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Biomedical subjects

E Nowak

Publications and source records attributed to E Nowak.

At least 55 records · Page 3Linked to original sources
PubMed1983

Some functional properties of nonpolymerizable and polymerizable tropomyosin.

The binding of 125I-labelled nonpolymerizable (brain or carboxypeptidase A-treated skeletal muscle) and polymerizable (intact skeletal muscle) tropomyosin to muscle F-actin was studied by ultracentrifugation under various conditions. The amount of nonpolymerizable tropomyosin bound to F-actin both in 0.1 M KCl and in 7 mM MgCl2 was much lower than that of the polymerizable one. In the presence of MgCl2 the amount of nonpolymerizable tropomyosin bound to F-actin approached saturation level. Under these conditions, however, the amount of skeletal muscle tropomyosin bound exceeded saturation, suggesting formation of both head-to-tail polymers and side-to-side aggregates. The latter seems to be responsible for the inhibition of acto-heavy meromyosin ATPase activity which is caused by skeletal muscle tropomyosin but not by nonpolymerizable tropomyosin. Nonpolymerizable tropomyosin can substitute for the rabbit skeletal muscle tropomyosin in the regulatory system operating in skeletal muscle. Inhibition of ATPase activity of acto-heavy meromyosin by nonpolymerizable tropomyosin in the presence of troponin and the absence of calcium ions is less than that obtained with polymerizable tropomyosin. The inhibition of ATPase activity is directly correlated with the extent of binding of nonpolymerizable tropomyosin to F-actin under the conditions of the ATPase assay.

Actins↗
PubMed1983

Upper G-I bleeding following intraarterial chemotherapy infusion.

Two cases of severe upper G-I bleeding associated with hepatic 5-PU infusion are presented. This bleeding originated from duodenal ulcers caused by perforation of the gastroduodenal artery by the infusion catheter. They were visualized both at angiography which showed contrast leakage to the duodenum, and at gastroscopy, where the infusion catheter could be seen in the ulcer crater. The incidence and possible pathogenesis of peptic ulcer disease following hepatic infusion chemotherapy is discussed.

Arteries↗
PubMed1980

Wheat germ protein kinase affects the translation of Brome Mosaic virus ribonucleic acid in vitro.

Wheat germ protein kinase inhibits in vitro translation of Brome Mosaic virus (BMV) RNA 1 and 2, without affecting the translation of RNA 4. Inhibition of formation of BMV polypeptides 1a and 2a is due to the arrest of initiation of polypeptide synthesis. It was found that protein kinase inhibits the formation of the 80S initiation complex with BMV RNA 1 and 2, without affecting the formation of the initiation complex with BMV RNA 4. Inhibition of protein synthesis by wheat germ protein kinase is accompanied by the phosphorylation of two ribosome-associated polypeptides, with molecular weights of 32 000 and 76 000, respectively. Both polypeptides are readily dephosphorylated by the enzyme(s) present in the cell-free extract. Their dephosphorylation is accompanied by restoration of the translational capacity of the system.

Mosaic Viruses↗
PubMed1980

Chicken-gizzard actin: polymerization and stability.

Preparations of chicken gizzard actin obtained from acetone-dried muscle powders prepared with various methods developed for skeletal muscle contain variable amounts of a beta-actinin-like protein. This contamination is minimized if the procedure of muscle powder preparation includes washing with EDTA solution, and can be completely removed by gel filtration of G-actin on Sephadex G-100. The presence of beta-actinin activity manifests itself in an increased rate of actin polymerization, low filament lengths resulting in low reduced viscosity and enhanced ATP-splitting activity of actin polymer, and instability of the polymer in the absence of free ATP. Gizzard actin purified on a Sephadex G-100 column does not differ from rabbit skeletal muscle actin in its polymerization properties. The distinct property of gizzard actin is the instability of its G form in the absence of added Ca2+, indicating that the affinity of this cation for the single high-affinity site in gizzard actin is lower than in skeletal muscle actin.

Actins↗
PubMed1980

The interaction of bovine pancreatic deoxyribonuclease I and skeletal muscle actin.

The rate of exchange of actin-bound nucleotide is decreased by a factor of about 20 when actin is complexed with DNAase I without affecting the binding constant of calcium for actin. Binding constants of DNAase I to monomeric and filamentous actin were determined to be 5 X 10(8) M-1 and 1.2 X 10(4) M-1 respectively. The depolymerisation of F-actin by DNAase I appears to be due to a shift in the G-F equilibrium of actin by DNAase I. Inhibition of the DNA-degrading activity of DNAase I by G-actin is of the partially competitive type.

Actins↗
PubMed1976

Interaction of tropomyosin with troponin components.

