Müller cell-mediated neurite outgrowth of the retinal ganglion cells via P2Y6 receptor signals.

Müller cells, the primary macroglia of the retina, support various functions of retinal ganglion cells (RGCs). Here, we demonstrate a nucleotide-mediated communication between these two types of cells, by which Müller cells control neurite outgrowth of RGCs by activation of P2 receptors such as P2Y6 . Cultured mouse RGCs had significantly enhanced neurite outgrowth when cultured with either cultured mouse Müller cells or conditioned medium derived from Müller cells, and this was completely inhibited by the nucleotide-degrading enzyme, apyrase. This increase in outgrowth was mimicked by exogenously applied nucleotides such as ATP, uridine triphosphate, and uridine diphosphate. Pharmacological and genetic analysis revealed that P2Y6 receptor in RGCs was responsible for the increased neurite outgrowth. P2Y6 receptor was expressed in the ganglion cell layer of the retina and in RGC primary cultures. High performance liquid chromatography has revealed that Müller cells constitutively release uridine triphosphate, which is immediately metabolized into uridine diphosphate, an endogenous agonist for P2Y6 receptor. In the in vitro ocular hypertension model (i.e., glaucoma model), neurite outgrowth in RGCs was significantly reduced, which was associated with a decrease in P2Y6 receptors. Taken together, Müller cells control neurite outgrowth of RGCs by activating P2 receptors such as P2Y6 receptor, and the receptor expression level might be down-regulated in glaucoma. Müller cells support various functions of retina including those of retinal ganglion cells (RGCs). Here, we report an importance of nucleotide-mediated communication between these two types of cells. Müller cells were found to release uridine diphosphate (UTD), uridine triphosphate (UTP), and activate P2Y6 receptors in RGCs, which was essential for neurite outgrowth of RGCs. In addition, P2Y6 receptors in RGCs were reduced in a glaucoma model in vitro, suggesting an involvement of their dysfunction in the pathogenesis of glaucoma.

Cultural differences in drawing movements between right-handed Japanese and German participants.

Differences in drawing movements with the dominant and nondominant hands by 41 right-handed students from Japan (9 men, 12 women; M age = 20.3 yr., SD = 1.4) and Germany (13 men, 7 women; M age = 23.4 yr., SD = 3.0) were investigated. Participants were asked to use each hand to draw a circle, a pentagon, and a rhombus in one stroke. Analysis showed that Japanese participants drew a circle clockwise with the dominant right hand, starting from 6 or 7 o'clock on the face of a clock, while the German participants drew the circle counterclockwise, starting from 11 or 12 o'clock. Moreover, when drawing a pentagon and a rhombus with the right hand, Japanese participants drew counterclockwise from the top-center vertex, whereas almost half of German participants drew clockwise from the left side and others drew counterclockwise from the top-center vertex. Using the left hand, no significant difference was found in starting positions or directionality. Cultural differences in the starting positions and directionality when using the dominant right hand probably reflect the influence of writing habits on the drawing movement of the dominant hand.

Relationship between directionality and orientation in drawings by young children and adults.

The present study examined the relationship between directionality of drawing movements and the orientation of drawn products in right-handed adults and young children for 27 Japanese kindergartners and 29 Japanese university students who were asked to draw with each hand fishes in side view and circles from several starting points. Significant values of chi2 for distributions of frequencies of orientation of the fish drawings and the direction of circular drawing movement indicated that adult right-handers drawing the fish facing to the left tended to draw a circle clock-wise when they drew with the dominant hand, while there was no such significant relationship in young children's drawings. This result may suggest that the reading and writing habits may be implicated in the direction of drawing movements with the dominant hand, and this directional bias of drawing movement in the dominant hand can appear in the orientation of finished drawings.

Developmental transition from object-centered to viewer-centered information in young children's drawings.

This study examined the developmental transition from object-centered to viewer-centered information in young children's drawings. 66 children, ages 4 to 6 years old, drew a miniature snowman as they saw it. The miniature snowman was presented to them with the head positioned to the (1) front, (2) back, (3) left, or (4) right. The face of the snowman was always down and concealed while the children were drawing. 4-yr.-olds more often made canonical drawings, 5-yr.-olds made conflicting drawings, and 6-yr.-olds made view-specific or vertical drawings. These findings suggested that the 4-yr.-olds drew an object using object-centered information, the 5-yr.-olds confused object- with viewer-centered information, and 6-yr.-olds represented an object by viewer-centered information.

Planning and drawing of occluded objects by young children.

When children under 8 yr. old draw an object occluded by another, they depict each object separately either horizontally or vertically. This study examined whether children aged 4-6-yr.-old intended to draw occluding and occluded objects separately at the planning stage like their drawn product. 25 4-yr.-olds (boys=14, girls=11), 28 5-yr.-olds (boys=14, girls=14), and 29 6-yr.-olds (boys=19, girls=10) were presented two cups, set one behind another, with handles visible at the side in partial occlusion and invisible in total occlusion. They were asked to draw the cups as they saw them and to select one among five picture cards (circle, horizontal, orientation-centered, vertical, view-specific) that matched their drawing plan. Analysis showed in both partial and total occlusions in the drawing 4-yr.-olds more often drew either a circle or the two cups horizontally; 5-yr.-olds drew the two cups vertically, while 6-yr.-olds made view-specific drawings, that is, drew the cups as seen. On the planning task for partial and total occlusions 4-yr.-olds selected the picture card representing a circle or two horizontally drawn cups, 5-yr.-olds tended to pick the card of two vertically drawn cups, while 6-yr.-olds chose the view-specific picture card, like their drawn products. These results suggested that planning and drawing were similar within and across age groups and that children's drawing reflected the representation of their planning.

An association analysis between mitochondrial DNA A10398G polymorphism and temperament in Japanese young adults.

The mitochondrial (mt) DNA C5178A and A10398G polymorphisms have been reported to be associated with mental disorders such as bipolar disorder. However, the effects of these polymorphisms on temperament in healthy people are poorly understood. Evaluating healthy subjects can have the advantage of providing new strategies for maintaining psychological health and preventing mental illness. We examined the association between mtDNA polymorphisms and temperament in Japanese students. There was no significant difference in examined temperament when analysed by genotypes, 5178-10398 haplotypes, or sex. The subgroup analysis based on sex indicated that there was an interactive effect of the mtDNA A10398G polymorphism and sex on anxiety and obsession. This finding is preliminary and cannot exclude the possibility of false-positive due to small sample size (144 subjects) and multiple statistical testing. Further studies involving a larger sample size or other ethnic groups are necessary to confirm that mtDNA A10398G polymorphism can be a genetic factor for temperament.