Comparing binary efficacy outcomes for systemic immunomodulatory treatments for atopic dermatitis in a living systematic review and network meta-analysis

BACKGROUND

Systemic treatments for atopic dermatitis (AD) are evaluated primarily in placebo-controlled trials with binary efficacy outcomes. In a living systematic review and network meta-analysis (NMA), we previously analysed continuous efficacy measures.

OBJECTIVES

To compare binary efficacy outcomes of systemic treatments for AD.

METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Latin American and Caribbean Health Science Information (LILACS) database, Global Resource for Eczema Trials (GREAT) database and trial registries up to 1 March 2023. We included randomized trials examining ≥ 8 weeks of treatment with systemic immunomodulatory medications for moderate-to-severe AD. We screened titles, abstracts and full texts and abstracted data independently, in duplicate. Outcomes included the proportion of patients achieving at least 50%, 75% and 90% improvements in Eczema Area and Severity Index (EASI 50, EASI 75 and EASI 90, respectively) and Investigator Global Assessment (IGA) success. We performed random-effects Bayesian NMAs to calculate odds ratios (OR) and 95% credible intervals (CrIs) between each intervention for each outcome.

RESULTS

Eighty-three trials with 22 122 participants were included in the systematic review. In analyses limited to trials of 8-16 weeks' duration with predominantly adult populations, abrocitinib 200 mg daily (OR 1.5, 95% CrI 1.1-2.2) and upadacitinib 15 mg daily (OR 1.7, 95% CrI 0.9-3.3) and 30 mg daily (OR 2.5, 95% CrI 1.3-5.0) were associated with higher odds of achieving EASI 50 vs. dupilumab. Abrocitinib 100 mg daily (OR 0.7, 95% CrI 0.5-1.0), baricitinib 2 mg daily (OR 0.4, 95% CrI 0.3-0.5) and 4 mg daily (OR 0.5, 95% CrI 0.3-0.7), and tralokinumab (OR 0.4, 95% CrI 0.3-0.6) were associated with lower odds of achieving EASI 50 vs. dupilumab. Results were similar for EASI 75, EASI 90 and IGA success.

CONCLUSIONS

Supporting results for continuous outcome measures, upadacitinib 30 mg daily and abrocitinib 200 mg daily are the most efficacious with regard to binary efficacy endpoints up to 16 weeks in adults with moderate-to-severe AD, followed by upadacitinib 15 mg daily, dupilumab and abrocitinib 100 mg daily. Dupilumab and both doses of upadacitinib and abrocitinib are more efficacious than baricitinib 4 and 2 mg daily and tralokinumab.

Cost-effectiveness of ropeginterferon alfa-2b-njft for the treatment of polycythemia vera

Aim: Patients with polycythemia vera (PV), a rare and chronic blood cancer, are at a higher risk for thromboembolic events, progression to myelofibrosis, and leukemic transformation. In 2021, ropeginterferon alfa-2b-njft (BESREMi®) was approved in the US to treat adults with PV. The purpose of this study is to estimate the cost-effectiveness of ropeginterferon alfa-2b-njft, used as a first- or second-line treatment, for the treatment of patients with PV in the US. Materials & methods: A Markov cohort model was developed from the healthcare system perspective in the United States. Model inputs were informed by the PROUD-PV and CONTINUATION-PV studies and published literature. The model population included both low-risk and high-risk patients with PV. The model compared ropeginterferon alfa-2b-njft used either as first- or second-line versus an alternative treatment pathway of first-line hydroxyurea followed by ruxolitinib. Results: Over the modeled lifetime, ropeginterferon alfa-2b-njft provided an additional 0.4 higher quality-adjusted life years (QALYs) and 0.4 life-years with an added cost of USD60,175, resulting in a cost per QALY of USD141,783. The model was sensitive to treatment costs, the percentage of patients who discontinue hydroxyurea, the percentage of ropeginterferon alfa-2b-njft users who switch to monthly dosing, the percentage of ropeginterferon alfa-2b-njft users as 2nd line treatment, and the treatment response rates. A younger patient age at baseline and a higher percentage of patients with low-risk disease improved the cost-effectiveness of ropeginterferon alfa-2b-njft. Conclusion: Ropeginterferon alfa-2b-njft is a cost-effective treatment option for a broad range of patients with PV, including both low- and high-risk patients and patients with and without prior cytoreductive treatment with hydroxyurea.

Systemic Immunomodulatory Treatments for Atopic Dermatitis: Update of a Living Systematic Review and Network Meta-analysis

Question

What is the association of systemic treatments for atopic dermatitis with Eczema Area and Severity Index (EASI) scores?

Findings

This systematic review with meta-analysis found that compared with dupilumab, abrocitinib, 200 mg daily, and upadacitinib, 30 mg daily, were associated with reductions in EASI scores; upadacitinib, 15 mg daily, was associated with similar reductions, and tralokinumab, 300 mg every other week, and baricitinib, 2 and 4 mg daily, were associated with fewer reductions.

Meaning

Compared with dupilumab, different doses of abrocitinib, baricitinib, tralokinumab, and upadacitinib were associated with reductions in EASI scores for patients with atopic dermatitis; the relative effect estimates reported herein may help clinicians and patients make informed treatment choices.

Importance

Systemic treatments for atopic dermatitis are being evaluated primarily in placebo-controlled trials; network meta-analysis can provide relative efficacy and safety estimates for treatments that have not been compared head to head.

Objective

To compare reported measures of efficacy and assessments of safety in clinical trials of systemic treatments for atopic dermatitis in a living systematic review and network meta-analysis.

Data Sources

The Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Latin American and Caribbean Health Science Information database, Global Resource of EczemA Trials database, and trial registries were searched through June 15, 2021.

Study Selection

Randomized clinical trials examining 8 or more weeks of treatment with systemic immunomodulatory medications for moderate-to-severe atopic dermatitis were included after screening titles, abstracts, and papers in duplicate.

Data Extraction and Synthesis

Data were abstracted in duplicate. Bayesian network meta-analyses and assessed Grading of Recommendations Assessment, Development and Evaluation certainty of evidence were performed. The updated analysis was completed from June to December 2021.

Main Outcomes and Measures

Outcomes include change in Eczema Area and Severity Index (EASI), Patient Oriented Eczema Measure (POEM), Dermatology Life Quality Index (DLQI), and Peak Pruritus Numeric Rating Scales (PP-NRS).

