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Biomedical subjects

M Fredrikson

Publications and source records attributed to M Fredrikson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Megagametophyte development in Potentilla nivea (Rosaceae) from northern Swedish Lapland.

An investigation of the embryology of Potentilla nivea was carried out using a confocal laser scanning microscope. The crassinucellate nature of the ovule as well as the presence of a multicellular archesporium was confirmed. A "nucellar cap" builds up as the result of mitotic divisions in the parietal cell tissue and the nucellar epidermis. Earlier reports that several mature megagametophytes are present in each ovule was confirmed. The processes of megasporogenesis and megagametogenesis in Potentilla turned out to differ from descriptions in previous reports, and we propose a reinterpretation. Most importantly, the "archesporium" of previous authors is here considered to be parietal cells, whereas the "chalazal cells" are here interpreted as the archesporium. Meioses commonly occur, giving rise to tetrahedral tetrads. Cytologically unreduced megagametophytes arise from generative tissue (archesporial cells or megasporocytes) only and are diplosporous. Apospory does not occur. The megagametophyte is monosporic and five-nucleate; the three antipodal nuclei normally present in eight-nucleate megagametophytes are missing.

Journal Article↗
PubMed1999

Nutritional and occupational factors influencing the risk of Parkinson's disease: a case-control study in southeastern Sweden.

PURPOSE AND METHODS: To investigate the possible impact of nutritional and environmental risk factors for idiopathic Parkinson's disease (IP), a case-control study was performed in the county of Ostergötland in southeastern Sweden. The study involved 113 cases of IP and 263 control subjects. Dietary, drinking, and smoking habits, as well as previous occupation, were requested in a structured questionnaire. RESULTS: No increased risk was found for any of the nutritional items in which information was requested. A reduced risk was found for coffee, wine, and liquor at various consumption levels but also for fried or broiled meat, smoked ham or meat, eggs, French loaf or white bread, and tomatoes. All these food and drink items contain niacin. As in many studies, the frequency of preceding and present smoking was reduced in IP patients. Various occupational groups and exposures were analyzed and increased risks of IP in men were found for agricultural work along with pesticide exposure; this was also the case for male carpenters and female cleaners. CONCLUSIONS: The findings indicate that nutritional factors and occupational exposures, especially to pesticides, could be of etiologic importance in IP.

Adult↗
PubMed1999

Social phobia in the general population: prevalence and sociodemographic profile.

BACKGROUND: The present study examined the prevalence of social phobia in the Swedish general population and demographic characteristics associated with this anxiety disorder. METHODS: Data were obtained by means of a postal survey administrated to 2000 randomly selected adults. A questionnaire, validated against clinical interviews and established social phobia scales, was used to assess social distress in a broad range of phobic situations, as well as the diagnostic criteria for social phobia corresponding to DSM-IV. Interpretable questionnaires were obtained from 1202 respondents (60.1%). RESULTS: The point prevalence of social phobia was estimated at 15.6%, but prevalence rates varied between 1.9 and 20.4% across the different levels of distress and impairment used to define cases. Public speaking was the most common social fear. Social phobia was associated with female gender, low educational attainment, psychiatric medication use, and lack of social support. CONCLUSIONS: Although the exact diagnostic boundaries for social phobia are difficult to determine, it can be concluded that social anxiety is a distressing problem for a considerable proportion of the general population.

Adult↗
PubMed1999

Functional anatomy of hypnotic analgesia: a PET study of patients with fibromyalgia.

Hypnosis is a powerful tool in pain therapy. Attempting to elucidate cerebral mechanisms behind hypnotic analgesia, we measured regional cerebral blood flow with positron emission tomography in patients with fibromyalgia, during hypnotically-induced analgesia and resting wakefulness. The patients experienced less pain during hypnosis than at rest. The cerebral blood-flow was bilaterally increased in the orbitofrontal and subcallosial cingulate cortices, the right thalamus, and the left inferior parietal cortex, and was decreased bilaterally in the cingulate cortex. The observed blood-flow pattern supports notions of a multifactorial nature of hypnotic analgesia, with an interplay between cortical and subcortical brain dynamics. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.

