Motor planning and movement execution during goal-directed sequential manual movements in 6-year-old children with autism spectrum disorder: A kinematic analysis

BACKGROUND

Atypical motor functioning is prevalent in children with autism spectrum disorder (ASD). Knowledge of the underlying kinematic properties of these problems is sparse.

AIMS

To investigate characteristics of manual motor planning and performance difficulties/diversity in children with ASD by detailed kinematic measurements. Further, associations between movement parameters and cognitive functions were explored.

METHODS AND PROCEDURES

Six-year-old children with ASD (N = 12) and typically developing (TD) peers (N = 12) performed a sequential manual task comprising grasping and fitting a semi-circular peg into a goal-slot. The goal-slot orientation was manipulated to impose different motor planning constraints. Movements were recorded by an optoelectronic system.

OUTCOMES AND RESULTS

The ASD-group displayed less efficient motor planning than the TD-group, evident in the reach-to-grasp and transport kinematics and less proactive adjustments of the peg to the goal-slot orientations. The intra-individual variation of movement kinematics was higher in the ASD-group compared to the TD-group. Further, in the ASD-group, movement performance associated negatively with cognitive functions.

CONCLUSIONS AND IMPLICATIONS

Planning and execution of sequential manual movements proved challenging for children with ASD, likely contributing to problems in everyday actions. Detailed kinematic investigations contribute to the generation of specific knowledge about the nature of atypical motor performance/diversity in ASD. This is of potential clinical relevance.

Kinematic characteristics of second-order motor planning and performance in 6- and 10-year-old children and adults: Effects of age and task constraints

This study explored age-related differences in motor planning as expressed in arm-hand kinematics during a sequential peg moving task with varying demands on goal insertion complexity (second-order planning). The peg was a vertical cylinder with either a circular or semicircular base. The task was to transport the peg between two positions and rotate it various amounts horizontally before fitting into its final position. The amount of rotation required was either 0°, 90°, 180°, or -90°. The reaching for the peg, the displacement of it, and the way the rotation was accomplished was analyzed. Assessments of end state comfort, goal interpretation errors, and type of grip used were also included. Participants were two groups of typically developing children, one younger (M_age  = 6.7 years) and one older (M_age  = 10.3 years), and one adult group (M_age  = 34.9 years). The children, particularly 6-year-olds, displayed less efficient prehensile movement organization than adults. Related to less efficient motor planning, 6-year-olds, mainly, had shorter reach-to-grasp onset latencies, higher velocities, and shorter time to peak velocities, and longer grasp durations than adults. Importantly, the adults rotated the peg during transport. In contrast, the children made corrective rotations after the hand had arrived at the goal.

Reaching skills of infants born very preterm predict neurodevelopment at 2.5 years

The purpose was to investigate associations between quality of reaching for moving objects at 8 months corrected age and neurodevelopment at 2.5 years in children born very preterm (gestational age (GA), 24-31 weeks). Thirtysix infants were assessed while reaching for moving objects. The movements were recorded by a 3D motion capture system. Reaching parameters included aiming, relative length of the reach, number of movement units, proportion of bimanual coupled reaches and number of hits. Neurodevelopment was assessed at 2.5 years by the Bayley Scales of Infant Development III. There were strong associations between infant reaching kinematics and neurodevelopment of cognition and language but the patterns differed: in children born extremely preterm (GA < 28 weeks), planning and control of reaching was strongly related to outcome, while in children born very preterm (GA 28-31 weeks) number of hits and bimanual strategies were of greater relevance. In conclusion, for extremely preterm infants, basic problems on how motion information is incorporated with action planning prevail, while in very preterm infants the coordination of bimanual reaches is more at the focus. We conclude that the results reflect GA related differences in neural vulnerability and that early motor coordination deficits have a cascading effect on neurodevelopment.

The Development of Sensorimotor Intelligence in Infants

Infancy is the most dynamic part of human development. During this period, all basic sensorimotor and cognitive abilities are established. In this chapter, we will trace some of the important achievements of this development with a focus on how infants achieve predictive control of actions, i.e., how they come to coordinate their behavior with the ongoing events in the world without lagging behind. With the maturation of the brain, new possibilities that have profound effects on cognition open up. Some of them are core abilities, i.e., they function at birth or very early in development. Important examples are the structured perception of objects and surfaces and the control of arm movements. Closely after birth, infants move their arms to the vicinity of objects in front of them demonstrating that they have some control of their arms and indicating that they perceive objects as such. Another example is the rapid onset of smooth-pursuit eye movements during the second month of life and the emerging ability to predict when and where an occluded moving object will reappear. At 4months of age, out of sight is no longer of mind. The child's sensorimotor system is especially designed to facilitate the extraction of knowledge about the world including other people. In addition, the infant is endowed with motives that ensure that the innate predispositions are transformed into a system of knowledge for guiding actions predictively. By perceiving and acting on the world, infants develop their cognition and through developmental studies; we can learn more about these processes.

