Characterization of the N-acetylaspartate biosynthetic enzyme from rat brain

Aspartate N-acetyltransferase (Asp-NAT; EC 2.3.1.17) activity was found in highly purified intact mitochondria prepared by Percoll gradient centrifugation as well as in the three subfractions obtained after the sucrose density gradient centrifugation of Percoll purified mitochondria; citrate synthase was used as a marker enzyme for mitochondria. The proportion of recoverable activities of Asp-NAT and citrate synthase were comparable in mitochondrial and synaptosomal fractions but not in the fraction containing myelin. Asp-NAT was solubilized from the pellet of the rat brain homogenate (26 000 g for 1 h) for the recovery of maximum activity and partially purified using three protein separation methods: DEAE anion exchange chromatography, continuous elution native gel electrophoresis and size-exclusion high performance liquid chromatography. Asp-NAT activity and the optical density pattern of the eluted protein from size-exclusion column indicated a single large protein (approximately 670 kDa), which on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed at least 10 bands indicative of an enzyme complex. This seemingly multi-subunit complex Asp-NAT was stable towards ionic perturbations but vulnerable to hydrophobic perturbation; almost 95% of activity was lost after 10 mm 3-[(3-cholamidopropyl)dimethylammonia]-1-propanesulfonate (CHAPS) treatment followed by size-exclusion chromatography. Asp-NAT showed an order of magnitude difference in Km between l-aspartate (l-Asp, approximately 0.5 mm) and acetyl CoA (approximately 0.05 mm). Asp-NAT showed high specificity towards l-Asp with 3% or less activity towards l-Glu, l-Asn, l-Gln and Asp-Glu. A model on the integral involvement of NAA synthesis in the energetics of neuronal mitochondria is proposed.

Neuroprotective effects of bilobalide, a component of Ginkgo biloba extract (EGb 761) in global brain ischemia and in excitotoxicity-induced neuronal death

In this study, we compared the protective effect of bilobalide, a purified terpene lactone component of ginkgo biloba extract EGb 761, (definition see editorial) and EGb 761 against ischemic injury and against glutamate-induced excitotoxic neuronal death. In ischemic injury, we measured neuronal loss and the levels of mitochondrial DNA (mtDNA)-encoded cytochrome oxidase (COX) subunit III mRNA in vulnerable hippocampal regions of gerbils. At 7 days of reperfusion after 5 min of transient global ischemia, a significant increase in neuronal death and a significant decrease in COX III mRNA were observed in the hippocampal CA1 neurons. Oral administration of EGb 761 at 25, 50 and 100 mg/kg/day and bilobalide at 3 and 6 mg/kg/day for 7 days before ischemia progressively protected CA1 neurons from death and from ischemia-induced reductions in COX III mRNA. In rat cerebellar neuronal cultures, addition of bilobalide or EGb 761 protected in a dose-dependent manner against glutamate-induced excitotoxic neuronal death (effective concentration [EC (50)] = 5 microg/ml (12 microM) for bilobalide and 100 microg/ml for EGb 761. These results suggest that both EGb 761 and bilobalide are protective against ischemia-induced neuronal death in vivo and glutamate-induced neuronal death in vitro by synergistic mechanisms involving anti-excitotoxicity, inhibition of free radical generation, scavenging of reactive oxygen species, and regulation of mitochondrial gene expression.

Neuroprotective effects of bilobalide, a component of the Ginkgo biloba extract (EGb 761), in gerbil global brain ischemia

The neuroprotective effect of Ginkgo biloba extract (EGb 761) against ischemic injury has been demonstrated in animal models. In this study, we compared the protective effect of bilobalide, a purified terpene lactone from EGb 761, and EGb 761 against ischemic injury. We measured neuronal loss and the levels of mitochondrial DNA (mtDNA)-encoded cytochrome oxidase (COX) subunit III mRNA in vulnerable hippocampal regions of gerbils. At 7 days of reperfusion after 5 min of transient global forebrain ischemia, a significant increase in neuronal death and a significant decrease in COX III mRNA were observed in the hippocampal CA1 neurons. Oral administration of EGb 761 at 25, 50 and 100 mg/kg/day and bilobalide at 3 and 6 mg/kg/day for 7 days before ischemia progressively protected CA1 neurons from death and from ischemia-induced reductions in COX III mRNA. In addition, both bilobalide and EGb 761 protected against ischemia-induced reductions in COX III mRNA in CA1 neurons prior to their death, at 1 day of reperfusion. These results suggest that oral administration of bilobalide and EGb 761 protect against ischemia-induced neuron death and reductions in mitochondrial gene expression.

Patent foramen ovale transcatheter closure device thrombosis

The role of patent foramen ovale (PFO) in patients with cryptogenic stroke (stroke of unknown cause) remains controversial, although an association seems likely in younger patients with atrial septal aneurysms and PFO. The mechanism of cryptogenic stroke in these patients is presumed to be paradoxical embolism via right-to-left shunt across the PFO. The available options for treatment include medical therapy with antiplatelet or anticoagulant therapy or closure of the PFO surgically or with use of transcatheter PFO closure devices. We describe 2 cases of bilateral device thrombosis associated with use of a transcatheter PFO closure device (CardioSEAL). To our knowledge, only 1 other case of thrombosis associated with use of this device has been reported.

