Magnesium Anode Protection by an Organic Artificial Solid Electrolyte Interphase for Magnesium-Sulfur Batteries

In the search for post-lithium battery systems, magnesium-sulfur batteries have attracted research attention in recent years due to their high potential energy density, raw material abundance, and low cost. Despite significant progress, the system still lacks cycling stability mainly associated with the ongoing parasitic reduction of sulfur at the anode surface, resulting in the loss of active materials and passivating surface layer formation on the anode. In addition to sulfur retention approaches on the cathode side, the protection of the reductive anode surface by an artificial solid electrolyte interphase (SEI) represents a promising approach, which contrarily does not impede the sulfur cathode kinetics. In this study, an organic coating approach based on ionomers and polymers is pursued to combine the desired properties of mechanical flexibility and high ionic conductivity while enabling a facile and energy-efficient preparation. Despite exhibiting higher polarization overpotentials in Mg-Mg cells, the charge overpotential in Mg-S cells was decreased by the coated anodes with the initial Coulombic efficiency being significantly increased. Consequently, the discharge capacity after 300 cycles applying an Aquivion/PVDF-coated Mg anode was twice that of a pristine Mg anode, indicating effective polysulfide repulsion from the Mg surface by the artificial SEI. This was backed by operando imaging during long-term OCV revealing a non-colored separator, i.e. mitigated self-discharge. While SEM, AFM, IR and XPS were applied to gain further insights into the surface morphology and composition, scalable coating techniques were investigated in addition to ensure practical relevance. Remarkably therein, the Mg anode preparation and all surface coatings were prepared under ambient conditions, which facilitates future electrode and cell assembly. Overall, this study highlights the important role of Mg anode coatings to improve the electrochemical performance of magnesium-sulfur batteries.

Prä- und intraoperative Volumenbestimmung bei Craniopharyngiomcysten

Die richtige Dosierung des 90Y für die intracavitäre Therapie bei monocystischen Craniopharyngiomen setzt die genaue Bestimmung des Cystenvolumens voraus. Der intraoperativen Volumenbestimmung mittels Radionuklid-Verdünnungsanalyse wurde die präoperative Volumetrie mit Hilfe von Computertomographieaufnahmen gegenübergestellt. Die Ergebnisse beider Verfahren zeigten eine gute übereinstimmung. Zur frühzeitigen Erkennung von Komplikationen werden Aufnahmen mit der Gammakamera als notwendig erachtet.

[Reduction of Tracheotomy Associated Tracheal Stenosis by Surgical Closure of the Tracheostomy]

BACKGROUND

The most common long-term complication of tracheotomy is the benign stenosis of the trachea, which is described for up to 20% of the cases. Typically, the stenosis occurs after decannulation in the context of secondary wound healing. This study examined whether the closure of the tracheostomy by surgical procedure reduces stenosis.

METHOD

With the help of our clinical database a retrospective analysis of 401 surgical tracheotomies was performed. Variables that were recorded were the indication for tracheotomy, the clinical course and complications occurred.

RESULTS

155 patients were successfully decannulated. In 92 of these patients the tracheostomy was closed by a surgical procedure, in 63 cases the closure occurred spontaneously by wound healing. After decannulation 3% (n=3) of the surgically closed and 22% (n=14) of the spontaneously closed tracheostomies developed a symptomatic tracheal stenosis (p<0.001).

CONCLUSION

Secondary wound healing of the tracheostomy often leads to symptomatic tracheal stenosis. The incidence of symptomatic tracheal stenosis was significantly reduced applying closure of the tracheostomy by surgical procedure.

Management and outcome of pallidal deep brain stimulation in severe Huntington's disease

Neurodegenerative movement disorders, such as Huntington's disease (HD), have become a promising field for Deep Brain Stimulation (DBS). This study aims to contribute to the establishment of a well-grounded database including both expected and unexpected effects of pallidal DBS in HD, and to discuss the ethical and legal restrictions of DBS in cognitively limited patients. Evaluation of the outcome data indicates that pallidal DBS exerted an independent effect on motor symptoms but probably also on the patient's cognitive and affective state. The cognitive decline, however, that characterizes the late stage of neurodegenerative disorders implicates ethical and legal problems given the patients' inability to give informed consent to DBS.

