Plasma arginine metabolites in health and chronic kidney disease

BACKGROUND

Elevated plasma asymmetric and symmetric dimethylarginine (ADMA and SDMA) are risk factors for chronic kidney disease (CKD) and cardiovascular disease. Using plasma cystatin C (pCYSC)-based estimated glomerular filtration rate (eGFR) trajectories, we identified a cohort at high risk of poor kidney-related health outcomes amongst members of the Dunedin Multidisciplinary Health and Development Study (DMHDS). We therefore examined associations between methylarginine metabolites and kidney function in this cohort.

METHODS

ADMA, SDMA, L-arginine and L-citrulline were measured in plasma samples from 45-year-olds in the DMHDS cohort by liquid chromatography-tandem mass spectrometry.

RESULTS

In a healthy DMHDS subset (n = 376), mean concentrations were: ADMA (0.40 ± 0.06 µmol/L), SDMA (0.42 ± 0.06 µmol/L), L-arginine (93.5 ± 23.1 µmol/L) and L-citrulline (24.0 ± 5.4 µmol/L). In the total cohort (n = 857), SDMA correlated positively with serum creatinine (Pearson's r = 0.55) and pCYSC (r = 0.55), and negatively with eGFR (r = 0.52). A separate cohort of 38 patients with stage 3-4 CKD (eGFR 15-60 mL/min/1.73 m2) confirmed significantly higher mean ADMA (0.61 ± 0.11 µmol/L), SDMA (0.65 ± 0.25 µmol/L) and L-citrulline (42.7 ± 11.8 µmol/L) concentrations. DMHDS members classified as high-risk of poor kidney health outcomes had significantly higher mean concentrations of all four metabolites compared with individuals not at risk. ADMA and SDMA individually predicted high-risk of poor kidney health outcomes with areas under the ROC curves (AUCs) of 0.83 and 0.84, and together with an AUC of 0.90.

CONCLUSIONS

Plasma methylarginine concentrations facilitate stratification for risk of CKD progression.

Electronic alerts and a care bundle for acute kidney injury-an Australian cohort study

BACKGROUND

Early recognition of hospital-acquired acute kidney injury (AKI) may improve patient management and outcomes.

METHODS

This multicentre study was conducted at three hospitals (H1-intervention; H2 and H3-controls) served by a single laboratory. The intervention bundle [an interruptive automated alerts (aAlerts) showing AKI stage and baseline creatinine in the eMR, a management guide and junior medical staff education] was implemented only at H1. Outcome variables included length-of-stay (LOS), all-cause in-hospital mortality and management quality.

RESULTS

Over 6 months, 639 patients developed AKI (265 at H1 and 374 at controls), with 94.7% in general wards; 537 (84%) patients developed Stage 1, 58 (9%) Stage 2 and 43 (7%) Stage 3 AKI. Median LOS was 9 days (IQR 4-17) and was not different between intervention and controls. However, patients with AKI stage 1 had shorter LOS at H1 [median 8 versus 10 days (P = 0.021)]. Serum creatinine had risen prior to admission in most patients. Documentation of AKI was better in H1 (94.8% versus 83.4%; P = 0.001), with higher rates of nephrology consultation (25% versus 19%; P = 0.04) and cessation of nephrotoxins (25.3 versus 18.8%; P = 0.045). There was no difference in mortality between H1 versus controls (11.7% versus 13.0%; P = 0.71).

CONCLUSIONS

Most hospitalized patients developed Stage 1 AKI and developed AKI in the community and remained outside the intensive care unit (ICU). The AKI eAlert bundle reduced LOS in most patients with AKI and increased AKI documentation, nephrology consultation rate and cessation of nephrotoxic medications.

Cigarette Smoke Exposure Induces Neurocognitive Impairments and Neuropathological Changes in the Hippocampus

Background and Objective

Neurocognitive dysfunction is present in up to ∼61% of people with chronic obstructive pulmonary disease (COPD), with symptoms including learning and memory deficiencies, negatively impacting the quality of life of these individuals. As the mechanisms responsible for neurocognitive deficits in COPD remain unknown, we explored whether chronic cigarette smoke (CS) exposure causes neurocognitive dysfunction in mice and whether this is associated with neuroinflammation and an altered neuropathology.

Methods

Male BALB/c mice were exposed to room air (sham) or CS (9 cigarettes/day, 5 days/week) for 24 weeks. After 23 weeks, mice underwent neurocognitive tests to assess working and spatial memory retention. At 24 weeks, mice were culled and lungs were collected and assessed for hallmark features of COPD. Serum was assessed for systemic inflammation and the hippocampus was collected for neuroinflammatory and structural analysis.

Results

Chronic CS exposure impaired lung function as well as driving pulmonary inflammation, emphysema, and systemic inflammation. CS exposure impaired working memory retention, which was associated with a suppression in hippocampal microglial number, however, these microglia displayed a more activated morphology. CS-exposed mice showed changes in astrocyte density as well as a reduction in synaptophysin and dendritic spines in the hippocampus.

Conclusion

We have developed an experimental model of COPD in mice that recapitulates the hallmark features of the human disease. The altered microglial/astrocytic profiles and alterations in the neuropathology within the hippocampus may explain the neurocognitive dysfunction observed during COPD.

The kinetic estimated glomerular filtration rate ratio predicts acute kidney injury

AIM

Kinetic estimated Glomerular Filtration Rate (KeGFR) approximates GFR under non-steady-state conditions. We investigated whether the ratio of KeGFR difference to baseline eGFR could predict acute kidney injury (AKI) earlier than a creatinine-based algorithm that triggered an AKI electronic Alert (eAlert).

METHODS

This retrospective, single-centre, proof-of-concept cohort study assessed all patients diagnosed with AKI by an automated serum creatinine-based eAlert. The kinetic eGFR, the kinetic eGFR difference from baseline and the ratio of difference to baseline was calculated in subjects with at least two serum creatinine (sCr) measurements within 72 h of AKI.

RESULTS

Patients in the AKI cohort (n = 140) had a significant decline in KeGFR ratio (AKI: 17% IQR 7% to 29%, Non-AKI: 0 IQR -12% to 9%; P-value <.0001). A decrease of the ratio greater than 10% predicted AKI with a sensitivity of 66%, a specificity of 77%, a positive predictive value of 63%, and negative predictive value of 80%. The median lead time between KeGFR ratio decrease and AKI was 24 h (IQR: 19-27 h).

