Information-based TMS to mid-lateral prefrontal cortex disrupts action goals during emotional processing

The ability to respond to emotional events in a context-sensitive and goal-oriented manner is essential for adaptive functioning. In models of behavioral and emotion regulation, the lateral prefrontal cortex (LPFC) is postulated to maintain goal-relevant representations that promote cognitive control, an idea rarely tested with causal inference. Here, we altered mid-LPFC function in healthy individuals using a putatively inhibitory brain stimulation protocol (continuous theta burst; cTBS), followed by fMRI scanning. Participants performed the Affective Go/No-Go task, which requires goal-oriented action during affective processing. We targeted mid-LPFC (vs. a Control site) based on the individualized location of action-goal representations observed during the task. cTBS to mid-LPFC reduced action-goal representations in mid-LPFC and impaired goal-oriented action, particularly during processing of negative emotional cues. During negative-cue processing, cTBS to mid-LPFC reduced functional coupling between mid-LPFC and nodes of the default mode network, including frontopolar cortex-a region thought to modulate LPFC control signals according to internal states. Collectively, these results indicate that mid-LPFC goal-relevant representations play a causal role in governing context-sensitive cognitive control during emotional processing.

A Rare Case of an Eosinophilic Pleural Effusion and Loculated Ascites Associated with Strongyloides stercoralis Hyperinfection Syndrome in California

Introduction. Strongyloides stercoralis causes a helminthic infection that occurs via penetration of the skin with migration to the bloodstream, tracheobronchial tree, and gastrointestinal system. Pulmonary manifestations are rare and are typically seen in immunosuppressed patients who have Strongyloides stercoralis hyperinfection syndrome. Eosinophilic pleural effusions are rare in strongyloidiasis and only cited in a few case reports. Case Presentation. A 45-year-old male with a past medical history of diabetes mellitus, alcoholic cirrhosis, and end-stage renal disease presented to the emergency department with abdominal pain and dyspnea. Imaging studies demonstrated large bilateral pleural effusions, and he subsequently underwent an ultrasound-guided thoracentesis on the right hemithorax, yielding an exudative eosinophilic pleural effusion. An extensive hematology, gastroenterology, and infectious work-up was pursued. Strongyloides immunoglobulin G was positive, and he was successfully treated with ivermectin. Discussion. Eosinophilic pleural effusions related to strongyloidiasis are exceedingly rare. Clinicians should consider Strongyloides stercoralis infection as a part of the differential diagnosis when evaluating immunosuppressed patients with eosinophilic pleural effusions. Loculated abdominal fluid may also be a rare manifestation of Strongyloides stercoralis hyperinfection syndrome.

Sclerosing epithelioid fibrosarcoma associated with WRN gene variant presenting as chronic dyspnea and pathologic cervical fracture: a case report and review of the literature

BACKGROUND

Sclerosing epithelioid fibrosarcoma is an aggressive sarcoma subtype with poor prognosis and limited response to conventional chemotherapy regimens. Diagnosis can be difficult owing to its variable presentation, and cases of sclerosing epithelioid fibrosarcoma are rare. Sclerosing epithelioid fibrosarcoma typically affects middle-aged individuals, with studies inconsistently citing gender predominance. Sclerosing epithelioid fibrosarcoma typically arises from the bones and soft tissues and often has local recurrence after resection and late metastases. Immunohistochemical staining typically is positive for mucin-4. Werner syndrome is due to an autosomal recessive mutation in the WRN gene and predisposes patients to malignancy.

CASE PRESENTATION

A 37-year-old Caucasian female presented to the emergency department with 4 months of dyspnea and back pain. She had been treated for pneumonia but had persistent symptoms. A chest, abdomen, and pelvis computed tomography showed near-complete right upper lobe collapse and consolidation, mediastinal lymphadenopathy, lytic spinal lesions, and a single 15-mm hypodense liver nodule. The patient underwent a transthoracic right upper lobe biopsy, bronchoscopy, endobronchial ultrasound with transbronchial lymph node sampling, and bronchoalveolar lavage of the right upper lobe. The bronchoalveolar lavage cytology was positive for malignant cells compatible with poorly differentiated non-small cell carcinoma; however, the cell block materials were insufficient to run immunostains for further investigation of the bronchoalveolar lavage results. Consequently, the patient also underwent a liver biopsy of the liver nodule, which later confirmed a diagnosis of sclerosing epithelioid fibrosarcoma. Next-generation sequencing revealed a variant of unknown significance in the WRN gene. She was subsequently started on doxorubicin.

