Pik3c3 expression profiling in the mouse kidney and its role in proximal tubule cell physiology.

The class 3 phosphatidylinositol 3-kinase (Pik3c3) plays critical roles in regulating autophagy, endocytosis, and nutrient sensing, but its expression profile in the kidney remains undefined. Recently, we validated a Pik3c3 antibody through immunofluorescence staining of kidney tissues from cell type-specific Pik3c3 knockout mice. Immunohistochemistry unveiled significant disparities in Pik3c3 expression levels across various kidney cell types. Notably, renal interstitial cells exhibit minimal Pik3c3 expression. Further, coimmunofluorescence staining, utilizing nephron segment- or cell type-specific markers, revealed nearly undetectable levels of Pik3c3 expression in glomerular mesangial cells and endothelial cells. Intriguingly, although podocytes exhibit the highest Pik3c3 expression levels among all kidney cell types, the renal proximal tubule cells (RPTCs) express the highest level of Pik3c3 among all renal tubules. RPTCs are known to express the highest level of the epidermal growth factor receptor (EGFR) in adult kidneys; however, the role of Pik3c3 in EGFR signaling within RPTCs remains unexplored. Therefore, we conducted additional cell culture studies. The results demonstrated that Pik3c3 inhibition significantly delayed EGF-stimulated EGFR degradation and the termination of EGFR signaling in RPTCs. Mechanistically, Pik3c3 inhibition surprisingly did not affect the initial endocytosis process but instead impeded the lysosomal degradation of EGFR. In summary, this study defines, for the first time, the expression profile of Pik3c3 in the mouse kidney and also highlights a pivotal role of Pik3c3 in the proximal tubule cells. These findings shed light on the intricate mechanisms underlying Pik3c3-mediated regulation of EGFR signaling, providing valuable insights into the role of Pik3c3 in renal cell physiology. NEW & NOTEWORTHY This is the first report defining the class 3 phosphatidylinositol 3-kinase (Pik3c3) expression profile in the kidney. Pik3c3 is nearly absent in renal interstitial cells, glomerular mesangial cells, and endothelial cells. Remarkably, glomerular podocytes express the highest Pik3c3 level in the kidney. However, the proximal tubule exhibits the highest expression level among all renal tubules. This study also unveils the pivotal role of Pik3c3 in regulating EGFR degradation and signaling termination in RPTCs, furthering our understanding of Pik3c3 in renal cell physiology.

Ion Channels in Cancer: Orchestrators of Electrical Signaling and Cellular Crosstalk.

Ion channels are pore-forming transmembrane proteins that govern ion flux to regulate a myriad of biological processes in development, physiology, and disease. Across various types of cancer, ion channel expression and activity are often dysregulated. We review the contribution of ion channels to multiple stages of tumorigenesis based on data from in vivo model systems. As intertumoral and intratumoral heterogeneities are major obstacles in developing effective therapies, we provide perspectives on how ion channels in tumor cells and their microenvironment represent targetable vulnerabilities in the areas of tumor-stromal cell interactions, cancer neuroscience, and cancer mechanobiology.

A metabolic function of FGFR3-TACC3 gene fusions in cancer.

Chromosomal translocations that generate in-frame oncogenic gene fusions are notable examples of the success of targeted cancer therapies. We have previously described gene fusions of FGFR3-TACC3 (F3-T3) in 3% of human glioblastoma cases. Subsequent studies have reported similar frequencies of F3-T3 in many other cancers, indicating that F3-T3 is a commonly occuring fusion across all tumour types. F3-T3 fusions are potent oncogenes that confer sensitivity to FGFR inhibitors, but the downstream oncogenic signalling pathways remain unknown. Here we show that human tumours with F3-T3 fusions cluster within transcriptional subgroups that are characterized by the activation of mitochondrial functions. F3-T3 activates oxidative phosphorylation and mitochondrial biogenesis and induces sensitivity to inhibitors of oxidative metabolism. Phosphorylation of the phosphopeptide PIN4 is an intermediate step in the signalling pathway of the activation of mitochondrial metabolism. The F3-T3-PIN4 axis triggers the biogenesis of peroxisomes and the synthesis of new proteins. The anabolic response converges on the PGC1α coactivator through the production of intracellular reactive oxygen species, which enables mitochondrial respiration and tumour growth. These data illustrate the oncogenic circuit engaged by F3-T3 and show that F3-T3-positive tumours rely on mitochondrial respiration, highlighting this pathway as a therapeutic opportunity for the treatment of tumours with F3-T3 fusions. We also provide insights into the genetic alterations that initiate the chain of metabolic responses that drive mitochondrial metabolism in cancer.