CONCLUSIONS

KeGFR ratio is a cheap, simple method that predicted AKI 24 h before laboratory detection. KeGFR may facilitate triaging patients to increased monitoring or intervention.

Cystatin C kidney functional reserve: a simple method to predict outcome in chronic kidney disease

BACKGROUND

Kidney Functional Reserve (KFR), the only clinical kidney stress test, is not routinely measured because complexity of measurement has limited clinical application. We investigated the utility of plasma cystatin C (CysC) after oral protein loading to determine KFR in stage 3 and 4 CKD.

METHODS

Following a 24 hour low protein diet, KFR was measured after oral protein by hourly plasma CysC and compared with simultaneous creatinine clearance (CrCl) and radionuclide Tc-99m-DTPA (mGFR) measurement in an observational, single-centre cohort study of adults with CKD 3 and CKD 4. Subjects were followed for three years for fast (F) or slow (S) CKD progression, dialysis requirement or death or a combination of major adverse kidney events (MAKE-F or -S).

RESULT

CysC, CrCl and Tc-99m DPTA mGFR measurements of KFR in 19 CKD 3 and 21 CKD 4 patients yielded good agreement. KFR was not correlated with baseline kidney function. Eight CKD 3 (42%) and 11 CKD 4 (52%) subjects reached their lowest serum CysC concentration four hours after protein loading. CysC KFR and baseline serum creatinine (sCr) predicted (death or dialysis) or MAKE-F with respective AUC = 0.73 (95% CI: 0.48 to 0.89) and 0.71 (95% CI: 0.51 to 0.84). Including CysC KFR, age, baseline sCr and nadir CysC predicted a decrease in sCr-eGFR greater than 1.2 mL/min per year (MAKE-S) with AUC = 0.89.

CONCLUSIONS

Serial CysC avoided timed urine collection and radionuclide exposure and yielded equivalent estimates of KFR. Serial CysC may facilitate monitoring of KFR in clinical practice.

Evidence supporting the benefits of marijuana for Crohn's disease and ulcerative colitis is extremely limited: a meta-analysis of the literature

Background

Medical marijuana is increasingly used to control inflammation and pain in inflammatory bowel disease (IBD). We performed a meta-analysis to investigate the effect of marijuana on the clinical response, induction of clinical remission, and maintenance of clinical remission compared to placebo/standard of care.

Methods

We performed a systematic search of PubMed, Embase, and Web of Science in June 2019, for cannabis/marijuana and IBD, Crohn’s disease or ulcerative colitis (UC). The statistical analysis was performed using Revman (version 5.3). GRADE methodology was used to assess the quality of the evidence.

Results

Of the 334 studies initially reviewed, 1 trial in UC and 2 trials in Crohn’s disease met eligibility. For UC, 29 patients were treated with marijuana and 31 with placebo/standard of care. There was no difference in failure to achieve clinical remission (relative risk [RR] 1.02, 95% confidence interval [CI] 0.76-1.37) or response (RR 0.99, 95%CI 0.65-1.21). Adverse events occurred in all patients receiving marijuana (RR 1.28, 95%CI 1.05-1.56). For Crohn’s disease, 21 patients were treated with marijuana and 19 with placebo/standard of care. There was no difference in failure to achieve clinical remission (RR 0.72, 95%CI 0.47-1.12) or failure to achieve clinical response (RR 0.15, 95%CI 0.02-1.05). Adverse events were not reported per patient. The quality of evidence was low to very low using GRADE methodology.

Conclusions

Data supporting the use of marijuana for the management of IBD are extremely limited. Further well-designed studies are needed before any positive conclusions regarding marijuana use can be drawn.

Selection and validation of reference genes for normalisation of gene expression in ischaemic and toxicological studies in kidney disease

Normalisation to standard reference gene(s) is essential for quantitative real-time polymerase chain reaction (RT-qPCR) to obtain reproducible and comparable results of a gene of interest (GOI) between subjects and under varying experimental conditions. There is limited evidence to support selection of the commonly used reference genes in rat ischaemic and toxicological kidney models. Employing these models, we determined the most stable reference genes by comparing 4 standard methods (NormFinder, qBase+, BestKeeper and comparative ΔCq) and developed a new 3-way linear mixed-effects model for evaluation of reference gene stability. This new technique utilises the intra-class correlation coefficient as the stability measure for multiple continuous and categorical covariates when determining the optimum normalisation factor. The model also determines confidence intervals for each candidate normalisation gene to facilitate selection and allow sample size calculation for designing experiments to identify reference genes. Of the 10 candidate reference genes tested, the geometric mean of polyadenylate-binding nuclear protein 1 (PABPN1) and beta-actin (ACTB) was the most stable reference combination. In contrast, commonly used ribosomal 18S and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were the most unstable. We compared the use of PABPN1×ACTB and 2 commonly used genes 18S and GAPDH on the expression of 4 genes of interest know to vary after renal injury and expressed by different kidney cell types (KIM-1, HIF1α, TGFβ1 and PECAM1). The less stable reference genes gave varying patterns of GOI expression in contrast to the use of the least unstable reference PABPN1×ACTB combination; this improved detection of differences in gene expression between experimental groups. Reduced within-group variation of the now more accurately normalised GOI may allow for reduced experimental group size particularly for comparison between various models. This objective selection of stable reference genes increased the reliability of comparisons within and between experimental groups.

Hyponatraemia in heart failure

Hyponatraemia is common in heart failure (HF). It is estimated that over 20% of patients admitted to hospital with HF have hyponatraemia. It has also been repeatedly shown to be a surrogate marker of increased morbidity and mortality in this specific population. This review focuses on the pathophysiology of hyponatraemia through the activation of neurohormonal cascades in HF, the clinical implications of sustained hyponatraemia and treatment options in the management of this challenging phenomenon.

