The effect of oral splint devices on sleep bruxism: a 6-week observation with an ambulatory electromyographic recording device

This study investigated the effect of stabilization splint (SS) and palatal splint (PS), which had the same design as SS except for the elimination of the occlusal coverage, on sleep bruxism (SB) using a portable electromyographic (EMG) recording system. Sixteen bruxers participated in this study. The EMG activities of the right masseter muscle during sleep were recorded for three nights each in the following five recording periods: before, immediately after, and 2, 4 and 6 weeks after the insertion of the splint. The crossover design, in which each splint was applied to each subject for 6 weeks with an interval of 2 months for a washout period, was employed in this randomized-controlled study. The number of SB events, duration and total activities of SB were analysed. The number of SB events before the insertion of splints (baseline) was 2.98 +/- 1.61 times h(-1). Both splints significantly reduced SB immediately after the insertion of devices (P < 0.05, one-way repeated-measures anova followed by Dunnett); however, no reduction was observed in 2, 4 or 6 weeks (P > 0.05). There was no statistical difference in the effect on SB between the SS and PS (P > 0.05, two-way repeated-measures anova). Both splints reduced the masseter EMG activities associated with SB; however, the effect was transient.

Analysis of sagittal condylar path inclination in consideration of Fischer's angle

This study investigated the sagittal condylar path during protrusive and lateral excursions by analysing the actually measured jaw movement data and re-evaluated the setting of the sagittal condylar path inclination in consideration of Fischer's angle. Protrusive and lateral excursions of 10 healthy subjects were measured using a three-dimensional mandibular movement analysing system. Condylar path inclinations at the hinge-axis point and the corresponding external point laterally extending from the condyle were evaluated in the sagittal plane. Fischer's angle was defined as the difference between the sagittal condylar inclinations during protrusive and lateral excursions on the non-working side, by keeping the corresponding horizontal distance from the intercuspal position (ICP) equivalent at the incisal point. Analysis was performed at three different magnitudes of excursions, where the incisal point was located at 1, 3 and 5 mm away from the ICP. There was no significant difference in the sagittal condylar path inclination or the Fischer's angle between two condylar reference points. However, they were significantly different across the three different magnitudes of excursions for both condylar reference points, i.e. sagittal condylar path inclination (P = 0.003 for protrusive excursion, and P < 0.001 for lateral excursion respectively; two-way repeated-measures anova), and Fischer's angle (P = 0.013, two-way repeated-measures anova) became smaller as the incisal point became distant from the ICP. Moreover, 3- and 5-mm eccentric positions were included in the 95% CI where Fischer's angle equals zero and were considered to be clinically acceptable to adjust the sagittal condylar inclination on the semiadjustable articulators.

Denture wearing and strong bite force reduce pressure pain threshold of edentulous oral mucosa

Pain in denture supporting tissue is one of the most common and critical problems affecting function and treatment outcomes in complete denture prosthetics. The objective of this study was to investigate the effects of denture wearing and bite force on the pressure pain threshold (PPT) of edentulous oral mucosa. PPT was measured in denture and non-denture-wearing patients by using an electronic-controlled pressure algometer. Bite force was measured in denture-wearing patients by using a pressure-detecting sheet. The mid palate showed 200-300% higher PPT than the buccal alveolar mucosa (two-way anova, P < 0.0001). Denture-wearing patients exhibited 40% lower palatal PPT than non-denture-wearing patients. In denture-wearing patients, PPT in the selected areas of the oral mucosa was negatively correlated with bite force. Denture wearing may reduce PPT in selected areas of the edentulous oral mucosa, and the PPT reduction may be associated with mechanical stress on the mucosa generated by bite force.

Neurovascular compression of the common peroneal nerve by varicose veins

Compression of the common peroneal nerve occurs sometimes, but compression caused by varicose veins has not been reported before. We report a case of common peroneal nerve compression syndrome which was confirmed and treated surgically. A 63-year-old woman complained of paraesthesia on the lateral aspect of the right leg, which was worse in the evening. A primary varicose vein arising from non-saphenous tributaries was seen in the posterior calf. Her symptoms resolved with the wearing of compression hosiery for 2 weeks. At operation, the common peroneal nerve was found to be surrounded by tortuous varicosities. After decompression the paraesthesia on the lateral aspect of the right leg resolved completely with no evidence of residual neuralgia.

Pressure-pain threshold of oral mucosa and its region-specific modulation by pre-loading

Once subjected to denture wearing, oral mucosa has to withstand mechanical loads of various levels and durations. However, how this load affects oral mucosal sensitivity is unknown. This study investigated the pressure-pain threshold (PPT) of oral mucosa with or without pre-loading. An electric pressure algometer was developed specifically for measuring the PPT of oral mucosa. Measurements of 10 dentulous maxillae showed that the baseline PPT (BPPT) of the palatal site was 4.9- and 3.7-fold greater than that of the labial or buccal sites, respectively. The PPT of the labial site decreased significantly compared with its BPPT after 2 s-100% BPPT and 5 s-100% BPPT pre-loading. The PPT of the palatal site increased after 5 s-50% BPPT and 5 s-80% BPPT and 0.2 s-100% BPPT and 2 s-100% BPPT pre-loading. The PPT of the buccal site did not change after all levels and durations of pre-loadings tested. These results indicated the disproportionate modulation of oral mucosal PPT following various loads, suggesting that oral mucosa possesses region-specific psychophysical tolerance to mechanical stimuli.

Mapping, profiling and clustering of pressure pain threshold (PPT) in edentulous oral mucosa

OBJECTIVES

Edentulous oral mucosa involves different tissue types, various innervation and wound healing process. We hypothesized that pressure pain threshold (PPT) of edentulous oral mucosa varies significantly among different regions. The objective of this study is to examine regional differences and correlations of PPT in edentulous oral mucosa.

METHODS

Pain threshold (PPT) was measured at 112 sites in 15 edentulous patients using an electric-controlled pressure algometer. PPT mapping was created by the level of PPT, and PPT clustering was undertaken based on the inter-site correlation of PPT.

RESULTS

PPT increased from the anterior to posterior alveolus in both maxilla and mandible, but decreased from the anterior palate to the posterior palate. PPT decreased from the ridge crest to the buccal vestibule. The inter-site difference was four fold within the maxilla and 2.4 fold within the mandible. Principal component analysis applied on PPT inter-site correlation matrix revealed that the maxilla and mandible could be differentiated statistically. The maxilla and mandible were divided into three and four clusters, respectively.

CONCLUSION

These results demonstrate that different areas of edentulous oral mucosa have different PPT and that the PPT varies proportionally in selected areas, providing useful diagnostic and therapeutic information in removable prosthodontics and a new opportunity for understanding pain underneath the denture.

A simplified sieve method for determining masticatory performance using hydrocolloid material

The purpose of this study was to develop a simplified technique for measuring masticatory performance by measuring the particle size distribution of masticated hydrocolloid impression material using a sieve method. Masticatory performance was defined as the rate of increase in the number of particles of masticated material on specific sieves with the increment in the number of chewing strokes. The number and weight of masticated hydrocolloid impression material on 10 sieves were compared with results for peanuts. The reproducibility of this method to determine masticatory performance was then examined. In seven sieves, there was a linear relationship between the number of particles and the number of chewing strokes for the hydrocolloid impression material; Pearson's correlation coefficient was higher for the hydrocolloid impression material than for peanuts. Measuring masticatory performance three times a day and three times every week revealed there were no differences in intra-individual variation in masticatory performance in six sieves. There was no significant difference between the masticatory performance calculated from two mastication tasks using the specific sieves and that calculated from seven tasks. These results suggest that this simplified sieve method using hydrocolloid materials can be reliably used for research purposes and in clinical situations.

