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At least 613 records · Page 34Linked to original sources
PubMed1985

Changes in O2 consumption of multicellular spheroids during development of necrosis.

Using O2-sensitive microelectrodes oxygen tension profiles were recorded in EMT6-spheroids either showing no necrosis or having developed a small necrotic area in the center. The profiles obtained were in accordance with those measured in previous investigations under similar conditions. The volume-related O2-consumption rate Q in the viable parts of the spheroids could be determined through theoretical considerations. The results show that there is a steep decrease in Q by a factor of three when the spheroids grow from diameters of 200 micron to diameters larger than 1000 micron. The drop in Q mainly occurs in a size range in which central necrosis develops in EMT6-spheroids cultured under these particular conditions. Among other factors, changes in the proliferative status, in extracellular volume fraction or in physiological parameters of the micromilieu in spheroids, such as accumulation of metabolic waste products or of toxic substances from the necrotic area may contribute to the variation in Q observed.

Animals↗
PubMed2002

Plant disease resistance: commonality and novelty in multicellular innate immunity.

Pathogen avirulence genes encode for effector molecules that play a crucial role in the process of pathogen colonization of plant tissue. Successful host defense requires rapid and efficient detection of the pathogen avirulence factors. In the last few years, much progress has been made in delineating the plant molecular sentinels that participate in pathogen identification. Because this ability is genetic information that is 'hard-wired' into the genome, it is called 'innate immunity' and it draws its origins from a phylogenetically ancient form of immunity common to plants and animals. Conservation is shown in many of the functional molecular motifs of innate genes such as the Toll/interleukin 1 receptor domains, nucleotide binding domains and structures that contain leucine rich repeats. Novel plant molecular surveillance domains also include pathogen pattern recognition by coiled-coil domains and specialized kinases. The rapid evolution of plant innate immunity genes is readily detected in their sequence polymorphism, by their massive amplification and appearance in the genome in a clustered organization. By comparative biology of highly diverged innate immunity systems we can enhance our appreciation of the truly basic forces that have shaped its evolution in mutlicellular organisms.

Amino Acid Sequence↗
PubMed1979

Sister chromatid exchange in murine alveolar macrophages, regenerating liver and bone marrow cells--a simultaneous multicellular in vivo assay.

Differential labeling of sister chromatids was achieved simultaneously in murine alveolar macrophages, regenerating liver, and bone marrow cells of partially hepatectomized mice as well as in alveolar macrophages and bone marrow cells of nonhepatectomized mice. The mean frequency of SCE/cell +/-S.D. and the percentage of second division cells for each cell type were determined. No significant differences in mean frequencies of SCE/cell were observed among the cell types or between hepatectomized (alveolar macrophages--3.6+/-2.2, bone marrow--3.4+/-2.2; regenerating liver--3.6+/-2.4) and nonhepatectomized (alveolar macrophages--3.4+/-1.9; bone marrow--2.9+/-1.8). Although the percentage of second division cells was dependent upon cell type, no significant differences were apparent between hepatectomized (alveolar macrophages--57+/-8%; bone marrow--37+/-6%; regenerating liver--65+/-6%) and nonhepatectomized mice )alveolar macrophages--53+/-6%; bone marrow--36+/-4%). Comparisons between BrdU treated and nontreated nonhepatectomized mice revealed no significant alteration in mitotic yields.

Animals↗
PubMed1994

The question of threshold doses for radiation damage: malformations induced by radiation exposure of unicellular or multicellular preimplantation stages of the mouse.

Mouse embryos of the one-cell stage or the 32- to 64-cell stage were exposed to various X-ray doses (one-cell stage: 0.25-2 Gy; 32- to 64-cell stage: 1-3 Gy). It turned out that the shape of the dose-response curves is statistically compatible with the assumption derived from biological considerations that there is no threshold for radiation-induced malformations in the case of the exposure of one-cell embryos, whereas there is a threshold dose (close to 1 Gy) in the case of the exposure of 32- to 64-cell embryos.

Animals↗
PubMed1994

Response of multicellular tumor spheroids to liposomes containing TNF-alpha.

This publication describes a new model to investigate the influence of tumor necrosis factor-alpha (TNF-alpha) on a three-dimensional glial cell aggregate under defined, standardized, reproducible conditions using the glioma cell line A 172. The cells are initially grown as normal monolayer culture until they reach a cell density of up to 1 x 10(6). Subsequently they are grown as spheroids by the liquid overlay technique. Spheroids grown in this way were divided into ten groups of more than 50 cell aggregates. Three groups were coincubated with free TNF-alpha in increasing dosages (100 ng/ml, 200 ng/ml and 1000 ng/ml); three groups were incubated with empty liposomes (0.2 mg/ml, 0.4 mg/ml and 2 mg/ml); three groups received liposomes which had been loaded with TNF-alpha, and one group, which received no treatment, served as control. The diameter of the spheroids ranged from 80 microns to 350 microns. There was no significant difference in growth between the 3 groups treated with 'free' TNF-alpha. Comparing spheroids treated with TNF-alpha with those which had been coincubated with empty liposomes, there was a significant difference (p < 0.001) in growth, which correlated with the amount of liposomes. Similarly, free TNF-alpha had a significantly (P < 0.001) stronger growth-inhibiting effect as compared to liposomes loaded with TNF-alpha. Comparing the groups treated with liposomes only to those treated with liposomes loaded with TNF-alpha, the latter exhibited a more marked (although not significantly) growth-inhibiting effect. The preliminary conclusion is that the major growth-inhibiting effect seems to be mediated by the liposomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Aggregation↗