Crowded, cell-like environment induces shape changes in aspherical protein

How the crowded environment inside cells affects the structures of proteins with aspherical shapes is a vital question because many proteins and protein–protein complexes in vivo adopt anisotropic shapes. Here we address this question by combining computational and experimental studies of a football-shaped protein (i.e., Borrelia burgdorferi VlsE) in crowded, cell-like conditions. The results show that macromolecular crowding affects protein-folding dynamics as well as overall protein shape. In crowded milieus, distinct conformational changes in VlsE are accompanied by secondary structure alterations that lead to exposure of a hidden antigenic region. Our work demonstrates the malleability of “native” proteins and implies that crowding-induced shape changes may be important for protein function and malfunction in vivo.     

Niche adaptation and genome expansion in the chlorophyll d-producing cyanobacterium Acaryochloris marina

Acaryochloris marina is a unique cyanobacterium that is able to produce chlorophyll d as its primary photosynthetic pigment and thus efficiently use far-red light for photosynthesis. Acaryochloris species have been isolated from marine environments in association with other oxygenic phototrophs, which may have driven the niche-filling introduction of chlorophyll d. To investigate these unique adaptations, we have sequenced the complete genome of A. marina. The DNA content of A. marina is composed of 8.3 million base pairs, which is among the largest bacterial genomes sequenced thus far. This large array of genomic data is distributed into nine single-copy plasmids that code for >25% of the putative ORFs. Heavy duplication of genes related to DNA repair and recombination (primarily recA) and transposable elements could account for genetic mobility and genome expansion. We discuss points of interest for the biosynthesis of the unusual pigments chlorophyll d and α-carotene and genes responsible for previously studied phycobilin aggregates. Our analysis also reveals that A. marina carries a unique complement of genes for these phycobiliproteins in relation to those coding for antenna proteins related to those in Prochlorococcus species. The global replacement of major photosynthetic pigments appears to have incurred only minimal specializations in reaction center proteins to accommodate these alternate pigments. These features clearly show that the genus Acaryochloris is a fitting candidate for understanding genome expansion, gene acquisition, ecological adaptation, and photosystem modification in the cyanobacteria.     

Differential association of retinal arteriolar and venular caliber with diabetes and retinopathy

Aims

To describe the relationship of retinal arteriolar and venular caliber with diabetes, retinopathy and hyperglycemia, in an Asian Indian population.

Methods

This was a population-based cross-sectional study of 3400 (75.6% response rate) Singapore ethnic Indians aged 40-80 years. Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were obtained using a validated computer-assisted program. Diabetes mellitus was identified using standardized criteria. Diabetic retinopathy was graded based on the modified Airlie House Classification System.

Results

There were 980 (32.2%) participants with diabetes. Of these, 327 (33.4%) had diabetic retinopathy. After multivariate adjustment, diabetic persons had a wider CRAE (145.23 μm vs 142.38 μm, P < 0.001). This relationship was stronger in persons without hyperlipidemia (P-interaction < 0.1). Among diabetic participants, wider CRVE was related to increasing severity of retinopathy (P for trend < 0.05) and this association may be altered by hypertensive status. Retinal arteriolar caliber widened with increasing glucose (P < 0.001) and HbA1C (P < 0.001) levels.

Conclusions

In Indian adults, wider retinal arteriolar caliber is associated with diabetes and hyperglycemia, while wider retinal venular caliber is associated with diabetic retinopathy. This is consistent with white populations and confirms the differential systemic association of retinal vascular caliber in Asian Indians.     

Aging well socially through engagement with life: adapting Rowe and Kahn's model of successful aging to Chinese cultural context

Although aging well socially (engagement with life) is as important as aging well personally (illness avoidance and functioning) (Rowe & Kahn, 1998), it has received less research attention. A caring (CE) and a productive (PE) form of engagement were derived from an analysis of Chinese cultural meanings of engagement, and combined with illness avoidance and functioning to form a 4-factor model. Confirmatory factor analysis based on 2970 Hong Kong Chinese (40 to 74 years) showed a good model fit that was replicated a year later with 2120 of the original sample. Further analysis led to a more parsimonious model where illness avoidance and functioning converged into a single second-order factor whereas CE and PE remained as distinct first-order factors. The results supported the differentiation of Rowe and Kahn's engagement with life component into caring and productive engagements.     

