The interaction effect of depressive symptoms and inflammation on the occurrence of cardiovascular diseases

BACKGROUND

Whether there was an interaction effect between depressive symptoms and inflammation on the occurrence of cardiovascular diseases (CVDs) was unclear.

METHODS

In this cross-sectional study, 3346 participants in the National Health and Nutrition Examination Survey (NHANES) were included. Multivariable regression analysis was performed to explore the associations of depressive symptoms or inflammation with CVDs. The attributable proportion of interaction (API), and synergy index (SI) were applied for evaluating the statistical significance of the interaction effect.

RESULTS

Depressive symptoms were associated with 2.31-fold risk of CVDs [odds ratio (OR) = 2.31, 95 % confidence interval (CI): 1.47-3.62). The increased risk of CVDs was observed in people with neutrophil to lymphocyte ratio (NLR) ≥1.88 group (OR = 1.36, 95%CI: 1.01-1.85) and neutrophil/[white blood cell (WBC)-neutrophil] ≥1.35 (OR = 1.52, 95%CI: 1.12-2.07) after adjusting for confounders. The interaction effect of depressive symptoms and high NLR on the risk of CVDs was statistically significant with an OR value of 2.60 (95%CI: 1.43-4.70) compared to low NLR and no depressive symptoms group after adjusting for confounders. The API was 0.66 (95%CI: 0.44-0.89) and SI was 4.23 (95%CI: 2.08-8.59). The interaction effect of depressive symptoms and high neutrophil/(WBC-neutrophil) was associated with the risk of CVDs compared to low neutrophil/(WBC-neutrophil) and no depressive symptoms group (OR = 3.59, 95%CI: 2.00-6.45). The API was 0.78 (95%CI: 0.63-0.93) and SI was 6.75 (95%CI: 3.55-12.82).

CONCLUSION

There was an interaction effect of depressive symptoms and inflammation on the occurrence of CVDs.

Liver fat volume fraction measurements based on multi-material decomposition algorithm in patients with nonalcoholic fatty liver disease: the influences of blood vessel, location, and iodine contrast

BACKGROUND

In recent years, spectral CT-derived liver fat quantification method named multi-material decomposition (MMD) is playing an increasingly important role as an imaging biomarker of hepatic steatosis. However, there are various measurement ways with various results among different researches, and the impact of measurement methods on the research results is unknown. The aim of this study is to evaluate the reproducibility of liver fat volume fraction (FVF) using MMD algorithm in nonalcoholic fatty liver disease (NAFLD) patients when taking blood vessel, location, and iodine contrast into account during measurement.

METHODS

This retrospective study was approved by the institutional ethics committee, and the requirement for informed consent was waived because of the retrospective nature of the study. 101 patients with NAFLD were enrolled in this study. Participants underwent non-contrast phase (NCP) and two-phase enhanced CT scanning (late arterial phase (LAP) and portal vein phase (PVP)) with spectral mode. Regions of interest (ROIs) were placed at right posterior lobe (RPL), right anterior lobe (RAL) and left lateral lobe (LLL) to obtain FVF values on liver fat images without and with the reference of enhanced CT images. The differences of FVF values measured under different conditions (ROI locations, with/without enhancement reference, NCP and enhanced phases) were compared. Friedman test was used to compare FVF values among three phases for each lobe, while the consistency of FVF values was assessed between each two phases using Bland-Altman analysis.

RESULTS

Significant difference was found between FVF values obtained without and with the reference of enhanced CT images. There was no significant difference about FVF values obtained from NCP images under the reference of enhanced CT images between any two lobes or among three lobes. The FVF value increased after the contrast injection, and there were significant differences in the FVF values among three scanning phases. Poor consistencies of FVF values between each two phases were found in each lobe by Bland-Altman analysis.

CONCLUSION

MMD algorithm quantifying hepatic fat was reproducible among different lobes, while was influenced by blood vessel and iodine contrast.

Highly expressed lncRNA FOXD3-AS1 promotes non-small cell lung cancer progression via regulating miR-127-3p/mediator complex subunit 28 axis

OBJECTIVE

The present study aimed to determine the expression of long non-coding RNA (lncRNA) FOXD3 antisense RNA 1 (FOXD3-AS1) in lung cancer tissues and to explore its underlying mechanisms in mediating non-small cell lung cancer (NSCLC) progression.

MATERIALS AND METHODS

Gene expression levels were determined by quantitative real-time PCR; lung cancer cell proliferation and invasion were determined by in vitro functional assays; protein levels were determined by Western blot assay; xenograft nude mice model was used to evaluate the in vivo tumor growth of lung cancer cells; Luciferase reporter assay determined the interactions among FOXD3-AS1, miR-127-3p, and mediator complex subunit 28 (MED28).

RESULTS

Data mining and analysis of the clinical sample showed that FOXD3-AS1 expression was significantly up-regulated in lung cancer tissues. In vitro functional assays demonstrated that FOXD3-AS1 overexpression promoted NSCLC cell proliferation and invasion, while FOXD3-AS1 knockdown exerted tumor-suppressive effects on NSCLC cells. Moreover, FOXD3-AS1 interacted with miR-127-3p by acting as a competing endogenous RNA to suppress miR-127-3p expression, while miR-127-3p repressed MED28 expression by targeting MED28 3' untranslated region in NSCLC cells. Mechanistically, the oncogenic effects of FOXD3-AS1 overexpression were significantly attenuated by miR-127-3p overexpression and MED28 knockdown in NSCLC cells. In the xenograft mice model, FOXD3-AS1 knockdown suppressed in vivo tumor growth of A549 cells, and also up-regulated miR-127-3p expression and repressed MED28 expression in the xenograft tumors. In the clinical aspect, the downregulation of miR-127-3p and up-regulation of MED28 were respectively detected in lung cancer tissues.

CONCLUSIONS

Our findings provided new evidence that the FOXD3-AS1 regulated NSCLC progression via targeting the miR-127-3p/MED28 axis.

SAT0096 DISCORDANCE BETWEEN SUBJECTIVE AND OBJECTIVE INDEX OF THE DISEASE ACTIVITY SCORE MAY REDUCE THE CORRELATION BETWEEN CLINICAL AND ULTRASOUND ASSESSMENT IN RHEUMATOID ARTHRITIS

Background:

There was discordance between subjective and objective index of the disease activity score, or between clinical parameters and ultrasound findings in some RA patients. Therefore, we set out to determine whether the discordance between subjective and objective index of the composite score could reduce the correlation between clinical and ultrasound parameters in RA.

Objectives:

To investigate whether the discordance between tender and swollen joint count (TJC and SJC) as well as patient’s and evaluator’s global assessment (PGA and EGA) influences the correlation between clinical and US parameters in RA.

Methods:

RA patients with available ultrasonography of 28 joints from Jan 2014 to Jan 2018 were enrolled in the study. Gray-scale (GS) synovial hypertrophy and Power Doppler (PD) synovitis were measured and semi-quantitatively graded. The total GS/PD score was the sum score of 28 joints. SJC and TJC based on 28 joints, PGA and EGA of all the patients were evaluated by one rheumatologist. The numeric difference between TJC and SJC (ΔTSJ) and that between PGA and EGA (ΔPEG) were calculated. The correlation between clinical and ultrasound parameters in different ΔTSJ and ΔPEG subgroups was explored.

Results:

Totally 163 patients were enrolled in the study. Clinical composite disease activity scores and all the components were significantly correlated with the total GS and PD scores (p<0.01 for all). But the relevance between the clinical disease parameters and total PD score became weak, with the increase of ΔTSJ. For the patients with ΔTSJ > 5, the total PD score was only correlated with CRP, EGA and PGA, while the total GS score was only correlated with CRP. Similarly, no correlation between total PD score and clinical parameters, except for SJC, was observed in patients with ΔPEG < 0 (p < 0.05).

