Direct determination of p-hydroxymethamphetamine glucuronide in human urine by high-performance liquid chromatography

High-performance liquid chromatography (HPLC) with UV detection for the simultaneous determination of the free form of p-hydroxymethamphetamine (p-OHMA) and its metabolite, glucuronide (p-OHMAG) was accomplished for the first time. We achieved this by employing 1) an ion pair reagent for retention of sample to a solid-phase extraction (SPE) cartridge, Sep-Pak Light C18 and 2) a simple two-step stepwise elution technique for subsequent ion pair RP-HPLC. The proposed method was optimized for resolution of p-OHMAG, p-OHMA and MA. The method was successfully applied to urine samples collected from MA abusers.     

Functional Changes in the Care-needing Elderly after Surface Electrical Stimulation to the Abdomen

Background: Strength of the trunk muscles is a key component of motor control, but it declines easily with the process of aging and/or disuse. Objectives: To investigate the effects of surface electrical stimulation (ES) to the abdominal muscles and the motor performance for care-needing elderly. Design: Controlled trial. Participants: Twenty-one elderly people (60–90 years) with care-needing, who were admitted to a nursing home or hospital for daily care and their score of Barthel Index had been stable from 55.3 ± 19.4 to 55.3 ± 19.8 during 3 months before intervention. Intervention: Common physical/occupational therapy was performed for all of the subjects during the study period. ES was applied to the abdomen of 15 subjects (ES group) twice a day for 8 weeks. Measurements: Functional measurements were performed before and after beginning of the study with some parameters as follows: grip strength; movement time for sitting up (MSU); maximum walking speed (WS). Results: No significant differences between two groups were noted for characteristics at baseline. In the ES group, MSU (from 21.1 ± 21.4 to 10.4 ± 8.3 sec) significantly improved (p < 0.05) after 8weeks. WS (from 17.7 ± 12.1 to 24.3 ± 15.3 m/min) were also improved (p < 0.05) after 8 weeks. Limitations: A limitation of this study was the small sample size. Conclusions: ES to the abdominal area has the potential to improve motor function in the care-needing elderly through reinforcement of the abdominal muscles.     

Formation of multiple shocklets in a transonic diffuser flow

Multiple shocklets are frequently generated in transonic diffuser flows. The present paper investigates the formation of these shocklets with a high-speed CCD camera combined with the schlieren method. It is observed that compression waves steepen while propagating upstream, and eventually become new shock waves. The ordinary shock wave is found to move upstream beyond the nozzle throat or to disappear while moving downstream depending on the pressure ratio across the nozzle. This phenomenon is also analyzed with the one-dimensional Euler equations by assuming a pressure disturbance given by the sine function at the channel exit. The calculated results are found to reproduce quite well the experimental behavior of the shocklets. The effect of the frequency of disturbance is also studied numerically, and it is shown that the multiple shocklet pattern appears when the amplitude of disturbance is not large and the diverging part of the channel downstream of the ordinary shock wave is long. Received 26 June 1998 / Accepted 15 March 1999     

An in situ study of plasticization of polymers by high-pressure gases

A high-pressure differential scanning calorimetric technique is described for studying polymer plasticization by compressed gases at pressures to 100 atm. The in situ measurements avoid problems due to gas desorption encountered with conventional DSCs, thus providing an accurate way to determine the change in glass transition temperature, T_g, with pressure, p. The entire T_g–p curve can be established in less than 2 days. The glass transition was observed as a sharp step in the case of 100–200-μm thin samples, whereas thicker samples gave a broad transition; highly reproducible results were obtained for the thin samples. For PS–CO₂, the measured T_gs under various pressures were found to be in good agreement with literature values. Results for the systems PS–HFC134a, PVC–CO₂, and PC–CO₂ are also reported. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 977–982, 1998     

Effects of an amphipathic alpha-helical peptide on lateral pressure and water penetration in phosphatidylcholine and monoolein mixed membranes

The physicochemical properties of mixed membranes of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and a nonlamellar-forming lipid, 1-monoolein (MO), and the effects of an amphipathic alpha-helical peptide, 18A (DWLKAFYDKVAEKLKEAF), on the membranes were investigated by fluorescence measurements and 31P NMR. The intramolecular excimer formation of dipyrenylphosphatidylcholines showed that the increased lateral pressure near the bilayer center by MO is reduced by the lamellar-cubic phase transition at an MO mole fraction of 0.7, while the lateral pressure near the polar-apolar interface increases even through the phase transition. The fluorescence lifetime of 2-(9-anthroyloxy)stearic acid revealed that water penetration into the interface region increases with the MO fraction. The insertion of the 18A peptide into the membrane interface region decreased both the lateral pressure near the interface and water penetration, and shifted the lamellar-cubic phase transition to a higher MO fraction. This suggests that 18A induces a positive curvature strain and lowers the lateral pressure and water penetration. Furthermore, the increase in the MO fraction in POPC/MO LUV promoted partitioning of 18A to the membranes. This preferential binding to the MO-containing membranes is presumably ascribed to the propensity of 18A to reduce the membrane strain.     

Preparative high-performance liquid chromatographic separation of naphthodianthrones from St. John's Wort

St. John's Wort (Hypericum perforatum), a perennial flowering plant, has been used medicinally for thousands of years and has most recently been identified as an effective treatment for mild to moderate depression and neuralgic disorders. This work presents a procedure for the isolation of naphthodianthrones from St. John's Wort by an accelerated extraction and separation of marker compounds by preparative high-performance liquid chromatography (HPLC) with photodiode array detection. The accelerated extraction method minimizes the extraction time and increases the yield, and the marker compounds obtained by preparative HPLC are of 98% purity. The compounds are characterized by liquid chromatography-mass spectrometry (electrospray ionization) and NMR spectra.     

The mechanism of formation of N-formylkynurenine by heme dioxygenases

Heme dioxygenases catalyze the oxidation of L-tryptophan to N-formylkynurenine (NFK), the first and rate-limiting step in tryptophan catabolism. Although recent progress has been made on early stages in the mechanism, there is currently no experimental data on the mechanism of product (NFK) formation. In this work, we have used mass spectrometry to examine product formation in a number of dioxygenases. In addition to NFK formation (m/z = 237), the data identify a species (m/z = 221) that is consistent with insertion of a single atom of oxygen into the substrate during O(2)-driven turnover. The fragmentation pattern for this m/z = 221 species is consistent with a cyclic amino acetal structure; independent chemical synthesis of the 3a-hydroxypyrroloindole-2-carboxylic acid compound is in agreement with this assignment. Labeling experiments with (18)O(2) confirm the origin of the oxygen atom as arising from O(2)-dependent turnover. These data suggest that the dioxygenases use a ring-opening mechanism during NFK formation, rather than Criegee or dioxetane mechanisms as previously proposed.     

-hyponormality is not translation-invariant

In this note we provide an example of a semi-hyponormal Hilbert space operator for which is not -hyponormal for some and all .