Showing papers by "Academy of Sciences of the Czech Republic published in 1990"

Electrochemistry and spectroelectrochemistry of 1,8-naphthalene- and 1,8-anthracene-linked cofacial binuclear metallophthalocyanines. New mixed-valence metallophthalocyanines

Abstract: : 1,8-Napthalene or 1,8-anthracene-linked cofacial dizinc, dicopper, and dicobalt diphthalocyanines have been studied by solution and surface electrochemistry, spectroelectrochemistry, and electron spin resonance (ESR). These derivatives are mixtures of syn and anti isomers which have very similar electrochemistry except where we comment specifically. The phthalocyanine ring first oxidation phthalocyanine, the Cobalt(III)/Cobalt(II) and Cobalt(II)/ cobalt(I) redox couples split into two couples as a consequence of intra-ring exchange interactions. The spectra of the electrochemically oxidised or reduced species, and in particular, those of the mixed valence species are recorded. Exciton coupling energies are derived and are seen to be related to the ground state mixed valence splitting energies. These are discussed in terms of structure and inter-ring distance. Cobalt derivatives immobilized onto ordinary pyrolytic graphite catalyze the electroreduction of oxygen by two electrons to hydrogen peroxide. (JG)

Ketamine suppresses both bicuculline- and picrotoxin-induced generalized tonic-clonic seizures during ontogenesis

Abstract: An anticonvulsant action of ketamine, a noncompetitive N-methyl-D-aspartate (NMDA) antagonist (5-40 mg/kg IP), on the bicuculline-induced (3-8 mg/kg IP) or picrotoxin-induced seizures (3-6 mg/kg IP) was assessed in male Wistar rats aged 7, 12, 18, 25 and 90 days. Ketamine alone caused moderate ataxia which was more pronounced in younger animals. In combination with both aforementioned convulsants, ketamine exerted anticonvulsant effects against generalized tonic-clonic seizures in all developmental stages studied. This effect was more pronounced in bicuculline-treated animals. Moreover, ketamine also suppressed the lethality induced by both drugs during all the development. On the contrary, the action of ketamine on minimal (clonic) seizures was moderate or absent. Our results suggest an important role of ketamine-affected transmission in the generation of the generalized tonic-clonic seizure pattern; moreover, an action of high doses of ketamine on GABA-A receptors might be present.

Phase structure of ternary composites consisting of polypropylene/elastomer/filler. Effect of functionalized components

Abstract: Composites consisting of polypropylene matrix/ethylene-propylene elastomer/calcium carbonate filler assume two phase structures: 1, elastomer and filler particles are dispersed separately; 2, elastomer encapsulates filler particles. Formation of these phase structures can be extensively promoted by adding functionalized polypropylene or functionalized elastomer to the composites. The former materials, with good adhesion at the matrix/filler interface, have noticeably higher stiffness and yield stress, while the latter ones are characterized by higher tensile impact strength and extensibility. The effects of maleic anhydride or acrylic acid used for functionalization on the phase structure and mechanical properties of the ternary composites are very similar at the concentration used

Kinetic theory of enzymatic reactions in reversed micellar systems. Application of the pseudophase approach for partitioning substrates.

Abstract: A kinetic theory is proposed for enzymatic reactions proceeding in reversed micellar systems in organic solvents, and involving substrates capable of partitioning among all pseudophases of the micellar system, i.e. aqueous cores of reversed micelles, micellar, membranes and organic solvent. The theory permits determination of true (i.e. with reference to the aqueous phase, where solubilized enzyme is localized) catalytic parameters of the enzyme, provided partition coefficients of the substrate between different phases are known. The validity of the kinetic theory was verified by the example of oxidation of aliphatic alcohols catalyzed by horse liver alcohol dehydrogenase in the system of reversed sodium bis(2-ethylhexyl)sulfosuccinate (AOT, aerosol OT) micelles in octane. In order to determine partition coefficients of alcohols between phases of the micellar system, flow microcalorimetry technique was used. It was shown that in the first approximation, the partition coefficient of the substrate in a simple biphasic system consisting of water and corresponding organic solvent can be used as an estimate for the partition coefficient of the substrate between aqueous and organic solvent phases of the micellar system. True values of the Michaelis constant of alcohols in the micellar system, determined using suggested approach, are equal to those obtained in aqueous solution and differ from apparent values referred to the total volume of the system. The results clearly show that the previously reported shift in the substrate specificity of HLADH, observed on changing from aqueous solution to the system of reversed aerosol OT micelles in octane, is apparent and can be explained on the basis of partitioning effects of alcoholic substrates between phases of the micellar system.