NF-kappaB activation and iNOS expression in the synovial membrane of rat temporomandibular joints after induced synovitis

NF-kappaB plays a pivotal role in pathogenesis in general arthritis. However, the participation of NF-kappaB in inflammation of the temporomandibular joint (TMJ) is poorly understood. We examined NF-kappaB expression in rat TMJs with synovitis induced by condyle hypermobility. By immunohistochemistry, NF-kappaB immunoreactivity was found mainly in the cytoplasm, not the nucleus, of the synovial lining cells of induced-synovitis and control TMJs. Southwestern histochemistry, a new method for detecting transcription factors, showed greater NF-kappaB expression in the nucleus of the synovial lining cells in the hypertrophic synovium than in control synovium. Increased numbers of the synovial lining cells with immunoreactivity for inducible nitric oxide synthase (iNOS), which is transcriptionally regulated by NF-kappaB, were also seen in the inflamed synovium. These findings indicate that excess mechanical stress increases NF-kappaB activation in the TMJ and suggest that active NF-kappaB is involved in the progression of TMJ inflammation.

Pressure-pain threshold determination in the oral mucosa: validity and reliability

Fundamental knowledge of pain in the oral mucosa is lacking. We determined the validity and reliability of the pressure-pain threshold (PPT) measurement in the oral mucosa using a newly developed hand-held pressure algometer. Ten dentulous subjects were recruited, and the PPT was measured at the bilateral buccal (on the attached gingiva apical to the midline of the upper first premolars, 3 mm from the mucogingival junction) and the palatal sites (mid-point between the bilateral upper first molars). The PPT linearly increased with an increase in load-rate (P < 0.0001). The PPT yielded a high intra-individual stability both for the same-day consecutive trials and weekly sessions. The palatal site revealed a 4- to 4.65-fold greater PPT than the buccal sites (Bonferroni, P < 0.0001), whereas no difference was found between the bilateral buccal sites (P=0.663). Despite a great interindividual variation in the PPT, significant intra-individual correlations were found among the measurement sites. This suggested differences in individual sensitivity to pain in the oral mucosa, which may determine overall pain sensation specific to an individual. A pressure algometer described herein reliably assessed the PPT in the oral mucosa and sensitively discriminated PPT differences at different sites and at different load-rates, suggesting the reliability and validity of PPT measurements in the oral mucosa for clinical and research investigations.

The relationship between non-working-side occlusal contacts and mandibular position

No clear description can be found regarding the lateral position when examining non-working-side occlusal contacts. The objective of this study was to test the hypothesis that the non-working-side contact pattern varies with the mandibular position. The characteristics of the non-working-side contact pattern were also determined relative to the working-side contact pattern. Occlusal contacts of 86 young adults were examined using shim stock in standardized lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation (MI), where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the MI and the 3 mm position as an edge-to-edge position. The frequency of non-working-side occlusal contacts decreased gradually from 0.5 to 3 mm position. The frequency of non-working-side contacts was significantly greater in the 0.5 and 1 mm positions than in the 3 mm position. Non-working-side occlusal contacts occurred in nearly half of the 0.5 mm positions. Non-working-side contacts were significantly less frequent with canine protection than with group function for the 0.5 and 1 mm positions. There were no significant differences between the two occlusal schemes for the 2 and 3 mm positions. In conclusions, the non-working-side contact pattern varied with the mandibular position. These results suggest that clinical examination should include contact patterns both in a position close to the MI and in an edge-to-edge position, i.e. in functional and parafunctional ranges. Likewise, data from occlusal contact research should include a standardized definition of mandibular position.

Different responses of masticatory movements after alteration of occlusal guidance related to individual movement pattern

We hypothesized that the motor response of the masticatory system to peripheral inputs varies according to the functional potential of an individual. The specific aim of the present study was to determine whether individually different types of masticatory patterns, especially with respect to the closing movement pattern, would produce different motor responses to an alteration of occlusal guidance. The inclination of the occlusal guidance was steepened by approximately 10 degrees by attaching a metal overlay to the lingual surface of the maxillary working-side canine. The masticatory movements of 20 young adults were measured using a three-dimensional mandibular movement analysis system before and after the alteration of occlusal guidance. The individual masticatory patterns were divided into two groups based on the closing movement pattern before the alteration of occlusal guidance, i.e. vertical and lateral types. The alteration of occlusal guidance significantly influenced the masticatory closing angle, closing time, occlusal time, the stability of the opening angle and the cycle time in the lateral-type group (n = 9, paired t-test; P < 0;05), while no significant changes were found in the vertical-type group (n = 11). These differences in motor response between the two groups were not found in the overall analysis of all the 20 subjects. We concluded that the oral motor response to the alteration of occlusal guidance depends on the individual masticatory movement pattern. Because the present analysis of subgroups of the subjects revealed motor response findings different from those in the overall analysis of all the 20 subjects, such potential subgroupings should be considered as an attempt to identify a specific effect of peripheral inputs on masticatory function in humans.

Dimer and superstructure of the active form of a vitamin D3; 1 alpha,24(R)dihydroxy-vitamin D3 monohydrate, C27O3H44.H2O

The crystals of 1alpha24(R)dihydroxy-vitamin D3 monohydrate, C27O3H44.H2O are orthorhombic in the space group P2(1)2(1)2(1) with cell dimensions a=25.719, b=42.572, c=9.851A and Z=16. The asymmetric unit consists of two subunits with b/8, and each subunit contains a dimer in which two molecules are hydrogen-bonded through water molecules into non-crystallographical symmetry of C2. The two-fold axes are the straight lines, x=1/2, z=0.256 and x=1/2, z=0.623. The two dimers are the same in the rigid ring part, but differ in the conformation of the flexible chains. The dimers further make C2 symmetry between the rigid ring parts to form a superstructure, and the two-fold axis of the straight line, y=1/8, z=0.435 goes through a point that is a little apart from the hypercenter (1/2, 1/8, 1/2). The structure was solved by integrated Patterson and direct methods and refined on Fo2 under restraints. The final R1 is 0.228 on Fo for 1623 reflections with Fo>3sigma, resolutions 1.0-3.0 A, 313 restraints, 490 parameters and average Ueq=0.120. Not all the atoms of the chains appeared nor the hydrogen atoms. The missing atoms of the dimer were modeled from another pair molecule by C2 symmetry and hydrogen atoms were added. The structure of the dimer was optimized by ab initio molecular orbital of HF/6-31G.

Setting characteristics of five autopolymerizing resins measured by an oscillating rheometer

STATEMENT OF PROBLEM

Ease of handling and the working time of autopolymerizing resins are directly associated with the setting characteristics during polymerization.