Conclusion:

Total PD/GS score was correlated well with the clinical parameters of disease activity, including both the subjective and objective indexes. But for patients with ΔTSJ > 5,there was no correlation between total GS/PD scores and clinical composite disease activity scores, except that only the objective index (CRP, SJC and EGA) were more likely to correlate with total GS/PD scores.

Disclosure of Interests:

None declared

microRNA-331-3p attenuates neuropathic pain following spinal cord injury via targeting RAP1A

Neuropathic pain (NP) after spinal cord injury (SCI) leads to compromised physical and cognitive functions in a majority of patients. Aberrant miRNA expression plays vital roles in the pathogenesis of SCI. This study aims to investigate the effect of miR-331-3p in rats following SCI. Microarray assay was performed in SCI- and sham-operated rats to evaluate the expression of miR-331-3p. Assigned SCI rats were treated with miR-331-3p agomiR alone or miR-331-3p agomiR plus RAP1A-expressing lentivirus or control agomiR. Rat locomotor performance was evaluated by BBB locomotor rating scale. Neuronal tissue damage and apoptosis were detected by histological analyses and Western blot. Inflammation in spinal cord was determined by detection of the expression of inflammatory genes with qRT-PCR, and ELISA. Downstream expression of RAP1A was measured by Western blot. The results showed that SCI induced the downregulation of miR-331-3p in the spinal cord of SCI rats. Overexpression of miR-331-3p improved the locomotor performance, reduced tissue damage, neuronal apoptosis and inflammation in rat SCI model. Rap1a (Ras-related protein Rap-1A) was predicted as a downstream target for miR-331-3p, and upregulation of RAP1A impaired the beneficial effect of miR-331-3p post- SCI, which was shown as worse locomotor activity, more severe tissue damage, as well as promoting apoptosis and inflammation in SCI rats. Furthermore, miR-331-3p reduced the activation of RAP1A downstream genes via inhibiting RAP1A expression. These findings indicate a protective role of miR- 331-3p in the development of SCI via the modulation of RAP1A, and may help to develop novel therapy against SCI-induced complications.

418 Ultrasound molecular imaging of the role of von willebrand factor-mediated platelet adhesion in atherogenesis

Funding Acknowledgements

JSPS Overseas Research Fellowship

Background

Platelets are known to be both pro-inflammatory and pro-mitogenic. However, the role of platelet-endothelial interactions in the initiation and growth of atherosclerotic lesions is not well understood.

Purpose

We used contrast-enhanced ultrasound (CEU) molecular imaging of the arterial endothelium to test the hypothesis that platelet attachment to endothelial Von Willebrand Factor (VWF) promotes atherogenesis.

Methods

We studied wild-type mice (WT), low-density lipoprotein deficient mice fed western diet to produce atherosclerosis (LDLR-/-), and LDLR-/- mice also deficient for ADAMTS-13 (LDLR-/-ADAMTS13-/-) which is the enzyme responsible for proteolytic cleavage of endothelial-associated VWF. Mice were studied at 20 weeks and 30 weeks of age. A subset of LDLR-/- mice were treated with recombinant ADAMTS13 1 hr prior to study. Proximal aortic CEU molecular imaging of P-selectin, vascular cell adhesion molecule (VCAM)-1, von Willebrand factor (VWF), and platelet GPIbα was performed. Aortic distensibility was assessed using high-frequency (30 MHz) transthoracic echocardiography and tail cuff blood pressure systems. NF-κB of aorta was assessed by ELISA kit. Plaque size and composition were assessed by histology. Platelets and macrophage immunohistochemistry were also performed on confocal microscopy.

Results

Aortic molecular imaging signal for P-selectin, VCAM-1, VWF, and platelet adhesion was significantly higher in LDLR-/- than WT mice, and increased by 2-fold between 20 and 30 wks of age. Signal for VWF and platelet adhesion was abolished 1 h after administration of ADAMTS13, confirming that platelet adhesion was VWF-mediated. At 20 and 30 wks of age, molecular imaging signal for all targets was 2-fold higher (p &lt; 0.01) in LDLR-/-ADAMTS13-/- versus LDLR-/- mice. The LDLR-/-ADAMTS13-/- mice also had lower aortic distensibility (p &lt; 0.05), had a 2-fold higher NF-κB signal (p &lt; 0.05), and had a 2-fold greater total plaque area (p &lt; 0.01). Fluorescent immunohistochemistry confirmed that the LDLR-/-ADAMTS13-/- mice also had greater platelets (p &lt; 0.05) and increased macrophage content (p &lt; 0.05) than LDLR-/- mice in aortic plaque.

Conclusion

In early to mid-stage atherosclerosis, abnormal regulation of endothelial-associated VWF results in platelet adhesion and secondary up-regulation of endothelial inflammatory adhesion molecules, thereby promoting atherosclerotic plaque progression. These results indicate an important role of platelet-endothelial interactions in early atherogenesis.

Abstract 418 Figure

TGF-β in Mice Ameliorates Experimental Autoimmune Encephalomyelitis in Regulating NK Cell Activity

Multiple sclerosis is a disease characterized by inflammation and demyelination located in the central nervous system. Experimental autoimmune encephalomyelitis (EAE) is the most common animal model for multiple sclerosis (MS). Although the roles of T cells in MS/EAE have been well investigated, little is known about the functions of other immune cells in the neuroinflammation model. Here we found that an essential cytokine transforming growth factor β (TGF-β) which could mediate the differentiation of Th17/regulatory T cells was implicated in the natural killer (NK) cells’ activity in EAE. In EAE mice, TGF-β expression was first increased at the onset and then decreased at the peak, but the expressions of TGF-β receptors and downstream molecules were not affected in EAE. When we immunized the mice with MOG antigen, it was revealed that TGF-β treatment reduced susceptibility to EAE with a lower clinical score than the control mice without TGF-β. Consistently, inflammatory cytokine production was reduced in the TGF-β treated group, especially with downregulated pathogenic interleukin-17 in the central nervous system tissue. Furthermore, TGF-β could increase the transcription level of NK cell marker NCR1 both in the spleen and in the CNS without changing other T cell markers. Meanwhile TGF-β promoted the proliferation of NK cell proliferation. Taken together, our data demonstrated that TGF-β could confer protection against EAE model in mice through NK cells, which would be useful for the clinical therapy of MS.

Mortality and prognostic factors in Chinese patients with systemic lupus erythematosus

Objectives

To investigate the mortality and causes of death in Chinese patients with systemic lupus erythematosus.

Methods

We collected the clinical data of all consecutive adult systemic lupus erythematosus patients at the Rheumatology department of Peking University First Hospital between January 2007 and December 2015. The primary causes of death were identified, the standardized mortality ratio and years of life lost were calculated, and the survival and variables associated with mortality were determined by Kaplan–Meier and Cox regression analysis respectively.

Results

The mean age of all 911 patients (814 females and 97 males) was 37.8 ± 14.7 years, the median disease duration at recruitment was 2.6 (0.5–7.0) years, and the median follow-up duration was 3.0 (1.4–5.1) years. Among the 911 patients who were successfully followed up, 45 patients died. Infection (31.1%) was the leading cause of death followed by renal failure, pulmonary arterial hypertension and cerebrovascular diseases. The overall age and sex-adjusted standardized mortality ratio was 3.2 (95% confidence interval 2.4–4.0), and the years of life lost for women and men were 29.8 and 9.4 respectively. Overall survival at 1, 5 and 10 years was 98.2%, 95.3% and 93.7% respectively. Older age at disease onset, infection, autoimmune hemolytic anemia, thrombocytopenia and pulmonary arterial hypertension were independent risk factors for the mortality of systemic lupus erythematosus patients, and longer disease duration at recruitment was an independent protective factor.

Conclusions

Mortality of systemic lupus erythematosus patients in China was substantial, especially in females, with infection the leading cause of death. Older age at disease onset, infection, autoimmune hemolytic anemia, thrombocytopenia and pulmonary arterial hypertension were associated with poor outcomes.

