Novel stable PACAP analogs with potent activity towards the PAC1 receptor

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38- or 27-amino acid neuropeptide with promising therapeutic applications for the treatment of several pathophysiological states related to neurodegenerative diseases. However, its use for therapeutic applications is actually limited by its restricted bioavailability and rapid degradation. Therefore, metabolically stable PACAP analogs represent promising tools to further investigate the physiological roles of PACAP and ascertain its usefulness in some clinical conditions. In this study, derivatives of PACAP27 and PACAP38 have been rationally designed to develop PAC1 receptor agonists resistant to peptidase action. Results showed that N-terminal modifications confer resistance to dipeptidyl peptidase IV, a major proteolytic process involved in PACAP degradation. Moreover, in vitro incubation of both PACAP isoforms in human plasma revealed that PACAP38 is rapidly metabolized, with a half-life of less than 5 min, while PACAP27 was stable in these experimental conditions. Hence, following the elucidation of its plasmatic metabolites, PACAP38 was modified at its putative endopeptidase and carboxypeptidase sites of cleavage. All peptide analogs were tested for their ability to bind the PAC1 receptor, as well as for their potency to induce calcium mobilization and inhibit PC12 cell proliferation through the PAC1 receptor. This approach revealed two leading compounds, i.e. acetyl-[Ala¹⁵, Ala²⁰]PACAP38-propylamide and acetyl-PACAP27-propylamide, which exhibited improved metabolic stability and potent biological activity. This study describes innovative data related to PACAP metabolism in human plasma and depicts the development of a metabolically stable PACAP38 analog, acetyl-[Ala¹⁵, Ala²⁰]PACAP38-propylamide, which behaves as a super-agonist towards the PAC1 receptor.     

An operator splitting method for solving the bidomain equations coupled to a volume conductor model for the torso

In this paper we present a numerical method for the bidomain model, which describes the electrical activity in the heart. The model consists of two partial differential equations (PDEs), which are coupled to systems of ordinary differential equations (ODEs) describing electrochemical reactions in the cardiac cells. Many applications require coupling these equations to a third PDE, describing the electrical fields in the torso surrounding the heart. The resulting system is challenging to solve numerically, because of its complexity and very strict resolution requirements in time and space. We propose a method based on operator splitting and a fully coupled discretization of the three PDEs. Numerical experiments show that for simple simulation cases and fine discretizations, the algorithm is second-order accurate in space and time.     

An assessment of sample processing methods for stable isotope analyses of marine food webs

Carbon and nitrogen stable isotope ratios are commonly used in the study of marine food webs. However, different sample processing methods can influence the measurement of these stable isotope ratios. The purpose of this study is to define an adequate methodology to be used in the construction of whole food webs. It is demonstrated that acidification of the samples results in a decrease in carbon stable isotope values for sedimentary organic matter, suspended particulate organic matter, plankton and invertebrates with carbonated structures. The response was variable for nitrogen isotope ratios. Based on our results we recommend sample acidification for carbon analysis in these compartments where effects of this treatment were observed. We observed a decrease in δ¹³C values after washing with distilled water, so we do not recommend washing with water after acidification. For nitrogen analysis, acidification should be avoided. The various dehydration treatments studied caused significant differences only in nitrogen isotope ratios.     

PBL健康教育模式在COPD稳定期患者中的应用

目的探讨PBL健康教育模式对慢性阻塞性肺疾病(COPD)稳定期患者疾病相关知识知晓率及治疗依从性的影响。方法将252例COPD稳定期患者随机分为观察组136例和对照组116例。对照组采用传统的健康教方法进行宣教,观察组按照PBL健康教育模式进行宣教,比较两组患者对疾病相关知识的知晓率及治疗依从性。结果与对照组比较,观察组对COPD相关知识知晓率及治疗依从性均较高,差异有统计学意义(P0.01)。结论 PBL在COPD稳定期患者的健康教育中更具有针对性,有效改善了患者对COPD相关知识的知晓率及治疗依从性,从而有利于疾病的康复。     

