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- Bengtsson, Jörgen, 1976-
(författare)
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Developmental Aspects of Drug Transport Across the Blood-Brain Barrier
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The developmental aspect of drug transport across the blood-brain barrier (BBB) was investigated. Microdialysis was used to study unbound morphine BBB transport at different ages in sheep. An in vitro study was performed to find differentially expressed genes in brain capillary-rich fractions of the brain in rats of different ages. Microdialysis and brain-to-plasma ratios were used to study the contribution of breast cancer resistance protein (Bcrp) to the transport of nitrofurantoin (NTF) across the BBB of rats during development as well as in adult rats and mice. A method of analysing morphine and its metabolites in plasma and microdialysis samples was developed and validated. The in vivo recovery of deuterated morphine, used as a calibrator in microdialysis experiments, was not affected by the presence of morphine in the tissue. A net influx of morphine was observed in premature lambs and adult sheep, in contrast to the efflux seen in other species. This influx decreased with age, indicating that the morphine transport across the BBB changes with age. In contrast, the transport of the morphine metabolite morphine-3-glucuronide (M3G) did not change with age. Microarray data indicated that several active transporters are differentially expressed with age. Moreover, the mRNA expression levels of Abcg2 (Bcrp) and Slc22a8 (organic anion transporter 3) changed with age when quantified using real-time polymerase chain reaction. In contrast, the expression of Abcb1 (P-glycoprotein) and occludin (a tight junction protein) did not change with age. In rats, the brain distribution of NTF decreased with age due to increased protein binding in plasma. The concentration ratio of unbound NTF across the BBB was low in the adult rat, due to intra-brain metabolism and/or efflux by other transporters. Bcrp did not appear to have a significant contribution in the developing rat or in knock-out mice compared to wild-type controls with regard to NTF BBB transport. In conclusion, in vitro studies showed that the expression levels of some genes changed with age, presumably affecting subsequent drug distribution to the brain. Further, in vivo studies showed that distribution across the BBB changed with age for morphine but not for M3G or NTF.
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| 2. |
- Bengtsson, Jörgen, 1976-, et al.
(författare)
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Differences in gene expression in the developing rat brain using cDNA microarray and real-time PCR
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The blood-brain barrier (BBB) is formed by endothelial cells, connected by tight junction proteins restricting paracellular transport. Transport of substances into the brain may also be limited due to active efflux transporters. Not much is known about the development of tight junction proteins and active transporters in the BBB, and how this affects drug distribution to the brain at different ages. The aim of this study was to analyze possible differences in expression of tight junction proteins and active transporters in the BBB at different postnatal ages in the rat. Brain capillary-rich fractions (BCRF) were collected and gene expression levels were compared at three postnatal ages using microarray analysis. BCRF was also analyzed for the mRNA expression levels of P-gp Abcb1 (P-gp), Abcg2 (Bcrp), Slc22a8 (Oat3) and occludin using real-time PCR at 12 different postnatal ages between postnatal Day 1 and Adult. In the array analysis, 28 genes of interest were found to be differentially expressed. The mRNA levels of Abcg2 decreased to one seventh from postnatal Day 1 to Day 15. The levels of Slc22a8 increased from birth and reached a plateau at Day 3 - 12 followed by a decrease to Day 15. These findings show that active transporters are differentially expressed in the developing BBB, possibly affecting drug distribution to the brain. No change in the mRNA levels for Abcb1 or occludin was observed.
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| 3. |
- Geranmayeh, Fatemeh, et al.
(författare)
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Microglia in gemistocytic astrocytomas
- 2007
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Ingår i: Neurosurgery. - 0148-396X .- 1524-4040. ; 60:1, s. 159-166
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Although gemistocytic astrocytomas, they behave more aggressively than other astrocytomas. Their proliferative potential is low, and it remains an intriguing question why these tumors are so biologically "successful". They show a high mutation rate of the P53 gene, cytological abnormalities, and frequent perivascular mononuclear infiltrates. Microglial cells, a feature of this astrocytoma variant, are of increasing interest in the context of glioma growth. Methods: We selected 23 tumor biopsies from 201 samples obtained from patients with gemistocytic astrocytomas operated at Mayo Clinic between 1985 and 1998. These tumors were formerly anaylzed for P53 mutations, P53 protein, and proliferative activity (9). Immunolabeling for three microglial markers, including CR3/43, Ki-M1P, and iba1, was performed on adjacent tissue sections. In additions, in situ hybridization for the alpha-chain of the major histocompatibility complex (MHC) Class II molecule recognized by the CR3/43 monoclonal antibody was performed. Results: A high number of microglia was detected in gemistoccytic astrocytomas. More microglia were present if the fraction of gemistocytic tumor cells was high (correlation coefficient = 0.699; P < 0.0002). Interestingly, a number of gemistocytes were immunoreactive for MHC Class II molecules, an observation confirmed by in situ hybridization. Importantly, the higher the number of Class II immunoreactive gemistocytes, the fewer Class II positive microglial cell could be detected (correlation coefficient = -0.5649; P < 0.005). Conclusion: Our results support the view that gemistocytic astrocytomas contain unusually high numbers of microglial cells. We propose that the finding of aberrant MHC Class II expression by gemistocytic tumor cells correlates with a loss of immune-competent MHC Class II-expressing microglia. This may be related to the expecially poor prognosis of gemistocytic astrocytomas for which induction of T cell anergy could provide one explanation.
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