Life stresses of the free black community as represented by the First African Baptist Church, Philadelphia, 1823-1841

The congregation of the Reverend Henry Simmons (First African Baptist Church at 8th & Vine, Philadelphia) from 1823 to 1841 used a cemetery rediscovered through subway expansion which was carefully excavated by M. Parrington and S. Pinter in 1983-1984; currently 75 adults were available for study. As an overall health indicator, longevity at 38.9 years (N = 39) female and 44.8 (N = 36) male indicates more stress on females. Probable causes of stress are inadequate nutrition for the performance of arduous labor, pregnancy, and childrearing, unsanitary living conditions, limited exposure to sun, and extensive exposure to infectious diseases. Nutritional indicators of stature, dental lesions, skull base height, and pelvic brim index scarcely advance over 1790-1820 Catoctin Furnace, Maryland, slaves' indicators. Disease evidence includes limb-distorting rickets in one child who died at age 8, anemia, and arthritis; but the incidence of arthritis was less than at Catoctin. Genetic traits are chiefly African. Family links show in details: os acromiale in about 30%. This plus less violence (fewer fractures) suggests community strength developing.     

Localization of the gene causing keratolytic winter erythema to chromosome 8p22-p23, and evidence for a founder effect in South African Afrikaans-speakers.

Keratolytic winter erythema (KWE), also known as "Oudtshoorn skin disease," or "erythrokeratolysis hiemalis," is an autosomal dominant skin disorder of unknown etiology characterized by a cyclical erythema, hyperkeratosis, and recurrent and intermittent peeling of the palms and soles, particularly during winter. Initially KWE was believed to be unique to South Africa, but recently a large pedigree of German origin has been identified. The disorder occurs with a prevalence of 1/7,000 in the South African Afrikaans-speaking Caucasoid population, and this high frequency has been attributed to founder effect. After a number of candidate regions were excluded from linkage to KWE in both the German family and several South African families, a genomewide analysis was embarked on. Linkage to the microsatellite marker D8S550 on chromosome 8p22-p23 was initially observed, with a maximum LOD score (Z(max)) of 9.2 at a maximum recombination fraction (theta(max)) of .0 in the German family. Linkage was also demonstrated in five of the larger South African families, with Z(max) = 7.4 at theta(max) = .02. When haplotypes were constructed, 11 of 14 South African KWE families had the complete "ancestral" haplotype, and 3 demonstrated conservation of parts of this haplotype, supporting the hypothesis of founder effect. The chromosome segregating with the disease in the German family demonstrated a different haplotype, suggesting that these chromosomes do not have a common origin. Recombination events place the KWE gene in a 6-cM interval between D8S550 and D8S552. If it is assumed that there was a single South African founder, a proposed ancestral recombinant suggests that the gene is most likely in a 1-cM interval between D8S550 and D8S265.     

Brief communication: Population variation in human maxillary premolar accessory ridges (MxPAR)

The purpose of this brief communication is to report the results of an analysis of maxillary premolar accessory ridges (MxPAR), a common but understudied accessory ridge that may occur both mesial and distal to the central ridge of the buccal cusp of upper premolars. We developed a new five‐grade scoring plaque to better categorize MxPAR variation. Subsequently, we conducted a population analysis of MxPAR frequency in 749 dental casts of South African Indian, American Chinese, Alaskan Eskimo, Tohono O'odham (Papago), Akimel O'odham (Pima), Solomon Islander, South African Bantu, and both American and South African Whites. Northeast Asian and Asian‐derived populations exhibited the highest MxPAR frequencies while Indo‐European samples (South African Indians, American and South African Whites) exhibited relatively low frequencies. The Solomon Islanders and South African Bantu samples exhibited intermediate frequencies. Our analysis indicates that statistically significant differences in MxPAR frequency exist between major geographic populations. As a result, the MxPAR plaque has now been added to the Arizona State University Dental Anthropology System, an important contribution as maxillary premolar traits are underrepresented in analyses of dental morphology. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Population genetics of Eldana saccharina Walker (Lepidoptera: Pyralidae) and the implications for management using biocontrol

