Biomedical subjects

T Wolf

Publications and source records attributed to T Wolf.

At least 19 recordsLinked to original sources

PubMed2006

Kinks, nodal bilayer splitting, and interband scattering in YBa2Cu3O(6+x).

We apply the new-generation angle-resolved photoemission spectroscopy methodology to the most widely studied cuprate superconductor YBa2Cu3O(6+x). Considering the nodal direction, we found noticeable renormalization effects known as kinks both in the quasiparticle dispersion and scattering rate, the bilayer splitting, and evidence for strong interband scattering--all the characteristic features of the nodal quasiparticles detected earlier in Bi2Sr2CaCu2O(8+delta). The typical energy scale and the doping dependence of the kinks clearly point to their intimate relation with the spin-1 resonance seen in the neutron scattering experiments. Our findings strongly suggest a universality of the electron dynamics in the bilayer superconducting cuprates and a dominating role of the spin fluctuations in the formation of the quasiparticles along the nodal direction.

Journal Article↗

PubMed2003

[Clinical presentation and management of the severe acute respiratory syndrome (SARS)].

BACKGROUND AND OBJECTIVE: In February 2003, a newly emerged infectious disease was described, the etiology of which was initially unknown. It is referred to under the term SARS. In the beginning, it spread in some regions South-East Asia. Import infections appeared in many other parts of the world. Based on the first cases in Germany, this report illustrates the clinical appearance, the diagnostic results and the management of this new disease. PATIENTS AND METHODS: We analysed the data of two patients with SARS and one suspected patient. The results of radiological, laboratory, microbiological and physical examinations were abstracted and compared with the data obtained in other regions. RESULTS: Two of the three patients under our care developed SARS disease. This is characterised by fever of sudden onset lasting for more than 5 days, rapidly changing consolidations in chest x-ray not affected by antimicrobial therapy, leuko-, lympho- as well as thrombopenia with a compromised pulmonary function later in the course. Close contacts with SARS patients does not regularly result in full development of the disease. Secretion of a coronavirus could be detected in respiratory samples during the febrile phase and in feces for a longer time. It is still an open question whether bedrest and antibiotic prophylaxis by themselves or an additional administration of ribavirin and corticosteroids can improve the outcome. CONCLUSION: SARS is a new and highly contagious lung disease. It is crucial to be able to recognize the clinical appearance and the diagnostic features of this disease at an early stage, in order to prevent a further dissemination of the disease.

Adult↗

PubMed2003

Measurement of spin-correlation parameters ANN, ASS, and ASL at 2.1 GeV in proton-proton elastic scattering.

At the Cooler Synchrotron COSY/Jülich spin-correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A(NN), A(SS), and A(SL) for c.m. scattering angles between 30 degrees and 90 degrees. Our data on A(SS)--the first measurement of this observable above 800 MeV--clearly disagrees with predictions of available pp scattering phase-shift solutions while A(NN) and A(SL) are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced.

Journal Article↗

PubMed2002

Pronounced in-plane anisotropy of phonon anomalies in YBa(2)Cu(3)O(6.6).

The dispersion of the Cu-O bond-stretching and bond-bending vibrations in YBa(2)Cu(3)O(6.6) has been studied by high resolution inelastic neutron scattering. While the behavior of the bond-bending vibrations can be well accounted for by a simple potential model, the bond-stretching vibrations show a highly anomalous behavior. The displacement pattern of the most anomalous phonons is in principle consistent with dynamic charge stripe formation. However, charge stripes would have to extend along the a axis and not the b axis as inferred from the magnetic fluctuations by Mook et al. [Nature (London) 404, 729 (2000)].

Journal Article↗

PubMed2002

Strong renormalization of phonon frequencies in Mg(1-x)Al(x)B2.

The phonon spectrum of Mg(1-x)Al(x)B2 shows a strong dependence on the aluminum content x. This is experimentally demonstrated by both Raman and inelastic neutron scattering and theoretically predicted by first-principles calculations. The observed changes in the phonon spectrum are put into perspective with respect to the superconducting properties within this family of materials.

Journal Article↗

PubMed2002

The pharmacologic stability of 35-year old theophylline.

