[Embryology and growth of the skull].
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Animals↗
Biomedical subjects
M Catala
Publications and source records attributed to M Catala.
The INSERM expert review on glycol ethers: findings and recommendations.
The use of glycol ethers and their effects on health have recently attracted the attention of the French health authorities. At their request, INSERM, the French Institute of Health and Medical Research, conducted a collective expertise review on glycol ethers in 1999. INSERM Expertise Reviews are independent procedures performed by experts from several disciplines, to guarantee the objectivity and the relevance of the report. During several work sessions, the experts carried out a critical analysis of and reviewed studies concerning the toxicity of glycol ethers. This process resulted in a series of recommendations and conclusions. All these data have been published in the form of a report and have been used to help the public authorities to make decisions on how to prevent risks for professionals and consumers.
Animals↗
[To live or to die, an embryonic dilemma].
The development and formation of an organ needs both cell proliferation and cell death. It is commonly possible to decipher three types of basic cell death: 1) the so-called morphogenetic cell death (an example is the formation of the digits); 2) the histogenetic cell death like the apoptotic processes taking place in the spinal cord and allowing to regulate the number of motoneurons according to their targets; and 3) the phylogenetic cell death in which vestigial structures are selectively removed (e.g. destruction of the pronephros or removal of the tail in the anuran larva).
Animals↗
[Spontaneous cholecystocutaneous fistula].
INTRODUCTION: Spontaneous cholecystocutaneous fistula is now a rare entity due to the advent of antibiotics, ultrasonography, and safe and early surgical treatment of biliary tract diseases. Such a case is reporting here, revealed by the systematic histological examination of the skin biopsy. OBSERVATION: A 65 year-old male presented with an inflammatory and ulcerated lesion located on his right flank, with a long-standing but asymptomatic course. Biological tests and biliary tract ultrasonography were not very contributive. Histopathological findings consisted in a granulomatous dermal reaction enclosing biliary fragments. Per-operative data were in favour of a compound biliocutaneous fistula complicating an inflammatory process of the gall-bladder. DISCUSSION: Spontaneous cholecystocutaneous fistula is unusual. Diagnosis might be difficult because of the lack of clinical specificity and a occasionally insidious evolution. Consequently, systemic histological examination is fundamental.
Aged↗
[Where have the neuronal stem cells of the subependymal zone gone in human beings?].
Stem cells are characterized by their ability for self-renewal (allowing them to be present throughout the entire life of the organism) and their ability to give rise to differentiated cells belong to one or more lineages. The strict definition of these cells is however still a matter of debate. There is new experimental evidence (including in human beings) that stem cells are present within the brain and may give rise to neurons. Ependymal cells have been proposed to play such a role. In fact, subependymal cells expressing GFAP would be more likely candidates. Such cells are observed in the brain of human beings. They are able to differentiate into neurons in vitro but such potential appears to be repressed in vivo.
Brain↗
Epidermal growth factor-based cancer vaccine for non-small-cell lung cancer therapy.
BACKGROUND: The role that growth factors and their receptors play in human cancer growth and progression makes them interesting targets for novel treatment modalities. Our approach consisted of active immunotherapy with the epidermal growth factor (EGF). Two pilot clinical trials were conducted to examine the safety and immunogenicity of a five-dose immunization protocol and to compare different adjuvants and treatment designs. PATIENTS AND METHODS: Forty patients with advanced non-small-cell lung cancer were enrolled in both trials. They were randomized to be treated with aluminum hydroxide or montanide ISA 51 as adjuvants in the EGF vaccine preparation. The use of cyclophosphamide prevaccination treatment was evaluated in the second trial. RESULTS: Pooled data from both trials showed that the use of montanide as adjuvant increased the percentage of good antibody responders (GAR). Cyclophosphamide prevaccination treatment did not provoke improvements in antibody response. GAR had a significant increase in survival as compared with poor antibody responders. Response duration was also related to a significant improvement in survival rates. CONCLUSIONS: Vaccination with five doses of EGF vaccine is safe and immunogenic. Montanide ISA 51 increased the percentage of GAR. There is a direct relationship between anti-EGF antibody titers and immune response duration with survival time.
Adjuvants, Immunologic↗
[Development and maturation of the pyramidal tract].
The pyramidal tract contains axons that originate from neurons located in layer 5 of the neocortex of the frontal areas 4 and 6 and of the parietal lobe. These neurons are generated during the first half of gestation in humans. The growth of these axons is highly regulated and the mechanisms that control this growth begin to be unravelled. For example, netrins could serve as chemattractants, the adhesion molecule L1 plays a crucial role in the control of axonal decussation at the level of the medulla, the ephrin B3-Eph A4 couple prevents the axons from crossing the midline. During development, the total number of pyramidal axons increases progressively and then decreases by regression of exuberant collaterals. The pyramidal tract is the sole unmyelinated tract in the human spinal cord at birth. This accounts for the protracted central conduction time in newborns. This immaturity of the pyramidal system could explain the existence of specific motor reflexes in newborns (the so-called primary reflexes) that disappear as the pyramidal system matures.
