Influence of O-H···Pt interactions on photoluminescent response in the (Bu4N)2{[Pt(bph)(CN)2][phenylene-1,4-diresorcinol]} framework.

Tunable photoluminescence (PL) is one of the hot topics in current materials science, and research performed on the molecular phases is at the forefront of this field. We present the new (Et4N)2[PtII(bph)(CN)2]·rez3·1/3H2O (Pt2rez3) (bph = biphenyl-2,2'-diyl; rez3 = 3,3",5,5"-tetrahydroxy-1,1':4',1"-terphenyl, phenylene-1,4-diresorcinol coformer, a linear quaternary hydrogen bond donor) co-crystal salt based on the recently appointed promising [PtII(bph)(CN)2]2- luminophore. Within the extended hydrogen-bonded subnetwork [PtII(bph)(CN)2]2- complexes and rez3 coformer molecules form two types of contacts: the  rez3O-H···Ncomplex ones in the equatorial plane of the complex and non-typical rez3O-H···Pt ones along its axial direction. The combined structural, PL, and DFT approach distinguished the rez3O-H···Pt synthons to promote the noticeable uniform redshift of bph ligand centered (LC) emission compared to the LC emission of (Et4N)2[PtII(bph)(CN)2]·H2O (Pt2) precursor owing to the direct interference of the phenol group into the PtII-bph orbital system via altering the CT processes. The high-resolution emission spectra for Pt2 and Pt2rez3 were successfully reproduced at 77 K by using the Franck-Cordon expressions. The possibility to tune PL properties along the plausible continuum of rez3O-H···Pt synthons is indicated, considering various scenarios of molecular occupation of the space above and below the complex plane.

Binding of anionic Pt(ii) complexes in a dedicated organic matrix: towards new binary crystalline composites.

The square-planar [PtX4]2- complexes (X = Cl, Br) were successfully incorporated into preprogrammed hybrid organic-inorganic systems, exploiting their expected strong anion-π interactions with π-acidic hexaazaphenylenehexacarbonitrile, HAT(CN)6. The formation and properties of {[PtCl4]2-; HAT(CN)6} aggregates in MeCN solution were evaluated based on their UV-Vis spectra to reveal the approximate binding constant KCT = 7.9(2) × 102 dm3 mol-1, molar absorption coefficient εCT = 1.47(2) × 103 dm3 mol-1 cm-1, extent of electronic coupling HCT = 2.18 × 103 cm-1, and electron delocalization α2 = 1.75 × 10-2 (α = 0.13). Strong [PtCl4]2-HAT(CN)6 interactions in such adducts were also confirmed by the distinct shifts |Δδiso| = 0.4 ppm of 13C NMR peaks, when compared to the π-acid alone. The crystal structures of the resulting (PPh4)2[PtX4][HAT(CN)6]·3MeCN (1-Cl- and 1-Br-) solids are isomorphous with (PPh4)2[Pt(CN)4][HAT(CN)6]·3MeCN (1-CN-) reported by us previously. The halogenoplatinates occupy exactly the same nodes in the supramolecular network as cyanoplatinate, forming stacked {[PtX4]2-;HAT(CN)6}∞ columns that are stabilized by [PPh4]+ cations. However, contrary to the pale yellow coloration of the [Pt(CN)4]2-/HAT(CN)6 systems, currently the dark violet or dark green coloration of solutions and crystalline phases were noted owing to the intense absorption in almost the whole visible region. DFT calculations reproduced the UV-Vis spectroscopic characteristics and linked it with the enhanced charge-transfer of the [PtX4]2-HAT(CN)6 electronic interactions. Based on the isomorphism of all three (PPh4)2[PtL4][HAT(CN)6]·3MeCN congeners we constructed and characterized the unprecedented, first ever anion-π-based binary rod-like core-shell crystalline composites 1-X@1-CN.

Association of norepinephrine transporter methylation with in vivo NET expression and hyperactivity-impulsivity symptoms in ADHD measured with PET.

