BACKGROUND AND PURPOSE:

Incidental findings on brain MRI and variations of the circle of Willis (CoW) are relatively common among the general population. Ethnic differences have been described before, but few studies have explored the prevalence of incidental intracranial cerebrovascular findings and CoW variants in the setting of a single multiethnic cohort. The purpose of this investigation was to describe both incidental cerebrovascular findings and the morphology of the CoW on high-resolution 3T TOF-MRA in a UK tri-ethnic population-based cohort and to present updated prevalence estimates and morphologic reference values.

BACKGROUND AND PURPOSE:

Intracranial vessel wall imaging is technically challenging to implement, given the simultaneous requirements of high spatial resolution, excellent blood and CSF signal suppression, and clinically acceptable gradient times. Herein, we present our preliminary findings on the evaluation of a deep learning–optimized sequence using T1-weighted imaging.

BACKGROUND AND PURPOSE:

Recently, artificial intelligence tools have been deployed with increasing speed in educational and clinical settings. However, the use of artificial intelligence by trainees across different levels of experience has not been well-studied. This study investigates the impact of artificial intelligence assistance on the diagnostic accuracy for intracranial hemorrhage and large-vessel occlusion by medical students and resident trainees.

BACKGROUND AND PURPOSE:

Physician-industry relationships can be useful for driving innovation and technologic progress, though little is known about the scale or impact of industry involvement in neuroradiology. The purpose of this study was to assess the trends and distributions of industry payments to neuroradiologists.

SUMMARY:

The 2021 World Health Organization Classification of Tumors of the Central Nervous System (CNS5), introduced significant changes, impacting tumors ranging from glial to ependymal neoplasms. Ependymal tumors were previously classified and graded based on histopathology, which had limited clinical and prognostic utility. The updated CNS5 classification now divides ependymomas into 10 subgroups based on anatomic location (supratentorial, posterior fossa, and spinal compartment) and genomic markers. Supratentorial tumors are defined by zinc finger translocation associated (ZFTA) (formerly v-rel avian reticuloendotheliosis viral oncogene [RELA]), or yes-associated protein 1 (YAP1) fusion; posterior fossa tumors are classified into groups A (PFA) and B (PFB), spinal ependymomas are defined by MYCN amplification. Subependymomas are present across all these anatomic compartments. The new classification kept an open category of "not elsewhere classified" or "not otherwise specified" if no pathogenic gene fusion is identified or if the molecular diagnosis is not feasible. Although there is significant overlap in the imaging findings of these tumors, a neuroradiologist needs to be familiar with updated CNS5 classification to understand tumor behavior, for example, the higher tendency for tumor recurrence along the dural flap for ZFTA fusion-positive ependymomas. On imaging, supratentorial ZFTA-fused ependymomas are preferentially located in the cerebral cortex, carrying predominant cystic components. YAP1-MAMLD1-fused ependymomas are intra- or periventricular with prominent multinodular solid components and have significantly better prognosis than ZFTA-fused counterparts. PFA ependymomas are aggressive paramedian masses with frequent calcification, seen in young children, originating from the lateral part of the fourth ventricular roof. PFB ependymomas are usually midline, noncalcified solid-cystic masses seen in adolescents and young adults arising from the fourth ventricular floor. PFA has a poorer prognosis, higher recurrence, and higher metastatic rate than PFB. Myxopapillary spinal ependymomas are now considered grade II due to high recurrence rates. Spinal-MYCN ependymomas are aggressive tumors with frequent leptomeningeal spread, relapse, and poor prognosis. Subependymomas are noninvasive, intraventricular, slow-growing benign tumors with an excellent prognosis. Currently, the molecular classification does not enhance the clinicopathologic understanding of subependymoma and myxopapillary categories. However, given the molecular advancements, this will likely change in the future. This review provides an updated molecular classification of ependymoma, discusses the individual imaging characteristics, and briefly outlines the latest targeted molecular therapies.