1. The TN-T and TN-I components of troponin both interact with tropomyosin and cause its precipitation in 0.1 M KC1 at neutral pH. The precipitate contains both end-to-end and side-by-side aggregates of tropomyosin molecules. 2. The TN-T and TN-I components change the band pattern of tropomyosin paracrystals formed in MgC1(2) solutions, although in different ways. TN-T causes the formation of hexagonal net structures, double-stranded net or paracrystals which result from the collapse of the double-stranded net. TN-I at pH 7.9 causes the formation of paracrystals with a 400 A periodic band pattern and a 200 A repeat. The same band pattern can also be seen in tropomyosin paracrystals formed at pH values below 6.0. 3. The TN-C component does not precipitate tropomyosin in 0.1 M KC1. The aggregates of tropomyosin obtained with either TN-T or TN-I can be solubilized by the addition of TN-C. No interaction of TN-C was observed with tropomyosin paracrystals formed in the presence of MgC12.

Animals↗
PubMed1975

Interaction of troponin components with F-actin and F-actin-tropomyosin complex.

1. Both TN-T and TN-I components of troponin interact with F-actin, causing its precipitation at 0.1 M KC1 and neutral pH in a form of highly ordered paracrystals, although the ability of TN-I component to precipitate of F-actin is much weaker. 2. F-actin paracrystals obtained in the presence of both TN-T and TN-I components consist of parallel arrays of F-actin filaments, although the fine structure is in each case different. 3. In the presence of tropomyosin in the proportion equal to that in muscle, less TN-T or TN-I component is needed to obtain full precipitation of F-actin. 4. Paracrystals of F-actin-tropomyosin-TN-T component and F-actin-tropomyosin-TN-I component show regular transverse striation spaced at about 380 A intervals. 5. The TN-C component of troponin solubilizes all precipitates of F-actin with TN-T or TN-I components, regardless of the presence of tropomyosin. 6. The results show that both TN-T or TN-I components can bind independently to F-actin-tropomyosin complex with the same periodicity, similar to that of the whole troponin in the living muscle.

Actins↗
PubMedDate not supplied

A new high sensitivity 19F probe for labeling cysteine groups of proteins.

A novel iodoacetamide label 4-perfluoro-tert-butyl-phenyliodoacetamide (PFP) containing nine fluorine atoms in equivalent positions has been synthesized. It provides a homogeneous 19F NMR resonance line which can be detected with high sensitivity when coupled to proteins. As an example, the sulfhydryl groups of actin have been labeled with PFP; < 100 nmol of this medium sized protein (corresponding to 2.5 mL of a 40 microM solution) can be detected easily in a single scan at 470 MHz.

Acetamides↗
PubMedDate not supplied

Effects of corticosterone and its synthesis blockade on the cocaine-induced discriminative stimulus effects in rats.

Several studies have argued that the hypothalamo-pituitary-adrenal (HPA) axis is of significance to behavioral effects evoked by drugs of abuse (e.g. cocaine). The role of the HPA axis in the subjective effects of cocaine was investigated in rats trained to discriminate cocaine (10 mg/kg, ip, -15 min) from saline (ip, -15 min) in a two-choice, water-reinforced fixed ratio (FR) 20 drug discrimination paradigm. In substitution tests, neither the exposure to a novel environment nor the social defeat stress, applied to rats after a dose of cocaine (2.5 mg/kg) which induced a ca. 42% drug-appropriate responding, influenced cocaine discrimination. Given alone, corticosterone (20 and 40 mg/kg, sc, -60 min) elicited a ca. 7% drug-appropriate responding. Combined injections of corticosterone and cocaine (0.625-5 mg/kg) did not affect the dose-response curve for cocaine. Surgical adrenalectomy did not modify the effects of cocaine; using a cumulative dosing procedure in the drug discrimination paradigm we found, that the dose-response curves for cocaine in adrenalectomized rats and sham-operated controls practically did not differ. Ketoconazole (an inhibitor of adrenocorticosteroid synthesis; 50 mg/kg, ip) given acutely (60 min) did not affect cocaine discrimination. Given subacutely (24, 16 and 1 h before tests), ketoconazole (50 mg/kg) produced a left-ward shift in the dose-response curve for cocaine and decreased its ED50 value. Another inhibitor of corticosterone secretion, metyrapone (50 mg/kg, sc), given acutely (120 min) did not affect the dose-response curve for cocaine. However, repeated injections (24, 16 and 2 h before tests) of metyrapone (50 mg/kg) with different doses of cocaine resulted in a rightward shift in the dose-response curve for cocaine and an increase in its ED50 value. The obtained results seem to exclude any role of the HPA axis in mediating subjective effects of cocaine, since neither corticosterone and stress nor adrenalectomy modified the discriminative stimulus effects of cocaine in rats. The reduction and potentiation of cocaine discrimination following subacute metyrapone and ketoconazole, respectively, may depend on changes in the levels of intermediate neurosteroids "upstream" from corticosterone in its biosynthesis pathway.

Adrenalectomy↗