A combined treatment approach using Fenton's reagent and zero valent iron for the removal of arsenic from drinking water

Studies on the development of an arsenic remediation approach using Fenton's reagent (H2O2 and Fe(II)) followed by passage through zero valent iron is reported. The efficiency of the process was investigated under various operating conditions. Potable municipal water and ground water samples spiked with arsenic(III) and (V) were used in the investigations. The arsenic content was determined by ICP-QMS. A HPLC-ICPMS procedure was used for the speciation and determination of both As(III) and (V) in the processed samples, to study the effectiveness of the oxidation step and the subsequent removal of the arsenic. The optimisation studies indicate that addition of 100 microl of H2O2 and 100 mg of Fe(II) (as ferrous ammonium sulphate) per litre of water for initial treatment followed by passing through zero valent iron, after a reaction time of 10 min, is capable of removing arsenic to lower than the US Environmental Protection Agency (EPA) guideline value of 10 microg/l, from a starting concentration of 2 mg/l of As(III). Using these suggested amounts, several experiments were carried out at different concentrations of As(III). Residual hydrogen peroxide in the processed samples can be eliminated by subsequent chlorination, making the water, thus, processed, suitable for drinking purposes. This approach is simple and cost effective for use at community levels.

ATP synthesis is coupled to rat liver mitochondrial RNA synthesis

Rat liver mitochondria respond to changes in energy demand by modulating the amount of RNA synthesized. Coupled rat liver mitochondria were used to determine the relationship between mitochondrial respiration, ATP levels, and mitochondrial transcription. This system included oxidizable substrates (malate and glutamate) and constituents that could support both mitochondrial respiration and transcription. The respiratory inhibitor rotenone, phosphorylation inhibitor oligomycin, and the uncoupler of oxidative phosphorylation carbonyl-cyanide p-triflouromethoxyphehylhydrazone inhibited RNA synthesis. Addition of ADP stimulated mitochondrial transcription and peak RNA synthesis was observed at 1-2 mM ADP. At ADP concentrations above 2 mM, RNA synthesis decreased. These results demonstrate that mitochondrial transcription is tightly coupled to ATP levels.

Mitochondrial cytochrome c oxidase subunit III is selectively down-regulated by aluminum exposure in PC12S cells

Aluminum (Al) has been implicated in several neurological diseases including dialysis dementia and Alzheimer's disease (AD). One possible mechanism of Al neurotoxicity could involve alteration of mitochondrial gene expression. We exposed PC12 cells to 0.1-100 microM AlCl3 for 6h at pH 7.4. Internalized Al, measured by atomic absorption spectrometry, was linearly proportional to the extracellular Al concentration. Northern blot analyses showed that cytochrome c oxidase subunit III (COX III) mRNA was significantly reduced by 70% after addition of 1 microM AlCl3. Higher concentrations of AlCl3 did not show a significant further effect. These results suggest that Al neurotoxicity involves a specific impairment of cytochrome c oxidase.

Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease: isolated channels between scars allow "focal" ablation

BACKGROUND

The purpose of this study was to characterize the circuit of macroreentrant right atrial tachycardia (MacroAT) in patients after surgical repair of congenital heart disease (SR-CHD).

METHODS AND RESULTS

Sixteen patients with atrial tachycardia (AT) after SR-CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained during 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (</=0.5 mV) involved most of the free wall in all patients and contained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width </=2.7 cm) between scars in all but 1 patient, who had a single scar and only focal AT. All 15 MacroATs were propagated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median 1) radiofrequency applications. Ablation was performed in 9 other channels identified during MacroAT (5 patients) and in 5 channels identified during atrial pacing (2 patients). Conduction block was obtained across 28 of 29 channels. After ablation, reproducible sustained right AT was not induced in any patient. During follow-up (median 13.5 months), new MacroATs, atrial fibrillation, or palpitations occurred in 3 of 16 patients.

CONCLUSIONS

MacroAT after SR-CHD requires a large area of low voltage containing >/=2 scars forming narrow channels. Ablation within the channels eliminates MacroAT.

Sildenafil citrate, a selective phosphodiesterase type 5 inhibitor: urologic and cardiovascular implications

Erectile dysfunction (ED) occurs in varying degrees in an estimated 20 to 30 million American men and is associated with adverse effects on quality of life; particularly personal well-being, family and social interrelationships. Research into ED has focused primarily on the physiologic mechanisms of corpus cavernosum smooth muscle relaxation, and penile erection as the end result of smooth muscle relaxation. These processes are mediated by cholinergic, nonadrenergic, noncholinergic (NANC, e.g., nitric oxide), vasoactive intestinal peptide (VIP), and potentially calcitonin gene-related peptide (CGRP) containing nerves. Release of nitric oxide following sexual stimulation from non-adrenergic, non cholinergic nerves and vascular endothelium activates guanylyl cyclase and induces intracellular cGMP synthesis. In turn, cGMP results in lowering intracellular concentrations, inhibits contractility of the penile smooth muscle, and induces an erectile response. Phosphodiesterase type 5 (PDE 5) is the predominant enzyme responsible for cGMP hydrolysis in trabecular smooth muscle. Activation of PDE 5 terminates NO-induced, cGMP-mediated smooth muscle relaxation, and subsequent penile flaccidity. Sildenafil citrate is a potent PDE type 5 reversible and selective inhibitor which blocks cGMP hydrolysis effectively. FDA approval of sildenafil citrate as the first oral agent for ED in males has resulted in significant interest. We discuss the clinical and pharmacologic properties of sildenafil citrate as well as the urologic and cardiac implications.

