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Acute myeloid leukemia (AML) with BCR::ABL1 has recently been recognized as a distinct subtype in international classifications. Distinguishing it from myeloid blast crisis chronic myeloid leukemia (BC-CML) without evidence of a chronic phase (CP), remains challenging. We aimed to better characterize this entity by integrating clonal architecture analysis, mutational landscape assessment, and gene expression profiling. We analyzed a large retrospective cohort study including CML and AML patients. Two AML patients harboring a BCR::ABL1 fusion were included in the study. We identified BCR::ABL1 fusion as a primary event in one patient and a secondary one in the other. AML-specific variants were identified in both. Real-time RT-PCR experiments demonstrated that CD25 mRNA is overexpressed in advanced-phase CML compared to AML. Unsupervised principal component analysis showed that AML harboring a BCR::ABL1 fusion was clustered within AML. An AML vs. myeloid BC-CML differential expression signature was highlighted, and while ID4 (inhibitor of DNA binding 4) mRNA appears undetectable in most myeloid BC-CML samples, low levels are detected in AML samples. Therefore, CD25 and ID4 mRNA expression might differentiate AML with BCR::ABL1 from BC-CML and assign it to the AML group. A method for identifying this new WHO entity is then proposed. Finally, the hypothesis of AML with BCR::ABL1 arising from driver mutations on a BCR::ABL1 background behaving as a clonal hematopoiesis mutation is discussed. Validation of our data in larger cohorts and basic research are needed to better understand the molecular and cellular aspects of AML with a BCR::ABL1 entity.

(1) Background: Since the emergence of SARS-CoV-2, responsible for the COVID-19 pandemic, efforts have been made to identify antiviral compounds against human coronaviruses. With the aim of increasing the diversity of molecule scaffolds, 42 natural compounds, of which 28 were isolated from lichens and 14 from their associated microorganisms (bacteria and fungi), were screened against human coronavirus HCoV-229E. (2) Methods: Antiviral assays were performed using HCoV-229E in Huh-7 and Huh-7/TMPRSS2 cells and SARS-CoV-2 in a Vero-81-derived clone with a GFP reporter probe. (3) Results: Four lichen compounds, including chloroatranol, emodin, perlatolic acid and vulpinic acid, displayed high activities against HCoV-229E (IC50 = 68.86, 59.25, 16.42 and 14.58 μM, respectively) and no toxicity at active concentrations. Kinetics studies were performed to determine their mode of action. The four compounds were active when added at the replication step. Due to their significant activity, they were further tested on SARS-CoV-2. Perlatolic acid was shown to be active against SARS-CoV-2. (4) Conclusions: Taken together, these results show that lichens are a source of interesting antiviral agents against human coronaviruses. Moreover, perlatolic acid might be further studied for its pan-coronavirus antiviral activity.

The immune system offers several mechanisms of response to harmful microbes that invade the human body. As a first line of defense, neutrophils can remove pathogens by phagocytosis, inactivate them by the release of reactive oxygen species (ROS) or immobilize them by neutrophil extracellular traps (NETs). Although recent studies have shown that bacteriophages (phages) make up a large portion of human microbiomes and are currently being explored as antibacterial therapeutics, neutrophilic responses to phages are still elusive. Here, we show that exposure of isolated human resting neutrophils to a high concentration of the Pseudomonas phage PAK_P1 led to a 2-fold increase in interleukin-8 (IL-8) secretion. Importantly, phage exposure did not induce neutrophil apoptosis or necrosis and did not further affect activation marker expression, oxidative burst, and NETs formation. Similarly, inflammatory stimuli-activated neutrophil effector responses were unaffected by phage exposure. Our work suggests that phages are unlikely to inadvertently cause excessive neutrophil responses that could damage tissues and worsen disease. Because IL-8 functions as a chemoattractant, directing immune cells to sites of infection and inflammation, phage-stimulated IL-8 production may modulate some host immune responses.

