Gun Agrup

Analysis of cysteinyldopas, dopa, dopamine, noradrenaline and adrenaline in serum and urine using high-performance liquid chromatography and electrochemical detection.

The catecholic amino acids, dopa, 2-S- and 5-S-cysteinyldopa, and 2,5-S,S-dicysteinyldopa were determined qualitatively in serum from patients with malignant melanoma by reversed-phase high-performance liquid chromatography, using electrochemical detection. In urine the catecholamines dopamine, noradrenaline and adrenaline were also determined qualitatively, as well as the above-mentioned compounds, in a single chromatographic run. The conditions were optimized by changing the pH of the mobile phase and by the addition of methanesulphonic acid. A comparison was made between the performance of four commercial reversed-phase packing materials containing chemically bonded octadecyl groups, using a standard mixture of catecholic amino acids. The influence of ionic strength, pH and amount of methanesulphonic acid on retention was investigated.

Sensitization studies in the guinea pig with the active ingredients of Euxyl K 400.

The preservative Euxyl® K 400 consists of the 2 active ingredients, 2‐phenoxyethanol and 1, 2‐dibromo‐2, 4‐dicyanobutane. Sensitization studies with the guinea pig maximization test were performed with these substances, but no sensitizing capacity was demonstrated in the case of either compound.

The effect of cysteine on oxidation of tyrosine dopa, and cysteinyldopas

SummaryThe influence of cysteine on the oxidation of tyrosine, dopa, and monocysteinyldopas by mushroom tyrosinase was reexamined. During oxidation of tyrosine in the presence of cysteine the concentration of dopa increased slowly, whereas the concentration of cysteinyldopas increased more rapidly. When the concentration of cysteine decreased the cysteinyldopas were rapidly consumed and dopa concentrations increased sharply.Experiments on the oxidation of dopa by tyrosinase in the presence of cysteine showed that this thiol does not inhibit the oxidation. Dopa concentrations decreased more rapidly in the presence of cysteine because cysteine addition to dopaquinone prevented reformation of dopa from dopaquinone.Both 2-S-cysteinyldopa and 5-S-cysteinyldopa are substrates for tyrosinase. The oxidation of cysteinyldopas was inhibited at high cysteine concentrations. The greater part of 2,5-S,S-dicysteinyldopa formed during the oxidation of monocysteinyldopas in the presence of cysteine is derived from 5-S-cysteinyldopa, which is a better substrate for tyrosinase than 2-S-cysteinyldopa. The fact that cysteine binds more rapidly to 5-S-cysteinyldopaquinone than to 2-S-cysteinyldopaquinone further stresses the importance of 5-S-cysteinyldopa in the formation of 2,5-S,S-dicysteinyldopa.Oxidation of dopa in the presence of cysteine and glutathione or methionine showed that glutathione is added to dopaquinone but less rapidly than cysteine. Methionine showed insignificant addition to dopaquinone.When dopa or 5-OH-dopa is added to an incubate of cysteinyldopa and tyrosinase the oxidation of cysteinyldopa is accelerated owing to oxidation of cysteinyldopa by dopaquinone or 5-OH-dopaquinone.

The quantitative determination of 5-S-cysteinyldopa and dopa in normal serum and in serum from patients with malignant melanoma by means of high-pressure liquid chromatography.

A method is described for quantitative determination of 5-S-cysteinyldopa and Dopa in serum involving high-pressure liquid chromatographic analysis (HPLC) and electrochemical detection. The chromatographic system allows estimation of injected amounts corresponding to 25 pg of 5-S-cysteinyldopa and Dopa. In normal subjects the mean serum 5-S-cysteinyldopa concentration was 2.8 ng/ml (range 0.4--12 ng/ml) and the mean serum Dopa 6.3 ng/ml (range 4--10 ng/ml). Patients with melanoma metastases showed increased serum concentrations of 5-S-cysteinyldopa.

SENSITIZATION INDUCED BY PATCH TESTING

SUMMARY.— Three hundred and seventy‐nine patients with hand dermatitis were patch tested with 11 substances on 2 occasions at an interval of 6–21 months. On the first occasion 196 reactions were positive, and 164 of them remained so on the second occasion. In addition, 108 reactions negative on the first occasion were positive on the second. Sensitization was commonly produced by p‐aminoazobenzene, p‐phenylenediamine, diaminodiphenylmethane, cobalt and chromium. This high incidence of sensitization by patch testing, necessitates re‐evaluation of this procedure.

Stability of the mercaptobenzothiazole compounds.

