Positive 131Cesium scanning in parathyroid adenoma

In a case of primary hyperparathyroidism, a palpable nodule, at the base of the right lobe of the thyroid, proved cool during ^99mTc scanning, but hot when scanned with radiocesium. The uptake of this tracer was higher than the uptake of ⁷⁵Se-selenomethionine after suppression with T₃.The authors discuss the possibility of cases of false-positive radiocesium uptake in extrathyroid nodules, and in particular, the use of this tracer for the detection of parathyroid adenoma by scanning.     

Scintigraphic visualisation of Walker carcinoma-256 in Sprague-Dawley rats by means of 99mTc-labelled monocytes

Labelled macrophages accumulate in Walker carcinosarcoma-256 after in vivo and in vitro stimulation with a lectin and are theretically suitable for scintigraphic tumour detection. At present, routine application of the technique in man is precluded by: (1) the use of PHA, and (2) a labelling method for macrophages with considerable limitations to its application and which results in significant uptake of activity in liver and spleen. However, the purpose of the study was primarily to demonstrate the principle of a possible alternative to the use of labelled monoclonal antibodies for the scintigraphic detection of tumours.     

Proportional anatomical stereotactic atlas for visual interpretation of brain SPET perfusion images

A semi-automatic method was developed to determine the anterior (AC) and posterior (PC) commissures on brain single-photon emission tomographic (SPET) perfusion images, and then to draw the proportional anatomical Talairach's grid on each axial SPET image. First, the AC-PC line was defined on SPET images from the linear regression of four internal landmarks (frontal pole of the brain, inferior limit of the anterior corpus callosum, sub-thalamic point and occipital pole). Second, the SPET position of AC and PC points on the AC-PC line was automatically determined from measurements made on hard copies of magnetic resonance (MR) images of the patients. Finally, a proportional Talairach's grid was automatically drawn on each axial SPET image. To assess the accuracy of localization of AC and PC points, co-registered technetium-99m hexamethylpropylene amine oxime SPET and MR images from 11 subjects were used. The mean displacements between estimated points on SPET and true points on MRI (x=sagittal, y=frontal and z=axial displacement) were calculated. The mean displacements (in mm) were x=–1.4±1.8, y=–1.7±3.3 and z=–1.1±2.5 for AC, and x=–1.8±1.8, y=0.3±3.2 and =–1.3±2.7 for PC. These displacements represented an error of less than 5 mm at the anterior or posterior pole of the brain or at the vertex. Intra- and inter-observer comparisons did not reveal significant differences in mean displacements. Thus, this semi-automatic method results in reproducible and accurate stereotactic localization of SPET perfusion abnormalities. This method can be used routinely for repeat follow-up studies in the same subject as well as in different individuals without requiring SPET MRI co-registration.     

Site-specific conjugation of HIV-1 tat peptides to IgG: a potential route to construct radioimmunoconjugates for targeting intracellular and nuclear epitopes in cancer

Purpose Our objective was to study the cellular and nuclear uptake of ¹²³I-mouse IgG (¹²³I-mIgG) linked to peptides [GRKKRRQRRRPPQGYGC] harbouring the membrane-translocating and nuclear import sequences of HIV-1 tat protein.Methods Carbohydrates on mIgG were oxidized by NaIO₄, then reacted with a 40-fold excess of peptides. Displacement of binding of anti-mouse IgG (Fab specific; -mFab) to ¹²³I-mIgG by tat-mIgG or mIgG was compared. Internalization and nuclear translocation of ¹²³I-tat-mIgG in MDA-MB-468, MDA-MB-231 or MCF-7 breast cancer cells were measured. The immunoreactivity of imported tat-mIgG was evaluated by measuring binding of ¹²³I--mFab to cell lysate and by displacement of binding of ¹²³I-mIgG to -mFab by cell lysate. Biodistribution and nuclear uptake of ¹²³I-tat-mIgG, ¹²³I-mIgG and ¹²³I-tat were compared in mice bearing s.c. MDA-MB-468 tumours.Results There was a 15-fold decrease in affinity of -mFab for tat-mIgG compared with mIgG. Internalized radioactivity imported into the nucleus for ¹²³I-tat-mIgG in MDA-MB-468, MDA-MB-231 and MCF-7 cells was 61.5±0.6%, 60.3±3.6% and 64.7±1.0%, respectively. The binding of ¹²³I--mFab to lysate from MDA-MB-468 cells importing tat-mIgG was 17-fold higher than that for cells not exposed to tat-mIgG. Imported tat-mIgG competed with tat-mIgG for displacement of binding of ¹²³I-mIgG to -mFab. Conjugation of mIgG to tat peptides did not change tissue distribution. Nuclear localization for ¹²³I-tat-mIgG in MDA-MB-468 tumours was 28.1±5.6%, and for liver, spleen and kidneys it was 41.7±2.7%, 13.8±0.8% and 36.9±3.3%, respectively.Conclusion ¹²³I-tat-mIgG radioimunoconjugates suggest a route to the design of radiopharmaceuticals exploiting intracellular and nuclear epitopes.     

