Using CHROMagar™ STEC medium exclusively does not recover all clinically relevant Shiga toxin-producing Escherichia coli in Aotearoa, New Zealand

Diagnostic laboratories in Aotearoa, New Zealand (NZ) refer cultures from faecal samples positive for Shiga toxin genes to the national Enteric Reference Laboratory for isolation of Shiga toxin-producing Escherichia coli (STEC) for epidemiological typing. As there was variation in the culture media being referred, a panel of 75 clinical isolates of STEC, representing 28 different serotypes, was used to assess six commercially available media and provide guidance to clinical laboratories. Recommendations were subsequently tested for a 3-month period, where STEC isolations and confirmations were assessed by whole genome sequencing analysis against the culture media referred. CHROMagar™ STEC (CH-STEC; CHROMagar Microbiology, Paris, France) or CH-STEC plus cefixime-tellurite sorbitol MacConkey agar was confirmed inferior to CH-STEC plus blood agar with vancomycin, cefsulodin, and cefixime (BVCC). The former resulted in fewer STEC types (n = 18) being confirmed compared to those from a combination of CH-STEC and BVCC (n = 42). A significant (P < .05) association with an STEC's ability to grow on CH-STEC and the presence of the ter gene cluster, and eae was observed. Culturing screen positive STEC samples onto both CH-STEC and BVCC ensures a consistently higher recovery of STEC from all clinical samples in NZ than CH-STEC alone.

Interleukin 17 Receptor C, but not Polo-like Kinase 4, Plays a Critical Role in the Development of Skin Papilloma and Psoriasis in Mouse Models

Introduction/Objective

Hyperproliferation of epidermis is a histopathological hallmark of skin cancers and psoriasis. As a master regulator of centriole replication, overexpression of Polo-like kinase 4 (PLK4) has been identified in skin cancers. The aberrant proliferation of epidermal keratinocytes provoked by interleukin 17 (IL17) leads to psoriasis. Thus, targeting centriole replication and IL17 signaling simultaneously has been speculated as a potential therapeutic strategy. We hypothesized that inhibition of centriole duplication enhances the blockade of epidermal proliferation through Il17rc knockout.

Methods/Case Report

To test our hypothesis, 37 mice were used to imbed a two-stage model of skin carcinogenesis using wild-type (WT), IL17 receptor A (T779A) knock-in (Il17ra(T779A)-KI), and IL17 receptor C knock-out (Il17rc-KO) C57BL/6J mouse strains. Furthermore, an imiquimod-induced psoriasis model was established using 69 mice with the same strains.

Results (if a Case Study enter NA)

In our two-stage skin carcinogenesis model, Il17ra(T779A)-KI mice showed significantly decreased tumor incidence, tumor multiplicity, and tumor volume compared to the WT mice. Il-17rc-KO mice didn’t develop any skin papilloma. The skin papilloma formed never progressed into squamous carcinoma. However, centrinone, a selective inhibitor of PLK4, didn’t affect skin papilloma formation or epidermal thickening. In our psoriasis model, the epidermis thickness of Il-17rc-KO mice was dramatically decreased compared to WT and Il17ra(T779A)-KI mice. There was no significant difference between WT and Il17ra(T779A)-KI mice in terms of skin lesion and thickening of the epidermis. Centrinone didn’t stall the thickening of the epidermis in the psoriasis model. IHC staining showed significantly increased Ki67+ basal keratinocytes in the untreated skin of Il17ra(T779A)-KI male mice compared to WT mice. In imiquimod-treated skin, the percentage of Ki67+ basal keratinocytes significantly decreased in the order from WT, Il17ra(T779A)-KI to Il17rc-KO mice.

Conclusion

Our data suggest that the proliferation of keratinocytes is not stalled by centrinone but is inhibited by Il17rc-KO. Il17ra(T779A)-KI significantly inhibits skin papilloma formation, but slightly decreases epidermal thickening in the psoriasis model. However, Il17ra(T779A)-KI increases keratinocyte proliferation based on Ki67 staining in the untreated normal skin.

