Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects.

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241-258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm.

Measurement of imatinib uptake by flow cytometry.

One of the essential parameters of targeted therapy efficiency in cancer treatment is the amount of drug reaching the therapeutic target area. Imatinib (IM) was the first specifically targeted drug to be developed and has revolutionized the treatment of patients with chronic myeloid leukemia (CML). To evaluate cellular uptake of IM, we developed a method based on the chemical structure of the molecule and using the natural UV fluorescence that we quantified by flow cytometry. In two CML cell lines, we obtained a satisfactory relationship between intracellular IM (ICIM) levels and media concentrations, and we found a strong correlation between ICIM at 1 h and IM efficacy at 24 h, demonstrating that ICIM at 1 h might be a relevant predictive parameter of cell sensitivity. Our method was more sensitive than the standard physicochemical method. We applied our method to primary cells and found cell morphology-dependent IM accumulation. Moreover, in CML cells from patients at diagnosis, IM accumulation was heterogeneous. In all cases, ICIM at the single-cell level was much higher than in culture media arguing in favor of a predominantly active uptake process. We developed a simple method directly applicable to primary cells that has shown two major advantages: only a small number of cells are required, and cell subsets can be identified according to morphological criteria and/or the presence of particular antigenic sites. This method provides a new tool to assess CML cell sensitivity to IM, and ICIM levels in native CML cells could be used to monitor therapeutic response.

Dynamics model for analyzing reaching movements during active and passive torso rotation.

We have developed an inverse dynamics model of unrestrained natural reaching movements. Such movements are usually not planar and often involve complex deformation of the shoulder girdle as well as rotary and linear torso motion. Our model takes as its input kinematic data about the positions of the finger, wrist, elbow, left and right acromion processes, and the sternum and produces the torques and forces developed at the shoulder, elbow, and wrist joints. The model can also be used to simulate the consequences of introducing passive torso rotation or linear acceleration on arm movements and to simulate the consequences of applying mechanical perturbations to the reaching limb. It separately quantifies the contributions of inertial forces resulting from torso rotation and translation. In experimental paradigms involving arm movements, different dynamic components can be present such as active or passive torso rotation and translation, external forces and Coriolis forces. Our model provides a means of evaluating the different sources of force and the total muscle force needed to control the trajectory of the arm in their presence.

Kinetic analysis of arm reaching movements during voluntary and passive rotation of the torso.

Reaching movements made to targets during exposure to passive constant velocity rotation show significant endpoint errors. By contrast, reaching movements made during voluntary rotation of the torso are accurate. In both cases, as a consequence of the simultaneous motion of the arm and the torso, Coriolis forces are generated on the arm tending to deflect its path. Our goal in the present paper was to determine whether during voluntary torso rotations arm movement accuracy is preserved by feed forward compensations for self-generated Coriolis forces. To test this hypothesis we analyzed and quantified the contribution of torso rotation and translation to arm dynamics and compared the kinematics and kinetics of pointing movements during voluntary and passive torso rotation. Coriolis torques at the shoulder increase nearly sixfold in voluntary turn and reach movements relative to reaches made without torso rotation, yet are equally accurate. Coriolis torques during voluntary turn and reach movements are more than double those produced by reaching movements during passive body rotation at 60 degrees /s. Nevertheless, the endpoints of the reaches made during voluntary rotation are not deviated, but those of reaches made during passive rotation are deviated in the direction of the Coriolis forces generated during the movements. We conclude that there is anticipatory pre-programmed compensation for self-generated Coriolis forces during voluntary torso rotation contingent on intended torso motion and arm trajectory.

Mesenchymal content of fresh bone marrow: a proposed quality control method for cell therapy.

The scarcity of mesenchymal stem cells (MSC) in bone marrow (BM) has justified their ex vivo expansion before therapeutic use, but a method to evaluate the quality of initial mesenchymal content and track the modifications induced by graft processing has not yet been proposed. The aim of this study was to establish such a procedure. Flow cytometric and functional assay methods were modified to count CD45(-) CD14(-)/CD73(+) subsets containing all MSC and used them to study BM from spongy bone (SB) and iliac crest aspirate (ICA). These methods detected the target subsets in all BM suspensions derived from SB (n = 154) and ICA, (n = 44) with a satisfactory correlation between immuno-phenotyping and functional tests by low-density plating. We noted a higher overall MSC frequency in SB cell suspensions but a lower plating efficiency of CD45(-) CD14(-)/CD73(+) SB cells under standard culture conditions. We propose a cell quality control on un-manipulated BM cell suspensions to quantify the mesenchymal compartment with regard to varying donor factors, such as age and sampling site, that influence expansion and define a therapeutic threshold value. Furthermore, we were able to confirm differences in plating efficiency and proliferative capacity between two BM origins.

Characterization of nonexpanded mesenchymal progenitor cells from normal adult human bone marrow.