Studies On The Role Of Ubiquinone In The Control Of The Mitochondrial Respiratory Chain

Abstract: This study examines the possible role of Coenzyme Q (CoQ. ubiquinone) in the control of mitochondrial electron transfer. The CoQ concentration in mitochondria from different tissues was investigated by HPLC. By analyzing the rates of electron transfer as a function of total CoQ concentration, it was calculated that, at physiological CoQ concentration NADH cytochrome c reductase activity is not saturated. Values for theoretical Vmax could not be reached experimentally for NADH oxidation, because of the limited mis-cibility of CoQ10 with the phospholipids. On the other hand, it was found that CoQ3 could stimulate α-glycerophosphate cytochrome c reductase over three-fold. Electron transfer being a diffusion-coupled process. we have investigated the possibility of its being subjected to diffusion control. A reconstruction study of Complex I and Complex III in liposomes showed that NADH cytochrome c reductase was not affected by changing the average distance between complexes by varying the protein: lipid rati...

Evolution of Immune Reactions

Abstract: The history and evolutionary pathways of defense reactions among various forms of life are reconstructed. The vertebrates evolved step-by-step from their invertebrate ancestors living in the distant past. The ancestry of vertebrate defense mechanisms must be traceable to them because these functions cannot be considered separately from the common evolutionary schema. The first part of this survey is therefore devoted to the description of major defense reactions and achievements in invertebrates. Particular emphasis is given to the taxa of present-day invertebrates most likely to exhibit some relationship to the chordates and thus to show real traces of vertebrate immune patterns. The second part involves three key assemblages of deuterostomate animals--the echinoderms, the nonvertebrate chordates, and the first vertebrates because these animals are believed to have created the prerequisites for transition from the invertebrate type of defense to the vertebrate type of adaptive immunity.

Bicyclization of a weak oxytocin agonist produces a highly potent oxytocin antagonist

