Biomedical subjects

C Pratesi

Publications and source records attributed to C Pratesi.

At least 55 records · Page 3Linked to original sources

PubMed1996

Further studies on the mechanism of the mineralocorticoid action of licorice in humans.

The pathogenesis of pseudohyperaldosteronism from licorice has been evaluated in 6 male volunteers taking daily 7 g of a commercial preparation of licorice for 7 days, corresponding to an intake of 500 mg/day of glycyrrhizic acid. Pseudohyperaldosteronism was evident during the treatment (increase of body weight, suppression of plasma renin activity and plasma aldosterone, reduction of serum potassium). The ratio (tetrahydrocortisol + allo tetrahydrocortisol)/tetrahydrocortisone in urine increased in 5 cases after 3 days of treatment, without an increase of plasma mineralocorticoid activity (PMA). In the 6th case the urinary ratio was unchanged and PMA increased from the pretreatment value. After 7 days of therapy the ratio remained high and PMA was not measurable in 3 cases, while in the other 3 cases the ratio returned to pretreatment and PMA was higher than pretreatment value. We conclude that the pseudohyperaldosteronism from licorice is initially related to decreased activity of 11 beta-hydroxysteroid-dehydrogenase and afterwards also a direct effect of licorice derivatives on mineralocorticoid receptors becomes evident in some cases. In other cases however the effect on the enzyme is prevailing probably due to individual factors.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1996

The [Ni-Fe] hydrogenase from the thermophilic bacterium Acetomicrobium flavidum.

Biochemical analysis of the soluble hydrogenase from the thermophilic organism Acetomicrobium flavidum revealed that the enzyme is an alpha 2 beta 2 tetramer, with the alpha and beta subunits having a molecular mass of 50 kDa and 25 kDa, respectively. The most important biochemical properties of the enzyme are a specific activity of 77 mumol min-1 (mg protein)-1, a Km for methylviologen of 0.2 mM, a pH optimum of 7.5 and a T50 of about 70 degrees C. In addition, the enzyme is remarkably stable to oxygen inactivation, retaining full activity after 24 h exposure to air. By using oligodeoxynucleotides designed on the basis of the N-terminal sequences of the two subunits, the corresponding genes have been isolated and sequenced. When compared to the other hydrogenases so far characterized, the A. flavidum hydrogenase appears to be a typical [Ni-Fe] enzyme. The hydrogenase was expressed in Escherichia coli at high levels in a soluble form but it was not active. The analysis of the recombinant large subunit showed that it was not post-translationally processed at its C-terminus.

Amino Acid Sequence↗

PubMed1996

Routine ultrasound surveillance after carotid endarterectomy.

Ultrasounds (US) are employed in preoperative carotid disease diagnosis and in carotid endarterectomy (CEA) follow-up. The authors present their experience about postoperative modifications in CEA site with US evaluation with particular interest in restenosis. Clinical and instrumental examinations were performed at intervals 1, 3, 6, 12, and 24 months following surgery. Follow-up data were available on 189 CEAs. In 58 cases a primary closure was performed, whereas in the other 131 cases, a patch was applied. 15 restenosis (7.9%) were seen during the follow-up control period with 2 cases of haemodynamic restenosis (1%). Good results were recorded with PTFE patch angioplasty (restenosis 4.4%), instead of vein (restenosis 14.2%) and a biosynthetic material called Omniflow (restenosis 9.5%). A vein patch dilatation was encountered in 13 applications (30.9%). In conclusion the routine application of US after carotid endarterectomy allowed us to monitor the evolution of the repair processes and of the stenotic lesions from the very beginning.

Angiography↗

PubMed1995

Pseudohypoaldosteronism: evaluation of type I receptors by radioreceptor assay and by antireceptor antibodies.