PURPOSE

This study assessed the setting characteristics of autopolymerizing resins by measuring viscosity changes and tested the hypotheses that: (1) different products have different viscosity increase patterns during polymerization, and (2) the increased rate of viscosity is not proportional to the length of the setting time.

MATERIAL AND METHODS

Viscosity change during polymerization was measured in 5 test materials (Unifast II, ADFA, META FAST, Miky, and Trim) with an oscillating rheometer. The working time was defined as the time required for a 5% reduction in the amplitude of the rheometer trace. The setting time was measured as the time required to reach zero amplitude on the rheometer trace.

RESULTS

The order of working times from longest to shortest was Trim, Unifast II and META FAST, ADFA, Miky (ANOVA, P<.0001). The order of setting times from longest to shortest was Trim, META FAST, Miky, ADFA, Unifast II. Materials that had rapid setting times did not necessarily have short working times. Unifast II showed well-balanced setting properties that satisfied both longer working time and faster setting time.

CONCLUSION

Autopolymerizing resins have setting characteristics specific to the brand. Knowledge of these characteristics is essential for selection of the appropriate resin product depending on the purpose of clinical usage and the individual dentist's technique.

Synchronisation of neurotransmitter release during postnatal development in a calyceal presynaptic terminal of rat

Mechanisms contributing to the synchronisation of transmitter release during development were studied in synapses of the medial nucleus of the trapezoid body (MNTB) using patch recording and Ca2+ imaging techniques in a rat brainstem slice preparation. Excitatory postsynaptic currents (EPSCs) were generated in an all-or-none manner at immature synapses (postnatal days earlier than P6). Many delayed miniature EPSC (mEPSC)-like currents followed EPSCs at immature synapses, while observations of delayed mEPSC-like currents were rare at mature synapses (later than P9). At immature synapses bath application of either omega-conotoxin GVIA or omega-agatoxin-IVA reduced EPSCs (both to 40% of control), and Ca2+ currents in the presynaptic terminal (both to 70% of control). The frequency of delayed mEPSC-like currents was reduced by omega-conotoxin GVIA, but not by omega-agatoxin IVA. At immature synapses delayed mEPSC-like currents were rare after incubation of the slice with extrinsic Ca2+ buffers (EGTA AM). At mature synapses many mEPSC-like currents followed evoked EPSCs after partial block of Ca2+ channels by bath application of a low concentration of Cd2+ (3 microM) or omega-agatoxin IVA (50 nM) but not by low [Ca2+]o (0.5-1 mM). Ca2+ transients induced by action potentials in presynaptic terminals were monitored by adding a high concentration of fura-2 (200 microM) to the pipette. Their decay time course was slower at immature presynaptic terminals than at mature terminals. Both the Ca2+ extrusion rate and the endogenous Ca2+ binding capacity were estimated to be smaller at immature terminals than at mature terminals. These results suggest that the maturation of synaptic transmission in MNTB progresses with the capacity for Ca2+ clearance from the presynaptic terminal. The possible importance of developmental increases in both Ca2+ clearance capacity and Ca2+ currents is discussed in relation to the synchronisation of transmitter release.

Neurons generated from adult rat hippocampal stem cells form functional glutamatergic and GABAergic synapses in vitro

Basic fibroblast growth factor-responsive neural stem cells (NSCs) derived from adult rat hippocampus were earlier demonstrated to generate neurons and glia. These stem-cell-derived neurons express GABA, acetylcholinesterase, tyrosine hydroxylase, or calbindin. It has not been clear, however, whether or not these stem-cell-derived neurons are able to form functional synapses. In the present study, we investigated the development of synapse formation by adult hippocampus-derived neural stem cells. NSCs from adult rat hippocampi and primary embryonic rat hippocampal neurons were cocultured on a glial feeder layer. Immunofluorescence studies revealed that some of the NSCs became immunoreactive for microtubule-associated protein 2ab, neurofilament 200, synaptobrevin, or synaptophysin. These cells possessed properties of functional neurons such as action potentials and miniature postsynaptic currents (mPSCs). The elicited mPSCs with rapid kinetics were blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX), but not by bicuculline (excitatory mPSCs). The remaining mPSCs had slower kinetics and were blocked by bicuculline, but not by DNQX (inhibitory mPSCs). We considered that the neurons derived from the adult NSCs expressed both non-NMDA glutamate receptors and the GABA(A) receptors and formed functional synapses. Our results demonstrate that adult NSCs can differentiate into neurons with functional glutamatergic and GABAergic synaptic transmission in vitro and support the concept that such neurons could integrate into the neuronal circuitry.

Effect of water temperature during polymerization on strength of autopolymerizing resin

STATEMENT OF PROBLEM

Breakage is a potential problem of provisional resin restorations. A method that effectively increases the strength of the resin is desirable.

PURPOSE

This study examined the effects of the curing environment, air or water, and water temperature during polymerization on the mechanical properties of autopolymerizing resin.

MATERIAL AND METHODS

After mixing the autopolymerizing methyl methacrylate resin for 10 seconds, it was placed in a stainless steel mold (2 x 2 x 25 mm). One minute and 50 seconds after the start of mixing, the mold containing the resin was placed under the following conditions: in air at 23 degrees C; or in water at 10 degrees C, 23 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Six minutes after mixing began, the resin specimen was removed from the mold and the transverse test (3-point flexural test) was performed.

RESULTS

Alteration of conditions during polymerization revealed a significant effect on both the transverse strength and modulus of the resin (P <.0001). Both increased with an increase in water temperature. Water conditions of 60 degrees C to 80 degrees C produced more than 2 times greater transverse strength and modulus of the resin compared with polymerization in 23 degrees C air (P <.0001).

CONCLUSION

Polymerization of the resin in hot water greatly increased its mechanical properties. The method of placing resin restorations in hot water during polymerization may be useful for improving mechanical requirements and obtaining long-lasting performance.

Ultrastructural and immunoelectron microscopic studies of the peri-implant epithelium-implant (Ti-6Al-4V) interface of rat maxilla

BACKGROUND

The role played by the internal basal lamina (IBL) and hemidesmosomes between an implant and the peri-implant epithelium (PIE) in the adherence of the epithelium to the implant is controversial. This study used rat maxilla implantation models to clarify the ultrastructure of the PIE-implant interface.

METHODS

Ti-6Al-4V implants were inserted either immediately or 2 weeks after the extraction of the upper left first molar of 6- or 4-week-old rats, respectively. The junctional epithelium (JE) of the upper right molars in the same animals was used as a control. Four weeks after implantation, the animals were sacrificed to prepare specimens for light and immunoelectron microscopy.

RESULTS

Under light microscopy, the PIE appeared to attach to the implant surface. Ultrastructurally, IBL, consisting of the lamina densa and lamina lucida, and hemidesmosomes were formed only in the lower region, and rarely in the middle region, of the PIE-implant interface. In control teeth, the IBL and hemidesmosomes formed throughout the dento-JE interface. Laminin-1 was found in the IBL and also in the vesicles and vacuoles of the PIE and JE cells. Statistical analysis showed that there was also a significant difference in the amount of IBL between the PIE-implant and dento-JE interfaces.

CONCLUSIONS

PIE attached to the implant via hemidesmosomes and IBL in the lower region of the PIE-implant interface. Although PIE cells may secrete laminin-1, which contributes to epidermal cell adhesion, the PIE which attaches to implants only in the lower region of the interface is considered to be the poorly adhered epithelium.

