[Portfolio-based learning in surgery : Making competencies "visible"]. / Portfoliobasiertes Lernen in der Chirurgie : Kompetenzen "sichtbar" machen.

BACKGROUND: Due to an increasing competence orientation of medical studies, surgical curricula are being adapted in many places. In addition to surgical knowledge and practical skills, these should also teach competencies in differential diagnostics and treatment. The teaching of surgical knowledge through lectures and seminars and the demonstration of practical skills, e.g., through the use of logbooks in the Bock Practical Surgery (BP), only allows limited active engagement with surgical competencies on differential diagnostics and treatment. A reflection-based portfolio allows, through the independent written elaboration of surgical topics, an active engagement with the competencies and promises a higher learning effect. In the context of the implementation of such a portfolio as part of the proof of activity in BP, the effects on the acquisition of competencies and on the way of learning were investigated. MATERIAL AND METHODS: Using a mixed methods approach, we compared competence acquisition using a reflection-based portfolio with learning using a logbook. Students conducted a self-assessment of competencies using questionnaire surveys before and after the BP. Through focus group interviews with discussions among students using a guideline, we explored the different ways of acquiring competencies. In addition, the examination and evaluation results of both cohorts were compared. RESULTS AND DISCUSSION: Students' self-assessed competency acquisition and examination and evaluation results showed no differences when comparing the two cohorts. During the focus group interviews, we were able to show that in the perception of the students, surgical competencies can be made more visible and thus more explicit with the help of a reflection-based portfolio. In addition, self-regulated learning was promoted without neglecting practical skills. Students demanded greater supervision and guidance by mentors in both groups.

Ankylosis of the knee after septic arthritis following anterior cruciate ligament reconstruction in a 13-year-old male.

We present the case of an adolescent male developing an ankylosis of the knee after septic arthritis following anterior cruciate ligament reconstruction (ACLR). The patient was shifted to our institution with postoperative septic arthritis associated with a systemic septic condition. Before, repeated arthroscopic surgery had been conducted without any improvement. MRI showed a concomitant osteomyelitis. The infection (Gächter IV, Staphylococcus aureus) was controlled by an open surgical approach and graft removal. An increasing joint stiffness was documented. X-rays showed an ankylosis at 30° of flexion and early closure of growth plates. Functional knee scores showed significantly worse results. Early diagnosis and a stage-adapted treatment in septic arthritis following ACLR are mandatory. In advanced stages or concomitant osteomyelitis an open approach and graft removal may be appropriate. The antibiotic treatment should be adapted consistently.

Evaluation of an integrated care program for schizophrenia: concept and study design.

Concept and design of an independent scientific evaluation of different pathways of care for schizophrenia patients in Germany with respect to effectiveness and efficiency are presented. In this prospective, observational study, schizophrenia patients receiving an integrated care treatment, the intervention group (IG), are compared with patients under routine care conditions treated by the same physician (first control group, CG 1). A second control group (CG 2) of patients treated by office-based psychiatrists not participating in the integrated care program will be recruited and their data compared with the two other groups. The total amount of psychiatric hospital days after 12 months is defined as primary outcome parameter. Secondary outcome parameters comprise the frequency of psychiatric inpatient readmissions, severity of schizophrenia symptoms, remission rates and quality of life. Patients undergo assessments at baseline, month 6 and 12 using standardized and experimental questionnaires. Routine data of a regional German social health insurance fund complement information on included patients. Additionally, a cost-effectiveness and cost-utility analysis will be performed. Until now, 137 psychiatrists included 980 patients in the integrated care project in Lower Saxony, Germany, and 47 psychiatrists (IG and both CGs) are willing to participate in the independent evaluation. For the first time, a prospective observational controlled evaluation study of a countrywide integrated care project planning to recruit 500 schizophrenia patients has started using comprehensive assessments as well as routine data of a social health insurance fund.

Local cluster of germ cell cancer in a cohort of male automotive workers in Germany not explained by previous or concurrent activities and exposures in farming and forestry.

