Biomedical subjects

S Beretta

Publications and source records attributed to S Beretta.

At least 19 recordsLinked to original sources

PubMed2001

Single molecule studies by means of the two-photon fluorescence distribution.

We have characterized a commercial confocal scanning head for the detection of single molecule fluorescence by two-photon excitation. We have verified that the distribution of the fluorescence emitted by dyes and labeled proteins on glass substrates is discrete with quanta proportional to a common reference signal. We describe and test a simple and quantitative tool to discriminate between single molecules and molecular aggregates on single snapshots based on the analysis of the intensity distribution. We have verified the square dependence of the fluorescence intensity vs. the excitation power, suggesting that no appreciable saturation and fast photo-damage of the chromophores takes place at the excitation power employed here.

Fluorescence↗

PubMed2001

Prospective follow-up study of chronic polyneuropathy of undetermined cause.

Forty consecutive patients with chronic sensorimotor polyneuropathy of undetermined cause were followed to determine disease progression and prognosis. They had had neurological symptoms for at least 1 year before presentation. Neurophysiological examination in all patients showed chronic axonal degeneration, which was confirmed by sural nerve biopsy. Patients were reviewed every 3 months. Laboratory tests were performed every 6 months for the first 2 years and then annually. Neurophysiological examination was performed annually in all patients. Patients were followed up for at least 4 years. In no instance was a possible etiological factor detected during follow-up. The clinical and electrophysiological findings had a slowly progressive course. We suggest that patients with a chronic polyneuropathy of undetermined cause despite detailed investigations do not require further extensive and expensive laboratory tests and neurophysiological studies during follow-up.

Aged↗

PubMed2001

Multiphoton fluorescence microscopy.

Multiphoton fluorescence microscopy has now become a relatively common tool among biophysicists and biologists. The intrinsic sectioning achievable by multiphoton excitation provides a simple means to excite a small volume inside cells and tissues. Multiphoton microscopes have a simplified optical path in the emission side due to the lack of an emission pinhole, which is necessary with normal confocal microscopes. This article illustrates examples in which this advantage in the simplified optics is exploited to achieve a new type of measurements. First, dual-emission wavelength measurements are used to identify regions of different phase domains in giant vesicles and to perform fluctuation experiments at specific locations in the membrane. Second, we show how dual-wavelength measurements are used in conjunction with scanning fluctuation analysis to measure the changes in the geometry of the domains and the incipient formation of gel domains when the temperature of the giant vesicles is gradually lowered.

Fluorescence Polarization↗

PubMed2001

Two-photon microscopy and spectroscopy based on a compact confocal scanning head.

We have combined a confocal laser scanning head modified for TPE (two-photon excitation) microscopy with some spectroscopic modules to study single molecules and molecular aggregates. The behavior of the TPE microscope unit has been characterized by means of point spread function measurements and of the demonstration of its micropatterning abilities. One-photon and two-photon mode can be simply accomplished by switching from a mono-mode optical fiber (one-photon) coupled to conventional laser sources to an optical module that allows IR laser beam (two-photon/TPE) delivery to the confocal laser scanning head. We have then described the characterization of the two-photon microscope for spectroscopic applications: fluorescence correlation, lifetime and fluorescence polarization anisotropy measurements. We describe the measurement of the response of the two-photon microscope to the light polarization and discuss fluorescence polarization anisotropy measurements on Rhodamine 6G as a function of the viscosity and on a globular protein, the Beta-lactoglobulin B labeled with Alexa 532 at very high dilutions. The average rotational and translational diffusion coefficients measured with fluorescence polarization anisotropy and fluorescence correlation methods are in good agreement with the protein size, therefore validating the use of the microscope for two-photon spectroscopy on biomolecules.

Animals↗

PubMed2000

Role of pyridoxal 5'-phosphate in the structural stabilization of O-acetylserine sulfhydrylase.