Validity of the examination method of occlusal contact pattern relating to mandibular position

OBJECTIVE

This study was based on the hypothesis that conflicting findings and inconclusive consensus regarding the role of occlusal factors in the masticatory system are due to the variations in the definitions and methods used to describe and examine the occlusal factors. The object of this study was to determine whether contact patterns during lateral movement vary with mandibular positions and whether the contact pattern in lateral positions close to the maximum intercuspation has characteristics distinct from those in an edge-to-edge position.

METHODS

Occlusal contacts of 86 young adults were examined using shim stock in regulated lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation, where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the maximum intercuspation and the 3 mm position as an edge-to-edge position.

RESULTS

The occlusal contact pattern in the 0.5 mm position showed a marked prevalence of posterior tooth contacts on the working and the non-working sides, compared with the 1, 2 and 3 mm positions. The occlusal contact pattern in the 3 mm position predicted the presence or absence of the occlusal contact in the 1 and 2 mm positions (sensitivity > 0.7) but not in the 0.5 mm position (sensitivity < 0.6).

CONCLUSION

The occlusal contact patterns during lateral movement varied greatly with mandibular positions. The examination method of the occlusal contact pattern in one unregulated position will be invalid. It is necessary to distinguish the occlusal contact patterns between a position close to the maximum intercuspation and an edge-to-edge position when investigating its role in the masticatory system and in oral disease.

Effect of water temperature on the fit of provisional crown margins during polymerization

STATEMENT OF PROBLEM

When fabricating a provisional crown with the direct technique, dentists are concerned with margin discrepancies that result from polymerization shrinkage.

PURPOSE

This in vitro study examined the effect of water temperature on the fit of provisional crown margins during resin polymerization.

MATERIAL AND METHODS

The experiment was designed to simulate a direct technique to fabricate provisional crowns. After mixing autopolymerizing methyl methacrylate resin, the material was placed in a preformed polycarbonate crown. The crown was seated on a prepared premolar-shaped die with a shoulder margin. After 1 minute and 50 seconds, the crown was removed and polymerization was continued under the following conditions: 20 degrees C air, and water at 0 degrees C, 10 degrees C, 20 degrees C, 30 degrees C, 40 degrees C, 60 degrees C, and 80 degrees C. Six minutes after polymerization, the crown was trimmed and reseated on the die. Discrepancy of crown margin was measured with a 3-dimensional digitizer.

RESULTS

Margin discrepancy varied with the condition during resin-polymerization (ANOVA, P <.001). The crowns polymerized in 20 degrees C and 30 degrees C water revealed the best margin fit, showing 3 times more accurate margin fit than those polymerized in 20 degrees C air (Bonferroni/Dunn procedure, P <.01).

CONCLUSION

Conditions during resin polymerization were significant factors that affected margin fit of provisional crowns using the direct technique. Water temperatures of 20 degrees C and 30 degrees C produced the best fit at the margin of the provisional crown.

Haemodynamic changes in human masseter and temporalis muscles induced by different levels of isometric contraction

This study evaluated the influence of low contraction forces on intramuscular haemodynamics in human masseter and temporalis using near-infrared tissue spectroscopy. This method allowed the intramuscular haemoglobin (Hb) to be assessed dynamically before, during and after a 5, 15, 25 and 100% maximum voluntary contraction (MVC). Twenty volunteers, 10 males and 10 females, without pain or dysfunction in the masticatory system were included in this study. Data were recorded for 30 s before, 30 s during and 5 min after the four sustained contraction tasks. The results showed that all four levels of voluntary contraction produced a clear haemodynamic response (during and after contraction) in both muscles. For analytical purposes, the maximum Hb achieved after 100% MVC was set equal to 1.00. In the masseter the mean peak Hb during the 5, 15, 25 and 100% MVC was 0.49, 0.92, 1.30 and 1.73 while after the contractions it was 0.50, 0.65, 0.78 and 1.00, respectively. In the temporalis the peak Hb during the contractions was 0.23, 0.36, 0.48 and 0.66 and after the contractions 0.32, 0.45, 0.56 and 1.00, respectively. Repeated-measures analysis of variance revealed a significant main effect for the different contraction levels both in the masseter (during contraction, p = 0.001; after contraction, p<0.001) and the temporalis (during contraction, p = 0.002; after contraction, p<0.001). These data suggest that low levels of contraction induce a clear haemodynamic response, even at 5% effort. When compared, the masseter and anterior temporalis showed clearly different patterns for the Hb signal during the contraction (p<0.001) as well as after it (p = 0.007). Specifically, the Hb during the contractions in the masseter appeared more stable than in the temporalis, which showed a strong return to baseline. Obviously the contracting masseter had a stronger and more sustained venous occlusion than the contracting temporalis. It is speculated that variation in architecture between the two muscles contributes to these differences in blood flow.

The effect of head posture on direction and stability of mandibular closing movement

This study investigated the effects of head posture on mandibular habitual closing movement. Ten healthy subjects were examined. Head posture was evaluated as a sagittally viewed inclination of the head, and was changed from 25 degrees forward bending up to 30 degrees backward bending in 5 degrees increments. The mandibular opening and closing movement was measured at each head posture. As the head bended forward, the closing path approached the maximum intercuspal position from the anterior region, and as the head was bent backward, the closing path approached the maximum intercuspal position from the posterior region. However, the limit of this relationship was found when the head was bent forward to some extent. There was also a correlation between the head posture and the stability of the closing movement. The forward bending of the head decreased the stability of the closing path, and conversely, the backward bending increased the stability of the closing path. It was concluded that the head posture affects the direction and stability of the mandibular closing movement. Possible underlying reasons for these findings are masticatory muscle activity and the tension and resistance of inframandibular soft tissue varying with the change of head posture.

Inclination of the occlusal plane and occlusal guidance as contributing factors in mastication

OBJECTIVES

The purpose of the present study was to compare the inclination of the occlusal plane with occlusal guidance as a contributing factor to masticatory movement.

METHODS

Masticatory movements of 41 young adults were measured using a 3-D mandibular movement analysing system. The inclination of the occlusal plane was measured in the sagittal plane using a 3-D digitizer. The contribution of the occlusal guidance and the inclination of the occlusal plane to the direction of the masticatory path of closure was evaluated at various closing levels.

RESULTS

The masticatory path of closure outside the intercuspal range was influenced mainly by the inclination of the occlusal plane, and the masticatory path of closure near the intercuspal range was only influenced by occlusal guidance. The so-called gliding type masticatory pattern was observed predominantly in subjects with a posteriorly inclined occlusal plane. In contrast, a chopping type masticatory pattern was observed predominantly in subjects with an anteriorly inclined occlusal plane.

CONCLUSIONS

The contribution of the inclination of the occlusal plane to masticatory movement was greater than that of occlusal guidance throughout the closing phase except near the intercuspal range.

Pattern of occlusal contacts in lateral positions: canine protection and group function validity in classifying guidance patterns

STATEMENT OF PROBLEM

The concept of canine protection and group function lack consistency in the definitions and examining methods, and a valid system for evaluating and classifying occlusal contact patterns has not been established.