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with a robust genetic influence. The norepinephrine transporter (NET) is of particular interest as it is one of the main targets in treatment of the disorder. As ADHD is a complex and polygenetic condition, the possible regulation by epigenetic processes has received increased attention. We sought to determine possible differences in NET promoter DNA methylation between patients with ADHD and healthy controls. DNA methylation levels in the promoter region of the NET were determined in 23 adult patients with ADHD and 23 healthy controls. A subgroup of 18 patients with ADHD and 18 healthy controls underwent positron emission tomography (PET) with the radioligand (S,S)-[18F]FMeNER-D2 to quantify the NET in several brain areas in vivo. Analyses revealed significant differences in NET methylation levels at several cytosine-phosphate-guanine (CpG) sites between groups. A defined segment of the NET promoter ("region 1") was hypermethylated in patients in comparison with controls. In ADHD patients, a negative correlation between methylation of a CpG site in this region and NET distribution in the thalamus, locus coeruleus, and the raphe nuclei was detected. Furthermore, methylation of several sites in region 1 was negatively associated with the severity of hyperactivity-impulsivity symptoms. Our results point to an epigenetic dysregulation in ADHD, possibly due to a compensatory mechanisms or additional factors involved in transcriptional processing.

Examiner training: A study of examiners making sense of norm-referenced feedback.

Purpose: Examiner training has an inconsistent impact on subsequent performance. To understand this variation, we explored how examiners think about changing the way they assess. Method: We provided comparative data to 17 experienced examiners about their assessments, captured their sense-making processes using a modified think-aloud protocol, and identified patterns by inductive thematic analysis. Results: We observed five sense-making processes: (1) testing personal relevance (2) interpretation (3) attribution (4) considering the need for change, and (5) considering the nature of change. Three observed meta-themes describe the manner of examiners' thinking: Guarded curiosity - where examiners expressed curiosity over how their judgments compared with others', but they also expressed guardedness about the relevance of the comparisons; Dysfunctional assimilation - where examiners' interpretation and attribution exhibited cognitive anchoring, personalization, and affective bias; Moderated conservatism - where examiners expressed openness to change, but also loyalty to their judgment-framing values and aphorisms. Conclusions: Our examiners engaged in complex processes as they considered changing their assessments. The 'stabilising' mechanisms some used resembled learners assimilating educational feedback. If these are typical examiner responses, they may well explain the variable impact of examiner training, and have significant implications for the pursuit of meaningful and defensible judgment-based assessment.

The influence of the rs6295 gene polymorphism on serotonin-1A receptor distribution investigated with PET in patients with major depression applying machine learning.

Major depressive disorder (MDD) is the most common neuropsychiatric disease and despite extensive research, its genetic substrate is still not sufficiently understood. The common polymorphism rs6295 of the serotonin-1A receptor gene (HTR1A) is affecting the transcriptional regulation of the 5-HT1A receptor and has been closely linked to MDD. Here, we used positron emission tomography (PET) exploiting advances in data mining and statistics by using machine learning in 62 healthy subjects and 19 patients with MDD, which were scanned with PET using the radioligand [carbonyl-11C]WAY-100635. All the subjects were genotyped for rs6295 and genotype was grouped in GG vs C allele carriers. Mixed model was applied in a ROI-based (region of interest) approach. ROI binding potential (BPND) was divided by dorsal raphe BPND as a specific measure to highlight rs6295 effects (BPDiv). Mixed model produced an interaction effect of ROI and genotype in the patients' group but no effects in healthy controls. Differences of BPDiv was demonstrated in seven ROIs; parahippocampus, hippocampus, fusiform gyrus, gyrus rectus, supplementary motor area, inferior frontal occipital gyrus and lingual gyrus. For classification of genotype, 'RandomForest' and Support Vector Machines were used, however, no model with sufficient predictive capability could be computed. Our results are in line with preclinical data, mouse model knockout studies as well as previous clinical analyses, demonstrating the two-pronged effect of the G allele on 5-HT1A BPND for, we believe, the first time. Future endeavors should address epigenetic effects and allosteric heteroreceptor complexes. Replication in larger samples of MDD patients is necessary to substantiate our findings.

Simple and rapid quantification of serotonin transporter binding using [11C]DASB bolus plus constant infusion.

