Silver Ring Research Articles

Light-driven circular plasmon current in a silver nanoring

A circular plasmon current in a silver nanoring is demonstrated and investigated with electrodynamics theory. The circular current is driven by the incident plane electromagnetic wave. For a silver ring with a thickness of 50 nm and inner and outer diameters of 200 and 300 nm, the circular current can be obtained when the incident wavelength is at 650 nm, which is about twice the diameter of the ring. The circular current can be observed only when the incident wave and the polarization directions are both parallel to the ring plane. The resonance wavelength shifts to red with the expansion of the ring diameter and the drop in the ring thickness. The discovery holds promise for the design of artificial materials with negative refractive index in the visible wavelengths and might stimulate new ideas for the development of nanoelectronic devices.

The renovated silver ring electrode in determination of lead traces by differential pulse anodic stripping voltammetry

The study of a new type of working electrode – the renovated silver ring electrode (RSRE) – for lead ions detection via differential pulse anodic stripping voltammetry (DP ASV) without removal of oxygen is reported. The only four constituents of the RSRE: a specially constructed silver ring electrode, a silver sheet used as silver counter/quasi-reference electrode and a silicon O-ring, are fastened together in a polypropylene body. The renovation of this electrode is carried out through mechanical removal of solid contaminants and electrochemical activation in the electrolyte which fills the RSRE body. Excellent repeatability and reproducibility – also in organic samples solutions – were reached in a period of a few weeks through the renovation of the electrode surface before each measurement. The reduction and stripping of lead on silver electrode under the DP ASV conditions are underpotential deposition/dissolution phenomena. The RSRE is used for the determination of Pb ions in concentrations ranging from 1 × 10 −9 to 1 × 10 −7 M. The repeatability of DP ASV runs in synthetic solutions covering the entire concentration range is better than 2%. Obtained calibration curves are represented by a correlation coefficient of at least 0.999. The detection limit (LOD) for the time of electrodeposition equal to 60 s is 0.2 × 10 −9 M. LOD for Pb 2+ detection at the RSRE is similar to this reported for a rotating silver electrode in subtractive anodic stripping voltammetry (E. Kirowa-Eisner, et al., Anal. Chim. Acta, 385 (1999) 325). The analysis of Pb 2+ in synthetic solutions with and without surfactants, certified reference materials and natural water samples have been performed.

Emmett Till’s Ring

On July 13, 1945, Mamie Till received a telegram at her home in Argo, Illinois, notifying her that her estranged husband, Private Louis Till, had been killed in Italy.1 The Department of Defense subsequently sent her his personal effects, including a silver ring he had bought in Casablanca, engraved with his initials and a date, May 25, 1943. During the following ten years, their son, Emmett Till, would occasionally try on his father's ring. Since Emmett was only four when Louis Till was killed, the ring was always too large for him. But in mid-August 1955, as he packed for what was to have been a two-week visit with relatives in Money, Mississippi, he tried the ring on again. Still too big for his ring finger, it now fit the middle finger perfectly. Emmett and his mother agreed that he could wear the ring on his trip to show his cousins and his friends. In her memoir, Death of Innocence: The Story of the Hate Crime that Changed America, written with Christopher Benson, Mamie Till-Mobley recalls that during the conversation about the ring, Emmett asked her about his father: We had talked about the fact that his father was a soldier in World War II and that he had been killed overseas. The only thing I could tell him at that point was the only thing I was told by the army. The cause of death, I explained to Emmett, was I didn't know what that meant, and when I tried to find out, I never got a satisfactory answer from the army. A lawyer and friend, Joseph Tobias, had tried to help in 1948. But he was told by the Department of the Army there would be no benefits for me due to the willful misconduct. (TillMobley and Benson 2003, 103) This incident occurs at the point in the narrative when Emmett's mother has begun to realize that her little boy is becoming an adult. In the preceding pages, she describes his heightened sense of responsibility, his first date, his impromptu driving lessons, his insistence on vacationing with his cousins instead of traveling with her, her hopes for his future. By giving Emmett his father's ring, she thus acknowledges his growing independence and maturity. Furthermore, she binds him symbolically to his paternity and his patrimony, despite the fact that irreconcilable differences had torn his parents' marriage apart. As he boarded the train called the City of New Orleans on Saturday, August 20, at Central Station, Chicago, Emmett kissed his mother goodbye and gave her his wristwatch to keep, telling her he wouldn't need it in Mississippi. Although he removed his watch, he decided to wear the ring. Eleven days later, on Wednesday, August 31, Robert Hodges, a seventeen-year-old white fisher, discovered Emmett's mutilated body floating in the Tallahatchie River, even though his murderers-J.W. Milam and Roy Bryant-had tied a cotton gin fan around his neck in hopes of weighing him down.2 For allegedly whistling at-or saying something inappropriate to-Bryant's wife, Carolyn, in their store, Emmett had been killed. According to his mother's description, his tongue had been choked out of his mouth and left hanging onto his chin. His right eyeball was resting on his cheek. Only two of his teeth remained in his mouth, and the bridge of his nose had been broken. His right ear had been cut almost in half and one of his murderers had taken a hatchet and cut through the top of his head from ear to ear. He had also been shot through the head (Till-Mobley and Benson 2003, 135-36). Given its condition, it is thus little wonder that Tallahatchie County sheriff H.C. Strider scrambled to get Emmett's body buried in Mississippi as quickly as possible. He and other local law enforcement officials wanted to try to minimize the impact of a heinous crime that had already captured national attention. Once Emmett's mother, then known as Mamie Bradley, learned that plans were being made to bury her son in Mississippi, however, she insisted that he be returned to Chicago. …

