Free-running circadian plasma cortisol rhythm in a blind human subject

The plasma cortisol rhythm in man has been presumed to be an endogenous circadian rhythm, synchronized by some external stimulus to an exact 24-h period. Sleep/wake and 'social activity' cycles have been considered as candidates for this synchronizer. Previous studies have suggested that the dark/light phase shifts associated with the sleep-wake cycle may be the external synchronizer, rather than the sleep/wake cycle itself. A totally blind, but otherwise normal subject was studied for a period of 50 days. Her hourly sleep/wake status and hourly integrated mean plasma cortisol concentrations were determined, and the data were subjected to non-parametric mathematical analysis. The subject was found to have a free-running rhythm in plasma cortisol with a period of approximately 24.5 h. Her sleep/wake rhythm, determined by similar analysis, had a period of exactly 24 h. In addition to the dominant 24.5-h cortisol rhythm, there appeared to be a minor 24-h cortisol rhythm with a peak that coincided approximately with the time of awakening. It was not possible to determine whether this sleep/wake-related peak represented a minor component of the circadian rhythm, synchronized by some stimulus associated with sleep/wake activity, or merely an acute response to awakening itself. Nevertheless, the two rhythms exhibited 'beating' behaviour, resulting in maximal peak cortisol concentrations when they were in synchrony and minimal peak concentrations when they were not. It is concluded that environment dark/light phase shifts are the dominant synchronizer of the circadian rhythm in plasma cortisol concentrations in man, as they are for a variety of circadian rhythms in other living things.

Influence of pinealectomy on serum estrogen and progesterone levels in blind-anosmic female rats

Previous studies show that the suppression of gonadal function in blind-anosmic rats is dependent on the pineal gland. The present results demonstrate that in young female rats both the pineal gland and dual sensory deprivation have additional independent antigonadal effects.

Mutual influence of rats having different circadian rhythm of adrenocortical activity

The possibility of a mutual influence between male adult rats having different circadian adrenocortical rhythms was studied under two different lighting conditions. Intact and optic-enucleated rats were housed together in the same cage in various ratios of intact to blinded rats. Twenty-four- or forty-eight-hour patterns of plasma corticosterone levels were determined individually at 4-h intervals. Under diurnal light-dark alternation, the circadian periodicity of the intact rats always synchronized with light, whereas single blinded rats in cages with three intact rats demonstrated free-running rhythms throughout the experimental period of 15 wk. Under constant light the circadian rhythm free-ran in both intact and blinded rats for the first 2 wk. A phase reversal of the rhythm was observed in the intact rats at the end of the 2nd wk, and between 5 and 8 wk after binding in the blinded rats. These results indicate that the circadian adrenocortical rhythms in intact and blinded rats are not entrained to each other, even when the two types of rats live together in the same cage.

Effects of age of blinding on rhythmic pituitary-adrenal function in female rats

These experiments were designed to study the effects of age of blinding on the circadian rhythm in pituitary-adrenal function in female rats. In the 1st experiment, the eyes were removed at 1 day of age and serial blood samples were obtained at 6-h intervals for 24 h at 45 days. In the 2nd experiment, rats were blinded at 1,26 or 60 days of age, and serial blood samples were collected at 4-h intervals for 44 h when the rats were 84, 112 and 142 days of age. Intact and sham-operated rats served as controls. Plasma corticosterone (cpd B) concentrations, measured fluorometrically, were used to assess pituitary-adrenal function. Blinding disrupted cpd B patterns in all groups on all occasions. However, steroid patterns of individual rats suggested the presence of free-running 24-h rhythms. This suggestion was supported by the results of aligning the steroid peaks of individual blinded rats. This procedure yielded group patterns of steroid levels which were comparable to those of controls. The periodic stimuli available to the blinded rats from intact rats in the same and adjacent cages did not synchronize this rhythm. These results suggest that the eyes and their central projections are not essential after birth for the development and maintenance of rhythmic pituitary-adrenal function; these structures appear necessary, however, for synchronization with light-dark cycles.

Effects of blinding, pinealectomy and superior cervical ganglionectomy on free thyroxine index of male golden hamsters

Blinding young male golden hamsters led to a depression of the plasma free thyroxine index after an 8 week period. Removal of either the pineal gland or the superior cervical ganglia of blind hamsters reversed the effects of blinding on free thyroxine index. No significant effects were observed 2 weeks after treatment. Previously reported effects of blinking, and removal of the pineal gland or the superior cervical ganglia on testicular weight were confirmed. A similar mechanism of pineal inhibition of thyroid function and gonadal function is suggested.

