Living with terror. How to keep a sense of control.
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Adaptation, Psychological↗
Biomedical subjects
L Beyer
Publications and source records attributed to L Beyer.
Theta power in the EEG of humans during ongoing processing in a haptic object recognition task.
Dynamic changes in spectral theta power (TP) in the EEG over frontal regions were reported previously during the processing of visually presented spatial and verbal tasks [Cereb. Cortex, 7 (1997) 374-385]. Lower TP was found at the beginning compared to the end of processing. In order to test another modality, we examined theta power during the exploration of haptic stimuli with different complexity. A linear correlation between theta power and mean exploration time (as a measure of stimulus complexity) was found at the end of exploration but not at its beginning. These data are in line with our hypothesis since one could expect minimal load of working memory independent of stimulus complexity at the beginning of exploration whereas working memory would have integrated the stimuli of differing complexity into a perceptual model at the end of exploration.
Adolescent↗
Drug treatment services for ethnic communities in Victoria, Australia: an examination of cultural and institutional barriers.
Under-representation of ethnic minorities at drug treatment services represents under-utilisation rather than a lower need. To explore barriers to drug treatment among ethnic communities we undertook a comprehensive review of international and Australian literature to identify problems their members experience upon the discovery of illicit drug use in their community, how drug treatment is addressed and challenges for improved drug treatment outcomes. The concepts and themes derived from the literature were then compared with our research findings from key informant interviews and consultations with non-illicit drug-using spokespersons from eight ethnic communities in Victoria, Australia. Intense shame and loss of face linked to illicit drug use was common in ethnic communities and as a consequence seeking help for drug treatment was fraught with difficulties. Accessing drug treatment services often occurred following a crisis, but a sense of despair and confusion often prevailed owing to a lack of knowledge of available assistance. Even when treatment services were accessed most key informants and ethnic communities viewed them as culturally insensitive, inflexible and with language barriers that obstructed the flow of effective information. Understanding of the ethnic family ethos was of pivotal importance but frequently ignored by treatment services, contributing to the exclusion of ethnic communities from appropriate assistance. Ethnic communities need to be assisted to participate in drug issue discussions and community development strategies in order for their utilisation of drug treatment services to be improved.
Communication Barriers↗
The motor and tail regions of myosin XV are critical for normal structure and function of auditory and vestibular hair cells.
Recessive mutations in myosin 15, a class XV unconventional myosin, cause profound congenital deafness in humans and both deafness and vestibular dysfunction in mice homozygous for the shaker 2 and shaker 2(J) alleles. The shaker 2 allele is a previously described missense mutation of a highly conserved residue in the motor domain of myosin XV. The shaker 2(J) lesion, in contrast, is a 14.7 kb deletion that removes the last six exons from the 3"-terminus of the Myo15 transcript. These exons encode a FERM (F, ezrin, radixin and moesin) domain that may interact with integral membrane proteins. Despite the deletion of six exons, Myo15 mRNA transcripts and protein are present in the post-natal day 1 shaker 2(J) inner ear, which suggests that the FERM domain is critical for the development of normal hearing and balance. Myo15 transcripts are first detectable at embryonic day 13.5 in wild-type mice. Myo15 transcripts in the mouse inner ear are restricted to the sensory epithelium of the developing cristae ampularis, macula utriculi and macula sacculi of the vestibular system as well as to the developing organ of Corti. Both the shaker 2 and shaker 2(J) alleles result in abnormally short hair cell stereocilia in the cochlear and vestibular systems. This suggests that Myo15 may be important for both the structure and function of these sensory epithelia.
Alleles↗
Power of theta waves in the EEG of human subjects increases during recall of haptic information.
Several studies have reported a functional relationship between spectral power within the theta-band of the EEG (theta-power) and memory load while processing visual or semantic information. We investigated theta power during the processing of different complex haptic stimuli using a delayed recall design. The haptic explorations consisted of palpating the structure of twelve sunken reliefs with closed eyes. Subjects had to reproduce each relief by drawing it 10 s after the end of the exploration. The relationship between mean theta power and mean exploration time was analysed using a regression model. A linear relationship was found between the exploration time and theta power over fronto-central regions (Fp1, Fp2, F3, F7, F8, Fz, C3) directly before the recall of the relief. This result is interpreted in favour of the hypothesis that fronto-central theta power of the EEG correlates with the load of working memory independent of stimulus modality.
Adolescent↗
[Haptic perception and EEG changes in anorexia nervosa].
