One Year's Experience in a Ministry of Health Dialysis Centre

A 10-bed dialysis unit, opened at the London Hospital in 1968, admitted 37 patients during its first year of operation. The aims of the unit were to prepare patients for renal transplantation and to provide instruction for dialysis treatment at home. A total of 2,012 days were spent in hospital, the average intervals between admission, the first dialysis, and discharge being 23·8 and 20 days, respectively. The overall number of readmissions was 1·5 per patient. These figures, together with the increasing number of patients accepted for such treatment, indicate the considerable number of supporting hospital beds, as well as medical and technical staff, required to maintain a dialysis unit.     

Integrated dialysis and renal transplantation: small is beautiful.

Many patients in Britain with chronic renal failure suitable for renal replacement treatment die because not enough treatment facilities are available. Moreover, the number of renal transplants performed is insufficient to meet even present needs, so the number of patients on dialysis is rising. The integrated dialysis and transplant unit in Aberdeen, which has a population base much smaller than the average British unit, meets community needs for dialysis and transplantation. The problem of harvesting cadaver kidneys has been solved; the present supply has not only enabled the number of patients on dialysis to remain stable but has resulted in a net export of kidneys. The Aberdeen unit shows how estimated needs for chronic dialysis and renal transplantation may be met.     

Statistical Approach to Planning an Integrated Haemodialysis/Transplantation Programme

A mathematical model has been constructed to assist in planning the future requirements of a combined haemodialysis and transplantation centre. It has been used to predict the number of patients in the dialysis unit, the general wards, and at home on dialysis, as well as providing further information on transplantation rates and overall costs. The model can be adapted for units with different facilities from our own.It can be primed with data from an individual unit or with pooled data from the whole country. The purpose of this paper is to demonstrate the methodology of a particular statistical approach.     

Patient load and medical staffing in adult dialysis units in the United Kingdom.

A survey of medical staffing in 50 adult dialysis units in the United Kingdom in 1986 showed a wide range of patient to staff ratios or staffing score ratios. The total patient load (patients receiving haemodialysis in hospital and at home and those receiving continuous ambulatory peritoneal dialysis) varied from 12 to 270 per unit. Patients receiving acute haemodialysis or who had received a transplant were not included. The unit staffing score, on a weighted scale based on experience, varied from 6.0 to 40.5. Previous surveys have all been regionally or nationally based so criteria for assessing the adequacy of staffing in single units do not exist. This survey attempts to provide a guideline by describing the range of medical staffing compared with patient load in single dialysis units. No unit considered itself to be overstaffed, and several considered themselves to be greatly understaffed. Individual dialysis units should plead their own case in the light of their own circumstances and up to date information provided in nationwide staffing surveys such as this one.     

Late referral for maintenance dialysis.

A study of patients accepted for maintenance dialysis at the Oxford renal unit in 1981 showed that 23 out of 55 patients were referred late, very shortly before the need for dialysis. This pattern of referral was associated with a higher morbidity at the start of dialysis which may have been preventable. In the late referral group 16 patients (70%) suffered major complications and three (13%) died; by contrast, in the early referral group three patients (9%) suffered complications and one died. Early referral to a renal unit plainly benefits the patient and allows Health Service resources to be used more economically.     

叶菜田节肢动物多样性系统调查与抽样技术研究

通过对以株和区组面积两种抽样单位，以随机取样和定点定株取样两种抽样方式下叶菜田节肢动物多样性测度的变异程度分析表现，在菜心田苗期以区组（０．１１ｍ＾２）为抽样单位，定苗后生长期～成熟期以株为抽样单位，采用随机抽样方式所获得的调查结果变异程度较小。在此基础上，通过对菜田节肢动物丰富度、多样性和均匀性等指标同样方数量间的关系分析表明，苗期、生长期、成熟期分别抽取１２、３０、２０个样方，可以达到各多样性     

Analysis of the interactions of multicomponents in Cornus officinalis Sieb. et Zucc. with human serum albumin using on-line dialysis coupled with HPLC

