With the introduction of the principle of automatic exposure control system,this paper discusses the relation between ionization chamber and photographic position,and analyzes its effect on X-ray image quality.

[ABSTRACT]AIM:Toinvestigatetheinteractionandthemechanismofsphingosine-1-phosphate(S1P)and phospholipid transfer protein (PLTP) in lipoprotein.METHODS:The S1P content in the plasma and lipoprotein from 10-week-old PLTP transgenic (PLTP-Tg) mice and wild-type (WT) mice (n=8 each) was assayed.The transport of S1P by PLTP was determined by S1P transfer assay.The content of specific S1P carrier, apolipoprotein M, was detected by West-ern blotting.RESULTS:Plasma S1P contents were decreased by 21.1%in PLTP-Tg mice compared with WT mice.S1P content in high-density lipoprotein ( HDL) fraction ( HDL-S1P) from PLTP-Tg mice was decreased by 35.1% compared with WT mice, whereas the S1P in low-density lipoprotein (LDL) fraction (LDL-S1P) was increased by 127.4%.The re-sults of S1P transfer assay indicated that PLTP facilitated S 1P transport from erythrocyte to recombinant liposome at 37℃in D-Hanks buffer solution .The plasma content of apolipoprotein M was not changed in PLTP-Tg mice compared with WT mice.CONCLUSION:PLTP is a key factor to maintain plasma HDL-S1P under physical condition .Overexpression of PLTP decreases the HDL-S1P but increases LDL-S1P.The mechanism might be related to the capability of PLTP on trans-ferring S1P from erythrocyte to lipoprotein.

Postoperative delirium (POD) is one of the common complications of central nervous system after operation. Severe POD can even develop into dementia, which seriously reduces the quality of life. Neuroinflammation and sleep disorder play important roles in the pathogenesis of POD. Dexmedetomidine (DEX) is a commonly used anesthetic in clinic, which is often used in the sedation of ICU patients and clinical anesthesia. DEX can reduce perioperative inflammatory response, improve patient's sleep, and reduce the incidence of POD. In this paper, the effects of DEX on neuroinflammation and sleep are discussed in order to provide evidence for clinical prevention and treatment of POD.

COVID-19 is the latest and most severe epidemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Besides the respiratory system, the effects of SARS-CoV-2 on central and peripheral nervous systems have been recognized by more and more people. Clinically, patients with COVID-19 have been reported from mild anosmia and hypoesthesia to acute necrotizing hemorrhagic encephalopathy and Guillain-Barre syndrome. In order to facilitate clinicians to recognize the nerve injury of COVID-19 patients and give timely treatment to these patients, this paper reviews the latest research progress on the possible pathways of nerve injury, clinical manifestations and pathogenesis of COVID-19 patients.