24-hour cerebrospinal fluid levels of vasopressin in hydrocephalic patients

The variation in vasopressin concentrations of ventricular cerebrospinal fluid and plasma throughout a 24-h period was studied in 10 patients with hydrocephalus. In 6 control patients, the diurnal variation in plasma vasopressin concentrations was studied. Vasopressin concentrations were determined by radioimmunoassay in plasma and in extracted and unextracted cerebrospinal fluid. Cortisol and osmolality in plasma were also measured. Vasopressin concentrations measured in extracted cerebrospinal fluid showed only small intra- and interindividual variation, while the corresponding values for unextracted cerebrospinal fluid were 2-5-fold higher and showed more variation. Plasma vasopressin concentrations varied considerably throughout the 24-h period in the individual hydrocephalic patient and between the patients. The pattern of variation was inconstant with no circadian rhythm, and the variation was not related to any changes in plasma osmolality, blood pressure or intracranial pressure. In some of the patients, the normal diurnal pattern of variation in plasma cortisol was broken, however, without a relation to the observed fluctuations in vasopressin concentrations. The abnormal variation of plasma vasopressin and cortisol was considered to reflect stress in connection with the intracranial pressure monitoring procedure. In the control patients, plasma vasopressin showed only small variations and plasma cortisol showed a normal diurnal rhythm. It is concluded that cerebrospinal fluid vasopressin concentration in patients with hydrocephalus is very constant throughout the day, even when plasma vasopressin concentrations show marked episodic increases. Thus, a circadian rhythm in the cerebrospinal fluid vasopressin concentration, as reported in several animal species, could not be confirmed in these patients.     

Metoclopramide increases plasma but not cerebrospinal fluid vasopressin levels in man: study in hydrocephalic patients.

Arginine vasopressin (AVP) concentrations were determined in plasma and in cerebrospinal fluid (CSF) in 8 adult male patients suffering from hydrocephalus of various etiologies, before and after intravenous administration of 10 mg metoclopramide. Metoclopramide was able to increase the plasma (2.6 +/- 0.2 ng/l in basal conditions and 6.1 +/- 0.6 ng/l at 30 min) but not the CSF AVP levels. The results suggest that the neurons which secrete AVP into the CSF may be functionally different from those secreting into the peripheral circulation.     

Diurnal rhythm of 3-methoxy-4-hydroxyphenylglycol (MHPG): relationship between plasma and urinary levels

Plasma and urinary levels of MHPG were determined in six normal volunteers. Samples were obtained at 3-hour intervals for plasma and at 12-hour intervals for urine. Acrophase, amplitude and period were determined for plasma MHPG levels. A sinusoidal pattern was obtained for diurnal plasma MHPG with a peak at 15:00 hrs. +/- 46 min. Urinary MHPG, corrected for creatinine levels, correlated with both 9 AM plasma MHPG and with baseline plasma MHPG. Furthermore, the relationship between plasma and urinary MHPG was linear when the rhythm of urinary levels was assumed to lag 6.2 hours behind the plasma rhythm. It was concluded that free MHPG is evenly distributed in the total body space and that conjugated MHPG is largely restricted to the blood.     

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Diurnal variations in the concentrations of major organic compounds occurred in xylem fluid extracted from Lagerstroemia indica L. The concentration of amino acids and the N/C ratio was at a maximum and that of organic acids was at a minimum between 1230 and 2030 h. Since the concentrations of total organic nitrogen, total amino acids and most individual amino acids (but not organic acids or sugars) were also proportional to xylem tension two experiments were performed to discern whether variations in chemistry were a consequence of diurnal changes in moisture stress. In the first experiment, L. indica , exposed to variable levels of moisture stress during midday, manifested an increase in organic acids and a reduction in the N/C ratio. In the second experiment, chemical profiles of xylem fluid were collected and compared for plants exposed to a natural photoperiod, constant darkness or continuous light at noon and midnight. After 1 day amino acids increased in concentration during midday for all treatments; the variation was greatest (10-fold) for plants in constant darkness where xylem tension varied from 0.20 to 0.25 MPa. Only plants exposed to continuous light lost a diurnal rhythm after 3 days. Thus, the circadian rhythm was endogenous, terminated in continuous light and was not mediated by changes in moisture stress. Glutamine accounted for most of the diurnal variation in total amino acids, organic nitrogen and the N/C ratio in xylem fluid.     