Purpose: Motor outputs are governed by dynamics organized around stable states and spontaneous transitions: we seek to investigate the swimmers' motor behavior flexibility as a function of speed and aquatic environment manipulations. Method: Eight elite male swimmers partook an eight-level incremental test (4% increment from 76% to 104% of their mean speed on 200 m front crawl) in a quasi-static aquatic environment (pool). Swimmers then partook another incremental test at similar effort in a dynamic aquatic environment (swimming flume) up to maximal speed. Stroke rate (SR), index of coordination (IdC) and intersegmental coupling of the upper limbs were computed from the inertial sensors located on the upper limbs and the sacrum. Results: With speed increase, SR values presented a steeper linear increase in the pool than in the flume. IdC values increased also in the pool but remained stable in the flume. Individual SR and IdC vs. speed increase displayed second-order polynomial dynamics, indicative of adaptive flexibility with a range of extremum values more restricted in the flume. Finally, a reduction of the in-phase coordination pattern was noted with flume speed increase. Conclusions: Action possibilities were strongly constrained in the flume at the highest speeds as the fluid flow led to discontinuity in the propulsive actions of the upper limbs and lack of in-phase inter-segmental coordination. This highlights that the behavioral flexibility was restricted in the flume in comparison to the pool, in which the exploitation of opportunities for action involved a larger number of degrees of freedom in the movement.

PurposeOut-of-hospital cardiac arrest (OHCA) has a poor prognosis, with an overall survival rate of about 5% at discharge. Shockable rhythm cardiac arrests (ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT)) have a better prognosis. In case of shockable rhythm, treatment is based on defibrillation, and thereafter, in case of failure of 3 external electric shocks (EES), on direct intravenous administration of 300 mg amiodarone, or lidocaine when amiodarone is unavailable or inefficient. During surgical procedures under extracorporeal circulation, a high potassium cardioplegia solution is administered to interrupt cardiac activity and facilitate surgical procedure. By extension, direct intravenous administration of potassium chloride (KCl) has been shown to convert VF, resulting in return to a hemodynamically efficient organized heart rate within a few minutes. The aim of this study is to provide clinical evidence that direct intravenous injection of KCl, into a patient presenting with OHCA due to refractory VF although 3 EES, should interrupt this VF and then allow rapid restauration of an organized heart rhythm, and thus return of spontaneous circulation (ROSC).MethodsA multicenter, prospective, single group, phase 2 study will be conducted on 81 patients presenting with refractory VF. After failure of 3 EES, each patient will receive direct intravenous injection of 20 mmol KCl instead of amiodarone. The primary outcome will be survival rate at hospital admission. Major secondary outcomes will include ROSC and time to ROSC in the prehospital setting, number of VF recidivism after KCl injection, survival rate at hospital discharge with a good neurologic prognostic, and survival rate 3 months after hospital discharge with a good neurologic prognostic.ResultsNo patient is currently included in the study.DiscussionConventional guideline strategy based on antiarrhythmic drug administration, i.e. amiodarone or lidocaine, for OHCA due to shockable rhythm, has not yet demonstrated an increase in survival at hospital admission or at hospital discharge. This may be related to the major cardiodepressant effect of those drugs.Trial registrationClinicalTrials.gov Identifier: NCT04316611. Registered on March 2020. AP-HP180577 / N° EUDRACT: 2019-002544-24. Funded by the French Health Ministry. https://clinicaltrials.gov/ct2/show/NCT04316611.

Background School cafeterias are a major point of influence for child nutrition. United States federal legislation requires the presence of important nutrients in school meals. However, legislation overlooks the potential presence of hyper-palatable foods in school lunches, a hypothesized factor that may influence children’s eating behavior and obesity risk. The study sought to 1) quantify the prevalence of hyper-palatable foods (HPF) served in US elementary school lunches; and 2) determine whether food hyper-palatability varied based on school geographic region (East/Central/West), urbanicity (urban/micropolitan/rural), or meal item (entrée/side/fruit or vegetable). Methods Lunch menu data (N = 18 menus; N = 1160 total foods) were collected from a sample of six states that represented geographic regions of the United States (Eastern/Central/Western; Northern/Southern) and that had variability in urbanicity (urban, micropolitan, and rural) within each state. A standardized definition from Fazzino et al (2019) was used to identify HPF in lunch menus. Results HPF comprised almost half of foods in school lunches (M = 47%; SD = 5%). Compared to fruit/vegetable items, entrées were >23 times more likely to be hyper-palatable and side dishes were >13 times more likely to be hyper-palatable (p values < .001). Geographic region and urbanicity were not significantly associated with food item hyper-palatability (p values >.05). The majority of entrée and side items contained meat/meat alternatives and/or grains and likely aligned with the US federal reimbursable meal components of meat/meat alternatives and/or grains. Conclusions and implications HPF comprised almost half of foods offered in elementary school lunches. Entrées and side items were most likely to be hyper-palatable. US school lunches may be a key point of regular exposure to HPF among young children, a risk factor that may elevate child obesity risk. Public policy regulating HPF in school meals may be needed to protect children’s health.

