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Biomedical subjects

G Spoto

Publications and source records attributed to G Spoto.

At least 19 recordsLinked to original sources
PubMed1998

Hypoxic and hyperoxic effect on blood phosphodiesterase activity in young and old rats.

In the present work we describe phosphodiesterase (PDEs) activity in the blood of young and old rats kept under hypoxic or hyperoxic normobaric conditions in order to correlate the age-change response with PDE levels and oxygen supply. PDE is important in the process of energy supply and as a modulator and mediator of several cellular functions. Three groups of Wistar rats were kept in room air, 10-12% oxygen for 12 days and 98-100% oxygen for 60 hrs respectively. Each group was composed of young rats (2 months of age) and old rats (25 months of age). After the exposure the rats were anaesthetized and blood samples were collected using an intracardiac catheter. The results show: a) in the control group, no significant difference between the PDE activities of old and young rats; b) a significant increase in PDE occurred after hypoxic and hyperoxic treatment in both young and aged rats; c) the increase in PDE activity was more evident in the young rather than the old rats; and d) the aged rats are less responsive to oxygen variation. The results demonstrate that young and aged rats respond to variations in the oxygen supply. Hypoxia and hyperoxia show different age-related intensity level response. We conclude that the alteration in PDE expression occurring in the blood as a consequence of hypoxic or hyperoxic treatment is probably a necessary protective response for the body against alteration from oxidative metabolism and to maintain the body in homeostatic ranges for energy requirements.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Hypoxanthine and xanthine levels in human aqueous humor from cataractous eyes.

Purine nucleotide degradation products have been determined by HPLC in aqueous humor obtained during cataract surgery and from plasma of 22 patients (12 women). Uric acid, cytosine, guanosine monophosphate, uracyl, guanine, adenosine, adenosine monophosphate, thymine, adenine, inosine, cyclic guanosine monophosphate, hypoxanthine and xanthine were evaluated. Uric acid and the last two were the only compounds detectable in measurable amounts in aqueous humor and in plasma of all patients. Aqueous humor xanthine levels were not significantly different from plasma; aqueous humor hypoxanthine concentrations were lower than those of xanthine and than plasma oxypurine levels. In 8 patients, treated with allopurinol, oxypurinol concentrations in aqueous humor and in plasma were comparable suggesting that oxypurines are transported through the blood-aqueous humor barrier.

Aqueous Humor↗
PubMed1995

Phosphodiesterase in human colon carcinoma cell line CaCo-2 in culture.

In a series of in vitro experiments we characterised the relationship between DNA distribution in the G1, S and G2/M phases of cell cycle and PDE and GST activity in CaCo-2 cells. The DNA distribution in CaCo-2 cells, was assessed by flow cytometry, with fluorescent dyes at different time points of culture. The exponential increase in cell number continued until day 10 when there was cell saturation. The effect of medium replacement on PDE activity was assayed in the first 10 h after medium replacement. The 6th hour is the time at which PDE activity was found to be highest. We have assayed the PDE enzyme with cGMP and cAMP as substrates. Only cAMP was consumed from this enzyme. We found a very close correlation between the DNA distribution in the various phases of the cell cycle and the PDE activity. PDE activity was very high during the active replication phase, whereas GST activity was high after confluency.

Carcinoma↗
PubMed1994

Reduced human lymphocyte blastogenesis and enhancement of adenosine triphosphate (ATP) by L-carnitine.

Carnitine is associated with lipid synthesis and its deficiency may lead to cardiomegaly with parenchymal lipid in the heart, kidney and liver. In our study we found that pretreatment of peripheral blood mononuclear cells (PBMC) with serial dilutions of L-Carnitine (100 micrograms/ml-1 pg/ml) inhibits, in a dose-dependent manner, lymphocyte DNA synthesis stimulated with PHA (20 micrograms/ml). L-Carnitine did not have any effect on resting PBMC. The maximum inhibition was found at 10 micrograms/ml of L-Carnitine. Moreover, in a time-course study and using an enzymatic analysis (ATP monitoring reagent), L-Carnitine enhanced ATP production on PBMC treated and untreated with PHA, reaching a maximum effect at 30 min incubation. In another set of experiments PBMC were treated with L-Carnitine alone and in combination with PHA, and the percent of receptors CD3, CD4, and CD8 were calculated with flow cytometry. After the cell incubation with L-Carnitine, the percent of all receptors studied did not change compared to L-Carnitine-untreated cells (controls). These data suggest that L-Carnitine inhibits, in a dose-dependent manner, lymphocyte blastogenesis induced by PHA, probably through the enhancement of ATP synthesis, which is considered an inhibitor of phospholipase C activity and a suppressor in lymphocyte cultures.