Intranasal and epicutaneous administration of Toll-like receptor 7 (TLR7) agonists provides protection against influenza A virus-induced morbidity in mice

Toll-like receptor 7 (TLR7) is a pattern recognition receptor that recognizes viral RNA following endocytosis of the virus and initiates a powerful immune response characterized by Type I IFN production and pro-inflammatory cytokine production. Despite this immune response, the virus causes very significant pathology, which may be inflammation-dependent. In the present study, we examined the effect of intranasal delivery of the TLR7 agonist, imiquimod or its topical formulation Aldara, on the inflammation and pathogenesis caused by IAV infection. In mice, daily intranasal delivery of imiquimod prevented peak viral replication, bodyweight loss, airway and pulmonary inflammation, and lung neutrophils. Imiquimod treatment also resulted in a significant reduction in pro-inflammatory neutrophil chemotactic cytokines and prevented the increase in viral-induced lung dysfunction. Various antibody isotypes (IgG1, IgG2a, total IgG, IgE and IgM), which were increased in the BALF following influenza A virus infection, were further increased with imiquimod. While epicutaneous application of Aldara had a significant effect on body weight, it did not reduce neutrophil and eosinophil airway infiltration; indicating less effective drug delivery for this formulation. We concluded that intranasal imiquimod facilitates a more effective immune response, which can limit the pathology associated with influenza A virus infection.

Measurement of Tissue Factor Activity in Whole Blood

High circulating levels of the procoagulant molecule tissue factor (TF) are associated with thrombosis in a variety of diseases including unstable angina, cancer, and sepsis. Currently, there are no clinical assays to measure the level of TF activity in whole blood. We present an assay called Tissue Factor Clotting Time (“TiFaCT™”) that detects fibrin formation in human blood. The mean baseline clotting time in a healthy population was 472 ± 94 s (mean ± SD, n = 150). Bacterial lipopolysaccharide (LPS or endotoxin) shortened the clotting time in a time-dependent manner. Inhibitory anti-TF antibodies prolonged the clotting time of LPS-stimulated blood, indicating that the shortened clotting time was due to induction of TF expression. Patients with unstable angina had shortened mean baseline clotting time (284 ± 86, n = 13) compared with healthy volunteers (474 ± 98, n = 30), suggesting that these patients had elevated levels of circulating TF. The TiFaCT assay should prove clinically useful in quantifying the levels of circulating TF in patients at risk of thrombosis.

Role of tissue factor in haemostasis, thrombosis, angiogenesis and inflammation: lessons from low tissue factor mice

Tissue factor (TF) contributes to a variety of biological processes by generating coagulation proteases and by the activation of protease activated receptors (PARs). Studies, using low TF mice, have provided us with novel insights into the role of TF in tissue-specific haemostasis. Low TF mice exhibit defects in the uterus, placenta, heart and lung, which are all tissues that normally express high levels of TF. We propose that these observed defects are primarily due to a reduction in the level of TF to below a critical threshold that is required to maintain adequate haemostasis. Nevertheless, a reduction in TF:FVIIa-dependent signaling may also reduce cell survival and/or compromise the integrity of the vasculature in these organs. Low TF mice are also a useful tool to study the role of TF and the coagulation cascade in other processes, such as thrombosis, inflammation and angiogenesis.

Histologic Normalization Occurs in Ulcerative Colitis and Is Associated With Improved Clinical Outcomes

BACKGROUND & AIMS

Mucosal healing, determined by histologic analysis, is a potential therapeutic target for patients with ulcerative colitis (UC). However, the histologic features of tissue normalization, as an outcome of treatment, have not been well described. We examined the prevalence and predictive values of normalization of the colonic mucosa, based on histologic analysis (histologic normalization) in patients with UC, and determined its association with risk of clinical relapse, compared with histologic disease quiescence and endoscopic mucosal healing.

METHODS

We performed a retrospective study of 646 patients with confirmed UC who underwent colonoscopy at a tertiary medical center from August 2005 through October 2013. We reviewed reports from pathology analyses of random mucosal biopsies from each colon segment, and categorized them into 3 groups based on histology findings: (1) normalization (completely normal mucosa with no features of chronicity present), (2) quiescence (crypt atrophy or branching without signs of active inflammation including erosions, abscesses, or focal neutrophil infiltration), or (3) active disease (epithelial infiltration by neutrophils, crypt abscesses, erosions, or ulceration). Histology findings were compared with clinical and endoscopic findings. We assessed variables associated with histology findings and, in patients in clinical remission (Simple Clinical Colitis Activity Index score ≤2 and subscore of ≤1 for stool frequency or rectal bleeding), predictive values for clinical relapse at follow-up evaluations 6 months later or more were calculated.

RESULTS

Of the 646 patients included in the study, 60% had endoscopic mucosal healing, 40% had histologic quiescence, and 10% had histologic normalization. The level of agreement between mucosal and histologic activity was moderate (agreement for 68% of samples; κ = 0.50; P < .001). On multivariate analysis, only proctitis associated with histologic normalization (P = .002). Of 310 patients in clinical remission at initial review, 25% had a clinical relapse, after a median time of 16 months (interquartile range, 10-23 months). Histologic normalization was independently associated with increased odds of relapse-free survival compared with histologic quiescence (hazard ratio, 4.31; 95% confidence interval, 1.48-12.46; P = .007) and histologic activity (hazard ratio, 6.69; 95% confidence interval, 2.16-20.62; P = .001); mucosal healing was not associated with increased odds of relapse-free survival compared with no mucosal healing (hazard ratio, 1.02; 95% confidence interval, 0.56-1.85; P = .954).

CONCLUSIONS

Histologic normalization of colonic mucosa can be used as a clinical endpoint for patients with UC. We associated histologic normalization with increased odds of relapse-free survival compared with endoscopic healing or histologic quiescence. Further studies are needed to determine whether histologic normalization should be a goal of treatment for patients with UC.

ACEIs for cardiovascular risk reduction--have we taken our eye off the ball?

BACKGROUND

Hypertensive patients have an increased risk of cardiovascular (CV) events. There is debate whether angiotensin converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) offer similar reductions in CV risk.

OBJECTIVE

This article discusses some of the recent evidence for the prevention of CV events and mortality with ACEIs and ARBs, and the rationale for using an ACEI as the preferred agent for comprehensive CV risk reduction in specific patient populations.

DISCUSSION

ACEIs and ARBs are structurally and functionally very different agents; they are not interchangeable. Prescriptions for ARBs are increasing in Australia. However, clinical trial evidence suggests possible advantages of ACEIs over ARBs, particularly in terms of survival benefit. Many patients with hypertension have other CV risk factors that may affect medication choice. The aim of treatment should not be just to lower blood pressure, but to reduce absolute CV risk.