PURPOSE

This study assessed the use of canine protection and group function in classifying occlusal guidance in the natural dentition.

MATERIAL AND METHODS

Occlusal contacts of 86 young adults were examined with shim stock in regulated lateral positions, 0.5,1,2 and 3 mm from the maximum intercuspation. The patterns of occlusal contacts varying with the lateral position were described.

RESULTS

Focusing on the working-side contact only, most contact patterns belonged to group function, and a few to canine protection. Focusing on both the working and nonworking side contacts, nearly half the contact patterns were those other than canine protection and group function and were classified into balanced occlusion.

CONCLUSION

The validity of the classification system using canine protection and group function is questionable. A new classification system of occlusal guidance is desirable.

Difference in the mechanism of balancing-side disclusion between 1st and 2nd molars

This study investigates the cusp angle and movement variables related to balancing-side disclusion and compares the characteristics between the 1st and 2nd molar regions. Fifty-six normal young adults were divided into two groups according to balancing-side contact: a disclusion group consisting of 40 subjects (80 excursions), and a non-disclusion group consisting of 16 subjects (20 excursions). Lateral excursions were measured in six-degrees of freedom, and the inclinations of the frontal paths were calculated on the working-side canine, balancing-side 1st and 2nd molars and balancing-side condylar point. The cusp angle was measured using a three-dimensional digitizer. While there were no differences between disclusion and non-disclusion groups in the inclination of the balancing-side condylar path, significant differences were found in the cusp angle and the inclination of the working-side canine path. In the non-disclusion group, the cusp angle of the 2nd molar was markedly greater than that of the 1st molar. It was concluded that the inclination of the anterior guidance and the cusp angle of related teeth have a great effect on the occurrence of balancing-side disclusion and that the mechanism of high frequent balancing-side contacts at the 2nd molar was characterized by its greater cusp angle compared to the 1st molar.

The role of GABAergic inputs for coincidence detection in the neurones of nucleus laminaris of the chick

1. Synaptic inputs to nucleus laminaris (NL) neurones were studied in a brainstem slice preparation of chick embryos (E15-20) using the whole-cell patch clamp technique. NL neurones are third order auditory neurones and are proposed to behave as coincidence detectors concerned with interaural timing discrimination. 2. Under voltage clamp conditions, electrical stimuli applied to either ventral or dorsal dendritic layers evoked EPSCs. These fast currents decayed with a time constant of 1.1 ms near the resting potential, reversed close to 0 mV, and were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 20 microM) or 6, 7-dinitro-quinoxaline-2,3-dione (DNQX, 20 microM). Coincident or near coincident stimulation of the ventral and the dorsal dendritic layers increased the probability of action potential generation (response probability). 3. In the presence of CNQX (40 microM) other postsynaptic currents (PSCs) were observed, which reversed close to the equilibrium potential for chloride (ECl), and were reversibly blocked by bicuculline (20 microM) and, therefore, were mediated by GABAA receptors. Spontaneous GABAergic PSCs were inward going near the resting membrane potential immediately after starting whole-cell recording with a low Cl- (5 mM, ECl = -90 mV) pipette medium, but became outward-going with time. This indicates that GABAergic inputs may generate depolarizing potentials in intact NL neurones. 4. Local GABA (10 microM) application reduced both the EPSP and EPSC amplitude and shortened the EPSP decay time constant (from 5.3 to 2. 1 ms), while the EPSC decay time constant was not affected (from 1.3 to 1.2 ms). These GABA effects were mostly due to the shunting conductance of the postsynaptic GABAA receptors. 5. Depolarizing current injections combined with electrical stimuli to a unilateral axon bundle simulated bilateral synaptic inputs. Response probability increased with decreased interstimulus intervals, while local GABA (10 microM) application to the soma narrowed the time dependence of the response probability. 6. These results suggest that GABAergic inputs to NL neurones may serve to improve coincidence detection of the bilateral excitatory inputs through an increase in membrane conductance.

Correlation between inclination of occlusal plane and masticatory movement

OBJECTIVES

The purpose of this study was to investigate the relationship between the inclination of the occlusal plane and masticatory movement.

METHODS

Masticatory movements of 41 young adults were measured using the three-dimensional Mandibular Movement Analyzing System. The inclination of the occlusal plane was measured in the sagittal plane using a three-dimensional digitizer.

RESULTS

In the sagittal plane, the masticatory closing path and the occlusal plane were consistent in maintaining a perpendicular relation with each other regardless of the inter-individual variation of the inclination of the occlusal plane. Subjects with an anteriorly inclined occlusal plane showed a vertical closing path, and subjects with a posteriorly inclined occlusal plane showed a flat closing path in the frontal plane. These characteristics were explained by the variation of the timing on the balancing-side condylar return correlated with the inclination of the occlusal plane.

CONCLUSIONS

There is a significant correlation between the inclination of the occlusal plane and the direction of the closing path during mastication.

Effect of altered canine guidance on condylar movement during laterotrusion

PURPOSE

The purpose of this study was to investigate the effect of an altered inclination of the canine guidance on the pattern of the condylar movements during laterotrusion.

MATERIALS AND METHODS

The inclination of the canine guidance was steepened approximately 10 degrees by attaching a metal overlay to the lingual surface of the maxillary working-side canine. The laterotrusive movements of 20 young adults were measured using a three-dimensional mandibular movement analyzing system before and after alteration of the canine guidance. The difference between anterior, lateral, and inferior components of the working- and nonworking-side condylar movements, the Bennett angle, and the sagittal inclination of the nonworking-side condylar path before and after steepening of the canine guidance was evaluated by a paired t test.

RESULTS

After the canine guidance was steepened, the working-side condyle moved even more anteriorly and inferiorly. In contrast, little change was found in the direction and the amount of the nonworking-side condylar movement.

CONCLUSION

The results of this study suggest that there is a relationship between the steepness of canine guidance and the pattern of the working-side condylar movement. but not between the steepness of the canine guidance and the pattern of the nonworking-side condylar movement.

The influence of canine guidance and condylar guidance on mandibular lateral movement

This study investigates the definite influence of the working-side canine and balancing-side condylar guidances on mandibular lateral movement. Lateral movements were measured on 40 young adults (22 males and 18 females), using the three-dimensional mandibular movement analysing system. The inclinations of the paths were calculated on the working-side canine, incisor, balancing-side first and second molars and balancing-side condylar points in the frontal plane. Multiple regression analysis enabled quantitative evaluation of the influence of the canine path and condylar path on the path of each tooth. The canine path showed greater influence than the condylar path even on the balancing-side second molar path. There was no difference between male and female subjects in the influential ratio of the canine guidance to the condylar guidance on any tooth path. It was concluded that the influence of the anterior and posterior guidance on the lateral movement varied according to the type of tooth, but not to the gender of the subject. This functional characteristic was confirmed by the morphological finding that the relative location of the molars in relation to canine and condyle does not differ between the sexes. The difference in the guiding system between the protrusive and lateral movement is also described in this paper.

