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Biomedical subjects

S Holm

Publications and source records attributed to S Holm.

At least 55 records · Page 3Linked to original sources
PubMed2000

Determination of the excitation function for the 10B(p,n)10C reaction with implications for the production of [10C]carbon dioxide for use as a PET tracer.

To evaluate the possibilities of producing useful amounts of 10C (T1/2 = 19 s) for use as an on-line, steady state positron emission tomography (PET) tracer, the excitation function and the thick target yield for the 10B(p,n)10C reaction up to 30 MeV were measured using an adapted version of the stacked-foil technique. The radionuclidic purity of the produced 10C versus the inevitable 11C contamination was evaluated as function of target thickness and incident proton beam energy.

Boron↗
PubMed2000

Rethinking risk.

Explore the source record for details and available documents.

Delivery of Health Care↗
PubMed2000

Ethical aspects of clinical trials: the attitudes of participants in two non-cancer trials.

OBJECTIVES: To investigate attitudes to clinical trials in non-cancer trial participants. DESIGN: Questionnaires at entry, during, and after participation in a clinical study. SETTING: Participants in: (i) ROC: a clinical study comparing systemic interferon-alpha-2A treatment vs. prednisolone enemas in ulcerative colitis; and (ii) MRCRUC: a clinical study investigating low-field magnetic resonance imaging as a new modality for the evaluation of patients with inflammatory bowel disease. SUBJECTS: Thirty-two patients in ROC and 47 patients in MRCRUC. OUTCOME MEASURES: Attitudes towards different aspects of clinical research. RESULTS: The majority found scientific testing of clinical methods necessary, having positive attitudes towards both participation by themselves and others. The creation of a personal moral problem by denying participation was rejected by a large majority, and still both personal and altruistic motives for participation were highly rated. An important motive for accepting inclusion was the expectation of being 'a special patient' during the trial. The presence of research ethics committees controlling clinical research had a significant positive impact on decisions to participate, and drawing lots and blinding were found problematic by only a minority. Patients valued their satisfaction with participation in the trials highly, and would almost all accept a request to participate in future trials. The most important reason for this was a feeling of receiving better care and information than expected outside a trial setting, primarily determined by the patients seeing only one physician during the trials. A pronounced wish to obtain follow-up information was expressed. CONCLUSION: Attitudes towards medical research are positive with both altruistic and nonaltruistic motives for participation. Expectations of being treated as 'a special patient' in the trial were important in accepting to participate. Seeing the same physician at control visits was an important factor for satisfaction with participation.

Adult↗
PubMed2000

Altered expression of members of the IGF-axis in hepatoblastomas.

Previous reports have demonstrated that expression of insulin-like growth factor 2 (IGF2) is altered in hepatoblastoma. Using RNAase protection analysis (RPA), we examined the gene expression for IGF1, IGF2, IGF1R, M6P/IGF2R, IGFBP-1 and IGFBP-2 in a series of hepatoblastomas with corresponding normal liver from the same individuals. The results show that the expression of the IGF-axis members included in the present study are altered between tumour and normal, and indicate that the IGF-axis may be involved in hepatoblastoma development.

Genes, Tumor Suppressor↗
PubMed2000

Invasive group A streptococcal infections in Sweden in 1994 and 1995: epidemiology and clinical spectrum.

A nationwide study of invasive group A streptococcal (GAS) infections in Sweden during 1994-1995 was carried out. All Swedish microbiological laboratories were asked to report isolates of GAS from normally sterile sites. During the study period they were also asked to send their isolates for T typing. Questionnaires were sent to the physicians in charge of each patient. The incidence, serotype, clinical presentation, symptoms and outcome were recorded. Clinical data were obtained for 468 of 556 patients with GAS bacteraemia. The lethality rate was 16%, but was much higher (37%) in the 113 patients who developed streptococcal toxic shock syndrome (STSS). Streptococci of serotype T1 dominated during the study period and were linked to the increase in invasive GAS infections. They also carried an increased risk of causing STSS. Invasive streptococcal disease with STSS most often has an unknown primary focus or is associated with soft tissue infections. Invasive streptococcal disease not associated with STSS most often has a skin infection as portal of entry or else an unknown focus.

Adolescent↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: I. Theory, error analysis, and stereologic comparison.

