Benchmarking of electro-optic monitors for femtosecond electron bunches

The longitudinal profiles of ultrashort relativistic electron bunches at the soft x-ray free-electron laser FLASH have been investigated using two single-shot detection schemes: an electro-optic (EO) detector measuring the Coulomb field of the bunch and a radio-frequency structure transforming the charge distribution into a transverse streak. A comparison permits an absolute calibration of the EO technique. EO signals as short as 60 fs (rms) have been observed, which is a new record in the EO detection of single electron bunches and close to the limit given by the EO material properties.

Continuous ambulatory peritoneal dialysis versus automated peritoneal dialysis for end-stage renal disease

BACKGROUND

Peritoneal dialysis (PD) can be performed either manually as in continuous ambulatory peritoneal dialysis (CAPD) or using mechanical devices as in automated PD (APD). APD has been considered to have several advantages over CAPD such as reduced incidence of peritonitis, mechanical complications and greater psychosocial acceptability.

OBJECTIVES

To assess the comparative efficacy of CAPD and APD in patients who are dialysed for end-stage renal disease (ESRD).

SEARCH STRATEGY

We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Renal Group's specialised register and CINAHL. Authors of included studies were contacted, reference lists of identified RCTs and relevant narrative reviews were screened. Date of most recent search: May 2006

SELECTION CRITERIA

RCTs comparing CAPD with APD in patients with ESRD.

DATA COLLECTION AND ANALYSIS

Data were abstracted independently by two authors onto a standard form. Relative risk (RR) for dichotomous data and a mean difference (MD) for continuous data were calculated with 95% confidence intervals (CI).

MAIN RESULTS

Three trials (139 patients) were included. APD did not differ from CAPD with respect to mortality (RR 1.49, 95% CI 0.51 to 4.37), risk of peritonitis (RR 0.75, 95% CI 0.50 to 1.11), switching from original PD modality to a different dialysis modality (RR 0.50, 95% CI 0.25 to 1.02), hernias (RR 1.26, 95% interval 0.32 to 5.01), PD fluid leaks (RR 1.06, 95% CI 0.11 to 9.83), PD catheter removal (RR 0.64, 95% CI 0.27 to 1.48) or hospital admissions (RR 0.96, 95% CI 0.43 to 2.17). There was no difference between either PD modality with respect to residual renal function (MD -0.17, 95% CI -1.66 to 1.32). One study found that peritonitis rates and hospitalisation were significantly less in patients on APD when results were expressed as episodes/patient-year. Another study found that patients on APD had significantly more time for work, family and social activities.

AUTHORS' CONCLUSIONS

APD has not been shown to have significant advantages over CAPD in terms of important clinical outcomes. APD may however be considered advantageous in select group of patients such as in the younger PD population and those in employment or education due to its psychosocial advantages. There is a need for a RCT comparing CAPD with APD with sufficiently large patient numbers looking at important clinical outcomes including residual renal function, accompanied by an economic evaluation to clarify the relative clinical and cost-effectiveness of both modalities.

Haemodiafiltration, haemofiltration and haemodialysis for end-stage kidney disease

BACKGROUND

Renal replacement therapy (RRT) for end-stage kidney disease (ESKD) can be achieved by several interventions including haemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation. HD, haemofiltration (HF), haemodiafiltration (HDF) and acetate-free biofiltration (AFB) are extracorporeal RRT methods. It has been suggested that HF and HDF may reduce the frequency and severity of intradialytic and post-dialytic adverse symptoms and may be more effective than HD in the removal of high molecular weight molecules.

OBJECTIVES

To compare convective modes of extracorporeal RRT (HF, HDF or AFB) with HD and to establish if any of these techniques is superior to each other in patients with ESKD.

SEARCH STRATEGY

We searched MEDLINE (1966-2006), EMBASE (1980-2006), Cochrane Central Register of Controlled Trials (CENTRAL, in The Cochrane Library issue 2, 2006) and CINAHL (1872-2006). Authors of included studies were contacted, reference lists of identified RCTs and relevant narrative reviews were screened.

SELECTION CRITERIA

RCTs comparing HF, HDF, AFB and HD for ESKD were included. Trials enrolling any patient undergoing RRT for ESKD were included.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Statistical analyses were performed using the random effects model and the results expressed as relative risk (RR) for dichotomous outcomes or weighted mean difference (MD) for continuous data with 95% confidence intervals (CI). Heterogeneity was measured using the Chi-square (chi(2)) and I(2) statistic.

MAIN RESULTS

Twenty studies (657 patients) were included. Seventeen studies compared HF, HDF or AFB with HD, two compared HDF with AFB and one compared HF with HDF. The studies were generally small with suboptimal quality. Convective modalities (HF, HDF, AFB) did not differ significantly from HD for mortality (RR 1.68, 95% CI 0.23 to 12.13; chi(2)= 2.58, P = 0.11, I(2) = 61.2%), number of hospital admissions/year (MD 0.20, 95% CI -0.07 to 0.47) and dialysis adequacy (Kt/V: MD 0.09, 95% CI 0.02 to 0.17; chi(2) = 3.73, P = 0.29, I(2) = 19.6%). No study assessed number of dialysis treatments associated with "any adverse symptoms", sessions that were stopped early, change of dialysis modality or dialysis-related amyloidosis.

