Space exploration is one of the dreams of humankind. However, the intriguing environment was a challenge for the human body, where we must counter with many extreme conditions such as thermal support, radiation, microgravity. Life, as well as the human body, developed and evolved in the continuous presence of gravity, especially when living creatures transfer from the ocean to the land. Once this gravitational force doesn't impact on the body, the drastic changes occur. Some of these changes were observed immediately, while others progress only slowly. Since the first orbital flight was performed, several hazards for the organs of the human body were identified [1]. These changes in human physiology can reverse when astronauts return to Earth. This article will review the published findings of the effects of microgravity exposure on the human body.

The relation between the low-dose radiation and the cognitive decline remains limited and controversial. However, the increasing use of high-dose radiation for medical purposes and some historical radiation-related accidents indicated that the low-dose radiation reduced cognitive ability, suggesting the reconsideration of the central nervous system’s low sensitivity to radiation, which has been advocated by conventional radiation biology. Although the continuous stimulation of low-dose radiation is known to be an environmental stressor that causes a critical decline in cognition during space exploration, the overall mechanisms from radiation exposure to cognitive alteration is still lacking. One of its main reasons is the inconsistent empirical results, and there are various possibilities to cause the contradictory consequences, such as the hormesis effect of low-dose radiation, the cellular adaptive responses, the radiation resistance, the bystander effects, and the genomic instability. In this review, we survey the low-dose radiation-induced cognitive studies, targeting learning achievement, emotional changes as well as fundamental cognitive behaviors in both humans and animals. Also, some relevant molecular studies are reappraised to understand the low-dose radiation-induced effects on the cognitive function.

OBJECTIVE: Growing hypotheses indicate the galvanic vestibular stimulation (GVS) as an alternative method to manage the symptoms of parkinson's disease (PD). GVS is easy and safe for use, and non-invasive. However, it is elusive how the neural information caused by GVS is transmitted in the central nervous system and relieves PD symptoms. To answer this question, we investigated the transmission of neural information by GVS in the central vestibular system, focused on vestibular nucleus (VN). METHODS: Twenty guinea pigs were used for this study for the extracellular neuronal recordings in the VN. The neuronal responses to rotation and GVS were analyzed by curve-fitting, and the numerical responding features, amplitudes and baselines, were computed. The effects of stimuli were examined by comparing these features. RESULTS: Twenty six vestibular neurons (15 regular and 11 irregular neurons) were recorded. Comparing the difference of baselines, we found the neural information was linearly transmitted with a reduced sensitivity (0.75). The linearity in the neural transmission was stronger in the neuronal groups with regular (correlation coefficient [Cor. Coef.]=0.91) and low sensitive units (Cor. Coef.=0.93), compared with those with irregular (Cor. Coef.=0.86) and high-sensitive neurons (Cor. Coef.=0.77). CONCLUSION: The neural information by GVS was linearly transmitted no matter what the neuronal characteristics were.
Animals ; Central Nervous System ; Guinea Pigs ; Methods ; Neurons ; Parkinson Disease ; Synaptic Transmission ; Vestibular Nuclei

Electrophysiological research has improved the understandings of various neural controls on motion and their functional connectivity in the central nervous system. Unlike medical imaging techniques, the electrophysiological approach can provide the neural signal processing between two or more specific regions and their temporal transmission of neural information. Using its unique advantages, the vestibular system has been also studied for more than 100 years. However, it is a recent finding that various higher functions, such as cognition, memory, learning, and even spatial navigation, are constructed partially by the vestibular neural information in the human brain. It is caused by the historical underestimation on the vestibular system and its supporting position to the main neural flow. Here, we seek for a new research theme with various approaches in the vestibular system by reviewing electrophysiological researches on the vestibular system and their experimental results.
Brain ; Central Nervous System ; Cognition ; Diagnostic Imaging ; Electrophysiology* ; Humans ; Learning ; Memory

BACKGROUND: Early identification and appropriate management of mild chronic renal failure has been increasingly recognized as an important opportunity to delay the progression of renal disease. Many physicians rely on serum creatinine (Scr) as a screening test for renal impairment; however, Scr levels can remain within the normal range even when renal function is significantly impaired in certain group of patients. METHODS: The subjects were 20, 245 persons who were enrolled a regular health check up program, Jan. 1997 to Jun. 2001, at Ajou University Hospital, Korea. We identified GFR below 60 mL/min/1.73 m2 as abnormal and found the percentage of patients with Scr value from 1.1 mg/dL to 1.4 mg/dL and their sex and age distribution, using GFRs calculated by Cockroft-Gault Equation, MDRD Equation, and Kang's Equation. RESULTS: Average Scr was 1.07+-0.13 mg/dL in male and 0.82+-0.11 mg/dL in female. Among 34 University hospital in metro Seoul area, 11 hospital used 1.4 mg/dL as normal upper limit of Scr and 7 hospital used 1.3 mg/dL. Taking normal Scr upper limit as 1.3 or 1.4 mg/dL, the frequency of GFR below 60 mL/min/1.73 m2 was 3.9-50% in males and 75-100% in females, although some differences existed according to the equation used. CONCLUSION: Currently used normal Scr upper limit 1.3, 1.4 mL/dL was found to be much too high and we concluded a downward adjustment is needed and one-time test is not adequate to conclude renal impairment but several regular tests are required.
Age Distribution ; Creatinine* ; Female ; Glomerular Filtration Rate ; Humans ; Kidney Failure, Chronic ; Korea ; Male ; Mass Screening ; Reference Values* ; Seoul

