The sequence in appearance and disappearance of impressiones gyrorum cerebri and cerebelli

We investigated the sequence and the intensity in the appearance and the disappearance of the impressiones gyrorum cerebri and cerebelli, of juga cerebralia and cerebellaria and of juga cerebellaria interlobularia in the collection of 34 macerated and disarticulated skull bones from the newborn to 30 years of age (68 specimens/halves of skulls) and 19 skulls in the period from 30 to 80 years of age (38 specimens). Juga cerebralia on the squama of the temporal bone and cerebral lamina of the frontal bone appeared already in the course of the first year of life, much earlier than cited in the literature. The intensity of the development of juga cerebralia increased to the third decade. After that age, the intensity decreased gradually, and the juga cerebralia disappeared completely in parietal bones, in the cerebral fossae of the occipital bones and finally in most cases also on the cerebral lamina of the frontal bones. Juga cerebellaria and impressiones gyrorum cerebelli appeared in the middle of the second year of age and persisted to the ten years of age, which coincides with the closure of the fissures among the parts of the occipital bone. Jugum cerebellare intersemilunare appeared in the first year of life and persisted in its complete length, or interrupted in different sections of its course, during the whole life. The intensity in appearance of juga is partly influenced by the increasing thickness of the diploe.     

Effects of maternal food restriction during lactation on craniofacial growth in weanling rats

Adult Holtzman rats were submitted during suckling period to a food restriction with or without protein or carbohydrate restoration. Twenty-one-day-old weanling pups were compared with controls of 9, 13, 17, and 21 days of age. Lateral craniofacial roentgenographies were taken. The length in midsagittal plane of each bone and its angle with respect to the vestibular line were measured in males. In females, the brain and the left masseter muscle were weighed, and the muscle/brain ratios (neuromuscular index) were calculated. Food restriction altered skull size and shape. Size changes were due to arrested lengths in all studied skull bones. Shape variation was evident by orthocephalization changes, reflected in angulation changes of bones belonging to the frontoethmofacial (frontal, nasal, and maxillary bones) and to the occipitointerparietal (interparietal bone) complexes. Partial restorations by both protein or carbohydrate supplementation were found. Nutritional stresses during lactation affected orthocephalization through an altered growth ratio between two soft tissues functionally associated to the craniofacial complex: brain and masticatory muscles.     

The Zagreb Skull Collection—The unique identified collection of human skulls from fetuses to centenarians

Skull anatomy and development have been extensively studied due to their significance in evolutionary biology, forensic anthropology, and clinical medicine. Bone collections are an indispensable resource for conducting such anthropological and anatomical studies. However, worldwide there are only few skull collections containing specimens covering the entire fetal and postnatal period. Herein we describe the Zagreb Skull Collection, an identified collection comprising more than 1100 skulls and skull bone sets from the early fetal period to centenarians. The Zagreb Skull Collection consists of two main parts: the unique Collection of Skull Bones containing 386 sets of separated skull bones from the early fetal period to adulthood and the Collection of Skulls containing 742 skulls (age range 4–101 years). The collection was the core source for numerous anatomical studies on the development, postnatal changes, and anatomical variations of the skull. However, the Zagreb Skull Collection is still an underexploited resource for anthropological, forensic, and anatomical studies with translatability to contemporary clinical practice.     

Cytochemical analysis of single villus peptidase activities in pig intestine during neonatal development

The present work uses a new technique of whole tissue cytochemistry and automated scanning to obtain measurements of peptidase activity and surface structure in intact villi microdissected from the jejunum of newborn and 28-day-old pigs. Intact villi from 28-day-old pigs are shown by this method to contain 30% more aminopeptidase N and 400% more dipeptidylpeptidase IV activity than is found on villi taken from newborn pig intestine. Villi taken from 28-day-old pig intestine are also half as long and twice as wide at their base as those taken from newborn animals. These changes in shape take place without significantly affecting the total surface area of the villus. Increases in peptidase activities occurring during postnatal development can be further subdivided into those dependent upon induced changes in enterocyte biochemistry and those dependent upon the changing geometry of villi. Over 90% of the total increase in peptidase activities occurring during neonatal development was shown, by this analysis, to involve enterocyte reprogramming of enzyme production. The present method of whole tissue cytochemistry appears to combine successfully the ability to measure peptidase activities at the cellular level in undisrupted tissue with a facility to relate these results to the overall shape of a single villus. These and more general applications of the method now provide new ways to analyse a variety of changes taking place in intestinal structure and function in a quantitative manner.     

