Congenital Hydrocephalus and Abnormal Subcommissural Organ Development in Sox3 Transgenic Mice

Congenital hydrocephalus (CH) is a life-threatening medical condition in which excessive accumulation of CSF leads to ventricular expansion and increased intracranial pressure. Stenosis (blockage) of the Sylvian aqueduct (Aq; the narrow passageway that connects the third and fourth ventricles) is a common form of CH in humans, although the genetic basis of this condition is unknown. Mouse models of CH indicate that Aq stenosis is associated with abnormal development of the subcommmissural organ (SCO) a small secretory organ located at the dorsal midline of the caudal diencephalon. Glycoproteins secreted by the SCO generate Reissner's fibre (RF), a thread-like structure that descends into the Aq and is thought to maintain its patency. However, despite the importance of SCO function in CSF homeostasis, the genetic program that controls SCO development is poorly understood. Here, we show that the X-linked transcription factor SOX3 is expressed in the murine SCO throughout its development and in the mature organ. Importantly, overexpression of Sox3 in the dorsal diencephalic midline of transgenic mice induces CH via a dose-dependent mechanism. Histological, gene expression and cellular proliferation studies indicate that Sox3 overexpression disrupts the development of the SCO primordium through inhibition of diencephalic roof plate identity without inducing programmed cell death. This study provides further evidence that SCO function is essential for the prevention of hydrocephalus and indicates that overexpression of Sox3 in the dorsal midline alters progenitor cell differentiation in a dose-dependent manner

Postnatal development of the Ammon's horn (CA1 and CA3 fields). A karyometric and topographic study

We have performed a karyometric study of the pyramidal neurons of CA1 and CA3 fields of the Ammon's horn, in male mice aged from the 5th to the 190th postnatal day. Nuclear sizes were measured with the aid of a Magiscan Analysis System, used in an interactive form, in both superficial and deep layers of the stratum pyramidal in those fields. The measurements were made at three different topographic levels: rostral; intermediate; and caudal, to detec any possible difference related to the topography of the neuron in the same field. We have found that both CAI and CA3 fields are correlated in the postnatal development of their nuclear pyramidal sizes and that al1 topographic levels of the hippocampus reach their highest karyometric sizes at the 10th-15th postnatal day. Caudal levels show higher karyometric values than the other levels and some differences between neurons of the superficial and deep layers of both fields are also described here and analysed in relation to the different ontogenetic gradients of these cells

The expression of p73 in the organum vasculosum of the lamina terminalis and choroid plexus of spontaneously hypertensive rats

The p73 proteins are present in different kinds of cells of the central nervous system, such as the choroid plexus, circumventricular structures and neuroepithelium. It has been reported that spontaneously hypertensive rats show ventricular dilation, changes in cerebrospinal fluid proteins and variations in the circumventricular structures such as the organum vasculosum of the lamina terminalis and the choroid plexus, which are altered in ventricular dilation. The aim of the present work is to study p73 expression in the organum vasculosum of the lamina terminalis and the choroid plexus and its variations in high blood pressure. Brains from control Wistar-Kyoto rats and spontaneously hypertensive rats were used. The organum vasculosum of the lamina terminalis and the choroid plexus were processed by immunohistochemistry and western blot with anti-TAp73. We found weaker markings in the organum vasculosum of the lamina terminalis and stronger markings in the choroid plexus of the hypertensive than the control rats. Therefore, hypertension in the spontaneously hypertensive rats produces alterations in choroid plexus protein p73 expression that is similar to that described for other circumventricular organs, but it is different in the organum vasculosum of the lamina terminalis. We can conclude that the functional balance between p73, organum vasculosum of the lamina terminalis and choroid plexus, which is probably necessary to maintain the normal functioning of these structures, is altered by the hypertension found in these rats

Effect of hypertension on the angiotensin II fibres arriving at the posterior lobe of the hypophysis of the rat. An immunohistochemical study

We studied immunohistochemically the posterior lobe of the hypophysis (PL) of 15-week-old spontaneously hypertensive rats (SHR) and of matched normotensive Wistar Kyoto rats (WKY), by using our own polyclonal antibody raised in mice against Angiotensin I1 (mouse-antiangiotensin 11, MAAII). The blood pressure, water intake and volume of the PL were also recorded. The SHR rats were hypertensive, drank more water and showed a clear hypertrophy of their hypophysial PL. Also the PL of the SHR animals showed an increase in the immunoreactivity to the antiangiotensin I1 antibody in the fibres arriving at the PL, with respect to the PL of WKY rats. This increase is compatible with the hyperactivity of the brain RAS, depletion of vasopressin content in the PL and increase in plasmatic levels of vasopressin described in SHR rats with respect to normotensive animals, as angiotensin I1 could locally stimulate vasopressin release to plasma from the neurohypophysis