Impaired cognitive ability at 2.5 years predicts later visual and ophthalmological problems in children born very preterm

AIM

To identify possible predictive factors for visual problems at 6.5 years in children born very preterm.

METHODS

During 2004-2007, all very preterm infants (gestational age [GA] <32 weeks) in Uppsala County, Sweden were screened for retinopathy of prematurity (ROP) neonatally; at four months, visual tracking was tested; at 2.5 years, visuospatial and cognitive tests were carried out. At 6.5 years, 84 preterm children and a reference group of 64 full-term children underwent ophthalmological testing.

RESULTS

Mean visual acuity (VA) did not differ between the groups, but subnormal VA (≤0.8) was more common in the preterm group (31% vs 14%; p < 0.05). More often than full-term children, preterm children had impaired contrast sensitivity (<0.5) (36% vs 19%; p < 0.05) and strabismus (8% vs 0%; p < 0.05). Low GA, ROP, intraventricular haemorrhage 3-4/periventricular leukomalacia and cognitive disability at 2.5 years predicted ophthalmological and visual problems at 6.5 years. Visual tracking ability at four months was not predictive of ophthalmological outcome.

CONCLUSION

Children born preterm had more ophthalmological problems at 6.5 years of age, including subtle dysfunctions. ROP, early brain injury and impaired cognitive function around 2.5 years predicted later ophthalmological dysfunctions.

Visual tracking in very preterm infants at 4 mo predicts neurodevelopment at 3 y of age

BACKGROUND

Typically developing infants track moving objects with eye and head movements in a smooth and predictive way at 4 mo of age, but this ability is delayed in very preterm infants. We hypothesized that visual tracking ability in very preterm infants predicts later neurodevelopment.

METHOD

In 67 very preterm infants (gestational age<32 wk), eye and head movements were assessed at 4 mo corrected age while the infant tracked a moving object. Gaze gain, smooth pursuit, head movements, and timing of gaze relative the object were analyzed off line. Results of the five subscales included in the Bayley Scales of Infant Development (BSID-III) at 3 y of age were evaluated in relation to the visual tracking data and to perinatal risk factors.

RESULTS

Significant correlations were obtained between gaze gain and cognition, receptive and expressive language, and fine motor function, respectively, also after controlling for gestational age, severe brain damage, retinopathy of prematurity, and bronchopulmonary dysplasia.

CONCLUSION

This is the first study demonstrating that the basic ability to visually track a moving object at 4 mo robustly predicts neurodevelopment at 3 y of age in children born very preterm.

Maturational and situational determinants of reaching at its onset

At 3 months of age, reaching behavior was measured in a group of 10 girls and 10 boys born at term. The assessments were carried out on the average 2 days after reaching onset. Reaching kinematics was measured in both supine and reclined positions. Girls reached more than boys, had straighter reaching trajectories and movements of shorter durations as well as fewer movement units. The reclined position gave rise to straighter trajectories in both girls and boys. Several anthropometric parameters were measured. Girls had less length and volume of the forearm than boys but similar upper arm volumes. There was a weak relation between kinematic and anthropometric variables.

Kinematic and Gait Similarities between Crawling Human Infants and Other Quadruped Mammals

Crawling on hands and knees is an early pattern of human infant locomotion, which offers an interesting way of studying quadrupedalism in one of its simplest form. We investigate how crawling human infants compare to other quadruped mammals, especially primates. We present quantitative data on both the gait and kinematics of seven 10-month-old crawling infants. Body movements were measured with an optoelectronic system giving precise data on 3-dimensional limb movements. Crawling on hands and knees is very similar to the locomotion of non-human primates in terms of the quite protracted arm at touch-down, the coordination between the spine movements in the lateral plane and the limbs, the relatively extended limbs during locomotion and the strong correlation between stance duration and speed of locomotion. However, there are important differences compared to primates, such as the choice of a lateral-sequence walking gait, which is similar to most non-primate mammals and the relatively stiff elbows during stance as opposed to the quite compliant gaits of primates. These finding raise the question of the role of both the mechanical structure of the body and neural control on the determination of these characteristics.

