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Biomedical subjects

B Dietz

Publications and source records attributed to B Dietz.

15 recordsLinked to original sources
PubMed2003

Observation of a chiral state in a microwave cavity.

A microwave experiment has been realized to measure the phase difference of the oscillating electric field at two points inside the cavity. The technique has been applied to a dissipative resonator which exhibits a singularity-called exceptional point-in its eigenvalue and eigenvector spectrum. At the singularity, two modes coalesce with a phase difference of pi/2. We conclude that the state excited at the singularity has a definitive chirality.

Journal Article↗
PubMed2003

Phase shift experiments identifying Kramers doublets in a chaotic superconducting microwave billiard of threefold symmetry.

The spectral properties of a two-dimensional microwave billiard showing threefold symmetry have been studied with a new experimental technique. This method is based on the behavior of the eigenmodes under variation of a phase shift between two input channels, which strongly depends on the symmetries of the eigenfunctions. Thereby a complete set of 108 Kramers doublets has been identified by a simple and purely experimental method. This set clearly shows Gaussian unitary ensemble statistics, although the system is time-reversal invariant.

Journal Article↗
PubMed2003

Late-onset cardiotoxicity of chemotherapy and radiotherapy.

An increasing number of patients with malignant lymphoma are becoming long-term survivors following treatment with chemotherapy (CT) and/or radiotherapy (RT). Therefore, late therapy-related complications are becoming increasingly clear. We present three young patients to illustrate the dire consequences of late-onset cardiotoxicity as sequel to potentially curative treatment. We advise yearly life-long follow-up of CT/RT patients treated with curative intent. Echocardiography should be performed when cardiac murmurs arise. Prevention of further cardiac damage by reducing other cardiac risk factors as well as endocarditis prophylaxis when indicated is recommended.

Adult↗
PubMed2002

Experimental test of a trace formula for a chaotic three-dimensional microwave cavity.

We have measured resonance spectra in a superconducting microwave cavity with the shape of a three-dimensional generalized Bunimovich stadium billiard and analyzed their spectral fluctuation properties. The experimental length spectrum exhibits contributions from periodic orbits of nongeneric modes and from unstable periodic orbits of the underlying classical system. It is well reproduced by our theoretical calculations based on the trace formula derived by Balian and Duplantier for chaotic electromagnetic cavities.

Journal Article↗
PubMed2002

Transport of alkamides from Echinacea species through Caco-2 monolayers.

To gain more insights into the human intestinal absorption of alkamides from Echinacea species, transport studies were performed with the human adenocarcinoma colonic cell line Caco-2 (ATCC) as a model to assess the epithelial transport of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (1/ 2). 30 minutes after apical loading of 25 microg/ml 1/ 2, about 15 % of these alkamides were detectable on the basolateral side. Close monitoring of the transport during 6 hours revealed a nearly complete transport to the basolateral side after 4 hours and no significant metabolism was observable. Transport experiments performed at 4 degrees C showed only a slight decrease in transport, which is a strong hint that dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (1/ 2) cross biological membranes by passive diffusion. Nearly the same results were obtained after preincubation of the Caco-2 cells with lipopolysaccharides (LPS) or phorbol 12-myristate-13-acetate (PMA) to mimic an inflammatory status. These results support the assumption that the alkamides can be easily transported from the intestinum and hence may contribute to the in vivo effects of Echinacea preparations.

Biological Transport↗
PubMed2001

Absorption of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides after oral application of Echinacea purpurea tincture.

Alkamides are suspected to contribute to the activity of Echinacea preparations. In preliminary experiments a quantification method for dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides in human blood has been developed by which it was possible to detect dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides in human blood after oral application of Echinacea purpurea mother tincture.

Administration, Oral↗
PubMed1998

The contribution of lead-contaminated house dust and residential soil to children's blood lead levels. A pooled analysis of 12 epidemiologic studies.

In 1992, the U.S. Congress passed the Residential Lead-Based Paint Hazard Reduction Act, which requires the promulgation of health-based dust lead and soil lead standards for residential dwellings to prevent undue lead exposure in children. Unfortunately, the levels of lead in house dust and soil that are associated with elevated blood lead levels among U.S. children remain poorly defined. This pooled analysis was done to estimate the contributions of lead-contaminated house dust and soil to children's blood lead levels. The results of this pooled analysis, the most comprehensive existing epidemiologic analysis of childhood lead exposure, confirm that lead-contaminated house dust is the major source of lead exposure for children. These analyses further demonstrate that a strong relationship between interior dust lead loading and children's blood lead levels persists at dust lead levels considerably below the U.S. Department of Housing and Urban Development's current postabatement standards and the Environmental Protection Agency's guidance levels. Finally, these analyses demonstrate that a child's age, race, mouthing behaviors, and study-site specific factors influence the predicted blood lead level at a given level of exposure. These data can be used to estimate the potential health impact of alternative health-based lead standards for residential sources of lead exposure.

