Fulvio Allegra

Studies on dapsone induced haemolytic anaemia. I. Methaemoglobin production and G-6-PD activity in correlation with dapsone dosage.

The present study was undertaken on the hypothesis that methaemoglobin production and haemolytic anaemia following dapsone administration could be ascribed to an impairment of glucose‐6‐phosphate dehydrogenase‐enzymatic activity. Analysis of the kinetic parameters of the G‐6‐PD (Vmax and KM) was performed in ten patients, normal with respect to G‐6‐PD, suffering from various dermatoses. It was concluded that haemolytic anaemia after dapsone therapy is not due to a functional impairment of the enzyme. The close relationship between dapsone dosage, methaemoglobin production and anaemia make reasonable the hypothesis that a toxic dapsone derivative (DDS‐NHOH) could be responsible for the methaemoglobin formation and the haemolytic anaemia.

Macrophage — T-lymphocyte interaction in lichen planus

SummaryPapular lichen planus lesions from 12 patients were studied by a double-step immunocyto-chemical method to detect T-lymphocytes. Semithin sections were studied by light microscopy and ultrathin sections examined by electron microscopy. In the dermal infiltrate, many T-lymphocytes appeared closely juxtaposed to macrophages or Langerhans cells, frequently arranged in a rosette-like pattern. In the epidermis, T-lymphocytes were juxtaposed to macrophages or Langerhans cells and to degenerated keratinocytes. The close relationship between T-lymphocytes, macrophages or Langerhans cells and degenerated keratinocytes supports the hypothesis that lichen planus is immunological in nature: T-lymphocytes, after interacting with macrophages or Langerhans cells, become cytotoxic for keratinocytes.

Distribution of khellin in excised human skin following iontophoresis and passive dermal transport

The aim of this work was to study in vitro khellin distribution into human skin after passive or iontophoretic transport. The experiments were performed on excised human skin, using vertical Franz-type diffusion cells. The effects of current application and reservoir pH were studied. At the end of the experiments the skin was sliced thinly and the drug was extracted and analyzed by HPLC. The results showed that khellin is able to penetrate through stratum corneum, to reach basal epidermis and upper dermis. The application time proved to be an important parameter. Current application (30 min; 0.5 mA/cm(2)), with a donor at pH 7.0, favored khellin accumulation even if the drug is not ionized. On the contrary, the use of a formulation at pH 3.2 inhibited drug accumulation. Leaving the drug reservoir in contact with the skin for 30 min after current application led to a dramatic increase of khellin concentration. A combination of dermal iontophoresis and passive diffusion is then a useful technique to govern khellin distribution in the skin.

In vitro and in vivo study of 5-methoxypsoralen skin concentration after topical application.

The aim of this work was to study the skin distribution of 5-methoxypsoralen (5-MOP) after application of topical gels, in vitro and in vivo, in both healthy and psoriatic skin sites of 6 psoriatic patients. Drug skin distribution was determined using the thin slicing technique and subsequent HPLC analysis. In the presence of dermatological disease, i.e. psoriasis, the permeability of the tissue changed considerably, leading to an important increase in the cumulative amount of 5-MOP recovered in the skin after topical application. The amount of 5-MOP found in vitro in the human skin was intermediate between those cumulated in healthy and psoriatic skin sites during an in vivo experiment. The gel formulation is an efficacious carrier for the topical photochemotherapy of psoriasis with 5-MOP, since it allows drug penetration in psoriatic skin.

Retinol binding protein in normal human skin and in cutaneous disorders

Circulating vitamin A is transported by a carrier termed retinol binding protein (RBP). Autoradiography and immunofluorescence studies showed that, in normal human skin, RBP is confined exclusively to the dermis. Following oral vitamin A loading, a large increase in dermal RBP but only a very small rise of serum RBP was found.

Something Old: Blood Vessels, Nerves and Hairs

“Something Old” was the title of a lecture that W. Montagna presented to the Society of Investigative Dermatology in 1970, when he was elected its President. We use this title because of our deep fondness for him. He has taught so many of us, and we believe that old methods still have something to teach us.

Demonstration of Treponema pallidum in tissues. By a modification of the rapid method of silver impregnation of Ito, Ohtani, and Haba (1968).

A new method for the demonstration of Treponema pallidum in tissues was described by Ito, Ohtani, and Haba (1968). Silver impregnation of treponemes could be carried out in a simple and rapid way, using their new method, which was based on the same property of silver nitrate as the older methods. Treponemes have been demonstrated by this method, subsequently modified by Ohtani (1969a), in papular lesions of secondary syphilis and in experimental syphilis in the rabbit. We have used essentially the same technique in five cases of recent syphilis, using experimentallyinduced syphilis in the rabbit testis as a control.