Morphological changes induced by colchicine in the chick optic cup in early stages of development. A stereological study.

In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described.

Stereological study of the synaptic profiles belonging to interneurons in the dorsal lateral geniculate nucleus of the rabbit.

This study is concerned with some characteristics of the interneurons belonging to the dLGN (dorsal Lateral Geniculate Nucleus) of the rabbit. The work deals with the distribution of such cells in the alpha E sector of the nucleus and their F1 and F2 presynaptic contacts. The F1 and the F2 profiles are present in all three of the alpha E zones studied. The F1 profiles are significantly more numerous in the upper zone (57 +/- 2 profiles per 10(4) microns2 of section) and the middle zone (59 +/- 3 profiles per 10(4) microns2 of section) than in the lower one (41 +/- 2 profiles per 10(4) microns2 of section). The F2 profiles are more abundant in the alpha E sector than the F1 ones are, particularly in the lower zone, where F2 profiles (104 +/- 4 profiles per 10(4) microns2 of section) are not only significantly more numerous than F1 profiles but also more abundant than the F2 profiles in the middle zone (84 +/- 3 profiles per 10(4) microns2 of section) and upper zone (88 +/- 2 profiles per 10(4) microns2 of section). These results and their comments reveal diverse density of the element distribution from the dorsal to the ventral part of the alpha E sector as well as the possible relationship or independence from the extranuclear afferent inputs.

Cytoarchitecture of the dorsal lateral geniculate nucleus in the rabbit.

The cytoarchitecture and morphometry of the neurons in the alpha E sector of the dorsal lateral geniculate nucleus of the rabbit have been studied. The preparation techniques used were those of Golgi-Adams and Klüver-Barrera. Our method was to subdivide the alpha E sector into three zones (superior, medial and inferior) and then to cut each zone along the horizontal, transverse and saggital planes in order to obtain precise measurements and descriptions of the neurons whatever their orientation. Differences exist in both the size and distribution of neurons in the inferior zone of the alpha E sector compared to the other two.

Neuron types and organisation of the rabbit dorsal lateral geniculate nucleus.

The Golgi technique was employed in order to study the types of neurons composing the dorsal lateral geniculate nucleus and to elucidate its organisational features in the rabbit. Four types of neurons were identified based on differences in perikaryon size or the particular features of their dendrites and dendritic appendages. Types 1 and 2 were comparable to the relay cells previously identified in functional and morphological studies in other mammals as projecting upon the visual cortex. Type 3 cells were morphologically identified as interneurons. Type 4 neurons, not described in detail in the present paper, were observed along the nuclear periphery underlying the optic tract. Types 1 and 2 neurons along with their dendritic trees were orientated in planes which converged radially in the anteromedial region of the nucleus. Retinal afferent fibres from the optic tract traversed the nucleus as part of a longitudinal fibre system, running parallel to the planes of cell orientation, to establish synapses with the relay neurons.

An electron microscopic study on the muscle cells and nerve fibres in the digestive gland of the snail Cryptomphallus aspersa.

This work is an electron microscopic study of the muscle cells and the nerve fibres which can be found between the connective tissue of the digestive gland of the gastropod mollusc Cryptomphallus aspersa. The muscle cells are smooth and are located immediately below the basal lamina of the secretory epithelium or in more central zones of the connective tissue of the gland. Two types of myofilaments can be found in the sarcoplasm: thin and thick. The thin ones have an approximate diameter of 5 nm, whereas the thick ones vary in diameter between 15 and 65 nm. The possibility exists that the myofilaments of 15 nm might belong to a third type. Nerve fibres can be found in central zones of the connective tissue of the digestive gland, at the base of the glandular tubules and within the secretory epithelium. In these fibres it is characteristic to find a large number of granules, of a diameter between 80 and 250 nm, surrounded by a membrane, the content of which varies in density. Small clear vesicles of 40 . . . 70 nm in diameter can also be observed. Occasionally granules, which fuse their membranes thus mixing their content, can be detected.

Quantitative alterations after long-term alcohol administration in the dorsal lateral geniculate nucleus (dLGN) in the rabbit (Oryctolagus cuniculus).

