Fluoride‐sensitivity of growth and acid production of oral Actinomyces: comparison with oral Streptococcus

Actinomyces are predominant oral bacteria; however, their cariogenic potential in terms of acid production and fluoride sensitivity has not been elucidated in detail and compared with that of other caries‐associated oral bacteria, such as Streptococcus. Therefore, this study aimed to elucidate and compare the acid production and growth of Actinomyces and Streptococcus in the presence of bicarbonate and fluoride to mimic conditions in the oral cavity. Acid production from glucose was measured by pH‐stat at pH 5.5 and 7.0 under anaerobic conditions. Growth rate was assessed by optical density in anaerobic culture. Although Actinomyces produced acid at a lower rate than did Streptococcus, their acid production was more tolerant of fluoride (ID_{acid production} 50 = 110–170 ppm at pH 7.0 and 10–13 ppm at pH 5.5) than that of Streptococcus (ID_{acid production} 50 = 36–53 ppm at pH 7.0 and 6.3–6.5 ppm at pH 5.5). Bicarbonate increased acid production by Actinomyces with prominent succinate production and enhanced their fluoride tolerance (ID_{acid production} 50 = 220–320 ppm at pH 7.0 and 33–52 ppm at pH 5.5). Bicarbonate had no effect on these variables in Streptococcus. In addition, although the growth rate of Actinomyces was lower than that of Streptococcus, Actinomyces growth was more tolerant of fluoride (ID_growth 50 = 130–160 ppm) than was that of Streptococcus (ID_growth 50 = 27–36 ppm). These results indicate that oral Actinomyces are more tolerant of fluoride than oral Streptococcus, and bicarbonate enhances the fluoride tolerance of oral Actinomyces. Because of the limited number of species tested here, further study is needed to generalize these findings to the genus level.     

A Novel Monoclonal Antibody disrupting Cell Type Specific Substratum Adhesion of Frog (Xenopus laevis) Epithelial Cells and Endothelial Cells

We isolated a mouse monoclonal antibody (FAD-II) that disrupts cell-substratum adhesion of amphibian ( Xenopus laevis ) epithelial cells and endothelial cells. The effect of the antibody was cell-type specific, and the antibody had no effect on fibroblastic cells while fibronectin peptide blocked cell-substratum adhesion of all the cell types examined. In developing frog embryos, the epitopes recognized by the antibody were detected in pronephrotic ducts and in other tissue cells of embryos (from stage 33/34 afterwards). In adult tissues, the antibody mainly recognized antigens in extracelluar matrices. The antigens recognized by the antibody seems to be novel glycoepitopes in frog cells.     

EHBP1L1 coordinates Rab8 and Bin1 to regulate apical-directed transport in polarized epithelial cells

The highly conserved Rab guanosine triphosphatase (GTPase) Rab8 plays a role in exocytosis toward the polarized plasma membrane in eukaryotic cells. In murine Rab8-deficient small intestine cells, apical proteins are missorted into lysosomes. In this study, we identified a novel Rab8-interacting protein complex containing an EH domain–binding protein 1–like 1 (EHBP1L1), Bin1/amphiphysin II, and dynamin. Biochemical analyses showed that EHBP1L1 directly bound to GTP-loaded Rab8 and Bin1. The spatial dependency of these complexes at the endocytic recycling compartment (ERC) was demonstrated through overexpression and knockdown experiments. EHBP1L1- or Bin1-depleted or dynamin-inhibited small intestine organoids significantly accumulated apical membrane proteins but not basolateral membrane proteins in lysosomes. Furthermore, in EHBP1L1-deficient mice, small intestine cells displayed truncated and sparse microvilli, suggesting that EHBP1L1 maintains the apical plasma membrane by regulating apical transport. In summary, our data demonstrate that EHBP1L1 links Rab8 and the Bin1–dynamin complex, which generates membrane curvature and excises the vesicle at the ERC for apical transport.     

Induction of drug metabolism-related enzymes by methylcholanthrene and phenobarbital in transgenic mice carrying human prototype c-Ha-ras gene and their wild type littermates.

