = 34.0, c = 147.2 A, respectively. They diffract to 2.0 and to 1.7 A resolution, respectively, using synchrotron radiation. The asymmetric units of crystal forms I and II contain one molecule of the enzyme, which corresponds to V(M) = 3.8 A(3) Da(-1) with a solvent content of 68% and V(M) = 1.9 A(3) Da(-1) with a solvent content of 37%, respectively.

MDP and 5-HT receptors. Does MDP interact with 5-HT(7) receptors?

A possible interaction of immunomodulator muramyl dipeptide (MDP) with 5-HT(7) (5-hydroxytryptamine) receptors was investigated. The activation of 5-HT(7) receptors relaxes the guinea-pig distal ileum. The whole ileum segments were, therefore, cut and placed into the bath. The preparations were precontracted by substance P and potently relaxed by adding incremental concentrations of 5-carboxamidotryptamine (5-CT) (0.01-3.2 microM), less potently by 5-hydroxytryptamine (5-HT) (1-100 microM). The preparations most sensitive to 5-CT were also relaxed by MDP (1-100 microM). Noncumulative concentration-response curves (CRCs) for 5-HT or 5-CT were established in the absence or presence of 5-HT antagonist metergoline (320 nM). Metergoline inhibited the relaxations and shifted the CRCs to the right. In the preparations most sensitive to the effects of both 5-CT and metergoline, the latter substance also inhibited the effect of the highest concentration (100 microM) in CRCs for MDP. In another type of experiments, CRCs for 5-HT or 5-CT were constructed in the presence of low concentrations of MDP (5-500 nM). The relaxations evoked by either drug remained unchanged. These results suggest that low concentrations of MDP do not interact with activation of 5-HT(7) receptors. In higher concentrations MDP acts on this receptor type as a very weak partial agonist.

Potential role of cannabinoids in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder caused by a progressive loss of dopaminergic neurons of the substantia nigra, resulting from an oxidative stress. The lack of dopaminergic neurons is reflected by a disturbed balance of the neural circuitry in the basal ganglia. Cannabinoids might alleviate some parkinsonian symptoms by their remarkable receptor-mediated modulatory action in the basal ganglia output nuclei. Moreover, it was recently observed that some cannabinoids are potent antioxidants that can protect neurons from death even without cannabinoid receptor activation. It seems that cannabinoids could delay or even stop progressive degeneration of brain dopaminergic systems, a process for which there is presently no prevention. In combination with currently used drugs, cannabinoids might represent, qualitatively, a new approach to the treatment of PD, making it more effective.

Past, present and future of psychoneuroimmunology

Psychoneuroimmunology was for the first time comprehensively described about 20 years ago. The influence of mental status on the course and outcome of a number of diseases, however, was suspected a long time before. Also the links between mental affective disorders and the immune status were repeatedly suggested. The authors in this paper shortly reviewed the most important clinical as well as experimental evidence which at present strongly supports the concept of a close and bidirectional communication between central nervous, neuroendocrine and immune systems. The most important anatomical, physiological as well as pharmacological experimental data, which were obtained by the authors during 20 years of research in this field, are presented. The data strongly suggest that in the very next future we will not only better understand a very complex communication between mind and body, but also completely new types of compounds might become available.

Capillary electrophoretic determination of sanguinarine and chelerythrine in plant extracts and pharmaceutical preparations

Capillary electrophoresis was employed to determine the principal quaternary benzo[c]phenanthridine alkaloids, sanguinarine and chelerythrine, in two plant extracts and one oral hygiene product. Phosphate-Tris buffer of pH 2.5 was used as a background electrolyte, limits of detection were 3 micromol/l(-1) (sanguinarine) and 2.4 micromol,l(-1) (chelerythrine) using UV detection at 270 nm. The method, which correlated well with HPLC, is suitable for serial determination of sanguinarine and chelerythrine in plant products and pharmaceuticals.

Capillary electrophoresis for detection of inherited disorders of purine and pyrimidine metabolism

BACKGROUND

Measurement of purine and pyrimidine metabolites presents complex problems for separations currently performed by HPLC and thin-layer chromatography in clinical practice. We developed a novel capillary electrophoresis method for this purpose.

METHODS

Separations were performed in 60 mmol/L borate-2-amino-2-methyl-1-propanol-80 mmol/L sodium dodecyl sulfate (pH 9.6) at 35 degrees C.

