Jorge Tolivia - Academia.edu (original) (raw)
Papers by Jorge Tolivia
International journal of molecular sciences, Apr 10, 2024
PubMed, May 9, 2000
The vestibular complex has been studied since the fifties. The general conclusion of research on ... more The vestibular complex has been studied since the fifties. The general conclusion of research on many mammals is that the vestibular complex has four main vestibular nuclei and some less constantly associated neuronal groups. The general distribution of the four main vestibular nuclei in the hamster does not differ substantially from that of other mammals: humans, many primates, cat, opossom, rabbit, chinchilla, guinea pig, etc. Of the many associated groups that have been described, we clearly identified groups <>, <>, <>, <>, and the interstitial nucleus of the vestibular nucleus of Cajal. However, the latter seems to be less developed than in other mammals. We present results and a map of serial sections of the vestibular area showing the most characteristic anatomic relations with brainstem structures, and the most relevant cytomorphometric results compared with other mammals.
PubMed, Oct 1, 1999
The hypothalamo-neurohypophysial tract of young, adult and aged male hamsters was studied at late... more The hypothalamo-neurohypophysial tract of young, adult and aged male hamsters was studied at lateral and ventral regions of hypothalamus by means of electron microscopy. Neurosecretory swelling axons (Herring bodies) were usually found as classically described containing abundant neurosecretory granules, mitochondria, few microtubules and profiles of smooth endoplasmic reticulum in all groups of age. However, in aged hamsters, starting at 18-month-old subjects, we observed that the size of some neurosecretory axons was highly increased. Autophagic and degenerative features were seen in the larger ones. These data could suggest abnormal axonal storage or axonal transport blocked during aging. The implications in the role of hypothalamus-neurohypophysial system during aging are discussed.
PubMed, Oct 1, 1995
The present paper describes the presence of a special cell located in the ependymal wall at the l... more The present paper describes the presence of a special cell located in the ependymal wall at the level of the paraventricular nucleus. At this level, ultrastructural observation of these ependymal cells, unlike most other mammalian species, shows the presence of nucleolus-like bodies in their cytoplasm and occasionally basal processes. These processes appear perpendicular to the ependymal surface and end in contact with the basal membrane of hypothalamic capillaries. Mitochondria, endoplasmic reticulum and numerous filaments are present in the basal processes. Nucleolus-like bodies or nematosomes consist of round or ovoid unbound masses of granular appearing material of variable density located in the apical cytoplasm of the cells. Some of their ultrastructural characteristics are similar to other ependymal specialized cells which are classically termed tanycytes. These findings point out the possibility that those special cells may also be implicated in a ventricle-blood vessel communication.
Cells Tissues Organs, 1987
Neuronal characteristics and location of the neurosecretory, magnocellular, fuchsin-paraldehyde-p... more Neuronal characteristics and location of the neurosecretory, magnocellular, fuchsin-paraldehyde-posi-tive (FA+) system of the fowl are described at the light-microscopic level on serial semithin sections. Three nuclei make up this system, the nucleus supraopticus, n. magnocellularis interstitialis and n. paraventricularis. These nuclei display magnocellular neurons, not showing a parvocellular component. The neurons of the three nuclei showed a scattered pattern of distribution and a dense surrounding neuropil. Groups formed by magnocellular neurons were found in the three nuclei and groups formed by one magnocellular and a parvocellular neurons were only found in the n. magnocellularis interstitialis and in the n. paraventricularis.The presence of neurons in apposition to blood vessels was frequent in the magnocellular FA+ system of the domestic fowl.
Journal of Neuroscience Methods, Feb 1, 1991
A simple and rapid method for the impregnation of neuronal bodies applicable to methacrylate embe... more 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.