Systemic Hypertension Effects on the Ciliary Body and Iris. An Immunofluorescence Study with Aquaporin 1, Aquaporin 4, and Na⁺, K⁺ ATPase in Hypertensive Rats

Aquaporin 1 (AQP1) and aquaporin 4 (AQP4) have been identified in the eye as playing an essential role in the formation of the aqueous humor along with the Na+/K+ ATPase pump. Different authors have described the relationship between blood pressure, aqueous humor production, and intraocular pressure with different conclusions, with some authors supporting a positive correlation between blood pressure and intraocular pressure while others disagree. The aim of this work was to study the effect of high blood pressure on the proteins involved in the production of aqueous humor in the ciliary body (CB) and iris. For this purpose, we used the eyes of spontaneously hypertensive rats (SHR) and their control Wistar-Kyoto rats (WKY). Immunofluorescence was performed in different eye structures to analyze the effects of hypertension in the expression of AQP1, AQP4, and the Na+/K+ ATPase α1 and α2 subunits. The results showed an increase in AQP1 and Na+/K+ ATPase α1 and a decrease in AQP4 and Na+/K+ ATPase α2 in the CB of SHR, while an increase in AQP4 and no significant differences in AQP1 were found in the iris. Therefore, systemic hypertension produced changes in the proteins implicated in the movement of water in the CB and iris that could influence the production rate of aqueous humor, which would be affected depending on the duration of systemic hypertension

Effects of alcohol and aging on the cingular (area 24) and frontal (area 6) cortical areas of the mouse

We have studied the morphometric changes of the neurons of the cingular area 24 and frontal area 6 of the mouse, produced by age andlor chronic alcohol intake. The parameters analyzed were nuclear area of these cortical neurons and cellular density (celllneuropil coefficient). Wc dctccted a decrease in the number of neurons with age in practically al1 layers of the control animals. In the animals that chronically ingested the alcoholic solution, we also detected a decrease in the number of neurons with age, but only in layer V of the frontal cortex and in layer VI of the cingular area 24. The comparison between the control and the alcoholic group showed that alcohol intake caused an incrcasc in the nuclear area of the neurons in layer 11-111 of the frontal cortcx at 180 days, while in the cingular cortex the increase in nuclear area of its neurons was significative at 180 days in layer 11-111 and at 35 and 180 days in layers V and VI. We think that these changes are the expression of the neurona1 plasticity in both cortical areas in response to the alcohol exposure

The effects of chronic administration of captopril on the mouse median eminence

The effects of Captopril (an angiotensinconverting enzyme inhibitor) on the median eminence (ME) of the male albino mouse have been examined using morphometric and immunohistochemical procedures. We measured the nuclear area of the ependymocytes of the ME and of the glial cells of the reticular external zone of the ME. We also determined the cell/neuropil coefficient (CNC), which expreses the relation between cellular area and neuropil of the ME, and the global volume of the ME in each animal. For the immunohistochemical study we used rabbit antiarginine- vasopressin, and compared the results in the different groups of mice. We detected an increase in the immunoreactive material (arginine-vasopressin, A-V) and an increase in the global volume of the organ and also an increase of the neuropil of the ME after the longest exposure to the drug. These alterations could be related to the inhibition of the brain angiotensin 11 by captopril and the accumulation of vasopressin in the fibrous tract that runs from the paraventricular nucleus (PVN) to the neurohypophysis

Effect of hypertension on the angiotensin II fibres arriving at the posterior lobe of the hypophysis of the rat. An immunohistochemical study

We studied immunohistochemically the posterior lobe of the hypophysis (PL) of 15-week-old spontaneously hypertensive rats (SHR) and of matched normotensive Wistar Kyoto rats (WKY), by using our own polyclonal antibody raised in mice against Angiotensin I1 (mouse-antiangiotensin 11, MAAII). The blood pressure, water intake and volume of the PL were also recorded. The SHR rats were hypertensive, drank more water and showed a clear hypertrophy of their hypophysial PL. Also the PL of the SHR animals showed an increase in the immunoreactivity to the antiangiotensin I1 antibody in the fibres arriving at the PL, with respect to the PL of WKY rats. This increase is compatible with the hyperactivity of the brain RAS, depletion of vasopressin content in the PL and increase in plasmatic levels of vasopressin described in SHR rats with respect to normotensive animals, as angiotensin I1 could locally stimulate vasopressin release to plasma from the neurohypophysis