Telemetric small intestinal motility recording in awake rats: a novel approach

INTRODUCTION: Ideally, gastrointestinal motility recording should be done in freely moving, stress-free animals. However, no such method is currently available for rats. METHODS: Two NiCr electrodes were sutured to the jejunum and connected to an implantable electromyographic (EMG) transmitter in rats. EMG signals were radio-transmitted to a receiver placed at the bottom of the rats' home cages. RESULTS: Fasting and postprandial jejunal EMG signals could be detected by telemetry. Phase III contractions of the MMC were easy to identify visually and occurred at a rate of about 4.8 per hour. Feeding disrupted the phasic contraction pattern 15 min after the start of food intake and lasted for 2 h. The motility index (MI, area under the curve) was calculated and increased postprandially. CONCLUSION: Telemetric transmission of rat gastrointestinal EMG signals is feasible and results are comparable to those given in the literature.     

A New Transcutaneous Energy Transmission System With Hybrid Energy Coils for Driving an Implantable Biventricular Assist Device

Abstract:  We have developed a new transcutaneous energy transmission (TET) system for a totally implantable biventricular assist device (BVAD) system in the New Energy and Industrial Development Organization (NEDO) artificial heart project. The TET system mainly consists of an energy transmitter, a hybrid energy coil unit, an energy receiver, an internal battery system, and an optical telemetry system. The hybrid energy coil unit consists of an air-core energy transmission coil and an energy-receiving coil having a ferrite core. Internal units of the TET system are encapsulated in a titanium alloy casing, which has a size of 111 mm in width, 73 mm in length, and 25 mm in height. In in vitro experiments, the TET system can transmit a maximum electric energy of 60 Watts, and it has a maximum transmission efficiency of 87.3%. A maximum surface temperature of 46.1°C was measured at the ferrite core of the energy-receiving coil during an energy transmission of 20 Watts in air. The long-term performance test shows that the TET system has been able to operate stably for over 4 years with a decrease of energy-transmission efficiency from 85% to 80%. In conclusion, the TET system with the hybrid energy coil can overcome the drawback of previously reported TET systems, and it promises to be the highest performance TET system in the world.     

前伸头位对咀嚼肌功能活动时的肌电影响

目的：研究前伸头位对牙尖交错位自主用力紧咬和吞咽两功能活动时咀嚼肌肌电活动的影响。方法：以30名健康正常青年女性受试者为研究对象,应用BioEMGII型表面肌电测量仪,测量正常人群分别在自然头位和最大前伸头位情况下,牙尖交错自主用力紧咬以及吞咽时颞肌前束（TA）、咬肌（MM）、胸锁乳突肌（SCM）、二腹肌前腹（DA）的肌电幅值,并对结果进行统计学分析。结果：最大前伸头位吞咽时TA、MM、SCM、DA的肌电幅值以及最大前伸头位牙尖交错位自主用力紧咬时MM和DA的肌电幅值与自然头位时相比增高且具有统计学意义（P〈0.05）;最大前伸头位牙尖交错位自主用力紧咬时TA以及SCM的平均肌电幅值高于自然头位时的肌电幅值,但差别没有统计学意义（P〉0.05）。结论：吞咽活动时各咀嚼肌对最大前伸头位有着明显的反应,牙尖交错位紧咬时MM和DA对前伸头位反应明显,最大前伸头位时各咀嚼肌肌紧张度增加,肌电活动增强。     

The association of low back pain, neuromuscular imbalance, and trunk extension strength in athletes

