Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions

In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2-3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5 ± 7.9 min) than the position-matching task (26.9 ± 15.11 min; p<0.01); however, both tasks caused the same amount of muscle fatigue (p = 0.59). There were no task-specific differences for the total amount or rate of change in the neurophysiologic outcome variables over time (p>0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p<0.02, ES = 0.35-0.52) coupled with a similar mean increase in measures of corticospinal excitability (p<0.03, ES = 0.30-0.41). Additionally, the amount of intracortical inhibition decreased (p<0.03, ES = 0.32) and the amount of intracortical facilitation (p>0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure.

Preliminary evidence that anodal transcranial direct current stimulation enhances time to task failure of a sustained submaximal contraction

The purpose of this study was to determine whether anodal transcranial direct current stimulation (tDCS) delivered while performing a sustained submaximal contraction would increase time to task failure (TTF) compared to sham stimulation. Healthy volunteers (n = 18) performed two fatiguing contractions at 20% of maximum strength with the elbow flexors on separate occasions. During fatigue task performance, either anodal or sham stimulation was delivered to the motor cortex for up to 20 minutes. Transcranial magnetic stimulation (TMS) was used to assess changes in cortical excitability during stimulation. There was no systematic effect of the anodal tDCS stimulation on TTF for the entire subject set (n = 18; p = 0.64). Accordingly, a posteriori subjects were divided into two tDCS-time groups: Full-Time (n = 8), where TTF occurred prior to the termination of tDCS, and Part-Time (n = 10), where TTF extended after tDCS terminated. The TTF for the Full-Time group was 31% longer with anodal tDCS compared to sham (p = 0.04), whereas TTF for the Part-Time group did not differ (p = 0.81). Therefore, the remainder of our analysis addressed the Full-Time group. With anodal tDCS, the amount of muscle fatigue was 6% greater at task failure (p = 0.05) and the amount of time the Full-Time group performed the task at an RPE between 8-10 ("very hard") increased by 38% (p = 0.04) compared to sham. There was no difference in measures of cortical excitability between stimulation conditions (p = 0.90). That the targeted delivery of anodal tDCS during task performance both increased TTF and the amount of muscle fatigue in a subset of subjects suggests that augmenting cortical excitability with tDCS enhanced descending drive to the spinal motorpool to recruit more motor units. The results also suggest that the application of tDCS during performance of fatiguing activity has the potential to bolster the capacity to exercise under conditions required to derive benefits due to overload.

Morphological and quantitative changes in paternal brood-pouch vasculature during embryonic development in two Syngnathus pipefishes

Vascular corrosion casts of Syngnathus floridae and Syngnathus fuscus brood pouches were examined by scanning electron microscopy. Morphological and quantitative data on the vasculature of the paternal brood pouch during each stage of embryonic development were investigated to explore potential changes during brooding, to consider interspecific differences and to provide structural evidence for previously reported functional roles of the brood pouch. The brood pouches of both species are highly vascularized structures with cup-like arrangements of brood-pouch vasculature developing around each embryo shortly after fertilization and breaking down before fry release. The density and size of paternally derived blood vessels in contact with the embryos were found to be consistent for S. fuscus once this structure was established early in development. On the contrary, these vasculature measurements varied with early S. floridae brood stages when the embryo still relied heavily on the yolk sac. Diameter measurements of S. fuscus brood-pouch blood vessels were also comparatively smaller during these early developmental stages, suggesting that the structural stability and opportunity for greater transport via slower blood flow may contribute to greater paternal allocation. This is the first study to document changes in brood-pouch vasculature during specific stages of embryonic development, to show regression of this vasculature before fry release and to provide morphological data for two syngnathid species for which information on brood-pouch physiology is available.

Relative safety of 4 weeks of blood flow-restricted resistance exercise in young, healthy adults

This study evaluated the effect of 4 weeks of low-load resistance exercise with blood flow restriction (BFRE) on increasing strength in comparison with high-load resistance exercise (HLE), and assessed changes in blood, vascular and neural function. Healthy adults performed leg extension BFRE or HLE 3 days/week at 30% and 80% of strength, respectively. During BFRE, a cuff on the upper leg was inflated to 30% above systolic blood pressure. Strength, pulse-wave velocity (PWV), ankle-brachial index (ABI), prothrombin time (PT) and nerve conduction (NC) were measured before and after training. Markers of coagulation (fibrinogen and D-dimer), fibrinolysis [tissue plasminogen activator (tPA)] and inflammation [high sensitivity C-reactive protein (hsCRP)] were measured in response to the first and last exercise bouts. Strength increased 8% with BFRE and 13% with HLE (P<0.01). No changes in PWV, ABI, PT or NC were observed following training for either group (P>0.05). tPA antigen increased 30-40% immediately following acute bouts of BFRE and HLE (P=0.01). No changes were observed in fibrinogen, D-dimer or hsCRP (P>0.05). These findings indicate that both protocols increase the strength without altering nerve or vascular function, and that a single bout of both protocols increases fibrinolytic activity without altering selected markers of coagulation or inflammation in healthy individuals.

The value of the post-take ward round: are new working patterns compromising junior doctor education?