Abstract: [Mpa1,GIu4,Cys6,Lys8]oxytocin was prepared and found to be a very weak agonist in the oxytocic assay with about 1 / 1400 the potency of the native hormone. Bicyclization of this compound via a lactam bridge between the Glu4 6-carboxyl group and the c-amino group of Lys8 led to the bicyclic analogue 4,8-cyclo[Mpa~,Glu4,Cys6,Lys6]oxytocin. This bicyclic peptide acts as a very potent antagonist of oxytocin in the rat uterus assay with an in vitro PA, value of 8.2. In the in vivo oxytocic assay the pA2 value was 6.45. The peptide displays mixed agonist/antagonist character in the in vivo galactogogic assay. The implications of these results to hormone agonist and antagonist activity are discussed with respect to earlier studies on constrained oxytocin antagonists and the results from the X-ray crystal structure of deaminooxytocin. I. Oxytocin ( H-Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2)2 is the neurohypophyseal peptide hormone generally accepted as physiologically important for its milk-ejecting and uterine-contracting activities in mammals. Oxytocin has been widely studied since the early 195O’s, when the structure of oxytocin was first elucidated and proven by total synthe~is .~ Oxytocin possesses a 20-membered disulfide-containing ring and an acyclic tripeptide tail. Numerous analogues of oxytocin have been synthesized in an effort to define structure-activity relationships for the h ~ r m o n e . ~ Detailed biophysical studies of oxytocin and several agonist and antagonist analogues have been made to determine the conformational properties of these peptides in solution and their possible relationships to biological activity.s These studies have led to proposed models for oxytocin-uterine receptor interaction. In the “cooperative modelm6 it was proposed (see ref 4a for a review) that the lipophilic side chain groups of amino acids in positions 3,4 , 7, and 8 (which lie a t the corners of proposed reverse turns) are important for the binding of oxytocin to this receptor, whereas the Tyr2 and AsnS positions are considered to be critical for initiation of the biological response (transduction). The complementary “dynamic modeln7 has emphasized the importance of conformational flexibility for agonist activity and relative conformational rigidity and steric constraints for antagonism. In the latter model the topological relationships of the Cys’, Tyr2, and Asn5 side-chain moieties of the residues in the 20-membered disulfide ring and the relationship of this ring to the more flexible acyclic C-terminal tripeptide moiety are emphasized as critical to binding and transduction. Evidence supporting this latter model has come from extensive biophysical studies of the conformational and dynamic properties of [ 1 -penicillamine]oxytocin and other related conformationally constrained oxytocin antagonist (inhibitor) analogues7** and corresponding biological activity studies. Recently the crystal structure of the potent oxytocin agonist deaminooxytocin has been reported.9 Two distinct conformations were observed for this peptide in the solid state, differing in disulfide chirality and several other conformational features. This study has demonstrated that although deaminooxytocin possessed conformational features in the crystal related to those suggested from conformational studies in solution such as the cooperative model of Walter et a1.,6 even in the crystal form it retains significant conformational flexibility, lending further support to the dynamic model of hormone-receptor interaction for o ~ y t o c i n . ~ Examination of the crystal structure of deaminooxytocin and of the three-dimensional relationships possible for the distorted 20-membered disulfide ring conformation and the C-terminal acyclic tripeptide extended away from this ring but parallel to it and considerations from structure-function analysis led us to *Author to whom correspondence should be addressed at the