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S Colombatto

Publications and source records attributed to S Colombatto.

At least 37 records · Page 2Linked to original sources
PubMed1995

Purification and kinetic characterization of gamma-aminobutyraldehyde dehydrogenase from rat liver.

Oxidative deamination of putrescine, the precursor of polyamines, gives rise to gamma-aminobutyraldehyde (ABAL). In this study an aldehyde dehydrogenase, active on ABAL, has been purified to electrophoretic homogeneity from rat liver cytoplasm and its kinetic behaviour investigated. The enzyme is a dimer with a subunit molecular weight of 51,000. It is NAD(+)-dependent, active only in the presence of sulphhydryl compounds and has a pH optimum in the range 7.3-8.4. Temperatures higher than 28 degrees C promote slow activation and the process is favoured by the presence of at least one substrate. Km for aliphatic aldehydes decreases from 110 microM for ABAL and acetaldehyde to 2-3 microM for capronaldehyde. The highest relative V-values have been observed with ABAL (100) and isobutyraldehyde (64), and the lowest with acetaldehyde (14). Affinity for NAD+ is affected by the aldehyde present at the active site: Km for NAD+ is approximately 70 microM with ABAL, approximately 200 microM with isobutyraldehyde and capronaldehyde, and > 800 microM with acetaldehyde. The kinetic behaviour at 37 degrees C is quite complex; according to enzymatic models, NAD+ activates the enzyme (Kact approximately 500 microM) while NADH competes for the regulatory site (Kin approximately 70 microM). In the presence of high NAD+ concentrations (4 mM), ABAL promotes further activation by binding to a low-affinity regulatory site (Kact approximately 10 mM). The data show that the enzyme is probably an E3 aldehyde dehydrogenase, and suggest that it can effectively metabolize aldehydes arising from biogenic amines.

Adenine Nucleotides↗
PubMed1994

Modulation of ornithine aminotransferase activity by oxygen in rat hepatocyte cultures.

In hepatocytes in culture, ornithine aminotransferase activity remained higher when the cells were cultured at low oxygen tension (5%) than at high tension (21%), that is, it was higher in hepatovenous conditions. Northern blot analysis showed that the amount of the specific mRNA for the enzyme was also higher. Results of experiments performed in the presence of CoCl2, to replace the central Fe2+ in heme, or succinylacetone, to inhibit heme synthesis, support the view that a heme protein participates in the regulation of ornithine aminotransferase activity by oxygen. The oxygen sensor does not appear to act through phosphorylation by kinase C, as TPA has no significant effect on the process, but a phosphorylation dependent on cAMP might be involved.

Animals↗
PubMed1994

Free and acetylated polyamines as markers of oral cavity tumors.

Differences in tissue concentrations of N1- and N8-acetylspermidine and cadaverine in squamous cell carcinoma of the oral cavity compared to the surrounding healthy tissue, as well as to epulides and other benign oral lesions (papillomas, lipomas, and fibromas) are assessed. The results indicate that only N1-acetylspermidine has use as a marker for diagnosis because its concentration is higher in malignant tissue. Its use in prognosis and posttreatment monitoring requires further exploration.

Acetyltransferases↗
PubMed1993

In vivo effect of berenil on rat liver polyamine metabolism.

1. Berenil, administered to rats in vivo, promoted a decrease in liver SAMDC activity, but an increase in ODC and SAT activity. 2. Its effect on ODC was completely prevented by cycloheximide, that on SAT only partially. 3. Berenil had no effect on ODC activity in adrenalectomized rats. Adrenergic antagonists counteracted the effect of Berenil on ODC activity. 4. Polyamine content was increased. The maximum modification was observed for putrescine and N1-acetylspermidine.

Acetyltransferases↗
PubMed1993

Effect of Berenil on polyamine metabolism in primary cultured rat hepatocytes.

1. Putrescine and spermidine content increased in hepatocytes during culture. In the presence of 10 microM Berenil, putrescine content was further increased, while the increase of spermidine was prevented. 2. Ornithine decarboxylase activity was markedly reduced, and to a lesser extent also S-adenosylmethionine decarboxylase activity. 3. Berenil appears to promote an increase in the transformation of spermidine into putrescine, and to inhibit the polyamine efflux.

Adenosylmethionine Decarboxylase↗
PubMed1993

Regulation of spermidine transport in L1210 cells.

1. 1 mM 2-amino isobutyric acid (AIB), glutamine or asparagine when preincubated for 3 hr with L1210 cells promoted a marked increase in the rate of spermidine uptake. 2. Cycloheximide also increased the transport rate and completely prevented the increase due to AIB. 3. Trifluoperazine and iso-H7 inhibited the uptake of spermidine, much less the uptake of AIB. 4. Adenosine promoted an increase in the uptake of AIB, a decrease in that of spermidine. 5. Hypotonic stress also increased the rate of spermidine transport. This modification was only partially prevented by cycloheximide. 6. Okadaic acid had no effect on this increase, whereas it prevented the increase of ODC activity.

Animals↗
PubMed1992

Efflux of polyamines from human lymphocytes and from L 1210 cells.

1. In human lymphocytes alkalinization of the cytoplasm with monensin or NH4Cl promotes release of polyamines. The effect of NH4Cl is abolished by EGTA and diltiazem. 2. Concanavalin A also promotes an increase of the efflux, counteracted again by EGTA and diltiazem. 3. By effect of TPA, polyamine efflux is decreased in the first 90 min, and later increased. The activation is partially prevented by H7 and by sphingosine. 4. In contrast with human lymphocytes, L 1210 cells release actively endogenous polyamines, but slowly radioactive polyamines. 5. Concanavalin A does not activate the latter process; A 23187 and NH4Cl on the contrary promote a much higher increase in the efflux rate than in normal lymphocytes. EGTA and diltiazem partially counteract the effect of NH4Cl on the release of radioactivity.

