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PubMed1986

In vitro colonization of thymic primordia by adult bone marrow cells: light scatter profile and separation by flow cytometry.

Adult mouse bone marrow showed a reproducible scatter profile on low angle vs. right angle scatter by flow cytometry and it was possible to sort cells from different regions of the profile. The colonization of the third pharyngeal pouch in vitro was used as a test of thymocyte precursors. Alleles of the Thy-1 surface antigen, as well as the nuclear chromatin pattern of the ichthyosis mutant, were used to monitor chimerism. Thymus-colonizing cells were found in one region of the scatter profile, and these cells were negative for Thy-1 and Ia markers.

Animals↗
PubMed1979

Simple computer quantitation of spleen-to-liver ratios in the diagnosis of hepatocellular disease.

Increased splenic uptake of radiocolloids is a helpful sign in the scintigraphic diagnosis of various hepatocellular diseases, but little attempt has been made to quantify this physiologic phenomenon. We have devised a simple computer method that compares average splenic activity to average right-lobe liver activity. The method is reproducible (r = 0.97) and exhibits little interobserver variation (r = 0.99). One hundred clinically normal subjects were found to have a nearly symmetrical distribution of S/L ratios around a mean of 0.77, with a s.d. of 0.20. Fifteen subjects normal by biopsy were found to have a similar mean spleen-to-liver (S/L) ratio of 0.74. Based upon a normal range of 0.37 to 1.17 (0.77 +/- 2 s.d.), elevated S/L ratios were found in fatty metamorphosis (85%), cirrhosis (67%), and chronic hepatitis (43%). Abnormal S/L ratios in the range from 1.17 to approximately 1.4 were not visually obvious. Overall sensitivity of the S/L ratio in these three diseases is 69%. When combined with the other scintigraphic indications of hepatocellular disease (nonhomogenous colloid uptake, hepatomegaly, splenomegaly, and bone-marrow colloidal uptake), the liver scan was found to have a sensitivity of 93%.

Colloids↗
PubMed1977

Peripheral venous contrast echocardiography.

Contrast echocardiography is the technique of injecting various echo-producing agents into the bloodstream and, with standard echocardiographic techniques, observing the blood flow patterns as revealed by the resulting cloud of echoes. These techniques have only recently been utilized to evaluate various cardiac defects. Two physical properties of these agents characterize their usefulness: (1) clouds of echoes can be observed downstream as well as at the injection site, and (2) the echo-producing quality of these agents is completely lost with a single transit through either the pulmonary or the systemic capillary bed. Thus, detection of resultant echoes in both the venous and the arterial blood pool is indicative of abnormal shunting. In 60 patients with a spectrum of cardiac defects and a wide range in age of presentation, studies were made of (1) the feasibility of performing contrast echocardiography with superficial peripheral venous injections, and (2) the clinical usefulness of this relatively noninvasive technique in detecting and localizing intracardiac right ot left shunting. Most superficial peripheral veins could be utilized, and the resultant contrast echograms were reproducible and similar in quality to those obtained more central (caval) injections. Right to left shunts could be localized in the atrial, ventricular or intrapulmonary level. Characteristic flow patterns were also recognized for tricuspid atresia and common ventricle.

Adolescent↗
PubMed1988

Cortical slow potentials in verbal and spatial tasks--the effect of material, visual hemifield and performing hand.

Fifteen right-handed students voluntarily initiated the tachistoscopic presentation of visual stimuli containing either verbal (abstract words) or spatial (stereogeometric figures) material. Subjects had to reproduce stimulus material which had been presented either in their right or their left hemifield of vision by writing or drawing, either with their right or their left hand. Material-specific effects were found during the reproduction period: amplitudes of the performance-related negative potential shifts were larger in parietal and occipital recordings (P4, O1, and O2) when drawing as compared to writing. The opposite was true in frontal and left central leads (F3, F4, and C3) where writing was associated with larger negative amplitudes than drawing. Although subjects were informed about the nature of the forthcoming stimulus before voluntarily initiating the task, material-specific effects were missing in the preparation period. The performing hand had an influence on potentials in central leads, whereas hemifield of vision had no effect on preparation- and performance-related slow potential shifts.

Adolescent↗
PubMed1996

Intermanual transfer of proximal and distal motor engrams in humans.

