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Biomedical subjects

S Castelli

Publications and source records attributed to S Castelli.

At least 19 recordsLinked to original sources
PubMed2005

Experimental and simulative dissociation of dimeric Cu,Zn superoxide dismutase doubly mutated at the intersubunit surface.

The equilibrium properties of dimeric Photobacterium leiognathi Cu,Zn superoxide dismutase mutant bearing two negative charges in the amino acid clusters at the association interface has been studied, experimentally and computationally, and compared to those of the native enzyme. Pressure-dependent dissociation is observed for the mutant, as observed by the fluorescence shift of the unique tryptophan residue located at the intersubunit surface. The spectral shift occurs slowly, reaching a plateau after 15-20 min, and is fully reversible. Measurement of the degree of dissociation allows us to calculate the standard volume variation upon association and the dissociation constant at atmospheric pressure. On the other hand the native protein is undissociable at any pressure. In the simulative approach, the dissociation free energy has been calculated through the blue moon calculation method for the case of a multidimensional reaction coordinate, corrected for the rotational contribution within the semiclassical approximation for a free rigid-body rotor. The scheme permits to define a definite path for the rupture of the dimer and to calculate the effective force involved in the process. The calculated free energy difference is close to the experimental one, and the value obtained for the mutant is well below that obtained for the native protein, indicating that the theoretical reaction scheme is able to reproduce the experimental trend. Moreover, we find that, when the separation distance increases, the protein structure of the monomer is stable in line with the fast recovery of the original fluorescence properties after decompression, which excludes the presence of partly unfolded intermediates during the dimer-monomer transition.

Amino Acids↗
PubMed2003

Active-site copper and zinc ions modulate the quaternary structure of prokaryotic Cu,Zn superoxide dismutase.

The influence of the constitutive metal ions on the equilibrium properties of dimeric Photobacterium leiognathi Cu,Zn superoxide dismutase has been studied for the wild-type and for two mutant protein forms bearing a negative charge in the amino acid clusters at the dimer association interface. Depletion of copper and zinc dissociates the two mutant proteins into monomers, which reassemble toward the dimeric state upon addition of stoichiometric amounts of zinc. Pressure-dependent dissociation is observed for the copper-depleted wild-type and mutated enzymes, as monitored by the fluorescence shift of a unique tryptophan residue located at the subunit association interface. The spectral shift occurs slowly, reaching a plateau after 15-20 minutes, and is fully reversible. The recovery of the original fluorescence properties, after decompression, is fast (less than four minutes), suggesting that the isolated subunit has a relatively stable structure, and excluding the presence of stable intermediates during the dimer-monomer transition. The dimer dissociation process is still incomplete at 6.5 kbar for the copper-depleted wild-type and mutated enzymes, at variance with what is generally observed for oligomeric proteins that dissociate below 3 kbar. Measurement of the degree of dissociation, at two different protein concentrations, allows us to calculate the standard volume variation upon association, Delta V, and the dissociation constant K(d0), at atmospheric pressure, (25 ml/mol and 3 x 10(-7)M, respectively). The holoprotein is fully dimeric even at 6.5 kbar, which allows us to evaluate a lower Delta G degrees limit of 11.5 kcal/mol, corresponding to a dissociation constant K(d0)<10(-9)M.

Binding Sites↗
PubMed2000

Specific combinations of zein genes and genetic backgrounds influence the transcription of the heavy-chain zein genes in maize opaque-2 endosperms.

The transcript levels of heavy-chain zein genes (zH1 and zH2) and the occurrence of the zH polypeptides in different opaque-2 (o2) lines were investigated by RNA-blot analyses and by sodium dodecylsulfate-polyacrylamide gel electrophoresis or two-dimensional gel electrophoresis protein fractionations. Four mutant alleles o2R, o2T, o2It, and o2-676 introgressed into different genetic backgrounds (GBs) were considered. The mono-dimensional gel electrophoresis zein pattern can be either conserved or different among the various GBs carrying the same o2 allele. Likewise, in the identical GB carrying different o2 alleles, the zein pattern can be either conserved or differentially affected by the different mutant allele. Zein protein analysis of reciprocal crosses between lines with different o2 alleles or the same o2 showed in some case a more than additive zH pattern in respect to the o2 parent lines. Electrophoretic mobility shift assay approaches, with O2-binding oligonucleotide and endosperm extracts from the above o2 lines, failed to reveal o2-specific retarded band in any of the o2 extracts. The results suggest that the promoter of some zH1 and zH2 contains motif(s) that can respond to factors other than O2.

Alleles↗
PubMed1997

[Postpartum myoglobin blood monitoring in newborns. Correlations with renal function in the first 48 hours of life].