CONCLUSION

Sclerosing epithelioid fibrosarcoma is a very rare entity, only cited approximately 100 times in literature to date. Physicians should be aware of this disease entity and consider it in their differential diagnosis. Though pulmonary involvement has been described in the context of sclerosing epithelioid fibrosarcoma, this malignancy may affect many organ systems, warranting extensive investigation. Through our diagnostic workup, we suggest a possible link between sclerosing epithelioid fibrosarcoma and the WRN gene. Further study is needed to advance our understanding of sclerosing epithelioid fibrosarcoma and its clinical associations as it is an exceedingly rare diagnosis.

The impact of impaired insulin regulation on severity of SARS-CoV-2 infection: a 2-year retrospective single-center analysis

Background

The COVID-19 pandemic has caused an international healthcare crisis and produced a large healthcare burden. Diabetes mellitus (DM) is a common disease that can be controlled via pharmacologic agents; however, many patients have poor glycemic control, leading to disease-related complications. DM has been reported in the literature to be associated with increasing morbidity and mortality in COVID-19 patients. The authors aim to assess the associations between glucose homoeostasis and COVID-19 disease severity and mortality.

Methods

A retrospective chart review of patients ages 18-100 years of age admitted with COVID-19 between January 2020 and December 2021 was performed. The primary outcome was COVID-19 mortality with respect to haemoglobin A1C levels of less than 5.7%, 5.7-6.4%, and 6.5% and greater. Disease severity was determined by degree of supplemental oxygen requirements (ambient air, low-flow nasal cannula, high-flow nasal cannula, non-invasive mechanical ventilation, and invasive mechanical ventilation). COVID-19 mortality and severity were also compared to blood glucose levels on admission as grouped by less than 200 mg/dl and greater than or equal to 200 mg/dl.

Results

A total of 1156 patients were included in the final analysis. There was a statistically significant association between diabetic status and mortality (P=0.0002). Statistical significance was also noted between admission blood glucose ≥200 mg/dl and mortality (P=0.0058) and respiratory disease severity (P=0.0381). A multivariate logistic regression for predicting mortality showed increasing haemoglobin A1C was associated with increased mortality (odds ratio 1.72 with 95% CI of 1.122-2.635).

Conclusions

In our 2-year retrospective analysis, there was an association between a diagnosis of DM and COVID-19-related mortality. Hyperglycaemia on admission was found to be statistically significant with mortality in patients diagnosed with COVID-19. Glucose homoeostasis and insulin dysregulation likely play a contributing factor to COVID-19 disease severity and mortality.

ABO blood group and rhesus factor association with inpatient COVID-19 mortality and severity: a two-year retrospective review

Background

Early reports have indicated a relationship between ABO and rhesus blood group types and infection with SARS-CoV-2. We aim to examine blood group type associations with COVID-19 mortality and disease severity.

Methods

This is a retrospective chart review of patients ages 18 years or older admitted to the hospital with COVID-19 between January 2020 and December 2021. The primary outcome was COVID-19 mortality with respect to ABO blood group type. The secondary outcomes were 1. Severity of COVID-19 with respect to ABO blood group type, and 2. Rhesus factor association with COVID-19 mortality and disease severity. Disease severity was defined by degree of supplemental oxygen requirements (ambient air, low-flow, high-flow, non-invasive mechanical ventilation, and invasive mechanical ventilation).

Results

The blood type was collected on 596 patients with more than half (54%, N=322) being O+. The ABO blood type alone was not statistically associated with mortality (P=0.405), while the RH blood type was statistically associated with mortality (P<0.001). There was statistically significant association between combined ABO and RH blood type and mortality (P=0.014). Out of the mortality group, the O+ group had the highest mortality (52.3%), followed by A+ (22.8%). The combined ABO and RH blood type was statistically significantly associated with degree of supplemental oxygen requirements (P=0.005). The Kaplan-Meier curve demonstrated that Rh- patients had increased mortality.

Conclusion

ABO blood type is not associated with COVID-19 severity and mortality. Rhesus factor status is associated with COVID-19 severity and mortality. Rhesus negative patients were associated with increased mortality risk.