The renovated silver ring electrode

In this preliminary note, a new type of working electrode – the renovated silver ring electrode (RSRE) – is presented. The main constituents of the RSRE: a specially constructed silver ring electrode, a silver sheet used as silver counter/quasi-reference electrode and a silicon O-ring are fastened together in a polypropylene body. The renovation of this electrode is carried out through mechanical removal of solid contaminants and electrochemical activation in the electrolyte which fills the RSRE body. The effectiveness of the renovation procedure was tested by designating the RF and E pzc and by recording C d– t curves. As shown on selected examples, RSRE exhibits good performance in underpotential deposition stripping voltammetry (UPD-SV) applied for the determination of Pb(II) traces in certified reference materials.

Simple Fabrication of a Silver Epoxy Coated Microelectrode for SECM Imaging in Small Volumes

This work describes a simple and practical way to fabricate a dual Pt-microelectrode/silver quasi-reference electrode, (ME/AgQRE). These dual electrodes are particularly useful in small volume electrochemical experiments and scanning electrochemical microscope (SECM) applications. The ME/AgQRE consists of a silver ring, formed with a conductive silver epoxy around a glass support, which insulates a Pt-microwire, which acts as a disk microelectrode. The performance of the ME/AgQRE was evaluated using cyclic voltammetry and sample volumes as small as one microliter. These results were also compared with voltammograms performed in solutions of about 50 mL with a standard reference electrode (Ag/AgCl) as well as a with silver wire quasi-references electrode. In addition, the ME/AgQRE was used to acquire SECM images of a 25 μm-diameter Pt substrate, immersed in a solution containing 2 mM KI in 0.1 M NaCl. Approach curves and line scans (in feedback mode) showed significant advantages of these electrodes.

Ligand and Counterion Control of Ag(I) Architectures: Assembly of a {Ag8} Ring Cluster Mediated by Hydrophobic and Ag···Ag Interactions

