Miniature Strain-gauge Transducers Research Articles

Effects of increasing the jaw opening on the maximum bite force and electromyographic activities of jaw muscles

Background/purposeIncreased occlusal jaw opening may lead to some changes in the bite force and electromyographic (EMG) activities of the jaw muscles. This in situ study was conducted to determine the immediate influence of three different occlusal vertical dimensions on the maximum bite force and EMG activities of the masseter and anterior temporalis muscles. Materials and methodsFive healthy subjects participated in the study. Two maxillary occlusal splints of 2 and 4 mm thickness were fabricated, and their use created, respectively, 8 and 10 mm of intermolar distances in the first molar region with a strain-gauge-mounted metal arch. EMG activities of the muscles and the maximum bite force were simultaneously recorded using an EMG device and two miniature strain-gauge transducers. Recordings were made in the first molar region without a splint, but with two splints to produce 6, 8, and 10 mm of intermolar distances. ResultsEMG activities of both muscles decreased with increased jaw opening; however, the differences were not statistically significant. The highest maximum bite force was found at a 6-mm intermolar distance, which significantly differed from those at 8- and 10-mm intermolar distances (P < 0.05). The most efficient bite force was exerted with 6 mm of intermolar distance. The least EMG activity of both muscles was found with 10 mm of intermolar distance. ConclusionAn increase in the vertical thickness of the splint to 10 mm may provide an immediate effect of reducing masseter and anterior temporalis muscle hyperactivity.

Ghrelin regulates gastric phase III‐like contractions in freely moving conscious mice

In humans and dogs, motilin regulates phase III contractions of migrating motor complex (MMC) in the interdigestive state, while ghrelin regulates MMC in rats. It still remains unclear whether ghrelin regulates phase III contractions of the mouse stomach. A miniature strain gauge transducer was sutured on the antrum to detect circular muscle contractions and gastric contractions of the interdigestive state were evaluated. Effects of ghrelin, a ghrelin receptor antagonist, and atropine on spontaneous gastric contractions were studied in freely moving conscious mice. Similar to the rat stomach, phase III-like contractions were observed in the interdigestive state, which disappeared immediately after the feeding. Ghrelin augmented spontaneous phase III-like contractions, while growth-hormone secretagogue receptor antagonists and atropine abolished the occurrence of spontaneous phase III-like contractions. The spontaneous phase III-like contractions were no more observed in vagotomized mice. These results suggest that ghrelin regulates phase III-like contractions in mice stomach via its own receptors. Ghrelin-induced gastric phase III-like contractions are mediated via vagal cholinergic pathways in mice. Our recording system of mice gastric motility may be useful to study the functional changes in gene knockout mice, in the future.

The effects of intestinal ischemia on colonic motility in conscious rats

The present study aimed to examine whether and how colonic motility is affected by mild ischemia-induced intestinal injury in conscious rats through in vivo monitoring of colonic contractions, specifically with regard to the interstitial cells of Cajal (ICC) and the effect of nitric oxide (NO). Using miniature strain-gauge transducers, colonic motility with or without ischemia was recorded in conscious rats on the 4th, 7th, and 14th days after surgery. Histological examination for c-kit-positive cells was performed. In control nonischemic rats, the number and duration of contractions (NC and DC, respectively) decreased gradually, but the mean amplitude of contractions (MC) and motility index (MI) did not change. On the 7th day, the NC in the ischemic group increased significantly when compared with that in the control group (P = 0.037). The DC in the ischemic group was lower than that in the control group; the difference was significant on the 4th day (P = 0.008). The MIs in the ischemic group were lower than those in the control group. In both groups, administration of NGnitro-L: -arginine methyl ester on the 7th day increased only the resting cecal motility. Pathological examinations revealed c-kit-positive cells in both groups. Changes such as increased NC with shortened DC accompanied with decreased MI must have occurred at the ischemic site and might have been induced by an ischemic event. However, there exists a possibility that ICC and NO do not play a role in mild ischemia-induced dysmotility.

Quantitative study of bite force during sleep associated bruxism.

