Distribution and development of P2Y1-purinoceptors in the mouse retina.

There is increasing evidence that ATP acts on purinergic receptors and mediates synaptic transmission in the retina. In a previous study, we raised the possibility that P2X-purinoceptors, presumably P2X(2)-purinoceptors in OFF-cholinergic amacrine cells, play a key role in the formation of OFF pathway-specific modulation. In this study, we examined whether the P2Y(1)-purinoceptors can function in cholinergic amacrine cells in the mouse retina since cholinergic amacrine cells in the rat retina express P2Y(1)-purinoceptors. P2Y(1)-purinoceptors were shown to be expressed in dendrites of both ON- and OFF-cholinergic amacrine cells in adults. At postnatal day 7, there was immunoreactivity for P2Y(1)-purinoceptors in the soma of cholinergic amacrine cells. At postnatal day 14, weak immunoreactivity for P2Y(1)-purinoceptors was detected in the dendrites but not in the soma of cholinergic amacrine cells. At postnatal day 21, strong immunoreactivity for P2Y(1)-purinoceptors was detected in dendrites of cholinergic amacrine cells. The expression pattern of P2Y(1)-purinoceptors was not affected by visual experience. We concluded that P2Y(1)-purinoceptors are not involved in the OFF-pathway-specific signal transmission in cholinergic amacrine cells of the mouse retina.

Peculiar tonsil-like structure near vagina of the laboratory shrew, Suncus murinus.

After finding tonsil-like structures near the entrance of vagina of a laboratory shrew (Suncus murinus), which we subsequently designated as vaginal tonsils, we performed detailed immunohistochemical and developmental studies. The location of T and B cells in the vaginal tonsils differed from that in the palatine tonsils or that in the lymphoid nodes of other animals. The boundary between the germinal center region and the region encompassing follicular interfollicular tissue was not clear. B cells were widely distributed and very dense in the parenchyma, but they were scattered in the epithelial area (B cells were present in around 90% of the vaginal tonsil tissue). In contrast, T cells were scattered in the parenchyma and in the epithelial area (T cells were present in around 10% of the vaginal tonsil tissue). B cells were more prominent than T cells throughout the development of these structures and the epithelium was invaded by many immigrating cells. The size of the vaginal tonsils changed during postnatal development. Vaginal tonsils are structurally similar to other tonsils, and they may function to protect the vagina from infection.

Lycopene inhibits ischemia/reperfusion-induced neuronal apoptosis in gerbil hippocampal tissue.

Plant lycopene exhibits antioxidant activity in animal tissues. Transient cerebral ischemia/reperfusion in Mongolian gerbils resulted in delayed neuronal death in hippocampal regions. We examined the antioxidant effects of lycopene because we expected lycopene to attenuate ischemia-related neuronal damage by controlling apoptosis at the gene level. The gerbils were divided into two groups: the normal feeding (control) group that received normal market food (MF) and the lycopene group that received MF containing lycopene (5 mg in 100 g MF food). After 1.5-2.0 months (when body weight were 60-65 g), the lycopene level was 38.2 ± 17.6 ng/ml in serum and 11.9 ± 4.0 µg/g-wet weight tissue in the liver. Levels of B cell leukemia-2, an apoptosis-suppressing protein, decreased in control animal brains 1, 3, and 7 days after surgery, whereas the levels increased in lycopene-treated animal brains. Moreover, cysteinyl aspartate-specific protease-3 activity increased gradually after ischemia, but was suppressed in the lycopene-treated animal brains 7 days after surgery. Finally, hippocampal superoxide dismutase (SOD) activity decreased in the control group 3 h after ischemia and, gradually increased thereafter, whereas it was significantly elevated in the lycopene group. Thus, orally administered lycopene is accumulated in the body, and provided protections against ischemia/reperfusion-induced brain injury by inducing an increase in SOD activity and inhibiting apoptosis.

The distribution of T lymphocytes, B lymphocytes, and dendritic-like cells of the anal tonsil in the laboratory shrew, Suncus murinus.

We investigated the distribution of T lymphocytes, B lymphocytes, and S-100 protein-immunoreactive dendritic-like in the anal tonsil of the laboratory shrew, Suncus murinus. In adult animals, T lymphocytes were located mainly at the periphery of the anal tonsil, especially around small blood vessels. B lymphocytes were located in the central and subepithelial region of the anal tonsil, which includes primary lymphoid follicles, and in which there are small numbers of scattered T lymphocytes. B and T lymphocytes were distributed over 72.7 and 27.3% of the tonsillar area, respectively. However, their areas of distribution were not clearly distinguished. The areas containing B lymphocytes were enriched in S-100 protein antibody-immunoreactive cells, which exhibited a dendritic shape. These S-100-positive cells appeared to be identical to the follicular dendritic cells (FDC) seen in the follicles of lymphoid organs. These results suggest that the anal tonsils constitute one of the gut-associated lymphoid tissues (GALT), and that a function of the anal tonsil includes the capture of intruding antigens that would generate protective antibody responses.

Observation of non-nucleated erythrocytes in the peripheral blood of medaka, Oryzias latipes.

The medaka, Oryzias latipes is a useful animal model for the study of vertebrate developmental genetics. Using May-Grünwald-Giemsa stain, we found non-nucleated erythrocytes in the peripheral blood of medaka. Eleven of 50 fish occasionally showed non-nucleated erythrocytes in their peripheral blood. We expect that this observation will be useful in future studies involving screening for hematologic mutants.

Light and electron microscopic observation of presumptive erythropoietic foci in the medaka yolk sacs.

The medaka, Oryzias latipes is a useful animal model for the study of primary vasculature in vertebrate embryos. Using benzidine stain for erythroid cells, we found presumptive erythropoietic foci in the yolk sac vitellolysis zone at stage 39. These foci were present in the yolk syncytial layer, in the extravascular and vitellolysis zone from 9 days post fertilization (dpf) to 11 dpf, and then declined between 12 to 13 dpf with yolk mass depletion. A table of previous reports on various species of fish showing yolk sac erythropoiesis is also presented.

Blood supply to the retina and the lens in the gerbil (Meriones unguiculatus).

The blood supply to the retina and the lens in 32 gerbils (Meriones unguiculatus) of both sexes from infancy to maturity was studied under light and stereoscopic microscopes, and a scanning electron microscope. Mercox (CL-2R; Dai Nippon Ink, Tokyo, Japan) was injected into the left ventricle of 30 animals in order to visualize the blood supply to the retina and the lens from the ophthalmic artery. The central retinal artery arises from the ophthalmic artery, passes through the papilla of the optic nerve together with the central retinal vein and penetrates the vitreous space (cavity of the eye) between the lens and the internal limiting membrane of the retina, where it divides into the central branches covering the lens and the parietal branches to supply the retina. The former passes through the hyaloid space after branching several arterioles and then covers the lens like a network from its medial and marginal sides. Different from small experimental animals, the parietal branches, just after separating from the central one, divides into the nasal, dorsal and temporal branches in the vitreous space, each of which then subdivides to distribute across the retina on the inner limiting membrane, then delineates the membrana vasculosa retinae. This basal pattern of vasculization 1 day after birth continues to death. Both the central and parietal branches of the central retinal artery correspond to the branches of the hyaloid artery in embryo and the latter is preserved in adult gerbils.