Inpatient Mortality and 30-Day Readmission Rates Associated with Troponin Testing in Patients without Acute Myocardial Infarction.

OBJECTIVE: Troponin values above the threshold established to diagnose acute myocardial infarction (AMI; >99th percentile) are commonly detected in patients with diagnoses other than AMI. The objective of this study was to compare inpatient mortality and 30-day readmission rate in patients with troponin I (TnI) above and below the 99th percentile in those with type 1 AMI and type 2 myocardial injury. METHODS: Between January 1, 2016 and December 31, 2016, there were 56,895 inpatient hospitalizations; of these 14,326 (25.2%) patients received troponin testing. We evaluated mortality and readmissions in the entire cohort based on the primary discharge International Classification of Diseases, Tenth Edition (ICD-10) diagnosis and grouped into type 1 AMI versus other diagnoses comprising the type 2 AMI group (including ICD-10 codes for congestive heart failure, sepsis, and other). Among those with TnI drawn, we evaluated in-hospital mortality and 30-day readmissions based on troponin values > 99th percentile (≥ 0.1 ng/ml). RESULTS: Among the entire cohort, the inpatient mortality rate was significantly higher in those with TnI testing (5.0%, 95% CI 4.6%-5.3%) compared to those without testing (0.7%, 95% CI 0.6%-0.7%, P < 0.01). In the tested cohort 3,743 (26%) patients had troponin levels above the 99th percentile (> 0.1 ng/ml), and 10,583 (74%) had troponin levels below the 99th percentile (≤ 0.1 ng/ml). Comparing type 2 AMI with type 1 AMI and troponin testing, TnI values ≥ 0.1 ng/ml were associated with higher inpatient mortality (11.6% vs. 3.9%) and 30-day readmission rates (16.9% vs. 10.7%). CONCLUSIONS: A higher inpatient mortality and 30-day readmission rates were found in patients with type 2 AMI compared to type 1 AMI group.

Myxomatous Mitral Valve with Prolapse and Flail Scallop.

BACKGROUND: Myxomatous mitral valve with prolapse are classically seen with abnormal leaflet apposition during contraction of the heart. Hemodynamic disorders can result from eccentric mitral regurgitation usually caused by chordae tendinae rupture or papillary muscle dysfunction. Echocardiography is the gold standard for evaluation of leaflet flail and prolapse due to high sensitivity and specificity. Though most mitral valve prolapse are asymptomatic those that cause severe regurgitation need emergent surgical intervention to prevent disease progression. CASE REPORT: We report a 54 year old Hispanic male who presented with progressively worsening dyspnea and palpitations. Initial evaluation was significant for atrial fibrillation on electrocardiogram with subsequent echocardiography revealing myxomatous mitral valve with prolapse. Following surgical repair of the mitral valve, the dyspnea and palpitations resolved. CONCLUSIONS: Mitral valve prolapse is a common valvular abnormality but the pathogenic cause of myxomatous valves has not been elucidated. Several theories describe multiple superfamilies of proteins to be involved in the process. Proper identification of these severe mitral regurgitation due to these disease valves will help relieve symptomatic mitral valve prolapse patients.

Clinical considerations of the glandular branch of the lacrimal artery.