Results

Since October 2019, 21 new studies were added, for a total of 60 trials with 16 579 patients. Up to 16 weeks of treatment in adults, abrocitinib, 200 mg daily (mean difference [MD], 2.2; 95% credible interval [CrI], 0.2-4.0; high certainty) and upadacitinib, 30 mg daily (MD, 2.7; 95% CrI, 0.6-4.7; high certainty) were associated with reduced EASI slightly more than dupilumab, 600 mg then 300 mg every 2 weeks. Abrocitinib, 100 mg daily (MD, −2.1; 95% CrI, −4.1 to −0.3; high certainty), baricitinib, 4 mg daily (MD, −3.2; 95% CrI, −5.7 to −0.8; high certainty), baricitinib, 2 mg daily (MD, −5.2; 95% CrI, −7.5 to −2.9; high certainty) and tralokinumab, 600 mg then 300 mg every 2 weeks (MD, −3.5; 95% CrI, −5.8 to −1.3; high certainty) were associated with reduced EASI slightly less than dupilumab. There was little or no difference between upadacitinib, 15 mg daily, and dupilumab (MD, 0.2; 95% CrI, −1.9 to 2.2; high certainty). The pattern of results was similar for POEM, DLQI, and PP-NRS.

Conclusions and Relevance

In this systematic review and meta-analysis, abrocitinib, 200 mg; and upadacitinib, 30 mg daily, were associated with slightly better scores than dupilumab, and upadacitinib, 15 mg daily, was associated with similar scores to dupilumab. Abrocitinib, 100 mg daily, baricitinib, 4 mg and 2 mg daily, and tralokinumab, 300 mg, every 2 weeks were associated with slightly worse scores.

Estimating the prevalence of Niemann-Pick disease type C (NPC) in the United States

BACKGROUND

Niemann-Pick Disease Type C (NPC) is an ultra-rare progressive neurodegenerative disease caused by autosomal recessive mutations in the NPC1 or NPC2 genes that lead to premature death, with most individuals dying between 10 and 25 years of age. NPC can present at any age and many individuals with NPC may be misdiagnosed or undiagnosed. A key challenge with recognizing NPC is the heterogeneous and nonspecific clinical presentation. Currently, there are no approved treatments for NPC in the United States; miglustat, an FDA-approved treatment for Gaucher disease, is used off-label for NPC and GM1 gangliosidosis.

OBJECTIVES

To estimate the number of people in the United States that 1) have an NPC diagnosis 2) have an NPC diagnosis and/or are treated off-label with miglustat for NPC and 3) are likely to have NPC.

METHODS

For the first two objectives, patients were identified using the Symphony Integrated DataVerse database (Oct 2015-Jan 2020). To identify the number of people with NPC for Objective 1, cases of NPC were defined as any patients with an ICD-10 code of E75.242 (NPC) during the study period. Objective 2 expands upon Objective 1, including (a) patients from Objective 1 and (b) patients with documented miglustat use (NDC 43975-0310 or 10,148-0201) who did not have any claim with Gaucher disease (ICD-10 E75.22) or GM1 gangliosidosis (ICD-10 E75.1) during the study period. For the third objective, published NPC incidence (1 per 89,000 live births) and expected mortality estimates were applied to the 2018 United States birth rate (11.6 per 1000) and population size (326.7 million).

RESULTS

A total of 308 million unique individuals were represented in the database. Of these, 294 individuals had an NPC diagnosis, yielding an identified NPC prevalence of 0.95 per million people in the United States. 305 individuals were diagnosed with NPC and/or were treated with miglustat without having a diagnosis for either Gaucher or GM1 gangliosidosis, yielding an NPC diagnosed or treated prevalence of 0.99 per million people in the United States. Based on the published literature, there are an estimated 42 new NPC cases per year. Applying this number to the distribution of NPC type (based on age of neurologic symptom onset) and corresponding mortality estimates generates an estimated 943 prevalent cases of NPC, or 2.9 cases of NPC per million people in the United States.

CONCLUSIONS

NPC is an ultra-rare, progressive neurodegenerative disease with approximately 1 per million people in the United States diagnosed with or treated off-label for NPC. Given that NPC is often misdiagnosed or undiagnosed, the estimated prevalence from the epidemiology calculations (2.9 per million) approximates the number of NPC cases if disease awareness, screening and diagnosis efforts were enhanced.

Active learning for efficiently training emulators of computationally expensive mathematical models

An emulator is a fast-to-evaluate statistical approximation of a detailed mathematical model (simulator). When used in lieu of simulators, emulators can expedite tasks that require many repeated evaluations, such as sensitivity analyses, policy optimization, model calibration, and value-of-information analyses. Emulators are developed using the output of simulators at specific input values (design points). Developing an emulator that closely approximates the simulator can require many design points, which becomes computationally expensive. We describe a self-terminating active learning algorithm to efficiently develop emulators tailored to a specific emulation task, and compare it with algorithms that optimize geometric criteria (random latin hypercube sampling and maximum projection designs) and other active learning algorithms (treed Gaussian Processes that optimize typical active learning criteria). We compared the algorithms' root mean square error (RMSE) and maximum absolute deviation from the simulator (MAX) for seven benchmark functions and in a prostate cancer screening model. In the empirical analyses, in simulators with greatly varying smoothness over the input domain, active learning algorithms resulted in emulators with smaller RMSE and MAX for the same number of design points. In all other cases, all algorithms performed comparably. The proposed algorithm attained satisfactory performance in all analyses, had smaller variability than the treed Gaussian Processes, and, on average, had similar or better performance as the treed Gaussian Processes in six out of seven benchmark functions and in the prostate cancer model.

Cost effectiveness of nusinersen for patients with infantile-onset spinal muscular atrophy in US

Background

Patients with infantile-onset spinal muscular atrophy (SMA), a rare, genetic neuromuscular disease, do not achieve key motor function milestones (e.g., sitting) and have short life expectancy in the absence of treatment. Nusinersen is a disease-modifying therapy for patients with SMA.

Objective

The aim of this study was to estimate the cost-effectiveness of nusinersen compared to best supportive care (BSC) in patients diagnosed with infantile-onset SMA in the US.

Methods

A de novo economic model was developed with the following health states: “permanent ventilation”, “not sitting”, “sitting”, “walking”, and “death”. Short-term data were sourced from the pivotal clinical trials and studies of nusinersen (ENDEAR and SHINE). Motor function milestones achieved at the end of follow-up in the clinical trials were assumed to be sustained until death. Mortality risks were based on survival modelling of relevant published Kaplan–Meier data. Costs, life years (LYs), and quality-adjusted life years (QALYs) were discounted at 3% per annum, and the analyses were performed from a US health care sector perspective. Scenario analyses and sensitivity analyses were conducted to assess the robustness of the results to key parameters.

Results

In our base-case analysis, nusinersen treatment achieves greater QALYs and more LYs (3.24 and 7.64, respectively) compared with BSC (0.46 QALYs and 2.40 LYs, respectively), resulting in an incremental cost per QALY gained of approximately $1,112,000 and an incremental cost per LY gained of $590,000 for nusinersen compared to BSC. The incremental cost effectiveness ratios did not fall below $990,000 per QALY gained in scenario and sensitivity analyses. Results were most sensitive to the length of survival, background health care costs, and utility in the “not sitting” and “sitting” health states.

Conclusions

The estimated incremental cost-effectiveness of nusinersen from a US health care sector perspective exceeded traditional cost-effectiveness thresholds. Cost-effectiveness was dependent on assumptions made regarding survival, costs, utilities, and whether the motor function milestones were sustained over lifetime. Given the relatively short-term effectiveness data available for the treatment, a registry to collect long-term data of infantile-onset SMA patients is recommended.

