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Biomedical subjects

A Haake

Publications and source records attributed to A Haake.

12 recordsLinked to original sources
PubMed2004

Positioning of small particles by an ultrasound field excited by surface waves.

A method for the controlled positioning of small particles in one or two dimensions by an ultrasound field excited by a surface wave is presented. Particles of a diameter between 10 and 100 microm placed on a surface can be concentrated at certain locations and moved over the surface. In other approaches it is possible to let the particle levitate freely in the fluid. However for the use of ultrasonic positioning in for example microassembling it is necessary to move particles over a surface as well as to let them levitate over the surface. Physical principle: A two- or three-dimensional ultrasound field is excited in a fluid filled gap between a rigid surface at the bottom and a vibrating surface of a solid at the top. The height of the gap varies between 0.1 and 2 mm. A one-dimensional sinusoidal vibration of the upper surface excites a two-dimensional ultrasound field in the fluid. Particles that are arbitrarily distributed on the lower surface will be concentrated in lines by the ultrasound field. First the calculation of the field of forces on particles in the fluid layer is presented. Then the dispersion relation of a vibrating plate which is in contact with a fluid on one side is derived. The technical setup will be introduced. Finally the experiments are shown and compared to the theoretical results.

Journal Article↗
PubMed2002

Micro-manipulation of small particles by node position control of an ultrasonic standing wave.

For the controlled positioning of small particles with ultrasound a standing wave in a fluid is used. The standing wave is implemented in a resonator, that consists of a fluid filled tube and two piezoelectric transducers on each end. A one-dimensional model of a piezo-device including the fluid-loading on one side and a backside support is introduced. This model allows the calculation of the transmitted wave as a function of the applied electric voltage and the incident wave. In addition, when an electrical impedance is connected to the piezo-device, the reflection coefficient can be varied in amplitude and phase, so that the parameters of the reflected wave can be controlled completely. The resonator itself, consisting of a piezo-device on each end and the fluid between, is included in the model. Several methods to shift the nodes of the standing wave in the resonator are investigated and the ability to position particles is discussed.

Journal Article↗
PubMed1998

Bcl-2 overexpression in the HaCaT cell line is associated with a different membrane fatty acid composition and sensitivity to oxidative stress.

Different mechanisms have been proposed for the activity of the Bcl-2 proto-oncogene product. A bona fide antioxidant activity and a pro-oxidant setting up of the cell have been suggested using different experimental models, yet many uncertainties exist about the biochemical mechanism of Bcl-2 action. In the present paper, we report the characterization of the cellular response to mild oxidative stress of a cultured cell line of immortalized keratinocytes (HaCaT), overexpressing the Bcl-2 oncogene product. A sublethal oxidative stress was induced by 1 h treatment with 200 microM tert-butyl-hydroperoxide (t-BOOH). Following peroxide treatment, the formation of reactive oxygen species was lower in Bcl-2 expressing cells, suggesting a better capacity to counter oxidative stress. Total Superoxide Dismutase activity was induced by oxidative t-BOOH treatment in bcl-2 transfected cells, which also accumulated less damage to membrane lipids and proteins, as assessed by TBA-RS and carbonyl formation respectively. On the other hand, the formation of 4-hydroxy-nonenal, a more specific marker of peroxidative damage to polyunsaturated fatty acids, was higher in bcl-2 transfected cells than in control cells. Bcl-2 over-expression was also associated with significant changes in the fatty acid composition of cell membranes. Transfected cells presented a higher proportion of mono-unsaturated fatty acids and omega6 poly unsaturated fatty acids and a lower proportion of penta-enoic PUFA, thus resulting in a higher unsaturation index with respect to control cells. Changes in protein kinase C activity were also associated to bcl-2 expression, possibly resulting from the differences in membrane fatty acid composition. These data may be an important background for the understanding of Bcl-2 involvement in the control of apoptotic response as well as in the induction of antioxidant cell defenses against oxidative stress.

Antioxidants↗
PubMed1997

Localized Darier disease. Implications for genetic studies.

