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Biomedical subjects

R Ricci

Publications and source records attributed to R Ricci.

At least 109 records · Page 6Linked to original sources
PubMed1997

Brain perfusion SPET and proton magnetic resonance spectroscopy in the evaluation of two systemic lupus erythematosus patients with mild neuropsychiatric manifestations.

The diagnosis of central nervous system (CNS) involvement appears to be a major problem in systemic lupus erythematosus (SLE), especially when the clinical signs are non-specific or neuroimaging is unremarkable. Two SLE patients with mild neuropsychiatric manifestations were studied with magnetic resonance imaging (MRI), single photon emission tomography (SPET) and localized proton magnetic resonance spectroscopy (H-1 MRS). MRI was normal in both patients. SPET revealed areas of hypoperfusion in both patients. H-1 MRS demonstrated metabolic abnormalities in the regions corresponding to the hypoperfused areas. A correlation between H-1 MRS and SPET was noted: patients with mild neuropsychiatric SLE may have disturbances evident on SPET and H-1 MRS in the presence of normal anatomy on MRI, suggesting that CNS involvement in SLE has very strong physiological and neurometabolic components in individual patients.

Adult↗
PubMed1997

Value of automatic processing and reliability of stored data in an implanted pacemaker: initial results in 59 patients.

Stored data in implantable pacemakers have rarely been used as a diagnostic tool because of the complexity. Our group has developed software called AIDA, providing an automatic interpretation of data stored in memories of the Chorus (ELA medical) pacemaker. We compared the results of AIDA analysis to surface ECG Holter interpretation in 59 patients (age 75 +/- 9 years). In 33 cases, neither AIDA nor the Holter found any anomaly. Eleven patients demonstrated episodes of supraventricular tachycardia (SVT), confirmed by AIDA in ten patients; AIDA failure was due to nonsustained episodes of SVT not inducing mode switch. Loss of atrial sensing, pacemaker-mediated tachycardia, and ventricular extrasystoles were detected by AIDA in ten patients. Traditional Holter missed three cases. This initial study confirms that stored pacemaker data, automatically interpreted can provide reliable information over a 24-hour period.

Aged↗
PubMed1997

Steroid-eluting electrodes prevent chronic pacing threshold rise in the atrial chamber after oral propafenone administration.

The aim of the study was to evaluate chronic atrial pacing threshold increase after oral propafenone therapy. Fifty patients affected by advanced AV block and sick sinus syndrome were studied at least 6 months after pacemaker implantation, before and after oral propafenone therapy (450-900 mg/day based on body weight). The patients were subdivided into three groups as to the type of electrode implanted, all three unipolar: group I (20 patients) Medtronic CapSure 4003, group II (13 patients) Medtronic Target Tip 4011, group III (17 patients) Medtronic 4057 screw-in leads. In all cases, Medtronic unipolar pacemakers were implanted with the same noninvasive autothreshold measurement method. Propafenone and 5-OH-propafenone blood levels were measured 3-5 hours after drug administration. The packing autothreshold was measured at 0.8, 1.6, and 2.5 V by reducing the pulse width. After propafenone, groups II and III showed a statistically significant threshold rise (P ranging from < 0.01 to 0.05), whereas no significant difference was found in group I. Propafenone and 5-OH-propafenone blood vessels did not show any significant difference among the three groups. Strength-duration curves were drawn for the three groups before and after propafenone: at baseline the curves shifted to the left with the steep part above the knee, clearly favoring CapSure over the other two groups. After propafenone, the curves shifted to the right, with the flat par progressively more evident in groups II and III. In the atrial chamber, steroid-eluting leads prevented threshold increase after propafenone therapy, in contrast with a significant threshold rise with conventional porous and screw-in leads.

Aged↗
PubMed1997

Dual modulation of Na/H antiport by atrial natriuretic factor in rat aortic smooth muscle cells.

