The Visible Ape Project: A free, comprehensive, web-based anatomical atlas for scientists and veterinarians designed to raise public awareness about apes.

The Visible Ape Project (VAP) is a free online platform providing unprecedented access to a suite of resources designed to comprehensively illustrate and educate about the anatomy of our closest relatives, the apes. It contains photographs, magnetic resonance images, and computed tomography scans, as well as three-dimensional models that can be manipulated to explore homologies and variations in soft and hard tissues in hylobatids, orangutans, gorillas, chimpanzees, and bonobos. Based at Howard University, a historically black university, it aims to reach communities underrepresented in anthropology and evolutionary biology, providing educational materials appropriate for K-12 and college classrooms in both English and Spanish. Accordingly, VAP incorporates outreach activities to disseminate science and promote awareness of apes, forming partnerships with veterinarians and conservationists in Africa and Asia. In this paper, we present an introduction to the website to illustrate how this accessible, evolving resource can support evolutionary anthropology and related disciplines.

Neuron numbers increase in the human amygdala from birth to adulthood, but not in autism.

Remarkably little is known about the postnatal cellular development of the human amygdala. It plays a central role in mediating emotional behavior and has an unusually protracted development well into adulthood, increasing in size by 40% from youth to adulthood. Variation from this typical neurodevelopmental trajectory could have profound implications on normal emotional development. We report the results of a stereological analysis of the number of neurons in amygdala nuclei of 52 human brains ranging from 2 to 48 years of age [24 neurotypical and 28 autism spectrum disorder (ASD)]. In neurotypical development, the number of mature neurons in the basal and accessory basal nuclei increases from childhood to adulthood, coinciding with a decrease of immature neurons within the paralaminar nucleus. Individuals with ASD, in contrast, show an initial excess of amygdala neurons during childhood, followed by a reduction in adulthood across nuclei. We propose that there is a long-term contribution of mature neurons from the paralaminar nucleus to other nuclei of the neurotypical human amygdala and that this growth trajectory may be altered in ASD, potentially underlying the volumetric changes detected in ASD and other neurodevelopmental or neuropsychiatric disorders.

Microglia: An Intrinsic Component of the Proliferative Zones in the Fetal Rhesus Monkey (Macaca mulatta) Cerebral Cortex.

Microglial cells are increasingly recognized as modulators of brain development. We previously showed that microglia colonize the cortical proliferative zones in the prenatal brain and regulate the number of precursor cells through phagocytosis. To better define cellular interactions between microglia and proliferative cells, we performed lentiviral vector-mediated intraventricular gene transfer to induce enhanced green fluorescent protein expression in fetal cerebrocortical cells. Tissues were collected and counterstained with cell-specific markers to label microglial cells and identify other cortical cell types. We found that microglial cells intimately interact with the radial glial scaffold and make extensive contacts with neural precursor cells throughout the proliferative zones, particularly in the rhesus monkey fetus when compared to rodents. We also identify a subtype of microglia, which we term 'periventricular microglia', that interact closely with mitotic precursor cells in the ventricular zone. Our data suggest that microglia are structural modulators that facilitate remodeling of the proliferative zones as precursor cells migrate away from the ventricle and may facilitate the delamination of precursor cells. Taken together, these results indicate that microglial cells are an integral component of cortical proliferative zones and contribute to the interactive milieu in which cortical precursor cells function.

Preliminary results of fixed, fiber-reinforced resin bridges on four 4- × 5-mm ultrashort implants in compromised bony sites: a pilot study.

