Biomedical subjects

K Hinkelmann

Publications and source records attributed to K Hinkelmann.

18 recordsLinked to original sources

PubMed2004

Abnormal excitability of premotor-motor connections in de novo Parkinson's disease.

The dorsal premotor cortex (PMd) is abnormally active in patients with idiopathic Parkinson's disease. This has been interpreted as a functional correlate of adaptive plasticity within the motor system to compensate for deficient activation of striato-mesial-frontal projections in these patients. Whether abnormal PMd activity influences excitability in the primary motor cortex (M1) in untreated Parkinson's disease patients and how this premotor-motor interaction might be altered by l-dopa is unclear. To this end, we studied the effects of 1 Hz premotor repetitive transcranial magnetic stimulation (rTMS) on M1 excitability in 10 previously untreated non-tremulous Parkinson's disease patients before (day 1) and after (day 8) their first ever l-dopa treatment and compared the results with those of a group of nine age- and sex-matched healthy controls. In each rTMS session, 1200 pulses of 1 Hz rTMS were applied at an intensity of 80% active motor threshold (AMT) to the PMd contralateral to the clinically more affected side in Parkinson's disease patients and to the left PMd in healthy controls. Intracortical paired pulse excitability of ipsilateral M1 was probed using a TMS paired pulse paradigm where subthreshold conditioning pulses (80% of AMT) were given 2-15 ms prior to a suprathreshold test pulse. In Parkinson's disease patients, abnormal baseline intracortical excitability at an interstimulus interval (ISI) of 5 ms was normalized by premotor rTMS. In contrast, rTMS led to an increased excitability at an ISI of 5 ms in healthy controls. Premotor rTMS effects lasted longer (for at least a week) in patients. These results show that the modifiability of premotor-motor connections is abnormal in untreated Parkinson's disease. A single dose of l-dopa reversed, i.e. normalized, the direction of excitability changes in M1 following premotor rTMS in Parkinson's disease patients, suggesting that dopamine depletion directly or indirectly influences premotor-motor interactions in Parkinson's disease. The rTMS conditioning approach described here provides a promising tool to delineate further the excitability changes in frontal motor areas in response to progressive degeneration of nigrostriatal dopaminergic neurons and also to chronic l-dopa treatment in Parkinson's disease.

Adult↗

PubMed1991

[Do strong static magnetic fields in NMR tomography modify tissue perfusion?].

Findings obtained in humans and test animals raised the question whether strong static magnetic fields as used in NMR-tomography may affect tissue perfusion. In two test series including 20 subjects, each skin blood flow at the thumb was determined by heat clearance, and forearm blood flow was measured by venous occlusion plethysmography. For comparative purposes, measurements were carried out bilaterally at both extremities. The experiments consisted of three sections that lasted 10 min each. During the second section the thumb or the forearm were unilaterally exposed to magnetic fields of 0.9 to 1 T and 0.4 to 0.5 T, respectively. The results of this section were compared with the values obtained during the experimental sections prior to and after the exposure to the magnetic field. The results were also compared with the blood flow measured at the contralateral extremity. Neither at the skin of the thumb nor at the forearm were there changes in local blood flow attributable to the magnetic fields applied.

Adult↗

PubMed1985

Exercise and protein intake effects on urinary 3-methylhistidine excretion.

A 28-day study was conducted with 13 adult men to determine the effect of weight lifting exercise and protein intake level on urinary 3-methylhistidine (3MH) excretion. Subjects were fed the RDA for protein [0.8 g/(kg BW X d)] or 3 X RDA; there were no-exercise and exercise groups at each intake. Comparisons of last 14-day, least-squares means among groups did not reveal differences in data treated by lean body weight [3MH/(kg LBW X d)] or by urinary creatinine excretion [3MH/(kg UCE X d)], but 3MH/(kg LBW X d) excretions were higher for exercise than no-exercise subjects. Regression analyses revealed linear, increasing trends in the 3MH/(kg LBW X d) data for RDA-exercise (p less than 0.03), 3 X RDA-exercise (p less than 0.01), and 3 X RDA-no-exercise (p less than 0.01) groups; 3MH/(g UCE X d) group data plots overlapped. Our findings for 3MH/(kg LBW X d) indicate that a weight lifting program was associated with increased 3MH excretions from adult males. As an index of skeletal muscle catabolism, an increase in 3HM excretion represents an increase in tissue catabolism. No significant effect of 3 X RDA protein intake on last 14-day 3MH excretions was observed; however, linear increases in 3MH/(kg LBW X d) for 3 X RDA-no-exercise subjects suggests a relationship. Trends of exercise- or protein intake-enhanced 3MH excretion could be masked by data as 3MH/(g UCE X d) if exercise or 3 X RDA protein intake can expand the body creatine pool independent of skeletal muscle mass.