The aim of the present work was to study the effect of the atrial natriuretic factor (ANF) on the Na/H antiport in rat aorta smooth muscle cells, evaluated as intracellular pH (pHi) recovery after an acid load with ammonium chloride. The Na/H antiport was studied using a fluorescent probe, sensitive to pHi, 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Our data indicate that ANF modulates the activity of the Na/H antiport in both a dose- and time-dependent manner. Hormone concentrations of 10(-10) M activate the antiport, increasing both the rate of recovery and the set point by approximately 0.2 pH units. This effect is mediated by diacylglycerol as a result of phospholipid hydrolysis by a phospholipase C, even if an involvement of adenosine 3',5'-cyclic monophosphate (cAMP) cannot be ruled out. ANF (10(-7) M) inhibits the antiport, decreasing both the rate of recovery and the set point by approximately 0.3 pH units, because of guanosine 3',5'-cyclic monophosphate production. Both inhibition and stimulation of pHi by ANF were more pronounced when the hormone was given before the acid load, perhaps because of the longer time exposure. We present new hypotheses on the mechanism of action of this paracrine/autocrine factor.

Ammonium Chloride↗
PubMed1997

Long-term haemodynamic and antiarrhythmic benefits of DDIR versus DDI pacing mode in sick sinus syndrome and chronotropic incompetence.

AIMS: The aim of this Italian multicentre study was to evaluate the haemodynamic and antiarrhythmic effects of DDIR versus DDI pacing mode in sick sinus syndrome with chronotropic incompetence. METHODS: Seventy-nine patients were implanted with a dual chamber rate-responsive pacemaker (Medtronic 7075) and centrally randomised to DDI or DDIR pacing mode. After six months, the pacing modality was crossed over. Follow-up included clinical data, rest ECG, echocardiography, Holter monitoring and exercise testing in DDIR. RESULTS: a) Haemodynamic effects. Comparing postimplant exercise testing in DDIR mode with preimplant tests, peak heart rate increased from 96 +/- 17 to 115 +/- 17 bpm (+20%, p < 0.0001), total work capacity from 7.0 +/- 3.5 to 8.8 +/- 4.3 minutes (+26%, p < 0.0001), peak oxygen uptake from 1238 +/- 406 to 1453 +/- 423 ml/min (+17%, p < 0.001) and oxygen uptake at anaerobic threshold from 977 +/- 343 to 1222 +/- 415 ml/min (+25%, p < 0.001). These benefits persisted unchanged during one-year follow-up. b) Antiarrhythmic effects. After six months, paroxysmal atrial fibrillation recurrence significantly decreased in the whole population: group I (DDI) 20.7 vs 48.3%, p < 0.02; group II (DDIR) 21.2 vs 36.4%, p < 0.05; group I + II (DDI + DDIR) 21.0 vs 41.9%, p < 0.001. After one year no significant differences were found between DDI and DDIR. Group I: DDI 23.8 vs DDIR 28.6%, ns; group II: DDI 22.7 vs DDIR 18.2%, ns. CONCLUSION: DDIR vs DDI significantly improves short- and long-term haemodynamic performance. Dual chamber pacing shows a significant reduction of paroxysmal atrial fibrillation recurrence, regardless of rate responsiveness.

Aged↗
PubMed1996

An electrophysiological study of calcium entry during normal human T-lymphocyte activation.

Our aim was to observe whether normal human T-cells respond to mitogenic stimulation with large whole-cell inward currents (composed of identifiable single-channel contributions) when [Ca2+]i is not markedly lowered but instead kept normal or moderately low, as has been reported in human leukaemic Jurkat T-cell line and T-cell clones [Kuno et al. (1986) Nature 323, 269-73; Kuno and Gardner (1987) Nature 326, 301-304; Gardner (1990) Annu. Rev. Immunol. 8, 231-252]. Whole-cell patch recordings showed no such currents in cells otherwise normally responding to depolarisation with the macroscopic IK described in T-lymphocytes and thus deemed viable, in agreement with the notion that Ca2+ influx in normal T-cells enterily depends on depletion of internal stores [Putney (1986) Cell Calcium 7, 1-12; Putney (1990) Cell Calcium 11, 611-624].