The effects of chronic excessive alcohol ingestion on the central nervous system were studied in neurons of the dorsal lateral geniculate nucleus (dLGN) in the rabbit (Oryctolagus cuniculus). In this nucleus, neuron density and other morphometric parameters such as the somatic volume of the cells have been investigated both under normal conditions and under alcohol intoxication. Special attention was given to the possibility that positive somatic heteropycnosis may be a sign of imminent cell death. In addition, the percentage volumes occupied by normal neuronal soma and by affected cells were determined. Continuous alcohol treatment for 6 months reduced the size of certain types of neurons, the alteration being specially intense in areas with an abundance of larger neurons. In these areas more intense signs of somatic heteropycnosis also appeared. We discuss the relationship between the condition of the inhibitory neurons (GABAergic interneurons), the distribution of these in the lower zone of the nucleus, and their greater resistance to the influence of alcohol. This type of stereological analysis is intended to provide a better interpretation of the different degrees of the effects of alcohol, and to give more detailed information about changes at cellular level, both for comparative purposes with other situations and to shed light on the alterations caused by alcoholism.

Stereological study on the mode of optic cup expansion and the accumulation of mitoses in the early stages of chick embryo development.

The present study was designed to contribute to our understanding of the factors that take part in the developmental transformation of the optic vesicle into the optic cup. The expansion and formation of this structure are dependent upon factors such as cellular proliferation, the space or zone occupied by the growing optic cup, and environmental influences. Our investigation in the chick embryo analyzes the relationship between retinal thickness and ventricular mitotic density. This relationship is shown in the study as PEI (proliferation-expansion index). That index varies in the superior, medial and inferior regions of the retina when the zones of the same stage are compared, as well as in the comparisons of values between the 13-14 stage and the 17-18 stage. These differences indicate a different behavior of the cells constituting the retinal regions. Also discussed is the influence of the retinal fissure on the morphological changes observed during optic cup development.

A modification of the chronic tartrate silver impregnation technique for block impregnation of the central nervous system and paraffin wax embedding.

This paper describes a block silver impregnation technique for the CNS. The procedure, which is quite simple, yields highly consistent and reproducible results. After fixation during 6-10 days in 10% saline formaldehyde, 4 mm thick blocks of brain are treated with chromic anhydride and sodium potassium tartrate solution for 4 days. After this period the specimens are rinsed in 0.75% silver nitrate solution to which 8-10 drops of pyridine per 100 ml of solution have been added. This is followed by impregnation for 4 days at 37 degrees C in silver nitrate-pyridine solution identical to that used in the previous rinsing step. The impregnated blocks are reduced during 20-26 h in 1% pyrogallol to which 6 ml commercial formaldehyde per 100 ml of solution have been added, followed by dehydration in dioxan and paraffin embedding. Sections no thicker than 30 microns are then cut for histological study. This fundamentally neurofibrillar method reveals: neuronal somata and their processes; synaptic structures; fibre bundles; and cell nuclei and nucleoli.

Determinations of gray cell coefficient in the dorsal lateral geniculate nucleus of the mouse.

This study is an analysis of the gray cell coefficient carried out in different regions of the dorsal lateral geniculate Nucleus (dLGN) of the mouse. We have analysed the contribution three different sized neuron types to the coefficient. Only about 6% of the total volume of the dLGN is occupied by nerve cell bodies, and the neurons that account for most of this 6% are medium sized (the largest diameter being between 8 and 11 microns.) The smallest neurons are mainly located in the more peripheral region of the nucleus.

Morphometry and frequency of afferent synaptic terminals in the rabbit dorsal-lateral geniculate nucleus.

Morphological and morphometric features of the retinal synaptic terminals (RLP) and cortical synaptic terminals (RSD) were analyzed in the alpha E sector of the rabbit dorsal-lateral geniculate nucleus (dLGN). A methodological approach was selected which allowed us to determine volume of the neuropil and elsewhere record variations in the size and distribution of the two types of terminals found in the three zones (superior, middle, and inferior) from up to down into which the alpha E sector of the dLGN was divided. After obtaining an isotropic, uniform, and pseudorandom (IUR) sample, the terminals were examined on the basis of a set of morphometric parameters. An analysis of these data showed the retinal terminals (RLP) to be more numerous and to occupy a greater total area of the neuropil in the dorsal (superior) zone of the nucleus, whereas the number and total area occupied by cortical terminals (RSD) did not vary in the superior, middle, and inferior zones. Upon comparing the two types of terminals, the RLP were larger and more widely distributed, the greatest differences between the two appearing in the dorsal (superior) zone of the dLGN.