Biomedical subjects

M V Gonchar

Publications and source records attributed to M V Gonchar.

30 records · Page 2Linked to original sources

PubMedDate not supplied

Ultralow concentrations of ibuprofen activate cell prostaglandin synthesis.

The interest in the prostaglandin (PG) synthesis by animal cells today grows steadily because of the difficulties in obtaining them by any other way. Murine peritoneal macrophages can under certain conditions synthesize large amounts of PGs. The effect of well-known nonsteroidal anti-inflammatory drug ibuprofen on PG synthesis by the cells using a high-performance liquid chromatography (HPLC) method with fluorescence detection of 4-bromomethyl-7-methoxy-coumarin (BrMMC) derivatives was studied. In our case, the main metabolites were PGE2 and PGF2a. The PG synthesis activation effect was shown by ibuprofen concentrations in the 10(-10)-10(-14) M range with the maximum effect of 10(-12)M. In this case, the ibuprofen effect was comparable in value with the effect of well-known cell PG synthesis activator--calcium ionophore A23187. Although the exact mechanism of such an effect is not clear at the moment, at low concentration, ibuprofen itself is able to activate PG synthesis in murine peritoneal macrophages.

Animals↗

PubMedDate not supplied

[Alternative mechanisms of detoxication of formaldehyde, formate, and hydrogen peroxide in methylotrophic yeasts].

A new concept based on own experimental results and published data and concerning the involvement under extreme conditions of additional (nontraditional) mechanisms of formaldehyde, formate and hydrogen peroxide detoxification in methylotrophic yeast has been proposed. It has been shown that neutralization of toxic effect of formaldehyde and formate, except the known ways, includes a system of energy-dependent extrusion of formic acid into extracellular space. Detoxification of hydrogen peroxide, besides of catalase way, can be realized by means of cytochrome c peroxidase reaction. The proposed concept has been built on the basis of physiological and biochemical analysis of specially constructed mutants strains of methylotrophic yeast with certain metabolic damages. The selected mutants, used as the instrument in fundamental studies of detoxification processes, also have been successfully used for practical purposes in construction of cell biosensors and creation of enzymatic kits.

Formaldehyde↗

PubMedDate not supplied

[New method for detection of enzymatic activity of flavocytochrome b2 in electrophoregrams].

A new method of visualization of the activity of flavocytochrome b2 (FC b2; L-lactate: ferricytochrome c oxidoreductase, EC 1.1.2.3) in electrophoretograms was developed, based on the interaction between ferrocyanide (generated during the enzymatic reaction) and Fe23+, resulting in the formation of intensely colored precipitates of Berlin blue. The main advantages of this method were its high sensitivity (less than 0.005 U FC b2 was detected within a suitable time period) and the stability of the dye formed. The method developed can be used for determining FC b2 activity in cell-free extracts (e.g., in the selection of FC b2 producers) and monitoring chromatographic purification of proteins, as well as in other cases associated with FC b2 assessment.

Electrophoresis↗

PubMedDate not supplied

[Cellular microbiosensors for methanol and ethanol determination on the basis of pH-sensitive field transistors].

Cellular sensors for methanol and ethanol determination were developed using immobilized mutant cells of methylotrophic yeasts Hansenula polymorpha and Pichia pinus (able to extrude protons in the presence of alcohol) and pH-sensitive field effect transistors (pH-SFETs). The intact cells of yeasts were immobilized in Ca-alginate gel to obtain a biomembrane. The minimal detectable response was obtained to approximately 0.5 mM of methanol and ethanol, a linear dependence of biosensor's response on the logarithmic alcohol concentration was observed in the range from 5 to 100 mM for both types of alcohol. The prospects for application of biosensors to determine alcohols in the analytical practice are discussed.

Biosensing Techniques↗

PubMedDate not supplied

[Selection and properties of mutant yeast Pichia guilliermondii strains resistant to chromium (VI)].

Yeast Pichia guilliermondii strains L3 and L2, exposed to UV mutagenesis, produced over 80 mutants capable of growing on media containing 1.5 mM bichromate (Cr(VI)). The mutations making the strains resistant to Cr(VI) were dominant or semidominant. The mutants varied in Cr(VI) resistance, the degree of chromium accumulation in the cells (from 0.1 to 11.6 mg/g dry cells), and the degree of Cr(VI) reduction (from 50% to complete disappearance of bichromate from the culture liquid). Chromium accumulation in mutant cells depended on medium composition, Cr(VI) concentration, and the time of exposure to Cr(VI). The resistance to bichromate can be caused by various reasons: decrease in chromium absorption, altered ability to reduce Nr(VI), or damage of sulfate transport mechanisms.

Chromium↗

PubMedDate not supplied

[Modern methods for formaldehyde, methanol and ethanol analysis].

