A review of quantification methods for light absorption enhancement of black carbon aerosol

Black carbon (BC) is a distinct type of carbonaceous aerosol that has a significant impact on the environment, human health, and climate. A non-BC material coating on BC can alter the mixing state of the BC particles, which considerably enhances the mass absorption efficiency of BC by directing more energy toward the BC cores (lensing effect). A lot of methods have been reported for quantifying the enhancement factor (Eabs), with diverse results. However, to the best of our knowledge, a comprehensive review specific to the quantification methods for Eabs has not been systematically performed, which is unfavorable for the evaluation of obtained results and subsequent radiative forcing. In this review, quantification methods are divided into two broad categories, direct and indirect, depending on whether experimental removal of the coating layer from an aged carbonaceous particle is required. The direct methods described include thermal peeling, solvent dissolution, and optical virtual exfoliation, while the indirect methods include intercept-linear regression fitting, minimum R squared, numerical simulation, and empirical value. We summarized the principles, procedures, virtues, and limitations of the major Eabs quantification methods and analyzed the current problems in the determination of Eabs. We pointed out what breakthroughs are needed to improve or innovate Eabs quantification methods, particularly regarding the need to avoid the influence of brown carbon, develop a broadband Eabs quantification scheme, quantify the Eabs values for the emissions of low-efficiency combustions, measure the Eabs of particles in a high-humidity environment, design a real-time monitor of Eabs by a proper combination of mature techniques, and make more use of artificial intelligence for better Eabs quantification. This review deepens the understanding of Eabs quantification methods and benefits the estimation of the contribution of BC to radiative forcing using climate models.

Evolution of Ozone Formation Sensitivity during a Persistent Regional Ozone Episode in Northeastern China and Its Implication for a Control Strategy

In recent years, the magnitude and frequency of regional ozone (O3) episodes have increased in China. We combined ground-based measurements, observation-based model (OBM), and the Weather Research and Forecasting and Community Multiscale Air Quality (WRF-CMAQ) model to analyze a typical persistent O3 episode that occurred across 88 cities in northeastern China during June 19-30, 2021. The meteorological conditions, particularly the wind convergence centers, played crucial roles in the evolution of O3 pollution. Daily analysis of the O3 formation sensitivity showed that O3 formation was in the volatile organic compound (VOC)-limited or transitional regime at the onset of the pollution episode in 92% of the cities. Conversely, it tended to be or eventually became a NOx-limited regime as the episode progressed in the most polluted cities. Based on the emission-reduction scenario simulations, mitigation of the regional O3 pollution was found to be most effective through a phased control strategy, namely, reduction of a high ratio of VOCs to NOx at the onset of the pollution and lower ratio during evolution of the O3 episode. This study presents a new possibility for regional O3 pollution abatement in China based on a reasonable combination of OBM and the WRF-CMAQ model.

The integrating sphere system plus in-situ absorption monitoring: A new scheme to study absorption enhancement of black carbon in ambient aerosols

Black carbon (BC) is the strongest light-absorbing aerosol in the atmosphere. The coating process causes lensing effects to enhance the BC absorption. The reported BC absorption enhancement values (E_abs) significantly differ partly due to the measurement methods used. The biggest difficulty in measuring the E_abs values is how to denude the coated particles so that the true value of absorption without coatings can be distinguished from lensing effects. In this study, we proposed a new approach based on an integrating sphere (IS) system plus in-situ absorption monitoring instrument to study E_abs in ambient aerosols. This approach is capable of (i) "de-lensing through solvent dissolution and solvent de-refraction", by which the absorption coefficient of denuded BC is acquired, and (ii) monitoring in-situ absorption with photoacoustic spectroscopy. With the help of the EC concentration measured by a thermal/optical carbon analyser, the E_abs values were calculated as the quotient of in-situ mass absorption efficiency divided by denude mass absorption efficiency. We applied this new approach to measure the E_abs values of four seasons in Beijing and found an annual mean of 1.90 ± 0.41 in 2019. More importantly, a previous assumption that BC absorption efficiency may be progressively enhanced by increased air pollution was validated and quantified using a logarithmic relationship of E_abs = 0.6 ln (PM_2.5 ̶ 3.59) ̶ 0.43 (R² = 0.99). This signals a continued drop of E_abs for future ambient aerosols with the sustained improvement in local air quality in China, meriting serious attention to its influences in climate, air quality, and atmospheric chemistry.

Identifying the fundamental drives behind the 10-year evolution of northern China's rural household energy and emission: Implications for 2030 and beyond

Rural household energy, particularly solid fuels, in northern China is thought to be a major source of air pollution. However, there is no complete, systematic, and reliable dataset for northern China's rural areas owing to the diversity of energy types used and the difficulty in acquiring data, particularly for solid fuels. Here we assessed existing progress in estimating solid fuels and proposed a practical route for deriving the information on rural household energy consumption and structure in northern China spanning 2010-2020, with important findings. (i) In 2010, the total rural household energy consumption for northern China was 287.51 million tons standard coal equivalent (TCE), while for 2020, it decreased to 205.14 million TCE, showing a 29 % decrease and an annual down 3.3 % averagely. Among a number of underlying reasons, China's urbanization process, which made the rural population shrink year by year, was primarily responsible. (ii) The share of clean energy in northern rural areas began at 4.2 % in 2010 and grew to 15.6 % in 2020, displaying a sustained improvement in energy structure. Particularly in the second 5 years, the clean energy share of policy priority areas grew by 20.0 percentage points (from 15.0 % in 2010 to 35.0 % in 2020), which is more than 18 percentage points higher than the growth of non-priority areas (from 2.9 % in 2010 to 4.5 % in 2020). Clean air policy, particularly the "two replacements" (replace coal with gas and electricity), in priority areas played a core role in changing the energy structure. (iii) Although both air pollutants and CO₂ are predicted to decrease in 2030, there is a large gap between expected 2030 emissions and hoped 2060 carbon neutrality in northern rural households. It is thus necessary to gradually boost the share of green electricity (non-fossil) and to reverse the trend of "biomass fuel curtailment" in rural residential sector. This calls for the improvement in biomass style (e.g., biomass pellets) and in stove efficiency (e.g., complete combustion).

