Expansion of transplanted hepatocytes during liver regeneration

A method for volume selective proton spectroscopy is presented based on a multiecho sequence with short refocusing interval tcp. It is demonstrated, that by appropriate choice of tcp on the order of 4-6 ms, signals from overlapping multiplets like the glutamine and glutamate (Glu/Gln) resonances in spectra of the human brain are considerably increased compared with a conventional PRESS volume selection scheme. Thus proton spectra from J-coupled multiplet signals can be acquired with TE on the order of 20-30 ms avoiding the baseline problems arising at shorter echo times due to broad resonances. This allows to selectively acquire spectra from substances with longer T2 without the confounding effects from J-coupling occurring in conventional volume selection techniques.     

The sleep of abstinent pure primary alcoholic patients: natural course and relationship to relapse

Sleep in male pure primary alcoholic inpatients was examined at a mean of 16 days (n = 29), 19 weeks (n = 29), 14 months (n = 9), and 27 months (n = 4) of abstinence. Results were as follows: (1) the sleep of abstinent alcoholic patients is short, fragmented, and shallow early in abstinence; (2) a patient's sleep improves slowly over at least the first year of abstinence; however, (3) some facets of a patient's sleep remain abnormal even after 27 months of abstinence; (4) insomnia and sleep fragmentation after approximately 5 months of abstinence may be related to relapse by 14 months. The mechanism underlying the relationship between sleep and withdrawal in alcoholic patients is not well understood, and the issue of treating sleep problems as an adjunct to prevention of relapse warrants further investigation.     

Conformation and ion-channeling activity of a 27-residue peptide modeled on the single-transmembrane segment of the IsK (minK) protein

IsK (minK) protein, in concert with another channel protein KVLQT1, mediates a distinct, slowly activating, voltage-gated potassium current across certain mammalian cell membranes. Site-directed mutational studies have led to the proposal that the single transmembrane segment of IsK participates in the pore of the potassium channel [Takumi, T. (1993) News Physiol. Sci. 8, 175-178]. We present functional and structural studies of a short peptide (K27) with primary structure NH2-1KLEALYILMVLGFFGFFTLGIMLSYI27R-COOH, corresponding to the transmembrane segment of IsK (residues 42-68). When K27 was incorporated, at low concentrations, into phosphatidylethanolamine, black-lipid membranes, single-channel activity was observed, with no strong ion selectivity. IR measurements reveal the peptide has a predominantly helical conformation in the membrane. The atomic resolution structure of the helix has been established by high-resolution 1H NMR spectroscopy studies. These studies were carried out in a solvent comprising 86% v/v 1,1,1,3,3,3-hexafluoro-isopropanol-14% v/v water, in which the IR spectrum of the peptide was found to be very similar to that observed in the bilayer. The NMR studies have established that residues 1-3 are disordered, while residues 4-27 have an alpha-helical conformation, the helix being looser near the termini and more stable in the central region of the molecule. The length (2. 6 nm) of the hydrophobic segment of the helix, residues 7-23, matches the span of the hydrocarbon chains (2.3 +/- 0.25 nm) of fully hydrated bilayers of phosphatidylcholine lipid mixture from egg yolk. The side chains on the helix surface are predominantly hydrophobic, consistent with a transmembrane location of the helix. The ion-channeling activity is believed to stem from long-lived aggregates of these helices. The aggregation is mediated by the pi-pi stacking of phenylalanine aromatic rings of adjacent helices and favorable interactions of the opposing aliphatic-like side chains, such as leucine and methionine, with the lipid chains of the bilayer. This mechanism is in keeping with site-directed mutational studies which suggest that the transmembrane segment of IsK is an integral part of the pore of the potassium channel and has a similar disposition to that in the peptide model system.     

Compression device to reduce motion artifacts at contrast-enhanced MR imaging in the breast

We reported previously that thymic lymphomas from mice expressing transgenic TCR autoreactive against male (HY) antigen were resistant to anti-CD3 antibody-mediated induction of apoptosis although they were responding to TCR triggering. To test whether thymic lymphomas were specifically resistant to TCR-dependent Ca(++)-mediated induction of apoptosis, we have measured apoptosis of cells treated with Ca(++)-dependent (ionomycin, A23187) and Ca(++)-independent (etoposide, dexamethasone) inducers of apoptosis. Here we show that, unlike thymocytes, all thymic lymphomas were resistant to Ca(++)-dependent but not to Ca(++)-independent induction of apoptosis. These results excluded a general defect of apoptosis in lymphoma cells and suggested a specific inhibition of the calcium-mediated (TCR-dependent) pathway of apoptosis in lymphomas. Interestingly however, nuclear expression of a specific mediator of TCR-dependent apoptosis Nur77 was induced in ionomycin-resistant lymphomas indicating that, unlike normal thymocytes, thymic lymphomas are resistant to Nur77-mediated apoptosis.     

Dilepton decay from excited states in 28Si populated via different isospin entrance channels

A four-stage model of pain processing was proposed, consisting of pain sensation intensity, pain unpleasantness (stage 1 affect), suffering (stage 2 affect), and pain behavior. We studied 506 chronic pain patients (230 male and 276 female) using a multivariate statistical technique (LISREL) in order to demonstrate the structural relationship among multiple indicators of pain processing; and to characterize these stages in terms of their interactions. A strong relationship was revealed between the majority of the underlying indicators of each pain processing stage. A linear stage sequence best fitted the relationship between the four stages. Successive stages did not have recursive effects on earlier pain components. A confirmatory LISREL analysis was conducted with an additional sample of 502 chronic pain patients. In this replication analysis the structural equation model consisted of pain intensity, unpleasantness (stage 1 affect), emotional suffering (stage 2 affect), and pain behavior. This study extends the validation of these pain dimensions, as well as the validity of the measure(s) of each separate stage.     

Cellular basis for the negative dromotropic effect of adenosine on rabbit single atrioventricular nodal cells

Detection and resolution of square patches of sinusoidal gratings were measured in central and peripheral vision (30 degrees horizontal temporal visual field) for high-contrast gratings as a function of the number of cycles in the stimulus. We determined performance in a forced-choice paradigm for a fixed number of stimulus cycles by arranging for stimulus diameter to vary inversely with spatial frequency. For both psychophysical tasks and for both target locations, the psychometric function relating performance to log spatial frequency shifted to higher frequencies without changing slope significantly as the number of cycles in the stimulus was increased. Thus the entire effect could be captured by an analysis of spatial acuity, which increased with increasing number of grating cycles over the range 0.5-6 cycles but remained constant over the range 6-14 cycles. In the central field, resolution acuity and detection acuity were equal regardless of the number of cycles in the stimulus. In the peripheral field, detection acuity exceeded resolution acuity and perceptual aliasing occurred for stimuli in the range 1-14 cycles. From this result we conclude that resolution acuity is sampling limited in the periphery, provided that the stimulus contains at least one full cycle of the grating. Essential features of the results could be accounted for by Fourier analysis of the stimulus.