Adjunctive ultrasonography during carotid artery stenting to minimize iodine contrast use

Carotid artery stenting (CAS) in patients with chronic kidney disease carries a significant risk of contrast-induced nephropathy. We report a case of CAS with adjunctive sonography to reduce the amount of contrast medium during angiography. A 71-year-old man presented with a symptomatic right carotid stenosis. He was selected for CAS due to significant medical comorbidity, which included severe renal impairment. A preoperative noncontrast CT was performed to assess anatomical suitability and to plan arch vessel cannulation. We undertook CAS with the use of intraoperative ultrasound. Sonography was used to monitor the manipulation of wires, catheters, and stents. Four milliliters of contrast was required to complete the procedure successfully with no deterioration in postoperative renal function. Adjunctive ultrasound is feasible to reduce contrast use in patients with severe renal impairment undergoing CAS.

Psychosocial risk and protective factors for depression in the dialysis population: a systematic review and meta-regression analysis

OBJECTIVE

Research into the association between psychosocial factors and depression in End-Stage Renal Disease (ESRD) has expanded considerably in recent years identifying a range of factors that may act as important risk and protective factors of depression for this population. The present study provides the first systematic review and meta-analysis of this body of research.

METHODS

Published studies reporting associations between any psychosocial factor and depression were identified and retrieved from Medline, Embase, and PsycINFO, by applying optimised search strategies. Mean effect sizes were calculated for the associations across five psychosocial constructs (social support, personality attributes, cognitive appraisal, coping process, stress/stressor). Multiple hierarchical meta-regression analysis was applied to examine the moderating effects of methodological and substantive factors on the strength of the observed associations.

RESULTS

57 studies covering 58 independent samples with 5956 participants were identified, resulting in 246 effect sizes of the association between a range of psychosocial factors and depression. The overall mean effect size (Pearsons correlation coefficient) of the association between psychosocial factor and depression was 0.36. The effect sizes between the five psychosocial constructs and depression ranged from medium (0.27) to large levels (0.46) with personality attributes (0.46) and cognitive appraisal (0.46) having the largest effect sizes. In the meta-regression analyses, identified demographic (gender, age, location of study) and treatment (type of dialysis) characteristics moderated the strength of the associations with depression.

CONCLUSION

The current analysis documents a moderate to large association between the presence of psychosocial risk factors and depression in ESRD.

Studying psychosocial adaptation to end-stage renal disease: the proximal-distal model of health-related outcomes as a base model

OBJECTIVE

Studying psychosocial adaptation in end-stage renal disease (ESRD) is increasingly important, as it may explain the variability in health outcomes unaccounted for by clinical factors. The Brenner et al. proximal-distal model of health-related outcomes provides a theoretical foundation for understanding psychosocial adaptation and integrating health outcomes, clinical, and psychosocial factors (Brenner MH, Curbow B, Legro MW. The proximal-distal continuum of multiple health outcome measures: the case of cataract surgery. Med Care. 1995;33(4 Suppl):AS236-44). This study aims to empirically validate the proximal-distal model in the dialysis population and examine the impact of psychosocial factors on the model.

METHODS

A cross-sectional observational study was conducted with a sample of long-term dialysis patients (n=201). Eleven factors: quality of life (QoL), depression, positive affect, comorbidity, symptoms, physical functioning, disease accommodation, loss, self-efficacy, illness acceptance, and social support were measured by standardized psychometric scales. A three-month average of hemoglobin was used. Latent composite structural equation modeling was used to examine the models.

RESULTS

The proximal-distal model with slight modification was supported by fit statistics [χ(2)=16.04, df=13, P=.25, root mean square error of approximation (RMSEA)=0.024], indicating that the impact of clinical factors on QoL is mediated through a range of functional and psychological factors, except for hemoglobin which impacts directly on QoL. The model with additional psychosocial factors was also supported by fit statistics (χ(2)=43.59, df=41, P=.36, RMSEA=0.018). These additional factors mainly impact on symptom status, psychological states, and QoL components of the model.

CONCLUSION

The present study supported the proximal-distal model in the dialysis population and demonstrated the considerable impact of psychosocial factors on the model. The proximal-distal model plus psychosocial factors as a biopsychosocial model can be applied to studying psychosocial adaptation in ESRD.

Measuring kidney disease-related loss in samples of predialysis and dialysis patients: validating the kidney disease loss scale

BACKGROUND AND OBJECTIVES

Kidney disease-related loss is clinically significant in patients with ESRD and is related to depression and quality of life. The Kidney Disease Loss Scale (KDLS) was recently developed for long-term dialysis patients as a means of studying loss and applying it to clinical practice; however, its validity and usability in the other developmental stages of ESRD-predialysis and early dialysis-remain unknown. This study examined the validity and reliability of the KDLS in the long-term dialysis, early dialysis, and predialysis populations.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Four groups of participants were recruited from four large university teaching hospitals in the Sydney metropolitan area. Participants were long-term dialysis (n=151), early dialysis (n=163), and predialysis (n=111) patients. An additional independent group of dialysis (n=50) patients were recruited to measure the test-retest reliability. Multisample confirmatory factor analysis and correlational analysis were used.

RESULTS

Results demonstrated good internal consistency and test-retest reliability for KDLS. Multisample confirmatory factor analysis indicated that the factor structure of KDLS was invariant across samples and thus supported its construct validity. The convergent and discriminant validities of KDLS were supported by its correlations with scales that measure health-related quality of life, depression, and positive affect in the expected directions and magnitudes. The KDLS was sensitive to the developmental stages of ESRD.

CONCLUSIONS

These findings demonstrated that the concept of loss exists in dialysis patients. The KDLS is a reliable measure of loss in ESRD and valid in the developmental stages of ESRD.

The effects of kidney-disease-related loss on long-term dialysis patients' depression and quality of life: positive affect as a mediator

BACKGROUND AND OBJECTIVES

In kidney disease, the concept of loss is widely discussed but minimally researched. It appears that dialysis patients who grieve a range of losses suffer increased depression and reduced quality of life (QoL). Limited research is partly due to the lack of a relevant loss measure. The study presented here developed a measure and tested the criterion validity of loss in relation to depression and QoL.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a cross-sectional observational study, 151 long-term dialysis patients were interviewed using standardized psychometric measures and the Kidney Disease Loss Scale (KDLS), developed for the study. Factor, path and multigroup analyses were conducted.

