Analysis of retromuscular drain output and postoperative outcomes for heavyweight versus mediumweight polypropylene mesh following open ventral hernia repair

PURPOSE

Heavyweight polypropylene (HWPP) mesh is thought to increase inflammatory response and delay tissue integration compared to mediumweight (MWPP). Reactive fluid volume (i.e., drain output) may be a reasonable surrogate for integration. We hypothesized that daily drain output is higher with HWPP compared to MWPP in open retromuscular ventral hernia repair (VHR).

METHODS

This is a post-hoc analysis of a multicenter, randomized clinical trial conducted March 2017-April 2019 comparing MWPP and HWPP for VHR. Retromuscular drain output in milliliters was measured at 24-h intervals up to postoperative day seven. Univariate analyses compared differences in daily drain output and time to drain removal. Multivariable analyses compared total drain output and wound morbidity within 30 days and hernia recurrence at 1 year.

RESULTS

288 patients were included; 140 (48.6%) HWPP and 148 (51.4%) MWPP. Daily drain output for days 1-3 was higher for HWPP vs. MWPP (total volume: 837.8 mL vs. 656.5 mL) (p < 0.001), but similar on days 4-7 (p > 0.05). Median drain removal time was 5 days for both groups. Total drain output was not predictive of 30-day wound morbidity (p > 0.05) or hernia recurrence at 1 year (OR 1, p = 0.29).

CONCLUSION

While HWPP mesh initially had higher drain outputs, it rapidly returned to levels similar to MWPP by postoperative day three and there was no difference in clinical outcomes. We believe that drains placed around HWPP mesh can be managed similarly to MWPP mesh.

Outcomes of posterior component separation with transversus abdominis release for repair of abdominally based breast reconstruction donor site hernias

PURPOSE

Abdominally based autologous breast reconstruction (ABABR) is common after mastectomy, but carries a risk of complex abdominal wall hernias. We report experience with posterior component separation (PCS) and transversus abdominis release (TAR) with permanent synthetic mesh repair of ABABR-related hernias.

METHODS

Patients at Cleveland Clinic Foundation and Penn State Health were identified retrospectively. Outcomes included postoperative complications, hernia recurrence, and patient-reported outcomes (PROs): Hernia Recurrence Inventory, HerQLes Summary Score, Patient-Reported Outcome Measurement Information System (PROMIS) Pain Intensity 3a Survey, and the Decision Regret Scale (DRS).

RESULTS

Forty patients underwent PCS/TAR repair of hernias resulting from pedicled (35%), free (5%), muscle-sparing TRAMs (15%), and DIEPs (28%) from August 2014 to March 2021. Following PCS, 30-day complications included superficial surgical site infection (13%), seroma (8%), and superficial wound breakdown (5%). Five patients (20%) developed clinical hernia recurrence. At a minimum of 1 year, 17 (63%) reported a bulge, 12 (44%) reported pain, median HerQLes Quality Of Life Scores improved from 33 to 63/100 (p value < 0.01), PROMIS 3a Pain Intensity Scores improved from 52 to 38 (p value < 0.05), and DRS scores were consistent with low regret (20/100).

CONCLUSION

ABABR-related hernias are complex and technically challenging due to missing abdominal wall components and denervation injury. After repair with PCS/TAR, patients had high rates of recurrence and bulge, but reported improved quality of life and pain and low regret. Surgeons should set realistic expectations regarding postoperative bulge and risk of hernia recurrence.

Abdominal wall mass resections: single-center closure practices and outcomes following oncologic resections of abdominal wall fascia

PURPOSE

Radical resections for abdominal wall tumors are rare, thus yielding limited data on reconstruction of defects. We describe surgical management and long-term outcomes following radical tumor resection.

METHODS

This was a single-center retrospective review of patients between January 2010 and December 2022. Variables included operative characteristics, wound complications, hernia development, tumor recurrence, and reoperation. A multivariable analysis compared wound morbidity for suture and mesh repairs while adjusting for defect width, fascial closure, and CDC wound class.

RESULTS

120 patients were identified. Mean follow-up was 3.9 ± 3.4 years. Seventy-five (62.5%) of the masses were primary; most commonly desmoid (n = 25) and endometrioma (n = 27). Forty-five masses were metastases. Mean tumor width was 6.2 ± 3.4 cm; mean defect width was 8.1 ± 4.1 cm. Sixty-one patients (50.8%) had mesh placed, with variation in technique. Postoperative CT scans were available for 88 (73.3%) patients. Forty SSOs (33.3%), 11 SSIs (9.2%), and 18 (15%) SSOPIs occurred within 30 days. On multivariable analysis, increased defect width was associated with SSOPI (OR 1.17, p = 0.041) and CDC wound class II-III was associated with SSI (OR 8.38 and 49.1, p < 0.05) and SSOPI (OR 5.77 and 17.4, p < 0.05); mesh was not associated with these outcomes. Seven patients (5.8%) underwent 30-day reoperations and 35 (20.8%) required additional operations after 30 days. Thirteen percent developed abdominal wall (n = 8) or intra-abdominal tumor recurrence (n = 8) requiring reoperation. Twenty-seven (22.5%) patients developed hernias with a mean fascial defect width of 9.8 ± 7.2 cm.

CONCLUSION

Abdominal wall mass resections are morbid, often contaminated cases with high postoperative complication rates. Risks and benefits of mesh implantation should be tailored on an individual basis.

Real-time x-ray abnormality alerts for emergency departments using a radiographer comment model - a multisite pilot study

INTRODUCTION

The timely communication of clinically significant image appearances to Emergency Department (ED) referrers is necessary for optimum patient care. Australian reliance on verbal communication only is time-limited, open to misinterpretation and lacks transparency. A combined radiographer alert and comment model was designed to reliably communicate image abnormalities to ED referrers in real-time.

METHODS

A multidisciplinary steering group designed the model for all ED general imaging. Protocols were developed to document radiographer comments (critical, urgent and clinically significant) in patients' medical records. Critical findings were communicated directly to ED. Five NSW hospitals varying in size, complexity and population demographics piloted the model between three to twelve months during 2021-2022. Site auditors compared comments with the radiology report and designated each as True Positive (TP), False Positive (FP), indeterminate and clinically significant. Indeterminate cases were analysed by an external radiologist. Inter-observer consensus was obtained for all classifications via two independent auditors. The Positive Predictive Value (PPV), or precision of the comment, was calculated for each site.