BACKGROUND: Darier disease is an uncommon genodermatosis characterized by the symmetrical eruption of keratotic reddish-brown papules occurring in the seborrheic areas of the body. A unilateral, or localized, variant has been identified. We report 4 new cases of localized Darier disease and review the English-language literature. The implications of these cases on future genetic studies are also discussed. OBSERVATIONS: Localized Darier disease occurred with equal frequency in males and females. The average age at onset was 27 years. The most frequent site of involvement was the trunk (40% [16/40]). This condition was aggravated by sunlight, heat, or sweating in 42% (19/40) of reported cases, and 38% (15/40) of the patients responded to treatment with topical tretinoin. CONCLUSIONS: Many of the clinical features of localized Darier disease suggest that it is a genetic mosaic of generalized Darier disease. Further studies of localized Darier disease may therefore prove to be instrumental in the search for the Darier disease gene.

Abdomen↗
PubMed1996

Localization of the Darier disease gene to a 2-cM portion of 12q23-24.1.

Positional cloning with microsatellite markers allowed further localization of the Darier disease gene to a 2-cM interval of chromosome 12, 12q23-24.1, between the polymorphic loci D12S234 and D12S129. A region this size is suitable for construction of a contig to identify the Darier disease gene. Use of a polymorphic intronic marker for nitric oxide synthetase 1 gene, which maps to the same chromosomal area as the Darier gene, allowed exclusion of that gene as the Darier disease gene.

Chromosome Mapping↗
PubMed1994

Localization of the gene for Darier disease to a 5-cM interval on chromosome 12q.

Darier disease is an autosomal dominant abnormality of epidermal differentiation characterized clinically by the presence of hyperkeratotic papules on the skin and histologically by the loss of cell cohesion and by disorderly keratinization. Two groups recently found evidence that the gene whose mutations underlie this disease is located at chromosome 12q23-q24.1, a site on chromosome 12 that clearly is distal to the type II keratin gene cluster. We report here evidence for sublocalization to a 5-cM region of that site in an additional ten families of European and Middle Eastern ancestry with a combined lod score in excess of 20.

Adult↗
PubMed1977

[Occurrence of malignant tumors in high-aged patients (author's transl)].

The analysis of macroscopic findings in 2385 autopsies for frequency and distribution for malignant tumors had the following results: Augmented frequency with increasing age was stated for cancer of the stomach, colon, prostate and breast. There is a clear decrease in the frequency of cancer of the lung and of the uterus with increasing age. Severe tumorindependent disease was an almost constant finding in tumor autopsies. The overall frequency of malignant tumors decreases with increasing age.

Age Factors↗
PubMed1976

[The occurence of multiple diseases in high-aged patients (author's transl)].

Analysis of 1385 autopsies of 80-102 year-old patients was performed to investigate the frequency of simultaneous occurence of the following functionally pertinent diseases in one organism (polypathia): Severe aortic, coronary and cerebral arteriosclerosis, chronic pulmonary emphysema, contracted kidneys, fractures of the femur and malignant tumors. 80% of all patients of both sexes suffered from 2-4 of the above diseases. Even in the highest age group, however, 5 and more of the above diseases were very rarely developed. Patients with none of the above diagnoses were almost never encountered. The "polypathia" was stated also in patients who died by suicide or accident.

Aged↗
PubMed1976

[Pathological-anatomical findings in 70-102 years old Caucasians (author's transl)].

The macroscopic findings of 2385 autopsy protocolls of 70-102 year-old males and females were analysed for frequency and functional significance of diseases. 1. Severe coronary arteriosclerosis was found up to 60% of the cases, with increasing frequency in higher age groups. However decrease of acute myocardial necrosis was stated including the highest age group. 2. The mean values of heart weights decrease in the highest age groups. 3. While the frequency of arteriosclerosis in the cerebral arteries increases the frequency of ischemic lesions of the brain decreases. 4. Benign hyperplasia of the prostate is found in 85% of the cases. 5. 80% of the patients had severe substantial chronic pulmonary emphysema and acute tracheobronchitis. These pulmonary lesions are supposed to be the functionally most important disease in patients of old age.

Aged↗