We investigated mRNA expression of tissue-type plasminogen activator (tPA) and inflammatory cell dynamics for wound age estimation of bruises in mice. Neutrophils were detected from 1 h post-injury. Up to 8 h, they accumulated in subcutaneous tissue and the lower part of the dermis, and thereafter they extended to all the layers. Macrophages became detectable 3 h post-injury, and moderate infiltration of lymphocytes was seen from 144 h. In addition, epidermal thickening was also seen from 72 h. tPA mRNA expression peaked at 1 h, and increased slightly at 72 h post-injury. tPA mRNA was detected in epidermal cells, fibroblasts, and endothelial cells before and after injury, from 3 h in neutrophils and from 72 h in macrophages, respectively. This study presents the time-dependent expression of tPA mRNA in bruises in relation to temporal histologic characteristics during wound healing, which was considered to be useful for wound age estimation. Furthermore, it is suggested that tPA plays an important role in the first step of tissue remodeling.

A number of mutations in coding and noncoding regions of mitochondrial DNA (mtDNA) have previously been studied. In the present study, we simultaneously typed six mutation sites in the coding region by use of amplified product-length polymorphism (APLP) analysis. The mtDNA variations of 2471 individuals from 20 populations of Japanese, Korean, Chinese, and German were examined and classified into 18 haplotypes. Two of these haplotypes, B1 (estimated ancestral haplotype) and C1, were distributed among all populations tested. However, the haplotypes A1, A2, B2, B3, and C2 were mostly restricted to the Mongoloid populations, whereas haplotypes B5 and C5 appeared almost exclusively in the German population. Phylogenetic analysis by the neighbor-joining method revealed that the Japanese populations were more closely related to each other than to the other East Asian populations surveyed. The multiplex APLP method is suitable for large-scale screening studies of mtDNA variability because it is both rapid and economical.

Epidermal nuclear elongation is one of the most important signs for the diagnosis of electrical injury. In this study, we investigated the mechanism responsible for this phenomenon by comparing the findings from burn injuries and those from contusions. Electrical and burn injuries were made in the dorsal skin of rats using energy ranging from 100 to 790 joules for electrical injury, and 170-690 joules for burn injury. Contusions were also made by compressing the skin with a vice. In electrical and burn injuries, the dermis under the epidermal elongated nuclei was homogeneous and without empty spaces between collagen bundles and the number of dermal fibroblasts per 0.01 mm2 below the damaged epidermis decreased significantly (P < 0.05). The incidence of this change correlated with the depth of denatured dermal collagen fibres and in both types of injuries, dermal cells had no nuclear antigenicity for ubiquitin. The width of the injured epidermis with nuclear elongation decreased significantly (P < 0.05) and the elongated nuclei were parallel to the basal membrane. In electrical injury however, nuclear elongation occurred more frequently near the external root sheath. Nuclear elongation of fibroblasts and external root sheath cells was also found, but those of sebaceous gland cells were not detected. Epidermal elongated nuclei were also found in contusions. The evidence strongly suggests that epidermal nuclear elongation in electrical and burn injuries is due to dermal expansion by heat.

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