RESULTS

Radiographers (n = 69) provided comments for 1102 cases. The pooled average PPV for TP was 0.96; (0.947-0.971; 95% CI). The weighted mean error (FP comments) was 3.9%; (2.9% - 5.3%.; 95% CI).

CONCLUSION

The Radiographer Comment model provided consistent levels of commenting precision and reproducibility across a range of sites with a pooled average PPV (0.96). The False Positive rate or weighted mean error (FP) of 3.9% (2.9% - 5.3%.; 95% CI) was low.

IMPLICATIONS FOR FUTURE PRACTICE

A strategic, interprofessional approach in the implementation of an image alert combined with a Radiographer Comment can be adapted across a variety of hospital settings for ED and other departments.

Opioid prescribing practices and patient-requested refill patterns following laparoscopic inguinal hernia repair

PURPOSE

Excessive post-operative opioid prescribing has led to efforts to match prescriptions with patient need after surgery. We investigated opioid prescribing practices, rate of patient-requested opioid refills, and associated factors after laparoscopic inguinal hernia repair (LIHR).

METHODS

LIHRs at a single institution from 3/2019 to 3/2021 were queried from the Abdominal Core Health Quality Collaborative for demographics, perioperative details, and patient-reported opioid usage. Opioid prescriptions at discharge and opioid refills were extracted from the medical record. Univariate and multivariable regression were used to identify factors associated with opioid refills within 30-days of surgery.

RESULTS

Four hundred and ninety LIHR patients were analyzed. The median number of opioid tablets prescribed was 12 [interquartile range (IQR) 10-15], and 4% requested a refill. On univariate analysis, patients who requested refills were younger [55 years (IQR 37-61) vs. 62 years (IQR 36.8-61), p = 0.012], more likely to have undergone transabdominal preperitoneal repair (75% vs. 26.4%, p < 0.001), have a scrotal component (30% vs. 11%, p = 0.022), and have permanent tacks used (80% vs. 49.4%, p = 0.014). There was a 12% increase in the odds of opioid refill for every 1 tablet of oxycodone prescribed at discharge (95% CI for OR 1.04-1.21, p = 0.003) after controlling for age and surgery type. Patient-reported opioid use was available for 289 (59%) patients. Post-operatively, 67% of patients used ≤ 4 opioid tablets, and 87% used no more than 10 opioid tablets.

CONCLUSION

Most patients use fewer opioid tablets than prescribed. Requests for opioid refills are rare following LIHR (4%) and associated with higher opioid prescribing.

Comparing anterior gastropexy to no anterior gastropexy for paraesophageal hernia repair: a study protocol for a randomized control trial

BACKGROUND

More than half of patients undergoing paraesophageal hernia repair (PEHR) will have radiographic hernia recurrence at 5 years after surgery. Gastropexy is a relatively low-risk intervention that may decrease recurrence rates, but it has not been studied in a prospective manner. Our study aims to evaluate the effect of anterior gastropexy on recurrence rates after PEHR, compared to no anterior gastropexy.

METHODS

This is a two-armed, single-blinded, registry-based, randomized controlled trial comparing anterior gastropexy to no anterior gastropexy in PEHR. Adult patients (≥18 years) with a symptomatic paraesophageal hernia measuring at least 5 cm in height on computed tomography, upper gastrointestinal series, or endoscopy undergoing elective minimally invasive repair are eligible for recruitment. Patients will be blinded to their arm of the trial. All patients will undergo laparoscopic or robotic PEHR, where some operative techniques (crural closure techniques and fundoplication use or avoidance) are left to the discretion of the operating surgeon. During the operation, after closure of the diaphragmatic crura, participants are randomized to receive either no anterior gastropexy (control arm) or anterior gastropexy (treatment arm). Two hundred forty participants will be recruited and followed for 1 year after surgery. The primary outcome is radiographic PEH recurrence at 1 year. Secondary outcomes are symptoms of gastroesophageal reflux disease, dysphagia, odynophagia, gas bloat, regurgitation, chest pain, abdominal pain, nausea, vomiting, postprandial pain, cardiovascular, and pulmonary symptoms as well as patient satisfaction in the immediate postoperative period and at 1-year follow-up. Outcome assessors will be blinded to the patients' intervention.

DISCUSSION

This randomized controlled trial will examine the effect of anterior gastropexy on radiographic PEH recurrence and patient-reported outcomes. Anterior gastropexy has a theoretical benefit of decreasing PEH recurrence; however, this has not been proven beyond a suggestion of effectiveness in retrospective series. If anterior gastropexy reduces recurrence rates, it would likely become a routine component of surgical PEH management. If it does not reduce PEH recurrence, it will likely be abandoned.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04007952 . Registered on July 5, 2019.

P-524 Bi-allelic CFAP61 variants cause male infertility in humans and mice with severe oligoasthenoteratozoospermia

Study question

Are mutations in cilia and flagella-associated protein 61 (CFAP61) associated with human male infertility?

Summary answer

Bi-allelic variants ([NM_015585.4: c.1654C&gt;T (p.R552C) and c.2911G&gt;A (p.D971N), c.144-2A&gt;G and c.1666G&gt;A (p.G556R)] in CFAP61 were identified as contributory genetics factor in severe oligoasthenoteratozoospermia (OAT).

What is known already

Cfap61 knockout mice were infertile due to multiple morphological abnormalities of the sperm flagella (MMAF). However, so far there is no direct evidence that mutations of CFAP61 cause OAT and male infertility.

Study design, size, duration

Variant screening was performed by whole-exome sequencing (WES) from 325 infertile patients with OAT and 392 fertile individuals. A knockout mouse model was generate to confirm the candidate disease-causing gene, intracytoplasmic sperm injection (ICSI) was used to evaluate the efficiency of clinical treatment.

Participants/materials, setting, methods

A total 325 OAT-affected patients and 392 men with normal fertility were recruited from China. WES was performed, followed by Sanger sequencing validation. In silico bioinformatics predictions and in vitro functional analyses were performed to evaluate the impacts of candidate disease-causing variants. Hematoxylin and eosin (H&E) staining, electron microscopy, and immunofluorescence assays were performed to evaluate the sperm morphology. Two OAT-affected men with CFAP61 variants were treated by ICSI, and pregnancy outcomes were followed.