Animals↗
[The formation of neurons in the bone marrow, the dream of alchemy in the new millenium].
In rodents, bone marrow contains stem cells that have the potentiality to differentiate into mesodermal and non-mesodermal cells, both in vitro and in vivo. These cells can populate a wide panel of organs such as the liver, the brain, the lungs, the heart.... They appropriately differentiate according to the environment in which they migrate and are known to assume specific functions. Even in adult animals, these cells can migrate and differentiate. Such a potentiality suggests exciting therapeutic outcomes. Brain lesions could benefit of such techniques. These experimental protocols should be precisely controlled before their use in medicine in order to solve problems that still remain such as the permeability of the hemato-encephalic barrier, the integration of differentiated grafted cells into local functional neural networks.
Animals↗
[Neurosurgical embryology. Part 1: Cell differentiation].
In pluricellular organisms, cell differentiation helps to decrease the total amount of energy needed for life. These differentiations can be evidenced at the tissular, the cellular or the molecular levels. Cell differentiation is a progressive process achieved during embryogenesis; different steps in the program can be described. One of the explanations to account for cell differentiation is the specific expression of proteins, called transcription factors, that can control the expression of selected genes. These factors are classified according to their biochemical pattern allowing description of several families of transcription factors. One of the salient questions during embryogenesis is to understand the mechanisms involved in cell differentiation. The first event is due to asymmetry of mitosis leading to the generation of two cell lineages. This is favored by the initial ovocyte polarization. The second event is due to cell interactions (namely inductions). These inductions may be explained either by cell-cell contact (favored by cell adhesion molecules) or by secreting factors that can be either hydrophilic or lipophilic.
Animals↗
[Neurosurgical Embryology. Part 2: Recent data on normal and pathological development of the cortex].
Understanding how the cortex develops has gained very important new data thanks to both experimental and clinical studies. Experimental studies have shown that: --neurons are generated in the ventricular zone by asymmetric mitoses; --the first cortical region to differentiate is the so-called pre-plate that plays a major role in the control of neuroblasts migration; --neuroblasts arise according to an inside-outside gradient; they migrate either along the processes of radial cells or according to a new type of non radial migration; --all the cortical neurons are not generated by the dorsal telencephalon; some of these neurons derive from the basal telencephalon; --neuroblasts acquire their specificity during their way to the cortical plate. There are several genetic syndromes leading to a malformation of the cortex. Classic lissencephaly is essentially due to mutations of the LIS1 or the DCX genes. These genes code for proteins that are involved in cytoskeleton functions. Reelin is responsible for a human syndrome associating pachygyria and cerebellar hypotrophy. Subventricular heterotopia can be X- inherited and are due to a mutation of the gene coding for filamin 1.
1-Alkyl-2-acetylglycerophosphocholine Esterase↗
[Neurosurgical Embryology. Part 3: Molecular control of corpus callosum development].
The corpus callosum is the most important cerebral commissure allowing axonal fibres to cross the midline. Corpus callosum agenesis is an important condition in man that can reveal numerous genetic syndromes. The corpus callosum develops from the commissural plate, a dorsal region of the telencephalon. Then, axons growing from pyramidal neurons of cortical layer III extend and cross the midline. In experimental models, it is possible to decipher two conditions in which the development of the corpus callosum is impaired. The first condition is characterized by an impairment of the formation of the roof of the telencephalon (the primordium of the commissural plate). This condition can be explained by an abortive induction of this region by an impairment of BMP signaling. This can generate all the forms of holoprosencephaly. Other forms are due to a defective gene coding Hesx1, a transcription factor involved in the control of telencephalic morphogenesis. Such a genetic defect can be observed in human dominant forms of septo-optic dysplasia. The second condition is explained by an impairment of the molecular control of axon growth: such is the case for the couple netrin 1 and DCC or for the adhesion molecule L1.
Agenesis of Corpus Callosum↗
[Neurosurgical embryology. Part 4: What are stem-cells?].
Stem-cells have been identified in the adult human brain in two zones which are the subventricular zone and the gyrus dentatus of the hippocampus. Improvement of techniques aimed to identify, to localize and to follow the lineage of these cells have been crucial to the understanding of the following processes: a) identification of cellular proliferation, b) specific immunostaining of differentiated glial and neuronal cells, c) transplantations to decipher between intrinsic stem-cell properties and influence of the environment on the fate of the cell. Furthermore, it seems that stem-cells from other sources than the brain can differentiate into neurons both in vitro and in vivo. The aim of this review is to sum up what is known about cerebral stem-cells and the challenging tools they mean for the future.
Animals↗
[Embryology of the sphenoid bone].
