ABSTRACT
Detection of moving objects is an essential skill for animals to hunt prey, recognize conspecifics and avoid predators. The zebrafish, as a vertebrate model, primarily uses its elaborate visual system to distinguish moving objects against background scenes. The optic tectum (OT) receives and integrates inputs from various types of retinal ganglion cells (RGCs), including direction-selective (DS) RGCs and size-selective RGCs, and is required for both prey capture and predator avoidance. However, it remains largely unknown how motion information is processed within the OT. Here we performed in vivo whole-cell recording and calcium imaging to investigate the role of superficial interneurons (SINs), a specific type of optic tectal neurons, in motion detection of larval zebrafish. SINs mainly receive excitatory synaptic inputs, exhibit transient ON- or OFF-type of responses evoked by light flashes, and possess a large receptive field (RF). One fifth of SINs are DS and classified into two subsets with separate preferred directions. Furthermore, SINs show size-dependent responses to moving dots. They are efficiently activated by moving objects but not static ones, capable of showing sustained responses to moving objects and having less visual adaptation than periventricular neurons (PVNs), the principal tectal cells. Behaviorally, ablation of SINs impairs prey capture, which requires local motion detection, but not global looming-evoked escape. Finally, starvation enhances the gain of SINs' motion responses while maintaining their size tuning and DS. These results indicate that SINs serve as a motion detector for sensing and localizing sized moving objects in the visual field.
ABSTRACT
Objective To investigate the changes of neurotransmitters and the relationship between neurotransmitters and nerve regeneration during the optic regeneration in zebrafish. Methods Using the classical retinotectal regeneration model and electromicroscopy, we observed the ultrastructural changes of synapses of the superficial fiber and gray stratum(SFGS) in the tectum. Results The morphological changes of synapses can be divided into 4 stages: 1. Synaptic degeneration at the early stage after lesion. 2. Regenerating optic nerve fibers entered the SFGS laminar of the tectum, the densities of large granule vesicles (LGV) and small granule vesicles(SGV) were increased. 3. Lots of synapses were formed, the densities of small round clear vesicles (SCV) and small flat clear vesicles(FCV)were increased dramatically .4. Morphological recovery and refinement of the retinotopic innervation. Conclusion Neurotransmitters might play an important role during the regeneration of optic nerve, and they exhibited their effects in a chronological way.
ABSTRACT
A case of congenital tectal lipoma found incidentally at an autopsy is reported. This female fetus was a product of pregnancy termination at 24 weeks of gestational age after sonographic detection of hydrocephalus. Autopsy revealed a small mass in the periaqueductal portion. The mass was composed of adipose tissue, cartilage, and mature bony tissue with hematopoiesis. The resultant diagnosis was tectal lipoma with osteocartilagenous element. It is uncertain whether the lesion represents a teratoma or hamartoma or mesenchymal metaplasia. The osteocartilagenous component suggests the latter.
Subject(s)
Adult , Female , Humans , Infant, Newborn , Pregnancy , Autopsy , Bone and Bones/pathology , Brain Neoplasms/congenital , Cartilage/pathology , Tectum Mesencephali/pathology , Lipoma/congenitalABSTRACT
By using dorsal root patientials (DRP) and ventral root patientials (VRP) as in dexes, the effects of descending volleys originating from the optic tectum on spinal activity were observed in bullfrogs. The experimental results obtained were as follows; 1.DRP was evoked by stimulation of the optic rectum. 2. VRP evoked by stimulation of the siatic nerve comsisted of two components. The early conponent was evoked chiefly by type Ⅰ and Ⅱ afferent fibers and also contributed by type Ⅲ fibers; the late one was evoked by type Ⅳ afferent fibers. 3. VRP evoked by stimulation of the siatic nerve was inhibited by stimulation of the optic tectum. The duration of inhibition of the early component was related to that of DRP. Thus, the results indicate that the optic tectum takes part in the centrifugal control of somatosensory afferent activity, affects the spinal reflex, and involves in the mechanism of analgesia by way of presynaptic inhibition.
