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Biomedical subjects

M Rossi

Publications and source records attributed to M Rossi.

At least 289 records · Page 16Linked to original sources
PubMed1998

Managing hearing loss in a patient with Alzheimer disease.

This case study reports the management of hearing loss in a patient with Alzheimer disease (AD) living at home with a spouse care giver. The report highlights the interaction between symptoms associated with AD and hearing loss and the lack of data regarding remediation of hearing loss in this population. Specifically, the case illustrates the modifications in evaluation and verification of the hearing aid fitting that may be advisable when working with patients with AD. The data for this patient illustrate some novel measurement techniques that may assist the professional in documenting the impact of treatment in this population.

Aged↗
PubMed1998

A new method to detect crackles in respiratory sounds.

In this paper, an automatic method to detect and analyze crackles in digitised respiratory sounds is presented. The method is based on two steps: (1) a threshold (T) value is applied to the first derivative absolute value (FDAV) of lung sound to locate the "zone of interest" and (2) in this zone a crackle is detected if certain conditions are verified. The first derivative (FD) is evaluated by means of a derivative-smoothing filter, preserving areas under the spectral lines of the signal (moment zero), its mean position in time (first moment) and its spectral line width (second moment). The conditions to verify step 2 concern the following: the number and height of the peaks of FDAV and their distances from the starting point of the crackle, within a temporal window TW. This method shows good performances as an automatic detector (sensitivity 84% and specificity 89%), and is specifically designed to find the starting point of the crackle.

Humans↗
PubMed1998

Placing crackles on the flow-volume plane: a study of the relationship between the time position, the flow and the volume.

The aim of this study was to analyse inspiratory crackles in patients with Pulmonary Fibrosis (PF) and Bronchiectasis (BE). One case of Chronic Obstructive Pulmonary Disease (COPD) has also been included. The relationships between the time of occurrence of crackles (T) in the breath cycle and the corresponding flow at the mouth (F) and volume (V) have been investigated. The linear correlations between the flow, volume and time have been investigated by Pearson's R-test and the same variables have been analysed by Principal Component Analysis (PCA) in order to verify the effective dimension of these data. The results show a strong correlation between the time of occurrence and the volume in all the examined cases. PCA shows that in all cases F and V account for more than 90% of variation. These results suggest that placing crackles on the flow-volume plane does not cause loss of information.

Bronchiectasis↗
PubMed1998

[Computerized tomography, magnetic resonance, and nuclear medicine in the non-invasive diagnosis of focal nodular hyperplasia of the liver].

INTRODUCTION: Focal nodular hyperplasia (FNH) is a benign liver lesion requiring a prompt diagnosis and a conservative management. Aim of our study was to prospectively integrate enhanced CT, MRI, nuclear medicine in the noninvasive diagnosis of FNH. MATERIAL AND METHODS: 20 FNH lesions (diameter ranging 1.5-13 cm) in 18 asymptomatic patients were investigated with MRI and nuclear medicine. MRI examinations were performed with a 1.5 T superconducting system (Philiphs NT) by acquiring T1-weighted, T2-weighted, T2-weighted fat-suppressed Turbo Spin-Echo and dynamic MRI sequences, with breath-hold T1-weighted Turbo Field Echo and Gd-DTPA. Nuclear medicine included in all cases 99mTc sulfur colloid or 99mTc iminodiacetic acid studies. Diagnostic sensitivity of MRI was compared with that of nuclear medicine, and the sensitivity of the two modalities combined. The definitive diagnosis was made by percutaneous core-needle biopsy (12 lesions), surgery (2 lesions) and longterm follow-up (6 lesions). RESULTS: In 13 lesions larger than 3.5 cm typical findings, such as the central scar and homogeneous pattern, were observed in 9 cases (75%) with enhanced CT, in 10 cases (83%) with unenhanced MRI and in 11 cases (91%) after gadolinium injection. Hepatobiliary scintigraphy showed increased tracer uptake in delayed scans in 10/12 cases (83%) while sulfur colloid studies were diagnostic in 2/12 cases only (16%), showing the same tracer uptake than the surrounding liver parenchyma. In 7 lesions smaller than 3.5 cm, only 1 case showed typical findings; dynamic MRI showed typical early hypervascularity in 5 of the 6 remaining lesions (71%) which persisted on late images. In lesions smaller than 3.5 cm, sulfur colloid studies were diagnostic in 1/7 lesions (14%) and hepatobiliary scintigraphy in 3/7 lesions (42%). Considering all 20 lesions, MRI-nuclear medicine integration performed better than MRI alone. CONCLUSIONS: Enhanced MRI and biliary scintigraphy are important tools to make the final diagnosis of FNH. In small lesions both examinations should performed, but in large lesions MRI may be sufficient to make an unquestionable diagnosis, limiting hepatobiliary scintigraphy to questionable cases.