We studied intermanual motor transfer for right-to-left or left-to-right direction of transfer between either proximal or distal upper extremity muscle groups. The influence of previously acquired motor engrams (original learning, OL) on learning efficiency of the contralateral side (transfer learning, TL) was examined in 26 right-handed healthy subjects. The task consisted of the drawing of meaningless figures. During TL, OL figures had to be reproduced as vertical mirror reversals. Data revealed a benefit for right-to-left but not left-to-right direction of transfer for time to complete a figure as well as a left-to-right transfer benefit for spatial motor precision. Furthermore, a benefit for intermanual transfer of training between proximal but not distal muscle groups was found when movement time to complete a figure was evaluated. Of special interest was the observation of a disadvantage due to prior contralateral learning for performance at right distal effectors. The asymmetrical transfer benefits with respect to side are in line with previous findings and support the proficiency model and the cross-activation model. Results further showed that intermanual transfer of training might differ with respect to muscle group involvement and suggest that, although primarily facilitating, previous opposite hand training may lead to inhibitory influences on subsequent contralateral reproduction.

Adult↗
PubMed1985

Factor analysis in left ventricular first-pass radionuclide angiography: value of the ventricular factor to measure ejection fraction.

Factor analysis theoretically generates the time-activity curves of the various physiological compartments, or factors, which are superimposed in a dynamic series of scintigraphic frames. An image of the spatial distribution of each of these factors is also displayed. We tested the ability of one of these, the ventricular factor, to measure the left ventricular ejection fraction (LVEF) in first-pass radionuclide angiography (FPRA). Forty-nine patients divided into three groups were studied. In a group of 32 patients, factor analysis was compared to a conventional scintigraphic method and to contrast angiography. The coefficient of correlation was similar for both techniques (r = 0.83). To test reproducibility, another group of 10 patients received two successive injections of Au-195m, three minutes apart. The reproducibility of LVEF was r = 0.78 with factor analysis and r = 0.81 with the conventional method. In a third group of seven patients, three successive injections of Au-195m were performed in the right and in the left anterior oblique projections. The reproducibility of LVEF was r = 0.71 with factor analysis. However LVEF was significantly lower in LAO than in RAO, 50 +/- 11% vs 58 +/- 17% respectively. It is concluded that factor analysis does not offer a more reliable means of calculating LVEF than a conventional method.

Factor Analysis, Statistical↗
PubMed1997

Perceiving and tracking kinesthetic stimuli: further evidence of motor-perceptual interactions.

Two experiments pursued previous studies (P. Viviani & P. Mounoud, 1990; P. Viviani & N. Stucchi, 1989) on motor-perceptual interactions. The right arm of blindfolded participants was moved passively along elliptic trajectories. Kinematics was either coherent or at variance with the relation (two-thirds power law) observed in active movements. In Experiment 1 participants compared the horizontal and vertical extent of the ellipses. Kinematics affected aspect ratio discrimination: The direction along which the movement decelerated was subjectively stretched. In Experiment 2 participants used the left arm to reproduce in real time the movement of the right arm. The trajectories of the left arm presented a stretch similar to the perceptual illusion demonstrated in Experiment 1. Between-arm asynchrony suggests that the motor control system cannot use kinesthetic information that is at variance with the flow of reafferences normally associated with voluntary movements. It is argued that these interactions occur at the level of a central amodal representation of the stimuli.

Arm↗
PubMed1989

Depression of myocardial force and stiffness without change in crossbridge kinetics: effects of volatile anesthetics reproduced by nifedipine.

The authors examined the effects of nifedipine, a sarcolemmal slow Ca2+ channel blocker, on dynamic stiffness and force of rabbit right ventricular trabeculum and papillary muscle in Ba2+ contracture, in an attempt to reproduce the effects of halothane, enflurane, and isoflurane on a similar preparation as reported by Shibata et al. Once barium contracture force was established, muscle length was perturbed with small amplitude sinusoidal oscillations in the frequency range of 0.1-100 Hz. Nifedipine 1 microM was then added to the superfusate and dynamic stiffness was again measured. Additional barium was used to determine restoration of contracture force to and beyond control levels. Nifedipine produced a significant decrease in contracture force and high-frequency stiffness with no effect on the frequency (fmin) at which stiffness amplitude exhibited a minimum (P less than 0.005). Contracture force and stiffness could be restored by adding additional barium to the nifedipine-treated muscles. These results are similar to those reported by Shibata et al. using volatile anesthetics. Since nifedipine, which acts specifically at the sarcolemmal slow Ca2+ channel, affects contracture force and dynamic stiffness in this preparation in a manner similar to the volatile anesthetics, the authors suggest that the anesthetics studied by Shibata et al. may well exert a significant component of their negative inotropic activity via their action on the sarcolemmal slow Ca2+ channel.