A strategy combining ligand design and counterion variation has been used to investigate the assembly of silver(I) complexes. As a result, dinuclear, octanuclear, and polymeric silver(I) species have been synthesized by complexation of the rigid aliphatic amino ligands cis-3,5-diamino-trans-hydroxycyclohexane (DAHC), cis-3,5-diamino-trans-methoxycyclohexane (DAMC), and cis-3,5-diamino-trans-tert-butyldimethylsilylanyloxycyclohexane (DATC) with silver(I) triflate, nitrate, and perchlorate. The compositions of these aggregates, established by X-ray crystallography and elemental analysis, are [{Ag(DAHC)}2](CF3SO3)2 (1), [{Ag(DAMC)}2](CF3SO3)2 (2), [{Ag(DAMC)}2](NO3)2 (3), [{Ag(DATC)}6{Ag(DAHC)}2](NO3)8 (4), and [{Ag(DATC}n](NO3)n (5), where the DAHC present in 4 is formed by in situ hydrolysis of the acid labile silyl ether group. The type of aggregate formed depends both upon the noncoordinating O-substituent of the ligand and the (also noncoordinating) counterion, with the normal preference of the ligand topology for forming Ag2L2 structures being broken by introduction of the bulky, lipophilic O-tert-butyldimethylsilyl (TBDMS) group. Of particular note is the octanuclear silver ring structure 4, which is isolated only when both the O-TBDMS group and the nitrate counteranion are present and is formed from four Ag2L2 dimers connected by Ag...Ag and hydrogen-bonding interactions. Diffusion rate measurement of this {Ag8} complex by 1H NMR (DOSY) indicates dissociation in CD3OD and CD3CN, showing that this supramolecular ring structure is formed upon crystallization, and establishing a qualitative limit to the strength of Ag...Ag interactions in solution. When solutions of the {Ag8} cluster in methanol are kept for several days though, a new UV-vis absorption is observed at around 430 nm, consistent with the formation of silver nanoparticles.

Damage to the bladder neck alters autonomous activity and its sensitivity to cholinergic agonists

To identify and describe changes to the motor component of the motor/sensory system, which contributes to sensation during the filling phase of the micturition cycle, as a result of surgically induced bladder pathology, i.e. damage to the bladder neck and outlet obstruction. Adult male guinea pigs (294-454 g) were assigned initially into three groups: (i) normal guinea pigs with no surgical intervention (control, seven); (ii) guinea pigs which, with full surgical anaesthesia, had a silver ring implanted around the bladder neck (obstructed, 13); and (iii) guinea pigs operated to expose the bladder neck but with no implantation of a ring (sham, six). At 2-4 weeks after surgery the bladders were isolated, weighed and the pressure recordings used to identify autonomous activity. The bladder weights in all operated groups, including the sham, were greater than controls. Bladder weights in the obstructed guinea pigs varied considerably, reflecting the degree of pathological change. Consequently, bladders from this group were divided into those with high (OBH) and those with low bladder weight (OBL). The mean (sd) amplitudes of the autonomous contractions were 1.1 (0.1), 10.8 (1.8), 11.4 (2.5) and 17.1 (4.0) cmH(2)O in control, sham, OBL and OBH bladders, respectively, indicating a progressive alteration in function with the pathology. The changes in the sham group suggested that the pathological changes were not the result of obstruction but damage to the bladder neck, the implantation of the silver rings exacerbating the damage. There were episodes of rapid phasic activity (bursts) in 10 of 13 of the ring-implanted bladders, and in two of six in the sham group, but never in controls. Neither the autonomous activity nor the bursts were affected by tetrodotoxin (1 microm) or atropine (3 microm) but they were abolished by noradrenaline (3 microm). In control bladders, adding the muscarinic agonist arecaidine produced a transient acceleration of phasic activity and increased the amplitude of the contractions. There was a similar acceleration of activity in all the operated groups but the concentrations needed to achieve an increase in frequency were significantly lower, the relative sensitivity to arecaidine being OBH >/= OBL > sham > control. The mechanism involved in controlling the frequency of the motor component of the motor/sensory system, the 'pacemaker', appears to become progressively 'supersensitive' to cholinergic stimulation with the development of pathology. These observations are discussed in relation to the motor/sensory system and the origins of sensation in the bladder. The argument is proposed that damage to the bladder neck, not obstruction per se, results in altered nonmicturition activity which contributes to increased afferent output. In turn this contributes to the increased sensations of urge associated with bladder dysfunction. The cholinergic regulation of this altered 'pacemaker' might be the target for one of the therapeutic actions of anticholinergic drugs.