This prospective observational study assessed the impact of the changes in junior doctors' working hours and waiting-time initiatives on teaching and learning opportunities for junior doctors in acute medicine. An audit cycle of post-take ward rounds including all medical admissions to an urban teaching hospital was conducted. During two seven-day periods in July 2006 and 2008, 317 and 354 patients were admitted respectively. In the two-year interval a number of changes were implemented resulting in a significant increase in patients reviewed by a consultant within 24 hours of admission. Target waiting times were being met but there were many missed learning opportunities for junior staff. Senior doctors continue to perform the majority of post-take reviews in the absence of the doctors who had admitted the patient. Similar patterns are likely to be found in other hospitals attempting to balance training with government targets for waiting times and junior doctors' working hours.

Factors Affecting Survival in Advanced Chronic Kidney Disease Patients Who Choose Not to Receive Dialysis

INTRODUCTION

Non-dialytic treatment (NDT) has become a recognized and important modality of treatment in end stage renal disease (ESRD) in certain groups of chronic kidney disease (CKD) patients. However, little is known about the prognosis of these NDT patients in terms of hospitalization rates and survival. We analyzed our experience in managing these NDT with a multidisciplinary team (MDT) approach over a three-year period.

PATIENTS AND METHODS

The Renal Unit at the Royal Liverpool University Hospital set up a dedicated MDT clinic to manage NDT patients in January 2003. Patients approaching end stage chronic kidney disease who chose not to dialyse were recruited from other nephrologists. The study group was classified according to age band (<70 years, 71-80 years, and >80 years), estimated glomerular filtration rate (eGFR) (<10 ml/min, 11-20 ml/min, and >20 ml/min) according to the Modified Diet In Renal Disease formula and Stoke comorbidity grade (SCG). The SCG is a validated scoring system for the survival of patients on renal replacement therapy. We also used the ERA-EDTA primary renal diagnosis codes. As there are no existing standards for NDT patients, we used the U.K. national set for haemodialysis patients as a reference and target for our NDT patients. Data was collected prospectively.

RESULTS

The median age was 79 years and the male: female ratio was approximately 1. The most common primary cause of kidney disease in the NDT study population was chronic renal failure of unknown cause n = 22 (31%), but the most common identifiable cause was diabetic nephropathy, n = 20 (28%). The most common comorbidity was ischaemic heart disease n = 25 (34%). Those achieving the standards for anaemia were 78% at referral. Only 30% of the NDT patients achieved the standard for blood pressure (<130/80 mmHg) at referral. Forty-three patients (60%) had no admissions at all. There were a total of 30 patients admitted on 58 occasions. Thirty-one (53%) of these were due to a non-renal cause. The median length of stay for the other NDT patients was 10 days. The median overall survival (life expectancy) was 1.95 years. The one-year overall survival was 65%. SCG was an independent prognostic factor in predicting survival in NDT patients studied (p = 0.005), the hazard ratio being 2.53, for each incremental increase in the SCG. At one year, the survival for comorbidity grade 0, 1 and 2 were 83%, 70% and 56% respectively. Of the 28 patients who died, 20 did so at home (71%).

DISCUSSION

The NDT of ESRD has become an important alternative modality in renal replacement therapy. With the emergence of epidemic proportions of CKD, more elderly patients with progressive renal disease will need to make informed decisions regarding renal replacement therapy. There is likely to be increasing number of elderly patients that will tolerate dialysis badly and who will be very dependent on others. We believe that there should be a multidisciplinary approach to assist the ESRD patients in choosing their modality of renal replacement therapy, and with an agreed care plan to support these patients in managing their chosen modality to achieve the best possible quality of life. There should be integrated services with primary care, community nurses, and palliative care teams to enable the majority of the patient's treatment to be carried out at home and to allow a dignified death. However. there was a statistically significant trend for shorter survival among those with greater comorbidities, as determined by the SCG. This is the first report of the potential importance of SCG as an independent prognostic factor in NDT patients. This will help us to counsel our patients in the future about their prognosis if they choose NDT as their modality of renal replacement therapy.

CONCLUSION

Our prospective study is the first and currently the largest observational study of a multidisciplinary approach in the management of NDT patients. SCG was an independent prognostic factor in predicting survival. In those patients who chose not to dialyse, SCG provides a potentially useful indication of expected prognosis.

Development of the Hand Active Sensation Test: reliability and validity

OBJECTIVE

To develop and establish the reliability and validity of a new quantitative functional measure of haptic perception in the hand, the Hand Active Sensation Test (HASTe).

DESIGN

Reliability was assessed by test-retest sessions. Validity was assessed via discriminant analysis, concurrent validity with 2-point discrimination and wrist position test, and receiver operating characteristic (ROC) curve construction.

SETTING

Subject preference.

PARTICIPANTS

Heterogeneous sample of 28 stroke survivors and 28 individually matched controls.

INTERVENTION

Subjects used 1 hand to manipulate HASTe objects that vary by weight or texture to complete 18 match-to-sample trials.

MAIN OUTCOME MEASURES

Two-point discrimination threshold, Wrist Position Sense Test (WPST) average error, and HASTe accuracy score.

RESULTS

Test-retest reliability was strong (intraclass correlation coefficient model 3,1 = .77). The HASTe score significantly discriminated the groups (t = 8.3, P < .001) and correlated with 2-point discrimination (r = -.67, P < .001) and WPST (r = -.60, P < .001). ROC curve area was .94 for test 1 and .92 for the average of 2 tests.

