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Biomedical subjects

W Wnuk

Publications and source records attributed to W Wnuk.

At least 19 recordsLinked to original sources
PubMed2000

[Heart rhythm variability of healthy newborns with congenital heart defects].

Short-term changes in heart rate (heart rate variability) are seen at every age and represent an important sign of normal homeostatic mechanisms of the cardiovascular system. The influence of premature birth on the maturation of the autonomic nervous system was established by studying heart rate variability in 12 pre-term newborns. The results were compared with a group of 88 full-term newborns and with a group of 14 newborns with congenital heart defects. Heart rate variability was measured by spectral- and time-domain analysis of interbeat intervals in 4-hour continuous ECG recordings. In comparison with full-term newborns, pre-term newborns had significantly lower (p < 0.05) time-domain indices (SDNN = 42.73 vs. 53.38; SDANN-i = 29.84 vs. 35.7) and spectral-domain indices (ULF = 7.91 vs. 10.29; VLF = 20.28 vs. 27.42; LF = 12.57 vs. 16.46). The present results point to a significant influence of gestational age on heart rate variability. Newborns with congenital heart defects present a different pattern of activity of the autonomic nervous system.

Arrhythmias, Cardiac↗
PubMed1998

[The applicability of phleboscintigraphy in diagnosis and treatment result evaluation of patients with disorders of leg venous circulation].

The aim of the paper was the applicability of phleboscintigraphy in the diagnosis and monitoring of the treatment in patients with various disorders of venous circulation in lower extremities. The study comprised eighty-eight patients with the suspicion of deep veins impatience. The examination was performed using DTPA 99mTc by means of a gamma camera connected with a computer. The radioisotope was injected into the foot dorsal veins. The dose was 185 MBq. Its activity was monitoring continuously for 1 min. The estimation of the results was performed by scintigraphy imaging and curves of activity changes of chosen regions over deep veins. Phleboscintigraphy was found out to be of a great value in the diagnostics and assessment of treatment results in thrombotic-embolic disease, extra-thrombotic syndromes and in qualification of patients with lower legs varices for surgical procedures. Because of easy performance, possibility of repeating, small invasiveness and rather low cost, the method can be recommended as an introductory examination in patients with above mentioned diseases.

Adult↗
PubMed1991

[Do ulcerogenic pepsins exist? Characterization of polymorphism of human pepsins].

Studies on the role of pepsin in the pathogenesis of peptic ulcer are hampered by lack of suitable methods for the separation, characterization and quantification of different forms of pepsin. As a contribution toward solving this problem, we have developed several electrophoretic systems which exhibit a high resolving power for pepsins and their precursors, pepsinogens. When human gastric juices were fractionated by discontinuous electrophoresis at pH 3.7 in polyacrylamide gel, pepsin was resolved into as many as 20 distinct forms: 3 major isoenzymes (C, A4, A3), 4 less abundant isoforms (C', A6, A4', A3' or A2), 8-10 minor isoforms of pepsin A1 and at least 3 dimeric isoforms of pepsin A (Ad). All the pepsin components were identified by means of bidimensional electrophoresis. Pepsinogens from gastric mucosa were separated by discontinuous electrophoresis at pH 5.5 in the first dimension, then converted to pepsins in the gel by acidification and resolved by electrophoresis at pH 3.7 in the second dimension. Based on discontinuous electrophoresis at low pH, a much needed method was elaborated for the quantification of different forms of pepsin(ogen) within the stomach. This technique will allow detailed clinical studies which may provide insight into the question whether or not there are specific forms of pepsin that are associated with peptic ulcer.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1989

Amino acid sequences of the two major isoforms of troponin C from crayfish.

The primary structure of the two major isoforms (alpha and gamma) of troponin C (TnC) from crayfish tail muscle has been determined by the application of manual and automated Edman degradation procedures to fragments generated by suitable chemical and proteolytic cleavages. Both amino acid sequences commence with an acetylated methionyl residue and contain 150 amino acid residues, including a single proline residue at position 29 and 2 residues of tyrosine at positions 95 and 102. No cysteine or tryptophan are present. The molecular weights calculated for alpha- and gamma-TnC are 17,157 and 16,974, respectively. The two crayfish proteins are invariable at 129 positions and conserved at 11 others. Pairwise comparisons show that the two sequences are 33-39% identical with those of seven TnCs reported so far and 39% identical with that of bovine brain calmodulin. The N-terminal end of about 10 residues, found in vertebrate TnCs, is absent in crayfish TnCs. In the latter proteins, domains I and III appear as abortive Ca2+-binding sites due to nonconservative amino acid replacements at the key Ca2+-coordinating positions in their loops. The remaining two Ca2+-binding loops (II and IV) show a remarkable similarity with the Ca2+-specific loops (I and II) found in vertebrate TnCs. These findings are consistent with the Ca2+-binding data (Wnuk, W. (1989) J. Biol. Chem. 264, 18240-18246) which indicate the presence of two Ca2+-specific sites in crayfish TnCs. These two sites display the same affinity for Ca2+ (log KCa = 4.3) on gamma-TnC but differ in their affinity (log KCa = 6.0 and 4.1) on alpha-TnC. The only structural difference between the dodecapeptide loops II and IV in both alpha- and gamma-TnC, which correlates with the existence of the high affinity (log KCa = 6.0) Ca2+-specific site on alpha-TnC, is position 11 occupied by a methionyl residue in the loop IV of alpha-TnC as opposed to negatively charged residues found in the other three loops. This suggests that the high affinity Ca2+-specific site on alpha-TnC is located in domain IV. Since the Ca2+-binding studies show that the formation of the complex of crayfish troponin I (TnI) with alpha- and gamma-TnC increases significantly the affinity of only one of their two Ca2+-specific sites and this TnI-sensitive site is not the high affinity Ca2+-specific site on alpha-TnC, we conclude that the binding of Ca2+ to site II controls the Ca2+-dependent interaction between crayfish TnCs and TnI.

