Bone histology of Iberosuchus macrodon (Sebecosuchia, Crocodylomorpha)
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Iberosuchus macrodon is a Cenozoic crocodyliform interpreted as a terrestrial, cursorial form. To assess whether this adaptation was accompanied by a high growth rate and an elevated resting metabolic rate (two features commonly attributed to several terrestrial Triassic Crocodylomorpha based on histology), we studied bone histology in the femora of two specimens attributed to I. macrodon. Beyond this question is the broader problem of the possible survival to the Cretaceous-Palaeogene extinction event of tachymetabolic sauropsids other than birds. At mid-diaphysis, bone cortices in Iberosuchus are made of a parallel-fibred tissue that turns locally to true lamellar bone. Cortical vascularization consists of simple longitudinal canals forming a network of medium density. The spacing pattern of conspicuous lines of arrested growth suggests asymptotic growth for Iberosuchus. This general histological structure prevails also in the metaphyseal region of the bones. It is basically similar to that encountered in certain large lizards adapted to active predation, the Varanidae and the Teidae. In one of the two Iberosuchus femora, however, an intracortical meniscus made of a tissue displaying a global radial architecture occurs in the region of the fourth trochanter. Histologically, the latter can be interpreted either as compacted spongiosa or as a fibro-lamellar complex with a gross radial orientation, a tissue corresponding to fast periosteal apposition. These observations suggest that Iberosuchus basically had a slow, cyclical growth indicative of an ecto-poikilothermic, lizard-like, resting metabolic rate. However, it might also have retained a limited capacity for fast periosteal accretion in relation to local morphogenetic requirements as, for instance, the development of crests or trochanters.Keywords:
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The effect of food consistency on the bone appositional pattern at the growth site in the palatal region of the maxillary complex in growing rats was examined by quantitative analysis employing bone histomorphometry. Sixty inbred male rats aged 14 days in the weaning period were divided into two groups. One group was fed a conventional solid diet in addition to milk, while the other received the same diet but in liquid form in addition to milk. They were weaned at 21 days of age. Vital staining was employed to enable a longitudinal recording of bone apposition. In rats fed a liquid diet, the amount of bone apposition on the occlusal surface of the palate was reduced in the region between the first molars, but was increased in the region between the third molars, indicating a more anteriorly directed growth rotation of the palate. The width and ossification rate of the synchondrosis of the midpalatal suture was smaller. Furthermore, lateral growth of the maxilla was inhibited considerably in the distal area. In conclusion, this study shows that food consistency affects the bone appositional pattern at the growth site in the palatal region of the maxillary complex. The results also suggest that the difference in the growth pattern in the upper viscerocranium induced by different food consistencies is caused not only by a difference in mechanical force of the masticatory muscles acting on the muscle insertion areas but also by a difference in the growth pattern in the region which receives occlusal loading.
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Mechanical stimulation is critical for bone architecture and bone mass. The aim of this study was to examine the effects of mechanical loads applied to the knee. The specific question was whether loads applied to the tibial epiphysis would enhance bone formation in the tibial diaphysis. In C57/BL/6 mice, loads of 0.5 N were applied for 3 min per day for 3 days at 5, 10, or 15 Hz. Bone samples were harvested 13 days after the last loading. The strains were measured 13 +/- 2 microstrains at 5 Hz in the diaphysis. The histomorphometric data in the diaphysis clearly showed enhanced bone formation. First, compared with nonloaded control the cross-sectional cortical area was increased by 11% at 5 Hz and 8% at 10 Hz (both P < 0.05). Second, the cortical thickness was elevated by 12% at 5 Hz (P < 0.01) and 8% at 10 Hz (P < 0.05). Third, mineralizing surface (MS/BS), mineral apposition rate (MAR), and bone formation rate (BFR/BS) were increased at 5 Hz (P < 0.01 for MS/BS; P < 0.001 for MAR and BFR/BS) and at 10 Hz (P < 0.05 for MS/BS; P < 0.01 for MAR and BFR/BS). Bone formation was enhanced more extensively in the medial side than the lateral or the posterior side. The results reveal that knee loading is an effective means to enhance bone formation in the tibial diaphysis in a loading-frequency dependent manner without inducing significant in situ strain at the site of bone formation.