INTRODUCTION: In-vivo quantification of serotonin transporters (SERT) in human brain has been a mainstay of molecular imaging in the field of neuropsychiatric disorders and helped to explore the underpinnings of several medical conditions, therapeutic and environmental influences. The emergence of PET/MR hybrid systems and the heterogeneity of SERT binding call for the development of efficient methods making the investigation of larger or vulnerable populations with limited scanner time and simultaneous changes in molecular and functional measures possible. We propose [11C]DASB bolus plus constant infusion for these applications and validate it against standard analyses of dynamic PET data. METHODS: [11C]DASB bolus/infusion optimization was performed on data acquired after [11C]DASB bolus in 8 healthy subjects. Subsequently, 16 subjects underwent one scan using [11C]DASB bolus plus constant infusion with Kbol 160-179min and one scan after [11C]DASB bolus for inter-method reliability analysis. Arterial blood sampling and metabolite analysis were performed for all scans. Distribution volumes (VT) were obtained using Logan plots for bolus scans and ratios between tissue and plasma parent activity for bolus plus infusion scans for different time spans of the scan (VT-70 for 60-70min after start of tracer infusion, VT-90 for 75-90min, VT-120 for 100-120min) in 9 subjects. Omitting blood data, binding potentials (BPND) obtained using multilinear reference tissue modeling (MRTM2) and cerebellar gray matter as reference region were compared in 11 subjects. RESULTS: A Kbol of 160min was observed to be optimal for rapid equilibration in thalamus and striatum. VT-70 showed good intraclass correlation coefficients (ICCs) of 0.61-0.70 for thalamus, striatal regions and olfactory cortex with bias ≤5.1% compared to bolus scans. ICCs increased to 0.72-0.78 for VT-90 and 0.77-0.93 for VT-120 in these regions. BPND-90 had negligible bias ≤2.5%, low variability ≤7.9% and ICCs of 0.74-0.87; BPND-120 had ICCs of 0.73-0.90. Low-binding cortical regions and cerebellar gray matter showed a positive bias of ~8% and ICCs 0.57-0.68 at VT-90. Cortical BPND suffered from high variability and bias, best results were obtained for olfactory cortex and anterior cingulate cortex with ICC=0.74-0.75 for BPND-90. High-density regions amygdala and midbrain had a negative bias of -5.5% and -22.5% at VT-90 with ICC 0.70 and 0.63, respectively. CONCLUSIONS: We have optimized the equilibrium method with [11C]DASB bolus plus constant infusion and demonstrated good inter-method reliability with accepted standard methods and for SERT quantification using both VT and BPND in a range of different brain regions. With as little as 10-15min of scanning valid estimates of SERT VT and BPND in thalamus, amygdala, striatal and high-binding cortical regions could be obtained. Blood sampling seems vital for valid quantification of SERT in low-binding cortical regions. These methods allow the investigation of up to three subjects with a single radiosynthesis.

Association of Protein Distribution and Gene Expression Revealed by PET and Post-Mortem Quantification in the Serotonergic System of the Human Brain.

Regional differences in posttranscriptional mechanisms may influence in vivo protein densities. The association of positron emission tomography (PET) imaging data from 112 healthy controls and gene expression values from the Allen Human Brain Atlas, based on post-mortem brains, was investigated for key serotonergic proteins. PET binding values and gene expression intensities were correlated for the main inhibitory (5-HT1A) and excitatory (5-HT2A) serotonin receptor, the serotonin transporter (SERT) as well as monoamine oxidase-A (MAO-A), using Spearman's correlation coefficients (rs) in a voxel-wise and region-wise analysis. Correlations indicated a strong linear relationship between gene and protein expression for both the 5-HT1A (voxel-wise rs = 0.71; region-wise rs = 0.93) and the 5-HT2A receptor (rs = 0.66; 0.75), but only a weak association for MAO-A (rs = 0.26; 0.66) and no clear correlation for SERT (rs = 0.17; 0.29). Additionally, region-wise correlations were performed using mRNA expression from the HBT, yielding comparable results (5-HT1Ars = 0.82; 5-HT2Ars = 0.88; MAO-A rs = 0.50; SERT rs = -0.01). The SERT and MAO-A appear to be regulated in a region-specific manner across the whole brain. In contrast, the serotonin-1A and -2A receptors are presumably targeted by common posttranscriptional processes similar in all brain areas suggesting the applicability of mRNA expression as surrogate parameter for density of these proteins.