OBJECTIVES: We predicted that due to diminished somatosensory integrative ability, the anorectic patients would have problems reproducing haptic stimuli. In addition we sought to determine whether EEGs from anorectic patients (AN) and the healthy controls (CO) would show discrepancies between the two groups during haptic explorations in theta-power over the right parietal region. METHOD: EEG power (theta-power) data of AN (n = 13) and CO (n = 13) were analyzed during haptic exploration tasks and rest intervals. The haptic explorations consisted of palpating the structure of six sunken reliefs in sequence with both hands, eyes closed. After each exploration the structure was drawn on a piece of paper. RESULTS: The reproductions of haptic stimuli submitted by the anorectic patients were of notably poorer quality than those of the healthy controls. During rest intervals and haptic explorations, spectral power was generally lower in the AN group in comparison to the healthy controls. Significant theta-power differences between groups showed over the right parietal cortex during haptic explorations. The decrease in EEG power in the anorectic patients in the theta bands across the right parietal region during haptic exploration tasks could be interpreted as a minor activation of visuo-spatial regions. The results of the haptic explorations as well as the EEG-power changes indicate a cortical dysfunction and deficits in somatosensory integration processing in anorexia nervosa patients.
Adolescent↗
Assessment of isometric contractions performed with maximal subjective effort: corresponding results for EEG changes and force measurements.
In order to find a parameter or parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were taken in connection with isometric muscle contractions performed with 80% of the subjective maximal force (IMC80) or with maximal subjective effort (IMC100). Criteria based on EEG recordings and force measurements have been considered as indicators for maximal subjective effort in a given movement. The following criteria were selected: A. If the mean spectral theta amplitude across the parieto-occipital area decreases from IMC80 to IMC100 then the isometric contraction is taken to be performed with maximal effort; B. If the obtained force values can be fitted to a switch function and if the achieved forces are only a predetermined percentage lower than the maximal force value obtained over all trials then this isometric contraction is accepted to be performed with maximal effort. 18 out of 24 cases fulfill the EEG criterion whereas the criterion for force measurements is fulfilled in 16 out of 24 trials. The comparison between the results obtained by means of the EEG criterion and by means of criterion for force measurement shows that the results are in agreement in 22 out of 24 cases (p < .001). The high correspondence of the assessments allows us to suspect that both criteria specify the same phenomenon, namely the performance of a motor task with maximal subjective effort.
Adult↗
Preconcentration and voltammetric behaviour of Ag(+) at carbon paste electrodes modified by N-benzoyl-N',N'-di-i-butyl-thiourea.
The preconcentration of silver at carbon paste electrodes (CPE) modified with N-benzoyl-N',N'-di-i-butyl-thiourea and its subsequent voltammetric determination is studied with test solutions. The preconcentration of silver at the surface of the modified CPE succeeds as well with open circuits as with applied potentials. The amount preconcentrated depends on the electrode potential with a maximum at +0.1 V vs. Ag/AgCl, thus enabling the preconcentration of silver without cathodic treatment. The detection limit is in the order of 10(-4) mmol/l Ag(+). The surface reactions during the preconcentration are discussed. It is assumed that silver complexes of the modifier are formed in a fast reaction followed by a slow reaction with participation of silver and of carbon surface groups.
Journal Article↗
Theta power decreases in preparation for voluntary isometric contractions performed with maximal subjective effort.
In order to find EEG parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were realized in connection with isometric contractions (IMC). IMC were performed with submaximal and maximal subjective effort. Mean spectral power density within the theta band was found as an indicator for maximal subjective effort. The theta power across the parieto-occipital area decreases from rest through movements performed with submaximal force to movements performed with maximal effort. It is argued that this theta decrease possibly reflects a down-regulation of the posterior attention system in order to minimize the influences of external stimuli during the preparation for voluntary IMC performed with maximal subjective effort.
Adult↗
Activation processes during mental practice in stroke patients.
In healthy subjects, mental practice is known to improve motor performance. It is also known to be accompanied by a higher central nervous activity. Since such effects seem to be desirable for rehabilitation, we investigated the possibility of detecting changes in central nervous activity by means of EEG in stroke patients, and whether these changes were similar to those observed in healthy subjects. 12 left-sided hemiplegic patients who underwent a specific post-stroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to image the same sequence without any real movement. EEG background activity was recorded during rest and imagination periods. After the calculation of z-transformed power values within the theta, alpha, and beta-1 band, differences between rest and imagination periods were evaluated for their significance. Stroke patients show significant decreases of theta, alpha, as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Theta power decreases in central and parietal leads. Central alpha power diminishes only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice.
Aged↗
Construction of K88- and K99-expressing clones of Salmonella typhimurium G30: immunogenicity following oral administration to pigs.
Salmonella typhimurium G30 was used as a vector to express the ETEC (enterotoxigenic Escherichia coli) fimbrial antigens K88 and K99. Two plasmids encoding K88 or K99 production and having a non-antibiotic selection marker (thyA+) were constructed. These were introduced into a thyA G30 derivative to give the vaccine strains EX841 and EX603, which were shown to express surface K88 or K99, respectively. When administered orally to adult pigs, a dose of 10(11) vaccine organisms elicited significant serum antibody responses to the respective fimbrial antigens. Two such immunizations with EX841 generated serum antibody levels comparable to those obtained with intramuscular injection of killed organisms. Attenuated salmonellae can thus be used to deliver ETEC fimbrial antigens to the porcine intestinal immune system.
Administration, Oral↗
Mental practice of motor skills used in poststroke rehabilitation has own effects on central nervous activation.