Mathematical and numerical analysis for a model of growing metastatic tumors

In cancer diseases, the appearance of metastases is a very pejorative forecast. Chemotherapies are systemic treatments which aim at the elimination of the micrometastases produced by a primitive tumour. The efficiency of chemotherapies closely depends on the protocols of administration. Mathematical modeling is an invaluable tool to help in evaluating the best treatment strategy. Iwata et al. [K. Iwata, K. Kawasaki, N. Shigesad, A dynamical model for the growth and size distribution of multiple metastatic tumors, J. Theor. Biol. 203 (2000) 177.] proposed a partial differential equation (PDE) that describes the metastatic evolution of an untreated tumour. In this article, we conducted a thorough mathematical analysis of this model. Particularly, we provide an explicit formula for the growth rate parameter, as well as a numerical resolution of this PDE. By increasing our understanding of the existing model, this work is crucial for further extension and refinement of the model. It settles down the framework necessary for the consideration of drugs administration effects on tumour development.     

On the optimal path in the dynamic pool model for a fishery

Ecosystem-based fishery management (EBFM) is a new direction for fishery management, essentially reversing the order of management priorities to start with the ecosystem rather than the target species. This concept of management is a direct extension of the concept of a holistic approach incorporating interspecific interactions and physical environmental influences. However, because of the limited understanding of the complexity of marine ecosystems, few fisheries are actually managed on a multispecies basis. Even now, in order to specify a practical fishing policy we need a single-species model and utilize it by partially taking account of the effects of other factors mentioned above on the target species biomass. In fact, it is contended that in systems with moderate amounts of data, EBFM could be characterized by effective single-species management with the addition of precautionary set-asides for unknown ecosystem components. Hence, it is still necessary to examine a single-species model so as to clarify the extent of its applicability. The model investigated in this paper is what is called the dynamic pool model, which was proposed by C.W. Clark in the mid-1970s as a dynamic optimization of the classic Beverton and Holt static model for a fishery, in an attempt to make the process of growth and aging inherent in each of the creature resources reflect directly into the economic process. This dynamic model has been applied to a wide variety of commercial fish species. However, the applications have been largely confined to computer simulations using the discrete-time stand-by of the original Clark continuous-time model. This situation is caused mainly by the complexity of the mathematical structure of the Clark model. In this paper, we first specify the material related to the complexity. Subsequently, we provide a rigorous proof for the long-standing conjecture due to Clark concerning the optimal path or harvesting schedule. In addition, two derivative cases are examined: one is the case in which a year-class of fish leaves a given fishing sea area permanently before its natural biomass peaks, the other is the case in which the escapement of a year-class is required to be more than a given minimum level.     

A proteomic method for the analysis of changes in protein concentrations in response to systemic perturbations using metabolic incorporation of stable isotopes and mass spectrometry

While several techniques exist for assessing quantitative differences among proteomes representing different cell states, methods for assessing how these differences are mediated are largely missing. We present a method that allows one to differentiate between cellular processes, such as protein synthesis, degradation and PTMs which affect protein concentrations. An induced systemic perturbation of a cell culture was coupled to a replacement of the growth medium to one highly enriched in the stable isotope 15N. The relative abundance of the 15N- and 14N-enriched forms of proteins, isolated from cell cultures harvested at time points following the onset of the perturbation, were determined by MS. Alterations in protein synthesis and degradation were quantified by comparing proteins isolated from perturbed and unperturbed cultures, respectively. The method was evaluated by subjecting HeLa cells to heat stress. As expected, a number of known heat shock proteins (Hsp) increased in concentration during heat stress. For Hsp27, increased de novo synthesis accounted for the concentration increase, while for Hsp70, decreased degradation accounted for the increase. A protein that was detected only after prolonged heat stress, vimentin, was not primarily synthesized de novo, but appeared rather as a result of PTM.     

