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Biomedical subjects

M Wieland

Publications and source records attributed to M Wieland.

18 recordsLinked to original sources
PubMed2002

Steering attosecond electron wave packets with light.

Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy.

Journal Article↗
PubMed2001

Caenorhabditis elegans as an environmental monitor using DNA microarray analysis.

In order to assist in the identification of possible endocrine disrupting chemicals (EDC) in groundwater, we are developing Caenorhabolitis elegans as a high throughput bioassay system in which responses to EDC may be detected by gene expression using DNA microarray analysis. As a first step we examined gene expression patterns and vitellogenin responses of this organism to vertebrate steroids, in liquid culture. Western blotting showed the expected number and size of vitellogenin translation products after estrogen exposure. At 10(-9) M, vitellogenin decreased, but at 10(-7) and 10(-5), vitellogenin was increased. Testosterone (10(-5) M) increased the synthesis of vitellogenin, but progesterone-treated cultures (10(-5) M) had less vitellogenin. Using DNA microarray analysis, we examined the pattern of gene expression after progesterone (10(-5), 10(-7), and 10(-9) M), estrogen (10(-5) M), and testosterone (10(-9) M) exposure, with special attention to the traditional biomarker genes used in environmental studies [vitellogenin, cytochrome P450 (CYP), glutathione s-transferase (GST), metallothionein (MT), and heat shock proteins (HSP)]. GST and P450 genes were affected by estrogen (10(-5) M) and progesterone (10(-5) and 10(-7) M) treatments. For vitellogenin genes, estrogen treatment (10(-5) M) caused overexpression of the vit-2 and vit-6 genes (2.68 and 3.25 times, respectively). After progesterone treatment (10(-7) M), the vit-5 and vit-6 were down-regulated and vit-1 up-regulated (3.59-fold). Concentrations of testosterone and progesterone at 10(-9) M did not influence the expression of the vit, CYP, or GST genes. Although the analysis is incomplete, and low doses and combinations of EDC need to be tested, these preliminary results indicate C. elegans may be a useful laboratory and field model for screening EDC.

Animals↗
PubMed2000

Advantages of stereo imaging of metallic surfaces with low voltage backscattered electrons in a field emission scanning electron microscope

High emission current backscattered electron (HC-BSE) stereo imaging at low accelerating voltages (</= 5 keV) using a field emission scanning electron microscope was used to display surface structure detail. Samples of titanium with high degrees of surface roughness, for potential medical implant applications, were imaged using the HC-BSE technique at two stage tilts of + 3 degrees and - 3 degrees out of the initial position. A digital stereo image was produced and qualitative height, depth and orientation information on the surface structures was observed. HC-BSE and secondary electron (SE) images were collected over a range of accelerating voltages. The low voltage SE and HC-BSE stereo images exhibited enhanced surface detail and contrast in comparison to high voltage (> 10 keV) BSE or SE stereo images. The low voltage HC-BSE stereo images displayed similar surface detail to the low voltage SE images, although they showed more contrast and directional sensitivity on surface structures. At or below 5 keV, only structures a very short distance into the metallic surface were observed. At higher accelerating voltages a greater appearance of depth could be seen but there was less information on the fine surface detail and its angular orientation. The combined technique of HC-BSE imaging and stereo imaging should be useful for detailed studies on material surfaces and for biological samples with greater contrast and directional sensitivity than can be obtained with current SE or BSE detection modes.

Journal Article↗
PubMed2000

Osteoblast proliferation and differentiation on dentin slices are modulated by pretreatment of the surface with tetracycline or osteoclasts.