The African sugarcane stalk borer, Eldona saccharina Walker (Lepidoptera: Pyralidae), is widely distributed throughout sub-Saharan Africa and is an important insect pest of maize and sugarcane. The insect shows significant variation in behaviour, host plant and natural enemy guild in different regions. Several attempts to redistribute the natural enemies of E. saccharina from West Africa to South Africa were unsuccessful. The significant behavioural, host plant and natural enemy variations as well as failures of biocontrol attempts evoked a hypothesis of genetic diversification. To evaluate this hypothesis a molecular analysis was conducted on geographically isolated populations of E. saccharina from East, North, South and West Africa, using the cytochrome c oxidase subunit I (COI) region of the mitochondrial genome. The results revealed that E. saccharina populations are separated into four major units corresponding to the West Africa, Rift Valley, South/East Africa and southern African populations. Mitochondrial DNA divergence among the four populations ranged from 1% to 4.98%. To examine the impact of the observed genetic variation on the fertility of inter-population crosses, a mating experiment was conducted between the Rift valley and South African population to produce an F1 generation, and these were backcrossed with the South African parent population. Fertility of eggs produced by the F1/parent population cross was significantly reduced when compared to fertility of the "true" South African line, and the F1/F1 cross. The contributions of the observed genetic differences and inter population incompatibility for the failure of previous biocontrol attempts are discussed and recommendations on future biocontrol practices are given.     

Association of serum lipid components and obesity with genetic ancestry in an admixed population of elderly women

The prevalence of metabolic disorders varies among ethnic populations and these disorders represent a critical health care issue for elderly women. This study investigated the correlation between genetic ancestry and body composition, metabolic traits and clinical status in a sample of elderly women. Clinical, nutritional and anthropometric data were collected from 176 volunteers. Genetic ancestry was estimated using 23 ancestry-informative markers. Pearsons correlation test was used to examine the relationship between continuous variables and an independent samples t-test was used to compare the means of continuous traits within categorical variables. Overall ancestry was a combination of European (57.49%), Native American (25.78%) and African (16.73%). Significant correlations were found for European ancestry with body mass index (r = 0.165; p = 0.037) and obesity (mean difference (MD) = 5.3%; p = 0.042). African ancestry showed a significant correlation with LDL (r = 0.159, p = 0.035), VLDL (r = −0.185; p = 0.014), hypertriglyceridemia (MD = 6.4%; p = 0.003) and hyperlipidemia (MD = 4.8%; p = 0.026). Amerindian ancestry showed a significant correlation with triglyceride levels (r = 0.150; p = 0.047) and hypertriglyceridemia (MD = 4.5%; p = 0.039). These findings suggest that genetic admixture may influence the etiology of lipid metabolism-related diseases and obesity in elderly women.     

Genome Evolution of the Cyanobacterium Nostoc linckia under Sharp Microclimatic Divergence at "Evolution Canyon," Israel

We describe the genomic DNA diversity and divergence of the cyanobacterium Nostoc linckia from "Evolution Canyon," a microsite consisting of ecologically contrasting slopes, south-facing slope (SFS) and north-facing slope (NFS), at lower Nahal Oren, Mt. Carmel, Israel. The opposing slopes share their limestone lithology but vary greatly in their ecology, primarily because of different levels of solar radiation (which is six times higher on the SFS than on the NFS). The warm and xeric SFS displays a tropical African savanna, whereas the cool and mesic NFS displays a temperate South European Mediterranean live-oak maquis shrub forest. The cyanobacterium Nostoc linckia tested here is a sessile microorganism, growing as a carpet on rock surfaces and constantly exposed to environmental fluctuations of solar radiation, temperature, and desiccation. We demonstrate remarkable interslope and intraslope genetic divergence of the genome (including both coding and noncoding regions) of Nostoc linckia, by using 211 AFLP (amplified fragment length polymorphism) DNA molecular marker loci. Genetic polymorphism of N. linckia subpopulations on the ecologically harsher SFS was significantly (p <0.05) higher (p = 99.53%) than was that of the subpopulations on the climatically milder nfs (p = 85.78%). genetic polymorphism (p) and gene diversity (he) were significantly correlated with variables influencing aridity stress: solar radiation (sr) (rp = 0.956; p = 0.046), temperature (tm) (rp = 0.993; p = 0.0068), and day-night temperature difference (tdd) (rp = 0.975; p = 0.025). as in other tested organisms from "evolution canyon", but even more exceptionally because of its completely sedentary nature, we suggest that the climatically stressed sfs environment is responsible for this marked increase of genetic polymorphism, which is maintained by the combined evolutionary forces of diversifying and balancing selection. This could highlight the importance of ecological stress and selection in evolution and its remarkable effect on the genetic system across the prokaryotic genome.     