The lacrimal artery is classically described as a branch of the ophthalmic artery supplied by the internal carotid. In this study, 25 orbits were dissected to identify variations in glandular branching and to compare them to previously published accounts. The glandular branching patterns of the lacrimal artery fall into two categories, those that branch (56%) and those that do not branch (44%). We found the medial and lateral glandular branches to be equal in diameter with a divergence of 2.67-40.58 mm proximal to the gland parenchyma. The long glandular branches run alongside the superolateral aspect of the orbit. The lateral branch runs lateral to the lateral rectus muscle. The medial branch runs superomedial to the lateral rectus muscle and lateral to the superior rectus muscle. In relation to the lacrimal gland, the medial branch enters the superior aspect of the gland parenchyma and the lateral branch enters its inferior aspect. The average branch lengths were 17.88 mm (medial) and 13.51 mm (lateral) as measured with a Mitutoyo Absolute 1/100 mm caliper. We could not confirm the existence of a third branch supplying the lacrimal gland, as posited by other authors. The key finding in this study is that the lacrimal gland is predominantly supplied by two significant arterial branches, both of which must be identified during procedures involving the lateral orbit.

Congenital Absence of Left Circumflex Presenting After an Emotional Stressor.

BACKGROUND: Absence of the left circumflex artery (LCX) is an extremely rare congenital anomaly of the coronary circulation. While some coronary circulation anomalies are associated with significant complications, including sudden cardiac death and premature atherosclerosis, absence of the LCX is largely considered benign, though it has been associated with exertional chest pain, which may mimic acute coronary syndrome. Diagnosis is made when heart catheterization is performed in the work up for acute coronary syndrome or when computed tomography coronary angiography is performed during evaluation of coronary artery disease. CASE REPORT: We report a 55 year old female who presented with non-exertional chest pain in the setting of an emotional stressor. The initial work up was only significant for elevated troponins, and subsequent left heart catheterization revealed findings consistent with congenital absence of the LCX. No significant stenosis was appreciated, and no intervention was performed. Following catheterization, the patient's troponins began to trend down, and her chest pain resolved. CONCLUSIONS: Congenitally absent LCX is a rare entity detected when work up is performed to rule out acute coronary syndrome in patients presenting with exertional chest pain. This is the first reported case of chest pain unrelated to physical activity reported in a patient with an absent LCX. There is no specific treatment for an absent LCX; however, proper identification of this anomaly and differentiation from complete occlusion of the LCX is important in making an accurate diagnosis of myocardial ischemia and for choosing the best intervention when ischemia is present.

Patterns of innervation of the lacrimal gland with clinical application.

Parasympathetic stimulation of the lacrimal gland is responsible for tear production, and this innervation originates from fibers conveyed in the facial nerve. After synapse in the pterygopalatine ganglion, postsynaptic parasympathetic fibers travel within the zygomatic and zygomaticotemporal nerves (ZTN) into the orbit. As described in most anatomy texts, ZTN communicates with the lacrimal nerve (LN) posterior to the gland and then secretomotor fibers enter the gland. This study was performed to gain a better understanding of the innervation of the lacrimal gland. Seventeen cadaver heads were bisected for a total of 34 sides, which then underwent dissection of the superolateral orbital region to observe the course for the LN and ZTN. Three variations of the course of the LN and ZTN were found. In 20 (60.6%) dissections it was documented that the ZTN entered directly into the lacrimal gland with no communication with the LN. In 12 (36.4%) of the bisected heads, ZTN had both a direct connection into the gland and a communicating branch with the LN. In only one (3.0%) bisected head, ZTN communicated with the LN before entering the gland as it is commonly described in anatomy texts. Our study reveals that the ZTN usually takes a different course than is classically described in most anatomy textbooks. A greater understanding of the typical course these nerves take may help surgeons identify them more easily and avoid damaging them.

Characteristic Cardiac Magnetic Resonance (CMR) Imaging Findings of Cocaine-Induced Myocardial Injury.

Cocaine is a widely available illicit substance with a costly financial and social burden on the healthcare infrastructure. Both acute and chronic cocaine use can lead to sequelae of cardiac diseases, including myocardial infarction, aortic dissection, and cardiomyopathy. Cardiac magnetic resonance (CMR) imaging is a powerful tool for detecting myocardial injury leading to prompt treatment and risk stratification. We present two differing cases of sequelae of myocardial injury as a result of cocaine use. We present critical findings on CMR imaging, including myocardial injury patterns, which can help differentiate between acute and chronic injury and assess the extent of damage. Cocaine exerts potent sympathomimetic effects, increasing myocardial oxygen demand and causing coronary vasospasm, thrombosis, and direct myocyte toxicity. Acute cocaine use significantly elevates the risk of myocardial infarction, while chronic use can lead to cardiomyopathy and heart failure. CMR features include wall motion abnormalities, myocardial perfusion defects, and fibrosis. Early identification and intervention can potentially reverse interstitial fibrosis before progression to irreversible damage. CMR is an essential diagnostic tool for characterizing myocardial injury, distinguishing between reversible and irreversible damage, and providing prognostic information on cocaine-induced myocardial injury. The cases highlight the importance of CMR in managing and understanding the full spectrum of cocaine-related cardiac damage.