The propensity to preserve and to hoard drugs over the years at home is a well-known phenomenon and offers the possibility for intentional and accidental drug poisoning in man. We report a case of acute theophylline poisoning in an 80-year old women after ingestion of 'Asthmo-Kranit', a 35-year old combined preparation containing theophylline and aminopyrine as the main ingredients. The patient developed the typical clinical picture of a symptomatic theophylline poisoning with flush, tremor, tachycardia, hyperventilation, hypotonia, and hyperglycaemia. The clinical course after treatment with beta-blockers was without complications. The determination of theophylline in tablets showed stability of 90% of the labelled amount of the drug 30 years beyond the expiration date. The case illustrates the prolonged shelf stability and pharmacological potency of some pharmaceuticals and points to the risk of long-outdated prescriptions. Physicians should primarily not underestimate drug toxicity in consequence of old-age pharmaceuticals.

Adrenergic beta-Antagonists↗

PubMed2001

History effects and phase diagram near the lower critical point in YBa2Cu3O7 single crystals.

Using a sensitive torque magnetometer we have studied magnetization curves for untwinned overdoped YBa2Cu3O7 single crystals in fields of up to 28 T. We demonstrate the existence of history effects below the lower critical point and provide a full demarcation of the Bragg-glass phase. A pronounced symmetry is observed in the behavior of the phase lines, irreversible magnetization, and value of the magnetization jump near both critical points.

Journal Article↗

PubMed2001

Low-energy laser irradiation reduces formation of scar tissue after myocardial infarction in rats and dogs.

BACKGROUND: Low-energy laser irradiation (LELI) has been found to attenuate various biological processes in tissue culture and experimental animal models. The aim of the present study was to investigate the effect of LELI on the formation of scar tissue in experimentally induced chronic infarct in rats and dogs. METHODS AND RESULTS: Myocardial infarction (MI) was induced in 50 dogs and 26 rats by ligation of the left anterior descending coronary artery. After induction of MI, the laser-irradiated (LI) group received laser irradiation (infrared laser, 803-nm wavelength) epicardially. Control MI-induced non-laser irradiated (NLI) dogs were sham-operated, and laser was not applied. All dogs were euthanized at 5 to 6 weeks after MI. Infarct size was determined by TTC staining and histology. The laser treatment (P:<0.05) lowered mortality significantly, from 30% to 6.5%, after induction of MI. The infarct size in the LI dogs was reduced significantly (P:<0.0001) (52%) compared with NLI dogs. Histological observation of the infarct revealed a typical scar tissue in NLI dogs and cellularity in most of the LI dogs. Only 14+/-3% of the mitochondria in the cardiomyocytes in the ischemic zone (4 hours after MI) of LI MI-induced rats were severely damaged, compared with 36+/-1% in NLI rats. Accordingly, ATP content in that zone was 7.6-fold (significantly) higher in LI than in NLI rats. CONCLUSIONS: Our observations indicate that epicardial LELI of rat and dog hearts after chronic MI caused a marked reduction in infarct size, probably due to a cardioprotective effect of the LELI.

Animals↗

PubMed2001

Adult-onset Leukoencephalopathy with vanishing white matter presenting with dementia.

We report on a case of dementia and extensive cerebral white matter abnormalities seen on magnetic resonance-images which meet the criteria for leukoencephalopathy with vanishing white matter. This is an inherited condition that was first thought to occur only in children. Our patient shows that vanishing white matter should be considered in adult patients with early-onset dementia and extensive white matter changes seen on magnetic resonance images.

Adult↗

PubMed2001

Attenuation of infarct size in rats and dogs after myocardial infarction by low-energy laser irradiation.

BACKGROUND AND OBJECTIVE: The aim of the present study was to investigate the possibility that low-energy laser irradiation attenuates infarct size formation after induction of chronic myocardial infarction (MI) in small and large experimental animals. STUDY DESIGN/MATERIALS AND METHODS: Laser irradiation was applied to the infarcted area of rats and dogs at various power densities (2.5 to 20 mW/cm(2)) after occlusion of the coronary artery. RESULTS: In infarcted laser-irradiated rats that received laser irradiation immediately and 3 days after MI at energy densities of 2.5, 6, and 20 mW/cm(2), there was a 14%, 62% (significant; P < 0.05), and 2.8% reduction of infarct size (14 days after MI) relative to non--laser-irradiated rats, respectively. In dogs, a 49% (significant; P < 0.01) reduction of infarct size was achieved. CONCLUSION: The results of the present study indicate that delivery of low-energy laser irradiation to infarcted myocardium in rats and dogs has a profound effect on the infarct size after MI.

Animals↗

PubMed2001

Characterisation of acute myocardial ischaemia in a canine model based on principal component analysis of unipolar endocardial electrograms.

