Organization of diencephalon of the sturgeons. External nuclei of the pretectal area

Single-unit recordings were performed from a retinorecipient pretectal area (corpus geniculatum laterale) in Scyliorhinus canicula. The function and homology of this nucleus has not been clarified so far. During visual stimulation with a random dot pattern, 45 (35%) neurons were found to be direction selective, 10 (8%) were axis selective (best neuronal responses to rotations in both directions around one particular stimulus axis), and 75 (58%) were movement sensitive. Direction-selective responses were found to the following stimulus directions (in retinal coordinates): temporonasal and nasotemporal horizontal movements, up- and downward vertical movements, and oblique movements. All directions of motion were represented equally by our sample of pretectal neurons. Additionally we tested the responses of 58 of the 130 neurons to random dot patterns rotating around the semicircular canal or body axes to investigate whether direction-selective visual information is mapped into vestibular coordinates in pretectal neurons of this chondrichthyan species. Again all rotational directions were represented equally, which argues against a direct transformation from a retinal to a vestibular reference frame. If a complete transformation had occurred, responses to rotational axes corresponding to the axes of the semicircular canals should have been overrepresented. In conclusion, the recorded direction-selective neurons in the Cgl are plausible detectors for retinal slip created by body rotations in all directions.

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A discrete diencephalic pretectal area critical for retention of visual habits in the rat

Experimental Neurology ◽

10.1016/0014-4886(61)90029-2 ◽

1961 ◽

Vol 4 (5) ◽

pp. 436-443 ◽

Cited By ~ 20

Author(s):

Robert Thompson ◽

Irene Rich

Keyword(s):

Pretectal Area

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Zebrafish aussicht mutant embryos exhibit widespread overexpression of ace (fgf8) and coincident defects in CNS development

Development ◽

10.1242/dev.126.10.2129 ◽

1999 ◽

Vol 126 (10) ◽

pp. 2129-2140 ◽

Cited By ~ 3

Author(s):

C.P. Heisenberg ◽

C. Brennan ◽

S.W. Wilson

Keyword(s):

Nervous System ◽

Neural Retina ◽

Cns Development ◽

Dominant Mutation ◽

Ace Gene ◽

Retinal Epithelium ◽

Ace Activity ◽

Pretectal Area ◽

Wnt1 Expression

During the development of the zebrafish nervous system both noi, a zebrafish pax2 homolog, and ace, a zebrafish fgf8 homolog, are required for development of the midbrain and cerebellum. Here we describe a dominant mutation, aussicht (aus), in which the expression of noi and ace is upregulated. In aus mutant embryos, ace is upregulated at many sites in the embryo, while noi expression is only upregulated in regions of the forebrain and midbrain which also express ace. Subsequent to the alterations in noi and ace expression, aus mutants exhibit defects in the differentiation of the forebrain, midbrain and eyes. Within the forebrain, the formation of the anterior and postoptic commissures is delayed and the expression of markers within the pretectal area is reduced. Within the midbrain, En and wnt1 expression is expanded. In heterozygous aus embryos, there is ectopic outgrowth of neural retina in the temporal half of the eyes, whereas in putative homozygous aus embryos, the ventral retina is reduced and the pigmented retinal epithelium is expanded towards the midline. The observation that aus mutant embryos exhibit widespread upregulation of ace raised the possibility that aus might represent an allele of the ace gene itself. However, by crossing carriers for both aus and ace, we were able to generate homozygous ace mutant embryos that also exhibited the aus phenotype. This indicated that aus is not tightly linked to ace and is unlikely to be a mutation directly affecting the ace locus. However, increased Ace activity may underly many aspects of the aus phenotype and we show that the upregulation of noi in the forebrain of aus mutants is partially dependent upon functional Ace activity. Conversely, increased ace expression in the forebrain of aus mutants is not dependent upon functional Noi activity. We conclude that aus represents a mutation involving a locus normally required for the regulation of ace expression during embryogenesis.

