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The significance of the "leaky" tight junction might be understood better if cells of the epithelial monolayer possessed mechanisms to regulate molecular flow through the junction. To test this possibility, Necturus gallbladder, a representative leaky epithelium, was studied before, during, and after mucosal exposure to plant cytokinins and two other microfilament-active drugs, cytochalasin B and phalloidin. Concomitant with morphological changes in microfilaments, cytokinins induced rapid reversible increases in transepithelial resistance and potential difference (PD) and decreases in NaCl dilution potentials, with no change in the ratio of relative cell membrane resistances. Cytochalasin B (0.2-1.2 microM) and phalloidin (0.6-12.7 microM) caused similar changes in transepithelial resistance and PD. When the intramembranous structure of tight junctions was studied by freeze fracture, peak cytokinin-induced increments in transepithelial resistance were associated with more disorder in the strand meshwork resulting in a small increase in tight junction depth, but there was no evidence of de novo strand assembly. These studies suggest that permeability of the tight junction of Necturus gallbladder is subject to rapid reversible modulation, possibly under cytoskeletal control.

Leakage of tight junctions as observed with electron microscopy and demonstration of solute transport across bladder epithelium was investigated in 13 patients with different bladder diseases: urinary retention and infection, bladder tumours and interstitial cystitis. The latter group showed consistent leakage of solutes through the urothelium. Electron microscopy revealed leaky tight junctions. This finding might be helpful in establishing the histological criteria and explain the pathogenesis of interstitial cystitis.

The Revised European American lymphoma (REAL) and World Health Organization (WHO) classification of non-Hodgkin's lymphoma (NHL) relies on the constellation of cytologic, phenotypic, genotypic, and clinical characteristics of NHL. For the most part, the classification does not rely on architectural pattern for classification of neoplasms. This classification makes it possible to diagnose and classify lymphomas by fine-needle aspiration (FNA). In this study, we attempted to evaluate the accuracy of FNA in diagnosing and classifying NHL within the context of the REAL/WHO classifications. Cases included only those in which FNA was the primary diagnosis, followed by a surgical biopsy for confirmation. Flow cytometry (FCM) for phenotyping was carried out whenever material was available. Two groups of pathologists were identified. Group A consisted of pathologists with background training in cytopathology and/or hematopathology (three pathologists). Group B consisted of experienced surgical pathologists with no training in cytopathology and/or hematopathology (four pathologists). Seventy-four cases were included in the study. FCM phenotyping was performed in 53 cases (71%). Large cell lymphoma constituted 63% of the cases. The remaining lymphomas included Burkitt's, small lymphocytic, lymphoblastic, follicle center cell, Ki-1, mantle cell, marginal zone, and natural killer cell lymphoma. The diagnosis of lymphoma was rendered for all cases. The correct classification was seen in 63% of the cases. Classification was more accurate in immunophenotyped than in nonimmunophenotyped cases (84% vs 33%; P = 0.00004). Group A pathologists showed higher incidence of proper classification than group B (80% vs 56%; P = 0.046). The diagnosis and classification of NHL can be achieved in a large number of cases on FNA material. This accuracy can be increased if cytomorphologic criteria are established for different entities of NHL aided by FCM for phenotyping.

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