OBJECTIVE: To examine whether exposures or activities in farming, forestry and related occupations explain the excess incidence of germ cell cancer (GCC) observed among male employees in one of the six car-manufacturing plants that is located in a geographic area where farming is frequent. METHODS: A cohort based case-control study was conducted among workers in six car-manufacturing plants located in areas with different industrial structure. The study involved 188 cases of germ cell cancer identified through active retrieval in 38 hospitals and 1000 controls, drawn from administrative accounting files, individually matched by year of birth (± 2 years). Information regarding tasks and exposures and potential confounding variables were obtained by face-to-face or telephone interviews. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using a conditional logistic regression model adjusted for cryptorchidism and other potential confounders. RESULTS: In this case-control study 5.3% of cases and 6.3% of controls ever worked in agriculture or livestock farming. No increased risks were observed for working in agriculture (OR=0.8 95% CI: 0.4-1.6), livestock farming (OR=0.8 95% CI: 0.4-1.6) or for exposure to pesticides (OR=0.7 95% CI: 0.3-1.7), for exposure to fertilizers (OR=0.8 95% CI: 0.4-1.8) and disinfectants (OR=1.0 95% CI: 0.3-2.8). There were no statistically significant increases in risk associated with ever exposure to salt based wood protection agents (OR=2.3 95% CI: 0.6-9.1), working with plywood (OR=1.4 95% CI: 0.6-3.2), coated wood (OR=1.4 95% CI: 0.5-3.9) or working in forestry (OR=1.7 95% CI: 0.5-6.4). Lagging of exposures did not alter the results. CONCLUSIONS: The observed excess incidence in the cohort of automotive workers can be hardly explained by previous or concurrent work in farming or forestry. Because of the small numbers of subjects ever employed in farming the statistical power in assessing associations between agricultural work and agricultural exposures was limited and does not allow final conclusions about the association of farming related exposures and GCC risk.

Prolactin acts on the hypothalamic-pituitary axis to modulate follicle-stimulating hormone gene expression in the female brushtail possum (Trichosurus vulpecula).

Brushtail possums exhibit a distinct preovulatory pattern of prolactin (Prl) secretion suggesting that Prl is involved in normal reproductive function. In some mammals, Prl is essential for corpus luteum (CL) function and/or modulation of steroidal effects on hypothalamic-pituitary activity. The aim of this study was to test the effects of biologically active recombinant possum Prl (recPosPrl) on both pituitary gland and CL function in possums. To confirm biological activity, administration of recPosPrl-N2C1 (10 µg) resulted in an 18-fold stimulation (P<0.05) of progesterone (P(4)) production by possum granulosa cells in vitro. Based on these findings, minipumps containing either recPosPrl-N2C1 (n=10) or saline (n=8) were inserted into lactating female possums. The expression levels of pituitary-derived PRL, LHB, FSHB and GNRHR and CL-derived LHR mRNA were quantified. Following a resumption of reproductive activity, no differences in ovulation incidence or plasma Prl concentrations were observed. Plasma Prl levels were less variable (P<0.001) in Prl-treated possums, confirming a self-regulatory role for Prl in this species. There was a marked down-regulation (P<0.001) of FSHB mRNA at the mid-luteal stage in Prl-treated possums, whereas mean PRL, LHB, GNRHR and LHR mRNA expression levels were not different between experimental groups. Plasma P(4) concentrations were not different (P=0.05) in Prl-treated possums, although tended to be higher in the peri-ovulatory and early-luteal phase. We conclude in the brushtail possum that Prl is self-regulated via a short-feedback loop common to all mammals studied and is able to modulate FSHB expression probably at the level of the hypothalamus and/or pituitary gland.

Occupational causes of testicular cancer in adults.

Testicular cancer is one of the commonest cancers in men of working age, and is increasing in incidence in Europe and North America. One suggested mechanism of causation is that there is impaired differentiation of germ cells in the pre- or perinatal period, followed by malignant transformation in later life, possibly by a hormonal mechanism. Endocrine disrupting chemicals (EDCs) have been a major focus of interest for etiological research into testicular cancer because they interact with various hormonal pathways. Several EDCs including bisphenol A, phthalates, metals, polychlorinated biphenyls, and organochlorines have been investigated, but there are few studies and those that exist have not been able to assess exposure well. In addition, several studies, particularly those with better exposure assessment, have suggested that workers in electrical occupations have increased risks of testicular cancer. Electromagnetic radiation may have subthermal effects or may disrupt hormone release. Chronodisruption such as due to shift-work could potentially increase the risk of testicular cancer via disruption of hormonal cycles, but only one study has so far investigated this possibility. Lastly, solvent exposure, particularly to dimethylformamide, has been suggested to be associated with testicular cancer, but almost all these studies are based on job title only, with no specific assessment of solvent exposure. In conclusion, there is little evidence available on which to base definitive statements about occupational causes of testicular cancer. Future studies need to improve exposure assessment and develop ways to adjust for possible prenatal factors.

