Potassium and calcium current blocking properties of the novel antiarrhythmic agent H 345/52: implications for proarrhythmic potential

OBJECTIVES

To study the blocking effects of H 345/52 on ionic currents of rabbit ventricular myocytes and how these features translate into a proarrhythmic potential.

METHODS

The single electrode voltage clamp technique was used to study the effects of H 345/52 on the rapid component of the delayed rectifying potassium current, I(Kr), and the L-type calcium current (I(Ca)). Differential effects of H 345/52 and almokalant on APD prolongation were studied in a rabbit Purkinje fibre/ventricular muscle preparation. The temporal variability of the action potential duration (APD) and its relation to proarrhythmias was examined in Langendorff-perfused rabbit hearts administered H 345/52 or almokalant. Anaesthetised, methoxamine-sensitised rabbits were used to assess the propensity of intravenous H 345/52 and ibutilide to induce torsades de pointes (TdP).

RESULTS

H 345/52 potently blocked I(Kr) (IC(50)=40 nM) without consequential use-dependency. The I(Ca) was also blocked, but at higher concentrations (IC(50)=1.3 microM). Block of I(Ca) was markedly frequency-dependent (positive) and influenced by membrane potential, such that H 345/52 was more effective following clamp steps from plateau potentials than from -80 mV. In the Purkinje fibre-ventricular muscle preparation, almokalant prolonged the Purkinje fibre APD preferentially, whereas H 345/52 homogeneously prolonged APD in both tissue types. In the perfused rabbit heart, H 345/52 (1 microM) and almokalant (0.3 microM) prolonged APD to a similar degree but increased the temporal variability of APD differently, from 3+/-0.4 ms in control hearts to 8+/-1.2 ms and to 38+/-7.5 ms (P<0.001 vs. H 345/52), respectively. Unequivocal early after-depolarisations were seen in 5/6 almokalant-perfused hearts but in no heart administered H 345/52 (P<0.05). In anaesthetised rabbits, H 345/52 (17.4 micromol/kg) or ibutilide (2.6 micromol/kg maximum), maximally lengthened the QT interval from 133+/-4.5 to 177+/-8.0 ms and from 125+/-5.1 to 166+/-9.3 ms (P<0.001, n=8). However, whereas ibutilide induced TdP in all animals at 0.06+/-0.009 micromol/kg, H 345/52 did not induce TdP (P=0.0002) at up to 17.4 micromol/kg.

CONCLUSIONS

H 345/52 blocks I(Kr) with high potency and I(Ca) with somewhat lower potency and was found to delay ventricular repolarisation without substantially increasing temporal or spatial dispersion and without inducing early after-depolarisations or TdP.

Study of B Decays to Charmonium States: B-->eta(c)K and B --> chi(c0)K

In a sample of 9.66x10(6)B&Bmacr; pairs collected with the CLEO detector we make the first observation of B decays to an eta(c) and a kaon. We measure branching fractions B(B+-->eta(c)K+) = (0.69(+0.26)(-0.21)+/-0.08+/-0.20)x10(-3) and B(B degrees -->eta(c)K degrees ) = (1.09(+0.55)(-0.42)+/-0.12+/-0.31)x10(-3), where the first error is statistical, the second is systematic, and the third is from the eta(c) branching fraction uncertainty. From these we extract the eta(c) decay constant in the factorization approximation, f(eta(c)) = 335+/-75 MeV. We also search for B decays to a chi(c0) and a kaon. No evidence for a signal is found and we set 90% C.L. upper limits: B(B+-->chi(c0)K+)<4.8x10(-4) and B(B degrees -->chi(c0)K degrees )<5.0x10(-4).

Vibrio cholerae cytolysin: assembly and membrane insertion of the oligomeric pore are tightly linked and are not detectably restricted by membrane fluidity

Hemolytic strains of Vibrio cholerae secrete a cytolysin that, upon binding as a monomer, forms pentameric pores in animal cell membranes. Pore formation is inhibited at low temperature and in the absence of cholesterol. We here posed the following questions: firstly, can oligomerization be observed in the absence of pore formation? Secondly, is membrane fluidity responsible for the effect of temperature or of cholesterol upon pore formation? The first issue was approached by chemical cross-linking, by electrophoretic heteromer analysis, and by electron microscopy. None of these methods yielded any evidence of a non-lytic pre-pore oligomer. The second question was addressed by the use of two susceptible liposome models, consisting of cholesterol admixed to bovine brain lipids and to asolectin, respectively. The two liposome species clearly differed in membrane fluidity as judged by diphenylhexatriene fluorescence polarization. Nevertheless, their permeabilization by the cytolysin decreased with temperature in a closely parallel fashion, virtually vanishing at 5 degrees C. Omission of cholesterol from the liposomes uniformly led to an increase in membrane fluidity but prevented permeabilization by the cytolysin. The effects of temperature and of cholesterol upon cytolysin activity are thus not mediated by fluidization of the target membrane. The findings of our study distinguish V. cholerae cytolysin from several previously characterized pore-forming toxins.