Development and validation of a trustworthy multisource feedback instrument to support nurse appraisals.

INTRODUCTION: Nurse appraisal is well established in the Western world because of its obvious educational advantages. Appraisal works best with many sources of information on performance. Multisource feedback (MSF) is widely used in business and in other clinical disciplines to provide such information. It has also been incorporated into nursing appraisals, but, so far, none of the instruments in use for nurses has been validated. We set out to develop an instrument aligned with the UK Knowledge and Skills Framework (KSF) and to evaluate its reliability and feasibility across a wide hospital-based nursing population. METHODS: The KSF framework provided a content template. Focus groups developed an instrument based on consensus. The instrument was administered to all the nursing staff in 2 large NHS hospitals forming a single trust in London, England. We used generalizability analysis to estimate reliability, response rates and unstructured interviews to evaluate feasibility, and factor structure and correlation studies to evaluate validity. RESULTS: On a voluntary basis the response rate was moderate (60%). A failure to engage with information technology and employment-related concerns were commonly cited as reasons for not responding. In this population, 11 responses provided a profile with sufficient reliability to inform appraisal (G = 0.7). Performance on the instrument was closely and significantly correlated with performance on a KSF questionnaire. DISCUSSION: This is the first contemporary psychometric evaluation of an MSF instrument for nurses. MSF appears to be as valid and reliable as an assessment method to inform appraisal in nurses as it is in other health professional groups.

Addressing learner disorientation: give them a roadmap.

This article describes the problem of disorientation in students as they become doctors. Disorientation arises because students have a poor or inaccurate understanding of what they are training to become. If they do not know what they are becoming it is hard for them to prioritise and contextualise their learning, to make sense of information about where they are now (assessment and feedback) or to determine the steps they need to take to develop (formative feedback and "feedforward"). It is also a barrier to the early development of professional identity. Using the analogy of a map, the paper describes the idea of a curriculum that is articulated as a developmental journey--a "roadmap curriculum". This is not incompatible with a competency-based curriculum, and certainly requires the same integration of knowledge, skills and attitudes. However, the semantic essence of a roadmap curriculum is fundamentally different; it must describe the pathway or pathways of development toward being a doctor in ways that are both authentic to qualified doctors and meaningful to learners. Examples from within and outside medicine are cited. Potential advantages and implications of this kind of curricular reform are discussed.

Implementing workplace-based assessment across the medical specialties in the United Kingdom.

OBJECTIVES: To evaluate the reliability and feasibility of assessing the performance of medical specialist registrars (SpRs) using three methods: the mini-clinical evaluation exercise (mini-CEX), directly observed procedural skills (DOPS) and multi-source feedback (MSF) to help inform annual decisions about the outcome of SpR training. METHODS: We conducted a feasibility study and generalisability analysis based on the application of these assessment methods and the resulting data. A total of 230 SpRs (from 17 specialties) in 58 UK hospitals took part from 2003 to 2004. Main outcome measures included: time taken for each assessment, and variance component analysis of mean scores and derivation of 95% confidence intervals for individual doctors' scores based on the standard error of measurement. Responses to direct questions on questionnaires were analysed, as were the themes emerging from open-comment responses. RESULTS: The methods can provide reliable scores with appropriate sampling. In our sample, all trainees who completed the number of assessments recommended by the Royal Colleges of Physicians had scores that were 95% certain to be better than unsatisfactory. The mean time taken to complete the mini-CEX (including feedback) was 25 minutes. The DOPS required the duration of the procedure being assessed plus an additional third of this time for feedback. The mean time required for each rater to complete his or her MSF form was 6 minutes. CONCLUSIONS: This is the first attempt to evaluate the use of comprehensive workplace assessment across the medical specialties in the UK. The methods are feasible to conduct and can make reliable distinctions between doctors' performances. With adaptation, they may be appropriate for assessing the workplace performance of other grades and specialties of doctor. This may be helpful in informing foundation assessment.