PubMed, Sep 15, 1997
We have analyzed the effect of 1,25-dihydroxyvitamin D3 on the expression of the gene encoding ap... more We have analyzed the effect of 1,25-dihydroxyvitamin D3 on the expression of the gene encoding apolipoprotein D (apoD), a protein component of the human plasma lipid transport system that is overproduced by a specific subset of breast carcinomas. Northern blot analysis revealed that 1,25-dihydroxyvitamin D3 strongly up-regulated apoD mRNA levels in T-47D human breast cancer cells in a time- and dose-dependent manner. The potency of this vitamin as an inducer of apoD expression was stronger than the effect observed for such steroid hormones as androgens and progesterone, described previously as hormonal up-regulators of apoD expression in these cells. A time course study demonstrated that the induction of apoD mRNA reached a level of 5-fold over the untreated cells after 48 h of incubation in the presence of 10(-7) M 1,25-dihydroxyvitamin D3. A dose-response analysis showed that a 10(-6) M concentration of this vitamin consistently induced a maximal accumulation of 7-fold over the control cells. Similar up-regulatory effects on the apoD gene expression were obtained by treatment of T-47D cells with 1,25-dihydroxyvitamin D3 analogues, including MC 903, which is relatively devoid of hypercalcemic side effects in clinical applications. Western blot analysis revealed that the inductive effect of 1,25-dihydroxyvitamin D3 was also reflected at the protein level as an increase of immunoreactive protein in the conditioned media of vitamin-treated cells. This increased expression of apoD was accompanied by an inhibition of cell growth and morphological changes in T-47D cells. By contrast, we did not detect any inductive effect of 1,25-dihydroxyvitamin D3 on apoD gene expression in MDA-MB-231 cells, which are refractory to the growth-inhibitory effects of this compound. On the basis of these results, we propose 1,25-dihydroxyvitamin D3 as an important regulator of the expression of the apoD gene in breast carcinomas. We also suggest that apoD may be of interest as a biochemical marker of the action of 1,25-dihydroxyvitamin D3 derivatives in current studies using these compounds as inhibitors of breast cancer cell growth or as chemotherapeutic agents in the prevention of breast cancer.
PubMed, Feb 1, 1994
Apolipoprotein D (apo D) is a glycoprotein involved in the human plasma lipid transport system an... more Apolipoprotein D (apo D) is a glycoprotein involved in the human plasma lipid transport system and present at large amounts in cyst fluid from women with gross cystic disease of the breast. Apo D expression in breast carcinomas was examined by immunoperoxidase staining of a series of 163 tumors. A total of 60 (36.8%) tumors were negative for apo D immunostaining, 28 (17.2%) carcinomas were weakly positive, 33 (20.2%) were moderately stained, whereas the remaining 42 (25.8%) tumors were strongly stained with the specific antibodies. No significant correlation was found between apo D content and tumor size, lymph node involvement, or biochemical parameters such as estrogen receptors, cathepsin D, or pS2 protein. However, the finding of a significant association between apo D and menopausal status of patients or differentiation grade of tumors, with apo D values being lower in tumors from premenopausal women or in poorly differentiated carcinomas, suggested a potential value of this glycoprotein as a prognostic factor in breast cancer. Preliminary analysis of relapse-free survival and overall survival in a subgroup of 152 women with a mean follow-up of 42 months confirmed that low apo D values were significantly associated to a shorter relapse-free survival and poorer survival. According to these data, we propose that apo D in combination with other well-established prognostic factors may contribute to more accurately identify subgroups of breast cancer patients with low or high risk for relapse and death.
PubMed, Apr 1, 2006
Apolipoprotein D (apo D), a lipocalin transporter of small hydrophobic molecules could play an im... more Apolipoprotein D (apo D), a lipocalin transporter of small hydrophobic molecules could play an important role in several neurodegenerative diseases. However, its role in those diseases remains unclear. Increments of apo D have been reported in relation with injury and degeneration in the nervous system. Recently increases of apo D level have been reported in schizophrenia, a neuropathologic disease where the oxidative stress and lipid abnormalities may be involved. Apo D could act as a sequestering molecule binding excess of arachidonic acid in cells. In order to determine the relationship between apo D expression and other neurodegenerative pathologies related to oxidative damage, we studied the presence of apo D in the substantia nigra of control and Parkinson disease (PD) subjects. We found dopaminergic neurons were not immunoreactive for apo D, control or PD subjects. However, surrounding glial cells showed immunostaining for apo D and signal increases in PD cases. These findings support the role of apolipoprotein D in neuroprotection and the importance of glia in the amount of this protein in the central nervous system.
Journal of Neuroscience Methods, May 1, 1985
A new and simple method for the simultaneous staining of nerve cells and fibers is described. The... more A new and simple method for the simultaneous staining of nerve cells and fibers is described. The use of formol-thionin under controlled conditions of concentration and pH provides a highly reliable method for the staining of nerve cells in blue and fiber tracts in red, making any posterior differentiation redundant. This technique provides constant and reproducible results allowing simultaneous staining of many sections.