BACKGROUND: Implant surface roughness and chemical composition, as well as other factors, affect the ability of osteogenic cells to form bone adjacent to an implant. The same principles may also apply to the tooth root and some reports have shown that surface modification of the root may lead to improved restoration of the periodontal apparatus. The most common of these surface modification techniques involves demineralization with citric acid or treatment with tetracycline to expose collagen fibrils. In addition, during normal bone remodeling, osteoclasts demineralize the extracellular matrix, leaving resorption pits and exposed collagen fibrils. In this study, the effect of different dentin surface-preparation techniques on osteoblasts were compared. METHODS: Slices of sperm whale dentin were mechanically polished and surfaces were treated with tetracycline-HCl (TCN) or were cultured with mouse bone marrow cells to create a surface with osteoclast (OC) resorption pits or left untreated. Profilometry, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were used to evaluate the 3 different dentin surfaces. MG63 osteoblast-like cells were cultured on the 3 different surfaces and the effect of dentin surface preparation technique on MG63 cell proliferation (cell number), differentiaton (alkaline phosphatase specific activity of isolated cells and cell layer lysates; osteocalcin production), and local factor production (transforming growth factor (TGF)-beta1 and prostaglandin E2 (PGE2) compared. RESULTS: Profilometry showed the polished and TCN surfaces were smooth with comparable Ra values, whereas the OC surfaces were slightly rougher due to resorption pits which covered 3.7% of the surface. XPS measurements showed that TCN treatment reduced the Ca and P content of the surface, indicating that it had dissolved the mineral. Osteoclast-resorption also reduced the Ca and P content, but to a lesser extent. MG63 cell proliferation on polished dentin and tissue culture polystyrene was equivalent. In contrast, cells grown on the TCN- and OC-treated surfaces exhibited increased proliferation. No effect of surface treatment on cell alkaline phosphatase activity was observed, but activity in the cell layer lysates was increased on the TCN- and OC-treated surfaces. Osteocalcin production was reduced on all dentin surfaces, but the greatest reduction was found on the TCN-treated surface. Production of both TGF-beta1 and PGE2 was increased on the treated surfaces. All effects were greatest in cultures grown on the TCN-treated dentin. CONCLUSIONS: These data indicate that demineralization of the dentin surface promotes proliferation of osteoblasts and early differentiation events like production of alkaline phosphatase and autocrine mediators such as PGE2 and TGF-beta1. However, later differentiation events like osteocalcin production are decreased. Osteoclast-mediated bone resorption elicits similar responses; less than 4% of the dentin surface resulted in approximately 75% of the response caused by TCN treatment. These observations suggest that greater attention should be paid to the effects of osteoclastic resorption in designing methods for enhancing bone and cementum formation adjacent to root surfaces.

Alkaline Phosphatase↗
PubMed1994

Treatment of severe cardiac allograft rejection with extracorporeal photochemotherapy.

Two patients were treated with photopheresis for marked cardiac allograft rejection with hemodynamic compromise that had become unresponsive to standard therapy. Multiple episodes of rejection had occurred, and initial response to standard therapy was favorable. However, progressive deterioration was documented by serial endomyocardial biopsies, fever, congestive heart failure, and abnormal cardiac catheterization findings. In the absence of retransplantation, death seemed imminent. Photopheresis was begun. Both patients received oral 8-methoxypsoralen and > or = 5 x 10(9) mononuclear cells were collected, treated with ultraviolet light A for 1.5 hours, and were reinfused. One procedure was performed weekly x4 and then monthly x5. Responses were striking with rapid loss of fever, improvement in exercise tolerance, normalization of cardiac hemodynamics, and improvement in endomyocardial biopsies. Although our experience with these two patients is anecdotal, photopheresis merits further study as treatment for severe cardiac allograft rejection.

Adult↗
PubMed1991

Concurrent comparison of the Cobe Spectra and Fenwal CS3000 for the collection of peripheral blood mononuclear cells for autologous peripheral stem cell transplantation.

