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Biomedical subjects

P Johnsson

Publications and source records attributed to P Johnsson.

At least 19 recordsLinked to original sources
PubMed2006

Attosecond pulse trains generated using two color laser fields.

We investigate the spectral and temporal structure of high harmonic emission from argon exposed to an infrared laser field and its second harmonic. For a wide range of generating conditions, trains of attosecond pulses with only one pulse per infrared cycle are generated. The synchronization necessary for producing such trains ensures that they have a stable pulse-to-pulse carrier envelope phase, unlike trains generated from one color fields, which have two pulses per cycle and a pi phase shift between consecutive pulses. Our experiment extends the generation of phase stabilized few cycle pulses to the extreme ultraviolet regime.

Journal Article↗
PubMed2005

Reconstruction of attosecond pulse trains using an adiabatic phase expansion.

We propose a new method to reconstruct the electric field of attosecond pulse trains. The phase of the high-order harmonic emission electric field is Taylor expanded around the maximum of the laser pulse envelope in the time domain and around the central harmonic in the frequency domain. Experimental measurements allow us to determine the coefficients of this expansion and to characterize the radiation with attosecond accuracy over a femtosecond time scale. The method gives access to pulse-to-pulse variations along the train, including the timing, the chirp, and the attosecond carrier envelope phase.

Journal Article↗
PubMed2005

Attosecond electron wave packet dynamics in strong laser fields.

We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (approximately 20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes.

Journal Article↗
PubMed2004

Predicting noncompliant levels of ochratoxin A in cereal grain from Penicillium verrucosum counts.

AIMS: To model the probability of exceeding the European legislative limit of 5 microg ochratoxin A (OTA) per kilogram grain in relation to Penicillium verrucosum levels and storage conditions, and to evaluate the possibilities of using P. verrucosum colony counts for predicting noncompliant OTA levels. METHODS AND RESULTS: Cereal samples were inoculated with P. verrucosum spores and stored for up to 9 months at temperatures and water activities ranging from 10-25 degrees C and aw 0.77-0.95. A logistic regression analysis showed that the probability of exceeding 5 microg OTA kg(-1) grain was related to colony counts of P. verrucosum and water activity. The sensitivity and specificity of various P. verrucosum count thresholds for predicting noncompliant OTA levels were estimated, using data from the storage trial and natural cereal samples. CONCLUSION: The risk of exceeding 5 microg OTA kg(-1) grain increased with increasing levels of P. verrucosum, and with increasing water activities. A threshold of 1000 CFU P. verrucosum per gram grain is suggested to predict whether or not the legislative limit is exceeded. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided a tool to evaluate the levels of P. verrucosum in grain in relation to OTA levels. Hence, mycological analyses can be used to identify cereal samples with high risk of containing OTA levels above the legislative limit.

Avena↗
PubMed2001

S100B as a predictor of size and outcome of stroke after cardiac surgery.

BACKGROUND: Stroke after cardiac surgery is a clinical problem with often fatal or disabling outcome. To assess severity and probable outcome in affected patients only from clinical and radiological examinations is difficult. The glial-derived protein S100B has been suggested to be a marker of cerebral ischemia, and increased blood concentrations of S100B have been shown to correlate with size of lesion and prognosis after stroke. We studied the validity of S100B as a predictor of size of brain lesion and median term outcome in a consecutive group of patients suffering from stroke after cardiac surgery. METHODS: During a period of 17 months, 20 patients with clinical signs of postoperative stroke were investigated with S100B measurement, sampled at 5, 15 and 48 hours after surgery. All patients were examined with computed tomography or magnetic resonance imaging to confirm the diagnosis, and the size of cerebral infarction was estimated from the radiological examinations. The patients were followed up for survival 24 to 39 months after surgery. RESULTS: S100B concentration in blood 48 hours after surgery correlated with the size of infarcted brain tissue (r = 0.68, p < 0.001). Nine patients had S100B levels exceeding 0.5 microg/L and a 2-year mortality of 78%, whereas the 11 patients with S100B below 0.5 microg/L had a mortality of 18%. CONCLUSIONS: Increased S100B in patients with a stroke following cardiac surgery correlate with the size of infarcted brain tissue. High S100B levels 48 hours after surgery have a negative predictive value for median term survival.