Erroneous diagnosis of chronic urinary retention in three women with pelvic cysts

Three cases are presented where pelvic masses were originally misdiagnosed as cases of chronic urinary retention. In all cases the erroneous diagnosis was made at outpatient assessment, where postmicturition ultrasound scan measurement of residual urine volume had been performed. This investigation, while a useful tool, must be viewed in the context of other clinical findings.

Measurements of the mass, total width, and two-photon partial width of the eta(c) meson

Using 13.4 fb(-1) of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudoscalar charmonium in the decay eta(c)-->K(0)(S)K-/+pi(+/-). We have measured the eta(c) mass to be [2980.4+/-2.3 (stat)+/-0.6 (syst)] MeV and its full width as [27.0+/-5.8 (stat)+/-1.4 (syst)] MeV. We have determined the two-photon partial width of the eta(c) meson to be [7.6+/-0.8 (stat)+/-0.4 (syst)+/-2.3 (br)] keV, with the last uncertainty associated with the decay branching fraction.

Study of charmless hadronic B meson decays to pseudoscalar-vector final states

We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.

A novel high throughput chemiluminescent assay for the measurement of cellular cyclic adenosine monophosphate levels

The second messenger 3', 5'-cyclic AMP (cAMP) is a highly regulated molecule that is governed by G protein-coupled receptor activation and other cellular processes. Measurement of cAMP levels in cells is widely used as an indicator of receptor function in drug discovery applications. We have developed a nonradioactive ELISA for the accurate quantitation of cAMP levels produced in cell-based assays. This novel competitive assay utilizes chemiluminescent detection that affords both a sensitivity and a dynamic assay range that have not been previously reported with any other assay methodologies. The assay has been automated in 96- and 384-well formats, providing assay data that are equivalent to, if not better than, data generated by hand. This report demonstrates the application of this novel assay technology to the functional analysis of a specific G protein-coupled receptor, neuropeptide receptor Y1, on SK-N-MC cells. Our data indicate the feasibility of utilizing this assay methodology for monitoring cAMP levels in a wide range of functional cell-based assays for high throughput screening.

Study of exclusive radiative B meson decays

We have studied exclusive, radiative B meson decays to charmless mesons in 9.7x10(6) B&Bmacr; decays accumulated with the CLEO detector. We measure B(B0-->K(*0)(892)gamma) = (4.55(+0.72)(-0. 68)+/-0.34)x10(-5) and B(B+-->K(*+)(892)gamma) = (3.76(+0.89)(-0. 83)+/-0.28)x10(-5). We have searched for CP asymmetry in B-->K(*)(892)gamma decays and measure A(CP) = +0.08+/-0.13+/-0.03. We report the first observation of B-->K(*)(2)(1430)gamma decays with a branching fraction of (1.66(+0.59)(-0.53)+/-0.13)x10(-5). No evidence for the decays B-->rhogamma and B0-->omegagamma is found and we limit B(B-->(rho/omega)gamma)/B(B-->K(*)(892)gamma)<0.32 at 90% C.L.

Search for the decay &Bmacr;(0)-->D(*0)gamma

We report results of a search for the rare radiative decay &Bmacr;(0)-->D(*0)gamma. Using 9.66x10(6) B&Bmacr; meson pairs collected with the CLEO detector at the Cornell Electron Storage Ring, we set an upper limit on the branching ratio for this decay of 5.0x10(-5) at 90% C.L. This provides evidence that the anomalous enhancement is absent in W-exchange processes and that weak radiative B decays are dominated by the short-distance b-->sgamma mechanism in the standard model.

