Mendelian randomization analysis using multiple biomarkers of an underlying common exposure

Mendelian randomization (MR) analysis is increasingly popular for testing the causal effect of exposures on disease outcomes using data from genome-wide association studies. In some settings, the underlying exposure, such as systematic inflammation, may not be directly observable, but measurements can be available on multiple biomarkers or other types of traits that are co-regulated by the exposure. We propose a method for MR analysis on latent exposures (MRLE), which tests the significance for, and the direction of, the effect of a latent exposure by leveraging information from multiple related traits. The method is developed by constructing a set of estimating functions based on the second-order moments of GWAS summary association statistics for the observable traits, under a structural equation model where genetic variants are assumed to have indirect effects through the latent exposure and potentially direct effects on the traits. Simulation studies show that MRLE has well-controlled type I error rates and enhanced power compared to single-trait MR tests under various types of pleiotropy. Applications of MRLE using genetic association statistics across five inflammatory biomarkers (CRP, IL-6, IL-8, TNF-α, and MCP-1) provide evidence for potential causal effects of inflammation on increasing the risk of coronary artery disease, colorectal cancer, and rheumatoid arthritis, while standard MR analysis for individual biomarkers fails to detect consistent evidence for such effects.

SURGE: uncovering context-specific genetic-regulation of gene expression from single-cell RNA sequencing using latent-factor models

Genetic regulation of gene expression is a complex process, with genetic effects known to vary across cellular contexts such as cell types and environmental conditions. We developed SURGE, a method for unsupervised discovery of context-specific expression quantitative trait loci (eQTLs) from single-cell transcriptomic data. This allows discovery of the contexts or cell types modulating genetic regulation without prior knowledge. Applied to peripheral blood single-cell eQTL data, SURGE contexts capture continuous representations of distinct cell types and groupings of biologically related cell types. We demonstrate the disease-relevance of SURGE context-specific eQTLs using colocalization analysis and stratified LD-score regression.

Single-cell allele-specific expression analysis reveals dynamic and cell-type-specific regulatory effects

Differential allele-specific expression (ASE) is a powerful tool to study context-specific cis-regulation of gene expression. Such effects can reflect the interaction between genetic or epigenetic factors and a measured context or condition. Single-cell RNA sequencing (scRNA-seq) allows the measurement of ASE at individual-cell resolution, but there is a lack of statistical methods to analyze such data. We present Differential Allelic Expression using Single-Cell data (DAESC), a powerful method for differential ASE analysis using scRNA-seq from multiple individuals, with statistical behavior confirmed through simulation. DAESC accounts for non-independence between cells from the same individual and incorporates implicit haplotype phasing. Application to data from 105 induced pluripotent stem cell (iPSC) lines identifies 657 genes dynamically regulated during endoderm differentiation, with enrichment for changes in chromatin state. Application to a type-2 diabetes dataset identifies several differentially regulated genes between patients and controls in pancreatic endocrine cells. DAESC is a powerful method for single-cell ASE analysis and can uncover novel insights on gene regulation.

Genome-wide association studies of 27 accelerometry-derived physical activity measurements identified novel loci and genetic mechanisms

Physical inactivity (PA) is an important risk factor for a wide range of diseases. Previous genome-wide association studies (GWAS), based on self-reported data or a small number of phenotypes derived from accelerometry, have identified a limited number of genetic loci associated with habitual PA and provided evidence for involvement of central nervous system in mediating genetic effects. In this study, we derived 27 PA phenotypes from wrist accelerometry data obtained from 88,411 UK Biobank study participants. Single-variant association analysis based on mixed-effects models and transcriptome-wide association studies (TWAS) together identified 5 novel loci that were not detected by previous studies of PA, sleep duration and self-reported chronotype. For both novel and previously known loci, we discovered associations with novel phenotypes including active-to-sedentary transition probability, light-intensity PA, activity during different times of the day and proxy phenotypes to sleep and circadian patterns. Follow-up studies including TWAS, colocalization, tissue-specific heritability enrichment, gene-set enrichment and genetic correlation analyses indicated the role of the blood and immune system in modulating the genetic effects and a secondary role of the digestive and endocrine systems. Our findings provided important insights into the genetic architecture of PA and its underlying mechanisms.

Single-cell sequencing reveals lineage-specific dynamic genetic regulation of gene expression during human cardiomyocyte differentiation

Dynamic and temporally specific gene regulatory changes may underlie unexplained genetic associations with complex disease. During a dynamic process such as cellular differentiation, the overall cell type composition of a tissue (or an in vitro culture) and the gene regulatory profile of each cell can both experience significant changes over time. To identify these dynamic effects in high resolution, we collected single-cell RNA-sequencing data over a differentiation time course from induced pluripotent stem cells to cardiomyocytes, sampled at 7 unique time points in 19 human cell lines. We employed a flexible approach to map dynamic eQTLs whose effects vary significantly over the course of bifurcating differentiation trajectories, including many whose effects are specific to one of these two lineages. Our study design allowed us to distinguish true dynamic eQTLs affecting a specific cell lineage from expression changes driven by potentially non-genetic differences between cell lines such as cell composition. Additionally, we used the cell type profiles learned from single-cell data to deconvolve and re-analyze data from matched bulk RNA-seq samples. Using this approach, we were able to identify a large number of novel dynamic eQTLs in single cell data while also attributing dynamic effects in bulk to a particular lineage. Overall, we found that using single cell data to uncover dynamic eQTLs can provide new insight into the gene regulatory changes that occur among heterogeneous cell types during cardiomyocyte differentiation.