University of Arizona. hypothesize that suitable side-chain-to-side-chain cyclization1° between the amino acids in the 4 and 8 positions of deaminooxytocin might be compatible with a strong hormone-receptor interaction. We report here that formation of the bicyclic analogue ( I ) (a) University of Arizona. (b) Current address: Department of Chemistry, Millersville University, Millersville, PA 17551. (c) Czechoslovak Academy of Sciences. A preliminary report on some aspects of this research was presented at the Tenth American Peptide Symposium, St. Louis, MO, May 23-28, 1987. Hill, P. S.; Slaninova, J.; Hruby, V. J. In Peptides: Chemistry and Biology; Marshall, G. R., Ed.; ESCOM Science Publishers B.V.: Leiden, The Netherlands, 1988; pp 468-470. (2) Symbols and abbreviations are in accord with the recommendations of the IUPAC-IUB Commission on Biochemical Nomenclature (J. Biol. Chem. 1972, 247, 977). All optically active amino acids are of the L variety unless otherwise stated. Other abbreviations include the following: Nu-Boc, Natert-butyloxycarbonyl; TLC, thin-layer chromatography; HPLC, high performance liquid chromatography; FAB-MS, fast atom bombardment mass spectrometry; TFA, trifluoroacetic acid; HOBt, N-hydroxybenzotriazole; DMF, N,N-dimethylformide; p-MBHA, p-methylbenzhydrylamine; DCM, dichloromethane; TEA, triethylamine; DPPA, diphenylphosphorylazide. (3) du Vigneaud, V.; Ressler, C.; Swan, J. M.; Katsoyannis, P. G.; Gordon, S. J. Am. Chem. Sac. 1953, 75, 4879. (4) (a) Hruby, V. J. In Biochemical Actions of Hormones; Litwack, G., Ed.; Academic Press: New York, 1986; Vol. XIII, pp 191-241. (b) Lebl, M. In Handbook of Neurohypophyseal Hormone Analogues; Jost, K., Lebl, M., Brtnik, F., Eds.; CRC Press: Boca Raton, FL, 1987; pp 75-121. (c) Hruby, V. J.; Smith, C. W. In The Peptides: Analysis, Synthesis, Biology; Smith, C. W., Ed.; Academic Press: New York, 1987; Vol. 8, pp 77-207. (5) (a) Glickson, J. D. In Peptides: Chemistry, Structure and Biology; Walter, R., Meienhofer, J., Eds.; Ann Arbor Science Publishers, Ann Arbor, MI, 1975; pp 787-802. (b) Hruby, V. J. In Chemistry and Biochemistry of Amino Acids, Peptides and Proreins; Weinstein, B., Ed.; Marcel Dekker: New York, 1974; Vol. 3, pp 1-188. (c) Hruby, V. J. In Topics in Molecular Pharmacology; Burgen, A. S . V., Roberts, G. C. K., Eds.; Elsevier/North Holland: Amsterdam, 1981; Vol. 1, pp 99-126. (d) Hruby, V. J. In Oxytocin: Clinical and Laboratory Studies; Amico, J. A., Robinson, A. G., Eds.; Elsevier/North Holland: New York, 1985; pp 405-414. (6) (a) Walter, R.; Schwartz, F. L.; Darnell, J. H.; Urry, D. W. Proc. Nod. Acad. Sci. U.S.A. 1971,68, 1355. (b) Walter, R. Fed. Proc. 1977, 36, 1972. (7) (a) Meraldi, J.-P Yamamoto, D.; Hruby, V. J.; Brewster, A. 1. R. In Peptides: Chemistry, Structure and Biology; 1975; pp 803-814. (b) Meraldi, J.-P.; Hruby, V. J.; Brewster, A. I. R. Proc. Natl. Acad. Sci. U.S.A. 1977, 74, 1373. (c) Hruby, V. J. In Perspectives in Peptide Chemistry; Eberle, A,, Geiger, R., Wieland, T., Eds.; S. Karger: Basel, Switzerland, 1981; pp (8) (a) Hruby, V. J.; Deb, K. K.; Fox, J.; Bjarnason, J.; Tu, A. T. J. Bid. Chem. 1978, 253, 6060. (b) Hruby, V. J.; Mosberg, H. I. In Neurohypophyseal Hormones and Other Biologically Active Peptides; Schlesinger, D. H., Ed.; Elsevier/North Holland: New York, 1981; pp 227-237. (c) Mosberg, H. I.; Hruby, V. J.; Meraldi, J.-P. Biochemistry 1981, 20, 2822. (d) Hruby, V. J.; Lebl, M. In Handbook of Neurohypophyseal Hormone Analogues; Jost, K., Lebl, M., Brtnik, F., Eds.; CRC Press: Boca Raton, FL, 1987; pp 105-155 for a review. (9) (a) Wood, S. P.; Tickle, I. J.; Treharne, A. M.; Pitts, J. E.; Mascarenkas, Y.; LI, J. Y.; Husain, J.; Cooper, S.; Blundell, T. L.; Hruby, V. J.; Buku, A,; Fishman. A. J.; Wyssbrod. H. R. Science 1986. 232, 633. (b) Hruby. V. J . Trends Pharm. Sci. 1987, 8, 336. 207-220. (10) Hruby, V. J. Life Sciences 1982, 31, 189. 0002-7863/90/1512-3110$02.50/0

