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PubMed2000

Regulation of the enzymatic and motor activities of myosin I.

Myosins I were the first unconventional myosins to be purified and they remain the best characterized. They have been implicated in various motile processes, including organelle translocation, ion channel gating and cytoskeletal reorganization but their exact cellular functions are still unclear. All members of the myosin I family, from yeast to man, have three structural domains: a catalytic head domain that binds ATP and actin; a tail domain believed to be involved in targeting the myosins to specific subcellular locations and a junction or neck domain that connects them and interacts with light chains. In this review we discuss how each of these three domains contributes to the regulation of myosin I enzymatic activity, motor activity and subcellular localization.

Actins↗
PubMed1991

Intermittent rectal motor activity: a rectal motor complex?

Prolonged nocturnal recordings from multiple sites in the anorectum and duodenum were performed in 12 healthy volunteers to investigate the presence and determine the characteristics of nocturnal rectal motor activity and assess any synchronicity with phase III of the small intestinal migrating motor complex. Runs of phasic contractions of two contractile frequencies (3 or 6/minute), sustained for more than three minutes, and preceded and followed by motor quiescence were observed in 10 of the 12 subjects. This phenomenon is similar to that described by other investigators and termed the 'rectal motor complex'. The runs of contractions showed considerable inter- and intrasubject variation, with a duration of 3-30 minutes (median 9.0), amplitude of 10-55 mm Hg (median 20.0), and periods of 10-420 minutes (median 55.5) between contractile activity. There was no propagation through the rectum, the phasic motor activity rarely occurred simultaneously at more than one rectal recording site. No consistent relation with phase III of the small intestinal migrating motor complex was observed in any subject. In view of these findings, we question whether this intermittent motor activity merits the term 'rectal motor complex'.

Adult↗
PubMed1990

Methamphetamine- and apomorphine-induced changes in spontaneous motor activity using a new system to detect and analyze motor activity in mice.

A new system was devised to detect animal spontaneous motor activity in more detail, and methamphetamine- and apomorphine-induced changes in spontaneous motor activity were analyzed using this system. The system consists of a doughnut-shaped cage with 36 units of detectors. Scanning of each detector unit was three-dimensionally carried out, and then scanning data were fed into a personal computer. These steps were completed within 0.1 sec and repeated. Spontaneous motor activity was analyzed as changes in parameters, such as total activity, locomotor activity, vertical activity (the number of rearings and the rearing time), motion time, and average speed. Regarding dependence on the dosages of methamphetamine and apomorphine, the time courses of changes in total activity and locomotor activity markedly differed from those for changes in vertical activity. Changes in the numbers of rearings and rearing time induced by 2 mg/kg methamphetamine peaked 40-80 min after administration, whereas those in other parameters did so 15-25 min after. Three mg/kg apomorphine-induced changes in total activity and locomotor activity showed two peaks 10-15 and 40-50 min after administration, respectively. At the same dosage, apomorphine markedly increased rearing time with slight but not significant effects on the number of rearings. These effects peaked 20-30 min after administration. These results indicate this system to be quite useful to detect and analyze drug-induced changes in spontaneous motor activity.

Animals↗
PubMed1989

Activity states and motor activity in an infant capuchin monkey (Cebus apella) from birth through eleven weeks.

Behavioral states and motor activity of an infant capuchin monkey reared by its mother in a social group were studied for 11 weeks after birth. Manipulative activity was infrequent through the first four weeks after birth; what little occurred was mediated by other animals interacting with the infant. The rate of manipulation increased the most between weeks 8 and 9. At the same time, the most frequent targets of manipulation shifted from the infant's own body and the bodies of others to surfaces and inanimate objects in the cage. Large increases in the proportion of time in an Alert/active state and improvement in postural control also occurred at the end of the second month. The data suggest that major organizational changes in motor coordination and the regulation of behavioral state occurred jointly over a short period of time at about 8 weeks of age. In comparison to other species of monkeys, the capuchin infant displayed later development of manipulation, postural control, and independent locomotion, and greater dependence on social contacts for early interaction with its environment. These characteristics are in accord with the greater neurological immaturity of the capuchin infant at birth compared to other monkeys.

Aging↗
PubMed1998

A hinge at the central helix of the regulatory light chain of myosin is critical for phosphorylation-dependent regulation of smooth muscle myosin motor activity.

