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PubMed1988

Spatial contrast sensitivity: effects of age, test-retest, and psychophysical method.

Spatial contrast sensitivity was tested twice in normal subjects from five age groups by using each of two different psychophysical methods. Results obtained by the method of adjustment showed a decline in sensitivity with increasing age at all spatial frequencies. In contrast, the forced-choice procedure yielded results indicating an age-related decline predominantly at high spatial frequencies, with the magnitude of the decline being generally similar to that obtained earlier by a tracking method [Vision Res. 23, 689 (1983)]. The decline that we observed cannot be due to pupillary changes with age, since this factor was controlled. Moreover, we suggest that the high-spatial-frequency decline in contrast sensitivity, although it is comparatively small, is too large to be due to changes in lens density. We therefore suggest that a neural component is responsible. In addition, interactions among the age of the subject, the spatial frequency used, and the psychophysical method used suggest that the method of adjustment should be avoided for age-related studies of vision.

Adult↗

PubMed1989

Conformation therapy to improve the irradiation of the spinal axis.

Techniques for the irradiation of the spine have remained largely unchanged since the introduction of megavoltage therapy. The main disadvantages of these techniques are the inhomogeneous dose distribution and the problems associated with field joins. The tracking method of conformation therapy employs a short field length and translates the patient through the beam on the couch of a computer controlled treatment unit. Dose uniformity along the spinal axis is achieved by controlling the speed at which the target travels through the radiation field. Treatment is given at standard source-axis distance (SAD) and the need for external shielding is eliminated by shaping the width of the field. The join with the cranial fields is independent of any skin marks, removing the risk of over- or under-dosage. Treatments are planned automatically from computed tomography (CT) information by an in-house planning system. The calculated doses have consistently shown good agreement with phantom measurements. Three cobalt dose distributions are presented and compared: a tracking treatment; a single posterior field, and two matched fields. The superiority of conformation therapy over the other commonly used treatment methods is clearly demonstrated.

Humans↗

PubMedDate not supplied

Pulse wave recording--development of a method for investigating foetal circulation in utero.

The need to investigate the elastic properties of arterial vessels 'in situ' for the early recognition of degenerative disorders in arteries has long been apparent. Volume pulses in defined segments of arteries can be evaluated for this purpose, and the present paper contains a survey of earlier attempts to quantify volume pulses by means of ultrasound. A presentation is given of a recently developed digital system, comprising a phase-locked echo tracker, capable of monitoring non-invasively the diameter and its pulsatile changes of a selected artery along two chosen image lines of a linear array ultrasound scanner. The physical limitations of tracking fast-moving ultrasound echoes by means of phase-locked range gating are reported and the advantage is emphasized of using a gate length of one full period. This system has been calibrated, tested and applied in measurements of pulse wave pattern and propagation velocity in the descending aorta of human foetuses in the last trimester of gestation. The present high-resolution echo-tracking method has yielded reproducible results in the foetus and appears suitable also for screening studies on adult vessels.

Blood Circulation↗

PubMed1987

Quantification of blood pressure tracking of children by tracking index: the Shimane Heart Study.

The tracking of systolic blood pressure (SBP) was analyzed in a cohort of children. The study population consisted of 1009 Japanese children in Izumo City, a rural community in the northwest of Honshu. There were 252 subjects in cohort (C)-1, 235 in C-2, 286 in C-3, 131 in C-4 and 105 in C-5. Follow-up periods were from 6 to 9 years of age in C-1, 9 to 12 in C-2, 12 to 15 in C-3, 6 to 12 in C-4 and 9 to 15 in C-5. BP was measured by conventional method. Tracking index (TI) was calculated as follows: TI = (2x + y - z)/N/.24; x, y and z are numbers of subjects who remained at the same quintile, who moved to the next quintile and who moved to a remote quintile, respectively; N = x + y + z; TI becomes 1.0 when SBP changes randomly. SBP tracking was apparent in both sexes of C-1 (TI = 2.4 in boys, 2.5 in girls), in girls of C-2 (TI = 3.5), in both sexes of C-3 (TI = 3.2 in boys, 2.7 in girls) and in girls of C-4 (TI = 4.1) and C-5 (TI = 3.3). TI agreed well with the tracking phenomena visualized by distribution bar graph. We conclude that TI can assess the degree of tracking quantitatively and can be applied to analysis of the tracking phenomena of BP and its related factors.

Blood Pressure↗

PubMed1990

Motion of individual human spermatozoa, both normal and lacking the outer dynein arms, during a continuous temperature rise.

