Structure-function relationships underlying calculation: a combined diffusion tensor imaging and fMRI study.

Both neuropsychological and functional neuroimaging studies have identified brain regions that are critical for the neurocognitive processes related to the calculation of arithmetic problems. In particular, the left angular gyrus (lAG) has been repeatedly implicated in arithmetic problem solving and found to be most activated during the retrieval of arithmetic facts. While significant progress has been made in determining the functional role of specific grey matter areas underlying calculation, very little is known about the relationship between these activated regions and their underlying white matter structures. In this study, we collected both diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) data while participants performed a mental arithmetic task. Fractional anisotropy (FA) values were extracted from predefined, hypothesis-driven, white matter regions and correlated with fMRI activation values, which were extracted from anatomically defined grey matter regions. Results indicated structure-function relationships on multiple levels. Specifically, a link between the integrity of the left superior corona radiata (SCR) and neural activity in the lAG during calculation was observed, which was found to be particularly strong for problems that have a high probability of being solved via the retrieval of arithmetic facts (problems with a relatively small problem size). The findings reported provide a link between functional activation and structural integrity of grey and white matter regions in the left temporoparietal cortex, thereby contributing to our understanding of the role of both the function and structure of this brain region in calculation.

EEG alpha band dissociation with increasing task demands.

In assuming functional differences between different EEG alpha frequency bands, recent studies emphasize the importance of using narrow (8-10 Hz or 10-12 Hz) instead of broad alpha frequency ranges (8-12 Hz). Due to individual differences in alpha activity, it has also been suggested to adjust alpha frequency bands individually for each participant. The present paper highlights the dissociating role of different task demands on the extent of event-related desynchronization (ERD) in different alpha frequency bands. In analyzing the data of four large-scale EEG studies (with sample sizes of 51, 58, 55, and 66, respectively) employing a wide range of cognitive tasks, we found evidence that the correlations between lower and upper alpha band ERD systematically decline as task demands increase.

Extraversion and cortical activation during memory performance.

In this study we analyzed the influence of the personality dimension extraversion-introversion (E) on the level and topographical distribution of cortical activation. In 62 participants (32 introverts and 30 extraverts), we measured the extent of Event-Related Desynchronization (ERD) in the EEG during performance of a short-term memory (i.e., temporary maintenance of information) and a more complex working memory task (i.e., temporary maintenance and active manipulation of information). The results indicate that during performance of both tasks, introverts display a larger amount of ERD than extraverted individuals. Moreover, the present E effects largely match previous studies as to the restriction of these effects to lower EEG frequency ranges (approx. 4-8 Hz). Topographical analyses show that the E effects are primarily present over (right-hemispheric) frontal and parietal regions of the cerebral cortex.

Intelligence and working memory systems: evidence of neural efficiency in alpha band ERD.

Starting from the well-established finding that brighter individuals display a more efficient brain function when performing cognitive tasks (i.e., neural efficiency), we investigated the relationship between intelligence and cortical activation in the context of working memory (WM) tasks. Fifty-five male (n=28) and female (n=27) participants worked on (1) a classical forward digit span task demanding only short-term memory (STM), (2) an attention-switching task drawing on the central executive (CE) of WM and (3) a WM task involving both STM storage and CE processes. During performance of these three types of tasks, cortical activation was quantified by the extent of Event-Related Desynchronization (ERD) in the alpha band of the human EEG. Correlational analyses revealed associations between the amount of ERD in the upper alpha band and intelligence in several brain regions. In all tasks, the males were more likely to display the negative intelligence-cortical activation relationship. Furthermore, stronger associations between ERD and intelligence were found for fluid rather than crystallized intelligence. Analyses also point to topographical differences in neural efficiency depending on sex, task type and the associated cognitive subsystems engaged during task performance.

Cytogenetic detection of a trans-species bystander effect: induction of sister chromatid exchanges in murine 3T3 cells by ganciclovir metabolized in HSV thymidine kinase gene-transfected Chinese hamster ovary cells.