Genetic polymorphism of desialyzed alpha2 HS-glycoprotein by ultrathin isoelectric focusing

Summary The genetically determined polymorphism of ₂ HS-glycoprotein was analyzed by immunoblotting ultrathin-layer polyacrylamide gel isoelectric focusing in the pH range 4–6.5 and neuraminidase pretreated sera. In a Libyan population sample from Tripoli (n=110) three common phenotypes, ₂ HSG 1–1, 2–1, and 2–2, were observed. The allele frequencies were ₂ HSG¹=0.8364 and ₂ HSG²=0.1636. The theoretical exclusion rate in cases of disputed paternity is 11.8%.     

‘Hot’ and ‘cold’ lesions detected by gallium-67 scintigraphy in a pyogenic liver abscess

Most pyogenic liver abscesses appear to be not in a ⁶⁷Ga-citrate study; rarely, a warm or cold area may also be seen. We present a patient with a pyogenic liver abscess that had both cold and hot areas in the ⁶⁷Ga-citrate study. This striking finding is probably related to the different stages of evolution of the abscess.     

In vitro and in vivo characterisation of nor-β-CIT: a potential radioligand for visualisation of the serotonin transporter in the brain

Radiolabelled 2-Cabomethoxy-3-(4-iodophenyl)tropane (-CIT) has been used in clinical studies for the imaging of dopamine and serotonin transporters with single-photon emission tomography (SPET). 2-Carbomethoxy-3-(4-iodophenyl)nortropane (nor--CIT) is a des-methyl analogue of -CIT, which in vitro has tenfold higher affinity (IC₅₀=0.36 nM) to the serotonin transporter than -CIT (IC₅₀=4.2 nM). Nor--CIT may thus be a useful radioligand for imaging of the serotonin transporter. In the present study iodine-125 and carbon-11 labelled nor--CIT were prepared for in vitro autoradiographic studies on post-mortem human brain cryosections and for in vivo positron emission tomography (PET) studies in Cynomolgus monkeys. Whole hemisphere autoradiography with [¹²⁵I]nor--CIT demonstrated high binding in the striatum, the thalamus and cortical regions of the human brain. Addition of a high concentration (1 M) of citalopram inhibited binding in the thalamus and the neocortex, but not in the striatum. In PET studies with [¹¹C]nor--CIT there was rapid uptake of radioactivity in the monkey brain (6% of injected dose at 15 min) and high accumulation of radioactivity in the striatum, thalamus and neocortex. Thalamus to cerebellum and cortex to cerebellum ratios were 2.5 and 1.8 at 60 min, respectively. The ratios obtained with [¹¹C]nor--CIT were 20%–40% higher than those previously obtained with [¹¹C]-CIT. Radioactivity in the thalamus and the neocortex but not in the striatum was displaceable with citalopram (5 mg/kg). In conclusion, nor--CIT binds to the serotonin transporter in the primate brain in vitro and in vivo and has potential for PET and SPET imaging of the serotonin transporter in human brain.     

