Retino-tectal projections from half-ventral and half-dorsal eye rudiments in Xenopus

Development ◽  
1978 ◽  
Vol 46 (1) ◽  
pp. 89-97
Author(s):  
Joan D. Feldman
Keyword(s):  
Mirror Image ◽  
Retinotectal Projection ◽  
Larval Stages

When the ventral half of a developing eye in Xenopus larvae was removed at stage 32, the remaining fragment rounded up and developed into an eye which looked macroscopically normal by mid-larval stages. Eyes from half-dorsal rudiments were usually small, had more than one ventral fissure, and showed abnormal pupils. The contralateral retinotectal projection was always found to be normally ordered when mapped in later tadpole stages, or, just after metamorphosis. No mirror-image duplicated maps were seen, as was found previously in eyes deriving from half-nasal and half-temporal rudiments. It is concluded that the ‘rule of distal transformation’ does not apply to eyes which are generated from embryonic rudiments.

A study of the retinotectal projection during regeneration of the optic nerve in the frog

1963 ◽  
Vol 157 (968) ◽  
pp. 420-448 ◽  
Keyword(s):  
Optic Nerve ◽  
Rana Temporaria ◽  
Complete Recovery ◽  
Mirror Image ◽  
Nerve Section ◽  
Retinotectal Projection ◽  
Negative Results ◽  
Partial Organization ◽  
Ipsilateral Projection ◽  
Normal Projection

The retinotectal projection was mapped electrophysiologically in 67 experiments on Rana temporaria at various intervals (from 23 to 247 days) after section of the optic nerve. In 18 animals regeneration had not occurred at the time of recording; in the others the pro­jections could be classified in the following way, according to the degree of normality of the pattern: Pattern 1: In 14 frogs there was disorganized anomalous regeneration from small regions of the retina. Tectal responses could not be evoked from the normal stimulus positions but could be evoked only from one or two localized regions of visual field. In 8 of these frogs there was one circumscribed region in the nasal half of the field and another in the temporal half from which responses could be obtained; in 4 animals there was only one region, in the nasal field, and in 2 animals there was one region, in the temporal field, from which tectal responses could be evoked. The earliest responses recorded after nerve section were of pattern 1. Pattern 2: In 4 frogs there was an abnormal projection showing partial organization in only one axis of the retina (nasotemporal, circumferential) and in only one axis of the tectum (mediolateral). This partial organization was only found at the rostral end of the tectum. Pattern 3: In 12 frogs there was recovery of the normal retinotectal projection. Pattern 4: In 15 frogs there was partial or complete recovery of the normal projection together with an anomalous but retinotopically organized projection to the wrong half to the brain. This latter projection was organized as a mirror image of the normal ipsilateral projection. One frog combined the elements of patterns 1 and 4 and the remaining 3 animals did not conform to any of the above patterns. Most of the negative results were obtained in the early days after nerve section and all recordings made later than 77 days after section gave responses. Patterns 3 and 4 were obtained more frequently the longer the interval between nerve section and recording.

scholarly journals Establishment of rostrocaudal polarity in tectal primordium: engrailed expression and subsequent tectal polarity

Development ◽  
1991 ◽  
Vol 113 (4) ◽  
pp. 1133-1144 ◽  
Author(s):  
N. Itasaki ◽  
H. Ichijo ◽  
C. Hama ◽  
T. Matsuno ◽  
H. Nakamura
Keyword(s):  
Staining Pattern ◽  
Mirror Image ◽  
Original Position ◽  
Positive Staining ◽  
Caudal Part ◽  
Retinotectal Projection ◽  
Projection Pattern ◽  
Rostrocaudal Axis ◽  
Positional Value ◽  
Tectal Polarity

In the E4 (embryonic day 4) chick tectal primordium, engrailed expression is strong at the caudal end and gradually weakens toward the rostral end. We used quail-chick chimeric tecta to investigate how the caudorostral gradient of engrailed expression is established and whether it is correlated with the subsequent rostrocaudal polarity of tectal development. To examine the positional value of the tectal primordium, we produced ectopic tecta in the diencephalon by transplanting a part of the mesencephalic alar plate heterotopically. In the ectopic tectum, the gradient of the engrailed expression reversed and the strength of the expression was dependent on the distance from the mes-diencephalon junction; the nearer the ectopic tectum was to the junction, the weaker the expression was. Consequently, the pattern of the engrailed expression in the host and ectopic tecta was nearly a mirror image, suggesting the existence of a repressive influence around the mes-diencephalon junction on the engrailed expression. We examined cytoarchitectonic development in the ectopic tecta, which normally proceeds in a gradient along the rostrocaudal axis; the rostral shows more advanced lamination than the caudal. In contrast, the caudal part of the ectopic tecta (near to the mes-diencephalon junction) showed more advanced lamination than the rostral. In both the host and ectopic tecta, advanced lamination was observed where the engrailed expression was repressed, and vice versa. Next we studied the correlation between engrailed expression and retinotectal projection from a view of plasticity and rigidity of rostrocaudal polarity in the tectum. We produced ectopic tecta by anisochronal transplantations between E3 host and E2 donor, and showed that there is little repressive influence at E3 around the mes-diencephalon junction. We then made chimeric double-rostral tectum (caudal half of it was replaced by rostral half of the donor tectum) or double-caudal tectum at E3. The transplants kept their original staining pattern in hosts. Consequently, the chimeric tecta showed wholly negative or positive staining of engrailed protein on the grafted side. In such tecta retinotectal projection pattern was disturbed as if the transplants retained their original position-specific characters. We propose from these heterotopic and anisochronal experiments that the engrailed expression can be a marker for subsequent rostrocaudal polarity in the tectum, both as regards cytoarchitectonic development and retinotectal projection.