Genetic correlation between circadian eclosion rhythm and photoperiodic diapause in Drosophila littoralis

Populations of Drosophila littoralis are known to be latitudinally highly variable in photoperiodic adult diapause and pupal eclosion rhythm. Phenotypic correlations between the two time-measuring systems among the strains from different latitudes are, however, weak. In the present study, two differing strains were crossed reciprocally in order to search for causal (genetic) correlations between the two traits in the strains. Segregation in the F2 generations showed that variation in each trait was based on a few variable loci only. In the F2, flies having different eclosion times also differed in their diapause. This association was not complete and could have been due to genetic linkage between the traits. For that reason, the hybrid generations were raised for eight generations more to allow recombination between the traits. In F8, selection against diapause was started in the lines by raising them in a light-dark cycle of 15:9, where only females of the southern type reproduce. After eight selected generations, the lines were studied for the traits. Diapause was completely of the southern type, and the eclosion rhythm had also changed in parallel. The change in the phase of the free-running rhythm was not complete. From the present experiment, and from earlier knowledge of the geographical variation in D. littoralis, I conclude that the same pacemaker that is seen in the eclosion rhythm could also participate in daylength measurement for diapause. However, there are also noncorrelated variable parts in the measuring systems of both traits, which may mask the correlated variation.     

Diurnal variations of plasma testosterone in men

Plasma testosterone (T) levels were assayed by a Competitive Protein Binding (CPB) technique in a group of 31 healthy males. In 22 subjects a single blood sample was taken between 8:00 and 9:00 A.M. and the mean T concentration was 6.84 ± 2.11 ng/ml. In the other 9 normal men, blood samples were taken every 4 hours. The existence of temporal variations for testosterone was confirmed by finding the highest mean plasma levels at 4:00 A.M. (9.28 ± 1.17 ng/ml) and lowest mean levels at 8:00 P.M. (2.66 ± 0.52 ng/ml).     

Diurnal variations in plasma ACTH, cortisol and beta-endorphin levels in cocaine addicts.

In order to establish possible alterations in the hypothalamic pituitary-adrenal axis and in ACTH-related opioids in cocaine addicts, plasma ACTH, cortisol and beta-endorphin levels were measured throughout the day in 9 cocaine addicts [age: 27 +/- 5 years (mean +/- SE); weight: 72 +/- 6.1 kg, duration of cocaine addiction: at least 2 years] on the day of their admission to a recovery community for drug abusers (first test) and after 15 days of abstinence (second test). Nine normal controls (age: 28 +/- 6 years; weight: 73 +/- 3.2 kg) were tested only once in a similar manner. Blood samples were taken at 06:00, 08:00, 10:00, 12:00, 18:00 and 20:00 h and served for hormonal assays. Urine samples were taken from cocaine addicts at 08:00 h on the experimental day and on the following day. Results of both urine assays were positive for cocaine catabolites, indicating cocaine administration during the day before the experimental test. From the day of their admission in the community (1st experimental day), the patients were forbidden to use cocaine. For 4 days after admission, they were treated with symptomatics to attenuate withdrawal symptoms. Thereafter, the patients underwent a washout period of pharmacological treatments for 10 days before being retested (second test). Urine samples taken at 08:00 h on this second experimental day and on the next day were negative for the presence of drug catabolites. During the first test, cocaine addicts showed higher plasma ACTH, cortisol and beta-endorphin levels than normal controls at all examined time points.(ABSTRACT TRUNCATED AT 250 WORDS)     

Direct correlation between the circadian sleep-wakefulness rhythm and time estimation in humans under social and temporal isolation

Several bodily functions in humans vary on a 24 h pattern and most of these variations persist with a circadian period ofca 25 h when subjects are studied under conditions of social and temporal isolation. We report in this paper that the estimates of short time intervals (TE) of 2 h are strongly coupled to the circadian rhythm in sleepwakefulness. There is a linear correlation between the number of hours humans stay awake (α) and their estimation of 2 h intervals. The coupling of TE to α appears to obtain only under conditions of physical well-being.     

