Psychological stress and ventricular arrhythmias during myocardial infarction in the conscious dog.
Explore the source record for details and available documents.
Animals↗
SEARCH · PubMed Health
Results for “threshold model”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Relationships between glucose levels and insulin secretion during a glucose challenge test.
The relationship between glucose and insulin levels was examined in a prospective study of 153 pregnant patients without diabetes who underwent a standard 50 gm glucose challenge test. One hundred eighteen women had normal screening results (glucose level less than 140 mg/dl) and 35 had abnormal screening values but a normal oral glucose tolerance test. Abnormal responders had greater insulin levels (149 vs 82 pmol/L, p less than 0.0001), and a higher insulin/glucose index (0.96 vs. 0.72, p less than 0.007). Patients with glucose levels less than 100 mg/dl had significantly lower insulin/glucose indices. Overall, obese patients had significantly greater glucose and insulin measurements than did nonobese women, but there was no difference within normal and abnormal groups. Glucose levels accounted for 52% of the insulin output and 29% of the insulin/glucose index variance. Neither age, parity, nor obesity contributed significantly to insulin levels in the multiple regression model. Therefore the accepted threshold for glucose screening reflects abnormal insulin output and this aberration may be indicative of the primary defect in gestational diabetes.
Adult↗
No continuous relationship between Veterans Affairs hospital coronary artery bypass grafting surgical volume and operative mortality.
BACKGROUND: The purpose of this study was to determine whether risk-adjusted coronary artery bypass grafting mortality rates are significantly related to coronary artery bypass grafting surgical procedure volume within the Department of Veterans Affairs hospital system. METHODS: From April 1987 to September 1992, expected mortality rates were calculated for 23,986 coronary artery bypass grafting procedures performed at 44 different Veterans Affairs hospitals. RESULTS: This study found a statistically significant relationship between annual hospital coronary artery bypass grafting volume and observed mortality rates (p < 0.02). However, no statistically significant relationship between coronary artery bypass grafting volume and risk-adjusted operative mortality was found (p = 0.10). Using analysis of variance on hospital-level data, hospitals with 100 or less cases per year have higher observed to expected mortality ratios than hospitals performing more than 100 cases per year (p = 0.03). Using Poisson regression models, however, a volume threshold could not be found. CONCLUSIONS: These findings are consistent with the current Veterans Affairs policy requirements to periodically review quality at low-volume hospitals.
Analysis of Variance↗
Stereoscopic aftereffects: evidence for disparity-specific neurones in the human visual system.
Explore the source record for details and available documents.
Adaptation, Ocular↗
The dissociation of sideways movements from movements in depth: psychophysics.
Explore the source record for details and available documents.
Depth Perception↗
Composite adaptation and spatial frequency interactions.
Explore the source record for details and available documents.
Adaptation, Ocular↗
A new hypothesis to explain why the increment threshold exceeds the decrement threshold.
Explore the source record for details and available documents.
Adaptation, Ocular↗
The effects of intrathecal morphine and naltrexone on autotomy in sciatic nerve sectioned rats.
Rats were implanted with an intrathecal catheter aimed at the lumbar enlargement (LE). Morphine hydrochloride (240 micrograms/day) was infused continuously on the spinal cord for 14 days with an osmotic minipump delivering 0.5 microliter/h solution or a bolus dose of naltrexone (37.5, 75 or 150 micrograms) was injected intrathecally. Intrathecally infused morphine delivered on the dorsum of the LE induced analgesia, as tested on the hot plate, whereas normal saline was without effect. Naltrexone caused hyperalgesia revealed as decreased threshold for vocalization to electrical stimulation of the tail. Rats with unilaterally sectioned sciatic nerves that were continuously infused with morphine on the dorsum of the LE autotomized significantly less than saline controls. Nerve sectioned rats injected with naltrexone had an overall level of autotomy similar to saline controls. However, autotomy had a somewhat earlier onset and was more severe with naltrexone than with saline. It is therefore concluded that intrathecal infusion of opiates specifically reduces autotomy, a behavior that may occur as a result of chronic discomfort or pain following nerve injury. Furthermore, the endogenous opiate system at the spinal level may be involved in the control of autotomy.
Animals↗
Complex interactions between pairs of forward maskers.