AUTHORS' CONCLUSIONS

We were unable to demonstrate whether convective modalities (either HF, HDF or AFB) have significant advantages over HD with regard to clinically important outcomes of mortality, dialysis-related hypotension and hospitalisation. More adequately-powered good quality RCTs assessing clinically important outcomes (mortality, hospitalisation, quality of life) are needed.

Temporally resolved electro-optic effect

The electro-optic effect between an ultrafast optical probe pulse and an ultrashort terahertz pulse is shown to depend on the time derivatives of the product of the probe and terahertz electric fields. Application of this theory to temporally resolved single-shot terahertz detection techniques, where the electro-optic effect is temporally localized within an optical probe pulse, shows that the description presented here differs fundamentally and verifiably from that commonly used in literature.

An inverse agonist selective for alpha5 subunit-containing GABAA receptors enhances cognition

Alpha5IA is a compound that binds with equivalent subnanomolar affinity to the benzodiazepine (BZ) site of GABA(A) receptors containing an alpha1, alpha2, alpha3, or alpha5 subunit but has inverse agonist efficacy selective for the alpha5 subtype. As a consequence, the in vitro and in vivo effects of this compound are mediated primarily via GABA(A) receptors containing an alpha5 subunit. In a mouse hippocampal slice model, alpha5IA significantly enhanced the burst-induced long-term potentiation of the excitatory postsynaptic potential in the CA1 region but did not cause an increase in the paroxysmal burst discharges that are characteristic of convulsant and proconvulsant drugs. These in vitro data suggesting that alpha5IA may enhance cognition without being proconvulsant were confirmed in in vivo rodent models. Hence, alpha5IA significantly enhanced performance in a rat hippocampal-dependent test of learning and memory, the delayed-matching-to-position version of the Morris water maze, with a minimum effective oral dose of 0.3 mg/kg, which corresponded to a BZ site occupancy of 25%. However, in mice alpha5IA was not convulsant in its own right nor did it potentiate the effects of pentylenetetrazole acutely or produce kindling upon chronic dosing even at doses producing greater than 90% occupancy. Finally, alpha5IA was not anxiogenic-like in the rat elevated plus maze nor did it impair performance in the mouse rotarod assay. Together, these data suggest that the GABA(A) alpha5-subtype provides a novel target for the development of selective inverse agonists with utility in the treatment of disorders associated with a cognitive deficit.

Electro-optic technique with improved time resolution for real-time, nondestructive, single-shot measurements of femtosecond electron bunch profiles

Electro-optic detection of the Coulomb field of a relativistic electron bunch combined with single-shot cross correlation of optical pulses is used to enable single-shot measurements of the shape and length of femtosecond electron bunches. This method overcomes a fundamental time-resolution limit of previous single-shot electro-optic measurements, which arises from the inseparability of time and frequency properties of the probing optical pulse. Using this new technique we have made real-time measurements of a 50 MeV electron bunch, observing the profile of 650 fs FWHM ( approximately 275 fs rms) long bunches.

High-temporal-resolution, single-shot characterization of terahertz pulses

A technique for noncollinear cross correlation of electro-optic modulated optical pulses is presented for the single-shot characterization of terahertz waveforms and is compared to established electro-optic terahertz characterization methods. This technique is free from the limitations on time resolution and faithful reproduction of previously demonstrated single-shot amplitude modulation spectral encoding.

End-stage renal disease in Indo-Asians in the North-West of England

BACKGROUND

The incidence of end-stage renal disease (ESRD) in England is increasing. There is a higher incidence of ESRD in British Indo-Asians than in the White population.

AIM

To determine to what degree the increasing demand for renal replacement therapy in the UK is due to Indo-Asian patients. To study the presentation to renal services of Indo-Asian patients with ESRD and report any inequalities in initial treatment of Indo-Asian patients with ESRD compared to their White counterparts.

DESIGN

Prospective, inception cohort study.

METHODS

Consecutive adult patients with ESRD who started renal replacement therapy between 1 April 2000 and 31 December 2001 in all 14 renal units serving an area from North Cheshire to South Cumbria, including Greater Manchester and Lancashire, were recruited and interviewed.

RESULTS

Of the 578 patients, 9.5% were Indo-Asian. The annual acceptance rate for renal replacement therapy was 342 per million population in Indo-Asians, compared with 91 per million population in the White population ( p < 0.001). Indo-Asian patients with ESRD were younger (median age 51 years vs. 60 yrs, p = 0.006) and more socially deprived (81% vs. 36.5% in the 5th Carstairs quintile, p < 0.001). A greater proportion of Indo-Asian patients with ESRD presented late to specialist renal services (31% vs. 19%, p = 0.03). Once adjusting for their younger age, atherosclerotic renovascular disease and/or hypertensive nephropathy was more prevalent in Indo-Asian patients (OR 4.9; p = 0.03). There was no difference in the initial mode of maintenance dialysis or the perception of choice the patients felt they had, based on their ethnicity.

