Mangiferin alleviates diabetic pulmonary fibrosis in mice via inhibiting endothelial-mesenchymal transition through AMPK/FoxO3/SIRT3 axis

Diabetes mellitus results in numerous complications. Diabetic pulmonary fibrosis (DPF), a late pulmonary complication of diabetes, has not attracted as much attention as diabetic nephropathy and cardiomyopathy. Mangiferin (MF) is a natural small molecular compound that exhibits a variety of pharmacological effects including anti-inflammatory, anti-cancer, anti-diabetes, and anti-fibrosis effects. In this study, we investigated whether long-term diabetes shock induces DPF, and explored whether MF had a protective effect against DPF. We first examined the lung tissues and sections of 20 diabetic patients obtained from discarded lung surgical resection specimens and found that pulmonary fibrosis mainly accumulated around the pulmonary vessels, accompanied by significantly enhanced endothelial-mesenchymal transition (EndMT). We established a mouse model of DPF by STZ injections. Ten days after the final STZ injection, the mice were administered MF (20, 60 mg/kg, i.g.) every 3 days for 4 weeks, and kept feeding until 16 weeks and euthanized. We showed that pulmonary fibrotic lesions were developed in the diabetic mice, which began around the pulmonary vessels, while MF administration did not affect long-term blood glucose levels, but dose-dependently alleviated diabetes-induced pulmonary fibrosis. In human umbilical vein endothelial cells (HUVECs), exposure to high glucose (33.3 mM) induced EndMT, which was dose-dependently inhibited by treatment with MF (10, 50 μM). Furthermore, MF treatment promoted SIRT3 expression in high glucose-exposed HUVECs by directly binding to AMPK to enhance the activity of FoxO3, which finally reversed diabetes-induced EndMT. We conclude that MF attenuates DPF by inhibiting EndMT through the AMPK/FoxO3/SIRT3 axis. MF could be a potential candidate for the early prevention and treatment of DPF.

[Analysis of the incidence and mortality of thyroid cancer in Shandong Province from 2012 to 2022 based on the age-period-cohort model]

Objective: To analyze the trend of incidence and mortality of thyroid cancer and estimate its age-period-cohort effect in Shandong Province from 2012 to 2022. Methods: The Joinpoint regression was used to analyze the trend of incidence and mortality of thyroid cancer and calculate the average annual percentage change (AAPC) based on the data on thyroid cancer from 2012 to 2022. The age-period-cohort model was used to analyze the age-effect, time-effect and cohort-effect of thyroid cancer risk in the population aged over 20 years. Results: From 2012 to 2022, the incidence of thyroid cancer in Shandong province showed a significant upward trend, with an AAPC of 21.68% (95%CI: 19.14%-24.27%, P<0.001). The incidence of females was higher than that of males, and the incidence of urban areas was higher than that of rural areas. The trend of thyroid cancer mortality was relatively stable with an AAPC of -3.04% (95%CI:-8.81%-3.09%, P=0.323). The age effect of incidence increased with age before 60 years old and decreased with age after 60 years old. The incidence peaked in the age group of 55-59. The period effect increased with time. The cohort effect showed that the cohort born before 1957 had a downward trend over time, while the cohort born after 1957 had an upward trend. Conclusion: The incidence of thyroid cancer in Shandong shows a rising trend from 2012 to 2022. Age is an important factor affecting the risk of thyroid cancer. The mortality of thyroid cancer remains stable.

Hydroxycitric Acid Alleviated Lung Ischemia-Reperfusion Injury by Inhibiting Oxidative Stress and Ferroptosis through the Hif-1α Pathway

Lung ischemia-reperfusion injury (LIRI) is a prevalent occurrence in various pulmonary diseases and surgical procedures, including lung resections and transplantation. LIRI can result in systemic hypoxemia and multi-organ failure. Hydroxycitric acid (HCA), the primary acid present in the peel of Garcinia cambogia, exhibits anti-inflammatory, antioxidant, and anticancer properties. However, the effects of HCA on LIRI remain unknown. To investigate the impact of HCA on LIRI in mice, the mice were randomly divided into four groups: the control group, the I/R model group, and the I/R + low- or high-dose HCA groups. Human umbilical vein endothelial cells (HUVECs) were subjected to hypoxia for 12 h followed by reoxygenation for 6 h to simulate in vitro LIRI. The results demonstrated that administration of HCA effectively attenuated lung injury, inflammation, and edema induced by ischemia reperfusion. Moreover, HCA treatment significantly reduced malondialdehyde (MDA) and reactive oxygen species (ROS) levels while decreasing iron content and increasing superoxide dismutase (SOD) levels after ischemia-reperfusion insult. Mechanistically, HCA administration significantly inhibited Hif-1α and HO-1 upregulation both in vivo and in vitro. We found that HCA could also alleviate endothelial barrier damage in H/R-induced HUVECs in a concentration-dependent manner. In addition, overexpression of Hif-1α counteracted HCA-mediated inhibition of H/R-induced endothelial cell ferroptosis. In summary, these results indicate that HCA alleviated LIRI by inhibiting oxidative stress and ferroptosis through the Hif-1α pathway.

[Role of Dipeptidyl peptidase inhibitors in lung ischemia-reperfusion injury]

Lung ischemia-reperfusion injury (LIRI)is a common complication after lung transplantation and cardiopulmonary bypass. It is an important factor affecting the success rate of transplantation. Its specific pathogenesis has not yet been fully elucidated. It is very significant to find the targets and drugs for the prevention and treatment of LIRI in order to improving the utilization rate of "marginal donor lung" and the long-term survival rate of lung transplant patients. Dipeptidyl peptidase 4(DPP4) inhibitors are a class of oral hypoglycemic agents. Previous studies have shown that DPP4 inhibitors have a variety of pharmacological activities, including anti-inflammatory, anti-fibrotic, immunomodulatory and other extrapancreatic functions. Recent studies have shown that DPP4 inhibitors may alleviate LIRI through various mechanisms, including inhibiting inflammatory responses, reducing oxidative stress, regulating blood glucose levels, and activating autophagy. This article reviewed the clinical and preclinical applications and mechanisms of DPP4 inhibitors in LIRI.

[Intraseasonal variation of the association between cold temperature and mortality risk in Shandong Province]

Objective: To explore the intraseasonal variation in mortality risk from cold temperature exposure in Shandong Province. Methods: Mortality data in Shandong province from 2013 to 2018 were collected from the cause of death surveillance system of Shandong Center for Disease Control and Prevention. The basic information mainly included the date of death, age, gender, education level, cause of death, home address, etc. The daily meteorological data from China Meteorological Data Network mainly included the grid coordinate data of 0.01°×0.01° latitude and longitude, such as daily average temperature (℃) and daily average relative humidity (%). The cold season was from November to February. The first two months were the early cold season and the last two months were the late cold season. The extreme cold temperature was defined as the 10^th percentile of the temperature range of cold season. Time-stratified case crossover design with distributed lag non-linear model analyzed the association between temperature and mortality and the association between extreme low temperature and mortality in different lag days in the cold season, and compared the intraseasonal differences between early (November-December) and late (January-February) cold season. Results: The temperature ranged from -17.3 ℃ to 18.6 ℃ in Shandong Province during the cold season from 2013 to 2018, and the P₁₀ (extreme low temperature) was -13.7 ℃. The average daily temperature in the early cold season was (3.63±4.66) ℃. The temperature in the late cold season was (-0.09±3.70) ℃. The average daily relative humidity was (63.89±14.75) % in the early cold season and (62.27±14.19) % in the late cold season. This study included 1 473 300 deaths in the cold season in Shandong Province between 2013 and 2018. There were 824 601 (55.97%) males and 349 824 (23.75%) cases aged<65 years. There were 803 691 (54.55%) deaths due to circulatory diseases and 140 415 (9.53%) deaths due to respiratory diseases. The results of DLNM showed that the cumulative OR of extreme low temperature in the four months of cold season was 1.74 (95%CI: 1.63, 1.86) with the optimal temperature of 18.6 ℃ as the reference. The cumulative OR values of early and late cold season were 1.50 (95%CI: 1.32, 1.71) and 2.56 (95%CI: 2.12, 3.09), respectively (P<0.001). The lag effect lasted for 12 d. Conclusion: There is an intraseasonal variation of the association between cold temperature and mortality risk in Shandong Province. The mortality risk related to cold temperature in the late cold season is higher than that in the early cold season.