Dynamic reaching in infants during binocular and monocular viewing

This study examined reaching in 6-, 8-, and 10-month-olds during binocular and monocular viewing in a dynamic reaching situation. Infants were rotated toward a flat vertical board and reached for objects at one of seven positions along a horizontal line at shoulder height. Hand selection, time to contact the object, and reaching accuracy were examined in both viewing conditions. Hand selection was strongly dependent on object location, not on infants' age or whether one eye was covered. Monocular viewing and age did, however, affect time to object contact and contact errors: Infants showed longer contact times when one eye was covered, and 6-month-olds made more contact errors in the monocular condition. For right-hand selection, contact times were longer when the covered right eye was leading during the chair rotation. For left-hand selection, there were no differences in contact time due to whether the covered eye was leading during rotation.

Perception-action in children with ASD

How do disturbances to perception and action relate to the deficiencies expressed by children with autism? The ability to predict what is going to happen next is crucial for the construction of all actions and children develop these predictive abilities early in development. Children with autism, however, are deficient in the ability to foresee future events and to plan movements and movement sequences. They are also deficient in the understanding of other people's actions. This includes communicative actions as they are ultimately based on movements. Today there are two promising neurobiological interpretation of Autism Spectrum Disorder (ASD). First, there is strong evidence that the Mirror Neuron System (MNS) is impaired. As stated by this hypothesis, action production and action understanding are intimately related. Both these functions rely on predictive models of the sensory consequences of actions and depend on connectivity between the parietal and premotor areas. Secondly, action prediction is accomplished through a system that includes a loop from the posterior parietal cortex (PPC) through the cerebellum and back to the premotor and motor areas of the brain. Impairment of this loop is probably also part of the explanation of the prediction problems in children with ASD. Both the cortico-cerebellar loop and the MNS rely on distant neural connections. There are multiple evidence that such connections are weak in children with autism.

Development of smooth pursuit eye movements in very preterm born infants: 3. Association with perinatal risk factors

AIM

To investigate the association between perinatal risk factors and neonatal complications and early oculo-motor development in very preterm infants.

METHODS

Perinatal risk factors were identified, and the potential association with early oculo-motor development was evaluated by measuring smooth pursuit eye movements (SP) at 2 and 4 months' corrected age (CA) in a population of very preterm infants born in Uppsala County 2004-2007 (n = 113).

RESULTS

Among the 15 tested factors, eight showed significant association in univariate analysis with lower levels of SP at 4 months' CA, namely administration of prenatal corticosteroids, gestational age, birthweight, bronchopulmonary dysplasia, retinopathy of prematurity, periventricular leukomalacia, intraventricular haemorrhage >grade 2, and persistent ductus arteriosus. At 2 months' CA, only retinopathy of prematurity >stage 2 was associated with lower levels of SP. When all factors significant in the univariate tests were included in multiple regressions aimed to assess each factor's independent relation to SP, periventricular leukomalacia was the only significant independent factor. When adding 2-5 of the significant factors using multiple regression analysis, the levels of SP became lower.

CONCLUSION

Perinatal risk factors were associated with lower levels of SP. This could be interpreted as delayed or disturbed development of normal oculomotor ability.

Development of smooth pursuit eye movements in very preterm infants: 1. General aspects

AIM

To investigate early oculo-motor development in a population-based cohort of very preterm infants.

METHODS

Early oculo-motor development was prospectively studied by measuring smooth pursuit eye movements at 2 and 4 months corrected age in a population of very preterm infants born in Uppsala County 2004-2007. Eighty-one preterm infants were studied, and 32 healthy term infants constituted the control group.

RESULTS

The study group consisted of infants with a mean gestational age of 28 + 5 weeks. At 2 and 4 months corrected age, infants born very preterm showed lower gain (p < 0.001) and proportion of smooth pursuit eye movements (p < 0.001) compared to the control group. The boys showed higher gain of smooth pursuit eye movements at both 2 and 4 months corrected age, compared to girls.

CONCLUSIONS

 Oculo-motor development measured by smooth pursuit eye movements is delayed in very preterm infants at 2 and 4 months corrected age. This might be a risk factor or early indicator of later perceptual and behavioural impairment.