Primary Mediastinal B-Cell Lymphoma Presenting as Cardiac Tamponade

Primary mediastinal B-cell lymphoma (PMBCL) is a rare subtype of non-Hodgkin lymphoma. Typical symptoms include cough, chest pain, and dyspnea; however, cardiac tamponade as the primary manifestation is exceedingly rare. We hereby present a case of a 34-year-old male with a past medical history of obesity, who presented to our emergency department with a chronic dry cough for 4 months. On admission, computed tomography demonstrated a large 11.1-cm diameter anterior mediastinal mass, and echocardiography demonstrated cardiac tamponade physiology. The patient underwent further workup including pericardiocentesis, subsequent pericardial window, and mediastinal biopsy, which demonstrated histopathology consistent with PMBCL. Our case highlights the importance of a complete and thorough workup for patients with chronic untraditional symptoms. This case is unique in that PMBCL is rarely associated with cardiac tamponade as the primary clinical presentation. Additionally, we recommend an extensive cardiac workup for patients presenting with a large mediastinal mass, as failure to do so may result in patient morbidity and mortality.

Acute Respiratory Distress Syndrome: A Rare Manifestation of Rhinovirus Infection

Human rhinovirus (HRV) is a common cause of respiratory infections. HRV-related lower respiratory tract infections, including community-acquired pneumonia, are seldom seen in the clinical setting, and progression to acute respiratory distress syndrome (ARDS) is even rarer. We report on a case of a young immunosuppressed host who presented to the hospital for respiratory distress. She was diagnosed with HRV-related pneumonia, which rapidly progressed to ARDS based on clinical examination. After orotracheal intubation and mechanical ventilation with a low tidal volume strategy, she made a rapid recovery. This case highlights the importance of understanding that HRV may be an etiology of community-acquired pneumonia in immunosuppressed hosts and that ARDS may be a complication of this infection. Rapid recognition and clinical suspicion are important to the care of these patients, as ARDS has a high mortality rate.

Symptomatic Bronchogenic Cyst in a Lipomatous Interatrial Septum

Intracardiac bronchogenic cysts are extremely rare congenital anomalies that arise during foregut development when the embryologic heart tube and ventral foregut are in close proximity to one another. We report a case of an interatrial septal bronchogenic cyst found on non-contrast enhanced computed tomography (CT) in a 66-year-old female who presented to the emergency department with chest pain. Further cardiac investigations, including contrast-enhanced CT angiogram of the heart, transthoracic echocardiogram, and transesophageal echocardiogram, revealed a cystic mass in the lipomatous interatrial septum. The patient was subsequently diagnosed with a bronchogenic cyst of the interatrial septum. No surgical intervention was pursued, as the mass remained stable, and the cardiothoracic surgeon did not recommend excision. This case highlights a rare case of a symptomatic bronchogenic cyst arising in the interatrial septum diagnosed by imaging modalities. Bronchogenic cysts should be included in the differential diagnosis of intracardiac tumors.

Disseminated Histoplasmosis in a Patient With Acquired Immunodeficiency Syndrome in a Non-Endemic Region (California)

Histoplasmosis is caused by infection with Histoplasma capsulatum (H. capsulatum). Progressive disseminated histoplasmosis is a more severe form of histoplasmosis and is seldom diagnosed in non-endemic regions of the world owing to the fungus's geographical distribution. In the United States (USA), Histoplasma capsulatum is classically known to be endemic to the Mississippi and Ohio River valleys, and cases in non-endemic areas, such as the southwest USA, are exceedingly rare. Patients with acquired immunodeficiency syndrome (AIDS) are at risk for infection with H. capsulatum, and failure to recognize and treat histoplasmosis may be devastating to patients. In non-endemic regions, the proposed mechanism for disseminated histoplasmosis in AIDS patients is reactivation of a previous infection. Here, we present the case of a young male patient who presented to a southern California hospital with diarrhea, was diagnosed with AIDS, and developed acute hypoxic respiratory failure. Chest imaging revealed diffuse reticulonodular opacities, and histoplasmosis was confirmed by urine and serologic examination. He was subsequently treated with liposomal amphotericin B and safely discharged from the hospital with oral itraconazole therapy. This case contributes to the current limited body of literature citing histoplasmosis infections in California, and clinicians should consider histoplasmosis as a differential diagnosis in non-endemic regions.

A Rare Case of a Giant Bladder Stone Associated With Post-obstructive Renal Failure Managed by Open Cystolithotomy

Urinary tract stones are found in many locations, such as in the kidney or ureter, and, less commonly, in the bladder. Bladder stones are solid calculi that are usually composed of calcified material, most commonly uric acid, and typically weigh less than 100 g. There is a higher prevalence of bladder stones in males than in females, which can be explained by the pathophysiology of how these stones are formed. Namely, bladder stones tend to form secondary to urinary stasis, such as in the setting of benign prostatic hyperplasia (BPH). However, bladder stones can form in otherwise healthy individuals without anatomic defects (e.g., urethral strictures) or urinary tract infections (UTIs). Foley catheters or any foreign bodies in the bladder can predispose to stone formation. Renal calculi, most commonly calcium oxalate or calcium phosphate in composition, can also travel through the ureter and get trapped in the bladder. The most significant risk factors for bladder stones include the presence of BPH and UTIs, both of which favor the development of additional layers of stone material. In exceptionally rare cases, bladder stones measure more than 10 cm in diameter and weigh more than 100 g. These entities have been referred to as giant bladder stones within the limited literature. Minimal data exist on the etiology, epidemiology, composition, and pathophysiology of giant bladder stones. We present the case of a 75-year-old male with a giant bladder stone composed of 100% carbonate apatite, measuring 10 cm × 6 cm and weighing 210 g.