Transient monocular blindness

This paper is a review of the causes of intermittent monocular blindness. The nature of cholesterol and platelet retinal emboli is discussed. Their sources, the frequency with which they may cause transient or fixed blindness and the association between these emboli and pathology of the major cerebral vessels and other organs is discussed. Consideration is given to the equally important abnormalities of platelet behavior and to some of the physiology of retinal blood flow and non-embolic blindness. The current treatment of this symptom may be anticoagulation, surgical correction of a stenotic artery or both. The effect of treatment is unpredictable and in some situations the rationale is suspect. This review may provide a summary on which to base future studies of the effectiveness of various therapeutic agents.

[The effect of natural and artificial light via the eye on the hormonal and metabolic balance of man (author's transl)]

Examinations of hormone levels in blind persons compared with almost blind and people with normal vision and hormone evaluation with increased artificial light exposure show a definite stimulating effect of light on the human hormonal balance. The effect of light is mediated by an intact perception of light by the eye over an "energetic part" of the visual pathway (Hollwich 1948) - hypothalamus - hypophysis - peripheral endocrine gland. Increasing the intensity of artificial light with "neon-tubes" (fluorescent tubes) leads to "light stress" proved by increased hormone production - especially the stress hormone Cortisol. The belief that artificial light is the same as natural light and that it can fully replace it, is inappropriate in the medical view and needs correction.

Free thyroxin index in normal, melatonin-treated and blind hamsters

The administration of melatonin to young male hamsters depressed thyroxin levels, as measured by radioimmunoassay, by 38.5% of saline controls. Free thyroxin index was also signficantly depressed by melatonin injections. The depression of thyroxin and free thyroxin index by melatonin injections was more effective in intact than in pinealectomized animals. Blinding of hamsters also reduced both thyroxin and free thyroxin index.

L-Dopa stimulated growth hormone release in the blind

Following L-Dopa administration (single oral dose of 500 mg), plasma Growth hormone (GH) levels significantly rose in 7 out of 8 normal subjects (aged between 64-83) and in 4 out of 8 blind subjects (aged between 60-88). The mean peak +/- SE in the 8 normal subjects was 24.9 +/- 4.9 ng/ml and in the 8 blind subjects was 11.5 +/- 2.8 ng/ml. These findings represent an additional anomaly in pituitary hormone release in the blind and may indicate that dopamine receptors in the hypothalamus are less sensitive to L-Dopa in blind people than in normal subjects.

Evidence for a free-running circadian rhythm in pituitary-adrenal function in blinded adult female rats

To study the eyes' role in maintaining the circadian rhythm in pituitary-adrenal function, 24-h patterns of corticosterone levels were compared in intact and blinded adult female rats. Rats were blinded by optic enucleation at approximately 80 days of age. Nonstress plasma corticosterone levels were determined fluorometrically in serial blood samples obtained from a tail vein at 4-h intervals for 44-h periods, 3 and 10 weeks after surgery. At 3 weeks after surgery, blinded and intact rats demonstrated comparable rhythms in corticosterone levels. At 10 weeks, steroid fluctuations in individual blinded rats still had an approximate 24-h periodicity. However, these fluctuations were no longer synchronized with the light-dark cycle or with those of other rats. These findings suggest that rats blinded as adults have a free-running pituitary-adrenal circadian rhythm.

Circadian rhythm of plasma cortisol in the aged (Cosinor method)

Plasma cortisol circadian rhythm was investigated in 18 apparently healthy elderly subjects, in 11 elderly patients affected by cerebrovascular hemiplegia and in 11 otherwise healthy blind elderly subjects. Results were microscopically analyzed by the least squares and Cosinor methods. The circadian rhythm of plasma cortisol was present and normal both in elderly subjects and in elderly patients with cerebrovascular hemiplegia. By contrast, a plasma cortisol rhythm was not found in blind elderly subjects.

