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I Azevedo

Publications and source records attributed to I Azevedo.

At least 37 records · Page 2Linked to original sources
PubMed2000

Differences between duodenal and jejunal rat alkaline phosphatase.

OBJECTIVES: The aim of this study was to kinetically characterize rat tissue-nonspecific-alkaline phosphatase (TNS-ALP) and intestinal (duodenal- and jejunal-IALP), and to determine the effect of substances known to affect phosphorylation/dephosphorylation on TNS- and IALP activity. DESIGN AND RESULTS: The ranking order of ALP activity (K(enzyme)) was duodenal mucosa (IALP) > jejunal mucosa (IALP) > kidney (TNS-ALP) > brain (TNS-ALP). Levamisole was found to produce a concentration-dependent decrease of ALP activity in kidney and brain. However, levamisole had no effect on duodenal ALP activity and produced a concentration-dependent increase on jejunum ALP activity. In brain and jejunum homogenates, octreotide, a stable somatostatin analogue, produced a concentration-dependent increase in ALP activity. In relation to duodenum ALP activity, octreotide produced a biphasic effect.Reverse transcription-polymerase chain reaction showed the presence of IALP-I mRNA both in duodenal and jejunal mucosa, but IALP-II only in duodenal mucosa. CONCLUSIONS: The results show that duodenal- and jejunal-IALP differ in kinetic parameters and in drug sensitivity. Thus, we can speculate on a different physiologic role for duodenal- and jejunal-IALP, particularly in relation to their dephosphorylation targets.

Adjuvants, Immunologic↗
PubMed2000

Physiologic concentrations of bile salts inhibit rat hepatic alkaline phosphatase but not the intestinal isoenzyme.

OBJECTIVE: The effect of bile salts on alkaline phosphatase (EC 3.1.3.1) activity from Wistar rat liver, duodenum, jejunum, and serum was investigated. DESIGN AND RESULTS: For concentrations higher than 1 mM conjugated bile salts (glycocholate, glycochenodeoxycholate, taurocholate, taurodeoxycholate, and taurochenodeoxycholate) inhibited hepatic ALP but, up to concentrations of 10 mM, had no effect on intestinal ALP. Also cholate, deoxycholate, and chenodeoxycholate, within the same concentration range, did not have any effect on intestinal ALP. ALP inhibition induced by conjugated bile salts was significantly higher in serum of starved rats than in serum of fed animals, what is in good agreement with the known higher proportion of hepatic ALP and lower proportion of intestinal ALP in serum of starved rats. CONCLUSIONS: Bile salts can, thus, be used to help discriminating between tissue-nonspecific and intestinal ALP isoenzymes and identifying pathologic conditions where the relative quantities of these isoenzymes are altered in serum. Inhibition of hepatic ALP by physiologic concentrations of bile salts may bear some relation to the bile salts effects on their own enterohepatic circulation and/or biosynthesis.

Alkaline Phosphatase↗
PubMed2000

Effect of P-glycoprotein modulators on alkaline phosphatase activity in cultured rat hepatocytes.

Alkaline phosphatases (orthophosphoric-monoester phosphohydrolase, E. C. 3.1.3.1) are a group of nonspecific phosphomonoesterases located primarily in the plasma membrane of the cells in which they occur [1]. It was recently demonstrated that alkaline phosphatase (ALP) concentration in different tissues is positively correlated with the extent of exchange surface per unit volume of the tissue, suggesting an association between ALP and transport systems [2]. Moreover, several groups [3,4,5] obtained evidence of an involvement of ALP in the modulation of P-glycoprotein activity in hepatocytes. The aim of the present study was to determine the putative influence of compounds known to modulate P-glycoprotein-mediated transport on hepatic ALP activity, by using primary cultured rat hepatocytes. The K(m) and V(max) values of ALP were determined (657.2 microM (306.8-933.1) and 32.0+/-1.5 nmol mg protein(-1) min(-1), respectively). Vanadate and corticosterone concentration-dependently reduced ALP activity, producing maximal reductions of 79% (100 microM) and 71% (100 microM), respectively. The IC50's were found to be 7.9 microM (2.1-29.5 microM) and 2.4 microM (0.2-35.2 microM), respectively. Cyclosporin A, verapamil, octreotide, kaempferol, daunomycin and genistein produced a concentration-dependent increase in ALP activity. ALP activity was maximally increased to 253%, 390%, 180%, 487%, 449% and 193% of control in the presence of 100 microM cyclosporin A, 50 microM verapamil, 10 microM octreotide, 100 microM kaempferol, 100 microM daunomycin and 1 microM genistein, respectively. The results show that all P-glycoprotein modulators tested were able to significantly affect the activity of hepatic-ALP. These effects on ALP activity may contribute to the modulation of P-glycoprotein activity by these drugs.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Characterization of the efflux of the organic cation MPP+ in cultured rat hepatocytes.