BACKGROUND: Myoglobin is a muscular tissue protein, and it is a very early damage index. As the newborn "thin mass" is less than that of the adult and knowing the renal dynamics of this protein clearance, the authors have analyzed the correlation between myoglobinemia and transitory renal failure, which is frequently present in newborns with fetal distress. METHODS: We examined a random population of 56 newborns (33 eutocic deliveries 14 caeserotomy, 9 various degrees of fetal distress) to which, after having had the parents' informed consent, the microsamples pattern was fixed at 0, 6, 12, 24, 48 hours from birth at the same time of ordinary exams to gauge: myoglobin with nephelometric method, CPK, creatininemia, azotemia and transaminase. The same exams were camed out on the mother at the beginning of labor and after delivery. RESULTS: We found that the placenta is not permeable to mother myoglobin, at the sixth hour from birth we have the highest value, while CPK is lower to increase, myoglobinemia associated with myoglobin variations. CONCLUSIONS: Myoglobinemia might be monitored to prevent distressed newborns from transitory renal tubular defect, justifying forced diuresis and urinary alkalosis.

Humans↗
PubMed1996

Relationship between hydration of lean body mass and visceral adipose tissue. A clinical study of women.

OBJECT: To study the relationship between hydration of lean body mass and adipose tissue location. DESIGN: Cross-sectional, clinical study of visceral adipose tissue area and total body water as a percentage of lean body mass. PATIENTS: Seventy-two adult, overweight, women, 52 pre- and 20 post-menopausal (age: 18-72 years, body mass index: 26-52). MEASUREMENTS: Total body water was obtained by electrical impedance measurement; visceral adipose tissue and lean body mass were obtained by computed tomography measurement of visceral adipose tissue area at the level of the 4th-5th lumbar vertebra. RESULTS: Visceral adipose tissue was found, by multiple regression analysis, to be the only predictor of the hydration of the lean body mass. The other independent variables: age, menopausal status, body mass index, glucose and insulin both fasting and after glucose load were not able to significantly improve the predictive power. CONCLUSION: Results of this study confirm the existence of a relationship between visceral adipose tissue content and hydration of the lean body mass.

Abdomen↗
PubMed1996

Effect of patient characteristics on hospital costs for cirrhosis: implications for the disease-related group (DRG) reimbursement system.

The Prospective Payment System uses Diagnosis-Related Groups (DRG) as a reimbursement system. DRG 202 is a disease-related group including liver cirrhosis as a whole. Patients referring to the inpatient unit complain of variable severity and complications of cirrhosis, possibly implying different expenditure of resources. Aim of the investigation was to identify factors affecting cost variability in patients with cirrhosis. A total of 73 consecutive, DRG 202-assigned, cirrhotic patients classified according to demographic and clinical variables were evaluated for length and costs of hospitalization calculated on a full-cost basis. Mean length of hospitalization was 10.2 +/- 7 days. Mean cost of hospitalization was Lit. 4.348.000 +/- 2.718.000. Medical, nursing, diagnostic, drug and general charges accounted for 13%, 29%, 37%, 5% and 16% of the cost, respectively. Child-Pugh score significantly correlated with drug consumption (p < 0.005), length (p < 0.01) and costs (p < 0.001) of hospitalization, but not with cost per day. Age, sex, admission status, referral reason, associated diseases and liver transplant susceptibility did not correlate with duration and costs of hospitalization. Disease severity significantly modifies costs of hospital admission in cirrhotic patients mostly on account of longer hospital stay. Surrogate indexes of disease severity, derived from ISTAT/DRG records, cannot identify patients consuming larger resources. In liver cirrhosis, the DRG system could be improved by introducing parameters, such as Child-Pugh score, directly taking into account disease severity.

Adolescent↗
PubMed1995

[Assessment of lead blood levels in children living in Lucca (Italy) in 1993. The study was conducted as part of the project METOS, in accordance with the decree 496 of June 1982 which adopted the directive CEE No.77/312].

OBJECTIVE: Lead poisoning is a major cause of environmental concern in all countries worldwide. Saturnism in children, especially if young and neglected, represents a peculiar phenomenon both in terms of the biology of growing subjects and the epidemiological nature of poisoning. In under five-year-olds, in addition to lead levels in the atmosphere, it is equally important to evaluate the presence of contaminated dust in the house, hand-to-mouth activities and the level of care provided by parents. It has been demonstrated that, in the presence of equivalent environmental lead levels, dust removal from the house and prevention of hand-to-mouth activities can successfully reduce lead blood levels (PbB) in children. AIM: The aim of this study was to evaluate the risk of chronic lead poisoning in children attending Local Health Unit 6 in Piana di Lucca and to assess the need for a possible health education campaign aimed at eliminating the specific pediatric risk for lead poisoning. MATERIALS AND METHODS: Assay of lead blood levels in 172 children from 0 to 14 years old consecutively attending the Emergency Ward at Campo di Marte Hospital in Lucca for reasons not relating to lead poisoning. RESULTS: Mean lead blood levels in children were 57.2 +/- 30.2 mg/l (mean 50 mg/l) without significant differences between the various age brackets (0-5, 6-10, 11-14 years old). Only one child presented pathological PbB levels (280 mg/l when first measured; 360 mg/l a few months later with normal values of erythrocytic Zn-protoporphyrin, 24-h urinary lead excretion and 24-h urinary delta-aminolevulinic acid). An epidemiological study is now being made of the causes. The general population within the same area presented mean PbB levels of 70.4 +/- 36.9 mg/l (mean 60 mg/l), measured in a total of 471 subjects (adults and children). DISCUSSION AND CONCLUSIONS: The PbB levels currently found in children resident in Lucca confirm a low-risk environmental situation. Preventive measures specifically aimed at children do not therefore appear to be justified at present.