Sodium bicarbonate-augmented stress thallium myocardial scintigraphy

It is well known that sodium bicarbonate in pharmacological doses induces transient alkalosis, causing intracellular transport of serum potassium. The aims of this study were (a) to investigate whether, in humans, myocardial thallium-201 uptake can be augmented by pretreatment with a single bolus of sodium bicarbonate at a pharmacological dose, (b) to verify general safety aspects of the intervention and (c) to evaluate the clinical implications of augmentation of ²⁰¹Tl uptake, if any. Routine exercise myocardial scintigraphy was performed twice in eight adult volunteers (five normal and three abnormal), once without intervention and the second time (within a week) following intravenous administration of sodium bicarbonate (88 mEq in 50 ml) as a slow bolus 1 h prior to the injection of ²⁰¹Tl. Conventional myocardial thallium study was compared with sodium bicarbonate interventional myocardial scintigraphy with respect to myocardial uptake (counts per minute per mCi injected dose), washout patterns in normal and abnormal myocardial segments, and overall clinical interpretation based on planar and single-photon emission tomographic (SPET) images. All patients remained asymptomatic after the intervention. A mean increase of 53% in myocardial uptake of thallium was noted in post-exercise acquisitions after the intervention, confirming uptake of the tracer via the potassium-hydrogen pump and its augmentation by transient alkalosis. The washout pattern remained unchanged. The visual quality of planar and SPET images improved significantly after the intervention. Out of the five abnormal myocardial segments identified in three cases, four showed significant filling-in after the intervention, causing the diagnosis to be upgraded from partial scar to ischaemia, or from ischaemia to normal. The overall scan impression changed in two out of three such cases. Sodium bicarbonate augmentation may have significant implications for stress-thallium scintigraphy and may be a new parameter for defining myocardial viability.     

Detection of ileocecal Crohn’s disease using ultrasound as the primary imaging modality

At our hospital ultrasound (US) is used as an initial screening procedure in all patients with abdominal symptoms. The purpose of this study was to assess the effect of this policy on the detection of ileocecal Crohns disease. We retrospectively studied all patients with a new diagnosis of ileocecal Crohns disease from our institute over the period 1990–2001. The final diagnosis was based on clinical follow-up and pathological, surgical, US, and other radiological findings. We noted who referred the patient to the radiology department, what the initial clinical presumption was, and what the first imaging study was. US diagnoses were determined from the initial US report and US findings were registered from the images. There were a total of 47 patients (20 men, 27 women) with a mean age of 30 years and a median age of 27 years (range 14–75 years). In all patients the initial imaging study was an abdominal US. Using US, a confident diagnosis of ileocecal Crohns disease was made in 35 of the 47 patients, Crohns disease was suggested among the differential diagnosis in 10, and an incorrect diagnosis was made in 2 patients. In 28 of 47 patients, the referring physician did not consider Crohns disease when requesting the initial US examination. In eight patients with appendicitis-like symptoms, the US findings strongly influenced the decision to refrain from operation at that point in time. US, when used as a low-threshold diagnostic procedure, is a reliable and noninvasive means for making an early diagnosis of ileocecal Crohns disease in patients who present with atypical symptoms. It may prevent both unnecessary therapeutic delay as well as unnecessary surgery.     

Effect of adrenergic receptor ligands on metaiodobenzylguanidine uptake and storage in neuroblastoma cells

The effects of adrenergic receptor ligands on uptake and storage of the radiopharmaceutical [¹²⁵I]metaiodobenzylguanidine (MIBG) were studied in the human neuroblastoma cell line SK-N-SH. For uptake studies, cells were incubated for 15 min with varying concentrations of -agonist (clonidine, methoxamine, and xylazine), -antagonist (phentolamine, tolazoline, phenoxybenzamine, yohimbine, and prazosin), -antagonist (proranolol, atenolol), -agonist (isoprenaline and salbutamol), mixed / antagonist (labetalol), or the neuronal blocking agent guanethidine, prior to the addition of [¹²⁵I]MIBG (0.1 M). The incubation was continued for 2 h and specific cell-associated radioactivity was measured. For the storage studies, cells were incubated with [¹²⁵I]MIBG for 2 h, followed by replacement with fresh medium with or without drug (MIBG, clonidine, or yohimbine). Cell-associated radioactivity was measured at various times over the next 20 h. Propanolol reduced [¹²⁵I]MIBG uptake by approximately 30% (P<0.01) at all concentrations tested, most likely due to nonspecific membrane changes. However, incubation with the other -agonists or antagonists failed to elicit significant reductions in uptake. In contrast, all of the -agonists significantly inhibited uptake (P<0.05); guanethidine >xylazine >clonidine=methoxamine. The -antagonists demonstrated a broad range of inhibition (phenoxybenzamine phentolamine prazosin yohimbine=tolazoline)(P<0.05). The mixed ligand, labetalol, inhibited MIBG uptake in a dose-dependent manner with an apparent IC₅₀ of 0.65 M. The retention studies demonstrated that unlabeled MIBG caused profound self-inhibition (P<0.01). Clonidine produced a modest inhibition of retention and yohimbine had no effect. Labetalol, phenoxybenzamine, guanethidine, and propranolol reduced uptake of [¹²⁵I]MIBG by neuroblastoma cells in culture. Although only labetalol has been reported to cause false-negative MIBG scans, our results suggest that these other drugs have the potential to interfere with MIBG imaging and therapy, particularly at high doses. Adrenergic drugs did not alter cytoplasmic retention of [¹²⁵I]MIBG in neuroblastoma cells but may have potential in tumors such as phenochromocytoma, where granular storage of MIBG has been observed. Inhibition of [¹²⁵I]MIBG retention by unlabeled MIBG supports the use of high specific activity radioiodinated MIBG for both diagnosis and therapy.     