The aim of this study was to characterize the efflux of organic cations from primary cultured rat hepatocytes, using 1-methyl-4-phenylpyridinium (MPP+) as a model compound. The efflux of [3H]MPP+ was temperature dependent, and pH and metabolic inhibition independent. It was either strongly reduced (verapamil, vinblastine and rhodamine123) or only moderately reduced (daunomycin) by other organic cations. The anti-P-glycoprotein antibody UIC2 (20 microg/ml) and the P-glycoprotein inhibitors vanadate and cyclosporine A had no effect on [3H]MPP+ efflux. Decynium22 and corticosterone, known inhibitors of rat Organic Cation Transporter 1 (rOCT1), markedly reduced [3H]MPP+ efflux. The uptake of [3H]MPP+ into hepatocytes, known to be mediated by rOCT1, was inhibited by verapamil and vinblastine (IC50s of 2.6 and 34.4 microM, respectively). In conclusion, [3H]MPP+ efflux from primary cultured rat hepatocytes appears to be mediated by rOCT1, a polyspecific organic cation transporter. Moreover, our results do not support the involvement of P-glycoprotein or of an organic cation/proton antiporter in the efflux of [3H]MPP+.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Inhibition by levamisole of the organic cation transporter rOCT1 in cultured rat hepatocytes.

Levamisole is known to be subject to hepatic removal and metabolism and to biliary excretion. The aim of our work was to study the mechanism involved in the removal of this compound by the liver. For this purpose, we studied the influence of levamisole on the uptake and efflux of the model organic cation 1-methyl-4-phenylpyridinium (MPP(+)) by primary cultured rat hepatocytes. Levamisole (500 microm) was found to produce a strong inhibition (to 31+/-2% of control) of [(3)H]MPP(+)uptake. Moreover, efflux of [(3)H]MPP(+)was also potently reduced by levamisole (500 microm). Our results show that levamisole interferes with an hepatic organic cation transporter which accepts MPP(+)as a substrate. This mechanism most probably corresponds to rOCT1, and it might be responsible for the hepatic removal of levamisole from the blood circulation.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Comparison between uptake2 and rOCT1: effects of catecholamines, metanephrines and corticosterone.

Active and specialized transmembrane transport systems are responsible for the functional inactivation of catecholamines. Uptake2, the classical extraneuronal uptake system, and rOCT1, a recently cloned organic cation transporter, share a number of properties. The present study was undertaken to investigate putative differences between these two transporters that might clarify their relative physiological roles. Uptake of [3H]MPP+ ([3H]1-methyl-4-phenylpyridinium) by Caki-1 cells (to study uptake2) and by primary cultured rat hepatocytes (to study rOCT1) was kinetically and pharmacologically characterized. In both cell types, [3H]MPP+ was avidly taken up and accumulated. All compounds tested (catecholamines, metanephrines and corticosterone) inhibited [3H]MPP+ uptake, albeit with different potencies. In Caki-1 cells, the ranking order of inhibitory potency was: (-)isoprenaline > (-)adrenaline >> (-)noradrenaline > dopamine. Metanephrine and normetanephrine were equipotent. Corticosterone had an IC50 of 102 nM. In cultured hepatocytes, the ranking order of inhibitory potency was: (-)isoprenaline > dopamine > (-)adrenaline >> (-)noradrenaline. Metanephrine was about seven times more potent than normetanephrine. Corticosterone had an IC50 of 72 microM, being about 700-fold less potent in inhibiting rOCT1 than uptake2. The results showed that uptake2 and rOCT1 can be clearly distinguished on a functional basis. On the one hand, uptake2 prefers adrenaline among the endogenous catecholamines, whereas rOCT1 has similar affinity for adrenaline and dopamine. On the other hand, corticosterone and normetanephrine are significantly more potent in inhibiting uptake2 than rOCT1. The results are compatible with a possible physiological role of corticosteroids in the modulation of adrenaline effects in tissues equipped with uptake2, without significant interference with the hepatic and renal excretion of catecholamines.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Dynamics of experimental vasogenic brain oedema in the rat: changes induced by adrenergic drugs.

