Pineal Gland Volume Research Articles

Reduced pineal gland volume across the stages of schizophrenia

A few magnetic resonance imaging (MRI) studies reported reduced pineal gland volume in chronic schizophrenia (Sz), implicating the involvement of melatonin in the pathophysiology of the illness. However, it is not known whether this abnormality, if present, exists at the early illness stages and/or develops progressively over the course of the illness. This MRI study examined pineal gland volume in 64 patients with first-episode schizophrenia (FESz), 40 patients with chronic Sz, 22 individuals with at-risk mental state (ARMS), and 84 healthy controls. Longitudinal changes in pineal volume (mean inter-scan interval = 2.5 ± 0.7 years) were also examined in a subsample of 23 FESz, 16 chronic Sz, and 21 healthy subjects. In the cross-sectional comparison, the ARMS, FESz, and chronic Sz groups had significantly smaller pineal volume to the same degree as compared with healthy controls. A longitudinal comparison demonstrated that pineal volume did not change over time in any group. There was no association between pineal volume and clinical variables (e.g., symptom severity, medication) in the ARMS and Sz groups. The results suggest that a smaller pineal gland may be a static vulnerability marker of Sz, which probably reflects an early neurodevelopmental abnormality.

Lifetime coffee consumption, pineal gland volume, and sleep quality in late life

Previous studies have shown that coffee consumption may suppress the production of melatonin in pinealocytes through competitive inhibition of adenosine A2 receptors by caffeine. We investigated the impact of lifetime coffee consumption on pineal gland volume and the resulting effects on sleep quality. We enrolled 162 cognitively normal elderly individuals among the participants in the Korean Longitudinal Study on Cognitive Aging and Dementia. We evaluated the patterns and amounts of coffee consumption using a study-specific standardized interview and assessed sleep quality using the Pittsburgh Sleep Quality Index. We measured the volume of pineal parenchyma (VPP) by manually segmenting the pineal gland on high-resolution three-dimensional T1-weighted magnetic resonance images. We examined the impact of lifetime coffee consumption on the VPP and the resulting effects on sleep quality using analysis of covariance, multiple linear regression, and mediation analyses. We found that smaller VPP was associated with higher cumulative lifetime coffee consumption. Participants who consumed more than 60 cup-years of coffee had VPPs that were smaller by about 20% than individuals who consumed less than 60 cup-years of coffee. The VPP mediated the association between lifetime coffee consumption and sleep efficiency and quality. Our findings suggest that high lifetime coffee consumption may reduce VPP, and that this reduction in VPP may impair the quality of sleep in late life.

Sex Difference in the Morphology of Pineal Gland in Adults Based on Brain Magnetic Resonance Imaging.

We aimed to figure out the anatomical features of pineal gland region on magnetic resonance imaging (MRI) and to explore the sex difference in pineal gland-related parameters with increasing age. We measured the pineal gland on MRI images from 198 healthy adults (96 males and 102 females). Included subjects were divided into 4 age groups. After 3-dimensional reconstruction, the anatomic features of pineal gland and its distances to superior colliculus and splenium of corpus callosum were analyzed in each group. The prevalence of cystic pineal gland was calculated. Moreover, we calculated the volume of pineal gland (PGV) and explored the differences of PGV in males and females across different age groups. Linear regression analysis was performed to detect the relationship between age and pineal gland-related parameters. In 198 subjects, the mean length, width, and height of pineal gland were 7.58 ± 0.45 mm, 4.92 ± 0.40 mm, and 2.90 ± 0.20 mm. The distances between pineal gland and superior colliculus as well as splenium of corpus callosum were 3.96 ± 0.92 mm and 4.3 ± 1.89 mm, respectively. The PGV was 54.1 ± 7.02 mm. Significant sex differences were found in pineal gland length (P < 0.001), cranial cavity diameter (P < 0.001), pineal gland index (P < 0.001) and PGV values (P = 0.02). The prevalence of cystic pineal gland was 36.4% in total subjects, 41.7% in males and 32.4% in females. No linear relationship was found between age and pineal gland parameters. We measured the pineal gland morphology based on MRI images. Significant influences on pineal gland parameters were found in subjects with different sex, whereas no effect was observed from age.