Calcium↗
PubMed1996

Usefulness of dipyridamole transesophageal echocardiography in the evaluation of myocardial ischemia and coronary artery flow.

High-dose dipyridamole transesophageal stress echocardiography has recently been proposed as a useful and safe method to assess myocardial ischemia in patients with poor transthoracic acoustic window. It has also been shown that transesophageal echocardiography (TEE) allows the study of coronary blood flow reserve (CBFR) in the left anterior descending artery (LAD). The aim of our study was to assess whether the morphologic information and pathophysiologic data on CBFR and myocardial ischemia can be collected by a single stress TEE without comprimizing its feasibility, safety and accuracy. We studied, 29 patient with known or suspected CAD (previous myocardial infarction or angina) (Group A), and as a control group, we studied 11 patients with mitral disease or mitral prostheses (Group B). All patients underwent the coronary angiography. None of Group B patients showed significant coronary artery stenosis (> 70%). In baseline conditions left ventricular wall motion and LAD coronary blood flow velocity (CBFV) were also evaluated. The following CBFV parameters were measured: maximal diastolic velocity (MaxDV), mean diastolic velocity (MnDV), maximal systolic velocity (MaxSV), mean systolic velocity (MnSV). The ratios of dipyridamole to rest maximal and o mean to diastolic velocities (MaxDV-Dip/Max DV-rest; MnDv-Dip/MnDV-rest) were measured as indexes of CBFR. No side effects were observed and the test could be completed in all patients (feasibility 100%). Wall motion analysis was adequate in all patients (feasibility 100%). Comparison between wall motion analysis was obtained and angiographic findings shown that the overall sensitivity and specificity of TEE were 84% and 93% respectively. Sensitivity for one, two and three vessel disease was 60%, 70% and 100%, respectively. LAD CBFV was adequately recorded in 85% of patients. CBFR parameters showed a significant difference between the two groups (Max DV-Dip/Max DV-rest: 1.67 +/- 0.7 vs. 2.73 +/- 0.6, P < 0.001); comparison between Group B patients and those of Group A with angiographically documented LAD stenosis showed a statistically significant difference in CBFR parameters (MaxDV-Dip/MnDV-rest, 2.73 +/- 0.6 vs. 1.65 +/- 0.7, P < 0.001, MnDV-Dip/MnDV-rest, 2.56 +/- 0.5 vs. 1.69 +/- 0.6 < 0.001). We conclude that transesophageal stress echocardiography is a useful method to study CAD and that it is possible to assess both morphologic and pathophysiologic information during a single examination.

Angina Pectoris↗
PubMed1996

Reliability of a new algorithm for automatic mode switching from DDDR to DDIR pacing mode in sinus node disease patients with chronotropic incompetence and recurrent paroxysmal atrial fibrillation.

To evaluate the safety and efficacy of a new algorithm for automatic mode switching (AMS) from DDD-DDDR to DDIR, 26 patients, 16 females and 10 males, mean age 73 +/- 6 years of age, affected by sinus node disease, chronotropic incompetence, and recurrent paroxysmal atrial fibrillation (PAF) received the Medtronic Thera DR pacemaker. The device continuously calculates, in ms, the running average of the intrinsic atrial rate (MAR) and compares the current atrial interval (CAI) with the stored MAR. When the CAI is greater than the MAR it increases by 8 ms, and when the CAI is less than the MAR, it decreases by 23 ms. When MAR < or = 330 ms (182 beats/min), tachycardia is detected and AMS is activated. All patients had clinical evaluation, 12-lead ECG, Holter monitoring, and exercise testing after implantation and every 3 months for 1 year. The results were compared with the data stored in the pacemaker memory: AMS episodes number; the histogram of the last 14 episodes; and atrial electrogram recording. Twenty-two Holter recordings in 13 patients showed PAF and in all of them AMS occurred simultaneously. AMS lasted between 10 seconds and 20 hours, and MAR ranged from 195-400 beats/min. No episode of PAF and no AMS were recorded in 39 Holter recordings in 22 patients. Appropriate AMS was confirmed in five patients by stored atrial electrogram and in nine by 12-lead ECG and pacemaker event markers. Mean atrial sensing was 2.13 +/- 1.04 mV during PAF and 3.18 +/- 1.46 mV during sinus rhythm. No PAF episode and no AMS were recorded during exercise testing. In conclusion, this new algorithm was very reliable, sensitive, and specific.