DISCUSSION

There is a silent epidemic of ESRD in Indo-Asian patients in the North-West, possibly vascular in aetiology, in which specialist intervention is late. This suggests that Indo-Asian patients should be prioritized for early intervention strategies to reduce the burden of ESRD.

Acute renal failure requiring renal replacement therapy: incidence and outcome

BACKGROUND

Renal replacement therapy (RRT) for acute renal failure (ARF) may be provided in many settings within the hospital. Such patients require a high level of care and often have a poor prognosis. No prospective studies have accurately defined this population, making the prediction of necessary resources and the planning of services difficult.

AIM

To ascertain the incidence, causes and outcomes of acute renal failure requiring renal replacement therapy in Scotland.

DESIGN

A prospective observational census of all clinical areas providing renal replacement therapy in three Scottish health boards (Grampian, Highland, Tayside).

METHODS

Patients were identified by liaison with each unit providing RRT. Factors precipitating renal failure and reasons for RRT were recorded at the time of initiation. Comorbid disease burden was scored using the Charlson index. Patient status at 90 days was assessed from case-notes, contacting general practitioners where necessary.

RESULTS

375 patients per million population per year received RRT; 203 per million per year for either ARF or acute-on-chronic renal failure. 73.5% of patients receiving RRT for ARF died within 90 days, 23.5% became independent of RRT. The median duration of hospital admission was 19 days.

DISCUSSION

The annual incidence of ARF requiring RRT is just over 200 per million population, almost twice that of end-stage renal disease requiring RRT. Such treatment places high demands upon health care resources.

Single-shot electron-beam bunch length measurements

We report subpicosecond electro-optic measurements of the length of individual relativistic electron bunches. The longitudinal electron-bunch shape is encoded electro-optically on to the spectrum of a chirped laser pulse. The electron-bunch length is determined by analyzing individual laser-pulse spectra obtained with and without the presence of an electron bunch. Since the length of the chirped laser pulse can be easily changed, the electron bunch can be visualized on different time scales. This single-shot imaging technique is a promising method for real-time electron-bunch diagnostics.

3-(4-Fluoropiperidin-3-yl)-2-phenylindoles as high affinity, selective, and orally bioavailable h5-HT(2A) receptor antagonists

The development of very high affinity, selective, and bioavailable h5-HT(2A) receptor antagonists is described. By investigation of the optimal position for the basic nitrogen in a series of 2-phenyl-3-piperidylindoles, it was found that with the basic nitrogen at the 3-position of the piperidine it was not necessary to further substitute the piperidine in order to obtain good binding at h5-HT(2A) receptors. This meant the compounds no longer had high affinity at the IKr potassium channel, an issue with previous series of 2-aryl-3-(4-piperidyl)indoles. Improvements could be made to oral bioavailability in this series by reduction of the pK(a) of the basic nitrogen, by adding a fluorine atom to the piperidine ring, leading to 3-(4-fluoropiperidin-3-yl)-2-phenyl-1H-indole (17). Metabolic studies with this compound identified oxidation at the 6-position of the indole as a major route in vitro and in vivo in rats. Blocking this position with a fluorine atom led to 6-fluoro-3-(4-fluoropiperidin-3-yl)-2-phenyl-1H-indole (22), an antagonist with 0.06 nM affinity for h5-HT(2A) receptors, with bioavailability of 80% and half-life of 12 h in rats.

Do the Y-set and double-bag systems reduce the incidence of CAPD peritonitis? A systematic review of randomized controlled trials

BACKGROUND

Peritonitis is the most frequent serious complication of continuous ambulatory peritoneal dialysis (CAPD). It has a major influence on the number of patients switching from CAPD to haemodialysis and has probably restricted the wider acceptance and uptake of CAPD as an alternative mode of dialysis. This systematic review sought to determine if modifications of the transfer set (Y-set or double-bag systems) used in CAPD exchanges are associated with a reduction in peritonitis and an improvement in other relevant outcomes.

METHODS

Based on a comprehensive search strategy, we undertook a systematic review of randomized or quasi-randomized controlled trials comparing double-bag and/or Y-set CAPD exchange systems with standard systems, or comparing double-bag with Y-set systems, in patients with end-stage renal disease (ESRD) treated with CAPD. Only published data were used. Data were abstracted by a single investigator onto a standard form and subsequently entered into Review Manager 4.0.4. Its statistical package, Metaview 3.1, calculated an odds ratio (OR) for dichotomous data and a (weighted) mean difference for continuous data with 95% confidence intervals.