Systemic Immunomodulatory Treatments for Patients With Atopic Dermatitis: A Systematic Review and Network Meta-analysis

Importance

Most clinical trials assessing systemic immunomodulatory treatments for patients with atopic dermatitis are placebo-controlled.

Objective

To compare the effectiveness and safety of systemic immunomodulatory treatments for patients with atopic dermatitis in a systematic review and network meta-analysis.

Data Sources

The Cochrane Central Register of Controlled Trials, MEDLINE, Embase, Latin American and Caribbean Health Science Information database, Global Resource of Eczema Trials database, and clinical trial registries were searched from inception to October 28, 2019.

Study Selection

English-language randomized clinical trials of 8 weeks or more of treatment with systemic immunomodulatory medications for moderate to severe atopic dermatitis were included. Titles, abstracts, and articles were screened in duplicate. Of 10 324 citations, 39 trials were included.

Data Extraction and Synthesis

Data were extracted in duplicate, and the review adhered to Preferred Reporting Items for Systematic Reviews and Meta-analyses for Network Meta-Analyses guidelines. Random-effects bayesian network meta-analyses were performed and certainty of evidence was assessed using Grading of Recommendations Assessment, Development and Evaluation criteria.

Main Outcomes and Measures

Prespecified outcomes were change in signs of disease, symptoms, quality of life, itch, withdrawals, and serious adverse events.

Results

A total of 39 trials with 6360 patients examining 20 medications and placebo were included. Most trials were conducted for adults receiving up to 16 weeks of therapy. Dupilumab, 300 mg every 2 weeks, was associated with improvement in the Eczema Area and Severity Index score vs placebo (mean difference, 11.3-point reduction; 95% credible interval [CrI], 9.7-13.1 [high certainty]). Cyclosporine (standardized mean difference, -1.1; 95% CrI, -1.7 to -0.5 [low certainty]) and dupilumab (standardized mean difference, -0.9; 95% CrI, -1.0 to -0.8 [high certainty]) were similarly effective vs placebo in clearing clinical signs of atopic dermatitis and may be superior to methotrexate (standardized mean difference, -0.6; 95% CrI, -1.1 to 0.0 [low certainty]) and azathioprine (standardized mean difference, -0.4; 95% CrI, -0.8 to -0.1 [low certainty]). Several investigational medications for atopic dermatitis are promising, but data to date are limited to small early-phase trials. Safety analyses were limited by low event rates.

Conclusions and Relevance

Dupilumab and cyclosporine may be more effective for up to 16 weeks of treatment than methotrexate and azathioprine for treating adult patients with atopic dermatitis. More studies directly comparing established and novel treatments beyond 16 weeks are needed and will be incorporated into future updates of this review.

Network meta-analyses of systemic treatments for psoriasis: a critical appraisal: Original Articles: Jabbar-Lopez ZK, Yiu ZZN, Ward V et al. Quantitative evaluation of biologic therapy options for psoriasis: a systematic review and network meta-analysis. J Invest Dermatol 2017; 137:1646-54. Sbidian E, Chaimani A, Garcia-Doval I et al. Systemic pharmacological treatments for chronic plaque psoriasis: a network meta-analysis. Cochrane Database Syst Rev 2017; 12:CD011535

AIM

There are numerous systemic medications in use for psoriasis, with additional investigational agents being studied. However, head-to-head, randomized clinical trials are rare and cannot feasibly compare all treatments. A network meta-analysis (NMA) synthesizes the available evidence to provide estimates for all pairwise comparisons. Here, we summarize and appraise two recent NMAs that assessed systemic therapies for moderate-to-severe psoriasis.

SETTING AND DESIGN

Two systematic reviews searched databases and the grey literature to identify relevant randomized clinical trials.

STUDY PARTICIPANTS

The reviews mostly included trials that involved adults with moderate-to-severe psoriasis. One of the reviews also included two trials involving children.

STUDY EXPOSURE

Interventions common to both reviews include adalimumab, etanercept, infliximab, ustekinumab, ixekizumab, secukinumab and methotrexate. One of the reviews included additional interventions, primarily other biological agents along with new small-molecule treatments and systemic conventional treatments.

PRIMARY OUTCOMES

One review focused on 'clear/nearly clear' and withdrawals from adverse events as study outcomes, while the second review focused on improvement of ≥ 90% measured on the Psoriasis Area and Severity Index (PASI 90) and serious adverse events.

OUTCOMES

Additional outcomes included quality of life, PASI 75, Physician's Global Assessment of 0/1 and any adverse event.

RESULTS

Overall, both NMAs are of high quality and provide a comprehensive summary of the evidence base and treatment effects. Results, in terms of both estimates and rankings, suggest that newer biologics targeting the interleukin (IL)-12/23 and IL-17 axes appear to be more effective than older biologics and oral agents.

CONCLUSIONS

Patients, clinicians and policy makers can use the relative efficacy assessments of NMAs to inform decision making regarding the clearance of psoriasis skin lesions at relevant time points and improvement in quality of life.

Propensity Score-Based Methods in Comparative Effectiveness Research on Coronary Artery Disease

This review examines the conduct and reporting of observational studies using propensity score-based methods to compare coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), or medical therapy for patients with coronary artery disease. A systematic selection process identified 48 studies: 20 addressing CABG versus PCI; 21 addressing bare-metal stents versus drug-eluting stents; 5 addressing CABG versus medical therapy; 1 addressing PCI versus medical therapy; and 1 addressing drug-eluting stents versus balloon angioplasty. Of 32 studies reporting information on variable selection, 7 relied exclusively on statistical criteria for the association of covariates with treatment, and 5 used such criteria to determine whether product or nonlinear terms should be included in the propensity score model. Twenty-five (52%) studies reported assessing covariate balance using the estimated propensity score, but only 1 described modifications to the propensity score model based on this assessment. The over 400 variables used in the 48 propensity score models were classified into 12 categories and 60 subcategories; only 17 subcategories were represented in at least half of the propensity score models. Overall, reporting of propensity score-based methods in observational studies comparing CABG, PCI, and medical therapy was incomplete; when adequately described, the methods used were often inconsistent with current methodological standards.

Advanced Age and Post-Acute Care Outcomes After Subarachnoid Hemorrhage

Background

Older patients with aneurysmal subarachnoid hemorrhage (aSAH) are unique, and determinants of post–acute care outcomes are not well elucidated. The primary objective was to identify hospital characteristics associated with 30‐day readmission and mortality rates after hospital discharge among older patients with aSAH.