A comprehensive evaluation of methods for Mendelian randomization using realistic simulations and an analysis of 38 biomarkers for risk of type 2 diabetes

BACKGROUND

Previous studies have often evaluated methods for Mendelian randomization (MR) analysis based on simulations that do not adequately reflect the data-generating mechanisms in genome-wide association studies (GWAS) and there are often discrepancies in the performance of MR methods in simulations and real data sets.

METHODS

We use a simulation framework that generates data on full GWAS for two traits under a realistic model for effect-size distribution coherent with the heritability, co-heritability and polygenicity typically observed for complex traits. We further use recent data generated from GWAS of 38 biomarkers in the UK Biobank and performed down sampling to investigate trends in estimates of causal effects of these biomarkers on the risk of type 2 diabetes (T2D).

RESULTS

Simulation studies show that weighted mode and MRMix are the only two methods that maintain the correct type I error rate in a diverse set of scenarios. Between the two methods, MRMix tends to be more powerful for larger GWAS whereas the opposite is true for smaller sample sizes. Among the other methods, random-effect IVW (inverse-variance weighted method), MR-Robust and MR-RAPS (robust adjust profile score) tend to perform best in maintaining a low mean-squared error when the InSIDE assumption is satisfied, but can produce large bias when InSIDE is violated. In real-data analysis, some biomarkers showed major heterogeneity in estimates of their causal effects on the risk of T2D across the different methods and estimates from many methods trended in one direction with increasing sample size with patterns similar to those observed in simulation studies.

CONCLUSION

The relative performance of different MR methods depends heavily on the sample sizes of the underlying GWAS, the proportion of valid instruments and the validity of the InSIDE assumption. Down-sampling analysis can be used in large GWAS for the possible detection of bias in the MR methods.

Linear and Nonlinear Mendelian Randomization Analyses of the Association Between Diastolic Blood Pressure and Cardiovascular Events: The J-Curve Revisited

BACKGROUND

Recent clinical guidelines support intensive blood pressure treatment targets. However, observational data suggest that excessive diastolic blood pressure (DBP) lowering might increase the risk of myocardial infarction (MI), reflecting a J- or U-shaped relationship.

METHODS

We analyzed 47 407 participants from 5 cohorts (median age, 60 years). First, to corroborate previous observational analyses, we used traditional statistical methods to test the shape of association between DBP and cardiovascular disease (CVD). Second, we created polygenic risk scores of DBP and systolic blood pressure and generated linear Mendelian randomization (MR) estimates for the effect of DBP on CVD. Third, using novel nonlinear MR approaches, we evaluated for nonlinearity in the genetic relationship between DBP and CVD events. Comprehensive MR interrogation of DBP required us to also model systolic blood pressure, given that the 2 are strongly correlated.

RESULTS

Traditional observational analysis of our cohorts suggested a J-shaped association between DBP and MI. By contrast, linear MR analyses demonstrated an adverse effect of increasing DBP increments on CVD outcomes, including MI (MI hazard ratio, 1.07 per unit mm Hg increase in DBP; P<0.001). Furthermore, nonlinear MR analyses found no evidence for a J-shaped relationship; instead confirming that MI risk decreases consistently per unit decrease in DBP, even among individuals with low values of baseline DBP.

CONCLUSIONS

In this analysis of the genetic effect of DBP, we found no evidence for a nonlinear J- or U-shaped relationship between DBP and adverse CVD outcomes; including MI.

Genome-wide association study identifies 32 novel breast cancer susceptibility loci from overall and subtype-specific analyses

Breast cancer susceptibility variants frequently show heterogeneity in associations by tumor subtype1-3. To identify novel loci, we performed a genome-wide association study including 133,384 breast cancer cases and 113,789 controls, plus 18,908 BRCA1 mutation carriers (9,414 with breast cancer) of European ancestry, using both standard and novel methodologies that account for underlying tumor heterogeneity by estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 status and tumor grade. We identified 32 novel susceptibility loci (P < 5.0 × 10-8), 15 of which showed evidence for associations with at least one tumor feature (false discovery rate < 0.05). Five loci showed associations (P < 0.05) in opposite directions between luminal and non-luminal subtypes. In silico analyses showed that these five loci contained cell-specific enhancers that differed between normal luminal and basal mammary cells. The genetic correlations between five intrinsic-like subtypes ranged from 0.35 to 0.80. The proportion of genome-wide chip heritability explained by all known susceptibility loci was 54.2% for luminal A-like disease and 37.6% for triple-negative disease. The odds ratios of polygenic risk scores, which included 330 variants, for the highest 1% of quantiles compared with middle quantiles were 5.63 and 3.02 for luminal A-like and triple-negative disease, respectively. These findings provide an improved understanding of genetic predisposition to breast cancer subtypes and will inform the development of subtype-specific polygenic risk scores.

