Independent, additive and interactive effects of acute normobaric hypoxia and cold on submaximal and maximal endurance exercise

PURPOSE

To evaluate the independent and combined effects of hypoxia (FiO2 = 13.5%) and cold (- 20 °C) on physiological and perceptual responses to endurance exercise.

METHODS

14 trained male subjects ( V . O2max: 64 ± 5 mL/kg/min) randomly performed a discontinuous maximal incremental test to exhaustion on a motorized treadmill under four environmental conditions: Normothermic-Normoxia (N), Normothermic-Hypoxia (H), Cold-Normoxia (C) and Cold-Hypoxia (CH). Performance and physiological and perceptual responses throughout exercise were evaluated.

RESULTS

Maximal WorkLoad (WL) and WL at lactate threshold (LT) were reduced in C (- 2.3% and - 3.5%) and H (- 18.0% and - 21.7%) compared to N, with no interactive (p = 0.25 and 0.81) but additive effect in CH (- 21.5% and - 24.6%). Similarly, HRmax and Vemax were reduced in C (- 3.2% and - 14.6%) and H (- 5.0% and - 7%), showing additive effects in CH (- 7.7% and - 16.6%). At LT, additive effect of C (- 2.8%) and H (- 3.8%) on HR reduction in CH (- 5.7%) was maintained, whereas an interactive effect (p = 0.007) of the two stressors combined was noted on Ve (C: - 3.1%, H: + 5.5%, CH: - 10.9%). [La] curve shifted on the left in CH, displaying an interaction effect between the 2 stressors on this parameter. Finally, RPE at LT was exclusively reduced by hypoxia (p < 0.001), whereas TSmax is synergistically reduced by cold and hypoxia (interaction p = 0.047).

CONCLUSION

If compared to single stress exposure, exercise performance and physiological and perceptual variables undergo additive or synergistic effects when cold and hypoxia are combined. These results provide new insight into human physiological responses to extreme environments.

Whole genome and transcriptome analysis enhances precision cancer treatment options

BACKGROUND

Recent advances are enabling delivery of precision genomic medicine to cancer clinics. While the majority of approaches profile panels of selected genes or hotspot regions, comprehensive data provided by whole genome and transcriptome sequencing and analysis (WGTA) presents an opportunity to align a much larger proportion of patients to therapies.

PATIENTS AND METHODS

Samples from 570 patients with advanced or metastatic cancer of diverse types enrolled in the Personalized OncoGenomics (POG) program underwent WGTA. DNA-based data, including mutations, copy number, and mutation signatures, were combined with RNA-based data, including gene expression and fusions, to generate comprehensive WGTA profiles. A multidisciplinary molecular tumour board used WGTA profiles to identify and prioritize clinically actionable alterations and inform therapy. Patient responses to WGTA-informed therapies were collected.

RESULTS

Clinically actionable targets were identified for 83% of patients, 37% of whom received WGTA-informed treatments. RNA expression data were particularly informative, contributing to 67% of WGTA-informed treatments; 25% of treatments were informed by RNA expression alone. Of a total 248 WGTA-informed treatments, 46% resulted in clinical benefit. RNA expression data were comparable to DNA-based mutation and copy number data in aligning to clinically beneficial treatments. Genome signatures also guided therapeutics including platinum, PARP inhibitors, and immunotherapies. Patients accessed WGTA-informed treatments through clinical trials (19%), off-label use (35%), and as standard therapies (46%) including those which would not otherwise have been the next choice of therapy, demonstrating the utility of genomic information to direct use of chemotherapies as well as targeted therapies.

CONCLUSIONS

Integrating RNA expression and genome data illuminated treatment options that resulted in 46% of treated patients experiencing positive clinical benefit, supporting the use of comprehensive WGTA profiling in clinical cancer care.

CLINICAL TRIAL NUMBER

NCT02155621.