The study presents a method for identifying endocardial electrical features relevant to local ischaemia detection at rest. The method consists of, first, normalisation of electrograms to a uniform representation; secondly, the use of principal component analysis to reduce the dimensionality of the electrogram vector space; and, thirdly, a search for a classification axis that matches the degree of ischaemia present in the tissue. Left ventricular myocardial states were assessed by echocardiography and NOGA mapping in eight dogs at baseline and then immediately after, 5h after and 3 days after occlusion of the left anterior descending coronary artery. Five principal components were required to approximate electrograms with an average error of less than 10% of the peak-to-peak amplitude. Correlations of 0.77, 0.80 and 0.84 were obtained between the principal component-based parameters and the echocardiography scores at the three ischaemic stages, respectively. Expression of these parameters in the time domain showed that the major changes occurred in the depolarisation segment of the endocardial electrogram as well as in the ST-segment. In conclusion, the proposed method provides a suitable alternative co-ordinate system for the classification of ischaemic regions and highlights signal segments that change as a result of pathology.

Acute Disease↗

PubMed2001

The lumbar paravertebral region provides a novel site to assess neuromuscular block at the diaphragm.

PURPOSE: We evaluated a novel, paravertebral site for assessment of neuromuscular block at the diaphragm. The neuromuscular blocking effect of 0.1 mg x kg(-1) cisatracurium at the adducting laryngeal muscles, the diaphragm and the adductor pollicis (AP) were compared. METHODS: In 24 patients undergoing thyroid surgery, evoked responses from the adducting laryngeal muscles and the AP muscle were obtained using surface electromyography (EMG). Skin electrodes were placed paravertebrally near T12/L1 or L1/L2 (novel position; n = 12) or conventionally (n = 12). After stimulation of the recurrent laryngeal, phrenic and ulnar nerves, the lag, onset time and maximum effect were measured (0.1 Hz, single twitch) as well as the time to reach 25% of T1/T0 (T 25%) using train-of-four stimulation every 20 sec. RESULTS: A mean maximum block of more than 94% was reached at all sites. Lag, onset time and T 25% at the adducting laryngeal muscles and the diaphragm were significantly (P <0.005) shorter than at the AP muscle and did not differ significantly between the two diaphragmatic monitoring sites (conventional: 64 +/- 21 sec, 166 +/- 41 sec and 20 +/- 3 min vs novel: 60 +/- 16 sec, 161 +/- 40 sec and 22 +/- 2 min respectively). CONCLUSION: Onset and duration of action of 0.1 mg x kg(-1) cisatracurium was shorter at the larynx and the diaphragm than at the AP muscle. EMG results obtained from the novel, paravertebral site did not differ from the conventional monitoring site at the seventh or eighth intercostal space and suggest this alternative site is appropriate for monitoring of the diaphragm.

Adult↗

PubMed2001

Three-dimensional electromechanical mapping: imaging in the operating room of the future.

BACKGROUND: Three-dimensional electromechanical mapping has previously been shown to be a clinically important tool for cardiac imaging and intervention. We hypothesized that this technology may be beneficial as an intraoperative modality for assessing cardiac hemodynamics and viability during cardiac surgery. We report here the use of this technology as an imaging modality for intraoperative cardiac surgery. METHODS: The tip of a locatable catheter connected to an endocardial mapping and navigating system is accurately localized while simultaneously recording local electrical and mechanical functions. Thus the three-dimensional geometry of the beating cardiac chamber is reconstructed in real time. The system was tested on 6 goats that underwent acute dynamic cardiomyoplasty and on 5 dogs that underwent left anterior descending (LAD) coronary artery ligation. RESULTS: The electromechanical mapping system provided an accurate three-dimensional reconstruction of the beating left ventricle during cardiomyoplasty. After the wrapping procedure, significant end-diastolic area reduction was noted in the base and mid parts of the heart (948 +/- 194 mm2 vs 1245 +/- 33 mm2, p = 0.021; and 779 +/- 200 mm2 vs 1011 +/- 80 mm2, p = 0.016). The area of the cross-section of the apex did not change during the operation. Acute infarcted tissue was characterized 3 days after LAD ligation by concomitant deterioration in both electrical and mechanical function. CONCLUSIONS: By providing both a clear view of the anatomical changes that occur during cardiac surgery, and an accurate assessment of tissue viability, electroanatomic mapping may serve as an important adjunct tool for imaging and analysis of the heart during cardiac surgery

Animals↗

PubMed2001

Novel thermoregulation system for enhancing cardiac function and hemodynamics during coronary artery bypass graft surgery.