Large differences in laboratory utilisation between hospitals in Sweden

There are large differences in the use of laboratory tests between hospitals in Sweden. These differences are not only due to differences between the patients treated but also to differences in practice. Use of laboratory test seems to reflect local traditions to a large extent. These large variations in practice are not compatible with the objective of providing care on equal terms and reduce the cost-effectiveness of clinical chemistry. Recently, several intervention studies have been performed in Sweden with the aim to optimise the use of clinical chemistry tests in primary care. The results show that it is possible to reduce the cost in primary care by SEK 100 million per year while increasing the clinical usefulness. This constitutes approximately 10% of the total cost for clinical chemistry tests in primary care. It should also be possible to reduce the cost for clinical chemistry tests in secondary and tertiary care. Hospitals order more tests than primary care and the potential savings are thus greater. We have studied the ordering habits for eleven Swedish hospitals. The comparison was made in the form of ratios between related laboratory tests to reduce the effects of differences in size between the studied laboratories. The large variation between hospitals indicates that a continuous discussion between the clinicians and the laboratories could reduce the cost. We have used the figures from the comparison and calculated the potential savings for seven frequently used tests. The potential yearly saving in Sweden for these tests is approximately SEK 150 million.

Staphylococcal alpha-toxin: repair of a calcium-impermeable pore in the target cell membrane

Staphylococcal alpha-toxin forms heptameric pores that render membranes permeable for monovalent cations. The pore is formed by an amphipathic beta-barrel encompassing amino acid residues 118-140 of each subunit of the oligomer. Human fibroblasts are susceptible to alpha-toxin but are able to repair the membrane lesions. Thereby, toxin oligomers remain embedded in the plasma membrane and exposed to the extracellular medium. In this study, we sought to detect structural changes occurring in the pore-forming sequence during lesion repair. Single cysteine substitution mutants were labelled with the environmentally sensitive fluorochrome acrylodan and, after mixing with wild-type toxin, incorporated into hybrid heptamers on fibroblast membranes. Formation of the lipid-inserted beta-barrel was accompanied by characteristic fluorescence emission shifts. After lesion repair, the environment of the residues at the outer surface of the beta-barrel remained unchanged, indicating continued contact with lipids. However, the labelled residues oriented towards the channel lumen underwent a green to blue shift in fluorescence, indicating reduced exposure to water. Pore closure proceeded in the presence of calmodulin inhibitors and of microtubule disruptors; however, it was prevented by cytochalasin D and by inhibitors of lipid metabolism. Our findings reveal the existence of a novel mechanism of membrane repair that may consist in constriction of the inserted proteinaceous pore within the lipid bilayer.

Epidermal growth factor receptor dimerization monitored in live cells

We present a method for monitoring receptor dimerization at the membrane of live cells. Chimeric proteins containing the epidermal growth factor (EGF) receptor extracellular and transmembrane domains fused to weakly complementing beta-galactosidase (beta-gal) deletion mutants were expressed in cells in culture. Treatment of the cells with EGF-like compounds for as little as 15 s resulted in chimeric receptor dimerization detectable as beta-gal enzymatic activity. The dose response of chimeric receptors was ligand specific. beta-galactosidase complementation was reversible upon removal of ligand and could be reinduced. Antibodies that block ligand binding inhibited receptor dimerization and beta-gal complementation. These results demonstrate that beta-gal complementation provides a rapid, simple, and sensitive assay for protein interactions and for detecting and monitoring the kinetics of receptor dimerization.

Bladder training for urinary incontinence in adults

BACKGROUND

Bladder training is widely used for the treatment of urinary incontinence. It is generally used for the treatment of people with urge incontinence or detrusor instability, although it is also thought that it might be of use for people with mixed incontinence or stress incontinence.

OBJECTIVES

To assess the effects of bladder training for the treatment of urinary incontinence.

SEARCH STRATEGY

We searched the Cochrane Incontinence Group trials register up to July 1999. Date of the most recent search: July 1999.

SELECTION CRITERIA

Randomised or quasi-randomised trials of bladder training for the treatment of incontinence.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data that were then cross-checked by the third reviewer. All three reviewers assessed trial quality.

MAIN RESULTS

We found seven eligible trials with a total of 259 predominantly female patients with urinary urge incontinence. The quality of trials was variable. Three trials involving 92 women compared bladder training with no bladder training. These tended to favour bladder training but data were available for only a limited number of pre-specified outcomes that varied across the three trials. No data describing long term follow up are available. One trial compared bladder training with drug therapy, but was inconclusive. Another trial compared bladder training with an electronic prompt device. The trial was small and included only 20 women. Data were not presented in a form suitable for quantitative analysis. Two further trials compared bladder training supplemented by drug therapy with bladder training alone. Again, the limited data provided insufficient evidence on which to draw conclusions.

