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L Stella

Publications and source records attributed to L Stella.

At least 37 records · Page 2Linked to original sources
PubMed1999

Patient-ventilator asynchrony during noninvasive ventilation: the role of expiratory trigger.

OBJECTIVE: Air leaks around the mask are very likely to occur during noninvasive ventilation, in particular when prolonged ventilatory treatment is required. It has been suggested that leaks from the mask may impair the expiratory trigger cycling mechanism when inspiratory pressure support ventilation (PSV) is used. The aim of this study was to compare the short-term effect of two different expiratory cycling mechanisms (time-cycled vs flow-cycled) during noninvasive inspiratory pressure support ventilation (NIPSV) on patient-ventilator synchronisation in severe hypoxemic respiratory failure. STUDY POPULATION: Six patients with acute lung injury (ALI) due to acquired immunodeficiency syndrome (AIDS)-related opportunistic pneumonia were enrolled in the protocol. INTERVENTION: Each subject was first studied during spontaneous breathing with a Venturi oxygen mask (SB) and successively submitted to a randomly assigned 20' conventional flow-cycling (NIPSVfc) or time-cycling inspiratory pressure support ventilation (NIPSVtc). The pre-set parameters were: inspiratory pressure of 10 cm H2O, PEEP of 5 cm H2O for the same inspired oxygen fraction as during SB. A tight fit of the mask was avoided in order to facilitate air leaks around the mask. The esophageal pressure time product (PTPes) and tidal swings (delta Pes) were measured to evaluate the patient's respiratory effort. A subjective "comfort score" and the difference between patient and machine respiratory rate [delta RR(p-v)], calculated on esophageal and airway pressure curves, were used as indices of patient-machine interaction. RESULTS: Air leaks through the mask occurred in five out of six patients. The values of PEEPi (< 1.9 cm H2O) excluded significant expiratory muscle activity. NIPSVtc significantly reduced PTPes, delta Pes, and delta RR(p-v) when compared to NIPS-Vfc [230 +/- 41 (SE) vs 376 +/- 72 cm H2O.s.min-1; 8 +/- 2 vs 13 +/- 2 cm H2O; 1 +/- 1 vs 9 +/- 2 br.min-1; respectively] with a concomitant significant improvement of the "comfort score". CONCLUSIONS: In the presence of air leaks a time-cycled expiratory trigger provides a better patient-machine interaction than a flow-cycled expiratory trigger during NIPSV.

AIDS-Related Opportunistic Infections↗
PubMed1999

A spectroscopic and molecular modeling study on novel pseudopeptides exhibiting biological activity.

A series of pseudopeptides, containing two fluorophores, such as naphthalene (N) and indole (I), and exhibiting interesting biological activity as tachykinin receptor antagonists, were investigated by electronic absorption, CD and steady-state fluorescence experiments. In polar solvents (e.g. methanol), bioactivity is coupled with a stacked, charge-separated complex between I and N, the amount of which depends on the stereochemical features and conformational mobility of the central scaffold in the molecules examined. This agrees with the idea that dipolar charged, spatially close, aromatic moieties are important topochemical elements in the mechanism of action of these receptor antagonists. Molecular mechanics calculations allowed us to build up hypothetical, low-energy conformations of a few representative pseudopeptides, whose structural features are consistent with the experimental findings.

Circular Dichroism↗
PubMed1998

Flexibility of helix 2 in the human glutathione transferase P1-1. time-resolved fluorescence spectroscopy.