Main results and the role of chance

We identified bi-allelic CFAP61 variants [NM_015585.4: c.1654C&gt;T (p.R552C) and c.2911G&gt;A (p.D971N), c.144-2A&gt;G and c.1666G&gt;A (p.G556R)] in two (0.62%) of the 325 OAT-affected men. In silico bioinformatics analysis predicted that all four variants were deleterious, and in vitro functional analysis confirmed the deleterious effects of the mutants. Notably, H&E staining and electron microscopy analyses of the spermatozoa revealed multiple morphological abnormalities of sperm flagella, the absence of central pair microtubules, and mitochondrial sheath malformation in sperm flagella from man with CFAP61 variants. Further immunofluorescence assays revealed markedly reduced CFAP61 staining in the sperm flagella. In addition, Cfap61-deficient mice showed the OAT phenotype, suggesting that loss of function of CFAP61 was the cause of OAT. Two individuals accepted ICSI therapy using their own ejaculated sperm, and one of them succeeded in fathering a healthy baby.

Limitations, reasons for caution

Limitations include the lack of in vivo data from the one of patients, and the exact molecular mechanism should be further investigated.

Wider implications of the findings

Our findings indicate that CFAP61 is essential for spermatogenesis and that bi-allelic CFAP61 variants lead to OAT and male infertility in humans and mice. In addition, our results show that ICSI treatment can be recommended for CFAP61-related OAT.

Trial registration number

not applicable

[High frequency hearing loss detection rate in occupational noise exposed workers in China: a Meta-analysis]

Objective: A Meta-analysis was used to evaluate the high frequency hearing loss detection rate, its area and time distributions in occupational noise exposed workers in China to provide evidence for the prevention and control of occupational noise-induced deafness. Methods: From February to April 2020, the number of hearing tests and the number of binaural high frequency average hearing threshold ≥40 dB of workers exposed to noise in key occupational disease monitoring and occupational health risk assessment project in China was collected from China National Knowledge Infrastructure (CNKI) , VIP database and PubMed database. The retrieval time was set from the establishment of the database to February 28, 2020. The R 3.6.2 software was used to calculate the pooled high frequency hearing loss detection rate. Results: A total of 28 studies, included 34 data and 1259571 occupational noise exposed workers, were enrolled. The articles covered 16 provinces in 2015-2018. The pooled high frequency hearing loss detection rate in occupational noise exposed workers was 9.45% (95%CI: 7.64%-11.64%) . The high frequency hearing loss detection rate (10.54%) was higher in 2018 than other years (2017: 10.17%, 2016: 9.21%, 2015: 7.88%) . The high frequency hearing loss detection rate (12.23%) was higher in central China than in eastern (10.21%) , western (7.91%) and north-eastern (5.21%) China. Conclusion: The overall high frequency hearing loss detection rate in occupational noise exposed workers is generally high in China. It is important to strengthen the hearing protection in occupational noise exposed workers to facilitate the occupational noise-induced deafness prevention and control in China.

Inhibition of Carbonic Anhydrase Using SLC-149: Support for a Noncatalytic Function of CAIX in Breast Cancer

Carbonic anhydrase IX (CAIX) is considered a target for therapeutic intervention in solid tumors. In this study, the efficacy of the inhibitor, 4-(3-(2,4-difluorophenyl)-oxoimidazolidin-1-yl)benzenesulfonamide (SLC-149), is evaluated on CAIX and a CAIX-mimic. We show that SLC-149 is a better inhibitor than acetazolamide against CAIX. Binding of SLC-149 thermally stabilizes CAIX-mimic at lower concentrations compared to that of CAII. Structural examinations of SLC-149 bound to CAIX-mimic and CAII explain binding preferences. In cell culture, SLC-149 is a more effective inhibitor of CAIX activity in a triple-negative breast cancer cell line than previously studied sulfonamide inhibitors. SLC-149 is also a better inhibitor of activity in cells expressing CAIX versus CAXII. However, SLC-149 has little effect on cytotoxicity, and high concentrations are required to inhibit cell growth, migration, and invasion. These data support the hypothesis that CAIX activity, shown to be important in regulating extracellular pH, does not underlie its ability to control cell growth.

Extracellular vesicles and diabetic kidney disease: a systematic review

Extracellular vesicles (EVs) are small lipid-encapsulated vesicles secreted from specific cells that can be taken up by other cells, thereby allowing for the efficient transport of macromolecules such as lipids, proteins, and nucleic acids between tissues and organs in vivo. These EVs have been found to play critical roles in normal tissue homeostasis and disease development, serving to regulate complex processes, including inflammation, immunity, and angiogenesis. At present, the leading global cause of the end-stage renal disease (ESRD) is diabetic kidney disease (DKD), with the prevalence of this latter condition being predicted to increase in the near future due to rising type 2 diabetes mellitus (T2DM) incidence. Recent work from several research groups has highlighted a potential role for EVs in the development of DKD. The present review, therefore, serves to explore the relevance of EVs to the development, detection, and treatment of DKD in an effort to better understand this complex disease state.

0834 Different Neural Circuits Were Associated With Different Parts of Relationships Among Sleep, Pain and Anxiety in Women with Primary Dysmenorrhoea

Introduction

Although the relationships amongst sleep, pain and anxiety have been evidenced, the underlying neurological mechanisms remain elusive. Primary dysmenorrhea is a good model of spontaneous pain with clear painful (menstruation, state) and pain free (e.g., peri-ovulatory phase, trait) conditions. We sought to investigate the state- and trait-related neural signatures that link sleep and anxiety in primary dysmenorrhea.

Methods

Thirty female subjects with primary dysmenorrhea and 30 healthy female controls completed resting-state functional magnetic resonance imaging, the State-Trait Anxiety Inventory and sleep quality assessments during menstruation and peri-ovulatory phases. As we have reported that there was altered default mode network in the primary dysmenorrhea, posterior parietal cortex (PPC) was therefore chosen as the seed to elucidate the functional connectivity that may correlate with sleep and anxiety.

Results

The primary dysmenorrheic subjects exhibited sleep disturbances throughout the menstrual cycle with increased state anxiety. The primary dysmenorrheic subjects demonstrated significantly higher correlations between the sleep quality and the PPC-insula and -putamen functional connectivity during the peri-ovulatory phase. During menstruation, the primary dysmenorrheic subjects demonstrated significantly lower correlations between their state-anxiety scores and the PPC-occipital cortex functional connectivity.

Conclusion

After regressing out the effects of trait anxiety, the correlation between sleep quality and the PPC-putamen functional connectivity was not significant, indicating anxiety-mediated sleep-pain relationship. The PPC-insula functional connectivity, by contrast, was remained significant. Furthermore, state anxiety was associated with the PPC-occipital cortex functional connectivity that was significantly impaired in primary dysmenorrheic subjects. These findings hinted pain and anxiety mediating sleep quality in different neurological circuits.