It is necessary to create very specific and sensitive methods for assaying formaldehyde and methanol which are produced on the large scale and are very toxic and have mutagenic and carcinogenic action on living organisms. The methods for determination of formaldehyde, methanol and ethanol in the environment and fermentation products published and developed by the authors are reviewed in this paper. Most of the known methods are not sufficiently selective and sensitive and some of them are very expensive. Classical chemical, enzymatic, chemosensor and biosensor approaches used for methanol and formaldehyde assay are described. Enzymatic methods exploiting alcohol oxidase isolated from the mutant over-producing strain of methylotrophic yeast Hansenula polymorpha permit efficient determination of formaldehyde in industrial wastewaters. Enzymatic-chemical method based on the use of alcohol oxidase and 4-amino-5-hydrazine-3-mercapto-1,2,4-triazole (AHMT) allows simultaneous determination of methanol and formaldehyde. The technology of biosensor construction and their bioanalytical characteristics are described. Experimental data concerning amperometric and potentiometric biosensors based on the use of genetically modified cells of methylotrophic yeast Hansenula polymorpha are reviewed. The possibility to use alcohol oxidase-based biosensor for the assay of methanol in wastewater is demonstrated.

Biosensing Techniques↗

PubMedDate not supplied

[Oxidase-peroxidase method for determination of ethanol in fermented musts and wine products].

A new alcohol oxidase-peroxidase method of determination of ethanol content in fermented musts and wine products is described and compared to conventional methods routinely used in winemaking. The sensitivity, accuracy, and reliability of this method were determined. The results of ethanol determination in fermented musts and wines correlated well with the data obtained by refractometry (correlation coefficient R = 0.9595, p < 0.0001) and densitometry (correlation coefficient R = 0.9384, p < 0.0001). This method is less time- and labor-consuming and allows simultaneous testing a series of wine samples.

Alcohol Oxidoreductases↗

PubMedDate not supplied

A new enzymo-chemical method for simultaneous assay of methanol and formaldehyde.

A new enzymo-chemical method for the simultaneous assay of methanol and formaldehyde in mixtures is described which exploits alcohol oxidase (AO) and aldehyde-selective reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH). The enzyme is used for methanol oxidation to formaldehyde and MBTH plays a double role: 1) at the first step of reaction, it forms a colorless azine adduct with pre-existing and enzymatically formed formaldehyde and masks it from oxidation by AO; 2) at the second step of reaction, non-enzymatic oxidation of azine product to cyanine dye occurs in the presence of ferric ions in acid medium. Pre-existing formaldehyde content is assayed by colorimetric reaction with MBTH without treating samples by AO, and methanol content is determined by a gain in a colored product due to methanol-oxidising reaction. Possibility of differential assay of methanol and formaldehyde by the proposed method has been proved for model solutions as well as for real samples of industrial waste and technical formaline. A threshold sensitivity of the assay method for both analytes is near 1 microM that responds to 30-32 ng analyte in 1 ml of reaction mixture and is 3.2-fold higher when compared to the chemical method with the use of permanganate and chromotropic acid. Linearity of the calibration curve is reliable (p < 0.0001) and standard deviation for parallel measurements for real samples does not exceed 7%. The proposed method, in contrast to the standard chemical approach, does not need the use of aggressive chemicals (concentrated sulfuric, phosphoric, chromotropic acids, permanganate), it is more simple in fulfillment and can be used for industrial wastes control and certification of formaline-contained stuffs.

Alcohol Oxidoreductases↗

PubMedDate not supplied

[Screening of yeasts producing stable L-lactate cytochrome c oxidoreductase and regulation of enzyme synthesis].

Screening of strains producing a stable form of L-lactate cytochrome c oxidoreductase (flavocytochrome b2, FC b2) was carried out among 14 yeast species. Enzyme activity was detected in polyacrylamide gel after the electrophoresis of cell-free extracts. The FC b2 of Hansenula polymorpha, Rhodotorula pilimanae, and Kluyveromyces lactis are characterized by high thermostability; in particular, the FC b2 of H. polymorpha retains its activity and tetrameric structure even after heating at 60 degrees C for 10 min. Constitutive synthesis of FC b2 was observed in H. polymorpha grown on either glucose, ethanol, or glycerol. L-Lactate induces de novo synthesis of FC b2, as proved by the use of cycloheximide, an inhibitor of protein synthesis.

Fungal Proteins↗

PubMedDate not supplied

[The effect of citrate and dihydroxyacetone on methanol oxidation in Hansenula polymorpha].

Citrate and dihydroxyacetone inhibited [14C] incorporation from radioactive methanol to CO2 by washed cells of methylotrophic yeast Hansenula polymorpha grown in the media containing mixture of methanol with citrate or dihydroxyacetone, respectively. These results are discussed in connection with the earlier hypothesis on participation of the tricarboxylic acid cycle in the energy supply of the methylotrophic growth.

Citrates↗

PubMedDate not supplied

[The nature of methanol-induced acidification of the medium by products of metabolism of methylotrophic yeasts].

The washed cells of Hansenula polymorpha and Pichia pinus grown on the medium with methanol rapidly acidify the medium during incubation with the mentioned alcohol or formaldehyde. It is found that proton extrusion is coupled with formate anion efflux. Acidification is proved to be energy-dependent process since it is inhibited by respiration poisons, uncouplers of oxidative phosphorylation, and by ATPase inhibitors.

Culture Media↗

PubMedDate not supplied

[Comparative analysis of the peroxidase activity of myoglobins in mammals].

Studies have been made on the peroxidase activity of metmyoglobins in animals from various ecological groups--the horse Equus caballus, cattle Bos taurus, beaver Castor fiber, otter Lutra lutra, mink Mustela vison and dog Canis familiaris. It was found that the level of this activity in diving animals depends on the duration of their diving, whereas in terrestrial species--on the strength of muscular contraction.

Amino Acid Sequence↗