Gq-activated fibroblasts induce cardiomyocyte action potential prolongation and automaticity in a three-dimensional microtissue environment

Cardiac fibroblasts (CFs) are known to regulate cardiomyocyte (CM) function in vivo and in two-dimensional in vitro cultures. This study examined the effect of CF activation on the regulation of CM electrical activity in a three-dimensional (3-D) microtissue environment. Using a scaffold-free 3-D platform with interspersed neonatal rat ventricular CMs and CFs, G_q-mediated signaling was selectively enhanced in CFs by Gα_q adenoviral infection before coseeding with CMs in nonadhesive hydrogels. After 3 days, the microtissues were analyzed by signaling assay, histological staining, quantitative PCR, Western blots, optical mapping with voltage- or Ca²⁺-sensitive dyes, and microelectrode recordings of CF resting membrane potential (RMP_CF). Enhanced G_q signaling in CFs increased microtissue size and profibrotic and prohypertrophic markers. Expression of constitutively active Gα_q in CFs prolonged CM action potential duration (by 33%) and rise time (by 31%), prolonged Ca²⁺ transient duration (by 98%) and rise time (by 65%), and caused abnormal electrical activity based on depolarization-induced automaticity. Constitutive G_q activation in CFs also depolarized RMP_CF from -33 to -20 mV and increased connexin 43 and connexin 45 expression. Computational modeling confers that elevated RMP_CF and increased cell-cell coupling between CMs and CFs in a 3-D environment could lead to automaticity. In conclusion, our data demonstrate that CF activation alone is capable of altering action potential and Ca²⁺ transient characteristics of CMs, leading to proarrhythmic electrical activity. Our results also emphasize the importance of a 3-D environment where cell-cell interactions are prevalent, underscoring that CF activation in 3-D tissue plays a significant role in modulating CM electrophysiology and arrhythmias.NEW & NOTEWORTHY In a three-dimensional microtissue model, which lowers baseline activation of cardiac fibroblasts but enables cell-cell, paracrine, and cell-extracellular matrix interactions, we demonstrate that selective cardiac fibroblast activation by enhanced G_q signaling, a pathophysiological trigger in the diseased heart, modulates cardiomyocyte electrical activity, leading to proarrhythmogenic automaticity.

MiR-133b ameliorates axon degeneration induced by MPP(+) via targeting RhoA

Increasing evidence suggests that microRNAs (miRs) play a significant role in the pathogenesis of Parkinson's disease (PD). MiR-133b, which is significantly decreased in the PD midbrain, has recently been shown to promote neurite outgrowth and enhance neural functional recovery. However, the role of miR-133b in PD has not been clearly established. Here, using a well-established PD model culture based on the neurotoxin 1-methyl-4-phenyl-pyridinium (MPP(+)), we demonstrated that miR-133b could promote axon outgrowth in dopaminergic neurons (DNs) and ameliorated MPP(+)-induced axon degeneration. Additional experiments suggested that the mechanisms of this miR-133b-mediated effect might rely on RhoA inhibition. We demonstrated that RhoA, an inhibitor of axonal growth, was increased in DNs under MPP(+) treatment, and this increase could be attenuated by miR-133b overexpression. Moreover, we demonstrated that the induced expression of miR-133b could inhibit α-synuclein, which is critically involved in the pathological process of PD. Furthermore, we found that overexpression of miR-133b abrogated the MPP(+)-induced decrease in the Bcl-2/Bax ratio and upregulated phosphorylated Akt (p-Akt), which is a pro-survival kinase. Together these findings reveal novel roles for miR-133b in the pathogenesis of PD and provide new therapeutic avenues for the treatment of the disease.

Excited-state lifetimes of far-infrared collective modes in proteins

Vibrational excitations of low frequency collective modes are essential for functionally important conformational transitions in proteins. Here we report the first direct measurement on the lifetime of vibrational excitations of the collective modes at 87 pm (115 cm(-1)) in bacteriorhodopsin, a transmembrane protein. The data show that these modes have extremely long lifetime of vibrational excitations, over 500 picoseconds, accommodating 1500vibrations. We suggest that there is a connection between this relativelyslow anharmonic relaxation rate of approximately 10 g sec(-1) and thesimilar observed rate of conformational transitions in proteins, which require require multi-level vibrational excitations and energy exchanges with othervibrational modes and collisional motions of solvent molecules.

Anti-interleukin-12/23p40 antibody attenuates chronic rejection of cardiac allografts partly via inhibition γδT cells

In our previous study, we showed that treatment with an anti-interleukin (IL)-12/23p40 antibody inhibits acute cardiac allograft rejection via inhibiting production of interferon (IFN)-γ and IL-17a. However, the impact of this antagonistic anti-p40 antibody on chronic cardiac rejection was unclear. Hearts of B6.C-H2bm12/KhEg mice were transplanted into major histocompatibility complex (MHC) class II-mismatched C57Bl/6J mice (wild-type, γδTCR (-/-) and IL-17(-/-) ), which is an established murine model of chronic allograft rejection without immunosuppression. The mice were treated with control immunoglobulin (Ig)G or 200 µg anti-p40 monoclonal antibody on post-operative days, respectively. Abdominal palpation and echocardiography were used to monitor graft survival. The mice administered with anti-p40 antibody showed a significant promotion in graft survival (median survival time >100 days), and histological analyses revealed that cardiac allograft rejection was attenuated. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence analyses demonstrated that anti-p40 antibody down-regulated the level of ingraft cytokine and chemokine expression (IL-6, IFN-γ, IL-17a, CCL2 and CCL20). Flow cytometry analyses showed that γδ T cells are an important ingraft source of IFN-γ and IL-17a and inhibit the production of inflammation cytokine by anti-p40 antibody. Compared with the wild-type group, the graft survival time in the γδ T cell receptor(-/-) and IL-17(-/-) mice was prolonged significantly. Therefore we propose that, in the chronic allograft rejection model, treatment with anti-p40 antibody prolongs graft survival possibly by reducing the amount of reactive inflammatory cells, especially γδ T cells.

Patient-specific modeling of cardiovascular and respiratory dynamics during hypercapnia

This study develops a lumped cardiovascular-respiratory system-level model that incorporates patient-specific data to predict cardiorespiratory response to hypercapnia (increased CO(2) partial pressure) for a patient with congestive heart failure (CHF). In particular, the study focuses on predicting cerebral CO(2) reactivity, which can be defined as the ability of vessels in the cerebral vasculature to expand or contract in response CO(2) induced challenges. It is difficult to characterize cerebral CO(2) reactivity directly from measurements, since no methods exist to dynamically measure vasomotion of vessels in the cerebral vasculature. In this study we show how mathematical modeling can be combined with available data to predict cerebral CO(2) reactivity via dynamic predictions of cerebral vascular resistance, which can be directly related to vasomotion of vessels in the cerebral vasculature. To this end we have developed a coupled cardiovascular and respiratory model that predicts blood pressure, flow, and concentration of gasses (CO(2) and O(2)) in the systemic, cerebral, and pulmonary arteries and veins. Cerebral vascular resistance is incorporated via a model parameter separating cerebral arteries and veins. The model was adapted to a specific patient using parameter estimation combined with sensitivity analysis and subset selection. These techniques allowed estimation of cerebral vascular resistance along with other cardiovascular and respiratory parameters. Parameter estimation was carried out during eucapnia (breathing room air), first for the cardiovascular model and then for the respiratory model. Then, hypercapnia was introduced by increasing inspired CO(2) partial pressure. During eucapnia, seven cardiovascular parameters and four respiratory parameters was be identified and estimated, including cerebral and systemic resistance. During the transition from eucapnia to hypercapnia, the model predicted a drop in cerebral vascular resistance consistent with cerebral vasodilation.