OBJECTIVE: Adult bone marrow (BM) mesenchymal stem/progenitor cells (MS/PC) are a potentially useful tool for cell therapy and tissue repair. However, the identification of cell subsets rich in MS/PC from fresh BM has not been described. We have developed a means of identifying such subsets from untouched bone marrow. MATERIAL AND METHODS: First, MS/PC were enriched by short-time adherence (D(1-3)) before any cell division to evaluate the efficiency of CD73, CD105, CDw90, and CD49a antigens to select highly purified CD45(-)CD14(-) fluorescence-activated sorted subsets enriched in clonogenic mesenchymal cells. Then, we adapted this method to unmanipulated BM mononuclear cells (MNC). RESULTS: Short-time (D(1-3)) adherent CD45(-)CD14(-) cells expressing CD73 or CD49a antigens contained all the CFU-F, even though the CD105(+) and CDw90(+) subsets comprised less than half the total. In fresh unmanipulated BM MNC, CD73 and CD49a were also highly discriminative and allowed up to a 3 log enrichment of CFU-F when compared to BM MNC. Normal culture conditions upregulated most of the tested antigens. CONCLUSION: The CD45(-)CD14(-)/CD73(+) and CD45(-)CD14(-)/CD49a(+) phenotypes identified subsets containing all the CFU-F and sufficiently enriched to detect them in fresh BM, enabling evaluation of mesenchymal content of BM collections for cell therapy.

CD34+CDw90(Thy-1)+ subset colocated with mesenchymal progenitors in human normal bone marrow hematon units is enriched in colony-forming unit megakaryocytes and long-term culture-initiating cells.

OBJECTIVE: The progress made in the supportive care of allografts and the identification of mesenchymal stem cells in adult human bone marrow (BM) has prompted renewed interest in the use of BM as a form of cell therapy. With the aim of optimizing the collection of BM cells, we evaluated the hematopoietic and mesenchymal immature cell contents of BM hematon units (HUs), which usually are eliminated during graft processing. MATERIALS AND METHODS: Hematopoietic CD34+ progenitors from HU and buffy coat (BC) compartments were characterized in short-term culture. The sorted CD34+CDw90(Thy-1)+ primitive subset was assessed in colony-forming cell (CFC) and long-term culture-initiating cell (LTC-IC) assays, then further characterized by the expression of additional antigens. In parallel, we evaluated the colony-forming unit fibroblast (CFU-F) number and phenotyped the fresh adherent (D1-3) cells. RESULTS: The plating efficiencies of CD34+ cells derived from HU and BC were identical. However, the HU CD34+CDw90(Thy-1)+ subset was enriched in colony-forming unit megakaryocyte (2.3x), LTC-IC (4.6x), and cells coexpressing CD105 (5x). We found a higher frequency of CFU-F (4.7x), considered to be the mesenchymal stem cell-containing population, correlated with an enrichment in fresh adherent (CD45/GPA)-CD14- cells. CONCLUSIONS: We show for the first time that functional properties of the CD34+CDw90+ subset are related to its in vivo location in HU, which may represent the BM mesenchymal reserve compartment. The location in HU of 35.6%, 59.1%, and 58.7% of CD34+ cells, CD34+CDw90+ LTC-IC, and CFU-F, respectively, justifies the development of a procedure to collect them in order to reduce the therapeutic BM volume.

Coordinated turn-and-reach movements. I. Anticipatory compensation for self-generated coriolis and interaction torques.

When reaching movements involve simultaneous trunk rotation, additional interaction torques are generated on the arm that are absent when the trunk is stable. To explore whether the CNS compensates for such self-generated interaction torques, we recorded hand trajectories in reaching tasks involving various amplitudes and velocities of arm extension and trunk rotation. Subjects pointed to three targets on a surface slightly above waist level. Two of the target locations were chosen so that a similar arm configuration relative to the trunk would be required for reaching to them, one of these targets requiring substantial trunk rotation, the other very little. Significant trunk rotation was necessary to reach the third target, but the arm's radial distance to the body remained virtually unchanged. Subjects reached at two speeds-a natural pace (slow) and rapidly (fast)-under normal lighting and in total darkness. Trunk angular velocity and finger velocity relative to the trunk were higher in the fast conditions but were not affected by the presence or absence of vision. Peak trunk velocity increased with increasing trunk rotation up to a maximum of 200 degrees /s. In slow movements, peak finger velocity relative to the trunk was smaller when trunk rotation was necessary to reach the targets. In fast movements, peak finger velocity was approximately 1.7 m/s for all targets. Finger trajectories were more curved when reaching movements involved substantial trunk rotation; however, the terminal errors and the maximal deviation of the trajectory from a straight line were comparable in slow and fast movements. This pattern indicates that the larger Coriolis, centripetal, and inertial interaction torques generated during rapid reaches were compensated by additional joint torques. Trajectory characteristics did not vary with the presence or absence of vision, indicating that visual feedback was unnecessary for anticipatory compensations. In all reaches involving trunk rotation, the finger movement generally occurred entirely during the trunk movement, indicating that the CNS did not minimize Coriolis forces incumbent on trunk rotation by sequencing the arm and trunk motions into a turn followed by a reach. A simplified model of the arm/trunk system revealed that additional interaction torques generated on the arm during voluntary turning and reaching were equivalent to < or =1.8 g (1 g = 9.81 m/s(2)) of external force at the elbow but did not degrade performance. In slow-rotation room studies involving reaching movements during passive rotation, Coriolis forces as small as 0.2 g greatly deflect movement trajectories and endpoints. We conclude that compensatory motor innervations are engaged in a predictive fashion to counteract impending self-generated interaction torques during voluntary reaching movements.