REVIEWER'S CONCLUSIONS

Bladder training may be helpful for the treatment of urinary urge incontinence, but this conclusion can only be tentative, based on the evidence available. There was not enough evidence to show whether drug therapy was better than bladder training or useful as a supplement to it.

Streptolysin O: inhibition of the conformational change during membrane binding of the monomer prevents oligomerization and pore formation

Streptolysin O is a four-domain protein toxin that permeabilizes animal cell membranes. The toxin first binds as a monomer to membrane cholesterol and subsequently assembles into oligomeric transmembrane pores. Binding is mediated by a C-terminally located tryptophan-rich motif. In a previous study, conformational effects of membrane binding were characterized by introducing single mutant cysteine residues that were then thiol-specifically derivatized with the environmentally sensitive fluorophoracrylodan. Membrane binding of the labeled proteins was accompanied by spectral shifts of the probe fluorescence, suggesting that the toxin molecule had undergone a conformational change. Here we provide evidence that this change corresponds to an allosteric transition of the toxin monomer that is required for the subsequent oligomerization and pore formation. The conformational change is reversible with reversal of binding, and it is related to temperature in a fashion that closely parallels the temperature-dependency of oligomerization. Furthermore, we describe a point mutation (N402E) that, while compatible with membrane binding, abrogates the accompanying conformational change. At the same time, the N402E mutation also abolishes oligomerization. These findings corroborate the contention that the target membrane acts as an allosteric effector to activate the oligomerizing and pore-forming capability of streptolysin O.

Effect of vitamin E and N-acetylcysteine on phosphatidylserine externalization and induction of coagulation by high-glucose-treated human erythrocytes

This study examines the effect of high glucose levels on the markers of oxidative stress, phosphatidylserine (PS) externalization, and induction of coagulation by high-glucose-treated red blood cells (RBCs). Washed normal RBCs were suspended to 15% hematocrit in phosphate-buffered saline and incubated with different concentrations of glucose for 24 hours in a shaking water bath at 37 degrees C. This treatment caused depletion of vitamin E and accumulation of vitamin E-quinone and malondialdehyde ([MDA] an end product of lipid peroxidation), externalization of PS in the membrane bilayer, and induction of coagulation by RBCs. Pretreatment of RBCs with N-acetylcysteine (NAC) and vitamin E reduced membrane lipid peroxidation, PS externalization, and the tendency of high-glucose-treated RBCs to clot plasma. This study provides further evidence for the increased oxidative stress in RBCs exposed to high glucose levels. In addition, it suggests a role for membrane lipid peroxidation in the PS externalization in the membrane bilayer and in the induction of clotting by RBCs exposed to hyperglycemia. It also suggests that certain antioxidants can decrease cellular damage and restore certain cellular functions in diabetes.

Effect of vulvovaginal estrogen on sensorimotor response of the lower genital tract: a randomized controlled trial

OBJECTIVE

To assess the effect of vulvovaginal estrogen on mucocutaneous sensory threshold and circumvaginal motor strength.

METHODS

Thirty-nine postmenopausal, hypoestrogenic women with mixed lower-genitourinary-tract complaints were placed in four masked treatment arms by permuted-block randomization for 6 weeks. One group received topical estradiol (E2) cream and pelvic muscle biofeedback training, the second received topical E2 cream and sham biofeedback, the third received placebo cream and pelvic muscle biofeedback training, and the fourth received placebo cream and sham biofeedback. Circumvaginal muscle strength was measured by averaging maximum intravaginal pressure (mmHg) generated over a set of four pelvic muscle contractions. Absolute changes in von Frey threshold (mN) and maximum intravaginal pressure (mmHg) over 4 and 6 weeks were reported as summary measures. Of 39 subjects, 30 completed the study.

RESULTS

Topical estradiol cream significantly improved mechanical sensitivity of the vulvar vestibule to von Frey hairs, a -1.2-mN threshold decrease at 4 weeks (F = 10.29; P = .004), and a -1.6-mN threshold decrease at 6 weeks (F = 8.24; P = .009) compared with placebo cream. Stratification by age showed significantly greater improvement in mechanical sensitivity in the older (70-79 years) age group randomized to estrogen cream and a -5.49-mN threshold reduction (F = 17.65; P = .002). Maximum intravaginal pressures during circumvaginal muscle contraction did not differ between estrogen and placebo cream users (F = 0.00; P = .99).