A bidirectional Mendelian randomization study supports causal effects of kidney function on blood pressure

Blood pressure and kidney function have a bidirectional relation. Hypertension has long been considered as a risk factor for kidney function decline. However, whether intensive blood pressure control could promote kidney health has been uncertain. The kidney is known to have a major role in affecting blood pressure through sodium extraction and regulating electrolyte balance. This bidirectional relation makes causal inference between these two traits difficult. Therefore, to examine the causal relations between these two traits, we performed two-sample Mendelian randomization analyses using summary statistics of large-scale genome-wide association studies. We selected genetic instruments more likely to be specific for kidney function using meta-analyses of complementary kidney function biomarkers (glomerular filtration rate estimated from serum creatinine [eGFRcr], and blood urea nitrogen from the CKDGen Consortium). Systolic and diastolic blood pressure summary statistics were from the International Consortium for Blood Pressure and UK Biobank. Significant evidence supported the causal effects of higher kidney function on lower blood pressure. Based on the mode-based Mendelian randomization method, the effect estimates for one standard deviation (SD) higher in log-transformed eGFRcr was -0.17 SD unit (95 % confidence interval: -0.09 to -0.24) in systolic blood pressure and -0.15 SD unit (95% confidence interval: -0.07 to -0.22) in diastolic blood pressure. In contrast, the causal effects of blood pressure on kidney function were not statistically significant. Thus, our results support causal effects of higher kidney function on lower blood pressure and suggest preventing kidney function decline can reduce the public health burden of hypertension.

Heritability informed power optimization (HIPO) leads to enhanced detection of genetic associations across multiple traits

Genome-wide association studies have shown that pleiotropy is a common phenomenon that can potentially be exploited for enhanced detection of susceptibility loci. We propose heritability informed power optimization (HIPO) for conducting powerful pleiotropic analysis using summary-level association statistics. We find optimal linear combinations of association coefficients across traits that are expected to maximize non-centrality parameter for the underlying test statistics, taking into account estimates of heritability, sample size variations and overlaps across the traits. Simulation studies show that the proposed method has correct type I error, robust to population stratification and leads to desired genome-wide enrichment of association signals. Application of the proposed method to publicly available data for three groups of genetically related traits, lipids (N = 188,577), psychiatric diseases (Ncase = 33,332, Ncontrol = 27,888) and social science traits (N ranging between 161,460 to 298,420 across individual traits) increased the number of genome-wide significant loci by 12%, 200% and 50%, respectively, compared to those found by analysis of individual traits. Evidence of replication is present for many of these loci in subsequent larger studies for individual traits. HIPO can potentially be extended to high-dimensional phenotypes as a way of dimension reduction to maximize power for subsequent genetic association testing.

Effect of different luteal support schemes on clinical outcome in frozen-thawed embryos transfer cycles

OBJECTIVE

To evaluate the clinical outcome of frozen-thawed embryo transfer (FET) when using different luteal support schemes.

STUDY DESIGN

Retrospective analysis of FET cycles was performed from June 2013 and December 2013. Infertile women, who underwent FET cycles utilizing embryos cryopreserved on day 3 post-insemination following an initial fresh IVF cycle. Patients were divided into three groups according to the luteal support scheme. Grade A (oral administration of progesterone, n=156), Group B (vaginal administration of progesterone, n=345), Group C (dissolved progesterone in oil with intramuscular infection, n=885), and group C was divided into two subgroups according to with (subgroup Cl, n=521) or without (subgroup C2 ,n=364) human chorionic gonadotrophi (hCG) injected intramuscularly. The authors compared patients' characteristics and the pregnancy outcomes of each group.

RESULTS

There was no difference in the patient characteristics of each group. There was no difference in the implantation rate or clinical and ongoing pregnancy rate among oral, vaginal, and intramuscular progesterone groups. The abortion and ectopic pregnancy rates were not significantly different among the three groups.

CONCLUSION

Oral progesterone in the FET cycles is convenient and has similar pregnancy outcomes compared with intramuscular or vaginal administration.

CO₂ sorption kinetics of scaled-up polyethylenimine-functionalized mesoporous silica sorbent

Two CO2 solid sorbents based on polyethylenimine, PEI (M(n) ∼ 423 and 10K), impregnated into mesoporous silica (MPS) foam prepared in kilogram quantities via a scale-up process were synthesized and systematically characterized by a range of analytical and surface techniques. The mesoporous silica sorbent impregnated with lower molecular weight PEI, PEI-423/MPS, showed higher capacity toward CO2 sorption than the sorbent functionalized with the higher molecular weight PEI (PEI-10K/MPS). On the other hand, PEI-10K/MPS exhibited higher thermal stability than PEI-423/MPS. The kinetics of CO2 adsorption on both PEI/MPS fitted well with a double-exponential model. According to this model CO2 adsorption can be divided into two steps: the first is fast and is attributed to CO2 adsorption on the sorbent surface; the second is slower and can be related to the diffusion of CO2 within and between the mesoporous particles. In contrast, the desorption process obeyed first-order kinetics with activation energies of 64.3 and 140.7 kJ mol(-1) for PEI-423/MPS and PEI-10K/MPS, respectively. These studies suggest that the selection of amine is critical as it affects not only sorbent capacity and stability but also the energy penalty associated with sorbent regeneration.

Bio-inspired laminated graphite nanosheets/copper composites

Bio-inspired laminated graphite nanosheets/copper composites with modified mechanical properties.