RESULTS

Twelve eligible trials with a total of 991 randomized patients were identified. In trials comparing either the Y-set or double-bag systems with the standard systems, significantly fewer patients (133/363 vs 158/263; OR 0.33, 95% CI 0.24-0.46) experienced peritonitis and the number of patient-months on CAPD per episode of peritonitis was consistently greater. When the double-bag systems were compared with the Y-set systems significantly fewer patients experienced peritonitis (44/154 vs 66/138; OR 0.44, 95% CI 0.27-0.71) and the number of patient-months on CAPD per episode of peritonitis was also greater.

CONCLUSIONS

Double-bag systems should be the preferred exchange systems in CAPD.

A default mode of brain function

A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge. Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF. The OEF is defined as the ratio of oxygen used by the brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and functional MRI. These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.

Evidence-based medicine in nephrology: identifying and critically appraising the literature

BACKGROUND

Uncertainties about best management of end-stage renal disease (ESRD) are reflected in wide variations in practice. Systematic reviews aim to reduce uncertainty by strengthening the evidence base for clinical practice, allowing estimation of the benefits and risks of particular interventions, whilst minimizing the potential for bias. This paper describes the methods and conduct of six systematic reviews of aspects of the management of ESRD, and the yield in terms of trials found.

METHODS

Our methodology was based on that recommended by the Cochrane Collaboration (an international initiative set up to perform and disseminate systematic reviews of health care). It involved a systematic search of electronic databases and bibliographic reference lists, together with handsearching of Kidney International for studies relevant to the management of ESRD, followed by a systematic assessment of study quality.

RESULTS

Around 12,000 abstracts were assessed which had been identified from electronic sources. Of these, 2085 (18%) were deemed to be reports of possible randomized or quasi-randomized controlled trials relevant to the management of ESRD. Three hundred and forty were relevant to the six specific reviews, and after assessment of the full manuscripts, 39 studies were finally included in our reviews. Reports of a further nine trials, which were identified from other sources, were also included. The broad search adopted allowed the parallel development of a register of trials of all aspects of the management of ESRD.

CONCLUSIONS

This study has demonstrated that the methodology of systematic reviews, as promoted by the Cochrane Renal Group, is feasible but has significant resource implications. The development of a register of randomized controlled trials (RCTs) related to the management of ESRD will facilitate this form of research in the future.

Subpicosecond electro-optic measurement of relativistic electron pulses

Time-resolved measurements of the transverse electric field associated with relativistic electron bunches are presented. Using an ultrafast electro-optic sensor close to the electron beam, the longitudinal profile of the electric field was measured with subpicosecond time resolution and without time-reversal ambiguity. Results are shown for two cases: inside the vacuum beam line in the presence of wake fields, and in air behind a beryllium window, effectively probing the near-field transition radiation. Especially in the latter case, reconstruction of the longitudinal electron bunch shape is straightforward.

Dipyridamole inhibits human mesangial cell proliferation

BACKGROUND

Many glomerular diseases are associated with mesangial cell proliferation and the accumulation of extracellular matrix. At present, there are, however, few treatments which can inhibit these processes. The current study assessed the effects of the anti-platelet and putative anti-proliferative drug dipyridamole (DP) on the growth of human mesangial cells in vitro and their production of the extracellular matrix protein, fibronectin.

METHODS

Human mesangial cell proliferation, both intrinsic and stimulated by platelet-derived growth factor, was assessed using 3H-thymidine incorporation and an MTT proliferation assay. A sandwich enzyme-linked immunosorbent assay was used to study the effects of DP on fibronectin synthesis, again in cells stimulated by transforming growth factor beta 1 and in unstimulated cells.

RESULTS

At concentrations compatible with the serum levels found in subjects consuming standard dosages, DP significantly inhibited the growth of human mesangial cells in vitro in a dose-dependent fashion. DP also abrogated the mitogenic effects of platelet-derived growth factor. It had no significant effects on the synthesis of fibronectin by these cells (either spontaneous or induced by transforming growth factor beta 1). There was no evidence of cytotoxicity.

CONCLUSION

These data suggest that DP may have a therapeutic role in proliferative glomerulonephritis and possibly other diseases characterized by cell proliferation.

Evaluation of clinical guidelines for the management of end-stage renal disease in europe: the EU BIOMED 1 study

BACKGROUND

There are wide national and international variations in the management of patients with end-stage renal disease (ESRD). The aim of this study was to develop, harmonize, implement, and evaluate consensus-based clinical guidelines for the management of renal anaemia and renal bone disease in patients with ESRD, and for the prevention and management of cytomegalovirus disease in renal transplant recipients across six renal centres in Europe.

METHODS

The trial was a prospective, multicentre, randomized balanced incomplete block design. Nephrologists from the six European renal units were randomized to develop and implement guidelines for two out of the three conditions and to act as a control for the third condition. Data were collected pre- (1 year) and post- (9 months) intervention on aspects of patient monitoring, management, and outcome.

RESULTS

Eight hundred and twenty-nine dialysis patients from the six European dialysis centres were included in the study. Multivariate analysis (adjusting for case-mix and secular trends) showed a significant increase in the number of monitoring events in the guideline group compared with control group (6%, 95% CI, 1-11%). There was no concomitant increase in either appropriate management or the number of favourable patient outcomes.

