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Biomedical subjects

A Benvenuti

Publications and source records attributed to A Benvenuti.

At least 19 recordsLinked to original sources
PubMed1999

Reconstruction of extensive long-bone defects in sheep using porous hydroxyapatite sponges.

The capacity of hydroxyapatite (HA) implants to support large defect repair in weight-bearing long bones of large size animals was investigated. Diaphyseal resections 3.5 cm of the tibia were performed in five adult sheep. They were substituted with HA macroporous ceramic cylinders anatomically shaped, and an external fixator was assembled. The sheep were sacrificed at 20, 40, 60, 120, and 270 days after surgery, respectively. Histology and micro X-ray study of resected implants and adjacent tissues showed proper integration of ceramic with newly formed periosteal bone as early as 20 days after surgery. In one sheep, the external fixator was removed 5 months after surgery. The animal gained the ability to walk with no functional impairment until it was sacrificed 4 months later. At this time, extensive integration of ceramic with bone was detected radiographically and confirmed by a morphological study of the resected sample. Our data indicate that large defects in a weight-bearing long bone can be repaired to the extent necessary for full functional recovery in large animals. These data set the stage for further intervention on material properties as well as for preliminary attempts to use ceramic prostheses for reconstruction of large bone defects in humans.

Animals↗
PubMed1999

Dyspnoea is associated with pulmonary function impairment in exposed workers.

This study aimed to evaluate the prevalence of dysponea and its predictors in studies on several working male groups in British Columbia (BC), Canada (cedar sawmill, grain elevator, pulpmill, and aluminum smelter workers), and Tuscany (T), Italy, (shoe and furniture makers, millers, bakers, and pharmaceutical workers). We performed cross-sectional health studies (interviews and pulmonary function tests) for 2498 BC and 1474 T workers exposed to air contaminants, and 1110 BC and 243 T controls. Similar questionnaires and the same definitions were used in BC and in T. Pulmonary function tests were also performed. The participation rates were >92% in BC workers and 82% in T workers. The overall prevalence of moderate dyspnoea was not different in exposed BC and T workers in comparison with controls. Slight dyspnoea was significantly more frequent in BC workers, but not in T workers, with respect to controls. After adjusting for age, body mass index (BMI), smoking, current asthma, and chronic bronchitis, forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were found to be significantly associated with slight and moderate dyspnoea in BC workers, and slight dyspnoea in T workers. Isolated dyspnoea is associated with reduction in FEV1 and FVC in working populations, after adjusting for potentially confounding variables.

Adult↗
PubMed1998

X-ray diffraction on cyclically loaded osteons.

The results of a study on the fine structural distortion due to the two previously observed types of degradation in cyclically loaded single osteons (i.e., stiffness degradation and pinching effect) are presented. Fully calcified longitudinal and alternate osteons were isolated from 350-microns-thick longitudinal sections of human femoral cortical bone. The samples were prepared from 500-microns-long central cylindrical portions of an osteon, whose two ends were penetrating into rectangular lugs for fixation to an electromechanical device that cyclically loaded the samples. This device was connected to a microwave micrometer and a recorder. The structural distortions induced by cyclic loading were investigated by high- and low-angle X-ray diffraction on conventional and synchrotron radiation sources. Cyclic loading results in a reduction in the degree of orientation of apatite crystallites, especially in longitudinal osteons, in which the most abundant longitudinal lamellae are not protected against buckling by transverse lamellae as they are in alternate osteons. In contrast, the degree of orientation of collagen fibrils does not seem to be affected by cycling loading in the two osteon types, possibly because the disorientation of collagen fibrils is, within limits, a reversible process. Finally, the contrast between the disorientation of inorganic crystallites and the apparently unaltered distribution of collagen fibrils suggests that the degradation of cyclically loaded osteons may be due to a separation of the crystallites from the fibrils.

Adult↗
PubMed1998

Asthma-like symptoms, atopy, and bronchial responsiveness in furniture workers.

