What factors are associated with food security among recently arrived refugees resettling in high-income countries? A scoping review.

OBJECTIVE: Refugees are vulnerable to food insecurity (FI). This is attributable to a combination of inequitable social determinants and cultural differences. In 2019, 92 % of refugee resettlement (host country provides residency/citizenship) occurred in high-income countries, but little is known about the factors impacting their food security status in this setting. The review's objective was to therefore thematically identify factors affecting food security among refugees resettling in high-income countries. DESIGN: This review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Between May-July 2020 and February 2021, peer-reviewed studies focused on FI, and published in English from 2000-2020, were searched on Medline, CINAHL, Scopus, Informit, PsychArticles, Proquest and EmBase. SETTING: Only studies set in high-income countries were included. PARTICIPANTS: Fifty percent or more of study participants had to be refugees who had resettled within 5 years. RESULTS: Twenty studies from six high-income countries were included. Culturally based food practices and priorities, confidence in navigating local foodways and transport, level of community connections and capabilities in local language and food preparation were key themes associated with food security. CONCLUSIONS: Utilising the four themes of culture, confidence, community and capabilities, there is an opportunity to improve the cultural sensitivity of measurement tools, develop understanding of how community-based resources (such as social capital) can be leveraged as food security buffers and modify existing food security initiatives to better serve refugee needs.

Does gene expression in laryngeal subsites differ between patients with laryngopharyngeal reflux and controls?

OBJECTIVE: To identify laryngeal mRNA gene changes in patients with laryngopharyngeal reflux (LPR). METHOD: Laryngeal biopsies from non-smoking LPR patients (n=10; Reflux Symptom Index (RSI) >12 and a Reflux Finding Score (RFS) >6) and controls (n=9; RSI <12 and RFS <6) were collected from four subsites (true vocal cord, false vocal cord, medial arytenoid and posterior commissure) of the larynx. qRT-PCR analyses were conducted on 20 reflux- and inflammation-related genes, including interleukins 6 and 8, cytokeratins 8 and 14, mucin genes MUC1, MUC2, MUC3B, MUC4, MUC5B, MUC6 and MUC7 and carbonic anhydrase III. Statistical analysis (Mann-Whitney U test) compared gene expression levels between LPR and control groups at each subsite. RESULTS: Site-specific differences in squamous metaplasia and gene expression were noted in LPR patients, with the majority present in the medial arytenoid region. Significant.differences were noted in genes related to mucosal defence and inflammation, including CRNN, CD1d, TGFß-1, MUC2, MUC5B and CDH1. CONCLUSION: Whilst the posterior commissure is commonly identified as the area demonstrating the most significant macroscopic change in LPR, the histological changes and genes assessed here showed more pronounced LPR associated differences in the medial arytenoid. We identified differences in expression of mucin genes, cytokeratin-14 and molecular markers of inflammation. Whilst some of these changes may be metaplasia-related, further evaluation of the mRNA expression of these genes may provide a useful biomarker panel for diagnosis and therapeutic monitoring of LPR.

Senile hair graying: H2O2-mediated oxidative stress affects human hair color by blunting methionine sulfoxide repair.

Senile graying of human hair has been the subject of intense research since ancient times. Reactive oxygen species have been implicated in hair follicle melanocyte apoptosis and DNA damage. Here we show for the first time by FT-Raman spectroscopy in vivo that human gray/white scalp hair shafts accumulate hydrogen peroxide (H(2)O(2)) in millimolar concentrations. Moreover, we demonstrate almost absent catalase and methionine sulfoxide reductase A and B protein expression via immunofluorescence and Western blot in association with a functional loss of methionine sulfoxide (Met-S=O) repair in the entire gray hair follicle. Accordingly, Met-S=O formation of Met residues, including Met 374 in the active site of tyrosinase, the key enzyme in melanogenesis, limits enzyme functionality, as evidenced by FT-Raman spectroscopy, computer simulation, and enzyme kinetics, which leads to gradual loss of hair color. Notably, under in vitro conditions, Met oxidation can be prevented by L-methionine. In summary, our data feed the long-voiced, but insufficiently proven, concept of H(2)O(2)-induced oxidative damage in the entire human hair follicle, inclusive of the hair shaft, as a key element in senile hair graying, which does not exclusively affect follicle melanocytes. This new insight could open new strategies for intervention and reversal of the hair graying process.

