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Biomedical subjects

M Lafarga

Publications and source records attributed to M Lafarga.

At least 73 records · Page 4Linked to original sources
PubMed1985

A Golgi and morphometric study of the ectopic granule cells in the molecular layer of the rat cerebellum.

The morphological types of isolated ectopic granule cells (EGCs) were examined with Golgi-Rio Hortega staining in the cerebellar molecular layer of adult normal rats. The EGCs showed a significant reduction in the number of dendrites (mean 2.42 +/- 0.07) with respect to the controls (mean 3.97 +/- 0.09), and they usually exhibited poorly developed dendritic terminals. The karyometric analysis on semithin sections indicated that the average nuclear area in EGCs was significantly smaller (16.62 +/- 0.20 micron 2) than in normally positioned granule cells (21.08 +/- 0.24 micron 2).

Animals↗
PubMed1985

Demyelination-induced plasticity in the axon membrane: an ultrastructural cytochemical study of lead neuropathy in the rat.

We examined the distribution of ferric ion-ferrocyanide stain (a marker for excitable regions of myelinated fibers) in the lead-induced demyelinating neuropathy of the rat. By electron microscopy, we found that paranodal degeneration resulted in spreading of the reaction product from nodal to internodal axolemma. During repair, nodal-like stained areas formed at the contact zones between preremyelinating Schwann cells. These data suggest that the location and extent of excitable axonal regions are influenced by axoglial relationships. Additionally, some fibers displayed staining at paranodal axolemma adjacent to demyelinated segments, suggesting it might be an alternative site for impulse generation in demyelinated fibers.

Animals↗
PubMed1985

Changes in nucleolar morphology and volume of the supraoptic nucleus neurons during postnatal development of the rat.

The changes in the volume and nucleolar ultrastructure of neurons of the supraoptic nucleus were examined during the postnatal period of the rat. This morphological maturation involved the gradual transformation from relatively compact nucleoli to reticulate ones which exhibited a typical nucleolonemal configuration with numerous nucleolar interstices and fibrillar centers. A progressive augmentation of the nucleolar volume was also observed during postnatal life; the average value on the first postnatal day was 2.94 +/- 0.42 micron3 while by the 40th day the mean had increased to 15.01 +/- 0.45 micron3. We suggest that this cytodifferentiation process is the morphological expression of the activation of nucleolar ribosomal RNA synthesis, which is required for the growth and maturation of the neurosecretory cells.

Animals↗
PubMed1984

Axon membrane remodeling in the lead-induced demyelinating neuropathy of the rat.

Single-teased fibers stained with the ferric ion-ferrocyanide method allowed us to study axonal remodeling in the lead-induced demyelinating neuropathy of the rat. Our findings, in agreement with recent physiological data, pointed to a transitory reorganization of the demyelinated axons to maintain impulse conduction until remyelination and formation of new cytochemically normal nodes had restored a secure saltatory conduction.

Animals↗
PubMed1984

The perineuronal net in the fastigial nucleus of the rat cerebellum. A Golgi and quantitative study.

The morphological study of the rat fastigial nucleus with the Golgi-Rio Hortega method showed the presence of glial perineuronal nets surrounding the large neurons, but not the small ones. This perineuronal net appeared as a mesh of tenuous glial processes which covers the neuronal perikarya and proximal dendrites. The small alveolate compartments in this mesh seem to correspond to the holes for the synaptic boutons. Our results also indicate that the perineuronal net is derived from interneuronal protoplasmic and velate astrocytes. Using camera lucida drawings of this perineuronal net we have made a quantitative estimation of the size and density of synaptic boutons on these large neurons. The average numerical density of synaptic boutons was about 19 per 100 micron 2 of the neuronal surface, the mean area of the synaptic holes being 2.5 micron 2. Furthermore, the quantitative data evidence that about 52.5% of the neuronal surface is presumably occupied by synaptic boutons whereas the remaining 47.5% is covered by the glial processes of the perineuronal net. Semithin sections prepared from thick Golgi sections were used for the cytological study of the neurons surrounded by this glial pericellular network. The possible functional significance of the perineuronal net in the regulation of synaptic transmission in the fastigial cerebellar nucleus is briefly discussed.

Animals↗
PubMed1983

Nuclear inclusions in immature glial cells of the rat hypothalamus during the postnatal period.