Methods and Results

This cohort study used Medicare patients ≥65 years discharged from US hospitals from January 1, 2008, to November 30, 2010, after aSAH. Medicare data were linked to American Hospital Association data to describe characteristics of hospitals treating these patients. Using multivariable logistic regression to adjust for patient characteristics, hospital factors associated with (1) hospital readmission and (2) mortality within 30 days after discharge were identified. A total of 5515 patients ≥65 years underwent surgical repair for aSAH in 431 hospitals. Readmission rate was 17%, and 8.5% of patients died within 30 days of discharge. In multivariable analyses, patients treated in hospitals with lower annualized aSAH volumes were more likely to be readmitted 30 days after discharge (lowest versus highest quintile, 1–2 versus 16–30 cases; adjusted odds ratio, 2.10; 95% confidence interval, 1.56–2.84). Patients treated in hospitals with lower annualized aSAH volumes (lowest versus highest quintile: adjusted odds ratio, 1.52; 95% confidence interval, 1.05–2.19) had a greater likelihood of dying 30 days after discharge.

Conclusions

Older patients with aSAH discharged from hospitals treating lower volumes of such cases are at greater risk of readmission and dying within 30 days. These findings may guide clinician referrals, practice guidelines, and regulatory policies influencing which hospitals should care for older patients with aSAH.

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta populations are associated with pollinator proboscis lengths, whether floral divergence occurs in the presence of different pollinators and whether floral convergence occurs between distantly related populations pollinated by the same pollinator. Finally, we ask whether tube length evolution is directional. Shifts between morphologically different pollinators were always associated with shifts in floral morphology, even when populations were very closely related. Distantly related populations had similar tube lengths when they were pollinated by the same pollinator. Shifts in tube length tended to be from short to long, although reversals were not infrequent. After correcting for the population-level phylogeny, there was a strong positive, linear relationship between floral tube length and pollinator proboscis length, suggesting that plants are functionally specialized on different pollinators at different sites. However, because tube length evolution in this system can be a bidirectional process, specialization to the local pollinator fauna is unlikely to result in evolutionary or ecological dead-ends such as canalization or range limitation.

Indirect comparison of bazedoxifene vs oral bisphosphonates for the prevention of vertebral fractures in postmenopausal osteoporotic women

OBJECTIVE

Compare the efficacy of bazedoxifene with oral bisphosphonates for reduction of vertebral fracture risk in postmenopausal osteoporotic (PMO) women and in higher-risk patients based on evidence from randomized controlled trials (RCTs).

METHODS

Eight RCTs assessing vertebral fracture risk reduction with oral bisphosphonates (n = 7) or bazedoxifene (n = 1) were identified by a systematic literature review. Individual study results were pooled in a network meta-analysis (NMA) to indirectly compare treatment effects for overall PMO women and a higher-risk subgroup (FRAX ≥ 20%). Three sets of NMA analyses were conducted: aggregate data (AD) from the bisphosphonate RCTs and bazedoxifene RCT for the full population or the FRAX ≥20% subgroup (NMA AD); bisphosphonate AD and bazedoxifene AD from each FRAX subgroup adjusted for baseline risk (NMA AD meta-regression); and bisphosphonate AD and bazedoxifene individual patient data (IPD) adjusted for baseline risk/FRAX (NMA AD/IPD meta-regression).

RESULTS

For the overall population, bisphosphonates had lower fracture risks versus bazedoxifene although there is considerable uncertainty in supporting one intervention over another. The relative risk reduction (RRR) for bazedoxifene was -0.23 (95% CrI: -1.11, 0.27) versus ibandronate, -0.17 (-0.76, 0.22) versus alendronate, and -0.06 (-0.62, 0.30) versus risedronate. RESULTS from the meta-regression analyses were similar. For the FRAX ≥20% population, estimated fracture rates with bazedoxifene were lower than with bisphosphonates, but again the uncertainty limits strong interpretation. The RRR for bazedoxifene was 0.51 (-0.31, 0.83) versus ibandronate, 0.53 (-0.18, 0.83) versus alendronate, and 0.57 (-0.07, 0.85) versus risedronate. The meta-regression analyses showed comparable findings.

CONCLUSION

The analyses only considered vertebral fractures for oral bisphosphonates versus bazedoxifene, and IPD was available only for bazedoxifene. In light of this, bazedoxifene is comparable to bisphosphonates in the overall PMO population and at least as effective as bisphosphonates for preventing vertebral fractures among higher-risk PMO patients. The findings suggest bazedoxifene performs better in higher-risk PMO than in the overall PMO.

Performance of formulas for estimating glomerular filtration rate in Indigenous Australians with and without Type 2 diabetes: the eGFR Study

AIMS

It has been proposed that the Chronic Kidney Disease Epidemiology Collaboration formula estimates glomerular filtration rate more accurately than the Modification of Diet in Renal Disease formula. With the very high incidence of diabetes and end-stage kidney disease in Indigenous Australians, accurate estimation of glomerular filtration rate is vital in early detection of kidney disease. We aimed to assess the performance of the Chronic Kidney Disease Epidemiology Collaboration, Modification of Diet in Renal Disease and Cockcroft-Gault formulas in Indigenous Australians with and without diabetes.

METHODS

Indigenous Australians with (n = 224) or without (n = 340) Type 2 diabetes had a reference glomerular filtration rate measure using plasma disappearance of iohexol (measured glomerular filtration rate) over 4 h. Serum creatinine was measured by an enzymatic method. Performance was assessed by bias (measured glomerular filtration rate - estimated glomerular filtration rate) and accuracy (percentage of estimated glomerular filtration rate within 30% of measured glomerular filtration rate).

RESULTS

The median measured glomerular filtration rate (interquartile range) in participants with or without diabetes was 97 (68-119) and 108 (90-122) ml min(-1)  1.73 m(-2) , respectively. The Chronic Kidney Disease Epidemiology Collaboration formula had smaller bias and greater accuracy than the Modification of Diet in Renal Disease and Cockcroft-Gault formulas overall, for participants both with and without diabetes. However, for estimated glomerular filtration rate > 90 ml min(-1)  1.73 m(-2) , the Chronic Kidney Disease Epidemiology Collaboration formula had greater bias in participants with diabetes, underestimating measured glomerular filtration rate by 7.4 vs. 1.0 ml min(-1)  1.73 m(-2) in those without diabetes. The Chronic Kidney Disease Epidemiology Collaboration formula was less accurate across the whole range of estimated glomerular filtration rates in participants with vs. those without diabetes (87.1% vs. 93.3%).

CONCLUSIONS

The Chronic Kidney Disease Epidemiology Collaboration formula outperforms the Modification of Diet in Renal Disease and Cockcroft-Gault formulas overall in Indigenous Australians with and without diabetes. However, the Chronic Kidney Disease Epidemiology Collaboration formula has greater bias in people with diabetes compared with those without diabetes, especially in those with normal renal function.

Bazedoxifene versus oral bisphosphonates for the prevention of nonvertebral fractures in postmenopausal women with osteoporosis at higher risk of fracture: a network meta-analysis

OBJECTIVE

To compare the efficacy of bazedoxifene and oral bisphosphonates for the prevention of nonvertebral fractures (NVFs) in women with higher risk of postmenopausal osteoporosis (i.e., the Fracture Risk Assessment Tool [FRAX] score ≥ 20%), based on currently available evidence from randomized controlled trials.

