66 research outputs found
Identification of sex hormone-binding globulin in the human hypothalamus
Gonadal steroids are known to influence hypothalamic functions through both genomic and non-genomic pathways. Sex hormone-binding globulin ( SHBG) may act by a non-genomic mechanism independent of classical steroid receptors. Here we describe the immunocytochemical mapping of SHBG-containing neurons and nerve fibers in the human hypothalamus and infundibulum. Mass spectrometry and Western blot analysis were also used to characterize the biochemical characteristics of SHBG in the hypothalamus and cerebrospinal fluid (CSF) of humans. SHBG-immunoreactive neurons were observed in the supraoptic nucleus, the suprachiasmatic nucleus, the bed nucleus of the stria terminalis, paraventricular nucleus, arcuate nucleus, the perifornical region and the medial preoptic area in human brains. There were SHBG-immunoreactive axons in the median eminence and the infundibulum. A partial colocalization with oxytocin could be observed in the posterior pituitary lobe in consecutive semithin sections. We also found strong immunoreactivity for SHBG in epithelial cells of the choroid plexus and in a portion of the ependymal cells lining the third ventricle. Mass spectrometry showed that affinity-purified SHBG from the hypothalamus and choroid plexus is structurally similar to the SHBG identified in the CSF. The multiple localizations of SHBG suggest neurohypophyseal and neuroendocrine functions. The biochemical data suggest that CSF SHBG is of brain rather than blood origin. Copyright (c) 2005 S. Karger AG, Base
Comparative histology of pineal calcification
The pineal organ (pineal gland, epiphysis cerebri) contains several calcified concretions called "brain sand7' or acervuli (corpora arenacea). These concretions are conspicuous with imaging techniques and provide a useful landmark for orientation in the diagnosis of intracranial diseases. Predominantly composed of calcium and magnesium salts, corpora arenacea are numerous in old patients. In smaller number they can be present in children as well. The degree of calcification was associated to various diseases. However, the presence of calcified concretions seems not to reflect a specific pathological state. Corpora arenacea occur not only in the actual pineal tissue but also in the leptomeninges, in the habenular commissure and in the choroid plexus.Studies with the potassium pyroantimonate (PPA) method on the ultrastructural localization of free calcium ions in the human pineal, revealed the presence of calcium alongside the cell membanes, a finding that underlines the importance of membrane functions in the production of calcium deposits. Intrapineal corpora arenacea are characterized by a surface with globular structures. Meningeal acervuli that are present in the arachnoid cover of the organ, differ in structure from intrapineal ones and show a prominent concentric lamination of alternating dark and light lines. The electron-lucent lines contain more calcium than the dark ones. There is a correlation between the age of the subject and the number of layers in the largest acervuli. This suggests that the formation of these layers is connected to circannual changes in the calcium level of the organ. The histological organization of the human pineal is basically the same as that of mammalian experimental animals.Pineal concretions present in mammalian animal species are mainly of the meningeal type. Meningeal cells around acervuli contain active cytoplasmic organelles and exhibit alkaline phosphatase reaction in the rat and mink, an indication of a presumable osteoblast-like activity. Using Kossa's method for the staining of calcium deposits, a higher calcium concentration was detected in the rat pineal than in the surrounding brain tissue. Since in parathyroidectomised rats calcified deposits are larger and more numerous than in controls, the regulation of the production of acervuli by the parathyroid gland has also been postulated.In most of submammalian species, the pineal organs (pineal-, parapineal organ, frontal organ, parietal eye) are photoreceptive and organized similarly to the retina. Acervuli were found in the pineal of some birds. The pineal organs of lower vertebrates (fish, amphibians, reptiles) exhibit a high calcium content by ultrastructural calcium histochemistry (PPA-method). However, concrements are not formed. The accumulation of ca2+ seems to depend on the receptor function of the organ. Comparing pineal and retinal photoreceptors in the frog, the photoreceptor outer segments of pinealocytes as well as retinal cones and rods show a large amount of Capyroantimonate deposits. In dark adapted animals calcium ions are present in both sides of the