Ultrastructural study of the hypothalamic ventromedial nucleus during the postnatal period showed the presence of nuclear inclusions in immature glial cells. These inclusions, identified as "coiled bodies", consist of round-to-oval formations of coiled electron-dense strands embedded in a less dense fibrillar matrix. Coiled bodies are located free within the nucleoplasm, showing no specific relationships with the nucleolus or the nuclear membrane. The cells containing coiled bodies were typified as oligodendrocyte precursors, mainly oligodendroblasts. The coiled bodies were not found in mature glial cells nor in other types of immature glial elements. The nature and possible functional role of coiled bodies are suggested in the light of recent morphological and biochemical data.

Animals↗
PubMed1983

The "accessory body" of Cajal in the neuronal nucleus. A light and electron microscopic approach.

The present light and electron microscopic study deals with the morphology and staining properties of two intranuclear inclusions - the "accessory body" of Cajal and the "coiled body"--in the supraoptic nuclei of adult rat hypothalamus, and supports the assumption that these structures represent the same intrinsic component of the neuronal nucleus. Consequently, we propose to term it "accessory body". The structure of this body was visualized by several different staining procedures: conventional electron microscopic techniques, a silver reaction, and the regressive EDTA staining for ribonucleoproteins. The silver-impregnation method employed here, which consists of a silver development sequence on hypothalamic tissue blocks prior to plastic embedding, permitted the study of supraoptic neurons at both light and electron microscopic levels. The nature and origin of "accessory bodies" are suggested and their possible functional role is briefly discussed.

Animals↗
PubMed1983

Transmission and scanning electron microscopy study on congenital dyserythropoietic anemia type I.

An ultrastructural study of the aspirated bone marrow of a patient with congenital dyserythropoietic anemia type I is presented. Both in transmission electron microscopy (TEM) and in scanning electron microscopy (SEM) ultrastructural abnormalities of the bone marrow erythroid precursors were seen. These abnormalities in TEM included uneven condensation of chromatin with spongy appearance and alterations of cellular division. The most striking among these alterations were: firstly, the intercellular bridges which were typified by the presence of chromatin and the absence of the midbody and contractile ring and, secondly, the anomalies of the nuclear membrane. Occasionally, autolytic areas within the cytoplasma and iron-laden mitochondria were to be seen. In the SEM the following features were notable: the length of the intercellular bridges, the absence of the central ridge in the midbody area, as well as the scanty number of cytoplasmic blebs on the surface of the bridges.

Adolescent↗
PubMed1982

Unusual ultrastructural findings in neuroblastoma.

A morphologic study was made of the cell population which had infiltrated the bone marrow of a five-year-old boy. These cells showed a tendency to form rosette-like structures. These structures as well as the presence (at ultrastructural level) of neurosecretory granules, cell processes, and microtubules in the neoplastic cells led to a diagnosis of neuroblastoma. Certain characteristics, not previously reported in neuroblastoma, were identified, such as gap junction type intercellular contacts, paracrystalline arrays in mitochondrial atpyical cristae and nucleolus-like bodies (nematosomes). Gap junctions are involved in the intercellular transfer of ions and low molecular weight metabolites and may explain the tendency to form cellular cluster in "rosettes" which are characteristic of this neoplasm. The presence of nematosomes in the tumor cell cytoplasm is one more piece of evidence which substantiates the nervous origin of these cells.

Bone Marrow↗
PubMed1981

Silver staining of the neuronal nucleus in electron microscopy: nucleolar organization in supraoptic nuclei of the rat hypothalamus.

The present paper describes a simple, efficient method for silver impregnation of supraoptic nuclei of the rat hypothalamus using a modification of the ammoniacal silver technique of Cajal (1903). This procedure, involving a silver-developer sequence in tissue blocks prior to plastic embedding, permits the simultaneous study of Ag-impregnated supraoptic neurons at both light and electron microscopic levels. Visualization of secretory magnocellular neurons impregnated by this technique using the electron microscope reveals a good preservation of nuclear structures. A selective accumulation of silver grains was observed over heterochromatin clumps and nucleoli, which allows the identification of the nucleolar fibrillar centers and also the dense fibrillar component as the main areas involved in the silver reaction. The meaning of such a silver-distribution pattern is discussed in the light of recent ultrastructural and biochemical data.

