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Biomedical subjects

U Zimmermann

Publications and source records attributed to U Zimmermann.

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

Rotation of cells and ion exchange beads in the MHz-frequency range.

Whereas human red blood cells and protoplasts of leaves of Avena sativa show rotation only at discrete frequencies in the kHz-range of a linear alternating electric field, rotation of these cells is observed at practically every frequency in the MHz range (15 to 200 MHz). The cell rotation in the MHz-range can be explained in terms of field induced polarisation and orientation of permanent dipoles within the membrane and the cell. This interpretation is supported by the finding that Chelex beads (polystyrene cross-linked with divinylbenzene and coupled to iminodiacetic acid) do exhibit rotation in the MHz-range, but not in the kHz-range. It is most interesting that the Cu2+- and Ca2+-forms of the Chelex beads show a shift in the rotation frequency spectrum in addition to an increase in the magnitude of the rotation speed with respect to the Na+-form. At frequencies in the MHz-range at which rotation of the Chelex beads is not observed, formation of chains of beads from the electrodes occurs instead. This is due to positive polarisation of the beads leading to positive dielectrophoresis. The results support the view that rotation needs negative polarisability which is determined by the functional groups.

Edible Grain↗
PubMedDate not supplied

Cell fusion by simulated atmospheric discharges: further support for the hypothesis of involvement of electrofusion in evolution.

Electrofusion of mesophyll cell protoplasts of Avena sativa was induced by simulated atmospheric discharges. It is shown both experimentally and theoretically that the potential differences which occur at quite long distances from the point of lightning stroke are large enough to induce fusion. Besides electromagnetic waves which are emitted during lightning (G. Küppers and U. Zimmermann, FEBS Lett. 164, 323 (1983] cell fusion may have also occurred directly by means of the voltage built-up on the earth during evolution in response to a lightning stroke.

Biological Evolution↗
PubMedDate not supplied

First successful xenotransplantation of microencapsulated human parathyroid tissue in experimental hypoparathyroidism: long-term function without immunosuppression.

Owing to the complexity of the parathyroid hormone's metabolic interactions, clinical hypoparathyroidism is one of the most difficult of all endocrine disorders to treat. Therefore, causative treatment of this disorder by transplantation of parathyroid glands is highly desirable. We have recently documented the long-term in vivo function of iso- and allotransplanted rat parathyroid tissue without systemic immunosuppression in an animal model. In view of the potential clinical use of this method, human parathyroid tissue has been microencapsulated and transplanted over the highest immunological barrier. In a controlled, long-term animal study in the parathyroidectomized rat, the effect of microencapsulation on xenotransplanted human parathyroid tissue was evaluated over 30 weeks (native and microencapsulated parathyroid tissue = 40 rats respectively). Functionally, human parathyroid tissue was able to replace that of the rat. All animals that had received microencapsulated parathyroid tissue were normocalcemic for 16 weeks; 27/40 at the end of the study. In contrast, serum calcium concentrations dropped to post-parathyroidectomy levels within 4 weeks in those animals that had received native tissue only. Histologic evaluation of the explanted, functionally successful xenografts showed vital parathyroid tissue inside intact microcapsules surrounded by a small rim of fibroblasts. Avital fibrotic remnants were demonstrated in animals with non-encapsulated parathyroid tissue. Thus, we have established the feasibility of microencapsulation of human parathyroid tissue, preserving its viability over long periods in vivo even if xenotransplanted. In combination with an improved tissue culture method, transplantation of human parathyroid tissue and maintenance of its physiological function is reproducibly achieved without postoperative systemic immunosuppression over the highest transplantation barrier. This may be a crucial step towards the first clinical application of this method.

Animals↗
PubMedDate not supplied

Tumor-specific apoptosis induced by the human monoclonal antibody SC-1: a new therapeutical approach for stomach cancer.

