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Biomedical subjects

R F Miller

Publications and source records attributed to R F Miller.

At least 325 records · Page 18Linked to original sources
PubMed1980

Electrophysiological analysis of taurine and glycine action on neurons of the midpuppy retina. I. Intracellular recording.

Intracellular recordings were carried out in the prefused retine-eyecup preparation of the mudpuppy. Taurine and glycine were added to the bathing medium to study their effects on different retinal neurons. In a few cases, gamma-aminobutyric acid was exogenously applied to compare GABA vs taurine/glycine action. Receptors and horizontal cells were relatively insensitive to taurine/glycine, while amacrines and ganglion cells were comparatively more sensitive to these agents. Bipolar cells proved to be differentially effected by inhibitory amino acids: hyperpolarizing (OFF) bipolars were depressed by taurine/glycine and proved less sensitive to GABA; depolarizing (ON) bipolars were suppressed by GABA and were comparatively less sensitive to glycine/taurine. Taurine and glycine had identical actions on neurons and both were about equally effective at the same concentration. Strychnine blocked the action of taurine and glycine. The patterns of glycine/taurine sensitivity and their effects on second order neurons eliminate taurine as a photoreceptor transmitter; one or both of these agents may be utilized by a subclass of amacrine cells which interact with hyperpolarizing bipolars, other amacrine cells and ganglion cells. It appears that taurine or glycine or both may be selectively involved in OFF channel activity, while GABA may subserve an equivalent role for the ON channel.

Animals↗
PubMed1980

Electrophysiological analysis of taurine and glycine action on neurons of the mudpuppy retina. II. ERG, PNR and Müller cell recordings.

Extracellular electrophysiological recordings of the electroretinogram (ERG) and proximal negative response (PNR) were carried out in the perfused retina-eyecup prepartation of the mudpuppy. Intracellular recordingws were obtained from Müller cells. Bath-applied taurine/glycine had identical effects on the ERG, PNR and Müller cell responses and the effects of both agents were blocked by strychnine. Taurine and glycine suppressed the d-wave of the ERG, the OFF response of Müller cells and ON and OFF responses of the PNR. These observations show that taurine/glycine sensitivity is predominantly found in the OFF channel of the ERG whose underlying neuronal basis appears to be dark evoked depolarization of OFF bipolars.

Animals↗
PubMed1979

Pathways and polarities of synaptic interactions in the inner retina of the mudpuppy: I. Synaptic blocking studies.

Intracellular recording techniques were applied to the perfused retina-eyecup of the mudpuppy (Necturus maculosus). The use of input resistance measurements and the application of cobalt as a synaptic blocking agent provided evidence about the mode of synaptic operation for depolarizing and hyperpolarizing bipolar cell input to cells of the inner retina. In addition, cobalt produced a more rapid block of hyperpolarizing bipolars compared to depolarizing bipolars; in some postbipolar neurons, a temporary simplification of neuronal response waveform was observed and such cells resembled the depolarizing bipolar. These experiments suggest that bipolar cell input is excitatory and that response characteristics of third-order neurons is partially dependent on the relative input from the two types of bipolar cells.

Animals↗
PubMed1979

Pathways and polarities of synaptic interactions in the inner retina of the mudpuppy: II. Insight revealed by an analysis of latency and threshold.

Intracellular recording experiments in the mudpuppy (Necturus maculosus) have demonstrated that depolarizing bipolars show a one-half to one log unit higher threshold to light stimuli and a longer latency when compared to hyperpolarizing bipolars. This threshold difference cannot be ascribed to differences in rod and cone connections. Experimentally it was possible to use these differences to evaluate postbipolar cell connections; such experiments support the idea that some neurons are connected to one or the other bipolar cell type, while on-off cells receive input from both.

Animals↗
PubMed1979

Modernizing an ambulatory care pharmacy in a large multi-clinic institution.

The steps involved in modernizing an outdated outpatient pharmacy, including the functional planning process, development of a work-flow pattern which makes the patient an integral part of the system, budget considerations and evaluation of the new pharmacy, are described. Objectives of the modernization were to: (1) provide a facility conductive to efficient and high quality services to the ambulatory patient; (2) provide an attractive and comfortable area for patients and staff; (3) provide a work flow which keeps the patient in the system and allows the pharmacist time for instruction and patient education; and (4) establish a patient medication record system. After one year of operation, average overall prescription volume increased by 50%, while average waiting time declined by 74%. Facility and procedural changes allowed the pharmacist to substantially increase patient counseling activity. The application of functional planning and facility design to the renovation and restructuring of an outpatient pharmacy allowed pharmacists to provide efficient, patient-oriented service.

Budgets↗
PubMed1977

Amacrine cells in Necturus retina: evidence for independent gamma-aminobutyric acid- and glycine-releasing neurons.

