The pineal gland: anatomy, physiology, and clinical significance

Sudden death in patients with pineal cyst: Evidence from autopsy studies

Pineal cysts are usually benign, fluid-filled sacs and most pineal cysts are asymptomatic. Sudden death specifically related to pineal cysts is extremely uncommon. A literature review of the pertinent databases, including PubMed, Google Scholar, Scopus, and Web of Science, was carried out to review the existing literature describing sudden death in patients with pineal cysts. In the evaluation of 49 articles, it was found that four reports discussed the unexpected death of patients who had pineal cysts. A total of four cases of sudden death and a pineal cyst were reported. There were 75% females and a mean age of 29 (range: 20-45). Cyst size on average was 1.3 cm (1.2-1.5). In each case, the cause of death and the involvement of important brain structures were confirmed by autopsy results. A pathological analysis of the pineal region and the surrounding brain tissue revealed a variety of lesions. Vascular malformation was found in one case, adding another layer of complexity to the study of sudden death syndrome. In this research, the authors highlight the fact that patients with pineal cysts can experience serious, even fatal, complications. Increased vigilance and early detection through neuroimaging and neurological assessments are required due to the wide variety of clinical manifestations and underlying mechanisms. To explain the mechanism and enhance the management and prevention of sudden deaths associated with pineal cysts, additional research with larger sample sizes is required.

Next-generation plasmids for transgenesis in zebrafish and beyond

Transgenesis is an essential technique for any genetic model. Tol2-based transgenesis paired with Gateway-compatible vector collections has transformed zebrafish transgenesis with an accessible modular system. Here, we establish several next-generation transgenesis tools for zebrafish and other species to expand and enhance transgenic applications. To facilitate gene regulatory element testing, we generated Gateway middle entry vectors harboring the small mouse beta-globin minimal promoter coupled to several fluorophores, CreERT2 and Gal4. To extend the color spectrum for transgenic applications, we established middle entry vectors encoding the bright, blue-fluorescent protein mCerulean and mApple as an alternative red fluorophore. We present a series of p2A peptide-based 3' vectors with different fluorophores and subcellular localizations to co-label cells expressing proteins of interest. Finally, we established Tol2 destination vectors carrying the zebrafish exorh promoter driving different fluorophores as a pineal gland-specific transgenesis marker that is active before hatching and through adulthood. exorh-based reporters and transgenesis markers also drive specific pineal gland expression in the eye-less cavefish (Astyanax). Together, our vectors provide versatile reagents for transgenesis applications in zebrafish, cavefish and other models.

Micromorphology of pineal gland calcification in age-related neurodegenerative diseases

BACKGROUND

The formation of concrements in human pineal gland (PG) is a physiological process and, according to many researchers, is associated with the involution of PG structures. The majority of scientific publications concern progressive calcification of PG, leaving out studies on the destruction of already formed calcified concrements. Our study fills the gap in knowledge about calcified zones destruction in PG in normal aging and neuropathological conditions, which has not been addressed until now.

PURPOSE

Our objective is to gain insight into human PG tissue impairment in both normal aging and neurodegenerative conditions. X-ray phase-contrast tomography (XPCT) allowed us to study PG tissue degeneration at high spatial resolution and, for the first time, to examine the damaged PG concrements in detail. Our research finding could potentially enhance the understanding of the PG involvement in the process of aging as well as in Alzheimer's disease (AD) and vascular dementia (VD).

METHODS

The research was carried out on human PG autopsy material in normal aging, VD, and AD conditions. Laboratory-based micro-computed tomography (micro-CT) was used to collect and evaluate samples of native, uncut, and unstained PG with different degrees of pineal calcification. The detailed high-resolution 3D images of the selected PGs were produced using synchrotron-based XPCT. Histology and immunohistochemistry of soft PG tissue confirmed XPCT results.

RESULTS

We performed via micro-CT the evaluation of the morphometric parameters of PG such as total sample volume, calcified concrements volume, and percentage of concrements in the total volume of the sample. XPCT imaging revealed high-resolution details of age-related PG alteration. In particular, we noted signs of moderate degradation of concrements in some PGs from elderly donors. In addition, our analysis revealed noticeable degenerative change in both concrements and soft tissue of PGs with neuropathology. In particular, we observed a hollow core and separated layers as well as deep ragged cracks in PG concrements of AD and VD samples. In parenchyma of some samples, we detected wide pinealocyte-free fluid-filled areas adjacent to the calcified zones.

CONCLUSION

The present work provides the basis for future scientific research focused on the dynamic nature of PG calcium deposits and PG soft tissue in normal aging and neurodegenerative diseases.

Benign and Malignant Tumors of the Pineal Region

Pineal region tumors fall into five broad categories: benign pineal region tumors, glial tumors, papillary tumors, pineal parenchymal tumors, and germ cell tumors. Genetic and transcriptional studies have identified key chromosomal alterations in germinomas (RUNDC3A, ASAH1, LPL) and in pineocytomas/pineoblastomas (DROSHA/DICER1, RB1). Pineal region tumors generally present with symptoms of hydrocephalus including nausea, vomiting, papilledema, and the classical Parinaud's triad of upgaze paralysis, convergence-retraction nystagmus, and light-near pupillary dissociation. Workup requires neuroimaging and tissue diagnosis via biopsy. In germinoma cases, diagnosis may be made based on serum or CSF studies for alpha-fetoprotein or beta-HCG making the preferred treatment radiosurgery, thereby preventing the need for unnecessary surgeries. Treatment generally involves three steps: CSF diversion in cases of hydrocephalus, biopsy through endoscopic or stereotactic methods, and open surgical resection. Multiple surgical approaches are possible for approach to the pineal region. The original approach to the pineal region was the interhemispheric transcallosal first described by Dandy. The most common approach is the supracerebellar infratentorial approach as it utilizes a natural anatomic corridor for access to the pineal region. The paramedian or lateral supracerebellar infratentorial approach is another improvement that uses a similar anatomic corridor but allows for preservation of midline bridging veins; this minimizes the chance for brainstem or cerebellar venous infarction. Determination of the optimal approach relies on tumor characteristics, namely location of deep venous structures to the tumor along with the lateral eccentricity of the tumor. The immediate post-operative period is important as hemorrhage or swelling can cause obstructive hydrocephalus and lead to rapid deterioration. Adjuvant therapy, whether chemotherapy or radiation, is based on tumor pathology. Improvements within pineal surgery will require improved technology for access to the pineal region along with targeted therapies that can effectively treat and prevent recurrence of malignant pineal region tumors.

