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Biomedical subjects

M Stepień

Publications and source records attributed to M Stepień.

At least 19 recordsLinked to original sources
PubMed2001

Palladium (II) complexes of oxybenziporphyrin.

8,19-Dimethyl-9,13,14,18-tetraethyloxybenziporphyrin coordinates palladium(II) to form the four-coordinate anionic complex [(OBP)Pd(II)](-). The NMR data provide evidence for the retention of macrocyclic aromaticity and coordination via a carbon sigma-donor. Protonation of the external oxygen atom to give [(HOBP)Pd(II)] switches the molecule to a less aromatic phenol-like state, which is manifested by a significant reduction of the macrocyclic ring current. [(AcOBP)Pd(II)] and [(TsOBP)Pd(II)], two ester derivatives of [(OBP)Pd(II)](-), are similar to the protonated species, and their benzenoid character is more pronounced. However, reaction of [(OBP)Pd(II)](-) with methyl iodide leads to selective methylation of the coordinating C(22) atom to form a novel organopalladium complex (OBPMe)Pd(II). The strong shielding of the inner Me(22) (delta((1)H) -2.00 ppm in CDCl(3)) indicates that the aromaticity of the macrocycle has been retained. At the same time the (13)C chemical shift of C(22) (44 ppm) shows that the palladium-bound carbon has undergone a drastic hybridization change. Alkylation with n-BuI yields a mixture of the O-substituted [(n-BuOBP)Pd(II)] and the C-substituted [(OBP-n-Bu)Pd(II)], which confirms the ambident nucleophilicity of [(OBP)Pd(II)](-). DFT calculations carried out for six tautomers of oxybenziporphyrin and the 22-methylated palladium species provide further insight into the electronic structure of the ligand and its complexes. Relative energies of the tautomers, increasing in the order [CH,NH,N,NH,O] < [CH,N,NH,N,OH] < [CH(2),N,NH,N,O] < [CH(2),N,N,N,OH], have been used to estimate the accessibility of four limiting delocalization modes postulated for oxybenziporphyrin and its derivatives. The state of macrocyclic aromaticity observed experimentally in the free base and the phenolic aromaticity of the O-protonated tautomer are the most favorable, and the latter has its energy higher by only 13 kcal/mol. The peculiar bonding situation in (OBPMe)Pd(II), which can be inferred from the NMR data, is also predicted by the DFT methods, which show a strongly distorted tetrahedral environment of C(22).

Journal Article↗
PubMed2001

Tetraphenylbenziporphyrin--a ligand for organometallic chemistry.

6,11,16,21-Tetraphenylbenziporphyrin (TPBPH)H, an analogue of tetraphenylporphyrin with one of the pyrrole groups replaced by a benzene ring, is formed in good yield in the condensation of the appropriate precursor with pyrrole and benzaldehyde. (TPBPH)H gives organometallic complexes with palladium(II) and platinum(II), [(TPBP)PdII] and [(TPBP)PtII], in which the metal ion is bound in the macrocyclic cavity by three pyrrolic nitrogen atoms and a carbon atom of the benzene ring. In the reaction with silver(I) acetate benziporphyrin does not yield a stable complex but undergoes selective acetoxylation at the internal carbon atom. (TPBPH)H is reversibly reduced to 6-benziphlorin and reacts with a water or methanol molecule to give 6-hydroxy- or 6-methoxy-6-benziphlorin, respectively.

Benzaldehydes↗
PubMed2001

Reactivity of mono-meso-substituted iron(II) octaethylporphyrin complexes with hydrogen peroxide in the absence of dioxygen. Evidence for nucleophilic attack on the heme.