METHODS

Randomized controlled trials evaluating the NVF relative risk reduction (RRR) with oral bisphosphonates or bazedoxifene were identified by a systematic literature review and combined by means of a network meta-analysis. A subgroup of patients with a FRAX score of 20% or more in the bazedoxifene phase III osteoporosis study was selected as the population of interest on the basis of the bazedoxifene label. In one analysis (analysis 1), the placebo response of the subgroup with a FRAX score of 20% or more was the benchmark to select comparable bisphosphonate trials. Additional analyses incorporated the aggregate data from the bisphosphonate trials with all the FRAX subgroups (analysis 2) or with the individual patient data from the bazedoxifene trial (analysis 3).

RESULTS

Nine identified bisphosphonate trials (alendronate, ibandronate, risedronate; N = 23,440 patients) with a similar placebo response as observed for the subgroup of high risk patients in the bazedoxifene trial were included in analysis 1. The results of the network meta-analysis of this study set suggest that bazedoxifene is expected to have an RRR of 0.43 (95% credible interval [CrI] -0.19 to 0.72) versus alendronate, 0.58 (95% CrI 0.05-0.81) versus ibandronate, and 0.39 (95% CrI -0.29 to 0.70) versus risedronate. Analyses in which treatment effects with bisphosphonates were projected to a population with a FRAX score of 20% or more with meta-regression approaches (analysis 2 and analysis 3) provide similar findings.

CONCLUSION

Based on an indirect comparison of randomized trials, bazedoxifene is expected to have at least a comparable RRR of NVF as alendronate, ibandronate, and risedronate in women with higher risk of postmenopausal osteoporosis.

Selfing ability and dispersal are positively related, but not affected by range position: a multispecies study on southern African Asteraceae

Dispersal and breeding system traits are thought to affect colonization success. As species have attained their present distribution ranges through colonization, these traits may vary geographically. Although several theories predict associations between dispersal ability, selfing ability and the relative position of a population within its geographic range, there is little theoretical or empirical consensus on exactly how these three variables are related. We investigated relationships between dispersal ability, selfing ability and range position across 28 populations of 13 annual, wind-dispersed Asteraceae species from the Namaqualand region of South Africa. Controlling for phylogeny, relative dispersal ability--assessed from vertical fall time of fruits--was positively related to an index of autofertility--determined from hand-pollination experiments. These findings support the existence of two discrete syndromes: high selfing ability associated with good dispersal and obligate outcrossing associated with lower dispersal ability. This is consistent with the hypothesis that selection for colonization success drives the evolution of an association between these traits. However, no general effect of range position on dispersal or breeding system traits was evident. This suggests selection on both breeding system and dispersal traits acts consistently across distribution ranges.

Is fosfomycin a potential treatment alternative for multidrug-resistant gram-negative prostatitis?

BACKGROUND

Multidrug-resistant gram-negative bacterial (MDR-GNB) infections of the prostate are an increasing problem worldwide, particularly complicating transrectal ultrasound (TRUS)-guided prostate biopsy. Fluoroquinolone-based regimens, once the mainstay of many protocols, are increasingly ineffective. Fosfomycin has reasonable in vitro and urinary activity (minimum inhibitory concentration breakpoint ≤64 µg/mL) against MDR-GNB, but its prostatic penetration has been uncertain, so it has not been widely recommended for the prophylaxis or treatment of MDR-GNB prostatitis.

METHODS

In a prospective study of healthy men undergoing a transurethral resection of the prostate for benign prostatic hyperplasia, we assessed serum, urine, and prostatic tissue (transition zone [TZ] and peripheral zone [PZ]) fosfomycin concentrations using liquid chromatography-tandem mass spectrometry, following a single 3-g oral fosfomycin dose within 17 hours of surgery.

RESULTS

Among the 26 participants, mean plasma and urinary fosfomycin levels were 11.4 ± 7.6 µg/mL and 571 ± 418 µg/mL, 565 ± 149 minutes and 581 ± 150 minutes postdose, respectively. Mean overall prostate fosfomycin levels were 6.5 ± 4.9 µg/g (range, 0.7-22.1 µg/g), with therapeutic concentrations detectable up to 17 hours following the dose. The mean prostate to plasma ratio was 0.67 ± 0.57. Mean concentrations within the TZ vs PZ prostate regions varied significantly (TZ, 8.3 ± 6.6 vs PZ, 4.4 ± 4.1 µg/g; P = .001). Only 1 patient had a mean prostatic fosfomycin concentration of <1 µg/g, whereas the majority (70%) had concentrations ≥4 µg/g.

CONCLUSIONS

Fosfomycin appears to achieve reasonable intraprostatic concentrations in uninflamed prostate following a single 3-g oral dose, such that it may be a potential option for prophylaxis pre-TRUS prostate biopsy and possibly for the treatment of MDR-GNB prostatitis. Formal clinical studies are now required.

Preclinical analysis of the analinoquinazoline AG1478, a specific small molecule inhibitor of EGF receptor tyrosine kinase

The tyrphostin 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) is a potent and specific inhibitor of EGFR tyrosine kinase whose favourable preclinical profile supports progression towards clinical trials. Microphysiometric evaluation revealed a short (<24 min) effective inhibition of cellular receptor response to EGF challenge in BaF/ERX cells indicating a need to maintain sustained levels of inhibitor. Initial pharmacokinetic evaluation in mice of novel AG1478 formulations in a beta-cyclodextrin (Captisol) showed monoexponential elimination from plasma (half-life 30 min) following subcutaneous administration. A two-fold dose escalation gave a 2.4-fold increase in the total AUC. Bolus i.v. and 6 h continuous infusion were investigated in rats to mimic a more clinically relevant administration regimen. Drug elimination following bolus i.v. administration was biphasic (terminal elimination half-life 30-48 min). The linear relationship between dose and AUC(0-->infinity) (r2=0.979) enabled the prediction of infusion rates and doses for sustained delivery using continuous 6 h infusions, where steady state was reached in 120 min. Plasma levels of AG1478>10 microM were achieved over the duration of the infusion. At the lowest dose, plasma drug levels after the cessation of infusion declined with a half-life of approximately 43 min. EGFR activity, measured both by autophosphorylation and downstream signalling, was inhibited in a dose-dependent manner by injection of AG1478 in mice bearing xenografts of the human glioblastoma cell line U87MG.delta2-7, which expresses a constitutively active variant of the EGF receptor. Taken together, these experiments provide essential data to assess the anti-tumour efficacy of AG1478 and will assist in the rational design of dose regimens for clinical studies.