A review of information theory in analytical chemometrics

Abstract: Information theory makes it possible to judge and evaluate methods and results in chemical analysis The obtained information can be expressed in different ways One way is to define information as the decrease of uncertainity after analysis Conditional probabilities are therefore considered when evaluating the information provided by qualitative analyses However, the use of other information measures, such as the information gain, is often preferable In multicomponent analysis the translation of information from signals to the amounts of the analytes has been investigated along with the relevance of individual components Information theory can also be applied to find the optimum experimental conditions The evaluation of the properties of analytical methods by information theory has been proposed

Use of protease inhibitors as antiexudative, antiphlogistic and antimicrobial agents

Abstract: A medcamentous form with antiexudation, antiphlogistic and antimicrobial effects in an aqueous or ointment base, suitable above all as an ophthalmologic, otolaryngologic, or dermatologic drug, which contains inhibitors or proteases, as are aprotinin, soyabean trypsine inhibitor, and elastatinal, either single or in a combination, in the amount of 0.1 mg to 20 mg per 1 ml of physiological saline or buffer solution, which is preferably ionically balanced and has pH 6.5 to 7.5, pr per 1 g of ointment base. The medicamentous form may further contain 0.05 to 1.5 wt.-% of steroidal antiphlogistics, for example, dexamethasone, and/or 0.05 to 5 wt.% of nonsteroidal antiphlogistics, for example, indomethacin, and/or 0.2 to 1 wt.-% of antibiotics suppressing the growth of microbes, as are, for example, neomycin, bacitracin, chloramphenicol, tetracycline.

Models of pigment-protein interactions in photosynthetic systems: Tetraphenylporphyrin complexes with polycationic sequential polypeptides. Absorption, circular dichroism and fluorescence properties

Abstract: Absorption and circular dichroism spectra and steady state and time-resolved fluorescence of complexes of 5,10,15,20-tetrakis (4-carboxyphenyl)porphyrin with sequential helical polypeptides (L-Lys-L-Ala) n , (L-Lys-L-Ala-L-Ala) n , and (L-Lys-L-Ala-L-Ala-L-Ala) n are studied. Changes of electronic transition energies, induction of optical activity and two-component fluorescence decay with components t 1 = 2–3 ns and t 2 = 180 ps characterize the complexed pigment. Dependence of these changes on relative number of lysine amino acids in polypeptide primary structures was observed and is discussed in terms of perturbational influence of polypeptide molecular field on mixing of porphyrin electronic states.

Ichnologic note: The ophiuroid Taeniaster as a tracemaker of Asteriacites, ordovician of czechoslovakia

Abstract: The brittle star Taeniaster bohemicus was found in association with the trace fossil Asteriacites lumbricalis in the Upper Ordovi‐cian of central Bohemia. Morphological features of the trace, coupled with spatial interrelationships between trace and body fossils, provide evidence that the brittle star represents the trace‐maker of this Asteriacites. The cubichnial burrows probably represent negative phototaxis among the ophiuroids.

Browning reactions of Heyns rearrangement products

Abstract: The browning rate of Heyns rearrangement products at 110°C under free access of oxygen is slower that that of Amadori rearrangement products. The maximum browning rate was observed at pH = 8.0. The browning was accelerated by Fe(III) and Cu(II) ions. The presence of Fe(II) ions, propyl gallate, and rutin caused lag periods but had no pronounced effect during the subsequent browning. Hydrogen peroxide bleached the melanoidin pigments but did not destroy the browning precursors. Sulphites inhibited the browning reaction. Fluorescence spectra differed from those of the respective Amadori products.

[Effect of carbohydrate-enriched diet and subsequent food restriction on life prolongation in Fischer 344 male rats].

Abstract: Increased proportion of carbohydrates (dextrin) in the diet has a life prolonging effect upon male Fischer 344 rats; however, the effect of this diet appears only when the rats aged from 6 weeks to 6 months are on diet, after this treatment median survival of experimental animals increases by 96 days and the 10th percentile increases on the average by 10 days (n-60). Further maintenance of animals on the same diet has minimum effect: animals being on this diet throughout the whole life exhibit a median lifespan increase by 120 days and an increase in the 10th percentile by 41 days. However, if such animals aged 6 months are transferred to a restricted (60%) food intake regimen (control diet, not enriched with carbohydrate) a further increase in median and 10th percentile lifespan prolongation can be observed reaching 328 and 396 days, respectively as compared to controls. The effects of this early feeding (from 6 weeks to 6 months) with a carbohydrate-enriched diet available ad libitum and food restricted (60% controls) regimen fed from the age of 6 months onwards are additive, the final results being identical as if the animals are kept on the 60% food restricted intake throughout the whole life.

The equation of state of hard Gaussian-overlap fluids

Abstract: Two methods proposed for the determination of the P-V-T behaviour of hard Gaussian-overlap fluids, employing the geometric properties of the corresponding hard ellipsoids and the hard convex-body equation of state, are discussed and the calculated compressibility factor compared with recent simulation data.