Development of smooth pursuit eye movements in very prematurely born infants: 2. The low-risk subgroup

AIM

To investigate the impact of premature birth on visual tracking in a group of 37 infants, born before the 32nd gestational weeks (mean 29 + 6 weeks) and diagnosed as being without major neonatal complications. This paper is a part of the LOVIS study (Strand Brodd, Ewald, Grönqvist, Holmström, Strömberg, Von Hofsten, et al. Acta Pediatrica, 2011).

METHODS

At 2 and 4 months corrected age, eye and head movements were measured when the infant tracked a moving object. The eye movements were analysed in terms of smooth pursuit and saccades (Vision Res, 37, 1997, 1799; Exp Brain Res, 146, 2002, 257). Accuracy of gaze, proportion of smooth pursuit, head movements and saccades were calculated.

RESULTS

  Between 2 and 4 months of age, all infants improved their ability to smoothly pursue a moving object. However, at both occasions, the preterm infants had less proportion smooth pursuit than the full-term infants. The groups did not differ with respect to gaze and head movements, but the saccade frequency was higher for the very preterms in some of the conditions.

CONCLUSION

The development of smooth pursuit in the low-risk preterm infant group was strongly delayed compared to typically developed infants. Thus, the 2 months or more extra visual experience did not have a distinguishable positive effect on visuo-motor development as expressed in smooth pursuit.

Movement planning reflects skill level and age changes in toddlers

Kinematic measures of children's reaching were found to reflect stable differences in skill level for planning for future actions. Thirty-five toddlers (18-21 months) were engaged in building block towers (precise task) and in placing blocks into an open container (imprecise task). Sixteen children were retested on the same tasks a year later. Longer deceleration as the hand approached the block for pickup was found in the tower task compared with the imprecise task, indicating planning for the second movement. More skillful toddlers who could build high towers had a longer deceleration phase when placing blocks on the tower than toddlers who built low towers. Kinematic differences between the groups remained a year later when all children could build high towers.

Integrated global motion influences smooth pursuit in infants

Smooth pursuit eye movements (SP) were studied in 5- and 9-month-old infants and adults in response to a rhombus oscillating horizontally behind three spatially separated vertical occluders. During motion, the rhombus vertices were never visible. Thus the perception of the global motion of the rhombus required integration of its moving visible segments. We tested whether infants were able to use such perceived global motion for SP in two different occluder conditions; one in which the occluder was clearly visible to the observer and one in which it was invisible. In adults, the presence of a visible occluder hiding the vertices of the rhombus strongly facilitates the perception of the global motion. It was found that adults and 9-month-olds performed significantly more horizontal SP in the presence of a visible occluder but not 5-month-olds. Furthermore, this tendency was strengthened over single trials, and this temporal pattern was very similar in all age groups. In the invisible occluder condition both adults and infants tracked the segments of the rhombus primarily with vertical SP. It was concluded that the ability to integrate moving object fragments into perceived global motion and use that to regulate SP develops into adult performance by 9 months of age.

Predictive tracking over occlusions by 4-month-old infants

Two experiments investigated how 16-20-week-old infants visually tracked an object that oscillated on a horizontal trajectory with a centrally placed occluder. To determine the principles underlying infants' tendency to shift gaze to the exiting side before the object arrives, occluder width, oscillation frequency, and motion amplitude were manipulated resulting in occlusion durations between 0.20 and 1.66 s. Through these manipulations, we were able to distinguish between several possible modes of behavior underlying 'predictive' actions at occluders. Four such modes were tested. First, if passage-of-time determines when saccades are made, the tendency to shift gaze over the occluder is expected to be a function of time since disappearance. Second, if visual salience of the exiting occluder edge determines when saccades are made, occluder width would determine the pre-reappearance gaze shifts but not oscillation frequency, amplitude, or velocity. Third, if memory of the duration of the previous occlusion determines when the subjects shift gaze over the occluder, it is expected that the gaze will shift after the same latency at the next occlusion irrespective of whether occlusion duration is changed or not. Finally, if infants base their pre-reappearance gaze shifts on their ability to represent object motion (cognitive mode), it is expected that the latency of the gaze shifts over the occluder is scaled to occlusion duration. Eye and head movements as well as object motion were measured at 240 Hz. In 49% of the passages, the infants shifted gaze to the opposite side of the occluder before the object arrived there. The tendency to make such gaze shifts could not be explained by the passage of time since disappearance. Neither could it be fully explained in terms of visual information present during occlusion, i.e. occluder width. On the contrary, it was found that the latency of the pre-reappearance gaze shifts was determined by the time of object reappearance and that it was a function of all three factors manipulated. The results suggest that object velocity is represented during occlusion and that infants track the object behind the occluder in their 'mind's eye'.