Characteristics of masticatory movement in relation to inclination of occlusal plane

The relationship between masticatory movement and the inclination of the occlusal plane in sagittal plane was analysed in 41 young adults. It was found that the occlusal plane and the masticatory closing path were consistent in maintaining an almost perpendicular relationship with each other, regardless of the variation in inclination of the occlusal plane. This finding can be explained by the observation that the timing of the balancing-side condylar translation during closure correlated with the inclination of the occlusal plane. The inclination of the occlusal plane also influenced the masticatory closing pattern in the sagittal plane. Anterior convex closure patterns dominated when the occlusal plane inclined in the anterior direction. In contrast, the majority of posterior convex closure patterns were induced by the posteriorly inclined occlusal plane. The appearance of these types seems to reflect a harmonious relationship between the inclination of the occlusal plane, tooth guidance, and other central and peripheral control. The correlation between the inclination of the occlusal plane and masticatory closing movement could serve as the functional background for the significance of the occlusal plane.

Neurotensin and substance P inhibit low- and high-voltage-activated Ca2+ channels in cultured newborn rat nucleus basalis neurons

Inhibition of Ca2+ currents by the excitatory neurotransmitters neurotensin and substance P was investigated in cultured nucleus basalis neurons with the use of the whole cell patch-clamp technique. The whole cell Ca2+ current, elicited from a holding potential of -80 mV by a step pulse to 0 mV and measured at 100 ms, was inhibited 67.9% by neurotensin and 57.6% by substance P. Low-voltage-activated (LVA) Ca2+ current, elicited by a step pulse to -40 mV from a holding potential of -90 mV, was inhibited by both neurotensin (26.2%) and substance P (24.1%). High-voltage-activated Ca2+ currents were separated with the use of the Ca2+ channel antagonists. Nimodipine (3 microM) inhibited 24.2% of the whole cell Ca2+ current elicited by a step to 0 or +10 mV and measured at 100 ms. Under the same conditions, omega-conotoxin (omega-CgTx)-GVIA (0.5 microM) inhibited 46.4%, omega-CgTx-GVIA + nimodipine 58.7%, and omega-CgTx-MVIIC (5 microM) + nimodipine 75.7% of the current. Omega-Agatoxin (omega-Aga)-IVA (100 nM) did not produce any effect. Neurotensin inhibition of the whole cell Ca2+ current was attenuated by each of these treatments except for the omega-Aga-IVA treatment, which did not change the neurotensin effect. In contrast, neither the omega-Aga-IVA nor the nimodipine treatment had any effect on the substance-P-induced inhibition; the rest of the treatments attenuated the substance-P-induced response. Thus the data indicate that nucleus basalis neurons express LVA as well as L-, N-, and Q-type, but not the P-type, Ca2+ currents. N- and Q-type HVA Ca2+ currents, as well as LVA Ca2+ currents, are inhibited by both neurotensin and substance P. In contrast, L-type current is inhibited by neurotensin but not by substance P. In addition, a fraction of the total whole cell current was resistant to all Ca2+ channel antagonists and thus may correspond to the R-type Ca2+ current. This residual current was inhibited by both neurotensin and substance P. The inhibition of the whole cell Ca2+ current produced by both neurotransmitters was voltage independent, because a large depolarization (+70 mV) was not able to relieve either effect. In cells loaded with 0.1 mM guanosine 5'-[gamma-thio]triphosphate, response to both neurotensin and substance P became irreversible, indicating that the effects of both neurotransmitters were mediated through G proteins. However, pertussis toxin did not affect either the neurotensin or the substance P response.

Lateral and medial olivocochlear neurons have distinct electrophysiological properties in the rat brain slice

Electrical properties of cochlear efferent (olivocochlear) neurons were investigated with the use of the whole cell patch recording technique in slice preparations of the neonatal rat (postnatal days 5-11). Lateral and medial olivocochlear (LOC and MOC, respectively) neurons were retrogradely labeled with a fluorescent tracer injected into the cochlea. Stained neurons were identified under a fluorescence microscope, and they were subjected to whole cell recording. LOC and MOC neurons showed different electrophysiological properties. Both showed spike trains of tonic pattern in response to injection of depolarizing current pulses at the resting membrane potential (-60 to -70 mV). However, when the membrane was slightly hyperpolarized (-72 to -76 mV), LOC neurons showed spike trains with a long first interspike interval (ISI), whereas MOC neurons showed spike trains with a long latency to the first spike. Extracellular application of 4-aminopyridine (4-AP; 0.5-2 mM) shortened these ISIs and latencies. In voltage-clamp experiments, two transient outward currents with different (fast and slow) decay kinetics were observed in LOC neurons. The fast outward current (I(A-LOC)) was inactivated by the preceding depolarization, and decayed with a time constant (tau) of 86 ms (at 0 mV). The preceding potential, which reduced the current size to the half-maximum (V1/2), was -72 mV. The slow current (I(KD)) decayed with a tau of 853 ms (at 0 mV). I(A-LOC) was sensitive to 4-AP (2 mM), and was less sensitive to tetraethylammonium chloride (TEA; 20 mM). I(KD) was partially blocked by TEA (20 mM), but was insensitive to 4-AP (2 mM). The recovery from inactivation of I(A-LOC) was time dependent with a time constant (tau(rec)) of 32 ms at -90 mV. MOC neurons also showed a transient outward current that consisted of a single transient component (I(A-MOC)) with a steady outward current. I(A-MOC) was inactivated by the preceding depolarization. Decay tau of I(A-MOC) was 33 ms (at 0 mV), and V1/2 was -75 mV. I(A-MOC) was sensitive to 4-AP (0.5-1 mM). The time-dependent recovery from inactivation of I(A-MOC) was faster than that of I(A-LOC), and tau(rec) was 15 ms at -90 mV. The different kinetics of transient outward currents between LOC and MOC neurons seems to be responsible for the difference in firing properties of these two neurons.

Effect of occlusal splint on masticatory movement in healthy individuals

To investigate the effects of wearing an occlusal splint on masticatory movements in healthy individuals, twelve healthy individuals were examined. A full maxillary stabilization splint made of heat-cured acrylic resin was fabricated for, and worn by, each individual for 24 hours. Masticatory movement was measured before and after the 24-hour period using a 3-D mandibular movement analyzing system. While the duration of a masticatory cycle+ did not change, the occlusal time significantly decreased after use of the splint. The lateral displacement of the opening phase to the balancing-side area also decreased after use of the splint, showing a vertical pattern of the opening path. Measurement in more healthy individuals and patients should help clarify the therapeutic mechanism of the splint in the treatment of temporomandibular disorders.

The influence of anterior guidance and condylar guidance on mandibular protrusive movement

This study reveals the influence of the incisal and condylar guidance on mandibular protrusive movement. The protrusive movements were measured on 54 young adults (27 females, 27 males) using a three-dimensional mandibular movement analysing system. The inclinations of the sagittal paths on the incisor, canine, 1st molar, 2nd molar and condylar points were calculated, and multiple regression analysis was performed to evaluate the influence of the incisal and condylar paths on the path of each tooth quantitatively. The influence of the incisal path on any tooth path was consistently greater than that of the condylar path. The condylar path had a greater influence on the paths of posterior teeth than on the paths of anterior teeth, especially in the female subjects. The influence of the condylar path on the molar paths was twice as great in the female than that in the male subjects. It was concluded that the influence of the incisal and condylar guidance on the protrusive movement path varies according to the kind of tooth and the gender of the subject. These guiding system characteristics were confirmed by morphological analysis.

