Temporal relationship between prolactin secretion and slow-wave electroencephalic activity during sleep

It is well established that plasma prolactin (PRL) concentrations exhibit a sleep-dependent pattern, with the highest levels occurring during sleep and the lowest during waking. Still, controversy exists concerning an association between rapid eye movement (REM) and non-REM sleep cycles and plasma PRL pulses. These studies were all based on conventional scoring of sleep stages. In the present study, plasma PRL concentrations were analyzed at 10-minute intervals in 10 subjects during the night when sleeping. PRL secretory rates were calculated by a deconvolution procedure. Spectral parameters of sleep electroencephalographic (EEG) recordings were analyzed together with PRL secretion using cross-correlation. Slow-wave activity of the EEG and PRL secretion ran parallel in all individuals. Conversely, alpha and beta bands and the EEG mean frequency were inversely proportional to PRL secretion. In 9 of the 10 subjects studied, PRL secretion was concomitant with delta waves or lagged behind by 10-20 minutes, depending on subjects, with maximum cross-correlation coefficients ranging between 0.40 and 0.67. This temporal relationship between PRL secretion and delta waves was further assessed by a pulse-by-pulse analysis based on the calculation of probability levels after computer simulations. Nine of the 10 subjects displayed significant concomitance between delta wave activity and PRL secretory oscillations. These results demonstrate that PRL secretion during sleep is coupled to delta waves in young healthy men.

Comparative effect of night and daytime sleep on the 24-hour cortisol secretory profile

To determine whether cortisol secretion interacts with daytime sleep in a similar manner to that reported for night sleep, 14 healthy young men were studied during two 24-hour cycles. During one cycle they slept during the night, during the other the sleep period was delayed by 8 hours. Secretory rates were calculated by a deconvolution procedure from plasma cortisol, measured at 10-minute intervals. The amount of cortisol secreted during night sleep was lower than during the corresponding period of sleep deprivation (12.7 +/- 1.1 vs. 16.3 +/- 1.6 mg; p < 0.05), but daytime sleep beginning at the habitual time of morning awakening failed to inhibit cortisol secretion significantly. There was no difference between the amount of cortisol secreted from 0700 to 1500 hours in sleeping subjects and in subjects who were awake during the same period of time (24.2 +/- 1.5 vs. 22.5 +/- 1.4 mg). Even if the comparison between sleeping and waking subjects was restricted to the period 0700-1100 hours or 0700-0900 hours, no significant difference was found. Neither secretory pulse amplitude nor frequency differed significantly in either period. However, detailed analysis of the secretory rates in day sleepers demonstrated a transient decrease in cortisol secretion at about the time of sleep onset, which began 10 minutes before and lasted 20 minutes after falling asleep. Spontaneous or provoked awakenings had a determining influence on the secretory profiles. Ten to 20 minutes after awakening from either night or day sleep cortisol secretion increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

The circadian thyrotropin rhythm is delayed in regular night workers

In order to determine whether the circadian thyrotropin (TSH) rhythm is adapted to a night-active schedule, plasma TSH and body temperature were measured for 28 h every 10-min in 8 regular night workers and in 8 day-active subjects. In night workers, the shift of 8-h in the sleep period induced a mean shift of 6 h 30 min of the TSH acrophase which remained located, as in day-active subjects, at about the time of sleep onset. The nadir of the body temperature rhythm was shifted by an equivalent amount and occurred systematically during the sleep period, so that both parameters maintained a fixed phase relationship. TSH and temperature rhythms had similar amplitudes in the two groups. However, mean TSH values in night workers returned more rapidly to basal values. These results demonstrate that, together with body temperature, TSH acrophase is adapted to regular night work, suggesting that TSH may be a good index for evaluating the orientation of the endogenous clock.

Prolactin secretion during sleep in obstructive sleep apnoea patients

Plasma prolactin (PRL) concentration exhibits a sleep-dependent pattern, with highest levels during sleep and lowest levels during the waking period. The syndrome of obstructive sleep apnoea (OSA) is associated with severe hypoxaemia and chronic sleep fragmentation, both of which could affect the sleep-entrained PRL rhythm. Treatment with nasal continuous positive airway pressure (CPAP) immediately restores a normal sleep structure by successful abolition of the apnoeas. In the present study, seven OSA patients underwent two night studies, once when no treatment was given and once during the first night of CPAP treatment. Sleep was recorded polygraphically in all experiments. Plasma PRL was measured at 10 min intervals and secretory rates were calculated by a deconvolution procedure. CPAP treatment greatly reduced hypoxaemia and improved sleep quality. The secretory pulse amplitude and the total amount of PRL secreted during the night remained constant regardless of whether patients were treated or not. The only difference found was a lower pulse frequency in untreated OSA patients as compared to treated patients, which may be attributed either to hypoxaemia or to sleep disturbance or to the combined action of both. Treatment may be considered to normalize PRL release by restoring pulse frequency to values similar to those observed for normal subjects.

