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D Hedley

Publications and source records attributed to D Hedley.

At least 19 recordsLinked to original sources
PubMed1996

Flow cytometric calibration of intracellular pH measurements in viable cells using mixtures of weak acids and bases.

We describe a new method for calibrating intracellular pH (pH1) measurements by flow cytometry, based on the null point method proposed originally by Eisner et al. (Pflügers Arch 413:553-558, 1989). The method involves suspending cells loaded with pH-sensitive dyes, such as SNARF-1 or BCECF, in defined mixtures of the weak acid butyric acid and the weak base trimethylamine. Only the uncharged forms of these agents freely permeate the plasma membrane. The weak acid donates protons intracellularly, whereas the weak base accepts them. In accordance with the Henderson-Hasselbalch equation, when cells are exposed to these mixtures, the steady-state pHi is displaced, and the fluorescence signal reflects this new pHi. The null point method described by Eisner et al. derives pHi by determining the molar ratio of acid to base that produces no change in fluorescence signal. In this paper, we show that it is not necessary to obtain the true null point, because a calibration curve can be derived from "pseudo null" values whose pHi is defined by the equation pHi = pHe -0.5 log [(AT)/(BT)], where pHe is the extracellular pH, and (AT) and (BT) are the total concentrations of weak acid and base in the suspension. We refer to this as the "pseudo null calibration method." It is rapid, technically simple, and reproducible. Compared with the widely used nigericin calibration method, it is not influenced by the intracellular potassium concentration; therefore, it may give a more reliable estimate of the absolute value of pHi.

Acid-Base Equilibrium↗
PubMed1995

Flow cytometric determination of glutathione in clinical samples.

Glutathione-based processes are believed to be important determinants of resistance to cancer chemotherapy, and measurement of glutathione (GSH) in tumor tissue is therefore of clinical relevance. Flow cytometric methods have been developed for measuring cellular GSH content that appear to correlate well with biochemical determinations. These flow cytometric techniques are rapid, allow tumor cells to be distinguished from stromal elements, and show considerable intratumoral heterogeneity in human tumor cell GSH content. Although large prospective studies are required to determine the correlations between GSH content and treatment outcome in cancer patients, this approach is a powerful alternative to standard biochemical assays for GSH.

Aneuploidy↗
PubMed1992

Flow cytometric measurement of lipid peroxidation in vital cells using parinaric acid.

A method for measuring lipid peroxidation using time resolved flow cytometry is described. Because of its chemical nature, the naturally fluorescent fatty acid cis-parinaric acid is readily consumed in lipid peroxidation reactions. It could be loaded into Chinese hamster ovary cells in a time and concentration dependent manner at 37 degrees C, with 5 microM for 60' giving consistent, bright fluorescence without evidence of cytotoxicity. Examination of cells by fluorescence microscopy showed diffuse staining of surface and internal membranes. Cells were maintained at 37 degrees C while being examined in an Epics Elite flow cytometer equipped with a 325 nm HeCd laser, and parinaric acid fluorescence at 405 nm was measured over time. Addition of the oxidant tert-butyl hydroperoxide resulted in a burst of intracellular oxidation, shown by simultaneously loading the cells with dichlorofluorescein, and loss of parinaric fluorescence over time. This was followed by cell death, indicated by loss of forward light scatter and uptake of propidium iodide. Pretreatment of the cells with the antioxidant alpha-tocopherol, 200 microM, reduced the rate of loss of parinaric acid fluorescence and delayed the onset of cell death. Simultaneous biochemical determination of the lipid peroxidation breakdown product malondialdehyde confirmed a close temporal relationship with loss of parinaric acid fluorescence, both with and without alpha-tocopherol pretreatment and suggested that the flow cytometric assay for lipid peroxidation is of comparable sensitivity. The mitochondrial stain dodecyl acridine orange and the cyanine dye DiOC(6)3 were combined with cis-parinaric acid staining and could be excited by the latter using resonance energy transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The hypothermic response of mice to delta-9-tetrahydrocannabinol is enhanced by chlorpromazine, thioxanthenes, alpha-adrenoceptor antagonists and pentolinium but not by SCH 23390 or sulpiride.

