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Biomedical subjects

J Dohnal

Publications and source records attributed to J Dohnal.

11 recordsLinked to original sources
PubMed1991

[Determination of mefenoxalone in substances, tablets and biological materials].

For the determination of mefenoxalon in substance, tablets and biological material (blood plasma), four variants were worked out. The first of them is based on the substitution of the benzene ring with bromine with the use of an excess of bromine, which is determined ionometrically. The second variant is based on direct titration of the hydrolytic product mefenoxalon, 3-(2-methoxyphenoxy)-2-hydroxypropylamine, with the use of the ion-selective electrode of the coated-wire type with a volumetric solution of tetraphenyl-borsodium. The third variant utilizes direct measurements of UV spectra of mefenoxalon in a solution of dichlorethane. The fourth variant consists in its fluorimetric measurement in a solution of dichlorethane, or ethylacetate. A detailed discussion of advantages and disadvantages of all above-mentioned variants of determination is presented.

Humans↗
PubMed1990

Distribution of microfilariae of Onchocerca lienalis and Onchocerca gutturosa in the skin of cattle in Germany and their development in Simulium ornatum and Culicoides nubeculosus following artificial infestation.

Onchocerca microfilariae were isolated form the umbilicus and neck of 438 cow hides at the abattoir in Tübingen, F.R.G. The overall Onchocerca infection rate was 40.4%. The presence of Onchocerca lienalis and O. gutturosa microfilariae, which are difficult to distinguish by morphological criteria, was retrospectively demonstrated after artifically infesting Simulium ornatum and Culicoides nubeculosus and identifying the infective larvae recovered. Nine of 16 samples of umbilical microfilariae fed to C. nubeculosus through a latex membrane developed to O. gutturosa third stage larvae (L3). Six of seven umbilical samples injected into the thorax of S. ornatum yielded O. lienalis L3. In six infestation trials in which microfilariae were introduced both into S. ornatum and C. nubeculosus, O. lienalis L3 were recovered exclusively from simuliids, while O. gutturosa L3 developed only in midges. Of six umbilical skins tested by cross-infestation, one contained exclusively O. gutturosa microfilariae, four only O. lienalis microfilariae and one was infected with both species. Developmental success of O. lienalis microfilariae to L3 in S. ornatum following intrathoracic injection was 22% of the mean inoculum. O. gutturosa microfilariae, ingested by C. nubeculosus through a latex membrane, developed to L3 at a rate of 2.3% of the mean microfilarial uptake.

Animals↗
PubMed1990

[Determination of sulbactam in human serum using capillary isotachophoresis].

A method of determination of sulbaktam in human serum by capillary isotachophoresis with the use of a conductivity detector was worked out. Prior to the proper analysis, a pretreatment of the sample of serum was carried out by extracting sulbaktam to butyl acetate. The total yield of the proposed analytical procedure with an extraction first stage approaches 94%. The smallest determinable amount of the sample corresponds to 1 micrograms of sulbaktam in 1 ml of serum. The reported method was employed to evaluate the samples of sera of volunteers after intravenous administration of the dosage form sulbaktam-ampicillin (VUFB) and the foreign pharmaceutical preparation Unasyn (Pfizer). Statistically insignificant differences in pharmacokinetic parameters have confirmed that the preparations are highly bio-equivalent.

Electrophoresis↗
PubMed1989

Use of cyclodextrins in isotachophoresis. VII. Resolution of structurally related and chiral phenothiazines.

Commercially available phenothiazine derivatives were used for the study of cyclodextrin complex formation by cationic isotachophoresis with alpha-, beta- and gamma-cyclodextrin and methylated analogues of beta-cyclodextrin as leading electrolyte additives. The relationships between the type of solute substituent in the 10- and/or 2-position and the stability of the created cyclodextrin complex were studied and the results were utilized for the optimization of isotachophoretic conditions suitable for the resolution of the studied phenothiazine derivatives. Successful resolution of three racemic solutes was achieved.

Chemical Phenomena↗
PubMed1989

Determination of sulphated glycosaminoglycans by automated potentiometric titration with simple coated-wire electrodes.

A method for the determination of sulphated glycosaminoglycans is based on their precipitation with (1-ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex), the excess of which is back-titrated with sodium tetraphenylborate. The titration is monitored by a simple coated-wire ion-selective electrode with a plasticized poly(vinyl chloride) membrane on aluminium wire. Under certain conditions the results are almost independent of the relative molecular mass of glycosaminoglycans. The method has been applied to the determination of the active ingredient in the pharmaceutical preparation, heparon injection.

Aluminum↗
PubMed1988

Use of cyclodextrins in isotachophoresis. VI. Cyclodextrins as leading electrolyte additives for the separation of bile acids.

Cyclodextrins (CDs) and some of their methyl derivatives have been used for the optimization of the isotachophoretic separation of bile acids in aqueous electrolyte systems. The addition of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin to the leading electrolyte proved useful for both the solubilization and the structural differentiation of the solutes studied and led to the successful separation of their mixtures. Other CDs tested, even if they gave a satisfactory solubilization effect, did not support the resolution of bile acid mixtures.

Bile Acids and Salts↗
PubMed1974

'DNA snapback' peptides.

Thermal denaturation studies show that 10-15% of the calf thymus DNA in the heat denatured (Tyr-Gly-Tyr-Gly-Tyr)-DNA complex renatures spontaneously after colling. The double-strandness of this DNA was verified by its resistance to single-strand Neurospora endonuclease and by its elution profile on hydroxypatite columns. The renatured DNA isolated by the latter technique was found to contain 56% GC compared to the 41% GC content of the whole thymus DNA. Alternating tryptophanyl-glycyl and histidyl-glycyl peptides also catalyze the same renaturation. A linear correlation was found between the thermal stabilization afforded to the DNA by the various peptides and their ability to "catalyze" DNA strand renaturation.

Amino Acid Sequence↗
PubMed1974

Interaction of tyrosyl, histidyl, and tryptophanyl peptides with DNA: specificity and mechanism of the interaction.

In the Tyr-(Gly)(1-4)-Tyr series maximal thermal stabilization of calf thymus DNA (deltaT(m)=10 degrees ) occurred with the Tyr-(Gly)(2)-Tyr peptide, where three base pairs could separate the two tyrosyl residues. Tyr-Gly-Tyr-Gly-Tyr stabilized the DNA by 6 degrees . The alternating Trp-Gly-Trp-Gly-Trp and His-Gly-His-Gly-His peptides were equally as effective as the Tyr-Gly-Tyr-Gly-Tyr peptide in stabilizing calf thymus DNA against thermal denaturation. But the alternating Phe-Gly-Phe-Gly-Phe peptide afforded little stabilization, suggesting that a sidechain possessing both a conjugated pi-electron system and an electron donor atom is necessary for DNA stabilization. Introduction of electron withdrawing iodo or nitro group into the tyrosyl sidechains almost completely abolished the stabilizing effect. Although the tyrosyl peptides seem to be specific for GC-base pairs, no correlation was found in natural DNA between% GC and% thermal stabilization. Eukaryotic DNAs showed twice the stabilization of prokaryotic DNAs with the same GC content.

Amino Acid Sequence↗