Breast Device Surgery in Australia: Early Results from the Australian Breast Device Registry

BACKGROUND

The Australian Breast Device Registry (ABDR) is a clinical quality registry designed to monitor the performance of breast devices; and the quality and safety of breast device surgery.

OBJECTIVE

To report on breast device surgery characteristics across Australia.

METHODS

Participants were registered patients in the ABDR from 2012 to 2018. Results are described using percentages, mean and median. Revision rates were calculated using survival analysis methods.

RESULTS

A total of 37,603 patients were registered and had undergone reconstruction (post-cancer 15.1%, risk-reducing mastectomy 3.4% and developmental deformity 2.4%) or cosmetic augmentation (74.7%) procedures. The majority of breast implant devices were silicone filled with textured surface (reconstruction 74.0% and augmentation 64.0%). Sub-pectoral plane was the most common for both reconstruction (60.1%) and augmentation (76.6%) procedures. For reconstruction surgery, the most common surgical incision was previous mastectomy scar (44.0%) and inframammary (31.8%), and for augmentation, it was inframammary (83.4%). Intraoperative/postoperative antibiotic usage for reconstruction was 85.8% and augmentation was 89.4%. Revision incidence due to complication at 12 months post-cancer reconstruction was 5.1%, risk-reducing reconstruction 5.7% and developmental deformity implants 4.5%. Revision incidence due to complication at 12 months after augmentation procedure was 1.1%. Patient-reported outcome measures (PROMs) indicate high levels of satisfaction at 1 year for augmentation and reconstruction procedures.

CONCLUSION

We report on early data from the ABDR and reflect on the uptake of the registry by surgeons and patients. The registry also benefits from international collaborative approaches to addressing challenges and is committed to facilitate international post-market surveillance.

Outcomes for patients with COVID-19 admitted to Australian intensive care units during the first four months of the pandemic

OBJECTIVES

To describe the characteristics and outcomes of patients with COVID-19 admitted to intensive care units (ICUs) during the initial months of the pandemic in Australia.

DESIGN, SETTING

Prospective, observational cohort study in 77 ICUs across Australia.

PARTICIPANTS

Patients admitted to participating ICUs with laboratory-confirmed COVID-19 during 27 February - 30 June 2020.

MAIN OUTCOME MEASURES

ICU mortality and resource use (ICU length of stay, peak bed occupancy).

RESULTS

The median age of the 204 patients with COVID-19 admitted to intensive care was 63.5 years (IQR, 53-72 years); 140 were men (69%). The most frequent comorbid conditions were obesity (40% of patients), diabetes (28%), hypertension treated with angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers (24%), and chronic cardiac disease (20%); 73 patients (36%) reported no comorbidity. The most frequent source of infection was overseas travel (114 patients, 56%). Median peak ICU bed occupancy was 14% (IQR, 9-16%). Invasive ventilation was provided for 119 patients (58%). Median length of ICU stay was greater for invasively ventilated patients than for non-ventilated patients (16 days; IQR, 9-28 days v 3 days; IQR, 2-5 days), as was ICU mortality (26 deaths, 22%; 95% CI, 15-31% v four deaths, 5%; 95% CI, 1-12%). Higher Acute Physiology and Chronic Health Evaluation II (APACHE-II) scores on ICU day 1 (adjusted hazard ratio [aHR], 1.15; 95% CI, 1.09-1.21) and chronic cardiac disease (aHR, 3.38; 95% CI, 1.46-7.83) were each associated with higher ICU mortality.

CONCLUSION

Until the end of June 2020, mortality among patients with COVID-19 who required invasive ventilation in Australian ICUs was lower and their ICU stay longer than reported overseas. Our findings highlight the importance of ensuring adequate local ICU capacity, particularly as the pandemic has not yet ended.

Victorian Lung Cancer Service Redesign Project: impacts of a quality improvement collaborative on timeliness and management in lung cancer

BACKGROUND

Lung cancer management is characterised by a high disease burden, poor survival and substantial variation in management and outcomes. Service redesign provides opportunities for quality improvement (QI) and this improvement may be leveraged across multiple sites using QI collaboration.

