Tubular hand bone growth during the latter half of the prenatal period: an allometric analysis

The growth of the 19 tubular hand bones from fetal months 5 to 9 was studied by the allometric method. The hand bones were carefully dissected under a low power stereoscopic microscope. The length and breadth of all bones was found to be monophasic in relation to crown-rump length. In general, maximum bone and ossified shaft lengths in the same row group demonstrate similar allometric coefficients. The specific growth rate of ossified shaft length for all fetal hand bones is greater than the growth rate of maximum length. The highest allometric coefficients for both maximum length and ossified shaft length were obtained from the middle phalanges. The shape of the metacarpals and distal phalanges becomes thinner, while the other bones become thicker or maintain their length-breadth ratio. The relative growth pattern of the first proximal phalanx differed from the middle phalangeal group of the other digits. This suggests that current nomenclatures for the three bones of the pollex is appropriate.     

Cell fate specification during calvarial bone and suture development

In this study we have addressed the fundamental question of what cellular mechanisms control the growth of the calvarial bones and conversely, what is the fate of the sutural mesenchymal cells when calvarial bones approximate to form a suture. There is evidence that the size of the osteoprogenitor cell population determines the rate of calvarial bone growth. In calvarial cultures we reduced osteoprogenitor cell proliferation; however, we did not observe a reduction in the growth of parietal bone to the same degree. This discrepancy prompted us to study whether suture mesenchymal cells participate in the growth of the parietal bones. We found that mesenchymal cells adjacent to the osteogenic fronts of the parietal bones could differentiate towards the osteoblastic lineage and could become incorporated into the growing bone. Conversely, mid-suture mesenchymal cells did not become incorporated into the bone and remained undifferentiated. Thus mesenchymal cells have different fate depending on their position within the suture. In this study we show that continued proliferation of osteoprogenitors in the osteogenic fronts is the main mechanism for calvarial bone growth, but importantly, we show that suture mesenchyme cells can contribute to calvarial bone growth. These findings help us understand the mechanisms of intramembranous ossification in general, which occurs not only during cranial and facial bone development but also in the surface periosteum of most bones during modeling and remodeling.     

Embryonic development of the coronal suture in man and rat.

Histological examination of skulls of 3- to 7-month-old human fetuses reveals in the fourth month of fetal life the development of a morphologically distinctive tissue in the area between the frontal and parietal bones. In this particular area, the pericranium tends to bulge outward while the dura mater shows the same in an inward direction. Consequently, a spindle-shaped blastema is enclosed. This spindle-like structure is only temporarily present; by about the sixth month of fetal life it has disappeared. Secondly, it was observed that prior to the development of this blastema mainly undifferentiated mesenchymal cells and only few fibroblasts are present in the area between the approaching ossification centres. In the full-grown blastema both types of cells are present in about equal numbers. However, once the blastema has been formed, fibroblasts predominate over mesenchymal cells. This tissue structure is also clearly distinguishable in the developing fetal rat skull. In this species, however, the spindle-shaped blastema appears at a later phase of fetal development, i.e. at about the 20th day. In both species, man and rat, the temporary presence of this blastema is not confined to the presumptive coronal suture only, but is demonstrable as well in other cranial sutures.     

A developmental constraint on the fledging time of birds

We examined the hypothesis that the rate of bone growth limits the minimum fledging time of birds. Previous observations in California gulls indicate that linear growth of wing bones may be the rate limiting factor in wing development. If bone growth is rate limiting, then birds with relatively long bones for their size could be expected to have longer fledging periods than birds with relatively short bones. We tested this by comparing the length of wing bones, relative to body mass, to the relative length of fledging periods among 25 families. The results support the hypothesis. A strong correlation exists between relative fledging period and relative bone length. Species which have relatively long bones for their body size tend to take longer to fly. In contrast, parameters that influence flight style and performance, such as size of the pectoralis muscle and wing loading, show little or no correlation with fledging time. The analysis also indicates that, when altricial and precocial species are considered together, bone length is more highly correlated with fledging time than is body mass or rate of increase in body mass during growth. These observations suggest that linear growth of bones does limit the growth of avian wings and that it is one of the factors that influences the fledging time of birds.     

Tissue origins and interactions in the mammalian skull vault.