CONCLUSION

Improved sensation to mechanical stimuli can result from a rapidly acting, direct effect of topical E2 cream on the vulvar vestibule.

Combined results of two phase II studies of Taxol (paclitaxel) in patients with relapsed or refractory lymphomas

This study was performed to determine the clinical activity and safety of paclitaxel in the treatment of patients with refractory or relapsing aggressive Non-Hodgkin's lymphoma (NHL). Between May 3, 1994 and February 16, 1996, 39 patients with refractory or relapsing NHL consented to be enrolled in two, multicenter, open-labelled studies to evaluate the efficacy, safety, time to progression and overall survival of paclitaxel given at a dose of 175 mg/m2 by a 3-hour IV infusion every three weeks without G-CSF use. Data from the two studies is combined. One patient, although registered, did not receive treatment. Of the remaining 38 patients, 17 men and 21 women aged 26-82 years (median 60) were given 104 courses of paclitaxel [median 2 (range 1-6)]. Seventeen patients had stage IV, 7 stage III, 8 stage II, 5 stage 1 and 1 unknown stage of disease. Histologic grades included 1 low, 33 intermediate, and 4 high. Three patients had bone marrow involvement. Median time from diagnosis to study entry was 19 months (1-160). The median number of previous chemotherapy regimens was 2 (range 1-6). Three of the 35 (8.6%) patients evaluable for response had partial remission (PR) of their disease for 1-7 months (median 2) and 11/35 (31.4%) stable disease (SD) for 1 to 19 months (median 3). All three responders and 3 of the 11 SD patients had received paclitaxel after relapsing from a CR. At analysis, nine of the 38 patients were alive. Median duration of follow up at analysis was 6 months (3 days-29 months). The estimated survival rates for all patients at 1 and 2 years are 34% and 27%, respectively (Kaplan-Meier) from the start of paclitaxel treatment. The median survival time was 5.4 months (3 days to 28+ months). Febrile neutropenia occurred in two patients. Seven (18%) patients developed a neutrophil nadir of < 0.5 x 10(9)/L and 2 (5%) patients developed a platelet nadir of < 50 x 10(9)/L. Six patients received blood transfusions. Non-hematologic toxicity was generally mild to moderate with all patients experiencing some toxicity. Twenty-seven patients experienced grade III toxicity including: alopecia (n = 19), pain (n = 9), fatigue (n = 5), nausea/vomiting (n = 3), diarrhoea (n = 2), pulmonary/shortness of breath (n = 2), anorexia (n = 1) and fluctuating levels of consciousness and somnolence (n = 1). Two patients experienced grade IV toxicity (infection, peripheral neuropathy, pain). No patient discontinued paclitaxel for a severe hypersensitivity reaction. In summary, administered as a 3-hour infusion, paclitaxel 175 mg/m2 results in mild myelotoxicity but minimal antitumor activity in patients with refractory NHL.

SNAP-25a and -25b isoforms are both expressed in insulin-secreting cells and can function in insulin secretion

The tSNARE (the target-membrane soluble NSF-attachment protein receptor, where NSF is N-ethylmaleimide-sensitive fusion protein) synaptosomal-associated protein of 25 kDa (SNAP-25) is expressed in pancreatic B-cells and its cleavage by botulinum neurotoxin E (BoNT/E) abolishes stimulated secretion of insulin. In the nervous system, two SNAP-25 isoforms (a and b) have been described that are produced by alternative splicing. Here it is shown, using reverse transcriptase PCR, that messages for both SNAP-25 isoforms are expressed in primary pancreatic B and non-B cells as well as in insulin-secreting cell lines. After transfection, both isoforms can be detected at the plasma membrane as well as in an intracellular perinuclear region in the insulin-secreting cell line, HIT. To test for the functional role of the two isoforms in insulin secretion, mutant forms of SNAP-25a and b resistant against cleavage by BoNT/E were generated. Such mutant SNAP-25, when expressed in HIT cells, is not inactivated by BoNT/E and its ability to restore insulin secretion can thus be investigated. To obtain the toxin-resistant mutant isoforms, the sequence around the BoNT/E cleavage site (R176QIDRIM182) was changed to P176QIKRIT182. This is the sequence of the equivalent region of human SNAP-23 (P187-T194), which has been shown to be resistant to BoNT/E. The mutant SNAP-25 was resistant to BoNT/E in vitro and in vivo and both mutant isoforms were able to reconstitute insulin secretion from toxin-treated HIT cells.