Digital histological morphometry of the human pineal gland in a postmortem study, with endocrine and neurological clinical implications

The pineal gland is a small-sized, photo neuroendocrine organ in the midline of the brain that synthesises and secretes melatonin and serotonin. Chords and islands of pinealocytes constitute the secretory parenchyma, while glial tissue and calcifications represent degenerative changes. This study examined human postmortem pineal glands to microscopically assess morphological changes possibly associated with clinical data, by using digital techniques. A retrospective autopsy study has been performed on 72 paediatric and adult autopsy cases. The glands have been processed for histological analysis and immunohistochemical staining with synaptophysin (SYN), neuron-specific enolase (NSE), and neurofilament (NF). Slides were digitally scanned. Morphometric data were obtained using CaseViewer and ImageJ. The comorbidities used for correlation with morphometric data were obesity, type 2 diabetes, adrenal gland adenoma, goitre, chronic pancreatitis, arterial hypertension, and mixed dementia. Thirty-three females and 39 males were included in the study. Increased secretory parenchyma was found in patients with chronic pancreatitis, arterial hypertension, and adrenal gland adenoma. Reduced activity was found in patients with type 2 diabetes, obesity, advanced pineal calcification, mixed dementia, and old age. There were no changes associated with goitre, cachexia, or Willis's polygon atherosclerosis. No significant differences between gender were found. The activity of the pineal gland can be assessed by quantitative immunohistochemistry of neuroendocrine and structural pinealocyte markers and observation of glial tissue and calcifications. There is a need for further research to evaluate the clinical impact of these morphological changes on the neuroendocrine systems, with clinical implications in endocrinology, neurology, and even psychiatry. Digital techniques offer a more exact analysis of histological data.

Physiological and pharmacological perspectives of melatonin

The pineal gland is a interface between light-dark cycle and shows neuro-endocrine functions. Melatonin is the primary hormone of pineal gland, secreted at night. The night-time melatonin peak regulates the physiological functions at dark. Melatonin has several unique features as it synchronises internal rhythm with daily and seasonal variations, regulates circadian rhythm and sleep-wake cycle. Physiologically melatonin involves in detoxification of free radicals, immune functions, neuro-protection, oncostatic effects, cardiovascular functions, reproduction, and foetal development. The precise functions of melatonin are exhibited by specific receptors. In relation to pathophysiology, impaired melatonin secretion promotes sleep disorder, cancer progression, type-2 diabetes, and neurodegenerative diseases. Several reports have highlighted the therapeutic benefits of melatonin specially related to cancer protection, sleep disorder, psychiatric disorders, and jet lag problems. This review will touch the most of the area of melatonin-oriented health impacts and its therapeutic aspects.

Occipital interhemispheric transtentorial approach to a pineoblastoma in a 4-year-old child

The authors present a pediatric case of a pineoblastoma treated with gross-total removal through an occipital interhemispheric transtentorial approach (OITA). The child presented with acute hydrocephalus that was treated by endoscopic third ventriculostomy (ETV) and tumor biopsy through a single burr hole. Histology revealed a pineoblastoma. Microsurgical total removal was performed 3 months after neoadjuvant chemotherapy. OITA was chosen on the basis of the tumor’s location below the Herophilus-Galen line of sight. In this video, the authors show the positioning, the operating devices, the approach, and the microsurgical dissection, indicating all the neurovascular structures encountered.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2122.

Age-Related Changes of the Pineal Gland in Humans: A Digital Anatomo-Histological Morphometric Study on Autopsy Cases with Comparison to Predigital-Era Studies

Background and objectives: The pineal gland is a photoneuroendocrine organ in the midline of the brain, responsible primarily for melatonin synthesis. It is composed mainly of pinealocytes and glial tissue. This study examined human postmortem pineal glands to microscopically assess age-related changes using digital techniques, and offers a perspective on evolutionary tendencies compared to the past. Materials and Methods: A retrospective autopsy study has been performed on 72 pediatric and adult autopsy cases. The glands have been processed for histological analysis and immunohistochemical staining with glial fibrillary acidic protein (GFAP). Slides were assessed under polarized light and digitally scanned. Morphometric data were obtained using CaseViewer and ImageJ. Results: Thirty-three females and 39 males were included in the study, grouped under three age groups: 0–25, 46–65, and 66–96 years of age. The peak gland volume was found within the 46–65 age group, the overall mean volume was 519 mm³, the main architectural types were lobular and insular, and the mean percentage of pineal calcification was 15% of the gland, peaking within the 66–96 age group, with a predominantly globular shape. Glial cysts were found in 20.8% of cases. The intensity of GFAP stain was maximal in the pediatric age group, but the extent of glial tissue was much larger in elderly patients. Discussion: The degenerative process of the pineal gland can be quantified by measuring normal parenchyma, calcifications, glial tissue, and glial cysts. Morphometric differences have been observed and compared to a similar studies performed in the published literature. The current study, unfortunately, lacks a 26–45 age group. Digital techniques seemed to offer a more exact analysis, but returned similar results to studies performed over 40 years ago, therefore offering important information on evolutionary tendencies. Conclusions: Increase in glial tissue, calcifications, and glial cysts have a defining role as age-related changes in the pineal gland.

Investigation of the human pineal gland 3D organization by X-ray phase contrast tomography

Pineal gland (PG) is a part of the human brain epithalamus that plays an important role in sleep, circadian rhythm, immunity, and reproduction. The calcium deposits and lesions in PG interfere with normal function of the organ and can be associated with different health disorders including serious neurological diseases. At the moment, the detailed mechanisms of PG calcifications and PG lesions formation as well as their involvement in pathological processes are not fully understood. The deep and comprehensive study of the structure of the uncut human PG with histological details, poses a stiff challenge to most imaging techniques, due to low spatial resolution, low visibility or to exceedingly aggressive sample preparation. Here, we investigate the whole uncut and unstained human post-mortem PGs by X-ray phase contrast tomography (XPCT). XPCT is an advanced 3D imaging technique, that permits to study of both soft and calcified tissue of a sample at different scales: from the whole organ to cell structure. In our research we simultaneously resolved 3D structure of parenchyma, vascular network and calcifications. Moreover, we distinguished structural details of intact and degenerated PG tissue. We discriminated calcifications with different structure, pinealocytes nuclei and the glial cells processes. All results were validated by histology. Our research clear demonstrated that XPCT is a potential tool for the high resolution 3D imaging of PG morphological features. This technique opens a new perspective to investigate PG dysfunction and understand the mechanisms of onset and progression of diseases involving the pineal gland.

