Enzymatic synthesis of melatonin in avian pineal body: extraretinal response to light.

In the chick pineal body, activity of the melatonin-forming enzyme hydroxyindole-O-methyl transferase is greater in the light than in darkness. Neither bilateral enucleation of the eyes nor sympathetic denervation prevented this light-induced elevation of enzyme activity. This fact indicates that in the bird, in contrast to mammals, neither the retinas nor sympathetic innervation of the pineal body are essential for environmental control of melatonin formation.

Lid suture myopia in chicks.

Domestic chicks reared under continuous light developed light-induced avian glaucoma (LIAG), including eye enlargement and flat cornea. Chicks reared under dim light developed dim light buphthalmos (DLB), a somewhat similar eye enlargement, superimposed on the LIAG effect when, as in one subgroup of the present experiments, the dim light was also continuous. Unilateral lid suture elicited experimental myopia on the operated side, additive to the LIAG and/or DLB effects. When the rearing conditions were diurnal (ie, not such as to induce LIAG eye enlargement), and the light of at least "normal" brightness, lid suture still caused unilateral myopia, accompanied by a pronounced bulging of the cornea. We discuss the probable effects of these changes on refraction and accommodation during the chick's development.

Retinal pigment epithelium: ring mitochondria and lesions induced by continuous light.

Electron micrographs of avian retinal pigment epithelium (RPE) reveal a basal zone of abundant mitochondria, approximately 15% of which present ring-shaped profiles. We infer that these ring profiles represent cross sections of "donut-shaped" bodies, randomly deployed in the RPE mitochondrial zone. The per cent of all RPE mitochondria which are in the ring form increases with age, and is further increased in chicks reared under continuous light, an environmental condition leading also to light-induced avian glaucoma (LIAG). We calculate that a given mitochondrion, on assuming the ring form, would more than double its surface area. Thus the RPE mitochondria of chicks developing LIAG may present to the surrounding cytoplasm a total surface area more than fourfold greater than in normal chicks.

Diurnal mitochondrial changes in avian retinal pigment epithelium: a search for correlation with thyroid state.

The avian retinal pigment epithelium (RPE) is well endowed with mitochondria, 10-15% of which appear to be "donut-shaped". The number of such mitochondria presenting ring profiles varies with the photoperiod, with a peak early in the dark period and a low early in the light period. This cycle is inversely correlated with the diurnal rhythm of plasma thyroxine (T4), but is in phase with the T3 cycle. We could detect no effect on the numbers of ring mitochondria when exogenous TSH, T4 or T3 was injected. Numbers and appearance of ring mitochondria were likewise unaltered in chicks breathing pure oxygen or spent air for 15 min. before sacrifice. We speculate that this aberrant mitochondrial form may have some relationship to the processing of shed outer segment discs, also a photoperiod-driven phenomenon. It has been suggested that the daily manufacture of hydrolytic enzymes for breakdown of disc proteins is probably highly energy-expensive. We also note that the peroxidation of the lipid components of these membranes must be another aspect of disc disposal. Ascorbic acid, whose photooxidation in the eye generates hydrogen peroxide, may play a role in this process.

Chicks blinded with formoguanamine do not develop lid suture myopia.

The involvement of the retina in avian lid suture myopia was investigated by use of formoguanamine (FG), which induces blindness in chicks, characterized by damage to the retinal pigment epithelium and photoreceptor layers. In control chicks reared under a diurnal lighting schedule of 12L/12D, unilateral eyelid suture at 3 days of age induced a typical lid suture myopia response on the operated side (eye enlargement and bulging cornea) by 4 wks. of age. On the other hand, in FG-treated blind chicks also reared under 12L/12D, there was no difference in eye parameters, between sutured and non-sutured eyes. All globe parameters measured were very similar in FG-treated and control non-sutured chicks. Corneal diameter and anterior chamber depth in the eyes of FG-treated chicks were significantly smaller than in non-sutured control eyes.

Ocular responses of genetically blind chicks to the light environment and to lid suture.

Blind rc chicks were examined as to growth characteristics of the developing eye. We also explored the relationship between hereditary blindness and two environmental interventions affecting eye development, light-induced avian glaucoma (LIAG) and the axial lengthening associated with lid-suture. Genetically blind rc chicks could be identified by their behavior even during the first hours after hatching. However, they retained the pupillary reflex, at least to 5 weeks of age. Blind chicks reared under a diurnal lighting schedule had eyes 18% larger (by eye weight) than sighted hatchmates, with corresponding increases in globe diameters. Of the anterior segment parameters, neither corneal diameter, anterior chamber depth nor corneal curvature was demonstrably different from sighted controls. When rc chicks were reared under continuous light, the environmental condition which brings on LIAG, their already enlarged eyes showed no superimposed increases in either eye weight or globe dimensions. The corneas showed some characteristic LIAG effects: small anterior chamber depth and increased corneal radius of curvature (flat cornea), as compared with diurnal rc birds. Some birds were subjected to unilateral eyelid-suture, a protocol which usually induces axial lengthening and corneal bulging. Blind rc birds did not respond to this surgical intervention: in comparison by paired t-test between sutured and contralateral eye, there was little or no difference in eye weight, globe diameters or anterior segment parameters. Thus vision, or at least an intact retina/RPE, seems to be necessary for development of the characteristic axial lengthening in response to eyelid suture. The globe enlargement of LIAG also appears to be vision-dependent, although the anterior segment manifestations of LIAG are systemic effects.

