The ATP-binding cassette (ABC) transporter 2 (ABCG2) is expressed by stem cells in many organs and in stem cells of solid tumors. These cells are isolated based on the side population (SP) phenotype, a Hoechst 3342 dye efflux property believed to be conferred by ABCG2. Because of the limitations of this approach we generated transgenic mice that express Nuclear GFP (GFPn) coupled to the Puromycin-resistance gene, under the control of ABCG2 promoter/enhancer sequences. We show that ABCG2 is expressed in neural progenitors of the developing forebrain and spinal cord and in embryonic and adult endothelial cells of the brain. Using the neurosphere assay, we isolated tripotent ABCG2-expressing neural stem cells from embryonic mouse brain. This transgenic line is a powerful tool for studying the expression of ABCG2 in many tissues and for performing functional studies in different experimental settings. 相似文献
A markedly reduced blood flow, an elevation of hematocrit and an increased aggregability of erythrocytes [red blood cells
(RBCs)] are risk factors for venous thrombus formation (intravascular blood coagulation). However, these risk factors alone
seem to be insufficient to stimulate the coagulation cascade in the absence of a primary triggering mechanism. In this paper,
our rheological and biochemical studies on blood coagulation, especially focusing on procoagulant activity of RBCs, are summarized.
It is shown that the intrinsic coagulation pathway is triggered by the activation of factor IX (F-IX) by RBCs. The F-IX-activating
enzyme in normal human erythrocyte (RBC) membranes was purified, identified and characterized. The activation of F-IX by RBCs
was enhanced by a decrease in flow shear rate and an elevation in hematocrit. The procoagulant ability of RBCs and coagulation
of blood obtained from individuals with a relatively high level of hypercoagulability were enhanced compared with those for
normals. The studies demonstrated a new triggering mechanism for coagulation or thrombus formation that may occur under stagnant
flow conditions. 相似文献
Since the results of the women health initiative study showing an overall negative risk-benefit ratio with 0.625 mg of conjugated estrogens plus 2.5 mg of medroxyprogesterone acetate, the use of the lowest effective dose of steroids in hormone replacement therapy (HRT) is recommended.
A low-dose regimen appears to induce less side effects such as breast tenderness or leg pain than do higher dose preparations.
The decrease in hot flashes with low-dose estrogens, range 60–70%, is less than the 80–90% reduction with standard dosing. But this mean that 60–70% of menopausal women do not need higher doses.
The same applies to bone preservation which is dose dependent: the number of non-respondant women will be higher than with standard doses. However, randomized double-blind, placebo controls trials have defined positive effects on bone of low doses of HRT with adequate calcium and Vitamin D in elderly women. The use of bone densitometry and of biochemical markers of bone turnover is mandatory in women using low or ultra-low-dose preparations.
In spite of the lack of trials conducted with low-dose HRT, this treatment seems to be safer:
• the plasma levels of estradiol are lower; as far as breast cancer risk is concerned, the decrease of this subrogate marker is considered as favourable;
• the increase in breast density is less pronounced;
• the nurses's health study found a dose relationship for stroke, with no increase in risk with low-dose of estrogens;
• the effects on subrogate markers of cardiovascular risk seem to be more favourable.
Beside the low-dose HRT, one must consider some other facts:
• the “critical window” theory: it is biologically plausible that HRT, if started early after the menopause can slow the progression of coronary atherosclerosis;
• the way of administration of HRT: some observational studies have shown no increase in the risk of venous thromboembolism risk among women treated with transdermal estrogens;
• the progestogen used: a French cohort study recently performed found no increase in breast cancer risk with the use of micronized progesterone meanwhile the increase in risk observed with other progestogens was similar to the findings of the WHI study.
In the future, it is conceivable that more comprehensive pharmacogenomic studies will lead to effective algorithms for individualizing the right dose of steroids to be used in HRT. 相似文献
Several studies have demonstrated that the myenteric plexus experiences quantitative and morphometric changes in rats inoculated orally with Toxoplasma gondii. This paper aims to verify if these alterations are also seen when the same animals are inoculated intraperitoneally with the parasite. In order to do that, six Wistar rats (Rattus norvegicus) 60 days of age were infected intraperitoneally with 106 tachyzoites of a genotype I T. gondii strain (BTU IV). After 60 days, the animals were anaesthetised and underwent laparotomy. All organs from the small and large intestines were removed, measured, dissected and underwent whole-mount Giemsa technique to stain the neurons in the myenteric plexus. A quantitative and morphometric analysis of these cells was made, and it showed that the parasite causes the death of myenteric neurons in the jejunum and morphometric alterations in these cells throughout the intestine. However, the cellular response of myenteric neurons to T. gondii is heterogeneous compared the different organs from the gut. 相似文献
To investigate the venoconstrictor effect of angiotensin II (Ang II) in spontaneously hypertensive rats (SHR), we used preparations of mesenteric venular beds and the circular muscle of the portal veins. Vessels were tested with Ang II in the presence or absence of losartan, PD 123319, HOE 140, L-NAME, indomethacin, or celecoxib. In the mesenteric venular bed of SHR, the effect of Ang II (0.1 nmol) was nearly abolished by losartan and enhanced by HOE 140, indomethacin, and celecoxib, while PD123319 and L-NAME had no effect. In portal vein preparations, cumulative-concentration response curves (CCRC) to Ang II (0.1–100 nmol/L) exhibited a lower maximal response (Emax) in SHR compared to Wistar rats. AT1 receptor expression was similar in the two strains, while AT2 receptor levels were lower in SHR portal veins when compared to Wistar. In SHR portal veins, losartan shifted the CCRC to Ang II to the right, while indomethacin and HOE 140 increased the Emax to Ang II. PD 123319, celecoxib, and L-NAME had no effect. Taken together, our results suggest that Ang II-induced venoconstriction in SHR is mediated by activation of AT1 receptors and this effect may be counterbalanced by kinin B2 receptor and COX metabolites. Furthermore, our data indicate that there are different cellular and molecular mechanisms involved in the regulation of venous tonus of normotensive and hypertensive rats. These differences probably reflect distinct factors that influence arterial and venous bed in hypertension. 相似文献
The release of cholesterol from choroid plexus epithelial cells (CPE) plays an important role in cholesterol homeostasis in the CSF. The purpose of this study was to clarify the molecules involved in cholesterol release in CPE and the regulation mechanisms of the cholesterol release by the liver X receptor (LXR) using a conditionally immortalized CPE line (TR-CSFB3). The mRNA expression of LXRalpha, LXRbeta and their target genes, ATP-binding cassette transporter (ABC)A1, ABCG1, ABCG4 and ABCG5, were detected in rat choroid plexus. ABCA1 and ABCG1 protein were detected in the plasma membrane of TR-CSFB3 cells. Following treatment with 24S-hydroxycholesterol, an endogenous LXR ligand, the expression of ABCA1 and ABCG1 were induced in TR-CSFB3 cells. Moreover, apolipoprotein (apo)AI- and high-density lipoprotein (HDL)-mediated cholesterol release to the apical side of TR-CSFB3 cells was facilitated by this treatment, whereas that to the basal side was not affected. Following 24S-hydroxycholesterol treatment, apoE3-dependent cholesterol release from TR-CSFB3 cells was enhanced more than the apoE4-dependent release. These results suggest that LXR activation facilitates cholesterol release into the CSF from CPE through the functional induction of ABCA1 and ABCG1. The difference between apoE3 and apoE4 suggests that the cholesterol release from CPE is related to the development of neurodegenerative diseases. 相似文献