CONCLUSIONS

In the first European collaboration on renal guidelines, the introduction of the guidelines improved the monitoring of the patients, but did not improve patient management or outcome. This study suggests the potential for creating clinical guidelines with the aim of standardizing treatment protocols across international boundaries, and improving the quality of the medical care provided.

Formation of low time-bandwidth product, single-sided exponential optical pulses in free-electron laser oscillators

The detailed shape of picosecond optical pulses from a free-electron laser (FEL) oscillator has been studied for various cavity detunings. For large values of the cavity detuning the optical pulse develops an exponential leading edge, with a time constant proportional to the applied cavity detuning and the quality factor of the resonator. This behavior has been observed at two separate FELs that have completely different resonator layouts and electron beam characteristics, and using different methods of optical pulse length measurement. The optical pulses have a full width at half maximum time-bandwidth product Deltat(FWHM)Deltaf(FWHM) of 0.2-0.3. The results presented here can be used to predict the optical pulse length and corresponding minimum spectral width that can be generated in a FEL pumped by short electron bunches. This is important for the design of new infrared free-electron laser user facilities, which need to make a balanced choice between short pulses for high temporal resolution and narrow bandwidth for linear and nonlinear spectroscopy.

Can we improve early mortality in patients receiving renal replacement therapy?

BACKGROUND

Approximately one in eight patients with end-stage renal disease (ESRD) die within the first three months of starting renal replacement therapy (RRT). We investigated which factors might improve this early mortality.

METHODS

We performed a prospective nationwide study of all patients commencing RRT for ESRD in Scotland over one year. Patients were classified according to how they presented to start RRT, their burden of comorbid diseases, access prepared for dialysis, and duration of care by a nephrologist prior to commencing RRT. Those factors most strongly associated with death within 90 days of commencing treatment were determined by logistic regression analysis.

RESULTS

Patients with an acute unexpected element to their presentation for RRT had early mortality rates between 6.0 and 8.9 times greater than those who commenced RRT electively after a period of care from a nephrologist. Patients in high and medium comorbidity risk groups had early mortality rates of 4.7 and 2.2 times greater than those in the low-risk group. Low serum albumin had a significant association with early death. Patients who progressed steadily to ESRD, who had a planned start to dialysis, and who had mature access were 3.6 times more likely to survive beyond three months than those with no access; they were, however, also younger with less comorbidity.

CONCLUSIONS

The factors principally associated with early mortality are nonelective presentation for RRT, comorbid illness, and low serum albumin. Patients cared for by a nephrologist before requiring RRT who have mature access have better short-term survival than those without access. They are also younger with less comorbidity. It may be possible to improve short-term survival in this "unplanned" group if referred early to facilitate reducing cardiovascular risk factors and preparation for RRT.

Active-site variants of Streptomyces griseus protease B with peptide-ligation activity

BACKGROUND

Peptide-ligating technologies facilitate a range of manipulations for the study of protein structure and function that are not possible using conventional genetic or mutagenic methods. To different extents, the currently available enzymatic and nonenzymatic methodologies are synthetically demanding, sequence-dependent and/or sensitive to denaturants. No single coupling method is universally applicable. Accordingly, new strategies for peptide ligation are sought.

RESULTS

Site-specific variants (Ser195-->Gly, S195G, and Ser195-->Ala, S195A) of Streptomyces griseus protease B (SGPB) were generated that efficiently catalyze peptide ligation (i.e., aminolysis of ester-, thioester- and para-nitroanilide-activated peptides). The variants also showed reduced hydrolytic activity relative to the wild-type enzyme. The ratio of aminolysis to hydrolysis was greater for the S195A variant, which was also capable of catalyzing ligation in concentrations of urea as high as 2 M.

CONCLUSIONS

Mutagenic substitution of the active-site serine residue of SGPB by either glycine or alanine has created a unique class of peptide-ligating catalysts that are useful for coupling relatively stable ester- and para-nitroanilide-activated substrates. Ligation proceeds through an acyl-enzyme intermediate involving His57. Serine to alanine mutations may provide a general strategy for converting proteases with chymotrypsin-like protein folds into peptide-coupling enzymes.

4-Hydroxy-1-[3-(5-(1,2,4-triazol-4-yl)-1H-indol-3-yl)propyl]piperidines: selective h5-HT1D agonists for the treatment of migraine

A series of 4-hydroxy-1-[3-(5-(1,2,4-triazol-4-yl)-1H-indol-3-yl)propyl] piperidines was investigated as potential selective h5-HT1D agonists for the treatment of migraine. The 4-[(N-benzyl-N-methyl)amino]methyl analog 12a was found to be a full agonist at the h5-HT1D receptor with good binding selectivity over the h5-HT1B receptor.

