Hox-A2 protein expression in avian jaws cartilages and muscle primordia development

OBJECTIVE

To elucidate the branchial origin of the articular and the square (homology of the malleus and the incus of mammals), we used immunohistochemistry to analyse the expression of the Hox-A2 protein during cephalogenesis in chickens.

MATERIALS AND METHODS

Immunohistochemistry on paraffin sections of embryos from stage HH16 to HH40.

RESULTS

In addition to the columella (equivalent to the mammalian stapes), the joint between the articular and the quadrate bones, and the retro-articular process of the articular (homologous to the short process of the malleus) express Hox-A2, suggesting an intervention of the 2nd arch in their formation. However, we fortuitously observed very intense expression within the early muscle plate of the second arch, which then generalized to all cephalic muscles, and extended to the trunk's myotomes. In the cartilage, the presence of the protein disappeared at stage 35.

DISCUSSION AND CONCLUSION

The present results, while confirming the contribution of the second arch to the development of avian equivalents of the mammalian ear ossicles, strongly suggest that the Hox-A2 gene plays a role in muscle development, which remains to be elucidated by more sophisticated techniques.

Are birds pseudoteeth and denticulations related to touch papilla? An investigation in parrot, goose, and chicken

We first studied the morphology and the development of goose denticulations, which develop mainly by a ripple process, and the touch papillae of the bill tip organ, which appears through an evagination process at the end of the beak. During their development, we observed the specific expression of PAX9, PITX2, and BMP4, while SHH was expressed mainly in the basal layer of the epithelium in a non-specific manner. Adult goose denticulations are associated with numerous columns. The goose denticulations and columns were filled with numerous Herbst and Grandry corpuscles, as well the touch papillae of the bill tip organ. Histological analysis of adult parrot pseudoteeth revealed that the osseous pseudoteeth were extended by similar columns filled with Herbst and Grandry corpuscles. We also examined adult and embryonic chicken beaks. During ontogeny, we observed a process of rostral evagination with folding associated with discrete ripples in the anterior part of the beak rudiment, in which PAX9, PITX2, and BMP4 are expressed. In the corresponding adult areas, there were numerous sensory corpuscles with rostral columns, which were similar to the features observed in goose. These observations support the hypothesis that pseudoteeth and denticulations constitute sensory organs, and that the touch papillae exhibit some similarities with pseudoteeth.

Healing of particulate allografts mixed with platelet concentrates in ridge preservation and sinus lift: a prospective histomorphometric study

The objective of the present study was to evaluate the bone quality of sinus and alveolar grafts following filling with particulate allogenous bone (DFDBA 300-500μm) and platelet concentrate (platelet-rich fibrin, PRF). A prospective interventional clinical study was carried out. A total of 40 bone cores, 2mm in diameter, were taken from 21 patients: 22 from grafted alveoli, 7 from grafted sinus sites, and 11 from native bone used as a control. Fixed, paraffin-embedded samples were subjected to histological staining with hematoxylin-eosin and Masson's trichrome. Bone maturity of the samples was evaluated by two independent operators using histomorphometric analysis. There existed a greater proportion of lamellar neoformed bone than woven neoformed bone as the healing time increased. Moreover, there was also an increasing proportion of newly formed bone in the grafted sockets as a function of healing time (average: 41.22% ≤ 5 months, 55.89% ˃ 5 months). Resorption of DFDBA particles also appears to be correlated with healing time in the grafted socket (average: 15.43 ≤ 5 months, 13.72% ˃ 5 months). In conclusion, performing sinus lift and alveolar socket preservation techniques using DFDBA and PRF results in high quality, mature bone tissue according to histological criteria.

