Semiconducting hematite facilitates microbial and abiotic reduction of chromium

Semi-conducting Fe oxide minerals, such as hematite, are well known to influence the fate of contaminants and nutrients in many environmental settings through sorption and release of Fe(II) resulting from microbial or abiotic reduction. Studies of Fe oxide reduction by adsorbed Fe(II) have demonstrated that reduction of Fe(III) at one mineral surface can result in the release of Fe(II) on a different one. This process is termed “Fe(II) catalyzed recrystallization” and is believed to be the result of electron transfer through semi-conducting Fe (hydr)oxides. While it is well understood that Fe(II) plays a central role in redox cycling of elements, the environmental implications of Fe(II) catalyzed recrystallization require further exploration. Here, we demonstrate that hematite links physically separated redox reactions by conducting the electrons involved in those reactions. This is shown using an electrochemical setup where Cr reduction is coupled with a potentiostat or Shewanella putrefaciens, a metal reducing microbe, where electrons donated to hematite produce Fe(II) that ultimately reduces Cr. This work demonstrates that mineral semi-conductivity may provide an additional avenue for redox chemistry to occur in natural soils and sediments, because these minerals can link redox active reactants that could not otherwise react due to physical separation.

52-year-old man • syncopal episode • chest pain • mild lightheadedness • Dx?

► Syncopal episode ►Chest pain ► Mild lightheadedness.

A Magic Bullet: Bullet Embolism From the Heart to the Femoral Artery

A case study a patient who was emergently evaluated with an intraoperative transesophageal echocardiography after suffering a gunshot wound to the back is provided. This diagnostic examination revealed a left atrium to aorta fistula, due to the path of the bullet through the body. Immediate postoperative imaging with computed tomography revealed that the bullet had embolized to the left femoral artery from which it was later surgically removed. This rare clinical phenomenon of bullet embolization, involving the heart and associated vasculature, is reviewed.

A case of premature ventricular contractions-related cardiomyopathy

Premature ventricular contractions (PVCs) are heart beats initiated in the ventricles instead of in the sinoatrial node. A high burden of PVCs can lead to a cardiomyopathy, characterised by reduced left ventricular (LV) systolic dysfunction. We present a case of PVC-related cardiomyopathy where the 65-year-old male was initially seen by his primary care provider for recent onset chest pain and dizziness. His transthoracic echocardiogram showed mild concentric LV hypertrophy and mildly reduced systolic function (LV ejection fraction 43%). There was also mild right ventricular (RV) systolic dysfunction. He was started on a beta-blocker and an angiotensin-converting enzyme inhibitor. A 24-hour Holter monitor showed a very high burden of PVCs (32% of all beats). He continued to have frequent PVCs and his echocardiogram did not improve. He was eventually referred for a PVC ablation. Following the ablation, a repeat Holter monitor showed a marked reduction in PVC burden (<1% of beats) and his echocardiogram had normalised.

Cardiovascular Complications of Acetylcholinesterase Inhibitors in Patients with Alzheimer's Disease: A Narrative Review

While acetylcholinesterase inhibitors are used to treat a wide range of patients with Alzheimer's disease, acetylcholinesterase inhibitor use has also been associated with a variety of cardiovascular complications, including bradycardia and syncope. Herein, we review the pathophysiology and clinical evidence for cardiovascular complications caused by acetylcholinesterase inhibitors in patients being treated for dementia and discuss options for their management.

An Unusual Case of Shock in an Octogenarian

An octogenarian presented to our hospital in shock after being “found down” at home. She was dehydrated, hypernatremic, and suffering from a urinary tract infection. Findings of a murmur and those on electrocardiography led to the performance of echocardiography, with all findings consistent with a diagnosis of hypertrophic obstructive cardiomyopathy. The patient was volume resuscitated and administered antibiotics; after stabilization, she was started on a low-dose beta-blocker. Hypertrophic cardiomyopathy is a common genetic disorder that is usually diagnosed in the second to fifth decades of life, rarely being diagnosed at an advanced age. It is also an uncommon cause or contributor to shock. We briefly review the diagnosis and management of hypertrophic cardiomyopathy in older adults, particularly in the setting of shock.

