Ontogeny of pineal melatonin rhythm in rats under 12:12-hr and 14:14-hr light:dark conditions.

The aim of the study was to determine whether a discrepancy between the genetically determined endogenous circadian period and an abnormally long Zeitgeber period disturbs the development of melatonin synthesis. Breeding pairs of rats were kept under 12:12- or 14:14-hr light:dark (LD) conditions. Pineal melatonin contents in the offspring were measured by radioimmunoassay.

Exogenous melatonin fails to counteract the light-induced phase delay of human melatonin rhythm.

Salivary melatonin levels were measured in 6 healthy volunteers in order to determine whether the phase shift caused by a single 60-min light pulse of 2000 lux might be inhibited by maintaining high melatonin concentration. In the control sessions, the samples were collected at 60-min intervals under lighting of < 10 lux from 18.00 to 11.

Daytime dark exposure increases pineal melatonin in rat pups.

Photic regulation of the pineal melatonin synthesis was studied in 3- to 21-day-old rat pups by exposing the animals to light at night (30-40 min) or to darkness during the day (30-240 min). The pineal melatonin contents were measured by radioimmunoassay. A significant day/night difference in the melatonin content and the nocturnal light-induced decrease were not found until second postnatal week.

Circadian rhythm studies in neuronal ceroid-lipofuscinosis (NCL).

Sleep disorders are common in NCL patients. The patients have problems such as frequent awakenings, difficulties with sleep onset, nightmares, and night terrors. The aim of the study was to examine whether the sleep disturbance in NCL can be explained on the basis of desynchronised circadian rhythms.

Locomotor activity and melatonin rhythms in rats under non-24-h lighting cycles.

The adjustment of pineal melatonin and locomotor activity rhythms to 10:10-h light:dark (LD) or 14:14-h LD cycles was studied in male Wistar rats. Both lighting conditions were thought to be outside the limits of entrainment of the rest-activity rhythm in this species. We assumed that the rhythm of pineal melatonin synthesis might be more adaptable.

Uncoupling of the pineal melatonin synthesis of rats from the circadian regulation.

We show that the pineal melatonin synthesis of rats can be uncoupled from the circadian regulation by exposing the animals to abnormally long light periods. Male rats were kept 7 days under 22.5/1.

The adjustment of the melatonin rhythm of rats by 90-min dark pulses.

The pineal melatonin patterns were measured in rats kept 1, 2, 3, 4, 6, 8, 16, or 28 days under the lighting conditions with a dark period of 90 min only (from 18:00 to 19:30 h). The samples were collected at 30-min intervals, and melatonin was measured by radioimmunoassay. During the first and second dark pulse the melatonin levels were low, but thereafter they were significantly higher than the usual daytime levels.

Twenty-four-hour rhythms in relation to the natural photoperiod: a field study in humans.

The daily rhythms of salivary melatonin, salivary cortisol, and axillary body temperature were measured in nine healthy volunteers in midsummer, around the autumn equinox, and in midwinter, at a latitude of 60 degrees N. The aim was to find out whether these rhythms were dependent on variations of the natural daylength. The samples were collected every 2 hr during 24-hr periods in everyday conditions.

One-hour exposure to moderate illuminance (500 lux) shifts the human melatonin rhythm.

Salivary melatonin levels were measured in 12 healthy volunteers in order to determine whether a moderate light intensity, which suppresses the nocturnal rise of melatonin, was able to shift the melatonin rhythm. The samples were collected at 1-hr intervals under lighting of < 100 lux (experiment 1) or < 10 lux (experiment 2). The control melatonin profiles were determined during the first night.

Melatonin, cortisol and body temperature rhythms in Lennox-Gastaut patients with or without circadian rhythm sleep disorders.

The daily rhythms of melatonin, cortisol and body temperature were studied in 16 institutionalized subjects with the Lennox-Gastaut syndrome. The results of 9 subjects with normal daily rhythms of sleep and wakefulness (group 1) were compared with those of 7 subjects with disordered sleep (group 2). Salivary samples were collected and axillary temperature was measured every 2 h during two or three separate 26-h periods.

Increase in testosterone sensitivity induced by constant light in relation to melatonin injections in rats.

In this experiment we investigated whether the lack of the nocturnal melatonin peak under constant light would cause an increase in testosterone sensitivity. Castrated rats were kept under periodic or constant light for one week. They received a daily injection of vehicle, testosterone propionate (125 micrograms), melatonin (50 micrograms) or testosterone plus melatonin (125 micrograms + 50 micrograms).

Platelet membrane fluidity in Alzheimer's disease and multi-infarct dementia: a spin label study.

The membrane fluidity of platelets isolated from 15 patients with probable Alzheimer's disease (AD), 11 patients with probable multi-infarct dementia (MID), and 7 neurologically healthy controls was studied by electron spin resonance (ESR) spectroscopy employing spin label techniques. Spin label I(12,3) probed the shallow site (hydrophilic region) and spin label I(5, 10) the deeper site (hydrophobic region) of the platelet membrane. With both probes, a significant increase in membrane fluidity was observed in patients with AD and MID, as compared to age-matched controls.

Dexamethasone attenuates exercise-induced dental analgesia in man.

The effect of dexamethasone on exercise-induced adrenocorticotropin (ACTH) secretion and dental analgesia was studied in healthy human subjects. Different levels of exercise (100-200 W) were produced by a cycle ergometer. Dental pain thresholds were tested with a constant current stimulator.