Agreement between emergency physician diagnosis and radiologist reports in patients discharged from an emergency department with community-acquired pneumonia

To evaluate the level of concurrence between radiologist reports and the diagnosis of community-acquired pneumonia (CAP) in patients discharged from an emergency department (ED), a retrospective chart audit of patients discharged with a diagnosis of pneumonia or possible pneumonia from the ED during a 2-year period was conducted. Emergency physician (EP) and radiology report (RR) diagnoses were categorized as pneumonia, possible pneumonia, non-pneumonia and normal, and categories from each were compared. 815 charts were analyzed. Of 671 EP diagnoses of pneumonia, 304 (45.3%) RRs reported pneumonia and 82 (12.2%), possible pneumonia. Of 815 EP diagnoses of pneumonia or possible pneumonia, 426 (52.3%) RRs were in agreement, while 216(26.5%) were of diagnoses other than pneumonia and 173 (21.1%) were read as normal. EPs and radiologists frequently disagree on whether a patient has pneumonia or not. Perhaps it is time to revisit the gold standard status of plain chest X-ray.Presented at the 9th International Conference of Emergency Medicine, Edinburgh, Scotland, 17–21 June, 2002.     

Non-invasive assessment of distribution volume ratios and binding potential: tissue heterogeneity and interindividually averaged time-activity curves

Due to the stochastic nature of radioactive decay, any measurement of radioactivity concentration requires spatial averaging. In pharmacokinetic analysis of time-activity curves (TAC), such averaging over heterogeneous tissues may introduce a systematic error (heterogeneity error) but may also improve the accuracy and precision of parameter estimation. In addition to spatial averaging (inevitable due to limited scanner resolution and intended in ROI analysis), interindividual averaging may theoretically be beneficial, too. The aim of this study was to investigate the effect of such averaging on the binding potential (BP) calculated with Logans non-invasive graphical analysis and the simplified reference tissue method (SRTM) proposed by Lammertsma and Hume, on the basis of simulated and measured positron emission tomography data {[¹¹C]d-threo-methylphenidate (dMP) and [¹¹C]raclopride (RAC) PET}. dMP was not quantified with SRTM since the low k ₂ (washout rate constant from the first tissue compartment) introduced a high noise sensitivity. Even for considerably different shapes of TAC (dMP PET in parkinsonian patients and healthy controls, [¹¹C]raclopride in patients with and without haloperidol medication) and a high variance in the rate constants (e.g. simulated standard deviation of K ₁=25%), the BP obtained from average TAC was close to the mean BP (error <5%). However, unfavourably distributed parameters, especially a correlated large variance in two or more parameters, may lead to larger errors. In Monte Carlo simulations, interindividual averaging before quantification reduced the variance from the SRTM (beyond a critical signal to noise ratio) and the bias in Logans method. Interindividual averaging may further increase accuracy when there is an error term in the reference tissue assumption E=DV ₂–DV (DV ₂ = distribution volume of the first tissue compartment, DV = distribution volume of the reference tissue). This can be explained by the fact that the distribution volume ratio (DVR=DV/DV) obtained from averaged TAC is an approximation for DV/DV rather than for DVR/n. We conclude that Logans non-invasive method and SRTM are suitable for heterogeneous tissues and that discussion of group differences in PET studies generally should include qualitative and quantitative assessment of interindividually averaged TAC.     