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Gastronome 101: How capitalism killed the sturgeons

Environmental Biology of Fishes ◽

10.1007/s10641-004-3152-6 ◽

2005 ◽

Vol 73 (1) ◽

pp. 111-116 ◽

Cited By ~ 1

Author(s):

Paul Vecsei

Keyword(s):

The Sturgeons

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Projections of single retinal ganglion cells to the visual centers: An intracellular staining study in a plethodontid salamander

Visual Neuroscience ◽

10.1017/s0952523899163053 ◽

1999 ◽

Vol 16 (3) ◽

pp. 435-447 ◽

Cited By ~ 11

Author(s):

WOLFGANG WIGGERS

Keyword(s):

Retinal Ganglion Cells ◽

Ganglion Cells ◽

Retinal Ganglion ◽

Fiber Layer ◽

Plethodontid Salamander ◽

Terminal Arbor ◽

Layer 2 ◽

Lateral Extent ◽

Pretectal Area

The projection specificity of retinal ganglion cells and the morphology of their terminals were studied in the plethodontid salamander Plethodon jordani. In an in vitro approach, ganglion cells were stained with biocytin and reconstructed by means of light microscopy. Single retinal ganglion cells often have multiple terminal structures in the thalamus, pretectum, and tectum. The projection pattern in the diencephalic neuropils is related to the depth of the terminal arbor within the tectal fiber layer. Terminal arbors in the tectum differ in location, size, and branching pattern. The following types could be distinguished: The most superficial of the optic terminals in layer 1 are relatively small with a diameter of about 100 μm. With the exception of a few varicosities (beads) in the pretectal neuropils, their stem axons have no further collaterals or terminal arbors in the diencephalic neuropils. Intermediate terminals in layer 2 fan out to form a dense plexus with a medio-lateral extent of 180 μm on average. Some terminals in this layer show obvious antenna-like fibers reaching toward the surface of the tectum. The axons of layer 2 projecting neurons have additional collaterals and terminal arbors in the thalamus and pretectum. The deep layer 3 terminals spread out over a diameter of 400 μm on average and their degree of branching is moderate. The axons of layer 3 projecting ganglion cells have dense additional terminal arbors in the thalamus and pretectum. The deepest retinal terminals in the tectum are found within the predominantly efferent fiber layers. This type consists of an unbranched, but beaded axon which runs rostro-caudally with several bends and loops. The stem axon has an additional very dense terminal arborization in the neuropil of the nucleus Bellonci pars medialis and additional sparse collaterals in the pretectal area.

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Regulation of 17α-Hydroxyprogesterone Production during Induced Oocyte Maturation and Ovulation in Amur Sturgeon (Acipenser schrenckii)

Journal of Marine Science and Engineering ◽

10.3390/jmse10010086 ◽

2022 ◽

Vol 10 (1) ◽

pp. 86

Author(s):

Yuya Hasegawa ◽

Ryohei Surugaya ◽

Shinji Adachi ◽

Shigeho Ijiri

Keyword(s):

Oocyte Maturation ◽

In Vitro Study ◽

Hydroxysteroid Dehydrogenase ◽

Mrna Levels ◽

Pituitary Extract ◽

Hydroxylase Activity ◽

Amur Sturgeon ◽

Lyase Activity ◽

The Sturgeons

In several teleosts, 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) has been identified as a maturation-inducing steroid. DHP is synthesized from 17α-hydroxyprogesterone (17OHP) by 17β-hydroxysteroid dehydrogenase type 12-like (hsd17b12L). Along with 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD), 17α-hydroxylase and C17-20 lyase are associated with 17OHP production. This study aimed to determine the roles of Amur sturgeon hsd3b, P450c17-I (cyp17a1), and P450c17-II (cyp17a2) in 17OHP production and to examine their enzyme activity and mRNA expression pattern during oocyte maturation. In the sturgeons used in this study, hsd3b encoded 3β-HSD, cyp17a1 catalyzed 17α-hydroxylase production with C17-20 lyase activity, and cyp17a2 processed 17α-hydroxylase activity alone. In the ovarian follicles of individuals that underwent induced ovulation, hsd3b mRNA levels increased rapidly, cyp17a1 expression was downregulated, and cyp17a2 expression was upregulated during oocyte maturation. Finally, an in vitro study revealed that salmon pituitary extract (SPE) stimulation rapidly induced hsd3b expression, whereas cyp17a1 expression was downregulated. In vitro, cyp17a2 expression did not rapidly increase with SPE stimulation. This rapid upregulation of hsd3b during oocyte maturation was first observed in teleosts. It was suggested that hsd17b12L expression is upregulated after 17OHP production, which is regulated by hsd3b, cyp17a1, and cyp17a2, resulting in DHP production.

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