Neuronal hypertrophy in the hypothalamus of older men

Arrested Sexual Development in Queen Conch (Lobatus gigas) Linked to Abnormalities in the Cerebral Ganglia

In the Florida Keys, queen conchs (Lobatus gigas) occur in two spatially distinct regions: nearshore in habitats immediately adjacent to the shoreline and offshore in habitats along the reef tract south of the islands. Our previous research demonstrated that adult conchs nearshore are not reproductively active, showing deficiencies in their gonadal condition compared to their offshore counterparts. Because sexual development in gastropods is controlled by hormones secreted by the cerebral ganglia, we hypothesized that the reproductive deficiencies seen in nearshore queen conchs involved the cerebral ganglia. We collected nearshore and offshore adults and made histological comparisons of their gonads and cerebral ganglia. Our results confirmed that gonadal maturity was delayed and that gamete production was reduced in nearshore conchs compared to offshore animals. These gonadal deficiencies in nearshore conchs were associated with abnormal cerebral ganglion histology (i.e., significant hypertrophy of ganglion cells and significantly lower density of ganglion cells). In addition, the shells of nearshore conchs were significantly lighter, which is particularly consequential because shell formation in gastropods is also mediated by hormones secreted by the cerebral ganglia. Given these results, it is apparent that some yet unidentified factor(s) is interfering with hormone production in the cerebral ganglia, to the detriment of gonad development and shell formation.

New Perspectives for Anatomical and Molecular Studies of Kisspeptin Neurons in the Aging Human Brain

The human infundibular nucleus (corresponding to the rodent arcuate nucleus) serves as an important integration center for neuronal signals and hormones released by peripheral endocrine organs. Kisspeptin (KP)-producing neurons of this anatomical site, many of which also synthesize neurokinin B (NKB), are critically involved in sex hormone signaling to gonadotropin-releasing hormone (GnRH) neurons. In recent years, the basic topography, morphology, neuropeptide content, and connectivity of human KP neurons have been investigated with in situ hybridization and immunohistochemistry on postmortem tissues. These studies revealed that human KP neurons differ neurochemically from their rodent counterparts and show robust aging-related plasticity. Earlier immunohistochemical experiments also provided evidence for temporal changes in the hypothalamus of aging men whose NKB and KP neurons undergo hypertrophy, increase in number, exhibit increased neuropeptide mRNA expression and immunoreactivity and give rise to higher numbers of immunoreactive fibers and afferent contacts onto GnRH neurons. Increasing percentages of KP-expressing NKB perikarya, NKB axons, and NKB inputs to GnRH neurons raise the intriguing possibility that a significant subset of NKB neurons begins to cosynthesize KP as aging advances. Although use of postmortem tissues is technically challenging, recently available single-cell anatomical and molecular approaches discussed in this review provide promising new tools to investigate the aging-related anatomical and functional plasticity of the human KP neuronal system.

Neuroanatomy of the human hypothalamic kisspeptin system

Hypothalamic kisspeptin (KP) neurons are key players in the neuronal network that regulates the onset of puberty and the pulsatile secretion of gonadotropin-releasing hormone (GnRH). In various mammalian species, the majority of KP-synthesizing neurons are concentrated in two distinct cell populations in the preoptic region and the arcuate nucleus (ARC). While studies of female rodents have provided evidence that preoptic KP neurons play a critical sex-specific role in positive estrogen feedback, KP neurons of the ARC have been implicated in negative sex steroid feedback and they have also been hypothesized to contribute to the pulse generator network which regulates episodic GnRH secretion in both females and males. Except for relatively few morphological studies available in monkeys and humans, our neuroanatomical knowledge of the hypothalamic KP systems is predominantly based on observations of laboratory species which are phylogenetically distant from the human. This review article discusses the currently available literature on the topographic distribution, network connectivity, neurochemistry, sexual dimorphism, and aging-dependent morphological plasticity of the human hypothalamic KP neuronal system.

