Biomedical subjects

K J Lindner

Publications and source records attributed to K J Lindner.

5 recordsLinked to original sources

PubMed1992

Brain kinetics of 11 C-labelled L-tryptophan and 5-hydroxy-L-tryptophan in the rhesus monkey. A study using positron emission tomography.

5-Hydroxy-L-tryptophan labelled with 11 C is introduced as a tracer for the in vivo assessment of brain serotonin synthesis in the Rhesus monkey using positron emission tomography, PET. Increasing radioactivities were seen in the striatal area in contrast to that seen in other brain regions. Following 11 C-labelled L-tryptophan an even spread of brain radioactivity was seen. This selective increase most probably results from the decarboxylation of tracer and retention of formed products since no striatal increase of radioactivity was seen when 5-hydroxy-L-tryptophan labelled with 11 C in the carboxy-position was administered. Furthermore, pretreatment of the monkey with a centrally active decarboxylase inhibitor (NSD 1015, 10 mg/kg) did not lead to increased striatal radioactivities after the administration of 5-hydroxy-(beta-11 C)-L-tryptophan. The selective utilization of the radiotracer in the striatal area increased with a rate constant calculated to be 0.0055 +/- 0.0015 min-1 (n = 5) using the surrounding brain as reference area. A non-significant influence of radiolabelled metabolites to the rate constants measured was shown after pretreatment of the monkeys with selective and non-selective monoamine oxidase inhibitors, respectively. These results may give a basis for the use of the new tracer 5-hydroxy-(beta-11 C)-L-tryptophan in PET-studies of brain serotonin metabolism in health and disease.

5-Hydroxytryptophan↗

PubMed1992

Regional brain kinetics of 6-fluoro-(beta-11C)-L-dopa and (beta-11C)-L-dopa following COMT inhibition. A study in vivo using positron emission tomography.

The regional brain kinetics of (beta-11C)-L-dopa and 6-fluoro-(beta-11C)-L-dopa was measured in six Rhesus monkeys using positron emission tomography (PET). Radioactivity accumulated specifically in the striatal region and the increase in L-dopa-derived radioactivity utilization with time was calculated using surrounding brain as a reference area, this being devoid of dopaminergic activity. The rate constant for selective striatal utilization i.e. grossly decarboxylation was 0.0110 +/- 0.0007 (S.D) and 0.0057 +/- 0.0006 min-1 for (beta-11C)-L-dopa and 6-fluoro-(beta-11C)-L-dopa, respectively. After pretreatment of the monkeys with the peripherally and centrally active catecholamine-O-methyl transferase (COMT) inhibitor Ro 40-7592 10 mg/kg, the decarboxylation rate remained unchanged (0.0112 +/- 0.0015 min-1) for (beta-11C)-L-dopa, whereas an increase in rate was measured for 6-fluoro-(beta-11C)-L-dopa (0.0092 +/- 0.0015 min-1). Differences in the distribution of radiolabelled metabolites i.e. the corresponding O-methyl-L-dopa in the reference area is most probably the reason for the difference in calculated decarboxylation rate seen between the radiotracers. The higher decarboxylation rate measured for 6-fluoro-(beta-11C)-L-dopa after blockade of COMT shows that the radiolabelled metabolites i.e. 6-fluoro-O-methyl-(beta-11C)-L-dopa significantly contributes to background radioactivity.

Animals↗

PubMed1991

Withdrawal predictors among physical and performance characteristics of female competitive gymnasts.

Future drop-outs (n = 27) and continuing (n = 41) female competitive gymnasts were compared with respect to their physical, performance and injury characteristics measured through a large battery of tests completed while they were participants in competition. Included were anthropometric variables, body composition and somatotype, strength, flexibility, endurance, power, speed and balance measurements, and previous injury information. Differences were examined through t-tests and through discriminant analyses of principal components. The results indicate that the drop-outs were as a group distinguishable from the continuing gymnasts: they were significantly older, taller and heavier which may account for the finding that they were significantly stronger, more powerful and faster, and had greater endurance. They also had a slightly more linear/ectomorphic physique with less muscularity, and performed better on most flexibility tests. Only in a gymnastic-specific flexibility variable did the continuing gymnasts out-perform the drop-outs. It was concluded that it was mainly the age factor, and presumably the social and psychological factors associated with it, that distinguished the future drop-outs from the continuing gymnasts, and that factors related to the physical make-up and performance capacities of gymnasts cannot readily predict withdrawal from the sport.

Adolescent↗

PubMed1990

Injury patterns of female competitive club gymnasts.

Gymnast and injury information on 178 competitive female gymnasts was collected through questionnaires and interviews in a 3-year prospective epidemiologic study. The injury rate was 30/100 gymnasts/year, .52 injuries/1000 h. Injury rates excluding risk exposure increased with competitive level, but the top level gymnasts had the lowest rate per 1000 h of practice. Fractures of the wrist, fingers and toes were most common, followed by sprains of ankle and knee. Nearly 40% of the sudden-onset injuries occurred in the floor event. 'Missed move' was most frequently cited as the injury mechanism, while somersaults and handsprings were the most injury-producing moves. Most injuries happened with moves that were basic or moderately difficult and well-established. There was an increased chance of injury when the gymnast had been on the apparatus for an extended period of time. One major source of injury is loss of concentration, and a key to injury prevention may be the reorganization of the practice session.

Adolescent↗

PubMed1988

Age changes in assembly performance: a component analysis.

100 children from Kindergarten to Grade 9 (i.e., 5 to 15 yr.) performed a one-handed manual dexterity assembly task. The videotaped performances were analyzed for the components, Grasping, Transporting, Positioning, Reaching, and Pauses. All five components contributed significantly to the improvements in the lower grades. The Grasping component deteriorated significantly in the older children, but Reaching and Positioning continued to improve up to Grade 9. There were no sex differences.

Adolescent↗