Parallel synthesis of 3-aryloxy-2-propanolamines and evaluation as dual affinity 5-HT(1A) and 5-HT re-uptake ligands

A solution phase synthesis for the preparation of 3-aryloxy-2-propanolamine libraries has been developed. This resulted in the identification of 5 as a ligand with dual affinity for 5-HT1A and serotonin reuptake receptors which shows excellent pharmacokinetic parameters.

Equity of renal replacement therapy utilization: a prospective population-based study

This 1-year prospective survey assessed the incidence and characteristics of all patients starting renal replacement therapy (RRT) for end-stage renal disease in Scotland, and whether there is equity of utilization of RRT in terms of age, domicile and social circumstance. In the year studied, 104 patients per million population (533 patients) started RRT (390 per million population aged 65-75). In 23.5% the cause of ESRD could not be determined. Diabetes was the single most frequently identified cause (16%). The requirement for RRT rose with age, but over the country as a whole, patients aged over 75 years were under-represented. The majority of health boards provided RRT at a rate within 20% of the national rate. There was no difference in the median age at starting RRT between health boards. The spectrum of social deprivation of patients starting RRT was the same as that of the general population. There was no evidence that social deprivation influences acceptance on to the RRT program, although the relationship between ESRD and deprivation is complex. The utilization of RRT exceeded the minimum rate recommended by the Renal Association, although there was fluctuation between health board areas. The national requirement for resources to provide RRT is likely to rise further to care for an increasingly elderly population.

Tactile attention tasks enhance activation in somatosensory regions of parietal cortex: a positron emission tomography study

We used positron emission tomography to study cortical regions mediating tactile attention. Cues selectively directed subjects to attend to the roughness or duration of contact with embossed gratings that rubbed against a single fingertip with controlled speed and force. The task required discriminating between paired gratings that differed in tactile features of roughness and/or length. For different blocks of trials, cues directed attention to one tactile feature or indicated a divided attention strategy to a change in either feature. All attention conditions unambiguously activated several somatosensory foci in the parietal cortex, including somatotopically appropriate portions of the primary somatosensory cortex in the postcentral gyrus (S1) and the secondary somatosensory region (S2) within parietal opercular regions. There was no evidence for separate processing foci for selective and divided attention strategies, or for selectively attending to roughness versus stimulus duration. We observed a greater magnitude blood flow change in S2 versus S1 during attention tasks, which suggests that S2 might actually influence S1 activity. Despite these differences, modulation of S1 and S2 supports concepts of early selection in tactile attention. There were also examples of non-sensory foci in frontal cortex, anterior cingulate gyrus and bilateral superior parietal regions at the fundus of the postcentral sulcus. Posterior parietal regions observed in this study did not overlap foci seen in studies of visual attention. Thus, the posterior parietal region may be subdivided into modality-specific subregions, each of which processes information needed to attend to a specific modality. These non-sensory areas may constitute a network that provides a source of modulating influences on the earlier stage, sensory areas.

Fluorination of 3-(3-(piperidin-1-yl)propyl)indoles and 3-(3-(piperazin-1-yl)propyl)indoles gives selective human 5-HT1D receptor ligands with improved pharmacokinetic profiles

It has previously been reported that a 3-(3-(piperazin-1-yl)propyl)indole series of 5-HT1D receptor ligands have pharmacokinetic advantages over the corresponding 3-(3-(piperidin-1-yl)propyl)indole series and that the reduced pKa of the piperazines compared to the piperidines may be one possible explanation for these differences. To investigate this proposal we have developed versatile synthetic strategies for the incorporation of fluorine into these ligands, producing novel series of 4-fluoropiperidines, 3-fluoro-4-aminopiperidines, and both piperazine and piperidine derivatives with one or two fluorines in the propyl linker. Ligands were identified which maintained high affinity and selectivity for the 5-HT1D receptor and showed agonist efficacy in vitro. The incorporation of fluorine was found to significantly reduce the pKa of the compounds, and this reduction of basicity was shown to have a dramatic, beneficial influence on oral absorption, although the effect on oral bioavailability could not always be accurately predicted.

3-(Piperazinylpropyl)indoles: selective, orally bioavailable h5-HT1D receptor agonists as potential antimigraine agents

Clinically effective antimigraine drugs such as Sumatriptan have similar affinity at h5-HT1D and h5-HT1B receptors. In the search for a h5-HT1D-selective agonist as an antimigraine agent, a novel series of 3-(propylpiperazinyl)indoles have been synthesized and evaluated at h5-HT1D and h5-HT1B receptors. This class of compounds has provided subnanomolar, fully efficacious h5-HT1D agonists with up to 200-fold selectivity for the h5-HT1D receptor over the h5-HT1B receptor. Unlike other h5-HT1D-selective series, several propylpiperazines demonstrate good oral bioavailability. The optimum compound was 1-(3-[5-(1,2, 4-triazol-4-yl)-1H-indol-3-yl]propyl)-4-(2-(3-fluorophenyl)ethyl)p ipe razine (7f) which has excellent selectivity for h5-HT1D receptors over other 5-HT receptor subtypes and good oral bioavailability in three species. Compound 7f has been selected for further investigation as a potential development candidate in the treatment of migraine.