PURPOSE: To determine the effectiveness of fixed, fiber-reinforced resin bridges on 4 ultrashort implants with a sufficient implant survival success rate of at least 90% in highly atrophic jaws. MATERIALS AND METHODS: A prospective temporal cohort study was designed, with the inclusion of 10 patients. Of the 10 patients, 8 had atrophic jaws (7 women, 1 man; mean age at implant placement 58.5 years, range 40.7 to 73.9) and 2 had fibula-mandibular transplants (1 woman, aged 76.5 years; and 1 man, aged 69.3 years). All 10 patients had their dentition restored with 4 ultrashort implants. The implant dimensions were 4 mm in diameter and 5 mm long, with a locking taper abutment connection supporting a fixed, fiber-reinforced and composite resin-facetted bridge. The postoperative follow-up period averaged 19.5 months (range 9.1 to 33.1). RESULTS: The survival and success rate was 97.25%. The average mesial and distal bone level was 0.2 ± 0.3 mm in the atrophic mandibles and 0.4 ± 1.2 mm in the fibula transplants at the last follow-up visit. Prosthetic-related patient issues were limited to decementation events. No chipping or fracturing of the prostheses was observed. CONCLUSION: Retention of fixed prosthetic restorations using 4 ultrashort implants showed promising short-term cumulative survival and success rates.

The arteries of the musculoskeletal system of siamangs, and a comparison with other hylobatids, greater apes, and humans.

Limited research on the gross anatomy of the blood vessels has been conducted on hylobatids, or lesser apes, so far. Here, we present a detailed study of the arteries of siamangs (Symphalangus) and compare our findings with data compiled from our previous studies as well as from the literature about other hylobatids, greater apes, and humans. In particular, a three-dimensional full-body computed tomography data set of a siamang neonate was analyzed in detail for this study, with notable findings in the head and neck, thorax, upper limb, abdomen and pelvis, and lower limb. Of the 62 arteries that we studied in detail, a total of 20 arteries that have never been described in detail in hylobatids are reported in this study. Key similarities to other apes differing from humans include the existence of a humeral common circumflex trunk and the origination of the dorsalis pedis from the posterior tibial artery or saphenous artery instead of the anterior tibial artery. Similarities to humans differing from other apes include the separation of the lingual and facial arteries and the origination of the profunda brachii from the brachial artery instead of the axillary artery. Our research and broader comparisons, therefore, contribute to knowledge about the soft tissues of hylobatids, other apes, and primates in general and facilitate a better understanding of the anatomical evolution and key differences and similarities among these taxa.

Periventricular microglial cells interact with dividing precursor cells in the nonhuman primate and rodent prenatal cerebral cortex.

Cortical proliferative zones have been studied for over 100 years, yet recent data have revealed that microglial cells constitute a sizeable proportion of ventricular zone cells during late stages of cortical neurogenesis. Microglia begin colonizing the forebrain after neural tube closure and during later stages of neurogenesis populate regions of the developing cortex that include the proliferative zones. We previously showed that microglia regulate the production of cortical cells by phagocytosing neural precursor cells (NPCs), but how microglia interact with NPCs remains poorly understood. Here we report on a distinct subset of microglial cells, which we term periventricular microglia, that are located near the lateral ventricle in the prenatal neocortex. Periventricular microglia exhibit a set of similar characteristics in embryonic rat and fetal rhesus monkey cortex. In both species, these cells occupy ~60 µm of the ventricular zone in the tangential axis and make contact with the soma and processes of NPCs dividing at the ventricle for over 50 µm along the radial axis. Periventricular microglia exhibit notable differences across species, including distinct morphological features such as terminal bouton-like structures that contact mitotic NPCs in the fetal rhesus monkey but not in rat. These morphological distinctions suggest differential functions of periventricular microglia in rat and rhesus monkey, yet are consistent with the concept that microglia regulate NPC function in the developing cerebral cortex of mammalian species.

Maximizing Explanatory Power in Stereological Data Collection: A Protocol for Reliably Integrating Optical Fractionator and Multiple Immunofluorescence Techniques.

