Neurosurgical anatomy of the floor of the third ventricle and related vascular structures.

PURPOSE: Anatomical knowledge of the floor of the third ventricle (FTV) is essential in avoiding surgical complications during endoscopic third ventriculostomy. The purpose of this study was to characterize the morphometry of FTV and related arteries, particularly the basilar artery (BA), as well as the factors that influence it. METHODS: Twenty-six formalin-fixed adult brains and two hundred adult brain MRIs were studied focusing on FTV and related arteries. Dimensions of interest were measured using image analysis software. Morphometric data obtained were statistically analysed. RESULTS: Distances between FTV, intermammillary sulcus (IMS), infundibulum, BA bifurcation, and posterior communicating arteries (PCoAs) were described on the cadavers and the MRIs. Distance between right and left PCoAs was greater at their anterior extremity (p < 0.001). Right PCoA was longer (p = 0.016). BA was lateralized in 58.4% of cases and its calibre was larger in males (p < 0.001). The distance from BA apex to FTV was inversely correlated with BA diameter (p < 0.001) and age (p = 0.004). Distance from IMS to infundibulum and the distance between both PCoAs were greater in MRI series when compared to cadaver series (p < 0.001). CONCLUSIONS: A quantitative description of the morphometry of the region of the FTV and related vessels was obtained, helping neurosurgeons in planning their surgical approach. The distance from BA apex to FTV was shorter in individuals with larger BA calibre and in older subjects. MRI studies were qualitatively superior to cadaveric studies in evaluating the anatomy of this region.

Genetic structure and diversity of native Guadua species (Poaceae: Bambusoideae) in natural populations of the Brazilian Amazon rainforest.

The Southwestern Region of the Brazilian Amazon is formed by forests dominated by bamboos. The genus Guadua is endemic to the Americas, and little is known about the genetic diversity and structure of species of this genus. This study aimed to evaluate the genetic diversity and structure of two native Guadua species in natural populations in the Southwestern region of the Brazilian Amazon. Therefore, the genetic diversity and structure of Guadua aff. chaparensis and Guadua aff. lynnclarkiae were evaluated with the use of microsatellite molecular markers (SSR). It was verified that the average genetic diversity for the populations studied was considered high ( H ^ e =0.5) compared to other species of bamboo. All populations had rare and private alleles, and none of them presented significant values of inbreeding. The populations were divergent ( G ^ ST = 0.46), resulting in a low apparent gene flow. The Bayesian analysis showed that among the 350 individuals analyzed, five groups (K=5) were formed, with little similarity among the groups (Populations), although two of them presented clonal individuals. According to the results obtained, it can be conclude that populations should be treated as having unique characteristics, mainly when accessed for management and for in situ and ex situ conservation studies.

Neurosurgical anatomy of the insular cortex.

OBJECTIVE: The purpose of this study was to clarify the morphology of the insular cortex focusing not only on the shape of the insula, but also on sulcal and gyral organization. PATIENTS AND METHODS: Sixty formalin-fixed adult brain hemispheres had their insula exposed and photographed. The dimensions of each gyrus and sulcus were measured using an image analysis software. The morphometric data obtained was statistically analysed. RESULTS: The insular cortex shape alternates between triangular and trapezoid, being the triangular shape the most common (75%). The angle between the posterior and inferior peri-insular sulcus in the trapezoid insulae had a mean range of 131.17° (SD = 12.277). A minimum of 3 and a maximum of 6 insular gyri were observed, being 5 the most common total number of gyri observed. The accessory gyrus was present in 66% of the insulae and well-developed in 38% of the cases. A statistical association between the number of gyri in the posterior lobe and the presence of a novel gyrus or a more developed accessory gyrus in the anterior lobe was found (P = 0.006). The posterior short gyrus was the longest of the short gyri (P <  0.001), followed by the anterior short gyrus (P < 0.001). The anterior long gyrus was the largest of the long gyri (P = 0.003). The contribution of each of the short gyri to the formation of the insular apex was inconstant. The most common observed apex arrangement was the combination of the anterior and of the middle short gyri. CONCLUSIONS: This study makes a strong contribution to the understanding of the insular cortex anatomy, allowing neurosurgeons to be more capable to decide the best approach to this cortical area.