An age-structured within-host HIV-1 infection model with virus-to-cell and cell-to-cell transmissions

In this paper, a within-host HIV-1 infection model with virus-to-cell and direct cell-to-cell transmission and explicit age-since-infection structure for infected cells is investigated. It is shown that the model demonstrates a global threshold dynamics, fully described by the basic reproduction number. By analysing the corresponding characteristic equations, the local stability of an infection-free steady state and a chronic-infection steady state of the model is established. By using the persistence theory in infinite dimensional system, the uniform persistence of the system is established when the basic reproduction number is greater than unity. By means of suitable Lyapunov functionals and LaSalle's invariance principle, it is shown that if the basic reproduction number is less than unity, the infection-free steady state is globally asymptotically stable; if the basic reproduction number is greater than unity, the chronic-infection steady state is globally asymptotically stable. Numerical simulations are carried out to illustrate the feasibility of the theoretical results.     

Verification and comparison of four numerical schemes for a 1D viscoelastic blood flow model

A reliable and fast numerical scheme is crucial for the 1D simulation of blood flow in compliant vessels. In this paper, a 1D blood flow model is incorporated with a Kelvin–Voigt viscoelastic arterial wall. This leads to a nonlinear hyperbolic–parabolic system, which is then solved with four numerical schemes, namely: MacCormack, Taylor–Galerkin, monotonic upwind scheme for conservation law and local discontinuous Galerkin. The numerical schemes are tested on a single vessel, a simple bifurcation and a network with 55 arteries. The numerical solutions are checked favorably against analytical, semi-analytical solutions or clinical observations. Among the numerical schemes, comparisons are made in four important aspects: accuracy, ability to capture shock-like phenomena, computational speed and implementation complexity. The suitable conditions for the application of each scheme are discussed.     

Positive solutions of an elliptic system arising from a model in evolutionary ecology

We give sufficient and almost necessary conditions for the existence of positive solutions to an elliptic system satisfying various Dirichlet boundary conditions. The elliptic system consists of the steady-state equations of a parabolic system used to model the growth and spread of a particular gene and population living in a bounded region. The model takes into account the fact that the fitness of the individuals in the population may depend on the population size. Some non-existence results are also included.Research partially supported by NSF grant no. DMS-8801968     

Enzymes used for the determination of HbA1C

To develop an enzymatic measurement of HbA(1C), two key enzymes, i.e., fructosyl peptide oxidase and Aspergillus protease were characterized. Fructosyl peptide oxidase from Eupenicillium terrenum was a flavoenzyme that could catalyze the oxidation of N-(1-deoxyfructosyl)-Val-His. The enzyme showed high specificity toward alpha-glycated molecules, therefore it seemed suitable for the HbA(1C) assay. Since high levels of FPOX expression seemed toxic to host cells, we applied a gene expression system using a bacteriophage vector and achieved high levels of expression in Escherichia coli. Next, we found that Aspergillus protease was able to digest N-(1-deoxyfructosyl)-hexapeptide, a glycated peptide that was released from the beta-chain of HbA(1C) by Glu-C endoproteinase. We showed that the N-(1-deoxyfructosyl)-Val-His released from N-(1-deoxyfructosyl)-hexapeptide by Aspergillus protease could be assayed enzymatically using fructosyl peptide oxidase, therefore these enzymes could be applied to the enzymatic measurement of HbA(1C).     

A lonely dot on the map: Exploring the climate signal in tree-ring density and stable isotopes of clanwilliam cedar,South Africa

Clanwilliam cedar (Widdringtonia cedarbergensis; WICE), a long-lived conifer with distinct tree rings in Cape Province, South Africa, has potential to provide a unique high-resolution climate proxy for southern Africa. However, the climate signal in WICE tree-ring width (TRW) is weak and the dendroclimatic potential of other WICE tree-ring parameters therefore needs to be explored. Here, we investigate the climatic signal in various tree-ring parameters, including TRW, Minimum Density (MND), Maximum Latewood Density (MXD), Maximum Latewood Blue Intensity (MXBI), and stable carbon and oxygen isotopes (δ¹⁸O and δ¹³C) measured in WICE samples collected in 1978. MND was negatively influenced by early spring (October-November) precipitation whereas TRW was positively influenced by spring November-December precipitation. MXD was negatively influenced by autumn (April-May) temperature whereas MXBI was not influenced by temperature. Both MXD and MXBI were negatively influenced by January-March and January-May precipitation respectively. We did not find a significant climate signal in either of the stable isotope time series, which were measured on a limited number of samples. WICE can live to be at least 356 years old and the current TRW chronology extends back to 1564 CE. The development of full-length chronologies of alternative tree-ring parameters, particularly MND, would allow for an annually resolved, multi-century spring precipitation reconstruction for this region in southern Africa, where vulnerability to future climate change is high.     

