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Biomedical subjects

M Hahn

Publications and source records attributed to M Hahn.

At least 127 records · Page 7Linked to original sources
PubMed1997

[The technical construction of a computer-supported measuring unit for in-vivo capillary pressure measurement in human nail fold capillaries].

Capillary pressure (CP) is an important determinant of microvascular function. According to Frank Starling, it governs not only the viscosity of the blood and the permeability of the capillary membrane, but also filtration and reabsorption in the microvascular bed. Despite its great significance, the technique of CP measurement is employed in only a few laboratories throughout the world owing to the technical difficulties involved in carrying out such measurements. The first attempts were made by Carrier and Rehberg in 1923. In 1979 Mahler carried out the first dynamic recordings of capillary pressure. The present paper explains the physical basis for direct capillary measurement, and recent progress in this technique is discussed in a review of the literature. We also introduce a newly developed computer-aided system that enables in vivo determination and evaluation of pressure in the nailfold capillaries of the hands and feet. The device permits the simultaneous recording of pressure and bloodflow in the capillaries of the skin, and thus provides additional information on important functions of the cutaneous microcirculation.

Blood Pressure↗
PubMed1997

Success of an outpatient claudication group training program for patients with peripheral arterial occlusive disease (PAOD): the Tübingen model.

Active exercise therapy plays a decisive role in the prognosis for early forms of peripheral arterial occlusive disease (stages I and II). We present a model project for an outpatient claudication group which has proved successful in the active exercise therapy of early forms of arterial occlusive disease (PAOD). In addition to the training principles familiar from intensified, performance-keyed walking programs, a newly developed pedal ergometer was employed which makes controlled endurance training possible for this patient group. The distance patients were able to walk without pain increased significantly in 17 out of the 26 patients taking part in the program. This clinical success was confirmed by an examination of arterial hemodynamics. The transformation of a theoretical concept into a functioning training program and the positive results achieved with it should encourage others to establish similar programs close to the patients' homes.

Adult↗
PubMed1997

Pediatric fracture without radiographic abnormality. Description and significance.

With an expanding application of magnetic resonance imaging in acute musculoskeletal injury, an increasing number of occult traumatic lesions of bone are being identified. The authors describe the entity of fracture without radiographic abnormality, which as the name suggests is a bony injury not apparent on plain radiographs. The clinical significance and potential sequelae have not been defined in the pediatric patient. Accordingly, the purpose of this study is to describe and classify the entity of the pediatric fracture without radiographic abnormality and delineate its importance and appropriate management. Twenty-five children were seen primarily or referred to The Children's Hospital of Philadelphia after having sustained an acute traumatic injury; all refused to bear weight or use their extremity, and all had initial plain radiographs that were interpreted as normal. Subsequent magnetic resonance images of all 25 children showed an occult fracture. These included Salter-Harris fracture Types II (two patients), III (one patient), and IV (three patients), intraosseous epiphyseal fractures (18 patients), and a metaphyseal diaphyseal fracture (one patient). Four patients with intraosseous epiphyseal fractures ultimately sloughed a portion of their articular cartilage, as observed at arthroscopy. The decision to proceed with magnetic resonance imaging in the evaluation of a child who refuses to use an extremity depends on many variables. However, magnetic resonance imaging has proven useful in revealing fractures without radiographic abnormality and in ruling out other pathosis.

Adolescent↗
PubMed1997

Cutaneous inflammation limited to the region of the ulcer in chronic venous insufficiency.