The sphenoid bone represents a complex structure in terms of anatomy and embryology. Indeed, it is formed by the fusion of different primordia whose embryonic origins are different. In mammals, it is possible to distinguish two components of this bone: the orbitosphenoid and the basi-post-sphenoid derive from the cephalic mesoderm whereas the alisphenoid and the basi-pre-sphenoid are from neural crest cell origin. The genetic control of the development of these two components is different further increasing the heterogeneity of these components. The sphenoid bone has been linked with several developmental diseases: chordomas, tumors arising from notochordal remnants; persistence of the craniopharyngeal canal may result in the occurrence of trans-sphenoidal encephaloceles.
Chordoma↗
[Neurosurgical embryology. Part 5: Temporal landmarks of the development of the central nervous system in humans].
The establishment of temporal landmarks of the development of the central nervous system was the primary goal of early human embryologists. The description of these landmarks has lost much of its interest since it is now largely accepted that the temporal profile of development is at best a poor indicator of the origin of malformative syndromes. However, we propose here a rapid review describing the principal data available. One of our goals is to present here the original data that are needed to understand the morphological aspect of the development of the central nervous system. The most important results are the presence of a developmental gradient within each anatomical area. This means that all the neurons of a specific anatomical region are not generated at the same time. There is also another gradient that could be described. This gradient is the rostro-caudal gradient: the spinal cord develops first, then the brain stem, and finally the encephalon. This rule is only a general rule with many exceptions like, for instance, the cerebellum that is a late derivative of the neural tube.
Central Nervous System↗
[Neurosurgical embryology. Part 6: The principal models that can be used in developmental biology].
To study the mechanisms controlling embryonic development, experimental analyses must be performed on animal models. There are different species that are currently used as models in developmental biology. In invertebrates, drosophila remains a very useful model thanks to its rapid development and to the extensive study of genes involved in the control of its development. C. elegans has been extensively used because of its simplicity due to the total restricted number of adult cells in this species. In vertebrates, amphibians remain a very useful model with the extensive analysis of Xenopus laevis. The zebrafish is now a widely used model because of its genetic analysis. Birds are still used for the accessibility of their embryo allowing experimental procedures to be performed in ovo. The mouse is now very widely used because it is possible to obtain transgenic mice to study both loss or gain of gene function.
Animals↗
[Neurosurgical embryology. Part 7: Development of the spinal cord, the spine and the posterior fossa].
The spinal cord arises from the most caudal domain of the neural tube whereas the vertebrae develop from the para-axial mesoderm (namely the somites). The development of the spinal cord and the vertebrae is so intimately linked that it is more convenient to present it in the same chapter. The neural tube is formed from the neural plate during neurulation. This tube is submitted to a double gradient of diffusible molecules that lead to the ventro-dorsal polarization of the tube. This polarization is figured as the emergence of sub-domains that contain progenitors engaged in a specific lineage. Axial organs induce the dissociation of the somites, giving rise to the dermatome, myotome and sclerotome. Vertebrae derive from the sclerotome after the so-called resegmentation of the somites. During this process, a caudal hemi-somite is associated with the rostral hemi-somite of the next caudal somite to differentiate into the vertebra. The occipital bone forms the major part of the walls of the posterior fossa. This bone develops from the para-axial mesoderm for its sub-tentorial part whereas its sus-tentorial derives from neural crest cells.
Cranial Fossa, Posterior↗
Genetic control of caudal development.
Several lines of evidence suggest that caudal development involves a distinct programme. This is illustrated by the fact that a specific pattern of malformations affects the caudal end of the human embryo. In addition, neurulation, the process leading to the formation of the neural tube, proceeds through different morphogenetic movements caudally. In mammals, as in birds, the caudal neural tube arises from cavitation and not from folding of the neural plate as in more rostral levels. However, recent fate mapping studies have suggested that the two modes of neurulation represent a continuous programme, possibly involving similar cellular or molecular mechanisms. Finally, analyses of mutant mice have shown that T-box transcription factors and components of the Wnt signalling pathway control cellular migration and the promotion of mesoderm formation in the caudal embryo. In humans, mutation in the HLXB9 transcription factor causes an autosomal dominant form of sacral agenesis. Thus, the combination of classical embryological and molecular genetics approaches has provided critical reference points for the delineation of the developmental programme of the caudal embryo.
Animals↗
[Recent contributions to the establishment of the axes of the mammalian embryo].
The study of the establishment of embryonic axes during early development has shown that this process is a very early event (occurRing either during ovogenesis or during fertilization) for invertebrates and for lower vertebrates. In mammals, it was considered that this establishment appears late during development because of the great plasticity of blastomeres. Recent data in the mouse embryon show that the mammalian ovocyte is a polarized cell, the polar body corresponding to the animal pole of this cell. The blastomeres that are generated by the zygote divide asynchronously. The first that divides is the one which inherits the plasma cell membrane where fertilization takes place. This blastomere will preferentially give rise to the cells of the embryonic pole of the blastocyst whereas the other yields the cells of the abembryonic pole. The mammalian ovocyte is thus a polarized cell with an already established animal-vegetal axis. The point of sperm entry will determine the embryonic-abembryonic axis.
Animals↗