[Association between serum lysophosphatidylcholine level and elderly health index in older people from longevity areas of Guangxi Province].

Objective: To investigate the relationship between serum lysophosphatidylcholine (LPC) level and the health index of the elderly. Methods: A total of 251 subjects were selected from the 2016 baseline survey of the Yongfu Longevity Cohort in Guangxi Province among whom 66, 63 and 122 were in the young and middle-aged group (≤59 years old), the young group (60-89 years old) and the longevity group (≥90 years old), respectively. Demographic data were collected and related indicators of height, weight, blood pressure and lipid metabolism were measured. The cognitive and physical functions of the elderly were assessed by the results of the simple mental state scale and the daily living activity scale to construct the health index of the elderly. The serum levels of LPC16∶0, LPC18∶0, LPC18∶1 and LPC18∶2 were determined by liquid chromatography-tandem mass spectrometry, and the differences among different ages and health status groups were compared. The logistic regression model was used to analyze the relationship between the serum LPC level and the health index of the elderly. Results: With the increase in age, the proportion of female subjects increased, and the rate of smoking and drinking decreased. BMI, TC, TG, LDL-C, diastolic blood pressure, and the four LPCs levels decreased with the increase of age, and systolic blood pressure levels increased with the increase of age (all P values<0.05). There was no significant difference in HDL-C levels among age groups (P>0.05). With the decline of health status in the elderly, serum levels of LPC16∶0, LPC18∶0, LPC18∶1 and LPC18∶2 showed a downward trend (all P values<0.001). After adjusting for age and gender, only LPC18∶0 was associated with the health status in old age [OR (95%CI): 0.48 (0.25-0.92)]. For every 1 standard deviation (16.87 nmol/L) increase in serum LPC18∶0 concentration, the risk of poor health status in old age decreased by 52%. Conclusion: Serum LPC18∶0 was associated with the health status in old age independent of age and sex.

[Research progress on main disease-related factors of healthy life expectancy].

International research on healthy life expectancy (HALE) focuses on inequality of socioeconomic status and individual natural attributes. With the acceleration of population ageing and the increase in average life expectancy, the extension of unhealthy life expectancy and the increase of social and economic burden caused by diseases have gradually attracted the attention of countries around the world. Therefore, the evaluation of disease factors affecting HALE is a meaningful direction in the future. This study introduces the development process and commonly used measurement methods of HALE. According to the definition of health from the Global Burden of Disease Study and World Health Organization, physical and mental diseases such as cardiovascular and cerebrovascular diseases, chronic respiratory diseases, diabetes, malignant tumors and depression were selected to summarize the impact of these diseases and pre-disease states on HALE. It is expected to provide a theoretical basis for the formulation of relevant public health policies and the improvement of quality of life in China.

[Value of glycosylated hemoglobin A1c and apolipoprotein A-1 ratio on predicting outcome of patients with acute coronary syndrome].