The value of bone imaging in multiple myeloma

In a series of 20 patients with a proven diagnosis of myeloma, both full radiographic skeletal surveys and full ratio-nuclide bone images were performed. When these were compared, they showed that (i) imaging underestimated the number of areas involved by 50%, but there were no false negative whole images when compared with the radiology, (ii) large lytic areas on X-ray show as cold areas on the bone image but small ones show as normal, (iii) images that show areas of increased uptake (hot) are almost always associated with fracture, and (iv) patients with bone pain very commonly had hot images corresponding to the region of pain.4th year medical student     

Positron emission tomography imaging of adrenal masses: <Superscript>18</Superscript>F-fluorodeoxyglucose and the 11β-hydroxylase tracer <Superscript>11</Superscript>C-metomidate

Purpose ¹¹C-metomidate (MTO), a marker of 11-hydroxylase, has been suggested as a novel positron emission tomography (PET) tracer for adrenocortical imaging. Up to now, experience with this very new tracer is limited. The aims of this study were (1) to evaluate this novel tracer, (2) to point out possible advantages in comparison with ¹⁸F-fluorodeoxyglucose (FDG) and (3) to investigate in vivo the expression of 11-hydroxylase in patients with primary aldosteronism.Methods Sixteen patients with adrenal masses were investigated using both MTO and FDG PET imaging. All patients except one were operated on. Five patients had non-functioning adrenal masses, while 11 had functioning tumours(Cushings syndrome, n=4; Conns syndrome, n=5; phaeochromocytoma, n=2). Thirteen patients had benign disease, whereas in three cases the adrenal mass was malignant (adrenocortical cancer, n=1; malignant phaeochromocytoma, n=1; adrenal metastasis of renal cancer, n=1).Results MTO imaging clearly distinguished cortical from non-cortical adrenal masses (median standardised uptake values of 18.6 and 1.9, respectively, p<0.01). MTO uptake was slightly lower in patients with Cushings syndrome than in those with Conns syndrome, but the difference did not reach statistical significance. The expression of 11-hydroxylase was not suppressed in the contralateral gland of patients with Conns syndrome, whereas in Cushings syndrome this was clearly the case. The single patient with adrenocortical carcinoma had MTO uptake in the lower range.Conclusion MTO could not definitely distinguish between benign and malignant disease. FDG PET, however, identified clearly all three study patients with malignant adrenal lesions. We conclude: (1) MTO is an excellent imaging tool to distinguish adrenocortical and non-cortical lesions; (2) the in vivo expression of 11-hydroxylase is lower in Cushings syndrome than in Conns syndrome, and there is no suppression of the contralateral gland in primary aldosteronism; (3) for the purpose of discriminating between benign and malignant lesions, FDG is the tracer of choice.     

Methamphetamin—ein Metabolit der Appetitzügler Benzphetamin und Furfenorex

Zusammenfassung Die Appetitzügler Didrex (1) [1-Phenyl-2-(N, N-methyl-benzyl-amino)propan — Benzphetamin] und Frugalan (2) [1-Phenyl-2-(N, N-methyl-furfuryl-amino)propan = Furfenorex] werden — wie GC-MS-Analysen ergaben — beim Menschen zu Methamphetamin (3) (1-Phenyl-2-methylamino-propan) metabolisiert. Käufliche Muster beider Präparate enthielten neben anderen Verunreinigungen Spuren von Methamphetamin (3).

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Summary The anorectics Didrex (1) [1-Phenyl-2-(N, N-methyl-benzyl-amino)propane = Benzphetamine] and Frugalan (2) [1-Phenyl-2-(N, N-methyl-furfuryl-amino)propane = Furfenorex] are metabolized to methamphetamine (3) (1-Phenyl-2-methylamino-propane) in man as demonstrated by GC-MS-analysis. Commercially available samples of the two drugs contained — besides other impurities — traces of methamphetamine (3).

Institut für Rechtsmedizin der Universität Göttingen.     

