Band structure and optical properties of hexagonal In-rich In(x)Al(1-x)N alloys.

Full potential linear augmented plane wave calculations have been performed to study the electronic and optical properties of In-rich In(x)Al(1-x)N alloys in the hexagonal wurtzite structure. Compositions of x = 0.9375, 0.8125 and 0.6875 are considered which follow from replacing one, three and five In atoms by Al in the 32-atom supercell. The new form of exchange correlation, i.e. Engel-Vosko's generalized gradient approximation within density functional theory, is employed. The calculations yield the band structure and total density of states as well as the imaginary part ε(2)(ω) of the ordinary and extraordinary dielectric function. The calculated dependence of the bandgap on the composition is in good agreement with recent experimental studies. A reversal of the valence band ordering is found between x = 0.8125 and 0.6875. The absorption features in the high-energy range of ε(2)(ω) are related to critical points of the band structure. The transition energies for these van Hove singularities are determined and their bowing parameters are discussed.

[Curative treatment in a patient with exercise induced syncope]. / Kurative Therapie bei einem Patienten mit belastungsabhängigen Synkopen.

HISTORY: A 38 year old man suffered from exercise-induced reproducible dizziness and syncopes. INVESTIGATIONS AND DIAGNOSIS: During exercise testing a ventricular tachycardia at a rate of 300 beats/min was identified as the cause of the symptoms. Because of the ventricular morphology with inferior axis, left bunde branch block and the typical monomorphic repetitive characteristics, idiopathic adenosine-sensitive ventricular tachycardia was diagnosed. TREATMENT AND CLINICAL COURSE: Curative catheter ablation of the arrhythmogenic focus in the right ventricular outflow tract was performed. The patient has now been free of symptoms for more than two years. The characteristics of idiopathic ventricular tachycardia and the electrophysiological techniques are described. CONCLUSION: Idiopathic ventricular tachycardia is a rare cause of syncope in young patients without underlying heart disease and can be cured by catheter ablation. Exclusion of cardiac diseases, especially arrhythmogenic right ventricular cardiomyopathy, is of prognostic value.

[Recurrent ventricular tachycardias following myocardial infarction: linear ablation strategy using an electroanatomical mapping system]. / Rezidivierende ventrikuläre Tachykardien nach Myokardinfarkt: Lineare Ablationsstrategie unter Einsatz eines elektroanatomischen Mappingsystems.

BACKGROUND AND AIM OF STUDY: The implantable cardioverter defibrillator (ICD) is the therapy of choice for patients with ventricular tachycardia (VT) after myocardial infarction. In some patients frequent ICD shocks occur, often resulting in clinical problems, if antiarrhythmic drugs insufficiently suppress them. Our aim was to describe electro-anatomical mapping and ablation techniques in patients with VTs, in which conventional strategy treatments have failed. PATIENTS AND METHODS: 17 patients (69.5 +/- 8 years, 12 male) were included. During 3 months before ablation the number of ICD shocks was 21 +/- 8 (mean +/- SD). Using an electro-anatomical mapping system (CARTO), activation mapping was performed in 12 patients during hemodynamically tolerable, stable VT. In 5 cases with "non-mappable" VT only voltage mapping during sinus rhythm was obtained. The aim was to characterize the underlying scar tissue precisely in order to modify the substrate with an individual strategic linear lesion, thus preventing re-induction of VT. RESULTS: Procedure time was 184 +/- 9 minutes, fluoroscopy time totalled 19 +/- 9 minutes. Lesion lines were established with 13 +/- 9 ablation pulses. In 15 patients (88 %) acute ablation of the VT was successful. During a follow-up of 8 +/- 7 months, 2 patients had a recurrence of the VT. Two patients developed a VT with a different morphology. In another case ventricular fibrillation occurred. No major complications were observed. CONCLUSION: Electro-anatomical mapping combined with an individual linear ablation strategy is a safe and effective method to prevent symptomatic VT in patients after myocardial infarction.

[Curative therapy in symptomatic atrial ectopy]. / Kurative Therapie bei symptomatischer atrialer Extrasystolie.