Parathyroid function in cardiac transplant patients: evaluation during physical exercise

The survival rate of heart transplant patients has increased considerably since the development of new immunosuppressive drugs. In the long term, however, cardiac transplantation results in a high incidence of osteoporosis which represents a major functional handicap. To examine whether patients in the early stages have impaired phosphocalcic metabolism, intact parathyroid hormone (PTH 1-84), native osteocalcin, ionized Ca++ and pH were measured at rest and during muscular exercises a dynamic test used to override circadian and ultradian PTH variations. A group of 12 patients receiving the usual immunosuppressive therapy, which is mainly an association of cyclosporin and prednisolone, and 8 sedentary control subjects performed a square-wave endurance test at the same relative intensity for 30 min. No patient had previous bone disease and the period since transplantation was 12.2 +/- 2.7 months. For the transplant patients, initial PTH concentrations and responses to exercise were higher (P < 0.01) compared to the control subjects with a dramatic increase after 10 min of recovery. From higher (P < 0.001) resting concentrations, osteocalcin further increased during exercise (P < 0.01) in the heart transplant group but not in the control subjects. In both groups pH showed the same time-course with a rapid fall during exercise (P < 0.05) and Ca++ concentrations increased during the exercise period. (P < 0.01 for patients; P < 0.05 for controls) with a significant fall in both groups after 10 min of recovery (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of alcohol on the hydromineral hormone responses to exercise in a warm environment

Alcohol consumption at rest is associated with disturbed water and salt regulation reflected by changed responses in the hydromineral hormones. This study investigated the effect of alcohol on endocrine systems involved in body fluid and electrolyte regulation under conditions of physical exercise in the heat, a situation in which under normal circumstances, the hydromineral hormones are stimulated in an attempt to preserve physiological homeostasis. Eight healthy male volunteers participated in two trials, which differed only in the presence or absence of alcohol (1.2 g alcohol.kg-1 body mass) in a cocktail drink. After consuming the cocktail, the subjects exercised for 60 min on a cycle ergometer (45% maximal oxygen consumption) at 35 degrees C. Compared to the control situation alcohol consumption (maximal plasma concentrations reaching about 1.08 g.l-1) produced an increase in body fluid loss (P < 0.05), but did not induce significant differences in plasma volume changes. Plasma volume decreased in both sessions during exercise (P < 0.01) and a significant rebound (P < 0.001) occurred during recovery. Osmolality was significantly higher (P < 0.001) during rest, exercise and recovery periods compared to the placebo trials, but no effect of alcohol on plasma Na+ and K+ concentrations was observed. In the alcohol test conditions, the arginine vasopressin (AVP) response to exercise was significantly dampened (P < 0.05). In contrast, alcohol had no effect on aldosterone or atrial natriuretic peptide (ANP). These results demonstrated that alcohol ingestion augmented body fluid losses due to a suppressive effect on AVP during physical exercise conducted in a warm environment. The increase in osmolality due to alcohol did not influence the aldosterone and ANP responses, which would suggest that total osmolality does not play a major role in the regulation of these hormones.

Clomipramine-induced sleep disturbance does not impair its prolactin-releasing action

The present study was undertaken to examine the role of sleep disturbance, induced by clomipramine administration, on the secretory rate of prolactin (PRL) in addition to the direct drug effect. Two groups of supine subjects were studied under placebo-controlled conditions, one during the night, when sleeping (n = 7) and the other at daytime, when awake (n = 6). Each subject received a single 50 mg dose of clomipramine given orally 2 hours before blood collection. Plasma PRL concentrations were analysed at 10 min intervals and underlying secretory rates calculated by a deconvolution procedure. For both experiments the drug intake led to significant increases in PRL secretion, acting preferentially on tonic secretion as pulse amplitude and frequency did not differ significantly from corresponding control values. During the night clomipramine ingestion altered the complete sleep architecture in that it suppressed REM sleep and the sleep cycles and induced increased wakefulness. As the relative increase in PRL secretion expressed as a percentage of the mean did not significantly differ between the night and day time studies (46 +/- 19% vs 34 +/- 10%), it can be concluded that the observed sleep disturbance did not interfere with the drug action per se. The presence of REM sleep was shown not to be a determining factor either for secretory pulse amplitude and frequency, as, for both, mean nocturnal values were similar with and without prior clomipramine ingestion.

