PubMed Health⌕ Search

Biomedical subjects

M Mazurek

Publications and source records attributed to M Mazurek.

At least 19 recordsLinked to original sources
PubMed1996

The paradoxical influence of thymine analogues on restriction endonuclease cleavage of oligodeoxynucleotides.

Thymine residues in the DNA of eucaryotes may be replaced occasionally by uracil (U) or 5-(hydroxymethyl)uracil (H) as consequences of dUMP misincorporation or thymine oxidation, respectively. In this study, we constructed a series of 44-base oligonucleotides containing site-specific U or H residues and 5'-fluorescein labels in order to probe the influence of such modifications on sequence-specific DNA-protein interactions using several type II restriction endonucleases. We find that substitution within the recognition sites of several restriction endonucleases increases initial cleavage velocity by up to an order of magnitude. These results contrast dramatically with several previous studies which demonstrated that U substitution in short oligonucleotides inhibits or prevents nuclease cleavage. We propose that this apparent paradox results because the rate-limiting step in the cleavage of longer oligonucleotides is product release whereas for shorter oligonucleotides substrate binding is most probably rate-limiting. For longer oligonucleotides and DNA, more rapid release of the cleaved, substituted oligonucleotides results in more rapid turnover and a faster apparent cleavage rate. The sequence length at which the transition in rate-limiting step occurs likely corresponds to the size of the enzyme footprint on its DNA recognition site. We conclude that both U and H do perturb sequence-specific DNA-protein interactions, and the magnitude of this effect is site-dependent.

Binding Sites↗
PubMed1996

Synthesis and hydrolysis of oligodeoxyribonucleotides containing 2-aminopurine.

A new method is reported for the synthesis of oligodeoxyribonucleotides containing 2-aminopurine residues at selected sites. This method involves protection of the 2-aminopurine ribonucleoside, reduction to the deoxyribonucleoside and standard preparation of the 5'-0- (4,4'-dimethoxytrityl)-3'-O-(2-cyanoethyl)-N,N- diisopropylphosphoramidite. The 2-aminopurine phosphoramidite prepared by this method couples with high efficiency and is stable under standard automated synthesis conditions. The presence and location of the 2-aminopurine residue is easily verified by treatment of the oligodeoxyribonucleotide with hot piperidine. The mechanism for selective hydrolysis of the 2-aminopurine residue in alkaline solution is predominantly direct cleave of the glycosidic bond.

2-Aminopurine↗
PubMed1995

Activities of acetylcholinesterase and NA+, K+ -ATP-ase in human erythrocytes after ethanol consumption.

The influence of ethanol consumption on acetylcholinesterase (AchE) and Na+, K+ -ATP-ase activities was examined in 14 healthy volunteers after 30 minutes of ethanol treatment at a dose 0.6 g/kg of body weight. It was observed that the activity of both enzymes decreased. The activity of AchE was significantly lower, and that of Na+, K+ -ATP-ase tended to be lower, but the difference was not significant. In vitro experiments showed that ethanol inhibited the AchE and N+, K+ -ATP-ase activities immediately and in proportion to the concentration of ethanol used.

Acetylcholinesterase↗
PubMed1994

[Effect of gamma radiation on levels of adenine nucleotides in erythrocytes of healthy individuals after submaximum physical exertion].

The authors studied the effect of gamma radiation and submaximum physical exercise on adenosine-5'-triphosphate (ATP), adenosine-5'-diphosphate (ADP) and adenosine-5'-monophosphate (AMP) contents in erythrocytes of healthy males. Twenty one men aged 20-22 years were examined. They underwent physical exercise at doses of 2 w/kg body weight for 15 min. Erythrocytes were exposed to gamma radiation (500 gy doses) from 60Co source. The concentration of adenine nucleotides in erythrocytes was measured by the Boehringer Mannheim tests. The submaximum physical exercise was found to decrease ATP content and to to increase ADP and AMP in erythrocytes. Gamma radiation at 500 Gy dose was found to decrease ATP concentration in erythrocytes both at rest and after submaximum exercise and to increase AD content. It was revealed that AMP content increased at rest and decreased after submaximum exercise in irradiated erythrocytes.

Adenosine Diphosphate↗
PubMed1991

[Reoperations after the treatment of retinal detachment].

Presented is an analysis of the clinical material comprising 100 patients in whom in the period of 1980-1989 one performed reoperations of retinal detachment. It was established that the most frequent causes--as well surgical failures as recurrences--were the vitreo-retinal proliferations and the insufficient closing of the holes. Reattachment of the retina after the second operation was attained in 42 p.c. of the eyes and after the third one in additionally 7 p.c. In cases with a reattached retina a very good visual acuity for far was found in 1/4 and for near in 1/2 of operated eyes. The results obtained are encouraging enough for the performance of reoperations.

Adolescent↗
PubMed1990

Chromatographic analysis of chemical warfare agents.