AIM

This initiative targeted Quality Improvement (QI) in lung cancer management, engaging a QI collaborative using service redesign methodologies in five Victorian hospitals. QI targets included timeliness from referral and diagnosis to treatment, multi-disciplinary meeting (MDM) presentation and supportive care screening. Redesign strategies targeted process sustainability through enhanced team capability.

METHODS

This study engaged a prospective quality improvement cohort design targeting newly diagnosed tissue confirmed lung cancer with 6-month pre-intervention period and 6-month redesign implementation period, between September 2016 and August 2017, evaluated using Interrupted Time Series Analysis. Hospital sites included three regional and two metropolitan hospitals in Victoria. QI redesign targeted time intervals from referral to first specialist appointment (FSA), referral to diagnosis, diagnosis to first treatment (any intent), MDM documented in medical records and Supportive Care Screening Tool documented in medical records.

RESULTS

There was a marked reduction in referral to FSA interval across all sites, with median (interquartile range) falling from 6 (0-15) to 4 (1-10) days, and proportion seen by a specialist within 14 days increased from 74.3% to 84.2%. The interval between diagnosis and treatment was not substantively changed in the 6-month implementation period. The proportion of subjects with documented presentation to the MDM increased from 61% to 67%. The proportion for which Supportive Care Screening documentation remained low at 26.3% post-intervention.

CONCLUSIONS

Data-driven redesign initiatives enable identification and analysis of clinical practice variation and may be utilised to enhance timeliness of cancer care and improve local data service capabilities.

Shared and task-specific muscle synergies of Nordic walking and conventional walking

Nordic walking is a form of walking that includes a poling action, and therefore an additional subtask, with respect to conventional walking. The aim of this study was to assess whether Nordic walking required a task-specific muscle coordination with respect to conventional walking. We compared the electromyographic (EMG) activity of 15 upper- and lower-limb muscles of 9 Nordic walking instructors, while executing Nordic walking and conventional walking at 1.3 ms^-1 on a treadmill. Non-negative matrix factorization method was applied to identify muscle synergies, representing the spatial and temporal organization of muscle coordination. The number of muscle synergies was not different between Nordic walking (5.2 ± 0.4) and conventional walking (5.0 ± 0.7, P = .423). Five muscle synergies accounted for 91.2 ± 1.1% and 92.9 ± 1.2% of total EMG variance in Nordic walking and conventional walking, respectively. Similarity and cross-reconstruction analyses showed that 4 muscle synergies, mainly involving lower-limb and trunk muscles, are shared between Nordic walking and conventional walking. One synergy acting during upper limb propulsion is specific to Nordic walking, modifying the spatial organization and the magnitude of activation of upper limb muscles compared to conventional walking. The inclusion of the poling action in Nordic walking does not increase the complexity of movement control and does not change the coordination of lower limb muscles. This makes Nordic walking a physical activity suitable also for people with low motor skill.

Cross-country skiing movement factorization to explore relationships between skiing economy and athletes' skills

We investigated the relationships between the biomechanics of the double poling (DP) technique in cross-country skiing, its economy, and athletes' skill. To this aim, skiers' motion has been factorized into components through principal component analysis (PCA). Eight high-level (HL) and eight regional level (RL) male cross-country skiers performed a 5-minute submaximal DP trial while roller skiing on a treadmill at 14 km h^-1 and 2° incline. Whole-body kinematics was recorded with a motion capture system. PCA was applied to markers coordinates to extract principal movements (PM_k ), which were ranked by their variance. Energy cost (EC) of locomotion was calculated from ergospirometric measurements. Results showed that 96.7%±0.6% of total skiing pattern variance can be described with the first three PM_k. (Shoulder and trunk flexion-extension are described PM₁ and PM₂ and elbow flexion-extension are mainly represented in PM₂ and PM_3. The variance of further components, consisting of residual movements (eg, slow postural changes or high-frequency vibrations), was greater for the RL than the HL skiers (4.0%±0.5% vs 2.6%±0.3%; P<.001) and was positively correlated with EC (R² =.646; P<.001). PCA permitted to describe the biomechanics of the DP technique through a limited set of principal movements. Skiing skills and economy appeared to be related to a skier's ability to simplify movement complexity, suggesting that an efficient skier is better able to reduce superfluous movement components during DP.

