AIM: To examine the effect of increasing dietary zinc (Zn) intake and the lack of metallothionein (MT) expression on activity of small intestinal disaccharidases. METHODS: MT-Ⅰ and Ⅱ knockout (MT-/-) and wild-type (...AIM: To examine the effect of increasing dietary zinc (Zn) intake and the lack of metallothionein (MT) expression on activity of small intestinal disaccharidases. METHODS: MT-Ⅰ and Ⅱ knockout (MT-/-) and wild-type (MT+/+) female mice at 3.5 wk of age were randomly fed with a diet containing 2 (2 Zn), 15 (15 Zn) or 50 (50 Zn) mg Zn/kg (n = 8/group/genotype) for 5 wk. Small intestinal segments (duodenum, jejunum and ileum) were collected and either fixed in 10% formalin for histological analysis or snap frozen in liquid nitrogen for sucrase, lactase and maltase activity analyses.RESULTS: Plasma Zn was significantly (P < 0.05) lower (33%) in MT-/- compared with MT+/+ mice fed the 2 Zn diet. Villus height and crypt depth were increased by approximately 15% in MT+/+ mice compared with MT-/- mice. Duodenal disaccharidase activities were significantly higher in MT+/+ compared with MT-/- mice particularly in those fed the 2 Zn diet. For the 50 Zn diet, jejunal sucrase and lactase activities were significantly higher in MT-/- (13 313 ± 2314; 4107 ± 364 μmol glucose/well/min/g tissue, respectively) compared with MT+/+ mice (7054 ± 608; 1818 ± 174). Similarly, ileal lactase activities were higher in MT-/- (1480 ± 192) compared with MT+/+ (629 ± 353) mice particularly those fed the 2 Zn diet. CONCLUSION: Increasing dietary Zn has little effect on disaccharidases activity in MT wild-type mice. The presence of MT may enhance morphological and functional development of the gut.展开更多
The effect of sex hormones on the biogenesis of brain tubulin has been studied in the ovariectomized middle-aged and ovary-intact old-aged female mouse.The results show the much stronger role estrogen plays in stimula...The effect of sex hormones on the biogenesis of brain tubulin has been studied in the ovariectomized middle-aged and ovary-intact old-aged female mouse.The results show the much stronger role estrogen plays in stimulating tubulin synthesis than testosterone. Estradiol increased the contents of brain tubulin by 15%-41%. Estradiol and progesterone together can produce a 23%-49% increase. Maybe this experiment revealed a kind of new action of estrogen, i.e., stimulates brain tubulin syntheses in adult mouse.It is important that the effect of estrogen on stimulating tubulin synthesis takes place after the critical period of brain development. All of these mean that estrogen still plays its role in stimulating tubulin synthesis wile thyroid hormones can't play this kind of role during this time.展开更多
基金Supported by (in part) the MS McLeod Post-Doctoral Fellowship obtained from the Women’s and Children’s Hospital Foundation (to Tran CD)
文摘AIM: To examine the effect of increasing dietary zinc (Zn) intake and the lack of metallothionein (MT) expression on activity of small intestinal disaccharidases. METHODS: MT-Ⅰ and Ⅱ knockout (MT-/-) and wild-type (MT+/+) female mice at 3.5 wk of age were randomly fed with a diet containing 2 (2 Zn), 15 (15 Zn) or 50 (50 Zn) mg Zn/kg (n = 8/group/genotype) for 5 wk. Small intestinal segments (duodenum, jejunum and ileum) were collected and either fixed in 10% formalin for histological analysis or snap frozen in liquid nitrogen for sucrase, lactase and maltase activity analyses.RESULTS: Plasma Zn was significantly (P < 0.05) lower (33%) in MT-/- compared with MT+/+ mice fed the 2 Zn diet. Villus height and crypt depth were increased by approximately 15% in MT+/+ mice compared with MT-/- mice. Duodenal disaccharidase activities were significantly higher in MT+/+ compared with MT-/- mice particularly in those fed the 2 Zn diet. For the 50 Zn diet, jejunal sucrase and lactase activities were significantly higher in MT-/- (13 313 ± 2314; 4107 ± 364 μmol glucose/well/min/g tissue, respectively) compared with MT+/+ mice (7054 ± 608; 1818 ± 174). Similarly, ileal lactase activities were higher in MT-/- (1480 ± 192) compared with MT+/+ (629 ± 353) mice particularly those fed the 2 Zn diet. CONCLUSION: Increasing dietary Zn has little effect on disaccharidases activity in MT wild-type mice. The presence of MT may enhance morphological and functional development of the gut.
文摘The effect of sex hormones on the biogenesis of brain tubulin has been studied in the ovariectomized middle-aged and ovary-intact old-aged female mouse.The results show the much stronger role estrogen plays in stimulating tubulin synthesis than testosterone. Estradiol increased the contents of brain tubulin by 15%-41%. Estradiol and progesterone together can produce a 23%-49% increase. Maybe this experiment revealed a kind of new action of estrogen, i.e., stimulates brain tubulin syntheses in adult mouse.It is important that the effect of estrogen on stimulating tubulin synthesis takes place after the critical period of brain development. All of these mean that estrogen still plays its role in stimulating tubulin synthesis wile thyroid hormones can't play this kind of role during this time.