The relationship between inclination of the occlusal plane and jaw closing path

The occlusal plane is determined according to morphologic guides such as Camper's plane and the position of the retromolar pad. However, there is no information available about the functional orientation of the occlusal plane. The purpose of this study was to investigate the relationship between the inclination of the occlusal plane and jaw closing movement path in the sagittal plane. Data from 38 young dentate subjects were obtained with a system that measures jaw movements. It was found that the occlusal plane and the masticatory closing path were consistent in maintaining an almost perpendicular relationship regardless of the variation in the inclination of the occlusal plane. This finding appears to be based on the functional formation of the occlusal plane according to the growth and change of masticatory muscles. The correlation between the inclination of the occlusal plane and masticatory closing movement could serve as the background for the functional significance of the occlusal plane.

Voltage-gated ionic currents and their roles in timing coding in auditory neurons of the nucleus magnocellularis of the chick

Avian cochlear neurons of the nucleus magnocellularis (NMC) are known to encode temporal information of sound. The neuron generated only a single action potential at a stable timing even though suprathreshold currents of long duration (> 100 ms) was injected. The threshold for the action potential was -42 mV. In voltage-clamp experiments, a TTX-sensitive Na current was activated at membrane potentials more positive than -50 mV. A low voltage activated (LVA) Ca current and a high voltage activated (HVA) Ca current were observed. The LVA Ca current was activated from -65 mV and showed a voltage dependent inactivation. The HVA Ca current was activated from -40 mV and did not show any inactivation. The LVA Ca current and the HVA Ca current were sensitive to Ni2+ (0.1 mM) and Nifedipine (10-20 mM), respectively. NMC neurons showed a TEA-sensitive K current and a 4-AP-sensitive K current. With 4-AP (0.5 mM) in a bathing medium, the threshold of action potential was decreased to -49 mV and the timing of action potential generation showed a wider distribution than that of control. Ni2+ (0.1 mM) reversed effects of 4-AP on the threshold and the variability of action potential onsets. It is concluded that a 4-AP-sensitive current counteracts the LVA Ca current that facilitates Na spike generation, and sets a threshold to a higher level for generating a single action potential at a precise timing following synaptic inputs from the auditory nerve.

Cellular approach to auditory signal transmission

The aim of this article is to review the findings of current research on the synaptic transmission of the auditory afferent tract from hair cells to brain-stem auditory nuclei. The depolarization of inner hair cells by the activation of mechano-electrical transduction channels induces the entry of Ca ions through the voltage-gated Ca2+ channel. This Ca2+ influx triggers the transmitter release. The transmitter is likely glutamate, and it generates EPSPs at the afferent terminal and elicits action potentials. The intensity and the temporal information of sounds are processed separately by specific auditory tracts and coded as frequency-selective and phase-locked behaviors of action potentials. Recent studies using the whole-cell patch-clamp technique revealed several voltage-gated and chemically gated ion channels; these channels characterize the intensity coding and the time-coding functions of auditory neurons.

Functional masticatory evaluation in hemifacial microsomia

The features of hemifacial microsomia with unilateral condylar hypoplasia in a 9-year-old female patient were analysed in a multidisciplinary fashion. Cephalometric roentgenograms revealed malformation of the mandible, with the right condylar process being smaller than the left. In addition, the right maxillary alveolar process was underdeveloped. Closed view radiography with oblique lateral transcranial projection (by modified Schüller's method) of the temporomandibular joint revealed an anterior dislocation of the condyle on the unaffected side. Computed tomography (CT) of the masticatory muscles demonstrated that the medial pterygoid muscle on the affected side, unlike the other muscles, was larger than that on the unaffected side. The surface electromyographic activities of the temporal and masseter muscles and reduction of the maximum bite force on the affected side during clenching corresponded with the CT findings. The hypertrophy of the medial pterygoid muscle on the affected side was considered likely to be a compensatory adjustment to keep the mandible centred. A three-dimensional study of the movement of the mandible revealed that the condyle on the affected side moved vertically and that the rotational centre was located antero-inferior to the condylar process during maximum jaw opening and closing movements. These findings suggested lack of articular guidance. Moreover, the unaffected condylar process showed considerable backward movement during retrusion and ipsilateral excursion of the mandible. The mandibular head on the unaffected side showed obvious protraction during all jaw movements, which might have induced the overgrowth of the condylar head on the unaffected side in this growing child.

Electromyographic signal changes during exercise in human chronic jaw-muscle pain

Twelve individuals (2 males, 10 females) with chronic masticatory muscle pain and 11 individuals (2 males, 9 females) without, had their bite force and surface electromyography from the right and left superficial masseter and anterior temporalis muscles recorded before, during and after a 30-s sustained submaximal clenching task. This task was performed at 50% of the force level of each subject's maximum voluntary contraction (MVC) for 30 s. Brief (3 s) 50% MVC efforts were recorded at 15-s intervals, three times before and six times after the sustained clench. Each subject performed this pattern of activities three times with a 15-min rest between each trial. The centre frequency (CF) of the electromyographic power spectrum was calculated by fast Fourier transformations. The mean CF at the end of the 30-s clench and the rate of change at the CF during the clenching task were analysed between groups, sides and muscles. The data indicated that the masseter CF decreased at a significantly faster rate for the first clenching trial in the muscle-pain group. Conversely, the rate of change of the temporalis CF did not significantly differ for the two groups during the three clenching trials. By the third trial the CF of the exercised masseter in the non-pain group exhibited a similar rate of change to that in the pain group. This suggests that both repeated exercise and the presence of chronic inflammation increase the rate of change of the electromyographic signal of the contracting masseter. The mechanism underlying this increased change is unknown.

Opposing mechanisms of regulation of a G-protein-coupled inward rectifier K+ channel in rat brain neurons

In locus coeruleus neurons, substance P (SP) suppresses an inwardly rectifying K+ current via a pertussis toxin-insensitive guanine nucleotide binding protein (G protein; GnonPTX), whereas somatostatin (SOM) or [Met]enkephalin (MENK) enhances it via a pertussis toxin-sensitive G protein (GPTX). The interaction of the SP and the SOM (or MENK) effects was studied in cultured locus coeruleus neurons. In neurons loaded with guanosine 5'-[gamma-thio]triphosphate (GTP[gamma S]), application of SOM (or MENK) evoked a persistent increase in the inward rectifier K+ conductance. A subsequent application of SP suppressed this conductance to a level less than that before the SOM (or MENK) application; the final conductance level was independent of the magnitude of the SOM (or MENK) response. This suppression by SP was persistent, and a subsequent SOM (or MENK) application did not reverse it. When SP was applied to GTP[gamma S]-loaded cells first, subsequent SOM elicited only a small response. In GTP-loaded neurons, application of SP temporarily suppressed the subsequent SOM- (or MENK)-induced conductance increase. These results suggest that the same inward rectifier molecule that responds to an opening signal from GPTX also responds to a closing signal from GnonPTX. The closing signal is stronger than the opening signal.

