CD59 blocks not only the insertion of C9 into MAC but inhibits ion channel formation by homologous C5b-8 as well as C5b-9

Activation of the complement system on the cell surface results in the insertion of pore forming membrane attack complexes (MAC, C5b-9). In order to protect themselves from the complement attack, the cells express several regulatory molecules, including the terminal complex regulator CD59 that inhibits assembly of the large MACs by inhibiting the insertion of additional C9 molecules into the C5b-9 complex. Using the whole cell patch clamp method, we were able to measure accumulation of homologous MACs in the membrane of CD59⁻ human B-cells, which formed non-selective ion channels with a total conductance of 360 ± 24 pS as measured at the beginning of the steady-state phase of the inward currents. C5b-8 and small-size MAC (MAC containing only a single C9) can also form ion channels. Nevertheless, in CD59⁺ human B-cells in spite of small-size MAC formation, an ion current could not be detected. In addition, restoring CD59 to the membrane of the CD59⁻ cells inhibited the serum-evoked inward current. The ion channels formed by the small-size MAC were therefore sealed, indicating that CD59 directly interfered with the pore formation of C5b-8 as well as that of small-size C5b-9. These results offer an explanation as to why CD59-expressing cells are not leaky in spite of a buildup of homologous C5b-8 and small-size MAC. Our experiments also confirmed that ion channel inhibition by CD59 is subject to homologous restriction and that CD59 cannot block the conductivity of MAC when generated by xenogenic (rabbit) serum.     

A "floral" variant of nodal marginal zone lymphoma

We describe 6 cases of a specific variant of nodal marginal zone lymphoma with "floral" lymph follicles in patients ranging in age from 18 to 66 years. All 6 patients had lymphadenopathy, either local (n = 5) or systemic (n = 1), and good performance status (0), and none had fever, weight loss, or night sweating. They all underwent excisional biopsy. Histologically, all lesions had a distinctive morphology, with proliferation of medium-sized atypical lymphoid cells in the marginal zone, hyperplastic lymph follicles with enlarged germinal centers, and a thickened mantle zone. In places, folliculolysis was observed. On immunohistochemical staining, the atypical lymphoid cells showed a B-cell phenotype (CD20 +), IgM positivity in 2 of 5 cases, and negativity for CD5, CD10, CD23, CD43, bcl-6, and IgD. Polymerase chain reaction examination for immunoglobulin heavy chain in 5 cases showed monoclonality in all. Five patients did not receive adjuvant chemotherapy and had no recurrences. The patient with systemic lymphadenopathy received chemotherapy and had a complete response without relapse. This variant should be differentiated from the usual nodal marginal zone lymphoma because of its specific clinical and pathological features.     

Inhibition of MAP kinase activity moderates changes in expression and function of Cx32 but not claudin-1 during DNA synthesis in primary cultures of rat hepatocytes

The signal transduction pathways and activation of the MAP kinase or PI3 kinase signaling cascade regulate a variety of cellular processes, including proliferation and differentiation in hepatocytes. To elucidate the mechanisms of signal transmission required for the regulation of gap and tight junctions during DNA synthesis in rat hepatocytes, we determined changes of expression and function of gap and tight junctions of cells grown in primary culture, using inhibitors of signaling pathways for MAP kinase (PD98059) and PI3 kinase (LY294002). During the stimulation of DNA synthesis induced by epidermal growth factor (EGF), immunoreactivity and mRNAs of gap junction protein Cx32 and of tight junction protein claudin-1 markedly decreased with reduction of gap junctional intercellular communication (GJIC) and the fence function of tight junctions. In Western blots, whole-cell lysate of claudin-1 protein decreased and phosphorylated Cx32 protein in the insoluble fraction of Triton X-100 increased during the stimulation of DNA synthesis. During reinhibition of DNA synthesis, the changes of Cx32 and claudin-1 returned to control levels, as did both functions. In treatment with the inhibitors before DNA synthesis, PD98059 inhibited the changes of expression and function of Cx32, but not claudin-1, without inhibition of cell growth, whereas LY294002 completely inhibited cell growth. These findings indicate that the PI3 kinase pathway rather than the MAP kinase pathway plays an important role for EGF-induced proliferation of rat hepatocytes, and that changes of Cx32 in hepatocytes during the stimulation of DNA synthesis may be in part controlled through MAP kinase. Furthermore, Cx32, but not claudin-1, protein may be a target of activated MAP kinase in hepatocytes.     