Diurnal and circadian variations in intraocular pressure in goats exposed to different lighting conditions

ABSTRACT

The effect of constant light and constant darkness on intraocular pressure (IOP) in goats has not been investigated. We hypothesized that IOP variations would differ between goats kept under a cycle of 12 hours of light and 12 hours of darkness (LD), constant darkness (DD), and constant light (LL). To test this hypothesis, goats were exposed to these conditions for five days (LD, 30 goats; DD, 10 goats; LL, 10 goats). IOP was measured by applanation tonometry at 9 a.m. (beginning of photophase in LD) and 9 p.m. (beginning of scotophase in LD) on the fourth and fifth days of exposure. We found that changes in mean IOP from 9 a.m. to 9 p.m. differed significantly between groups (χ²(2) = 23.04, p < .0001). Most goats in LD showed a regular pattern of higher IOP in the morning and lower IOP in the evening, whereas those in DD and LL did not follow this pattern. In LD conditions, mean IOP was 2.4 mm Hg lower at 9 p.m. than at 9 a.m. (95% confidence interval for the difference (CI): ?2.8 to ?1.9 mm Hg, p < .0001). In DD conditions, mean IOP did not differ between 9 p.m. and 9 a.m. (CI: ?0.9 to 0.8 mm Hg, p = .90). In LL conditions, it was 0.6 mm Hg lower at 9 p.m. (CI: ?1.5 to 0.2 mm Hg, p = .12). Our results indicate that IOP in goats kept in LD is higher in the morning than in the evening, and that IOP variations are reduced in goats kept in DD and LL. These results suggest that exposure to alternating periods of light and darkness is important for maintaining rhythmic variations in IOP in this species.     

Analysis of trough and peak of plasma melatonin circadian rhythm in ewes

This study evaluates the pattern of plasma melatonin during the trough and the peak of its daily rhythm. Blood samples from 8 ewes were collected every 3 h for a 48-h period. On the third day, blood samples were collected from 10:00 to 13:00 (trough) and from 20:00 to 23:00 (peak) every 20 min. Our results showed a robust daily rhythm of melatonin in both days of monitoring, with nocturnal acrophase. During the trough, a significant decrease was observed starting from the 10:40 with a progressive decrease about every 40 min. During the peak of the plasma melatonin daily rhythm, an increase was observed starting from the 20:40 with a progressive increase about every 40 min. These data could be taken in consideration to monitor the plasma melatonin variations during the 24 h, and for the administration of melatonin for breeding in ewes.     

Diurnal variations in the toxicity and tissue levels of spermidine in mice

The LD50 of spermidine shows significant diurnal variability when given IV or IP to mice. It is most toxic during the light phase of a programmed light-dark cycle (12L:12D) and least toxic during the transition from light to dark when motor activity is highest and when whole brain, myelencephalon and liver tissue levels of spermidine and histamine are maximal. Pretreatment with either triplennamine or cyproheptadine significantly reduced the LD50 of spermidine.     

Diurnal variations in circulating leukocytes and subsets: relation to plasma cortisol and ACTH]

Surface cellular antigens of leukocytes, lymphocytes and corresponding subpopulations have been analysed by using monoclonal antibodies marked with fluorescein (PITC), parallel to those marked with phycoerythrin (PE). Cortisol and ACTH plasmatics have also been determined through RIA, on two samples at 8am. and 8pm. During this twelve hour evolution, a highly significant dependence of the leukocytes, T, T4 and T8 lymphocytes on the circulating ACTH has also been found. In general during the experiment time leukocytes, lymphocytes and subpopulations, have experimented an increase which is significantly related to the pituitary hormone secretion. The existence of this significant correlation establishes the presence of a possible mechanism that connects the cellular immunity to determined hypothalamus hormones.     