[Occupational epidemiology]. / Epidemiologie in der Arbeitswelt.

The aim of occupational epidemiology is to describe workplace-related diseases and to identify their underlying causes. Its primary goal is to protect workers from hazardous effects of the working process by applying work-related primary and secondary prevention measures. To assess health risks different study designs and a wide array of complex study instruments and methods are frequently employed that cannot be replaced by toxicological investigations. This paper primarily addresses health risks by agent exposures. In this context a central task of occupational epidemiology is careful assessment of exposure. Different data sources, such as work site measurements, register data, archive material, experts' opinion, and the workers' personal estimates of exposure may be used during this process. In addition, biological markers can complement exposure assessment. Since thorough occupational epidemiologic studies allow assessment of disease risks under realistic exposure conditions, their results should be more frequently used to derive workplace-related threshold limit values.

Occupation and malignant lymphoma: a population based case control study in Germany.

AIMS: To identify occupations suspected to be associated with malignant lymphoma and to generate new hypotheses about occupational risks in a multicentre, population based case control study. METHODS: Male and female patients with malignant lymphoma (n = 710) aged 18-80 years of age were prospectively recruited in six study regions in Germany. For each newly recruited lymphoma case, a sex, region, and age matched control was drawn from the population registers. Odds ratios and 95% confidence intervals for major occupations and industries were calculated using conditional logistic regression analysis, adjusted for smoking (in pack-years) and alcohol consumption. Patients with specific lymphoma subentities were additionally compared with the entire control group using unconditional logistic regression analysis. RESULTS: The following economic/industrial sectors were positively associated with lymphoma: food products, beverages, tobacco; paper products, publishing and printing; and metals. Chemicals; real estate, renting, and business activities were negatively associated with lymphoma diagnosis. The authors observed an increased overall lymphoma risk among architects; maids; farmers; glass formers; and construction workers. Shoemaking and leather goods making was negatively associated with the lymphoma diagnosis (although based on small numbers). In the occupational group analysis of lymphoma subentities, Hodgkin's lymphoma was significantly associated only with rubber and plastic products making; diffuse large B cell lymphoma risk was considerably increased among metal processors; follicular lymphoma showed highly significant risk increases for several occupational groups (medical, dental, and veterinary workers; sales workers; machinery fitters; and electrical fitters); and multiple myeloma showed a particularly pronounced risk increase for farmers as well as for agriculture and animal husbandry workers. CONCLUSIONS: The results partly confirm previously defined occupational risks. Occupational risk factors for follicular lymphomas might differ from the overall risk factors for malignant lymphoma.

Inhibition of the cardiac sarcolemma Na+/Ca2+ exchanger by conformationally constrained small cyclic peptides.

Positively charged cyclic peptides (three to seven amino acids) have been tested for their inhibitory effects on Na+/Ca2+ exchange in the cardiac sarcolemma vesicles. The lead structure of Phe-Arg-Cys-Arg-Cys-Phe-CONH2 (FRCRCFa) has been systematically modified for identification of important pharmacophores. In cyclic peptides (intramolecular S-S bond, the carboxyl terminal is locked with amide (CONH2), and positive charge is retained by one or two arginines, ornithines, or lysines. Thirty-five different cyclic peptides show IC50 values in the range of 2-800 microM, suggesting that some specific structure-activity relationships may determine the inhibitory effects. Shortening of the FRCRCFa length to four amino acids decreases the inhibitory potency by 10-80-fold. The substitution of Arg2 or Arg4 in FRCRCFa with lysine or ornithine decreases the inhibitory potency by 5-12-fold, suggesting that both arginines are beneficial for inhibition. The substitution of Phe1 in FRCRCFa by 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid produces a potent inhibitor (IC50 = 2-4 microM). The N-myristoylated FRCRCFa exhibits an inhibitory potency (IC50 = 8-10 microM) similar to that of the parent FRCRCFa peptide, thereby arousing a new possibility for the development of a cell-permeable blocker of the Na+/Ca2+ exchanger, D-Arg4 or D-Cys5 substitutions in FRCRCFa do not alter the inhibitory effect, whereas the L-to-D substitutions of other amino acids in FRCRCFa reduce the inhibitory potency by 4-5-fold. Thus, the L-to-D substitutions of Arg4 and/or Cys5 have a potential to increase the peptide stability to proteolytic degradation. The insertion of proline outside of the ring of FRCRCFa diminishes the inhibitory potency by 3-6-fold, whereas proline introduction into the ring decreases the inhibitory potency by 16-20-fold. The replacement of Cys3 and Cys5 in FRCRCFa with beta, beta-dimethylcystein has no significant effect on the inhibitory potency, suggesting that the S-S bond is not exposed to the interface of the peptide/receptor interaction. In conclusion, the current data support a proposal that the conformationally constrained Arg-Cys-Arg-Cys structure is obligatory for inhibition of Na+/Ca2+ exchange, whereas hydrophobic additions at the carboxyl and amino ends have limited effects in increasing the inhibitory potency.

