α<Subscript>1</Subscript>-Antitrypsinmangel

α₁-antitrypsin deficiency is characterized by a pathologic reduction of the serum concentration of α₁-antitrypsin, the most important antiprotease in man. It is one of the most common hereditary diseases in Caucasians. Approximately 2% of obstructive airway diseases are caused by α₁-antitrypsin deficiency. Patients above 35 years may develop lung emphysema, especially in the lower lobes. Symptoms are those of chronic obstructive pulmonary disease such as cough, sputum expectoration, and progressive dyspnoea. Patients with homozygous defect often develop cholestatic hepatitis in the neonatal period. However, only few adult patients develop chronic liver disease up to liver cirrhosis with an elevated risk for malignant liver tumors. The diagnostic hallmark is the reduced serum concentration of α₁-antitrypsin while genetic testing proves the defect. An early recognition of the disease is decisive for prophylactic and therapeutic measures. Smoking should be stopped immediately. Treatment of lung disease includes physiotherapy, antiobstructive and antiinflammatory medication, augmentation with human α₁-antitrypsin and lung surgery including lung transplantation. Liver toxins should be avoided. Besides experimental therapeutic approaches, liver disease can only be treated by liver transplantation.     

Long-Acting β<Subscript>2</Subscript>-Agonists

Salmeterol and formoterol are both long-acting β₂-adrenoceptor agonists (β₂-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting β₂-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting β₂-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting β₂-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting β₂-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting β₂-agonists. Monotherapy with long-acting β₂-agonists is not recommended.     

Pharmacological Stimulation of β <Subscript>2</Subscript>-adrenergic Receptors (β <Subscript>2</Subscript>AR) Enhances Therapeutic Effectiveness of β <Subscript>1</Subscript>AR Blockade in Rodent Dilated Ischemic Cardiomyopathy

Background. We have reported that β ₂ adrenoreceptor (β ₂AR) stimulation is anti-apoptotic, and has strong beneficial effect on cardiac remodeling in an experimental model of post myocardial infarction chronic heart failure (CHF) in rats. Here we investigate whether the addition of chronic pharmacological β ₂AR stimulation enhances the therapeutic effects of β ₁AR blockade on cardiac remodeling in the same model. Methods and Results. Metoprolol, a β ₁AR blocker, given alone (β ₁) or in combination with β ₂AR agonist, fenoterol (β ₁β ₂) were administered to rats via drinking water for 6 weeks, beginning 2 weeks following permanent coronary ligation. Progressive left ventricular (LV) remodeling of untreated animals, assessed by repeated echocardiography, occurred during the observation time, i.e., 42% and 25% increases in end-systolic and end-diastolic LV volumes respectively, 27% fall in ejection fraction, and 35% infarct expansion. Pressure-volume loop analyses at 2d and 8th post infarction weeks showed continuous deterioration of systolic and diastolic functions and arterio-ventricular mismatch. Histological evaluation at the end of 8 weeks revealed the MI expansion and hypertrophy of cardiomyocytes. β ₁β ₂ prevented LV remodeling, MI expansion and cardiomyocytes hypertrophy to a greater degree than β ₁, due, in large part, to a vasodilatory effect of β ₂AR stimulation and thus improvement of arterio-ventricular mismatch. The abnormal diastolic performance improved only in β ₁β ₂. β ₁β ₂ treatment reduced myocardial apoptosis throughout myocardium, but β ₁ reduced apoptopsis only in the areas remote from MI. Conclusion. The therapeutic effects of chronic β ₁AR blockade on cardiac remodeling of heart failure are enhanced and extended when supplemented with β ₂AR stimulation. This research was supported by the Intramural Research Program of the National Institute on Aging, NIH.     