Time-resolved fluorescence spectroscopy and site-directed mutagenesis have been used to probe the flexibility of alpha-helix 2 (residues 35-46) in the apo structure of the human glutathione transferase P1-1 (EC 2.5.1.18) as well as in the binary complex with the natural substrate glutathione. Trp-38, which resides on helix 2, has been exploited as an intrinsic fluorescent probe of the dynamics of this region. A Trp-28 mutant enzyme was studied in which the second tryptophan of glutathione transferase P1-1 is replaced by histidine. Time-resolved fluorescence data indicate that, in the absence of glutathione, the apoenzyme exists in at least two different families of conformational states. The first one (38% of the total population) corresponds to a number of slightly different conformations of helix 2, in which Trp-38 resides in a polar environment showing an average emission wavelength of 350 nm. The second one (62% of the total population) displays an emission centered at 320 nm, thus suggesting a quite apolar environment near Trp-38. The interconversion between these two conformations is much slower than 1 ns. In the presence of saturating glutathione concentrations, the equilibrium is shifted toward the apolar component, which is now 83% of the total population. The polar conformers, on the other hand, do not change their average decay lifetime, but the distribution becomes wider, indicating a slightly increased rigidity. These data suggest a central role of conformational transitions in the binding mechanism, and are consistent with NMR data (Nicotra, M., Paci, M., Sette, M., Oakley, A. J., Parker, M. W., Lo Bello, M., Caccuri, A. M., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3020-3027) and pre-steady state kinetic experiments (Caccuri, A. M., Lo Bello, M., Nuccetelli, M., Nicotra, M., Rossi, P., Antonini, G., Federici, G., and Ricci, G. (1998) Biochemistry 37, 3028-3034) indicating the existence of a pre-complex in which GSH is not firmly bound to the active site.

Binding Sites↗
PubMed1998

Metabotropic glutamate receptors modulate serotonin release in the rat periaqueductal gray matter.

The role of metabotropic (mGluRs) and N-methyl-D-aspartate (NMDA) glutamate receptors on 5-hydroxytryptamine (5-HT) release has been studied in rat periaqueductal gray (PAG) matter by using in vivo microdialysis. (1S,3R)-aminocyclopentane- 1,3-dicarboxylic acid [(IS,3R)-ACPD; 0.5 or 1 mM], a group I/group II mGluRs agonist, increased the dialysate 5-HT concentration. (2S)-alpha-ethylglutamic acid (EGlu; 1 mM), an antagonist of group II mGluRs, but not (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA; 1 mM), an antagonist of group I mGluRs, antagonized the 1S,3R-ACPD-induced effect. (S)-3,5-dihydroxyphenylglycine (DHPG; 0.5 and 1 mM), an agonist of group I mGluRs, did not modify dialysate 5-HT. (2S, 3S, 4S)-alpha-(carboxycyclopropyl)-glycine (L-CCG-I; 0.5 and I mM), an agonist of group II mGluRs, increased extracellular 5-HT. This effect was antagonized by EGlu. Similarly, L-serine-O-phosphate (L-SOP; 1 and 10 mM), an agonist of group III mGluRs, increased extracellular 5-HT and this effect was antagonized by (RS)-(alpha-methylserine O-phosphate (M-SOP; 1 mM), an antagonist of group III mGluRs. Out of the several N-methylD-aspartate concentrations used (NMDA; 10, 50, 100, 500 and 1000 microM) only the 50 microM infusion significantly decreased dialysate 5-HT. The GABA(A) receptor agonist, bicuculline (30 microM), increased 5-HT release on its own and antagonized the decrease caused by the opiate antagonist, naloxone (2 mM), as well as the increases caused by CCG-I or L-SOP. These data show that stimulation of PAG's group II/group II mGluRs increases 5-HT release, while stimulation of NMDA glutamate receptors may decrease it. We speculate that glutamate does not modulate 5-HT release in the PAG directly, but via activation of tonically active GABAergic interneurons.

Animals↗
PubMed1998

The role of A3 adenosine receptors in central regulation of arterial blood pressure.

1. Pharmacological studies have suggested that A3 receptors are present on central neurons. Recently this adenosine receptor subtype has been identified in the rat and its presence in the central nervous system has been confirmed. 2. In this study we investigated the effects of acute intracerebroventricular (i.c.v.) injections of N6-2-(4-aminophenyl)-ethyladenosine (APNEA), a non-selective A3 adenosine receptor agonist, on arterial blood pressure (ABP) and heart rate (HR), after treatment with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective antagonist of A1 adenosine receptors. 3. Anaesthetized rats, after DPCPX (12 microg(-1) kg i.c.v.), were treated with APNEA (0.4-4 microg kg(-1) i.c.v.) resulting in a transitory and dose-dependent decrease in arterial blood pressure without a change in heart rate. APNEA also induced hypotensive responses after i.c.v. pretreatment with aminophylline, at a dose of 20 microg kg(-1). In contrast, pretreatment 48 h before, with 4 microg kg(-1) i.c.v. of pertussis toxin reduced the hypotensive effect induced by APNEA. Administration of APNEA at a higher dose (20 microg kg(-1) i.c.v.), after DPCPX, induced a decrease in ABP of -66+/-5.4 mmHg and after 3 min a decrease in heart rate of -62+/-6.0 beats min(-1). Transection of the spinal cord abolished this significant fall in ABP, but not the decrease of HR. 4. These results suggest that a population of A3-receptors is present in the CNS, whose activation induces a decrease in blood pressure with no change of heart rate.