photoreceptor membranes of the outer segment, whereas calcium is shifted extra-cellularly following light adaptation.Overviewing the data available about the pineal calcification, we can conclude that a multifactorial mechanism may be responsible for the calcification. The pineal of higher vertebrates is not just a simple endocrine gland, rather, its histological organization resembles a folded retina having both hormonal and neural efferentation. Mammalian pinealocytes preserve several characteristics of submammalian receptor cells and accumulate free ca2+ on their membranes (1). In the thin walled retina and in the similarly organized pineal of submammalian species, the diffusion of extracellular calcium is probably easy and there is a lesser tendency to form concrements. In the larger mammalian pineal the compaction of a high amount of pineal cells actively exchanging calcium ions is supposed to increase the local concentration of calcium (2). Further, neural elements of more developed species exhibit a higher rate of calcium exchange and consequently, a higher number of calcium deposits (3). Finally, the barrier effect of the multilayered pineal arachnoid and the tight-junctions among their cells in mammals presumably promote the intrapincal concentration of calcium ions. The formaction of acervuli may be regulated by calcitonin, and the periacervular arachnoid cells ("acervuloblasts") act like ostoblasts (4
Comparative histology of pineal calcification
The pineal organ (pineal gland, epiphysis
cerebri) contains several calcified concretions called
"brain sand7' or acervuli (corpora arenacea). These
concretions are conspicuous with imaging techniques
and provide a useful landmark for orientation in the
diagnosis of intracranial diseases. Predominantly
composed of calcium and magnesium salts, corpora
arenacea are numerous in old patients. In smaller
number they can be present in children as well. The
degree of calcification was associated to various
diseases. However, the presence of calcified concretions
seems not to reflect a specific pathological state.
Corpora arenacea occur not only in the actual pineal
tissue but also in the leptomeninges, in the habenular
commissure and in the choroid plexus.
Studies with the potassium pyroantimonate (PPA)
method on the ultrastructural localization of free calcium
ions in the human pineal, revealed the presence of
calcium alongside the cell membanes, a finding that
underlines the importance of membrane functions in the
production of calcium deposits. Intrapineal corpora
arenacea are characterized by a surface with globular
structures. Meningeal acervuli that are present in the
arachnoid cover of the organ, differ in structure from
intrapineal ones and show a prominent concentric
lamination of alternating dark and light lines. The
electron-lucent lines contain more calcium than the dark
ones. There is a correlation between the age of the
subject and the number of layers in the largest acervuli.
This suggests that the formation of these layers is
connected to circannual changes in the calcium level of
the organ. The histological organization of the human
pineal is basically the same as that of mammalian experimental animals.
Pineal concretions present in mammalian animal
species are mainly of the meningeal type. Meningeal
cells around acervuli contain active cytoplasmic organelles and exhibit alkaline phosphatase reaction in
the rat and mink, an indication of a presumable
osteoblast-like activity. Using Kossa's method for the
staining of calcium deposits, a higher calcium
concentration was detected in the rat pineal than in the
surrounding brain tissue. Since in parathyroidectomised
rats calcified deposits are larger and more numerous than
in controls, the regulation of the production of acervuli
by the parathyroid gland has also been postulated.
In most of submammalian species, the pineal organs
(pineal-, parapineal organ, frontal organ, parietal eye)
are photoreceptive and organized similarly to the retina.
Acervuli were found in the pineal of some birds. The
pineal organs of lower vertebrates (fish, amphibians,
reptiles) exhibit a high calcium content by ultrastructural
calcium histochemistry (PPA-method). However,
concrements are not formed. The accumulation of ca2+
seems to depend on the receptor function of the organ.
Comparing pineal and retinal photoreceptors in the frog,
the photoreceptor outer segments of pinealocytes as well
as retinal cones and rods show a large amount of Capyroantimonate
deposits. In dark adapted animals
calcium ions are present in both sides of the
photoreceptor membranes of the outer segment, whereas
calcium is shifted extra-cellularly following light
adaptation
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