RESULTS

The factor structure and reliability of KDLS were supported. The path analyses supported the criterion validity of loss. It was a stronger contributor to depression than other clinical variables. Its effect on QoL was fully mediated by depression and positive affect (coping). The magnitude of the paths from loss to QoL through depression and positive affect was larger in home-based dialysis patients than in hospital-based patients.

CONCLUSIONS

KDLS is a promising measure of loss. Patient-defined losses may contribute to the high level of depression and in turn a reduction in patients' coping and QoL. These findings suggest several points of intervention to improve long-term dialysis patients' QoL.

The cytoplasmic domain of tissue factor contributes to leukocyte recruitment and death in endotoxemia

Tissue factor (TF) is an integral membrane protein that binds factor VIIa and initiates coagulation. The extracellular domain of TF is responsible for its hemostatic function and by implication in the dysregulation of coagulation, which contributes to death in endotoxemia. The role of the cytoplasmic domain of tissue factor in endotoxemia was studied in mice, which lack the cytoplasmic domain of TF (TF(deltaCT/deltaCT)). These mice develop normally and have normal coagulant function. Following i.p injection with 0.5 mg of lipopolysaccharide (LPS), TF(deltaCT/deltaCT) mice showed significantly greater survival at 24 hours compared to the wt mice (TF(+/+)). The serum levels of TNF-alpha and IL-1beta were significantly lower at 1 hour after LPS injection and IL-6 levels were significantly lower at 24 hours in TF(deltaCT/deltaCT) mice compared to TF(+/+)mice. Neutrophil recruitment into the lung was also significantly reduced in TF(deltaCT/deltaCT) mice. Nuclear extracts from tissues of endotoxemic TF(deltaCT/deltaCT) mice also showed reduced NFkappaB activation. LPS induced leukocyte rolling, adhesion, and transmigration in post-capillary venules assessed by intravital microscopy was also significantly reduced in TF(deltaCT/deltaCT) mice. These results indicate that deletion of the cytoplasmic domain of TF impairs the recruitment and activation of leukocytes and increases survival following endotoxin challenge.

Tissue factor deficiency causes cardiac fibrosis and left ventricular dysfunction

Exposure of blood to tissue factor (TF) activates the extrinsic (TF:FVIIa) and intrinsic (FVIIIa:FIXa) pathways of coagulation. In this study, we found that mice expressing low levels of human TF ( approximately 1% of wild-type levels) in an mTF(-/-) background had significantly shorter lifespans than wild-type mice, in part, because of spontaneous fatal hemorrhages. All low-TF mice exhibited a selective heart defect that consisted of hemosiderin deposition and fibrosis. Direct intracardiac measurement demonstrated a 30% reduction (P < 0.001) in left ventricular function in 8-month-old low-TF mice compared with age-matched wild-type mice. Mice expressing low levels of murine FVII ( approximately 1% of wild-type levels) exhibited a similar pattern of hemosiderin deposition and fibrosis in their hearts. In contrast, FIX(-/-) mice, a model of hemophilia B, had normal hearts. Cardiac fibrosis in low-TF and low-FVII mice appears to be caused by hemorrhage from cardiac vessels due to impaired hemostasis. We propose that TF expression by cardiac myocytes provides a secondary hemostatic barrier to protect the heart from hemorrhage.

Prevalence and genomic variation of Norwalk-like viruses in central Australia in 1995-1997

Norwalk-like viruses (NLVs) have now been found to be important causes of gastroenteritis amongst infants and young children as well as older children and adults. Although detected, such viruses appeared not to be a major cause amongst infants and young children hospitalized with gastroenteritis in Alice Springs, central Australia over the period January 1995-December 1997. Nine NLV-positive cases were identified amongst stools from 360 different patients. From the nine cases however, eight different NLV strains were identified from comparisons of the sequence of a section of the RNA polymerase gene, and a high degree of genomic diversity was evident amongst them. In general, these strains were more similar to those identified in other countries than to those identified in central Australia over the three year period. Of the strains identified, six (and most probably seven) were classified in genogroup I, while only one was classified in genogroup II. This predominance of genogroup I strains is in contrast to most of the more recent findings made elsewhere, including those made in other parts of Australia. Phylogenetic analysis indicated that the central Australian strains spanned a range of known representative NLV strains, with one of the genogroup I strains showing a 96% nucleotide identity to Saratoga virus.

Functional implications of tissue factor localization to cell-cell contacts in myocardium

Recently published studies suggest that the procoagulant receptor protein tissue factor (TF) is involved in vitro in cell adhesion and migration, via an interaction of its cytoplasmic domain with cytoskeletal proteins. Interestingly, TF is abundantly expressed in myocardium, but not in skeletal muscle. To elucidate the possible roles of TF in the myocardium, this study examined the cellular distribution of TF in relation to cytoskeletal proteins, as well as its relative amounts in different segments of premature, mature, and pathologically altered cardiac muscle. In juvenile and adult hearts, TF was predominantly detectable in the transverse part of the intercalated discs, where it co-localized with cytoskeletal proteins such as desmin and vinculin. The lowest amount of TF was observed in right atrial and the highest in left ventricular myocardium, which correlated with the number of contact sites of cardiomyocytes in these segments of the cardiac muscle. Lower levels of TF were present in structurally altered myocardium from patients with hypertension or ventricular hypertrophy. In addition, TF expression was decreased in human heart during sepsis and transiently decreased in rabbit heart in an endotoxaemia model, which indicates that a reduction in TF may contribute to cardiac failure in sepsis. The microtopography of TF at cardiomyocyte contact sites indicates that TF may play a structural role in the maintenance of cardiac muscle.

Quasilocalization of gravity on a brane by resonant modes

We examine the behavior of gravity in brane theories with extra dimensions in a nonfactorizable background geometry. We find that for metrics which are asymptotically flat far from the brane there is a resonant graviton mode at zero energy. The presence of this resonance ensures quasilocalization of gravity, whereby at intermediate scales the gravitational laws on the brane are approximately four dimensional. However, for scales larger than the lifetime of the graviton resonance the five-dimensional laws of gravity will be reproduced due to the decay of the four-dimensional graviton. We also give a simple classification of effective gravity theories for general background geometries.