The bleeding phenotype of hereditary coagulation disorders is caused by the low or undetectable activity of the proteins involved in hemostasis, due to a broad spectrum of genetic alterations. Most of the affected coagulation factors are produced in the liver. Therefore, two-dimensional (2D) cultures of primary human hepatocytes and recombinant overexpression of the factors in non-human cell lines have been primarily used to mimic disease pathogenesis and as a model for innovative therapeutic strategies. However, neither human nor animal cells fully represent the hepatocellular biology and do not harbor the exact genetic background of the patient. As a result, the inability of the current in vitro models in recapitulating the in vivo situation has limited the studies of these inherited coagulation disorders. Induced Pluripotent Stem Cell (iPSC) technology offers a possible solution to overcome these limitations by reprogramming patient somatic cells into an embryonic-like pluripotent state, thus giving the possibility of generating an unlimited number of liver cells needed for modeling or therapeutic purposes. By combining this potential and the recent advances in the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology, it allows for the generation of autologous and gene corrected liver cells in the form of three-dimensional (3D) liver organoids. The organoids recapitulate cellular composition and organization of the liver, providing a more physiological model to study the biology of coagulation proteins and modeling hereditary coagulation disorders. This advanced methodology can pave the way for the development of cell-based therapeutic approaches to treat inherited coagulation disorders. In this review we will explore the use of liver organoids as a state-of-the-art methodology for modeling coagulation factors disorders and the possibilities of using organoid technology to treat the disease.

IntroductionThe impact of multi-domain preventive interventions on older adults, in particular on those with higher risk to develop Alzheimer's disease (AD), could be beneficial, as it may delay cognitive decline. However, the precise mechanism of such positive impact is not fully understood and may involve brain reserve and adaptability of brain functional connectivity (FC).MethodsTo determine the effect of multidomain interventions (involving physical activity, cognitive training, nutritional counseling alone or in combination with omega-3 fatty acid supplementation and vs. a placebo) on the brain, longitudinal FC changes were assessed after 36 months of intervention on 100 older adults (above 70 year-old) with subjective cognitive complaints.ResultsNo global change in FC was detected after uni or multidomain preventive interventions. However, an effect of omega-3 fatty acid supplementation dependent on cognitive decline status was underlined for frontoparietal, salience, visual and sensorimotor networks FC. These findings were independent of the cortical thickness and vascular burden.DiscussionThese results emphasize the importance of patient stratification, based on risk factors, for preventive interventions.

In this reply to S. Durbin's comment on our original paper "Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3," we concur that his final equations 8 and 9 more accurately describe the change in diffracted intensity as a function of Ti displacement. We also provide an alternative derivation based on an ensemble average over unit cells. The conclusions of the paper are unaffected by this correction.

