Blood-brain barrier and foetal-onset hydrocephalus, with a view on potential novel treatments beyond managing CSF flow.

Despite decades of research, no compelling non-surgical therapies have been developed for foetal hydrocephalus. So far, most efforts have pointed to repairing disturbances in the cerebrospinal fluid (CSF) flow and to avoid further brain damage. There are no reports trying to prevent or diminish abnormalities in brain development which are inseparably associated with hydrocephalus. A key problem in the treatment of hydrocephalus is the blood-brain barrier that restricts the access to the brain for therapeutic compounds or systemically grafted cells. Recent investigations have started to open an avenue for the development of a cell therapy for foetal-onset hydrocephalus. Potential cells to be used for brain grafting include: (1) pluripotential neural stem cells; (2) mesenchymal stem cells; (3) genetically-engineered stem cells; (4) choroid plexus cells and (5) subcommissural organ cells. Expected outcomes are a proper microenvironment for the embryonic neurogenic niche and, consequent normal brain development.

Meningitis por Streptococcus agalactiae en el anciano / Streptococcus agalactiae meningitis in the elderly

La meningitis bacteriana continúa siendo una enfermedad con una alta mortalidad en ancianos, a pesar de la moderna antibioterapia. En los últimos años, la meningitis bacteriana ha cambiado y es frecuente en adultos, especialmente en ancianos. El déficit de la función inmunológica relacionada con el envejecimiento y la mayor propensión a padecer enfermedades agudas o crónicas comórbidas pueden predisponer a la infección por estreptococos del grupo B en el anciano. Las manifestaciones clínicas pueden ser atípicas en la población geriátrica. La fiebre, la cefalea y la rigidez de nuca pueden estar ausentes. Presentamos un caso de meningitis por Streptococcus agalactiae en una mujer anciana sin factores comórbidos. Debemos tener presente esta enfermedad como posible diagnóstico ante un paciente anciano con confusión o bajo nivel de conciencia. (AU)

A second look at the barriers of the medial basal hypothalamus.

The cell bodies of hypothalamic secretory neurons are localized in areas protected by the blood-brain barrier (BBB), whereas their axon terminals are localized in the median eminence, which lacks a BBB. This implies a complex barrier system, allowing neurons of the central nervous system to secrete into the blood stream without making the BBB leaky. In the present study, three experimental protocols were applied to clarify certain relevant aspects of the barriers operating in the medial basal hypothalamus of the rat. We established that the milieu of the arcuate nucleus is exposed to both the ventricular and the subarachnoidal cerebrospinal fluid (CSF). The median eminence milieu, the perivascular space of the portal vessels, and the subarachnoid space appear to be in open communication; also, beta2-tanycytes establish an efficient barrier between the median eminence milieu and the ventricular CSF. Similarly, beta1-tanycytes establish a lateral barrier, separating the intercellular space of the median eminence from that of the arcuate nucleus. We also found that the glucose transporter I (GLUT I), a BBB marker, is localized throughout the whole plasma membrane of beta1-tanycytes, but is missing from beta2-tanycytes. Expression of GLUT I by tanycytes progressively develops during the first postnatal weeks; while the degree of damage of the arcuate nucleus by administration of monosodium glutamate, at different postnatal intervals, parallels that of the GLUT I immunoreactivity of beta1-tanycytes. An explanation is offered for the selective destruction of the arcuate neurons by the parenteral administration of monosodium glutamate to infant rats.

Lateral evaginations from the third ventricle into the rat mediobasal hypothalamus: an amplification of the ventricular route.