Objective: To investigate the predictive value of glycosylated hemoglobin A1c/apolipoprotein A-1 (HbA1c/ApoA-1) ratio for major adverse cardiovascular events (MACEs) in patients with acute coronary syndrome (ACS). Methods: The present study is a retrospective cohort study. ACS patients who were hospitalized and underwent coronary angiography at Beijing Hospital from March 2017 to March 2019 were enrolled. Baseline information such as sex, age, previous history, Gensini score, HbA1c and ApoA-1 were analyzed. Patients were divided into two groups according to presence or absence of MACEs and the difference on HbA1c/ApoA-1 ratio was compared between the two groups. According to the tertiles of HbA1c/ApoA-1 levels, patients were divided into high (5.87-16.12), medium (4.50-5.83) and low (2.11-4.48) HbA1c/ApoA-1 groups. Cox proportional risk model was used to evaluate the differences in MACEs and all-cause mortality among the three groups. Kaplan-Meier survival analysis was used to compare the differences of MACEs between the various HbA1c/ApoA-1 groups. Results: A total of 366 ACS patients were included in this study. The mean age of the patients was (65.9±10.3) years. There were 59 MACEs and 10 all-cause deaths during the mean of (22.3±4.4) months follow-up. After adjusting for age, systolic blood pressure, history of diabetes and Gensini score, the incidence of MACEs was 2.45 times higher in the high HbA1c/ApoA-1 group than in the low HbA1c/ApoA-1 group (95%CI 1.16-5.18, P=0.019). There was no significant difference in all-cause mortality between the high and low HbA1c/ApoA-1 groups (P=1.000). Kaplan-Meier survival analysis showed that patients in the high HbA1c/ApoA-1 group had the highest risk of MACEs, while patients in the low HbA1c/ApoA-1 group had the lowest risk of MACEs (P<0.01). Spearman rank correlation analysis showed that HbA1/ApoA-1 ratio was positively correlated with Gensini score in ACS patients (r=0.274, P<0.01). Conclusion: High HbA1c/ApoA-1 ratio was an independent risk factor for MACEs in ACS patients. Patients with high HbA1c/ApoA-1 ratio had more severe coronary artery disease lesions. HbA1c/ApoA-1 ratio may be used as a potential risk stratification biomarker for ACS patients, it might be useful for the early identification of high-risk population and for predicting the incidence of MACEs among ACS patients.

[Application of indocyanine green fluorescence visualization in surgical resection of abdominal wall endometriosis].

Objective: To investigate the feasibility, effectiveness and safety of indocyanine green (ICG) navigation in the surgical resection of abdominal wall endometriosis (AWE). Methods: Seven women undergoing surgery for AWE in First Affiliated Hospital of Sun Yat-sen University (from July 1, 2021 to October 1, 2021) were collected. After exposure of the focus, ICG were used intravenously (0.25 mg/kg) as fluorescent dye for the intraoperative evaluation of AWE vascularization. Resection of the AWE was guided by direct visualization of the focus under standard laparoscopy with a near-infrared (NIR) camera head. Surgical margin around the AWE (3, 6, 9 and 12 point) and the margin under the focus were obtained for postoperative pathological examination of endometriosis. Time from injection to fluorescence visualization, the proportion of fluorescence visualization, time of fully resection of AWE, side effects related to the use of ICG, perioperative complications as well as the pathological result of the surgical margins were recorded. Results: ICG fluorescence of the AWE were seen in 5 patients (5/7). The mean time from injection to fluorescence visualization was (46.7±9.8) s. The mean time of fully resection of AWE was (16.4±7.0) minutes. There were no side effects related to the use of ICG. The rate of class-A wound healing was 7/7. All of the surgical margins were confirmed endometriosis-negative by postoperative pathological examination. Conclusion: ICG fluorescence visualization could conduct accurate resection of AWE, which is clinically safe and effective.

[Dysregulated proportion of intrahepatic Treg cells and Th17 along with CD8+ T lymphocytes drives disease progression after kasai biliary atresia surgery].

