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Biomedical subjects

J L Arias

Publications and source records attributed to J L Arias.

At least 55 records · Page 3Linked to original sources
PubMed1997

Changes of cytochrome oxidase activity in rat suprachiasmatic nucleus.

This paper evaluates the changes of cytochrome oxidase (CO) activity that take place in the suprachiasmatic nucleus (SCN) during the light-dark cycle. CO is a mitochondrial energy-generating enzyme used as a marker of neural oxidative metabolism. We measured CO activity using quantitative histochemistry calibrated with brain tissue standards and a computerized analysis image system. The results indicate that the CO enzyme activity changes on the basis of a circadian pattern, with the higher levels during the light phase (P < 0.0001). These changes are detected over a period of hours, in accordance with other studies on the possible short-term regulation of CO activity in the nervous system. It is, therefore, possible to apply this methodology to the study of the SCN and other brain areas which show functional rhythmicity.

Animals↗
PubMed1997

NOR activity in hippocampal areas during the postnatal development and ageing.

The silver staining of the nucleolar organizer regions (Ag-NORs) was used in order to estimate the biosynthetic activity of three hippocampal areas (dentate gyrus, CA1 and CA3) during postnatal development and ageing. 32 Wistar rats were used and 4 groups were formed according to the age of the animals (14, 21, 90 days and 23 months). Several Ag-NOR parameters such as mean Ag-NOR area and the ratio between Ag-NOR and nuclear areas per neuronal cell were quantified using an image analysis system. High values of these parameters are associated with a high rate of rRNA transcription. In this way, the neural biosynthetic activity in all regions studied decreased as the older ages are reached. Differences between areas are shown with the dentate gyrus and CA1 areas decreasing faster. The different activity among these areas is discussed, taking into account the particular affect on these areas of some injuries and the ageing process. Our results support the hypothesis of NOR loss as a main cause of ageing as reported by other authors.

Aging↗
PubMed1997

Eggshells are shaped by a precise spatio-temporal arrangement of sequentially deposited macromolecules.

The avian eggshell is a composite bioceramic which is formed by a controlled interaction of an organic and an inorganic phase. The organic phase contains, among other constituents, type X collagen and proteoglycans, mainly keratan and dermatan sulfate. Understanding the principles governing the synthesis and temporo-spatial distribution of such macromolecules, and their influence on the organization of the crystalline phase, is an essential aspect of establishing the biological basis of the quality of eggshell, both as an embryonic chamber and as a natural food package. In the present study, we have examined the process of eggshell formation by immunohistochemistry, scanning electron microscopy and energy dispersive X-ray microanalysis. Precise sites and timing of secretion were established for the deposition of particular macromolecules. Type X collagen is detected at the very first moment of shell membrane formation. The appearance of keratan sulfate coincides with the appearance of mammillae, while dermatan sulfate is deposited later, coincident with shell matrix deposition. We propose that keratan sulfate, due to its precise localization, temporal appearance and calcium-binding affinity, relates to the maintenance of calcium reserve bodies, the primary source of calcium for the embryo. On the other hand, dermatan sulfate may control crystal growth, resulting in a preferential orientation of calcite crystals within the palisade layer.

Animals↗
PubMed1997

Hydroxyapatite coatings: a comparative study between plasma-spray and pulsed laser deposition techniques.

A comparative study between hydroxyapatite coatings produced by two different techniques, plasma spray (PS) and pulsed-laser deposition (PLD) was carried out. Plasma spray is currently commercially used for coating dental and orthopaedical implant devices, and pulsed-laser deposition (or laser-ablation deposition) gave good results in the field of high critical temperature superconductive thin films, and is being applied to produce calcium phosphate coatings for biomedical purposes. X-ray diffraction was used to control the crystallinity of the coatings, scanning electron microscopy for the surface and cross-sectional morphology, and the pull test to determine the tensile strength of the coatings. This study reveals that the pulsed-laser deposition technique appears to be a very good candidate to replace the plasma spray in many biomedical applications, because it overcomes most of the drawbacks of the plasma spray.

Journal Article↗
PubMed1997

Structural analysis of calcium phosphate coatings produced by pulsed laser deposition at different water-vapour pressures.

Calcium phosphate coatings have been produced by pulsed laser deposition (PLD) at different water-vapour pressures. Rietveld refinement of X-ray diffraction (XRD) data allows us to determine that the structure of these coatings is apatitic with carbonate substitution for phosphate. The carbonate substitution decreases when the chamber pressure is raised, a fact that has been corroborated by Fourier transform-infrared (FT-IR) spectroscopy. Carbonate concentrations between 5 and 17 wt% have been calculated for the crystalline samples. Amorphous coatings are produced at the lowest and highest pressures due to the high carbonate concentration in the first case, and possibly to another type of substitution (Mg(2+), HPO(2-)4, P2O(4-)7) or the inherent kinetics of the PLD process, in the second case.

Journal Article↗
PubMed1997

Changes in the nucleolar organizer regions in the tuberomammillar region after dehydration.