During mammalian evolution, expansion of the cerebral hemispheres was accompanied by expansion of the frontal and parietal bones of the skull vault and deployment of the coronal (fronto-parietal) and sagittal (parietal-parietal) sutures as major growth centres. Using a transgenic mouse with a permanent neural crest cell lineage marker, Wnt1-Cre/R26R, we show that both sutures are formed at a neural crest-mesoderm interface: the frontal bones are neural crest-derived and the parietal bones mesodermal, with a tongue of neural crest between the two parietal bones. By detailed analysis of neural crest migration pathways using X-gal staining, and mesodermal tracing by DiI labelling, we show that the neural crest-mesodermal tissue juxtaposition that later forms the coronal suture is established at E9.5 as the caudal boundary of the frontonasal mesenchyme. As the cerebral hemispheres expand, they extend caudally, passing beneath the neural crest-mesodermal interface within the dermis, carrying with them a layer of neural crest cells that forms their meningeal covering. Exposure of embryos to retinoic acid at E10.0 reduces this meningeal neural crest and inhibits parietal ossification, suggesting that intramembranous ossification of this mesodermal bone requires interaction with neural crest-derived meninges, whereas ossification of the neural crest-derived frontal bone is autonomous. These observations provide new perspectives on skull evolution and on human genetic abnormalities of skull growth and ossification.     

Growth inhibition of human embryonic and fetal rat bones in organ culture by rubella virus.

Paired organ cultures of metacarpal, metatarsal, and long bones of previable human embryos of 7 to 12 weeks' gestation and tibias of 17-day rat fetuses with inoculated with live or ultraviolet-inactivated rubella virus or control fluids and the growth of the bones was measured by increase in wet weight. In several cultures the ability of the human bones to incorporate 35S, a measure of rate of mucopolysaccharide synthesis, was tested. Growth of human and rat bones was retarded in cultures inoculated with live virus but not in cultures inoculated with inactivated virus or control fluids. Mean 35S uptake was increased by approximately 25% in virus-inoculated cultures of bones of 9- to 12-week human embryos. No histological abnormalities were seen. These findings suggest that (1) defective bone growth in congenital rubella is a direct effect of viral infection of bone, (2) a disorder of mucopolysaccharide syntheses may contribute to the osseous lesions that occur in this disease, and (3) organ cultures of human embryonic and fetal rat bones may serve as convenient models for studying the pathogenesis of this virus-induced congenital osteopathy.     

Scaling of the appendicular skeleton of the giraffe (Giraffa camelopardalis)

Giraffes have remarkably long and slender limb bones, but it is unknown how they grow with regard to body mass, sex, and neck length. In this study, we measured the length, mediolateral (ML) diameter, craniocaudal (CC) diameter and circumference of the humerus, radius, metacarpus, femur, tibia, and metatarsus in 10 fetuses, 21 females, and 23 males of known body masses. Allometric exponents were determined and compared. We found the average bone length increased from 340 ± 50 mm at birth to 700 ± 120 mm at maturity, while average diameters increased from 30 ± 3 to 70 ± 11 mm. Fetal bones increased with positive allometry in length (relative to body mass) and in diameter (relative to body mass and length). In postnatal giraffes bone lengths and diameters increased iso‐ or negatively allometric relative to increases in body mass, except for the humerus CC diameter which increased with positive allometry. Humerus circumference also increased with positive allometry, that of the radius and tibia isometrically and the femur and metapodials with negative allometry. Relative to increases in bone length, both the humerus and femur widened with positive allometry. In the distal limb bones, ML diameters increased isometrically (radius, metacarpus) or positively allometric (tibia, metatarsus) while the corresponding CC widths increased with negative allometry and isometrically, respectively. Except for the humerus and femur, exponents were not significantly different between corresponding front and hind limb segments. We concluded that the patterns of bone growth in males and females are identical. In fetuses, the growth of the appendicular skeleton is faster than it is after birth which is a pattern opposite to that reported for the neck. Allometric exponents seemed unremarkable compared to the few species described previously, and pointed to the importance of neck elongation rather than leg elongation during evolution. Nevertheless, the front limb bones and especially the humerus may show adaptation to behaviors such as drinking posture. J. Morphol. 276:503–516, 2015. © 2014 Wiley Periodicals, Inc.     