Stomach cancer is one of the most frequently occurring cancers worldwide, with a very poor prognosis, even after complete gastrectomy. We describe here an alternative therapeutical approach using a human monoclonal antibody (SC-1), which was isolated from a patient with diffuse-type gastric adenocarcinoma. We demonstrate that the antibody significantly reduces stomach cancer growth in vivo, by inducing tumor-specific apoptosis and that the antibody, even delivered in high doses, shows no toxic crossreactivity to other organs or tissues. The data presented here show that tumor-specific apoptosis can be induced and they give rise to the hope that human monoclonal antibodies with biological activity might present a completely new type of adjuvant cancer therapy.

Adenocarcinoma↗
PubMedDate not supplied

Adjuvant therapy for gastric adenocarcinoma with the apoptosis-inducing human monoclonal antibody SC-1: first clinical and histopathological results.

In a first clinical trial with the apoptosis-inducing human antibody SC-1 eight patients with poorly differentiated stomach adenocarcinoma of diffuse-type received 20 or 30 mg of purified SC-1 antibody intravenously, followed 24 or 48 h later by gastrectomy and lymphadenectomy. In seven cases a significant induction of apoptotic activity was measured in primary tumors as compared with earlier biopsy material and in five patients a significant regression of tumor mass could be determined histopathologically. No toxic crossreactivity was observed with normal tissue or organs of patients.

Adenocarcinoma↗
PubMedDate not supplied

[Organ specific application of drugs by means of cellular capsule systems (author's transl)].

It is suggested to use living cells (red blood cells, lymphocytes and leucocytes) as drug delivery systems for temporal and spatial drug administration in human therapeutics and diagnosis. The effectiveness of drug loaded cells is demonstrated for the drug methotrexate which is used in cancer treatment. Red blood cells are loaded with methotrexate using the dielectric breakdown technique. Dielectric breakdown leads to a transient increase of permeability of the cell membrane. Red blood cells loaded with tritium-labelled methotrexate were injected into mice and the activity level was measured in several organs as a function of time. It is shown that with this drug delivery system more than 50% of the drug (after 10 min) can be accumulated in the liver and that a high activity level can be sustained in this or gan for more than 3 hours. On the other hand, administration of this drug by injecting solutions in the usual manner leads only to an 25% accumulation of methotrexate (after 10 min) in the liver. The drug is excreted completely after 1 to 2 hours. It is proposed to load red blood cells simultaneously with para- or ferromagnetic substances to obtain organ-specificity for any selected site of the body.

Animals↗
PubMedDate not supplied

High yields of DNA-transfer into mouse L-cells by electropermeabilization.

DNA transfection in mouse L-cells was performed by means of the electropermeabilization technique (U. Zimmermann, G. Pilwat, and F. Riemann, Z. Naturforsch. 29, 304 (1974)). The plasmid pSV 2-neo used leads to neomycin-resistance in stably transfected L-cells. Optimized conditions resulted in high yields of clones at relatively low DNA concentration. The influence of temperature during pulse application and during the subsequent resealing process as well as the field parameters and medium composition are discussed.

Animals↗
PubMedDate not supplied

Fracture toughness of pin-retained class 4 restorations.

Standardized class 4 cavities were prepared in bovine incisors and restored with a microfilled composite resin. The composite restorations were retained either by acid etching technique (AET) alone or by acid etching technique in combination with a self-threading retentive pin. Pins covered with a bonding/opaquer coating (PCR pin) and uncovered pins (FO pin) were used. After having been aged for 3 days, the fracture resistance of the restorations was determined with a Universal Testing Machine. The restorations were loaded at an angle of 45 degrees. The restorations retained by AET and a PCR pin showed the highest failure load. The restorations accomplished with AET and a FO pin yielded the lowest fracture load. The fracture toughness of the restorations retained by AET and a PCR pin was slightly but statistically significant, higher compared to the restorations exclusively attached by acid etching technique. It was concluded that there was only a small increase of fracture toughness of large class 4 composite restorations if the acid etching technique was combined with the application of bonding/opaquer-covered retentive pins.

Acid Etching, Dental↗