颈动脉窦内压的变化速率对反射性降压效应的影响

在成年狗身上制备右侧孤离颈动脉窦,借助灌流装置用饱和氧的任氏液对其进行灌流。灌流压为搏动性的。通过改变每搏泵出量、灌流管道的阻力和弹性来调节灌流压及其变化速率。用多导生理记录仪同步记录股动脉血压、窦内灌流压及其变化速率。本文主要观察窦内压的变化速率对降压反射的影响。在8只狗身上共进行了93次实验。结果表明,在窦内压相同的情况下,灌流压的上升速率愈快,降压效应愈明显,而其下降速率则无显著作用。已有资料证明搏动性窦内压所引起的降压效应较非搏动性压力更为明显。由此可见,狗的颈动脉窦压力感受器不仅对搏动性压力而且对其上升的变化速率也很敏感。     

Lipid status association with 25-hydroxy vitamin D: Cross sectional study of end stage renal disease patients

BackgroundSome observational studies indicate an association of 25-hydroxy vitamin D (25(OH)D) insufficiency and atherogenic cholesterol concentrations. The aim of this study was to investigate relationship between 25(OH)D concentrations and lipid parameters in end stage renal disease (ESRD) patients, separately for predialysis, hemodialysis and peritoneal dialysis patients.MethodsWe have adjusted 25(OH)D concentrations for seasonal variability with cosinor analysis, and performed all further analysis using these corrected 25(OH)D concentrations. Concentrations of 25(OH)D and the lipid parameters were determined in 214 ESRD patients and 50 control group participants. The analysis included the measurement of 25(OH)D by HPLC, apolipoprotein (Apo) AI, ApoB and Lp(a) by nephelometry, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) by spectrophotometry and manually calculated ApoB/ApoAI and LDL-C/HDL-C ratio.ResultsESRD patients with adjusted 25(OH)D concentrations of 50 nmol/L had significantly higher TC (P = 0.005) and ApoAI (P = 0.049). Significantly higher HDLC (P = 0.011) and ApoAI (P = 0.020) were found in hemodialysis patients with the 25(OH)D concentrations of 50 nmol/L. The other analyzed lipid parameters differed significantly between predialysis, hemodialysis and peritoneal dialysis patients with 25(OH)D concentrations of < 50 nmol/L.ConclusionsOur study indicate the significant relationship between 25(OH)D repletion and optimal concentrations of lipid parameters in ESRD patients. Further research is necessary to explain whether joint evaluation of vitamin D status and lipid abnormalities could improve cardiovascular outcome in ESRD patients.     

Improved gossip protocol for blockchain applications

Cluster Computing - Blockchain is a distributed digital ledger consisting of sequence of blocks. These blocks are groups of transactions that make up a sequence where each block contains the...     

木犀草素通过调节凝血活性物质及凝血因子含量维持机体血液循环功能的稳定

目的 探讨木犀草素通过调节凝血活性物质及凝血因子含量维持机体血液循环功能的作用机制.方法 采用试剂盒和试管法测定木犀草素作用后的凝血酶原时间和血浆复钙时间;采用酶联免疫吸附法检测木犀草素对血液凝血活性物质血栓素(TXB2)、纤维酶原激活物抑制剂(PAI-1)、促红细胞生成素(EPO)和凝血因子Ⅶ(FⅦ)、凝血因子Ⅸ(F...     

Comparative proteomic analysis of mesenchymal stem cells derived from human bone marrow,umbilical cord,and placenta: Implication in the migration

Umbilical cord (UC) and placenta (P) have been suggested as alternatives to bone marrow (BM) as sources of mesenchymal stem cells (MSC) for cell therapy, with both UC‐ and P‐MSC possess immunophenotypic and functional characteristics similar to BM‐MSC. However, their migration capacity, which is indispensable during tissue regeneration process, is unclear. Under defined conditions, the migration capacity of BM‐ and P‐MSC was found 5.9‐ and 3.2‐folds higher than that of UC‐MSC, respectively. By the use of 2‐DE and combined MS and MS/MS analysis, six differentially expressed proteins were identified among these MSC samples, with five of them known to be involved in cell migration as migration enhancing or inhibiting proteins. Consistent with their migration capacity, the levels of migration enhancing proteins including cathepsin B, cathepsin D and prohibitin,were significantly lower in UC‐MSC when compared with those in BM‐ and P‐MSC. For the migration inhibiting proteins such as plasminogen activator inhibitor‐1 (PAI‐1) and manganese superoxide dismutase, higher expression was found in the UC‐MSC. We also showed that the overexpression of the PAI‐1 impaired the migration capacity of BM‐ and P‐MSC while silencing of PAI‐1 enhanced the migration capacity of UC‐MSC. Our study indicates that PAI‐1 and other migration‐related proteins are pivotal in governing the migration capacity of MSC.     