British Journal of Cancer, Sep 1, 1993
Histochemistry (Berlin), 1994
Journal of Microscopy, Oct 1, 1987
Anatomy and Embryology, Dec 1, 1992
Otolaryngology-Head and Neck Surgery, Aug 1, 1995
Breast Cancer Research and Treatment, 1994
We have studied the hormonal regulation of the gene encoding Zn-a2-glycoprotein (Zn-a2-gp), a hum... more We have studied the hormonal regulation of the gene encoding Zn-a2-glycoprotein (Zn-a2-gp), a human protein with a high degree of amino acid sequence similarity to class I histocompatibility antigens that is produced by a specific subset of breast carcinomas. Northern blot analysis revealed that dexamethasone and 5a-dihydrotestosterone strongly induced the accumulation of Zn-a2-gp mRNA in T-47D human breast cancer cells.
Journal of Neuroscience Methods, Nov 1, 1987
A simple and rapid method for the impregnation of neuronal bodies applicable to methacrylate embe... more 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.
Journal of Neuroscience Methods, Jul 1, 1986
A reconstruction program is described for personal computers, permitting threedimensional image r... more A reconstruction program is described for personal computers, permitting threedimensional image reconstructions from serial sections. This program also makes it possible to calculate the volume of structures from their twodimensional images in histological sections. In this paper we show a program written in BASIC and debugged on a Sharp MZ-700 personal computer, equipped with the Sharp MZ-1P01 plotter. The program is explained in detail and is easily adapted to run on any personal computer.
Mechanisms of Ageing and Development, Aug 1, 1997
A quantitative study regarding the age-related changes occurring in the nucleus and the somatic o... more A quantitative study regarding the age-related changes occurring in the nucleus and the somatic organelles of neurosecretory magnocellular neurons of the hypothalamo neurohypophyseal system (HNS) was carried out in the hamster at six age-points during animal life. The magnocellular cells of both parts of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of male Syrian hamsters between 3 and 30 months of age were examined ultrastructurally. Cells of all age groups present the same morphological ultrastructure. Standard manual morphometric techniques are used to calculate the following parameters related directly or indirectly with cellular activity: nuclear area, nucleolar area, nuclear invagination index and volumetric fractions of some intracellular structures (Golgi apparatus, mitochondria, rough endoplasmic reticulum and lipofuscin). With respect to the cell nucleus, the parameters are not modified during aging. No significant differences in the volume density of subcellular components, except lipofuscin, were detected at the age groups studies. However, there is a positive linear trend among all parameters and age except for the rough endoplasmic reticulum. Our results suggest maintenance of the synthetic activity of the magnocellular neurons in the hamster during aging but in no case an increase in their metabolic activity.
International journal of molecular sciences, Apr 10, 2024
PubMed, May 9, 2000
The vestibular complex has been studied since the fifties. The general conclusion of research on ... more The vestibular complex has been studied since the fifties. The general conclusion of research on many mammals is that the vestibular complex has four main vestibular nuclei and some less constantly associated neuronal groups. The general distribution of the four main vestibular nuclei in the hamster does not differ substantially from that of other mammals: humans, many primates, cat, opossom, rabbit, chinchilla, guinea pig, etc. Of the many associated groups that have been described, we clearly identified groups <>, <>, <>, <>, and the interstitial nucleus of the vestibular nucleus of Cajal. However, the latter seems to be less developed than in other mammals. We present results and a map of serial sections of the vestibular area showing the most characteristic anatomic relations with brainstem structures, and the most relevant cytomorphometric results compared with other mammals.
PubMed, Oct 1, 1999
The hypothalamo-neurohypophysial tract of young, adult and aged male hamsters was studied at late... more The hypothalamo-neurohypophysial tract of young, adult and aged male hamsters was studied at lateral and ventral regions of hypothalamus by means of electron microscopy. Neurosecretory swelling axons (Herring bodies) were usually found as classically described containing abundant neurosecretory granules, mitochondria, few microtubules and profiles of smooth endoplasmic reticulum in all groups of age. However, in aged hamsters, starting at 18-month-old subjects, we observed that the size of some neurosecretory axons was highly increased. Autophagic and degenerative features were seen in the larger ones. These data could suggest abnormal axonal storage or axonal transport blocked during aging. The implications in the role of hypothalamus-neurohypophysial system during aging are discussed.
PubMed, Oct 1, 1995
The present paper describes the presence of a special cell located in the ependymal wall at the l... more The present paper describes the presence of a special cell located in the ependymal wall at the level of the paraventricular nucleus. At this level, ultrastructural observation of these ependymal cells, unlike most other mammalian species, shows the presence of nucleolus-like bodies in their cytoplasm and occasionally basal processes. These processes appear perpendicular to the ependymal surface and end in contact with the basal membrane of hypothalamic capillaries. Mitochondria, endoplasmic reticulum and numerous filaments are present in the basal processes. Nucleolus-like bodies or nematosomes consist of round or ovoid unbound masses of granular appearing material of variable density located in the apical cytoplasm of the cells. Some of their ultrastructural characteristics are similar to other ependymal specialized cells which are classically termed tanycytes. These findings point out the possibility that those special cells may also be implicated in a ventricle-blood vessel communication.
