Organization of voluntary movement.

There have recently been a number of advances in our knowledge of the organization of complex, multi-joint movements. Promising starts have been made in our understanding of how the motor system translates information about the location of external targets into motor commands encoded in a body-based coordinate system. Two simplifying strategies for trajectory control that are discussed are parallel specification of response features and the programming of equilibrium trajectories. New insights have also been gained into how neural systems process sensory information to plan and assist with task performance. A number of recent papers emphasize the feedforward use of sensory input, which is mediated through models of the external world, the body's physical plant, and the task structure. These models exert their influence at both reflex and higher levels and permit the preparation of predictive default parameters of trajectories as well as strategies for resolving task demands.     

Dr Samuel Johnson's movement disorder.

Dr Samuel Johnson was noted by his friends to have almost constant tics and gesticulations, which startled those who met him for the first time. He also made noises and whistling sounds; he made repeated sounds and words and irregular or blowing respiratory noises. Further, he often carried out pronounced compulsive acts, such as touching posts, measuring his footsteps on leaving a room, and performing peculiar complex gestures and steps before crossing a threshold. His symptoms of (a) involuntary muscle jerking movements and complex motor acts, (b) involuntary vocalisation, and (c) compulsive actions constitute the symptom complex of Gilles de la Tourette syndrome (Tourette''s syndrome), from which Johnson suffered most of his life. This syndrome is of increasing interest recently because it responds to haloperidol, and because there are new insights into a possible biochemical basis for the tics, vocalisations, and compulsions.     

Magnesium movement in hypothyroid sheep.

We described magnesium transport in hypothyroid and normal sheep with an eight-compartment biomodel fitted by a least-squares technique to data from multiple compartments and routes of entry of 28-Mg. Isotopic equilibrium was not attained during this period of observation in hypothyroid or control sheep. Hypothyroidism reduced transfer coefficients for absorption (P less than 0.01) of 28-Mg from the GI tract but did not change the rate coefficient for endogenous 28-Mg losses to feces (P less than 0.05). Nutritional balance data indicated higher absorption and retention of Mg in hypothyroid sheep, and the observed decrease in rate of passage of digestive residues suggested that mean retention time of GI tract contents had a definite effect on the availability of Mg.     

RNA silencing movement in plants.

Higher eukaryotes have developed a mechanism of sequence-specific RNA degradation which is known as RNA silencing. In plants and some animals, similar to the nematode Caenorhabditis elegans, RNA silencing is a non-cell-autonomous event. Hence, silencing initiation in one or a few cells leads progressively to the sequence-specific suppression of homologous sequences in neighbouring cells in an RNA-mediated fashion. Spreading of silencing in plants occurs through plasmodesmata and results from a cell-to-cell movement of a short-range silencing signal, most probably 21-nt siRNAs (short interfering RNAs) that are produced by one of the plant Dicer enzymes. In addition, silencing spreads systemically through the phloem system of the plants, which also translocates metabolites from source to sink tissues. Unlike the short-range silencing signal, there is little known about the mediators of systemic silencing. Recent studies have revealed various and sometimes surprising genetic elements of the short-range silencing spread pathway, elucidating several aspects of the processes involved. In this review we attempt to clarify commonalities and differences between the individual silencing pathways of RNA silencing spread in plants.     

Temperature effects on bacterial movement.

Details are presented for the construction of a simple precision temperature-controlled chamber for investigating bacterial motile behavior. Independent of original incubation temperature, all species of motile bacteria observed showed a five- to sevenfold increase in average translational velocity (micrometers per second) as the environment temperature was incremented over the range from 10 to 50 degrees C. Temperature jumps downward produced transient tumbling or reciprocal behavior responses, depending on the mode of flagellar distribution, in all species examined. Upward temperature jumps induced accelerated velocities without tumbling or reversal. A partial capacity adaptation to temperature was noted, in that the greatest average translational velocity at any given observation temperature occurred when the organisms were grown at temperatures less than the optimum.     

Temperature effects on bacterial movement.

Details are presented for the construction of a simple precision temperature-controlled chamber for investigating bacterial motile behavior. Independent of original incubation temperature, all species of motile bacteria observed showed a five- to sevenfold increase in average translational velocity (micrometers per second) as the environment temperature was incremented over the range from 10 to 50 degrees C. Temperature jumps downward produced transient tumbling or reciprocal behavior responses, depending on the mode of flagellar distribution, in all species examined. Upward temperature jumps induced accelerated velocities without tumbling or reversal. A partial capacity adaptation to temperature was noted, in that the greatest average translational velocity at any given observation temperature occurred when the organisms were grown at temperatures less than the optimum.     

A model of plant-to-plant movement of aphids III. Studies of actual movement and apparent movement by simulation technique

The plant-to-plant movement of aphids was investigated by the simulation technique in this report. Trials satisfying the following conditions are repeated and the results are compared withShiyomi 's model (1967).

1. An arbitrary individual moves at any moment.
2. The individual moves straightly forward an arbitrary direction and climbs up the plant that he first encounters with.
3. There is no concentrative birth and death.

Some of the results are as follows:

1. For an ideal state of movement, an equation describing the relationship between the frequency of actual movement and the degree of changes in the spatial distribution by movement was obtained.
2. The actual movements, whose frequency we cannot count, changes the spatial distribution of insects, and this change can be evaluated by the changes of values of the parameters contained inShiyomi 's model. Using the statement (i), we can also estimate the frequency of movements of aphids in the ideal (extreme) state.

     

Ultrasonic monitoring of fetal respiratory movement.

Ultrasonic monitoring of fetal respiratory movement including velocity measurements is described. Both proximal and distal walls of the fetal chest are imaged simultaneously. The time-position mode clearly defines fetal respiratory movement and rejects artefacts.