SUMMARY:

The ASNR Neuroradiology Division Chief Working Group's 2023 survey, with responses from 62 division chiefs, provides insights into turnaround times, faculty recruitment, moonlighting opportunities, and academic funds. In emergency cases, 61% aim for a turnaround time of less than 45–60 minutes, with two-thirds meeting this expectation more than 75% of the time. For inpatient CT and MR imaging scans, 54% achieve a turnaround time of 4–8 hours, with three-quarters meeting this expectation at least 50% of the time. Outpatient scans have an expected turnaround time of 24–48 hours, which is met in 50% of cases. Faculty recruitment strategies included 35% offering sign-on bonuses, with a median of $30,000. Additionally, 23% provided bonuses to fellows during fellowship to retain them in the practice upon completion of their fellowship. Internal moonlighting opportunities for faculty were offered by 70% of divisions, with a median pay of $250 per hour. The median annual academic fund for a full-time neuroradiology faculty member was $6000, typically excluding license fees but including American College of Radiology and American Board of Radiology membership, leaving $4000 for professional expenses. This survey calls for further dialogue on adapting and innovating academic institutions to meet evolving needs in neuroradiology.

Rare genetic conditions are challenging for the primary care provider to manage without proper guidelines. This clinical review is designed to assist the pediatrician, family physician, or internist in the primary care setting to manage the complexities of 16p11.2 deletion syndrome. A multidisciplinary medical home with the primary care provider leading the care and armed with up-to-date guidelines will prove most helpful to the rare genetic patient population. A special focus on technology to fill gaps in deficits, review of case studies on novel medical treatments, and involvement with the educational system for advocacy with an emphasis on celebrating diversity will serve the rare genetic syndrome population well.

Metastatic porocarcinomas (PCs) are vanishingly rare, highly aggressive skin adnexal tumors with mortality rates exceeding 70%. Their rarity has precluded the understanding of their disease pathogenesis, let alone the conduct of clinical trials to evaluate treatment strategies. There are no effective agents for unresectable PCs. Here, we successfully demonstrate how functional precision medicine was implemented in the clinic for a metastatic PC with no known systemic treatment options. Comprehensive genomic profiling of the tumor specimen did not yield any actionable genomic aberrations. However, ex vivo drug testing predicted pazopanib efficacy, and indeed, administration of pazopanib elicited remarkable clinicoradiological response. Pazopanib and its class of drugs should be evaluated for efficacy in other cases of PC, and the rationale for efficacy should be determined when PC tumor models become available. A functional precision medicine approach could be useful to derive effective treatment options for rare cancers.

Inositol 1,4,5-triphosphate receptor type 1 (ITPR1) is an endoplasmic reticulum–bound intracellular inositol triphosphate receptor involved in the regulation of intracellular calcium. Pathogenic variants in ITPR1 are associated with spinocerebellar ataxia (SCA) types 15/16 and 29 and have recently been implicated in a facial microsomia syndrome. In this report, we present a family with three affected individuals found to have a heterozygous missense c.800C > T (predicted p.Thr267Met) who present clinically with a SCA29-like syndrome. All three individuals presented with varying degrees of ataxia, developmental delay, and apparent intellectual disability, as well as craniofacial involvement—an uncommon finding in patients with SCA29. The variant was identified using clinical exome sequencing and validated with Sanger sequencing. It is presumed to be inherited via parental germline mosaicism. We present our findings to provide additional evidence for germline mosaic inheritance of SCA29, as well as to expand the clinical phenotype of the syndrome.

Veterans are at an increased risk for prostate cancer, a disease with extraordinary clinical and molecular heterogeneity, compared with the general population. However, little is known about the underlying molecular heterogeneity within the veteran population and its impact on patient management and treatment. Using clinical and targeted tumor sequencing data from the National Veterans Affairs health system, we conducted a retrospective cohort study on 45 patients with advanced prostate cancer in the Veterans Precision Oncology Data Commons (VPODC), most of whom were metastatic castration-resistant. We characterized the mutational burden in this cohort and conducted unsupervised clustering analysis to stratify patients by molecular alterations. Veterans with prostate cancer exhibited a mutational landscape broadly similar to prior studies, including KMT2A and NOTCH1 mutations associated with neuroendocrine prostate cancer phenotype, previously reported to be enriched in veterans. We also identified several potential novel mutations in PTEN, MSH6, VHL, SMO, and ABL1. Hierarchical clustering analysis revealed two subgroups containing therapeutically targetable molecular features with novel mutational signatures distinct from those reported in the Catalogue of Somatic Mutations in Cancer database. The clustering approach presented in this study can potentially be used to clinically stratify patients based on their distinct mutational profiles and identify actionable somatic mutations for precision oncology.