Evolution and development of parrot pseudoteeth

Parrot embryos carry peculiar appendages at their developing beak that have been described as pseudoteeth. To better characterize the pattern of development responsible for the emergence of these dental appendages, we examined parrot embryos combining conventional histology and microtomography approaches. Using immunohistochemistry, we observed the epithelial and mesenchymal expression of several proteins involved in tooth development in mammals. Parrot pseudoteeth arose by epithelial and mesenchymal evagination, and their early development was similar to the ontogeny of scales and feathers. There was no enamel tissue, and the evaginations were surrounded by the rhamphotheca. In adults, the rhamphotheca covers entirely the appendages, now represented by bone evaginations, which were more numerous in the lower than in the upper beak, being similar to the osseous teeth of the fossil Pelagornithidae. These embryonic pseudoteeth resembled reptile's first-generation teeth and dental appendages of chicken talpid² mutants. Proteins involved in mammalian odontogenesis, such as SHH, BMP4, PITX2, and PAX9, were found to be generally expressed in beak epithelium and mesenchyme during parrot pseudoteeth development, with clusters of high-level expression in the pseudoteeth rudiments. This suggests that a similar, highly conserved gene expression program gives rise to the appearance of odontode derivatives in numerous species, despite their divergent developmental paths. These results provide new insights into the development and evolution of odontode-derived structures in vertebrates.

Quantification of the relative orientation and position of the mandibular condyles

The human temporomandibular joint (TMJ) is involved in vital functions such as feeding and talking, while its disorder prevalence is reported to be between 5% and 12%. Functional evaluation using quantitative motion analysis tools is interesting in order to better understand normal and abnormal TMJ behavior. But, for the same mandibular displacement, left and right condyles will most certainly give different motion representation: both condyles showing a different shape and volume, being most of the time asymmetric and highly individual. This study performs quantification on relative left and right condyle orientation and position using the spatial location of palpated anatomical landmarks (ALs) and anatomical frames (AFs), on three-dimensional (3D) models created from computerized tomography (CT) performed on 94 mandibles from Université Libre de Bruxelles bone repository, and magnetic resonance imaging (MRI) performed on 11 living subjects. Our aim was to gather as much data as possible on the morphological aspect of the condyle's orientation asymmetry within the same mandible, in order to better address the difference of motion representation that will be observed for the right and left condyles in further kinematic studies.

Triceps, quadriceps or pentaceps femoris? Need for proper muscle definition

INTRODUCTION

Over the last years, the definition of quadriceps femoris (QF) has evolved somewhat and some authors now define a fifth head: the tensor of vastus intermedius (TVI). Descriptions of the different components of QF in textbooks and recent findings remain confusing. Therefore, the aim of this study is to obtain more information on this possible fifth head.

MATERIALS AND METHODS

Twenty lower limbs of 10 embalmed cadavers, six females and four males, were investigated by macro-dissection. The dissection and separation of the different heads were performed with the fingers and a distinction between the different parts of the quadriceps was noted only if it was possible to separate the heads without scalpel to avoid artificial separation of muscle parts.

RESULTS

In 9 lower limbs we found a QF as classically described in textbook. TVI was found in only 7 limbs and in 4 cases we were not able to differentiate VI and VM or VI and VL (triceps femoris as described by Testut). These results, and the diversity of descriptions found in the literature have led us to review the definition of an isolated muscle.

CONCLUSION

In this study, the presence of TVI was not demonstrated in all limbs unlike previously published studies on the subject. Harmonisation of dissection techniques, but also a clear definition of a muscle is required in order to be able to compare studies and draw clear conclusions.

A reviewed chronology of primordial germ cells migration in the chick embryo

INTRODUCTION

Primordial Germ Cells (PGCs) are present in all sexually reproducing animals. They differentiate into spermatozoa or oocytes and are therefore responsible for the transmission of genetic and epigenetic information across generations. In birds, PGCs are first observed in the center of the blastodisc at stage Eyal-Giladi X. With the formation of the primitive streak, germ cells are translocated anteriorly to the germinal crescent. At stage Hamburger- Hamilton 10-12, they enter the vasculature before migrating through the dorsal mesentery towards the genital ridges.

MATERIAL AND METHODS

Embryos from stages Hamburger-Hamilton (HH) 16 to 22 were collected. Blood samples were taken from the dorsal aorta and from the heart in order to perform blood smears and PAS staining. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining. A sample of each embryo was collected for DNA extraction and PCR in order to determine the sex of the embryos.

RESULTS

PGCs were observed in blood circulation until stage HH 20 on blood smears and until stage HH 19 on histological sections. The first PGCs arrived in the genital ridges were observed from stage HH 17. A few germ cells were still migrating in the dorsal mesentery at stage HH 22. The aim of this study was to review the chronology of the migration of PGCs in chick embryos.