Rapid interaction of FRCRCFa with the cytosolic side of the cardiac sarcolemma Na(+)-Ca2+ exchanger blocks the ion transport without preventing the binding of either sodium or calcium.

Positively charged cyclic hexapeptide Phe-Arg-Cys-Arg-Cys-Phe-CONH2 (FRCRCFa) represents a group of conformationally constrained peptides that block the cardiac sarcolemma Na(+)-Ca2+ exchanger [Khananshvili et al. (1995b) J. Biol. Chem. 270, 16182-16188]. Here, we study the kinetic mechanisms of FRCRCFa-induced inhibition of Na(+)-Ca2+ exchange and its partial reaction, the Ca(2+)-Ca2+ exchange. The Nai-dependent 45Ca uptake and Cai-dependent 45Ca uptake were measured by adding the EGTA quench in the semirapid mixer. The reverse mode of Na(+)-Ca2+ exchange (Nao-dependent Ca efflux) was monitored (t = 10-5000 ms) in the stopped-flow machine by measuring extravesicular free calcium with a fluorescence probe fluo-3. Saturating concentrations of FRCRCFa inhibit completely the forward and reverse modes of exchange, suggesting that the inside-out vesicles contribute to most (if not all) of the exchange activity. A short time exposure (t = 10-20 ms) of FRCRCFa with the vesicles is enough to reach a rapid equilibrium between FRCRCFa and a putative inhibitory site at the extravesicular (cytosolic) side of the membrane. A lower limit for the second-order rate constant of FRCRCFa binding can be estimated as a kon of > 10(6) M-1 s-1. A possible competition between FRCRCFa and either Na+ or Ca2+ has been tested at the extravesicular (cytosolic) side of the membrane. At different extravesicular Cao concentrations of 13-250 microM, FRCRCFa inhibits the Na(+)-Ca2+ and Ca(2+)-Ca2+ exchanges with an IC50 of 11-16 microM, suggesting no competition between FRCRCFa and Ca2+. At different extravesicular Nao concentrations of 40-160 mM, FRCRCFa inhibits Nao-dependent Ca efflux with an IC50 of 12-18 microM, suggesting that FRCRCFa and Na+ do not compete for binding at the extravesicular side. A mild proteolytic treatment of vesicles activates the Nai-dependent 45Ca uptake, but has a little effect on the FRCRCFa-induced inhibition. Thus, the "inhibitory site" is still functional after the proteolytic treatment of the inside-out vesicles. In conclusion, a rapid (< 20 ms) interaction of extravesicular (cytosolic) FRCRCFa with the exchanger prevents the ion translocation through the exchanger, while the inhibitory peptide does not interact with the ion transport sites of the exchanger at the cytosolic side of the membrane.

Expression of matrix-metalloproteinases and their inhibitors in human cholesteatomas.

The proteolytic erosion of the temporal bone is the key event in the pathognomonic course of cholesteatoma progression. The molecular mechanisms of bone resorption, endangering the ossicles, the inner ear, the facial nerve, large vessels or the brain, are not understood. Recently, a new family of proteolytic enzymes, the matrix-metalloproteinases (MMP's) has been described and identified, which seems to play a pivotal role in matrix- and bone homeostasis and inflammatory osteolytic diseases, e.g. osteoarthritis and periodontitis. These enzymes are sophisticatedly controlled by specific inhibitors and activation cascades. We investigated whether human cholesteatoma tissue expresses MMP's and MMP-inhibitors. By immunocytochemistry of cholesteatoma-cryosections, the expression of MMP-2 (72 kD collagenase), MMP-9 (92 kD collagenase), and MMP-3 (stromelysin-1) could be seen to be strictly confined to the basal and suprabasal cell layer of the cholesteatoma epithelium. The neutrophil collagenase (MMP-8) showed a more disseminated expression in the epithelium and the granulation tissue as well. The tissue inhibitor of metalloproteases, TIMP-1, could be detected only in very limited areas of the granulation tissue in a quite randomized manner. Therefore, a derailment in favor of proteolysis of the normally tightly controlled MMP-system might be postulated. The results indicate that members of the MMP-family could play an active role in the molecular mechanisms of cholesteatoma invasion into the temporal bone. This offers new insights into the pathophysiology of the disease and of potential therapeutic approaches.