Pressure effects on the dark-adaptation of bacteriorhodopsin

The influence of hydrostatic pressure (340 MPa) on the dark-adaptation kinetics and the relaxation of dark-adapted bacterio-rhodopsin following a pressure jump (0.1 MPa --> 340 MPa) have been studied. We have also measured the temperature dependence of the equilibrium isomeric ratio of all-trans and 13-cis retinal in dark-adapted bacteriorhodopsin at 340 MPa. The results show that hydrostatic pressure affects both the dark-adaptation rate and the dark equilibrium isomeric ratio. With increasing pressure, the fraction of all-trans isomers decreases. The kinetics have been analyzed with a two-state model. The description of the pressure dependence using transition state theory is inappropriate for two reasons; (a) pressure changes the viscosity of the protein and its environment, and (b) pressure changes the population of conformational substates within either isomeric form of bacteriorhodopsin. The temperature independent ratio of all-trans and 13-cis isomers indicates that the all-trans and 13-cis conformations have the same conformational volume.

The Treg/Th17 imbalance in patients with idiopathic dilated cardiomyopathy

To assess whether Treg/Th17 balance was broken in patients with idiopathic dilated cardiomyopathy (DCM). We studied 25 patients who were diagnosed as idiopathic DCM (18 men and seven women, mean age 35.6 +/- 5.2) and 25 normal persons (18 men and seven women, mean age 33.8 +/- 4.9). Then, we detected Treg/Th17 functions on different levels including cell frequencies, related cytokine secretion and key transcription factors in patients with idiopathic DCM and controls. The results demonstrated that patients with idiopathic DCM revealed significant increase in peripheral Th17 number, Th17-related cytokines (IL-17, IL-6, IL-23) and transcription factor (RORgammat) levels and obvious decrease in Treg number, Treg-related cytokines (TGF-beta1 and IL-10) and transcription factor (Foxp3) levels when compared to normal persons. Results indicated that Treg/Th17 functional imbalance existed in patients with idiopathic DCM, suggesting a potential role for Treg/Th17 imbalance in the development of idiopathic DCM.

Heart failure among younger rheumatoid arthritis and Crohn's patients exposed to TNF-alpha antagonists

OBJECTIVES

New onset heart failure (HF) has been associated with the use of TNF-alpha antagonists etanercept and infliximab based upon spontaneous adverse event reports. HF clinical trials of these agents were stopped early due to futility or worsening of existing HF. A potential association between etanercept and infliximab and new onset HF has been studied minimally at a population level.

METHODS

Using administrative claims from a large U.S. health care organization, we identified rheumatoid arthritis (RA) and Crohn's disease (CD) patients receiving infliximab or etanercept (exposed), and comparator cohorts of RA and CD patients receiving non-biologic immunosuppressives (unexposed). We studied adults < 50 years to reduce potential confounding related to common age-related comorbidities. Based on abstracted medical records of suspected HF cases, a physician panel adjudicated cases as definite, possible or no HF.

RESULTS

Among 4018 RA and CD patients with mean duration follow-up of 18 months, 9 of 33 suspected HF cases (identified using claims data) were adjudicated as definite (n = 5) or possible (n = 4) HF. The relative risk of HF among TNF-alpha antagonist-treated RA and CD patients was 4.3 and 1.2, respectively (P = NS for both). The absolute difference in cumulative incidence of HF among infliximab or etanercept-exposed compared to unexposed patients was 3.4 and 0.3 cases per 1000 persons for RA and CD (P = NS), respectively, yielding a number needed to harm of 294 for RA and 3333 for CD.

CONCLUSION

We found only a small number of presumed HF cases (n = 9, or 0.2%) in a large population of relatively young RA and CD patients. Although there was an increased relative risk of incident, HF that was not statistically significant among those exposed to TNF-alpha antagonists compared to those unexposed, larger cohorts are needed to provide more precise risk estimates and permit adjustment for potential confounding.

Prevalence and predictors of osteoporosis treatment in nursing home residents with known osteoporosis or recent fracture

SUMMARY

We studied nursing home residents with osteoporosis or recent fracture to determine the frequency and predictors of osteoporosis treatment. There was wide variation in performance, and both clinical and systems variables predicted use. This study shows that improvement in osteoporosis care is possible and important for many nursing homes.

INTRODUCTION

We determined the prevalence and predictors of osteoporosis evaluation and treatment in high-risk nursing home residents.

METHODS

We identified 67 nursing facilities in North Carolina and Arizona with > 10 residents with osteoporosis or recent hip fracture. Medical records (n=895) were abstracted for osteoporosis evaluation [dual-energy X-ray absorptiometry (DXA), vitamin D level, serum calcium), treatment (calcium, vitamin D, osteoporosis medication, hip protectors), clinical, and systems covariates. Data were analyzed at the facility level using mixed models to account for the complex nesting of residents within providers and nursing facilities.

RESULTS

Calcium and vitamin D was prescribed for 69% of residents, bisphosphonates for 19%, calcitonin for 14%, other pharmacologic therapies for 6%, and hip protectors for 2%. Overall, 36% received any bone protection (medication or hip protectors), with wide variation among facilities (0-85%). Factors significantly associated with any bone protection included female gender [odds ratio (OR) 2.4, (1.5-3.7)] and nonurban/suburban location [1.5, (1.1-2.2)]. Residents with esophagitis, peptic ulcer disease (PUD), or dysphagia [0.6, (0.4-0.9)] and alcohol abuse [0.2, (0.0-0.9)] were less likely to receive treatment.

CONCLUSIONS

There is substantial variation in the quality of osteoporosis treatment across nursing homes. Interventions that improve osteoporosis quality of care are needed.

Axial length and optic disc size in normal eyes

AIM

To investigate the relationship between optic disc area and axial length in normal eyes of white and black people.

METHODS

Consecutive eligible normal subjects were enrolled. Ocular biometry was obtained using A-scan ultrasonography, and reliable images of the optic disc were obtained using a confocal scanning laser ophthalmoscope. The relationship between optic disc area and axial length was assessed using univariate and multivariate models.

RESULTS

281 eyes of 281 subjects were enrolled. Black subjects (n = 157) had significantly larger discs (mean (SD) disc area, 2.12 (0.5) mm(2)) than white subjects (n = 124; 1.97 (0.6) mm(2); t test, p = 0.02). Optic disc area increased with axial length (Pearson's correlation coefficient, r = 0.13, p<0.035) for the entire study population. Multivariate regression models including race, disc area and axial length showed that a significant but weak linear relationship exists between axial length and disc area (partial correlation coefficient 0.14; p<0.024), and with race and disc area (partial correlation coefficient 0.19; p<0.017) when adjusted for the effects of other terms in the model.

CONCLUSION

Increased disc area is associated with longer axial length measurements and African ancestry. This may have implications for pathophysiology and risk assessment of glaucoma.

The relation between C reactive protein and age related macular degeneration in the Cardiovascular Health Study

AIM

To test the hypothesis that individuals with age related macular degeneration (AMD) have increased C reactive protein (CRP) levels.

METHODS

A cross sectional study design using data from the Cardiovascular Health Study (CHS), a longitudinal study that enrolled older adults from four communities in the United States from 1989 to 1990, was employed to investigate the existence of an association between AMD and CRP levels in this population. Fundus photographs from 1997 and 1998 were used to identify individuals with (n=390) and without AMD (n=2365). The association between AMD and CRP levels (measured at baseline) was compared, adjusting for the potentially confounding effect of demographic, lifestyle, and health related characteristics.

RESULTS

Among the 2755 CHS participants with gradable fundus photographs, 390 were identified as having AMD. Overall, median CRP levels among those with AMD (1.76 mg/l) were similar to those without AMD (1.77 mg/l). CRP levels were categorised into quartiles and compared between those with and without AMD. Relative to those in the lowest quartile (0.07-0.93 mg/l), the odds ratios (OR) in the higher quartiles, adjusted for demographic, lifestyle, and health related characteristics were increased but not statistically significant (0.94-1.77 mg/l: OR=1.14, 95% CI 0.82 to 1.60; 1.78-3.04 mg/l: OR=1.24, 95% CI 0.88 to 1.75; >3.04 mg/l: OR=1.24, 95% CI 0.87 to 1.78).