Afferent neuronal control of type-I gonadotropin releasing hormone neurons in the human

Understanding the regulation of the human menstrual cycle represents an important ultimate challenge of reproductive neuroendocrine research. However, direct translation of information from laboratory animal experiments to the human is often complicated by strikingly different and unique reproductive strategies and central regulatory mechanisms that can be present in even closely related animal species. In all mammals studied so far, type-I gonadotropin releasing hormone (GnRH) synthesizing neurons form the final common output way from the hypothalamus in the neuroendocrine control of the adenohypophysis. Under various physiological and pathological conditions, hormonal and metabolic signals either regulate GnRH neurons directly or act on upstream neuronal circuitries to influence the pattern of pulsatile GnRH secretion into the hypophysial portal circulation. Neuronal afferents to GnRH cells convey important metabolic-, stress-, sex steroid-, lactational-, and circadian signals to the reproductive axis, among other effects. This article gives an overview of the available neuroanatomical literature that described the afferent regulation of human GnRH neurons by peptidergic, monoaminergic, and amino acidergic neuronal systems. Recent studies of human genetics provided evidence that central peptidergic signaling by kisspeptins and neurokinin B (NKB) play particularly important roles in puberty onset and later, in the sex steroid-dependent feedback regulation of GnRH neurons. This review article places special emphasis on the topographic distribution, sexual dimorphism, aging-dependent neuroanatomical changes, and plastic connectivity to GnRH neurons of the critically important human hypothalamic kisspeptin and NKB systems.

Reactivation of atrophic neurons in Alzheimer's disease

Decreased metabolic rate may precede cognitive impairment in Alzheimer's disease (AD) and is thus an early occurring hallmark. Several observations in post-mortem brain indicate that activated neurons are better able to withstand aging and AD, a phenomenon paraphrased by us as 'use it or lose it'. Moreover, a number of pharmacological and nonpharmacological studies support the concept that activation of the brain has beneficial effects and may to a certain degree restore several aspects of cognition and other central functions. For instance, the circadian system may be restimulated in Alzheimer patients by exposing them to more light or transcutaneous nerve stimulation. A procedure has been developed to culture human post-mortem brain tissue that allows testing of the efficacy of putative stimulatory compounds such as neurotrophins.

Morphological evidence for enhanced kisspeptin and neurokinin B signaling in the infundibular nucleus of the aging man

Peptidergic neurons synthesizing kisspeptin (KP) and neurokinin B (NKB) in the hypothalamic infundibular nucleus have been implicated in negative sex steroid feedback to GnRH neurons. In laboratory rodents, testosterone decreases KP and NKB expression in this region. In the present study, we addressed the hypothesis that the weakening of this inhibitory testosterone feedback in elderly men coincides with enhanced KP and NKB signaling in the infundibular nucleus. This central hypothesis was tested in a series of immunohistochemical studies on hypothalamic sections of male human individuals that were divided into arbitrary "young" (21-49 yr, n = 11) and "aged" (50-67 yr, n = 9) groups. Quantitative immunohistochemical experiments established that the regional densities of NKB-immunoreactive (IR) perikarya and fibers, and the incidence of afferent contacts they formed onto GnRH neurons, exceeded several times those of the KP-IR elements. Robust aging-dependent enhancements were identified in the regional densities of KP-IR perikarya and fibers and the incidence of afferent contacts they established onto GnRH neurons. The abundance of NKB-IR perikarya, fibers, and axonal appositions to GnRH neurons also increased with age, albeit to lower extents. In dual-immunofluorescent studies, the incidence of KP-IR NKB perikarya increased from 36% in young to 68% in aged men. Collectively, these immunohistochemical data suggest an aging-related robust enhancement in central KP signaling and a moderate enhancement in central NKB signaling. These changes are compatible with a reduced testosterone negative feedback to KP and NKB neurons. The heavier KP and NKB inputs to GnRH neurons in aged, compared with young, men may play a role in the enhanced central stimulation of the reproductive axis. It requires clarification to what extent the enhanced KP and NKB signaling upstream from GnRH neurons is an adaptive response to hypogonadism or, alternatively, a consequence of a decline in the androgen sensitivity of KP and NKB neurons.

