Anti-hyperalgesic effects of anti-serotonergic compounds on serotonin- and capsaicin-evoked thermal hyperalgesia in the rat.

The peripheral serotonergic system has been implicated in the modulation of an array of pain states, from migraine to fibromyalgia; however, the mechanism by which serotonin (5HT) induces pain is unclear. Peripherally released 5HT induces thermal hyperalgesia, possibly via modulation of the transient receptor potential V1 (TRPV1) channel, which is gated by various noxious stimuli, including capsaicin. We previously reported in vitro that 5HT increases calcium accumulation in the capsaicin-sensitive population of sensory neurons with a corresponding increase in proinflammatory neuropeptide release, and both are antagonized by pretreatment with 5HT(2A) and 5HT(3) antagonists, as well as the anti-migraine drug sumatriptan. In the current study, we extended these findings in vivo using the rat hind paw thermal assay to test the hypothesis that peripheral 5HT enhances TRPV1-evoked thermal hyperalgesia that can be attenuated with 5HT(2A) and 5HT(3) receptor antagonists, as well as sumatriptan. Thermal hyperalgesia and edema were established by 5HT injection (0.1-10 nmol/100 µl) into the rat hind paw, and the latency to paw withdrawal (PWL) from noxious heat was determined. Rats were then pretreated with either 5HT before capsaicin (3 nmol/10 µl), the 5HT(2A) receptor antagonist ketanserin or the 5HT(3) receptor antagonist granisetron (0.0001-0.1 nmol/100 µl) before 5HT and/or capsaicin, or the 5HT(1B/1D) receptor agonist sumatriptan (0.01-1 nmol/100 µl) before capsaicin, and PWL was determined. We report that 5HT pretreatment enhances TRPV1-evoked thermal hyperalgesia, which is attenuated with local pretreatment with ketanserin, granisetron, or sumatriptan. We also report that peripheral 5HT induced a similar magnitude of thermal hyperalgesia in male and female rats. Overall, our results provide in vivo evidence supporting an enhancing role of 5HT on TRPV1-evoked thermal hyperalgesia, which can be attenuated by peripheral serotonergic intervention.

A comparative analysis of parvalbumin expression in pinfish (Lagodon rhomboides) and toadfish (Opsanus sp.).

This study examines the role of a myoplasmic protein, parvalbumin, in enhancing muscle relaxation by fishes. Parvalbumin is thought to bind free Ca(2+) during muscle contraction, thereby reducing intracellular [Ca(2+)] in muscle and speeding muscle relaxation by reducing Ca(2+) availability to the troponin complex. We hypothesized that parvalbumin expression is ubiquitously expressed in fish muscle and that its expression levels and role in muscle relaxation would depend on the activity level and the thermal environment of a given fish species. Muscle contractile properties and patterns of parvalbumin expression were examined in pinfish (Lagodon rhomboides) and two species of toadfish (gulf toadfish, Opsanus beta, and oyster toadfish, Opsanus tau). Unlike another sparid (sheepshead), the active swimming pinfish does not express parvalbumin in its slow-twitch red muscle. However, both sheepshead and pinfish have relatively high levels of parvalbumin in their myotomal white muscle. Gulf toadfish from the Gulf of Mexico expressed higher levels of parvalbumin and had faster muscle relaxation rates than oyster toadfish from more northern latitudes. The faster muscle of gulf toadfish also expressed relatively more of one parvalbumin isoform, suggesting differences in the binding properties of the two isoforms observed in toadfish swimming muscle. Parvalbumin expression and its role in muscle relaxation appear to vary widely in fishes. There are many control points involved in the calcium transient of contracting muscle, leading to a variety of species-specific solutions to the modulation of muscle relaxation.

Morphine preferentially activates the periaqueductal gray-rostral ventromedial medullary pathway in the male rat: a potential mechanism for sex differences in antinociception.

