Quantification of neurons expressing androgen receptor and volume estimation of the basolateral nuclear group of the canine amygdaloid body

The Microscopic Structure of the Omentum in Healthy Dogs: The Mystery Unravelled

The canine omentum has many valuable properties but is still an underestimated organ. It contributes in many ways to the protection of the peritoneal cavity through its versatility on immunological level, but also through its role during angiogenesis, absorption, adhesion and fat storage. Despite a wide range of applications, the basic structure of the omentum is not well documented. This study provides an insight in the microscopic structure of the canine omentum through both light microscopic and electron microscopic investigations. Two regions could be distinguished in the canine omentum: translucent and adipose-rich regions. The translucent regions were composed of two different layers: a continuous flattened mesothelium on top of a submesothelial connective tissue matrix. The adipose-rich regions consisted of a substantial layer of adipocytes on which a flattened continuous mesothelium was present. Between those two layers, a few strands of collagen fibres could be detected. Large aggregates of immune cells, the so-called milky spots, were not observed in the omentum of healthy dogs. Only a limited number of leucocytes, macrophages and neutrophils were found, scattered throughout the connective tissue in the translucent regions. At the level of the adipose-rich regions, the immunological population was virtually non-existent.

Corticosterone and related receptor expression are associated with increased beta-amyloid plaques in isolated Tg2576 mice

Previously, we reported that the stress associated with chronic isolation was associated with increased beta-amyloid (Abeta) plaque deposition and memory deficits in the Tg2576 transgenic animal model of Alzheimer's disease (AD) [Dong H, Goico B, Martin M, Csernansky CA, Bertchume A, Csernansky JG (2004) Effects of isolation stress on hippocampal neurogenesis, memory, and amyloid plaque deposition in APP (Tg2576) mutant mice. Neuroscience 127:601-609]. In this study, we investigated the potential mechanisms of stress-accelerated Abeta plaque deposition in this Tg2576 mice by examining the relationship between plasma corticosterone levels, expression of glucocorticoid receptor (GR) and corticotropin-releasing factor receptor-1 (CRFR1) in the brain, brain tissue Abeta levels and Abeta plaque deposition during isolation or group housing from weaning (i.e. 3 weeks of age) until 27 weeks of age. We found that isolation housing significantly increased plasma corticosterone levels as compared with group-housing in both Tg+ mice (which contain and overexpress human amyloid precursor protein (hAPP) gene) and Tg- mice (which do not contain hAPP gene as control). Also, isolated, but not group-housed animals showed increases in the expression of GR in the cortex. Furthermore, the expression of CRFR1 was increased in isolated Tg+ mice, but decreased in isolated Tg- mice in both cortex and hippocampus. Changes in the components of hypothalamic-pituitary-adrenal (HPA) axis were accompanied by increases in brain tissue Abeta levels and Abeta plaque deposition in the hippocampus and overlying cortex in isolated Tg+ mice. These results suggest that isolation stress increases corticosterone levels and GR and CRFR1 expression in conjunction with increases in brain tissue Abeta levels and Abeta plaque deposition in the Tg2576 mouse model of AD.

Neurons expressing serotonin-1B receptor in the basolateral nuclear group of the amygdala in normally behaving and aggressive dogs

The present study aimed to quantify neurons expressing the serotonin-1B receptor and evaluate numerical differences in normally behaving and pathologically aggressive dogs in order to assess whether the serotonin-1B receptor is involved in pathological canine aggression. Because previous studies have reported structural alterations in the basolateral nuclear group (BNG) of the amygdaloid body of aggressive dogs, this structure was selected as region of interest in the present study. Indirect immunohistochemistry was applied to visualise the serotonin-1B-receptor-positive neurons. Immunoreactivity was located predominantly within the neuronal cell bodies and adjacent neuronal processes. In the aggressive dogs the BNGs contained a significantly higher number of serotonin-1B-receptor-positive neurons compared to the normally behaving dogs. This number was strongly correlated with the total number of neurons per BNG, which was also significantly increased in aggressive dogs compared to normal dogs. The percentage of neurons expressing the serotonin-1B receptor did not differ significantly between both groups. No significant asymmetries were observed for the number and percentage of serotonin-1B-receptor-positive neurons. Potential relationships between the present findings and the etiology of aggressive behaviour, the neuroprotective role of the serotonin-1B receptor and receptor dysfunction are discussed.

