Recent advances in studies of the genetic and molecular basis of microbial life on solid surfaces have brought the realization that bacteria can sense environmental changes, modulate their own gene expression and establish a structure with community properties known as a biofilm. Cell-to-cell communication in biofilm-associated bacteria is involved in successful pathogenic or symbiotic interaction of a variety of bacteria with animal hosts. Acyl-homoserin lacton quorum-sensing in gram-negative bacteria is known to be important not only for sensing population density, but also for controlling a number of virulence factors necessary for continued success in the host. Pseudomonas aeruginosa, one of the top three causes of opportunistic human infections, has been thoroughly studied as a model of biofilm infections regulated with a quorum-sensing system. In this review, we discuss in detail the virulence factors of P. aeruginosa, especially exopolysaccharide (alginate) synthesis along with the multisteps of biofilm formation. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 217-226.

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We attempted to determine how various light source in the examination room affect clinical digital images. We found that natural light affected the degree of illumination and chromaticity under various light sources. By opening the window blinds, it was possible to modify the degree of illumination,but not the chromaticity of the images. Adjustments using the tone curve compensation method of computer imaging software significantly affected the color reproduction of clinical photographic data. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 227-234.

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We studied the identification and the biological characterization of adherent bacteria isolated from the oral cavities of adults and elementary school children in order to analyze differences in these bacteria in Chinese and Japanese. Bacterial strains used were isolated from the bacteria adhered on surfaces of tooth hung in saliva, dental plaque and tongue dorsum suspensions. The 364 Chinese strains included 132 from saliva, 119 from dental plaque, and 113 from the tongue. The 349 Japanese strains included 100, 144, and 105 strains, respectively. The ratio of Gram positive cocci occupying each sample in the Chinese was between 86% and 100%,and of these, 62% were streptococci. In Japanese, 87-89% were Gram positive cocci, of which 72% were streptococci. No differences were observed in the streptococcal species between Chinese and Japanese. In vitro plaque formation was observed in 62% of the Chinese streptococcal strains and 68% of the Japanese ones. Although results suggest that there is a slight differ ence in the distribution of the streptococci adhered without sucrose in the normal oral microbial flora between Chinese and Japanese, their in vitro plaque formation is the same. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 235-240.

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We investigated immunohistochemically the changes in Fas and Fas ligand (FasL) expression during carcinogenesis induced by 4-nitroquinoline 1-oxide (4NQO). Cultured cells were obtained by cloning tissues of carcinoma induced by 4NQO. Fas/FasL expression in these cells were detected by Western blot analysis using anti-Fas and anti-FasL monoclonal antibodies. Further, apoptosis of these cells after preincubation with anti-Fas monoclonal antibody was examined by flowcytometry and by polymerase chain reaction (PCR) based assay for apoptotic ladder detection. Cultured cells obtained from normal tongue epithelium were used as controls. From these experiments, Fas/FasL expression was found not only in normal epithelium but also in its malignant counterpart. Both in vivo tissues and cultured cells derived from normal and malignant tissues also showed Fas/FasL expression, which mediated apoptosis by anti-Fas antibody stimulation. We found that Fas/FasL expression exists through the process of 4NQO-induced carcinogenesis and plays an important role in apoptosis. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 241-247.

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We investigated the influence of stress caused by dental anesthesia on salivary cortisol and chromogranin A concentrations.
The experiment was carried out on eight healthy volunteers after informed consent. Each subject was exposed to two different sessions, one the control and the other with anesthesia. The two sessions were done at the same time of day on different days in the week. In both sessions, the subjects rested in the supine position for 10 minutes, and then saliva was collected for two minutes. After resting for 8 minutes, saliva was again collected for 2 minutes. Collection of saliva in this was repeated for a total of 6 times. During the anesthesia sessions, dental anesthesia was administered for 30 seconds, beginning 7 minutes 15 seconds after the first saliva collection. The salivary hormone concentrations were measured by the EIA method and compared by the analysis of variance. Coefficient of variation for each session was compared by the paired t-test. The results showed that the stress of dental anesthesia did not influence the concentration of salivary cortisol or chromogranin A. The supine posture reduced salivary cortisol concentrations in this experimental dental procedure environment. Stress of dental anesthesia caused a higher coefficient of variation for salivary cortisol concentration compared with the resting level. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 248-254.

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It is thought that information from deep sensations in the tongue muscle projects to the brainstem through the hypoglossal nerve. I investigated the distribution of nociceptive neurons responding to electrical stimulation of the hypoglossal afferent nerve supplying the tongue muscle in the caudal medulla oblongata and the thalamus of a cat anesthetized with urethane and chloralose, using glass capillary microelectrodes filled with 2% pontamine sky blue in 0.5 M sodium acetate. The extracellular activity of single neurons was obtained from the subnucleus reticularis ventralis (SRV), the nucleus ventralis posteromedialis proper (VPM) and nucleus ventralis posterolateralis (VPL) of the ventrobasal (VB) complex, and the nucleus centralis lateralis (CL). A majority of the SRV neurons, and some of the VB complex and CL neurons were excited by noxious and/or innocuous stimulation to the tongue muscle. This suggests that the hypoglossal nerve contains afferent nerve fibers that project the deep sensation of the tongue centrally, and that tongue muscle inputs as well as superficial inputs are conveyed to the VB complex and CL neurons. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 255-265.

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We examined the correlation between signal intensity and setting angulations for magnetic resonance imagesobtained using a surface coil, which had a three inch surface coil,and dual coil, which had a three inch surface coil and an anterior neck coil. We took T2-3D weighted, T2-2D weighted and T1-2D weighted images with the angulated three-inch surface coil at 0-90 degrees with the magnetic direction.
In every sequence, the maximum intensity with the dual coil was taken with angulations of 50-60 degrees. The intensity of the dual coil could be as much as the three times that of the single coil. As the angulations increased with the dual coil, the thickness of the effective intensity was decreased until it reached 50% of the maximum thickness. With the single coil it decreased until it reached 10%.
When using a high-resolution coil that cannot be setup parallel with the magnetic direction, we recommend using a dual coil rather than a single coil to increase the signal intensity. In the oral cavity, the intraoral coil should be used with the extraoral coil as the phased array coil. This is the optimum condition of coil angulation for taking high resolution images. Shika Igaku (J Osaka Odontol Soc) 2002 Dec; 65(3/4 combined): 266-274.

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