A scanning electron microscopic study of the veliger larvae of the scallop argopecten purpuratus

1988 ◽  
Vol 46 ◽  
pp. 284-285
Author(s):  
G.C. Bellolio ◽  
K.S. Lohrmann ◽  
E.M. Dupré
Keyword(s):  
Morphological Description ◽  
Electron Microscopic ◽  
Larval Stages ◽  
Scanning Electron Microscopic Study ◽  
The Pacific ◽  
Argopecten Purpuratus ◽  
Veliger Larvae ◽  
20 Nm ◽  
Ethanol Series ◽  
Scanning Electron

Argopecten purpuratus is a scallop distributed in the Pacific coast of Chile and Peru. Although this species is mass cultured in both countries there is no morphological description available of the development of this bivalve except for few characterizations of some larval stages described for culture purposes. In this work veliger larvae (app. 140 pm length) were examined by the scanning electron microscope (SEM) in order to study some aspects of the organogenesis of this species.Veliger larvae were obtained from hatchery cultures, relaxed with a solution of MgCl2 and killed by slow addition of 21 glutaraldehyde (GA) in seawater (SW). They were fixed in 2% GA in calcium free artificial SW (pH 8.3), rinsed 3 times in calcium free SW, and dehydrated in a graded ethanol series. The larvae were critical point dried and mounted on double scotch tape (DST). To permit internal view, some valves were removed by slightly pressing and lifting the tip of a cactus spine wrapped with DST, The samples were coated with 20 nm gold and examined with a JEOL JSM T-300 operated at 15 KV.

Mirror-image stimulation.

1968 ◽  
Vol 70 (6, Pt.1) ◽  
pp. 782-793 ◽  
Author(s):  
Gordon G. Gallup
Keyword(s):  
Mirror Image

How are object shape axes defined? Evidence from mirror-image confusions.

2019 ◽  
Vol 45 (1) ◽  
pp. 111-124 ◽  
Author(s):  
Thitaporn Chaisilprungraung ◽  
Joseph German ◽  
Michael McCloskey
Keyword(s):  
Mirror Image ◽  
Object Shape

Larval and juvenile development of the Iceland cockle Ciliatocardium ciliatum (Fabricius, 1780) (Bivalvia: Cardiidae)

2020 ◽  
Vol 324 (2) ◽  
pp. 242-251
Author(s):  
L.P. Flyachinskaya ◽  
P.A. Lezin
Keyword(s):  
Lateral Position ◽  
Larval Shell ◽  
Subtidal Zone ◽  
Larval Stages ◽  
Posterior Shoulder ◽  
Blade Shape ◽  
The Right ◽  
Lateral Structures ◽  
Juvenile Development ◽  
Concentric Structure

The paper considers the development of Ciliatocardium ciliatum from the stage of straight hinge to juvenile. In the White Sea the spawning of C. ciliatum begins at the end of June, larvae at different stages of development occur in plankton until the end of September. The earliest of the larvae found had shell lengths of 123–130 µm. The paper first examined the anatomy and structure of the larval shell of C. ciliatum. During the development, the main stages of organogenesis were described and special attention was paid to the formation of the digestive and muscular systems. The digestive system begins to function when the larva reaches a size of 170–180 µm. The digestive gland has a two-blade shape and is shifted to the right side. The foot is formed at a size of 230 µm, the gill rudiments appear when the larva reaches 270 µm. The development of the larval shell and larval hinge of the mollusc is considered in detail. The development of the larval shell of C. ciliatum is similar to the development of other family members. Throughout all the larval stages, the shell has a rounded shape with a low umbos, and the prodissoconch II has a clearly visible concentric structure. The C. ciliatum larval hinge is characterized by weak differentiation and the absence of pronounced cardinal teeth typical for other Cardiidae. However, the lateral structures of the castle – ridges and flanges – are well developed. The ligament begins to form at a size of 240–250 µm and occupies a lateral position. The settlement of the cockle takes place in September in the subtidal zone. After the metamorphosis, a large radial sculpture is formed on the dissoconch and a number of small spikes are formed at the rib of the posterior shoulder.

Active control of the scattered radiation with a reflecting surface

2019 ◽  
Vol 67 (3) ◽  
pp. 190-196
Author(s):  
Ning Han
Keyword(s):  
Control System ◽  
Active Control ◽  
Scattered Radiation ◽  
Sound Pressure ◽  
Sound Field ◽  
Control Area ◽  
Mirror Image ◽  
Three Dimension ◽  
Control Effect ◽  
Reflecting Surface

Based on a prediction method of the scattered sound pressure, an active control system was proposed in previous work for the three-dimension scattered radiation, where all the relevant simulations and experiments were implemented in three-dimensional free sound field. However, for practical applications, such as the anti-eavesdropping system or the stealth system for submarines, the sound field conditions are usually complex, and the most common case is the one with reflecting surface. It is questionable whether the previous control system is still effective in non-free sound field, or what improvements should be operated to ensure the control effect. In this article, based on the mirror image principle, two methods of calculating the control source strengths are proposed for the scattered radiation control, and numerical simulations with one-channel and multi-channel system are implemented to detect the corresponding control effect. It is seen that the local active control for the scattered radiation is still effective, and the reduction of the sound pressure level as well as the control area is extended with the increasement of the error sensors and control sources.

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