Emphysema in α<Subscript>1</Subscript>-Antitrypsin Deficiency

Severe alpha(1)-antitrypsin (AAT) deficiency is an inherited disorder that leads to the development of emphysema in smokers at a relatively young age; most are disabled in their forties. Emphysema is caused by the protease-antiprotease imbalance when smoking-induced release of neutrophil elastase in the lung is inadequately inhibited by the deficient levels of AAT, the major inhibitor of neutrophil elastase. This protease-antiprotease imbalance leads to proteolytic damage to lung connective tissue (primarily elastic fibers), and the development of panacinar emphysema. AAT replacement therapy, most often applied by weekly intravenous infusions of AAT purified from human plasma, has been used to partially correct the biochemical defect and raise the serum AAT level above a theoretically protective threshold level of 0.8 g/L. A randomized controlled clinical trial was not considered feasible when purified antitrypsin was released for clinical use. However, AAT replacement therapy has not yet been proven to be clinically effective in reducing the progression of disease in AAT-deficient patients. There was a suggestion of a slower progression of emphysema by computed tomography (CT) scan in a small randomized trial. Two nonrandomized studies comparing AAT-deficient patients already receiving replacement therapy with those not receiving it, and a retrospective study evaluating a decline in FEV(1) before and after replacement therapy, suggested a possible benefit for selected patients. Because of the lack of definitive proof of the clinical effectiveness of AAT replacement therapy and its cost, we recommend reserving AAT replacement therapy for deficient patients with impaired FEV(1) (35-65% of predicted value), who have quit smoking and are on optimal medical therapy but continue to show a rapid decline in FEV(1) after a period of observation of at least 18 months. A randomized placebo-controlled trial using CT scan as the primary outcome measure is required. Screening for AAT deficiency is recommended in patients with chronic irreversible airflow obstruction with atypical features such as early onset of disease or disability in their forties or fifties, or positive family history, and in immediate family members of patients with AAT deficiency.     

Loss of β<Subscript>1</Subscript>D-integrin function in human ischemic cardiomyopathy

Integrins play a pivotal role in cardiomyocyte survival and function, with integrin loss leading to myocyte apoptosis and heart failure. The aim of this study was to characterize whether regulation of integrins may contribute to cardiac remodeling in human ischemic cardiomyopathy (ICM). Myocardial tissues of the left ventricle were obtained from patients with ICM (n = 8) undergoing cardiac transplantation and from unused donor hearts (NF, n = 8). In addition, tissue samples from patients with dilated cardiomyopathy (DCM, n = 5) were analyzed. Expression of integrins β₁D and β₃, the effector proteins focal adhesion kinase (FAK) and melusin, and FAK phosphorylation were examined by Western blotting, real-time-PCR and immunofluorescence analysis, respectively. β₁D-integrin protein was decreased in ICM vs. NF by 36%. β₁D-integrin mRNA levels and β₁D-integrin shedding were unchanged. Corresponding to β₁D-integrin regulation, FAK and phosphorylated FAK were decreased in ICM vs. NF by 54% and 49%, respectively. β₃-integrin and melusin were not altered in ICM. As a mediator of integrin effects, AKT kinase activity was examined. In parallel to β₁D-integrin and FAK, AKT activity was decreased in ICM by 44%. In contrast, none of the proteins were significantly altered in DCM compared to NF. Integrins and integrin signaling are regulated differentially in ICM and DCM with a decrease of β₁D-integrin and FAK in ICM. The loss of the β₁Dintegrin-FAK-complex in ICM was paralleled by a reduced AKT activity supporting in vitro data which demonstrate the pivotal role of intact integrin function in anti-apoptotic signaling and cell survival.     