BACKGROUND: The role of inflammatory reactions in the pathogenesis of chronic venous insufficiency and the persistence of venous ulcerations is still not totally clear and remains a hotly debated topic. An investigation of the intensity and distribution of ICAM-1 expression and different inflammatory cells should help clarify whether inflammatory processes are limited locally to the area of the ulcer or if an upregulation can also be observed in clinically unaffected skin of CVI-III patients, as a sign of a primary inflammatory process. PATIENTS AND METHODS: We examined two skin areas in 10 patients with venous ulcerations. One area was at the border of the ulcer and another in clinically unaffected skin (distance from the ulcer: 12.6 +/- 5.1 cm). In addition skin specimens were obtained from the perimalleolar skin of 10 healthy controls. Our histological and immunohistochemical examinations were focused on inflammatory cells (B and T lymphocytes, macrophages, and mast cells) and on the adhesion molecule ICAM-1. RESULTS: A very strong expression of ICAM-1 could be seen at the border of the ulcer. This tissue also showed a dense infiltration, mainly by T lymphocytes and macrophages. In some cases the tissue was infiltrated by an increased number of mast cells. This is the typical picture of a chronic inflammatory reaction. Compared to healthy controls, the clinically unaffected skin of patients showed not an increased expression of ICAM-1 and only in some cases we could find a slight perivascular infiltrate of T lymphocytes. CONCLUSIONS: These data imply that the upregulation of endothelial adhesion molecules (ICAM-1) and dermal infiltration by T lymphocytes and macrophages in CVI-III patients is limited to the region of the ulcer, or at least to skin areas with a severe microangiopathy, and is part of a secondary elimination of necrotic issue (an 'injury and repair' process). These local chronic inflammatory reactions are certainly an important factor in the persistence and recurrence of venous ulcerations.

Adult↗
PubMed1997

[Development of a computer-assisted thermoelectric Peltier cold test procedure with integrated photoplethysmography unit for noninvasive evaluation of acral skin circulation].

Local cold provocation tests are an important, non-invasive diagnostic tool for collecting information about skin perfusion during exposure to cold. In patients suffering from vasospastic circulatory disorders such as Raynaud's phenomenon, it is of particular importance to be able to collect data about acral circulation during the cooling test in the asymptomatic intervals between naturally occurring attacks. By carrying out a series of cold provocation tests, for example, patient response to a newly initiated therapy can be assessed. Here we present a recently developed, computer-aided thermoelectric Peltier device with an integrated finger holder for carrying out local cold provocation tests. The electronic control unit of the Peltier element make it possible to cool or heat to predefined temperatures. At the same time, the temperature of both the finger holder and the skin can be measured. A photoplethysmographic sensor is also integrated within the device, enabling the response of the pulse waves to the controlled temperature changes to be monitored accurately. It is also possible to measure simultaneously laser Doppler flux and capillary pressure in the nailfold and to perform nailfold capillaroscopy to determine red blood cell velocity. The new device provides us with the technical means to study the interrelationship between acral skin perfusion and the thermal regulation of the skin.

Blood Flow Velocity↗
PubMed1996

Tetrahydrobiopterin biosynthesis in C6 glioma cells: induction of GTP cyclohydrolase I gene expression by lipopolysaccharide and cytokine treatment.

The possibility that 5,6,7,8-tetrahydrobiopterin (BH4) biosynthesis is stimulated in glial cells by treatment with lipopolysaccharide (LPS) and tumor necrosis factor (TNF-alpha) was examined in the astrocyte-derived C6 glioma cell line. Under basal culture conditions BH4 levels were found to be at the limit of detection. Concurrent treatment with 10 micrograms/ml LPS and 50 ng/ml TNF-alpha caused a time-dependent 13-fold increase in the levels of BH4. This treatment paradigm also induced nitric oxide synthase activity, as evidenced by increased levels of nitrite, an oxidized metabolite of NO, in the culture medium. LPS and TNF-alpha treatment led to a 25-fold increase in GTPCH enzyme activity, the first and rate-limiting enzyme in BH4 synthesis, and a corresponding 23-fold increase in GTPCH protein levels. Northern blot analysis showed that increased levels of GTPCH mRNA preceded changes in GTPCH protein, GTPCH enzyme activity and BH4 levels and reached a maximal of 44-fold that was sustained for at least 48 h. These results demonstrate that LPS and TNF-alpha stimulate de-novo BH4 biosynthesis and suggest that C6 cells offer a model system for studying the molecular events that control the induction of GTPCH gene expression and BH4 synthesis in glial cells.

Animals↗
PubMed1996

Drosophila goosecoid participates in neural development but not in body axis formation.

