Ectopic adenoviral vector-directed expression of Sema3A in organotypic spinal cord explants inhibits growth of primary sensory afferents.
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Sema3A (Sema III, SemD, collapsin-1) can induce neuronal growth cone collapse and axon repulsion of distinct neuronal populations. To study Sema3A function in patterning afferent projections into the developing spinal cord, we employed the recombinant adenoviral vector technique in embryonic rat spinal cord slices. Virus solution was injected in the dorsal aspect of organotypic spinal cord cultures with segmentally attached dorsal root ganglia (sc-DRG). In cultures grown in the presence of nerve growth factor (NGF), injected either with the control virus AdCMVLacZ or with vehicle only, afferent innervation patterns were similar to those of control. However, unilateral injection of AdCMVSema3A/AdCMVLacZ in sc-DRG slices revealed a strong inhibitory effect on NGF-dependent sensory afferent growth. Ectopic Sema3A in the dorsal spinal cord, the target area of NGF-responsive DRG fibers in vivo, created an exclusion zone for these fibers and as a result they failed to reach and innervate their appropriate target zones. Taken together, gain of Sema3A function in the dorsal aspect of sc-DRG cultures revealed a dominant inhibitory effect on NGF-dependent, nociceptive sensory DRG afferents, an observation in line with the model proposed by E. K. Messersmith et al. (1995, Neuron 14, 949-959), suggesting that Sema3A secreted by spinal cord cells can act to repel central sensory fibers during the formation of lamina-specific connections in the spinal cord. (+info)
Overexpression of rice OSH genes induces ectopic shoots on leaf sheaths of transgenic rice plants.
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Five rice homeobox (OSH) genes were overexpressed under the control of the cauliflower mosaic virus 35S promoter or the rice actin gene promoter in transgenic rice plants. Almost all of the transgenic plants showed abnormal phenotypes, which could be classified into three types according to their severity. Plants with the most severe phenotype formed only green organs, with many shoot apices on their adaxial sides. Plants with an intermediate phenotype formed bladeless leaves with normally developed leaf sheaths. Plants with a mild phenotype formed normal leaf sheaths and blades, but lacked ligules and showed diffusion of the blade-sheath boundary. The leaf structure of this phenotype was similar to that of dominant maize mutants, such as Kn1, Rs1, Lg3, and Lg4. Based on these phenotypes, we suggest that ectopic expression of the rice OSH genes interferes with the development of leaf blades and maintains leaves in less differentiated states. These results are discussed in relation to the leaf maturation schedule hypothesis (M. Freeling et al., 1992, BioEssays 14, 227-236). (+info)
Phakomatous choristoma of the eyelid.
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This article describes the first report of phakomatous choristoma of the eyelid in Korea. A six-month-old boy underwent excision of a congenital inferonasal orbital mass arising from the left lower lid. A dermoid cyst was suspected, however a diagnosis of phakomatous choristoma was made following conventional histology. An immunohistochemical study of this rare benign congenital tumor was conducted. The cuboidal epithelial cells comprising this choristoma showed strongly positive cytoplasmic staining with S-100 protein and vimentin. They also showed focally positive staining with a neuron-specific enolase, while they showed no immunoreactivity to cytokeratin or epithelial membrane antigen. The results of the immunohistochemical study support the conclusion that this tumor is of lenticular anlage origin. (+info)
Accessory spleens in the thoracic and abdominal cavities after a relapse of idiopathic thrombocytopenic purpura: a case report.
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This case report presents a highly unusual finding of ectopic splenic tissue in both the thoracic and abdominal cavities in a patient with recurrent idiopathic thrombocytopenic purpura (ITP). (+info)
Engrailed-1 misexpression in chick embryos prevents apical ridge formation but preserves segregation of dorsal and ventral ectodermal compartments.
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Using lineage tracers, we recently showed dorsal and ventral ectodermal compartments along the sides of the body in chick embryos. The compartments are formed both in presumptive limb-forming regions where they position the apical ridge and also in presumptive interlimb (flank). Here we show, using a novel technique combining fate mapping and in situ hybridisation, that the ventral compartment coincides with the Engrailed-1 (En-1) domain of expression. This coincidence suggests that En-1 could maintain the ventral compartment and be necessary for apical ridge formation. To test this hypothesis, we ectopically expressed En-1 via retroviral transfer and then examined limb development and cell lineage restriction in the ectoderm. En-1 misexpression can completely prevent formation of both normal limbs and ectopic limbs induced in the flank by application of FGF-2. In both cases, there are no morphological signs of apical ectodermal ridge formation and expression of ridge-associated genes is undetectable. In striking contrast, the lineage restriction between dorsal and ventral ectoderm is not altered. Therefore, En-1 is involved in the regulation of ridge formation but not compartment maintenance. (+info)
Posterior pituitary ectopia: another hint toward a genetic etiology.
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We report the MR and clinical findings of two patients with growth hormone deficiency and posterior pituitary ectopia (PPE). Possible causes of PPE are discussed. (+info)
A heterotopic cerebellum presenting as a suprasellar mass with associated nasopharyngeal teratoma.
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We present a case of nasopharyngeal teratoma that was discovered in association with a suprasellar heterotopic cerebellum in a newborn. Well-differentiated, heterotopic, cerebellar masses have been reported in the orbits, spine, and frontal encephalocele but not, to our knowledge, in the suprasellar region. In this report, we describe the imaging findings and discuss the possible origins of the two masses discovered in this case. (+info)
Morphogenesis of craniopharyngeal derivatives in the neurohypophysis of Fisher 344 rats: abnormally developed epithelial tissues including parotid glands derived from the stomatodeum.
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Morphogenesis of craniopharyngeal derivatives of the neurohypophysis found in 14 Fischer 344 (F344) rats was studied. The incidence of the craniopharyngeal derivatives was 0.17% in male (7 out of 4,200) and 0.16% in female (7 out of 4,450) F344 rats. Neither a sex-related difference in their incidence nor a strain-related difference in their morphological features was observed. Craniopharyngeal derivatives were composed of aberrant epithelial structures consisting of serous acinar and tubular and fusiform cell structures, and most of these derivatives were associated with Rathke's cleft cysts, which are suggestive of a congenital background. The acinar structures were positive for periodic acid-Schiff reaction and negative for Alcian blue stain. Immunohistochemically, cells forming these structures were positive for cytokeratin, and basal cells of the acinar or tubular structures and some of the fusiform cells showed positive staining for alpha-smooth muscle actin. Electron microscopically, these spindle-shaped basal cells had intracytoplasmic myofilaments with focal density in their cytoplasm, and they were regarded to be myoepithelial cells. These findings strongly indicate that the craniopharyngeal derivatives are not a neoplastic lesion but rather are a developmental aberration derived from the stomatodeum, which is known to be the origin of both nasal and oral epithelial tissues, including the parotid glands, other than Rathke's pouch. (+info)