Proteins belonging to the superfamily of pyridoxal 5'-phosphate-dependent enzymes are currently classified into three functional groups and five distinct structural fold types. The variation within this enzyme group creates an ideal system to investigate the relationships among amino acid sequences, folding pathways, and enzymatic functions. The number of known three-dimensional structures of pyridoxal 5'-phosphate-dependent enzymes is rapidly increasing, but only for relatively few have the folding mechanisms been characterized in detail. The dimeric O-acetylserine sulfhydrylase from Salmonella typhimurium belongs to the beta-family and fold type II group. Here we report the guanidine hydrochloride-induced unfolding of the apo- and holoprotein, investigated using a variety of spectroscopic techniques. Data from absorption, fluorescence, circular dichroism, (31)P nuclear magnetic resonance, time-resolved fluorescence anisotropy, and photon correlation spectroscopy indicate that the O-acetylserine sulfhydrylase undergoes extensive disruption of native secondary and tertiary structure before monomerization. Also, we have observed that the holo-O-acetylserine sulfhydrylase exhibits a greater conformational stability than the apoenzyme form. The data are discussed in light of the fact that the role of the coenzyme in structural stabilization varies among the pyridoxal 5'-phosphate-dependent enzymes and does not seem to be linked to the particular enzyme fold type.

Cysteine Synthase↗

PubMed2000

Prospective randomized trial comparing Tannenbaum Teflon and standard polyethylene stents in distal malignant biliary stenosis.

BACKGROUND: Our aim was to compare the clinical efficacy of the Tannenbaum (TB) biliary prostheses, a recently designed Teflon stent without side holes, with the Cotton-Huibregtse (CH) polyethylene stent. METHODS: Fifty-seven patients (26 men, mean age 75.5 years) with unresectable malignant tumors and distal biliary stenosis were included (38 pancreatic head cancer, 17 cholangiocarcinoma, 2 ampullary cancer). Patients were prospectively randomized to have a 10F, 7 cm long TB (29 patients) or CH (28 patients) stent inserted endoscopically. Four patients (2 TB and 2 CH) were excluded: 3 because of the failure of stent insertion and 1 because of a protocol violation. The patients were evaluated clinically and, if necessary, with biochemical tests every month until death or until they needed surgery for symptoms of gastric outlet obstruction. When occlusion or dislocation occurred, the stent was replaced with one of the same type. Cumulative stent patency and patient survival were estimated with the Kaplan-Meier life-table analysis and compared by log-rank chi-square test. RESULTS: The two groups were comparable in mean age, gender, and diagnosis. The patients were followed for a mean of 145.5 days (range 24 to 613); by the end of the study 47 patients (81%) had died or developed symptoms of gastric outlet obstruction. Median survival was 88 days (range 24 to 613) in the TB group and 75.6 days (23 to 486) in the CH group. Stent exchange (occlusion 16, dislocation 3) was necessary for 5 patients in the TB group and 7 in the CH group. No statistical difference was found on comparing the mean duration of function of the first, second, and third stents (analysis of variance, p = 0.80). The median duration of stent function was 96 days (range 11 to 613) in the TB group and 75.5 days (range 23 to 323) in the CH group. No significant difference was found in either survival time (p = 0.48) or stent patency (p = 0.12). CONCLUSION: This study found no significant advantage of the Tannenbaum prostheses over the standard polyethylene stent in the palliation for patients with distal malignant biliary stenosis with regard to survival or length of stent patency.

Aged↗

PubMed2000

Early cardioversion of atrial fibrillation and atrial flutter guided by transoesophageal echocardiography: a single centre 8.5-year experience.