Aged↗
PubMed1996

[Prognostic value of echo-dobutamine test in patients with ischemic heart disease: comparison with exercise test].

BACKGROUNDS: The aim of the study was to assess the relative prognostic accuracy of dobutamine echocardiography (TED) vs maximal bicycle exercise electrocardiography (TE) in patients with proven coronary artery disease. METHODS: One hundred and thirty consecutive patients (70 patients with uncomplicated recent myocardial infarction, 19 asymptomatic patients with previous myocardial infarction and 41 patients with stable angina pectoris and previous myocardial infarction or previous myocardial revascularization procedure) underwent TED (incremental dobutamine infusion: 5 to 40 ncg/kg/min, continued with atropine 0.25 to 1 mg iv if necessary) and TE on different days and in random order. Criteria for positivity were: new or worsening regional dyssynergy for TED; ST segment shift > or = 1 mm from baseline for TE. End points were defined as spontaneous events (cardiac death, myocardial infarction and unstable angina) and total events (spontaneous events plus myocardial revascularization procedures). RESULTS: During 15.4 +/- 7.9 (range 1-33) months of follow-up, 33 events occurred: cardiac death (1), myocardial infarction (4) unstable angina (21) myocardial revascularization (7). Sensitivity, specificity, positive and negative predictive value, prognostic accuracy were similar for TED and TE (P = NS). Cumulative event-free survival curves as a function of TED and TE results were both statistically significant. A Cox stepwise regression analysis identified TED positivity obtained without atropine administration as the best predictor of spontaneous and total events (Odds ratio 5.33 and 4.38, respectively). Cumulative survival curves obtained by the combination of TED and TE results were statistically different (P < 0.05 and P < 0.001 for spontaneous and total events, respectively) and showed a poor clinical outcome in patients with both tests or only TED positive. TED correctly predicted clinical outcome in 24/39 patients in whom there was disagreement between the two tests. CONCLUSIONS: In patients with proven coronary artery disease, TED and TE have a similar accuracy for predicting clinical outcome. Where a discrepancy is seen between the two tests, TED appears to have a slightly higher prognostic value.

Aged↗
PubMed1995

Prognostic value of high dose dipyridamole echocardiography in patients with chronic coronary artery disease and preserved left ventricular function.

