25 years of RIFE-a brief history and highlights

In 2020, the UK environmental regulators and food safety agencies, published the 25th edition of the Radioactivity in Food and the Environment (RIFE) report. This marks a quarter of a century since the landmark RIFE report was first published by the Ministry of Agriculture, Fisheries and Food in 1996, which represented the first joint monitoring and assessment report for the United Kingdom. This paper provides a summary of the RIFE report, how it has evolved and presents some case studies from over the 25 year period.

CYP2E1-mediated modulation of valproic acid-induced hepatocytotoxicity

OBJECTIVES

To determine the cytotoxicity of valproic acid (VPA) and its metabolite, 4-ene-valproic acid (4-ene-VPA) in human hepatoblastoma cells (Hep G2), and to study the modulatory effect of cytochrome P450 2E1 induction in this model.

METHODS

Cells were exposed to VPA or 4-ene-VPA in the presence of either ethanol (EtOH), or EtOH combined with disulphiram (DS). Some cells were exposed to alpha-fluoro-VPA or to alpha-fluoro-4-ene-VPA in the absence of CYP2E1 inducers. Apoptosis and necrosis were measured by analyzing 6000 cells per sample using transmission electron microscopy, while cytokine release and apoptosis were quantitated by ELISA.

RESULTS

VPA + EtOH increased VPA cytotoxicity. 4-ene-VPA + EtOH significantly increased toxicity, while DS + EtOH significantly reduced this toxicity. Alpha-fluorinated analogues reduced cytotoxicity compared to the corresponding VPA compounds. Neither VPA nor alpha-fluorinated VPA increased the release of IL-6 or TNF-alpha in media. A significant increase in the release of TNF-alpha was observed in cells exposed to 4-ene-VPA that further increased with EtOH exposure.

CONCLUSIONS

Cells exposed to 4-ene-VPA experience greater cytotoxicity than those treated with VPA. Cytochrome P450 2E1 inducers enhance toxicity in VPA-exposed cells, while alpha-fluorination of VPA diminishes cytotoxicity by directly interfering with the beta-oxidation of the 4-ene-VPA metabolite.

Attenuation of morphine-induced delirium in palliative care by substitution with infusion of oxycodone

We have observed among patients of the Southern Community Hospice Programme that up to 25% experience acute delirium when treated with morphine and improve when the opioid is changed to oxycodone or fentanyl. This study aimed to confirm by a prospective trial that oxycodone produces less delirium than morphine in such patients. Oxycodone was administered by a continuous subcutaneous infusion, as this allowed more flexible and reliable dosing, and patients were monitored for any adverse reactions to the drug. Thirteen patients completed the study. Statistically significant improvements in mental state and nausea and vomiting occurred following a change from morphine to oxycodone. Pain scores improved but did not reach a level of statistical significance. The phenotype status of the patients was tested to establish their capacity to metabolize oxycodone. One patient who did not achieve adequate pain control proved to be a poor metabolizer. These results show that oxycodone administered by the subcutaneous route can provide effective analgesia without significant side effects in patients with morphine-induced delirium. This treatment allows patients to remain more comfortable and lucid in their final days. A small proportion of patients who do not metabolize oxycodone effectively may not receive this benefit.

Setting up a shared care glaucoma clinic

This article describes how a nurse-led clinic to care for patients with glaucoma was set up and provides some initial evidence of its success. The authors also explain how they have developed the clinic further and their plans for the future.