Due to the very limited transduction capacity of hitherto available vectors, the success of gene therapy of tumours by means of suicide genes has so far essentially depended on the transfer of toxic drug metabolites from transduced (metabolizing) cells to adjacent non-transduced cells via gap junctions (bystander effect). Most experimental systems for the detection of a bystander effect yield net data of cell losses and cannot differentiate between killed transduced versus killed bystander cells. Here we report on metabolic cooperation in vitro between CHO cells stably transfected with the thymidine kinase gene of herpes simplex virus type-1 (HSVtk) (metabolizing cells) and Swiss albino 3T3 cells (bystander cells). Both cell lines are readily distinguishable by single cell and colony morphology and by their chromosomal constitution. While 3T3 cells cultured alone were refractory to the antiviral drug ganciclovir (GCV), co-culture with CHO-HSVtk(+) cells led to a dramatic reduction in plating efficiency as well as to a 4-fold increase in sister chromatid exchange rates induced by very low GCV concentrations in the 3T3 bystander cells. The modulator of gap junctional cooperation, all-trans retinoic acid, caused a strong augmentation of the bystander effect, while 18alpha-glycyrrhetinic acid, an inhibitor of gap junctional communication, drastically diminished the toxicity of GCV in the bystander cells. Whereas CHO-HSVtk(+) cells showed a distinct immunoreactivity for connexin43 in the cell membranes, 3T3 cells were almost negative. The co-culture system described here allows unequivocal distinction between metabolizing and bystander cells. In this way, mechanistic aspects of the transfer of genotoxic/cytotoxic metabolites to cells, which per se are unable to form them, become accessible to investigation.

Sensitivity of human EEG alpha band desynchronization to different working memory components and increasing levels of memory load.

Event-related alpha band desynchronization is frequently used to analyze spatiotemporal cortical activation patterns during the performance of cognitive tasks. In the present paper the sensitivity of alpha band desynchronization to increasing levels of cognitive load and to different cognitive working memory components is investigated. A 27-channel electroencephalogram of 62 participants while solving (a) a short-term memory and (b) a working memory task (dual task), each with five levels of memory load, was analyzed. We found (a) a linearly increasing desynchronization in the upper alpha band with ascending cognitive load, and (b) evidence of the involvement of distinguishable cognitive components (storage and controlled attention) in the memory tasks.

Atomic-precision multilayer coating of the first set of optics for an extreme-ultraviolet lithography prototype system.

We present our results of coating a first set of optical elements for an extreme-ultraviolet (EUV) lithography system. The optics were coated with Mo-Si multilayer mirrors by dc magnetron sputtering and characterized by synchrotron radiation. Near-normal incidence reflectances above 65% were achieved at 13.35 nm. The run-to-run reproducibility of the reflectance peak wavelength was maintained to within 0.4%, and the thickness uniformity (or gradient) was controlled to within +/-0.05% peak to valley, exceeding the prescribed specification. The deposition technique used for this study is an enabling technology for EUV lithography, making it possible to fabricate multilayer-coated optics to accuracies commensurate with atomic dimensions.

Hypochlorite-modified low density lipoprotein inhibits nitric oxide synthesis in endothelial cells via an intracellular dislocalization of endothelial nitric-oxide synthase.

Hypochlorous acid/hypochlorite, generated by the myeloperoxidase/H(2)O(2)/halide system of activated phagocytes, has been shown to oxidize/modify low density lipoprotein (LDL) in vitro and may be involved in the formation of atherogenic lipoproteins in vivo. Accordingly, hypochlorite-modified (lipo)proteins have been detected in human atherosclerotic lesions where they colocalize with macrophages and endothelial cells. The present study investigates the influence of hypochlorite-modified LDL on endothelial synthesis of nitric oxide (NO) measured as formation of citrulline (coproduct of NO) and cGMP (product of the NO-activated soluble guanylate cyclase) upon cell stimulation with thrombin or ionomycin. Pretreatment of human umbilical vein endothelial cells with hypochlorite-modified LDL led to a time- and concentration-dependent inhibition of agonist-induced citrulline and cGMP synthesis compared with preincubation of cells with native LDL. This inhibition was neither due to a decreased expression of endothelial NO synthase (eNOS) nor to a deficiency of its cofactor tetrahydrobiopterin. Likewise, the uptake of l-arginine, the substrate of eNOS, into the cells was not affected. Hypochlorite-modified LDL caused remarkable changes of intracellular eNOS distribution including translocation from the plasma membrane and disintegration of the Golgi location without altering myristoylation or palmitoylation of the enzyme. In contrast, cyclodextrin known to deplete plasma membrane of cholesterol and to disrupt caveolae induced only a disappearance of eNOS from the plasma membrane that was not associated with decreased agonist-induced citrulline and cGMP formation. The present findings suggest that mislocalization of NOS accounts for the reduced NO formation in human umbilical vein endothelial cells treated with hypochlorite-modified LDL and point to an important role of Golgi-located NOS in these processes. We conclude that inhibition of NO synthesis by hypochlorite-modified LDL may be an important mechanism in the development of endothelial dysfunction and early pathogenesis of atherosclerosis.

