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F Valverde

Publications and source records attributed to F Valverde.

At least 55 records · Page 3Linked to original sources
PubMed1992

Formation of an olfactory glomerulus: morphological aspects of development and organization.

We have studied the development of olfactory nerves in the rat from their first contact with the telencephalic vesicle until the formation of glomerular structures in the olfactory bulb at early postnatal period. The study is based on serial semithin and ultrathin sections of material prepared for electron microscopy and antibodies to label radial glial cells, glial fibrillary acidic protein and Rat-401. Beginning on embryonic day 12, developing olfactory axons from the olfactory placode are accompanied by migratory cells, also derived from the olfactory placode, that reach the prospective olfactory bulb by embryonic day 13. The mass of migratory cells accumulate superficial to the telencephalic vesicle. The cells increase in number by mitotic divisions. The majority of these cells represent precursor elements that will later develop into the ensheathing cells of the olfactory nerves and olfactory nerve layer of the adult. Some migratory cells penetrate into the prospective olfactory bulb early during development. The first synaptic contacts of olfactory axons with dendritic processes in the olfactory bulb were observed at embryonic day 18. Glomerular formation is initiated by penetration of cells from the migratory mass into the prospective glomerular layer by embryonic day 20 to postnatal day 0. These cells form walls surrounding zones of high synaptic density forming protoglomeruli. Postnatally, the peripheral processes of radial glial cells branch profusely delimiting glomerular formations and transform into periglomerular astrocytes. Rat-401 stains radial glial cells from embryonic day 14. Immunoreactivity becomes restricted to the olfactory glomeruli during the first postnatal weeks and it virtually disappears by the end of the first postnatal month. We conclude that the early penetration of cells from the migratory mass into the prospective olfactory bulb, observed immediately after the first synaptic contacts were established, initiates the formation of olfactory glomeruli which becomes completed by the transformation of radial glial cells into periglomerular astrocytes.

Animals↗
PubMed1992

Determination of salicylic acid by HPLC in plasma and saliva from children with juvenile chronic arthritis.

A high performance liquid chromatography (HPLC) method has been developed for measuring salicylic acid in the plasma and saliva of children with juvenile chronic arthritis (JCA). Samples were extracted with diethyl ether and, after drying, redissolved in methanol to be chromatographed. Quantitation of salicylic acid was performed by reverse phase HPLC on a spherisorb ODS-2 column, using methanol: water: acetic acid as mobile phase. Phenolic was monitored by absorbance at 237 nm. Linearity between the amount of mass injected and the response in the detector was determined. This method was applied to compare concentrations of salivary and plasma salicylic acid. The method also permitted the quantitation of salivary salicylate as a non-invasive, indirect method for monitoring the concentration of plasma salicylate in patients with JCA.

Adolescent↗
PubMed1991

Neuroglial arrangements in the olfactory glomeruli of the hedgehog.

The olfactory glomeruli represent morphological and functional units in which olfactory information is processed in specialized synaptic arrangements established between the central processes of sensory neurons, whose cell bodies are located in the olfactory epithelium, and the terminal (intraglomerular) portions of the dendrites of periglomerular, tufted, and mitral cells. The olfactory glomeruli are surrounded by distinctive glial formations in which the peripheral glia interacts with the central glia. We have studied the morphology and organization of neuroglial cells in the layer of olfactory nerves and the glomerular layer of the olfactory bulb in the insectivorous hedgehog (Erinaceus europaeus) with the electron microscope, Golgi method, and immunohistochemistry by using antibodies to glial fibrillary acidic protein (GFAP) and "rip," a monoclonal antibody that stains oligodendrocytes and their processes in the rat (Friedman et al.: Glia 2:380-390, '89). The peripheral glia is represented by a special category of cells that are closely related to astrocytes and known as sheathing cells. They accompany olfactory axons to their entrance in the glomeruli where they interact with the central glia, represented by astrocytes and oligodendrocytes. The sheathing cells typically display indented nuclei and protoplasmic expansions forming laminar processes wrapping several axons together. Astrocytes surrounding the glomerular neuropil belong to the velate type. They display numerous sheet-like processes enveloping dendritic segments and periglomerular cell bodies. Oligodendrocytes were found surrounding the glomeruli and at the interstices separating different glomeruli. Myelinated dendritic segments and cell bodies were found surrounding the olfactory glomeruli. These myelin coverings probably derive from oligodendrocytes. Together with the astrocytic lamellar expansions, they provide a rigid structural support that contributes to the segregation of group of different cells while remaining relatively isolated from other influences at the periphery of the glomeruli.

