Fibulin-5 contributes to microfibril assembly in human periodontal ligament cells.

The elastic system fibers comprise oxytalan, elaunin and elastic fibers, which differ in their relative microfibril and elastin content. Human periodontal ligaments (PDL) contain only oxytalan fibers (pure microfibrils) among them. Since fibulin-5 regulates the organization of elastic fibers to link the fibers to cells, we hypothesized that fibulin-5 may contribute to the formation of oxytalan fibers. We used siRNA for fibulin-5 in PDL cell culture to examine the extracellular deposition of fibrillin-1 and -2, which are the major components of microfibrils. Fibulin-5 was labeled on microfibrils positive for fibrillin-1 and -2. Fibulin-5 suppression reduced the level of fibrillin-1 and -2 deposition to 60% of the control level. These results suggest that fibulin-5 may control the formation of oxytalan fibers, and play a role in the homeostasis of oxytalan fibers.

Analysis of masseter muscle oxygenation and mandibular movement during experimental gum chewing with different hardness.

OBJECTIVE: The purpose of this study was to analyze masseter muscle oxygenation changes and mandibular movements in the experimental chewing of gums with different hardness. MATERIAL AND METHODS: Subjects for this experiment comprised 23 male volunteers with normal occlusion. Mean age (SD) was 28.3 (2.2) years. Three kinds of gum with mean fracture stresses of 3.52 x 10(4) N/m(2) (Gum 1), 5.35 x 10(4) N/m(2) (Gum 2), and 14.0 x 10(4) N/m(2) (Gum 3) were used. The subjects were instructed to chew gum for 80 s (100 strokes) on the voluntary chewing side at a pace of 1.25 strokes/s. Oxygen saturation in the masseter muscle and mandibular movement during gum chewing were recorded simultaneously using near-infrared spectroscopy tissue oximetry and mandibular kinesiography. RESULTS: For Gum 1, no subjects showed any significant changes in oxygen saturation during gum chewing. For Gum 2, 10 subjects showed no significant changes, whereas the other 13 showed significant decreases in oxygen saturation. For Gum 3, significant decreases were seen in all subjects. Chewing motions were larger and velocity was higher in gum chewing with decreases in masseter muscle oxygen saturation compared to chewing showing no significant changes. CONCLUSIONS: The results suggest that the harder texture of gum enlarges chewing motion and increases chewing velocity, with an increase in the contribution of anaerobic metabolism to energy yield in masseter muscle. Differences in the responses to gum hardness may indicate individual differences in muscle fatigue tendencies when chewing harder foods.

Effects of basic fibroblast growth factor administration on vascular changes in wound healing of rat palates.

OBJECTIVE: The purpose of this study was to investigate the vascular changes induced by mucoperiosteal denudation of rat palate and to elucidate the effects of basic fibroblast growth factor (bFGF) administration on the palatal vascular network in wound healing. METHODS: A total of 117 male Wistar rats were used for the study on their 20th postnatal day. The animals were divided into three groups: a scar formation group, a basic fibroblast growth factor group, and a control group. The scar formation and basic fibroblast growth factor groups had lateral mucoperiosteum excised from the palate. In the basic fibroblast growth factor group, a solution of basic fibroblast growth factor was injected into the operated area 1 week after excision. At 6, 8, and 10 weeks postoperatively, palatal vascular changes were investigated by immunohistochemical staining and corrosion cast techniques. RESULTS: Throughout the experimental period, there were significantly fewer vessels in the scar formation group than in the control and basic fibroblast growth factor groups. In the basic fibroblast growth factor group, the elongation of new vessels and capillary proliferation proceeded, and after 10 weeks a highly organized vascular network was established. The scar formation group showed few Volkmann's canals that were shrunken or closed, whereas the basic fibroblast growth factor group evidenced Volkmann's canals with arterioles or venules, as seen in the control. CONCLUSIONS: The results suggested that injection of basic fibroblast growth factor into palatal wounds improves the vascular supply to the operated mucosa and underlying bone during and after palatal wound healing, which may contribute to tissue remodeling of the palate during growth.

Three-dimensional structure of apical vesicles of tuft cells in the main excretory duct of the rat submandibular gland.

Tuft cells are present in the mucosal epithelium of a number of hollow organs including the main excretory duct (MED). Despite their distinctive features such as the long, thick, blunt microvilli with prominent rootlets and the large number of vesicles in the apical cytoplasm, the hypolemmal terminal-tuft cell relationship and the true form of the various vesicles and tubules are still controversial. The present study investigated the above mentioned features of tuft cells in the MED of rat submandibular gland by computer three-dimensional (3-D) reconstruction with focus on their function. Computer 3-D reconstruction revealed that nerve endings are present at both sides of the basal portion of the lateral cytoplasmic branch of tufts cells and that the apical tubulovesicular system of these cells consists of two separate components: the complex and coherent vesicles and the small network of tubules. We suggest that such a system may be involved in the rapid changes of surface area observed in tuft cells. Furthermore, our findings demonstrate that the images seen in thin sections and formerly regarded as evidence for the presence of variations in the shape of the tubules and of the vesicles are in reality the product of the different angles at which the tubulovesicular system was sectioned. Finally, a few vesicles and tubules that were not part either of the complex or of the network, also were found.