Contrast Media↗
PubMed1997

Thioredoxin from Bacillus acidocaldarius: characterization, high-level expression in Escherichia coli and molecular modelling.

The thioredoxin (Trx) from Bacillus acidocaldarius (BacTrx) was purified to homogeneity by anion-exchange chromatography and gel-filtration chromatography, based on its ability to catalyse the dithiothreitol-dependent reduction of bovine insulin disulphides. The protein has a molecular mass of 11577 Da, determined by electrospray mass spectrometry, a pI of 4.2, and its primary structure was obtained by automated Edman degradation after cleavage with trypsin and cyanogen bromide. The sequences of known bacterial Trxs were aligned at the active site: BacTrx has an identity ranging from 45 to 53% with all sequences except that of the unusual Anabaena strain 7120 Trx (37% identity). The gene coding for BacTrx was isolated by a strategy based on PCR gene amplification and cloned in a plasmid downstream of a lac-derived promoter sequence; the recombinant clone was used as the expression vector for Escherichia coli. The expression was optimized by varying both the time of cell growth and the time of exposure to the inducer isopropyl beta-d-thiogalactoside; expressed BacTrx represents approx. 5% of the total cytosolic protein. CD spectra and differential scanning calorimetry measurements demonstrated that BacTrx is endowed with a higher conformational heat stability than the Trx from E. coli. Nanogravimetry experiments showed a lower content of bound water in BacTrx than in E. coli Trx, and a transition temperature approx. 10 degrees C higher for BacTrx. The three-dimensional model of the oxidized form of BacTrx was constructed by a comparative molecular modelling technique, using E. coli Trx and Anabaena strain 7120 Trx as reference proteins. Increased networks of ion-pairs and shorter loops emerged as major features of the BacTrx structure compared with those of the template proteins. The findings are discussed in the light of the current knowledge about molecular determinants of protein stability.

Amino Acid Sequence↗
PubMed1997

Peptide analogue studies of the hypothalamic neuropeptide Y receptor mediating pituitary adrenocorticotrophic hormone release.

Hypothalamic neuropeptide Y (NPY) is thought to be important in the regulation of feeding and also in the release of Adrenocorticotrophic hormone (ACTH). Intracerebroventricular administration of NPY to male rats significantly increased plasma ACTH 10 min after injection and stimulated 2-h food intake. A series of analogues of NPY that have a greatly reduced affinity for the Y1 [human pancreatic polypeptide (human PP), NPY(3-36)], the Y2 ([Pro34]NPY, human PP), the Y3 (peptide YY), and the Y6 (human PP) receptor, all markedly stimulated ACTH release. Rat PP, which binds with high affinity to the Y4 receptor, was unable to stimulate ACTH release. A novel analogue fragment [Pro34]NPY(13-36) was synthesized as a ligand with low Y1 and Y2 receptor affinity. Interestingly, neither [Pro34]NPY(13-36) nor the selective Y5 receptor agonist [D-Trp32]NPY stimulated food intake, whereas both significantly increased plasma ACTH. Thus the hypothalamic NPY receptor mediating increases in plasma ACTH has a fragment activation profile unlike the Y1-Y4 or Y6 receptors and appears distinct from the NPY receptor controlling food intake.

Adrenocorticotropic Hormone↗
PubMed1997

Leptin interacts with glucagon-like peptide-1 neurons to reduce food intake and body weight in rodents.

The adipose tissue hormone, leptin, and the neuropeptide glucagon-like peptide-1 (7-36) amide (GLP-1) both reduce food intake and body weight in rodents. Using dual in situ hybridization, long isoform leptin receptor (OB-Rb) was localized to GLP-1 neurons originating in the nucleus of the solitary tract. ICV injection of the specific GLP-1 receptor antagonist, exendin(9-39), at the onset of dark phase, did not affect feeding in saline pre-treated controls, but blocked the reduction in food intake and body weight of leptin pre-treated rats. These findings suggest that GLP-1 neurons are a potential target for leptin in its control of feeding.