ABSTRACT
Objective To study the morphological characteristics of tectal cells in stratum griseum centrale(SGC) which project to nucleus rotundus(Rt) in chick. Methods Tectal cells projecting to the Rt were retrogradely labeled by using the injection or implantation of a small amount of carbocyanine fluorescent tracer(DiI) into Rt postmortemly in chicks.Results Labeled SGC cells were classified into four types according to the location of the soma and dendritic endings in the tectal layers.Type 1 cells of the SGC,whose somata were located in superficial part of the SGC,gave off dendritic endings to layer F.Type 2 cells in the SGC,whose somata were also located in superficial part of the SGC,gave off dendritic endings to layer D.Type 3 cells,whose somata were located in deep part of the SGC,gave off primary dendrites obliquely in layer H-J of SGFS.Type 4 SGC cells,whose somata were located in the deep part of the SGC,gave off dendrites horizontally and their dendrites were located within the SGC.The labeled dendrites of type I and 2 cells of the SGC formed bush-like or bifurcated endings extending horizontally in layer F and bottle brush endings vertically in layer D,respectively.The dendrites of type 3 and type 4 cells mainly formed free endings in their extending deep tectal layers.Conclusion The dendrites of superficial SGC cells(type 1 and type 2 cells) extend to retinorecipient tectal layers(layer F and layer D,respectively),having the shape of bush-like or bifurcated endings extending horizontally in layer F and bottle brush endings vertically in layer D,respectively corresponding to the shapes of terminals of optic nerves in these layers.The dendrites of deep SGC cells(type 3 and type 4 cells) do not extend to the retinorecipient tectal layers,mainly forming free endings in the tectal layers deeper than layer H.
ABSTRACT
Objective To investigate the changes of neurotransmitters and the relationship between neurotransmitters and nerve regeneration during the optic regeneration in zebrafish.Methods Using the classical retinotectal regeneration model and electromicroscopy,we observed the ultrastructural changes of synapses of the superficial fiber and gray stratum(SFGS)in the tectum. Results The morphological changes of synapses can be divided into 4 stages:1.Synaptic degeneration at the early stage after lesion.2. Regenerating optic nerve fibers entered the SFGS laminar of the tectum,the densities of large granule vesicles(LGV)and small granule vesicles(SGV)were increased.3. Lots of synapses were formed,the densities of small round clear vesicles(SCV)and small flat clear vesicles(FCV)were increased dramatically.4. Morphological recovery and refinement of the retinotopic innervation.Conclusion Neurotransmitters might play an important role during the regeneration of optic nerve,and they exhibited their effects in a chronological way.
ABSTRACT
We have investigated the growth and interactions between dissociated cells from different visual structures obtained from neonatal albino rats, namely, retina (R), superficial gray of the tectum (T), the lateral posterior portion of the dieneephalon (G), and occipital cortex (C). Dissociated cells obtained were either cultured separately or mixed with another cell type in 24-well plates coated with laminin. After 3 days of culture surviving cells were quantified by the MTT colorimetric microassay.The optical densities obtained from mixed cultures with cells from any two of the four types (G, R, T, C) of brain tissues were 1.3 to 3 times higher than the sum of their corresponding individual cultures except for those of G+C and T+G. Among them R+T and R+G were the most active cultures, followed by R+C and T+C. Further, condition medium from tectal cells (Tc) increased the activities of R and G for 3 and 2 times, respectively, and condition medium from retinal cells (Re) increased the activities of G and C for 1.3 and 2 times, respectively. Therefore it is suggested that neuronotrophic factors may be present in Tc and Rc.
