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Biomedical subjects

M Hahn

Publications and source records attributed to M Hahn.

320 records · Page 18Linked to original sources
PubMedDate not supplied

Radiation damage of proteins in the solid state: changes of amino acid composition in catalase.

Catalase has been irradiated with 100 keV electrons under conditions simulating the hazards of electron microscopic imaging. Amino acid analysis reveals a definite pattern of amino acid destruction which is well correlated with the particular chemical structures of amino acid side chains. This pattern appears to be distinctly different from the sensitivity pattern for monoamino acid systems, which fact is ascribed to intramolecular energy transfer and selective attack of liberated radicals.

Amino Acids↗
PubMedDate not supplied

Relation between 2- and 3-dimensional architecture of trabecular bone in the human spine.

By means of a new preparation technique which allows the combined 2- and 3-dimensional analysis of trabecular bone we analyzed the vertebral bodies of 22 autopsy cases. None of these cases had any skeletal disease. With increasing age bone volume was decreased in all vertebral bodies (2nd cervical to 5th lumbar body) but this decrease was more pronounced in the lower vertebrae. In the upper cervical spine there was nearly no age-related loss of trabecular bone volume. 3-D analysis demonstrated that the loss of bone tissue is due to a loss of trabecular plates which are transformed to trabecular rods by perforations. The number of plates and rods could be measured directly. In the 2nd lumbar vertebra at the age of 20 years the density of plates was 0.61 mm, the density of rods was 0.2/mm. At the age of 80 years the density of plates was 0.2/mm. The density of rods remained constant at all ages. Perforations could be seen directly. They were located mainly in trabecular plates. At higher ages they occurred in rods either. The number of vertically oriented trabeculae was about twice the number of horizontal ones. The rate of age-dependent reduction of trabeculae was the same in horizontal and vertical trabeculae. It was possible to do real 3-dimensional measurements of the diameter of trabecular rods. These values were compared to the calculated values of trabecular plates. In mean trabecular plates are thinner than rods. It could be demonstrated that microcallus formation is a common feature in the human spine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Age- and sex-dependent cancellous bone changes in a 4000y BP population.

We studied cancellous bone loss in a 4000y BP population, using several methods designed to detect age-related changes, in order to investigate the pattern of cancellous bone loss in this ancient population and to compare the results deriving from different methods used on identical specimens. We used 10-mm sections of fourth lumbar vertebral bodies and left femoral necks of 18 individuals of both sexes with estimated ages from 20 to 60 years of a 4000y BP bronze-age population. Stereoscopic photographs were used for three-dimensional analysis and trabecular number (TN) counting. After embedding, the following parameters were measured in different image analysis systems using plane parallel block samples: bone mineral density (BMD) in water by DEXA, and by evaluation of standardized radiographic images; fractional bone volume (BV/TV) in backscattered electron images of the trabecular surface layer and in optical images of trabeculae in a surface-stained layer; and trabecular bone pattern factor (TBPf) in the latter images. There was a high correlation between the results of morphological methods for measuring fractional bone volume. Reasonable correlations were found between the x-ray photon methods and poor correlations between these and the morphological methods. These poor correlations may be due to the diagenetic substitution occurring in archaeological skeletons, which would strongly influence x-ray-based density measurements. However, all the methods demonstrated that the most dramatic loss of quantity and quality in cancellous bone occurred in females between 40 and 60 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Austria↗
PubMedDate not supplied

[Morphologic study of iliac crest spongiosa in patients with osteoporosis treated according to the ADFR (activation, depression of resorption, formation, repeat the cycle) with parathyroid hormone and diphosphonates (Hannover PTH I study)].

Treatment of osteoporosis with a complete reconstruction of the normal three dimensional architecture of trabecular bone is an unsolved problem. In addition to the well established fluoride therapy new concepts in the treatment of osteoporosis were developed. There is growing interest in the so called ADFR concept (activation, depression of resorption, formation, repeat the cycle) as a physiological stimulation of osteoblastic bone formation. The histological results following ADFR treatment in 8 patients are reported. After 12 months of treatment with parathyroid hormone [1-38)hPTH) (stimulation of the basic metabolic units) and the diphosphonate EHDP (depression of osteoclastic resorption) no change of remodelling processes at the trabecular bone surface could be observed. The results demonstrate many doubts in the importance of the ADFR concept for the treatment of osteoporosis.

Adult↗
PubMedDate not supplied

Cultivar-specific elicitation of barley defense reactions by the phytotoxic peptide NIP1 from Rhynchosporium secalis.

Resistance of barley to the phytopathogenic fungus, Rhynhosporium secalis race US238.1, was found to be controlled by resistance gene Rrs1, which segregated in a manner characteristics for a codominant gene. PRHv-1, a thaumatin-like pathogenesis-related protein, was shown to be encoded by a gene family on chromosome 1. As part of the barley defense response, significant accumulation of PRHv-1 and peroxidase transcripts was induced early during pathogenesis in two Rrs1 cultivars but not or to a lower level in a near-isogenic, susceptible rrs1 cultivar or a cultivar lacking known resistance genes. R. secalis secretes a small group of necrosis-inducing peptides. One of these, NIP1, which was detected in culture filtrates only of fungal race US238.1, was found to elicit the accumulation of PRHv-1 and peroxidase mRNAs in Rrs1 cultivars with a time course similar to that upon fungal infection. Therefore, NIP1 is a candidate for the product of fungal avirulence gene avrRrs1, which, together with barley resistance gene Rrs1, determines incompatibility of the interaction.

Amino Acid Sequence↗
PubMedDate not supplied

Accumulation of genetic alterations in brain metastases of sporadic breast carcinomas is associated with reduced survival after metastasis.