Symptomatic Ventricular Bigeminy and Trigeminy Associated With COVID-19

Cardiac manifestations of COVID-19 are well-described in the current literature, although electrocardiogram analyses of COVID-19 patients are limited. The most common arrhythmias experienced by patients with COVID-19 include sinus tachycardia and atrial fibrillation. Ventricular bigeminy associated with COVID-19 is exceedingly rare and requires further studies to determine its incidence and clinical significance. Here, we present the case of a 57-year-old male with no prior cardiac history who was found to have COVID-19 and new-onset, symptomatic premature ventricular contraction bigeminy. This case highlights a rare potential association between COVID-19 and ventricular bigeminy/trigeminy.

Atypical Seropositive Striated Muscle Antibody Myasthenia Gravis Presentation With Metastatic B1 Thymoma: A Rare Case

The association between myasthenia gravis (MG) and thymomas is well-documented. Thymomas are rare epithelial cell tumors that arise from the thymus gland and occur in the mediastinum. Myasthenia gravis is a neuromuscular disorder that causes skeletal muscle weakness due to the presence of anti-acetylcholinesterase antibodies. Roughly 60% of thymomas are associated with MG, while only 10% of MG patients have thymomas. We present an atypical presentation of myasthenia gravis with an associated unusual metastatic thymoma. This case is of a young, previously healthy 26-year-old male with no previous medical history who presented with non-specific symptoms of fatigue, diarrhea, abdominal pain, back pain, blurry vision, and unintended weight loss. He underwent treatment with intravenous immunoglobulins (IVIG), had two surgical resections of the thymoma, and ultimately received radiotherapy. Based on our experience with this case, diagnosing myasthenia gravis by testing for specific muscle antibodies for patients with ptosis in the setting of non-specific complaints, including fatigue, vomiting, diarrhea, and abdominal or back pain, should be considered. Routine imaging should follow with a chest computed tomography to screen for thymomas if the specific anti-titin and anti-ryanodine receptor (anti-RyR) muscle antibodies are positive and myasthenia gravis is suspected. If a thymoma is confirmed, it is best to confirm; and mass characterizes with chest magnetic resonance imaging. A treatment approach of IVIG followed by surgical resection and possible debulking if the lesion is deemed metastatic could also be considered thereafter, especially in young patients with few comorbidities. Treatment with Pyridostigmine 30 mg twice daily for 25 days post-surgically and radiation for treatment of any remaining unresectable tumor should also be considered.

Marijuana-Induced Lung Injury: A Case Report and a Review of the Literature

Marijuana is a commonly abused illicit substance around the world, and lung injury related to its use has seldom been cited in the literature. Most cases describe marijuana-induced lung injury via vaping and the use of butane hash oil; however, no cases, to our knowledge, have associated lung injury related to marijuana smoke in the form of rolled "blunts" or cigarettes. We describe the case of a patient who presented to the hospital due to chest computed tomography findings demonstrating diffuse bilateral opacifications without signs of systemic inflammatory response syndrome. Bronchoscopy with bronchoalveolar lavage and sputum cultures failed to identify an infectious etiology, and serologies were negative for autoimmune etiologies. We aim to contribute to the limited body of literature describing marijuana-induced lung injury.

Bronchopulmonary Fistula Development in an Elderly Male With COVID-19 Infection

COVID-19 pneumonia can cause a wide range of complications including pneumothorax and empyema. However, in severe cases, it can lead to bronchopulmonary fistula (BPF) formation and a persistent air leak due to a connection between the pleural space and the bronchial tree. We report the case of a 77-year-old man with a history of hypertension, who presented to the emergency department for evaluation of dyspnea. Admission labs were significant for a positive rapid antigen SARS-Cov-2 test and elevated troponin I. A chest x-ray demonstrated patchy interstitial opacification and ground glass appearance bilaterally. Within the first 24 hours of presentation, the patient developed a right-sided spontaneous pneumothorax and had a 14 French pigtail catheter placed. The patient subsequently developed a persistent air leak after chest tube placement and required video-assisted thoracoscopic surgery (VATS) with talc pleurodesis and a 32 French chest tube placement. In this unique case, we describe an elderly patient's experience of bronchopulmonary fistula formation as a complication of COVID-19 pneumonia and the successful management of this complication with VATS.

