Global/local processing and negative priming: the influence of selection difficulty and stimulus exposure.

Negative priming is a decrement in performance observed when a previously ignored stimulus is re-presented as a target. The present study examined the relation between selection difficulty and negative priming in five experiments that used hierarchical stimuli (large letters made up by small letters). The results show that negative priming is greater when subjects direct attention to the local level (more difficult selection) than when they direct attention to the global level (less difficult selection). However, that occurs only when exposure of prime and probe is sufficiently long. With shorter presentations, negative priming is still observed but is no longer modulated by selection difficulty. These results suggest that both anticipatory and reactive mechanisms are responsible for the occurrence of negative priming and that instantiation of the reactive mechanism depends on the time available for prime and probe selection.

Evaluation of attention process training and brain injury education in persons with acquired brain injury.

Fourteen patients with stable acquired brain injuries exhibiting attention and working memory deficits were given 10 weeks of attention process training (APT) and 10 weeks of brain injury education in a cross-over design. Structured interviews and neuropsychological tests were used prior to rehabilitation and after both treatments to determine the influence of the interventions on tasks of daily life and performance on attentional networks involving vigilance, orienting, and executive function. The overall results showed that most patients made improvements. Some of these gains were due to practice from repetitive administration of the tests. In addition, the type of intervention also influenced the results. The brain injury education seemed to be most effective in improving self-reports of psychosocial function. APT influenced self-reports of cognitive function and had a stronger influence on performance of executive attention tasks than was found with the brain injury education therapy. Vigilance and orienting networks showed little specific improvement due to therapy. However, vigilance level influenced the improvement with therapy on some tests of executive attention. We consider the implications of these results for future studies of the locus of attentional improvement and for the design of improved interventions.

An experimental model of liver damage and portal hypertension induced by a single dose of monocrotaline.

BACKGROUND/AIMS: Hepatic cirrhosis accompanied by portal hypertension is a common cause of death in human beings. The aim of the present study was to develop an experimental model of hepatic portal hypertension associated with liver damage. METHODOLOGY: To develop liver damage in rats, we used the toxic alkaloid monocrotaline. Two groups of male Wistar rats were used. Group 1 was injected with a single dose of monocrotaline (60 mg/kg of body weight) intraperitoneally. Group 2 was injected with an equal volume of saline solution. After 44 days, the animals underwent the following tests: splenoportography and measurement of portal pressure, hepatic serum biochemical tests, and light and electron microscopy. RESULTS: Group 1 showed a significant increase in splenic pressure, superior and inferior collateral circulation, and an increase in portal vein diameter. Serious alterations were detected in hepatic serum markers. Light microscopy showed different degrees of hepatocyte damage, varying from edema to focal necrosis. Ultrastructural changes were of membrane disruption, mitochondrial and nuclear alterations. CONCLUSIONS: The present experimental model could be useful in establishing the pathophysiological changes associated with portal hypertension due to liver damage.

Anatomy of word and sentence meaning.

Reading and listening involve complex psychological processes that recruit many brain areas. The anatomy of processing English words has been studied by a variety of imaging methods. Although there is widespread agreement on the general anatomical areas involved in comprehending words, there are still disputes about the computations that go on in these areas. Examination of the time relations (circuitry) among these anatomical areas can aid in understanding their computations. In this paper, we concentrate on tasks that involve obtaining the meaning of a word in isolation or in relation to a sentence. Our current data support a finding in the literature that frontal semantic areas are active well before posterior areas. We use the subject's attention to amplify relevant brain areas involved either in semantic classification or in judging the relation of the word to a sentence to test the hypothesis that frontal areas are concerned with lexical semantics and posterior areas are more involved in comprehension of propositions that involve several words.

Symbolic distance between numerosity and identity modulates Stroop interference.

Thirty undergraduates participated in an experiment investigating the effect of the arithmetic difference between stimulus identity and stimulus numerosity in a numerical version of the Stroop task. It was found that digits symbolically close to the enumeration response reliably produced larger interference than digits that were farther from the enumeration response. This semantic distance effect was found with different numerosities (1-9) and different enumeration processes (counting and subitizing), and it increased as a function of numerosity in the subitizing range. These findings suggest that digit identity autonomously activates a magnitude representation organized as a compressed number line.

The influence of affective factors on time perception.