Hematopoietic stem cells, collected by leukapheresis from peripheral blood, can be used as an alternative to autologous bone marrow transplantation following high-dose chemotherapy as treatment of several malignancies. We compared the ability of the Cobe Spectra and the Fenwal CS3000 to collect peripheral blood mononuclear cells (MNC) for autologous peripheral blood stem cell transplantation. Ten patients experienced repeated leukapheresis (10 L blood processed per procedure) using both instruments. Procedures were alternated between the two until a total of 7 x 10(8) MNC/kg was collected. Data from 61 Spectra and 50 CS3000 collections were analyzed. The yield (mean per procedure) of nucleated cells (NC) and MNC was higher (P less than .005) with the Spectra (0.77 x 10(10) NC and 0.54 x 10(10) MNC) than with the CS3000 (0.59 x 10(10) NC and 0.40 x 10(10) MNC). However, colony forming units (CFU-GM) were not different (P greater than .05) for Spectra (0.92 x 10(4)) and Fenwal (0.65 x 10(4) collections. Platelet contamination was lower (P less than .001) with the Spectra (2.2 x 10(11)) than the CS3000 (5.0 x 10(11)). This correlated with a higher patient blood platelet count immediately following Spectra collections (117 x 10(9)/L) versus the CS3000 (86 x 10(9)/L). Using the methods described, the Spectra product contained greater yields of NC and MNC with less platelet contamination than did the CS3000.

Antineoplastic Agents↗
PubMed1991

Animal model experimentation using the expansile hydrogel intraocular lens.

To determine the biocompatibility of the expansile hydrogel intraocular lens, a two-year animal study was undertaken. After phacoemulsification, hydrogel expansile intraocular lenses were implanted in four Dutch-belted rabbit eyes. Slitlamp examinations revealed minimal anterior chamber reaction and lens synechias. Gross pathology and histology demonstrated hyperplastic residual cortex, but confirmed our clinical impression that the lenses were well tolerated. Electron diffraction energy dispersive X-ray microanalysis revealed deposition of aluminum, silicon, magnesium, and calcium, but there was no evidence of matrix penetration.

Animals↗
PubMed1988

Phagocytosis-associated functions in neonatal monocyte-derived macrophages.

Using a Teflon culture system we analyzed different aspects of cell maturation and phagocytic activities in neonatal monocyte-derived macrophages. Morphological and cytochemical characteristics as well as the protein composition of neonatal macrophages were identical with those of adult controls; actin binding protein (265,000 Da), myosin (210,000), alpha-actinin (102,000) and actin (42,000) could be identified in cells from either source. All phagocytic functions were shown to be perfectly normal in neonatal macrophages when compared with adult cells: random migration, chemotactic response to zymosan-activated serum and formyl-methionyl-leucyl-phenylalanine, ingestion, and killing of Staphylococcus aureus, phagocytosis-associated chemiluminescence, production of oxygen intermediates (superoxide anion, O2-; hydrogen-peroxide, H2O2). Phorbol myristate acetate-stimulated O2(-)-generation by 1 x 10(5) macrophages was 11.8 +/- 4.7 nmol/h for neonates, and 10.2 +/- 3.9 for controls; production of H2O2 was 7.6 +/- 3.5 nmol/h in neonatal macrophages and 6.4 +/- 2.8 in adult controls. It is unlikely, then, that the increased susceptibility of human neonates to systemic bacterial infections can be related to an abnormality in the essential phagocyte functions of macrophages.

Cell Movement↗
PubMed1988

Use of digital compression following glaucoma surgery.

A survey of American glaucoma specialists showed that digital compression of the globe following filtering surgery for glaucoma is used extensively. Consensus regarding the method and timing of "massage" is lacking, as are controlled clinical studies supporting its assumed benefits.

Glaucoma↗
PubMed1986

Phagocytic activities in neonatal monocytes.

Monocytes play an essential role in cellular host defense as circulating phagocytes, as well as precursors of macrophages. We investigated the principal phagocytic activities in monocytes from cord blood of term infants by analysing adherence, random migration, chemotaxis, bactericidal activity, phagocytosis-associated chemiluminescence, production of superoxide anion (O-2) and generation of hydrogen peroxide (H2O2). All phagocytic functions of monocytes from neonates were shown quantitatively to be comparable to those of cells from healthy adult volunteers. The increased susceptibility of the human neonate to serious systemic infections cannot be related to an abnormality in monocyte function.