Improving the quality of outpatient clinic letters using the Sheffield Assessment Instrument for Letters (SAIL).

AIM: To improve the quality of outpatient letters used as communication between hospital and primary care doctors. METHODS: On 2 separate occasions, 15 unselected outpatient letters written by each of 7 hospital practitioners were rated by another hospital doctor and a general practitioner (GP) using the Sheffield Assessment Instrument for Letters (SAIL). Individualised feedback was provided to participants following the rating of the first set of letters. The audit cycle was completed 3 months later without forewarning by repeat assessment by the same hospital and GP assessors using the SAIL tool to see if there was any improvement in correspondence. SETTING: Single centre: general paediatric outpatient department in a large district general hospital. RESULTS: All 7 doctors available for reassessment completed the audit loop, each providing 15 outpatient letters per assessment. The mean of the quality scores, derived for each letter from the summation of a 20-point checklist and a global score, improved from 23.3 (95% CI 22.1-24.4) to 26.6 (95% CI 25.8-27.4) (P = 0.001). CONCLUSIONS: The SAIL provides a feasible and reliable method of assessing the quality and content of outpatient clinic letters. This study demonstrates that it can also provide feedback with a powerful educational impact. This approach holds real potential for appraisal and revalidation, providing an effective means for the quality improvement required by clinical governance.

Value of three-dimensional US for optimizing guidance for ablating focal liver tumors.

PURPOSE: To determine if three-dimensional ultrasound (3D US), by nature of its ability to simultaneously evaluate structures in three orthogonal planes and to study relationships of devices to tumor(s) and surrounding anatomic structures from any desired orientation, adds significant additional information to real-time 2D US used for placement of devices for ablation of focal liver tumors. MATERIALS AND METHODS: Sixteen patients underwent focal ablation of 23 liver tumors during two intraoperative cryoablation (CA) procedures, three intraoperative radiofrequency ablation (RFA) procedures, 11 percutaneous ethanol injections (PEI) procedures, and six percutaneous RFA procedures. After satisfactory placement of the ablative device(s) with 2D US guidance, 3D US was used to reevaluate adequacy to device position. Information added by 3D US and resultant alterations in device deployment were tabulated. RESULTS: 3D US added information in 20 of 22 (91%) procedures and caused the operator to readjust the number or position of ablative devices in 10 of 22 (45%) of procedures. Specifically, 3D US improved visualization and confident localization of devices in 13 of 22 (59%) procedures, detected unacceptable device placement in 10 of 22 (45%), and determined that 2D US had incorrectly predicted device orientation to a tumor in three of 22 (14%). CONCLUSIONS: Compared to conventional 2D US, 3D US provides additional relationship information for improved placement and optimal distribution of ablative agents for treatment of focal liver malignancy.

Fetal lip and primary palate: three-dimensional versus two-dimensional US.

PURPOSE: To determine if three-dimensional (3D) ultrasonography (US) improves the ability to define the location and extent of facial clefting prenatally compared with two-dimensional (2D) US. MATERIALS AND METHODS: Thirty-one fetuses suspected of having a facial cleft were examined prospectively with 2D and 3D US. Follow-up was performed in all fetuses. RESULTS: Twenty-eight fetuses had a cleft lip at birth. The location of the cleft lip was correctly identified in all fetuses with 3D US and in 26 of 28 with 2D US. Twenty-two fetuses had a cleft primary palate. Nineteen and nine of 22 cleft palates were identified by using 3D and 2D US, respectively. Three fetuses suspected of having a facial cleft at 2D US had a normal palate at 3D US and at birth. CONCLUSION: Three-dimensional US is useful to identify the location and extent of facial clefting. The advantages of 3D US are the following: (a) The face may be viewed in a standard orientation, (b) the defect may be viewed systematically by using an interactive display, and (c) the rendered image provides landmarks for the planar images. Patient decisions may be affected, since they can view the abnormality on a recognizable 3D rendered image.