Pineal Gland Metastasis From Poorly Differentiated Carcinoma of Unknown Primary Origin

Pineal metastasis is an exceedingly rare finding in patients with systemic malignancies. Such lesions are typically the manifestation of a primary lung cancer; nonetheless, a variety of malignancies have been reported to disseminate to the pineal gland including gastrointestinal, endocrine, and skin cancers, among others. However, to our knowledge, pineal gland metastasis without a primary origin has yet to be described. Carcinoma of unknown primary origin is a heterogeneous group of cancers characterized by the presence of metastatic disease without an identifiable primary tumor on metastatic workup. Here, we present a case of a 65-year-old male found to have a heterogeneously enhancing lesion of the pineal gland as well as an enhancing lesion of the left cerebellar hemisphere. Comprehensive metastatic workup demonstrated multifocal metastatic adenopathy without an identifiable primary lesion. Stereotactic biopsy of the pineal lesion revealed poorly differentiated carcinoma with an immunophenotype most consistent with gastrointestinal origin. To our knowledge, this is the first case to describe a pineal gland metastasis without a primary origin. We discuss the relevant literature on pineal gland metastases as well as carcinoma of unknown primary origin.

Protective effects of melatonin and vitamin E in acetamiprid-induced nephrotoxicity

Investigation of probable toxic effects of acetamiprid (ACMP) on kidney and comparative analysis of the probable protective effects of vitamin E and melatonin were conducted in the present study. The ethics committee approval was obtained from Inonu University Medical Faculty Ethics Committee. Fifty Balb-c mice were randomly assigned to control, corn oil, ethyl alcohol, ACMP, ACMP + melatonin, ACMP + vitamin E, and ACMP + melatonin + vitamin E groups. At the end of the experiments, rat kidney tissues were incised under anesthesia. Blood samples and kidney tissues were examined. After 21 days of ACMP administration, it was observed that malondialdehyde (MDA), total oxidant status (TOS), BUN, creatinine, IL-6, IL-1β, and TNF-α levels, histopathological damage, and Caspase-3 immunoreactivity scores increased, and glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and total antioxidant status (TAS) levels decreased, and histopathological damages were observed. Melatonin and vitamin E administration led to improvements in oxidative stress parameters, renal functions, inflammatory markers, and histopathological findings. ACMP administration led to nephrotoxicity in rat kidney tissues. Although melatonin and vitamin E administrations were effective on ACMP nephrotoxicity separately, co-administration of both was quite effective. Concomitant use of melatonin and vitamin E could be effective on prevention of toxicity.

Protective effects of melatonin on lung damage associated with one-lung ventilation: An experimental study

Background

This study aims to investigate the protective effect of melatonin on lung damage induced by one-lung ventilation in a rat model.

Methods

A total of 20 healthy, Sprague-Dawley male rats were randomized into two equal groups as control (n=10) and melatonin groups (n=10). The control group underwent 60 min of one-lung ventilation, followed by 30 min of two-lung ventilation. In the melatonin group, the rats were administered 10 mg/kg melatonin intraperitoneally 10 min before the start of the experiment. At the end of both ventilation periods, tissue samples were obtained from the lungs of the control and melatonin groups for biochemical analysis and histopathological examinations. Tissue superoxide dismutase, malondialdehyde, and tumor necrosis factor-alpha levels were measured. Lung tissue samples were examined based on the presence and amount of alveolar congestion, intra-alveolar bleeding, and leukocyte and lymphocyte infiltration.

Results

At the end of the study, lung tissue malondialdehyde (3.8±0.9 vs. 1.8±0.8 μM; p<0.001) and tumor necrosis factor-alpha levels (47.2±15.0 vs. 21.8±7.2 pg/mL; p<0.001) of the melatonin group were found to significantly decrease, compared to the control group. Superoxide dismutase levels of the melatonin group increased at the end of both ventilation periods, and the increase at the end of one-lung ventilation was found to be statistically significant (0.6±0.2 vs. 1.3±0.7 U/mL; p<0.05). Histopathological examination demonstrated that the tissue damage was less in the melatonin group. There was a significant decrease in the alveolar congestion in this group (p=0.0401). Although other histopathological parameters decreased in the melatonin group, no significant difference was found.

Conclusion

Our study results demonstrate that melatonin has protective effects on the lung damage induced by one-lung ventilation both at biochemical and histopathological levels in rats.

Determination of Melatonin Deprivation Impact on Sepsis With Acute Phase Reactants

BACKGROUND

The aim of the present study is to determine the association of melatonin hormone level on CRP, Total Antioxidant Status, Leukocyte, Procalcitonin, and Malondialdehyde, all acute phase reactants in the dark and light cycle of rats with sepsis model.

MATERIALS AND METHODS

In this study, 54 rats were divided into three groups. Whereas the first and third groups had a 12 h dark-light cycle, the second group was exposed to light for 24 h at 21°C-22°C for 10 d without any water and food restrictions. In the second and third groups, sepsis model was formed by cecal ligation and puncture (CLP) method at the end of 10th day, and blood samples were taken at the end of the 10th day. C-reactive protein, Malondialdehyde, Procalcitonin in the blood samples were analyzed by ELISA, and the levels of Total Antioxidant Status and leukocyte were determined by colorimetric method in the subsequent 12 and 24 h.

RESULTS

CRP values increased in the second group rats, which were kept continuously under light and had undergone CLP, from 288.8 mg/L to 584.0 mg/L at the end of the 12 h and the end of the 24 h, approximately, two times. In rats, which were kept under 12 h of light, 12 h of darkness, and applied CLP (group 3), these values increased from 416.9 to 619.1; an increase of 1.5 times. When assessed for MDA, it was determined that the differences between Group 2 and Group 3 were more prominent between 0 h and 12 h. While the MDA values in group 2 increased from 16.53 nmol/mL at the 12 h to 17.66 nmol/mL at the 24 h. However, MDA values did not yield statistically significant changes in the third group. Changes in the in PCT values were similar to the MDA values obtained. Increase coefficient of the PCT values between 0 h and 12 h in the second group 2 was 1.26; however, in the third group, it was negligible.

