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Biomedical subjects

R Binder

Publications and source records attributed to R Binder.

At least 19 recordsLinked to original sources
PubMed2006

Large excitonic enhancement of optical refrigeration in semiconductors.

We present a theoretical analysis for laser cooling of bulk GaAs based on a microscopic many-particle theory of absorption and luminescence of a partially ionized electron-hole plasma. Our cooling threshold analysis shows that, at low temperatures, the presence of the excitonic resonance in the luminescence is essential in competing against heating losses. The theory includes self-consistent energy renormalizations and line broadenings from both instantaneous mean-field and frequency-dependent carrier-carrier correlations, and it is applicable from the few-Kelvin regime to above room temperature.

Journal Article↗
PubMed2005

Distortionless light pulse delay in quantum-well Bragg structures.

We describe a reflection scheme that allows Bragg-spaced semiconductor quantum wells to be used to trap, store, and release light. We study the temporal and spectral distortion of delayed light pulses and show that this geometry allows multibit delays and offers a high degree of distortion compensation.

Journal Article↗
PubMed2004

Quantum-dot quantum-interference infrared design proposal photodetector: and modeling of performance characteristics.

A novel design of an IR photodetector operating at wavelengths around 10 microm is presented. It is based on a three-level quantum coherence effect in semiconductor quantum dots as measured in balanced-homodyne detection in a Mach-Zehnder interferometer. The advantage of this design is the combination of room-temperature operation and fast response time, whereas the major drawback is the high noise-equivalent power.

Computer Simulation↗
PubMed2003

Electromagnetically induced transparency in semiconductors via biexciton coherence.

We report an experimental demonstration and theoretical analysis of electromagnetically induced transparency in a GaAs quantum well, in which the absorption of an exciton resonance is reduced by more than twentyfold. The destructive quantum interference in this scheme is set up by a control pulse that couples to a resonance of biexcitons. These studies illustrate that many-particle interactions, which are inherent in semiconductors and are often detrimental to quantum coherences, can also be harnessed to manipulate these coherences.

Journal Article↗
PubMed2001

Evidence for intervalence band coherences in semiconductor quantum wells via coherently coupled optical Stark shifts.

We report the experimental observation of coherently coupled heavy-hole-light-hole Stark shifts, i.e., light-hole exciton shifts under heavy-hole exciton pumping conditions, in InGaAs quantum wells. The theoretical analysis of the data is based on a full many-body approach (dynamics-controlled truncation formalism) in the third-order nonlinear optical regime. It is shown that the Stark shift data can be interpreted as strong evidence of suitably defined nonradiative intervalence band coherences in a semiconductor quantum well. Hence, the observations establish a semiconductor analog of Raman coherences in three-level atoms.

Journal Article↗
PubMed2001

[Chronic anemia and abdominal pain as a sequela of lead poisoning].

HISTORY AND ADMISSION FINDINGS: 3 years ago, a 63-year-old man underwent laparotomia due to clinical signs of acute abdominal pain. The anemia was treated with erythrocyte concentrates. Several weeks before the current admission to our outpatient department, the patient was again hospitalized because of acute abdominal pain and anemia. The patient was then transferred to the University clinic for further medical tests. INVESTIGATIONS: In addition to a normocytic anemia, a secondary porphyria was found. Further medical tests demonstrated lead poisoning. DIAGNOSIS, TREATMENT AND COURSE: Initially, the cause of the lead poisoning remained unclear because the patient had reported neither an occuppational nor an environmental exposure to lead. Finally, a prescription-prepared ointment was evaluated, which the patient had applied to his feet and lips over the past 3 years. CONCLUSION: Lead poisoning can be found outside the realm of occupational exposure; therefore, the knowledge of lead poisoning is still important.

Abdomen, Acute↗
PubMed2000

Quantitative whole-body autoradiography: recommendations for the standardization of the method.