Eye enlargement in birds induced by dim light.

We here report changes in eye weight and other measurements, in chickens reared in dim light. These effects are distinguished from those seen in light-induced avian glaucoma (brought on by exposure to continuous light). We confirm and extend the results of Berkovitz and Harrison on the dim light effect, but we differ from Axmith and Morin, who were apparently unable to reproduce light-induced avian glaucoma. We cannot yet offer an explanation as to the mechanism(s) of eye damage in either light-induced avian glaucoma or dim light-induced macrophthalmos.

The water provocative test in preglaucomatous chickens.

Our ability to induce glaucoma in birds provides an experimental system for exploring the mechanisms involved in the provocative water test. Waters loads of a level comparable to those used clinically produced larger intraocular pressure (IOP) changes in preglaucomatous and glaucomatous birds than in control birds. The magnitude of the response corresponded to the level of IOP before testing, that is, to the severity of the glaucoma. Changes in systemic blood pressure were not involved in the response. While hyotonicity of plasma may be the systemic determinant, the normal range of variation in this factor does not allow us at present to consider this a causal relationship.

Timolol and pilocarpine are hypotensive in light-induced avian glaucoma.

Two antiglaucoma drugs were tested on Hubbard chicks with light-induced avian glaucoma (LIAG). This animal model for open-angle glaucoma was further assessed by a novel method for monitoring aqueous inflow and outflow simultaneously. When the chicks were 8 to 9 weeks of age the preglaucomatous eyes were significantly enlarged (p less than 0.001), weighing a mean of 3.37 g, compared with 2.59 g for a group of normal eyes, but the intraocular pressure (IOP) was slightly lower in the former (13.79 v. 16.46 mm Hg; p less than 0.05). At this age the aqueous outflow was markedly reduced (to 0.70 v. 2.47 microL/min; p less than 0.05), but no change in aqueous inflow could be demonstrated. By 18 to 20 weeks the glaucomatous eyes were further enlarged (mean weight 4.67 v. 3.76 g; p less than 0.001) and hypertensive (mean IOP 29.85 v. 22.27 mm Hg; p less than 0.05). Timolol elicited a 29% to 33% reduction in the IOP at 8 to 9 weeks in both groups of eyes. At 18 to 20 weeks it reduced the IOP of the glaucomatous eyes to normal values but caused a less marked reduction in the normal eyes. Pilocarpine elicited an initial sharp rise in the IOP but was ultimately hypotensive, causing about a 33% decrease from the preinfusion IOP, in both young and adult birds.

Adjustment of sleep and the circadian temperature rhythm after flights across nine time zones.

The adjustment of sleep-wake patterns and the circadian temperature rhythm was monitored in nine Royal Norwegian Air-force volunteers operating P-3 aircraft during a westward training deployment across nine time zones. Subjects recorded all sleep and nap times, rated nightly sleep quality, and completed personality inventories. Rectal temperature, heart rate, and wrist activity were continuously monitored. Adjustment was slower after the return eastward flight than after the outbound westward flight. The eastward flight produced slower readjustment of sleep timing to local time and greater interindividual variability in the patterns of adjustment of sleep and temperature. One subject apparently exhibited resynchronization by partition, with the temperature rhythm undergoing the reciprocal 15-h delay. In contrast, average heart rates during sleep were significantly elevated only after westward flight. Interindividual differences in adjustment of the temperature rhythm were correlated with some of the personality measures. Larger phase delays in the overall temperature waveform (as measured on the 5th day after westward flight) were exhibited by extraverts, and less consistently by evening types.

International aircrew sleep and wakefulness after multiple time zone flights: a cooperative study.

An international research team has carried out an electroencephalographic study of sleep and wakefulness in flight crews operating long-haul routes across seven or eight time zones. Following baseline recordings, volunteer crews (n = 56) from four airlines spent their first outbound layover at a sleep laboratory. This paper provides an overview of the project's history, its research design, and the standardization of procedures. The overall results are remarkably consistent among the four participating laboratories and strongly support the feasibility of cooperative international sleep research in the operational arena.