Morphology and quantification of sheep pineal glands at pre-pubertal, pubertal and post-pubertal periods.

The pineal gland is a neuroendocrine organ associated with photoperiodic regulation in mammals. The aim of this study was to evaluate the pineal gland at the pre-pubertal, pubertal and post-pubertal periods by means of morphology and stereology. The study examined at total of 24 ovine pineal glands collected from healthy female Akkaraman breed. Thick sections (40μm) were cut and treated with synaptophysin. Following each thick section, six consecutive sections at a thickness of 5μm were cut. Each thin section was stained with one of the following dyes: Crossman's modified triple dye, glial fibrillary acidic protein (GFAP), melatonin marker, periodic acid-Schiff, Von Kossa and AgNOR. The pineal gland volume was measured using Cavalieri's method. The optical fractionator was used to estimate the total number of pinealocytes. The percentage of parenchyma and connective tissue and degree of vascularization were estimated by the area fraction fractionator method. The pineal gland volumes in the pre-pubertal, pubertal and post-pubertal groups were 7.53±1.715mm3 , 11.20±1.336mm3 and 17.75±1.188mm3 , respectively (p<.5). The number of pinealocytes in the pre-pubertal, pubertal and post-pubertal groups was 3,244,000±228,076, 4,438,000±243,610, 7,381,766±406,223, respectively (p<.05). The glands of the post-pubertal group contained the highest amount of connective tissue (11.49±2.103%; p<.5) and the largest GFAP staining area (p<.05). The melatonin staining density was the highest in the pubertal group. The density of lipofuscin staining was higher in the pubertal and post-pubertal groups.

Neural Correlates of Sleep Disturbance in Alzheimer's Disease: Role of the Precuneus in Sleep Disturbance.

Background:Sleep disturbance may affect the development of Alzheimer’s disease (AD), but the neural correlates of sleep disturbance in AD have not been fully clarified.Objective:To examine the factors associated with sleep disturbance in AD.Methods:A retrospective study was performed in 63 patients with AD. None of the patients had been prescribed antidementia or psychoactive drugs, and all underwent brain magnetic resonance imaging (MRI) before medication. Sleep disturbance was defined as a score of at least 1 point on the sleep disturbance subscale of the Neuropsychiatric Inventory (NPI). Whole brain image analysis was performed using SPM8 and VBM8. A two-sample t-test was used to compare patients with AD with (n = 19) and without (n = 44) sleep disturbance, with age and gender included as covariates. The statistical thresholds were set to an uncorrected p-value of 0.001 at the voxel level and a corrected p-value of 0.05 at the cluster level. In addition, pineal gland volume (PGV) measured using MRI, and white matter hyperintensity (WMH) assessed with the modified Fazekas scale were compared between patients with AD with and without sleep disturbance using independent group t-tests.Results:In whole brain analysis, the precuneus volume in patients with AD with sleep disturbance was significantly smaller than those without sleep disturbance. There were no significant differences in PGV and WMH between the two groups.Conclusion:Sleep disturbance in AD was associated with reduction of precuneus volume. This suggests that the precuneus might be an important region in sleep disturbance in AD.

Reduced Pineal Volume in Alzheimer Disease: A Retrospective Cross-sectional MR Imaging Study.