OBJECTIVES: To study the role of individual and occupational risk factors for asthma in furniture workers. METHODS: 296 workers were examined (258 men, 38 women) with a questionnaire of respiratory symptoms and diseases, baseline spirometry, bronchial provocative test with methacholine, and skin prick tests. Non-specific bronchial hyperreactivity was defined as when a provocative dose with a fall of 20% in forced expiratory volume in 1 second (PD20FEV1) was < 0.8 mg and atopy in the presence of at least one positive response to skin prick tests. Workers were subdivided into spray painters (exposed to low concentrations of diisocyanates and solvents), woodworkers (exposed to wood dusts), and assemblers (control group). RESULTS: The prevalences of attacks of shortness of breath with wheezing and dyspnoea were higher in spray painters (13.5% and 11.5% respectively) than in woodworkers (7.7% and 6.3%) or in assemblers (1.6% and 1.6%); prevalences of chronic cough, asthma, and rhinitis were also slightly but not significantly higher in spray painters and in woodworkers than in assemblers. The difference in the prevalence of respiratory symptoms among the job titles was due to the atopic subjects, who showed a higher prevalence of chronic cough, wheeze, shortness of breath with wheeze, dyspnoea, and asthma in spray painters than in the other groups. The prevalence of non-specific bronchial hyperreactivity in subjects who performed bronchial provocative tests was 17.7%, with no significant difference among groups. Asthma symptoms were significantly associated with non-specific bronchial hyperreactivity. Asthma-like symptoms plus non-specific bronchial hyperreactivity was found in 4% of assemblers, 10% of woodworkers, and 13.3% of spray painters (chi 2 = 2.6, NS). Multiple logistic analysis taking into account individual (smoke, atopy, age) and occupational (job titles) risk factors confirmed that spray painters had higher prevalence of chronic cough than assemblers, and a trend in increasing the prevalence of shortness of breath with wheeze, dyspnoea, and asthma. CONCLUSIONS: Painters in the furniture industry, particularly atopic subjects, are at higher risk of asthma-like symptoms than other job titles. In these workers asthma-like symptoms are more sensitive than non-specific bronchial hyperreactivity in detecting a negative effect of the occupational exposure.

Adult↗
PubMed1997

Pinching in longitudinal and alternate osteons during cyclic loading.

Pinching is a degrading phenomenon which occurs during cyclic loading of certain materials. A change in the slope of the deflection curve reveals pinching lesions, either flexural cracks or bond degradation, cause pinching. This paper investigates pinching for 20 longitudinal and 18 alternate fully calcified osteonic samples of cylindrical shape and 500 micron length. Each sample was axially loaded beyond the proportional limit using an electromechanical device acting as a transducer of the variations in length of the sample into changes in the resonance frequency of a microwave micrometer. A cubic polynomial served as a mathematical model to investigate the stress-strain diagrams at the first and last cycles through the study of strain limits, stiffness and pinching behaviours, and energy absorption. The hysteretic behaviour of the two types of osteons differs and is far from ideal. The presence of pinching may derive from the existence of longitudinal fibrils, in particular the yielding of the incompletely calcified ones. In longitudinal osteons consisting mainly of longitudinal collagen fibrils, the deformation under compression is not protected by lamellae consisting of transverse fibrils, therefore the lesions inducing pinching are magnified. In contrast, in alternate osteons, where the fibrils having a longitudinal orientation are reduced and protected by lamellae containing transversely oriented fibrils, the lesions-inducing pinching are lessened.

Adult↗
PubMed1995

[Air pollution and daily mortality among Milan residents, 1980-89. Preliminary results].

Short term effects of air pollutant levels on daily mortality were studied, using time series approach, in Milan from the year 1980 to 1989. The Poisson regression with autocorrelated residuals was applied. This paper reports preliminary results of the analyses on the association between total daily number of deaths and the 24h mean concentrations, on the same day, for two air pollutants: sulphur dioxide and total suspended particulate. A positive and curvilinear relation (with a logarithmic shape) has been found between total daily mortality and concentration levels for each pollutant. This result confirm a steeper increase in mortality at low concentrations, lower than the international standards in use at the moment.

Air Pollutants↗
PubMed1994

The torsional properties of single selected osteons.

The aim of the present investigation is to determine the mechanical behavior of single selected osteons loaded by torsion along their axis. Two osteon types were chosen: (a) fully calcified 'longitudinal' osteons, whose fibers (and, consequently, crystallites) have a marked longitudinal spiral course in successive lamellae, (b) fully calcified 'alternate' osteons, whose fibers (and, consequently, crystallites) have a marked longitudinal spiral course in one lamella, and an apparently transverse or circular course in the next. The osteon samples, which were cylindrically shaped, and whose extremities fitted into two rectangular lugs, were prepared on a microturning lathe. The principle of the specially manufactured torsional device was that of a pendulum set oscillating around a very sharp wedge so as to reduce friction to negligible levels. The results indicate that longitudinal osteons are those most resistant to torsional loading. The low resistance to torsional loading of the lamellae whose fibers apparently have an almost transversal course is discussed with reference to recent views on the microstructure of this type of lamella.

Adult↗
PubMed1990

The bending properties of single osteons.

