摘要:

Acid extracts of the brain of a urodele amphibian, Ambystoma tigrinum, were screened with radioimmunoassays specific for enkephalin-related products and dynorphin-related products. Following Sephadex G-50 column chromatography a peak of enkephalin-sized immunoreactive material was detected near the total volume of the column. The enkephalin-sized immunoreactivity was further analyzed by reversed phase HPLC. This analysis detected peaks of authentic Met-enkephalin and Leu-enkephalin. However, the molar ratio of Met-enkephalin to Leu-enkephalin in the brain of this amphibian was approximately 80:1. These observations would suggest that the Leu-enkephalin detected in the brain of Ambystoma may be derived from a source other than the Proenkephalin precursor. Neither Met-enkephalin-RGL or Met-enkephalin-RF were detected by radioimmunoassay in brain extracts from this urodele. However, following digestion with trypsin and carboxypeptidase B, a novel peak of C-terminally extended Met-enkephalin was detected. Two peaks of Prodynorphin-related products were also detected following gel filtration chromatography. These immunoreactive forms were detected using antisera specific for α-neo-endorphin and dynorphin B(1–13). No immunoreactive forms with antigenic determinants similar to mammalian dynorphin A(1–17) or dynorphin A(1–8) were detected in this species. Reversed phase HPLC analysis indicated that the major form of urodele α-neo-endorphin eluted with the same retention time as synthetic mammalian α-neo-endorphin. Urodele dynorphin B(1–13)-related immunoreactivity eluted as a single peak, however this form did not elute with the same retention time as synthetic mammalian dynorphin B(1–13). The forms of α-neo-endorphin and dynorphin B detected in urodele and anuran amphibians appear to be very similar, however it appears that amphibian dynorphin A has diverged significantly from mammalian dynorphin A. Analysis of enkephalin-related products in the brain of Ambystoma indicates that Met-enkephalin is the major opioid produced by the urodele Proenkephalin gene, and supports the contention that urodele Proenkephalin, like anuran Proenkephalin, lack a Leu-enkephalin sequence.

ISSN:0006-8977    

DOI:10.1159/000114141

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The retina and choriocapillaris of the Florida garfish, Lepisosteus platyrhincus (Ginglymodi), was examined at the light and electron microscopic levels. The inner limiting membrane is covered by an extensive system of vitreal blood vessels emanating from the hyaloid artery, which enters the eye ventrally at the proximal end of the elongated optic nerve head. Two size classes of ganglion cell soma are segregated by optic axon fascicles and Müller cell endfeet, all of which lie at the level of the ganglion cell layer. A third class of 'displaced' ganglion cells lies at the border of the inner plexiform and inner nuclear layers amidst tightly packed amacrine, bipolar and Müller cell soma. Two layers of horizontal cells lie vitread of a synaptic zone consisting of a complex arrangement of horizontal and bipolar dendrites invaginating rod spherules and cone pedicles to form single and multiple (three to six) synaptic ribbon connections, respectively. Immediately vitread of the photoreceptor nuclei lie a population of 'displaced' bipolars. Three types of photoreceptors are characterised: unequal double cones, single cones (large and small) and rods. These show retinomotor movements where the rods elongate in the light and are masked by the pigment epithelium and contract in the dark as the pigment migrates sclerad. Ultrastructurally, 4 types of dark-staining (osmophilic) granules are described: (1) Small glycogen granules (0.033 μm) aggregated at the bases of the photoreceptor nuclei and larger similar granules (0.078 μm and termed paraboloids) vitread to the ellipsoid; (2) tapetal granules (0.32 μm) distributed throughout the dorsal four-fifths of the retinal pigment epithelium (RPE); (3) pigment granules (0.5–2.0 μm) in the RPE, concentrated in ventral retina; (4) granules or melanosomes (0.813 μm) of the choriocapillaris. The second class of granules constitute a tapetum lucidum eliciting a yellow eyeshine when viewed in the dark. Two other tapeta also exist, a guanine tapetum (irregular guanine crystals) and a tapetum fibrosum (stacks of collagen fibrils). Functional correlations are made, and the putative ancestral (primitive) condition of particular visual characters is established for the ray-finned fishes by out-group comparisons.