Here, we highlight the case of a 31-yr-old man who had clinical features of primary hypertrophic osteoarthropathy (PHOAR) and harbored a homozygous variant (c.38C > A, p.Ala13Glu) in the HPGD gene, as indicated by whole-exome sequencing (WES). This variant has been previously classified by our laboratory as a variant of uncertain significance (VUS). However, another patient with the same phenotype and the same homozygous variant in HPGD was subsequently reported. In reassessing the variant, the absence of this variant in the gnomAD population database, supporting computational predictions, observation in homozygosity in two probands, and specificity of the phenotype for HPGD, all provide sufficient evidence to reclassify the HPGD c.38C > A, p.Ala13Glu variant as likely pathogenic.

Diffuse large B-cell lymphoma (DLBCL) is a heterogenous group of lymphoid malignancies. Based on gene expression profiling, it has been subdivided into germinal center (GC)-derived and activated B-cell (ABC) types. Advances in molecular methodologies have further refined the subclassification of DLBCL, based on recurrent genetic abnormalities. Here, we describe a distinct case of DLBCL that presented in leukemic form. DNA sequencing targeting 275 genes revealed pathogenically relevant mutations of CD79B, MyD88, TP53, TBL1XR1, and PIM1 genes, indicating that this lymphoma would be best classified as MCD/C5 DLBCL, an ABC subtype. Despite an initial good clinical response to BTK inhibitor ibrutinib, anti-CD20 antibody rituxan, alkylating agent bendamustine, and hematopoietic stem-cell transplant, the lymphoma relapsed, accompanied by morphologic and molecular evidence of disease progression. Specifically, the recurrent tumor developed loss of TP53 heterozygosity (LOH) and additional chromosomal changes central to ABC DLBCL pathogenesis, such as PRDM1 loss. Acquired resistance to ibrutinib and rituxan was indicated by the emergence of BTK and FOXO1 mutations, respectively, as well as apparent activation of alternative cell-activation pathways, through copy-number alterations (CNAs), detected by high-resolution chromosomal microarrays. In vitro, studies of relapsed lymphoma cells confirmed resistance to standard BTK inhibitors but sensitivity to vecabrutinib, a noncovalent inhibitor active against both wild-type as well as mutated BTK. In summary, we provide in-depth molecular characterization of a de novo leukemic DLBCL and discuss mechanisms that may have contributed to the lymphoma establishment, progression, and development of drug resistance.

Pilocytic astrocytomas are the most common pediatric brain tumors, typically presenting as low-grade neoplasms. We report two cases of pilocytic astrocytoma with atypical tumor progression. Case 1 involves a 12-yr-old boy with an unresectable suprasellar tumor, negative for BRAF rearrangement but harboring a BRAF p.V600E mutation. He experienced tumor size reduction and stable disease following dabrafenib treatment. Case 2 describes a 6-yr-old boy with a thalamic tumor that underwent multiple resections, with no actionable driver detected using targeted next-generation sequencing. Whole-genome and RNA-seq analysis identified an internal tandem duplication in FGFR1 and RAS pathway activation. Future management options include FGFR1 inhibitors. These cases demonstrate the importance of escalating molecular diagnostics for pediatric brain cancer, advocating for early reflexing to integrative whole-genome sequencing and transcriptomic profiling when targeted panels are uninformative. Identifying molecular drivers can significantly impact treatment decisions and improve patient outcomes.

