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Biomedical subjects

A Ohman

Publications and source records attributed to A Ohman.

At least 37 records · Page 2Linked to original sources
PubMed1997

Relationships between social support, social coping and life events in the relapse of schizophrenic patients.

The vulnerability-stress model for schizophrenia posits that relapses are at least partly determined by interacting triggering and protecting psychosocial factors. This study examined social support and general coping style in 42 consecutively admitted DSM:III schizophrenic patients, who were followed prospectively for up to four years. In a second part of the study, a subgroup of the patients were interviewed using the Life Event and Difficulty Schedule 9 months after discharge or at relapse. Patients contented with low social integration had a higher relapse rate over four years than patients lacking of social provisions, but wanting more. We found an excess of life events three weeks before relapse compared to events reported in the non-relapsing group. Suggesting a buffering effect of social factors, time between life event and relapse was significantly extended among patients with a high availability of attachment and a coping strategy characterised of active support seeking.

Adaptation, Psychological↗
PubMed1997

Prenatal and neonatal risk factors for schizophrenia.

BACKGROUND: The present study examines the effects of independent, single pre- and perinatal risk factors and rates of obstetric complications upon the subsequent development of schizophrenia. METHOD: This study was based on prospectively recorded birth records of 107 cases (82 with schizophrenic disorders and 25 with other psychotic reactions) and 214 controls, individually matched by gender and time and place of birth. Variables univariately associated with significantly elevated risk were entered in a logistic regression model. RESULTS: A high non-optimality summary score (> or = 7 complications of 34 possible) was a significant risk estimate for the total index group (OR 4.58, 95% CI 1.74-12.03) and the 82 schizophrenic patients (OR 3.67, CI 1.30-10.36). Patients with 2-6 complications also had an increased, although lower, risk (OR 1.67, CI 1.02-2.75). A disproportionate birth weight for body length (OR 3.57, CI 1.77-7.19) and a small head circumference (OR 3.93, CI 1.32-11.71) were the strongest independent risk factors. CONCLUSIONS: A contribution of obstetric complications to the risk of schizophrenia was confirmed. Only aberrations in physical size remained as individual independent risk factors.

Adolescent↗
PubMed1996

A study of melittin, motilin and galanin in reversed micellar environments, using circular dichroism spectroscopy.

Circular dichroism spectroscopy has been used to study the behaviour of the cytolytic peptide melittin, the intestinal peptide hormone motilin (porcine) and the neuropeptide galanin (porcine) in various reversed micellar systems. The micellar systems used contained sodium dodecyl sulphate, bis(2-ethylhexyl) sulfosuccinate, n-dodecyltrimethylammonium chloride or polyoxyethylene(7) lauryl ether. Various structural changes of the peptides, induced either by varying the water content or the surface charge of the reversed micelles, could be monitored. Melittin has in all micellar systems a large amount of alpha-helix, and is almost unaffected by both water content and the surface charge of the reversed micelles. Motilin on the other hand attains an alpha-helical structure at low water content only. The surface charges seem to be of importance for the association between motilin and the hydrated reversed micellar surface. Galanin has the most complicated behaviour with a large dependence on surface charge and with a water content dependence which varies with the surfactant used. Stabilization of alpha-helical secondary structures was only seen in negatively charged reversed micelles. These observations indicate a specific interaction between galanin and surfactant, probably of electrostatic nature.

Amino Acid Sequence↗
PubMed1996

Electrodermal activity and social network as predictors of outcome of episodes in schizophrenia.

The predictive value of electrodermal activity and social network was examined among 48 consecutively admitted schizophrenic patients. The patients were followed from an initial admission, through hospital stay, discharge, follow-up (M = 31 months), and possible relapse. Outcome variables were the length of stay in the hospital at the key episode and time to relapse, defined as a marked exacerbation or return of schizophrenic symptoms requiring inpatient or expansion of outpatient treatment. Multivariate analyses showed that a psychosocial variable, the availability of attachment, was the only independent predictor of length of stay in the hospital. Age at admission was a strong predictor of time to relapse. Age interacted with both outcome and electrodermal activity, and young electrodermal nonresponders were found to have the shortest time to relapse. At the 1-year follow-up, a main relapse effect was found for patients with a low skin conductance level.