[Mortality level and tendency of road traffic injury in Shandong Province from 2012 to 2020]

Objective: To analyze the mortality level and tendency of road traffic injury in Shandong province from 2012 to 2020. Methods: Based on the data of road traffic deaths from the cause of death registration system in Shandong province from 2012 to 2020, the mortality rates of road traffic injury were calculated by sex, age, area, and injury type. The mortality was standardized based on the age structure of the Chinese population in the sixth Population Census in 2010. The annual percent change (APC) and average annual percent change (AAPC) of the mortalities and the standarized mortalities were calculated by using Joinpoint regression model, and the trends were also examined. Results: In 2020, the crude mortality of road traffic injury in Shandong Province was 15.58/100 000, and the standardized mortality was 12.90/100 000. From 2012 to 2020, the standardized mortality of road traffic injury in Shandong province showed a downward trend with AAPC of -5.4%. The standardized mortality of middle-south mountain areas, male and children aged 0-14 years in Shandong showed a significantly decreasing trend with AAPC of -6.8%, -6.1% and -6.0%, respectively. The standardized mortality of people aged 65 years and over did not decrease significantly, but the number of deaths increased significantly by 50.96% in 2020 (5 780 cases), compared with those in 2012 (3 829 cases). The standardized mortality of pedestrian and motorcyclists decreased significantly with AAPC of -7.5% and -6.7%, respectively. There was no significant change in the standardized mortality among people who rode motor vehicles or bicycles. Conclusion: From 2012 to 2020, the standardized mortality of road traffic injury in Shandong Province showed an obvious downward trend, but the standardized mortality of people aged 65 years and over did not decrease significantly. In the future, it is still necessary to take government-led, multi-sectoral collaboration, with a focus on comprehensive preventive measures, to further reduce road traffic injury mortality.

[Cancer survival during 2012-2018 in cancer registries of Shandong Province]

Objective: To analyze the 5-year cancer relative survival rate in cancer registries of Shandong Province during 2012-2018. Methods: 399 072 new cancer cases were collected in 23 cancer registries in Shandong Province during 2012-2018. All malignant tumors (C00-C97, D45-D47), benign central nervous system tumors (D32-D33), and central nervous system tumors (D42-D43) were registered according to the 10th revision of international classification of diseases (ICD). The survival of cancer patients was obtained by passive and active follow-up. The follow-up date was December 31, 2020. The diagnostic years were divided into three periods: 2012-2014, 2015-2017 and 2018-2020. The 5-year cancer survival rates were calculated by cohort approach, period analysis and hybrid approach, and the survival status of different sex, urban and rural areas, cancer species and age groups were analyzed. Results: The age of 399 072 new cancer cases was (63.5±13.7) years old, with 57.77% (230 538 cases) about male and 32.89% (131 247 cases) from urban. During 2012-2014, 2015-2017 and 2018-2020, the 5-year cancer survival rates in Shandong Province were 32.3%, 34.7% and 40.2%, respectively. In 2018-2020, the first five cancers with survival rates were thyroid cancer (86.0%), breast cancer (78.2%), testicular cancer (75.7%), bladder cancer (70.3%) and uterine cancer (69.2%), and the last five cancers with survival rates were pancreatic cancer (15.5%), liver cancer (16.8%), gallbladder cancer (19.6%), bone cancer (22.7%) and lung cancer (24.4%). The 5-year survival rate for cancer of women (47.8%) was higher than that of men (33.8%), and the rate of urban areas (45.7%) was higher than that of rural areas (37.3%) during 2018-2020. The first five cancers in men were thyroid (87.1%), testicular (75.7%), bladder (70.9%), kidney (65.6%) and prostate (62.8%) cancers, and the last five cancers were pancreatic (14.3%), liver (16.8%), gallbladder (18.2%), bone (19.9%) and lung (21.7%) cancers. The first five cancers in women were thyroid (85.5%), breast (78.0%), uterine (69.2%), bladder (68.8%) and kidney (66.8%) cancers, and the last five cancers were liver (17.2%), pancreatic (17.2%), gallbladder (22.0%), bone (27.2%) and lung (29.1%) cancers. Conclusion: The 5-year cancer survival rate in Shandong Province was on the rise from 2012 to 2018, and the survival rates of different cancers were different.

[Spatio-temporal trend of female breast cancer mortality in Shandong Province from 1970 to 2013]

The mortality of female breast cancer in Shandong Province has increased since the 1970. The differential decomposition analysis found that the slight decline in the crude mortality of breast cancer among women was entirely due to non-demographic factors during the 1970-1990, and the significant increase in the crude mortality was due to a combination of demographic and non-demographic factors since the 1990. The contribution rate of demographic factor has gradually increased from 53.5% in 2004-2005 to 59.5% in 2011-2013, while that of non-demographic factor has decreased from 46.5% to 40.5%. The women aged 45-64 years old were the major population of female breast cancer deaths, accounting for 40%-60% of total breast cancer deaths in different times, and then the mortality in female aged 55-64 years old increased rapidly, with increases of 52.12%, 115.19% and 29.01% in 2011-2013 over the 1970-1974, 1990-1992 and 2004-2005, respectively (Z=-7.342,P<0.001). Compared with 1970-1974, the age-standardized mortality rate of rural women increased by 41.86% in 2011-2013 (Z=-17.933, P<0.001), and that of urban women increased by 18.62% in 2011-2013 (Z=-25.642, P<0.001). The age-standardized mortality rate of breast cancer in urban women was higher than that in rural women in different times (all P<0.05). The spatial scan analysis found that eastern Shandong Province was found to be a sustained high-risk area for death, and other high-risk areas were transferred from north to southwest of Shandong between 1970 and 2013.

[Spatial clustering analysis and trend of liver cancer death rate in Shandong province, 1970-2013]

Objective: To explore the spatial clustering and trend of liver cancer mortality in different counties of Shandong province from 1970 to 2013, and provide scientific basis for the development of liver cancer prevention and control plan. Methods: Cancer mortality data were obtained from Shandong Death Registration System and three national death cause surveys in China. Mortality rate and age adjusted mortality rate were used to describe the trend of liver cancer in different years. Difference decomposing method was applied to estimate the contribution of demographic and non-demographic factors to the change of mortality. Software ArcGIS 10.2 was used for spatial analysis, and software SaTScan 9.4 was used for spatial clustering analysis on liver cancer mortality. Results: From 2011 to 2013, the crude mortality rate of liver cancer (29.89/100 000) in Shandong increased by 208.00% and 35.37% respectively compared with that during 1970-1974 (9.72/100 000) and 1990-1992 (22.08/100 000) and was similar to that during 2004-2005 (30.44/100 000). While age standardized mortality rate (ASMR) increased first and then decreased. The ASMR during 2011-2013 (12.62/100 000) increased by 60.97% compared with that during 1970-1974 and decreased by 22.38% and 21.81% compared with that during 1990-1992 and 2004-2005, respectively. According to the difference decomposition analysis on liver cancer mortality in different years, the contribution of population factors to the liver cancer mortality rate increased from 3.38% during 1990-1992 to 29.36% during 2004-2005 and 46.16% during 2011-2013. However, the contribution of non-population factors to the increase of liver cancer mortality decreased. According to the spatial distribution of liver cancer mortality, the crude mortality rate of liver cancer in different counties were quite different, ranging from 9.33/100 000 to 65.33/100 000. Using the spatial scanning statistical software to analyze the spatial clustering of liver cancer mortality, multi areas with high mortality rate of liver cancer were found, and they were mainly distributed in Jiaodong peninsula from 2011 to 2013, covering 20 counties (cities, districts) in Qingdao, Yantai and Weihai. The risk of liver cancer mortality in this area was 1.54 times higher than that in other areas. The spatial clustering distribution of liver cancer mortality during 1970-1974 was significantly different from that during 2011-2013, the areas with high mortality rate during 1970-1974 were mainly distributed in central and western Shandong. Conclusions: There were significant temporal and spatial distribution changes in the mortality rate of liver cancer in Shandong from 1970 to 2013. According to these trends and their geographical and spatial distribution, we should further explore the risk factors of liver cancer, and formulate feasible and area specific prevention and control measures for liver cancer.