Nocturnal bite force during sleep associated bruxism was measured in 10 subjects. Hard acrylic dental appliances were fabricated for the upper and lower dentitions of each subject. Miniature strain-gauge transducers were mounted to the upper dental appliance at the right and left first molar regions. In addition, thin metal plates that contact the strain-gauge transducers were attached to the lower dental appliance. After a 1-week familiarization with the appliances, nocturnal bite force was measured for three nights at the home of each subject. From the 30 recordings, 499 bruxism events that met the definition criteria were selected. The above described system was also used to measure the maximum voluntary bite forces during the daytime. The mean amplitude of detected bruxism events was 22.5 kgf (s.d. 13.0 kgf) and the mean duration was 7.1 s (s.d. 5.3 s). The highest amplitude of nocturnal bite force in individual subjects was 42.3 kgf (15.6-81.2 kgf). Maximum voluntary bite force during the daytime was 79.0 kgf (51.8-99.7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53.1% (17.3-111.6%). These data indicate that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime.

睡眠時ブラキシズムにおけるこう合力の研究

Nocturnal bite force during sleep associated bruxism was measured in ten subjects. Hard acrylic dental appliances were fabricated for each subject's upper and lower jaws. Miniature strain-gauge transducers were mounted on the right and left sides in the first molar regions of the upper dental appliance. Thin metal plates that contact strain-gauge transducers were also attached to the lower dental appliance. Nocturnal bite force was measured for three nights at each subject's home after one-week familiarization of these appliances. Bite force signals were obtained with dynamic data logger, and then transferred to a computer. In this study, we defined bruxism event by using the following criteria: 1) Elevations of bite force signal above 5 kgf were selected as bruxism events; 2) When the inter-events interval was equal to or less than 2 seconds, these events were linked and treated as a single event ; and 3) When the duration of the event was less than 2 seconds, the event was rejected.Four hundred ninety-nine bruxism events that satisfied the above criteria were selected from recordings for a total of 30 nights. The maximum voluntary bite force during the daytime was also measured with this system. The mean amplitude of detected bruxism events was 22.5 kgf (s.d. 13.0 kgf), and the mean duration was 7.1 sec (s.d. 5.3 sec). The mean amplitude of the highest nocturnal bite force in individual subjects was 42.3 kgf (range 15.6-81.2 kgf). The mean maximum voluntary bite force during the daytime was 79.0 kgf (range 51.8-99.7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53.1%(range 17.3-111.6%). These data suggested that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime.

Studies on opossum esophageal longitudinal muscle function

To characterize the neuromuscular mechanisms responsible for control of esophageal longitudinal muscle function, in vivo and in vitro preparations of the intact opossum esophagus were studied using both miniature strain gauge transducers and a specially designed transducer that measured longitudinal axis movement of the entire esophagus. Esophageal shortening in response to swallowing was abolished by atropine in virtually all animals, whereas in 4 of 11 animals there was a significant noncholinergic component to shortening evoked by vagal efferent nerve stimulation. Balloon distention evoked atropine-sensitive esophageal shortening due to contractions occurring at and below the site of distention, which was then followed, upon balloon deflation, by noncholinergic longitudinal muscle contractions aboral to the balloon. A similar two-component response was recorded in response to electrical stimulation or balloon distention in vitro. Although the shortening occurring during stimulation was atropine sensitive, both components could be activated in the presence of tetrodotoxin. These studies indicate that the primary functional innervation to the opossum longitudinal muscle esophagus is cholinergic; noncholinergic and myogenic mechanisms are also demonstrable, but it is unclear whether they have a significant functional role.

Studies on opossum esophageal longitudinal muscle function

To characterize the neuromuscular mechanisms responsible for control of esophageal longitudinal muscle function, in vivo and in vitro preparations of the intact opossum esophagus were studied using both miniature strain gauge transducers and a specially designed transducer that measured longitudinal axis movement of the entire esophagus. Esophageal shortening in response to swallowing was abolished by atropine in virtually all animals, whereas in 4 of 11 animals there was a significant noncholinergic component to shortening evoked by vagal efferent nerve stimulation. Balloon distention evoked atropine-sensitive esophageal shortening due to contractions occurring at and below the site of distention, which was then followed, upon balloon deflation, by noncholinergic longitudinal muscle contractions aboral to the balloon. A similar two-component response was recorded in response to electrical stimulation or balloon distention in vitro. Although the shortening occurring during stimulation was atropine sensitive, both components could be activated in the presence of tetrodotoxin. These studies indicate that the primary functional innervation to the opossum longitudinal muscle esophagus is cholinergic; noncholinergic and myogenic mechanisms are also demonstrable, but it is unclear whether they have a significant functional role.