OBJECTIVES: The prognostic value of dipyridamole echocardiography was assessed in patients with chronic coronary artery disease and preserved left ventricular function. BACKGROUND: Few data are available on the prognostic value of dipyridamole echocardiography in patients with a low risk of cardiac events. METHODS: Two hundred sixty-eight consecutive patients with stable, proven or suspected coronary artery disease and ejection fraction > or = 0.40 underwent high dose (up to 0.84 mg/kg body weight) dipyridamole echocardiography. In 204 patients definite exercise electrocardiographic (ECG) results were also available. RESULTS: During a mean (+/- SD) follow-up period of 16 +/- 8 months (range 6 to 36), 33 spontaneous events occurred: 15 "hard" events (cardiac death [n = 6], myocardial infarction [n = 9]) and 18 "soft" events (unstable angina). Events occurred more frequently in patients with positive findings on dipyridamole echocardiography (59% vs. 3%, p < 0.001; hard events 24% vs. 2%, p < 0.01). A positive response at the low dose (up to 0.56 mg/kg) identified patients with a high incidence of hard events (7 of 16 patients, sensitivity 50%, specificity 96%). In patients with an exercise ECG, a comparable sensitivity for cardiac events was found (89% vs. 93%, p = NS), but dipyridamole echocardiography was more specific (91% vs. 61%, p < 0.01). A positive response on the low work load exercise ECG (< 8 min) and a positive response to low dose dipyridamole echocardiography had similar accuracy (82% vs. 90%, p = NS). Cox analysis identified dipyridamole echocardiography as the best predictor of cardiac events (odds ratio [OR] 20.9, 95% confidence interval [CI] 10.8 to 37.9); the highest risk of hard events was found in patients with a positive response to low dose dipyridamole echocardiography (OR 25.4, 95% CI 12.2 to 54.1). CONCLUSIONS: In patients with chronic coronary artery disease and a low incidence of cardiac events, dipyridamole echocardiography was effective in prognostic stratification, and positive low work load exercise ECG results were a reliable predictor of subsequent events. Consequently, dipyridamole echocardiography should be considered a complementary tool in the presence of high work load positivity or ambiguous exercise ECG results.

Coronary Disease↗
PubMed1995

Tamoxifen and quercetin interact with type II estrogen binding sites and inhibit the growth of human melanoma cells.

The mechanism of the antiproliferative activity of tamoxifen on melanoma cells in vitro and in vivo is poorly understood, as it is not mediated by the antiestrogenic properties of tamoxifen. Using a whole-cell assay and nuclear and cytosolic radio-binding experiments with [3H]-estradiol as tracer, we found that MNT1, M10, and M14 melanoma cell lines as well as primary tumors expressed type II estrogen binding sites that bind tamoxifen and the flavonoid quercetin with similar affinity (KD 10-25 nM). Cell count and clonogenic assay showed both compounds to inhibit melanoma cell growth in a concentration-dependent manner in the range of concentrations between 1 nM and 1 microM. Neither the pure antiestrogen ICI-182780 nor the 3-rhamnosylglucoside of quercetin, rutin, bound to type II estrogen binding sites or inhibited cell growth. Our results suggesting that tamoxifen and quercetin can inhibit melanoma cell growth by interacting with type II estrogen binding sites help explain the reported effectiveness of tamoxifen, particularly in estrogen-receptor-negative tumors, and stress the potential role of quercetin in the treatment of melanoma.

Binding Sites↗
PubMed1995

Mitral valve prolapse in a case of Marfan syndrome with congenital cardiac disease, chronic obstructive pulmonary disease and schizophrenia.

Mitral valve prolapse (MVP) is a common pathological finding in several inherited connective-tissue diseases among which the Marfan syndrome. In the literature several cases of Marfan syndrome characterized by schizophrenia, chronic obstructive pulmonary disease and severe mitral regurgitation due to a MVP have been reported. Our case of MVP was observed in a patient with Marfan syndrome with its characteristic musculoskeletal disorders associated with congenital cardiac disease, severe chronic obstructive pulmonary disease and schizophrenia. According to the latest genetic studies, Marfan syndrome seems to result from genetic mutations in an extracellular matrix glycoprotein, fibrillin. Authors believe that MVP represents only one of several pathological alterations which may be seen in the Marfan syndrome, as expression of a more generalized genetic disorder.

Adult↗
PubMed1995

Cellular basis of ventricular remodeling after myocardial infarction in rats.

