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Biomedical subjects

J Kajander

Publications and source records attributed to J Kajander.

13 recordsLinked to original sources
PubMed2003

Measurement of striatal and thalamic dopamine D2 receptor binding with 11C-raclopride.

11C-Raclopride is a widely used positron emission tomography (PET) tracer for measurement of striatal D2 dopamine receptor binding characteristics. Recently, 11C-raclopride has also been used for quantification of thalamic D2 receptor binding. We studied reproducibility and validity issues on the thalamic D2 binding measurements using healthy volunteer test-retest data and simulated data. Eight healthy male volunteers received 11C-raclopride as a bolus injection in a standard test-retest design using 3-dimensional PET. The displacement of thalamic 11C-raclopride binding by the D2 receptor antagonist haloperidol was studied in two female schizophrenic patients. With regards to reproducibility and reliability, thalamic 11C-raclopride binding could be described with a simplified reference tissue model resulting in binding potentials (BPs) between 0.38 and 0.66. In comparison, the model failed to describe 11C-raclopride binding consistently in temporal cortex due to low specific signal. Measurement of thalamic 11C-raclopride BP was reproducible with a test-retest variability of 7.6+/-6.2% and reliable with an intraclass correlation coefficient (ICC) of 0.87. Comparable ICCs were observed in caudate and putamen (0.84-0.96). With regard to validity, subchronic low dose haloperidol treatment reduced specific 11C-raclopride binding equally in putamen and thalamus but a higher dose induced clearly higher D2 receptor occupancy in putamen than in thalamus. Noise simulations indicated that this can partly be explained by an over-estimation of thalamic D2 receptor BP in noisy conditions (low signal, high occupancy). The D2 receptor BP in putamen was clearly more resistant to noise. We conclude that the reproducibility and reliability of thalamic 11C-raclopride BP is good and equal to, or only slightly less than, those observed in caudate or putamen. However, the signal-to-noise ratio for quantification may become too low especially in receptor occupancy-type studies, leading to an artefactual underestimation of measured D2 receptor occupancy.

Adult↗
PubMed2001

Measurement of cortical dopamine d1 receptor binding with 11C[SCH23390]: a test-retest analysis.

[11C]SCH 23390 is a standard ligand for positron emission tomography (PET) studies on striatal dopamine D1 receptors. Its usefulness for cortical D1 receptor quantification in human PET studies has been questioned but has not been addressed previously. The authors tested the reproducibility of [11C]SCH 23390 binding potential (BP) in cortical areas in five healthy volunteers using three-dimensional PET. Measurement of D1 receptor BP was reproducible in basal ganglia, as well as in all cortical areas studied (intraclass correlation coefficients between 0.81 and 0.92). The absolute variability in cortical areas was 9.21% +/- 0.07%. The reproducibility of cortical D1 receptor BP measurement with [11C]SCH 23390 is equal to that observed with a more recent D1-ligand, [11C]NNC 112. [11C]NNC 112 produces slightly higher specific-to-nonspecific binding ratios but has markedly slower kinetics resulting in a need for a longer scan time. These aspects should be considered when designing studies on the cortical D1-like receptors.

Adult↗
PubMed2000

Measurement of extrastriatal D2-like receptor binding with [11C]FLB 457--a test-retest analysis.

[11C]FLB 457 is a radioligand for positron emission tomography (PET) that possesses high affinity to D2/D3 receptors. It has been suggested to be useful for quantification of low-density dopamine D2 receptor populations, e.g. in cortical and limbic brain areas. We explored the reproducibility of five methods for measuring extrastriatal D2-like receptor binding potential with [11C]FLB 457. Seven healthy male volunteers were examined twice with [11C]FLB 457 (high specific radioactivity) on the same day, at least 3 h apart. Four brain areas, frontal cortex, nucleus thalamus, temporal cortex and cerebellar cortex, were examined. Binding potentials (BPs) were derived from (1) a target to cerebellum distribution volume ratio, (2/3) two reversible reference tissue compartment models and (4) a transient equilibrium approach. For comparison, BP values were also calculated with the standard three-compartment kinetic model that does not assume a receptor-free reference region. The use of the standard three-compartment model did not result in reproducible BP estimates. The distribution volume (DV) ratio, reference tissue compartment models and the transient equilibrium method all had good to excellent intraclass correlation coefficients (ICCs) in the studied brain areas ranging from 0.56 to 0.93. Absolute variability was also relatively low, ranging from 5.3% to 10.4%. There were no marked differences in the ICC or absolute and relative variability between the four methods based on a reference tissue (cerebellum). In addition, we did not observe systematic differences in the BP between the first and the second scan. These data indicate that the reproducibility of the DV ratio, reference tissue models and the transient equilibrium method is good or excellent. However, each of these methods includes assumptions affecting their validity. Thus, the choice of method will be critically dependent on the purpose of the study.

Adult↗
PubMed2000

Quantification of [Carbonyl-(11)C]WAY-100635 binding: considerations on the cerebellum.