AIMS: To analyse the safety and impact on maintenance of sinus rhythm of transoesophageal echocardiographically guided early cardioversion associated with short-term anticoagulation in a large series of patients with atrial fibrillation and atrial flutter. METHODS AND RESULTS: Patients who were candidates for cardioversion were eligible for inclusion if they had atrial fibrillation or atrial flutter lasting longer than 2 days or of unknown duration. Patients received short-term anticoagulation with warfarin or heparin and underwent transthoracic echocardiography followed by transoesophageal echocardiography. Early cardioversion was performed if no thrombus was seen on the transoesophageal study. Warfarin was maintained for 1 month after cardioversion. In patients with atrial thrombi, cardioversion was deferred and prolonged anticoagulation was prescribed. The study population included 183 patients. One hundred and sixty nine patients without atrial thrombi underwent early cardioversion. Fourteen patients with atrial thrombi (7.6%) underwent a second transoesophageal echocardiogram after a median of 4 weeks of oral warfarin, and cardioversion was performed if clot regression was documented. No patient in our study population had a clinical thromboembolic event at 1 month follow-up (95% C.I. 0-0.016). The immediate success rate of cardioversion was better among patients with atrial fibrillation < 4 weeks duration compared with patients with atrial fibrillation of longer or of unknown duration: 96.6% vs 85%, respectively (P = 0.014). At 1 month follow-up, the percentage of arrhythmia relapses in patients with initially successful cardioversion was similar in the two groups (29% vs 26%, P = ns); thus the initial better outcome in patients with recent-onset arrhythmia was not lost. CONCLUSION: Transoesophageal echocardiography-guided early cardioversion in concert with short-term anticoagulation is safe. This approach permits abbreviation of the overall duration of atrial fibrillation and has a better impact on the maintenance of sinus rhythm for patients in whom the duration of atrial fibrillation is < 4 weeks.

Adult↗

PubMed2000

Isolated noncompaction of the ventricular myocardium. A study in an adult male and literature review.

Noncompaction of the ventricular myocardium is a rare congenital disorder characterized by the presence of numerous prominent trabeculations and deep intertrabecular recesses which communicate with the left ventricular cavity. The disease uniformly affects the left ventricle, sometimes also affecting the right ventricle. Noncompaction of the ventricular myocardium is believed to be a disorder of endomyocardial embryogenesis. Familial occurrence has been observed. It may be accompanied by depressed ventricular function, cardiac arrhythmia and systemic embolism. Although noncompaction of the ventricular myocardium is a congenital myocardial disorder, the onset of symptoms is frequently delayed until adulthood. We describe a case of noncompaction of the ventricular myocardium in a 33-year-old male with the typical echocardiographic and cardiac magnetic resonance imaging features of this disease.

Adult↗

PubMed1999

Reproducibility of head-up tilt testing potentiated with sublingual nitroglycerin in patients with unexplained syncope.

Head-up tilt testing (HUTT) potentiated with sublingual nitroglycerin has gained acceptance as means of diagnosing neurally mediated syncope. To evaluate the reproducibility of HUTT potentiated with sublingual nitroglycerin, 48 patients with unexplained syncope prospectively underwent 2 consecutive tests 1 to 28 days apart. The initial test ended in syncope in 34 patients (71%). In 9 patients (19%) the test was positive during the drug-free phase, whereas 25 patients (52%) had syncope after nitroglycerin administration. Of these 34 patients with an initial positive test result, 27 (79%) had a reproducible outcome on repeat testing. Of 12 patients (25%) with an initial negative test result, 10 (83%) had a reproducible outcome on repeat testing. Of 2 patients (4%) with a first test ending in exaggerated response, both had a negative repeat test response. The overall reproducibility of sublingual nitroglycerin tilt-table testing was 77%. In a group of 23 patients with both positive tests, 19 (83%) had the same response modality (2 vasodepressor, 4 cardioinhibitory, 13 mixed response). In the same group of patients, individual trough heart rates correlated well with each other between tests. Finally, in the 27 patients with both positive tests, intrapatient time of onset of symptoms did not significantly correlate between tests. Thus, in patients with syncope of unknown origin, HUTT potentiated with sublingual nitroglycerin provides an adequate reproducibility when repeated on different days.

Administration, Sublingual↗

PubMed1999

Polyion character of globular proteins detected by translational and rotational diffusion.

Photon correlation spectroscopy measurements are performed on a solution of lysozyme, a small, highly charged protein at pH=4, in glycerol-buffer mixtures. From the correlation functions of the polarized and depolarized scattered intensity, we derive an effective protein radius by inverting the Stokes Einstein relation for either the translational or the rotational diffusion, as a function of the protein concentration 0< or =C< or =40 g/L. The translational radius decreases with the protein concentration and extrapolates at C approximately 0 to a value slightly larger than the mean rotational radius, which is independent of the protein concentration. By employing recent calculations on electrolyte friction effects (eletrolyte-protein interactions) on both the translational and rotational radius and by keeping also into account the protein-protein electrostatic interactions, we are able to account for the observed differences, suggesting also that lysozyme is more highly hydrated in glycerol mixtures than in the pure buffer. These results indicate that depolarized photon correlation spectroscopy measurements can be used as a valuable tool to detect small changes in the overall protein size.