The existence of efferent connections between tuberomammillary (TM) and the supraoptic (SON) nuclei led us to study the morphological changes at these levels during dehydration induced in rats by repeated administration of hypertonic saline. The dehydration effects are evaluated by three parameters: nucleus area, argyrophilic nucleolar organizer regions (Ag-NOR) area, and mean number of Ag-NORs. These parameters reflect the level of transcriptional activity of the rRNA genes, which in turn is closely related to the protein synthesis activity of the cell. The technique used is argyrophilic staining which labels the nucleolar organizer regions (NORs) of the nucleoli in the neurons and their area, permitting their quantification with an image analysis system. The statistical analysis reflects the sensitivity to dehydration of these structures at TM level. Our results support the regulatory role of vasopressin secretion by SON through the histaminergic pathways arising from TM in rat dehydration processes.

Animals↗
PubMed1997

Effect of beta-aminoproprionitrile on eggshell formation.

1. Eggshells are bioceramic-biopolymer composites made by a cell-mediated deposition of an extracellular matrix which drives the organisation of the inorganic phase. Ultrastructurally, eggshells are composed of shell membranes, mammillary knobs, palisade, and cuticle. Shell membranes are two nets of type X collagen-containing fibrils. On to these membranes, the mammillary knobs, that is, the crystal nucleation sites, are deposited. Type X collagen is highly cross-linked and insoluble. 2. In order to evaluate the role of type X collagen cross-linking on eggshell formation, hens were injected with different doses of beta-aminoproprionitrile, which specifically interferes with cross-link formation. 3. Changes in egg size and shape were observed. Scanning electron micrographs analysis of these eggs demonstrated marked changes in crystal growth and shell membrane structure and arrangement. A dot-blot analysis, using a monoclonal antibody against chicken type X collagen, shows a dose-dependent increase in shell membrane collagen extractability. 4. It is concluded that the formation of beta-aminoproprionitrile-sensitive cross-links among the type X collagen molecules of the shell membranes play an essential role in normal eggshell formation.

Aminopropionitrile↗
PubMed1997

Portacaval shunt control animals: physiological consequences derived from the sham operation.

The portacaval shunt in the rat is a frequently used experimental model of portosystemic encephalopathy. Among other consequences of this surgical preparation is an important decrease in hepatic and testicular volume. Different sham-operation methods including a laparotomy were used as controls in each case. Given that the liver volume varies greatly in comparison to body weight in the sham-operated animals, this paper aims to evaluate the possible consequences of the sham operation. It concludes that control animals without manipulation, in addition to the respective controls of portacaval shunt, should be used in every case.

Analysis of Variance↗
PubMed1997

Role of type X collagen on experimental mineralization of eggshell membranes.

Type X collagen is a transient and developmentally regulated collagen that has been postulated to be involved in controlling the later stages of endochondral bone formation. However, the role of this collagen in these events is not yet known. In order to understand the function of type X collagen, if any, in the process of biomineralization, the properties of type X collagen in eggshell membranes were further investigated. Specifically, calvaria-derived osteogenic cells were tested for their ability to mineralize eggshell membranes in vitro. Immunohistochemistry with specific monoclonal antibodies was used to correlate the presence or absence of type X collagen or its propeptide domains with the ability of shell membranes to be mineralized. The extent of mineralization was assessed by Von Kossa staining, scanning electron microscopy and energy-dispersive spectroscopy. The results indicate that the non-helical domains of type X collagen must be removed to facilitate the cell-mediated mineralization of eggshell membranes. In this tissue, intact type X collagen does not appear to stimulate or support cell-mediated mineralization. We postulate that the non-helical domains of type X collagen function in vivo to inhibit mineralization and thereby establish boundaries which are protected from mineral deposition.

Amino Acid Sequence↗
PubMed1996

Functional sexual dimorphism of the nucleolar organizer regions in the tuberomamillary nucleus.

The tuberomamillary nucleus (TM) is a cluster of magnocellular neurons that are located close to the mamillary recess or basal surface of the mamillary body (MBs) and is the only known source of histamine (HA). The nucleolar organizer regions (NORs) of the nervous cells of the subnuclei E1, E2 and E3 of the TM are quantified in this paper to discern the existence of possible sexual differences in the overall neuronal protein synthesis between male and female rats in two phases of the oestrous cycle (oestrous-dioestrous). We have used the argentic impregnation technique of the NORs (AgNORs) in both bilateral nuclei of the TM and found functional bilateral symmetry in its AgNORs. Furthermore, we demonstrate the existence of significant differences (P < 0.001) between sexes and between two phases of the oestrous cycle studied (oestrous-dioestrous) in the parameter of number of AgNORs per neuron. Hormonal manipulation of the TM in the rat during the two periods, postnatal or adult, shows the importance of the activational effect of the hormones on the activity of cellular protein synthesis.

Aging↗
PubMed1996

Behaviour laterality in male rats: influence of practice and stress.