Investigating the relationship between mass concentration of particulate matter and reactive oxygen species based on residential coal combustion source tests

Particulate matter (PM) has been considered to be closely related to human health, especially fine particulate matter. However, whether PM mass concentration alone is a good indicator for health impact remains a challenging question. In this study, emissions from residential coal combustion (RCC), one of the important PM sources in northern China, were tested to examine the relationship between the emission factors of particle-generated reactive oxygen species (ROS) (EF_ROS) and PM (EF_PM). A total of 24 combinations of source tests were conducted, including eight types of coal with different geological maturities (two anthracites and six bituminous) burned in three types of stoves (one honeycomb coal stove, one old chunk stove, and one new chunk stove). Here, ROS was defined as generated hydroxyl radical (·OH) by PM, and results showed EF_ROS from 24 residential coal combustion varied greatly by nearly 20 times. EF_ROS ranged 0.78-14.85 and 2.99-12.91 mg kg^-1 for the emissions from honeycomb and chunk coals, respectively. Moreover, the correlation between EF_ROS and EF_PM was significantly positive in honeycomb coal emissions (r = 0.82, p < 0.05), but it was insignificant in chunk coal emissions (r = 0.07, p > 0.05). For honeycomb coal emissions, organic carbon (OC) was quite abundant in PM and it might be the predominant contributor to both EF_PM and EF_ROS, resulting in a strong and positive correlation. For chunk coal emissions, high EF_ROS was mainly related to relatively high metal emissions in AN and LVB, while the metals were not major components in PM, leading to a poor correlation between EF_PM and EF_ROS. Therefore, this study revealed that PM was not always positively correlated with ROS from residential coal burning, and the relationship was mainly determined by the compositions of PM, suggesting PM mass concentration alone may not be the best indicator for assessing health impacts.

A preliminary study on pollution characteristics of surfactant substances in fine particles in the Beibu Gulf Region of China

The pollution characteristics of surfactant substances in fine particles (PM_2.5) in spring were studied in the Beibu Gulf Region of China, 68 samples of PM_2.5 were collected at Weizhou Island in Beihai City from March 12 to April 17, 2015. The Anionic Surfactant Substances (ASS) and Cationic Surfactant Substances (CSS) in the samples were analyzed using Byethyl Violet Spectrophotometry and Disulfide Blue Spectrophotometry, respectively. Combined with the data from backward trajectory simulation, the effects of air pollutants from remote transport on the pollution characteristics of surfactant substances in PM_2.5 in the Beibu Gulf Region were analyzed and discussed. The results showed that the daily mean concentrations of ASS and CSS in spring in the Beibu Gulf Region were 165.20 pmol/m³ and 8.05pmol/m³, and the variation ranges were 23.21-452.55 pmol/m³ and 0.65-31.31 pmol/m³, accounting for 1.82‰ ± 1.65‰ and 0.12‰ ± 0.11‰ of the mass concentration of PM_2.5, respectively. These concentrations were lower than those in comparable regions around the world. There was no clear correlation between the concentrations of ASS and CSS in PM_2.5 and the mass concentrations of PM_2.5. Tourism and air transport had a positive contribution on the concentrations of ASS. The concentration of surfactant substances in PM_2.5 was significantly impacted by wind speed and wind direction. Atmospheric temperature, air pressure and precipitation had little effect on the concentrations of surfactant substances. Surfactant substances in PM_2.5 significantly impacted visibility. Results also showed that the main sources of surfactant substances were from the southern China and Southeast Asia.

Toward a national emission inventory for the catering industry in China

Catering oil fumes are a major hazard to human health. In particular, the typical Chinese cooking style is characterised by a high temperature frying process that produces high levels of cooking oil fumes. However, limited data relating to this sector mean that national emission inventory data specific to the catering service industry do not exist. To address above deficiency and thus to establish the inventory of a city, or a province, or even a country, a door-to-door survey campaign was launched in the Chinese cities of Heze and Linfen to determine the structure of local catering industries. Data revealed that the number of catering businesses per 10⁴ people was 17 ± 4. Of these, 3.0 ± 1.4, 15.0 ± 1.4, and 82.0 ± 0.0% were classified as large, medium, and small enterprises, respectively. Furthermore, the installation rates of fume purifiers were 74 ± 13, 66 ± 9, and 51 ± 14% for large, medium, and small enterprises, respectively, with net removal efficiencies of 63 ± 11, 50 ± 7, and 31 ± 8%, respectively. This information was extrapolated across all provincial regions of China to construct a provincial and national emission inventory. In 2017, China's national catering industry released approximately 34 kt of volatile organic compounds (VOCs), 38 kt of particulate matter with a diameter less than 2.5 μm (PM_2.5), 48 kt of particulate matter with a diameter less than 10 μm (PM₁₀), 1 kt of black carbon (BC), and 27 kt of organic carbon (OC). A significant correlation was observed between vegetable oil consumption and emissions (e.g., for VOCs, y = 14.94 x + 76.50, R² = 0.87, where y is VOCs emissions and x is vegetable oil consumption), indirectly corroborating the rationality of the inventory. Moreover, this correlation provides the potential for a dynamic inventory based on vegetable oil consumption. Future studies are proposed to address more influential factors to improve the reliability of the national inventory and refer to big data, rather than door-to-door investigation, to identify the amount of catering service businesses in a region.

Algorithm developed for dynamic quantification of coal consumption for and emission from rural winter heating

Coal-dominated winter heating practices in China are largely accepted to be a leading cause of winter haze in the region though the amount of coal for heating is actually much lower than for power generation or industrial process. However, little is known about how the total rural coal weight in a region could be attributed to real time (e.g., daily) patterns, limiting the understanding of dynamic impacts of coal emissions and the adoption of timely measures against predicted haze. Considering that winter heating essentially protects against cold temperatures, coal burning strength may be related to the temperatures that people experience. A field study was organized to test the validity of this hypothesis. A system was designed to continuously monitor every instance of coal addition, and coal consumption on any given day for a whole village (W_DAY) was calculated by summating all the additions. Meanwhile, a new term, composite temperature (T_COM), which incorporates a few weather-related elements, was introduced to represent cold temperatures that individuals experience. It was found that W_DAY and T_COM presented opposite variations, and a negative linear correlation was observed (W_DAY = -0.75T_COM + 11.86, R² = 0.75), revealing the feasibility of estimating coal consumption on a certain day (W_DAY) based on weather data (T_COM) for a given village. An extensive form of the algorithm for any area of interest (e.g., a district, city, or province) can be expressed as W_DAY = (-0.75T_COM + 11.86)‧N_H/834, where N_H denotes the number of households in a region. This algorithm reflects the essence of winter heating (to resist cold temperatures), and therefore its logic is highly likely to be useful for any countries of the world regardless of what forms of energy used (coal or other energy forms) provided the energy involved is unexceptionally used for winter heating, though there may be some uncertainties in estimated coal consumption due to multiple factors.

Village energy survey reveals missing rural raw coal in northern China: Significance in science and policy

Burning coal for winter heating has been considered a major contributor to northern China's winter haze, with the district heating boilers holding the balance. However a decade of intensive efforts on district heating boilers brought few improvements to northern China's winter air quality, arousing a speculation that the household heating stoves mainly in rural area rather than the district heating boilers mainly in urban area dominate coal emissions in winter. This implies an extreme underestimation of rural household coal consumption by the China Energy Statistical Yearbooks (CESYs), although direct evidence supporting this speculation is lacking. A village energy survey campaign was launched to gather the firsthand information on household coal consumption in the rural areas of two cities, Baoding (in Hebei province) and Beijing (the capital of China). The survey data show that the rural raw coal consumption in Baoding (5.04 × 10³ kt) was approximately 6.5 times the value listed in the official CESY 2013 and exceeded the rural total of whole Hebei Province (4668 kt), revealing a huge amount of raw coal missing from the current statistical system. More importantly, rural emissions of particulate matter (PM) and SO₂ from raw coal, which had never been included in widely distributing environmental statistical reports, were found higher than those from industrial and urban household sectors in the two cities in 2013, which highlights the importance of rural coal burning in creating northern China's heavy haze and helps to explain why a number of modeling predictions on ambient pollutant concentrations based on normal emission inventories were more bias-prone in winter season than in other seasons. We therefore recommend placing greater emphasis on the "missing" rural raw coal to help China in its long-term ambition to achieve clean air in the context of rapid economic development.

