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Biomedical subjects

G B Principato

Publications and source records attributed to G B Principato.

At least 37 records · Page 2Linked to original sources
PubMed1985

Alkaline phosphatase in Hirudo medicinalis L.: partial purification and study of certain molecular and catalytic properties.

The authors carried out extraction and purification of an alkaline phosphatase (AP) from Hirudo medicinalis and studied certain characteristics of the enzyme. After homogenizing specimens of H. medicinalis and centrifuging the homogenate at 70,000 g, the enzyme, likely membrane-bound, was obtained in a soluble form by treating the sediment with n-butanol. It was then purified by acetone fractionation and Sephadex G-200 chromatography. A fairly good purification degree was achieved; the enzyme appears to be in a single form and displays a molecular weight of about 268,000. The optimum pH (9.5) is lower than the ones generally observed as regards APs from both Invertebrata and Mammalia. The studied AP displays a strong substrate inhibition, similar to that concerning Metazoa at a higher evolutionary level (Mollusca, Echinodermata). On the contrary, the enzyme-substrate affinity, as shown by Km value (2.447 mM), is lower than as regards APs from more advanced organisms (Echinodermata, Mammalia).

Alkaline Phosphatase↗
PubMed1985

Effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system.

The authors studied the effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system, in order to establish if these substances influence cell proliferation by interfering with glyoxalase activity. The results demonstrate that both ascorbic and dehydroascorbic acid do not alter glyoxalase activity in vitro, even if employed at high doses.

Animals↗
PubMed1984

Purification and characterization of four different alkaline phosphatases from Spirographis spallanzanii.

Alkaline phosphatases (APs) present in Spirographis spallanzanii were extracted by water homogenization of butanol treatment. The enzymes solubilized as above were purified by acetone fractionation and then by DEAE-cellulose and Sephadex G-200 chromatography; separation of four AP forms was achieved, which were characterized by studying their molecular and catalytic properties. The various APs differ in molecular weight, electrophoretic mobility, optimum pH, but show similar Km values and substrate inhibition pattern. Kinetic studies carried out with several inhibitors show, in particular, the existence in these APs of a second binding site and suggest a possible role for them in the metabolism of phosphoric esters of the sugars.

Alkaline Phosphatase↗
PubMed1984

Active site kinetics of horse serum cholinesterase.

Horse serum Cholinesterase hydrolyzes choline and p-nitrophenol esters at different rates. Deacylation and acylation seem to be the rate-limiting step for charged and uncharged substrates respectively. Activation energy is similar for the acetic, propionic, and butyric esters of thiocholine, but it is higher for p-nitrophenylpropionate. Inhibition by the tetramethyl-ammonium ion is competitive. Tetraethyl-, tetrapropyl-, and tetrabutyl-ammonium ions are mixed-type inhibitors. The pH studies demonstrated the existence of a residue, pK = 6.33, involved in catalysis.

Animals↗
PubMed1984

Purification of S-2-hydroxyacylglutathione hydrolase (Glyoxalase II) from calf brain.

S-2-Hydroxyacylglutathione hydrolase (Glyoxalase II) from calf brain has been purified 8333-times compared to 65,000 g supernatant of brain homogenate. The purification procedure employs Affi-Gel blue and preparative isoelectric focussing and offers a suitable method for the preparation of highly purified enzyme. Calf brain Glyoxalase II is a basic protein with a pl of 7.63 determined by isoelectric focusing. An evaluation of the relative molecular mass by gel filtration gave a value of about 23,000. During the purification procedure a constant Km value of about 0.325 mM was observed. A turnover number of 16,100 min-1 was calculated for the purified enzyme.

Animals↗
PubMed1983

Synthesis of brain DNA during acquisition of an active avoidance task.

The possible involvement of cerebral DNA synthesis in the learning process was examined in rats injected intracerebrally with 3H thymidine. During the period of incorporation (4.5 hr) one rat was trained to an active avoidance task while a second animal was kept in the same experimental room. In comparison with control rats paired to learning animals, the concentration of PCA-soluble radioactivity and of radioactive DNA of the cerebral cortex increased in all animal groups, i.e., control rats paired to non-learning animals, learning rats and non-learning rats. No change occurred in liver. In the cerebral cortex the slope of the regression line obtained by plotting the concentration of radioactive DNA versus the concentration of PCA-soluble radioactivity was lower in learning rats than in the group of pooled control animals. A comparable effect was noted in the hippocampus. In non-learning animals a similar decrease was present in the cerebral cortex and in cerebellum. In addition, it was found that in learning animals the percent incorporation was inversely related to the total number of avoidances only in the cerebral cortex. In non-learning rats a similar inverse relationship was present in the cerebral cortex and in cerebellum. In the former region the regression line of learning rats was shifted upwards in comparison with the regression line of non-learning animals. These results are interpreted to indicate that the incorporation of 3H-thymidine into cerebral DNA is directly related to the level of stress and is increased by learning.