During recent decades, the existence of cerebral and behavioural asymmetries has been manifested in many different animal species. In this work, the asymmetric spatial preference recorded in the water T-maze has been analysed. Fifty-five male rats were tested in this maze for 8 consecutive days. Spatial preference, the number of times each arm was chosen, and the percentages of animals that showed right, left, or no spatial preference were calculated. The results show the evolution of this asymmetric behaviour. Most of the animals tested preferred the right arm (populational laterality). Recently, the influence of factors such as stress and practice in the process of acquiring this behaviour has been investigated. We used 40 male rats divided into two groups with two different stress levels: water temperature at 21 degrees C and 14 degrees C. Our results, based on these two criteria, hypothesize that both variables, stress and practice, are involved in the acquisition of spatial preference behaviour.

Animals↗
PubMed1996

The development of oxidative metabolism in diencephalic structures of the rat: a quantitative study.

A new method for quantitative determination of cytochrome oxidase (C.O.) activity was applied to diencephalic structures of the limbic system that are closely connected anatomically, that is, the mammillary bodies (MB) and the anterior nucleus of the thalamus (AT). This method makes it possible to easily evaluate the oxidative metabolic capacity of brain regions, an index of their functionality. By using this technique, we studied the postnatal development of both structures in Wistar rats of 14, 21, 30, and 120 days of age. Furthermore, animals of 730 days were included in order to evaluate the effects of aging on C.O. activity of these structures. The results showed a significant increase in the C.O. activity of the subdivisions of the AT, its levels remaining constant until the adult age, with a significant decrease in its activity in aged animals. In the MB, only the increase in C.O. activity of the medial mammillary nucleus (pars medialis) was significant until the adult age. A decrease of C.O. values with aging was significant only in the lateral mammillary nucleus. These data suggest that there is a wide heterogeneity in the maturation and aging of brain oxidative metabolism in diencephalic structures.

Aging↗
PubMed1996

Ethanol- and diazepam-induced cytochrome oxidase activity in mammillary bodies.

This study aims to analyze the effect of the administration of diazepam and alcohol on cytochrome c oxidase activity (COX) in the mammillary bodies (MB) with a quantitative densitometry method. The histochemical reaction of the COX is used as a reflection of energy consumption. Our results show an increase in the COX activity after treatment with diazepam in the different nuclei of MB: medial medial nucleus (MMNm), lateral medial nucleus (MMN1), and lateral nucleus (LMN) of the MB, the MMNm and LMN being significantly more active compared to the MMN1. Furthermore, the consequences of administering these drugs become manifest in spatial learning (water T maze). The performance in a spatial discrimination task did not prove to be impaired.

Animals↗
PubMed1996

Functional sexual differences in rat mammillary bodies: a quantitative Ag-NOR study.

The mammillary bodies of the posterior hypothalamus are one of the CNS structures in which structural sexual dimorphism has already been described. This study quantifies the argyrophilic nucleolar organizer regions (NORs) of the neurons from this region in the male and female rats, the latter during two major phases of the estrous cycle (estrus-diestrus). The number and relative area of these NORs stained with a silver nitrate technique are considered as an index of the global protein synthesis of the neurons in the different nuclei from the mammillary bodies. Our results show the existence of statistically significant differences between sexes and estrous cycle phases. These findings suggest a significant influence of gender and the hormonal state on the neural activity of the MB.

Animals↗
PubMed1996

The avian eggshell extracellular matrix as a model for biomineralization.

The avian eggshell is a complex, extracellularly assembled structure which contains both mineralized and non-mineralized regions. The composition of the hen eggshell organic matrix was examined by immunohistochemistry with antibodies to different extracellular matrix molecules. Type I collagen is found in the shell membranes, but only after treatment of the tissue sections with pepsin. When incomplete eggshells are removed from the oviduct and immunostained, type I collagen can be detected in the shell membranes without pepsin treatment. The shell membranes, which are non-mineralized, also contain type X collagen, and this immunostaining does not require pepsin treatment. The occurrence of type X collagen in the shell membranes is surprising, since this collagen has not been found in any tissue other than hypertrophic cartilage. Immunostaining for various glycosaminoglycans shows the presence of keratan sulfate and dermatan sulfate. Several different antibodies to keratan sulfate stain different regions of the eggshell; one keratan sulfate epitope is prominent in the calcium reserve assemblies. Dermatan sulfate staining is very intense in the palisade region. Demineralized matrix from the palisade region was extracted with guanidine and fractionated by ion exchange chromatography. A approximately 200-kDa dermatan sulfate proteoglycan is found in these extracts, along with a number of protein components. This preparation was tested for its ability to affect calcium carbonate crystal formation in vitro. Pieces of demineralized shell membranes were used as a substrate for crystal formation and various amounts of the palisade matrix dermatan sulfate proteoglycan preparation were added to the solution from which the crystals were formed. This material causes a concentration-dependent change in crystal morphology to one in which the crystals are smaller and more rounded, which more closely approximates the crystals normally observed in eggshells. These results suggest that the dermatan sulfate proteoglycans may be important in modulating crystal morphology in the hen eggshell and correlate with mineralization-modulating biomolecules from other calcified tissue, which are generally anionic.

Animals↗