Repeated loss of frontal sinuses in arctoid carnivorans

Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Within the Carnivora, frontal sinuses are usually present, but vary widely in size and shape. The causes of this variation are unclear, although there are some functional associations, such as a correlation between expanded frontal sinuses and a durophagous diet in some species (e.g., hyenas) or between absent sinuses and semiaquatic lifestyle (e.g., pinnipeds). To better understand disparity in frontal sinus morphology within Carnivora, we quantified frontal sinus size in relationship to skull size and shape in 23 species within Arctoidea, a clade that is ecologically diverse including three independent invasions of aquatic habitats, by bears, otters, and pinnipeds, respectively. Our sampled species range in behavior from terrestrial (rarely or never forage in water), to semiterrestrial (forage in water and on land), to semiaquatic (forage only in water). Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape. Among terrestrial species, frontal sinus size was positively allometric overall, but several terrestrial species completely lacked sinuses, including two fossorial badgers, the kinkajou (a nocturnal, arboreal frugivore), and several species with small body size, indicating that factors other than aquatic habits, such as space limitations due to constraints on skull size and shape, can limit sinus size and presence. J. Morphol. 276:22–32, 2015. © 2014 Wiley Periodicals, Inc.     

Pubertal growth spurt in the thickness of the bones of the human cranium

Frontal saw-cuts of 60 human cranial fornices (age 1-21 years) served as the material for the investigation. By means of the microscope MBC-2 thickness of the bones was measured. The age changes of the bone thickness in the cranial fornix are approximated by the function of asymptotic growth TK' = 5.3-3.5 X 10(-0.14(X-1) (mm), where X = 1.2,..., 8 and logistic function TK' = 1/(1 + 10(11.4 - 0.74X) +4.93 (mm), where X = 8.9,..., 21 (years). Thus the bone thickness of the cranial fornix undergoes the pubertal spurt of growth, when the maximal rate in increasing thickness is noted between 15 and 16 years of age. This phenomenon should determine certain increase in dimentions of the skull during the pubertal period.     

Craniometry of cranial vault bones in newborn infants

10 craniometric measurements of the skull bones' fornix have been performed on 89 dried infant skulls. The authors have shown that the craniometric variability of the skull bone's fornix is connected with the skull length rather than with its height. The skull length is determined mostly by the squama of the temporal bone and occipital squama. The shape of the skull vault is determined mainly by parietal bone and squama of the frontal bone. Parietal bones shut unpaired fontanelle, but the remaining bones, under investigation, contribute to the closure of anterolateral and postero-lateral fontanelle.     

Studies on orthocephalization. 2. Flexions of the rat head in the period between 14 and 60 days after gestation

The present paper considers the significance of a variety of cranial flexions in the process of orthocephalization of the rat skull between 14 and 60 days postnatally. The study is based on a sample of 27 male rats, who have been x-rayed at 14, 30 and 60 days with subsequent analyses of the photographs obtained. In this period the angle between the cranial base and the facial part of the skull becomes more obtuse, i.e. the skull becomes more orthocranial. The cranial base becomes at the same time more airobasal (lordotic). Angular changes between the individual bones in the cranial vault straightens the vault markedly. By this it becomes orthodorsal. As the angle between the basisphenoid and the parietal bones stays more or less constant between 14 and 60 days, the impression is created that both the anterior and posterior parts of the neural skull rotate upwards relative to this bone complex. Thus, orthocephalization in the period between 14 and 60 days both consists of flexions between the facial and neural parts of the skull (prebasal flexions), and may be more importantly of interosseous ventral and dorsal flexions.     