CircC3P1 attenuated pro-inflammatory cytokine production and cell apoptosis in acute lung injury induced by sepsis through modulating miR-21

Acute lung injury (ALI) induced by sepsis is characterized by an inflammatory process related to the up‐regulation of inflammatory cytokines and chemokines. In the present study, we explored the role of circC3P1 in sepsis‐induced ALI in vitro and in vivo. The caecal ligation and puncture (CLP)‐induced sepsis model was established through CLP surgery. Forty adult male C57BL/6 mice were randomly assigned into sham, CLP, CLP + vector and CLP + circC3P1 (each n = 10). Primary murine pulmonary microvascular endothelial cells (MPVECs) were transfected with circC3P1 or empty vector 24 hours prior to LPS treatment via Lipofectamine 2000. The expressions of circC3P1, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6) and IL‐1β were evaluated after 6‐h LPS treatment. Cell apoptosis was evaluated via flow cytometry. The CLP group demonstrated pulmonary morphological abnormalities, increased concentrations of TNF‐α, IL‐6 and IL‐1β in the lung tissue, compared with the sham group. MPVECs treated with LPS significantly elevated TNF‐α, IL‐6 and IL‐1β levels and increased cell apoptosis than that in the control group. The circC3P1 overexpression in sepsis‐induced ALI mice attenuated pulmonary injury, inflammation and apoptosis. Besides, circC3P1 revealed anti‐inflammatory and anti‐apoptotic effect in MPVEC‐treated LPS. CircC3P1 overexpression reduced cell apoptosis and pro‐inflammatory cytokines levels via down‐regulating miR‐21. CircC3P1 attenuated pro‐inflammatory cytokine production and cell apoptosis in ALI induced by sepsis through modulating miR‐21, indicating that circC3P1 is a promising therapeutic biomarker for sepsis‐induced ALI.

[Etiology and clinical features of primary adrenal insufficiency]

Objective: To summarize the etiology of primary adrenal insufficiency (PAI) and analyze its clinical features. Methods: A retrospective analysis was performed in the Department of Endocrinology, Peking Union Medical College Hospital from October 1981 to June 2019. Patients with PAI as the first symptom were enrolled. The etiology of PAI was analyzed and the clinical characteristics was also summarized. Results: A total of 131 patients with PAI were enrolled, including 87 males and 44 females (57 adolescents, and 74 adults). The age ranged from 0 to 73 years. The primary cause of PAI in adolescents was genetic defects (52.6%, 30/57), in which congenital adrenal dysplasia caused by DAX1 gene deficiency accounted for 50.0% (15/30), followed by autoimmunity (22.8%, 13/57). The primary cause of adult PAI was infection (58.1%, 43/74), of which tuberculosis accounted for the majority (93.0%, 40/43), and autoimmune adrenalitis accounted for 19.0% (14/74). Compared with the tuberculosis group, female patients were more common, and the onset age was younger, the plasma cortisol, serum sodium, fasting blood glucose, creatinine and aldosterone were lower (all P<0.05), and serum potassium and renin levels were higher in the autoimmune adrenalitis group (both P<0.05). Conclusions: In the current study, the proportion of PAI caused by infection in the adult group was higher than that in the adolescent group. The most common cause of adult PAI was tuberculosis infection. The most common cause of childhood PAI was genetic defects. Autoimmune damage to the adrenal glands may be more severe than tuberculosis infection.

[Trend of mortality and decomposition on malignant tumors in Shandong province, 1970-2013]

Objective: To describe the mortality trend of major malignant tumors in Shandong province, from 1970 to 2013. Methods: Data related to cancer mortality were obtained from the Shandong Death Registration System and three nationwide retrospective cause-of-death surveys. Trends of overall mortality and major causes of death were described using the indicators as: mortality rates and age-standardized mortality rates, through comparing the three large-scale mortality surveys in Shandong province. Difference decomposing method was applied to estimate the contribution of demographic and non-demographic factors for the change of mortality. Results: From 1970 to 2013, the crude mortality rate of malignant tumors in Shandong was increasing. The age standard mortality rate was increasing and then decreasing. The composition of cancer deaths in the all-cause-deaths was seen increasing and then decreasing as well. Both demographic and non-demographic factors contributed to the increase of crude cancer mortality rate. With the gradual increase of the proportion of population, its role exceeded the non-demographic factors. The age-standardized mortality rate of malignant tumors in 2011-2013 was lower than that in 2004-2005. Lung cancer mortality rose from the fifth to the first place, with an increase of 6.81 times from 1970-1974 to 2011-2013. Ranking of gastric cancer mortality dropped from first to the third place, with esophageal cancer dropped from second to the fourth. After adjusted by China's standard population in 1964, the mortality rate of lung cancer was still rapidly increasing, but the age-standardized mortality rates of esophageal cancer was gradually decreasing. The crude and age-standardized mortality rates of cervical cancer showed a rapid downward trend, reduced 87.00% and 93.00% respectively from 1970-1974 to 2011-2013. Conclusions: Malignant tumors were still major threats to the residents of Shandong province. The changing trend of different malignant tumors presented an inconsistent nature which called for different intervention strategies be carried out, accordingly.

[Analysis of mortality and probability of premature death caused by four main non-communicable diseases in Shandong Province, 2015]

Based on the data from Shandong Province death registration system in 2015, the mortality rate was adjusted by the results of underreporting rate investigation, and the probability of premature death of non-communicable diseases was calculated by life table method. A total of 728 287 deaths caused by four main non-communicable diseases (NCDs) including cardiovascular and cerebrovascular diseases, malignant tumor, diabetes, and chronic respiratory disease, accounting for 85.83% of the total death in 2015. The death of cardiovascular and cerebrovascular diseases and malignant tumor accounted for 50.90% and 25.69% respectively. The probability of premature death was 17.84%. The probability in males was higher than that in females (23.12% vs 12.25%). The highest probability of premature death in urban was cancer, but in rural was cardiovascular and cerebrovascular diseases. The probability increased from the East areas to the West. The highest probability reached at 21.50% in the Western underdeveloped areas, and the lowest probability was in Dongying City (14.84%) and Weihai City (14.94%) in the coastal areas.