Three-dimensional ultrasonographic imaging of the neonatal brain in high-risk neonates: preliminary study.

The aim of this investigation was to compare the utility of three-dimensional ultrasonography versus two-dimensional ultrasonography in imaging the neonatal brain. Thirty patients in the neonatal intensive care unit underwent two-dimensional and three-dimensional ultrasonography. The resultant two- and three-dimensional images recorded on film and three-dimensional volumes (reviewed on a workstation) were evaluated independently. Comparable numbers of normal and abnormal studies were diagnosed by each modality. Axial images were considered useful in approximately 50% of three-dimensional cases. Image quality, overall and in the far-field, was rated higher on two-dimensional images. Three-dimensional sonographic acquisition time in the neonatal intensive care unit (1.7 min+/-0.7 standard deviation) was significantly shorter than that for two-dimensional sonography (9.0+/-4.5 min). The total time for evaluation on the three-dimensional workstation (4.4+/-1.1 min) was significantly less than that for two-dimensional images on film (10.6+/-4.7 min). In conclusion, three-dimensional ultrasonography is a promising, diagnostically accurate, and efficient imaging tool for evaluation of the neonatal brain; however, visualization must improve before it can replace two-dimensional ultrasonography.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures.

PURPOSE: To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US. RESULTS: 3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001). CONCLUSION: 3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.

Adjunctive 3D US for achieving portal vein access during transjugular intrahepatic portosystemic shunt procedures.

PURPOSE: To evaluate the usefulness of information provided by three-dimensional ultrasound (3D US) and to determine whether 3D US decreased the number of passes required to obtain portal vein (PV) access during creation of transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS: Intermittent 3D US volume acquisitions were obtained during creation of TIPS in 20 patients. Useful information provided by 3D US was tabulated. The number of passes required to achieve PV access was recorded and results were compared retrospectively to 25 patients who underwent TIPS without 3D US. RESULTS: 3D US documented that the operator's opinion of which hepatic vein had been selected was incorrect in nine patients (45%), detected unfavorable PV anatomy that required modification of equipment or technique in seven patients (35%), permitted estimation of the trajectory required to access the targeted PV in all patients (100%), assisted in selecting the optimal point along the hepatic vein for origination of the needle pass in 11 patients (55%), allowed avoidance of a large hepatocellular carcinoma in one patient (5%), and confirmed that access into the main PV was intrahepatic in four patients (20%). The mean number of needle passes decreased from 10.4 in the historic control group to 4.6 in the 3D US group (P = .0001). CONCLUSION: 3D US provided imaging information that detected technical errors and altered anatomy, and provided positional and directional information to significantly improve needle pass efficiency.

Interaction between neutral endopeptidase and angiotensin converting enzyme inhibition in rats with myocardial infarction: effects on cardiac hypertrophy and angiotensin and bradykinin peptide levels.

Combined inhibition of neutral endopeptidase 24.11 (NEP) and angiotensin converting enzyme (ACE) is a candidate therapy for hypertension and cardiac failure. Given that NEP and ACE metabolize angiotensin (Ang) and bradykinin (BK) peptides, we investigated the effects of NEP inhibition and combined NEP and ACE inhibition on Ang and BK levels in rats with myocardial infarction. We administered the NEP inhibitor ecadotril (0, 0.1, 1, 10, and 100 mg/kg/day), either alone or together with the ACE inhibitor perindopril (0.2 mg/kg/day) by 12-hourly gavage from day 2 to 28 after infarction. Ecadotril increased urine cyclic GMP and BK-(1-9) excretion. Perindopril potentiated the effect of ecadotril on urine cyclic GMP excretion. Neither perindopril nor ecadotril reduced cardiac hypertrophy when administered separately, whereas the combination of perindopril and 10 or 100 mg/kg/day ecadotril reduced heart weight/body weight ratio by 10%. Administration of ecadotril to perindopril-treated rats decreased plasma Ang-(1-7) levels, increased cardiac BK-(1-9) levels, and increased Ang II levels in plasma, kidney, aorta, and lung. These data demonstrate interactions between the effects of NEP and ACE inhibition on remodeling of the infarcted heart and on Ang and BK peptide levels. Whereas increased cardiac BK-(1-9) levels may contribute to the reduction of cardiac hypertrophy, the reduction in plasma Ang-(1-7) levels and increase in Ang II levels in plasma and tissues may compromise the therapeutic effects of combined NEP/ACE inhibition.

