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E V Simons

Publications and source records attributed to E V Simons.

8 recordsLinked to original sources
PubMed1979

The effects of experimental unilateral anotia on skull development in the chick embryo. V. The development of the brain and its meningeal envelope in embryos of 9-20 days of incubation.

In a total number of 27 normal and 27 unilaterally anotic chick embryos, varying in age from 9-19 days, the morphogenetic relationships between the neurocranium on the one hand and the brain and its meningeal envelope on the other were studied. The results showed that, in general, unilateral anotia slightly interferes with the development of the bain. Only the homolateral nucleus tangentialis and cerebellar auricle proved to be underdeveloped. However, the brain of the anotic embryos progressively develops asymmetrically: In an antero-posterior and a ventro-dorsal direction abnormal flexures are present, and various components of the brain on the anotic side undergo changes in shape and position. These changes in brain morphology are interpreted as secondary features. Hence, the conclusion is drawn that the neurocranium, through the intermediary of the meningeal envelope, controls--or at least is capable to control--the general morphological development of the brain.

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PubMed1977

The effects of experimental unilateral anotia on skull development in the chick embryo. IV. Development of the bony skull in embryos of 9-20 days of incubation.

The study of the development of the bony skull in chick embryos with unilateral (right-sided) anotia revealed the following characteristics: 1. The perichondral bones initially follow exactly the cartilaginous structures to which they are related. Later, they may expand desmally to fill up the gaps and diminish the degree of pre-existing asymmetry. 2. The desmal bones which develop in close contact with cartilage, develop parallel to its margins and, hence, appear to be greatly dependent on the chondrocranium. 3. Among the desmal bones which arise independently from cartilage, only the bones of the cranial vault proved to be influenced by the unilaterally anotic condition.

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PubMed1976

The effects of experimental unilateral anotia on skull development in the chick embryo. III. Chondrocranial development in anotic embryos of 7-20 days of incubation.

The study of the development of of the chondrocranium in chick embryos with unilateral (right-sided) anotia revealed the following main characteristics. 1. The median axes of the chordal and the prechordal part of the cranial base are not in a straight line but show a deviation toward the right side. The angle between the two axes has its vertex in the region of the foramen hypophyseos. 2. The metotic cartilage and the foramina of the IXth and Xth cranial nerves are normal in position. 3. The tectum synoticum develops later and to a lesser extent than normal. 4. Between the basal plate, the metotic cartilage, the occipital arch and the supracapsular cartilage a foramen is formed which, later in development, is closed by outgrowths of the metotic cartilage and the basal plate. 5. The "optic area" shows a practically normal appearance which indicates that the cartilaginous ventral wall of the lagenal capsule is of basal plate origin. 6. The pro-otic process develops practically normal and, hence, is independent of the ear capsule. 7. The quadrate cartilage and the right lower jaw are displaced ventro-posteriorward. The earliest development of the perichondral bones shows some particularities which are closely correlated with the development of the various cartilaginous structures.

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PubMed1975

The effects of experimental unilateral anotia on skull development in the chick embryo. II. Essentials of the development of the chondrocranium in normal embryos of 7-20 days of incubation.

In order to be able to describe adequately the developmental anomalies of the chondrocranium in unilateral anotia in the chick embryo, it seemed necessary to describe the essentials of the normal chondrocranial development. The following observations proved to be different from the available descriptions: 1. the occipital processes do not fuse with the ear capsules; 2. the tectum synoticum fuses only with the ear capsules; the occipital processes fuse later with the tectum synoticum by outgrowth to dorsal; 3. in the chick embryo there is no evidence for the existence of a tectum posterius; 4. the metotic fissure is in the cartilaginous stage of development not closed, but shifts laterally; 5. there is strong evidence that the pro-otic processes arise as independent structures which later fuse with the ear capsules. The results of the study of the development of the chondrocranium in the embryos in which experimentally unilateral anotia is produced, will be described in a following paper.

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