CONCLUSIONS

In the CHS, there is no evidence that CRP levels are associated with AMD. These data do not support the theory alleging non-specific systemic inflammation in the aetiology and natural history of this disease.

Exposure to hypoxia produces long-lasting sympathetic activation in humans

The relative contributions of hypoxia and hypercapnia in causing persistent sympathoexcitation after exposure to the combined stimuli were assessed in nine healthy human subjects during wakefulness. Subjects were exposed to 20 min of isocapnic hypoxia (arterial O(2) saturation, 77-87%) and 20 min of normoxic hypercapnia (end-tidal P(CO)(2), +5.3-8.6 Torr above eupnea) in random order on 2 separate days. The intensities of the chemical stimuli were manipulated in such a way that the two exposures increased sympathetic burst frequency by the same amount (hypoxia: 167 +/- 29% of baseline; hypercapnia: 171 +/- 23% of baseline). Minute ventilation increased to the same extent during the first 5 min of the exposures (hypoxia: +4.4 +/- 1.5 l/min; hypercapnia: +5.8 +/- 1.7 l/min) but declined with continued exposure to hypoxia and increased progressively during exposure to hypercapnia. Sympathetic activity returned to baseline soon after cessation of the hypercapnic stimulus. In contrast, sympathetic activity remained above baseline after withdrawal of the hypoxic stimulus, even though blood gases had normalized and ventilation returned to baseline levels. Consequently, during the recovery period, sympathetic burst frequency was higher in the hypoxia vs. the hypercapnia trial (166 +/- 21 vs. 104 +/- 15% of baseline in the last 5 min of a 20-min recovery period). We conclude that both hypoxia and hypercapnia cause substantial increases in sympathetic outflow to skeletal muscle. Hypercapnia-evoked sympathetic activation is short-lived, whereas hypoxia-induced sympathetic activation outlasts the chemical stimulus.

Effect of hypoxia on the hypopnoeic and apnoeic threshold for CO(2) in sleeping humans

1. Rhythmic breathing during sleep requires that P(CO2) be maintained above a sensitive hypocapnic apnoeic threshold. Hypoxia causes periodic breathing during sleep that can be prevented or eliminated with supplemental CO(2). The purpose of this study was to determine the effect of hypoxia in changing the difference between the eupnoeic P(CO2) and the P(CO2) required to produce hypopnoea or apnoea (hypopnoea/apnoeic threshold) in sleeping humans. 2. The effect of hypoxia on eupnoeic end-tidal partial pressure of CO(2) (P(ET,CO2)) and hypopnoea/apnoeic threshold P(ET,CO2) was examined in seven healthy, sleeping human subjects. A bilevel pressure support ventilator in a spontaneous mode was used to reduce P(ET,CO2) in small decrements by increasing the inspiratory pressure level by 2 cmH2O every 2 min until hypopnoea (failure to trigger the ventilator) or apnoea (no breathing effort) occurred. Multiple trials were performed during both normoxia and hypoxia (arterial O(2) saturation, S(a,O2) = 80 %) in a random order. The hypopnoea/apnoeic threshold was determined by averaging P(ET,CO2) of the last three breaths prior to each hypopnoea or apnoea. 3. Hypopnoeas and apnoeas were induced in all subjects during both normoxia and hypoxia. Hypoxia reduced the eupnoeic P(ET,CO2) compared to normoxia (42.4 +/- 1.3 vs. 45.0 +/- 1.1 mmHg, P < 0.001). However, no change was observed in either the hypopnoeic threshold P(ET,CO2) (42.1 +/- 1.4 vs. 43.0 +/- 1.2 mmHg, P > 0.05) or the apnoeic threshold P(ET,CO2) (41.3 +/- 1.2 vs. 41.6 +/- 1.0 mmHg, P > 0.05). Thus, the difference in P(ET,CO2) between the eupnoeic and threshold levels was much smaller during hypoxia than during normoxia (-0.2 +/- 0.2 vs. -2.0 +/- 0.3 mmHg, P < 0.01 for the hypopnoea threshold and -1.1 +/- 0.2 vs. -3.4 +/- 0.3 mmHg, P < 0.01 for the apnoeic threshold). We concluded that hypoxia causes a narrowing of the difference between the baseline P(ET,CO2) and the hypopnoea/apnoeic threshold P(ET,CO2), which could increase the likelihood of ventilatory instability.

[Influence of calcium carbonate on the microstructure of bovine serum albumin]

The influence of calcium carbonate on the microstructure of bovine serum albumin (BSA) in aqueous solution was studied by ultraviolet spectrum and ultraviolet second order derivative spectrum and Fourier transform infrared spectrum. The results showed the changes of the microenvironment of the aromatic amino acid residues and secondary structure of BSA. It was the changes that provided a favorable condition for biomineral formation.

Formation of a new buried charge drives a large-amplitude protein quake in photoreceptor activation

Photoactive yellow protein (PYP) is a eubacterial photoreceptor and a structural prototype of the PAS domain superfamily of receptor and regulatory proteins. We investigate the activation mechanism of PYP using time-resolved Fourier transform infrared (FTIR) spectroscopy. Our data provide structural, kinetic, and energetic evidence that the putative signaling state of PYP is formed during a large-amplitude protein quake that is driven by the formation of a new buried charge, COO(-) of the conserved Glu46, in a highly hydrophobic pocket at the active site. A protein quake is a process consisting of global conformational changes that are triggered and driven by a local structural "fault". We show that large, global structural changes take place after Glu46 ionization via intramolecular proton transfer to the anionic p-coumarate chromophore, and are suppressed by the absence of COO(-) formation in the E46Q mutant. Our results demonstrate the significance of buried charge formation in photoreceptor activation. This mechanism may serve as one of the general themes in activation of a range of receptor proteins. In addition, we report the results of time-resolved FTIR spectroscopy of PYP crystals. The direct comparison of time-resolved FTIR spectroscopic data of PYP in aqueous solution and in crystals reveals that the structure of the putative signaling state is not developed in P6(3) crystals. Therefore, when the structural developments during the functional process of a protein are experimentally determined to be very different in crystals and solutions, one must be cautious in drawing conclusions regarding the functional mechanism of proteins based on time-resolved X-ray crystallography.

[Study on the formation mechanism of soluble complexes containing bovine serum albumin and calcium hydroxyapatite and calcium carbonate]

Fourier transform infrared spectroscopy was used to study the composition and microstructure of soluble complexes produced by different initial mole ratios of bovine serum albumin(BSA) and calcium hydroxyapatite [Ca10(OH)2(PO4)6] and calcium carbonate (CaCO3) in aqueous solution. The band shifts and intensity variations suggested that calcium complexes with multiple ligands such as BSA, apatite, carbonate as well as the hydrogen bond network formed in titled system. The interactions increased the solubility of Ca10 (OH)2(PO4)6 and CaCO3 and the composition of soluble complexes is nonstoichiometric. The results provided an ideal model to investigated biomineralization process.