Sexual dimorphism of kisspeptin and neurokinin B immunoreactive neurons in the infundibular nucleus of aged men and women

The secretory output of gonadotropin-releasing hormone (GnRH) neurons is critically influenced by peptidergic neurons synthesizing kisspeptins (KP) and neurokinin B (NKB) in the hypothalamic infundibular nucleus (Inf). These cells mediate negative feedback effects of sex steroids on the reproductive axis. While negative feedback is lost in postmenopausal women, it is partly preserved by the sustained testosterone secretion in aged men. We hypothesized that the different reproductive physiology of aged men and women is reflected in morphological differences of KP and NKB neurons. This sexual dimorphism was studied with immunohistochemistry in hypothalamic sections of aged human male (≥50 years) and female (>55 years) subjects. KP and NKB cell bodies of the Inf were larger in females. The number of KP cell bodies, the density of KP fibers, and the incidence of their contacts on GnRH neurons were much higher in aged women compared with men. The number of NKB cell bodies was only slightly higher in women and there was no sexual dimorphism in the regional density of NKB fibers and the incidence of their appositions onto GnRH cells. The incidences of NKB cell bodies, fibers, and appositions onto GnRH neurons exceeded several-fold those of KP-IR elements in men. More NKB than KP inputs to GnRH cells were also present in women. Immunofluorescent studies identified only partial overlap between KP and NKB axons. KP and NKB were colocalized in higher percentages of afferents to GnRH neurons in women compared with men. Most of these sex differences might be explained with the lack of estrogen negative feedback in aged women, whereas testosterone can continue to suppress KP, and to a lesser extent, NKB synthesis in men. Overall, sex differences in reproductive physiology of aged humans were reflected in the dramatic sexual dimorphism of the KP system, with significantly higher incidences of KP-IR neurons, fibers and inputs to GnRH neurons in aged females vs. males.

Neurokinin B and the hypothalamic regulation of reproduction

Loss-of-function mutations in the genes encoding either neurokinin B (NKB) or its receptor, NK3 (NK3R), result in hypogonadotropic hypogonadism, characterized by an absence of pubertal development and low circulating levels of LH and gonadal steroids. These studies implicate NKB and NK3R as essential elements of the human reproductive axis. Studies over the last two decades provide evidence that a group of neurons in the hypothalamic infundibular/arcuate nucleus form an important component of this regulatory circuit. These neurons are steroid-responsive and coexpress NKB, kisspeptin, dynorphin, NK3R, and estrogen receptor α (ERα) in a variety of mammalian species. Compelling evidence in the human indicates these neurons function in the hypothalamic circuitry regulating estrogen negative feedback on gonadotropin-releasing hormone (GnRH) secretion. Moreover, in the rat, they form a bilateral, interconnected network that projects to NK3R-expressing GnRH terminals in the median eminence. This network provides an anatomical framework to explain how coordination among NKB/kisspeptin/dynorphin/NK3R/ERα neurons could mediate feedback information from the gonads to modulate pulsatile GnRH secretion. There is substantial (but indirect) evidence that this network may be part of the neural circuitry known as the "GnRH pulse generator," with NK3R signaling as an important component. This theory provides a compelling explanation for the occurrence of hypogonadotropic hypogonadism in patients with inactivating mutations in the TAC3 or TACR3 genes. Future studies will be needed to determine whether NKB signaling plays a permissive role in the onset of puberty or is part of the driving force initiating the maturation of reproductive function.

Estrogen regulation of neurokinin B gene expression in the mouse arcuate nucleus is mediated by estrogen receptor alpha

Neurokinin B (NKB) gene expression is elevated in the infundibular (arcuate) nucleus of the hypothalamus in postmenopausal women. Estrogen replacement decreases both the number of NKB mRNA-expressing neurons and the level of expression within individual cells. Similarly, NKB gene expression is elevated in ovariectomized rats and reduced after estrogen treatment. The actions of estrogen in the brain can be mediated via either estrogen receptor alpha (ERalpha) or estrogen receptor beta (ERbeta). In the rodent arcuate nucleus (ARC), more ERalpha- than ERbeta-containing cells are present, suggesting that ERalpha might be directly responsible for estrogen regulation of NKB gene expression. However, an indirect effect via ERbeta could not be ruled out. Here we used ERalpha knockout and ERbeta knockout mice to identify the type of ER responsible for mediating estrogen action on NKB gene expression in the ARC. Using in situ hybridization histochemistry, we have found that estrogen treatment significantly reduced NKB gene expression in the ARC of ovariectomized ERbeta knockout mice, but had no effect on NKB mRNA levels in ERalpha knockout mice. These data indicate that ERalpha mediates the increase in NKB gene expression associated with ovariectomy in rodents and might also be responsible for the increase in NKB in postmenopausal women.

