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Biomedical subjects

F Gubensek

Publications and source records attributed to F Gubensek.

At least 91 records · Page 5Linked to original sources
PubMed1982

Neuromuscular and lethal effects of phospholipase A from Vipera ammodytes venom.

Four homogeneous proteins having phospholipase A activity were separated and studied for their i.v. lethal effects in mice and nerve-muscle activity in the guinea pig diaphragm preparation. Fraction "j" had an LD50 of 0.30 mg/kg, with 3.6 microgram/ml of bath solution causing a decrease in the indirectly-elicited nerve-muscle contractions to 20% of control, without significantly changing the directly-elicited muscle contractions. Fraction "k2" had an LD50 of 0.021 mg/kg and caused a similar nerve or nerve-muscle block at 5 micrograms/ml of bath solution, without altering the directly-elicited contractions. Fraction "k1" had an LD50 of 0.58 mg/kg and produced less distinct but dose-related changes in the nerve or in nerve-muscle transmission, as well as weakening directly-elicited muscle contractions to within 60% of control. Fraction "I" had an LD50 of 3.6 mg/kg but high doses of the fraction were required to produce changes in diaphragm contractility. High doses (60 and 195 micrograms/ml) produced marked effects on both the directly- and indirectly-elicited contractions, suggesting that this fraction affects the muscle directly.

Animals↗
PubMed1982

Distribution of vipera ammodytes toxic phospholipase A in the cat and its ability to cross the blood-brain barrier.

Several phospholipases A could be isolated from the venom of the European viper, Vipera ammodytes, having different specific activities toward egg lecithin and different lethalities. The most lethal of these enzymes is fraction "k2" having an intravenous LD50 for white mice of 0.021 mg per kg and a specific activity of 280 microM/min mg at 40 degrees C. The enzyme could be labeled with 131I without loosing its enzymatic activity and lethality. The passage of this enzyme from blood into cerebrospinal fluid (CSF) was followed in anesthetized cats. Approximately 1% of the blood level of the enzyme was found in CSF indicating the ability of this protein to penetrate the blood-brain barrier. Although the lethality of fraction "k2" becomes as low as 0.085 microgram/kg when applied intraventricularly, it is not very likely that the central effects of this fraction are of major importance in envenomation since the distribution pattern of the labeled enzyme shows that most of the protein remains in liver, lungs and kidneys, presumably non-selectively bound to membranes and only 0.2% of the injected fraction can reach the brain. Relatively high amount of enzyme was also found in the diaphragm. The penetration of the blood-brain barrier of the radiolabeled phospholipase is within the limits for the proteins of this size (M.w. 14500).

Animals↗
PubMed1982

Coagulant proteinase from Bothrops colombiensis venom.

The venom of Bothrops colombiensis, like other Crotalidae venoms, contains thrombin-like activity. We purified a mixture of isoenzymes by chromatography of the crude venom on DEAE-Sephacel where coagulant proteinase were separated from other proteolytic enzymes. By subsequent chromatography on Sephadex G-100 we obtained coagulant proteinase as a single band on acrylamide gel electrophoresis at pH 7.5 which showed 4 major protein bands when subjected to flat gel isoelectric focusing. This heterogeneity is presumably due to carbohydrates present in this glycoprotein. The native molecular weight of the coagulant proteinase was found to be over 90000 by gel filtration. SDS electrophoresis showed, however, that the monomer molecular weight is around 67000. The specific coagulant activity of the purified enzyme was increased 13 fold by purification and was 231 NIH units/mg. The optimal pH for coagulation of bovine fibrinogen was at pH 7.0. The enzyme shows maximal stability in the pH range 5-6 when incubated for 1 hr at 37 degrees C. The intraperitoneal LD50 for white mice was 4.0 mg/kg. The enzyme is similar to other known coagulant proteinases from snake venoms and thus potentially useful as a therapeutic agent.

Animals↗
PubMed1981

Bovine intracellular cysteine proteinases.

Cathepsins B, H and S were isolated from bovine lymph nodes and bovine spleen. It was shown that the incubation of homogenate at 37 degrees C at acid pH increased the total BANA hydrolase activity and LeuNA activity, whereas it decreased the total activity of cathepsin S. All three enzymes are electrophoretically homogeneous and probably composed of a single polypeptide chain. They exist in multiple forms as shown by isoelectric focusing. Far UV CD spectra revealed a rather high percentage of unordered structure. The three cysteine proteinases were inhibited by thiol blocking reagents, leupeptin and by an inhibitor isolated from Vipera ammodytes venom. Results on the specificity toward various substrates and the influence of pH on enzymatic activity are presented.

Animals↗
PubMed1977

Studies on bovine spleen cathepsin D.

The purification procedure of cathepsin D which includes autolysis results in the destruction of the molecule to smaller polypeptide chains. Pure catepsin D obtained by the method which includes affinity chromatography, contains single polypeptide chain of 42000 daltons. The N-terminal amino acid is glycine. The specificity was studied using synthetic substrates. CD measurement of cathepsin D shows mainly unordered structure, about 26% of beta-structure and only 5% of alpha-helix. Binding of pepstatin shows pronounced changes in the CD spectrum between 250 and 300 nm; above 7.5 no interaction was observed.

Animals↗
PubMed1977

Inactivation studies of cathepsin D with diazo compounds.

Cathepsin D was inactivated with various diazo compounds at very high concentration. Reaction proceeded maximally at pH 4.5 in the presence of cupric ions. With 3-diazo-indazole and triazene the inactivation was noted also in the absence of cupric ions what indicates that the mechanism is mediated through triazene. CD-spectrum of partially inactivated enzyme shows that conformational changes occurred after treatment with diazo compound.

Animals↗