Wound Botulism in the Setting of Pregnancy: A Literature Review and Case Report

Botulism is a rare neuroparalytic illness caused by Clostridium botulinum that can manifest as a descending flaccid paralysis, progressing from cranial neuropathies to respiratory failure. Wound botulism, constituting a minority of cases, is majorly associated with the injection of black tar heroin (BTH) in the western United States. A patient population of particular concern is pregnant women, who may experience a more severe course due to the physiological changes that occur in pregnancy. Because botulism in pregnancy lacks pathognomic features, physicians should maintain a high clinical suspicion when faced with a pregnant patient with neurological symptoms and a history of BTH use. Here, we report the case of a 25-year-old G3P1A1 female with a history of BTH use who presented with cranial neuropathies and respiratory insufficiency.

Pantoprazole-Associated Thrombocytopenia: A Literature Review and Case Report

Proton-pump inhibitors (PPIs) are commonly utilized in the treatment of upper gastrointestinal bleeds (UGIBs) due to their ability to stabilize blood clot formation. PPIs have been shown to reduce rebleeding after endoscopic hemostasis and reduce signs of bleeding at index endoscopy. While PPIs are well-tolerated and commonly administered to patients suffering from acute UGIBs, significant adverse effects may occur. Patients have reported various mild systemic symptoms during short-term PPI use, including headache, rash, dizziness, nausea, abdominal pain, flatulence, constipation, and diarrhea. In general, serious side effects of PPIs tend to be mild during treatment periods under two weeks; however, as the treatment duration increases, side effects have been observed to increase in frequency and severity. PPI-induced thrombocytopenia is an exceedingly rarely reported adverse reaction that remains largely unstudied due to the dearth of patient cases. This adverse effect continues to be a diagnosis of exclusion, and there are no current evidence-based recommendations to approach this complication. Thrombocytopenia increases the risk of rebleeding and hemodynamic instability, which may be devastating to patients suffering from UGIBs. Here, we present a case of thrombocytopenia that began after the introduction of pantoprazole in the setting of a UGIB. The thrombocytopenia resolved promptly after cessation of the medication. We highlight this case to increase awareness of this rare finding given the lack of recommendations for short-term PPI-induced thrombocytopenia.

Diffuse Alveolar Hemorrhage in the Setting of Cytarabine Therapy in a Critically Ill Patient

Diffuse alveolar hemorrhage (DAH) is a potentially life-threatening pulmonary condition characterized by hypoxemia with progression to respiratory failure, rapid onset of dyspnea, and blood loss anemia. While hemoptysis may be present and corroborates the diagnosis, it is absent in about half of the cases, resulting in a diagnostic challenge with variable presenting symptoms. Imaging findings on chest x-ray or computed tomography (CT) scans are also non-specific, often showing diffuse bilateral alveolar opacities. Because DAH is an under-recognized diagnosis, physicians should maintain a degree of clinical suspicion for DAH in patients with unexplained airspace opacities and no signs of an infectious etiology. This is especially important in higher-risk populations such as patients with hematological malignancies, who have a propensity for thrombocytopenia and coagulopathy compounded by the use of anticoagulants. Patients with hematological malignancies, namely acute myeloid leukemia (AML), are also at risk for drug-induced DAH due to the use of cytotoxic medications like cytarabine. Here, we present the case of a 48-year-old male with a past medical history of AML and myeloid sarcoma who developed shortness of breath after receiving cytarabine chemotherapy. Chest radiography revealed diffuse bilateral infiltrates. He was intubated and underwent flexible bronchoscopy, which resulted in a bloody effluent consistent with DAH. After ruling out infectious etiologies, we reached a final diagnosis of DAH and started the patient on corticosteroid therapy.