The remodeling of the spared non-ischemic left ventricular myocardium after different time intervals from the occlusion of the left coronary artery was examined in rats. In the presence of large infarcts, ventricular failure developed two to three days after surgery, because of chamber dilation and thinning of the wall, resulting in an average 7.5-fold increase in diastolic stress on the surviving myocardium. Mural thinning of the ventricular wall remote from and bordering the infarction occurred through side-to-side slippage of myocytes and capillaries within the wall. Although an average hypertrophic growth of 22% of the spared myocytes has been found, this amount of hypertrophy was insufficient to restore normal myocardial function. Long-term cardiac restructuring after infarction was characterized by the persistence of chamber dilatation and thinning of the ventricular wall. In addition to the side-to-side slippage, lengthening of the myocytes was an important cause of ventricular changes. As the reactive hypertrophy of the unaffected ventricle was insufficient to re-establish the ratio of ventricular mass to chamber volume, the diastolic stress remained elevated and decompensated eccentric ventricular hypertrophy developed. The anatomical remodeling of the spared left ventricular myocardium is an important conditioning factor in the short- and long-term outcome of ischemic cardiomyopathy.

Animals↗
PubMed1995

[Use of high doses of atropine during dipyridamole echocardiography: safety and efficacy of the combined test].

BACKGROUND: Recent reports demonstrated an increased accuracy of dipyridamole echocardiography test with the intravenous infusion of 0.25 to 1 mg of atropine in 1-4 consecutive administrations at the end of the test. The effect of higher doses of atropine during dipyridamole echocardiography, potentially able to further increase heart rate and myocardial oxygen consumption, has not been evaluated. The aim of the study was to evaluate the effect of high doses of atropine during dipyridamole echocardiography and to investigate the possible pharmacological interference between dipyridamole and atropine. METHODS: One-hundred consecutive patients (M = 81, F = 19; mean age 58 yrs) without inducible wall motion abnormalities at 14th minute of a high-dose (0.84 mg/Kg in 10') dipyridamole echocardiography test were studied. Seventy-five patients referred to the test in pharmacological wash-out were randomly divided in three groups: 25 patients (Group 1) received 10 mcg/Kg of atropine in 60"; 25 patients (Group 2) received 15 mcg/Kg of atropine in 120"; 25 patients (Group 3) received 20 mcg/Kg of atropine in 120"; moreover, 25 patients with a full-dose oral beta-blocker therapy (Group 4) received 20 mcg/Kg of atropine in 120". Atropine was infused during the 15th and 16th minute of the test. Heart rate (HR) changes and new wall motion abnormalities induced by atropine were considered and compared for each Group. In 60 patients (15 randomly selected from each Group) the effect on mean HR and R-R interval (msec) of the same dose of atropine infused during dipyridamole echocardiography was evaluated in resting conditions 24 hours apart. RESULTS: The dipyridamole-atropine test was well tolerated and accomplished in all patients. HR increased significantly in all Groups of patients in comparison with pre-atropine HR values (Group 1: +14 +/- 8 b/m', p < 0.0001; Group 2: +19 +/- 8 b/m', p < 0.0001; Group 3: +22 +/- 9 b/m', p < 0.0001; Group 4: +19 +/- 8 b/m', p < 0.0001; Groups 2, 4 vs Group 1: p = 0.03, Group 3 vs Group 1: p = 0.002). No patients in Group 1 (0%), 3 patients in Groups 2 and 3 (12%), and 5 patients in Group 4 (20%) showed new wall motion abnormalities after atropine infusion (Group 4 vs Group 1: p = 0.06). Effects of atropine on HR and mean R-R interval were significantly more pronounced in resting conditions than during dipyridamole test (HR: +25 +/- 11 vs +18 +/- 9 b/m', p < 0.001; R-R: -256 +/- 122 vs -127 +/- 68 msec, p < 0.0001). CONCLUSIONS: High doses of atropine during dipyridamole echocardiography test are safe and more effective for induction of new wall motion abnormalities than usual doses, particularly in patients tacking beta-blockers. The likelihood of an antagonistic mechanism between atropine and endogenous, dipyridamole-induced adenosine on sinus node is supported from our results.

Administration, Oral↗
PubMed1995

[Multiplane transesophageal echocardiography and adenosine in the study of coronary blood reserve].

