Doris B. Wilson

Fourth branchial pouch sinus: Principles of diagnosis and management

The fourth branchial pouch sinus is a congenital anomaly which most frequently manifests itself by recurrent episodes of neck abscess or acute suppurative thyroiditis. This lesion usually becomes symptomatic before the age of 10 years and is more common than has previously been suspected. It has been found on the left side in 93% of the 28 cases reported in the English literature. Barium swallow during periods of quiescence and nasopharyngoscopy have frequently been successful in identifying the presence of these embryological remnants. Definitive therapy consists of total excision of the sinus tract, which can be facilitated by direct endoscopic placement of a Fogarty® catheter into the sinus lumen before surgical exploration. The embryological basis for the occurrence of these sinuses is discussed.

Histological defects in the cerebellum of adult lurcher (Lc) mice.

The adult cerebellum of the heterozygous lurcher mouse (Lc/+) shows severe defects which affect particularly the Purkinje cells and granule cells. The cytoarchitecture of the cerebellar cortex is disturbed, and the granular and molecular layers are poorly defined. The population of Purkinje cells is depleted, except for a few large neurons scattered in the granular layer and white matter. Although a discrete Purkinje cell layer does not exist, pyridine-silver preparations reveal a row of arborizing basket cell axons and climbing fiber terminals which suggests the site previously occupied by Purkinje cell bodies. Granule cells are also affected and are distributed throughout the molecular layer, granular layer, and white matter.

Pathogenesis of Neural Dysraphism in the Mouse Mutant Vacuolated Lens (vl)

Abstract The pathogenesis and expression of caudal neural dysraphism were studied by means of tritiated thymidine autoradiography in the mouse mutant vacuolated lens (vl) at 11–13 days of gestation. In homozygous litters, all of the embryos microscopically exhibited spinal cord defects, even though dysraphism could be detected grossly only in the most severely affected ones. The defects ranged from extreme eversion of widely open neural folds to a dorsally expanded neurocoel with an attenuated or distorted roof plate. Incorporation of tritiated thymidine occurred in cells in the defective roof plates, in severely distorted areas of the neural tube where cellular disaggregation occurred, and in isolated areas within the developing intermediate layer, as well as in normal sites of cellular proliferation. The frequently observed central mass of distorted but proliferating neural tissue associated with bilateral attenuations of the roof plate suggests a failure of, or defect in, the normal process of apposition and fusion of the neural folds, rather than a failure in opposition. The range in severity and the gross and microscopic manifestations of neuropathological lesions in the homozygous vl embryos indicate that this heretofore unexplored mutant has considerable potential as an experimental model for analyzing the origins and mechanisms of human neural dysraphism.

Analysis of hindbrain neural crest migration in the long-tailed monkey (Macaca fascicularis)

Neural crest cells make a substantial contribution to normal craniofacial development. Despite advances made in identifying migrating neural crest cells in avian embryos and, more recently, rodent embryos, knowledge of crest cell migration in primates has been limited to what was obtained by conventional morphological techniques. In order to determine the degree to which the nonhuman primate fits the mammalian pattern, we studied the features of putative neural crest cell migration in the hindbrain of the long-tailed monkey (Macaca fascicularis) embryo. Cranial crest cells were identified on the basis of reported distributional and morphological criteria as well as by immunocytochemical detection of the neural cell adhesion molecule (N-CAM) that labels a subpopulation of these cells. The persistent labeling of a sufficient number of crest cells with antibodies to N-CAM following their exit from the rostral, preotic and post-otic regions of the hindbrain facilitated tracking them along subectodermal pathways to their respective destinations in the first, second and third pharyngeal arches. Peroxidase immunocytochemistry was also employed to localize laminin and collagen-IV in neuroepithelial basement membranes. At stage 10 (8–11 somites), crest emigration occurred in areas of unfused neural folds through focal disruptions in the neuroepithelial basement membrane in both the rostral and pre-otic regions, although there was little evidence of crest migration in the post-otic hindbrain. By stage 11 (16–17 somites), the neural folds were fused (pre- and post-otic hindbrain) or in the process of fusing (rostral hindbrain), yet crest cell emigration was apparent in all three areas through discontinuities in the basement membrane. Emigration was essentially complete at stage 12 (21 somites) as indicated by nearly continuous cranial neural tube basement membranes. At this stage the pre-ganglia (trigeminal, facioacoustic and glossopharyngeal) were consistently stained with N-CAM. The current study has provided new information on mammalian neural crest in a well-established experimental model for normal and abnormal human development, including its use as a model for the retinoic acid syndrome. In this regard, the current results provide the basis for probing the mechanisms of retinoid embryopathy which may involve perturbation of hindbrain neural crest development.

Quantitative aspects of growth hormone cell maturation in the normal and little mutant mouse.