RESULTS

The conditions reported allowed separation of all diagnostic metabolites from major urinary constituents in an analysis time of 3 min and with a separation efficiency of 220 000 theoretical plates/m. The clinically important metabolites were detectable at concentrations of 0.85-4.28 micromol/L. The method was linear over the range 5-500 micromol/L (r >0.99). The within-run and intra- and interday imprecision (CV) was <5%. Characteristic abnormalities were detected in the electropherograms of urine samples from patients with purine and pyrimidine enzyme deficiencies. We provide the electrophoretic and spectral characteristics of many intermediates in purine and pyrimidine metabolism and describe common artifacts from medication and ultraviolet-absorbing compounds.

CONCLUSION

Capillary electrophoresis is a valuable screening tool in the detection of inborn errors of purine and pyrimidine metabolism.

The evolution of starch-binding domain

Amylolytic enzymes belonging to three distinct families of glycosidases (13, 14, 15) contain the starch-binding domain (SBD) positioned almost exclusively at the C-terminus. Detailed analysis of all available SBD sequences from 43 different amylases revealed its independent evolutionary behaviour with regard to the catalytic domains. In the evolutionary tree based on sequence alignment of the SBDs, taxonomy is respected so that fungi and actinomycetes form their own separate parts surrounded by bacteria that are also clustered according to taxonomy. The only known N-terminal SBD from Rhizopus oryzae glucoamylase is on the longest branch separated from all C-terminal SBDs. The 3-dimensional (3-D) structures of fungal glucoamylase and bacterial CGTase SBDs are compared and used to discuss the interesting SBD evolution.

[New, modern, centrally active antihypertensive agents in the treatment of essential hypertension]

It was recently found that the rise of blood pressure leads to the excitation of a vasomotor centre in the brain stem and that the accompanying decrease in brain cortex excitability results in the reduced sensitivity to various adverse stimuli. Centrally acting antihypertensives, moxonidine and rilmenidine, do not impair circulatory reflexes and therefore do not deprive the patient of a chance to resist the pressure; thus the compliance of the patient might be increased. Both drugs activate I1-imidazoline receptors on the neurons of the rostral ventrolateral medulla oblongata. The reduction of neuronal firing rate results in the decrease of sympathetic activity and arterial pressure. Beside other advantages, centrally acting antihypertensives might be more promising than peripherally acting drugs due to their possible more favourable psychopharmacological profile; this component of their action might be underestimated at present.

Determination of adenosine deaminase activity in human erythrocytes by on-column capillary isotachophoresis-capillary zone electrophoresis in the presence of electroosmotic flow

Transient capillary isotachophoresis (CITP)-capillary zone electrophoresis (CZE) in presence of electroosmotic flow (EOF) was utilized for the measurement of adenosine deaminase activity in human erythrocytes. Phosphates, dominant anions of the sample matrix, were used as leading ions for transient isotachophoresis, and borates (0.3 M, pH 10) were used as terminating ions and background electrolyte for CZE. Final experimental conditions made it possible to inject 70% of the total capillary volume (1.45 microL) with the sample. Enzymatic conversion products (inosine and hypoxanthine), present in the sample in the low-micromolar range, were determined using optimized conditions. The limit of detection was 28 nM using UV detection at 202 nm. The presented data shows that CITP-CZE can be performed in uncoated capillaries in the presence of strong EOF.

The interaction of immunomodulatory muramyl dipeptide with peripheral 5-HT receptors: overview of the current state

Immunomodulator muramyl dipeptide (MDP) exerts also pronounced neuropharmacological activities which are probably mediated by an interaction with 5-HT receptors. Some of these effects are considered as undesirable by its clinical use. More precise information concerning MDP effects on 5-HT receptors with respect to their many subtypes could result from studies using isolated organs in vitro. Earlier conducted studies of this type provided data that are concisely overviewed and reinterpreted here from the view of current 5-HT receptor classification. Since new 5-HT receptor types have emerged recently, new studies are under way. The results might contribute to the development of novel immunomodulatory drugs devoid of adverse effects.

Recognition of RNase Sa by the inhibitor barstar: structure of the complex at 1.7 A resolution

We report the 1.7 A resolution structure of RNase Sa complexed with the polypeptide inhibitor barstar. The crystals are in the hexagonal space group P65 with unit-cell dimensions a = b = 56.9, c = 135.8 A and the asymmetric unit contains one molecule of the complex. RNase Sa is an extracellular microbial ribonuclease produced by Streptomyces aureofaciens. Barstar is the natural inhibitor of barnase, the ribonuclease of Bacillus amyloliquefaciens. It inhibits RNase Sa and barnase in a similar manner by steric blocking of the active site. The structure of RNase Sa is very similar to that observed in crystals of the native enzyme and its complexes with nucleotides. Barstar retains the structure found in its complex with barnase. The accessible surface area of protein buried in the complex is about 300 A2 smaller and there are fewer hydrogen bonds in the enzyme-inhibitor interface in RNase Sa-barstar than in barnase-barstar, providing an explanation of the reduced binding affinity in the former. Previous studies of barstar complexes have used mutants of the inhibitor and this is the first structure which includes wild-type barstar.

