<Superscript>1</Superscript>H MR chemical shift imaging detection of phenylalanine in patients suffering from phenylketonuria (PKU)

Short echo time single voxel methods were used in previous MR spectroscopy studies of phenylalanine (Phe) levels in phenylketonuria (PKU) patients. In this study, apparent T ₂ relaxation time of the 7.3-ppm Phe multiplet signal in the brain of PKU patients was assessed in order to establish which echo time would be optimal. ¹H chemical shift imaging (CSI) examinations of a transverse plain above the ventricles of the brain were performed in 10 PKU patients and 11 persons not suffering from PKU at 1.5 T, using four echo times (TE 20, 40, 135 and 270 ms). Phe was detectable only when the signals from all CSI voxels were summarized. In patients suffering from PKU the T ₂ relaxation times of choline, creatine and N-acetyl aspartate (NAA) were similar to those previously reported for healthy volunteers (between 200 and 325 ms). The T ₂ of Phe in brain tissue was 215±120 ms (standard deviation). In the PKU patients the brain tissue Phe concentrations were 141±69 M as opposed to 58±23 M in the persons not suffering from PKU. In the detection of Phe, MR spectroscopy performed at TE 135 or 270 ms is not inferior to that performed at TE 20 or 40 ms (all previous studies). Best results were obtained at TE=135 ms, relating to the fact that at that particular TE, the visibility of a compound with a T ₂ of 215 ms still is good, while interfering signals from short-TE compounds are negligible.     

Assessment of lung water by magnetic resonance in three types of pulmonary edema

Summary Pulmonary edema was produced in nine mongrel dogs by: (a) saline lavage; (b) intravenous injection of oleic acid; and (c) intravenous injection of propranolol followed by ureteral ligation. The resulting effect could be characterized by varying the protein concentration in the pulmonary edema fluid. After induction, all dogs were killed and 20 samples from each passively deflated lung were obtained. Proton T₁ and T₂ values were measured on a Praxis II NMR spectrometer operated at 10.7 MHz and 37°C. The water content of all samples was determined gravimetrically.Correlation between T₁ or T₂ measured in vitro and the ratio of wet to dry weight was highly significant (r>0.95,P<0.001) in each pathological state. Regression curves indicate that although all three types of pulmonary edema can be characterized by slightly different slopes, the differences are statistically insignificant. Moreover, the slopes of previous studies, when recast in the same format, are very similar to our findings despite the use of different magnetic field strengths and different animal models. This study indicates that quantitation of pulmonary edema is possible, but in vitro measurements do not give useful information for characterizing the etiology of pulmonary edema.     

Effects of gender, age and hypertension on β-adrenergic receptor function in rat urinary bladder

β-Adrenoceptors mediate urinary bladder relaxation, and gender, age and hypertension have been linked to bladder dysfunction. Therefore, we have studied whether any of these factors affects the ability of β-adrenoceptor agonists to relax rat bladder detrusor muscle in vitro. For this purpose we have compared male and female Wistar rats, young and old male Wistar rats, and male normotensive and spontaneously hypertensive rats (SHR). Comparisons were done using KCl-precontracted bladder strips (length about 15–20 mm) and the endogenous agonist noradrenaline, the synthetic non-subtype-selective agonist isoprenaline, and the prototypical β₃-adrenoceptor agonists BRL 37,344 and CGP 12,177. While all agonists yielded numerically weaker relaxation in female as compared to male rats (for example for noradrenaline E_max 40±4% vs 53±6% relaxation, pEC₅₀ 5.41±0.13 vs 5.60±0.14), this difference reached statistical significance only for the weak partial agonist CGP 12,177. Responses to all agonists were attenuated in old as compared to young rats, largely due to a reduced maximum effect, although the difference did not reach statistical significance for isoprenaline. The maximum relaxation responses to noradrenaline and isoprenaline were significantly lower in SHR than in normotensive rats, but both strains exhibited similar responses to the partial agonist BRL 37,344. We conclude that factors associated with bladder dysfunction, such as gender, age and hypertension, can be associated with impaired β-adrenoceptor-mediated bladder relaxation. However, these alterations are not always consistent across various agonists, and the extent of the differences can be small. Therefore, we propose that β-adrenoceptor dysfunction may contribute to the pathophysiology of such conditions, but is unlikely to be the only or even the major factor in this regard. We speculate that β-adrenoceptor agonists may be effective in the treatment of bladder dysfunction under all of these conditions.     

The effect of small rotations on R2* measured with echo planar imaging

Several modern MRI techniques, such as functional MRI (fMRI), rely on the detection of microscopic changes in magnetic susceptibility. However, differences in magnetic susceptibility between brain tissue, bone, and air also produce local magnetic field gradients that may interfere with the contrast of interest, particularly at high field strengths. Since the magnetic field distribution depends on the orientation of the human head in the MRI scanner, head rotations can change the effective transverse relaxation rate (R(2)*) and confound fMRI studies. The size of the R(2)* changes produced by small head rotations was estimated from a brain-shaped gel-phantom at 4 T, by measuring the signal decay at 96 different echo times. Similar measurements were carried out in a human study. Rotations larger than 2 degrees changed R(2)* more than 1.5 Hz in the phantom, and indicate that even small rotations may compromise fMRI results.     