The effects of adrenergic drugs on the formation and resolution of cerebral oedema in a rat model of cold-induced vasogenic brain oedema were studied. Evans blue dye extravasation, water content and ultrastructural alterations (pinocytotic vesicle formation in capillary endothelial cells and apparent water accumulation in the brain parenchyma) were evaluated in parietal cortex. Previous administration of the alpha-adrenoceptor antagonist phenoxybenzamine produced a reduction of Evans blue extravasation and water content, diminished vesicle formation and reduced water accumulation. Previous administration of the beta2-adrenoceptor agonist clenbuterol reduced Evans blue extravasation and water content, but did not change vesicle frequency. The effects of clenbuterol on Evans blue passage to the brain were blocked by timolol (beta-adrenoceptor antagonist) but not by metoprolol (selective beta1-adrenoceptor antagonist). When given after the application of cold, clenbuterol was also able to reduce Evans blue and water content in the brain. Isoprenaline (beta-adrenoceptor agonist that does not cross the blood-brain barrier) showed a reduction in Evans blue extravasation only when given intracerebroventricularly. Vinblastine (a drug that prevents vesicle formation) produced a reduction of the amount of pinocytotic vesicles. We conclude that there is an influence of the central adrenergic nervous system on the formation and/or resolution of vasogenic brain oedema and that the alterations on water movement and Evans blue transport mediated by adrenergic drugs seem to be due, at least in part, to alterations of pinocytotic activity in capillary endothelial cells.

Adrenergic Agents↗
PubMed1998

Postnatal development of organic cation transport in the rat liver.

Previous studies have demonstrated that the small permanently charged organic cation 1-methyl-4-phenylpyridinium (MPP+) is avidly taken up by rat hepatocytes. The aim of this study was to characterise the postnatal development of hepatic uptake of organic cations, using the model compound MPP+. Accumulation of [3H]MPP+ by liver slices obtained from rats ranging from 1 day to 7 weeks was measured, and the effect of a series of compounds on [3H]MPP+ uptake was examined. The accumulation of [3H]MPP+ by liver slices was similar in adult (87.5 +/- 19.9 pmol g-1; n = 7) and neonatal rats (110.6 +/- 11.5 pmol g-1; n = 15). Verapamil, quinidine (100 microM) and progesterone (200 microM) produced very marked reductions on [3H]MPP+ uptake at all ages, and the inhibitory effect of verapamil and quinidine was maximum in livers from 1-day-old rats. Bilirubin (200 microM) significantly reduced [3H]MPP+ uptake by liver slices from 1 day, 1 week and 7-week-old rats. However, [3H]MPP+ accumulation was reduced by cimetidine, vinblastine and daunomycin (100 microM) in 1-day-old rats, but the effect of these drugs disappeared as the animals age increased. These findings demonstrate that hepatic organic cation uptake capacity is remarkably high shortly after birth and suggest that at least two distinct uptake mechanisms are involved in this process. These uptake systems are the type I hepatic transporter of organic cations, active from birth to adulthood, and P-glycoprotein, active only in very young rats.

1-Methyl-4-phenylpyridinium↗
PubMed1998

Effect of mechanogated membrane ion channel blockers on experimental traumatic brain oedema.

