Group IV organometallic complexes are promising systems for C-H bond activation. We are interested in the C-H bond activation of the CH2 positions of the adamantyl group, since these positions are particularly hard to activate and to functionalize. As a potential platform for activation of that important alkyl group, we consider the alkyl bonded to the cyclopentadienyl in a substituted bis-cyclopentadienyl group IV metal diphenyl complex. The mechanism proposed in the classic paper reporting such activation using Zr(IV) (Erker and Mühlenbernd, 1987) involves an η2-benzyne complex intermediate. This current work reports a computational analysis of the problem through Density Functional Theory (DFT). We found that the two-step mechanism proposed for activation of C(Me)2-Ph or tert-Bu groups using Zr(IV) is indeed confirmed by DFT and that it can be extended to Ti and Hf. We further found that the system can be successfully extended to the adamantyl group. The first step involves formation of the benzyne complex, which can also be described as a metallacyclopropene. In the second step, the cyclopentadienyl-bound alkyl is activated in the coordination sphere of the metal via proton transfer to the bound benzyne, which, if the metallacyclopropene description is chosen, resembles a σ-bond metathesis. The C-H bond activation of adamantyl through this approach is thermodynamically and kinetically feasible. Selective α-CH bond activation should be achievable with Ti (under thermodynamic control), and selective γ-CH bond activation with Zr (under kinetic or thermodynamic control).

Background: For subjects who had previous hypersensitivity (HSR) to low-osmolar contrast media (LOCM), changing contrast media is recommended. However, determining the safest alternative LOCM is uncertain. We investigated the cross-reactivity among LOCMs and the outcomes of re-exposure in patients with previous immediate HSRs. Methods: The outcomes of re-exposure were assessed in the cohort with previous LOCM-associated HSR by the skin testing results and the presence of a common N-(2,3-dihydropoxypropyl) carbamoyl side chain. Results: Among 431 patients with previous HSR who underwent 482 skin tests, 250 cases (51.9%) showed positivity to intradermal tests, which was positively associated with the severity of HSR. The cross-reactivity among LOCMs was higher between LOCMs sharing common side chain compared to those not sharing (21.5% vs. 13.3%, P = .008). The recurrent HSRs was significantly reduced from 46.6% on re-exposure to culprit LOCM to 12.3% with changing LOCM based on the skin test results (P = .004). The overall recurrence rate was not further reduced when the LOCM was changed based on presence or absence of common side chain (15.1% vs. 11.8%, P = .428). However, for those who had severe index HSRs, skin test non-reactive LOCMs exposures, without the common side chain, resulted in a significant reduction in recurrent HSRs compared to LOCMs with the common side chain (24.0% vs. 7.8%, P = .049). Conclusion: In patients who experienced a severe index HSR to LOCM, avoidance of re-exposure to LOCMs with a common side chain or a positive skin test result is safer.

Background: Effects of soy-containing infant formulas on the thyroid gland is not clear We aimed to evaluate the effects of infant formulas with different quantities of soy content on the functional and histopathological characteristics of the thyroid gland. Method: Twenty-eight female Sprague-Dawley rats were divided into four groups. Group 1 was fed with standard pellet rat food (8g/day); Group 2 soy-free infant formula (8g/day); Group 3 low-dose (1.12g/100ml) soy-containing formula (8g/day), and Group 4 high-dose (2.64g/100ml) soy-containing formula (8g/day). Blood samples were collected from the subjects on day 0, 30, 60, and 90 to evaluate thyroid functions. All subjects were sacrificed on day 90. Thyroid glands were excised and examined histopathologically. Results: Serum levels of free T3, free T4, TSH, anti TPO, and anti TG were significantly higher in Group 4 compared to other groups (p<0.001, p<0.01,p<0.001,p=0.002). No differences were found in the histopathological findings between the groups. Conclusion: Infant formulas with high soy content induce hyperthyroidism with high TSH levels. High levels of anti TPO and anti TG suggest that observed changes might have occurred via inflammatory mechanism.