A Clinical Study of Parenchymal and Subdural Miniature Strain-Gauge Transducers for Monitoring Intracranial Pressure

OBJECTIVE: Previous studies have shown that a new strain-gauge MicroSensor(Codman/Johnson & Johnson Professional, Inc., Randolph, MA) for measuring intracranial pressure (ICP) performs well in the intraventricular space. We hoped to evaluate the MicroSensor in the subdural space and the brain parenchyma, because ICP is often measured in these compartments when the ventricles are difficult to cannulate. METHODS: Fifteen patients had simultaneous recordings of ICP from an externally transduced fluid-filled subdural catheter, a MicroSensor placed within the subdural catheter, and a nearby MicroSensor placed intraparenchymally in the right frontal lobe. RESULTS: The total number of valid simultaneous recordings of ICP was 95,946. A highly significant correlation was found between the tissue MicroSensor ICP(TMICP) and the subdural MicroSensor ICP (SMICP) (n = 95,946; r = 0.89;P < 0.00005), the TMICP and the fluid-transduced subdural catheter ICP (r = 0.86, P < 0.00005), and the fluid-transduced subdural catheter ICP and SMICP (r = 0.88, P < 0.00005). The mean simultaneous difference between the TMICP and the SMICP was 0.1 ± 3.8 mm Hg with no obvious bias. The fluid-transduced subdural catheter ICP was 2.8± 3.9 mm Hg lower than the TMICP and 2.7 ± 3.9 mm Hg lower than the SMICP (P < 0.0005). The mean zero drifts of the tissue and subdural MicroSensors were 0.312 and 0.475 mm Hg/d, respectively. The tissue MicroSensor recordings showed the best quality wave form with the least damping. CONCLUSION: The strain-gauge MicroSensor is highly accurate and stable in the tissue and subdural spaces.

Clinical Evaluation of a Miniature Strain-Gauge Transducer for Monitoring Intracranial Pressure

In 25 patients, we evaluated the accuracy of a new miniature strain-gauge transducer developed for the measurement of intracranial pressure (ICP). The ICP in each patient was measured with the intraventricular, miniature strain-gauge transducer, and that value was compared with the ICP measured with a ventriculostomy catheter coupled to an external strain-gauge transducer. From the two monitors, 2218 simultaneous measurements of ICP were obtained. The average ICP measured with the miniature strain-gauge transducer was 15.9 +/- 10.0 mm Hg (range, -3 to 104 mm Hg). The ICP measured with the ventriculostomy-catheter transducer averaged 15.4 +/- 10.1 mm Hg (range, -9 to 104 mm Hg). A highly significant correlation was found over the wide range of pressures observed (n = 2218, r = 0.97, P < 0.001). The average difference between the two measurements of the ICP was 0.5 +/- 2.6 mm Hg, and the differences were equally positive and negative, demonstrating no consistent bias. The two values for the ICP were within 2 mm Hg of each other on 63% of the measurements and within 4 mm Hg of each other on 89% of the measurements. The average zero drift of the miniature strain-gauge transducer, measured at ambient pressure after removal of the catheter, was 0.2 +/- 0.5 mm Hg. The results indicate that this miniature strain-gauge transducer is highly accurate and stable and that it is a reliable alternative to a ventriculostomy for monitoring the ICP.

Clinical Evaluation of a Miniature Strain-Gauge Transducer for Monitoring Intracranial Pressure

Clinical Evaluation of a Miniature Strain-Gauge Transducer for Monitoring Intracranial Pressure

Mechanical and electrical activity of esophageal smooth muscle during peristalsis.