Structure of glucoamylase from Saccharomycopsis fibuligera at 1.7 A resolution

The yeast Saccharomycopsis fibuligera produces a glucoamylase which belongs to sequence family 15 of glycosyl hydrolases. The structure of the non-glycosyl-ated recombinant enzyme has been determined by molecular replacement and refined against 1.7 A resolution synchrotron data to an R factor of 14.6%. This is the first report of the three-dimensional structure of a yeast family 15 glucoamylase. The refinement from the initial molecular-replacement model was not straightforward. It involved the use of an unrestrained automated refinement procedure (uARP) in combination with the maximum-likelihood refinement program REFMAC. The enzyme consists of 492 amino-acid residues and has 14 alpha-helices, 12 of which form an (alpha/alpha)6 barrel. It contains a single catalytic domain but no starch-binding domain. The fold of the molecule and the active site are compared to the known structure of the catalytic domain of a fungal family 15 glucoamylase and are shown to be closely similar. The active- and specificity-site residues are especially highly conserved. The model of the acarbose inhibitor from the analysis of the fungal enzyme fits tightly into the present structure. The active-site topology is a pocket and hydrolysis proceeds with inversion of the configuration at the anomeric carbon. The enzyme acts as an exo-glycosyl hydrolase. There is a Tris [2-amino-2-(hydroxymethyl)-1,3-propanediol] molecule acting as an inhibitor in the active-site pocket.

Methamphetamine--properties and analytical methods of enantiomer determination

Methamphetamine is one of the most frequently abused drugs of today. Due to its stereogenic center, it can exist as single enantiomer. Like many other chiral compounds, methamamphetamine enantiomers exhibit different pharmacological effects on living organisms. For this reason, it is necessary to develop enantioselective and sufficiently sensitive methods of determination. This review focuses on methamphetamine with an accent on analytical chemistry and especially on chiral separations of this toxicologically important compound.

Is nitric oxide involved in 5-HT3 receptor-mediated neurogenic relaxation of guinea pig proximal colon?

The relaxations mediated by the activation of 5-HT receptors in the guinea pig proximal colon were investigated. Longitudinal strips were cut from the colon segment and placed into the bath. In the presence of atropine (0.2 microM), the relaxations were evoked by adding increasing concentrations of 5-HT (1-100 microM). Noncumulative concentration-response curves were established in the absence and presence of either 5-HT or nitric oxide synthase (NOS) antagonists. Selective 5-HT3 antagonists tropisetron (10 and 100 nM) and ondansetron (1 microM) inhibited the relaxations and shifted the concentration-response curves to the right. Similar effects were observed in the presence of the NOS inhibitor N(G)-nitro-L-arginine (3.2, 10, 32 microM) and partly reversed with L-arginine (100, 320 microM). N(G)-nitro-D-arginine, serving as a negative control, was ineffective. The relaxations were further inhibited in the presence of the soluble guanylate cyclase blocker methylene blue (10 microM) or NO scavenger hemoglobin (32 microM). These results suggest that the 5-HT3 receptor plays a role in neurogenic relaxations of guinea pig proximal colon, which are at least partly mediated via release of NO from nerve endings.

Ca(2+)-activated K+ channel and the activation of Ca2+ influx in vanadate-treated red blood cells

The mechanism by which K+ inhibits vanadate-induced 45Ca2+ influx by human red blood cells (RBC) was studied using several independent approaches. The following results were found: 1. The inhibitory effect of K+ was absent when RBC were loaded with a Ca(2+)-chelator. This treatment at the same time inhibited the vanadate-induced K+ efflux, and the membrane hyperpolarization induced by Ca2+ in vanadate-treated cells. 2. The potency of K+, Rb+, and Cs+ to inhibit vanadate-induced Ca2+ influx corresponded to their ability to depolarize the RBC membrane via the Ca(2+)-activated K+ channel (K(Ca)). 3. Inhibition of the vanadate-induced 45Ca2+ influx by a protonophore proceeded in parallel with the inhibition of the vanadate-plus-Ca(2+)-induced membrane hyperpolarization. 4. Valinomycin in part released the inhibition of the vanadate-induced Ca2+ influx by known K(Ca) inhibitors (quinine, oligomycin, 4-aminopyridine) but not by inhibitors of the Ca2+ channel (Cu2+, HS-reagents, organic Ca2+ channel blockers). 5. K+ did not inhibit the vanadate-induced Ca2+ influx in dog RBC which have K(Ca) but no transmembrane K+ gradient. The inhibition of the vanadate-induced Ca2+ influx by external K+ appears to be due to the elimination of the electrical component of the Ca(2+)-motive force imposed by opening of the K(Ca). This implies that the Ca2+ carrier mediating the influx of Ca2+ in the presence of vanadate is of uniport type, and that the activity of K(Ca) may serve as a supporting element for Ca2+ influx.