The Effect of Oxybutynin on Structural Changes of the Obstructed Guinea Pig Bladder

Oxybutynin is used clinically to lower intravesical pressure and detrusor overactivity. In vitro it inhibits stretch induced bladder smooth muscle cell proliferation. We tested whether oxybutynin also prevents hypertrophic bladder changes in vivo in a model of partial bladder obstruction. Subvesical obstruction was induced in immature guinea pigs by a silver ring around the urethra. Eight animals received 0.4 mg oxybutynin per kg body weight per day in 2 doses. Control groups were obstructed without oxybutynin treatment or sham operated. Urodynamic pressure flow studies were performed at 1-week intervals for 10 weeks in all animals under anesthesia with ketamine/xylazine. After 10 weeks the animals were sacrificed and the bladder was removed for structural analysis with periodic acid-Schiff stain, in which the number of glycogen granules was also scored as a measure of previous ischemia. Compared to the sham treated group obstructed animals had significantly higher intravesical pressure and detrusor overactivity, lower compliance and increased contractility. Obstructed animals that received oxybutynin retained normal intravesical pressure, detrusor overactivity and compliance. Their bladder contractility increased as in obstructed animals. The oxybutynin group showed less collagen infiltration in the detrusor and fewer glycogen granules compared to those in obstructed animals. Our results demonstrate that oxybutynin has a protective effect on bladder function and structure. Prevention of hypertrophic and ischemic bladder changes is an argument for an early start of oxybutynin treatment in children with inborn neurogenic bladder dysfunction, such as spina bifida, or in patients with urethral valves.

Detrusor glycogen reflects the functional history of bladders with partial outlet obstruction

To assess the relationship between glycogen content in bladder detrusor tissue and historical bladder function in a guinea-pig model of partial bladder outlet obstruction (PBOO). In male immature guinea pigs PBOO was created with a silver ring around the proximal urethra; a control group had a sham operation for comparison. Longitudinal individual urodynamic data were obtained weekly, so that guinea pigs were killed at different levels of bladder dysfunction. Bladder sections were stained with periodic acid-Schiff (PAS) to assess overall morphology and glycogen granule density, scored from 0 (no glycogen) to 3. Glycogen scores were related to both the end-stage and historical extremes of bladder function values. Glycogen granules were seen only in the detrusor; as their number increased their location expanded from only close to the serosa (glycogen score 1), through the detrusor (score 2) up to the urothelium (score 3). A glycogen score of 0 correlated with normal values for all urodynamic variables. Compared with a glycogen score of 0 a score of 1 correlated with significant (P < 0.05) changes in end-stage compliance (decrease) and contractility (increase) and significantly higher historical values for contractility, pressure and number of unstable contractions (NUC). In the group with a glycogen score of 2 there were significant changes in both the end-stage values and historical extremes for compliance, pressure, contractility and NUC (all P < 0.05). In the group with a glycogen score of 3 all these changes were even more dramatic, except for the end-stage contractility, for which the increase was not significant. From glycogen score 0 to score 3 all changes increased in magnitude. A high glycogen content reflects a history of abnormal urodynamic function. This finding exemplifies the added value of structural analysis to urodynamic studies. Further studies are needed to relate bladder structure to the potential for functional recovery.

The Reduction Welding Technique Used in Pre-Columbian Times: Evidences from a Silver Ring from Incallajta, Bolivia, Studied by Microscopy, SEM-EDX and PIXE

AbstractA pre-Columbian silver ring from Incallajta, Bolivia, recovered from an archaeological excavation is composed of a thin sheet of silver bent to form the ring. Two small wires in the shape of the infinity sign are joined to the surface of the ring. Four green stone beads were laid inside the four cavities formed by the wires. Energy dispersive spectroscopy (EDX) and Particle Induced X-rays Emission (PIXE) analyses of the beads proved that they were turquoise. Examination with a stereoscopic binocular microscope indicated that the two wires could have been soldered to the ring by reduction welding, because copper corrosion products were found in the interface of the welding, similar to those seen on two modern silver objects from Indonesia, decorated with granulation. Since reduction welding is a technique not reported before in pre-Columbian metallurgy, further analyses were carried out to prove that it was used here. Thus, the ring was analyzed with Scanning Electron Microscopy (SEM-EDX) and external beam PIXE, showing with certainty that the copper content in the area of the welding was higher than in any other part of the ring, with increasing copper amounts towards the center of the weld.

