Paddy fields located in water storage zones could take over the wetland plant community.

Land use change could affect not only local species richness but also community assemblies. Essentially, the possible patterns of plant community assemblies are nonrandom species loss (nestedness) and species turnover. Plant community assemblies in human-mediated land use have a combination of both nestedness and turnover. This is because of historical effects that cause nonrandom species loss due to previous and/or original habitat quality and because of direct effects of human activities that cause species turnover. We investigated the complexity of the process of plant community assemblage in a paddy field, which is a typical agricultural land use in the monsoon season in central Japan. Using multi-temporal plant monitoring records, we tested the relationship between the ratio of species nestedness/turnover through multi-temporal and both the original habitat conditions and the extent of human modification. The findings revealed that paddy fields that originated from wetland habitat had a high nestedness ratio, whereas paddy fields that were largely consolidated had a high turnover ratio. Thus, we could divide the community assembly processes in human-mediated land use based on original habitat conditions and human activities. This concept could help land managers establish conservation and/or restoration plans that take into account community assembly.

Stochastic tunneling in the colonization of mutualistic organisms: primary succession by mycorrhizal plants.

In mutualism under spatial structure, asynchrony between the dispersions of the interacting species can be a key determinant of their dynamics. We focused on the plant-mycorrhizal fungi system to theoretically analyze the colonization process by calculating the probability of colony establishment under environmental fluctuation. This can be considered a joint process of two sub-processes before and after the association between the host plant and the mycorrhizal fungi in a novel habitat. When colony growth undergoes environmental fluctuation, the dynamics of colony size can be considered a combination of the two stochastic sub-processes that mediated the association event between the plant and the fungi. Therefore, properties of whole system are influenced by five parameters, means and variances of colony growth rates of two sub-systems, and a rate of association of plant and fungi. For the successful establishment of a colony, the second sub-process must start before the first sub-process finishes (i.e., extinction), which we refer to as "stochastic tunneling." Our analysis of the establishment probability of a plant colony based on this concept revealed that (1) the mean colony growth rates of the host alone and the symbiotic association affect establishment probability in different ways, (2) the variance of colony growth rate of the symbiotic association reduces the establishment probability, although the variance of growth rate of the host alone facilitates the establishment probability when the mean growth rate of the host alone is negative, and (3) a trade-off between the mean colony growth rates of the host alone and the symbiotic association could result in the evolution of either a symbiotic or parasitic relationship, based on a host decision. The model we present is widely applicable to the colonization processes of both positive and negative species relationships, where the interacting species disperse independently.

Three cases of malignant melanoma arising on burn scars.

It is well known that up to 2% of chronic burn scar lesions can transform into malignant tumors. Most of them are squamous cell carcinoma (SCC) and, more occasionally, basal cell carcinoma (BCC). The incidence of malignant melanoma (MM) is extremely low. To the best of our knowledge, there are only 23 such cases reported in the literature. We report here three cases of MM arising on burn scars and analyze the 23 cases reported previously. Case 1: a 74-year-old Japanese man sustained a burn injury on about 54% of his whole body surface when he was accidentally bathed in boiling oil at the age of 37 years old. Some small tumors developed on the burn scar on his right lumbar region. A wide excision of the tumor was performed. Case 2: a 51-year-old Japanese woman was injured on her right forearm and face by deep burns from a flame when she was 7 months old. She presented with a rapidly growing, painless black nodule on the dark skin lesion on her right forearm. She was treated with a wide excision followed by a full-thickness skin graft. Intravenous administration of one unit of OK-432 every week has been continued. Case 3: a 73-year-old Japanese woman was burned on her left leg and hand from a flame when she was 6 years old. A nodular lesion appeared within the ulcer two months previously and it was growing rapidly. This lesion was ulcerated on the top of its central area and was slightly reddish without any pigmentation. The patient was treated with a wide excision and a split-thickness skin graft. The 5-year survival rate of MM in an old burn scar is 53.6%. It is suggested that the prognosis of burn scar carcinoma is not worse than that of non-burn scar carcinoma.

CD56: a useful marker for diagnosing Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC) of the skin is an aggressive but rare malignant neuroendocrine tumor. For its pathological diagnosis, we use a panel of immunohistochemical markers, such as cytokeratin 20 (CK 20), epithelial membrane antigen (EMA), chromogranin A, neuron specific enolase (NSE), synaptophysin, and Leu7 (CD57) to demonstrate its epithelial and neuroendocrine features. CD56, or neural cell adhesion molecule (NCAM), has been demonstrated recently as the tumor marker of the pulmonary neuroendocrine cell system. Its expression in MCC, however, has still rarely been investigated. Furthermore, in such very few previous studies on NCAM expression in MCC, all the tumor cells were not necessarily demonstrated to express NCAM. OBJECTIVES: To study the immunoreactivity of CD56 in MCC, especially using a monoclonal antibody of a clone 1B6, different from those adopted in the previous reports. METHODS: We reexamined CD56 expression immunohistochemically in five MCC cases, along with the conventional panel of markers described above, using paraffin-embedded tissue sections. RESULTS: CD56 revealed the most diffuse and intense positive staining, which was noted along the cell borders, in all specimens compared with other neuroendocrine tumor markers. CONCLUSIONS: The results of our study indicate that CD56, especially a new monoclonal antibody (clone 1B6), is a useful immunohistochemical marker for MCC.