A female patient without underlying heart disease was highly symptomatic from short runs of atrial ectopy. Sustained atrial tachycardia or atrial fibrillation never occurred. Due to ineffective pharmacological therapy, catheter ablation combined with electroanatomic mapping (CARTO) was performed effectively. Characteristics of ectopic atrial tachycardia and the electrophysiological techniques are described.

Identification and ablation of atypical atrial flutter. Entrainment pacing combined with electroanatomic mapping.

Differentiation between typical and atypical atrial flutter solely based upon surface ECG pattern may be limited. However, successful ablation of atrial flutter depends on the exact identification of the responsible re-entrant circuit and its critical isthmus. Between August 2001 and June 2003, we performed conventional entrainment pacing within the cavotricuspid isthmus in 71 patients with sustained atrial flutter. In patients with positive entrainment we considered the arrhythmia as typical flutter and treated them with conventional ablation of the cavotricuspid isthmus. As a consequence of negative entrainment we performed 3D-electroanatomic activation mapping (CARTO trade mark ). Conventional ablation of the right atrial isthmus was successful in all patients (n = 54) with positive entrainment. We performed electroanatomic mapping in the remaining 17 patients (14 male; age 60.9 +/- 16 years) resulting in the identification of 6 cases with typical and 11 cases with atypical flutter. Therefore, entrainment pacing was able to predict the true presence of typical atrial flutter in 91.5%. Atypical flutter was right sided in 4 patients and left sided in 7 cases. Electrically silent ("low voltage") areas probably demonstrating atrial myopathy were identified in all cases with left sided and in 2 patients with right sided flutter. In these patients targets for ablation lines were located between silent areas and anatomic barriers (inferior pulmonary veins, mitral respectively tricuspid annulus, or vena cava inferior). In 1 patient, the investigation was stopped due to variable ECG pattern and atrial cycle lengths. In the remaining cases, ablation was acutely successful. One patient, after surgical closure of a ventricular septal defect, demonstrated a dual-loop intra-atrial reentry tachycardia dependent on two different isthmuses. This arrhythmia required ablation of those distinct isthmuses to be interrupted. After a mean follow-up of 8.8 +/- 3.4 months, there was one patient with a recurrence of left-sided atrial flutter. Another patient developed permanent atrial fibrillation shortly after the procedure. Mean duration time of the procedure was 235.6 +/- 56.4 min (right atrium: 196 +/- 17.3 min; left atrium: 267.2 +/- 59.5 min), and average fluoroscopy time was 21.8 +/- 11.7 min (right atrium: 9.5 +/- 6 min; left atrium: 28.9 +/- 7 min). There was no incidence of serious complications associated with these procedures. In conclusion, conventional pacing in the cavotricuspid isthmus combined with electroanatomic mapping was an effective method to differentiate between typical and atypical atrial flutter. Electroanatomic mapping was a powerful tool both for identification of different atrial re-entrant circuits including their critical isthmuses as well as for effective application of individual ablation line strategies.

Cardiogenic shock due to thrombotic thrombocytopenic purpura.

We report the case of a 49-year-old man with thrombotic thrombocytopenic purpura (TTP) leading to cardiogenic shock. Laboratory data were typical for TTP with thrombocytopenia and microangiopathic hemolytic anemia. The electrocardiogram recorded significant ST-segment elevations in the anterior and inferior leads. In addition' coronary angiography showed normal epicardial coronary arteries with slow flow. The patient died due to electromechanical dissociation six hours after admission. During autopsy typical features of thrombotic thrombocytopenic purpura were found. Histological preparation of the heart showed a diffuse myocardial necrosis due to microvascular thrombosis. Cardiac involvement is common in TTP but extended myocardial necrosis has been reported in only a few cases.

Frequency and quantity of the parvovirus B19 genome in endomyocardial biopsies from patients with suspected myocarditis or idiopathic left ventricular dysfunction.