Ribonucleotide reductase in blue-green algae: dependence on adenosylcobalamin.

Ten species of freshwater blue-green algae exhibit an adenosylcobalamin-dependent ribonucleotide reductase, thuse explaining the requirement for cobalt by these organisms. The evidence suggests a phylogenetic affinity between the cyanophytes and bacteria, such as Clostridium and Rhizobium, and the euglenoid flagellates, which also use the cofactor-dependent reductase. In contrast, the ribonucleotide reductase reaction in the few green algae surveyed shows no dependence on cobalamins.

Role of vitamin B12 in methyl transfer for methane biosynthesis by Methanosarcina barkeri.

When Methanosarcina barkeri is grown on methanol as the sole carbon source, a B12-containing protein is synthesized by this organism. This B12 protein contains bound aquocobalamin, and when this cofactor is reduced and methylated with [14C]methyl iodide, the resultant [14C]methyl B12 protein is extremely active in the biosynthesis of 14C-labeled methane. These findings indicate that a B12-dependent system is operative in the biological formation of methane in addition to other systems that are B12-independent.

Isolation of chlorine-containing antibiotic from the freshwater cyanobacterium Scytonema hofmanni.

Scytonema hofmanni, a filamentous freshwater cyanobacterium (blue-green alga), produces secondary metabolites which inhibit the growth of other cyanobacteria and green algae. A rapid, qualitative assay for this inhibition has been developed with Synechococcus as the test organism. This assay procedure has led to the isolation and characterization of an antibiotic (named cyanobacterin) from Scytonema. The antibiotic has a molecular weight of 430 and an empirical formula of C23H23O6Cl and contains a gamma-lactone and a chlorinated aromatic nucleus. It inhibits the growth of various algae but has limited effect on nonphotosynthetic bacteria or protozoans and thus may have potential use as a specific algicide.

Regulation of melanin biosynthesis in the human epidermis by tetrahydrobiopterin.

The participation of (6R) 5,6,7,8-tetrahydrobiopterin (6-BH4) in regulating the tyrosine supply for melanin biosynthesis was investigated by the examination of human keratinocytes, melanocytes, and epidermal suction blisters from normal human skin and from patients with the depigmentation disorder vitiligo. Cells, as well as total epidermis, contained high phenylalanine hydroxylase activities and also displayed the capacity to synthesize and recycle 6-BH4, the essential cofactor for this enzyme. In vitiligo, 4a-hydroxy-BH4 dehydratase activity was extremely low or absent, yielding an accumulation of the nonenzymatic by-product 7-tetrahydrobiopterin (7-BH4) at concentrations up to 8 x 10(-6) M in the epidermis. This by-product is a potent competitive inhibitor in the phenylalanine hydroxylase reaction with an inhibition constant of 10(-6) M. Thus, 6-BH4 seems to control melanin biosynthesis in the human epidermis, whereas 7-BH4 may initiate depigmentation in patients with vitiligo.

H(2)O(2) increases de novo synthesis of (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin via GTP cyclohydrolase I and its feedback regulatory protein in vitiligo.

Patients with vitiligo accumulate up to 10(-3) mol/L concentrations of H(2)O(2) in their epidermis, which in turn affects many metabolic pathways in this compartment, including the synthesis and recycling of the cofactor (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (6BH(4)). De novo synthesis of 6BH(4) is dependent on the rate-limiting enzyme GTP cyclohydrolase I (GTPCHI) together with its feedback regulatory protein (GFRP). This step is controlled by 6BH(4) and the essential amino acid L-phenylalanine. In the study presented here we wanted to investigate whether H(2)O(2) affects the GTPCHI/GFRP cascade in these patients. Our results demonstrated concentration-dependent regulation of rhGTPCHI where 100 micromol/L H(2)O(2) was the optimum concentration for the activation of the enzyme and >300 micromol/L resulted in a decrease in activity. Oxidation of GFRP and GTPCHI does not affect feedback regulation via L-phenylalanine and 6BH(4). In vitiligo a constant upregulation of 6BH(4) de novo synthesis results from epidermal build up of L-phenylalanine that is not controlled by H(2)O(2). Taking the results together, 6BH(4) de novo synthesis is controlled by H(2)O(2) in a concentration-dependent manner, but H(2)O(2)-mediated oxidation does not affect the functionality of the GTPCHI/GFRP complex.