85 kDa cytosolic phospholipase A2 is a target for chronic lithium in rat brain

The mechanism by which chronic lithium exerts its therapeutic effect in brains of bipolar patients is not known. One possibility, suggested by our demonstration in the rat brain, is that chronic lithium inhibits turnover of arachidonic acid (AA) by reducing the activity of an AA-specific phospholipase A2 (PLA2). To test this further, mRNA levels of two AA-specific PLA2s, cytosolic PLA2 (cPLA2) type IV and intracellular PLA2 (iPLA2) type VIII, and protein level of cPLA2 were quantified in the brain of rats given lithium for 6 weeks. Chronic lithium markedly reduced brain mRNA and protein level of cPLA2, but had no effect on mRNA level of iPLA2. These results suggest that the final common path effect of chronic lithium administration is to reduce turnover of AA in brain by down-regulating cPLA2.

Low backache during pregnancy. Acute hemodynamic effects of a lumbar support

OBJECTIVE

To determine whether a commercially available elastic/Velcro lumbar and abdominal support (Mother-To-Be, CMO, Inc., Barberton, Ohio) affects the hemodynamics of the fetus and pregnant woman.

STUDY DESIGN

Healthy volunteers with low backache at 24-36 weeks' gestation were sought from our obstetric clinic population. The fetal heart rate (FHR), maternal blood pressure and maternal cardiac output were monitored for 20-minute intervals before, during and after placement of the support while standing and sitting. A sufficient number of subjects was used to detect a difference of 10% in cardiac output.

RESULTS

Twenty-five women were enrolled between 24 and 36 weeks' gestation. No significant changes were encountered in the FHR baseline or beat-to-beat variability during placement of the support. The few FHR decelerations were isolated and not attributable to the support. The maternal systolic, diastolic and mean arterial blood pressures were unaffected by the support. The right-sided and left-sided cardiac outputs were unchanged during the monitoring periods. Each woman, when questioned two weeks later, reported improvement in back discomfort while sitting and standing.

CONCLUSION

This elastic/Velcro lumbar and abdominal support, available to relieve low backache, did not acutely affect the hemodynamics of the fetus and mother.

Ross operation and aneurysm or dilation of the ascending aorta

Aortic valve disease and aneurysmal dilation of the ascending aorta are managed by prosthetic valve conduit replacement or homograft replacement. Requirement of anticoagulation, risk of thromboembolism or bleeding, and increased risk for homograft degeneration in young patients suggest that a Ross root replacement with replacement or reduction of the ascending aorta could be a preferred alternative. To assess efficacy, the present review was undertaken. Between April 19, 1995, and February 1999, 64 patients (age, 8 months to 59 years; median age, 37 years) had a Ross operation, with resection of the ascending aorta in 30 and reduction aortoplasty in 34. Annular fixation was performed in 57 patients, with aortic annulus reduction in 39. Clinical evaluation with echocardiogram was completed within 1 year of closure in 62 patients. There was one operative death and one non-valve-related late death. Autograft valve insufficiency (AI) was 0 to trace in the perioperative period in all patients. One patient developed progressive annular dilation with moderate AI at 2 months. Reoperation with annular reduction and fixation restored autograft valve function. Postoperative mean aortic annulus diameter was 22.5+/-0.4 mm (Z-value, -0.2+/-0.2) and 23.2+/-0.8 mm (Z-value, -0.02+/-0.5) at 1 year. Aortic sinus diameter was 33+/-6 postoperative and 36+/-5 at 1 year. The autograft root sinus diameter was greater than 39 mm in 11 patients at the most recent echocardiogram. Mean echocardiography measurements of the aortic root have been constant during the postoperative follow-up period. Two patients have required reoperation for homograft obstruction 1.3 and 2.1 years after operation. Ross root replacement of the aortic valve with resection or reduction aortoplasty can be performed with a low operative risk and limited morbidity. Its early durability appears to be similar to other Ross operations.

Hyperhomocysteinemia, aortic thrombus, and peripheral arterial emboli--a case report

A young Native American woman presented with ischemia of the left lower limb resulting from embolic occlusion of the left common iliac artery and left femoral artery. The source of her emboli was aortic thrombus. The only underlying abnormality responsible for her hypercoagulability appeared to be hyperhomocysteinemia.

Advantage of autograft and homograft valve replacement for complex aortic valve endocarditis

BACKGROUND

There are advantages to using homografts and autografts as aortic valve replacements, particularly in patients with infective endocarditis. To better define these advantages, we reviewed our 13-year experience with the surgical management of infective endocarditis involving the aortic valve and root.

METHODS

From 1986 through 1998, 81 adults with aortic valve endocarditis underwent valve replacement (AVR). The mean age of the 65 men and 16 women was 44 +/- 14 years. Sixty-three (78%) patients had active endocarditis at the time of operation. Non-native valve endocarditis was present in 29 (36%) patients, in 9 of whom the infection was a recurrence. Aortic valve replacements were performed with 46 homografts (homo-AVR), 25 autografts (Ross-AVR), and 10 prosthetic valves (prosth-AVR). Among Ross-AVR and homo-AVR patients, 11 required mitral valve replacement or repair (homo-Ross DVR). Follow-up was 90% complete within 2 years of the end of the study with a mean of 3.7 +/- 3.4 years.

RESULTS

Early mortality was 16% (13 of 81 patients). This was 12% (3 of 25 patients) for Ross-AVR, 17% (8 of 46 patients) for homo-AVR, and 20% (2 of 10 patients) for prosth-AVR. Overall late mortality was 10% (7 of 68 patients) with a valve-related late mortality of 7% (5 of 68 patients). Actuarial survival at 5 years was 88% +/- 9% in Ross-AVR, 69% +/- 11% in homo-AVR, and 29% +/- 22% in prosth-AVR (p = 0.03). Endocarditis recurred in 12.5% (1 of 8 patients) with prosth-AVR and 3% (2 of 60 patients) in homo-Ross AVR.