Cortical processing of visual motion in young infants

High-density EEG was used to investigate the cortical processing of a rotating visual pattern in 2-, 3-, and 5-month-old infants and in adults. Motion induced ERP in the parietal and the temporal-occipital border regions (OT) was elicited at all ages. The ERP was discernable in the 2-months-olds, significant and unilateral in the 3-month-olds and significantly bilateral in the 5-month-olds and adults. The motion induced ERP in the primary visual area was absent in the 2-month-olds and later than in the OT area for the 3-month-olds indicating that information to OT may be supplied by the V1 bypass at these ages. The results are in agreement with behavioural and psychophysical data in infants.

Visual tracking and its relationship to cortical development

Measurements of visual tracking in infants have been performed from 2 weeks of age. Although directed appropriately, the eye movements are saccadic at this age. Over the first 4 months of life, a rapid transition to successively smoother eye movements takes place. Timing develops first and at 7 weeks of age the smooth pursuit is well timed to a sinusoidal motion of 0.25 Hz. From this age, the gain of the smooth pursuit improves rapidly and from 4 months of age, smooth pursuit dominates visual tracking in combination with head movements. This development reflects massive cortical and cerebellar changes. The coordination between eyes-head-body and the external events to be tracked presumes predictive control. One common type of model for explaining the acquisition of such control focuses on the maturation of the cerebellar circuits. A problem with such models, however, is that although Purkinje cells and climbing fibers are present in the newborn, the parallel and mossy fibers, essential for predictive control, grow and mature at 4-7 months postnatally. Therefore, an alternative model that also includes the prefrontal cerebral cortex might better explain the early development of predictive control. The prefrontal cortex functions by 3-4 months of age and provides a site for prediction of eye movements as a part of cerebro-cerebellar nets.

Infants' emerging ability to represent occluded object motion

The emerging ability to represent an oscillating moving object over occlusions was studied in 7-21-week-old infants. The object moved at 0.25 Hz and was either occluded at the center of the trajectory (for 0.3 s) or at one turning point (for 0.7 s). Each trial lasted for 20 s. Both eye and head movements were measured. By using two kinds of motion, sinusoidal (varying velocity) and triangular (constant velocity), infants' ability to take velocity change into account when predicting the reappearance of the moving object was tested. Over the age period studied, performance at the central occluder progressed from almost total ignorance of what happened to consistent predictive behavior. From around 12 weeks of age, infants began to form representations of the moving object that persisted over temporary occlusions. At around 5 months of age these representations began to incorporate the dynamics of the represented motion. Strong learning effects were obtained over single trials, but there was no evidence of retention between trials. The individual differences were profound.

Development of gaze tracking of small and large objects

A longitudinal study was designed to address the relationships between the smooth pursuit (SP) and the optokinetic response (OKR). Eye and head movements were measured in infants between 7 and 14 weeks of age. They were placed in front of a moving object subtending visual angles of 2.5, 5, 7, 14, 21, 28, and 35 degrees. The object oscillated sinusoidally along a horizontal path with a frequency of 0.25 Hz and an amplitude of +/-25 degrees visual angle. It was found that the number of saccades was dependent on object size: at 6 and 9 weeks of age there were more saccades for the smallest objects. With increasing age, the number of saccades decreased. The composite eye movement gain (smooth tracking + saccades) did not change with age but for the 6.5-week group the gain was higher for smaller objects. The gain of the smooth eye tracking increased with age and showed no dependency on object size. In conclusion, the results do not support the concept of two separate systems, the OKR and the SP, each of them processing eye tracking of small and large objects. Finally, it was observed that two infants at 6.5 weeks of age who used considerable head movements did not inhibit the vestibular-ocular response.