Animals↗
PubMed1983

Activity changes of glyoxalases I-II and glutathione reductase in regenerating rat liver.

In regenerating rat liver Glyoxalase I activity shows a significant increase 24-48 hrs after partial hepatectomy. Glyoxalase II activity is significantly increased at 16, 48, and 72 hrs, and shows a transient decrease at 24 hrs after surgery. It is likely that the observed changes in Glyoxalases I and II activities during hepatic regeneration are correlated with the different roles of these enzymes. Glutathione reductase activity, significantly reduced within 8-72 hrs after surgery, does not show any correlation with Glyoxalases. These studied enzyme activities do not display significant changes in the sham-operated animals.

Animals↗
PubMed1982

Partial purification and characterization of an alkaline phosphatase in Helix nemoralis and in Octopus vulgaris.

1. Alkaline phosphatase (AP) present in the liver of Helix nemoralis and of Octopus vulgaris; enzyme was purified by homogenization, ultracentrifugation, n-butanol treatment, acetone fractionation and Sephadex G-200 chromatography. 2. The two enzymes show a similar enzyme-substrate affinity, but differ in several properties (molecular weight, electrophoretic mobility, optimum pH, substrate inhibition); a possible correlation of them with different evolutionary adaptations is suggested. 3. Possible roles of AP in Mollusca are discussed.

Alkaline Phosphatase↗
PubMed1979

[Derivation of a velocity equation for a reaction model witwh two binding sites for acetylcholinesterase].

The authors suggest a kinetic model with two binding sites for acetylcholinesterase; it is suitable to study particular enzyme forms that show a kinetic pattern which cannot be explained by the model with a single binding site of Krupka and Laidler. The velocity equation was obtained using the algorithm of King and Altman and carrying out elementary calculations.

Acetylcholinesterase↗
PubMed1979

[Kinetic analysis of a reaction model with two binding sites for acetylcholinesterase].

After having suggested a kinetic model with two binding sites for acetylcholinesterase, the authors obtained the various function of [I] (1/vi; (vo/vi-1)/[I]; 1/Vi; Ki/Vi) starting from the velocity equation. An analytical study was then carried out showing the theoretical shape of such functions at different values of the kinetic parameters.

Acetylcholinesterase↗
PubMed1978

Erythrocyte acetylcholinesterase activity changes in the early stages of anemic and hypobaric hypoxia or after CoCl2 treatment in rabbits.

The authors studied the changes of erythrocyte acetylcholinesterase (AChE) activity in rabbits respectively subjected to bleeding, hypobaric hypoxia and CoCl2 treatment; in such conditions a rise of the enzyme activity was observed. Similar increases take place also as a consequence of intravenous infusions carried out by using lactic or hydrochloric acid. The authors suggest that these increases in the erythrocyte AChE activity are connected with the decrease of the pCO2 that occurs in the various experimental conditions achieved.

Acetylcholinesterase↗
PubMed1978

Early effects of cobalt chloride treatment on certain blood parameters and on urine composition.

The authors studied the variations of some blood parameters and urine composition during the first hours after CoCl2 treatment in rats and rabbits. These showed an increase in hematocrit with a decrease in plasma volume and, at the same time, a decrease in total proteinemia as well as in the albumin (rabbits) and gamma-globulin fractions. On the basis of observations carried out in rabbits, these phenomena are not seen if the cobalt is complexed with cysteine before treatment; moreover, they are at least partly reversed by cysteine administration soon after cobalt. Plasma Na+ and K+ concentrations do not show significant changes in CoCl2-treated rabbits; on the contrary, the excretion of such electrolytes, as well as urinary protein content, decreases. In addition, the urine of CoCl2-treated rabbits contains at least two pigmented substances with different molecular weights, which are separable by dialysis and DEAE-cellulose chromatography and both contain cobalt in different percentages. The authors believe that CoCl2 treatment leads to an early and profound increase in vascular permeability with depletion of plasmatic material in the tissues and hemoconcentration; moreover, the above stated phenomena seem to be correlated with the forming of cobalt complexes.

Animals↗