BACKGROUND CONTEXT: Imbalanced patterns of erector spinae activity and reduced trunk extension strength have been observed among patients with low back pain (LBP). The association between LBP and neuromuscular imbalance still remains unclear. PURPOSE: To examine the relationship between LBP, neuromuscular imbalance, clinical symptoms, and trunk extension strength on two independent occasions, after dynamic neuromuscular changes through a back exercise program. STUDY DESIGN/SETTING: Experimental longitudinal study of the lower back in a clinical setting. PATIENT SAMPLE: Eighty-two elite amateur tennis players with and without LBP. OUTCOME MEASURES: Clinical testing of spinal mobility and muscular flexibility of the lower back. Isometric voluntary maximum trunk extension strength. Surface electromyography (EMG) of lumbar erector spinae. METHODS: Athletes underwent a standardized clinical examination with common tests for spinal mobility and muscular flexibility, followed by an isometric trunk extension tests in a specially built apparatus with simultaneous surface EMG recording from right and left lumbar erector spinae. Imbalance quotients were calculated using integrated EMG (IEMG) measures. The relationships between LBP, neuromuscular imbalance, trunk extension strength, and clinical findings were investigated before and after a back exercise program using univariate and multivariate logistic regression models. RESULTS: A significant association between neuromuscular imbalance of erector spinae and the occurrence of LBP was observed, whereas no significant imbalances were found in subjects without LBP. The number of subjects with LBP decreased proportionally with the occurrence of neuromuscular imbalance in the lumbar region after the completion of a back exercise program. However, neuromuscular imbalances were still present during retesting among subjects whose LBP did not resolve; the relationship between neuromuscular imbalance of lumbar erector spinae and LBP was significant again. On the contrary, no significant association between LBP and maximum isometric trunk extension strength or neuromuscular imbalance and maximum isometric trunk extension strength was found before or after the exercise program. No clear relationship between LBP and clinical testing of the lumbar spine or neuromuscular imbalance and clinical testing was found on the two independent testing occasions. CONCLUSION: A direct relationship between LBP and neuromuscular imbalance was documented in athletes with LBP. Maximum isometric trunk extension strength had no relationship to the presence of LBP or the occurrence of neuromuscular imbalance of erector spinae. Common clinical testing of spinal mobility and muscular flexibility had only limited correlation to LBP and neuromuscular imbalance.     

诱发肌电图刺激电流阈值与螺钉位置关系模型研究

目的建立在常用手术环境下术中诱发肌电图刺激电流阈值与椎弓根螺钉距离腰椎椎体内侧壁量化关系的方程模型,并探讨这一方程模型的临床意义。方法对腰椎后路椎弓根固定的28例患者118个螺钉通过术中对刺激电流阈值与每个椎弓根螺钉与椎体后壁内侧之间的距离线性回归分析,建立阈值推算椎弓根螺钉与椎体后壁内侧之间距离的回归方程,并对所建立的回归方程对35例患者134个螺钉位置的预测及诊断。结果刺激电流阈值推算椎弓根螺钉与椎体后壁内侧之间距离的回归方程为y=0.445x-2.30;将预测值与CT重建后的真实值进行配对,结果显示两者之间的差异无统计学意义。结论所建立的方程适用于常规手术环境下椎弓根螺钉与椎体后壁内侧之间的距离推算,可以减少医源性神经根损伤。     

Frowning and Jaw Clenching Muscle Activity Reflects the Perception of Effort During Incremental Workload Cycling

The present study aimed to investigate whether facial electromyography (EMG) recordings reflect the perception of effort and primary active lower limb muscle activity during incremental workload cycling. The effects of exercise intensity on EMG activity of the corrugator supercilii (CS), masseter and vastus lateralis (VL) muscles, heart rate (HR) and the rating of perceived exertion (RPE) were investigated, and the correlations among these parameters were determined. Eighteen males and 15 females performed continuous incremental workload cycling exercise until exhaustion. CS, masseter and VL muscle activities were continuously recorded using EMG during exercise. HR was also continuously monitored during the test. During the final 30 s of each stage of cycle ergometer exercise, participants were asked to report their feeling of exertion on the adult OMNI-Cycle RPE. HR and EMG activity of the facial muscles and the primary active lower limb muscle were strongly correlated with RPE; they increased with power output. Furthermore, facial muscle activity increased significantly during high-intensity exercise. Masseter muscle activity was strongly and positively correlated with HR, RPE and VL activity. The present investigation supports the view that facial EMG activity reflects the perception of effort. The jaw clenching facial expression can be considered an important factor for improving the reporting of perceived effort during high-intensity exercise in males and females.