CONCLUSIONS

Valve replacement in the presence of native and prosthetic endocarditis remains a formidable challenge. Autografts and homografts are the preferred replacement aortic valves for these patients even if concomitant mitral valve replacement is required, and risk of valve-related death or recurrent endocarditis is low at medium-term follow-up.

Aortic valve involvement in calciphylaxis: uremic small artery disease with medial calcification and intimal hyperplasia

Calciphylaxis is a rare manifestation of abnormal calcium metabolism seen in some patients with renal disease. We describe the transesophageal echocardiographic (TEE) findings in a patient with calciphylaxis. These findings included calcification of ascending aorta and aortic valve. TEE was normal before the development of calciphylaxis.

No association between Alzheimer plaques and decreased levels of cytochrome oxidase subunit mRNA, a marker of neuronal energy metabolism

It has been proposed that neuritic plaques or toxic substances diffusing from them contribute to neurodegeneration in Alzheimer disease. We examined this hypothesis by looking for evidence of decreased neuronal energy metabolism in the proximity of neuritic plaques. Levels of mitochondrial DNA-encoded mRNA for subunit III of cytochrome oxidase, a marker of neuronal energy metabolism, were determined in post mortem brain samples. Consistent with earlier results, overall cytochrome oxidase subunit III mRNA levels were decreased in Alzheimer midtemporal cortex compared with controls. However, this reduction did not correlate with plaque density. In Alzheimer brains, cytochrome oxidase subunit III mRNA levels in neurons bearing neurofibrillary tangles were lower than in tangle-free neurons. However, neuronal cell bodies in close proximity of neuritic plaques showed no decrease in cytochrome oxidase subunit III mRNA or total polyadenylated mRNA compared with more distant neurons. Cytochrome oxidase enzyme activity in neuronal processes also showed no local reduction around neuritic plaques. These results suggest that neuritic plaques do not contribute to reduced neuronal energy metabolism in Alzheimer disease.

Downregulation of oxidative phosphorylation in Alzheimer disease: loss of cytochrome oxidase subunit mRNA in the hippocampus and entorhinal cortex

Messenger RNA (mRNA) for cytochrome oxidase subunit II (COX II) was localized by in situ hybridization in the entorhinal cortex and hippocampal formation of postmortem brain tissue from normal human subjects and from patients with Alzheimer disease (AD). In the control entorhinal cortex, COX II mRNA was detected mainly in neuronal cell bodies of layers II and IV. In control hippocampal formation, highest levels were localized in neuronal cell bodies of the dentate gyrus and the CA3 and CA1 regions, neurons that are involved in the major input and output pathways of the hippocampal formation. In AD brain, COX II mRNA was markedly reduced in the entorhinal cortex and the hippocampal formation compared with control brain. In the AD hippocampal formation, reductions were in regions severely affected by AD pathology as well as in regions that were relatively spared. These results are consistent with the hypothesis that reduced mitochondrial energy metabolism reflects loss of neuronal connections in AD.

Emboli observed with use of transesophageal echocardiography immediately after tourniquet release during total knee arthroplasty with cement

The right atrium and the right ventricle of fifty-five patients were imaged with transesophageal echocardiography during fifty-nine total knee arthroplasties performed with cement and the use of general anesthesia. The patients ranged in age from thirty-two to eighty-three years (mean, 65.5 years). Cardiopulmonary parameters were measured with use of hemodynamic monitoring systems, such as pulse oximeters, pulmonary artery catheters, and radial artery catheters. In addition, a femoral vein catheter was inserted on the side of the operation in ten of the fifty-five patients. Showers of echogenic material traversing the right atrium, the right ventricle, and the pulmonary artery after the tourniquet was deflated were observed to various degrees in all patients and lasted three to fifteen minutes. The mean peak intensity occurred within thirty seconds (range, twenty-four to forty-five seconds) after the tourniquet was released. The mean mixed venous oxygen saturation (and standard error of the mean) decreased (from 83+/-0.9 to 72+/-1.5 per cent) and the mean pulmonary arterial pressure increased (from 20+/-1.0 to 27+/-1.0 millimeters of mercury [2.67+/-0.13 to 3.60+/-0.13 kilopascals]), compared with the values before the tourniquet was released, in all patients. The pulmonary vascular resistance index increased after release of the tourniquet (to a maximum of 328+/-29 dyne.s.cm(-5).m2; p = 0.00002) only in the patients who had echogenic material that was at least 0.5 centimeter in diameter. Clinical pulmonary embolism developed postoperatively in three patients; all three had had echogenic particles that were more than 0.5 centimeter in maximum diameter on imaging. Blood aspirated from one of the pulmonary artery catheters and from five of the ten femoral vein catheters demonstrated fresh venous thrombus. Histological evaluation of the aspirates failed to demonstrate fat, marrow, or particles of polymethylmethacrylate. Surgeons should consider acute pulmonary embolism as a diagnosis when evaluating a patient who has hemodynamic collapse during total knee arthroplasty performed with cement.

