The MLC assay as a test for HLA-D region compatibility between patients and unrelated donors: results of a national marrow donor program involving multiple centers

Mixed lymphocyte culture (MLC) assays from 763 patients and prospective unrelated marrow transplant donors identified through the National Marrow Donor Program (NMDP) were analyzed for their overall utility in measuring HLA-D region compatibility. The assays were performed at 31 different transplant centers (range, 1 to 197; median, 9 assays per center). A total of 325/763 (42.6%) of the tests were judged to be uninterpretable, either due to lack of sufficient control cells included in the assay (89 tests) or to insufficient reactivity by patient and/or donor cells (236 tests). Among the 438 tests that could be interpreted, HLA-Dw phenotyping with HLA-D homozygous cells was performed for a subset of 190. The relative response (RR) values from these 190 tests, however, were not clearly separable into distinct populations; i.e., RR values corresponding to Dw identity versus nonidentity between patient and donor could not be reliably discriminated. The predictive value of a nonreactive MLC for Dw identity was calculated to be 0.91 for RRs of < or = 20%, while the predictive value of a reactive MLC for Dw nonidentity was 0.35 for RRs of > 20%. These results, based on an analysis of data submitted from multiple transplant centers testing patients who had a variety of hematologic disorders, suggest that the MLC assay is a relatively imprecise method for determining HLA-D region compatibility between patient and prospective unrelated marrow donor.     

Scattering induced crosstalk in active directional couplers

Scattering from defects in an integrated optical device causes phase randomization and depolarization. Scattered light can be recaptured by the waveguides of the device and perturbs modal fields. This leads to crosstalk in directional coupler switches. A defect-scattering-induced crosstalk model is developed and crosstalk in one-, two-, and three-electrode directional couplers is investigated with the model. The number of independent electrode voltages needed to tune out crosstalk is studied. Simulations show that scattering-induced crosstalk can be tuned out completely in active directional couplers with two independent electrode voltages. When modal differential loss and unequal taper coupling are taken into account, two independent electrode voltages are insufficient to tune out the crosstalk, whereas three independent electrode voltages are sufficient. This agrees with the conclusion from previous three-electrode directional coupler experiments     

Semiconductor laser stabilization by external optical feedback

A report is presented on a general theory describing the effect of external optical feedback on the steady-state noise characteristics of single-mode semiconductor lasers. The theory is valid for arbitrarily strong feedback and arbitrary optical feedback configuration and spectrum. A generalized Langevin rate equation is derived. The equation is, in general, infinite order in d/dt constituting an infinite-order correction to the low-frequency weak-feedback analysis. The general formalism includes relaxation oscillations and permits analysis of the effect of feedback on the laser linewidth, frequency noise, relative intensity noise, and the relaxation oscillation sidebands in the field spectrum. The theory is applied to two important feedback configurations: the laser coupled to a single mirror and the laser coupled to a high-Q cavity     

Eigenmode analysis of symmetric parallel waveguide couplers

An analysis of a laterally symmetric parallel waveguide structure has been carried out by using symmetric and antisymmetric eigenmodes in the coupled mode equations. As opposed to modes of each individual guide, eigenmodes are orthogonal and therefore comply with coupled mode formalism. Of particular interest has been the popular configurationZ-cut LiNbO3with Wave propagation along the crystalY-axis. The theory shows that output versus voltage characteristics are nonperiodic in voltage, and furthermore, they are asymmetric if the eigenmodes are not equally excited. The uniform electrode coupler can easily be explained in terms of eigenmode coupling and interference.     

Backscattering signatures from graded-index fibres with diameter variations

The effect of slow diameter changes on backscattering signatures is considered. Experimental measurements of back-scattered power from fibres with programmed core diameter variations are presented. A simple model is proposed to explain the experimental results.     