Key points

• Frowning and jaw clenching muscle activity reflects the perception of effort during incremental workload cycling.
• EMG activity of the masseter muscle was strongly and positively correlated with RPE, HR and lower limb EMG activity during incremental workload cycling.
• The jaw clenching facial expression can be considered an important factor for estimating the intensity of effort.

Key words: Perceived exertion, facial electromyography, masseter muscle, corrugator supercilii muscle, incremental exercise testing     

大鼠颈6和颈8神经根切断术后肢体功能变化的实验研究

目的通过观察切断一侧颈６和颈８神经根大鼠肢体功能的变化,试图进一步发现可作为动力源的新神经根。方法在分别确定大鼠颈６与肱二头肌、颈８与指深屈肌的支配关系的基础上,将大鼠右侧颈６和颈８神经根切断作为实验侧;左侧为正常侧进行自身对照。定期观察姿态、步态、有无溃疡及自残现象;分别于术后即刻、２周及４周检测肱二头肌和指深屈肌的肌电图、肌肉拉力,对两侧进行ｔ检验比较。结果术后大鼠两侧姿态对称,未见跛行,无溃疡及自残现象,对疼痛刺激敏感;实验侧肱二头肌和指深屈肌肌电图均呈正常波形;两侧肌电图波幅、等长收缩时最大强直收缩张力及持续时间进行自身ｔ检验比较均无显著差异。结论大鼠一侧颈６和颈８神经根切断术后肢体功能无明显影响。     

Changes in the Masseter Muscle After Curved Osteotomy of the Prominent Mandibular Angle

Background This study aimed to explore the changes in the masseter muscle after curved osteotomy of the prominent mandibular angle and to supply guidance for resection of the mandibular angle. Methods Ultrasonography was used to assess changes in the thickness of the masseter muscle after curved osteotomy for 10 patients (20 hemimandibles) at the 6-month following-up assessment. The measurements were performed under both relaxing and maximal clenching positions through three cross sections of the masseter muscle (planes A, B, and C). Plane A contains the line from the mouth angle to the ipsilateral ear lobe. Planes B and C are parallel planes above and below plane A with a distance of 1 cm between them. Results No significant difference between the preoperative and postoperative thicknesses of the masseter muscle for planes A and B (p > 0.05) was found, but there was a significant difference (p < 0.05) for plane C. The postoperative thickness of the masseter muscle in plane C was reduced by 0.244 ± 0.121 cm in the relaxing position and by 0.244 ± 0.142 cm in the clenching position, which were respectively 19.22% ± 7.785% and 15.404% ± 7.648% of its original thickness. There was no significant difference in the contraction amplitude of the masseter muscle under maximal clenching (p > 0.05) for any of the three cross sections postoperatively. Conclusions The masseter muscle around the mandibular angle becomes atrophied but without functional defect after curved osteotomy. Patients with prominent mandibular angles can be treated simply with curved osteotomy instead of masseter excision.     

微囊包膜新生猪胰岛移植逆转糖尿病大鼠甲状腺形态学改变

目的探讨糖尿病大鼠胰岛移植后的甲状腺形态学的变化。方法给用链脲霉素所致的糖尿病大鼠腹腔内移植微囊包膜的新生猪胰岛８００个。术后３个月将动物处死,取甲状腺切片观察。结果动物处死前对照组及移植组的血糖水平分别为（４．８７±０．４７）ｍｍｏｌ／Ｌ和（６．４４±１．８２）ｍｍｏｌ／Ｌ,糖尿病组为（１６．１２±１．４７）ｍｍｏｌ／Ｌ,移植组与对照组比较,差异不显著（Ｐ＞０．０５）,糖尿病组与对照组比较,差异显著（Ｐ＜０．００１）;甲状腺滤泡腔内胶质的面积,移植组、糖尿病组分别与对照组比较,差异不显著,但甲状腺滤泡上皮细胞的高度,糖尿病组与对照组相比,差异显著（Ｐ＜０．００１）,而移植组与对照组相比,差异不显著（Ｐ＞０．０５）。结论胰岛移植后若受体的血糖控制良好,其甲状腺滤泡上皮细胞的形态改变可以逆转,这可能是纠正糖尿病时甲状腺分泌功能低下的重要因素之一。     