CONCLUSIONS

An increase in the oxidative stress was observed in the rats that underwent CLP and melatonin deprivation via continuous 24 h light exposure for 10 d. Accordingly, deprivation of light is considered to be effective in sepsis treatment due to the increase in melatonin levels in intensive care unit patients.

The morphological and functional characteristics of the pineal gland

Introduction

The pineal gland is a photo-neuro-endocrine organ situated inside the brain, that secretes serotonin, melatonin and N,N-dymethyltriptamine. This narrative review will address the latest information gathered on this function of the gland as well as the unknown roles it may have. The different histological and pathological findings of the pineal gland have demonstrated a role in clinical manifestations of numerous endocrine, neurological and psychiatric pathologies.

Materials

For this narrative review we used the NCBI website database PubMed. The search terms were “Pineal Gland” AND/OR “histology, melatonin, DMT, pathology”. Total number of articles included were 86.

Results

We have reviewed physiological information of melatonin and DMT, anatomical, histological and histopathological information on the pineal gland and its role in endocrine, neurological and psychiatric pathology.

Conclusion

The role of melatonin in immunity and its potential therapeutic effects show promising potential for further research. DMT seems to have a role in psychiatric pathology and potential therapeutic effects. Proper tumoral screening and diagnostic protocol are required.

New insights into the function of melatonin and its role in metabolic disturbances

INTRODUCTION

Melatonin is a pineal hormone that has acquired several unique modes of regulating the physiological effects in mammals due to its characteristic phylogenetic history. While melatonin exhibits immediate nocturnal effects, it also has next-day prospective effects that take place in the absence of this hormone. Besides that, the daily repetition and the annual variation in the duration of its synthesis determine its circadian and seasonal effects that characterize melatonin as a chronobiotic, a molecule that encodes time to the internal environment. Additionally, it presents transgenerational effects that are important for fetal programming, leading to a balanced energy metabolism in the adult life.

AREAS COVERED

Physiology, pathophysiology and therapeutic value of melatonin in metabolism and metabolic disorders.

EXPERT OPINION

The typical mechanisms of action of melatonin (immediate, prospective, chronobiotic and transgenerational) should be considered to adequately understand its physiological effects on the regulation of metabolism in humans and, as a result, to understand the metabolic pathophysiological consequences caused by its synthesis and/or signaling disturbances. That points to the importance of a broader understanding of melatonin actions, besides the classical endocrinological point of view, that would allow the clinician/research to proper interpret its role in health maintenance.

Biomarkers of Pineal Region Tumors: A Review

Background: The pineal gland, a small, pinecone-shaped organ deep within the brain, is responsible for producing melatonin. The gland consists of pineal parenchymal cells and glial cells that can form neoplasms. Pineal region neoplasms can also arise from germ cells and adjacent structures. This review focuses on detection of serum and cerebrospinal fluid (CSF) biomarkers of germ cell tumors and pineal parenchymal cell tumors, as these types comprise most neoplasms specific to the pineal region. Methods: For this review, we searched PubMed using the following keywords: biomarkers, germ cell tumor, germinoma, melatonin, pineal, pineal gland, pineal neoplasm, pinealoma, pineal parenchymal cell tumor, pineal region, and pineal tumor. We limited our search to full-text English articles and identified other relevant sources from the reference lists of identified articles. Results: Serum and CSF biomarker assays have a role in cases of suspected pineal germ cell or parenchymal neoplasms. Biomarkers including alpha-fetoprotein, beta-human chorionic gonadotropin, and placental alkaline phosphatase inform diagnosis and treatment and are important for monitoring germ cell tumor response to treatment. No biomarkers are currently available that inform diagnosis or treatment of pineal parenchymal tumors, although melatonin assays may have a role in monitoring response to treatment. Conclusion: Serum and CSF biomarkers in conjunction with clinical and radiographic evidence of a pineal region mass can inform the decision whether to undertake stereotactic biopsy or surgical excision or whether to proceed straight to medical treatment.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Effect of Photoperiod Extension on the Testicular Sonographic Appearance and Sexual Behavior of Captive Yangtze Finless porpoise (Neophocaena asiaeorientalis asiaeorientalis)

Xueying Yu, Yujiang Hao, Brian CW Kot, and Ding Wang (2016) Photoperiod plays an important role in the seasonal regulation of reproduction in mammals. In the present study, we examined the effect of an extended photoperiod (light/dark: 14 h/10 h) during the usual sexually inactive phase (Jan-Mar) on testicular sonographic appearance and sexual behaviors of two captive Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis, YFP). During the extended photoperiod treatment, the parenchyma pixel intensity, cross- sectional area of testicular sonographic images, as well as the frequency of sexual behaviors of the two male porpoises increased significantly compared to the control treatment. Parenchyma pixel intensity, the cross- sectional area of testicular sonographic images and the frequency of sexual behaviors of the two captive males all increased in response to extended photoperiod. These results may suggest that photoperiod is a potent factor regulating the reproductive seasonality in YFPs.

Microsurgical resection of pineal region tumors

The extensive variety of possible histologic subtypes makes it imperative to establish a tissue diagnosis in patients with pineal region tumors. Management decisions regarding adjuvant therapy, prognosis, and follow-up strategies vary with the histologic diagnosis. Specialized surgical and stereotactic techniques have evolved to provide the neurosurgeon with an array of safe and effective options for obtaining a tissue diagnosis. Advanced microsurgical techniques combined with improved preoperative management and postoperative critical care methods have made aggressive surgical resection a mainstay of management. Aggressive surgical resection has resulted in excellent long-term prognoses for nearly all patients with benign tumors and a large percentage of patients with malignant tumors. However, pineal region surgery remains fraught with potential pitfalls, and these favorable results are dependent on an advanced level of surgical expertise.