The emerging SARS-CoV-2 virus has affected the entire world with over 600 million confirmed cases and 6.5 million deaths as of September 2022. Since the beginning of the pandemic, several variants of SARS-CoV-2 have emerged, with different infectivity and virulence. Several studies suggest an important role of neutrophils in SARS-Cov-2 infection severity, but data about direct activation of neutrophils by the virus is scarce. Here, we studied the in vitro activation of human neutrophils by SARS-CoV-2 variants of concern (VOCs). In our work, we show that upon stimulation with SARS-Cov-2 infectious particles, human healthy resting neutrophils upregulate activation markers, degranulate IL-8, produce Reactive Oxygen Species and release Neutrophil Extracellular Traps. Neutrophil activation was dependent on TLR7/8 and IRF3/STING. We then compared the activation potential of neutrophils by SARS-CoV-2 variants and showed a significantly increased activation by the Delta variant and a decreased activation by the Omicron variant as compared to the initial strain. In this study, we demonstrate that the SARS-Cov-2 virus can directly activate neutrophils in COVID-19 and that the different VOCs had differences in neutrophil activation intensity that mirror the differences of clinical severity. These data highlight the need to address neutrophil-virus interactions as a potential target for therapeutic intervention in SARS-CoV-2 infection.

AimWe aimed to describe the characteristics of individuals infected by BA.4 or BA.5 in France in comparison to BA.1, and analyze the factors associated with hospitalization among BA.4 and BA.5 cases.MethodsA standardized questionnaire was used to collect information on confirmed and probable Omicron cases. Hospitalization risk factors among BA.4/BA.5 cases were analyzed using Poisson regression. Variables with a p-value below 0.2 in the univariate analysis and a priori confounders were included in the multivariable regression model.ResultsThe median age of the 301 cases investigated was 47 years and 97% of cases were symptomatic. The most common clinical signs were asthenia/fatigue (75.7%), cough (58.3%), fever (58.3%), headache (52.1%) and rhinorrhea (50.7%). Twelve cases were hospitalized, and 27.1% reported risk factors. No admissions to intensive care and no deaths were reported. Vaccination status was available for 292 cases, 20.9% were unvaccinated, 1.4% had received one dose, 38.3% two doses and 39.4% three doses. Cases presenting at least one risk factor were almost seventeen times more likely to be hospitalized than those with no risk factors (aRR = 16.72 [95% CI2.59–326.86]).ConclusionDespite the longer duration of and the differences in symptoms and their possible immune escape, BA.4/BA.5 Omicron sub-lineages globally showed no severe clinical presentation. The presence of at least one risk factor for severe disease significantly increased the risk of hospitalization for those infected with BA.4 or BA.5.

Quaternary ammonium compounds (QAC) are commonly used disinfectants, antiseptics, preservatives, and detergents due to their antibacterial property and represent the first used biocides before phenolic or nitrogen products. Their common structure consists of one or more quaternary ammonium bound with four lateral substituents. Their amphiphilic structure allows them to intercalate into microorganism surfaces which induces an unstable and porous membrane that explains their antimicrobial activity towards bacteria, fungi, and viruses. QAC are thus found in many areas, such as household products, medicines, hygiene products, cosmetics, agriculture, or industrial products but are also used in medical practice as disinfectants and antiseptics and in health care facilities where they are used for cleaning floors and walls. QAC exposure has already been involved in occupational asthma in healthcare workers or professional cleaners by many authors. They also have been suggested to play a role in contact dermatitis (CD) and urticaria in workers using cosmetics such as hairdressers or healthcare workers, inciting reglementary agencies to make recommendations regarding those products. However, distinguishing the irritant or sensitizing properties of chemicals is complex and as a result, the sensitizing property of QAC is still controverted. Moreover, the precise mechanisms underlying the possible sensitization effect are still under investigation, and to date, only a few studies have documented an immunological mechanism. Besides, QAC have been suggested to be responsible for neuromuscular blocking agents (NMBA) sensitization by cross-reactivity. This hypothesis is supported by a higher prevalence of quaternary ammonium (QA)-specific IgE in the professionally exposed populations, such as hairdressers, cleaners, or healthcare workers, suggesting that the sensitization happens with structurally similar compounds present in the environment. This review summarizes the newest knowledge about QAC and their role in hypersensitivities. After describing the different QAC, their structure and use, the most relevant studies about the effects of QAC on the immune system will be reviewed and discussed.