Changes in upper and lower body muscle involvement at increasing double poling velocities: an ecological study

This study evaluated muscle activity changes in different body compartments during on-snow double poling at increasing velocities. 21 well-trained, male cross-country skiers performed five 3-min double poling trials on a snowy track at 15, 16.5, 18, 19.5, and 21 km/h (set by an audio-pace system). A sixth trial was performed by maintaining a constant maximal speed. Actual skiing velocities were verified using a photocell system. Only 11 subjects met the pre-defined inclusion criteria during the trials and were included in the data analysis. Electromyographical signals from seven muscles, wrist acceleration and heart rate during the last minute of each trial were recorded. Cycle and poling times were measured from acceleration signals; mean muscular activation over a cycle was calculated for each muscle. With increasing double poling velocities from aerobic to maximal intensity (from 65% to 100% of maximal heart rate), upper limb muscles activation was maintained constant (P > 0.05), while trunk and lower limb involvement increased significantly (P < 0.01) with a linear trend. Rectus abdominis and rectus femoris muscles showed the higher rate of change. Trunk and lower limbs provide a progressively greater contribution to the propulsion when increasing double poling velocities are performed, to support the limited capacity of exercise response of upper body muscles. The remarkable rate of involvement of the muscles near the core region of the body becomes strategic to cope with the increased demands of propulsive power.

Central and peripheral fatigue in knee and elbow extensor muscles after a long-distance cross-country ski race

Although elbow extensors (EE) have a great role in cross-country skiing (XC) propulsion, previous studies on neuromuscular fatigue in long-distance XC have investigated only knee extensor (KE) muscles. In order to investigate the origin and effects of fatigue induced by long-distance XC race, 16 well-trained XC skiers were tested before and after a 56-km classical technique race. Maximal voluntary isometric contraction (MVC) and rate of force development (RFD) were measured for both KE and EE. Furthermore, electrically evoked double twitch during MVC and at rest were measured. MVC decreased more in KE (-13%) than in EE (-6%, P = 0.016), whereas the peak RFD decreased only in EE (-26%, P = 0.02) but not in KE. The two muscles showed similar decrease in voluntary activation (KE -5.0%, EE -4.8%, P = 0.61) and of double twitch amplitude (KE -5%, EE -6%, P = 0.44). A long-distance XC race differently affected the neuromuscular function of lower and upper limbs muscles. Specifically, although the strength loss was greater for lower limbs, the capacity to produce force in short time was more affected in the upper limbs. Nevertheless, both KE and EE showed central and peripheral fatigue, suggesting that the origins of the strength impairments were multifactorial for the two muscles.

Improvement of the accuracy of noise measurements by the two-amplifier correlation method

We present a novel method for device noise measurement, based on a two-channel cross-correlation technique and a direct "in situ" measurement of the transimpedance of the device under test (DUT), which allows improved accuracy with respect to what is available in the literature, in particular when the DUT is a nonlinear device. Detailed analytical expressions for the total residual noise are derived, and an experimental investigation of the increased accuracy provided by the method is performed.

Biomechanical analysis of the herringbone technique as employed by elite cross-country skiers

This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces.