Objective: To analyze the clinicopathological characteristics and intrahepatic immune cells infiltration condition after Kasai biliary atresia surgery. Methods: Data of 28 cases who underwent liver transplantation in the liver transplantation center of our hospital from June 2017 to March 2019 were enrolled. Of which, 20 cases were in the biliary atresia group (divided into two subgroups: 10 cases without Kasai surgery and 10 cases after Kasai surgery, and latter subsided cholestasis) and 8 cases in the control group. Clinical and pathological morphological characteristics of the groups were compared. Liver tissue sections were stained with immunohistochemistry and CD3, CD4, CD8, CD20, Foxp3, and interleukin-17A were quantitatively analyzed. Kruskal-Wallis test was used to measure the above indicators, and rank-sum test or Fisher's exact test was used to compare the count data. Results: The degree of clinical and pathological cholestasis in the biliary atresia group after Kasai surgery was significantly lower than that of the group without Kasai surgery, and the degree of liver fibrosis was also significantly reduced (P < 0.05), but there was no statistically significant difference in the degree of inflammation in the portal vein area between the two groups (P > 0.05). There was statistically significant difference in the types of immune cells infiltrated in the liver (P < 0.05). Compared with the group without Kasai surgery, the infiltration of CD3, CD8, IL-17A and Foxp3 positive cells in the portal vein area after Kasai surgery group (P < 0.05) was significantly reduced, but there was no statistically significant difference in the proportion of Foxp3/CD4 positive cells between the two groups (P > 0.05), which continued to be lower than that of the control group (P < 0.05). Compared with the non-Kasai surgery group, the proportion of Foxp3/IL-17A and Foxp3/CD8 positive cells in the portal vein area did not increase significantly after Kasai surgery group (P > 0.05), and remained lower than the control group. However, the proportion of Foxp3/IL-17A and Foxp3/CD8 positive cells was significantly reduced (P ​​< 0.05). Conclusion: Intrahepatic inflammatory cell infiltration and regulatory/effector T lymphocyte proportion dysregulation exist in patients with subsided cholestasis after Kasai biliary atresia surgery, which may be an important factor to promote the disease progression.

[Plasm trimethylamine-N-oxide level and association with lesion severity in coronary heart disease patients with type 2 diabetes mellitus].

Objective: To investigate the association between trimethylamine-N-oxide (TMAO) and the degree of coronary atherosclerosis in coronary heart diseases (CHD) patients with type 2 diabetes mellitus. Methods: Consecutive patients, who underwent coronary angiography due to suspected CHD in Beijing Hospital from November 2016 to January 2018, were screened in this cross-sectional study. According to blood glucose level, previous medical history and coronary angiography results, they were divided into CHD without type2 diabetes mellitus(CHD-nDM) group and CHD with type2 diabetes mellitus(CHD-DM) group. Plasma TMAO levels in each group were measured by LC-MS/MS. Spearman correlation analysis was used to evaluate the correlation between TMAO and the number of diseased vessels and Gensini scores. Multivariate logistic regression was used to analyze the correlation between TMAO and high Gensini scores. Results: A total of 590 patients were enrolled in the study, including 238 patients in CHD-DM group and 352 patients in CHD-nDM group. Patients were older, body mass index, blood pressure level, prevalence of history of hypertension and statins use were higher in CHD-DM group than in CHD-nDM group (all P<0.05). The proportion of patients with multivessel disease (2 or more vessels) was also higher in CHD-DM group than in CHD-nDM group (P<0.001). Gensini score was higher in CHD-DM group than in CHD-nDM group (P<0.05). Fasting blood glucose, glycosylated hemoglobin and urea were significantly higher, while low-density lipoprotein cholesterol and hemoglobin were significantly lower in CHD-DM group than in CHD-nDM group (all P<0.05). The levels of TMAO was significantly higher in CHD-DM group than in CHD-nDM group (P<0.001). Spearman correlation analysis showed that TMAO was positively correlated with the number of diseased vessels, Gensini score, age and blood glucose level (r=0.178, 0.189, 0.260, 0.111, respectively, all P<0.01). Multivariate logistic regression analysis showed that, TMAO level was still positively correlated with high Gensini score in CHD-DM group (OR=2.25, 95%CI 1.16-4.38, P=0.017), but not in CHD-nDM group (OR=1.29, 95%CI 0.72-2.31, P=0.386) after adjusting for age, sex, body mass index, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, total cholesterol, triglyceride, history of hypertension, hyperlipidemia, smoking and statin use. Conclusions: In CHD patients with tupe 2 diabetes mellitus, the plasma TMAO level is significantly increased and is independent and positively correlated with the degree of coronary artery disease.

Identification of serum metabolites associated with obesity and traditional risk factors for metabolic disease in Chinese adults.