Purpose To evaluate pineal volume in patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and healthy control subjects and to correlate the findings with results of cognitive testing and brain parenchymal volumes. Materials and Methods The ethics committee approved this retrospective study. The participants included 63 patients with AD, 33 patients with MCI, and 24 healthy control subjects. There were 36 men and 84 women, with a mean age (±standard deviation) of 76.7 years ± 7.6. The pineal gland volume and pineal parenchymal volume were measured by using three-dimensional volumetric magnetic resonance imaging (T1-weighted magnetization-prepared rapid gradient-echo sequence; spatial resolution, 0.9 × 0.98 × 0.98 mm). With age and total intracranial volume as covariates, analysis of covariance with the Bonferroni post hoc test was performed to compare the pineal volume among the AD, MCI, and control groups. Multiple regression analyses were used to identify predictor variables associated with pineal volume. Results The mean pineal gland volume in patients with AD (72.3 mm3 ± 5.4; 95% confidence interval [CI]: 61.5 mm3, 83.1 mm3) was significantly smaller than that in control subjects (102.1 mm3 ± 9.0; 95% CI: 84.4 mm3, 119.9 mm3) (P = .019). The mean pineal parenchymal volume in patients with AD (63.8 mm3 ± 4.2; 95% CI: 55.4 mm3, 72.1 mm3) was significantly smaller than that in patients with MCI (81.7 mm3 ± 5.8; 95% CI: 70.3 mm3, 93.1 mm3; P = .044) and control subjects (89.1 mm3 ± 6.9; 95% CI: 75.4 mm3, 102.9 mm3; P = .009). Multiple regression analyses demonstrated that the Mini-Mental State Examination score and total intracranial volume were significant independent predictors of both pineal gland volume and pineal parenchymal volume (P < .001). Conclusion Pineal volume reduction showed correlation with cognitive decline and thus might be useful to predict cognitive decline in patients with AD. © RSNA, 2017.

Pineal volume and evening melatonin in young people with affective disorders.

Affective disorders in young people have been associated with disruptions in circadian rhythms, including abnormalities in secretion of the pineal hormone melatonin. Previous research reports relationships between pineal gland volumes, melatonin secretion, and sleep-wake cycles, but the relationship between these factors has not been explored in affective disorders. This study aimed to characterize these factors and explore associations with mood symptoms and functioning in a sample of young people with affective disorders. Pineal volume from magnetic resonance imaging and melatonin assay from evening dim-light saliva collection were evaluated in 50 individuals (15-30years old; 72% female) with bipolar, depressive, or anxiety disorders. Actigraphy monitoring was also conducted for approximately two weeks to derive sleep-wake measures. Pineal volume was associated with melatonin secretion across the evening, replicating previous findings in psychiatrically healthy individuals. Pineal volume was smaller in participants in which melatonin onset was not detected. Timing of melatonin secretion was related to sleep timing, but amount of melatonin and pineal volume were not related to any sleep-wake measures. A shorter phase angle between onset of melatonin secretion and sleep onset was associated with longer total sleep time. Lower melatonin levels were associated with poorer social and occupational functioning. Although pineal volume is not directly related to sleep disturbances or symptoms, melatonin may influence both sleep-wake cycles and functioning in the early stages of affective disorder. Causal links remain to be established, however, treatments that target circadian rhythms may be useful in improving functioning in young people with affective disorders.

Pineal Gland Volume Assessed by MRI and Its Correlation with 6-Sulfatoxymelatonin Levels among Older Men.

The pineal gland produces the hormone melatonin, and its volume may influence melatonin levels. We describe an innovative method for estimating pineal volume in humans and present the association of pineal parenchyma volume with levels of the primary melatonin metabolite, 6-sulfatoxymelatonin. We selected a random sample of 122 older Icelandic men nested within the AGES-Reykjavik cohort and measured their total pineal volume, their parenchyma volume, and the extent of calcification and cysts. For volume estimations we used manual segmentation of magnetic resonance images in the axial plane with simultaneous side-by-side view of the sagittal and coronal plane. We used multivariable adjusted linear regression models to estimate the association of pineal parenchyma volume and baseline characteristics, including 6-sulfatoxymelatonin levels. We used logistic regression to test for differences in first morning urinary 6-sulfatoxymelatonin levels among men with or without cystic or calcified glands. The pineal glands varied in volume, shape, and composition. Cysts were present in 59% of the glands and calcifications in 21%. The mean total pineal volume measured 207 mm(3) (range 65-536 mm(3)) and parenchyma volume 178 mm(3) (range 65-503 mm(3)). In multivariable-adjusted models, pineal parenchyma volume was positively correlated with 6-sulfatoxymelatonin levels (β = 0.52, p < 0.001). Levels of 6-sulfatoxymelatonin did not differ significantly by presence of cysts or calcification. By using an innovative method for pineal assessment, we found pineal parenchyma volume to be positively correlated with 6-sulfatoxymelatonin levels, in line with other recent studies.

