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Biomedical subjects

J L Arias

Publications and source records attributed to J L Arias.

At least 73 records · Page 4Linked to original sources
PubMed1994

Postnatal development of argyrophilic nucleolar organizer regions in the mammillary body of undernourished rats.

The effects of undernutrition during pregnancy and/or lactation periods on cortical structures have already been reported. However, its effect on non-cortical areas like the hypothalamic, that participates in the regulation of the autonomic nervous system or food intake, has not been extensively investigated. We studied the postnatal development of the medial mammillary nucleus (hypothalamus) in the rat offspring that had a dietary restriction in utero and during lactation. The argyrophilic nucleolar regions (Ag-NORs), that represent the transcriptional activity of the cell, were quantified in their neurons. No statistically significant differences were found in the results between the control and undernourished groups in the ages studied (7, 14, 21 and 30 days). However, a delay in the neuronal activity of the latter group was observed. A critical period in the development of this nucleus, at about 21 days of age, was also seen in both groups. After this age, the activity levels remained steady.

Animals↗
PubMed1994

Structural dimorphism in the mammillary bodies of the rat.

Diverse structures of the CNS show sexual differences in the anatomical and functional organization. In particular, many dimorphic nuclei have been found in the hypothalamus: the preoptic area, suprachiasmatic nucleus and ventromedial hypothalamus. Our investigation has shown a statistically significant difference in relation to volume of the medial mammillary and left lateral nuclei, and the number of glial cells of the medial mammillary nucleus. The volume and glial cell population is greater in the male than in the female. Thus, the existence of dimorphic functions in which this structure could be involved are discussed herein.

Animals↗
PubMed1994

Behaviour of nucleolar organizer regions in the different Wistar rat liver lobes.

The area and number of silver-nucleolar organizer regions (Ag-NORs) in the hepatic lobes were determined in 3 male Wistar rats. There was a statistically significant increase in the percentage of Ag-NORs per nucleus in the right lateral and caudate lobe in relation to the left lateral and middle lobes. The area and number of Ag-NORs are greater in the caudate and right lateral lobes in relation to the left lateral and middle lobes. Since the Ag-NOR is a parameter which indicates hepatocytic protein synthesis, the different activity which corresponds to each lobe of the rat's liver makes it possible to assume that there is a functional heterogeneity which should be considered in the study of the hepatic regeneration according to the type of partial hepatectomy carried out.

Animals↗
PubMed1994

Behavior of nucleolar organizer regions in the different hepatic lobes after end-to-side portacaval shunt in the rat.

Protein synthesis activity in the hepatic lobes in control and end-to-side portacaval shunt rats was studied by assaying one of the argyrophilic components (Ag-NOR) of the hepatocytic nucleolus. The differences found in the area and number of Ag-NOR for each nucleus and in the percentage of Ag-NOR area to nucleus area in each hepatic lobe in control rats as well as in the end-to-side portacaval shunt rats suggest that there are interlobular differences in the control rats related to this parameter that are indicative of protein synthesis and cell proliferation. Furthermore, the changes that occur in these parameters after the deprivation of portal flow produced by an end-to-side portacaval shunt make it possible to hypothesize on the existence of a hepatic lobular functional heterogeneity in the rat liver.

Animals↗
PubMed1993

Syncope and long QT syndrome with an initially normal QT interval.

We present two patients who were admitted to our Hospital because of repetitive syncopal attacks. The study previous to their admission included electrocardiograms in which the QT interval was normal. During their admission, an striking lengthening of the QT interval, in addition to other criteria of the long QT syndrome, was observed in both patients. We suggest that one normal measurement of the QT interval should not rule out this diagnosis.

Adult↗
PubMed1992

Innovative materials processing strategies: a biomimetic approach.

Many organisms construct structural ceramic (biomineral) composites from seemingly mundane materials; cell-mediated processes control both the nucleation and growth of mineral and the development of composite microarchitecture. Living systems fabricate biocomposites by: (i) confining biomineralization within specific subunit compartments; (ii) producing a specific mineral with defined crystal size and orientation; and (iii) packaging many incremental units together in a moving front process to form fully densified, macroscopic structures. By adapting biological principles, materials scientists are attempting to produce novel materials. To date, neither the elegance of the biomineral assembly mechanisms nor the intricate composite microarchitectures have been duplicated by nonbiological processing. However, substantial progress has been made in the understanding of how biomineralization occurs, and the first steps are now being taken to exploit the basic principles involved.