Integrating biosystematic data into conservation planning: perspectives from southern Africa's Succulent Karoo

In this paper we explore the role that biosystematists can play in conservation planning. Conservation planning concerns the location and design of reserves that both represent the biodiversity of a region and enable the persistence of that biodiversity by maintaining key ecological and evolutionary processes. For conservation planning to be effective, quantitative targets are needed for the spatial components of a region that reflect evolutionary processes. Using examples from southern Africa's Succulent Karoo, we demonstrate how spatially explicit data on morphological variation within taxa provide essential information for conservation planning in that such variation represents an important surrogate for the spatial component of lineage diversification. We also provide an example of how the spatial components of evolutionary processes can be identified and targeted for conservation action. Key to this understanding are the recognition and description of taxonomic units at all spatial scales. Without the recognition of subspecific variation, it is difficult to formulate evolutionary hypotheses, let alone set quantitative targets for the conservation of this variation. Given the escalating threats to biodiversity, and the importance of planning for persistence by incorporating ecological and evolutionary processes into conservation plans, it is essential that systematists develop hypotheses on the spatial surrogates for these processes for a wide range of lineages. The important questions for systematists to be asking are (1) how is variation distributed in the landscape, and (2) how did it come about? Conservation planners too need to highlight these spatial components for conservation action.

High-performance liquid chromatographic analysis of the tyrphostin AG1478, a specific inhibitor of the epidermal growth factor receptor tyrosine kinase, in mouse plasma

The tyrphostin 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) is undergoing evaluation as a potential new anticancer agent. We have developed a specific and sensitive reversed-phase HPLC assay for AG1478 in mouse plasma. The method involves a rapid and simple extraction process followed by separation on a Symmetry C8 stationary phase with a gradient of acetonitrile in ammonium acetate buffer. A linear response was achieved over the concentration range of 0.2-100 microM using multilevel calibration with internal standard method of calculation. Inter- and intra-assay accuracy and precision were better than +/-10%. The limit of quantitation was 0.2 microM. We have used this method to study the preclinical pharmacokinetics of this new agent in mice.

Reproductive health in women with cystic fibrosis

The life expectancy of women with cystic fibrosis has doubled in the last 20 years. A major implication of this is the advent of previously unseen reproductive health problems. We review the management problems presented by these women throughout their reproductive lives, including pregnancy.

Geriatric dentistry in long-term-care facilities: current status and future implications

The status of oral health care of geriatric patients in long-term-care facilities is reviewed. Barriers to improving the dental management of institutionalized geriatric patients are discussed. The elderly population segment is the fastest-growing population, which presents a great burden to dental health professionals. Institutionalized geriatric patients are currently not receiving adequate care, and the number of these patients will double by the year 2020. The future implications are of considerable importance. Commitment by dental professionals to meet the oral health needs of this underserved population is key to the improvement of and change in the current status of this population.

Inhibition of paclitaxel elimination in the isolated perfused rat liver by Cremophor EL

PURPOSE

Cremophor can alter the pharmacokinetics of cytotoxic drugs, including doxorubicin and etoposide. In view of its presence in the formulation of paclitaxel, the aim of this study was to investigate the influence of Cremophor on the hepatobiliary elimination of paclitaxel.

METHODS

In a recirculating isolated perfused rat-liver system the elimination of 1.7 mg paclitaxel given as a bolus into the perfusate reservoir was monitored in perfusate and bile in controls and after the administration of either 80 or 800 microl Cremophor. The higher dose of Cremophor yields clinically relevant perfusate concentrations. Paclitaxel was measured in perfusate, bile, and liver tissue by high-performance liquid chromatography.

RESULTS

Cremophor caused a dose-dependent inhibition of the elimination of paclitaxel, with a statistically significant mean value +/-SD, n=3; (P < 0.05 versus controls Bonferroni t-test) 9-fold increase in AUC (2227+/-106 versus 245+/-40 microg ml(-1) min), 9-fold decrease in total clearance (0.8+/-0.1 versus 7.0+/-1.1 ml/min), and 5-fold increase in elimination half-life (92+/-14 versus 18+/-4 min) being observed after a dose of 800 microl Cremophor. With the addition of Cremophor the amount of paclitaxel remaining after 3 h increased in perfusate from none to 20%, increased in liver tissue from 4% to 18%, and remained constant in bile at 11-13%. In the control group, 86% of the paclitaxel dose was recovered in bile as five putative metabolites, which were measured in paclitaxel equivalents, with the major metabolite. M3 co-eluting with 3'-p-hydroxypaclitaxel. This decreased to 45% of the dose on the addition of Cremophor, and the ratio of M3 to paclitaxel in bile decreased.

CONCLUSIONS

Cremophor inhibits the hepatic elimination of paclitaxel in the isolated perfused rat liver, primarily by preventing the drug from reaching sites of metabolism and excretion. The presence of Cremophor in the paclitaxel formulation may therefore contribute to the nonlinear pharmacokinetics and pharmacodynamics of paclitaxel.

Risk factors for infection with verocytotoxigenic Escherichia coli in cattle on Ontario dairy farms

Risk factors for prevalent infection with verocytotoxigenic Escherichia coli (VTEC) were studied in a random sample of 886 cows and 592 calves under 3 months of age on 80 randomly selected dairy farms in southern Ontario. Fecal-culture supernatants from each animal were screened for verocytotoxicity using a Vero cell assay (VCA) and for verocytotoxin (VT) genes by a polymerase chain reaction (PCR) procedure. Up to 20 F. colt isolates from positive samples were tested for VT production using VCA and PCR. VTEC isolates were serotyped. Farm managers were interviewed using a standardized questionnaire to obtain information on farm- and individual animal-level management practices and characteristics. There was a significant (P < 0.001) positive association between age of calves and their VTEC infection status, and calves were significantly more likely to be infected than cows. The proportion of calves infected on the farm was positively associated with both the use of regular pails for feeding calves (as opposed to nipple bottles or nipple pails) and bringing new animals into the herd in the previous year.

Chlamydia pneumoniae as a new source of infectious outbreaks in nursing homes

OBJECTIVE

To determine the extent and severity of illness and mode of transmission of Chlamydia pneumoniae infection in 3 nursing home outbreaks.

DESIGN AND SETTING

Retrospective cohort study in 3 nursing homes in Ontario from September to November 1994.

SUBJECTS

A total of 549 residents and 65 staff members.

MAIN OUTCOME MEASURES

Morbidity and mortality were determined by a review of disease surveillance forms, residents' charts, and a self-administered questionnaire to staff. Single and paired serum samples for C pneumoniae serological testing and nasopharyngeal swabs for C pneumoniae culture were collected, and direct fluorescent antibody assays were performed to confirm C pneumoniae infection.

RESULTS

The attack rates for confirmed and suspected cases combined were 68%, 46%, and 44% among residents in nursing homes A, B, and C, respectively, and 34% among nursing home C staff. A total of 16 cases of pneumonia confirmed by chest x-ray and 6 deaths were identified. The spectrum of illness among nursing home C residents included a new cough in 58 (100%), fever in 37 (64%), sore throat in 14 (24%), and hoarseness in 8 (14%). Staff members at nursing home C were more likely to report hoarseness (P<.001) and sore throat (P<.001). Residents who smoked had onset of illness earlier than nonsmokers (P=.007), which perhaps is related to airborne transmission in a designated smoking room.