Animals↗
PubMed1991

A method using DiI to study the connectivity of cortical transplants.

Carbocyanine DiI is described as a suitable fluorescent tracer to investigate the connectivity of cortical transplants. DiI was applied in 2 ways: in tissue previously fixed with aldehydes, and in vivo for labelling the donor tissue prior to transplantation. When applied in fixed tissue DiI travelled anterogradely, allowing the study of efferent connections from the transplant to the host. When DiI was applied in vivo, it travelled retrogradely showing the afferents to the transplant from the host.

Animals↗
PubMed1990

Structure of the olfactory bulb of the hedgehog (Erinaceus europaeus): a Golgi study of the intrinsic organization of the superficial layers.

The intrinsic organization of the mitral cell, external plexiform, and glomerular layers of the main olfactory bulb of the insectivore hedgehog were studied with the Golgi method. This study completes our previous description of the cell types in the granule cell layer in the same subject (López-Mascaraque et al., J. Comp. Neurol. 253:135-152, '86). In the present contribution the morphology of mitral, internal, and middle tufted cells is described with particular interest in the formation and arrangement of glomerular tufts by the primary dendrites, and the disposition of the secondary dendrites. Three types of intrinsic cells were found in the external plexiform layer: Van Gehuchten cells, satellite cells, and horizontal cells. All these cells display unusual patterns of branching processes that were difficult to classify as dendritic or axonal. The close relationship between some processes of the satellite cells with the mitral or tufted cell dendrites is noted, suggesting that these cells may be inhibitory in nature. The external tufted cells are described, and several aspects pertaining to their morphology were considered in order to distinguish them from periglomerular cells and from the remaining tufted cells. External tufted and periglomerular cells appear to be intrinsic neurons, having axons distributed in the periglomerular region, most probably devoted to relating different olfactory glomeruli. The arrangement of glomeruli in the glomerular layer and distinctive characteristics with respect to other mammals were considered from a comparative point of view.

Animals↗
PubMed1990

Transplant connectivity in the rat cerebral cortex. A carbocyanine study.

Previous reports suggest that the specificity of connectivity between cortical areas and their related thalamic nuclei is established during development. We have used heterotopic E15, E17 and E19 transplants to determine at which embryonic age the cortex is mature enough to establish such specific connections. Carbocyanine DiI or Fluoro-Gold were used for labelling transplants. Efferent cortico-cortical, callosal and collicular connections were observed when DiI was applied in fixed tissue. Thalamic nuclei were labelled when DiI was used 'in vivo' or the transplants were labelled with Fluoro-Gold. The connections of the transplants were those corresponding to the area in which the transplants were placed. This suggests that up to E19 the embryonic cortex is too immature to define the specific thalamo-cortical connections.

Animals↗
PubMed1990

Distribution and morphology of Alz-50-immunoreactive cells in the developing visual cortex of kittens.

The population of interstitial cells of the white matter in the postlateral gyrus of the cat was studied at different postnatal ages using the antibody Alz-50. These neurons are among the first cells to develop in the cortex, and many of them are transitory, disappearing by cell death during the first postnatal days. In the present study, we found that immunoreactivity to Alz-50 is expressed during the first three postnatal weeks, and that positive neurons were not detected after postnatal day (P) 23. In addition to marking cells in the white matter, Alz-50 also recognizes many pyramidal cells in the cortical layers II-III and V of the visual cortex at postnatal day 4. The staining of cortical cells was not observed at other ages. We found that the number of positive cells in the white matter decreases by postnatal days 12 and 16, showing an apparent increase in number at postnatal day 23. In this study we also attempted to correlate the morphology of Alz-50-immunoreactive cells with the interstitial cells of the white matter, as seen in Golgi preparations. We conclude that Alz-50 immunoreactivity may be related to specific developmental changes and not particularly associated to the occurrence of cell death.

