PubMed Health⌕ Search

Biomedical subjects

N Cuenca

Publications and source records attributed to N Cuenca.

23 records · Page 2Linked to original sources
PubMed1990

Development of morphological types and distribution patterns of amacrine cells immunoreactive to tyrosine hydroxylase in the cat retina.

Using an antibody against tyrosine hydroxylase on newborn to 30-day kitten retinas, we have been able to follow the development of the dopaminergic amacrine cells of the cat retina by light-microscopical investigations of retinal wholemounts. The Type 1 or large Toh+ amacrine cells described by others (Oyster et al., 1985; Törk & Stone, 1979) and named A18 from a Golgi study (Kolb et al., 1981), is at birth (P1) an immature neuron with a small cell body and two or three simple thick radiating dendrites stratifying in stratum 1 with many of the dendrites ending in enlarged growth cones. With increasing postnatal age, the cell body size increases from 12.5 microns diameter to reach 15.5 microns diameter at P30. The dendritic fields also increase in size and complexity. At P1, cells of the central area exhibit dendritic appendages which then develop progressively until at P13 (after eye opening) they are part of rudimentary rings and by P30 the dendritic plexus of Toh+ dendrites and rings in stratum 1, typical of the adult cells, are complete. Toh+ stained processes with growth cones that run deep in stratum 5 of the inner plexiform layer and processes passing to the outer plexiform layer first become apparent at P1 in cells of central inferior retina but not till after P13 are these processes clearly expressed. At P1, the total number of Toh+ Type 1 cells is approximately 4000 and this number remains unchanged to the adult retina. However, the retina increases in size over the P1-P30 stage and thus the mean density of Type 1 Toh+ cells decreases from 30/mm2 at P1 to 18/mm2 at P30. The maximum density of Type 1 Toh+ cells occurs in central retina 2-4 mm superior temporal to the area centralis, corresponding to the maximum rod photoreceptor concentration. A second type of small Toh+ amacrine cell can be visualized at P1. This Type 2 cell is characterized by a much smaller cell body than Type 1 cells (9 microns diameter), and with faintly stained dendrites located in stratum 3 of the inner plexiform layer. During later postnatal days, Type 2 cells gradually become unstainable and only few are still seen in far peripheral retina by P23. Type 2 Toh+ cells from a total population of 40,000 cells at P1 with their highest density occurring in peripheral retina. By P13, they cannot be seen in central retina and are reduced to a total population of cells staining for the antibody of 7400 cells in far peripheral retina.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Morphology and distribution of neurons immunoreactive for substance P in the turtle retina.

Immunocytochemical staining procedures with the HRP-complexed antibody to substance P have been carried out on the turtle retina. Examination by light microscopy of wholemount retinas has allowed us to evaluate the morphology and distribution of the substance P immunoreactive cell types. Two amacrine cell types and two or more ganglion cell types are stained in our hands. Type A amacrines are tri-stratified wide-field amacrines. They have their major dendrites in S1 and S3 of the inner plexiform layer and they emit fine dendrites from the major dendrites that end in varicose boutons in S5 on and around cell bodies in the ganglion cell layer. Some of the dendrites in S1 radiate out in axon-like fashion for 1 mm across the retina. The type B amacrine cells are small to medium-field in dendritic extent. They have smaller cell bodies than type A and a single or, at most, two primary dendrites that pass directly to S3 before branching profusely into an intricate net-like dendritic field. The ganglion cells that are stained with substance P antibodies appear to be of several types but their exact morphologies are in doubt because only portions of their major dendrites are stained. Substance P immunoreactive axons are clearly seen to project from the cell bodies to the optic nerve head and axons are stained in the optic nerve itself. The substance P-stained ganglion cells occur in an irregular distribution that reaches a peak density in an elongated band parallel to and 1 mm below the visual streak. The type B amacrine cells reach a maximum density in the visual streak and are distributed in a highly regular mosaic decreasing in density in elliptical isodensity contours from the visual streak. In contrast the type A amacrine cells are rare or absent in the streak, being located in an irregular mosaic in peripheral retina.

Animals↗
PubMed1989

[Relevancy of the clinical subjects in medical training].

A judgment of the relevance of twelve clinical science courses for preparing the students to the practice of medicine and to the development of the scientific mind, was tested by the Pair Comparison and Equal-Appearing Interval methods. The test groups consisted of medical school faculty members, medical students and physicians. Three groups of clinical sciences, according its relevancy for preparing the students for a career as physicians, were identified Internal Medicine, Pediatrics, Surgery and Public Health, comprised the group of maximum relevancy; History of Medicine, Medicolegal and Radiological studies, formed a group of lowest relevancy. The remainder sciences (Ophthalmology, Obstetrics and Gynecology, Otorhinolaryngology, Dermatology and Psychiatry, formed a middle group. Few differences were found when we considered the relevancy to the development of the scientific mind.

Curriculum↗
PubMed1987

Postnatal development of microtubules and neurofilaments in the rat optic nerve: a quantitative study.

In this paper the postnatal changes in the cytoskeleton of the rat optic nerve fibers are described and quantified. These changes are also compared with other parameters such as myelination and axonal caliber with the aim of describing a general pattern of optic nerve maturation from a morphological point of view. The results showed that during the first postnatal week microtubules outnumbered neurofilaments but between days 8 and 20 the neurofilaments rapidly increased and on day 20 were about twice as numerous as microtubules. This proportion remained almost unaltered from the end of the third week to the 44th postnatal day. The comparison with other parameters suggested that the cytoskeleton, and in particular the proportion between its components, may be a more reliable index for measuring optic nerve maturation than other variables commonly used.

Animals↗