Support

Taipei City Goverment(10401-62-046 and 10501-62-046)

Animal rabies in the People's Republic of China

Since the late 1990s, the People's Republic of China (China) has consistently reported the second largest number of human rabies cases in the world; in this country, rabid dogs are the major source of rabies virus (RABV) transmission for both human and domestic animal rabies cases. In addition, other animal species have been reported to contract and transmit the virus. In this paper, an overview of the animal rabies situation in China is presented by referring to published articles (both English and Chinese) and governmental documents (guidelines, plans, notices and reports), which summarise the rabies situation in dogs, livestock, ferret badgers, bats, canids and rodents, and its threat to public health and animal husbandry in the country. Additionally, to obtain the complete phylogeny, full nucleoprotein gene sequences of representative field RABV strains circulating in China and its surrounding countries have been subjected to phylogenetic analysis, which showed, in agreement with previous studies, that RABVs in China have a broad genetic diversity that can be classified into three major clades, seven lineages and a number of sub-lineages. While significant progress on animal rabies epidemiology in China has been made, animal cases are still underestimated when compared with reported human cases. Rabies continues to spread into new areas even though human cases have been declining steadily since 2007. To minimise infection at the transmission source and to realise the goal of eliminating dog-mediated human rabies by 2030, surveillance and control.

3,17β-Bis-sulfamoyloxy-2-methoxyestra-1,3,5(10)-triene and Nonsteroidal Sulfamate Derivatives Inhibit Carbonic Anhydrase IX: Structure-Activity Optimization for Isoform Selectivity

3,17β-Bis-sulfamoyloxy-2-methoxyestra-1,3,5(10)-triene (STX140), a bis-sulfamate derivative of the endogenous steroid 2-methoxyestradiol, has shown promising anticancer potency both in vitro and in vivo, with excellent bioavailability. Its activity against taxane-resistant xenografts makes it a potential drug candidate against triple-negative breast cancer (TNBC). These properties are linked to the ability of STX140 to act in a multitargeting fashion in vivo as a microtubule disruptor, leading to cell cycle arrest and with both proapoptotic and anti-angiogenic activities. Carbonic anhydrase IX (CA IX) is a well-established biomarker for aggressive cancers, including TNBC. This study reports, for the first time, the inhibitory activities of a series of steroidal and nonsteroidal sulfamate derivatives against CA IX in comparison to the ubiquitous CA II, with some compounds demonstrating 100-200-fold selectivity for CA IX over CA II. X-ray crystallographic studies of four of the most promising compounds reveal that isoform-specific residue interactions are responsible for the high specificity.

Selective inhibition of carbonic anhydrase IX over carbonic anhydrase XII in breast cancer cells using benzene sulfonamides: Disconnect between activity and growth inhibition

Carbonic anhydrases (CAs) have been linked to tumor progression, particularly membrane-bound CA isoform IX (CA IX). The role of CA IX in the context of breast cancer is to regulate the pH of the tumor microenvironment. In contrast to CA IX, expression of CA XII, specifically in breast cancer, is associated with better outcome despite performing the same catalytic function. In this study, we have structurally modeled the orientation of bound ureido-substituted benzene sulfonamides (USBs) within the active site of CA XII, in comparison to CA IX and cytosolic off-target CA II, to understand isoform specific inhibition. This has identified specific residues within the CA active site, which differ between isoforms that are important for inhibitor binding and isoform specificity. The ability of these sulfonamides to block CA IX activity in breast cancer cells is less effective than their ability to block activity of the recombinant protein (by one to two orders of magnitude depending on the inhibitor). The same is true for CA XII activity but now they are two to three orders of magnitude less effective. Thus, there is significantly greater specificity for CA IX activity over CA XII. While the inhibitors block cell growth, without inducing cell death, this again occurs at two orders of magnitude above the K_i values for inhibition of CA IX and CA XII activity in their respective cell types. Surprisingly, the USBs inhibited cell growth even in cells where CA IX and CA XII expression was ablated. Despite the potential for these sulfonamides as chemotherapeutic agents, these data suggest that we reconsider the role of CA activity on growth potentiation.

Differential expression and function of CAIX and CAXII in breast cancer: A comparison between tumorgraft models and cells

Carbonic anhydrase IX (CAIX) and XII (CAXII) are transmembrane proteins that are associated with cancer progression. We have previously described the catalytic properties of CAIX in MDA-MB-231 breast cancer cells, a line of cells that were derived from a patient with triple negative breast cancer. We chose this line because CAIX expression in breast cancer is a marker of hypoxia and a prognosticator for reduced survival. However, CAXII expression is associated with better survival statistics than those patients with low CAXII expression. Yet CAIX and CAXII have similar catalytic activities. Here we compare the potential roles of CAIX and CAXII in the context of TNBC and estrogen receptor (ER)-positive breast cancer. In tumor graft models, we show that CAIX and CAXII exhibit distinct expression patterns and non-overlapping. We find the same pattern across a panel of TNBC and luminal breast cancer cell lines. This affords an opportunity to compare directly CAIX and CAXII function. Our data suggest that CAIX expression is associated with growth potentiation in the tumor graft model and in a TNBC line using knockdown strategies and blocking activity with an impermeant sulfonamide inhibitor, N-3500. CAXII was not associated with growth potentiation. The catalytic activities of both CAIX and CAXII were sensitive to inhibition by N-3500 and activated at low pH. However, pH titration of activity in membrane ghosts revealed significant differences in the catalytic efficiency and pKa values. These features provide evidence that CAIX is a more efficient enzyme than CAXII at low pH and that CAIX shifts the equilibrium between CO₂ and bicarbonate in favor of CO₂ production by consuming protons. This suggests that in the acidic microenvironment of tumors, CAIX plays a role in stabilizing pH at a value that favors cancer cell survival.

Detection of Babesia spp., Theileria spp. and Anaplasma ovis in Border Regions, northwestern China

Babesia spp., Theileria spp. and Anaplasma ovis are important intracellular agents that are transmitted by tick bites. However, Babesia spp., Theileria spp. and A. ovis in ticks have not been systematically reported along the border of northwestern China. In this study, a total of 1,084 adult ticks, including 134 Haemaphysalis punctata, 337 Hyalomma asiaticum, 233 Dermacentor nuttalli, 69 Rhipicephalus turanicus and 265 Dermacentor marginatus were collected from 11 counties or cities of Xinjiang Uygur Autonomous Region. The ticks were identified from morphological and molecular characteristics. Two fragments of 18S rRNA gene were used to determine the species level of Babesia and Theileria. Msp4 gene encoding major surface protein 4 was used to determine A. ovis. Of the 1,084 samples, five species of Babesia (B. occultans, B. caballi, B. motasi, B. major and Babesia sp. detected in this study), two kinds of Theileria (Theileria ovis and Theileria sp. detected in this study) and A. ovis with six phylogenic branches were detected in the border of northwestern China. Babesia occultans, first found in China, was first molecularly detected in D. nuttalli. Babesia caballi and Babesia sp. detected in this study were first molecularly detected in Hy. asiaticum. Genotype III of A. ovis was predominant in the border regions of northwestern China.