Twenty-four-hour profiles of plasma renin activity in relation to the sleep-wake cycle

OBJECTIVE

To evaluate the relative contribution of sleep and the endogenous circadian rhythmicity in producing the 24-h variations in the plasma renin activity.

METHODS

Ten normal young men were studied, under basal conditions with normal nocturnal sleep from 2300-0700 h and once after a night of total sleep deprivation followed by 8 h daytime sleep from 0700 to 1500 h. Plasma renin activity was measured every 10 min for 24 h and the profiles were analysed using the pulse detection program ULTRA.

RESULTS

During the 8 h night-time sleep a significant increase in the mean plasma renin activity levels occurred compared with the subsequent 8-h waking periods. After the shift in the sleep period, a sleep-associated increase was clearly apparent during the daytime hours. The number of the amplitude of the oscillations, linked to the non-rapid eye movement-rapid eye movement sleep cycles, increased during sleep (at whatever time it occurred), and were dependent on the regularity and the length of the sleep cycles. In awake subjects the plasma renin activity generally fluctuated in a more damped and irregular manner, but occasionally the plasma renin activity oscillated at a regular periodicity with two dominant peaks centred around 100 and 50 min.

CONCLUSION

These results demonstrate that the 24-h plasma renin activity variations are not circadian in nature but are related to sleep processes, which create the nycthemeral rhythm by increasing both the frequency and the amplitude of the oscillations.

Prolactin secretion and sleep

To clarify the relationship between prolactin (PRL) secretion and sleep, three experimental procedures were employed and secretory rates were estimated from plasma levels using a deconvolution procedure. Eight healthy young men participated in two 24-hour studies, one using normal night sleep and one using delayed sleep, to determine the influence of sleep as a whole on the PRL rhythm. Another group of 24 subjects underwent a 1-night study to investigate the relationship between PRL secretion and the internal sleep structure. The influence of sleep quality was studied in two more groups of eight subjects. Secretory rates were calculated by deconvolution from plasma PRL measured at 10-minute intervals. Sleep was recorded polygraphically in all experiments. PRL secretory pulses occurred throughout the 24-hour cycle without significant variation in frequency, but with enhanced pulse amplitude for both night and day sleep periods. Sleep onset was rapidly followed by an increase in secretion, and awakenings coincided with an immediate offset of active secretion. Analyzing the association between secretory pulses and sleep stages demonstrated that PRL secretory rate is low at the time of rapid eye movement sleep onset. Sleep quality appeared not to affect the PRL secretory profile. These results confirmed that PRL secretion is enhanced during the whole sleep period, as inferred from plasma levels. Considering secretory pulses provides a precise determination of the temporal relations between PRL and sleep structure and demonstrates that occasionally poor sleep does not influence PRL secretion in normal humans.

Successful introduction of an intravenous line insertion team at a municipal hospital

An intravenous line insertion and blood drawing team was introduced as a pilot project in a large municipal hospital in the New York City. The program successfully accomplished the goals of reducing house staff workload, improving house staff morale and patient care, and increasing available time for house staff education.

Immunoregulatory activity of substance P fragments

The C-terminal SP7-11 pentapeptide (Phe-Phe-Gly-Leu-Met-NH2) was found to suppress in vitro the immune response in a dose of 1-5 micrograms/ml. It produced also a distinct immunosuppression in vivo, by both per os and intraperitoneal, applications. In contrast, the N-terminal SP1-4 fragment (Arg-Pro-Lys-Pro) suppressed the response at a dose of 0.1 microgram/ml, but stimulated it slightly at higher doses (1-5 micrograms/ml). A structural analog of SP1-4 (Gly-Pro-Arg-Pro tetrapeptide) was found to be a strong immunosuppressor at a dose of 5 micrograms/ml, indicating the importance of N-terminal basic residue for the immunoregulatory activity of intact SP.

Survey of nonphysician tasks performed by medicine residents at a municipal hospital

In June 1988, the New York State Hospital Review and Planning Council approved major revisions in the state hospital code (Part 405). Among the most controversial of these changes were the recommendations of the Bell Commission concerning limitations on resident work hours, new emergency service requirements, and enhancements in ancillary staffing. The ancillary staffing mandated by the new code regulations for teaching hospitals include the provision at all times of intravenous services, phlebotomy services, messenger services, transport services, nurses aides, housekeeping services, and other ancillary support in a manner sufficient to meet patient care needs and to prevent adverse impact on the delivery of medical and nursing care. The intent of the new health code requirements is to reduce or eliminate many of the nonphysician tasks performed by residents so as to effectively reduce their workload. We conducted a survey of Medicine residents at Queens Hospital Center to assess the amount of time they presently devote to nonphysician tasks, their perceptions of the need for ancillary staff to relieve them of the burden of these nonphysician tasks, and their evaluation of the effectiveness of a recently instituted intravenous therapy team.

