PLAC1 Expression Decreases in Chorionic Villi in Response to Labor

PLAC1 (Placenta-Specific 1) is a recently described, trophoblast-expressed gene essential for normal placental development. The protein localizes to the microvillus membrane surface of the syncytiotrophoblast in direct proximity to the maternal compartment. Although its role has not been defined, increased circulating levels of human PLAC1 mRNA in maternal blood are associated with preeclampsia. Furthermore, PLAC1-null mice exhibit decreased viability in the peripartum period suggesting a role in pregnancy maintenance late in gestation. We examined PLAC1 gene expression in the human placenta during normal pregnancy and pregnancies associated with maternal diabetes and preeclampsia using quantitative, real time PCR (q-RT-PCR). Although there was no apparent difference in PLAC1 gene expression among human pregnancies complicated by diabetes or preeclampsia, an unexpected effect of labor was noted at term. PLAC1 expression in placentae delivered vaginally following induced or spontaneous labor was significantly reduced compared to placentae not exposed to labor making it one of only a few placental genes influenced by labor. The significance of this finding is unknown. Viewed in the context of its importance in placental development, however, these findings are consistent with a role for PLAC1 in the maintenance of the maternal-fetal interface.

Lactobacillus casei as a probiotic in malnourished Giardia lamblia-infected mice: a biochemical and histopathological study

The study describes the in vivo activity of Lactobacillus casei in malnourished Giardia lamblia -infected BALB/c mice. By experimentation, it was found that daily administration of the probiotic 7 days before inoculation with Giardia trophozoites in malnourished mice efficiently reduced both the severity and duration of giardiasis. More specifically, excretion of Giardia cysts and trophozoites counts were reduced, while faecal lactobacilli counts increased significantly in probiotic-fed malnourished mice, compared with control mice. Interestingly, it was also observed that oral feeding of the probiotic to malnourished mice abrogated all the anthropometric and biochemical anomalies. Histologically, morphological and cellular alteration of microvillus membrane integrity revealed that probiotic administration ameliorated the mucosal damage in malnourished, probiotic-inoculated, Giardia-infected mice compared with the severe microvillus atrophy, œdematous and vacuolated epithelial cells, and ileitis in malnourished Giardia-infected mice. The results clearly show the antigiardial effect of the probiotic in vivo by modulating the gut cells to inhibit the colonization and multiplication of Giardia trophozoites, thus reducing the severity and duration of murine giardiasis.

Region-specific ontogeny of α-2,6-sialyltransferase during normal and cortisone-induced maturation in mouse intestine

Regional differences in the ontogeny of mouse intestinal α-2,6-sialyltransferase activities (α-2,6-ST) and the influence of cortisone acetate (CA) on this expression were determined. High ST activity and α-2,6-ST mRNA levels were detected in immature small and large intestine, with activity increasing distally from the duodenum. As the mice matured, ST activity (predominantly α-2,6-ST) in the small intestine decreased rapidly to adult levels by the fourth postnatal week. CA precociously accelerated this region-specific ontogenic decline. A similar decline of ST mRNA levels reflected ST activity in the small, but not the large, intestine. Small intestinal sialyl α-2,6-linked glycoconjugates displayed similar developmental and CA induced-precocious declines when probed using Sambucus nigraagglutinin (SNA) lectin. SNA labeling demonstrated age-dependent diminished sialyl α2,6 glycoconjugate expression in goblet cells in the small (but not large) intestine, but no such regional specificity was apparent in microvillus membrane. This suggests differential regulation of sialyl α-2,6 glycoconjugates in absorptive vs. globlet cells. These age-dependent and region-specific differences in sialyl α-2,6 glycoconjugates may be mediated in part by altered α-2,6-ST gene expression regulated by trophic factors such as glucocorticoids.

Effects of sulfate and chloride on three separate oxalate transporters reconstituted from rabbit renal cortex

Understanding the mechanism of sulfate-dependent, oxalate-stimulated chloride reabsorption in the mammalian proximal tubule is complicated by the presence of multiple oxalate and sulfate transport pathways. Accordingly, we developed a method of reconstituting functional oxalate transport from the rabbit renal cortex so that the individual transporters might be examined. Solubilized microvillus membrane proteins were separated by hydroxyapatite chromatography and then reconstituted into proteoliposomes. Two peaks of oxalate/oxalate exchange activity were observed. Sulfate (10 mM) cis-inhibits oxalate transport in the early peak by 93% and in the later peak by 41%. In contrast, 20 mM chloride inhibits oxalate/oxalate exchange by only 32% in the early peak but inhibits oxalate exchange by 70% in the later peak. Oxalate-stimulated sulfate uptake was observed in the early fractions but not in the later fractions. These data are consistent with the recovery of the sulfate/oxalate exchanger in the early hydroxyapatite fractions and the chloride/oxalate exchanger in the later fractions. The basolateral membrane sulfate/oxalate exchanger was also reconstituted. The reconstituted basolateral and apical membrane sulfate/oxalate exchangers demonstrate nearly identical patterns of substrate specificities. However, 98% of apical sulfate/oxalate exchange activity is lost following exposure to octylglucoside at room temperature, whereas the basolateral sulfate/oxalate exchange activity was reduced 67% ( P < 0.05). In conclusion, functional reconstitution of solubilized membrane proteins demonstrates that apical membrane chloride/oxalate exchange and sulfate/oxalate exchange are mediated by different transport proteins. Apical and basolateral sulfate/oxalate exchange may also represent transport on two separate exchangers.