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Biomedical subjects

E Lozupone

Publications and source records attributed to E Lozupone.

At least 37 records · Page 2Linked to original sources
PubMed1988

The rate of bony tissue deposition in the spongiosa of the extremities of long bones in the dog.

9 mongrel dogs ranging from 5 months to 3 years of age were given 3 single endovenous Alizarin injections at 20-day intervals. In transverse sections of the epiphyses and metaphyses of the proximal and distal ends of the femur, tibia, radius and humerus, we measured the thickness of the bony tissue newly formed during the period between the 1st and 2nd Alizarin administration, and separately of that laid down between the 2nd and the 3rd. The weighted means and histograms set up by us of the values severely gathered in the tubular (peripheral) and lamellar (deeply placed) spongiosa in each metaphyseal and epiphyseal sections, are the expression of the mean linear rate of bony tissue deposition. The mean linear rate of bone deposition (1) declines with age; (2) is higher in the metaphyses than in the epiphyses; (3) in single metaphyses it is higher in the tubular than in the lamellar type of trabeculae. These differences are much marked in the animals undergoing body growth, tending to become appreciably reduced in adult specimens. Significant differences in bone deposition rates between corresponding regions of different bones from the same individual were not seen to occur. The differences in bony tissue deposition rate between the tubular and lamellar spongiosa networks seem to depend upon the action exerted by local factors functionally closely associated with the remodelling of metaphyses during growth in length of the skeletal segments, hence upon predominantly mechanical factors.

Animals↗
PubMed1988

The barrier systems in the choroidal plexuses of the chick embryo studied by means of horseradish peroxidase.

The development of the blood-cerebrospinal fluid (CSF) and cerebrospinal fluid-blood barriers, and the differentiation of the choroidal vessel wall, have been ultrastructurally investigated in the choroidal plexuses of the lateral ventricles of 10, 15, 18 and 21 day chicken embryos, fixed in normal conditions and also after intracardial and intraventricular injection of horseradish peroxidase. In all the analyzed developmental stages the choroidal epithelial cells seem able to endocytose and degradate, in their lysosomal apparatus, the tracer molecules reaching their ventricular and basolateral sides. The intravascularly injected horseradish peroxidase can enter the ventricular cavity by interepithelial route only at 10th incubation day, when the tight intercellular junctions are not formed everywhere, while a transepithelial transport is always hindered. The marker injected into the ventricular cavity reaches the subepithelial compartment and the blood stream, at 10th incubation day by interepithelial as well as transepithelial route and, successively, by transepithelial vesicular transport alone. The differentiation processes undergone by the choroidal blood vessels consist in a progressive thinning of the endothelial cells, appearance of pores, already numerous at 15th incubation day, and formation of the endothelial basement lamina, the final event in vessel wall maturation.

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↗
PubMed1985

The structure of the trabeculae of cancellous bone. 1. The calcaneus.

87 either cylindroid or laminar trabeculae, isolated from the perpendicular or inferior bundles of the human calcaneus, were embedded in methylmatecrylate and serially cut along longitudinal and transversal planes with a rotatory-blade saw. The microscopical study of the sections showed that in 83% of the samples secondary osteons run along the longitudinal axis of the trabeculae and their lumina either form a continuous channel network throughout each trabecula (37% of cases) or are restricted to discrete segments (46% of cases). The trabeculae entirely devoid of osteons (17%) are the thinnest, never exceeding 400 microns in thickness. This value is not even exceeded by the segments devoid of osteons in the trabeculae in which the Haversian canals occur only intermittently; conversely, the segments containing Haversian canals can reach and exceed 600 microns in thickness. The maximum distance of the osteocytic lacunae from filtering surfaces--i.e. outer surface of the trabeculae or inner surface of the Haversian canals--was found to be almost the same in the segments of the trabeculae that enclose or not osteons, even though the average trabecular thickness is greater in the former than in the latter regions. On the basis of these findings the formation of endotrabecular osteons may be viewed as a device that indirectly favours the metabolic exchange of deep-seated osteocytes while increasing the free surface area available for bone tissue reconstruction. It remains doubtful whether the Haversian systems may also contribute to improve the mechanical properties of the trabeculae. The arrangement of the collagen fibrils, which differs between cylindroid and laminar trabeculae, is apparently well suited to ensure the resistance of the trabeculae to mechanical loading through the use of the least amount of building material, in accordance with Wolff's law.

Adult↗
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 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↗
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↗
PubMed1979

A quantitative analysis of bone tissue formation in different regions of the spongiosa in the dog skeleton.

An investigation has been carried out on the relationship between the extent of bone tissue formation and the architecture of the "tubular" and "lamellar" components of the spongiosa within shaft bone ends, the anterior and posterior epiphyses and the intermediate portions of vertebral bodies in 3 dogs (aged 6 months, 2 and 3 years) treated for 3 consecutive days with tetracycline. The ratio of the extent of labelled surfaces to the sum of labelled plus unlabelled ones indicates the bone formation rate, referred to as osteogenic activity (OA). In the growing animal, a higher osteogenic activity is displayed by the "tubular" spongiosa, which lies peripherally in the metaphyses of shaft bones and consists of strong trabeculae nearly parallel to one another, and apparently arranged according to the distribution of mechanical stresses. In the adult dogs, the relatively higher osteogenic activity recorded in "lamellar" spongiosa appears to depend on a marked reduction in the osteogenic activity in the "tubular" spongiosa. In the vertebrae, osteogenic activity is higher in the central portion than in extremities solely during the period of growth in length: in the adult, the value of osteogenic activity was found to be practically uniform throughout the vertebral body. The "tubular" spongiosa, therefore, would be more actively involved in the remodelling of the metaphyses while the bone increases in length; the same would occur in the intermediate portion of the vertebral body. The reconstruction of the "lamellar" spongiosa, presumably less involved mechanically than the "tubular" spongiosa, would rather be an expression of bone mineral metabolism. A close relationship between spongiosa structure and osteogenic activity would occur at the ends of long bones and within the vertebral body.

Aging↗