Animals↗
PubMed1990

Hematologic data in 825 cases of beta-thalassemia trait in Spain.

We present the hematologic data of 825 cases of beta-thalassemia trait (687 cases of beta-thalassemia trait and 138 cases of delta beta-thalassemia trait). There were no significant differences between the red cell indices of the patients with beta and delta beta-thalassemia trait. In patients with beta-thalassemia trait, MCV was significantly reduced in 97% of the males and 99% of the females. All the patients with delta beta-thalassemia trait showed low MCV values. Red cell morphology was altered in the vast majority of cases, with basophilic stippling in 96% of the patients. Most patients came from provinces with the highest incidence of malaria in the past.

Adolescent↗
PubMed1989

Development and differentiation of early generated cells of sublayer VIb in the somatosensory cortex of the rat: a correlated Golgi and autoradiographic study.

Autoradiographic and Golgi techniques are used to study the origin, developmental characteristics, and adult morphology of the cells of sublayer VIb in the somatosensory cortex of the rat. In the adult rat, this sublayer forms a stratum of two to three rows of cells located immediately above the white matter. It is clearly separated from the remaining cortical layers by a light plexus of fibers. The cortical plate begins to appear in the lateral wall of the brain hemisphere at embryonic day 15 (E15). By using tritiated thymidine autoradiography, we can see that cells generated between E12 and E14 become located in layers I, V, and VI in the adult. After injections on E12, heavily labeled cells were found almost exclusively in layer I and in sublayer VIb, indicating that these are the earliest generated cells in the neocortex of the rat. No labeled cells were found in sublayer VIb after injection on E15. We describe the morphology of cells of layer VI from E15 to the adult using the Golgi technique. Our observations show the existence of different types of cells, among which we found horizontal bipolar cells very early during development. They transform into horizontal and inverted pyramidal cells, which are the predominant morphological types found in the adult. Horizontal cells lie at the lower part of sublayer VIb. Inverted pyramidal cells have descending apical dendrites penetrating the white matter. Their axons form ascending loops turning into projection fibers. A correlation with previous studies and some functional implications indicating the unique role of sublayer VIb in the rat during development and in the adult are discussed.

Animals↗
PubMed1989

Structure of the nucleus olfactorius anterior of the hedgehog (Erinaceus europaeus).

The cytoarchitecture, topography, and cellular structure of the nucleus olfactorius anterior (NOA) in the hedgehog have been studied in Nissl-stained and Golgi preparations. The NOA is an important receptive allocortical formation for olfactory fibers and the major source of association fibers relating the main olfactory bulb with the rest of the olfactory brain. It was divided into a bulbar part; four subdivisions named lateral, dorsal, medial, and ventral; an external part; and a posterior part. Except for the external and posterior subdivisions, the NOA is relatively homogeneous and, in spite of the apparent lack of sublamination in Niss-stained material, four clearly defined cellular laminae were distinguished by the Golgi method. These layers were found to be strikingly similar to those in the piriform cortex. Layer I contains the terminal ramifications of apical dendrites of pyramidal cells and the collaterals of the lateral olfactory tract. The superficial part of layer II contains extraverted pyramidal cells with two or three apical dendrites ramifying in layer I. Most pyramidal cells in the deep part of layer II and layer III are typical pyramidal cells with axons entering the commissura anterior. Some pyramidal cell axons bifurcate into two branches running in opposite directions in the commissura anterior. The interstitial zone below layer III contains deep pyramidal cells and polymorphic cells with ascending branches. Cells with intrinsic axons were classified into four main categories according to the distribution of their axonal ramifications: 1) cells with very restricted axons, 2) cells with axons oriented tangentially in the superficial part of layer II, 3) cells with ascending axons located in the deep part, and 4) chandelierlike cells. Finally, some functional considerations are discussed.

Animals↗
PubMed1989

Connections of the olfactory bulb and nucleus olfactorius anterior in the hedgehog (Erinaceus europaeus): fluorescent tracers and HRP study.

