Tokuzo Matsuya

Interaction of plexin-B1 with PDZ domain-containing Rho guanine nucleotide exchange factors

The Rho family GTPase has been implicated in plexin-B1, a receptor for Semaphorin 4D (Sema4D), mediating signal transduction. Rho may also play a function in this signaling pathway as well as Rac, but the mechanisms for Rho regulation are poorly understood. In this study, we have identified two kinds of PDZ domain-containing Rho-specific guanine nucleotide exchange factors (RhoGEFs) as proteins interacting with plexin-B1 cytoplasmic domain. These PDZ domain-containing RhoGEFs showed significant homology to human KIAA0380 (PDZ-RhoGEF) and LARG (KIAA0382), respectively. Both KIAA0380 and LARG could bind plexin-B1 and a deletion mutant analysis of plexin-B1, KIAA0380 and LARG revealed that KIAA0380 and LARG bound plexin-B1 cytoplasmic tail through their PDZ domains. The tissue distribution analysis indicated that plexin-B1 was co-localized with KIAA0380 and LARG in various tissues. Immunocytochemical analysis showed that LARG was recruited to plasma membrane by plexin-B1. These results suggest that PDZ domain-containing RhoGEFs play a role in Sema4D-plexin-B1 mediating signal transduction.

Migration of a dental implant into the maxillary sinus. A case report.

This article reports a rare case of a displaced dental implant that migrated into the maxillary sinus.

Hedgehog Proteins Stimulate Chondrogenic Cell Differentiation and Cartilage Formation

Sonic hedgehog (Shh) and Indian hedgehog (Ihh) are important regulators of skeletogenesis, but their roles in this complex multistep process are not fully understood. Recent studies have suggested that the proteins participate in the differentiation of chondrogenic precursor cells into chondrocytes. In the present study, we have tested this possibility more directly. We found that implantation of dermal fibroblasts expressing hedgehog proteins into nude mice induces ectopic cartilage and bone formation. Immunohistological and reverse‐transcription polymerase chain reaction (RT‐PCR) analyses revealed that the ectopic tissues derived largely if not exclusively from host cells. We found also that treatment of clonal prechondrogenic RMD‐1 and ATDC5 cells in culture with Ihh or recombinant amino half of Shh (recombinant N‐terminal portion of Shh [rShh‐N]) induced their differentiation into chondrocytes, as revealed by cytoarchitectural changes, Alcian blue staining and proteoglycan synthesis. Induction of RMD‐1 cell differentiation by Ihh or rShh‐N was synergistically enhanced by cotreatment with bone morphogenetic protein 2 (BMP‐2) but was blocked by cotreatment with fibroblast growth factor 2 (FGF‐2). Our findings indicate that hedgehog proteins have the ability to promote differentiation of chondrogenic precursor cells and that their action in this process can be influenced and modified by synergistic or antagonist cofactors.

Localization of oral-motor rhythmogenic circuits in the isolated rat brainstem preparation

Using an in vitro isolated brainstem preparation from neonatal rat (0-2 days), the minimal circuitry for production of rhythmical oral-motor activity was determined. In the presence of the excitatory amino acid agonist, N-methyl-D,L-aspartate (NMA), and the GABAA antagonist, bicuculline (BIC), rhythmical oral-motor activity was recorded from the motor branch of the trigeminal nerve. In preparations where the brainstem was isolated in continuity between the rostral inferior colliculus and the obex, oral-motor activity was not observed. However, when the brainstem was serially transected in the coronal plane starting at the obex and proceeding rostrally, rhythmogenic activity emerged and became more stable until the level of the rostral facial nucleus (facial colliculus, FC) was approached. Transections more rostral than the FC produced rhythms that progressively deteriorated until the trigeminal motor nucleus (MoV) was reached, at which point all activities ceased. Surgical isolation of an ipsilateral quadrant of the brainstem encompassing the tissue between the FC and inferior colliculus, rostro-caudally, and the midline to lateral brainstem, medio-laterally, exhibited oral-motor activity as well. The remaining contralateral side of brainstem was devoid of rhythmical trigeminal activity. However, further coronal transection of the remaining brainstem at the level of the FC induced rhythmical oral-motor activity in the trigeminal nerve. The data suggest the existence of bilaterally coordinated rhythmogenic circuits in each half of brainstem between the rostral trigeminal nucleus and the rostral facial nucleus, which are tonically inhibited by brainstem circuits caudal to the facial nucleus.

Mouse Semaphorin H Induces PC12 Cell Neurite Outgrowth Activating Ras-Mitogen-activated Protein Kinase Signaling Pathway via Ca2+ Influx

We recently showed that mouse semaphorin H (MSH), a secreted semaphorin molecule, acts as a chemorepulsive factor on sensory neurites. In this study, we found for the first time that MSH induces neurite outgrowth in PC12 cells in a dose-dependent manner. Comparison of Ras-mitogen-activated protein kinase (MAPK) signaling pathways between MSH and nerve growth factor (NGF) revealed that these pathways are crucial for MSH action as well as NGF. K-252a, an inhibitor of tyrosine autophosphorylation of tyrosine kinase receptors (Trks), did not inhibit the action of MSH, suggesting that MSH action occurs via a different receptor than NGF. L- and N-types of voltage-dependent Ca2+ channel blockers, diltiazem and ω-conotoxin, inhibited MSH-induced neurite outgrowth and MAPK phosphorylation in a Ca2+-dependent manner. A transient elevation in intracellular Ca2+ level was observed upon MSH stimulation. These findings suggest that extracellular Ca2+ influx, followed by activation of the Ras-MAPK signaling pathway, is required for MSH induced PC12 cell neurite outgrowth.