Mathematical modeling of appendicular bone growth in glaucous‐winged gulls

Development of locomotor activity is crucial in tetrapods. In birds, this development leads to different functions for hindlimbs and forelimbs. The emergence of walking and flying as very different complex behavior patterns only weeks after hatching provides an interesting case study in animal development. We measured the diaphyseal lengths and midshaft diameters of three wing bones (humerus, ulna, and carpometacarpus) and three leg bones (femur, tibiotarsus, and tarsometatarsus) of 79 juvenile (ages 0–42 days) and 13 adult glaucous‐winged gulls (Larus glaucescens), a semiprecocial species. From a suite of nine alternative mathematical models, we used information‐theoretic criteria to determine the best model(s) for length and diameter of each bone as a function of age; that is, we determined the model(s) that obtained the best tradeoff between the minimized sum of squared residuals and the number of parameters used to fit the model. The Janoschek and Holling III models best described bone growth, with at least one of these models yielding an R² ≥ 0.94 for every dimension except tarsometatarsus diameter (R² = 0.87). We used the best growth models to construct accurate allometric comparisons of the bones. Early maximal absolute growth rates characterize the humerus, femur, and tarsometatarsus, bones that assume adult‐type support functions relatively early during juvenile development. Leg bone lengths exhibit more rapid but less sustained relative growth than wing bone lengths. Wing bone diameters are initially smaller than leg bone diameters, although this relationship is reversed by fledging. Wing bones and the femur approach adult length by fledging but continue to increase in diameter past fledging; the tibiotarsus and tarsometatarsus approach both adult length and diameter by fledging. In short, the pattern of bone growth in this semiprecocial species reflects the changing behavioral needs of the developing organism. J. Morphol., 2009. © 2008 Wiley‐Liss, Inc.     

Secular change in long bone length and proportion in the United States, 1800-1970.

We examine secular change in long bone lengths and allometry of Americans dating from the mid-19th century to the 1970s. Skeletal samples were derived from the Huntington Collection, Terry Collection, World War II casualties, and the Forensic Anthropology Data Bank. Regression of bone length on year of birth allowed evaluation of the secular change in bone length. Size was computed as the geometric mean of all bone lengths, and shape as the ratio of each bone to size. These variables were then regressed on year of birth, allowing evaluation of allometric secular change. The results revealed a pattern of change that can be summarized as follows: male secular change is stronger than female, lower limb bone secular change is more pronounced than upper limb bone change, and distal bones change more than proximal bones, particularly in the lower limb. In males, white changes are uniformly higher than black but these differences do not rise to the level of statistical significance. Environmental forces, such as nutrition and disease, are the usual causes of secular changes in overall size. This paper shows that long bone proportions also respond to these same environmental factors. Moreover, the changes in body proportion are likely to be due to allometric consequences of growth changes that occur early in life. Am J Phys Anthropol 110:57-67, 1999.     

Osteohistological insight into the early stages of growth in Mussaurus patagonicus (Dinosauria,Sauropodomorpha)

Here, we describe the bone histology of juvenile specimens of the basal sauropodomorph Mussaurus patagonicus and interpret its significance in terms of the early growth dynamics of this taxon. Thin sections from three juvenile specimens (femur length, 111–120 mm) of Mussaurus were analysed. The sampled bones consist of multiple postcranial elements collected from the Late Triassic Laguna Colorada Formation (El Tranquilo Group, Patagonia). The cortical bone is composed of fibrolamellar bone tissue. Vascularisation is commonly laminar or plexiform in the long bones. Growth marks are absent in all the examined samples. The ‘epiphyses’ of long bones are all formed by well-developed hypertrophied calcified cartilage. The predominance of woven-fibred bone matrix in cortical bones indicates a fast growth rate in the individuals examined. Moreover, given the existence of growth marks in adult specimens of Mussaurus, as in other sauropodomorphs, and assuming that the first lines of arrested growth was formed during the first year of life, the absence of growth marks in all the bones suggest that the specimens died before reaching their first year of life. Compared with the African taxon Massospondylus carinatus (another basal sauropodomorph for which the bone histology has been previously studied), it appears that Mussaurus had a higher early growth rate than Massospondylus.     

Effects of dexamethasone on expression and maintenance of cartilage in serum-containing cultures of calvaria cells

Summary The effects of dexamethasone on the ability of cells enzymatically isolated from 21-day fetal rat calvaria to produce cartilage in vitro has been investigated. Primary cultures of single-cell suspensions of rat calvaria were grown for up to 28 days in vitro in -minimal essential medium containing 15% fetal bovine serum, 50 /ml ascorbic acid, 10 mM Na -glycerophosphate and dexamethasone at concentrations of 1 M to 1 nM. Two types of nodules were present in dexamethasone-containing cultures. One has been characterized previously as bone (Bellows et al. 1986). The second morphologically resembled hyaline cartilage, possessed a strong Alcian blue-positive matrix and contained type-II, but not type-I, collagen. Both bone and cartilaginous nodules were spatially distinct and developed in isolation from each other. Cartilaginous nodules were found in the highest number at a dexamethasone concentration of 100 nM. Time-course experiments revealed that while the number of bone nodules increased continuously at least to day 28, the number of cartilaginous nodules remained constant after cultures had reached confluency. When cells were isolated separately from frontal and parietal bones and suturai regions, the greatest number of cartilaginous nodules developed from parietal bones. Since 21-day fetal rat calvaria contains 2 distinct patches of cartilage at the periphery of the parietal bones, it seems likely that this cartilaginous tissue is the origin of the cartilage cells. The results demonstrate that cultures of rat calvaria cells contain chondrocytes and possibly chondroprogenitor cells that are distinct from osteoprogenitors. Results support previous data that 100 nM dexamethasone permits the expression of and maintains the phenotype of chondrocytes in serum-containing cultures in vitro.     