Aged↗
PubMed2001

The troubled self in women with severe eating disorders (anorexia nervosa and bulimia nervosa). A study using interviews, self-reports, and percept-genetic methods.

Fifteen anorectic (A) and 13 bulimic (B) patients aged 20-49 years, all seriously ill, and 21 controls were studied, using a half-structured interview, the Tennessee Self Concept Scale, the tachistoscopic Identity Test (IT), and two other percept-genetic tests. The differences between A and B were not particularly pronounced, A patients being on the whole more sensitive and self-directed, and B patients more depressive and object-directed. The IT differentiated between patients and controls very powerfully with regard to alexithymia. A type of response in that test, emphasizing the eyes, was seen as a search for guidance. Descriptions of mother were generally negative.

Adult↗
PubMed2000

Neuron-specific enolase increases in plasma during and immediately after extracorporeal circulation.

BACKGROUND: Minor cerebral complications are common after cardiac surgery. Several biochemical markers for brain injury are under research; one of these is neuron-specific enolase (NSE). The purpose of this study was to investigate the release of this enzyme into the blood during and immediately after extracorporeal circulation and to evaluate the effect of hemolysis on this release. METHODS: Sixteen patients scheduled for elective heart surgery were included in the study. Blood samples for analysis of NSE and free hemoglobin in plasma were drawn before, during, and up to 48 hours after the end of extracorporeal circulation. The release of NSE from erythrocytes and its correlation to the release of free hemoglobin was studied by serial dilution and hemolysis in vitro. RESULTS: The peri- and postoperative course was uneventful in all patients. Extracorporeal circulation initiated a release of NSE that reached a maximum 6 hours after the end of perfusion. Thereafter, the levels declined with an estimated t1/2 of 30 hours. The concentration of free hemoglobin increased during the perfusion, with maximum levels at the end of perfusion, after which they fell rapidly to normal values. The in vitro study showed a strong linearity between the release of NSE and free hemoglobin after induced hemolysis. CONCLUSIONS: The increased levels of enolase at the end of cardiopulmonary bypass can, to a major part, be explained by the release from hemolysed erythrocytes. The value of NSE as a marker for brain injury in these situations is therefore doubtful.

Adult↗
PubMed2000

HPLC method for analysis of secoisolariciresinol diglucoside in flaxseeds.

A method was developed for the analysis of secoisolariciresinol diglucoside (SDG) in flaxseeds. The analytical method involves extraction of defatted flaxseed flour with dioxane/ethanol, aqueous base-hydrolysis, solid-phase purification of an SDG-containing fraction, and quantitative analysis by high-performance liquid chromatography (HPLC). Pure SDG was isolated from flaxseed using different column chromatographic methods and used, as external standard, for the calibration of the method and for quantification. The method was then applied to study the variation in SDG content in flaxseeds from 14 cultivars grown in Sweden and 15 cultivars grown in Denmark. The SDG content varied between 11.7 and 24.1 mg/g in defatted flaxseed flour and between 6.1 and 13.3 mg/g in whole flaxseeds.

Butylene Glycols↗
PubMed2000

Elimination of S100B and renal function after cardiac surgery.

OBJECTIVES: To determine the biologic half-life of the S100B protein and to investigate if the elimination of S100B depends on glomerular filtration rate (GFR). DESIGN: Prospective human study. SETTING: University hospital. PARTICIPANTS: Sixteen patients who underwent cardiac surgery with cardiopulmonary bypass. INTERVENTIONS: Shed mediastinal blood (autotransfusion) was returned to the patients postoperatively and used to study the kinetics of S100B. Iohexol was infused simultaneously to estimate GFR. S100B was measured at 0, 20, 40, 60, and 180 minutes after infusion. Iohexol was measured at 180 and 240 minutes after infusion. MEASUREMENTS AND MAIN RESULTS: S100B followed first-order kinetics, and the biologic half-life for S100B was determined to be 25.3 +/- 5.1 minutes. GFR was determined to be 63.8 +/- 34.4 mL/min. No correlation was found between GFR and S100B half-life. CONCLUSIONS: The elimination of S100B after cardiac surgery is faster than reported earlier and not affected by a moderate decrease in GFR. This finding is important when evaluating S100B levels after cardiac surgery.