A criterion for the establishment of a stable polymorphism of higher order with an application to the evolution of polymorphism

This note gives some further useful properties of the constant fitness selection model for multiple alleles which pertain to the effects of adding a new allele to n preexisting alleles in stable equilibrium. In particular the conditions are derived for the establishment of a stable equilibrium involving all n + 1 alleles. For 3 alleles (i.e. n = 2) I give a complete qualitative solution, including the case of the replacement of one diallelic polymorphism by another. As an application I discuss a possible mechanism for the evolution of polymorphism using Monte Carlo methods similar to Lewontin, Ginzburg and Tuljapurkar (1978).     

An adaptive numerical method for the Richards equation with root growth

An efficient new numerical method for simultaneously simulating soil water flow and plant root growth is presented. It allows the calculation of the water uptake of an entire root system while preserving the local impact of single roots. The approach is based on the adaptive finite-element method, which enables a flexible fine resolution along individual roots, which cannot be achieved by classical non-adaptive algorithms.     

Pulse wave propagation in a model human arterial network: assessment of 1-D numerical simulations against in vitro measurements

A numerical model based on the nonlinear, one-dimensional (1-D) equations of pressure and flow wave propagation in conduit arteries is tested against a well-defined experimental 1:1 replica of the human arterial tree. The tree consists of 37 silicone branches representing the largest central systemic arteries in the human, including the aorta, carotid arteries and arteries that perfuse the upper and lower limbs and the main abdominal organs. The set-up is mounted horizontally and connected to a pulsatile pump delivering a periodic output similar to the aortic flow. Terminal branches end in simple resistance models, consisting of stiff capillary tubes leading to an overflow reservoir that reflects a constant venous pressure. The parameters required by the numerical algorithm are directly measured in the in vitro set-up and no data fitting is involved. Comparison of experimental and numerical pressure and flow waveforms shows the ability of the 1-D time-domain formulation to capture the main features of pulse wave propagation measured throughout the system test. As a consequence of the simple resistive boundary conditions used to reduce the uncertainty of the parameters involved in the simulation, the experimental set-up generates waveforms at terminal branches with additional non-physiological oscillations. The frequencies of these oscillations are well captured by the 1-D model, even though amplitudes are overestimated. Adding energy losses in bifurcations and including fluid inertia and compliance to the purely resistive terminal models does not reduce the underdamped effect, suggesting that wall visco-elasticity might play an important role in the experimental results. Nevertheless, average relative root-mean-square errors between simulations and experimental waveforms are smaller than 4% for pressure and 19% for the flow at all 70 locations studied.     

A model of radioiodine transfer to goat milk incorporating the influence of stable iodine