The projections of the main olfactory bulbs (MOBs) and the dorsal part of the anterior olfactory nucleus (NOA) in the hedgehog (Erinaceus europaeus) have been studied by fluorescent tracers and the horseradish peroxidase method (HRP), respectively, to reveal the pattern of labeling from these structures. After different dye injections in both MOBs, labeled cells were present in the following structures: tenia tecta, vertical limb of the diagonal band of Broca, and medial septal nucleus in the ipsilateral injection site; and the NOA, piriform cortex, nucleus of the lateral olfactory tract, horizontal limb of the diagonal band of Broca, posterolateral cortical amygdaloid nucleus, anterior amygdaloid area, and dorsal raphe nucleus in both hemispheres. Structures showing double-labeled cells were the NOA, horizontal limb of the diagonal band of Broca, nucleus of the lateral olfactory tract, anterior amygdaloid area, and posterolateral cortical amygdaloid nucleus. After HRP injections in the dorsal part of the NOA, labeled cells were distributed in the NOA, nucleus of the lateral olfactory tract, posterolateral cortical amygdaloid nucleus, piriform cortex, horizontal and vertical limbs of the diagonal band of Broca, mitral cell layer of the MOB, tenia tecta, anterior amygdaloid area, and the contralateral NOA. We suggest that the contralateral projection nuclei to the MOB of the hedgehog, unusual in other mammals, and the large number of cells with axonal collaterals projecting to both hemispheres, may be a strategy in these animals to bilaterally integrate brain functions at the expense of its reduced corpus callosum.

Animals↗
PubMed1988

Postnatal development of interstitial (subplate) cells in the white matter of the temporal cortex of kittens: a correlated Golgi and electron microscopic study.

The early postnatal development of interstitial cells (IC) in the white matter of the temporal cortex in kittens was studied. Counts in Nissl-stained preparations show that the number of IC diminishes by about 60% during the second postnatal week. In Golgi preparations, IC are bipolar or bitufted with long, beaded dendrites coursing in the white matter toward the ventricular surface. Ascending, shorter dendrites are thinner, often branch in a short bush, and possess long spines resembling filopodia. The majority of their axons descend in the white matter, emitting numerous recurrent collaterals that become ascending fibers reaching various cortical layers. Most IC resemble inverted pyramidal cells. They appear well developed at the time of birth and continue to develop elaborate axonal complexes in the white matter of older animals. Electron microscopic observations of degenerating IC were detected in all cases studied and their presence was related to the existence of cell death responsible for elimination of a fraction of IC. They were recognized by their dark aspect and by dilations of the endoplasmic reticulum. Synapses contacting degenerating profiles were also observed. It is concluded that IC belong to the population of early generated subplate cells which may have a transient function involved in certain morphogenetic events during the development of the cortical plate. Some persist in the adult where they can be recognized as IC of the white matter.

Animals↗
PubMed1988

Hemolytic anemia and susceptibility to hydrogen-peroxide hemolysis in children with vitamin E-deficiency and chronic liver disease.

Thirty-four children, aged 1-14 years, with severe chronic liver disease were studied to determine the incidence of chronic hemolytic anemia and the mechanism underlying it. Sixteen children were grouped as vitamin E-deficient patients (Group I, serum vitamin E level below 5.0 micrograms/ml) and compared with 18 vitamin E-sufficient children (Group II) and 20 healthy controls. Group I patients had a significantly lower hemoglobin level (11.6 +/- 0.4 g/dl) when compared with Group II (12.9 +/- 0.4 g/dl, less than 0.05), their RBC's were less resistant to H2O2-induced hemolysis (53.1 +/- 8.0% in Group I, vs. 1.07 +/- 0.23% in Group II), and the average hemolysis correlated with serum vitamin E levels. H2O2-induced hemolysis reverted to normal in five patients after vitamin E therapy. With respect to controls, cirrhotic children in both groups showed a slight increase in total RBC membrane lipids, but no difference in either phospholipid content or in cholesterol/phospholipid molar ratio that could have changed RBC membrane properties and sensitivity to lysis. In our experience, vitamin E-deficient cirrhotics have a slight degree of chronic hemolytic anemia and their RBC's are much more sensitive to H2O2 lysis, although this abnormal lysis susceptibility does not seem apparently related to membrane peroxidation.

Adolescent↗