Adhesiveness↗
PubMed1986

Left-sided endocarditis due to Pseudomonas aeruginosa. A report of 10 cases and review of the literature.

Ten confirmed cases of left-sided endocarditis due to Pseudomonas aeruginosa were reported in detail and the English literature was reviewed. In recent years, venous access (usually illicit) has been the major predisposing factor to this infection and abuse of pentazocine and tripelennamine has been particularly associated with endocarditis due to this organism. This infection involves previously damaged as well as normal valves. The development of congestive heart failure did not adversely affect the prognosis of this infection. However, the development of azotemia was associated with a greater likelihood of a fatal outcome. In the current series, deaths were due to uncontrolled infection. This often occurred despite inhibitory and bactericidal activity in serum generally considered adequate for treatment of endocarditis. Medical treatment alone rarely produced cure of infection. Our experience with a high frequency of major vessel embolization (4/10) and the improved survival after medical/surgical treatment suggests that prompt valve replacement combined with high doses of an aminoglycoside plus carbenicillin or ticarcillin provide the best opportunity for successful outcome in patients with left-sided endocarditis due to P. aeruginosa.

Adult↗
PubMedDate not supplied

Tumor-biological factors uPA and PAI-1 as stratification criteria of a multicenter adjuvant chemotherapy trial in node-negative breast cancer.

In axillary node-negative primary breast cancer, 70% of the patients will be cured by locoregional treatment alone. Therefore, adjuvant systemic therapy is only needed for those 30% of node-negative patients who will relapse after primary therapy and eventually die of metastases. Traditional histomorphological and clinical factors do not provide sufficient information to allow accurate risk group assessment in order to identify node-negative patients who might benefit from adjuvant systemic therapy. In the last decade various groups have reported a strong and statistically independent prognostic impact of the serine protease uPA (urokinase-type plasminogen activator) and its inhibitor PAI-1 (plasminogen activator inhibitor type 1) in node-negative breast cancer patients. Based on these data, a prospective multicenter therapy trial in node-negative breast cancer patients was started in Germany in June 1993, supported by the German Research Association (DFG). Axillary node-negative breast cancer patients with high levels of either or both proteolytic factors in the tumor tissue were randomized to adjuvant CMF chemotherapy versus observation only. Recruitment was continued until the end of 1998, by which time 684 patients had been enrolled. Since then, patients have been followed up in order to assess the value of uPA and PAI-1 determination as an adequate selection criterion for adjuvant chemotherapy in node-negative breast cancer patients. This paper reports on the rationale and design of this prospective multicenter clinical trial, which may have an impact on future policies in prognosis-oriented treatment strategies.

Biomarkers, Tumor↗
PubMedDate not supplied

Wavelength-dependent roughness: a quantitative approach to characterizing the topography of rough titanium surfaces.

Topographies of grit-blasted, etched, grit-blasted and etched, and microfabricated and etched surfaces of commercially pure titanium have been investigated. Such surface topographies vary across the scale range of interest for dental implants, extending from nanometers to millimeters. The complete characterization of topography requires the use of complementary methods. This study compared the topographic characterization methods of non-contact laser profilometry, interference microscopy, stereo-scanning electron microscopy (stereo-SEM), and atomic force microscopy. Non-contact laser profilometry was shown to be a useful method to characterize topographic features in the micron to millimeter range, whereas interference microscopy and stereo-SEM can be employed down to the submicron range. Stereo-SEM is particularly useful for quantifying topographies with complex, strongly corrugated ("sharp"), and high-aspect-ratio features and was shown to be complementary to non-contact laser profilometry and interference microscopy. Because of tip-related envelope problems, atomic force microscopy was not found to be suitable for the type of surfaces investigated in this study. Independent of the method used, the commonly used "integral" amplitude roughness parameters, such as Ra, Rq, or Rt, were often of limited value in the description of actual implant surfaces. The application of the wavelength-dependent roughness approach was shown to be an effective method for the description of surface topographies in the complete range of characteristic roughness and is also a useful means of examining the effects of surface treatment processes.

Analysis of Variance↗