A high intake of licorice can cause hypermineralocorticoidism with sodium retention and potassium loss, edema, increased blood pressure and depression of renin-angiotensin-aldosterone system. Glycyrrhizic acid, a component of licorice, produces hypermineralocorticoidism through the inhibition of 11beta-hydroxysteroid dehydrogenase. We report a 55-year-old woman with severe muscle weakness with hypokalemia(Serum K+ : 1.7 mEq/ L) due to raw licorice tea. She boiled the licorice 50 g in water and drunk intermittently for 4 months due to her foreign body sensation on her throat. In Korea there is a traditional recipe that licorice works out for the above symptom. Her serum renin activity and aldosterone level were far beyond normal range which was typical to licorice ingestion. She also had metabolic alkalosis with pH 7.55 and hypertension. After quitting the licorice, hypokalemia and muscle weakness gradually improved and her blood pressure returned to normal.
11-beta-Hydroxysteroid Dehydrogenases ; Aldosterone ; Alkalosis ; Blood Pressure ; Depression ; Eating ; Edema ; Female ; Foreign Bodies ; Glycyrrhiza* ; Glycyrrhizic Acid ; Humans ; Hydrogen-Ion Concentration ; Hypertension ; Hypokalemia* ; Korea ; Middle Aged ; Muscle Weakness ; Pharynx ; Potassium ; Reference Values ; Renin ; Renin-Angiotensin System ; Sensation ; Sodium ; Tea ; Water

PURPOSE: Disturbances of mineral metabolism are common during the course of chronic kidney disease (CKD) and may lead to serious and debilitating complications unless properly treated. The purpose of this study is to quantify the prevalence of secondary hyperparathyroidism and vitamin D deficiency in non-dialysed chronic kidney disease 3, 4, and 5 in Korea. METHODS: This study included patients who had documented eGFR<60 mL/min/1.73m2 and non-dialysed and had not received any vitamin D compounds. eGFR was calculated by simplified MDRD (Modification of Diet in Renal Disease study) equation. Blood samples were collected for serum creatinine, calcium, phosphate, intact PTH and vitamin D metabolites between May 2006 and April 2007. RESULTS: According to K/DOQI guideline, the prevalence of hyperparathyroidism was 46.9% (15/32) in stage 3 (iPTH>70 pg/mL),45.9% (17/37) in stage 4 (iPTH>110 pg/mL) and 20.5% (9/44) in stage 5 patients (iPTH>300 pg/mL). The prevalence of 25-hydroxyvitamin D deficiency (25(OH)D3<15 ng/mL) was 86.2% (25/29) in stage 3, 75.7% (28/37) in stage 4 and 88.4% (38/43) in stage 5. There was a negative correlation between eGFR and intact PTH (r=-0.531, p=0.000) and a positive correlation between eGFR and 1,25-dihydroxyvitamin D (r=0.587, p=0.000). Conclusions: So far as non-dialysed CKD patients in Korea are concerned, quantification of the prevalence of abnormality of intact PTH and vitamin D deficiency has been described in this study. More research should be conducted in the future in a prospective, multi-center community cohort study, of which subjects include the early stages like CKD 1 and 2.
Calcium ; Cohort Studies ; Creatinine ; Diet ; Glomerular Filtration Rate ; Humans ; Hyperparathyroidism ; Hyperparathyroidism, Secondary ; Kidney Failure, Chronic ; Korea ; Parathyroid Hormone ; Prevalence ; Renal Insufficiency, Chronic ; Vitamin D ; Vitamin D Deficiency ; Vitamins

Objective: Insomnia is associated with elevated high-frequency electroencephalogram power in the waking state. Although affective symptoms (e.g., depression and anxiety) are commonly comorbid with insomnia, few reports distinguished objective sleep disturbance from affective symptoms. In this study, we investigated whether daytime electroencephalographic activity explains insomnia, even after controlling for the effects of affective symptoms. Methods: A total of 107 participants were divided into the insomnia disorder (n = 58) and healthy control (n = 49) groups using the Mini-International Neuropsychiatric Interview and diagnostic criteria for insomnia disorder. The participants underwent daytime resting-state electroencephalography sessions (64 channels, eye-closed). Results: The insomnia group showed higher levels of anxiety, depression, and insomnia than the healthy group, as well as increased beta [t(105) = −2.56, p = 0.012] and gamma [t(105) = −2.44, p = 0.016] spectra. Among all participants, insomnia symptoms positively correlated with the intensity of beta (r = 0.28, p ＜ 0.01) and gamma (r = 0.25, p ＜ 0.05) spectra. Through hierarchical multiple regression, the beta power showed the additional ability to predict insomnia symptoms beyond the effect of anxiety (ΔR2 = 0.041, p = 0.018). Conclusion Our results showed a significant relationship between beta electroencephalographic activity and insomnia symptoms, after adjusting for other clinical correlates, and serve as further evidence for the hyperarousal theory of insomnia. Moreover, resting-state quantitative electroencephalography may be a supplementary tool to assess insomnia.