BACKGROUND AND AIMS: Obesity is a major worldwide health problem and is often associated with many metabolic diseases. Levels of several serum-specific metabolites may be altered in patients with these metabolic diseases. We aimed to investigate the associations of serum metabolite levels with obesity and traditional risk factors for metabolic disease in Chinese individuals. METHODS AND RESULTS: Six-hundred Chinese individuals undergoing annual physical exams were recruited and categorized into overweight/obese and control groups (1:1 ratio). We simultaneously quantified the serum lysophosphatidylcholine (LPC), branched-chain amino acids (BCAA), aromatic amino acids (AAA), 25-hydroxyvitamin D, glutamine (Gln), glutamic acid (Glu), and Gln/Glu ratio levels using our previously established targeted serum metabolomic method. The overweight/obesity group had significantly higher levels of BCAA, AAA, and Glu, as well as lower levels of unsaturated LPC, Gln, and Gln/Glu, than the control group. Correlation analyses revealed significant and positive relationships of saturated LPC, BCAA, AAA, and Glu with blood pressure, glucose, triglycerides, apolipoprotein B, and high-sensitivity C-reactive protein, while unsaturated LPC, Gln, Gln/Glu, and 25-hydroxyvitamin D exhibited an opposite trend. In the multifactor logistic regression model, low unsaturated LPC and Gln/Glu, as well as high BCAA and AAA levels, were found to be independent risk factors for obesity; the odds ratios (95% confidence interval) of the highest quartile compared to the lowest quartile were 0.241 (0.139-0.417), 0.436 (0.252-0.755), 3.944 (2.094-7.430), and 2.357 (1.274-4.361) (P < 0.01), respectively. CONCLUSION: LPC, BCAA, AAA, and Gln/Glu are significantly related to obesity development and risk factors of some metabolic diseases.

[Personalized repeat Gamma Knife Radiosurgery treatment in patients with recurrent refractory trigeminal neuralgia].

Objective: To analyze the prognosis and untoward effect in recurrent refractory trigeminal neuralgia (RRTN) patients who underwent repeat Gamma Knife Radiosurgery treatment (GKRS) retrospectively, and to summarize the experience of repeat Gamma Knife Radiosurgery treatment of recurrent refractory trigeminal neuralgia. Methods: RRTN patients who treated with repeat GKRS during 1998.8.1 to 2014.10.1 in Gamma Knife treatment Center of the Fifth Affiliated Hospital of Zhengzhou University were involved. The factors influencing long-term prognosis and facial numbness adverse reactions were statistically analyzed. Results: Therapeutic dose was an independent factor that influence long-term prognosis of RRTN patients. Therapeutic dose was a dangerous factor that influence long-term facial numbness. Interval time between twice GKRS treatment was a favorable factor for facial numbness. Long-term prognosis of repeat GKRS treatment was positively correlated with therapeutic dose. Untoward effect of facial numbness after repeat GKRS treatment was positively correlated with therapeutic dose and negatively correlated with interval time between twice GKRS treatment. Conclusions: Repeat GKRS for RRTN patients is safe and effective, but personalized treatment plan should be given according to the patient's own condition.

Association of branched-chain amino acids with coronary artery disease: A matched-pair case-control study.

BACKGROUND AND AIM: Several recent studies have found an independent relationship between levels of plasma branched-chain amino acids (BCAAs) and risk factors for coronary artery disease (CAD); however, few studies have investigated the associations of BCAAs with CAD and the risk of cardiovascular events. Therefore, the aim of this study was to investigate the relationship between BCAAs and CAD. METHODS AND RESULTS: We studied 143 patients with CAD diagnosed by coronary angiography at Beijing Hospital (Beijing, China) during 2008-2011. Apparently healthy control individuals (n = 286) and the patients with CAD were matched (2:1 ratio) by age and gender. The healthy control individuals were selected at random from a set of subjects who attended an annual physical examination at the same hospital in 2011. Conditional logistic regression models were used to evaluate the associations between measured variables and CAD. After multivariate adjustment for traditional CAD risk factors, each one-standard-deviation increase in BCAA concentration was associated with an approximately twofold increase in the risk of CAD (odds ratio = 1.63, 95% confidence interval (CI): 1.21-2.20, P = 0.001). As compared with subjects in the lowest quartile of BCAA levels, the odds ratios (95% CIs) for CAD risk in subjects belonging to quartiles 2, 3, and 4 were 1.65 (0.75-3.61), 2.04 (0.92-4.53), and 3.86 (1.71-8.69), respectively (P trend = 0.01). CONCLUSION: Our results demonstrate that BCAAs are significantly related to CAD development. This relationship is independent of diabetes, hypertension, dyslipidemia, and body mass index.