Soon after the release of the new anti-COVID mRNA vaccines, reports came in from the US and the UK of anaphylactic reactions. Fueled by the necessary caution toward these new vaccine platforms, these reports had a great impact and were largely commented upon in the scientific literature and global media. The current estimated frequency is of 5 cases per million doses. Very little biological data are presented in the literature to support the anaphylaxis diagnosis in these patients in addition to skin tests. Allergic reactions to vaccines are rare and mostly due to vaccine excipient. Therefore, the poly-ethylene-glycol (PEG) present in both mRNA formulation, and already known to be immunogenic, was soon suspected to be the potential culprit. Several hypersensitivity mechanisms to PEG or to other vaccine components can be suspected, even if the classical IgE-dependent anaphylaxis seems to be one of the most plausible candidates. In the early 2022, the international guidelines recommended to perform skin prick tests and basophil activation tests (BAT) in people experiencing allergic reaction to the first dose of COVID-19 vaccine or with a history of PEG allergy. The aim of this review is to discuss the main potential mechanisms of immediate allergy to COVID19 vaccines based on published data, together with the various techniques used to confirm or not sensitization to one component.

Abstract Background Malignant pleural mesothelioma (MPM) is a rare, highly aggressive and deadly disease with a poor patient life expectancy. A few years ago, the main challenge was the histological diagnosis of this disease; at present, the search for the best therapeutic strategy is now a priority. However, an optimal therapeutic strategy is not yet clear, despite growing efforts in the treatment armamentarium and research, and at the era of tailored and individualized treatment, tools to predict patient survival are needed for therapeutic decision‐making. Among them, the LENT scoring system was developed to predict prognosis in patients with malignant pleural effusion. The aim of this study was to assess the performance of the LENT score in predicting prognosis in patients with MPM. Methods A retrospective observational study was conducted by analyzing the prospective collected databases of patients undergoing medical thoracoscopy in a single center with a final diagnosis of MPM confirmed by the MESOPATH National Reference Center. Results A total of 41 patients with MPM were studied. All patients underwent platinum‐based chemotherapy combined with pemetrexed ± bevacizumab. No high‐risk category patients were found using the LENT scoring system in this cohort. The median (range) LENT score at the time of medical thoracoscopy was 0 (0–3) and the median survival was 15.5 (2–54) months for the entire cohort. The median survival of low‐risk and moderate‐risk category patients was 21.4 months (2–54, 32 patients) and 6.7 months (2–19, nine patients), respectively. A total of 27 patients with MPM of epithelial subgroup had a median LENT score of 1 (0–2) with a 26 (2–54) months median survival. The median LENT score and median survival of nonepithelial mesothelioma patients (biphasic MPM subgroup, eight patients; sarcomatoid MPM subgroup, six patients) were 0 (0–3) and 11 (2–52) months, respectively. Conclusions Applied to a homogenous cohort of MPM patients, the LENT score underestimated prognosis and was not useful per se for the management of this disease, as evidenced in the epithelial mesothelioma subgroup of patients in our study.

X-ray crystallography at X-ray free-electron laser sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy, both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing insights into the interplay between the protein structure and dynamics and the chemistry at an active site. The implementation of such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly affects the data quality. We present here a robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method.

The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott-Hubbard material V2O3 presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds. For both the insulating and the metallic phase, the formation of the transient configuration is triggered by the excitation of electrons into the bonding a1g orbital, and is then stabilized by a lattice distortion characterized by a hardening of the A1g coherent phonon, in stark contrast with the softening observed upon heating. Our results show the importance of selective electron-lattice interplay for the ultrafast control of material parameters, and are relevant for the optical manipulation of strongly correlated systems.

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.

The flat oyster Ostrea edulis is an oyster species native to Europe. It has declined to functional extinction in many areas of the NE Atlantic for several decades. Factors explaining this decline include over-exploitation of natural populations and diseases like bonamiosis, regulated across both the EU and the wider world and caused by the intracellular protozoan parasite Bonamia ostreae. To date, very limited sequence data are available for this Haplosporidian species. We present here the first transcriptome of B. ostreae. As this protozoan is not yet culturable, it remains extremely challenging to obtain high-quality -omic data. Thanks to a specific parasite isolation protocol and a dedicated bioinformatic pipeline, we were able to obtain a high-quality transcriptome for an intracellular marine micro-eukaryote, which will be very helpful to better understand its biology and to consider the development of new relevant diagnostic tools.