Large pulmonary vein varix diagnosed by transesophageal echocardiography: an unusual site for thrombus in atrial fibrillation

An elderly man with pulmonary vein varix and atrial fibrillation is described. The diagnosis of pulmonary varix, a localized dilatation of pulmonary vein, was made by transesophageal echocardiography. The patient had chronic atrial fibrillation, and transesophageal echocardiography demonstrated thrombus in the pulmonary varix. In patients with atrial fibrillation, pulmonary varix may be an unusual site for thrombus formation.

Study of the feasibility of involving male student volunteers in case holding in an urban tuberculosis programme

This paper reports the feasibility of involving unpaid National Service Scheme (NSS) male student volunteers in a city-based tuberculosis (TB) programme in supplying drugs and retrieving non-complaint TB patients. Twenty-five students were selected after assessing their attitude and were trained on TB drug delivery, home visits and motivation of non-compliant patients. Twenty-three sputum positive patients identified in a medical camp were started on an 8-month short-course chemotherapy regimen. Students supplied the drugs on a weekly basis and defaulters were visited. The treatment completion rate was 83% and defaulter retrieval was 57%. All patients had sputum smear conversion by 2 months and one relapsed during the 24-month follow-up.

Giant coronary artery pseudoaneurysm causing pulmonary artery obstruction: a rare complication of coronary bypass surgery--a case report

The authors report the diagnosis and successful management of a 57-year-old man with right ventricular outflow tract obstruction from a large pseudoaneurysm of the left anterior descending coronary artery 5 years after he had undergone redo coronary artery bypass grafting.

Lack of arrhythmogenicity with ST-segment elevation during high-dose of dobutamine atropine stress in patients with documented or suspected coronary artery disease

The angiographic, echocardiographic, and electrocardiographic correlates of ST-segment elevation during high-dose dobutamine-atropine stress were prospectively looked at in a group of high-risk patients. Unlike exercise-induced ST elevation, ST-segment elevation with dobutamine-atropine stress, while indicating transmural ischemia, did not increase rate of arrhythmias and hence by itself may not be an indication to terminate the test.

Decreased expression of nuclear and mitochondrial DNA-encoded genes of oxidative phosphorylation in association neocortex in Alzheimer disease

We recently reported 50% decreases in mRNA levels of mitochondrial DNA (mtDNA)-encoded cytochrome oxidase (COX) subunits I and III in Alzheimer disease (AD) brains. The decreases were observed in an association neocortical region (midtemporal cortex) affected in AD, but not in the primary motor cortex unaffected in AD. To investigate whether the decreases are specific to mtDNA-encoded mRNA, we extended this analysis to nuclear DNA (nDNA)-encoded subunits of mitochondrial enzymes of oxidative phosphorylation (OXPHOS). Brains from five AD patients showed 50-60% decreases in mRNA levels of nDNA-encoded subunit IV of COX and the beta-subunit of the F0F1-ATP synthase in midtemporal cortex compared with mRNA levels from midtemporal cortex of control brains. In contrast, these mRNAs were not reduced in primary motor cortices of the AD brains. The amount of nDNA-encoded beta-actin mRNA and the amount of 28S rRNA were not altered in either region of the AD brain. The results suggest that coordinated decreases in expression of mitochondrial and nuclear genes occur in association cortex of AD brains and are a consequence of reduced neuronal activity and downregulation of OXPHOS machinery.

Brain energy metabolism, cognitive function and down-regulated oxidative phosphorylation in Alzheimer disease

Reduced brain glucose utilization in early stages of Alzheimer disease, as measured with in vivo positron emission tomography, reflects potentially reversible down-regulation of gene expression for oxidative phosphorylation within neuronal mitochondria. Such down-regulation may occur when neuronal energy demand is first reduced by synaptic dysfunction or loss.

Evidence for physiological down-regulation of brain oxidative phosphorylation in Alzheimer's disease

In vivo imaging of patients with Alzheimer's disease using positron emission tomography (PET) demonstrates progressive reductions in brain glucose metabolism and blood flow in relation to dementia severity, more so in association than primary cortical regions. These reductions likely follow regional synaptic loss or dysfunction and reflect physiological down-regulation of gene expression for glucose delivery, oxidative phosphorylation (OXPHOS), and energy consumption in brain. Indeed, the pattern of down-regulation of expression for both mitochondrial and nuclear genes coding for subunits of OXPHOS enzymes in the Alzheimer brain resembles the pattern of down-regulation in normal brain caused by chronic sensory deprivation. In both cases, down-regulation likely is mediated by changes in transcriptional and posttranscriptional regulatory factors. Physiological down-regulation of OXPHOS gene expression in Alzheimer's is consistent with PET evidence that cognitive or psychophysical activation of mildly to moderately demented Alzheimer's patients can augment brain-blood flow and glucose metabolism to the same extent as in control subjects. If the primary neuronal defect that leads to reduced brain energy demand in Alzheimer's disease could be prevented or treated, brain glucose transport and OXPHOS enzyme activities might recover to normal levels.

Transesophageal echocardiography during removal of central venous catheter associated with thrombus in superior vena cava

Thrombosis of upper extremity veins and superior vena cava (SVC) can occur in patients with indwelling central venous catheters. Contrary to earlier reports, pulmonary embolism (PE) can result from these thrombi, especially when they are attached to catheters (sleeve thrombi) in contrast to venous wall (mural thrombi). Removal of catheters may be required when sepsis occurs or to reduce risk of sepsis when lines have been left in for several days. We describe two patients with thrombi in SVC related to central venous catheters in whom transesophageal echocardiography (TEE) was performed during catheter removal to monitor for thrombus dislodgement. TEE may have a role in showing thrombus dislodgement and embolization during removal of venous catheters complicated by SVC thrombi. Direct visualization of thrombus dislodgement may aid in early diagnosis of PE because signs and symptoms of PE are often missed or mistaken for underlying cardiopulmonary disease. TEE may also play a role in implementing appropriate treatment in patients with PE who show right ventricular strain.