Diminished regional cerebral blood flow response to vibration in patients with blepharospasm

OBJECTIVE

To determine whether patients with blepharospasm have abnormal sensorimotor processing similar to patients with writer's cramp.

BACKGROUND

Blepharospasm is a focal dystonia manifest by involuntary, excessive blinking and squeezing of the eyes. Altered sensorimotor processing may contribute to the development of dystonic movements. Previously the authors demonstrated decreased vibration-induced cortical blood flow responses in hand primary sensorimotor area (PSA) in patients with hand dystonia.

METHODS

In this prospective, case-control study, seven patients with blepharospasm were compared with seven normal subjects. PET measurements of regional blood flow were obtained using bolus administration of H(2)15O at rest or during sequential vibration of either the left or the right hand or side of the mouth.

RESULTS

PSA activation decreased significantly in the patients with blepharospasm both ipsilateral (-68%; p = 0.0004) and contralateral to the side of facial stimulation (-56%; p = 0.0009). Patients had a 31% lower mean contralateral PSA response to hand vibration and a 51% smaller right supplementary motor area response to left-hand vibration than normal subjects, but these differences did not reach statistical significance.

CONCLUSIONS

Patients with blepharospasm have abnormal sensorimotor processing in response to lower face vibration. They may also have abnormal brain responses to stimulation of clinically uninvolved parts of the body, but this requires confirmation.

Functional independence training program: an example of a sub-acute care model for patients following primary joint replacement

The Orthopaedic and Arthritic Hospital is a specialty institution dedicated to the provision of elective reconstructive orthopaedic surgery and rehabilitation to individuals with musculoskeletal disorders. This facility is the largest volume joint replacement centre in Canada, performing over 1,000 hip and knee replacement/revision procedures annually. In 1995, the hospital established a Functional Independence Training (FIT) program--a seven-day reactivation program for patients following primary joint replacement. The program aims to promote early independence, improve functional level and return patients to normal activity as quickly and cost-effectively as possible. The program has received positive patient feedback and has demonstrated the potential to save the health care system approximately $479,655 annually through the reduction of 1,453 acute and rehabilitation hospital inpatient days, based on the hospital's annual primary joint replacement caseload.

4,4-Disubstituted piperidine high-affinity NK1 antagonists: structure-activity relationships and in vivo activity

Previously reported studies from these laboratories described the design of a novel series of high-affinity NK1 antagonists based on the 4,4-disubstituted piperidine ring system. Further structure-activity studies have now established that for high NK1 affinity the benzyl ether side chain must be 3,5-disubstituted and highly lipophilic, the optimal side chain being the 3, 5-bis(trifluoromethyl)benzyl ether, 12 (hNK1 IC50 = 0.95 nM). Additional studies have shown that this class of NK1 antagonist tolerates a wider range of substituents on the piperidine nitrogen, including acyl (38) (hNK1 IC50 = 5.3 nM) and sulfonyl (39) (hNK1 IC50 = 5.7 nM) derivatives. Following preliminary pharmacokinetic analysis, two compounds (32 and 43) were selected for in vivo study in the resiniferotoxin-induced vascular leakage model, both showing excellent profiles (ID50 = 0.22 and 0.28 mg/kg, respectively).

The expression of beta 1 integrins in human coronary artery

The beta 1 integrin adhesion receptors mediate the binding of cells to extracellular matrices, facilitating their growth, migration, and capacity to deposit matrix proteins: important factors in arterial restenosis and atherosclerosis. The expression of integrins in human coronary artery is, however, unexplored. The aim of the current study was, therefore, to define the expression of beta 1 integrins by cultured human coronary artery vascular smooth muscle cells (hCAVSMC) and in normal human coronary artery; confirming whether or not this differs from the repertoire found in other species and human vessels. The expression of beta 1 integrins by hCAVSMC was assessed by immuno-precipitation and the alkaline phosphatase anti-alkaline phosphatase (APAAP) immunochemical technique. In addition, mRNA expression was defined by reverse transcription polymerase chain reaction (RT-PCR). Normal adult human coronary arteries (n = 4) were also stained by the APAAP method. In vitro hCAVSMC express alpha 2 beta 1 (a collagen and occasional laminin receptor) and alpha 5 beta 1 (a fibronectin receptor) with lesser expression of alpha 3 beta 1 (a multifunctional receptor). They do, however, possess mRNA for several other integrins. Cells within the media of human coronary artery wall express alpha 3 beta 1 and alpha 5 beta 1 but not alpha 2 beta 1: instead the alternative collagen/laminin receptor, alpha 1 beta 1, is expressed in vivo. This pattern of expression differs subtly from that described in rats through it closely parallels that found in other human arteries.

Serine derived NK1 antagonists. 1: The effect of modifications to the serine substituents

A series of novel serine derived NK1 antagonists is described. The effect of variations in the N-benzyl, O-benzyl and serine groups are used to define the elements which are necessary for binding.

