Biomedical subjects

M Fredrikson

Publications and source records attributed to M Fredrikson.

At least 19 recordsLinked to original sources

PubMed2005

Trauma exposure and post-traumatic stress disorder in the general population.

OBJECTIVE: To examine the lifetime prevalence of trauma experiences and post-traumatic stress disorder (PTSD). METHOD: Questionnaire-assessed PTSD, the type of traumatic event experienced, perceived trauma impact, and trauma frequency in 1824 randomly selected men and women. RESULTS: PTSD lifetime prevalence was estimated at 5.6% with a 1 : 2 male-to-female ratio, in spite of men reporting greater trauma exposure. The highest PTSD risk was associated with sexual and physical assault, robbery and multiple trauma experiences. Controlling for trauma type did not account for gender differences, while controlling for experienced distress did. CONCLUSION: The conditional probability for PTSD varied as a function of trauma type, frequency and impact of the event, with increased rates associated with prevalent trauma exposure and higher perceived distress. The latter accounted for the gender effect, suggesting that gender differences in PTSD in part represent a generally greater vulnerability to stress in women.

Adolescent↗

PubMed2002

Long-term adaptation to prism-induced inversion of the retinal images.

For 1 week, healthy human participants ( n=7) were devoid of normal vision by exposure to prism lenses that optically rotated their perceived world around the line of sight by 180 degrees. Adaptation to such prisms involved sustained and vigorous practice of the ability to redirect the unadapted efferent motor command; because prior to all visually guided movements, the to-be-executed efferent command was based on incorrect (prismatically reversed) spatial information. The time course of this sort of adaptation was systematically explored in Cooper-Shepard mental rotation (MR) tests and in naturalistic motor-tasks for the purpose of investigating whether mental rotations of the direction of the intended movement share common aspects with the process of MR. A control group ( n=7) intermittently exposed to the distorted spatial organization of the central visual field was studied in parallel. The main results were as follows: (a) the MR reaction times (RTs) day 1 with prisms appeared to be very similar to the normal RTs (day 1, no-prisms) with the one exception that subjects now responded within a prism (rotated) frame of spatial reference rather than within the environmentally upright. The visuomotor performance became grossly irregular and dysmetric. (b) The majority of the visuomotor adaptation functions began to level off on the 3rd day. (c) The increases in natural motor proficiency were accompanied by a systematic and noticeable decrease in magnitude of the MR Y-intercept obtained from the linear regression line calculated between each subject's RT and the various stimulus angles. MR slopes were stable through days 1-7 for both the experimental and control group. An increased correlation between rotational stimulus angle and RT suggested that the MR function also became progressively more tightly coupled to the stimulus angles. (d) Postadaptation measures of performance indicated the occurrence of selective and minimal adaptation in the natural motor tasks only. It is suggested that these results reflect an improved attentional (strategic) ability to replace incorrect (error producing) control signals with correct (error reducing) control signals. As a result, perceptual-motor start-up processes directly related to spatial coding and to the planning, initiation and correction of the intended direction of motor-or-mental movement improved while the subprocess ("stage") concerned with transformations of such movements remained unchanged. Visuomotor adaptation to inverting prisms engages, and thereby stimulates, a cortical system also invoked in the preparatory process of MR.

Adaptation, Physiological↗

PubMed2002

Phytate degradation by micro-organisms in synthetic media and pea flour.

AIMS: To screen micro-organisms for the ability to produce phytase enzyme(s) and to use promising strains for the fermentation of pea flour. METHODS AND RESULTS: Two methods using the indirect estimation of phytate degradation were evaluated and both shown to be inadequate. A third method, measuring the inositol phosphate (IP3-IP6) content directly during fermentation, was used instead of the indirect estimations of phytate degradation. In synthetic media, some strains required customized conditions, with no accessible phosphorus sources other than phytate, to express phytase activity. The repression of phytase synthesis by inorganic phosphorus was not detected during fermentation with pea flour as substrate and seemed to be less significant with a higher composition complexity of the substrate. None of the tested lactic acid bacteria strains showed phytase activity. CONCLUSIONS: The methodology for the phytase screening procedure was shown to be critical. Some of the screening methods and media used in previous publications were found to be inadequate. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper highlights the pitfalls and difficulties in the evaluation of phytase production by micro-organisms. The study is of great importance for future studies in this area.