CONCLUSIONS

The HASTe is a reliable and valid functional measure of haptic perception, appears to detect impairment of haptic perception even in stroke survivors with no reported sensory deficits, and may provide valuable quantitative clinical data about complex sensory loss and hand function after stroke.

A data analysis algorithm for programmed field-flow fractionation

An algorithm that employs numerical integration for analysis of field-flow fractionation (FFF) data is presented. The algorithm utilizes detector response, field strength, and channel flow rate data, monitored at discrete time intervals during sample elution to generate a distribution of sample components according to particle size or molecular weight. The field strength and channel flow rate may either be held constant or programmed as functions of time, and it is not necessary for these programs to follow specific mathematical functions. If experimental conditions are monitored during a run, the algorithm can account for any deviation from nominal set conditions. The algorithm also allows calculation of fractionating power for the actual conditions as monitored during the run. The method provides greatly increased flexibility in the application of the FFF family of techniques. It removes the limitations on experimental conditions incurred by adherence to analytically available solutions to FFF theory, allowing ad hoc variation of field strength and other experimental parameters as necessary to increase sensitivity and specificity of the method. An implementation of the algorithm is described that is independent of the FFF technique (i.e., independent of field type) and mode of operation. To reduce computation time, it uses mathematical techniques to reduce the required number of numerical integrations. This is of particular importance when the perturbations to ideal FFF theory, such as those due to the effects of hydrodynamic lift forces, particle-wall or particle-particle interactions, and secondary relaxation, necessitate relatively lengthy numerical calculations.

Dissipative exponentially-fitted methods for the numerical solution of the Schrödinger equation

The first dissipative exponentially fitted method for the numerical integration of the Schrödinger equation is developed in this paper. The technique presented is a nonsymmetric multistep (dissipative) method. An application to the bound-states problem and the resonance problem of the radial Schrödinger equation indicates that the new method is more efficient than the classical dissipative method and other well-known methods. Based on the new method and the method of Raptis and Allison (Comput. Phys. Commun. 14 (1978) 1-5) a new variable-step method is obtained. The application of the new variable-step method to the coupled differential equations arising from the Schrödinger equation indicates the power of the new approach.

New insights in the development of Numerov-type methods with minimal phase-lag for the numerical solution of the Schrödinger equation

Explicit Numerov-type methods with minimal phase-lag are developed in this paper. These methods are of algebraic order five and have phase-lag order eight and ten. The methods have new features; namely that they are dissipative, i.e. they are not symmetric and they have no interval of periodicity. Numerical illustrations using (i) the radial Schrödinger equation and (ii) coupled differential equations arising from the Schrödinger equation, indicate that these new methods are more efficient than older ones. It is seen that the property of the phase-lag is more important than the non-empty interval of periodicity in constructing numerical methods for the solution of the Schrödinger equations and related problems.

Aspirin for vascular dementia

BACKGROUND

For patients with a diagnosis of vascular dementia there is evidence that aspirin is widely prescribed - in one study, completed by geriatricians and psychiatrists in the UK, 80% of patients with cognitive impairment (with vascular risk factors) were prescribed aspirin. However, a number of queries remain unanswered: Is there convincing evidence that aspirin benefits patients with vascular dementia? Does aspirin affect cognition or improve prognosis? In addition, does the risk of cerebral or gastric haemorrhage outweigh any benefit? The aim of this review is to assess the evidence of effectiveness of aspirin in those with a diagnosis of vascular dementia.

OBJECTIVES

To assess the evidence of effectiveness of the use of aspirin for vascular dementia.

SEARCH STRATEGY

Computerised databases were searched independently by two reviewers. In addition, relevant websites were searched and some journals were handsearched. Specialists in the field were approached for unpublished material and also any publications found were searched for additional references.

SELECTION CRITERIA

All randomised controlled trials investigating the effect of aspirin for vascular dementia are included. Inclusion/exclusion of studies comprised systematic assessment of the quality of study design and the risk of bias.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by both reviewers, using a previously tested data extraction form and, where required, authors were contacted for data not provided in the papers. The aim was to evaluate data recorded via tools assessing cognitive and behavioural changes along with mortality, morbidity and institutionalisation data.

MAIN RESULTS

One randomised controlled trial ( approximately approximately Meyer 1989 approximately approximately ) was included, and yielded data for analysis on a total of 70 patients. The only relevant outcome assessed in this trial was cognition. Change in cognitive outcome was towards being in favour of treatment.

REVIEWER'S CONCLUSIONS

There is very limited evidence that aspirin is effective in treating patients with a diagnosis of vascular dementia. Further research is needed to assess the effect of aspirin on cognition, and also on additional outcomes such as behaviour, and quality of life. At present it is not possible to provide evidence for other queries regarding the use of aspirin for dementia (these are described in the Background section of this review).

Quantification of cellular properties from external fields and resulting induced velocity: cellular hydrodynamic diameter

An experimental technique is discussed in which the size distribution of a population of cells is determined by calculating each cell's settling velocity. The settling velocity is determined from microscopically obtained images which were recorded on SVHS tape. These images are then computer imaged and processed, and the cell's location and velocity are determined using a computer algorithm referred to as cell tracking velocimetry (CTV). Experimental data is presented comparing the distribution of human lymphocytes and a human breast cancer cell line, MCF-7, determined using a Coulter counter and the CTV approach.