Animals↗
PubMed1998

L-Cysteinesulfinic acid modulates cardiovascular function in the periaqueductal gray area of rat.

L-Cysteinesulfinic acid (CSA) involvement in modulating periaqueductal gray (PAG) pressor neurons has been evaluated in the rat. Intra-PAG CSA induced an increase in mean blood pressure partially antagonized by (2S)-alpha-ethylglutamic acid (EGA), a group II metabotropic glutamate receptors (mGluRs) antagonist. Conversely, the NMDA antagonist, DL-AP5, or the mGluRs antagonists, (+)-MCPG, UPF523, or (RS)-alpha-methylserine-O-phosphate (MSOP), were devoid of any activity on the CSA effect. These data show that the excitatory amino acid CSA, probably by stimulating an mGluR, contributes with glutamate in modulating cardiovascular function at the PAG matter.

Animals↗
PubMed1996

Effect of Lys-->Arg mutation on the thermal stability of Cu,Zn superoxide dismutase: influence on the monomer-dimer equilibrium.

The thermal stability of two single (K3R, K67R) and one double (K3R-K67R) mutants of Xenopus laevis B Cu, Zn superoxide dismutase has been studied to test Lys --> Arg substitution as an 'electrostatically conservative' strategy to increase protein stability. The K3R mutant displays an increased thermostability with respect to the wild-type enzyme, whilst a decreased stability was observed in the case of the K67R and K3R-K67R mutants. Concentration dependence of the apparent inactivation constant (kapp) of the latter mutants, as compared to that of the wild type enzyme and K3R mutant, indicates that their higher sensitivity to heat inactivation is due to a perturbation of the dimer association. These results are confirmed also by fluorescence anisotropy measurements of the internal probe Tyr149. The possible role of Arg67 in perturbing the dimer dissociation equilibrium toward the monomeric form is discussed.

Animals↗
PubMed1996

Antiarrhythmic effects of LR-A/113 a new calcium antagonistic drug.

LR-A/113 is a benzothiazepine drug similar to diltiazem with Ca(2+)-antagonist properties. Our previous studies showed that LR-A/113 determines anthypertensive effects comparable to diltiazem in normotensive and hypertensive rats. The aim of this study is to determine LR-A/113 effects respect to verapamil and diltiazem on CaCl2, aconitine and ouabain arrhythmias. Experiments were carried out on normotensive anesthetized rats and guinea pigs treated with CaCl2, aconitine and ouabaine and pretreated or not with verapamil, diltiazem or LR-A/113. Verapamil, diltiazem and LR-A/113, significantly delayed onset of arrhythmias and cardiac standstill induced by CaCl2 and aconitine. Moreover, pretreatments with verapamil, diltiazem or LR-A/113 reduced occurrence of arrhythmias in animals. In our models of arrhythmias LR-A/113 showed a significant antiarrhythmic effect of a magnitude almost similar to diltiazem but lower than for verapamil.

Aconitine↗
PubMed1996

Fronto-ethmoidal and orbital osteomas with intracranial extension. Report of two cases.

Osteomas involving the anterior cranial base are quite rare lesions. Intracranial and orbital extension of these tumors, causing neurological and ophthalmological symptoms and signs is a rare event. Two such cases are reported. In the first one, the tumor arose from the frontal sinus and extended upward to the medial and superior wall of the right orbital cavity and the lower part of the right frontal convexity. In the second case the osteoma arose from the left orbital roof and extended to the lower part of the homolateral frontal convexity and the splenoid wing. After the operation the symptoms disappeared and the cosmetic deficits were corrected. Skull-films, CT and MR well define the bony extension and the displacement of the orbital and intracranial structures. Indications to the surgery include progressive ophthalmologic and neurologic signs and significant cosmetic deformations. The surgical techniques and the postoperative complications are briefly discussed.