About one-half of on-off ganglion cells have inhibitory postsynaptic potentials (IPSP's) which are blocked by strychnine, while the remainder have IPSP's which are blocked by picrotoxin or bicuculline. These antagonists do not abolish light activity of the presynaptic inhibitory neuron, the amacrine cell. The existence of separate gamma-aminobutyric acid- and glycine-releasing amacrine cells is implied by these results.

Aminobutyrates↗
PubMed1977

Spontaneous slow potentials and spreading depression in amphibian retina.

1. In frog and mudpuppy eye cups perfused with low-chloride solution, two types of slow potential phenomena were studied. One type, "spontaneous slow potentials" (SSPs), appeared both in the dark and during light stimuli. The other type, the slow potential change (SPC) of spreading depression (SD), appeared at termination of long-duration light stimuli. 2. The SSPs were analyzed by depth-profile studies, pharmacologic studies, and the use of potassium-specific electrodes. Results indicated that SSPs may represent spontaneous d-waves that travel across the retina. The SSPs are associated with potassium activity, and the main response is probably generated by Müller cells. Initiation and/or propagation appear to require chemically mediated synaptic transmission and impulse activity. 3. Depth-profile studies were also done of the SPC of SD induced by termination of long-duration light stimuli. Results indicated that the SPC is not an exaggerated d-wave. The SPC consists of two components, the second of which reverses more superficially than the d-wave. The main SPC response is probably generated by Müller cells. Although impulse activity does not appear to be necessary for SD, it may contribute to this complex response.

Action Potentials↗
PubMed1976

Photoreceptor-bipolar cell transmission in the perfused retina eyecup of the mudpuppy.

The hypothesis that a synaptic transmitter is released by photoreceptors in the dark is supported by experiments in which cobalt was used as a synaptic blocking agent, while intracellular recordings of receptors and neurons that are directly postsynaptic to receptors were maintained. In the dark the depolarizing bipolars are hyperpolarized, whereas the hyperpolarizing bipolars are depolarized.

Animals↗
PubMed1976

Synaptic organization and ionic basis of on and off channels in mudpuppy retina. I. Intracellular analysis of chloride-sensitive electrogenic properties of receptors, horizontal cells, bipolar cells, and amacrine cells.

Intracellular recordings from receptors, horizontal cells, bipolars, and amacrines have been carried out in the perfused mudpuppy eyecup. The introduction of a chloride-free (c-f) medium results in initial transient potential changes in many cells followed by a slow loss of light-evoked activity of the depolarizing bipolar, the horizontal cell, and the on depolarization of amacrine cells. The hyperpolarizing bipolar remains responsive to light stimulation in a c-f medium, but the antagonistic surround mechanism is abolished. These effects are reversible after returning to a normal ionic medium. The results of this study provide insight into the retinal connections which underlie ganglion cell receptive field organization. It is concluded that the depolarizing bipolar is excitatory to on ganglion cells and is also the pathway for on-excitation of on-off cells. The hyperpolarizing bipolar mediates the off discharge of off and on-off cells. Amacrine cells receive input from both depolarizing and hyperpolarizing bipolar cells. These findings raise the possibility that transmembrane movements of chloride ions are critical for the light responsiveness of horizontal and depolarizing bipolar cell activity.

Animals↗
PubMed1976

Synaptic organization and ionic basis of on and off channels in mudpuppy retina. II. Chloride-dependent ganglion cell mechanisms.

Extracellular ganglion cell recordings in the perfused mudpuppy eyecup show that a chloride-free (c-f) perfusate abolishes the center and surround excitation of on-center cells, the surround excitation of off-center cells, and the on discharge of on-off cells. These changes in ganglion cell receptive field organization are anticipated in view of the effects of a c-f environment on the neurons which are presynaptic to the ganglion cells. However, chloride-dependent inhibitory postsynaptic (IPS) responses have been observed in on-off ganglion cells. These inhibitory postsynaptic potentials (IPSP's) are preceeded by (ESPS's) exitatory postsynaptic potentials and are apparently mediated by amacrine cells. The light-activated hyperpolarization of off cells is not the result of a chloride-dependent IPSP and probably results from disfacilitation.

Animals↗
PubMed1976

Synaptic organization and ionic basis of on and off channels in mudpuppy retina. III. A model of ganglion cell receptive field organization based on chloride-free experiments.

A chloride-free environment produces selective changes in the retinal network which include a separation of on and off channels. The identification of chloride-sensitive and insensitivie neuronal activity permits identification of some of the connections and intervening polarities of synaptic interactions which are expressed in ganglion cell receptive field organization. These experiments support previous suggestions that surround antagonism is dependent on horizontal cell activity. In addition they suggest a model of the neuronal connections which subserve on-center, off-center, and on-off ganglion cells. Experimental tests of the on-off ganglion cell model favor the idea that this type of ganglion cell receives inhibitory input from amacrine cells and excitatory activation from depolarizing and hyperpolarizing bipolar cells.

Animals↗