牛奶和钙盐在胃肠道内的钙吸收

目的和方法目前尚不清楚，摄入非水溶性钙盐的钙吸收是否比摄入水溶性差的钙盐钙吸收更好；另外也不清楚，牛奶制品的钙吸收是否比钙盐钙吸收更好。作者采用一种单次服用就能精确测定钙的净吸收率的方法，给８例健康空腹受试者服用含５００mg钙的５种不同水溶性的钙盐和牛奶，服用顺序是随机的。结果按钙盐的水溶性递减次序排列，以平均钙的净吸收率±标准误表示：醋酸钙（３２±４）％，乳酸钙（３２±４）％，葡萄糖酸钙（２７±３）％，柠檬酸钙（３０±３）％；碳酸钙（３９±３）％。按方差分析，钙盐和牛奶的钙吸收率差异无统计学意义…     

Granulocyte-macrophage colony-stimulating factor mRNA stabilization enhances transgenic expression in normal cells and tissues

To increase transgenic production of granulocyte-macrophage colony- stimulating factor (GM-CSF), we mutated the mRNA's 3'-untranslated region, AUUUA instability elements. Expression vectors containing human or murine GM-CSF cDNAs coding for wild-type (GM-AUUUA) or mutant versions with reiterated AUGUA repeats (GM-AUGUA) were transfected into cells in culture or animals using particle-mediated gene-transfer technology. Normal peripheral blood mononuclear cells accumulated 20- fold greater levels of GM-CSF mRNA and secreted comparably greater amounts of cytokine after transfection with hGM-AUGUA expression vectors versus hGM-AUUUA. hGM-AUGUA mRNA was fivefold more stable (t 1/2 = 95 minutes) than hGM-AUUUA mRNA (t 1/2 = 20 minutes), accounting for elevated steady-state levels. Transfection site extracts and serum samples obtained 24 hours after gene transfer of hGM-AUGUA cDNA into mouse skin contained greater than 32 ng/mL and 650 pg/mL of GM-CSF protein, respectively, compared with 0.33 ng/mL and less than 8 pg/mL for hGM-AUUUA cDNA. GM-CSF produced from mGM-AUGUA cDNA transfected into rat abdominal epidermis induced a profound neutrophil infiltrate. These data suggest a novel strategy for enhanced production of biologically active cytokines by normal cells after in vivo gene transfer.