Is Vasa such a highly specific marker for primordial germ cells? A comparison of VASA and HSP90 proteins expression in young chicken embryos

INTRODUCTION

Primordial germ cells (PGCs) have been studied since the 19^th century with several different methods. The earliest works were based on the morphological criteria of these cells associated or not with a particular staining. Different markers have been proposed in immunohistochemistry among which we can quote the Stage-specific embryonic antigene-1 (SSEA-1), the embryonic mouse antigen-1 (EMA-1) or the heat shock protein 90. Unfortunately, none of them are germline specific. The VASA protein is considered as one of the most reliable marker for PGCs by some authors with its expression being considered to limited to the germ cells. However, other studies have reported its expression in somatic cells. Here, we described the expression of the heat shock protein, HSP90, and the VASA protein in the early chick embryo.

MATERIAL AND METHODS

Embryos from stages Hamburger-Hamilton (HH) 19, 21 and 28 were collected. Embryos were dissected and fixed in Serra's medium. Sections were placed on slides for PAS staining and for double immunohistochemistry with HSP90 and VASA.

RESULTS

VASA and HSP90 expression have been observed in germ cells but as well in other cell lineages with a spatio-temporal gradient in respect to the characteristics of development of each organ. The conclusion is that VASA expression is not limited to the germ line in chick embryo.

External and computed tomography analysis of a strophocephalic lamb

CONTEXT

The Museum of Anatomy and Embryology Louis Deroubaix attached to the Laboratory of Anatomy, Biomecanics and Organogenesis, ULB, Brussels, possesses in its liquid collections a cephalic extremity of a lamb suffering from strophocephaly. The origins have not been determined. The trunk and the limbs are resected.

MATERIAL AND METHODS

The piece has been studied and photographed. A volumic computed tomography acquisition has been performed with a Siemens Volume Zoom. For pedagogic and museological purposes, surface reconstructions and 3D printing have been obtained.

RESULTS

An otocephaly is observed. Both ears are located in place of the oral cavity. The mandible is welded to the braincase. The eyeballs are close together (synophtalmia) which confirms the presence of a cyclotocephaly. They are surmounted by a rudimentary snout rather than a proboscis. The presence of this muzzle allows the anomaly to be classified as a strophocephaly, a malformation already described in sheeps. CT slices of the brain show a semi-lobar holoprosencephaly with incomplete division of the cerebral hemispheres and ventricules.

DISCUSSION AND CONCLUSION

The CT examination allows the facial anomalies to be allocated to a holoprosencephaly. The singularity of this case, compared to the human cyclotocephalies, is the presence of a differentiated muzzle rather than a simple proboscis. The holoprosencephaly is uncomplete. Such anomalies have been associated with an entire absence of cerebral differentiation but with a complete absence of the muzzle. The tridimensional printing represents an interesting educational tool easily transportable in contrast to the original specimen.

Hox-A2 protein expression in mouse embryo middle ear ossicles

The origin of the mammalian middle ear ossicles from mandibular and hyoid pharyngeal arches remains controversial and discussed. Two adverse theories are proposed. The first claims that malleus and incus derive from the Meckel's cartilage of the mandibular arch, and stapes from Reichert's cartilage of the hyoid arch. The second postulates that handle of malleus and long process of the incus are derived from the second arch as well as the stapes. Contradictory analyses support alternatively each theory without any experimental evidence. In order to bring new data, we analyzed by immunohistochemistry the expression of Hox-A2 protein in ossicular anlagen in E11 to 13 mouse embryos. HOXA2 gene is known to be expressed in second arch cells and to be absent from mandibular arch derivatives. Surprisingly, Hox-A2 protein was present in all ossicular primordia, as well in Reichert's cartilage. Meckel's cartilage was free of staining. Unlabeled cells were also present in ossicular blastemata. These results suggest that ossicular condensations could arise from mixed cell populations originated in both mandibular and hyoid pharyngeal arches. However, we cannot exclude that diffuse Hox-A2 immunoreactivity could correspond to a secondary expression in craniofacial mesenchyme independently from the branchial origin of cells.

