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Nose-associated lymphoid tissue (NALT) in the rat
201
Abstracts of TheNernerlands Society of Electron Microscopy
the sexual resting period, it was assumed that they might be involved in Typical lysogonadotropin breakdown. somal enzymes, like arylsulphatase and acid phosphatase, could indeed be located in the central areas of the IMS. AS the bulk of gonadotropin is contained in granules and globules, these structures have to fuse under the formation of IMs. Because membrane fusion iSmOSt likely Ca-dependent, a cytochemical reaction for the ultrastructural localization of calcium was carried out. This resulted in the presence of deposits in the cytoplasm, but also in the central areas of the IMs and in the peripheral zone of some granules, apparently fusing with each other or with an IM. THE FUNCTION OF SURFACE ECTODERM PLACODES IN MESODERM FORMATION IN THE RAT A.E. Smits-van Prooije, Chr. VermeijKeers and E. Marani of Anatomy and Embryology, Dept. State University Leiden, Wassenaarseweg 62, NL-2333 AL Leiden, The Netherlands
Mesoderm in vertebrate embryos is formed by three different tissues, the primitive streak, the neural crest and the surface ectodermal placodes. The contribution of the former two tissues to the mesodermal compartment is well studied, but less is known of the extent of mesectoderm formation by the placodes. The contribution of surface ectoderm placodes to the mesodermal compartment was therefore studied on somite-stage Wheat rat embryos, cultured in vitro. germ agglutinin-gold was injected into their amniotic cavity. This probe is endocytosed by all cells surrounding the amniotic cavity, among them the surface If cells miectoderm placodal cells. grate from the (labeled) ectoderm into the mesodermal compartment, they can be recognised among the other cells in the mesodermal compartment by membrane-bound vacuoles containing electron-dense gold particles. In accordance with published data, surface ectodermal placodes were found in the nasal fields (contributing to the olfactory nerve), on the branchial arches (to the cranial ganglia) and in the otic vesicles (to the acoustic Moreover, labeled cells were ganglion). found in the transverse septum, forelimb
buds, abdominal wall and hindlimb buds. The presence of placodes at the involved sites was confirmed by discontinuity of the basal lamina underneath these placodes, as seen with both TEM and immunohistochemistry using anti-laminin and anti-collagen type IV. It is likely that this circum-abdominal placode induces closure of the abdomen, and not, as is often assumed, a fusion process.
NOSE-ASSOCIATED IN THE RAT
LYMPHOID
TISSUE
(NALT)
B.J. Spit, E.C.J. Hendriksen, J.P. Bruyntjes and C.F. Kuper TNO-CIVO Toxicology and Nutrition Institute, P. 0. BOX 360, 3700 AJ Zeist, The Netherlands
Mucosa-associated lymphoid tissue (MALT) in rats is found in the gastrointestinal and lower respiratory tract. Investigation of cross-sections of the nose of rats revealed paired lymphoid tissue at the left and right side of the entrance of the pharyngeal duct. In accordance with the definitions of the cross-sections given by Young (1986) at the levels 3 and 4. Light- and electron-microscopical examination was performed to investigate the architecture and organisation of this lymphoid tissue. Each of this paired tissue in conventionally housed untreated rats measured about 1 x 0.5 mm2. Immunohistochemistry on frozen sections revealed T- and B-cell areas in a few follicular structures. Examined by EM, the epithelium overlying the lymphoid tissue differed from normal respiratory epitheliwn. The cilicated cells were cuboidal instead of columnar; no mucuscontaining cells were observed, and single M-like cells were seen. The M-like cells demonstrated the typical luminal microvilli with filaments extending into the cytoplasm and the characteristic area with lymphocytes. On the basis of the morphological characteristics and the localization it was suggested that the lymphoid tissue in the nose of the rat belongs to the MALT, and therefore could be named noseassociated lymphoid tissue (NALT). These preliminary results open perspectives in the local immunological defense mechanism of the respiratory tract, with consequences for the relation between the different partners in the MALT.