Interactions of three iridoid glycosides extracted from Cornus officinalis Sieb. et Zucc. (CIG) with protein were simultaneously explored by on-line dialysis sampling coupled with high-performance liquid chromatography (DS-HPLC). Three main compounds in CIG were unequivocally identified as loganin, sweroside and cornuside by comparing their t(R), MS data and UV spectra with those of reference compounds. Dialysis recoveries and quantitative characteristics of DS-HPLC for three iridoid glycosides were determined. Recoveries of dialysis sampling ranged from 73.9 to 91.7% with the RSD below 3.0%. Based on the determination of concentrations before and after interaction with human serum albumin (HSA), the binding parameters of loganin, sweroside and cornuside with HSA were obtained and the binding mechanisms were investigated.     

Microdialysis sampling of cytokines

Microdialysis sampling is a well-known method for collection of low molecular weight hydrophilic analytes. Due to the success of this sampling technique for these analytes, many researchers have wanted to extend the use of this method to a wider range of analytes-particularly proteins and peptides. These analytes pose unique challenges during microdialysis sampling. The primary challenges are the reduced recovery across the dialysis semi-permeable membrane and the volume limitations/requirements for the typical immunoassay methods used for detection of proteins. This review covers the practical and theoretical aspects needed for in vivo microdialysis sampling of cytokines, which are a vitally important class of signaling proteins. In addition to the basics of the microdialysis method for sampling cytokines, the use of the microdialysis device as a localized cytokine delivery method is also described. Since relative recovery of cytokines is often low during microdialysis sampling, methods to improve the membrane recovery are discussed for in vitro and in vivo applications.     

How to obtain a precise and representative estimate for parameters in LCA

Background, Aim and Scope  Quite often there is need for precise and representative parameters in LCA studies. Probably the most relevant have direct influence on the functional unit, whose definition is crucial in the conduct of any LCA. Changes in the functional unit show directly in LCI and LCIA results. In comparative assertions, a bias in the functional unit may lead to a bias in the overall conclusions. Since quantitative data for the functional unit, such as geometric dimensions and specific weight, often vary, the question arises how to determine the functional unit, especially if a comparative assertion shall be representative for a region or market. Aim and scope of the study is to develop and apply methods for obtaining precise and representative estimates for the functional unit as one important parameter in an LCA study. Materials and Methods  Statistical sampling is applied in order to get empirical estimates for the weight of yoghurt cups, as a typical parameter for the functional unit. We used a two-stage sampling design, with stratified sampling in the first stage and three different sampling designs in the second stage, namely stratified, clustered, and a posteriori sampling. Sampling designs are motivated and described. In a case study, they are each used to determined a representative weight for 150 g yoghurt cups in Berlin, at the point of sale and within a specific time. In the first sampling stage, food markets are randomly selected, while in the second stage, yoghurt cups in these food markets are sampled. The sampling methods are applicable due to newly available internet data. These data sources and their shortcomings are described. Results  The random sampling procedure yields representative estimates, which are compared to figures for market leaders, i.e. yoghurt cups with very high occurrence in the supermarkets. While single types of yoghurt cups showed moderate uncertainty, representative estimates were highly precise. Discussion results show, for one, the performance of the applied statistical estimation procedures, and they show further that adding more information in the estimation procedure (on the shape of the cup, on the type of plastic, on the specific brand) helps reducing uncertainty. Conclusions  As conclusions, estimates and their uncertainty depend on the measurement procedure in a sensitive manner; any uncertainty information should be coupled with information on the measurement procedure, and it is recommended to use statistical sampling in order to reduce uncertainty for important parameters of an LCA study. Recommendations and Perspectives  Results for market leaders differed considerably from representative estimates. This implies to not use market leader data, or data with a high market share, as substitute for representative data in LCA studies. Statistical sampling has been barely used for Life Cycle Assessment. It turned out to be a feasible means for obtaining highly precise and representative estimates for the weight of yoghurt cups in the case study, based on empirical analysis. Further research is recommended in order to detect which parameters should best be investigated in LCA case studies; which data sources are available and recommended, and which sampling designs are appropriate for different application cases. ESS-Submission Editor: Seungdo Kim. PhD (kimseun@msu.edu)     