NMR structure of the N-terminal J domain of murine polyomavirus T antigens. Implications for DnaJ-like domains and for mutations of T antigens

The NMR structure of the N-terminal, DnaJ-like domain of murine polyomavirus tumor antigens (PyJ) has been determined to high precision, with root mean square deviations to the mean structure of 0.38 A for backbone atoms and 0.94 A for all heavy atoms of ordered residues 5-41 and 50-69. PyJ possesses a three-helix fold, in which anti-parallel helices II and III are bridged by helix I, similar to the four-helix fold of the J domains of DnaJ and human DnaJ-1. PyJ differs significantly in the lengths of N terminus, helix I, and helix III. The universally conserved HPD motif appears to form a His-Pro C-cap of helix II. Helix I features a stabilizing Schellman C-cap that is probably conserved universally among J domains. On the helix II surface where positive charges of other J domains have been implicated in binding of hsp70s, PyJ contains glutamine residues. Nonetheless, chimeras that replace the J domain of DnaJ with PyJ function like wild-type DnaJ in promoting growth of Escherichia coli. This activity can be modulated by mutations of at least one of these glutamines. T antigen mutations reported to impair cellular transformation by the virus, presumably via interactions with PP2A, cluster in the hydrophobic folding core and at the extreme N terminus, remote from the HPD loop.

[The blocking effects of extracellular Mn2+ on the inward rectifier potassium channel (IRK1)]

AIM AND METHODS

Two-microelectrode voltage clamp (TEV) method was used to study the blocking effects of extracellular Mn2+ on the inward rectifier potassium channel (IRK1) expressed in the Xenopus oocytes.

RESULTS

Mn2+ can concentration-, time- and vol-tage dependently block IRK1 instantaneous currents (2 ms after voltage applied). Mn2+ has almost no effect on the gating property of IRK1. IRK1 can not permeate Mn2+ because reverse potential did not changed. External Mn2+ can inhibit IRK1 macroscopic currents more powerfully when external Mn2+ concentration is lower and external Mn2+ can increases standard chord conductance of IRK1.

CONCLUSION

External Mn2+ works through surface potential mechanism. Ba2+ is considered as one fast open channel blocker of IRK1 and three exponential fitting results indicates that external Mn2+ can compete with Ba2+ in the same binding site in IRK1 when external Ba2+ concentration is 30 mumol/L. These mean two different mechanisms about external Mn2+ blocking exist.

Neurocirculatory consequences of intermittent asphyxia in humans

We examined the neurocirculatory and ventilatory responses to intermittent asphyxia (arterial O(2) saturation = 79-85%, end-tidal PCO(2) =3-5 Torr above eupnea) in seven healthy humans during wakefulness. The intermittent asphyxia intervention consisted of 20-s asphyxic exposures alternating with 40-s periods of room-air breathing for a total of 20 min. Minute ventilation increased during the intermittent asphyxia period (14.2 +/- 2.0 l/min in the final 5 min of asphyxia vs. 7.5 +/- 0.4 l/min in baseline) but returned to the baseline level within 2 min after completion of the series of asphyxic exposures. Muscle sympathetic nerve activity increased progressively, reaching 175 +/- 12% of baseline in the final 5 min of the intervention. Unlike ventilation, sympathetic activity remained elevated for at least 20 min after removal of the chemical stimuli (150 +/- 10% of baseline in the last 5 min of the recovery period). Intermittent asphyxia caused a small, but statistically significant, increase in heart rate (64 +/- 4 beats/min in the final 5 min of asphyxia vs. 61 +/- 4 beats/min in baseline); however, this increase was not sustained after the return to room-air breathing. These data demonstrate that relatively short-term exposure to intermittent asphyxia causes sympathetic activation that persists after removal of the chemical stimuli. This carryover effect provides a potential mechanism whereby intermittent asphyxia during sleep could lead to chronic sympathetic activation in patients with sleep apnea syndrome.

Long-lived amide I vibrational modes in myoglobin

Pump-probe experiments in the infrared measure vibrational relaxation rates. Myoglobin, which is almost entirely alpha helix in secondary structure, has an unusually long, nonexponential excited state relaxation generated by optically pumping at the blue side ( 5. 85 microm) of the amide I band. The amino acid alanine and the predominantly beta sheet protein photoactive yellow protein do not have such a long-lived state, suggesting that the alpha helix in proteins can support nonlinear states of 15 ps characteristic times.

Bispectrum analysis of focal ischemic cerebral EEG signal using third-order recursion method

In this paper, a model for Sprague-Dawley (SD) rat focal ischemic cerebral injury is presented. Based on this experimental model, the electroencephalogram (EEG) from the ischemic region and from a normal region are collected during the first 30 min of ischemia. The EEG bispectrum analysis is carefully investigated by using the third-order recursion method. We found that some characteristics of the bispectrum are very sensitive to focal ischemic cerebral injury. The maximum magnitude and the weighted center of EEG bispectrum (WCOB) change according to the extent and the place of the injury region. The bispectrum analysis results have been verified by the heat shock protein (HSP) test. The study indicates that the EEG bispectrum analysis may be useful to distinguish the ischemic region from the normal one and to estimate the ischemic extent.

[Blocking effects of extracellular Ba(2+) on the inward rectifier potassium channel]

Two-microelectrode voltage clamp (TEV) method was used to study the blocking effects of extracellular Ba(2+) on the inward rectifier potassium channel (IRK1) expressed in Xenopus oocytes. Blockage of Ba(2+) on IRK1 (1 ms after voltage applied) is Ba(2+) concentration (0,1,3,10 or 100 micromol/L) dependent with 10 or 90 mmol/L potassium and also voltage-dependent. Ba(2+) almost has no effect on the open/close of IRK1. IRK1 is not permeable to Ba(2+). Three exponential fitting analysis indicates that Ba(2+) and K(+) compete the same binding site in IRK1 when external Ba(2+) concentration is lower (1 or 3 micromol/L). The time constant of IRK1 does not increase, but the concentration dependency of the weights of the fittings increases with the increase of external Ba(2+) concentration. As a result, the inactivation becomes faster and faster as the external Ba(2+) concentration increases. Moreover, since the time constant of the channel decreases and the weights of the fittings concentration dependently increase with the increase of external Ba(2+) concentration (10 or 100 micromol/L), the inactivation becomes faster and faster. It is demonstrated that Ba(2+) can contact with deeper binding sites in IRK1 as external Ba(2+) concentration increases. It is suggested that two different mechanisms may underlie the external Ba(2+) blocking effect. External Mn(2+) or Mg(2+) can compete with external Ba(2+) at the IRK1 binding site at an external Ba(2+) concentration of 30 mol/L and K(+) concentration of 90 mmol/L. Inactivation becomes slower and slower and Ba(2+) is repelled from the IRK1 binding site when Mg(2+) or Mn(2+) con-centration is further increased. Mg(2+), but not Mn(2+), can contact with deeper binding sites of IRK1 to block the channel, suggesting that multiple-ion blockage may exist in IRK1.

Daytime blood pressure elevation after nocturnal hypoxia

The purpose of this study was to investigate whether nocturnal hypoxia causes daytime blood pressure (BP) elevation. We hypothesized that overnight exposure to hypoxia leads the next morning to elevation in BP that outlasts the hypoxia stimulus. We studied the effect on BP of two consecutive night exposures to hypobaric hypoxia in 10 healthy normotensive subjects. During the hypoxia nights, subjects slept for 8 h in a hypobaric chamber at a simulated altitude of 4,000 m (barometric pressure = 462 mmHg). Arterial O(2) saturation and electrocardiogram were monitored throughout the night. For 30 min before the nocturnal simulated ascent and for 4 h after return to baseline altitude the next morning, BP was measured every 5 min while the subject was awake. The same measurements were made before and after 2 normoxic nights of sleep in the hypobaric chamber at ambient barometric pressure (745 mmHg). Principal components analysis was applied to evaluate patterns of BP response after the second night of hypoxia and normoxia. A distinct pattern of diastolic BP (DBP) elevation was observed after the hypoxia night in 9 of the 10 subjects but in none after the normoxia night. This pattern showed a mean increase of 4 mmHg in DBP compared with the presleep-awake baseline in the first 60 min and a return to baseline by 90 min. We conclude that nocturnal hypoxia leads to a carryover elevation of daytime DBP.