Air pollutant emission from the underestimated households' coal consumption source in China

In order to improve the regional air quality, many control strategies have been developed by Chinese government for reducing air pollutant emission from power plants, industrial and transport sources during the past decade. However, little attention has been paid to residential combustion sources. To fill the knowledge gap, a series of surveys were carried out to investigate the residential energy use in Beijing-Tianjin-Hebei (BTH) region during the period of 2013-2014. Study shows that the actual average amount of residential coal consumption is over 0.7tyr^-1 per capita in 2013, which is much higher than that of 0.15tyr^-1 per capita reported in the 2014 China Energy Statistical Yearbook (CESY). Combining the investigated activities data with the best available emission factors (EFs), bottom-up method was used to evaluate the potential air pollutant emissions from residential coal combustion in BTH region in 2013. The results indicate that Baoding is the top contributor to the whole BTH region and accounts for approximately 15% of the regional residential emissions in 2013. The spatial pattern of air pollutants shows that high emissions locate in the southeast, along the Yanshan and Taihang Mountains, where much more rural people live and coal combustion is prevalent in winter. The future emission scenario at the end of the 13th Five Year Plan (in 2020) was also predicted based on the policy guidance for the residential coal consumptions in the BTH region. The scenario analysis indicates that air pollutant emissions will drop substantially around 90% because more strict rules will be made for reducing the residential coal consumption. With combined survey information and statistical data, the uncertainty of the emission inventory which was established in this study for the residential sector in the BTH region is reduced and the emission inventory is more reliable for air quality decision making.

Increase in polycyclic aromatic hydrocarbon (PAH) emissions due to briquetting: A challenge to the coal briquetting policy

Both China and UNEP recommend replacing raw coal chunks with coal briquettes in household sector as clean coal technology (CCT), which has been confirmed by the decreased emissions of particulate matter and black carbon. However, the clean effect has never been systematically checked by other pollutants like polycyclic aromatic hydrocarbons (PAHs). In this study, 5 coals with different geological maturities were processed as both chunks and briquettes and burned in 3 typical coal stoves for the measurement of emission factors (EFs) of particle-bound PAHs. It was found that the EFs of 16 parent PAHs, 26 nitrated PAHs, 6 oxygenated PAHs, and 8 alkylated PAHs for coal briquettes were 6.90 ± 7.89, 0.04 ± 0.03, 0.65 ± 0.40, and 72.78 ± 18.23 mg/kg, respectively, which were approximately 3.1, 3.7, 1.9, and 171 times those for coal chunks, respectively. Such significant increases in PAH emissions increased human health risk and challenged the policy of CCT.

NADPH oxidase contributes to the left ventricular dysfunction induced by sinoaortic denervation in rats

The aim of this work was to investigate the role nicotinamide adenine dinucleotide phosphate (NADPH) oxidase on left ventricular dysfunction of rats submitted to sinoaortic denervation (SAD). Experiment 1: 8 weeks after SAD of rats, NADPH oxidase in left ventricles was assayed by Western blotting analysis. Experiment 2: Rats were subjected to SAD and received treatment with apocynin (an NADPH oxidase inhibitor, 30 mg/kg/day, intragastric administration) for 8 weeks; 8 weeks after SAD, Nox2 and Nox4 expressions and Rac1 activity of left ventricles were higher in SAD rats than those in sham-operated rats. Although treatment of SAD rats with apocynin did not affect blood pressure, blood pressure variability (BPV), and baroreflex function, it significantly attenuated left ventricular hypertrophy marked by reduced expression of atrial natriuretic factor and β-myosin heavy chain. Treatment of SAD rats with apocynin abated oxidative stress marked by reduced malondialdehyde formation and suppressed nuclear factor-kappa B (NFκB) activation; inflammation marked by reduced monocyte chemoattractant protein-1 expression and myeloperoxidase activity; attenuated endoplasmic reticulum stress marked by reduced expression of CCAAT-enhancer-binding protein homologous protein, chaperone-glucose-regulated protein 78, and X-box protein 1; and alleviated cardiac fibrosis marked by reduced mRNA levels of collagens I and III and transforming growth factor beta. In conclusion, exaggerated BPV induces chronic myocardial oxidative stress and thereby aggravates cardiac remodeling in rats. These data suggest a potential role of NADPH oxidases in the pathogenesis of cardiac dysfunction induced by exaggerated BPV.

Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

Studies specifically addressing the elemental carbon (EC)/black carbon (BC) relationship during the transition from clean-normal (CN) air quality to heavy haze (HH) are rare but have important health and climate implications. The present study, in which EC levels are measured using a thermal-optical method and BC levels are measured using an optical method (aethalometer), provides a preliminary insight into this issue. The average daily EC concentration was 3.08 ± 1.10 μg/m(3) during the CN stage but climbed to 11.77 ± 2.01 μg/m(3) during the HH stage. More importantly, the BC/EC ratio averaged 0.92 ± 0.14 during the CN state and increased to 1.88 ± 0.30 during the HH state. This significant increase in BC/EC ratio has been confirmed to result partially from an increase in the in situ light absorption efficiency (σap) due to an enhanced internal mixing of the EC with other species. However, the exact enhancement of σap was unavailable because our monitoring scheme could not acquire the in situ absorption (bap) essential for σap calculation. This reveals a need to perform simultaneous measurement of EC and bap over a time period that includes both the CN and HH stages. In addition, the sensitivity of EC to both anthropogenic emissions and HH conditions implies a need to systematically study how to include EC complex (EC concentration, OC/EC ratio, and σap) as an indicator in air quality observations, in alert systems that assess air quality, and in the governance of emissions and human behaviors.

Harmonizing aerosol carbon measurements between two conventional thermal/optical analysis methods

Although total carbon (TC) can be consistently quantified by various aerosol carbon measurement methods, the demarcation of TC into organic carbon (OC) and elemental carbon (EC) has long been inconsistent. The NIOSH and IMPROVE protocols are most widely used for thermal/optical analysis (TOA), but current knowledge rests in the description that the NIOSH protocol usually gives lower EC values than does the IMPROVE protocol. This study seeks to explore the possibility of quantitatively linking the difference between the two TOA protocols. Residential coal-burning samples that had been collected and analyzed following the NIOSH protocol in previous studies were directly reanalyzed following the IMPROVE protocol for this study. A comparison of each pair of NIOSH and IMPROVE EC values reveals the dynamic relation between the two protocols, which can be expressed as a regression equation, y=(1-x)/(1+4.86x2) (R2=0.96), where the independent x is the EC/TC ratio R(EC/TC) for the IMPROVE protocol, and the dependent y is the difference between IMPROVE and NIOSH REC/TC relative to IMPROVE REC/TC. This regression equation may be the first effort in formulating the relationship between the two TOA protocols, and it is very helpful in harmonizing inconsistent TOA measurements, for example, source characterization, ambient monitoring, and atmospheric modeling.