Development of a novel microfluidic device to study metal geochemistry in situ using X-ray fluorescence microprobe spectroscopy

The study of in situ microscale biogeochemical processes represents a major challenge in the environmental sciences. The combination of microfluidic devices with X-ray fluorescence microprobe spectroscopy may address this need, but typical materials used in these devices attenuate the X-rays needed to analyze key elements of interest, such as Fe or As. In this work, a method is presented for fabricating an etched silicon microfluidic device that is sealed with a 30 µm thin glass window that is sufficiently transparent for X-ray fluorescence microprobe spectroscopy. The capabilities of these devices for X-ray microprobe spectroscopy are demonstrated using an Fe (hydr)oxide solid that is loaded with As and then infused with sulfide, on beamline 4-BM at NSLS-II, resulting in time-variant Fe precipitation reactions and As sorption. Key results include in situ X-ray fluorescence time-series maps of Fe, As and a Br flow tracer, as well as spot XANES at both the Fe K edge and As K edge. Additionally, multiple energy mapping is used to examine the spatial speciation of As over time. The results of this work clearly demonstrate the capabilities of this novel microfluidic system that can be analyzed using X-ray fluorescence microprobe spectroscopy and can be made to study a wide range of complex microscale geochemical systems.

Atherosclerosis, its risk factors, and cognitive impairment in older adults

OBJECTIVE

To examine the association of atherosclerotic cardiovascular disease (ASCVD) and its risk factors with cognitive impairment in older adults.

METHODS

Six hundred and fourteen subjects, aged ≥ 65 years, from one center (2016-2018) underwent clinical, laboratory assessments and the Montreal Cognitive Assessment (MoCA). Using regression analysis, the relationship between ASCVD and its risk factors was evaluated in subjects with and without cognitive impairment (MoCA score < 26).

RESULTS

Older age (β = -1.3 per 5 years, 95% CI: -1.7 to -0.9, P < 0.001), history of stroke (β = -1.6, 95% CI: -3.0 to -0.3, P = 0.01), and myocardial infarction (MI; β = -2.2, 95% CI: -3.6 to -0.8, P = 0.003) were independently associated with lower MoCA scores, whereas more education (β = 1.5 per 3 years, 95% CI: 1.1 to 1.9, P < 0.001), higher body mass index (BMI; β = 0.5 per 3 kg/m², 95% CI: 0.0 to 1.0, P = 0.04), higher estimated glomerular filtration rate (eGFR; β = 0.8 per 15 U, 95% CI: 0.1 to 1.4, P = 0.03), left ventricular ejection fraction (LVEF; β = 0.4 per 5%, 95% CI: 0 to 0.8, P = 0.04) and statin use (β = 1.3, 95% CI: 0.3 to 2.3, P = 0.01) were associated with a higher MoCA score. Cognitive impairment was independently associated with older age (OR = 1.51 per 5 yrs, 95% CI: 1.28 to 1.79, P < 0.001), less education (OR = 0.55 per 3 years, 95% CI: 0.45 to 0.68, P < 0.001), lower BMI (OR = 0.78 per 3 kg/m², 95% CI: 0.62 to 0.98, P = 0.03) and higher levels of high sensitivity c-reactive protein (hsCRP; OR = 1.08 per 1 mg/L, 95% CI: 1.02 to 1.15, P = 0.01).

CONCLUSIONS

Beyond age, cognitive impairment was associated with prior MI/stroke, higher hsCRP, statin use, less education, lower eGFR, BMI and LVEF.