Traumatic head injury leads to marked swelling of endothelial cells, both in human patients and in Marmarou's rat model. We used this model to test the hypothesis of mechanogated ion channels being involved in the formation of traumatic brain oedema. All mechanogated channel blockers tested (gadolinium, amiloride, gentamicin) significantly reduced traumatic brain oedema evaluated by Evans blue extraction ratio, either when given 15 minutes before or 30 minutes after induction of trauma (evaluation 2 hours after trauma). These results clearly support our hypothesis, opening a new way for the investigation of the treatment of a clinical situation endowed with high morbidity and mortality.

Amiloride↗
PubMed1998

Cerebral edema associated with meningiomas: the role of peritumoral brain tissue.

We undertook a morphological study of small pieces of peritumoral brain tissue removed from seven patients with meningiomas submitted to surgery. All patients had cerebral edema, as shown by preoperative C.T. and N.M.R.. Control specimens were obtained from five patients undergoing ventriculo-peritoneal shunt. The tissue fragments were fixed in glutaraldehyde-osmium and embedded in Epon. In semi-thin sections observed under light microscopy peritumoral endothelial cells exhibited voluminous cytoplasm and nucleus. Morphometrical evaluation confirmed that these endothelial cell nuclei were significantly larger than controls. Under the electron microscope those cells showed nuclei rich in euchromatin and cytoplasm rich in pinocytotic vesicles. The morphological changes observed suggest a process of dedifferentiation of brain peritumoral capillary cells and are compatible with an increase in permeability. Both events, which may be due to diffusion of a tumoral vascular permeability factor, favour the hypothesis that peritumoral brain tissue contributes to edema fluid that accumulates around meningiomas.

Adult↗
PubMed1998

Uptake of [3H]-adrenaline by freshly isolated rat hepatocytes: putative involvement of P-glycoprotein.

1. The liver has an important role in the elimination of circulating catecholamines. Adrenaline and noradrenaline are avidly taken up and metabolized by rat hepatocytes, but the nature of the mechanism(s) involved remains partially unknown. 2. The aim of this work was to further characterize the uptake of catecholamines by isolated rat hepatocytes. For that purpose, the effects of a series of chemically unrelated compounds, including substrates/inhibitors of P-glycoprotein, on [3H]-adrenaline removal was investigated. 3. Freshly isolated rat hepatocytes were incubated in Krebs-Henseleit solution at 37 degrees C with 50 nM [3H]-adrenaline for 5 min. Removal of [3H]-adrenaline was calculated as the sum of [3H]-adrenaline present in cells, and its [3H]-metabolites present both in cells and in the incubation medium. Radioactivity was determined by liquid scintillation counting. 4. Verapamil, quinidine, 1-methyl-4-phenylpyridinium, cimetidine, tetraethylammonium, d-tubocurarine, taurocholate, daunomycin and vinblastine (100 microM), progesterone, bilirubin (200 microM), vecuronium (45 microM), and amiloride (1 mM) significantly reduced [3H]-adrenaline removal. On the other hand, cyclosporine A (100 microM) apparently had no effect. The O-methylated metabolite of adrenaline, metanephrine (30 microM), produced a 40% reduction of [3H]-adrenaline removal. 5. Vinblastine and corticosterone produced concentration-dependent decreases of [3H]-adrenaline removal, with IC50 values of 23.3 and 116.0 microM, respectively. 6. In the presence of verapamil (100 microM), desipramine (1 microM) was devoid of significant effect on [3H]-adrenaline removal. Corticosterone (40 microM) produced a further decrease (+/- 50%) on removal of the [3H]-amine. 7. Removal of [3H]-adrenaline by isolated cells did not show pH-dependence since an increase or a decrease in the pH of incubation medium (to 8.2 or 6.2, respectively) caused no alteration of that parameter. 8. In conclusion, [3H]-adrenaline is efficiently removed and subsequently metabolized by isolated rat hepatocytes. The results are compatible with the involvement of multiple mechanisms in the hepatic uptake of this amine including the type I and the type II hepatic transporters for organic cations, uptake2 and P-glycoprotein.

1-Methyl-4-phenylpyridinium↗
PubMed1998

[CHARGE association].