The specific binding of [carbonyl-(11)C]WAY-100635 to 5-hydroxytryptamine(1A) receptors was quantitated using different kinetic models. Ten healthy subjects were studied using a GE Advance PET scanner. We suggest that tissue heterogeneity explains part of the nonspecific binding seen in cerebellum, which leads to an underestimation of binding potential with reference tissue methods. The nonlinear three-compartmental model with metabolite-corrected plasma input provides accurate estimates of receptor binding because of the favorable kinetics of tracer in the brain and circulation.

Adult↗
PubMed2000

Prediction of detached personality in healthy subjects by low dopamine transporter binding.

OBJECTIVE: Low striatal dopamine D(2) receptor binding in healthy human subjects has been associated with detached personality in studies using positron emission tomography (PET) and the Karolinska Scales of Personality questionnaire. The authors investigated whether a similar correlation exists between striatal dopamine transporter binding and detached personality. METHOD: Eighteen healthy volunteers participated in a PET study with the specific dopamine transporter ligand [(18)F]CFT ([(18)F]WIN 35,428) and completed the Karolinska Scales of Personality questionnaire form. RESULTS: Age-corrected dopamine transporter binding in the putamen, but not in the caudate, correlated negatively with detachment personality scores, especially in the right hemisphere. CONCLUSIONS: This finding supports the hypothesis that low dopaminergic neurotransmission is associated with detached personality. Furthermore, since [(18)F]CFT binding is thought to reflect the density of dopaminergic nerve terminals in the brain, the authors suggest that the neurodevelopmental formation of the brain dopaminergic system may influence adult personality traits.

Adult↗
PubMed1996

Future trends in the health care economy.

Most articles on the future of health care are by professionals involved in the delivery of health care services. This article is unique in that trends are examined from the perspective of the public and purchasers of care. The authors focus on 12 trends that are or will be affecting the industry, and on the sometimes unintended consequences and new conflicts that may develop.

Capital Financing↗
PubMed1994

Serum levels, absorption efficiency, faecal elimination and synthesis of cholesterol during increasing doses of dietary sitostanol esters in hypercholesterolaemic subjects.

1. Serum cholesterol reduction and changes in cholesterol metabolism were studied during rapeseed oil feeding without and with increasing amounts of sitostanol trans-esterified with rapeseed oil fatty acids and dissolved in rapeseed oil mayonnaise. Fifteen mildly hypercholesterolaemic subjects replaced 50 g of their usual dietary fat by 50 g of rapeseed oil fat mayonnaise for 6 weeks followed by randomization so that eight subjects continued on rapeseed oil mayonnaise alone (control group) for 15 weeks and seven on rapeseed oil mayonnaise with a small dose of sitostanol ester (800 mg/day of sitostanol) for 9 weeks followed by 6 weeks with higher dose of sitostanol ester (2000 mg/day of sitostanol). 2. During the rapeseed oil period the reduction in serum low-density lipoprotein cholesterol was 14% from the home diet. The control-adjusted reduction by the low sitostanol ester dose was 7.4% (not significant) and by the higher dose it was 15.7%. 3. The low dose of sitostanol ester had no consistent effect on cholesterol precursors or cholestanol in serum, reduced serum levels of campesterol and sitosterol by 28.2% and 23.6%, respectively, and reduced cholesterol absorption efficiency significantly from 28.7% to 23.4%. In accordance, faecal excretion of neutral and particularly endogenous neutral sterols increased (16.7% and 19.7%, respectively), but faecal cholesterol elimination and cholesterol synthesis were only insignificantly increased. 4. During the high dose of sitostanol ester the high-density lipoprotein-to low-density lipoprotein-cholesterol ratio increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Analysis of chromosomal aberrations, sister chromatid exchanges and micronuclei among power linesmen with long-term exposure to 50-Hz electromagnetic fields.

Chromosomal aberrations, sister chromatid exchanges (SCEs), replication indices and micronuclei in peripheral blood lymphocytes were analysed among 27 nonsmoking power linesmen with considerable long-term exposure to 50-Hz electromagnetic (EM) fields, and among 27 nonsmoking telephone linesmen serving as a reference group, pairwise matched with the exposed workers for age and geographical region. Blood samples from the two groups were collected, cultured and analysed in parallel. No differences between the groups were observed on analysis of SCEs, replication indices or micronuclei. However, the mean rate of lymphocytes with chromatid-type breaks was higher among the power linesmen (0.96% gaps excluded, 1.41% gaps included) than among the reference group (0.44% and 0.70%, respectively). The excess of aberrant cells was concentrated among those power linesmen who had worked earlier in their life. Although the interpretation is somewhat complicated by the confounding effect of previous smoking, these results suggest that exposure to 50-Hz EM fields is associated with a slight increase in chromatid breaks.

Adult↗
PubMedDate not supplied

Ensuring health care quality: a purchaser's perspective--an employer.

This paper explores the idea of accountability in the managed care arena and the need for employers to demand accountability if they are to establish themselves as customers. Four key principles for establishing greater accountability are outlined: addressing health care issues at the local level; focusing on quality of health care as well as cost; collecting data on quality; and creating an accountable health care system through value-based purchasing. A review of methods for establishing accountability when negotiating contracts with managed care organizations (MCOs) focuses on the significance of collecting and understanding claims data, defining performance standards, and establishing and using MCO incentives.

Employer Health Costs↗