Quantification of cellular properties from external fields and resulting induced velocity: magnetic susceptibility

An experimental technique is discussed in which the magnetic susceptibility of immunomagnetically labeled cells can be determined on a cell-by-cell basis. This technique is based on determining the magnetically induced velocity that an immunomagnetically labeled cell has in a well-defined magnetic energy gradient. This velocity is determined through the use of video recordings of microscopic images of cells moving in the magnetic energy gradient. These video images are then computer digitized and processed using a computer algorithm, cell tracking velocimetry, which allows larger numbers (>10(3)) of cells to be analyzed.

Flow rate optimization for the quadrupole magnetic cell sorter

The quadrupole magnetic cell sorter is a form of split-flow thin-channel (SPLITT) separation device. It employs a quadrupole magnetic field and annular channel geometry. Immunomagnetic labels are used to bind to specific receptors on the surface of the cells of interest. It is the interaction of these labels with the magnetic field that brings about the selective isolation of these cells. The SPLITT separation devices have generally been based on parallel-plate geometry, usually with effectively constant field strength applied across the channel thickness. The nonconstant field strength and annular channel geometry of the magnetic cell sorter require that a new strategy be developed for optimization of inlet and outlet flow rates. We present such a strategy here based on a consideration of certain specific cell trajectories within the system.

Numerical simulation of band-broadening during hydrodynamic relaxation in frit-inlet field-flow fractionation channels

The frit-inlet technique is a promising implementation of hydrodynamic relaxation of samples in field-flow fractionation (FFF). The optimization of the process is of great importance in order to maximize overall system efficiency. The mechanism of band-broadening that takes place during hydrodynamic relaxation has been examined using a three-dimensional simulation of the flow inside the triangular end-piece of the channel. This is the first time this contribution to band-broadening has been considered and studied. Particle trajectories in the absence of a transverse field were numerically calculated, thereby isolating this effect from the familiar field-driven relaxation effect. As a first step towards an optimization of the system, the influence of the length of frit element was examined. Band-broadening was examined by determining the number of particles passing through the triangular end-piece as a function of transit time for a uniform particle distribution at the injection point. Due to the complexity of the flow patterns within the system, it is concluded that such numerical simulations are necessary for the optimization of the design and operation of this type of channel.

'Progressive' versus 'indolent' idiopathic membranous glomerulonephritis

There is still controversy about safe and effective therapy for idiopathic membranous glomerulonephritis (MGN). Over 20 years, we have simply observed our patients clinically after diagnosis, and only used aggressive therapy with steroids in high dosage and azathioprine for 21 patients with progressive renal failure. The other 42 were thus classified as 'indolent' MGN. Those with 'progressive' MGN had heavier proteinuria and worse renal function on presentation, but the overlap was considerable. Patients with progressive MGN were treated after 1-4 years. All responded promptly, and 5 years after presentation all were alive, and only one was on dialysis. By 10 years, most were still alive, and of these most were off dialysis. In five patients, dialysis was delayed by several years. There were two deaths on dialysis, and three other deaths, mostly in older patients. All but one patient with indolent MGN remained stable on symptomatic treatment only, for at least 5 years after presentation. In many, proteinuria fell to insignificant levels over 4 years. In these remitting patients, there was a prevalence of thyroid disease (7), rheumatoid disease (3) and nephrotic presentation in pregnancy (4). After 6-10 years three patients developed worsening proteinuria and renal failure. Five older patients died from unrelated causes.

Theory of field-programmed field-flow fractionation with corrections for steric effects

This paper deals with the principal perturbation to ideal normal-mode elution of particles in field-flow fractionation (FFF). This perturbation is due to the finite size of particles undergoing migration in the FFF channel. The effects of a first-order correction for particle size are examined. Equations are derived for retention time, fractionating power, and steric inversion diameter for operation at constant field strength, as well as under conditions of both exponential and power programmed field decay. Useful limiting equations for fractionating power are derived and their validity is confirmed for typical experimental conditions. The derived equations are necessary for the future development of a systematic optimization strategy for the selection of operating conditions for particle size analysis by FFF. Calculations confirm our previous conclusion that the fractionating power for exponential field programming varies strongly with particle size; this variation is only slightly reduced by steric perturbations. The uniform fractionating power of power programming is slightly disturbed by steric effects although fractionating power remains much more uniform than for exponential programming. It is shown that a higher uniformity in fractionating power can be gained by manipulating the parameters of power programming but that no improvement is possible with exponential programming. Phenomena giving rise to higher order perturbations and to secondary relaxation are discussed and the conditions identified under which these effects are minimized.

