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J S Bryan

Publications and source records attributed to J S Bryan.

10 recordsLinked to original sources
PubMed1994

Experimental vitreous replacement with perfluorotri-n-propylamine.

OBJECTIVE: To evaluate perfluorotri-n-propylamine, a perfluorocarbon oil, as a temporary vitreous replacement in rabbits. METHODS: After undergoing gas compression vitrectomy, rabbits were injected with perfluorotri-n-propylamine for 24 hours or 2 weeks. The rabbits were evaluated clinically and with electroretinography. The globes were then enucleated and processed for histological evaluation. RESULTS: Clinical results showed droplet dispersion in the 2-week but not in the 24-hour group. Histological evaluation showed no changes in the retinal pigment epithelium or photoreceptor outer segments. Foam cells were seen in the 2-week but not in the 24-hour group. There was a marked dampening of the electroretinographic response that normalized after the removal of the oil. CONCLUSIONS: Perfluorotri-n-propylamine demonstrated no retinal toxic side effects in rabbits and is a promising liquid perfluorocarbon oil.

Animals↗
PubMed1994

Management of retinal detachments secondary to cytomegalovirus retinitis.

Nine patients with acquired immune deficiency syndrome underwent surgery for rhegmatogenous retinal detachments related to cytomegalovirus (CMV) retinitis. The patients were followed for at least 6 months or until death. Two patients with localized peripheral detachments for 3 to 4 clock hours or less initially underwent laser retinopexy. Although in both cases the treatment ultimately failed, one patient maintained 20/20 vision for 5 months. In four patients in whom the retinal detachment was more extensive but could be explained on the basis of a single or multiple well-defined peripheral break(s), a scleral buckle procedure was performed, with anatomic success in three, two of whom maintained 20/40 vision for 7 and 8 months. Six patients with retinal detachments associated with multiple atrophic holes that were not amenable to scleral buckling were treated with pars plana vitrectomy, air-fluid exchange and endolaser, with anatomic success in three; the visual acuity ranged from 20/30 to 20/400. One patient with failed pars plana vitrectomy underwent repeat vitrectomy with long-term internal tamponade by silicone oil, and he regained hand movements vision. We suggest a graduated approach to the management of retinal detachments secondary to CMV retinitis tailored to each patient based on the number and location of the retinal breaks, the extent of the detachment, the extent of necrotic retina and the overall health of the patient.

AIDS-Related Opportunistic Infections↗
PubMed1992

Levator-sparing nuclear oculomotor palsy. Clinical and magnetic resonance imaging findings.

Two patients with diplopia presented with unilateral oculomotor palsy, defective elevation of the contralateral eye, and sparing of the levator palpebrae muscle. In each case, magnetic resonance imaging disclosed an infarction of the oculomotor nuclear complex in the mesencephalon. This clinical neuroradiological correlation is consistent with Warwick's scheme pertaining to the neuroanatomy of the oculomotor nuclear complex and demonstrates the utility of MRI in diagnosing ocular motility disorders of brainstem origin.

Aged↗
PubMed1977

Protection from habituation of the crayfish lateral giant fibre escape response.

1. Habituation of the lateral giant fibre escape response in the crayfish to repetitive tactile stimuli is believed to result from homosynaptic depression at the first synapse of the reflex, between tactile afferents and interneurones. Normally, habituation of escape responses to repeated innocuous stimuli is presumed to be adaptive. Experiments reported here were undertaken to determine whether habituation would occur under circumstances when it would presumably be maladaptive - in particular, when tactile receptors are stimulated by an animal's own tail-flip movements.2. Experiments were carried out on the crayfish isolated abdominal nerve cord, which contains the lateral giant reflex pathway.3. Compound e.p.s.p.s elicited in the lateral giant by electrical stimulation of tactile afferents decline by from 25 to 36% over a series of eleven trials at 1/5 sec (control series).4. To determine whether such a decline would occur when sensory afferents are stimulated during a ;tail-flip', stimuli were given as in the control series but each stimulus occurred 20 msec after direct electrical stimulation of a medial giant or lateral giant escape-command fibre at which time tail flexion movements of an intact animal would be in progress. Under these conditions% e.p.s.p. decline over 11 trials at 1/5 sec was only 16-45% of that occurring on the control series.5. This protective effect starts at about 10 msec after escape command neurone firing, is maximal at 20 msec, and thereafter declines, remaining weakly detectable at 100 msec. This time course is commensurate with that required for execution of a tail-flip movement. Thus, sensory afferent-to-lateral giant transmission is protected from depression if stimuli occur when a tail-flip movement is or should be occurring.6. Giant fibre spikes do not superimpose facilitation upon a depressed reflex pathway, nor accelerate rate of recovery from depression; rather, protection is attributable to actual prevention of development of the depressed state.7. Protection was also examined at the first synapse of the reflex, where the depression responsible for habituation is believed to occur, by recording intracellularly in the largest of the first-order interneurones (interneurone A) of the pathway. In absence of protection, ten stimuli presented at 1/4 sec caused a mean decline of 32% in the e.p.s.p. in interneurone A. When such stimuli followed directly evoked escape command neurone firing by 20 msec this decline was reduced by 59-100%.8. We suggest that protection serves to prevent crayfish from habituating to stimuli produced by their own tail-flip movements.

Action Potentials↗
PubMed1977

Presynaptic inhibition: the mechanism of protection from habituation of the crayfish lateral giant fibre escape response.

1. Mechanism of protection from habituation of the lateral giant escape reflex of the crayfish was studied. Experiments were designed to determine whether presynaptic inhibition of primary afferents for the reflex occurs following escape command neurone firing, and if so, whether it could account for protection of the first synapse from depression. 2. Synaptic transmission between afferents and interneurone A of the escape reflex is strongly inhibited following giant fibre spikes. 3. Giant fibre firing results in post-synaptic inhibition of interneurone A. However, inhibition of afferent input to interneurone A consistently outlasts both i.p.s.p.s and post-synaptic conductance increases in the neurone; the inhibition, therefore, is probably not exclusively post-synaptic. 4. Giant fibre firing results in excitability changes in sensory afferent terminals as measured by the amplitude of antidromic compound action potentials to focal electrical stimuli applied in the region of afferent terminals in the last abdominal ganglion. The time course of this effect parallels those of protection and inhibition of the first synapse. 5. The magnitude and time course of protection and inhibition of transmission to interneurone A parallel each other closely. Both processes considerably outlast measurable signs of post-synaptic inhibition. 6. We conclude that following giant fibre activity the first synapse of the lateral giant reflex is presynaptically inhibited and the presynaptic inhibition is responsible for the protection effect described in the preceding paper.

Action Potentials↗
PubMed1973

Habituation: regulation through presynaptic inhibition.

During tail-flip escape responses of crayfish, synaptic transmission at the habituation-prone synapses of the lateral giant reflex pathway is presynaptically inhibited. This prevents transmitter release and all subsequent postsynaptic actions and spares the reflex from becoming habituated to stimuli produced by an animal's own escape movements. These observations demonstrate the existence of a control circuit whose adaptive function is to regulate the malleability of inherently plastic synapses. They also suggest that regulation of plasticity could be a common use of presynaptic inhibition.

Action Potentials↗