Measurements of black and organic carbon emission factors for household coal combustion in China: implication for emission reduction

Household coal combustion is considered as the greatest emission source for black carbon (BC) and an important source for organic carbon (OC) in China. However, measurements on BC and OC emission factors (EF(BC) and EF(OC)) are still scarce, which result in large uncertainties in emission estimates. In this study, a detailed data set of EF(BC) and EF(OC) for household coal burning was presented on the basis of 38 coal/stove combination experiments. These experiments included 13 coals with a wide coverage of geological maturity which were tested in honeycomb-coal-briquette and raw-coal-chunk forms in three typical coal stoves. Averaged values of EF(BC) are 0.004 and 0.007 g/kg for anthracite in briquette and chunk forms and 0.09 and 3.05 g/kg for bituminous coal, respectively; EF(OC) are 0.06 and 0.10 g/kg for anthracite and 3.74 and 5.50 g/kg for bituminous coal in both forms, respectively. Coal maturity was found to be the most important influencing factor relative to coal's burning forms and the stove's burning efficiency, and when medium-volatile bituminous coals (MVB) are excluded from use, averaged EF(BC) and EF(OC) for bituminous coal decrease by 50% and 30%, respectively. According to these EFs, China's BC and OC emissions from the household sector in 2000 were 94 and 244 gigagrams (Gg), respectively. Compared with previous BC emission estimates for this sector (e.g., 465 Gg by Ohara et al., Atmos. Chem. Phys. 2007, 7, 4419-4444), a dramatic decrease was observed and was mainly attributed to the update of EFs. As suggested by this study, if MVB is prohibited as household fuel together with further promotion of briquettes, BC and OC emissions in this sector will be reduced by 80% and 34%, respectively, and then carbonaceous emissions can be controlled to a large extent in China.

Deployment of coal briquettes and improved stoves: possibly an option for both environment and climate

The use of coal briquettes and improved stoves by Chinese households has been encouraged by the government as a means of reducing air pollution and health impacts. In this study we have shown that these two improvements also relate to climate change. Our experimental measurements indicate that if all coal were burned as briquettes in improved stoves, particulate matter (PM), organic carbon (OC), and black carbon (BC) could be annually reduced by 63 +/- 12%, 61 +/- 10%, and 98 +/- 1.7%, respectively. Also, the ratio of BC to OC (BC/OC) could be reduced by about 97%, from 0.49 to 0.016, which would make the primary emissions of household coal combustion more optically scattering. Therefore, it is suggested that the government consider the possibility of: (i) phasing out direct burning of bituminous raw-coal-chunks in households; (ii) phasing out simple stoves in households; and, (iii) financially supporting the research, production, and popularization of improved stoves and efficient coal briquettes. These actions may have considerable environmental benefits by reducing emissions and mitigating some of the impacts of household coal burning on the climate. International cooperation is required both technologically and financially to accelerate the emission reduction in the world.

Effects of temperature parameters on thermal-optical analysis of organic and elemental carbon in aerosol

Thermal-optical analysis (TOA) is a popular method to determine aerosol elemental carbon (EC) and organic carbon (OC) collected on quartz fiber filter. However, temperature protocol adopted in TOA has great effects on OC and EC results. The purpose of this study is to investigate and quantify the effects of maximum temperature (T(max)) and residence time (RT) for each step in helium stage on ECOC measurements. Fourteen typical source samples and 20 ambient samples were collected and six temperature programs were designed for this study. It was found that EC value decreases regularly as T(max ) ascends, i.e., EC results from T(max) of 650 degrees C, 750 degrees C and 850 degrees C are 0.89 +/- 0.06, 0.76 +/- 0.10, 0.62 +/- 0.13 times EC value from T( max) of 550 degrees C, respectively, and the magnitude of EC drop (EC(d), percent) is significantly correlated with OC abundance in total carbon (R(OC/TC)), expressed as EC(d) = 66.8R(OC/TC)-14.4 (r = 0.87); pyrolized OC(POC) values are also sensitive to T(max), but there are various trends for samples with different OC constituents. On average of the samples studied here, prolonged RT reduces EC values by only 3%, almost negligible compared to the effect of T(max), and reduces POC by 9%, much less than that by previous report.

Emission characteristics of carbonaceous particles from various residential coal-stoves in China

China is thought to be the most important contributor to the global burden of carbonaceous aerosols, and residential coal combustion is the greatest emission source of black carbon (BC). In the present study, two high-efficiency household coal-stoves are tested together with honeycomb-coal-briquettes and raw-coal-chunks of nine different coals. Coal-burning emissions are collected onto quartz fiber filters (QFFs) and analyzed by a thermal-optical transmittance (TOT) method. Emission factors (EFs) of particulate matter (PM), organic carbon (OC), and elemental carbon (EC) are systematically measured, and the average EFs are calculated by taking into account our previous data. For bituminous coal-briquette and -chunk, EFs of PM, OC, and EC are 7.33, 4.16, and 0.08 g/kg and 14.8, 5.93, and 3.81 g/kg, respectively; and for anthracite-briquette and -chunk, they are 1.21, 0.06, and 0.004 g/kg and 1.08, 0.10, and 0.007 g/kg, respectively. Annual estimates for PM, OC, and EC emissions in China are calculated for the years of 2000 and 2005 according to the EFs and coal consumptions, and the results are consistent with our previous estimates. Bituminous coal-chunk contributes 68% and 99% of the total OC and EC emissions from household coal burning, respectively. Additionally, a new model of Aethalometer (AE90) is introduced into the sampling system to monitor the real-time BC concentrations. On one hand, AE90 provides a set of EFs for optical BC in parallel to thermal-optical EC, and these two data are generally comparable, although BC/EC ratios vary in different coal/stove combinations. On the other hand, AE90 offers a chance to observe the variation of BC concentrations during whole burning cycles, which demonstrates that almost all BC emits into the flue during the initial period of 15 min after coal addition into household stoves.