Anesthetics↗
PubMed1997

'Mouseyes': an aid to wound measurement using a computer.

The aim of this study was to assess the efficacy of an image-area and perimeter-length measurement system consisting of a personal computer with integral mouse device and a computer program, 'Mouseyes', written for the purpose. The study was designed to see how image area, perimeter length and curvature affected the overall accuracy and reproducibility of measurement. Five volunteers (three male, four right-handed, one left-handed) were recruited to carry out the task of digitising a series of 12 shapes of known dimensions. The difference between derived and true image measurements were investigated. The accuracy and reproducibility of area measurement increased with increasing area magnitude. Digitised areas were typically calculated with an error of 1.3% or less. The coefficient of variation was less than 2%, indicating a high reproducibility of measurement; the greatest inaccuracies and variability occurred with smaller sizes. The system has been proved to be a reliable, accurate and reproducible method for the measurement of irregularly shaped areas and linear dimensions.

Anthropometry↗
PubMed1986

Comparison of the reproducibility of EMG signals recorded from human masseter and lateral pterygoid muscles.

EMG recordings of the left and right masseter and lateral pterygoid muscles were repeated three times in 15 young adults to test the reproducibility of the signals. Two tests were made on the same day (morning and afternoon) and one test three days later (morning). Needle and hook electrodes were used for the masseter muscle and needle electrodes for the lateral pterygoid muscle. The superficial areas of recording were tattooed on the skin. An intra-oral approach was selected for the lateral pterygoid muscle. The subjects were asked to perform three definite tasks for the masseter muscle (intercuspid occlusion, maximum protrusion, and centric relation with a bite opening of 3mm) and two for the pterygoid muscle (maximum opening and maximum protrusion). The EMG signals were directly integrated, and root mean squares of the AC components were computed. The selection of the signals to discard possible artefacts was performed by displaying EMG and RMS outputs on a six-channel UV oscillograph. The selected RMS values were submitted to different analyses of variance to define additive and non-additive models of effects. The results may be summarized as follows: The between-day sessions showed more variation than the within-day sessions. The variations related to the method accounted for a very high percentage of the total variance (48.9%). The recordings with needle electrodes displayed a large percentage of the individual variation (masseter, 31.2%; lateral pterygoid muscle, 65.9%) and significantly lower values for the variations related to the session or the side of recording. The one-side recordings were more suitable for distinguishing the biological variations than were the bilateral ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Ultrarapid subthreshold stimulation for termination of atrioventricular node reentrant tachycardia.

OBJECTIVES: We investigated the efficacy and safety of ultrarapid subthreshold electrical stimuli in terminating sustained atrioventricular (AV) node reentrant tachycardia. BACKGROUND: Subthreshold stimuli, singly and in trains, have been reported to prolong the effective refractory period, inhibit the response to subsequent suprathreshold extrastimuli and to terminate ventricular tachycardia and reciprocating tachycardia. METHODS: Seventeen consecutive patients with inducible sustained slow-fast AV node reentrant tachycardia (mean tachycardia cycle length 358 +/- 61 ms) were studied. Trains of subthreshold stimuli were tested at various right atrial sites. RESULTS: Trains of subthreshold stimuli reproducibly terminated AV node reentrant tachycardia in 15 patients without administration of adjunctive pharmacologic agents. Effective subthreshold current strength ranged from 0.5 to 1.5 mA (mean 0.9 +/- 0.3). The cycle length of effective subthreshold stimuli trains ranged from 30 to 80 ms (mean 57 +/- 17), and the number of stimuli in the train ranged from 4 to 16 (mean 8 +/- 4). The site of successful termination was the proximal coronary sinus in 6 patients and the right low atrial septum in 12. During successful subthreshold termination, no atrial capture could be detected. Neither atrial fibrillation nor flutter nor tachycardia acceleration occurred. CONCLUSIONS: Low current, high frequency trains of stimuli, when applied at a site presumed to be close to the reentrant circuit, provided a safe and effective method of terminating the common type of AV node reentrant tachycardia. This technique could be used to identify critical parts of the reentrant circuit suitable for ablation and further investigations with this method are warranted.

