The effect of regioisomerism on the photophysical properties of alkylated-naphthalene liquids.

Novel regioisomeric alkylated-naphthalene liquids were designed and synthesized. In the solvent-free liquid state, 1-alkyloxy regioisomers showed excimeric luminescence, whereas 2-alkyloxy analogues exhibited monomer-rich luminescence features. Correlations among the molecular structures and the photophysical, calorimetric, and rheological properties are presented, demonstrating the impact of regioisomerism on the alkylated-chromophore liquid systems.

Ultrastructural identification of the primitive muscle spindle in the Xenopus laevis larvae.

The initial formation of muscle spindles was studied with electron microscopy using the toe muscle of Xenopus laevis. At the larval stage 57 (Nieuwkoop and Faber 1967), muscle spindles were first identified primarily by the presence of sensory endings associated with a thin bundle of myotubes, e.g. intrafusal (IF) myotubes which were partly invested by a single cellular layer. The number of IF myotubes per spindle was 5 to 6; the adult complement. IF- and extrafusal (EF) myotubes were almost identical in their size and structure. A few thinner IF myotubes with scarce myofibrils were also present. The reticular zone had been undeveloped. Sensory endings were smaller in size and in number per spindle than those in the adult, forming irregular beaded chains with occasional tubular expansions. The endings and IF myotubes were rarely in direct contact, being frequently interposed by a satellite cell and its process. Incipient fusimotor endings were widely distributed from the juxta-equatorial to the polar region. Large cored vesicles resembling the neurosecretory vesicles occurred in sensory and motor endings as well as in intramuscular nerve fibers. The vesicles may be involved in the neuronal influence upon the spindle differentiation. The results were compared with the formative process of mammalian spindles.

High-dose tocopherol acetate therapy in epidermolysis bullosa siblings of the Cockayne-Touraine type.

We have employed a successful therapy for epidermolysis bullosa with high-dose oral tocopherol acetate. Two siblings with dominant dystrophic epidermolysis bullosa of the Cockayne-Touraine type were reported. Both siblings suffered from tense blisters and erosions healing with scars and transient milia on the extremities. Electron microscopic study of the blisters revealed a cleavage beneath the lamina densa in both siblings. High-dose oral tocopherol acetate therapy was administered to them with satisfactory clinical reduction of the blister formation.

Merkel cell carcinoma and multiple Bowen's disease: incidental association or possible relationship to inorganic arsenic exposure?

An 81-year-old Japanese male was referred to our clinic in 1991 with multiple Bowen's disease. The associated hyperpigmentation of the trunk and extremities and palmoplantar keratotic nodules indicated that he had suffered from chronic arsenic poisoning. Interestingly, he was a native of Namikata in Ehime, Japan, where many residents have suffered from multiple Bowen's disease with internal malignancy. Arsenic exposure was strongly suspected. Two years later, Merkel cell carcinoma developed on the dorsum of his right hand, where Bowen's disease lesions were absent. Metastasis of this Merkel cell carcinoma led to his eventual death one year later. To our knowledge, this is the first report of Merkel cell carcinoma associated with multiple Bowen's disease. Chronic arsenic poisoning may be responsible for the association of these two rare skin neoplasms.

Acantholytic variant of seborrheic keratosis.

From among 524 histologic specimens of seborrheic keratosis (SK), 29 showed acantholysis, not related to pemphigus, Darier's disease, actinic keratosis or acantholytic squamous cell carcinoma. Acantholysis was found in 24 (23.3%) of the irritated type of SK, almost exclusively in the squamous cell nests showing dyskeratosis and spongiosis between and around squamous eddies or horn cysts. Clinically, 65.5% of the lesions were located on the face and scalp, 20.7% on the trunk and 13.8% on the limbs. It was speculated that dyskeratotic, degenerative changes of the keratinocytes together with spongiosis were responsible for the acantholysis.

Synthesis and photoisomerization of dithienylethene-bridged diporphyrins.

Dithienylethene-bridged diporphyrins 1-6 were prepared as photochemical switching molecules. Porphyrin and dithienylethene are directly linked in 1, and linked, respectively, through a 1,4-phenylene spacer in 2, through a 4-ethynylphenylene spacer in 3, and through a di-4-phenylethynylene spacer in 4, while meso-ethynylated porphyrin and dithienylethene are directly connected in 5 and linked through a 1,4-phenylene spacer in 6. Compounds 1, 2, and 5 do not undergo any photochemical isomerization, probably due to efficient quenching of the excited dithienylethene by the attached porphyrin moiety via intramolecular energy transfer. Compounds 4 and 6 undergo open-to-closed and closed-to-open photoisomerizations in quantum yields of 4.3 x 10(-)(2) and 1.8 x 10(-)(3), and 2.6 x 10(-)(3) and 7.5 x 10(-)(4), respectively, by irradiation with 313 and 625 nm light, which are considerably smaller than quantum yields of 0.52 and 3.8 x 10(-)(3) for reference dithienylethene molecule 7. The fluorescence of 4 was regulated in a reversible manner by the photoisomerization of the dithienylethene moiety. In addition, the absorption properties of the porphyrin in 6 changed in response to the photochromic reaction of the dithienylethene bridge.