6-Phytase↗

PubMed2001

Dispositional pessimism and amygdala activity: a PET study in healthy volunteers.

The present study used scores from Seligman's Attribution Style Questionnaire and [15O] water positron emission tomographic measurements of regional cerebral blood flow (rCBF) to investigate the relation between individual differences in dispositional pessimism and amygdala activity. During scanning 13 healthy non-snake-phobic females passively viewed a snake videotape. Using one-tailed tests, significant negative correlations were evident between pessimism scores, with low scores reflecting relatively more pessimism, and right (r=-0.60; p=0.014) and left amygdala rCBF (r=-0.53; p=0.032). These results extend previous neuroimaging findings in healthy subjects indicating a role for the amygdala in transient negative emotional states, and suggest that this multimodal brain region also is involved in more durable negative affects such as dispositional pessimism.

Adult↗

PubMed2001

Brain function in a patient with torture related post-traumatic stress disorder before and after fluoxetine treatment: a positron emission tomography provocation study.

We report positron emission tomographic measurements of regional cerebral blood flow (rCBF) in a male patient with war and torture related post-traumatic stress disorder (PTSD) during symptom provocation. The subject was exposed to war related sounds before and after treatment with a selective serotonin reuptake inhibitor (SSRI; Fluoxetine; Fontex((R))). Therapy reduced PTSD symptoms, provoked anxiety and heart rate. Before treatment trauma reminders resulted in decreased rCBF in the insula, prefrontal, and inferior frontal cortices. Increased activity was evident in the cerebellum, precuneus and supplementary motor cortex. This was normalized after SSRI administration. Prefrontal and cingulate rCBF correlated with heart rate. Hence, the anxiolytic effect of SSRI for PTSD could be mediated by prefrontal and paralimbic cortices. Data suggest that SSRI treatment normalize provocation induced rCBF alterations in areas involved in memory, emotion, attention and motor-control.

Anxiety↗

PubMed2001

Social phobia and avoidant personality disorder as related to parental history of social anxiety: a general population study.

Using a validated and DSM-IV compatible questionnaire, the present study related family history of excessive social anxiety to social phobia and avoidant personality disorder (APD) in epidemiologically identified probands in the general population. Probands met diagnostic criteria for social phobia with or without APD and APD with or without social phobia. A two- to three-fold increased relative risk of social anxiety was observed for all diagnostic groups. Increasing severity in probands by varying diagnostic criteria did not affect the relative risk. Because familial aggregation of social anxiety was not modulated by Axis I or II diagnosis or diagnostic cut-off levels, data imply that social phobia and APD may represent a dimension of social anxiety rather than separate disorders. Thus, having an affected family member is associated with a two- to three-fold risk increase for both social phobia and APD.

Adolescent↗

PubMed2001

Personality traits in social phobia.

The purpose was to assess personality traits in subjects with a DSM-IV diagnosis of social phobia. Thirty-two subjects were administered the Structured Clinical Interview for DSM-IV for Axes I and II disorders (SCID I and II). Personality traits were assessed by means of the Karolinska Scales of Personality (KSP). Current and lifetime axis I co-morbidity was diagnosed in 28% and 53% of the subjects, respectively. In total, 59% had at least one personality disorder and 47% were diagnosed with an avoidant personality disorder. The social phobics scored significantly higher than a Swedish normative sample on the KSP measuring anxiety proneness, irritability, detachment, and indirect aggression but lower on the scales for socialisation and social desirability. The presence as compared to absence of avoidant personality disorder in the social phobics was associated with significantly higher psychic anxiety and inhibition of aggression. In addition, symptom severity was higher in social phobics with an avoidant personality disorder. Generally, the results support the view that social phobia and avoidant personality disorder reflect different aspects of a social anxiety spectrum.

