Analysis of gastric electrical signals from surface electrodes using phaselock techniques Part 2—System performance with gastric signals

The 0·05 Hz (3 cycle/min) electrical activity from the human stomach was first recorded in 1922 by Alvarez, using electrodes placed on the skin. The major problem with surface electrode recording is the poor signal/noise ratio. The application of a phaselock system, using a smaller number of readily available integrated circuits, to this problem has been described and in the paper the performance of this system is discussed.     

Conditioning stimulus can influence an external urethral sphincter contraction evoked by a magnetic stimulation

AIMS: To study the effect of a conditioning stimulus on an external urethral sphincter (EUS)contraction evoked by a magnetic stimulation at different time intervals. METHODS: Seven healthy male volunteers underwent EUS pressure measurement. At baseline, magnetic stimulation of the lumbosacral spinal cord above the motor threshold was performed and evoked EUS pressure responses were recorded. The lumbosacral magnetic stimulation was repeated with same intensity, while a selective electrical dorsal penile nerve stimulation below the bulbocavernosus reflex (BCR) threshold was preceding at five different intervals (10, 20, 30, 50, 100 msec). The protocol was performed with empty and full bladder (BLA), and baseline responses were statistically compared to those with combined stimulation. RESULTS: When the dorsal penile nerve electrical stimulation preceded the lumbosacral magnetic stimulation by 20 msec (P=0.0048), 50 msec (P=0.0039), or 100 msec (P=0.0002), the amplitudes of the EUS pressure response with empty BLA were significantly reduced compared to lumbosacral magnetic stimulation alone. With a filled BLA, the amplitudes of the EUS were significantly reduced only at an interval of 50 msec (P<0.0001). CONCLUSIONS: A conditional sensory pudendal stimulation seems to have the capacity to inhibit the external urethral sphincter contraction induced by a magnetic stimulation. The inhibitory effect seems to depend on the latency between the peripheral and lumbosacral stimulation as well as on the degree of BLA filling. It remains to be proved if the neuromodulative effect of the conditional stimulus occurs at a spinal or supraspinal level.     

Sacral neuromodulation for refractory detrusor overactivity in women with an artificial urinary sphincter

PURPOSE: We assessed the efficacy of sacral neuromodulation as an alternative therapeutic option in women with an artificial urinary sphincter (AUS) who had de novo irritative urinary symptoms (urgency/frequency) refractory to conventional treatment. MATERIALS AND METHODS: Between 1984 and 2002 we implanted an AUS in 350 women and detrusor overactivity developed in 14. Six of the 14 patients responding positively to a percutaneous nerve evaluation test (greater than 50% subjective/objective improvement) were implanted with an S3 neuromodulator within 42.8 weeks (range 21 to 106) of AUS implantation. Followup included analysis of the voiding diary, a pad test and urodynamic assessment. RESULTS: After 30.5 months followup (range 14 to 40) 1 patient was dry, 4 were improved and treatment failed in 1. At 12 months mean voiding frequency daily had decreased from 17 (range 12 to 23) to 8 (range 4 to 12) and the mean number of leakages episodes daily had decreased from 14.7 (range 8.5 to 17) to 6 (range 4 to 10). Mean voided volume had increased from 121.7 (range 90 to 170) to 180 ml (range 120 to 225), mean first desire to void volume had increased from 117 (range 88 to 190) to 183 ml (range 130 to 275) and mean functional bladder capacity had increased from 325 (range 200 to 530) to 372 ml (range 250 to 580). Uninhibited bladder contractions had resolved in 4 of 5 patients. CONCLUSIONS: In women who already have an AUS with urge incontinence sacral neuromodulation can help resolve symptoms. Because this therapy does not compromise the potential for future treatment, it appears to be an alternative option in these patients. It can postpone or avoid more mutilating surgery and self-catheterization.     

Can functional electric stimulation-assisted rowing reproduce a race-winning rowing stroke?

OBJECTIVE: To compare the ergometer rowing technique of a person with spinal cord injury (SCI), using functional electric stimulation (FES) of his leg muscles, with that of a well-defined group of able-bodied rowers. DESIGN: Whole-body kinematics and kinetics and electric activity of selected muscles were measured during ergometer rowing. SETTING: A hospital-based motion analysis laboratory. PARTICIPANTS: Five male university varsity-level rowers and 1 male rower with SCI. INTERVENTIONS: Eight rowing trials were collected on the university-level rowers, 2 trials each at 20, 24, 28, and 32 strokes/min. The rower with SCI had surface electrodes applied to his medial hamstrings and medial quadriceps muscle bellies. The electrodes were attached to a stimulator that was activated using a button in the ergometer handle. The subject with SCI rowed at a self-selected stroke rate. MAIN OUTCOME MEASURES: Forces at the ergometer handle and foot cradle, 3-dimensional whole-body kinematics, net joint moments, and phasic activity of muscles. RESULTS: Motion of the arms, ankles, and knees of the rower with SCI was similar to those of the university-level rowers; other joint motions and forces applied to the ergometer differed. CONCLUSIONS: FES-assisted rowing in its current implementation cannot reproduce a race-winning rowing stroke. Further development work is required.     