Growth hormone (GH) cells were analyzed by means of ultrastructural morphometry in the pars distalis of pituitary glands from male adult and immature normal (C57BL) and homozygous little (lit/lit) mutant mice. Thin sections were exposed to anti-GH serum and processed immunocytochemically with the colloidal-gold technique. In the pars distalis of adult lit/lit mice, the mean volume density of GH cells/total tissue was 24% of the normal value, granules/GH cells was 58% of normal, and granules/total tissue was only 12% of normal. Deficits in all of these parameters likewise occurred in immature glands, though to a lesser extent than in the adults. The results indicate that the GH deficiency in this mutant reflects quantitative deficits in both the secretory granule content of GH cells, as well as the GH cell content of the gland, with the latter being the more severely affected.

Distribution of Extracellular Matrix Components during Early Embryonic Development in the Macaque

The distribution of fibronectin (FN), laminin (LM), hyaluronic acid (HA) and chondroitin sulfate (CS) were examined by peroxidase immunocytochemistry in long-tailed monkey embryos during the period of neural tube and notochord formation (stages 8-11). Reactivity for each component in the neuroepithelial basement membrane (BM) increased with advancing development. Discontinuous staining was observed in areas of epithelial-to-mesenchymal transformation, i.e. in dorsolateral sites of neural crest emigration and in the axial region of the primitive streak. The BM forming around the developing notochord also showed increased reactivity for FN, LM, HA and CS between stages 8 and 11. No staining occurred within the notochord. Stage-related increases in reactivity in the mesenchymal matrix was particularly notable for FN and HA which were ubiquitous throughout the mesoderm by stage 11. The results of this study are consistent with the proposed role of these components in maintaining epithelial integrity and providing a permissive substrate for cell migration during development. The observed temporal and regional staining patterns suggest that these glycoproteins and glycosaminoglycans are important morphogenetic factors in the macaque.

Distribution of 3H-Thymidine in the Postnatal Hypophysis of the C57BL Mouse

The distribution of cells labelled with 3H-thymidine was determined autoradiographically in the adenohypophysis and neurohypophysis of the C57BL mouse during postnatal phases ranging from the newborn to 24 days of age, as well as in the adult. In the newborn, labelled cells are scarce in the neurohypophysis but common in the adenohypophysis. The neurohypophysis shows a surge in labelling at 5-9 days, with a sharp decline thereafter. In the adenohypophysis, labelled nuclei are scarce in the pars tuberalis after 19 days, whereas the pars intermedia and pars distalis continue to show labelled cells. In the pars distalis, at all phases, label occurs in the marginal cells along the hypophysial cleft as well as in deeper-lying cells representing follicular cells. In the adult, follicular cells are more commonly labelled relative to other cells of the hypophysis.

Early development of the brain and spinal cord in dysraphic mice

SummaryThe development and closure of the neural folds was studied in C57BL/6J and loop-tail (Lp) mutant mice by means of scanning electron microscopy on a series of embryos ranging in age from 7.5 to 9.0 days of gestation. The normal embryos (C57BL/6J; +/+; Lp/+) showed a transitional zone of flattened cells lying between the surface ectoderm and neuroepithelial cells at the apices of the neural folds in the presumptive hindbrain and spinal cord, and ruffles occurred at the boundary between the flattened cells and surface ectoderm in regions of the folds which were about to fuse. In the abnormal loop-tail homozygotes (Lp/Lp) which exhibit dysraphism, the ruffles were arranged erratically along the zone of flattened cells. Moreover, at the stage when the folds became apposed and fused in the normal embryos, the abnormals showed ruffles extending the entire length of the unfused folds, thereby distinguishing the abnormals from retarded n normal embryos. Within the neural groove of the hindbrain region, the lateral neuroepithelial cells of the abnormal dysraphic embryos exhibited more flattened surfaces and fewer villous projections than in the normal embryos. The abnormal embryos also lagged behind their normal littermates in converting the body axis from the initial V-shape to the C-shaped configuration.

The cell cycle during closure of the neural folds in the C57BL mouse

An analysis of cellular kinetics during closure of the cranial neural folds in the C57BL mouse at 8 and 9 days gestations was obtained by means of tritiated thymidine autoradiography. At 8 days the short generation time (7.5 h) and high labeling index (61.4%) are evidence of intensive proliferative activity occurring concurrently with significant changes in cell shape and movement during neural fold elevation and approximation.

Cellular proliferation in the exencephalic brain of the mouse embryo

Autoradiographic studies were conducted on the midbrain and cerebral hemispheres of abnormal (Lp/Lp) exencephalic embryos and normal littermates at 12--18 days of gestation. At 12 days of gestation the percentage of cells labeled (labeling index, LI) in the abnormal brains was similar to that in the normals; however, by 14 and 16 days, the LI had decreased in the normal brains but remained the same in the abnormals. Although an accurate labeling index could not be determined in the 18-day abnormals because of the necrosis and severe histological distortion, incorporation of tritiated thymidine continued to occur, but at an apparently reduced level from earlier stages. On the basis of differences in the LI at 14--16 days of gestation, it appears that cells in the abnormal brains retain their ability to proliferate for longer periods of development than is the case in normal brains.