The bending properties of two fully calcified osteon types (longitudinal and alternate) have been investigated in 62 cylindrical samples by applying the technique of three-point bending loading. The bending of each sample was recorded using a microwave micrometer based on the cavity and pulse technique. It has been shown that alternate osteons are better able to withstand bending stress than longitudinal ones. This result offers a definitive explanation for the high concentration of transverse lamellae in pathologically bowed bone shaft.

Biomechanical Phenomena↗
PubMed1986

Orientation of collagen fibers at the boundary between two successive osteonic lamellae and its mechanical interpretation.

By applying an original technique, an investigation has been carried out to determine the orientation of collagen fibrils at the boundary between two successive lamellae in alternate osteons. Evidence is reported that the predominant fiber direction does not change abruptly from one lamella to the next; there is an intermediate system of criss-crossed fibers whose main orientation makes an angle of nearly 45 degrees with the direction of the fibers in the two adjacent lamellae. Taking a composite orthogonally reinforced laminate as a model, a mechanical interpretation of this intermediate system of collagen fibers is given.

Adult↗
PubMed1985

[Kaposi's sarcoma: on its frequent association with lymphoreticular neoplasms and diabetes mellitus].

Kaposi's sarcoma (K.S.) is associated relatively frequently with diabetes mellitus and with a second often lymphoreticular neoplasia. On the basis of the three cases reported, which presented an association of diabetes mellitus, chronic lymphatic leukaemia, Hodgkin's lymphoma and K.S., the relationship between neoplastic diseases, immunological and lymphoproliferative disorders and virus infections is considered.

Aged↗
PubMed1985

Mechanical hysteresis loops from single osteons: technical devices and preliminary results.

The purpose of this paper is to describe an original apparatus for recording hysteresis loops from single osteons and a special microgrinding lathe for preparing osteonic samples for testing. The results obtained by testing isolated osteons, and composite bone samples ground to the same size as an osteon sample justify one to draw the following main conclusions: at an equal degree of calcification, longitudinal osteons show larger hysteresis loops under compression and alternate osteons show larger hysteresis loops under tension; there seems to be little chance of acquiring detailed information on the mechanical effects of osteon calcification recording hysteresis loops; collagen orientation in lamellae is the main factor determining the kind of hysteresis loops displayed by a composite bone sample.

Adolescent↗
PubMed1984

[2 cases of tularemia observed at Monte Amiata].

Two cases of tularemia caused by direct contact with an infected hare are described. Recent epidemiological discoveries about the disease are reported with reference to other known foci in Tuscany and the measures taken to control and isolate the infected areas.

Adult↗
PubMed1983

Metallic debris arising from prosthetic abrasion: investigation of biodegradation of the materials and physiopathology of the bone.

The authors investigated the tissue around a failed knee prosthesis which had a metal-on-metal bearing made of chromium-cobalt-molybdenum alloy. Histological examination and the quantitative analysis of metallic particles found in the bone marrow (by fluorescent spectrometry and laser microsound) provided a detailed picture of the quantity, nature and distribution of the wear debris. The type and nature of the tissue response to the presence of the metal particles was determined by fluorescent microscopy and microradiography.

Aged↗
PubMed1982

The tensile properties of single osteonic lamellae: technical problems and preliminary results.

An investigation on the tensile properties of osteonic lamellae whose fiber bundles have an almost transversal spiral course has been carried out, using samples obtained from alternately structured osteons by applying a procedure described in detail by Ascenzi et al. (1973). A very sensitive microwave extensometer based on cavity and pulse technique was employed in order to record the tensile curve from each lamellar sample. The inhomogeneity in thickness within, and between, single lamellae has ruled out any form of comparison between the curves recorded for ultimate tensile strength and modulus of elasticity. This result is in agreement with the morphological finding that there is usually a wide, continuous range of variation in thickness even along the length of single osteonic lamellae.

Bone and Bones↗
PubMedDate not supplied

[First results of varietal comparison and nitrogen fertilization of rapeseed in Italy (author's transl)].

Some experiments of varietal comparison of various cultivars of rapeseed were carried out, determining the productivity, the oil yield and the analytical characteristics of the oils. Moreover the effects of nitrogen fertilization on the seed production and on oil characteristics were tested. The achieved results have pointed out that, referring to the chosen environment, the cv. "Matador" and "Leonessa" show the highest seed and oil productions, whereas oils extracted from the cv. "Sinus", "Erusine" and "Sinera" contain the minor quantities of erucic acid. It seem that nitrogen fertilization exerts no appreciable influence on rapeseed oil composition. The possibility of the utilization of cv. with law content in erucic acid confirms the practical validity of the cultivation of rapeseed as on oil plant.

Agriculture↗