正畸全冠修复在前牙冠根折患者中的应用效果

目的 探究对前牙冠根折患者采用正畸全冠修复治疗的临床效果。方法 选取2019年1月-2021年 12月张家口市口腔医院收治的80例前牙冠根折患者为研究对象,按照随机数字表法分为对照组和观察组, 每组40例。对照组予以烤瓷全冠修复,观察组予以正畸牵引后烤瓷全冠修复,比较两组临床疗效、前牙 咬合功能[牙尖交错位习惯咬合状态（ICP-HB）肌电值、最大力紧咬合状态（ICP-MC）肌电值]及美学 效果[红色美学指数（PES）]。结果 观察组治疗优良率为95.00%,高于对照组的77.50%,差异有统计学 意义（P＜0.05）;两组修复后ICP-HB肌电值、ICP-MC肌电值均高于修复前,且观察组高于对照组, 差异有统计学意义（P＜0.05）;两组修复后PES评分均高于修复前,且观察组高于对照组,差异有统计 学意义（P＜0.05）。结论 正畸全冠修复在前牙冠根折患者中的应用效果确切,可有效改善患者的前牙 咬合功能及牙周、牙龈状况,修复后美学效果较好,值得临床应用。     

A reliable and readily available method of measuring limb blood flow in intermittent claudication

To evaluate isotope limb blood flow measurement in intermittent claudication we have assessed 58 non-diabetic patients comparing our new method with treadmill testing and Doppler assessment. Limb blood flow was applicable to all 58 patients; 25 patients were unable to walk on a treadmill and of the 33 who could 12 failed to walk for one minute, making a standard one minute exercise test inappropriate. In those patients who could perform exercise tests there was a significant correlation between maximum walking distance and limb blood flow (r = 0.35, P = 0.02). Resting, post-exercise and post-hyperaemic ankle-brachial systolic pressure indices bore no relationship to the maximum walking distance. Isotope limb blood flow measurement is reproducible (r = 0.97), can be applied to those patients who cannot walk on a treadmill and provides information about both legs. It correlated significantly with all the other tests and can be recommended for the minimally invasive assessment of intermittent claudication.     

Interleukin-1-induced alterations in glomerular proteoglycans: biochemical and tissue autoradiographic aspects.

The effect of interleukin-1 alpha (IL-1) on the synthesis of glomerular basement membrane heparan sulfate-proteoglycan (HS-PG) was investigated. An ex vivo recirculating organ perfusion system was used. Kidneys were perfused with a medium containing (35S) sulfate and IL-1 (0.625 to 6.25 ng/mL). After radiolabeling was performed, a small cortical piece was saved for tissue autoradiography; the remaining kidney and perfusion medium were used for biochemical studies. Renal cortices were dissected out, and glomeruli were isolated; the PG were extracted and characterized. With exposure to IL-1 (5 ng/mL), an approximately twofold increase of the radioactivity in the glomerular fraction was noted. The increase was unaffected by indomethacin treatment. By Sepharose CL-6B chromatography, a single peak of radioactivity with Kav = 0.25 (macromolecular form of PG) was observed in the control group. The IL-treated group had two peaks of radioactivity with Kav = 0.25 and 0.45: the first peak contained PG, and the second peak consisted of free glycosaminoglycan (GAG) chains. Elution profiles of hydrolyzed tissue GAG chains were similar. No change in the ratio of chondroitin to heparan sulfate was observed. By DEAE-Sephacel chromatography, the glomerular PG/GAG of the IL-treated group eluted at a relatively lower salt concentration, suggesting a change in the charge density characteristics. No differences in the elution profiles of media PG/GAG were observed. (35S)methionine labeling of proteins showed no significant increase of the total radioincorporation in the IL-treated group. Immunoprecipitation studies revealed an approximately 88% increase in the de novo synthesis of PG. Tissue autoradiography revealed an approximately twofold increase of (35S) sulfate radioactivity over the glomerular mesangium, epithelium, and basement membranes. These results indicate that IL-1 enhances the synthesis of the macromolecular form of PG and the generation of free chains. Conceivably, such alterations may lead to defective macromolecular interactions among various components of the glomerular basement membrane and compromise the integrity of the ultrafiltration unit of the glomerulus.     

