Neuronal expression, cytosolic localization, and developmental regulation of the organic solute carrier partner 1 in the mouse brain.

Organic solute carrier partner 1 (OSCP1) is a mammalian, transporter-related protein that is able to facilitate the uptake of structurally diverse organic compounds into the cell when expressed in Xenopus laevis oocytes. This protein has been implicated in testicular handling of organic solutes because its mRNA expression is almost exclusive in the testis. However, in this study, we demonstrated significant expression of OSCP1 protein in mouse brain, the level of which was rather higher than that in the testis, although the corresponding mRNA expression was one-tenth of the testicular level. Immunohistochemistry revealed that OSCP1 was broadly distributed throughout the brain, and various neuronal cells were immunostained, including pyramidal cells in the cerebral cortex and hippocampus. However, there was no evidence of OSCP1 expression in glia. In primary cultures of cerebral cortical neurons, double-labeling immunofluorescence localized OSCP1 to the cytosol throughout the cell body and neurites including peri-synaptic regions. This was consistent with the subcellular fractionation of brain homogenates, in which OSCP1 was mainly recovered after centrifugation both in the cytosolic fraction and the particulate fraction containing synaptosomes. Immunoelectron microscopy of brain sections also demonstrated OSCP1 in the cytosol near synapses. In addition, it was revealed that changes in the expression level of OSCP1 correlated with neuronal maturation during postnatal development of mouse brain. These results indicate that OSCP1 may have a role in the brain indirectly mediating substrate uptake into the neurons in adult animals.

Bile acid-induced elevated oxidative stress in the absence of farnesoid X receptor.

The major function of farnesoid X receptor (FXR) is to maintain bile acid and lipid homeostasis. Fxr-null mice, in which the levels of hepatic bile acid and lipid have been elevated, develop spontaneous liver tumors. We evaluated differences in hepatic bile acid and triglyceride concentrations, and in generation of oxidative stress between wild-type mice and Fxr-null mice. The hepatic levels of 8-hydroxy-2'-deoxyguanosine (8OHdG), thiobarbituric acid-reactive substance (TBARS) and hydroperoxides, oxidative stress-related genes, and nuclear factor (erythroid-2 like) factor 2 (Nrf2) protein in Fxr-null mice were significantly higher than those in wild-type mice. An increase in the hepatic bile acid concentration in Fxr-null mice fed a cholic acid (CA) diet resulted in an increase in the hepatic levels of hydroperoxides, TBARS and 8OHdG, whereas a decrease in the hepatic concentration in mice fed a diet containing ME3738 (22beta-methoxyolean-12-ene-3beta,24(4beta)-diol) resulted in a decrease in these oxidative stress marker levels. A good correlation was observed between the hepatic bile acid concentrations and the hepatic oxidative stress marker levels, although there was no significant correlation between the hepatic triglyceride concentrations and oxidative stress. The results show that oxidative stress is spontaneously enhanced in Fxr-null mice, which may be attributable to a continuously high level of hepatic bile acids.

Intratesticular localization of the organic solute carrier protein, OSCP1, in spermatogenic cells in mice.

Organic solute carrier protein 1 (OSCP1) is a recently described human gene that facilitates the transport of various organic solutes into the cell, when expressed in frog eggs. In this study, we cloned a mouse ortholog of OSCP1 encoding 379 amino acid protein, with 94% homology to the human counterpart. The mouse OSCP1 mRNA was predominantly expressed in the testis, in which it was attributed to the spermatogenic cells, except the spermatogonia. Immunohistochemistry confirmed that OSCP1 protein is continuously expressed during spermatogenesis in a stage- and cell type-specific manner, in the leptotene spermatocytes at stage IX through step 15 spermatids. Subcellular fractionation of mouse testis homogenates indicated that OSCP1 is a 45-kDa cytosolic protein. Moreover, when green fluorescent protein-OSCP1 fusion constructs were transfected into cultured cells, the fluorescence localized evenly in the cytoplasm. These results suggest that mouse testis OSCP1 may indirectly mediate substrate uptake into meiotic and spermiogenic germ cells, within the cytosol.