The roles of Transforming growth Factor Type β<Subscript>3</Subscript>(TGF-β<Subscript>3</Subscript>) and mast cells in the pathogenesis of scleroderma

Scleroderma is a connective tissue disorder characterised by excessive accumulation of collagen in the skin and internal organs. The most likely explanation for this process is local activation of collagen synthesis from fibroblasts. Our intention was to elucidate whether TGF-₃ and mast cells play a pathogenic role in abnormal connective tissue formation in scleroderma. In this study, skin biopsies from 20 patients with scleroderma and five from healthy individuals were studied by an indirect immunoperoxidase technique to determine the immunoreactivity of TGF-₃ in the dermis. In addition, skin samples were stained with toluidine blue to count the number of mast cells in scleroderma, and tissues were examined under the electron microscope to evaluate the ultrastructural changes. Increased TGF-₃ immunoreactivities were detected in the dermis in the patient's skin, suggesting the presence of a subpopulation responsible for the increased collagen production. Mast cell counts in the skin of patients with scleroderma were significantly greater (19.2 ± 4.1/unit) than those of normal controls (4.4 ± 1.2/unit). Ultrastructural observations indicated that there is a close relationship between the mast cells and fibroblasts. These results suggest that fibrosis in scleroderma could evolve through the activation of fibroblasts and the regulatory mechanisms that appear to modulate the behavior of these cells with respect to collagen production.AcknowledgementWe are grateful for the support of Professor M. Kaya in our work with the electron microscope and thank Professor E. Erten for supplying tissue samples.     

In situ validation of VEGFR-2 and <Emphasis Type="Italic">α</Emphasis><Subscript><Emphasis Type="Italic">v</Emphasis></Subscript><Emphasis Type="Italic">ß</Emphasis><Subscript>3</Subscript> integrin as targets for breast lesion characterization

Vascular endothelial growth factor receptor 2 (VEGFR-2) and α _v ß ₃ integrin are the most frequently addressed targets in molecular imaging of tumor angiogenesis. In preclinical studies, molecular imaging of angiogenesis has shown potential to detect and differentiate benign and malignant lesions of the breast. Thus, in this retrospective clinical study employing patient tissues, the diagnostic value of VEGFR-2, α _v ß ₃ integrin and vascular area fraction for the diagnosis and differentiation of breast neoplasia was evaluated. To this end, tissue sections of breast cancer (n = 40), pre-invasive ductal carcinoma in situ (DCIS; n = 8), fibroadenoma (n = 40), radial scar (n = 6) and normal breast tissue (n = 40) were used to quantify (1) endothelial VEGFR-2, (2) endothelial α _v ß ₃ integrin and (3) total α _v ß ₃ integrin expression, as well as (4) the vascular area fraction. Sensitivity and specificity to differentiate benign from malignant lesions were calculated for each marker by receiver operating characteristics (ROC) analyses. Whereas vessel density, as commonly used, did not significantly differ between benign and malignant lesions (AUROC: 0.54), VEGFR-2 and α _v ß ₃ integrin levels were gradually up-regulated in carcinoma versus fibroadenoma versus healthy tissue. The highest diagnostic accuracy for differentiating carcinoma from fibroadenoma was found for total α _v ß ₃ integrin expression (AUROC: 0.76), followed by VEGFR-2 (AUROC: 0.71) and endothelial α _v ß ₃ integrin expression (AUROC: 0.68). In conclusion, total α _v ß ₃ integrin expression is the best discriminator between breast cancer, fibroadenoma and normal breast tissue. With respect to vascular targeting and molecular imaging of angiogenesis, endothelial VEGFR-2 appeared to be slightly superior to endothelial α _v ß ₃ for differentiating benign from cancerous lesions.     

Shear stress inhibition of H<Subscript>2</Subscript>O<Subscript>2</Subscript> induced p66<Superscript>Shc</Superscript> phosphorylation by ASK1–JNK inactivation in endothelium