Urethral pressure variations in women with neurourological symptoms: I. Relationship to urethral and pelvic floor striated muscle

Simultaneous urethrocystometry and electromyography (EMG) of the urethral and pelvic floor striated muscle were performed in 42 gynecological patients with neurourological symptoms. Their maximum urethral pressure varied between 20 and 124 cm H₂O. A correlation analysis was performed between the maximum urethral pressure and the integrated EMG of the urethral striated muscle and the pelvic floor striated muscle. The analyses were performed on results obtained in 1-min periods during bladder filling before first desire to void was reported, when first desire to void was reported, and when a strong desire to void was reported. In 21 patients no correlation was found between the urethral and pelvic floor striated muscle activity and the maximum urethral pressure at any stage of bladder filling. In the other 21 patients a correlation was found in at least 1 of the 3 stages. At all stages of bladder filling a correlation was found significantly more often between the maximum urethral pressure and the striated urethral muscle EMG than between the maximum urethral pressure and the striated pelvic floor muscle EMG. Thus, activity of the urethral striated muscle cannot be reliably studied in an EMG recording from the pelvic floor striated muscle. In the same patient, periods with a correlation could be succeeded by periods without a correlation. Thus, the urethral pressure variations may in the same patient sometimes be caused mainly by the urethral striated muscle and sometimes mainly by the urethral smooth muscle.     

Quantification of lumbar function. Part 3: Preliminary data on isokinetic torso rotation testing with myoelectric spectral analysis in normal and low-back pain subjects

A prototype isokinetic torso rotation unit and an EMG signal processing system were utilized to obtain preliminary information on torso rotation. In Study 1, range-of-motion was found to be surprisingly uniform between low-back pain patients and normal subjects, although there was a significant strength variation between them at all isokinetic speeds tested. Both female patients and normal females showed approximately 70%-75% of the strength (torque/body weight) levels relative to their male counterparts. The decrement in trunk strength at high speeds was proportional for both patients and controls and was not nearly as dramatic as the decrement seen in the sagittal plane. In Studies 2 and 3, anatomic relationships evaluated by EMG testing of obliques and erector spinae showed that the contralateral abdominal obliques were the most consistent muscles providing a significant torsional moment to the spine.     

Influence of intravesical potassium on pelvic floor activity in women with recurrent urinary tract infections: comparative urodynamics might lead to enhanced detection of dysfunctional voiding

OBJECTIVES: To investigate the influence of intravesical potassium on pelvic floor activity (PFA) during voiding in women with recurrent urinary tract infections (rUTIs) by using comparative urodynamics (CUD). PATIENTS AND METHODS: CUD was conducted in 49 women (mean age 34.6 years, range 15-82) with rUTI. Every patient had two sessions of pressure-flow studies with simultaneous measurement of PFA by perineal surface electromyography (EMG); the first was with 0.9% saline and in the second the bladder was filled with 0.2 m KCl solution. All patients had voiding cysto-urethrography, and dysfunctional voiding (DV) was diagnosed when significant PFA was measured by EMG during voiding. RESULTS: Overall, DV was diagnosed in 37 patients (76%) using CUD; 16 (32%) had DV with saline on the pelvic floor EMG. In all these patients there were significantly greater EMG signals in the presence of KCL. In 21 patients (43%) DV was only detected using KCL; this improvement in the detection rate of DV was statistically significant (P = 0.006). Filling with KCl also prompted a statistically significant difference (P < 0.05) in maximum bladder capacity, maximum and average flow rates and in postvoid residual urine volume. CONCLUSION: The present data show that DV is present in most women with rUTI but cannot sufficiently be diagnosed by conventional urodynamics with standard 0.9% saline. The present study suggests that CUD might enhance the detection rates of DV.     