Volumetric relief map for intracranial cerebrospinal fluid distribution analysis

Cerebrospinal fluid imaging plays a significant role in the clinical diagnosis of brain disorders, such as hydrocephalus and Alzheimer's disease. While three-dimensional images of cerebrospinal fluid are very detailed, the complex structures they contain can be time-consuming and laborious to interpret. This paper presents a simple technique that represents the intracranial cerebrospinal fluid distribution as a two-dimensional image in such a way that the total fluid volume is preserved. We call this a volumetric relief map, and show its effectiveness in a characterization and analysis of fluid distributions and networks in hydrocephalus patients and healthy adults.

Anatomy of the pineal region applied to its surgical approach

INTRODUCTION

The pineal region is situated in the posterior part of the incisural space. This region includes the pineal body inside the quadrigeminal arachnoidal cistern. This article reviews the anatomic features of this region, with particular emphasis on those aspects of importance for surgical access to the pineal region.

MATERIAL & METHODS

Five cadaver heads fixed in 10% formalin and injected with colored latex were used for anatomic dissection (five other specimens were also prepared and dissected to illustrate the articles on surgical techniques and approaches presented elsewhere in this issue).

RESULTS

The pineal body is surrounded by several important structures such as: posterior part of the third ventricle, tectum, the complex of the great cerebral vein of Galen, pulvinar nuclei of the thalamus and splenium of corpus callosum.

CONCLUSION

The surgical approach of the pineal body, whatever the route or the technique used (microsurgical, endoscopic or stereotactic), creates a great challenge for the neurosurgeons due to its location in the deep part of the brain and its close relationships with complex surrounded vascular structures.

Adaptations of the aging animal to exercise: role of daily supplementation with melatonin

The pineal gland, through melatonin, seems to be of fundamental importance in determining the metabolic adaptations of adipose and muscle tissues to physical training. Evidence shows that pinealectomized animals fail to develop adaptive metabolic changes in response to aerobic exercise and therefore do not exhibit the same performance as control-trained animals. The known prominent reduction in melatonin synthesis in aging animals led us to investigate the metabolic adaptations to physical training in aged animals with and without daily melatonin replacement. Male Wistar rats were assigned to four groups: sedentary control (SC), trained control (TC), sedentary treated with melatonin (SM), and trained treated with melatonin (TM). Melatonin supplementation lasted 16 wk, and the animals were subjected to exercise during the last 8 wk of the experiment. After euthanasia, samples of liver, muscle, and adipose tissues were collected for analysis. Trained animals treated with melatonin presented better results in the following parameters: glucose tolerance, physical capacity, citrate synthase activity, hepatic and muscular glycogen content, body weight, protein expression of phosphatidylinositol 3-kinase (PI3K), mitogen-activated protein kinase (MAPK), and protein kinase activated by adenosine monophosphate (AMPK) in the liver, as well as the protein expression of the glucose transporter type 4 (GLUT4) and AMPK in the muscle. In conclusion, these results demonstrate that melatonin supplementation in aging animals is of great importance for the required metabolic adaptations induced by aerobic exercise. Adequate levels of circulating melatonin are, therefore, necessary to improve energetic metabolism efficiency, reducing body weight and increasing insulin sensitivity.

Maternal melatonin programs the daily pattern of energy metabolism in adult offspring

Background

Shift work was recently described as a factor that increases the risk of Type 2 diabetes mellitus. In addition, rats born to mothers subjected to a phase shift throughout pregnancy are glucose intolerant. However, the mechanism by which a phase shift transmits metabolic information to the offspring has not been determined. Among several endocrine secretions, phase shifts in the light/dark cycle were described as altering the circadian profile of melatonin production by the pineal gland. The present study addresses the importance of maternal melatonin for the metabolic programming of the offspring.

Methodology/Principal Findings

Female Wistar rats were submitted to SHAM surgery or pinealectomy (PINX). The PINX rats were divided into two groups and received either melatonin (PM) or vehicle. The SHAM, the PINX vehicle and the PM females were housed with male Wistar rats. Rats were allowed to mate and after weaning, the male and female offspring were subjected to a glucose tolerance test (GTT), a pyruvate tolerance test (PTT) and an insulin tolerance test (ITT). Pancreatic islets were isolated for insulin secretion, and insulin signaling was assessed in the liver and in the skeletal muscle by western blots. We found that male and female rats born to PINX mothers display glucose intolerance at the end of the light phase of the light/dark cycle, but not at the beginning. We further demonstrate that impaired glucose-stimulated insulin secretion and hepatic insulin resistance are mechanisms that may contribute to glucose intolerance in the offspring of PINX mothers. The metabolic programming described here occurs due to an absence of maternal melatonin because the offspring born to PINX mothers treated with melatonin were not glucose intolerant.

Conclusions/Significance

The present results support the novel concept that maternal melatonin is responsible for the programming of the daily pattern of energy metabolism in their offspring.

Melatonin in experimental seizures and epilepsy

Although melatonin is approved only for the treatment of jet-lag syndrome and some types of insomnia, clinical data suggest that it is effective in the adjunctive therapy of osteoporosis, cataract, sepsis, neurodegenerative diseases, hypertension, and even cancer. Melatonin also modulates the electrical activity of neurons by reducing glutamatergic and enhancing GABA-ergic neurotransmission. The indoleamine may also be metabolized to kynurenic acid, an endogenous anticonvulsant. Finally, the hormone and its metabolites act as free radical scavengers and antioxidants. The vast majority of experimental data indicates anticonvulsant properties of the hormone. Melatonin inhibited audiogenic and electrical seizures, as well as reduced convulsions induced by pentetrazole, pilocarpine, L-cysteine and kainate. Only a few studies have shown direct or indirect proconvulsant effects of melatonin. For instance, melatonin enhanced low Mg2+-induced epileptiform activity in the hippocampus, whereas melatonin antagonists delayed the onset of pilocarpine-induced seizures. However, the relatively high doses of melatonin required to inhibit experimental seizures can induce some undesired effects (e.g., cognitive and motor impairment and decreased body temperature). In humans, melatonin may attenuate seizures, and it is most effective in the treatment of juvenile intractable epilepsy. Its additional benefits include improved physical, emotional, cognitive, and social functions. On the other hand, melatonin has been shown to induce electroencephalographic abnormalities in patients with temporal lobe epilepsy and increase seizure activity in neurologically disabled children. The hormone showed very low toxicity in clinical practice. The reported adverse effects (nightmares, hypotension, and sleep disorders) were rare and mild. However, more placebo-controlled, double-blind randomized clinical trials are needed to establish the usefulness of melatonin in the adjunctive treatment of epilepsy.

