Biomedical subjects
Publications and source records attributed to L Sisto Daneo.
Transverse, frontal and sagittal notochord sections of chick embryos at different developmental stages were ultrastructurally examined. The notochord tissue organization appears to be more likely to build a stiff but flexible body axis than to have an inducting role on the surrounding embryonic structures.
Since in literature the question of the spatio-temporal sequence of the cartilage maturation in the developing vertebra is still controversial, the authors studied by light and electron microscope, the chondrification of the vertebral body in chick embryo from the 6th to the 13th incubation days, in order to define the correlations between morphology and distribution of the cartilage cells in this phase of vertebral development. The results show that the chondrogenesis follows spatio-temporal gradients, starting at about the 8th incubation day from a zone located between notochord and neural tube, slightly cranially to the midvertebral level. From this starting point the chondrification proceeds with dorso-lateral and radial progression, and at the same time extends towards the cranial and caudal plates of the developing vertebra. These data are compared to the findings obtained by other authors on the ultrastructural and biochemical aspects of the vertebral development.
Some of the cells that migrate to the dorsal myocardium of the chick embryo in stage 21 H-H begin to synthesize desmin. They retain this property even when they reach the subendothelial layers of the heart bud, i.e. the characteristic site of the cardiac conducting cells.
Immunohistochemical techniques with anti-desmin, anti-acetylcholine receptor and anti-fibronectin antisera and autohistoradiography were used to determine the dynamics of neuromuscular synaptogenesis. Fast twitching muscles were taken from chick embryos at 5 to 14 days of incubation. "Primitive eminences" at terminal arborizations of motor neurons were composed of Karnowsky positive, anti-desmin and anti-acetylcholine receptor positive cells which contained sites bound to alpha-bungarotoxin. These cells, characterized as myoblasts, fused with the myotubes during formation of neuromuscular junctions in the sites of contact with terminal arborizations of motor neurons. Their nuclei and cytoplasmic organelles become the nuclei and organelles in the soleplate.
Substance P-immunoreactive neurons were demonstrated in chick embryonic and adult trigeminal ganglion and jugular-superior ganglionic complex using FITC-immunohistochemical methods. Both small-size and large ganglion cells exhibited SP immunoreactivity, without apparent changes during embryonic and post-hatching development. SP-positive fibers could be detected in a good number in the sympathetic cranial cervical ganglion, either during embryonic development or in adult chick. No immunoreactive perikarya were observed in this ganglion. In the ciliary ganglion, both choroidal and ciliary neurons were SP-negative, whereas SP immunoreactive fibers surrounded the perikarya of both cell populations.
A study was made of the distribution of Substance P-immunoreactive fibers in chick cornea and uvea in whole mount preparation, using the indirect immunofluorescence technique. The development of these fibers during embryogenesis was also investigated. SP-fibers were present in all chick eye structures, in the various prenatal and postnatal stages examined. Their distribution was comparable with that observed by other workers in mammals. Transformation of the iris musculature from smooth to striated, during development, is not accompanied by significant changes in SP-ergic innervation.
Localization and development of chick heart peptidergic innervation (Substance P, VIP and Somatostatin) were investigated by means of immunofluorescence technique. The peptidergic component of the heart innervation was observed, for the first time, in older than 11 day chick embryos, i.e., subsequently to the appearance of the cholinergic component. The peptidergic structures achieve nearly full development in about 16-17 day embryos. Substance P is the most represented of the three peptides. It is localized both in nerve bundle fibers and in isolated fibers within the myocardium, the pericardium, the vessel walls; it is also present in fibers of some heart base ganglia. VIP is mostly contained in some thick single fibers travelling along the vessel walls of the heart base, the myocardium and the pericardium. Some VIP immunoreactive cells were also observed in the base ganglia. Somatostatin is mostly contained in some ganglia cells, whilst thin Somatostatin-immunoreactive fibers form a rich plexus among the atrial and ventricular myofibers, without contacting the vessel walls.
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The origin of the iridial sphincter muscle in chick embryo was investigated by means of immunohistochemistry. Desmin immunoreactive cells are shown in the mesenchymal stroma overlying the anterior epithelial layer of the iris in 4 1/2-day chick embryos. In 9-11-day chick embryos also some cells of the posterior epithelium near the pupillary margin, and of the iridial lamella show a slighter desmin-immunoreactivity. This finding agrees with a double origin of the iridial sphincter muscle: an early mesenchymal one and a later epithelial other.
Serial sections of stage 18-27 HH (3-5 days of incubation) chick embryo myotomes were investigated by electron microscope. Two morphologically different types of contractile elements (myoblasts and myotubes) with an exact and constant localization were identified. Myotome sections of other chick embryos in the same stages were examined with the immunofluorescence technique, after treatment with antisera directed against fast and slow adult myosins. As from stage 24 HH, some contractile elements react positively with anti-fast adult myosin antiserum, others with anti-slow antiserum. A very precise correspondence was constantly found between the ultrastructural and immunohistochemical findings. An identical pattern was observed in the buds of the fast-twitching pectoralis major and posterior latissimus dorsi and slow-twitching anterior latissimus dorsi muscles.
The distribution of fibronectin (FN) in the dental pulp and gingiva of the human adult was investigated by indirect immunofluorescence and indirect immunoperoxidase techniques. FN could not be demonstrated in the connective tissue of the dental pulp even in the blood vessels. On the contrary, a positive stain was obtained in the ground substance at the base of the odontoblast cell bodies and in various structures of a denticle which was accidentally found in the pulp of one of the examined teeth. The lack of FN in the dental pulp could mean that this tissue, sometimes considered to be of an immature and undifferentiated type, is instead a mature one. The subepithelial connective tissue and the epithelium of the gingiva were examined. The distribution of FN in the connective tissue of the gingiva was found to be similar to that described in other types of connective tissue; high concentrations were found both in the epithelial cells and around them. This finding is described here for the first time and remains to be verified in other types of stratified epithelia.
Autoradiographic investigation of the migration of myotomal cells into the muscle buds. Autoradiography following the administration of 3H-thymidine in chick embryos showed that myogenically differentiated muscle plate cells leave the mitotic cycle, and remain in that state even after their migration to muscle buds derived from the myotome itself.
Autoradiography was used to demonstrate the presence of alpha-bungarotoxin binding sites in the medial wall cells of thoracic somites from 44th hr incubation chick embryos. It is suggested that these cells are presumptive myoblasts about to migrate to form the myotome.
This paper reports immunofluorescence data concerning fibronectin distribution in chick embryo striated muscle buds, i.e. myotomes and heart bud, in stages following their differentiation. At earliest developmental stages (12-15 HH) no fibronectin could be observed between the still poorly differentiated myoblasts of myotomes and of the splanchnopleure. Fibronectin, however, was observed among differentiated myoblasts of the myocardial ventral portion. In myotomes at later stages (16-18 HH), a few thin strands of fibronectin were observed between the myotomal and dermatomal laminae; this pattern became more marked between stages 17 and 26 HH. It is concluded that during myogenesis, fibronectin is absent at the earliest differentiation stages. A faint fibronectin-containing matrix is detectable at later stages and becomes more evident only in mature muscle tissue. This pattern is consistent with a role of fibronectin in the process of tissue organization.
Peripheral and central prolongations of chick embryo spinal ganglia neuroblasts were studied and compared at an ultrastructural level during development. Important differences in the terminal tracts of the prolongations and their endings were demonstrated. The possibility of environmental influences being responsible for structural differences in the two prolongations is suggested. It was not possible, at any stage of development, to demonstrate significant polarization of any cytoplasmatic structure in the emerging cones.
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