Light and electron microscopic analyses of immediate and late tissue damage caused by radiofrequency ablation in porcine liver

Radiofrequency ablation (RFA) is an effective procedure for localized hepatocellular carcinoma. Contrast-enhanced CT depicts the ablated area as a hypoattenuated area without hepatic blood flow; however, light microscopy does not show obvious necrosis in the ablated area. We evaluated liver tissue changes after RFA by light microscopy and electron microscopy. The normal livers of three anesthetized pigs were coagulated using RFA after laparotomy. The liver was examined immediately, and 1 week after operation by light and electron microscopy. After RFA, the liver parenchyma surrounding the needle electrode was brown in color and surrounded by a red marginal zone separate from the normal liver parenchyma. Hematoxylin-eosin staining of the central area did not show cell necrosis, and the structures of liver sinusoids, liver cell cord and the nuclei of hepatocytes were preserved. However, electron microscopic examination of tissue immediately after RFA showed destruction of mitochondria of hepatocytes and fixation of sinusoidal cells. One week later, there was a large quantity of debris in the enlarged sinusoids, in addition to irreversible destruction of hepatocyte organelles. RFA of the porcine liver causes hepatocyte damage. This damage was not evident by light microscopy but clearly identified by electron microscopy.     

Ghrelin Induces Fasted Motor Activity of the Gastrointestinal Tract in Conscious Fed Rats

Ghrelin is a newly discovered orexigenic peptide originating from the stomach. However, its action in regulating the fed and fasted motor activity of the digestive tract is not fully understood. In the present study, we examined the effects of intracerebroventricular ( i.c.v. ) and intravenous ( i.v. ) injection of ghrelin on the physiological fed and fasted motor activities in the stomach and duodenum of freely moving conscious rats. i.c.v. and i.v. injection of ghrelin induced fasted motor activity in the duodenum in normal fed rats, while i.v. injection of ghrelin induced fasted motor activity in both the stomach and duodenum in vagotomized rats. The effects of i.c.v. and i.v. injected ghrelin were blocked by growth hormone secretagogue receptor (GHS-R) antagonist given by the same route and also blocked by immunoneutralization of neuropeptide Y (NPY) in the brain. The effects of i.v. injected ghrelin were not altered by i.c.v. injection of GHS-R antagonist in vagotomized rats. Injection of GHS-R antagonist blocked the fasted motor activity in both the stomach and duodenum in vagotomized rats but did not affect the fasted motor activity in normal rats. Low intragastric pH inhibited the effect of ghrelin. The present results indicate that ghrelin is involved in regulation of fasted motor activity in the stomach and duodenum. Peripheral ghrelin may induce the fasted motor activity by activating the NPY neurons in the brain, probably through ghrelin receptors on vagal afferent neurons. Once the brain mechanism is eliminated by truncal vagotomy, ghrelin might be primarily involved in the regulation of fasted motor activity through ghrelin receptors on the stomach and duodenum. The action of ghrelin to induce fasted motor activity is strongly affected by intragastric pH; low pH inhibits the action.     

Ultrastructural localization of laminin-5 (gamma2 chain) in the rat peri-implant oral mucosa around a titanium-dental implant by immuno-electron microscopy

Laminin-5 (Ln-5) is an important molecule associated with epithelial cell adhesion and migration. In the gingiva around the tooth, Ln-5 localizes within basement membranes between the junctional epithelium (JE) and the tooth or connective tissue. Recently, we reported that in the oral mucosa around a dental implant, Ln-5 is expressed within the basement membranes at the implant-peri-implant epithelium (PIE) interface, and at the PIE-connective tissue interface. However, the ultrastructural localization of Ln-5 within or along the PIE has not yet been reported. Therefore, peri-implant oral mucosa was treated with anti-Ln-5 (gamma2 chain) antibody and examined using immuno-electron microscopy. Ln-5 was localized in the cells of the innermost-third layer and basal layer of the PIE. A 100-nm-wide Ln-5-positive internal basal lamina (basement membrane) and hemidesmosomes as adhesion structures were formed at the apical portion of the implant-PIE interface. However, at the upper-middle portion of the interface, these adhesion structures were not observed. Furthermore, at the PIE-connective tissue interface, the Ln-5-positive external basal lamina (basement membrane) and hemidesmosomes were partially deficient. Judging from these findings, we concluded that Ln-5 contributes to the attachment of the PIE to the titanium surface, and that PIE attached to titanium at the apical portion of the dental implant-PIE interface.     