In this work we report the existence of several evaginations extending out of the third ventricle within the mediobasal hypothalamus of the rat. In coronal sections, these evaginations appear as very narrow canaliculi integrating a canalicular system, which increases the contact surface between the ventricular lining and the nervous tissue. Consequently these evaginations enlarge the ventricular route for the transport of active principles present in the cerebrospinal fluid, such as (neuro)hormones and neurotransmitters. The mediobasal hypothalamus includes the arcuate nucleus and the median eminence (both involved in neuroendocrine mechanisms and in the regulation of pituitary function). A possible implication of our finding is that the neuroactive substance-containing ventricular cerebrospinal fluid may reach the intercellular spaces of the surrounding neuropil of the arcuate nucleus. According to literature these substances cross the ependyma of the lateral wall of the infundibular recess of the third ventricle. We suggest that such substances might also pass through the ependymal lining of the canalicular system, which displays the same ultrastructural characteristics as the rest of the ependyma of the lateral wall of the third ventricle. Therefore, the arcuate neurons may be influenced not only by synaptic inputs (afferent fibers) but also by non-synaptic diffusion neurotransmission (by means of neuroactive substances present in the cerebrospinal fluid).

Lectinhistochemistry and ultrastructure of microglial response to monosodium glutamate-mediated neurotoxicity in the arcuate nucleus.

In this study we describe the most relevant morphological features of the microglial reaction that takes place in the arcuate nucleus (AN) after neurotoxic injury induced by a single subcutaneous injection of monosodium glutamate (MSG) in neonatal rats. The time course of the reaction was evaluated by lectinhistochemistry. Microglial/macrophagic cells were labelled with the lectin obtained from Lycopersicon esculentum and with B4 isolectin from Griffonia simplicifolia. The microglial response was also studied by ultrastructural observations. The histochemical study revealed the presence of few reactive microglial cells at 6 h post-injection. These cells were intensely stained and had a globular morphology but contained no neuronal debris inside them when observed under the electron microscope. At 12 h post-injection, the number of microglial cells had increased and, at the same time, intense phagocytic activity was observed ultrastructurally. The microglial reaction peaked at 24 and 36 h post-injection, when the number of microglial/macrophagic cells was maximum, although the ultrastructural observations showed that at 36 h the amount of debris ingested by macrophages was decreased with respect to animals sacrificed at 24 h. Finally, at 4 days after neurotoxic injection the number and morphology of microglial cells were similar to those observed in the control rats. The ultrastructural study also revealed the existence of microglial cell mitosis in the territory of the AN together with a strong increase in the number of supraependymal cells resembling macrophages in the third ventricle during the lesion. Our data demonstrate that activated microglial cells initially extend throughout the damaged territory, but from 24-36 h onwards they are especially patent in the ventrolateral portions of the AN.

Ultrastructural features of rat arcuate nucleus neurons during pregnancy.

The ultrastructure of the arcuate nucleus was studied in Sprague-Dawley rats sacrificed at 7, 10, 14 and 20 days of gestation, using conventional techniques of electron microscopy. Our results revealed an increase in granular filamentous bodies and whorled bodies that appear in arcuate neurons as early as on the 7th day of gestation. A further increase of these structures was showed by day 10 and, especially, by day 14. In the arcuate nucleus of rats sacrificed on day 14 of gestation, some compact, homogeneous and very large (up to 5.5 microm diameter) granular filamentous bodies may be seen both in neuronal bodies and in dendrites. In some neurons of arcuate nucleus of these gestational phases (days 10 and 14), besides the whorled bodies dense-core vesicles were found. Neurons with cilia were occasionally observed, and some neuronal bodies were in close apposition and joined by intercellular bridges. Open synapses were observed during all the gestational phases. The smallest number of these synapses was seen in the arcuate nucleus of rats sacrificed on day 14 of gestation.

Giant granular filamentous bodies in the cytoplasm of arcuate nucleus neurons of castrated rats.