Several studies have suggested that both affective valence and arousal affect the perception of time. However, in previous experiments, the two affective dimensions have not been systematically controlled. In this study, standardized photographic slides rated for emotional valence and arousal were projected to two groups of subjects for 2, 4, and 6 sec. One group of subjects estimated the projection duration on an analog scale, whereas the second group of subjects reproduced the intervals by pushing a button. Heart rate and skin conductance responses were also recorded during stimulus presentation as indices of attention and arousal. Time estimation results showed neither a main effect of valence nor a main effect of arousal. A highly significant valence x arousal interaction affected duration judgments. For low-arousal stimuli, the duration of negative slides was judged relatively shorter than the duration of positive slides. Fog high-arousal stimuli, the duration of negative slides was judged longer than the duration of positive slides. The same interaction pattern was observed across judgment modalities. These results are interpreted in terms of a model of action tendency, in which the level of arousal controls two different motivational mechanisms, one emotional and the other attentional.

[Increase of acetaminophen conjugation ability in experimental cholestasis]. / Aumento de la capacidad de conjugación del acetaminofene en colestasis experimental.

Acetaminophen glucuronidation ability and its relationship to hepatic microsomal phospholipid changes were studied during experimental extrahepatic cholestasis. This study included two groups of Wistar rats: 1) normal rats and 2) cholestatic rats. UDP-Glucuronyltransferase activity (UDP-GT) towards acetaminophen resulted increased in 38% (p < 0.05) in the cholestatic group when compared to normal rats. We also found important changes in hepatocyte microsomal phospholipid profile. When phosphatidylcholine fatty acid composition was analysed, all of them resulted diminished except for an increment on oleic acid content (36%). This fatty acid increase in the main membrane phospholipid had a parallel behaviour with acetaminophen glucuronidation activity. This fact could support an activation role for oleic acid over this enzymic system.

Aumento de la capacidad de conjugación del acetaminofene en colestasis experimental / [Increase of acetaminophen conjugation ability in experimental cholestasis]

Acetaminophen glucuronidation ability and its relationship to hepatic microsomal phospholipid changes were studied during experimental extrahepatic cholestasis. This study included two groups of Wistar rats: 1) normal rats and 2) cholestatic rats. UDP-Glucuronyltransferase activity (UDP-GT) towards acetaminophen resulted increased in 38

(p < 0.05) in the cholestatic group when compared to normal rats. We also found important changes in hepatocyte microsomal phospholipid profile. When phosphatidylcholine fatty acid composition was analysed, all of them resulted diminished except for an increment on oleic acid content (36

). This fatty acid increase in the main membrane phospholipid had a parallel behaviour with acetaminophen glucuronidation activity. This fact could support an activation role for oleic acid over this enzymic system.

Aumento de la capacidad de conjugación del acetaminofene en colestasis experimental. / [Increase of acetaminophen conjugation ability in experimental cholestasis]

Acetaminophen glucuronidation ability and its relationship to hepatic microsomal phospholipid changes were studied during experimental extrahepatic cholestasis. This study included two groups of Wistar rats: 1) normal rats and 2) cholestatic rats. UDP-Glucuronyltransferase activity (UDP-GT) towards acetaminophen resulted increased in 38

(p < 0.05) in the cholestatic group when compared to normal rats. We also found important changes in hepatocyte microsomal phospholipid profile. When phosphatidylcholine fatty acid composition was analysed, all of them resulted diminished except for an increment on oleic acid content (36

). This fatty acid increase in the main membrane phospholipid had a parallel behaviour with acetaminophen glucuronidation activity. This fact could support an activation role for oleic acid over this enzymic system.

Changes in microsomal phospholipid fatty acids composition in cholestatic rats.

In the rat, the effect of the bile duct ligation on liver microsomal phospholipid fatty acid composition and on phosphatidylcholine, phosphatidylserine and phosphatidylinositol pattern were studied. After two days of cholestasis, microsomal phospholipid fatty acids showed a decrease in linoleic, stearic and arachidonic acids and an increase in oleic and docosahexaenoic ones, as compared to controls. Phosphatidylcholine showed an increment in oleic and palmitic acid content and a concomitant decrease in arachidonic acid. Phosphatidylserine showed a progressive increase while phosphatidylinositol showed a progressive decrease in all fatty acids. Eight-days post-cholestatic rats showed a marked increase in oleic acid, whereas linoleic, arachidonic, stearic and palmitic acids concentration decreased. Phosphatidylcholine showed a global decrease in its fatty acid content, except for oleic which is increased. Phosphatidylserine showed an increase over the two-days cholestasis fatty acids values. Phosphatidylinositol decreased in most fatty acids except in docosahexaenoic acid that recovered normal values. It was concluded that cholestasis produced significative changes in the fatty acid composition of the major phospholipids constituents of the microsomal membranes.

