A.S. Breathnach

Antimitochondrial effect of saturated medium chain length (C8-C13) dicarboxylic acids

In isolated rat liver mitochondria, respiration was competitively inhibited by medium chain length (C8 to C13) dicarboxylic acids to different extents: the higher the number of carbon atoms up to C12, the greater the inhibition. In particular, experiments on submitochondrial particles showed that the competitive inhibition concerned the following enzymes: NADH dehydrogenase, succinic dehydrogenase and reduced ubiquinone: cytochrome c oxido-reductase. These results tend to confirm the suggestion that the melanocytotoxic effect of dicarboxylic acids, which are also competitive inhibitors of tyrosinase, may be primarily due to an antimitochondrial effect rather than being tyrosinase-dependent.

Beneficial effect of 15% azelaic acid cream on acne vulgaris

Patients treated with azelaic acid (15%) cream for chloasma reported simultaneous improvement of acne lesions within the treated areas. This prompted an open study of its effect in cases of acne without chloasma. One hundred patients with acne vulgaris were treated for 3–9 months by twice‐daily application of the cream with significant improvement in every case.

Ultrastructure of retinal pigment epithelium of the human fetus

The ultrastructure of retinal pigment epithelium was studied in eyes of six human fetuses ranging in age from 8 to 14 weeks. General features of the cytoplasm and plasma membranes of cells at different stages are described, in comparison with the fully developed condition. The mode of development of the pigment granules of retinal cells is essentially similar to that occurring within the epidermal melanocytes. Small, membrane-limited vesicles, probably of Golgi origin, become larger and ovoid in shape, and acquire a system of concentric or folded inner membranes upon which melanin is deposited. The fine structure of the inner membranes of the granules and the manner in which they become melanized is likewise similar.

Mechanism of antitumoral activity of catechols in culture

Cell lines Raji and K 562, lacking tyrosinase, and two melanotic human melanoma cell lines (IRE 1 and IRE 2), were exposed to concentrations from 5 X 10(-3) M to 10(-5) M of different phenols which are substrates of tyrosinase, i.e. l-dopa, dopamine, hydroquinone, terbutylcatechol, and of phenols which are not substrates of the tyrosinase, i.e. resorcinol, butylated hydroxyanisole and hydroquinone dimethyl ether. Cultures were carried out in the presence or in the absence of oxygen radical scavenger enzymes superoxide dismutase, catalase and peroxidase. The stability of each substance in culture medium was assayed by high performance liquid chromatography (HPLC). Results showed that: catechols which are substrates of tyrosinase decompose fully after 24 hr in medium; they are equally toxic for melanoma and non-melanoma cell lines; their toxicity increases when they are preincubated in medium for 24 hr and 48 hr before addition of cells; their toxicity is significantly reduced by addition of scavenger enzymes; on the contrary, phenols not substrates of tyrosinase are stable in medium and their toxicity is not reduced by scavenger enzymes. It is concluded that tyrosinase does not play a major role in catechol toxicity in vitro, which is probably due to some products of catechol decomposition, especially oxygen radicals, acting outside the cells.

DIGITAL FIBROUS SWELLINGS IN CHILDREN

SUMMARY.— Clinical, histological and ultrastructural features of digital fibrous swellings in children are described. The clinical progress of these cases indicates that the lesions tend to regress spontaneously, and that they are recurrent only in the sense that growth may continue after incomplete surgical excision. A characteristic feature of the lesions is the occurrence of cells with dense cytoplasmic deposits. These cells appear to be abnormal fibroblasts, but electron microscopy provides no clues as to the origin, nature, or causation of the cytoplasmic deposits. No evidence was obtained to support a suggestion that the lesions may have an infective viral origin. Elastic fibres were very scarce within the swellings, and showed some evidence of abnormality. Collagen fibres, constituting the bulk of the swellings, appeared essentially normal.

Hypopigmented sarcoidosis in the negro. Report of eight cases with ultrastructural observations.

The dermatological aspects of eight negro patients with hypopigmented sarcoid lesions are described. Light microscope histochemical studies in two patients did not reveal the mechanism of the hypopigmentation. However, electronmicroscopy of lesions in two patients showed melanocytes undergoing changes resembling those observed in other acquired hypopigmentary conditions. It is suggested that in these disorders, melanocytes react morphologically in a similar non‐specific manner, whatever the prime pathological process.