Effects of 420-nm intense pulsed light in an acne animal model.

BACKGROUND: Blue light in the 400-420 nm range has been shown to reduce the levels of Propionibacterium acnes (P. acnes) in the skin. P. acnes has been postulated to be a critical trigger for inflammatory acne. Thus, treatment with 420 nm-intense pulsed light should reduce inflammatory activity in acne. AIM: To evaluate the clinical and histological effects of 420 nm-intense pulsed light treatment on acne in animal model. METHOD: Inflammation acne animal model was constructed by intradermal injection of P. acnes of rat auricular. Levels of tumour necrosis factor alpha (TNF-α) and matrix metalloproteinase 2 (MMP-2), markers of inflammation implicated in acne, were assessed in treated and untreated animals by immunohistochemistry and quantitative polymerase chain reaction (PCR). RESULT: Treatment with 420 nm intense pulsed light led to marked improvement after 6 biweekly treatments. Immunohistochemistry and PCR showed that TNF-α and MMP-2 levels correlated with the extent of acneiform activity and were reduced by treatment with 420 nm light. CONCLUSION: A 420-nm intense pulsed light may exert its beneficial effects on inflammatory acne by reducing the levels of P. acnes and secondarily reducing inflammation induced by the bacteria.

Carotenoids retention and in vitro iron bioavailability of traditional cowpea leaf dishes of rural Tanzania.

Food preparation methods play a role in micronutrient retention and ultimately intake. Analyses for carotenoids retention and in vitro iron bioavailability of five cowpea leaf dishes prepared according to the traditional methods of rural Tanzania were carried out. All the five dishes are commonly eaten as relishes for staple meals of maize or rice. Laboratory analyses were carried out at the Nutrition Laboratory of the World Vegetable Centre in Taiwan. Carotenoids were analysed by high-performance liquid chromatography while iron bioavailability was analysed by an in vitro method. Results showed that traditional cowpea leaf dish consisting of sunflower oil, onion, tomatoes and coconut milk cooked for 30 min had the highest retention of ß-carotene (40.83 ± 7.00%) and lutein (34.60 ± 3.30%) compared to other traditional recipes (p < 0.05). The highest iron bioavailability (10.04 ± 0.49%) was observed in the traditional recipe which involved boiling fresh cowpea leaves for 15 min. Although recipe variation can affect carotenoids retention and iron bioavailability, simple practices such as reduced cooking time and avoiding direct sun drying also need to be promoted.

Menaquinone-7 protects astrocytes by regulating mitochondrial function and inflammatory response under hypoxic conditions.