The present study was conducted to determine to what extent the combined effects of two forward maskers can be predicted from addition of their individual effects. The maskers were 50-Hz wide noise bands with center frequencies ranging from 1.8 to 2.2 kHz. The signal was a brief, 2.0-kHz tone burst. When the maskers were gated on and off together, the combination produced sometimes more and sometimes less masking than predicted depending on the particular pair and the relative amounts of masking produced by the individual members of the pair. The greatest discrepancy occurred, however, when the masker pair was presented simultaneously with the signal or when the forward maskers were presented in sequence. In the latter case, the obtained threshold exceeded the predicted threshold by as much as 34 dB.
Adolescent↗
Responses of inferior colliculus neurons in C57BL/6J mice with and without sensorineural hearing loss: effects of changing the azimuthal location of an unmasked pure-tone stimulus.
Azimuth functions (discharge rates evoked by tone bursts as a function of stimulus azimuth) were obtained from neurons in the inferior colliculus (IC) of C57 mice aged 2, 7 and 12 months. Because of a gene that affects the cochlea, C57 mice exhibit high-frequency sensorineural hearing loss at 7 and 12 months. Azimuth functions were examined for differences that might be related to the decline in localization acuity that accompanies hearing loss in this strain. Irrespective of age group, nearly all neurons in the central area of the IC were sensitive to the azimuth of a best frequency (BF) stimulus, as revealed by azimuth functions in which firing rates varied by more than 50% from maximum to minimum at one or more intensities. The age groups were similar in many respects (e.g., there were no significant differences in the proportion of functions meeting the criterion for direction sensitivity, the proportion of neurons with direction sensitive functions over a range of intensities, azimuth function shapes, the locations or stability of 'borders' separating angles evoking high versus low discharge rates). However, in 7- and 12-month-olds: the proportion of IC neurons in which the strongest excitatory driving was evoked by ipsilateral stimulation was significantly larger; azimuth function borders were more likely to be 'reversed' (i.e., the high rates being evoked by the more ipsilateral angle); and a greater proportion of azimuth functions met the criterion for direction sensitivity only minimally. The findings suggest that binaural excitatory-inhibitory interactions are altered in IC neurons of hearing-impaired mice.
Acoustic Stimulation↗
Responses of inferior colliculus neurons in C57BL/6J mice with and without sensorineural hearing loss: effects of changing the azimuthal location of a continuous noise masker on responses to contralateral tones.
Extracellular recordings were obtained from inferior colliculus neurons of young adult (2-month-old) C57 mice with normal hearing and middle-aged (6-month-old) C57 mice with sensorineural hearing loss as they responded to best frequency (BF) tones (signal) in the presence of a continuous background noise (masker). Rate/level functions were obtained for the signal alone, noise bursts alone, and the signal in continuous noise as a function of masker location. For both groups of mice, thresholds for BF tones were significantly elevated in the presence of noise at all three noise locations. Separating the signal and masker sources significantly improved masked tone thresholds of 2-month-old mice but not hearing-impaired mice. The decreased ability of middle-aged mice to benefit from separation of the signal and masker sources may reflect alterations in binaural processing as a result of sensorineural hearing loss.
Acoustic Stimulation↗
Noise induced hearing loss in fetal sheep.
The auditory brainstem response (ABR) was recorded in utero from chronically instrumented fetal sheep prior to and following exposure of pregnant ewes to intense broadband noise (120 dB SPL for 16 h). ABRs were elicited by clicks and tone bursts (0.5, 1, 2, and 4 kHz) delivered through a bone oscillator secured to the fetal skull. Latency-intensity functions for most of the four vertex-positive waves (labelled I-IV) were prolonged and ABR thresholds were temporarily elevated by an average of 8 dB following the noise exposure. Results show that exogenous sounds can penetrate the uterus and result in alterations of the fetal ABR.
Acoustic Stimulation↗
Age-related changes in auditory evoked potentials of gerbils. III. Low-frequency responses and repetition rate effects.
The auditory brainstem response (ABR) was recorded non-invasively from Mongolian gerbils ranging in age from 6 to 36 months. The ABR was elicited using gaussian tone bursts at octave intervals from 1 to 16 kHz. Responses were bandpass filtered from 30 to 300 Hz (LF-ABR; low-frequency component) and from 300 to 3000 Hz (HF-ABR; high-frequency component). In Experiment A, the thresholds of the two components (HF- and LF-ABR) were compared in 6- and 36-month subjects. The LF-ABR varied more with age than did the HF-ABR, particularly at stimulus frequencies of 2 kHz and above. As shown previously for the HF-ABR, the latencies of the LF-ABR increased as a function of hearing loss in aged gerbils whereas amplitudes of the LF-ABR were reduced in all aged gerbils, regardless of age-related threshold elevation. In Experiment B, tone bursts were presented at rates of 11-91/s to gerbils aged 6, 18, 30, and 36 months. Increased repetition rate resulted in an increase in the latency of both the HF- and LF-ABR, but to the same degree in each age group. Similarly, the interpeak intervals of the HF-ABR increased as a function of repetition rate in all subjects to the same degree. Increased age and increased repetition rate both resulted in significant reductions in ABR amplitudes, but rate did not interact with age. The data suggest that (1) the LF-ABR may be more sensitive to aging than is the HF-ABR and (2) there are no age-related changes in the HF- or LF-ABR which are dependent upon the repetition rate.