Vanadate changes Ca2+ influx pathway properties in human red blood cells

The properties of the basal Ca2+ influx (measured using cells labelled with 45Ca2+) in intact human red blood cells (RBC) were compared with those of 45Ca2+ influx induced by vanadate. The basal Ca2+ influx was not sensitive to inhibitors of vanadate-induced Ca2+ influx such as the HS-reagent p-chloromercuribenzoate and low concentrations of Cu2+, and also the sensitivity to nifedipine was significantly weaker. High K+ known to suppress vanadate-induced 45Ca2+ influx had no effect on the basal Ca2+ influx. Both processes were saturated with Ca2+ but the latter was saturated at higher Ca2+ concentrations (KM(Ca) 2.1 vs. 0.5 mmol/l). These experiments favour the notion that vanadate changes the properties of the inward-directed Ca(2+)-transport pathway in human RBC membrane. Vanadate-induced 45Ca2+ influx was insensitive to pertussis toxin and cholera toxin, and several non-steroidal antiinflammatory agents did not influence it in a consistent manner. Li+ partly inhibited the 45Ca2+ uptake. Vanadate stimulated the incorporation of 32P(in) into PIP2 in human but not in pig RBC which are known to be defective in the phosphoinositide metabolism and in the vanadate-induced 45Ca2+ uptake. These results suggest that the change in the Ca2+ influx pathway properties induced by vanadate may involve changes in the metabolism of phosphoinositides but not of the arachidonate metabolism nor G-protein activation.

Crystallization and preliminary X-ray analysis of the Saccharomycopsis fibuligera glucoamylase expressed from the GLU1 gene in Escherichia coli

The active non-glycosylated glucoamylase, overexpressed from the Saccharomycopsis fibuligera GLU1 gene in Escherichia coli BL21(DE3), has been purified from the solubilized inclusion bodies and then renatured in vitro. Crystals of the recombinant glucoamylase were obtained by vapour diffusion using PEG as precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell dimensions of a = 58.1, b = 87.8 and c = 99.9 A, and diffract to 1.7 A resolution. This is the first report of the crystallization of the full-length glucoamylase corresponding to the mature enzyme.

Determination of purine nucleoside phosphorylase activity in human erythrocytes by capillary electrophoresis

Purine nucleoside phosphorylase (EC 2.4.2.1) activity in human erythrocytes was measured using capillary electrophoresis. Enzyme samples were directly loaded into the capillary without preconcentration or purification. The electrophoretic separations were carried out in an uncoated fused-silica capillary (75 microm internal diameter, effective length of 45 cm, total 72 cm) at an electric field of 415 V/cm at ambient temperature (25 degrees C). UV detection at 200 nm was used. Borate buffer (100 mmol/l, pH 9.5) was used as background electrolyte. The results obtained by CE compared favourably (r=0.989) with those of standard HPLC methods. The method presented is reliable, slightly faster and less expensive than the routinely performed HPLC method.

[Serotonin and treatment of mental disorders. Present status and future perspectives]

Serotoninergic system is involved in the regulation of diverse biological and psychological functions and a variety of serotonin receptor subtypes represent a possible target for a new generation of medications. 5-HT receptors play an important role in both schizophrenia and depression. Modern strategies for treating schizophrenia profit from the existence of interaction between serotonin and dopamine systems. New drugs called serotonin-dopamine antagonists (SDAs) offer wider spectra of activity and lower extrapyramidal side effects liability. The principle of the SDAs is that the drug should be a potent serotonin 5-HT 2A antagonist, with slightly less potent dopamine D2 receptor-blocking properties. New pharmacological agents with great therapeutic potential and fewer side effects were recently developed also for the treatment of depression. Among these new antidepressives the serotonin selective reuptake inhibitors (SSRIs) currently play the most important role.