Diurnal change in plasma natriuretic factor and arginine vasopressin in young jersey calves.

Diurnal changes in plasma ANF and AVP levels were investigated in four calves under standardized conditions. Both levels in plasma were measured at hourly intervals for 24 h along with arterial blood pressure, blood haematocrit, plasma cGMP, sodium, potassium, osmolality, proteins and albumin. Plasma ANF exhibited a first peak at mid-day while plasma AVP was low and a second peak at evening while plasma AVP was high. Changes in plasma cGMP correlated with variations in plasma ANF. feeding and/or plasma volume elevation probably accounted for both peaks in plasma ANF and the low mid-day level of plasma AVP, but the rise in plasma AVP at evening may represent a diurnal rhythm.     

Diurnal and circadian rhythm in compound eye of cricket (Gryllus bimaculatus): changes in structure and photon capture efficiency

Day-night changes in rhabdom size of compound eyes were investigated in three groups of crickets (Gryllus bimaculatus): nymphs and adult males and females. In both adults and nymphs, the rhabdoms were larger at night than during a day. In adults, the mean rhabdom occupation ratios (RORs) of ommatidial retinulae at midnight were about two times greater than the values at midday. This change contributes to control of the photon capture efficiency (PCE) of the eye according to photic environment. The RORs of adult males at midnight were higher than those of both adult females and nymphs. This suggests that the PCE of the compound eye of adult males is the greatest of all groups. Under constant darkness, day-night changes in ROR were detected only in adult males, but neither in adult females nor in nymphs. On the other hand, no day-night changes were detected in any experimental group under constant light. These results suggest that the change in rhabdom size between day and night is an adaptation to the photic environment that is controlled mainly by the light-dark (day-night) cycle. However, the change in male adults is induced by an endogenous circadian clock.     

Seasonal variations in circadian rhythms of plasma melatonin in ruin lizards

We examined melatonin profiles of ruin lizards in different seasons (spring, summer, and autumn) under light:dark (LD) and concomitant responses when transferred to continuous darkness (DD) to determine the degree to which previously reported seasonally dependent effects of pinealectomy on locomotor behavior are related to melatonin secretion. The amplitude of the melatonin rhythm and the amount of melatonin produced over 24 h varied with season. In spring, the amount of melatonin produced was greatest and the amplitude 4- 5 times that found in summer or autumn. The degree of self-sustainment of the melatonin rhythm when transferred to DD also varied with season. In DD, melatonin levels remained high but did not exhibit circadian variation in spring. In summer, the melatonin profile persisted virtually unchanged in DD, showing the existence of a circadian rhythm. Finally, in the fall there was no circadian variation in DD and levels remained low. These responses correspond closely to previously reported effects of pinealectomy on locomotor behavior where there is little or no effect of pinealectomy in spring or fall but a profound alteration of locomotor behavior in summer. These results suggest that the seasonally dependent effects of pinealectomy on locomotor behavior in ruin lizards are related to a seasonally mediated change in the degree of self-sustainment of some component of the circadian pace-making system of which melatonin plays some role.     

Evidence for a correlation between ambient cholesterol levels and soluble plasma sialyltransferase enzyme activity

While soluble forms of the sialyltransferase (sialyl-T) enzyme have been detected in significant quantities in serum, the exact source(s) of the enzyme, or the factors controlling its secretion are poorly understood. In this study, we have examined the relationship between ambient plasma cholesterol concentrations and sialyl-T activities and also levels of constituent plasma sialoglycoproteins (SGP). There was an inverse relationship between levels of the 2,6 sialyl-T enzyme and both total plasma cholesterol and HDL, although no such relationship was observed for the 2,3 enzyme. While there was no correlation between total cholesterol and the levels of plasma SGPs, there was an inverse relationship between the HDL component and 2,3 SGPs.