| 1. |
- Baez, Sofia, 1963-
(author)
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Dopachrome and aminochrome, the oxidized metabolites of dopa and dopamine : studies on the molecular mechanisms underlying their reduction and conjugation with glutathione
- 1999
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Doctoral thesis (other academic/artistic)abstract
- Dopamine, like other catecholamines can be oxidized to the corresponding ortho-quinone, which undergoes cyclization of its amino chain to cyclized dopamine ortho-quinone (aminochrome). Both o-quinones are toxic metabolites that may contribute to neurotoxic effects of these catecholamines. The oxidation of dopamine to o-quinone is believed to be one of the causes of the neurodegenerative process of Parkinson's disease.Although it is in generally accepted that free radicals are involved in the neurodegenerative process occurring in the dopaminergic neuron system in Parkinson's disease, the exact mechanism of neurodegeneration in vivo is still unknown. However, one possible source of free radicals in the dopaminergic neuron system in the central nerve system may involve the oxidation of dopamine to the corresponding o-quinone.L-Dopa is commonly used in the clinical management of Parkinson's disease. However, this treatment becomes gradually ineffective, due either to loss of efficacy or to appearance of side-effects, probably produced by the oxidative injury generated by the oxidation of dopa or of its metabolites.We report in this study that the oxidation of dopa and dopamine to the corresponding o-quinone and the followed cyclization, at physiological pH, is not itself responsible for the formation of reactive oxygen species. In addition, we show that the reduction of cyclized o-quinones of dopamine and the subsequent autoxidation is the step in which reactive species are formed.Formation of reactive oxygen species during one- or two-electron reduction of aminochrome and dopachrome has been studied in vitro by using NADPH-cytochrome P450 reductase and DT-diaphorase, respectively. The results suggest that DT-diaphorase, SOD, catalase (glutathione peroxidase) and sulfotransferase constitute the cellular defenses against formation of reactive oxygen species during reduction of aminochrome and dopachrome.We also studied the ability of human glutathione transferases to conjugate cyclized catechol o-quinones such as aminochrome and dopachrome and found that GSTs, in particularly GST M2-2 catalyzes GSH conjugation of dopachrome and aminochrome, preventing the formation of ROS and reactive catechol metabolites. The neuroprotective role of GST M2-2 suggested in the present study is depend on the presence of the enzyme in relevants regions of the human brain, regions where cell damage is observed in diseases such as schizoprenia and Parkinson's disease.
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| 5. |
- Burnham, Denis, et al.
(author)
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Perception of lexical tone across languages : Evidence for a linguisticmode of processing
- 1996
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In: Proceedings of the 4th InternationalConference on Spoken Language Processing. ; , s. 2514-2517
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Conference paper (peer-reviewed)abstract
- Pairs of Thai tones were presented for perceptual discrimination inthree linguistic contexts (normal speech, low-pass filtered speech,and as musical (violin) sounds) to tonal language speakers, Thaiand Cantonese, and non-tonal (English) language speakers.English speakers discriminated the tonal contrasts significantlybetter in the musical context than in filtered speech, and in filteredspeech better than in full speech. On the other hand, both Thaiand Cantonese speakers perceived the tonal contrasts equally wellin all three contexts. Thus developmental absence of exposure tolexical tone results in a linguistic mode of processing whichinvolves the attenuation of a basic psychoacoustic ability, pitchdiscrimination.