The effects of changes in loading conditions and modulation of inotropic state on the myocardial performance index: comparison with conductance catheter measurements.

AIM: The myocardial performance index (MPI), or Tei index, has been shown to be useful in the assessment of global myocardial performance. There are few invasive data however, which examine its load dependence or sensitivity to acute changes in contractile function. The purpose of this study was therefore to study formally the effect of clinically relevant changes in these parameters in an animal model. METHODS AND RESULTS: We examined 10 Yorkshire pigs using echocardiographic assessment and simultaneous measurements of intraventricular pressure and volume by conductance catheterization. With dobutamine infusion, there was no significant change in the MPI (0.26+/-0.13-0.22+/-0.11; p=0.42), but dP/dtmax increased significantly (1001+/-240-1569+/-532 mm Hg/s, p<0.001). Afterload increase (40% change in ventricular pressure) and preload reduction (20% change in ventricular volume) were associated with significant increases in the MPI (0.26+/-0.13-0.49+/-0.20; p<0.005 and 0.26+/-0.13-0.51+/-0.20; p<0.001, respectively) without any significant change in maximal elastance (Ees). CONCLUSIONS: The MPI, or Tei index, is significantly affected by acute changes in loading conditions but is unable to consistently detect acute changes in contractile function.     

Detection of inadvertent catheter movement into a pulmonary vein during radiofrequency catheter ablation by real-time impedance monitoring

Introduction: During radiofrequency ablation to encircle or isolate the pulmonary veins (PVs), applications of radiofrequency energy within a PV may result in stenosis. The aim of this study was to determine whether monitoring of real-time impedance facilitates detection of inadvertent catheter movement into a PV.
Methods and Results: In 30 consecutive patients (mean age 53 ± 11 years) who underwent a left atrial ablation procedure, the three-dimensional geometry of the left atrium, the PVs, and their ostia were reconstructed using an electroanatomic mapping system. The PV ostia were identified based on venography, changes in electrogram morphology, and manual and fluoroscopic feedback as the catheter was withdrawn from the PV into the left atrium. Real-time impedance was measured at the ostium, inside the PV at approximately 1 and 3 cm from the ostium, in the left atrial appendage, and at the posterior left atrial wall. There was an impedance gradient from the distal PV (127 ± 30 Ω) to the proximal PV (108 ± 15 Ω) to the ostium (98 ± 11 Ω) in each PV (P < 0.01). There was no significant impedance difference between the ostial and left atrial sites. During applications of radiofrequency energy, movement of the ablation catheter into a PV was accurately detected in 80% of the cases (20) when there was an abrupt increase of ≥4 Ω in real-time impedance.
Conclusion: There is a significant impedance gradient from the distal PV to the left atrium. Continuous monitoring of the real-time impedance facilitates detection of inadvertent catheter movement into a PV during applications of radiofrequency energy. (J Cardiovasc Electrophysiol, Vol. 15, pp. 1-5, June 2004)     

Effectiveness of noninvasive positive pressure ventilation in the treatment of acute respiratory failure in severe acute respiratory syndrome