A striking example of the founder effect in the mollusc Littorina saxatilis

Two South African populations of Littorina saxatilis were examined by starch-gel electrophoresis at 16 enzyme loci and compared with 13 populations of North Atlantic saxatilis from both American and European coasts, and with six British populations of the closely related species Littorina arcana. The South African animals showed a severely reduced heterozygosity (– 0.052) compared with Atlantic populations of saxatilis ( = 0.181), and the mean genetic distance between the two areas was high ( = 0.203) compared with distances within the North Atlantic saxatilis populations (D = 0.034). In fact, the saxatilis from South Africa were genetically more distant from the North Atlantic samples of L. saxatilis than were the arcana from British shores. The reduced genetic heterozygosity and genetic divergence of the South African populations is attributed to founder effects following a postulated recent introduction by man.     

Markers of physiological stress in juvenile bonobos (Pan paniscus): Are enamel hypoplasia,skeletal development and tooth size interrelated?

A reduction in enamel thickness due to disrupted amelogenesis is referred to as enamel hypoplasia (EH). Linear EH in permanent teeth is a widely accepted marker of systemic physiological stress. An enigmatic, nonlinear form of EH commonly manifest in great ape and human deciduous canines (dc) is known as localized hypoplasia of primary canines (LHPC). The etiology of LHPC and what it signifies—localized traumatic or systemic physiological stress—remains unclear. This report presents frequency data on LHPC, hypostotic cranial traits, and tooth size in a sample of juvenile bonobos, then tests hypotheses of intertrait association that improve knowledge of the etiology and meaning of LHPC. The fenestration hypothesis is tested using hypostotic cranial traits as a proxy for membrane bone ossification, and the relationship between tooth size, LHPC, and hypostosis is investigated. Macroscopic observations of EH, hypostotic traits, and measurements of buccolingual tooth size were conducted according to established standards. LHPC was found in 51.2% of bonobos (n = 86) and in 26% of dc teeth (n = 269). Hypostotic traits were observed in 55.2% of bonobos (n = 96). A test of the association between LHPC and hypostosis yielded nonsignificant results (χ² = 2.935; P = 0.0867). Primary canines were larger in specimens with LHPC than in unaffected specimens (paired samples t test; udc, P = 0.011; ldc, P = 0.018), a result consistent with the fenestration hypothesis of LHPC pathogenesis. Hypostosis was not associated with differences in tooth size (P > 0.05). LHPC may be an indirect indicator of physiological stress, resulting from large, buccally displaced primary canines. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc.     

Contrasting the ancestry patterns of three distinct population groups from the northernmost region of South America

Colombia, located in the north of the South American subcontinent is a country of great interest for population genetic studies given its high ethnic and cultural diversity represented by the admixed population, 102 indigenous peoples and African descent populations. In this study, an analysis of the genetic structure and ancestry was performed based on 46 ancestry informative INDEL markers (AIM-INDELs) and considering the genealogical and demographic variables of 451 unrelated individuals belonging to nine Native American, two African American, and four multiple ancestry populations. Measures of genetic diversity, ancestry components, and genetic substructure were analyzed to build a population model typical of the northernmost part of the South American continent. The model suggests three types of populations: Native American, African American, and multiple ancestry. The results support hypotheses posed by other authors about issues like the peopling of South America and the existence of two types of Native American ancestry. This last finding could be crucial for future research on the peopling of Colombia and South America in that a single origin of all indigenous communities should not be assumed. It then would be necessary to consider other events that could explain their genetic variability and complexity throughout the continent.     

Why dengue and yellow fever coexist in some areas of the world and not in others?

Urban yellow fever and dengue coexist in Africa but not in Asia and South America. In this paper, we examine four hypotheses (and various combinations thereof) to explain the absence of yellow fever in urban areas of Asia and South America. In addition, we examine an additional hypothesis that offers an explanation of the coexistence of the infections in Africa while at the same time explaining their lack of coexistence in Asia. The hypotheses we tested to explain the nonexistence of yellow fever in Asia are the following: (1) the Asian Aedes aegypti is relatively incompetent to transmit yellow fever; (2) there would exist a competition between dengue and yellow fever viruses within the mosquitoes, as suggested by in vitro studies in which the dengue virus always wins; (3) when an A. aegypti mosquito that is infected by or latent for yellow fever acquires dengue, it becomes latent for dengue due to internal competition within the mosquito between the two viruses; (4) there is an important cross-immunity between yellow fever and other flaviviruses, dengue in particular, such that a person recovered from a bout of dengue exhibits a diminished susceptibility to yellow fever. This latter hypothesis is referred to below as the "Asian hypothesis." Finally, we hypothesize that: (5) the coexistence of the infections in Africa is due to the low prevalence of the mosquito Aedes albopictus in Africa, as it competes with A. aegypti. We will refer to this latter hypothesis as the "African hypothesis." We construct a model of transmission that allows all of the above hypotheses to be tested. We conclude that the Asian and the African hypotheses can explain the observed phenomena, whereas other hypotheses fail to do so.     