Some questions provoked by a chronic headache (with mixed migraine and cluster headache features) in a woman with a pineal cyst. Answers from a literature review

The main known function of the pineal gland in humans is the production of melatonin. Benign cysts of the gland have been related to headache, although the mechanism of production of this assumed clinical manifestation has not been clearly determined, due to the lack of large prospective studies. The question is complicated by the fact that pineal cysts are frequently found on brain magnetic resonance imaging. Much has been published about the possible role of benign pineal cysts in the pathophisiology of headaches and the potential of melatonin in headache therapy, as well as in other disorders. The aim of this article is to review the current state of the suject. We have tried to place accurately the relation between headache and pineal cysts based on the available evidence, as well as the actual role of melatonin in physiology and pharmacology, more specifically in headache therapy. We include a clinical case to illustrate the subject.

EFFECTS OF PHOTOPERIOD ON THE ULTRASTRUCTURE OF LEYDIG CELLS IN RAT

The aim of this study was to examine effects of photoperiod on the ultrastructure of Leydig cells in rat. For this purpose, 21 male Wistar rats were used. Animals were divided into three groups: Control rats in group I were kept under 12 hrs light: 12 hrs dark conditions (12L: 12D) for 10 weeks. Animals in group II were exposed to long photoperiods (18L: 6D), while rats in group III were exposed to short photoperiods (6L:18D) for 10 weeks. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum testosterone levels were determined with the use of a chemiluminescent enzyme immunoassay. The testes of all rats were removed and weighed, then processed for light and electron microscopy. For morphometric comparison, diameters of seminiferous tubules in each group were measured. In rats exposed to long photoperiods, testicular weights, diameters of seminiferous tubules and serum testosterone levels were significantly increased as compared to those in control rats, whereas exposure of rats to short photoperiods resulted in a significant decrease of testicular weights, diameters of seminiferous tubules and serum testosterone levels as compared to those in control rats and rats maintained in long photoperiods. The amount of mitochondria and cytoplasmic secretory granules were increased in the cytoplasm of Leydig cells of rats exposed to long photoperiods. Furthermore, an increase in extensiveness of rough endoplasmic reticulum in the cell cytoplasm was noticed in this group, whereas a decrease in mitochondria and cytoplasmic secretory granules of the Leydig cell cytoplasm was seen in rats exposed to short photoperiods. The results of our study indicate that testicular functions increase after exposure to long photoperiods and decrease after exposure to short photoperiods.

MAGNETIC STIMULATION OF THE BRAIN INCREASE Na+, K+-ATPase ACTIVITY DECREASED BY INJECTION OF AlCl3INTO NUCLEUS BASALIS MAGNOCELLULARIS OF RATS

This article reports here on the influence of the static magnetic fields (MFs), locally applied to the brain area, on Na, K-ATPase activity in the rat with lesioned nucleus basalis magnocellularis (NBM) by intracerebral injection of 5 microl, 1% AlCl3 into the nucleus. Two AKMA micromagnets (M) flux density of 60 miliTesla, 5 mm in diameter, were bilaterally implanted with "N" polarity facing down to the cranial bones in the vicinity of the pineal gland (PG), immediately after the lesioning of NBM, during the same operation procedure. Ten days after the lesions of NBM, Na, K-ATPase activity on the erythrocyte membranes in the peripheral blood, measured spectrophotometrically, was completely inhibited. Magnetic stimulation (60 mT) of the brain during the 10 days significantly increased Na, K-ATPase activity on the erythrocyte membranes of rats with lesioned NBM. This results suggests that altered by lesions Na, K-ATPase activity in an experimental model of Alzheimer's disease might be ameliorated by magnetic stimulation of the brain.

The relationship of pineal calcification and melatonin secretion to the pathophysiology of tardive dyskinesia and tourette's syndrome

Despite current intensive research, the pathophysiology of tardive dyskinesia (TD), a serious neurological side effect of neuroleptic treatment, is poorly understood. Prompted by the observation of an increased incidence and severity of abnormal perioral movements in neuroleptic-treated pinealectomized, as compared to intact rats, we suggested that the pineal gland exerts a protective effect which mitigates against the development of TD and, by inference, that reduced melatonin secretion may be related to the pathophysiology of TD. To investigate this proposition further, we studied the association of TD with pineal calcification (PC) on CT scan in chronic schizophrenic patients. Our findings revealed a significant association between TD and PC and suggest, furthermore, that PC may be a neuroradiological marker of TD. Since PC may reflect diminished secretory activity of the gland, these findings support the hypothesis that the pathophysiology of TD is linked to disturbances of melatonin secretion. The clinical and therapeutic implications of these novel findings are discussed. In the following communication, in which we introduce the hypothesis that disturbances of 5-HT and melatonin secretion are related to the pathophysiology of TD. Subsequently, we present a series of studies which relate to the association of TD with PC. We conclude by presenting the hypothesis that disturbances in melatonin secretion may also be relevant to the pathophysiology of Tourette's syndrome.

Malignant pineal germ-cell tumors: an analysis of cases from three tumor registries

The exact incidence of pineal germ-cell tumors is largely unknown. The tumors are rare, and the number of patients with these tumors, as reported in clinical series, has been limited. The goal of this study was to describe pineal germ-cell tumors in a large number of patients, using data from available brain tumor databases. Three different databases were used: Surveillance, Epidemiology, and End Results (SEER) database (1973-2001); Central Brain Tumor Registry of the United States (CBTRUS; 1997-2001); and National Cancer Data Base (NCDB; 1985-2003). Tumors were identified using the International Classification of Diseases for Oncology, third edition (ICD-O-3), site code C75.3, and categorized according to histology codes 9060-9085. Data were analyzed using SAS/STAT release 8.2, SEER*Stat version 5.2, and SPSS version 13.0 software. A total of 1,467 cases of malignant pineal germ-cell tumors were identified: 1,159 from NCDB, 196 from SEER, and 112 from CBTRUS. All three databases showed a male predominance for pineal germ-cell tumors (>90%), and >72% of patients were Caucasian. The peak number of cases occurred in the 10- to 14-year age group in the CBTRUS data and in the 15- to 19-year age group in the SEER and NCDB data, and declined significantly thereafter. The majority of tumors (73%-86%) were germinomas, and patients with germinomas had the highest survival rate (>79% at 5 years). Most patients were treated with surgical resection and radiation therapy or with radiation therapy alone. The number of patients included in this study exceeds that of any study published to date. The proportions of malignant pineal germ-cell tumors and intracranial germ-cell tumors are in range with previous studies. Survival rates for malignant pineal germ-cell tumors are lower than results from recent treatment trials for intracranial germ-cell tumors, and patients that received radiation therapy in the treatment plan either with surgery or alone survived the longest.