The development of the brine shrimp Artemia salina (L.): a morphometric approach

Growth allomentry in the development of the brine shrimp Artemia salina (L.) was studied. Body width and abdomen length show a negative allometric relation to body length ( k =0.35 and 0.72 respectively) over th eight instars studied. Antennule length shows a negative allometric relation in respect to body length, with a change in the value of the growth constant at Instar Five from 0.31 to 0.75. Thoracic limb length shows a high positive relation to body length ( k =3.0) until Instar Six, when a negative allometric phase ( k =0.4) follows. A change in the sign of the growth constant from positive ( k =0.45) to negative ( k =-1.4) is noted for the length of the 2nd antenna in relation to body length.     

Radiographic determination of prenatal basicranial ossification

In a previous investigation on prenatal development of the human cranial base, the sequence in which the bones develop in the midsagittal region was elucidated. The purpose of the present study was to identify fetal ossification on horizontal plane roentgenograms of the occipital and sphenoid bones in the central part of the cranial base, and establish stages in bone appearance related to general fetal developmental parameters. This study is based upon roentgenograms of the cranial base of 145 human fetuses from the first half of the prenatal period. Two different maturation patterns of the sphenoid bone were observed. The first, most common pattern is characterized by a midsagittal centre of ossification and the second by bilateral centres of ossification in the corpus of the sphenoid bone. These bilateral centres might in some cases be connected by a slight bony bridge. It appears that these different maturation patterns are maintained throughout the period investigated. The material was divided into five well-defined developmental stages for both maturation patterns and general parameters of fetal development. Mapping different aspects of ossification in normal cranial development is necessary for understanding deviations of cranial maturation and growth.     

太行山猕猴髋骨异速增长和性别判定研究

目的是了解太行山猕猴髋骨性差特征及异速增长模式。太行山猕猴髋骨标本66例(雄21例,雌45例)。选择髋骨4个比值变量。数据分析采用SPSS 20.0。组间均值比较采用单因素方差分析。性别判别分析采用逐步判别法。结果表明:成年太行山猕猴大部分髋骨变量性差显著(P0.05)。根据髋骨变量的异速增长分析可以得到3种模式。回归模型检验有统计学意义(P<0.01)。用少量髋骨变量可以有效地识别性别,性别正确判别率是87.0%。结论:髋骨变量的性差与异速增长模式主要与雌性髋骨变量青春期异速增长有关,髋骨的形态特征是猕猴运动功能与生殖功能交互作用的结果。     

Kinematics of cranial vault growth in rabbits

To characterize mathematically the spatial rearrangement of cranial vault bones of the rabbit during growth, a longitudinal study was undertaken from age 4-20 weeks. Initially, at least three nonlinear tantalum bone markers were implanted in the parietal, frontal, and the combined nasal bones. Thereafter, the animals were followed regularly with roentgen stereophotogrammetrical analysis. The parietal bones were found to rotate laterally upward (3 degrees), while the frontal bones rotated downward (2 degrees) relative to their contralaterals. The frontal bones rotated rostrally upward (12 degrees) and outward (3 degrees) as well as laterally downward (5 degrees) in relation to the parietal bones. Due to the morphology of the rabbit head, the examination positioning used in this study, and the direction of the growth process, growth at the coronal suture correlated fairly well with longitudinal axis translations; but the growth at the frontonasal suture relative to the frontal bones was directed about 45 degrees downward. This points to the importance of the bone-marker positioning, so that their connecting line is directed along the axis of growth. Also, this approach makes it possible to obtain new information on the development and treatment of craniofacial aberrations.     

The Parietal Problem: How to Cut This Gordian Knot?