[Diagnostic value of protein markers in plasma exosomes of lung squamous cell carcinoma]

Objective: To investigate the tumor-associated protein molecules carried by plasma exosomes of patients with lung squamous cell carcinoma before treatment and analyze their value as clinical markers. Methods: Exosomes from 2 patients with lung squamous cell carcinoma before treatment and 2 healthy controls were collected by ultracentrifugation. Proteomics was applied to analyze the protein expression profiles of exosomes. Candidate molecules were verified in another 30 exosomes samples from lung squamous cell carcinoma and healthy controls using enzyme-linked immunosorbent assay (ELISA). Results: Electron microscopy and particle-counting assay showed that high-quality exosomes were collected. The number of exosomes distributed from 45 to 135 nm in 2 cases of lung cancer patients were 7.89×10(11)/ml and 9.71×10(11)/ml, respectively, significantly higher than 2.76×10(11)/ml and 1.41×10(11)/ml in healthy controls. Proteomic analysis showed that proteins of exosomes in lung squamous cell carcinoma patients were very different from those of healthy controls, and some proteins are related to important functions in tumor progression. 14-3-3ζ from exosomes was selected and further verified as a marker, and the area under the receiver operating characteristic curve (ROC) was 0.68. The sensitivity and specificity of 14-3-3 ζ from exosomes were 60.0% and 80.0%, respectively, suggested that it could be used as a diagnostic marker for lung squamous cell carcinoma. Conclusion: The exosome counts in plasma and the protein molecules from exosomes, such as 14-3-3ζ, are closely related to the tumorigenesis, which can be used to assist clinical diagnosis of lung squamous cell carcinoma patients.

[Prevalence, awareness, treatment and control of hypertension in adults in Shandong province, 2013]

Objective: To understand the prevalence, awareness, treatment and control of hypertension in adults in Shandong province in 2013. Methods: Adults aged ≥18 were selected through multistage clustering sampling in 19 counties and districts in Shandong province. Design-based methods were adopted to analyze the prevalence, awareness, treatment and control of hypertension among local residents. Results: A total of 11 270 adults aged 18-69 years were surveyed, the prevalence of hypertension was 27.9% (31.4% in males, 24.3% in females) in Shandong province. The awareness rate of hypertension was 37.4% (34.7% in males, 41.0% in females), and the treatment rate of hypertension was 26.6% (23.4% in males, 30.7% in females). The treatment control rate of hypertension was 26.7% (28.3% in males, 25.1% in females) and the control rate of hypertension was 7.1% (6.6% in males, 7.7% in females). Conclusions: The prevalence of hypertension was high, but the awareness rate of hypertension, the treatment rate and the control rate of hypertension were low in adults in Shandong province. It is necessary to strengthen the health education about hypertension in young population, the prevention and control of hypertension in old population and those with low education level, the standardized management of hypertension cases and the reduction of risk factors for hypertension.

[The localization diagnosis of patients with adrenocorticotropic hormone-dependent Cushing's syndrome in adolescence]

Objective: To elucidate the clinical characteristics and localization diagnosis of patients with adrenocorticotropic hormone (ACTH)-dependent Cushing's syndrome (CS) in adolescence. Methods: The clinical data, laboratory examination and localization diagnosis from 35 patients aged less than 18 years old with adolescent CS who were treated at Peking Union Medical College Hospital between January 1990 and March 2012 were analyzed. Results: There were 29 cases of Cushing's disease (CD) and 6 cases of ectopic ACTH syndrome (EAS). Compared to patients with EAS, those with CD were older at diagnosis[(15.2±2.7) vs (12.8±4.4) years], and had longer disease course[(1.9±1.5) vs (0.7±0.3) years]and higher serum potassium[(3.8±0.6) vs (2.5±0.7) mmol/L], however the plasma ACTH level[(15.4±14.9) vs (42.5±22.7) pmol/L]was lower (all P<0.05). If the cut-off of the ratio of 24-hour urine free cortisol (24 h UFC) after low-dose dexamethasone suppression test (LDDST) to before LDDST was 0.65, the sensibility to diagnose CD was 70.8%, and the specificity was 100%. If the cut-off of the 24 h UFC ratio after high-dose dexamethasone suppression test (HDDST) to before HDDST was 0.54, the sensibility to diagnose CD was 91.7%, and the specificity was 100%. If the cut-off of the plasma ACTH ratio of inferior petrosal vein[bilateral inferior petrosal sinus sampling (BIPSS)]to peripheral vein was 2, only 6 CD patients (6/8) met it. Conclusion: The study suggested that HDDST was more meaningful in the localization diagnosis of patients with ACTH-dependent CS in adolescence.

[Comparison of efficacy between the serum cortisol and 24 hour urine free cortisol in combined dexamethasone suppression test in the diagnosis of Cushing syndrome]

OBJECTIVE

To compare the sensitivity and specificity between the 24 hour urine free cortisol (24 h UFC) and serum cortisol in dexamethasone suppression test (DST) in the diagnosis of Cushing syndrome (CS).

METHODS

Combined low dose DST (LDDST) and high dose DST (HDDST) were carried out in 67 cases of CS with surgically confirmed cases in recent 3 years(from January 2011 to November 2015). The serum cortisol and 24 h UFC were collected simultaneously for each subject and the sensitivity and specificity of serum cortisol and 24 h UFC were compared.

RESULTS

There were Cushing disease (CD) group (n=53), ectopic adrenocorticotropic hormone (ACTH) syndrome group (n=7) and ACTH-independent Cushing syndrome group (n=7) according to the etiology of hypercorticordism.There were no significant differences among 3 groups in gender and age.The sensitivity of serum cortisol of different cut off points(50, 110, 140 nmol/L and 50% of control)after LDDST was 97.01%, 86.57%, 83.58% and 70.15% respectively.Meanwhile, the sensitivity of cutoff point of 24 h UFC <32 nmol in combined LDDST was 92.54% in the diagnosis of Cushing syndrome.There was no significant differences in two groups between serum cortisol <110 nmol/L and 24 h UFC <32 nmol.However, the sensitivity of serum cortisol <50 nmol/L was significantly higher than 24 h UFC<32 nmol (P<0.05). Furthermore, in combined HDDST, if the suppression rate was ≥50%, the sensitivity of serum cortisol and 24 h UFC in differentiating the etiology of Cushing disease was 60.38% and 90.57%, and the specificity was 91.43% and 96.00% respectively.There were significant differences between serum cortisol and 24 h UFC in both of sensitivity and specificity (both P<0.05). In addition, if the suppression rate of 24 h UFC in HDDST was adjusted to 60.85% according to receiver operating characteristic (ROC) curve, it could have the best levels of sensitivity (92.6%) with the specificity of 85.7%. If the suppression rate of serum cortisol was adjusted to 61.53% in HDDST according to ROC curve, it could have the best sensitivity (64.8%) with the specificity of 78.6% accordingly.

CONCLUSION

In combined LDDST, the serum cortisol <50 nmol/L had a higher sensitivity than the 24 h UFC<32 nmol when they were used as the criteria in determining the diagnosis of CS.In HDDST, the sensitivity and specificity of suppression rate of 24 h UFC ≥50% were better than serum cortisol to differentiate the etiology of CS.

Prevalence of overweight and obesity and their associations with blood pressure among children and adolescents in Shandong, China

BACKGROUND

Obesity and high blood pressure (BP) are public health problems all over the world. Some studies have reported a positive association between them in children and adolescents. The purpose of this study was to assess the prevalence of overweight and obesity and their associations with BP among school children and adolescents in Shandong, an important province in eastern China.

METHODS

In 2011, we conducted a cross-sectional population-representative survey in Shandong, China. A total of 4 898 children and adolescents aged 6-17 years were randomly selected from 140 counties/districts using a multistage random cluster sampling. Weight, height and BP were measured by a trained physician or pediatrician, and information about age, gender and place of residence was obtained using questionnaires. Obesity and high BP were defined according to age- and gender-specific Chinese reference data for children.

RESULTS

A total of 4 898 (100%) children and adolescents provided complete information. The prevalence of overweight, obesity and overweight plus obesity were 10.9%, 8.7% and 19.6%, respectively. Boys were more likely to be overweight or obese than girls (P < 0.05 for overweight; P < 0.001 for obesity). The prevalence of overweight plus obesity was highest among children aged 6-11 years (22.3%). BP and the prevalence of high BP increased with increasing body mass index (BMI). With age and sex adjusted, odds ratios (ORs) for high BP were [OR 2.2;95% CI 1.7-2.8) in overweight and [OR 3.6;95% CI 2.6-4.9] in obese children.