Quality of life in patients with spinal cord injury--basic issues, assessment, and recommendations

INTRODUCTION

Spinal cord injury (SCI) often causes severe disabilities. The degree of functional impairment strongly depends on the level and completeness of lesion (tetraplegic, paraplegic). But evaluation of outcomes also needs to consider the broader concept of health-related quality of the life (HRQL) for SCI patients. A multinational group of clinicians and researchers assessed this concept and reviewed the available instruments for measurement of quality of life in this group of patients.

TIME POINTS

Phase I is in the acute clinic; phase II during rehabilitation; phase III after discharge home. Annual follow-up investigations should be maintained. The phase of initial care (phase 0) is important for prognosis and should, therefore, be part of the documentation.

INSTRUMENTS

Criteria used to evaluate current QoL measures: reliability, validity, responsiveness, availability of translations, application in SCI patients, existing population norms. Several specific instruments or subscales exist for the following domains: physical and psychological functioning, pain, and handicap. Well-known generic measures of HRQL also have been applied to SCI patients, and a disease-specific instrument has been developed (SCIQL-23). A variety of subjective quality of life measures were evaluated as well.

GROUP CONSENSUS/GUIDELINE

Prior to discharge from rehabilitation, the group suggested the use of the Functional Independence Measure, the Hospital Anxiety and Depression Scale and a Visual Analogue Scale for pain. Following discharge from the acute clinic, the SF-36, the Craig Handicap Assessment and Reporting Technique, the Quality of Well-being Scale, or the Life Satisfaction questionnaire were proposed. However, the evidence supporting the use of these instruments is sparse.

Contralateral cerebellar diaschisis 7 hours after MCA-occlusion in primates

2,3,5-triphenyltetrazoliumchloride (TTC) as an indicator of mitochondrial function in combination with regional cerebral blood flow measurements was used in six baboons 6.9 +/- 1.2 h after permanent occlusion of the left middle cerebral artery. Staining with TTC was compared with blood flow data obtained during normocapnia using the microsphere method. Five animals showed a focal area of unstained tissue in the left middle cerebral artery territory. Mean blood flow in the unstained area was 28.3 +/- 15.4 ml min-1 100 g-1. Five of 6 animals showed a significant decrease of contralateral cerebellar blood flow in the presence of normal TTC staining. We conclude that at this early stage of infarction contralateral cerebellar diaschisis is caused by functional deactivation.

Immersion and perfusion staining with 2,3,5-triphenyltetrazolium chloride (TTC) compared to mitochondrial enzymes 6 hours after MCA-occlusion in primates

2,3,5-triphenyltetrazolium chloride (TTC) is commonly applied in rodents and cats as a marker of infarcted tissue as early as 20 min after the onset of focal ischaemia. At this stage it is suggested that it reflects hypoperfusion rather than failure of respiratory chain. Immersion of brain slices in TTC solution is preferable in comparison to perfusion with TTC in order to ensure, that enough TTC enters the post-occlusion tissue. We compared immersion technique versus perfusion technique 6 h after permanent occlusion of the left middle cerebral artery in 18 baboons. In addition, we assessed the function of the respiratory chain enzymes of stained and unstained tissue in three baboons. The immersion technique revealed an absence of TTC staining limited to subcortical structures in two animals. In seven experiments TTC indicated involvement of almost the entire MCA territory. The extent of the ischaemic lesion indicated by the perfusion technique was very similar. Tissue samples from the presumed infarcted areas revealed normal mitochondrial function. We conclude that perfusion and immersion technique do not cause significant different ischaemic delineation 6 h after middle cerebral artery occlusion. TTC staining appears to be a reliable method of evaluating volume of infarction in primates. Furthermore, absence of TTC staining 6 h after stroke onset is caused by energy or oxygen depletion rather than by mitochondrial injury.

