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001-es BibID:BIBFORM029894
Első szerző:Fekete István (neurológus, pszichiáter)
Cím:Rate of buthionine sulfoximine entry into brain and xenotransplanted human gliomas / Istvan Fekete, Owen W. Griffith, Kurt E. Schlageter, Darell D. Bigner, Henry S. Friedman, Dennis R. Groothuis
Dátum:1990
ISSN:0008-5472
Megjegyzések:Buthionine sulfoximine (BSO) is an inhibitor of glutathione synthesis and can be used to potentiate the effects of chemotherapeutic alkylating agents and radiotherapy. We examined the rates of influx and efflux of [35S]BSO administered to athymic mice with and without xenografted D-54MG human gliomas. Three analytic approaches were applied to the experimental data to obtain values of the blood-to-tissue influx constant, K1, of BSO. Multiple time point experiments in tumor-bearing mice were analyzed with a two-compartment model and nonlinear fitting routines, and by graphical analysis which assumed no backflux of BSO from tissue to blood. A third approach used single time point data in nontumor-bearing mice and assumed no backflux. Calculated values of the K1 of BSO ranged from 0.23 to 1.35 microliters/g/min in tumor-free cortex, and from 5.3 to 6.3 microliters/g/min in the D-54MG gliomas. The tissue-to-blood efflux constant, k2, was zero in both cortex and tumor, suggesting that BSO entered cells and was trapped once it crossed the blood-brain barrier. Estimates of plasma vascular space (Vp) ranged from 2 to 20 microliters/g in cortex, and from 103 to 169 microliters/g in tumor. Another set of experiments, done in normal mice with different doses of BSO, suggested that BSO competes for neutral amino acid transport sites at the blood-brain barrier, but that the capacity of the carrier-mediated transport system is low and saturates at administered doses of about 0.5 mmol/kg (corresponding to plasma concentrations of about 12 mumol/ml). The rate of entry into brain was proportional to the octanol/water partition coefficient and molecular weight of BSO, which also supports passive diffusion as the means of entry. Consequently, although the rate of BSO entry into D-54MG gliomas was between 4 and 30 times higher than the rate of entry into tumor-free cortex, the results of these experiments suggest that most of the BSO that enters brain tumors in the doses commonly used in experimental situations will cross capillaries by passive diffusion.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
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Megjelenés:Cancer Research. - 50 : 4 (1990), p. 1251-1256. -
További szerzők:Griffith, Owen W. Schlageter, Kurt E. Bigner, Darell Friedman, Henry S. Groothuis, Dennis
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2.

001-es BibID:BIBFORM029725
Első szerző:Groothuis, Dennis
Cím:The effect of an amino acid-lowering diet on the rate of melphalan entry into brain and xenotransplanted glioma / Groothuis D. R., Lippitz B. E., Fekete I., Schlageter K. E., Molnar P., Colvin O. M., Roe C. R., Bigner D. D., Friedman H. S.
Dátum:1992
ISSN:0008-5472
Megjegyzések:Melphalan (L-phenylalanine mustard, L-PAM, alkeran; molecular weight, 305,000) is transported across tumor cell membranes and the blood-brain barrier by the large neutral amino acid (LNAA) transport system. Normally, plasma LNAA levels are high enough and the affinity low enough that this system does not transport much melphalan into the brain. However, plasma amino acids can be reduced by fasting and protein-free diet. We used this method to reduce competition and to increase melphalan transport into brain tumors. In nude mice fasted for 12 h and then fed a protein-free diet for 2 and 6 h, mean plasma LNAA levels were 46% and 42% of control values. Nude mice with xenotransplanted D-54MG human gliomas were used to study tissue distribution and uptake kinetics of [3H]melphalan in a control group and a diet group (after a 12-h fast and 2 h of a 0% protein diet). The K1 (blood-to-tissue transfer constant) of melphalan, determined by graphical analysis and by nonlinear fitting to a 2-compartment model, was higher in the diet group in all tumor regions except the necrotic center of subcutaneous tumors; the increase was significant in the tumor periphery of brain and s.c. tumors. The ratio of K1s (diet to control) varied from 1.2 to 1.3 in brain tumors, 1.9 to 2.1 in subcutaneous tumors, and 1.8 to 3.1 in tumor-free brain. The apparent [3H]melphalan distribution space was significantly higher in the tumor periphery of both brain and subcutaneous tumors of the 15- and 30-min diet group. We also measured blood-brain barrier transport of [alpha-14C]aminoisobutyric acid and blood flow (with [131I]iodoantipyrine): the K1 of [alpha-14C]aminoisobutyric acid was 28.1 +/- 6.6 (SE) in brain tumors and 24.3 +/- 8.9 microliters/g/min in subcutaneous tumors. Blood flow was 58.2 --> 3.9 in brain tumors and 5.2 +/- 0.4 ml/100 g/min in subcutaneous tumors. Fasting, when combined with a protein-free diet, reduces plasma amino acid levels and thereby reduces competition between melphalan and LNAAs. This may increase the amount of melphalan that can enter a brain tumor without increasing the administered drug dose and suggests a therapeutic manipulation that can be used to increase the delivery of melphalan.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Cancer Research. - 52 : 20 (1992), p. 5590-5596. -
További szerzők:Lippitz, Bodo E. Fekete István (1951-) (neurológus, pszichiáter) Schlageter, Kurt E. Molnár Péter Pál (1951-) (pathológus) Colvin, Michael O. Roe, Charles R. Bigner, Darell Friedman, Henry S.
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3.

001-es BibID:BIBFORM029720
Első szerző:Molnár Péter Pál (pathológus)
Cím:Absence of host-site influence on angiogenesis, blood flow, and permeability in transplanted RG-2 gliomas / Molnar P., Fekete I., Schlageter K. E., Lapin G. D., Groothuis D. R.
Dátum:1999
ISSN:0090-9556
Megjegyzések:The host site is believed to regulate tumor angiogenesis, which could result in site-dependent drug delivery parameters, greatly affecting experimental tumor research. In RG-2 rat gliomas we measured cellular proliferation; cell cycle time was the same for RG-2 cells in brain and s.c. tumors (25 h), and was the same for endothelial cells in these tumors (46 h). We measured the transcapillary transfer constant (K) of alpha-aminoisobutyric acid and blood flow (F) with iodoantipyrine in RG-2 gliomas transplanted into brain, liver, kidney, muscle, s.c. tissue, and into the abdominal cavity. Data was evaluated by quantitative autoradiography and direct tissue sampling. The variation of F (12.6-84.0 ml/g/min) and K (26.1-49.2 microl/g/min) in RG-2 tumors in the different host sites was less than in surrounding tumor-free tissue (F = 20-1500 ml/g/min and K = 1.6-700 microl/g/min). In contrast to other models, RG-2 does not result in tumors with host site-dependent behavior. The RG-2 tumor cells appear to participate in, if not dominate, the angiogenesis process regardless of the host site. Values of F and K were more dependent on tumor topography (center versus periphery) and local histological features (necrosis versus viable tumor) than host site. We believe that the methods used for data acquisition may introduce as much variability in Results as the tumors themselves and that to better understand how tumor angiogenesis affects the vascular phenotype, comparative studies are needed to validate the results obtained with newer methodologies.
Tárgyszavak:Orvostudományok Klinikai orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Drug Metabolism And Disposition. - 27 : 9 (1999), p. 1085-1091. -
További szerzők:Fekete István (1951-) (neurológus, pszichiáter) Schlageter, Kurt E. Lapin, Gregory D. Groothuis, Dennis
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