Cloning and sequencing of the gene coding for dextranase from Streptococcus salivarius.

We cloned and sequenced the dextranase (Dex) (1,6-alpha-glucanhydrolase; EC 3.2.1.11)-encoding gene from Streptococcus salivarius (Ss) strain M-33. Recombinant clones from an Ss genomic library specifying Dex activity were identified as colonies surrounded by transparent halos on blue dextran plates. One of the clones had a 4.3-kb KpnI fragment containing the gene coding for an 826-amino-acid polypeptide with a molecular mass of 87.9 kDa, which corresponds well to that of native Dex from the Ss culture supernatant. There was no sequence homology between the gene encoding Ss Dex and the gene encoding dextran glucosidase of S. mutans, or between their protein products.

Physiologic and morphologic properties of motoneurons and spindle afferents innervating the temporal muscle in the cat.

Little is known about physiology and morphology of motoneurons and spindle afferents innervating the temporalis and on synaptic connections made between the two. The present study was aimed at investigating the above issues at the light microscopic level by using the intracellular recording and horseradish peroxidase or biotinamide labeling techniques and by the use of succinylcholine (SCh) for the classification of spindle afferents in the cat. Temporalis motoneurons had dendritic trees that ranged from a spherical form to an egg‐shaped form. The shape deformation was more prominent for the dendritic trees made by motoneurons located closer to the nuclear border. No axon collaterals of the motoneurons were detected. On the basis of the values for the dynamic index after SCh infusion, temporalis spindle afferents were classified into two populations: presumptive groups Ia and II. The spindle afferents terminated mainly in the supratrigeminal nucleus (Vsup), region h, and the dorsolateral subdivision (Vmo.dl) of the trigeminal motor nucleus (Vmo). The proportion of group Ia afferent terminals was lower in the Vsup than that of group II afferents. In the Vmo.dl, the proportion of group Ia afferent terminals was nearly even throughout the nucleus, but that of group II afferent terminals increased in the more outlying regions. The proportion of terminal distribution in the central region of Vmo.dl was higher for group Ia than group II. The frequency of contacts (presumptive synapses) made by a single spindle afferent on a motoneuron was higher for group Ia than group II. The present study provided evidence that the central organization of spindle afferent neurons is different between groups Ia and II. J. Comp. Neurol. 406:29–50, 1999.

Breast feeding for cleft lip and palate patients, using the Hotz-type plate.

OBJECTIVE Oral-cavity feeding movements were analyzed during sucking and used to modify a Hotz-type plate to facilitate sucking in infants with cleft lip and palate. DESIGN Sucking movements were analyzed using lateral view cine radiography as three adults fed from a bottle. A Hotz-type plate was then modified to better isolate the oral cavity and to occlude the oral airway. The plate was then utilized in direct breast feeding by 10 babies. OUTCOME MEASURES Sucking rate, amount of milk taken, and duration of use of the plate were assessed. RESULTS Wearing this plate, four babies with cleft lip and palate could suck their mothers breast, drinking about 22 g/trial. CONCLUSIONS Although supplemental bottle feeding was required to provide enough nourishment, this is the first step to reaching ideal breast feeding situation for these patients.

Functional recovery of swallowing, speech, and taste in an oral cancer patient with subtotal glossectomy

5. Dinsworth AR, Byrd DL, Allen JW: Zygomatic complex 7. Laskin D: Oral and Maxillofacial Surgery, vol 2. St Louis. fracture with an avulsed tooth causing malocclusion: reCV Mosby, 1985, pp 79-80 port of case. J Oral Surg 32: 131, 1974 8. Winkler T. von Wowern N. Bittmann S: Retrieval of an 6. Kruger GO: Textbook of Oral and Maxillofacial Surgery, 6th upper third molar from the infratemporal space. J Oral ed. St Louis, CV Mosby, 1985, p 101 Surg 30:730-733. 1970: 35:130. 1977

Electrophysiological analysis of rhythmic jaw movements in the freely moving mouse

Although rhythmic jaw movement in feeding has been studied in mammals, such as rats, rabbits and monkeys, the cellular and molecular mechanisms underlying it are not well understood. Transgenic and gene-targeting technologies enable direct control of the genetic makeup of the mouse, and have led to the development of a new category of reagents that have the potential to elucidate the cellular and molecular mechanisms of neural networks. The present study attempts to characterize rhythmic jaw movements in the mouse and to demonstrate its relevance to rhythmic jaw movements found in higher mammals using newly developed jaw-tracking systems and electromyograms of the masticatory muscles. The masticatory sequence of the mouse during feeding was classified into two stages, incision and chewing. Small and rapid (8 Hz) open-close jaw movements were observed during incision, while large and slow (5 Hz) open-close jaw movements were observed during chewing. Integrated electromyograms of the masseteric and digastric muscles were larger during chewing than those observed during incision. Licking behavior was associated with regular (8 Hz), small open-close jaw movements with smaller masseteric activity than those observed during mastication. Grooming showed variable patterns of jaw movement and electromyograms depending on the grooming site. These results suggest that there are neuronal mechanisms producing different frequencies of rhythmic jaw movements in the mouse, and we conclude that the mouse is useful for understanding rhythmic jaw movements in higher mammals.