The positional preference of an animal can be very informative regarding the choices it makes about how to interact with its environment. The fruit fly Drosophila melanogaster has been used as a robust system for examining neurobiological mechanisms underlying behavior. Fruit fly positional preference can be gathered from TriKinetics Drosophila activity monitors (DAMs), which contain four infrared beams, allowing for tracking the position of individual flies along the length of a tube. Here, we describe a method for using DAM5Ms to examine food preference. Specifically, we show an example in which circadian changes in food preference are compared between different Drosophila species. More information about the evolution of behavior can be gathered by measuring feeding preference relative to time of day. Noni, fruit from Morinda citrifolia, contains octanoic acid, a chemical toxic to many species of Drosophila. D. melanogaster and D. simulans, both food generalists, show high sensitivity to octanoic acid, whereas D. sechellia, a specialist, can tolerate high concentrations. When two different food substrates are provided at each end of a tube, food preference can be inferred at various times of the day, using the sleep and circadian analysis MATLAB program (SCAMP) to extract and analyze positional data from DAM5Ms. Data gathered from these analyses can be used to compare avoidance or attraction to nutrients, tastants, or odors between species and genotypes or after specific different treatments. Additionally, such data can be examined as a function of time of day.

BackgroundLong-term health conditions are major challenges for care systems. Social prescribing link workers have been introduced via primary care networks (PCNs) across England since 2019 to address the wider determinants of health by connecting individuals to activities, groups, or services within their local community.AimTo assess whether the rollout of social prescribing link workers was in areas with the highest need.Design and settingA retrospective study of social prescribing link workers in England from 2019 to 2023.MethodWorkforce, population, survey, and area-level data at the PCN-level from April 2020 to October 2023 were combined. Population need before the rollout of link workers was measured using reported lack of support from local services in the 2019 General Practice Patient Survey. To assess if rollout reflected need, linear regression was used to relate provision of link workers (measured by full-time equivalent [FTE] per 10 000 patients) in each quarter to population need for support.ResultsPopulations in urban, more deprived areas and with higher proportions of people from minority ethnic groups had the highest reported lack of support. Geographically these were in the North West and London. Initially, there was no association between need and provision; then from July 2022, this became negative and significant. By October 2023, a 10-percentage point higher need for support was associated with a 0.035 (95% confidence interval = −0.634 to −0.066) lower FTE per 10 000 patients.ConclusionRollout of link workers has not been sufficiently targeted at areas with the highest need. Future deployments should be targeted at those areas.

BackgroundAttention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder, for which there are effective pharmacological treatments that improve symptoms and reduce complications. Guidelines published by the National Institute for Health and Care Excellence recommend that primary care practitioners prescribe medication for adult ADHD under shared-care agreements with Adult Mental Health Services (AMHS). However, provision remains uneven, with some practitioners reporting a lack of support.AimThis study aimed to describe elements of support, and their availability/use, in primary care prescribing for adult ADHD medication in England to improve access for this underserved population and inform service improvement.Design and settingCross-sectional surveys were used to elicit data from commissioners, health professionals (HPs), and people with lived experience of ADHD (LE) across England about elements supporting pharmacological treatment of ADHD in primary care.MethodThree interlinked cross-sectional surveys were used to ask every integrated care board in England (commissioners), along with convenience samples of HPs and LEs, about prescribing rates, AMHS availability, wait times, and shared-care agreement protocols/policies for the pharmacological treatment of ADHD in primary care. Descriptive analyses, percentages, and confidence intervals were used to summarise responses by stakeholder group. Variations in reported provision and practice were explored and displayed visually using mapping software.ResultsData from 782 responders (42 commissioners, 331 HPs, 409 LEs) revealed differences in reported provision by stakeholder group, including for prescribing (95% of HPs versus 64% of LEs). In all, >40% of responders reported extended AMHS wait times of ≥2 years. There was some variability by NHS region – for example, London had the lowest reported extended wait time (25%), while East of England had the highest (55%).ConclusionElements supporting appropriate shared-care prescribing of ADHD medication via primary care are not universally available in England. Coordinated approaches are needed to address these gaps.