An Exceedingly Rare Case of Antithrombin III Deficiency and Catastrophic Antiphospholipid-Like Disease

Antithrombin III (AT III) is a critical component of the coagulation cascade that functions primarily to inhibit activated coagulation factors IIa and Xa. AT III deficiency is a disorder that predisposes patients to thromboemboli. Antiphospholipid syndrome (APS) is an autoimmune disorder that predisposes patients to vascular and microvascular thrombosis, which can often be devastating and lead to multiorgan involvement. The mainstay of treatment for both conditions involves the use of lifetime vitamin K antagonists. Recent studies suggest that patients with APS refractory to warfarin therapy may benefit from the addition of aspirin, statin, or hydroxychloroquine; low weight molecular heparin; or a combination regimen. Studies have also suggested that patients with AT III deficiency refractory to warfarin therapy may see improvement with use of a novel oral anticoagulant. This case report describes the recurrent hospitalizations of a 45-year-old patient who presented with multiorgan thrombosis involving the descending aorta, deep lower extremity veins, superior mesenteric artery and artery of the brain. This led to mesenteric ischemia, limb necrosis and a subacute frontal cortex infarct. Initial anticoagulation therapy was refractory to the use of warfarin. Enoxaparin therapy was initiated, resulting in no further thrombotic events. Clinicians should consider poor gastrointestinal absorption of warfarin in patients who fail to reach therapeutic anticoagulation goals. In addition, a thorough workup for hereditary and acquired thrombophilias should be performed in patients who present with recurrent thromboemboli, as these disorders increase the risk of poor patient outcomes if left untreated.

Emergent Inpatient Administration of Casirivimab and Imdevimab Antibody Cocktail for the Treatment of COVID-19 Pneumonia

Infection by severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is known to have the highest mortality rate among the elderly and those with pre-existing medical conditions. Viral load has been directly correlated with increased risk of mortality in hospitalized patients. Once infected, symptoms first arise approximately six to seven days later followed by immunoglobulin M (IgM) antibodies appearing 8-12 days after onset of clinical symptoms. Recent studies have noted that the monoclonal antibody combination of casirivimab and imdevimab (REGN-COV2) effectively reduces viral load in infected seronegative non-hospitalized patients. However, research supporting the use of REGN-COV2 in an inpatient setting is limited. We present the case of a 45-year-old male with confirmed SARS-CoV-2 infection with moderate dyspnea and progressive worsening of his symptoms over a week period. The patient showed drastic improvement of his symptoms after a single low-dose regimen of REGN-COV2 infusion while admitted to the hospital and was subsequently discharged without further medical complications.

Intramolecular i-Motif Structures of Telomeric DNA

Abstract The i-motif is an intercalated structure formed by association in a head to tail orientation of two parallel duplexes whose strands are held together by hemiprotonated C·C(+) pairs. The i-motif may be formed by a single strand containing four cytidine repeats, by association of two strands containing two cytidine repeats or by four strands containing a single cytidine stretch. The repeated C-rich sequences of centromeric and telomeric regions can potentially fold into an intramolecular i-motif. We have investigated by NMR spectroscopy the structure of d(CCCTA(2)CCCTA(2)CCCTA(2)CCCT), a fragment of the vertebrate telomere. It includes an i-motif core of six intercalated C·C(+) pairs. At one end (the "top"), the central TA(2) linker loops across one of the narrow grooves, and the core is extended by base stacking in the loop. At the bottom, where the two other TA(2) linkers loop across the wide grooves, the NMR spectra reveal motions in the microsecond to millisecond scale. The pseudo-symmetry of the structure, which results in degenerate spectra and poor resolution, was broken by appropriate substitution of T by U and of C by 5-methylcytidine (5mC). This allowed us to solve the structure of d(CCCTA(2)5mCCCTA(2)CCCUA(2)CCCT). The motion is restricted to a flip of A18 around the glycosidic bond. Returning to the pseudo-symmetrical sequence, we find that each of the bottom loops switches between the structures of the first and third loops of the non-symmetrical sequence. We also analyzed the effects of the loop sequence and of the length of the C-stretches on the topology and stability of the intramolecular i-motif structure.

Through-bond correlation of sugar and base protons in unlabeled nucleic acids

This work presents two methods for through-bond correlation between sugar and base protons in view of model-independent assignment in unlabeled or slightly enriched nucleic acids. Each method uses a combination of multiple-bond and one-bond heteronuclear J-couplings to the aromatic carbon C6 for pyrimidines ((3)J(H1',C6) and (1)J(H6,C6)) or C8 for purines ((3)J(H1',C8) and (1)J(H8,C8)). The techniques are demonstrated in the duplex [d(CGCGAATTCGCG)](2) and the dimeric G-quadruplex [d(GGGTTCAGG)](2) at natural abundance.