Cells Tissues Organs, 1987
Neuronal characteristics and location of the neurosecretory, magnocellular, fuchsin-paraldehyde-p... more Neuronal characteristics and location of the neurosecretory, magnocellular, fuchsin-paraldehyde-posi-tive (FA+) system of the fowl are described at the light-microscopic level on serial semithin sections. Three nuclei make up this system, the nucleus supraopticus, n. magnocellularis interstitialis and n. paraventricularis. These nuclei display magnocellular neurons, not showing a parvocellular component. The neurons of the three nuclei showed a scattered pattern of distribution and a dense surrounding neuropil. Groups formed by magnocellular neurons were found in the three nuclei and groups formed by one magnocellular and a parvocellular neurons were only found in the n. magnocellularis interstitialis and in the n. paraventricularis.The presence of neurons in apposition to blood vessels was frequent in the magnocellular FA+ system of the domestic fowl.
Journal of Neuroscience Methods, Feb 1, 1991
A simple and rapid method for the impregnation of neuronal bodies applicable to methacrylate embe... more 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.
PubMed, Sep 15, 1997
We have analyzed the effect of 1,25-dihydroxyvitamin D3 on the expression of the gene encoding ap... more We have analyzed the effect of 1,25-dihydroxyvitamin D3 on the expression of the gene encoding apolipoprotein D (apoD), a protein component of the human plasma lipid transport system that is overproduced by a specific subset of breast carcinomas. Northern blot analysis revealed that 1,25-dihydroxyvitamin D3 strongly up-regulated apoD mRNA levels in T-47D human breast cancer cells in a time- and dose-dependent manner. The potency of this vitamin as an inducer of apoD expression was stronger than the effect observed for such steroid hormones as androgens and progesterone, described previously as hormonal up-regulators of apoD expression in these cells. A time course study demonstrated that the induction of apoD mRNA reached a level of 5-fold over the untreated cells after 48 h of incubation in the presence of 10(-7) M 1,25-dihydroxyvitamin D3. A dose-response analysis showed that a 10(-6) M concentration of this vitamin consistently induced a maximal accumulation of 7-fold over the control cells. Similar up-regulatory effects on the apoD gene expression were obtained by treatment of T-47D cells with 1,25-dihydroxyvitamin D3 analogues, including MC 903, which is relatively devoid of hypercalcemic side effects in clinical applications. Western blot analysis revealed that the inductive effect of 1,25-dihydroxyvitamin D3 was also reflected at the protein level as an increase of immunoreactive protein in the conditioned media of vitamin-treated cells. This increased expression of apoD was accompanied by an inhibition of cell growth and morphological changes in T-47D cells. By contrast, we did not detect any inductive effect of 1,25-dihydroxyvitamin D3 on apoD gene expression in MDA-MB-231 cells, which are refractory to the growth-inhibitory effects of this compound. On the basis of these results, we propose 1,25-dihydroxyvitamin D3 as an important regulator of the expression of the apoD gene in breast carcinomas. We also suggest that apoD may be of interest as a biochemical marker of the action of 1,25-dihydroxyvitamin D3 derivatives in current studies using these compounds as inhibitors of breast cancer cell growth or as chemotherapeutic agents in the prevention of breast cancer.
PubMed, Feb 1, 1994
Apolipoprotein D (apo D) is a glycoprotein involved in the human plasma lipid transport system an... more Apolipoprotein D (apo D) is a glycoprotein involved in the human plasma lipid transport system and present at large amounts in cyst fluid from women with gross cystic disease of the breast. Apo D expression in breast carcinomas was examined by immunoperoxidase staining of a series of 163 tumors. A total of 60 (36.8%) tumors were negative for apo D immunostaining, 28 (17.2%) carcinomas were weakly positive, 33 (20.2%) were moderately stained, whereas the remaining 42 (25.8%) tumors were strongly stained with the specific antibodies. No significant correlation was found between apo D content and tumor size, lymph node involvement, or biochemical parameters such as estrogen receptors, cathepsin D, or pS2 protein. However, the finding of a significant association between apo D and menopausal status of patients or differentiation grade of tumors, with apo D values being lower in tumors from premenopausal women or in poorly differentiated carcinomas, suggested a potential value of this glycoprotein as a prognostic factor in breast cancer. Preliminary analysis of relapse-free survival and overall survival in a subgroup of 152 women with a mean follow-up of 42 months confirmed that low apo D values were significantly associated to a shorter relapse-free survival and poorer survival. According to these data, we propose that apo D in combination with other well-established prognostic factors may contribute to more accurately identify subgroups of breast cancer patients with low or high risk for relapse and death.
