When prelocomotor infants are supported on a motorized treadmill, they perform well-coordinated, alternating stepping movements that are kinematically similar to upright bipedal locomotion. This behavior appeared to be a component of independent walking that could not be recognized without the facilitating context of the treadmill. To understand the ontogenetic origins of treadmill stepping and its relation to later locomotion, we conducted a longitudinal study using an experimental strategy explicitly derived from dynamic systems theory. Dynamic systems theory postulates that new forms in behavior emerge from the cooperative interactions of multiple components within a task context. This approach focuses on the transitions, often nonlinear, where one preferred mode of behavior is replaced by a new form. Specific predictions about these transitions help uncover the processes by which development proceeds. Chapters II, III, and IV introduce dynamic principles of pattern formation and their application to development. In our application of these principles, we tested nine normal infants twice each month beginning from month 1 in a task where the treadmill speed was gradually scaled up and in an additional condition where each leg was driven by the treadmill at a different speed. Kinematic variables were derived from computerized movement analysis equipment and videotaped records. We also collected a number of anthropometric measurements, Bayley motor scores, and a behavioral mood scale for each month. Several infants stepped on the treadmill in their first month, but in all infants performance showed a rapidly rising slope from month 3 to month 6. Infants also showed corresponding improvement in adjustments to speed and relative coordination between the legs. In dynamic terminology, we found evidence that alternating stepping on the treadmill became an increasingly stable attractor during the middle months of the first year. Dynamic predictions that transitions would be characterized by increased variability and sensitivity to perturbation were borne out. Identifying the transitions enabled us to suggest a control parameter or variable moving the system into the stable response to the treadmill. This appeared to be the waning of flexor dominance in the legs during posture and movement that allowed the leg to be stretched back on the treadmill and so elicited the bilaterally alternating response. Further studies are needed to test this hypothesis. This dynamic analysis confirmed earlier suggestions that skill in general, and locomotion in particular, develops from the confluence of many participating elements and showed how emergent forms may result from changes in nonspecific components. A dynamic approach may be useful for understanding ontogenetic processes in other domains as well.

ABSTRACT. Objective. On average, infants with Down syndrome (DS) learn to walk about 1 year later than nondisabled (ND) infants. The purpose of this study was to determine if practice stepping on a motorized treadmill could help reduce the delay in walking onset normally experienced by these infants.Methods. Thirty families of infants with DS were randomly assigned to the intervention or control group. All infants were karyotyped trisomy 21 and began participation in the study when they could sit alone for 30 seconds (Bayley Scales of Infant Development, Second Edition 1993, item 34). Infants received traditional physical therapy at least every other week. In addition, intervention infants received practice stepping on a small, motorized treadmill, 5 days per week, for 8 minutes a day, in their own homes. Parents were trained to support their infants on these specially engineered miniature treadmills. Every 2 weeks research staff went into the homes and tested infants' overall motor progress by administering the Bayley Scales of Infant Development, Second Edition, 1 monitored growth status via a battery of 11 anthropometric measures, and checked parents' compliance with physical therapy and treadmill intervention. The primary measures of the intervention's effectiveness were comparisons between the groups on the length of time elapsed between sitting for 30 seconds (entry into the study) and 1) raising self to stand; 2) walking with help; and 3) walking independently.Results. The experimental group learned to walk with help and to walk independently significantly faster (73.8 days and 101 days, respectively) than the control group, both of which also produced large effect size statistics for the group differences. The groups were not statistically different for rate of learning to raise self to stand but there was a moderate effect size statistic suggesting that the groups were meaningfully different in favor of the experimental group.Conclusions. These results provide evidence that, with training and support, parents can use these treadmills in their homes to help their infants with DS learn to walk earlier than they normally would. Current research is aimed at 1) improving the protocol to maximize outcome; 2) determining the impact of treadmill practice on walking gait patterns; 3) testing the application to other populations with a history of delays in walking; and 4) determining the long-term benefits that may accrue from this form of activity. Pediatrics 2001;108(5). URL: http:// www.pediatrics.org/cgi/content/full/108/5/e84; motor development, Down syndrome, early intervention, walking.