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In a series of studies of morphology and morphogenesis of os penis in the rat, the present study deals with initial formation and growth of the bone. Os penis in the rat develops at 1 day p.n. as a membrane bone. It becomes associated with a proximally situated growth cartilage at 3-4 days. Until 10 days it increases in width by periosteal apposition on all surfaces. After 10 days the growth in width takes place by differential processes of apposition and resorption. Results from vital staining with alizarin red S of bones at different ages indicate that os penis during its growth becomes transformed in a ventral direction in the period between 10 and 35 days, while it after that age is transformed in a dorsal direction. No reasonable explanation on this phenomenon is offered. However, the observed periods of time of uniform growth pattern are comparable to time periods of uniform growth patterns of a number of cranial bones.
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Mechanical stimulation is critical for bone architecture and bone mass. The aim of this study was to examine the effects of mechanical loads applied to the knee. The specific question was whether loads applied to the tibial epiphysis would enhance bone formation in the tibial diaphysis. In C57/BL/6 mice, loads of 0.5 N were applied for 3 min/day for 3 days at 5, 10, or 15 Hz. Bone samples were harvested 13 days after the last loading. The strains were measured 13±2 mu strains at 5 Hz in the diaphysis. The histomorphometric data in the diaphysis clearly showed enhanced bone formation. First, compared with nonloaded control the cross‐sectional cortical area was increased by 11% at 5 Hz and 8% at 10 Hz (both P <0.05). Second, the cortical thickness was elevated by 12% at 5 Hz ( P <0.01) and 8% at 10 Hz ( P <0.05). Third, mineralizing surface (MS/BS), mineral apposition rate (MAR), and bone formation rate (BFR/BS) were increased at 5 Hz ( P <0.01 for MS/BS; P <0.001 for MAR and BFR/BS) and at 10 Hz ( P <0.05 for MS/BS; P <0.01 for MAR and BFR/BS). Bone formation was enhanced more extensively in the medial side than the lateral or the posterior side. The results reveal that knee loading is an effective means to enhance bone formation in the tibial diaphysis in a loading frequency‐dependent manner without inducing significant in situ strain at the site of bone formation.
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This study evaluates the bone-healing patterns on the surface of titanium implants at the cortical and marrow compartments of bicortically-installed implants in the diaphysis and metaphysis of rabbit tibiae. In 27 New Zealand rabbits, two implants, one for each macro-design and with equal resorbable blasted media (RBM) implant surfaces, were randomly implanted in the diaphysis or metaphysis of each tibia. The flaps were sutured to allow submerged healing. The animals were sacrificed after two, four, or eight weeks, with nine weeks used for the period of healing. Ground sections were prepared and analyzed. No statistically significant differences were found between the two groups for newly formed bone in contact with the implant surface after two, four, and eight weeks of healing. Bone apposition in the marrow compartment was slightly higher in the diaphysis compared to metaphysis regions across healing stages. Despite the limitations of the present study, it can be concluded that new bone apposition was better than average in the cortical compartment as compared to the marrow compartments. Bone morphometry and density may affect bone apposition onto the implant surface. The apposition rates were slightly better at both the cortical and marrow compartments in diaphysis as compared to metaphysis sites. The new bone formation at the marrow compartment showed slightly better increasing values at diaphysis compared to metaphysis implantation sites.