Prolonged progressive hypermetabolism during COVID-19 hospitalization undetected by common predictive energy equations

Background & aims

Indirect calorimetry (IC) is the gold-standard for determining measured resting energy expenditure (mREE) in critical illness. When IC is not available, predicted resting energy expenditure (pREE) equations are commonly utilized, which often inaccurately predict metabolic demands leading to over- or under-feeding. This study aims to longitudinally assess mREE via IC in critically ill patients with SARS-CoV-2 (COVID-19) infection throughout the entirety of, often prolonged, intensive care unit (ICU) stays and compare mREE to commonly utilized pREE equations.

Methods

This single-center prospective cohort study of 38 mechanically ventilated COVID-19 patients from April 1, 2020 to February 1, 2021. The Q-NRG® Metabolic Monitor was used to obtain IC data. The Harris-Benedict (HB), Mifflin St-Jeor (MSJ), Penn State University (PSU), and weight-based equations from the American Society of Parenteral and Enteral Nutrition – Society of Critical Care Medicine (ASPEN-SCCM) Clinical Guidelines were utilized to assess the accuracy of common pREE equations and their ability to predict hypo/hypermetabolism in COVID-19 ICU patients.

Results

The IC measures collected revealed a relatively normometabolic or minimally hypermetabolic mREE at 21.3 kcal/kg/d or 110% of predicted by the HB equation over the first week of mechanical ventilation (MV). This progressed to significant and uniquely prolonged hypermetabolism over successive weeks to 28.1 kcal/kg/d or 143% of HB predicted by MV week 3, with hypermetabolism persisting to MV week 7. Obese individuals displayed a more truncated response with significantly lower mREE versus non-obese patients in MV week 1 (19.5 ± 1.0 kcal/kg/d vs 25.1 ± 1.8 kcal/kg/d, respectively; p < 0.01), with little change in weeks 2–3 (19.5 ± 1.5 kcal/kg/d vs 28.0 ± 2.0 kcal/kg/d; p < 0.01). Both ASPEN-SCCM upper range and PSU pREE equations provided close approximations of mREE yet, like all pREE equations, occasionally over- and under-predicted energy needs and typically did not predict late hypermetabolism.

Conclusions

Study results show a truly unique metabolic response in COVID-19 ICU patients, characterized by significant and prolonged, progressive hypermetabolism peaking at 3 weeks’ post-intubation, persisting for up to 7 weeks in ICU. This pattern was more clearly demonstrated in non-obese versus obese patients. This response is unique and distinct from any previously described model of ICU stress response in its prolonged hypermetabolic nature. This data reaffirms the need for routine, longitudinal IC measures to provide accurate energy targets in COVID-19 ICU patients. The PSU and ASPEN-SCCM equations appear to yield the most reasonable estimation to IC-derived mREE in COVID-19 ICU patients, yet still often over-/under-predict energy needs. These findings provide a practical guide for caloric prescription in COVID-19 ICU patients in the absence of IC.

Assessing the Feasibility of a Novel mHealth App in Hematopoietic Stem Cell Transplant Patients

Hematopoietic stem cell transplantation (HCT) is a curative treatment option for patients with hematologic conditions but presents many complications that must be managed as a complex, chronic condition. Mobile health applications (mHealth apps) may permit tracking of symptoms in HCT. In seeking strategies to manage the complexities of HCT, our team collaborated with Sicklesoft, Inc., to develop an mHealth app specifically for HCT patients to allow for daily evaluation of patient health, Technology Recordings to better Understand Bone Marrow Transplantation (TRU-BMT). The primary value of this application is that of potentially enhancing the monitoring of symptoms and general health of patients undergoing HCT, with the ultimate goal of allowing earlier detection of adverse events, earlier intervention, and improving outcomes. To first evaluate patient interest in mHealth apps, we designed and administered an interest survey to patients at the 2017 BMT-InfoNet reunion. As a follow-up to the positive feedback received, we began testing the TRU-BMT app in a Phase 1 pilot study. Thirty patients were enrolled in this single-arm study and were given the TRU-BMT mHealth app on a smartphone device in addition to a wearable activity tracker. Patients were followed for up to 180 days, all the while receiving daily app monitoring. Adherence to TRU-BMT was approximately 30% daily and 44% weekly, and greater adherence was associated with increased meal completion, decreased heart rate, and shorter hospital stay. TRU-BMT assessments of symptom severity were significantly associated with duration of hospital stay and development of chronic graft-versus-host disease. Our findings suggest that using TRU-BMT throughout HCT is feasible for patients and established a proof-of-concept for a future randomized control trial of the TRU-BMT application in HCT. © 2021 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.