In vertebrate embryos, the homeobox gene goosecoid (gsc) is expressed in the gastrula organizer region and in later arising embryonic tissues including the foregut anlage. Ectopic expression and loss-of-function studies have demonstrated that Xenopus gsc elicits a dorsalizing activity that contributes to body axis formation. Here we report that the gsc gene is conserved in invertebrates. In Drosophila, D-gsc is expressed most strongly in the foregut anlage, which gives rise to the foregut proper and the stomatogastric nervous system (SNS). D-gsc expression overlaps with one of the three SNS precursor groups invaginating from the foregut anlage. Embryos mutant for D-gsc gastrulate normally but show disrupted invagination in the SNS primordium and lack one specific SNS ganglion. In addition, D-gsc mutant embryos show a less well defined defect in foregut arrangement. Our results indicate that this invertebrate homolog of gsc is not required for gastrulation but plays a role in neurogenesis in post-gastrula Drosophila embryos.

Amino Acid Sequence↗
PubMed1996

Heterogeneity of the skeleton: comparison of the trabecular microarchitecture of the spine, the iliac crest, the femur, and the calcaneus.

The objective of this study was to elucidate the structure of cancellous bone and its age-related changes at different skeletal sites. Therefore, the lumbar spine, iliac crest, femur, and calcaneus of 12 age- and sex-matched skeletal healthy autopsy cases (6 females, 6 males, aged 28-84 years, mean 54 years) were removed. The following analysis includes an evaluation of the trabecular bone volume (BV/TV, %) and the trabecular interconnection (TBPf, mm-1) as well as a qualitative investigation of the structure of trabecular bone. BV/TV shows the following mean values: lumbar spine, 8.3% (+/- 0.8%); iliac crest, 11.5% (+/- 1.6%); intertrochanteric, 10.2% (+/- 1.2%); femoral neck, 15.8% (+/- 1.6%); and calcaneus, 15.4% (+/- 2.0%). There are significant differences between the BV/TV of the femoral neck and that of the lumbar spine as well as between that of the calcaneus and the lumbar spine (p < 0.01). However, a positive correlation can be seen between the bone mass of the spine and that of all other investigated sites (r = 0.67 to r = 0.80; pr < 0.1). The trabecular interconnection of the lumbar spine (2.7 mm-1, SEM +/- 0.2 mm-1) and the femoral neck (0.3 mm-1, SEM +/- 0.3 mm-1) differs significantly. Only these two sites show a significant positive correlation of TBPf (r = 0.60; pr < 0.1). Age-dependent alteration of the spine and the femoral neck in bone mass and bone structure is nearly the same. The trabecular microarchitecture of the iliac crest varies systematically. A region 4-10 cm behind and 1-3 cm below the anterior superior iliac spine turns out to be the most suitable biopsy site because of its closest relation to the lumbar bone mass. However, drawing information about the trabecular interconnection within the lumbar spine by measurement of the iliac crest at any site seems to be impossible. The horizontal specimens reveal a vertical running tubular spongiosa pattern that is arranged in concentric rings starting from the dorsal shell like a honeycomb. The comparison of TBPf in horizontal and vertical planes and its age-related changes indicates the age-related bone loss to be predominantly a loss of horizontal trabeculae. Thus, the presented data provide further information about the skeletal distribution and heterogeneity of the trabecular microarchitecture.

Adult↗
PubMed1996

Plasma Membrane H+-ATPase Activity in Spores, Germ Tubes, and Haustoria of the Rust Fungus Uromyces viciae-fabae

Using plasma membrane-enriched vesicles, the properties of the H+-ATPase (EC 3.6.1.35) from the rust fungus Uromyces viciae-fabae were studied. The enzyme is strictly Mg2+-dependent and is inhibited by vanadate. The pH-optimum is at 6.7. By Western blot analysis using a monoclonal antibody against corn plasma membrane H+-ATPase a polypeptide of approximately 104 kDa could be detected. The vanadate-sensitive H+-ATPase activity of microsomal vesicles obtained from different stages of rust development was determined. Uredospores had only a very low enzyme activity (1.9 μmol Pi x mg-1 protein x h-1). In germ tubes the ATPase activity was about twofold higher (4.0 μmol Pi x mg-1 protein x h-1). An eightfold higher ATPase activity (16.1 μmol Pi x mg-1 protein x h-1) was found in microsomal vesicles from haustoria which had been isolated from rust-infected Vicia faba leaves. These results suggest, that the electrochemical gradient generated by the H+-ATPase of haustoria plays an important role for their function, possibly by promoting nutrient uptake from host cells.