Influence of chronic beta-adrenoreceptor blocker treatment on melatonin secretion and sleep quality in patients with essential hypertension

The nocturnal production of melatonin synthesis has been associated with circadian mechanisms of the organization of sleep. It is well known that the synthesis of melatonin is under the control of pineal beta 1-adrenoreceptors. In this study the effect of ten weeks treatment with the beta-adrenoreceptor (beta-AR) blockers propranolol and ridazolol on melatonin synthesis and on sleep quality was examined in 42 patients suffering from essential hypertension. Before and after 6 and 10 weeks of beta-AR-blocker administration urinary sulfatoxymelatonin excretion rates were measured and sleep factors were evaluated by using a standardized sleep inventory consisting of self-rating sleepiness scales. After 6 and 10 weeks of treatment, a significant about 50 percent reduction of sulfatoxymelatonin was measured. No relationship between these reductions and changes in sleep factors was found. The results indicate that a reduced nightly amplitude of melatonin has minor significance for the organization of physiological sleep. Furthermore, it is suggested that pineal mechanisms beside the beta 1-adrenergic receptor transduction system serve to maintain the melatonin signal to a considerable extent during a chronic beta 1-AR blockade.

PET study of changes in local brain hemodynamics and oxygen metabolism after unilateral middle cerebral artery occlusion in baboons

Local cerebral hemodynamics and oxygen metabolism were measured by positron emission tomography (PET) with the oxygen-15 (15O) steady-state method in baboons, immediately before (T0), 1 (T1), and 3-4 (T2) h after permanent middle cerebral artery occlusion (MCAO). At T1, there was a marked fall in both cerebral blood flow (CBF) and the CBF/cerebral blood volume (CBV) ratio in the occluded territory; these changes were sustained at T2, indicating stable reduction in cerebral perfusion pressure and lack of spontaneous reperfusion within this time range. Compared with preocclusion conditions, the oxygen extraction fraction (OEF) in the occluded territory was elevated at both T1 and T2, indicative of a persistent oligemia/ischemia for up to 3 h after MCAO. At T2, however, this OEF increase had lessened, concomitantly with a decline in cerebral metabolic rate of oxygen (CMRO2). This impairment of oxidative metabolism occurred earlier in the deep, compared with the cortical, MCA territories; in the latter, the CMRO2 was essentially preserved at T1 and only moderately reduced at T2, possibly suggesting prolonged viability. Finally, no significant changes in CBF or CMRO2 were observed in the contralateral MCA territory in this time range after MCAO. Despite methodological limitations (mainly partial volume effects related to PET imaging, which may have resulted in an underestimation of true changes and an overlooking of heterogeneous changes) our study demonstrates the feasibility of the combined PET-MCAO paradigm in baboons; this experimental approach should be valuable in investigating the pathophysiology and therapy of acute stroke.

CO2 reactivity in the ischaemic core, penumbra, and normal tissue 6 hours after acute MCA-occlusion in primates

Testing vasoreactivity with CO2 or Diamox is a common diagnostic procedure for the study of haemodynamics in stroke patients. CO2 reactivity (CO2R) was tested in 5 baboons six hours after permanent occlusion of the left middle cerebral artery (MCA) in order to attain new insights into interpretation of vasoreactivity tests. Using the microsphere method, cerebral blood flow (CBF) was determined in the various vascular territories as well as in the centre of the ischemia, the penumbra and the remaining MCA-tissue. CBF decreased significantly in the affected MCA in all animals and in addition in the contralateral cerebellum in one animal (p < 0.05). In addition, the left anterior cerebral artery (ACA) demonstrated a similar decrease. During hypercapnia CBF increased in all areas with the exception of the left, occluded MCA territory. Thus CO2 enhanced the difference between ischaemic and non-ischaemic tissue (i.e., tissue with diaschisis). Mean CO2 R was 3.37 ml/100 g/min/mmHg in the right MCA, 0.16 in the left. While the left ACA demonstrated a decreased perfusion during normocapnia in a similar range to the MCA territory, only CO2R was able to identify precisely the territory of the occluded vessel. CO2 R was zero or negative in the ischaemic core, close to zero in the penumbra and profoundly decreased in the remaining MCA tissue. The overall CO2 R of the MCA was almost zero, suggesting vasoparalysis in response to hypercapnia in the core and penumbra and exhausted CO2 R even in non-infarcted, non-penumbral tissue. One animal displayed a negative CO2 R equivalent to an intracerebral steal-phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of MHC class II antigen blockade by perfusion with a monoclonal antibody on rat renal graft survival