Identification of a calcium/calmodulin-dependent protein kinase that phosphorylates the Neurospora circadian clock protein FREQUENCY

Phosphorylation of circadian clock proteins represents a major regulatory step that controls circadian clocks. In Neurospora, the circadian clock protein FREQUENCY (FRQ) is progressively phosphorylated over time, and its level decreases when it is hyperphosphorylated. In this study, we showed that most of the kinase activity phosphorylating FRQ in vitro was calcium/calmodulin-dependent, and the endogenous FRQ in the Neurospora extracts was phosphorylated by a Ca/CaM-dependent kinase-like activity. From Neurospora cell extracts, an approximately 50-kDa Ca/CaM-dependent kinase (CAMK-1) that can specifically phosphorylate FRQ was purified. In vitro, this kinase accounts for near half of the FRQ kinase activity, and it can phosphorylate the FRQ region that contains the three known functionally important phosphorylation sites. To understand the function of camk-1 in vivo, it was disrupted in Neurospora by gene replacement. After germination from ascospores, the camk-1 null strains grew slowly, indicating that CAMK-1 plays an important role in growth and development of Neurospora. This phenotype was transient however, revealing redundancy in the system. Analysis of the camk-1 null strain revealed that the deletion of camk-1 affected phase, period, and light-induced phase shifting of the circadian conidiation rhythm. Taken together, our results suggest that multiple kinases may phosphorylate FRQ in vivo.

Myosin light chain kinase binding to a unique site on F-actin revealed by three-dimensional image reconstruction

Ca2+-calmodulin-dependent phosphorylation of myosin regulatory light chains by the catalytic COOH-terminal half of myosin light chain kinase (MLCK) activates myosin II in smooth and nonmuscle cells. In addition, MLCK binds to thin filaments in situ and F-actin in vitro via a specific repeat motif in its NH2 terminus at a stoichiometry of one MLCK per three actin monomers. We have investigated the structural basis of MLCK-actin interactions by negative staining and helical reconstruction. F-actin was decorated with a peptide containing the NH2-terminal 147 residues of MLCK (MLCK-147) that binds to F-actin with high affinity. MLCK-147 caused formation of F-actin rafts, and single filaments within rafts were used for structural analysis. Three-dimensional reconstructions showed MLCK density on the extreme periphery of subdomain-1 of each actin monomer forming a bridge to the periphery of subdomain-4 of the azimuthally adjacent actin. Fitting the reconstruction to the atomic model of F-actin revealed interaction of MLCK-147 close to the COOH terminus of the first actin and near residues 228-232 of the second. This unique location enables MLCK to bind to actin without interfering with the binding of any other key actin-binding proteins, including myosin, tropomyosin, caldesmon, and calponin.

Familial hypertrophic cardiomyopathy mutations in the regulatory light chains of myosin affect their structure, Ca2+ binding, and phosphorylation

The effect of the familial hypertrophic cardiomyopathy mutations, A13T, F18L, E22K, R58Q, and P95A, found in the regulatory light chains of human cardiac myosin has been investigated. The results demonstrate that E22K and R58Q, located in the immediate extension of the helices flanking the regulatory light chain Ca(2+) binding site, had dramatically altered Ca(2+) binding properties. The K(Ca) value for E22K was decreased by approximately 17-fold compared with the wild-type light chain, and the R58Q mutant did not bind Ca(2+). Interestingly, Ca(2+) binding to the R58Q mutant was restored upon phosphorylation, whereas the E22K mutant could not be phosphorylated. In addition, the alpha-helical content of phosphorylated R58Q greatly increased with Ca(2+) binding. The A13T mutation, located near the phosphorylation site (Ser-15) of the human cardiac regulatory light chain, had 3-fold lower K(Ca) than wild-type light chain, whereas phosphorylation of this mutant increased the Ca(2+) affinity 6-fold. Whereas phosphorylation of wild-type light chain decreased its Ca(2+) affinity, the opposite was true for A13T. The alpha-helical content of the A13T mutant returned to the level of wild-type light chain upon phosphorylation. The phosphorylation and Ca(2+) binding properties of the regulatory light chain of human cardiac myosin are important for physiological function, and alteration any of these could contribute to the development of hypertrophic cardiomyopathy.

Activation of myosin light chain kinase requires translocation of bound calmodulin

A novel translocation step is inferred from structural studies of the interactions between the intracellular calcium receptor protein calmodulin (CaM) and one of its regulatory targets. A mutant of CaM missing residues 2-8 (DeltaNCaM) binds skeletal muscle myosin light chain kinase with high affinity but fails to activate catalysis. Small angle x-ray scattering data reveal that DeltaNCaM occupies a position near the catalytic cleft in its complex with the kinase, whereas the native protein translocates to a position near the C-terminal end of the catalytic core. Thus, CaM residues 2-8 appear to facilitate movement of bound CaM away from the vicinity of the catalytic cleft.

Transcatheter closure of secundum atrial septal defects using Amplatzer device

OBJECTIVE

To evaluate the feasibility and short term results of transcatheter closure of secundum atrial septal defects (TCSASDs) using Amplatzer occluder device. A new self-centering device, the Amplatzer atrial septal occluder, has recently been evaluated in an animal model with excellent results. This paper reports our clinical research with this device.

METHODS

30 patients underwent an attempt at TCSASDs at an average age of 35.6 +/- 15.9 y (range, 5-62 y) and average weight of 63.6 +/- 14.5 kg (range, 17-78 kg) using the Amplatzer atrial septal occluder. The average ASD diameter measured by transesophageal echocardiography (TEE) was 23.6 +/- 4.0 mm (range, 16-31 mm), and the average atrial septal defects (ASD) balloon stretched diameter was 25.2 +/- 5.8 mm (range, 9-34 mm). All patients had right atrial and ventricular volume overload with a Qp/Qs of 3.4 +/- 1.2 (1.4-5.2). A F8-12 catheter was used for delivery of the device in all patients.

RESULTS

The device was placed correctly in all patients. There was immediate and complete closure in 30 patients. The average device waist size used to close the defect was 25.6 +/- 5.9 mm (range, 9-34 mm). There was no episode of device embolization or any other complication. Follow-up was performed using transthoracic echocardiography (TTE) 1 day, 1 month, 3 months, 6 months and 1 year after the procedure. The first day after operation; there was complete closure of the ASD in all patients; there have been no episodes of endocarditis, thromboembolism, or wire fracture.

CONCLUSION

TCSASDs using the Amplatzer occluder device was an efficient nonsurgical method which had a very high technical success rate and satisfactory short term and follow-up results.

Identification of a novel actin binding motif in smooth muscle myosin light chain kinase

Phosphorylation of the 20-kDa regulatory light chain of myosin catalyzed by a Ca(2+)/calmodulin-dependent myosin light chain kinase is important in the initiation of smooth muscle contraction and other contractile processes in non-muscle cells. It has been previously shown that residues 1-142 of smooth muscle myosin light chain kinase are necessary for high-affinity binding to actin-containing filaments in cells (1). To further localize the region of the kinase required for binding, a series of N-terminal deletion mutants as well as several N-terminal glutathione S-transferase fusion proteins were constructed. Cosedimentation assays showed that a peptide containing residues 1-75 binds to purified smooth muscle myofilaments. Furthermore, the N-terminal peptide was sufficient for high-affinity binding to actin stress fibers in smooth muscle cells in vivo. Alanine scanning mutagenesis in the fusion protein identified residues Asp-30, Phe-31, Arg-32, and Leu-35 as important for binding in vitro. There are two additional DFRXXL motifs located at residues 2-7 and 58-63. The DFR residues in these three motifs were individually replaced by alanine residues in the full-length kinase. Each of these mutations significantly decreased myosin light chain kinase binding to myofilaments in vitro, and each abolished high-affinity binding to actin-containing filaments in smooth muscle cells in vivo. These results identify a unique structural motif comprised of three repeat consensus sequences in the N terminus of myosin light chain kinase necessary for high-affinity binding to actin-containing filaments.