PubMed, Apr 1, 2006
Apolipoprotein D (apo D), a lipocalin transporter of small hydrophobic molecules could play an im... more Apolipoprotein D (apo D), a lipocalin transporter of small hydrophobic molecules could play an important role in several neurodegenerative diseases. However, its role in those diseases remains unclear. Increments of apo D have been reported in relation with injury and degeneration in the nervous system. Recently increases of apo D level have been reported in schizophrenia, a neuropathologic disease where the oxidative stress and lipid abnormalities may be involved. Apo D could act as a sequestering molecule binding excess of arachidonic acid in cells. In order to determine the relationship between apo D expression and other neurodegenerative pathologies related to oxidative damage, we studied the presence of apo D in the substantia nigra of control and Parkinson disease (PD) subjects. We found dopaminergic neurons were not immunoreactive for apo D, control or PD subjects. However, surrounding glial cells showed immunostaining for apo D and signal increases in PD cases. These findings support the role of apolipoprotein D in neuroprotection and the importance of glia in the amount of this protein in the central nervous system.
Journal of Neuroscience Methods, May 1, 1985
A new and simple method for the simultaneous staining of nerve cells and fibers is described. The... more A new and simple method for the simultaneous staining of nerve cells and fibers is described. The use of formol-thionin under controlled conditions of concentration and pH provides a highly reliable method for the staining of nerve cells in blue and fiber tracts in red, making any posterior differentiation redundant. This technique provides constant and reproducible results allowing simultaneous staining of many sections.
British Journal of Cancer, Sep 1, 1993
Histochemistry (Berlin), 1994
Journal of Microscopy, Oct 1, 1987
Anatomy and Embryology, Dec 1, 1992
Otolaryngology-Head and Neck Surgery, Aug 1, 1995
Breast Cancer Research and Treatment, 1994
We have studied the hormonal regulation of the gene encoding Zn-a2-glycoprotein (Zn-a2-gp), a hum... more We have studied the hormonal regulation of the gene encoding Zn-a2-glycoprotein (Zn-a2-gp), a human protein with a high degree of amino acid sequence similarity to class I histocompatibility antigens that is produced by a specific subset of breast carcinomas. Northern blot analysis revealed that dexamethasone and 5a-dihydrotestosterone strongly induced the accumulation of Zn-a2-gp mRNA in T-47D human breast cancer cells.
Journal of Neuroscience Methods, Nov 1, 1987
A simple and rapid method for the impregnation of neuronal bodies applicable to methacrylate embe... more 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.
Journal of Neuroscience Methods, Jul 1, 1986
A reconstruction program is described for personal computers, permitting threedimensional image r... more A reconstruction program is described for personal computers, permitting threedimensional image reconstructions from serial sections. This program also makes it possible to calculate the volume of structures from their twodimensional images in histological sections. In this paper we show a program written in BASIC and debugged on a Sharp MZ-700 personal computer, equipped with the Sharp MZ-1P01 plotter. The program is explained in detail and is easily adapted to run on any personal computer.
Mechanisms of Ageing and Development, Aug 1, 1997
A quantitative study regarding the age-related changes occurring in the nucleus and the somatic o... more A quantitative study regarding the age-related changes occurring in the nucleus and the somatic organelles of neurosecretory magnocellular neurons of the hypothalamo neurohypophyseal system (HNS) was carried out in the hamster at six age-points during animal life. The magnocellular cells of both parts of the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of male Syrian hamsters between 3 and 30 months of age were examined ultrastructurally. Cells of all age groups present the same morphological ultrastructure. Standard manual morphometric techniques are used to calculate the following parameters related directly or indirectly with cellular activity: nuclear area, nucleolar area, nuclear invagination index and volumetric fractions of some intracellular structures (Golgi apparatus, mitochondria, rough endoplasmic reticulum and lipofuscin). With respect to the cell nucleus, the parameters are not modified during aging. No significant differences in the volume density of subcellular components, except lipofuscin, were detected at the age groups studies. However, there is a positive linear trend among all parameters and age except for the rough endoplasmic reticulum. Our results suggest maintenance of the synthetic activity of the magnocellular neurons in the hamster during aging but in no case an increase in their metabolic activity.