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Biomedical subjects

B W Fox

Publications and source records attributed to B W Fox.

At least 55 records · Page 3Linked to original sources
PubMed1984

Collateral sensitivity of a methotrexate-resistant L1210 cell line to the vinca alkaloids.

L1210 mouse leukaemia cell lines showing a 20,000-fold differential sensitivity to methotrexate have been shown to exhibit some collateral sensitivity to at least two of the vinca alkaloids, vinblastine and vindesine. Vinblastine is the more cytotoxic for both cell lines. The extent of the collateral sensitivity decreases in the order vindesine greater than vinblastine greater than vincristine. Total cellular uptake studies with radiolabelled methotrexate showed only a two- to three-fold greater incorporation in the sensitive line. On the other hand, a two-fold greater incorporation of labelled vincristine occurred in the resistant line. No significant difference in the uptake occurred following labelled vinblastine treatment by the two cell lines. It is unlikely that differences in uptake account for the altered drug responses observed in the two cell lines.

Animals↗
PubMed1984

The effect of vinca alkaloids in enhancing the sensitivity of a methotrexate-resistant (L1210/R7A) line, studied by flow cytometric and chromosome number analysis.

Two L1210 murine lymphoma cell lines sensitive and resistant to methotrexate (L1210 and L1210/ R7A , respectively) and previously shown to exhibit collateral sensitivity to the vinca alkaloids have been studied by flow cytofluorimetric techniques following propidium iodide staining of the DNA. Following treatment with a range of concentrations of vincristine, both cell lines showed a build-up of fluorescence in the 4n position. However, the methotrexate-resistant cell line exhibited this effect at lower doses of vincristine. On an equimolar basis, the vinca alkaloids ranked for intensity of this effect in the order vinblastine greater than vindesine greater than vincristine. DNA fluorescent histograms following various times of continuous exposure to vincristine showed an accumulation of material at the 8n position, which was shown by chromosome analysis to be due to polyploidy. It was concluded that methotrexate-resistant cells (L1210/ R7A ) experience difficulty in traversing mitosis and this difficulty is enhanced by the vinca alkaloids.

Animals↗
PubMed1984

The use of a fluorescent methotrexate probe to monitor the effects of three vinca alkaloids on a mixed population of parental L1210 and gene-amplified methotrexate-resistant cells by flow cytometry.

Cells resistant to methotrexate (L1210/R7A) and possessing an increased level of dihydrofolate reductase due to gene amplification can be detected by the technique of flow cytofluorimetry using a new fluorescent derivative of methotrexate (F-MTX) based on a putrescine linker. Comparative studies of dihydrofolate reductase enzyme and cell growth inhibition following treatment with methotrexate and F-MTX suggest that the two agents possess similar modes of action. In an artificially mixed population of cells sensitive and resistant to methotrexate it is possible, using F-MTX, to recognise and separate distinct cell subpopulations showing differential fluorescence using a fluorescence-activated cell sorter (FACS IV). The selective removal of the resistant cells within a mixed population of sensitive and resistant cells has been demonstrated for 5 X 10(-8) M vinblastine by means of flow cytometry. The effectiveness of the vinca alkaloids decreases in the order vinblastine greater than vindesine greater than vincristine, which previously was shown to be the order of effectiveness in producing collateral sensitivity.

Animals↗
PubMed1983

DNA-DNA interstrand crosslinking by dimethyanesulphonic acid esters. Correlation with cytotoxicity and antitumour activity in the Yoshida lymphosarcoma model and relationship to chain length.

Members of the homologous series of nine antitumour dimethanesulphonic acid esters, with the exception of ethylene dimethanesulphonate (EDMS), were found to cause DNA-DNA interstrand crosslinking in cells derived from the transplantable rodent Yoshida lymphosarcoma. The ability of the series to induce interstrand crosslinks was compared with in vitro cytotoxicity and in vivo antitumour activity and is discussed in relation to their chain length and ability to span critical target distances in DNA.

Animals↗
PubMed1983

Comparative studies of the uptake of daunorubicin in sensitive and resistant P388 cell lines by flow cytometry and biochemical extraction procedures.

The intracellular accumulation of daunorubicin as determined by flow cytometry correlates well with that as determined by extraction of the drug from cell homogenates. Two P388 mouse leukaemia cell lines showing differential sensitivity to the drug have been used to investigate the transport changes associated with resistance. Resistance to daunorubicin in these cell lines occurs through an alteration in the intracellular accumulation of the drug, resulting from the increased efflux of the anthracycline from the resistant cells. The effect of temperature, drug concentration, pH, and metabolic inhibitors on this process have been investigated. Uptake by a carrier-mediated process of the un-ionised form of the drug (pK = 8.25), coupled with an energy-dependent efflux process, is proposed as the mechanism of cellular accumulation in the case of the resistant cell line.

