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Biomedical subjects

R Ientile

Publications and source records attributed to R Ientile.

At least 55 records · Page 3Linked to original sources
PubMed1996

Magnesium levels in plasma, erythrocyte, and platelet in hypertensive and normotensive patients with type II diabetes mellitus.

The authors, by means of a recently introduced method, evaluated the intraplatelet concentrations of magnesium in 45 normotensive patients with type II diabetes mellitus, in 45 hypertensive diabetics and in 15 healthy controls. They also evaluated plasma and erythrocyte concentrations of the cation through direct current plasma spectrometer. Both normotensive and hypertensive diabetics showed a reduction in plasma, erythrocyte, and platelet concentrations of magnesium compared to controls. On the contrary, no significant difference was found between hypertensive and normotensive diabetics with regard to plasma and erythrocyte magnesium, whereas intraplatelet assay of the ion pointed out significantly lower concentrations of magnesium in hypertensive compared to normotensive patients (56.4 +/- 9.0 vs 60.7 +/- 10.2 micrograms/10(8) cells--p < 0.05). The authors believe that intraplatelet assay of magnesium may be the most reliable method for the evaluation of the cation in hypertensive diabetics, probably because platelets share common features with smooth muscle cells, including the alpha-2-adrenoceptor cyclase system and a coupling mechanism concerning the calcium-dependent contraction.

Aged↗
PubMed1996

Altered platelet magnesium and plasma and urinary soluble form of intercellular adhesion molecule I (sICAM-1) concentrations in insulin dependent diabetes mellitus (IDDM) patients with microalbuminuria.

Magnesium concentrations in plasma, erythrocyte and platelet, and plasma and urine levels of the soluble form of Intercellular Adhesion Molecule-1 (sICAM-1) were evaluated in subjects with insulin dependent diabetes mellitus (IDDM) with or without microalbuminuria, and in a control group of healthy subjects. Using a recently introduced technique, we found that magnesium concentrations in platelets in diabetic subjects with microalbuminuria were lower than in diabetics with normal albuminuria (1.859 +/- 0.47 vs 2.065 +/- 0.62 mumol/10(8) cells; P < 0.05). Moreover, IDDM subjects had higher plasma sICAM-1 levels than control subjects; no difference, however, was found between sICAM-1 concentrations in the two groups of diabetics. An inverse correlation was found between intraplatelet magnesium and plasma sICAM-1 levels (r = - 0.64; P < 0.05) in the diabetics with microalbuminuria. It is concluded that the reduced intraplatelet magnesium content may contribute to the progression of the vascular complications in IDDM subjects with microalbuminuria.

Adolescent↗
PubMed1992

Polyamines are involved in retinoic acid-mediated induction of tissue transglutaminase in human peripheral blood monocytes.

The differentiation of human peripheral blood monocytes (HPBM) into macrophages, when cultured in vitro, has been associated with an increase in the expression of tissue transglutaminase (TGc). Retinoic acid (RA) addition to 5-day-old cultured monocytes, 36 h later induced about 5-folds increase of TGc content. The preliminary exposure of cultured monocytes to alpha-difluoromethylornithine (DFMO) significantly reduced TGc induction caused by RA. DFMO alone does not induce significant changes in the time-course of TGc activity. In cultured monocytes exposed to DFMO, putrescine and spermidine, but not spermine were significantly depleted. The supplementation of putrescine (1 mM) or spermidine (0.5 mM) to culture medium reversed the inhibiting effect of DFMO on RA-mediated induction of TGc. However, the addition of polyamines in the absence of RA or DFMO did not mimic the induction of TGc by RA. We conclude that TGc induction by RA during in vitro maturation of monocytes to macrophages may be modulated by polyamine availability.

Cell Differentiation↗
PubMed1988

Glucocorticoid regulation of spermidine acetylation in the rat brain.

The effect of glucocorticoids on polyamine metabolism has been elucidated further by measuring putrescine, spermidine, and spermine levels as well as ornithine decarboxylase, S-adenosylmethionine decarboxylase, and N1-acetylspermidine transferase activities in the hippocampus, cerebellar cortex, vermis, and deep nuclei of adrenalectomized rats. At 6 h after corticosterone or dexamethasone administration, the specific activities of ornithine decarboxylase and N1-acetylspermidine transferase showed the greatest increases in all brain tissues examined, and at 12 h, S-adenosylmethionine decarboxylase activity was not increased significantly. The hippocampus and cerebellar regions displayed different responses to corticosterone and dexamethasone, corresponding to the distribution of glucocorticoid and mineralocorticoid receptors. Corticosterone and dexamethasone increased ornithine decarboxylase and N1-acetylspermidine transferase activities in a dose-dependent manner, with dexamethasone being more active than corticosterone in all tissues. However, estradiol, progesterone, testosterone, and aldosterone were only active at doses greater than 5 mg/kg. The great increases in ornithine decarboxylase and N1-acetylspermidine transferase activities were accompanied by a marked increase in putrescine level and a small decrease in spermidine level. Our data confirm that the hippocampus and cerebellum are glucocorticoid target tissues and suggest that the increase in the content of putrescine, following acute treatment with glucocorticoids, is dependent on ornithine decarboxylase as well as N1-acetylspermidine transferase induction.