Associations of pineal volume, chronotype and symptom severity in adults with attention deficit hyperactivity disorder and healthy controls

The pineal gland, as part of the human epithalamus, is the main production site of peripheral melatonin, which promotes the modulation of sleep patterns, circadian rhythms and circadian preferences (morningness vs. eveningness). The present study analyses the pineal gland volume (PGV) and its association with circadian preferences and symptom severity in adult ADHD patients compared to healthy controls. PGV was determined manually using high-resolution 3T MRI (T1-magnetization prepared rapid gradient echo) in medication free adult ADHD patients (N=74) compared to healthy controls (N=86). Moreover, the Morningness–Eveningness Questionnaire (MEQ), the ADHD Diagnostic Checklist and the Wender–Utah Rating Scale were conducted. PGV differed between both groups (patients: 59.9±33.8mm3; healthy controls: 71.4±27.2mm3, P=0.04). In ADHD patients, more eveningness types were revealed (patients: 29%; healthy controls: 17%; P=0.05) and sum scores of the MEQ were lower (patients: 45.8±11.5; healthy controls 67.2±10.1; P<0.001). Multiple regression analyses indicated a positive correlation of PGV and MEQ scores in ADHD (β=0.856, P=0.003) but not in healthy controls (β=0.054, P=0.688). Patients’ MEQ scores (β=−0.473, P=0.003) were negatively correlated to ADHD symptoms. The present results suggest a linkage between the PGV and circadian preference in adults with ADHD and an association of the circadian preference to symptom severity. This may facilitate the development of new chronobiological treatment approaches for the add-on treatment in ADHD.

Assessment of Pineal Gland Volume and Calcification in Healthy Subjects: Is it Related to Aging?

Purpose: The human pineal gland is a small neuroendocrine organ which produces melatonin. The main goal of this study was to provide a reference range for pineal volume in all age groups and to determine calcified and noncalcified tissue and their proportions, which may be a reflection of melatonin production in all age groups, by using very thin computerized tomography (CT) slices.Materials and methods: A total of 167 outpatients had undergone cranial CT. Each of the subject’s total pineal volume (TPV), calcified pineal volume (CPV) and noncalcified pineal volume (NPV) according to age groups were calculated in cubic millimeters. Also, proportion of calcification (POC) was noted.Results: The median values were 88.5 mm3 (12.3 mm3–411mm3) for TPV, 74.3 mm3 (12.3 mm3–298 mm3) for NPV, and 3.9 mm3 (0 mm3–141 mm3) for CPV. POC showed a gradual increase from 0–49 years. In the ≥70 group, when compared with the 60–69 age group, CPV and POC values were significantly lower (P: 0.036, P: 0.034, respectively).Conclusion: This study brings a radiological point of view to the distribution of pineal calcification according to age that has a link with melatonin secretion.

