Biology subjects

Warmlander, S. K. T. S.

Publications and source records attributed to Warmlander, S. K. T. S..

6 recordsLinked to original sources

bioRxiv2021

Sexual dimorphism in mastoid process volumes measured from 3D models of dry crania from medieval Croatia

3D analysis of skeletal volumes has become an important field in digital anthropology studies. The volume of the mastoid process has been proposed to display significant sexual dimorphism, but it has a complex shape and to date no study has quantified the full mastoid volume for sex estimation purposes. In this study we compared three different ways to isolate the volume of the mastoid process from digital 3D models of dry crania, and then evaluated the performance of the three different volume definitions for sex estimation purposes. A total of 170 crania (86 male, 84 females) excavated from five medieval Croatian sites were CT-scanned and used to produce 3D stereolitographic models. The three different isolation techniques were based on various anatomical landmarks and planes, as well as the anatomy of the mastoid process itself. Measurements of the three different mastoid volumes yielded different accuracies and precisions. Interestingly, anatomical structures were sometimes more useful than classical landmarks as demarcators of mastoid volume. For all three volume definitions, male mastoid volumes were significantly larger than female volumes, in both relative and absolute numbers. Sex estimation based on mastoid volume showed a slightly higher precision and better accuracy (71 % correct classifications) than visual scoring techniques (67 %) and linear distance measurements (69 %) of the mastoid process. Sex estimation based on cranial size performed even better (78 %), and multifactorial analysis (skull size + mastoid volume) reached up to 81% accuracy. These results show that measurements of the mastoid volume represent a promising metric to be used in multifactorial approaches for sex estimation of human remains.

paleontology↗

bioRxiv2021

Differential taphonomic effects of petroleum seeps and karstic sinkholes on ancient dire wolf teeth: Hydrocarbon impregnation preserves fossils for chemical and histological analysis

Histological analysis of teeth can yield information on an organisms growth and development, facilitating investigations of diet, health, environment, and long-term responses to selective pressures. In the Americas, an extraordinary abundance of Late Pleistocene fossils including teeth has been preserved in petroleum seeps, constituting a major source of information about biotic changes and adaptations at the end of the last glacial period. However, the usefulness of these fossils for histological studies is unclear, due to the unknown taphonomic effects of long-term deposition in petroleum. Here, we compare histological and chemical analyses on dire wolf (Canis dirus) teeth obtained from two different environments, i.e. a petroleum seep (Rancho La Brea tar pits, California) and a carstic sinkhole (Cutler Hammock sinkhole, Florida). Optical and scanning electron microscopy (SEM) together with X-ray diffraction (XRD) analysis revealed excellent preservation of dental microstructure in the seep sample, and the petroleum-induced discoloration was found not to interfere with the histological and chemical examination. By comparison, teeth from the sinkhole sample showed severe degradation and contamination of the dentine by exogenous substances. These results indicate that petroleum seep assemblages are useful, or even ideal, environments for preserving the integrity of fossil material for chemical and histological analysis.

paleontology↗

bioRxiv2021

Lithium ions display weak interaction with amyloid-beta (Aβ) peptides and have minor effects on their aggregation

Alzheimers disease (AD) is an incurable disease and the main cause of age-related dementia worldwide, despite decades of research. Treatment of AD with lithium (Li) has showed promising results, but the underlying mechanism is unclear. The pathological hallmark of AD brains is deposition of amyloid plaques, consisting mainly of amyloid-{beta} (A{beta}) peptides aggregated into amyloid fibrils. The plaques contain also metal ions of e.g. Cu, Fe, and Zn, and such ions are known to interact with A{beta} peptides and modulate their aggregation and toxicity. The interactions between A{beta} peptides and Li+ ions have however not been well investigated. Here, we use a range of biophysical techniques to characterize in vitro interactions between A{beta} peptides and Li+ ions. We show that Li+ ions display weak and non-specific interactions with A{beta} peptides, and have minor effects on A{beta} aggregation. These results indicate that possible beneficial effects of Li on AD pathology are not likely caused by direct interactions between A{beta} peptides and Li+ ions.

biochemistry↗

bioRxiv2021

6-gingerol interferes with amyloid-beta (Aβ) peptide aggregation

Alzheimers disease (AD) is the most prevalent age-related cause of dementia. AD affects millions of people worldwide, and to date there is no cure. The pathological hallmark of AD brains is deposition of amyloid plaques, which mainly consist of amyloid-{beta} (A{beta}) peptides, commonly 40 or 42 residues long, that have aggregated into amyloid fibrils. Intermediate aggregates in the form of soluble A{beta} oligomers appear to be highly neurotoxic. Cell and animal studies have previously demonstrated positive effects of the molecule 6-gingerol on AD pathology. Gingerols are the main active constituents of the ginger root, which in many cultures is a traditional nutritional supplement for memory enhancement. Here, we use biophysical experiments to characterize in vitro interactions between 6-gingerol and A{beta}40 peptides. Our experiments with atomic force microscopy imaging, and nuclear magnetic resonance and Thioflavin-T fluorescence spectroscopy, show that the hydrophobic 6-gingerol molecule interferes with formation of A{beta}40 aggregates, but does not interact with A{beta}40 monomers. Thus, together with its favourable toxicity profile, 6-gingerol appears to display many of the desired properties of an anti-AD compound.

biochemistry↗

bioRxiv2021

The engineered peptide construct NCAM1-Aβ inhibits aggregation of the human prion protein (PrP)

In prion diseases, the prion protein (PrP) becomes misfolded and forms fibrillar aggregates, which are resistant to proteinase degradation and become responsible for prion infectivity and pathology. So far, no drug or treatment procedures have been approved for prion disease treatment. We have previously shown that engineered cell-penetrating peptide constructs can reduce the amount of prion aggregates in infected cells. The molecular mechanisms underlying this effect are however unknown. Here, we use atomic force microscopy (AFM) imaging to show that the aggregation of the human PrP protein can be inhibited by equimolar amounts of the 25 residues long engineered peptide construct NCAM1-A{beta}.

biochemistry↗

bioRxiv2021

Comparing frontal inclination angles measured from digital 3D models and 2D photographs of dry male and female crania from Croatia

The frontal bone is one of the sexually dimorphic elements of the human skull that can be used for sex estimation of unidentified human remains. Numerous morphological features of the frontal bone, such as its angle of inclination, maximum anterior projection (glabella), and rounded elevations (frontal eminences) have been shown to differ between males and females. Various approaches have been developed to assess the frontal inclination in particular, and recently a method has been proposed where the angle of the frontal slope is measured from snapshots of digital three-dimensional (3D) models of human crania. However, as 3D-based investigations of skeletal material can be time-consuming and expensive, we here compare measurements of frontal angle inclination from 3D model snapshots to measurements from 2D photographs for a large sample (61 females and 61 males) of dry archaeological crania from medieval Croatia. Although angles measured from 3D snapshots and 2D photographs produced discriminant functions that classified crania by sex with similar accuracy (around 73%), the angles recorded from the 2D photographs were systematically one degree smaller than the angles recorded from the 3D images. Thus, even though both data sets were useful for sex estimation, we conclude that angles measured with the two different techniques should not be combined.

paleontology↗