Biomedical subjects
Publications and source records attributed to G Schmidt.
We report on electrical spin-injection measurements into a nonmagnetic semiconductor in the nonlinear regime. For voltage drops across the interface larger than a few mV the spin-injection efficiency decreases strongly. The effect is caused by repopulation of the minority spin level in the magnetic semiconductor due to band bending at the interface.
Primary cutaneous B cell lymphomas are rare malignant lymphoproliferative disorders of the skin. The prognosis is dependent on the clinical and histologic subtype; generally, these disorders show an indolent clinical course. We describe a 80-year-old woman with a large cutaneous B cell lymphoma of the lower leg. In contrast to other variants of cutaneous B cell lymphomas, this entity is characterized by an aggressive clinical course with an unfavorable prognosis. The mean survival rate is approximately 50%. This should be taken into account in the choice of treatment.
A new control scheme for uncalibrated robotic visual tracking problem is proposed that compromises the computational expenses of overall system with offline modeling and online control. A nonlinear visual mapping model for the uncalibrated hand-eye coordination is first proposed with an artificial neural network implementation. An online visual tracking controller is then developed together with a real-time motion planner. To improve the system performance, the control scheme is also integrated with a feedforward controller to compensate unknown object motions. Extensive simulations and experiments demonstrate the effectiveness of the proposed control scheme.
AIM: Face seeking flies have long been thought to transmit Chlamydia trachomatis, the causative agent of trachoma, but this has never been proven. The four criteria proposed by Barnett, previously used to incriminate other arthropods suspected of transmitting disease, were examined. One of these criteria remains unmet: the repeated demonstration of the presence of C trachomatis on flies. The authors used polymerase chain reaction (PCR) to look for the presence of C trachomatis DNA on flies in the Gurage Zone of Ethiopia. METHODS: Using sticky paper, one fly was collected from the face of each of 103 children aged 1-10 years. The piece of fly paper to which the fly was attached was cut out, followed by the collection of an empty piece from an arbitrary area of the fly paper, which served as control. Roche Amplicor PCR kits were used to detect C trachomatis DNA. RESULTS: Evidence of C trachomatis by PCR was found on 15 of 103 flies versus 0 of 103 controls (p = 0.0001). CONCLUSION: These results meet the final criterion needed to incriminate flies as a vector of trachoma. However, interventional studies will be needed to show the importance of fly control.
OBJECTIVES: To establish dose proportionality among four doses of a new estradiol transdermal system (ETS), Estradot, in healthy postmenopausal women and to evaluate the wear and irritation properties of the ETS. METHODS: In an open label, single-dose, randomized, four-period crossover study, healthy postmenopausal women, age range 44-64 years, wore four different sizes of Estradot, 2.5, 3.75, 5.0 and 10.0 cm(2) that were expected to release estradiol at 0.025, 0.0375, 0.05 and 0.10 mg/day, respectively. Each patch was worn for 84 h with a 7-day washout period between treatments. Blood samples were drawn prior to medication, then at various time points following patch application. Serum concentrations of estradiol and estrone were determined by validated gas chromatography/mass spectrometry (GS/MS) methods. Skin irritation, (erythema and edema), patch adherence and local skin reaction were assessed and recorded following patch removal. After removal, the patches were assayed for residual estradiol to estimate the apparent dose delivered. RESULTS: The baseline-corrected, mean maximum serum estradiol concentrations (C(max)) for the 2.5, 3.75, 5.0 and 10.0 cm(2) patches were 24.0, 34.8, 50.1 and 96.0 pg/ml, respectively, and for estrone were 10.5, 15.2, 21.8 and 41.0 pg/ml, respectively. The four Estradot patches adhered well during the study. No significant skin irritation was observed with any of the four treatments. CONCLUSIONS: The results indicate a dose proportional relationship of increased serum concentrations of estradiol with increasing size of the Estradot patches. The four doses of Estradot demonstrated good systemic and local skin tolerability.