Noncompaction cardiomyopathy and multiple coronary-cameral fistulae in an octogenarian

An 85-year-old man was admitted to the emergency department with chest pain. His electrocardiogram showed a right bundle branch block as well as increased voltages suggesting left ventricular hypertrophy and t-wave inversions consistent with a strain pattern (versus ischemia). He underwent echocardiography which showed regional noncompaction and associated hypokinesis. These findings led to coronary angiography which revealed multiple coronary-cameral fistulae involving all three coronary arteries. He was initially treated for acute coronary syndrome but after his diagnostic procedures this was narrowed to a beta blocker, to reduce myocardial oxygen demand, and an angiotensin-converting enzyme inhibitor due to the cardiomyopathy. Although the fistulae may have caused the patient's chest pain, intervention was not possible due to the diffuse nature of the fistulae. He did well in follow-up without the development of heart failure symptoms or continued angina. <Learning objective: Noncompaction cardiomyopathy and coronary cameral fistulae are two rare disorders that have even more rarely been described in a single patient. They may be a part of a spectrum of a single disease that results from arrest of the normal sequence of embryologic development of the heart. The management of the two conditions includes aspects of standard heart failure care as well as medical and possibly interventional therapy for coronary ischemia (angina) related to fistulae.>.

Radium Sorption to Iron (Hydr)oxides, Pyrite, and Montmorillonite: Implications for Mobility

Radium (Ra) is a radioactive element commonly found within soils, sediments, and natural waters. Elevated Ra activities arising through natural and anthropogenic processes pose a threat to groundwater resources and human health, and Ra isotope ratios are used to decipher groundwater movement, estimate submarine discharge flux, and fingerprint contamination associated with hydraulic fracturing operations. Although adsorption to metal (hydr)oxides and certain clay minerals is well established as a dominant mechanism controlling Ra transport and retention, the extent of Ra sorption to other minerals and under variable environmental conditions (e.g., pH and salinity) is limited. Accordingly, we present results of sorption studies and surface complexation modeling (SCM) of Ra to ferrihydrite, goethite, montmorillonite, and pyrite, for a range of pH values and common background cations. Ra sorption to all substrates is observed under geochemical conditions considered, but varies according to mineral, solution pH and specific competing cations. Literature derived SCMs for Ra sorption were fitted to match either sorption impacts due to pH or different background cations, but were not able to predict the impacts of different geochemical conditions. Despite this, the use of SCMs provided a more mechanistic understanding of Ra sorption as compared to commonly used distribution coefficients.

Frailty and cardiovascular disease: potential role of gait speed in surgical risk stratification in older adults

Frailty is a state of late life decline and vulnerability, typified by physical weakness and decreased physiologic reserve. The epidemiology and pathophysiology of frailty share features with those of cardiovascular disease. Gait speed can be used as a measure of frailty and is a powerful predictor of mortality. Advancing age is a potent risk factor for cardiovascular disease and has been associated with an increased risk of adverse outcomes. Older adults comprise approximately half of cardiac surgery patients, and account for nearly 80% of the major complications and deaths following surgery. The ability of traditional risk models to predict mortality and major morbidity in older patients being considered for cardiac surgery may improve if frailty, as measured by gait speed, is included in their assessment. It is possible that in the future frailty assessment may assist in choosing among therapies (e.g., surgical vs. percutaneous aortic valve replacement for patients with aortic stenosis).

Effect of age on aortic atherosclerosis

Objective

To examine the association of atherosclerosis burden in the survivors of an asymptomatic elderly cohort study and its relationship to other coronary risk factors (specifically, age) by evaluating aortic atherosclerotic wall burden by magnetic resonance imaging (MRI).

Methods

A total of 312 participants in an ongoing observational cohort study underwent cardiac and descending thoracic aorta imaging by MRI. Maximum wall thickness was measured and the mean wall thickness calculated. Wall/outer wall ratio was used as a normalized wall index (NWI) adjusted for artery size difference among participants. Percent wall volume (PWV) was calculated as NWI × 100.