Rapid breakthrough measurement of void volume for field-flow fractionation channels

A peak breakthrough technique is described and evaluated for measuring the void volume of field-flow fractionation (FFF) channels, particularly those used for flow FFF. This technique uses a high-molecular-mass macromolecular or particulate probe that can be displaced rapidly by flow through the FFF channel with minimal transverse diffusion. The particles that emerge first are those carried through the entire length near the channel centerline at the apex of the parabolic flow profile. These particles generate a sharp breakthrough profile. The measured breakthrough time is two thirds of the void time, thus making it possible to calculate both the void time and the associated void volume. This method, although applicable to all FFF channels (and capable of extension to open tubes), is particularly useful for flow FFF because conventional low-molecular-mass void probes can diffuse into the permeable walls and thus distort void measurements. The theoretical basis of the breakthrough technique and an explanation for the sharpness of the breakthrough front are given. A method for compensating for deviations from perfect sharpness is developed in which the breakthrough time is identified with the time needed to reach 85-88% of the breakthrough peak maximum. Preliminary experimental results are shown using various protein probes in four different FFF channel systems.

Hydrodynamic relaxation in flow field-flow fractionation using both split and frit inlets

Two means are described for achieving hydrodynamic relaxation and thus avoiding the stopflow injection procedure in field-flow fractionation (FFF): split flow injection and frit inlet injection. The advantages, disadvantages, and the theoretical basis of these procedures are discussed. Incremental band broadening due to the final relaxation step is examined theoretically and shown to be negligible when the flow rate of the sample inlet substream is small compared to the total channel flow rate. The optimization of the sample inlet flow rate is discussed. Experimental results for both injection procedures are reported for flow/steric (or hyperlayer) FFF applied to latex standards, confirming the expected trends. However, closer examination shows that the observed incremental band broadening associated with hydrodynamic relaxation is somewhat larger than the value predicted.

Failure of dietary protein and phosphate restriction to retard the rate of progression of chronic renal failure: a prospective, randomized, controlled trial

Ninety-five patients (63 male, 32 female), age 45 +/- 2 years (mean +/- SEM) with chronic renal failure of varied aetiology were randomized to receive either a conventional low protein diet (0.6 g/kg/day protein, 800 mg phosphate; n = 33), a low phosphate diet (providing approximately 1000 mg phosphate plus an orally administered phosphate binder, minimum protein intake 0.8 g/kg/day; n = 30) or to control (minimum protein intake 0.8 g/kg/day, no phosphate restriction; n = 32). Patients were reviewed for a minimum of 6 months before randomization and were withdrawn from the study if plasma creatinine exceeded 900 mumol/l, plasma phosphate was greater than 2.0 mmol/l or at the onset of uraemic symptoms. Following randomization patients were studied for an average of 19 +/- 3 months. Mean plasma creatinine rose from 398 +/- 33 to 600 +/- 50 mumol/l. Dietary protein intake was estimated at 0.69 +/- 0.02 g/kg/day in the low protein group, 1.02 +/- 0.05 in the low phosphate and 1.14 +/- 0.05 in the controls, phosphate intake was 815 +/- 43, 1000 +/- 47, and 1315 +/- 57 mg/day, respectively. Urinary urea excretion and protein catabolic rates were significantly reduced (p less than 0.01) only in those on protein restriction, at 213 +/- 9 mmol/24 hours and 0.71 g/kg/day, respectively. Phosphate excretion was significantly lower (p less than 0.05) in both the low protein group (17.9 +/- 0.8 mmol/24 hours) and the low phosphate group (18.6 +/- 1.0 mmol/24 hours) compared to controls. Changes in body weight, muscle mass and serum transferrin, albumin and immunoglobulins were comparable between the groups. Mean blood pressure following randomization was 150/89 +/- 3/1 (low protein), 148/87 +/- 3/1 (low phosphate) and 146/87 +/- 3/1 (controls). Progression of renal failure was analysed by rate of all of creatinine clearance (ml/min/1.73 m2/month), by rate of deterioration derived from reciprocal plasma creatinine against time plots (1/mmol/year) and to assess individual patient's response to treatment by two phase linear regression ('breakpoint') analysis of reciprocal plasma creatinine/time plots. Progression was analysed only in patients seen for at least 3 months following randomization. The rate of fall of creatinine clearance was not significantly different between the groups (ANOVA): 0.56 +/- 0.08 ml/min/1.73 m2/month (low protein, n = 28), 0.44 +/- 0.07 (low phosphate, n = 23) and 0.69 +/- 0.11 (control, n = 27).(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of power and exponential field programming in field-flow fractionation

Field programming in field-flow fractionation has the purpose of expanding the molecular weight or particle diameter range subject to a single analytical run. The two most widely used field programs are those in which the field strength decays with time according to an exponential function and a power function, respectively. The performances of these two programming functions are compared by obtaining limiting equations showing how retention time tr, standard deviation in retention sigma t, and fractionating power Fd vary with particle diameter d. It is shown that uniform fractionating power (Fd independent of d) can be obtained with power programming but that in exponential programming Fd is always non-uniform, varying as d-1/2. In exponential programming a linear relationship arises between tr and log d. This particular relationship is impossible to realize in power programming but an alternative linear relationship can be obtained by plotting tr versus dt/3. These results are made more concrete by plotting and comparing field strength, relative field strength, Fd and tr for specific programming cases.