OBJECTIVES: To compare the relative bioavailability of Estradot, a small size, new generation estradiol transdermal system (ETS) to Menorest, in healthy postmenopausal women. METHODS: In two open-label, single center, randomized, crossover, bioequivalence studies, healthy postmenopausal women aged 40-65 years received treatment with all the test regimens. In Study 1 (single-dose study), patients wore 5 cm(2) (50 microg/day), 10 cm(2) (100 microg/day) Estradot and 29 cm(2) (100 microg/day) Menorest for 84 h. In Study 2 (multiple-dose study), patients wore a regimen of four consecutive treatments with a 5 cm(2) (50 microg/day) new generation patch, Estradot and a 14.5 cm(2) (50 microg/day) patch, Menorest. Blood samples were drawn at various time-points in both studies. Estradiol and estrone serum levels were determined by gas chromatography/mass spectrometry or radioimmunoassay methods. Skin irritation (erythema and edema), patch adherence and local skin reaction were assessed following patch removal. RESULTS: In Study 1, baseline-uncorrected C(max) for estradiol for Estradot 50 and 100 microg/day and Menorest 100 microg/day was 54.8, 106.2 and 101.6 pg/ml, respectively, and C(max) for estrone was 75.6, 97.0 and 98.3 pg/ml, respectively. In Study 2, the baseline-uncorrected mean maximum serum concentration (C(max)) for estradiol for Estradot 50 microg/day and Menorest 50 microg/day patches was 56.7 and 52.7 pg/ml, respectively, and C(max) for estrone was 41.7 and 41.3 pg/ml, respectively. No significant skin irritation was observed in either study, but Estradot caused less skin irritation than Menorest. CONCLUSIONS: Estradot produced comparable serum concentrations of estradiol and estrone and caused less skin irritation than Menorest.
We have fabricated (Ga,Mn)As nanostructures in which domain walls can be pinned by sub-10 nm constrictions. Controlled by shape anisotropy, we can switch the regions on either side of the constriction to either parallel or antiparallel magnetization. All samples exhibit a positive magnetoresistance, consistent with domain-wall trapping. For metallic samples, we find a magnetoresistance up to 8%, which can be understood from spin accumulation. In samples where, due to depletion at the constriction, a tunnel barrier is formed, we observe a magnetoresistance of up to 2000%.
Certain pathogenic strains of E. coli produce the cytotoxic necrotizing factors-1 or -2. Cytotoxic necrotizing factor-1 irreversibly activates the small GTPases of the Rho family Rho, Rac and Cdc42. Cytotoxic necrotizing factor-2 may have similar effects. Since the Rho proteins play an important role in the organization of the actin cytoskeleton and neuronal differentiation, we have investigated whether cytotoxic necrotizing factor-2 affects the morphology of cultured hippocampal neurons. The toxin indeed caused dendrite retraction and axon shortening. Within 4 h of application, cytotoxic necrotizing factor-2 induced a transient formation of short finger-like extensions. To study the role of the Rho proteins in the morphological changes caused by cytotoxic necrotizing factor-2, we transfected neurons with recombinant Rho proteins. Dominant-negative forms of Rac or Rho but not of Cdc42 prevented the formation of short extensions induced by cytotoxic necrotizing factor-2, indicating synergistic effects of Rac and Rho. In contrast, the retraction of dendrites induced by cytotoxic necrotizing factor-2 was only prevented by dominant-negative Rho. Analysis with pull-down assays showed that cytotoxic necrotizing factor-2 strongly activated Rac and Rho, whereas an effect on Cdc42 was not observed. Cytotoxic necrotizing factor-2 also diminished the total amount of Rac and Rho. The degradation of Rac was so pronounced that the increase in Rac activity was only transient. In organotypic cultures of the hippocampus, cytotoxic necrotizing factor-2 reduced the number of neurites per neuron, suggesting that neurons in the tissue context were also vulnerable. We conclude that cytotoxic necrotizing factor-2 has pronounced effects on neuronal morphology, which are due to activation of the GTPases Rho and Rac.
We have fabricated all II-VI semiconductor resonant tunneling diodes based on the (Zn,Mn,Be)Se material system, containing dilute magnetic material in the quantum well, and studied their current-voltage characteristics. When subjected to an external magnetic field the resulting spin splitting of the levels in the quantum well leads to a splitting of the transmission resonance into two separate peaks. This is interpreted as evidence of tunneling transport through spin polarized levels, and could be the first step towards a voltage controlled spin filter.
