The amygdaloid complex (AC) is involved in very relevant cognitive and emotional pathways and exhibits changes in aging and in some neurological and psychiatric disorders. The quantitative estimators ...of AC could be useful to understand the impact of amygdaloid pathology in these processes, both globally and for each nucleus in particular, and their neurons. The present study analyzes morphometric and stereological estimators in the whole AC and its three main nuclei (lateral La, basal Ba, and accessory basal AB) in six Macaca fascicularis monkeys. All the brains were fixed and sectioned in the coronal plane; Nissl‐stained sections were used for estimation of size and form parameters in both, the AC, and the La, Ba, and AB nuclei separately. The study includes stereological estimates of the volume and surface area of the AC; also, volume of the neurons in the amygdaloid nuclei was estimated using the point‐sampled intercepts method. Our results show that the AB nucleus is smaller than both the La and Ba nuclei in both morphometric and stereological estimators. Brain hemispheric side had not significant influence on any of quantitative estimates. The neuron volume was higher in the AB nucleus relative to LA and Ba of the nuclei. These data describe some quantitative parameters of the amygdaloid complex and their main nuclei that could help us to detect small changes in neurodegenerative and other pathological processes.
The amygdaloid volume in Macaca fascicularis monkeys is of 174 mm3 with a surface area of 151 mm2. The accessory basal nuclei are smaller than the lateral and basal nuclei, showing no brain interhemispheric differences. In opposite, the greater size of neuronal volume appears in the accessory basal nuclei.
The cortical mantle is not homogeneous, so that three types of cortex can be distinguished: allocortex, periallocortex and isocortex. The main distinction among those three types is based on ...morphological differences, in particular the number of layers, overall organization, appearance, etc., as well as its connectivity. Additionally, in the phylogenetic scale, this classification is conserved among different mammals. The most primitive and simple cortex is the allocortex, which is characterized by the presence of three layers, with one cellular main layer; it is continued by the periallocortex, which presents six layers, although with enough differences in the layer pattern to separate three different fields: presubiculum (PrS), parasubiculum (PaS), and entorhinal cortex (EC). The closest part to the allocortex (represented by the subiculum) is the PrS, which shows outer (layers I-III) and inner (V-VI) principal layers (
and
), both separated by a cell poor band, parallel to the pial surface (layer IV or
). This layer organization is present throughout the anterior-posterior axis. The PaS continues the PrS, but its rostrocaudal extent is shorter than the PrS. The organization of the PaS shows the layer pattern more clearly than in the PrS. Up to six layers are recognizable in the PaS, with layer IV as
between superficial (layers I-III) and deep (V-VI) layers, as in the PrS. The EC presents even more clearly the layer pattern along both mediolateral and rostrocaudal extent. The layer pattern is a thick layer I, layer II in islands, layer III medium pyramids, layer IV as
(not present throughout the EC extent), layer V with dark and big pyramids and a multiform layer VI. The EC borders laterally the proisocortex (incomplete type of isocortex). Variations in the appearance of its layers justify the distinction of subfields in the EC, in particular in human and nonhuman primates. EC layers are not similar to those in the neocortex. The transition between the periallocortical EC and isocortex is not sharp, so that the proisocortex forms an intervening cortex, which fills the gap between the periallocortex and the isocortex.
Neuronal volume of the hippocampal regions in ageing Delgado‐González, José Carlos; Rosa‐Prieto, Carlos; Tarruella‐Hernández, Diana Lucía ...
