k-tree method for high-speed spatial normalization

The general approach to spatial normalization using a deformation field is presented. Current high degree-of-freedom deformation methods are extremely time-consuming (10-40 hr), and a k-tree method is proposed to greatly reduce this time. A general k-tree method for analysis of source and target images and synthesis of deformation fields is described. The k-tree method simplifies scale control and feature extraction and matching, making it highly efficient. A two-dimensional (2-D), or quadtree, application program was developed for preliminary testing. The k-tree method was evaluated with 2-D images to test rotating ability, nonhomologous region matching, inner and outer brain-structure independence, and feasibility with human brain images. The results of these tests indicate that a three-dimensional (3-D), or octree, method is feasible. Preliminary work with an octree application program indicates that a processing time of under 10 min for 256(3) image arrays is attainable on a Sun Ultra30 workstation.     

Interactions of the components of the prothrombinase complex

1. Acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) of house-fly head tissue was solubilized as a 7.4-S form by autolysis for 80-100 h at 25 degrees C and pH 8.0. 2. The autolysed enzyme was purified by affinity chromatography, firstly on Con-A-Sepharose and subsequently on m-trimethylammoniumaniline-Affi-Gel 202. This sequence permitted overall purification yields of approx. 50% of the solubilized enzyme. 3. The 7.4-S purified enzyme was essentially homogeneous on polyacrylamide gel electrophoresis, and its specific activity coincided with the highest previously reported for fly-head acetylcholinesterase. 4. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate and beta-mercaptoethanol revealed two major polypeptide components of molecular weight 82 000 and 59 000. Each of these polypeptides contained diisopropylphosphofluoridate-binding sites, as shown with [3H] diisopropylphosphofluoridate. 5. The results suggest a strong structural similarity between fly-head acetylcholinesterase and the purified electric eel enzyme.     

Role of the pituitary gland in adaption of the fish Tilapia mossambica (Peters) to contrasting backgrounds

The fish Tilapia mossambica were exposed for 30 days to continuously illuminated black or white backgrounds. When compared with the controls the black-adapted fish showed multiplication of the melanophores with a maximal dispersion of the melanosomes. The white background induced blanching of the fish because of depletion of the melanophores and aggregation of the melanosomes. The treatment evoked major changes in the pars intermedia cells. Of these, the amphiphils were stimulated in the black-adapted and regressed in the white-adapted fish indicating that these cells secrete melanophore stimulating hormone. The cyanophils showed depressed activity in the black-adapted fish, but in the white-adapted animals they were stimulated. These alterations suggest the elaboration of a melanophore concentrating hormone by the cyanophils. Regressive effects were also recorded in the gonadotrops and gonads of the experimental T. mossambica.     

Experimental evaluation of three single-particle dissolution models

The dissolution of the 60-85-mesh fraction os recording, flow-through dissolution apparatus equipped with a dissolution cell; it was particularly suitable for kinetic analysis of multiparticulate systems. By using a time-scaling approach, experimental data are compared with theoretical calculations to evaluate, quantitatively, which of three single-particle dissolution models best describes the data and how well the multiparticulate kinetics can be explained mathematically. The nonspherical tolbutamide particles are replaced in the calculations by a hypothetical system of spherical particles that appears to be log-normally distributed. This procedure permits the calculation of the intrinsic dissolution profile, considering both size distribution and particle shape effects.     

异味掩盖剂的研究理论与应用

<正> 在食品的生产过程中,人造甜味剂的使用可能给某些产品带来苦味或不良后味,防腐剂如山梨酸盐和苯甲酸盐的添加也可能导致苦味的出现;此外,过度处理产品或使用营养疗效添加剂和咖啡因也可能引致其他异味的出现。这些异味可能是很突出的。食物的苦味可能来源于天然存在的苦味化合物,或由于保存及加工处理中发生的化学反应所致。因此,异味掩盖剂的开发一直是行业的重点研究课题。     

Reduced stretch-reflex sensitivity after exhausting stretch-shortening cycle exercise

The stretch-shortening cycle (SSC) is an effective and natural form of muscle function but, when repeated with sufficient intensity or duration, it may lead to muscle damage and functional defects. A reduced tolerance to impact has been reported, which may be partly attributed to a reduced stretch-reflex potentiation. The aim of the present study was to examine the influence of SSC-induced metabolic fatigue and muscle damage on the efficacy of stretch reflexes, as judged by the electromyograph (EMG) response of two shank muscles (lateral gastrocnemius LG, soleus SOL) to controlled ramp stretches. These EMG responses were recorded before and immediately after exhausting SSC-type leg exercise and 2 h, 2 days and 4 days later. Serum concentrations of creatine kinase ([CK]), myoglobin and lactate were measured repetitively along the protocol. Two maximal vertical drop jumps and counter-movement jumps were performed after each reflex test. The exhausting SSC-type exercise induced an immediate reduction (P < 0.05) with a delayed short-term recovery of the LG peak-to-peak reflex amplitude. This was not accompanied by significant changes in the reflex latency. The drop jump performance remained slightly but significantly reduced (P < 0.05) until the 2nd day postexercise. Peak [CK] appeared for all the subjects on the 2nd day, suggesting the presence of muscle damage. The increase in [CK] between the 2nd h and the 2nd day postexercise was found to be negatively related (P < 0.001) to the relative changes in the drop jump height. Furthermore, a significant relationship (P < 0.05) was found between recovery of the stretch reflex in LG and the decrease of [CK] between the 2nd and the 4th day. These findings support the hypothesis of a reduced stretch-reflex sensitivity. While the exact mechanisms of the reflex inhibition remain unclear, it is emphasized that the delayed recovery of the reflex sensitivity could have resulted from the progressive inflammation that develops in cases of muscle damage.     

Analytic treatment of resolution precision in electronically collimated SPECT imaging involving multiple-interaction gamma rays

The widely applied single-interaction analytic expression characterizing the energy resolution component of the angular resolution precision for an electronically collimated point source is extended to include multiple-interaction Compton scatter sequences as well as sequences terminated by photoelectric absorption. The analytic formulation is developed using the statistical variance of the mean for components comprising composite, multivariate resolution precision estimators. It is demonstrated that enhanced resolution precision in the incident interaction scatter angle is attained when use is made of information from multiple interactions. An improvement in the resolution precision of up to approximately 40% is observed for triple Compton scatter. Comparison of the analytic estimates with Monte Carlo/chi-square results shows good agreement.