In the last years it has been shown that the use of the EMG triggered electrical myostimulation (ETEM) brings good results in poststroke rehabilitation. It has been hypothesized that the relearning effects obtained by means of ETEM are due to the reinstatement of proprioceptive feedback. However, the technique is most powerful if imagination of motor acts (the so called mental practice) is used as an initial part of ETEM. Since mental practice in healthy people leads to central nervous activation processes as well as to an improvement of motor skills, we investigated the effects of mental practice alone on central nervous activity by means of EEG in stroke patients. Twelve left-sided hemiplegic patients who underwent a specific poststroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to imagine the same sequence without any real movement. EEG background activity was recorded during baseline and imagination periods. After the calculation of z-transformed power values within the alpha and beta-1 band, differences between rest and imagination periods were evaluated for significance. Stroke patients showed significant decreases of alpha as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Central alpha power diminished only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice. We conclude that mental practice of motor skills might have own effects in poststroke rehabilitation.
Aged↗
Motor imagination--a model for motor performances?
The effect of training competition (TC) on central nervous activation was investigated in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control. EEG was recorded before and immediately after the TC. The mean alpha frequency (MAF) was computed from the EEG power density spectra. A significant increase of MAF was found after the TC. Similar changes were found during motor imagination. Thus, motor imagination seems to be a good model to examine activation processes.
Electroencephalography↗
The human humoral immune response to Salmonella typhi Ty21a.
The short-term kinetics and the effects of different dose regimens and formulations on the humoral immune response induced in human subjects by the live attenuated typhoid vaccine Salmonella typhi Ty21a were examined. Antibody responses in jejunal fluid and serum and by specific antibody production in vitro by peripheral blood lymphocytes to S. typhi lipopolysaccharide were determined. A short vaccination schedule of three doses of 10(11) live organisms over 5 days induced significantly greater intestinal IgA antityphoid antibody responses than did two comparable doses 21 days apart. The humoral immune response was dose dependent with 10(10) and 10(11) live organisms stimulating greater intestinal immune responses than did 10(11) killed organisms. No responses were evident with either 10(9) viable organisms or with an enteric-coated preparation. In the continued development and assessment of oral typhoid vaccines, the effects of different doses and formulations and the timing of sampling on the humoral immune response should be considered.
Administration, Oral↗
Characterization and immunogenicity of EX880, a Salmonella typhi Ty21a-based clone which produces Vibrio cholerae O antigen.
EX645 is a derivative of Salmonella typhi Ty21a which carries a plasmid specifying production of Vibrio cholerae O antigen. When cultured with exogenous galactose to overcome the galE defect of the vector, EX645 also synthesizes S. typhi O antigen, and this can result in the masking of the shorter V. cholerae O antigen on the bacterial surface. To determine whether the potential for such masking at least partly underlies the inconsistency of anti-V. cholerae responses elicited by EX645, a derivative of this strain has been isolated, characterized, and tested for immunogenicity in human volunteers. EX880 has an rfb defect which prevents synthesis of S. typhi O antigen, and consequently V. cholerae O antigen is still detectable on the surface of the clone following growth in the presence of galactose. Compared with EX645, EX880 more consistently elicited significant rises in serum bactericidal antibody levels, although individual responses within a cohort still varied widely.
Antibodies, Bacterial↗
Dynamics of central nervous activation during motor imagination.
Central nervous processes of sensorimotor and behaviour control are prerequisites of skills and motor performance. Eight students (Ss) in sports were tested during motor imagination. They were requested to imagine their own movements when swimming over a distance of 100 m (sitting in a resting position, without any real or imitated movements). Electroencephalograms (EEG), heart rate (HR), skin conductance (SC), and respiration rate (RR) were recorded before, during and after one series of 3 periods of mental training (MT). HR, RR and SC increased during MT. The highest level of SC can be found at the beginning of the first period of imagination. Mean alpha-frequency of the EEG over the left occipital and precentral area in all Ss was higher during MT. The degree of these changes varied during the 3 imagination periods.
Brain↗
Neutrophil chemotactic heterogeneity to N-formyl-methionyl-leucyl-phenylalanine detected by the under-agarose assay.
Human polymorphonuclear neutrophils (PMNs) are heterogeneous in their response to the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). By using a computerized imaging method for analysis of agarose chemotaxis plates, the chemotactic sensitivity of the population of PMNs at the leading front to FMLP was greater than the mean sensitivity of all migrating PMNs. When PMNs were treated with the membrane-perturbing agent butanol at concentrations up to 0.25%, chemotaxis of the fastest PMN population in response to 10(-7) mmol/L FMLP was increased to 140% of control, whereas the mean of all populations was increased to only 110% of control. These data show that the PMN population at the leading front has a different chemotactic sensitivity to FMLP. Furthermore, the susceptibility to butanol treatment of the PMN population suggests that an alteration in membrane properties may partly account for this difference.
Butanols↗
Lack of functional asplenia in HIV infection.
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Acquired Immunodeficiency Syndrome↗