Biomedical subjects

D Tolivia

Publications and source records attributed to D Tolivia.

At least 19 recordsLinked to original sources

PubMed1996

Neurohormone melatonin prevents cell damage: effect on gene expression for antioxidant enzymes.

It is well known that porphyrins cause a toxic light-mediated effect due to their capability to generate free radicals. Several reports have proved that melatonin is a potent free radical scavenger. The aim of this work has been to study the ability of melatonin to prevent the cell damage caused by porphyrins in the Harderian gland of female Syrian hamsters. Cell injury was evaluated estimating the percentage of damaged cells found in the gland and analyzing the degree of this damage at ultrastructural level. To explain the mechanism by which this hormone could prevent the cell damage caused by porphyrins, its capability to both decrease porphyrin synthesis and increase the mRNA levels for antioxidant enzymes was evaluated. Our results demonstrate that melatonin administration decreases the percentage of damaged cells, porphyrin synthesis, and aminolevulinate synthase (ALA-S) mRNA levels and increases the mRNA levels for manganese superoxide-dismutase and copper-zinc superoxide dismutase. When observed under an electron microscope, the lesions in the clear cells of the treated females were much less severe than in the corresponding cells of the control animals. Melatonin exerts a cytoprotective effect by inhibiting the ALA-S gene expression (and so porphyrin synthesis) and by raising the mRNA levels for several antioxidant enzymes.

5-Aminolevulinate Synthetase↗

PubMed1994

Porphyrin accumulation in the harderian glands of female Syrian hamster results in mitochondrial damage and cell death.

BACKGROUND: The Harderian glands of female Syrian hamsters contain very high concentrations of protoporphyrin (in the range of micrograms per mg of tissue) which accumulate in the tubulo-alveoli of the gland. We have studied the process of synthesis, accumulation, and secretion of this cyclic compound by the secretory cells of the hamster Harderian glands. METHODS: The animals used were female Syrian hamster of 15, 35, 75, 180, and 360 days of age. Items first examined were (1) percentage of the "clear cells," (2) area occupied by intraluminal porphyrins, and (3) histological characteristics of "clear cells" by light and transmission electron microscopy (TEM). In a second study the total content of porphyrins was determined. Finally, the levels of mRNA for the enzyme aminolevulinate synthase (ALV-S) were measured. RESULTS: In the glands of female hamsters, both the tissue concentration and the intraluminal area occupied by protoporphyrin correlate with the appearance of a special type of cell (clear cells) which show signs of cell degeneration. In addition, the expression of the gene for ALV-S, which is the limiting enzyme in porphyrin production, also parallels the relative number of clear cells. Analyzed under TEM, these clear cells display dilated mitochondria and short and swollen endoplasmic reticulum cisternae. In a late phase of necrosis, the nuclear envelope appears disorganized with scarce chromatin. The mitochondria undergo complete destruction, resulting in electron-dense bacillary formations which progressively coalesce in large and dense areas of protoporphyrin. The cell dies after this accumulation, being secreted by a "cytogen" mechanism. CONCLUSIONS: In view of our results, the Harderian gland of female Syrian hamster may provide a useful model for the study of the mechanism by which the anomalous accumulation of protoporphyrin induces cell damage in human protoporphyria.

5-Aminolevulinate Synthetase↗

PubMed1994

Differential staining of nerve cells and fibres for sections of paraffin-embedded material in mammalian central nervous system.

A differential staining method is described of myelinated fibres and nerve cell bodies applicable to sections of mammalian, including human, central nervous system specimens embedded in paraffin wax. Experimental and human necropsy material fixed in acetic paraformaldehyde in phosphate buffer was used. Sections of 15-20 microns in thickness were obtained, attached to slides, deparaffinized and hydrated. After hydration, sections are oxidized (30 s) in 2% potassium permanganate, bleached (1 min) in 5% oxalic acid and rinsed in distilled water. Staining is for 2-5 h in the following solution: 0.06% thionin, 1% formaldehyde, 10% acetic acid in distilled water. Sections are subsequently washed in distilled water, dehydrated through 96% and absolute ethanol, cleared in eucalyptol and mounted in Eukitt. Using the method described in the present paper, a differential coloration of myelin and neurons is obtained. Myelinated fibres appear red, whereas nerve cell bodies and glial nuclei are stained blue. This procedure provides a high contrast between myelin and cells suitable for observation and photography of sections. Simultaneous and differential coloration of both myelin and cells is easily and directly obtained with constant and homogeneous results.