Amino Acid Sequence↗
PubMed1989

Resolution and calcium-binding properties of the two major isoforms of troponin C from crayfish.

Crayfish tail muscle troponin C (TnC) has been fractionated into its five components and the Ca2+-binding properties of the two major isoforms (alpha and gamma) determined by equilibrium dialysis. alpha-TnC contains one Ca2+-binding site with a binding constant of 1 x 10(6) M-1 and one Ca2+ site with a binding constant of 1 x 10(4) M-1. In the complex of alpha-TnC with troponin I (TnI) or with TnI and troponin T (TnT), both sites bind Ca2+ with a single affinity constant of 2-4 x 10(6) M-1. gamma-TnC contains two Ca2+-binding sites with a binding constant of 2 x 10(4) M-1. In the gamma-TnC.TnI and gamma-TnC.TnI.TnT complexes, the binding constant of one of the sites is increased to 4-5 x 10(6) M-1, while Ca2+ binding to the second site is hardly affected (KCa = 4-7 x 10(4) M-1). In the presence of 10 mM MgCl2, the two Ca2+-binding sites of both TnC isoforms exhibit a 2-3-fold lower affinity. Assuming competition between Ca2+ and Mg2+ for these sites, their binding constants for Mg2+ were 120-230 M-1. In the absence of Ca2+, however, alpha-TnC and gamma-TnC bind 4-5 mol of Mg2+/mol with a binding constant of 1 x 10(3) M-1. These results suggest that the effect of Mg2+ on Ca2+ binding at the two Ca2+ sites is noncompetitive, i.e. Mg2+ does not bind directly to these sites (Ca2+-specific sites). Since the formation of the complex of crayfish TnI with alpha-TnC or gamma-TnC increases significantly the affinity of one of their two Ca2+-specific sites, I conclude that the binding of Ca2+ to only one site (regulatory Ca2+-specific site) controls the Ca2+-dependent interaction between crayfish TnCs and TnI.

Animals↗
PubMed1989

Complete amino acid sequence of the sarcoplasmic calcium-binding protein (SCP-I) from crayfish (Astacus leptodactylus).

The complete amino acid sequence of the alpha chain of the dimeric sarcoplasmic Ca2+-binding protein (SCP-I = alpha 2) from crayfish (Astacus leptodactylus) has been determined by partial automatic sequencing of the peptides derived from tryptic digests of the protein after citraconylation or treatment with 1,2-cyclohexanedione. Overlapping peptides were obtained by cleavage with o-iodosobenzoic acid, or digestion with Staphylococcus aureus protease, thermolysin and pepsin. The acetylated N-terminus was identified by fast atom bombardment mass spectrometry. The monomeric protein contains 192 amino acids and has an Mr of 21,643. The sequence shows the presence of three calcium-binding sites and perhaps of two others that may be degenerated.

Amino Acid Sequence↗
PubMed1986

A novel 40,000 Da Ca2+-dependent actin modulator from bovine brain.

A monomeric protein of Mr 40,000 that modulates the polymer state of actin has been isolated from bovine brain. When added either to preformed actin filaments or to monomeric actin, prior to polymerization, the modulator reduces the low-shear viscosity of F-actin provided that Ca2+ is present. The 40 kDa protein also inhibits the rate of actin polymerization. The inhibition is fully suppressed by removal of Ca2+ and restored by subsequent readdition of Ca2+, suggesting that the Ca2+-controlled interaction of actin with the 40 kDa modulator is freely reversible.

Actins↗
PubMed1984

Regulation of actomyosin ATPase by a single calcium-binding site on troponin C from crayfish.