Chlorpromazine, given either subcutaneously (0.375 mg/kg) or unilaterally into the preoptic/anterior hypothalamic area through a chronically implanted cannula (20 micrograms), was found to enhance the hypothermic response to delta-9-tetrahydrocannabinol (THC; 5 mg/kg i.p.) in unrestrained adult male MF1 mice, kept at 22 degrees C. In mg/kg terms, chlorpromazine was no more potent when injected into the preoptic/anterior hypothalamic area than when given subcutaneously. Phentolamine (54 micrograms) had no significant effect on hypothermia induced by THC when injected into the hypothalamus although it did enhance this response when given subcutaneously (15 mg/kg). Hypothermia induced by THC was also enhanced by flupentixol (0.375 mg/kg s.c.), piflutixol (23.4 micrograms/kg s.c.), pentolinium (5 mg/kg s.c.), prazosin (0.1875 mg/kg s.c.) and indoramin (6 mg/kg s.c.) but not by SCH 23390 (6 mg/kg s.c.) or sulpiride (40 mg/kg s.c.). When taken together with the results from a previous study, these data support the hypothesis that chlorpromazine enhances hypothermia induced in mice by THC by antagonizing alpha-adrenoceptors so as to decrease the capacity of the animals to minimise peripheral blood flow by vasoconstriction. The present data also support the hypothesis that flupentixol and piflutixol interacted with THC not by antagonizing dopamine at D1 or D2 receptors but rather by blocking alpha-adrenoceptors.

Adrenergic alpha-Antagonists↗
PubMed1987

Relationship between cytoplasmic pH and proliferation during exponential growth and cellular quiescence.

Flow cytometry was used to measure intracellular pH (pHi) on an individual cell basis during exponential and plateau phases of growth. In all three cell lines examined a range of pHi values was associated with exponential growth. When cells from the extremes of the pHi distribution were sorted using a fluorescence-activated cell sorter and then restained for cellular DNA content, it was found that the higher pHi values were associated with enrichment of the S, G2, and M phases of the cell cycle, with a corresponding increase in the percentage of G1 cells at the lower pH1 range, suggesting cell-cycle dependence of pHi. It has been shown previously (I. W. Taylor and P. Hodson, 1984, J. Cell Physiol. 121, 517) that PMC-22 human melanoma cells are capable of entering a distinct pH-dependent quiescent state in response to the acidification of the growth medium which occurs naturally during growth to plateau phase. Simultaneous measurement of pHi and external pH showed that under these conditions pHi was maintained at control values down to an external pH of approximately 6.5, below which cytoplasmic acidification took place. This fall in pHi coincided with the onset of the transition to quiescence. Individual quiescent cells (defined by failure to incorporate bromodeoxyuridine during a 24-h exposure) could not be identified as such on the basis of a low pHi, suggesting that the probability of cell cycling is reduced by lowering pHi. Those cells which remained in cycle showed a markedly reduced rate of DNA synthesis, but a cell-cycle phase distribution similar to that in exponential growth, indicating that prolongation of all cell-cycle phases is an additional factor influencing overall population growth. The external pH at which both of these effects on cell proliferation kinetics took place in vitro is similar to that which occurs regionally within solid tumors, suggesting that pH effects could play a significant role in determining tumor cell growth in vivo.

Animals↗
PubMed1987

Chemotherapy of adult soft tissue sarcoma with combination of doxorubicin and methotrexate.

Thirty-six adult patients with measurable advanced soft tissue sarcoma were treated with a combination of doxorubicin (70 mg/m2) and methotrexate (50 mg/m2) iv every 21 days. Partial remission was seen in ten of 33 evaluable patients (30%). Median duration of remission was 23 weeks, and median survival was 42 weeks. Bone marrow toxicity was the main toxic effect; 23% of the patients had a nadir leukocyte count less than 2.0 X 10(9)/L during therapy. These results do not suggest any therapeutic advantage in adding methotrexate to doxorubicin in this context.

Adult↗
PubMed1986

Flow cytometric measurement of cytoplasmic pH: a critical evaluation of available fluorochromes.