Acoustic Stimulation↗
Genetics of age-related hearing loss in mice. III. Susceptibility of inbred and F1 hybrid strains to noise-induced hearing loss.
Some humans and mice are genetically predisposed to age-related hearing loss (AHL), and others are variously susceptible to noise-induced hearing loss (NIHL). The inbred C57BL/6J (B6) mice exhibit AHL at an early age, whereas the inbred CBA/CaJ (CB) mice do not. The B6 mice are much more susceptible to NIHL than are the CB mice (Shone et al., 1991; Li, 1992a). The B6 mice possess an Ahl gene which maps to chromosome 10 (Erway et al., 1995). This study was designed, using these two inbred strains plus two F1 hybrid strains of mice, to begin to test the hypothesis that the Ahl genotypes may influence the susceptibility to NIHL. These strains of mice (with putative genotypes) are: inbred CB (+/+) and B6 (Ahl/Ahl); hybrid CBB6F1 (+/Ahl) and B6D2F1 (Ahl/Ahl; D2 represents inbred DBA/2J). Twenty-four mice of each of these four strains were exposed to noise (110 dB for 0, 1 or 2 h) and tested for auditory-evoked brainstem response (ABR) thresholds. The CB and CBB6F1 strains of mice did not differ significantly from each other, exhibiting mostly temporary threshold shifts. The B6 and B6D2F1 strains of mice did not differ significantly from each other, but did exhibit permanent threshold shifts. These results support the hypothesis that genetic predisposition to AHL may be revealed at a younger age by NIHL. This suggests that it may be possible to use the NIHL to distinguish segregating genotypes (+/Ahl vs. Ahl/Ahl) among backcross progeny and thereby to identify and map single genes for AHL.
Acoustic Stimulation↗
Lactate extraction and myocardial damage after countershock at different energy levels.
The relationship between myocardial lactate metabolism and the energy dose of direct countershock was studied in 15 dogs anesthetized with halothane. Five dogs received two shocks of 5 joules delivered energy each, five animals received two shocks of 10 joules delivered energy each, and five dogs received two shocks of 20 joules delivered energy each. All animals had positive myocardial lactate extraction in the baseline state (5 joules, 38% +/- 23.7 (SD); 10 joules, 59.6% +/- 11.4; 20 joules, 38% +/- 11.1). Lactate extraction after countershock progressively decreased with increasing energy dose and then returned to baseline. The maximal reduction in percent lactate extraction increased with increasing energy dose (5 joules, 13.9% +/- 16.1; 10 joules, 33% +/- 37; 20 joules, 30.5% +/- 37.5) and seemed to reach a threshold below which no further decrease occurred. Myocardial damage, as measured by a damage index derived from myocardial uptake of technetium-99 pyrophosphate, increased steadily with increasing energy dose (2.0 +/- 2.5 with 5-joule shocks; 38 +/- 32 with 10 joules; and 99 +/- 70 with 20 joules). These results show a consistent reduction in aerobic metabolism immediately following electric countershock. Even at low-energy doses, myocardial lactate extraction showed a detectable decrease and at higher energies approached net lactate production. Reductions of global lactate extraction did not completely predict the amount of myocardial damage. Localized measures of anaerobic metabolism or mitochondrial function might provide a better correlation with localized damage.
Anesthetics, Inhalation↗
Characteristic findings of auditory brainstem response and otoacoustic emission in the Bronx waltzer mouse.
Auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) were evaluated serially from 1 to 22 months in Bronx waltzer homozygotes (bv/bv), heterozygotes (+/bv) and control (+/+) mice, which were differentiated by means of PCR of marker DNA (D5Mit209). The wave IV threshold of the click-evoked ABR was higher than the DPOAE threshold with the DP growth method in each bv/bv, although the two thresholds were almost the same in the +/+ group. The DP value at 2f(1) - f(2) in the bv/bv showed an apparent decrease at 2 to 3 months of age with 80 dB SPL stimulation using f(2) frequency 7996 Hz and frequency ratio f(2)/f(1) = 1.22, compared to control or heterozygote mice. It was characteristic that the 2f(2) - f(1) DP signal-to-noise ratio (SNR) value was more preserved from 80 to 60 dB SPL than the 2f(1) - f(2) DP value at f(2) frequency 7996 Hz in most bv/bv, however, control mice showed almost the same levels of 2f(1) - f(2) and 2f(2) - f(1) SNR value at both f(2) frequencies of 6006 and 7996 Hz. The preservation of a substantial 2f(2) - f(1) DP suggested that it would be generated basal to the primary-tone place on the basilar membrane and there might be a reflection of the unique function of the remaining outer hair cells in the Bronx waltzer mice. These findings suggest that combination of ABR with DPOAE could offer useful information about differentiating the mechanism of hair cell dysfunction of the hereditary hearing impairment in the clinical fields.
Acoustic Stimulation↗
An investigation into the deformable characteristics of the human foot using fluoroscopic imaging.
BACKGROUND: To determine the behaviour of the human foot during in vivo loading and unloading. METHODS: Fluoroscopic imaging was used to investigate the movement of the bones and 13 skin markers during loading and unloading for the medial aspect of the left foot. A foot-pressure measuring system was compared with a force plate used to gather kinetic information, simultaneously. Four male and two female subjects performed three tasks that mimicked jumping, walking, and sprinting. Two-dimensional vector displacements were calculated between bone landmarks over time. Foot rigidity was assessed by a 5 mm length variability threshold determined as the difference between the third and first quartiles of the data set. FINDINGS: The displacement between the first metatarso-phalangeal joint and distal aspect of the calcaneous varied more than the 5 mm threshold. A new foot model was developed which included three rigid segments joined together by hinge joints located at the first metatarso-phalangeal joint and between the anterior talus and navicular. The comparison between skin mounted markers and bone landmarks yielded a range of correlation slopes close to 1.00 for both the x- and y-directions. Foot pressure and force plate comparisons were promising (%RMS(error) approximately 10%) for the vertical ground reaction forces but not so for the centres of pressure (%RMS(error) up to 50%). INTERPRETATION: A multi-segment foot model is required to better represent the behaviour of a human foot. No consistent skin marker movement was determined. Better pressure distribution devices need to be developed to determine more accurate foot kinetics. Precise foot kinematics are required in order that accurate ankle moments and reaction forces be determined for the purpose of assessing foot and ankle function.
Biomechanical Phenomena↗
SeqQC-former: A sequence-quality fusion framework for QC-aware review prioritization of candidate somatic SNVs in cancer genomics.
The accurate prioritization of candidate somatic single-nucleotide variants (SNVs) remains a challenge due to the substantial variability in sequencing quality across genomic loci. SeqQC-Former is a sequence-quality fusion framework that integrates the local nucleotide context with read-level quality-control (QC) covariates derived from matched tumor-normal sequencing data. This integration generates QC-aware prioritization scores for the downstream review of candidate variants. Unlike conventional variant callers, SeqQC-Former is designed not to infer biological truth but to support post-calling review and prioritization under heterogeneous sequencing conditions. The framework was trained and evaluated on a SEQC2-derived dataset comprising 89,447 candidate loci, including 1378 positive and 88,069 negative loci. In chromosome-held-out validation, which aims to reduce potential genomic-position leakage, SeqQC-Former demonstrated strong discrimination (AUROC = 0.9479; AUPRC = 0.9448), indicating good generalization to previously unseen chromosomes. Given that the SEQC2-derived labels contain QC-associated information; these results should be interpreted as an evaluation of QC-aware prioritization capability rather than an independent validation of biological variant correctness. Ablation analyses revealed that structured QC covariates provided the dominant predictive signal under the current SEQC2-derived labeling regime. SeqQC-Former achieved a significantly higher AUROC than classical machine-learning baselines, as determined by DeLong's test (p < 0.01). Application to 53,164 glioblastoma variants demonstrated that external predictions were sensitive to QC scaling and threshold selection, underscoring that model outputs should be interpreted as QC-dependent prioritization scores rather than calibrated probabilities or definitive biological classifications. Overall, SeqQC-Former offers a reproducible post-calling QC-aware prioritization framework for large-scale somatic SNV review and underscores the importance of explicitly modeling sequencing-quality information when interpreting structured cancer genomics datasets.
Humans↗
Refine your search to explore more results.