Adolescent↗

PubMed2001

Production process for high-quality pea-protein isolate with low content of oligosaccharides and phytate.

A process for pea-protein isolate production, resulting in low content of phytate and oligosaccharides, has been developed. Oligosaccharides were removed from the protein fraction through ultrafiltration. Ultrafiltration of 50- and 100-kD molecular-weight cutoffs (MWCOs) were tested, and both effectively separated the oligosaccharides from the protein. Phytate degradation was achieved by incubation of the pea-protein solution by addition of exogenous phytase enzyme. An almost complete degradation of inositol hexa-, penta-, tetra-, and triphosphates was reached using an incubation time of 1 h. The reduced content of oligosaccharides and inositol phosphates is likely to result in reduced flatulence and improved mineral bioavailability. These qualities of the pea-protein isolate make it a suitable protein source for infant formula production.

Biological Availability↗

PubMed2001

Cerebral blood flow in subjects with social phobia during stressful speaking tasks: a PET study.

OBJECTIVE: The central nervous system representation of social phobia (social anxiety disorder) is largely unknown. The aim of this study was to examine brain activity during symptom provocation in social phobics. METHOD: Positron emission tomography with the use of (15)O water was used to measure regional cerebral blood flow (rCBF) in 18 subjects with DSM-IV-defined social phobia and a nonphobic comparison group while they were speaking in front of an audience and in private. Heart rate and subjective anxiety were also recorded. RESULTS: During public versus private speaking, subjective anxiety increased more in the social phobics than in the comparison group. Increased anxiety was accompanied by enhanced rCBF in the amygdaloid complex in the social phobics relative to the comparison subjects. Cortically, brain blood flow decreased in the social phobics and increased in the comparison subjects more during public than private speaking in the orbitofrontal and insular cortices as well as in the temporal pole and increased less in the social phobics than in the comparison group in the parietal and secondary visual cortices. Furthermore, rCBF increased in the comparison group, but not in the social phobics, in the perirhinal and retrosplenial cortices. CONCLUSIONS: An rCBF pattern of relatively increased cortical rather than subcortical perfusion was observed in the nonphobic subjects, indicating that cortical evaluative processes were taxed by public performance. In contrast, the social phobia symptom profile was associated with increased subcortical activity. Thus, the functional neuroanatomy of social phobia involves the activation of a phylogenetically older danger-recognition system.

Adult↗

PubMed2001

Human fear conditioning is related to dopaminergic and serotonergic biological markers.

Biological markers for acquisition and extinction of fear conditioning were studied in 40 individuals selected for displaying either good or poor acquisition of fear conditioning. as estimated by the skin conductance response. Participants with a short serotonin transporter (5-HTT) promoter allele or low monoamine oxidase activity in platelets (trbc-MAO) displayed better acquisition than those with only long alleles or high trbc-MAO, whereas participants with a long dopamine D4 receptor (D4DR) exon III allele showed delayed extinction compared with those with only short alleles. The findings, that D4DR exon III and 5-HTT promoter genotypes and trbc-MAO activity are related to human fear conditioning, a basic form of associative learning, are consistent with animal studies suggesting a genetic contribution to fear conditioning. The authors suggest that in humans these genetic mechanisms are partly dopaminergic and serotonergic in origin.

Alleles↗

PubMed2001

Psychosocial work characteristics and perceived control in relation to cardiovascular rewind at night.

This study examined the effects of psychosocial work characteristics on cardiovascular rewind at night. Ambulatory 24-hr recordings of blood pressure (BP) and heart rate (HR) of 75 borderline hypertensive and 74 normotensive men were related to diary ratings of perceived control (PC) and to scores of psychological demand (P), control (C), and social support (S) at work determined by an occupational classification system. Multiplicative interaction terms for job strain (P x C), isostrain (P x C x S), and Job Strain x Perceived Control (P x C x PC) were calculated. The P x C x PC interaction predicted diastolic BP at night but not at work. A delayed latency to attain the lowest systolic BP during the night was found for jobs with high job strain and isostrain. Low perceived control and social support were associated with higher HR at work and at night. A logistic regression analysis indicated that the interaction between P x C x PC and the body mass index was independently associated with borderline hypertension.