An analytical quantitative high‐pressure liquid chromatography (HPLC) method was developed for simultaneous determination of all mercaptobeazothiazole derivatives in the mercapto mix patch testing standard. The stability of the mercaptobenzothiazoles constituting the mercapto mix was studied both in petrolatum and in buffer solution at pH 6.5, with and without glutathione. In petrolatum vehicle, dibenzothiazyl disulfide was the dominant compound found in stored mercapto mix. In buffer solution at pH 6.5, 2‐mercaptobenzothiazole and the sulfenamide derivatives morpholinyl mercaptobenzothiazole and N‐cyclohexyl‐2‐benzothiazyl sulfenamide were converted into dibenzothiazyl disulfide. In the presence of glutathione, both the sulfenamide derivatives and the dibenzothiazyl disulfide were rapidly converted into 2‐mercaptobenzothiazole. The findings explain the “cross‐sensitivities” reported for the mercaptobenzothiazole group as a result of chemical reactions resulting in one main hapten. The use of a single substance for patch testing for mercaptobenzothiazole hypersensitivity is proposed.

Fluorescence histochemical demonstration of dopa thioethers by condensation with gaseous formaldehyde.

SummaryThe usefulness of the formaldehyde (FA) and glyoxylic acid (GA) methods for the fluorescence histochemical demonstration of dopa thioethers has been tested using protein droplet models. Similar fluorescence intensities were recorded from these compounds after either FA or GA treatment. Cysteinyldopa gave a high fluorescence yield similar to that obtained from dopamine and dopa in the FA reaction, whereas glutationedopa showed a lower, although clearly visible fluorescence. Since the FA method seemed to be the most useful one for demonstration of catechol thioethers, the FA-induced fluorophores of these compounds were further characterized by microspectrofluorometry. The spectral characteristics of the thioether fluorophores (excitation maxima at 420 nm and emission maxima at 480–485 nm) distinguish these substances from dopa and other compounds fluorogenic in the Falck-Hillarp method. Dopa thioethers are proposed to form fluorophores with FA in a manner analogous to that of the primary catecholamines i.e. via low-fluorescent tetrahydroisoquinolines, along two different pathways, to strongly fluorescent 3,4-dihydroisoquinolines and 2-methyl-dihydroisoquinolinium compounds. These dihydroisoquinolines are in a pH-dependent tautomeric equilibrium with their quinoidal forms as reflected by a characteristic spectral shift upon acidification. The results of this study provide the guide-lines for the characterization of fluorogenic compounds in pigment-forming cells.

Routine patch testing with ether extract of Primula obconica.

SUMMARY. An ethyl ether extract of the fresh leaves and stems of Primula obconica was used to prepare “ready‐made” patch test units for routine testing of 2457 patients with dermatitis. The prepared patches could be stored wrapped in aluminium foil in a refrigerator for a minimum of 3 years without losing potency.

CONTACT DERMATITIS X

Pharmacologists determine the systemic and toxic properties of drugs and cosmetics but their ability to irritate and sensitize the skin is the concern of the dermatologist. Cutaneous investigations, to assess these effects, have been described and modified during the past 25 years and still remain unsatisfactory, mainly because the conditions of the tests may differ so radically from the conditions of normal application. It is however important to know the potential of chemicals to irritate and sensitize the skin and this can be revealed by stressing them in maximization tests but it is difficult to translate this information into the hazard such chemicals may constitute in the much milder conditions of every-day use. With composite preparations it is necessary to determine not only the irritating and sensitizing potential of each component but that of the whole product, as these may not be the same. Although an irritant effect or a sensitizing risk may be acceptable in an effective therapeutic preparation the same disadvantage would be quite unjustified in a cosmetic.

CONTACT DEKMATITIS XIV

Our speciality, like many others, has no reason to feel proud of the terms coined or selected for designating clinical phenomena. The terminology of contact dermatitis is no exception in this respeet. The members of the International Contact Dermatitis Research Group have recently published recommendations for the nomenclature and use of terms in contact dermatitis (Wilkinson et al., 1970). The report is an interesting contribution by the Group, whose members include many of the leading dermatologists working in the field of elinical contact dermatitis. Their recommendations will surely infiuence the use of nomenclature by all concerned with contact dermatitis. Tho committee emphasizes that the recommendations constitute compromises and that neologisms have been avoided. The Group invites criticism of the suggestions and the reviewer takes the opportunity of drawing attention to this important paper and to certain merits and demerits of some sections of the report and some of tle terms recommended. The signs and symbols used for recording the results of patch tests vary from one department to another and standardization may be difficult even within a single department. It is therefore to be regretted that the recommendations are not more thoroughly motivated and explained. The committee suggests: NT not tested ? + doubtful reaction + weak (non-vesicular) reaction + + strong (oedematous or vesicular) reaction It was agreed that