With the promise of greater reliability and replicability of estimates, stereological techniques have revolutionized data collection in the neurosciences. At the same time, improvements in immunohistochemistry and fluorescence imaging technologies have facilitated easy application of immunofluorescence protocols, allowing for isolation of multiple target proteins in one tissue sample. Combining multiple immunofluorescence labeling with stereological data collection can provide a powerful tool to maximize explanatory power and efficiency, while minimizing tissue use. Multiple cell classes, subtypes of larger populations, or different cell states can be quantified in one case and even in one sampling run. Here, we present a protocol integrating stereological data collection and multiple immunofluorescence using commonly employed widefield epifluorescence filter sets, optimized for blue (DAPI), green (FITC), and far red (CY5) channels. Our stereological protocol has been designed to accommodate the challenges of fluorescence imaging to overcome limitations like fixed filter sets, photobleaching, and uneven immunolabeling. To enhance fluorescence signal for stereological sampling, our immunolabeling protocol utilizes both high temperature antigen retrieval to improve primary antibody binding and secondary antibodies conjugated to optimally stable fluorophores. To illustrate the utility of this approach, we estimated the number of Ctip2 immunoreactive subcerebral projection neurons and NeuN immunoreactive neurons in rat cerebral cortex at postnatal day 10. We used DAPI (blue) to define the neocortex, anti-NeuN (far red) to identify neurons, and co-labeling of anti-Ctip2 (green) and anti-NeuN (far red) to isolate only subcerebral projection neurons. Our protocol resulted in estimates with low sampling error (CE < 0.05) and high intrarater reliability (ICC > 0.98) that fall within the range of published values, attesting to its efficacy. We show our immunofluorescence techniques can be used to reliably identify other cell types, e.g., different glial cell classes, to highlight the broader applications of our approach. The flexibility of the technique, increasingly reduced costs of fluorescence technologies, and savings in experimental time and tissue use make this approach valuable for neuroscientists interested in incorporating stereology to ask precise neurophysiological and neuroanatomical questions.

Differential serotonergic innervation of the amygdala in bonobos and chimpanzees.

Humans' closest living relatives are bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), yet these great ape species differ considerably from each other in terms of social behavior. Bonobos are more tolerant of conspecifics in competitive contexts and often use sexual behavior to mediate social interactions. Chimpanzees more frequently employ aggression during conflicts and actively patrol territories between communities. Regulation of emotional responses is facilitated by the amygdala, which also modulates social decision-making, memory and attention. Amygdala responsiveness is further regulated by the neurotransmitter serotonin. We hypothesized that the amygdala of bonobos and chimpanzees would differ in its neuroanatomical organization and serotonergic innervation. We measured volumes of regions and the length density of serotonin transporter-containing axons in the whole amygdala and its lateral, basal, accessory basal and central nuclei. Results showed that accessory basal nucleus volume was larger in chimpanzees than in bonobos. Of particular note, the amygdala of bonobos had more than twice the density of serotonergic axons than chimpanzees, with the most pronounced differences in the basal and central nuclei. These findings suggest that variation in serotonergic innervation of the amygdala may contribute to mediating the remarkable differences in social behavior exhibited by bonobos and chimpanzees.

Stereological study of pyramidal neurons in the human superior temporal gyrus from childhood to adulthood.

The association cortex of the superior temporal gyrus (STG) is implicated in complex social and linguistic functions. Thus, reliable methods for quantifying cellular variation in this region could greatly benefit researchers interested in addressing the cellular correlates of typical and atypical function associated with these critical cognitive abilities. To facilitate this task, we first present a general set of cytoarchitectonic criteria targeted specifically toward stereological analyses of thick, Nissl-stained sections for the homotypical cortex of the STG, referred to here as BA22/TA. Second, we use the optical fractionator to estimate pyramidal neuron number and the nucleator for pyramidal somal and nuclear volume. We also investigated the influence of age and sex on these parameters, as well as set a typically developing baseline for future comparisons. In 11 typically developing cases aged 4-48 years, the most distinguishing features of BA22/TA were the presence of distinct granular layers, a prominent, jagged layer IIIc, and a distinctly staining VIa. The average number of neurons was 91 ± 15 million, the volume of pyramidal soma 1,512 µm(3) , and the nuclear volume 348 µm(3) . We found no correlation with age and neuron number. In contrast, pyramidal somal and nuclear volume were both negatively correlated and linearly associated with age in regression analyses. We found no significant sex differences. Overall, the data support the idea that postnatal neuron numbers are relatively stable through development but also suggest that neuronal volume may be subject to important developmental variation. Both measures are critical variables in the study of developmental neuropathology.

Specific Regional and Age-Related Small Noncoding RNA Expression Patterns Within Superior Temporal Gyrus of Typical Human Brains Are Less Distinct in Autism Brains.