Journal of anatomy,
August 2020, Letnik:
237, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The hippocampal formation (HF) has an important role in different human capacities, such as memory processing and emotional expression. Both extensive changes and limited variations of its components ...can cause clinically expressed dysfunctions. Although there remains no effective treatment for diseases caused by pathological changes in this brain region, detection of these changes, even minimally, could allow us to develop early interventions and establish corrective measures. This study analysed the neuronal islands of layer II of the entorhinal cortex (EC), the neuronal clumps of the external principal layer of the presubiculum (PrS) and the dentate granule cells of the dentate gyrus (DG), which represent the prominent structural regions within the HF circuit. Subjects from two age groups (younger or older than 65 years) were studied and their neuronal size assessed by the point‐sampled intercepts stereological method. The quantitative v¯v(soma) estimate was a volume of roughly 8,500 µm3 for EC layer II neurons, and DG granule neurons and presubicular neurons were five and 10 times smaller, respectively. The older age group showed a v¯v(soma) increase of 2%, 18% and 28% with respect to the younger group in the PrS, DG and EC regions, respectively. None of these regions showed interhemispheric differences. This quantitative estimation is relevant because the observed variance in the v¯v(soma) estimates suggests that biological variation is the main contributory factor, with intercepts and measurements having a smaller impact. Therefore, we suggest that age has a limited influence on neuronal volume variation in these HF regions, which needs to be compared with similar measurements in neurodegenerative disorders such as Alzheimer’s.
The v¯v(soma) in the PrS and DG hippocampal regions was not significantly influenced by age, but the neuronal volume of the islands of layer II of the EC was greater in the older age group. The higher variance in the v¯v(soma) estimates (with a coefficient of variation of 19%, 33%, and 18% for EC, PrS and DG, respectively) was mainly due to biological variation.
Introduction
Neurodegenerative disorders are associated with different pathologies that often co‐occur but cannot be measured specifically with in vivo methods.
Methods
Thirty‐three brain hemispheres ...from donors with an Alzheimer's disease (AD) spectrum diagnosis underwent T2‐weighted magnetic resonance imaging (MRI). Gray matter thickness was paired with histopathology from the closest anatomic region in the contralateral hemisphere.
Results
Partial Spearman correlation of phosphorylated tau and cortical thickness with TAR DNA‐binding protein 43 (TDP‐43) and α‐synuclein scores, age, sex, and postmortem interval as covariates showed significant relationships in entorhinal and primary visual cortices, temporal pole, and insular and posterior cingulate gyri. Linear models including Braak stages, TDP‐43 and α‐synuclein scores, age, sex, and postmortem interval showed significant correlation between Braak stage and thickness in the parahippocampal gyrus, entorhinal cortex, and Broadman area 35.
Conclusion
We demonstrated an association of measures of AD pathology with tissue loss in several AD regions despite a limited range of pathology in these cases.
Highlights
Neurodegenerative disorders are associated with co‐occurring pathologies that cannot be measured specifically with in vivo methods.
Identification of the topographic patterns of these pathologies in structural magnetic resonance imaging (MRI) may provide probabilistic biomarkers.
We demonstrated the correlation of the specific patterns of tissue loss from ex vivo brain MRI with underlying pathologies detected in postmortem brain hemispheres in patients with Alzheimer's disease (AD) spectrum disorders.
The results provide insight into the interpretation of in vivo structural MRI studies in patients with AD spectrum disorders.
The decrease of volume estimates in different structures of the medial temporal lobe related to memory correlate with the decline of cognitive functions in neurodegenerative diseases. This study ...presents data on the association between MRI quantitative parameters of medial temporal lobe structures and their quantitative estimate in microscopic examination. Twelve control cases had ex-vivo MRI, and thereafter, the temporal lobe of both hemispheres was sectioned from the pole as far as the level of the splenium of the corpus callosum. Nissl stain was used to establish anatomical boundaries between structures in the medial temporal lobe. The study included morphometrical and stereological estimates of the amygdaloid complex, hippocampus, and temporal horn of the lateral ventricle, as well as different regions of grey and white matter in the temporal lobe. Data showed a close association between morphometric MRI images values and those based on the histological determination of boundaries. Only values in perimeter and circularity of the piamater were different. This correspondence is also revealed by the stereological study, although irregular compartments resulted in a lesser agreement. Neither age (< 65 yr and > 65 yr) nor hemisphere had any effect. Our results indicate that ex-vivo MRI is highly associated with quantitative information gathered by histological examination, and these data could be used as structural MRI biomarker in neurodegenerative diseases.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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