To decrease immunogenicity of the rat kidney, grafts were perfused with an anti-MHC class II monoclonal antibody (mAb). How effectively this procedure blocked class II-positive cells, which were mainly dendritic in appearance, was checked by immunostaining renal sections after perfusion and comparing them with in vitro stained sections. Optimum conditions were applied for graft pretreatment before transplantation. This procedure prolonged graft survival, though not satisfactorily from the biological point of view (9.6 +/- 0.8 versus 7.7 +/- 0.5 days in the control group; P less than 0.02). The dendritic cells were not killed but blocked. Several hours after transplantation, the mAb dissociated from these class II-positive cells. It was also shown that donor cells migrate into the recipient's spleen early after transplantation. The number of these cells was smaller when the transplanted organ was perfused with the mAb. Further studies are suggested to deplete the graft of donor dendritic cells more adequately. They should also combine graft perfusion with anti-class II mAb and recipient immunosuppression at reduced doses.

Hemodilution in cerebral infarcts

To evaluate the effect of hypervolemic hemodilution on cerebral blood flow (CBF) two protocols have been performed: A) Ten randomly selected baboons have been treated with either low molecular dextrane (10 ml/kg) or normal saline (10 ml/kg). Regional cerebral ischemia was produced in all baboons. CBF increased selectively in the ischemic territory but not in the normally perfused tissue. B) Forty patients with acute cerebral ischemia were treated on day onset of symptoms with either dextrose, low molecular weight dextrane, hydroxyethyl starch or pentoxifylline. After intravenous infusion of the substances CBF increased only in the groups treated with dextrane- or starch-solution. Ischemic tissue benefitted more from hypervolemic hemodilution than normally perfused tissue. It was concluded that hypervolemic hemodilution leads to increase of cerebral blood flow, more in ischemic than in normally perfused brain tissue.

Effect of flunarizine on cerebral blood flow in baboons with or without focal cerebral ischaemia

In baboons with or without regional cerebral ischaemia (achieved by transorbital clip of the middle cerebral artery), cerebral blood flow (CBF) was measured using the intra-arterial Xenon-133 technique during steady-state, slight hypotension, and hypocapnia before and after administration of various doses of the calcium antagonist flunarizine (0.5 mg kg-1, 1.0 mg kg-1, or 10 micrograms kg-1 min-1 over 30 min). In normal baboons flunarizine did not alter CBF significantly, but at reduced blood pressure it increased CBF by 19.9% owing to exaggerated vasodilatory autoregulation. During hypocapnia flunarizine impaired the physiological reduction in CBF owing to reduced vasoconstriction. In baboons with cerebral ischaemia, CBF measurements were stable and comparable with those in a control group using an arterial clip unless flunarizine was added. In a group of five flunarizine-treated animals, mean CBF after positioning of the clip was higher than in the control group. However, the increase in mean CBF varied significantly between animals, indicating that a secondary reduction in CBF due to postischaemic pathophysiological processes was not prevented consistently.

[Prevention of stress-induced hemorrhage of the upper gastrointestinal tract in neurosurgical intensive care patients. A controlled, randomized double-blind study with ranitidine alone and in combination with pirenzepine]

During a controlled, randomized, double blind study, 30 patients of a neurosurgical intensive care unit were treated with ranitidin and placebo (group 1) or ranitidin and pirenzepin (group 2). No significant difference in the effectivity of both methods was established, presumably due to the small number of cases. The pH values of group 2 lay in the median above 3.5, whereby the difference only became statistically significant after a seven-day period of therapy. In how far the increase of the pH value represents the only factor of a stress ulcer prophylaxis requires further investigation, particularly in connection with pulmonary risks caused by this.