BACKGROUND: Coronary blood reserve is the capacity of coronary vessels to vasodilate and thereby to increase the blood flow, when the heart needs more energy. However, when a coronary stenosis occurs, the capacity to vasodilate is reduced or completely diminished. It is then necessary to use all the tools useful in evaluating the functional conditions of the coronary vessels. Above all, the intracoronary Doppler technique is used to measure the velocity of blood flow. Our purpose was to evaluate a non-invasive tool "Multiplane Transesophageal Echocardiography" in the study of velocity of the anterior descendent artery before and after adenosine infusion. METHODS: At first, we studied 28 patients (pts), which we divided in two groups: Group A, 18 pts 59.38 +/- 8.23 mean age, 15 M. and 3 F., with anterior descending disease; Group B 10 pts, 59.20 +/- 8.48 mean age, 7 M. and 3 F, without significant stenosis (> 75%). Echocardiography examinations were performed with a 5 MHz multiplane probe, connected to a 1000 Hewlett Parkard echocardiography. Before the test, Diazepam 1 mg i.v. and Lidocaine spray were administered to the patients. We introduced the transesophageal probe and after choosing the best position of the aortic short axis view, we studied the anterior descending artery and measured the maximum and mean diastolic and sistolic velocities (V.MAX D., V.MN.D., V.MAX S., V.MN.S.). RESULTS: Transesophageal echocardiography allowed us to study the anterior descending artery in 95% of pts. There were no side effects, except for one pt affected by severe bradicardia. In Group B there was an increase of the diastolic and sistolic velocity after adenosine infusion, resulting twice greater they the rest values. The adenosine/rest velocities ratios were statistically significant (V.MAX D. p < 0.02) (V.MN.D. p < 0.03). CONCLUSION: Our results demonstrated an higher capacity of the Multiplane Transesophageal Echocardiography in studiing coronary blood reserve. We used adenosine, as a vasodilator drug, because of its short half-life and because it can be replatedly infused. The flow velocity values increased up to more than twice the rest values only in normal subjects.

Adenosine↗
PubMed1994

Influence of lipophilicity on the biological activity of cyclic pseudopeptide NK-2 receptor antagonists.

A series of cyclic pseudopeptides of the formula cyclo(Leu psi[CH2NH]Xaa-Gln-Trp-Phe-beta Ala), where Xaa represents the residue of an alpha-amino acid, has been synthesized in order to establish the role of the Xaa side chain for tachykinin NK-2 receptor antagonist activity. Syntheses have been carried out in solid phase with either Fmoc or Boc strategy. The antagonist potency on NK-2 receptors in the hamster isolated trachea (HT) and the rabbit isolated pulmonary artery (RPA) bioassays increases with Xaa lipophilicity; cyclo(Leu psi[CH2NH]Cha-Gln-Trp-Phe-beta Ala) and cyclo(Leu psi[CH2NH]Asp(NHBzl)-Gln-Trp-Phe-beta Ala) resulted in being the two most active antagonists (pA2 = 9.06 and 9.26 on HT, respectively). A significant linear correlation was found between pA2 values determined in HT and RPA bioassays and capacity factors measured in reversed phase HPLC. The comparison between the biological activities of cyclic hexapeptides containing or not containing the aminomethylene moiety proved the crucial role of the pseudopeptide bond for determining high antagonist potency at the NK-2 receptor.

Alkylation↗
PubMed1994

Cobalt powdersintering industry (stone cutting diamond wheels): a study of environmental-biological monitoring, workplace improvement and health surveillance.

This communication deals with an aspect of occupational hygiene in a factory producing granite cutting diamond wheels by sintering, in moulds, of fine cobalt powder. The factory has been studied between 1988 and 1991; the Department of Preventive and Occupational Medicine of the Local Sanitary Unit of Reggio Emilia has followed the evolution of the local exhaust ventilation equipment supplied by the employer in that period. At the same time, the following measurements and observations were carried out: (a) cobalt exposure by personal sampling, (b) airborne cobalt measurements by area sampling, (c) biological monitoring of cobalt in urine, (d) health surveillance.

Adult↗