The usefulness and applications of the particular types of chromatography in the analysis of chemical warfare agents have been reviewed. A major problem in the chromatographic analysis of chemical warfare agents is the collection and preparation of the samples. The importance of this problem differs for the various types of chromatography. Significant differences occur in the way in which samples are collected from air, water, soil, vegetables or animal organisms. The analyses are characterized by the main groups of chemical warfare agents, e.g., organophosphorus, vesicants, irritants, etc. Account has been taken of the relationships between their properties and the possibilities of their chromatographic analysis. The advantages and disadvantages of particular types of chromatography in the analysis of the particular groups and individual agents have been considered. The detectability of particular chemical warfare agents has been assessed, together with the separating efficiency for their mixtures. Examples of applications of chromatographic systems and conditions of chromatographing are summarized in tables. It is concluded that chromatography is a very useful tool in the analysis of chemical warfare agents; GC and TLC have the most advantageous properties, HPLC being slightly inferior.

Animals↗
PubMed1990

Primary structure of the oligosaccharide chain of lipopeptidophosphoglycan of epimastigote forms of Trypanosoma cruzi.

The lipopeptidophosphoglycan of epimastigote forms of Trypanosoma cruzi is composed of a glycan linked through a non-N-acetylated glucosamine residue to an inositol phosphorylceramide. Using conventional analysis techniques, including 1H, 13C, and 31P NMR spectroscopy and negative ion fast atom bombardment mass spectroscopy, the structure of the carbohydrate-containing part of the molecule is determined as: (Sequence: see text). There is uncertainty as to which 2-O-substituted alpha-D-Manp unit is attached the side chain or whether it is distributed between the two units. Some of the structures lack the Galf side chain. The inositol unit is linked to ceramide via a phosphodiester bridge. The major aliphatic components of the ceramide portion were lignoceric acid and sphinganine.

Animals↗
PubMed1990

Dose-response profiles of plasma growth hormone and vasopressin after clonidine challenge in man.

The objective of the study was to determine dose-response relationships of growth hormone, vasopressin, blood pressure, heart rate, and behavioral responses to clonidine. Ten healthy male volunteers were tested with each of three doses of clonidine (0.7, 1.4, and 2.1 micrograms/kg) with at least 1 week between tests. All doses gave a significant growth hormone response with a peak at 50 min. The high dose gave a significantly higher response than either the medium dose or the low dose, which did not differ from each other. Within individual subjects, there was a consistency of response to the different doses; thus, three of the volunteers had responses of 5 ng/ml or higher to the low dose. Those three subjects had higher growth hormone peaks after the highest dose than did six other subjects. Vasopressin showed a drop following clonidine after the two higher doses. Systolic blood pressure dropped following clonidine, showing a significantly greater drop for the medium and high doses than for the low dose. Diastolic blood pressure also showed a drop, but responsiveness did not differ between doses. There was significant dryness of mouth produced by clonidine, but no difference between doses. There was a significant sedative effect following clonidine which was greater for the high dose than for the medium or low dose. The finding that some subjects had a growth hormone peak of 5 ng/ml or greater after the low dose supports the hypothesis that use of a low dose strategy may be useful in confirming supersensitivity in conditions where increased responsiveness is suspected. The lack of difference between blood pressure responses to the medium and high doses of clonidine--doses that have different effects on growth hormone--supports the hypothesis that differences in responsiveness of presynaptic and postsynaptic alpha 2-adrenergic receptors exist.

Adult↗
PubMed1987

Anticonvulsant evaluation of some 3-oxo and 3-thiosemicarbazono analogues of 1-aryl-1-ethylthio-nonanes and related compounds.

A number of 3-oxo and 3-thiosemicarbazono analogues of 1-aryl-1-ethylthio-nonanes and related compounds were synthesized. Solutions of the thiosemicarbazones in deuterochloroform were shown by PMR spectroscopy to exist principally in the anti configuration at equilibria except when an ortho-methoxy group was present in the aryl ring. In this case intramolecular hydrogen bonding probably accounts principally for the presence of equal amounts of anti and syn isomers. Evaluation of these compounds for anti-convulsant properties revealed that 1-(2-aminoethylthio)-1-(2-chlorophenyl)nonan-3-one hydrochloride (6a) and sodium 2-(N-acetylamino)-3-[1-(2-chlorophenyl)-3-oxononylthio]propionate (6c) were active and thus they could serve as prototype molecules for future development.

Animals↗
PubMed1986

Alpha 1-adrenergic receptor activation releases vasopressin and oxytocin from perfused rat hypothalamic explants.

Norepinephrine and the alpha-agonist phenylephrine in concentrations of 10(-5) to 10(-3) M prompted the release of radioimmunoassayable vasopressin (up to 150 pg/min) and oxytocin (up to 20 pg/min) from intraarterially perfused explants of rat basal forebrain. Drug effects were markedly reduced or abolished in the presence of the non-specific alpha-antagonists phentolamine and phenoxybenzamine, and the specific alpha 1-antagonist prazosin. In concert with recent in vivo and in vitro electrophysiological observations, these data imply that endogenous noradrenergic pathways to magnocellular neurosecretory cells are excitatory, mediated through activation of their alpha 1-receptors, thereby enhancing the release of both vasopressin and oxytocin in the neurohypophysis.

Animals↗