The midbrain periaqueductal gray (PAG), and its descending projections to the rostral ventromedial medulla (RVM), provide an essential neural circuit for opioid-produced antinociception. Recent anatomical studies have reported that the projections from the PAG to the RVM are sexually dimorphic and that systemic administration of morphine significantly suppresses pain-induced activation of the PAG in male but not female rats. Given that morphine antinociception is produced in part by disinhibition of PAG output neurons, it is hypothesized that a differential activation of PAG output neurons mediates the sexually dimorphic actions of morphine. The present study examined systemic morphine-induced activation of PAG-RVM neurons in the absence of pain. The retrograde tracer Fluorogold (FG) was injected into the RVM to label PAG-RVM output neurons. Activation of PAG neurons was determined by quantifying the number of Fos-positive neurons 1 h following systemic morphine administration (4.5 mg/kg). Morphine produced comparable activation of the PAG in both male and female rats, with no significant differences in either the quantitative or qualitative distribution of Fos. While microinjection of FG into the RVM labeled significantly more PAG output neurons in female rats than male rats, very few of these neurons (20%) were activated by systemic morphine administration in comparison to males (50%). The absolute number of PAG-RVM neurons activated by morphine was also greater in males. These data demonstrate widespread disinhibition of PAG neurons following morphine administration. The greater morphine-induced activation of PAG output neurons in male compared with female rats is consistent with the greater morphine-induced antinociception observed in males.

A hybrid equation for simulation of perfused tissue during thermal treatment.

Bio-heat equations (BHEs) are necessary for predicting tissue temperature during thermal treatment. For some applications, however, existing BHEs describe the convective heat transfer by the blood perfusion in an unsatisfactory way. The two most frequently used equations, the BHE of Pennes and the k(eff) equation, use for instance either a heat sink or an increased thermal conductivity in order to account for the blood perfusion. Both these methods introduce modelling inaccuracies when applied to an ordinary tissue continuum with a variety of vessel sizes. In this study, a hybrid equation that includes both an increased thermal conductivity and a heat sink is proposed. The equation relies on the different thermal characteristics associated with small, intermediate and large sized vessels together with the possibilities of modelling these vessels using an effective thermal conductivity in combination with a heat sink. The relative importance of these two terms is accounted for by a coefficient beta. For beta = 0 and beta = 1, the hybrid equation coincides with the BHE of Pennes and the k(eff) equation, respectively. The hybrid equation is used here in order to simulate temperature fields for two tissue models. The temperature field is greatly affected by beta, and the effect is dependent on, e.g. the boundary conditions and the power supply. Since the BHE of Pennes and the k(eff) equation are included in the hybrid equation, this equation can also be useful for evaluation of the included equations. Both these heat transfer modes are included in the proposed equation, which enables implementation in standard thermal simulation programmes.

Analysis of temperature measurement for monitoring radio-frequency brain lesioning.

During ablative neurosurgery of movement disorders, for instance therapy of Parkinson's disease, temperature monitoring is crucial. This study aims at a quantitative comparison of measurement deviations between the maximum temperature located outside the lesioning electrode and two possible thermocouple locations inside the electrode. In order to obtain the detailed temperature field necessary for the analysis, four finite element models associated with different surroundings and with different power supplies are studied. The results from the simulations show that both the power level and the power density as well as the surrounding medium affect the temperature measurement and the temperature field in general. Since the maximum temperature is located outside the electrode there will always be a deviation in time and level between the measured and the maximum temperature. The deviation is usually 2-7 s and 3-12 degrees C, depending on, for example, the thermocouple location and surrounding medium. Therefore, not only the measured temperature but also the relation between measured and maximum temperature must be accounted for during therapy and device design.

An audio- and speech-based interface for computer-controlled scientific instruments.

Laboratory instruments are intrinsic to research and work in a wide array of scientific fields. They are used for the control of devices, data storage, and data analysis. The control of instruments is increasingly changing from independent on-instrument controls to multiple instrument integrate software control. Unfortunately, the graphical representation of controls and data makes it difficult for an individual with a visual impairment to independently operate laboratory instruments. Alternative interfaces have been previously developed for these individuals but have often proved limited in scope and accuracy, or otherwise expensive. The resulting inaccessibility to affordable and accurate scientific instrumentation, unfortunately, discourages many individuals with a visual impairment from entering scientific fields of research or work. This paper introduces an alternative interface method developed for LabVIEW, National Instruments' instrumentation software package. The method is specifically designed for individuals with visual impairments, and uses alternative navigation techniques as well as audio feedback. The developed user interface uses simple keyboard inputs to traverse through a hierarchical tree-based menu system. Speech and audio tones are used to alert the user to system settings and errors, as well as a help mechanism and data analysis tool. At this time, alternative interfaces have been developed for the following basic laboratory instruments: an oscilloscope and function/arbitrary waveform generator. The interface methodology, however, can be extended to include any scientific instrument that can be controlled by LabVIEW.

A comparison between in vitro studies of protein lesions generated by brain electrodes and finite element model simulations.