Small noncoding RNAs play a critical role in regulating messenger RNA throughout brain development and when altered could have profound effects leading to disorders such as autism spectrum disorders (ASD). We assessed small noncoding RNAs, including microRNA and small nucleolar RNA, in superior temporal sulcus association cortex and primary auditory cortex in typical and ASD brains from early childhood to adulthood. Typical small noncoding RNA expression profiles were less distinct in ASD, both between regions and changes with age. Typical micro-RNA coexpression associations were absent in ASD brains. miR-132, miR-103, and miR-320 micro-RNAs were dysregulated in ASD and have previously been associated with autism spectrum disorders. These diminished region- and age-related micro-RNA expression profiles are in line with previously reported findings of attenuated messenger RNA and long noncoding RNA in ASD brain. This study demonstrates alterations in superior temporal sulcus in ASD, a region implicated in social impairment, and is the first to demonstrate molecular alterations in the primary auditory cortex.

Atypical miRNA expression in temporal cortex associated with dysregulation of immune, cell cycle, and other pathways in autism spectrum disorders.

BACKGROUND: Autism spectrum disorders (ASDs) likely involve dysregulation of multiple genes related to brain function and development. Abnormalities in individual regulatory small non-coding RNA (sncRNA), including microRNA (miRNA), could have profound effects upon multiple functional pathways. We assessed whether a brain region associated with core social impairments in ASD, the superior temporal sulcus (STS), would evidence greater transcriptional dysregulation of sncRNA than adjacent, yet functionally distinct, primary auditory cortex (PAC). METHODS: We measured sncRNA expression levels in 34 samples of postmortem brain from STS and PAC to find differentially expressed sncRNA in ASD compared with control cases. For differentially expressed miRNA, we further analyzed their predicted mRNA targets and carried out functional over-representation analysis of KEGG pathways to examine their functional significance and to compare our findings to reported alterations in ASD gene expression. RESULTS: Two mature miRNAs (miR-4753-5p and miR-1) were differentially expressed in ASD relative to control in STS and four (miR-664-3p, miR-4709-3p, miR-4742-3p, and miR-297) in PAC. In both regions, miRNA were functionally related to various nervous system, cell cycle, and canonical signaling pathways, including PI3K-Akt signaling, previously implicated in ASD. Immune pathways were only disrupted in STS. snoRNA and pre-miRNA were also differentially expressed in ASD brain. CONCLUSIONS: Alterations in sncRNA may underlie dysregulation of molecular pathways implicated in autism. sncRNA transcriptional abnormalities in ASD were apparent in STS and in PAC, a brain region not directly associated with core behavioral impairments. Disruption of miRNA in immune pathways, frequently implicated in ASD, was unique to STS.

Stereological study of amygdala glial populations in adolescents and adults with autism spectrum disorder.

The amygdala undergoes aberrant development in autism spectrum disorder (ASD). We previously found that there are reduced neuron numbers in the adult postmortem amygdala from individuals with ASD compared to typically developing controls. The current study is a comprehensive stereological examination of four non-neuronal cell populations: microglia, oligodendrocytes, astrocytes, and endothelial cells, in the same brains studied previously. We provide a detailed neuroanatomical protocol for defining each cell type that may be applied to other studies of the amygdala in neurodevelopmental and psychiatric disorders. We then assess whether cell numbers and average volumes differ between ASD and typically developing brains. We hypothesized that a reduction in neuron numbers in ASD might relate to altered immune function and/or aberrant microglial activation, as indicated by increased microglial number and cell body volume. Overall, average non-neuronal cell numbers and volumes did not differ between ASD and typically developing brains. However, there was evident heterogeneity within the ASD cohort. Two of the eight ASD brains displayed strong microglial activation. Contrary to our original hypothesis, there was a trend toward a positive correlation between neuronal and microglial numbers in both ASD and control cases. There were fewer oligodendrocytes in the amygdala of adult individuals with ASD ages 20 and older compared to typically developing controls. This finding may provide a possible sign of altered connectivity or impaired neuronal communication that may change across the lifespan in ASD.

Evidence for evolutionary specialization in human limbic structures.

