Study of general toxic and organotropic properties of clindamycin in long-term experiments]

The action of clindamycin monohydrate on the general state and weight rise, liver and kidney functions, peripheral blood count and pathomorphological state of the viscera was studied on rats in chronic experiments. Clindamycin was administered to laboratory animals orally in doses of 50, 100, 150 and 300 mg/kg. It was shown that some adverse reactions to the drug and in particular disorders in blood coagulation and morphological changes in the intestine did not depend on its dose and were due to duration of the drug use and probable development of dysbacteriosis. At the same time the disorders in the liver and kidney functions though transitory did depend, to a greater extent, on the dose and were evident after the antibiotic overdosage.     

Study of general toxic and organotropic properties of ampicillin combined with sulbactam]

The effect of sulacillin, a combination of sulbactam and ampicillin (1:2), on the functions of the liver and kidneys, peripheral blood count, cardiovascular and central nervous systems was studied in acute and chronic experiments on animals of various species. The allergenic and local irritating properties of the combination were also studied. It was shown that the combination was low toxic and the interaction of sulbactam and ampicillin by the lethal effect was additive. When the combination was administered intravenously to mice, its LD50 amounted to 6 g/kg. In chronic experiments on rats parenterally given the combination in doses equivalent to the therapeutic ones there were no changes in the examined systems and organs. When used in the doses exceeding the therapeutic ones, sulacillin used during long periods induced a transitory elevation of blood levels of transaminases and alkaline phosphatases, an increase in the relative weight of the liver and kidneys, elongation the typhlon and an increase in glycogen levels in the hepatocytes without morphological changes. The combination had no significant effect of sulacillin and the painful injections alleviated by local anesthesia were recorded. The allergenic properties of the combination were moderate and did not differ from those of ampicillin. The data indicate that the combined sulacillin preparation greatly resembles its foreign analogue.     

Studies on the properties of immobilized urokinase: effects of pH and temperature

Human urokinase was immobilized on an ethylene vinyl acetate copolymer surface. Soluble urokinase showed its maximum activity at pH 8.5, while the immobilized enzyme was most active at pH 9.0. Apparently, the shift in optimal pH was due to the polyanionic nature of the carrier surface on which the enzyme was immobilized. Optimal temperatures of soluble urokinase and immobilized enzyme were identical, i.e., 37 degrees C. The stability of immobilized enzyme against thermal degradation was several times higher than that of the soluble enzyme. Its stability at higher temperatures is one of the main reasons for the clinical use of immobilized urokinase as an antithrombotic material.     

Preparation of immobilized enzymes by N-vinylpyrrolidone and the general properties of the glucoamylase gel

Immobilized glucoamylase, invertase, and β-galactosidase were prepared by using N-vinylpyrrolidone monomer (VP) under γ-ray irradiation. The enzyme-VP solutions were gelled by irradiation with 2.9 Mrad and the added enzymes were almost completely entrapped. Activity losses on entrapping were 55% for the VP-glucoamylase gel, and more than 90% in the case of VP-invertase and VP-β-galactosidase gels. No leakage of enzyme from these gels could be detected within 1 hr. The VP-glucoamylase gel was capable of hydrolyzing dextrin (mol wt 10,400) to glucose and the glucose equivalent was equal to that obtain able with native enzyme. The optimum temperature, heat stability, pH activity curve, and pH stability of VP-glucoamylase gel were slightly inferior to those of native enzyme, while Km was a little larger than that of native enzyme.     

Solvent effects on fluorescence properties of protochlorophyll and its derivatives with various porphyrin side chains

Fluorescence spectra and fluorescence lifetimes of protochlorophyll (Pchl) were measured in organic solvents having different physical and chemical properties and were analyzed taking into account the nonspecific (dependent on bulk solvent parameters), and specific (e.g. H bonds, Mg coordination) solvent–solute interactions. The energy of the fluorescence emission band decreased, while the Stokes shift increased for increasing solvent orientation polarizability, which is a function of both the dielectric constant (ε) and the refractive index (n). The extent of the dependence of the Stokes shift on solvent orientation polarizability was higher in protic (i.e. those able to form hydrogen-binding) than in aprotic solvents. High value of the Stokes shift was also observed in pyridine and methanol, i.e. in solvents hexacoordinating the central Mg atom. The fluorescence decay of Pchl was monoexponential in all of the investigated solvents. The fluorescence lifetime decreased for increasing solvent orientation polarizability from 5.5 ± 0.1 ns in 1,4-dioxane to 3.3 ± 0.1 ns in methanol. Longer lifetime values were observed in the case of aprotic solvents than in protic solvents. The hexacoordination of Mg had no effect on the fluorescence lifetime. The present data are discussed with respect to results found for protochlorophyllide (Pchlide) (My?liwa-Kurdziel et al. in Photochem Photobiol 79:62–67, 2004), and they indicate that the presence of phytol chain in the porphyrin ring influences the spectral properties of the whole chromophore. This is the first complex analysis comparing the fluorescence emission and fluorescence lifetimes of purified Pchl and Pchlide.     