Random Loss and Selective Fusion of Bones Originate Morphological Complexity Trends in Tetrapod Skull Networks

The tetrapod skull has undergone a reduction in number of bones in all major lineages since the origin of vertebrates, an evolutionary trend known as Williston’s Law. Using connectivity relations between bones as a proxy for morphological complexity we showed that this reduction in number of bones generated an evolutionary trend toward more complex skulls. This would imply that connectivity patterns among bones impose structural constraints on bone loss and fusion that increase bone burden due to the formation of new functional and developmental dependencies; thus, the higher the number of connections, the higher the burden. Here, we test this hypothesis by exploring plausible evolutionary scenarios based on selective versus random processes of bone loss and fusion. To do this, we have built a computational model that reduces iteratively the number of bones by loss and fusion, starting from hypothetical ancestral skulls represented as Gabriel networks in which bones are nodes and suture connections are links. Simulation results indicate that losses and fusions of bones affect skull structure differently whether they target bones at random or selectively depending on the number of bone connections. Our findings support a mixed scenario for Williston’s Law: the random loss of poorly connected bones and the selective fusion of the most connected ones. This evolutionary scenario offers a new explanation for the increase of morphological complexity in the tetrapod skull by reduction of bones during development.     

Ontogeny of the Middle-Ear Air-Sinus System in Alligator mississippiensis (Archosauria: Crocodylia)

Modern crocodylians, including Alligator mississippiensis, have a greatly elaborated system of pneumatic sinuses invading the cranium. These sinuses invade nearly all the bones of the chondrocranium and several bony elements of the splanchnocranium, but patterns of postnatal paratympanic sinus development are poorly understood and documented. Much of crocodylomorph—indeed archosaurian—evolution is characterized by the evolution of various paratympanic air sinuses, the homologies of which are poorly understood due in large part to the fact that individual sinuses tend to become confluent in adults, obscuring underlying patterns. This study seeks to explore the ontogeny of these sinuses primarily to clarify the anatomical relations of the individual sinuses before they become confluent and thus to provide the foundation for later studies testing hypotheses of homology across extant and extinct Archosauria. Ontogeny was assessed using computed tomography in a sample of 13 specimens covering an almost 19-fold increase in head size. The paratympanic sinus system comprises two major inflations of evaginated pharyngeal epithelium: the pharyngotympanic sinus, which communicates with the pharynx via the lateral (true) Eustachian tubes and forms the cavum tympanicum proprium, and the median pharyngeal sinus, which communicates with the pharynx via the median pharyngeal tube. Each of these primary inflations gives rise to a number of secondary inflations that further invade the bones of the skull. The primary sinuses and secondary diverticula are well developed in perinatal individuals of Alligator, but during ontogeny the number and relative volumes of the secondary diverticula are reduced. In addition to describing the morphological ontogeny of this sinus system, we provide some preliminary exploratory analyses of sinus function and allometry, rejecting the hypothesis that changes in the volume of the paratympanic sinuses are simply an allometric function of braincase volume, but instead support the hypothesis that these changes may be a function of the acoustic properties of the middle ear.     

Study of lead accumulation in bones of Wistar rats by X-ray fluorescence analysis: aging effect