Refining Cardiovascular Calcification in the Appraisal of Ischemic Heart.

BACKGROUND: Even in asymptomatic patients, there is a high association of ischemia on myocardial perfusion scans in those with coronary artery calcification or valvular calcifications. Patients without coronary artery calcifications have exceeding-low rates of cardiovascular events. The absence of cardiovascular calcification, including coronary artery, valvular, and thoracic aorta is a strong negative predictor of myocardial ischemia. In individuals with suspected ischemia who had chest computed tomography imaging, evaluation for cardiovascular calcification (coronary artery, valves, and thoracic aorta) is an invaluable tool to guide management for further diagnostic imaging. We hypothesize that the complete absence of cardiovascular calcification has a high negative predictive value for defects in myocardial perfusion imaging such as single-photon emission computed tomography (SPECT) or positron emission tomography (PET). METHODS: Non-contrast computed tomography performed for SPECT/PET CT attenuation correction from March 1, 2017, to September 30, 2017, were retrospectively reviewed for the absence of cardiovascular calcification by a cardiologist and radiologist who were blinded to patients' medical history. Medical records were reviewed to include patient demographics and medical history. A total of 132 patients were analyzed. RESULTS: Of the 132 patients without calcifications, seven patients had small myocardial perfusion defects suggestive of ischemia or infarct, but none were considered significant defects. Of these seven patients, six were managed medically and one was from an outside institution with no follow-up data. Two of the seven patients had follow-up invasive angiography or coronary CTA that did not show significant atherosclerotic coronary artery disease. CONCLUSION: A complete absence of cardiovascular calcification indicates a 100% negative predictive value for a significant perfusion defect on same-day confirmatory nuclear stress testing. Patients with suspected ischemia but absent cardiovascular calcifications can be safely managed medically without further testing for ischemia.

Case Illustration of the Natural History of Left Dominant Arrhythmogenic Cardiomyopathy.

Background: Arrhythmogenic left ventricular cardiomyopathy is an increasingly recognized cause of recurrent myocarditis, a mimicker of acute coronary syndrome, and an important cause of malignant ventricular arrythmias and heart failure. Desmoplakin is a protein that is critical to maintaining the structural integrity of the myocardium. Disruption of desmoplakin leads to fibrofatty infiltration of the myocardium which leads to congestive heart failure, cardiac arrhythmias, and sudden cardiac death. However, desmoplakin cardiomyopathy is often misdiagnosed, resulting in significant morbidity and mortality. We report 2 contrasting cases illustrating the natural history-hot and cold phases-of arrhythmogenic left ventricular cardiomyopathy. Case Series: The first case demonstrates a common phenotypic presentation of desmoplakin cardiomyopathy manifested as recurrent myocarditis and myocardial injury representing the hot phase. The second case is an undulating course of chronic systolic heart failure and ventricular arrhythmias representing the cold phase. Conclusion: Arrhythmogenic cardiomyopathy manifests as a spectrum of disease processes that involve the right, left, or both ventricles. Mutations in the desmoplakin gene are often associated with a left dominant ventricular cardiomyopathy. Diagnosis remains difficult as the condition has no signature clinical presentation, and imaging findings are variable.

Sealing of transected neurites of rat B104 cells requires a diacylglycerol PKC-dependent pathway and a PKA-dependent pathway.