BackgroundIncident benzodiazepine prescriptions in primary care for anxiety decreased between 2003 and 2018. However, from 2008, incident prescribing of benzodiazepines for anxiety increased among those aged 18–34 years. There are increasing concerns around prescribing of benzodiazepines. Further, although guidelines state benzodiazepines should only be prescribed short term, in 2017, 44% of incident prescriptions were prescribed for longer than the recommended duration of 2–4 weeks.AimTo understand when and why GPs prescribe benzodiazepines for anxiety in young adults.Design and settingA qualitative study was undertaken using in-depth interviews with 17 GPs from 10 general practices in South West England.MethodInterviews were conducted by telephone or videocall. A topic guide was used to ensure consistency across interviews. Interviews were audio-recorded, transcribed verbatim, and data analysed using reflexive thematic analysis.ResultsGPs described caution in prescribing benzodiazepines for anxiety in young adults, but thought they had an important role in acute situations. GPs described caution in prescribing duration, but some thought longer-term prescriptions could be appropriate. In light of these views, some GPs questioned whether primary care needs to revisit how clinicians are using benzodiazepines. GPs perceived that some young adults requested benzodiazepines and suggested this might be because they wanted quick symptom relief. GPs noted that refusing to prescribe felt uncomfortable and that the number of young adults presenting to general practice, already dependent on benzodiazepines, had increased.ConclusionPatient-driven factors for prescribing benzodiazepines suggest there are current unmet treatment needs among young adults with anxiety. Given increases in prescribing in this age group, it may be timely to revisit the role of benzodiazepines in the management of people with anxiety in primary care.

BackgroundBetween 2003 and 2018, incident prescriptions of beta-blockers for anxiety increased substantially, particularly for young adults. National Institute for Health and Care Excellence guidance for anxiety does not recommend beta-blockers, probably due to a lack of evidence to support such use. Recent reports have highlighted the potential risks of beta-blockers.AimTo understand when and why GPs prescribe beta-blockers for people with anxiety.Design and settingIn-depth interviews with 17 GPs in Bristol and the surrounding areas.MethodInterviews were held by telephone or video call. A topic guide was used to ensure consistency across interviews. Interviews were audio-recorded, transcribed verbatim, and analysed thematically.ResultsMany GPs viewed beta-blockers as ‘low risk’, particularly for young adults. Some GPs viewed beta-blockers as an alternative to benzodiazepines, acting quickly and not leading to dependence. GPs reflected that some patients appeared to want an ‘immediate fix’ to their symptoms, which GPs thought beta-blockers could potentially offer. This is salient in light of substantial waiting lists for talking therapies and delays in antidepressants taking effect. GPs described how some patients seemed more willing to try beta-blockers than antidepressants, as patients did not perceive them as ‘mental health drugs’ and therefore viewed them as potentially more acceptable and less stigmatising. Further, GPs viewed beta-blockers as ‘patient-led’, with patients managing their own dose and frequency, without GP input.ConclusionMany GPs believe that beta-blockers have a role to play in the management of anxiety. Given recent increases in the prescribing of these drugs in primary care, there is a need to assess their safety and effectiveness as a treatment for people with anxiety disorders.

BackgroundThere has been significant investment in pharmacists working in UK general practice to improve the effective and safe use of medicines. However, evidence of how to optimise collaboration between GPs and pharmacists in the context of polypharmacy (multiple medication) is lacking.AimTo explore GP and pharmacist views and experiences of in-person, interprofessional collaborative discussions (IPCDs) as part of a complex intervention to optimise medication use for patients with polypharmacy in general practice.Design and settingA mixed-method process evaluation embedded within the Improving Medicines use in People with Polypharmacy in Primary Care (IMPPP) trial conducted in Bristol and the West Midlands, between February 2021 and September 2023.MethodAudio-recordings of IPCDs between GPs and pharmacists, along with individual semi-structured interviews to explore their reflections on these discussions, were used. All recordings were transcribed verbatim and analysed thematically.ResultsA total of 14 practices took part in the process evaluation from February 2022 to September 2023; 17 IPCD meetings were audio-recorded, discussing 30 patients (range 1–6 patients per meeting). In all, six GPs and 13 pharmacists were interviewed. The IPCD was highly valued by GPs and pharmacists who described benefits, including: strengthening their working relationship; gaining in confidence to manage more complex patients; and learning from each other. It was often challenging, however, to find time for the IPCDs.ConclusionThe model of IPCD used in this study provided protected time for GPs and pharmacists to work together to deliver whole-patient care, with both professions finding this beneficial. Protected time for interprofessional liaison and collaboration, and structured interventions may facilitate improved patient care.