[Fluidity of hepatic microsomal membrane and its relation with aging]. / Fluidificación de la membrana microsomal hepática y su relación con el envejecimiento.

The effect of aging on hepatic microsomal membrane phospholipid composition was studied composition was studied in both young (2 months) and mature (6 months) Wistar rats. When total microsomal phospholipid content was analysed the aged group showed a significant increment (73%). Microsomal phospholipid pattern also showed a different behavior between both groups, with a significative increase in phosphatidylcholine (62%), phosphatidylserine (124%), phosphatidylinositol (31%) and sphingomyelin (10%) and appearance of phosphatidylethanolamine and phosphatidylglycerol in the six-month group. A higher microsomal membrane fluidity in the aged animals was revealed by the increase in PC/EM index (47%). This increment jin fluidity during aging process may reflect an adaptative response resulting in changes on the enzyme activities responsible for drug and carcinogen metabolism.

Fluidificación de la membrana microsomal hepática y su relación con el envejecimiento. / [Fluidity of hepatic microsomal membrane and its relation with aging]

The effect of aging on hepatic microsomal membrane phospholipid composition was studied composition was studied in both young (2 months) and mature (6 months) Wistar rats. When total microsomal phospholipid content was analysed the aged group showed a significant increment (73

). Microsomal phospholipid pattern also showed a different behavior between both groups, with a significative increase in phosphatidylcholine (62

), phosphatidylserine (124

), phosphatidylinositol (31

) and sphingomyelin (10

) and appearance of phosphatidylethanolamine and phosphatidylglycerol in the six-month group. A higher microsomal membrane fluidity in the aged animals was revealed by the increase in PC/EM index (47

). This increment jin fluidity during aging process may reflect an adaptative response resulting in changes on the enzyme activities responsible for drug and carcinogen metabolism.

Fluidificación de la membrana microsomal hepática y su relación con el envejecimiento. / [Fluidity of hepatic microsomal membrane and its relation with aging]

The effect of aging on hepatic microsomal membrane phospholipid composition was studied composition was studied in both young (2 months) and mature (6 months) Wistar rats. When total microsomal phospholipid content was analysed the aged group showed a significant increment (73

). Microsomal phospholipid pattern also showed a different behavior between both groups, with a significative increase in phosphatidylcholine (62

), phosphatidylserine (124

), phosphatidylinositol (31

) and sphingomyelin (10

) and appearance of phosphatidylethanolamine and phosphatidylglycerol in the six-month group. A higher microsomal membrane fluidity in the aged animals was revealed by the increase in PC/EM index (47

). This increment jin fluidity during aging process may reflect an adaptative response resulting in changes on the enzyme activities responsible for drug and carcinogen metabolism.

[Phospholipid composition of the hepatic microsomal membrane and its relationship to bilirubin UDP glucuronyltransferase in human cholestasis]. / Composición fosfolipídica de la membrana microsomal hepática y su relación con la actividad de la bilirrubina UDP-glucuroniltransferasa en colestasis humana.

A number of morphological and functional changes on liver cells were reported during experimental cholestasis. Some specific metabolic pathways catalyzed by "membrane bound" enzymes were described to be altered by lipid microenvironment changes. The purpose of he present study is to establish Bilirubin UDP-Glucuronyltransferase activity--a microsomal integral enzyme responsible for bilirubin conjugation--and microsomal phospholipid profile in cholestatic and normal patients. Surgical liver biopsies were taken fron five patients suffering prolonged extrahepatic cholestasis, and five patients submitted to abdominal surgery excluding hepato-biliary diseases that were considered as controls. The following biochemical parameters were determined in both groups: bilirubin concentration, alkaline phosphatase, gamma-glutamyltranspeptidase, oxalacetic and pyruvic transaminases, and pseudo-cholinesterase activities. Serum cholestatic markers showed significative increments in cholestatic patients (Table 1). Total Bilirubin UDP-Glucuronyltransferase activity was similar comparing normal and cholestatic individuals (1.11 +/- 0.66 and 1.93 +/- 0.82 nmol conjugated bilirubin/mg protein in 10 min. respectively). When final reaction product was analysed, the normal group showed 80% of bilirubin diglucuronide; but resulted undetectable in cholestatic patients yielding 100% of bilirubin monoglucuronide. Microsomal phospholipid analysis showed a decrease in phosphatidylcholine and phosphatidylethanolamine contents in the cholestatic group; probably due to the action of bile acids accumulated into the hepatic cells. Simultaneously we found an increment in phosphatidylserine and sphingomyelin levels in cholestatic patients compared to normals (Figure 1). This fact could be explained by the existence of special sites in the membrane for the latter phospholipids, protected against bile acids detersive action.(ABSTRACT TRUNCATED AT 250 WORDS)