Occupancy-abundance relationships and sampling scales

The area of occupancy of a species and its abundance are dependent on the spatial scale at which they are measured. However, it is less obvious how the scale of sampling affects their correlation. This study investigated and modeled the effects of sampling unit size and a real extent on the interspecific occupancy-abundance relationships for a tropical tree species assemblage at a local scale and a temperate bird species assemblage at a regional scale. The results showed that both sampling unit size and study extent had profound quantitative effects on the occupancy-abundance relationship, although it remained positive. Several properties of the occupancy-abundance relationship can result from the effects of scale: 1) the linearity of the relationship decreases with the increase of sampling unit size; 2) for a given abundance, the area of occupancy increases with sampling unit size; and 3) variation in the area of occupancy increases with the increase of both sampling unit size and extent, and if the extent is large enough may be sufficient that no occupancy-abundance relationship is observed. Although the occupancy-abundance relationship can be satisfactorily modeled, the parameters depend on the scale used. This suggests that a model derived from one scale cannot be applied to another. In other words, to estimate the rarity or commonness of species using such a model, the estimation must be strictly done using the same sampling scale for all the species.     

A Study of Membrane Permeability in Haemodialysis

The efficiency of haemodialysis has been determined when a Watson-Marlow (Kiil) dialyser was used repetitively without changing the membranes. Dialysis efficiency was assessed from the clearance of creatinine and of urea from the patient''s blood. No significant deterioration in dialysis could be detected in six dialyses through the same membrane. Leaving the dialyser unit for up to eight hours before washing it out after the completion of each dialysis did not appear to have any effect on dialysis efficiency.It was concluded that repetitive haemodialysis through the same membranes is possible, but careful monitoring of the patient to assess suitability for such treatment, and subsequently at each dialysis, is essential.     

Sequential sampling protocols for Spodoptera frugiperda (Lepidoptera: Noctuidae), on Zea mays fields: influence of sampling unit size

Spodoptera frugiperda (J.E. Smith) is a major pest in maize fields in Argentina. However, a sampling method that accounts for spatial pattern and allows reliable pest density estimations is still lacking. This paper addresses the issue of how sampling unit size can influence the characterization of S. frugiperda spatial pattern and the performance of sampling plans. An intensive sampling programme for S. frugiperda larvae was carried out in maize fields from October until March in four growing seasons. On each sampling date, 12 to 20 sampling units were taken at random. Each unit consisted of 1, 2, 4, 6, 8, 10 or 12 consecutive plants along a row. The linearized version of the Taylor's power law (TPL) was fitted to mean and variance estimated for each sampling date and data set through least squares regression. In general, b values from TPL were significantly >1 (P<0.05), indicating an aggregated sampling distribution. Regression slopes (b) ranged from 1.28 to 1.48 in small larvae and from 1.06 to 1.24 in large larvae, indicating stronger clumping in the former. TPL parameters were used to develop constant precision sampling plans. The efficiency of these plans in terms of expected total cost (searching and handling sampling units) was very sensitive to the size of the sampling units with small larvae but not with large larvae. The influence of sampling unit size and spatial pattern on TPL parameters and sampling costs is discussed.     

Analysis of purines

The fact that purine nucleotides and nucleosides are so important in normal cellular functions makes their analysis complicated. In order to measure tissue levels, samples have to be very rapidly fixed. Measurement in blood is complicated by the risk of releasing purine nucleotides during the sampling procedure and by the possibility of very rapid inactivation by cellular mechanisms as well as extracellular enzymes. Dialysis probes may offer a possibility of sampling extracellular fluid, but the trauma of placing the dialysis fibre can in itself provide a major stimulus for purine release. Once an adequate sample is taken, there are several methods for the actual quantitation, but most commonly various HLPC procedures are used.     