Adult↗

PubMed2000

GSTM1 and mEPHX polymorphisms in Parkinson's disease and age of onset.

Both environmental and genetic factors are involved in the development of PD and biotransformation of exogenous and endogenous compounds and may play a role in inter-individual susceptibility. Therefore, we investigated the presence of null genotypes of GSTM1, GSTT1, and two polymorphisms of mEPHX in subjects with Parkinson's disease and in a reference population. The study included 35 male PD patients and a male control group including 283 subjects. Homozygosity of the histidine (H) 113 isoform of mEPHX was significantly increased in PD patients (odds ratio = 3.8 CI 95% 1. 2-11.8) and analysis of allele frequencies displayed an increased frequency of the H-allele among PD patients (odds ratio = 1.9 CI 95% 1.1-3.3). However, a significantly elevated median age for the onset of PD was found among GSTM1 gene carriers (median age = 68 years) compared to PD patients being GSTM1 null genotypes (median age = 57 years). Our observations suggest that (H) 113 isoform of mEPHX, which has been suggested as a low activity isoform, is overrepresented in PD patients and that inherited carriers of the GSTM1 gene postpone the onset of PD. These detoxification pathways may represent important protective mechanisms against reactive intermediates modifying the susceptibility and onset of PD.

Adult↗

PubMed2000

Neuroimmune relations in patients with fibromyalgia: a positron emission tomography study.

To study relations between neural and immune activity in patients with chronic pain, we correlated regional cerebral blood flow measured with [(15)O]butanol positron emission tomography to immune function in five patients with fibromyalgia. Partly replicating previous data in healthy volunteers, natural killer cell activity correlated negatively with right hemisphere activity in the secondary somatosensory and motor cortices as well as the thalamus. Moreover, natural killer cell activity was negatively and bilaterally related to activity in the posterior cingulate cortex. Thus, immune parameters were related to activity in brain areas involved in pain perception, emotion, and attention. Implicated from a small study population, these strong neuro-immune associations are discussed in view of recent findings concerning mechanisms and adaptive values in immuno-cortical communication and regulation.

Adult↗

PubMed2000

Brain representation of habituation to repeated complex visual stimulation studied with PET.

To investigate CNS habituation (i.e. response decrement due to stimulus repetition) the present study used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in eight healthy women during two repetitions of complex visual stimuli. Repeated visual stimulation resulted in neural habituation bilaterally in the secondary visual cortex and in the right medial temporal cortex including the amygdala and the hippocampus. Regional CBF in the left thalamus was elevated as a function of repeated stimuli presentations. Thus, repeated presentation of complex visual stimuli result in rCBF habituation in later stages of the visual processing chain. The elevated neural activity in the thalamus might be associated with interruption of further neural transmission related to suppression of non-meaningful behavior.

Adult↗

PubMed2000

Aspects of delayed chemotherapy-induced nausea. Dexamethasone and adrenal response patterns in patients and healthy volunteers.

Delayed chemotherapy-induced nausea is still a clinical problem, and the underlying mechanisms are poorly understood. Previous studies have suggested that corticosteroids are involved, although the mechanisms by which corticosteroids exert their antiemetic effect are largely unknown. We have previously found impaired control of delayed nausea after injection of dexamethasone. The possibility of differences in the recovery of the hypothalamic-pituitary-adrenal (HPA) axis after injection of dexamethasone was investigated in patients (n = 5) with gynaecological cancer being treated with platinum-based chemotherapy and in healthy female volunteers (n = 10). Urinary free cortisol was used to assess the levels of endogenous cortisol. Results showed that in both patients and controls injections of dexamethasone led to a significant decline in endogenous cortisol levels in 24 h and a subsequent significant recovery in the next 24 h. We conclude that the recovery of the HPA axis is rapid after a single dose of dexamethasone in patients and controls. The absence of an abnormal response pattern in patients makes it probable that the suppression and recovery of the HPA axis after injection of dexamethasone does not influence the corticosteroid-induced rebound effect on delayed platinum-induced nausea.