OBJECTIVES: To compare the relationship between body mass index (BMI) and body fat percentage (BF%) in children of different ethnic background. DESIGN: Cross-sectional observational study. SETTINGS: The study was performed in three different locations, Singapore, Beijing and Wageningen (The Netherlands). SUBJECTS: In each centre 25 boys and 25 girls, aged 7-12 y, were selected. They were matched on age, sex and body height. METHODS: Body weight and body height was measured following standardized procedures. The body mass index (BMI) was calculated as weight/height squared (kg/m(2)). Body fat was measured by densitometry in Beijing and Wageningen and by dual energy X-ray absorptiometry (DXA) in Singapore. The DXA measurements in Singapore were validated against densitometry. RESULTS: There were no significant differences in BF% or BMI within each gender group across the three study sites. However, after controlling for (non-significant) differences in age and BF%, the Singapore children had a lower (mean+/-s.e.) BMI (15.6+/-0.3) than the Beijing 17.6+/-0.3) and Wageningen (16.9+/-0.3) children. For the same BMI, age and sex the Singapore children had a significant higher BF% (24.6+/-0.7) than the Beijing (19.2+/-0.8) and Wageningen (20.3+/-0.7) children. CONCLUSIONS: The study strongly suggests that the relationship between BF% and BMI (or weight and height) is different among children of different ethnic background. Consequently growth charts and BMI cut-off points for underweight, overweight and obesity in children may have to be ethnic-specific.
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Phosphorylation of microtubule-associated protein 2 (MAP2) has a profound effect on microtubule stability and organization. In this work a consensus protein kinase A (PKA) phosphorylation site, T(220), of juvenile MAP2c is characterized. As confirmed by mass spectrometry, this site can be phosphorylated by PKA but shows less than average reactivity among the 3.5 +/- 0.5 phosphate residues incorporated into the protein. In contrast, T(220) is uniquely sensitive to dephosphorylation: three major Ser/Thr protein phosphatases, in the order of efficiency PP2B > PP2A(c) > PP1(c), remove this phosphate group first. MAP2c specifically dephosphorylated at this site binds and stabilizes microtubules stronger than either fully phosphorylated or nonphosphorylated MAP2c. Phosphorylation of this site also affects proteolytic sensitivity of MAP2c, which might represent a further level of control in this system. Thus, the phosphorylation state of T(220) may be a primary determinant of microtubule function.
Experimental results are presented from vacuum-ultraviolet free-electron laser (FEL) operating in the self-amplified spontaneous emission (SASE) mode. The generation of ultrashort radiation pulses became possible due to specific tailoring of the bunch charge distribution. A complete characterization of the linear and nonlinear modes of the SASE FEL operation was performed. At saturation the FEL produces ultrashort pulses (30-100 fs FWHM) with a peak radiation power in the GW level and with full transverse coherence. The wavelength was tuned in the range of 95-105 nm.
Unilateral diaphragmatic paralysis has many causes. Tumor and trauma are the two most frequent identifiable causes. Infectious processes involving the lung and/or mediastinum may result in temporary or permanent diaphragmatic paralysis. We report the case of an 81-year old man who suffered from right-sided pneumonia followed by a period of several months with exertion dyspnea. Radiological examinations showed an elevated right diaphragm, abnormal restrictive lung function, and impaired diaphragmatic muscle strength. The neurophysiological studies provided evidence of a partial phrenic nerve lesion. We discuss the differential diagnosis of isolated phrenic nerve lesions with particular regard to infections.
The increasing application of 13C-labelled urea in medicine requires simple and reasonable methods for measuring highly enriched C in urea. The combination: ultimate organic analysis--mass spectrometry so far prescribed is complicated and expensive. For medical diagnosis, however, isotope selective nondispersive infrared spectrometers (NDIRS) have been available for many years. One of these tools is FANci2 which is very reasonable and easily to be operated. By means of such devices also urea highly enriched in 13C can be analysed, provided that the samples are first diluted with a defined amount of urea of natural isotopic composition and then transformed into carbon dioxide by means of urease. The relative abundance of 13C in this carbon dioxide, measured by nondispersive infrared spectrometry, is then a measure of the 13C abundance in the initial urea sample. Comparison of results of such measurements with those attained by mass spectrometry proves that this procedure is feasible and yields precis results.