Local Administration of NF-κ B Decoy Oligonucleotides to Prevent Restenosis after Balloon Angioplasty: An Experimental Study in New Zealand White Rabbits

Purpose To evaluate the efficacy of NF- B oligonucleotides (ODN) administered by local administration with the channeled balloon catheter to prevent restenosis after balloon angioplasty in restenotic iliac arteries of New Zealand white rabbits.Materials and Methods In vitro, 8000 rabbit vascular smooth muscle cells (rVSMC) where transfected with a liposomal carrier (TfX50) with 100 ng of decoy and scrambled ODN. Inhibition of proliferation was measured using a MTT assay after 24 hours in comparison to control. In vivo, 22 male New Zealand White rabbits were fed a 1% cholesterol diet and received denudation of both common iliac arteries with a 3 mm balloon catheter to induce an arterial stenosis. Four weeks after stenosis induction, local application of NF- B in two different concentrations (1 g: n=14; 10 g: n=8) was performed randomly on one common iliac artery. Scrambled oligonucleotides without specific binding capacities were injected into the contralateral side. The channeled balloon catheter allows simultaneous balloon dilation (8 atm) of the stenosis and local application of a drug solution (2 atm). Four weeks after local drug delivery the animals were killed and the vessels were excised and computerized morphometric measurements were performed.Results NF- B decoy ODN but not scrambled ODN inhibited proliferation of rVSMC in vitro. Following local ODN application in the animals, no acute vascular complications were seen. NF- B ODN resulted in a statistically non significant reduction of neointimal area compared to the control group. The neointimal area was 0.97 mm² using 1 g NF- B ODN compared to 0.98 mm² in the control group. The higher dose resulted in a neointimal area of 0.97 mm² compared to 1.07mm² at the control side.Conclusions Local drug delivery of NF- B ODN using the channeled balloon catheter could not reduce neointimal hyperplasia in stenostic rabbit iliac arteries. Application modalities have to be improved to enhance the effect of the local application to prevent restenosis after balloon angioplasty.     

Serial MRI of olivary hypertrophy: Long-term follow-up of a patient with the “top of the basilar” syndrome

We describe a patient with the top of the basilar syndrome, in whom MRI documented the appearance and regression of olivary hypertrophy.     

Uptake and release of two new Tc-99m labeled myocardial blood flow imaging agents in cultured cardiac cells

Two new neutral lipophilic ^99mTc labeled molecules, chloro (methyboron (1-)-tris[1,2-cyclohexane-dionedioxime 91-)]-N,NNNN) (SQ 30217) and Bis [1,2-cyclohexanedione dioximato (1-)-0]-[1,2-cyclohexanedione dioximato (2-)-0] borato (2-N,NNNN) -chloro Tc (SQ 32014), were studied in cultures of beating myocardial cells of newborn rats. The uptake and release kinetics, the effects of various pH levels of the medium, and the effects of three metabolic inhibitors, i.e, ouabain, cyanide and iodoacetate were assessed. Results show that T_1/2 of uptake were 2 min with both tracers, and T_1/2 of release were 12 and 13 min with SQ 32014 and SQ 30217, respectively. The intra/extracellular tracer concentrations was about 15 times higher with SQ 30217 than with SQ 32014. Intracellular concentration was decreased for both tracers at high pH levels, and was only moderately modified otherwise, including in the presence of the metabolic inhibitors. It is concluded that both tracers present very interesting properties for myocardial blood flow imaging, although a higher contrast should be expected with SQ 30217 than with SQ 32014.     

Morphological detection of X- and Y-chromosomes in smears and paraffin-embedded tissues using a non-isotopic in situ hybridization technique (NISH)

Pharyngeal smears and paraffin-embedded tissue specimens (skeletal muscle, kidney) obtained from 10 male and 10 female individuals were evaluated using non-isotopic in situ hybridization (NISH) with commercial X- and Y-specific biotinylated probes which recognize the pericentromeric regions DXZ1 and DYZ1/DYZ3 of the X- and Y-chromosome, respectively. The results provide evidence that the morphological sex determination of a single cell can be performed by critical application of this staining method leading to one nuclear signal in male cells using the Y-specific probe whereas female cells are negative. In situ hybridization of female tissues with an X-specific probe results regularly in 2 signals whereas male cells show only one spot in the nucleus.     

The phenomenon of ‘tired moly-99Mo’

The phenomenon of tired moly-⁹⁹Mo results in poor yields of ^99mTcO ₄ ^- obtained from ⁹⁹MoO ₄ ^2- . The solvated electron has been conceived to explain this phenomenon, especially when it occurs in highly alkaline media as obtained in the solvent extraction type of separation system.