Expression of calmodulin-binding domain of neuronal nitric synthase and its binding activity to calmodulin

To facilitate the study of associations of nNOS functions with its calmodulin (CaM) binding domain and to prepare nNOS specific inhibiting peptides from phage peptide library, we have amplified the coding gene of nNOS CaM-binding domain (nNOS 2544-2988 bp) and expressed it in E.coli. The recombinant product in the size of 22 kDa was purified (over 90% in pure) by His.Tag-Sepharose column and its obvious CaM-binding activity was detected with CaM overlay assay. Since it possesses the sequence specificity and effective calmodulin-binding activity, the protein was considered an ideal target for screening nNOS specific peptides from peptide library and also an antigen for marking nNOS antibody.

Phosphorylation-dependent structural changes in the regulatory light chain domain of smooth muscle heavy meromyosin

Smooth muscle heavy meromyosin, a double-headed proteolytic fragment of myosin lacking the COOH-terminal two-thirds of the tail, has been shown previously to be regulated by phosphorylation. To examine phosphorylation-dependent structural changes near the head-tail junction, we prepared five well regulated heavy meromyosins containing single-cysteine mutants of the human smooth muscle regulatory light chain labeled with the photocross-linking reagent, benzophenone-iodoacetamide. For those mutants that generated cross-links, only one type of cross-linked species was observed, a regulatory light chain dimer. Irradiated mutants fell into two classes. First, for Q15C, A23C, and wild type (Cys-108), a regulatory light chain dimer was formed for dephosphorylated but not thiophosphorylated heavy meromyosin. These data provide direct chemical evidence that in the dephosphorylated state, Gln-15, Ala-23, and Cys-108 on one head are positioned near (within 8.9 A) the regulatory light chain of the partner head and that thiophosphorylation abolishes proximity. This behavior was also observed for the Q15C mutant on a truncated heavy meromyosin lacking both catalytic domains. For the actin-heavy meromyosin complex, cross-links were formed in both de- and thiophosphorylated states. S59C and T134C mutants were in a second mutant class, where regulatory light chain dimers were not detected in dephosphorylated or thiophosphorylated heavy meromyosin, suggesting positions outside the region of interaction of the regulatory light chains.

Calmodulin binding to myosin light chain kinase begins at substoichiometric Ca2+ concentrations: a small-angle scattering study of binding and conformational transitions

We have used small-angle scattering to study the calcium dependence of the interactions between calmodulin (CaM) and skeletal muscle myosin light chain kinase (MLCK), as well as the conformations of the complexes that form. Scattering data were measured from equimolar mixtures of a functional MLCK and CaM or a mutated CaM (B12QCaM) incompetent to bind Ca2+ in its N-terminal domain, with increasing Ca2+ concentrations. To evaluate differences between CaM-enzyme versus CaM-peptide interactions, similar Ca2+ titration experiments were performed using synthetic peptides based on the CaM-binding sequence from MLCK (MLCK-I). Our data show there are different determinants for CaM binding the isolated peptide sequence compared to CaM binding to the same sequences within the enzyme. For example, binding of either CaM or B12QCaM to the MLCK-I peptide is observed even in the presence of EGTA, whereas binding of CaM to the enzyme requires Ca2+. The peptide studies also show that the conformational collapse of CaM requires both the N and C domains of CaM to be competent for Ca2+ binding as well as interactions with each end of MLCK-I, and it occurs at approximately 2 mol of Ca2+/mol of CaM. We show that CaM binding to the MLCK enzyme begins at substoichiometric concentrations of Ca2+ (< or = 2 mol of Ca2+/mol of CaM), but that the final compact structure of CaM with the enzyme requires saturating Ca2+. In addition, MLCK enzyme does bind to 2Ca2+ x B12QCaM, although this complex is more extended than the complex with native CaM. Our results support the hypothesis that CaM regulation of MLCK involves an initial binding step at less than saturating Ca2+ concentrations and a subsequent activation step at higher Ca2+ concentrations.

Myosin light chain kinase: functional domains and structural motifs

Conventional myosin light chain kinase found in differentiated smooth and non-muscle cells is a dedicated Ca2+/calmodulin-dependent protein kinase which phosphorylates the regulatory light chain of myosin II. This phosphorylation increases the actin-activated myosin ATPase activity and is thought to play major roles in a number of biological processes, including smooth muscle contraction. The catalytic domain contains residues on its surface that bind a regulatory segment resulting in autoinhibition through an intrasteric mechanism. When Ca2+/calmodulin binds, there is a marked displacement of the regulatory segment from the catalytic cleft allowing phosphorylation of myosin regulatory light chain. Kinase activity depends upon Ca2+/calmodulin binding not only to the canonical calmodulin-binding sequence but also to additional interactions between Ca2+/calmodulin and the catalytic core. Previous biochemical evidence shows myosin light chain kinase binds tightly to actomyosin containing filaments. The kinase has low-affinity myosin and actin binding sites in Ig-like motifs at the N- and C-terminus, respectively. Recent results show the N-terminus of myosin light chain kinase is responsible for filament binding in vivo. However, the apparent binding affinity is greater for smooth muscle myofilaments, purified thin filaments, or actin-containing filaments in permeable cells than for purified smooth muscle F-actin or actomyosin filaments from skeletal muscle. These results suggest a protein on actin thin filaments that may facilitate kinase binding. Myosin light chain kinase does not dissociate from filaments in the presence of Ca2+/calmodulin raising the interesting question as to how the kinase phosphorylates myosin in thick filaments if it is bound to actin-containing thin filaments.

Neutron-scattering studies reveal further details of the Ca2+/calmodulin-dependent activation mechanism of myosin light chain kinase

Previously, we utilized small-angle X-ray scattering and neutron scattering with contrast variation to obtain the first low-resolution structure of 4Ca2+.calmodulin (CaM) complexed with a functional enzyme, an enzymatically active truncation mutant of skeletal muscle myosin light chain kinase (MLCK). These experiments showed that, upon binding to MLCK, CaM undergoes a conformational collapse identical to that observed when CaM binds to the isolated peptide corresponding to the CaM binding sequence of MLCK. CaM thereby was shown to release the inhibition of the kinase by inducing a significant movement of its CaM binding and autoinhibitory sequences away from the surface of the catalytic core [Krueger, J. K., Olah, G. A., Rokop, S. E., Zhi, G., Stull, J. T., and Trewhella, J. (1997) Biochemistry 36, 6017-6023]. We report here similar scattering experiments on the CaM.MLCK complex with the addition of substrates; a nonhydrolyzable analogue of adenosine-triphosphate, AMPPNP, and a peptide substrate for MLCK, a phosphorylation sequence from myosin regulatory light chain (pRLC). These substrates are shown to induce an overall compaction of the complex. The separation of the centers-of-mass of the CaM and MLCK components is shortened (by approximately 12 A), thus bringing CaM closer to the catalytic site compared to the complex without substrates. In addition, there appears to be a reorientation of CaM with respect to the kinase upon substrate binding that results in interactions between the N-terminal sequence of CaM and the kinase that were not observed in the complex without substrates. Finally, the kinase itself becomes more compact in the CaM.MLCK.pRLC.AMPPNP complex compared to the complex without substrates. This observed compaction of MLCK upon substrate binding is similar to that arising from the closure of the catalytic cleft in cAMP-dependent protein kinase upon binding pseudosubstrate.