Treatment of the mono-meso-substituted iron(II) octaethylporphyrin complexes, (py)2Fe(II)(meso-NO2-OEP), (py)2Fe(II)(meso-CN-OEP), (py)2Fe(II)(meso-HC(O)-OEP), (py)2Fe(II)(meso-Cl-OEP), (py)2Fe(II)(meso-OMe-OEP), (py)2Fe(II)(meso-Ph-OEP), and (py)2Fe(II)(meso-n-Bu-OEP), with hydrogen peroxide in pyridine-d5 at -30 degrees C in the strict absence of dioxygen has been monitored by 1H NMR spectroscopy. The product oxophlorin complexes are stable as long as the samples are protected from exposure to dioxygen. Hydrogen peroxide reacts cleanly with mono-meso-substituted iron(II) porphyrins in pyridine solution under an inert atmosphere to form mixtures of three possible oxygenation products, (py)2Fe(cis-meso-R-OEPO), (py)2Fe(trans-meso-R-OEPO), and (py)2Fe(OEPO). The yields of (py)2Fe(OEPO), which results from replacement of the unique meso substituent, as a function of the identity of the meso substituent decrease in the order NO2 > HC(O) approximately equal to CN approximately equal to Cl > OMe > Ph, Bu, which suggests that the species responsible for attack on the porphyrin periphery is nucleophilic in nature. A mechanism involving isoporphyrin formation through attack of hydroxide ion on a cationic iron porphyrin with an oxidized porphyrin ring is suggested. The identity of the unique meso functionality also affects the regiospecificity of substitution when the unique meso group is retained. Although random attack at the two different meso sites is expected to yield a cis/trans product ratio of 2, the observed ratios vary in the following order: cyano, 5.0; n-butyl, 4.9; chloro, 3.2; formyl, 2.6; methoxy, 1.9; phenyl 1.4.

Ferrous Compounds↗
PubMed2001

[Neurological picture and selected diagnostic indices of vitamin b12 malabsorption syndrome].

Funicular myelosis is considered to be the main neurological syndrome in vitamin B12 deficiency. However, many authors tend to think that sensory neuropathy is the most common neurological manifestation of vitamin B12 deficiency. The aim of this paper was to assess neurological condition of patients with vitamin B12 malabsorption. The absorption of vitamin B-12 was assessed by Schilling's test. Patients with abnormal results of this test underwent neurological and medical examinations as well as series of accessory investigations. 16 cases of deficient vitamin B12 absorption accompanied by neurological symptoms were presented. The results of the investigation showed that the most common clinical manifestation of vitamin B12 deficiency was sensory neuropathy. In over 93% of described cases pathologic changes in gastric mucous membrane were found.

Adult↗
PubMed2001

[Ischaemic heart disease and chronic helicobacter pylori infection--present views].

In connexion with the high prevalence of coronary heart disease its additional reasons are searched, which could lead to the occurrence and development of the disease. Chronic infections have been lately recognized as an additional reason. In the article we presented opinions regarding the influence of long-lasting Helicobacter pylori infection on the development of inflammation process, atheromatous changes, initiation and development of ischaemic heart disease.

Coronary Artery Disease↗
PubMed1999

[Chronobiologic aspects of therapy for cardiovascular diseases].

A chronobiological considerations of time-dependent incidents of cardiovascular diseases including triggering mechanisms and their role in chronotherapy are presented in the article. Circadian and seasonal variation has been demonstrated especially in myocardial infarction, stable and unstable angina pectoris, sudden cardiac death and stroke. Chronopharmacological considerations of therapy of coronary heart disease and hypertension are also reviewed.

Cardiovascular Agents↗
PubMed1996

Application of 2-halopyridinium salts as ultraviolet derivatization reagents and solid-phase extraction for determination of captopril in human plasma by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the determination of captopril in human plasma. 1-Benzyl-2-chloropyridinium bromide (BCPB) was used as a precolumn derivatizing reagent. The mercapto group of captopril was arylated by the reagent to generate a stable UV-sensitive product. The derivative was solid-phase extracted (SPE), separated on a C18 column using reversed-phase ion-paring chromatography and monitored by a spectrophotometric detector at 314 nm. The method enabled sensitive determination of captopril and its disulphides in human plasma in patients after oral administration. Disulphides of captopril with captopril itself and with endogenous thiol compounds are reduced with triphenylphosphine to form captopril, followed by derivatization with the same reagent. The quantification limit was 10 ng/ml. Calibration curves were prepared for human plasma samples spiked with captopril and captopril disulphide. The calibration curves were linear in the range of 10 to 500 ng/ml for captopril and 10 to 1000 ng/ml for captopril disulphide.