Geldanamycin administration reduces the amount of primordial germ cells in the mouse embryo

INTRODUCTION

Heat shock proteins (HSPs) are expressed or overexpressed in response to exposure to stress. They act as molecular chaperones, ensuring the correct folding of numerous client proteins. HSP90 is one of the most conserved HSPs. Its role extends beyond stress tolerance. HSP90 also contributes to development, differenciation, apoptosis and oncogenesis. Numerous tumors are associated with an overexpression of HSP90 and this expression can be used to evaluate its metastatic capacity. Primordial germ cells (PGCs) exhibit HSP90 expression under normal conditions. PGCs arise early in development and migrate by a combination of passive and active movements towards the gonads. The aim of this work was to study the impact of an inhibition of HSP90 on the migration of the PGCs. Geldanamycin, a well established HSP90 inhibitor with potent antitumor properties was used to achieve this inhibition.

MATERIEL AND METHODS

5mg of Geldanamycin were administered to E8 pregnant mice. E17 embryos were removed and fixed for staining and Immunohistochemistry with anti-HSP90 and anti-VASA antibodies.

RESULTS

Geldanamycin-treated mouse embryos exhibited less VASA-immunopositive cells compared to the non-treated ones. These results suggest that geldanamycin administration at the time of PGCs migration reduces the number of PGCs in the gonads. HSP90 and VASA stainings were identical. We therefore expressed the idea that HSP90 could be used as a reliable marker for PGCs.

[Contributions of embryology and comparative anatomy for teaching of cranial nerves]

Some authors propose a global approach, including imaging, to describe cranial nerves from a clinical point of view. If we can agree to a certain extent with this proposal, we consider that the use of a medical point of view can neglect histological and embryological features which contribute to a better understanding of nerve function. For example, it is false to consider totally "nerves" I and II as "sensory cranial nerves". They are not true nerves, but derive manly from direct expansions of the central nervous system. They differ fundamentally from cranial nerves, except for the fibers present at the roof of olfactory fossa. The cranial nerve nuclei arise from "Herrick's columns", which originate from alar and basal plates. These columns, which correspond to "functional components" of these nerves are extremely important for the understanding of cranial nerve functions (as "viscero-efferent", "somato-afferent", etc.), which also helps students to memorize these nerves. The usual classification of cranial nerves neglect the terminal nerve, present in adult humans and associated to the vomero-nasal organ. It includes in the cranial nerves a trunk nerve secondary associated with the head, the hypoglossal nerve, and creates a supernumerary cranial nerve (the accessory nerve) by fusion of vagous fibers with cervical roots. Close consideration of the development and the comparative anatomy can lead to a new synthesis useful to understand the cranial nerves from a general biological point of view and can facilitate their study.

Body mass prediction from femoral volume and sixteen other femoral variables in the elderly: BMI and adipose tissue effects

OBJECTIVES

The frequently used prediction equations of body mass do not seem appropriate for elderly individuals. Here, we establish the relationship between femoral dimensions and known body mass in elderly individuals in order to develop prediction formulas and identify the factors affecting their accuracy.

MATERIALS AND METHODS

The body mass linear least-squares regression is based on 17 femoral dimensions, including femoral volume, and 66 individuals. Body proportion and composition effects on accuracy are analyzed by means of the body mass index (BMI) and on a subset sample (n = 25), by means of the masses of adipose, bone and muscle tissues.

RESULTS

Most variables significantly reflect body mass. Among them, six dimensions (e.g., biepicondylar breadth, femoral volume, and head femoral diameter) present percent standard errors of estimate ranging from 9.5 to 11% (r = 0.72-0.81) in normal BMI samples. Correlations are clearly lower in samples with normal and abnormal BMI [r = 0.38-0.58; % of standard error of estimate (SEE) = 17.3-19.6%] and not significantly correlated in females (femoral volume) who present high proportions of abnormal BMI and adipose tissue. In the subset, femoral volume is well correlated with bone mass (r = 0.88; %SEE = 7.9%) and lean body mass (r = 0.67; %SEE = 17.2%).

DISCUSSION

Our body mass estimation equations for elderly individuals are relevant since relatively low correlations are recurrent in studies using younger individuals of known body mass. However, age, sex, lifestyle, and skeleton considerations of studied populations can provide information about the relevance of the body mass estimation, which is dependent on the BMI classification and the proportion of adipose tissue. Our general considerations can be used for studies of younger individuals.