Visual-vestibular interaction in early infancy

The development of visual and vestibular control of smooth gaze adjustments was studied longitudinally in 3- to 18-week-old infants. Eye and head movements were measured with electro-oculography (EOG) and an optoelectronic system, respectively. The infant was placed in a chair providing full support to the trunk but allowing relatively free head movements. The chair was positioned at the center of a striped-patterned drum. The chair and the drum were oscillated sinusoidally, either individually or in synchrony at 0.25 Hz. When the drum oscillated around the infant (the optokinetic response condition, OKR), the gain of both smooth eye and head tracking components was low up to 6 weeks of age, after which the eye gain increased dramatically and the lag decreased. The most substantial increase in head gain was observed at 13-18 weeks of age. When only the chair was oscillated (visual VOR, VVOR), the compensatory eye gain was high at 3 weeks and the head contributed significantly to the compensation (vestibulocollic reflex, VCR). The head gain increased significantly at 13-18 weeks of age as in the OKR case. When the drum and the chair were oscillated synchronously (inhibition of VOR, VORINHIB), the compensatory eye gain was significantly lower than in the VVOR, indicating suppression of VOR. This effect was considerable at 3 weeks. However, VCR was not suppressed but comparable to the VVOR condition at all ages studied. In summary, we found that the vestibular control of smooth gaze adjustment functions earlier than the visual control. At 2 months, the visual control improves dramatically and at 3-4 months head participation increases considerably. The eye gain in the VORINHIB condition could be well predicted by vector addition of the eye position signals in the OKR and VVOR conditions.

Predictive action in infancy: tracking and reaching for moving objects

Because action plans must anticipate the states of the world which will be obtained when the actions take place, effective actions depend on predictions. The present experiments begin to explore the principles underlying early-developing predictions of object motion, by focusing on 6-month-old infants' head tracking and reaching for moving objects. Infants were presented with an object that moved into reaching space on four trajectories: two linear trajectories that intersected at the center of a display and two trajectories containing a sudden turn at the point of intersection. In two studies, infants' tracking and reaching provided evidence for an extrapolation of the object motion on linear paths, in accord with the principle of inertia. This tendency was remarkably resistant to counter-evidence, for it was observed even after repeated presentations of an object that violated the principle of inertia by spontaneously stopping and then moving in a new direction. In contrast to the present findings, infants fail to extrapolate linear object motion in preferential looking experiments, suggesting that early-developing knowledge of object motion, like mature knowledge, is embedded in multiple systems of representation.

Development of smooth pursuit tracking in young infants

Eye and head movements were measured in a group of infants at 2, 3, and 5 months of age as they were attentively tracking an object moving at 0.2 or 0.4 Hz in sinus or triangular mode. Smooth pursuit gain increased with age, especially until 3 months. At 2-3 months, the lag of the smooth pursuit was small for the sinusoidal motion but large for the triangular one. At 5 months, smooth pursuit was leading the sinusoidal motion and the lag for the triangular one was small. Head tracking increased substantially with age and its lag was always large.

The development of gaze control and predictive tracking in young infants

Eye and head tracking of an oscillating visual flow was studied in 1-, 2-, and 3-month-old infants using EOG and an opto-electronic system. A pronounced decrease in phaselag of gaze velocity was observed over this age period, from 170 to 70 msec, but gain changed only marginally. Latency of the onset of tracking decreased with age from 860 to 560 msec. During tracking, the velocity of the head showed high frequency components in the 1-6 Hz range, to which the eye movements were reciprocal and without systematic phase lag. This coordination improved with age.

DNA damage in human endothelial cells after irradiation in anoxia

Endothelial cells and fibroblasts have been reported to respond differently to oxidative stress. Both the effects of high oxygen tension and radiation involve the action of free radicals. DNA damage (single strand breaks, SSB, and double strand breaks, DSB) was assayed in human umbilical cord vein (HUV) cells and in Chinese hamster fibroblasts (V79) after irradiation under oxic or anoxic conditions. The cells were exposed to single doses in the range of 2-18 Gy of gamma-radiation from 60Co. Significantly more DNA damage was induced in the V79 cells than in the HUV cells. As a consequence, a higher oxygen enhancement ratio was obtained for the HUV cells (6.3) as compared to the V79 cells (2.8). The repair of SSB was slower in the HUV cells than in the V79 cells, irrespective of oxic state. For the higher doses, the damage remaining at 60 min after anoxic irradiation, i.e. DSB, was only detected in the V79 cells.