Particle size distribution by sedimentation/steric field-flow fractionation: development of a calibration procedure based on density compensation

Because of the important but mathematically complex role played by hydrodynamic lift forces in sedimentation/steric FFF, applied generally to particles greater than 1 micron in diameter, retention cannot readily be related to particle diameter on the basis of simple theory. Consequently, empirical calibration is needed. Unfortunately, retention is based on particle density as well as size so that a purely size-based calibration (e.g., with polystyrene latex standards) is not generally valid. By examining the balance between driving and lift forces, it is concluded that equal retention will be observed for equal size particles subject to equal driving forces irrespective of particle density. Therefore by adjusting the rotation rate to exactly compensate for density, retention can be brought in line with that of standards, a conclusion verified by microscopy. Linear calibration plots of log (retention time) versus log (diameter) can then be used. This approach is applied to two glass bead samples (5-30 and 5-50 microns) using both a conventional and a pinched inlet channel. The resulting size distribution curves are self consistent and in good agreement with results obtained independently.

Multiple organ failure--a role for plasma exchange?

Two patients with multiple organ failure, septicaemia and a deteriorating clinical course were treated by plasma exchange in addition to standard supportive measures. Dramatic improvements were seen in cardio-respiratory (patient 1), neurological and renal parameters (patient 2) which were attributable to the exchanges. Plasma exchange might be of value as adjunctive therapy where overwhelming septicaemia occurs with multiple organ failure.

Reducing sepsis in severe combined acute renal and respiratory failure by selective decontamination of the digestive tract

Fifteen patients with severe combined acute renal and respiratory failure (SCARRF), who required mechanical ventilation and renal replacement therapy for at least 5 days, were treated with a regimen to selectively decontaminate the digestive tract (SDD). In these patients the incidence of significant infection was compared with the infection rate in 12 similar patients with SCARRF who had not received SDD, treated over the preceding 12 months. Both groups were comparable for age, study period, sepsis score, and therapeutic intervention scoring system on admission, although the Acute Physiology and Chronic Health Evaluation score was higher (p less than .05) in the SDD-treated group. Ten (83%) of 12 control patients developed definable infections compared with five (33%) of 15 in the SDD group (p less than .05). Gram-negative bacteria and fungi were responsible for 14 of the 17 infections affecting ten control patients, compared with six of the seven infections in only four SDD patients (p less than .05). The most notable site to benefit was the respiratory tract, with only one patient in the SDD group developing a pulmonary infection compared with five in the control patients (p less than .05). Urine infections may have been reduced from six (50%) of the 12 control patients to two (13%) of the 15 SDD patients, but this difference was not significant. Although survival in the control and SDD group was comparable (42% vs. 40%), mortality overall seemed related to infection. Eleven (73%) of 15 patients with definite infection died, in contrast with five (42%) of 12 who had no infections, although this was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunosuppression can arrest progressive renal failure due to idiopathic membranous glomerulonephritis

The effect of pulse intravenous methylprednisolone therapy followed by oral immunosuppression was evaluated in ten patients with idiopathic membranous glomerulonephritis who had developed progressive renal failure--a group generally considered to have a poor prognosis. The patients (six male, four female, mean age 50 years) were monitored over 9-30 months during which time creatinine clearance reduced from (mean +/- SEM) 83 +/- 10 to 29 +/- 6 ml/min, and plasma creatinine increased from 135 +/- 22 to 297 +/- 35 mumol/l. All patient were nephrotic with mean 24-h urinary protein excretion ranging from 5.8 to 19.6 g. Treatment administered was pulse intravenous methyl-prednisolone 1 g X 3 then oral prednisolone 30 mg and azathioprine 50 mg (nine patients) or cyclophosphamide 50 mg (one patient). Mean prednisolone dosage was 25 mg at 3 months, 16 mg at 6, and 10 mg at 12 months. Patients have been followed up for between 12 and 57 months on therapy. Creatinine clearance increased to 39 +/- 6, 47 +/- 5 and 48 +/- 18 ml/min after 3, 6 and 12 months treatment with a fall in proteinuria to 6.2 +/- 1.7, 5.7 +/- 1.4, and 3.1 +/- 1.1 g/24h. The deterioration of renal function was reversed in six patients (associated with a reduction in proteinuria to less than 1 g/24 hours in five), slowed in three (with a significant reduction in proteinuria in two), and only one patient with more advanced renal failure before treatment progressed to end-stage failure without any retardation of the rate of deterioration or change in proteinuria.(ABSTRACT TRUNCATED AT 250 WORDS)

Novel inhibitors of enkephalin-degrading enzymes. I: Inhibitors of enkephalinase by penicillins

Several penicillins have been found to have pro-antinociceptive properties and also to be enkephalinase (neutral endopeptidase-24.11) inhibitors, carfecillin being the most potent. Carfecillin i.c.v. (but not i.p.) had significant antinociceptive activity in the mouse tail immersion test and completely suppressed abdominal constrictions (acetic acid) in mice (IC50 = 23 micrograms/animal). In combination with (D-Ala2-D-leu5)-enkephalin (DADL) i.c.v. in the abdominal constriction test the complete protection observed was reversed by the opioid receptor antagonist naltrexone. Carfecillin was a competitive inhibitor of enkephalinase from mouse brain striata (IC50 = 207 + 57 nM, cf thiorphan 10.6 +/- 1.9 nM) but did not inhibit other known enkephalin- degrading enzymes. Carfecillin provides a new lead structure for the development of more potent enkephalinase inhibitors.