Mixing and modes of mass transfer in the third cerebral ventricle: a computational analysis

Anatomic, velocimetric, and brain motion MRI scans were combined with a computational fluid dynamics model to investigate cerebrospinal fluid (CSF) mixing in the third cerebral ventricle of a healthy male adult. It was found that advection dominates over diffusion in most of the third ventricle. Three zones where diffusion plays an important role in the mixing process were identified. One of these zones, consisting of recessus infundibulus, recessus opticus and the adjacent regions up to commissura anterior, is likely to exist in the general population. We hypothesize that this zone may act as a buffer to flatten concentration peaks of pituitary gland hormones released into the CSF of the third ventricle. We further hypothesize that this zone may facilitate the communication between hypothalamus and the pituitary gland through the third ventricle cerebrospinal fluid by prolonging residence times of the communicated hormones.

Potential therapeutic use of melatonin in migraine and other headache disorders

There is increasing evidence that headache disorders are connected with melatonin secretion and pineal function. Some headaches have a clearcut seasonal and circadian pattern, such as cluster and hypnic headaches. Melatonin levels have been found to be decreased in both migraine and cluster headaches. Melatonin mechanisms are related to headache pathophysiology in many ways, including its anti-inflammatory effect, toxic free radical scavenging, reduction of pro-inflammatory cytokine upregulation, nitric oxide synthase activity and dopamine release inhibition, membrane stabilisation, GABA and opioid analgesia potentitation, glutamate neurotoxicity protection, neurovascular regulation, 5-HT modulation and the similarity in chemical structure to indometacin. The treatment of headache disorders with melatonin and other chronobiotic agents, such as melatonin agonists (ramelteon and agomelatin), is promising and there is a great potential for their use in headache treatment.

Melatonin, the pineal gland and their implications for headache disorders

There is now evidence that melatonin may have a role in the biological regulation of circadian rhythms, sleep, mood, and ageing. Altered melatonin levels in cluster headache and migraine have been documented. Melatonin mechanisms are related to headache pathophysiology in many ways, including its anti-inflammatory effect, toxic free radical scavenging, reduction of proinflammatory cytokine up-regulation, nitric oxide synthase activity and dopamine release inhibition, membrane stabilization, GABA and opioid analgesia potentiation, glutamate neurotoxicity protection, neurovascular regulation, serotonin modulation, and the similarity of chemical structure to that of indomethacin. Treatment of headache disorders with melatonin and other chronobiotic agents is promising. A double-blind, placebo-controlled trial shows melatonin is effective in cluster headache prevention, other studies also show benefit in other disorders. Melatonin plays an important role in headache disorders, offering new avenues for studying their pathophysiology and treatment.

Melatonin enhances leptin expression by rat adipocytes in the presence of insulin

Leptin and melatonin play an important role in the regulation of body mass and energy balance. Both hormones show a circadian rhythm, with increasing values at night. In addition, melatonin receptors were recently described in adipocytes, where leptin is synthesized. Here, we investigated the influence of melatonin and its interaction with insulin and dexamethasone on leptin expression. Isolated rat adipocytes were incubated with melatonin (1 nM) alone or in combination with insulin (5 nM) and/or dexamethasone (7 nM) for 6 h. Melatonin or insulin alone did not affect leptin expression, but together they increased it by 120%. Dexamethasone increased leptin mRNA content (105%), and this effect was not enhanced by melatonin. Simultaneous treatment with the three hormones provoked a further increase in leptin release (250%) and leptin mRNA (100%). Melatonin prevented the forskolin-induced inhibition (95%) of leptin expression. In addition, melatonin's ability to stimulate leptin release (in the presence of insulin) was completely blocked by pertussis toxin and luzindole. To gain further insight into the molecular basis of melatonin and insulin synergism, the insulin-signaling pathway was investigated. Melatonin increased the insulin-induced insulin receptor-beta tyrosine phosphorylation, which led to an increased serine phosphorylation of the downstream convergent protein Akt. We concluded that melatonin interacts with insulin and upregulates insulin-stimulated leptin expression. These effects are caused by melatonin binding to the pertussis toxin-sensitive G(i) protein-coupled membrane receptor (MT1 subtype) and the cross talk with insulin, since insulin receptor and its convergent target Akt are coactivated by melatonin.

Melatonin is an efficient antioxidant

We have compared the peroxyl radical scavenger ability of melatonin with that of vitamin E, ascorbic acid (As.A.), reduced glutathione (GSH) and mannitol. All the antioxidants, except mannitol, prevented the lysis of human erythrocytes exposed to an azo-initiator of peroxyl radicals (2,2'-azo-bis(2-amidinopropane)dihydrochloride) at 37 degrees C. The percentage of this inhibition of erythrocyte lysis varied with the concentration of antioxidants, but the efficiency was melatonin > vitamin E > As.A. > GSH. Based on the assumption that each molecule of vitamin E scavenges two peroxyl radicals, the scavenging capacity of melatonin was four peroxyl radicals/molecule.

An enigmatic eye: the histology of the tuatara pineal complex

AIM

To examine the histology of the tuatara pineal complex and to compare findings with those of Dendy. Some reptiles have an anatomically sophisticated pineal complex with a median pineal eye, a paraphysis and a pineal sac. In comparison, the human pineal gland is simple and homogenous and thought to be a phylogenetic relic. It is now considered a neuroendocrine gland the function of which is still not fully understood. Its simple anatomical structure is in contrast to its biochemical complexity; its secretions (the most studied being melatonin) modifying the function of the adeno- and neurohypophysis, thyroid and parathyroids, adrenal cortex and medulla, endocrine pancreas and the gonads.