Mylotarg (gemtuzumab ozogamicin) therapy is associated with hepatic venoocclusive disease in patients who have not received stem cell transplantation

BACKGROUND

Mylotarg (Wyeth-Ayerst Laboratories, St. Davids, PA) is the brand name for a calicheamicin-conjugated humanized anti-CD33 monoclonal antibody (gemtuzumab ozogamicin, CMA-676) and has been approved recently for the treatment of a subset of elderly patients who have relapsed acute myeloid leukemia (AML). Mylotarg is associated with an incidence of approximately 20% Grade 3 or 4 hyperbilirubinemia and liver transaminitis in this patient population. Hepatic venoocclusive disease (VOD) has been reported in patients who have undergone stem cell transplantation (SCT) after Mylotarg therapy. Outside of the SCT setting, VOD has been associated very rarely with cytotoxic therapy.

METHODS

The authors assessed the incidence of VOD in 119 patients who were receiving Mylotarg-containing non-SCT regimens. VOD was diagnosed through the use of standard Seattle and Baltimore criteria.

RESULTS

A cohort of 119 (61 previously untreated, 58 with relapsed disease) patients with AML (92 patients), advanced myelodysplastic syndrome (25 patients), or chronic myeloid leukemia in blast phase (2 patients), received Mylotarg-based regimens. Fourteen (12%) developed VOD. The diagnosis of VOD was supported by histology in 2 patients and radiologic studies in a further 10 patients. Five (36%) of 14 patients with VOD had received no prior antileukemic cytotoxic therapy, including 2 patients who received single-agent Mylotarg therapy.

CONCLUSIONS

Mylotarg was shown to be associated with the development of potentially fatal VOD in patients with leukemia who had not received SCT. VOD occurred when Mylotarg was used either as a single agent or when it was given with other cytotoxic agents. VOD occurred in Mylotarg-treated patients who had received no prior cytotoxic therapy. The current study concluded that risk factors for VOD should be assessed when considering Mylotarg therapy, and that attempts to avoid and treat VOD are warranted in patients who receive Mylotarg therapy.

The solution structure and internal motions of a fragment of the cytidine-rich strand of the human telomere

We present the solution structure of d(CCCTA2CCCTA2CCCTA2CCCT), a fragment of the vertebrate telomere which folds intramolecularly. The four cytidine stretches form an i-motif which includes six intercalated C.C+ pairs and terminates with the cytidines at the 5' extremity of each stretch. Above, the second TA2 linker loops across one of the narrow grooves, while at the bottom, the first and third linkers loop across the wide grooves. At 30 degrees C, the spectra of the first and third linkers are quasi-degenerate. Severe broadening at lower temperature indicates that this results from motional averaging between at least two structures of each bottom loop, and makes it impossible to solve the configuration of the bottom loops directly, in contrast to the rest of the structure. We therefore turned to the modified sequence d(CCCTA(2)5MCCCTA2CCCUA2CCCT) in which the two base substitutions (underlined) break the quasi-symmetry between linkers 1 and 3. The three loops follow approximately the hairpin "second pattern" of Hilbers. In the first loop, T4 is in the syn orientation, whereas its analog in the third loop, U16, oriented anti, is in a central location, where it interacts with bases of both loops, thus contributing to their tight association. The only motion is a syn/anti flip of A18 in the third loop. Returning to the telomere fragment, we show that each of the bottom loops switches between the structures identified in the first and third loops of the modified structure. The motions are concerted, and the resulting configurations of the bottom loop cluster present a bulge to either right (T4 syn) or left (T16 syn).

Long-range imino proton-13C J-couplings and the through-bond correlation of imino and non-exchangeable protons in unlabeled DNA

Thanks to rather large (5-9 Hz) long-range imino proton-13C J-couplings, heteronuclear correlation experiments in H2O provide unambiguous assignment of imino protons by intranucleotide through-bond connectivities to guanosine H8 and thymidine CH3 protons, or sequence-specific assignment of non-exchangeable protons when the imino protons are identified independently. This method is demonstrated in the Dickerson dodecamer [d(CGCGAATTCGCG)]2 and in a human telomeric fragment of 22 nucleotides.

Determination of the residence time of water molecules hydrating B'- DNA and B-DNA, by one-dimensional zero-enhancement nuclear Overhauser effect spectroscopy