Aged↗

PubMed2000

Social phobia subtypes in the general population revealed by cluster analysis.

BACKGROUND: Epidemiological data on subtypes of social phobia are scarce and their defining features are debated. Hence, the present study explored the prevalence and descriptive characteristics of empirically derived social phobia subgroups in the general population. METHODS: To reveal subtypes, data on social distress, functional impairment, number of social fears and criteria fulfilled for avoidant personality disorder were extracted from a previously published epidemiological study of 188 social phobics and entered into an hierarchical cluster analysis. Criterion validity was evaluated by comparing clusters on the Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale (SIAS). Finally, profile analyses were performed in which clusters were compared on a set of sociodemographic and descriptive characteristics. RESULTS: Three clusters emerged, consisting of phobics scoring either high (generalized subtype), intermediate (non-generalized subtype) or low (discrete subtype) on all variables. Point prevalence rates were 2.0%, 5.9% and 7.7% respectively. All subtypes were distinguished on both SPS and SIAS. Generalized or severe social phobia tended to be over-represented among individuals with low levels of educational attainment and social support. Overall, public-speaking was the most common fear. CONCLUSIONS: Although categorical distinctions may be used, the present data suggest that social phobia subtypes in the general population mainly differ dimensionally along a mild moderate-severe continuum, and that the number of cases declines with increasing severity.

Adult↗

PubMed2000

Fear conditioning and brain activity: a positron emission tomography study in humans.

Regional cerebral blood flow (rCBF) was measured with H2 (15)O positron emission tomography in 8 healthy women before and after fear conditioning (i.e., paired shocks) and unpaired shocks to videotape cues. Conditioning was supported by enhanced peripheral nervous system recordings and subjective ratings. Fear conditioning increased rCBF in the central gray of the midbrain; bilaterally in the hypothalamus, the thalamus, and the left striatum; and in the right and left anterior cingulate and right prefrontal cortices. Regional CBF was attenuated bilaterally in the right and left prefrontal, temporal (including the amygdala), parietal, and occipital cortices, and in the left orbitofrontal cortex. When compared with unpaired shock presentations, fear conditioning resulted in elevated rCBF in the left cerebellum. Hence, in the present paradigm, only neural activity in the left cerebellum solely reflected processes associated with true Pavlovian conditioning.

Adult↗

PubMed2000

Regional cerebral blood flow during tinnitus: a PET case study with lidocaine and auditory stimulation.

Brain imaging of tinnitus has suggested central correlates of tinnitus perception. This study presents positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) in a female tinnitus patient with bilateral left dominant tinnitus. Lidocaine infusion (75 mg during 5 min (0.2 mg/kg/min)) resulted in a 75% reduction of tinnitus and a temporary abolition of the dominant tinnitus in her left ear. Regional CBF was measured in four conditions: i) at rest while concentrating on tinnitus, ii) following maximum effect of lidocaine, iii) during sound stimulation, and iv) the following day at rest while concentrating on tinnitus. Subtraction analyses showed that tinnitus was associated with increased rCBF in the left parieto-temporal auditory cortex, including the primary and secondary auditory cortex with a focus in the parietal cortex (Brodmann areas 39, 41, 42, 21, 22). Activations were also found in right frontal paralimbic areas (Brodmann areas 47, 49 and 15). Sound stimulation resulted in bilateral activation of auditory areas. It is suggested that tinnitus is processed in primary, secondary and integrative auditory cortical areas. Tinnitus perception may involve areas related to auditory attention, while emotional processing relates to temporofrontal paralimbic areas.

Acoustic Stimulation↗