Animals↗
PubMed1997

Crystal structure of the beta-glycosidase from the hyperthermophilic archeon Sulfolobus solfataricus: resilience as a key factor in thermostability.

Enzymes from hyperthermophilic organisms must operate at temperatures which rapidly denature proteins from mesophiles. The structural basis of this thermostability is still poorly understood. Towards a further understanding of hyperthermostability, we have determined the crystal structure of the beta-glycosidase (clan GH-1A, family 1) from the hyperthermophilic archaeon Sulfolobus solfataricus at 2.6 A resolution. The enzyme is a tetramer with subunit molecular mass at 60 kDa, and crystallises with half of the tetramer in the asymmetric unit. The structure is a (betaalpha)8 barrel, but with substantial elaborations between the beta-strands and alpha-helices in each repeat. The active site occurs at the centre of the top face of the barrel and is connected to the surface by a radial channel which becomes a blind-ended tunnel in the tetramer, and probably acts as the binding site for extended oligosaccharide substrates. Analysis of the structure reveals two features which differ significantly from mesophile proteins; (1) an unusually large proportion of surface ion-pairs involved in networks that cross-link sequentially separate structures on the protein surface, and (2) an unusually large number of solvent molecules buried in hydrophilic cavities between sequentially separate structures in the protein core. These factors suggest a model for hyperthermostability via resilience rather than rigidity.

Amino Acids↗
PubMed1997

Effects of temperature and SDS on the structure of beta-glycosidase from the thermophilic archaeon Sulfolobus solfataricus.

The effects of temperature and SDS on the three-dimensional organization and secondary structure of beta-glycosidase from the thermophilic archaeon Sulfolobus solfataricus were investigated by CD, IR spectroscopy and differential scanning calorimetry. CD spectra in the near UV region showed that the detergent caused a remarkable change in the protein tertiary structure, and far-UV CD analysis revealed only a slight effect on secondary structure. Infrared spectroscopy showed that low concentrations of the detergent (up to 0.02%) induced slight changes in the enzyme secondary structure, whereas high concentrations caused the alpha-helix content to increase at high temperatures and prevented protein aggregation.

Bacterial Proteins↗
PubMed1997

Annealing of complementary DNA strands above the melting point of the duplex promoted by an archaeal protein.

One enigma in the biology of hyperthermophilic microorganisms, living near or above 100 degrees C, is how their genomes can be stable and, at the same time, plastic at temperatures above the melting point. The nonspecific DNA-binding protein Sso7d of the hyperthermophilic archaeon Sulfolobus solfataricus is known to protect DNA from thermal denaturation. We report here that Sso7d promotes the renaturation of complementary DNA strands at temperatures above the melting point of the duplex. This novel annealing activity is strictly homology-dependent, and even one mismatch in a stretch of 17 complementary bases severely reduces its efficiency. Since pairing of homologous single strands is a key step in all fundamental processes involving nucleic acids, such as transcription, replication, recombination, and repair, Sso7d is a candidate component of the protein machinery devoted to the coupling of DNA stability to metabolic flexibility at high temperature.

Archaeal Proteins↗
PubMed1997

Identification of the active site nucleophile in the thermostable beta-glycosidase from the archaeon Sulfolobus solfataricus expressed in Escherichia coli.

Sulfolobus solfataricus beta-glycosidase expressed in Escherichia coli was fully inactivated at 65 degrees C, according to pseudo-first-order kinetics, by [3H]conduritol B epoxide (DL-1,2 anhydro-myo-inositol) synthesized as the active site directed inhibitor by a slight modification of Legler's procedure [Legler, G. (1977) Methods Enzymol. 46, 368-381]. The determination of kinetic constants for the inactivation showed that the process took place through the formation of a stabilized inhibitor-enzyme intermediate. Inactivation and reactivation studies suggested that the inhibitor-enzyme intermediate complex was formed more rapidly and hydrolyzed at a lower rate than it was for other glycosidases. Moreover, the stoichiometry of the binding, determined by electrospray mass spectrometric analysis, revealed that one molecule of the inhibitor was covalently bound to each enzyme subunit. The binding site for [3H]conduritol B epoxide was identified by the isolation and partial sequence analysis of the radioactive peptide obtained by cyanogen bromide and pepsin digests. Electrospray tandem mass analysis of the labeled peptide showed that the inhibitor was covalently bound to E387. This result, in agreement with data obtained from sequence alignments of S. solfataricus beta-glycosidase with other gluco- and galactosidases of the glycosyl hydrolase family 1 [Henrissat, B. (1991) Biochem. J. 280, 309-316], indicates that the conserved E387 is the nucleophilic amino acid residue in the active site of the enzyme.