Acetylation↗
PubMed1987

Cerebral GABAergic control of arterial blood pressure and heart rate in diabetic rats.

Cardiovascular responsiveness to intracerebroventricular (icv) administration of dopamine (50, 100 and 200 micrograms/kg), muscimol (1 and 2 micrograms), and ethanolamine-O-sulphate (EOS; 5, 10, 20 and 40 mumol) as well as GABA content in several brain areas were examined in rats, made diabetic by an intravenous (iv) injection of streptozotocin (STZ; 40 mg/Kg). Citrate buffer (pH 4.5) treated animals were used as controls. Experiments were carried out in conscious rats with chronically implanted icv cannulae and iv and intraarterial catheters, 1 and 3 weeks after STZ injection. Diabetic rats exhibited: 1) higher hyperglicaemia after 1 week than after 3 weeks; 2) normal mean arterial pressure (MAP) both after 1 and 3 weeks, and 3) bradycardia only after 3 weeks. Icv injections of muscimol, a GABA receptor agonist, and EOS, an inhibitor of GABA breakdown, caused a dose-dependent decrease in MAP and heart rate (HR), which was significantly higher than that elicited in control animals. GABA content was reduced in the hypothalamus (already after 1 week), and in the brainstem (but only after 3 weeks). No changes in GABA content were detected in other brain areas. Icv injection of dopamine elicited a dose dependent decrease in MAP and HR either in diabetic or in control rats, with no difference between groups. The results suggest that diabetes alters cerebral GABAergic control of arterial blood pressure and heart rate in the rat.

Animals↗
PubMed1986

Polyamine localization and biosynthesis in chemically fractionated rat retina.

For elucidation of polyamine localization and biosynthesis in various cell types of rat retina, the putrescine, spermidine, and spermine contents as well as the ornithine decarboxylase and S-adenosylmethionine decarboxylase activities have been measured in retinal cell layers obtained by the selective cytotoxic action of iodoacetate on photoreceptor cells and of monosodium glutamate on higher-order retinal neurons. A notable depletion only in spermine content was associated with loss of the visual cell layer. Total ornithine decarboxylase and S-adenosylmethionine decarboxylase activities per retina were significantly lower in all chemically fractionated tissue, but loss of the photoreceptor layer produced the greatest decrease. The specific activities of these enzymes did not show marked changes in rat retinas deprived of inner neurons. The data support the suggestions that polyamine synthesis, storage, and catabolism have different distributions in the retinal layers and that the spermine levels and the high value of the spermine/spermidine molar ratio might depend essentially on the proportion of rods to cones.

Adenosylmethionine Decarboxylase↗
PubMed1985

gamma-Aminobutyric acid metabolism and behavioral effects after intraventricular injection of spermine in chicks.

Effects of intraventricularly injected spermine on behavior and electrocortical activity and gamma-aminobutyric acid (GABA) metabolism after a single dose of 1.13 mumol/animal were studied. Decrease in locomotor activity, sedation or sleep, and electrocortical synchronization that lasted approximately 2 h were observed. In addition spermine caused a significant increase in GABA content in diencephalon and brainstem, 30 min after administration. Concomitantly a significant increase of glutamate decarboxylase (GAD) activity was observed in cerebral hemispheres, diencephalon, and brainstem. Reduction in gamma-aminobutyrate: alpha-oxoglutarate amino-transferase (GABA-T) levels occurred in the diencephalon along with a significant increase of GABA-T in the brainstem. The present results demonstrate that spermine has the capacity to affect GABA metabolism and are in favor of the suggestion that endogenous polyamines may modulate GABAergic mechanisms.

4-Aminobutyrate Transaminase↗
PubMed1985

Effect of intraventricular putrescine on adenosylmethionine decarboxylase in rat hypothalamus and caudate nucleus.

Effects of intracerebroventricularly injected putrescine on adenosylmethionine decarboxylase activity in rat hypothalamus and caudate nucleus were studied. Doses that lacked the capacity to produce behavioral and electrocortical epileptogenic disorder caused a significant activation of enzyme occurring between 10 and 15 min after injection. The changes in hypothalamic and caudate nucleus enzyme activity after putrescine administration were dose-dependent, and they supported the assumption that limiting putrescine concentration in vivo may play a role in adenosylmethionine decarboxylase regulation.

