Characterization of thylakoid membrane in a heterocystous cyanobacterium and green alga with dual-detector fluorescence lifetime imaging microscopy with a systematic change of incident laser power.

Fluorescence Lifetime Imaging Microscopy (FLIM) has been applied to plants, algae and cyanobacteria, in which excitation laser conditions affect the chlorophyll fluorescence lifetime due to several mechanisms. However, the dependence of FLIM data on input laser power has not been quantitatively explained by absolute excitation probabilities under actual imaging conditions. In an effort to distinguish between photosystem I and photosystem II (PSI and PSII) in microscopic images, we have obtained dependence of FLIM data on input laser power from a filamentous cyanobacterium Anabaena variabilis and single cellular green alga Parachlorella kessleri. Nitrogen-fixing cells in A. variabilis, heterocysts, are mostly visualized as cells in which short-lived fluorescence (≤0.1 ns) characteristic of PSI is predominant. The other cells in A. variabilis (vegetative cells) and P. kessleri cells show a transition in the status of PSII from an open state with the maximal charge separation rate at a weak excitation limit to a closed state in which charge separation is temporarily prohibited by previous excitation(s) at a relatively high laser power. This transition is successfully reproduced by a computer simulation with a high fidelity to the actual imaging conditions. More details in the fluorescence from heterocysts were examined to assess possible functions of PSII in the anaerobic environment inside the heterocysts for the nitrogen-fixing enzyme, nitrogenase. Photochemically active PSII:PSI ratio in heterocysts is tentatively estimated to be typically below our detection limit or at most about 5% in limited heterocysts in comparison with that in vegetative cells.

Reduced expression of dermcidin, a peptide active against propionibacterium acnes, in sweat of patients with acne vulgaris.

Dermcidin (DCD), an antimicrobial peptide with a broad spectrum of activity against bacteria such as Propionibacterum acnes, is expressed constitutively in sweat in the absence of stimulation due to injury or inflammation. The aim of this study was to determine the relationship between DCD expression and acne vulgaris associated with P. acnes. The antimicrobial activity of recombinant full-length DCD (50 µg/ml) was 97% against Escherichia coli and 100% against Staphylococcus aureus. Antimicrobial activity against P. acnes ranged from 68% at 50 µg/ml DCD to 83% at 270 µg/ml DCD. DCD concentration in sweat from patients with acne vulgaris (median 9.8 µg/ml, range 6.9-95.3 µg/ml) was significantly lower than in healthy subjects (median 136.7 µg/ml, range 45.4-201.6 µg/ml) (p = 0.001). DCD demonstrated concentration-dependent, but partial, microbicidal activity against P. acnes. These results suggest that reduced DCD concentration in sweat in patients with inflammatory acne may permit proliferation of P. acnes in pilosebaceous units, resulting in progression of inflammatory acne.

Mycostatic effect of recombinant dermcidin against Trichophyton rubrum and reduced dermcidin expression in the sweat of tinea pedis patients.

Trichophytosis, a common dermatophytosis, affects nearly 20-25% of the world's population. However, little is known about mechanisms for preventing colonization of Trichophyton on the skin. Dermcidin, an antimicrobial peptide that provides innate immunity to the skin and is constitutively secreted even in the absence of inflammatory stimulation, was studied to elucidate its antimycotic activity against Trichophyton. Recombinant dermcidin was determined to have antimycotic activity against Trichophyton rubrum, as evaluated by colony-forming unit (CFU) assays. The killing rate of dermcidin was 40.5% and 93.4% at 50 µg/mL (the average dermcidin concentration in healthy subjects) and 270 µg/mL, respectively. An effect of dermcidin treatment was found to be a reduction of the metabolic activity of Trichophyton as determined by nicotinamide adenine dinucleotide assay. Further, dermcidin concentrations in sweat of tinea pedis patients were found to be lower than those of healthy subjects. These findings suggest a mycostatic role for dermcidin, at normal sweat concentrations. Accordingly, we suspect that dermcidin, at normal sweat concentrations, inhibits growth of Trichophyton, where Trichophyton is subsequently eliminated in conjunction with epidermis turnover. Dermcidin, therefore, appears to play a role in the skin protection mechanism that prevents colonization of tinea pedis.

Acquired reactive perforating collagenosis in a patient with lung fibrosis.

Reactive perforating collagenosis (RPC) is a rare disorder characterized by the transepidermal elimination of altered collagen. The inherited form of RPC begins in early childhood, but acquired reactive perforating collagenosis (ARPC) begins in adult life. ARPC is associated with diabetes mellitus, renal disease, and malignancy. ARPC with lung fibrosis has not previously been reported in the literature, and the relationship between ARPC and lung fibrosis has not been studied. The etiological relationship between the two disorders appears to be uncertain. Although their association in this case could be due to chance, it may be due to the transforming growth factor beta abnormalities seen in both diseases. In this report, we describe a case of ARPC with lung fibrosis and propose an etiological association between the two diseases.