Enhanced performance configuration for fast-switching deformed helix ferroelectric liquid crystal continuous tunable Lyot filter

In this paper, we present a novel design configuration of double DHFLC wave plate continuous tunable Lyot filter, which exhibits a rapid response time of 185 μs, while the high-contrast ratio between the passband and stop band is maintained throughout a wide tunable range. A DHFLC tunable filter with a high-contrast ratio is attractive for realizing high-speed optical processing devices, such as multispectral and hyperspectral imaging systems, real-time remote sensing, field sequential color display, and wavelength demultiplexing in the metro network. In this work, an experimental prototype for a single-stage DHFLC Lyot filter of this design has been fabricated using photoalignment technology. We have demonstrated that the filter has a continuous tunable range of 30 nm for a blue wavelength, 45 nm for a green wavelength, and more than 50 nm for a red wavelength when the applied voltage gradually increases from 0 to 8 V. Within this tunable range, the contrast ratio of the proposed double wave plate configuration is maintained above 20 with small deviation in the transmittance level. Simulation and experimental results showed the proposed double DHFLC wave plate configuration enhances the contrast ratio of the tunable filter and, thus, increases the tunable range of the filter when compared with the Lyot filter using a single DHFLC wave plate. Moreover, we have proposed a polarization insensitive configuration for which the efficiency of the existing prototype can theoretically be doubled by the use of polarization beam splitters.

Proinflammatory protein CARD9 is essential for infiltration of monocytic fibroblast precursors and cardiac fibrosis caused by Angiotensin II infusion

Background

Angiotensin II (Ang II)–induced cardiac remodeling with the underlying mechanisms involving inflammation and fibrosis has been well documented. Cytosolic adaptor caspase recruitment domain 9 (CARD9) has been implicated in the innate immune response. We aimed to examine the role of CARD9 in inflammation and cardiac fibrosis induced by Ang II.

Methods

Two-month-old CARD9-deficient (CARD9^−/−) and wild-type (WT) male mice were infused with Ang II (1,500 ng/kg/min) or saline for 7 days. Heart sections were stained with hematoxylin and eosin and Masson trichrome and examined by immunohistochemistry; and activity and protein levels were measured in macrophages obtained from mice.

Results

WT mice with Ang II infusion showed a marked increase in CARD9⁺ macrophages in the heart, but CARD9^−/− mice showed significantly suppressed macrophage infiltration and expression of proinflammatory cytokines, including interleukin-1β (IL-1β) and connective tissue growth factor (CTGF). Importantly, Ang II–induced cardiac fibrosis (extracellular matrix and collagen I deposition) was diminished in CARD9^−/− hearts, as was the expression of transforming growth factor-β (TGF-β) and level of myofibroblasts positive for α-smooth muscle actin (α-SMA). Furthermore, Ang II activation of nuclear factor-κB (NF-κB), JNK and p38 mitogen-activated protein kinases (MAPKs) in WT macrophages was reduced in CARD9^−/− macrophages.

Conclusion

CARD9 plays an important role in regulating cardiac inflammation and fibrosis in response to elevated Ang II.

An optimised, small-scale preparation of high-quality RNA from dry seeds of Davidia involucrata

INTRODUCTION

The dormancy of Davidia involucrata seeds normally lasts for an extended period of time and because of this unique property the species is an excellent model for studying the molecular mechanisms of plant dormancy. The use of minimal plant material is desirable for RNA extraction since D. involucrata is a rare plant and it is relatively difficult to collect large amounts of seeds in order to perform molecular biology studies.

OBJECTIVE

To improve the quality of RNA obtained from seeds of D. involucrata by eliminating the oxidation of polyphenols during extraction and by preventing polysaccharides and other impurities from being extracted.

METHODS

A previously described method was modified by the addition of 4% (w/v) poly(N-vinyl-2-pyrrolidone) to the dry seeds during grinding and by adding 5% (v/v) beta-mercaptoethanol and 28% (v/v) ethanol to the extraction buffer. Two further centrifugation steps (5000 and 8000 rpm) were utilised and one-seventh volume of ethanol was incubated with the supernatant at 4 degrees C for 2-3 h prior to the precipitation of RNA.

RESULTS

Following these modifications, an effective method was established for total RNA extraction from a small amount of dry seeds of D. involucrata. The isolated RNA was shown to have high purity and integrity by gel electrophoresis and spectrophotometry, and was confirmed to be suitable for RT-PCR and the construction of cDNA libraries.

CONCLUSION

The modified method reduced the amount of seeds required for extraction of total DNA and was beneficial for preserving the endangered species.

Bacterial virus phi29 pRNA as a hammerhead ribozyme escort to destroy hepatitis B virus

The DNA-packaging pRNA of bacterial virus phi29, which forms dimers and then hexamers, contains two independent tightly self-folded domains. Circularly permuted pRNAs were constructed without impacting pRNA folding. Connecting the pRNA 5'/3' ends with variable sequences did not disturb its folding and function. These unique features, which help prevent two common problems - exonuclease degradation and misfolding in the cell, make pRNA an ideal vector to carry therapeutic RNAs. A pRNA-based vector was designed to carry hammerhead ribozymes that cleave the hepatitis B virus (HBV) polyA signal. The chimeric HBV-targeting ribozyme was connected to the pRNA 5'/3' ends as circularly permuted pRNA. Two cis-cleaving ribozymes were used to flank and process the chimeric ribozyme. The hammerhead ribozyme including its two arms for HBV targeting was able to fold correctly while escorted by the pRNA. The chimeric ribozyme cleaved the polyA signal of HBV mRNA in vitro almost completely. Cell culture studies showed that the chimeric ribozyme was able to enhance the inhibition of HBV replication when compared with the ribozyme not escorted by pRNA, as demonstrated by Northern blot and e-antigen assays. pRNA could also carry another hammerhead ribozyme to cleave other RNA substrate. These findings suggest that pRNA can be used as a vector for imparting stability to ribozymes, antisense, and other therapeutic RNA molecules in vivo.