Animals↗

PubMed1994

Polychromatic staining of epoxy semithin sections: a new and simple method.

A simple, rapid method is described for the polychromatic coloration of semithin sections, which is applicable to material routinely processed for transmission electron microscopy. Material fixed with a glutaraldehyde-paraformaldehyde mixture and postfixed in osmium tetroxide with or without potassium ferrocyanide and embedded in different types of resin (Durkupan-ACM, Spurr resin, Taab resin) can be used. Constant and homogenous results are obtained with this technique, the staining procedure being achieved at room temperature in no more than 10 min. Sections of 0.5-1 microns in thickness are oxidised and bleached. After washing, sections are stained in two steps with carbol methylene blue/carbol gentian violet solution and pararosaniline solution. Using the method described in this paper, a polychromatic coloration of the different cells and tissues was obtained (epithelial cells in various shades of blue-violet, connective tissue and elastic laminae of blood vessels in pink or red, etc.). This procedure provides greater contrast between cytoplasm and nuclei, and among the different types of cells and tissues than is seen with toluidine blue, which is very useful for observation and photography of semithin sections. Polychromatic methods found in the literature are normally complex and require a lengthy staining time or cannot be applied on material routinely processed for transmission electron microscopy. Our method is simple, rapid and can be used on any type of material routinely processed for transmission electron microscopy and embedded in epoxy resins.

Animals↗

PubMed1994

Photoperiod and the pineal gland regulate the male phenotype of the Harderian glands of male Syrian hamsters after androgen withdrawal.

The Harderian glands of Syrian hamsters exhibit a marked sexual dimorphism in cell types and porphyrin production. The glands of male hamsters have two secretory cell types (Type I and II) while the glands of females consist of a single secretory cell type (female Type I) and large intraluminal deposits of porphyrins. Besides androgens, there is evidence that the pineal gland, through the secretion of melatonin, contributes to the maintenance of the "male" and "female" phenotypes. In this study, we investigated the effects of castration, short photoperiods, and pinealectomy on the distribution of secretory cells and porphyrin deposits in the Harderian glands of male Syrian hamsters. Two groups of animals were maintained in long days (14 hr light/day). Hamsters in one group were left intact and those in the other were castrated. Another three groups were maintained in short days (8 hr light/day); these animals were either left intact, castrated, or both castrated and pinealectomized. The duration of the experiment was 5 weeks. Castration of long photoperiod-exposed animals resulted in a significant drop in the number of Type II cells and a large increase in the porphyrin deposits (P < 0.01). However, castrated animals exposed to short photoperiod showed a significant smaller change in both parameters compared with those exposed to long days (P < 0.05). Pinealectomy prevented the effects of short days in castrated animals. No significant changes were observed in the relative number of mitotic figures or in the number of cell nuclei, indicating that the changes observed were due in part to a transformation of Type II into Type I cells. In a second experiment, male hamsters were injected daily either with 25 micrograms of melatonin late in the afternoon or with the saline for 8 weeks. The administration of melatonin resulted in a significant (P < 0.05) increase in the percentage of Type II cells. We conclude that when circulating androgens are very low or absent, pineal melatonin maintains the male phenotype in the Syrian hamster Harderian gland.

Androgens↗

PubMed1993

Development and androgen regulation of the secretory cell types of the Syrian hamster (Mesocricetus auratus) Harderian gland.

The secretory cell types of the hamster Harderian glands were studied in both male and female Syrian hamsters. As previously demonstrated, female hamsters showed a single secretory cell type (type I), while male hamsters displayed two secretory cell types (type I and type II). Type-II cells were observed after the first month of age correlating with the increase in testosterone levels. The administration of testosterone to adult female hamsters resulted in a marked increase in the percentage of type-II cells without a significant increase in the number of mitotic figures. Very low levels of serum testosterone were able to maintain the percentage of type-II cells. Castration of male hamsters produced a decrease in the percentage of type-II cells. This drop correlated with the reduction in serum testosterone levels. The chronic administration of a luteinizing hormone-releasing hormone agonist to male Syrian hamsters induced a significant reduction in both serum luteinizing hormone and testosterone. However, the percentage of type-II cells was similar to that of control hamsters suggesting that very low levels of circulating testosterone are able to maintain the percentage of type-II cells. In a final experiment male Syrian hamsters were treated with the antiandrogen cyproterone acetate. No changes were observed in the percentage of type-II cells, whereas serum luteinizing hormone and testosterone levels were significantly modified. We concluded that (1) type-II cells differentiate from type-I cells; (2) gonadal androgens are the major factor controlling this differentiation; and (3) the disappearance of type-II cells after androgen deprivation occurs through holocrine and apocrine mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗

PubMed1993

The Harderian gland of the rodent Octodon degus: a structural and ultrastructural study.