The residence time of water in the minor groove of the d(CGCGAATTCGCG) duplex has been determined by a recent measurement combining nuclear Overhauser enhancements (NOE, ROE) and 17O relaxation dispersion. The time is in the range of nanoseconds, so that it may be measured by a rather simple method proposed here, namely the choice of conditions such that the NOE between the observed DNA proton and a nearby water proton is zero. This condition is realized when the residence time of the water molecule is 0.178 times the nuclear magnetic resonance period (e.g. 0.297 ns at 600 MHz). It may be achieved by varying the magnetic field and/or the temperature. The zero-NOE measurement may be performed by one-dimensional NMR, and has therefore good sensitivity. We have developed excitation sequences which suppress two spurious contributions to the NOE: from neighboring exchangeable protons and from H3' protons whose chemical shift is close to that of water. The method is applied here to the comparison of residence times of water next to B-DNA and next to B'-DNA, the latter corresponding to better stacked, propeller-twisted base-pairs and a correspondingly narrower minor groove. In the minor groove of [d(CGCGAATTCGCG)]2, a B'-DNA duplex, the residence time of the water molecule next to H2 of adenine(6) (underlined), is 0.6 ns at 10 degreesC, in good agreement with the value obtained previously. The residence time is slightly but distinctly shorter for the water next to A5, suggesting non-cooperative departure of these two molecules which are presumed to be part of the hydration spine. Near A5 and A4 of [d(AAAAATTTTT)]2, another B'-DNA duplex, the residence times are approximately twice as long, but the activation enthalpies are about the same, ca. 38 kJ/mol. The residence time in the minor groove of the regular B-DNA sequence d(CGCGATCGCG) was 0.3 ns at 10 degreesC, shorter than in the case of the B'-DNA sequences by factors of 2 and 4, respectively. The temperature dependence is less, with an activation enthalpy of 27 kJ/mol. The major groove residence times are comparable for the three sequences, and a few times shorter than those of minor groove water. A value of 0.36 ns, or even more in case of rotation of water, is obtained around -8 degreesC. The most striking aspect of these results is the relatively small difference in the residence times of reputedly fast and slow-exchanging water molecules bound to DNA in biological conditions. This suggests that the spine of hydration is perhaps not a major stabilizer of the B'-DNA structure as compared with B-DNA.

Following G-quartet formation by UV-spectroscopy

Oligodeoxynucleotides which include stretches of guanines form a well-known tetrameric structure. We show that the recording of reversible absorbance changes at 295 nm allows to precisely monitor intramolecular guanine (G)-quartet formation and dissociation. Accurate Tm and thermodynamic values could be easily extracted from the data, whereas classical recordings at 260 nm led to a much larger uncertainty and in extreme cases, to completely inaccurate measurements. This inverted denaturation profile was observed for all G-quartet-forming oligonucleotides studied so far. This technique is very useful in all cases where intramolecular or intermolecular quadruplex formation is suspected.

Solution structure and base pair opening kinetics of the i-motif dimer of d(5mCCTTTACC): a noncanonical structure with possible roles in chromosome stability

BACKGROUND

Repetitive cytosine-rich DNA sequences have been identified in telomeres and centromeres of eukaryotic chromosomes. These sequences play a role in maintaining chromosome stability during replication and may be involved in chromosome pairing during meiosis. The C-rich repeats can fold into an 'i-motif' structure, in which two parallel-stranded duplexes with hemiprotonated C.C+ pairs are intercalated. Previous NMR studies of naturally occurring repeats have produced poor NMR spectra. This led us to investigate oligonucleotides, based on natural sequences, to produce higher quality spectra and thus provide further information as to the structure and possible biological function of the i-motif.

RESULTS

NMR spectroscopy has shown that d(5mCCTTTACC) forms an i-motif dimer of symmetry-related and intercalated folded strands. The high-definition structure is computed on the basis of the build-up rates of 29 intraresidue and 35 interresidue nuclear Overhauser effect (NOE) connectivities. The i-motif core includes intercalated interstrand C.C+ pairs stacked in the order 2*.8/1.7*/1*.7/2.8* (where one strand is distinguished by an asterisk and the numbers relate to the base positions within the repeat). The TTTA sequences form two loops which span the two wide grooves on opposite sides of the i-motif core; the i-motif core is extended at both ends by the stacking of A6 onto C2.C8+. The lifetimes of pairs C2.C8+ and 5mC1.C7+ are 1 ms and 1 s, respectively, at 15 degrees C. Anomalous exchange properties of the T3 imino proton indicate hydrogen bonding to A6 N7 via a water bridge. The d(5mCCTTTTCC) deoxyoligonucleotide, in which position 6 is occupied by a thymidine instead of an adenine, also forms a symmetric i-motif dimer. However, in this structure the two TTTT loops are located on the same side of the i-motif core and the C.C+ pairs are formed by equivalent cytidines stacked in the order 8*.8/1.1*/7*.7/2.2*.

CONCLUSIONS

Oligodeoxynucleotides containing two C-rich repeats can fold and dimerize into an i-motif. The change of folding topology resulting from the substitution of a single nucleoside emphasizes the influence of the loop residues on the i-motif structure formed by two folded strands.