Bovine leukemia virus high tax molecular clone experimentally induces leukemia/lymphoma in sheep.

Sheep were inoculated with high tax coded pBLV-IF (H group, Nos.1-5) of bovine leukemia virus (BLV), wild tax coded pBLV-IF (W group, Nos. 6-11), or control plasmid (C group, Nos. 12-14). During the observation period (4 to 46 months), 5 of 5 cases in H group and 3 of 6 cases (Nos. 6, 7, 9) in W group became positive for gp 51. Only 1 case in H group became leukemic, and one case each of H and W groups developed lymphoma. In No. 3, lesions were found in multiple organs including the lymph nodes, gastrointestinal tract following abomasum, and heart. In No. 6, lesions of lymphoma were found only in the jejunum and heart. Morphologically, small to middle-sized lymphocytic neoplastic (NP) cells were found in both cases, but lymphoblastic NP cells were found only in No. 3. By immunohistochemical examination, the phenotypes of NP cells were determined as CD1-, CD4-, CD5- -, CD8alpha-, sIgM+, lambda light chain+, B-B4+, MHC class II+ in both case. The results of this study indicate that inoculation of pBLV-IF can induce lymphocytic and lymphoblastic leukemia/lymphoma in sheep. Additionally, it is suggested that the expression rate of tax gene is not associated with the development of leukemia/lymphoma in sheep experimentally inoculated with pBLV-IF.

Relation between phenotype of tumor cells and clinicopathology in bovine leukosis.

Thirty-three cases of enzootic bovine leukosis (EBL) and 14 cases of sporadic bovine leukosis (SBL) were examined by immunohistochemistry using 6 monoclonal antibodies against leukocyte differentiation molecules of bovine leukocytes. There were 17 cases of B-1a cell type, 10 cases of B-1b cell type and 6 cases of B-2 cell type in EBL, and 5 cases originating from B cells (B-2 cell type) and 9 cases originating from immature T cells in SBL. The average age for the EBL cases of B-1a cell type was 8.6 years, B-1b cell type was 6.5 years, and of B-2 cell type was 4.5 years. In cases of SBL, immature T cell type patients were younger than B-2 cell type ones. The lymphoma originating from B cells differed from that originating from T cells in morphology. In T cell tumors, the nucleus of tumor cells was round, the edge of the cytoplasm obvious, and tumor cells were sporadically present and proliferated. When compared with T cells, the region among B cells was obscure. But, there was no relation between phenotype and the histologic classification of tumor cells. In EBL, beyond the lymph node, tumors of B-1a and B-1b types had developed in the heart and abomasum, and those of the B-2 type tended to occur in liver. In SBL, B-2 type and T type cells formed tumors in the liver, kidney, thymus, and one case of T-cell type tumor formed on the skin. We would like to propose a new classification of bovine leukosis as EBL, calf type B-cell lymphoma, juvenile T-cell lymphoma and skin type T-cell lymphoma.

Delayed-type hypersensitivity in sheep induced by synthetic peptides of bovine leukemia virus encapsulated in mannan-coated liposome.

Four sheep were immunized with synthesized peptides, derived from bovine leukemia virus (BLV) envelope glycoprotein, encapsulated in mannan coated liposomes as adjuvant. On the seventh day after the immunization, the sheep were intradermally challenged with BLV antigen, or synthesized peptides. The areas challenged with antigen were increased skin thickness and biopsied sequentially for immunohistological examinations. Strong delayed-type hypersensitivity was induced in sheep immunized and challenged with peptides encapsulated in mannan-coated liposomes. The major phenotype of the infiltrating lymphocytes was CD5(+). The ratio of CD4(+) to CD8(+) cells was about 1:1.