Animals↗
PubMed1983

Blood clearance of radioactively labelled cis-diammine 1,1-cyclobutane dicarboxylate platinum (II) (CBDCA) in cancer patients.

The blood and urinary clearances of cis-diammine 1,1-cyclobutane dicarboxylate platinum(II) (CBDCA, JM8) were determined in four patients with malignancy. A 40 muCi iv injection of 191 Pt/193 Pt (3:1)-labelled CBDCA was followed by serial blood and urine sampling to 72 h. The blood clearance was triphasic, mean values for the fast, intermediate, and slow phases being 10.8 min, 2.5 h, and 125 h, respectively. The fraction of activity excreted in the urine within the first 6 h had a mean value of 66.7%, contrasting with 26.4% for cisplatin. There was only a small fraction of CBDCA excreted by the slow phase (1.5%) as against an average of 20% for CHIP and 27% for cisplatin. The early and rapid renal clearance of CBDCA may account for reduced nephrotoxicity.

Antineoplastic Agents↗
PubMed1982

Repair of DNA interstrand crosslinks after busulphan. A possible mode of resistance.

The technique of alkaline elution has been used to study the interaction between the antineoplastic drug busulphan and the DNA of cells derived from the transplantable rodent Yoshida sarcoma. A dose-dependent proteinase-resistant filter retention was observed after drug treatment, which indicated the presence of DNA interstrand cross-links. Such cross-links were removed after 6 h in cells resistant to busulphan but not in the busulphan-sensitive parent cells, even after 24 h. Such temporal differences in DNA cross-linking could be correlated with cell survival and also with the level of anaphase chromosome aberrations, which was found to be four-fold higher in the sensitive line than in the resistant line.

Animals↗
PubMed1982

Blood clearance of three radioactively labelled platinum complexes: cis-dichlorodiammine platinum II, cis, trans-dichlorodihydroxy-bis-(isopropylamine) platinum IV, and cis-dichloro-bis-cyclopropylamine platinum II, in patients with malignant disease.

The blood clearances of three platinum compounds, cis-dichlorodiammine platinum II (DDP), cis, trans-dichloro-dihydroxy-bis-(isopropylamine) platinum IV (CHIP), and cis-dichloro-bis-cyclopropylamine platinum II (CP), were determined in nine patients with malignant disease. The complexes were prepared using radioactive platinum (191Pt and 193Pt). A 10-mu Ci dose of each complex, containing the equivalent of 1-2 mg elemental platinum, was injected IV into groups of three patients. Serial blood and urine samples were collected over 72 h. No obvious difference was found between the three complexes for blood clearance, median t1/2a being 16.8 (range 11.2-23.5) min and median t1/2 beta 89 (range 63.7-127) h. The urinary excretion was greatest for CHIP, 60% of injected dose as against 42.6% for CP and 38.8% for DDP. Differences in renal excretion of DDP analogues could indicate potentially less nephrotoxic agents. The use of radioactive Pt will allow in vivo dynamic imaging of the distribution of platinum compounds in areas of interest.

Aged↗
PubMed1982

The effects of bifunctional alkylating agents on DNA synthesis in sensitive and resistant Yoshida cells.

The effects of the alkylating agents methylene dimethanesulphonate (MDMS), sulphur mustard (SM) and methyl methanesulphonate (MMS) on DNA synthesis have been investigated in Yoshida sarcoma cell lines sensitive (YS) and resistant (YR) to these agents. Measurement of overall DNA synthesis by [3H]thymidine uptake into DNA indicated that both MDMS and SM, but not MMS, induced a greater depression of DNA synthesis in YS cells than in YR cells. Analysis of the sizes of newly synthesised strands of DNA by pulse labelling and alkaline sucrose gradient sedimentation revealed that MDMS inhibited the initation of new replicons and also reduced the size of new DNA strands. The relative extents of inhibition of replicon initation in MDMS-treated YS and YR cells were similar and reduced by caffeine while YR cells were comparatively less sensitive to the effect of MDMS on the sizes of DNA molecules synthesised. Similarly, YR cells apparently synthesised longer DNA strands following SM treatment compared to YS cells suggesting an association between the size of DNA molecules synthesized and the sensitivity of Yoshida cells to bifunctional alkylating agents.