Flow cytometric determination of E-selectin, vascular cell adhesion molecule-1, and intercellular cell adhesion molecule-1 in formaldehyde-fixed endothelial cell monolayers.

BACKGROUND: Endothelial cell adhesion molecules are involved in initiation and progression of vascular diseases. The purpose of this study was to determine conditions of fixation and dissociation of human umbilical vein endothelial cell (HUVEC) monolayers that permit a reliable flow cytometric determination of intracellular and surface content of E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1). METHODS: TNFalpha-treated HUVEC monolayers were fixed with 0.5% formaldehyde at the end of the experimental incubation. Subsequently, either the monolayer was trypsinized and thereafter the cells were subjected to indirect fluorescence labeling or the monolayer was first labeled and then dissociated by trypsinization. Cell integrity was assessed by vimentin staining. Total adhesion molecule content was detected in saponin-permeabilized cells. RESULTS: HUVEC integrity was maintained when the fixation time of the monolayer did not exceed 5 min and trypsin/EDTA was used for dissociation. Surface adhesion molecules were partially hydrolyzed by trypsin when trypsinization preceded labeling but antibody binding protected adhesion molecules from degradation. VCAM-1 and E-selectin exhibited substantial trypsin-sensitive surface fractions but surface ICAM-1 was mainly trypsin resistant. Permeabilization with 0.06% saponin allowed the detection of considerable intracellular pools of the investigated adhesion molecules. CONCLUSIONS: The described method permits the reliable determination of surface and intracellular fractions of adhesion molecules in formaldehyde-fixed HUVEC monolayers and may be used for studies on the regulation of adhesion molecule expression.

Nitric oxide inhibits proliferation of human endothelial cells via a mechanism independent of cGMP.

Endothelial cell-derived nitric oxide (NO) has been suggested to inhibit smooth muscle cell proliferation, resulting in the reduction of intimal hyperplasia during atherogenesis. The present study investigates the role of NO from exogenous and endogenous sources on the proliferation of human umbilical vein endothelial cells (HUVEC) and human coronary artery endothelial cells (CAEC). Three different NO-generating compounds [sodium nitroprusside (SNP), S-nitroso-glutathione (GSNO) and S-nitroso-acetylpenicillamine (SNAP)] were found to inhibit endothelial cell proliferation measured with three independent methods (cell counting, [3H]thymidine incorporation, DNA histograms) with significant inhibition occurring at concentrations > or = 100 microM. Growth-inhibiting effects were observed after long-term treatment (18-96 h) as well as after short stimulation with NO donors (10 min with a subsequent NO donor-free culture period of 18 h) and were comparable in culture medium (20% serum, growth factor supplementation) and serum-deficient medium (1% serum). The NO donor effects were mediated by the release of NO as they were prevented by NO scavenging. Superoxide dismutase (SOD) was found not to interfere with these effects suggesting that peroxynitrite formation was unlikely to be involved. 1H-[l,2,4]Oxadiazolo[4,3,-alpha]quinoxalin-1-one (ODQ), a specific inhibitor of the soluble guanylate cyclase, was observed not to alter the antiproliferative effects of NO donors although it completely prevented NO-mediated increase of cyclic guanosine 3',5'-monophosphate (cGMP), suggesting that the NO-induced growth inhibition was not mediated by cGMP. Furthermore, inhibition of endogenous NO production by N-nitro-L-arginine methylester (L-NAME) did not affect endothelial cell growth regardless of using serum plus growth factor supplement, growth factor supplement alone, or thrombin to stimulate proliferation. We suggest that constitutively synthesized NO may not regulate endothelial cell proliferation whereas the growth-inhibiting NO effects may occur when an inducible NO synthase associated with a persistently high NO production is expressed in the atherosclerotic vessel wall.