Plasma concentrations of fentanyl with subcutaneous infusion in palliative care patients

1. Plasma concentrations of fentanyl were measured by g.c. in 20 patients (median age: 75 years and range: 54-86 years; eight females) in palliative care receiving the drug by continuous s.c. infusion (median rate: 1200 micrograms day-1 and range: 100-5000 micrograms day-1). 2. The infusion rate was significantly related to the duration of therapy (Spearman rho = 0.56, P < 0.05). The total steady-state plasma concentrations of fentanyl ranged between 0.1 and 9 ng ml-1, with a median of 1 ng ml-1. The unbound fraction of fentanyl in the plasma ranged from 17.8 to 44.4%, with a median value of 33.6%. Infusion rates and both total and unbound plasma concentrations of fentanyl were correlated (Spearman rho = 0.92, P < 0.05 in each case). Even with standardization for dosage, there was an eightfold variation in total plasma concentrations and 3.5-fold variation in unbound plasma concentrations of fentanyl. 3. There is considerable inter-patient variability in the pharmacokinetics of fentanyl with s.c. infusion in the palliative care setting, which necessitates careful titration of dosage according to individual clinical response.

In vivo formation of the thiol conjugates of reactive metabolites of 4-ene VPA and its analog 4-pentenoic acid

The terminal olefin metabolite of valproic acid (VPA), 4-ene VPA, is an analog of the experimental hepatotoxin 4-pentenoic acid and is believed to play a role in the hepatotoxicity of VPA. The formation of glutathione and N-acetylcysteine conjugates of the putative electrophilic metabolites of 4-ene VPA and 4-pentenoic acid was studied in vivo in the rat. Animals were treated intraperitoneally with the sodium salts of VPA, 4-ene VPA, (E)-2,4-diene VPA, 4-pentenoic or (E)-2,4-pentadienoic acids, and methylated bile and urine extracts were analyzed by LC/MS/MS and GC/MS techniques. The alpha,beta-unsaturated reactive metabolite of 4-pentenoic acid, 3-oxo-4-pentenoic acid, was isolated and identified as its thiol conjugates. In contrast, 3-oxo-4-ene VPA or its thiol conjugates could not be demonstrated as metabolites even though synthetic standards were available to facilitate their detection. Isolation of the thiol conjugates of 3-oxo-4-pentenoic acid provides the first direct spectroscopic evidence for the in vivo formation of the metabolite of 4-pentenoic acid considered responsible for the irreversible inhibition of fatty acid metabolism. The biliary and urinary metabolite profiles of 4-ene VPA and 4-pentenoic acid revealed basic differences between the in vivo metabolism of these two unsaturated carboxylic acids.

Treatment of chronic severe alopecia areata with topical diphenylcyclopropenone and 5% minoxidil: a clinical and immunopathologic evaluation

BACKGROUND

Topical diphenylcyclopropenone (DPCP) and minoxidil have been used in the treatment of alopecia areata with variable results.

OBJECTIVE

This study was designed to evaluate the efficacy of DPCP alone or in combination with topical 5% minoxidil for the treatment of chronic severe alopecia areata. The effect of therapy on cutaneous T-cell and Langerhans cell subpopulations and intercellular adhesion molecule-1 (ICAM-1) expression was also examined.

METHODS

Fifteen patients with chronic (more than 2 years), severe (more than 50% scalp involvement) alopecia areata participated in a 24-week trial. Half of the scalp was treated with DPCP once weekly and with either 5% minoxidil solution or a vehicle solution twice daily in a randomized double-blind design. Skin biopsy specimens from each half of the scalp were obtained before therapy and after 12 and 24 weeks of therapy for histologic and immunophenotypic analysis.

RESULTS

Thirteen patients completed the study. Five of 13 patients (38%) showed marked regrowth of coarse terminal hair after 24 weeks of treatment with DPCP. The addition of topical 5% minoxidil did not produce any significant clinical benefit in this 24-week trial. Immunophenotypic analysis showed no differences between responders and nonresponders at baseline. During treatment, Leu-4, Leu-2, Leu-3, and keratinocyte ICAM-1 expression were significantly reduced in biopsy specimens of responders versus nonresponders.

CONCLUSION

DPCP treatment showed a 38% success rate in producing cosmetically acceptable regrowth in patients with chronic severe alopecia areata.