Adolescent↗
PubMed1995

Solvent stabilized solution structures of galanin and galanin analogs, studied by circular dichroism spectroscopy.

Circular dichroism spectroscopy has been used to study how different solvents stabilize secondary structure in the neuropeptide galanin (rat), two N-terminal fragments of galanin, galanin(1-12) and galanin(1-16), and six other differently charged analogs. Among these analogs, the peptide M40, galanin(1-13)-Pro-Pro-Ala-Leu-Ala-Leu-Ala amide, is a high affinity, receptor subtype specific galanin receptor antagonist. The different solvents include sodium dodecyl sulfate (SDS) micelle solutions, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-phosphoglycerol (DOPG) vesicle solutions. 100% 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) and 100% 2,2,2-trifluoroethanol (TFE). DOPC vesicles did not change the structure of the peptides as compared to aqueous solvent. The negatively charged DOPG vesicles and SDS micelles induced similar changes towards alpha-helical structures in all peptides. The HFP and TFE solvents have an even stronger tendency to stabilize alpha-helical conformations in these peptides. Since DOPG vesicles can be considered as a model system for negatively charged biological membranes, the solution structures observed in the presence of DOPG or SDS may be the most relevant for the in vivo situation. Correlations between the binding affinity of the peptides to hippocampal galanin receptors and their observed structures in the DOPG solvent were investigated.

Amino Acid Sequence↗
PubMed1995

Cardiovascular reactivity, Type A behavior, and coronary heart disease: comparisons between myocardial infarction patients and controls during laboratory-induced stress.

Cardiovascular responses to a series of laboratory stressors were examined in middle-aged Type A and Type B men. The subjects were 30 patients with diagnosed myocardial infarction (NYHA Class 1) and 26 age-matched healthy controls. All subjects were nonsmokers in the normotensive range, and none were on medication. Blood pressure, heart rate, forearm blood flow and resistance, and impedance cardiography-determined response variables were obtained during performance and recovery periods of both mental and physical tasks. The patients showed elevated reactivity in systolic blood pressure and cardiac output and prolonged systolic time ratio during mental stress tasks and elevated total peripheral resistance and lower cardiac output and stroke volume during physical tasks, as compared with control subjects. Thus, the difference in blood pressure reactivity between patients and controls appeared to be primarily dependent on the vascular component during physical tasks, whereas the mental tasks promoted a hemodynamic response pattern more consistent with beta adrenergic activation. Type A men, irrespective of coronary status, showed larger systolic and diastolic blood pressure response to both mental and physical stress than did Type B men.

Adult↗
PubMed1994

"Unconscious anxiety": phobic responses to masked stimuli.

We tested the hypothesis that an unconscious preattentive perceptual analysis of phobic stimuli is sufficient to elicit human fear responses. Selected snake- and spider-fearful Ss, as well as normal controls, were exposed to pictures of snakes, spiders, flowers, and mushrooms. A separate forced-choice recognition experiment established backward masking conditions that effectively precluded recognition of experimental stimuli both for fearful and nonfearful Ss. In the main experiment, these conditions were used to compare skin conductance responses (SCRs) to masked and nonmasked phobic and control pictures among fearful and nonfearful Ss. In support of the hypotheses, snake- and spider-fearful Ss showed elevated SCRs to snake and spider pictures as compared with neutral pictures and with responses of the nonfearful Ss under both masking conditions. Ratings of valence, arousal, and dominance indicated that the fearful Ss felt more negative, more aroused, and less dominant in relation to both masked and nonmasked phobic stimuli.

Adult↗
PubMed1994

Electrodermal activity as a predictor of social functioning in female schizophrenics.

