Anatomy and Embryology最新文献

The aim of this work is to investigate the growth of the vasculature in the rat humeral head cartilage after the initial development of the secondary ossification centre until the adult organization. Rats aging from 5 weeks to 12 months were used. Histological observations on humeral heads were implemented with morphometrical analysis. Subsequently, vascular corrosion cast, that permits a three-dimensional observation of the vasculature, were prepared and observed by scanning electron microscopy. In young animals the epiphysis contains thin bone trabeculae and most of the epiphysis is occupied by bone marrow spaces. With age, the bone trabeculae progressively enlarge up to double their thickness. The percentage of bone tissue increases from 33.6 to 58.6% of the entire epiphysis, while the bone marrow spaces tend to increase very little in their mean dimension. Vascular corrosion casts show that the epiphyseal microcirculation is well distinguished from that of the diaphysis, and arises from the vessels present in the capsule and the periosteal networks. In young animals the only capillaries are bone marrow sinusoids and few subchondral capillaries. In adult animals small vessels run between the clusters of sinusoids forming the trabecular circulation. Capillary sprouts from sinusoids are always observed both in the young and adult animals. Thus, in adult rats different proper microcirculatory districts can be distinguished in the epiphysis: (a) the sinusoidal network, that supplies the hematopoiesis of the bone marrow and the adjacent osteogenic tissue; (b) the bone tissue microcirculation, limited to small vessels that supply the metabolism and the remodelling of the bone tissue. The reported microvascular organization and its adaptation to the epiphyseal growth represent the morphological basis for understanding the reciprocal interaction among the different tissues in developing and adult rat epiphysis.

During the initial phase of cardiac looping, known as c-looping, the heart bends and twists into a c-shaped tube with the convex outer curvature normally directed toward the right side of the embryo. Despite intensive study for more than 80 years, the biophysical mechanisms that drive and regulate looping remain poorly understood, although some investigators have speculated that differential cytoskeletal contraction supplies the driving force for c-looping. The purpose of this investigation was to test this hypothesis. To inhibit contraction, embryonic chick hearts at stages 10-12 (10-16 somites, 33-48 h) were exposed to the myosin inhibitors 2,3-butanedione monoxime (BDM), ML-7, Y-27632, and blebbistatin. Experiments were conducted in both whole embryo culture and, to focus on bending alone, isolated heart culture. Measurements of heart stiffness and phosphorylation of the myosin regulatory light chains showed that BDM, Y-27632, and blebbistatin significantly reduced myocardial contractility, while ML-7 had a lesser effect. None of these drugs significantly affected looping during the studied stages. These results suggest that active contraction is not required for normal c-looping of the embryonic chick heart between stages 10 and 12.

The distribution of the intermediate filament molecular markers, glial fibrillary acidic protein (GFAP) and vimentin, has been studied in the central nervous system (CNS) of the soft-shell turtle (Trionyx sinensis) with immunoperoxidase histochemistry. GFAP immunohistochemistry pointed out the presence of different astroglial cell types. The brain pattern consists of ependymal radial glia whose cell bodies are located in the ependymal layer throughout the brain ventricular system. In the spinal cord, the ependyma is immunonegative, whereas positive radial astrocyte cell bodies are displaced from the ependyma into the periependymal position. Star-shaped astrocytes are observed only in the posterior intumescence of the spinal cord. The different regions of the CNS show a different intensity in GFAP immunostaining even in the same cellular type. Vimentin-immunoreactive structures are absent in the brain and spinal cord. The present study reports an heterogeneous feature of the astroglial pattern in the spinal cord compared to the brain which shows an ancestral condition.