Retrospective study of porcine circovirus 3 infection in China

PCV3 is an emerging swine virus associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure, respiratory diseases and systematic inflammation. Although first identified in 2015, the earliest case has been traced back to 2009 in the United States. In China, PCV3 infection was first detected in 2015, but little information has been available about its occurrence and prevalence there before 2015. In this study, 200 porcine clinical samples collected from 20 provinces, five autonomous regions and four municipalities between 1990 and 1999 were analysed for PCV3 infection by PCR. Results showed that 6.5% of the porcine samples collected from eight provinces and one autonomous region were PCV3 positive, with the earliest cases occurring in 1996. Nucleotide sequence analysis showed that PCV3 strains obtained in this study shared 96.6%-99.7% and 97.1%-99.4% sequence identity at the ORF2 gene and genome levels with all available reference strains from China and other countries, indicating the high genetic stability of PCV3 over the past 20 years.

Carbonic anhydrase II does not exhibit Nitrite reductase or Nitrous Anhydrase Activity

Carbonic anhydrase II (CA II) is a zinc metalloenzyme that catalyzes the reversible interconversion of water and CO₂ to bicarbonate and a proton. CA II is abundant in most cells, and plays a role in numerous processes including gas exchange, epithelial ion transport, respiration, extra- and intracellular pH control, and vascular regulation. Beyond these CO₂ and pH-linked roles, it has been postulated that CA II might also reduce nitrite (NO₂^-) to nitric oxide (NO), as bicarbonate and NO₂^- both exhibit sp² molecular geometry and NO also plays an important role in vasodilation and regulation of blood pressure. Indeed, previous studies by Aamand et al. have shown that bovine CA II (BCA II) possesses nitrite dehydration activity and paradoxically demonstrated that CA inhibitors (CAIs) such as dorzolamide and acetazolamide significantly increased NO production (Aamand et al., 2009; Nielsen and Fago, 2015) [1,2]. Hence, the goal of this work was to revisit these studies using the same experimental conditions as Aamand et al. measuring NO generation by two methods, and to examine the structure of CA II in complex with NO₂^- in the presence and absence of dorzolamide. Our results contradict the previous findings and indicate that CA II does not exhibit nitrite reductase or dehydration activity, and that this is not enhanced in the presence of CA inhibitors. In addition, a structural examination of BCA II in complex with NO₂^- and superimposed with dorzolamide demonstrates that CA inhibitor binding at the active site to the zinc moiety blocks potential NO₂^- binding.

Concurrent Umbilical Hernia Repair at the Time of Liver Transplantation: A Six-Year Experience from a Single Institution

BACKGROUND

Umbilical hernias are common in patients with end-stage liver disease undergoing liver transplantation. Management of those persisting at the time of liver transplantation is important to define.

OBJECTIVE

To evaluate the long-term results of patients undergoing simultaneous primary umbilical hernia repair (UHR) at the time of liver transplantation at a single institution.

METHODS

Retrospective chart review was performed on patients undergoing simultaneous UHR and liver transplantation from 2010 through 2016. 30-day morbidity and mortality outcomes and long-term hernia recurrence were investigated.

RESULTS

59 patients had primary UHR at the time of liver transplantation. All hernias were reducible with no overlying skin breakdown or leakage of ascites. 30-day morbidity and mortality included 5 (8%) superficial surgical site infections, 1 (2%) deep surgical site infection, and 7 (12%) organ space infections. Unrelated to the UHR, 10 (17%) patients had an unplanned return to the operating room, 16 (27%) were readmitted within 30 days of their index operation, and 1 (2%) patient died. With a mean follow-up of 21.8 months, 7 (18%) patients experienced an umbilical hernia recurrence.

CONCLUSION

Despite the high perioperative morbidity associated with the transplant procedure, concurrent primary UHR resulted in an acceptable long-term recurrence rate with minimal associated morbidity.

Retrospective study of porcine circovirus type 2 infection reveals a novel genotype PCV2f

Porcine postweaning multisystemic wasting syndrome (PMWS) caused by porcine circovirus type 2 (PCV2) is a disease causing severe economic losses annually worldwide to the pig industry. PCV2 infection was first reported in China in 2000, and currently has three major genotypes, PCV2a, b and d, circulating in this country. To further elucidate the origin and prevalence of PCV2 in China, 123 clinical pig tissue samples collected in 25 provinces between 1990 and 1999 were analysed by PCV2-specific PCR, resulting in identification of 23 PCV2 strains collected between 1996 and 1999. Phylogenetic analysis based on the nucleotide sequences of open reading frame 2 (ORF2) showed that 20 of the 23 grouped within PCV2a, while the remaining three strains formed an independent clade, so far unreported and therefore named PCV2f. This genotype shared lower sequence identity with other known genotypes. This study provides further understanding of the genetic diversity and evolution of PCV2 and has tracked PCV2 infection in China back to 1996 rather than 2000.

Abstract 5936: Comparison of carbonic anhydrase & activity between triple-negative & luminal breast cancer cells

Tumor microenvironment substantially influences the process of tumorigenesis. Extracellular acidification within the tumor microenvironment is an indicator of an aggressive cancer and a marker for poor patient outcome. In solid tumors, hypoxia leads to extracellular acidosis. Carbonic anhydrases (CA) are thought to regulate intracellular and extracellular pH (pHi and pHe, respectively). To explore the effect of CAs in breast cancer, we compared the expression and activity of two membrane bound CAs, CAIX and CAXII, between triple negative breast cancer cells (TNBCs) and luminal breast cancer cells (LBCs).

