Roger M. Hawk

Effects of antipsychotic drugs on metabolite ratios in rat brain in vivo

Localized in vivo proton magnetic resonance spectroscopy at 4.7 T was used to examine the brains of rats that were given the antipsychotic drugs haloperidol, clozapine, or olanzapine for 1 week. Spectra were collected before and during treatment. The ratios of N‐acetylaspartate (NAA) to creatine (Cr) and choline to Cr were determined from the spectra. No significant differences in these ratios were seen among the rats given the various antipsychotic medications or between the control rats and the treated rats. No significant time‐dependent changes were seen in most cases, except for a small reduction of NAA/Cr after 7 days of olanzapine administration. These results suggest that differences in brain metabolite ratios in vivo in schizophrenics relative to controls, at least for short‐term treatment, arise from the disease, and not as a metabolic effect of the medication. Magn Reson Med 43:355–358, 2000.

Competition of Li(I) and Mg(II) for ATP binding: a 31P NMR study.

We have examined the changes in the 31P NMR chemical shifts of ATP in aqueous solution, upon addition of NaCl and LiCl at ambient temperature. NaCl and LiCl cause qualitatively similar downfield changes, although the effect of LiCl is somewhat larger. For a 2:1 mixture of Na-ATP or tris-ATP and MgCl2 at 0 degrees C, separate beta-P peaks are observed for uncomplexed ATP and ATP complexed with Mg(II) at 121.6 MHz. Addition of LiCl slightly shifts the uncomplexed Na-ATP or tris-ATP peak downfield but does not measurably shift the Mg-ATP peak or change relative intensities. Thus, Li behaves more like Na than Mg in its ATP complexation behavior, making this system a poor model for competition between Li and Mg for macromolecular binding.

Identification of trifluoperazine metabolites using HPLC–NMR of test mixtures

The metabolites of the antipsychotic drug trifluoperazine (TFP) were investigated with on‐line coupling of high‐performance liquid chromatography (HPLC) and NMR spectroscopy. A chromatographic method was developed using a reversed‐phase C30 silica gel column. Rats were given a cumulative dose of 90 mg kg−1 TFP dihydrochloride and samples of brain and muscle tissues were extracted after 29 h. The peaks obtained on chromatographic separation were assigned to trifluoperazine and its metabolites. With the help of chromatograms obtained from test mixtures, 1D and 2D HPLC–NMR were used to identify the peaks found for these mixtures. Copyright

In vivo relaxation time measurements on a murine tumor model—Prolongation of T1 after photodynamic therapy

RIF tumors implanted on mice feet were investigated for changes in relaxation times (T1 and T2) after photodynamic therapy (PDT). Photodynamic therapy was performed using Photofrin II as the photosensitizer and laser light at 630 nm. A home-built proton solenoid coil in the balanced configuration was used to accommodate the tumors, and the relaxation times were measured before, immediately after, and up to several hours after therapy. Several control experiments were performed untreated tumors, tumors treated with Photofrin II alone, or tumors treated with laser light alone. Significant increases in T1s of water protons were observed after PDT treatment. In all experiments, 31P spectra were recorded before and after the therapy to study the tumor status and to confirm the onset of PDT. These studies show significant prolongation of T1s after the PDT treatment. The spin-spin relaxation measurements, on the other hand, did not show such prolongation in T2 values after PDT treatment.

Contribution of trifluoperazine metabolites to the in vivo 19F NMR spectrum of rat brain

Fluorine‐19 NMR spectra were acquired from extracts of tissues from heads of rats given the antipsychotic drug trifluoperazine (TFP). Contributions to the in vivo 19F spectra from tissues other than brain were negligible. The in vivo 19F resonance at ‐62.3 ppm from CCl3F consisted of 6–8 resolved resonances in vitro. Some in vitro resonances were assigned to previously identified TFP metabolites. Multiple resonances in vitro partially explain the relatively large line width seen in vivo for TFP. Unidentified metabolites were observed at about ‐74 to ‐75 ppm in a number of spectra of extracts of brain and muscle. Magn Reson Med 43:756–759, 2000.

A Versatile Potentiostat With Optional Computer Control

ABSTRACT A versatile potentiostat which can supply a maximum of 125 ma is described. The potentiostat uses readily available electronic components and an interface is detailed which allows the potentiostat optional computer control.

ELECTROSTATIC DEPOSITION OF LARGE GRAINED POLYCRYSTALLINE SILICON FILMS FOR SOLAR CELL APPLICATIONS

ABSTRACT Large grained (> 50 μm < 100 μm) poly crystalline silicon films have been formed using a patented electrostatic deposition method which utilizes charged panicle motion in an electric field. After deposition, the films are heat treated at varying times and temperatures in a programmable furnace maintained under a purified argon atmosphere Solar cells were fabricated using these large grained polycrystalline silicon films by sputtering pure gold as back contacts and using high quality silver paint as front contacts. The cells have shown efficiencies of 1.8% indicating that great potential exists for significant improvement.

Responses to photodynamic therapy in a murine tumor model—31P NMR and water proton relaxation studies

Abstract In this study we report the tumor responses to photodynamic therapy (PDT) as measured by in vivo 31P NMR and water relaxation measurements on a murine tumor model. We evaluate the PDT responses to two new photosensitizers by monitoring the tumor volumes post PDT for one tumor and by in vivo 31P NMR for the other. Both photosensitizers are structurally well defined, pure compounds, unlike Photofrin II (PF II), which is a complex chemical mixture of a variety of porphyrin species. Dramatic increases in inorganic phosphate (Pi) were noticed following PDT treatment. The tumor water relaxation time measurements also suggest corresponding increases in Tl values of water after PDT treatment. From a combined study of relaxation times, 31P NMR, and tumor volumes, we conclude that the relaxation measurements can serve as a useful and sensitive method of monitoring PDT.