A rapid and simple screening method for detection of orotic aciduria by capillary zone electrophoresis

A rapid and selective capillary zone electrophoretic method for screening of patients with orotic aciduria is described. The method is based on direct measurement of orotic acid in untreated urine. Total analysis time is 5 min with the limit of quantification of 10 mumol/l. Selectivity of the method is given by the use of a low pH of background electrolyte at which practically no interferences from native urine appeared, as well as by using a fast scanning detector which enables the identification of orotic acid via its characteristic UV spectra. This method can be used for quantitative assessment of orotic acid present in urine at physiological conditions after an ion exchange chromatography-clean up and preconcentration procedure. Urine samples containing orotic acid at pathological concentrations (typically more than 1 mol/mol creatinine) could be successfully analysed. The method described was applied to urine specimens collected from both healthy volunteers and patients with orotic acidurias of various origin.

Which type of 5-hydroxytryptamine receptor mediates relaxation of the longitudinal muscle of guinea pig proximal colon in vitro?

Concentration-dependent 5-hydroxytryptamine (5-HT) relaxations of guinea pig proximal colon were evoked in the presence of atropine (0.2 microM). 5-HT effect was neuronally mediated since it was blocked by tetrodotoxin (TTX) (0.5 microM). The type of 5-HT receptor mediating the relaxations was investigated using both 5-HT agonists and antagonists. Selective 5-HT3 antagonists tropisetron (10, 50, 500 nM) and ondansetron (1 microM) shifted the concentration-response curves for 5-HT to the right. Another 5-HT3 antagonist MDL 72222 (0.5 microM), 5-HT1/5-HT2 antagonists methiothepin (0.1 microM) and metergoline (0.1 microM), 5-HT(1A,B) antagonist propranolol (l microM) and 5-HT1B antagonist isamoltane (10 nM) were ineffective. Specific agonist of 5-HT3 receptors 2-methyl-5-hydroxytryptamine (2-methyl-5-HT) and agonist of 5-HT1 receptors 5-carboxamidotryptamine (5-CT) also relaxed the preparation, although the relaxation was not 5-HT relaxation. Neither was it neurogenic because it persisted in the presence of TTX (0.5 microM). The concentration-response curve for 2-methyl-5-HT was not affected by ondansetron (1 microM) or tropisetron (0.5 microM), but it was shifted to the right in the presence of 5-HT1/5-HT2 receptor antagonists methiothepin (0.1 microM) and metergoline (0.1 microM) and in the presence of 5-HT(1Da)/5-HT2A receptor antagonist ketanserin (1 microM). Methiothepin (0.1 microM) also inhibited the relaxations evoked in the presence of 5-CT. Specific agonist of 5-HT4 receptors 5-methoxytryptamine did not exert any effect on the preparation. It is suggested that there are two different mechanisms of relaxation in the guinea pig proximal colon. One is neurogenic and involves the activation of 5-HT3 receptors located on inhibitory neurons to the muscle; the other is myogenic and might be mediated via yet unclassified 5-HT receptors located on the muscle.

Capillary electrophoretic enantioseparation of selegiline, methamphetamine and ephedrine using a neutral beta-cyclodextrin epichlorhydrin polymer

This paper describes the development of a capillary zone electrophoretic method for chiral separation of three basic compounds of the selegiline synthetic pathway: ephedrine, methamphetamine and selegiline. The method developed allows one to separate the studied compounds in one run using a neutral beta-cyclodextrin epichlorhydrin polymer. The effect of various experimental parameters, such as chiral selector concentration, concentration and composition of background electrolyte, pH, temperature, and the addition of some organic solvents, on the resolution and migration time is discussed. For selegiline and methamphetamine, it is possible, under optimal conditions, to quantify less than 0.5% of the minor isomer in an excess of the major one.

Quantitative structure-chromatographic retention relationship study of six underivatized equine estrogens

Underivatized estrone (ES), equilin (EQ), equilenin (EQN) and their corresponding 17 alpha-diols 17 alpha-estradiol (ESD), 17 alpha-dihydroequilin (DHEQ) and 17 alpha-dihydroequilenin (DHEQN) were separated by TLC, RP-HPLC and capillary GC. Their dipole moments (mu) and Randić's connectivity indices ((1)chi) were determined as parameters of importance for the separation. The number of H atoms was taken as an additive structural parameter of importance for the quantitative structure-chromatographic retention relationship study (QSRR). Principal component analysis (PCA) was applied in order to find similarities and dissimilarities between 9 TLC and 10 RP-HPLC systems. PCA indicated that proton donor-proton acceptor interactions play the most important role for the TLC and RP-HPLC separation. The two-dimensional non-linear map of PC variables showed that the keto-estrogens (ES, EQ and EQN) and the corresponding diols (ESD, DHEQ and DHEQN) form two separate clusters. The relationship between GC retention of equine estrogens characterized by Kováts indices (KI), their (1)chi and mu was expressed by the equation KI/100 = al(1)chi+ b/mu(2) + c. The biological activity of the estrogens was related to log 1/mu(2).

