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Biomedical subjects

G Simonelli

Publications and source records attributed to G Simonelli.

6 recordsLinked to original sources
PubMed1997

Age-related cortical bone loss at the metacarpal.

In order to evaluate in vivo the entity of endosteal and periosteal changes with age in the two sexes, and their relative contribution to age-related cortical bone loss, we undertook a cross-sectional study on a population of normal Caucasian subjects. The group included 189 women and 107 men who were studied by photodensitometry and radiogrammetry of the second metacarpal bone, derived from the same standard hand X-ray. Of the subjects, 134 were 65 years of age or older (75 women and 59 men). Metacarpal bone mineral density (BMD) correlated with age in both sexes, with an annual bone loss rate of 0.5% in women and 0.15% in men. In the over 65 group, correlation was significant only in women, who underwent an acceleration in the rate of bone loss (1% per year). Marrow cavity width (M), cortical index at the second metacarpal shaft (MI) and external width (W) all correlated with age in both sexes, although generally better in the female than in the male sex. M almost doubled from the fourth to the ninth decade in women and increased 50% in men. In the same age interval, MI showed an annual decrease of 0.49% in females and 0.33% in males. In the over 65 group, cortical thinning rate was significant in women (0.39% per annum) but not in men (0.14% per annum), whereas correlation of W was not significant in either sex. Finally, MI correlated with BMD in the whole study population and in the over 65, with a female prevalence in correlation strength maintained throughout life. The following conclusions can be derived for metacarpal aging: (1) an acceleration in cortical bone loss occurs in females after age 65; (2) age-related growth in periosteal diameter, although significant in the whole population, is negligible in the elderly of both sexes; (3) age-related cortical bone loss is generally more dependent on cortical thinning in women than in men.

Adult↗
PubMed1995

The effect of dental prophylaxis instruments on the surface roughness of metals used for metal ceramic crowns.

Prophylactic instruments may cause surface deterioration of metal crown margins, which could cause or aid the retention and accumulation of plaque. In this investigation, highly polished metal disks of high content gold (RX Y), low content gold (Aspen), silver palladium (RX 91), and nickel-chrome alloy (REX III) had their surfaces tracked with an explorer, hand scaler, curette, and a Dentsply Cavitron instrument. The surface roughness was measured with a profilometer. The results indicate that the high content gold was the least resistant to surface deterioration and the ultrasonic scaler caused the most surface deterioration to all the metals.

Analysis of Variance↗
PubMed1985

Cells of origin and topographic organization of corticospinal neurons in the guinea pig by the retrograde HRP method.

In the guinea pig, horseradish peroxidase (HRP) was injected in the cervical or lumbar enlargements of the spinal cord in order to examine the origin and topographical organization of corticospinal (CS) neurons. The cortex was divided into granular and agranular regions to attempt correlations with the location of labeled CS neurons. These, of all sizes, are found only in pyramidal layer V of both kinds of cortical regions and could be seen as single, grouped or organized in clusters of 3-5 or more cells. The soma diameters of HRP CS neurons ranged from 13 to 49 microns. The largest labeled cells were present in the medial part of both agranular and granular cortices and included the giant pyramidal neurons which were found only in the rostromedial agranular cortex. The predominating intermediate-size cells were mostly present in lateral granular areas. The smaller cells were distributed in rostrolateral agranular and caudal granular regions. Morphological evidence suggests that an aggregation in clusters of labeled neurons and the different groups of CS neurons identified in different cortical areas may have additional differences in organization with respect to their precise topographical relations and functional properties. Neurons projecting to cervical levels were more abundant compared to projecting to the lumbar spinal cord, being distributed widely more lateral and anterior on the hemisphere to cortical neurons projecting to lumbar enlargement. These were located only medially on the dorsal surface of the brain. The two groups of labeled neurons were distributed in both agranular and granular cortices and occur adjacent to each other with only a narrow strip of overlap. The findings i.e. laminar organization, the pyramidal shape of CS neurons of all sizes, the presence of clusters and the somatotopic distribution of CS neurons seen in the guinea pig are discussed in comparison with equivalent findings on the corticospinal tract (CST) system of other species. The presence of labeled neurons within the cortex on both sides following unilateral HRP injections in the spinal cord points to a bilateral origin of the CST. This finding is discussed on the basis of the present study and previous autoradiographic findings.

Animals↗
PubMed1981

The distribution of descending brain stem projections to spinal cord in the guinea pig. A horseradish peroxidase study.

In the guinea pig brain stem neurons projecting to the spinal cord were identified by the horseradish peroxidase (HRP) method. Following lumbar injection labelled neurons were found in the RF, VL, R, MNV, TMNV, RTP, NR, PVG, LH and DMH. The distribution of HRP-positive neurons following cervical injection was roughly the same as that observed after lumbar injection except for the presence of labelled cells in the NSNV and their absence in the MNV and TMNV.

Animals↗