CONCLUSIONS

Chlamydia pneumoniae caused serious morbidity and mortality among residents and morbidity among staff; C pneumoniae is an important cause of respiratory disease outbreaks in nursing homes, and diagnostic tests must be readily available for early recognition of C pneumoniae infections.

Comparison of Vero cell assay and PCR as indicators of the presence of verocytotoxigenic Escherichia coli in bovine and human fecal samples

Comparisons were made between Vero cell assay (VCA) and PCR as indicators for the detection of verocytotoxigenic Escherichia coli (VTEC; also known as Shiga-like toxin-producing E. coli) and as predictors of VTEC isolation from bovine and human fecal samples. Fecal samples were collected as part of a survey on the prevalence of VTEC on dairy farms in southern Ontario (J. B. Wilson et al., J. Infect. Dis., 174:1021-1027, 1996). A total of 2,655 samples were examined by VCA and PCR, 2,153 originating from cattle and 502 originating from humans. Overall, 36.2% of the samples were positive in the VCA and 38.7% were positive by PCR. Of the VCA-positive samples screened, 41.6% yielded a VTEC isolate. For both human and bovine samples, a significant positive association between PCR result and VCA titer (P = 0.0001) was found. In addition, there was a significant positive association between the PCR result and VTEC isolation from VCA-positive samples for cattle (odds ratio = 9.1, P < 0.0001). For bovine samples positive in the VCA, VCA titer was significantly associated with the probability of obtaining a VTEC isolate. Agreement between VCA and PCR was good for both bovine and human samples (kappa = 0.69 and 0.64, respectively). The sensitivity and specificity of the PCR with respect to the VCA for bovine samples were 82.0 and 86.5%, respectively, and those for human samples were 59.3 and 98.1%, respectively. Although correlation between VCA and PCR results was not absolute, when used in conjunction, these tests complemented one another as predictors of VTEC isolation.

Inhibition of etoposide elimination in the isolated perfused rat liver by Cremophor EL and Tween 80

Cremophor EL, a surfactant used in the clinical formulation of cyclosporine and paclitaxel, will reverse the multidrug resistance (MDR) phenotype in vitro. As other MDR modulators can alter the pharmacokinetics of cytotoxic drugs, the aim of this study was to examine the effect of Cremophor and another MDR-reversing surfactant, Tween 80, on the hepatic elimination and biliary excretion of etoposide. Using the isolated perfused rat-liver model with 80 ml recirculating perfusate containing 20% red blood cells and 4% bovine serum albumin, etoposide (1.6 mg) with and without Cremophor (800 or 80 mg) or Tween 80 (80 mg) was given into the perfusate reservoir, and perfusate and bile samples were collected for 3 h. Etoposide was measured by high-performance liquid chromatography (HPLC) and Cremophor was measured using a bioassay. Both surfactants changed the etoposide elimination profile from biphasic to monophasic. High-dose Cremophor increased the AUC (from 334 +/- 23 to 1540 +/- 490 microgram min ml(-1), P<0.05) and decreased the total clearance (from 4.8 +/- 0.3 to 1.1 +/- 0.3 ml/min, P<0.05) and biliary clearance (from 2.6 +/- 1.1 to 0.5 +/- 0.2 ml/min, p<0.05) but decreased the elimination half-life (from 62 +/- 17 to 40 +/- 5 min, P<0.05) and volume of distribution (from 424 +/- 85 to 65 +/- 19 ml, P<0.05). Low-dose Cremophor and Tween 80 caused intermediate effects on these parameters that were statistically significant for total clearance, half-life, and volume of distribution. Cremophor had no adverse effect on liver function, whereas Tween 80 caused haemolysis and cholestasis. The initial high-dose Cremophor perfusate concentration was 0.8 mg/ml, which previous studies have shown to be clinically relevant and close to the optimal level for MDR reversal in vitro (1.0 mg/ml). Cremophor may be a clinically useful MDR modulator, but it may alter the pharmacokinetics of the cytotoxic drug.

Metabolism and elimination of 5,6-dimethylxanthenone-4-acetic acid in the isolated perfused rat liver

5,6-Dimethylxanthenone-4-acetic acid (DXAA) is a synthetic xanthenone derivative that is active against murine solid tumors and is being formulated for clinical trials. This study used the isolated perfused rat liver to compare the hepatic metabolism and biliary excretion of DXAA with flavone-8-acetic acid (FAA), a synthetic flavonoid undergoing clinical evaluation as an anticancer drug. Perfusate, bile, and liver samples were assayed for parent drug and metabolites by HPLC. Three FAA metabolites were present in bile, and one of these coeluted with FAA acyl glucuronide. Alkaline hydrolysis of high-dose DXAA bile samples resulted in the disappearance of 5 of 7 metabolite peaks. One biliary metabolite was identified by mass spectrometry as the acyl glucuronide and its presence in bile accounted for > 50% of the DXAA dose. A second compound that was resistant to alkaline hydrolysis was characterized as a hydroxylated DXAA metabolite. A total of 28% of the high dose DXAA was recovered unchanged in the perfusate, liver, and bile, compared with 11% of the low dose DXAA and 40% of the FAA dose. Protein binding of DXAA in perfusate was saturable, ranging from 94.5% at 112 microM to 72.4% at 1125 microM, whereas binding in human plasma was > 99% at concentrations between 11.5 and 1243 microM. This study demonstrates that DXAA undergoes extensive acyl glucuronidation followed by biliary excretion in the isolated perfused rat liver. Its hepatic metabolism may be saturable, and DXAA seems to be more extensively metabolized than FAA. Finally, DXAA protein binding in human plasma is high and not dose-dependent at concentrations likely to be clinically relevant.

Effect of toremifene on antipyrine elimination in the isolated perfused rat liver

Toremifene is a triphenylethylene antioestrogen with significant antitumor activity. It is structurally very similar to tamoxifen. Both drugs undergo extensive hepatic metabolism, and tamoxifen is known to inhibit hepatic mixed-function oxidases (MFO). Using the isolated perfused rat-liver model, we investigated the effect of toremifene on the elimination of antipyrine, a standard marker of MFO activity. Perfusate consisted of 20% red cells in a modified Krebs-Henseleit buffer, and 80 ml was recirculated at 14 ml/min for 3 h. High but clinically relevant steady-state toremifene levels of 3 and 10 micrograms/ml were achieved using bolus plus constant infusion into the reservoir. Elimination of 2.5 mg antipyrine was not inhibited by steady-state toremifene, but methanol (maximal perfusate concentration, 1.29%), the vehicle used for toremifene administration, caused a statistically significant increase in the antipyrine elimination half-life (mean, 1.4 +/- 0.2 h for controls vs 2.2 +/- 0.3 h for methanol; P < 0.05, n = 4). Whereas the methanol had no apparent effect on liver viability as assessed by bile flow and perfusate back-pressure, toremifene at a steady-state concentration of 10 micrograms/ml caused a statistically significant decrease in bile flow (value at 180 min, 0.22 +/- 0.05 ml/h as compared with 0.52 +/- 0.06 ml/h in the methanol control; P < 0.05) and a statistically significant increase in perfusate back-pressure (value at 180 min, 17.5 +/- 1.8 cm vs 11.0 +/- 2.6 cm in the methanol control; P < 0.05). Therefore, toremifene used at high doses can impair liver function in the isolated perfused rat liver, but it does not have any effect on antipyrine elimination.