A new analogue of nifurtimox.

1-¿[(5-Nitro-2-furyl)methylene]amino¿-1,2,4-triazole, C7H5N5O3, is a new analogue of nifurtimox with activity against Tripanosoma cruzi. In the crystal structure, the molecule lies on a mirror plane and has an E-sZ conformation along the N = C-C moiety. The molecules are linked through C-H...O and C-H...N interactions.

Mode of action of iron (III) chelators as antimalarials: II. Evidence for differential effects on parasite iron-dependent nucleic acid synthesis.

Iron chelation treatment of red blood cells infected with Plasmodium falciparum selectively intervenes with iron-dependent metabolism of malaria parasites and inhibits their development. Highly permeant hydroxamate iron chelator RSFileum2 affects all parasite stages when cultures are continuously exposed to drug, but affects primarily ring stages when assessed for irreversible effects, ie, sustained inhibition remaining after drug removal. On the other hand, the hydrophilic and poorly permeant desferrioxamine (DFO) affects primarily trophozoite/schizont stages when tested either in the continuous mode or irreversible mode. Unlike parasites, mammalian cells subjected to similar drug treatment show complete growth recovery once drugs are removed. Our studies indicate that parasites display a limited capacity to recover from intracellular iron depletion evoked by iron chelators. Based on these findings we provide a working model in which the irreversible effects of RSFs on rings are explained by the absence of pathways for iron acquisition/utilization by early forms of parasites. Trophozoite/schizonts can partially recover from RSFileum2 treatments, but show no DNA synthesis following DFO treatment even after drug removal and iron replenishment by permeant iron carriers. At trophozoite stage, the parasite uses a limited pathway for refurnishing its iron-containing enzymes, thus overcoming iron deprivation caused by permeant RSFileum2, but not by DFO because this latter drug is not easily removable from parasites. Their DNA synthesis is blocked by the hydroxamate iron chelators probably by affecting synthesis of ribonucleotide reductase (RNRase). Presumably in parasites, prolonged repression of the enzyme leads also to irreversible loss of activity. The action profiles of RSFileum2 and DFO presented in this study have implications for improved chemotherapeutic performance by combined drug treatment and future drug design based on specific intervention at parasite DNA synthesis.

The SOS function-inducing activity of the new nitrothiophenic derivatives in Escherichia coli.

Genotoxicity and cytotoxic effects of eight new nitrothiophenic compounds with trypanocidal activity were determined by means of the SOS Chromotest assay. Our results indicate that all nitro compounds with one aromatic ring in the R group were genotoxic without and with metabolic activation. The compounds with two aromatic rings in the R group, except for indazol-1-yl, were strongly cytotoxic but they were unable to induce SOS functions without metabolic activation. However, after metabolic activation no cytotoxic effect was observed for these compounds. The role of the nitroreductases to explain the different genotoxic responses of these nitrothiophenic derivatives is discussed.

In vivo antimalarial action of a lipophilic iron (III) chelator: suppression of Plasmodium vinckei infection by reversed siderophore.

We assessed in vivo antimalarial action of a lipophilic iron (III) chelator belonging to a new synthetic family of biomimetic siderophores previously termed reversed siderophores (RSFs). The family member, RSF ileum2, was chosen for its high membrane permeability and fast irreversible inhibition of human malaria parasite growth in vitro. [Shanzer A, et al., Proc Natl Acad Sci USA 88:6585, 1991 and Lytton SD, et al., Blood 81:214, 1993]. The lipophilic drug was administered to Swiss mice by subcutaneous route in fractionated coconut oil at a dosage of 0.37 g/kg every 8 hr with no adverse reactions observed. After 3-4 injections demonstrable suppression of Plasmodium vinckei petteri infection was observed and an additional 3-4 injections resulted in 2-3-fold lower parasitemia with prolonged survival time over sham-injected control mice.

The antimalarial action of desferal involves a direct access route to erythrocytic (Plasmodium falciparum) parasites.

