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S Langer

Publications and source records attributed to S Langer.

95 records · Page 6Linked to original sources
PubMedDate not supplied

Comparison of the new OPS imaging technique with intravital microscopy: analysis of the colon microcirculation.

BACKGROUND: The OPS imaging technique has been introduced for in vivo assessment of microcirculation in humans. The aim of this study was to validate the new technique against intravital fluorescence microscopy (IFM) for the visualization of colon microcirculation in a murine model of inflammatory bowel disease (IBD). METHOD: IBD was induced in Balb/c mice by dextran sulfate sodium, controls received normal water. In each animal, both the CYTOSCAN A/R and IFM were used to image the microcirculation (n = 7 in each group). The postcapillary venular diameter was analyzed on the colon muscularis and mucosa. RESULTS: The venular diameter correlated significantly between both methods representing the good correspondence between both methods. CONCLUSION: Our study demonstrates that the new technique for visualization of microcirculation without use of fluorescent dyes, the OPS imaging, allows for quantitative measurement of a key microcirculatory parameters of the mouse colon.

Animals↗
PubMedDate not supplied

Fractions from commercial collagenase preparations: use in enzymic isolation of the islets of Langerhans from porcine pancreas.

Transplantation of isolated islets of Langerhans is an intriguing possibility for the treatment of diabetes mellitus. The isolation of islets from pancreata requires the specific dissociation of the tissue. Commercial collagenases from Clostridium histolyticum are widely used for this purpose. Unfortunately, the effectiveness of these commercial enzymes is not predictable and differs considerably between suppliers and even from lot to lot. This is due mainly to differences in their specific collagenase activity and to the presence of other lytic enzymes, as well as to other contaminants. Free flow zone electrophoresis (FFZE) was used to separate the effective protein components from undesired compounds and to prepare a digestive enzyme mixture with controlled composition of lytic activities. Fractionation of crude collagenases by FFZE resulted in partially purified protein fractions that were enriched for collagenase and tryptic activities, and contained only trace amounts of neutral protease. These preparations proved to be highly effective in an in vitro assay for the libration of viable islets from porcine pancreas. To scale up the production of these collagenases with defined enzyme composition, we fractionated two different lots of a commercial collagenase from C. histolyticum (one lot effective in islet isolation, the other not) by using fast protein liquid chromatography (FPLC) on hydroxyapatite. Again, high efficacy of islet release from pancreatic tissue was correlated to high specific tryptic and collagenase activities and low levels of neutral protease. The chromatographic protocol developed in this study converted a non-effective collagenase lot into a preparation that allowed successful islet isolation.

Animals↗
PubMedDate not supplied

Application of the time-dependent Green's function and Fourier transforms to the solution of the bioheat equation.

A theory for solving the bioheat equation is developed using a time-dependent Green's function and Fourier transform techniques. The description of both steady-state and time-dependent data are placed into a single framework which can also describe the effects of inhomogeneous blood perfusion. The theory is illustrated by examples including the modelling of a thermal conduction hyperthermia system and a new RF interstitial system. A possibility for measuring the blood perfusion parameter and thermal conductivity from the steady state temperature distribution of a point source is also proposed.

Fourier Analysis↗
PubMedDate not supplied

Tissue distribution and penetration of 5-ALA induced fluorescence in an amelanotic melanoma after topical application.

BACKGROUND: Photodynamic therapy (PDT) following topical application of 5-aminolevulinic acid (ALA) is increasingly employed for several types of malignancies. However, data with respect to tissue penetration and distribution of ALA-induced porphyrins after topical application are scarce. Therefore, it was our aim to study tissue distribution and the penetration potency of topically applied ALA. MATERIAL AND METHODS: We used Syrian golden hamsters implanted with the amelanotic melanoma A-Mel-3 growing in a transparent dorsal skinfold chamber. ALA was topically applied in aqueous solution at a concentration of 3% for 4 hours. The fluorescence pattern was quantified by fluorescence microscopy and digital image analysis from cryosections and given as percentage of a reference standard in medians (25%, 75% quartiles). RESULTS: Fluorescence intensities in tumors were 90.8% (56.2%, 115.2% of a reference standard, p < 0.01 vs. normal tissue) significantly exceeding normal surrounding host tissue yielding fluorescence intensities of 12.1% (9.1%, 16.1%). The tumor selectivity, that is the ratio of fluorescence intensities between tumor and normal tissue, was 7.3 (6.1, 9.1). For superficial tumors with a thickness of approximately 1 mm no fluorescence gradients after topical application of ALA could be observed. CONCLUSION: In superficial cancerous lesions the fluorescence distribution of ALA induced porphyrins is tumor selective without significant fluorescence gradients throughout the tumor. Thus, by optimising the treatment modalities for topical ALA-PDT an enhanced efficacy and selectivity will be reached.

Administration, Topical↗