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| 6. |
- Colomer Sanmartin, Francisco, 1966
(author)
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High Resolution Studies of Circumstellar Masers
- 1996
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Doctoral thesis (other academic/artistic)abstract
- This thesis describes in detail the observational procedures that we have followed and developed to analyze several research projects organized at Onsala since 1990 to study the regions of SiO maser emission at 43 GHz in the circumstellar envelopes of late-type stars with very high angular resolution. The compact nature of these SiO maser regions has been demonstrated in this work. In fact, we find that they are an order of magnitude smaller than previously reported. As a consequence, they can be studied with the available VLBI instruments. We have used the EVN and VLBA telescopes to produce images of the distribution of the SiO maser features in several sources, in particular R Cassiopeiae and VX Sagittarii. Through this work, we discuss in detail the procedures involved in all the project steps, from the scheduling of the observations to the calibration, imaging, and modelling of the source structure. We compare our results with those of other instruments at different frequencies for the same objects. This thesis also describes the analysis of observations of water masers at 22 GHz in several late-type stars using the VLA. The limited resolution of these observations made us develop a computer program, "FG3", that would search for the maser sources (blended spatially and in frequency) and extract them via 3D least squares fitting to Gaussian functions. This is, to our knowledge, a new approach in this kind of investigations. This program provides information of the source structure distribution and kinematics, and also measures parameters that are directly related with the physical conditions in the masing regions. In particular, we conclude by the study of the fitted maser linewidths that water masers in late-type stars are unsaturated. We are not able to reach a clear conclusion for the SiO masers in the supergiant star VX Sgr, but there are indications that they might be saturated.
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| 7. |
- da Cruz Francisco, José, et al.
(author)
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A Comparative Study of Gelatinization of Cassava and Potato Starch in an Aqueous Lipid Phase (L2) Compared to Water
- 1996
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In: Food Hydrocolloids. - 0268-005X. ; 10:3, s. 317-322
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Journal article (peer-reviewed)abstract
- The competition for water between an aqueous lipid phase (L2) and gelatinizing starch was investigated. Differential scanning calorimetry and light microscopy, were used to study the gelatinization behaviour of cassava and potato starch in the thermodynamically stable water containing (i.e. 13% w/w water) oil-continuous L2-phase. This was compared to the gelatinization of the two starches in limited and excess water (i.e. 56 and 77% w/w eater). The heating of 10.0% w/w cassava and potato starch in the L2-phase resulted in a 20 degrees shift upwards in temperature for the onset temperature and the temperature of peak maximum of the starch gelatinization compared with the starch-water samples with limited or excess water. Results from the microscopy, study showed that heating a gradually increasing amount of starch in the L2-phase shifts the gelatinization interval to increasingly higher temperatures. The enthalpy of gelatinization was reduced with >50% when the 10.0% w/w cassava and potato starch were gelatinized in the L2-phase. This is due to that part of the water is associated to the lipids in the L2-phase in such a way that it is not available for the starch. X-ray diffraction examinations of the cassava starch showed that the diffraction pattern was of the A-type. When the water content was increased the pattern changed towards the C-type.
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| 10. |
- Globisch, Jutta, et al.
(author)
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Fear appears fast : Temporal course of startle reflex potentiation in animal fearful subjects
- 1999
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In: Psychophysiology. - 0048-5772 .- 1469-8986. ; 36:1, s. 66-75
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Journal article (peer-reviewed)abstract
- The temporal course of startle reflex modulation and autonomic response patterns to fear‐relevant and fear‐irrelevant pictures in subjects with high and low levels of animal fear was investigated. Thirty‐eight high‐fear and 48 low‐fear volunteers viewed photos of snakes and spiders and pictures of neutral and pleasant content. The slides were presented for 6 s or for only 150 ms, depending on the group. Acoustic startle probes were presented at five different times after slide onset. Relative potentiation of the startle responses started 300 ms after onset of snake/spider pictures in fearful subjects. This fear‐potentiated startle effect was maintained for the later probe times and was identical in the 150‐ms condition. Fear‐relevant pictures also prompted a sympathetically dominated autonomic response profile in fearful persons. These data support the idea that fear can be activated very rapidly, requiring only minimal stimulus input.
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| 11. |
- Islam, M. Shahidul, et al.
