Immunohistochemical localization of GABA in chameleon retina (Chamaleo Chamaleo).

We used a policlonal antiserum against GABA and demonstrated GABA-immunoreactivity (GABA-IR) in several populations of amacrine cells in the inner nuclear layer (INL), and other cells in the inner plexiform layer (IPL) of the central and peripheral retina of the chameleon. Horizontal cells do not contain GABA-IR and the chameleon retina is therefore an exception among non-mammals. GABA-IR was not seen in cell bodies in the position of photoreceptor, bipolar and interplexiform cells suggesting that GABA is not involved in synaptic transmission in the outer plexiform layer of chameleon retina.

DNA synthesis in the embryonic chick lens epithelium is arrested after experimental lens rotation.

Using autoradiographic technique, we have studied DNA synthesis in normal embryonic chick lens epithelium and after experimental lens rotation. Analysis of the autoradiograms clearly demonstrates that when the lens primordium was rotated 180 degrees, so that lens epithelium was placed facing the interior of the optic cup, the lens epithelial cells completely stop DNA synthesis. This fact suggests that some retinal and vitreal factors are responsible for differentiation and replicative capacity of the lens epithelial cells.

Late events in the migrative behaviour of the retinal ganglion cells. A Golgi study in the chick retina.

The final displacement of the prospective ganglion neurons toward the ganglion cell layer (GCL) has been analyzed in chicken embryos during days 8 and 9 of incubation with the help of the Golgi method and computer-assisted image processing. Our findings indicate that some ganglionar soma are still located in the inner nuclear layer (INL) while others pierce the inner plexiform layer (IPL), exhibiting morphological adaptation of their perikaryon. The changing morphology of these delayed retinal ganglion neuroblasts seems to be due to the late translocation of the cell perikaryon to the GCL.

Development of retinal displaced ganglion cells in the chick: neurogenesis and morphogenesis.

The time of birth of displaced ganglion cells (DGCs) was determined by autoradiography. DGCs start to leave the cell cycle early, on embryonic day 3, in the central and peripheral retina, and end on embryonic day 8, also in both areas of the retina. During the period of neurogenesis, unlabeled (born) DGCs do not appear distributed in spatial gradients as do the ganglion, amacrine, and other cell types in the retina (Prada et al.

Effect of ethanol on the morphohistogenesis and differentiation of cerebellar granule cells in the chick embryo.

In this present study we analyse, with the help of the Golgi method, the effect of ethanol on the morphological differentiation of the cerebellar granule cells in the chick embryo. Ethanol seems to affect the process of cell migration from the early stages of differentiation. Some granule cells appear to differentiate in an inverted position.

Effect of ethanol on the cerebellar cortex of the chick embryo.

The effect of ethanol on the cerebellar cortex of chick embryos was studied in semi-thin sections of material prepared for electron microscopy. The embryos were injected with ethanol on the 3rd or 6th day of incubation and observed until days 13, 15, 17 and 21 of development. A decrease was seen in the number of germinal cells generated, together with defects in neuronal migration and the existence of a lower quantity of cells due to a generalised process of cell death.

Transplantation of the chick early eye primordium into a lensectomized optic cup of a host embryo.

Eye primordia of young chick embryos (stage XII) were transplanted into lensectomized optic cups of older embryos (stage XVII) to analyze the influence of the host retina on the degree of morphological differentiation attained by the donor lens. Embryos were sacrificed 24-96 h later. The donor lens primordium showed a differentiation more in correlation with the host eye cup (stage XXIII) after 24-96 h of incubation.

Two modes of cell migration in the ventral horn of the spinal cord in the chick embryo. A Golgi study.

The migration process of the ventral horn in chick embryo spinal cord cells has been studied between 2.5 and 5 days of incubation (HH-17, HH-26), using the Golgi technique. Two different migratory modes are observed.

Morphological differentiation of the Müller cell: Golgi and electron microscopy study in the chick retina.

The sequence of morphological differentiation of Müller cells in the chick retina was investigated in relation to the differentiation of the retinal neurons using the Golgi method. From the beginning of differentiation, the Müller cell develops spurs and lateral processes. Some of these glial processes become transformed into accessory prolongations of the Müller cell.

Regional adaptation of Müller cells in the chick retina. A Golgi and electron microscopical study.

We report the morphological differences of Müller cells in relation to their topography, using the Golgi method. Müller cells in the central retina are long and slender, with numerous inner prolongations. In the peripheral retina, the morphology of the Müller cells adapts to the reduced thickness of the retinal layers.

The extracellular matrix architecture relating to myotendinous pattern formation in the distal part of the developing chick limb: an ultrastructural, histochemical and immunocytochemical analysis.