METHODS

Histological sections of the brain of a neonatal tuatara were studied by light microscopy.

RESULTS

The histological findings of the pineal eye demonstrated a cornea-like structure, rudimentary lens and simple retina. The adjacent paraphysis was a large, multisaccular organ and the pineal sac a very large saccular organ with a poorly differentiated retina.

CONCLUSION

The pineal eye of the tuatara has a remarkably eye-like structure with photoreceptors that in other reptiles have been shown to exhibit photoreceptive capabilities. The paraphysis appeared to have a secretory function that is as yet undetermined, while the pineal sac had the appearance of a poorly differentiated retina. Thus it appears that the complex biochemistry of the human pineal gland is reflected in the complex anatomical structure of this primitive reptile.

Effects of melatonin on Leydig cells in pinealectomized rat: an immunohistochemical study

We have investigated immunohistochemically the effects of melatonin on Leydig cells in rat. Three groups of Wistar rats were used. Rats in group I and II were sham-pinealectomized (control) and pinealectomized, respectively, whereas rats in group III were pinealectomized and injected daily with melatonin for 2 months. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum testosterone levels were determined with the use of a chemiluminescent enzyme immunoassay. Testicular tissue was collected and processed for semiquantitative evaluation of immunohistochemical testosterone staining. Intensity of immunostaining was determined on a scale between 0 (no staining) and 5 (heavy staining). In pinealectomized rats, serum testosterone levels were significantly increased as compared to sham-pinealectomized rats. Daily administration of melatonin after pinealectomy resulted in significant decreased serum testosterone levels as compared to levels in control and pinealectomized rats. Immunostaining of testosterone was moderate (3+) in sham-pinealectomized rats, heavy (5+) in pinealectomized rats and low (1+) in pinealectomized rats that were treated with melatonin, respectively. The results of our study indicate that pinealectomy induces increased testosterone secretion in Leydig cells and this increased secretion can be prevented by administration of melatonin.

Ultrastructural interrelationship between the pineal gland and the testis in the male rat

The ultrastructural interrelationship between the pineal gland and testis was evaluated in the rat. Wistar rats were divided into 6 groups. Groups I and II were sham-orchidectomized and orchidectomized rats, respectively. Rats in group III were orchidectomized and daily injected with testosterone propionate (TP) for 1 month. Groups IV and V were sham-pinealectomized and pinealectomized, respectively. Group VI was pinealectomized and daily injected with melatonin for 2 months. All animals were anesthetized with ketamine for fixation by vascular perfusion. Pineal glands of groups I, II, and III and the testes of groups IV, V, and VI were removed and weighed. All specimens were examined by electron microscopy. Orchidectomy caused an increase of lipid droplets, cytoplasmic dense bodies, and lysosomes. Rough endoplasmic reticulum, Golgi apparatus, and mitochondria were extensive in the cytoplasm. TP administration to orchidectomized rats resulted in formation of less extensive lipid droplets and mitochondria. In pinealectomized rats, golgi complex, mitochondria, and enlarged smooth endoplasmic reticulum were extensive in the cytoplasm of Leydig cells. Formation of cytoplasmic secretory granules and osmiophilic bodies was observed. Testicular weight increased compared to group IV. Melatonin decreased testicular weight in comparison to group V and prevented ultrastructural changes. Pinealectomy and orchidectomy caused hyperactivity in Leydig cells and pinealocytes, respectively, which suggests a mutual relationship between the pineal gland and testis in the rat.

Comparison of the effects of melatonin and methylprednisolone in experimental spinal cord injury

OBJECT

Melatonin is a very effective antioxidant agent. This study was performed to investigate the effects of melatonin in experimental spinal cord injury (SCI). The authors also compared its effects with those of methylprednisolone, which also protects the spinal cord from secondary injury because of its antioxidant effect on membrane lipids.

METHODS

Adult male albino rats were used for the study, and paraplegia was produced using a previously described weight-drop technique. Melatonin and methylprednisolone were given intraperitoneally by bolus injections of 100 mg/kg and 30 mg/kg, respectively, immediately after induction of trauma. The animals were killed, and 1-cm samples of injured spinal cord were obtained at 1, 24, and 48 hours postinjury. Lipid peroxidation was estimated by thiobarbituric acid test. Electron microscopic studies were performed to determine the effects of melatonin on neurons, axons, and subcellular organelles after experimental SCI. A grading system was used for quantitative evaluation. Following SCI, there was significant increase in lipid peroxidation. In melatonin- and methylprednisolone-treated groups, lipid peroxidation was found to decrease to the baseline (preinjury) levels. There was a significant difference between trauma-alone and treatment groups, but no statistical difference was found between the melatonin- and methylprednisolone-treated groups. Electron microscopic findings showed that SCI produced by the weight-drop technique resulted in profound tissue damage.

CONCLUSIONS

Both melatonin and methylprednisolone have been shown to protect neuron, axon, myelin, and intracellular organelles including mitochondrion and nucleus. However, this study provides quantitative evidence that this protection of neurons and subcellular organelles of spinal cord after secondary injury is much more obvious in melatonin-treated rats than those treated with methylprednisolone. In view of these data, melatonin has been shown to be very effective in protecting the injured spinal cord from secondary injury.

The effect of pinealectomy on immune parameters in different age groups in rats: results of the weekly alteration of the zinc level and the effect of melatonin administration on wound healing

It is generally accepted that the pineal gland is a neuroendocrine organ. Several recent experiments have shown that the pineal gland has functional and anatomic connections with many organs and systems, particularly with the immune system, and, therefore, the gland is now recognised as an important immunoneuroendocrine organ both in man and animals. The present study investigates the effect of pinealectomy on some immune parameters including zinc pool alterations and wound healing process in different age group in rats and also investigates the effect of melatonin administration on wound healing in different age groups. Experiments were performed on two different age groups of rats (neonatal and young). We have experimentally shown the induction of immune depression by pinealectomy and the restorative competence of melatonin administration in the present study. The results also showed that the plasma zinc level was significantly reduced in the third week after the pinealectomy particularly in pinealectomised neonatal rats and the wound healing process affected only in pinealectomised neonatal rats but restored to normal by melatonin administration. In view of these data, as described previously, the pineal gland has a main regulatory function in immune physiology, but our study indicates that only neonatal immune functions are significantly affected by pinealectomy.