Correlation between salivary and serum melatonin: dependence on serum melatonin levels.

Saliva and serum samples were collected from eight healthy volunteers every two hours during a 26-hour period. Melatonin concentrations were measured by radioimmunoassay after chloroform extraction using radioiodinated melatonin as a tracer. Five of the subjects had high serum melatonin levels at night (peak levels higher than 75 pg/ml); in three subjects the highest serum melatonin concentration was 20-40 pg/ml.

Daily illuminance levels affect pituitary prolactin in male rats.

The 24-h patterns of melatonin, PRL, and gonadotropins in male rats maintained under natural lighting conditions have been found to differ from the patterns in rats kept under artificial lighting. In the present experiments we studied the role of different daily illuminances as a possible causative factor for the variation of the hormonal patterns. Three groups of male rats were kept under artificial lighting conditions (12 h on/12 h off), where the daily illuminance was 550, 110 or 25 lux.

REM sleep deprivation increases early morning pineal melatonin in castrated rats.

Recently nighttime melatonin levels have been shown to be attenuated in depressive patients or patients with dementia of the Alzheimer type. On the other hand, depression can be transiently relieved by deprivation of rapid eye movement sleep. Since exogenous melatonin administration increases rapid eye movement sleep and slow wave sleep in the rat, could rapid eye movement sleep deprivation then inversely influence endogenous melatonin production? We found indices that in castrated Wistar rats 4 days of rapid eye movement sleep deprivation by the cuff pedestal method elevates the pineal content of melatonin by a factor of two at 1 to 2 h after light onset.

Effect of different nocturnal illuminances on melatonin, prolactin, and gonadotropins in male rats.

We studied the role of nocturnal illuminance as a possible regulatory factor in the production and secretion of reproductive hormones. Adult male rats were kept under artificial lighting conditions (LD 12/12 hours) where the daily illuminance was 520-550 lx and the nocturnal illuminance 0, less than 0.1, or 1-1.

Twenty-four-hour patterns of pineal melatonin and pituitary and plasma prolactin in male rats under 'natural' and artificial lighting conditions.

Natural lighting differs from usual artificial lighting mainly as follows: it has larger spectral composition, fluctuations of intensity during the day, higher intensity levels during the night (moonlight, starlight), and gradual changes of illuminance at dawn and dusk. The present experiment was performed in order to study whether these features of lighting affect the 24-hour patterns of melatonin and prolactin in male rats. The rats were kept 7 days in 'natural' lighting (sunlight through windows) or in artificial lighting (cool white fluorescent lamps) of similar periodicities (13/11 h light/dark).

A simple and rapid high-pressure liquid chromatographic assay for pentobarbital and other barbiturates in serum.

A single extraction technique for measuring pentobarbital and other barbiturates in serum involved high-pressure liquid chromatography and UV detection yielding a sensitivity for pentobarbital of about 1 microgram/ml. We concluded that the assay provides a practical method for use in pharmacokinetic studies and in serum concentration monitoring in experimental animals.

Effect of biliary obstruction on muscle relaxation with vecuronium.

Vecuronium bromide was used as a muscle relaxant in 30 patients undergoing biliary surgery. Ten patients had biliary obstruction, 10 patients without biliary obstruction were elderly (78 +/- 1.2 yrs; mean +/- SEM) and 10 patients without biliary obstruction were young or middle-aged (35 +/- 3.

Absorption of bupivacaine, etidocaine, lignocaine and ropivacaine into n-heptane, rat sciatic nerve, and human extradural and subcutaneous fat.

Absorption of four amide local anaesthetics, including a new experimental agent, ropivacaine, in n-heptane, rat sciatic nerve and human extradural and subcutaneous fat was studied in vitro. The relative n-heptane/buffer (37 degrees C) partitioning of bupivacaine:etidocaine:lignocaine:ropivacaine was 10:39:1:2.9.

GABA inhibits inhalation anaesthetic-induced membrane fluidization: a spin label study in synaptic and phospholipid membranes.

The hydrophobic interaction of GABA (10(-3)-10(-9) M) with the inhalation anaesthetic enflurane was studied in synaptic plasma membranes of whole rat brain or of the striatum, synaptic mitochondrial membranes and dipalmitoyl lecithin (DPL) vesicles. Stearic acid spin labels, probing either the C-5 level (hydrophilic end) or the C-12 level (hydrophobic end) of the lipid bilayer, were used as indicators of fluidity. Inhalation anaesthetic at 2 mM fluidized the C-5 and the C-12 level of the membranes.

Accumulation of thymol in halothane vaporizers.

Thymol may accumulate in halothane vaporizers and influence their accuracy. We determined the thymol concentration in residual liquid halothane of 28 vaporizers in regular use. Two halothane samples were brownish, probably due to a long exposure to light and irregular drainage.

Bupivacaine blood levels after intravenous regional anesthesia of the arm.

Toxic reactions have been reported in patients after immediate release of the tourniquet cuff following intravenous regional anesthesia (I.V.R.

Hydrophobic membrane interaction of etidocaine, bupivacaine and 2-chloroprocaine. A spin and fluorescent probe study.

It has been suggested that local anesthetics may block sodium conductance through nervous membranes also by hydrophobic interaction, e.g., by expanding the membrane.