Journal Article↗
PubMed1999

Some risk factors for non-Hodgkin's lymphoma.

Non-Hodgkin's lymphoma (NHL) has been subject to several epidemiological studies and various occupational and non-occupational exposures have been identified as determinants. The present study is a pooled analysis of two earlier methodologically similar case-referent studies encompassing 199 cases of NHL and 479 referents, all alive. Exposure information, mainly on occupational agents, was obtained by mailed questionnaires to the subjects. Exposure to white spirits, thinner, and aviation gasoline as well as work as a painter was connected with increased odds ratios, whereas no increased risk was noted for benzene. Farming was associated with a decreased odds ratio and exposure to phenoxy herbicides, wood preservatives, and work as a lumberjack showed increased odds ratios. Moreover, exposure to plastic and rubber chemicals and also contact with some kinds of pets appeared with increased odds ratios. Office employment and housework showed decreased odds ratios. This study indicates the importance of investigating exposures not occurring very frequently in the general population. Solvents were studied as a group of compounds but were also separated into various specific compounds. The present findings suggest that the carcinogenic property of solvents is not only related to the aromatic ones or to the occurrence of benzene contamination, but also to other types of compounds.

Humans↗
PubMed1998

Brain correlates of an unexpected panic attack: a human positron emission tomographic study.

Previous brain imaging studies on symptom provocation in panic anxiety have used either drug-infusions or sensory related stimulation to induce panic attacks. We here report positron emission tomographic measurements of regional cerebral blood flow (rCBF) during an unexpected panic attack in a healthy female volunteer participating in a fear conditioning study. During a first but not a second run with electric shock presentations the woman unexpectedly experienced a panic attack that fulfilled the DSM-IV criteria. Panic was associated with decreased rCBF in the right orbitofrontal (Brodmann area 11), prelimbic (area 25), anterior cingulate (area 32) and anterior temporal cortices (area 15). These findings suggest that neural activity in brain regions previously associated with symptom provocation in specific phobics and subjects with posttraumatic stress disorder also are involved during panic in healthy individuals.

Adult↗
PubMed1998

Human brain-immune relationships: a PET study.

To study brain-immune relations, we correlated positron emission tomographic (PET) measures of regional cerebral blood flow (rCBF) with immune measures in 10 female volunteers. The natural killer (NK) activity correlated negatively with activity bilaterally in the secondary sensory cortex, whereas the Concanavalin A (Con A) response correlated positively with rCBF bilaterally in secondary visual, motor, and sensory cortices, the thalamus, the putamen, and the left hippocampus. Although representing preliminary data from a small number of subjects, these observations provide further support for the presence of interactions between the brain and the immune system.

Adult↗
PubMed1998

Distress due to unwanted side-effects of prostate cancer treatment is related to impaired well-being (quality of life).

Based on traditional quality of life scales, it has been suggested that known side-effects of prostate cancer treatment do not influence the quality of life. The present authors have developed an alternative approach to quality of life assessment applying epidemiological methods. Using a self administered questionnaire, we investigated 431 prostate cancer patients and an age stratified sample of 435 randomly selected men. Patients reporting any level of distress due to waning sexual functions (66%) or urine or bowel symptoms (38%), reported a lower psychological well-being compared to patients not reporting these symptoms or patients not distressed by their symptoms. Our results stress that an intact sexual and urinary and bowel functions are important for the quality of life among elderly men with or without prostate cancer.

Journal Article↗
PubMed1998

Some aspects of the etiology of non-Hodgkin's lymphoma.

In epidemiologic studies, non-Hodgkin's lymphoma (NHL) has been associated with exposure to chemicals such as phenoxyacetic acids; chlorophenols; dioxins; organic solvents including benzene, polychlorinated biphenyls, chlordanes; and immunosuppressive drugs. Experimental evidence and clinical observations indicate that these chemicals may impair the immune system. The risk is increased for NHL in persons with acquired and congenital immune deficiency as well as autoimmune disorders. Also, certain viruses have been suggested to be of etiologic significance for NHL. In some cases of NHL the common mechanism for all these agents and conditions may be immunosuppression, possibly in combination with viruses.