Neuropeptides in hypothalamic neuronal disorders

A few examples of hypothalamic, peptidergic disorders leading to clinical signs and symptoms are presented in this review. Increased activity of corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus (PVN) and decreased activity of the vasopressin neurons in the biological clock and of the thyroxine-releasing hormone (TRH) neurons in the PVN contribute to the signs and symptoms of depression. In men, the central nucleus of the bed nucleus of the stria terminalis (BSTc) is about twice as large and contains twice as many somatostatin neurons as in women. In transsexuals this sex difference is reversed, pointing to a role of this structure in gender. Luteinizing hormone-releasing hormone (LHRH) neurons are formed in the fetal olfactory placade and migrate along the terminal nerve fibers into the hypothalamus. In Kallmann's syndrome the migration process of the LHRH (gonadotropin-releasing hormone) neurons is aborted, which explains the joint occurrence of hypogonadotropic hypogonadism and anosmia in this syndrome. In postmenopausal women, the neurons of the infundibular nucleus hypertrophy and become hyperactive because of the disappearance of the estrogen feedback and contain hyperactive peptidergic neurons. Climacteric flushes may be caused by hyperactivity of the neurokinin-B or LHRH neurons in this nucleus. The hypocretin (orexin) neurons in the perifornical area are involved in sleep. In narcolepsy with cataplexy, a loss of these neurons, probably due to an autoimmune process, is found. Obese subjects with a mutation in the gene that encodes for leptin, the preproghrelin gene, or the alpha-melanocyte-stimulating hormone (alpha-MSH) gene have been described. Decreased numbers and activity of the oxytocin neurons in the PVN may be responsible for the absence of satiety in Prader-Willi syndrome. Moreover, a glucocorticoid receptor polymorphism is associated with obesitas and dysregulation of the hypothalamus-pituitary-adrenal axis. In contrast, two single nucleotide polymorphisms (SNPs) of the AGRP gene have been associated with anorexia nervosa.

Brain aging and Alzheimer's disease; use it or lose it

(1) Alzheimer's disease is a multifactorial disease in which age and APOE-epsilon 4 are important risk factors. (2) The neuropathological hallmarks of AD, i.e. amorphous plaques, neuritic plaques (NPs), pretangles, neurofibrillary tangles (NFT) and cell death are not part of a single pathogenetic cascade but may occur independently. (3) In brain areas where classical AD changes, i.e. NPs and NFTs, are present, such as the CA1 area of the hippocampus, the nucleus basalis of Meynert and the tuberomamillary nucleus, a decreased metabolic rate is found. The decreased metabolic rate appears not to be induced by the presence of pretangles, NFT or NPs. (4) Decreased metabolic rate may precede cognitive impairment and is thus an early occurring hallmark of AD, which, in principle, may be reversible. The observation that the administration of glucose or insulin enhances memory in AD patients also supports the view that AD has a metabolic basis. (5) Moreover, several observations in postmortem brain indicate that activated neurons are better able to withstand aging and AD, a phenomenon paraphrased by us as 'use it or lose it'. (6) It is, therefore, attractive to direct the development of therapeutic strategies towards restimulation of neuronal metabolic rate in order to improve cognition and other symptoms in AD. A number of pharmacological and non-pharmacological studies support the concept that activation of the brain has beneficial effects and may, to a certain degree, restore several aspects of cognition and other central functions. For instance, the circadian system may be restimulated in AD patients by exposing them to more light or transcutaneous nerve stimulation. A procedure has been developed to culture human postmortem brain tissue that allows testing of the efficacy of putative stimulatory compounds such as neurotrophins.

Sex-dependent cytoskeletal changes of the human hypothalamus develop independently of Alzheimer's disease

