Frequency dependence of phase shifts in human calcaneus in vitro.

2010 ◽  
Vol 127 (3) ◽  
pp. 2007-2007
Author(s):  
Keith A. Wear
Keyword(s):  
Frequency Dependence ◽  
Phase Shifts

Neuropeptide Y and glutamate block each other's phase shifts in the suprachiasmatic nucleus in vitro

Neuroscience ◽  
1997 ◽  
Vol 77 (4) ◽  
pp. 1049-1057 ◽  
Author(s):  
S.M Biello ◽  
D.A Golombek ◽  
M.E Harrington
Keyword(s):  
Neuropeptide Y ◽  
Suprachiasmatic Nucleus ◽  
Phase Shifts

Changes in ultrasonic attenuation indicative of early myocardial ischemic injury

1979 ◽  
Vol 236 (2) ◽  
pp. H340-H344 ◽  
Author(s):  
J. W. Mimbs ◽  
M. O'Donnell ◽  
J. G. Miller ◽  
B. E. Sobel
Keyword(s):  
Creatine Kinase ◽  
Frequency Dependence ◽  
Coronary Occlusion ◽  
Ultrasonic Attenuation ◽  
Ischemic Injury ◽  
Quantitative Indices ◽  
Myocardial Ischemic Injury ◽  
Definition Of ◽  
Early Manifestation

This study was designed to determine whether quantitative alterations in ultrasonic attenuation are associated with myocardial changes occurring after acute ischemic injury. Five hundred seventeen regions of myocardium from 41 dogs were studied in vitro at five intervals after coronary occlusion: 15 min, 1 h, 6 h, 24 h, 3 days, and 6 wk. Quantitative indices of ultrasonic attenuation were determined from the measured frequency dependence of the ultrasonic attenuation coefficient characterizing each myocardial region over the range 2-10 MHz. Independent definition of regions of ischemic injury was provided by either creatine kinase depletion or colloidal carbon dye distribution. Results of this study indicate that ischemic myocardial regions investigated 15 min to 24 h after coronary occlusion demonstrated ultrasonic attenuation significantly decreased from nonischemic regions (P less than 0.05). In contrast, ultrasonic attenuation was significantly increased in zones of ischemia or infarction investigated at 3 days and 6 wk after coronary occlusion (P less than 0.05 and P less than 0.01, respectively). These results indicate that altered attenuation of transmitted ultrasound by myocardium in vitro is an early manifestation of ischemia.

scholarly journals CT2A Cell Viability Modulated by Electromagnetic Fields at Extremely Low Frequency under No Thermal Effects

2019 ◽  
Vol 21 (1) ◽  
pp. 152 ◽  
Author(s):  
Olga García-Minguillán ◽  
Raquel Prous ◽  
Maria del Carmen Ramirez-Castillejo ◽  
Ceferino Maestú
Keyword(s):  
Cell Viability ◽  
Frequency Dependence ◽  
Electromagnetic Fields ◽  
Thermal Effects ◽  
Low Frequency ◽  
Human Beings ◽  
Cellular Mechanisms ◽  
Low Frequencies ◽  
Hsp90 Expression

The effects produced by electromagnetic fields (EMFs) on human beings at extremely low frequencies (ELFs) have being investigated in the past years, across in vitro studies, using different cell lines. Nevertheless, the effects produced on cells are not clarified, and the cellular mechanisms and cell-signaling processes involved are still unknown. This situation has resulted in a division among the scientific community about the adequacy of the recommended level of exposure. In this sense, we consider that it is necessary to develop long-term exposure studies and check if the recommended levels of EMFs are under thermal effects. Hence, we exposed CT2A cells to different EMFs at different ELFs at short and long times. Our results showed frequency dependence in CT2A exposed during 24 h to a small EMF of 30 μT equal to those originated by the Earth and frequency dependence after the exposure during seven days to an EMF of 100 µT at different ELFs. Particularly, our results showed a remarkable cell viability decrease of CT2A cells exposed to EMFs of 30 Hz. Nevertheless, after analyzing the thermal effects in terms of HSP90 expression, we did not find thermal damages related to the differences in cell viability, so other crucial cellular mechanism should be involved.

Frequency dependence of synaptic transmission in nucleus of the solitary tract in vitro

1986 ◽  
Vol 55 (5) ◽  
pp. 1076-1090 ◽  
Author(s):  
R. Miles
Keyword(s):  
Frequency Dependence ◽  
Stimulus Frequency ◽  
Cardiovascular Reflexes ◽  
Solitary Tract ◽  
Postsynaptic Inhibition ◽  
Similar Frequency ◽  
Synaptic Circuits ◽  
Long Latency ◽  
Excitatory Component

Afferent fibers from visceral sensory receptors enter the medulla oblongata, form the solitary tract, and synapse with neurons in the nucleus of the solitary tract. In the present study longitudinal slices were prepared from guinea pig medulla in order to examine the properties of transmission at these synapses in vitro. Synaptic responses to selective stimulation of solitary tract fibers were recorded intracellularly from neurons in an area, close to the obex and immediately medial and lateral to the tract, where arterial baroreceptor fibers are known to terminate. The amplitude of maximally evoked postsynaptic potentials (PSPs) in solitary tract neurons was strongly dependent on stimulus frequency. On increasing frequency from 0.5 to 20 Hz, a PSP depression of 80% was reached in 4-8 s. The mean depression was 35% at 5 Hz and 60% at 10 Hz. Sufficient local connections were retained in vitro that solitary tract stimulation evoked disynaptic inhibitory potentials and long latency, possibly polysynaptic, excitatory potentials in some neurons. The possibility that frequency-dependent changes in the efficacy of these local synaptic circuits contributed to PSP depression was examined. The role of postsynaptic inhibition in synaptic depression was tested by examining the frequency dependence of PSPs at membrane potentials close to the reversal of their excitatory component. The resulting hyperpolarizing PSPs were also depressed suggesting that a facilitation of postsynaptic inhibition at high frequency does not underlie the depression. The contribution of depression in multisynaptic excitatory pathways to PSP depression was assessed by exclusion. At low stimulus intensities, excitatory synaptic events with no long latency components were evoked. These events exhibited a similar frequency dependence to that of maximal PSPs. These results suggest that mechanisms operating at synapses made by solitary tract fibers are responsible for the frequency dependence of PSPs recorded in solitary tract neurons. Such mechanisms might contribute to the adaptation of some cardiovascular reflexes initiated by baroreceptors.

Identification of human myocardial infarction in vitro based on the frequency dependence of ultrasonic backscatter

1992 ◽  
Vol 91 (5) ◽  
pp. 3018-3025 ◽  
Author(s):  
Samuel A. Wickline ◽  
Edward D. Verdonk ◽  
Burton E. Sobel ◽  
James G. Miller
Keyword(s):  
Myocardial Infarction ◽  
Frequency Dependence ◽  
Ultrasonic Backscatter
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