OBJECTIVE: Astrocytes play a key role in hypoxic brain injury. The aim of our research was to determine the effects of menaquinone-7 (MK-7), a subtype of vitamin K2 (VK2), on astrocytes during hypoxia and its potential mechanisms. MATERIALS AND METHODS: Astrocytes from the palliums of newborn Sprague Dawley rats were cultured. An astrocyte-hypoxia model was established using a hypoxia workstation. Cell Counting Kit-8 (CCK-8) and BrdU assays were used to determine the effects of MK-7 on hypoxic astrocytes. 2',7'-Dichlorodihydrofluorescein diacetate (DCFDA) or dihydroethidium (DHE) assays were conducted to detect the levels of reactive oxygen species (ROS). An ATP assay was used to measure intracellular ATP production. The levels of proinflammatory cytokines and chemokines containing interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), CC-chemokine ligand 2 (CCL2), and CXC-chemokine ligand 10 (CXCL10), as well as vitamin K-dependent protein growth arrest-specific 6 (Gas6), were determined in hypoxia-induced astrocytes, in the presence or absence of MK-7 pretreatment. Small interfering RNA (siRNA) was used to knockdown Gas6 expression to determine its role in hypoxic astrocytes pretreated with MK-7. RESULTS: Hypoxia reduced astrocyte viability and proliferation significantly; however, when pretreated with MK-7, these conditions remarkably increased. MK-7 also inhibited hypoxia-induced ROS production and enhanced ATP generation of hypoxic astrocytes. Pretreatment with MK-7 effectively reduced the expression of IL-6, TNF-α, CCL2, and CXCL10 but enhanced the expression of Gas6 in hypoxic astrocytes. Gas6 inhibition markedly attenuated the decline in MK-7-induced ROS generation and IL-6 expression, and weakened MK-7-induced cell viability and ATP production in hypoxic astrocytes. CONCLUSIONS: Our study is the first to confirm that MK-7 can protect astrocytes from hypoxia-induced cytotoxicity, possibly by inhibiting mitochondrial dysfunction and the expression of proinflammatory cytokines. Gas6 may also participate in these protective effects.

Characterization of interparticle forces in the packing of cohesive fine particles.

We numerically investigate force structures in the packing of fine cohesive particles using the discrete element method. By changing the particle size and therefore the van der Waals force, the effect of cohesion on the normal contact force and the total normal force, which is the sum of the normal contact forces and the van der Waals forces, is analyzed. It is shown that, with decreasing particle size, the normal contact forces become more uniform and have a narrower and more symmetric distribution, while the distributions of the total normal forces widen. Spatial correlation between the interparticle forces exists for the packing of coarse noncohesive particles. As the particle size decreases, this correlation becomes weaker for the contact forces but stronger for the total normal forces. A comparison between the effective weight of particles and the internal force structure suggests that there are differences between the particle-particle and particle-wall forces. The bimodal distribution of the effective weight indicates that there may exist two phases in the packings when cohesion is present, governed by the compressive and tensile stresses.

Pore structure of the packing of fine particles.

This paper presents a numerical study of the pore structure of fine particles. By means of granular dynamics simulation, packings of mono-sized particles ranging from 1 to 1000 microm are constructed. Our results show that packing density varies with particle size due to the effect of the cohesive van der Waals force. Pores and their connectivity are then analysed in terms of Delaunay tessellation. The geometries of the pores are represented by the size and shape of Delaunay cells and quantified as a function of packing density or particle size. It shows that the cell size decreases and the cell shape becomes more spherical with increasing packing density. A general correlation exists between the size and shape of cells: the larger the cell size relative to particle size, the more spherical the cell shape. This correlation, however, becomes weaker as packing density decreases. The connectivity between pores is represented by throat size and channel length. With decreasing packing density, the throat size increases and the channel length decreases. The pore scale information would be useful to understand and model the transport and mechanical properties of porous media.

Galectin-1 induces nuclear translocation of endonuclease G in caspase- and cytochrome c-independent T cell death.

Galectin-1, a mammalian lectin expressed in many tissues, induces death of diverse cell types, including lymphocytes and tumor cells. The galectin-1 T cell death pathway is novel and distinct from other death pathways, including those initiated by Fas and corticosteroids. We have found that galectin-1 binding to human T cell lines triggered rapid translocation of endonuclease G from mitochondria to nuclei. However, endonuclease G nuclear translocation occurred without cytochrome c release from mitochondria, without nuclear translocation of apoptosis-inducing factor, and prior to loss of mitochondrial membrane potential. Galectin-1 treatment did not result in caspase activation, nor was death blocked by caspase inhibitors. However, galectin-1 cell death was inhibited by intracellular expression of galectin-3, and galectin-3 expression inhibited the eventual loss of mitochondrial membrane potential. Galectin-1-induced cell death proceeds via a caspase-independent pathway that involves a unique pattern of mitochondrial events, and different galectin family members can coordinately regulate susceptibility to cell death.