Twenty-nine female schizophrenics and 20 female controls were presented with a series of moderately intense tones in a standard orienting habituation paradigm while skin conductance was monitored. Premorbid adjustment and symptoms were also rated, and the schizophrenics were observed 2 years later. The total schizophrenic group was divided into a good-outcome group and a poor-outcome group. Good social functioning outcome required both self-supporting ability in the job market and at least a minimal social life. The poor-outcome group had a significantly higher skin-conductance level and frequency of spontaneous skin-conductance fluctuations than the control group, whereas the few patients with good outcome did not differ from controls. These results are contrary to previous findings with a group of schizophrenic men in which poor social functioning was associated with low electrodermal activity. This discrepancy is discussed in terms of sex differences in schizophrenic disorder.

Acoustic Stimulation↗
PubMed1994

Nonconscious associative learning: Pavlovian conditioning of skin conductance responses to masked fear-relevant facial stimuli.

We examined the possibility of nonconscious associative learning in a context of skin conductance conditioning, using emotional facial expressions as stimuli. In the first experiment, subjects were conditioned to a backwardly masked angry face that was followed by electric shock, with a masked happy face as the nonreinforced stimulus. In spite of the effectively masked conditioned stimuli, differential conditioned skin conductance responses were observed in a subsequent nonmasked extinction phase. This effect could not be attributed to differential sensitization or pseudo-conditioning. In the second experiment, the differential responding during extinction was replicated with angry but not with happy faces as conditioned stimuli. It was concluded that with fear-relevant facial expressions as the conditioned stimulus, associative learning was possible even in conditions where the subjects remained unaware of the conditioned stimulus and its relationship to the unconditioned stimulus.

Adult↗
PubMed1994

Psychophysiological effects of cardiac rehabilitation in post-myocardial infarction patients.

Psychophysiological reactivity and cardiovascular functioning were assessed in 40 patients with coronary heart disease before and after taking part in either a Type A modification training program or a control condition. Treated patients showed an overall attenuated heart rate (HR) response and prolonged diastolic time to mental stress performance, during recovery and rest periods, as compared lo control patients. No other measure, including impedance-cardiography-derived measures, differentiated the two groups. The treatment group showed reduction from before lo after treatment in 24-hr minimum IIR level and decreased frequencies of premature ventricular contractions, whereas the control group showed an opposite trend. Results from an exercise test suggested the same direction for resting IIR and double-product levels. The two groups did not differ in maximal systolic and diastolic blood pressure or in maximal double-product levels, despite a differential development, in favor of the treatment group, in maximal work capacity.

Journal Article↗
PubMed1993

A refined three-dimensional solution structure of a carboxy terminal fragment of apolipoprotein CII.

The three-dimensional structure of a synthetic fragment of human apolipoprotein CII (apo-CII) in 35%, 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) has been determined on the basis of distance and intensity constraints derived from two-dimensional proton nuclear magnetic resonance measurements. The NOE crosspeak build-up rates were converted to distance constraints which were used in the distance geometry program DI-ANA. A set of one hundred structures were generated and of these ten structures were used in molecular dynamics simulations using the program XPLOR. This program enabled a direct minimization between the difference of the two-dimensional NOE intensities and those calculated from the full relaxation matrix. In this way spin diffusion is fully taken into account, which can be seen from the considerable improvement of the R-factor after the relaxation matrix refinement. These calculations show that this fragment, which corresponds to the carboxy terminal 30 amino acids of intact apo-CII and which retains its ability to activate lipoprotein lipase, is essentially flexible, but has three defined secondary structural elements. The most significant one is an alpha-helix between residues 67 and 74. The following three residues adopt a turn-like structure. Another turn of alpha-helix is seen between residues 56 and 59. The effect of the solvent system on the secondary structure was studied by circular dichroism spectroscopy. The results show that the mixed aqueous 35% HFP solvent induces secondary structure of a very similar nature to the one induced by sodium dodecyl sulphate.