Effects of pinealectomy, anosmia and blinding on serum and pituitary prolactin in intact and castrated male rats

Serum prolactin was measured in lightly etherized rats between 4 and 5 a.m. and between 11 a.m. and 12 noon at various times after operation in intact rats and rats that had been operated on. Serum prolactin was elevated in the late nocturnal samples from intact rats and this elevation was prevented by pinealectomy. With time following the operation, daytime serum prolactin was also lowered in pinealectomized animals. In animals rendered anosmic by olfactory bulb removal, serum prolactin was also lowered. Superimposed pinealectomy only lowered late nocturnal serum prolactin in anosmic rats. Blinding the rats by ocular enucleation lowered nocturnal serum prolactin initially and dampened the daily rhythm in prolactin, but superimposed pinealectomy had no effect on the blinded animals. The combined sensory deprivation produced by both blinding and olfactory bulb removal resulted in low prolactin titers regardless of whether blood samples were taken during the day or late at night and, as in the case of blinded animals, there was no effect of pinealectomy. Superior cervical ganglionectomy also lowered serum prolactin. Serum prolactin declined following castration in intact animals and this decline was accentuated by pinealectomy. Either blinding or anosmia also lowered serum prolactin in the castrated animals but, as in intact animals, pinealectomy had little effect on the sensory-deprived rats. A further lowering of prolactin occurred in castrated animals which were both blinded and anosmic; in these animals, pinealectomy again had no additional effect. Measurement of the pituitary prolactin content in the castrated animals at sacrifice revealed a significant lowering of values in blinded animals, with restoration of the values to control levels by pinealectomy. Anosmia also lowered the pituitary prolactin content but this was not reversed by pinealectomy. The lowest pituitary prolactin was found in blinded, anosmic animals and these changes were not reversed by pinealectomy. The weight of the pineal gland increased significantly in anosmic, blinded, or blinded and anosmic rats. It is concluded that pineal secretions in the male rat elevate serum prolactin, particularly late at night, and that loss of input from olfactory and to a lesser extent from visual pathways results in a decrease in the titer of the hormone. This decrease is especially apparent in blinded, anosmic rats.

The pineal gland of the blind-anosmic female rat: its influence on medial basal hypothalamic lrh, pif and/or prf activity in vivo

25-day-old female rats were left intact, or rendered either blind-anosmic or blind-anosmic-pinealectomized. Five weeks later, blind-anosmic animals were found to possess significantly depressed body, anterior pituitary, uterine and ovarian weights. The pituitary levels of LH were elevated while pituitary prolactin was depressed in the dual sensory-deprived rats. Blind-anosmic animals also had significantly depressed plasma levels of LH and elevated plasma levels of prolactin. The effects of blinding and anosmia were effectively reversed by pinealectomy. Ovariectomized, estrogen and progesterone-treated (OVX, EP-treated) rats that received an intracarotid injection of a medial basal hypothalamic (MBH) extract from intact or from blind-anosmic-pinealectomized female rats exhibited a marked rise in plasma LH to a peak at 10 min after injection. This peak was followed by a steady decline in plasma LH concentration. Animals injected with MBH extract from blind-anosmic rats also demonstrated a rise in plasma LH with the levels remaining more or less constant for the 10 and 20-min samples. Rather than declining, the plasma LH levels in 3 out of 4 rats exhibited a further increase until the 40-min sample. The injection of either cortical extract or saline had no effect on plasma LH levels. OVX, EP-treated rats receiving either MBH extracts from intact or blind-anosmic rats or cortical extract exhibited a depression in plasma prolactin titers 5 min following injection. This response was followed by a slight increase in plasma prolactin at 10 and 20 min with a subsequent decrease. Each of the OVX, EP-treated recipients injected with MBH extract from blind-anosmic-pinealectomized rats responded with an obvious increase in plasma prolactin levels within 5 min after injection, followed by a decrease. It was concluded that the MBH of the blind-anosmic rat was high in LRH activity while PIF appeared to predominate over PRF activity. On the other hand, in the MBH of the blind-anosmic-pinealectomized rat, LRH activity was lower while PRF appeared to predominate over PIF activity.

Effects of the pineal gland in unilaterally adrenalectomized rats

The following experiments were undertaken to determine the effects that the pineal secretory substance might have on compensatory adrenal hypertrophy and corticosterone plasma levels in unilaterally adrenalectomized rats. It was demonstrated that blinded animals and animals administered with a bovine pineal extract exhibited a reduction in the percentage compensatory adrenal hypertrophy, a reduction in the thickness of the zona fasciculata, and a reduction in the plasma corticosterone level. These inhibitory effects were reversed by pinealectomy and ACTH injections, suggesting that the pineal gland, acting as a mediator for environmental lighting, might influence synthesis and/or release of ACTH.