Plant-cell bioreactors with simultaneous electropermeabilization and electrophoresis.

Experimental investigations on using low-level electric currents and voltages to extract, transport, and collect intracellular secondary metabolites from plant cells while maintaining their viabilities were conducted focusing on the production of: (1) ionic betalains, mainly negatively-charged betanin, from Beta vulgaris cells, and (2) ionic alkaloids, particularly positively-charged ajmalicine and yohimbine, from Catharanthus roseus cells. Three versions of tubular membrane reactors in which electropermeabilization of cell membranes and electrophoresis and diffusion of ionic products take place simultaneously, with or without convective flow, to achieve desirable extraction were developed. Concentrations of secondary metabolites produced from these plant-cell reactors under steady and oscillatory electrical forcings were recorded and the viabilities of treated cells examined. Oscillatory application of electrical field appears to produce more products while retaining higher cell viability.

Self-sustained pH oscillations in immobilized proteolytic enzyme systems.

This work represents our first step toward fulfilling the need to discover a model system for experimental investigations of temporal oscillations, pattern formations, and other non-linearity related dynamic behavior in immobilized-enzyme-membrane systems. In this paper, the regions in the parameter space where self-sustained pH oscillations can be induced were determined via extensive numerical simulation for five enzyme-membrane systems involving four proteolytic enzymes: alpha-chymotrypsin, trypsin, bromelain, and ficin. From this study, we concluded that, even with current enzyme-immobilization techniques, the possibility of experimentally observing self-sustained pH oscillations in a flat membrane immobilized with alpha-chymotrypsin and using N-acetyl-L-tryptophan ethyl ester as a substrate is high. Under suitable conditions and with extra efforts, self-sustained oscillations may also occur in membrane systems immobilized with ficin, trypsin and bromelain.

Self-sustained pH oscillations in a compartmentalized enzyme reactor system.

This work represents our continued effort toward fulfilling the need to discover a model system for experimental investigations of temporal oscillations in an enzyme-membrane system. In this paper, the regions in the parameter space where self-sustained pH oscillations can be induced for a compartmentalized enzyme reactor system, which consists of a well-stirred reactor, a reservoir and a membrane containing no enzyme, were determined via numerical simulation with two proteolytic enzymes: papain (EC 3.4.22.2) and alpha-chymotrypsin (EC 3.4.21.1). The sizes of the regions were qualitatively compared with those associated with enzymic membrane system. As a result, we found that the possibility of experimentally observing self-sustained oscillations in the compartmentalized papain reactor system, as well as in the papain-membrane system, is high. However, self-sustained pH oscillations are less likely in the compartmentalized alpha-chymotrypsin reactor system than in the alpha-chymotrypsin-membrane system.

Voronoi tessellation of the packing of fine uniform spheres.

The packing of uniform fine spherical particles ranging from 1 to 1000 microm has been simulated by means of discrete particle simulation. The packing structure is analyzed, facilitated by the well established Voronoi tessellation. The topological and metric properties of Voronoi polyhedra are quantified as a function of particle size and packing density. The results show that as particle size or packing density decreases, (i) the average face number of Voronoi polyhedra decreases, and the distributions of face number and edge number become broader and more asymmetric; (ii) the average perimeter and area of polyhedra increase, and the distributions of polyhedron surface area and volume become more flat and can be described by the log-normal distribution. The topological and metric properties depicted for the packing of fine particles differ either quantitatively or qualitatively from those reported in the literature although they all can be related to packing density. In particular, our results show that the average sphericity coefficient of Voronoi polyhedra varies with packing density, and although Aboav-Weaire's law is generally applicable, Lewis's law is not valid when packing density is low, which are contrary to the previous findings for other packing systems.