Step-tracking movements of the wrist. IV. Muscle activity associated with movements in different directions

We examined the patterns of muscle activity associated with multiple directions of step-tracking movements of the wrist in humans and monkeys. Human subjects made wrist movements to 12 different targets that required varying amounts of flexion-extension and radial-ulnar deviation. Wrist muscles displayed two patterns of electromyographic (EMG) modulation as movement direction changed: amplitude graded and temporally shifted. The amplitude-graded pattern was characterized by modulation of the quantity of muscle activity that occurred during two distinct time periods, an agonist burst interval that began before movement onset and an antagonist burst interval that began just after movement onset. The timing of muscle activity over the two intervals showed little variation with changes in movement direction. For some directions of movement, EMG activity was present over both time intervals, resulting in "double bursts." Modulation of activity during the agonist burst interval was particularly systematic and was well fit by a cosine function. In contrast, the temporally shifted pattern was characterized by a gradual change in the timing of a single burst of muscle activity. The burst occurred at a time intermediate between the agonist and antagonist burst intervals. The temporally shifted pattern was seen less frequently than the amplitude-graded pattern and was present only in selected wrist muscles for specific directions of movement. Monkeys made wrist movements to 8-16 different targets that required varying amounts of flexion-extension and radial-ulnar deviation. These movements were performed more slowly than those of human subjects. The wrist muscles of the monkeys we examined displayed the amplitude-graded pattern of activity but not the temporally shifted pattern. Stimulation of individual wrist muscles in monkeys resulted in wrist movements that were markedly curved, particularly for the wrist extensors. These results indicate that step-tracking movements of the wrist are generated mainly by using the amplitude-graded pattern to modulate muscle activity. We propose that this pattern reflects a central process that decomposes an intended movement into an agonist, "propulsive" component and an antagonist, "braking" component. Separate bursts of muscle activity then are generated to control each component. On the other hand, we argue that the temporally shifted pattern may function to reduce the amount of movement curvature associated with the activation of wrist muscles.     

Culture method for detection of Salmonella in dried active yeast: collaborative study

A method for detecting Salmonella in dried active yeast was subjected to collaborative study. This method employs trypticase soy broth as the pre-enrichment medium, a sample-to-broth ratio of 1:10, and subsequent transfers to lauryl sulfate tryptose broth and tetrathionate before streaking onto selective agars. Each collaborating analyst received ten 25 g samples of dried active yeast. Duplicate 25 g samples were each inoculated with Salmonella oranienburg at a low level (28 cells) and a high level (107 cells). Similarly, duplicate 25 g samples were each inoculated with S. senftenberg at a low level (30 cells) and a high level (114 cells). The remaining 2 of 10 samples were not inoculated. Results from 12 of 13 collaborators were evaluated. Only 2 (8.2%) of the 24 low level S. oranienburg samples were reported incorrectly as negative. Twelve of the analysts detected S. senftenberg at both levels and S. oranienburg at the high level in the inoculated samples. Results from 12 collaborators used in the final evaluation show that 117 of 119 (98.3%) collaborative determinations are in agreement. The official final action method for the detection and identification of Salmonella, 46.013-46.026, has been revised official first action to include applicability to dried active yeast.     

Lateralization in stroke syndromes as a factor in ambulation

Lateralization should not be ignored in any rehabilitation program for patients with stroke syndromes. Despite the known differences resulting from the localization in the dominant versus the nondominant hemisphere (spatial perception, speech, etc.), practical application of this knowledge in gait training is sparse. The authors looked into different stages of ambulation and the time sequence between these stages and the onset of disease. Standing and walking in parallel bars and outside, as well as elevation activities were given numerical values in an effort to assess abilities quantitatively. The assessment of each patient was recorded graphically (stage of gait against time) and then the different graphs were summated in order to form a common right hemiparetic versus left hemiparetic curve. This study of 236 out of 298 patients (129 left hemiparetics and 107 right ones) showed the following: (1) The right hemiparetics progressed more rapidly in all stages of ambulation, statistically significant figures being obtained for the first two stages; (2) a greater percentage of right versus left hemiparetics reached the assigned levels of ambulation: and (3) 89% out of the 236 patients included in our study were able to ambulate in parallel bars, 81% outside the bars and 38.5% were proficient in stair climbing. Out of the original total number of patients (298), 64% were able able to ambulate outside the bars.     

Polygraphic recordings in subacute sclerosing panencephalitis. A study of the pathophysiology of the periodic EEG complexes

Polygraphic whole night recordings were performed in 10 patients with SSPE. In most cases sleep states could not be classified according to the usual criteria, but two different states with differing EEG patterns were always seen. A significant correlation was obtained between EEG complexes and phase of the respiratory cycle in 8 out of 9 patients, irrespective of the sleep state. Slowing of heart rate for one R-R interval was observed to occur during the onset of the complex in 7 patients in both sleep states, and in 2 patients only in one state. Periodic occurrence of complexes was stable throughout the night. This stability seems to be maintained by a mechanism regulating the duration of an interval according to the duration of the preceding one. It is suggested that diffuse involvement of subcortical structures rather than a localized change is responsible for the generation of the EEG complexes in SSPE.     

Altered protein metabolism in arrested populations of aging human diploid fibroblasts

Protein synthesis and turnover were measured in human diploid fibroblasts which were arrested in an essentially nonmitotic state by reducing the serum concentration in the incubation medium to 0.5%. Through the first 4 days of the arrested period both early and late passage cells lost about 20% of their cellular protein. There was a reduction in the rate of protein synthesis at both passage levels during this period, but there was no significant age-related difference in the synthetic rate or the rate of protein turnover. After day 4 both early and late passage cells maintained a constant protein content, but late passage cells did this while processing more protein through faster rates of both synthesis and turnover than did early passage cells. These results support those theories of cellular senescence which predict altered protein metabolism as a major consequence of the aging process.     

Bioavailability of 17 ampicillin products

The bioavailability of single lots of 250-mg ampicillin capsules, available from 17 distributors and/or manufactures, was determined. Each product was evaluated in terms of the serum ampicillin levels achieved at 1, 2, 3, 4, 6, and 8 hr postadministration, the peak serum levels, the time of peak serum level, and the area under the serum level-time curve. There was no statistically significant difference (p is greater than 0.05) between any of the 17 products tested.