We chose five different TNBC and LBC lines. Our data show that, among the TNBC lines, CAIX expression increased in three of the five lines: HBL100, SUM159, and the new UFH-001 cells under hypoxic condition. UFH-001 cells also showed strong constitutive expression. None of these TNBC lines expressed CAXII or estrogen receptor (ER). In LBC lines, four of the five lines constitutively expressed CAXII: T47D, MCF7, SKBR and SUM52 cells. CAXII expression was not hypoxia-dependent. Each of the five luminal lines expressed ER. We also examined CA expression in a tumor graft model. In tumors grown from cells derived from TNBC patients, we observed CAIX expression in four of six sample sets. In tumors derived from ER-positive LBC patients, all five expressed CAXII.

We also used the 18O exchange method to assess CA activity. Two TNBC lines: UFH-001 and HBL100 cells showed that CAIX activity increased in hypoxic conditions which was blocked by an impermeant sulfonamide CA inhibitor (N3500). In the luminal lines, we detected CAXII activity in T47D and MCF7 cells that was also inhibited by N3500. Like CAXII protein expression in these cells, CAXII activity was not affected by hypoxia. We also evaluated the effect of pH on CA activity in TNBC and LBC lines. Both CAIX and CAXII showed increased activity in response to reduced pH, which is expected in a bicarbonate-based system. However, UFH-001 cells also exhibited a hypoxic-dependent increase in CAIX activity which is associated with increased protein expression.

In conclusion, these observations demonstrate that CAIX expression is associated with the TNBC phenotype. Based on our activity data, we would predict that CA activity in TNBC tumors will be sensitive to both hypoxia (based on enhanced expression) and reduced pH. This change in activity may serve to regulate pH in the tumor microenvironment favoring an aggressive phenotype. On the other hand, LBC tumors, which are ER-positive, are only associated with CAXII expression. In luminal cells, we expect that only pH and not hypoxia will affect CAXII activity. This may, in part, explain the more positive prognosis in patients with CAXII expression.

Note: This abstract was not presented at the meeting.

Citation Format: Zhijuan Chen, Mam Y. Mboge, Chingkuang Tu, Lingbao Ai, Coy Heldermon, Susan C. Frost. Comparison of carbonic anhydrase & activity between triple-negative & luminal breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5936. doi:10.1158/1538-7445.AM2017-5936

Correlation between circulating tumor cells EGFR expression and T cell subsets in advanced non-small cell lung cancer patients after tyrosine kinase inhibitor treatment

Research indicates that after EGFR-tyrosine kinase inhibitors (EGFR-TKIs) treatment of non-small cell lung cancer (NSCLC), patient immune function significantly improved, and that circulating tumor cells (CTCs) measurements and peripheral blood epidermal growth factor receptor (EGFR) mutation data can guide TKIs treatment. Sixty-six advanced NSCLC patients treated with TKIs were enrolled and CTCs, EGFR expression, T cell subsets and natural killer (NK) cells in peripheral blood were measured using flow cytometry before and after treatment and assessed with respect to patient prognosis. CTCs and EGFR expression were negatively correlated with cellular immune function and immune recovery after EGFR-TKI treatment. Thus, CD4+/ CD8+ ratios and NK cells may be useful prognostic indicators for advanced NSCLC patients who receive TKIs treatment.

The Structure of Carbonic Anhydrase IX Is Adapted for Low-pH Catalysis

Human carbonic anhydrase IX (hCA IX) expression in many cancers is associated with hypoxic tumors and poor patient outcome. Inhibitors of hCA IX have been used as anticancer agents with some entering Phase I clinical trials. hCA IX is transmembrane protein whose catalytic domain faces the extracellular tumor milieu, which is typically associated with an acidic microenvironment. Here, we show that the catalytic domain of hCA IX (hCA IX-c) exhibits the necessary biochemical and biophysical properties that allow for low pH stability and activity. Furthermore, the unfolding process of hCA IX-c appears to be reversible, and its catalytic efficiency is thought to be correlated directly with its stability between pH 3.0 and 8.0 but not above pH 8.0. To rationalize this, we determined the X-ray crystal structure of hCA IX-c to 1.6 Å resolution. Insights from this study suggest an understanding of hCA IX-c stability and activity in low-pH tumor microenvironments and may be applicable to determining pH-related effects on enzymes.

Mate choice and host discrimination behavior of the parasitoid Trichogramma chilonis

Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) is an important natural enemy of many species of lepidopterous pests and a widely used biological control agent. Detailed knowledge about its mate choice and host discrimination behavior is lacking. In this study, we studied the mate choice and host discrimination behavior of T. chilonis in experimental arenas through video tracking. Males' mate recognition capacity was realized by perceiving the sex pheromone of females. When offered two females of different species, male could distinguish the conspecific female from Trichogrammatoidea bactrae Nagaraja (Hymenoptera: Trichogrammatidae), a species that has overlapping hosts with T. chilonis. When placed with two females of different mating status, male preferred mating with the virgin female to the mated female. T. chilonis females could distinguish unparasitized host eggs from parasitized ones (parasitized by conspecific females or heterospecific females). They preferred to stay on and lay eggs in unparasitized host eggs. When T. chilonis females were only provided with parasitized host eggs (parasitized by T. chilonis and T. bactrae females), conspecific superparasitism occurred more often than heterospecific superparasitism. Furthermore, the host egg discrimination ability of T. chilonis females was mainly achieved through antennal perception.

Substrate Binding Mode and Molecular Basis of a Specificity Switch in Oxalate Decarboxylase

Oxalate decarboxylase (OxDC) catalyzes the conversion of oxalate into formate and carbon dioxide in a remarkable reaction that requires manganese and dioxygen. Previous studies have shown that replacing an active-site loop segment Ser¹⁶¹-Glu¹⁶²-Asn¹⁶³-Ser¹⁶⁴ in the N-terminal domain of OxDC with the cognate residues Asp¹⁶¹-Ala¹⁶²-Ser-¹⁶³-Asn¹⁶⁴ of an evolutionarily related, Mn-dependent oxalate oxidase gives a chimeric variant (DASN) that exhibits significantly increased oxidase activity. The mechanistic basis for this change in activity has now been investigated using membrane inlet mass spectrometry (MIMS) and isotope effect (IE) measurements. Quantitative analysis of the reaction stoichiometry as a function of oxalate concentration, as determined by MIMS, suggests that the increased oxidase activity of the DASN OxDC variant is associated with only a small fraction of the enzyme molecules in solution. In addition, IE measurements show that C–C bond cleavage in the DASN OxDC variant proceeds via the same mechanism as in the wild-type enzyme, even though the Glu¹⁶² side chain is absent. Thus, replacement of the loop residues does not modulate the chemistry of the enzyme-bound Mn(II) ion. Taken together, these results raise the possibility that the observed oxidase activity of the DASN OxDC variant arises from an increased level of access of the solvent to the active site during catalysis, implying that the functional role of Glu¹⁶² is to control loop conformation. A 2.6 Å resolution X-ray crystal structure of a complex between oxalate and the Co(II)-substituted ΔE162 OxDC variant, in which Glu¹⁶² has been deleted from the active site loop, reveals the likely mode by which the substrate coordinates the catalytically active Mn ion prior to C–C bond cleavage. The “end-on” conformation of oxalate observed in the structure is consistent with the previously published V/K IE data and provides an empty coordination site for the dioxygen ligand that is thought to mediate the formation of Mn(III) for catalysis upon substrate binding.