Measurement of tissue factor activity in whole blood

High circulating levels of the procoagulant molecule tissue factor (TF) are associated with thrombosis in a variety of diseases including unstable angina, cancer, and sepsis. Currently, there are no clinical assays to measure the level of TF activity in whole blood. We present an assay called Tissue Factor Clotting Time ("TiFaCT") that detects fibrin formation in human blood. The mean baseline clotting time in a healthy population was 472 +/- 94 s (mean +/- SD, n = 150). Bacterial lipopolysaccharide (LPS or endotoxin) shortened the clotting time in a time-dependent manner. Inhibitory anti-TF antibodies prolonged the clotting time of LPS-stimulated blood, indicating that the shortened clotting time was due to induction of TF expression. Patients with unstable angina had shortened mean baseline clotting time (284 +/- 86, n = 13) compared with healthy volunteers (474 +/- 98, n = 30), suggesting that these patients had elevated levels of circulating TF. The TiFaCT assay should prove clinically useful in quantifying the levels of circulating TF in patients at risk of thrombosis.

Etiology of acute lower respiratory tract infection in Central Australian Aboriginal children

BACKGROUND

Aboriginal children in central Australia have attack rates for acute lower respiratory tract infection (ALRI) that are similar to those in developing countries. Although mortality rates are much lower than in developing countries, morbidity is high and ALRI is still the leading cause of hospitalization. However, there are no data on the etiology of ALRI in this population.

METHODS

We prospectively studied 322 cases of ALRI in 280 Aboriginal children admitted to the hospital. Blood, urine and nasopharyngeal aspirate samples were examined for evidence of bacterial, viral and chlamydial infection.

RESULTS

The combination of blood culture, viral studies and chlamydial serology provided at least 1 etiologic agent in 170 of 322 (52.5%) cases. Assays for pneumolysin immune complex and pneumolysin antibody increased etiologic diagnosis to 219 (68.0%). Blood cultures were positive in 6% but pneumolysin immune complex and pneumolysin antibody studies were positive in one-third of cases. Evidence of viral infection was present in 155 (48%) of cases compared with 12% in controls (P < 001). There were only 7 possible cases and 2 definite cases of Chlamydia trachomatis and 3 cases of Chlamydia pneumoniae. Coinfection was common in these children.

CONCLUSION

These findings have implications for both standard treatment protocols and vaccine strategies. The high rate of coinfection may make it difficult to develop simple clinical predictors of bacterial infection. In the setting of a developed country with efficient patient evacuation services, management algorithms that focus on disease severity and need for hospital referral will be most useful to health staff in remote communities. Pneumococcal conjugate vaccines will be required to reduce the high attack rate of pneumococcal disease.

Tissue factor is required for uterine hemostasis and maintenance of the placental labyrinth during gestation

We employed a novel mouse line that expresses low levels of human tissue factor (TF) in the absence of murine TF to analyze the role of TF in gestation. Low-TF female mice had a 14-18% incidence of fatal postpartum uterine hemorrhage, suggesting that TF plays an important role in uterine hemostasis. Low-TF female mice mated with low-TF male mice had a 42% incidence of fatal midgestational hemorrhage (n = 41), whereas no fatal midgestational hemorrhages were observed in low-TF female mice mated with wild-type male mice (n = 43). Placentas of low-TF embryos from both low-TF and normal (+/-) TF females were abnormal and contained numerous maternal blood pools in the labyrinth. Placentas of TF null embryos surviving beyond embryonic day 10.5 exhibited similar defects. The mouse maternal-embryonic placental barrier consists of four cellular layers (layers I, II, and III and endothelial cells), where layer I lines the maternal lacunae. Comparison of TF-deficient placentas with control placentas by immunohistochemical and ultrastructural analyses revealed thinning of layer I and a reduction in the number of cellular contacts of layer I trophoblasts spanning the maternal blood space between adjacent trabeculae. These structural changes in low-TF and TF null placentas result in enlarged maternal lacunae, as determined by morphometric analysis, and placental hemorrhage, which leads to midgestational death of low-TF female mice. This study demonstrated that TF is required for uterine hemostasis and revealed an unexpected role of TF in the maintenance of the placental labyrinth.

Lipopolysaccharide induction of tissue factor expression in rabbits

Tissue factor (TF) is the major activator of the coagulation protease cascade and contributes to lethality in sepsis. Despite several studies analyzing TF expression in animal models of endotoxemia, there remains debate about the cell types that are induced to express TF in different tissues. In this study, we performed a detailed analysis of the induction of TF mRNA and protein expression in two rabbit models of endotoxemia to better understand the cell types that may contribute to local fibrin deposition and disseminated intravascular coagulation. Northern blot analysis demonstrated that lipopolysaccharide (LPS) increased TF expression in the brain, lung, and kidney. In situ hybridization showed that TF mRNA expression was increased in cells identified morphologically as epithelial cells in the lung and as astrocytes in the brain. In the kidney, in situ hybridization experiments and immunohistochemical analysis showed that TF mRNA and protein expression was increased in renal glomeruli and induced in tubular epithelium. Dual staining for TF and vWF failed to demonstrate TF expression in endothelial cells in LPS-treated animals. These results demonstrate that TF expression is induced in many different cell types in LPS-treated rabbits, which may contribute to local fibrin deposition and tissue injury during endotoxemia.

Low activity of key phospholipid catabolic and anabolic enzymes in human substantia nigra: possible implications for Parkinson's disease

To determine whether increased oxidative stress in substantia nigra of patients with idiopathic Parkinson's disease might be related to decreased ability of nigral cells to detoxify oxidized membrane phospholipids, we compared levels of the major phospholipid metabolizing enzymes in autopsied substantia nigra with those in non-nigral (n = 11) brain areas of the normal human brain. Whereas most enzymes possessed a relatively homogeneous distribution, the activity of the major phospholipid catabolizing enzyme phospholipase A2, assayed in the presence of calcium ions, varied amongst different regions, with substantia nigra possessing the lowest activity. Similarly, calcium-independent phospholipase A2 activity, although possessing a relatively homogeneous regional distribution, was also low in the substantia nigra. This, coupled with low activity of phosphoethanolamine- and phosphocholine-cytidylyltransferases, major regulatory enzymes of phospholipid synthesis, in this brain region, suggest that the rate of phospholipid turnover is low in the substantia nigra. Low activity of key phospholipid catabolic and anabolic enzymes in human substantia nigra might result in reduced ability to repair oxidative membrane damage, as may occur in Parkinson's disease.