The effect of increasing temperature from 22-25 degrees C to 37 degrees C on various motion characteristics of individual normal human spermatozoa and spermatozoa lacking the outer dynein arms (LODA) was studied by using a new automatic microscopic tracking method. It was found that: 1) The curvilinear velocity (Vc, measured between 1-3 sec) of both normal and LODA spermatozoa, fluctuated more or less intensely between spermatozoa; this fluctuation was not thermodependent. 2) The average Vc in the two groups of spermatozoa increased with the rise in temperature at a similar rate (1 micron/sec/degrees C), but LODA spermatozoa had an initial Vc lower than that of normal spermatozoa (12.5 +/- 5.3 microns/sec and 34.2 +/- 8.2 microns/sec, respectively). 3) The profile of the Vc increase associated with the temperature rise was different for the two groups of spermatozoa: for LODA spermatozoa it was linear between 25-37 degrees C, whereas for normal spermatozoa a plateau was reached at about 31 degrees C. 4) Various patterns of trajectory were found for both normal and LODA spermatozoa; these patterns were unrelated to temperature. However, LODA spermatozoa had more linear trajectories than normal spermatozoa. 5) Plots derived from reaction rate theory showed that the activation enthalpy, delta H was a function of the increase of Vc for both normal and LODA spermatozoa, but that delta H was higher for LODA spermatozoa.

Adenosine Triphosphatases↗

PubMed1990

Velocity imaging of slow coherent flows using stimulated echoes.

We measure the velocity distribution of slow fluid flow in model systems using stimulated echoes and velocity phase encoding. We show velocity images of slow coherent flow with velocities of the order of 0.1 mm/s which is slower than can be obtained by the bolus-tracking method. The eddy current errors were compensated by phase correction.

Humans↗

PubMed1988

Disorder in reciprocal innervation upon initiation of voluntary movement in patients with Parkinson's disease.

Reciprocal innervation of the soleus motoneurones upon initiation of voluntary ankle dorsiflexion was investigated in eight patients with Parkinson's disease. H-reflex and visually guided step tracking methods were used for testing motoneurone excitability and for controlling the timing of movement initiation, respectively. While reciprocal inhibition appeared almost simultaneously with the agonist electromyographic (EMG) onset in normal subjects (Kagamihara and Tanaka 1985), facilitation appeared in the majority of patients under the same onset condition. It increased slowly, reaching a maximum at about 100 ms after the EMG onset. It then subsided slowly at around 200-300 ms, and was replaced thereafter by an inhibitory effect. No coactivation of the soleus muscle was detected electromyographically. The facilitation between the EMG onset and the onset of mechanical contraction was attributed to the direct effect of the descending command from the brain, suggesting a certain disorder in controlling the system for reciprocal innervation.

Adult↗

PubMed1987

Rheumatic complaints in Tokelau. I. Migrants resident in New Zealand. The Tokelau Island migrant study.

The three Tokelau atolls are 8 degrees south of the equator. In 1966 the islands were involved in a severe hurricane which drew attention to overcrowding and led to resettlement of more than half the population in New Zealand. One thousand three hundred and eighty one migrants over 15 years old were examined in New Zealand in 1980 and 1981 for rheumatic complaints as part of a continuing assessment. Clinical criteria for osteoarthritis (COA), including crepitus in any joint and in the knee, showed an increase in prevalence with age and weight in both sexes. Partial correlation coefficient analysis showed an association of the number of affected joints or the severity of knee COA (COAK) with both age and weight. Stepwise regression showed that age was the best predictor of both COA and COAK scores. Weight had predictive value only for COAK and only in women. Using the tracking method, previous high and/or increasing weight was related to COAK observed at this assessment. Heberden nodes increased with age and were more prevalent in women but were not associated with weight. Low back, dorsal and neck pain showed no association with age or sex. Low back pain was associated with weight. Joint pain following injury occurred in 15.4% of men. Gout, more common in men, was the only frequent inflammatory arthritis found. Two definite cases of rheumatoid arthritis (RA) were identified and four had criteria 1 and 2 for the New York criteria.

Adolescent↗

PubMed1985

Extracellular matrix (ECM) modulates the EGF-induced migration of liver epithelial cells in serum-free, hormone-supplemented medium.

The influence of the extracellular matrix (ECM) glycoproteins collagen IV, laminin (LN), and fibronectin (FN) on the in vitro migration of epithelial cells was studied using the ECM migration track method (4) with preparations immunostained for LN and FN. The locomotion of rat liver epithelial cells stimulated to migrate in serum-free medium by epidermal growth factor (EGF) in the presence of insulin is inhibited by substratum-bound FN. The inhibition is concentration-dependent up to 0.7 microgram of the protein per cm2. Neither LN nor collagen IV decreased the number of migrating cells, indicating that the inhibition is a specific effect of fibronectin. The data also indicate that the FN-mediated inhibition of migration is an additional and not alternative mechanism to the well-established contact inhibition of locomotion (1) which also occurs in liver epithelial cell cultures. The system is being used for a further analysis of the factors that influence migration of normal and neoplastic epithelial cells and the biochemical mechanisms underlying the migration reaction.