ABSTRACT
The present paper studies the neuronal pathways connecting the optic tectum(?)the nucleus profundus mesencephali(NPM)and the nucleus isthmi,and the morph-ology of their originating cells in Gekko gekko and Shinisaurus crocodilurus byusing horseradish peroxidase(HRP)tracing method.The results indicate that 1.There exist reciprocal topographic projections between the tectum and the nucleus.isthmi pars magnocellularis(Imc);2.The ipsilateral tecto-Imc projection originatesfrom cells mainly located in layer 7,which have piriform somata with radical den- drites;the ipsilateral Imc-tectal projection originates from piriform or polygonalneurons with a small dendritic field;3.Cells labeled in NPM following tectal injections are fusiform in shape,paler in color,whereas NPM cells labeled followingisthmic injections are numerous,whose thick dendrites often go up to the tectum(?)4.NPM injections label both tectal and isthmic cells.The former are mainly loca-ted within layer 7,while the latter are in Imc and Ipc.
ABSTRACT
Objective To study the histological structures of retinotectal system in zebrafish. Methods The structures of tectum and retina were examined histologically and the total number and diameter of the optic nerve fibers were studied quantitatively. Results The retina includes 10 layers, and the tectum is differentiated into 6 layers. The mean thickness of the tectum is about 219^7?8^3?m. The optic nerve of zebrafish has approximately 78?960 myelinated fibers. The mean of the outer diameter (D) of the myelinated fibers was 0^50?0^18?m, while the mean of the inner diameter (d) is 0^35?0^14?m. Virtually all axons within optic nerves are myelinated.Conclusion\ The results not only accord with the typical pattern of retina and tectum in vertebrates, but also reflect the characteristic of diurnal activity and good vision in zebrafish.\;[
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This paper, using acetylcholinesterase (AChE) histochemistry, brain-lesion and di-isopropylfluorophosphate (DFP) pretreatment techniques, studies AChE distribution in the tectum-nucleus isthmi systems in frogs and pigeons. In these two species of animals, the tectal laminae densely stained for AChE are roughly coincided with the retinotectal projections. Staining pattern in the frog nucleus isthmi consists of 3 areas with different staining intensities. The dorsolateral area being most densely stained. In pigeons, the nucleus isthmi pars parvocellularis (Ipc) and pars magnocellularis (Imc) are densely and evenly stained. Following local lesion of tectum, stainings in the frog nucleus isthmi and pigeon Ipc are topographically reduced or disappeared. DFP-treatment shows that tectal cells, with the exception of cells in layer III containing rich AChE, have moderate or low concentrations of AChE. The isthmic cells are rich in AChE. In the tectum-lesioned pigeons, AChE-stained isthmic cells in the topographical area are reduced in number and paler in color. These results suggest that in amphibians and birds both the tectoisthmic projection and the isthmotectal projection could be cholinergic pathways in nature.
ABSTRACT
Objective To study the morphological types of the retinal ganglion cells (RGCs) projecting to tectum in the chick. Methods The tectal projecting RGCs in the chick were identified by retrograde axonal transport of Fast blue and their dendrites were labeled by intracellular injection of Lucifer Yellow.The retinotectal projecting ganglion cells were classified according to somal areas,dendritic field sizes and dendritic branching pattern. Results Retinotectal projecting ganglion cells were divided into 3 groups and 5 subgroups,Group Ic/Is,Group IIc/IIs,Group IVc.Group I cells had small somal area and small dendritic field.They contained 2 subgroups of Is(simple)and Ic(complex).Group II cells had medium sized soma and dendritic field,and also included 2 subgroups of IIs and IIc.Group IV cells had large soma and dendritic field,and only contained a subgroup IVc.The proportion of each subgroup was 27.7%(Ic),33.6%(Is),2.5%(IIc),24.4%(IIs),and 11.8%(IVc),respectively. Conclusion The types of retinotectal projecting ganglion cell were prominently composed of small to medium sized neurons(88.2%)and some large neurons(11.8%).Ofthese,subgroup Ic cells which were very similar to ? cells were found in the chick and subgroup Is and IIs were not reported in the mammalin retina.The cells in group Ⅲ,which were found in the chick central retina,did not project to the tectum. [