Glomerular mesangial cells and inflammatory macrophages ingest neutrophils undergoing apoptosis

Apoptosis or programmed cell death of senescent neutrophils leading to their uptake by phagocytes is a general mechanism by which neutrophils may be removed from inflamed sites in vivo, promoting resolution rather than persistence of inflammation. We now report morphological evidence of neutrophil apoptosis leading to uptake by glomerular cells in rats with experimental glomerulonephritis. In addition to confirming that inflammatory macrophages take up apoptotic neutrophils, these studies indicated that glomerular mesangial cells can also participate in this mode of neutrophil clearance. Furthermore, human neutrophils which had been "aged" in vitro so as to undergo apoptosis were ingested by 31.5 +/- 1.3% (mean +/- SE) of cultured human mesangial cells, but there was minimal recognition of freshly isolated neutrophils (2.2 +/- 0.1%). Centrifugal elutriation of aged neutrophil populations yielded fractions with varying degrees of apoptosis (from 11.1 to 79.4%). Uptake of these fractions (by 8.2% to 59.8% of mesangial cells) was closely correlated with apoptosis (r = 0.96, P less than 0.0001). This demonstrated that recognition was dependent upon apoptosis, as in previous reports of macrophage recognition of aged neutrophils. However, by contrast, a partial requirement for serum was observed. These data indicate a hitherto unexpected function for the mesangial cell in clearance of senescent neutrophils from the glomerulus which may supplement inflammatory macrophage uptake of leucocytes undergoing apoptosis.

Interleukin-1 beta stimulates human mesangial cells to synthesize and release interleukins-6 and -8

Interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF) have been reported to stimulate human mesangial cells (HMC) to proliferate and synthesize eicosanoids. We have examined whether they also induce HMC to release cytokines. In this study we show that both IL-1 and TNF stimulate HMC to release IL-6 and IL-8. Cycling and quiescent HMC were stimulated with various concentrations of either recombinant IL-1 beta or TNF for 1 to 24 hours. IL-1 beta at doses as low as 6 pg/ml stimulated mesangial cells to synthesize mRNA for both IL-6 and IL-8 as assessed by Northern analysis; mRNA for tubulin remained constant, which demonstrated a specific increase in mRNA. Secretion of IL-6 and IL-8 into the culture medium increased (4.5 to 18 ng/ml and 4 to 40 ng/ml, respectively) measured by ELISAs. TNF had similar effects but only in high concentrations (greater than 100 ng/ml). IL-1 beta did not stimulate cells to proliferate, as measured by 3H thymidine incorporation. TNF caused proliferation but only in concentrations over 100 ng/ml. We conclude that IL-1 beta is a potent stimulator of human mesangial cell production of IL-6 and IL-8, both of which may influence injury in nephritis. TNF also stimulates mesangial cells but only in pharmacological doses.

Identification and characterization of the glutathione and N-acetylcysteine conjugates of (E)-2-propyl-2,4-pentadienoic acid, a toxic metabolite of valproic acid, in rats and humans

The severe hepatotoxicity of valproic acid (VPA) is believed to be mediated through reactive metabolites. The formation of glutathione (GSH) and N-acetylcysteine (NAC) adducts of reactive intermediates derived from VPA and two of its metabolites, 2-propyl-4-pentenoic acid (4-ene-) and 2-propyl-2,4-pentadienoic acid [(E)-2,4-diene VPA], was investigated in the rat. Rats were dosed ip with 100 mg/kg of VPA, 4-ene-, or 2,4-diene-VPA, and methylated bile and urine extracts were analyzed by LC/MS/MS and GC/MS, respectively. The GSH conjugate of (E)-2,4-diene VPA was detected in the bile of rats treated with 4-ene- and (E)-2,4-diene VPA. The NAC conjugate was a major urinary metabolite of rats given (E)-2,4-diene VPA and was a prominent urinary metabolite of those animals given 4-ene VPA. The NAC conjugate was also found to be a metabolite of VPA in patients. Both the GSH and NAC adducts were chemically synthesized and their structures established to be 5-(glutathion-S-yl)3-ene VPA and 5-(N-acetylcystein-S-yl)3-ene VPA by NMR and mass spectrometry. In contrast to the very slow reaction of the free acid of (E)-2,4-diene VPA with GSH, the methyl ester reacted rapidly with GSH to yield the adduct. In vivo it appears the diene forms an intermediate with enhanced electrophilic reactivity to GSH as indicated by the facile reaction of the diene with GSH in vivo [about 40% of the (E)-2,4-diene VPA administered to rats was excreted as the NAC conjugate in 24 hr]. The characterization of the GSH and NAC (in humans and rats) conjugates of (E)-2,4-diene VPA suggests that VPA is metabolized to a chemically reactive intermediate that may contribute to the hepatotoxicity of the drug.