The objective of this article is to identify the best conditions for preparing, handling, and exposing radioactive sections by using the Fujix BAS 2000 system for quantitative radioluminography. Regarding the influence of thickness of sections, thicker sections may allow shorter exposure times due to the increased radioactivity, but on the other hand they take more time for the freeze-drying process, resolution will be reduced, and the recovery of radioactivity will be lower due to increased self-absorption particularly in organs like bones or teeth. The pretreatment of the sections should depend on the method of exposure. Powdering with talcum is the most recommendable method when vacuum packaging the imaging plates and sections. Spraying with Nobecutan is recommended when using the cartridge method. Particularly for low concentrations, the vacuum-contact method should be the method of choice. To avoid a flare effect, the geometrical arrangement of the sections on the imaging plate (IP) should always be vertical to the scanning direction of the laser. An exposure time longer than 10 days is not recommended and the time between the end of exposure and start of scanning should be as short as possible. In order to reduce the background signal, it is necessary to expose the IPs in a shielding box in a cold environment. No positive chemographic effects of sections were found.

Animals↗
PubMed2000

Sensitivity of radioluminography using (14)C-labeled tracers in whole-body sections of rats.

Radioluminography using photostimulated luminescence recently became popular for the quantitation of radioactivity in whole-body sections. In order to estimate the limits of the method, the sensitivity was investigated using routinously prepared blood standards with known amounts of radioactivity. The blood standards underwent the typical steps similar to conventional whole-body autoradiography including freezing, sectioning, and lyophilizing. The limit of detection, defined as 3 times the standard deviation of background values, decreases with exposure time from 18 Bq/g wet tissue for 1 day of exposure to 6 Bq/g for 7 days of exposure. The respective limit of quantitation defined as 10 times the standard deviation of background is 60 to 20 Bq/g. A similar sensitivity is found when the quantitation limit is defined as reproducible measurement with coefficients of variance below 20%: 60 Bq/g can be quantified if the measure area is above 3.5 mm(2).

Animals↗
PubMed2000

Quantification of tissue self-absorption of weak beta-radiation in lyophilized whole-body sections of rats.

Whole-body autoradiography has been widely used in the investigation of the distribution of radiolabeled compounds in animals. The newly introduced radioluminography offers a reliable way of quantifying the radioactivity distribution within whole-body sections. Since the radioactivity is distributed over the entire depth of the section, self-absorption of beta-radiation in tissues is supposed to relevantly affect the detection of radioactivity at the section surface. The self-absorption of radiation energy ((14)C) was investigated in 28 organs/tissues of routinely produced lyophilized rat sections. Nonradioactive whole-body sections with different thickness between 20 and 120 microm were placed between a homogeneous (14)C source and the imaging plates to detect the transmitted radioactivity. The self-absorption was expressed in terms of percentage of transmission of the radioactivity through the sections. Transmission decreased with increasing section thickness, e.g., from 44% (20 microm) to 28% (120 microm) for blood. Comparison of three complete sets of data disclosed intertissue variations of up to about 30% (i.e., +/-15%) disregarding bone. A defined bandwidth of +/-15% around the blood transmission would cover the transmission of almost all tissues. Thus, for most organs radioactivity can be quantified by direct comparison with radioactive blood calibration samples.

Absorption↗
PubMed2000

Quantitative distribution studies in animals: cross-validation of radioluminography versus liquid-scintillation measurement.

The results of a cross-validation of the radioluminography (RLG) and liquid scintillation counting (LSC) methods are presented. The methods for the determination of radioactivity concentrations were compared in 16 organs, after administration of (14)C-labeled substances to rats. LSC measurements of two kinds were used as reference methods for RLG: (1) quantitative determination of radioactivity after conventional dissection (interindividual comparison) and (2) quantitative determination of radioactivity in tissue punches taken from the whole-body sections after they had undergone RLG measurement (intraindividual comparison). Blood standards containing known concentrations were used for calibration. For statistical evaluation log-linear regression analysis of paired concentration values and organ-specific 95% confidence intervals of the log-transformed RLG/LSC concentration quotients were compared. For most organs, the slopes of the regression lines and the means of the concentration quotients were within the defined equivalence range of 0.80-1.25. Deviations were distinctly smaller in the intraindividual comparison. For some organs, however, it became clear that found concentrations were affected by self-absorption (RLG) and by differences in sample preparation (LSC). In conclusion, quantification with RLG is a reliable and reproducible method with comparable measurement precision and greater accuracy in respect of tissue localization, compared to LSC (dissection).