This study examines a sex-dependent variant of neurofibrillary pathology recently identified in the hypothalamus of elderly human males. Here we focus upon the relationship between the sex-dependent hypothalamic changes and Alzheimer's disease (AD)-related neurofibrillary pathology. To this end, autopsy brains of 31 males (mean age 84.1 years) and 26 age-matched females (mean age 86.7 years) were examined. Both the male and the female subjects exhibited either particularly mild (stage I) or fully developed (stage V) AD-related neurofibrillary brain pathology. Serial 100-micron hypothalamic sections were cut in the frontal plane and stained for hyperphosphorylated tau protein using the monoclonal antibody AT8. Argyrophilic neurofibrillary pathology was demonstrated using a modified Gallyas silver-iodide technique. A conspicuous pathology, characterized by neurofibrillary tangles, a network of dystrophic neurites, and terminal-like vessel-associated processes, was identified in the infundibular nucleus which is located in the mediobasal tuber cinereum. This pathology was noted in 20 males (64.5%), but did not occur in the female group. No statistically significant correlation was noted between the degree of sex-dependent pathology and the presence of AD-related cortical pathology. In particular, the expression of the sex-dependent changes did not differ between males with AD stage I and males with AD stage V. In summary, the existence of a sex-dependent variant of neurofibrillary pathology was confirmed. In addition, our findings strongly suggest that the sex-dependent changes develop independently of the neurofibrillary changes associated with senile dementia of the Alzheimer type. Instead, the sex-dependent hypothalamic pathology probably corresponds to a distinct neurodegenerative entity preferentially affecting elderly males.

Stereological age-related changes in neurons of the rat dorsal lateral geniculate nucleus

Quantitative methods were used to compare the changes taking place in the volume of the dorsal lateral geniculate nucleus (dLGN) and corresponding neurons of young, adult and old rats. The study was carried out on male albino rats aged 3, 18, 24 and 28 months. In order to estimate the volume of the dLGN, neuronal volume density, numerical density and total number of neurons, we used serial sections stained according to the Klüver-Barrera technique and stereological methods. We found that dorsal lateral geniculate nucleus volume increases between 3 and 28 months, with a larger increase between 24 and 28 months. Neuronal volume density and numerical density of neurons are greater at 3 months and undergo a significant decrease between 24 and 28 months. Finally, the total number of neurons is shown to be smaller in adult and old animals than in younger ones, even though no significant variations are found between 18 and 28 months. Furthermore, this study confirms the need to analyze the total number of neurons and not just neuronal density if we want to correctly evaluate some of the microscopic changes occurring during senescence.

Sex steroid modulation of neurokinin B gene expression in the arcuate nucleus of adult male rats

Human menopause is associated with hypertrophy and increased gene expression of neurokinin (NKB) neurons in the infundibular (arcuate) nucleus of the hypothalamus. We have hypothesized that these changes are secondary to gonadal failure. In the present study, we determined that orchidectomy resulted in an increase in the mean profile area and the number of neurons expressing NKB mRNA in the rat arcuate nucleus. No changes were seen when orchidectomy was combined with testosterone or estradiol replacement. These findings support our hypothesis and demonstrate that gonadal steroids modulate NKB neurons in the arcuate nucleus of adult male rats.

Reduced neuronal activity and reactivation in Alzheimer's disease

1. Alzheimer's disease is a multifactorial disease in which age and APOE-epsilon 4 are important risk factors. Various mutations and even viral infections such as herpes simplex (Itzhaki et al., 1997) may play an additional role. 2. The neuropathological hallmarks of Alzheimer's disease (AD), i.e. amorphous plaques, neuritic plaques (NPs), pretangles, neurofibrillary tangles (NFT) and cell death are not part of a single pathogenetic cascade but are basically independent phenomena. 3. Pretangles can occur in neurons from which the metabolic rate is not altered. However, in brain areas where classical AD changes, i.e. NPs and NFTs, are present, such as the CA1 area of the hippocampus, the nucleus basalis of Meynert and the tuberomamillary nucleus, a decreased metabolic rate is found. Decreased metabolic rate appears to be an independent phenomenon in Alzheimer's disease. It is not induced by the presence of pretangles, NFT or NPs. 4. Decreased metabolic rate may precede cognitive impairment and is thus an early occurring hallmark of Alzheimer's disease, which, in principle, may be reversible. The observation that the administration of glucose or insulin enhances memory in Alzheimer patients also supports the view that Alzheimer's disease is basically a metabolic disease. Moreover, several observations indicate that activated neurons are better able to withstand aging and AD, a phenomenon paraphrased by us as "use it or lose it". It is, therefore, attractive to direct the development of therapeutic strategies towards restimulation of neuronal metabolic rate in order to improve cognition and other symptoms in Alzheimer's disease. A number of pharmacological and non-pharmacological studies support the concept that activation of the brain indeed has beneficial effects on several aspects of cognition and other central functions.