Mapping slow waves and spikes in chronically instrumented conscious dogs: implantation techniques and recordings

Myoelectric recordings from the intestines in conscious animals have been limited to a few electrode sites with relatively large inter-electrode distances. The aim of this project was to increase the number of recording sites to allow high-resolution reconstruction of the propagation of myoelectrical signals. Sets of six unipolar electrodes, positioned in a 3x2 array, were constructed. A silver ring close to each set served as the reference electrodes. Inter-electrode distances varied from 4 to 8 mm. Electrode sets, to a maximum of 4, were implanted in various configurations allowing recording from 24 sites simultaneously. Four sets of 6 electrodes each were implanted successfully in 11 female Beagles. Implantation sites evaluated were the upper small intestine (n=10), the lower small intestine (n=4) and the stomach (n=3). The implants remained functional for 7.2 months (median; range 1.4-27.3 months). Recorded signals showed slow waves at regular intervals and spike potentials. In addition, when the sets were positioned close together, it was possible to re-construct the propagation of individual slow waves, to determine their direction of propagation and to calculate their propagation velocity. No signs or symptoms of interference with normal GI-function were observed in the tested animals. With this approach, it is possible to implant 24 extracellular electrodes on the serosal surface of the intestines without interfering with its normal physiology. This approach makes it possible to study the electrical activities of the GI system at high resolution in vivo in the conscious animal.

Silver Ring Splints improve dexterity in patients with rheumatoid arthritis

To study the effect of Silver Ring Splints (SRSs) on hand function in patients with rheumatoid arthritis (RA). RA patients with stable disease and finger deformities eligible for splinting received 1 or more SRSs. Primary outcome was dexterity, which was measured with the Sequential Occupational Dexterity Assessment (SODA). Secondary outcome measures were self-reported hand function (Dutch Arthritis Impact Measurement Scales 2), hand pain, grip and pinch strength, Disease Activity Score in 28 joints (DAS28), and patient satisfaction. Seventeen patients (median age 65 years; median disease duration 21 years) received a total of 72 SRSs. After 1 year, 48 SRSs were regularly used. Two patients dropped out because of adverse events related to SRSs. In the remaining 15 patients, SODA dexterity scores increased significantly (median 71 at baseline, 81 at 3 months, and 85 at 12 months), Wilcoxon signed ranks test P=0.005 and P=0.026. DAS28 scores did not change at 3 months and improved slightly after 12 months (-0.5; P=0.019). Grip strength, self-reported hand function, and hand pain showed no significant changes. Eleven patients stated they would continue using their splints. SRSs can improve dexterity in selected patients with rheumatoid hand deformities. For a satisfactory result, careful patient preassessment and optimal adjustment of SRSs are essential.

A wide-aperture Pockels cell with three ring electrodes

A wide-aperture Pockels cell based on a DKDP crystal having an optical diameter of 70 mm is studied. Three silver ring electrodes deposited on the side surface of the crystal were used to apply a high-voltage rectangular pulse of variable duration from 50 to 150 ns to the cell. Chains of KT6117A (2N5551) transistors operating in the avalanche regime served as fast electron switches. The duration of the leading and trailing edges of the pulse formed by these switches did not exceed 15 ns. The nonuniformity of the transmission coefficient over the cross section of the cell caused by the inhomogeneity of the electric field inside the crystal was close to 3.5%.

Urodynamic follow-up of experimental urethral obstruction in individual guinea pigs.

It is unknown whether changes in bladder function due to urethral obstruction follow a specific sequence. To answer this, we adapted a small animal model to allow repeated complete pressure-flow studies, enabling individual follow-up of changes in bladder function on urethral obstruction. Obstruction was induced in guinea pigs by placing a silver ring around the urethra. Urodynamic studies were repeated under anesthesia with ketamine/xylazine. Bladders were filled and bladder pressure measured through a single suprapubic catheter. Urine flow rate was measured using an ultrasound probe around the penis. Accurate measurements of bladder pressure and urine flow rates were obtained at 1-week intervals for 11 weeks in individual guinea pigs. In the control animals, the urodynamic parameters did not show significant changes. In the obstructed group, urethral resistance (P(low,ave)) increased from 20 to 35 cm H(2)O after 4 weeks and remained at that level. The maximum flow rate (Q(max)) increased from 0.17 to 0.24 mL/s after 2 to 3 weeks. After this peak, it gradually decreased to lower than the starting value after 10 to 11 weeks. The pressure at maximum flow rate (p(Qmax)) increased from 24 to 47 cm H(2)O after 6 to 7 weeks and thereafter declined. During weeks 1 through 4 of obstruction, unstable contractions were seen. All animals followed a similar sequence of patterns but at variable rates. Our animal model allows complete urodynamic follow-up of individual animals with urethral obstruction. We observed a specific sequence of changes in urodynamic patterns and parameters of bladder function.