In the later developmental stages (Hamburger and Hamilton, 25-34) the distal part of the chick leg possesses a distinctive extracellular matrix (ECM) architecture which relates to myotendinous patterning. There are two components: firstly, a system of dorsoventrally oriented fibrils which link the two ectodermal surfaces through the undifferentiated distal mesenchyme and secondly, a 'mesenchyme lamina' originates at the basement membrane distally, but proximally runs through the mesoderm, subjacent and parallel to the basement membrane. The 'mesenchyme lamina' appears to be a precursor of developing tendons and is spatially related to the distal tips of the myogenic blocks.

Displaced ganglion cells in the chick retina.

New morphological and cytological data on the displaced ganglion cells (DGCs) in the chick retina are presented. Analysis of the topographic distribution, cellular number, dendritic field, perikaryon size and ultrastructural characteristics are included. The DGCs were found predominantly in the peripheral retina.

Amacrine cells with a rectilinear dichotomy of dendrites in the chick retina.

With Golgi impregnation, a simple amacrine cell type is described in the chick retina. The most relevant morphological feature of these retinal neurons is a single straight, radial trunk which dichotomizes tangentially in a rectilinear expansion in the 5th stratum of the inner plexiform layer (IPL).

Short axon ganglion cells in the chick retina.

Using Golgi's staining technique, we investigated some ganglion cells whose axons do not project out of the retina area. These axons, after following a short trajectory through the optic nerve fiber layer or through the 5th stratum of the inner plexiform layer (IPL), change their direction and end in the inner stratum of the IPL.

Bipolar cells in the chicken retina.

Using the Golgi staining method with the modification suggested by Colonnier (J. Anat. 98:327, 1964), we have carried out a morphological study of the bipolar cells of the chicken and classified them into various morphological types.

Star-shaped cells of the amacrine cell layer.

Using silver impregnation techniques and light microscopy we have described a new type of interneuron in the adult chicken retina. These cells are located in the innermost level of the INL. Expansions arise from the basal portion of the perikaryon and ascend from there, ending in the inner third of the INL.

The photoreceptors of the chameleon retina (Chamaleo chamaleo). A Golgi study.

Using the Golgi method two types of cones were found in the chameleon retina: single and double cones, whose axons give a different pattern in the central and in the peripheral areas of the retinal. No rods were observed by this method in the retina of this animal.

Two modes of free migration of amacrine cell neuroblasts in the chick retina.

The migration of amacrine neuroblasts toward the prospective amacrine cell layer in the chick embryo retina has been studied, in Golgi-stained sections, between days 5 and 9 of embryogenesis. Two distinct populations of presumptive amacrine neuroblasts have been identified on the basis of their shape and migratory behavior. One population (smooth amacrine neuroblasts) display smooth, monopolar or bipolar contours, moving freely across the retina without major changes in the original postmitotic shape, and give processes only after reaching the primitive inner plexiform layer.

Localized morphological differentiation in the bipolar cells of the chick retina.

On a morphological and ultrastructural level, we studied a thickening which appears on the ascending prolongation of bipolar cells in the chick retina. We first observed this thickening on day 10 of incubation and it remains unchanged throughout the postnatal life of the chick. Its presence seems to be related to the synaptic activity at a dendritic level in certain bipolar cells.

The midget bipolar cells in the chick retina.

This paper reports the existence of midget bipolar cells on the chick retina, as determined by the staining methods of Golgi-Stensaas and Golgi-Colonnier. We date the appearance of these cell types at days 13 (HH-39) and 14 (HH-40) of incubation and describe them morphologically throughout their development until the time of hatching, at which time the cells show an adult structure. As an adjunct to this work we classify the midget bipolar cells into four groups.

Morphological and structural study of Landolt's club in the chick retina.

Light and electron microscopy were used to study Landolt's club of the bipolar cells in the newborn chick retina as well as in early embryonic stages. In the embryo, the bipolar cells were connected to the outer limiting membrane by Landolt's club. Some of the bipolar cells disconnect from this membrane, by complete retraction of Landolt's club, giving rise to bipolar cells without this process.

Photoreceptor nuclei outside of the limiting membrane in the chick retina.

The present work describes the presence of some photoreceptor nuclei in the embryonic and adult chick retina which are situated outside of the external limiting membrane. We also discuss their possible degenerative character.

Displaced horizontal cells in the chick retina.

The retina of the chick contains retinal cells of a morphology very similar to that of the horizontal cells, but the perikarya, axons, and axon terminals lie in the inner plexiform layer. The discovery of this neuronal ectopia appears to support the idea that some horizontal and amacrine cells derive from a common, freely migrating cell.