The aim of this study was to develop a finite element model for simulation of the thermal characteristics of brain electrodes and to compare its performances with an in vitro experimental albumin model. Ten lesions were created in albumin using a monopolar electrode connected to a Leksell Neuro Generator and a computer-assisted video system was used to determine the size of the generated lesions. A finite element model was set up of the in vitro experiments using the same thermal properties. With a very simple heat source applied to the finite element model in the proximity of the upper part of the tip, a good agreement (no deviations in width and distance from tip but a deviation in length of -1.6 mm) with the in vitro experiments (width 4.6 +/- 0.1 mm and length 7.4 +/- 0.1 mm) was achieved when comparing the outline of the lesion. In addition, a gelatinous albumin-model was set up and compared to computer simulations resulting in deviations in width of -0.4 mm, length of -2.2 mm and distance from the tip of -0.1 mm. Hence, the utilisation of finite element model simulations may be a useful complement to in-vitro experiments.

Understanding continuous-wave Doppler signal intensity as a measure of regurgitant severity.

Continuous-wave Doppler signal intensity is commonly expected to reflect the severity of mitral regurgitation. Physical principles predict that alignment of the imaging beam, flow velocity, and turbulence can also be important or even dominant determinants of continuous-wave Doppler signal intensity. The reliability of tracking regurgitant severity with continuous-wave Doppler signal intensity was assessed in vitro with varying volume, velocity, turbulence, and beam alignment. The conditions wherein continuous-wave Doppler signal intensity increased with regurgitant volume were specific but poorly predictable combinations of orifice size, flow volume, and perfect beam alignment. Under other conditions flow velocity and turbulence effects dominated, and continuous-wave Doppler signal intensity did not reflect changing regurgitant volume. Continuous-wave Doppler signal intensity-based impressions of regurgitant severity may be unreliable and even misleading under some circumstances.

High throughput analysis and purification in support of automated parallel synthesis.

Rapid reverse-phase analytical and preparative HPLC methods have been developed for application to parallel synthesis libraries. Gradient methods, short columns, and high flow rates allow analysis of over 300 compounds per day on a single system, or purification of up to 200 compounds per day on a single preparative system. Hardware and software modifications allow continuous unattended use for maximum efficiency and throughput.

Thermal injury during TUMT.

A 71-year-old man was treated with transurethral microwave thermotherapy because of symptoms of benign prostatic hyperplasia. The treatment session was performed without any abnormal complaints from the patient. Two hours post-treatment the patient felt pain in his penile shaft and noticed a wound. A thorough investigation revealed that the only possible explanation for the injury was a dislocation of the catheter.

Heat transfer evaluation of the nasal thermistor technique.

When analyzing transvalvular and venous flow velocity patterns, it is important to relate them to respiration. An accurate recording of respiratory phase can be carried out with different methods. One of these methods is the use of a thermistor, which reacts to the variation in air temperature, placed in the noise of the patient. The thermistor used has a diameter for 1.0 mm and is of standard bead type. Although small, it has a considerable long time-constant and a long time-delay. The high time-constant gives a low cutoff frequency, well below the respiratory frequency and thereby causing a large phase difference. The thermistor was analyzed with the lumped heat capacity method, where it was easy to study the influence from design parameters, time-dependent air temperature, and velocity. The analysis was extended using the finite element method and the temperature field in the thermistor and the probe was calculated as a function of space and time. These calculations confirmed the result from the lumped model. The result showed that timing of respiration was not accurately obtained with the thermistor analyzed. To improve the timing, it was necessary either to change the measuring method or to use signal processing in order to achieve faster response.

Determination of regurgitant flow and volume by integrating actual proximal velocities over hemispheres (IPROV) in two orthogonal planes.

The proximal acceleration technique is a promising technique for quantification of regurgitant valve flow. Although the shape of the regurgitant proximal isovelocity field has been shown to vary with orifice size, geometry, and driving pressure, normally the centerline velocity alone is used for estimation of flow. In this model study of pulsatile flow, two-dimensional and spectral Doppler data were transferred digitally to a computer in which proximal velocity fields were corrected for time and angle errors. With the purpose of improving accuracy, flow was estimated by integrating proximal velocities over nonisovelocity spheric control surfaces in the best zone of measurement (0.15 to 0.45 m/sec at an angle up to +/- 45 degrees from the center line) in two perpendicular planes. Three regurgitant volumes in the range of 5 to 21 ml were studied for circular (diameters of 4, 6, and 8 mm), crescent, and diagonal orifices. The quotient between effective orifice area, estimated by dividing peak flow with peak velocity in the vena contracta, and true orifice area (Aeff = Q(tm)/Vo(tm)) was 0.66 (range 0.60 to 0.79), 0.50 (0.48 to 0.52), and 0.67 (0.66 to 0.68) for the circular, crescent, and diagonal orifices, respectively. Regurgitant volume estimated by multiplying effective orifice area by the velocity-time integral in the vena contracta (V = Aeff.velocity-time integral) ranged from 92% to 115% of the true volume for the circular, 89% to 92% for the crescent, and 105% to 112% for the diagonal orifices, respectively. It is possible to calculate regurgitant volume correctly with data acquisition from multiple hemispheres and planes and postprocessing of data. This amendment of the proximal acceleration technique has great advantage over the center-line method, especially when the orifice is asymmetric.