Adolescent↗
PubMed1994

Familial infantile myasthenia: a neuromuscular cause of respiratory failure.

Acute respiratory failure can be the product of any of a great number of muscular, neuromuscular, and neurologic causes. The family history may be extremely helpful in narrowing the differential diagnosis. We report the case of a girl who, during the course of a slight upper respiratory infection, presented with acute respiratory failure requiring mechanical ventilation. The family history was significant for a brother who had arthrogryposis and died at 15 h of life, also from respiratory failure. The patient herself had a history of palpebral ptosis in the evening. The absence of electromyographic and muscle biopsy abnormalities and the patient's positive response to anticholinesterase therapy supported the diagnosis of familial infantile myasthenia. We emphasize the importance of considering the myasthenic syndromes in the differential diagnosis of acute respiratory failure, since appropriate therapy can rapidly resolve the symptoms. Furthermore, an accurate diagnosis allows appropriate genetic counseling for the hereditary forms.

Child, Preschool↗
PubMed1994

Interrelationships between intraabdominal fat and total serum testosterone levels in obese women.

Thirty-six women aged 18 to 52 years with body mass indexes (BMIs) between 27 and 52 were studied. Visceral and subcutaneous fat areas and body fat were evaluated by computerized tomography with a single scan at the IV-V lumbar vertebra level. Glucose, insulin, and C-peptide levels were measured before and after a glucose load. Total and free serum testosterone and 24-hour urinary cortisol excretion were measured. A stepwise multiple regression equation showed the visceral to subcutaneous fat area ratio to be the most powerful predictor for glucose alterations both during fasting and after a glucose load, and showed BMI to be the most powerful predictor for insulin and C-peptide levels. Total serum testosterone, after matching for age and BMI, demonstrates a significant negative correlation with visceral fat area. We conclude that in obese women, as in men, intraabdominal fat negatively correlates with serum testosterone levels.

Abdomen↗
PubMed1994

Measured and predicted total and visceral adipose tissue in women. Correlations with metabolic parameters.

The aim of this study was the verification of the clinical utility of predictive equations for total and intra-abdominal adipose tissue areas. Formulas were calculated using computed tomography (CT) as the gold standard. Ninety-three females were randomly divided into two groups. The predictive equation group was used to calculate the predictive equations for computed tomography adipose tissue areas at the L4-L5 level. These equations were then used to predict total and intra-abdominal adipose tissue area in the validation group. Correlations were made between metabolic parameters and both measured and calculated areas and single predictors. The following measurements were carried out: age, weight/height ratio, body mass index, waist, hip, waist/hip ratio, ultrasound measurement of intra-abdominal distance between abdominal muscle and aorta, sagittal abdominal diameter by CT, adipose tissue intra-abdominal area by CT, total abdominal adipose tissue area by CT. Blood glucose and insulin both fasting and after glucose load. Fasting cholesterol and triglycerides. The best predictors of total and visceral adipose tissue areas were, respectively: weight/height ratio and ultrasound intra-abdominal measurement. Correlations between metabolic parameters and adipose tissue areas both as measured and as calculated by predictive equations were quite similar. Correlations between metabolic parameters and single best predictors of measured adipose tissue areas also gave the same results. Some simple and safe anthropometric measurements can be used, instead of total and visceral adipose tissue area as assessed by CT, when studying associations between adipose tissue and metabolic parameters on sufficiently large groups of patients.

Adipose Tissue↗
PubMed1992

Resting metabolic rate, body-fat distribution, and visceral fat in obese women.

Resting metabolic rate (RMR) was evaluated in 27 obese women aged 16-49 y [body mass index (in kg/m2) 27-51] by indirect calorimetry. Visceral and subcutaneous adipose tissue areas, body fat, and fat-free mass (FFM) were measured by a single scan with computed tomography (CT); the waist-hip circumference ratio (W/H) was also used. Comparison between the lowest and the highest RMR quartiles--adjusted for age and FFM--revealed a higher W/H in the highest quartile (0.78 +/- 0.08 vs 0.88 +/- 0.08; P < 0.05). No difference was observed in CT indexes. No differences in W/H were observed after RMR was adjusted for age, FFM, and body fat. Our results point out that RMR, adjusted for FFM and age, correlates with body-fat distribution as evaluated by W/H, but not with visceral fat, as evaluated by CT. Correlations disappeared after RMR was adjusted for body fat as well.

Adipose Tissue↗