ISSN:0006-8977    

DOI:10.1159/000114142

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The retina and choriocapillaris of the Florida garfish, Lepisosteus platyrhincus (Ginglymodi), was examined at the light and electron microscopic levels. The inner limiting membrane is covered by an extensive system of vitreal blood vessels emanating from the hyaloid artery, which enters the eye ventrally at the proximal end of the elongated optic nerve head. Two size classes of ganglion cell soma are segregated by optic axon fascicles and Müller cell endfeet, all of which lie at the level of the ganglion cell layer. A third class of 'displaced' ganglion cells lies at the border of the inner plexiform and inner nuclear layers amidst tightly packed amacrine, bipolar and Müller cell soma. Two layers of horizontal cells lie vitread of a synaptic zone consisting of a complex arrangement of horizontal and bipolar dendrites invaginating rod spherules and cone pedicles to form single and multiple (three to six) synaptic ribbon connections, respectively. Immediately vitread of the photoreceptor nuclei lie a population of 'displaced' bipolars. Three types of photoreceptors are characterised: unequal double cones, single cones (large and small) and rods. These show retinomotor movements where the rods elongate in the light and are masked by the pigment epithelium and contract in the dark as the pigment migrates sclerad. Ultrastructurally, 4 types of dark-staining (osmophilic) granules are described: (1) Small glycogen granules (0.033 μm) aggregated at the bases of the photoreceptor nuclei and larger similar granules (0.078 μm and termed paraboloids) vitread to the ellipsoid; (2) tapetal granules (0.32 μm) distributed throughout the dorsal four-fifths of the retinal pigment epithelium (RPE); (3) pigment granules (0.5–2.0 μm) in the RPE, concentrated in ventral retina; (4) granules or melanosomes (0.813 μm) of the choriocapillaris. The second class of granules constitute a tapetum lucidum eliciting a yellow eyeshine when viewed in the dark. Two other tapeta also exist, a guanine tapetum (irregular guanine crystals) and a tapetum fibrosum (stacks of collagen fibrils). Functional correlations are made, and the putative ancestral (primitive) condition of particular visual characters is established for the ray-finned fishes by out-group comparisons.

ISSN:0006-8977    

DOI:10.1159/000316116

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The cornea of the Florida gar, Lepisosteus platyrhincus (Ginglymodi) was examined at the scanning and transmission electron microscopic levels. In addition, the schematic eye of the garfish was revealed by frozen sectioning of the whole orbit in the horizontal and transverse planes. The lens is spherical, obeys Matthiessen's ratio, and is supported by a dorsal suspensory ligament and a ventral retractor lentis muscle. The cornea, devoid of a spectacle, is comprised anteriorly of an epithelium (eight to ten cells thick) and covered by a layer of flattened cells up to 26 μm in diameter. On the scanning electron microscope, these cells appear to be covered in microplicae and microvilli. Beneath the epithelium lies a granular basement membrane abutting a true Bowman's layer, composed of a random arrangement of collagen fibrils with no keratocytes. The corneal stroma constitutes 54% of the total thickness and contains 55–65 collagen fibril lamellae, oriented perpendicular to neighbouring lamellae. Scattered keratocytes, containing large amounts of mitochondria, lipid droplets and glycogen granules lie in between the perpendicularly oriented lamellae. Posterior to the stroma is a thin and partially broken basement membrane (no true Descemet's membrane exists), adjacent to a monolayered endothelium covered in microvilli. In the periphery, an autochthonous layer is found between the stroma and the endothelium. Stromal pigment granules, enveloped in large nucleated cells, act as a non-occlusible yellow filter in the dorsal cornea. Functional correlations are made and the presence and/or thickness of corneal structures discussed in relation to the evolution of the vertebrate cornea.

ISSN:0006-8977    

DOI:10.1159/000114143

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The single-locus X-chromosome theory was proposed to explain the unique intra- and inter-species variation in the colour vision found in New World monkeys. The colour vision of only five species of these monkeys has been studied in any detail, and although this data does show some minor deviations from the theory, it is generally consistent with the theory. It has been suggested that the colour vision of New World monkeys may represent an intermediate stage in between the dichromatic colour vision of non-primate mammals and the uniform trichromacy of Old World primates. Alternatively, the colour vision system of New World monkeys may represent a method of obtaining the maximum variation in the colour vision of closely related family groups.

ISSN:0006-8977    

DOI:10.1159/000114144

出版商:S. Karger AG    

年代:1993

数据来源: Karger

摘要:

The topographic organization of corticonuclear projections from the paraflocculus was studied in rats by an autoradiographic orthograde tracing method. The corticonuclear fibers from the paraflocculus terminated primarily in the caudo-ventral part of the lateral cerebellar nucleus and in the lateral part of the posterior interpositus nucleus. The rostrolateral part of the ventral paraflocculus projected only to the lateral nucleus, and the caudomedial part projected only to the posterior interpositus nucleus. Although differential projections from the dorsal and ventral paraflocculi were not clearly observed, the dorsal paraflocculus appeared to project to slightly more dorsal parts of the lateral and posterior interpositus nuclei than did the ventral paraflocculus. The lateral, medial, rostral, and caudal parts of each sublobule tended to project to the ventral, dorsal, rostral, and caudal regions within the caudoventral part of the lateral nucleus, respectively, despite massive overlap in the individual terminal fields. The corticonuclear projection from the dorsal and ventral paraflocculi to the posterior interpositus nucleus were organized in different directions; those from the dorsal paraflocculus were organized rostrocaudally, while those from the ventral paraflocculus were organized mediolaterally. These results suggest that in rats the corticonuclear projections from the paraflocculus are topographically organized in the mediolateral and rostrocaudal directions as well as in the dorsoventral direction.

ISSN:0006-8977    

DOI:10.1159/000114145

出版商:S. Karger AG    

年代:1993

数据来源: Karger