Adenosylmethionine Decarboxylase↗
PubMed1984

Phenolic and tyrosyl ring deiodination in thyroxine from rat retina during postnatal development.

To elucidate tetraiodothyronine (T4) metabolism in developing rat retina 5-monodeiodinating and 5'-monodeiodinating activities were studied. T4 was incubated with aliquots of homogenate or crude primary subcellular fractions, and the 3,3',5'-triiodothyronine (rT3) or 3,5,3'-triiodothyronine (T3) produced were measured by radioimmunoassay. Reaction rates were dependent on incubation time, tissue amount, temperature and pH. The optimum pH values were 7.8 and 7.2 respectively for rT3-forming and T3-forming systems. Conversion of T4 to either T3 or rT3 was dependent on dithiothreitol concentration, and the T4-5'-deiodinating activity was inhibited by propylthiouracil. Deiodinase activities were mainly found in the crude microsomes. The retinal 5'-monodeiodination rate of T4 was immeasurably low by the 2nd day and the highest values were reached on 15th day of postnatal development. On the other hand deiodination of the T4 tyrosyl ring shows a progressive decline from birth, and adult values were reached on the 15th day. Data support the hypothesis that, in developing rat thyroxine, phenolic and tyrosyl-ring deiodinase activities are present in the retina and their reciprocal changes may regulate morphological and biochemical cell maturation.

Animals↗
PubMed1984

Retina maturation following administration of thyroxine in developing rats: effects on polyamine metabolism and glutamate decarboxylase.

The effects of subcutaneous daily treatment with thyroxine on cell proliferation, differentiation, polyamines, and gamma-aminobutyric acid metabolism in the rat retina were studied during the first 20 postnatal days. The retinal layers of the treated rats displayed an enhanced cell differentiation which reached its maximum 9-12 days from birth; but this effect stopped very quickly and was finished by the 20th postnatal day. Primarily there was an increase in ornithine decarboxylase activity which was accompanied by an increase in putrescine, spermidine, and spermine levels. S-Adenosylmethionine decarboxylase was induced later than ODC; corresponding with the enhanced synaptogenesis, glutamate decarboxylase increased 15-fold between the fourth and 15th days. Our data are consistent with the hypothesis that thyroxine may exert some of its effects by inducing the enzymes which regulate polyamine metabolism and synaptogenesis.

Adenosylmethionine Decarboxylase↗
PubMed1983

Lack of relation between dopaminergic and gabaergic mechanisms in chick retina.

The effects of apomorphine and bromocriptine on GABA content, GAD and GABA-T activities in the chick retina, both in conditions of a light cycle of 12 h/day and in conditions of light deprivation for 72 h, were studied. In addition, the effects of a treatment with 2 neuroleptics, having a different action on dopamine receptors, i.e. haloperidol and sulpiride, on the same biochemical parameters were examined. The present results show that all the pharmacological manipulations at the dopaminergic transmission by means of agonists and antagonists at dopamine receptors did not affect GABAergic mechanisms in the chick retina and seem to suggest a lack of relations between dopaminergic and GABAergic mechanisms at this level.

4-Aminobutyrate Transaminase↗
PubMed1982

Effects of apomorphine on glutamate decarboxylase activity in chick paleostriatum augmentatum.

In young chicks the effects of two different doses of apomorphine, a small dose, producing behavioural and electrocortical sleep and a larger one producing arousal, on GABA content, GAD and GABA-T activities in the paleostriatum augmentatum were studied. The small dose of apomorphine did not affect GABAergic mechanisms in this area, whereas the dose producing behavioural and electrocortical arousal significantly increased GAD activity and GABA content. The results of the present experiments are in favour of an interaction between dopaminergic and GABAergic mechanisms in the avian paleostriatum augmentatum.

Animals↗
PubMed1982

S-adenosylmethionine decarboxylase levels in rat retina during postnatal development.

S-Adenosylmethionine decarboxylase from rat retina is similar to that isolated from other rat tissues with regard to kinetic parameters, pH optimum, putrescine requirement, and sensitivity to spermine. The enzymic activity increases during the first 7 days of postnatal life but decreases until the 20th day. After this period AdoMet decarboxylase activity increases, to reach the highest values at the 90th day. This behavior suggests that such enzymic activity is responsible for spermidine and spermine levels in rat retina and that a high content of retinal spermine might have a role in the photoreceptor outer segment renewal.

Adenosylmethionine Decarboxylase↗