Animals↗
PubMed1991

Difference in polyamine transport in human B and T lymphocytes.

Preparations enriched in human blood B lymphocytes are able to take up polyamines efficiently. Uptake by T cells is barely detectable. Human non-circulating B cells (from tonsils) have a much lower ability to take up polyamines, as do mixed populations of bovine lymph nodes. B cells contain a higher amount of endogenous polyamines and show higher ornithine decarboxylase activity than T cells.

B-Lymphocytes↗
PubMed1991

Enhancement of ouabain and calcium ionophore A23187 of outward transport of polyamines from lymphocytes.

Human lymphocytes in culture loaded with radioactive polyamines slowly release radioactivity into the medium. N1-Acetylspermidine is mostly released from spermidine and spermine. Both ouabain and calcium ionophore A23187 increase the outward transport, but by different mechanisms. Ouabain inhibits the acetylation of spermidine, and free spermidine is released, whereas A23187 increases both acetylation of spermidine and the efflux of N1-acetylspermidine.

Acetylation↗
PubMed1991

Polyamines in rat hepatocyte cultures.

In rat hepatocytes cultured for 120 h polyamine content was markedly modified. Putrescine concentration reached a maximum at 48 h, spermidine increased for 48 h and then remained constant, spermine after a decrease returned to its initial values. Total polyamine amount was increased by 75%. Both ornithine decarboxylase and the retroconversion pathway were responsible for these modifications. The possible correlation between polyamine metabolism and retrodifferentiation process was investigated by studying them in conditions which are known to preserve differentiated functions.

Animals↗
PubMed1990

Transport and metabolism of polyamines in human lymphocytes.

1. Polyamines are taken up by human peripheral lymphocytes in a concentration, time and pH dependent manner, with an energy-dependent transport system. 2. Each polyamine inhibits the uptake of the others, with the exception of putrescine. Spermine appears to have the highest affinity for the transporter/s. 3. Inhibition by ouabain, amiloride and vanadate suggests that the transport is dependent on Na+. 4. Polyamine content inside the cells increases by ca 6 and 3 times respectively during incubation with spermidine or spermine. 5. The incorporated polyamines are partially transformed into each other.

Amiloride↗
PubMed1990

Biochemical aspects of the hormonal therapy of endometrial adenocarcinoma.

This paper reports an investigation of the mechanism involved in the response of endometrial adenocarcinoma to MPA. The following protocol was used for a period of 8 years: 1 g/day MPA per os for 30 days and 60 days after surgery, following by 500 mg/day for 1 year. Adenocarcinoma glycolytic activity, G-6-P cycle, polyamine concentration, and the activity of ornithine decarboxylase (ODC), i.e. the first enzyme in polyamine synthesis, were compared before and after the 30/day treatment. The modifications induced by MPA are discussed and related to the pathological picture in an attempt to determine the characteristics of responding tumors.

Adenocarcinoma↗
PubMed1989

Modification of ornithine decarboxylase activity by adrenergic stimulation in cultured chicken spleen cells.

1. In vivo, adrenergic agonists promote an increase of ornithine decarboxylase activity (ODC) in chicken spleen, as opposed to a decrease in thymus and bursa of Fabricius. The increase is not due to the cell fraction separated on Lymphoprep, i.e. the spleen cells, but it could be due to the macrophages. 2. With spleen cells in culture, a marked increase of ODC activity is observed during the first 3 hr, followed by a decrease. 3. cAMP drastically decreases after 10 min in culture. 4. Adrenergic agonists promote a decrease of activity, both alpha and beta receptors being involved in these modifications. TPA promotes partial desensitization. 5. Selenite, which in vivo has the same effect as epinephrine, enhances ODC activity in culture. Propranolol partially counteracts this effect, while prazosin has a synergistic effect. TPA partially desensitizes spleen cells to selenite.

Adrenergic alpha-Agonists↗
PubMed1989

Polyamines in lymphocytes from patients infected by human immunodeficiency virus.

Lymphocytes from patients with antibodies against the AIDS associated human immuno-deficiency virus (HIV-1) have elevated concentrations of polyamines. Spermidine and spermine are similar in amount in patients with Persistent Generalized Lymphadenopathy (PGL) and overt AIDS, while putrescine is much higher in the latter. Spermidine-acetyltransferase activity is also increased in lymphocytes from patients with PGL. Diamine-oxidase activity is decreased in serum of patients with PGL, but not in those with AIDS.

Acetyltransferases↗
PubMed1989

[Polyamines in tumors of the oral cavity].

The polyamines putrescine, spermidine and spermine are essential for normal growth and differentiation and the activity of the enzymes participating in their synthesis and catabolism are markedly modified in actively proliferating cells in vitro and in vivo. In some neoplastic cells a good correlation is observed between polyamine concentration and histology, so that a potential usefulness as diagnostic and prognostic markers has been suggested. In the study of ornithine decarboxylase, S-adenosylmethionine decarboxylase and spermidine acetyltransferase activities and of polyamine concentration in tumors of the oral cavity we have shown a marked increase in the tumor cells. In the epulis the ratio spermidine/spermine is inverted, so that it could be useful in differentiating benign from malign tumors.

Adenosylmethionine Decarboxylase↗