On modelling the kinestatic charge detector for digital radiographic diagnostic and portal imaging

The kinestatic charge detection (KCD) principle has been a digital radiography technique for more than a decade. The advances of the KCD technique have gone from diagnostic imaging to portal imaging. However, little work has been done on understanding the selection of key KCD parameters and relationships between them. In the present study, an engineering model was established that could be used to optimize the placements of key parameters in terms of KCD system mechanical design. In the proposed KCD engineering model, the basic energy conservation law was applied to the process of ion transmission. It allows for the computation of the KCD design parameters such as the optimum grid placement, high voltage board tilt angle and grid wire space, as well as to provide recommendations on high voltage board and electric potentials and their ratio.

[Activation of transcription factors and induction of cytokines from macrophages in chronic obstructive pulmonary disease]

OBJECTIVE

To investigate the activation of transcription factors and induction of cytokines from alveolar macrophages in chronic obstructive pulmonary disease (COPD).

METHODS

Alveolar macrophages were collected by fibrobronchoscopy from 8 patients with chronic bronchitis, 8 patients with COPD, and 8 healthy volunteers. All patients were at stable stage. The macrophages thus collected were cultured and stimulated with lipopolysaccharide (LPS, 10 micrograms/ml). The IL-8, IL-1 beta, TNF alpha and IL-6 thus produced were measured by ELISA in the supernatant. Nuclear factor-kappa B (NF kappa B), activator protein-1 (AP-1), AP-2 and AP-3 were detected by electrophoretic mobility shift assay.

RESULTS

The concentration of IL-8 released from macrophages of patients with COPD at stable stage before LPS stimulation was about 3 times higher than that in the healthy control (F = 4.34, P < 0.05). The concentration of IL-8 released from macrophages in patients with COPD was increased further after LPS stimulation in comparison to that in healthy controls(F = 3.56, P < 0.05). The concentration of IL-1 beta and that of TNF alpha released from macrophages of COPD patients were further increased after LPS stimulation (P < 0.05) in the COPD patients, but there was no difference in the concentration of IL-1 beta and between the control and COPD patients before LPS stimulation. The constitutive activity of AP-1 and the activity of NF kappa B induced by LPS were higher in the patients with COPD than in the controls.

CONCLUSION

The alverlar macrophages of patients with COPD at stable stage may release higher concentration of IL-8 and IL-1 beta. LPS stimulation increases the release of IL-1 beta and TNF alpha of alveolar macrophages. Enhancement of activity of NF kappa B and AP-1 may positively regulate the production of IL-8 and IL-1 beta in the airflow obstruction.

Protective effect of gypenosides on DNA and RNA of rat neurons in cerebral ischemia-reperfusion injury

AIM

To observe the protective effect of gypenosides (GP) on the neurons of hippocampus, cerebral cortex, corpus striatum, and dentate gyrus in cerebral ischemia-reperfusion injury of rats.

METHODS

Modified 4-vessel occlusion (4-VO) method was used to establish the model of acute global ischemia. The acridine orange (AO) staining method was used to observe the DNA and RNA contents of cerebral ischemia-reperfusion injury model in the areas.

RESULTS

The fluorescent intensity (reflecting DNA and RNA contents) of the DNA and RNA in the areas of cerebral ischemia-reperfusion injury was markedly abated compared with the normal control group. In the group of ig GP (100 mg/kg) it was enhanced compared with the model group and was the same as the normal control group.

CONCLUSION

The injury of the DNA and RNA in the areas of ischemia-reperfusion model was decreased by GP.

3-D AE visualization of bone-cement fatigue locations

This study addresses the visualization of crack locations in bone-cement material using a three-dimensional acoustic emission source location technique. Computer software based on an earthquake location technique was developed to determine AE source locations and was used to investigate material cracks formed at the tip of a notch in bone cement. The computed locations show that the cracks form linear features with dimensions between 0.1 and 0.2 mm although larger linear features (almost 3.5 mm) also are present. There is a difference of about 2.5 mm between the average of the event locations, and the location of the tip of the notch is 2.5 mm, which may be due to the finite size of the sensors (5 mm in diameter).

Attenuation of acoustic emission body waves in acrylic bone cement and synthetic bone using wavelet time-scale analysis

This article addresses acoustic emission (AE) wave attenuation in acrylic bone cement and wave attenuation due to the existence of material interface between acrylic bone cement and sawbone. In this article, a series of tests were performed using standard pencil lead break sources. The attenuation features inside acrylic bone cement and sawbone materials and the attenuation due to the existence of material interfaces such as cement-cement and cement-sawbone were studied. In addition, the discrete wavelet-based signal energy decomposition method was introduced to examine detail breakdown of signal energy distribution of attenuation. From the tests, it was observed that the attenuation of AE signal was linear with respect to the wave travel distance for both energy and amplitude. Furthermore, AE energy attenuation was more sensitive than AE amplitude attenuation. In the analysis of attenuation due to material interfaces, the couplant plays a major role in reducing the attenuation at the interfaces. The attenuation at an interface composed by different material is less compared with an interface composed by the same material.

Detecting residual ischemia and identifying coronary artery disease after myocardial infarction using dobutamine technetium-99m-MIBI SPECT

OBJECTIVE

To evaluate dobutamine technetium-99m methoxy isobutyl nitrile (sestamibi) single-photon emission computed tomography (Dobu-ECT) in detecting residual ischemia and identifying coronary vessel disease after myocardial infarction.