Abstracts of TheNernerlands Society of Electron Microscopy
the sexual resting period, it was assumed that they might be involved in Typical lysogonadotropin breakdown. somal enzymes, like arylsulphatase and acid phosphatase, could indeed be located in the central areas of the IMS. AS the bulk of gonadotropin is contained in granules and globules, these structures have to fuse under the formation of IMs. Because membrane fusion iSmOSt likely Ca-dependent, a cytochemical reaction for the ultrastructural localization of calcium was carried out. This resulted in the presence of deposits in the cytoplasm, but also in the central areas of the IMs and in the peripheral zone of some granules, apparently fusing with each other or with an IM. THE FUNCTION OF SURFACE ECTODERM PLACODES IN MESODERM FORMATION IN THE RAT A.E. Smits-van Prooije, Chr. VermeijKeers and E. Marani of Anatomy and Embryology, Dept. State University Leiden, Wassenaarseweg 62, NL-2333 AL Leiden, The Netherlands
Mesoderm in vertebrate embryos is formed by three different tissues, the primitive streak, the neural crest and the surface ectodermal placodes. The contribution of the former two tissues to the mesodermal compartment is well studied, but less is known of the extent of mesectoderm formation by the placodes. The contribution of surface ectoderm placodes to the mesodermal compartment was therefore studied on somite-stage Wheat rat embryos, cultured in vitro. germ agglutinin-gold was injected into their amniotic cavity. This probe is endocytosed by all cells surrounding the amniotic cavity, among them the surface If cells miectoderm placodal cells. grate from the (labeled) ectoderm into the mesodermal compartment, they can be recognised among the other cells in the mesodermal compartment by membrane-bound vacuoles containing electron-dense gold particles. In accordance with published data, surface ectodermal placodes were found in the nasal fields (contributing to the olfactory nerve), on the branchial arches (to the cranial ganglia) and in the otic vesicles (to the acoustic Moreover, labeled cells were ganglion). found in the transverse septum, forelimb
buds, abdominal wall and hindlimb buds. The presence of placodes at the involved sites was confirmed by discontinuity of the basal lamina underneath these placodes, as seen with both TEM and immunohistochemistry using anti-laminin and anti-collagen type IV. It is likely that this circum-abdominal placode induces closure of the abdomen, and not, as is often assumed, a fusion process.
NOSE-ASSOCIATED IN THE RAT
LYMPHOID
TISSUE
(NALT)
B.J. Spit, E.C.J. Hendriksen, J.P. Bruyntjes and C.F. Kuper TNO-CIVO Toxicology and Nutrition Institute, P. 0. BOX 360, 3700 AJ Zeist, The Netherlands
Mucosa-associated lymphoid tissue (MALT) in rats is found in the gastrointestinal and lower respiratory tract. Investigation of cross-sections of the nose of rats revealed paired lymphoid tissue at the left and right side of the entrance of the pharyngeal duct. In accordance with the definitions of the cross-sections given by Young (1986) at the levels 3 and 4. Light- and electron-microscopical examination was performed to investigate the architecture and organisation of this lymphoid tissue. Each of this paired tissue in conventionally housed untreated rats measured about 1 x 0.5 mm2. Immunohistochemistry on frozen sections revealed T- and B-cell areas in a few follicular structures. Examined by EM, the epithelium overlying the lymphoid tissue differed from normal respiratory epitheliwn. The cilicated cells were cuboidal instead of columnar; no mucuscontaining cells were observed, and single M-like cells were seen. The M-like cells demonstrated the typical luminal microvilli with filaments extending into the cytoplasm and the characteristic area with lymphocytes. On the basis of the morphological characteristics and the localization it was suggested that the lymphoid tissue in the nose of the rat belongs to the MALT, and therefore could be named noseassociated lymphoid tissue (NALT). These preliminary results open perspectives in the local immunological defense mechanism of the respiratory tract, with consequences for the relation between the different partners in the MALT.