The tuatara genome reveals ancient features of amniote evolution

The tuatara (Sphenodon punctatus)-the only living member of the reptilian order Rhynchocephalia (Sphenodontia), once widespread across Gondwana1,2-is an iconic species that is endemic to New Zealand2,3. A key link to the now-extinct stem reptiles (from which dinosaurs, modern reptiles, birds and mammals evolved), the tuatara provides key insights into the ancestral amniotes2,4. Here we analyse the genome of the tuatara, which-at approximately 5 Gb-is among the largest of the vertebrate genomes yet assembled. Our analyses of this genome, along with comparisons with other vertebrate genomes, reinforce the uniqueness of the tuatara. Phylogenetic analyses indicate that the tuatara lineage diverged from that of snakes and lizards around 250 million years ago. This lineage also shows moderate rates of molecular evolution, with instances of punctuated evolution. Our genome sequence analysis identifies expansions of proteins, non-protein-coding RNA families and repeat elements, the latter of which show an amalgam of reptilian and mammalian features. The sequencing of the tuatara genome provides a valuable resource for deep comparative analyses of tetrapods, as well as for tuatara biology and conservation. Our study also provides important insights into both the technical challenges and the cultural obligations that are associated with genome sequencing.

Abstract B24: Dysregulated Transcription Drives Splicing Defect in Ewing Sarcoma

Ewing sarcoma (EwS) is a pediatric and young adult cancer that is driven by the EWSR1-FLI1 translocation. Despite decades of work, this cancer is still an enigma, with poorly understood biology and no targeted treatments. Our recent work published in Nature demonstrated a previously overlooked consequence of EWSR1-FLI1, that this fusion causes hyperphosphorylated RNA polymerase II (pRNAPII) due to loss of EWSR1 inhibition of CDK7 and CDK9. We observed high levels of transcription, with high levels of R-loops present in locations that R-loops normally (physiologically) occur. Based upon these findings, we began to reconsider cellular phenotypes of EwS to identify the molecular basis of these phenotypes and ask whether these changes provide a fundamental defect in all EwS. One phenotype that was previously identified in EwS is that these cells display altered splicing profiles. In our prior work we reported that the normal dephosphorylation of pRNAP in response to damage does not occur, and this results in trapping of BRCA1 protein with the active transcription complex. It was recently shown that the splicing machinery is bound to pRNAPII. This observation raises the interesting possibility that in EwS, like BRCA1 protein, the splicing machinery is also sequestered with pRNAPII. Interestingly, in recent years, there have been several reports linking R-loops to splicing, with splicing defects causing R-loop accumulation and R-loops being associated with sites of alternative splicing. We therefore asked if there is an association between the R-loops and alternative splicing phenotype in EwS cells and whether this results in a defect that can be leveraged to specifically target EwS cells and tumors.

Citation Format: L. Lawrence, A. Gorthi, H. Miller, A. J. R. Bishop. Dysregulated Transcription Drives Splicing Defect in Ewing Sarcoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B24.

Oxygen consumption rate of Caenorhabditis elegans as a high-throughput endpoint of toxicity testing using the Seahorse XFe96 Extracellular Flux Analyzer

Caenorhabditis elegans presents functioning, biologically relevant phenotypes and is frequently used as a bioindicator of toxicity. However, most C. elegans in vivo effect-assessment methods are laborious and time consuming. Therefore, we developed a novel method to measure the oxygen consumption rate of C. elegans as a sublethal endpoint of toxicity. This protocol was tested by exposing 50 larval stage one C. elegans individuals for 48 h (at 20 °C) to different concentrations of two toxicants i.e. benzylcetyldimethylammonium chloride (BAC-C16) and cadmium (Cd). Following exposures, the oxygen consumption rate of the C. elegans individuals were measured using the high-throughput functionality of the Seahorse XFe96 Extracellular Flux Analyzer. Dose-response curves for BAC-C16 (R2 = 0.93; P = 0.001) and Cd (R2 = 0.98; P = 0.001) were created. Furthermore, a strong, positive correlation was evidenced between C. elegans oxygen consumption rate and a commonly used, ecologically relevant endpoint of toxicity (growth inhibition) for BAC-C16 (R2 = 0.93; P = 0.0001) and Cd (R2 = 0.91; P = 0.0001). The data presented in this study show that C. elegans oxygen consumption rate can be used as a promising functional measurement of toxicity.