Effects of neutral endopeptidase inhibition and combined angiotensin converting enzyme and neutral endopeptidase inhibition on angiotensin and bradykinin peptides in rats.

The combination of neutral endopeptidase 24.11 (NEP) and angiotensin converting enzyme (ACE) inhibition is a candidate therapy for hypertension and cardiac failure. Given that NEP and ACE metabolize angiotensin (Ang) and bradykinin (BK) peptides, we investigated the effects of NEP inhibition and combined NEP and ACE inhibition on the levels of these peptides. We administered the NEP inhibitor ecadotril (0, 0.1, 1, 10, 100 mg/kg per day), either alone or together with the ACE inhibitor perindopril (0.2 mg/kg per day), to rats by 12 hourly gavage for 7 days. Ecadotril produced diuresis, natriuresis, increased urine cyclic guanosine monophosphate and BK-(1-9) levels, increased Ang II and Ang I levels in plasma, and increased Ang I levels in heart. Perindopril reduced Ang II levels in kidney, and increased BK-(1-9) levels in blood, kidney and aorta. Combined NEP/ACE inhibition produced the summation of these effects of separate NEP and ACE inhibition. In addition, perindopril potentiated the ecadotril-mediated diuresis, natriuresis and decrease in urine BK-(1-7)/BK-(1-9) ratio, which is an index of BK-(1-9) metabolism. Moreover, combined NEP/ACE inhibition increased Ang II levels in plasma and lung. These data indicate that summation of the effects of separate NEP and ACE inhibition provides the basis for the therapeutic efficacy of their combination. Whereas potentiation by perindopril of the diuretic and natriuretic effects of ecadotril may contribute to the therapeutic effects, increased Ang II levels in plasma and lung may compromise the therapeutic effects of combined NEP/ACE inhibition.

Marked difference between angiotensin-converting enzyme and neutral endopeptidase inhibition in vivo by a dual inhibitor of both enzymes.

Dual inhibition of neutral endopeptidase 24.11 (NEP) and angiotensin-converting enzyme (ACE) offers the potential for improved therapy of hypertension and cardiac failure. S 21402-1 [(2S)-2-[(2S,3R)-2-thiomethyl-3-phenylbutanamido] propionic acid] is a sulfhydryl-containing potent inhibitor of both NEP (Ki = 1.7 nM) and ACE (Ki = 4.5 nM). S 21402-1 and the sulfhydryl-containing ACE inhibitor captopril were administered to rats by intraperitoneal injection (0, 0.3, 3, 30, 300 mg/kg). Urine was collected for 4 h; then plasma and kidneys were collected. The difference in NEP and ACE inhibition by S 21402-1 in vivo was greater than 1000-fold. All doses of S 21402-1 inhibited NEP, as indicated by plasma NEP activity, radioinhibitor binding to kidney sections, urinary sodium excretion and bradykinin-(1-7)/bradykinin-(1-9) ratio. However, only 300 mg/kg S 21402-1 inhibited ACE, as indicated by plasma angiotensin II/angiotensin I ratio, renin and angiotensinogen levels. Although S 21402-1 (30 and 300 mg/kg) inhibited renal NEP, as indicated by the bradykinin-(1-7)/bradykinin-(1-9) ratio in kidney, S 21402-1 had no effect on renal ACE, as indicated by the angiotensin II/angiotensin I ratio in kidney. Moreover, captopril was greater than 10-fold more potent than S 21402-1 as an ACE inhibitor in vivo. In separate experiments, the pressor response of anesthetized rats to angiotensin I showed more rapid decay in ACE inhibition by S 21402-1 than by captopril. These studies indicated that in vivo modification of S 21402-1 caused a much greater decrease in potency of ACE inhibition than NEP inhibition. Consequently, effective ACE inhibition by S 21402-1 required doses much higher than those required for NEP inhibition.