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Biomedical subjects

A Favia

Publications and source records attributed to A Favia.

At least 37 records · Page 2Linked to original sources
PubMed1990

The structure of the trabeculae of cancellous bone. 2. Long bones and mastoid.

The trabeculae of the mastoid, the upper end of the femur, and the tibia were examined to ascertain whether they contain vascular channels according to a pattern similar to that observed in the calcaneus. The trabeculae were serially sectioned in transverse planes. Each section was microradiographed and photographed under ordinary and polarized light. On the photos of the individual sections (1) the number of the vascular channels, (2) the thickness of the trabecular segments with or without osteons, and (3) the maximum distance of the osteocytic lacunae from filtering surfaces (i.e., haversian canal walls or trabecular surfaces), were evaluated. About 80% of the vascular channels are haversian. Their frequency increases through the increase of the trabecular thickness and reaches 100% in those thicker than 428 microns. The distance of the deep-seated osteocytes from filtering surfaces appears almost the same in the thinner trabeculae, devoid of osteons, and in the thicker ones, containing osteons. Evidence is provided that osteons are present in numerous spongy trabeculae. Osteon formation is strictly related to the trabecular thickness so that the distance of the osteocytes from filtering surfaces does not exceed the critical value of 230 microns (in the mastoid). These findings are in agreement with those recorded in the calcaneus spongiosa. As the trabeculae studied in this research and those of the calcaneus are submitted to different mechanical loads, the main function of the endotrabecular osteons is conceivably to improve the deep-seated cell metabolism rather than the mechanical resistance of the trabeculae. On the other hand, the circumstance that most of the osteons are secondary indicates that they participate to the renewal of bone tissue.

Bone and Bones↗
PubMed1990

[Survival of bone tissue in organotypic culture under intermittent mechanical loading. Preliminary results].

With the aim to study the mechanism of transduction of mechanical stimuli in biological ones we have realized an experimental device for the application of intermittent mechanical forces on bone specimens in vitro. The scheme of the device is reported in Fig. 1. It is constituted by a drive shaft which rotates on eccentric axis (1) supporting a longitudinal bar (2) with the load (3). The latter rests on a piston (4) only during a limited period of every shaft revolution, so that the load becomes intermittent. The bone specimen (5) is placed under the piston and the two are placed in a tube containing the culture medium. This latter is BGJ mod. Fitton-Jackson (Gibco), enriched with fetal calf serum (10%) and ascorbic acid (70 microliters/ml). Right metatarsi from 18-day-old rats were removed aseptically and placed under the piston for 2-6 days after resection of both ends. The homotypic ones, unloaded, were placed in 30 mm Petri dishes, and used as a control. The incubator environment was 5% CO2 in air (A group), or enriched with O2 (25-35%) (B group). At the end of the experimental period the bone specimens were fixed in 4% formalin buffered and treated for conventional histologic methods. In the A group most of the osteocytic lacunae were empty. The osteoblasts disappeared already at the 2nd day; the periosteal fibroblast dedifferentiated and multiplied. The deposition or calcification of osteoid were completely lacking. The application of mechanical load promoted deposition of granular degenerative material around the bone, and the periosteal cells, well differentiated, were surrounded by metachromatic material, which resembles cartilage matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of a low calcium maternal and weaning diet on the thickness and microhardness of rat incisor enamel and dentine.