Acetates↗

PubMed1999

Atrial thrombi resolution after prolonged anticoagulation in patients with atrial fibrillation.

BACKGROUND: Cardioversion of atrial fibrillation in nonanticoagulated patients may be associated with clinical thromboembolism. Prolonged anticoagulation with warfarin before cardioversion of atrial fibrillation produces a marked reduction of cardioversion-related thromboembolism. The benefit of anticoagulant therapy is generally believed to be due to atrial thrombi organization. PATIENTS AND METHODS: Transesophageal echocardiography (TEE) is highly accurate for diagnosis of atrial thrombi and gives the possibility to serially evaluate the effects of anticoagulant therapy. One hundred twenty-three patients with atrial fibrillation lasting longer than 2 days underwent TEE before cardioversion. An atrial thrombus was identified in 11 patients (9%), and was always confined to the left atrial appendage. TEE was repeated after a median of 4 weeks of oral warfarin. Atrial thrombus had completely resolved in 9 of 11 patients (81.8%; 95% CI, 48.2 to 97.7%); in two patients, clot was still present. No patient had clinical thromboembolism between the two TEE studies. CONCLUSIONS: In the population of our study, a prolonged course of warfarin therapy was associated with resolution of atrial thrombi in the majority of patients. According to these data, the mechanism of thromboembolism reduction with 4 weeks of anticoagulation before cardioversion in patients with atrial fibrillation seems to be related mainly to thrombus lysis rather than organization. Due to the possibility of thrombus persistence even after prolonged anticoagulation, follow-up with TEE before cardioversion is necessary to document thrombus resolution.

Administration, Oral↗

PubMed1998

Increased cortical inhibition induced by apomorphine in patients with Parkinson's disease.

The electromyographic silent period following the motor potential evoked by cortical magnetic stimulation is decreased in parkinsonian patients. In this study we investigated whether the decrease in the silent period is connected only with parkinsonian symptoms. We evaluated the effect of apomorphine (a potent and rapid dopamine-agonist) on the changes in the peripheral and central silent period in 29 patients with Parkinson's disease and in two patients affected by multisystem atrophy (MSA). Apomorphine injection was found to induce a significant improvement in the central silent period in parkinsonian patients but not in the MSA patients, suggesting a relation between the clinical parkinsonian symptoms (akinesia and rigidity) and the silent period duration. The central silent period changes after apomorphine injection could be used as an adjunctive, safe and effective diagnostic tool to assess dopamine responsiveness of parkinsonian syndromes.

Aged↗

PubMed1998

Peripheral neuropathy in chronic respiratory insufficiency.

Peripheral neuropathy commonly occurs in patients with chronic obstructive lung disease (COPD). We report the presence of peripheral neuropathy in 19 of our 30 COPD patients (63.3%): 7 patients had clinical signs of a symmetric motor and sensory polyneuropathy, 12 patients had only subclinical evidence of peripheral nervous system involvement. Neurophysiological studies showed low amplitude compound muscle action potentials (CMAP) and sensory action potentials (SAP) with only slight reduction of nerve conduction velocity in affected patients: these data confirm an axonal polyneuropathy. The severity of the peripheral nervous system involvement in COPD patients was correlated with hypercapnia, the degree of disability and thus with the severity of COPD. Hypoxia, age and duration of the disease were not related with the presence of polyneuropathy. Improvement of respiratory function produced slight but progressive improvement of neurological symptoms. Within one year, also neurophysiological studies revealed a progressive and statistically significant improvement in CMAP and SAP amplitude and motor and sensory conduction velocity and, in some cases, normal electromyography.

Action Potentials↗

PubMed1997

Time-resolved fluorescence of hemoglobin species.

