Application of an Ovate Leaf Shape Model to Evaluate Leaf Bilateral Asymmetry and Calculate Lamina Centroid Location

Leaf shape is an important leaf trait, with ovate leaves common in many floras. Recently, a new leaf shape model (referred to as the MLRF equation) derived from temperature-dependent bacterial growth was proposed and demonstrated to be valid in describing leaf boundaries of many species with ovate leaf shape. The MLRF model’s parameters can provide valuable information of leaf shape, including the ratio of lamina width to length and the lamina centroid location on the lamina length axis. However, the model wasn’t tested on a large sample of a single species, thereby limiting its overall evaluation for describing leaf boundaries, for evaluating lamina bilateral asymmetry and for calculating lamina centroid location. In this study, we further test the model using data from two Lauraceae species, Cinnamomum camphora and Machilus leptophylla, with >290 leaves for each species. The equation was found to be credible for describing those shapes, with all adjusted root-mean-square errors (RMSE) smaller than 0.05, indicating that the mean absolute deviation is smaller than 5% of the radius of an assumed circle whose area equals lamina area. It was also found that the larger the extent of lamina asymmetry, the larger the adjusted RMSE, with approximately 50% of unexplained variation by the model accounted for by the lamina asymmetry, implying that this model can help to quantify the leaf bilateral asymmetry in future studies. In addition, there was a significant difference between the two species in their centroid ratio, i.e., the distance from leaf petiole to the point on the lamina length axis associated with leaf maximum width to the leaf maximum length. It was found that a higher centroid ratio does not necessarily lead to a greater investment of mass to leaf petiole relative to lamina, which might depend on the petiole pattern.

Geometric Morphometrics of Bilateral Asymmetry in Eunotia bilunaris (Eunotiales, Bacillariophyceae) as a Tool for the Quantitative Assessment of Teratogenic Deviations in Frustule Shapes

A number of pennate diatom genera typically have teratogenic deformations of their siliceous frustules due to the effects of environmental stress, such as high concentrations of heavy metals and low pH. However, the quantitative assessment of these deformations has rarely been applied. One species in which aberrations have frequently been reported is Eunotia bilunaris, which typically has bilaterally symmetric frustules with dorso-ventral differentiation. In this study, we aimed to illustrate the geometric morphometric analysis of symmetry as a tool for assessing the severity of teratogenic deformations. These were quantified by Procrustes superimposition of equidistant points placed along the valvar outlines in pairs of configurations based on their bilateral reflection symmetry. The shape deformations were mostly confined to central parts of the ventral outlines and were captured both by the symmetric and asymmetric subspaces of the variation. The amount of bilateral asymmetry in individual cells was negatively related to frustule size via the allometric power law relationship, illustrating that asymmetry increased in the asexual diminution series. The presented analysis provides a framework for the quantitative assessment of frustule deformations in eunotioid diatoms that can be used for the comparative scoring of teratogenic deviations among cells, populations, or species.

Bilateral Asymmetry in Ocular Counter-Rolling Reflex Is Associated With Individual Motion Sickness Susceptibility

Accumulating evidence suggests that individual variations in vestibular functions are associated with motion sickness (MS) susceptibility. We investigated whether vestibular functions in the reflex and cortical pathways could predict the susceptibility of individuals to MS. MS-susceptible and control adults were recruited according to the Motion Sickness Susceptibility Questionnaire (MSSQ) score. Otolith reflex and cortical functions were assessed using the ocular counter rolling test and the head-tilt subjective visual vertical (HT-SVV) test, respectively. The bilateral asymmetry of each function was compared between the MS-susceptible and the control groups. Although the two tests for otolith functions were conducted using the same stimulation (lateral head tilt), bilateral asymmetry of otolith reflex rather than cortical function was significantly associated with MS susceptibility. Our data suggests that bilateral asymmetry in the otolith reflex pathway is capable of predicting susceptibility to MS to some extent. Our data also suggest that the association between vestibular function and MS susceptibility can vary based on the vehicle types. Future vehicles, such as self-driving cars, will make us aware of other vestibular functions associated with MS susceptibility.

Inter-Incisive Index in South Bulgarians and Its Application in Aesthetic Dentistry

Background: In recent years, aesthetic dentistry has become a major focus for the public. Facial attractiveness plays a key role on modern society and the creation of harmonious smile is an aim for every dentist.The aim of this study was to define certain values of the inter-incisive index in South Bulgarians, the sexual dimorphism and bilateral asymmetry and to verify differences of this index between Bulgarians and other Balkan populations.Materials and methods: The present study included 86 males and 83 females of Bulgarian origin living in South Bulgaria aged 20-40 years. Mesiodistal dimensions of maxillary central and lateral incisors were measured by Dentistry Sliding Vernier Caliper. We used the technique of Martin-Saller, modified by Prof. Y. Yordanov. We calculated the inter-incisive index as ratio of the mesiodistal dimension of maxillary lateral incisor to the mesiodistal dimension of the maxillary central incisor. The measurements were analyzed with SPSS 23. The level of statistical significance was set at P< 0.05. Results: The inter-incisive index showed no statistically significant differences between left and right side of the dental arch in both sexes. We did not find statistically significant differences between males and females as well. On the other hand we found statistically significant differences in MD values of incisors between Bulgarians and other Balkan nations.Conclusion: Inter-incisive index shows no sexual dimorphism and bilateral asymmetry in South Bulgarians. This can be helpful in aesthetic dentistry, in prosthodontics and in orthodontic treatment planning.

