A fast and compact elimination method of empty elements from a double‐array structure

A double‐array is a well‐known data structure to implement the trie. However, the space efficiency of the double‐array degrades with the number of key deletions because the double‐array keeps empty elements produced by the key deletion. This paper presents a fast and compact elimination method of empty elements using properties of the trie nodes that have no siblings. The present elimination method is implemented by C language. From simulation results for large sets of keys, the present elimination method is about 30–330 times faster than the conventional elimination method and maintains high space efficiency. Copyright © 2003 John Wiley & Sons, Ltd.     

Extraction,selection and ranking of Field Association (FA) Terms from domain-specific corpora for building a comprehensive FA terms dictionary

Field Association (FA) Terms—words or phrases that serve to identify document fields are effective in document classification, similar file retrieval and passage retrieval. But the problem lies in the lack of an effective method to extract and select relevant FA Terms to build a comprehensive dictionary of FA Terms. This paper presents a new method to extract, select and rank FA Terms from domain-specific corpora using part-of-speech (POS) pattern rules, corpora comparison and modified tf-idf weighting. Experimental evaluation on 21 fields using 306 MB of domain-specific corpora obtained from English Wikipedia dumps selected up to 2,517 FA Terms (single and compound) per field at precision and recall of 74–97 and 65–98. This is better than the traditional methods. The FA Terms dictionary constructed using this method achieved an average accuracy of 97.6% in identifying the fields of 10,077 test documents collected from Wikipedia, Reuters RCV1 corpus and 20 Newsgroup data set.     

The positional distribution of dioleoyl-palmitoyl glycerol influences lymph chylomicron transport, composition and size in rats

The effects of 1,3-dioleoyl-2-palmitoyl glycerol (OPO) on lymph chylomicron transport, composition and size in rats were investigated in comparison with 1,2-dioleoyl-3-palmitoyl glycerol (OOP). The OPO and OOP were prepared by enzymatic transesterification reactions. The concentrations of OPO and OOP in the preparations were 65.7 g/100 g, and the composition of fatty acids was similar for each. The OPO preparation contained triacylglycerols with 76.6% of the palmitic acid in the sn-2 position, whereas 100% of the oleic acid was esterified to the sn-2 position in the OOP preparation. Rats were infused with lipid emulsion containing 150 g/L of OPO or OOP via a stomach catheter. Lymph was collected through the mesenteric lymphatic trunk at 1-h intervals for 12 h. Collected lymph chylomicrons were analyzed for triacylglycerol, fatty acids, apolipoprotein A-I and particle size. The maximum transport rates of triacylglycerols in the OPO group were higher than those in the OOP group. The overall absorption of triacylglycerols, palmitic acid and oleic acid in the OPO group was also higher than that in the OOP group. In the chylomicrons, 60-70% of the fatty acids at the sn-2 position of the infused triacylglycerol was transported at the original position. The transport rates of dioleoyl-palmitoyl glycerol in the OPO group were higher than those in the OOP group. The transport rates of apolipoprotein A-I did not differ between groups, whereas the mean diameter of the chylomicrons in the OPO group was larger than that in the OOP group. These results indicate that OPO is absorbed and transported more effectively than OOP.     

The KDEL receptor, ERD2, regulates intracellular traffic by recruiting a GTPase-activating protein for ARF1

The small GTPase ADP-ribosylation factor 1 (ARF1) is a key regulator of intracellular membrane traffic. Regulators of ARF1, its GTPase-activating protein (GAP) and its guanine nucleotide exchange factor have been identified recently. However, it remains uncertain whether these regulators drive the GTPase cycle of ARF1 autonomously or whether their activities can be regulated by other proteins. Here, we demonstrate that the intracellular KDEL receptor, ERD2, self-oligomerizes and interacts with ARF1 GAP, and thereby regulates the recruitment of cytosolic ARF1 GAP to membranes. Because ERD2 overexpression enhances the recruitment of GAP to membranes and results in a phenotype that reflects ARF1 inactivation, our findings suggest that ERD2 regulates ARF1 GAP, and thus regulates ARF1-mediated transport.     