A fast and simple screening method for detection of 2,8-dihydroxyadenine urolithiasis by capillary zone electrophoresis

2,8-Dihydroxyadenine urolithiasis is an inherited disorder caused by adenine phosphoribosyltransferase deficiency. A fast, simple, sensitive and selective capillary zone electrophoretic method for diagnosis of 2,8-dihydroxyadenine urolithiasis in adenine phosphoribosyltransferase deficiency is described. The method is based on direct measurement of 2,8-dihydroxyadenine in untreated urine in phosphate buffer at pH 3.0 within 8 min. Under the given separation conditions 2,8-dihydroxyadenine is very well separated from other purine and pyrimidine substances and presents characteristic UV spectra which enable identification in case of doubt. The urine samples containing pathological 2,8-dihydroxyadenine could be successfully analysed in levels approaching those relevant for bioanalytical applications. The reliability of the method presented for screening of patients with adenine phosphoribosyltransferase deficiency is demonstrated on a urine sample of a patient with the defect who was already treated with allopurinol at the time of obtaining the sample. No interfering substances were found in 50 urine samples from healthy infants under the analytical condition described.

Further evidence on the interaction of muramyl dipeptide with the serotonergic system

The mode of interaction between muramyl dipeptide (MDP), a compound with immunopharmacological activities, and 5-hydroxtryptamine (5-HT, serotonin) was studied in isolated nerve-smooth muscle preparations of the carp stomach. Application of exogenous 5-HT evoked direct smooth muscle contractions; electric neurogenic stimulation evoked twitches due to release of 5-HT from nerve endings. Contractions evoked by a high concentration of 5-HT (3-30 microM) were resistant to atropine and potentiated in the presence of MDP. Isamoltan (5-HTID antagonist) decreased the amplitude of contractions, whereas ketanserin (5-HT2 antagonist) and MDL 72,222 (5-HT3 antagonist) had no effect. The addition of low concentrations (0.1-1.5 microM) of 5-HT did not contract the preparation but caused a decrease in the amplitude of neurogenic twitches, which might be due to the presynaptic inhibition of serotonin release. This effect of 5-HT was not changed by isamoltan or ketanserin, but it was largely reduced in the presence of 5-HT3 antagonists tropisetron and MDL 72,222. This inhibitory effect of 5-HT on twitch amplitude was potentiated by MDP. The interaction of MDP with the serotonergic system thus involved not only potentiation of the postsynaptic effect of higher 5-HT concentrations, which might have been mediated via the 5-HT1 subsystem, but also presynaptic inhibition. MDP enhancement of 5-HT's inhibitory effect, mediated via 5-HT3 receptors, might represent a new feature in mutual 5-HT-MDP interactions.

The Ca(2+)-dependent activation by fluoride of human red cell membrane sodium permeability: evidence for a chemically activated tetrodotoxin-sensitive Na+ channel

Fluoride (NaF) (5-15 mM) activated the 22Na+ uptake by human red blood cells (RBC). The effect was Ca(2+)-dependent. Sr2+, but not Ba2+, Mg2+, Mn2+, substituted Ca2+ in supporting the 22Na+ uptake. The NaF-induced 22Na+ uptake was sensitive to tetrodotoxin (TTX), pertussis toxin but not to amiloride nor valinomycin. The value of the influx was 8.6 +/- 5.0 mmol/l cells. Thus, the TTX-sensitive Na(+)-transport system is present in the RBC membrane in an inactive form which could be activated with NaF by a mechanism involving G-protein(s) but not the depolarization.

Vanadate and fluoride activate red cell Na+ permeability by different mechanism

Fluoride and vanadate are known to induce the Ca(2+)-dependent K+ efflux. We found that both agents concomitantly induced the Ca(2+)-dependent 22Na+ influx. The extent of the Ca(2+)-dependent 22Na+ influx induced by vanadate was very small in human red blood cells but clearly visible in guinea-pig red blood cells. The effect of fluoride has been studied in human red blood cells only. The 22Na+ influx induced by vanadate was inhibited by amiloride but was resistant to tetrodotoxin, whereas that induced by fluoride was resistant to amiloride but sensitive to tetrodotoxin. The effects of inhibitors indicate that vanadate activates the Na/H antiporter and that fluoride opens a tetrodotoxin-sensitive Na+ channel in red blood cells in the Ca(2+)-dependent manner. The results also indicate that both agents activate the Ca(2+)-dependent Na+ permeabilities by unknown auxiliary mechanisms.