Neuronal activity and early neurofibrillary tangles in Alzheimer's disease

We studied neuronal activity and its relation to the accumulation of neurofibrillary tangles in Alzheimer's disease (AD) neurons by in situ hybridization to cytochrome oxidase subunit III messenger RNA, a marker of mitochondrial energy metabolism. In AD midtemporal cortex, levels of cytochrome oxidase subunit III messenger RNA were decreased by 26% in neurons bearing early-stage neurofibrillary tangles as compared to tangle-free neurons (p < 0.01). However, levels of 12S ribosomal RNA, also encoded by mitochondrial DNA, and of total messenger RNA were decreased only in later stages of tangle development. Comparing tangle-free neurons of 4 AD brains to tangle-free neurons of 3 control brains, levels of cytochrome oxidase subunit III messenger RNA were found to be 25% lower (p < 0.001) in AD tangle-free neurons. Because energy metabolic needs of neurons are mainly determined by synaptic input, the observed decreases in cytochrome oxidase subunit III messenger RNA likely reflect downregulation due to impaired synaptic function in AD. Thus, a failure in synaptic transmission may precede tangle formation. A further decline in neuronal activity is seen as tangle formation progresses. However, these results can also be viewed as showing the viability and continuing activity, albeit at a lower level, of neurons in the early stages of neurofibrillary pathology.

Unusual presentation of late regional cardiac tamponade after aortic surgery

Localized pericardial effusion leading to cardiac tamponade is seen occasionally in patients after cardiac surgery. This condition may be difficult to diagnose clinically because of unusual presenting symptoms and absence of conventional signs of cardiac tamponade. A case of localized pericardial effusion with presenting symptoms of fever and increasing fatigue is described in this study. The definitive diagnosis was made using transesophageal echocardiography. Surgical drainage of localized effusion resulted in prompt hemodynamic and symptomatic improvement.

Risk of catheter-related emboli in patients with atherosclerotic debris in the thoracic aorta

The aim of this study was to evaluate the risk of performing cardiac catheterization or intraaortic balloon pump placement in patients with transesophageal echocardiographically detected atherosclerotic aortic debris. Cardiac catheterization was performed in 70 patients with atherosclerotic aortic debris (in 11 via the brachial approach and in 59 via the femoral approach) and in 71 control patients. An embolic event occurred in 10 (17%) of 59 patients with atherosclerotic aortic debris after femoral catheterization compared to 2 (3%) of 71 control patients without atherosclerotic aortic debris (p = 0.01). None of the 11 patients with atherosclerotic aortic debris who underwent brachial catheterization had an embolic event. An intraaortic balloon pump was placed in 10 patients with atherosclerotic aortic debris and in 12 control patients. An embolic event related to placement of the intraaortic balloon pump occurred in 5 (50%) of 10 patients with atherosclerotic aortic debris; no control patient had an embolic event (p = 0.02). Patients with mobile atherosclerotic aortic debris were at the highest risk for catheter-related embolism. The strongest clinical predictors of atherosclerotic aortic debris were advanced age and peripheral vascular disease. Transesophageal echocardiographic recognition of atherosclerotic aortic debris identifies patients at high risk of stroke or peripheral embolism after cardiac catheterization or intraaortic balloon pump placement. If the aortic debris is mobile, the risk is particularly high. When atherosclerotic aortic debris is detected, especially if the debris is mobile, substituting brachial for femoral catheterization and avoiding placement of an intraaortic balloon pump may reduce the risk of embolism.

Gene expression of ND4, a subunit of complex I of oxidative phosphorylation in mitochondria, is decreased in temporal cortex of brains of Alzheimer's disease patients

Gene expression of mitochondrial DNA-encoded ND4 in brains of Alzheimer's disease (AD) patients and age-matched controls was measured using Northern blot. The level of ND4 message in temporal cortex of control subjects was higher than in motor cortex, whereas the level of ND4 gene expression in temporal cortex of AD brains was decreased compared with that in temporal cortex of controls. A control probe showed no difference in expression between the two areas of AD and control brains. These and previous data suggest that neurons vulnerable to AD express higher levels of enzymes of oxidative phosphorylation than do spared neurons, and that this difference may promote selective neuronal vulnerability of AD.

Pilot prospective evaluation of counterpulsation with different intra-aortic balloon volumes on cardiac performance in humans

Smaller intra-aortic balloons (IAB) may minimize peripheral vascular complications. To determine the influence of different IAB volumes on cardiac performance, we studied 20 hemodynamically stable patients on IAB counterpulsation. Variables were measured with either a 40cc or 32cc IAB displacement, at an assist ratio of 1:1 or 1:8: Heart rate, Ao and PA pressures, and Fick cardiac output. By echo-Doppler, the velocity time integral (VTI) across the LV outflow tract, a measure of stroke volume was also calculated. The mean age was 60 yr (range 18-77), height 5'6" (5'2"-5'11"), and body surface area 1.9M2 (1.5-2.3). Results presented as mean values were: [table: see text] *P < 0.005 1:1 vs 1:8 for both 40 and 32cc IAB.

CONCLUSION

IAB pumping at 1:1 with either 40 cc or 32 cc volume displacement yields similar degrees of improvement in cardiac performance. A larger cohort is required to determine if smaller balloons may decrease complications without compromising efficacy.