We have previously demonstrated a deficiency of mineralocorticoid receptors in pseudohypoaldosteronism, by radioreceptorassay. We now report findings with an antireceptor antibody derived from the immunogenic region of the receptor. Lymphocytes from normal controls and from two cases of pseudohypoaldosteronism previously shown to lack receptor binding were tested. After the plasma membrane of lymphocytes was permeabilized with methanol the cells were incubated with a 1:200 dilution of antibody followed by fluorescent antirabbit immunoglobulin mouse serum. After washing fluorescence was detected by microscopy and cytofluorimetry in both controls and patients with pseudohypoaldosteronism. Recent studies on mineralocorticoid receptor cDNA in pseudohypoaldosteronism have not established a mutation in the sequence. We thus suggest that the pathogenesis of pseudohypoaldosteronism is not related to an abnormality of the receptor but rather due to intracellular factor(s) which can block the binding of aldosterone to its receptor.

Adult↗

PubMed1995

Characterization of the locus encoding the [Ni-Fe] sulfhydrogenase from the archaeon Pyrococcus furiosus: evidence for a relationship to bacterial sulfite reductases.

The hydBGDA genes, which encode the four subunits beta, gamma, delta and alpha of the [Ni-Fe] hydrogenase from the archaeon Pyrococcus furiosus, have been isolated and sequenced using a PCR/IPCR-based strategy. From the sequence analysis it appears that the four structural genes are tightly linked and organized in a single transcription unit. The hydD and hydA gene products are related to the small and the large subunits of several archaeal and eubacterial [Ni-Fe] hydrogenases with an overall degree of sequence relatedness ranging from 35% to 50% (identity + similarity). In particular, the amino acid sequence motifs involved in the accommodation of nickel and iron-sulfur clusters are conserved. In addition, the database search revealed that the hydB and hydG gene products are homologous to the asrA- and asrB-encoded subunits of the sulfite reductase enzyme from Salmonella typhimurium. This is particularly interesting in view of the recent finding that the P. furiosus hydrogenase appears to be a bifunctional enzyme endowed with both proton- and sulfur-reducing activities.

Amino Acid Sequence↗

PubMed1995

The role of endovascular surgery in carotid restenosis.

PURPOSE: To report the immediate and long-term outcome of intraoperative balloon angioplasty for the treatment of recurrent disease in the internal carotid arteries (ICAs). METHODS: Three patients (2 males, 1 female; ages 53 to 70 years) presented with > 80% restenotic lesions (bilateral in one patient) at the distal aspect of a previous carotid endarterectomy. Two patients exhibited hemianopia, while the third was asymptomatic but had a contralateral ICA occlusion. All four lesions appeared smooth and fibrous on ultrasonography and were located high in the ICA. The location and morphology of the lesions made balloon angioplasty a more potentially successful treatment option. RESULTS: Through open access to the common carotid artery, the lesions were approached and dilated under fluoroscopic guidance with monitoring of evoked potentials. The lesions were successfully dilated as determined by control arteriography, and no complications were encountered. Over a follow-up period extending to 18 months in one patient and 24 months in the other two, ultrasound imaging and arteriography have shown no restenosis at any treatment site. CONCLUSIONS: Although caution is prudent when dealing with lesions in the cervical arteries, balloon angioplasty may have a role in treating surgically inaccessible restenotic carotid lesions that demonstrate a low potential for embolic complications. More experience with this technique will be required before widespread application of balloon angioplasty in the cervical vessels can occur.

Aged↗

PubMed1995

Diagnosis and surgical treatment of the carotid body tumors.

Resection of carotid body tumors can be difficult to perform because of its site, vascularity, arterial adherence and local cranial nerve involvement. Advances in vascular surgical technique have reduced the risks of perioperative complications such as carotid injury, stroke and death. From January 1980 to May 1994 20 patients (22 carotid body tumors) were examined. All patients except one were evaluated with a preoperative angiography. No preoperative embolization was performed. Thirteen patients underwent ultrasonography, nine a CT scan of the neck, 5 magnetic resonance scanning and two magnetic resonance angiography. One old patient refused operation. The authors report their experience on 21 carotid body tumor resections (14 Shamblin group I and 7 group II paragangliomas). Surgical technique is based on subadventitial resection (18 excisions) and 3 resections were performed from the medial surface of the carotid bifurcation which had been partially absorbed into the mass. In the last 15 operations intraoperative Somatosensorial Evoked Potential (SEP) monitoring has been used. Only two patient required arterial repair because intimal dissection and another patient needed vagus nerve section. The ligation of external carotid artery and internal carotid resection with graft replacement were never necessary in these patients. No early or late deaths occurred and no recurrences were detected at follow-up.