METHODS

Sixty-two patients with confirmed myocardial infarction were studied with Dobu-ECT at the time of coronary artery angiography. Dobutamine was administered intravenously in incremental rates from 5 to 40 micrograms.kg-1.min-1 at 3-minute intervals. At the highest infusion rate, 7.4 x 10(8) Bq 99mTc-MIBI was injected intravenously, and tomographic imaging was performed after one hour. Resting images were taken after 24 hours, with a second dose of 99mTc-MIBI.

RESULTS

The sensitivity of Dobu-ECT in detecting residual ischemia of myocardial infarction was 76%, which was higher than dobutamine electrocardiography (Dobu-ECG). Regardless of the single-, double- or triple-vessel diseases, Dobu-ECT was superior to Dobu-ECG in identifying residual ischemia (56% vs 4%, 86% vs 27%, 100% vs 47%, P < 0.01, respectively). The incidence of residual ischemia in patients receiving thrombolytic therapy was 67%, lower than patients without thrombolysis (72%) or those with an old myocardial infarction (94%). But the differences were not statistically significant. Dobu-ECT detected only 56% of ischemias in non-infarct related myocardium. Eighty-two percent of all significantly stenosed vessels were detected with Dobu-ECT, and 84% of patients with multivessel disease could be accurately identified. The sensitivity of Dobu-ECT was significantly greater for detecting severe stenosis over moderate stenosis. The sensitivity for detecting stenosis in the right coronary artery was greater than left anterior descending or left circumflex, but its specificity was lower.

CONCLUSION

Dobu-ECT can identify residual ischemia, as well as its location and extent after myocardial infarction. Dobu-ECT can also accurately detect significantly stenosed vessels.

Smoking in China: findings of the 1996 National Prevalence Survey

CONTEXT

As the world's largest producer and consumer of tobacco products, China bears a large proportion of the global burden of smoking-related disease and may be experiencing a tobacco epidemic.

OBJECTIVE

To develop an evidence-based approach supporting tobacco control initiatives in China.

DESIGN AND SETTING

A population-based survey consisting of a 52-item questionnaire that included information on demographics, smoking history, smoking-related knowledge and attitudes, cessation, passive smoke exposure, and health status was administered in 145 disease surveillance points in the 30 provinces of China from March through July 1996.

PARTICIPANTS

A nationally representative random sample of 128766 persons aged 15 to 69 years were asked to participate; 120298 (93.8%) provided data and were included in the final analysis. About two thirds of those sampled were from rural areas and one third were from urban areas.

MAIN OUTCOME MEASURES

Current smoking patterns and attitudes; changes in smoking patterns and attitudes compared with results of a previous national survey conducted in 1984.

RESULTS

A total of 41187 respondents smoked at least 1 cigarette per day, accounting for 34.1% of the total number of respondents, an increase of 3.4 percentage points since 1984. Current smoking continues to be prevalent among more men (63%) than women (3.8%). Age at smoking initiation declined by about 3 years for both men and women (from 28 to 25 years). Only a minority of smokers recognized that lung cancer (36%) and heart disease (4%) can be caused by smoking. Of the nonsmokers, 53.5% were exposed to environmental tobacco smoke at least 15 minutes per day on more than 1 day per week. Respondents were generally supportive of tobacco control measures.

CONCLUSION

The high rates of smoking in men found in this study signal an urgent need for smoking prevention and cessation efforts; tobacco control initiatives are needed to maintain or decrease the currently low smoking prevalence in women.

[The effects of Xuezhikang on neointimal proliferation and C-myc gene expression after angioplasty in rabbits]

OBJECTIVE

To investigate the effects of Xuezhikang (XZhK) on the neointimal proliferation and C-myc gene expression after angioplasty in rabbits.

METHODS

Angioplasty for atherosclerotic stenosis of celiac arteries was performed in 30 male white rabbits after being fed with cholesterol-supplemented diet for 8 weeks, which were then randomized to control group, high-cholesterol group and XZhK group. After 4 weeks, the local vessels were collected for morphological observation. C-myc mRNA level was measured with RT-PCR and C-myc protein with immunohistochemical analysis.

RESULTS

Morphological observation showed that the neointimal area in the XZhK group were less than the control group (P < 0.05), and that in control group were less than that in the high-cholesterol group (P < 0.05). The levels of C-myc mRNA measured with RT-PCR and the percentage of C-myc protein positive cell by immunohistochemical analysis were lower in the XZhK group than in the control and high-cholesterol group (P < 0.05), The levels in the latter two groups showed no difference (P > 0.05).

CONCLUSION

XZhK can inhibit the neointimal proliferation and the expression of C-myc gene after angioplasty in rabbits.

Knowledge of HIV/AIDS among health care workers in China

This study was designed to assess knowledge of AIDS among health professionals in China via a cross-sectional survey. A self-administered questionnaire requesting demographic characteristics and basic AIDS knowledge was given to health professionals in 11 provinces, cities, and autonomous regions. Questionnaires were completed by 1,400 of 1,500 (93%) health professionals surveyed. The percentages of correct answers ranged from 3% to 68%. Findings included that public health workers had more knowledge than clinicians; having attended training workshops was not associated with an adequate levels of knowledge; and knowledge differed by professional level and by the geographic region in which they worked. Although most health professionals questioned knew that AIDS is caused by an infectious agents, their knowledge of transmission routes, the "window period" and the length of the incubation period is still inadequate. Thus, health professionals in China urgently need both more training and more effective training. The effectiveness of future HIV/AIDS workshops should be evaluated.