Novel inhibitors of enkephalin-degrading enzymes. II: N5'-substituted-4-thioxohydantoic acids as aminopeptidase inhibitors

Some 2-substituted-(2'-aminophenyl)-4-thioxohydantoic acids (o-amino PTC-amino acids) have antinociceptive activity when administered (icv) alone (IC50 = 0.04-0.87 microM/animal) and show a striking prolongation of the antinociceptive action of (D-Ala-2 D-Leu5)-enkephalin (DADL) in combination. The effects are thought to be mediated via opioid receptors since they are naloxone-reversible. Although inhibitors of the enkephalin degrading puromycin-insensitive, bestatin-sensitive aminopeptidase (possibly aminopeptidase M) their action is weak (IC50 = 32 microM leucine, 536 microM, glycine) and they might be considered to have a direct antinociceptive effect on opioid receptors. The titled compounds constitute novel 'lead' compounds for the development of potent aminopeptidase M inhibitors.

Increased incidence of anti-glomerular basement membrane antibody (anti-GBM) nephritis in the Mersey Region, September 1984-October 1985

We report an increase in the incidence of anti-glomerular basement membrane antibody nephritis in the Mersey Region over the 13 months from September 1984 to October 1985. During this period anti-glomerular basement membrane antibody nephritis was diagnosed in 10 patients: seven cases occurred between 1 June and 31 October 1985. We could identify no common infective agent or history of toxic exposure. Although outbreaks of parvovirus infection were reported in the region during this period, no patient had serological evidence of recent infection with parvo- or other virus. The only atypical feature was the high incidence of allergic rash which was seen in four of six patients treated with antibiotics before admission. Only two patients recovered sufficient renal function to make dialysis unnecessary. Both had a longer duration of prodromal symptoms, lower levels of circulating anti-glomerular basement membrane antibody antibodies and histological evidence of less aggressive disease.

Sepsis: a cause of aluminum release from tissue stores associated with acute neurological dysfunction and mortality

We report six cases of patients with renal failure and exposure to aluminum who developed septicemia. In all cases the serum aluminum increased markedly. This may have contributed to the neurological dysfunction seen in five, and the deaths of four of the patients. We suggest that the rise in serum aluminum was due to the release of tissue-bound aluminum, resulting in an increase in free, diffusable aluminum and that this jeopardized both neurological function and immunocompetence.

Renal pathology and proteinuria determine progression in untreated mild/moderate chronic renal failure

The progression of renal failure was analyzed in 108 patients with mild to moderate renal impairment, none of whom had received any form of dietary protein, phosphate restriction or immunosuppressive treatment. The reciprocal of plasma creatinine was plotted against time using a minimum of six plasma creatinine values taken over at least six months (mean 13 values over 41 months). Plots indicated there was linear deterioration in 70 patients, non-linear deterioration in 15 and stable renal function in 24. Progressive renal failure was common in patients with glomerulonephritis, diabetic nephropathy, chronic pyelonephritis and polycystic kidney disease. Most patients with hypertensive nephrosclerosis, analgesic nephropathy and renal impairment following acute renal failure were stable. Among those with progressive impairment the mean rates of deterioration were significantly faster for patients with glomerulonephritis and diabetic nephropathy compared to those with chronic pyelonephritis, polycystic kidney disease and undiagnosed renal disease (p less than 0.01). Hence the underlying renal pathological changes appear to be important in determining progression of renal failure and also the subsequent rate of deterioration. For those with linear progression of renal failure there was a significant correlation between 24-h urinary protein excretion and the rate of deterioration. This relationship held for glomerulonephritis and chronic pyelonephritis as separate diagnostic groups only. Proteinuria, therefore, may be a useful prognostic index for the rate of progression of established renal failure. Calcium phosphate product correlated poorly with the rate of deterioration. We were unable to demonstrate a relationship between spontaneous protein intake and deterioration of renal function. However, patients prescribed high protein diets were not included in dietary analysis and we cannot, therefore, exclude the possibility that a high dietary protein intake may accelerate renal failure. Similarly we were unable to show a significant relationship between blood pressure and progression of renal failure although there were weak correlations between mean arterial pressure and rate of deterioration for chronic pyelonephritis and glomerulonephritis.

Hypoglycaemia following treatment of hyperkalaemia with insulin and dextrose

We describe four patients who developed symptomatic hypoglycaemia following treatment of hyperkalaemia with insulin and dextrose. Two patients had a delayed onset of hypoglycaemia, between 5 and 6 hours after treatment despite use of a 'soluble' type of insulin. A review of the literature revealed a variety of insulin and dextrose regimes but no research to assess the metabolic effects of such therapy in patients with renal failure. The possibility of significant hypoglycaemia following use of insulin and dextrose in the recommended dosages is rarely mentioned. The cases we describe demonstrate that there is no 'correct' dose of insulin and dextrose to suit every circumstance. Regular blood glucose estimations should be performed in all patients receiving such therapy for hyperkalaemia.

