Myelin dysfunction drives amyloid-β deposition in models of Alzheimer's disease

The incidence of Alzheimer's disease (AD), the leading cause of dementia, increases rapidly with age, but why age constitutes the main risk factor is still poorly understood. Brain ageing affects oligodendrocytes and the structural integrity of myelin sheaths1, the latter of which is associated with secondary neuroinflammation2,3. As oligodendrocytes support axonal energy metabolism and neuronal health4-7, we hypothesized that loss of myelin integrity could be an upstream risk factor for neuronal amyloid-β (Aβ) deposition, the central neuropathological hallmark of AD. Here we identify genetic pathways of myelin dysfunction and demyelinating injuries as potent drivers of amyloid deposition in mouse models of AD. Mechanistically, myelin dysfunction causes the accumulation of the Aβ-producing machinery within axonal swellings and increases the cleavage of cortical amyloid precursor protein. Suprisingly, AD mice with dysfunctional myelin lack plaque-corralling microglia despite an overall increase in their numbers. Bulk and single-cell transcriptomics of AD mouse models with myelin defects show that there is a concomitant induction of highly similar but distinct disease-associated microglia signatures specific to myelin damage and amyloid plaques, respectively. Despite successful induction, amyloid disease-associated microglia (DAM) that usually clear amyloid plaques are apparently distracted to nearby myelin damage. Our data suggest a working model whereby age-dependent structural defects of myelin promote Aβ plaque formation directly and indirectly and are therefore an upstream AD risk factor. Improving oligodendrocyte health and myelin integrity could be a promising target to delay development and slow progression of AD.

Comparison of cryogenic low-pass filters

Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.

Changes in free radical generation and antioxidant capacity during ultramarathon foot race

BACKGROUND

Exhaustive exercise has been implicated in the generation of reactive oxygen species, resulting in oxidative stress. We studied the effect of a long-distance, endurance exercise on oxidative stress parameters in athletes who participated in the ultramarathon race Spartathlon (246 km).

MATERIALS AND METHODS

This study included 18 runners (16 men and 2 women) aged 42.8 +/- 1.4 years. Blood samples were obtained 24 h before (prerace), at the end (postrace) and 48 h after the end of the race (48 h postrace). We measured oxidative stress indices, including red cell glutathione, malonyldialdehyde and 8-iso-prostaglandin F(2a), as well as the total antioxidant capacity.

RESULTS

8-Iso-prostaglandin F(2a) level increased significantly at the end of the race, compared to prerace levels (up to 914.7 +/- 61.4 pg mL(-1) from 197.6 +/- 8.4 pg mL(-1)), and remained 2.5-fold increased over the baseline 48 h after the race (532.0 +/- 54.2 pg mL(-1), P < 0.000). The total antioxidant capacity of the athletes increased from a baseline of 289.6 +/- 9.0 micromol L(-1) to 358.7 +/- 11.0 micromol L(-1) immediately after the race and remained elevated 48 h later (350.6 +/- 7.6 micromol L(-1)) (P < 0.001).

CONCLUSIONS

Prolonged exercise induces a marked response of oxidative stress biomarkers, which in part is compensated by serum ability to scavenge free radicals. Whether these changes have long-term negative effects in the organism needs further investigation.

Compromising bradycardia: management in the emergency department

AIM OF THE STUDY

Bradycardia may represent a serious emergency. The need for temporary and permanent pacing is unknown.

METHODS

We analysed a registry for the incidence, symptoms, presenting rhythm, underlying mechanism, management and outcome of patients presenting with compromising bradycardia to the emergency department of a university hospital retrospectively during a 10-year period.

RESULTS

We identified 277 patients, 173 male (62%), median age 68 (IQR 58-78), median ventricular rate 33 min(-1) (IQR 30-40). The leading symptoms were syncope [94 (33%)], dizziness [61 (22%)], collapse [46 (17%)], angina [46 (17%)] and dyspnoea/heart failure [30 (11%)]. The initial ECG showed high grade AV block [134 (48%)], sinus bradycardia/AV block [46 (17%)], sinuatrial arrest [42 (15%)], bradycardic atrial fibrillation [39 (14%)] and pacemaker-failure [16 (6%)]. The underlying mechanisms were primary disturbance of cardiac automaticity and/or conduction [135 (49%)], adverse drug effect [58 (21%)], acute myocardial infarction [40 (14%)], pacemaker failure [16 (6%)], intoxication [16 (6%)] and electrolyte disorder [12 patients (4%)]. In 107 (39%) patients bed rest resolved the symptoms. Intravenous drugs to increase ventricular rate were given to 170 (61%) patients, 54 (20%) required additional temporary transvenous/transcutaneous pacing. Two severely intoxicated patients could be stabilised only by cardiopulmonary bypass. A permanent pacemaker was implanted in 137 patients (50%). Mortality was 5% at 30 days.