BACKGROUND: Myocardial ischemia, arrhythmias, and coagulopathies are associated with postoperative hypothermia. This study assessed the efficacy of a novel thermoregulation system in alleviating these events during coronary artery bypass graft (CABG) surgery. METHODS: Elective CABG surgery patients were randomized into either Allon thermoregulation (AT, n = 40) or routine thermal care (RTC, n = 20) groups in whom the maintenance of normothermia during the nonbypass phases of the operation was compared. The AT used patients' rectal temperature as reference data to monitor the maintenance of the water temperature circulating at 37 degrees C in a garment. Rectal temperature, patient hemodynamics, and cardiac-specific troponin I (cTnI) levels were assessed at the induction of anesthesia, 30 minutes into surgery, at discontinuation of bypass, end of surgery, and 2 hours postoperatively. RESULTS: Body temperature was higher in the AT group compared to the RTC group at all five time points. Cardiac index (CI) (L/min) was higher in the AT group, 2.5 +/- 0.5, 2.6 +/- 0.5*, 3.2 +/- 0.6*, 3.3 +/- 0.5*, 3.1 +/- 0.7 at the respective time points, compared to the RTC group, 2.3 +/- 0.6, 2.1 +/- 0.2, 2.6 +/- 0.7, 2.7 +/- 0.7, 2.7 +/- 0.7 (*p < 0.05). Systemic vascular resistance (SVR) (dyne x s)/cm5) was consistently lower in the AT patients. Enzyme levels were elevated in both groups but were less so in the AT patients. CONCLUSIONS: The AT system can efficiently maintain normothermia. The beneficial effects are expressed by reduced SVR, elevated CI, and lower levels of cTnI, which may show a possible attenuation of myocardial injury.

Adult↗

PubMed2001

Detailed endocardial mapping accurately predicts the transmural extent of myocardial infarction.

OBJECTIVES: This study delineates between infarcts varying in transmurality by using endocardial electrophysiologic information obtained during catheter-based mapping. BACKGROUND: The degree of infarct transmurality extent has previously been linked to patient prognosis and may have significant impact on therapeutic strategies. Catheter-based endocardial mapping may accurately delineate between infarcts differing in the transmural extent of necrotic tissue. METHODS: Electromechanical mapping was performed in 13 dogs four weeks after left anterior descending coronary artery ligation, enabling three-dimensional reconstruction of the left ventricular chamber. A concomitant reduction in bipolar electrogram amplitude (BEA) and local shortening indicated the infarcted region. In addition, impedance, unipolar electrogram amplitude (UEA) and slew rate (SR) were quantified. Subsequently, the hearts were excised, stained with 2,3,5-triphenyltetrazolium chloride and sliced transversely. The mean transmurality of the necrotic tissue in each slice was determined, and infarcts were divided into <30%, 31% to 60% and 61% to 100% transmurality subtypes to be correlated with the corresponding electrical data. RESULTS: From the three-dimensional reconstructions, a total of 263 endocardial points were entered for correlation with the degree of transmurality (4.6 +/- 2.4 points from each section). All four indices delineated infarcted tissue. However, BEA (1.9 +/- 0.7 mV, 1.4 +/- 0.7 mV, 0.8 +/- 0.4 mV in the three groups respectively, p < 0.05 between each group) proved superior to SR, which could not differentiate between the second (31% to 60%) and third (61% to 100%) transmurality subgroups, and to UEA and impedance, which could not differentiate between the first (<30%) and second transmurality subgroups. CONCLUSIONS: The degree of infarct transmurality extent can be derived from the electrical properties of the endocardium obtained via detailed catheter-based mapping in this animal model.

Animals↗

PubMed2001

Hemodynamic evaluation of descending aortomyoplasty versus intra-aortic balloon pump performed in normal animals: an acute study.