We primary care clinicians, scholars, and leaders ascribe value to Barbara Starfield’s core tenets of primary care—the 4 Cs: first contact, comprehensiveness, coordination, and continuity. In today’s era of rapid technological advancements and dwindling resources, what are the implications for face-to-face interactions of patient-clinician relationships? We propose adding a 5th C: "Contiguity." Contiguity—or physical proximity and presence—is a key dimension that not only enables the necessary technical aspects of a physical exam but also authenticates the most human aspects of a relationship and occurs specifically when we are physically vulnerable and responsible for the other before us. This, in turn, may best enable us to bridge difference and nurture trust with our patients. We measure what we value and, thus, naming Contiguity as a core tenet assures that we will not lose sight of this keystone in a patient’s relationship with their personal physician.

PURPOSE

HIV pre-exposure prophylaxis (PrEP) may increase rates of bacterial sexually transmitted infections (STIs) among gay, bisexual, and other men who have sex with men (GBM) through risk compensation (eg, an increase in condomless sex or number of partners); however, longitudinal studies exploring the time-dependent nature of PrEP uptake and bacterial STIs are limited. We used marginal structural models to estimate the effect of PrEP uptake on STI incidence.

PURPOSE

Chest pain frequently poses a diagnostic challenge for general practitioners (GPs). Utilizing risk stratification tools might help GPs to rule out acute coronary syndrome (ACS) and make appropriate referral decisions. We conducted a systematic review of studies evaluating risk stratification tools for chest pain in primary care settings, both with and without troponin assays. Our aims were to assess the performance of tools for ruling out ACS and to provide a comprehensive review of the current evidence.

Patient expectations of receiving antibiotics for common symptoms can trigger unnecessary use. We conducted a survey (n = 564) between January 2020 to June 2021 in public and private primary care clinics in Texas to study the prevalence and predictors of patients’ antibiotic expectations for common symptoms/illnesses. We surveyed Black patients (33%) and Hispanic/Latine patients (47%), and over 93% expected to receive an antibiotic for at least 1 of the 5 pre-defined symptoms/illnesses. Public clinic patients were nearly twice as likely to expect antibiotics for sore throat, diarrhea, and cold/flu than private clinic patients. Lack of knowledge of potential risks of antibiotic use was associated with increased antibiotic expectations for diarrhea (odds ratio [OR] = 1.6; 95% CI, 1.1-2.4) and cold/flu symptoms (OR = 2.9; 95% CI, 2.0-4.4). Lower education and inadequate health literacy were predictors of antibiotic expectations for diarrhea. Future antibiotic stewardship interventions should tailor patient education materials to include information on antibiotic risks and guidance on appropriate antibiotic indications.

PURPOSE

The impact of digital health on medically underserved patients is unclear. This study aimed to determine the early impact of a digital innovation to grow quality care through an interprofessional care team (DIG IT) on the blood pressure (BP) and 10-year atherosclerotic cardiovascular disease (ASCVD) risk score of medically underserved patients.

PURPOSE

We undertook a trial to test the efficacy of a technology-assisted health coaching intervention for weight management, called Goals for Eating and Moving (GEM), within primary care.

PURPOSE

Despite being key to better health outcomes for patients from racial and ethnic minority groups, the proportion of underrepresented in medicine (URiM) physicians remains low in the US health care system. This study linked a nationally representative sample of family physicians (FPs) with Medicaid claims data to explore the relative contributions to care of Medicaid populations by FP race and ethnicity.

PURPOSE

Currently, 40% of counties in the United States do not have an obstetrician or midwife, and in rural areas the likelihood of childbirth being attended to by a family medicine (FM) physician is increasing. We sought to characterize the effect of the FM presence on unit culture and a key perinatal quality metric in Iowa hospital intrapartum units.

BACKGROUND

For many patients with post–COVID-19 condition (long COVID), primary care is the first point of interaction with the health care system. In principle, primary care is well situated to manage long COVID. Beyond expressions of disempowerment, however, the patient’s perspective regarding the quality of long COVID care is lacking. Therefore, this study aimed to analyze the expectations and experiences of primary care patients seeking treatment for long COVID.