Induction of cytolytic activity by anti-T3 monoclonal antibody. Activation of alloimmune memory cells and natural killer cells from normal and immunodeficient individuals

The ability of the monoclonal antibody directed at the T3 antigen (anti-T3) to induce cytolytic activity was investigated since several agents that can activate T cells induce the acquisition of cytolytic activity in a variety of test systems. Pretreatment of human alloimmune memory cells, generated in primary long-term mixed lymphocyte cultures, with anti-T3 resulted in the induction of statistically significant specific secondary cytolytic activity and natural killer (NK) cell-like activity. No such augmentation or induction of cytolytic activity was found with anti-T3 pretreatment when syngeneic cells or inappropriate allogeneic cells (HLA-A, B antigens different from the original priming stimulus) were used as target cells and pretreatment of memory cells with anti-T4 or anti-T8 did not induce cytolytic activity to allogeneic or syngeneic target cells. Differential effects were observed when anti-T3 was added to the cytotoxicity assay in which anti-T3 pretreated alloimmune memory cells were effectors. The addition of anti-T3 to the assay prior to the introduction of target cells resulted in 39 +/- 8% inhibition of specific secondary cytolytic activity and only 5 +/- 8% inhibition of NK cell activity. NK cell activity mediated by large granular lymphocyte-enriched fraction of peripheral blood mononuclear cells (PBM) obtained from normal individuals was significantly augmented by anti-T3 when NK-sensitive cell lines MOLT-4 or K-562 were used as target cells. This augmentation in NK cell activity was not associated with nonspecific cytotoxicity to syngeneic or allogeneic PBM, and anti-T3 failed to activate the LGL fraction depleted of T cells. The monoclonal antibodies, anti-T4 or anti-T8, did not increase NK cell activity. NK cell activity mediated by PBM from eight immunodeficient individuals (four with acquired immunodeficiency syndrome and four with renal allografts) was also significantly augmented by anti-T3 pretreatment. Our findings, in addition to providing a rationale for the frequent occurrence of re-rejection episodes in renal graft recipients treated with anti-T3, suggest that anti-T3 might be utilized to enhance the cytotoxic armamentarium of immunodeficient patients.

Recovery from severe pulmonary damage due to paraquat administered intravenously and orally

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Proliferative glomerulonephritis associated with Crohn's disease

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Captopril-induced acute renal artery thrombosis and persistent anuria in a patient with documented pre-existing renal artery stenosis and renal failure

We describe an elderly man, with pre-existing renal failure and atheromatous renal artery stenosis, who developed persistent anuria due to renal artery thrombosis after acute hypotension following captopril administration. Caution should be used when captopril is first administered to patients with impaired renal function in whom renal artery stenosis is known or suspected.

Hydroxyl radical scavengers inhibit human natural killer cell activity

As natural killer (NK) cell activity is an essential constituent of host defence systems and reactive oxygen intermediates participate in such defence, the effect of scavengers of oxygen radicals on NK cell activity was investigated. Hydroxyl radical (OH) scavengers (dimethyl sulphoxide (DMSO), thiourea, dimethylurea, tetramethylurea, benzoic acid, ethanol, methanol and ethylene glycol) inhibited NK cell activity. Catalase, a scavenger of H2O2, and superoxide dismutase (SOD), a scavenger of O-2, either alone or in combination, did not inhibit NK cell activity. Inhibition of the lipoxygenase pathway of arachidonic acid metabolism, a potential source of cellular OH, with nordihydroguaiaretic acid and 5,8,11,14-eicosatetraynoic acid (ETYA) resulted in marked inhibition of NK cell activity. Inhibition of the cyclooxygenase pathway with acetylsalicylic acid or indomethacin had minimal effects on NK cell activity. Taken together, these findings suggest that OH, possibly generated via the lipoxygenase pathway of arachidonic acid metabolism, is critical for NK cell cytotoxicity.

An evaluation of the dorset sheep as a predictive animal model for the response of G-6-PD deficient human erythrocytes to a proposed systemic toxic ozone intermediate, methyl oleate hydroperoxide

Erythrocytes of both G-6-PD deficient humans and Dorset sheep, an animal model with an erythrocyte G-6-PD deficiency, both responded in a dose dependent manner to the oxidant stress of MOHP as measured by decreases in G-6-PD activity, increases in METHB levels and decreases in GSH. However, the human G-6-PD deficient erythrocytes were considerably more sensitive to the formation of METHB than the sheep erythrocytes while the reverse was the case for the GSH parameter. The results suggest a qualitative difference in the response of sheep erythrocytes and human G-6-PD deficient erythrocytes to MOHP that seriously questions the value of the sheep erythrocyte as a quantitatively accurate predictive model.

An evaluation of the dorset sheep as a predictive animal model for the response of glucose-6-phosphate dehydrogenase-deficient human erythrocytes to a proposed systemic toxic ozone intermediate, methyl oleate ozonide

Erythrocytes of both glucose-6-phosphate dehydrogenase (G-6-PD)-deficient humans and Dorset sheep, an animal model with an erythrocyte G-6-PD deficiency, responded in a dose-dependent manner to the oxidant stress of methyl oleate ozonide (MOO) as measured by decreases in G-6-PD activity, increases in methemoglobin (METHB) levels, and decreases in GSH. However, the human G-6-PD-deficient erythrocytes were considerably more sensitive to the formation of METHB than the sheep erythrocytes while the reverse was the case for the GSH parameter. The results suggest a qualitative difference in the response of sheep erythrocytes and human G-6-PD-deficient erythrocytes to MOO that seriously questions the value of the sheep erythrocyte as a quantitatively accurate predictive model.