Regulatory segments of Ca2+/calmodulin-dependent protein kinases

Catalytic cores of skeletal and smooth muscle myosin light chain kinases and Ca2+/calmodulin-dependent protein kinase II are regulated intrasterically by different regulatory segments containing autoinhibitory and calmodulin-binding sequences. The functional properties of these regulatory segments were examined in chimeric kinases containing either the catalytic core of skeletal muscle myosin light chain kinase or Ca2+/calmodulin-dependent protein kinase II with different regulatory segments. Recognition of protein substrates by the catalytic core of skeletal muscle myosin light chain kinase was altered with the regulatory segment of protein kinase II but not with smooth muscle myosin light chain kinase. Similarly, the catalytic properties of the protein kinase II were altered with regulatory segments from either myosin light chain kinase. All chimeric kinases were dependent on Ca2+/calmodulin for activity. The apparent Ca2+/calmodulin activation constant was similarly low with all chimeras containing the skeletal muscle catalytic core. The activation constant was greater with chimeric kinases containing the catalytic core of Ca2+/calmodulin-dependent protein kinase II with its endogenous or myosin light chain kinase regulatory segments. Thus, heterologous regulatory segments affect substrate recognition and kinase activity. Furthermore, the sensitivity to calmodulin activation is determined primarily by the respective catalytic cores, not the calmodulin-binding sequences.

Gender-associated differences in left ventricular geometry in patients with aortic valve disease and effect of distinct overload subsets

Gender-associated differences may play an important role in the way the left ventricle adapts to overload. The purpose of this study is to evaluate left ventricular (LV) geometry in patients referred for aortic valve replacement with distinct overload subsets. The echocardiograms of 128 patients with isolated aortic stenosis (n = 44), mixed aortic valvular disease (n = 51), and pure aortic regurgitation (n = 33) before aortic valve replacement were evaluated. Women had better LV function as measured by ejection fraction (58% vs 52%; p = 0.01) and were slightly older (67 vs 62 years, p = 0.11). LV dimensions and volumes indexes were distinctively smaller in women irrespective of the subgroups analyzed. Men had larger LV mass and LV mass index, but women had higher LV mass/volume ratio. Gender-related differences in LV mass/volume ratio were most prominent in the aortic stenosis patients (3.1 g/ml for women vs 2.3 g/ml for men; p = 0.001), tended to decrease in mixed aortic disease (2.3 g/ml for women vs 1.8 g/ml for men; p = 0.01), and were not present in patients with pure aortic regurgitation (1.7 g/ml for women vs 1.7 g/ml for men; p = 0.83). Multivariate analysis showed that gender was independently associated with LV mass/volume ratios, after adjusting for the severity of the valvular lesion, age, LV function, and concomitant coronary bypass graft surgery. Thus, in a selected population of patients with severe aortic valvular disease, there were significant gender-related differences in LV geometry, mainly in patients exposed to chronic pressure overload.

Incidence and natural history of left ventricular thrombus following anterior wall acute myocardial infarction

Previous studies have reported left ventricular (LV) thrombus in 20% to 56% of patients after anterior wall acute myocardial infarction (AMI). The Healing and Early Afterload Reducing Therapy (HEART) study was a prospective study comparing effects of early (24 hours) or delayed (14 days) initiation of ramipril, an angiotensin-converting enzyme inhibitor, on LV function after anterior wall AMI. This ancillary study assessed prevalence of LV thrombus. Two-dimensional echocardiography was performed on days 1, 14, and 90 after myocardial infarction. The cohort consisted of 309 patients. Q-wave anterior wall AMI occurred in 78%; 87% received reperfusion therapy. The prevalence of LV thrombus was 2 of 309 (0.6%) at day 1, 11 of 295 (3.7%) at day 14, and 7 of 283 (2.5%) at day 90. One patient had thrombus at 2 examinations. The day 1 echocardiogram was not correlated with thrombus development. LV size increased more in patients with thrombus than in those without thrombus. Patients with thrombus had more wall motion abnormality after day 1 than patients without thrombus (p = 0.03). Thus, the current prevalence of LV thrombus in anterior wall AMI is lower than previously reported, possibly due to changes in AMI management. Preservation of LV function is likely to be an important mechanism. Most thrombi are seen by 2 weeks after AMI. Resolution documented by echocardiography is frequent.

Structures of calmodulin and a functional myosin light chain kinase in the activated complex: a neutron scattering study

Calmodulin (CaM) is the major intracellular receptor for Ca2+ and is responsible for the Ca2+-dependent regulation of a wide variety of cellular processes via interactions with a diverse array of target enzymes. Our current view of the structural basis for CaM enzyme activation is based on biophysical studies of CaM complexed with small peptides that model CaM-binding domains. A major concern with interpreting data from these structures in terms of target enzyme activation mechanisms is that the larger enzyme structure might be expected to impose constraints on CaM binding. Full understanding of the molecular mechanism for CaM-dependent enzyme activation requires additional structural information on the interaction of CaM with functional enzymes. We have utilized small-angle X-ray scattering and neutron scattering with contrast variation to obtain the first structural view of CaM complexed with a functional enzyme, an enzymatically active truncation mutant of skeletal muscle myosin light chain kinase (MLCK). Our data show that CaM undergoes an unhindered conformational collapse upon binding MLCK and activates the enzyme by inducing a significant movement of the kinase's CaM binding and autoinhibitory sequences away from the surface of the catalytic core.

