Noninvasive detection of temozolomide in brain tumor xenografts by magnetic resonance spectroscopy.

Poor drug delivery to brain tumors caused by aberrant tumor vasculature and a partly intact blood-brain barrier (BBB) and blood-brain tumor barrier (BTB) can significantly impair the efficacy of chemotherapy. Determining drug delivery to brain tumors is a challenging problem, and the noninvasive detection of drug directly in the tumor can be critically important for accessing, predicting, and eventually improving effectiveness of therapy. In this study, in vivo magnetic resonance spectroscopy (MRS) was used to detect an anticancer agent, temozolomide (TMZ), in vivo in murine xenotransplants of U87MG human brain cancer.

Effect of paramagnetic manganese cations on (1)H MRS of the brain.

Manganese cations (Mn(2+)) can be used as an intracellular contrast agent for structural, functional and neural pathway imaging applications. However, at high concentrations, Mn(2+) is neurotoxic and may influence the concentration of (1)H MR-detectable metabolites. Furthermore, the paramagnetic Mn(2+) cations may also influence the relaxation of the metabolites under investigation.

Slice profile optimization in arterial spin labeling using presaturation and optimized RF pulses.

Objective: An important source of error in arterial spin labeling (ASL) is incomplete static tissue subtraction due to imperfect slice profiles. This effect can be reduced by saturating the spins in the imaging area prior to labeling. In this study, the use of optimized presaturation is compared with the use of optimized RF pulses for minimizing this error.

Expression of short-chain acyl-CoA dehydrogenase (SCAD) proteins in the liver of SCAD deficient mice after hydrodynamic gene transfer.

Hydrodynamic administration of naked DNA was investigated as a method for in vivo expression of variant proteins involved in metabolic diseases, using short-chain acyl-CoA dehydrogenase (SCAD) deficient mice (BALB/cByJ) as a model. Human SCAD wild-type (WT) and two disease-associated SCAD variant proteins (R147W and G185S) were expressed in mouse liver by means of single injections of SCAD cDNA under the control of a ubiquitin promoter. SCAD expression was detected two days after injection.

Potential optical gain with two crossed Fabry-Perot resonators: the influence of absorption.

A crossed resonator Fabry-Perot device is analyzed for a collection of nonlinear-optical materials, including bulk semiconductors, the intraband transition in a multiple quantum well, organic polymers, and semiconductor-doped glasses, to determine its suitability for photonic switching and optical computing. We find that as an optical switch the crossed resonator offers a considerably steeper threshold and somewhat flatter wings than a single Fabry-Perot resonator and that to achieve optical gain the absorption per pass must be lower than 0.05.

Generation of squeezed states by nondegenerate multiwave mixing in two-level media.

Using our quantum theory of multiwave mixing, we derive formulas for the intracavity squeezed variances generated by nondegenerate four-wave mixing in a cavity and illustrate the results with variance spectra as functions of side-mode/pump beat frequency.

Theory of two-photon resonance fluorescence.

We present calculations of the spontaneous-emission spectrum from a two-photon two-level system in the presence of an arbitrarily intense monochromatic field at half of the two-photon transition frequency. The single-photon counterpart to this is called resonance fluorescence. Because of the complexity of the two-photon two-level model, many effects arise that are absent in the one-photon problem.