Background: Several medications may worsen heart failure (HF), and they are considered as potentially inappropriate medications for patients with heart failure (PIMHF). No studies have reported the prevalence of PIMHF use and its associated factors in Thai HF patients. Objective: To determine the prevalence of PIMHF use and identify the factors associated with PIMHF use. Materials and Methods: A cross-sectional analytical study was conducted using data on HF patients obtained from the electronic medical databases (EMD) of two hospitals, including a secondary- and a tertiary-care hospital. Data collected included demographics, diagnoses, and medication items prescribed during 2016–2019. The prevalence of PIMHF use identified by the Thailand list of PIMHF was determined. Patient and clinical factors were examined for association with PIMHF use by calculating the adjusted odds ratio (aOR) and 95% confidence interval (95% CI) using a binary logistic regression analysis. Results: From the EMD, 972 and 2,888 eligible HF patients from a secondary- and a tertiary-care hospital, respectively, were included in this study. The prevalence of PIMHF use was 45.16% and 33.07% at a secondary- and a tertiary-care hospital, respectively. The PIMHF distribution appeared similar between the two study hospitals, with oral corticosteroids being the most frequently prescribed, followed by NSAIDs, COX-2 inhibitors, and thiazolidinediones. The factors associated with PIMHF use were non-cardiovascular (non-CVD) co-morbidities, including diabetes mellitus (aOR = 1.68, 95%CI = 1.42–1.99), chronic pulmonary diseases (aOR = 2.69, 95%CI = 2.07–3.48), connective tissue diseases (aOR = 7.16, 95%CI = 3.09–16.57), and cancer (aOR = 1.97, 95%CI = 1.20–3.22). Conclusion: PIMHF use was prevalent in Thai HF patients and associated with certain non-CVD co-morbidities. A careful prescription and a review of medication use should focus on HF patients with specific non-CVD co-morbidities. Keywords: Heart failure; Potentially inappropriate medications; Thailand criteria; Prevalence; Factors associated

Background: Chronic rhinosinusitis (CRS) is a heterogenous group of inflammatory sinonasal disorders with key defining symptoms, but traditionally separated into phenotypes by clinical/endoscopic findings. It is not known if the two phenotypes have differing socioeconomic, co-morbidity and lifestyle differences. Objective: This analysis of the Chronic Rhinosinusitis Epidemiology Study (CRES) database sought to analyse any key differences in the socioeconomic variables between those with CRS with nasal polyps (CRSwNPs) and those without nasal polyps (CRSsNP). We also sought to analyse differences in comorbidities, lifestyle and quality of life. Methods: Patients with a confirmed diagnosis of CRS in secondary and tertiary care outpatient settings were invited to participate in a questionnaire based case-control study. Variables included demographics, comorbidities, socioeconomic factors, lifestyle factors and health related quality of life. Results: A total of 1204 patients’ data were analysed; 553 CRSsNP and 651 CRSwNP participants. The key socioeconomic variables did not demonstrate any notable differences, nor did lifestyle variables other than alcohol consumption being higher in those with CRSwNP (p=0.032). Aside from confirmation of asthma being more common in CRSwNP, it was notable that this group complained less of URTIs and CRSsNP participants showed evidence of lower HRQoL scores in respect of body pain (p=0.001). Conclusions: Patients with CRSwNP experience higher rates of asthma and lower rates of URTIs but otherwise do not demonstrate significant socioeconomic, comorbidity, lifestyle or quality of life issues other than for body pain and alcohol consumption.