Adult↗
PubMed1995

Nitric oxide participates in the hypotensive effect induced by adenosine A2 subtype receptor stimulation.

In a previous study, we demonstrated that adenosine plays an important role in the central control of the cardiovascular system with involvement of adenosine A2 rather than A1 subtype receptors. In the present study, we investigated the putative relationship between nitric oxide (NO) and adenosine in the central and peripheral control of the cardiovascular system. Adult male normotensive anesthetized rats were treated with N6-cyclohexyladenosine (CHA), an A1-purinoceptor agonist, and 5'-N-cyclopropyl-carboxamidoadenosine (CPCA), an A2-purinoceptor agonist intracerebroventricularly (i.c.v. 3rd ventricle; 0.05-0.1-0.5 microgram/rat) and by intravenous injection (0.5-1-5 microgram kg-1 i.v.). CPCA and CHA induced a significant and dose-dependent decrease in arterial blood pressure (BP). CHA effects were less marked than CPA. Rats were pretreated with xanthine amine congener (XAC), and A1 adenosine antagonist, with 3,7-dimethyl-1-propargylxanthine (DMPX), an A2 adenosine antagonist (both administered at doses of 0.05 microgram/rat i.c.v. or 0.5 microgram kg-1 i.v.) and with N omega-nitro-L-arginine methyl ester, an NO synthase inhibitor, (L-NAME, 90 microgram/rat i.c.v. and 0.3 mg kg-1 i.v.). The intracerebroventricular and intravenous pretreatment with DMPX or L-NAME inhibited CPCA-induced hypotension; the effect of L-NAME was weaker than that of DMPX. The L-NAME inhibitory effect was reversed both in the central nervous system (CNS) and at the peripheral level by pretreatment with L-arginine (L-Arg; 90 mg kg-1 i.v.), a precursor of NO synthesis. Pretreatment with XAC, but not with L-NAME, reduced the hypotensive effect of CHA. Moreover, intracerebroventricular pretreatment with L-Arg (174 micrograms/rat) increased the hypotensive effect of CPCA.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1995

Survival to lipopolysaccharide, cytokine release and phagocyte functions in mice treated with different total parenteral nutrition regimens.

Effects on host defenses of Total Parenteral Nutrition (TPN) with long- (LCT) and medium-chain triglycerides (MCT) were studied. Survival to lipopolysaccharide (LPS) challenge, blood clearance of Escherichia coli, in vivo and in vitro production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were investigated. In BALB/c mice, LCTs produced a 25% reduction in mortality, compared with controls. TPN performed with a LCT plus MCT mixture reduced mortality by 50%. Spasms appeared after 18 h and 12 h respectively in mice treated with LCT-MCT mixture or LCTs alone, respect to controls (8 h). The LCT-MCT mixture produced a 67% blood clearance of E. coli after 1 h, while the treatment with LCTs alone had no significant effects compared to controls (about 40%). The LCT-MCT mixture induced a 50% increase in chemiluminescence respect to controls. A 33% increase was observed in rats treated with LCTs alone. TNF-alpha serum levels after challenge with LPS were not modified by any of the triglycerides or their combinations. IL-6 increased by 43% with LCT-MCT mixture and by 39% with LCTs alone versus controls. After a 3 h in vitro treatment with LCTs, human monocytes were stimulated to release TNF-alpha at levels higher than those stimulated with the LCT-MCT mixture, and respect to controls. In contrast after 3 h the stimulation with LCT-MCT mixture induced a higher IL-6 release than controls and cells stimulated with LCTs alone, or with LPS.

Animals↗
PubMed1994

Evidence that arcaine increases the N-methyl-D-aspartate-induced cardiovascular effects into the periaqueductal gray area of anesthetized rats.