Frequency and explanation of false negative diagnosis of aortic dissection by aortography and transesophageal echocardiography

OBJECTIVES

This study was designed to define the frequency and explanation of false negative diagnosis of aortic dissection by aortography and transesophageal echocardiography.

BACKGROUND

Aortography and transesophageal echocardiography have been widely utilized to diagnose aortic dissection. Previous reports have not fully addressed the reasons why these studies yield false negative results in a large number of patients with aortic dissection.

METHODS

Sixty-five consecutive patients with aortic dissection underwent aortography and transesophageal echocardiography. Diagnosis of aortic dissection was confirmed at operation or by computed tomography in all patients.

RESULTS

Biplane transesophageal echocardiograms yielded false negative results in two patients (sensitivity 97% [63 of 65]). Both patients had well localized DeBakey type II aortic dissection. The diagnosis was probably missed because of image interference from the air-filled trachea and mainstem bronchi. In both patients, the dissection was readily identified by aortography. Aortograms yielded false negative results in 15 patients (sensitivity 77% [50 of 65]); the aortic dissection was type I in 7 patients, type II in 1 and type III in 7. The dissection in all 15 patients was readily identified by transesophageal echocardiography. The missed diagnosis was probably due to a completely thrombosed false lumen or intramural hematoma with noncommunicating dissection in 13 patients and to a large ascending aortic aneurysm with nearly equal flow on both sides of the intimal flap in 2. In no patient was the diagnosis missed by both aortography and transesophageal echocardiography.

CONCLUSION

Transesophageal echocardiography is an excellent screening tool for aortic dissection. However, it may miss small type II aortic dissections localized to the upper portion of the ascending aorta because of image interference from the air-filled trachea. An intramural hematoma cannot be easily visualized by aortography, and this lesion is the principal reason for false negative aortographic findings.

Endocarditis-associated paravalvular abscesses. Do clinical parameters predict the presence of abscess?

STUDY OBJECTIVE

To determine whether standard clinical and transthoracic echocardiographic criteria considered to be suggestive of the presence of endocarditis-associated paravalvular abscess are predictive of which patients would benefit from reliable but invasive transesophageal echocardiographic investigations for abscess.

DESIGN

Retrospective chart review.

SETTING

A 630-bed university hospital.

PATIENTS

Forty-eight patients with 51 episodes of definite endocarditis and 24 paravalvular abscesses.

MEASUREMENTS AND RESULTS

A comparison of abscess and nonabscess populations revealed that clinical parameters (patient demographics, valvular involvement, presence of a prosthesis, infection with a virulent organism, pericarditis, persistent fever, persistent bacteremia, congestive heart failure, history of intravenous drug use, embolization) and transthoracic echocardiographic parameters were insensitive predictors of the presence of abscess. The only statistically significant correlate was the presence of previously undetected atrioventricular or bundle branch block. Paravalvular abscesses were common in our population and were associated with increased mortality. Improved survival correlated with the absence of mitral valve involvement and the absence of moderate-to-severe congestive heart failure.

CONCLUSIONS

Given the accuracy and safety of transesophageal echocardiography and the unreliability of clinical and transthoracic echocardiographic criteria, we recommend that transesophageal echocardiography be considered in all endocarditis patients with previously unrecognized conduction disturbances, aortic or prosthetic valve involvement, or both, or indications for valve replacement, or all of the foregoing.

In vivo diagnosis of pulmonary atherosclerosis. Role of intravascular ultrasound

The application of intravascular ultrasound (IVUS) in diagnosing pulmonary artery atherosclerosis is described. To the best of our knowledge, this is the first description of the use of this technique in the recognition of pulmonary atherosclerosis. We describe a patient with long-standing primary pulmonary hypertension with evidence of pulmonary artery calcification seen on a chest x-ray film. The IVUS imaging of the pulmonary arteries identified intimal disruption with complex atherosclerosis. Thus, IVUS can be a useful tool in the diagnosis of pulmonary artery atherosclerosis.

Impairment in mitochondrial cytochrome oxidase gene expression in Alzheimer disease

Brains from 5 patients with Alzheimer's disease (AD) showed a 50%-65% decrease in mRNA levels of the mitochondrial-encoded cytochrome oxidase (COX, a marker of oxidative metabolism) subunits I and III in the middle temporal association neocortex, but not in the primary motor cortex, as compared to 5 control brains. The amount of mitochondrial-encoded 12S rRNA was not altered, nor was the amount of nuclear-encoded lactate dehydrogenase B mRNA (a marker of glycolytic metabolism). These data suggest that the decrease in COX I and III subunits mRNA in affected brain regions may contribute to reduced brain oxidative metabolism in AD.

Transesophageal echocardiographic diagnosis of pulmonary arteriovenous malformation. Role of contrast and pulsed Doppler echocardiography

Contrast echocardiography produced by peripheral injection of agitated saline solution is widely used for detecting intracardiac and intrathoracic extracardiac shunts, like pulmonary arteriovenous malformation (PAVM). Currently, localization of PAVM requires pulmonary angiography even after detection by computed tomography of the chest. Pulsed Doppler along with contrast echocardiography of the pulmonary veins performed during transesophageal echocardiography may aid in the localization of PAVM and in its diagnosis.