Effects of chondroitin sulfate and interleukin-1beta on human chondrocyte cultures exposed to pressurization: a biochemical and morphological study

Objective This study investigated the in vitro effects of chondroitin sulfate (CS) on human articular chondrocytes cultivated in the presence or in the absence of interleukin-1beta (IL-1beta) during 10 days of culture with and without pressurization cycles. Design The effects of CS (10 and 100 microg/ml) with and without IL-1beta were assessed in the culture medium of cells exposed to pressurization cycles in the form of synusoidal waves (minimum pressure 1 Mpa, maximum pressure 5 Mpa) and a frequency of 0.25 Hz for 3 h by immunoenzymatic method on microplates for the quantitative measurement of human proteoglycans (PG). On the 4th and 10th day of culture the cells were used for morphological analysis by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).Results The presence of IL-1beta determines a significant decrease in PG concentration measured in the culture medium. When the cells are cultured in the presence of IL-1beta and CS, a statistically significant restoration of PG levels is observed. Under pressurization conditions, we observed that PG concentration in the medium of cells presents a significant increase at baseline conditions, in the presence of IL-1beta+CS10 and IL-1beta+CS100, but not with IL-1beta alone. The results concerning metabolic evaluation are confirmed by the morphologic findings obtained by TEM and SEM. Conclusions These in vitro studies confirm the protective role of CS, which counteracts the IL-1beta induced effects and they confirm the importance of pressure on chondrocyte metabolism and morphology.     

A New Transcutaneous Bidirectional Communication for Monitoring Implanted Artificial Heart Using the Human Body as a Conductive Medium

A transcutaneous communication system (TCS) is a key technology for monitoring and controlling artificial hearts and other artificial organs in the body. In this study, we developed a new TCS that uses the human body as a conductive medium. Direct data exchange provides a higher level of communication security compared to that of wireless methods without physical constraints such as an external wire. The external and internal units of the new TCS each consist mainly of a data transmitter and a data receiver. The data transmitter has an amplitude shift keying (ASK) modulator (carrier frequencies: 4 and 10 MHz) and an electrode. The ASK‐modulated data current is led into the body through the electrode, and it flows back to the energy source through the body, the data receiver, and the earth ground that includes all conductors and dielectrics in the environment that are in close proximity to the patient. Performance of the TCS was evaluated by a communication test on the surface of the human body and in an animal experiment using a goat. The TCS was able to transmit data concurrently for 4 weeks between everywhere on the surface of the body and everywhere inside the body under full‐duplex communication at a transmission rate of 115 kbps. The power consumption of each TCS unit was 125 mW with an ASK‐modulated current of 7 mA (root‐mean‐square). While further study is required to secure its safety, the newly developed TCS has promise to be a next‐generation transcutaneous communication device.     

A preliminary comparison of myoelectric and cyclic control of an implanted neuroprosthesis to modulate gait speed in incomplete SCI

Abstract

Objective

Explore whether electromyography (EMG) control of electrical stimulation for walking after incomplete spinal cord injury (SCI) can affect ability to modulate speed and alter gait spatial-temporal parameters compared to cyclic repetition of pre-programmed stimulation.

Design

Single case study with subject acting as own concurrent control.

Setting

Hospital-based biomechanics laboratory.

Participants

Single subject with C6 AIS D SCI using an implanted neuroprosthesis for walking.