To survive, neurons and other eukaryotic cells must rapidly repair (seal) plasmalemmal damage. Such repair occurs by an accumulation of intracellular vesicles at or near the plasmalemmal disruption. Diacylglycerol (DAG)-dependent and cAMP-dependent proteins are involved in many vesicle trafficking pathways. Although recent studies have implicated the signaling molecule cAMP in sealing, no study has investigated how DAG and DAG-dependent proteins affect sealing. By means of dye exclusion to assess Ca(2+)-dependent vesicle-mediated sealing of transected neurites of individually identifiable rat hippocampal B104 cells, we now report that, compared to non-treated controls, sealing probabilities and rates are increased by DAG and cAMP analogs that activate PKC and Munc13-1 and PKA. Sealing is decreased by inhibiting DAG-activated novel protein kinase C isozymes η (nPKCη) and θ (nPKCθ) and Munc13-1, the PKC effector myristoylated alanine rich PKC substrate (MARCKS) or phospholipase C (PLC). DAG-increased sealing is prevented by inhibiting MARCKS or protein kinase A (PKA). Sealing probability is further decreased by simultaneously inhibiting nPKCη, nPKCθ, and PKA. Extracellular Ca(2+), DAG, or cAMP analogs do not affect this decrease in sealing. These and other data suggest that DAG increases sealing through MARCKS and that nPKCη, nPKCθ, and PKA are all required to seal plasmalemmal damage in B104 and likely all eukaryotic cells.

COVID-19 online medical education and outcomes on Internal Medicine In-Training Examination scores.

Background: COVID-19 presented a unique opportunity to explore new methods to deliver medical education virtually due to requirements for social distancing. We provided webcams and microphones in each of our core teaching team rooms. We used existing teleconferencing systems with share screen, polling, and audio/video capabilities to continue fostering a group learning environment. Methods: The Internal Medicine In-Training Examination (IM-ITE) was used as a surrogate measurement of the effectiveness of virtual medical education, comparing composite scores from 2015 to 2019 (pre-COVID, in-person conference) to 2020 (post-COVID, virtual conference) for each postgraduate class. Results: No statistically significant differences between the mean or median scores on the IM-ITE were noted for all three classes. Conclusion: Although COVID-19 presented many challenges to residency programs across the United States, our pilot study demonstrated that virtual medical education did not result in lower IM-ITE scores and may be an innovative solution to bridge the education gap during COVID-19.

Mechanical nanosurgery of chemoresistant glioblastoma using magnetically controlled carbon nanotubes.

Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Despite multimodal treatment including surgery, radiotherapy, and chemotherapy, median patient survival has remained at ~15 months for decades. This situation demands an outside-the-box treatment approach. Using magnetic carbon nanotubes (mCNTs) and precision magnetic field control, we report a mechanical approach to treat chemoresistant GBM. We show that GBM cells internalize mCNTs, the mobilization of which by rotating magnetic field results in cell death. Spatiotemporally controlled mobilization of intratumorally delivered mCNTs suppresses GBM growth in vivo. Functionalization of mCNTs with anti-CD44 antibody, which recognizes GBM cell surface-enriched antigen CD44, increases mCNT recognition of cancer cells, prolongs mCNT enrichment within the tumor, and enhances therapeutic efficacy. Using mouse models of GBM with upfront or therapy-induced resistance to temozolomide, we show that mCNT treatment is effective in treating chemoresistant GBM. Together, we establish mCNT-based mechanical nanosurgery as a treatment option for GBM.

Mechanosensitive brain tumor cells construct blood-tumor barrier to mask chemosensitivity.

Major obstacles in brain cancer treatment include the blood-tumor barrier (BTB), which limits the access of most therapeutic agents, and quiescent tumor cells, which resist conventional chemotherapy. Here, we show that Sox2+ tumor cells project cellular processes to ensheathe capillaries in mouse medulloblastoma (MB), a process that depends on the mechanosensitive ion channel Piezo2. MB develops a tissue stiffness gradient as a function of distance to capillaries. Sox2+ tumor cells perceive substrate stiffness to sustain local intracellular calcium, actomyosin tension, and adhesion to promote cellular process growth and cell surface sequestration of ß-catenin. Piezo2 knockout reverses WNT/ß-catenin signaling states between Sox2+ tumor cells and endothelial cells, compromises the BTB, reduces the quiescence of Sox2+ tumor cells, and markedly enhances the MB response to chemotherapy. Our study reveals that mechanosensitive tumor cells construct the BTB to mask tumor chemosensitivity. Targeting Piezo2 addresses the BTB and tumor quiescence properties that underlie treatment failures in brain cancer.