The accumulation of lead in several bones of Wistar rats with time was determined and compared for the different types of bones. Two groups were studied: a control group (n = 20), not exposed to lead and a contaminated group (n = 30), exposed to lead from birth, first indirectly through mother's milk, and then directly through a diet containing lead acetate in drinking water (0.2%). Rats age ranged from 1 to 11 months, with approximately 1 month intervals and each of the collections had 3 contaminated rats and 2 control rats. Iliac, femur, tibia-fibula and skull have been analysed by Energy Dispersive X-ray Fluorescence Technique (EDXRF). Samples of formaldehyde used to preserve the bone tissues were also analysed by Electrothermal Atomic Absorption (ETAAS), showing that there was no significant loss of lead from the tissue to the preservative. The bones mean lead concentration of exposed rats range from 100 to 300 μg g(-1) while control rats never exceeded 10 μg g(-1). Mean bone lead concentrations were compared and the concentrations were higher in iliac, femur and tibia-fibula and after that skull. However, of all the concentrations in the different collections, only those in the skull were statistically significantly different (p < 0.05) from the other types of bones. Analysis of a radar chart also allowed us to say that these differences tend to diminish with age. The Spearman correlation test applied to mean lead concentrations showed strong and very strong positive correlations between all different types of bones. This test also showed that mean lead concentrations in bones are negatively correlated with the age of the animals. This correlation is strong in iliac and femur and very strong in tibia-fibula and skull. It was also shown that the decrease of lead accumulation with age is made by three plateaus of accumulation, which coincide, in all analysed bones, between 2nd-3rd and 9th-10th months.     

Muscle‐induced loading as an important source of variation in craniofacial skeletal shape

The shape of the craniofacial skeleton is constantly changing through ontogeny and reflects a balance between developmental patterning and mechanical‐load‐induced remodeling. Muscles are a major contributor to producing the mechanical environment that is crucial for “normal” skull development. Here, we use an F₅ hybrid population of Lake Malawi cichlids to characterize the strength and types of associations between craniofacial bones and muscles. We focus on four bones/bone complexes, with different developmental origins, alongside four muscles with distinct functions. We used micro‐computed tomography to extract 3D information on bones and muscles. 3D geometric morphometrics and volumetric measurements were used to characterize bone and muscle shape, respectively. Linear regressions were performed to test for associations between bone shape and muscle volume. We identified three types of associations between muscles and bones: weak, strong direct (i.e., muscles insert directly onto bone), and strong indirect (i.e., bone is influenced by muscles without a direct connection). In addition, we show that although the shape of some bones is relatively robust to muscle‐induced mechanical stimulus, others appear to be highly sensitive to muscular input. Our results imply that the roles for muscular input on skeletal shape extend beyond specific points of origin or insertion and hold significant potential to influence broader patterns of craniofacial geometry. Thus, changes in the loading environment, either as a normal course of ontogeny or if an organism is exposed to a novel environment, may have pronounced effects on skeletal shape via near and far‐ranging effects of muscular loading.     

Ontogenetic changes in the mechanical properties of the femur of the polar bear Ursus maritimus

The mechanical properties of the bone material of femora of five wild polar bears, ranging in age from three months to seven and three-quarter years, were compared with those of humans and axis deer. There are changes in mechanical properties in all three species with age, but their time course and extent vary greatly between species. The age-related changes in mechanical properties are attributable mainly to changes in mineralization. At any age, the properties of the polar bear's bones lie between those of humans and the deer. The architecture of the bear's bones, and the mechanical properties of their bone material, were related to the weight of the bears. The calculated stresses in the bones, and their deflection under load, were relatively constant compared with the very large differences in the weights of the bears and the sizes of their bones.     