Amino Acid Sequence↗
PubMed1997

Multitryptophan-fluorescence-emission decay of beta-glycosidase from the extremely thermophilic archaeon Sulfolobus solfataricus.

The emission decay of intrinsic fluorescence of the extremely thermophilic beta-glycosidase from Sulfolobus solfataricus has been investigated as functions of temperature and of iodide-quencher concentration by frequency-domain fluorometry. This protein contains 68 tryptophans and provides a matrix for correlation of the average spectroscopic behaviour with solvent exposure and local dynamics. At each temperature, the emission is very heterogeneous and interpretable in terms of quasicontinuous bimodal distribution of fluorescence lifetimes. We associate the component of the bimodal distribution to two distinct classes of tryptophanyl residues that differ in microenvironmental characteristics. Temperature and quenching experiments show that the long-lived component includes tryptophanyl residues located in buried regions with high rigidity; the short distributional component corresponds to tryptophans embedded in more flexible and exposed regions. This proposal has been confirmed by examination of the crystallographic structure. The data suggest that, at least for this protein, there is a good correlation between residue exposure and lifetime distributional components. The conformational dynamics of the two classes of tryptophanyl residues is affected differently by temperature, suggesting that the protein regions in which they are located give different contributions to enzyme properties, such as flexibility, stability and function.

Circular Dichroism↗
PubMed1997

Hydro-CT in patients with gastric cancer: preoperative radiologic staging.

A total of 35 patients (age range 35-78 years) with gastric tumors on the lesser curve, or in the antro-pyloric region, underwent angio-CT in the prone position after filling the stomach with 500 ml of water and intravenous administration of glucagon. The films were reviewed by three radiologists independently, staging each tumor according to the TNM classification preoperatively. The overall accuracy of tumor staging ranged between 66-77 %, overstaging between 17-25 %, and understaging between 3-8.5 %. The diagnostic sensitivity, specificity, and accuracy for serosal invasion ranged between 90 and 100, 76 and 84, and 80-88 %, respectively, and the overall accuracy for N staging was 46, 48, and 51 % for the three observers. If, however, N1 and N2 tumors were considered as a single group, N-stage accuracy increased, ranging between 63 and 77 %. The "K test" for analyzing the interobserver agreement was 60 %, i. e., the diagnostic results are reproducible. Water filling of the stomach optimizes visualization of the gastric wall on contrast-enhanced CT. The prone position and drug-induced hypotony allows for good distension without any disturbing artifact reduction obscuring the lower gastric body.

Adult↗
PubMed1997

One-year follow-up after laparoscopic Heller-Dor operation for esophageal achalasia.

BACKGROUND: The Heller-Dor operation has recently been proposed for the treatment of esophageal achalasia even via a laparoscopic approach. METHODS: To measure the medium-term effectiveness of this new minimally invasive technique, an evaluation of pre- and postoperative symptoms, esophagogram, endoscopic findings, esophageal manometry, and pH monitoring was prospectively designed in 43 patients with primary esophageal achalasia. The mean clinical follow-up for all the patients is 12 months (range 3-43), while the mean radiological follow-up is 11 months (range 1-23). Endoscopic data 1 year after surgery are currently available for 27 patients (63%), whereas a 12-month (range 1-26) functional follow-up (including manometric and pH-monitoring studies of the esophagus) is currently available for 35 patients (81.4%). RESULTS: No dysphagia was reported in 38 cases (88.4%); two (4.6%) complained of occasional swallowing discomfort which regressed spontaneously; two (4.6%) had persistent dysphagia which regressed with pneumatic dilatation. One patient (2.8%) reported mild occasional dysphagia after a 1-year asymptomatic period. Preoperatively, esophagograms showed an average maximum diameter of 40.6 +/- 9.1 mm which decreased to 24.1 +/- 6.0 mm after operation. Mean lower esophageal sphincter (LES) resting and residual pressures decreased significantly from 28.6 +/- 10.7 mmHg to 8.8 +/- 4.1 mmHg and from 17.0 +/- 9.7 mmHg to 4.7 +/- 4.0 mmHg, respectively (p < 0.0001). These effects on esophageal diameter and LES function seem to persist over time. The complete absence of any peristaltic contractions recorded preoperatively in all cases remained unchanged after surgery in all but four patients. However, this rare recovery of peristalsis proved to be transient, and patients revealed a manometric impairment of their esophageal body function, but without complaining of dysphagia. Twenty-four-hour pH monitoring showed abnormal gastroesophageal reflux episodes in two (5.7%) of the 35 patients who were monitored: one was asymptomatic; the other had heartburn and endoscopically demonstrated grade II esophagitis. CONCLUSIONS: Laparoscopic Heller-Dor operation achieves excellent medium-term results which, together with the already-demonstrated advantages of a minimal surgical trauma and rapid convalescence, validate the use of such a minimally invasive approach to treat patients with primary achalasia of the esophagus.