Variations in ultrastructural appearance of Langerhans cells of normal human epidermis

GEYER, L . (1898) Uber die chromischen Hautveranderungen beim Arsenicismus und Betrachtungen uber die Massenerkrankungen in Reichenstein in Schlesien. Archiv fiir Dermatologie und Syphilis, 43, 221. HuTCHiNSON, J. (1888) On some examples of arsenic keratosis of the skin and of arsenic cancer. J. Trans, path. Soc. hand., 39, 352. ROTH, F . (1957) The sequelae of chronic arsenic poisoning in Moselle vintners. German Medical Monthly, 2 Qirne), 172. SANDERSON, K.V. (1963) Arsenic and skin cancer. Transactions of the St Johns Hospital Dermatological Society, 49) 115-•

Activity of azelaic acid on cultures of lymphoma- and leukemia-derived cell lines, normal resting and stimulated lymphocytes and 3T3 fibroblasts

Azelaic acid (C9- -dicarboxylic acid) is a competitive inhibitor of tyrosinase and some oxidoreductase in vitro, and in vivo has a beneficial effect on lentigo maligna and malignant melanoma. A definite cytotoxic effect in cultures of malignant melanocytes was also reported. In order to establish if the cytotoxic effect of the diacid is exerted equally in the absence of tyrosinase, lymphoma- and leukemia-derived cell lines were cultured for 72 hr with 10(-3) M, 10(-2) M and 5 X 10(-2) M C9 disodium salt. Normal resting lymphocytes, lymphocytes activated by phytohemoagglutinin, and mouse Balb/c 3T3 fibroblasts were also tested to study a possible effect of azelaic acid on DNA synthesis and cell duplication. At 10(-3) M C9 had no effect on the viability of all the cells tested; at 10(-2) M and 5 X 10(-2) M, C9 2Na had a 50-80% cytotoxic effect on lymphoma- and leukemia-derived cell lines, while at the same concentrations it was not toxic to normal lymphocytes, either resting or stimulated, or to 3T3 fibroblasts. The experiments on cellular incorporation of (1-9 14C) azelaic acid showed that the radiocarbon uptake was two to three times higher for lymphoma- and leukemia-derived cell lines than for lymphocytes, either resting or stimulated, or 3T3 fibroblasts. Biochemical analysis revealed that the diacid underwent beta-oxidation in all the cell cultures. Fractionated centrifugations of 3T3 fibroblasts cultured in the presence of radiolabelled azelaic acid (2 X 10(-4) M) plus cold C9 2Na (10(-2) M), showed that the radioactivity was mainly concentrated in the cytoplasm. The results, being similar to those obtained by adding azelaic acid to cultures of melanoma cells, suggest that the cytotoxic effect of azelaic acid may be due to interference with mitochondrial oxido-reductase enzymes, rather than with tyrosinase. The difference in reaction between lymphoma- and leukemia-derived cell lines and normal or stimulated lymphocytes, and 3T3 fibroblasts, could be explained on the basis of a different degree of permeability of the cell membrane, and/or to a possible different sensitivity of reaction of mitochondrial functions. A similar argument could be used to explain the absence of an effect of dicarboxylic acids upon normal as compared with hyperactive or malignant melanocytes in vivo.

Effect of dicarboxylic acids on normal human melanocytes in dispersed tissue culture

Since dicarboxylic acids are competitive inhibitors of tyrosmase, and effective in treatment of hyperpigmentary disorders, such as chloasma and lentigo maligna, probably due to a cytotoxic effect on abnormal melanocytes, it is of interest to examine their effect on normal melanocytes in tissue culture. Azelaic or dodecandioic acids were added (150–200 μg ml) to dispersed cultures of epidermal cells, and melanocytes were examined by electron microscopy after 7, 10, 15, 20 and 30 days. Apart from a umulation of melanogenesis, the presence of dicarboxylic acids in the culture medium caused no detectable damage to melanocytes, nor did they prevent growth of a second generation of cells.

Ultrastructural observations on the effect of azelaic acid on normal human melanocytes and a human melanoma cell line in tissue culture.

Azelaic acid has been shown clinically to have a cytotoxic effect on the abnormally active and malignant human melanocyte, but it has no apparent effect upon normal melanocytes. This difference in reactivity between normal and abnormal cells in vivo is further examined here in vitro.