Coordinated turn-and-reach movements. II. Planning in an external frame of reference.

The preceding study demonstrated that normal subjects compensate for the additional interaction torques generated when a reaching movement is made during voluntary trunk rotation. The present paper assesses the influence of trunk rotation on finger trajectories and on interjoint coordination and determines whether simultaneous turn-and-reach movements are most simply described relative to a trunk-based or an external reference frame. Subjects reached to targets requiring different extents of arm joint and trunk rotation at a natural pace and quickly in normal lighting and in total darkness. We first examined whether the larger interaction torques generated during rapid turn-and-reach movements perturb finger trajectories and interjoint coordination and whether visual feedback plays a role in compensating for these torques. These issues were addressed using generalized Procrustes analysis (GPA), which attempts to overlap a group of configurations (e.g., joint trajectories) through translations and rotations in multi-dimensional space. We first used GPA to identify the mean intrinsic patterns of finger and joint trajectories (i.e., their average shape irrespective of location and orientation variability in the external and joint workspaces) from turn-and-reach movements performed in each experimental condition and then calculated their curvatures. We then quantified the discrepancy between each finger or joint trajectory and the intrinsic pattern both after GPA was applied individually to trajectories from a pair of experimental conditions and after GPA was applied to the same trajectories pooled together. For several subjects, joint trajectories but not finger trajectories were more curved in fast than slow movements. The curvature of both joint and finger trajectories of turn-and-reach movements was relatively unaffected by the vision conditions. Pooling across speed conditions significantly increased the discrepancy between joint but not finger trajectories for most subjects, indicating that subjects used different patterns of interjoint coordination in slow and fast movements while nevertheless preserving the shape of their finger trajectory. Higher movement speeds did not disrupt the arm joint rotations despite the larger interaction torques generated. Rather, subjects used the redundant degrees of freedom of the arm/trunk system to achieve similar finger trajectories with differing joint configurations. We examined finger movement patterns and velocity profiles to determine the frame of reference in which turn-and-reach movements could be most simply described. Finger trajectories of turn-and-reach movements had much larger curvatures and their velocity profiles were less smooth and less bell-like in trunk-based coordinates than in external coordinates. Taken together, these results support the conclusion that turn-and-reach movements are controlled in an external frame of reference.

Normal human bone marrow CD34(+)CD133(+) cells contain primitive cells able to produce different categories of colony-forming unit megakaryocytes in vitro.

OBJECTIVE: To evaluate the megakaryocyte potential of normal bone marrow (NBM) CD34(+)CD133(+) cells, a subset offering a possible alternative for clinical CD34 immunoselection, we evaluated their colony-forming unit megakaryocyte (CFU-Mk) content and their ability to produce clonogenic Mk progenitors in comparison with the CD133(-) subset. MATERIALS AND METHODS: Sorted NBM CD34(+)CD133(+) and CD34(+)CD133(-) subsets were evaluated for Mk clonogenic capacity before and after in vitro proliferation in serum-free liquid culture containing kit ligand, Flt3 ligand, thrombopoietin, interleukin-3, and interleukin-6. The segregation of CFU-Mk according to the expression of CD34, CD133, and CD41 was compared between fresh BM cells and expanded cells. RESULTS: Although the fresh NBM CD133(-)CD34(+) subset included two thirds CFU-Mk, only the CD133(+) subset contained primitive cells able to produce all categories of CFU-Mk in vitro. Immunophenotyping confirmed that CD41 antigen is nonspecific for Mk lineage and showed that the usual CD34(+)CD41(+) subset does not specifically define a CFU-Mk population. The segregation of CFU-Mk before and after expansion according to CD34, CD41, or CD133 was modified in relation with down-regulation of CD34 and CD133 antigens and up-regulation of CD41 antigen. CONCLUSIONS: The NBM CD133(+) subset contains primitive cells able to generate CFU-Mk, a subset probably relevant to platelet recovery after infusion. The alteration of antigen expression during in vitro proliferation calls for caution in the identification of the different categories of Mk subsets produced and in the assessment of their predictivity for in vivo platelet production.