Although no one has disputed that the piscine progenitors of the tetrapods have a homologue of the human parietal bone, opinions differ as to where in the skull roof this homologue is located. One view holds it to be either of two interorbital bones that together surround the foramen neuroepiphysium (and the so-called pineal plates); another, that it is each of the two mesial bones which comes next in order, behind the orbital cavities. Both of these views are untenable because neither of the proposed bones has proved to be amenable to conversion to the parietal bone of man. In seeking a solution to this issue thoughts turn to the tentorium cerebelli, whose topographic relationships and comparative morphology place it in the key position as a plausible derivative of the posterior half of the cranium of the tetrapod forerunners. Following this line of reasoning, it can be suggested that the tentorial exoskeleton, here called the pluteal bones, originally was situated in the dermis superjacent to the synotic tectum. In early therian phylogeny, these skull bones were covered by the backwardly expanding cerebral hemispheres which, concomitantly, became overgrown and thus protected by epiotic exoskeleton. It follows that the likely homologues of the human parietal bones are those parts of the skull roof of the piscine progenitors of the tetrapods that lie dorsolateral to the otic capsules.     

Ossification of the human fetal basicranium

Previous investigations of prenatal development of the human cranium have not identified the sequence of its ossification. The purpose of the present study was to elucidate the pattern of skeletal maturity of the cranial bones in the midsagittal region anterior to the foramen magnum. This study is based upon a radiographic and histochemical investigation of midsagittal tissue blocks of the cranial bases of 73 human fetuses derived from the first half of the prenatal period. A marked regularity in the ossification pattern of the bones in the midsagittal part of the human cranium was observed. Ossification starts in the frontal bone. The sequence in which the next bones ossify is occipital bone, basisphenoid bone, presphenoid bone, and ethmoid bone. The material was divided into 7 maturity stages devised for this analysis. The stages were related to general fetal size (crown-rump length) and to general fetal maturation (composite number of ossified bones in hand and foot). Skeletal development of the median part of the human cranium is not strictly correlated with the size or the stage of general maturation of the fetuses. Knowledge of normal skeletal development is necessary for understanding anomalies of development.     

Effect of bovine fetal growth plate as a new xenograft in experimental bone defect healing: radiological,histopathological and biomechanical evaluation

Bone grafting is used to enhance healing in osteotomies, arthrodesis, and multifragmentary fractures and to replace bony loss resulting from neoplasia or cysts. They are source of osteoprogenitor cells and induce bone formation and provide mechanical support for vascular and bone ingrowth. Autografts are used commonly but quantity of retrieved bone is limit. This study was designed to evaluate autograft and new xenograft (Bovine fetal growth plate) effects on bone healing process. Twenty male White New Zealand rabbits were used in this study. In autograft group the defect was filled by fresh autogenous cortical graft, in xenograft group the defect was filled by a segment of bovine fetal growth plate and was fixed by cercelage wire. Radiological, histopathological and biomechanical evaluations were performed blindly and results scored and analyzed statistically. Statistical tests did not support significant differences between two groups at the 14th and 28th postoperative day radiographically (P > 0.05). There was a significant difference for remodeling at the 42nd postoperative radiologically (P < 0.05). Xenograft was superior to autograft at the 56th postoperative day for radiological bone formation (P < 0.03). Histopathological and biomechanical evaluation revealed no significant differences between two groups. The results of this study indicate that satisfactory healing occurred in rabbit radius defect filled with calf fetal growth plate. Complications were not identified and healing was faster than cortical autogenous grafting. It was concluded that the use of calf fetal growth plate as a new xenograft is an acceptable alternative to cortical autogenous graft and could reduce the morbidity associated with harvesting autogenous graft during surgery.     

GROWTH PATTERNS OF THRINAXODON LIORHINUS, A NON-MAMMALIAN CYNODONT FROM THE LOWER TRIASSIC OF SOUTH AFRICA

Abstract:  The growth dynamics of the Early Triassic non-mammalian cynodont Thrinaxodon liorhinus were assessed through bone histology. Several limb bones of various sizes were examined, revealing a rapidly deposited, uninterrupted, fibro-lamellar bone tissue. A region of slowly deposited parallel-fibred bone occurs peripherally in most skeletal elements studied, becoming more extensively developed in the larger limb bones. On the basis of the bone histology, it is proposed that Thrinaxodon liorhinus grew rapidly during early ontogeny, and at a slower rate with increasing age, possibly once sexual maturity was reached. Variation in bone tissue patterns at different stages of ontogeny is noted and discussed. Given that growth rings are generally absent from the skeletal elements studied, and that the environment was seasonal, it appears that Thrinaxodon liorhinus growth was unaffected by environmental fluctuations.