Adult↗
PubMed2005

Reproducibility of 3D free-breathing magnetic resonance coronary vessel wall imaging.

AIMS: Although the coronary artery vessel wall can be imaged non-invasively using magnetic resonance imaging (MRI), the in vivo reproducibility of wall thickness measures has not been previously investigated. Using a refined magnetization preparation scheme, we sought to assess the reproducibility of three-dimensional (3D) free-breathing black-blood coronary MRI in vivo. METHODS AND RESULTS: MRI vessel wall scans parallel to the right coronary artery (RCA) were obtained in 18 healthy individuals (age range 25-43, six women), with no known history of coronary artery disease, using a 3D dual-inversion navigator-gated black-blood spiral imaging sequence. Vessel wall scans were repeated 1 month later in eight subjects. The visible vessel wall segment and the wall thickness were quantitatively assessed using a semi-automatic tool and the intra-observer, inter-observer, and inter-scan reproducibilities were determined. The average imaged length of the RCA vessel wall was 44.5+/-7 mm. The average wall thickness was 1.6+/-0.2 mm. There was a highly significant intra-observer (r=0.97), inter-observer (r=0.94), and inter-scan (r=0.90) correlation for wall thickness (all P<0.001). There was also a significant agreement for intra-observer, inter-observer, and inter-scan measurements on Bland-Altman analysis. The intra-class correlation coefficients for intra-observer (r=0.97), inter-observer (r=0.92), and inter-scan (r=0.86) analyses were also excellent. CONCLUSION: The use of black-blood free-breathing 3D MRI in conjunction with semi-automated analysis software allows for reproducible measurements of right coronary arterial vessel-wall thickness. This technique may be well-suited for non-invasive longitudinal studies of coronary atherosclerosis.

Adult↗
PubMed1990

Evaluation of a dynamometer measuring torque of uni- and bilateral concentric and eccentric muscle action.

A dynamometer designed for torque measurements of uni- and bilateral concentric and eccentric muscle actions of the quadriceps and hamstring muscle groups is described. Torque reproducibility and control of lever-arm position were studied using known standards. In vivo measurements assessed angular velocity, lever-arm acceleration, variability of torque between limbs and reproducibility of torque. Torque obtained from left and right leg attachments was equal when using weights and during dynamic in vivo conditions. Static torque recorded at different lever-arm positions and known torque were equal. Likewise, lever-arm position output equated with known angles. In vivo test-retest of peak torque was found to be reliable. Acceleration of the lever arm was greater for concentric bilateral than for unilateral muscle actions but equal during eccentric muscle actions. The dynamometer is suggested to provide valid and reproducible torque measurements up to at least 700 N m at constant angular velocities up to 2.62 rad s-1. Besides being a research tool the dynamometer is useful in clinical settings for rehabilitation and evaluation of skeletal muscle function.

Adult↗
PubMed1997

Reproducibility of ultrasound assessment of carotid plaque occurrence, thickness, and morphology. The Tromsø Study.

BACKGROUND AND PURPOSE: Ultrasonography is increasingly used in vascular research, but there is limited information about the reproducibility of the ultrasound method for screening purposes. In this study the reproducibility of ultrasound assessment of carotid plaque occurrence, thickness, and morphology was examined within the setting of a population health survey. METHODS: In 1994/1995, 6720 participants in the Tromsø Study, Norway, underwent B-mode ultrasound scanning of the right carotid artery. The between- and within-sonographer reproducibility of ultrasound assessment of plaque occurrence and thickness was estimated by repeated scanning of a random sample of 107 participants. The between- and within-sonographer reproducibility of plaque morphology classification (echogenicity, four categories and heterogeneity, two categories) was determined by repeated reading of videotaped images of 119 randomly selected arteries with plaques. RESULTS: Between- and within-sonographer agreement on plaque occurrence was substantial with kappa values (95% CI) of 0.72 (0.60 to 0.84) and 0.76 (0.63 to 0.89), respectively. Reproducibility of plaque thickness measurements was moderate, with mean absolute differences ranging between 0.25 and 0.55 mm (coefficients of variation between 13.8% and 22.4%). Agreement on plaque morphology classification was high, with kappa values ranging between 0.54 and 0.73. CONCLUSIONS: Population screening using B-mode ultrasound provides a valuable means for the detection and morphological evaluation of carotid plaques, whereas measurements of plaque thickness are subject to considerable measurement error.