Shear stress protects endothelium from a variety of risk factors for vascular disease. Here, we demonstrate a novel mechanism whereby shear stress inhibited reactive oxygen species (ROS)-triggered signaling cascades in endothelial cells. Stimulation of bovine aortic endothelial cells (BAECs) with H₂O₂ induced a 3.07-fold increase in p66^Shc phosphorylation. This response was fully blocked by pretreatment of cells with specific JNK but not p38 or ERK MAP kinase inhibitor. Further study showed that knocking down of apoptosis signal-regulating kinase 1 (ASK1) by siRNA transfection in cells dramatically inhibited phosphorylation of JNK and p66^Shc elicited by H₂O₂. Pre-perfusion of BAECs cultured in silastic tubes with laminar flow generated by a servo-pump system for 30 min also significantly suppressed H₂O₂-induced phosphorylation of p66^Shc. This was accompanied by quantitatively similar inhibition of ASK1 and JNK phosphorylation and activation. These results suggested that shear stress protects endothelium against oxidant stress by suppression of ASK1–JNK-mediated p66^Shc phosphorylation.     

Non-inferiority multicenter prospective randomized controlled study of rectal cancer T<Subscript>2</Subscript>–T<Subscript>3s</Subscript> (superficial) N<Subscript>0</Subscript>, M<Subscript>0</Subscript> undergoing neoadjuvant treatment and local excision (TEM) vs total mesorectal excision (TME)

Purpose

The standard treatment of rectal adenocarcinoma is total mesorectal excision (TME), in many cases requires a temporary or permanent stoma. TME is associated with high morbidity and genitourinary alterations. Transanal endoscopic microsurgery (TEM) allows access to tumors up to 20 cm from the anal verge, achieves minimal postoperative morbidity and mortality rates, and does not require an ostomy. The treatment of T2, N0, and M0 cancers remains controversial. Preoperative chemoradiotherapy (CRT) in association with TEM reduces local recurrence and increases survival. The TAU-TEM study aims to demonstrate the non-inferiority of the oncological outcomes and the improvement in morbidity and quality of life achieved with TEM compared with TME.

Methods

Prospective, multicenter, randomized controlled non-inferiority trial includes patients with rectal adenocarcinoma less than 10 cm from the anal verge and up to 4 cm in size, staged as T2 or T3-superficial N0-M0. Patients will be randomized to two areas: CRT plus TEM or radical surgery (TME). Postoperative morbidity and mortality will be recorded and patients will complete the quality of life questionnaires before the start of treatment, after CRT in the CRT/TEM arm, and 6 months after surgery in both arms. The estimated sample size for the study is 173 patients. Patients will attend follow-up controls for local and systemic relapse.

Conclusions

This study aims to demonstrate the preservation of the rectum after preoperative CRT and TEM in rectal cancer stages T2–3s, N0, M0 and to determine the ability of this strategy to avoid the need for radical surgery (TME).

Trial registration

ClinicalTrials.gov identifier: NCT01308190. Número de registro del Comité de Etica e Investigación Clínica (CEIC) del Hospital universitario Parc Taulí: TAU-TEM-2009-01.

     

Prevalence of Anticardiolipin and Anti-β<Subscript>2</Subscript>-Glycoprotein I Antibodies in Celiac Disease

The aim of this study was to evaluate the prevalence of anticardiolipin antibodies (aCL) and anti-β₂-glycoprotein I antibodies (aβ2GPI) in patients with celiac disease and to analyze the clinical features of antiphospholipid syndrome in these patients. We conducted a prospective case-control study based on the evaluation of IgG, IgM and IgA aCL, and IgG and IgA aβ2GPI in celiac disease patients and in controls. All patients were asked about any occurrence of thrombotic manifestations. In addition, women were asked about pregnancy morbidity. Fifty celiac disease patients and 50 healthy controls were studied. IgM aCL were not detected in study group or in controls. IgG aCL were found in two patients and in one control. IgA aCL were significantly more frequent in celiac disease patients compared with controls (13/50 (26%) vs. 2/50 (4%), p=0.004, OR [95% CI]=9.09 [1.81–50]). There was no statistically significant difference for the prevalence of IgG and IgA aβ2GPI between patients and controls. Clinical features of antiphospholipid syndrome were noted in two patients with negative antibodies. Prevalence of IgM and IgG aCL and of aβ2GPI were not increased in celiac disease. IgA aCL were more frequently detected in celiac disease. However, no clinical features of antiphospholipid syndrome were noted.     