Aim: To evaluate the accuracy in histologic grading of MRI/US image fusion biopsy by comparing conventional 12-core TRUS-Bx at radical prostatectomy specimens (RP). Methods: Consecutive patients diagnosed prostate cancer (127 with combination of both targeted biopsy (TBx) plus systematic biopsies (SBx) and separate patient cohort of 330 conventional TRUS-Bx without mpMRI) with a PSA level of <20 ng/ml prior to RP were included. The primary end point was the grade group concordance between biopsy and RP pathology according to biopsy technique. Results: Clinically significant prostate cancer detection was 51.2 % for TRUS-Bx, 49.5 % for SBx, 67% for TBx and 75.7% for TBx+SBx . Upgrading and downgrading of at least one Gleason Grade Group (GGG) was recorded in 43.3% / 6.7% patients of the TRUS-Bx, and in 20.5% / 22 % of the TBX+SBx group, respectively (all p<0.001). Concordance level was detected to be significantly higher for ISUP 1 in combined TBx + SBx method compared to conventional TRUS-Bx (61.3% vs 37.9%, p=0.014). In ISUP 1 exclusively, significant upgrading was seen in TRUS-Bx (62.1%) when compared to TBx (41.4%) and TBx+SBx (38.7%). Conclusions: MRI-targeted biopsies detected more significant PCa than TRUS-Bx but, superiority in significant cancer detection appears as a result of inadvertant selective sampling of small higher grade areas. within an otherwise low grade cancer and does not reflect accurate GGG final surgical pathology. TBx+SBx has the greatest concordance in ISUP Grade 1 with less upgrading which is utmost important for active surveillance.

Conservation genomics research often relies on accurate sex information to make inferences about species demography, dispersal, and population structure. However, field determined sex data are not always available and can be subject to human error, while laboratory sex determination is costly and often challenging for non-model species. Conservation genomics programs increasingly use reduced-representation genome sequencing to assess neutral and functional genetic diversity, population structure, gene flow and pedigrees in threatened species. Here we demonstrate that sex can be determined from reduced-representation sequencing data produced by the increasingly popular Diversity Arrays Technology sequencing workflow (DArT-seq) using a program originally designed for application to shotgun data. This program – sexassign – compares the “dosage” of sequencing reads mapping to autosomes versus the X chromosome. In the present study, sexassign accurately determined the sex of 60 field-collected Greater Stick-Nest Rat (Leporillus conditor) samples, despite the absence of an annotated reference genome for the species. This “read-dosage” approach is not only more accurate and affordable than traditional sex determination methods, but can be applied to any diploid organism with a heterogametic sex determination system – including non-model and understudied species of conservation importance – by using FASTQs generated by DArT.

Synthetic biology research and technology translation has garnered increasing interest from the governments and private investors in Asia, where the technology has great potential in driving a sustainable bio-based economy. This Perspective reviews the latest developments and future directions in synthetic biology research and applications, with highlights of important developments from Asia. It also suggests plans for more effective multi-lateral collaborations that promote a sustainable development of the field and mitigate potential biosecurity risks. Through these discussions, stakeholders from different groups, including academia, industry and government, are expectantly better positioned to contribute towards the establishment of innovation and bio-economy hubs in Asia.

Postural Orthostatic Tachycardia Syndrome (POTS) is a variant of cardiovascular autonomic disorder characterised by an excessive heart rate on standing and orthostatic intolerance. We present a rare case of a 38-year old man who underwent open repair of a thoracoabdominal aortic aneurysm (TAAA) for a chronic Stanford type B aortic dissection whose recovery was complicated by POTS. He was received blood transfusions, and was commenced on metoprolol, fludrocortisone and ivabradine with significant improvement in his symptoms.

Admixture is a fundamental evolutionary process that has influenced genetic patterns in numerous species. Maximum-likelihood approaches based on allele frequencies and linkage-disequilibrium have been extensively used to infer admixture processes from genome-wide datasets, mostly in human populations. Nevertheless, complex admixture histories, beyond one or two pulses of admixture, remain methodologically challenging to reconstruct. We develop an Approximate Bayesian Computation (ABC) framework to reconstruct highly complex admixture histories from independent genetic markers. We built the software package MetHis to simulate independent SNPs or microsatellites in a two-way admixed population for scenarios with multiple admixture pulses, monotonically decreasing or increasing recurring admixture, or combinations of these scenarios; and draw model-parameter values from prior distributions set by the user. For each simulation, MetHis calculates 24 summary-statistics describing genetic diversity and moments of individual admixture fractions. We coupled MetHis with existing machine-learning ABC algorithms and investigate the admixture history of hybrid populations. Results show that Random-Forest ABC scenario-choice can accurately distinguish most complex admixture scenarios and errors are mainly found in regions of the parameter space where scenarios are highly nested, and, thus, biologically similar. We focus on African American and Barbadian populations as case studies. We find that Neural-Network ABC posterior parameter estimation is accurate and reasonably conservative under complex admixture scenarios. For both admixed populations, we find that monotonically decreasing contributions over time, from Europe and Africa, explain the observed data more accurately than multiple admixture pulses. This approach will allow for reconstructing detailed admixture histories when maximum-likelihood methods are intractable.