OBJECTIVE: Aortomyoplasty is a surgical procedure that aims to induce hemodynamic benefits similar to those of the intra-aortic-balloon-pump (IABP). The objective of this study was to compare the coronary blood flow augmentation and afterload reduction produced by IABP and descending aortomyoplasty counterpulsation. METHODS: From a series of fifteen mongrel dogs (18-35 kg), eight underwent acute descending aortomyoplasty and seven had IABP application. Left anterior descending (LAD) coronary artery blood flow was measured using a Doppler flow probe. Left ventricular pressure in addition to aortic pressures both proximal and distal to either the aortomyoplasty site or the IABP position were monitored continuously. All experiments were acute and performed in normal hearts. RESULTS: Descending aortomyoplasty induced a 27% increase in the LAD blood flow integral during assisted beats (14.0+/-6 ml/min integral compared to 10.8+/-4 ml/min integral in unassisted beats [P<0.001]). This was comparable to an 18% rise in the LAD blood flow integral during IABP counterpulsation (from 8.6+/-3 ml/min to 10.2+/-4 ml/min [P<0.001]). Conversely, while IABP counterpulsation reduced the left ventricular afterload by 16% (from 102+/-23 mmHg to 86+/-26 mmHg [P<0.001]), descending aortomyoplasty did not result in afterload reduction. CONCLUSIONS: Descending aortomyoplasty produces coronary blood flow augmentation comparable to that achieved by the IABP. This may be important for end-stage ischemic patients. However, afterload reduction achieved by the IABP was not reproduced during descending aortomyoplasty counterpulsation. The surgical technique of descending aortomyoplasty should be modified to attain afterload reduction, thus improving treatment for congestive heart failure patients.

Cardiomyoplasty↗

PubMed2001

A novel thermoregulatory system maintains perioperative normothermia in children undergoing elective surgery.

BACKGROUND: Body heat loss during anaesthesia may result in increased morbidity, particularly in high-risk populations such as children. To avoid hypothermia, a novel thermoregulatory system (Allon) was devised. We tested the safety and efficacy of this system in maintaining normothermia in children undergoing routine surgical procedures. METHODS: The system consists of a computerized body, which receives continuous afferent data, i.e. core (rectal) temperature. These data are then compared with a preset temperature (37 degrees C) and a microprocessor heating/cooling unit warms/cools the temperature of circulating water in a garment that is specially designed to allow maximal coverage of body surface area, without impingement on the surgical field. Water temperature to the garment was limited to a maximum of 39.5 degrees C. Continuous perioperative monitoring of skin and rectal temperature, heart rate and blood pressure was performed. Postoperative shivering and adverse effects were also assessed. RESULTS: The Allon system was used in 38 patients aged 3 months to 14 years undergoing surgery under general anaesthesia lasting more than 30 min. Fifty to 80% body surface area was covered by the garment. Mean operative and postoperative core temperatures were 36.9 +/- 0.5 degrees C and 36.7 +/- 0.5 degrees C, respectively. Intraoperative skin temperatures were maintained at 34.4 +/- 2.7 degrees C. The average core- to-periphery intraoperative gradient was 2.9 +/- 4.9 degrees C. Postoperative shivering was absent in 36 cases and mild in two cases. No device-related adverse effects were observed. CONCLUSIONS: Perioperative thermoregulation using the Allon system is safe and effective in maintaining body temperature within a narrow range in children undergoing brief surgical procedures.

Adolescent↗

PubMed2001

Accurate linear radiofrequency lesions guided by a nonfluoroscopic electroanatomic mapping method during atrial fibrillation.

Catheter-based continuous linear lesions may become a curative procedure for AF. The accuracy of guiding the application of continuous RF lesions by a nonfluoroscopic mapping system (NFM) during AF in goats was tested. The NFM system (Carto) uses magnetic fields to determine, in real time, the location and orientation of a 7 Fr ablation catheter tip. AF was induced in nine goats by intravenous infusion of methacholine (3-4 microg x kg(-1) min(-1)) and burst pacing. The three-dimensional atrial geometry was reconstructed using the median location of the mapping catheter tip during 30 seconds when in contact with each endocardial site. Sequential RF energy (60 seconds in a temperature-controlled mode [60 degrees C]) was delivered along a predetermined path to create longitudinal lesions in both atria. Sites to which RF energy was applied were tagged on the NFM map, enabling the operator to accurately navigate the catheter tip to the adjacent sites. In all cases (n = 14) the location, shape, length, and continuity of the linear lesions on the electroanatomic maps highly correlated with the autopsy findings. Average line length on the reconstructed maps was 32.3+/-4.1 mm, which highly correlated (r = 0.98, P<.001) with the lesions created in the pathological specimen (31.7+/-3.9 mm). The NFM system can guide the application of RF linear lesions in a highly accurate manner during AF. Moreover, the ability to tag the ablation sites on the three-dimensional maps together with real-time monitoring of the ablation catheter tip location enables delivery of RF energy to create reproducible, continuous, longitudinal lesions without the use of fluoroscopy.

Animals↗