CONCLUSION

The representative survey confirms high prevalence of overweight and obesity among children and adolescents in Shandong. Childhood obesity is a strong risk factor for high BP. Intervention programs should be implemented to combat the growing obesity epidemic.

The microstructure and electrochemical characteristics of LiFePO4/carbon-network composite

LiFePO4/carbon-network composite was synthesized by a high temperature solid-state method using the natural sawdust as carbon precursor. The microstructure of the as-synthesized sample was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), respectively. The results revealed that the LiFePO4 particles with diameters ranging from 30 to 150 nm were well connected by carbon networks. The electrochemical performance of the composite was characterized using galvanostatic charge-discharge technique. The initial discharge capacity of LiFePO4/carbon-network cathode reached 126 mAh x g(-1) with 0.2 C rate.

Coronary heart disease in China

Coronary heart disease (CHD) is the second leading cause of cardiovascular death in the Chinese population. It accounts for 22% of cardiovascular deaths in urban areas and 13% in rural areas. Although mortality from CHD in China is relatively low compared with Western levels, the burden of CHD has been increasing. This is partly because of a worsening profile of risk factors, such as an increased prevalence of hypertension, hyperlipidaemia, overweight/obesity, diabetes, etc and partly because of an increase in the aged population. Large-scale, randomised controlled trials on thrombolytic, blood-pressure-lowering, antiplatelet and blood-cholesterol-lowering treatment as well as cardiac intervention have been conducted for Chinese patients with myocardial infarction. The studies provide important information for the prevention and management of chronic CHD and acute myocardial infarction in the Chinese population.

Full-wave and half-wave processes in second-order motion and texture

A theory of human second-order motion perception is proposed and further applied to the discrimination of texture slant. The computational algorithms for deriving the direction of left-right motion from a sequence of images are equivalent to the algorithms for deriving the direction of slant (e.g. from top left to bottom right or top right to bottom left) in a single 2D image. There is a broad range of phenomena for which Fourier analysis of the image plus a few simple rules gives a good account of human perception. The problem with this first-order analysis is that there exists a broad class of 'microbalanced' stimuli in which the motion or slant is completely obvious to human subjects but is invisible to first-order analysis. Microbalanced stimuli require second-order analysis which consists of non-linear preprocessing (spatiotemporal filtering followed by rectification of the input signal) before standard motion or slant analysis. To determine whether the second-order rectification is half-wave or full-wave, we construct two special microbalanced stimulus types: 'half-wave stimuli' whose motion (or texture slant) is interpretable by a half-wave rectifying system but not by full-wave or a first-order (Fourier) analysis and 'full-wave stimuli' which are interpretable only after full-wave rectification. Such experiments show that second-order texture-slant perception utilizes both half-wave and full-wave processes, second-order motion-direction discrimination depends predominantly on full-wave rectification and second-order spatial interactions such as lateral contrast-contrast inhibition and second-order Mach bands are exclusively full-wave.

Large Low-Field Magnetoresistance in Nanocrystalline Magnetite Prepared by Sol−Gel Method

Nanocrystalline magnetite Fe3O4 samples with a grain size of about 40 nm have been synthesized by an optimized sol-gel method. The single phase of spinel magnetite was confirmed by both X-ray diffraction and transmission electron microscopy. It has been found that the magnetoresistance of the samples at low field (LFMR) is relatively large, and with the decrease of temperature its value at a field of 0.5 T changes dramatically from -2.5% at 300 K to -17.0% at 55 K. With the further decrease of temperature a sharp drop occurs for the magnitude of the magnetoresistance (MR), regarded as a spin (cluster) glass transition in the surface region of the grains that can be confirmed by the zero-field-cooled and field-cooled magnetization and ac susceptibility measurement. The mechanism of the magnetic and transport properties was discussed.

[Combination effects of vitamin A and zinc on human's PMBC DNA damage in vitro]

OBJECTIVE

To study the combination effects of vitamin A (Vit. A) and zinc on human's PBMC DNA damage in vitro. Methods The PBMC from healthy volunteer was purification and cultured in the basic culture medium with Vit.A of 10(-4), 10(-5) and 10(-6) mol/L, or/and with Zn of 10(-6), 10(-5) 10(-4) and 10(-3) mol/L. The basic culture medium with K2Cr2O7 of 1 mmol/L was the male control. The damage of PBMC DNA was respectively examined by SCGE and the image analyzer measured the comet tail rate and length. The apoptosis of each group PBMC was detected by FCM.

RESULTS

The overdose supplement of zinc and Vit. A can damage the PBMC DNA in vitro culture (P < 0.01), while the suitable supplement doesn't find. When the Vit. A supplement has been excessive, giving suitable zinc could repair the damage of DNA, but would expand the injured cell. While when the zinc supplement has been excessive, giving suitable Vit. A could protect the healthy cells, but would aggravate the damage degree of injured cell.

CONCLUSION

In vitro culture, the overdose Vit. A and zinc supplement could damage the human's PBMC DNA significantly. This need more researches to provide.

Scanning mutagenesis studies of the M1 muscarinic acetylcholine receptor

Following the solution of the structure of bovine rhodopsin by X-ray crystallography, it has been possible to build an improved homology model of the M(1) muscarinic acetylcholine receptor. This has been used to interpret the outcome of an extensive series of scanning and point mutagenesis studies on the transmembrane domain of the receptor. Potential intramolecular interactions enhancing the stability of the protein fold have been identified. The residues contributing to the binding site for the antagonist, N-methylscopolamine, and the agonist, acetylcholine have been mapped. The positively charged headgroups of these ligands appear to bind in a charge-stabilized aromatic cage formed by amino acid side chains in transmembrane (TM) helices 3, 6, and 7, while residues in TM 4 may participate in a peripheral docking site. Closure of the cage around the headgroup of acetylcholine may help to transduce binding energy into receptor activation, possibly disrupting a set of Van der Waals interactions between a set of residues underlying the binding site which help to constrain the receptor to the inactive state, in the absence of agonist. This may trigger the reorganization of a hydrogen bonding network between highly conserved residues in the core of the receptor, whose integrity is crucial for activation.

Scanning mutagenesis studies of the M1 muscarinic acetylcholine receptor

Following the solution of the structure of bovine rhodopsin by X-ray crystallography, it has been possible to build an improved homology model of the M(1) muscarinic acetylcholine receptor. This has been used to interpret the outcome of an extensive series of scanning and point mutagenesis studies on the transmembrane domain of the receptor. Potential intramolecular interactions enhancing the stability of the protein fold have been identified. The residues contributing to the binding site for the antagonist, N-methylscopolamine, and the agonist, acetylcholine have been mapped. The positively charged headgroups of these ligands appear to bind in a charge-stabilized aromatic cage formed by amino acid side chains in transmembrane (TM) helices 3, 6, and 7, while residues in TM 4 may participate in a peripheral docking site. Closure of the cage around the headgroup of acetylcholine may help to transduce binding energy into receptor activation, possibly disrupting a set of Van der Waals interactions between a set of residues underlying the binding site which help to constrain the receptor to the inactive state, in the absence of agonist. This may trigger the reorganization of a hydrogen bonding network between highly conserved residues in the core of the receptor, whose integrity is crucial for activation.