Further consideration of the curvature of the Neandertal Femur

OBJECTIVES

Neandertal femora are particularly known for having a marked sagittal femoral curvature. This study examined femoral curvature in Neandertals in comparison to a modern human population from Belgium by the use of three-dimensional (3D) quadric surfaces modeled from the bone surface. 3D models provide detailed information and enabled femoral curvature to be analyzed in conjunction with other morphological parameters.

MATERIALS AND METHODS

3D models were created from CT scans of 75 modern human femora and 7 Neandertal femora. Quadric surfaces (QS) were created from the triangulated surface vertices in all areas of interest (neck, head, diaphyseal shaft, condyles) extracted from previously placed anatomical landmarks. The diaphyseal shaft was divided into five QS shapes and curvature was measured by degrees of difference between QS shapes. Each bone was placed in a local coordinate system enabling each bone to be analyzed in the same way.

RESULTS

The use of 3D quadric surface fitting allowed the distribution of curvature with similarly curved femora to be analyzed and the different patterns of curvature between the two groups to be determined. The Neandertals were shown to have a higher degree of femoral curvature and a more distal point of femoral curvature than the modern human population from Belgium.

CONCLUSIONS

Morphological aspects of the Neandertal femur are different from this modern human population although mainly seem unrelated to femoral curvature. The relative lack of correlations with other femoral bony morphological factors suggests femoral curvature variations may be related to other aspects.

[The dorsoventral inversion: An attempt of synthesis]

The invertebrates, with known exception of echinoderms, are hyponeurian and protostomian. By contrast, echinoderms, chordates and vertebrate are epineurian and deuterostomian. Convinced of the uniqueness origin of all species, Etienne Geoffroy Saint Hilaire (1772-1844), had postulated a complete inversion of body plan to explain this difference. He had to face up to the hostility of the fixist Georges Cuvier (1763-1832). Much later, famous embryologists such as Maurice Caullery still believed that this idea was erroneous. However, the progress of comparative embryology and of developmental biology gradually contributed to validate this idea. Based upon ancient and recent literature review, and re-examination of arthropods (Acanthoscelides obtectus Say), amphibians (Discoglossus), echinoderms (sea urchin) and mammals (rodents) embryos, we can raise up difference and common points of the gastrulation processes. The dorsoventral gradient is ensured by the couple Dpp (dorsal in arthropods)/SOG/chordin (ventral in arthropods), which appears as "inverted" in epineurians. Blastopore invagination occurs in arthopods in the ventral region, opposite to the vitellus mass (initially diffuse, then predominant on the dorsal side), whereas it occurs at the vegetative side in other hyponeurians and epineurians. It has been accepted that the BMP inhibits oral development in protostomian, whereas it activates it in Chordates. Therefore we assume, as Lowe does, that the oral cavity of deuterostomians might constitute a new structure related to the branchial system. The comparative analysis of the blastopore' orientation, the sperm penetration site, and the polarity axes of various embryos species allows to follow the different modifications and to hypothesize their relative chronology during evolution.

How different are the Kebara 2 ribs to modern humans?

This study analyses rib geometric parameters of individual ribs of 14 modern human subjects (7 males and 7 females) in comparison to the reconstructed ribs of the Kebara 2 skeleton which was taken from the reconstruction of a Neandertal thorax by Sawyer & Maley (2005). Three-dimensional (3D) models were segmented from CT scans and each rib vertex cloud was placed into a local coordinate system defined from the rib principal axes. Rib clouds were then analysed using best fitting ellipses of the external contours of the cross-section areas. The centroid of each ellipse was then used to measure the centroidal pathway between each slice (rib midline). Curvature of the ribs was measured from the mid-line of the ribs as the sum of angles between successive centroids in adjacent cross sections. Distinct common patterns were noted in all rib geometric parameters for modern humans. The Kebara 2 reconstructed ribs also followed the same patterns. This study demonstrated that there are differences between the sexes in rib geometrical parameters, with females showing smaller rib width, chord length and arc length, but greater curvature (rib torsion, rib axial curvature, rib anterior-posterior bending) than males. The Kebara 2 reconstructed ribs were within the modern human range for the majority of geometrical parameters.