Phospholipid-metabolizing enzymes in Alzheimer's disease: increased lysophospholipid acyltransferase activity and decreased phospholipase A2 activity

Damage to brain membrane phospholipids may play an important role in the pathogenesis of Alzheimer's disease (AD); however, the critical metabolic processes responsible for the generation and repair of membrane phospholipids affected by the disease are unknown. We measured the activity of key phospholipid catabolic and anabolic enzymes in morphologically affected and spared areas of autopsied brain of patients with AD and in matched control subjects. The activity of the major catabolic enzyme phospholipase A2 (PLA2), measured in both the presence and absence of Ca2+, was significantly decreased (-35 to -53%) in parietal and temporal cortices of patients with AD. In contrast, the activities of lysophospholipid acyltransferase, which recycles lysophospholipids into intact phospholipids, and glycerophosphocholine phosphodiesterase, which returns phospholipid catabolites to be used in phospholipid resynthesis, were increased by approximately 50-70% in the same brain areas. Brain activities of enzymes involved in de novo phospholipid synthesis (ethanolamine kinase, choline kinase, choline phosphotransferase, phosphoethanolamine cytidylyltransferase, and phosphocholine cytidylyltransferase) were either normal or only slightly altered. The activities of PLA2 and acyltransferase were normal in the degenerating cerebellum of patients with spinocerebellar atrophy type 1, whereas the activity of glycerophosphocholine phosphodiesterase was reduced, suggesting that the alterations in AD brain were not nonspecific consequences of neurodegeneration. Our data suggest that compensatory phospholipid metabolic changes are present in AD brain that reduce the rate of phospholipid loss via both decreased catabolism (PLA2) and increased phospholipid resynthesis (acyltransferase and glycerophosphocholine phosphodiesterase).

Increased phospholipid breakdown in schizophrenia. Evidence for the involvement of a calcium-independent phospholipase A2

BACKGROUND

Magnetic resonance spectroscopy studies have suggested above-normal turnover of membrane phospholipids in brains of patients with schizophrenia. One possible explanation for these findings is increased activity of the phospholipid-catabolizing enzyme phospholipase A2 (PLA2). However, attempts to demonstrate higher PLA2 activity in the serum of subjects with schizophrenia have led to conflicting results. We hypothesized that this was due to serum PLA2 activity consisting of a family of different enzymes, with each group of investigators measuring activity of different PLA2 forms.

DESIGN

Activity of PLA2 in serum samples obtained from 24 individuals with schizophrenia was compared with serum obtained from 33 age- and sex-matched control subjects, using both fluorometric and radiometric assays with different substrates. Each method had previously yielded conflicting results concerning the status of the enzyme in schizophrenia.

RESULTS

With the fluorometric assay, serum PLA2 activity in individuals with schizophrenia was markedly increased by 49% compared with control subjects (P < .001). In contrast, radiometric assay of the same serum samples resulted in PLA2 activity not significantly different between patients and control subjects. Further investigations demonstrated that, whereas the radiometric assay measured activity of a calcium-dependent enzyme, the fluorometric assay detected a calcium-insensitive enzyme possessing an acid-neutral pH optimum.

CONCLUSIONS

Increased calcium-independent PLA2 activity was seen in the serum of patients with schizophrenia. This change, if present also in the brain, may well explain the increased levels of phosphodiesters observed using magnetic resonance spectroscopy and therefore may contribute to the pathophysiological features of the disorder.

Distribution of capsular types and antibiotic susceptibility of invasive Streptococcus pneumoniae isolated from aborigines in central Australia

Streptococcus pneumoniae strains isolated from 203 episodes of invasive disease in central Australian Aborigines were studied. Capsular types from children aged 0 to 4 years (n = 89) belonged most commonly to types 14, 6B, 9V, 4, 18C, and 19F, which together accounted for 67% of the pediatric strains. In adults (n = 98), types 1, 7F, 3, 4, 12F, and 8 contributed 68% of the isolates. Of 114 pneumococci from patients 5 years and older, 102 (89.5%) were types represented in the 23-valent pneumococcal polysaccharide vaccine. The MICs of five antibiotics were determined for 201 strains by using the E-Test (AB Biodisk). No chloramphenicol or ceftriaxone resistance was found, but 46 strains (22.9%) showed diminished susceptibility to one or more of the drugs penicillin, erythromycin, and trimethoprim-sulfamethoxazole. Penicillin resistance occurred in 15.4% of all isolates tested but only within the intermediate range (0.1 to 1.0 microgram/ml). Resistance to trimethoprimsulfamethoxazole affected 13.9% of the pneumococci tested. All type 23F and most type 19F organisms were resistant to one or more antibiotics. Resistance was significantly more common in pediatric isolates than in those from adults (chi 2(1) = 14.1; P < 0.001).

Invasive pneumococcal disease in central Australia

OBJECTIVES

To document the incidence, case fatality, clinical and demographic features of invasive pneumococcal disease in central Australia.

DESIGN

Invasive isolates from the regional central laboratory were prospectively recorded over five years and case notes retrospectively reviewed. Population denominators were calculated from national Census data from 1986 and 1991.

RESULTS

The population estimates for the region were 14,568 for Aboriginals and 28,680 for non-Aboriginals. There were 185 episodes of invasive pneumococcal disease over the five years, 162 (87.5%) in Aboriginals and 23 (12.5%), in non-Aboriginals. The incidence in Aboriginal children under two years of age was 2052.7 per 100,000 and for those 20-59 years was 178.2 per 100,000. The relative risk in Aboriginals compared with non-Aboriginals was 10.8 (95% CI, 5.6-20.7; P < 0.0001) for those aged 0-4 years and 20.4 (95% CI, 9.7-42.5; P < 0.0001) for those 15-59 years. Forty-one Aboriginal adults aged over 14 (62%) had at least one conventional risk factor for pneumococcal disease; alcohol abuse was present in 27 (41%). There were 13 Aboriginal deaths and the case fatality rose from 2% in those under four years to 40% for those over 59 years.

CONCLUSIONS

Central Australian Aboriginals have the highest incidence of invasive pneumococcal disease reported. The rate for children under two years is 59 to 80 times the rates for children in the United States and Sweden. These data have implications for improving vaccine use, health service delivery and environmental health in Aboriginal communities.