The deposition and mineralization of incisor hard tissues have been studied in rat pups nursed by mothers on a low calcium diet or weaned with the maternal diet. Animals were killed at 30 days (control and low calcium diets; maternally fed) or 60 days (after 30 days weaning on maternal diet). The degree of mineralization of enamel and dentine was evaluated by a microhardness method on thick transverse sections. The enamel and dentine thickness, and the diameters of the incisor sections and pulp cavity were measured on microradiographs from the sections. Microhardness values of enamel were similar in groups killed after 30 days maternal feeding, but the microhardness of root enamel was 73-74% less in the low calcium-diet weaned group. Peripulpar dentine had mean microhardness values lower than controls in the group fed maternally for 30 days, whereas the whole root dentine appeared significantly less hard in the low calcium-diet weaned group than in the controls. A significant reduction of the incisor bucco-lingual diameter was observed only in this last experimental group. Enamel thickness was significantly lower in the roots of both experimental groups and in the necks of the low calcium weaned group. The reduction in dentine thickness was greater (from -30 to -56%); in the root it was more evident on the lingual aspect. Thus calcium deficiency in the mother's diet did not influence either the deposition or the mineralization of the pup's incisor enamel and dentine. However, when the offspring were weaned with the maternal calcium-deficient diet, mineralization of the tooth hard tissue was retarded.

Animals↗
PubMed1988

Distribution of resorption processes in the compacta and spongiosa of bones from lactating rats fed a low-calcium diet.

An attempt has been made to determine if the structural renewal of bone tissue takes place to a greater extent in the spongiosa than in the compacta and how this is related to the more extensive free surface area in the former. To this purpose, on transverse sections of the femur and 2 degrees lumbar vertebral body of the female lactating rats fed a normal (L group) or a calcium free diet (H group) the area of compact and spongy bone, and the perimeter of the trabeculae were measured. Then TBV, MTPT, MTPD, MTPS, Sv and S/V, according to the Parfitt et al. (1983) method were calculated. In the femurs of rats maintained on a normal calcium diet bone loss takes place to a higher degree in the spongiosa than in the compacta. In the distal metaphysis, moreover, the bone loss is more elevated than in other femoral regions. In the second lumbar vertebral body the bone rarefaction appears to have a similar extent in the compacta and spongiosa and in the three levels inspected. In rats maintained on a restricted calcium intake the osteoporosis is enhanced but the bone is removed predominantly from the compacta in all the femoral regions except in the distal metaphysis and, to a similar degree, from the compacta and the spongiosa of the vertebral body. In the centrodiaphyseal compacta the bone is reabsorbed exclusively at the endosteal level, while in the spongiosa the frameworks subjected to a more extensive resorption occupy a topographic position specific for each single region, and are often formed of thin trabeculae. The dynamic of the trabecular resorption seems to be different in the various spongy frameworks: in each of these it would take place by the removal of the entire trabecula or the thinning of the single trabeculae or by both mechanisms. Lastly, significative correlation was found between trabecular bone loss and trabecular thickness, none with trabecular surfaces. This study shows that bone removal is not regulated by the extent of the trabecular free surface. The mechanisms involved in the control of the distribution of bone removal are strictly connected with those controlling the trabecular thickness. They are probably of a mechanical nature.

Animals↗
PubMed1985

[Structure of alveolar bone during tooth eruption in the dog: preliminary findings].

The structure of the alveolar bone during the tooth eruption in the young dog mandibles was investigated by microradiographic and polarized light techniques. Around the first erupting molar root a trabecular network of primary alveolar bone, less mineralized than the surrounding cortical one, was found. Numerous calcified spicules parallel one to others radiate out the spongiosa near the periodontal ligament. The collagen fiber bundles of the alveolar, woven, bone are continuous with the periodontal ligament ones. This finding indicates that the alveolar bone increases by ossification of the periodontal ligament. Therefore the latter is the forming alveolar bone substratum. The trabeculae of the occlused premolar alveolar bone are ticker and more mineralized. This modification of the occlused tooth alveolar bone could be related to the occlusal stresses.

Alveolar Process↗
PubMed1985

[Structure of the periodontal ligament during tooth eruption in the dog: descriptive aspects].