The effects of auditory satellite navigation instructions and visual blur on road hazard perception.

The distracting effects of mobile telephone use while driving are well known, however the effects of other sources of distraction, such as auditory navigation devices, are less well understood. Whether the effects of auditory distraction might interact with other sensory impairments, such as vision impairment, is of interest given that visual impairment is relatively common within the population, particularly as a result of uncorrected refractive error. In this experiment, 20 current drivers (mean age of 29.4 ± 3.2 years), binocularly viewed video recordings of traffic scenes presented as part of the Hazard Perception Test and responded to potential hazards within the traffic scenes. Half of the presented scenes included auditory navigation instructions as an auditory distractor. Additionally, some of the scenes were viewed through optical lenses to induce different levels of refractive blur (+0.50 DS, +1.00 DS and +2.00 DS). Hazard perception response times increased significantly (p < 0.05) with increasing blur. Participants were significantly slower in reacting to hazards for the +1.00 DS and +2.00 DS blur conditions compared to the control condition (with no blur). There was also a significant increase in response times to hazards in the presence of the auditory navigation instructions. The combined effect of blur and auditory instructions was additive, with the worst performance being in the presence of both blur and auditory instructions. These results suggest that the delivery of auditory navigation guidance for those with visual impairments, such as blur, which are relatively common in the population, should be further investigated.

Osmosensing by bacteria: signals and membrane-based sensors.

Bacteria can survive dramatic osmotic shifts. Osmoregulatory responses mitigate the passive adjustments in cell structure and the growth inhibition that may ensue. The levels of certain cytoplasmic solutes rise and fall in response to increases and decreases, respectively, in extracellular osmolality. Certain organic compounds are favored over ions as osmoregulatory solutes, although K+ fluxes are intrinsic to the osmoregulatory response for at least some organisms. Osmosensors must undergo transitions between "off" and "on" conformations in response to changes in extracellular water activity (direct osmosensing) or resulting changes in cell structure (indirect osmosensing). Those located in the cytoplasmic membranes and nucleoids of bacteria are positioned for indirect osmosensing. Cytoplasmic membrane-based osmosensors may detect changes in the periplasmic and/or cytoplasmic solvent by experiencing changes in preferential interactions with particular solvent constituents, cosolvent-induced hydration changes, and/or macromolecular crowding. Alternatively, the membrane may act as an antenna and osmosensors may detect changes in membrane structure. Cosolvents may modulate intrinsic biomembrane strain and/or topologically closed membrane systems may experience changes in mechanical strain in response to imposed osmotic shifts. The osmosensory mechanisms controlling membrane-based K+ transporters, transcriptional regulators, osmoprotectant transporters, and mechanosensitive channels intrinsic to the cytoplasmic membrane of Escherichia coli are under intensive investigation. The osmoprotectant transporter ProP and channel MscL act as osmosensors after purification and reconstitution in proteoliposomes. Evidence that sensor kinase KdpD receives multiple sensory inputs is consistent with the effects of K+ fluxes on nucleoid structure, cellular energetics, cytoplasmic ionic strength, and ion composition as well as on cytoplasmic osmolality. Thus, osmoregulatory responses accommodate and exploit the effects of individual cosolvents on cell structure and function as well as the collective contribution of cosolvents to intracellular osmolality.

Gene products that promote mRNA turnover in Saccharomyces cerevisiae.

We showed previously that the increased rate of mRNA turnover associated with premature translational termination in the yeast Saccharomyces cerevisiae requires a functional UPF1 gene product. In this study, we show that the UPF1 gene codes for a 109-kDa primary translation product whose function is not essential for growth. The protein contains a potential zinc-dependent nucleic acid-binding domain and a nucleoside triphosphate-binding domain. A 300-amino-acid segment of the UPF1 protein is 36% identical to a segment of the yeast SEN1 protein, which is required for endonucleolytic processing of intron-containing pre-tRNAs. The same region is 32% identical to a segment of Mov-10, a mouse protein of unknown function. Dominant-negative upf1 mutations were isolated following in vitro mutagenesis of a plasmid containing the UPF1 gene. They mapped exclusively at conserved positions within the sequence element common to all three proteins, whereas the recessive upf1-2 mutation maps outside this region. The clustering of dominant-negative mutations suggests the presence of a functional domain in UPF1 that may be shared by all three proteins. We also identified upf mutations in three other genes designated UPF2, UPF3, and UPF4. When alleles of each gene were screened for effects on mRNA accumulation, we found that the recessive mutation upf3-1 causes increased accumulation of mRNA containing a premature stop codon. When mRNA half-lives were measured, we found that excess mRNA accumulation was due to mRNA stabilization. On the basis of these results, we suggest that the products of at least two genes, UPF1 and UPF3, are responsible for the accelerated rate of mRNA decay associated with premature translational termination.