Limited spatial resolution of positron emission tomography (PET) can cause significant underestimation in the observed regional radioactivity concentration (so-called partial volume effect or PVE) resulting in systematic errors in estimating quantitative physiologic parameters. The authors have formulated four mathematical models that describe the dynamic behavior of a freely diffusible tracer (H215O) in a region of interest (ROI) incorporating estimates of regional tissue flow that are independent of PVE. The current study was intended to evaluate the feasibility of these models and to establish a methodology to accurately quantify regional cerebral blood flow (CBF) corrected for PVE in cortical gray matter regions. Five monkeys were studied with PET after IV H2(15)O two times (n = 3) or three times (n = 2) in a row. Two ROIs were drawn on structural magnetic resonance imaging (MRI) scans and projected onto the PET images in which regional CBF values and the water perfusable tissue fraction for the cortical gray matter tissue (hence the volume of gray matter) were estimated. After the PET study, the animals were killed and stereologic analysis was performed to assess the gray matter mass in the corresponding ROIs. Reproducibility of the estimated parameters and sensitivity to various error sources were also evaluated. All models tested in the current study yielded PVE-corrected regional CBF values (approximately 0.8 mL x min(-1) x g(-1) for models with a term for gray matter tissue and 0.5 mL x min(-1) x g(-1) for models with a term for a mixture of gray matter and white matter tissues). These values were greater than those obtained from ROIs tracing the gray matter cortex using conventional H2(15)O autoradiography (approximately 0.40 mL x min(-1) x g(-1)). Among the four models, configurations that included two parallel tissue compartments demonstrated better results with regards to the agreement of tissue time-activity curve and the Akaike's Information Criteria. Error sensitivity analysis suggested the model that fits three parameters of the gray matter CBF, the gray matter fraction, and the white matter fraction with fixed white matter CBF as the most reliable and suitable for estimating the gray matter CBF. Reproducibility with this model was 11% for estimating the gray matter CBF. The volume of gray matter tissue can also be estimated using this model and was significantly correlated with the results from the stereologic analysis. However, values were significantly smaller compared with those measured by stereologic analysis by 40%, which can not be explained by the methodologic errors. In conclusion, the partial volume correction was essential in quantitation of regional CBF. The method presented in this article provided the PVE-corrected regional CBF in the cortical gray matter tissue. This study also suggests that further studies are required before using MRI derived anatomic information for PVE correction in PET.

Animals↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: II. Normal values and gray matter blood flow response to visual activation.

One of the most limiting factors for the accurate quantification of physiologic parameters with positron emission tomography (PET) is the partial volume effect (PVE). To assess the magnitude of this contribution to the measurement of regional cerebral blood flow (rCBF), the authors have formulated four kinetic models each including a parameter defining the perfusable tissue fraction (PTF). The four kinetic models used were 2 one-tissue compartment models with (Model A) and without (Model B) a vascular term and 2 two-tissue compartment models with fixed (Model C) or variable (Model D) white matter flow. Furthermore, rCBF based on the autoradiographic method was measured. The goals of the study were to determine the following in normal humans: (1) the optimal model, (2) the optimal length of fit, (3) the model parameters and their reproducibility, and (4) the effects of data acquisition (2D or 3D). Furthermore, the authors wanted to measure the activation response in the occipital gray matter compartment, and in doing so test the stability of the PTF, during perturbations of rCBF induced by visual stimulation. Eight dynamic PET scans were acquired per subject (n = 8), each for a duration of 6 minutes after IV bolus injection of H2(15)O. Four of these scans were performed using 2D and four using 3D acquisition. Visual stimulation was presented in four scans, and four scans were during rest. Model C was found optimal based on Akaike's Information Criteria (AIC) and had the smallest coefficient of variance after a 6-minute length of fit. Using this model the average PVE corrected rCBF during rest in gray matter was 1.07 mL x min(-1) x g(-1) (0.11 SD), with an average coefficient of variance of 6%. Acquisition mode did not affect the estimated parameters, with the exception of a significant increase in the white matter rCBF using the autoradiographic method (2D: 0.17 mL x min(-1) x g(-1) (0.02 SD); 3D: 0.21 mL x min(-1) x g(-1) (0.02 SD)). At a 6-minute fit the average gray matter CBF using Models C and D were increased by 100% to 150% compared with Models A and B and the autoradiographic method. There were no significant changes in the perfusable tissue fraction by the activation induced rCBF increases. The largest activation response was found using Model C (median = 39.1%). The current study clearly demonstrates the importance of PVE correction in the quantitation of rCBF in normal humans. The potential use of this method is to cost-effectively deliver PVE corrected measures of rCBF and tissue volumes without reference to imaging modalities other than PET.

Adult↗
PubMed2000

Electrical admittance for filling of the heart during lower body negative pressure in humans.

