Citations

Background and Purpose α4β2 nicotinic acetylcholine (nACh) receptors assemble in two stoichiometric forms, one of which is potentiated by calcium. The sites of calcium binding that underpin potentiation are not known. Experimental Approach To identify calcium binding sites, we applied cryo‐electron microscopy (cryo‐EM) and molecular dynamics (MD) simulations to each stoichiometric form of the α4β2 nACh receptor in the presence of calcium ions. To test whether the identified calcium sites are linked to potentiation, we generated mutants of anionic residues at the sites, expressed wild type and mutant receptors in clonal mammalian fibroblasts, and recorded ACh‐elicited single‐channel currents with or without calcium. Key Results Both cryo‐EM and MD simulations show calcium bound to a site between the extracellular and transmembrane domains of each α4 subunit (ECD‐TMD site). Substituting alanine for anionic residues at the ECD‐TMD site abolishes stoichiometry‐selective calcium potentiation, as monitored by single‐channel patch clamp electrophysiology. Additionally, MD simulation reveals calcium association at subunit interfaces within the extracellular domain. Substituting alanine for anionic residues at the ECD sites reduces or abolishes stoichiometry‐selective calcium potentiation. Conclusions and Implications Stoichiometry‐selective calcium potentiation of the α4β2 nACh receptor is achieved by calcium association with topographically distinct sites framed by anionic residues within the α4 subunit and between the α4 and β2 subunits. Stoichiometry‐selective calcium potentiation could result from the greater number of calcium sites in the stoichiometric form with three rather than two α4 subunits. The results are relevant to modulation of signalling via α4β2 nACh receptors in physiological and pathophysiological conditions.

Abstract Background: HER2-positive (HER2+) breast cancer accounts for 20–30% of all breast cancers. Although trastuzumab has significantly improved the survival of patients with HER2+ breast cancer, more than 70% of patients develop drug resistance within one year of treatment. Understanding the molecular mechanisms of trastuzumab resistance and identifying biomarkers that predict early trastuzumab resistance would greatly benefit patients receiving trastuzumab therapy. Methods: Differential-gene-expression analysis of trastuzumab-sensitive and resistant HER2+ breast cancer cell lines from GSE15043 was performed to identify the biomarkers associated with trastuzumab resistance. Differential biomarker expression was confirmed in FFPE tissues collected from clinical HER2+ breast cancer tumor samples that were sensitive or resistant to trastuzumab treatment. The function of the biomarkers associated with trastuzumab resistance was studied using western blotting, immunofluorescence, electron microscopy, and siRNA knockdown and overexpression to elucidate the role and mechanisms of the biomarker in affecting the trastuzumab response. Results: UGT1A7, a member of the uronic acid transferase family, was associated with trastuzumab resistance. UGT1A7 expression was downregulated in trastuzumab-resistant tumor tissues and in a cell line that developed trastuzumab resistance (BT474TR). Overexpressing UGT1A7 in BT474TR restored their sensitivity to trastuzumab treatment, whereas downregulating UGT1A7 expression in parental cells led to trastuzumab resistance. Importantly, UGT1A7 localized to the endoplasmic reticulum and altered stress responses. Furthermore, downregulating UGT1A7 expression promoted epithelial-to-mesenchymal transition (EMT) by affecting TWIST, SNAIL, and GRP78 expression and the AMP-activated protein kinase signaling pathway, thus contributing to trastuzumab resistance. Conclusions: This study demonstrated the important role and novel mechanisms of UGT1A7 in tumor responses to trastuzumab. Low UGT1A7 expression plays an important role in EMT and contributes to trastuzumab resistance. UGT1A7 has the potential to be developed as a biomarker for identifying patients who are resistant to trastuzumab treatment.

Case: A 4-year-old girl patient presented with complete amputation of the second toe close to the distal interphalangeal joint. Replantation was performed using a novel midlateral approach. The procedure used the dorsal subcutaneous vein on the foot as a graft for the artery. Four months postoperatively, the toe healed without any complication. The patient reported pain-free physical exercise without limitations in daily activity. Conclusion: This report demonstrates that this approach has the potential to provide a safe and viable alternative for treating toe amputations and offers advantages such as simplified artery identification, straightforward anastomosis, and improved vein graft harvesting.