Alkylating Agents↗
PubMed1981

Measurements of daunorubicin uptake of Yoshida sarcoma cells in culture using flow cytofluorimetry.

A comparative measurement of the transport and localisation of daunorubicin into Yoshida sarcoma cells, was undertaken by a biochemical extraction process and a flow cytometric method. An advantage of this latter procedure would be to identify subpopulation of cells which have enhanced or impaired daunorubicin incorporation as well as the ability to exclude any non-specific incorporation into cell debris, which would otherwise interfere with the overall estimation. It has been possible to use the Biophysics argon ion laser at a wavelength of 488 nm which coincides with the visible absorption bands of daunorubicin and doxorubicin (adriamycin) and the cytofluorimetric estimations of daunorubicin incorporation have now been compared with biochemically determined uptake in Yoshida cells. A high lethal dose of 10 microM was required to achieve the direct measurement by cytofluorimetry procedures on the Biophysics instrument. From cell fractionation and CHCl3/amyl alcohol extraction, it was possible to show that during a 5-h exposure period to daunorubicin (10 microM), the uptake into the nucleus was at first rapid and that into the cytoplasm was much slower. After about 3-h incubation, the level in the cytoplasm decreased, followed by a decrease from the nucleus 1 h later. This could be equated when observed microscopically to the gain in fluorescent cell debris. If all nuclear binding is to DNA, then at the level of (10 microM) concentration in the medium, the number of base pairs to daunorubicin would be 9 : 1, respectively. Cytofluorimetry showed a broad spread of intracellular daunorubicin fluorescence which increases with cell size. Increasing external concentration caused a more rapid incorporation as well as a quicker release from the cells.

Animals↗
PubMed1981

The role of formaldehyde in methylene dimethanesulphonate-induced DNA cross-links and its relevance to cytotoxicity.

The interaction of the antitumour dialkanesulphonate ester, methylene dimethanesulphonate (MDMS) with the DNA of Yoshida sarcoma cells has been studied using the technique of alkaline elution. A marked retention which was reversed by proteolytic treatment indicated the presence of DNA-protein cross-links. A small proteinase-resistant retention was also observed which indicated that a low level of DNA-DNA interstrand cross-links also occurred. Treatment of cells with the amounts of formaldehyde expected by hydrolysis of the drug showed proteinase-reversible DNA-protein cross-linking which on proteolytic removal revealed a small number of single-strand breaks. Thus, MDMS causes both DNA-protein and DNA-DNA interstrand cross-links, the former component being attributed totally to the formaldehyde produced on the drug's hydrolysis. Cell survival data showed formaldehyde to be comparatively non-cytotoxic, providing evidence that DNA-DNA cross-links observable by this technique may be associated with the cytotoxicity of MDMS.

Alkylating Agents↗
PubMed1981

DNA strand breaks and repair synthesis in Yoshida sarcoma: cells with differential sensitivities to bi-functional alkylating agents and UV light.

The induction of DNA-strand breaks and repair synthesis has been examined in cultured Yoshida sarcoma cell lines sensitive (YS) and resistant (YR) to methylene dimethanesulphonate (MDMS). Using an alkaline DNA unwinding-hydroxylapatite technique, we were able to detect breaks in DNA immediately after MDMS treatment and at similar levels in both YS and YR cells. MDMS treatment and post-treatment incubation in the presence of 1-beta-D-arabino-furanosylcytosine (araC) lead to a large increase in the numbers of breaks when compared with MDMS treatment alone which indicated that many of the DNA-strand breaks seen after MDMS treatment were intermediates in excision repair. The magnitude of break incidence with the araC treatment was again equal in YS and YR cells indicating that these 2 lines made enzymic incisions next to MDMS-induced lesions with equal capacities. During incubation following MDMS treatment, the levels of DNA-strand breaks in YR cells were found to decrease more rapidly than in YS cells. Parallel DNA-repair synthesis estimations, using BND-cellulose chromatography, revealed that the increased rate of decline in breaks in YR cells was accompanied by an increase in repair-synthesis activity compared to YS cells. This was interpreted as indicating that an intermediate step in an excision-repair pathway for MDMS-induced lesions was relatively deficient in YS compared to YR cells. A similar difference in the rates of decline of DNA-strand breaks between YS and YR cells was also observed following treatment with UV light to which MDMS-resistant YR cells also display cross-resistance. However, no such difference was detected following treatment with the monofunctional alkylating agent, methyl methanesulphonate, to which YS and YR cells are equally sensitive. These results suggest that resistance to MDMS in the YR cell line is achieved by an increased efficiency in the gap-sealing component of the excision-repair process.

Alkylating Agents↗