[Morphologic and tomodensitometric comparative analysis of two cyclotocephalic newborns]

Two specimens of cyclotocephalic newborns, coming from museum collections, have been the subject of a comparative morphologic analysis. This one comprised an external examination and a CT scan exploration. If the craniofacial features were similar, one had a quasi-normal brain, while the second specimen displayed alobar holoprosencephaly. This observation relatively surprising is discussed in the light of current knowledge on the developmental genetics of this family of malformations.

[The dental collection Hyacinthe Brabant: A pedagogic and scientific tool]

Among the numerous specimens preciously preserved in the Anatomical and Embryological Museum of ULB, there lies also a dental collection assembled by Professor Hyacinthe Brabant. This collection, previously unlabelled, shows several dental anomalies and pathologies as well as tumours. The objective of our study was to conduct an inventory of this collection and to set up an electronic iconographic tool through the Iconography website of ULB. A descriptive study was carried out and it was based on the analysis of 125 models and 90 extracted human teeth. The inspection of the models showed some non-odontological tumours as well as multiple dental anomalies. The extracted teeth showed generalised, coronal or radicular anomalies. The conducted inventory allowed us to classify and label the specimens and therefore to showcase this dental collection which is unique owing to its rich content and didactic display. Finally, the iconographic site will be a useful tool to raise awareness about several dental pathologies and anomalies among students and young practionners.

[Hermann Joris (1875-1910), a forgotten histologist]

Hermann Joris (1875-1910) was professor of histology at the Medical college of the Université libre de Bruxelles between 1908 and 1910. At the time of its nomination, its work relating to the pituitary gland and the neurons was the object of critical sharp by Albert Brachet. The author analyzes in what these criticisms rested certainly on sometimes debatable interpretations scientific, but betray also a quarrel between two generations of teachers of the University.

[A neonate with aprosopia, monomelia and celosomy]

The specimen of which it is a matter here takes part of the heritage of the Museum of Anatomy and Embryology of the Faculty of Medicine of the Université Libre de Bruxelles. Its medical history is completely unknown, because it takes part of an ancient collection of pathological anatomy saved from destruction and recovered by the laboratory of Anatomy and Embryology. The specimen is strongly folded up on itself ("in extension"), its length so arranged is about 25 cm; unfolded, it develops to 45 cm. Cranial perimeter is of 31 cm. Unfortunately, the brain was removed during the initial analysis, and only the examination of the braincase allows to draw some conclusions on the probable state of the encephalon. The face is rudimentary, without any orbit, and the oral cavity is limited to a vertical slit, revealing small strongly tipped up maxillary bones. A double proboscis is present. The trunk is characterised by a rather broad celosomy, with exhibition of the intestines, the liver and the pancreas. Anal atresia is observed, and the external sexual organs are hypoplastic and ambiguous. The whole left lower limb is absent, including the left half of the pelvis, corresponding to a left unilateral complete ectromelia. The neck is in hyperextension, so that the occipital region seems extremely welded in the cervical spine. However, CT examination does not confirm the presence of such fusion, but on the other hand, reveals a severe axial diversion of the spine with hyperextension. Extremely rare in humans, the aprosopia is more readily present in some animals (sheep). Its association with a monomelia and a celosomy seems not yet described.

[The teaching of anatomy in Brussels before the founding of the Université libre de Bruxelles]

Between 1733 and 1788, a "College of Medicine" assured the training of the students of Brussels. The lessons of anatomy were successively given by Adrien Charles Joseph Van Rossum, Paul Ignace De Bavay and François Du Rondeau. From 1788 and until 1797, the Faculty of Medicine of the University of Louvain was displaced in Brussels, and the anatomical lessons were given by Pierre Corneille de Brabant. Under French domination, the College and the University were closed, and replaced with a School of Surgery, which became Medical School under Dutch regime. Anatomy was taught by Jean-Baptiste Terrade, François Antoine Curtet, then Pierre-Joseph Graux, who became the first professor of anatomy of ULB when the young university absorbed the school during its foundation.