Preferential requirement of CD3 zeta-mediated signals for development of immature rather than mature thymocytes

Antigen recognition signals by the TCR are transduced through activation motifs present in the cytoplasmic region of CD3 chains. In vitro analysis has suggested that the CD3zeta chain mediates different signals from other CD3 chains. To analyze the in vivo function of CD3zeta-mediated signals for T cell development, mice expressing a mutant CD3zeta chain lacking all the activation motifs were generated by introducing the transgene into zeta-knockout mice. Mature CD4(+) single-positive (SP) thymocytes in these mice were greater in number than in zeta-deficient mice, and the promoted differentiation was indicated by the changes of CD69 and HSA phenotypes. We found that even in the absence of activation motifs in CD3zeta, these mature cells became functional, being able to induce Ca2+ mobilization and proliferation upon stimulation. On the other hand, CD4(-)CD8(-) double-negative (DN) thymocytes, most of which were arrested at the CD44(-)CD25(+) stage similarly to those in zeta-deficient mice, could not be promoted for differentiation into CD4(+)CD8(+) double-positive thymocytes in these mice in spite of the fact that the expression of the transgene in DN thymocytes was higher than that of zeta in wild-type mice. These results demonstrate the preferential dependence of the promotion of development and/or expansion of DN thymocytes rather than mature thymocytes upon the activation signals through the zeta chain and suggest differential requirements of TCR signaling for mature SP and immature DN thymocyte developments in vivo.     

Lung preservation with low-potassium dextran flush in a primate bilateral transplant model

We used a bilateral lung transplant model to confirm, in primates, the results of lung preservation studies previously obtained in a canine single-lung transplant model. The donor lungs were flushed with low-potassium dextran solution and maintained semiinflated with 100% oxygen at 10 degrees C for a planned ischemic time of 12 hours for the lung implanted first. Of eight experiments performed, results in the 6 operative survivors form the basis of this report. After bilateral lung transplantation, animals were maintained on a ventilator for 6 hours; arterial oxygen tension, pulmonary artery pressure, and pulmonary vascular resistance were determined in the recipients at 2, 4, and 6 hours after transplantation and compared with donor values, which served as controls. Arterial oxygen tension in the recipients did not differ from the controls (p = not significant), whereas the pulmonary artery pressure and pulmonary vascular resistance showed significant elevation (p < 0.05 versus control values). After the 6 hours of assessment, the animals were extubated and 3 survived for 48 to 72 hours with a mean arterial oxygen tension of 69 mm Hg on room air. These results demonstrate excellent lung function after a minimum of 12 hours of preservation in a primate model in which the animal is totally dependent on the function of transplanted lung tissue, and confirm the potential for prolonged clinical lung preservation.     

A method of compressing trie structures

A trie structure can immediately determine whether a desired key is in a given key set or not, and can find its longest match easily. Thanks to these attractive properties, a trie structure is frequently used for various fields, such as natural language dictionaries, database systems and compilers. However, the total number of states of a trie becomes large, so space requirements are not good for a huge key set. To resolve this disadvantage a new structure which reduces the total number of states in a traditional trie, called a double-trie, is introduced in this paper. Insertion and deletion operations, as well as key retrieval for this double-trie, are presented. The efficiency of this method is shown by the results of simulations for various key sets.     

An efficient implementation of trie structures

A new internal array structure, called a double-array, implementing a trie structure is presented. The double-array combines the fast access of a matrix form with the compactness of a list form. The algorithms for retrieval, insertion and deletion are introduced through examples. Although insertion is rather slow, it is still practical, and both the deletion and the retrieval time can be improved from the list form. From the comparison with the list for various large sets of keys, it is shown that the size of the double-array can be about 17 per cent smaller than that of the list, and that the retrieval speed of the double-array can be from 3–1 to 5–1 times faster than that of the list.     

Towards immuno-modulation through the molecular mechanism of lymphocyte activation

Recognition of the antigen/MHC complex by the T cell receptor (TCR)-CD3 complex in T cells triggers early activation events such as tyrosine phosphorylation, phosphatidylinositol turnover, intracellular Ca2+ mobilization or activation of protein kinases, and finally exhibits effector functions such as lymphokine secretion by helper T cells or cytotoxicity by killer T cells as late activation events. Several key molecules have been shown to engage in these signaling cascades. In addition to the TCR-CD3 molecules, other surface molecules such as CD28 or LFA-1 contribute to the regulation of T cell activation as a co-stimulator. Growing knowledge about the downstream of antigen recognition is promoting the attempt to modulate the signal transduction by specific drugs, mAbs, altered peptides or cytokines. Further investigations on the molecular mechanism of T cell activation will provide clinical successes to control immune responses.