We designed the N-methylanthranilic-desferrioxamine (MA-DFO) as a fluorescent iron (III) chelator with improved membrane permeation properties. Upon binding of iron (III), MA-DFO fluorescence is quenched, thus allowing traceability of drug-iron (III) interactions. MA-DFO is well tolerated by mammalian cells in culture. Its antimalarial activity is pronounced: IC50 values on in vitro (24-h) growth of Plasmodium falciparum were 3 +/- 1 microM for MA-DFO compared with 30 +/- 8 for DFO. The onset of growth inhibition of rings or trophozoites occurs 2-4 h after exposure to 13 microM MA-DFO. This effect is commensurate with MA-DFO permeation into infected cells. In a 24-h exposure to MA-DFO or DFO, trophozoites take up either compound to approximately 10% of the external concentration, rings to 5%, and noninfected cells to < 1%. Red cells encapsulated with millimolar concentrations of DFO or MA-DFO fully support parasite invasion and growth. We conclude that extracellular MA-DFO and DFO gain selective access into parasites by bypassing the host. The rate-limiting step is permeation through the parasite membrane, which MA-DFO accomplishes faster than DFO, in accordance with its higher hydrophobicity. These views are consistent with the proposed duct, which apparently provides parasitized cells with a window to the external medium.

Mode of action of iron (III) chelators as antimalarials: I. Membrane permeation properties and cytotoxic activity.

We have designed two subfamilies of lipophilic iron (III) chelators previously termed reversed siderophores (RSFs). The agents display physicochemical properties that favor extraction of iron beyond membrane barriers of Plasmodium falciparum-infected red blood cells. We studied the in vitro antimalarial potency of RSFs and their relationship to the membrane permeation properties of these agents. The mode of RSF action involves: (1) fast access to intracellular compartments of parasitized cells; (2) selective and high-affinity chelation of iron (III) from parasitized cells; (3) fast exit from cells after iron (III) complexation; and (4) exertion of cell damage on parasites exposed for 3 to 5 hours to drugs, irrespective of the stage of parasite development. These results suggest that on reaching a critical intraerythrocyte target, RSFs induce an iron deficit that parasites in general, and rings in particular, have limited capacity to restore.

Formal potentials of new analogues of nifurtimox: relationship to activity.

Electrochemical studies (Formal Potentials and Coulometry) were performed on several analogues of Nifurtimox, in order to gain insight on the proposed mechanism of action of these drugs. It is thought that Nifurtimox shows part of its trypanocidal activity via an electron transfer process, leading to the production of active oxygen species that kill the parasite. Formal potentials provide relevant data about the feasibility of electron transfer in vivo. All analogues tested contained the nitro group, which is the most easily reducible group in the parent drug Nifurtimox. The formal potentials values determined ranged from -1.86 to -0.46 V. Coulometric runs were carried out to study the one-electron transfer process. A good correlation between formal potentials and biological activity was found.

Monitoring of iron(III) removal from biological sources using a fluorescent siderophore.

We present here the physicochemical and biochemical properties of NBD-DFO, the 7-nitrobenz-2-oxa-1,3-diazole (NBD) derivative of the siderophore, desferrioxamine B (DFO) (Lytton et al., Mol. Pharmacol. 40, 584, 1991). Modification of DFO at its terminal amine renders it more lipophilic, imparts to it fluorescent properties, and is conservative of the high-affinity iron(III) binding capacity. NBD-DFO partitions readily from aqueous solution into n-octanol (Pcoeff = 5) and displays solvent-induced shifts in absorption and fluorescence spectra. The relative quantum yield of the probe's fluorescence increases over a 10-fold range with decreasing dielectric constant of the solvent. Fluorescence is quenched upon binding of iron(III) to the probe. We demonstrate here the application of NBD-DFO for the specific detection and monitoring of iron (III) in solutions and iron(III) mobilization from cells. Interactions between fluorescent siderophore and the ferriproteins ferritin and transferrin were monitored under physiological conditions. Iron removal from ferritin was evident by the demonstrable quenching of NBD-DFO fluorescence by scavenged iron(III). Quantitation of iron sequestered from cells by NBD-DFO or from other siderophore-iron(III) complexes was accomplished by dissociation of NBD-DFO-Fe complex by acidification and addition of excess ethylenediamin-etetraacetic acid. The sensitivity of the method and the iron specificity indicate its potential for monitoring chelatable iron under conditions of iron-mediated cell damage, iron overload, and diseases of iron imbalance such as malaria.