Poling force analysis in diagonal stride at different grades in cross country skiers

The aim of this study was to characterize the dynamic parameters of poling action during low to moderate uphill skiing in the diagonal stride technique. Twelve elite cross country skiers performed an incremental test using roller skis on a treadmill at 9 km/h at seven different grades, from 2° to 8°. The pole ground reaction force and the pole inclination were measured, and the propulsive force component and poling power were then calculated. The duration of the active poling phase remained unchanged, while the recovery time decreased with the increase in the slope. The ratio between propulsive and total poling forces (effectiveness) was approximately 60% and increased with the slope. Multiple regression estimated that approximately 80% of the variation of the poling power across slopes was explained by the increase of the poling force, the residual variation was explained by the decrease of the pole inclination, while a small contribution was provided by the increase of the poling relative to the cycle time. The higher power output required to ski at a steeper slope was partially supplied by a greater contribution of the power generated through the pole that arises not only by an increase of the force exerted but also by an increase of its effectiveness.

Smokers of illicit tobacco report significantly worse health than other smokers

INTRODUCTION

The aim of this study was to ascertain whether the health of past and current smokers of illicit tobacco (chop-chop) differs from that of smokers of licit tobacco.

METHODS

The design was a telephone survey, stratified by state, using computer aided telephone interviewing, with households selected by random digit dialing from the telephone white pages. Setting was all Australian states and territories, 1,621 regular tobacco smokers aged 18+ years. Measures were social and personal characteristics of tobacco smokers, smoking histories and patterns, and health status (SF-8 and disability weights). Binary logistic regression was used to identify variables associated with current and lifetime chop-chop use.

RESULTS

Compared with licit-only tobacco smokers, current users of chop-chop had significantly greater odds of beginning smoking aged <16 years (odds ratio [OR] 1.65, 95% CI = 1.09-2.50), of reporting below-average social functioning (OR 1.61, 95% CI = 1.06-2.44), and of a measurable disability (OR 1.95, 95% CI = 1.08-3.51). Lifetime chop-chop users were relatively likely to be less than 45 years of age (OR 1.82, 95% CI = 1.38-2.39), report below-average mental health (OR 1.61, 95% CI = 1.22-2.13) and above-average bodily pain (OR 1.40, 95% CI = 1.06-1.85), smoke more than 120 cigarettes/week (OR 1.39, 95% CI = 1.06-1.83), and to have begun smoking aged <16 years (OR 1.33, 95% CI = 1.01-1.75).

DISCUSSION

Current and lifetime users of chop-chop report significantly worse health than smokers of licit tobacco. Investigation of how to communicate this finding to current and potential chop-chop smokers is warranted.

Assessment of the reliability of a custom built Nordic Ski Ergometer for cross-country skiing power test

AIM

Despite the recent development of cross-country ski technique having led to an increase in the importance of upper body power, there is a substantial lack of specific equipment for upper body force and power evaluation. In order to achieve good reproducibility of the skiing motion, a new upper body ergometer has been developed in our lab and tested by elite cross-country skiers. In this study, the reliability of this device was assessed comparing upper body power measurements with double poling ski performance in the field.

METHODS

The new apparatus consists of an electric motor acting as load and actively controlled by a personal computer on the basis of force and velocity data. Nine cross-country skiers (age: 21.7+/-3.12 years; body weight: 72.2+/-3.8 kg), competing at international level, performed a ski test on a 1.2 km long sprint track and a 50 s exercise on the Nordic Ski Ergometer. The velocity of the last section (180 m, slope 1.37%) of the track, performed using the double poling technique at maximal voluntary intensity, was related to the upper body power measured at the ergometer.

RESULTS

Mean upper body power was 9.22+/-2.29 W kg(-1), while average velocity on the section considered was 6.66+/-0.67 m s(-1). A high correlation (R(2)=0.871) was found between upper body power and ski velocity.

CONCLUSION

In addition to overcoming the main limitations that affect traditionally used equipment, the strong relationship between the parameters obtained with the new ergometer and ski velocity indicates their ability to assess athletes performance. The new apparatus could therefore be considered a ski specific testing equipment for cross-country skiers which is useful for reproducing upper body involvement in cross-country ski-ing in a laboratory setting.