Genetic contribution of tumor necrosis factor (TNF)-alpha gene promoter (-1031, -863 and -857) and TNF receptor 2 gene polymorphisms in endometriosis susceptibility

PROBLEM: Tumor necrosis factor (TNF)-alpha is a major cytokine involved in inflammatory and immune function. The aim of this study was to investigate whether polymorphisms at positions -1031, -863 and -857 in the TNF gene promoter region (TNFA) and TNF receptor type 2 gene (TNFR2) are responsible in part for genetic susceptibility to endometriosis. METHODS OF STUDY: TNFA and TNFR2 polymorphisms were determined in 123 patients with endometriosis and 165 fertile healthy women by the polymerase chain reaction (PCR) - preferential homoduplex formation assay and PCR-restriction fragment length polymorphism, respectively. RESULTS: The frequency of the TNFA-U01 haplotype was increased significantly in patients with endometriosis compared with controls (P = 0.045, OR = 1.45). The TNFA-U01 haplotype was strongly associated with HLA-B*0702. No difference was found in TNFR2 polymorphism between patients and controls. CONCLUSION: Our results indicated that TNFA promoter polymorphism was associated with susceptibility to endometriosis. However, this association was not independent of HLA-class I polymorphisms.     

Phase stability after aging and its influence on pin-on-disk wear properties of Ce-TZP/Al2O3 nanocomposite and conventional Y-TZP

Recently zirconia/alumina composites have been examined by many researchers as the new generation of bearing materials in total joint replacements. In this study, the phase stability of a Ce-TZP/Al(2)O(3) nanocomposite and conventional Y-TZP after aging, and its influence on wear resistance, were investigated. Very slight phase transformation was observed in both types of ceramics 18 months after the implantation of Ce-TZP/Al(2)O(3) or Y-TZP samples into rabbit tibiae. However, Y-TZP showed marked phase transformation (approximately 80%) after aging in an autoclave (121 degrees C) for 190 h or in physiological saline at 62 degrees C for 18 months, whereas the new composite remained almost resistant to degradation. According to the results of self-pairing pin-on-disk wear tests using ceramic specimens with or without autoclave aging, the wear factor was almost the same between Ce-TZP/Al(2)O(3) samples with and without aging (6.74 +/- 0.36 x 10(-8) and 6.04 +/- 0.95 x 10(-8) mm(3)/Nm, respectively). In contrast, although non-aged Y-TZP had the lowest wear factor (4.88 +/- 0.51 x 10(-8) mm(3)/Nm) of all specimens tested, aged Y-TZP showed 10-fold greater wear than nonaged Y-TZP. The present study suggests that Ce-TZP/Al(2)O(3) nanocomposite has much greater phase stability than Y-TZP, and that its wear properties are not influenced by aging.     

Asymmetries of prefrontal cortex in human episodic memory: effects of transcranial magnetic stimulation on learning abstract patterns

Functional neuroimaging suggests asymmetries of memory encoding and retrieval in the prefrontal lobes, but different hypotheses have been presented concerning the nature of prefrontal hemispheric specialization. We studied an associative memory task involving pairs of Kanji (Chinese) pictographs and unfamiliar abstract patterns. Subjects were ten Japanese adults fluent in Kanji, so only the abstract patterns represented novel material. During encoding, transcranial magnetic stimulation (TMS) was applied over the left and right dorsolateral prefrontal cortex (DLPFC). A significant (P<0.05) reduction in subsequent recall of new associations was seen only with TMS over the right DLPFC. This result suggests that the right DLPFC contributes to encoding of visual-object associations, and is consistent with a material-specific rather than a process-specific model of mnemonic function in DLPFC.     

Type-specific evolution of amyloid plaque and angiopathy in APPsw mice

To clarify how Aβ deposits start in the brain, we examined the early to late stages of senile plaques and amyloid angiopathy in APPsw mice. All types of human senile plaques were observed in the mouse brains. The premature forms of cored plaques appeared first in the cerebral cortex of mice at 7–8 months old. Then, amyloid angiopathy emerged, followed by diffuse plaques consisting of Aβ1–42. Modifications of the N-terminus of Aβ were late phase phenomena. The premature forms of cored plaques were composed of central Aβ1–40 amyloid cores, surrounding amorphous Aβ1–42 deposits, and accumulation of Aβ1–42 in some peripheral cells. These cells were incorporated in amyloid cores, and these plaques developed to large cored plaques composed of Aβ1–40 and Aβ1–42. The size and number of cored plaques were increased with age. These findings indicate different evolution paths for cored plaques and diffuse plaques, and suggest the presence of a pathway that initiates with the intracellular accumulation of Aβ1–42 and leads to the development of classic plaques in human brain tissues.