Three pH-sensitive fluorochromes-4-methyl-umbelliferone(4MU),2, 3-dicyano-hydroquinone (DCH), and 2',7'-bis(carboxyethyl)-5,6-carboxy fluorescein (BCECF)--were evaluated for their resolution, range, and stability of cellular fluorescence. Flow cytometric techniques for determining cytoplasmic pH (pHi) have been fully described for 4MU and DCH; BCECF has previously been used for fluorimetric estimation of pHi, and was adapted to flow cytometry. For each fluorochrome, the ratio of fluorescence intensity at two wavelengths gives a measure of pHi, which may be calibrated by obtaining the fluorescence ratios for cells suspended in buffers of varying pH in the presence of a proton ionophore. Reliable calibration proved difficult using 4MU, partly because of poor retention within cells. Both DCH and BCECF could be calibrated using a fluorescence ratio and had resolutions of 0.2 and 0.4 pH units, respectively. The fluorescence of DCH is so strongly pH dependent that there were practical difficulties in its use over a wide pH range; however, pHi measurements are possible between pH 6.0 and pH 7.5 using either DCH or BCECF. Substantial dye leakage was found for 4MU and, to a lesser extent, DCH, while BCECF was retained by cells for up to 2 hours. Despite its lower resolution BCECF had a usable range of more than 1.5 pH units and this coupled with its stable fluorescence and excitation at 488 nm rather than UV suggests a wide application.

Cell Line↗
PubMed1985

Modulation of transferrin receptor expression by inhibitors of nucleic acid synthesis.

We investigated the effects of the iron chelator desferrioxamine on the expression of transferrin receptors (TfR) by CCRF-CEM human T-cell leukaemia and B16 mouse melanoma cells growing in tissue culture. Desferrioxamine (DFOA) enhanced TfR expression when added in the dose range of 10(-5)-10(-4) to CCRF-CEM cells, but was toxic to these cells, the lower concentrations producing a slowing of cell growth with a build up in S-phase, while higher concentrations caused cell death with a block at the G1/S-phase interface. These toxic effects are compatible with its previously reported inhibition of the non-haem iron containing (M2) subunit of ribonucleotide reductase. In marked contrast, DFOA caused the growth of B16 melanoma cells to arrest in G1, without loss of cloning efficiency, and resulted in a fall in TfR expression to approximately 50% of control values. These results suggested that the effects of DFOA on TfR expression were linked to DNA synthesis rather than to a more generalised inhibition of iron-dependent cellular processes. It was subsequently found that inhibition of the M2 subunit of ribonucleotide reductase in CCRF-CEM cells with 5 X 10(-5) M hydroxyurea, which is not an iron chelator, also enhanced TfR expression, as did thymidine and cytosine arabinoside, which have different enzyme targets. By measuring cellular DNA and RNA content simultaneously it was shown that all of these agents caused unbalanced growth, i.e., inhibited DNA synthesis more than RNA synthesis. In contrast, 6-thioguanine was more inhibitory to RNA synthesis, and treatment with this drug caused a fall in TfR expression. Thus, although CCRF-CEM cells treated with DFOA show enhanced TfR expression, similar effects are also seen with other inhibitors of DNA synthesis, provided that RNA synthesis is allowed to continue. These results provide further evidence that the regulation of TfR expression by proliferating cells is specifically linked to DNA synthesis rather than to the iron requirements of other cellular processes.

Animals↗
PubMed1985

Cisplatin, vinblastine, and bleomycin in inoperable non-small cell lung cancer.

Forty two patients with inoperable non-small cell lung cancer were entered into a phase II study of the combination chemotherapy regimen PVB (cisplatin 60 mg/m2 by intravenous infusion over two hours on day 1, vinblastine 4 mg/m2 by intravenous bolus on days 1 and 2, and bleomycin 15 mg intramuscularly on days 1, 8, and 15), repeated at three weekly intervals. Twelve of 40 evaluable patients (30%) achieved partial responses; there were no complete responses. The median duration of response was 16 weeks (range greater than 8-73 weeks). The median survival of responding patients calculated from entry to the study until death (40 weeks) was superior to that of patients failing to respond (15 weeks). Treatment was accompanied by signs of moderate toxicity, particularly myelosuppression, nausea and vomiting, alopecia, and neuropathy. One patient died from a neutropenic infection. PVB is a moderately toxic regimen for non-small cell lung cancer and appears similar in efficacy and toxicity to high dose cisplatin and vindesine.