L-Ascorbic acid potentiates nitric oxide synthesis in endothelial cells.

Ascorbic acid has been shown to enhance impaired endothelium-dependent vasodilation in patients with atherosclerosis by a mechanism that is thought to involve protection of nitric oxide (NO) from inactivation by free oxygen radicals. The present study in human endothelial cells from umbilical veins and coronary arteries investigates whether L-ascorbic acid additionally affects cellular NO synthesis. Endothelial cells were incubated for 24 h with 0.1-100 microM ascorbic acid and were subsequently stimulated for 15 min with ionomycin (2 microM) or thrombin (1 unit/ml) in the absence of extracellular ascorbate. Ascorbate pretreatment led to a 3-fold increase of the cellular production of NO measured as the formation of its co-product citrulline and as the accumulation of its effector molecule cGMP. The effect was saturated at 100 microM and followed a similar kinetics as seen for the uptake of ascorbate into the cells. The investigation of the precursor molecule L-gulonolactone and of different ascorbic acid derivatives suggests that the enediol structure of ascorbate is essential for its effect on NO synthesis. Ascorbic acid did not induce the expression of the NO synthase (NOS) protein nor enhance the uptake of the NOS substrate L-arginine into endothelial cells. The ascorbic acid effect was minimal when the citrulline formation was measured in cell lysates from ascorbate-pretreated cells in the presence of known cofactors for NOS activity. However, when the cofactor tetrahydrobiopterin was omitted from the assay, a similar potentiating effect of ascorbate pretreatment as seen in intact cells was demonstrated, suggesting that ascorbic acid may either enhance the availability of tetrahydrobiopterin or increase its affinity for the endothelial NOS. Our data suggest that intracellular ascorbic acid enhances NO synthesis in endothelial cells and that this may explain, in part, the beneficial vascular effects of ascorbic acid.

Phagocytosis of surfactant by alveolar macrophages in vitro.

Because of their localization and function as phagocytes, alveolar macrophages could take part in the catabolism of surfactant, including surfactants used for treatment. Conditions of the ingestion of the surfactant preparation AWD 56-02 by alveolar macrophages in vitro are described in this paper. The surfactant was labeled with rhodaminyl phosphatidylethanolamine and incubated with alveolar macrophages lavaged from rat lungs. Membrane binding and phagocytosis were evaluated by fluorescence microscopy and quantified fluorimetrically after extraction of the dye. The surfactant was phagocytosed only in the presence of rat serum. The opsonins in the serum are related to complement and Fc receptors as demonstrated by the heat lability of the factor and the inhibition by aggregated gamma-globulins. Furthermore, the phagocytosis depends on calcium and on a factor in the surfactant preparation. Experiments with inhibitors and competition with unlabeled surfactant show that the phagocytosis is a specific and energy-dependent process. Catabolism by alveolar macrophages might be an important step in the metabolism of surfactant, especially when administered in pathological conditions characterized by the presence of serum in the airspaces.

Influence of cationic amphiphilic drugs on the phosphatidylcholine hydrolysis by phospholipase A2.

On chronic treatment certain amphiphilic drugs induce a generalized phospholipidosis. This drug side effect has been related to an inhibition of the lysosomal phospholipases due to the interaction of the drugs with phospholipids (PL). In the present experiments, the influence of the amphiphilic drugs ambroxol, imipramine, chloroquine and chlorphentermine on the hydrolysis of dipalmitoyl-phosphatidylcholine (DPPC) unilamellar liposomes by bee venom phospholipase A2 (PLase A2) was studied. Special emphasis was laid on the initial phase and temperature dependence. The activity of PLase A2 was measured continuously with a spectrophotometric assay using cresol red as indicator. In most cases a lag-phase of different duration was observed before the enzyme exhibited its full activity. The duration of the lag-phase and the rate of hydrolysis in the second phase are inversely related. The temperature dependence of the hydrolysis reveals a maximum of activity near the phase transition of the bilayer and a gradually decreasing activity at lower and higher temperatures, respectively. The analysis of the influence of amphiphilic drugs reveals three types of interaction. Imipramine and ambroxol shift the temperature activity profile towards lower temperatures without a substantial influence on the shape of the profile and on the maximal rate of hydrolysis. Chloroquine inhibits the enzyme activity without any temperature dependence. Chlorphentermine, the classical lipidosis inducing drug, exhibits a third type of interaction which seems to be a combination of the two former types.