Equilibrium-binding studies at 4 degrees C show that, in the instance of crayfish, troponin C contains only one Ca-binding site with an affinity in the range of physiological free [CA2+] (K = 2 X 10(5) M-1). At physiological levels of Mg2+, this site does not bind Mg2+. In the complexes of troponin C-troponin I, troponin and troponin-tropomyosin, the regulatory Ca-specific site exhibits a 10- to 20-fold higher affinity (K = 2-4 X 10(6) M-1). The latter affinity is reduced to that of troponin C upon incorporation of the troponin-tropomyosin complex into the actin filament (regulated actin), as determined at 4 degrees C by the double isotope technique. The Ca-binding constant is again shifted to a higher value (7 X 10(6) M-1) when regulated actin is associated with nucleotide-free myosin. Both crayfish myofibrils and rabbit actomyosin regulated by crayfish troponin-tropomyosin display a steep rise in ATPase activity with [Ca2+]. Comparison of the pCa/ATPase relationship and the Ca-binding properties at 25 degrees C for the crayfish troponin-regulated actomyosin indicates that while the threshold [Ca2+] for activation corresponds to the range of [Ca2+] where the regulatory site in its low affinity state (K = 1 X 10(5) M-1) starts to bind Ca2+ significantly, full activation is reached at [Ca2+] for which the Ca-specific site in its high affinity state (K = 3 X 10(6) M-1) approaches saturation. These results suggest that, in the actomyosin ATPase cycle, there are at least two calcium-activated states of regulated actin (one low and one high), the high affinity state being induced by interactions of myosin with actin in the cycle.

Actins↗
PubMed1983

Polymorphism in high-affinity calcium-binding proteins from crustacean sarcoplasm.

The sarcoplasmic calcium-binding proteins (SCP) from crayfish, lobster and shrimp myogen have been purified to homogeneity. These proteins exist as dimers and dissociate in the presence of sodium dodecyl sulfate or urea in subunits of 22000 molecular weight. During the last step of purification (DEAE-cellulose chromatography), SCP emerges in three peaks in the ratio of 14:1.5:1 for crayfish, of 7:2:1 for lobster and of 3:2:1 for shrimp. Gel electrophoresis and isoelectrofocusing experiments, under native and denaturing conditions, indicate that among the three SCP isotypes there are only two different polypeptide chains, alpha and beta, which appear in the form of three dimers: alpha 2, alpha beta and beta 2. The alpha and beta subunits differ slightly in polypeptide chain composition as found by amino acid analyses of the crayfish and lobster SCPs, and also by comparison of tryptic peptides for crayfish SCPs. The polymorphism observed in crustacean SCPs, which is increased by their ability to form dimers, contrasts with the situation prevailing among other invertebrate SCPs and vertebrate parvalbumins where only monomeric isotypes are found. Equilibrium binding studies show that all three SCP isotypes from both crayfish and lobster display the same metal-binding properties. They have in their dimeric form six Ca2+-binding sites: two calcium-specific sites, two Ca/Mg sites that interact with positive cooperativity and two Ca/Mg sites that interact with negative cooperativity. Interactions between the two subunits of SCP seem to result in cooperative binding of Ca2+, which in turn may control more efficiently Ca2+ fluxes in crustacean muscle.

Amino Acids↗
PubMed1977

Cellular distribution of sarcoplasmic calcium-binding proteins by immunofluorescence.

Specific antibodies against carp paravalbumin, crayfish calcium binding protein and crayfish arginine kinase were used for indirect immunofluorescence localization of the respective proteins. Simultaneous staining of the same muscle sections with human serum containing anti-actin autoantibodies served as a probe to identify the isotropic band. Parvalbumin appears to be evenly distributed in carp white muscle. The crayfish calcium binding protein however shows a distinct localization, in the isotropic band, coincident with the actin staining. Arginine kinase, which has the same molecular weight and is extractible in the same way as the calcium binding protein does not show this distinct localization, but is evenly present in crayfish tail muscle, similarly to parvalbumin. The possible meaning of the different distribution of the two calcium binding proteins is discussed.

Animals↗
PubMed1976

Isolation and properties of a sarcoplasmic calcium-binding protein from crayfish.

The sarcoplasmic calcium-binding protein from crayfish muscle has been purified to homogeneity. The protein has a molecular weight of 44000, as determined by sedimentation equilibrium and Sephadex chromatography. It dissociates in the presence of sodium dodecyl sulfate, 8 M urea, or, after succinylation, into two subunits of 22000 molecular weight. The protein is free of carbohydrate and phosphorus but contains 4 g-atoms of calcium/44000 at a free calcium concentration of 0.1 muM. Approximately 45% of the polypeptide backbone appears to be alpha-helical. The amino acid composition reveals a high proportion of alanine and acidic amino acids, a normal content of aromatic amino acids, and the absence of histidine. The isoelectric point, as determined by isoelectric focusing, is 5.1. The protein contains a free threonyl NH2 terminal. Two thiols react rapidly in the native protein, six in the calcium-free form. Immunochemically, there is no difference between the protein from tail, claw, and heart muscle. In these three crayfish tissues, the concentrations of calcium-binding protein, as determined by rocket immunoelectrophoresis, are markedly different: 2.73 g/kg in tail, 0.72 in claw, and 0.073 in heart muscle. A functional analogy with the parvalbumins of vertebrates can be postulated.

Amino Acids↗