Tumor progression is characterized by stepwise accumulation of genetic alterations. To identify alterations associated with breast cancer metastasis, an analysis of comparative loss of heterozygosity (LOH) was performed on 38 primary sporadic breast carcinomas and 16 distant metastases. Two loci at 5q21 and 18q21 were chosen because of their reported increased deletion frequency in metastatic tumors. LOH at 17q21, 13q12-13, 17p13.1 and 11q22-23 was analyzed to determine whether there is a specific involvement of these breast cancer-associated gene loci in the metastatic process. Our data show that distant metastases are characterized by markedly increased LOH frequency at all loci examined. In both gene locus groups, significantly more distant metastases are affected by combined LOH. Furthermore, a significantly reduced postmetastatic survival time has been observed in patients with brain metastases affected by synchronous allelic loss at the four breast cancer-associated gene loci. Our results suggest that cumulative LOH of breast cancer-related gene loci is associated with a more aggressive phenotype of metastatic breast tumors.

Ataxia Telangiectasia Mutated Proteins↗
PubMedDate not supplied

A new technique for controlling the finger skin temperature in microcirculatory research demonstrated in a local cold stress test in healthy controls and patients with Raynaud's phenomenon.

Changes in skin temperature cause great changes in blood flow and capillary blood pressure. The new technique presented here makes it possible to control the temperature of the finger during nailfold capillaroscopy. Automatic temperature control, both for warming and cooling, is made possible with the aid of a temperature-controlled finger holder. The temperature of the finger holder can be automatically matched to the spontaneous skin temperature of the examined finger, or the finger holder temperature and temperature change velocity can be set digitally to a desired value. We used this new technique in a local cold stress test on 9 healthy controls (3 men, 6 women) and 9 patients (3 men, 6 women) with Raynaud's phenomenon due to systemic sclerosis. We simultaneously measured capillary red blood cell velocity (CBV) and laser Doppler flux (LDF) in adjacent areas of the finger nailfold with three different cooling procedures (8, 10, 12 degrees C for 5 min). CBV and LDF values showed the most pronounced differences between patients and controls at 12 degrees C. This new technique supplements capillaroscopy with full temperature control and defined temperature changes. It can also be combined with measurements of LDF and capillary blood pressure. In view of the disadvantages of other cooling methods we recommend this new and easy-to-handle technique for clinical practice and research.

Adult↗
PubMedDate not supplied

Newly developed software for capillary blood pressure analysis in microcirculatory research.

The introduction of the servonulling technique by Wiederhielm in 1963 allowed for the first time continuous and dynamic recording of capillary blood pressure (CP). In 1979 Mahler used this technique for the first measurements in humans. Data analysis was limited to manual analysis of chart recordings. Nowadays fast analog-digital converters with ay high sampling frequency are used for data recordings, and consequently there is a need for an easy-to-use software for data analysis of CP data. The presented newly developed computer software allows analysis of mean CP, taking into account the zero pressure measured before and after capillary cannulation. The simultaneously recorded electrocardiogram R wave is used as a marker for the calculation of the mean capillary pulse pressure waves and of their characteristic data. This may help determine the significance of the capillary pulse waveform for microvascular function. Changes in the pulse waveform may be the only detectable difference between patients and healthy controls. Analysis of simultaneously recorded temperature, the display of markers for valid readings, and the possibility of excluding nonvalid data or artefacts from analysis are additional features.

Adult↗
PubMedDate not supplied

Disturbed blood flow regulation in venous leg ulcers.

Microangiopathy of the skin has been recognized as an important factor in the development of skin diseases connected with chronic venous insufficiency (CVI). Here the relationship between postcapillary transmural pressure and precapillary vaso-constriction - we call it the postural feedback system - was examined in venous ulcers (n = 12) and compared to blood flow regulation in the inner ankle area of healthy controls (n = 12). Blood flow changes were measured by laser Doppler fluxmetry. Changes in the laser Doppler flux (LDF) minus the biological zero value were measured after 3 min of arterial occlusion, during 3 min of venous occlusion, while the leg was elevated and while it was lowered and expressed relative to the pretest resting value. In venous ulcers the LDF remained nearly unchanged after arterial occlusion (3 vs. 190%, p < 0.001), leg elevation caused an LDF decrease contrary to what was seen in the controls (-17 vs. +80%, p < 0.001), in the lowered leg an LDF decrease was found (-51 vs. -65%) and venous occlusion led to a profound reduction of flux (-78 vs. -84%). In severe CVI the precapillary arterioles seem to be dilated even with the leg at heart level. This finding means that the postural feedback system under resting conditions is upregulated, and 'luxus' hyperperfusion results. The upregulated postural feedback system contributes to the cutaneous microangiopathy due to chronic venous congestion.

Adult↗
PubMedDate not supplied

A new apparatus for non-invasive positioning of laser Doppler flux (LDF) probes in skin areas where local attachment is impossible.

BACKGROUND/AIMS: Laser Doppler flux (LDF) measurements are used in various medical fields, e.g. in the evaluation of microangiopathy. LDF measurements can be performed on unaltered skin as well as in wounds or skin flaps to measure blood flow properties under different conditions. In day-to-day practice, it is often difficult to carry out LDF measurements in the mentioned areas because a probe cannot be fixed accurately on a sterile wound or in an ulcer. The inadequacy of the peripheral equipment presently available for such potentially significant areas of application contrasts with the high technological standard of laser Doppler fluxmetry touted by the manufacturers. CONCLUSION: We have developed a completely new tripod probe holder (Pat. pending) for both standard and special probes. This new probe holder allows measurements without touching the surface by fixing the holder in remote distance to the area measured. Even in wounds or other critical areas as skin flaps LDF measurements can be performed. The construction and possible applications of this novel peripheral device will be discussed.

Blood Flow Velocity↗