Eosinophilic oesophagitis: an otolaryngologist's perspective.

Eosinophilic oesophagitis is a diagnosis that is being made more frequently in the assessment of dysphagia in both adults and children. It is unclear whether this is a result of increased prevalence or improved diagnostic methods. Children present commonly to paediatric institutions with foreign body impaction. Research indicates that food impaction may predispose to eosinophilic oesophagitis. This article presents eosinophilic oesophagitis from an otolaryngologist's point of view. It details the clinical features present in the disease as well as how it is diagnosed and managed. It illustrates early signs of eosinophilic oesophagitis so that primary physicians and emergency physicians know when to refer on to otolaryngologists.

Therapeutic potential of NADPH oxidase 1/4 inhibitors.

The NADPH oxidase (NOX) family of enzymes produces ROS as their sole function and is becoming recognized as key modulators of signal transduction pathways with a physiological role under acute stress and a pathological role after excessive activation under chronic stress. The seven isoforms differ in their regulation, tissue and subcellular localization and ROS products. The most studied are NOX1, 2 and 4. Genetic deletion of NOX1 and 4, in contrast to NOX2, has revealed no significant spontaneous pathologies and a pathogenic relevance of both NOX1 and 4 across multiple organs in a wide range of diseases and in particular inflammatory and fibrotic diseases. This has stimulated interest in NOX inhibitors for therapeutic application. GKT136901 and GKT137831 are two structurally related compounds demonstrating a preferential inhibition of NOX1 and 4 that have suitable properties for in vivo studies and have consequently been evaluated across a range of disease models and compared with gene deletion. In contrast to gene deletion, these inhibitors do not completely suppress ROS production, maintaining some basal level of ROS. Despite this and consistent with most gene deletion studies, these inhibitors are well tolerated and slow or prevent disease progression in a range of models of chronic inflammatory and fibrotic diseases by modulating common signal transduction pathways. Clinical trials in patients with GKT137831 have demonstrated excellent tolerability and reduction of various markers of chronic inflammation. NOX1/4 inhibition may provide a safe and effective therapeutic strategy for a range of inflammatory and fibrotic diseases. LINKED ARTICLES: This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Bilateral cataract surgery and driving performance.

BACKGROUND: Cataract surgery is one of the most common medical procedures undertaken worldwide. AIMS: To investigate whether cataract surgery can improve driving performance and whether this can be predicted by changes in visual function. METHODS: 29 older patients with bilateral cataracts and 18 controls with normal vision were tested. All were licensed drivers. Driving and vision performance were measured before cataract surgery and after second eye surgery for the patients with cataract and on two separate occasions for the controls. Driving performance was assessed on a closed-road circuit. Visual acuity, contrast sensitivity, glare sensitivity and kinetic visual fields were measured at each test session. RESULTS: Patients with cataract had significantly poorer (p<0.05) driving performance at the first visit than the controls for a range of measures of driving performance, which significantly improved to the level of the controls after extraction of both cataracts. The change in contrast sensitivity after surgery was the best predictor of the improvements in driving performance in patients with cataract. CONCLUSIONS: Cataract surgery results in marked improvements in driving performance, which are related to concurrent improvements in contrast sensitivity.

Melanocortins in human melanocytes.