Hydrological analyses and their associated uncertainties are a function of their supporting observational datasets. Publicly available large-sample hydrology datasets covering a range of climates, times, and locations can be used to support inter-watershed comparisons, pattern identification, and watershed regionalization studies. However, most of the large-sample datasets are limited to a series of basic measurements such as precipitation, air temperature, and streamflow. Here we synthesized data from 30 intensively monitored catchments with soil moisture, snowmelt, and other hydrometeorological observations at daily scale across the US. This data synthesis product, CHOSEN (CONUS/Comprehensive Hydrologic Observatory SEnsor Network), includes watersheds from the Long-Term Ecological Research (LTER) and Critical Zone Observatory (CZO) networks, and several other ecological and hydrological observatories. Catchments span diverse climate gradients and encompass multiple biomes and ecosystems. To achieve a consistent and standardized data product, we first implemented data cleaning and control procedures with strict variable naming conventions and unit conversions. Following data quality control, data processing methods, including gap filling by interpolation, linear regression, and climate catalog-based techniques, were implemented to produce alternative level-2 products. The data and metadata were written into self-describing NetCDF files, facilitating ease of access by multiple computer platforms. All python coding scripts, ranging from processing to accessing the NetCDF files, are publicly available, along with a user-friendly tutorial. The standardizations adopted here, and the availability of the data-processing pipeline, will facilitate future additions of new observations to this database. We anticipate that this synthesis will support comparative long-term hydrological studies and contribute to a growing body of open-source research in watershed and ecosystem science.

Diapause is an adaptive dormancy strategy by which arthropods endure extended periods of adverse climatic conditions. Seasonal variation in larval diapause initiation and duration in Ostrinia furnacalis influences adult mating generation number (voltinism) across different local environments. The degree of mating period overlap between sympatric voltine ecotypes influence hybridization level, but impacts on O. furnacalis population genetic structure and evolution of divergent adaptive phenotypes remains uncertain. Genetic differentiation was estimated between voltine ecotypes collected from 8 locations. Mitochondrial haplotypes were significantly different between historically allopatric univoltine and bivoltine locations. Haplotypes from sympatric locations were clustered more-closely to bivoltine locations, but influenced by local demographics. Additionally, analyses of single nucleotide polymorphism (SNP) genotypes implicate voltinism, as opposed to geographic distance, as contributing to low, but significant levels of variation among voltine ecotypes. Regardless, only 11 of 257 SNP loci were predicted to be under selection, suggesting population genetic homogenization except at loci proximal to factors putatively responsible for locally adaptive or voltinism-specific traits. These findings provide evidence that divergent voltine ecotypes may be maintained in allopatric and sympatric areas despite relatively high rates of nuclear gene flow, yet influence of voltinism on maintenance of observed haplotype divergence remains unresolved.

The koala, Phascolarctos cinereus, is an iconic Australian wildlife species, but faces rapid decline in South-East Queensland (SEQLD). For conservation planning, estimating koala populations is crucial. Systematic surveys are the most common approach to estimate koala populations, but such surveys are restricted to small geographic areas, they are costly and conducted infrequently. Public interest and participation in the collection of koala sightings is increasing in popularity, but such data is generally not used for population estimation. We used incidental sightings of koalas reported by members of the public from 1997-2013 in SEQLD to estimate the yearly spatio-temporal koala sightings density. For this, a spatio-temporal point process model was developed accounting for observed koala density, spatio-temporal detection bias and clustering. The density of koalas varied throughout the study period due to the heterogeneous nature of koala habitat in SEQLD, with density estimates ranging between 0.005 to 8.9 koalas per km2. The percentage of land areas with very low sightings densities (0-0.25 koalas per km2) remained similar throughout the study period representing in average (SD) 68.3% (0.06) of the total study area. However, land areas with more koalas per km2 showed larger annual variations, with koala mean (SD) densities of 0.25-0.5, 0.5-1, 1-2, 2-5 and > 5 koalas per km2 representing 16.8% (0.21), 13.8% (0.25), 0.7% (0.20), 0.3% (0.13), and 0.2% (0.1) of the study area in South-East Queensland, respectively.We did find that clustering of koala sightings was not prominently different between the mating and non-mating seasons of koalas. While acknowledging the limitations associated sightings data, we developed a statistical model that addressed the spatio-temporal bias associated with observed koala sightings and provided long-term relative koala density estimates for one of the largest koala populations of Australia.