Urease immobilized on nylon: preparation and properties

Urease (EC 3.5.1.5) was covalently attached through glutaraldehyde to partially hydrolysed nylon 6/6 tubes. The highest activity of immobilized enzyme was obtained at 65?°C and pH 6.5, while the optimum temperature for free urease was found to be 25?°C. Immobilized urease showed an improved thermal stability in comparison to free urease. It retained 76% of the original activity after 60 days when stored at 4?°C and 78% of the activity after 5 repeated uses.     

Preparation and properties of immobilized amyloglucosidase

Amyloglucosidase was immobilized on a copolymer of methyl methacrylate and 2-dimethylaminoethyl methacrylate. The resulting immobilized amyloglucosidase has 19% of the soluble enzyme specific activity. The pH optimum of immobilized amyloglucosidase is shifted towards acidity by 1.9 units. The temperature optimum of immobilized enzyme is shifted upward by 5°C. The immobilized amyloglucosidase has the maximum stability at pH 4.6, whereas the soluble enzyme has maximum stability at pH 5.5. While soluble amyloglucosidase has a maximum thermal stability at 50°C, the stability of the immobilized amyloglucosidase steadily decreases with the increase in temperature.     

Microwave effects on immobilized peroxidase chemiluminescence

Protein gels formed by crosslinking bovine serum albumin and horseradish peroxidase with glutaraldehyde were used to measure effects on peroxidase activity of 400-MHz (CW) radiofrequency radiation (RFR) at an average specific absorption rate (SAR) of 1.45 W/kg. The enzyme activity was measured by luminol chemiluminescence recorded on photographic film after hydrogen peroxide activation. Activity was measured during RFR exposure of gels or after exposure of gels polymerized in the RFR field. During exposure, a significant (P less than .05) reversible increase occurred in overall mean peroxidase activity of gels activated with 0.88 M H2O2 but not in those activated with 8.8 M H2O2. Gels containing solubilized luminol and formed in the field showed no overall mean increase in peroxidase activity, but did display a highly significant (P less than .001) alteration in the distribution of local activities when compared to unexposed gels. These results are apparently due to changes in the rate of diffusion (concentration equilibration) of hydrogen peroxide in the gel.     

Study of the toxic effects of an insecticide and copper sulphate on chicken embryos

The toxic effects of the BI 58 EC insecticide (38% dimethoate) applied alone or in combination with copper sulphate were studied on chicken embryo in the early phase of development. The test materials were injected in 0.1-0.1 ml volume into the air chamber of eggs on the first day of incubation. Subsequently, on days 2 and 3 of incubation permanent preparations were made from the embryo in order to study the early developmental stage. Embryos fixed on slides and stained with osmium tetroxide solution were studied under light microscope. According to the result of the statistical evaluation, to sum up, we can say that the simultaneous administration of the test materials did not result in a significant increase in the embryo mortality, but after the combined administration the rate of embryonic mortality markedly increased. As a result of combined administrations the developmental anomalies included the apperance of a blood ring, poor development or absence of somites, the retarted development of the vascular system, the head and the body, irregular differentiation of the brain vesicles. Summarising the findings, it can be established that the insecticide treatment combined with heavy metal resulted in enhanced embryotoxicity in the case of both combinations, which was primarily manifested in an increased embryonic mortality rate.     

Some inhibitory effects of gentamicin on plant tissue cultures

Summary Tracheary element differentiation in cultured explants of pith parenchyma isolated from heads of romaine lettuce (Lactuca sativa L. var. Romana) was strongly inhibited by concentrations of gentamicin sulfate recommended for tissue culture media (50 to 100 μg/ml). Similar results were obtained with cultured explants of Jerusalem artichoke tuber (Helianthus tuberosus L.). Callus formation was suppressed in the presence of increasing levels of gentamicin sulfate in both tissue systems. Plant tissue culture media employed in studies on cell division and xylem differentiation should be supplemented with this antibiotic in concentrations of 10 μg/ml or less according to these results.     

Various properties of immobilized aldolase

The pH dependence of direct and reverse aldolase reaction rate was studied in the presence of Sephadex-immobilized fructoso-1,6-diphosphate aldolase. The immobilized enzyme retains its activity in the presence of sulfhydryl inhibitors: iodacetate and n-chloromercury benzoate.     