Peroxynitrite-induced relaxation in isolated rat aortic rings and mechanisms of action

The present study was designed to evaluate the effects of peroxynitrite (ONOO-), the product of superoxide and nitric oxide, on isolated segments of rat aorta. In the absence of any vasoactive agent, ONOO- (from 10(-8) to 10(-4) M) failed to alter the basal tension. In phenylephrine (PE; 5 x 10(-7) M)-precontracted rat aortic rings (RAR), ONOO- elicited concentration-dependent relaxation at concentrations of from 10(-8) to 10(-4) M. The effective concentrations producing approximately 50% of maximal relaxation (ED50) to ONOO- were 1.84 x 10(-5) M and 1.96 x 10(-5) M in intact and denuded RAR, respectively (P > 0.05). No significant differences in the relaxation responses were found between RAR with or without endothelium (P > 0.05). The presence of either 5 microM methylene blue (MB) or 5 microM 1H-[1,2,4]oxadiazolo-[4,3-alpha]quinoxalin-1-one (ODQ) significantly inhibited the relaxations induced by ONOO-. Sildenafil (10(-7) M), on the other hand, significantly potentiated the ONOO--induced relaxations. Tetraethylammonium chloride (T-2265) significantly decreased the ONOO--induced relaxations in a concentration-dependent manner. However, ONOO- had no effect on RAR precontracted by high KCL (40 mM, n = 6, P > 0.05). Addition of calyculin A also significantly decreased the ONOO--induced relaxation in a dose-dependent manner. Furthermore, ONOO- significantly inhibited calcium-induced contractions of K+-depolarized aortic rings in a concentration-related manner. Lastly, a variety of other pharmacological agents and antagonists including L-NMMA, L-arginine, indomethacin, atropine, naloxone, diphenhydramine, cimetine, glibenclamide, haloperidol, superoxide dismutase (SOD), and catalase did not influence the relaxant effects of ONOO- on RAR. Our new results suggest that ONOO--triggered relaxation on rat aortic rings is mediated by elevation of cGMP levels, membrane hyperpolarization via K+-channel activation, activation of myosin phosphatase activity, and interference with calcium movement and cellular membrane Ca2+ entry.     

The stimulated acoustic relaxation emission of maize starch tablets

Stimulated acoustic relaxation emissions from maize starch tablets after compression were detected and recorded in the audible region. Stimulation was found to enhance the detected acoustic emission and to maintain recordable acoustic emission level longer. Based on the fact, that the stimulation by a halogen lamp and a preheated chamber produced similar results, the effect of stimulation on acoustic relaxation emission is proposed to be connected to the temperature rather than the visible emission. A mathematical model of acoustic activity and its dependence on stimulation temperature is also introduced.     

On the dynamics of memorization processes

Learning can be considered as an optimization problem which is solved either by using a linear programming algorithm or by using a relaxation algorithm. Both approaches appeal to the same hypotheses. The linear programming algorithm has been introduced by Krauth and Mezard. Here we study learning rules based on relaxation algorithms which do not use strict constraints on the norm of efficacies but only boundary constraints. The algorithm comes in the form of an Hebbian rule weighted by a factor which hinders the memorization of already well imprinted patterns. We show that the norm either increases steadily up to its limit if M < 2·N (the Venkatesh limit) or remains finite if M > 2·N. This property allows the system to be never stuck into overcrowding conditions making it reusable for long-term memory even though it used to be overcrowded at a given moment in its history. It also accounts for palimpsest effects. Possible biological implementations are discussed. Finally the algorithm is easily generalized to systems comprising hidden units.     

Controlled Examination of Effects of Progressive Relaxation Training on Seizure Reduction

We determined the efficacy of progressive muscle relaxation in reducing seizure frequency. Subjects were 24 people with epilepsy attending an urban neurology clinic. The experimental design consisted of an 8-week baseline period, a treatment period of six sessions of progressive relaxation training (PRT, n = 13) or quiet sitting (QS, n = 11) and an 8-week follow up. In the PRT group, 11 subjects reported a decrease in seizure frequency (p less than 0.01), and in the QS group, 7 reported a decrease (p greater than 0.05). The mean decrease in seizure frequency was 29% for the PRT group (p less than 0.01) but only 3% for the QS group (p greater than 0.05). This is the fifth recent report of a controlled study documenting the success of progressive relaxation therapy in seizure reduction. PRT is inexpensive and noninvasive and facilitates patient participation. Such a technique should be incorporated into clinical practice.     

Characterization of atherosclerotic plaque components by high resolution quantitative MR and US imaging

High resolution MRI at 3 T and US imaging at 50 MHz were used for atherosclerotic plaque characterization. For 14 excised segments of human arteries, conventional MR and US images, quantitative MR T2 maps, US integrated attenuation (IA) maps, and histologic sections were produced and compared. The MR T2 and US attenuation mean values estimated in selected regions of interest were related with tissue type as identified on histologic sections. Significant distinction between media or collagen and lipid or collagen lipidic plaque was achieved with both techniques (MR: P < .001; US: P < .01). Significant distinction was obtained between media and collagen (P < .0001) and between iliac and aortic media (P < .05) with MR T2 but not with IA. MR and US native and parametric images, with different sensitivities to tissue type, provide complementary information useful for quantitative plaque characterization.     

1-(4-烃氧基)苄基四氢异喹啉类化合物及相关化合物的合成与生物活性

以有心血管活性的异喹啉生物碱为先导物，设计合成了１５个３，４二氢（ＩＩ１，２）和１，２，３，４四氢（４烃氧基）苄基四氢异喹啉化合物（ＩＩ３～１５）。药理实验表明：大部分化合物有舒张血管条作用，其中化合物ＩＩ９对低钾诱导的血管收缩有较强的抑制作用，而对高钾诱导的血管收缩无作用，对硝酸乌头碱诱发的大鼠室性心律失常有明显保护作用。