Basal membrane localization of MRP1 in human placental trophoblast

The placental trophoblast is considered to act as a barrier between mother and fetus, mediating the exchange of various materials across the placenta. ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp) and multidrug-resistance protein (MRP) are expressed in the placenta and function as efflux transport systems for xenobiotics. In the present study, we aimed to determine the localization of MRP1 in the human placenta in comparison with that of P-gp. Western blotting analysis with human placental membrane vesicles indicated that P-gp and MRP1 are localized on the brush-border membranes and basal membranes, respectively. Immunohistochemical analysis with human normal full-term placenta showed that anti-P-gp monoclonal antibody F4 stained the brush-border side of the trophoblast cells, whereas anti-MRP1 monoclonal antibody MRPr1 stained the basal side. These results confirm that P-gp and MRP1 are located on the brush-border membranes and basal membranes, respectively, of human full-term placental trophoblast. MRP1 was also detected on the abluminal side of blood vessels in the villi. Accordingly, MRP1 may play a role distinct from that of P-gp, which is considered to restrict the influx of xenobiotics into the fetus.     

Kinetic Analysis of P-Glycoprotein-Mediated Transport by Using Normal Human Placental Brush-Border Membrane Vesicles

Purpose. P-Glycoprotein (Pgp) plays an important role in drug disposition and excretion in various tissues such as the brain, intestine, and kidney. Moreover, we have demonstrated that Pgp is expressed on the brush-border membranes of trophoblast cells in the placenta and restricts drug transfer from the maternal circulation to the fetus. However, the transport kinetics of physiologically expressed Pgp has scarcely been investigated. Methods. In this study, we assessed the functional kinetics of transport mediated by Pgp that is physiologically expressed in normal tissue by using human placental brush-border membrane vesicles (BBMVs). Digoxin and vinblastine were used as typical substrates of Pgp. Results. The uptakes of [³H]digoxin and [³H]vinblastine into BBMVs were significantly increased in the presence of an ATP-regenerating system. The ATP-dependent uptakes of [³H]digoxin and [³H]vinblastine into BBMVs exhibited saturable kinetics. The Michaelis constants (K _t values) were 2.65 ± 1.80 M and 21.9 ± 3.37 M, respectively. In the presence of a Pgp inhibitor such as verapamil, cyclosporine A, or progesterone, the ATP-dependent uptakes of [³H]digoxin and [³H]vinblastine into BBMVs were significantly reduced. Anti-Pgp monoclonal antibody C219 completely inhibited the uptake of [³H]digoxin. Conclusions. The transport kinetics of [³H]digoxin and [³H]vinblastine by physiologically expressed Pgp were successfully evaluated by using BBMVs prepared from normal human placenta. The present method enabled us to evaluate the function of physiologically expressed Pgp and is superior to the use of cultured transfectants in terms of the yield of vesicles. The present method may also be applicable to investigating the influence of various factors such as the genotype of the MDR1 gene or various pathophysiologic states of neonates on the function of Pgp.     

Gestational changes in mechanical properties of skinned muscle tissues of human myometrium

We developed a technique to obtain very thin myometrial muscle strips that allowed comparison of characteristic features of contraction from the same strip under intact and membrane-permeable ("skinned") conditions. Absolute tension development per unit of cross-sectional area induced by high potassium and oxytocin concentrations in the intact condition, or by Ca2+ in the skinned condition, markedly increased in human myometrium at term compared with the nonpregnant state. The maximum tension in skinned strips was 8.3 mN/mm2 in nonpregnant strips and 47.5 mN/mm2 at term (both obtained at 10 mumol/L Ca2+). The Ca2+ sensitivity of the contractile proteins in skinned strips also increased at term compared with the nonpregnant state; the half-maximal response of Ca2+ sensitivity was 0.7 mumol/L in the nonpregnant state and 0.3 mumol/L at term. These results suggest that in human myometrium both the amount of contractile proteins and their sensitivity to Ca2+ may increase at term compared with the nonpregnant state.     

Central administration of neuromedin U suppresses food intake in chicks

The appetite-suppressive action of brain–gut peptides is similar in both chickens and mammals. In mammals, the brain–gut peptide neuromedin U (NMU) suppresses food intake via hypothalamic neuropeptides, corticotropin-releasing factor (CRF), oxytocin, and arginine–vasopressin. In chickens, central administration of CRF, oxytocin, or arginine–vasotocin (AVT, a nonmammalian equivalent of arginine–vasopressin) suppresses food intake. However, the anorexigenic action of NMU in chickens has not yet been identified. In the present study, we analyzed the effects of the central administration of NMU on food intake and hypothalamic mRNA levels of CRF, AVT and mesotocin (a nonmammalian equivalent of oxytocin) in chicks. Intracerebroventricular administration of NMU in chicks significantly suppressed food intake and induced wing-flapping behavior. NMU also significantly upregulated mRNA expression of CRF and AVT, but did not influence mRNA expression of mesotocin in the hypothalamus. These results suggest that NMU functions as an appetite-suppressive peptide via CRF and AVT in the central nervous system in chicks.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from patients with urinary tract infections (2003). III. Secular changes in susceptibility

The bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella spp. and Pseudomonas aeruginosa) isolated from 565 patients diagnosed as urinary tract infections (UTIs) in 14 institutions in Japan were collected between August 2003 and July 2004. The susceptibilities of these bacteria to various antimicrobial agents were examined. The bacteria were divided into 2 groups consisting of uncomplicated UTIs and complicated UTIs (with and without indwelling catheter) based on their isolation origins. The results were compared with those obtained between 1994 and 2002. The drug sensitivity of S. aureus in this year was similar to those in up to the previous years and S. aureus showed the best susceptibility to vancomycin. The drug sensitivity of E. faecalis in this year also was similar to those in up to the previous years. The drug sensitivity of E. coli in this year was generally good except penicillins and was similar to those in up to the previous years. Among cephems, cefozopran (CZOP) and cefpirome (CPR) showed the highest potency activity (MIC90: < or = 0.125 microg/mL). An antibacterial activity of cefotiam (CTM) was stable for 10 years and was fine (MIC0: < or = 0.5 microg/mL). The sensitivity of E. coli to carbapenems and carumonam (CRMN) also was good like to CZOP. The sensitivity of the complicated UTIs group to quinolones, however, has decreased after 2000 and it was suggested that the resistance to the drug has developed. Kiebsiella spp. showed a decrease in the susceptibility to some of cephems. The drugs indicating a big decrease in the sensitivity were cefazolin, CTM, cefaclor, and cefpodoxime. Imipenem, carbapenems, also indicated a decrease in the sensitivity. The susceptibility of the strain to the other drugs was similar to that in up to the previous years. Among them, CZOP maintained good susceptibility (MIC90: > or = 0.125 microg/mL against uncomplicated UTIs, 0.25 microg/mL against complicated UTIs) like meropenem. The drug sensitivity of P. aeruginosa was generally low and was not much different from that in up to the previous years.