Effect of magnetic field and iron content on NMR proton relaxation of liver, spleen and brain tissues

Iron accumulation is observed in liver and spleen during hemochromatosis and important neurodegenerative diseases involve iron overload in brain. Storage of iron is ensured by ferritin, which contains a magnetic core. It causes a darkening on T2 -weighted MR images. This work aims at improving the understanding of the NMR relaxation of iron-loaded human tissues, which is necessary to develop protocols of iron content measurements by MRI. Relaxation times measurements on brain, liver and spleen samples were realized at different magnetic fields. Iron content was determined by atomic emission spectroscopy. For all samples, the longitudinal relaxation rate (1/T1 ) of tissue protons decreases with the magnetic field up to 1 T, independently of iron content, while their transverse relaxation rate (1/T2 ) strongly increases with the field, either linearly or quadratically, or a combination thereof. The extent of the inter-echo time dependence of 1/T2 also varies according to the sample. A combination of theoretical models is necessary to describe the relaxation of iron-containing tissues. This can be due to the presence, inside tissues, of ferritin clusters of different sizes and densities. When considering all samples, a correlation (r(2)  = 0.6) between 1/T1 and iron concentration is observed at 7.0 T. In contrast the correlation between 1/T2 and iron content is poor, even at high field (r(2)  = 0.14 at 7.0 T). Our results show that MRI methods based on T1 or T2 measurements will easily detect an iron overloading at high magnetic field, but will not provide an accurate quantification of tissue iron content at low iron concentrations.

[The scientific works of the teachers of human anatomy in the "Université Libre de Bruxelles" (ULB)]

The "Université Libre de Bruxelles" was founded in 1834. Between this year and 1904, the teachers of human anatomy were essentially clinicians and surgeons. Their works were mainly practical. Until 1904 (arrival of Albert Brachet) since present, the researches of the anatomical laboratory were devoted to embryology, and included the beginning of causal embryology. More recently, biomechanics appeared in the field of activity of the laboratory.

["Human races": history of a dangerous illusion]

The multiplication of offences prompted by racism and the increase of complaints for racism leads us to consider the illusory concept of "human races". This idea crossed the history, and was reinforced by the discovery of remote tribes and human fossils, and by the development of sociobiology and quantitative psychology. Deprived of scientific base, the theory of the "races" must bow before the notions of genetic variation and unicity of mankind.

Sex determination using the Probabilistic Sex Diagnosis (DSP: Diagnose Sexuelle Probabiliste) tool in a virtual environment

The hip bone is one of the most reliable indicators of sex in the human body due to the fact it is the most dimorphic bone. Probabilistic Sex Diagnosis (DSP: Diagnose Sexuelle Probabiliste) developed by Murail et al., in 2005, is a sex determination method based on a worldwide hip bone metrical database. Sex is determined by comparing specific measurements taken from each specimen using sliding callipers and computing the probability of specimens being female or male. In forensic science it is sometimes not possible to sex a body due to corpse decay or injury. Skeletalization and dissection of a body is a laborious process and desecrates the body. There were two aims to this study. The first aim was to examine the accuracy of the DSP method in comparison with a current visual sexing method on sex determination. A further aim was to see if it was possible to virtually utilise the DSP method on both the hip bone and the pelvic girdle in order to utilise this method for forensic sciences. For the first part of the study, forty-nine dry hip bones of unknown sex were obtained from the Body Donation Programme of the Université Libre de Bruxelles (ULB). A comparison was made between DSP analysis and visual sexing on dry bone by two researchers. CT scans of bones were then analysed to obtain three-dimensional (3D) virtual models and the method of DSP was analysed virtually by importing the models into a customised software programme called lhpFusionBox which was developed at ULB. The software enables DSP distances to be measured via virtually-palpated bony landmarks. There was found to be 100% agreement of sex between the manual and virtual DSP method. The second part of the study aimed to further validate the method by analysing thirty-nine supplementary pelvic girdles of known sex blind. There was found to be a 100% accuracy rate further demonstrating that the virtual DSP method is robust. Statistically significant differences were found in the identification of sex between researchers in the visual sexing method although both researchers identified the same sex in all cases in the manual and virtual DSP methods for both the hip bones and pelvic girdles.

[Application of the musculo-skeletal modelling software lhpFusionBox to a paleoanthropological problem: the Spyrou Neandertal moves!]