CONCLUSION

In our cohort, about 20% of the patients presenting with compromising bradycardia required temporary emergency pacing for initial stabilisation, in 50% permanent pacing had to be established.

Proton pump inhibition prevents gastrointestinal bleeding in ultramarathon runners: a randomised, double blinded, placebo controlled study

BACKGROUND

Ultra-endurance running is emerging as a popular sport in Western industrialised countries. Gastrointestinal bleeding has been reported to be an adverse effect in these runners.

OBJECTIVE

To see if the oral administration of a proton pump inhibitor would reduce the incidence of gastrointestinal bleeding in an ultramarathon.

METHODS

In a randomised, double blinded, placebo controlled study, a prophylactic regimen of three days of an oral proton pump inhibitor (pantoprazole 20 mg) was tested in healthy athletes participating in the Spartathlon ultramarathon. The incidence of gastrointestinal bleeding was assessed by a stool guaiac test.

RESULTS

Results were obtained for 70 healthy volunteers. The data for 20 of 35 runners in the intervention group and 17 of 35 runners in the placebo group were entered into the final analysis. At the end of the ultramarathon, two subjects in the intervention group and 12 in the placebo group had positive stool guaiac tests (risk difference 0.86; 95% confidence interval 0.45 to 0.96; p = 0.001).

CONCLUSION

A short prophylactic regimen of oral proton pump inhibition can successfully decrease the incidence of gastrointestinal bleeding in participants in an ultramarathon.

The Role of Chlamydia Pneumoniae in Human Aortic Disease—A Hypothesis Revisited

BACKGROUND

The role of Chlamydia pneumoniae in the pathogenesis of aortic aneurysm is controversial. We investigated the presence of C. pneumoniae in tissue samples excised from patients and controls.

METHODS

Aortic wall specimens were obtained from 17 patients with acute Stanford type A aortic dissection, 25 patients with thoracic aortic aneurysms (TAA) and 23 patients with abdominal aortic aneurysms (AAA). Eighty-three tissue samples of 73 control patients free of aortic disease were obtained either at surgery or autopsy. The presence of Chlamydia subspecies DNA (sequences specific for all known Chlamydiaceae) and DNA of C. pneumoniae, C. trachomatis and C. psittaci were assessed by a validated highly sensitive and specific real time polymerase chain reaction (PCR) analysis. Atherosclerotic risk factors were assessed in all patients.

RESULTS

We failed to detect C. pneumoniae and C. psittaci-DNA in any of the 148 vessel specimens. C. trachomatis-DNA was detected in 1/65 patients and in none of 83 controls (P=0.43). Chlamydia subspecies DNA was found in samples of eight cases and in one control (P=0.01), however, no significant differences were found between the subgroups aortic dissection (P=0.09), TAA (P=0.99) and AAA (P=0.15) and respective controls.

CONCLUSIONS

C. pneumoniae does not play a clinically relevant role in acute and chronic aortic disease. The impact of other organisms of the family Chlamydiaceae needs further evaluation.

Resuscitation in near drowning with extracorporeal membrane oxygenation

We report a case of near drowning of a 3-year-old girl, who was admitted to our emergency room with a core temperature of 18.4 degrees C. After rewarming on cardiopulmonary bypass and restitution of her circulation, respiratory failure resistant to conventional respiratory therapy prohibited weaning from cardiopulmonary bypass. Therefore, we instituted extracorporeal membrane oxygenation (ECMO). Fifteen hours later, she could be weaned from ECMO but required assisted ventilation for another 12 days. Twenty months later there are no neurologic deficits.

Off-pump coronary bypass operations significantly reduce S100 release: an indicator for less cerebral damage?

