Simpson's paradox and the analysis of memory retrieval.

According to Simpson's paradox (E. H. Simpson, 1951), if 2 or more contingency tables are collapsed into one, the resulting table may show a relationship between variables different from those shown by any of the original tables. Thus, a positive or negative relationship or stochastic independence may be shown by every component table, but be masked, in the collapsed table, by one of the other characteristics. This paradox has implications for the analysis of memory retrieval, particularly when the focus of interest is the relationship between success and failure on 2 retrieval attempts. Several recent issues in the memory literature are discussed in this connection, with emphasis on confounding effects of S differences, item differences, and S-item interactions. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is there a classification of pelvic ring injuries, which takes the trauma mechanism, morphology and stability relations into consideration and thereby gives references for subsequent therapy?

In contrast to earlier classifications, Tile's classification of pelvic ring disruptions considers mechanism of injury, clinical and x-ray evaluations and is therefore almost universally accepted. We propose a more comprehensive classification which gives a guide for treatment of these complex injuries. Moreover it can be used to compare results from different authors. We classify types A-D pelvic injuries according to stability. Type A consists of fractures of the pelvis not involving the ring, type B of stable rotational injuries. Type C and D encompass the unstabile injuries: C is purely rotational and D has a combined rotational and vertical instability. The location of injury is indicated by adding numbers 1-9 (1: rupture of symphysis pubis; 2: transpubic fracture; 3: acetabular fracture; 4: iliac wing fracture; 5: sacroiliac fracture-dislocation; 6: sacroiliac disruption; 7: sacral wing fracture; 8: transforaminal sacral fracture; 9: central sacral fracture). These numbers are arranged in increasing order, one hemipelvis after the other. Thus, in case of a complex pelvic injury with rotational instability on one side and vertical instability on the other each hemipelvis may be classified separately.     

Mutations in the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) that overcome the inhibitory effect of eIF-2 alpha phosphorylation on translation initiation

Phosphorylation of eIF-2 alpha in Saccharomyces cerevisiae by the protein kinase GCN2 leads to inhibition of general translation initiation and a specific increase in translation of GCN4 mRNA. We isolated mutations in the eIF-2 alpha structural gene that do not affect the growth rate of wild-type yeast but which suppress the toxic effects of eIF-2 alpha hyperphosphorylation catalyzed by mutationally activated forms of GCN2. These eIF-2 alpha mutations also impair translational derepression of GCN4 in strains expressing wild-type GCN2 protein. All four mutations alter single amino acids within 40 residues of the phosphorylation site in eIF-2 alpha; however, three alleles do not decrease the level of eIF-2 alpha phosphorylation. We propose that these mutations alter the interaction between eIF-2 and its recycling factor eukaryotic translation initiation factor 2B (eIF-2B) in a way that diminishes the inhibitory effect of phosphorylated eIF-2 on the essential function of eIF-2B in translation initiation. These mutations may identify a region in eIF-2 alpha that participates directly in a physical interaction with the GCN3 subunit of eIF-2B.     

Mitochondrial tRNALeu isoforms in lung carcinoma cybrid cells containing the np 3243 mtDNA mutation

We have investigated the representation of structural isoforms of the two mitochondrial leucyl tRNAs in lung carcinoma cybrid cell lines containing the np 3243 (MELAS) mtDNA mutation, alone or in combination with the np 12300 suppressor mutation. The mutant tRNALeu(UUR) is aminoacylated very poorly or not at all, whereas the suppressor tRNALeu(CUN) is efficiently aminoacylated. Deacylated mitochondrial tRNALeu(CUN) is present, in all human cells tested, in two structural isoforms that are separable on denaturing gels, indicating a difference in primary structure. The ratio of the two isoforms differs between cell types and is strongly biased towards one isoform in lung carcinoma cybrids containing high levels of the np 3243 mutation, compared with control cybrids. We propose that structural modification of tRNALeu(CUN) could be a natural suppression mechanism for the np 3243 and other mitochondrial tRNALeu(UUR) mutations and could underlie some of the phenotypic variability of np 3243 disease.     

Left-right asymmetry of striatal dopamine D2 receptors

Brain functions may be lateralized to the right or the left hemisphere. However, the biochemical characteristics accompanying these functions are largely unknown. To test possible lateralization of striatal dopamine D2 receptors, we examined 18 volunteers using 123I-iodobenzamide and single photon emission tomography. The striatum-to-cerebellum D2 binding ratio was 1.93 +/- 0.22 (mean +/- S.D.) on the right side and 1.85 +/- 0.19 on the left side. In 14 subjects, D2 binding was higher in the right compared to the left striatum (P < 0.05). These results are supported by a meta-analysis performed on 15 studies reported in the literature. We conclude that side differences of striatal dopamine D2 receptors exist. We propose that motor activity could be responsible for our findings.     