Metabolic profiling of valproic acid in patients using negative-ion chemical ionization gas chromatography-mass spectrometry

A negative-ion chemical ionization gas chromatographic-mass spectrometric method for the determination of valproic acid (VPA) and fourteen of its metabolites in a single chromatographic run is reported. The assay features the use of four internal standards and is applicable to the analysis of small serum and urine volumes. A combination of pentafluorobenzyl and trimethylsilyl derivatization resulted in the [M - 181]- ion as the base peak for all the metabolites measured. When these ions were monitored sensitivities in the low picogram levels were achieved. The VPA metabolite profile was determined in pediatric patients on VPA monotherapy and on combined VPA therapy with either carbamazepine or clobazam. The recently characterized diene metabolite, (E,E)-2,3'-diene-VPA, was found to be a major serum metabolite of VPA. In the patient groups taking VPA in combination with carbamazepine, the induction of omega and omega-1 pathways of VPA metabolism was apparent, while the levels of the beta-oxidation products were significantly decreased.

Monoamine oxidase inhibitors in South American hallucinogenic plants: tryptamine and beta-carboline constituents of ayahuasca

Ayahuasca is a hallucinogenic beverage derived by boiling the bark of the Malpighiaceous liana Banisteriopsis caapi together with the leaves of various admixture plants, viz. Psychotria viridis, Psychotria carthagenensis , or Diplopterys cabrerana . B. caapi contains harmine, harmaline, and tetrahydroharmine while the admixtures contain N,N-dimethyltryptamine (DMT). DMT, a potent hallucinogen, is inactive orally due to degradation by visceral monoamine oxidase (MAO). The beta-carbolines, however, are highly active reversible inhibitors of MAO and may protect the DMT from deamination by MAO and render it orally active. This mechanism has been proposed to underlie the oral activity of ayahuasca but has not been experimentally confirmed. In the present study the constituents of the admixture plants and the alkaloids of eight ayahuasca samples from Peru were qualitatively and quantitatively analyzed using two-dimensional thin-layer chromatography (TLC), high pressure liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). Several B. caapi cultivars were quantitatively compared for variations in alkaloid content. Three admixture plants used rarely in the manufacture of ayahuasca were also screened for alkaloids. A selected sample of beta-carbolines were screened for activity as MAO inhibitors using an in vitro assay system, and structure/activity relationships were compared. Inhibition observed with single compounds was compared with the activity of selected samples of ayahuasca which were screened in the system and also with the activity of mixtures of beta-carbolines. The levels of DMT and beta-carbolines found in the ayahuasca samples examined in the present study were an order of magnitude greater than the levels reported in a previous study. Ayahuasca was found to be an extremely effective inhibitor of MAO in vitro and the degree of inhibition was directly correlated with the concentration of MAO-inhibiting beta-carbolines. Inhibition experiments using mixtures of beta-carbolines indicated that their effects in combination are additive, rather than synergistic or antagonistic. Implications of the results in understanding the pharmacology of ayahuasca are discussed.