Stroke frequency in front crawl: its mechanical link to the fluid forces required in non-propulsive directions

Two hypotheses were tested: (a) stroke frequency is predictable from the amplitudes of bodyroll and the turning effect around the body's long-axis generated by the non-propulsive fluid forces (that is, the torque driving bodyroll), and (b) swimmers exhibit at least one alteration in the factors influencing the bodyroll cycle as they increase the stroke frequency for faster swimming, so that they can reduce the fluid forces "wasted" in non-propulsive directions. The mechanical formula that links stroke frequency and the kinetics of bodyroll was derived on the basis of Euler's equation of motion. Experimental data were collected from competitive swimmers to validate the derived mechanical relations and to examine the strategy that skilled swimmers would use to change the stroke frequency as they swam faster. A strong correlation (slow: r = 0.70 and fast: r = 0.85) and a non-significant difference between the observed stroke frequency and the formula-based estimates supported the first hypothesis. As the subjects increased stroke frequency (38%) for faster swimming, bodyroll decreased (19%) and the trunk twist increased (40%). The combined alterations resulted in a small reduction in the shoulder roll (12%), enabling the swimmers to gain the benefits associated with a large rolling action of the upper trunk, while limiting the amount of increase in the turning effect of fluid forces in non-propulsive directions (40%). The second hypothesis was, therefore, supported. The derived mechanical formula provides a theoretical basis to explore mechanisms underlying the interrelations among stroke frequency, stroke length and swimming speed, and sheds light on a possible reason that swimmers generally adopt six-beat kicks.     

Biochemical genetic stock structure of the southern African anchovy, Engraulis capensis Gilchrist

The geographical distributions of inherited biochemical markers were used to measure the amount of genetic isolation between stocks of Namibian and South African anchovy, Engraulis capensis . A contingency-table analysis of allele frequencies for 10 polymorphic protein-coding loci revealed no significant frequency differences between spawning areas. The average Nei genetic distance between samples was 0.0003 and there were no geographic trends in the amount of genetic distance between populations. Average population heterozygosity for 31 loci was 0.115 and this accounted for 99.26% of the total genetic variation. The remaining 0.24% was due to all temporal and spatial differences combined. The observed amount of genetic divergence between populations was used to estimate the amount of migration between spawning areas, using the stepping-stone model of migration. As few as 13 migrants may account for the observed genetic divergence between spawning areas. The validity of using the genetic stock concept in the management of marine fishes is discussed.     

Genotypic Diversity Is Associated with Clinical Outcome and Phenotype in Cryptococcal Meningitis across Southern Africa

Cryptococcal meningitis is a major cause of mortality throughout the developing world, yet little is known about the genetic markers underlying Cryptococcal virulence and patient outcome. We studied a cohort of 230 Cryptococcus neoformans (Cn) isolates from HIV-positive South African clinical trial patients with detailed clinical follow-up using multi-locus sequence typing and in vitro phenotypic virulence assays, correlating these data with clinical and fungal markers of disease in the patient. South African Cn displayed high levels of genetic diversity and locus variability compared to globally distributed types, and we identified 50 sequence types grouped within the main molecular types VNI, VNII and VNB, with 72% of isolates typed into one of seven ''high frequency'' sequence types. Spatial analysis of patients’ cryptococcal genotype was not shown to be clustered geographically, which might argue against recent local acquisition and in favour of reactivation of latent infection. Through comparison of MLST genotyping data with clinical parameters, we found a relationship between genetic lineage and clinical outcome, with patients infected with the VNB lineage having significantly worse survival (n=8, HR 3.35, CI 1.51-7.20, p=0.003), and this was maintained even after adjustment for known prognostic indicators and treatment regimen. Comparison of fungal genotype with in vitro phenotype (phagocytosis, laccase activity and CSF survival) performed on a subset of 89 isolates revealed evidence of lineage-associated virulence phenotype, with the VNII lineage displaying increased laccase activity (p=0.001) and ex vivo CSF survival (p=0.0001). These findings show that Cryptococcus neoformans is a phenotypically heterogeneous pathogen, and that lineage plays an important role in cryptococcal virulence during human infection. Furthermore, a detailed understanding of the genetic diversity in Southern Africa will support further investigation into how genetic diversity is structured across African environments, allowing assessment of the risks different ecotypes pose to infection.     