Adenocarcinoma↗
PubMed1984

Transferrin receptor expression during exponential and plateau phase growth of human tumour cells in culture.

Transferrin receptor expression by the human tumour cell lines CCRF-CEM leukaemia and PMC-22B melanoma was studied, measuring the specific binding of fluorescein isothiocyanate (FITC)-labelled transferrin using a fluorescence-activated cell sorter. By measuring the fluorescence of cells stained at subsaturating concentrations of conjugate it was possible to calculate the average numbers of receptors per cell and the binding affinity by Scatchard analysis. These values (1.9 X 10(5) binding sites/cell, KA 1.2 X 10(9) M-1 for CCRF-CEM during exponential growth and 6.9 X 10(4) binding sites/cell, KA 1.4 X 10(-9) M-1 for PMC-22B) are in close agreement with previously published data obtained using radiolabelled transferrin. The present method, however, allowed the transferrin receptor expression of individual cells within a population to be measured and thus it has been possible to test the hypothesis that transferrin receptor is a marker for cycling cells. Frequency-distribution histograms of transferrin receptor showed a wide range of values for both cell lines during exponential growth. When the extreme ranges were sorted and the cells examined for cellular DNA content it was found that those with the highest transferrin receptor expression were enriched with cells in S, G2, and M phases of the cell cycle, whereas those with low transferrin receptor expression were mainly in G1. However, two-parameter-correlated dot plots of transferrin receptor expression versus DNA content showed there was considerable overlap between the ranges of receptor expression for the different cell cycle compartments. Using a stathmokinetic method we have measured the proportion of quiescent cells in fed plateau phase cultures. Transferrin receptor expression was downgraded under these growth conditions but, contrary to expectation, the decline affected the population uniformly, without the emergence of a distinct, transferrin receptor-negative subpopulation corresponding to the increasing proportion of quiescent cells. Thus, although transferrin receptor expression bears some relation to cell cycle phase and reflects the proliferative activity of populations of cells, it is incapable of identifying individual cells which are out of cycle.

Apoproteins↗
PubMed1984

Advanced breast cancer: response to high dose oral medroxyprogesterone acetate.

We treated 105 patients with advanced breast cancer, using the progestational agent medroxyprogesterone acetate (MPA), 200 mg orally tds in a non-randomised trial. In general they were a poor risk population, since 78 had received prior endocrine therapy (21 more than one type) and 58 prior chemotherapy. Treatment was well tolerated. Side effects included weight gain, muscle cramps, fine tremor and fluid retention, but these were usually mild, resolved if the dose of drug was reduced, and only one patient stopped treatment because of toxicity. Seventeen patients died within six weeks of starting MPA, and disease progression occurred in a further 58. Nine have had stable disease for periods ranging from two to 11 months, and there were 21 who showed disease regression. Response to treatment continues in 13 of these patients, and at the time of writing the median duration of response is 10 months. Response rates were similar in pre- and post-menopausal patients. The dose of MPA was double to 400 mg tds in 16 patients whose disease had progressed on 200 mg tds, but no additional responses were seen in this group. Seven out of 24 (29%) patients who had not received prior endocrine therapy responded to high dose oral MPA, a response rate similar to that seen following other hormonal manipulations, but because the drug also has activity against hormone-resistant tumours and is well tolerated, it should have role in the treatment of advanced breast cancer.

Antineoplastic Agents↗
PubMed1984

Combination therapy with methotrexate and 5-fluorouracil: a prospective randomized clinical trial of order of administration.