The motor function of smooth muscle myosin is activated by phosphorylation of the regulatory light chain (RLC) at Ser19. However, the molecular mechanism by which the phosphorylation activates the motor function is not yet understood. In the present study, we focused our attention on the role of the central helix of RLC for regulation. The flexible region at the middle of the central helix (Gly95-Pro98) was substituted or deleted to various extents, and the effects of the deletion or substitution on the regulation of the motor activity of myosin were examined. Deletion of Gly95-Asp97, Gly95-Thr96, or Thr96-Asp97 decreased the actin-translocating activity of myosin a little, but the phosphorylation-dependent regulation of the motor activity was not disrupted. In contrast, the deletion of Gly95-Pro98 of RLC completely abolished the actin translocating activity of phosphorylated myosin. However, the unregulated myosin long subfragment 1 containing this RLC mutant showed motor activity the same as that containing the wild type RLC. Since long subfragment 1 motor activity is unregulated by phosphorylation, i.e. constitutively active, these results suggest that the deletion of these residues at the central helix of RLC disrupts the phosphorylation-mediated activation mechanism but not the motor function of myosin itself. On the other hand, the elimination of Pro98 or substitution of Gly95-Pro98 by Ala resulted in the activation of actin translocating activity of dephosphorylated myosin, whereas it did not affect the motor activity of phosphorylated myosin. Together, these results clearly indicate the importance of the hinge at the central helix of RLC on the phosphorylation-mediated regulation of smooth muscle myosin.

Actins↗
PubMedDate not supplied

Effect of prenatal exposure to styrene on the neurobehavioral development, activity, motor coordination, and learning behavior of rats.

Maternal Wistar rats were exposed via inhalation to 0, 50, or 300 ppm styrene for 6 h/day during gestation days 7 to 21, and offspring were subsequently evaluated in several neurobehavioral tests. Preliminary results with a small number of litters revealed significant dose-dependent effects in tests performed prior to weaning (surface righting, pivoting locomotion, and bar holding), as well as in tests performed after weaning (motor coordination, open-field behavior, and motor activity). Exposure to low concentrations of styrene (50 ppm) caused disturbances in motor coordination in addition to delaying some motor and reflex developments. Large doses (300 ppm) led to changes in open-field behavior and increases in spontaneous activity in addition to the delay in neurobehavioral developments. Exposure of dams to styrene did not clearly affect the learning behavior of the offspring. It was also observed that age played a role in the differences in styrene's effects on neurobehavioral function. Only subtle effects were found in both open-field behavior and motor-coordination function when compared with control rats at 120 days of age. These results suggest that the functional neurobehavioral development of progeny of dams exposed to styrene (or other solvents) should be further investigated.

Animals↗
PubMed1988

Effects of osmoreceptor stimulation on human duodenal motor activity.

The motor responses of the human duodenum to saline solutions of varying osmolality were examined in order to investigate the possible role played by the upper intestine in the control of gastric efflux of hyperosmolar material. During fasting, delivery of the solutions into the duodenum increased duodenal motor activity and intraduodenal pressure, the magnitude of the response increasing with osmolality. At the highest osmolalities, a regular duodenal motor pattern was induced in some individuals which was indistinguishable from fasting phase III activity. After feeding, hyperosmolar saline again increased motor activity. In addition, the transit of an intraduodenal marker to the caecum was accelerated. These findings support the concept that the duodenum is both sensitive and responsive to its intraluminal content. The motor responses additionally appear to function to clear excessively stimulating intraluminal material from the duodenal lumen and may also contribute to the 'postpyloric' resistance which is known to exert control of normal gastric emptying.

Adult↗
PubMed1979

[Vegetative functions and motor activity in endogenous depression. Longitudinal study on salivary secretion, temperature, and motor activity in a patient with 48-hour cycles (author's transl)].

Vegetative functions were studied in a 66-year-old-male patient with 48-h unipolar cycles of depression. Salivary secretion, body temperature, and motor activity were measured at 3-h-intervals during the day and once at night. The mood state was assessed by two self-rating scales. There was a regular alternation between 'good' and 'bad' days. Salivary secretion was higher on good days, especially in the morning (P less than 0.002, 10:00). The shape of the 24-h-prolife was different on good and bad days, with a maximum at 10:00 on good at 16:00 on bad days. The mimimum in the night was the same on both good and bad days. Body temperature was increased, as compared with normal subjects (mean 37.2 degrees C) and the diurnal variation was slight. On good days, body temperature during the day was about 0.1 degree C higher than on bad days. Motor activity (arm and leg), registrated by means of the 'activity watch', was higher (during the day) on good days. The present data give some hints for a central dyregulation of vegetative functions in endogenous depression.

