study on the postnatal development and aging changes of the neurosecretory nuclei of the hypothalamus [supraoptic and paraventricular nuclei] in the albino rat

The hypothalamus is a distinct neurological entity concerned with a variety of regulatory processes. Recently, the prescence of variations in the level of neurosecretions wth the progress of age was reported. To study the changes in the structure of magnocellular neurons in the paraventricular and supraoptic nuclei during the period of postnatal development. Furthermore, to study the changes which occurred in the structure of these neurons in the old age had been studied. A total of 52 albino rats were used. The age groups of the animals include: one day, 10 days, 20 days, 2 months and 2 years old animals. Brains were processed to be studied with Einarson's gallocyanin-chrome alum stain, Golgi- Cox method and transmission electron microscope. In addition, the number of cells in the magnocellular part of the paraventricular and supraoptic nuclei were measured in all studied age groups and statistically analyzed. In the newly born rats, the paraventricular and supraoptic nuclei were composed of small rounded condensed cells. At the age of 10 days old rats, the paraventricular nucleus appeared to be well differentiated into ventromedial [parvocellular] and dorsolateral [magnocellular] parts. With the progress of age from 10 days up to the adult stage, the cells of the supraoptic nucleus and the magnocellular part of the paraventricular nucleus appeared to be densely stained which indicated increase in the Nissl granules. Ultrastructural study showed that the cells had abundant amount of free ribosomes, rough endoplasmic reticulum and mitochondria. The nucleus had fine dispersed chromatin. Golgi-Cox study showed marked increase in extension and branching of dendrites with the progress of age during the developmental period. Morphometric study showed significant increase in the number of cells from the new born up to the adult stage. In old aged rats, the cells of the paraventricular nucleus and the supraoptic nucleus appeared to be faintly stained. Some cells had vacuolated cytoplasm. Ultrastructural study showed marked decrease in the free ribosomes and the presence of many lipofuscin pigment in the cytoplasm of cells. The nucleus showed chromatin condensation and irregularity of the nuclear membrane. In addition, there was apparent decrease in the amount of the synaptic vesicles in the presynaptic terminals making contacts with the magnocellular neurons. Golgi-Cox study revealed marked decrease in the extension and branching of dentrites. Morphometric analysis showed significant decrease in the number of cells. This study demonstrated in the presence of structural changes in the magnocellular part of the paraventricular nucleus and supraoptic nucleus during the period of development. In old age, the presence of many degenerative changes was observed. This cytoarchitectonic analysis and morphological study could help in the explanation of the functional differences in the various ages

Bases psiconeuroendócrinas del dimorfismo sexual cerebral / Psychoneuroendocrine bases for brain sexual dimorphism

Con el avance de las neurociencias, cada vez se conoce más sobre las características morfológicas y funcionales del cerebro, la acción de los neuroesteroides y los aspectos genómicos y no genómicos involucrados en la modulación de las características específicas de cada sexo, con sus aspectos biomorfológicos, fisiológicos, psicológicos y sociales. El presente artículo aborda los avances en el conocimiento del dimorfismo sexual cerebral a fin de intentar comprender estas peculiaridades biológicas y funcionales y su posible influencia en las conductas sanas y en las diferencias sexuales clínicamente evidentes en las formas de expresión, evolución, pronóstico y respuesta al tratamiento de las enfermedades mentales. Pone además el énfasis en el estudio integrativo de la persona, desde un abordaje psiconeuroinmunoendocrinológico.

Neonatal handling and the expression of immunoreactivity to tyrosine hydroxylase in the hypothalamus of adult male rats

Neonatal handling has long-lasting effects on behavior and stress reactivity. The purpose of the present study was to investigate the effect of neonatal handling on the number of dopaminergic neurons in the hypothalamic nuclei of adult male rats as part of a series of studies that could explain the long-lasting effects of neonatal stimulation. Two groups of Wistar rats were studied: nonhandled (pups were left undisturbed, control) and handled (pups were handled for 1 min once a day during the first 10 days of life). At 75-80 days, the males were anesthetized and the brains were processed for immunohistochemistry. An anti-tyrosine hydroxylase antibody and the avidin-biotin-peroxidase method were used. Tyrosine hydroxylase-immunoreactive (TH-IR) neurons were counted bilaterally in the arcuate, paraventricular and periventricular nuclei of the hypothalamus in 30-æm sections at 120-æm intervals. Neonatal handling did not change the number of TH-IR neurons in the arcuate (1021 + or - 206, N = 6; 1020 + or - 150, N = 6; nonhandled and handled, respectively), paraventricular (584 + or - 85, N = 8; 682 + or - 62, N = 9) or periventricular (743 + or - 118, N = 7; 990 + or - 158, N = 7) nuclei of the hypothalamus. The absence of an effect on the number of dopaminergic cells in the hypothalamus indicates that the reduction in the amount of neurons induced by neonatal handling, as shown by other studies, is not a general phenomenon in the brain

Pacemaker interactions in the mammalian circadian system

Circadian rhythms in mammals are generated by pacemaker cells located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. The identity of these cells, however, is not known, and little information exists regarding the mechanisms by which they communicate with each other and with the organism. Nonetheless, pacemaker interactions must occur to produce single, coherent rhythms of behavior and physiology. Recently it has become possible to observe the result of these interactions using circadian chimeras, animals with two clocks with distinct periods, that have been produced by SCN transplantation. Using the tau mutation in golden hamsters, chimeras expressing two circadian rhythms of behavior simultaneously were created. The two rhythms exhibited complex interactions including cases of relative coordination. This basic result indicates that pacemaker interactions are rhythmic and phase dependent. Further analysis should help to elucidate the nature of the coupling signal and the identity of the pacemaker cells.