Activity and anion inhibition studies of the α-carbonic anhydrase from Thiomicrospira crunogena XCL-2 Gammaproteobacterium

Thiomicrospira crunogena XCL-2 expresses an α-carbonic anhydrase (TcruCA). Sequence alignments reveal that TcruCA displays a high sequence identity (>30%) relative to other α-CAs. This includes three conserved histidines that coordinate the active site zinc, a histidine proton shuttling residue, and opposing hydrophilic and hydrophobic sides that line the active site. The catalytic efficiency of TcruCA is considered moderate relative to other α-CAs (k(cat)/K(M)=1.1×10(7) M(-1) s(-1)), being a factor of ten less efficient than the most active α-CAs. TcruCA is also inhibited by anions with Cl(-), Br(-), and I(-), all showing Ki values in the millimolar range (53-361 mM). Hydrogen sulfide (HS(-)) revealed the highest affinity for TcruCA with a Ki of 1.1 μM. It is predicted that inhibition of TcruCA by HS(-) (an anion commonly found in the environment where Thiomicrospira crunogena is located) is a way for Thiomicrospira crunogena to regulate its carbon-concentrating mechanism (CCM) and thus the organism's metabolic functions. Results from this study provide preliminary insights into the role of TcruCA in the general metabolism of Thiomicrospira crunogena.

A sucrose-binding site provides a lead towards an isoform-specific inhibitor of the cancer-associated enzyme carbonic anhydrase IX

Human carbonic anhydrase (CA; EC 4.2.1.1) isoform IX (CA IX) is an extracellular zinc metalloenzyme that catalyzes the reversible hydration of CO2 to HCO3(-), thereby playing a role in pH regulation. The majority of normal functioning cells exhibit low-level expression of CA IX. However, in cancer cells CA IX is upregulated as a consequence of a metabolic transition known as the Warburg effect. The upregulation of CA IX for cancer progression has drawn interest in it being a potential therapeutic target. CA IX is a transmembrane protein, and its purification, yield and crystallization have proven challenging to structure-based drug design, whereas the closely related cytosolic soluble isoform CA II can be expressed and crystallized with ease. Therefore, we have utilized structural alignments and site-directed mutagenesis to engineer a CA II that mimics the active site of CA IX. In this paper, the X-ray crystal structure of this CA IX mimic in complex with sucrose is presented and has been refined to a resolution of 1.5 Å, an Rcryst of 18.0% and an Rfree of 21.2%. The binding of sucrose at the entrance to the active site of the CA IX mimic, and not CA II, in a non-inhibitory mechanism provides a novel carbohydrate moiety binding site that could be further exploited to design isoform-specific inhibitors of CA IX.

Structural and biophysical characterization of the α-carbonic anhydrase from the gammaproteobacterium Thiomicrospira crunogena XCL-2: insights into engineering thermostable enzymes for CO2 sequestration

Biocatalytic CO2 sequestration to reduce greenhouse-gas emissions from industrial processes is an active area of research. Carbonic anhydrases (CAs) are attractive enzymes for this process. However, the most active CAs display limited thermal and pH stability, making them less than ideal. As a result, there is an ongoing effort to engineer and/or find a thermostable CA to fulfill these needs. Here, the kinetic and thermal characterization is presented of an α-CA recently discovered in the mesophilic hydrothermal vent-isolate extremophile Thiomicrospira crunogena XCL-2 (TcruCA), which has a significantly higher thermostability compared with human CA II (melting temperature of 71.9°C versus 59.5°C, respectively) but with a tenfold decrease in the catalytic efficiency. The X-ray crystallographic structure of the dimeric TcruCA shows that it has a highly conserved yet compact structure compared with other α-CAs. In addition, TcruCA contains an intramolecular disulfide bond that stabilizes the enzyme. These features are thought to contribute significantly to the thermostability and pH stability of the enzyme and may be exploited to engineer α-CAs for applications in industrial CO2 sequestration.

Structural and catalytic effects of proline substitution and surface loop deletion in the extended active site of human carbonic anhydrase II

Bioengineering of a thermophilic enzyme starting from a mesophilic scaffold has proven to be a significant challenge, as several stabilizing elements have been proposed to be the foundation of thermal stability, including disulfide bridges, surface loop reduction, ionic pair networks, proline substitutions and aromatic clusters. This study emphasizes the effect of increasing the rigidity of human carbonic anhydrase II (HCA II; EC 4.2.1.1) via incorporation of proline residues at positions 170 and 234, which are located in surface loops that are able to accommodate restrictive main-chain conformations without rearrangement of the surrounding peptide backbone. Additionally, the effect of the compactness of HCA II was examined by deletion of a surface loop (residues 230-240) that had been previously identified as a possible source of thermal stability for the hyperthermophilic carbonic anhydrase isolated from the bacterium Sulfurihydrogenibium yellowstonense YO3AOP1. Differential scanning calorimetry analysis of these HCA II variants revealed that these structural modifications had a minimum effect on the thermal stability of the enzyme, while kinetic studies showed unexpected effects on the catalytic efficiency and proton transfer rates. X-ray crystallographic analysis of these HCA II variants showed that the electrostatic potential and configuration of the highly acidic loop (residues 230-240) play an important role in its high catalytic activity. Based on these observations and previous studies, a picture is emerging of the various components within the general structural architecture of HCA II that are key to stability. These elements may provide blueprints for rational thermal stability engineering of other enzymes.

DATABASE

Structural data have been submitted to the Protein Data Bank under accession numbers 4QK1 (K170P), 4QK2 (E234P) and 4QK3 (Δ230-240).

Wnt5a is involved in the pathogenesis of cutaneous lichen planus

BACKGROUND

Cutaneous lichen planus (CLP) is a chronic inflammatory and immune-mediated disease. Wnt5a is one of the most extensively studied Wnt proteins, and has important functions in stimulating inflammation, cell proliferation, cell fate determination and cell differentiation. Wnt5a expression in CLP has not been comprehensively studied to date.