Effect of β-Blockers on β<Subscript>3</Subscript>-Adrenoceptor Expression in Chronic Heart Failure

Objectives To investigate the expression of β₃-adrenoceptors in rats with chronic heart failure, and to explore the effect of β-blockers on β₃-adrenoceptor expression. Materials and methods Thirty-two male Wistar rats were divided into Sham (n = 10) and heart failure (n = 22) groups. The heart failure group was treated with normal saline (Heart Failure Control, n = 6), Metoprolol (n = 8) or Carvedilol (n = 8) for 3 months. Results The left ventricular end systolic pressure (LVESP) and the absolute values of maximal rate of rise and fall of left ventricular pressure (±dP/dt max) in the heart failure group were lower than in the Sham group (P < 0.01), whereas the left ventricular end diastolic pressure (LVEDP) was higher (P < 0.01). The LVESP and dP/dtmax in the Carvedilol group were higher than the Metoprolol group whereas LVEDP was lower (P < 0.01). The left ventricular mass index (LVMI) in the Carvedilol group was less than the Metoprolol and Heart Failure Control groups (P < 0.01). The level of β₃-adrenoceptor expression in the study groups was significantly higher than the Sham group (P < 0.01). β₃-adrenoceptor expression in the Carvedilol group was lower than the Heart Failure Control and Metoprolol groups (P < 0.01). Conclusion β₃-adrenoceptor expression is increased in the failing ventricles in rats. Carvedilol is more effective than Metoprolol for improving the hemodynamics and in attenuating ventricular remodeling after heart failure. Carvedilol, rather than Metoprolol, diminishes β₃-adrenoceptor expression in the failing ventricles.     

CHA<Subscript>2</Subscript>DS<Subscript>2</Subscript>–VASc score predicts short- and long-term outcomes in patients with acute ischemic stroke treated with intravenous thrombolysis

The CHA₂DS₂–VASc score is a validated tool to assess the thromboembolic risk in patients with atrial fibrillation. Pre-stroke CHA₂DS₂–VASc score may predict outcome in patients with acute ischemic stroke (AIS) without atrial fibrillation. The aim of this study was to investigate if the pre-stroke CHA₂DS₂–VASc score is able to predict short- and long-term outcomes in AIS patients treated with intravenous thrombolysis (IVT). The study group consisted of 256 consecutive patients admitted to the Udine University Hospital with AIS and underwent IVT between January 2015 to March 2017. The pre-stroke CHA₂DS₂–VASc score for each patient was calculated from the collected baseline data. Patients were classified into three groups according to their pre-stroke CHA₂DS₂–VASc score: a score of 0 of 1, a score of 2 or 3 and a score above 3. Primary outcome measures were: rate of favorable outcome at 90-days and at 1-year, and mortality at 90-days and at 1-year. Data on functional outcome and mortality 1 year after stroke were collected in 165 patients (65% of the entire sample). Favorable outcome was defined as a modified Rankin Scale score?≤?2. Compared with the CHA₂DS₂–VASc score 0–1 group, patients with higher CHA₂DS₂–VASc scores had a worse outcome and a higher mortality 3 months and 1 year after stroke. The diagnostic performance of the CHA₂DS₂–VASc score as judged with AUC-ROC was 0.70 (95% CI, 0.64–0.76; p?<?0.001) for favorable outcome at 90-days, 0.78 (95% CI, 0.71–0.85; p?<?0.001) for favorable outcome at 1-year, 0.71 (95% CI 0.61–0.79) for mortality at 90-days, 0.73 (95% CI 0.64–0.80; p?<?0.001) for mortality at 1-year. Pre-stroke CHA₂DS_2–VASc score represents a good predictor for short- and long-term outcomes in AIS patients treated with IVT.     