Role of the renin-angiotensin system in the adaptation to high salt intake in immature rats.

Abstract: The response of the renin-angiotensin system, extracellular fluid volume, plasma volume, plasma sodium and mean arterial blood pressure to an increase in salt intake (8% NaCl in the diet for 10 days) was compared in immature (20 days) and adult (80 days) rats which were either sham-operated or uninephrectomised. Salt feeding induced a significant increase in plasma sodium in immature animals, and a greater suppression of the renin-angiotensin system in immature than in adult rats, although extracellular fluid volume, plasma volume and blood pressure remained unchanged. Following uninephrectomy, however, the renin-angiotensin system was maximally suppressed in both age groups and in younger animals extracellular fluid volume, plasma volume and blood pressure were significantly increased. It is concluded that (i) the renin-angiotensin system in immature rats is more responsive to a chronically increased salt intake, (ii) this greater responsiveness partly compensates for the lower natriuretic efficiency of the kidneys of immature rats, which becomes evident after reduction of renal mass, and (iii) these events bear a relation to the higher susceptibility of prepubertal rats to the hypertensive effect of a chronically increased salt intake.

3p and 3d core-level widths in metallic technetium : a study by internal-conversion electron spectroscopy

Abstract: On identifie l'elargissement de Coster-Kronig d'une raie de conversion interne dans le cas de la transition M 4 . On presente l'existence d'effets chimiques sur la duree de vie du trou de cœur 3d 3/2 pour NH 4 TcO 4 . Determination de l'energie de transition E3

Effect of external pH on the respiration activity of Candida utilis induced by ethanol

Abstract: The kinetics of ethanol oxidation by non-growing cells of Candida utilis in different media at various external pH values was determined experimentally. The statistical discrimination between two rival mathematical models has shown that the mechanism of non-specific substrate inhibition of respiration kinetics fits better the experimental data. It has been found that the maximum respiration activity is controlled by the buffering properties of organic polycarbonic acids in the medium. The pH values at which the maximum respiration rate was observed were close to the pK values of the organic acids in the buffer solution, independently of whether the acids were metabolized or not.

Xps investigation of lpe garnet films

Abstract: XPS spectra of YIG, YIG:Bi, YIG:Ca and YIG:Co(Ge, Ca) epitaxial garnet films were measured at room temperature. The positions of the main iron, yttrium, oxygen, bismuth, cobalt and lead spectral lines were determined and their changes with the surface treatments were investigated. It was found that divalent and trivalent states of iron and cobalt ions can be resolved, the chemical shifts being in oposite directions.

Molecular characteristics of pepsinogen and pepsin from duck glandular stomach.

Abstract: 1. 1. Two procedures were developed for the preparation of duck pepsinogen, an enzyme from the family of aspartic proteases (EC 3.4.23.1) and its zymogen. 2. 2. The amino acid composition, sugar content and the partial N - and C -terminal sequences of both the enzyme and the zymogen were determined. These sequences are highly homologous with the terminal sequences of chicken pepsin(ogen). 3. 3. Duck pepsinogen and pepsin are unlike other pepsin(ogen)s in being relatively stable in alkaline media: pepsinogen is inactivated at pH 12.1, pepsin at pH 9.6. 4. 4. Duck pepsin is inhibited by diazoacetyl- d,l -norleucine methyl ester (DAN), 1,2- epoxy -3(p- nitrophenoxy)propane (EPNP), pepstatin and a synthetic pepsin inhibitor Val- d -Leu-Pro-Phe-Phe-Val- d -Leu. The pH-optimum of duck pepsin determined in the presence of synthetic substrate is pH 4. 5. 5. Duck pepsin has a marked milk-clotting activity whereas its proteolytic activity is lower than that of chicken pepsin. 6. 6. The activation of duck pepsinogen is paralleled by two conformational changes. The activation half-life determined in the presence of a synthetic substrate at pH 2 and 14°C is 20 sec.