Abstract Quantifying the continuous variation in human scalp hair morphology is of interest to anthropologists, geneticists, dermatologists and forensic scientists, but existing methods for studying hair form are time-consuming and not widely used. Here, we present a high-throughput sample preparation protocol for the imaging of both longitudinal (curvature) and cross-sectional scalp hair morphology. Additionally, we describe and validate a new Python package designed to process longitudinal and cross-sectional hair images, segment them, and provide measurements of interest. Lastly, we apply our methods to an admixed African-European sample (n = 140), demonstrating the benefit of quantifying hair morphology over classification, and providing evidence that the relationship between cross-sectional morphology and curvature may be an artefact of population stratification rather than a causal link.
more »
« less
Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
-
null (Ed.)Hox11 genes are expressed around the developing wrist and ankle and are known to substantially impact pisiform shape and length in mice. The calcaneus is a tarsal bone that is paralogous to the pisiform in the wrist, but previous descriptions of mice with Hox11 mutations have suggested that little morphological change takes place unless Hoxa11 and Hoxd11 are both knocked out, at which point the calcaneus fails to form. However, these studies primarily relied on cleared and stained whole-mount specimens which limit resolution of morphological features. This study seeks to determine if calcaneus morphology is altered by three or fewer loss-of-function Hoxa11 and Hoxd11 alleles. We obtained microCT scans of 8 week old mice and compared calcaneus morphology in wild type mice and mice with one, two, and three Hoxa11 and Hoxd11 loss-of-function alleles. We used auto3dgm to conduct a 3D geometric morphometric analysis of shape variation using surface semi-landmarks. Principle components (PC) analysis indicates that calcaneus morphology is altered in mice with Hoxa11 and Hoxd11 loss-of-function mutations. PC1 accounts for 35.4% of shape variation and results from changes to the width and height of the calcaneal neck and shape of peroneal tubercle/process. PC2 accounts for 11.9% of shape variation and results from changes to the width of the calcaneal tuberosity and height of the posterior talar facet. Most specimens with either combination of three out of four Hoxa11 and Hoxd11 loss-of-function alleles cluster together. The other genotypes form a gradient of morphological change with WT, Hoxd11 heterozygotes, and Hoxd11 knockouts being most similar to each other and Hoxa11 heterozygotes, Hoxa11 knockouts, and heterozygotes for both genes being most similar to each other. These results suggest that Hox11 loss-of-function mutations result in altered calcaneus morphology and Hoxa11 and Hoxd11 loss-of-function mutations alter the shape of the calcaneus in different ways when fewer than three alleles are knocked out.more » « less
-
more » « less
Abstract Objectives The objective of this study is to demonstrate a new method for analyzing trabecular bone volume fraction and degree of anisotropy in three dimensions.
Methods We use a combination of automatic mesh registration, point‐cloud correspondence registration, and
P ‐value corrected univariate statistical tests to compare bone volume fraction and degree of anisotropy on a point by point basis across the entire calcaneus of two human groups with different subsistence strategies.Results We found that the patterns of high and low bone volume fraction and degree of anisotropy distribution between the Black Earth (hunter‐gatherers) and Norris Farms (mixed‐strategy agriculturalists) are very similar, but differ in magnitude. The hunter‐gatherers exhibit higher levels of bone volume fraction and less anisotropic trabecular bone organization. Additionally, patterns of bone volume fraction and degree of anisotropy in the calcaneus correspond well with biomechanical expectations of relative forces experienced during walking and running.
Conclusions We conclude that comparing site‐specific, localized differences in trabecular bone variables such as bone volume fraction and degree of anisotropy in three‐dimensions is a powerful analytical tool. This method makes it possible to determine where similarities and differences between groups are located within the whole skeletal element of interest. The visualization of multiple variables also provides a way for researchers to see how the trabecular bone variables interact within the morphology, and allows for a more nuanced understanding of how they relate to one another and the broader mechanical environment.
-
more » « less
Abstract Objectives Variation in human trabecular bone morphology can be linked to habitual behavior, but it is difficult to investigate in vivo due to the radiation required at high resolution. Consequently, functional interpretations of trabecular morphology remain inferential. Here we introduce a method to link low‐ and high‐resolution CT data from dry and fresh bone, enabling bone functional adaptation to be studied in vivo and results compared to the fossil and archaeological record.