Volatile anesthetics inhibit dihydropyridine binding to malignant hyperthermia-susceptible and normal pig skeletal muscle membranes

BACKGROUND: Surface membrane dihydropyridine receptor Ca2+ channels may play a role in the response of malignant hyperthermia-susceptible skeletal muscle to volatile anesthetics. METHODS: We determined the effect of halothane, enflurane, and isoflurane on the binding of the Ca2+ channel blocker PN200-110 to skeletal muscle membranes isolated from malignant hyperthermia-susceptible and normal pigs. RESULTS: In the presence of 0.4 mM halothane, the maximal [3H]PN200-110 binding to both normal and malignant hyperthermia membranes was reduced by 37-43% (P < 0.05). There was no difference in the equilibrium constant for the halothane-dependent inhibition of [3H]PN200-110 binding to these two types of membranes. There also was no significant difference among halothane, enflurane, or isoflurane in their ability to inhibit [3H]PN200-110 binding to either normal or malignant hyperthermia membranes. CONCLUSIONS: Volatile anesthetics inhibit the binding of PN200-110 to skeletal muscle membranes by decreasing the number of functionally active dihydropyridine receptor proteins. This inhibition is similar for membranes isolated from both normal and malignant hyperthermia-susceptible muscle, thus providing no evidence for a halothane-induced functional defect in this protein in malignant hyperthermia-susceptible muscle. However, the results of this study also indicate that the mechanism by which volatile anesthetics decrease surface membrane Ca2+ currents in skeletal muscle is by reducing the number of functional dihydropyridine receptor Ca2+ channels.     

Structure‐Dependent Binding of Arylimidamides to the DNA Minor Groove

Heterocyclic diamidines are strong DNA minor‐groove binders and have excellent antiparasitic activity. To extend the biological activity of these compounds, a series of arylimidamides (AIAs) analogues, which have better uptake properties in Leishmania and Trypanosoma cruizi than diamidines, was prepared. The binding of the AIAs to DNA was investigated by T_m, fluorescence displacement titration, circular dichroism, DNase I footprinting, biosensor surface plasmon resonance, X‐ray crystallography and molecular modeling. These compounds form 1:1 complexes with AT sequences in the DNA minor groove, and the binding strength varies with substituent size, charge and polarity. These substituent‐dependent structure and properties provide a SAR that can be used to estimate K values for binding to DNA in this series. The structural results and molecular modeling studies provide an explanation for the differences in binding affinities for AIAs.     

Remote Laboratories for Optical Circuits

This paper presents a remote laboratory implementation for an optical circuits course. The process from design and implementation towards assessment and continuous improvement phase is outlined. The design of the experiments involved the research on remote access technology and the investigation of best practices for an experimental setup. The first pilot implementations were used to determine the possible shortfalls during an ldquoIntroduction to an Optical Communicationsrdquo course in fall 2004 at the University of Colorado, Boulder, and an ldquoOptical Circuitsrdquo course in fall 2005 at the University of Houston, Houston, TX. After improvements, two experiments were pilot tested during spring 2006 at the University of Houston. Assessment of learning outcomes and teaching methods were performed. The remote access methods, in addition to the delivery of the class and lectures, are presented in the paper. Delivery of a class with remote laboratories and videotaped lectures are also outlined under future directions of this project.     

Analysis of an experimental technique for determining Van der Polparameters of a transistor oscillator

The Van der Pol (VDP) model of a transistor oscillator describes the behaviour of the oscillator with three parameters. When operating in steady state, only two parameters can be determined by spectrum analysis, these being the oscillation frequency and amplitude of oscillation. In this paper, a technique for measuring the other VDP parameter is examined. In this approach, a periodically modulated voltage is added to the bias of the oscillator to perturb the operational state. A theoretical derivation shows that the power spectrum of the perturbed oscillator contains additional information for determination of the other VDP parameter. A simple analytical perturbation formula predicts the oscillator's response to the ramped bias. Our experimental results agree with the analytical perturbation solution and therefore, this allows one to read off the other VDP parameter from the experimental data. The VDP model allows one to predict the behaviour of coupled transistor oscillators more accurately and simply than does the traditional large-signal model of the transistor. This VDP model will simplify oscillator array design since the number of parameters needed to describe each oscillator is reduced from that which would be required using a large-signal circuit model