Structure and activation of muscarinic acetylcholine receptors

A homology model of the M(1) muscarinic acetylcholine receptor, based on the X-ray structure of bovine rhodopsin, has been used to interpret the results of scanning and point mutagenesis studies on the receptor's transmembrane (TM) domain. Potential intramolecular interactions that are important for the stability of the protein fold have been identified. The residues contributing to the binding site for the antagonist, N -methyl scopolamine, and the agonist, acetylcholine, have been mapped. The positively charged headgroups of these ligands probably bind in a charge-stabilized aromatic cage formed by amino acid side chains in TM helices TM3, TM6 and TM7, while residues in TM4 may participate as part of a peripheral docking site. Closure of the cage around the headgroup of acetylcholine may be part of the mechanism for transducing binding energy into receptor activation, probably by disrupting a set of Van der Waals interactions between residues lying beneath the binding site that help to constrain the receptor to the inactive state, in the absence of agonist. This may trigger the reorganization of a hydrogen-bonding network between highly conserved residues in the core of the receptor, whose integrity is crucial for achievement of the activated state.

Transmembrane domains 4 and 7 of the M(1) muscarinic acetylcholine receptor are critical for ligand binding and the receptor activation switch

Activation of the muscarinic acetylcholine receptors requires agonist binding followed by a conformational change, but the ligand binding and conformation-switching residues have not been completely identified. Systematic alanine-scanning mutagenesis has been used to assess residues 142-164 in transmembrane helix 4 and 402-421 in transmembrane helix 7 of the M(1) muscarinic acetylcholine receptor. Several inward-facing amino acid side chains in the exofacial parts of transmembrane helices 4 and 7 contribute to acetylcholine binding. Alanine substitution of the aromatic residues in this group reduced signaling efficacy, suggesting that they may form part of a charge-stabilized aromatic cage, which triggers rotation and movement of the transmembrane helices. The mutation of adjacent residues modulated receptor activation, either reducing signaling or causing constitutive activation. In the buried endofacial section of transmembrane helix 7, alanine substitution mutants of the conserved NSXXNPXXY motif displayed strongly reduced signaling efficacy, despite having increased or unchanged acetylcholine affinity. These residues may have dual functions, forming intramolecular contacts that stabilize the receptor in the inactive ground state, but that are broken, allowing them to form new intramolecular bonds in the activated state. This conformational rearrangement is critical to produce a G protein binding site and may represent a key mechanism of receptor activation.

Three-systems theory of human visual motion perception: review and update

Lu and Sperling [Vision Res. 35, 2697 (1995)] proposed that human visual motion perception is served by three separate motion systems: a first-order system that responds to moving luminance patterns, a second-order system that responds to moving modulations of feature types-stimuli in which the expected luminance is the same everywhere but an area of higher contrast or of flicker moves, and a third-order system that computes the motion of marked locations in a "salience map," that is, a neural representation of visual space in which the locations of important visual features ("figure") are marked and "ground" is unmarked. Subsequently, there have been some strongly confirmatory reports: different gain-control mechanisms for first- and second-order motion, selective impairment of first- versus second- and/or third-order motion by different brain injuries, and the classification of new third-order motions, e.g., isoluminant chromatic motion. Various procedures have successfully discriminated between second- and third-order motion (when first-order motion is excluded): dual tasks, second-order reversed phi, motion competition, and selective adaptation. Meanwhile, eight apparent contradictions to the three-systems theory have been proposed. A review and reanalysis here of the new evidence, pro and con, resolves the challenges and yields a more clearly defined and significantly strengthened theory.

Characterizing the spatial-frequency sensitivity of perceptual templates

Filtered external noise has been an important tool in characterizing the spatial-frequency sensitivity of perceptual templates. Typically, low-pass- and/or high-pass-filtered external noise is added to the signal stimulus. Thresholds, the signal energy necessary to maintain given criterion performance levels, are measured as functions of the spatial-frequency passband of the external noise. An observer model is postulated to segregate the impact of the external noise and the internal noise. The spatial-frequency sensitivity of the perceptual template is determined by the relative impact exerted by external noise in each frequency band. The perceptual template model (PTM) is a general observer model that provides an excellent account of human performance in white external noise [Vision Res. 38, 1183 (1998); J. Opt. Soc. Am. A 16, 764 (1999)]. We further develop the PTM for filtered external noise and apply it to derive the spatial-frequency sensitivity of perceptual templates.

Sensitive calibration and measurement procedures based on the amplification principle in motion perception

We compare two types of sampled motion stimuli: ordinary periodic displays with modulation amplitude m(o=e) that translate 90 degrees between successive frames and amplifier sandwich displays. In sandwich displays, even-numbered frames are of one type, odd-numbered frames are of the same or different type, and (1) both types have the same period, (2) translate in a consistent direction 90 degrees between frames, and (3) even frames have modulation amplitude m(e), odd frames have modulation amplitude m(o). In both first-order motion (van Santen, J.P.H. & Sperling, G. (1984). Temporal covariance model of human motion perception. Journal of the Optical Society of America A, 1, 451-73) and second-order motion (Werkhoven, P., Sperling, G., & Chubb, C. (1993). Motion perception between dissimilar gratings: a single channel theory. Vision Research, 33, 463-85) the motion strength of amplifier sandwich displays is proportional to the product m(o)m(e) for a wide range of m(e). By setting m(e) to a large value, an amplifier sandwich stimulus with a very small value of m(o) can still produce visible motion. The amplification factor is the ratio of two threshold modulation amplitudes: ordinary circumflexm(o=e) over amplified circumflexm(o), circumflexm(o=e)/circumflexm(o). We find amplification factors of up to about 8x. Light adaptation and contrast gain control in early visual processing distort the representations of visual stimuli so that inputs to subsequent perceptual processes contain undesired distortion products or 'impurities'. Motion amplification is used to measure and thence to reduce these unwanted components in a stimulus to a small fraction of their threshold. Such stimuli are certifiably pure in the sense that the residual impurity is less than a specified value. Six applications are considered: (1) removing (first-order) luminance contamination from moving (second-order) texture gratings; (2) removing luminance contamination from moving chromatic gratings to produce pure isoluminant gratings; (3) removing distortion products in luminance-modulated (first-order) gratings - by iterative application, all significant distortion products can be removed; (4) removing second-order texture contamination from third-order motion displays; (5) removing feature bias from third-order motion displays; (6) and the same general principles are applied to texture-slant discrimination in which x,y spatial coordinates replace the x,t motion coordinates. In all applicable domains, the amplification principle provides a powerful assay method for the precise measurement of very weak stimuli, and thereby a means of producing visual displays of certifiable purity.

The conformational switch in muscarinic acetylcholine receptors

The recently-determined structure of rhodopsin has provided a suitable basis for modeling the three-dimensional structure of the M1 muscarinic acetylcholine receptor. Using this as a framework for interpreting mutagenesis studies, we have been able to suggest most of the contacts which the receptor makes with acetylcholine and many of the intramolecular contacts which are important for the ground-state structure of the receptor. It is possible to outline a mechanism of G-protein interaction.

Spatial attention: different mechanisms for central and peripheral temporal precues?

The external noise paradigm (Z.-L. Lu & B. A. Dosher, 1998) was applied to investigate mechanisms of spatial attention in location precuing. Observers were precued or simultaneously cued to identify 1 of 4 pseudocharacters embedded in various amounts of external noise. The cues were either central or peripheral. Both central and peripheral precuing significantly reduced threshold in the presence of high external noise (16% and 17.5%). Only peripheral precuing significantly reduced threshold in the presence of low, or no, external noise (11%). A perceptual template model identified different mechanisms of attention for central and peripheral precuing, external noise exclusion for central precuing, and a combination of external noise exclusion and stimulus enhancement (or equivalently, internal additive noise reduction) for peripheral cuing.