Identification of a conserved hydrophobic cluster in partially folded bovine beta-lactoglobulin at pH 2

BACKGROUND: NMR studies of denatured states, both fully unfolded and partially folded, give insight into the conformations and interactions formed during folding. Although the complete structural characterization of partially folded proteins is a very difficult task, the identification of structured subsets, such as hydrophobic clusters, is of value in understanding the structural organization of such states. Here, we report the NMR characterization, in acidic conditions (pH 2), of a well-defined hydrophobic cluster localized in the core of bovine beta-lactoglobulin. RESULTS: The existence of a small hydrophobic cluster present in the lipocalin protein family has been assessed on the basis of structural alignment and NRM data obtained for the partially folded bovine beta-lactoglobulin. The presence of the cluster had been predicted identifying those residues that are highly conserved in most members of the family. An NMR study conducted at pH 2, where the protein exhibits a very stable beta-core together with disordered regions, reveals the presence of NOEs among sidechains of 11 hydrophobic residues centered around Trp19 and pointing towards the interior of the protein. This buried cluster is found to be unusually stable at pH 2, not only at room temperature but also at 323K. Furthermore, conserved hydrophobic residues pointing towards the surface of the protein define a hydrophobic surface patch located in a groove between the strands and the helix. CONCLUSIONS: The detected buried cluster most likely plays an important role in bovine beta-lactoglobulin stability. The analysis of five structurally related proteins reveals that the same extended cluster is present in these structures. We propose that the buried cluster may represent the internal binding site as well and that the hydrophobic surface patch is involved in a second external binding site.     

The three-dimensional structure of glucose 6-phosphate dehydrogenase from Leuconostoc mesenteroides refined at 2.0 A resolution

BACKGROUND: Glucose 6-phosphate dehydrogenase (G6PD) is the first enzyme of the pentose phosphate pathway. Normally the pathway is synthetic and NADP-dependent, but the Gram-positive bacterium Leuconostoc mesenteroides, which does not have a complete glycolytic pathway, also uses the oxidative enzymes of the pentose phosphate pathway for catabolic reactions, and selects either NAD or NADP depending on the demands for catabolic or anabolic metabolism. RESULTS: The structure of G6PD has been determined and refined to 2.0 A resolution. The enzyme is a dimer, each subunit consisting of two domains. The smaller domain is a classic dinucleotide-binding fold, while the larger one is a new beta+ alpha fold, not previously seen, with a predominantly antiparallel nine-stranded beta-sheet. There are significant structural differences in the coenzyme-binding domains of the two subunits, caused by Pro 149 which is cis in one subunit and trans in the other. CONCLUSIONS: The structure has allowed us to propose the location of the active site and the coenzyme-binding site, and suggests the role of many of the residues conserved between species. We propose that the conserved Arg46 would interact with both the adenine ring and the 2'-phosphate of NADP. Gln47, which is not conserved, may contribute to the change from NADP to dual coenzyme specificity. His178, in a nine-residue peptide conserved for all known sequences, binds a phosphate in the active site pocket. His240 is the most likely candidate for the base to oxidize the 1-hydroxyl group of the glucose 6-phosphate substrate.     

Increase of empty pool-activated Ca2+ influx using an intracellular Ca2+ chelating agent

We demonstrate here that stimulated 45Ca2+ influx in A7r5 vascular smooth muscle cells induced either by receptor activation with [Arg]8 vasopressin or by the SR-Ca(2+)-ATPase inhibitor thapsigargin was increased more than threefold if cells were preloaded with the intracellular calcium chelator BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). The increased influx is probably due to an attenuation of negative feedback of Ca2+ on its own entry accompanied by increased Ca2+ storage capacity of BAPTA-loaded cells leading to diminished cellular Ca2+ release. We propose that BAPTA preloading could be a useful approach to investigate receptor-induced Ca2+ influx.     