Comparison of angioscopy, intravascular ultrasound imaging and quantitative coronary angiography in predicting clinical outcome after coronary intervention in high risk patients.

OBJECTIVES: The purpose of this study was to identify qualitative or quantitative variables present on angioscopy, intravascular ultrasound imaging or quantitative coronary arteriography that were associated with adverse clinical outcome after coronary intervention in high risk patients. BACKGROUND: Patients with acute coronary syndromes and complex lesion morphology on angiography are at increased risk for acute complications after coronary angioplasty. Newer devices that primarily remove atheroma have not improved outcome over that of balloon angioplasty. Intravascular imaging can accurately identify intraluminal and intramural histopathologic features not adequately visualized during coronary arteriography and may provide mechanistic insight into the pathogenesis of abrupt closure and restenosis. METHODS: Sixty high risk patients with unstable coronary syndromes and complex lesions on angiography underwent angioscopy (n = 40) and intravascular ultrasound imaging (n = 46) during interventional procedures. In 26 patients, both angioscopy and intravascular ultrasound were performed in the same lesion. All patients underwent off-line quantitative coronary arteriography. Coronary interventions included balloon (n = 21) and excimer laser (n = 4) angioplasty, directional (n = 19) and rotational (n = 6) atherectomy and stent implantation (n = 11). Patients were followed up for 1 year for objective evidence for recurrent ischemia. RESULTS: Patients whose clinical presentation included rest angina or acute myocardial infarction or who received thrombolytic therapy within 24 h of procedure were significantly more likely to experience recurrent ischemia after intervention. Plaque rupture or thrombus on preprocedure angioscopy or angioscopic thrombus after intervention were also significantly associated with adverse outcome. Qualitative or quantitative variables on angiography, intravascular ultrasound or off-line quantitative arteriography were not associated with recurrent ischemia on univariate analysis. Multivariate predictors of recurrent ischemia were plaque rupture on preprocedure angioscopy (p < 0.05, odds ratio [OR] 10.15) and angioscopic thrombus after intervention (p < 0.05, OR 7.26). CONCLUSIONS: Angioscopic plaque rupture and thrombus were independently associated with adverse outcome in patients with complex lesions after interventional procedures. These features were not identified by either angiography or intravascular ultrasound.

Successful treatment of chronic total peripheral occlusions that failed conventional techniques using the stiff backend of the Glidewire.

The vast majority of failures of transcatheter interventions in patients with peripheral vascular disease are due to inability to cross the lesion with a guidewire. Although the use of the Glidewire has clearly improved the success rate, failures with especially chronic total occlusions still occur. We describe a new technique using the very stiff backend of the Glidewire, which we have found very successful, when conventional techniques fall in crossing highly resistant lesions.

Estimation of volume flow rate by surface integration of velocity vectors from color Doppler images.

A new Doppler echocardiographically based method has been developed to quantify volume flow rate by surface integration of velocity vectors (SIVV). Electrocardiographic-gated color Doppler images acquired in two orthogonal planes were used to estimate volume flow rate through a bowl-shaped surface at a given time and distance from the probe. To provide in vitro validation, the method was tested in a hydraulic model representing a pulsatile flow system with a restrictive orifice. Accurate estimates of stroke volume (+/- 10%) were obtained in a window between 1.2 and 1.6 cm proximal to the orifice, just before the region of prestenotic acceleration. By use of the Bernoulli's equation, the estimated flows were used to generate pressure gradient waveforms across the orifice, which agreed well with the measured flows. To demonstrate in vivo applicability, the SIVV method was applied retrospectively to the determination of stroke volume and subaortic flow from the apical three-chamber and five-chamber views in two patients. Stroke volume estimates along the left ventricular outflow tract showed a characteristic similar to that in the in vitro study and agreed well with those obtained by the Fick oxygen method. The region where accurate measurements can be obtained is affected by instrumental factors including Nyquist velocity limit, wall motion filter cutoff, and color flow sector angle. The SIVV principle should be useful for quantitative assessment of the severity of valvular abnormalities and noninvasive measurement of pulsatile volume flows in general.