[Measurement of liver volume and its clinical significance in cirrhotic patients]

OBJECTIVE

To evaluate whether, preoperative measurement of liver volume is of value to the evaluation of tolerance to operation and long-term prognosis in cirrhotic patients with portal hypertension.

METHODS

We assessed liver volume in 18 cirrhotics and 31 noncirrhotic controls with 3-dimensional shaded surface display by CT twin.

RESULTS

The liver volume in controls was positively correlated to the height (r = 0.42, P < 0.05). The average of liver volume in controls was (1 070.68 +/- 227.52) cm(3) and was different from that of cirrhotics (797.02 +/- 135.11) cm(3) (P < 0.05). Liver volume of cirrhotic patients with portal hypertension was related to their Child classification. The liver volume of patients in Child C group was significantly smaller than that of patients of Child B group.

CONCLUSIONS

The patients with smaller liver volume are likely complicated by encephalopathy after shunting procedure. However, the liver volume is not significantly correlated with portal blood flux and portosystemic shunt index.

[The effects of inhaled bronchodilators on central inspiratory drive in patients with COPD]

OBJECTIVE

To evaluate the effects of inhaled bronchodilators on the central inspiratory drive in patients with COPD.

METHODS

91 patients with COPD were divided into three groups (A, B, C) randomly. Lung functions and P(0.1) were measured at baseline and 20 min and 60 min after inhalation (A: albuterol; B: iprotropium; C: albuterol + iprotropium).

RESULTS

P(0.1) decreased after inhalation in all three groups (P < 0.05 approximately 0.001). A positive correlation between DeltaP(0.1) and DeltaFRC was found in the three groups (r = 0.4325 - 0.5230, P < 0.05 approximately 0.01). V(E)/P(0.1) increased in the three groups after inhalation (P < 0.05 approximately 0.005). There was significant improvement of V(E)/P(0.1) in group B and C as compared with that of group A (P < 0.05, P < 0.001); There was a different correlative factor with V(E)/P(0.1) in group B and C.

CONCLUSIONS

(1) P(0.1) decreased after inhalation, It may be caused by decreased FRC. (2) V(E)/P(0.1) became appropriate after inhalation in all groups; The improvement in group B and C was superior to that of group A. There may be different mechanisms to improve V(E)/P(0.1) by different inhalators.

Reversion of multidrug resistance in the P-glycoprotein positive breast cancer cell line (MCF-7/ADR) by introduction of hammerhead ribozyme

A hammerhead ribozyme which site-specifically cleaved the GUC position in codon 880 of the mdr1 mRNA was designed. The target site was chosen between the two ATP binding sites, which may be important for the function of the P-Gp as an ATP-dependent pump. A DNA sequence encoding the ribozyme gene was then incorporated into a eukaryotic expression vector (pH beta Apr-1 neo) and transfected into the breast cancer cell line MCF-7/Adr, which is resistant to adriamycin and expresses the MDR phenotype. The ribozyme was stably expressed in the cell line by the RNA dot blotting assay. The result of Northern blot assay showed that the expressed ribozyme could decrease the level of mdr1 mRNA expression by 83.5%; and the expressed ribozyme could inhibit the formation of P-glycoprotein detected by immuno-cytochemistry assay and could reduce the cell's resistance to adriamycin; this means that the resistant cells were 1,000-fold more resistant than the parental cell line (MCF-7), whereas those cell clones that showed ribozyme expression were only 6-fold more resistant than the parental cell line. These results show that a potentially useful tool is at hand which may inactivate MDR1 mRNA and revert the multidrug resistance phenotype.

Physiological basis for long life span

A collection of clinical data is reported on nonagenarians in comparison to an 'average' population of younger age. The results of these clinical data indicated that a vital physiological basis for long life span probably existed. The basis include a better micro-blood-flow state, a better cardiac, immune (nature killer cell activity), adrenocortical, hepatic and renal function, and a higher level of high density lipoprotein cholesterol. It is suggested that the method, including Chinese traditional medicine, to improve the micro-blood-flow, nature killer cell activity, high density lipoprotein cholesterol and vital organ function may be beneficial for life preservation and aging retarding.

[Gastric mucosal hemodynamics of prehepatic portal hypertensive rat model]

OBJECTIVE

To observe the changes of gastric mucosal hemodynamics and discuss the possible regulatory factors of prehepatic portal hypertensive rat.

METHOD

Prehepatic portal hypertensive (PHT) rat model was produced by various degree of portal vein constriction, and gastric mucosal hemodynamics was measured by radioactive microsphere technique. Statistical analysis was performed by ANOVA, the student t test, and linear correlation.

RESULT

The gastric mucosal blood flow was significantly reduced in PHT rats, whereas the blood flow in submucosa, muscular layer prominently increased. The resistance of mucosal vasculature was elevated in PHT rats, however, that of submucosa and muscular layer was decreased remarkably. There was a negative correlation between the gastric mucosal blood flow and portal pressure.

CONCLUSION

The gastric mucosa of prehepatic portal hypertensive rat model is poorly perfused prominently. It may be due to the increased mucosal vascular resistance and elevated portal pressure.

[Portal-systemic shunting and hemodynamics of prehepatic portal hypertensive rat models]

Hemodynamics and relationship between portal-systemic shunting and portal pressure were measured by radioactive microsphere techniques in 31 rats after various degree portal vein constriction. Prominent hyperdynamic state was present in prehepatic portal hypertensive rats models. Both cardiac output and index were increased, the mean arterial pressure and pripheral resistance were reduced significantly. The total splanchnic blood flow was increased but splanchnic resistance reduced remarkably. Portal-systemic shunting flow was higher. There was a significant positive correlation between them, Y = 26.14 + 5.32X (r = 0.76, P < 0.001). For this reason, elevated systemic and portal venous flow provided main impetus for maintaining portal hypertension.