Alteration of intracranial pressure, cerebral blood flow, autoregulation and carbondioxide-reactivity by hypotensive agents in baboons with intracranial hypertension

Intracranial pressure (ICP) was recorded by epidural transducer and cisterna magna catheter, and regional cerebral blood flow (rCBF) using the intraarterial Xenon 133-technique were measured in baboons with normal and during increased ICP provoked by an inflatable balloon positioned subdurally. Arterial blood pressure was altered by controlled infusion of Sodium-nitroprusside (SNP), Nitroglycerine (NG) or Trimetaphan (TMP) with the aim of reducing blood pressure by about 20%. During exflated balloon SNP provoked an increase of ICP which was more prominent than with NG and TMP. During increased ICP (due to inflation of the balloon) again SNP led to a higher further increase of ICP than both NG and TMP. rCBF rose during the state of normal ICP when SNP was infused. This was not observed with infusion of NG or TMP. When ICP was increased again by inflation of the balloon all 3 substances reduced rCBF, indicating damage to the autoregulation. CO2-reactivity as measured by induced hyperventilation with reduction of arterial CO2-tension was affected by all 3 substances thus indicating impairment of vasoconstriction during increase of ICP and simultaneous decrease of blood pressure. However, this impairment of physiological vasoconstriction was more prominent with SNP than with NG and TMP. The results indicate that all 3 substances should be used with care to reduce blood pressure during surgery or under intensive care condition, particularly in patients with increased ICP.

Glucocorticosteroid treatment of vasogenic oedema

The components of vasogenic oedema associated with brain tumours were investigated in human biopsy material sampled from tumour and peritumoural tissue intraoperatively. Sixty patients with glioblastomas, gliomas, meningiomas and metastases, which had been treated with dexamethasone prior to surgery were employed for tissue measurements of water, electrolyte, haemoglobin, serum protein and dexamethasone concentrations. The quantification of serum proteins was achieved with the method described by Bodsch et al. Accordingly, serum proteins in the brain tissue and the blood were determined with 125J labelled antihuman antibody. Taking into account brain haematocrit and blood-volume, quantitative measurements of the so-called oedema proteins as a measure of tumour oedema were performed. With the exception of metastases positive correlations were obtained between water and both serum proteins and sodium contents in tumours and peritumoural tissue. The serum protein content varied considerably being high in glioblastomas and low in peritumoural tissue surrounding metastases. However water and serum protein contents decreased with increasing dexamethasone concentrations in glioblastomas, while this effect was virtually absent in gliomas and meningiomas. Our results suggest a previously unknown selectivity among tumour types for the reduction of water content and serum proteins in corticosteroid treated oedematous tissue.

Measurements of regional cerebral blood flow in patients following superficial temporal artery-middle cerebral artery anastomosis

Regional cerebral blood flow (rCBF) was measured using the inhalation xenon 133 technique in 25 patients undergoing superficial temporal artery-middle cerebral artery anastomotic surgery. rCBF was measured once before and 3 times after operation, up to one year. Data were compared to rCBF-measurement in 16 patients with similar diagnosis, age distribution and medical treatment except that they were not operated on. Mean rCBF increased in some patients 4-8 weeks after surgery on the ipsilateral side. Compared to the non-surgical patients mean rCBF at this time was higher over both hemipheres. However, taking a flow increase of at least 15% as being significant only one third of all patients presented with a significant flow increase. Regional flow data indicated that the amount of hypoaemic areas in the operated side decreased significantly. Areas with normal flow increased in number from CBF 1 to the 4-8th week. There were no significant changes in flow distribution over the contralateral side. It was concluded that extracranial-intracranial bypass improves flow in patients with TIA or PRIND respectively only in some cases. Also a return to normal flow distribution can be achieved in only a few cases.