Progesterone, a key female sex hormone with pleiotropic functions in maintenance of pregnancy, has profound effects on regulation of immune responses. We report here a novel function of progesterone in regulation of naïve cord blood (CB) fetal T cell differentiation into key regulatory T cell subsets. Progesterone drives allogeneic activation-induced differentiation of CB naive, but not adult peripheral blood (PB), T cells into immune suppressive T regulatory cells (Tregs), many of which express FoxP3. Compared to those induced in the absence of progesterone, the FoxP3+ T cells induced in the presence of progesterone highly expressed memory T cell markers. In this regard, the Treg compartment in progesterone-rich CB is enriched with memory type FoxP3+ T cells. Moreover, CB antigen presenting cells were more efficient in inducing FoxP3+ T cells than their PB counterparts. Another related function of progesterone that we discovered was to suppress the differentiation of CB CD4+ T cells into inflammation-associated Th17 cells. Progesterone enhanced activation of STAT5 in response to IL-2 while it decreased STAT3 activation in response to IL-6, which is in line with the selective activity of progesterone in generation of Tregs versus Th17 cells. Additionally, progesterone has a suppressive function on the expression of the IL-6 receptor by T cells. The results identified a novel role of progesterone in regulation of fetal T cell differentiation for promotion of immune tolerance.

We study Rees algebras of modules within a fairly general framework. We introduce an approach through the notion of Bourbaki ideals that allows the use of deformation theory. One can talk about the (essentially unique) generic Bourbaki ideal I(E) of a module E which, in many situations, allows one to reduce the nature of the Rees algebra of E to that of its Bourbaki ideal I(E). Properties such as Cohen–Macaulayness, normality and being of linear type are viewed from this perspective. The known numerical invariants, such as the analytic spread, the reduction number and the analytic deviation, of an ideal and its associated algebras are considered in the case of modules. Corresponding notions of complete intersection, almost complete intersection and equimultiple modules are examined in some detail. Special consideration is given to certain modules which are fairly ubiquitous because interesting vector bundles appear in this way. For these modules one is able to estimate the reduction number and other invariants in terms of the Buchsbaum–Rim multiplicity. 2000 Mathematics Subject Classification 13A30 (primary), 13H10, 13B21 (secondary)

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The uncontrolled manifold (UCM) approach allows us to address issues concerning the nature of variability. In this study we applied the UCM analysis to gait and to a population known for exhibiting high levels of performance variability, Down syndrome (DS). We wanted to determine if preadolescents (ages between 8 and 10) with DS partition goal-equivalent variability (UCM( ||)) and non-goal equivalent variability differently than peers with typical development (TD) and whether treadmill practice would result in utilizing greater amounts of functional, task-specific variability to accomplish the task goal. We also wanted to determine how variance is structured with respect to two important performance variables: center of mass (COM) and head trajectory at one specific event (i.e., heel contact) for both groups during gait. Preadolescents with and without DS walked on a treadmill below, at, and above their preferred overground speed. We tested both groups before and after four visits of treadmill practice. We found that children with DS partition more UCM( ||) variance than children with TD across all speeds and both pre and post practice. The results also suggest that more segmental configuration variance was structured such that less motion of COM than head position was exhibited at heel contact. Overall, we believe children with DS are employing a different control strategy to compensate for their inherent limitations by exploiting that variability that corresponds to successfully performing the task.

Our goal was to examine the gait patterns of older adults with Down syndrome (DS) for precocious stabilizing adaptations during comfortable over-ground walking and in more challenging conditions. Twelve participants with DS and 12 with typical development (TD) were matched for height, weight and age (range 35 to 62 years). We used a 6-camera motion capture system to assess foot trajectories over obstacles. Participants first walked at their preferred speed over a 5.3 m instrumented gait mat (unperturbed condition). Subsequent walking trials included perturbations mid-walkway: a) minimal obstacle to step over (12 cm high), b) moderate obstacle to step onto with both feet and then off (standard step), c) maximum obstacle to step onto with only one foot and over with the other (standard step).Adults with DS walked slower with shorter, wider strides while spending more time in both stance and double support. These adaptations increased during the moderate and maximal perturbations. They stepped with the minimal perturbation obstacle further forward in their crossing step and produced a lower, flatter trajectory of the lead foot, with less dorsiflexion at crossing. This strategy decreased trailing toe clearance but did not alter leading heel clearance.The combined effects of ligamentous laxity, low tone, obesity, inactivity and physiological decrements associated with aging lead to these stability-enhancing adaptations at a younger chronological age in adults with DS. We believe intervention to increase overall stability will be beneficial in helping adults with DS maintain optimal functional mobility and health.