ABSTRACT
Green tea has been reported to result in improvements in a range of health parameters. However, most research has only documented the effects of green tea brewed from leaves or leaf extracts. In addition to the leaves, the roots of tea plants also possess unique properties because of their requirements for growth, which may enable them to have useful physiological effects. We used a hydroponic system to grow the plants and explored the physiological effects of the roots, which biosynthesize one of the rarest functional amino acids, theanine (?-ethylamide-L-glutamic acid). The level of theanine was much higher in the roots than in the leaves, and the roots also differed in other aspects of their chemical composition. We evaluated the effects of tea-root extract on the cognitive function and emotions of aged rats. Our results show that, in the object recognition test, aged rats drinking tea-root extract tended to show improved cognitive function and were more relaxed than the control group, which drank tap water. Furthermore, using a mouse model of human aging, we found that the average life span of mice that consumed the root extract was significantly increased. We suggest that tea roots contain unique components that may improve impaired physiological functions, and we therefore propose tea-root extract as a novel nutraceutical.
ABSTRACT
The retina is a highly differentiated tissue with a complex layered structure that has been extensively characterized. However, most of the previous studies focused on the histology of the central retina while little is known about the cellular composition, organization and function of the marginal retina. Recent research has identified a subpopulation of multipotential progenitor cells in the marginal regions of the retina, closest to the ciliary body ("ciliary marginal zone"). These cells are capable of differentiation in response to an appropriate stimulus. Thus, it is possible that the structure and composition of the marginal retina are distinct from those of the central retina to accommodate the potential addition of newly formed neurons. To characterize the cellular profile of the chick marginal retina, we labeled it immunohistochemically for markers whose staining pattern is well established in the central retina: calbindin, calretinin, protein kinase C, and choline acetyltransferase. Calbindin was present at very low levels in the marginal retina putative photoreceptor layer. Calretinin-positive horizontal cells were also sparse close to the ciliary marginal zone. The bipolar cells in the marginal outer plexiform layer were positive for anti-protein kinase C antibodies, but the density of labeling was also decreased in relation to the central retina. In contrast, the marginal starburst cholinergic amacrine cell pattern was very similar to the central retina. From these data we conclude that the structure of the marginal retina is significantly different from that of the central retina. In particular, the expression of late retina markers in the marginal retina decreased in comparison to the central retina.