Human epidermal keratinocytes and melanocytes express proopiomelanocortins (POMC) and all of the enzymes for POMC processing, i.e. prohormone convertases PC-1 and PC-2 including the regulatory protein 7B2. In melanocytes POMC processing also occurs in the melanosome, a lysosome-derived organelle that specializes in the biosynthesis of melanin. Consequently, the autocrine synthesis and release of the key hormones ACTH, alpha and beta-MSH and beta-endorphin takes also place in melanocytes. All four hormones have been reported to promote the biosynthesis of eumelanin in melanocytes. ACTH and alpha-MSH bind to the melanocortin-1 receptor (MC-1-R) on the plasma membrane and activate the signalling pathway predominantly coupled to production of cAMP, and in some cell lines raising intracellular calcium levels. In the melanocyte this signalling is redundant due to the high expression of alpha1 and beta2-adrenoceptors. Downstream events increase melanocyte this signalling is redundant due to the high expression of a tyrosinase expression / activity to stimulate eumelanogenesis. Studies with rMC-1-R transfected COS cells showed that both ACTH and alpha-MSH bind to the receptor with similar or different affinity depending on the species (human vs mice). We have modelled the MC-1-R based on the X-ray crystal structure of a homologous 7 receptor rhodopsin. Docking studies with ACTH1-39, ACTH1-17 and ACTH11-17 and alpha-MSH1-13 revealed that all 3 ACTH peptides yield thermodynamically stable (key ACTH1-13 in-lock) complexes. Interestingly, alpha-MSH is predicted to only have a kinetic effect on the MC-1-R and beta-MSH has even a weaker affinity for the MC-1-R than alpha-MSH. Based on these results the relative importance of ACTH versus alpha-MSH in the human epidermis has been re-evaluated.

PTK787/ZK 222584, a novel and potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, impairs vascular endothelial growth factor-induced responses and tumor growth after oral administration.

PTK787/ZK 222584 (1-[4-chloroanilino]-4-[4-pyridylmethyl] phthalazine succinate) is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, active in the submicromolar range. It also inhibits other class III kinases, such as the platelet-derived growth factor (PDGF) receptor beta tyrosine kinase, c-Kit, and c-Fms, but at higher concentrations. It is not active against kinases from other receptor families, such as epidermal growth factor receptor, fibroblast growth factor receptor-1, c-Met, and Tie-2, or intracellular kinases such as c-Src, c-Abl, and protein kinase C-alpha. PTK787/ZK 222584 inhibits VEGF-induced autophosphorylation of kinase insert domain-containing receptor (KDR), endothelial cell proliferation, migration, and survival in the nanomolar range in cell-based assays. In concentrations up to 1 microM, PTK787/ZK 222584 does not have any cytotoxic or antiproliferative effect on cells that do not express VEGF receptors. After oral dosing (50 mg/kg) to mice, plasma concentrations of PTK787/ZK 222584 remain above 1 microM for more than 8 h. PTK787/ZK 222584 induces dose-dependent inhibition of VEGF and PDGF-induced angiogenesis in a growth factor implant model, as well as a tumor cell-driven angiogenesis model after once-daily oral dosing (25-100 mg/kg). In the same dose range, it also inhibits the growth of several human carcinomas, grown s.c. in nude mice, as well as a murine renal carcinoma and its metastases in a syngeneic, orthotopic model. Histological examination of tumors revealed inhibition of microvessel formation in the interior of the tumor. PTK787/ZK 222584 is very well tolerated and does not impair wound healing. It also does not have any significant effects on circulating blood cells or bone marrow leukocytes as a single agent or impair hematopoetic recovery after concomitant cytotoxic anti-cancer agent challenge. This novel compound has therapeutic potential for the treatment of solid tumors and other diseases where angiogenesis plays an important role.

The activity and purification of membrane-associated thioredoxin reductase from human metastatic melanotic melanoma.

Electron spin resonance spectroscopy has been used to measure the reduction of nitroxide radicals on a spin-labeled quaternary ammonium substrate by plasma membrane-associated thioredoxin reductase (EC 1.6.4.5) at the surface of cutaneous and subcutaneous melanoma metastases from one patient (B.M.). Enzyme activity in these metastases was shown to be hyperactive compared to normal skin and was subject to inhibition by calcium. From the remainder of the tissue (50.6 g), plasma membrane-associated thioredoxin reductase has been isolated and its molecular properties were compared with the same enzyme purified from the cytosol of rat liver and Escherichia coli. The enzyme from melanoma possessed an identical molecular weight to that from rat liver as determined by SDS-polyacrylamide gel electrophoresis (Mr 58,000). Upon fluorescence spectroscopic examination, the enzyme from melanoma was shown to contain flavin adenine dinucleotide as previously shown in the enzymes from E. coli and rat liver. The increased activities in plasma membrane-associated thioredoxin reductase in metastases of malignant melanotic melanoma are discussed in terms of the cellular functions of this important enzyme.

