Optimal trait scoring for age estimation

What are the effects that genetics has had on Anthropological research and how can we think anthropologically about Genetics? Just as genetic data have encouraged new hypotheses about human phenotypic variation, evolutionary history, population interaction, and environmental effects, so too has Anthropology offered to genetic studies a new interpretive locus in its history and perspective. This introduction examines how the fields of Anthropology and Genetics have arrived at a crucial moment at which their interaction requires careful examination and critical reflection. The papers discussed here exemplify how we may engage in such a trans-disciplinary conversation. They speak to the future of thoughtful interaction between genetic and anthropological literature and seek a new integration that embodies the holism of the human biological sciences.     

Predicting Agenesis of the Mandibular Second Premolar from Adjacent Teeth

Early diagnosis of agenesis of the mandibular second premolar (P2) enhances management of the dental arch in the growing child. The aim of this study was to explore the relationship in the development of the mandibular first molar (M1) and first premolar (P1) at early stages of P2 (second premolar). Specifically, we ask if the likelihood of P2 agenesis can be predicted from adjacent developing teeth. We selected archived dental panoramic radiographs with P2 at crown formation stages (N = 212) and calculated the likelihood of P2 at initial mineralisation stage ‘Ci’ given the tooth stage of adjacent teeth. Our results show that the probability of observing mandibular P2 at initial mineralisation stage ‘Ci’ decreased as both the adjacent P1 and M1 matured. The modal stage at P2 ‘Ci’ was P1 ‘Coc’ (cusp outline complete) and M1 ‘Crc’ (crown complete). Initial mineralisation of P2 was observed up to P1 ‘Crc’ and M1 stage ‘R½’ (root half). The chance of observing P2 at least ‘Coc’ (coalescence of cusps) was considerably greater prior to these threshold stages compared to later stages of P1 and M1. These findings suggest that P2 is highly unlikely to develop if P1 is beyond ‘Crc’ and M1 is beyond ‘R½’.     

Enhanced tolerance to autoimmune uveitis in CD200-deficient mice correlates with a pronounced Th2 switch in response to antigen challenge

A single exposure to inhaled Ag 10 days before immunization leads to long term, Ag-specific tolerance. Respiratory tract myeloid APCs are implicated, but how regulation is invoked, and how tolerance is sustained are unclear. This study examines the in vivo function of the myeloid regulatory molecule CD200 in the process of tolerance induction. Despite earlier onset of experimental autoimmune uveitis in sham-tolerized, CD200-deficient mice, disease incidence and subsequent severity were actually reduced compared with those in wild-type mice. Protection was more effective and long term, lasting at least 28 days. Halting disease progression and tolerance in CD200(-/-) mice correlated with a marked increase in Th2-associated cytokine production by Ag-challenged splenocytes. Reduced overall disease and enhanced tolerance in the CD200-deficient mice in this model system were unexpected and may be related to altered populations of MHC class II(low) APC in the respiratory tract compared with wild-type mice together with associated activation of STAT6 in draining lymph nodes of tolerized mice. These data indicate that in the absence of default inhibitory CD200 receptor signaling, alternative, powerful regulatory mechanisms are invoked. This may represent either permissive dominant Th2 activation or an altered hierarchy of negative signaling by other myeloid cell-expressed regulatory molecules.     

Differentiation to the CCR2+ inflammatory phenotype in vivo is a constitutive, time-limited property of blood monocytes and is independent of local inflammatory mediators

It is proposed that CCR2+ monocytes are specifically recruited to inflammatory sites, whereas CCR2- monocytes are recruited to normal tissue to become resident macrophages. Whether these subsets represent separate lineages, how differential trafficking is regulated and whether monocytes undergo further differentiation is uncertain. Using a mouse model of autoimmune uveoretinitis we examined monocyte trafficking to the inflamed retina in vivo. We show that bone marrow-derived CD11b+ F4/80- monocytes require 24 to 48 h within the circulation and lymphoid system before acquiring the CCR2+ phenotype and trafficking to the inflamed retina is enabled. This phenotype, and the capacity to traffic were lost by 72 h. Monocyte CCR2 expression followed a similar time course in normal mice indicating that differentiation to an inflammatory phenotype is a constitutive, time-limited property, independent of local inflammatory mediators. Phenotypic analysis of adoptively transferred cells indicated that circulating inflammatory monocytes also differentiate into CD11c+ and B220+ dendritic cells and F4/80+ tissue macrophages in vivo. Our data supports the hypothesis of continuous extravasation and progressive differentiation over time of inflammatory monocytes in the circulation rather than replication within the actively inflamed tissue, and supports the concept of myeloid dendritic cell differentiation from trafficking monocytes under physiological conditions in vivo.     