Mechanisms of perceptual attention in precuing of location

What are the mechanisms of spatial attention underlying precue validity effects? We answer this question within the framework of a perceptual template model (PTM) [Lu & Dosher (1998). External noise distinguishes attention mechanisms. Vision Research, 38, 1183-1198; Dosher & Lu (1999). Mechanisms of perceptual learning. Vision Research, 39, 3197-3221] and an external noise plus attention paradigm for orientation judgments in two- to eight-location displays. Attentional mechanisms correspond to behavioral signatures: External noise exclusion produces cuing effects in high external noise and stimulus enhancement produces cuing effects in noiseless displays. We found that external noise exclusion was the primary mechanism of cue validity effects, with large effects in high-noise displays. Stimulus enhancement coexisted as a secondary mechanism in noiseless displays for a subset of observers and display conditions. Contrast threshold ratio tests ruled out attentionally mediated changes in gain control. The ratio rules were also shown to hold for a stochastic PTM model. Effects were equivalent for four-alternative (Experiment 1) and two-alternative (Experiment 2) orientation identification. Precues allow observers to reduce noise and focus on the target in the precued location. External noise exclusion was more important in larger displays. Previous results are reclassified and understood within the PTM framework.

4,5-Diazafluoren-9-one benzoylhydrazone monohydrate

The title compound, C(18)H(12)N(4)O.H(2)O, adopts the keto tautomeric form and the azomethine C=N double bond is in the E configuration. The dihedral angle between the planes of the diazafluorene moiety and the phenyl ring is 11.3 (1) degrees. In the solid state, the molecules form infinite chain-like structures via O-H.N hydrogen bonds involving the water molecules and diazafluorene moieties.

Attention mechanisms for multi-location first- and second-order motion perception

We applied the external noise plus attention paradigm to study attention mechanisms involved in concurrent first-order and second-order motion perception at two spatial locations. Cued to attend to one of the locations, the observer was instructed to independently judge direction of motion of either first-order (Experiment 1) or second-order (Experiment 2) motion stimuli at both locations in every trial. Across trials, systematically controlled amounts of external noise were added to the motion displays. We measured motion threshold at three performance criteria in every attention x external noise condition. We find that observers could, without any loss, simultaneously compute first-order motion direction at two widely separated spatial locations across a broad range of external noise conditions. However, considerable loss occurred at the unattended location in processing second-order motion direction at two separated spatial locations. We conclude that, under the conditions investigated in the current study, (1) in first-order motion perception, the visual system could simultaneously process motion direction at two widely separated locations without any capacity limitation; (2) in second-order motion perception, attending to a spatial location enhances stimulus contrast at that location by a factor of about 1.37 (or equivalently, reduces the internal additive noise by a factor of about 0.73).

Noise exclusion in spatial attention

Precue validity affects the performance of perceptual tasks. These spatial attention effects have been variously attributed to facilitation of processing, capacity allocation, or noise reduction. We used a new attention-plus-external (stimulus)-noise paradigm and model to identify the mechanisms of attention in cue-validity paradigms. A new phenomenon is reported: a large effect of location cue validity in an orientation identification task that specifically occurs when the stimulus is embedded in external (environmental or stimulus) noise. This result identifies the mechanism of the effect as external-noise exclusion, distinguished from stimulus enhancement that manifests itself only in noiseless stimulus environments.

A network of conserved intramolecular contacts defines the off-state of the transmembrane switch mechanism in a seven-transmembrane receptor

Activation of the rhodopsin-like 7-transmembrane (7-TM) receptors requires switching interhelical constraints that stabilize the inactive state to a new set of contacts in the activated state, which binds the cognate G-protein. The free energy to drive this is provided by agonist binding, which has higher affinity to the active than to the inactive conformation. We have sought specific interhelical constraint contacts, using the M(1) muscarinic acetylcholine receptor as a model. Histidine substitutions of particular groups of amino acids, in transmembrane domains 3, 6, and 7, created high-affinity Zn(2+) binding sites, demonstrating the close proximity of their side chains in the inactive state. Alanine point substitutions have shown the effect of weakening the individual intramolecular contacts. In each case, the acetylcholine affinity was increased, implying promotion of the activated state. These amino acids are highly conserved throughout the 7-TM receptor superfamily. We propose that they form an important part of a network of conserved interhelical contacts that defines the off-state of a general transmembrane switch mechanism.

Perceptual motion standstill in rapidly moving chromatic displays

In motion standstill, a quickly moving object appears to stand still, and its details are clearly visible. It is proposed that motion standstill can occur when the spatiotemporal resolution of the shape and color systems exceeds that of the motion systems. For moving red-green gratings, the first- and second-order motion systems fail when the grating is isoluminant. The third-order motion system fails when the green/red saturation ratio produces isosalience (equal distinctiveness of red and green). When a variety of high-contrast red-green gratings, with different spatial frequencies and speeds, were made isoluminant and isosalient, the perception of motion standstill was so complete that motion direction judgments were at chance levels. Speed ratings also indicated that, within a narrow range of luminance contrasts and green/red saturation ratios, moving stimuli were perceived as absolutely motionless. The results provide further evidence that isoluminant color motion is perceived only by the third-order motion system, and they have profound implications for the nature of shape and color perception.

Invariance of brain-wave representations of simple visual images and their names

In two experiments, electric brain waves of 14 subjects were recorded under several different conditions to study the invariance of brain-wave representations of simple patches of colors and simple visual shapes and their names, the words blue, circle, etc. As in our earlier work, the analysis consisted of averaging over trials to create prototypes and test samples, to both of which Fourier transforms were applied, followed by filtering and an inverse transformation to the time domain. A least-squares criterion of fit between prototypes and test samples was used for classification. The most significant results were these. By averaging over different subjects, as well as trials, we created prototypes from brain waves evoked by simple visual images and test samples from brain waves evoked by auditory or visual words naming the visual images. We correctly recognized from 60% to 75% of the test-sample brain waves. The general conclusion is that simple shapes such as circles and single-color displays generate brain waves surprisingly similar to those generated by their verbal names. These results, taken together with extensive psychological studies of auditory and visual memory, strongly support the solution proposed for visual shapes, by Bishop Berkeley and David Hume in the 18th century, to the long-standing problem of how the mind represents simple abstract ideas.

Invariance between subjects of brain wave representations of language

In three experiments, electric brain waves of 19 subjects were recorded under several different experimental conditions for two purposes. One was to test how well we could recognize which sentence, from a set of 24 or 48 sentences, was being processed in the cortex. The other was to study the invariance of brain waves between subjects. As in our earlier work, the analysis consisted of averaging over trials to create prototypes and test samples, to both of which Fourier transforms were applied, followed by filtering and an inverse transformation to the time domain. A least-squares criterion of fit between prototypes and test samples was used for classification. In all three experiments, averaging over subjects improved the recognition rates. The most significant finding was the following. When brain waves were averaged separately for two nonoverlapping groups of subjects, one for prototypes and the other for test samples, we were able to recognize correctly 90% of the brain waves generated by 48 different sentences about European geography.

Measuring the amplification of attention

An ambiguous motion paradigm, in which the direction of apparent motion is determined by salience (i.e., the extent to which an area is perceived as figure versus ground), is used to assay the amplification of color by attention to color. In the red-green colored gratings used in these experiments, without attention instructions, salience depends on the chromaticity difference between colored stripes embedded in the motion sequence and the yellow background. Selective attention to red (or to green) alters the perceived direction of motion and is found to be equivalent to increasing the physical redness (or greenness) by 25-117%, depending on the observer and color. Whereas attention to a color drastically alters the salience of that color, it leaves color appearance unchanged. A computational model, which embodies separate, parallel pathways for object perception and for salience, accounts for 99% of the variance of the experimental data.