Adolescent↗
PubMed1997

Reduction of 0.1 Hz microcirculatory fluctuations as evidence of sympathetic dysfunction in insulin-dependent diabetes.

OBJECTIVE: Loss of spontaneous fluctuations in resting microcirculatory flow has been described in diabetes mellitus, but its mechanism remains unexplained. METHODS: The autonomic control of forearm skin microcirculation was investigated in 23 insulin-dependent diabetic human subjects (median age 39 years, range 27-50) and in 23 age-matched controls (median age 38 years, range 20-57), by laser-Doppler flowmetry. Using spectral analysis of spontaneous microvascular fluctuations, we measured the power of 0.1 Hz ('10-second rhythm') fluctuations, dependent on sympathetic control, and of respiration-related, high-frequency fluctuations, due to the transmission of mechanical chest activity. Autonomic function abnormalities were assessed by 5 tests of cardiovascular reflexes. RESULTS: Abnormalities in cardiovascular autonomic tests were present in 7/23 patients: deep breathing was abnormal 4 in patients, standing in 2, handgrip in 3, cross-correlation in 4, and Valsalva ratio in 0. The power of 0.1 Hz microcirculatory fluctuations was significantly lower in diabetic than in control subjects (2.57 +/- 0.16 vs 3.48 +/- 0.09 In-mV2, mean +/- s.e.m., P < 0.001), whereas that of respiratory fluctuations was similar (2.60 +/- 0.24 vs 2.56 +/- 0.19 In-mV2, P = n.s.). The 0.1 Hz power was 2 standard deviations below the mean of controls (P < 0.05) in 13/23 diabetic patients; this abnormality was significantly more frequent than abnormalities in any other autonomic test (P < 0.001). CONCLUSIONS: Since the observed reduction was confined to those microvascular fluctuations under autonomic control, but not to those dependent on passive mechanical transmission, the reduction in spontaneous microcirculatory vasomotion appears to be determined mainly by sympathetic dysfunction. Sympathetic impairment of skin microvascular control seems to be a common finding, and is probably an early index of autonomic dysfunction in insulin-dependent diabetes.

Adult↗
PubMed1997

Lactase persistence versus decline in human adults: multifactorial events are involved in down-regulation after weaning.

BACKGROUND & AIMS: In nonhuman mammals, lactase activity declines during or after weaning. In contrast, about one half of the human species maintains high lactase activity even in adulthood. To clarify this difference, this study examined some parameters for which contrasting observations have been reported in connection with lactase decline. METHODS: Lactase activity, lactase messenger RNA (mRNA) levels, and in vitro lactase biosynthesis were determined in normal jejunal samples from a large group of white adults, all born in or near Naples. RESULTS: Of 44 individuals, 10 were lactase persistent and 34 were hypolactasic. Biosynthesis of prolactase correlated well with lactase mRNA levels, indicating transcriptional control; it did less so with steady-state lactase activity. Examination of lactase mRNA levels and lactase activity/lactase mRNA ratios revealed a heterogeneous pattern of lactase mRNA level, lactase synthesis, and activity in both lactase persistent and hypolactasic subjects. CONCLUSIONS: Both transcriptional and posttranscriptional factors cause the decline of intestinal lactase. This probably explains the multifarious observations that most studies on adult-type hypolactasia have reported. The single overriding factor distinguishing lactase-persistent subjects from hypolactasic subjects is the high rate of lactase biosynthesis.

Adult↗