Neurons expressing serotonin-1B receptor in the basolateral nuclear group of the amygdala in normally behaving and aggressive dogs

The present study aimed to quantify neurons expressing the serotonin-1B receptor and evaluate numerical differences in normally behaving and pathologically aggressive dogs in order to assess whether the serotonin-1B receptor is involved in pathological canine aggression. Because previous studies have reported structural alterations in the basolateral nuclear group (BNG) of the amygdaloid body of aggressive dogs, this structure was selected as region of interest in the present study. Indirect immunohistochemistry was applied to visualise the serotonin-1B-receptor-positive neurons. Immunoreactivity was located predominantly within the neuronal cell bodies and adjacent neuronal processes. In the aggressive dogs the BNGs contained a significantly higher number of serotonin-1B-receptor-positive neurons compared to the normally behaving dogs. This number was strongly correlated with the total number of neurons per BNG, which was also significantly increased in aggressive dogs compared to normal dogs. The percentage of neurons expressing the serotonin-1B receptor did not differ significantly between both groups. No significant asymmetries were observed for the number and percentage of serotonin-1B-receptor-positive neurons. Potential relationships between the present findings and the etiology of aggressive behaviour, the neuroprotective role of the serotonin-1B receptor and receptor dysfunction are discussed.

Spatial relationship between synapse loss and beta-amyloid deposition in Tg2576 mice

Although there is evidence that beta-amyloid impairs synaptic function, the relationship between beta-amyloid and synapse loss is not well understood. In this study we assessed synapse density within the hippocampus and the entorhinal cortex of Tg2576 mice at 6-18 months of age using stereological methods at both the light and electron microscope levels. Under light microscopy we failed to find overall decreases in the density of synaptophysin-positive boutons in any brain areas selected, but bouton density was significantly decreased within 200 mum of compact beta-amyloid plaques in the outer molecular layer of the dentate gyrus and Layers II and III of the entorhinal cortex at 15-18 months of age in Tg 2576 mice. Under electron microscopy, we found overall decreases in synapse density in the outer molecular layer of the dentate gyrus at both 6-9 and 15-18 months of age, and in Layers II and III of the entorhinal cortex at 15-18 months of age in Tg 2576 mice. However, we did not find overall changes in synapse density in the stratum radiatum of the CA1 subfield. Furthermore, in the two former brain areas we found a correlation between lower synapse density and greater proximity to beta-amyloid plaques. These results provide the first quantitative morphological evidence at the ultrastructure level of a spatial relationship between beta-amyloid plaques and synapse loss within the hippocampus and the entorhinal cortex of Tg2576 mice.

Increased Number of Neurons Expressing Androgen Receptor in the Basolateral Amygdala of Pathologically Aggressive Dogs

The present study aimed to determine the extent to which the androgen receptor (AR) is directly involved in the hormonal modulation of pathological canine aggressive behaviour in the basolateral nuclear group (BNG) of the amygdaloid body. A stereological quantification of AR-positive neurons was performed in the BNGs of normally behaving and aggressive male dogs. The BNG was selected because it is involved in sexual and behavioural activities that are influenced by androgens. In the aggressive dogs the BNG contained a significantly higher number of AR-positive neurons compared with normally behaving dogs suggesting differences in androgen activity within the BNGs of both the groups. However, additional mechanisms are likely to be involved because the AR-negative fraction of BNG neurons was also increased in the aggressive dogs. It was concluded that most of the AR was unliganded because a cytoplasmic staining pattern of AR positivity was observed in the canine BNG neurons. This indicates that genomic androgen actions, which are mediated through the AR are of minor importance in the testosterone modulation of canine aggression within the BNG. Other non-genomic mechanisms through which androgens may exert their action in the BNG are discussed. The aromatase pathway is suggested to be the main mechanism through which testosterone exerts its action within the BNG.