Animals↗
PubMed1992

Partial biochemical and immunochemical characterization of avian eggshell extracellular matrices.

There is evidence to suggest that extracellular matrix molecules, such as proteoglycans, are involved in the regulation of mineral deposition in calcifying tissues. One mineralizing system which is characterized by extremely rapid mineralization is the hen eggshell. This eggshell consists of a pair of nonmineralized eggshell membranes subjacent to the calcified eggshell proper; the eggshell proper is organized into palisades (columns) of mineralized matrix separated by pores. Between the membranes and the shell proper are compacted foci of tissue called mammillary knobs, which are thought to be sites where mineralization is initiated. Previous work from this laboratory has shown the presence of types I, V, and X collagen in the shell membranes. To address the question of the possible role of proteoglycans and glycosaminoglycans in mineralization of the eggshell, two approaches were used. First, immunohistochemistry was performed with monoclonal antibodies to various proteoglycan and glycosaminoglycan epitopes. This analysis indicates that different glycosaminoglycans are localized to discrete regions within the eggshell. Dermatan sulfate is present within the matrix of the shell proper and, to a lesser extent, the mammillary knobs and the outer portion of the shell membranes. In contrast, keratan sulfate is found in the shell membranes and prominently in the mammillary knobs. Interestingly, different keratan sulfate antibodies immunostain distinct regions of the eggshell, which suggests that various types of keratan sulfate are distributed differently. The second approach utilized was to extract the eggshell membranes and recover anionic molecules by anion-exchange chromatography. This resulted in the extraction of material which was recognized by antibodies to keratan sulfate, but not to chondroitin sulfate. This material was very large, as evidenced by its elution in the void volume of a Sepharose CL-2B column. The large size may be due to the extensive cross-links known to occur in the eggshell. If eggshell membranes are extracted at elevated temperature, the material recovered is of much smaller size. These results indicate that molecules recognized by antibodies to glycosaminoglycans are present in the eggshell, and their localized distribution relative to the calcified matrix suggests that they may be involved in the regulation of mineral deposition.

Animals↗
PubMed1991

The fabrication and collagenous substructure of the eggshell membrane in the isthmus of the hen oviduct.

The eggshell of the chicken consists of a bi-layered shell membrane overlaid with a thick, calcified shell matrix. The shell membranes and matrix are deposited onto the egg as it passes through the oviduct. To assess the temporal and spatial aspects of the fabrication of type X collagen within the eggshell extracellular matrix, the immunohistochemical localization of type X collagen was studied in three regions of the hen oviduct (magnum, isthmus and uterus), in the membranes of uncalcified eggshells obtained from the oviduct prior to mineral deposition and in eggshell membrane and calcified eggshell matrix. Additionally, immunohistochemical localization of type I and III collagens was done in order to determine possible co-localization of collagen types or to define tissue compartments. None of the collagen epitopes assayed was found in the shell matrix. Type X collagen epitope was immunohistochemically localized only to the epithelial cell layer lining the isthmus region of the oviduct and in the shell membranes of both uncalcified and calcified eggshells. Antitype III collagen monoclonal antibody delineated the inter-tubular gland connective tissue of the oviduct and was negative in the shell layers under conditions which gave strong connective tissue reactivity. Type I collagen epitope was exposed after pepsin treatment of the tissue and co-localizes with the distribution of type III collagen. Type I collagen co-localized with type X collagen in the shell membranes of uncalcified shells. The type I collagen epitope was reactive in the shell membrane of the uncalcified shells, but could only be detected in calcified shells following pepsin digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Collagens of the chicken eggshell membranes.

An immunohistochemical analysis of the eggshell membranes shows the occurrence of type X collagen while type I collagen was not detected by using an appropriate monoclonal antibody with untreated shell membranes. A positive immuno-reaction for type I collagen was obtained after digestion of the shell membranes with pepsin. These observations indicate the possibility that type I collagen epitope was masked by type X collagen and that type X collagen may serve as an inhibitory boundary for biomineralization.

Acetates↗
PubMed1991

[Endogenous digitalis].