Transgenic mice hemizygously carrying human c-Ha-ras proto-oncogene, Tg-rasH2 show very sensitive and facilitated carcinogenicity to various carcinogens. In this study, activities of certain enzymes related to drug metabolism and energy metabolism were measured in microsome and cytosol fractions of livers of Tg-rasH2 mice and their wild type littermates with both sexes treated with 3-methylcholanthrene (MC) and phenobarbital (PB). Aminopyrine N-demethylase activities increased significantly in livers of all mice treated with PB. MC and PB treatments induced significant increases in activities of UDP-glucuronosyltransferase and S-adenosyl homocysteinase compared to those in the non-treated groups in microsome fractions from all mice. In cytosol fractions of livers of all mice, glutathione S-transferase activity was significantly induced in the PB treated groups. There were no significant differences in activities of lactate dehydrogenase, glucose 6-phosphate dehydrogenase, pyruvate kinase and glucose 6-phosphatase related to energy metabolism in livers and kidneys among all mice. Tg-rasH2 mice showed stable activities of enzymes related to drug detoxication and energy metabolism similar to those of non-transgenic mice. These results suggest that the human c-Ha-ras transgene may not affect drug metabolism-related enzymes, and the facilitated carcinogenic response in the Tg-rasH2 mouse is not due to these enzymatic disorders.     

Significant gene expression of insulin-like growth factor II and proliferating cell nuclear antigen in a rapidly growing recurrent pituitary acth-secreting adenoma.

BACKGROUND: We quantified the expression of various growth-related factors in an adrenocorticotropic hormone (ACTH)-secreting adenoma that had recurred very rapidly as invasive macroadenoma. METHODS/RESULTS: A 43-year-old woman underwent successful transsphenoidal surgery for Cushing's disease. Seven years later, she was admitted to our ward for further endocrine examinations. In spite of a very high plasma ACTH level, the serum cortisol level was normal. Discrepancies between ACTH and cortisol levels were detected on the basis of diurnal rhythms, dexamethasone suppression tests, and corticotropin-releasing hormone test. The patient showed no clinical features of Cushing's disease. Magnetic resonance imaging of the pituitary showed an almost empty sella, and no microadenoma was found. These results, along with those of Sephadex column gel filtration and high-performance liquid chromatography of plasma-immunoreactive ACTH, suggested that the patient's residual corticotrophs secreted biologically inactive ACTH. Two years later, the patient suddenly developed diplopia and right abducens nerve palsy. She was slightly moonfaced and centrally obese. Her plasma ACTH and serum and urinary free cortisol levels were elevated, although discrepancies between ACTH and cortisol still existed. Magnetic resonance imaging revealed a large pituitary mass with suprasellar and cavernous sinus extensions. The tumor was excised, and the proopiomelanocortin gene and the expression of growth-related factors were analyzed. No mutations were found in the ACTH-coding region of the proopiomelanocortin gene. A significant expression of insulin-like growth factor II and proliferating cell nuclear antigen mRNAs was demonstrated. A high MIB-1 antibody labeling index was also detected in the adenoma tissue, suggesting high Ki-67 expression. CONCLUSION: These growth- and proliferation-related factors might be involved in the rapid growth and aggressiveness of this patient's pituitary adenoma.     

Low Latency High Bandwidth Message Transfer Mechanisms for a Network Interface Plugged into a Memory Slot

The communication architecture of the DIMMnet-1 network interface based on MEMOnet is described. MEMOnet is a class of a network interface plugged into a memory slot. This paper proposes three message transfer mechanisms named atomic on-the-fly sending (AOTF), block on-the-fly sending (BOTF) and OTF receiving with selective address translation. The DIMMnet-1 prototype will have an ASIC named Martini, two banks of PC133 based SO-DIMM slots and an 8 Gbps full duplex optical link. The software overhead incurred to generate a message is only 1 CPU cycle and the estimated hardware delay is 105 ns using AOTF. The estimated hardware delay for receiving to on chip memory using OTF receiver is 90 ns. The estimated achievable sending bandwidth of DIMMnet-1 using BOTF is 984 MB/s which was observed in our experiments. This bandwidth is 7.4 times higher than the maximum bandwidth of PCI. This high performance is available even when simultaneous sending and receiving are executed on a cheap personal computer with DIMM slots. This paper also discribes the effects of BOTF for a PCI-based NIC.