Searching for archaic contribution in Africa

Abstract

Context: Africa’s role in the narrative of human evolution is indisputably emphasised in the emergence of Homo sapiens. However, once humans dispersed beyond Africa, the history of those who stayed remains vastly under-studied, lacking the proper attention the birthplace of both modern and archaic humans deserves. The sequencing of Neanderthal and Denisovan genomes has elucidated evidence of admixture between archaic and modern humans outside of Africa, but has not aided efforts in answering whether archaic admixture happened within Africa.

Objectives: This article reviews the state of research for archaic introgression in African populations and discusses recent insights into this topic.

Methods: Gathering published sources and recently released preprints, this review reports on the different methods developed for detecting archaic introgression. Particularly it discusses how relevant these are when implemented on African populations and what findings these studies have shown so far.

Results: Methods for detecting archaic introgression have been predominantly developed and implemented on non-African populations. Recent preprints present new methods considering African populations. While a number of studies using these methods suggest archaic introgression in Africa, without an African archaic genome to validate these results, such findings remain as putative archaic introgression.

Conclusion: In light of the caveats with implementing current archaic introgression detection methods in Africa, we recommend future studies to concentrate on unravelling the complicated demographic history of Africa through means of ancient DNA where possible and through more focused efforts to sequence modern DNA from more representative populations across the African continent.     

Heat-shock protein (HSP70-2) allelic frequencies in three distinct Mexican populations

The major histocompatibility complex (MHC) genes are highly polymorphic and therefore have been useful in population genetics and disease association studies. We analyzed restriction fragment length polymorphism of HSP70-2 alleles in healthy unrelated Mestizo, Mazatecan and Nahua populations. Both Indian groups, Mazatecans and Nahuas, were in Hardy-Weinberg equilibrium, while Mestizos were in disequilibrium (chi 2 = 0.399; P < 0.05). The Mazatecan Indians presented a high frequency of BB homozygosity (17.35%) compared to Mestizos (5%) (P = 0.01). Mexican ethnic groups present differences in distribution of BB genotype. The low frequency of BB genotype in Mestizos may be the result of a negative selection process.     

Range of motion of foot joints following total ankle replacement and subtalar fusion

BackgroundIn severe cases of ankle and subtalar arthritis, arthrodesis of the subtalar joint is performed in combination with ankle arthroplasty. In these special cases gait analysis reveals real motion at the replaced tibiotalar joint.MethodsTwenty-three patients affected by ankle and subtalar arthritis, treated either with a 3-component or a 2-component prosthesis in combination with subtalar arthrodesis, were clinically evaluated preoperatively and at a minimum of 1-year follow-up. Gait analysis was performed postoperatively using a multi-segment foot protocol. Foot kinematics were compared to corresponding data from a healthy control group.ResultsClinical scores significantly improved from preoperative to follow-up. The clinically measured passive ankle dorsiflexion/plantarflexion significantly improved at the follow-up. Patients’ normalized walking speed and stride length were significantly lower than those in control. With exception of the ankle frontal-plane motion, sagittal-plane mobility of foot joints was about 50% than that in healthy joints.ConclusionsImprovement in clinical scores was found for both prostheses. Normal spatio-temporal parameters were not restored. In these patients, fusion of the subtalar joint appeared to be compensated by larger frontal-plane motion at the tibiotalar joint.Level of evidenceLevel III- retrospective comparative study.The study was approved by the local Ethics Committee as protocol MAT (protocol registration at clinicaltrials.gov NCT03356951).     

XPS Study on Calcining Mixtures of Brucite with Titania

In this work, we studied the phases in a Mg-Ti-O system using a 1:1 formulation of MgO:TiO₂, mixing synthetic brucite of Mexican origin with TiO₂ microparticles of high purity, with a heat treatment at 1100 °C for 1 h. Due to its valence electrons, TiO₂ can contribute to the sintering process to improve density in MgO products. The raw materials and formulation by XPS and X-RD techniques were characterized. The results demonstrate the presence of different oxidation states in titania and the formation of different oxides in the Mg-Ti-O system when mixed and calcined at 1100 °C; additionally, we estimated the formation of vacancies in the crystal lattice during the transformation from hexagonal brucite to magnesia with a cubic structure centered on the faces. Its thermal behavior is indicated by the MgO-TiO₂ phase diagram.     

Acute Effects of Caffeine on Overall Performance in Basketball Players—A Systematic Review

Caffeine supplementation has become increasingly popular among athletes. The benefits of caffeine include delaying the negative effects of fatigue, maintaining a high level of physical and mental performance, and improving certain abilities necessary for sport success. Given the complex nature of basketball, caffeine could be a legal, ergogenic stimulant substance, which will positively affect overall basketball performance. The purpose of this systematic review was to summarize evidence for the effect of acute caffeine ingestion on variables related to the basketball performance. Web of Science, PubMed, Scopus and ProQuest, MEDLINE, and ERIC databases were searched up to February 2021. Studies that measured the acute effect of caffeine on basketball performance were included and analyzed. Eight studies published between 2000 and 2021 were included in the analysis. Pre-exercise caffeine intake increased vertical jump height, running time at 10 and 20 m without the ball, overall basketball performance (number of body impacts, number of free throws, rebounds, and assists) during simulated games, and reduced the time required to perform a basketball-specific agility test. Equivocal results between caffeine and placebo groups were found for aerobic capacity, free throw and three-point accuracy, and dribbling speed. Pre-exercise caffeine ingestion did not affect RPE, but insomnia and urinary excretion were increased. The pre-exercise ingestion of 3 and 6 mg/kg caffeine was found to be effective in increasing several physical performance variables in basketball players during sport-specific testing and simulated matches. However, considering the intermittent nature and complexity of basketball, and individual differences between players, future studies are needed.     

Half or more of the somatic mutations in cancers of self-renewing tissues originate prior to tumor initiation

Although it has been hypothesized that some of the somatic mutations found in tumors may occur before tumor initiation, there is little experimental or conceptual data on this topic. To gain insights into this fundamental issue, we formulated a mathematical model for the evolution of somatic mutations in which all relevant phases of a tissue’s history are considered. The model makes the prediction, validated by our empirical findings, that the number of somatic mutations in tumors of self-renewing tissues is positively correlated with the age of the patient at diagnosis. Importantly, our analysis indicates that half or more of the somatic mutations in certain tumors of self-renewing tissues occur before the onset of neoplasia. The model also provides a unique way to estimate the in vivo tissue-specific somatic mutation rates in normal tissues directly from the sequencing data of tumors. Our results have substantial implications for the interpretation of the large number of genome-wide cancer studies now being undertaken.     

Evaluation of a Neural Network-Based Control Strategy for a Cost-Effective Externally-Powered Prosthesis

ABSTRACT

This paper presents a control strategy that compensates for the nonlinearity in the inexpensive sensors and hardware of a cost effective prosthetic hand. The control strategy uses neural network-based force control and sensory feedback to detect disturbance induced by slippage. The neural network approach is chosen over other nonlinear models because it is easy to implement and it offered the additional advantage of having its parameters easily adjusted over the life span of the device. The proposed strategy was evaluated on a functional multi-digit underactuated prosthetic hand. The initial and incremental forces exerted from each finger were adjusted to balance the amount of disturbance and the deformation of the objects. Experiments were conducted to test the performance of the protocol in situations encountered in activities of daily living. The displacement of each object under three grasping configurations was measured as a performance criterion while the object's mass was changed. The results showed that with the adjusted parameters for each grasping configuration, the control strategy was able to detect the dynamic changes in mass of the object and was also able to successfully adjust the grasping force before the object drops from the hand.