Introduction. Significant variations in the management of bronchiolitis are often recorded, and, in parallel, to recommend a univocal clinical approach it is not easy and is still questioned. This study is aimed to evaluate the diagnostic and therapeutic management of bronchiolitis in children adopted by Italian paediatricians following the national guidelines. Material and methods. A survey study was designed and carried out by sending an email an open-ended questionnaire developed by an expert panel of the Scientific Board of the Italian Society of Pediatric Allergology and Immunology (SIAIP). Questions were designed according to the national inter-society consensus document on treatment and prevention of bronchiolitis in newborns and infants. Results. Overall, 234 paediatricians were taking part in the study. When diagnosing bronchiolitis, only 44.01% (103/234) of participants were correctly following the national guidelines. All participants (100%) would perform laboratory tests and/or radiological exams. 44.01% administered oxygen (O2) when O2 saturation was major than 92%. About the therapeutic regimen, marked discrepancies between national guidelines and recorded answers were reported. Indications for hospital admission and discharge criteria were in line with the national guidelines. Conclusions. There is a significant practise variation in the management of acute bronchiolitis among Italians physicians. Some wrong attitudes need to be further discouraged, such use of diagnostic procedures and therapeutic approaches. Further research is urgently required to define the best management of patients with bronchiolitis as well as implement strategies to standardize care and improve the quality of care.

Background: Left atrial appendage occlusion with the Watchman device is an alternative strategy for stroke risk reduction in patients with non-valvular atrial fibrillation. There are rare case reports of Watchman associated infection. Currently, there is no formal study that evaluated the incidence and outcomes of Watchman-related infections. Methods: All patients who underwent Watchman implantation over a 14 year study period (July 2004 through December 2018) comprised our cohort. Baseline characteristics, procedural data, and post-implantation events were identified. Primary study outcomes included Watchman related infection, other cardiovascular device related infection, bacteremia, and mortality. Results: A total of 181 patients with an average age of 75, and a median CHA2DS2-VASc Score of 4 (interquartile range 2) and a median HAS-BLED Score of 3 (interquartile range 1), were included for analysis. A total of 534.7 patient years of follow up was accrued with an average of 2.9 years per patient. The most common indications for implantation included gastrointestinal bleeding (56 patients; 30.9%) and intracerebral bleeding (51 patients; 28.2%). During follow up, 38 patients (21%) died. Six developed evidence of bacteremia. Only one developed an implantable cardioverter defibrillator (ICD) infection that required complete system extraction. None of the cohort developed Watchman-related device infection during the study period. Conclusion: In a single center study spanning a 14 year period, we report no Watchman-related devices infections. This is despite the presence of patients with bacteremia, as well as an ICD infection requiring extraction. These data suggest that Watchman devices are extremely unlikely to become infected.

Background: A patient with ischemic cardiomyopathy and left bundle branch block (LBBB) who did not respond to standard bi-ventricular pacing underwent attempted left bundle area (LBA) pacing to achieve better cardiac resynchronization (CRT). Methods: LBA pacing failed to correct the LBBB or narrow the QRS. However, simultaneous pacing through the coronary sinus (CS) and LBA pacing leads resulted in marked shortening of the QRS Results: The patient’s EF improved from 30% to 45% two months post procedure and heart failure symptoms improved by one functional class. Conclusions: Simultaneous LBA and CS pacing may improve clinical outcomes compared to either alone.