Author Correction: Forearc carbon sink reduces long-term volatile recycling into the mantle

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Patient experiences of nurse-facilitated advance care planning in a general practice setting: a qualitative study

BACKGROUND

Advance care planning (ACP) can offer benefits to patients and their families, especially when delivered in outpatient settings, but uptake remains low. Common barriers for health professionals include a perceived lack of time and adequate training, experience, and confidence in conducting ACP. Patient-reported barriers include a lack of awareness of ACP or discomfort initiating or engaging in discussions about end-of-life.

METHODS

We aimed to explore patients' perspectives of an ACP intervention designed to address common barriers to uptake in the general practice setting. We provided training and support to doctors and general practice nurses (GPNs) to initiate and lead ACP discussions at their respective practices (2014 to 2015). Following the intervention, we conducted interviews with patients to explore their experience of engaging in ACP in the general practice setting. Thematic analysis was used to inductively code transcripts and identify key themes from semi-structured interviews with patients.

RESULTS

Six major themes relating to patient experiences of GPN-facilitated ACP were identified: working through ideas, therapeutic relationship with nurses, significance of making wishes known, protecting family from burden, autonomy in decision-making, and challenges of family communication. The patients valued the opportunity to speak about issues that are important to them with the GPN who they found to be compassionate and caring. The patients felt that ACP would lead to significant benefits not only to themselves but also for their family. Despite encouragement to involve other family members, most patients attended the ACP discussions alone or as a couple; many did not see the relevance of their family being involved in the discussions. Some patients felt uncomfortable or reluctant in communicating the results of their discussion with their family.

CONCLUSIONS

With adequate training and support, GPNs are able to initiate and facilitate ACP conversations with patients. Their involvement in ACP can have significant benefits for patients. Psychosocial and relational elements of care are critical to patient satisfaction. Our findings show that some patients may feel uncomfortable or reluctant to communicate the results of their ACP discussions with their family. A future larger study is required to verify the findings of this pilot study.

Is the aging human ovary still ticking?: Expression of clock-genes in luteinized granulosa cells of young and older women

Background

It has been shown – mostly in animal models - that circadian clock genes are expressed in granulosa cells and in corpora luteum and might be essential for the ovulatory process and steroidogenesis.

Objective

We sought to investigate which circadian clock genes exist in human granulosa cells and whether their expression and activity decrease during aging of the ovary.

Study design

Human luteinized granulosa cells were isolated from young (age 18–33) and older (age 39–45) patients who underwent in-vitro fertilization treatment. Levels of clock genes expression were measured in these cells 36 h after human chorionic gonadotropin stimulation.

Methods

Human luteinized granulosa cells were isolated from follicular fluid during oocyte retrieval. The mRNA expression levels of the circadian genes CRY1, CRY2, PER1, PER2, CLOCK, ARNTL, ARNTL2, and NPAS2 were analyzed by quantitative polymerase chain reaction.

Results

We found that the circadian genes CRY1, CRY2, PER1, PER2, CLOCK, ARNTL, ARNTL2, and NPAS2, are expressed in cultured human luteinized granulosa cells. Among these genes, there was a general trend of decreased expression in cells from older women but it reached statistical significance only for PER1 and CLOCK genes (fold change of 0.27 ± 0.14; p = 0.03 and 0.29 ± 0.16; p = 0.05, respectively).

Conclusions

This preliminary report indicates that molecular circadian clock genes exist in human luteinized granulosa cells. There is a decreased expression of some of these genes in older women. This decline may partially explain the decreased fertility and steroidogenesis of reproductive aging.