Influence of imipramine and chloroquine on lung phospholipid content and lung structure in newborn rats.

In continuation of previous experiments in adult rats the alteration in content and composition of lung phospholipids (PL) and lung structure of newborn rats of different gestational age was studied after three administrations of the amphiphilic drugs imipramine (75 mg/kg b.w.) and chloroquine (50 mg/kg b.w.). The fetuses were obtained by Cesarean section on day 20, 21, or 22 of gestation. Morphological examinations of the lungs of drug treated 21-day-old fetuses revealed a substantially better aeration than nontreated controls. 20 and 22 days old fetuses showed no differences in aeration between drug and saline treated rats. Analogous results were obtained with respect to the 1 h survival rate of newborns. Furthermore, imipramine and chloroquine cause a premature development of the pneumocytes type II as shown by electron microscopy. An increased PL content as well as disaturated phosphatidylcholine (DSPC) and phosphatidylglycerol (PG) proportion of fetal lungs, especially in animals born on day 21 of gestation, were found after drug treatment. The results suggest an acceleration of maturation of the pneumocytes type II in fetal lungs induced by amphiphilic drugs.

Acetylcholinesterase activities in association with congenital malformation of the terminal ureter in infants and children.

Acetylcholinesterase activity was found to be higher than normal in intravesical segments of ureters taken from children with vesicoureteral reflux. The ratio of acetylcholinesterase activity to total cholinesterase activity was also found to be high. Acetylcholinesterase activity was normal in intravesical segments taken from the constricted area of ureters from children with obstructive megaureter but it was high in segments taken from the juxtavesical part, immediately adjacent to the constricted area. These findings complement histological studies which have revealed a hyperplasia of cholinergic nerve fibres in the tunica muscularis of reflux ureters whereas obstructive megaureters show a hypoplasia of the beta-adrenergic system.

Incorporation in liposomes as a method for the application of genotoxins of low water solubility in the SCE assay.

Benzo[alpha]pyrene BaP), freely dissolved or incorporated in liposomes prepared from egg yolk lecithin, was checked for SCE induction in Chinese hamster V79-E and rat liver RL-19 cells in vitro. SCE induction in V79-E was observed only when freely dissolved BaP was added together with S9 mix. RL-19 cells were per se highly sensitive to SCE induction by BaP either freely dissolved or incorporated in liposomes. It is suggested that the incorporation of genotoxins in liposomes is a practicable method for the application, in mammalian genotoxicity assays, of agents which are barely soluble or completely insoluble in water, provided no exogenous metabolizing system is required.

Effect of sucralfate on peptic ulcer recurrence: a controlled double-blind multicenter study.

We entered 174 patients with healed duodenal ulcer and 77 with healed gastric ulcer into a double-blind, placebo-controlled, 6-month trial to investigate the efficacy of 1 g sucralfate twice daily in preventing ulcer recurrence. Endoscopy was performed after 6 months or earlier for symptoms compatible with ulcer disease. The relapse rate in the 126 patients with duodenal ulcer who could be evaluated for efficacy was 14/66 (21.2%) under sucralfate and 30/60 (50%) under placebo treatment (p less than 0.01). No significant difference in relapse rate was found in the 55 gastric ulcer patients who could be evaluated; 11 of 30 (37%) relapsed on sucralfate and 11 of 25 (44%) relapsed on placebo. Among the duodenal ulcer patients in the placebo group, those who had been treated initially with H2-receptor blockers for acute ulcer had significantly more relapses than patients who had been treated with other drugs. The recurrence rate was independent of prior treatment in the sucralfate group. Duodenal ulcer patients with a history of multiple episodes of active ulcer disease had a significantly higher rate of relapse than patients with only a few previous episodes. Both treatments were well tolerated. Two patients in each treatment group complained of nausea and epigastric pain immediately after drug intake. No other drug-related symptoms were observed. We conclude that sucralfate is effective in the prophylaxis of duodenal ulcer. No significant effect was found in the prevention of gastric ulcer recurrence.(ABSTRACT TRUNCATED AT 250 WORDS)

Imipramine and chloroquine induced alterations in phospholipid content of rat lung.