Interventions

Lower extremity muscle activation via an implanted system with two different control methods: (1) pre-programmed pattern of stimulation, and (2) EMG-controlled stimulation based on signals from the gastrocnemius and quadriceps.

Outcome measures

Gait speed, distance, and subjective rating of difficulty during 2-minute walks. Range of walking speeds and associated cadences, stride lengths, stride times, and double support times during quantitative gait analysis.

Results

EMG control resulted in statistically significant increases in both walking speed and distance (P < 0.001) over cyclic stimulation during 2-minute walks. Maximum walking speed with EMG control (0.48 m/second) was significantly (P < 0.001) faster than the fastest automatic pattern (0.39 m/second), with increased cadence and decreased stride and double support times (P < 0.000) but no change in stride length (z = ?0.085; P = 0.932). The slowest walking with EMG control (0.25 m/second) was virtually indistinguishable from the slowest with automatic cycling (z = ?0.239; P = 0.811).

Conclusion

EMG control can increase the ability to modulate comfortable walking speed over pre-programmed cyclic stimulation. While control methods did not differ at the lowest speed, EMG-triggered stimulation allowed significantly faster walking than cyclic stimulation. The expanded range of available walking speeds could permit users to better avoid obstacles and naturally adapt to various environments. Further research is required to definitively determine the robustness, generalizability, and functional implications of these results.     

Urethral pressure variations in women with neurourological symptoms: III. Relationship to urethral wall venous plexus

Twenty-five women were investigated in order to find out if the urethral submucous venous plexus may influence urethral pressure variations. Urethral and bladder pressure were measured with a microtip transducer catheter. Electromyography (EMG) and integrated EMG from the urethral striated muscle were recorded using a concentric needle electrode. Blood volume in the urethral submucous venous plexus was measured with a urethral photopletysmograph probe. In 9 women without neurourological symptoms, during squeezing there was increased urethral striated muscle activity, increased urethral pressure and decreased blood volume. When they were asked to void the opposite was found. In 16 patients with marked urethral pressure variations a negative correlation was found between the maximum urethral pressure and the photopletysmograph tracing. In 7 of 8 patients a negative correlation was found also between the integrated EMG tracing and the photopletysmograph tracing, but a positive correlation was found between the maximum urethral pressure and the EMG of the urethral striated muscle. In 1 of the 8 patients no correlation was found between EMG activity and maximum urethral pressure and between EMG activity and the photopletysmograph tracing. The results demonstrate that the urethral venous plexus becomes emptied secondary to contractions of the urethral striated and/or smooth muscle and filled with blood secondary to relaxation of the same muscles. Hence, the urethral venous plexus does not influence the urethral pressure actively.     

Effect of knee joint angle on motor unit synchronization.

Activity of the vasti has been argued to vary through knee range of movement due to changes in passive support of the patellofemoral joint and the relative contribution of these muscles to knee extension. Efficient function of the knee is dependent on optimal control of the patellofemoral joint, largely through coordinated activity of the medial and lateral quadriceps. Motor unit synchronization may provide a mechanism to coordinate the activity of vastus medialis (VMO) and vastus lateralis (VL), and may be more critical in positions of reduced passive support for the patellofemoral joint (i.e., full extension). Therefore, the aim of this study was to determine whether the degree of motor unit synchronization between the vasti muscles is dependent on joint angle. Electromyographic (EMG) recordings of single motor unit action potentials (MUAPs) were made from VMO and multiunit recordings from VL during isometric contractions of the quadriceps at 0 degrees, 30 degrees, and 60 degrees of knee flexion. The degree of synchronization between motor unit firing was evaluated by identification of peaks in the rectified EMG averages of VL, triggered from MUAPs in VMO. The proportion of cases in which there was a significant peak in the triggered averages was calculated. There was no significant difference in the degree of synchronization between the vasti at different knee angles (p=0.57). These data suggest that this basic coordinative mechanism between the vasti muscles is controlled consistently throughout knee range of motion, and is not augmented at specific angles where the requirement for dynamic control of stability is increased.