CHANGES IN BLADDER CONTRACTILITY AND COMPLIANCE DUE TO URETHRAL OBSTRUCTION: A LONGITUDINAL FOLLOWUP OF GUINEA PIGS

Purpose: We established the longitudinal changes in bladder contractility and compliance as a result of urethral obstruction using a guinea pig model.Materials and Methods: Obstruction was induced in guinea pigs by a silver ring around the urethra. Urodynamic studies were performed longitudinally in individual animals. Bladder contractility and compliance were calculated from the measured bladder pressure and urine flow rate.Results: Bladder contractility developed in distinct phases. It reached a maximum 200% increase after an average of 3.25 weeks concomitant with an almost 2-fold increase in urethral resistance, remained 150% to 200% increased during weeks 4 to 7 and then decreased to starting levels again, while urethral resistance remained almost 2-fold increased. Bladder compliance decreased by 80% during the first 3 weeks and continued to decrease to 5% of its original value after 10 to 11 weeks.Conclusions: Our data indicate that as a result of obstruction bladder function passes through a specifi...

Changes in bladder contractility and compliance due to urethral obstruction: a longitudinal followup of guinea pigs.

We established the longitudinal changes in bladder contractility and compliance as a result of urethral obstruction using a guinea pig model. Obstruction was induced in guinea pigs by a silver ring around the urethra. Urodynamic studies were performed longitudinally in individual animals. Bladder contractility and compliance were calculated from the measured bladder pressure and urine flow rate. Bladder contractility developed in distinct phases. It reached a maximum 200% increase after an average of 3.25 weeks concomitant with an almost 2-fold increase in urethral resistance, remained 150% to 200% increased during weeks 4 to 7 and then decreased to starting levels again, while urethral resistance remained almost 2-fold increased. Bladder compliance decreased by 80% during the first 3 weeks and continued to decrease to 5% of its original value after 10 to 11 weeks. Our data indicate that as a result of obstruction bladder function passes through a specific sequence of stages, including first a compensatory increase in contractility, then a stabilization phase and finally a decompensation state. In contrast bladder compliance shows a continuous decrease. The data suggest that for assessing how far a bladder has deteriorated due to obstruction a combination of functional and structural data may be warranted.

End-to-side microvascular anastomosis using an external metal ring

Enthusiasm for developing safer and faster anastomotic techniques and complementary devices continues. We report on a new microvascular end-to-side anastomosis technique using a silver ring around the anastomotic circumference. The purpose of this study was to compare the effectiveness of this technique with conventional end-to-side vessel anastomosis. Forty Sprague-Dawley rats were divided into two groups. Twenty rats were used to assess the external ring method in end-to-side anastomosis between carotid arteries and anterior jugular veins and the remaining 20 formed the control group with conventional end-to-end anastomosis. The anastomosis time was 26.4 min for standard suture anastomosis and 18.4 min for the external ring technique (P< 0.01). Patency was 95% with standard technique and 100% using the external ring (P> 0.05). The external ring technique of end-to-side microvascular anastomosis is a safe and reliable method and may reduce the operation time. Its clinical applicability should be further evaluated.

Analysis of the contractions evoked by sympathetic nerve stimulation, and thermal effect on the guinea-pig vas deferens--study as a model for the thermotherapy of benign prostatic hyperplasia