To evaluate whether electrical admittance of intracellular water is applicable for monitoring filling of the heart, we determined the difference in intracellular water in the thorax (Thorax(ICW)), measured as the reciprocal value of the electrical impedance for the thorax at 1.5 and 100 kHz during lower body negative pressure (LBNP) in humans. Changes in Thorax(ICW) were compared with positron emission tomography-determined C(15)O-labeled erythrocytes over the heart. During -40 mmHg LBNP, the blood volume of the heart decreased by 21 +/- 3% as the erythrocyte volume was reduced by 20 +/- 2% and the plasma volume declined by 26 +/- 2% (P < 0.01; n = 8). Over the heart region, LBNP was also associated with a decrease in the technetium-labeled erythrocyte activity by 26 +/- 4% and, conversely, an increase over the lower leg by 92 +/- 5% (P < 0.01; n = 6). For 15 subjects, LBNP increased thoracic impedance by 3.3 +/- 0.3 Omega (1.5 kHz) and 3.0 +/- 0.4 Omega (100 kHz), whereas leg impedance decreased by 9.0 +/- 3.3 Omega (1.5 kHz) and 6.1 +/- 3 Omega (100 kHz; P < 0.01). Thorax(ICW) was reduced by 7.1 +/- 1.9 S. 10(-4) (P < 0.01) and intracellular water in the leg tended to increase (from 37.8 +/- 4.6 to 40.9 +/- 5.0 S. 10(-4); P = 0.08). The correlation between Thorax(ICW) and heart erythrocyte volume was 0.84 (P < 0.05). The results suggest that thoracic electrical admittance of intracellular water can be applied to evaluate changes in blood volume of the heart during LBNP in humans.

Adult↗
PubMed2000

Expression of genes involved with cell cycle control, cell growth and chromatin modification are altered in hepatoblastomas.

Hepatoblastoma is a rare pediatric liver tumor. While much progress has been made in the treatment of the disease, very little is known about the moleculer events underlying the pathogenesis of this disease. We sought to investigate a series of hepatoblastomas for alterations in gene expression patterns with emphasis on important cell regulatory genes, including chromatin modifying enzymes, cyclin dependent kinase inhibitors, growth factors, oncogenes and cell cycle regulators. Total RNA was extracted from a series of sporadic hepatoblastomas with matched normal liver, some unmatched tumors and fetal livers, and gene expression was measured for various genes using RNase Protection Analysis (RPA). The results of this analysis show that the expression of many important regulatory genes are distinctly altered in these tumors, and a subset of tumors can be distinguished on the basis of these gene expression differences and histopathological features. Because the molecular events underlying the pathogenesis of this rare tumor are so poorly understood, this study represents a first step in determining some of the possible mechanisms involved which may provide future avenues of research.

Case-Control Studies↗
PubMed2000

Cognitive studies of ethical reasoning based on the KARDIO-simulator.

Empirical investigations in medical ethics are often questionnaire studies relying on the respondents' written responses about their attitudes and actions. This approach is valuable, but there may be quite large discrepancies between responses and actual behaviour. Unfortunately actual behaviour is often difficult to observe, especially where sensitive or very time dependent clinical decisions are concerned. We have tried to circumvent this problem by using a micro-world computer simulation of a cardiac care unit to study treatment decisions in "life or death" situations. The task facing the physician in this simulation is to be in charge of a 6-bed cardiac care unit for a period of 14 "days" controlling admissions, discharges, and treatment of all patients. The simulation dynamically generates the disease states of the patients in the unit including physical findings, laboratory findings, ECG, X-ray descriptions etc., as well as the patients responses to treatment. The simulation also presents new patients from the emergency room, thereby forcing the physician to decide whether the new patient should be admitted, and whether one of the present patients should be discharged or moved to another ward if no bed is free. The paper describes this simulator, the mathematical model underlying the simulation of patients with acute myocardial infarction, and the results of the initial studies using the simulator.

Computer Simulation↗
PubMed2000

The extent of written trial information: preferences among potential and actual trial subjects.

AIM: To investigate the preferred extent of written information in clinical trials among potential and actual trial participants. MATERIALS AND METHODS: Questionnaire survey among citizens of Copenhagen County (PUB, N=508), patients attending an out-patient clinic (OPC, N=200), and finally among participants in two clinical trials (ROC, N=32; MRCRUC, N=47--see Abbreviations). Questions concerned attitudes to and preferences towards a relatively short ("short form") and a more detailed information form ("long form") about a hypothetical, but realistic trial. RESULTS: Approximately 1/8 of the respondents in PUB were satisfied with the "short form", whereas this was the case for approximately 1/6 of outpatients and 1/5 of actual trial participants. Regarding the "long form" approximately three quarters of respondents in all groups were satisfied. Outpatients as a whole were satisfied to a larger extent that respondents from the PUB trial concerning the "short form" (p=0.04). The "long form" was preferred by a little less than 4/5 of respondents in all groups. CONCLUSION: Written information to trial subjects should be detailed, as a majority of both potential and actual research participants prefers this, given the choice between two information forms of different extent on the same trial.