Adolescent↗

PubMed1984

Log-linear-model analysis of the association between disease and genotype.

In this paper, log-linear-model analysis is employed to provide further insight into the disease-genotype association problem, as discussed by Norwood and Hinkelmann (1978, Biometrics 34, 593-602). It is shown how this approach can take account of the structure of the data when testing hypotheses about the type of association, by specifying the form of recurrence risks and allowing estimation of such recurrence risks by maximum likelihood. The notation of conditional recurrence risk is introduced and its usefulness is illustrated.

Alleles↗

PubMed1978

Measures of association between disease and genotype.

This paper is concerned with the statistical aspects of the phenomenon of disease occurring more frequently in individuals with some genotypes than in individuals with others. A correlation coefficient is defined to quantify association between disease and genotype. A distinction is made between the concepts of independence of allele and disease and independence of genotype and disease. This distinction is used to define two components of association which describe separate aspects of association of disease with genotype. One component is a measure of the association of disease with allele; the other a measure of the effect of allele interaction on association of disease and genotype. One aspect of the usefulness of the partition into components which is discussed is in expressing the recurrence risk of disease for a relative of an affected individual. A chi-squared analysis is provided to test hypotheses about the components of association and other hypotheses of genetic interest. This analysis is illustrated using a study done to determine the effect of the sex-linked dwarfing gene in male chickens on resistance to E. coli infection. This analysis shows a significant allele interaction effect on resistance to disease but no association of disease with alleles. In conclusion, some extensions and limitations of the proposed concepts and procedures are discussed.

Alleles↗

PubMed1976

Genetic analysis of behaviors related to the solution of a detour learning task.

A diallel cross involving five noninbred (purebred) lines of Japanese quail indicated that additive and nonadditive genetic effects had important influences on behaviors involved in a detour learning task. Social isolation for 3 hr was used to provide additional motivation which enabled detection of differences among strains. The percentage of quail, within purebred lines, that solved a 4-min detour task three or more consecutive times ranged from 52 to 72. Differences among purebreds were significant for most of the components of the learning task. Further, the data suggested strain differences associated with the successful attainment of the desired goal when there was a similar level of general activity.

Animals↗

PubMed1976

Volumes and cellularity in populations of hematopoietic clones.

Volumes of hematopoietic spleen colonies were estimated by measuring parameters of superimposed triaxial ellipsoids. Observations were made on groups of colonies that contained only undifferentiated cells or had differentiated to varying degrees into purely erythropoietic, purely granulocytic or purely megakaryocytic colonies. The average volume occupied by one cell and surrounding matrix, the so-called single cell space, was determined for each type of colony. The estimated colony cellularity was then computed from the measured colony volume and the tabulated single cell space. The techniques of measurement are described. Formulas are provided to estimate mean and variance of volumes and their cell contents. Data on the distribution of spleen colony size and cellularity after seven days of growth are given.

Animals↗

PubMed1975

Diallel analysis of growth traits in mice.

Two replications of a complete diallel cross experiment were performed among four partially inbred lines of mice. These inbred lines originated from a random-bred ICR strain and were produced by 12 generations of full sibbing (F congruent to 92%). Individual body weight was recorded for each animal at 12, 21, 42 and 56 days of age. Body weight gain traits were examined for intervals 12-21, 21-42 and 42-56 days. Simultaneous least squares analyses of inbred and linecrossed groups were used. Sex differences were highly significant for all traits. Replicate differences were significant but made a small contribution to the total variation. Inbred lines differed greatly. Crosses showed growth trends similar to their contemporary maternal and paternal inbreds. Heterosis was highly significant for all traits except 21-day weight. Inbreds were heavier at 12 days of age, but linecrossed progeny were superior to inbreds for all postweaning weights. General combining ability was highly significant for 12- and 56-day weights and 21-42-day gain. Specific combining ability was highly significant for 21-day weight, 12-21- and 42-56-day gain. Significant maternal effects were found for all individual weights but not for 12-21- and 21-42-day gain. Residual reciprocal effects were significant for all traits. Estimated variances among linecrossed groups contained a large maternal component, a fluctuating additive genetic component and consistent non-additive genetic influence on all growth parameters measured.

Alleles↗

PubMed1972