Adenosine Triphosphate↗
PubMed1992

Isolation of a novel nuclear glycoprotein from pig kidney.

A nuclear glycoprotein with an apparent Mr of 66,000 Da has been isolated from pig kidney chromatin after extraction with urea, guanidine-HCl and 2 M NaCl, and some of its structural features have been characterized. It belongs to the group of N-glycosylated proteins, which in the nucleus has so far received little attention. From its monosaccharide composition and recognition by lectins its oligosaccharides appear to be of high mannose and/or hybrid types. Some properties of its protein moiety suggest that it has a role in the packing of the DNA loops in the condensed chromatin.

Amino Acid Sequence↗
PubMed1991

A reverse-phase HPLC method for cAMP phosphodiesterase activity.

A simple and fast method based on reverse-phase HPLC has been developed for measuring the activity of cAMP phosphodiesterase. It allows quantitation of product and substrate in less than 10 min. The sensitivity (1*10(-11) mol AMP), the accurate evaluation of nucleotides, the unequivocal analysis of product, and the reproducibility of the system, make this method suitable for the evaluation of cAMP phosphodiesterase in biological material, at different levels of purification, and also in kinetic studies.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

Nuclear glycoproteins in higher vertebrates.

Nuclear glycoproteins recognized by Concanavalin A have been isolated from pig, rabbit and chicken tissues. Mono and bidimensional electrophoresis patterns of proteins loosely and tightly bound to DNA have been examined. The tissue specificity rather than species-specificity appears to be a quite general property of these proteins, suggesting for them a role in the mechanism of regulation of chromatin functions.

Animals↗
PubMed1988

The active site sulfhydryl of aconitase is not required for catalytic activity.

Previous reports have demonstrated that aconitase has a single reactive sulfhydryl at or near the active site (Johnson, P. G., Waheed, A., Jones, L., Glaid, A. J., and Gawron, O. (1977) Biochem. Biophys. Res. Commun. 74, 384-389). On the basis of experiments with phenacyl bromide in which enzyme activity was abolished while substrate afforded protection, it was concluded that this group was an essential sulfhydryl. We have further examined the reactivity of this group and confirmed the result that, when reagents with bulky groups (e.g. N-ethylmaleimide or phenacyl bromide) modify the protein at the reactive sulfhydryl, activity is lost. However, when smaller groups, e.g. the SCH3 from methylmethanethiosulfonate or the CH2CONH2 from iodoacetamide, are introduced, there is only partial (50%) or no loss of activity. Experiments were performed to obtain evidence that these reagents are modifying the same residue. Methylmethanethio-sulfonate-treated enzyme showed an increase in the Km for citrate from 200 to 330 microM. EPR spectra were taken of the reduced N-ethylmaleimide- and iodoacetamide-modified enzyme in the presence of substrate. The former gave a spectrum typical of the substrate-free enzyme, while the spectrum of the latter was identical to enzyme with bound substrate. We, therefore, conclude that modification of this sulfhydryl affects activity by interfering with the binding of substrate to the active site and is not essential in the catalytic process.

Acetophenones↗
PubMed1988

Reversed phase high performance liquid chromatography of adrenocorticotropin 1-39 and its fragments in the native and oxidized forms.

This paper reports HPLC separations of human ACTH 1-39 and its fragments (ACTH 1-10, 4-10, 11-24) making use of original gradient systems. Both H2O2 or chloramine T were demonstrated to oxidize the Met 4 present in ACTH 1-39, 1-10, and 4-10; the oxidized forms were HPLC separated from the corresponding native polypeptides, indicating that this method is suitable for the identification in biological fluid of ACTH, its fragment and their methionine-sulphoxide derivatives with possible relevance to the problem of ageing and inactivation of active polypeptide.

Adrenocorticotropic Hormone↗
PubMed1987

Cysteamine oxygenase: possible involvement of superoxide ion in the catalytic mechanism.

The reaction catalyzed by cysteamine oxygenase on cysteamine in the presence of phenazine methosulphate as cofactor like compound is inhibited by nitroblue tetrazolium, a scavenger of superoxide ions. The reaction is not inhibited by superoxide dismutase and allyl alcohol and it is not activated by superoxide ions produced in solution. Nitroblue tetrazolium is reduced by cysteamine or mercaptoethanol and phenazine methosulphate. This reaction is completely inhibited by superoxide dismutase. In the presence of cysteamine oxygenase the reduction with mercaptoethanol is greatly enhanced and it is only partially inhibited by superoxide dismutase. According to these data a reaction mechanism is proposed in which superoxide ions and thiyl radicals are produced at the active site during catalysis.

1-Propanol↗