Communication↗
PubMed1999

A longitudinal study of cerebral glucose metabolism, MRI, and disability in patients with MS.

OBJECTIVE: To study the time-related changes in cerebral metabolic rate of glucose (CMRglc) in MS patients and to correlate these with changes in MRI lesion load and disability. BACKGROUND: Measurements of MRI lesion load and neurologic disability are used widely to monitor disease progression in longitudinal studies of MS patients, but little is known about the associated changes in cerebral neural function. METHODS: The authors studied 10 patients with clinically definite MS who underwent serial measurements of CMRglc, MRI T2-weighted total lesion area (TLA), and clinical evaluation of disability (Expanded Disability Status Scale [EDSS]) over a period of approximately 2 years (three examinations). CMRglc was calculated using PET and 18-fluorodeoxyglucose (FDG). RESULTS: The global cortical CMRglc decreased with time (p<0.001) and the most pronounced reductions of CMRglc were detected in frontal and parietal cortical areas. There was a statistically significant increase of disability (p<0.01) and TLA (p<0.05) measurements during the study, but changes in CMRglc were not correlated to changes in TLA and EDSS. CONCLUSIONS: Global cortical cerebral metabolism in MS is decreased significantly during a 2-year observation period, suggesting a deterioration of cortical activity with disease progression. The time-related changes of cortical CMRglc are statistically stronger than changes in TLA measurements and neurologic disability, and might be a useful secondary measure of treatment efficacy.

Adult↗
PubMed1999

[How detailed information and how long consideration time do the potential trial subjects want?].

Questionnaires were sent to 508 citizens in Copenhagen county and given to 200 patients attending two out-patient clinics. Questions concerned attitudes and preferences towards either a short or a more detailed information form about an invented trial, and preferences regarding required time for reflection before giving informed consent. One sixth of responders were satisfied with the short form, while about three quarters preferred the long form. Three quarters of the non-hospitalized citizens and the patients from one of the out-patient clinics required at least 24 hours before answering about consent. Among responders in the other outpatient clinic half of the patients only required 15 minutes, or stated that they could answer at once. We conclude that written information to trial patients should be detailed, as a majority of potential research participants prefer this. At least 24 hours should be given before an informed consent is obtained.

Adult↗
PubMed1999

Prediction of neurological outcome after cardiopulmonary resuscitation.

In 231 patients with circulatory arrest of primary cardiovascular or pulmonary aetiology guidelines were established for predicting neurological outcome within the first year after cardiopulmonary resuscitation. Outcome measures were brain death, persistent unconsciousness, persistent disability after awakening and complete recovery. A total of 116 patients remained unconscious while 115 regained consciousness. Brain stem areflexia with apnoea (brain death) was demonstrated in 40 patients. No other finding per se could predict a specific outcome. The time for recovery of individual neurological functions seemed to be the key to prognostication. Testing the caloric vestibular reflex or stereotypic reactivity thus differentiated patients regaining consciousness from those remaining unconscious, with positive predictive values of 0.79 and 0.77 at 1 h and negative values of 1.0 and 0.97 at 24 h as compared with 50/50 prior odds. The presence of speech at 24 h or the ability to cope with personal necessities at 72 h predicted complete recovery with positive predictive values of 0.91 and 0.92 as compared with prior odds of 0.17, whereas, the negative predictive values never exceeded prior odds of 0.83.

Brain Death↗
PubMed1999

The course of circulatory and cerebral recovery after circulatory arrest: influence of pre-arrest, arrest and post-arrest factors.

We evaluated the influence of pre-arrest, arrest and post-arrest factors on circulatory and neurological recovery for up to 1 year following circulatory arrest of cardio-pulmonary aetiology in 231 patients. Initially, all patients were unconscious and 106 had some cortical activity recorded in the immediate post-resuscitation EEG (Group I), while 125 had no such activity initially (Group II). The following variables were explored: age, sex, medical history, cause and location of arrest, initial cardiac dysrhythmia, duration of life support, metabolic acidosis, pulse-pressure product and heart pump function capacity early after resuscitation. Outcome measures were duration and quality of circulatory survival, cause of death, neurological recovery and ultimate outcome. First year survival was 33% in Group I and 16% in Group II. Severe heart failure and brain death occurred mainly in Group II. Circulatory recovery was negatively influenced by out-of-hospital arrest, metabolic acidosis and pulse-pressure products below 150. Neurological recovery was negatively influenced by initial dysrhythmias other than ventricular fibrillation, pulse-pressure products below 150, post-arrest heart failure and/or pulmonary complications. It seems that circulatory and cerebral outcomes are mainly determined by the global ischaemic insults sustained during the circulatory arrest period.

Aged↗