Composición fosfolipídica de la membrana microsomal hepática y su relación con la actividad de la bilirrubina UDP-glucuroniltransferasa en colestasis humana. / [Phospholipid composition of the hepatic microsomal membrane and its relationship to bilirubin UDP glucuronyltransferase in human cholestasis]

A number of morphological and functional changes on liver cells were reported during experimental cholestasis. Some specific metabolic pathways catalyzed by [quot ]membrane bound[quot ] enzymes were described to be altered by lipid microenvironment changes. The purpose of he present study is to establish Bilirubin UDP-Glucuronyltransferase activity--a microsomal integral enzyme responsible for bilirubin conjugation--and microsomal phospholipid profile in cholestatic and normal patients. Surgical liver biopsies were taken fron five patients suffering prolonged extrahepatic cholestasis, and five patients submitted to abdominal surgery excluding hepato-biliary diseases that were considered as controls. The following biochemical parameters were determined in both groups: bilirubin concentration, alkaline phosphatase, gamma-glutamyltranspeptidase, oxalacetic and pyruvic transaminases, and pseudo-cholinesterase activities. Serum cholestatic markers showed significative increments in cholestatic patients (Table 1). Total Bilirubin UDP-Glucuronyltransferase activity was similar comparing normal and cholestatic individuals (1.11 +/- 0.66 and 1.93 +/- 0.82 nmol conjugated bilirubin/mg protein in 10 min. respectively). When final reaction product was analysed, the normal group showed 80

of bilirubin diglucuronide; but resulted undetectable in cholestatic patients yielding 100

of bilirubin monoglucuronide. Microsomal phospholipid analysis showed a decrease in phosphatidylcholine and phosphatidylethanolamine contents in the cholestatic group; probably due to the action of bile acids accumulated into the hepatic cells. Simultaneously we found an increment in phosphatidylserine and sphingomyelin levels in cholestatic patients compared to normals (Figure 1). This fact could be explained by the existence of special sites in the membrane for the latter phospholipids, protected against bile acids detersive action.(ABSTRACT TRUNCATED AT 250 WORDS)

The arachnoid granulations of the newborn human: An ultrastructural study.

Portions of the superior sagittal sinus and lacunae laterales containing arachnoid villi and granulations from 8 full-term newborn babies were studied by transmission electron microscopy. Arachnoid proliferations from 3 subjects were distended and fixed in vitro by applying a differential pressure of 8 cm H2O to the subarachnoid aspect of the tissues. The remaining cases were fixed in a collapsed state. Distended arachnoid proliferations showed morphologic characteristics associated with similar functional structures in experimental animals: shortened and enlarged interendothelial spaces; micropinocytotic activity and a system of endothelial-lined tubules. All this is taken as evidence that arachnoid proliferations in newborn babies could already be engaged in cerebrospinal fluid absorption.

Development of arachnoid villi and granulations in man.

The superior sagittal sinus and confluens sinuum of 27 fetuses and newborns ranging from postmenstrual intervals of 26-54 weeks were studied by scanning electron microscopy and histology. 26-week specimens showed oval depressions in the final portions of tributary veins to the sinus. Histologically there were arachnoid tissue clusters within the dural wall. The walls of the depressions were more irregular by the 30th week. Arachnoid villi were apparent by the 35th week and granulations were observed after the 39th weeks. The granulations increased in complexity as development proceeded.

Subacute reactions to intrathecal amipaque (metrizamide), conray and dimer X: a structural and ultrastructural study.

Adult New Zealand rabbits were injected intrathecally with 200 or 300 mgI/ml of metrizamide, meglumine iocarmate or meglumine iothalamate. They were placed in the Trendelenburg position for 20 min and allowed to survive for 1, 2 or 3 weeks. Sacrifice was by intraarterial perfusion of aldehydes under anesthesia followed by preparation of brain and major venous sinuses for light and electron microscopy. Major findings were subpial edema and inflammatory reaction of superficial brain, leptomeninges, subarachnoid space and arachnoid granulations. They were most severe after iothalamate and milder after metrizamide. The severity decreased with time. It is of significance that severe reactions occurred after 300 mgI/ml concentration of metrizamide.