Harderian glands from male and female Octodon degus were examined by light and transmission electron microscopy. Two types of secretory units, designated as type I and type II, were observed. Type I secretory units comprise three types of epithelial cells: Cells packed with numerous lipid droplets (Type a), cells with few lipid droplets (Type b), and cells with numerous mitochondria and a very well developed Golgi complex (Type c). Type II secretory units were found exclusively in female Octodon degus and comprised a type of secretory cells which contained numerous basophilic granules in their apical cytoplasm. In addition, in female Octodon degus, clusters of lymphocyte-like cells and plasmatic cells were also observed. The vascularization of the gland appeared very well developed. The most unique feature of the blood supply was the existence of large sinusoidal vessels extremely variable in shape. In the medullar region, the sinsoidal wall adapts its contour to that of the tubuloalveolar surface. Unmyelinated and myelinated nerve fibers were found in the connective stroma of the gland.

Animals↗

PubMed1993

Mast cells in the Harderian gland of female Syrian hamsters during the estrous cycle and pregnancy: effects of the light/dark cycle.

The number of identifiable mast cells and the intraluminal area occupied by porphyrin deposits was studied on semithin sections from female hamster Harderian glands during the estrous cycle and pregnancy. Although the serum levels of estradiol, progesterone, luteinizing hormone and follicle stimulating hormone exhibited significant changes throughout the cycle, no correlation between these changes and the variations in the number of recognizable mast cells was observed. However both during diestrous 1 and proestrous cycles, the number of identifiable mast cells was higher at midnight than at noon (in 14 h light:10 h dark photoperiod with lights on at 07:00 h). A more exhaustive study revealed the presence of 'degranulated mast cells' which were not stained with toluidine blue. Thus, a diurnal cycle in degranulation might occur in the Harderian glands from female hamsters. No significant variations were observed in the area occupied by intraluminal porphyrin deposits during the estrous cycle. However, both the relative number of mast cells and the area occupied by intraluminal porphyrins decreased from day 4 of pregnancy to day 14 showing a strong correlation. The Harderian glands from female Syrian hamsters might provide a useful model for the study of mast cell degranulation during porphyria.

Animals↗

PubMed1992

Female Syrian hamster Harderian gland: development and effects of high environmental temperature and melatonin injections on histology and porphyrin deposits.

We have investigated the development of the Harderian glands of female Syrian hamsters from birth to 8 months of age. The effects of melatonin injections on Harderian gland histology and porphyrin deposits of female hamsters exposed to two different temperatures were also studied. The morphology of the Harderian glands from 30-day-old female hamsters resembled those of sexually mature adult animals. The intraluminal area occupied by porphyrins increased significantly between 20 to 30 days of age. However, the relative number of mast cells per mm2 rose between 30 to 90 days. Both porphyrins and mast cell numbers appeared clearly reduced in the 8-month-old group. Secretory cells characterized by large lipid droplets (type II cells) were not observed. Daily afternoon injections of 25 micrograms of melatonin to female hamsters exposed to 22 degrees C for 14 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the intraluminal area occupied by porphyrins, a reduction of the number of mast cells per mm2, and in a marked augmentation of the number of type II cells per mm2. Although the administration of similar dosages of melatonin to hamsters exposed to an environmental temperature of 32 degrees C did not interrupt estrous cycles, a clear reduction of the area occupied by porphyrins was observed. However, the number of mast cells and type II cells per mm2 was unaffected in these animals. Our results suggest that hormones other than ovarian steroids are involved in the regulation of the female hamster Harderian glands. The possible role of melatonin on Harderian gland metabolism is discussed.

Animals↗

PubMed1992

Lymphoid cells in the harderian gland of the rodent Octodon degus.