Animals↗

PubMed1990

Genetic studies of variation in Rayleigh and photometric matches in normal trichromats.

The inheritance of Rayleigh match midpoints and photometric matches (551-667 nm) was studied in observers with normal color vision. An analysis was performed to evaluate whether the measured interobserver variations in these two traits were consistent with single gene allelic variation, polygenic variation, or environmental factors. A bipartite 2 deg field and a computerized tracking method were used to obtain Rayleigh matches; a new photometric technique, termed heterochromatic modulation photometry (HMP), was used to obtain photometric matches. Data were collected from 72 nonrelated males to determine distribution characteristics for the normal population. The distributions were analyzed for evidence of multimodality and the results indicated that the distributions for Rayleigh match midpoints and HMP matches obtained in this study were unimodal and symmetrical. Data from 52 observers from 5 families were used to study the transmission of the two traits in pedigrees. Statistical analysis of the pedigree data suggested that the major source of variations for Rayleigh match midpoints and for HMP matches were each due to allelic variation at single gene loci; that is, each may be determined by a single gene. Results were inconclusive as to whether variation in the two traits could be determined by the same gene.

Adolescent↗

PubMed1987

The effects of ethanol on eye tracking in rhesus monkeys and humans.

The effects of ethanol on eye tracking function were compared in rhesus monkeys and humans using a similar experimental procedure. In Experiment 1, 3 rhesus monkeys were trained to visually track a projected image of a disk that oscillated sinusoidally along a horizontal plane on a screen. This training was accomplished using a procedure in which responses on a lever resulted in the delivery of water when the central area of the projected disk image was dimmed for a brief period. Intragastric administrations of ethanol at doses of 0.25 to 2 g/kg were tested during one-day test sessions using a cumulative dose procedure. Pursuit eye movements were disrupted at doses of 0.5 g/kg while lever pressing behavior was not disrupted until a dose of 2 g/kg was reached. In Experiment 2, pursuit eye movements of 6 humans were not disrupted when ethanol was given orally at cumulative doses of 0.25 to 1 g/kg, while microswitch pressing behavior was disrupted in some of the subjects at a dose of 0.5 g/kg. Blood ethanol levels increased in a dose-dependent manner in both species with higher levels in humans than in monkeys. The dose dependent effects observed in both species and qualitative similarities in some of the effects such as saccadic pursuit eye movements suggest that the eye tracking method employing monkeys is useful for predicting drug effects on sensory motor function in humans.

Adult↗

PubMed1991

Single particle tracking. Analysis of diffusion and flow in two-dimensional systems.

Analysis of the trajectories of small particles at high spatial and temporal resolution using video enhanced contrast microscopy provides a powerful approach to characterizing the mechanisms of particle motion in living cells and in other systems. We present here the theoretical basis for the analysis of these trajectories for particles undergoing random diffusion and/or systematic transport at uniform velocity in two-dimensional systems. The single particle tracking method, based on observations of the trajectories of individual particles, is compared with methods that characterize the motions of a large collection of particles such as fluorescence photobleaching recovery. Determination of diffusion coefficients or transport velocities either from correlation of positions or of velocities of the particles is discussed. A result of practical importance is an analysis of the dependence of the expected statistical uncertainty of these determinations on the number of position measurements. This provides a way of judging the accuracy of the diffusion coefficients and transport velocities obtained using this approach.

Diffusion↗

PubMed1992

Facilitation of agonist motoneurons upon initiation of rapid and slow voluntary movements in man.

The time course of facilitation of the agonist motoneurons upon initiation of voluntary ankle dorsiflexion was investigated in eight healthy subjects. The H-reflex and visually guided tracking methods were used for testing the excitability of the motoneuron pool and for controlling the initiation of movement as well as speed and force. Since the onset of voluntary EMG activity (EMG reaction time: EMGvRT) was delayed and/or obscured by test H-reflexes which were evoked very close to the behavioral responses, the subject was instructed to make response movements bilaterally, and EMGvRT was measured on the side without stimulation. In every subject, the EMGvRT was invariably longer in the ramp movement than in the step movement. The onset of H-reflex facilitation prior to EMG onset, which was regarded as indicating the arrival time of the descending motor command to the motoneuron pool, always started earlier in the ramp movement than in the step movement. The difference in facilitation onset between the two tasks was smaller than that in EMGvRT. Since the amplitude of the H-reflex at the onset of the voluntary EMG was equivalent in both movements, the development of H-reflex towards the behavioral EMG onset was more gradual in the ramp movement than in the step movement. The present results demonstrate that the longer reaction time in the slow ramp task depends on 2 factors: delay in the arrival of descending facilitatory impulses to the agonist motoneuron pool, and its slow recruitment thereafter.