Results

In this asymptomatic cohort (mean age: 76 years), the mean (SD) aortic wall area and wall thickness were 222 ± 45 mm² and 2.7 ± 0.4 mm, respectively. Maximum wall thickness was 3.4 ± 0.6 mm, and PWV was 32% ± 4%. Women appeared to have smaller wall area, but after correcting for their smaller artery size, had significantly higher PWV than men (P = 0.03). Older age was associated with larger wall area (P = 0.04 for trend) with similar PWVs. However, there were no statistically significant associations between standard risk factors, Framingham global risk, or metabolic syndrome status, therapy for cholesterol or hypertension, coronary or aortic calcium score, and the aortic wall burden. Aortic calcification was associated with coronary calcification.

Conclusions

Asymptomatic elderly in this cohort had a greater descending thoracic aortic wall volume that correlated with age, and women had a significantly increased PWV compared to men. In these survivors, the atherosclerotic aortic wall burden was not significantly associated with traditional risk factors or with coronary or aortic calcium scores or coronary calcium progression. Results suggest that age, or as yet unidentified risk factor(s), may be responsible for the increase in atherosclerosis.

Transient stress cardiomyopathies in the elderly: Clinical & Pathophysiologic considerations

Transient stress-induced cardiomyopathies have been increasingly recognized and while rare, they tend to affect elderly women more than other demographic groups. One type, often called tako-tsubo cardiomyopathy (TTC), is typically triggered by significant emotional or physical stress and is associated with chest pain, electrocardiogram (ECG) changes and abnormal cardiac enzymes. Significant left ventricular regional wall motion abnormalities usually include an akinetic “ballooning” apex with normal or hyperdynamic function of the base. A second type, often called neurogenic stunned myocardium, typically associated with subarachnoid hemorrhage, also usually presents with ECG changes and positive enzymes, but the typical wall motion abnormalities seen include normal basal and apical left ventricular contraction with akinesis of the mid-cavity in a circumferential fashion. The pathophysiology, clinical care and typical courses, are reviewed.

Real time three-dimensional echocardiography evaluation of intracardiac masses

The evaluation of cardiac masses is often a challenge for cardiac imaging techniques. The traditional standby has been two-dimensional echocardiography (2DE). Real time three-dimensional echocardiography (RT3DE) offers incremental value for the evaluation of intracardiac masses by providing more accurate assessment of the size and shape of the mass as well as in some cases, composition of the mass. RT3DE aids with the relationship between the mass and adjacent structures. Therefore, here we discuss the subject of RT3DE evaluation of cardiac masses is reviewed and discussed in detail.

Burkitt Lymphoma of the Heart

The incidence of non-Hodgkin lymphoma has increased over the past 10 years, particularly in association with human immunodeficiency virus (HIV) infection. Burkitt lymphoma is a highly aggressive non-Hodgkin lymphoma that involves the heart in up to a third of cases. This case describes an HIV-positive patient with cardiac involvement of Burkitt lymphoma who presented with atrial flutter and heart failure with pulmonary edema. Transthoracic echocardiography showed extensive heterogeneous lymphomatous infiltration of the heart (including the right atrium), with associated wall motion abnormalities. Within a day of starting chemotherapy, the patient had converted to normal sinus rhythm. His heart failure rapidly improved, and a repeat echocardiogram performed on day 5 of chemotherapy showed a significant reduction in myocardial tumor burden and improved cardiac function. This case demonstrates how echocardiography plays a significant role in diagnosis, management, and follow-up of lymphoma (in this case Burkitt) with cardiac involvement.

Heart failure with preserved ejection fraction in older adults

Age-associated physiologic changes predispose older adults to develop heart failure, even when left ventricular ejection fraction is normal or near normal. Heart failure with a preserved ejection fraction is particularly common in older hypertensive women, and hypertension plays a key role in its pathophysiology. In contrast with heart failure with a reduced ejection fraction, the treatment of heart failure with a preserved ejection fraction has a limited empiric basis, although some basic principles are useful. Ongoing studies provide hope of improving care of these patients.

Echocardiographic Assessment of Dyssynchrony for Predicting a Favorable Response to Cardiac Resynchronization Therapy

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Impact of in-home defibrillators on postmyocardial infarction patients and their significant others: an interview study

OBJECTIVE

To investigate the impact of automated external defibrillator (AED) placement in the homes of postmyocardial infarction (MI) patients and their significant others.