OBJECTIVES: To compare the local tolerability, adhesion and estradiol delivery of a 5-cm(2) transdermal patch (Estradot), Novartis Pharmaceuticals, Basel, Switzerland) and a 12.5-cm(2) patch (Climara, Berlex Laboratories, Wayne, NJ, USA). METHODS: This was an open-label, randomized, intrapatient, comparative study. One hundred healthy postmenopausal women applied the 50 micro g/day 5-cm(2) patch and the 12.5-cm(2) patch concurrently for 7 days; safety and tolerability were assessed. Twelve women continued to apply the 5-cm(2) and 12.5-cm(2) patches separately for 7 days in a two-way cross-over study, to investigate the reproducibility of estradiol delivery. RESULTS: The proportion of subjects with a clinically significant erythema score was higher with the 12.5-cm(2) patch. The 5-cm(2) patch had a significantly lower incidence of very slight erythema than the larger patch (21.4% vs. 32.3%; p = 0.0028). Overall erythema scores were 0.22 and 0.41, respectively. More 5-cm(2) patches had > 90% adherence than the 12.5-cm(2) patches (87.5% vs. 82.0%, not significant) and fewer became detached (0.5% vs. 3.0%). Both the patches showed reproducible delivery of estradiol. CONCLUSION: The 5-cm(2) patch was associated with less skin irritation and better adherence than the 12.5-cm(2) patch, although the majority of the differences were not significant. The 5-cm(2) patch was well tolerated and showed reproducible estradiol delivery, as did the 12.5-cm(2) patch.
A novel magnetoresistance effect, due to the injection of a spin-polarized electron current from a dilute magnetic into a nonmagnetic semiconductor, is presented. The effect results from the suppression of a spin channel in the nonmagnetic semiconductor and can theoretically yield a positive magnetoresistance of 100%, when the spin flip length in the nonmagnetic semiconductor is sufficiently large. Experimentally, our devices exhibit up to 25% magnetoresistance.
OBJECTIVES: The aim of this prospective study was to evaluate the role of programmed ventricular stimulation (PVS) after noninvasive risk stratification to identify a subgroup of acute myocardial infarction (AMI) survivors considered at risk for ventricular arrhythmias and whether these patients could benefit from internal cardioverter-defibrillators (ICDs). BACKGROUND: The predictive value of noninvasive and invasive risk stratifiers after AMI has been questioned. The question of whether the group of patients with inducible monomorphic ventricular tachycardia (VT) after AMI could profit from ICD implantation is unanswered. METHODS: A consecutive series of 1,436 AMI survivors was screened noninvasively by Holter monitoring, heart rate variability, ventricular late potentials, and ejection fraction. A subgroup of 248 patients (17.3%) were identified as high-risk patients and scheduled for PVS. Due to the study design, 54 patients >75 years were excluded; thus, 194 patients were eligible for PVS. Triple extrastimuli at two paced cycle lengths (600 ms and 400 ms) were applied. RESULTS: In a subgroup of 98 (51%) high-risk patients, PVS was performed; 21 patients had an abnormal response, and in 20 patients an ICD was implanted. During a mean follow-up of 607 days the arrhythmic event rate (sudden cardiac death, symptomatic VT, cardiac arrest) was 33% with a positive electrophysiological test versus 2.6% (p < 0.0001) with a negative electrophysiological test. A subgroup of 96 high-risk patients declined electrophysiological study. In this nonconsent group, cardiac mortality (combined sudden and nonsudden) was significantly higher (log-rank chi-square 9.38, p = 0.0022, relative risk 4.7, 1.6 to 13.9) compared to the group guided by electrophysiological testing and consecutive ICD implantation. CONCLUSIONS: After a two-step risk stratification, PVS is helpful in selecting a subgroup of AMI survivors without spontaneous ventricular arrhythmias who benefit from prophylactic ICD implantation.