[Experimental studies of high frequency jet ventilation improved by enhancing expiratory turbulence]

OBJECTIVE

To improve the effect on CO2 elimination during high frequency jet ventilation by enhancing expiratory turbulence.

METHODS

Nine healthy dogs with steam-induced type I respiratory failure were basically applied with high frequency jet ventilation (HFJV), and high frequency two-way jet ventilation (HFTJV), HFJV combined with thoracicoabdominal compression (HFJV+TAC), and HFJV combined with thoracicoabdominal compression-decompression (HFJV+ TACD) randomly for 30 min, respectively. The parameters were determined and the Reynolds numbers (NR) were calculated.

RESULTS

Reynolds numbers were more than 3000 in all patterns, suggesting that the airflow was turbulent. Expiratory Na was higher. The NR of the latter three patterns was more significantly higher than that of HFJV (P < 0.01). CO2 elimination was 126, 111, 137 ml. min-1 in the latter three patterns, respectively and significant (P < 0.05) or very significant (P < 0.01) compared with 98.0 ml.min-1 in HFJV. Corresponding changes occurred in PaCO2. NO significant differences (P > 0.05) were observed in hemodynamic parameters.

CONCLUSION

HFJV combined with inverse jet or thoracicoabdominal compression or decompression on expiratory phase could enhance expiratory turbulence and facilitate CO2 elimination in 9 dogs with steam-induced type I respiratory failure.

[Influence of gypenoside on serum lipoprotein and atherosclerosis in hyperlipidaemia animals]

The result of the study indicates that gypenoside (GP, i.g.) can suppress the rise of serum cholesterol (CHO) and triglyceride (TRIG) in hyperlipidaemia mice and lower the content of CHO, TRIG and LDL in hyperlipidaemia quails. The study also shows that GP has a protective effect on diffuse lipoidosis in liver and atherosclerosis in hyperlipidaemia quails, and that GP can lower the lipoprotein levels in hyperlipidaemia animals.

[Surgical treatment of ventricular septal defect complicated by pulmonary hypertension at high altitude]

103 patients (52 males, 51 females) suffered from ventricular septal defect associated with pulmonary hypertension were operated on under sardiopulmonary bypass from 1981-1995 at high altitude. The age of the patients ranged from 2 to 29 years. The ratio of pulmonary systemic arterial pressure was more than 0.91 (0.91 to 1.21). The defects were closed by using dacron patch. The operative mortality was 4.8% among the survivals. 98 patients were followed up for a period from 3 months to 3 years (mean 2.4 years). Excellent results were observed in 93 patients, and good in 4. There was a late death. On account of the improvement in surgical technique, myocardial protection and postoperative care, the result of operation was improved markedly.

[Comparative observation on the relationship between the MEFV and the visual inspection of small airway]

OBJECTIVE

To compare the relationship between the MEFV and the visual inspection of small airway.

METHODS

According to the result on small airway function test (MEFV), the patients were divided into two group: MEFV abnormal group and MEFV normal group. Their bronchus and peripheral airway were observed with bronchofiberscope and ultra-thin bronchofiberscope. The visual appearance of the airways was scored in the light of the presence or absence of erythema, edema, secretions, etc.

RESULTS

The score of visual appearance observed or bronchitis index (BI) in small airway was 7.7 +/- 0.8 (BI: 3.0 +/- 0.8) and 4.7 +/- 1.6 (BI: 1.5 +/- 0.5) respectively in MEFV abnormal group and in MEFV normal group, namely the score in MEFV abnormal group was significantly higher than that of normal group (P < 0.01). The degree of pathological change in small airway was significantly correlated with the results of V25, V50, r = -0.6271, (P < 0.05) and r = 0.6964, (P < 0.02).

CONCLUSION

The abnormal of MEFV may reflect inflamative pathological changes of small airway.

Stable expression of anti-HPV 16 E7-ribozyme in CV-1 cell lines

The HPV16 (human papilloma virus type 16) E7 gene product, an oncoprotein, has been considered to be involved in the pathogenesis of anogenital cancer, particularly of cervical cancer. In order to evaluate the effect of suppression of the expression of the E7 gene in CV-1 cells by ribozyme, Rz523 with a transacting ribozyme targeted to the E7 RNA and two processing ribozyme genes at the 5' and 3' flank was cloned into the eukaryotic expression plasmid pREP9 under the control of RSV-LTR promoter. The resultant plasmid pRSV-Rz523 was transfected into CV-1 cells by calcium phosphate coprecipitation. The expression of the ribozyme in G418-resistant cells was detected by dot-blot hybridization. Ribozymes stably expressed in the CV-1 cells were at a level of 9.0 pmol per 10(6) cells, in which the active ribozyme molecules were more than 50 fmol per 10(6) cells. The result of RNase protection assay showed that the steady-state level of the E7 RNA fragment in CV-1 cell lines was significantly reduced by about 90% in ribozyme-expressing cells. In contrast, the antisense control plasmid pRSV-AE7 only exhibited about 20%. This result implicated the possibility of reversing the malignant phenotype of cervical cancer by means of suppressing the expression of the E7 gene with ribozyme.