Apolipoprotein C-II↗
PubMed1993

Preattentive processing, preparedness and phobias: effects of instruction on conditioned electrodermal responses to masked and non-masked fear-relevant stimuli.

We hypothesized that autonomic responses conditioned to fear-relevant stimuli, in contrast to responses conditioned to neutral stimuli, can be elicited after only an automatic, non-conscious analysis of the stimulus. Consequently, they may be expected to be insensitive to verbal instructions. Normal subjects were conditioned to either fear-relevant stimuli (snakes or spiders) or neutral stimuli (flowers or mushrooms) in a differential conditioning paradigm with shock as the unconditioned stimulus. In a subsequent extinction series, half of the subjects were shown the conditioned stimuli under masking conditions preventing their conscious recognition, whereas the other half were exposed to non-masked stimuli. Then half of the subjects in each of the masking conditions were verbally instructed that no more shocks would be delivered and then the extinction trials followed. Consistent with our hypothesis, differential responses to the fear-relevant CSs+ and CSs- remained unaffected by both masking and instruction, whereas differential responding to neutral stimuli was wiped out by the masking procedure and the verbal instruction.

Adolescent↗
PubMed1993

On the automatic nature of phobic fear: conditioned electrodermal responses to masked fear-relevant stimuli.

Normal subjects (n = 64) were exposed either to pictures of snakes and spiders or to pictures of flowers and mushrooms in a differential conditioning paradigm in which one of the pictures signaled an electric shock. In a subsequent extinction series, these stimuli were presented backwardly masked by another stimulus for half of the subjects, whereas the other half received non-masked extinction. In support of a hypothesis that suggests that nonconscious information-processing mechanisms are sufficient to activate responses to fear-relevant stimuli, differential skin conductance response to masked conditioning and control stimuli was obvious only for subjects conditioned to fear-relevant stimuli. These results were replicated in a second experiment (n = 32), which also demonstrated that the effect was unaffected by which visual half-field was used for stimulus presentation.

Adult↗
PubMed1993

Masking the face: recognition of emotional facial expressions as a function of the parameters of backward masking.

Four experiments are reported investigating recognition of emotional expressions in very briefly presented facial stimulus. The faces were backwardly masked by neutral facial displays and recognition of facial expressions was analyzed as a function of the manipulation of different parameters in the masking procedure. The main conclusion was that stimulus onset asynchrony between target and mask proved to be the principal factor influencing recognition of the masked expressions. In general, confident recognitions of facial expressions required about 100-150 msec, with shorter time for happy than for angry expressions. The manipulation of the duration of both the target and the mask, by itself, had only minimal effects.

Adolescent↗
PubMed1993

Backward masking and skin conductance responses after conditioning to nonfeared but fear-relevant stimuli in fearful subjects.

The present study examined two issues. Are skin conductance responses conditioned to fear-relevant stimuli, as contrasted with responses conditioned to fear-irrelevant stimuli, elicited after merely an automatic, nonconscious analysis of the stimulus content? Do fearful subjects show better conditioning to nonfeared but fear-relevant stimuli (e.g., conditioning to spiders in snake-fearing subjects) than do nonfearful subjects? Subjects afraid of snakes, but not of spiders, or vice versa (n = 32) and nonfearful subjects (n = 32) were shown either fear-relevant stimuli (snakes or spiders and rats) or fear-irrelevant stimuli (flowers and mushrooms) in a differential conditioning paradigm, where one of the stimuli was followed by an electric shock. During a subsequent extinction phase, the conditioned stimuli were presented under backward masking conditions, preventing their conscious recognition. Consistent with our hypothesis, during the masked extinction of the conditioned stimuli, differential skin conductance responses to conditioning and control stimuli remained only for subjects conditioned to fear-relevant stimuli. Both fearful and nonfearful control subjects had significantly larger differential electrodermal responses to fear-relevant than to fear-irrelevant stimuli. However, contrary to our hypothesis, fearful subjects did not show enhanced conditionability to their nonfeared but fear-relevant stimuli as compared with nonfearful control subjects.

Adolescent↗