Heterophilic interactions between cell adhesion molecule L1 and α<Subscript>v</Subscript> β<Subscript>3</Subscript>-integrin induce HUVEC process extension <Emphasis Type="Italic">in vitro</Emphasis> and angiogenesis <Emphasis Type="Italic">in vivo</Emphasis>

Cell adhesion molecule L1 was implicated in angiogenic processes, tumor formation and metastasis. Here, we provide evidence that the sixth Ig-like domain of L1 (L1Ig6) interacts with _{v 3} to induce process extension of human umbilical vein endothelial cells (HUVECs) in vitro and angiogenesis in vivo. HUVECs formed network-like structures on full-length L1 or L1Ig6 substrates comparable to structures found on matrigel. In the presence of mab _{v 3} or cyclic RGD, apoptosis was induced. In fibrin matrices where L1Ig6 was covalently incorporated, HUVECs formed multicellular and hollow processes through interactions between cell-surface _{v 3} and RGD-sites of matrix-immobilized L1Ig6. No such processes were induced by L1Ig6 having non-functional RDG-sites, or in the presence of mab _{v 3} or cyclic RGD. In those matrices, increased apoptosis was found. Co-immunoprecipitation of L1 or L1Ig6 with _{v 3} suggests close interactions. Furthermore, L1Ig6 stimulated HUVECs showed increased tyrosine phosphorylation of _{v 3} and phosphorylation of MAP kinases (ERK1 and ERK2) but not AKT indicating specific activation of _v and _{v 3} followed by activation of downstream kinases. Application of L1Ig6-modified fibrin matrices on CAMs induced 50–60% increased _v and _v3 protein expression and in vivo angiogenesis indicated by ~50% increased mean vascular length density. The results demonstrate angiogenic potential of L1Ig6 involving ligation and activation of _v3     

Anti-β<Subscript>2</Subscript>-glycoprotein I in Sjogren’s syndrome is associated with parkinsonism

The nervous system may be involved in up to 30% of patients with Sjogren’s syndrome (SS). We describe three patients with Sjogren’s syndrome and a concomitant parkinsonian syndrome. Elevated titers of anti-β₂-glycoprotein I IgG were found in the serum of all three patients. This autoantibody is strongly associated with anticardiolipin (aCL) antibodies, antiphospholipid syndrome (APS), and thromboembolic phenomena, but its role in the pathogenesis of the parkinsonian disorder in SS is unclear. These patients may present a subtype of SS patients in which the presence of aCL antibodies is associated with central nervous system involvement predominantly in the basal ganglia. Sharon Hassin-Baer and Levy Yair contributed equally to this work.     

Fucosylation of serum α<Subscript>1</Subscript>-acid glycoprotein in rheumatoid arthritis patients treated with infliximab

To analyze fucosylation of α₁-acid glycoprotein (AGP) and to identify relations between AGP fucosylation and clinical and biochemical indices of disease activity in patients with rheumatoid arthritis (RA) treated with monoclonal antitumor necrosis factor (TNF) antibody infliximab, we examined 22 patients with RA who underwent a 54-week treatment with infliximab according to ATTRACT protocol. Blood samples were collected at baseline and before every infusion of infliximab. AGP fucosylation was measured using lectin-binding enzyme-linked immunosorbent assay utilizing fucose-specific lectin Aleuria aurantia (AAL). Moreover, the clinical status/activity, erythrocyte sedimentation rate, serum C-reactive protein (CRP), antitrypsin, α₁-antichymotrypsin, AGP reactivity with concanavalin A, serum C3 and C4 complement components, and serum concentrations of TNF and soluble TNF type 1 and type 2 receptors were determined. In most patients, the fucosylation of AGP decreased rapidly after first infusion of infliximab and remained low during the 54-week therapy (p < 0.001). The decrease in AGP affinity to AAL closely followed changes in clinical and laboratory activity of RA and correlated with pretreatment concentrations of CRP (r = 0.4986, p < 0.05) and TNF (r = 0.5181, p < 0.05). The fucosylation of AGP can be a part of a negative feedback loop regulating migration of inflammatory cells and collagenase-3 activity in RA. The decrease in AGP fucosylation accompanied by improvement in clinical and biochemical parameters of RA could possibly reflect reduced migration of inflammatory cells to inflamed joints and AGP-mediated inhibition of collagenase-3 as a response to infliximab treatment.     