Animals↗
PubMed1999

Modulation of C5a-mediated effector functions of human polymorphonuclear leukocytes by tumor necrosis factor alpha and granulocyte macrophage colony-stimulating factor.

At the site of acute inflammation, leukocytes are confronted with multiple mediators which are expected to modulate each other with respect to cell responses to the individual ligand. In the present study, we compared the effects of the classical chemoattractants FMLP, PAF and LTB4, of the chemokine IL-8 and of TNFalpha, GM-CSF, IFN-gamma and IL-1beta on C5a-induced chemotaxis, degranulation, oxidative burst and expression of adhesion molecules of human neutrophils in vitro. Upon preincubation, TNFalpha as well as GM-CSF dose-dependently inhibited C5a-mediated chemotaxis, but augmented the release of elastase as well as respiratory burst activity. The effects of the two cytokines were accompanied by a downregulation of C5a receptors as determined by Scatchard analysis using (125)I-labeled C5a. Compared on a molar basis, TNFalpha was more effective than GM-CSF. C5a-induced expression of beta(2)-integrins was only moderately influenced by TNFalpha and GM-CSF. C5a itself diminished chemotaxis as well as degranulation and oxidative burst in response to a second dose of the same ligand (homologous desensitization), whereas heterologous desensitization by FMLP and IL-8 was restricted to C5a-induced degranulation or not observed (PAF, LTB4]. The cytokine effects are likely to be a consequence of altered C5a receptor expression as well as of postreceptor events. In concert with C5a, certain cytokines may shift neutrophil effector functions from migration to exocytosis, an essential step within the sequence of events in a coordinated inflammatory response.

CD18 Antigens↗
PubMed1996

Pharmacokinetic studies of the fragrance compound 1,8-cineol in humans during inhalation.

The present study was undertaken to investigate the pharmacokinetics of 1,8-cineol in human subjects during prolonged inhalation. The results showed that 1,8-cineol is well absorbed from breathing air, with a peak plasma concentration after approximately 18 min. The elimination of this fragrance compound from the blood is biphasic, with a mean distribution half-life of 6.7 min and an elimination half-life of 104.6 min.

Administration, Inhalation↗
PubMed1996

Suicidal chloroquine poisoning: clinical course, autopsy findings, and chemical analysis.

Suicidal overdose of chloroquine is rare. We present a 14-year-old girl who was admitted to our Emergency Department after intentional ingestion of 7.5 g of chloroquine base followed by cardiac and respiratory arrest. Despite early mechanical ventilation, cardiac support, and treatment with high doses of diazepam, the patient died. Laboratory investigation indicated disseminated intravascular coagulation confirmed by petechial hemorrhages in the leptomeninges at autopsy, a finding that has not previously been described. Postmortem tissue analysis demonstrated early drug distribution to the medulla oblongata and cerebellum.

Adolescent↗
PubMed1995

Functional activity of the membrane-associated complement inhibitor CD59 in a pig-to-human in vitro model for hyperacute xenograft rejection.

Hyperacute rejection triggered by activation of the recipient's complement system represents the major barrier to successful xenotransplantation. Transfer of human membrane-associated complement regulators to donor organs has been suggested as one strategy to interfere with complement-mediated hyperacute xenograft rejection. Pigs are discussed as potential organ donors. We therefore investigated a putative protective function of the membrane-bound complement inhibitor CD59 in a pig-to-human in vitro model of hyperacute xenograft rejection. Aortic porcine endothelial cells were transfected with human CD59 cDNA. Expression of human CD59 was demonstrated by cytofluorimetric and RNA analysis. Removal of CD59 from the cell surface by phosphatidylinositol-specific phospholipase C (PI-PLC) demonstrated its production as a glycosyl phosphatidylinositol (GPI)-anchored protein. Functional activity of the transfected CD59 was tested by a lactate dehydrogenase (LDH) release assay for complement-mediated lysis. Porcine endothelial cells expressing human CD59 were significantly protected from lysis by human serum complement compared with CD59- cells. The protective effect was abolished by preincubating the cells with anti-CD59 antibodies or PI-PLC. We calculated by Scatchard analysis that the established CD59+ cell line expressed a CD59 level comparable to that of human endothelial cells. Our results recommend the production of pigs transgenic for CD59.

Animals↗