Biocatalytic properties of immobilized inulinase

A heterogeneous biocatalyst based on inulinase immobilized on a nonionic sorbent of Stirosorb series was proposed. Thermal and acid inactivation of free and immobilized inulinase was examined and the corresponding inactivation constants were calculated. An increase in the thermal stability of the immobilized enzyme in comparison to the free one was found. The possibility of using the immobilized enzyme in the hydrolysis of inulin for ten cycles was determined.     

Various properties of immobilized AMP-aminohydrolase

Properties of immobilized AMP-aminohydrolase from rabbit muscles are studied. The enzyme retains its activity for a year, is stable under manifold treatment with the substrate or under single treatment with 1 M NaCl which contains 50% ethylene glycol or 10% isopropanol and under treatment with 5 M K2 HPO4 (pH 8.5). The established pH-optimum (6.5-7.0) and the temperature optimum (30-40 degrees C) for immobilized AMP-aminohydrolase as well as inhibition of its activity by Co2+, Cd2+, Zn2+ and n-chloromercury benzoate indicate similarity of its properties with those of the purified enzyme.     

Preparation and properties of soluble-insoluble immobilized proteases

In order to carry out an effective enzyme reaction, the preparation of soluble-insoluble immobilized enzyme was investigated. Proteases were selected as model enzymes, and their immobilization was carried out by using an enteric coating polymer as a carrier. Among the polymers tested, methacrylic acid-methylacrylate-methylmethacrylate copolymer (MPM-06) gave the most active soluble-insoluble immobilized papain. This immobilized papain showed insoluble from below pH 4.8 and soluble form above pH 5.8; it was also soluble in water-miscible organic solvent. It was reusable and more stable with heat and water-miscible organic solvents than native proteases. Furthermore, various proteases could be immobilized by using MPM-06 with high activity. Chymotrypsin immobilized by this method catalyzed the effective peptide synthesis in a heterogeneous reaction system containing water-miscible organic solvent.     

Preparation and properties of immobilized methanol oxidase

Methanol oxidase produced by the yeast Hansenula polymorpha DL-1 was used for the enzymatic oxidation of methanol to formaldehyde. The kinetics of enzyme and protein release during cell desruption were studied at the laboratory scale with a Braun homogenizer and the pilot plant scale with a Manton–Gaulin homogenizer. Conditions were defined for maximum release and retention of high activity in cell-free extracts. Methanol oxidase was immobilized by adsorption on DEAE-cellulose from enzymes in cell-free extracts or from ammonium sulfate purified purified fractions. The kinetics of formaldehyde formation with both soluble and immobilized enzyme was studied in batch and continuous reactors.     

Preparation and properties of immobilized flavokinase.

Flavokinase (ATP: riboflavin 5'-phosphotransferase, EC 2.7.1.26) purified from rat liver by affinity chromatography, has been immobilized by amide linkage to omega-aminoalkyl-agarose beads. The immobilized enzyme differs from the soluble enzyme in having greater stability, slightly higher Km for the substrates, riboflavin and ATP, a broader pH optimum, and a lower energy of activation. These results suggest that the immobilized enzyme is influenced by the microenvironment of the bead and is subject to some degree of internal diffusional limitation. A small (3 ml), continuous, plug-flow reactor prepared with immobilized flavokinase effects 50% conversion of riboflavin to riboflavin 5'-phosphate (FMN) with a flow rate of 0.16 ml/min, which corresponds to an output of 5 nmol FMN/min. Immobilized flavokinase is effective for phosphorylating riboflavin and numerous riboflavin analogs and provides a facile method for preparing exclusively, unlike other synthetic methods, the 5'-phosphates.     

Comments on diffusive and electrostatic effects with immobilized enzymes

Shuler, Aris &; Tsuchiya (1972) have recently considered the combined effects of diffusive resistance and electrostatic field on the rate of reaction catalyzed by an enzyme immobilized on a non-porous surface. They employed a potential distribution for the electrical double layer which is asymptotically valid when surface potential is small.The complete Gouy-Chapman solution, which is valid for higher surface potential, is employed here. Numerical values of the effectiveness factor calculated with this potential distribution agree very closely with the results of Shuler et al. for most cases. It is shown that the effectiveness factor can (i) attain magnitudes much greater than unity in physically realizable systems, (ii) approach the solution for “infinite” surface potential at reasonable values of surface charge density, and (iii) pass through a maximum as bulk substrate concentration is varied. This behavior leads to the existence of an optimum surface concentration for enzyme immobilized on a highly charged non-porous support such that the most effective catalytic action on a charged substrate is ensured. Finally, it is established that significant electrical and/or diffusive effects result in non-linear Lineweaver-Burk plots of reciprocal observed reaction velocity against reciprocal bulk substrate concentration. These non-linear plots cannot be interpreted in the same way as linear plots obtained when enzyme is unbound.