Pharmacological and behavioral properties of A-349821, a selective and potent human histamine H3 receptor antagonist

Histamine H3 receptors regulate the release of a variety of central neurotransmitters involved in cognitive processes. A-349821 ((4'-(3-((R,R)2,5-dimethyl-pyrrolidin-1-yl)-propoxy)-biphenyl-4-yl)-morpholin-4-yl-methanone) is a novel, non-imidazole H3 receptor ligand, displaying high affinity for recombinant rat and human H3 receptors, with pKi values of 9.4 and 8.8, respectively, and high selectivity for the H3 receptor versus H1, H2, and H4 histamine receptors. A-349821 is a potent H3 receptor antagonist in a variety of models using recombinant human and rat receptors, reversing agonist induced changes in cyclic AMP formation (pKb= 8.2 and pKb= 8.1, respectively), [35S]-GTPgammaS binding (pKb= 9.3 and pKb= 8.6, respectively) and calcium levels (human pKb= 8.3). In native systems, A-349821 competitively reversed agonist induced inhibition of electric field stimulated guinea-pig ileum (pA2= 9.5) and histamine-mediated inhibition of [3H]-histamine release from rat brain cortical synaptosomes (pKb= 9.2). Additionally, A-349821 inhibited constitutive GTPgammaS binding at both rat and human H3 receptors with respective pEC50 values of 9.1 and 8.6, demonstrating potent inverse agonist properties. In behavioral studies, A-349821 (0.4 mg/kg-4 mg/kg) potently blocked (R)-alpha-methylhistamine-induced dipsogenia in mice. The compound also enhanced cognitive activity in a five-trial inhibitory avoidance model in spontaneously hypertensive rat (SHR) pups at doses of 1-10mg/kg, with the 1mg/kg dose showing comparable efficacy to a fully efficacious dose of ciproxifan (3mg/kg). These doses of A-349821 were without effect on spontaneous locomotor activity. Thus, A-349821 is a novel, selective non-imidazole H3 antagonist/inverse agonist with balanced high potency across species and favorable cognition enhancing effects in rats.     

Repositioning of charged I-II loop amino acid residues within the electric field by beta subunit as a novel working hypothesis for the control of fast P/Q calcium channel inactivation

We have investigated the contribution of the Ca(v)beta subunits to the process of inactivation dependent of the I-II loop of Ca(v)alpha(2.1). Two amino acid residues located in the alpha1 interaction domain (AID) of the I-II loop of Ca(v)alpha(2.1) (Arg(387) and Glu(388)) have been directly implicated in voltage-dependent inactivation of this channel. Various point mutations of these residues disrupt the interaction between the I-II loop and the III-IV loop, and thereby modify the inactivation properties of the channel by accelerating its kinetics and shifting the steady-state inactivation curve towards hyperpolarized potentials. A similar disruption is produced by Ca(v)beta(4) subunit association with the I-II loop. Moreover, in the presence of Ca(v)beta(4) subunit, introducing negatively charged residues at positions 387 or 388 slows inactivation kinetics down, whereas introducing positive charges has the opposite effect. The shift of the steady-state inactivation curve is also amino acid charge-dependent. In contrast, mutation of Arg(387) or Glu(388) does not alter the differential regulation of the different Ca(v)beta isoforms on inactivation. These results suggest that the expression of Ca(v)beta(4) alters the contribution of charged residues at positions 387 and 388 to inactivation. We discuss these results with regard to the actual hypotheses on the mechanisms of calcium channel inactivation. We introduce the working concept that Ca(v)beta-subunits produce a conformational repositioning of charged AID residues within the electric field.     

The relationship between dorsal horn neurotransmitter content and allodynia in neuropathic rats treated with high-frequency transcutaneous electric nerve stimulation