The present study was designed to investigate the mechanism of thermotherapy on benign prostatic hyperplasia (BPH), using the guinea-pig vas deferens as a model for BPH. The components of contractions elicited by electrical field stimulation and nicotine were analyzed, and the thermal effect on the vas deferens was examined. The vas deferens was dissected, suspended vertically through two silver ring electrodes, and attached to an isometric transducer. The electrical stimulation of 10 constant current pulses (10 mA) with 0.3 msec in duration of 5, 10, and 40 Hz was achieved under air-gap condition. Drugs were added directly to a 5 ml Magnus tube containing Tyrode solution (36 degrees C) gassed with a 95% O2-5% CO2 mixture. The components of contractions evoked by electrical stimulation and nicotine were investigated by tetrodotoxin (TTX), and blocking agents of alpha 1-adrenoceptors and/or purinoceptors. Thermal effect on electrically evoked contractions was examined at incubation temperature of 25 degrees C (control), 43 degrees C, 45 degrees C, 46 degrees C and 47 degrees C for 1 hour. Nicotine (200 microM) elicited biphasic contractions, which were triggered by corelease of noradrenaline (NA) and ATP (N-ATP) from sympathetic nerve terminals by activation of prejunctional nicotine receptors. NA and N-ATP caused the corresponding contractions, alpha 1 and N-ATP components, respectively. Combined application of prazosin (1 microM) and suramin (50 microM) abolished these contractions. Activation of post-junctional alpha 1-adrenoceptors by NA caused release of ATP from muscle cells to produce the contraction (alpha 1-ATP component), which was sensitive to both suramin and prazosin. N-ATP and alpha 1 components attributed to fast and slow part of the contraction, respectively. Electrical field stimulation caused biphasic contractions which consisted of both neurogenic (TTX-sensitive) and non-neurogenic (TTX-insensitive) components. An increase in stimulation frequency (5 to 40 Hz) increased the neurogenic components, which contained alpha 1 and N-ATP components, as well as the case of nicotine. The non-neurogenic components consisted of alpha 1-ATP, muscle-derived ATP (m-ATP) and unknown substance 'X' components. Nifedipine (10 microM). L-type Ca2+ channel blocker, markedly reduced the contractions induced by bath applied phenylephrine (alpha 1-agonist, 100 microM) but only partially blocked the contractions produced by bath applied ATP (500 microM). The contractile force in amplitude and neurogenic components induced by electrical field stimulation did not change at 43 degrees C, but both declined significantly above 45 degrees C. The neurogenic components at 45 degrees C and 46 degrees C were suppressed to 22 +/- 6% and 14 +/- 3% (mean +/- SD) of control, respectively. All the contractile responses were abolished at 47 degrees C. The contractions of the guinea-pig vas deferens evoked by electrical field stimulation consisted of alpha 1, N-ATP, alpha 1-ATP, m-ATP and X components. Sympathetic nerve fibers in the muscles were completely inactivated by thermal exposure at 47 degrees C for 1 hour. The results suggest that the minimal temperature for thermotherapy of BPH should be 47 degrees C.

Asymptomatic Blue Nevus—like Macule

<h3>REPORT OF A CASE</h3> A 38-year-old woman presented with a 18-year history of a pigmented lesion located on the dorsal aspect of the proximal phalange of the left ring finger. It had slowly enlarged but was asymptomatic, and the patient had no other medical complaints except for her concerns about the cosmetic appearance of her skin. Her medical history revealed that at the age of 19 years she had had a tragic accident, after which her silver ring was embedded in her skin. She was subsequently operated on, and the surgery left her with a little scar. One year later she observed a bluish macule surrounding her scar. On physical examination, we saw a blue-gray oval macule, 1 cm in diameter, with a little scar in the middle. The macule had a smooth surface and was firm and mobile, with clinical features similar to those of a blue nevus

Accelerating fronts in an electrochemical system due to global coupling.

We examine spatiotemporal patterns during the reduction of peroxodisulfate to sulfate at silver ring electrodes in an electrochemical cell. The reaction displays bistable behavior in the current-voltage characteristics under potentiostatic conditions. The two stable states are characterized by different voltage drops across the double layer. We investigate transitions in the bistable region between the different states. Spatiotemporally resolved measurements of the voltage drop across the electrode-electrolyte interface show that the transition occurs via fronts. We are able to trigger these fronts by local perturbations of the electric field and thus to examine their dependence on operating parameters. It is shown that the movement of the fronts results from migration currents (movement of ions due to the electric field), and hence the system is described by reaction-migration-diffusion equations. The velocity of the fronts increases with time; hence they are accelerated. This contrasts with usual front solutions of reaction-diffusion systems, which possess a constant velocity in one-dimensional geometries. This acceleration is shown to be a consequence of a global, or more precisely nonlocal, coupling mediated through the electric field.