Adult↗

PubMed1983

Demonstration of presbycusis across repeated measures in a nonhuman primate species.

The progress of age-related hearing loss in three 31-yr-old, two 24-yr-old, and two 9-yr-old rhesus monkeys (Macaca mulatta) was repeatedly examined over a period of 3 yr. Pure-tone audiograms for seven frequencies, .125, .500, 2.000, 4.000, 16.000, 22.667, and 32.000 kHz, were obtained through the use of the psychophysical tracking method. Analysis indicated the presence of presbycusis in the older animals. Animals demonstrating presbycusis showed a progressive decrement in the ability to detect higher frequencies and an overall hearing loss at all frequencies.

Aging↗

PubMed1978

Effects of stimulus duration and stimulus off time on the auditory and acoustic reflex thresholds.

The effects of stimulus duration and stimulus off time on the thresholds of hearing and the acoustic reflex were investigated in 10 normal-hearing subjects and 10 subjects with sensorineural hearing loss. A 1000-Hz stimulus with on-off times of 500-500 msec and 30-30 msec was used to obtain hearing sensitivity and acoustic reflex thresholds via a tracking method. Auditory threshold was poorer for the 30-30 msec tone than the 500-500 msec stimulus in both groups. Using the different stimuli, no significant difference in acoustic reflex threshold was observed in either group. These results suggest that the addition of a short off time modifies the previously observed effects of both duration and off time on the acoustic reflex and auditory threshold.

Adult↗

PubMed1987

Evaluation of sepsis in a critically ill surgical population.

We report a new clinical rating system which assesses septic patients' ongoing disease course and its severity. Our system incorporates the Therapeutic Intervention Scoring System (TISS) and Acute Physiology and Chronic Health Evaluation to measure discrete organ system abnormalities, plus a multiple system organ failure scale to quantify the number of abnormal organ systems. The resulting score, which reflects the severity of multiple organ dysfunction and grades responsiveness to therapy, was validated against the actual disease course. Retrospective and prospective profiles of individual surgical ICU patients demonstrated that this tracking method was a more effective indicator of severity of sepsis and more sensitive to the day-to-day changes in clinical status than either the TISS or APACHE II components alone. We also demonstrate that a graphic illustration of daily system scores yields clinically useful information relevant to the patients' septic course.

Bacterial Infections↗

PubMed1986

Poststenotic flow disturbance in the dog aorta as measured with pulsed Doppler ultrasound.

Blood flow velocity was measured in the dog aorta distal to mechanically induced constrictions of various degrees of severity employing an 8-MHz pulsed Doppler ultrasound velocimeter and a phase-lock loop frequency tracking method for extracting velocity from the Doppler quadrature signals. The data were analyzed to construct ensemble average velocity waveforms and random velocity disturbances. In any individual animal the effect of increasing the degree of stenosis beyond approximately 25 percent area reduction was to produce increasing levels of random velocity disturbance. However, variability among animals was such that the sensitivity of random behavior to the degree of stenosis was degraded to the point that it appears difficult to employ Doppler ultrasound measurements of random disturbances to discriminate among stenoses with area reductions less than approximately 75 percent. On the other hand, coherent vortex structures in velocity waveforms consistently occurred distal to mild constrictions (25-50 percent area reduction). Comparison of the phase-lock loop Doppler ultrasound data with simultaneous measurements using invasive hot-film anemometry, which possesses excellent frequency response, demonstrates that the ultrasound method can reliably detect those flow phenomena in such cases. Thus, the identification of coherent, rather than random, flow disturbances may offer improved diagnostic capability for noninvasively detecting arteriosclerotic plaques at relatively early stages of development.

Animals↗

PubMed1987

Individual differences in auditory capabilities. I.

Twenty-eight audiometrically normal adult listeners were given a variety of auditory tests, ranging from quiet and masked thresholds through the discrimination of simple and moderately complex temporal patterns. Test-retest reliability was good. Individual differences persisted on a variety of psychoacoustic tasks following a period of training using adaptive threshold-tracking methods, and with trial-by-trial feedback. Large individual differences in performance on temporal-sequence-discrimination tasks suggest that this form of temporal processing may be of clinical significance. In addition, high correlations were obtained within given classes of tests (as, between all tests of frequency discrimination) and between certain classes of tests (as, between tests of frequency discrimination and those of sequence discrimination). Patterns of individual differences were found which support the conclusion that individual differences in auditory performance are, in part, a function of patterns of independent abilities.

Adolescent↗