Somers DL, Clemente FR. The relationship between dorsal horn neurotransmitter content and allodynia in neuropathic rats treated with high-frequency transcutaneous electric nerve stimulation. Arch Phys Med Rehabil 2003;84: 1575-83.Objective: To examine the relation between axon terminal neurotransmitter content in the dorsal horn and allodynia in neuropathic rats treated with high-frequency transcutaneous electric nerve stimulation (TENS).Design: A completely randomized experimental design. Two groups of rats received a chronic constriction injury to the right sciatic nerve, and 2 groups did not. The rats were either treated or not treated with TENS.Setting: Research laboratory.Animals: Adult male Sprague-Dawley rats (150-165g).Interventions: TENS was delivered daily for 1 hour to the chronic constriction injury rats or to the uninjured rats through self-adhesive electrodes applied to the skin innervated by the right dorsal rami of lumbar spinal nerves 1 to 6.Main Outcome Measures: Thermal and mechanical pain thresholds were assessed bilaterally in the hind paws of all rats twice before the chronic constriction injury surgery (baseline) and then 12 days after the surgery. An analogous time frame of assessment was used for rats that did not have chronic constriction injury surgery. Thermal and mechanical allodynia were expressed as difference scores between the pain thresholds of the right and left hind paws. These values were normalized to differences that existed between the 2 paws at baseline. The amino acid content of dorsal horn axon terminals was assessed bilaterally with high-pressure liquid chromatography, and values were normalized to wet weight.Results: The mean level of thermal and mechanical allodynia did not differ between the TENS-treated and untreated rats with chronic constriction injury. However, there was a significant relation between the dorsal horn, axon terminal content of glutamate (adjusted R²=.45, P<.01) and glycine (adjusted R²=.51, P<.005) and the magnitude of mechanical allodynia present in TENS-treated chronic constriction injury rats, but not in any other group. As axon terminal glutamate and glycine decreased in the right dorsal horn and increased in the left, mechanical allodynia was reduced or absent. When this trend was reversed, mechanical allodynia was more severe. Daily TENS also reduced the mean axon terminal content of aspartate, glutamate, and glycine bilaterally in the chronic constriction injury rats from the level observed in untreated neuropathic rats (P<.05).Conclusion: The variability in responsiveness of mechanical allodynia to daily TENS treatment in neuropathic rats is related to the axon terminal content of glutamate and glycine in the dorsal horn. These findings may help explain a similar variability in humans when TENS is used to treat neuropathic pain.     

Bi-directional migration of lens epithelial cells in a physiological electrical field

An endogenous electric field (EF) exists in the vertebrate lens, but the influences of this on the functions of lens epithelial cells (LECs) are unclear. Because LECs from different regions experience different patterns of endogenous EFs and show striking differences in morphology and function, bovine LECs from different regions were cultured in an applied EF to mimic that occurring naturally. The migration of LECs from central and peripheral regions was both stimulated and directed by an applied EF. Field-directed cell migration required serum, or growth factors. Cells cultured in serum free medium lost directed migration completely and this was restored partially by the addition of basic fibroblast growth factor. The direction of cell migration depended on both EF-strength and the origin of the LECs. Both central and peripheral LECs moved anodally at 150-250mVmm(-1). In a low EF (50mVmm(-1)), peripheral LECs migrated in the opposite direction, cathodally, but central LECs did not respond. Peripheral LECs alone therefore showed field strength dependent, bi-directional migration. A physiological EF enhanced activation of ERK1/2, a signaling molecule in the MAP kinase pathway, and this also required serum. Interestingly, expression of active ERK1/2 was enhanced in peripheral LECs at both 50 and 200mVmm(-1), which stimulated migration in different directions. In central LECs, which showed directed migration only at higher EFs, active ERK1/2 was increased only at 200mVmm(-1). The MAP kinase inhibitor U0126 prevented activation of ERK1/2 in LECs and inhibited EF-directed migration, implicating MAP kinase signaling in directing the migration of LECs in a physiological EF.     

Impact of rectal distention on the results of evaluations of lower urinary tract sensation

PURPOSE: To our knowledge no systematic studies have been performed in humans to test the interaction of normal bladder and rectal sensory function. However, symptoms affecting the different pelvic viscera often coexist. MATERIALS AND METHODS: In 15 healthy female volunteers sensations of bladder filling were evaluated during 2 consecutive cystometric studies, including 1 with an empty rectum and 1 with a full rectum. Similarly the electrical perception threshold was determined in the bladder when the rectum was empty and again when the rectum was full. RESULTS: Rectal distention did not change bladder compliance during filling. When the rectum was distended, sensations of bladder filling were reported at smaller volumes. On the other hand, electrical perception thresholds in the bladder were higher when the rectum was full. CONCLUSIONS: The state of the rectum significantly influences the sensations of bladder filling and electrical bladder stimulation. These results show that before sensory testing of the bladder rectal fullness should be examined and if necessary the rectum should be emptied. The different effect of rectal distention on filling and electrical sensations represents an additional argument for different innervation of the 2 sensations in the lower urinary tract.     

经尿道电切术治疗女性膀胱颈部梗阻36例

目的探讨经尿道膀胱颈部电切术治疗女性膀胱颈梗阻的疗效。方法回顾性分析采用经尿道电切术治疗的36例女性膀胱颈部梗阻患者的临床治疗情况。结果术后生活质量指数、排尿症状评分、最大尿流率(Qmax)、平均尿流率(AFR)、尿量均得到显著改善,无严重并发症发生。随访期间疗效稳定,上述指标无显著变化,膀胱镜复查未有异常发现。结论经尿道膀胱颈部电切术治疗女性膀胱颈梗阻具有安全、效果好、创伤小的优点,是首选手术方法。