Case A 40-year-old gentleman underwent electrophysiology study for WPW syndrome with recurrent orthodromic atrioventricular reentrant tachycardia (AVRT). He had a right anterior accessory pathway (AP) which was ablated closer to the septum anterior to His catheter, ablation-distal (ABL) not recording any His signal during and after ablation (Appendix 1ABC). During the study, parahisian pacing (PHP) was performed before and after ablation as a routine protocol to determine the route of VA conduction (VAC). During the study 4 catheters were used: one quadripolar catheter for His region, One roving ablation catheter [for RV pacing/ mapping (MAP)/ablation], 2 decapolar catheters for coronary sinus (CS) and right atrium (RA). During PHP, both the His and MAP/ABL catheters were placed at His region. The CS catheter could not be placed fully deep inside, hence CS-12 was located near middle CS whereas the CS-34 was 2-3 cm inside proximal CS (Appendix 1BC). The decapolar catheter, placed in RA, was on the atrial aspect of tricuspid annulus, with RA-5 bipole near high right atrium (HRA). Pacing was performed at 600 ms cycle length (PCL) as her sinus CL was 700-750 ms. Starting at 20 mA current @ 2 ms pulse width and keeping the PCL and catheter position fixed, the current output was gradually reduced in a stepwise manner when various responses were noted. What are the responses observed in Fig.1 and Fig. 2?

Objective: Minimally Invasive Ponto Surgery (MIPS) is a type of bone anchored hearing system performed through a puncture hole that has been reported to minimize soft tissue trauma, decrease operative time, and have favorable outcomes. Due to it being a relatively new procedure there remains a paucity of pediatric outcomes data. Our objective was to study MIPS outcomes in the pediatric population. Design: Retrospective review. Setting: The study was performed at two tertiary pediatric otolaryngology centres between 2016-2019. Participants: Pediatric patients from two tertiary pediatric otolaryngology clinics who underwent MIPS between 2016-2019. Main Outcome Measures: Outcomes included indication for surgery, implant and abutment type, overlying skin thickness, skin-to-skin time, Holgers score at three, six and twelve months, revision surgery and time to abutment fitting. Results and Conclusions: Fourteen patients, two with bilateral procedures met inclusion criteria (mean age= 8.07 ± 2.87years). The main etiology for the hearing loss was microtia (64%). The mean overlying skin thickness was 5.13 ± 3.18mm. Across all visits, 9.44% had Holger’s scores >2, which is classified as an adverse skin reaction. One of these patients required surgery to address skin overgrowth. One implant loss (6.3%) was reported, but found to be in the setting of trauma. Mean MIPS Skin to skin times were found to be 12.4 ± 2.6 minutes, markedly different that the Baha® Attract and Connect found to be 56 and 53 minutes respectively. This study represents the largest pediatric MIPS cohort to date, and our results are similar to published adult studies.

Natal teeth are the teeth present at birth, while neonatal teeth are those that erupted during the first month of life. Both are not uncommon anomalies with an incidence of 1:700 to 1:3500, respectively. Natal teeth occur more frequently than neonatal teeth at a ratio of approximately 3:1. Natal teeth

Understanding which foodwebs thrive or collapse is a major challenge that has been mostly studied in terms of topology and interaction strength. Yet the relative importance of these properties is hotly debated due to limited research on how they interact and which forces generate them. Here, we construct a foodweb model that incorporates mass-based constraints on density dependence, maximum consumption rate, and the likelihood and strength of interactions, which in turn control overall topologies and interaction strength distributions. Our model predicts both stability and connectivity that closely match real foodwebs ranging widely in size (29-163 species) and connectivity (113-1086 interactions). Despite their absence in most research, density dependence and maximum consumption rate are not only required to accurately predict stability but have stronger impacts than the more-frequently-studied interaction strength. Our results demonstrate that predicting foodweb stability requires simultaneously considering multiple foodweb properties—all of which naturally emerge from species masses.