AIM

To determine the expression and distribution of Wnt5a in CLP.

METHODS

Skin samples were obtained from patients with CLP and healthy controls (HCs). The WNT5A gene was detected by real-time quantitative PCR, and Wnt5a protein by immunohistochemical analysis and western blotting.

RESULTS

WNT5A mRNA was upregulated in CLP samples compared with the HC skin samples (P < 0.001). Wnt5a protein was overexpressed in all layers of the epidermis and dermis in CLP lesions compared with HC skin (all P < 0.001). These results were confirmed by western blotting.

CONCLUSIONS

The data presented in this study suggest that Wnt5a pathway may play an important role in the pathogenesis of CLP.

NMR studies of active-site properties of human carbonic anhydrase II by using (15) N-labeled 4-methylimidazole as a local probe and histidine hydrogen-bond correlations

By using a combination of liquid and solid-state NMR spectroscopy, (15) N-labeled 4-methylimidazole (4-MI) as a local probe of the environment has been studied: 1) in the polar, wet Freon CDF3 /CDF2 Cl down to 130 K, 2) in water at pH 12, and 3) in solid samples of the mutant H64A of human carbonic anhydrase II (HCA II). In the latter, the active-site His64 residue is replaced by alanine; the catalytic activity is, however, rescued by the presence of 4-MI. For the Freon solution, it is demonstrated that addition of water molecules not only catalyzes proton tautomerism but also lifts its quasidegeneracy. The possible hydrogen-bond clusters formed and the mechanism of the tautomerism are discussed. Information about the imidazole hydrogen-bond geometries is obtained by establishing a correlation between published (1) H and (15) N chemical shifts of the imidazole rings of histidines in proteins. This correlation is useful to distinguish histidines embedded in the interior of proteins and those at the surface, embedded in water. Moreover, evidence is obtained that the hydrogen-bond geometries of His64 in the active site of HCA II and of 4-MI in H64A HCA II are similar. Finally, the degeneracy of the rapid tautomerism of the neutral imidazole ring His64 reported by Shimahara et al. (J. Biol. Chem.- 2007, 282, 9646) can be explained with a wet, polar, nonaqueous active-site conformation in the inward conformation, similar to the properties of 4-MI in the Freon solution. The biological implications for the enzyme mechanism are discussed.

Human carbonic anhydrase II-cyanate inhibitor complex: putting the debate to rest

The binding of anions to carbonic anhydrase II (CA II) has been attributed to high affinity for the active-site zinc. An anion of interest is cyanate, for which contrasting binding modes have been reported in the literature. Previous spectroscopic data have shown cyanate behaving as an inhibitor, directly binding to the zinc, in contrast to previous crystallographic data that implied that cyanate acts as a substrate mimic that is not directly bound to the zinc but overlaps with the binding site of the substrate CO2. Wild-type and the V207I variant of CA II have been expressed and X-ray crystal structures of their cyanate complexes have been determined to 1.7 and 1.5 Å resolution, respectively. The rationale for the V207I CA II variant was its close proximity to the CO2-binding site. Both structures clearly show that the cyanate binds directly to the zinc. In addition, inhibition constants (∼40 µM) were measured using (18)O-exchange mass spectrometry for wild-type and V207I CA II and were similar to those determined previously (Supuran et al., 1997). Hence, it is concluded that under the conditions of these experiments the binding of cyanate to CA II is directly to the zinc, displacing the zinc-bound solvent molecule, and not in a site that overlaps with the CO2 substrate-binding site.

Insights into Activity Enhancement of H64A Carbonic Anhydrase by Imidazoles

Human carbonic anhydrases (CAs) are zinc metalloenzymes that catalyze the hydration and dehydration of CO2 and HCO3-, respectively. The reaction follows a ping-pong mechanism, where the rate limiting step is the transfer of a proton from the zinc-bound solvent out of the active site, via His64 which is widely believed to be the proton shuttling residue. Being involved in a number of physiological processes such as respiration, pH regulation, ureagenesis etc., CAs are therapeutic targets for inhibition to treat various diseases. However, the physiologically dominant isoform is CA II, which is catalytically highly efficient and is easily crystallizable. Thus, most of our knowledge in the design of CA inhibitors with pharmacological applications is based on detailed CA II crystallographic studies. The catalytic activity of a variant of CA II in which His64 is replaced with Ala (H64A CA II) can be enhanced by exogenous proton donors/acceptors, usually derivatives of imidazoles and pyridines. This article examines the mechanism through which this activity enhancement might occur. X-ray crystal structures of H64A CA II in complex with four imidazole derivatives have been determined and reveal multiple binding sites. We have identified two molecules of imidazoles that bind in region that is otherwise occupied by the "in" and "out" dual conformation of the side chain of His64 in wild-type CA II. The data presented here not only corroborates the importance of imidazole side chain of His64 in proton transfer during CA catalysis, but also provides a complete structural understanding of the mechanism by which imidazoles enhance (and inhibit when used in higher concentrations) the activity of H64A CA II. In addition to inhibition of CA by these imidazoles, the presence of a large number of binding sites also gives insights and preliminary data required to fragment addition approach of drug design against CA.

Membrane inlet mass spectrometry reveals that Ceriporiopsis subvermispora bicupin oxalate oxidase is inhibited by nitric oxide

Membrane inlet mass spectrometry (MIMS) uses a semipermeable membrane as an inlet to a mass spectrometer for the measurement of the concentration of small uncharged molecules in solution. We report the use of MIMS to characterize the catalytic properties of oxalate oxidase (E.C. 1.2.3.4) from Ceriporiopsis subvermispora (CsOxOx). Oxalate oxidase is a manganese dependent enzyme that catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction that is coupled with the formation of hydrogen peroxide. CsOxOx is the first bicupin enzyme identified that catalyzes this reaction. The MIMS method of measuring OxOx activity involves continuous, real-time direct detection of oxygen consumption and carbon dioxide production from the ion currents of their respective mass peaks. (13)C2-oxalate was used to allow for accurate detection of (13)CO2 (m/z 45) despite the presence of adventitious (12)CO2. Steady-state kinetic constants determined by MIMS are comparable to those obtained by a continuous spectrophotometric assay in which H2O2 production is coupled to the horseradish peroxidase catalyzed oxidation of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid). Furthermore, we used MIMS to determine that NO inhibits the activity of the CsOxOx with a KI of 0.58±0.06 μM.