Dioxins↗
PubMed1998

Case-control study on risk factors for testicular cancer.

Occupational exposures were assessed in a case-control study on testicular cancer using self administered questionnaires. Answers were obtained for 148 (91%) cases and 314 (87%) controls. Of the cases 101 had seminoma and 47 had embryonal testicular cancer. Occupational plastics work yielded odds ratio (OR) 2.9 with 95% confidence interval (CI) 1.3-6.5. Increased risk was found for embryonal cancer regarding farming (OR 3.1; CI 1.03-9.1) and contact with farm animals (OR 3.3; CI 1.00-10.9), but not for seminoma. For all testicular cancer exposure to insects repellents, mostly containing N,N-diethyl-m-toluamide (DEET) gave OR 1.7; CI 1.03-2.8, with a dose-response effect. Somewhat increased risks were found for amateur radio operators (OR 2.2; CI 0.7-6.6), work with radar equipment (OR 2.0; CI 0.3-14.2) and engineers in electronics and telecommunication industry (OR 2.3; CI 0.8-6.7) based on few exposed subjects, however. Video display unit work gave OR 1.5; CI 0.98-2.3 and for exposure 480 working days (median number) the risk increased further to OR 1.8; CI 1.1-3.2. Because of low numbers of exposed subjects in some calculations some of these results might be spurious and need to be further studied.

Adult↗
PubMed1998

Functional neuroanatomical correlates of electrodermal activity: a positron emission tomographic study.

To reveal areas in the central nervous system of importance for electrodermal control, regional cerebral blood flow (rCBF) was correlated to nonspecific skin conductance fluctuations (NSF) during aversive and nonaversive conditions. Participants viewed a TV screen displaying white noise or snake videotapes presented both with and without electric shocks given to the right hand. H2 15 O positron emission tomography was used to measure rCBF, and the constant voltage technique was used to measure NSF from the left hand. Electrodermal activity was positively related to rCBF in the left primary motor cortex (MI, Brodmann's Area 4) and bilaterally in the anterior (Areas 24 and 32) and posterior cingulate cortex (Area 23). Negative relations were observed bilaterally in the secondary visual cortex (Areas 18 and 19) and the right inferior parietal cortex (Area 39), with a tendency also for the right insular cortex (Areas 13, 15, and 16). Because results from lesion and stimulation studies in humans converge with the present imaging results, we conclude that the cingulum and the motor cortex, in addition to the parietal and possibly the insular cortex, form part of one or several distributed neural network(s) involved in electrodermal control. Because these areas also support anticipation, affect, and locomotion, electrodermal responses seem to reflect cognitively or emotionally mediated motor preparation.

Acoustic Stimulation↗
PubMed1997

The amygdala and individual differences in human fear conditioning.

While animal research on fear conditioning suggests crucial involvement of the amygdala, this has not been corroborated in humans when using subtractive neuroimaging methodology. Correlation analyses might be more able to reveal relations between individual differences in conditionability and central neural activity. Hence, we performed a directed search for amygdalar participation in human fear conditioning by correlating central and autonomic nervous activity. [15O]Butanol positron emission tomography evaluated regional cerebral blood flow (rCBF) in six subjects before and after aversive conditioning to visual snake stimuli. Non-specific electrodermal fluctuations (EDA) were recorded simultaneously. A significant positive correlation was obtained between conditioned EDA and conditioned rCBF in the right amygdala (r = 0.75, p < 0.05), supporting involvement of the amygdala in human fear conditioning.

Adult↗
PubMed1997

Occupational exposure to polyvinyl chloride as a risk factor for testicular cancer evaluated in a case-control study.

Occupational exposures were assessed in a case-control study on testicular cancer using self-administered questionnaires. In total, answers were obtained for 148 (91%) cases and 315 (87%) controls. Of the cases, 101 had seminoma and 47 had embryonal testicular cancer. An increased odds ratio (OR) was found for exposure to polyvinyl chloride (PVC) yielding an OR of 6.6 (95% confidence interval, 1.4-32). The risk increased further if cases with self-reported cryptorchidism or orchitis were excluded. Six of the 7 exposed cases had seminoma. Exposure to other types of plastics did not significantly increase the risk of testicular cancer.