Because of biochemical and tissue culture evidence casting doubt on the physiologic relevance of reported synergy afforded by sequential administration of methotrexate (MTX) followed by 5-fluorouracil (5-FU), a randomized controlled clinical trial was conducted in 108 patients with advanced cancer, including 70 with squamous cell carcinoma (SCC) of the head and neck, nine with SCC of other primary sites, 24 with colorectal, and five with gastric adenocarcinomas. Patients were randomized to receive weekly therapy consisting of MTX followed one hour later by 5-FU, or 5-FU followed one hour later by MTX. There was a trend to higher tumor response rates in patients treated with MTX before 5-FU (45% v 33% overall; 65% v 39% in patients with previously untreated head and neck cancer), but these differences were not significant, either by chi-square test or by multivariate stepwise logistic regression. The trend in survival favoring the reverse sequence of 5-FU before MTX was not significant in univariate analyses. Stepwise multivariate Cox model analysis showed that Eastern Cooperative Oncology Group performance status at study entry was the major prognostic factor for survival (P less than 0.001), but among the 70 patients with head and neck cancer, the sequence of drug administration was the only other significant prognostic factor for survival, and favored the sequence of 5-FU followed by MTX (P less than 0.025).

Adenocarcinoma↗
PubMed1983

Mismatched family donors for bone-marrow transplantation as treatment for acute leukaemia.

35 patients were treated for acute myeloid leukaemia or acute lymphoblastic leukaemia with allogeneic bone-marrow grafts from a parent, child, or sibling who was mismatched at the major histocompatibility complex (MHC). 11 of these patients are alive at least 6 months after grafting, 5 of them after more than 2 years. Of the 15 patients aged under 20 at the time of the graft, 8 are alive and well 6 months to 3 years later. Cyclosporin A was given to all patients after grafting. 1 patient died of acute graft-versus-host disease and in 2 other cases this was a major factor in their death. Graft failure caused the death of 2 patients. 4 patients died of recurrent leukaemia. A fatal complication in 12 patients was pulmonary oedema, often associated with convulsions, intravascular haemolysis, and renal failure. Some of these patients had viral or bacterial infections, but in the majority the syndrome was not associated with demonstrable infection. This syndrome, in which the essential lesion appears to be vascular, was much more common in recipients of mismatched than matched grafts. 3 others died from lung disease in which infection was a factor.

Acute Disease↗
PubMed1983

Lorazepam as an adjunct to antiemetic therapy with haloperidol in patients receiving cytotoxic chemotherapy.

Twenty-seven consecutive patients were treated with 3 mg oral lorazepam and 2.5 mg intravenous haloperidol in an effort to improve patient tolerance of cytotoxic chemotherapy and decrease nausea and vomiting. Antiemetic efficacy and side-effects were assessed using a patient questionnaire. Vomiting either did not occur, or was considered to be of only moderate intensity in 22 patients (81%) and usually ceased within 24 hours of commencing chemotherapy. Similarly, nausea was either absent or of only moderate severity, lasting less than 48 hours in the majority of patients. Eight of 11 patients who had received similar previous cytotoxic treatment with antiemetic agents but not lorazepam considered that lorazepam and haloperidol had considerably improved their tolerance of chemotherapy. The side-effects of haloperidol and lorazepam were mild and well tolerated.

Anti-Anxiety Agents↗
PubMed1980

The place of bone-marrow transplantation in acute myelogenous leukaemia.

28 patients with acute myeloid leukaemia (AML) in first remission were maintained on chemotherapy, consisting of courses of cytosine arabinoside and daunorubicin, and immunotherapy with irradiated AML cells and BCG. The relapse rate and survival rate of these patients were compared with those of a simultaneously treated group of 22 patients in first remission who received sibling bone-marrow transplants after cyclophosphamide (60 mg/kg) given for 2 days and followed by a single dose of 1000 rads total body irradiation. Substantially fewer transplanted patients (4 out of 22) than chemo-immunotherapy patients (19 out of 28) relapsed (p less than 0.005) and 14 (64%) transplanted patients remain alive, well, and disease-free. Survival curves of the two groups of patients show that the transplanted patients never fared worse than the chemo-immunotherapy patients. We suggest that when possible young AML patients in remission should be offered transplantation as an alternative form of treatment.

Adolescent↗
PubMed1974

Antibiotics.

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Anti-Bacterial Agents↗