The influence of the amphiphilic drugs imipramine (150 mg/kg b. w./day) and chloroquine (75 mg/kg b. w./day) on the phospholipid (PL) -metabolism of rat lung, its PL-content and PL-composition were measured in the cell free lung lavage fluid (alveolar surfactant), in the free alveolar cells (mainly alveolar macrophages), and in the residual lung tissue. In addition to the long-term administration (15 applications during a period of 3 weeks), the influence of short-term administration (2 or 4 applications, resp., during a period of 2 or 4 days) was examined. The alveolar macrophages show the largest increase in PL-content. As revealed by its composition the stored PL are of surfactant origin. In chloroquine treated rats the number of macrophages is increased as well. The concentration of stored PL is higher in macrophages of imipramine treated rats. The excessive accumulation of PL in this animal group possibly impairs the clearance function of alveolar macrophages. This is suggested to be the reason for the accumulation of alveolar surfactant in imipramine treated rats. The influence of the drugs on the PL-content of the residual lung tissue was weak. The results of this study show that amphiphilic drugs cause an accumulation of surfactant-PL within the alveolar macrophages and can promote the alveolar surfactant content even after short-term application. The role of alveolar macrophages in alveolar surfactant catabolism is demonstrated.

[A comparative morphological and chemical study of the ambroxol and chlorphentermine action on the lung phospholipid content (author's transl)]. / Vergleichende morphologische und chemische Untersuchungen zur Wirkung von Ambroxol und Chlorphentermin auf den Phospholipidgehalt der Lunge.

The influence of chronic administration of ambroxol on the phospholipid-(PL-) content and ultrastructure of lungs has been studied and compared with the effect of chlorphentermine (chlph.). Both drugs are amphiphilic substances. The causative factor of the well-known chlph. induced phospholipidosis-like alterations was suggested to be an inhibition of enzymatic degradation of PL. Rats were intraperitoneally treated five times per week for two weeks with chlph. (0,2 mMol per kg b.w.) and ambroxol (0.2 mMol per kg b.w.), respectively. Lung, heart, liver, kidney and spleen were light microscopically examined, and the lung was studied by electron microscopy. Furthermore, the PL-content of the whole lung tissue, the proportion of phosphatidylcholine (PC), the lung weight/body weight ratio (LM/KM) as well as the dry weight/wet weight ratio (TM/FM) of the lung was calculated. The application of chlph, induced an excessive PL-storage in the lung as indicated by an increase of the PL-content, of the PC-proportion as well as of the LM/KM and TM/FM ratio. The accumulated PL are detectable by electron microscopy, mainly in the lysosomes of macrophages appearing as lamellar or crystalloid inclusions. On the contrary, chronic application of ambroxol does not cause any substantial changes especially no abnormal lysosomal PL-inclusions. Therefore, it is suggested that ambroxol does not interfere with the PL-metabolism in a way comparable to that of the chlph. action.

[Liver alterations in newborn rabbits after maternal thrombin shock (author's transl)]. / Morphologische Leberveränderungen bei neugeborenen Kaninchen nach thrombininduziertem Schock der Muttertiere.

Intrauterine asphyxia has been induced in immature and mature newborn rabbits by means of experimental shock of the pregnant doe. Typical changes of clotting parameters and morphological alterations in different organs specific for shock were used as criteria of the maternal shock. For the detection of asphyxia conditioned neonatal organ lesions, liver, lung, kidney and heart muscle were studied light microscopically. Special attention was devoted to liver alterations, i.e. changes of hepatocyte structure, glycogen content and microcirculation disturbances as well as to alterations of the hematopoietic system. The asphyxia related effects were vacuolic degeneration of hepatocytes, centroacinar hyperemia and persistence of hematopoietic cells in the neonatal liver. The alterations of the hepatocytes as well as of the hematopoietic system were more conspicuous in mature then in immature asphyxiated rabbits. On the contrary, the microcirculatory changes are similar in both animal groups.