Aged↗
PubMed1999

[Good quality of life after heart surgery. Comparable ratings by patients and their relatives].

In a series of 83 patients undergoing coronary artery bypass grafting for angina, perceived QOL (quality of life) was rated by the patients and their spouses, preoperatively and at two and 12 months postoperatively, using the SWED-QUAL instrument. One year after surgery, QOL had improved to a level which might be expected of a normal population comparable in age and gender distribution. Good correlation existed between patient and spouse ratings, especially on physical measures.

Angina Pectoris↗
PubMed1999

Serum S100B and hypothermic circulatory arrest in adults.

BACKGROUND: Cerebral injury is the most important complication of cardiac operations with cardiopulmonary bypass. Prolonged total circulatory arrest (TCA) can expose patients to an even greater risk of cerebral injury. We sought to detect the degree of cerebral injury in adults who had thoracic aortic operations with TCA by measuring S100B protein, which is released into the circulation after cerebral injury. METHODS: Serial measurements of S100B protein, a highly specific serum marker of astroglial damage, were performed in 26 patients who had complex aortic operations, of whom 13 required cardiopulmonary bypass alone (for aortic root replacement), and in 13 patients who required an additional period of TCA (for type A aortic dissections and arch aneurysms). Blood samples were taken preoperatively, at skin closure, and 5 and 24 hours postoperatively. RESULTS: There were significant increases in serum S100B concentrations in all patients, and peak levels occurred at skin closure. The magnitude of the increase in S100B was significantly greater at all postoperative time points and persisted longer in the TCA group. There was a significant correlation between the duration of the TCA and S100B concentration at 5 hours (r = 0.66, p = 0.01) and 24 hours (r = 0.63, p = 0.02) postoperatively. CONCLUSIONS: S100B levels were higher in all patients who had complex aortic operations and were significantly greater in patients requiring a period of TCA. The duration of the TCA period correlated with S100B levels 5 hours and at 24 hours postoperatively. Circumstantial evidence, in accordance with other studies, suggests that S100B protein is a marker for cerebral injury during cardiac operations.

Adult↗
PubMed1999

S100beta after coronary artery surgery: release pattern, source of contamination, and relation to neuropsychological outcome.

BACKGROUND: S100beta has been suggested as a marker of brain damage after cardiac operation. The aim of this study was to characterize the early S100beta release in detail and relate it to neuropsychological outcome. METHODS: Three groups of patients were investigated. All patients underwent coronary artery bypass surgery (CABG) with extracorporeal circulation. In group A, 110 patients had sampling of S100beta for the first 10 postoperative hours and also underwent neuropsychological testing. In group B, 14 patients were examined for the effect of autotransfusion on S100beta levels. Eight patients in group C had their intraoperative bleeding processed with a cell-saving device. RESULTS: Group A had a heterogeneous release pattern with several rapid elevations in S100beta concentration. In group B, high concentrations of S100beta were found in the autotransfusion blood (range 0.2 to 210 microg/L) with a concurrent elevation of serum S100beta levels after transfusion of shed blood. In group C, high levels of S100beta were found in the blood from the surgical field (12.0+/-6.0 microg/L) and decreased (1.1+/-0.64 microg/L) after wash. Group C had significantly lower S100beta values at the end of cardiopulmonary bypass compared to group A (0.53+/-0.35 microg/L versus 2.40+/-1.5 microg/L). S100beta values were corrected for extracerebral contamination with a kinetic model. With this correction, an association was found between adverse neuropsychological outcome and S100beta release in group A (r = 0.39, p < 0.02). CONCLUSIONS: A significant amount of S100beta is found both in the blood from the surgical field and in the shed mediastinal blood postoperatively. Infusion of this blood will result in infusion of S100beta into the blood and interfere in the interpretation of early systemic S100beta values.

Blood Transfusion, Autologous↗
PubMed1998

Significance of serum S100 release after coronary artery bypass grafting.