Previously reported models for radioiodine in ruminants cannot account for the effect of variations in stable iodine intake including large countermeasure doses of stable iodine on the transfer of radioiodine to goat milk. A metabolically based model of radioiodine transfer in goats has been parameterised using new experimental data on the effect of countermeasure doses of stable iodine on radioiodine transfer to milk. To account for the effect of dietary stable iodine levels, the model represents the transfer of iodine from the extracellular fluid to milk with Michaelis-Menten kinetics. The model shows good agreement with the experimental data, and the estimated parameters compare favourably with values which can be estimated from the literature. The parameterised model accounts for 95% of the variation in the observed data for milk, faeces, urine and thyroid (n=199). The model has been used to predict the effects of variation in stable iodine intake and the extent of consequent chemical contamination of milk by stable iodine. The time taken for radio-iodine to reach peak concentrations in milk following a deposition event is predicted to vary significantly (ca. 2 days) over a range of expected stable iodine intakes. Doses of stable iodine sufficient to reduce the radioiodine transfer to milk will result in stable iodine concentrations in milk greatly in excess of internationally advised limits. Therefore, we recommend that stable iodine supplementation not be used as a countermeasure to reduce radioiodine transfer to milk. Indeed, model predictions suggest that reductions in stable iodine intake would be a more effective countermeasure. However, this is unlikely to be feasible since the short physical half-life of ¹³¹I may not allow adequate time to implement changes in feed manufacture. The model described in this paper is freely available in ModelMaker 3.0 format (http://www.notingham.ac.uk/environmental-modelling/). Received: 16 August 1999 / Accepted in revised form: 15 November 1999     

An improved numerical method for the analysis of a floristic pasture survey

A classical ecologist is usually equally interested in groups of sites and groups of species, so that symmetrical numerical models are appropriate for the elucidation of floristic pattern. It is suggested that an agronomist is primarily interested in the pattern of site- (usually paddock-) groups, and is only interested in those species-groups whose members are present in sufficient abundance to be quickly recognizable, and which serve to discriminate clearly between the site-groups. An‘asymmetric inverse’model is defined for the purpose of extracting species-groups of this type, which can be combined with a site classification into a two-way table. The method is applied to a floristic survey carried out at the end of a grazing experiment, and is shown to produce meaningful and profitable results.     

An efficient numerical method for distributed-loop models of the urine concentrating mechanism

In this study we describe an efficient numerical method, based on the semi-Lagrangian (SL) semi-implicit (SI) method and Newton's method, for obtaining steady-state (SS) solutions of equations arising in distributed-loop models of the urine concentrating mechanism. Dynamic formulations of these models contain large systems of coupled hyperbolic partial differential equations (PDEs). The SL method advances the solutions of these PDEs in time by integrating backward along flow trajectories, thus allowing large time steps while maintaining stability. The SI approach controls stiffness arising from transtubular transport terms by averaging these terms in time along flow trajectories. An approximate SS solution of a dynamic formulation obtained via the SLSI method can be used as an initial guess for a Newton-type solver, which rapidly converges to a highly accurate numerical approximation to the solution of the ordinary differential equations that arise in the corresponding SS model formulation. In general, it is difficult to specify a priori for a Newton-type solver an initial guess that falls within the radius of convergence; however, the initial guess generated by solving the dynamic formulation via the SLSI method can be made sufficiently close to the SS solution to avoid numerical instability. The combination of the SLSI method and the Newton-type solver generates stable and accurate solutions with substantially reduced computation times, when compared to previously applied dynamic methods.     

一种利用Profile-1 生物发光仪快速测定土壤中微生物量的改良方法

开发了一种利用Profile-1生物发光仪测定土壤中微生物量的改良方法,并以此方法分别测定了标准大肠杆菌茵液以及3种不同类型的土壤(九段沙湿地土壤,崇明东滩大田土壤和崇明实验地改良土壤)的微生物量,并将结果与Profile-1生物发光仪自带的标准分析方法以及传统的菌落计数法进行比较。结果显示,改良的ATP提取方法(BAB改良分析法)和Profile-1生物发光仪自带的标准分析方法都可用于液体样品中微生物量的测定,其灵敏度和准确度无显著差异(P0.05)。但在测定土壤样品时,菌落计数法测定结果大约占BAB改良分析法测定结果的1%～5%,占Profile-1生物发光仪自带的标准分析方法的测定结果的22%～99%。这表明在分析土壤样品时,BAB改良分析法较Profile-1生物发光仪自带的标准分析方法的ATP提取效率更高,可显著提高仪器检测土壤样品的灵敏度和可靠性,因此可有效应用于各类土壤的微生物量的监测,为土壤环境监控提供微生物量的可靠数据。