Variability,morphometrics, and co-variation of the os lacrimale in Cervidae

In Ruminantia, the lacrimal bone forms a considerable part of the facial skeleton, and the morphology of its facial facet is highly variable when compared to other mammals. In this study, we quantify the species-specific variability in size and shape of the lacrimal facial facet in species of Cervidae (deer) and relate it to systematics and various aspects of their ecology and behavior. We sampled 143 skull specimens from 10 genera; 12 Moschus and 3 Tragulus specimens were used as outgroups. We find that size and shape of the lacrimal facial facet allow differentiating most species analyzed here, except for Mazama gouazoubira and Capreolus capreolus. Size and shape of the lacrimal facial facet vary widely across Cervidae regardless of their systematic relationships, ecology or behavior. Thus, we could not detect a unique signature of adaptational criteria in lacrimal morphology. Our data indicate that the lacrimal facial facet scales allometrically with skull size, in particular, the lacrimojugal length scales positively and the lacrimomaxillar length scales negatively. However, correlation analyses did not reveal any differences in the integration of the lacrimal bone with any specific skull module in any of the species compared. Lastly, we could not ascertain any correlation between the size and position of the preorbital depression with the size and shape of the lacrimal facial facet. We conclude that the lacrimal facial facet is highly flexible and may rapidly adjust to its surrounding bones. Its allometric growth appears to be an example of exaptation: changes in size and shape in the context of the increase of the skull length provide lacrimal contacts, in particular, a lacrimojugal one, which may serve to reduce mechanical loads resulting from increasingly larger antlers in large cervids.     

Infant skull and suture properties: measurements and implications for mechanisms of pediatric brain injury

The mechanical properties of the adult human skull are well documented, but little information is available for the infant skull. To determine the age-dependent changes in skull properties, we tested human and porcine infant cranial bone in three-point bending. The measurement of elastic modulus in the human and porcine infant cranial bone agrees with and extends previous published data [McPherson, G. K., and Kriewall, T. J. (1980), J. Biomech., 13, pp. 9-16] for human infant cranial bone. After confirming that the porcine and human cranial bone properties were comparable, additional tensile and three-point bending studies were conducted on porcine cranial bone and suture. Comparisons of the porcine infant data with previously published adult human data demonstrate that the elastic modulus, ultimate stress, and energy absorbed to failure increase, and the ultimate strain decreases with age for cranial bone. Likewise, we conclude that the elastic modulus, ultimate stress, and energy absorbed to failure increase with age for sutures. We constructed two finite element models of an idealized one-month old infant head, one with pediatric and the other adult skull properties, and subjected them to impact loading to investigate the contribution of the cranial bone properties on the intracranial tissue deformation pattern. The computational simulations demonstrate that the comparatively compliant skull and membranous suture properties of the infant brain case are associated with large cranial shape changes, and a more diffuse pattern of brain distortion than when the skull takes on adult properties. These studies are a fundamental initial step in predicting the unique mechanical response of the pediatric skull to traumatic loads associated with head injury and, thus, for defining head injury thresholds for children.     

Structural Constraints in the Evolution of the Tetrapod Skull Complexity: Williston’s Law Revisited Using Network Models

Ever since the appearance of the first land vertebrates, the skull has undergone a simplification by loss and fusion of bones in all major groups. This well-documented evolutionary trend is known as “Williston’s Law”. Both loss and fusion of bones are developmental events that generate, at large evolutionary scales, a net reduction in the number of skull bones. We reassess this evolutionary trend by analyzing the patterns of skull organization captured in network models in which nodes represent bones and links represent suture joints. We also evaluate the compensatory process of anisomerism (bone specialization) suggested to occur as a result of this reduction by quantifying the heterogeneity and the ratio of unpaired bones in real skulls. Finally, we perform simulations to test the differential effect of bone losses in skull evolution. We show that the reduction in bone number during evolution is accompanied by a trend toward a more complex organization, rather than toward simplification. Our results indicate that the processes by which bones are lost or fused during development are central to explain the evolution of the morphology of the skull. Our simulations suggest that the evolutionary trend of increasing morphological complexity can be caused as a result of a structural constraint, the systematic loss of less connected bones during development.     

Preservation of femoral bone thickness in middle age predicts survival in genetically heterogeneous mice

To see whether age-related changes in bone could predict subsequent lifespan, we measured multiple aspects of femur size and shape at 4, 15, and 24 months of age in genetically heterogeneous mice. Mice whose cortical bone became thicker from 4 to 15 months, associated with preservation of the endosteal perimeter, survived longer than mice whose endosteal cavity expanded, at the expense of cortical bone, over this age range. Femur size at age 4 months was also associated with a difference in life expectancy: mice with larger bones (measured by length, cortical thickness, or periosteal perimeter) had shorter lifespans. Femur length, midlife change in cortical bone thickness, and midlife values of CD8 T memory cells each added significant power for longevity prediction. Mice in the upper half of the population for each of these three endpoints lived, on average, 103 days (12%) longer than mice with the opposite characteristics. Thus, measures of young adult bone dimensions, changes as a result of bone remodeling in middle age, and immunological maturation provide partially independent indices of aging processes that together help to determine lifespan in genetically heterogeneous mice.     