Effects of opiates on sodium excretion in the isolated perfused rat kidney

1. A rat isolated perfused kidney preparation was utilized to define clearly a renal site of action. The variables measured were perfusate pressure and flow, glomerular filtration rate, urine volume, sodium excretion and potassium excretion. 2. Dextromethorphan (3 nmol/L) and dextrorphan (10 nmol/L) reduced sodium excretion in kidneys from rats on either control or high K+ diet, in the absence of any other measured renal effects. Dextromethorphan (10 nmol/L) produced a decrease in glomerular filtration rate as well as a decrease in sodium excretion. Naloxone (1 mumol/L) inhibited the effect of dextromethorphan on sodium excretion but had no effect when administered alone. 3. The levorotatory opiates levorphanol and levomethorphan, the kappa agonist ketocyclazocine and a range of other opiates had no effect on sodium excretion. 4. The results suggest a renal action specific for dextrorotatory opiates. This renal action is consistent with earlier binding studies suggesting preferential recognition of dextrorotatory opiates.

Comparison of the effects of parathyroid hormone (PTH) and recombinant PTH-related protein on bicarbonate excretion by the isolated perfused rat kidney

The isolated perfused rat kidney was used to study the effects of amino-terminal fragments of human parathyroid hormone, hPTH(1-34), bovine parathyroid hormone, bPTH(1-84) and of PTH-related proteins, PTHrP(1-34), PTHrP(1-84), PTHrP(1-108) and PTHrP(1-141) on urinary bicarbonate excretion. PTHrP(1-34) (7 nmol/l), bPTH(1-84) (5.5 nmol/l) and hPTH(1-34) (7 nmol/l) had similar effects in increasing bicarbonate excretion with respect to the control. At lower concentrations (0.7 nmol/l) all PTHrP components, but not hPTH(1-34) or bPTH(1-84) increased bicarbonate excretion significantly. Infusions of PTHrP(1-108) and PTHrP(1-141) at 0.7 nmol/l, while associated with a rise in urinary bicarbonate concentration and excretion during the early stages of perfusion, produced a sharp decline in bicarbonate concentration and excretion in the latter part of perfusion. The different peptides produced no significant differences in glomerular filtration rate, fractional excretion of sodium or urine volume. The absence of substantial differences between the effects of hPTH(1-34) and PTHrP(1-34) are as noted in previous studies. The differences between PTHrP(1-108)/PTHrP(1-141) and PTHrP(1-34) demonstrated here are consistent with (1) the clinical manifestations of acidosis in hyperparathyroidism and alkalosis in humoral hypercalcaemia of malignancy, and (2) an independent action of a component of PTHrP beyond amino acids 1-34.

Potassium excretion in renal failure in the rat: the role of distal tubule flow and aldosterone

1. This study examines the contribution of an increased distal tubule flow and of aldosterone to the handling of a potassium load in conscious rats with renal failure induced by subtotal nephrectomy or by gentamicin on a control of high K+ diet. 2. Glomerular filtration rate was reduced by subtotal nephrectomy to 40% and by gentamicin treatment to 60% of control. Subtotal nephrectomy induced significant hypertrophy of glomeruli and proximal and distal tubules, but gentamicin did not. Both experimental groups had a normal iothalamate space and plasma potassium after a 20 h fast. 3. Two hours after an acute KCl load rats with renal failure excreted less potassium than control rats. There was also a lesser natriuretic effect of KCl in the renal failure groups. 4. A high K+ diet, given for 5-7 days, increased excretion of an acute KCl load in control rats and rats with renal failure. 5. (UNaV + UKV) was used as an estimate of distal tubule flow. Potassium excretion, related to distal tubule flow, was similar in the renal failure and control rats when on the same diet. This is consistent with potassium excretion being strongly, but not necessarily solely, dependent on distal flow. 6. Adrenalectomy reduced, and aldosterone restored, potassium excretion in the renal failure and control groups. This suggests a role for aldosterone in excretion of an acute potassium load with this degree of renal failure.

Aldosterone is a physiologically significant kaliuretic hormone

To study the role of aldosterone in the short-term control of potassium excretion, rats were gavaged with a liquid diet containing 10-20% of their daily caloric and potassium intake, with a range of sodium intakes. Levels of (effective) aldosterone at the time of gavage were manipulated by administration of spironolactone, aldosterone, and adrenalectomy. Urinary sodium, potassium, and creatinine excretion were measured in conscious unrestrained rats for 2 h after the food load, and then blood was collected for measurement of plasma potassium, aldosterone, and renin activity. Potassium excretion was dependent on both dietary potassium and a minimum dietary sodium content. Potassium excretion was reduced by spironolactone and adrenalectomy and increased by acute aldosterone treatment in most dietary groups. These results strongly suggest that the ambient levels of aldosterone are important in determining potassium excretion following food ingestion. Plasma aldosterone was higher with the higher potassium and lower sodium content diets. Changes in plasma aldosterone, with variations in dietary potassium or sodium, suggest a role for aldosterone in subsequent potassium excretion.

In vivo estimation of changes in distal tubule flow and their role in dexamethasone-induced kaliuresis in control and potassium-adapted rats

The aim of this study was to determine whether the kaliuresis associated with glucocorticoids is due to a direct tubular action or is secondary to effects of glucocorticoids on distal tubule flow. A whole kidney technique was used to avoid the problem, inherent in microperfusion and micropuncture studies, of deciding whether (all) the appropriate nephron segment(s) are being studied. The method used was to determine the best whole kidney measure of distal tubule flow (the independent variable) by correlating this with the dependent variable (potassium excretion, corrected for differences in plasma potassium, UkV/PIK+) in conscious intact and adrenalectomized control and potassium-adapted rats. After an intragastric potassium chloride load, the correlation of UkV/PIK+ with UkV + UNaV was better than with either UNaV or UV, as measures of distal tubule flow. From the relationship a measure of potassium excretion independent of distal tubule flow can thus be calculated as UkV/PIK+ divided by (UkV + UNaV), defined as UK#. Measurement of UK# clearly demonstrates decreases in potassium excretion with adrenalectomy and increases in potassium excretion with aldosterone and in the potassium-adapted rat, consistent with described changes in potassium secretion. In contrast, with dexamethasone treatment, whilst there was an increase in UkV and UkV/PIK+, there was no change in UK# either in the control of potassium-adapted rats. These results suggest that the kaliuretic effect of dexamethasone cannot be attributed to direct tubular effects of glucocorticoids but rather can be explained by its effect on distal tubule flow.

A Case of Osteitis Deformans

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