We have performed an ultrastructural and quantitative study of granular filamentous bodies (GFBs) present in the cytoplasm of some arcuate nucleus neurons of rats of both sexes castrated at one month of age and sacrificed one or three months later, as well as untreated and sham-operated animals of the same ages. GFBs appear as round or ovoid cytoplasmic inclusions of granular-filamentous texture and generally lack a limiting membrane; their sizes vary from 0.7 to 2.8 microns (average 1.7 microns). GFBs are present more frequently in the perikarya, but they also occur in dendrites. In rats of both sexes castrated at one month of age and sacrificed three months later a noticeable finding was the presence of some giant GFBs, whose major axis could reach up to 6 microns. The nomenclature, the origin and the possible significance and function of GFBs are discussed.

Transependymal diapedesis: reality or speculation?

The present study attempts to describe the possible origin of certain elements situated inside the infundibular recess of the third ventricle, such as supraependymal cells and Herring bodies, together with the way in which they reach the ventricular lumen. We used albino Sprague-Dawley rats and cats of both sexes sacrificed at different ages. The results point to the possible existence of a transependymal diapedesis of some Herring bodies and supraependymal cells into the infundibular recess.

The ependymal surface of the fourth ventricle of the rat: a combined scanning and transmission electron microscopic study.

The morphological features of the ependymal surface and supraependymal elements of the fourth ventricle of the rat were examined by scanning electron microscopy (SEM) and by the transmission electron microscopy (TEM). The results confirm the following aspects: 1) The presence of supraependymal elements and microvilli in the ependymal territories, including the sites where the cilia completely cover the ependymal surface; 2) The existence of cilia with oval or spherical thickenings together with supraependymal bulbs similar in size to those of the larger ciliary swellings; 3) Identification of the long supraependymal fibres with intermittent fusiform dilations observed under the SEM with the nerve fibres seen under the TEM; 4) The existence of intraventricular axodendritic synapses.

[Morphologic substrates of the ventricular route of secretion and transport of substances in the tubero-infundibular region of the hypothalamus. Ultrastructural study]. / Sustratos morfológicos de la vía ventricular de secreción y transporte de sustancias en la región tuberoinfundibular del hipotálamo. Estudio ultraestructural.

Ultrastructural studies of the ependyma of the tuberoinfundibular region of the rat hypothalamus have revealed the existence of intraventricular axonal endings and of cytoplasmic blebs and bulbs that project from the apical surface of the ependymal cells to the ventricular lumen. All these structures account for the processes of ependymal apocrine secretion and the neuroventriculocrinia, and hence the release of biologically active substances into the cerebrospinal fluid (CSF). These substances contained in the CSF must act on the nervous nuclei of the tuberoinfundibular region, such as the arcuate nucleus, which is very important in the neuroendocrine regulation of the anterior pituitary gland. Dilated intercellular spaces among neighbouring ependymocytes of this region, small intraependymal cisternae and, in particular, a lateral prolongation of the infundibular recess, which courses through the nervous tissue between the arcuate nucleus and the median eminence from the vertex of the lateral angle of the infundibular recess, may be the route followed by the CSF from the third ventricle to the tissue compartment of the tuberoinfundibular region. Also studied are the cisternae of the region and the relationships of these with the lateral prolongation of the infundibular recess. Some of these cisternae may be filled by the CSF through the prolongation. In this way, the tissue compartment of CSF would be enlarged, and hence the ventricular route for the secretion and transport of biologically active substances would be potentiated.

Sustratos morfológicos de la vía ventricular de secreción y transporte de sustancias en la región tuberoinfundibular del hipotálamo: estudio ultraestructural / Morphologic substrates of the ventricular route of secretion and transport of substances in the tubero-infundibular region of the hypothalamus: ultrastructural study