Chronic ethanol intake induces partial microglial activation that is not reversed by long-term ethanol withdrawal in the rat hippocampal formation.

Neuroinflammation has been implicated in the pathogenesis of several disorders. Activation of microglia leads to the release of pro-inflammatory mediators and microglial-mediated neuroinflammation has been proposed as one of the alcohol-induced neuropathological mechanisms. The present study aimed to examine the effect of chronic ethanol exposure and long-term withdrawal on microglial activation and neuroinflammation in the hippocampal formation. Male rats were submitted to 6 months of ethanol treatment followed by a 2-month withdrawal period. Stereological methods were applied to estimate the total number of microglia and activated microglia detected by CD11b immunohistochemistry in the hippocampal formation. The expression levels of the pro-inflammatory cytokines TNF-α, COX-2 and IL-15 were measured by qRT-PCR. Alcohol consumption was associated with an increase in the total number of activated microglia but morphological assessment indicated that microglia did not exhibit a full activation phenotype. These data were supported by functional evidence since chronic alcohol consumption produced no changes in the expression of TNF-α or COX-2. The levels of IL-15 a cytokine whose expression is increased upon activation of both astrocytes and microglia, was induced by chronic alcohol treatment. Importantly, the partial activation of microglia induced by ethanol was not reversed by long-term withdrawal. This study suggests that chronic alcohol exposure induces a microglial phenotype consistent with partial activation without significant increase in classical cytokine markers of neuroinflammation in the hippocampal formation. Furthermore, long-term cessation of alcohol intake is not sufficient to alter the microglial partial activation phenotype induced by ethanol.

Neurosurgical relevance of the dissection of the diencephalic white matter tracts using the Klingler technique.

OBJECTIVE: The Klingler fiber dissection technique is a relevant and reliable method for neurosurgery to identify with accuracy the fine structure of the brain anatomy highlighting white matter tracts. In order to demonstrate the significance of the application of this technique, we aimed to observe the course and relations of the mammillothalamic and habenulo-interpeduncular tracts as there are very few papers showing these important diencephalic tracts. MATERIAL AND METHODS: Twelve formalin-fixed brains were dissected using the Klingler technique in order to expose the medial diencephalic surface. Diencephalic white matter tracts, particularly the mammillothalamic and habenulo-interpeduncular tracts, were dissected using wooden spatulas and metallic dissectors with different sizes and tips. Several measurements were performed in both dissected hemispheres relative to the mammillothalamic and habenulo-interpeduncular tracts. RESULTS: The course and length of these two tracts were visualized and the relations with other fiber systems and with the neighboring gray matter structures quantified and registered. The mammillothalamic tract approximately marks the anteroposterior coordinate of the anterior pole of the subthalamic nucleus in the anterior commissure - posterior commissure plane. CONCLUSION: The present study helps to understand the three-dimensional architecture of the white matter systems of tracts when the Klingler technique is used. The numerical data obtained may be helpful to neurosurgeons while approaching brain paraventricular and ventricular lesions and deep brain stimulation. Finally, the anatomical knowledge can lower surgical complications and improve patient care particularly in the field of neurosurgery.

Neuroanatomy: The added value of the Klingler method.

