A double-blind, placebo-controlled trial of the effect of chronically administered oral acyclovir on sperm production in men with frequently recurrent genital herpes.
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Acyclovir↗
Biomedical subjects
J D Conner
Publications and source records attributed to J D Conner.
Ionic and electrophysiological properties of retinal Müller (glial) cells of the turtle.
The ionic and electrophysiological properties of Müller cells, the principal glial element of the vertebrate retina, were investigated. The membrane potential of enzymatically dissociated and in situ Müller cells was about -80 mV and depended on external K+ concentration in a manner that was described by the Goldman-Hodgkin-Katz equation with a Na+-K+ permeability ratio of 0.037. The current-voltage relation showed marked inward rectification, with the input resistance at the resting potential being about 30 M omega for dissociated cells and about 3 M omega for in situ cells. In situ Müller cells were found to be electrically coupled to each other which could explain their lower resistance. We conclude that Müller cells are similar to other types of glia. In spite of a finite Na+ permeability their membrane potential is determined mainly by K+, they are electrically inexcitable and form an electrically coupled network in the retina.
Animals↗
Gigaseal patch clamp recordings from outer segments of intact retinal rods.
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Animals↗
The relation between excitation and adaptation within the rod's outer segment.
The relation between excitation and adaptation in vertebrate rod photoreceptors was studied by measuring the membrane current of toad rod outer segments in light the darkness. Steady illumination attenuated and sped and rod response to flashes, and it suppressed membrane current noise. When steady illumination ended, the rod's electrical response, the presumably the internal transmitter which caused it, decayed quickly, but adaptation's effects persisted temporarily. This new observation suggests that excitation and adaptation are loosely coupled phenomena which may be mediated by different chemical signals.
Acclimatization↗
Toad and frog rod photocurrents.
The size of Bufo marinus and rana pipiens rod photocurrents is similarly affected by changes in flash intensity. These species' rods also produce similar photocurrents during steady illumination, to which they both adapt. Thus, their transduction mechanisms are probably alike. Previous reports that frog and toad rod responses are different may have resulted from the use of an unusual procedure in which the rod outer segment was isolated from its inner segment.
Animals↗
The temporal properties of rod vision.
1. Profiles which represent rod thresholds for flickering fields seen against backgrounds of various intensity have shapes which depend on flicker frequency. Low frequency profiles rise smoothly as background intensity is increased. High frequency profiles are only affected by bright backgrounds, which cause them to rise steeply. Intermediate frequency profiles contain two distinct branches which resemble separate increment threshold functions. 2. The high intensity branches of two-branched threshold profiles cannot be attributed to cone intrusion. Instead, both branches of such profiles are mediated by visual mechanisms which have the spectral properties, the dark adaptation properties and the directional insensitivity of rod vision. Thus, the stimuli are detected by rods. 3. Plots of critical flicker frequency (c.f.f.) as a function of intensity contain two rising branches which are separated by a plateau (when modulation depth is large), or they form two enclosed lobes so that only intermediate frequencies, but neither high nor low ones, are seen (when modulation depth is small). C.f.f. is profoundly depressed by very bright light (above 100 scotopic trolands) which saturates rod vision. 4. In dim light rod modulation sensitivity functions resemble those of low-pass filters, but in bright light they resemble those of band-pass filters. 5. Several forms of rod mediated interference occur at moderate intensities, where rod vision's temporal properties ordinarily improve abruptly. With certain stimuli, rod signals conveying temporal information disrupt one another so completely that suprathreshold flicker cannot be seen within a ten-fold intensity range. 6. Many of these observations can be explained by the hypothesis that rod vision comprises two temporal channels which have different properties.
Flicker Fusion↗
Methionine enkephalin-induced shaking behavior in rats: dissociation from brain serotonin mechanisms.
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Animals↗
Rod photoreceptors detect rapid flicker.
It is widely believed that human rods cannot detect rapid flicker. With rod-isolation techniques, however, light-adapted rods detect flicker frequencies as high as 28 hertz, and the function relating rod critical flicker frequency to stimulus intensity contains two distinct branches. Human rod vision may, therefore, depend on two independent mechanisms.
Dark Adaptation↗