Factors responsible for the retention of fluid in human tumor edema and the effect of dexamethasone

The components of vasogenic edema associated with brain tumors were investigated in human biopsy material sampled from tumor and peritumoral tissue during neurosurgical operations. Tissue from 60 patients with glioblastomas, gliomas, meningiomas, and metastases who had been treated with dexamethasone prior to surgery was used for measurement of water, electrolyte, hemoglobin, serum protein, and dexamethasone concentrations. In all samples except metastases, positive correlations were obtained between water content and both serum protein levels and sodium content in tumors and peritumoral edema, suggesting that these components simultaneously determine forces for extravasation of plasma-derived edema fluid. However, the mean serum protein content varied considerably, being high in glioblastomas (16 mg/ml) and low in peritumoral edema surrounding metastases (4 mg/ml). The mean cerebral blood volume in all samples, as calculated from the tissue hemoglobin content, was 2.5 ml/100 gm wet weight in tumor tissue and 1.6 to 2.0 ml/100 gm wet weight in peritumoral tissue. Sodium concentrations were not significantly different among the tumor types. Both water and serum protein content decreased with increasing dexamethasone concentrations in glioblastomas, while this effect was virtually absent in gliomas and meningiomas. A therapeutic threshold of dexamethasone at 500 mg/gm wet weight was obtained for tumoral and peritumoral tissue of glioblastomas and was effective in a dose-dependent manner as long as the water content and the serum protein concentration remained below 6 ml/gm dry weight and 30 mg/gm dry weight, respectively. These results suggest a previously unknown selectivity among tumor types for the reduction of both water content and serum proteins in corticosteroid-treated edematous tissue.

Effect of dexamethasone on serum protein extravasation in experimental brain infarcts of monkey: an immunohistochemical study

Experimental brain infarcts were produced in 12 adult baboons (Papio cynocephalus) by transorbital permanent clipping of the left middle cerebral artery. One group (seven monkeys) received daily injections of 1 mg/kg dexamethasone, starting 1 h after vascular occlusion and continuing till the end of the experiment. Another group (five monkeys) was not treated. One week after vascular occlusion the volume of infarcts and peri-infarct edema was estimated morphometrically on histological sections, using Masson's trichrome stain and the peroxidase-anti-peroxidase (PAP) technique for visualization of serum protein extravasation. In the untreated animals the average volume of infarct was 6.57 +/- 4.23% (mean +/- SD) and the volume of edema 7.83 +/- 2.93% of ipsilateral hemisphere. In the treated animals the infarct volume was not different (7.95 +/- 3.00%), but the volume of peri-infarct edema was significantly lower (2.82 +/- 3.06%, p less than 0.05). The results obtained indicate that dexamethasone treatment reduces the development of peri-infarct edema but does not influence the size of infarcts.

Surgical treatment of anterior nasoethmoid encephaloceles

Two cases are reported with anterior nasoethmoid encephaloceles. The clinical, radiological and surgical results are described. The significance of a primary intracranial and intradural treatment of the defect of the base of the skull is pointed out. Secondary extirpation of the encephalocele and plastic correction of the face is recommended. Interdisciplinary cooperation with related specialties in the treatment of anterior encephaloceles is emphasised.

Development of ganglioglioma in computed tomography

A 2-year computed tomographic progress investigation in a young, female patient with a history of attacks over several years with final histological verification of ganglioglioma is presented. Although there are evidently no absolute pathognomonic signs of this rare intracranial tumor in the CT scan, together with the age of the patient, the tumor localization and the clinical history, CT findings can suggest the tentative diagnosis of a ganglioglioma pre-operatively. The case communicated here is so far the only one in the scanty CT literature on gangliogliomas in which the space-occupying development of this tumor (it was mainly cystic) could be exactly documented.

[Pre and intraoperative volume determination of craniopharyngioma cysts (author's transl)]

Exact cystic volume measurement is a prerequisite to proper 90Y dosage in the therapy of of intracavitary monocystic craniopharyngiomas. The method of intraoperative volume measurement by a radionuclide dilution technique is compared to results obtained by preoperative volumetry using computer tomography. Both methods gave congruous results. It is pointed out that gamma camera scintigrams are essential for the early detection of complications.