Choice of reference axis in ocular wave-front aberration measurement

The geometrical center of the pupil has often been used as the reference axis in ocular wave-front aberration measurement. However, the geometrical center of the pupil may shift when the pupil size changes under different conditions. In particular, for subjective methods, defining the center of the pupil precisely during the actual measurement is not always practical. Furthermore, the geometrical center of the pupil may not define the chief ray of the ocular optics because of the Stiles-Crawford apodization effect, which has a peak location that often deviates from the geometrical center of the pupil. We present the coefficient transformation table of the Taylor polynomial up to the sixth order with respect to reference axis shift. We illustrate the effect of wave-front aberration change with reference axis shift with experimental data. This type of wave-front aberration change could be a true measurement error if there is an error in defining the reference axis. We also propose using the coaxially sighted corneal reflex as a better reference axis in aberration measurement.     

Pathological features of inflammatory bowel disease in childhood

We report on eight children who suffered from cerebrovascular ischemia or stroke at the age of 2 or up to 11 years. Antiphospholipid antibodies (APLA) were detected in two cases during the ischemic event and in six cases during follow-up examinations (after six weeks or within a span of six years). In two patients multiple stenoses of basal cerebral arteries were found; one of them suffered from moyamoya syndrome. The acute hemiplegia in one patient was linked to an asymptomatic mycoplasmal infection and APLA. In three cases, one of the parents was also APLA-positive. Seven patients were treated with acetylsalicylic acid, and in four cases immunoglobulin infusions were given. Transient ischemic attacks subsided after the child with the moyamoya syndrome received immunoglobulins. No effect of medication could be established in the other children. The concept of the antiphospholipid syndrome is still evolving. As none of the common risk factors pertaining to strokes in adults apply to children, pediatric research may offer a suitable platform for specific investigations on the causal, pathogenetic role of APLA. We propose that all children suffering from stroke or transient ischemic attacks should be tested for APLA.     

基于扫描向量的属性约简方法

针对粗糙集理论中属性约简问题,提出了一种基于扫描向量的属性约简方法.根据粗糙集理论知识,定义了一个新概念——差别向量,利用差别向量将信息表转换成差别向量组;根据差别向量的结构特征,定义了差别向量加法法则;运用这个加法法则仅需对差别向量组扫描一次,就可以形成结构简洁却能代表原信息表属性特征的扫描向量.以扫描向量中的属性频率项作为属性约简搜索的启发信息,提高了属性约简效率.数值实例及数据库测试的结果表明该属性约简算法是有效可行的.     

Oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells transformed with c-myc and H-ras form high-grade glioma after stereotactic injection into the rat brain

The oligodendrocyte-type-2 astrocyte lineage (O-2A) comprises a progenitor cell that is able to differentiate into an oligodendrocyte or astrocyte in vitro. The lineage was originally identified in the neonatal rat central nervous system but evidence suggests that the equivalent O-2A lineage also exists in humans. Apart from its putative and widely studied role in glial repair, this cell type could potentially be involved in malignant glioma formation. In this study we demonstrate that a rat O-2A progenitor cell line carrying the bacterial beta-galactosidase reporter gene and transformed with the c-myc and H-ras oncogenes which has lost its differentiation capacity in vitro generates glioma-like growth after stereotactic injection into the adult rat brain. Tumour pathology was similar to human glioblastoma, suggesting that one of the pathways in the generation of human glioblastomas may be the transformation of adult O-2A progenitor cells. Parallel studies demonstrated the presence of a DNA-binding protein complex, termed APprog, in a panel of human glioma cell lines. This protein was initially identified in O-2A progenitor cells and not their differentiated progeny. These data lead us to propose that APprog could be used as an indicator of the lineage origin of gliomas.     

A prospective evaluation of magnetic resonance cholangiopancreatography in patients with suspected bile duct obstruction

The occurrence of mutations in peripheral myelin protein 22 is one of the genetic mechanisms associated with Dejerine-Sottas neuropathy (DSN). On direct sequencing 2 of such patients we have found the first mutation in the third transmembrane domain associated with this neuropathy and the fourth Ser72Leu. We propose that the Ser72 may be a "hot spot" for DSN and that this should be considered for molecular analysis.     

Thoracoscopic surgery of the oesophagus in rats: a training concept for the treatment of tracheo-oesophageal malformations in preterm infants

In extremely preterm babies with type Vogt III b oesophageal atresia, the primary operative management can be restricted to a gastrostomy and ligation of the fistula. Some of these patients, however, may not even tolerate a thoracotomy or placement on the operating table. We developed a minimally invasive procedure to prepare and ligate the oesophagus thoracoscopically and perform laparoscopic gastrostomy in a rat model. In 15 operations we observed only one complication. This study implies that after adequate practice, thoracoscopic dissection of the oesophagus with ligation of a tracheo-oesophageal fistula could be performed even in every small infants.     