Malnutrition Has No Effect on the Timing of Human Tooth Formation

The effect of nutrition on the timing of human tooth formation is poorly understood. Delays and advancements in dental maturation have all been reported as well as no effect. We investigated the effect of severe malnutrition on the timing of human tooth formation in a large representative sample of North Sudanese children. The sample (1102 males, 1013 females) consisted of stratified randomly selected healthy individuals in Khartoum, Sudan, aged 2-22 years using a cross-sectional design following the STROBE statement. Nutritional status was defined using WHO criteria of height and weight. Body mass index Z-scores and height for age Z-scores of ≤−2 (cut-off) were used to identify the malnourished group (N = 474) while the normal was defined by Z-scores of ≥0 (N = 799). Clinical and radiographic examination of individuals, with known ages of birth was performed including height and weight measurements. Mandibular left permanent teeth were assessed using eight crown and seven root established tooth formation stages. Mean age at entry and mean age within tooth stages were calculated for each available tooth stage in each group and compared using a t-test. Results show the mean age at entry and mean age within tooth stages were not significantly different between groups affected by severe malnutrition and normal children (p>0.05). This remarkable finding was evident across the span of dental development. We demonstrate that there is little measurable effect of sustained malnutrition on the average timing of tooth formation. This noteworthy finding supports the notion that teeth have substantial biological stability and are insulated from extreme nutritional conditions compared to other maturing body systems.     

Some aspects of the biology of the cercaria and metacercaria of Stephanostomum baccatum (Nicoll, 1907) Manter, 1934 (Digenea: Acanthocolpidae)

Experimental proof is presented that Cercaria neptunae Lebour is the cercaria of Stephanostomum baccatum and that the gastropods Buccinum undatum (L.) and Neptunea antiqua (L.) both act as its first intermediate hosts in the north-east Atlantic. Heavy experimental infections were associated with mortalities of 0+plaice Pleuronectes platessa (L.). The probable effects on plaice of infections at intensities below the lethal level are discussed. Under natural conditions almost all S. baccatum infection of plaice occurs in the first year of life, but newly emerged cercariae were shown experimentally to be capable of encysting in the musculature of plaice up to three years old. The thicker epidermis of older plaice may account for their resistance to infection. Common dabs were more easily infected than plaice. The ability of S. baccatum cercariae to infect plaice and common dabs is inversely related to the length of time between emergence and contact with the host. The differences in skin structure between opposite sides of the plaice body may account for the asymmetrical distribution of metacercariae in the musculature. The potential use of S. baccatum as a biological tag is discussed.     

Variation in crown and root formation and eruption of human deciduous teeth

The aim of this study was to document variation of deciduous tooth formation and eruption. The material comprises 121 individuals of known or estimated age (using tooth length) from Spitalfields in London, and radiographs of 61 healthy living children aged 2-5 years. Other skeletal material from two medieval Scottish archaeological sites (Whithorn, N=74; Newark Bay, N=59) was also examined. Stages of crown and root formation as well as eruption (alveolar, midway, and occlusal levels) were assessed for each developing maxillary and mandibular tooth from radiographs or direct vision. Age of attainment for individual stages was calculated by probit analysis, and these data were also adapted for use in estimating age. The timing of crown completion was similar to previously reported studies, but apex completion times were later. Analysis of data relative to the first and second molars at the two stages D (crown complete) and F (root length > or =crown height) allowed comparison with the Scottish material. No significant differences were observed between population groups for tooth formation or eruption. These data fill several gaps in the literature, and will be useful in assessing maturity and predicting age during early childhood.