Aged↗
PubMed1981

Lung volume and pleural pressure effects on ventricular function.

To investigate the changes in ventricular function that occur during continuous positive-pressure ventilation, we studied the effects of separate increases in lung volume, pleural pressure, and right ventricular afterload in 15 dogs. Isovolume increases of pleural pressure caused changes in right and left ventricular hemodynamics indistinguishable from those induced by preload reduction. Lung distension with the chest open to atmosphere caused both right and left atrial intracavitary pressures to rise as cardiac output fell, suggesting altered function of both ventricles. Raising right ventricular afterload by pulmonary artery constriction did not reproduce the hemodynamic changes observed during increases of lung volume. These data indicate that the apparent alteration of ventricular function that occurs during continuous positive-pressure ventilation is produced by the associated increase in lung volume and that a right ventricular afterload-ventricular interdependence effect is not the responsible mechanism.

Animals↗
PubMed1999

Defibrillation-guided radiofrequency ablation of atrial fibrillation secondary to an atrial focus.

OBJECTIVES: Our aim was to evaluate a potential focal source of atrial fibrillation (AF) by unmasking spontaneous early reinitiation of AF after transvenous atrial defibrillation (TADF), and to describe a method of using repeated TADF to map and ablate the focus. BACKGROUND: Atrial fibrillation may develop secondary to a rapidly discharging atrial focus that the atria cannot follow synchronously, with suppression of the focus once AF establishes. Focus mapping and radiofrequency (RF) ablation may be curative but is limited if the patient is in AF or if the focus is quiescent. Early reinitiation of AF has been observed following defibrillation, which might have a focal mechanism. METHODS: We performed TADF in patients with drug-refractory lone AF using electrodes in the right atrium (RA) and the coronary sinus. When reproducible early reinitiation of AF within 2 min after TADF was observed that exhibited a potential focal mechanism, both mapping and RF ablation were performed to suppress AF reinitiation. Clinical and ambulatory ECG monitoring was used to assess AF recurrence. RESULTS: A total of 44 lone AF patients (40 men, 4 women; 32 persistent, 12 paroxysmal AF) with a mean age of 58+/-13 years underwent TADF. Sixteen patients had early reinitiation of AF after TADF, nine (20%; 5 paroxysmal) exhibited a pattern of focal reinitiation. Earliest atrial activation was mapped to the right superior (n = 4) and the left superior (n = 3) pulmonary vein, just inside the orifice, in the seven patients who underwent further study. At the onset of AF reinitiation, the site of earliest activation was 86+/-38 ms ahead of the RA reference electrogram. The atrial activities from this site were fragmented and exhibited progressive cycle-length shortening with decremental conduction to the rest of the atrium until AF reinitiated. Radiofrequency ablation at the earliest activation site resulted in suppression of AF reinitiation despite pace-inducibility. Improved clinical outcome was observed over 8+/-4 months' follow-up. CONCLUSIONS: Transvenous atrial defibrillation can help to unmask, map, and ablate a potential atrial focus in patients with paroxysmal and persistent AF. A consistent atrial focus is the cause of early reinitiation of AF in 20% of patients with lone AF, and these patients may benefit from this technique.

Atrial Fibrillation↗
PubMed1989

Standardized panoramic radiography in assessment of mandibular augmentation with hydroxylapatite material: preliminary report.

This study evaluates the usefulness of a head-positioner/cephalostat in producing standardized panoramic radiographs by assessing the reproducibility of the radiographs and comparing the standardized panoramic radiographic findings with those obtained from 45 degrees right and left lateral cephalograms. Comparison of measurements indicated that this cephalostat produced reproducible panoramic radiographs. Measurements on each panoramic radiograph showed standard deviations ranging from 0.0 to 0.24 mm (pooled SD = 0.12), whereas the SDs for the 45 degrees lateral cephalograms ranged from 0.0 to 0.45 (pooled SD = 0.14). This indicates that the panoramic radiographs obtained with this head-positioner/cephalostat were comparable to those obtained by 45 degrees lateral cephalograms.

Alveolar Process↗