Association of the COQ2 V393A Variant with Parkinson's Disease: A Case-Control Study and Meta-Analysis

Both Parkinson’s disease (PD) and multiple system atrophy (MSA) are neurodegenerative diseases of uncertain etiology, but they show similarities in their pathology and clinical course. The fact that the gene encoding α-synuclein is associated with both diseases also suggests that they share some genetic determinants. Recent studies in Japan associating MSA with a variant in the COQ2 gene led us to question whether variants in the COQ2 gene are associated with PD in Han Chinese in a case-control study. A total of 564 patients with PD were genotyped using the ligase detection rection, together with 484 gender- and age-matched healthy subjects. The M128V and R387X variants of COQ2 were not detected in patients or controls; instead, we detected only the heterozygous V393A variant (CT genotype). The frequency of the CT genotype encoding the V393A mutation was significantly higher in patients PD (4.08%) than in controls (1.86%), corresponding to an odds ratio of 2.24 (95%CI 1.03 to 4.90, p = 0.037). The frequency of the C allele of the V393A variant was significantly higher in patients with PD than in controls (OR 2.22, 95%CI 1.02 to 4.82, p = 0.039), and this was also observed in a meta-analysis of studies from mainland China, Taiwan and Japan. Subgroup analysis of our data showed that the V393A variant was significantly associated with early-onset PD (OR 3.71, 95%CI 1.51 to 9.15, p = 0.002) but not with late-onset disease (OR 1.65, 95%CI 0.69 to 3.95, p = 0.260). Gender was not significantly associated with either genotype or minor allele frequencies. In conclusion, our findings show for the first time that the V393A variant in the COQ2 gene increases risk of PD among the population of east Asia. These results, combined with research on Japanese, lend genetic support to the hypothesis that oxidative stress underlies pathogenesis of both PD and MSA.     

Ethnic differences in guideline-indicated statin initiation for people with type 2 diabetes in UK primary care, 2006–2019: A cohort study

BackgroundType 2 diabetes is 2–3 times more prevalent in people of South Asian and African/African Caribbean ethnicity than people of European ethnicity living in the UK. The former 2 groups also experience excess atherosclerotic cardiovascular disease (ASCVD) complications of diabetes. We aimed to study ethnic differences in statin initiation, a cornerstone of ASCVD primary prevention, for people with type 2 diabetes.Methods and findingsObservational cohort study of UK primary care records, from 1 January 2006 to 30 June 2019. Data were studied from 27,511 (88%) people of European ethnicity, 2,386 (8%) people of South Asian ethnicity, and 1,142 (4%) people of African/African Caribbean ethnicity with incident type 2 diabetes, no previous ASCVD, and statin use indicated by guidelines. Statin initiation rates were contrasted by ethnicity, and the number of ASCVD events that could be prevented by equalising prescribing rates across ethnic groups was estimated. Median time to statin initiation was 79, 109, and 84 days for people of European, South Asian, and African/African Caribbean ethnicity, respectively. People of African/African Caribbean ethnicity were a third less likely to receive guideline-indicated statins than European people (n/N [%]: 605/1,142 [53%] and 18,803/27,511 [68%], respectively; age- and gender-adjusted HR 0.67 [95% CI 0.60 to 0.76], p < 0.001). The HR attenuated marginally in a model adjusting for total cholesterol/high-density lipoprotein cholesterol ratio (0.77 [95% CI 0.69 to 0.85], p < 0.001), with no further diminution when deprivation, ASCVD risk factors, comorbidity, polypharmacy, and healthcare usage were accounted for (fully adjusted HR 0.76 [95% CI 0.68, 0.85], p < 0.001). People of South Asian ethnicity were 10% less likely to receive a statin than European people (1,489/2,386 [62%] and 18,803/27,511 [68%], respectively; fully adjusted HR 0.91 [95% CI 0.85 to 0.98], p = 0.008, adjusting for all covariates). We estimated that up to 12,600 ASCVD events could be prevented over the lifetimes of people currently affected by type 2 diabetes in the UK by equalising statin prescribing across ethnic groups. Limitations included incompleteness of recording of routinely collected data.ConclusionsIn this study we observed that people of African/African Caribbean ethnicity with type 2 diabetes were substantially less likely, and people of South Asian ethnicity marginally less likely, to receive guideline-indicated statins than people of European ethnicity, even after accounting for sociodemographics, healthcare usage, ASCVD risk factors, and comorbidity. Underuse of statins in people of African/African Caribbean or South Asian ethnicity with type 2 diabetes is a missed opportunity to prevent cardiovascular events.