Adult↗

PubMed1994

Characterization of the surfactin synthetase multi-enzyme complex.

Three subunits (srfAORF1, srfAORF2 and srfAORF3) of the Bacillus subtilis surfactin synthetase multi-enzyme complex have been identified by SDS-PAGE and Western blot analyses. In accordance with the sequence analysis of the surfactin (srfA) operon, the protein subunits have a molecular mass of 402,000 Da, 401,000 Da and 144,000 Da, respectively. Confirmation of the identity of the proteins was obtained by analysing the total protein content of a number of mutant strains which harbour deletions or insertions either in the srfA promoter or in different positions within the srfA operon. The three subunits were partially purified by means of a series of chromatographic steps including ion-exchange chromatography, hydrophobic chromatography and gel filtration chromatography. The partially purified proteins were used in activity assays to establish their amino-acid recognition specificity. In agreement with previously published results, this analysis showed that srfAORF1 recognizes glutamic acid and Leu, srfAORF2 recognizes Val, aspartic acid and Leu and srfAORF3 recognizes Leu. In addition, the subunits can activate and bind other amino acids, although with lower specificity. In particular, srfAORF1 binds Val, Ile and aspartic acid, srfAORF2 glutamic acid and Ile and srfAORF3 Ile and Val. Competition experiments as well as sequence comparison strongly suggest that the Leu binding sites of the three subunits can accept, beside Leu, Ile and Val. The kinetic parameters of srfAORF3 for Leu, Ile and Val have been determined.

Amino Acid Sequence↗

PubMed1993

Solution structure of peptides containing two dehydro-phenylalanine residues: a CD investigation.

The peptides Ac-delta Phe-Ala-delta Phe-NH-Me (1), Ac-delta Phe-Val-delta Phe-NH-Me (2), Ac-delta Phe-Gly-delta Phe-Ala-OMe (3), and Boc-Ala-delta Phe-Gly-delta Phe-Ala-OMe (4), containing two dehydro-phenylalanine (delta Phe) residues, were synthesized and the solution structure investigated in various solvents. The nmr and CD measurements indicate that all the dehydropeptides examined adopt 3(10)-helical conformations in solution. The tripeptides 1 and 2 exhibited an intense negative CD exciton couplet, which was assigned to the right-handed screw sense, while the tetrapeptide 3 displayed a CD couplet having opposite sign, which was assigned to the left-handed helical sense. In the pentapeptide 4 the sense of the helix was found to vary with solvent and temperature, as demonstrated by the sign reversal of the CD spectrum. The right-handed sense dominates in hexafluoro-2-propanol, whereas a left-handed helix prevails in chloroform, acetonitrile and methanol. A crucial role for this behavior is likely to be played by the two alanine residues positioned respectively at the head and tail of the sequence, which favor conformations having opposite screw senses.

Amino Acid Sequence↗

PubMed1993

A nonsecreting pheochromocytoma presenting as an incidental adrenal mass. Report on a case.

A 25 year old women presented an incidental adrenal mass which was diagnosed to be a pheochromocytoma before surgery by means of a positive 131-I-MIBG scintigraphy. Urinary vanilmandelic acid resulted repeatedly normal as well as basal plasma norepinephrine (NE), epinephrine (E) and dopamine (DA). Urinary homovannilic acid resulted in the normal range. Stimulation tests with iv glucagone, tyramine and metoclopramide evoked normal NE and E responses while a slight increase in plasma DA was observed after metoclopramide. Oral clonidine suppressed plasma catecholamines (CA) normally. Histologic and immunohistochemical studies confirmed that the tumor was a pheochromocytoma showing positivity for tyrosine hydroxylase but not for dopamine-beta-hydroxylase activity. This case is the first report on a completely asymptomatic pheochromocytoma presenting as an incidental adrenal mass which was investigated with repeated biochemical tests before surgery and demonstrates that, among the extremely variable functional attitudes of pheochromocytomas, a defect in CA synthesis and secretion is also to be included.