Journal Article↗
PubMed1996

Architecture and distribution of cancellous bone yield vertebral fracture clues. A histomorphometric analysis of the complete spinal column from 40 autopsy specimens.

The objective of this study was to analyze the structure of cancellous bone and its significance for vertebral fractures. Therefore, the complete spinal column from 40 autopsy cases (18 without diseases affecting the skeleton and 12 osteoporotic) was removed and sectioned in the sagittal plane to a thickness of 1 mm. A surface-stained block grinding technique allowed combined two- and three-dimensional histomorphometric analysis, which included an evaluation of the trabecular bone volume (BV/TV, in %) and the trabecular interconnection (TBPf, in mm). In addition, qualitative investigation of the structure of trabecular bone was done. The distribution of trabecular bone volume within the spinal column of a normal skeleton shows a curve, with the highest values in the cervical spine and a decline in the thoracic and lumbar spine. Osteoporosis presents itself with a pathologically diminished trabecular bone volume, whereas the distribution within the spine is comparable to that of the controls. Osteoporotic patients show an apparently reduced trabecular interconnection. It is important that the measured values for TBPf are not only in general higher, but also more widely dispersed. The age-related decrease of trabecular bone mass is due to the transformation from plates to rods. This is quantitatively indicated by the close correlation of BV/TV and TBPf (P < 0.001, r = 0.85). The bone loss in osteoporosis is a loss of structure and a loss of whole trabeculae, which is caused by perforations. It involves a gradual change from normal bone. However, the polyostic heterogeneity in osteoporosis is immense. These structural differences demonstrate the development of regions of least resistance within the spine, serving as an explanation of osteoporotic fractures. Due to the polyostotic heterogeneity it is impossible to define a threshold mineral content for crash fractures by diagnostic measurements at any reference site.

Adolescent↗
PubMed1996

[Spongiosa structure and polyostotic heterogeneity in osteoporosis. Mechanism of bone transformation, morphology, clinical significance].

Osteoporosis is the most frequent generalized bone disease. The clinical expression of postmenopausal osteoporosis is characterized by spontaneous fractures of the vertebral bodies which affect mainly the trabecular bone structure. Thus the morphological bone transformation in osteoporosis is of clinical relevance. The object of this study was to analyze quantitatively and qualitatively the distribution of three-dimensional structure of cancellous bone in the human spine in osteoporosis. Therefore the complete anterior column of the spine and bone biopsies of the iliac crest of 11 autopsy cases with proven osteoporosis and 26 autopsy cases without primary or secondary bone disease were removed. A 1-mm-thick prepared sagittal section through the center of all vertebral bodies was embedded undecalcified in plastic and stained on the surface using a modification of the von Kossa method. This technique allowed combined two- and three-dimensional measurements simultaneously; these included evaluation of trabecular bone volume, trabecular interconnection, trabecular thickness, and trabecular number. The quantitative spine deformity index and qualitative analysis of the trabecular bone structure completed the investigation. The bone loss in osteoporosis is a loss of structure and the loss of whole trabeculae caused by perforations. The age-related decrease of trabecular bone mass is due to the transformation from plates to rods. Patient with osteoporosis show pathologically diminished trabecular bone volume and apparently reduced trabecular interconnection, while trabecular thickness and trabecular number show age-dependent change. The polyostotic heterogeneity in osteoporosis is immense. Neighboring vertebral bodies show differences of up to 100% in bone volume and bone structure. Due to this fact it is impossible to define a threshold for osteoporotic fractures. At the moment the transformation and loss of trabecular bone structure in osteoporosis is assumed to be irreversible; therefore, early prophylaxis is necessary to prevent clinical manifestations of these changes of bone.

