R esearchers studying human movement have attempted to define skilled motor performance by employing a range of kinematic variables, such as movement speed, movement time, timing accuracy, etc. In recent research, temporal and spatial intrasubject variability in kinematic variables is regarded as an important measure of motor skill and practice effects. Intrasubject variability of kinematic variables is an index of movement consistency or stability and thereby provides us with a measure to evaluate motor skill for a given task (8).The variability was examined in human gait, in particular, for its temporal and spatial parameters. It was expected that stability of gait could be assessed using the variability measure, especially for older persons (3-5) and physically disabled subjects (1). In fact, there was a negative correlation between variability in step width and balance performance for women 60 years of age and over (5) and also an increased variability in step length for hospitalized fallers compared with nonfallers (4). The results suggest that the variability measure can be an index of stability of gait performance.These studies, however, measured variability in the gait parameters at the preferred speed of each subject. Maruyama and Nagasaki (8) for treadmill walking of normal s u b jects that intrasubject variability in the duration of every walking phase decreased with increased speed, thereby supporting the hypothesis that faster movement is more consistent than slower movement. Furthermore, they showed that the coeficients of variation (CV) were the lowest at the specific step rates (cadence) that were linearly dependent on walking speed. The relationship between speed and step rate for walking with the lowest temporal CV was very close to the speed-rate relationship found in free walk. They suggested that stability of gait in terms of CV for the duration of the walking phase was optimal for walking with a freely chosen step rate at any given speed.There is also an optimal method of walking, both in terms of energy cost and attentional demand. At preferred walking speed, energy consumption per unit of distance was at a minimum (13). Furthermore, freely chosen step rates required the least oxygen consumption at a given speed (6,17). Kurosawa (7) measured reaction time to a probe during treadmill walking and demonstrated that walking at a subject's preferred speed called for a minimum attentional de-

Although being an atmospheric pressure ion source, electrospray ionization (ESI) has rarely been used directly for ambient imaging mass spectrometry because the sample has to be introduced as liquid solution through the capillary. Instead of capillary, probe electrospray ionization (PESI), which has been developed recently, uses a solid needle as the sampling probe, as well as the electrospray emitter, and has been applied not only for liquid solutions but also for the direct sampling on wet samples. Biological tissues are composed of cells that contain 70-90% water, and when the surface is probed by the needle tip, the biological fluid adhering to the needle can be electrosprayed directly or assisted by additional solvent added onto the needle surface. Here, we demonstrate ambient imaging mass spectrometry of mouse brain section using PESI, incorporated with an auxiliary heated capillary sprayer. The solvent vapor generated from the sprayer condensed on the needle tip, re-dissolving the adhered sample, and at the same time, providing an indirect means for needle cleaning. The histological sections were prepared by fixation using paraformaldehyde, and the spatial analysis was automated by maintaining an equal sampling depth into the sample in addition to raster scan. Phospholipids and galactosylceramides were readily detected from the mouse brain section in the positive ion mode, and were mapped with 60 microm lateral resolution to form mass spectrometric images.

The primary purposes of this study were 1) to confirm age-related deterioration of physical performance in older adults longitudinally, and 2) to predict future functional status and mortality by initial level of physical performances. The subjects were 517 older adults examined both in 1992 and 1996 in the Tokyo Metropolitan Institute of Gerontology, Longitudinal Interdisciplinary Study on Aging. The same battery consisting of muscle strength, balance, walking, and manual speed was administered to the subjects in the baseline and follow-up examinations. A significant longitudinal decline was observed in all physical performances except for grip strength. The age-related decline accelerated with aging for preferred walking velocity. Inter-subject variability in walking velocity significantly increased for 4 years period. Maximum walking velocity was a common predictor for functional status and mortality. The results suggest that physical performance measures, especially maximum walking velocity, is a valid means for physical therapy to evaluate physical functioning of community-living older persons.

The distribution pattern of Leu-7 (HNK-1) in developing human embryonic hearts and rat hearts was studied by immunohistochemistry. Human and rat embryos at Streeter's stages XIII approximately XX and fetus stage I were used. Leu-7, which is absent in the newborn rat heart, is expressed transiently in the embryo and fetus I stages. The earliest embryonic heart shows two incomplete circular structures with immunoreactivity in the myocardium along the primitive atrioventricular cushion and bulboventricular canal. These two structures become localized topographically in the definitive atrioventricular node and atrioventricular bundle after rearrangement and partial disappearance during embryonic development. At Streeter's stages XVIII approximately XX, Leu-7 immunoreactivity appears to localize topographically in almost all the pathways of the conduction system, although some discontinuities are observed in the atrioventricular junction and atrial internodal tracts. Thereafter, immunoreactivity decreases gradually and differentially by site and stage. The precise nature of Leu-7 immunoreactive cells, that is, whether or not they are neurogenic or myogenic, is not revealed by this study. The present observations are discussed in connection with the hypothesis that specialized ring tissue is the primordium of the conduction system.