DESIGN

This qualitative study used a semistructured interview to examine a nonrandomized convenience sample recruited from a larger study of home AEDs.

SETTING AND PARTICIPANTS

Patients (and their significant others) were recruited from an ongoing study of AED use in the home. Seventeen interviews with 15 patients (14 men, 1 woman) and 16 significant others (1 man, 15 women) aged 39 to 80 years were performed in patients' homes.

METHODS

Verbatim transcripts of audiotaped interviews were reviewed, and responses were categorized. Other data were obtained from hospital chart abstraction.

RESULTS

The majority of subjects noted only positive effects of the presence of home AEDs (eg, giving them feelings of security and control). There was no evidence that AED presence in the home caused excessive anxiety or stress either in patients or their significant others, nor were they perceived to cause relationship stress. On average, patients and their significant others estimated a 38% and 43% (respectively) risk of cardiac arrest and a 92% and 87% likelihood of a successful resuscitation with the use of the AED. Subjects' perceived risk of cardiac arrest were subjectively related to their estimate of current health status, size of infarction, and symptoms during their MI. Subjects also related their estimates of risk to their likelihood of traveling with their AED and whether they would consider purchasing one. Significant others had high confidence in their ability to properly use the AED.

CONCLUSIONS

AEDs were valued highly by subjects and enhanced their perceived control over their heart disease. This was especially true for subjects who believed that their risk of cardiac arrest was high. The possible effects of providing education regarding expert estimates of the likelihood of cardiac arrest and of a successful resuscitation at the time of AED placement are discussed.

The role of external loop regions in serotonin transport. Loop scanning mutagenesis of the serotonin transporter external domain

Chimeric transporters were constructed in which the predicted external loops of the serotonin transporter (SERT) were replaced one at a time with a corresponding sequence from the norepinephrine transporter (NET). All of the chimeric transporters were expressed at levels equal to or greater than those of wild type SERT, but the transport and binding activity of the mutants varied greatly. In particular, mutants in which the NET sequence replaced external loops 4 or 6 of SERT had transport activity 5% or less than that of wild type, and the loop 5 replacement was essentially inactive. In some of these mutants, binding of a high affinity cocaine analog was less affected than transport, suggesting that the mutation had less effect on the initial binding steps in transport than on subsequent conformational changes. The more severely affected mutants also displayed an altered response to Na(+). In contrast to the dramatic reduction in transport and binding, the specificity of ligand binding was essentially unchanged. Chimeric transporters did not gain affinity for dopamine, a NET substrate, or desipramine, an inhibitor, at the expense of affinity for serotonin or paroxetine, a selective SERT inhibitor. The results suggest that external loops are not the primary determinants of substrate and inhibitor binding sites. However, they are not merely passive structures connecting transmembrane segments but rather active elements responsible for maintaining the stability and conformational flexibility of the transporter.

An extracellular loop region of the serotonin transporter may be involved in the translocation mechanism

The serotonin transporter (SERT) is a member of a highly homologous family of proteins responsible for the reuptake of biogenic amines from the synaptic cleft. We took advantage of native restriction sites in SERT to construct a chimeric transporter containing a small (34 amino acid) region of the norepinephrine transporter. The substituted region corresponds to about half of the largest extracellular loop. This chimera transports serotonin very slowly compared to wild type SERT. However, it binds serotonin and the cocaine analog 2beta-carbomethoxy-3beta-(4-[125I]iodophenyl)tropane with a high affinity indistinguishable from wild type. It has the same specificity as wild type SERT for the antidepressants paroxetine and desipramine. The low rate of transport does not appear to be due to poor expression, since the chimeric transporter is expressed at the membrane surface at close to wild type levels as measured by cell surface biotinylation. These observations lead us to conclude that, rather than playing a role in substrate or drug binding, this region of the large extracellular loop may be involved in the conformational changes associated with substrate translocation into the cell.