Three-dimensional volumetric ultrasound imaging of arterial pathology from two-dimensional intravascular ultrasound: an in vitro study

The objectives of this study were to evaluate: (1) the feasibility of generating three-dimensional (3-D) ultrasound (US) volumetric images of arterial segments from intravascular (IV) US images by retaining full range of gray levels; (2) the feasibility of volumetric quantitation of various arterial wall pathology from the 3-D volume US images of arterial segments. IVUS provides morphologic details of arterial wall diseases. This is seen as variation in gray levels. However, when a 3-D US image is generated currently, the full range of gray levels is not utilized. This limits optimal assessment of arterial wall pathology. Sequential cross-sectional IVUS images from 11 arterial segments consisting of various pathology were obtained in vitro by calibrated withdrawal of an IVUS catheter. These images were digitized by an 8 bit digitizer to retain full 256 gray levels of brightness. 3-D volume generation was carried out using "ANALYZE" software. After the IVUS imaging, arterial segments were sectioned transversely in a 0.3-0.4 mm cross section and stained with hematoxylin, eosin and elastin. Geometrical measurements and gross morphological changes of the arterial segments were noted and correlated with the corresponding section of the image from the three-dimensional volume. Arterial wall pathology, its extent and its effect on lumen geometry were easily appreciated in multiple tomographic sections of a 3-D volume image. Similarly, arterial wall pathology was easily quantitated from 3-D volume. The above assessments were only feasible by retaining full range of gray levels in the 3-D volume image. This study indicates that (1) it is feasible to generate a 3-D US volume image by retaining full range of gray levels from IVUS images, (2) retaining full range of gray levels allows optimal assessment of arterial wall pathology and its extent in 3-D volume, and (3) IVUS allows quantitation of arterial wall pathology, and thereby one can assess the effect of intervention.

Impact of the incidental diagnosis of clinically unsuspected central pulmonary artery thromboembolism in treatment of critically ill patients

Mortality is high in unrecognized pulmonary embolism (PE), but the diagnosis is difficult to establish, especially in patients with coexisting cardiopulmonary disorders. We describe a group of 14 patients with pulmonary thromboemboli in whom transesophageal echocardiography (TEE) performed for coexisting cardiopulmonary conditions established the clinical diagnosis of PE not suspected prior to TEE. The patients had initial clinical diagnoses of heart failure (eight patients), cardiogenic shock (two patients), atrial septal defect (two patients), aortic dissection (one patient), and pneumonia (one patient). Thirteen patients had risk factors for PE. Transthoracic echocardiography (TTE) demonstrated right heart strain in eight patients but did not visualize PE in any of the patients. The TEE diagnosis of occult central pulmonary artery thromboembolism changed treatment in all 14 patients. Ten of the 14 patients were successfully discharged from the hospital. We conclude that occult central pulmonary artery thromboemboli are not uncommon in patients presenting with acute cardiopulmonary disorders and the presence of risk factors for PE and right heart strain on TTE should alert the physician to suspect PE. If and when TEE is performed in patients with acute cardiopulmonary disorders with risk factors for PE and right heart strain, the physician should evaluate the main pulmonary artery and its branches for central pulmonary artery thromboemboli.

Spontaneous arterial embolization after thrombolytic therapy for acute myocardial infarction: the role of transesophageal echocardiography

Arterial embolization from thrombolytic therapy for acute myocardial infarction is rare. We report two cases of spontaneous arterial embolization following the use of tissue plasminogen activator for acute myocardial infarction. Transesophageal echocardiography was able to identify the source of embolism as mobile atherosclerotic debris within the thoracic aorta. This information was of value in the management of these patients, in that femoral catheterization which could have precipitated further embolization was avoided.

Acute thoracic aortic occlusion resulting from complex aortic dissection and presenting as paraplegia

Acute paraplegia from an aortic occlusion or dissection is a surgical emergency. Prompt recognition and treatment may mitigate irreversible spinal cord injury. Aortography is commonly used when an aortic lesion is suspected as the cause of acute paraplegia. Transesophageal echocardiography is becoming increasingly used for the evaluation of aorta, diagnosing aortic dissection promptly at the bedside, and was able to define the cause of the spinal cord ischemia.

The role of echocardiography in blunt chest trauma: a transthoracic and transesophageal echocardiographic study

Previous studies assessing the value of transthoracic echocardiography (TTE) in blunt chest trauma are limited because patients with severe chest wall injury often have suboptimal echocardiographic findings. Transesophageal echocardiography (TEE) can provide high quality images when the transthoracic image quality is poor. To provide complete echocardiographic assessment of cardiac structure and function we prospectively performed TTE in 105 patients with severe blunt chest trauma and TEE in 20 of the 105 patients (19%) whose TTE examination results were suboptimal. Myocardial contusion was diagnosed in 31 patients (30%), 22 by TTE and nine by TEE. Cardiac complications developed in 8 of 31 patients (26%) with myocardial contusion compared with 2 of 74 patients (3%) with normal echocardiographic findings (p = 0.001). Cardiac complications required treatment in only four patients. Echocardiography was of value in detecting severe right ventricular dysfunction as the cause of hypotension in two patients with suspected cardiac tamponade. Four patients with myocardial contusion died compared with two patients with normal echocardiographic findings (p = NS). No death was related to the cardiac status. In addition, TEE detected aortic injury in five patients, four with focal intimal tears and one with an aortic transection. We conclude that myocardial contusion is common following blunt chest trauma, rarely requires treatment, and is associated with a favorable prognosis. Only patients who develop cardiac complications benefit from echocardiography. Transesophageal echocardiography is of value when the TTE examination results are suboptimal and when aortic injury is suspected.