Mechanical events and membrane potential changes in response to evoked swallows and cervical vagal stimulation (10 and 40 Hz) were recorded in anesthetized opossums. Miniature strain-gauge transducers monitored the mechanical activity of the two layers. A suction electrode recorded from the intact esophagus, from a proximally based pedicle flap of longitudinal muscle (LM), and from circular muscle (CM). The onset of swallowing was marked by the onset of mylohyoid activity. During swallows LM contraction preceded CM contraction and was of longer duration. The latencies of LM and CM contraction were 1,980 +/- 38 and 2,250 +/- 101 ms, respectively. The durations of contraction of LM and CM were 5,590 +/- 260 and 3,330 +/- 67 ms, respectively. LM showed no hyperpolarization but showed depolarization and spike burst. The CM showed prompt hyperpolarization followed by depolarization and spike burst. Responses to vagal stimulation were qualitatively similar to swallows. The different components of the responses were quantitatively modified by changes in stimulus frequency. These studies show that, during peristalsis in response to swallows and vagal stimulation, 1) LM contraction occurs before CM and is of longer duration, and 2) unlike CM, LM does not hyperpolarize prior to depolarization.

Effect of dopamine on pentagastrin-stimulated gastric antral motility in dogs with gastric fistula.

The purpose of the present study was to evaluate the effect of dopamine on gastric antral motility in conscious dogs with gastric fistula by using miniature strain-gauge transducers. Infusion of pentagastrin changed the contractile activity to a digestive state. Dopamine, an endogenous catecholamine, was used alone and in conjunction with selective blockade or adrenergic and dopaminergic receptors. The stimulated antral motility was inhibited by dopamine. The effect was significantly blocked by the peripherally acting dopaminergic blocker domperidone and by cis-flupenthixol, which blocks both peripheral and central dopaminergic receptors. The effect of dopamine was not significantly altered by the beta 1-adrenoceptor blocker practolol, the alpha-adrenoceptor blocker phentolamine, or the alpha + beta-adrenoceptor blocker labetalol. Consequently, this study indicates that dopamine acts on gastric antral motility through dopaminergic receptors. beta-Adrenergic receptors, which are active in the impairment of gastric acid secretion, seem not to be involved in the motility response.

Simultaneous measurement of antroduodenal motility, gastric emptying, and duodenogastric reflux in man.

In six healthy individuals, the relationship between antroduodenal motor activity, duodenogastric reflux, and gastric emptying were simultaneously examined by combined use of multiple marker perfusion and miniature strain gauge transducers. An interdigestive pattern of motor activity was observed during the fasting period;duodenogastric reflux was of variable magnitude, but reproducible in each individual. Fasting reflux was significantly reduced during phase III of the interdigestive complex. Administration of 0.15 M sodium chloride into the stomach resulted in minor and inconsistent changes in antroduodenal motility, despite the rapid and similar pattern of gastric emptying in the six subjects. This study supports the concept that motor activity in the antroduodenal region does not affect gastric emptying of inert, isotonic fluids but may be involved in the regulation of duodenogastric reflux.

Miniature force transducer for myocardial stimulation and local tension measurements.

The commercially available transducers for direct measurement of myocardial tension are either large in size or lack the ability of isometric measurement. Moreover, none of them enables measurement of local isometric tension just around the site of electrical stimulation of the heart. A miniature strain gauge transducer was developed in our laboratories and is herewith described. It weighs 150 mg, and consists of two arms with adjustable distance between 1-5 mm. It is applied to the heart by 2 needles which may serve also as stimulating or sensing electrodes. A full bridge made of constantan foil strain gauges ensures low drift. The device enables in vivo measurement of isometric tension of a myocardial segment of the site where the tension is being measured and permits simultaneous recording of the electrogram. Attachment of the gauge to the ventricular wall by means of needles makes simple the transfer of the transducer from one measuring point to another. The performance of the miniature force transducer was compared to that of a standard Walton-Brodie strain gauge arch demonstrating marked similarity of response at low heart rates. At high frequencies however differences in mechanical response of the heart were obtained by the two force transducers.