Mechanisms of perceptual learning

Systematic measurements of perceptual learning were performed in the presence of external or stimulus noise. In the new external noise method (Dosher, B, & Lu, Z.-L. (1997). Investigative Ophthalmology and Visual Science, 38, S687; Lu, Z.-L., & Dosher, B. (1998). Vision Research, 38, 1183-1198), increasing amounts of external noise (white Gaussian random noise) is added to the visual stimulus in order to identify mechanisms of perceptual learning. Performance improved (threshold contrast was reduced) over days of practice on a peripheral orientation discrimination task--labelling Gabor patches as tilted slightly to the right or left. Practice improvements were largely specific to the trained quadrant of the display. Performance improved at all levels of external noise. The external noise method and perceptual template model (PTM) of the observer identifies the mechanism(s) of performance improvements as due to stimulus enhancement, external noise exclusion, or internal noise suppression. The external noise method was further extended by measuring thresholds at two threshold performance levels, allowing identification of mixtures in the PTM model. Perceptual learning over 8-10 days improved the filtering or exclusion of external noise by a factor of two or more, and improved suppression of additive internal noise--equivalent to stimulus enhancement--by 50% or more. Coupled improvements in external noise exclusion and stimulus enhancement in the PTM model may reflect channel weighting. Perceptual learning may not reflect neural plasticity at the level of basic visual channels, nor cognitive adjustments of strategy, but rather plasticity at an intermediate level of weighting inputs to decision.

Second-order reversed phi

In a first-order reversed-phi motion stimulus (Anstis, 1970), the black-white contrast of successive frames is reversed, and the direction of apparent motion may, under some conditions, appear to be reversed. It is demonstrated here that, for many classes of stimuli, this reversal is a mathematical property of the stimuli themselves, and the real problem is in perceiving forward motion, which involves the second- or third-order motion systems or both. Three classes of novel second-order reversed-phi stimuli (contrast, spatial frequency, and flicker modulation) that are invisible to first-order motion analysis were constructed. In these stimuli, the salient stimulus features move in the forward (feature displacement) direction, but the second-order motion energy model predicts motion in the reversed direction. In peripheral vision, for all stimulus types and all temporal frequencies, all the observers saw only the reversed-phi direction of motion. In central vision, the observers also perceived reversed motion at temporal frequencies above about 4 Hz, but they perceived movement in the forward direction at lower temporal frequencies. Since all of these stimuli are invisible to first-order motion, these results indicate that the second-order reversed-phi stimuli activate two subsequent competing motion mechanisms, both of which involve an initial stage of texture grabbing (spatiotemporal filtering, followed by fullwave rectification). The second-order motion system then applies a Reichardt detector (or equivalently, motion energy analysis) directly to this signal and arrives at the reversed-phi direction. The third-order system marks the location of features that differ from the background (the figure) in a salience map and computes motion in the forward direction from the changes in the spatiotemporal location of these marks. The second-order system's report of reversed movement dominates in peripheral vision and in central vision at higher temporal frequencies, because it has better spatial and temporal resolution than the third-order system, which has a cutoff frequency of 3-4 Hz (Lu & Sperling, 1995b). In central vision, below 3-4 Hz, the third-order system's report of resolvable forward movement of something salient (the figure) dominates the second-order system's report of texture contrast movement.

The mechanism of isoluminant chromatic motion perception

An isoluminant chromatic display is a color display in which the component colors have been so carefully equated in luminance that they stimulate only color-sensitive perceptual mechanisms and not luminance-sensitive mechanisms. The nature of the mechanism by which isoluminant chromatic motion is perceived is an important issue because color and motion processing historically have been associated with different neural pathways. Here we show that isoluminant chromatic motion (i) fails a pedestal test, (ii) has a temporal tuning function that declines to half-amplitude at 3-6 Hz, and (iii) is perceived equally well when the entire motion sequence is presented monocularly (entire motion sequence to one eye) versus interocularly (the frames of motion sequence alternate between eyes so that neither eye individually could perceive motion). These three characteristics indicate that chromatic motion is detected by the third-order motion system. Based on this theory, it was possible to take a moving isoluminant red-green grating and, by simply increasing the chromatic contrast of the green component, to generate the full gamut of motion percepts, from compelling smooth motion to motion standstill. The perception of motion standstill when the third-order mechanism is nullified indicates that there is no other motion computation available for purely chromatic motion. It follows that isoluminant chromatic motion is not computed by specialized chromatic motion mechanisms within a color pathway but by the third-order motion system at a brain level where binocular inputs of form, color, depth, and texture are simultaneously available and where selective attention can exert a major influence.

The conformational switch in 7-transmembrane receptors: the muscarinic receptor paradigm

The rhodopsin-like superfamily of 7-transmembrane receptors is the largest class of signalling molecules in the mammalian genome. Recently, a combination of mutagenesis, biophysical and modelling studies have suggested a credible model for the alpha-carbon backbone in the transmembrane region of the 7-transmembrane receptors, and have started to reveal the structural basis of the conformational switch from the inactive to the active state. A key feature may be the replacement of a network of radial constraints, centred on transmembrane helix three, which stabilise the inactive ground state of the receptor by a new set of axial interactions which help to stabilise the activated state. Transmembrane helix three may act as a rotary switch in the activation mechanism.

The functional topography of transmembrane domain 3 of the M1 muscarinic acetylcholine receptor, revealed by scanning mutagenesis

Alanine-scanning mutagenesis has been applied to residues 100-121 in transmembrane domain 3 of the M1 muscarinic acetylcholine receptor. This study complements a previous investigation of the triad Asp122-Arg123-Tyr124 (Lu, Z-L., Curtis, C. A., Jones, P. G., Pavia, J., and Hulme, E. C. (1997) Mol. Pharmacol. 51, 234-241). The results demonstrate the alpha-helical secondary structure of the domain and suggest its orientation with respect to the other transmembrane domains. The C-terminal part of the helix appears to be largely buried within the receptor structure. On its surface, there is a patch of three residues, Val113, Leu116, and Ser120, which may form intramolecular contacts that help to stabilize the inactive ground state of the receptor. Mutagenic disruption of these increased agonist affinity and signaling efficacy. In two cases (L116A and S120A), this led to constitutive activation of the receptor. Parallel to the helix axis and spanning the whole transmembrane region, a distinct strip of residues on one face of transmembrane domain 3 forms intermolecular (acetylcholine-receptor, receptor-G protein) or intrareceptor bonds that contribute to the activated state. The binding of acetylcholine may destabilize the first set of contacts while favoring the formation of the second.

Characterizing human perceptual inefficiencies with equivalent internal noise

A widely used method for characterizing and comparing inefficiencies in perceptual processes is the method of equivalent internal noise--the amount of random internal noise necessary to produce the degree of inefficiency exhibited by the perceptual system in processing [J. Opt. Soc. Am. 46, 634 (1956)]. One normally estimates the amount of equivalent internal noise by systematically increasing the amount of external noise added to the signal stimulus and observing how threshold--signal stimulus energy required for an observer to maintain a given performance level--depends on the amount of external noise. In a variety of perceptual tasks, a simple noisy linear amplifier model [D. Pelli, Ph.D. dissertation (University of Cambridge, Cambridge, UK 1981)] has been utilized to estimate the equivalent internal noise Ninternal by fitting of the relation between threshold contrast c tau and external noise N(ext) at a single (d') performance level: c tau 2 =(d'/beta)2(N(ext)2 + Ninternal2). This model makes a strong prediction: Independent of observer and external noise contrast, the ratio between two thresholds at each external noise level is equal to the ratio of the two corresponding d' values. To our knowledge, this potential test for the internal consistency of the model had never been examined previously. In this study we estimated threshold ratios between multiple performance levels at various external noise contrasts in two different experiments: Gabor orientation identification, and Gabor detection. We found that, in both identification and detection, the observed threshold ratios between different performance levels departed substantially from the d' ratio predicted by the simple noisy linear amplifier model. An elaborated perceptual template model [Vision Res. 38, 1183 (1998)] with nonlinear transducer functions and multiplicative noise in addition to the additive noise in the simple linear amplifier model leads to a substantially better description of the data and suggests a reinterpretation of earlier results that relied on the simple noisy linear amplifier model. The relationship of our model and method to other recent parallel and independent developments [J. Opt. Soc. Am. A 14, 2406 (1997)] is discussed.