Low prevalence of the ret/PTC3r1 rearrangement in a series of papillary thyroid carcinomas presenting in Belarus ten years post-Chernobyl

Many neurosurgeons prefer to use intraoperative computed tomographic (CT) scanning, when possible, to check whether there is residual lesion or unexpected bleeding. We report a practical intraoperative CT imaging system using a high-speed CT scanner installed in the operating room along with a digitally controlled neurosurgical operating table. We designed a rail-track system to mobilize the CT gantry. The gantry is fixed onto a motorized carrier that can be moved smoothly on a rail-track embedded in the floor and with a maximum reach of 2.85 m from the room's wall to the operating table. The longitudinal motion of the operating table is easily adjusted by a foot switch from manual control to automatic control directly from the CT scanner's computer like an ordinary CT scanner bed in increments of 2, 5 or 10 mm during CT scanning. Either a carbon-made radiolucent head frame or carbon-made head plate is used as a headrest. Using this CT scanner system, pre- and intraoperative CT scannings were performed on 46 patients with brain tumors, cervical lesions or other intracranial lesions. We could operate on the patient with enough working space between the mobile CT gantry and the operating table for microneurosurgery. We could obtain intraoperative CT imaging of a patient on the operating table while the surgical wound remained open, the surgical drapes kept in place, and the surgical position unchanged, saving time in intraoperative CT scanning and preparation for further surgery when needed. This intraoperative CT imaging system installed in the operating room should be useful for neurosurgery.     

Identifying the Effects of Soil and Climate Types on Seasonal Variation of Pavement Roughness Using MML Inference

Pavement roughness is a common measure of pavement distress and one regularly measured by road authorities. While permanent pavement deterioration that equates to increased roughness is commonly modeled, cyclical or seasonal variations are often not included. While these variations may be small, they may be important when alternate pavements are compared directly for performance. We propose that seasonal variation may be described by partitioning the data into groups that are modeled as a segmentation problem. We developed a minimum message length (MML) segmentation tree (MMLST) criterion for partitioning and segmentation of the data. We performed simulated comparisons comparing common segmentation criterion (MMLST, maximum likelihood, Akaike information criterion, and Bayesian information criterion) and conclude that MMLST is the preferred criterion. MMLST assists in answering the following questions. First, is the observed segmentation pattern due to seasonal variation or merely random scatter? Second, given evidence of seasonal variation, what type of segmentation pattern should model these trends? Furthermore, does the interaction of climatic and soil conditions appear to affect this variation?     

Bax is an important determinant of chemosensitivity in pediatric tumor cell lines independent of Bcl-2 expression and p53 status

Susceptibility of a tumor cell to undergo chemotherapy-induced apoptosis appears to be dependent upon the balance of proapoptotic and survival factors that are expressed within any given cell. We have chosen to evaluate how expression of several of these proteins influences chemosensitivity of a panel of 10 pediatric tumor cell lines chosen from three tumor histiotypes: neuroblastoma, rhabdomyosarcoma, and pediatric glial tumors. The proteins evaluated were p53 and six members of the Bax/Bcl-2 family: three proapoptotic proteins (Bax, Bak, and Bcl-xS) and three survival factors (Bcl-2, Bcl-xL, and Mcl-1). We investigated whether there was any relationship between endogenous expression of these proteins and chemosensitivity (or resistance) to three chemotherapeutic agents that directly damage DNA (doxorubicin, actinomycin D, and topotecan) and a mitotic spindle poison (vincristine). Even though exogenous overexpression of wild-type p53 has been associated with a chemosensitive phenotype in several model systems we demonstrated no such relationship in these studies. In addition, expression levels of Bcl-2, Bcl-xL, Bcl-xS, Bak, or Mcl-1 did not correlate with sensitivity or resistance to the four drugs. However, there was a statistically significant correlation between endogenous levels of Bax protein and sensitivity to both doxorubicin and actinomycin D. We conclude that even though many proteins such as p53 and Bcl-2 have been shown to influence drug response when exogenously overexpressed in model systems, in unmodified cell lines endogenous protein levels may not generate the same results. We have demonstrated that endogenous Bax expression was the only protein found to be associated with chemosensitivity across the three different tumor histiotypes and propose that analysis of Bax may be a more useful prognostic indicator for tumor response to therapy than either p53 or Bcl-2.