Adolescent↗
PubMed1996

Morphometric analysis of noninvasively assessed bone biopsies: comparison of high-resolution computed tomography and histologic sections.

This article describes a new method to analyze the structural behavior of trabecular bone structure by means of noninvasive measurements of the three-dimensional cancellous bone architecture. For the noninvasive data acquisition, a high-resolution quantitative computed tomography system for peripheral measuring sites (pQCT) was used. With this system and the help of a multiple thin-slice measuring technique, it became possible to examine three-dimensional bone structure with a resolution of 0.25 mm. Using a special three-dimensional segmentation algorithm, mineralized bone was separated from bone marrow and muscle tissue within the three-dimensional stack of CT slices. These segmented data sets can then be processed nondestructively and, even more important, repetitively in either two or three dimensions. In order to validate this noninvasive procedure, a two-dimensional comparative morphometric study was performed including CT slices and corresponding histologic sections prepared after CT measurement. Three representative sections from the three-dimensional stack of CT slices were selected and the morphometric indices of the segmented CT slices were compared with the indices stemming from the corresponding histologic sections prepared after CT measurement. Although the presented approach can only give an example of the method, the results from the morphometric analysis support the assumption that cancellous bone structures based on noninvasive high-resolution CT measurements are representative for trabecular microstructures assessed from histologic bone sections. The study demonstrates the potential of high-resolution CT imaging for in vivo applications of quantitative bone morphometry. This is especially true for repetitive follow-up measurements, which cannot be performed using histologic sections. Additionally, the method offers an easy access to the three-dimensional structure of trabecular bone, which is mandatory for the analyses of the anisotropic mechanical behavior of cancellous bone.

Algorithms↗
PubMed1996

Primary bone malignancies in children.

The evaluation and treatment of primary bone malignancies in children have evolved considerably over the past decade, with a measurable improvement in prognosis. Disease-free survival has improved mainly due to intensive multiple-agent chemotherapy, refinement in radiotherapeutic techniques, better imaging, and wide surgical resection. Reconstruction techniques after "limb-sparing" surgery have used allograft, composite allograft-prosthesis, or "expandable" prostheses reconstruction after adequate removal of the tumor with wide margins. The diagnosis and understanding of these tumor has also improved with advances in molecular genetics. Both osteosarcoma and Ewing's sarcoma treatment have undergone this dramatic change; recent advances in molecular genetics, treatment, magnetic resonance imaging, and "limb-sparing" surgery are highlighted.

Antineoplastic Agents↗
PubMed1996

Synchronous measurements of blood pressure and red blood cell velocity in capillaries of human skin.

We have devised a system for analyzing the temporal coherence of capillary pressure (CP) and capillary red blood cell velocity (CBV) variations in humans. The system is designed to measure human blood pressure in skin capillaries by direct cannulation while simultaneously measuring red blood cell velocity in the same capillary by video microscopy. The servo-nulling pressure measurement system allows the dynamic recording of capillary pressure with a flat frequency response of about 12 Hz. Computerized data acquisition is synchronized with the frame code of a U-matic video recorder, which records the capillaroscopic picture for later computerized off-line analysis of capillary red blood cell velocity. Measurements of simultaneously recorded CP and CBV in healthy volunteers show synchronized pulsation. Minimal pulsatile variations in CP values result in marked variations of CBV. In addition, minor fluctuations (3-4 cycles per minute) in CP are accompanied by marked changes in CBV. This system may help provide information about microvascular pathophysiology in skin diseases before and after treatment.

Adult↗
PubMed1996

Morphogenesis and mechanisms of penetration by plant pathogenic fungi.

Infection structures of phytopathogenic fungi are modified hyphae specialized for the invasion of plant tissues. Initial events are adhesion to the cuticle and directed growth of the germ tube on the plant surface. At the site of penetration, appressoria are often formed that may have melanized walls and develop high turgor pressure to support the penetration process. The penetration hypha accumulates components of the cytoskeleton in the tip and secretes a variety of cell wall-degrading enzymes in a highly regulated fashion in order to penetrate the cuticle and the plant cell wall. This article reviews recent papers on the cytology, physiology, and molecular biology of the penetration process.

Journal Article↗