Characterization of arm-gun movement during air pistol aiming phase

AIM

Air pistol shooting is a sport requiring extreme movement precision. The purpose of our study is to collect and analyze kinematic data of arm/gun complex during the pointing phase in order to characterize movement and between segment coordination by means of time and frequency domain analysis techniques.

METHODS

Thirteen air pistol athletes participated to the recording sessions held at the 10 m shooting range. Kinematic data of neck, shoulder, elbow, wrist and gun were collected during the aiming phase using an optoelectronic motion capture system. Displacement series were split up in slow drift and tremor components. Amplitude of the movement of each segment and strength of the relationship between adjacent segments were estimated in time domain respectively by means of standard deviation and coefficient of regression. Moreover, coherence and phase spectral functions were calculated to assess between-segment coupling at different frequencies.

RESULTS

Significantly larger movements were seen for slow drift component with respect to tremor one for all segments especially for lateral movements. Higher between segment correlation were found for lateral direction and for slow drift component. The coherence calculated on vertical series of tremor component showed significant coupling at 1.5 Hz and 5-7 Hz with phase opposition between wrist and gun motion at 5-7 Hz.

CONCLUSIONS

Slow drift motion appears to affect mainly lateral movements and all the segments were equally involved indicating a probable origin in postural body sway. Vertical displacements could be referred to shoulder and wrist motion with features typical of physiological tremor. Quantitative characterization of segments displacements during aiming phase may serve as a basis for scientific evaluation and training in competitive precision shooting.

At what stage of manual visual reaction time does interhemispheric transmission occur: controlled or ballistic?

Interhemispheric transfer (IT) time through the corpus callosum can be measured with a manual reaction time (RT) to lateralized visual stimuli (the so-called Poffenberger paradigm) by subtracting mean RT of faster uncrossed hemifield-hand combinations (not requiring an IT) from slower crossed combinations (requiring an IT). That the corpus callosum is involved in IT has been demonstrated by its dramatic lengthening in patients with a section of the corpus callosum. However, it is still unclear whether the signal transmitted by the corpus callosum concerns perceptual or motor stages of RT. To try and cast light on this question, in a first experiment we tested normal subjects on a partially modified Poffenberger paradigm with stop trials intermingled with go trials. In the former, subjects are supposed to refrain from responding following a stop signal (stop-signal paradigm). This paradigm can tease apart the contribution of the controlled and ballistic stages to overall RT and, used together with the Poffenberger task, enables one to assess the stage at which IT occurs. The controlled stage lies before the point of no return, i.e. the point beyond which the response cannot be inhibited, and concerns perceptual and pre-motor processes, while the ballistic stage occurs after the point of no return and concerns the motoric aspect of the response. We found that the slower responses typically obtained in the crossed conditions were more likely to be inhibited than the faster uncrossed responses and this suggests that IT occurs prior to the point of no return. Since the precise locus of the point of no return is uncertain, in a second experiment we used response force as a dependent variable reflecting the activation of the motor cortex. We found that none of the force parameters studied differed between crossed and uncrossed conditions while the temporal parameters confirmed the presence of an advantage of the uncrossed combinations. Altogether these results suggest that callosal IT of visuomotor information occurs at the stage of controlled (perceptual and pre-motor) processes and rule out the possibility of an IT at the motoric stage.

Substance P (neurokinin-1) and neurokinin A (neurokinin-2) receptor gene and protein expression in the healthy and inflamed human intestine