Child, Preschool↗
PubMed1998

Approaches to the genetics of cardiovascular disease through genetic field work.

Successful molecular genetic studies of complex disease require exact, careful phenotypization, which is more difficult than that performed for monogenic diseases. We have developed a family-oriented field working approach, which relies on index patients, their primary care physicians, and a minimum number of field working staff. The patients are responsible for recruiting their family members. Packets containing an explanatory pamphlet, an informed consent statement, a questionnaire, and blood cuvettes are provided. Data are transferred from questionnaire and from the laboratory into a computer program that facilitates construction of the family tree. We have applied this genetic field working approach primarily to patients with lipid disorders. Coupling results from genetic field working with modern DNA diagnostic tests such as the oligonucleotide ligation assay, has enabled us to effectively identify patients with familial hypercholesterolemia in the German population. We are now extending genetic field working to hypertension. Hypertension is much more difficult to study, because the phenotype is more difficult to discern and document. Both complex diseases have the disadvantage that the parents of the index patients are likely to already be dead. Nevertheless, we concentrate on the recruitment of large pedigrees, sibling pairs with parents whenever possible, and trios consisting of index patient and both parents or index patient, parent and sibling. With these constellations we can conduct association studies, linkage analysis, and novel combinations of both approaches.

Automation↗
PubMed1997

Hereditary motor and sensory neuropathy with spastic paraplegia and optic atrophy: report on a family.

We describe two siblings affected by a motor and sensory neuropathy starting in childhood. Already in infancy, a spastic gait disturbance had become obvious, leading later to multiple surgical interventions. In adolescence, progressive loss of vision developed. At the time of our examination, both siblings showed severe weakness and atrophy of the distal muscles of legs and arms. Tendon jerks were brisk in proximal muscles; in the lower extremities, muscle tone was increased. Visual acuity was severely decreased. Nerve conduction studies revealed an axonal degeneration. This finding was confirmed by evaluation of a sural biopsy specimen in one patient, showing only few remaining myelinated fibres without signs of demyelination. This combination of hereditary motor and sensory neuropathy with spastic paraplegia and optic atrophy shows features of both hereditary motor and sensory neuropathy V and VI according to the classification of Dyck, indicating that these subtypes may not represent distinct entities.

Aged↗
PubMed1986

Correlation of antibodies to LAV/HTLV III in hemophiliacs with the use of virus-inactivated clotting factors.

The retrovirus LAV/HTLV III, highly likely to be responsible for the acquired immunodeficiency syndrome (AIDS) in some recipients of blood products, can be inactivated by chemical and/or heat treatment, so the use of virus-inactivated factor VIII and factor IX preparations for treating hemophilia A and B has become important. We examined hemophilic children and found that those children treated since 1979 with virus-inactivated preparations did not develop antibodies against LAV/HTLV III. In contrast, 77% of patients treated with conventional factor VIII or factor IX preparations had antibodies against this virus.

Alanine Transaminase↗
PubMed1979

Successful re-treatment with cis-dichlorodiammineplatinum(II) after apparent allergic reactions.

Allergic or anaphylactic-like reactions have been reported with cis-dichlorodiammineplatinum(II) (CDDP) administration. We have seen two reactions among 50 patients treated in a phase II trial of CDDP. Both patients were successfully rechallenged after diphenhydramine pretreatment, and therapy was continued. In vivo and in vitro studies performed in one patient included negative skin tests, negative histamine release assay, negative lymphocyte stimulation studies, and normal total serum IgE. We conclude that some apparent allergic reactions occurring with CDDP may have a non-allergic etiology, and treatment may be successfully continued in selected patients.

Adult↗
PubMedDate not supplied

[Hyperuricemia as the main symptom of medium-chain acyl-Co-A dehydrogenase deficiency].

Between 1991 and 1996 three cases of MCAD-deficiency (medium-chain-acyl-Co-A dehydrogenase deficiency) were diagnosed in the Vestische Kinderklinik. All patients showed hypoketotic hypoglycaemia with hyperuricaemia. In the group of hypoketotic hypoglycaemia without lactat acidosis MCAD-deficiency is the only metabolic disease presenting regularly with hyperuricaemia. Thus, hyperuricaemia in a patient with hypoketotic hypoglycaemia is a strong indicator for MCAD-deficiency. Measurement of uric acid is easily available before sophisticated metabolic analysis are completed.

Acyl-CoA Dehydrogenase↗