We produced two novel rat monoclonal antibodies (LA102 and LA5) to identify mouse lymphatic vessels and blood vessels, respectively. We characterized the two antibodies as to the morphological and functional specificities of endothelial cells of both types of vessels. The antibodies were produced by a rapid differential immunization of DA rats with collagenase- and neuraminidase-treated mouse lymphangioma tissues. LA102 specifically reacted with mouse lymphatic vessels except the thoracic duct and the marginal sinus of lymph nodes, but not with any blood vessels. In contrast, LA5 reacted with most mouse blood vessels with a few exceptions, but not with lymphatics. LA102 recognized a protein of 25-27 kDa, whereas LA5 recognized a molecule of 12-13 kDa. Neither antibody recognized any currently identified lymphatic or vascular endothelial cell antigens. Immunoelectron microscopy revealed that the antigens recognized by LA102 and LA5 were localized on both luminal and abluminal endothelial cell membranes of each vessel type. Interestingly, LA102 immunoreactivity was strongly expressed on pinocytic or transport vesicle membrane in the cytoplasm of lymphatic endothelium. Besides endothelial cells, both antibodies also recognized some types of lymphoid cells. Since, the LA102 antigen molecule is expressed on some lymphoid cells, it may play important roles in the migration of lymphoid cells and in some transport mechanisms through lymphatic endothelial cells.

Lectin binding patterns in the olfactory bulb of the Japanese common toad, Bufo japonicus, were examined using 21 types of lectin. Ten out of 21 lectins, WGA, s-WGA, LEL, STL, DBA, VVA, SJA, RCA-I, PNA, and PHA-L, stained the olfactory nerve, the glomeruli in the main olfactory bulb (MOB), the vomeronasal nerve, and the glomeruli in the accessory olfactory bulb (AOB). The binding patterns of LEL, STL, DBA, and PHA-L subdivided AOB glomeruli into rostral and caudal regions, where LEL, STL, and DBA stained the rostral region more intensely than the caudal region, and PHA-L had the opposite effect. Another lectin, BSL-I, stained both AOB glomeruli and the vomeronasal nerve, but not MOB glomeruli or the olfactory nerve. This is the first report of histological subdivision in the AOB of an amphibian, which suggests that the AOB development in Bufo may be unique.

The spatial and temporal distribution of nestin, cytokeratins (CKs), vimentin, glial fibrillary acidic protein (GFAP), neurofilaments (NFs), beta-tubulin as well as fibroblast growth factor receptors (FGFRs) and platelet-derived growth factor receptor beta (PDGF-Rbeta) were investigated in the developing human eye in eight conceptuses of 5-9 postovulatory weeks using immunostaining. Nestin was found in the neuroglial precursors and the radial glial fibres of the optic nerve. In the pigmented retina, nestin was present only in the 5th week, while at later stages (6-9th week), co-expression of CKs and vimentin was seen. Nestin, CKs, vimentin, and GFAP were observed in the precursors to various cell types in the neural retina. Additionally, their expression was also apparent in the lens epithelium, showing its gradual fading following the lens fibre elongation. They appeared in the mesenchymal cells of the cornea, the choroid, the sclera, and the corpus vitreum, too. In the corneal epithelium, co-expression of nestin and CKs was detected. NFs and beta-tubulin were confined to the differentiating retinal neuroblasts. Growth factor receptors were seen in the retina, the lens epithelium while less intensely in the lens fibres, the corneal epithelium, and the mesenchymal cells. During the early eye development (5-9th week), IFs expressing normal pattern of distribution as well as acting in concert might contribute to the normal developmental processes occurring in certain parts of the human eye. Additionally, NFs and beta-tubulin seem to have an important role in the retinal ganglion cell differentiation, while FGFRs and PDGF-Rbeta may regulate the cell proliferation, differentiation, and survival in various parts of the developing eye.