[Total serum cholesterol in children 8-15 years of age]

The authors evaluated the difference in the health status of two groups of boys and girls aged 8-15 years, a total of 1037 children. The larger group, 790 children is from Teplice and the other group, a total of 347 children from Roudnice nad Labem. The authors discuss the total serum cholesterol level in the two groups. They provide information on mean serum cholesterol levels in children of comparable age and the significance of differences in relation to age and sex. The assembled values made it possible to calculate percentile values at the 90th and 95th percentile level for children of both areas and thus to examine and evaluate larger groups of children incl. their relatives and to detect critical total cholesterol levels calling for treatment and intervention.

An attempt to localize the site of action of different agents within cholinergic motor neurones of the myenteric plexus-longitudinal muscle preparation of the guinea pig ileum by the triple bath method

The site of action of cholinergic, adrenergic, peptidergic and opioid agents was studied in myenteric plexus-longitudinal muscle strips from the guinea pig ileum. A preparation in a special triple bath was drawn through two rubber membranes, dividing the strip into three segments. Neurogenic stimulation of the oral segment, set up nerve action potentials also in the neurones projecting axons up to the aboral segment. These axons, turning into varicose nerve terminals, conducted action potentials aborally across the middle segment, that was up to 10 mm wide. Finally, the nerve terminals, extending into the aboral segment, might be also invaded triggering twitches. Agents were added, either to the oral segment, to affect the genesis and spread of action potentials in the proximal parts of cholinergic neurones (cell bodies, axon hillocks, initial segments and axon preterminals) or they were added to the middle segment to affect propagation of action potentials in varicose nerve terminals. As a result, the amplitude of aboral twitches reflected their effects at each site, quantitatively. Noradrenaline and ethylketocyclazocine were more effective at the site of varicose nerve terminals, whereas substance P, acetylcholine and oxotremorine were more effective at the proximal parts; pilocarpine and nicotine were effective at both sites. Changes in membrane polarization might be the final common effect in the mechanism of action of all the stimulatory agents used.

Non-synaptic cholinergic modulation of neurogenic twitches of the guinea-pig ileum

The effect of cholinergic and anticholinergic compounds on conduction of neuronal excitation has been studied in myenteric plexus-longitudinal muscle strips from the guinea-pig ileum. A preparation in a special triple bath was drawn through two rubber membranes dividing the strip into three segments. Neurogenic stimulation of the oral segment set up nerve action potentials propagating aborally across the middle segment (10 mm) so that the aboral segment might be also invaded, eventually. Drugs were added to the middle segment to affect neuronal propagation (non-synaptic effects) which was monitored by twitch height of the aboral segment. The application of acetylcholine to the middle segment augmented aboral twitches. The effects of nicotine, pilocarpine and oxotremorine were selectively blocked by (+)-tubocurarine, pirenzepine and atropine, respectively. The effect of acetylcholine was suppressed by pirenzepine and atropine and mimicked by doubling of KCl concentration. The effect of acetylcholine may be thus explained by the facilitated propagation of nerve action potentials in partially depolarized cholinergic terminals via stimulation of muscarinic receptors. The adenylate cyclase system is not directly involved in the mechanism of muscarinic facilitation of neuronal propagation in the terminals; however, it may participate in the modulation of a final common effector mechanism.

Non-junctional modulation of neurogenic twitches of the guinea-pig ileum by some peptides and other compounds in the triple bath

The effects of some neuropeptide transmitter candidates and of some other neurotoxins or drugs on conduction of neural excitation were studied in myenteric plexus-longitudinal muscle strips from the guinea-pig ileum. A preparation in a special triple bath was drawn through two rubber membranes dividing the strip into three segments. Neurogenic stimulation of the oral segment set up nerve action potentials propagating aborally across the middle segment so that the aboral segment might also be invaded. Drugs were added to the middle segment to affect neuronal propagation (non-junctional effects) which was monitored by twitch amplitude of the aboral segment. The application of bradykinin and cromakalim did not affect aboral twitches although strong contractile and relaxatory effects were observed when the drugs were applied directly to the aboral segment; no neurogenic effects thus manifested. Capsaicin and neurotensin, when applied both to the middle and aboral segments, elevated the tone of the preparations accompanied with a decrease in twitch amplitude; these effects may have been due to neurogenic stimulation and release of other motor neurotransmitters. The application of VIP, apamin and dendrotoxin to the middle as well as to the aboral segments augmented aboral twitches, which might be at least partly due to facilitation of nerve action potential propagation in nerve terminals of cholinergic motor fibres.