Increasingly, functional and evolutionary research has highlighted the important contribution emotion processing makes to complex human social cognition. As such, it may be asked whether neural structures involved in emotion processing, commonly referred to as limbic structures, have been impacted in human brain evolution. To address this question, we performed an extensive evolutionary analysis of multiple limbic structures using modern phylogenetic tools. For this analysis, we combined new volumetric data for the hominoid (human and ape) amygdala and 4 amygdaloid nuclei, hippocampus, and striatum, collected using stereological methods in complete histological series, with previously published datasets on the amygdala, orbital and medial frontal cortex, and insula, as well as a non-limbic structure, the dorsal frontal cortex, for contrast. We performed a parallel analysis using large published datasets including many anthropoid species (human, ape, and monkey), but fewer hominoids, for the amygdala and 2 amygdaloid subdivisions, hippocampus, schizocortex, striatum, and septal nuclei. To address evolutionary change, we compared observed human values to values predicted from regressions run through (a) non-human hominoids and (b) non-human anthropoids, assessing phylogenetic influence using phylogenetic generalized least squares regression. Compared with other hominoids, the volumes of the hippocampus, the lateral nucleus of the amygdala, and the orbital frontal cortex were, respectively, 50, 37, and 11% greater in humans than predicted for an ape of human hemisphere volume, while the medial and dorsal frontal cortex were, respectively, 26 and 29% significantly smaller. Compared with other anthropoids, only human values for the striatum fell significantly below predicted values. Overall, the data present support for the idea that regions involved in emotion processing are not necessarily conserved or regressive, but may even be enhanced in recent human evolution.

Neuronal populations in the basolateral nuclei of the amygdala are differentially increased in humans compared with apes: a stereological study.

In human and nonhuman primates, the amygdala is known to play critical roles in emotional and social behavior. Anatomically, individual amygdaloid nuclei are connected with many neural systems that are either differentially expanded or conserved over the course of primate evolution. To address amygdala evolution in humans and our closest living relatives, the apes, we used design-based stereological methods to obtain neuron counts for the amygdala and each of four major amygdaloid nuclei (the lateral, basal, accessory basal, and central nuclei) in humans, all great ape species, lesser apes, and one monkey species. Our goal was to determine whether there were significant differences in the number or percent of neurons distributed to individual nuclei among species. Additionally, regression analyses were performed on independent contrast data to determine whether any individual species deviated from allometric trends. There were two major findings. In humans, the lateral nucleus contained the highest number of neurons in the amygdala, whereas in apes the basal nucleus contained the highest number of neurons. Additionally, the human lateral nucleus contained 59% more neurons than predicted by allometric regressions on nonhuman primate data. Based on the largest sample ever analyzed in a comparative study of the hominoid amygdala, our findings suggest that an emphasis on the lateral nucleus is the main characteristic of amygdala specialization over the course of human evolution.

A comparative volumetric analysis of the amygdaloid complex and basolateral division in the human and ape brain.

The amygdaloid complex functions to facilitate effective appraisal of the social environment and is an essential component of the neural systems subserving social behavior. Despite its critical role in mediating social interaction, the amygdaloid complex has not attracted the same attention as the isocortex in most evolutionary analyses. We performed a comparative analysis of the amygdaloid complex in the hominoids to address the lack of comparative information available for this structure in the hominoid brain. We demarcated the amygdaloid complex and the three nuclei constituting its basolateral division, the lateral, basal, and accessory basal nuclei, in 12 histological series representing all six hominoid species. The volumes obtained for these areas were subjected to allometric analyses to determine whether any species deviated from expected values based on the other hominoids. Differences between groups were addressed using nonparametric comparisons of means. The human lateral nucleus was larger than predicted for an ape of human brain size and occupied the majority of the basolateral division, whereas the basal nucleus was the largest of the basolateral nuclei in all ape species. In orangutans the amygdala and basolateral division were smaller than in the African apes. While the gorilla had a smaller than predicted lateral nucleus, its basal and accessory basal nuclei were larger than predicted. These differences may reflect volumetric changes occurring in interconnected cortical areas, specifically the temporal lobe and orbitofrontal cortex, which also subserve social behavior and cognition, suggesting that this system may be acted upon in hominoid and hominid evolution.