Adrenal Gland Neoplasms↗

PubMed1993

Regulation of aldosterone receptors in hypertension.

Mean mineralocorticoid receptor number in mononuclear leukocytes of patients with increased plasma aldosterone (Conn's syndrome, nephrovascular hypertension, preeclampsia) is lower than in controls and this reduction could be the consequence of a down-regulation of the receptor. A similar pattern is evident also in situations of excess of other mineralocorticoids (Cushing's syndrome, chronic licorice ingestion). In essential hypertension 20% of cases have reduced number of mineralocorticoid receptors in mononuclear leukocytes without increase of aldosterone and normal serum potassium. We postulate that in some cases with essential hypertension the reduction of mineralocorticoid receptors is an index of mineralocorticoid excess due to mineralocorticoids other than aldosterone.

Adolescent↗

PubMed1993

Corticosteroid receptors and aging.

We have measured plasma aldosterone, plasma cortisol, and glucocorticoid and mineralocorticoid receptors in mononuclear leukocytes in 54 healthy aged subjects (60-97 years old) and in a group of 21 controls (21-50 years old). In addition all parameters and age were plotted for correlation. Plasma cortisol was significantly higher in the aged group (346 +/- 140 nmol/l) than in controls (260 +/- 120). Mean plasma aldosterone was not different in the two groups. Both Type I and II receptors in mononuclear leukocytes were lower in the aged group than in controls (Type I 198 +/- 96 and 272 +/- 97 receptors per cell; Type II 1738 +/- 801 and 3339 +/- 918 receptors per cell). A direct correlation was found between cortisol and age and between Type I and II receptors in aged subjects, and between cortisol and Type I receptors, and cortisol and Type II receptors in controls. When all subjects are plotted together, a direct correlation was observed between cortisol and age and between Type I and II receptors, and an inverse correlation between age and Type I and age and Type II receptors. We conclude that the parallel reduction of both Type I and II receptors with age is not due to prior cortisol increase, but the increase of plasma cortisol can be considered the result of age-dependent involution of these receptors.

Adult↗

PubMed1993

A comparison of nimesulide and diclofenac in the treatment of acute superficial thrombophlebitis.

In a double-blind study, the efficacy and tolerability of nimesulide (100mg twice daily) were compared with those of diclofenac (50mg twice daily) when administered orally to 50 patients with acute superficial thrombophlebitis of the lower limbs. Pain relief and amelioration of inflammation were apparent in patients treated with either nimesulide or diclofenac; however, gastric intolerance was noted more frequently in those receiving diclofenac. The results of this study suggest that nimesulide should be considered as an alternative to diclofenac and other first-line NSAIDs in the treatment of acute superficial thrombophlebitis.

Acute Disease↗

PubMed1993

New devices for carotid reconstruction.

An analysis of the reason for re-exploration of the carotid bifurcation immediately after surgery has demonstrated that in the majority of cases it is a question of defects of the distal part of the seat of CEA. The aim of this paper is to illustrate the use of an originally planned catheter and shunt during carotid surgery that may obviate some of the problems faced daily by surgeons during carotid reconstruction.

Carotid Stenosis↗

PubMed1993

Early and late results of biosynthetic ovine carotid angioplasty.