Preservation of endothelium-dependent vasodilation with low-potassium University of Wisconsin solution

University of Wisconsin solution has provided excellent myocardial preservation. However, the high potassium content of the currently available University of Wisconsin solution has been implicated in coronary artery endothelial damage. We placed 16 neonatal (age 1 to 3 days) Duroc piglet hearts on an isolated nonworking perfusion circuit. Endothelium-dependent and endothelium-independent vasodilation were tested by measuring coronary blood flow after intracoronary infusion of bradykinin (10(-6) mol/L) and nitroprusside (10(-6) mol/L), respectively. In addition, nitric oxide levels were measured after bradykinin infusion. The hearts were then arrested blindly with either a modified University of Wisconsin solution (group 1; n = 8, K+ = 25 mEq/L) or standard University of Wisconsin solution (group 2; n = 8, K+ = 129 mEq/L) by infusion of cardioplegic solution every 20 minutes for a total of 2 hours. After bradykinin infusion, the mean coronary blood flow increased by 237.1% +/- 14.0% of baseline valves before arrest and by 232.8% +/- 16.0% after arrest in group 1 (p = not significant). As in the first group, the mean coronary blood flow in group 2 increased by 231.1% +/- 13.7% before arrest; however, the increase in mean coronary blood flow after arrest was significantly attenuated (163.3% +/- 12.8%, p < 0.01). The loss of endothelium-dependent coronary blood flow response in group 2 correlated with a decreased capacity to release nitric oxide after arrest (prearrest 8.25 +/- 2.30 nmol/min per gram versus postarrest -2.46 +/- 2.29 nmol/min per gram, p < 0.01). Endothelium-independent vasodilatory response revealed no significant difference between groups before and after arrest. These results suggest that the low-potassium University of Wisconsin solution provides superior protection of the endothelium by preserving the endothelium-dependent vasodilatory response to nitric oxide release.

Mutations of keratin 9 in two families with palmoplantar epidermolytic hyperkeratosis

The hereditary palmoplantar keratodermas are a heterogeneous group of diseases unified by thickening of the stratum corneum of the palms and soles with consequent painful fissuring, discomfort on pressure, and resultant disability. One of the histologic patterns underlying palmoplantar hyperkeratosis is that of epidermolytic hyperkeratosis. Because that histologic pattern has been found in its generalized form to be due to keratin gene mutations, we assessed the inheritance of the form localized to the palms and soles. In each of two families studied, the mutant gene causing the disease is linked strongly to the chromosome 17 cluster of genes encoding type I keratins, and mutations are present in the conserved helix initiation region of keratin 9 in affected members of both kindreds. These data, as well as those generated recently by others, indicate that keratin gene mutations may underlie not only the generalized phenotype but also this more localized phenotype of epidermolytic hyperkeratosis and suggest one mechanism by which skin diseases can achieve their characteristic localization.

Evidence against keratin gene mutations in a family with ichthyosis hystrix Curth-Macklin

Ichthyosis hystrix Curth-Macklin is a rare autosomal dominant disease characterized clinically by hyperkeratosis and ultrastructurally by disruption of the keratin intermediate filament network of suprabasal keratinocytes. We have used linkage analysis to test whether a keratin gene mutation might underlie this disease. This analysis excluded the keratin gene loci as the sites for the disease-causing mutation in one affected kindred.

Linkage of the epidermolytic hyperkeratosis phenotype and the region of the type II keratin gene cluster on chromosome 12

Bullous congenital ichthyosiform erythroderma (epidermolytic hyperkeratosis) is a severe, generalized, lifelong disease of the skin. As in epidermolysis bullosa simplex, intraepidermal blisters and clumping of keratin intermediate filaments are characteristic. We report here linkage of the inheritance of this disease to the region of chromosome 12q containing the genes encoding type II keratins. This suggests that keratin gene mutations may underlie this complex hyperproliferative and hyperkeratotic phenotype.