Pineal gland volume in primary insomnia and healthy controls: a magnetic resonance imaging study

Little is known about the relation between pineal volume and insomnia. Melatonin promotes sleep processes and, administered as a drug, it is suitable to improve primary and secondary sleep disorders in humans. Recent magnetic resonance imaging studies suggest that human plasma and saliva melatonin levels are partially determined by the pineal gland volume. This study compares the pineal volume in a group of patients with primary insomnia to a group of healthy people without sleep disturbance. Pineal gland volume (PGV) was measured on the basis of high-resolution 3 Tesla MRI (T1-magnetization prepared rapid gradient echo) in 23 patients and 27 controls, matched for age, gender and educational status. Volume measurements were performed conventionally by manual delineation of the pineal borders in multi-planar reconstructed images. Pineal gland volume was significantly smaller (P<0.001) in patients (48.9±26.6mm(3) ) than in controls (79±30.2mm(3) ). In patients PGV correlated negatively with age (r=-0.532; P=0.026). Adjusting for the effect of age, PGV and rapid eye movement (REM) latency showed a significant positive correlation (rS =0.711, P<0.001) in patients. Pineal volume appears to be reduced in patients with primary insomnia compared to healthy controls. Further studies are needed to clarify whether low pineal volume is the basis or the consequence of functional sleep changes to elucidate the molecular pathology for the pineal volume loss in primary insomnia.

Incidental pineal cysts in children who undergo 3-T MRI

Pineal cysts, both simple and complex, are commonly encountered in children. More cysts are being detected with MR technology; however, nearly all pineal cysts are benign and require no follow-up. To discover the prevalence of pineal cysts in children at our institution who have undergone high-resolution 3-T MRI. We retrospectively reviewed 100 consecutive 3-T brain MRIs in children ages 1month to 17years (mean 6.8 ± 5.1years). We evaluated 3-D volumetric T1-W imaging, axial T2-W imaging, axial T2-W FLAIR (fluid attenuated inversion recovery) and coronal STIR (short tau inversion recovery) sequences. Pineal parenchymal and cyst volumes were measured in three planes. Cysts were analyzed for the presence and degree of complexity. Pineal cysts were present in 57% of children, with a mean maximum linear dimension of 4.2mm (range 1.5-16mm). Of these cysts, 24.6% showed thin septations or fluid levels reflecting complexity. None of the cysts demonstrated complete T2/FLAIR signal suppression. No cyst wall thickening or nodularity was present. There was no significant difference between the ages of children with and without cysts. Cysts were more commonly encountered in girls than boys (67% vs. 52%; P = 0.043). There was a slight trend toward increasing pineal gland volume with age. Pineal cysts are often present in children and can be incidentally detected by 3-T MRI. Characteristic-appearing pineal cysts in children are benign, incidental findings, for which follow-up is not required if there are no referable symptoms or excessive size.

Microstructural analysis of pineal volume using trueFISP imaging

To determine the spectrum of pineal microstructures (solid/cystic parts) in a large clinical population using a high-resolution 3D-T2-weighted sequence. A total of 347 patients enrolled for cranial magnetic resonance imaging were randomly included in this study. Written informed consent was obtained from all patients. The exclusion criteria were artifacts or mass lesions prohibiting evaluation of the pineal gland in any of the sequences. True-FISP-3D-imaging (1.5-T, isotropic voxel 0.9 mm) was performed in 347 adults (55.4 ± 18.1 years). Pineal gland volume (PGV), cystic volume, and parenchyma volume (cysts excluded) were measured manually. Overall, 40.3% of pineal glands were cystic. The median PGV was 54.6 mm(3) (78.33 ± 89.0 mm(3)), the median cystic volume was 5.4 mm(3) (15.8 ± 37.2 mm(3)), and the median parenchyma volume was 53.6 mm(3) (71.9 ± 66.7 mm(3)). In cystic glands, the standard deviation of the PGV was substantially higher than in solid glands (98% vs 58% of the mean). PGV declined with age (r = -0.130, P = 0.016). The high interindividual volume variation is mainly related to cysts. Pineal parenchyma volume decreased slightly with age, whereas gender-related effects appear to be negligible.