Undergraduate neuroanatomy students are usually not able to achieve a clear comprehension of the spatial relationships existing between the white matter fiber tracts in spite of numerous neuroanatomy textbooks, atlases and multimedia tools. The objective of this paper is to show the educational value of the application of the Klingler fiber dissection technique and the use of these dissections in the understanding of the three-dimensional intrinsic anatomy of the brain white matter for medical students. Four formalin-fixed brains were dissected using the Klingler methodology in order to reveal the inner anatomical organization of the brain white matter. The most important fiber systems were dissected and their relationships to the cerebral and cerebellar gray matter structures visualized. These dissections were used as a learning tool in teaching the brain white matter structural and topographical connectivity. The white matter fiber systems were presented to undergraduate medical students during a neuroanatomy course. They observed and manipulated the dissected specimens leading to a thorough understanding of the configuration and location of the white matter fiber tracts, and their relationships to the ventricular system and gray matter structures. Subsequently, students were asked to answer a survey concerning the importance of the utilization of this material in their understanding of the three-dimensional intrinsic anatomy of the brain white matter. The knowledge acquired with this technique, complemented by conventional formalin-fixed sections may improve the neuroanatomical knowledge and future retention of medical students.

Changes in the female arcuate nucleus morphology and neurochemistry after chronic ethanol consumption and long-term withdrawal.

Ethanol is a macronutrient whose intake is a form of ingestive behavior, sharing physiological mechanisms with food intake. Chronic ethanol consumption is detrimental to the brain, inducing gender-dependent neuronal damage. The hypothalamic arcuate nucleus (ARN) is a modulator of food intake that expresses feeding-regulatory neuropeptides, such as alpha melanocyte-stimulating hormone (α-MSH) and neuropeptide Y (NPY). Despite its involvement in pathways associated with eating disorders and ethanol abuse, the impact of ethanol consumption and withdrawal in the ARN structure and neurochemistry in females is unknown. We used female rat models of 20% ethanol consumption for six months and of subsequent ethanol withdrawal for two months. Food intake and body weights were measured. ARN morphology was stereologically analyzed to estimate its volume, total number of neurons and total number of neurons expressing NPY, α-MSH, tyrosine hydroxylase (TH) and estrogen receptor alpha (ERα). Ethanol decreased energy intake and body weights. However, it did not change the ARN morphology or the expression of NPY, α-MSH and TH, while increasing ERα expression. Withdrawal induced a significant volume and neuron loss that was accompanied by an increase in NPY expression without affecting α-MSH and TH expression. These findings indicate that the female ARN is more vulnerable to withdrawal than to excess alcohol. The data also support the hypothesis that the same pathways that regulate the expression of NPY and α-MSH in long-term ethanol intake may regulate food intake. The present model of long-term ethanol intake and withdrawal induces new physiological conditions with adaptive responses.

nNOS is involved in cardiac remodeling induced by chronic ethanol consumption.

Chronic ethanol consumption has deleterious effects on the cardiovascular system by directly damaging the myocardial structure and/or by neurohormonal activation. Moreover, nitric oxide (NO) derived from neuronal NO synthase (nNOS) seems to be important to balance the harmful effects of ethanol consumption, because it influences several aspects of cardiac physiology and attenuates pathological cardiac remodeling. However, the impact of chronic ethanol consumption on nNOS expression is unknown. We address this subject in the present study by evaluating whether chronic ethanol consumption induces cardiac remodeling and hypertension, and if these changes are associated with alterations in the expression of nNOS. Male Wistar rats were examined after ingesting a 20% alcohol solution for 6 months. Blood alcohol concentration and brain natriuretic peptide (BNP) levels were measured. The cardiac remodeling was assessed by histomorphometric analysis and the nNOS expression was evaluated by immunofluorescence and western blot analysis. Our results show that chronic ethanol consumption induces cardiac remodeling, namely thinning of left ventricular wall, cardiomyocyte hypertrophy and increased fibrosis, and elevations of arterial blood pressure. They also show that in rats fed with ethanol for 6 months, the circulating BNP levels had decreased as well as the expression of nNOS in left ventricle cardiomyocytes. These findings suggest that the effects of chronic ethanol consumption on BNP levels and/or on nNOS expression in cardiomyocytes may contribute to aggravate the cardiac remodeling and leads to progression of cardiomyopathy.