Clinical Efficacy of Inhaler Devices Containing β<Subscript>2</Subscript>-Agonist Bronchodilators in the Treatment of Asthma

Background: A number of different inhaler devices are available to deliver β₂-adrenoceptor agonist (β₂-agonist) bronchodilators in asthma. These include hydrofluoroalkane or chlorofluorocarbon (CFC)-free propelled pressurized metered-dose inhalers (pMDIs), many dry powder inhalers and breath-actuated inhalers. Objective: To determine the clinical efficacy of all available hand-held inhaler devices compared with the standard CFC-containing pMDI for the delivery of short-acting β₂-agonist bronchodilators in nonacute asthma in both children and adults. Methodology: A systematic review and meta-analysis was carried out of all available randomized, controlled trials (RCTs) using the standard pMDI compared with any other hand-held inhaler device, delivering short-acting β₂-agonist bronchodilators in patients with stable asthma. Results: One hundred and eighteen RCTs were included in this review. No clinical differences were found between the standard CFC-containing pMDI and 12 other hand-held inhaler devices for most outcome measures. We found no evidence of clinical differences between studies using either a 1 : 1 (pMDI: another inhaler) or a 2 : 1 dosing ratio. Conclusions: In patients with stable asthma, short-acting β₂-agonist bronchodilators in standard CFC-pMDIs are as effective as any other hand-held inhaler device; therefore the cheapest available device that the patient is able to use should always be considered. Pharmaceutical companies should in future submit to regulatory authorities clinical outcome data (as opposed to in vitro data) in support of any dosing schedules greater than 1 : 1 when compared with the standard pMDI. Clinical effectiveness studies that use an intention-to-treat analysis and report more patient-centered outcomes are required.     

Contribution of <Emphasis Type="Italic">I</Emphasis><Subscript>Kr</Subscript> and <Emphasis Type="Italic">I</Emphasis><Subscript>K1</Subscript> to ventricular repolarization in canine and human myocytes: is there any influence of action potential duration?

Background  The aim of the present work was to study the profile of the rapid delayed rectifier potassium current (I _Kr) and the inward rectifier potassium current (I _K1) during ventricular repolarization as a function of action potential duration and rate of repolarization. Methods  Whole cell configuration of the patch clamp technique was used to monitor I _Kr and I _K1 during the action potential plateau and terminal repolarization. Action potentials recorded at various cycle lengths (0.4–5 s) and repolarizing voltage ramps having various slopes (0.5–3 V/s) were used as command signals. I _Kr and I _K1 were identified as difference currents dissected by E-4031 and BaCl₂, respectively. Results  Neither peak amplitudes nor mean values of I _Kr and I _K1 recorded during the plateau of canine action potentials were influenced by action potential duration. The membrane potential where I _Kr and I _K1 peaked during the terminal repolarization was also independent of action potential duration. Similar results were obtained in undiseased human ventricular myocytes, and also in canine cells when I _Kr and I _K1 were evoked using repolarizing voltage ramps of various slopes. Action potential voltage clamp experiments revealed that the peak values of I _Kr, I _K1, and net outward current during the terminal repolarization were independent of the pacing cycle length within the range of 0.4 and 5 s. Conclusions  The results indicate that action potential configuration fails to influence the amplitude of I _Kr and I _K1 during the ventricular action potential in dogs and humans, suggesting that rate-dependent changes in action potential duration are not likely related to rate-dependent alterations in I _Kr or I _K1 kinetics in these species. Returned for 1. Revision: 5 February 2008 1. Revision received: 11 April 2008 Returned for 2. Revision: 14 May 2008 2. Revision received: 15 May 2008