Background Infantile-type dural arteriovenous shunts (IDAVS) are rare and heterogeneous vascular lesions, complicating their classification and management. The current tripartite classification of pediatric dural arteriovenous shunts (DAVS) into dural sinus malformation, infantile-type, and adult-type, does not stand up to scrutiny, given the variable presentations of the latter two types in children. We estimate the prevalence of IDAVS and evaluate the long term outcomes after endovascular treatment (EVT). Methods A retrospective review of a pediatric cerebrovascular database between 2006 and 2023 was conducted. Clinical and radiographic data were analyzed to evaluate the presentation and long term outcomes of IDAVS. Results IDAVS were identified in 8 (0.5%) of 1463 patients, with mean age at diagnosis of 34.7 months; male infants comprised 62.5%. The most common clinical presentations included macrocephaly (37.5%), seizures (25%), and dilated scalp veins (25%). EVT was performed in 87.5% of cases, averaging 5.8 procedures per patient. Radiographic obliteration was observed in 28.6%. Good clinical outcomes (modified Rankin Scale score of ≤2) were achieved in 85.7%. Our findings showcased discrepancies and limitations in the current classification of pediatric DAVS, prompting a re-evaluation. Conclusion IDAVS accounted for a small proportion of pediatric cerebrovascular pathologies, with markedly heterogeneous presentations. Stepwise selective embolization was associated with favorable outcomes, and is recommended over an aggressive approach with the goal of complete angiographic obliteration. Our proposed revised classification system bifurcates pediatric DAVS into dural sinus malformations and all other DAVS that are manifest in children, thereby enhancing diagnostic clarity and therapeutic approaches.

AbstractDisease OverviewChronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes and myeloproliferative neoplasms, characterized by prominent monocytosis and an inherent risk for leukemic transformation (~15%–20% over 3–5 years).DiagnosisNewly revised diagnostic criteria include sustained (>3 months) peripheral blood (PB) monocytosis (≥0.5 × 109/L; monocytes ≥10% of leukocyte count), consistent bone marrow (BM) morphology, <20% BM or PB blasts (including promonocytes), and cytogenetic or molecular evidence of clonality. Cytogenetic abnormalities occur in ~30% of patients, while >95% harbor somatic mutations: TET2 (~60%), SRSF2 (~50%), ASXL1 (~40%), RAS pathway (~30%), and others. The presence of ASXL1 and DNMT3A mutations and absence of TET2 mutations negatively impact overall survival (ASXL1WT/TET2MT genotype being favorable).Risk StratificationSeveral risk models serve similar purposes in identifying high‐risk patients that are considered for allogeneic stem cell transplant (ASCT) earlier than later. Risk factors in the Mayo Molecular Model (MMM) include presence of truncating ASXL1 mutations, absolute monocyte count >10 × 109/L, hemoglobin <10 g/dL, platelet count <100 × 109/L, and the presence of circulating immature myeloid cells; the resulting 4‐tiered risk categorization includes high (≥3 risk factors), intermediate‐2 (2 risk factors), intermediate‐1 (1 risk factor), and low (no risk factors); the corresponding median survivals were 16, 31, 59, and 97 months. CMML is also classified as being “myeloproliferative (MP‐CMML)” or “myelodysplastic (MD‐CMML),” based on the presence or absence of leukocyte count of ≥13 × 109/L.TreatmentASCT is the only treatment modality that secures cure or long‐term survival and is appropriate for MMM high/intermediate‐2 risk disease. Drug therapy is currently not disease‐modifying and includes hydroxyurea and hypomethylating agents; a recent phase‐3 study (DACOTA) comparing hydroxyurea and decitabine, in high‐risk MP‐CMML, showed similar overall survival at 23.1 versus 18.4 months, respectively, despite response rates being higher for decitabine (56% vs. 31%).Unique Disease AssociationsThese include systemic inflammatory autoimmune diseases, leukemia cutis and lysozyme‐induced nephropathy; the latter requires close monitoring of renal function during leukocytosis and is a potential indication for cytoreductive therapy.

AbstractObjectivesThis study sought to explore and externally validate the Carpenter instrument's efficacy in predicting postdischarge fall risk among older adults admitted to the emergency department (ED) for reasons other than falls or related injuries.MethodsA prospective cohort study was conducted on 779 patients aged ≥ 65 years from a tertiary hospital in São Paulo, Brazil, who were monitored for up to 6 months post‐ED hospitalization. The Carpenter instrument, which evaluates the four risk factors nonhealing foot sores, self‐reported depression, inability to self‐clip toenails, and prior falls, was utilized to assess fall risk. Follow‐up by telephone occurred at 30, 90, and 180 days to identify falls and mortality. Fine–Gray models estimated the predictive power of Carpenter instrument for future falls, considering death as a competing event and sociodemographic factors, frail status, and clinical measures as confounders.ResultsAmong 779 patients, 68 (9%) experienced a fall within 180 days post‐ED admission, and 88 (11%) died. The majority were male (54%), with a mean age of 79 years. Upon utilizing the Carpenter score, those with a higher fall risk (≥2 points) displayed more comorbidities, greater frailty, and increased clinical severity at baseline. Regression analyses showed that every additional point on the Carpenter score increased the hazard of falls by 73%. Two primary contributors to its predictive potential were identified: a history of falls in the preceding year and an inability to self‐clip toenails. However, the instrument's discriminative accuracy was suboptimal, with an area under the curve of 0.62.ConclusionsWhile the Carpenter instrument associated with a higher 6‐month postadmission fall risk among older adults post‐ED visit, its accuracy for individual patient decision making was limited. Given the significant impact of falls on health outcomes and health care costs, refining risk assessment tools remains essential. Future research should focus on enhancing these assessments and devising targeted proactive strategies.