Aged↗
PubMed1988

Localization of tactile stimuli and body parts in space: two dissociated perceptual experiences revealed by a lack of constancy in the presence of position sense and motor activity.

Two motor acts were analyzed at the level of tongue and fingers. These motor acts generated illusions. When subjects voluntarily rotated the tongue by 90 degrees, the perceived orientation of a tactile stimulus applied to the tongue did not covary with the perceived orientation of the tongue itself. Analogously, when subjects voluntarily crossed two adjacent fingers, the perceived position of two tactile stimuli applied to the fingers did not covary with the perceived position of the fingers themselves. Although tongue and fingers were positioned accurately in space, a lack of perceptual constancy occurred for tactile stimuli applied to these body parts. Therefore, whereas position sense was preserved, correct localization of objects was lost. The occurrence of this perceptual dissociation suggests that spatial localization of tactile stimuli may be independent both of knowledge of body part location and motor activity.

Attention↗
PubMed1995

Effects of intracerebroventricular administration of pituitary adenylate cyclase-activating polypeptide (PACAP) on the motor activity and reserpine-induced hypothermia in murines.

We investigated the effects of i.c.v. administration of pituitary adenylate cyclase-activating polypeptide (PACAP) on the spontaneous motor activity and reserpine-induced hypothermia in murines. The administration of PACAP (1 or 2 nmol) caused a dose-dependent increase in both spontaneous motor activity and rearing behavior in the rat. The peptide (0.1 or 0.2 nmol) counteracted reserpine-induced hypothermia in a dose-dependent manner in mice. On the other hand, i.c.v. injection of vasoactive intestinal polypeptide, which is structurally similar to PACAP, at a dose similar to that of PACAP (2 nmol in rats, 0.2 nmol n mice) did not show a significant effect on either behavior or body temperature. Therefore, the stimulating effect of PACAP observed here may be mediated by PACAP-specific (type I) receptors. PACAP was more potent and longer-lasting than a known potent stimulating peptide, thyrotropin-releasing hormone, in both stimulating motor activity and counteracting reserpine-induced hypothermia. Results of the present study, in combination with those of previous studies identifying endogenous PACAP in the brain, suggest that PACAP may play a important role in the CNS as a stimulant in regulating motor activity and body temperature.

Animals↗
PubMed2006

Ipsilateral motor activation during unimanual and bimanual motor tasks.

OBJECTIVE: To test for the presence and possible asymmetry of ipsilateral motor activation during unimanual and bimanual motor tasks. METHODS: Twelve right-handed healthy subjects underwent motor evoked potential (MEP) measurement of one hand (target-hand) while the other hand (task-hand) performed different motor tasks. The target-hand was either at rest (first experiment) or performed a Perdue PegBoard task (second experiment). The task-hand was either at rest, performed a simultaneous pegboard task, or rotated a coin (second experiment). RESULTS: In the first experiment, the motor task resulted in significant increase in MEP area in the target-hand, regardless which hand was the task-hand, with a greater increase when the left hand was the task-hand. In the second experiment, ipsilateral motor activation was not present for either hand, however, when the right hand was the task-hand, performance of continuous coin rotation by the right hand resulted in a significant decrease in the MEP area of the left hand. CONCLUSIONS: Hemispheric asymmetry and task-dependence of ipsilateral motor cortex activation supports the postulate that motor activity may start bilaterally with subsequent interhemispheric inhibition. Furthermore, in right-handers, the left motor cortex is either more active in ipsilateral hand movements or exerts more effective inhibitory control over the right motor cortex than vice versa. SIGNIFICANCE: We suggest that hemispheric asymmetry in ipsilateral motor control is a factor in determining motor dominance in right-handed individuals.

Adult↗
PubMed1980

Behavioral states and state-related heart rate and motor activity patterns in the newborn infant and the fetus ante partum. A comparative study. III. Analysis of sleep state-related motor activity patterns.

Evaluation of fetal movements revealed a striking difference of motor activity during assumed quiet sleep and active sleep in the fetus. Furthermore, motor activity was found to be enhanced in post-term fetuses. Consequences for the methods of fetal acceleration determination (FAD) and daily fetal movement count (DFMC) are discussed.

Female↗