The strength of reproductive isolation (RI) between two or more lineages during the process of speciation can vary by the ecological conditions. However, most speciation research has been limited to studying how ecologically dependent RI varies among a handful of broadly categorized environments. Very few studies consider the variability of RI and its effects on speciation at finer scales—that is, within each environment due to spatial or temporal environmental heterogeneity. Such variation in RI across time and/or space may inhibit speciation through leaky reproductive barriers or promote speciation by facilitating reinforcement. To investigate this overlooked aspect of speciation research, we conducted a literature review of existing studies of variation in RI in the field and then conducted individual-based simulations to examine how variation in hybrid fitness across time and space affects the degree of gene flow. Our simulations indicate that the presence of variation in hybrid fitness across space and time often leads to an increase in gene flow compared to scenarios where hybrid fitness remains static. This observation can be attributed to the convex relationship between the degree of gene flow and the strength of selection on hybrids. Our simulations also show that the effect of variation in RI on facilitating gene flow is most pronounced when RI, on average, is relatively low. This finding suggests that it could serve as an important mechanism to explain why the completion of speciation is often challenging. While direct empirical evidence documenting variation in extrinsic RI is limited, we contend that it is a prevalent yet underexplored phenomenon. We support this argument by proposing common scenarios in which RI is likely to exhibit variability and thus influence the process of speciation.

Surprisingly little attention has been given to the impact of selfing on speciation, even though selfing reduces gene flow between populations and affects other key population genetics parameters. Here we review recent theoretical work and compile empirical data from crossing experiments and genomic and phylogenetic studies to assess the effect of mating systems on the speciation process. In accordance with theoretical predictions, we find that accumulation of hybrid incompatibilities seems to be accelerated in selfers, but there is so far limited empirical support for a predicted bias toward underdominant loci. Phylogenetic evidence is scarce and contradictory, including studies suggesting that selfing either promotes or hampers speciation rate. Further studies are therefore required, which in addition to measures of reproductive barrier strength and selfing rate should routinely include estimates of demographic history and genetic divergence as a proxy for divergence time.

The broad application of noninvasive imaging has transformed preclinical cancer research, providing a powerful means to measure dynamic processes in living animals. While imaging technologies are routinely used to monitor tumor growth in model systems, their greatest potential lies in their ability to answer fundamental biological questions. Here we present the broad range of potential imaging applications according to the needs of a cancer biologist with a focus on some of the common biological processes that can be used to visualize and measure. Topics include imaging metastasis; biophysical properties such as perfusion, diffusion, oxygenation, and stiffness; imaging the immune system and tumor microenvironment; and imaging tumor metabolism. We also discuss the general ability of each approach and the level of training needed to both acquire and analyze images. The overall goal is to provide a practical guide for cancer biologists interested in answering biological questions with preclinical imaging technologies.

Vision is initiated by capturing photons in highly specialized sensory cilia known as the photoreceptor outer segment. Because of its lipid and protein composition, the outer segments are prone to photo-oxidation, requiring photoreceptors to have robust antioxidant defenses and high metabolic synthesis rates to regenerate the outer segments every 10 days. Both processes required high levels of glucose uptake and utilization. Retinitis pigmentosa is a prevalent form of inherited retinal degeneration characterized by initial loss of low-light vision caused by the death of rod photoreceptors. In this disease, rods die as a direct effect of an inherited mutation. Following the loss of rods, cones eventually degenerate, resulting in complete blindness. The progression of vision loss in retinitis pigmentosa suggested that rod photoreceptors were necessary to maintain healthy cones. We identified a protein secreted by rods that functions to promote cone survival, and we named it rod-derived cone viability factor (RdCVF). RdCVF is encoded by an alternative splice product of the nucleoredoxin-like 1 (NXNL1) gene, and RdCVF was found to accelerate the uptake of glucose by cones. Without RdCVF, cones eventually die because of compromised glucose uptake and utilization. The NXNL1 gene also encodes for the thioredoxin RdCVFL, which reduces cysteines in photoreceptor proteins that are oxidized, providing a defense against radical oxygen species. We will review here the main steps of discovering this novel intercellular signaling currently under translation as a broad-spectrum treatment for retinitis pigmentosa.