The Harderian gland of the degu (Octodon degus) is composed of tubulo-alveolar secretory units that share most of morphological features found in the Harderian glands of other rodents. However, a peculiar characteristic observed in the glands of female degus is the existence of lymphoid cell clusters within the connective tissue surrounding the secretory adenomeres. Lymphocytes and lymphoblasts are found associated with blood vessels and especially with nerve bundles in the medullary region of the gland. Occasionally, macrophages and plasma cells are also observed. Although the Golgi apparatus appears well developed, the ultrastructural characteristics of most of these lymphoid elements correspond to those of inactive lymphocytes. Unmyelinated fibers containing clear and dense-core vesicles are found closely related to lymphocytes. On some occasions, lymphocytes present extensive areas of apposition with structures resembling intercellular junctions. The analogy of the lymphoid clusters reported in this study with those described in the avian Harderian gland is discussed.

Animals↗

PubMed1992

Development and hormonal regulation of mast cells in the Harderian gland of Syrian hamsters.

The morphological features and relative number of mast cells per mm2 were studied in the Harderian glands of male and female Syrian hamsters (Mesocricetus auratus) under different experimental conditions. The structural and ultrastructural characteristics of Harderian mast cells corresponded to those of connective tissue mast cells. The Harderian glands from female hamsters contained more mast cells than those of male hamsters. A subcutaneous implant of testosterone (2 mg/24 mg beeswax) resulted in a rapid decrease in the number of recognizable mast cells 6 h after the implantation. Neither orchidectomy nor ovariectomy significantly altered the relative number of mast cells. However, the daily subcutaneous injection of 20 IU of human chorionic gonadotropin during 20 days resulted in a significant decrease of identifiable mast cells. The administration of another steroid such as progesterone or the induction of states of hypo- and hyperthyroidism did not alter the distribution of mast cells in the Harderian glands of female Syrian hamsters.

Age Factors↗

PubMed1992

Effects of human chorionic gonadotropin and progesterone administration on porphyrin biosynthesis and histology of the Harderian glands in male and female Syrian hamsters.

We investigated the influence of hCG and progesterone on the control of porphyrin biosynthesis and histology in the Syrian hamster Harderian glands. Castration of male hamsters caused a marked elevation in porphyrin biosynthesis as revealed by the concentrations of porphyrins and the mRNA levels of the porphyrin pathway rate-limiting enzyme, 5-aminolevulinate synthase (ALV-S). Injection of hCG into castrated male hamsters also resulted in a significant increase in both porphyrin concentrations and levels of ALV-S mRNA compared with those in saline-injected castrated hamsters. Type II cells, which are filled with large lipid vacuoles and are characteristic of male phenotype, disappeared after castration, but administration of hCG partially prevented this change. On the other hand, neither administration of hCG nor progesterone implants could increase the very high porphyrin concentrations and ALV-S mRNA levels characteristic of female Syrian hamsters. As in the case of castrated male hamsters, injections of 20 IU hCG to female Syrian hamsters increased the relative number of Type II cells per square millimeter, whereas progesterone administration did not modify the relative number of Type II cells. These results indicate that hCG can modify Harderian gland morphology in both male and female hamsters and can exert a positive control in the expression of ALV-S gene in castrated male hamsters.

5-Aminolevulinate Synthetase↗

PubMed1992

The pineal gland of the trumpet-tailed rat (Octodon degus).

The structure and ultrastructure of the pineal gland of the degu or trumpet-tailed rat (Octodon degus), a rodent inhabiting tropical-equatorial areas, was examined under light and electron microscopy. On the basis of its form, size, and location, the pineal gland of the degu is classified as a proximal or "A" type. The connective tissue appeared poorly developed and the gland contained non-fenestrated capillaries. A single population of typical pinealocytes was found. In addition, a small number of glial cells and cells with electron dense bodies appeared scattered throughout the gland. Cells with dense granules were found isolated or forming small groups always in close proximity to blood vessels. Numerous sympathetic nerve fibers with small dense-core vesicles were found. Also, some myelinated nerve fibers were observed. The physiological significance of the presence of large electron-dense granules in some pineal cells and their particular location around the blood vessels in discussed.

Animals↗

PubMed1991

A new rapid silver impregnation for neuronal bodies on methacrylate sections.