Biomechanical Evaluation on the Bilateral Asymmetry of Complete Humeral Diaphysis in Chinese Archaeological Populations

Diaphyseal cross-sectional geometry (CSG) is an effective indicator of humeral bilateral asymmetry. However, previous studies primarily focused on CSG properties from limited locations to represent the overall bilateral biomechanical performance of humeral diaphysis. In this study, the complete humeral diaphyses of 40 pairs of humeri from three Chinese archaeological populations were scanned using high-resolution micro-CT, and their biomechanical asymmetries were quantified by morphometric mapping. Patterns of humeral asymmetry were compared between sub-groups defined by sex and population, and the representativeness of torsional rigidity asymmetry at the 35% and 50% cross-sections (J35 and J50 asymmetry) was testified. Inter-group differences were observed on the mean morphometric maps, but were not statistically significant. Analogous distribution patterns of highly asymmetrical regions, which correspond to major muscle attachments, were observed across nearly all the sexes and populations. The diaphyseal regions with high variability of bilateral asymmetry tended to present a low asymmetrical level. The J35 and J50 asymmetry were related to the overall humeral asymmetry, but the correlation was moderate and they could not reflect localized asymmetrical features across the diaphysis. This study suggests that the overall asymmetry pattern of humeral diaphysis is more complicated than previously revealed by individual sections.

БИЛАТЕРАЛЬНАЯ АСИММЕТРИЯ ДЛИННЫХ КОСТЕЙ СКЕЛЕТА У ТОБОЛО-ИРТЫШСКИХ ТАТАР

В статье представлены результаты изучения билатеральной асимметрии длинных костей скелета у четырёх групп тоболо-иртышских татар: аялынских, тобольских, тюменских и коурдакско-саргатских татар. Для каждой группы мужчин и женщин была рассчитаны коэффициенты асимметрии (использовалась формула R–L), процентное соотношение которых показывает, что наиболее симметричная скелетная система у аялынских татар, а самая асимметричная у коурдакско-саргатских татар. При анализе коэффициентов асимметрии отдельных костей, было выявлено, что во всех исследуемых группах у мужчин и женщин самой асимметричной костью является плечевая кость. Анализ коэффициентов асимметрии по отдельным признакам показал, что во всех группах наибольшей асимметрией отличаются продольные диаметры костей верхних конечностей. Левосторонняя асимметрия в группах тоболо-иртышских татар в основном характерна для признаков костей нижних конечностей как у мужчин, так и у женщин. Закономерности в половом распределении коэффициентов асимметрии в группах тоболо-иртышских татар выявлены не были. Для наглядности изменчивости коэффициентов асимметрии для мужских и женских групп тоболо-иртышских татар были построены комбинационные полигоны, форма которых показала, что наиболее схожи между собой мужчины тобольских и коурдакско-саргатских татар, а аялынские и тюменские татары заметно отличаются как от этих групп, так и между собой. Формы комбинационных полигонов женских серий тоболо-иртышских татар не обнаруживают видимого сходства между собой. Таким образом, выявленные различия в асимметрии скелетной системы этно-территориальных групп тоболо-иртышских татар, возможно, связаны с хозяйственным укладом жизни татар, который, ввиду различной территории расселения тех или иных этно-территориальных групп, заметно отличался. The article presents the results of studying the limb bone bilateral asymmetry in four groups of the Tobol-Irtysh Tatars: Ayalyn, Tobolsk, Tyumen and Kourdak-Sargat Tatars. The asymmetry coefficients were calculated for the male and female samples of each group (using the R – L formula). The Ayalyn Tatars resulted to have the most symmetric skeletal system, while the Kourdak-Sargat Tatars – the least symmetrical one. The analysis of the asymmetry coefficients of individual bones revealed that the humerus is the most asymmetric bone in both sexes among all the studied groups. The lengths of the upper limb bones resulted to be the most asymmetrical measurement in all groups. Left-sided asymmetry was mainly seen in the lower limb bones among the Tobol-Irtysh Tatars. No sex differences in the asymmetry coefficients were revealed. Combination polygons were produced to illustrate the variability of the asymmetry coefficients for the male and female samples. Male samples of the Tobolsk and Kourdak-Sargat Tatars were found to be most similar to each other, and the Ayalyn and Tyumen Tatars are noticeably different both from these groups and from each other. The combination polygons of the female samples of the Tobol-Irtysh Tatars do not reveal any visible similarity between them. Thus, the revealed differences in the asymmetry of the skeletal system of the Tobol-Irtysh Tatars ethno-territorial groups are possibly associated with different economy systems of the groups.