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The effect of food consistency on the bone appositional pattern at the growth site in the palatal region of the maxillary complex in growing rats was examined by quantitative analysis employing bone histomorphometry. Sixty inbred male rats aged 14 days in the weaning period were divided into two groups. One group was fed a conventional solid diet in addition to milk, while the other received the same diet but in liquid form in addition to milk, They were weaned at 21 days of age. Vital staining was employed to enable a longitudinal recording of bone apposition. In rats fed a liquid diet, the amount of bone apposition on the occlusal surface of the palate was reduced in the region between between the first molars, but was increased in the region between the third molars, indicating a more anteriorly directed growth rotation of the palate. The width and ossification rate of the synchondrosis of the midpalatal suture was smaller. Furthermore, lateral growth of the maxilla was inhibited considerably in the distal area. In conclusion, this study shows that food consistency affects the bone appositional pattern at the growth site in the palatal region of the maxillary complex. The results also suggest that the difference in the growth pattern in the upper viscerocranium induced by different food consistencies is caused not only by a difference in mechanical force of the masticatory muscles acting on the muscle insertion areas but also by a difference in the growth pattern in the region which receives occlusal loading.
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Vomer
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Abstract Results of autoradiographic investigations utilizing tritiated proline reveal an intricate mechanism of rat calvarial growth and reshaping from age two days through 75 days. Generalized intramembranous bone growth dominates the growth process from two through eight days; however, this simple bony enlargement is terminated early. At eight days a differential apposition‐resorption process begins dorsally in the calvarium and progresses rostrally within a ten day period. This process includes differential apposition on the ectocranial and endocranial periosteal surfaces accompanied by a differential apposition‐resorption pattern on the endosteal surfaces. The wave‐like process begins in the occipital bone and progresses ventrally to the frontal bone resulting in a flattening of the bony components. At 35 days bone accretion is again generalized on most calvarial surfacse. However, at 40 days another change in the growth process evolves on the occipital and frontal bones. These bones are now seemingly displaced in a superior direction as bone apposition continues on their superior surfaces, namely, the ectocranial periosteal and endocranial endosteal surfaces and resorption progresses on the two inferior surfaces. The magnitude and duration of the process described in this paper is sufficient to account for calvarial flattening in the absence of bony spatial reorientation due to bending at sutures. The findings described here when compared to proposed in vitro studies can help put the importance of the so‐called “functional matrix” related to bone growth into its proper perspective.
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Occipital bone
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Intramembranous ossification
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In order to study bone growth conducting capacities of new biomaterials under standardized conditions, a goat model was developed based on a canine model by Soballe. Titanium alloy implants with and without a hydroxyapatite coating were used as positive and negative controls, and these were implanted with a circumferential gap of one millimeter in the spongious bone of the knee condyles of two groups of four goats. These goats were sacrificed at 6 and 25 weeks. A second experiment was done on two groups of four goats with the same type of titanium alloy and hydroxyapatite-coated implants as controls and with Polyactive® 55-45 coated titanium alloy implants for testing. These goats were sacrificed at 9 and 25 weeks, respectively. Qualitative and quantitative differences in gap healing were evaluated through light microscopy, and initiation and direction of bone apposition were determined with fluorescence microscopy. Apposition of bone was seen directly on all hydroxyapatite surfaces and on some of the noncoated titanium alloy surfaces. The difference between the percentage of bone growth on the titanium alloy implants and the hydroxyapatite-coated implants appeared to be divergent in time: the bone growth on the noncoated implants declined after 9 weeks in contrast to the steady increase of bone growth on the hydroxyapatite-coated implants towards the 25 week follow-up time (p = 0.02). No significant difference was found between the first and the second experiment: apposition of bone on the implants differed only 6.6% on a scale of 0% to 100%. Only scarce bone growth was seen on the polyactive-coated implants in this model. The newly tested Polyactive® 55-45 coating apparently needs initial bone contact for bone-bonding and therefore showed hardly any direct bone formation on its surface. The clear differences in the reaction of bone to the coated and noncoated implants in this goat study and the reproducibility of these reactions of bone to the different controls indicate the sensitivity of the currently used animal model and its suitability for use as a bioactivity assay. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 265–273, 1997.
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Titanium alloy
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Nickel titanium
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