BACKGROUND: S100 protein has been suggested to be a serum marker for cerebral complications after cardiac operation and extracorporeal circulation. The aim of this study was to characterize the S100 release pattern after extracorporeal circulation in 515 consecutive patients undergoing coronary artery bypass grafting. METHODS: Clinical variables and outcome were prospectively registered. The cerebral outcome was determined by clinical examination. S100 was measured at the end of extracorporeal circulation, and after 5, 15, and 48 hours. RESULTS: After operation, 13 patients had stroke, 12 had delayed awakening, and 17 had encephalopathy. Early S100 release, immediately after extracorporeal circulation, was associated with age and perfusion time, but not with cerebral outcome. However, S100 release after 5 to 48 hours was associated with cerebral complications and risk factors for such outcome. Patients with stroke had higher S100 levels after 15 to 48 hours. A subset of patients with renal failure had overall higher S100 levels at 5 hours. CONCLUSIONS: Early and late S100 release indicate different mechanisms for release and emphasizes the potential power of this new biochemical marker for cerebral damage.

Adult↗
PubMed1998

Serum S-100 and neuron-specific enolase for prediction of regaining consciousness after global cerebral ischemia.

BACKGROUND AND PURPOSE: The aim of our study was to assess the use of S-100 protein (S-100) and neuron-specific enolase (NSE) in serum and cerebrospinal fluid (CSF) for the prediction of patients' regaining consciousness after acute global cerebral ischemia. METHODS: Sixty-four unconscious patients were followed until the return of consciousness or until death/vegetative state. Serum and CSF samples for measurement of S-100 and NSE using an immunoradiometric assay technique were obtained 24 hours (serum) and 48 hours (CSF) after the acute event and correlated with patient outcome. RESULTS: Values for serum S-100 protein, serum NSE, CSF S-100, and CSF NSE were significantly different in the 2 outcome groups. A serum S-100 value of >0.7 micrograms/L was found to be a predictor of not regaining consciousness, with a high positive predictive value (95%) and high specificity (96%). CONCLUSIONS: S-100 protein used as serum marker 24 hours after acute global cerebral ischemia gives reliable and independent information on the outcome of the patient that is comparable or superior to that obtained with CSF markers. Therefore, S-100 may be a serum marker of brain cell damage useful for clinical assessment of these patients.

Adult↗
PubMed1997

The appearance of S-100 protein in serum during and immediately after cardiopulmonary bypass surgery: a possible marker for cerebral injury.

OBJECTIVE: To investigate the appearance and elimination of brain-specific S-100 protein in serum during and immediately after cardiopulmonary bypass. DESIGN: Prospective study. PARTICIPANTS: Twenty-nine patients undergoing elective cardiac surgery. INTERVENTIONS: Twenty-seven patients were operated on for coronary artery disease; two patients had valve replacement. Serial measurements of S-100 in arterial blood during and up to 48 hours after cardiopulmonary bypass were made. MEASUREMENTS AND MAIN RESULTS: The perioperative and postoperative course was uneventful in 25 patients, with no clinical signs of neurologic complications. S-100 was not detected before extracorporeal circulation was started. Detectable concentrations (detection limit, 0.2 microgram/L) appeared in serum after 10 minutes of perfusion and reached maximum levels, 2.43 +/- 0.3 micrograms/L, at the end of bypass. The levels then declined with elimination t1/2 of 2.2 hours. Only two patients had detectable concentrations of S-100 48 hours after the end of bypass. In four patients who developed clinical signs of cerebral injury, levels of S-100 were significantly higher at the end of bypass and 24 hours after the end of bypass. CONCLUSIONS: Cardiopulmonary bypass initiates a release of brain-specific S-100 to the systemic circulation. The release and elimination of S-100 seem to follow a reproducible pattern in patients with no signs of cerebral injury. In patients who developed cerebral injury, the concentrations of S-100 in blood were increased, thus suggesting that S-100 may be a usable marker for cerebral injury after extracorporeal circulation.

Adult↗
PubMed1997

Alexithymia in patients with eating disorders: an investigation using a new projective technique.

The concept of alexithymia was scrutinized in a group of female patients with eating disorders: 15 anorectics and 13 bulimics (mean age of 27 yr.), plus a control group of 21 (mean age 38 yr.). Subjects were interviewed and tested. In the main test an ambiguous face was flashed briefly on a screen opposite the viewer who had to describe her impressions. To enhance the ego-involvement, subliminal words (I, I ILL, I WELL) were presented before each exposure. Contrary to expectations the present patients used more emotional words than controls. Instead, they employed alternative strategies to avoid empathizing. The results were interpreted as indicating a pronounced incapacity for emotional understanding.

Adult↗