Expression of cAMP response element-binding protein in the duct system of the mouse submandibular gland.

The submandibular gland (SMG) of mice shows a marked sexual dimorphism in which a duct portion called the granular convoluted tubule (GCT) is developed preferentially in males during puberty. The administration of testosterone to female mice causes the conversion of striated duct (SD) cells into GCT cells, but the underlying molecular mechanisms are unclear. Cyclic AMP response element-binding protein (CREB) is a transcription factor functioning downstream of a variety of signal transduction pathways. In the present study, we examined the expression, activation and cellular localization of CREB in the mouse SMG using Western blotting and immunohistochemistry. Both total CREB (t-CREB) and phosphorylated CREB (p-CREB) were significantly more abundant in the female than in the male gland and were localized to the nuclei of intercalated duct cells and a subpopulation of SD cells. In contrast, the GCT cells in males were negative for t- and p-CREB. The levels of CREB in the SMG were increased by castration in males and decreased by repeated administration of testosterone to females or castrated males. From 3 h after a single administration of testosterone to females, many SD cells temporarily gained nuclear immunoreactivity for both t- and p-CREB, which was lost as the cells were converted to GCT cells by 24 h. These results suggest the involvement of CREB in the androgen-dependent differentiation of the duct system in the mouse SMG.

Coexpression of menin and JunD during the duct cell differentiation in mouse submandibular gland.

In the submandibular gland (SMG) of mice, a duct portion called the granular convoluted tubule (GCT) is developed preferentially in males with puberty. This sexual dimorphism is androgen-dependent, but the underlying molecular mechanisms are unclear. We have demonstrated that the expression of a transcription factor JunD is regulated in association with the androgen-induced differentiation of GCT cells from striated duct (SD) cells. Menin, a nuclear protein encoded by the MEN1 tumor-suppressor gene, is known to bind JunD, thereby inhibiting its activity. In the present study, we examined the expression of menin in the mouse SMG by use of Northern blotting, Western blotting, and immunohistochemistry. Immunoreactivity for menin was higher in the female than male gland, and localized to the nuclei of intercalated duct cells and a subpopulation of SD cells. In contrast, GCT cells in males appeared negative for menin. The levels of menin in the SMG were increased with castration in males and decreased by repeated administration of testosterone to females or to castrated males. After a single administration of testosterone to females, many SD cells newly gained nuclear menin, which was lost as the cells converted to GCT cells by 48 hrs. These patterns of the expression and localization of menin were quite similar to those of JunD. Furthermore, the coimmunoprecipitation analysis of the SMG homogenates indicated that menin binds JunD in vivo. The present study suggests that the JunD-menin complex plays significant roles in the androgen-dependent differentiation of the duct system in the mouse SMG.

Expression and localization of receptor protein tyrosine phosphatase ß and its ligand pleiotrophin in the submandibular gland of mice.

OBJECTIVES: The family of receptor protein tyrosine phosphatase ß (RPTPß) is composed of 4 splice variants and thought to play roles in the neural migration and outgrowth. Several ligands including the growth factor pleiotrophin (PTN) bind to RPTPß and inhibit its phosphatase activity, thereby activating cellular signalling pathways. We examined the expression and localization of RPTPß and its ligands in the submandibular gland (SMG) of mice, which is known for a prominent sexual dimorphism in the duct system. DESIGN: The homogenates and tissue sections of male and female mouse SMG were analysed with RT-PCR, Western blotting, and immunohistochemistry. RESULTS: The short receptor type of RPTPß (RPTPß-S) was dominantly expressed in the SMG, and the male gland had significantly higher levels of RPTPß-S expression than the female gland. In the male, RPTPß-S was localized predominantly in intercalated duct (ID) cells, but was not found in granular convoluted tubule (GCT) cells or acinar cells. In the female, weaker reactivity was demonstrated in both ID and striated duct (SD) cells. Of the known ligands for RPTPß, PTN was expressed in the SMG, without sexual difference in levels. In the male, PTN was localized in ID cells as well as in cells located in the distal ends of GCT that are in close vicinity to the ID, whereas in the female PTN was colocalized with RPTPß-S throughout ID and SD cells. CONCLUSIONS: These results indicated that the distribution of RPTPß-S and its ligand PTN has a close relation to the sexual dimorphism in the duct system of mouse SMG.

Productivity and quality of volatile oil extracted from Mentha spicata and M. arvensis var. piperascens grown by a hydroponic system using the deep flow technique.

The purpose of this study was to determine the differences between spearmint (Mentha spicata L.) and Japanese mint (M. arvensis L. var. piperascens Malinv.) cultivated in either soil or nutrient solution using the deep flow technique (DFT). The differences were measured in terms of harvest period (full bloom period) and quantity and chemical components of volatile oils. The spearmint and Japanese mint were cultivated in four different nutrient formulas: plant standard nutrient, plant standard nutrient with an amino acid mixture, plant standard nutrient with a sulphur compound, and a combination of plant standard nutrient with an amino acid mixture and a sulphur compound. We observed that cultivation of spearmint and Japanese mint in nutrient solution using DFT is an effective method to provide high production of volatile oil, since it results in an earlier harvest period and higher quantity of volatile oil. We determined that for spearmint an amino acid mixture is an appropriate nutrient supplement to enhance production of volatile oil with optimum carvone content. Finally, we observed high menthol content in Japanese mint grown in all four nutrient formulas; however, supplementation with a combination of sulphur fertilisation and amino acid mixture yields the highest quantity of volatile oil.