No abstract

Enterotoxigenic Escherichia coli (ETEC) strains possessing colonization factor antigen I (CFA/I), CFAIII, CFA/III, and antigen 2230 were tested for their ability to adhere to the following cell lines: HeLa, HEp-2, HRT 18, Hutu 80, MDBK, MDCK, Vero, and Caco-2. ETEC strains adhered only to the Caco-2 cell line. Irrespective of the known adhesive factors, the ETEC strains that adhered to the brush border of human enterocytes also adhered to the Caco-2 cell line. The negative variants, which were cured of the plasmid encoding the adhesive factor, did not adhere. Adhesion of ETEC strains no longer occurred when the Caco-2 cells were pretreated with the homologous colonization factor antigen or when the bacterial cells were pretreated with homologous antibodies raised against the adhesive factors. This indicates that this adhesion is specific and that a different receptor exists for each type of adhesion factor. Electron micrographs of cross sections of the monolayer showed that the adhesion of ETEC strains to the brush border microvilli does not induce any lesion. Therefore, the Caco-2 cell line behaves in the same way as human enterocytes do.

No abstract

Medullary thyroid carcinoma (MTC), a C cell neoplasm, synthesizes large amounts of calcitonin (CT), its biological marker. However, in some cases with a poor prognosis, MTC is associated with low basal CT levels owing to a decrease in the thyroid CT content. Using a murine model of human MTC, we studied the relationships between CT biosynthesis, C cell proliferation, and the circulating CT level during MTC progression. Cell proliferation was revealed by autoradiography of radioactive thymidine incorporation in dividing nuclei, after CT or CT mRNA detection by immunocytochemistry (ICC) or in situ hybridization (ISH). All rat thyroids showed a severe hyperplasia of C cells containing significant amounts of CT and CT mRNA, and a very low mitotic index. Tumours were found in 68% of the thyroids. In the strongly immunoreactive small nodules (ICC+), many labelled nuclei were observed. Subsequently some nodular cells, still containing detectable CT mRNA (ISH+), were not detected by immunocytochemistry (ICC-) owing to a dramatic decrease in secretory granules. Their mitotic index increased, and a rise of the basal CT plasma level was noted. These ISH+, ICC- tumour MTC cells represent a modified aggressive tumour C cell population exhibiting an increased ability to proliferate and were detected by the rise in the basal circulating CT level.

A 42-year-old woman was observed during 3 bouts of eosinophilic cellulitis over a 6-year-period. Skin biopsies were taken at each relapse and processed for histological, immunofluorescent and ultrastructural studies. Histologically the eosinophilic infiltrate extended to the deep dermis and the subcutaneous fat. High levels of circulating immune complexes, and complement and IgG deposits around the vessels were detected for as long as the cutaneous lesions lasted. Under the electron microscope eosinophils were numerous, half of them degranulated and some granules had a double cristal core. No injury to the vessel walls was observed. The 3 recurrences occurred respectively after lincomycin, nesdonal, acetyl salicylic acid and pholcodin ingestion and responded to sulfone and steroid therapy.

Hyperpigmentation is a well-recognized feature of cutaneous graft-versus-host disease (GVHD), and is usually restricted to sites where lichenoid or sclerodermiform lesions have occurred. Since 1975, two of 745 patients treated by allogeneic bone marrow transplantation in our institution have developed diffuse melanoderma which differed considerably from the classic presentations. They both developed acute GVHD, then lichen planus-like chronic lesions and diffuse melanoderma. Histology of biopsies of the pigmented skin showed intense pigment deposition in the basal and suprabasal layers, and in dermal macrophages. On split-dopa, melanocyte counts were 98 and 93 per field, respectively. Electron microscopy showed melanocytes protruding into the dermis, and dark melanosomes in all epidermal layers and in macrophages. These findings were suggestive of post-inflammatory hyperpigmentation. In bone marrow recipients, de novo melanoderma is a rare event which could represent a feature of cutaneous GVHD in pigmented subjects.

No abstract

A 55-year-old women with eosinophilic fasciitis was biopsied 8 weeks after the onset of her illness. Under the electron microscope the changes were almost exclusively located in the fascia with many active fibroblasts, accumulation of protocollagen fibrils (10-50 A diameter), elastic fibre remodelling and numerous degranulating mast cells. The inflammatory infiltrate was dense and mostly composed of lymphocytes and plasma cells, with 16% eosinophils. The connective tissue changes may be part of a healing process following microinjury of the fascia. However, large numbers of lymphocytes and plasma cells are unusual in the healing process and are more common in the cellular reaction of morphea. Nevertheless, the absence of macrophages in subcutaneous fat, together with large number of eosinophils in the fascia may be considered to be distinctive features of eosinophilic fasciitis.