Oligomerization of Vibrio cholerae cytolysin yields a pentameric pore and has a dual specificity for cholesterol and sphingolipids in the target membrane

Vibrio cholerae cytolysin permeabilizes animal cell membranes. Upon binding to the target lipid bilayer, the protein assembles into homo-oligomeric pores of an as yet unknown stoichiometry. Pore formation has been observed with model liposomes consisting of phosphatidylcholine and cholesterol, but the latter were much less susceptible to the cytolysin than were erythrocytes or intestinal epithelial cells. We here show that liposome permeabilization is strongly promoted if cholesterol is combined with sphingolipids, whereby the most pronounced effects are observed with monohexosylceramides and free ceramide. These two lipid species are prevalent in mammalian intestinal brush border membranes. We therefore propose that, on its natural target membranes, the cytolysin has a dual specificity for both cholesterol and ceramides. To assess the stoichiometry of the pore, we generated hybrid oligomers of two naturally occurring variants of the toxin that differ in molecular weight. On SDS-polyacrylamide gel electrophoresis, the mixed oligomers formed a pattern of six distinct bands. Ordered by decreasing electrophoretic mobility, the six oligomer species must comprise 0 to 5 subunits of the larger form; the pore thus is a pentamer. Due to both lipid specificity and pore stoichiometry, V. cholerae cytolysin represents a novel prototype in the class of bacterial pore-forming toxins.

Haematological and non-haematological toxicity after 5-fluorouracil and leucovorin in patients with advanced colorectal cancer is significantly associated with gender, increasing age and cycle number. Tomudex International Study Group

5-Fluorouracil (5-FU) has been widely used for over 30 years. Recently, investigators have described interactions between toxicity with 5-FU and age and gender. Pharmacokinetics of infusional 5-FU are known to be gender dependent, with drug clearance being lower in females. The full impact of age and gender on both toxicity and response has not been fully explored and is worthy of further investigation. 439 patients were entered into a phase III trial comparing a novel thymidylate synthase (TS) inhibitor Tomudex (raltitrexed, formerly ZD1694) with 5-FU and leucovorin (LV) for the treatment of advanced colorectal cancer. Approximately 20-24% of patients in each treatment group were aged 70 years or older and 41% of the patients were female. In a multiple regression analysis, female patients receiving 5-FU + LV experienced significantly more grade 3/4 leucopenia, whilst those receiving raltitrexed had more rises in transaminase levels. Grade 3/4 leucopenia and mucositis were significantly correlated with age (especially > 70 years) only in patients receiving 5-FU + LV. Patients receiving 5-FU + LV were significantly more at risk of experiencing grade 3/4 haematological and non-haematological toxicity in the first three cycles than patients receiving raltitrexed. Female gender and increased age predict for increased grade 3/4 toxicity in patients receiving modulated 5-FU. Further studies with modulated 5-FU which utilise a modified dose reduction schema for female patients, or patients aged 70 years or over, may be appropriate.

Accumulation of amphotericin B in human macrophages enhances activity against Aspergillus fumigatus conidia: quantification of conidial kill at the single-cell level

A cytofluorometric assay that allowed assessment of damage to phagocytosed Aspergillus fumigatus conidia at the single-cell level was developed. After ingestion by monocyte-derived macrophages (MDMs), conidia were reisolated by treatment of the cells with streptolysin O, a pore-forming toxin with lytic properties on mammalian cells but not on fungi. The counts obtained by staining of damaged conidia with propidium iodide and quantification by cytofluorometry correlated with colony counts. By the use of this method, we demonstrate that MDMs differentiated in vitro by low-dose granulocyte-macrophage colony-stimulating factor and gamma interferon have only a limited capacity to damage Aspergillus conidia in vitro. The killing rate 12 h after phagocytosis was found to be only 10 to 15%. However, intracellular loading of the phagocytes with amphotericin B (AmB) dose dependently enhanced the anticonidial activity. Preincubation of macrophages with only 1 microg of AmB per ml resulted in an uptake of 18 fg of AmB/cell, leading to killing rates of 50 to 60%. The experimental protocol provides a new tool for the rapid quantification of anticonidial activity against A. fumigatus in vitro. Intracellular accumulation of AmB may represent an important factor underlying the efficacy of this antifungal drug in the prophylaxis and treatment of Aspergillus infections.