Translational regulation of somatostatin in cultured sympathetic neurons

Coculture of sympathetic neurons with ganglion nonneuronal cells elevated levels of preprosomatostatin mRNA but did not alter neuronal synthesis, content, or release of somatostatin. Treatment of sympathetic neurons with culture medium conditioned by exposure to ganglion nonneuronal cells similarly elevated preprosomatostatin mRNA. Treatment with conditioned medium elevated somatostatin levels in pure neuronal cultures, but not in neurons cocultured with nonneuronal cells. Conditioned medium also failed to increase peptide levels in neurons cultured on a substratum of killed nonneuronal cells, despite a large increase in preprosomatostatin mRNA. These observations suggest that contact of sympathetic neurons with nonneuronal cell membranes inhibits the increase in peptide synthesis, but not the increase in preprosomatostatin mRNA after treatment with conditioned medium. Thus neuronal interactions with nonneuronal cells regulate somatostatin metabolism at both the mRNA and peptide levels. Regulatory effects on the mRNA and the peptide are separable and do not necessarily occur in parallel, and translational controls may be the rate-limiting factors.

Differences in the effects of membrane depolarization on levels of preprosomatostatin mRNA and tyrosine hydroxylase mRNA in rat sympathetic neurons in vivo and in culture

Regulation of preprosomatostatin mRNA and tyrosine hydroxylase mRNA were examined in sympathetic neurons of the rat superior cervical ganglion (SCG). Surgical denervation of the adult SCG increased ganglion levels of preprosomatostatin (SS) mRNA more than 11-fold, and levels of the mRNA remained elevated 14 days after surgery. By contrast, denervation decreased levels of tyrosine hydroxylase (TH) mRNA. Potassium- or veratridine-induced membrane depolarization of cultured neonatal sympathetic neurons decreased levels of SS mRNA but elevated levels of TH mRNA. Sodium channel blockade with tetrodotoxin prevented the effects of veratridine on SS and TH mRNAs. In toto these observations suggest that transsynaptic nerve impulse activity and sympathetic neuron membrane depolarization decrease SS synthesis but increase TH synthesis at the mRNA level. Thus nerve impulse activity may alter the relative levels of different transmitters co-expressed in the same neuronal population by inhibiting levels of some species of mRNA while simultaneously stimulating levels of others.

Conformational modification of the PRP-hexapeptide by a direct covalent attachment of aromatic side chain groups

PRP-hexapeptide possessing the azo-bridge between Tyr1 and Phe5 residues, called azo-PRP-hexapeptide: (formula; see text), was synthesized and tested for immunoregulatory activity. High biological activity of the synthesized azo-PRP-hexapeptide suggests that the biologically active conformation of PRP-hexapeptide must be such that both aromatic rings (Tyr and Phe) are apparently close to each other.

Immunoregulatory properties of synthetic peptides, fragments of a proline-rich polypeptide (PRP) from ovine colostrum

It has been previously found that a proline-rich polypeptide (PRP) isolated from ovine colostrum has a regulatory effect on the immune response. A nonapeptide fragment Val-Glu-Ser-Tyr-Val-Pro-Leu-Phe-Pro was isolated from the chymotryptic digest of PRP. The nonapeptide showed biological activity similar to PRP. The determined amino acid sequence was now confirmed by synthesis. Synthetic nonapeptide as well as its C-terminal hexapeptide, Tyr-Val-Pro-Leu-Phe-Pro, showed biological activity similar to PRP and the nonapeptide obtained from PRP.

Application of a microseparation technique allowing for extensive marker studies on small bone marrow specimens

The characterization of surface and intracellular markers of hematopoietic cells by immunocytochemical methods is widely used. While examination of cells of the peripheral blood can easily be performed, investigations of bone marrow cells can be hampered by technical difficulties in labeling routine marrow smears or by limited size of specimens required for cytocentrifugation. A simple and highly efficient method for isolation of bone marrow cells by a microseparation technique is described. Only two to three drops of a routine bone marrow aspirate are necessary for preparation of up to 100 cytocentrifuge slides thereby exceeding separation efficiency of conventional gradient centrifugation by three- to more than four-fold. The application of the method for marker studies on normal marrow and marrow from patients with hematologic malignancies is exemplified.