Animals↗
PubMed1980

Coiled bodies in supraoptic nuclei of the rat hypothalamus during the postnatal period.

In electron microscopic studies of the supraoptic nuclei of the rat hypothalamus, structures identified as "coiled bodies" were found in magnocellular neurons. Although they could be seen elsewhere in mature neurosecretory cells, coiled bodies were commonly encountered in developing neurons during the postnatal period in both sexes. They appeared as distinctive nuclear inclusions consisting of round-to-oval networks of short electron-dense strands embedded in a less dense, fibrillar matrix, and lacking a limiting membrane. In fine structure and stain-affinity, they bore a resemblance to the fibrillar component of the nucleolus. Coiled bodies were located either in close association with the nucleolus or free within the nucleoplasm, showing no specific relationships with the perinucleolar chromatin or with the nuclear envelope. Their origin and functional meaning is discussed in the light of recent ultrastructural and biochemical data on cellular differentiation and nucleolar behavior.

Animals↗
PubMed1980

Ciliated neurons in supraoptic nucleus of rat hypothalamus during neonatal period.

Cilia 9+0 have been found in differentiating neurosecretory neurons of the hypothalamic supraoptic nuclei of Wistar rats. These ciliated neurosecretory cells were always observed during the neonatal period of the rat and no more than one cilium per cell has been encountered. Single cilia arising from typical basal bodies were usually located in deep invaginations of the neuronal perikaryon, but can also be seen in superficial positions. Their basal bodies were commonly found in the vicinity of Golgi complexes, and associated structures such as striated rootlets and alar sheets were also present. In addition, single centrioles frequently appeared in these neurons, occurring close to basal bodies but also in centrosomatic areas. The respective roles of these morphological features are suggested and their possible ontogenetic significance is briefly discussed.

Animals↗
PubMed1979

Subsurface cisterns in paraventricular nuclei of the hypothalamus of the rat.

Structures identified as subsurface cisterns (SSC's) were found in neurons of the paraventricular nuclei of the rat hypothalamus. They appeared as cytoplasmic organelles consisting most often of stacks of parallel cisterns apposed to the neuronal plasmalemma. These SSC's were located in the interneurons of the parvocellular system, but not in neurosecretory cells and glial cells. SSC's were seen at zones of cytoplasm apposed to neuronal or glial cell processes, showing in some instances specific relationships with synaptic areas. The morphological features of these SSC's are described, and their possible functional significance is briefly discussed.

Animals↗
PubMed1979

Nuclear inclusions in paraventricular nucleus neurons of the rat hypothalamus.

This paper deals with the ultrastructure of two types of intranuclear inclusions, "microfilamentous spindle-shaped" and "crystalloid", present in paraventricular nucleus neurons of adult normal rats. These inclusions appear occasionally in some non-secretory neurons of the parvocellular system, but have never been seen in neurosecretory cells of the magnocellular system. The microfilamentous spindle-shaped inclusions show a close spatial relationship with the granulofibrillar body and interchromatin granules. The distribution and functional significance of such structures are discussed in the light of recent ultrastructural and biochemical studies on nuclear inclusions.

Animals↗
PubMed1979

Nuclear bodies in the rat adrenal glomerular zone in normal and experimental conditions.

The presence of nuclear bodies in the glomerular zone of the rat adrenal cortex has been shown both in normal conditions and after the stimulus of low sodium diets causing an increase in their number. These results indicate that these organelles are a normal nuclear component of the cells of this zone, and that they can experience significant increases in quantity and complexity due to various functional stimuli.

Adrenal Cortex↗
PubMed1978

Intranuclear inclusions in pericytes of the hypothalamus of the rat.

This paper deals with the ultrastructure of two types of intranuclear inclusions, "nuclear bodies" and "membranous lamellar bodies", present in hypothalamic pericytes of intact adult rats. The nuclear bodies exhibited "simple" and "granular" forms, whereas the membranous lamellar bodies were entirely made up of myelin-like membrane whorls. The occurrence of these bodies in nuclei of pericytes has never been previously reported. The origin and functional meaning of such structures is discussed in the light of recent ultrastructural and biochemical studies on nuclear inclusions.

Animals↗