Study of the thermal stability of D-amino acid oxidase from Trigonopsis variabilis reveals enzyme inactivation via multiple steps

The thermal stability of a highly purified preparation of D-amino acid oxidase from Trigonopsis variabilis (TvDAO), which does not show microheterogeneity due to the partial oxidation of Cys-108, was studied based on dependence of temperature (20-60°C) and protein concentration (5-100 µmol L^-1). The time courses of loss of enzyme activity in 100 mmol L^-1 potassium phosphate buffer, pH 8.0, are well described by a formal kinetic mechanism in which two parallel denaturation processes, partial thermal unfolding and dissociation of the FAD cofactor, combine to yield the overall inactivation rate. Estimates from global fitting of the data revealed that the first-order rate constant of the unfolding reaction (k _a) increased 10⁴-fold in response to an increase in temperature from 20 to 60°C. The rate constants of FAD release (k _b) and binding (k _-b) as well as the irreversible aggregation of the apo-enzyme (k _agg) were less sensitive to changes in temperature, their activation energy (E _a) being about 52 kJ mol^-1 in comparison with an E _a value of 185 kJ mol^-1 for k _a. The rate-determining step of TvDAO inactivation switched from FAD dissociation to unfolding at high temperatures. The model adequately described the effect of protein concentration on inactivation kinetics. Its predictions regarding the extent of FAD release and aggregation during thermal denaturation were confirmed by experiments. TvDAO is shown to contain two highly reactive cysteines per protein subunit whose modification with 5,5'-dithio-bis (2-nitrobenzoic acid) was accompanied by inactivation. Dithiothreitol (1 mmol L^-1) enhanced up to 10-fold the recovery of enzyme activity during ion exchange chromatography of technical-grade TvDAO. However, it did not stabilize TvDAO at all temperatures and protein concentrations, suggesting that deactivation of cysteines was not responsible for thermal denaturation.     

Biotransformation of cephalosporin C to 7-aminocephalosporanic acid with coimmobilized biocatalyst in a batch bioreactor

The permeabilized cells of Trigonopsis variabilis CCY 15-1-3 having D-amino acid oxidase (DAAO) activity were used to convert cephalosporin C (CPS-C) into 7-(-ketoadipyl amido) cephalosporanic acid (CO-GL-7-ACA) in a batch bioreactor with good aeration and stirring during the process. The deacylation of 7--(4-carboxybutanamido)-cephalosporanic acid (GL-7-ACA) to 7-cephalosporanic acid (7-ACA) by permeabilized cells of Pseudomonas species 3635 having 4--(4-carboxybutamido)-cephalosporanic acid acylase (GL-7-ACA acylase) activity was performed in a batch bioreactor. A spectrophotometric method for the determination of CO-GL-7-ACA and 7-ACA was proposed. Experimental data were fitted by non-linear regression with parameters optimization. The sorption method (without reaction) was applied for the determination of cephalosporin effective diffusion coefficients in Ca-pectate gel beads. These beads were prepared by dropping a potassium pectate gel suspension of inactive permeabilized cells of Trigonopsis variabilis and Pseudomonas species, crosslinked with glutaraldehyde, into a stirred 0.2 M calcium chloride solution. Concentrations of appropriate cephem components were measured by the refractive method. Values of effective diffusion coefficients were calculated by the Fibbonacci optimization method.List of Symbols c _L mol/dm³ concentration on the surface of a bead - c _L0 mol/dm³ initial cephalosporin concentration - c _L mol/dm³ equilibrium cephalosporin concentration in the solution - c _s1 mol/dm³ concentration of CPS-C - c _s2 mol/dm³ concentration of GL-7-ACA - D _ei m²/s effective diffusion coefficient of the components - K _i mol/dm³ inhibition parameter in Eq. (2) - K _{m i} mol/dm³ Michaelis constant in Eq. (1) - K _{m 2} mol/dm³ Michaelis constant in Eq. (2) - n number of beads - q _n nonzero positive roots in Eq. (7) - r ₁ mol/(dm³·s) rate of the conversion of CPS-S to CO-GL-7-ACA - r ₂ mol/(dm³·s) rate of the conversion of GL-7-ACA to 7-ACA - R m radius of the bead - S( ) symbol for total residual sum of squares in Eq. (1) - t s time - V _{m 1} mol/(dm³·s) max. reaction rate in Eq. (1) - V _{m 2} mol/(dm³·s) max. reaction rate in Eq. (2) - V _L dm³ volume of the solution excluding the space occupied by beads - V _s dm³ volume of beads - y _i mol/(dm³ · s) symbol for experimental data in Eq. (1) - _i mol/(dm³· s) symbol for calculated data in Eq. (1) - _P porosity, defined by Eq. (5) - dimensionless parameter, defined by Eq. (6) The authors wish to thank Dr. P. Gemeiner of Slovak Academy of Sciences for rendering of pectate gel. This work is supported by Ministry of Education (Grant No. 1/990 935/93)     