Effects of chronic alcohol consumption and withdrawal on the response of the male and female hypothalamic-pituitary-adrenal axis to acute immune stress.

The hypothalamic-pituitary-adrenal (HPA) axis plays a central role in the response to stress, and its activity is sexually dimorphic and modulated by sex steroids. Recent work indicates that HPA axis functioning is disturbed by chronic alcohol consumption and subsequent withdrawal in rats of both sexes, but particularly in females. To examine the influence of sex steroid hormones in HPA axis response to acute stress after ingestion of a 20% ethanol solution over 6months and subsequent withdrawal (2months), intact males, and estradiol- and oil-injected ovariectomized females received a single intraperitoneal injection of lipopolysaccharide (LPS). Six hours after LPS administration, corticosterone concentrations were increased in all male groups; however, in ethanol-treated rats they remained below those of control and withdrawn rats. mRNA levels of corticotrophin-releasing hormone (CRH) increased, and were identical in all groups after LPS stimulation, whereas those of vasopressin, although increased, remained below control levels. LPS stimulation elevated corticosterone concentrations in all oil-injected female groups, but did not alter those of estradiol-injected females. In oil- and estradiol-injected ethanol-treated females, CRH mRNA levels did not change in response to LPS stimulation, whereas those of vasopressin increased, but stayed below control levels. In withdrawn oil- and estradiol-injected females, CRH and vasopressin gene expression increased, but did not reach control levels. These data show that prolonged alcohol consumption produces long-lasting, possibly irreversible, changes in the neuroendocrine system that regulates the production of corticosteroids, and that these consequences are more profound in females, particularly when estrogen levels are low.

Sexually dimorphic response of the hypothalamo-pituitary-adrenal axis to chronic alcohol consumption and withdrawal.

In males, long-term alcohol consumption provokes neurochemical changes in the medial parvocellular division of the PVN (PVNmp) that are partially reversed by withdrawal. Because gonadal steroids modulate the activity of the hypothalamo-pituitary-adrenal axis, we analyzed the possibility that the repercussions of chronic alcohol consumption and withdrawal on the anatomy and neurochemistry of the PVNmp might differ between the sexes. Male and female Wistar rats were examined after ingesting a 20% alcohol solution for 6 months or after 2 months of withdrawal from 6 months of alcohol consumption. The levels of gonadal steroids and the basal concentrations of corticosterone were also evaluated. Chronic alcohol consumption and withdrawal did not alter the global cytoarchitectonic features of the PVNmp in rats of both sexes. However, alcohol consumption was associated with a decrease in the number of vasopressin (VP) neurons only in females and of corticotropin releasing hormone (CRH) neurons in males and females. Further, the response to withdrawal was sexually dimorphic because in males there was a partial recovery of the number of CRH neurons whereas in females there was a further loss of VP and CRH neurons. Corticosterone levels were unchanged by alcohol consumption, but they were decreased by withdrawal in females. Alcohol consumption and withdrawal did not alter estrogen and progesterone concentrations in females, but decreased testosterone levels in males. These findings show that the response of CRH and VP neurons to excess alcohol is gender-specific, with females being more vulnerable during alcohol consumption and, most notably, after withdrawal.

Timed hypocaloric food restriction alters the synthesis and expression of vasopressin and vasoactive intestinal peptide in the suprachiasmatic nucleus.