Arousal from sleep shortens sympathetic burst latency in humans

1. Bursts of sympathetic activity in muscle nerves are phase-locked to the cardiac cycle by the sinoaortic baroreflexes. Acoustic arousal from non-rapid eye movement (NREM) sleep reduces the normally invariant interval between the R-wave of the electrocardiogram (ECG) and the peak of the corresponding sympathetic burst; however, the effects of other forms of sleep disruption (i.e. spontaneous arousals and apnoea-induced arousals) on this temporal relationship are unknown. 2. We simultaneously recorded muscle sympathetic nerve activity in the peroneal nerve (intraneural electrodes) and the ECG (surface electrodes) in seven healthy humans and three patients with sleep apnoea syndrome during NREM sleep. 3. In seven subjects, burst latencies were shortened subsequent to spontaneous K complexes (1.297 +/- 0.024 s, mean +/- s. e.m.) and spontaneous arousals (1.268 +/- 0.044 s) compared with latencies during periods of stable NREM sleep (1.369 +/- 0.023 s). In six subjects who demonstrated spontaneous apnoeas during sleep, apnoea per se did not alter burst latency relative to sleep with stable electroencephalogram (EEG) and breathing (1.313 +/- 0.038 vs. 1.342 +/- 0.026 s); however, following apnoea-induced EEG perturbations, burst latencies were reduced (1.214 +/- 0.034 s). 4. Arousal-induced reduction in sympathetic burst latency may reflect a temporary diminution of baroreflex buffering of sympathetic outflow. If so, the magnitude of arterial pressure perturbations during sleep (e.g. those caused by sleep disordered breathing and periodic leg movements) may be augmented by arousal.

Global conformational changes upon receptor stimulation in photoactive yellow protein

Biological signal transduction starts with the activation of a receptor protein. Two central questions in signaling are the mechanism of activation by a stimulus and the nature and extent of the protein conformational changes involved. We report extensive evidence for the occurrence of large structural changes upon the light activation of photoactive yellow protein (PYP), a eubacterial photosensor. Absorption of a blue photon by the p-coumaric acid (pCA) chromophore in pG, the initial state of PYP, results in the formation of pB, a putative signaling state. In the presence of an adequate hydration shell, large structural changes in the protein backbone, involving both solvent accessible and core regions, were detected using Fourier transform infrared (FTIR) difference spectroscopy. A significant part (23%) of the amide groups which are buried in pG become exposed to the solvent in pB, as measured through light-induced H/D exchange, using both electrospray ionization mass spectrometry and FTIR spectroscopy. Exposure of previously buried hydrophobic sites would lead to an increase in heat capacity during pB formation and a decrease in heat capacity during pB decay. Thermodynamic studies indeed show that the heat capacity change of pB activation is -2.35 +/- 0.08 kJ/(mol/K), independent of pH from pH 2.4-7.5. A model for photoactivation of PYP is proposed, which provides a framework for a deeper understanding of receptor activation in general.

Characterization of the photoconversion of green fluorescent protein with FTIR spectroscopy

Green Fluorescent Protein (GFP) is a bioluminescence protein from the jelly fish Aequorea victoria. It can exist in at least two spectroscopically distinct states: GFP395 and GFP480, with peak absorption at 395 and 480 nm, respectively, presumably resulting from a change in the protonation state of the phenolic ring of its chromophore. When GFP is formed upon heterologous expression in Escherichia coli, its chromophore is mainly present as the neutral species. UV and visible light convert (the chromophore of) GFP quantitatively from this neutral- into the anionic form. On the basis of X-ray diffraction, it was recently proposed (Brejc, K. et al. (1997) Proc. Natl. Acad. Sci. USA 94, 2306-2311; Palm, G. J. et al. (1997) Nat. Struct. Biol. 4, 361-365) that the carboxylic group of Glu222 functions as the proton acceptor of the chromophore of GFP, during the transition from the neutral form (i.e., GFP395) to the ionized form (GFP480). However, X-ray crystallography cannot detect protons directly. The results of FTIR difference spectroscopy, in contrast, are highly sensitive to changes in the protonation state between two conformations of a protein. Here we report the first characterization of GFP, and its photoconversion, with FTIR spectroscopy. Our results clearly show the change in protonation state of the chromophore upon photoconversion. However, they do not provide indications for a change of the protonation state of a glutamate side chain between the states GFP395 and GFP480, nor for an isomerization of the double bond that forms part of the link between the two rings of the chromophore.

[The influences of TBP on the partially saponified DMHPA-heptane systems and the extracted organic phases containing rare earth]

The aggregation states of partially saponified [di-(1-methylheptyl) phosphoric acid] (DMHPA)-tributyl phosphate (TBP) heptane (C7H16) and the extracted organic phases containing rare earth were studied. The result demonstrates that TBP can widen the range of the microemulsion formation in DMHPA-C7H16-NaOH-H2O systems. It also influence the states of the extracted organic phases of DMHPA-RE (III) and the behavior of water clearly. The gel could be formed in DMHPA-TBP-RE (III) systems under proper conditions. FT-IR spectra analysis shows that both DMHPA and TBP may coordinate with RE3+ and the hydrogen bonds of TBP with DMHPA and H2O contribute to the three dimensional network structure of the gels.

Neural mechanism of the pressor response to obstructive and nonobstructive apnea

Obstructive and nonobstructive apneas elicit substantial increases in muscle sympathetic nerve activity and arterial pressure. The time course of change in these variables suggests a causal relationship; however, mechanical influences, such as release of negative intrathoracic pressure and reinflation of the lungs, are potential contributors to the arterial pressure rise. To test the hypothesis that apnea-induced pressor responses are neurally mediated, we measured arterial pressure (photoelectric plethysmography), muscle sympathetic nerve activity (peroneal microneurography), arterial O2 saturation (pulse oximeter), and end-tidal CO2 tension (gas analyzer) during sustained Mueller maneuvers, intermittent Mueller maneuvers, and simple breath holds in six healthy humans before, during, and after ganglionic blockade with trimethaphan (3-4 mg/min, titrated to produce complete disappearance of sympathetic bursts from the neurogram). Ganglionic blockade abolished the pressor responses to sustained and intermittent Mueller maneuvers (-4 +/- 1 vs. +15 +/- 3 and 0 +/- 2 vs. +15 +/- 5 mmHg) and breath holds (0 +/- 3 vs. +11 +/- 3, all P < 0.05). We conclude that the acute pressor response to obstructive and nonobstructive voluntary apnea is sympathetically mediated.

[Study on the properties and microstructure of the gel in the extracted organic phase containing DMHPA-RE(III)]

The content of Na+, RE3+ and the swelling characteristic of dried gel containing DMHPA[di-(1-methylheptyl)phosphoric acid]-RE(III) have been studied by FTIR and ICP/AES spectroscopy methods. The result demonstrates that (1) the mechanism of microemulsion extracting lanthanide ions is complicated and it is difficult to be explained with simple chemical equations, (2) The dried gel can swell, but the aggregation states and microstructure change as the used solvents and its content vary, (3) The far infrared spectroscopy shows that there are ring structures in the gel and differences of the ability in coordination with DMHPA between light and heavy lanthanide ions.

[Study on FTIR spectra of HDEHP and DMHPA in different states]

FTIR spectra of pure di (2-ethylhexyl) phosphoric acid (HDEHP), di (1-methylheptyl) phosphoric acid (DMHPA) and their sodium salts, microemulsions, extracted organic phases containing rare earth were studied. It was seen that the microstructures of the two extractants changed with their different alkyl structures and aggregation states.