BACKGROUND

Cardiac operations using extracorporeal circulation bear a risk of cerebral complications. The aim of our study was to investigate if off-pump operations without heart-lung machines can reduce cerebral injury.

METHODS

S100, a protein specific for cerebral tissue, was used as a marker for cerebral impairment in 108 randomized patients undergoing coronary bypass operation: 67 patients (group A) were operated on with extracorporeal circulation and cardioplegic cardiac arrest, and 41 patients (group B) underwent off-pump beating heart revascularization. Both groups were similar regarding age, sex, ejection fraction, and number of anastomoses. S100 levels were measured from induction of anesthesia until 24 hours after the operation.

RESULTS

Data collection was 100% complete. There was no in-hospital death. Nonfatal myocardial infarctions occurred in 2 patients in group A, and 1 patient in group B required resternotomy for bleeding. There was no neurologic deficit in either group. S100 levels increased only slightly in the off-pump patients (group B), whereas in group A there was a sharp rise in S100 concentration during extracorporeal circulation, only returning to baseline 6 hours after the end of the operation. Peak S100 levels were four times higher in group A than in group B (2.1 microg/L versus 0.5 microg/L; p < 001).

CONCLUSIONS

The results of our study suggest that perioperative cerebral impairment is reduced in cardiac operations without the use of extracorporeal circulation. Further large-scale studies are needed to show whether this result is reflected by fewer neurologic deficits.

Crystalloid versus blood cardioplegia in coronary by-pass surgery. A prospective, randomized, controlled study in 100 consecutive adults

In a prospective randomized trial we investigated the benefit of blood versus asanguinous cardioplegia in routine coronary by-pass grafting. One hundred consecutive adult patients were randomly assigned to two groups: Group A (53 patients) received cold blood cardioplegia and group B (47 patients) had standard St. Thomas solution. In all patients we combined ante- and retrograde administration, in group A warm reperfusion was carried out before aortic declamping. Aortic cross clamp times, amount of cardioplegic solution and blood potassium levels at the end of cardio-pulmonary by-pass were higher in group A than in group B. The need for inotropic support at the end of the operation as well as in the postoperative period was more frequent in the crystalloid cardioplegia group. The occurrence of atrial fibrillation showed no clear correlation to the kind of cardioplegia used. Perioperative infarction was less frequent in the blood cardioplegia group (3.7% vs 6.3%; p < 0.01) and 30-day-mortality was nil (0% vs 3.2%; p < 0.01). Hospital stay did not differ between the two groups. In this clinical trial we could demonstrate the superiority of blood versus crystalloid cardioplegia in routine coronary by-pass grafting. Ante- and retrograde delivery of cold blood cardioplegia followed by warm reperfusion is a safe and simple method yielding satisfactory results.

The effects of dobutamine therapy in critically ill patients measured by transoesophageal echocardiography and intracardiac monitoring

Fourteen patients with severe hypotension and adult respiratory distress syndrome after trauma (n = 7), general surgery (n = 6) or burns (n = 1) were studied. After volume loading with 6 ml.kg-1 hydroxyethyl starch over 30 min (time I), dobutamine was infused intravenously at 5 micrograms.kg-1.min-1 (time II) and 10 micrograms.kg-1.min-1 (time III). A 5 MHz transoesophageal echocardiographic probe was used to image a standard transgastric short axis view of the left ventricle. Haemodynamic data were obtained from thermodilution studies using pulmonary flotation catheterisation. Echocardiographic measurements (off-line from videotape) and qualitative visual assessment of left ventricular function (visual assessment, on-line) were performed. All measurements were made after fluid replacement, and during infusion of the two dobutamine doses. An improvement in mean systemic arterial blood pressure and mean stroke volume occurred from time I to the end of dobutamine infusion (p < 0.05). All patients, after volume infusion, were normovolaemic according to transoesophageal echocardiography and there was a good correlation between end-diastolic area and stroke volume (r = 0.73). During dobutamine infusion, echocardiographic measurements showed no significant dose-related increase in mean (SD) percentage left ventricular short axis area change from baseline after hydroxyethyl starch (time I: 60 (2); time II: 63 (2); time III: 64 (2)). However, a significant increase in short axis area change was seen in nine of the 14 patients (67%). Analysis of the end-diastolic area/short axis area change relationship revealed a heterogeneous response to dobutamine.(ABSTRACT TRUNCATED AT 250 WORDS)