Further data on the development of SRIF-like immunoreactive nerve cell populations in the chick embryo brain stem. I. Medulla and pons.

Further immunocytochemical analysis of the neuroblasts with SRIF-like immunoreactivity (ir) was carried out on the chick embryo medulla and pons. 5 or 100 microns rombencephalon sections were obtained from 60 White Leghorn chick embryos at stages (E = Embryonic days) ranging from E4 1/2 to E18 and incubated with rabbit polyclonal antibodies against synthetic cyclic Somatostatin-14, according to PAP-DAB technique. In the medulla and pons the ir appeared as from E12. From E12 to E13 1/2-E14 the ir distribution gradually changed. From E14 to E18 numbers and spatial arrangement of the positive neuroblast groups did not show substantial changes; in these respects the ir distributional pattern proved to be markedly different from the one observed by the Authors in adult animals. Moreover, from E13 to E15 the positive neuroblast density appeared to be higher than that of positive neurons in adults. These results are consistent with a possible SRIF local regulative role.

Further data on the development of SRIF-like immunoreactive nerve cell populations in the chick embryo brain stem. II. Midbrain tegmentum.

Further immunocytochemical analysis of the neuroblasts with SRIF-like immunoreactivity (ir) was carried out on the chick embryo midbrain tegmentum. 5 or 100 microns mesencephalon sections were obtained from 60 White Leghorn chick embryos at stages (E = Embryonic days) ranging from E4 1/2 to E18 and incubated with rabbit polyclonal antibodies against synthetic cyclic Somatostatin-14, according to PAP-DAB technique. In the midbrain tegmentum the ir appeared as from E12. From E12 to E13 1/2-E14 the ir distribution gradually changed. From E14 to E18 numbers and spatial arrangement of the positive neuroblast groups did not show substantial changes; in these respects the ir distributional pattern proved to be similar to the one observed by the Authors in adult animals. From E17 to E18 a decrease in the positive neuroblast density appeared to occur, particularly in a ventrally placed group. These results are consistent with a possible local regulative role of the SRIF.

Medullary and mesencephalic neuronal groups reacting to antibodies against VIP, somatostatin and bombesin in adult Gallus gallus domesticus.

The caudo-cranially intermediate one-third of medullary dorsal region, the periaqueductal grey and the rostro-ventral portion of the midbrain tegmentum of adult chickens were studied in detail by means of the PAP-DAB procedure, to define further the main morphological features of the neuronal populations that in previous studies had shown VIP (Vasoactive Intestinal Polypeptide),-Somatostatin (SRIF)-, and Bombesin-like immunoreactivities. In the medulla, VIP-like immunoreactivity was detected within neuronal bodies and processes and extended down to the cervical spinal cord. SRIF-like immunoreactivity was seen only within nerve cell processes, at least a part of which could be sensitive fibre terminals. Bombesin-like immunoreactivity was observed only within neuronal processes. In the periaqueductal grey, all 3 immunoreactivities were detected within perikarya and neuronal processes, with a higher density cranially. In the rostro-ventral portion of the midbrain tegmentum, VIP-like and Bombesin-like immunoreactivities were detected (the latter being located somewhat more cranially) both in neuronal bodies and in processes. SRIF-like immunoreactivity was found in this region only in long neuronal processes.

[Effects of monolateral ablations of the presumptive limb buds on the early developmental phases of the central and peripheral nervous system]. / Effetti della ablazione monolaterale dei territóri presuntivi degli arti sulle fasi precoci dello sviluppo del SNC e del SNP.

The size of the spinal ganglia, as well as of the posterior and lateral funiculi of the spinal cord, at the cervical, thoracic, lumbar and sacral levels, was carefully evaluated, on both sides, by measuring their surfaces on each transverse histological section from chick embryos submitted, at the second-second and a half day, to ablations of the right presumptive limb buds, and fixed at the 9th - 13th day. On the extirpation side, the ganglion and posterior funiculus size always resulted significantly smaller, the average degree of reduction being nearly the same at the levels of the brachial and the lumbo-sacral plexuses (-50-60% for the ganglia, -25-30% for the posterior funiculus). However, within the same group of metameres (e.g., the corresponding to the brachial plexus), the analysis carried out metamere by metamere showed that the reduction degree was not homogeneous, owing probably to a) the extent of the different peripheral fields supplied by the various metameres, b) the degree of the regulative processes occurred after the ablations, and/or c) the extent of the extirpated regions. The size reduction of the posterior funiculus, observed also in the neuromeres immediately cranial to those related to the plexuses, could depend upon its peculiar composition, relatively short intersegmental tracts representing the majority of its fibers. No significant reduction was remarked for the lateral funiculus size.

[Vessel work development phases in the neural part of the pons in chick embryos]. / Osservazioni sullo sviluppo delle reti vascolari e della componente nervosa nel ponte dell'embrione di pollo.

By means of intravascular India ink injections we have analyzed the early developmental phases of the vessel network in the cranial part of the chick embryo pons. At four and one half days of incubation the first radial endoneural vessels have already entered the ventral portion of the pons and formed with their branches a perigerminative network. Both the external and deep network progressively extend during the subsequent days, and at the 7th day the previously segregated cell groups begin to be encircled by tiny branches from the radial vessels. On the 8th day vessels appear also within the cellular groups and differences in vascular density between the various groups become detectable, apparently depending on their different cell density and differentiation degree. From this stage until the 12th day the vessel denseness undergoes a gradual, general increase, although differences in the vascularization degree between various groups are still appreciable.

Vascular patterns in the chick embryo spinal cord in normal and experimentally modified development.

The development of the vascular patterns of the lumbosacral segments of the chick embryo spinal cord has been analyzed in normal as well as in experimental conditions, after complete removal of the hind limb primordium. The results indicate that in both conditions the development of the vascular network follows the time-space sequence of the cytoarchitectural modifications of the cord, supporting the view that the vascularization does not exert a morphogenetic influence.