Biomedical subjects

W Lesniak

Publications and source records attributed to W Lesniak.

5 recordsLinked to original sources

PubMed2001

Coordination of heavy metals by dithiothreitol, a commonly used thiol group protectant.

D,L-Dithiothreitol (DTT), known also as Cleland reagent, is a thiol group protectant, used commonly in peptide and protein chemistry. Therefore, it is often added at high concentrations in preparations of proteins relevant to heavy metal biochemistry. The coordination of five of these metal ions, Zn(II), Cd(II), Pb(II), Ni(II) and Cu(I) to DTT was studied by means of potentiometric titrations, and UV-Vis and NMR spectroscopies. It was found that DTT forms specific and very stable polymeric and monomeric complexes with all of these metal ions, using both of its sulfur donors. The quantitative description of these complexes in solution and the solid state provides the basis for predictions of interference from DTT in studies of metal ion binding of thiol-containing biomolecules.

Chelating Agents↗

PubMed2001

Copper(II)-lincomycin: complexation pattern and oxidative activity.

Coordination of Cu(II) to lincomycin was studied by potentiometry, UV-Vis, circular dichroism (CD), EPR, NMR, cyclic voltammetry (CV) and ESI-MS. Only mononuclear complexes of stoichiometries ranging from CuL to CuH(-3)L were found. In the main species present at neutral pH, CuH(-2)L, lincomycin bonds Cu(II) through both of its nitrogen donors, and a deprotonated oxygen donor at C4 of the sugar moiety. High pressure liquid chromatography (HPLC) of products of 2'-deoxyguanosine (dG) oxidation and agarose gel electrophoresis of plasmid DNA confirmed that lincomycin complexes effectively facilitate dG oxidation by H2O2, but are not able to cleave double-stranded plasmid DNA.

Anti-Bacterial Agents↗

PubMed1996

Ca2+-dependent interaction of calcyclin with membrane.

The presence of calcyclin in the microsomal fraction of Ehrlich ascites tumor cells was detected using polyclonal antibodies. Association of calcyclin with the microsomes depended on the presence of calcium ions in the buffer used for cell fractionation. The interaction of calcylcin with Ehrlich ascites tumor cells microsomes was confirmed in the in vitro conditions by cosedimentation assay using exogenous calcyclin. It was shown that phospholipids extracted from natural membranes and purified phosphatydylserine or phosphatydylcholine were not involved in the binding. Instead, several low molecular weight polypeptides in the Triton X-100 resistant membrane fraction were found to interact with calcyclin.

Animals↗

PubMed1995

Effect of alpha adrenergic stimulation and carnitine palmitoyl transferase I inhibition on hypertrophying adult rat cardiomyocytes in culture.

Long-term, serum supplemented cultures of rat adult ventriculocytes were utilized to study the tropic effects of the alpha-agonist phenylephrine and of the carnitine palmitoyltransferase I inhibitor etomoxir. Cell protein and the rate of incorporation of phenylalanine were measured, corrected for cellular DNA content and utilized as an index for hypertrophy and of anabolic activity of the cells, respectively. The mRNA level of ANF was utilized as an index for the pathological phenotypic change (i.e., switch to fetal gene program), and that of the Na-channel--a constantly expressed gene in normal and hypertrophic cardiomyocytes--served as an internal control. Both mRNAs were quantified at various stages in culture by competitive reverse transcriptase PCR. The size of control myocytes steadily increased for over 3 weeks. The cells were completely redifferentiated and reached a maximum of anabolic activity 2 weeks after plating. Secretion and mRNA levels of ANF were increased severalfold after 7-8 days. Addition of 10 microM phenylephrine considerably speeded up cell growth. Maximum anabolic activity and complete redifferentiation were reached already after 1 week. Levels of mRNA and of ANF release increased 30-40 fold. Interestingly, induction of ANF gene transcription lagged behind the redifferentiation of the cells. Ten microM etomoxir inhibited the oxidation of palmitic acid and stimulated that of exogenous glucose by adult cardiomyocytes. In spite of its clear effect on fuel utilization, etomoxir had no direct hypertrophic effect on the myocytes in culture and did not inhibit the stimulatory action of alpha-agonists. Reactivation of the fetal gene program, as visualized by ANF production, was not reversed by etomoxir.

Animals↗

PubMed1994

Reversible inactivation of the sarcoplasmic reticulum Ca(2+)-ATPase coupled to rearrangement of cytoplasmic protein domains as revealed by changes in trypsinization pattern.

Repetitive homogenization of skeletal muscle sarcoplasmic reticulum (SR) membranes in the presence of chelating agents at low ionic strength leads to the loss of the Ca-ATPase activity. This inactive state of the enzyme is coupled to an extensive rearrangement of the cytosolic domains as visualized by a completely different trypsinization pattern of the enzyme. In addition to the primary cleavage site (Arg 505), a novel trypsinization site (Arg 334), just N-terminal of the phosphorylation domain and localized on the primary tryptic fragment A, becomes exposed. Cleavage at the latter site yields a soluble fragment of M(r) 20,117 and the membrane-bound N-terminal one-third of the ATPase of M(r) 35,279. Two additional trypsinization sites C-terminal of the nucleotide binding domain become exposed in the inactive Ca(2+)-ATPase conformation. Rapid cleavage at these sites yields two soluble fragments of about 15 and 10 kDa. All together, the three soluble fragments comprise most of the large cytosolic loop of the Ca(2+)-ATPase. The inactivation and the change in trypsinization pattern can be reversed by rehomogenization of the extracted membranes in the presence of divalent cations. The results suggest the presence of an occluded site for divalent cations which can be depleted or refilled during application of sheer forces. Occupation of this site is essential to confer to the enzyme an active conformation.

Animals↗