Parvovirus B19 (PB19) has been identified as a possible cause of myocarditis and heart failure in both children and adult patients. This study used real time PCR analysis, to determine the frequency and to quantify PB19 viral genomes in endomyocardial tissue samples from 80 adult patients with clinically suspected myocarditis or idiopathic left ventricular dysfunction and from 36 controls. Histological (Dallas classification) and immunohistological analyses were performed to detect myocardial inflammation in the endomyocardial biopsies.PB19 genomic DNA was found in nine of 80 patients (11.2%), 4 out of 31 (12.9%) patients with inflammatory infiltrates detected via immunohistological methods and 5 out of 49 (10.2%) patients with left ventricular dysfunction without myocardial inflammation. The copy numbers for PB19 DNA ranged between 30 and 3900 per microg of cellular DNA. Four patients with clinically suspected myocarditis had copy numbers for PB19 DNA of 70, 740, 3400 and 3900, respectively, per microg of cellular DNA in the endomyocardial biopsy. Five patients with idiopathic left ventricular dysfunction had copy numbers for PB19 DNA of 30, 38, 52, 58 and 90, respectively, per microg of cellular DNA in the endomyocardial biopsy. The amplicon of one of the nine positive PCR fragment was sequenced and was found to be fully identical in the highly conserved sequence of published Parvovirus B19 VP1/VP2 genes (NCBI gene bank). In all patients, acute myocarditis was excluded according to the Dallas classification. All biopsies of 36 controls with no history of myocarditis or recent viral infection were negative for myocardial inflammation and parvovirus B19 genomes. In summary, Parvovirus B19 DNA is present within the myocardium of patients with suspected myocarditis and idiopathic left ventricular dysfunction and can be detected and quantified in endomyocardial specimens via real time PCR.

[Catheter ablation of ectopic atrial tachycardia by electrical pulmonary vein disconnection]. / Katheterablation einer ektopen atrialen Tachykardie mittels elektrischer Pulmonalvenendiskonnektion.

We report a 25-year-old female patient with a long history of symptomatic paroxysmal supraventricular tachycardia. Electroanatomic activation mapping demonstrated a focal tachycardia originating in the right upper pulmonary vein, 3 cm distal to the ostium. Due to the recent experiences in the management of focal atrial fibrillation with catheter ablation, direct ablation applied inside the pulmonary vein was avoided. Instead, an electrical disconnection of the pulmonary musculature from the left atrium guided by a circumferential 10-electrode mapping catheter was performed. The patient has since been asymptomatic during follow-up.

The immune-enhancing effects of dietary fibres and prebiotics.

The gastrointestinal tract is subjected to enormous and continual foreign antigenic stimuli from food and microbes. This organ must integrate complex interactions among diet, external pathogens, and local immunological and non-immunological processes. It is critical that protective immune responses are made to potential pathogens, while hypersensitivity reactions to dietary antigens are minimised. There is increasing evidence that fermentable dietary fibres and the newly described prebiotics can modulate various properties of the immune system, including those of the gut-associated lymphoid tissues (GALT). This paper reviews evidence for the immune-enhancing effects of dietary fibres. Changes in the intestinal microflora that occur with the consumption of prebiotic fibres may potentially mediate immune changes via: the direct contact of lactic acid bacteria or bacterial products (cell wall or cytoplasmic components) with immune cells in the intestine; the production of short-chain fatty acids from fibre fermentation; or by changes in mucin production. Although further work is needed to better define the changes, mechanisms for immunomodulation, and the ultimate impact on immune health, there is convincing preliminary data to suggest that the consumption of prebiotics can modulate immune parameters in GALT, secondary lymphoid tissues and peripheral circulation. Future protocols on the physiological impact of consuming prebiotics should be designed to include assessments of the gut microflora, gut physiology and the function and composition of the various regions of GALT.

Efficient retrovirus-mediated gene transfer to transplantable human bone marrow cells in the absence of fibronectin.