Recent major technical improvements in the field of carotid surgery have been related to anesthesiology and cerebral monitoring. However early embolic events and recurrent stenosis are, after intraoperative ischaemia, the main problems of carotid endarterectomy (CEA) and therefore technical improvements that reduce the incidence of these complications are required. The choice between primary closure and angioplasty is still debated. In the case of angioplasty, the choice of patching material seems to be important in preventing these complications. The Authors present their experience with a biosynthetic ovine patch in carotid surgery. In the period from January 1982 to November 1991, 1013 carotid endarterectomies were performed on 866 patients (659 men, 207 women) with atherosclerotic disease at the carotid bifurcation. In 147 cases a bilateral CEA was performed. Recently, in 37 cases of patch angioplasty, the Authors used the biosynthetic ovine patch. No deaths and no permanent neurological deficit were registered in this series either during awakening or the immediate postoperative period. Of these 37 patients, all except 4, had a minimum follow-up of 24 months. Two cases of non-hemodynamic restenosis were detected, one at 6 and one at 12 months; both were asymptomatic. In this series the total restenosis ratio was 5.5% (2/36), and the cumulative mortality rate 10.8% (4/37) (IMA 2, hepatic insufficiency 1, cerebral hemorrhage 1). The Authors' preliminary experience with this biosynthetic graft as a patching material has been satisfactory. They believe that this biosynthetic graft (Omniflow) on account of its handling and particularly its healing characteristics can be considered as a graft material for patching at the carotid level.

Aged↗

PubMed1992

Monitoring of somatosensory evoked potentials during carotid endarterectomy.

Somatosensory evoked potentials (SEPs) were monitored in the course of 368 carotid endarterectomies (CEAs) carried out in 312 patients. In an initial group of 26 patients the shunt was used routinely while in a second group, involving 342 CEAs, it was applied selectively on the basis of modifications which the SEP underwent during clamping. The criterion for shunting was the progressive reduction, up to 50%, of the N20-P25 amplitude. New postoperative neurological deficits appeared in 6 patients, all of whom displayed a transitory SEP flattening. The SEPs of 2 of these returned to normal by the time they awoke and both showed a clinical deficit homolateral to the operated side. In only 2 cases did the deficit fail to regress completely and their postoperative CT scans revealed ischaemic lesions. A positive relationship emerged between SEP changes and back pressure values; nonetheless, as many as 75% of the patients with low residual back pressure values (less than 25 mmHg) tolerated the clamping. SEP monitoring appears to provide a reliable basis for selectively applying a shunt when there is a high risk of haemodynamic ischaemia during clamping.

Adult↗

PubMed1992

Mineralocorticoid effector mechanism in preeclampsia.

Mineralocorticoid effector mechanisms were evaluated in 29 patients with preeclampsia and in 25 uncomplicated pregnancies by measurement of plasma aldosterone, levels of mineralocorticoid receptor (MR) in mononuclear leucocytes, and subtraction potential difference (SPD; rectal minus oral values). Mean values for plasma aldosterone were not different between the two groups, but significant differences were observed for MR (preeclampsia, 81 +/- 44 receptors/cell; controls, 306 +/- 168) and SPD (preeclampsia, 65 +/- 7 mV; controls, 12 +/- 5 mV). In six cases we determined MR, plasma aldosterone, and SPD in patients with preeclampsia before and 3 months after delivery. MR were reduced before delivery (96 +/- 27 receptors/cell), and SPD increased (64 +/- 8 mV), with both parameters normalizing after delivery (MR, 242 +/- 79; SPD, 14.0 +/- 4 mV). Aldosterone levels returned to normal nonpregnant values after delivery. These data suggest an important role for abnormalities in mineralocorticoid effector mechanisms in the etiology of preeclampsia and could be an useful marker for diagnosis.

Adult↗

PubMed1992

[The choice of approach in the surgical therapy of the superior thoracic outlet syndrome].

The symptoms of thoracic outlet syndrome (TOS) may be improved or cured either by physiotherapy or by a surgical operation. The choice of patients to be submitted to surgery must be performed on the basis of clinical picture and of non invasive and invasive assessment. Moreover the surgeon must choose the best procedure to relieve symptoms. The Authors on the basis of their experience and of a literature review refer to the various surgical approaches used in the treatment of TOS.

Adult↗