Serially stained uncalcified sections of young dog mandibles were examined to study the structure of the periodontal ligament of the erupting first right molar. The periodontal ligament around tooth crown presents three zones. The first, near the dental follicle, is a tick layer of parallel collagen bundles with numerous flattened fibroblasts. The second, intermediate, contains a blood vessels network, particularly veins and capillaries. The third, outer, is occupied by a continuous layer of osteoclasts and osteoblasts. Also the periodontal ligament around the tooth presents three layers, the outer and the intermediate rich of cells more than the inner. Particularly, the outer layer shows numerous osteoblasts surrounding the developing trabeculae of the alveolar bone and the collagen fiber bundles of the periodontal ligament. These penetrate into the trabeculae and appear similar to the osteoid layer. These results indicate that the alveolar bone increases by ossification of the connective tissue of the periodontal ligament.

Alveolar Process↗
PubMed1983

[The rate of linear deposition of bone tissue in the bone spongiosum of lactating rats on a low calcium diet].

In the epiphysis and metaphysis of lactating rats, submitted to a Ca++ depletion for 10 and 30 days and a Ca++ repletion diet for 10 days, the density of spongiosa framework and the bone tissue linear accretion rate were compared with those of control rats. The distal metaphyses of femora of the rats fed a calcium free diet for 10 and 30 days lose 50% and 90% of the trabecular framework respectively, while the epiphysis of the same bone lose only 45% and 56%. The linear accretion rate in these regions increases by 7.9 and 24.7% in the epiphysis and by 11.3% and 75.6% in the metaphysis of rats fed a calcium-free diet for 10 and 30 days respectively. Our data indicate that the bone tissue linear accretion rate changes not only between the corresponding regions of control and experimental rats but, in the latter, also in different regions of the same bone. Moreover, the higher the bone loss is, the higher bone accretion rate will be. The correlation between the bone tissue linear accretion rate and the bone loss indicates that the same local factor - probably mechanical - controls the activity and distribution of osteoblasts and osteoclasts.

Animals↗
PubMed1983

[Distribution of bone tissue renewal processes in the skeleton of rats on a hypocaloric diet].

The present study was undertaken to confirm if the mechanical forces can control the pattern of bone turnover as previously demonstrated in our researches on the skeleton of dog. The bone turnover pattern in spongy and compact long bones of lactating female rats submitted to a Calcium deficient diet has been investigated. One group of female rats was maintained on a Ca++ deficient diet for 10 days and a second group for 30 days. Both groups were submitted after this period to a normal diet for 10 days. A third group of female rats of the same age maintained to a normal diet was used as control. The results obtained are in agreement with our previous researches and indicate that mechanical stresses appreciably control the bone turnover pattern. In fact the diminished assumption of Ca++ with diet has caused bone loss at first in the metaphyseal deeply located spongiosa, region less essential to mechanical resistance; only if the ipocalcic diet is protracted, the epiphyseal spongiosa and compact bone of the metaphysis and diaphysis -more heavily mechanical loaded portions of the long bones- were removed.

Animals↗
PubMed1982

Density of trabecular framework and osteogenic activity in the spongiosa of long bones subjected to drastic changes in mechanical loading in the dog.

In 2 groups of dogs aged from 4 months to 3 years, we estimated the density of the spongiosa and the distribution of osteogenic activity in transverse sections of the metaphyses and epiphyses of the experimentally overloaded or unloaded right radii, together with those of the contralateral control bones. Overloading elicited an increase in the density of the spongiosa framework to a higher degree within the peripheral than the deeper metaphyseal spongiosa or within the epiphyses. Some time after operation, the osteogenic activity appeared reduced through the spongiosa in every district although to a greater extent in the regions in which its more pronounced condensation had occurred, i.e. within the metaphyseal subcortical spongiosa. In the unloaded bones, the density of the spongiosa was markedly reduced compared to the control. The differences in the architectural pattern between subcortical and deeper spongiosa were attenuated. Conversely, osteogenic activity was enhanced in every district, being evenly distributed within the spongiosa framework both in the metaphysis and the epiphysis. From comparison between the results obtained by the 2 sets of experiments it seems reasonable to infer that mechanical stress appreciably stimulates bone mass increase and the ensuing remodelling of the spongiosa architecture; at the same time, the more heavily loaded portions of the framework would be subjected to a lesser degree of structural renewal than that occurring in the spongiosa regions less essential to mechanical resistance. The latter, therefore, would rather perform the function of labile stores of mineral salts.