Upper airway carriage by Haemophilus influenzae and Streptococcus pneumoniae in Australian aboriginal children hospitalised with acute lower respiratory infection

When nasopharyngeal secretions from 171 Australian Aboriginal children hospitalized with acute lower respiratory tract infections (ALRI) were cultured selectively for Streptococcus pneumoniae and Haemophilus influenzae, 136 (79.5%) and 151 (88.3%) children yielded 166 and 254 isolates of S. pneumoniae and H. influenzae, respectively. In colonized subjects multiple populations of S. pneumoniae (20% of carriage-positive patients) and H. influenzae (55%) were common. Pneumococci belonging to 27 types or groups were identified. H. influenzae serotype b colonized 16.4% of all children studied. More than one half of 152 children tested were excreting antibiotics at the time of admission to hospital. Significantly fewer children with serum antibiotic residues were colonized with S. pneumoniae than were antibiotic free children. Antibiotic usage had no measurable impact on the isolation rate of H. influenzae.

Glomerular fibrinolytic activity in anti-GBM glomerulonephritis in rabbits

Fibrin is an important mediator of injury in severe proliferative forms of glomerulonephritis (GN). Normal glomeruli express fibrinolytic activity, which may protect against the injurious effects of fibrin deposition. Changes in glomerular fibrinolytic activity (GFA) may play an important role in modulating fibrin accumulation in GN. To study the changes in GFA associated with fibrin deposition in GN, autologous phase anti-glomerular basement antibody initiated GN (anti-GBM GN) was studied in rabbits. Net GFA was significantly reduced in association with glomerular fibrin deposition (1.3 +/- 0.8 ng fibrin lysed/10(3) glomeruli/2 hr, normal 57.1 +/- 25.4 ng fibrin lysed/10(3) glomeruli/2 hr, P < 0.02). Reduced GFA in fibrin associated GN was associated with decreased expression of tissue type plasminogen activator (tPA) and increased expression of plasminogen activator inhibitor type-1 (PAI-1) and glomerular macrophage infiltration. In a fibrin independent model of anti-GBM induced GN (heterologous phase), with equivalent injury (proteinuria), net GFA was increased (174 +/- 64 ng fibrin lysed/10(3) glomeruli/2 hr). This was associated with increased tPA and uPA, and decreased PAI-1 in the absence of significant macrophage infiltration. These studies demonstrate that fibrin deposition in GN is associated with a net reduction of GFA, attributable to reduced expression of plasminogen activators and augmentation of PAI-1. Reduction of GFA may potentiate glomerular fibrin deposition and consequent glomerular injury. The association between glomerular macrophage influx and reduction in GFA suggests that this change may be directed by macrophages.

An outbreak of serotype 1 Streptococcus pneumoniae infection in central Australia

An outbreak of serotype 1 Streptococcus pneumoniae infection involving both adults and children occurred in central Australia during the winter months of 1991. Eighteen patients, mainly Aboriginal men, presented with culture-positive serotype 1 bacteraemic pneumonia. In this group, 11 of 12 adults for whom medical records were available were alcohol dependent. Thirteen children who were separately studied were hospitalised with acute lower respiratory tract infection: none had bacteraemia but all had upper airway colonisation by type 1 pneumococci. Antibiotics taken by 8 of the 13 children before admission to hospital may have compromised the isolation of type 1 pneumococci from blood cultures. Since the availability of antibiotics, epidemic pneumococcal infection is infrequent and has not been reported in Australia. In three outbreaks of type 1 disease recorded elsewhere crowding and alcoholism were identified as contributory factors. In the 16 month period before this outbreak none of 162 strains of pneumococci isolated from blood (32 strains) and nasopharyngeal secretions (130 strains) from Aborigines with acute lower respiratory tract infection and meningitis in the Alice Springs region were serotype 1 organisms.

Exocrine pancreatic dysfunction in malnourished Australian aboriginal children

Pancreatic exocrine dysfunction has been frequently recorded in protein-energy malnutrition in underdeveloped countries. In addition, the pancreas requires optimal nutrition for enzyme synthesis and potentially correctable pancreatic enzyme insufficiency may play a role in the continuation of protein-energy malnutrition. This problem has not been previously evaluated in Australian Aborigines. We have applied a screening test for pancreatic dysfunction (human immunoreactive trypsinogen [IRT] assay) to the study of 398 infants (6-36 months) admitted to the Alice Springs Hospital over a 20-month period. All infants were assessed by anthropometric measures and were assigned to three nutritional groups (normal, moderate or severely malnourished) and two growth groups (stunted or not stunted). Of the 198 infants who had at least a single serum cationic trypsinogen measurement taken, normal values for serum IRT (with confidence limits) were obtained from 57 children, who were normally nourished. IRT levels were significantly correlated with the degree of underweight but there was no correlation with the degree of stunting or age. Mean IRT levels for the moderate and severely underweight groups were significantly greater than the mean for the normal group (P less than 0.01). Seventeen children (8.6%) had trypsinogen levels in excess of the 95th percentile for the normally nourished group, reflecting acinar cell damage or ductal obstruction. We conclude that pancreatic dysfunction may be a common and important overlooked factor contributing to ongoing malnutrition and disease in malnourished Australian Aboriginal children.

Molecular epidemiology of Shigella infection in Central Australia

Shigellosis is endemic in Central Australia and the infections are predominantly due to Shigella flexneri 6, Shigella flexneri 2a and Shigella sonnei. Plasmid profiles of isolates collected from 1985-9, suggested that infections caused by Shigella flexneri 6 were predominantly due to a single clone, whereas those caused by Shigella flexneri 2a and Shigella sonnei were due to several genetically diverse strains, although strains with identical plasmid profiles were found in widely separated geographical areas and in different years.

Enterotoxigenic Escherichia coli in Central Australia: diagnosis using cloned and synthetic nucleic acid probes

Feces from 169 children admitted with diarrhea to Alice Springs Hospital, were screened for enterotoxigenic E. coli (ETEC) using specific DNA probes. E. coli which hybridized with probes for ST-P, ST-H and LT were confirmed by bioassay for toxin production. Fifty children were shown to excrete ETEC. The probes for LT correlated well with bioassay; however, probes for ST-H and ST-P hybridized with more E. coli than were shown to produce toxin by bioassay. When probing for ST was repeated using a synthetic oligonucleotide probe, only those specimens which were bioassay-positive hybridized with the probe.