Spanish medical graduates who apply for a medical specialty training position (MIR) must take an examination that will shape their future personal and professional lives. Preparation for the test represents an important stressor that persists for several months. The aim of this study was to elucidate the stress pattern of this group and evaluate possible changes in the circadian rhythm of cortisol release in medical graduates preparing for this test. A repeated-measures longitudinal study was performed, measuring the salivary cortisol concentrations in 36 medical graduates (13 males and 23 females; mean age of 24.2 years) on five sampling days. Five cortisol samples were collected from 07:00 to 21:00 h in order to monitor changes in the circadian rhythm. On all sampling days (except on the day of the official examination), anxiety and psychological stress were evaluated with the Spanish versions of the State-Trait Anxiety Inventory (STAI) and the Perceived Stress Scale (PSS). During the study period, participants showed higher levels of anxiety than the Spanish reference population as well as a progressive increase in self-perceived stress. A significant increase in salivary cortisol concentration was observed in both chronic (study and examination preparation) and acute (examinations) situations. Our results suggest that the cortisol awakening response (CAR) may be a good indicator of anticipatory stress but is unaffected by long-term examination preparation. Comparison of results between the official examination day and the mock examination days yielded evidence that learning may modulate the behavior of the hypothalamic-pituitary-adrenal axis.
The quantitative morphological changes in neurons and glia during the aging process were analyzed in the different cortical layers, grouped as I, II-IV, V, and VI, of the frontal cortex of the rat. The parameters analyzed were cortical volume, neuronal density, glial density, and neuronal soma and nucleus areas. No changes with age were found in the volume of the layers, in neuronal density (with the exception of layer I), or in the area of the neuronal soma. However, older animals showed a 10 to 20% increase in glial density, depending on the layer studied. In addition, there was an age-related decrease in the area of the neuronal nucleus in layers II-IV, V, and VI. These results support the idea that the aging frontal cortex undergoes structural changes that may be involved in the morphological basis of memory and cognitive impairments characteristic of aging.
The frequency of astrocytes, microglia plus oligodendrocytes, and pericytes displaying nuclei was analyzed and quantified in 160-µm-wide strips of the parietal cortex (Par1 region) from young and aged Wistar rats. The study was performed on two groups of rats aged 3-4 and 32-36 months. Quantifications of the glial cell types and pericytes were made in 1-µm-thick sections stained with toluidine blue. Ultrathin sections were also made to analyze the ultrastructural features of these cells during aging. Astrocytes and pericytes increased in number by about 20% and 22%, respectively, with age. These increases were most significant in layers II-IV and V for both cellular types. Clusters of astrocytes were common in these layers of aging rats. The ultrastructural analysis also indicated changes in all cell types that stored inclusions and vacuoles with age, which were particularly abundant in microglial cells. End-feet astrocytes and pericytes surrounding the vascular wall also contained vacuoles and inclusions, and consequently the vascular wall increased in thickness. In conclusion, the aging process increased astrocyte and pericyte populations, but not microglia plus oligodendrocyte populations, in the rat parietal cortex. Although no significant change in nuclear size could be observed in any cell type, all glial cells as well as pericytes underwent morphological ultrastructural changes. These modifications may result from the need to correct possible homeostatic imbalances during aging.
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