Post-Natal Growth in the Rat Pineal Gland: A Stereological Study

The purpose was to observe the changes in a rat pineal gland using stereological techniques during lactation and post-weaning periods. Thirty Wistar albino rats were studied during different post-natal periods using light microscopy. Pineal gland volume was estimated using the Cavalieri Method. Additionally, the total number of pinealocytes was estimated using the optical fractionator technique. Pineal gland volume displayed statistically significant changes between lactation and after weaning periods. A significant increase in pineal gland volume was observed from post-natal day 10 to post-natal day 90. The numerical density of pinealocytes became stabilized during lactation and decreased rapidly after weaning. However, the total number of pinealocytes continuously increased during post-natal life of all rats in the study. However, this increment was not statistically significant when comparing the lactation and after weaning periods. The increase in post-natal pineal gland volume may depend on increment of immunoreactive fibres, capsule thickness or new synaptic bodies.

Comparison of Three Methods for the Estimation of Pineal Gland Volume Using Magnetic Resonance Imaging

Pineal gland is a very important neuroendocrine organ with many physiological functions such as regulating circadian rhythm. Radiologically, the pineal gland volume is clinically important because it is usually difficult to distinguish small pineal tumors via magnetic resonance imaging (MRI). Although many studies have estimated the pineal gland volume using different techniques, to the best of our knowledge, there has so far been no stereological work done on this subject. The objective of the current paper was to determine the pineal gland volume using stereological methods and by the region of interest (ROI) on MRI. In this paper, the pineal gland volumes were calculated in a total of 62 subjects (36 females, 26 males) who were free of any pineal lesions or tumors. The mean ± SD pineal gland volumes of the point-counting, planimetry, and ROI groups were 99.55 ± 51.34, 102.69 ± 40.39, and 104.33 ± 40.45 mm3, respectively. No significant difference was found among the methods of calculating pineal gland volume (P > 0.05). From these results, it can be concluded that each technique is an unbiased, efficient, and reliable method, ideally suitable for in vivo examination of MRI data for pineal gland volume estimation.

MRI CHANGES IN THE “NORMAL” PINEAL GLAND FOLLOWING CHEMOTHERAPY FOR SUPRASELLAR GERM CELL TUMORS

Primary CNS germ cell tumors (GCT) arise in the suprasellar and pineal regions. Suprasellar GCT may remain radiographically occult during the early symptomatic period. Although theoretically possible, it is more difficult to identify presymptomatic disease in the pineal region. Given the sensitivity of GCT to cytotoxic therapy, a decrease in size of the “normal” pineal gland following chemotherapy (CHT) could divulge preexisting disease. Such information may impact radiation treatment (RT). The authors reviewed MRIs of 15 patients with suprasellar GCT treated with pre-RT CHT. They defined a ≥50% reduction in volume of the pineal gland as a substantial decrease suspicious for preexisting occult disease. As controls, MRIs of 11 medulloblastoma patients who received cytotoxic therapy were reviewed. Pineal gland volumes could be determined for 12 of 15 patients with GCT and 7 of 11 patients with medulloblastoma. The study radiologists concurred that 2/12 GCT patients and 0/7 medulloblastoma patients had ≥50% volumetric reduction. When radiation is delivered as the sole treatment modality, the pineal region is included in at least the initial volume, but in certain clinical trials RT volume is reduced to only the suprasellar region if a complete response is achieved following pre-RT CHT. Noting changes in the “normal” pineal gland following CHT may indicate disease. CHT alone may not be sufficient to control this disease, even in cases in which a complete response is achieved. If the intent is to deliver RT to all areas of initial disease and this phenomenon can be demonstrated on a larger scale, inclusion of the pineal should be considered for patients demonstrating a substantial decrease in the size of the pineal gland after CHT.