In mammals, the main circadian pacemaker is located in the suprachiasmatic nucleus (SCN) and its most potent synchronizer is the daily variation of the intensity of light. However, other nonphotic cues, such as timed food restriction, can induce changes in the circadian rhythms, leading also to the appearance of a food-entrained oscillator. The present study was designed to establish if the alterations of the circadian rhythms induced by timed hypocaloric food restriction are accompanied by structural changes in the SCN. Two groups of adult rats, both maintained on 12-h light/12-h dark cycles, were used; in one group, animals had permanent free access to food, whereas in the other they were subjected to a restricted hypocaloric early morning feeding during 7 months. Using stereological techniques and in situ hybridization, we have examined the structure of the SCN and the synthesis and expression of vasopressin (AVP) and vasoactive intestinal peptide (VIP). The volume of the SCN and the total number of neurons did not vary between the two groups. However, the total number of AVP- and VIP-immunoreactive neurons and the AVP and VIP mRNA levels were significantly decreased in timed hypocaloric food-restricted animals. The results indicate that timed hypocaloric food restriction has led to changes of AVP and VIP content of the neurons. They furthermore suggest the existence of a coupling between the food-entrainable oscillator and the light-entrainable pacemaker.

Prolonged alcohol intake leads to reversible depression of corticotropin-releasing hormone and vasopressin immunoreactivity and mRNA levels in the parvocellular neurons of the paraventricular nucleus.

The ability of alcohol to activate the hypothalamic-pituitary-adrenal (HPA) axis is well documented in investigations based in acute and short-term experimental paradigms. Herein, we have addressed the possibility that the prolonged exposure to ethanol concentrations that are initially effective in stimulating corticosteroid secretion might induce alterations in the response of the HPA axis that cannot be evinced by shorter exposures. Using conventional histological techniques, immunohistochemistry and in situ hybridization, we have examined the medial parvocellular division of the paraventricular nucleus (PVNmp), and the synthesis and expression of corticotropin-releasing hormone (CRH) and vasopressin (VP) by its constituent neurons, in rats submitted to 6 months of ethanol treatment and to withdrawal (2 months after 6 months of alcohol intake). Ethanol treatment and withdrawal did not produce neuronal loss in the PVNmp. However, the total number of CRH- and VP-immunoreactive neurons and the CRH mRNA levels were significantly decreased by ethanol treatment. In withdrawn rats, the number of CRH- and VP-immunostained neurons and the gene expression of CRH were increased relative to ethanol-treated rats and did not differ from those of controls. No significant variations were detected in VP mRNA levels as a result of ethanol treatment or withdrawal. These results show that prolonged alcohol intake blunts the expression of CRH and VP in the parvocellular neurons of the PVN, and that this effect is, partially at least, reversible by withdrawal. They also suggest that the development of tolerance to the effects of ethanol involve changes that take place at the hypothalamic level.

Prolonged alcohol intake leads to irreversible loss of vasopressin and oxytocin neurons in the paraventricular nucleus of the hypothalamus.

Previous data revealed that numerous neurons in the supraoptic nucleus degenerate after prolonged ethanol exposure, and that the surviving neurons increase their activity in order to prevent dramatic changes in water metabolism. Conversely, excess alcohol does not induce cell death in the suprachiasmatic nucleus, but leads to depression of neuropeptide synthesis that is further aggravated by withdrawal. The aim of the present study is to characterize the effects of prolonged ethanol exposure on the magnocellular neurons of the paraventricular nucleus (PVN) in order to establish whether or not magnocellular neurons display a common pattern of reaction to excess alcohol, irrespective of the hypothalamic cell group they belong. Using conventional histological techniques, immunohistochemistry and in situ hybridization, the structural organization and the synthesis and expression of vasopressin (VP) and oxytocin (OXT) in the magnocellular component of the PVN were studied under normal conditions and following chronic ethanol treatment (6 or 10 months) and withdrawal (4 months after 6 months of alcohol intake). After ethanol treatment, there was a marked decrease in the number of VP- and OXT-immunoreactive magnocellular neurons that was attributable to cell death. The surviving neurons were hypertrophied and the VP and OXT mRNA levels in the PVN unchanged. Withdrawal did not alter the number of VP- and OXT-producing neurons or the gene expression of these peptides. These results substantiate the view that after prolonged ethanol exposure numerous neurons of the hypothalamic magnocellular system degenerate, but the mRNA levels of VP and OXT are not decreased due to compensatory changes undergone by the surviving neurons.