The role of arachidonic acid metabolism in somatostatin and substance P effects on inward rectifier K conductance in rat brain neurons

Somatostatin enhances an inward rectifier K conductance in cultured locus coeruleus neurons, while substance P reduces an inward rectifier K conductance in cultured nucleus basalis and locus coeruleus neurons. The role of arachidonic acid metabolites in these responses was studied. The somatostatin-induced response was reduced by phospholipase A2 inhibitors, non-specific lipoxygenase inhibitors and specific 5-lipoxygenase inhibitors. A cyclooxygenase inhibitor and a 12-lipoxygenase inhibitor had no effect. 5(S)-HPETE occasionally increased the K conductance, but failed to occlude the somatostatin response. The substance P response was suppressed by a 5-lipoxygenase inhibitor but not by a 12-lipoxygenase inhibitor. These results suggest that the 5-lipoxygenase pathway is not a specific messenger of either one of these responses, but that it plays a more general role in maintaining or enhancing the effectiveness of both somatostatin and substance P responses.

Two signal transduction mechanisms of substance P-induced depolarization in locus coeruleus neurons

Effects of substance P on cultured neurons of the locus coeruleus of the rat were studied using the whole-cell patch clamp technique. In some cells substance P produced a decrease in a K conductance which showed an inwardly rectifying property. In other cells substance P produced an initial inward current which was accompanied by a conductance increase. The rest of the cells showed responses which were mixtures of the above two responses. The measurement of the reversal potential of the initial inward current after suppressing the voltage-gated Ca and K conductances suggests that it is caused by an increase in a non-selective ionic conductance. In cells loaded with 260 microM GTP gamma S, application of substance P produced an irreversible reduction of the K conductance, while the initial inward current could still be recorded, suggesting that the former is mediated by a G protein, whereas the latter may be activated by a different signal transduction mechanism. The initial inward current was not eliminated by external application of high concentrations of tetrodotoxin, d-tubocurarine or amiloride. Nor was it affected by the intracellular application of cyclic GMP or cyclic AMP.

Oral motor disorders in humans

Motor disorders affecting the orofacial musculature include bruxism, chronic orofacial muscle pain affecting the jaw and neck muscles and the involuntary waking period disorders such as orofacial dyskinesia, oral mandibular dystonia, tremor and others. Research at UCLA has touched these and many other areas. Current results have indicated the usefulness of contingent afferent electrical stimulation of the lip to control bruxism; provided information regarding the fatigue, endurance and recovery faculties of the protrusive jaw muscles; explored the issue of chronic muscle hyperactivity inducing headache pain; and worked with botulin toxin as a method to treat orofacial dystonia and dyskinesia.

The coexistence of abdominal aortic aneurysm and early gastric cancer: report of three cases

The surgical approach for patients with abdominal aortic aneurysm (AAA) and coexistent abdominal malignancy remains controversial. We report herein three cases of coincident AAA and early gastric cancer, all of whom were treated by a two-stage operation and underwent curative surgery for their gastric cancer. The principles of our surgical approach are as follows: (1) the lesion which requires urgent surgery should be operated on first, and if both lesions show absolute indications, a one-stage surgical procedure should then be performed; (2) a two-stage surgical procedure in which aneurysmectomy is performed first should be undertaken when no absolute indications for urgent surgery exist for either lesion; (3) a one-stage surgical procedure should only be performed when surgery on one lesion makes the other lesion highly dangerous; and (4) in patients with a poor prognosis because of far advanced cancer in whom the AAA shows no sign of rupturing, only a gastrectomy should be performed.

[Principle of treatment of intermittent claudication due to arteriosclerosis obliterans--reconstruction or conservative treatment]

MATERIALS AND METHODS

Two hundred and one patients of arteriosclerosis obliterans (ASO) with intermittent claudication (IC) were studied. Improvement of IC, score of return to social life, change of life condition and prognosis were compared between the two groups of reconstructive and conservative treatment.

RESULTS

Improvement of IC was seen in 88.0% of the patients in the group of reconstruction and only 30.4% in the conservative treatment group. In the reconstructive group, the score of return to social life improved from 2.10 to 1.31 and the score of life condition also improved from 2.71 to 1.66. However in the conservative treatment group these score showed no significant improvement. Moreover the long term mortality rate was lower in the treatment group of reconstruction.

CONCLUSION

The arterial reconstruction for IC is significant for improving the quality of life and exerts a favorable effect on life prognosis.

[The comparison of postoperative multiple organ failure with arterial disease to that with gastrointestinal cancer]

The clinical features of 22 postoperative multiple organ failure (MOF) patients, comprised of 8 with arterial disease (A-MOF) and 14 with gastrointestinal cancer (G-MOF), were investigated. Differences in the operative time, blood loss, and mortality were not significant. The initial organ impaired was the lungs in 78.6% of G-MOF patients and the heart or kidneys in all A-MOF patients. Infection developed in over 80% of both groups. In many A-MOF patients, the pneumonia or septicemia developed secondary to organ failure, while intraabdominal infection triggered respiratory failure in many G-MOF patients. Our organisms in infected specimens and their antibiotic sensitivities was valuable for the early administration of effective antibiotics. Upper gastrointestinal tract bleeding was important in the prognosis of both groups and occurred more frequently in A-MOF than in G-MOF patients. Consumption coagulopathy in A-MOF patients and DIC induced by infection in G-MOF patients mainly caused such bleeding. Preoperative administration of heparin was effective in improving coagulopathy. Furthermore, measurement of intramural pH with tonometer in the stomach and gastric irrigation with oxygenated perfluorochemicals were effective in the prediction and prevention of gastrointestinal bleeding.

A patch-clamp study on the muscarine-sensitive potassium channel in bullfrog sympathetic ganglion cells

1. A voltage-independent K+ channel was characterized and effects of muscarine were studied in cultured bullfrog sympathetic ganglion cells using the cell-attached patch-clamp configuration. 2. Three types of single-channel current were recorded from 2- to 10-day-old cultured cells in the presence of tetraethylammonium (2-20 mM), tetrodotoxin (1-2 microM), Cd2+ (0.1 mM) and apamin (20 nM). 3. The most frequently observed channel was a voltage-independent K+ channel which was open at the resting membrane potential and had a conductance of 52.6, 78.9 and 114.9 pS at a [K+]o of 2, 40 and 100 mM, respectively. This channel was designated background K+ channel. 4. Two other channel types were observed less frequently. One had a conductance of 26 pS (external K+, 118 mM) and a long open time of several seconds at the resting membrane potential. The second channel had a smaller conductance (20 pS) and displayed a voltage-dependent activation. 5. The open probability of the background K+ channel varied between patches, ranging from 0.0005 to 0.486. The open time distribution was fitted by a single exponential with a time constant of 0.51 ms. Both of these parameters were independent of the membrane potential. The closed time distribution consisted of at least four exponentials having time constants of 0.17, 3.7, 120 ms and several seconds. 6. Muscarine (10-20 microM) applied to the membrane outside the patch pipette reversibly enhanced the activity of the background K+ channel. This effect was associated with an increase in the open probability, which resulted from an increase in the mean open time concomitant with a decrease in the mean closed time. Muscarine did not change the single-channel conductance of this channel. 7. The effects of muscarine were blocked by atropine (1 microM). 8. It is concluded that there exists a muscarine-sensitive, voltage-independent K+ channel in cultured bullfrog ganglion cells. This K+ channel appears to contribute to the generation of the resting membrane potential and underlie the slow inhibitory postsynaptic potential of these neurones in situ.