Animals↗
PubMed1981

[The physical resistance of secondary osteons in relation to the arrangement of collagen fibers].

In two dogs, 6 months and 4 years aged, the microhardness of secondary osteons was studied in its relationship to the arrangement of collagen fibers. The results obtained indicate that there are no differences when osteons with the same degree of mineralization but different arrangement of collagen fibers are tested. The possible role played by collagen bundles on the microhardness of bone are briefly discussed.

Animals↗
PubMed1981

[The rate of bone tissue deposition in the spongiosa of long bones subjected to mechanical overload].

In three dogs of various age (8-11 months, 3 years), injected twice with Alizarin red (20 mg/Kg) 27 and 7 days before sacrifice, the linear appositional growth rate of bone tissue have been studied in the distal metaphysis and epiphysis of the right radius submitted to mechanical overload by removing a piece of the ulnar shaft. The normally loaded left radius was used as control. In the overloaded metaphysis the linear appositional growth rate appeared significantly increased in the peripherally located spongiosa; no change in the linear appositional accretion of bone tissue as compared to the control was observed in the deep-seated spongiosa and in the epiphysis. These findings are briefly discussed in connection with the role presumably played by the mechanical stresses on osteogenesis.

Animals↗
PubMed1981

[Variations in mineralization of cortical and medullary bone in laying hens during and after hypocalcemic diet].

Compact and medullary bone of femur, tibia and humerus during a period of calcium depletion and repletion have been studied by microradiographic and microdurimetric method. From our preliminary results it appears that the degree of mineralization varies only in medullary bone, where the existing trabeculaea are eroded and substituted by others that don't complete mineralization. The cortical bone is deeply eroded during the diet and slowly reconstructed during the period of calcium repletion.

Animals↗
PubMed1979

[Quantitative evaluation of the degree of bone tissue deposition in sponge-like skeletal segments submitted to a physiological overload].

In a 14-month old dog, injected twice with Alizarian red 27 and 7 days before sacrifice, both the distribution of the osteogenic areas and the rate of new bone tissue formation have been studied in the distal metaphysis of the right radius submitted to mechanical overloading by removing a piece of the ulnar shaft. The normally loaded left radius was used as a control. Following a four-month overloading, the bone tissue deposition rate appeared markedly reduced in the more peripherally located "tubular" spongiosa which underwent in parallel conspicuous structural changes. No alterations in the reconstruction rate and in the microscopical structure as compared to the control radius were observed instead in the deep-seated "laminar" spongiosa. The present, as well as previous findings, seem to support the view that (1) the two types of trabecular bone, i.e. the "tubular" and the "laminar" spongiosa, are subjected to quantitatively diverse loading, and (2) mechanical factors play a significant role in the control of the topographic distribution of bone tissue reconstruction.

Animals↗
PubMed1979

[Quantitative evaluation of the degree of bone tissue deposition in sponge-like skeletal segments experimentally subjected to mechanical stress].

A 12-month old dog was sacrificed 4 months after fixation of the left anterior limb, in a cutaneous pouch, to the thoracic wall, and division of the ipsilateral brachial plexus; 27 and 7 days before sacrifice, Alizarin red (20 mg/Kg) was injected intravenously. Rarefaction of spongy bone and increase in the rate of osteogenic activity were recorded from the sections of the distal end of the unloaded left radius compared to the corresponding part of the control bone. The events mentioned appeared more marked in the "tubular" than in the "lamellar" spongiosa. These findings seem to offer new evidence supporting the suggestion that in adult life bone tissue reconstruction rate is relatively higher in the areas of spongy bone comparatively less involved in the mechanical resistance.

Animals↗