LhpFusionBox is a program originally designed for biomechanical and clinical studies relating to the musculoskeletal system of anatomically modern humans (AMH). The program has recently been adapted for paleontological purposes and used to reconstruct and biomechanically analyse a fossil hominid. There is no complete Neandertal skeleton in the fossil record. The aim of the study was to reconstruct a complete three-dimensional (3D) model of a Neandertal using the relatively complete Spy II Neandertal and to conduct biomechanical feasibility studies on the knee and hamstring moment arms of the skeleton. Different Neandertal specimens were scaled to the size of Spy II to replace incomplete or missing bones. Biomechanical feasibility studies performed on the knee seem to show that Neandertal and AMHh gait is similar and Neandertals were shown to have larger moment arms in the hamstring muscles, which would have given them a mechanical advantage. The complete Neandertal was printed in 3D and used as the base to create the artistic model of "Spyrou" housed at l'Espace de l'Homme de Spy (EHoS) museum.

[Pierre-Joseph-Cécilien Simonart (1816-1847) and the problem of amniotic bands]

Pierre-Joseph-Cécilien Simonart (1816-1847) was an obstetrician and an anatomist in the Université libre de Bruxelles. He described and analyzed the "amniotic bands" and their effects on the fetus. In this contribution, we situate his work in the evolution of the knowledge relative to this pathology.

[Maurice Herlant (1887-1920), a shooting star of embryology]

Maurice Herlant (1887-1920) was a Belgian embryologist who worked at the Université libre de Bruxelles during his brief career. He was the assistant of Professor Albert Brachet and was interested by polyspermia and experimental parthenogenesis. His promising career was interrupted by an early death at 33 years of age.

[Several streets of the area around Brugmann Hospital received the names of distinguished professors of Medicine of the Université Libre de Bruxelles]

Several streets in the area of the Brugmann Hospital in Brussels have received the names of distinguished professors of medicine of the Université libre de Bruxelles. These physicians are: Jean-Joseph Crocq, Edouard Kufferath, Guillaume Rommelaere, Adrien Bayet, Leon Stiénon, Albert Brachet and Jules Thiriar. In this short review, we resume their biography and locate their street.

[Supervision of anatomical demonstrations between 1834 and 1940]

Between 1834, year of the founding of the Université libre de Bruxelles, since 1940, many distinguished physicians and surgeons were in charge to participate to the anatomical demonstrations. We review successively the life and contributions of Hippolyte Guillery, Sébastien Tirifahy, Léon Warnots, Edmond Rouffart, Rémy Lavisé, Edouard Willems, Auguste Brunin, Alexandre Wilmart and Lucien Wilmart to the teaching of human anatomy.

Craniofacial embryology and postnatal development of relevant parts of the upper respiratory system

OBJECTIVES

To compare historical and current knowledge relating to the development of the paranasal sinuses, the nose and face, the Eustachian tube and temporal bones, particularly with respect to chronic inflammation during childhood.

METHODOLOGY

Traditional literature data, mainly emanating from text books, were supplemented with information based on a non-structured PubMed search covering the last two decades.

RESULTS

Historical knowledge has most often been confirmed, sometimes supplemented and only rarely challenged by present-day studies. Recent studies focus mainly on the clinical application of modern imaging techniques.

CONCLUSIONS

Interest in the development of relevant parts of the upper respiratory system remains as lively as ever. Imaging techniques with low or absent radiation exposure may give rise to a novel field of research, especially with respect to paediatric rhinosinusitis.

[Immunohistochemical study of Dlx1 and Msx1 expression during cephalic development of Dumbo and Wistar rats. Correlation with morphological data]

The Dumbo rat is characterized by a short snout, low ears and relative hypoplasia of maxillar and zygomatic bones. It corresponds to an autosomal recessive genotype. Previous study demonstrated a global deficit of Dlx1 and Msx1 genes expression in comparison to Wistar embryos as considered as control animals. We performed a histological study of cephalic development of Dumbo rats compared to Wistar embryos and an immunohistochemical analysis of Dlx1 and Msx1 protein expression during cephalogenesis. Our data indicate that the pattern of expression of both genes is similar in both strains, but that quantitative differences in gene expression can be the result of delayed organogenesis in Dumbo rat in comparison to Wistar. Some data about gene expressions are discussed at the light of the postulated function of Dlx1 and Msx1 in cephalic development.