Activation and degeneration during aging: a morphometric study of the human hypothalamus

During the course of aging both activation and degenerative changes are found in the human hypothalamus. Degeneration may start around middle-age in some neurotransmitter- or neuromodulator-containing neurons. For instance, a decreased number of vasoactive intestinal polypeptide (VIP) neurons was observed in the suprachiasmatic nucleus (SCN) of middle-aged males. The normal circadian fluctuations seen in the number of vasopressin (AVP) neurons in the SCN of young subjects diminished in subjects older than 50 years. Moreover, a sharp decline in cell number was found in the sexually dimorphic nucleus (SDN) after 50 years in males. On the other hand, many hypothalamic systems remain perfectly intact during aging like the oxytocin (OXT) neurons in the paraventricular nucleus (PVN). The AVP neurons in the PVN are activated during aging as appears from their increasing cell number. Also the corticotrophin-releasing hormone (CRH) neurons of the PVN are activated in the course of aging, as indicated by their increased number and their increased AVP coexpression. Part of the infundibular nucleus, the subventricular nucleus, contains hypertrophic neurokinin B neurons in postmenopausal women. It can be concluded that a multitude of changes in the various hypothalamic nuclei may be the biological basis for many functional changes in aging, i.e., both endocrine and central alterations, and that only a minority of the possible human hypothalamic changes have so far been studied.

Lifespan changes in the human hypothalamus

The various cell groups in the human hypothalamus show different patterns of aging, which are the basis for changes in biological rhythms, hormone production, autonomic functions, and behavior. The suprachiasmatic nucleus (SCN), the clock of the brain, exhibits circadian and seasonal rhythms in vasopressin synthesis that are disrupted later in life. Furthermore, the age-related sexual differences in the number of vasoactive intestinal polypeptide neurons in this nucleus reinforces the idea that the SCN is not only involved in the timing of circadian rhythms but also in the temporal organization of reproductive functions. The sexually dimorphic nucleus of the preoptic are (SDN-POA), or intermediate nucleus, is twice as large in men as in women, a difference that arises between the ages of two to four years and puberty. During aging a dramatic, sex-dependent decrease in cell number occurs, leading to values which are only 10-15% of the cell number found in early childhood. The vasopressin and oxytocin producing cells in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) are examples of neuron populations that seem to stay perfectly intact in old age. Parvocellular corticotropin-releasing hormone-containing neurons are found throughout the PVN and are even activated in the course of aging, as indicated by their increase in number and by their coexpression with vasopressin. Part of the arcuate nucleus of the hypothalamus (ARH), or tubero-infundibular nucleus, contains hypertrophic neurons in postmenopausal women. These hypertrophied neurons contain neurokinin-B, substance P, and estrogen receptors and probably act on LHRH neurons as interneurons. The tuberal lateral nucleus (NTL), involved in feeding behavior and energy metabolism, does not show any neuronal loss in senescence. These findings indicate that each cell group of the human hypothalamus has its own sex-specific pattern of aging. In fact, some hypothalamic nuclei show a dramatic functional decline with aging, whereas others seem to become more active later in life.

Quantitative morphological changes in neurons from the dorsal lateral geniculate nucleus of young and old rats

BACKGROUND

We studied the morphological changes occurring in neurons from the dorsal lateral geniculate nucleus (dLGN) during aging by analysing the size and shape of cell bodies and nuclei.

METHODS

Male albino Wistar rats, aged 3, 18, 24, and 30 months, were used. After appropriate tissue preparation and following the usual histological procedure, the profiles of 1,920 neuronal bodies and nuclei were drawn using a camera lucida. Data was later recorded and processed with a semiautomatic image analyser.

RESULTS AND CONCLUSIONS

We observed that dLGN neurons do not change in size from the age of 3-24 months. Between 24 and 30 months, the soma and nucleus of the cell undergo hypertrophy, 32.8% and 35.6%, respectively, when compared to those from 3-month-old animals (P < 0.01). Furthermore, we found a high correlation between cell body size/nucleus size, which does not disappear with age. The r values (correlation coefficient) were 0.7998, 0.8662, 0.8433 and 0.7304, and R2 (determination coefficient) was equal to 0.6397, 0.7504, 0.7112, and 0.5335. These latter values show that in 63.97%, 75.04%, 71.12%, and 53.35% of cases, respectively, modifications in somata size were accompanied by similar changes in nucleus size, and vice-versa. The study of the shape of the soma and nucleus of the cell revealed that both structures have a rounded-oval configuration that does not change in a significant way from adulthood to old age.