The microvascular anatomy of the small intestine of metamorphosing tadpoles of the South African Clawed Toad, Xenopus laevis (Daudin) is studied from developmental stages 55 to 65 and in adults by scanning electron microscopy (SEM) of vascular corrosion casts (VCCs) and light microscopy. Up to stage 62, VCCs reveal a dense two-dimensional vascular network ensheating the intestinal tube, whose proximal portion forms a clockwise spiralling outer and its distal portion an anti-clockwise spiralling inner coil. Vessels of the intestinal network impose flat and run circularly to slightly obliquely. Locally, dense capillary plexus with small "holes" indicating ongoing intussusceptive microvascular growth (IMG) and vessel maturation, are present. The typhlosole, an invagination along the proximal portion of the small intestine, reveals a dense capillary bed with locally ongoing IMG. VCCs of stages 62/63 for the first time reveal a three-dimensional vascular bed with longitudinal intestinal folds of varying size and heights greatly enlarging the luminal exchange area of the intestinal tube. From stage 65 onwards, longitudinal intestinal folds undulate and, though smaller in size and less mature as indicated in VCCs by the presence of wider, sinus-like vessels with small "holes" interposed between, closely resemble the intestinal folds present in the small intestine of adult Xenopus. Our data suggest that maturation of the vascular pattern in the small intestine of X. laevis tadpoles takes place successively after stages 62-63, and growth during this period is preferentially by intussusception.

The efferent duct of the ostrich consists of two segments, the proximal efferent duct (PED) and the distal efferent duct (DED) that are continuous, as in some other birds. Both segments of the duct possess an epithelium comprising non-ciliated and ciliated cells in varying proportions between the two segments. The non-ciliated cell (type I) of the PED contains a well-developed, subapical endocytic apparatus of apical tubules and endocytic vacuoles, a solitary, large, heterogeneous lipid droplet, and numerous, oval, dense bodies in the supranuclear region of the cell. Mitochondria tend to concentrate in the basal part of the cell. Intercellular spaces between the non-ciliated cells are enlarged, especially in the basal half of the epithelium. Together, these morphological features confer on the PED an efficient fluid absorption capability. The DED epithelium displays the type II non-ciliated cell whose poorly developed subapical endocytic apparatus as well as the absence of dilated basal intercellular spaces indicate its limited fluid absorptive capacity.

Neurotrophins acting through Trk signal-transducing receptors play essential roles in the nervous system, and probably in some non-neuronal tissues. In the present study, we used RT-PCR, Western-blot and immunohistochemistry to investigate the occurrence and cellular localization of TrkB in the mouse liver, from newborns to 6 months. Furthermore, the structure of the liver in mice carrying a mutation in the trkB gene, resulting in a non-functional protein, was studied. The analysis of the DNA sequence showed that hepatic trkB gene is identical to the cerebral one, and TrkB mRNA and TrkB full-length protein (145 kDa) were detected at all the ages sampled. Immunohistochemistry revealed age-dependent changes in the pattern of TrkB expression. From 0 to 15 days, the TrkB was detected in morphologically and immunohistochemically identified monocyte-macrophage-dendric cells scattered throughout the organ, while in animals 3- and 6-months-old it was restricted to nerve fibres. Interestingly, there was a parallelism between TrkB expression by monocyte-macrophage-dendric cells and the presence of hepatic erythroblastic islands. In agreement with a possible role of TrkB on hepatic haematopoiesis, the liver of 15 days old TrkB (-/-) mice still contained erythroblastic islands, whereas they were absent in the wild-type littermates. Another striking finding was the absence of nerve profiles in the TrkB (-/-) animals. All together, present results support the role of TrkB in the murine liver in maintaining the innervation of the organ, and more importantly throughout an unknown mechanism in controlling the hepatic haematopoietic function.

The Wnt family of secreted signalling molecules control a wide range of developmental processes in all metazoans. The intracellular response to Wnt signalling depends on the choice of signalling cascade activated in the responding cell. Cells can activate either the canonical pathway that modulates gene expression to control cellular differentiation and proliferation, or the non-canonical pathway that controls cell polarity and movement. Recent work has identified the protein Naked Cuticle to act as an intracellular switch to promote the non-canonical pathway at the expense of the canonical pathway. We have cloned chick Naked Cuticle-1 (cNkd-1) and show that it is expressed in a dynamic manner during early embryogenesis. We show that it is expressed in the somites and in particular regions where cells are undergoing movement. Lastly, we show that the expression of cNkd-1 is regulated by Wnt expression originating from the neural tube. This study provides evidence that non-canonical Wnt signalling plays a part in somite development.