Identification of valproic acid metabolites in human serum and urine using hexadeuterated valproic acid and gas chromatographic mass spectrometric analysis

Valproic acid, an antiepileptic drug, is extensively metabolized in humans. A hexadeuterated valproic acid was used in this study to aid the identification of metabolites and their artifacts in serum and urine extracts. A 600 mg oral dose of hexadeuterated valproic acid was administered to a human volunteer at steady state serum concentrations of unlabelled valproic acid. By using gas chromatography mass spectrometry, metabolites were characterized as their methyl, tert-butyldimethylsilyl, or trimethylsilyl derivatives. A di-unsaturated metabolite with concentrations comparable to 2-ene valproic acid was identified in serum and urine. The presence of a molecular ion doublet in the mass spectrum corresponding to the unlabelled and hexadeuterated dienes reduces the possible structures for this metabolite. A new metabolite, 2-propyl-4-ketopentanoic acid was also identified in serum and in urine. The dicarboxylic acids, 2-propylsuccinic and 2-propylmalonic were identified in the urine extract as metabolites. Identification of isolated metabolites was aided by comparison of the retention times and mass spectra to those of synthesized reference compounds. Diagnostic fragment ions and ion doublets in the mass spectra of the derivatives of newly identified metabolites were compared to those of known metabolites.

CLEO 1981

The Optical Society of America, together with the Institute of Electrical and Electronics Engineers, Quantum Electronics and Applications Society, sponsored the first Conference on Laser and Electrooptics held in Washington, D.C., in June 1981. The 15 May 1982 issue of Applied Optics contains sixteen of the papers presented.

Fluorescence energy-transfer measurements between the calcium binding site and the specificity pocket of bovine trypsin using lanthanide probes

Using fluorescence energy-transfer experiments we have measured the distance between the specificity pocket and the calcium ion binding site of bovine pancreatic trypsin. Proflavin and thionine were used to block the specificity site, whereas various lanthanide ions were substituted for the calcium. It was then possible to choose various donor-acceptor pairs which exhibit suitable energy transfer. We have calculated the distance between proflavin and Nd(III), Pr(III), and Ho(III) to be 10.9, and 10.3, and 10.3 A, respectively. This agrees very well with the value of approximately 10 A we obtained between the methyl protons of p-toluamidine (a competitive inhibitor) and Gd(III) using nuclear magnetic resonance techniques (Abbott, F., Gomez, J.E., Birnbaum, E.R., and Darnall, D.W. (1975), Biochemistry 14, 4935). This is strong evidence that, in solution, the calcium binding site is composed of the side chains of Ser-190 and Asp-194.

The location of the calcium ion binding site in bovine alpha-trypsin and beta-trypsin using lanthanide ion probes

The effect of Gd3+ on the nuclear magnetic resonance (NMR) relaxation rates, T1m-1 and T2m-1, of inhibitor protons in metal-inhibitor-trypsin ternary complexes has been measured. The Solomon-Bloembergen equations have been used to calculate distances of 10.0 +/- 0.5, 8.8 +/- 0.5, and 9.5 +/- 0.5 A between the metal ion and the methyl and ortho protons of p-toluamidine, and the methyl protons of acetamidine, respectively. Essentially the same results are obtained for both alpha-trypsin and beta-trypsin. Binding constants of 3.3 x 10(3) and 4.1 x 10(3) M-1 for the association of Gd(III) with alpha-trypsin and beta-trypsin, respectively, in the presence of p-toluamidine at pH 6.0 have been obtained by equilibrium dialysis. Calcium binding constants of 260 and 3700 M-1 at pH 6.0 and 8.0, respectively, with beta-trypsin have also been obtained. Calcium ion and gadolinium ion compete for the same site on the protein. Calcium has been shown to protect alpha-trypsin from further autolytic degradation to psi-trypsin. From examination of the crystal structure of the enzyme we propose that the calcium ion binding site of bovine trypsin is comprised of the side chains of Asp-194 and Ser-190 (based on the chymotrypsin sequence numbering system). This seems to be the only site which is comprised of at least one carboxyl group; which fits our distance requirements and which is conisistent with other chemical data.