Effects of inhaled CO2 and added dead space on idiopathic central sleep apnea

We hypothesized that reductions in arterial PCO2 (PaCO2) below the apnea threshold play a key role in the pathogenesis of idiopathic central sleep apnea syndrome (ICSAS). If so, we reasoned that raising PaCO2 would abolish apneas in these patients. Accordingly, patients with ICSAS were studied overnight on four occasions during which the fraction of end-tidal CO2 and transcutaneous PCO2 were measured: during room air breathing (N1), alternating room air and CO2 breathing (N2), CO2 breathing all night (N3), and addition of dead space via a face mask all night (N4). Central apneas were invariably preceded by reductions in fraction of end-tidal CO2. Both administration of a CO2-enriched gas mixture and addition of dead space induced 1- to 3-Torr increases in transcutaneous PCO2, which virtually eliminated apneas and hypopneas; they decreased from 43.7 +/- 7.3 apneas and hypopneas/h on N1 to 5.8 +/- 0.9 apneas and hypopneas/h during N3 (P < 0.005), from 43.8 +/- 6.9 apneas and hypopneas/h during room air breathing to 5.9 +/- 2.5 apneas and hypopneas/h of sleep during CO2 inhalation during N2 (P < 0.01), and to 11.6% of the room air level while the patients were breathing through added dead space during N4 (P < 0.005). Because raising PaCO2 through two different means virtually eliminated central sleep apneas, we conclude that central apneas during sleep in ICSA are due to reductions in PaCO2 below the apnea threshold.

Glu46 donates a proton to the 4-hydroxycinnamate anion chromophore during the photocycle of photoactive yellow protein

Photoactive yellow protein (PYP) is a photoreceptor containing a unique 4-hydroxycinnamic acid (pCA) chromophore. The trans to cis photoisomerization of this chromophore activates a photocycle involving first a short-lived red-shifted intermediate (pR), then a long-lived blue-shifted intermediate (pB), and finally recovery of the original receptor state (pG). The pCA chromophore is deprotonated in pG and protonated in pB, but the proton donor for this process has not yet been identified. Here we report the first FTIR spectroscopic data on pG, pR, and pB. The IR difference signals in the carbonyl stretching region of COOH groups (1700-1800 cm-1) reveal that a buried carboxylic group close to the chromophore (i) is protonated in pG, (ii) develops a stronger hydrogen bonding in pR, and (iii) becomes deprotonated in pB. These signals are unambiguously assigned to Glu46, on the basis of the IR data and the 1.4 A X-ray structure of PYP [Borgstahl et al. (1995) Biochemistry 34, 6278-6287]. Our data demonstrate that in pR Glu46 remains in hydrogen bonding contact with the negatively charged phenolic oxygen of pCA after chromophore photoisomerization. This strongly implies that the chromophore is isomerized to the 7-cis 9-s-trans conformation in pR, resulting from co-isomerization of both the C7 = C8 and C9-C10 bonds. In the pR to pB transition, Glu46 becomes deprotonated, concomitant with chromophore protonation. Therefore, we conclude that Glu46 functions as the proton donor for the protonation of pCA during the PYP photocycle. We propose a molecular mechanism in which intramolecular proton transfer in PYP leads to global protein conformational changes involved in signal transduction.

Cycle length of periodic breathing in patients with and without heart failure

Because apnea length during periodic breathing varies according to the preceding increase in ventilation and reduction in PaCO 2, differences in the cycle length of periodic breathing among patients with normal and impaired cardiac function might be explained by the influence of lung-to-carotid body circulatory delay, as reflected by lung-to-ear circulation time (LECT), on hyperpnea length rather than on apnea length. It was therefore hypothesized that circulatory delay is an important determinant of periodic-breathing hyperpnea length but not apnea length. To test this hypothesis, LECT, periodic-breathing cycle length, apnea length, and hyperpnea length were compared in 10 patients with idiopathic central sleep apnea (ICSA), whose cardiac function was normal, as opposed to 10 with Cheyne-Stokes respiration and central sleep apnea (CSR-CSA) in association with congestive heart failure (CHF). As compared with ICSA patients, cycle length was significantly longer in patients with CSR-CSA (37.3 +/- 3.0 s versus 59.0 +/- 4.9 s, p < 0.005). This difference was due to significantly longer hyperpnea length in the CSR-CSA patients (16.7 +/- 2.8 s versus 36.7 +/- 3.4 s, p < 0.001), since apnea length was similar in the two groups. In addition, LECT was longer in the CSR-CSA patients (24.3 +/- 2.0 s versus 10.3 +/- 1.0 s, p < 0.001), and correlated strongly with cycle length (r = 0.88, p < 0.001) and hyperpnea length (r = 0.90, p < 0.001) but not with apnea length. LECT correlated inversely with cardiac output (r = -0.72, p < 0.006), indicating that LECT is a valid measure of circulatory delay. Thus, circulatory delay is an important determinant of hyperpnea length but not of apnea length in patients with ICSA and CSR-CSA.

Hypocapnia and increased ventilatory responsiveness in patients with idiopathic central sleep apnea

We previously demonstrated that central apneas during sleep in patients with idiopathic central sleep apnea (ICSA) are triggered by abrupt hyperventilation. In addition, baseline PCO2 at the time of augmented breaths which triggered central apneas was lower than for augmented breaths which did not trigger apneas. These observations led us to hypothesize that patients with ICSA chronically hyperventilate maintaining their PCO2 close to the threshold for apnea during sleep owing to increased chemical respiratory drive. To test these hypotheses, we recorded transcutaneous PCO2 (PtcCO2) during overnight sleep studies on nine consecutive patients with ICSA and nine sex-, age-, and body-mass-index-matched control subjects. Daytime PaCO2 as well as rebreathing and single breath ventilatory responses to CO2 were also measured. Compared with the control subjects, the patients had significantly lower mean PtcCO2 during sleep (37.8 +/- 1.2 versus 42.7 +/- 10.9 mm Hg, p < 0.01) and lower PaCO2 while awake (35.1 +/- 1.3 versus 38.8 +/- 0.9 mm Hg, p < 0.05). Furthermore, patients with ICSA had significantly higher ventilatory responses to CO2 for both the rebreathing (3.14 +/- 0.34 versus 1.60 +/- 0.32 L/min/mm Hg, p < 0.005) and single breath methods (0.51 +/- 0.10 versus 0.25 +/- 0.04 L/min/mm Hg, p < 0.05). We conclude that: (1) patients with ICSA chronically hyperventilate awake and asleep and (2) chronic hyperventilation is probably related to augmented central and peripheral respiratory drive which predisposes to respiratory control system instability.

Interaction of hyperventilation and arousal in the pathogenesis of idiopathic central sleep apnea

Central apneas during sleep may arise as a result of reduction in PaCO2 below the apnea threshold. We therefore hypothesized that hyperventilation and arousals from sleep interact to cause hypocapnia and subsequent central apneas in patients with idiopathic central sleep apnea (ICSA). Accordingly, the relationships among preapneic ventilation, arousal from sleep, and the onset and duration of subsequent central apneas were examined during Stage 2 non-REM sleep in eight patients with ICSA (mean +/- SEM, 45.4 +/- 4.7 central apneas and hypopneas/h of sleep). During Stage 2 sleep, all episodes of periodic breathing with central apneas were triggered by hyperventilation. Minute ventilation (VI) was greater (6.3 +/- 0.7 versus 5.4 +/- 0.8 L/min, p < 0.05) and mean transcutaneous PCO2 (PtcCO2) was lower (37.8 +/- 1.3 versus 38.9 +/- 1.6 mm Hg, p < 0.05) during periodic breathing than during stable breathing. VI during the ventilatory phase of the periodic breathing cycle increased progressively with increasing grades of associated arousals from Grade 0 (no arousal) (10.3 +/- 1.4 L/min) to Grade 1 (EEG arousal) (12.6 +/- 1.6 L/min) to Grade 2 (movement arousal) (14.1 +/- 1.6 L/min, p < 0.01). There was a corresponding progressive increase in central apnea length following the ventilatory period from no arousal (14.1 +/- 2.0) to EEG arousal (16.4 +/- 1.8) to movement arousal (18.1 +/- 2.0 s, p < 0.01). We conclude that arousals and hyperventilation interact to trigger hypocapnia and central apneas in ICSA.