OBJECTIVES: To study the effectiveness of noninvasive positive pressure ventilation (NIPPV) in the treatment of acute respiratory failure (ARF) in severe acute respiratory syndrome (SARS), and the associated infection risk. METHODS: All patients with the diagnosis of probable SARS admitted to a regional hospital in Hong Kong from March 9 to April 28, 2003, and who had SARS-related respiratory distress complications were recruited for NIPPV usage. The health status of all health-care workers working in the NIPPV wards was closely monitored, and consent was obtained to check serum for coronavirus serology. Patient outcomes and the risk of SARS transmission to health-care workers were assessed. RESULTS: NIPPV was applied to 20 patients (11 male patients) with ARF secondary to SARS. Mean age was 51.4 years, and mean acute physiology and chronic health evaluation II score was 5.35. Coronavirus serology was positive in 95% (19 of 20 patients). NIPPV was started 9.6 days (mean) from symptom onset, and mean duration of NIPPV usage was 84.3 h. Endotracheal intubation was avoided in 14 patients (70%), in whom the length of ICU stay was shorter (3.1 days vs 21.3 days, p < 0.001) and the chest radiography score within 24 h of NIPPV was lower (15.1 vs 22.5, p = 0.005) compared to intubated patients. Intubation avoidance was predicted by a marked reduction in respiratory rate (9.2 breaths/min) and supplemental oxygen requirement (3.1 L/min) within 24 h of NIPPV. Complications were few and reversible. There were no infections among the 105 health-care workers caring for the patients receiving NIPPV. CONCLUSIONS: NIPPV was effective in the treatment of ARF in the patients with SARS studied, and its use was safe for health-care workers.     

Twenty-four-hour ambulatory BP in snoring children with obstructive sleep apnea syndrome

INTRODUCTION: Obstructive sleep apnea syndrome (OSAS) is a known risk factor for hypertension in adults. This relationship is less clear in childhood OSAS. OBJECTIVE: This study examined the relationship between OSAS and 24-h ambulatory BP (ABP), a more accurate assessment than casual BP, in children with snoring. METHODS: Snoring children aged 6 to 15 years who underwent polysomnography in the sleep laboratory were recruited. Measurement: Twenty-four-hour ABP monitoring was initiated a few hours before polysomnography. The children were classified into two groups: a high apnea-hypopnea index (AHI) group (obstructive AHI > 5/h), and a low-AHI group (AHI < or = 5/h). Mean sleep, wake, and 24-h systolic BP (SBP) and diastolic BP (DBP) were recorded. A child was considered a "nondipper" if his or her mean SBP and DBP did not decrease by >/= 10% during sleep. RESULTS: Ninety-six children (mean age +/- SD, 9.4 +/- 2.8 years) were recruited. Forty-one children were obese. When awake, the high-AHI group children had a significantly higher SBP. When asleep, both SBP and DBP were higher in the high-AHI group. Age, body mass index (BMI) z score, and desaturation index (DI) were significant predictors for elevated sleep DBP. BMI z score was the only significant predictor for wake and sleep SBP. Sixteen children (17%) had hypertension, and all were nondippers. Obese children in the high-AHI group had a significantly higher prevalence of hypertension than obese children in the low-AHI group. This relationship was not found in nonobese children. CONCLUSION: The current study shows that increased DI contributed to the elevation of sleep DBP elevation.     

Chemical cleaning of titanium tray for reconstructive surgery

AIMS: To find out the extent of chemical contamination on the surface of titanium wrought mesh before and after swaging, and to assess the effectiveness of cleaning off these contaminants by various chemical methods. MATERIALS AND METHODS: Qualitative analysis of the surfaces of 6 wrought titanium meshes by scanning electron microscopy (EM) and radiological microanalyser. One of these meshes was subjected to experimental cleaning by different methods. Qualitative chemical analysis of 20 titanium trays fabricated for clinical use before and after acid cleansing. RESULTS: All 6 titanium meshes had surface contaminants, with silicon being the most common. The effective cleaning methods were chemical cleaning with Titaclean, mechanical trimming, or polishing with diamond paste. The 20 swaged titanium trays were effectively cleaned with either Titaclean or Chemi-Polish solution. CONCLUSION: Previously unknown surface contamination was common on wrought titanium mesh. Ultrasonic cleansing with Titaclean or Chemi-Polish effectively removed most of the contaminants on the titanium trays before they were implanted.