Isamu Ikeda

Selective phototoxic destruction of rat Merkel cells abolishes responses of slowly adapting type I mechanoreceptor units.

1. The fluorescent dye quinacrine which accumulates in Merkel cells in touch domes was administered to rats and the effects of excitation light irradiation on the mechanical responses of slowly adapting (SA) type I units innervating the touch domes were investigated. 2. Histological examination showed that after 10 min of irradiation degeneration was specifically localized to Merkel cells loaded with quinacrine. Nerve terminals associated with Merkel cells remained intact, even after treatment. 3. In SA type I units, responses to standard stimulation (a 100 ms ramp followed by a 2.9 s plateau of 400 microns constant displacement) decreased significantly after irradiation of the domes with quinacrine‐excitation light through a ‘B’ filter (‘B’ light). With 5 min irradiation, the response decreased to 52 +/‐ 7% (n = 10, mean +/‐ S.E.M.) of the pretreated value, to 17 +/‐ 4% with a 10 min treatment and practically disappeared within 20 min. 4. In SA type I units with non‐loaded Merkel cells, the response increased to 119 +/‐ 8% (n = 13) with 5 min irradiation and was 99 +/‐ 9% with the 10 min treatment. At around 15 min after the onset of irradiation there was a gradual decrease and within 60 min the response disappeared. 5. When responses were divided into phasic (0‐120 ms after the onset of stimulation) and tonic (120‐3000 ms) components, ‘tonic’ responses were more affected than ‘phasic’ ones in quinacrine‐loaded SA type I units. 6. Stimulus‐response curves shifted to the right and downwards in SA type I units with quinacrine‐loaded Merkel cells after irradiation, but no significant change was seen in SA type I units without quinacrine. 7. Our observations are consistent with the hypothesis that Merkel cells are responsible for mechanoelectric transduction in SA type I units.

GABAergic inhibition and modifications of taste responses in the cortical taste area in rats

Using multibarrel electrodes, recordings were made in the cortical taste area (CTA), specifically in the granular and dysgranular parts of the insular cortex (areas GI and DI), of urethane-anesthetized rats. The effects of an iontophoretic application of gamma-aminobutylic acid (GABA) and bicuculline methiodide (BMI), a specific antagonist to the GABA(A) receptor, were tested. GABA decreased background discharges in ca. 69% of 509 neurons in both areas, and in ca. 58% of 64 taste neurons. BMI antagonized the inhibitory action of GABA in CTA neurons and facilitated background discharges in ca. 51% of the 390 neurons tested, including ca. 69% of the 52 taste neurons, which indicates that CTA neurons have GABA(A) receptors to receive inhibitory inputs from interneurons. In both areas, the effects of BMI (6-20 nA) on taste responses of the 85 CTA neurons (49 and 36 in areas GI and DI, respectively) to the four basic taste stimuli were examined: 65 neurons were recognized in the absence of BMI, whereas 20 only in the presence of the drug. BMI increased taste responses in 25 of the former group and changed the type of their response profiles in 25 including 12 neurons whose responses were increased. It also changed the best stimulus in 34 neurons. The drug affected the receptive fields in almost all cases examined (n = 23) and increased the size in 78.2% when the value for all four basic taste stimuli were totaled. New receptive fields were uncovered by BMI in varying regions of the oral cavity depending on the taste stimulus. But the drug decreased taste responses in several neurons (n = 8). These findings indicate that the GABAergic inhibitory system apparently contributes to modifying or selecting taste information in both areas of the CTA.

Basal cell carcinoma originating from an epidermoid cyst.

Basal cell carcinoma (BCC) originating from an epidermoid cyst which existed for about 50 years was seen in a 78‐year‐old Japanese male. Nests of basal cell carcinoma were connected with the epidermoid cyst, partially replacing the cyst wall.

A pitfall in clinical photography: the appearance of skin lesions depends upon the illumination device.

Abstract Background. Pictures of skin lesions are usually recorded with a camera equipped with a ring-type electric flash. In some cases the photographs do not reproduce the image perceived by the naked eye. Objective. To investigate the quality of photographs taken with the ring-type electric flash. Methods. Photographs of skin lesions and an experimental skin model were taken under different illumination conditions including a standard light source, full-spectrum fluorescent ceiling lights and the ring-type electric flash. Results. Images taken under illumination with a standard light source box resembled those perceived by the naked eye. The full-spectrum fluorescent ceiling lights produced adequate results. Pictures taken with the ring-type electric flash showed some deficiencies including reduction in contrast, loss of shading and excess reflection. Conclusions. The ring-type electric flash is not an ideal device for recording skin lesions. An illumination device compatible with a standard light source should be employed to yield maximum fidelity.

Widefield Microscopy Images of Tissue Sections by Computer Imaging Techniques

A fine photomicrograph covering one whole specimen is very useful in the study of skin histopathology. However, because it is almost impossible to take such a picture with a conventional photomicroscope, we attempted to make one with the aid of a computer. The large field was divided into small fields, which were individually recorded through a photomicroscope. The images were then digitized and processed with a computer to reconstruct the largefield image. A fine seamless image was reconstructed with this method. We can thus extend the field of a photomicroscope with the aid of computer imaging techniques, without impairing the quality. (J Histochem Cytochem 45:461–466, 1997)

Case of Fusarium paronychia successfully treated with occlusive dressing of antifungal cream

We report a case of refractory Fusarium paronychia in a 42‐year‐old man with Behçets disease receiving oral cyclosporin and corticosteroid. Symptoms resembling candidal paronychia of his little finger could not be cured by topical ketoconazole and oral terbinafine. The pathogen was identified as Fusarium solani species complex by gene analysis, and was multiple drug resistant. The case eventually resolved by occlusive dressing therapy with 0.5% amorolfine cream for 3 months.

Gigantic Pyoderma Gangrenosum

A 71‐year‐old Japanese female with gigantic pyoderma gangrenosum is reported. The pyoderma lesions had been treated as an infectious condition for seventeen months and had extended to enormously large areas. The nature of the chronic type of pyoderma gangrenosum may need to be stressed, even for dermatologists.