The low frequency of transplantable hematopoietic stem cells in adult human bone marrow (BM) and other differences from cord blood stem cells have impeded studies to optimize the retroviral transduction of stem cells from adult sources. To address this problem, first a cytokine combination was defined that would both maximize the kinetics of adult BM CD34(+)CD38(-) cell mitogenesis and minimize the period of prestimulation required for the transduction of these cells by a MSCV-GFP/neo(r) virus in tissue culture dishes in the absence of fibronectin. Three days of stimulation with flt3-ligand, Steel factor, interleukin (IL)-3, and hyper-IL-6 proved both necessary and sufficient to obtain 83% +/- 2% GFP(+) CD34(+)CD38(-) cells, 75% +/- 10% G418-resistant clonogenic progenitors, and 50% +/- 20% transduced long-term culture-initiating cells as recovered 48 hours after a single exposure to virus. Moreover, this was accompanied by a several-fold increase in viral receptor (pit-1) messenger RNA transcripts in the target cells. Using this prestimulation protocol, repeated daily exposure to new virus (3x) did not alter the proportion of transduced cells over that obtained with a single exposure. Adult human BM cells able to engraft immunodeficient (NOD/SCID-beta(2)M(-/-)) mice were also efficiently transduced (10%-20% GFP(+) human lymphoid and myeloid cells present 6-8 weeks after transplant) using a 6-day prestimulation and infection protocol. A clinically useful efficiency of retrovirus-mediated gene transfer to transplantable adult human BM stem cells can thus be obtained with a protocol that allows their semisynchronous activation into cycle and concomitant increased expression of virus receptor transcripts before virus exposure.

High-efficiency retroviral transduction of mammalian cells on positively charged surfaces.

The efficiency of retroviruses as transducing agents has been appreciated for many years, particularly for hematopoietic cell targets for which alternative strategies applicable to adherent cells are not effective. Advances in vector design, pseudotyping, and infection conditions have eliminated the need to cocultivate the target cells with virus-producing cells. Nevertheless, improvements are still needed for many applications, including those with a therapeutic or clinical cell-tracking objective. In this study we show that more positively charged surfaces, including those designed for the culture of anchorage-dependent cells, allow measurable levels of adhesion by different pseudotypes of retroviruses, which can result in increased gene transfer efficiencies to a variety of target cells including normal primary human hematopoietic cells as well as human leukemic cell lines and rat and murine fibroblasts. In the experiments with primary human cells, equal aliquots of enriched CD34+ cord blood cells were first stimulated for 2 days with cytokines (Flt3 ligand, Steel factor, IL-3, IL-6, and G-CSF) and then exposed for 4 days to a green fluorescent protein (GFP)- and Neo(r)-encoding retrovirus produced in PG13 cells. Both the final yield (approximately 300% relative to initial numbers), and the proportion (approximately 60%) of transduced CD34+ cells, colony-forming cells, and long-term culture-initiating cells were the same for cells infected either in tissue culture dishes or in fibronectin-coated petri dishes. Similar proportions (approximately 10%) and absolute yields of GFP+ human cells were also found in multilineage engrafted NOD/SCID mice assessed 6 to 8 weeks after being transplanted with these two types of transduced, but unselected, cells. These findings suggest a new and simpler approach for achieving high gene transfer efficiencies to hematopoietic cells.

[Sexual differentiation of newborn rabbits with karyotype analysis for experimental use (author's transl)]. / Geschlechtsdifferenzierung von neugeborenen Kaninchen mit Hilfe der Karyotypanalyse zu Versuchszwecken.

The sex of newborn rabbits is differentiated. A three-day blood culture of the blood of the retrobulbar venous plexus and a short term culture within one hour was followed by the preparation of the chromosome metaphases. The mitoses have a good spreading, and they are numerous for the sex differentiation. The sex determination is carried out with the Focomat microscope (E. Leitz, Wetzlar) after having photographed the metaphases.

[The elimination of the sense of smell and its effect on the suckling behavior in young rabbits]. / Die Ausschaltung des Geruchsvermögens und sein Einfluss auf das Saugverhalten von Jungkaninchen.

In the experiments described the ability to smell was eliminated in rabbits aged 1-7 days with two different methods: destruction of the nasal mucous membranes with 2% ZnSO4 solution administered in 2 doses of 100 microliter with a time interval of 12 hours between the two applications and destruction of the olfactory bulbs with high-frequency coagulation (20 V, 80 mA for 12 se.). Both treatments disturbed the suckling behavior, as the young rabbits failed to find the mammary gland. These results suggest that a releaser phenomon is secreted in the mammary gland region, which enables the rabbit to find the test and thus to initiate suckling behavior.