During the past 10 years, several groups of researchers from different laboratories have carried out research on an endogenous substance or substances which had cross immunoreacted to digoxin antibodies in patients without previous cardiotonic treatment. The increase has been demonstrated in various clinical cases which involve an augmentation of plasmatic volume. A considerable amount is known about its molecular structure and anatomic origin; the competitive inhibition of the sodium pump being quite clear.

Animals↗
PubMed1991

A spectrophotometric modification of a sensitive densitometric Safranin O assay for glycosaminoglycans.

Recently, an assay for quantification of glycosaminoglycans has been reported based on precipitation with Safranin O (Lammi, M. and Tammi, M. (1988) Anal. Biochem. 168, 352-357). In this procedure, the precipitate which forms when the glycosaminoglycan or proteoglycan is mixed with the Safranin O is collected with a dot-blot apparatus onto a membrane filter. The intensity of the color in the dots is measured densitometrically and is proportional to the amount of glycosaminoglycan or proteoglycan in the sample. This report describes a modification of the densitometric Safranin O assay which allows its use as a spectrophotometric assay. For this, the precipitates are solubilized in cetylpyridinium chloride and the absorbance determined for the resulting solutions. As with the densitometric method, guanidinium chloride diminishes the color intensity. However, the color is stable, even after solubilization, for at least one week. The precipitates collected from as much as 10 micrograms of material can be solubilized in as little as 100 microliters of cetylpyridinium chloride, so that increased sensitivity may be obtained if the solubilized precipitate is measured in a microcuvet. Thus, solubilization with cetylpyridinium chloride allows use of the Safranin O assay for glycosaminoglycans and proteoglycans even when a densitometer is unavailable.

Cetylpyridinium↗
PubMed1991

An ultrastructural and biochemical analysis of the epithelial-mesenchymal interface of the ruminal mucosa during development.

The ultrastructure of fetal and adult bovine epithelial-mesenchymal interface of the ruminal mucosa was described and then correlated to the biochemical analysis for glycosaminoglycans (GAGs). During development a progressive undulation of the basement membrane, increase of connective tissue filamentous material, and folding of the cellular membrane of the basal epithelial cells were observed. Coincidently, a decrease in the relative composition of hyaluronic acid and an increase in chondroitin sulfate was observed. These results suggest a correlation between glycosaminoglycans composition and the expression of some cellular events resulting in morphological changes which operate during ruminal morphogenesis.

Animals↗
PubMed1987

Quantitative variations in nucleolar components within pineal gland cells during the rat estrous cycle.

Quantitative changes in the size of pinealocyte nucleoli have been reported in various studies on this cell type. However, the significance of quantitative changes in the nucleolar components is unknown. The present study is an attempt to analyze ultrastructural and morphometric modifications occurring in the pinealocyte nucleolar components during the estrous cycle in female rats. The fibrillar centers showed an increase during estrus consistent with a decrease in pinealocyte nucleolar activity and melatonin pineal levels. The fibrillar components and granular components tended to display a reciprocal relationship. An increase in the dense fibrillar component took place at metaestrus and diestrus when melatonin synthesis increased in pinealocytes. Maximum values of granular and interstitial components were found at the proestrus phase before the day of ovulation.

Animals↗
PubMed1986

Ultrastructural and cytochemical study of the pinealocyte nucleolus in rats.

The pinealocyte nucleolus has practically not been studied, although many studies have been carried out on this particular cell. In order to study the pinealocyte nucleolus, we have used conventional electron microscopy techniques, as well as cytochemical methods: silver nitrate, phosphotungstic acid (PTA) and ethylenediaminetetraacetic acid (EDTA). The pinealocyte nucleolus shows a reticular structure formed by a dense fibrillar component and closely packed granules (granular component), as well as electron lucent spaces which contain nucleoplasm. There are also places of light fibrillar material (fibrillar centers). Using the Ag-staining we have observed spherical aggregates of argyrophylic granules densely packed (fibrillar centers) and other granules loosely packed in its periphery (dense fibrillar component). PTA stains preferentially the fibrillar centers. We have identified as heterochromatin a dense granular aggregate that appears associated to the nucleolus. We present the pinealocyte nucleolus as an excellent model for the study of the functional meaning of nucleolar components.

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