Oxidative burst and cognate redox signalling reported by luciferase imaging: identification of a signal network that functions independently of ethylene, SA and Me-JA but is dependent on MAPKK activity.

Recognition of avirulent microbial pathogens activates an oxidative burst leading to the accumulation of reactive oxygen intermediates (ROIs), which are thought to integrate a diverse set of defence mechanisms resulting in the establishment of plant disease resistance. A novel transgenic Arabidopsis line containing a gst1:luc transgene was developed and employed to report the temporal and spatial dynamics of ROI accumulation and cognate redox signalling in response to attempted infection by avirulent strains of Pseudomonas syringae pv. tomato (Pst). Strong engagement of the oxidative burst was dependent on the presence of functional Pst hrpS and hrpA gene products. Experiments employing pharmacological agents suggested that at least two distinct sources, including an NADPH oxidase and a peroxidase-type enzyme, contributed to the generation of redox cues. The analysis of gst1 and pal1 gene expression in nahG, coi1 and etr1 plants suggested that engagement of the oxidative burst and cognate redox signalling functioned independently of salicylic acid, methyl jasmonate and ethylene. In contrast, studies using a panel of protein kinase and phosphatase inhibitors and in-gel kinase assays in these mutant backgrounds suggested that a 48 kDa mitogen-activated protein kinase (MAPK) activity was required for the activation of gst1 and pal1 in response to redox cues. Thus the engagement of a bifurcating redox signalling pathway possessing a MAPK module may contribute both to the establishment of plant disease resistance, and to the development of cellular protectant mechanisms.

Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis.

AIMS: To describe the clinical and histopathological features of a rare variant of naevoid melanoma, small cell melanoma, and discuss the histological differential diagnoses. METHODS: The clinical and histological features of cases of malignant melanoma with the histological features of small (non-Merkel like) melanoma were reviewed and documented. In addition, five cases had available material for immunohistochemistry and this was performed using antibodies to the S100 protein and melan-A, and the HMB-45 antibody. RESULTS: There were 15 cases of small cell melanoma from 14 (10 female, four male) patients, aged between 30 and 77 (mean, 48.6) years. The trunk was the most common location. In more than half the cases, the provisional diagnosis was melanoma/borderline lesion. All shared similar histological appearances of an intraepidermal component of in situ melanoma and a dermal component of nests of cells with hyperchromatic nuclei and scanty cytoplasm, usually in tightly packed nests. All components (junctional and intradermal) of the lesions investigated by immunohistochemistry were positive both for S100 protein and melan-A. All junctional components were positive with HMB-45, but with variable staining of the dermal components with this antibody. CONCLUSIONS: Small cell malignant melanoma is postulated to be a distinct histopathological entity and a rare variant of naevoid melanoma. Such lesions can be difficult to interpret and easily missed at scanning magnification because the cells of the dermal component mimic benign naevus cells.

Comparison of immunohistochemical staining of the novel antibody melan-A with S100 protein and HMB-45 in malignant melanoma and melanoma variants.

AIMS: The staining pattern of the recently described antibody melan-A was compared with those of S100 protein and HMB-45 in a variety of melanocytic lesions to assess the specificity and sensitivity of these antibodies. METHODS AND RESULTS: Immunohistochemical staining of paraffin sections of a range of melanocytic lesions was carried out following a high temperature antigen retrieval technique. The pattern and intensity of staining was semiquantitatively scored. S100 remains the most sensitive marker of melanocytic differentiation being diffusely positive in all benign and all primary and secondary malignant lesions including naevoid melanomas, and in most desmoplastic/spindle cell melanomas. Of the two more specific melanocytic markers melan-A stains the majority of benign and malignant lesions diffusely but with occasional patchy positivity only in some secondary melanoma deposits and with little staining of desmoplastic/spindle cell melanomas. HMB-45 is the least sensitive of the three showing little positivity of benign mature naevus cells, only variable patchy positivity of primary and secondary melanoma cells and limited positivity in naevoid, desmoplastic and metastatic melanomas. CONCLUSIONS: Melan-A is a useful addition to antibody panels as it is apparently specific for melanocytic lesions and is more sensitive than HMB-45; however, it has less value than S100 in the detection of spindle cell and desmoplastic melanomas.

Thyroid gland papillary carcinoma with fibromatosis-like stroma: case report.

Papillary carcinoma of the thyroid may show a variable degree of fibrosis of the stroma, but proliferation of the stromal fibroblasts mimicking fibromatosis is rare. There appears to be a new variant of papillary carcinoma of the thyroid associated with exuberant proliferation of the fibroblasts resembling fibromatosis. We present one such case in a 50 year old woman and succinctly reviewed the relevant literature of this rare variant. The necessity of a diligent search for a papillary carcinoma in thyroid gland which shows a proliferative fibrous lesion is stressed.

Transforming growth factor-alpha expression in in situ epidermal neoplasia.

Twenty cases of solar keratosis and 15 cases of Bowen's disease were investigated for the expression of transforming growth factor alpha (TGF-alpha) by an indirect immunoperoxidase technique using monoclonal antibody TGF-alpha AB-2 in formalin-fixed wax-embedded tissue. Twelve cases (60%) of solar keratosis and 13 cases (86%) of Bowen's disease showed marked overexpression of TGF-alpha in both membranous and cytoplasmic distributions. This suggests that overexpression of TGF-alpha may play an important role in the evolution of these two neoplastic conditions.