We used time-resolved fluorescence in the pico- to nanosecond time range to monitor the presence of tetramers, dimers and monomers in carbonmonoxyhemoglobin (COHb) solutions and to investigate how their distributions change under different experimental conditions. Comparison of fluorescence lifetime computed from the atomic coordinates of COHb (Vasquez et al., 1996) with those experimentally measured allowed identification of molecular species present in the hemoglobin solution. It was possible to observe modification of the distribution of tetramers, dimers, monomers and species with disordered hemes produced by different experimental conditions. Protein concentration affected the detectable lifetimes, indicating increasing amounts of dimers and monomers at low protein concentrations, while the amount of inverted hemes was not modified. Titration with up to 1 M NaCl modified only the extent of dissociation of hemoglobin into dimers, without affecting heme inversion and monomer formation. Hyperbaric pressure increased the amounts of dimers and monomers. This is the first time that monomeric subunits of hemoglobin have been detected at neutral pH in the normal system.

Carboxyhemoglobin↗

PubMed1997

Auditory event-related potentials in Parkinson's disease.

We studied 49 patients with Parkinson's disease (PD) by a neuropsychological battery examining the temporo-spatial orientation, short-term memory, comprehension, non-verbal intelligence, long-term memory and anomia and the Auditory Event-Related Potentials. In the patients the latencies of the N100 and N200 waves were prolonged and the amplitude of the P300 wave was reduced compared with controls. No difference was found in the ERP of patients with and without cognitive deficits. Equally, no correlation was found between the ERP, the cognitive impairment, the length or the severity of the disease evaluated by Hoehn-Yahr's and Webster's scales.

Aged↗

PubMed1993

Routine endometrial curettage is not indicated at the time of cervical cone biopsy.

Endometrial currettage is commonly performed after cervical cone biopsy to detect occult endometrial abnormalities. Recently, this practice has been questioned and specific criteria promulgated to reduce the number of concomitant endometrial curettages performed at the time of cone biopsy. To investigate the reliability of these criteria, we reviewed the records of 370 women who underwent cold-knife cervical cone biopsy, 323 (87.3 percent) of whom underwent concomitant endometrial curettage. Significant endometrial abnormalities were present in only 18 women, each of whom met at least one specific criterion for endometrial currettage. In contrast, 23 endometrial currettings either contained cervical tissue (five patients) or were insufficient for diagnosis (18 patients). The incidence of complications directly attributable to endometrial curettage was 1.6 percent. We conclude that limiting endometrial curettage at the time of cone biopsy to those women meeting specific criteria would significantly reduce the number of endometrial currettings performed, without hindering the ability to detect significant endometrial abnormalities. Such a reduction would minimize surgical morbidity and could save $13 million annually in the United States.

Adolescent↗

PubMed1992

High-dose intravenous human immunoglobulin in polymyositis resistant to treatment.

Two patients were treated with treatment-resistant polymyositis with intravenous immunoglobulin over four days at a dose of 0.4 g/kg/day. Clinical recovery followed within two months. Serum creatine kinase (CK) activity decreased to normal, and a clear improvement in muscle strength was observed. One patient showed neither clinical relapses nor increase in serum CK activity after 20 months. The other showed a mild increase in serum CK activity after 24 months and was successfully retreated with intravenous immunoglobulin. There were no significant adverse side effects.

Antiviral Agents↗

PubMed1990

The ontogenesis of Fc gamma receptors and complement receptors CR1 in human peripheral nerve.

The ontogenesis of Fc gamma receptors (FcR) and C3b/C4b receptors (CR1) was studied in peripheral nerves from ten fetuses aged from 20 to 38 weeks using immunohistochemical and functional assays. Monoclonal antibodies (mAbs) against FcR and CR1 stained nerve fibers at 10 weeks of gestation and the staining intensity increased during nerve maturation. FcR and CR1 are probably expressed on Schwann cells and are early markers during the development of peripheral nerves. Functional FcR activity was detected in nerve sections before initiation of myelination, which occurs at approximately 18-19 weeks, whereas functional CR1 activity was found in the sections after myelination. Functional CR1 activity may, therefore, be related to myelin. The ontogenesis of FcR and CR1 was also studied on Schwann cells in culture from three fetuses aged 14, 16 and 19 weeks, using immunofluorescence technique with mAbs. The FcR and CR1 are lost on cultured Schwann cells. This suggests that the receptors are not intrinsic to the cells or that Schwann cells require axonal contact for the expression of FcR and CR1.

Antibodies, Monoclonal↗