Abstract Background Metastatic castration‐resistant prostate cancer (mCRPC) patients have a poor prognosis, and curcumin is known to have antineoplastic properties. On the basis of previous phase I and phase II studies, we investigated whether the association of curcumin with docetaxel could improve prognosis among mCRPC patients. Methods A total of 50 mCRPC patients (included from June 2014 to July 2016) treated with docetaxel in association with oral curcumin (6 g/d for 7 days every 3 weeks) versus placebo were included in this double‐blind, randomized, phase II study. The primary endpoint was to evaluate the time to progression. Among the secondary endpoints, compliance, overall survival, prostate‐specific antigen (PSA) response, safety, curcumin absorption, and quality of life were investigated. An interim analysis was planned in the modified intention‐to‐treat population with data at 6 months (22 patients per arm). Results Despite good compliance and a verified absorption of curcumin, no difference was shown for our primary endpoint: progression‐free survival (PFS) between the placebo and curcumin groups was, respectively, 5.3 months versus 3.7 months, p = 0.75. Similarly, no difference was observed for the secondary objectives: PSA response rate (p = 0.88), overall survival (p = 0.50), and quality of life (p = 0.49 and p = 0.47). Conclusion Even though our previous studies and data in the literature seemed to support an association between curcumin and cancer therapies in order to improve patient outcome and prognosis, the results from this interim analysis clearly showed that adding curcumin to mCRPC patients’ treatment strategies was not efficacious. The study was discontinued on the grounds of futility.

Introduction: The constraints-led approach (CLA) and more generally a complex systems perspective on motor learning emphasizes the role of perceptual-motor exploration during learning in order to ensure the acquisition of a highly individualized, adapted and adaptable movement pattern. Recent studies have shown that human beings have a strong tendency to exploit already stable patterns rather than looking for new potentially more efficient patterns. In order to shape the amount of exploration, we implemented two learning designs based on a CLA where constraints were used to limit the boundaries of the perceptual-motor workspace of the learners. We sought to highlight how practitioners can play with the perceptual motor workspace boundaries in order to (i) promote the use of exploratory behaviours and (ii) guide the learner towards task-relevant functional areas. Method: For the experiment, twenty-four beginners in breaststroke swimming were allocated to three groups of learning: a "control group" receiving only the goal of the learning, an "analogy group" receiving the goal of learning accompanied by an analogy about 'how to perform', a "pacer group" receiving information on the goal of learning and the use of a metronome to continuously push them to 'perform better'. Based on their assigned group, each learner then followed a learning protocol of 16 sessions with a 10*25 m swimming distance per session with the goal of increasing the stroke length for a fixed swimming speed. Both performance (i.e. stroke length) and motor behaviour (i.e. arm-leg coordination) were collected for each session. The arm-leg coordination patterns were computed by the continuous relative phase between knee and elbow angles. Thereafter, a cluster analysis was performed on the coordination in order to get a qualitative label for every cycle performed during the entire process of learning. Based on the use of cluster analysis, an exploration/exploitation ratio was calculated and the increase in performance was determined based on the increase in stroke length. Results and Discussion: With reference to the exploration/exploitation ratio, our results showed that additional temporary constraints-led learners to increase both the nature of their exploration and also the quantity of their exploration. In the meantime, the three groups showed an equivalent final performance enhancement. The aim of manipulating the constraints was not only to push the learner out of his comfort zone, but also to provide relevant information about 'where' to explore during learning. For this purpose, the use of analogy appeared as the most relevant constraint to encourage the emergence of efficient behaviour. Interestingly the impact of the analogy was modified by adding the metronome, showing an interaction effect of both constraints. The group using the metronome exhibited different behaviours as compared to the analogy group and showed an increase in exploration during learning compared to the control group. However, although the metronome constantly pushed the learner to improve performance, it did not actually lead to a better improvement of performance when compared to the analogy group. The simple assumption that the constraints forced the learner to explore therefore does not seem a mandatory condition to promote an exploratory learning. Rather, the qualitative nature of the constraint seems the most relevant characteristic that can be manipulated to promote an exploratory learning by "guiding" the learner within the perceptual motor workspace.