Adult↗
PubMed1997

Magnetic brain imaging of extinction processes in human classical conditioning.

By recording neuromagnetic events during aversive classical conditioning, we examined the extinction of a previously described conditioned response. Averaging over non-reinforced exposures to the conditioned stimulus revealed magnetic activity in the secondary somatosensory and insular cortices, appearing between 110 and 140 ms after the omitted unconditioned electric shock. We suggest this activity to be elicited by the discrepancy between shock expectancy and perceptual processes associated with the omission of the unconditioned stimulus, reflecting one of several brain processes in extinction.

Adult↗
PubMed1997

Head-up tilt test. A nonspecific method of evaluating patients with bifascicular block.

BACKGROUND: Patients with bifascicular block have an increased risk of syncopal attacks, but the underlying mechanism often remains unclear despite an extensive diagnostic workup. The head-up tilt test has been established as an important diagnostic tool in the unmasking of vasovagal syncope in patients with unexplained syncope. Its role in the evaluation of patients with bifascicular block has not been studied. METHODS AND RESULTS: A head-up tilt test, using a 60 degrees angle of tilt for 45 minutes without pharmacological provocation, was performed in 25 patients with bifascicular block and syncope that remained unexplained after an extensive invasive and noninvasive electrophysiological investigation. As a control group, 25 subjects with bifascicular block without syncope, matched for age, sex, left ventricular function, and underlying heart disease, were included. A positive head-up tilt test was found in 7 (28%) of the syncope patients and in 8 (32%) of the control subjects (P = NS). Six patients, of whom 3 had a positive tilt test, had recurrent syncopal attacks during 32 months of follow-up. None of the control subjects had syncope during follow-up. CONCLUSIONS: This study gives rise to serious concern regarding the specificity of the head-up tilt test in patients with bifascicular block. A head-up tilt test should therefore be interpreted with caution, and its role as a diagnostic tool in this patient category remains to be established.

Aged↗
PubMed1997

Parental history, aversive exposure and the development of snake and spider phobia in women.

Parental history and experiential factors in the development of snake and spider phobia were studied. Phobic women (DSM-IV, n = 158) reported on family history of animal phobia and whether direct (being frightened by the phobic object) or indirect (seeing someone else being frightened by and/or being warned of the phobic object) fear exposure predated phobia development. Fifty-nine mothers (37%) and 11 fathers (7%) had snake or spider phobia, which is higher than the upper 95% confidence interval in the populations (Fredrikson, Annas, Fischer & Wik, Behavior Research and Therapy, 34, 33-39). Lifetime Relative Risk, RR, of animal phobia in probands' mother and fathers as a function of at least one phobic grandparent was 3.3 and 13.7 respectively. Indirect fear exposures were more common in snake (45%) than spider (27%) phobics (RR = 1.4). Indirect fear exposures were more common among probands with a positive parental history, the RRs being 3.6 and 2.1 as a function of maternal and paternal family history. Direct exposures were unrelated to parental history. The familial resemblance and transmission of specific phobia could be experiential in origin mediated by indirect exposures or of hereditary origin mediated by genetic factors. It may represent genetically facilitated learning and exemplify imprinting in humans.

Animals↗
PubMed1997

Healthy dietary practices among European students.

Predictors of 5 healthy dietary habits were examined in data from the European Health and Behaviour Survey (A. Steptoe & J. Wardle, 1996), a study of over 16,000 students from 21 European countries. The level of practice of these healthy dietary habits was low. Significant univariate associations with healthy dietary habits were identified for gender, weight, dieting status, dietary health beliefs, nutrition knowledge, and health locus of control. In multivariate analyses, only gender, dieting status, and dietary health beliefs were significant predictors of healthy dietary habits. The practical implications of these results for dietary health promotion are discussed.

Adult↗