Captopril↗
PubMed1991

Stilbestrol as a factor modifying the toxicity of Ekatin for the Pharaoh quail (Coturnix coturnix Pharaoh). I. Young birds.

1. The noted fall of the erythrocyte count, haemoglobin and haematocrit levels after stilbestrol indicate that this hormone disturbs erythropoiesis, probably by depressing the maturation of erythroid cells in the bone marrow. 2. The reaction of the erythrocyte system of birds intoxicated with Ekatin indicates that this pesticide has a haemolytic influence on the morphotic elements of the blood. 3. Estrogenisation enhances the action of Ekatin on the erythrocyte system by as it seems increasing the susceptibility of the red blood cells to the haemolytic action of this pesticide. 4. The high heterophilic leucocytosis in birds receiving stilbestrol is evidence that this hormone causes by an increased release of corticoids, hyperplasia of the granulopoietic tissue in the bone marrow and depresses the marrow barrier for heterophils. 5. Changes in the leucocyte system of quails intoxicated with Ekatin indicate a stressogenic action of this poison. 6. The reaction of the latter system to Ekatin administered after estrogenisation seems to be an indication that stilbestrol reduces the susceptibility of the quails to the stressogenic action of the pesticide.

Animals↗
PubMed1982

ATP citrate lyase in cholinergic nerve endings.

The activity of ATP-citrate lyase in homogenates of five selected rat brain regions varied from 2.93 to 6.90 nmol/min/mg of protein in the following order: cerebellum less than hippocampus less than parietal cortex less than striatum less than medulla oblongata and that of the choline acetyltransferase from 0.15 to 2.08 nmol/min/mg of protein in cerebellum less than parietal cortex less than hippocampus = medulla oblongata less than striatum. No substantial differences were found in regional activities of lactate dehydrogenase, pyruvate dehydrogenase, citrate synthase or acetyl-CoA synthase. High values of relative specific activities for both choline acetyltransferase and ATP-citrate lyase were found in synaptosomal and synaptoplasmic fractions from regions with a high content of cholinergic nerve endings. There are significant correlations between these two enzyme activities in general cytocol (S3), synaptosomal (B) and synaptoplasmic (Bs) fractions from the different regions (r = 0.92-0.99). These data indicate that activity of ATP-citrate lyase in cholinergic neurons is several times higher than that present in glial and noncholinergic neuronal cells.

ATP Citrate (pro-S)-Lyase↗
PubMed1979

Hereditary neurocutaneous angioma: a new genetic entity?

A family pedigree with a possible new genetic syndrome characterised by the presence of angiomas, systemic in nature, affecting particularly the skin and the central nervous system, is described. Angiomas of the CNS seem to have a marked tendency to bleed. The condition shows a clearly dominant mode of transmission, four subjects in three generations being affected. Differentiation from other conditions belonging to the vascular abnormalities subgroup of phakomatoses is presented.

Arteriovenous Malformations↗
PubMed1976

Effect of (-)hydroxycitrate on the activities of ATP citrate lyase and the enzymes of acetyl-CoA metabolism in rat brain.

1. (-)Hyrdoxycitrate is a potent inhibitor of ATP citrate (pro-3S)lyase (EC 4.1.3.8) from rat brain, the inhibition being uncompetitive with respect to MgATP2-and competitive with citrate (Ki 0.8 muM). 2. The rate of oxygen consumption by rat brain synaptosomes and the activities of fatty acid synthetase, carnitine acetyltransferase, glucose-6-phosphate dehydrogenase and acetyl-CoA-synthetase are not affected by (-)hydroxycitrate. 3. (-)Hydroxycitrate inhibits the activities of isocitrate dehydrogenase, malate dehydrogenase (decarboxylating) and aconitate hydratase at millimolar concentrations.

ATP Citrate (pro-S)-Lyase↗