Increasing evidence suggests that tachykinins are involved in the control of pathophysiological states, such as inflammation. The precise localization of tachykinin receptors is of paramount importance in the search for their possible physiological and pathological role; in this study, therefore, we attempted to define cellular sites of substance P (NK-1R) and neurokinin A (NK-2R) receptor expression in the healthy and the inflamed human intestine by in situ hybridization and immunohistochemistry. In the normal ileum and colon, NK-1R and NK-2R were localized to smooth muscle cells of the muscularis mucosae and propria and a few inflammatory cells of the lamina propria; NK-1R expression was also found in the muscular wall of submucosal blood vessels, enteric neurons and, to a lesser degree, in surface epithelial cells. Patients with Crohn's disease and ulcerative colitis showed a dramatic increase in NK-1R density relative to controls, in both the inflamed and the uninvolved mucosa. Up-regulation of NK-1R was particularly evident on epithelial cells lining the mucosal surface and crypts, as well as on endothelial cells of capillaries and venules. Also, a marked increase in NK-2R expression was found in both groups of patients on inflammatory cells of the lamina propria, especially eosinophils. Our findings demonstrate that in the normal human intestine NK-1R and NK-2R are expressed in multiple cell types, which are endowed with different physiological functions; in addition, they demonstrate that both NK-1R and NK-2R are up-regulated in patients with Crohn's disease and ulcerative colitis. Taken together, these observations may have important physiological and pathophysiological implications, and provide the rationale for the use of NK-1R and NK-2R antagonists in the treatment of inflammatory bowel disease.

Rhesus polymorphism in New Caledonia. II. Genetic comparison with other Oceanians

Rhesus haplotype frequencies computed for 804 and 546 Wallisians from New Caledonia are compared to the data collected for 13 Oceanian samples belonging to the same Austronesian linguistic family. Genetic distances are computed between the 15 populations and used for a principal coordinate analysis. Kanaks are genetically close to Fidjians, while the Wallisian sample share a high genetic similarity with the Tonga islanders. The results obtained for the whole area including the Wallis homeland for the Wallisian sample indicate a tight relationship between geographical and genetic differentiations in the Pacific, supported by a high correlation coefficient between the two distance matrices. However, the observed patterns are better explained by the history of migrations reconstructed from archaeological and linguistic data than by a pure isolation-by-distance model.

New data for AG haplotype frequencies in Caucasoid populations and selective neutrality of the AG polymorphism

We present the results of AG antigen typings of three Caucasoid population samples: Lebanese, Tunisians, and Finns. AG haplotype frequencies estimated by maximum-likelihood methods are compared with the frequencies observed in 13 world populations previously tested for AG specificities by computing a genetic distance matrix used in a multivariate analysis. A high degree of polymorphism characterizes the three samples, with 10 haplotypes detected in the Lebanese and 11 haplotypes detected in the Tunisians and Finns; high heterozygosity levels are also present in the three populations. The genetic distance analysis shows that the three populations possess a genetic structure intermediate between those observed in sub-Saharan Africans and in Caucasoids from the Near East and India. This tight correspondence between AG differentiation and geography is confirmed by a highly significant correlation coefficient found between genetic and geographic distances computed worldwide, suggesting that an isolation by distance model of evolution applies to the AG system. The Ewens-Watterson test for selective neutrality on all world populations tested for AG specificities also supports the hypothesis that the AG system behaves like a neutral polymorphism. Overall, the AG differentiation pattern appears to be close to the patterns observed for other serological polymorphisms, such as RH, GM, and HLA, whose evolutionary mechanisms are also discussed.

Spatial differentiation of RH and GM haplotype frequencies in Sub-Saharan Africa and its relation to linguistic affinities

This study analyzes patterns of variation in eight GM and seven Rhesus (RH) haplotypes across sub-Saharan Africa. We examine the concordance with genetic patterns of both geographic and language-family relationships by spatial analysis and ordination techniques. The genetic variation has significant spatial structure, but positive autocorrelation declines neither asymptotically nor proportionally with increasing distance. Evidently, neither isolation by distance with increasing distance. Evidently, neither isolation by distance nor clinical migration-selection models account for the observed genetic structure. Language-family relationship is the best predictor of genetic relationship and may reflect historic migrations and expansions of ethnically different peoples within sub-Saharan Africa. Yet the greatest part of the genetic variance remains unexplained by the models we have tested.