PubMed · 4180604
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
Declan M Sister. 1969. Loop induction system.. https://pubmed.ncbi.nlm.nih.gov/4180604/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A new method for fast perfusion of single adherent cells during whole-cell and single-channel patch-clamp measurements is described. The main advantages over previous methods are: (1) the solution surrounding a single cell in a Petri dish (or cover slip) can be exchanged without contamination of the entire cell population, and (2) only small quantities of test solution (50 microliters) are required. The method consists of inserting a patch pipette into a micro-perfusion chamber (MPC) where whole-cell and single-channel currents can be studied. A small volume (2-3 microliters) surrounding adherent single cells in a Petri dish is separated by enclosing it in a ring of Silicone rubber which is then pressed to the bottom of the dish. A drug-containing test solution (50 microliters) is supplied to a funnel at the chamber inflow. The MPC volume isolated from the main solution in the Petri dish is rapidly changed when suction is applied to the chamber outflow. The speed of solution exchange in the MPC (16 +/- 5 ms, n = 12) was estimated by observing changes in the tip potential of 1-M omega patch pipettes during rapid chamber perfusion with solutions of different ionic composition. The seal of the MPC with the surface of a Petri dish was approximated by measuring the electrical resistance between the MPC interior and a reference electrode placed in the Petri dish outside the MPC (range 300-500 M omega). Additionally, a radioactive calcium channel ligand [3H]isradipine was added to the MPC and the appearance of radioactivity in the Petri dish (outside the MPC) subsequently measured.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential input amplifiers are commonly used in the measurement of biopotential signals. This is because of their ability to reject common-mode signals, for example power-line interference. Rejection is further enhanced by referencing the subject to the instrumentation system. One such referencing technique uses a third subject electrode connected either to circuit common or to ground. However, these techniques are rarely explained or quantified in the literature. Four recording configurations are examined, isolated and non-isolated amplifiers with two and with three electrodes, and existing models are extended. From a brief assessment of power-line interference sources, it is concluded that only displacement currents induced into the leads and the body need be considered. The effect of these on the four configurations is analysed using SPICE. Results show that interference from displacement currents induced into the leads and into the body is dependent upon the recording configuration used and is significantly lower in three-electrode than in two-electrode amplifiers. Isolation also reduces levels of interference. It is concluded that the choice of referencing may affect interference levels on the biopotential signal significantly. Experimental and further analytical work is planned to confirm this.
OBJECTIVE: The feasibility and practicalities of performing probe-tube microphone measures with infants is addressed, as well as two aspects of acoustic functioning of infant ears: the real ear unaided response (REUR) and the real ear to coupler difference (RECD). DESIGN: Part 1 is a longitudinal study involving 12 infants. Serial measures of REUR were obtained over an 18-mo period. Infants were < or = 3 mo for the first test and < or = 21 mo at the last test visit. Practicalities of probe-tube microphone testing of unsedated infants and changes in the position (i.e., frequency) of the primary REUR peak were addressed. For part 2 of the project, 33 infants under 12 mo of age took part. A comparison of real ear hearing aid gain versus coupler gain was made. Test-retest differences for real ear aided response were estimated. RESULTS: Part 1 results indicate that probe-tube microphone measures in unsedated infants are feasible and show good within-subject repeatability. REUR measures for the more alert and mobile older subjects, as for the younger infants, showed an acceptably small degree of intersubject variability. The frequency of the primary REUR peak decreased during the first year of life, with a group mean of 2932 Hz reached at the end of the first year. However, thereafter, instead of stabilizing at around this value there was considerable fluctuation in the frequency of REUR peak. For Part 2, results a) confirmed the large RECD value for infants in the first year of life and b) showed a high degree of intersubject variability. Test retest measures of real ear aided response (REAR) gave values small enough to indicate the clear potential of probe-microphone use with infants during the hearing aid selection and fitting process. CONCLUSION: These findings should encourage attempts to carry out individual probe-tube microphone measurements with very young infants. They point to the need for infant hearing aid fitting procedures which involve such measurements to secure appropriate amplification.