Materials and methods We examine 51 human dry bone distal tibiae from Nile Valley and UK and two pig tibiae containing soft tissues. We compare low‐resolution peripheral quantitative computed tomography (pQCT) parameters and high‐resolution micro CT (μCT) in homologous single slices at 4% bone length and compare results to our novel Bone Ratio Predictor (BRP) method.
Results Regression slopes between linear attenuation coefficients of low‐resolution pQCT images and bone area/total area (BA/TA) of high‐resolution μCT scans differ substantially between geographical subsamples, presumably due to diagenesis. BRP accurately predicts BA/TA (R2= .97) and eliminates the geographic clustering. BRP accurately estimates BA/TA in pigs containing soft tissues (R2= 0.98) without requiring knowledge of true density or phantom calibration of the scans.
Discussion BRP allows automated comparison of image data from different image modalities (pQCT, μCT) using different energy settings, in archeological bone and wet specimens. The method enables low‐resolution data generated in vivo to be compared with the fossil and archaeological record. Such experimental approaches would substantially improve behavioral inferences based on trabecular bone microstructure.
-
more » « less
Abstract Objectives Variation in trabecular and cortical bone properties is often used to infer habitual behavior in the past. However, the structures of both types of bone are rarely considered together and may even contradict each other in functional interpretations. We examine trabecular and cortical bone properties in various athletes and sedentary controls to clarify the associations between combinations of cortical and trabecular bone properties and various loading modalities.
Materials and methods We compare trabecular and cortical bone properties using peripheral quantitative computed tomography scans of the tibia between groups of 83 male athletes (running, hockey, swimming, cricket) and sedentary controls using Bayesian multilevel models. We quantify midshaft cortical bone rigidity and area (J, CA), midshaft shape index (Imax/Imin), and mean trabecular bone mineral density (BMD) in the distal tibia.
Results All groups show unique combinations of biomechanical properties. Cortical bone rigidity is high in sports that involve impact loading (cricket, running, hockey) and low in nonimpact loaded swimmers and controls. Runners have more anteroposteriorly elliptical midshafts compared to other groups. Interestingly, all athletes have greater trabecular BMD compared to controls, but do not differ credibly among each other.
Discussion Results suggest that cortical midshaft hypertrophy is associated with impact loading while trabecular BMD is positively associated with both impact and nonimpact loading. Midshaft shape is associated with directionality of loading. Individuals from the different categories overlap substantially, but group means differ credibly, suggesting that nuanced group‐level inferences of habitual behavior are possible when combinations of trabecular and cortical bone are analyzed.
-
The talar morphology of a hypochondroplasic dwarf: A case study from the Italian Late Antique periodmore » « less
Abstract This project aims to test whether geometric morphometric (GM) and trabecular analyses may be useful tools in identifying talar characteristics related to hypochondroplasia. We quantified the external and internal talar morphology of a hypochondroplasic dwarf (T17) from Modena (northern Italy) dated to the sixth century AD. External talar morphology of T17 was compared with a broad sample of modern human tali (
n = 159) using GM methods. Additionally, a subsample of these tali (n = 41) was used to investigate whole talar trabecular changes in T17. Our results show that GM and trabecular analyses identify a combination of traits linked to the dwarfing disorder of hypochondroplasia. These traits include decreased scaled talar dimensions compared with normal‐sized individuals, presence of an accessory antero‐lateral talar facet, high bone volume fraction, and high anisotropy values throughout the entire talus. In our case study, hypochondroplasia does not appear to substantially modify external talar morphology probably due to the fast growth of the talus. We suggest that small talar dimensions are associated with hypochondroplasia. An antero‐lateral talar facet may result from the talus and calcaneus coalition (i.e., talocalcaneal abnormal bridging) possibly related to an everted foot posture that was limited by overgrowth of the fibula. We suggest that high talar trabecular density and strut orientation provide insights into pathological development of the trabecular plates in T17. Finally, our study suggests that high talar trabecular density and strut orientation, and small talar dimensions, may be added as possible concomitant talar hallmarks for hypochondroplasia.
Full Text Available