In the present study the influence of arcaine (0.01-1 microgram/rat), an in vitro putative non-competitive antagonist of the NMDA receptors, on cardiovascular changes induced by intracerebral administration of N-methyl-D-aspartate (NMDA) (0.1 microgram/rat) has been evaluated. Both NMDA and arcaine were microinjected into the periaqueductal gray (PAG) area of anesthetized rats. Arcaine did not decrease NMDA-induced arterial hypertension and tachycardia, but, in a dose-related manner, increased the NMDA-induced cardiovascular effects. Moreover, treatment with arcaine was not able per se to modify arterial blood pressure and heart rate basal values. Although updated in vitro reports indicate arcaine as a blocker of the NMDA receptors by an open channel mechanism, our in vivo results, at the level of the PAG area, show this not to be true. Indeed the drug may facilitate NMDA receptor activation.

2-Amino-5-phosphonovalerate↗
PubMed1994

Conformational dynamics of bovine Cu, Zn superoxide dismutase revealed by time-resolved fluorescence spectroscopy of the single tyrosine residue.

The structural dynamics of bovine erythrocyte Cu, Zn superoxide dismutase (BSOD) was studied by time-resolved fluorescence spectroscopy. BSOD is a homodimer containing a single tyrosine residue (and no tryptophan) per subunit. Frequency-domain fluorometry revealed a heterogeneous fluorescence decay that could be described with a Lorentzian distribution of lifetimes. The lifetime distribution parameters (center and width) were markedly dependent on temperature. The distribution center (average lifetime) displayed Arrhenius behavior with an Ea of 4.2 kcal/mol, in contrast with an Ea of 7.4 kcal/mol for the single-exponential decay of L-tyrosine. This indicated that thermal quenching of tyrosine emission was not solely responsible for the effect of temperature on the lifetimes of BSOD. The distribution width was broad (1 ns at 8 degrees C) and decreased significantly at higher temperatures. Furthermore, the width of the lifetime distribution increased in parallel to increasing viscosity of the medium. The combined effects of temperature and viscosity on the fluorescence decay suggest the existence of multiple conformational substrates in BSOD that interconvert during the excited-state lifetime. Denaturation of BSOD by guanidine hydrochloride produced an increase in the lifetime distribution width, indicating a larger number of conformations probed by the tyrosine residue in the denatured state. The rotational mobility of the tyrosine in BSOD was also investigated. Analysis of fluorescence anisotropy decay data enabled resolution of two rotational correlation times. One correlation time corresponded to a fast (picosecond) rotation that contributed 62% of the anisotropy decay and likely reported local mobility of the tyrosine ring. The longer correlation time was 50% of the expected value for rotation of the whole (dimeric) BSOD molecule and appeared to reflect segmental motions in the protein in addition to overall tumbling. Comparison between rotational correlation times and fluorescence lifetimes of BSOD indicates that the heterogeneity in lifetimes does not arise from mobility of the tyrosine per se, but rather from dynamics of the protein matrix surrounding this residue which affect its fluorescence decay.

Animals↗
PubMed1994

[Comparative clinical evaluation of 4 heat and moisture exchangers (HME) in general anesthesia].

OBJECTIVE: To determine the efficiency, during general anaesthesia, of four commercially available HMEs, with particular attention to the change of performances due to the new modifications introduced by the manufacturers. DESIGN: Comparisons of the performances of each HMEs with psychometric method in terms of T degree C, RH (%), AH (mgH2O/1) of inhaled and expired gases. PATIENTS: A sample of 28 patients under general anesthesia longer than 150 minutes, undergone elective urological surgery. Patients with cardiological, respiratory and metabolic impairments have been excluded. MEASUREMENTS AND RESULTS: The measurements of T degree C, RH and AH have been performed with thermometric probes every minute. The collected data have been analyzed by Student's "t"-test for unpaired data. CONCLUSIONS: The obtained data show that a good conditioning of the inhaled gases is possible, although only few HMEs satisfy the requirements indicated in the ISO and BSI standards.

Adult↗
PubMed1994

[Sciatic and femoral nerve block with electro-neural stimulator (ENS) in surgery of the knee in day-care surgery].