[Nitric oxide--a new and nontraditional transmitter]

NO is obviously identical with the relaxation factor produced by the vascular endothelium (EDRF) and is also the substance responsible for some other biological activities. It is formed in the organism from L-arginine by the action of the enzyme NO synthetase. The main mechanism of action is the activation of the enzyme guanyl cyclase and the result is an increase of the intracellular level of cyclic guanyl monophosphate. Depending on the type of effector cell, either vasodilatation occurs and adhesion is inhibited and the blood platelets coagulate or the cytotoxicity of macrophages increases. With the development of new, more effective inhibitors of NO synthetase there is also the possibility to study the physiological importance of NO in more detail. These new discoveries provide a more profound biochemical and pharmacological basis and perhaps also new indications or preventive possibilities of the known treatment of vascular spasms by nitroderivatives; moreover, there is the possibility to seek new ways in the anti-tumourous and antimicrobial treatment and elsewhere.

[Foreign substances in maternal milk]

In 1984-1985 72 specimens of human milk were examined for hexachlorobenzene, DDE and polychlorinated biphenyls and 69 specimens for lead and cadmium. The residual levels (expressed in mg.kg-1 milk fat) were as follows: hexachlorobenzene 1.97 (0.24-5.58), DDE 1.56 (0.17-5.80) and polychlorinated biphenyls 3.18 (1.28-9.08). All specimens were positive. The lead levels were 1.68 (less than 0.10-6.75), cadmium levels 0.31 (less than 0.05-1.08) ng.ml-1 milk. Lead was present in 94.2%, cadmium in 98.6% specimens. The results were compared with other areas of the CSSR, data from the literature and hygienic standards. The authors discuss limited or discontinued breastfeeding in high occupational exposure. Finally they emphasize advantages associated with breastfeeding and the justification of a prolactation programme.

Amino acid sequence determination of guanyl-specific ribonuclease Sa from Streptomyces aureofaciens

Using automated Edman degradation of two nonfractionated peptide mixtures of tryptic and staphylococcal protease digests of the protein, the complete amino acid sequence of the guanyl-specific ribonuclease Sa from Streptomyces aureofaciens was established. Ribonuclease Sa contains 96 amino acid residues (Mr 10,566). A 50% sequence homology of ribonuclease Sa to the guanyl-specific ribonuclease St from S. erythreus was found.

The number and role of histidine residues in the active site of guanyloribonuclease Sa

The number and role of histidine residues in the active site of extracellular guanyloribonuclease Sa produced by Streptomyces aureofaciens (RNAase Sa) were studied via chemical modification by ethoxyformic anhydride by means of circular dichroism measurements. It was shown that only one of two histidines of RNAase Sa is situated in the active site of the enzyme. Ethoxyformylation of RNAase Sa in the presence of Guo-3'-P, Guo-5'-P and dGuo-5-P, all of them being competitive inhibitors of the enzyme, supported the assumption that an essential histidine residue is bound to the phosphate group in the position 3' of the ribose ring. The circular dichroism measurements of native and modified RNAase Sa and of its complex with Guo-3'-P showed that the modification of the essential histidine residue resulted in alteration of binding of RNAase Sa to Guo-3'-P; histidine thus may play a key role in the formation of such a complex.

In vitro and in vivo inhibitory effect of dehydroepiandrosterone on respiration

The inhibitory effect of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulphate (DHEA-S) was tested either in vitro with the use of Clark electrode combined with polarography or in vivo using the Spirolyt apparatus. In vitro, DHEA and progesterone showed a marked inhibitory effect on oxygen consumption by the rat heart liver mitochondria. A decrease of oxygen consumption was also observed with electron transporting particles (ETP). However, in both instances DHEA-S was without effect. In vivo, DHEA inhibited whole body oxygen consumption in rats, provided the steroid was injected in a dose of 50 mg kg-1 and 1--16 h before the measurement. No effect was obtained 9 h after DHEA injected in a dose of 5 mg kg-1. Also DHEA administered per os (25 mg kg-1) for six days was without effect as measured 16 h after the last dose. These data are discussed in connection with the beneficial effect of DHEA-S administered to patients with angina pectoris.