Talking to children about their HIV status: a review of available resources, tools, and models for improving and promoting pediatric disclosure

As children living with HIV (CLHIV) grow into adolescence and adulthood, caregivers and healthcare providers are faced with the sensitive challenge of when to disclose to a CLHIV his or her HIV status. Despite WHO recommendations for CLHIV to know their status, in countries most affected by HIV, effective resources are often limited, and national guidance on disclosure is often lacking. To address the need for effective resources, gray and scientific literature was searched to identify existing tools and resources that can aid in the disclosure process. From peer-reviewed literature, seven disclosure models from six different countries were identified. From the gray literature, 23 resources were identified including children's books (15), job aides to assist healthcare providers (5), and videos (3). While these existing resources can be tailored to reflect local norms and used to aid in the disclosure process, careful consideration must be taken in order to avoid damaging disclosure practices.

Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya

The nature of inter-group relations among prehistoric hunter-gatherers remains disputed, with arguments in favour and against the existence of warfare before the development of sedentary societies. Here we report on a case of inter-group violence towards a group of hunter-gatherers from Nataruk, west of Lake Turkana, which during the late Pleistocene/early Holocene period extended about 30 km beyond its present-day shore. Ten of the twelve articulated skeletons found at Nataruk show evidence of having died violently at the edge of a lagoon, into which some of the bodies fell. The remains from Nataruk are unique, preserved by the particular conditions of the lagoon with no evidence of deliberate burial. They offer a rare glimpse into the life and death of past foraging people, and evidence that warfare was part of the repertoire of inter-group relations among prehistoric hunter-gatherers.

The effect of probiotics on CD4 counts among people living with HIV: a systematic review

Probiotics are defined by the WHO as 'live microorganisms which when administered in adequate amounts confer a health benefit on the host'. Ongoing research has shown probiotics provide benefits to humans, including protection and restoration of the gastrointestinal and other mucosal tracts. As human immunodeficiency virus (HIV) activates gut-associated lymphoid tissue (GALT), several studies have investigated the effect of probiotics on CD4 cell count and related outcomes among those living with HIV. These studies are summarised here. Manuscripts were identified using the search terms 'probiotics', 'synbiotics', 'HIV', and 'CD4', and were reviewed for relevance and inclusion of CD4 count as an immunologic endpoint. Bibliographies of relevant manuscripts were also reviewed for additional studies matching inclusion and exclusion criteria. The search yielded 91 results; 13 included relevant outcomes. Seven of these studies produced beneficial CD4 outcomes, while the remaining 6 reported on insignificant beneficial or negative CD4 outcomes. The studies summarised here collectively suggest that daily consumption of probiotics over a prolonged period of time may improve CD4 count in people living with HIV.

First confirmation of Pseudogymnoascus destructans in British bats and hibernacula

White-nose syndrome (WNS) is a fatal fungal infection of bats in North America caused by Pseudogymnoascus destructans. P. destructans has been confirmed in Continental Europe but not associated with mass mortality. Its presence in Great Britain was unknown. Opportunistic sampling of bats in GB began during the winter of 2009. Any dead bats or samples from live bats with visible fungal growths were submitted to the Animal Health and Veterinary Laboratories Agency for culture. Active surveillance by targeted environmental sampling of hibernacula was carried out during the winter of 2012/2013. Six hibernacula were selected by their proximity to Continental Europe. Five samples, a combination of surface swabs or sediment samples, were collected. These were sent to the Center for Microbial Genetics and Genomics, Northern Arizona University, for P. destructans PCR. Forty-eight incidents were investigated between March 2009 and July 2013. They consisted of 46 bat carcases and 31 other samples. A suspected P. destructans isolate was cultured from a live Daubenton's bat (Myotis daubentonii) sampled in February 2013. This isolate was confirmed by the Mycology Reference Laboratory, Bristol (Public Health England), as P. destructans. A variety of fungi were isolated from the rest but all were considered to be saprophytic or incidental. P. destructans was also confirmed by the Center for Microbial Genetics and Genomics in five of the six sites surveyed.

Treatment of cannabis dependence using escitalopram in combination with cognitive-behavior therapy: a double-blind placebo-controlled study

BACKGROUND

Cannabis is the most frequently used illegal substance in the United States and Europe. There is a dramatic increase in the demand for treatment for cannabis dependence. Cannabis users frequently have co-morbid mood symptoms, especially depression and anxiety, and regular cannabis users may self-medicate for such symptoms.