Bio-acoustic signals from stenotic tube flow: state of the art and perspectives for future methodological development.

To study the degree of stenosis from the acoustic signal generated by the turbulent flow in a stenotic vessel, so-called phonoangiography was first suggested over 20 years ago. A reason for the limited use of the technique today may be that, in the early work, the theory of how to relate the spectrum of the acoustic signal to the degree of the stenosis was not clear. However, during the last decade, the theoretical basis for this and other biological tube flow applications has been clarified. Now there is also easy access to computers for frequency analysis. A further explanation for the limited diagnostic use of bio-acoustic techniques for tube flow is the strong competition from ultrasound Doppler techniques. In the future, however, applications may be expected in biological tube flow where the non-invasive, simple and inexpensive bio-acoustic techniques will have a definite role as a diagnostic method.

A bioacoustic method for timing of respiration at cardiac investigations.

At cardiac investigations Doppler echocardiography is an established technique for the recording of intracardial and intravascular flow velocities. Transvalvular and venous flows are, however, markedly influenced by respiration. Since the start of inspiration is the important time of reference, accurate recording of the respiratory phase is important when analysing these flow velocities. A bioacoustic technique was therefore adopted to meet this demand and was tested in 10 normal subjects. Oesophageal balloon technique was used as a reference, and the bioacoustic technique was compared with a respiratory inductive plethysmograph. The average delay for the acoustic sensor signal compared to the oesophageal pressure changes was 205 +/- 46 (SD) ms, ranging from 160 to 320 ms for normal breathing, and is comparable to that of the respiratory inductive plethysmograph (210 +/- 90 ms). The bioacoustic technique is easier to apply than the respiratory inductive plethysmograph. The sensitivity to disturbances can be further reduced by signal processing and the method has clinical potential for the future.

Regurgitant heart valve flow from 2-D proximal velocity field: continued search for the ideal method.

It has been suggested that flow through a leaking heart valve can be determined by studying the proximal velocity field. Normally, only the centre-line velocity is studied as a potential method. The aim of the study is to improve this method by using information from the entire reconstructed proximal velocity field. Four methods are compared: use of the centre-line velocity; use of velocities at three different angles; integration of velocities over a hemisphere; and integration of velocities over an estimated hemi-elliptical isovelocity line. Measurements are performed in a hydraulic model with 4, 6 and 8 mm circular orifices, and these are compared with those from computer simulation. From the results presented in the study, it is suggested that the velocities should be integrated over a hemisphere within a best zone. This zone is dependent on the instrument settings, but in this case it is positioned 1.2-1.4 orifice diameters from the orifice inlet, with an angle of up to +/- 45 degrees from the centre axis, and contains velocities in the range 0.15-0.45 ms-1.

Mathematical model that characterizes transmitral and pulmonary venous flow velocity patterns.

The transmitral and pulmonary venous flow velocity (TMFV and PVFV, respectively) patterns are related to the physiological state of the left heart by use of an electrical analog model. Filling of left ventricle (LV) through the mitral valve is characterized by a quadratic Bernoulli's resistance in series with an inertance. Filling of the left atrium (LA) through the pulmonary veins is represented by a lumped network of linear resistance, capacitance, and inertance. LV and LA are each represented by a time-varying elastance. A volume dependency is incorporated into the LV model to produce physiological pressure-volume loops and Starling curves. The state-space representation of the analog model consists of 10 simultaneous differential equations, which are solved by numerical integration. Model validity is supported by the following. First, the expected effects of aging and decreasing LV compliance on TMFV and PVFV are accurately represented by the model. Second, the model-generated TMFV and PVFV waveforms fit well to pulsed-Doppler recordings in normal and postinfarct patients. It is shown that the TMFV deceleration time is prolonged by the increase in LV compliance and, to a lesser extent, by the increase in LA compliance. A shift from diastolic dominance to systolic dominance in PVFV occurs when LA compliance or pulmonary perfusion pressure increases or when LV compliance or mitral valve area decreases. The present model should serve as a useful theoretical basis for echocardiographic evaluation of LV and LA functions.