Pineal Gland Post‐natal Growth in Rat Revisited

We studied the pineal gland (PG) growth separating two critical moments of the rat post-natal development: the lactation and post-weaning periods. We studied 30 Wistar rats in the post-natal day - PN day 6, 10, 21, 45, 60 and 90 using light microscopy and quantitative methods (allometry and stereology). We estimated the PG volume (using the Cavalieri's principle) and the number of pineal gland cell nuclei (PGCN, using the disector method). We analysed the correlation of the PG volume (y) versus brain weight (x) in the different age groups (the bivariate study used log-transformed data and the allometric model log y = log a + b log x). The PG growth gradually decelerated in older rats than in younger rats. The major increment of the PG growth was observed between PN day 6 and PN day 10, while the minor increment was observed after weaning between PN day 45 and PN day 60. After 60 days of age differences were no more observed. The relative growth of the PG was allometrically positive in all age groups, and growth curves separated the lactation from the after weaning periods. The number of PGCN of rat continuously increased during post-natal life and differences between the lactation and after weaning periods were significant. It is possible that the supporting cells, fibres and new synapses are responsible for that PG late post-natal increase.

Reduced pineal volume in male patients with schizophrenia: no relationship to clinical features of the illness

Several investigations have suggested pineal gland abnormalities in the pathogenesis of schizophrenia. The pineal volume on brain magnetic resonance imaging scans was calculated in 15 male schizophrenic inpatients and in 16 matched control subjects. The statistical comparison found a significant difference of pineal gland volume between schizophrenics and controls ( P=0.022), with a smaller pineal volume in the schizophrenics. These results do not confirm the previous data of Schizophrenia Res. 14 (1995) 253, showing no significant pineal volumetric differences between schizophrenics and normal controls. Since the present study is based on a smaller but more homogeneous sample of patients, this could reduce the heterogeneity features of the schizophrenic disease. No correlation was found between pineal volume and clinical and psychopathological features of the schizophrenic subjects. Volume reduction in schizophrenia could be at least partially included in the wider brain developmental abnormalities of the illness or in the late effects of previous neuroleptic treatments.

Magnetic resonance imaging study of pineal gland volume and positive symptoms in schizophrenia

Observations of planetary wave (PW) activity in the northern hemisphere, polar summer mesosphere and lower thermosphere (MLT) are presented. Meteor winds from a northern hemisphere chain of SuperDARN radars have been used to monitor the meridional wind along a latitude band (51–66°N) in the MLT. A stationary PW-like longitudinal structure with a strong zonal PW number 1 characteristic is persistently observed year-to-year during summer. Here we characterize the amplitude and the phase structure of this wave in the MLT. The Modern-Era Retrospective Analysis for Research and Application (MERRA) of the NASA Global Modelling and Assimilation Office has been used to evaluate possible sources of the observed longitudinal perturbation in the mesospheric meridional wind by investigating the amplitudes and phases of PWs in the underlying atmosphere. The investigation shows that neither gravity wave modulation by lower atmospheric PWs nor direct propagation of PWs from the lower atmosphere are a significant cause of the observed longitudinal perturbation. However, the data are not of sufficient scope to investigate longitudinal differences in gravity wave sources, or to separate the effects of instabilities and inter-hemispheric propagation as possible causes for the large PW present in the summer MLT.

A New Concept for Melatonin Deficit: On Pineal Calcification and Melatonin Excretion

Even though exogenous melatonin has proven to influence sleep and circadian parameters, low endogenous melatonin is not related to sleep disturbances, nor does it predict response to melatonin replacement therapy. In this manuscript, we present a new concept towards a definition of a melatonin deficit. The purpose of the study was to introduce a marker for an intra-individual decrease in melatonin production. Therefore, we developed a method to quantify the degree of pineal calcification (DOC) using cranial computed tomography. Combining pineal DOC with the organs's size, we estimated the uncalcified pineal gland volume. This estimation was positively and significantly associated with 6-sulfatoxymelatonin (aMT6s), collected over 24 hours in urine, in 26 subjects. Data yielded evidence that the decline in aMT6s excretion with age can be sufficiently explained by an increased pineal calcification. These results suggest that DOC might be useful as an indicator of an intra-individual, decreased capability of the pineal gland to produce melatonin. DOC might prove to be a response-marker for melatonin replacement therapy and a vulnerability marker of the circadian timing system.