摘要:

The morphology of nucleus rotundus, a visual thalamic nucleus, was investigated in one species of reptiles, Caiman crocodilus, using Nissl stained material in transverse, sagittal, and horizontal planes. The topographical location of nucleus rotundus and its relationship to surrounding thalamic nuclear groups are described. Nucleus rotundus in Caiman can be subdivided into three areas: (1) an outer shell; (2) an inner core; and (3) a cell poor zone located between the shell and core. Most rotundal core neurons were round, fusiform, triangular, pear-shaped, or elliptical. Core neurons were not distributed evenly throughout the nucleus but, in many instances, were arranged in clusters composed of two to ten neurons. Quantitative measurements of area, perimeter, and eccentricity (greatest width/greatest length), which served as an index of cell roundness, were made on rotundal core neuron profiles in transverse, sagittal, and horizontal planes of section. Qualitative and quantitative observations were not appreciably different regardless of the plane of orientation. Both qualitative and quantitative data suggest that relay cells located in the core of nucleus rotundus are not a homogeneous population of neurons but comprise several subtypes.

ISSN:0006-8977    

DOI:10.1159/000112995

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Juvenile chinook salmon (Oncorhynchus tshawytscha) memorize odors characteristic of their natal stream, then use these imprinted olfactory cues to return to that same stream years later as sexually mature adults. In a preliminary effort to identify neuroanatomical changes in the salmon olfactory system that may underlie these behavioral capabilities, the structure of the olfactory bulb (OB) was studied at three developmental periods across the life history: in early juvenile development (0.1–4 months of age), in late juvenile development (11–16 months), and as spawning adults (48 months). Using antibodies that selectively label primary olfactory afferents (anti-keyhole limpet hemocyanin), combined with a thionin countemain, the telencephalon (TEL), OB, and two of the bulb''s laminar components, the olfactory nerve-glomerular layer (ONL-GL) and inner cell layer (ICL), could be easily identified. Laminar organization and relative volume (i.e. percent of OB comprised by ONL-GL or ICL) were then compared across groups, and absolute volumes of the OB, ONL-GL, and ICL were compared to that of the TEL at each stage. Three age-related processes were observed across the life history. First, a rapid increase in organizational and structural maturity of the OB was found to be confined to early juvenile life. Second, an increase in OB, ONL-GL, and ICL volume, relative to TEL volume, was found to occur across the entire life history. Lastly, the composition of the OB itself changed, in that an increase in the relative volume of the ONL-GL, and a decrease in that of the ICL, were observed across the life history. Taken together, these results indicate that the OB of young salmon matures dramatically while the fish is still in the freshwater phase of its life history. Then, during migration to the ocean and growth to the adult stage, the volume of the OB, relative to that of the telencephalon, and the relative volume of the input layer of the bulb, both undergo a marked, continuous increase. These changes in the structure, and presumably the function, of the olfactory bulb of salmon may be important in the behavioral phenomena of olfactory imprinting as juveniles and homing as adu

ISSN:0006-8977    

DOI:10.1159/000112996

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

We are utilizing the Brazilian short-tailed opossum, Monodelphis domestica, to study the development of the vasopressinergic system. Earlier studies demonstrated that arginine vasopressin-like immunoreactivity was present very early in the Brazilian opossum brain, suggesting a role for vasopressin in the developing central nervous system of mammals. In this study, we have utilized [3H]arginine vasopressin autoradiography to describe the distribution of arginine vasopressin binding sites in adult and developing Brazilian opossum brains. In general, arginine vasopressin binding patterns in adult opossum brains resembled those of other species. However, we found very few labelled areas in neonatal Brazilian opossum brains. At birth, only the ventral tegmental area and the nucleus of the solitary tract were labelled. Binding was not evident in the forebrain until 25 days of postnatal age. The anterior pituitary was heavily labelled from birth onward, but binding in the brain itself remained at low levels until 35 days postnatal. Heavy binding was observed in only a few areas of the brain in adults, including the dorsal part of the lateral septal nucleus, the suprachiasmatic nucleus, the dorsal and median raphe, the nucleus of the solitary tract, and the caudal part of the spinal trigeminal nucleus. Surprisingly, arginine vasopressin binding sites in the Brazilian opossum appeared much later than arginine vasopressin im-munoreactivity and, in many cases, after neurogenesis was complete. These findings suggest that the arginine vasopressin binding sites are not playing a developmental role in opossums, although the peptide is present at an early age.

ISSN:0006-8977    

DOI:10.1159/000112997

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

We have studied the cyto- and myeloarchitectural organisation of the spinal cord of an echidna (Tachyglossus aculeatus) with the aid of Nissl staining, darkfield examination and p-phenylenediamine staining. We have also examined the distribution of unmyelinated afferents by labelling with a peroxidase-conjugated lectin derived from Griffonia simplicifolia (B4 isolectin). The cytoarchitectural features characterising the laminar organisation of the spinal cord in eutherian mammals were broadly applicable to the spinal cord of this monotreme. In addition, we identified a distinct group of large neurons in the ventral part of lamina X, extending into the ventral funiculus, that we have called the median nuclear group. We were unable to identify a central cervical nucleus in this echidna on the basis of cytoarchitectural criteria, although all other spinal cord nuclei found in eutherians could be found in this monotreme. Lectin labelling with the Griffonia simplicifolia isolectin B4 revealed a subpopulation of dorsal root ganglion cells similar to those labelled in Eutheria. In this echidna, labelling of unmyelinated fibres was found in Lissauer''s zone and laminae I and II, as seen in rats (Rattus norvegicus); there were also deeper patches extending into laminae III to V and what appeared to be commissural axons approaching the dorsal grey commissure, which have not been seen in Eutheria. Fibre calibre in the dorsal and ventral roots of this echidna was similar to that reported in Eutheria, suggesting similar proportions of afferent fibre classes and α and γ motoneurons. In the echidna, mean diameter of myelinated dorsal root axons was 4.65 µm at T1 and 5.22 µm at L3, with a clear bimodal distribution in the L3 dorsal root showing distinct groups at 1 to 5 µm and 6 to 12 µm. These made up approximately 45 and 55% of the total myelinated axon population, respectively. Myelinated fibres in the ventral root at L3 showed two major peaks in distribution. These were at 1 to 4 µm (approximately 32% of the total myelinated fibre population) and at 7 to 14 µm (approximately 58% of the total myelinated fibre population). The cross-sectional area of the dorsal columns of this monotreme was comparable to that of a eutherian mammal of similar body weight, and myelinated axon calibre was similar to that seen in the domestic cat. Our findings indicated that spinal cord cytoarchitectural organisation is highly conserved across class Mammalia, although the lectin labelling findings suggested that termination of unmyelinated afferents in echidnas may differ from that found in Eutheria. The dorsal column system appears to be as anatomically well developed in this monotreme as in those eutherian mammals considered to have a pronounced discriminative tactil

ISSN:0006-8977    

DOI:10.1159/000112998

出版商:S. Karger AG    

年代:1997

数据来源: Karger