A new cost‐effective approach to survey ecological communities

Surveying ecological communities often means the tedious work of collecting detailed information on each species within each sampling unit (e.g. trap, transect, quadrat). In this paper, we first argue that presence–absence and abundance data are the two extremes of a spectrum of data formats. By counting individuals of each species within a sampling unit until either a predefined (user‐defined) number of individuals is reached or all individuals of the species are counted, all intermediate cases can be generated. By independently correlating each intermediate case with the complete abundance data, we show that it is not necessary to count all individuals to recover the patterns of variation characterizing a community data table. When the same procedure is applied in combination with different distance coefficients such as the Hellinger, chord, χ², percentage difference or modified Gower, or the distance between species profiles, an even lower number of individuals per species need to be counted within a sampling unit for the patterns of variation defining a community to be recovered. By applying the same counting procedure to data collected during a pilot study, we show that the maximum number of individuals that need to be counted within a sampling unit for a species can be estimated from a pilot study containing as little as 3% of randomly selected sampling units throughout the complete survey area. An example of how to apply this new counting method is presented, using data from a boreal forest Carabidae community sampled in northwestern Alberta, Canada.     

基于土芯法的亚热带常绿阔叶林细根空间变异与取样数量估计

树木细根具有高度空间异质性,确定合理的细根取样策略是林木细根研究的前提。通过在福建省三明米槠天然常绿阔叶林内随机钻取96个土芯,分析细根生物量和形态特征的空间变异特征,并估计各指标所需的取样数量。结果表明:(1)随着径级增加,细根各指标变异系数增大,相应的取样数量增加;(2)随着土壤深度增加,单位面积细根生物量变异程度和相应的取样数量均增加。在置信水平为95%、精度为80%的条件下,直径为0-1 mm和1-2 mm的细根,分别采集16和42个样品可以满足测定单位面积细根生物量,采集17和31个样品可以满足测定单位面积细根长度,采集25和33个样品可以满足测定单位面积细根表面积。Shapiro-Wilk检验表明,除表层土壤0-1 mm细根单位面积生物量符合正态分布外,其余细根生物量和形态指标数据均不符合正态分布。研究结果为亚热带常绿阔叶林细根的合理取样提供了科学依据。     

Preliminary characterization by X-ray diffraction of crystals of photochemical reaction centres from wild-type Rhodopseudomonas spheroides

Reaction centres from wild-type Rhodopseudomonas spheroides (strain Y) in a solution of octylglucoside have been crystallized with polyethylene glycol as precipitant, either by vapour diffusion or dialysis. Orthorhombic crystals (space group P2(1)2(1)2(1)) diffract to 3.5 A resolution. The unit cell parameters are a = 142.5 A, b = 141.5 A, c = 80 A; they are compatible with the presence of one reaction centre per asymmetric unit.     

Regular short haemodialysis in end-stage renal failure.

A study was made of thrice weekly haemodialysis of 3-3 1/2 hours'' duration using a large surface area dialyser in patients with end-stage renal failure. Body water, potassium, and blood pressure control were satisfactory and comparable with the more widely used long dialysis schedules (6-9 hours thrice weekly). Patient rehabilitation was improved overall and the regimen enabled the dialysis unit to treat more patients despite a reduction in technical and nursing staff. The technique proved inadequate, however, in two patients with an intercurrent infection, and more intensive dialysis in recommended in such cases.     

Variance deficit is not reliable evidence for niche limitation

Variance deficit in the number of species per sampling unit, as compared to a null model with species occurring independently of each other has been considered by various authors to be evidence for niche limitation. I show that simpler mechanisms could explain this phenomenon. Of those, the competition of individuals for space limits the number of individuals per sampling unit, resulting in decrease of variance in species richness. Testing the proportions of species belonging to various guilds seems to be more ecologically interesting, although here also the variance deficit can hardly be taken as reliable evidence for niche limitation.     

Automated modification of Duncombe's method for the ultramicro determination of serum free fatty acids.

An automated continuous-flow method is described for estimating free fatty acids in serum using 25-mul samples. The procedure depends on the formation of copper soaps on the surface of a semipermeable membrane, their transfer into chloroform, and subsequent determination of dissolved copper. The membrane separating copper reagent and chloroform is supported between thin-channel dialysis plates. Chloroform extracts of serum free fatty acids are passed through the dialysis unit, and dissolved copper in the outflow is estimated colorimetrically. The procedure gives values that agree with a standard titrimetric method.