Serine derived NK1 antagonists. 2: A pharmacophore model for arylsulfonamide binding

Modifications to the spirocyclic aryl sulfonamide portion of serine derived NK1 antagonists allow a partial pharmacophore model to be developed.

Comparing outcomes in renal replacement therapy: how should we correct for case mix?

The need to evaluate the effectiveness of clinical practice to justify expensive therapy in the face of financial constraints in all areas of health care delivery makes it necessary to identify groups of patients who are likely to benefit most from treatment. Various risk stratification methods have been used for analyzing survival probabilities for patients receiving renal replacement therapy. Complicated risk stratification methods produce large numbers of risk groups of small sizes, which makes comparison between individual centers difficult. We compared three simple methods of risk stratification, that divided patients into low-, medium-, and high-risk groups, in a cohort of 1,407 patients who commenced renal replacement therapy in five European countries during a 7-year period. Method 1 considered age (>55 years) and diabetes alone; method 2 used a higher age limit (>70 years) and comorbid illnesses, including those other than diabetes; and method 3 used only the number of comorbidities (none, 1, or > or =2) for stratification. Kaplan-Meier survival curves were constructed for comparison between risk groups and Cox's regression model used to assess strength of relationship with mortality. Although patient survival was significantly different between the low-, medium-, and high-risk groups using all three methods, Cox's regression analysis showed that method 2 provided the greatest discrimination between risk groups. In predicting mortality, method 2 (based on comorbidities and age) showed the highest sensitivity and specificity (84% and 80%, respectively) compared with method 1 (80% and 74%) and method 3 (64% and 82%). Validation of this approach in other populations in a prospective study is required before this method, which takes into account the influences of both age and comorbidity for risk stratification, can be used for comparing survival data and for presenting results of renal replacement therapy.

Increased functional vascular response in the region of a glioma

Functional imaging of a language task using positron emission tomography was performed as part of the preoperative assessment of a patient with a left supplementary motor area (SMA) tumor. Positron emission tomography scans were obtained during language tasks (verb generation and word reading of visually presented nouns) that normally lead to increased blood flow in the SMA relative to a control condition (visual fixation). In the patient, the normal SMA response was an order of magnitude larger in the region of the tumor. Other regions, such as left inferior frontal cortex and right cerebellum, showed equivalent activation in the patient and normal subjects. Histopathologic study revealed an anaplastic astrocytoma. Thus, this exaggerated vascular response to local neuronal activation occurred in the setting of a proliferation of glial cells. This is consistent with models of coupling of regional CBF and neuronal activity that implicate glia as the mediator between neurons and vasculature. The concept that tumoral disruption of normal vascular responses could, in some cases, potentially enhance rather than dampen the response is proposed.

Upregulation and co-localization of connexin43 and cellular adhesion molecules in inflammatory renal disease

Connexin43 (Cx43) is a major component of gap junctions. These are widely distributed in the human kidney and are thought to be involved in the inflammatory response and in the regulation of cell growth. Cellular adhesion molecules (CAMs) are also thought to be important in these processes, where they possibly facilitate gap junction formation. The aims of the current study were to define for the first time the expression of Cx43 in inflammatory glomerulonephritis and to compare the localization of this connexin with that of the intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Human renal biopsies and control sections of normal human kidney were stained using the alkaline phosphatase/anti-alkaline phosphatase immunohistochemical technique, demonstrating that Cx43 was strongly expressed on inflammatory cells, on damaged tubular cells, and on interstitial cells. This pattern of expression was paralleled closely by that of ICAM-1 and, to a lesser extent, by that of VCAM-1. Cx43 is therefore primarily implicated in tubulointerstitial inflammation.

MRI CAN PREVENT UNNECESSARY ARTHROSCOPY

We compared the practice of four orthopaedic consultants as regards the use of MRI and arthroscopy to diagnose problems of the knee. In one year 324 arthroscopies and 66 MR scans were performed for this purpose.

We found that MRI is a reliable and cheaper alternative to ‘diagnostic arthroscopy’. We consider that patients with definite clinical signs merit an early ‘therapeutic arthroscopy’, but that all other knees should be investigated by MRI. This policy spares patients from unnecessary and expensive surgery.

Arthroscopy for diagnostic purposes should be used only with a specific purpose. Modern MRI can and should replace “having a look”.

MRI can prevent unnecessary arthroscopy

We compared the practice of four orthopaedic consultants as regards the use of MRI and arthroscopy to diagnose problems of the knee. In one year 324 arthroscopies and 66 MR scans were performed for this purpose. We found that MRI is a reliable and cheaper alternative to 'diagnostic arthroscopy'. We consider that patients with definite clinical signs merit an early 'therapeutic arthroscopy', but that all other knees should be investigated by MRI. This policy spares patients from unnecessary and expensive surgery. Arthroscopy for diagnostic purposes should be used only with a specific purpose. Modern MRI can and should replace "having a look".