(author)
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In situ activation of the type 2 ryanodine receptor in pancreatic beta cells requires cAMP-dependent phosphorylation
- 1998
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 95:11, s. 6145-6150
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Journal article (peer-reviewed)abstract
- Molecular mechanisms that regulate in situ activation of ryanodine receptors (RY) in different cells are poorly understood. Here we demonstrate that caffeine (10 mM) released Ca2+ from the endoplasmic reticulum (ER) in the form of small spikes in only 14% of cultured fura-2 loaded beta cells from ob/ob mice. Surprisingly, when forskolin, an activator of adenylyl cyclase was present, caffeine induced larger Ca2+ spikes in as many as 60% of the cells. Forskolin or the phosphodiesterase-resistant PKA activator Sp-cAMPS alone did not release Ca2+ from ER. 4-Chloro-3-ethylphenol (4-CEP), an agent that activates RYs in other cell systems, released Ca2+ from ER, giving rise to a slow and small increase in [Ca2+]i in beta cells. Prior exposure of cells to forskolin or caffeine (5 mM) qualitatively altered Ca2+ release by 4-CEP, giving rise to Ca2+ spikes. In glucose-stimulated beta cells forskolin induced Ca2+ spikes that were enhanced by 3,9-dimethylxanthine, an activator of RYs. Analysis of RNA from islets and insulin-secreting betaTC-3-cells by RNase protection assay, using type-specific RY probes, revealed low-level expression of mRNA for the type 2 isoform of the receptor (RY2). We conclude that in situ activation of RY2 in beta cells requires cAMP-dependent phosphorylation, a process that recruits the receptor in a functionally operative form.
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| 12. |
- Kuhl, Patricia K, et al.
(author)
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Cross-language analysis of phonetic units in language addressed to infants.
- 1997
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In: Science. - 0036-8075. ; 277:5326, s. 684-6
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Journal article (peer-reviewed)abstract
- In the early months of life, infants acquire information about the phonetic properties of their native language simply by listening to adults speak. The acoustic properties of phonetic units in language input to young infants in the United States, Russia, and Sweden were examined. In all three countries, mothers addressing their infants produced acoustically more extreme vowels than they did when addressing adults, resulting in a "stretching" of vowel space. The findings show that language input to infants provides exceptionally well-specified information about the linguistic units that form the building blocks for words.
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| 13. |
- Lundqvist, Daniel, et al.
(author)
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The face of wrath : Critical features for conveying facial threat
- 1999
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In: Cognition & Emotion. - : Informa UK Limited. - 0269-9931 .- 1464-0600. ; 13:6, s. 691-711
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Journal article (peer-reviewed)abstract
- We examined the role of different facial features (shape of eyebrows, eyes, mouth, nose, and the direction of gaze) in conveying the emotional impact of a threatening face. In two experiments, a total of 100 high school students rated their impression of two sets of schematic faces in terms of semantic differential scales (Activity, Negative Evaluation, and Potency). It was found that the different facial features could be ordered hierarchically, with eyebrows as the most important feature, followed by mouth and eyes. Eyebrows thus fundamentally categorised faces as threatening or nonthreatening. The different shapes of mouth and eyes provided subsequent categorisations of faces within these primary categories.
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| 15. |
- Parra, Cristina, et al.
(author)
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Pavlovian conditioning to social stimuli : Backward masking and the dissociation of implicit and explicit cognitive processes.
- 1997
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In: European Psychologist. - : Hogrefe Publishing Group. - 1016-9040 .- 1878-531X. ; 2:2, s. 106-117
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Journal article (peer-reviewed)abstract
- 24 university students (average age 22.1 yrs) were conditioned to pictures of angry faces with a mild electric shock unconditioned stimulus/stimuli (UCS). They were then tested with backward masking conditions preventing conscious recognition of the facial stimuli. In the 1st experiment, a shock followed a particular nonmasked angry face exposed among many other faces. Although the Ss did not rate this face as familiar in a subsequent test when it was presented masked among other masked and nonmasked faces, it elicited larger skin conductance responses than did nonshocked control faces. This dissociation between explicit recognition and implicit skin conductance differentiation was replicated in the 2nd experiment, in which the Ss rated their shock expectancy. Although conditioning resulted in much better differentiation between conditioned and control faces during nonmasked than masked test trials, skin conductance differentiation did not differ between the 2 masking conditions.
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