Ultrastructural studies of the ependyma of the tuberoinfundibular region of the rat hypothalamus have revealed the existence of intraventricular axonal endings and of cytoplasmic blebs and bulbs that project from the apical surface of the ependymal cells to the ventricular lumen. All these structures account for the processes of ependymal apocrine secretion and the neuroventriculocrinia, and hence the release of biologically active substances into the cerebrospinal fluid (CSF). These substances contained in the CSF must act on the nervous nuclei of the tuberoinfundibular region, such as the arcuate nucleus, which is very important in the neuroendocrine regulation of the anterior pituitary gland. Dilated intercellular spaces among neighbouring ependymocytes of this region, small intraependymal cisternae and, in particular, a lateral prolongation of the infundibular recess, which courses through the nervous tissue between the arcuate nucleus and the median eminence from the vertex of the lateral angle of the infundibular recess, may be the route followed by the CSF from the third ventricle to the tissue compartment of the tuberoinfundibular region. Also studied are the cisternae of the region and the relationships of these with the lateral prolongation of the infundibular recess. Some of these cisternae may be filled by the CSF through the prolongation. In this way, the tissue compartment of CSF would be enlarged, and hence the ventricular route for the secretion and transport of biologically active substances would be potentiated

Myelinated Herring bodies in the median eminence of the cat.

An electron-microscopic study was carried out on the median eminence of cats during post-natal development. From the moment of birth (observations performed 12 hours later) Herring bodies were seen in the fibrillary layer of the median eminence. At 45 days after birth, myelinated nerve fibres could be observed, some of them containing neurosecretory granules. The number of myelinated fibres in the median eminence increased with age and at 90 days some Herring bodies appeared surrounded by myelin sheaths; these mainly contained neurosecretory granules and a few mitochondria.

Atrial natriuretic factor increases cyclic GMP and cyclic AMP levels in a directly photosensitive pineal organ.

Atrial natriuretic factor (ANF) stimulates accumulation of cyclic GMP in a photosensitive organ, as evidenced for the first time in cultured trout pineals. Stimulation was rapid (within a few min), dose-dependent, and stronger in organs cultured in darkness than in those cultured under light. After 30 min in the dark, (i) cyclic AMP levels were slightly increased at 10(-7) mole/l of ANF, (ii) cyclic GMP and cyclic AMP increased dramatically after inhibition of the phosphodiesterases by isobutylmethylxanthine (IBMX), (iii) ANF and IBMX effects were more than additive on cyclic GMP, (iv) pertussis toxin decreased the cyclic GMP response to ANF. These responses were affected by light. The possibility that cyclic GMP might be a second messenger of both light and chemical (ANF) inputs, in pineal photoreceptor cells, is hypothetized.

Arginine-vasopressin immunoreactive material in the gastrointestinal tract.

Like many other neuropeptides, vasopressin is not confined to the hypothalamic neurohypophysial system. Furthermore, vasopressin was found to be a potent vasoconstrictor in the rat jejunum, reducing myenteric artery flow. These associations were the basis of this investigation on the presence of vasopressin in the gastrointestinal (GI) tract by both RIA and immunohistochemistry. Portions of the gastrointestinal tract and pancreatic islets of the rat were extracted with 0.1 N HCl for RIA measurements of AVP content. Similar portions from the male cat GI tract were used for immunohistochemistry studies. Acid extracts of the GI tract were found to contain immunoreactive AVP with the highest concentration (pg/mg protein) in the fundus portion of the stomach (15.0 +/- 1.6) and slightly lower values down along the antrum-pylorus portion (6.7 +/- 0.6), proximal jejunum (8.6 +/- 0.2), distal ileum (9.7 +/- 0.3) and colon (11.9 +/- 0.5). In the pancreatic islets the concentration was much higher (72.0 pg/mg protein). The extract inhibition curves showed parallelism with the appropriate standard preparation of AVP in the specific RIA. Immunohistochemical localization showed IR-AVP in the nerve fibers around the myenteric plexus of the second portion of the duodenum. It was also found in fibers starting from where the myenteric plexus goes through the layer of muscle fibers, penetrating the submucosa and duodenal mucosa, ending near the capillaries situated along the basal side of the villous epithelium cells. Similar IR-AVP activity was found in cells located in the mucosal epithelium of the duodenum, jejunum, ileum, colon and rectum.(ABSTRACT TRUNCATED AT 250 WORDS)