Biotransformation of cephalosporin C to 7-aminocephalosporanic acid with coimmobilized biocatalyst in a batch bioreactor

Biotransformation of cephalosporin C (CPS-C) to 7-aminocephalosporanic acid (7-ACA) was carried out with coimmobilized permeabilized cells of Trigonopsis variabilis and Pseudomonas species entrapped in Ca-pectate gel beads. Good aeration and stirring during the process was assured. The analysis of this complicated biochemical process in a heterogeneous system was based on the identification of individual effects (internal diffusion, reaction) running simultaneously. A spectrophotometric method was proposed for the determination of 7-(-ketoadipyl amido) cephalosporanic acid (CO-GL-7-ACA) and 7-ACA. The reaction-diffusion model containing dimensionless partial differential equations was solved by using the orthogonal collocation method. A good agreement between experimental values and values predicted by the mathematical model was obtained. Numerical simulations were performed on the basis of following the two assumptions:- several times higher activity of both cells,- hydrogen peroxide was continuously supplied in the bioreactor.List of Symbols A m² surface of the bead - c _i mol/dm³ concentration of component in the bead and/or in the solution - c _i0 mol/dm³ initial concentration of component in the solution - c _l0 mol/dm³ initial concentration of CPS-C in the solution - C _jl orthogonal collocation weights of the first derivation - D _ei m²/s effective diffusion coefficient of the components - D _jl orthogonal collocation weights of the second derivation - k ₅ dm³/(mol · s) kinetic parameter of non-enzyme reaction - K _inh mol/dm³ inhibition parameter for the first enzyme reaction - K _i dimensionless Michaelis constant for the first and second enzyme reaction, defined in Eq. (7) - K _l dimensionless inhibition parameter for the first enzyme reaction, defined in Eq. (7) - K _mi mol/dm³ Michaelis constant for the first and second enzyme reaction - n number of beads - P( _i ) symbol of dimensionless reaction rate, defined in Eq. (13) - r m radial coordinate inside the bead - R m radius of the bead - R(c _i ) mol/(dm³ · s) symbol for reaction rate, defined in Eq. (6) - t s time - V _max mol/(dm³ · s) max. reaction rate for the first and second enzyme reaction - V _L dm³ volume of solution excluding the space occupied by beads - voidage in batch bioreactor - _P porosity of the bead - i dimensionless effective diffusion coefficient of the components, defined in Eq. (7) - dimensionless time, defined in Eq. (7) - _mi Thiele modulus, defined in Eq. (7) - _i dimensionless concentration, defined in Eq. (7) - dimensionless radial position inside the bead, defined in Eq. (7) - _l0 initial dimension concentration of CPS-C, defined in Eq. (9), (10) - _i0 initial dimension concentration of component, defined in Eq. (9), (10) The authors wish to thank Dr. P. Gemeiner of Slovak Academy of Sciences for rendering of pectate gel. This work is supported by Ministry of Education (Grant No. 1/990 935/93).