The effect of cold after whole-body irradiation of the mouse

Mice were placed in a cold environment (4 degrees C) directly after whole-body irradiation. Those irradiated with a lethal dose showed higher lethality than mice irradiated with the same dose but placed in room temperature. The response was also altered after irradiation with a sublethal dose. At various periods after irradiation mice were injected with 125IUdR, the tissue uptake of which is an index of DNA synthesis. The result showed that cold treatment after irradiation caused slower cell renewal in the spleen and bone marrow, but that the thymus was only marginally affected. Furthermore, the concentrations of erythrocytes in the peripheral blood reached a lower level in the cold-treated group. Finally, the levels of the thyroid hormones T3 and T4 in the blood were measured and it was found that the T3/T4 ratio was higher in the cold-treated mice. It is suggested that during prolonged exposure to cold after irradiation the cell recovery in the haemopoietic system is exposed to hormonal action that induces significant alterations in the postirradiation cell kinetics.

DNA damage in irradiated endothelial cells of the rat cerebral cortex. Protective action of cysteamine in vivo

The induction and repair of DNA damage in single endothelial cells of rat cerebral cortex capillaries were studied in vivo and in vitro. Capillaries from the cerebral cortex were prepared in suspension, embedded in agarose on microscope slides, and treated with alkaline solution (unwinding of DNA). After neutralization the slides were stained with the fluorescent dye acridine orange and endothelial cell nuclei were evaluated in a microscope photometer. The intensity of the red fluorescence (from single-stranded DNA) divided by the green fluorescence (from double-stranded DNA) was used as a measured of DNA strand breaks. The results showed that most DNA strand breaks were repaired within 30 min postirradiation. A linear dose-effect relationship was found up to 18 Gy. Similar results were obtained from in vitro and in vivo experiments. Cysteamine administered 20 min before irradiation in vivo gave a protective effect on the cells studied. An EMF of 1.3 was determined.

Permeability of the blood-brain barrier in the rat after local proton irradiation

Rats were irradiated laterally through the brain with 200 MeV protons. The beam was of circular cross-section with a diameter of 5 or 7 mm. The doses were 50, 70, 100 and 150 Gy. After irradiation the rats were examined several times by use of injected 99Tcm-pertechnetate. The uptake of the substance increased to a maximum after 20 to 30 days and then decreased to a normal level. Differences in maximum uptake with respect to dose were significant only for the smaller beam diameter.

Effects of proton irradiation of the lumbar intumescence on intra-axonal transport of acetylcholine and cholinergic enzymes in rat sciatic nerve

The content and intra-axonal transport of acetylcholine (ACh) and the cholinergic enzymes cholineacetyltransferase (CAT) and ACh-esterase (AChE) in sciatic nerve were investigated in rats following single dose proton irradiation of the lumbar intumescence of the spinal cord with 60 Gy or 200 Gy. One, 7 or 30 days after irradiation nerve-crush operations were performed 12 hours before killing and the levels of ACh and enzyme activities in nerve segments relative to the crushes were estimated by biologic (ACh) or chemical (enzyme) methods. The results indicate that alterations in intraneuronal dynamics of ACh and related enzymes are not a major cause for the development of neurologic symptoms of the motor system after irradiation, and that descending myelinated axons are of minor importance for the regulation of cholinergic substances in rat motor nerves.

Radiation-induced DNA strand breaks and their repair in the developing rat brain

Rats, 5, 10 or 25 days old, were 60 Co gamma irradiated. The induction of DNA strand breaks was studied after killing the rats within 1 min after irradiation, and the repair of the induced breaks after various intervals up to 180 min. Cell suspensions were prepared from the brain and samples were transferred into alkaline solutions. The fraction of DNA remaining double-stranded after 30 min alkali treatment was estimated after separation of single- and double-stranded DNA on hydroxylapatite. The amount of DNA strand breaks induced per Gray (1--8 Gray) was found to be in accordance with earlier in vivo studies of the mouse small intestine and mouse spleen. The DNA strand breaks in the rat brain induced by 4 Gray 60Co gamma irradiation were repaired 30 min after irradiation in all age groups studied.

Influence of absorbed dose and field size on the geometry of the radiation-surgical brain lesion

Specimens from a number of patients locally irradiated in the thalamus for intractable pain with a multiple gamma beam technique have been examined. The geometry of well circumscribed necrotic lesions was ascertained. No correlation was seen between the dimensions of the lesions and the size of the field, 3 mm X 5 mm or 3 mm X 7 mm, within the clinically useful dose range, 16 to 25 krad.