Idiopathic Intracranial Hypertension and Multiple Sclerosis Overlap.

Idiopathic intracranial hypertension (IIH) and multiple sclerosis (MS) occur with a higher incidence in women of childbearing age and may be associated with other clinical entities. Both disease processes alter cerebrospinal fluid (CSF) dynamics and may present similarly with headache and visual changes. We report a case of a 33-year-old morbidly obese woman who developed progressive worsening blurry vision and unilateral temporal headache. She was found to have papilledema which prompted workup for intracranial hypertension. Her imaging and CSF findings were suggestive of a demyelinating process such as MS in addition to IIH.

Castleman Disease Presenting as a Mediastinal Mass.

Castleman disease is a complex benign lymphoproliferative disorder characterized by the enlargement of a single lymph node or a group of lymph nodes. Its etiology is unclear, with the mechanism of action of IL-6 and HHV-8 implicated as possibly associated with the development of the disease. Diagnosis depends on the histopathological findings of the involved lymph nodes. Surgical resection can be curative, but a small number of cases may be unresectable and need radiation and chemotherapy with subsequent resection if possible.

Nonpenetrating trauma resulting in hemopericardium presenting as syncope.

Hemopericardium is a life-threatening condition that needs to be treated promptly to prevent serious complications. It typically results from penetrating trauma directly into the pericardial sac resulting in cardiac tamponade and death if not promptly treated. High clinical suspicion should prompt further workup even in the absence of significant injury. We present a case of a 38-year-old man who presented with blunt force trauma from a rock while mowing the lawn that resulted in syncope and hemopericardium.

Myeloid sarcoma as a manifestation of acute myeloid leukemia.

We report a case of a 43-year-old man who presented with dyspnea because of large bilateral pleural effusions and imaging findings of a large periaortic mass with compression of the esophagus and left atrium. Subsequent soft tissue biopsy was consistent with myeloid sarcoma, and bone marrow biopsy was consistent with acute myeloid leukemia. He was started on induction and subsequent consolidation chemotherapy with complete remission and shrinkage of the tumor.

Association of Maximum Troponin Levels With Diagnosis of Acute Myocardial Infarction and Elevated Risk of Mortality.

Background: Cardiac troponins I and T are highly sensitive and specific markers for acute myocardial infarction (AMI). However, a wide range of non-AMI conditions can also cause significant elevations in cardiac troponins. Given the deleterious impact of misdiagnosis of AMI, the ability to risk-stratify patients who present with an elevated troponin is paramount. We hypothesized that the maximum troponin level would be more predictive of mortality and the diagnosis of AMI than the initial troponin level or change in troponin level. Methods: Patient records from a 9-hospital system (n=30,173) in Texas were reviewed during a 24-month period in 2016-2017. Data collected for patients aged ≥40 years included International Classification of Diseases, Tenth Revision diagnoses, troponin I, demographic data (age, sex, smoking history, and chronic medical conditions), and death during hospitalization. We used logistic regression with the Firth penalized likelihood approach to determine the predictive ability of initial, maximum, and change in troponin level for mortality and the diagnosis of AMI. Results: Demographic characteristics of our cohort included a median age of 70 years, with 48.05% male and 51.95% female. The most common preexisting risk factor was hypertension in 78.81% of the cohort. Notable findings from the logistic regression include the predictive ability of maximum troponin on the odds of death by 0.7% for each unit of increase in troponin value. Also, the odds of AMI increased by 3.1% for each unit of increase in the maximum troponin value. Conclusion: Regardless of the level, a detectable amount of troponin in the serum results in a significantly elevated risk of mortality. Many patients with elevated troponin levels leave the hospital without a specific diagnosis, which can lead to poor outcomes because a detectable troponin does not represent a no-risk population. Our study demonstrates that maximum troponin level is a more sensitive and specific predictor of mortality than initial or change in troponin. Similarly, maximum troponin is the most predictive of AMI vs other causes of troponin elevation, likely because of the correlation between rising troponin levels and cardiomyocyte damage. Further studies are needed to correlate maximum troponin levels and clinical manifestations, which may be helpful in redefining AMI so that AMI can be distinguished more easily from non-AMI diagnoses.