Posterior choanal atresia is a congenital malformation which can occur isolated or in combination to additional malformations. In CHARGE association the other anomalies are: coloboma, heart disease, retarded development/growth or central nervous system abnormalities, genital hypoplasia or hypogonadism and ear abnormalities or deafness. The authors present three cases of CHARGE association and they also review the clinical findings required for the diagnosis.

Abnormalities, Multiple↗
PubMed1998

[The role of external radiotherapy in the treatment of medullary carcinoma of the thyroid].

Medullary carcinoma of the thyroid represents 3 to 10% of all thyroid cancers. Surgery is the main treatment. External beam radiotherapy has a fundamental role in the treatment of residual disease following surgery, in cases of cervical node involvement, and in unresectable tumors. Between 1975 and 1993, 12 patients with medullary carcinoma of the thyroid were treated at the Department of Radiotherapy of the Portuguese Institute of Oncology in Oporto. Nine of these patients (75%) were male and 3 (25%) female, ranging from 24 to 80 years of age (mean = 43). All of them had residual tumor after surgery and underwent treatment with external beam radiotherapy. The follow-up period ranged from 36 to 180 months, with a median of 78 months; 8 patients (66.7%) are alive, 5 of them show no evidence of disease. Average survival was 70 months, and 4 patients (33%) died with metastatic disease. The aim of this paper is to analyse the role of external beam radiotherapy in local control of these tumors, with a brief review of the literature.

Adult↗
PubMed1997

Angiomatoid fibrous histiocytoma of the arm treated by radiotherapy for local recurrence--case report.

The Angiomatoid Fibrous Histiocytoma is a rare tumor of soft tissues, which occurs mainly in children and young adults, with low malignancy grade. It has the capacity of local recurrence, but rarely metastizes. It is frequently difficult to differentiate this from vascular tumors, namely hemangioendotheliomas and angiosarcomas, or simply organized hematomas. The authors present a case of a patient with an angiomatoid fibrous histiocytoma of the arm, treated with radiotherapy after three postsurgical recurrences.

Arm↗
PubMed1997

Squamous cell carcinoma of the cervix metastatic to the spleen--case report.

Squamous cell carcinoma of the cervix metastatic to the spleen is an uncommon occurrence which has only been reported in small numbers in autopsy series. We present a case of a 47-year-old patient with a Stage IIb carcinoma of the cervix, treated with radiotherapy in 1990. Four years after completion of primary treatment she presented with a voluminous left hypochondrium and epigastrium mass. An exploratory laparotomy was performed and a splenic cyst 19 cm in diameter was found. The pathological examination revealed metastatic squamous cell carcinoma of the cervix in the spleen. Peritoneal washings were positive for malignant cells, due to incidental rupture of the cyst capsule. The patient received six courses of chemotherapy with a palliative intent and is alive, without further evidence of disease, 15 months posttreatment. To our knowledge this is the only case reported in the literature of squamous cell carcinoma of the uterine cervix metastatic to the spleen, diagnosed clinically as the only site of distant spread.

Carcinoma, Squamous Cell↗
PubMed1997

Ultrastructural study of brain microvessels in patients with traumatic cerebral contusions.

Brain tissue from 11 patients with traumatic cerebral contusions submitted to surgery was studied. Control biopsy specimens were obtained from 5 patients undergoing ventriculo-peritoneal shunts for "communicating" hydrocephalus. After collection, the small fragments were fixed by immersion in glutaraldehyde-osmium and embedded in Epon. Semi-thin sections stained with toluidine blue were observed with the light microscope. Thin sections stained with lead citrate and uranyl acetate were observed using a Jeol electron microscope. In tissues from patients with head trauma a clear space most probably corresponding to fluid accumulation was systematically observed around microvessels. Ultrastructurally endothelial cells from these specimens exhibited signs of marked intracellular oedema, tight junctions being intact. Pinocytotic activity was increased, mainly at the abluminal surface. Swelling of astrocytic perivascular processes and the appearance of macrophagic cells with voluminous lysosomes were also observed. The authors conclude that the oedema of endothelial cells probably represent a central fact in the pathophysiology of traumatic brain oedema and speculate on the putative involvement of stretch-activated receptors in this condition.

Adult↗