Photoaffinity labeling of a peptide substrate to myosin light chain kinase

The substrate binding properties of skeletal muscle myosin light chain kinase were investigated with a synthetic peptide containing the photoreactive amino acid p-benzoylphenylalanine (Bpa) incorporated amino-terminal of the phosphoacceptor serine (BpaKKRAARATSNVFA). When photolyzed at 350 nm, the peptide was cross-linked stoichiometrically to myosin light chain kinase in a Ca2+/calmodulin-dependent manner. Peptide incorporation into kinase inhibited light chain phosphorylation, and the loss of kinase activity was proportional to the extent of peptide incorporated. After peptide I was incorporated into myosin light chain kinase, it was partially phosphorylated in the absence of Ca2+/calmodulin. The extent of phosphorylation increased in the presence of Ca2+/calmodulin. The cross-linked photoadduct was digested, labeled peptides were purified by high performance liquid chromatography, and sites of covalent modification were determined by amino acid sequencing and analysis. The covalent modification in the catalytic core occurred on Ile-373 (66%) and in a peptide containing residues Asn-422 to Met-437 (14%), respectively. Lys-572 in the autoinhibitory region accounted for 20% of the incorporated label. The coincident covalent modification of the autoinhibitory domain suggests that it is located near the catalytic site. Based upon a model of the catalytic core, the substrate peptide is predicted to bind in the cleft between the two lobes of the kinase. The orientation of the substrate peptide on myosin light chain kinase is similar to the orientation of the substrate recognition fragment, but not the high affinity binding fragment, of inhibitor peptide of cAMP-dependent protein kinase in the catalytic subunit of the cAMP-dependent protein kinase.

Structural requirements for phosphorylation of myosin regulatory light chain from smooth muscle

Site-directed and chimeric mutations of myosin regulatory light chains were used to identify residues important for phosphorylation of Ser19 by smooth muscle myosin light chain kinase. Arg16 and hydrophobic residues C-terminal of Ser19 in smooth muscle light chain were important substrate determinants in the intact protein. However, changes in the kinetic properties with mutations in the light chain were substantially smaller than results reported with structurally similar synthetic peptide substrates. These results together with the low Vmax value for short peptide substrates containing the consensus phosphorylation sequence suggest that there may be additional sites of interactions between the kinase and protein substrate. Chimeras of skeletal and smooth muscle light chains were constructed with exchanges at the N terminus and subdomains I, II, III, and IV. Analysis of results obtained on the kinetic properties for phosphorylation showed that subdomains I and II contribute to high Vmax values. Thus, a region distant from the consensus phosphorylation sequence in smooth muscle light chain is also an important substrate determinant for myosin light chain kinase.

Charge replacement near the phosphorylatable serine of the myosin regulatory light chain mimics aspects of phosphorylation

Phosphorylation of the myosin regulatory light chains (RLCs) activates contraction in smooth muscle and modulates force production in striated muscle. RLC phosphorylation changes the net charge in a critical region of the N terminus and thereby may alter interactions between the RLC and myosin heavy chain. A series of N-terminal charge mutations in the human smooth muscle RLC has been engineered, and the mutants have been evaluated for their ability to mimic the phosphorylated form of the RLC when reconstituted into scallop striated muscle bundles or into isolated smooth muscle myosin. Changing the net charge in the region from Arg-13 to Ser-19 potentiates force in scallop striated muscle and maintains smooth muscle myosin in an unfolded filamentous state without affecting ATPase activity or motility of smooth muscle myosin. Thus, the effect of RLC phosphorylation in striated muscle and its ability to regulate the folded-to-extended conformational transition in smooth muscle may be due to a simple reduction of net charge at the N terminus of the light chain. The ability of phosphorylation to regulate smooth muscle myosin's ATPase activity and motility involves a more complex mechanism.

[Color Doppler evaluation of valvular regurgitation in normal subjects]

430 apparently healthy subjects were studied with color Doppler flow imaging system. There were 216 females and 214 males, their age ranged from 4-80 years (mean 41.2 years). They were divided into 6 groups by every ten years of age, with group I having age below 19 and group VI age above 70. None of the subjects had previous diagnosis of cardiovascular diseases. Mitral regurgitation was detected in 30.9-52.8% in all the groups except group I, in which it was found in 20.0% only. The prevalence rate of tricuspid regurgitation was 9.8-36% in the six groups. Pulmonary regurgitation signals were detected in 43.8-4.8% in these groups with a tendency of lower incidence in the elderly. Aortic regurgitation were detected only in the three elder groups with an incidence of 5.5% in group 4 and 13.6% in group 6. The reason for that may be the degeneration of aortic valve with aging. Our study showed that in a large proportion of normal persons color Doppler echocardiography allows recording of regurgitation signals behind cardiac valves except for aortic valve. The regurgitation volume was small and there was no significant hemodynamic effect. The size and diameter of the heart chambers were normal when compared with other studies.

[The changes in and clinical significance of Doppler echocardiography in patients with acute myocardial infarction]

To evaluate the changes of cf cardiac function in patients with acute myocardial infarction (AMI) and compare the difference between patients and controls, Doppler echocardiographic examination was performed in 80 patients within 72 hours after the heart attack and 97 matched normal subjects. The mitral, tricuspid, pulmonary and aortic flow velocity was recorded with pulsed Doppler. The peak early diastolic flow velocity (EPV), peak late diastolic velocity (APV), ventricular ejection time (VET), pre-ejection time (pre ET) and velocity-time integral (VTI) of each flow were measured. The EPV of mitral and tricuspid flow and the VTI and VET of aortic and pulmonary flow were significantly decreased. APV was increased and EPV/APV ratio was decreased in AMI patients. Thus, Doppler echocardiographic evaluation of ventricular diastolic and systolic function provides an excellent tool for early detection and noninvasive monitoring in patients with AMI.

[Hemodynamic study of a single oral dose of enalapril in patients with heart failure]

Clinical and hemodynamic studies were carried out for the purpose of evaluating the effects of enalapril in the treatment of chronic heart failure. Enalapril 10-20 mg was given once to 10 patients with moderate to severe congestive heart failure (coronary 6, hypertensive heart disease 2 and idiopathic congestive cardiomyopathy). Hemodynamic studies were done on the first day after drug administration and the same dose was maintained for 2 weeks. The results showed a decrease of mean BP of 18.29% (P less than 0.01), CVP 40.4% mPAP 23.9%, PCWP 41.2%, SVR 39.9% and PVR 41.3% respectively (P less than 0.001). Cardiac index increased 44.16% (P less than 0.001). The therapeutic action lasted more than 24 hours after a single dose. No further drop of BP was found weeks later, 6 patients in NYHA class III and 2 in class IV improved to class II. No severe side effects were found. The results showed that enalapril is well tolerated after a single dose and its therapeutic action lasts 2 weeks with improvement both in hemodynamics and subjective symptoms.

[Fructose-1,6-diphosphate in the treatment of chronic heart failure]

Fructose-1,6-diphosphate (FDP) was given to 30 patients with chronic heart failure (CHF) caused by various kinds of heart diseases with the purpose to evaluate the effects of FDP on CHF patients. Definite hemodynamic and clinical improvement has been found in this group. CO increased by 1.61 +/- 0.31 L/Min (35%) (P less than 0.01) PCWP decreased by 5.5 +/- 1.08 mmHg (31%); mean PAP decreased by 5.8 +/- 2.07 mmHg (P less than 0.05). EF increased by 6.9 +/- 1.5 (15.1%) as shown by echocardiography and the peak effect of the drug appeared at 2 hours after administration. The results showed that FDP is effective in the treatment of heart failure, especially in patients with dysfunction of other organs.