OBJECTIVES

We report a double-blind, placebo-controlled treatment study, for the prevention of cannabis use in cannabis-dependent individuals.

METHOD

Regular cannabis-dependent users (n = 52) were treated for 9 weeks with weekly cognitive-behavior and motivation-enhancement therapy sessions together with escitalopram 10 mg/day. Urine samples were collected to monitor delta-9 tetrahydrocannabinol (THC) during treatment and questionnaires were administered to assess anxiety and depression.

RESULTS

We observed a high rate of dropout (50%) during the 9-week treatment program. Fifty-two patients were included in the intention-to-treat analysis. Of these, ten (19%) remained abstinent after 9 weeks of treatment as indicated by negative urine samples for THC. Escitalopram provided no advantage over placebo in either abstinence rates from cannabis or anxiety and depression scores during the withdrawal and abstinent periods.

CONCLUSIONS

Escitalopram treatment does not provide an additional benefit either for achieving abstinence, or for the treatment of the cannabis withdrawal syndrome. Due to limitations of our study, namely, a high dropout rate and effects of low abstinence rates on measures of anxiety, depression and withdrawal, it is premature to conclude that selective serotonin reuptake inhibitors are not effective for treatment of the cannabis withdrawal syndrome.

Abstract P6-08-11: Count us, know us, join us global survey: Comparing the feelings and needs of advanced breast cancer patients in the United States with patients in Latin America, Europe, and Asia

Background: Advanced breast cancer (stage III and stage IV/metastatic) (ABC) is the most serious form of breast cancer, with nearly 250,000 people across the globe living with the disease. Because ABC often metastasizes to the brain, bone, or liver, it has important health implications, requires life-long treatment, and is usually fatal. Support needs for this patient group are unique, yet rarely met. Hoping to identify new approaches to meeting the needs of this community, a global survey was commissioned by Novartis Oncology in partnership with the global advocacy community. Method: Harris Interactive conducted an online survey between October 2012 and March 2013. It was completed by 1,273 female metastatic breast cancer patients ages 21+ from 12 countries (United States [US], Canada, Mexico, Brazil, Argentina, United Kingdom, Germany, Russia, India, Lebanon, Taiwan, and Hong Kong). Total sample data are not weighted and are representative only of the individuals surveyed. A global post-weight was applied to ensure that all countries received an equal weight in the global and regional data. Results: Patients in the US (70%) are more likely than patients in most other countries surveyed to feel isolated from the non-metastatic community (40% globally). In addition, US patients (73%) are significantly more likely than their counterparts in most other countries to often feel that no one understands what they are going through (63% globally). Patients in the US (53%) are also more likely than those in most other countries to say that support from friends and family has diminished since their initial advanced diagnosis (41% globally), and employed US patients (34%) are more likely than those in many other countries to believe their colleagues look at them differently as a result of their metastatic breast cancer (17% globally). Women in the US were most likely to be actively seeking information (97%) compared with patients in other countries (77% globally). Although more US women patients are active information seekers, they are most likely to be unsatisfied with the information that is currently available compared to patients in the other countries (31%; 51% globally). Conclusions: Despite the significant amount of attention paid to breast cancer in the US and the resources available, many US women with metastatic breast cancer feel more alone and isolated than do their counterparts in most other countries surveyed. These US women are also significantly more likely than their counterparts in other countries to often feel as though no one understands what they are going through. More needs to be done to help women in the US feel supported emotionally throughout their entire ABC journey.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-08-11.

The Form and Function of “Bullying” Behaviors in a Strong Occupational Culture

The study examines the persistence of bullying in a high-teamwork environment using self-categorization theory (SCT) and interaction ritual chain theory (IRCT). Findings from a qualitative study suggest that “isolation” is the key behavior police officers label as bullying and that other behaviors thought of as bullying may be tolerated, providing there is no exclusion. IRCT clarified the dynamics, whereas SCT explained the motivation for engaging in rituals containing behaviors that included bullying. The study posits a new framework for bullying in high-pressured teams and accounts for the tolerance to “bullying” behaviors in such work environments. Implications for addressing workplace bullying in these contexts are discussed.