Role of the suprachiasmatic nuclei in the circadian timing system of the squirrel monkey. II. Light-dark cycle entrainment.

The role of the suprachiasmatic nuclei (SCN) in light-dark (LD) cycle entrainment in the squirrel monkey (Saimiri sciureus) was evaluated by continuously monitoring core body temperature and drinking behavior in both intact and SCN-lesioned animals exposed to different LD conditions. In a 24-h LD cycle with 12 h of light per day (LD 12:12), both intact and SCN-lesioned monkeys had a prominent rhythm in body temperature with an acrophase 6.51 +/- 0.

Role of the suprachiasmatic nuclei in the circadian timing system of the squirrel monkey. I. The generation of rhythmicity.

The circadian organization of squirrel monkey (Saimiri sciureus) drinking behavior was evaluated before and after the placement of radiofrequency lesions which completely destroyed the suprachiasmatic nuclei (SCN) in 4 monkeys and partially ablated the SCN in another 4 animals. In continuous illumination (LL: 600 lux) prior to surgery, each monkey had a precise free-running circadian rhythm of drinking behavior with a period of 25.31 +/- 0.

Vasopressin injected into the hypothalamus triggers a stereotypic behavior in golden hamsters.

Microinjection of arginine vasopressin into the medial preoptic area of the hypothalamus of male and female golden hamsters triggered a complex, stereotypic behavior--flank marking--a type of scent marking used in olfactory communication. The flank marking was not elicited by saline, oxytocin, neurotensin, or angiotensin II. Vasopressin was ineffective when injected into other areas of the hypothalamus or into the lateral cerebroventricle.

Avian pancreatic polypeptide phase shifts hamster circadian rhythms when microinjected into the suprachiasmatic region.

The suprachiasmatic nucleus has been identified tentatively as a circadian pacemaker. To examine the functional role of peptides found within suprachiasmatic neurons, avian pancreatic polypeptide and vasopressin were microinjected into the suprachiasmatic region. Avian pancreatic polypeptide, but not vasopressin, shifted the phase of the wheelrunning rhythm as a function of the time of its injection within the circadian cycle.

Sex differences in circadian control of LH secretion.

Sex differences in the hourly values of serum LH were examined in male and female Syrian hamsters exposed to either long photoperiods (14 h light: 10 darkness; 14L: 10D) or short photoperiods (6L: 18D). In long photoperiods, females exhibited a pro-oestrous surge of LH in response to high levels of circulating oestradiol (1047.36 +/- 90.

Auditory entrainment of primate drinking rhythms following partial suprachiasmatic nuclei lesions.

In the absence of other environmental cycles, daily variations in auditory stimuli are normally not capable of entraining the circadian rhythms of drinking behavior in the squirrel monkey (Saimiri sciureus). However, the drinking rhythm appears to become entrainable by previously ineffective auditory cues after lesions are placed which destroy only the caudal portion of the hypothalamic suprachiasmatic nuclei. The results suggest specificity of function within the SCN and an increased influence of auditory stimuli in animals with impaired SCN function.

Circadian organization of locomotor activity in the Turkish hamster (Mesocricetus brandti).

The circadian organization of locomotor activity was examined in Turkish hamsters while exposed to a light-dark (LD) cycle, constant illumination (LL), and following blinding and gonadectomy. Under LD 16:8 the activity rhythm of all hamsters became well entrained with activity beginning approximately 30 min after dark onset. In contrast, when activity rhythms free-ran as the result of exposure to LL or blinding, a variety of spontaneous perturbations in the period and/or phase of the activity rhythm were observed.

Entrainment and masking of circadian drinking rhythms in primates: influence of light intensity.

The entrained drinking rhythms of squirrel monkeys were studied during exposure to 24 hr illumination cycles of three different intensities (60:0, 66:6, 76:16 lux). Increasing the intensity of ambient illumination significantly delayed the offset of drinking but had no effect on either the onset or the total amount of daily drinking behavior. Comparison of drinking behavior under an alternating schedule of LD 66:6 lux and constant light of 6 lux indicated that the twice daily light transitions consistently altered the temporal distribution of drinking behavior.

Three-dimensional structure of the mammalian suprachiasmatic nuclei: a comparative study of five species.

The suprachiasmatic nuclei from five mammalian species (rat, hamster, cat, rhesus, and squirrel monkey) were reconstructed in three-dimensions by use of computer graphics and conventional histological techniques. The gross nuclear structures of the suprachiasmatic nuclei have complex three-dimensional geometries in every plane of orientation, and between the five species there are marked differences in the three-dimensional morphology of the suprachiasmatic nuclei. These dimensionally accurate reconstructions are discussed in relation to previous data suggesting morphological and/or functional specialization within specific regions of the suprachiasmatic nuclei.

Gradual decay of circadian drinking organization following lesions of the suprachiasmatic nuclei in primates.

The circadian organization of squirrel monkey drinking behavior was examined in constant illumination following lesions which totally destroyed the suprachiasmatic nuclei. Although these lesions eventually led to a severe disruption in the temporal organization of drinking behavior, a statistically significant circadian pattern of drinking was observed in each monkey for at least 4-6 weeks after lesioning.

Circadian rhythm of body temperature persists after suprachiasmatic lesions in the squirrel monkey.

Squirrel monkeys (Saimiri sciureus) demonstrate prominent circadian (approx 24 h) rhythms in many behavioral and physiological variables including drinking and body temperature. Both of these rhythms can be entrained by a 24-h light-dark cycle (LD 12:12) but will free-run with an endogenous period in a constantly illuminated (LL:600 lx) environment free of time cues. After radio-frequency lesions were placed stereotaxically in the suprachiasmatic nuclei (SCN) of five monkeys, the circadian rhythm of drinking behavior was disrupted when the monkeys were maintained in LL.

Circadian rhythm dissociation in the rat: effects of long-term constant illumination.

Long-term exposure to constant dim illumination dissociated the circadian activity rhythms of female rats. Evaluation of this phenomenon by visual and spectral analysis indicated that ultradian rhythms survive the breakdown of circadian organization.

Gonadal hormones organize and modulate the circadian system of the rat.

The circadian wheel-running rhythms of gonadectomized adult male, female, and perinatally androgenized female rats, maintained in constant darkness, were examined before and after implantation of Silastic capsules containing cholesterol (C) or estradiol-17 beta (E). The free-running period of the activity rhythm (tau) before capsule implantation tended to be shorter in animals exposed to perinatal androgen. Administration of C did not reliably alter tau in any group.

[Biochemical and morphologic studies on prostaglandins E and F in the normal and inflamed gingiva].

With the help of a radioimmunoassay for prostaglandins E and F, an attempt was made to determine the actual concentration of these substances in normal and inflammatorily altered gingival tissue. The content of PGE and PGF was significantly higher in the inflammatorily altered gingiva than in normal tissue. Morphologic examination using immunologic methods showed prostaglandin E particularly in the monocytes.

[The problem of characterization of sterins in the gingiva by means of gas chromatography--mass spectrometry].

Methods suitable for demonstrating previously unidentifiable substances in healthy and diseased gingiva via gas chromatography/mass spectrometry were described. The advantage of these methods is that the substances can be directly demonstrated from the tissue available. The steps necessary to isolate and demonstrate the substances were explained on the basis of the phytosterol campesterol.