In a retrospective cohort study, Sophie Eastwood and colleagues investigate the association between ethnicity and statin initiation for people with type 2 diabetes in UK.     

African ancestry and its correlation to type 2 diabetes in African Americans: a genetic admixture analysis in three U.S. population cohorts

The risk of type 2 diabetes is approximately 2-fold higher in African Americans than in European Americans even after adjusting for known environmental risk factors, including socioeconomic status (SES), suggesting that genetic factors may explain some of this population difference in disease risk. However, relatively few genetic studies have examined this hypothesis in a large sample of African Americans with and without diabetes. Therefore, we performed an admixture analysis using 2,189 ancestry-informative markers in 7,021 African Americans (2,373 with type 2 diabetes and 4,648 without) from the Atherosclerosis Risk in Communities Study, the Jackson Heart Study, and the Multiethnic Cohort to 1) determine the association of type 2 diabetes and its related quantitative traits with African ancestry controlling for measures of SES and 2) identify genetic loci for type 2 diabetes through a genome-wide admixture mapping scan. The median percentage of African ancestry of diabetic participants was slightly greater than that of non-diabetic participants (study-adjusted difference = 1.6%, P<0.001). The odds ratio for diabetes comparing participants in the highest vs. lowest tertile of African ancestry was 1.33 (95% confidence interval 1.13-1.55), after adjustment for age, sex, study, body mass index (BMI), and SES. Admixture scans identified two potential loci for diabetes at 12p13.31 (LOD = 4.0) and 13q14.3 (Z score = 4.5, P = 6.6 × 10(-6)). In conclusion, genetic ancestry has a significant association with type 2 diabetes above and beyond its association with non-genetic risk factors for type 2 diabetes in African Americans, but no single gene with a major effect is sufficient to explain a large portion of the observed population difference in risk of diabetes. There undoubtedly is a complex interplay among specific genetic loci and non-genetic factors, which may both be associated with overall admixture, leading to the observed ethnic differences in diabetes risk.     

The effect of muscle fatigue on in vivo tibial strains

Stress fracture is a common musculoskeletal problem affecting athletes and soldiers. Repetitive high bone strains and strain rates are considered to be its etiology. The strain level necessary to cause fatigue failure of bone ex vivo is higher than the strains recorded in humans during vigorous physical activity. We hypothesized that during fatiguing exercises, bone strains may increase and reach levels exceeding those measured in the non-fatigued state. To test this hypothesis, we measured in vivo tibial strains, the maximum gastrocnemius isokinetic torque and ground reaction forces in four subjects before and after two fatiguing levels of exercise: a 2km run and a 30km desert march. Strains were measured using strain-gauged staples inserted percutaneously in the medial aspect of their mid-tibial diaphysis. There was a decrease in the peak gastrocnemius isokinetic torque of all four subjects' post-march as compared to pre-run (p=0.0001), indicating the presence of gastrocnemius muscle fatigue. Tension strains increased 26% post-run (p=0.002, 95 % confidence interval (CI) and 29% post-march (p=0.0002, 95% CI) as compared to the pre-run phase. Tension strain rates increased 13% post-run (p=0.001, 95% CI) and 11% post-march (p=0.009, 95% CI) and the compression strain rates increased 9% post-run (p=0.0004, 95% CI) and 17% post-march (p=0.0001, 95% CI). The fatigue state increases bone strains well above those recorded in rested individuals and may be a major factor in the stress fracture etiology.     