Do changes in skull size of South American sea lions reflect changes in population density?

Populations of the South American sea lion (SASL, Otaria byronia) have been intensely exploited for leather and oil in different parts of its distribution range throughout the 19th and 20th centuries, generating large changes in abundance. In Patagonia, the SASL population was reduced by more than 90% of its original abundance, and it began to recover after sealing ended. The aim of this work was to assess changes in size and shape of the skull related to changes in population abundance during the last 100 years. Using geometric morphometry techniques, we analyzed 145 individuals (68 males and 77 females) from Patagonia. Skulls were classified by sex, time period (harvest vs. postharvest), and decades of individual's birth. Results indicated that there were differences in skull size but not in shape discriminated by time period. Moreover, individuals of the postharvest period showed a decrease in the skull size during the last two decades, coinciding with the recovery in population abundance. Our results suggest the existence of a density-dependence response in somatic growth of SASL population of Patagonia.     

Extensive enlargement of the maxillary sinus in Alouatta caraya (mammalia, primates, cebidae): an allometric approach to skull pneumatization in Atelinae

In contrast to the paranasal sinuses of Old World monkeys and hominoids, little information is available about the paranasal sinuses of New World monkeys. Because this information is crucial in order to draw further conclusions about the evolution and biological role of skull pneumatization, this study investigates the morphology of the paranasal sinuses in adult black-and-gold howler monkeys (Alouatta caraya). Volumes of the paranasal sinuses were calculated using computer software (SURFdriver or Allegro) from serial coronal CT scans of 20 skulls of both sexes. Skull pneumatization in A. caraya is more complex than in other higher primates. In both sexes, the maxillary sinus (MS) is the only pneumatic cavity and enlarges regularly into neighboring bones such as the frontal bone and the basisphenoid. The resulting pansinus is often partitioned by several vertical septa. As in most external cranial dimensions, mean MS volume of A. caraya (male 4.08 cm(3); female 2.00 cm(3)) shows significant sexual dimorphism. Reduced major axis regression analysis between MS volume and different cranial dimensions for A. caraya (and for available data from other platyrrhines) suggests a distinct association for this group, with Alouatta having one of the largest pneumatic cavities. The combination of this unusual expansion of the MS of Alouatta and the occurrence of distinct septa within the sinus may be a consequence of the distinct skull architecture of Alouatta.     

Observations on the skulls of sturgeons (Acipenseridae): shared similarities of <Emphasis Type="Italic">Pseudoscaphirhynchus kaufmanni</Emphasis> and juvenile specimens of <Emphasis Type="Italic">Acipenser stellatus</Emphasis>

A novel hypothesis uniting Acipenser stellatus and Pseudoscaphirhynchus as sister groups has recently been proposed based on analysis of DNA sequences. In this paper I compare specimens of A. stellatus and P. kaufmanni, and show that they share several putatively derived similarities in the structure of their skulls, including: the presence of large spines on the dermal bones of skull; lateral extrascapular bones that enclose the confluence of the posttemporal, supratemporal, and otic sensory canals; elongate dorsal rostral bones; border rostral bones distinct in shape from dorsal rostral bones; greatly enlarged jugal that lacks a median flange; rostral canal bones that loop posteriorly at the anterior commissure of the rostral sensory canals; and the presence of an elongate, flat, and broad posterior ventral rostral bone. These similarities support a close relationship between A. stellatus and Pseudoscaphirhynchus, but still remain to be critically tested.