Separation of opioid analgesia from respiratory depression: evidence for different receptor mechanisms

Pretreating rats 24 hr earlier with naloxonazine (10 mg/kg i.v.) virtually eliminates the analgesic response observed with morphine at 3.5 mg/kg (i.v.) and significantly reduces the elevation in tail-flick latencies seen with higher morphine doses. Full dose-response curves show a 4-fold shift to the right (P less than .001) following naloxonazine treatment. At 3.5 mg/kg (i.v.), morphine depresses respiratory function, as determined by arterial blood gas (pO2, pCO2 and pH) measurements. Unlike analgesia, prior treatment of rats with naloxonazine does not alter the respiratory depressant actions of morphine. This inability of naloxonazine to antagonize the respiratory depressant actions of morphine is supported by full dose-response curves. Thus, prior treatment of rats with the mu-1-selective antagonist naloxonazine selectively antagonizes analgesia without affecting respiratory depression, implying different receptor mechanisms for the analgesic and respiratory depressant effects of morphine. Further comparisons of the analgesic and respiratory depressant effects of morphine and two opioid peptides, metkephamid and D-Ala2-D-Leu5-enkephalin, strongly suggest the involvement of mu-2 rather than delta mechanisms in opioid respiratory depression.

Meptazinol: a novel Mu-1 selective opioid analgesic

Meptazinol is a unique centrally active opioid analgesic, differing in many respects from the classical opiates or mixed antagonists. Although the overall binding of a series of 3H-labeled opioids is displaced poorly (IC50 values greater than 55 nM), detailed competition studies show that meptazinol inhibits a portion of 3H-labeled opiate and opioid peptide binding quite potently, with IC50 value under 1 nM. Both additional competition studies and saturation studies indicate that the meptazinol-sensitive binding of the 3H-ligands corresponds to the high affinity, or mu-1, binding site. In other binding studies meptazinol has a sodium shift of 8.7, midway between that of morphine (22.5) and naloxone (1.6), suggesting that it is a partial agonist. Naloxonazine treatment 24 hr earlier attenuates meptazinol analgesia in both the mouse writhing and rat tail-flick assays. Spinal transection in the mouse completely eliminates the analgesic activity of high doses of meptazinol in the tail-flick assay, implying a supraspinal mechanism of action in that species. Given at equianalgesic doses, morphine (3.5 mg/kg i.v.) significantly lowers the pO2 over 20 mm Hg and raises the pCO2 over 10 mm Hg as measured in arterial blood samples, whereas meptazinol (10 mg/kg i.v.) has no significant effects on either. Equally important, meptazinol administered with morphine does not reverse the respiratory depressant actions seen with morphine alone, distinguishing meptazinol from other mixed agonist/antagonists. Thus, both the binding and in vivo pharmacological studies are consistent with a mu-1 selective mechanism for the opioid actions of meptazinol.

Analgesic activity of tricyclic antidepressants

Amitriptyline (median effective dose [ED50] 1.2 mg per kilogram of body weight), imipramine (ED50 2.3 mg/kg), and their demethylated derivatives nortriptyline (ED50 1.9 mg/kg) and desimipramine (ED50 3.2 mg/kg) are active analgesics as indicated by the mouse writhing assay. Although not as potent as morphine (ED50 0.2 mg/kg), the antidepressants were up to 70 times more potent than aspirin (ED50 91 mg/kg). The actions of amitriptyline were not affected by the specific opiate antagonist naloxone but were markedly attenuated in animals whose monoamine levels had been depleted with reserpine. Central mechanisms appear important since amitriptyline (ED50 4.6 micrograms) was potent when administered intracerebroventricularly.

Biochemical and pharmacological evidence for opioid receptor multiplicity in the central nervous system

Evidence from a variety of experimental models has suggested the existence of mu 1, mu 2 and delta binding sites for morphine and the enkephalins in the central nervous system. Additional biochemical experiments now support this concept of a common high affinity site for opiates and opioid peptides. Mu sites have now been implicated in a number of pharmacological actions, including supraspinal analgesia, prolactin release, and catalepsy, but not in others (spinal analgesia, respiratory depression, and the guinea pig ileum). The hypothesis of mu 1 sites was supported by the unique opioid meptazinol, which selectively bound to mu 1 sites. As expected from its mu 1 binding selectivity, its analgesic actions in the mouse, localized supraspinally, were antagonized by the selective mu 1 antagonist naloxonazine and it had no respiratory depressant actions. Other binding studies suggested the presence of discrete SKF10,047-selective (KD approximately 5 nM) binding sites in rat brain which differed from both kappa sites and the previously reported PCP-binding sigma sites. Additional binding and autoradiographical studies have also implied the presence of beta-endorphin, or epsilon, sites in the CNS.