This study was designed to evaluate locoregional anesthesia (double block of sciatic and femoral nerves with ENS) for ambulatory knee arthroscopic surgery. A statistical evaluation was performed in 50 adult outpatients (41 males, 9 females, ASA class 1 or 2) undergoing ambulatory knee arthroscopic procedures. Basal and intraoperative BP, HR SaO2 were recorded and the intensity of analgesia was also assessed according to the patient's subjective evaluation. Extra sedative or analgesic requirements were also recorded. There were no statistical changes in hemodynamic parameters during the perioperative period. The effectiveness of the anaesthetic block was classified as very good in 84% of patients, good in 2%, sufficient in 6% and inadequate in 8%. All patients were discharged in four hours after surgery. Our study shows that in ambulatory arthroscopic surgery, sciatic and femoral block with ENS is a valuable alternative to general anaesthesia.

Adolescent↗
PubMed1994

Effects of dietary vitamin D deficiency on the cardiovascular system.

Experiments were performed on normotensive rats exposed to vitamin D deficient and control diets from the 22nd to the 180th day of age. In 60-120- and 180-day-old rats. The following parameters were evaluated: a) The vasomotor responses elicited by receptor agonists in the absence and in the presence of the respective antagonists [L-norepinephrine (NE) before and 5 min after prazosin; L-isoprenaline (I) before and 5 min after DL-propranolol; L-dopamine (DA) before and 5 min after L-sulpiride or SCH 23390 or chlorpromazine; acetylcholine (Ach) before and 5 min after atropine; histamine (H) before and after chlorpheniramine; 5-hydroxytryptamine (5-HT) before and 5 min after methysergide or ketanserin]; by carotid-sinus baroreceptor stimulation (CO) before and 5 min after hexamethonium, and by electrical stimulation of the vagus peripheral head (V) before and after atropine; b) Reflex tachycardia elicited by bilateral carotid occlusion (CO) (for 40 sec) and by sodium nitroprusside; c) Catecholamine (norepinephrine, epinephrine) and arginine-vasopressin plasma levels; d) Cholesterol, triglyceride and electrolyte (Na+, K+, Cl-, Ca2+) serum levels. Our results showed that vitamin D deficient diets induced a decrease in pressor responses to NE and CO, and an increase in hypotensive responses to I, DA, Ach, H, 5-HT and V. Changes of arterial blood pressure, heart rate, catecholamine and arginine-vasopressin plasma levels were not observed. Cholesterol, triglyceride and electrolyte (Na+, K+, Cl-) serum levels were not modified, while Ca2+ serum levels decreased. In conclusion, our data suggest that vitamin D depletion can induce changes of pressor and depressor vasomotor responses and suppose a direct role for vitamin D in regulating vasomotor reactivity.

Animals↗
PubMed1993

Cardiovascular effects of adenosine and its analogs in anaesthetized rats.

In order to define the purinergic receptors subtype involved in the control of cardiovascular activity, the effects of intracerebroventricular (icv 3rd ventricle) or intravenous (i.v.) injection of purinergic agonists and antagonists were evaluated on arterial blood pressure and heart rate of anaesthetized normotensive adult male rats. Adenosine (Ado) an A1 and A2 purinergic receptors agonist, N6-cyclohexyladenosine (CHA), an A1 receptor agonist and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA), an A2 purinergic receptor agonist, were administered in rats by icv (0.01-0.05-0.1 microgram) and i.v. (0.1-0.5-1 microgram/kg) injections. The animals treated with adenosine were either pretreated with an A1 (8-cyclopenthyl-1,3-dimethylxanthine, CPT) an A2 (3,7dimethyl-1-propargylxanthine, DMPX) or an A1-A2 (aminophylline, APH) purinergic receptor antagonist by icv (0.05 microgram) or i.v. (0.5 microgram/kg) injected or not at all pretreated. Ado, CPCA and CHA produced a dose-dependent decrease in arterial blood pressure and heart rate. The effects of CHA were less marked than those caused by Ado and CPCA. The icv and i.v. pretreatment with aminophylline, CPT and DMPX inhibited arterial hypotension and bradycardia induced by Ado, CHA and CPCA. The inhibitor effects of aminophylline and DMPX were stronger than those caused by CPT. These results showed that in the cerebral areas near the 3rd ventricle the purinergic system plays an important role in the control of cardiovascular function. The involvement of A2 purinergic receptors after administration of adenosine or its analogs on central and peripheral cardiovascular activity was also confirmed.

Adenosine↗