A simple and rapid method for the impregnation of neuronal bodies applicable to methacrylate embedded sections is described in the present paper. Sections of 10-12 microns in thickness were attached to slides, placed in mordant for 1 min, rinsed in distilled water and impregnated in ammoniacal silver solution for 1 min. They were then rinsed in absolute ethanol for 30 s and developed in 50% formalin. Sections were toned in 0.25% gold chloride, reduced in 10% oxalic acid and fixed in 5% sodium thiosulfate. After washing, the sections were dehydrated through 90% and absolute ethanol, cleared in eucalyptol, and mounted in the usual way. When this method is used most of the neuronal somata and proximal dendritic trees are impregnated. Frequently some glial cell are also weakly impregnated but their density does not obscure the neurons.

Animals↗

PubMed1991

Chronic administration of melatonin induces changes in porphyrins and in the histology of male and female hamster harderian gland: interrelation with the gonadal status.

In this paper, we have investigated the influence of melatonin on the histology and porphyrin content of the Syrian hamster Harderian glands. Daily afternoon injections of 25 micrograms of melatonin to female hamsters for 12 weeks resulted in the discontinuity of estrous cyclicity, a marked decrease in the Harderian gland intraluminal area occupied by porphyrins, and in a significant rise in the number of Type II cells. A similar decrease in porphyrins was observed after 8 weeks of ovariectomy. However, if the melatonin injections were given for only 8 weeks (without inducing gonadal atrophy), no changes were observed in the area occupied by intraluminal porphyrins, suggesting that the effects of melatonin in female Syrian hamsters might be associated with the subsequent gonadal atrophy. Castration of male hamsters induced a significant increase in porphyrins and a clear drop in the number of Type II cells. These changes were totally prevented when melatonin was administered daily from the day of castration. Our results suggest that melatonin, at least in male Syrian hamsters, plays a role in Harderian metabolism, acting directly on the Harderian secretory cells or indirectly through pituitary hormones.

Animals↗

PubMed1990

Ultrastructural study of the cellular types in the pineal organ of Gambusia affinis (teleost).

The pineal organ of Gambusia affinis was studied via light and electron microscopy. The cell types studied included photoreceptor cells, supporting cells, and a third cell type. The photoreceptor cells, which appear to form clusters, are divided into four regions: outer segment, inner segment, cell soma, and synaptic pedicle. Synaptic ribbons are commonly observed in the synaptic pedicle. The supporting cells separate the photoreceptor cells from the thick basal lamina that surrounds the entire pineal organ. The supporting cells show highly organized membrane formations, some lipid-like inclusions, and a diplosome. One of the centrioles gives rise to an invaginated cilium. The third cell type is observed infrequently and appears to be located mainly in the vicinity of the outer segments. The morphological characteristics of this cell type are similar to those of phagocytic cells. The ultrastructural features of the pineal organ of G. affinis are compared with those of other teleosts.

Animals↗

PubMed1990

Ultrastructure of the blood vessels in the Harderian gland of the hamster (Mesocricetus auratus): existence of sinusoids.

The Harderian gland blood supply of female and male hamsters was studied using light and electron microscopy. A profuse vascularization surrounding secretory acini was observed. Among the blood vessels, the existence of large and irregular sinusoidal capillaries was apparent. These sinusoids appeared in close association to the basal aspect of the secretory cells. Typical, small, fenestrated capillaries were also observed within the connective tissue. The existence of this particular vascularization together with other morphological features of the secretory cell basal pole suggest a possible endocrine function of these orbital glands.

Animals↗

PubMed1989

Differential thionin block staining of nerve cells and fibers for paraffin-embedded material in mammalian central nervous system.

A differential staining method of myelinated fibers and nerve cell bodies applicable to whole blocks of mammalian central nervous tissue is described. Experimental material fixed by perfusion or necropsy material fixed in block can be used. Blocks of 2 mm in thickness were obtained with a vibratome, immersed in 50% ethanol for 7 h and stained for 1 week in the following solution: 0.3% thionine, 5% formaldehyde and 5% acetic acid. After the staining period the blocks were washed in distilled water, dehydrated through graded alcohols, cleared in butyl acetate and infiltrated in paraffin. Sections of 10 microns in thickness were obtained, attached to slides, dewaxed in xylene and coverslipped with mounting media in the usual manner.

Animals↗