Objective: The present study was designed to investigate whether acellular dermal matrix (ADM) graft could prevent Frey’s syndrome (FS) and improve aesthetic score following parotidectomy. Study Design: Retrospective study. A propensity score matched analysis. Setting:From January 2015 to December 2019, 175 patients underwent parotidectomy. Methods: We divided the patients into two groups with ADM group and Control group. We included each group of 30 patients according a propensity score matched analysis. Results: The subjective of FS was recorded in 1 patient (3%) from the ADM group and 9 patients (30%) from the Control group(P=0.015). Patients in the ADM group had a subjective aesthetic score of 6.1+1.7 compared with 5.2+1.7 in the Control group. The subjective aesthetic score for patients in the ADM group was higher than those in the Control group (P =0.040). Conclusion: The present clinical study suggests that ADM graft are effective in preventing FS and improving aesthetic score after parotidectomy.

We present a patient who was on active surveillance for lung adenocarcinoma and hypertrophic septal cardiomyopathy (HCM), was referred for cardiac magnetic resonance (CMR) assessment for risk stratification due to HCM. CMR revealed a large myocardial metastasis obstructing mid-apical left and right ventricular cavity. Any wall thickening in oncology patients should prompt to perform further imaging before establishing certain diagnosis.

1. SITE DESCRIPTIONThe Cathedral Peak research catchments, which form part of a strategic water source area for South Africa, consist of ten (named I – X) well defined hydrological catchments, ranging in altitude from 1 820 m.a.s.l to 2 463 m.a.s.l (Figure 1). The catchments fall within the summer rainfall region of South Africa, experiencing wet, humid summers and cold, dry winters (Everson et al ., 1998). The mean annual precipitation (MAP) for the area is approximately 1 400 mm (Bosch, 1979), with 84 % of this rainfall occurring between the months of October and March (Schulze, 1976). Half of the rainfall events in the catchments are thunderstorms (Schulze, 1976). Approximately 49 % of the rainfall is converted to streamflow, with two thirds of the streamflow yield occurring during the four months from January to April (Bosch, 1979). The natural vegetation of the catchments is fire-adapted montane grassland, dominated by the grass (Themeda triandra) . Woody communities dominated by Leucosidea sericea and Buddleia salvifolia occur in narrow, fire-protected zones along the streams in some catchments (Bosch, 1979).

Aim Rivaroxaban, an oral anticoagulant, undergoes the metabolism mediated by human cytochrome P450 (CYP). The present study is to quantitatively analyze and compare the contributions of multiple CYPs in the metabolism of rivaroxaban to provide new information for medication safety. Methods The metabolic stability of rivaroxaban in the presence of human liver microsomes (HLMs) and recombinant CYPs was systematically evaluated to estimate the participation of various CYP isoforms. Furthermore, the catalytic efficiency of CYP isoforms was compared via metabolic kinetic studies of rivaroxaban with recombinant CYP isoenzymes, as well as via CYP-specific inhibitory studies. Additionally, docking simulations were used to illustrate molecular interactions. Results Multiple CYP isoforms were involved in the hydroxylation of rivaroxaban, with decreasing catalytic rates as follows: CYP2J2 > 3A4 > 2D6 > 4F3 > 1A1 > 3A5 > 3A7 > 2A6 > 2E1 > 2C9 > 2C19. Among the CYPs, 2J2, 3A4, 2D6 and 4F3 were the four major isoforms responsible for rivaroxaban metabolism. Notably, the intrinsic clearance of rivaroxaban catalyzed by CYP2J2 was nearly 39-, 64- and 100-fold that catalyzed by CYP3A4, 2D6 and 4F3, respectively. In addition, rivaroxaban hydroxylation was inhibited by 41.1% in the presence of the CYP2J2-specific inhibitor danazol, which was comparable to the inhibition rate of 43.3% by the CYP3A-specific inhibitor ketoconazole in mixed HLMs. Furthermore, molecular simulations showed that rivaroxaban principally bound to CYP2J2 by π-alkyl bonds, carbon-hydrogen bonds and alkyl interactions. Conclusion CYP2J2 dominated the hydroxylation of rivaroxaban, which may provide new insight into clinical drug interactions involving rivaroxaban.