Studies on the reactions between human tyrosinase, superoxide anion, hydrogen peroxide and thiols.

Human tyrosinase (5.5 mg) has been purified from a single human melanotic melanoma metastasis (50.5 g). In the presence of dioxygen, L-tyrosine proved to be a very poor substrate for this enzyme with barely detectable activity compared to L-dopa. However, saturating superoxide anion (i.e., greater than 5 x 10(-3) M) enhanced the oxidation rate of L-tyrosine to dopachrome 40-fold. Hydrogen peroxide was shown to be a competitive inhibitor of tyrosinase when L-tyrosine was the substrate. This reversible inhibition is based on a slow pseudocatalase activity for tyrosinase. Monothiols and dithiols inhibit tyrosinase by different mechanisms. Reduced human thioredoxin and 2,3-dithiopropanol are allosteric inhibitors of tyrosinase yielding bis-cysteinate complexes with one of the copper atoms in the enzyme active site. Bis-cysteinate tyrosinase activity is down-regulated to 30% of native enzyme activity in the L-dopa assay; suggesting a true regulatory role for dithiols. Monothiols such as reduced glutathione and beta-mercaptoethanol are much less reactive with tyrosinase although 10(-3) M monothiol totally inhibits enzyme activity. Reduced thioredoxin inhibits tyrosinase 23-fold more than reduced glutathione under the same experimental conditions.

Prevention of Ca(2+)-induced or thromboxane B2-induced hepatocyte plasma membrane bleb formation by thromboxane receptor antagonists.

Isolated hepatocytes incubated in the presence of either Ca2+ ionophore A23187 or thromboxane B2 develop many plasma membrane blebs which are a characteristic feature of toxic or ischaemic cell injury. When hepatocytes are incubated in the presence of both Ca2+ ionophore A23187 and any one of three thromboxane receptor antagonists (SK and F 88046, B.M. 13505, B.M. 13177), bleb formation is strongly inhibited. Hepatocytes incubated in the presence of both thromboxane B2 and any one of the three thromboxane receptor antagonists are also well protected from the formation of blebs. Treatment of isolated hepatocytes with Ca2+ ionophore A23187 is known to stimulate the production of thromboxanes. The data presented are consistent with thromboxane B2 acting as an intermediary in a proposed mechanism of cell injury and death in which elevated cytosolic free Ca2+ levels activate phospholipase A2 and the arachidonate cascade.

Sensitivity and resistance in human metastatic melanoma to the new chloroethylnitrosourea anti-tumor drug Fotemustine.

Fotemustine is a novel chloroethylnitrosourea derivative currently used in Phase III clinical trials for disseminated metastatic melanoma. This drug has been shown to inhibit enzymes in the ribonucleotide reduction pathway (i.e., thioredoxin reductase, glutathione reductase and ribonucleotide reductase). 14C chloroethyl-labelled Fotemustine covalently labels the thiolate active sites of thioredoxin reductase and glutathione reductase yielding 14C chloroethyl-thioether enzyme-inhibitor complexes. Enzyme activities can be restored by a reduced thioredoxin or reduced glutathione mediated beta-elimination of the chloroethyl group. 14C Fotemustine has been used to determine its reactivity and metabolism in drug sensitive and resistant melanoma metastases and in cultures of sensitive and resistant clones of human melanoma cells. Melanoma metastases from four different patients who were treated with Fotemustine could be labelled with radioactive drug only under reducing conditions with NADPH as electron donor and DTNB as substrate. FPLC analysis of these extracts revealed two radioactive proteins (I) glutathione reductase and (II) an unidentified protein with 95 and 50 kDa subunits. A similar labelling pattern was also found in extracts of Fotemustine sensitive melanoma cells (Cal 1). Fotemustine resistant tumors were melanotic and contained more glutathione reductase than thioredoxin reductase, whereas sensitive tumors were clinically amelanotic with more thioredoxin reductase than glutathione reductase. Fotemustine resistant melanoma cells (Cal 7) showed a slower uptake of 14C-label with 34% less isotope intracellularly in 1 h compared to sensitive melanoma cells (Cal 1). These results strongly indicate (I) the induction of alternate electron donors thioredoxin reductase or glutathione reductase for ribonucleotide reduction determines tumor and melanoma cell responses to the drug and (II) Fotemustine transport and the intracellular redox status seems to regulate resistance in melanoma cells and tissues.