The population genetics of Quechuas, the largest native South American group: autosomal sequences, SNPs, and microsatellites evidence high level of diversity

Elucidating the pattern of genetic diversity for non-European populations is necessary to make the benefits of human genetics research available to individuals from these groups. In the era of large human genomic initiatives, Native American populations have been neglected, in particular, the Quechua, the largest South Amerindian group settled along the Andes. We characterized the genetic diversity of a Quechua population in a global setting, using autosomal noncoding sequences (nine unlinked loci for a total of 16 kb), 351 unlinked SNPs and 678 microsatellites and tested predictions of the model of the evolution of Native Americans proposed by (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496). European admixture is <5% and African ancestry is barely detectable in the studied population. The largest genetic distances were between African versus Quechua or Melanesian populations, which is concordant with the African origin of modern humans and the fact that South America was the last part of the world to be peopled. The diversity in the Quechua population is comparable with that of Eurasian populations, and the allele frequency spectrum based on resequencing data does not reflect a reduction in the proportion of rare alleles. Thus, the Quechua population is a large reservoir of common and rare genetic variants of South Amerindians. These results are consistent with and complement our evolutionary model of South Amerindians (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496), proposed based on Y-chromosome data, which predicts high genomic diversity due to the high level of gene flow between Andean populations and their long-term effective population size.     

Wider sampling reveals a non‐sister relationship for geographically contiguous lineages of a marine mussel

The accuracy of phylogenetic inference can be significantly improved by the addition of more taxa and by increasing the spatial coverage of sampling. In previous studies, the brown mussel Perna perna showed a sister–lineage relationship between eastern and western individuals contiguously distributed along the South African coastline. We used mitochondrial (COI) and nuclear (ITS) sequence data to further analyze phylogeographic patterns within P. perna. Significant expansion of the geographical coverage revealed an unexpected pattern. The western South African lineage shared the most recent common ancestor (MRCA) with specimens from Angola, Venezuela, and Namibia, whereas eastern South African specimens and Mozambique grouped together, indicating a non‐sister relationship for the two South African lineages. Two plausible biogeographic scenarios to explain their origin were both supported by the hypotheses‐testing analysis. One includes an Indo‐Pacific origin for P. perna, dispersal into the Mediterranean and Atlantic through the Tethys seaway, followed by recent secondary contact after southward expansion of the western and eastern South African lineages. The other scenario (Out of South Africa) suggests an ancient vicariant divergence of the two lineages followed by their northward expansion. Nevertheless, the “Out of South Africa” hypothesis would require a more ancient divergence between the two lineages. Instead, our estimates indicated that they diverged very recently (310 kyr), providing a better support for an Indo‐Pacific origin of the two South African lineages. The arrival of the MRCA of P. perna in Brazil was estimated at 10 [0–40] kyr. Thus, the hypothesis of a recent introduction in Brazil through hull fouling in wooden vessels involved in the transatlantic itineraries of the slave trade did not receive strong support, but given the range for this estimate, it could not be discarded. Wider geographic sampling of marine organisms shows that lineages with contiguous distributions need not share a common ancestry.     

Frequency analysis of the delta32ccr5 HIV resistance allele in a medieval plague mass grave

The 32 basepair deletion in the gene for the human chemokine receptor CCR5 (delta32ccr5) conferring resistance against HIV-1 infection is present in Caucasian populations. The mutant allele is believed to have originated by a single mutational event in historic times and to have reached its present population frequency of an average 10 % in Europe through selective pressure by a pathogenic agent. Because of their great impact on European populations, the medieval Plague epidemics have been considered as a possible candidate. To test this hypothesis, we studied the delta32ccr5-frequency in 35 individuals from a mass grave containing victims of the 14th century Plague pandemic in Lübeck, Northern Germany, and compared them to the frequency in a control group from the same burial site, dating from the time before the first Plague pandemic. If the delta32ccr5 allele conferred an at least partial resistance against the medieval Plague, its frequency would be expected to be lower in those that died in the pandemic, than it was in the local population before the arrival of the Plague. The CCR5 locus could be typed successfully for 14 Plague victims and for 20 individuals from the medieval control group. We found a delta32ccr5 allelic frequency of 14.2% and 12.5%, respectively. The difference between these figures is not statistically significant. Furthermore, they are comparable to the delta32ccr5 frequency for nowadays Northern Europe. We therefore conclude that the medieval Plague pandemic has not contributed to an increase in the allelic frequency of the mutant delta32ccr5 allele and that, if there has been a positive selection of this allele, it is likely to have occurred before the 14th century and thus before the arrival of the Plague in Europe.