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Biomedical subjects

M Wrischer

Publications and source records attributed to M Wrischer.

14 recordsLinked to original sources
PubMed1999

An in vitro model of the early genetic events in multistage carcinogenesis of malignant insulinoma.

The aim of this study was to establish an in vitro model to confirm earlier observations on the role of the myc/ras oncogenes as promoting factors in the process of normal Langerhans islet beta cell transformation. For that purpose we infected primary mouse Langerhans islets with a recombinant retrovirus containing the v-H-ras and v-myc oncogenes, before or after treatment with transforming growth factor alpha (TGFalpha). Normal Langerhans islets, when grown in culture, are viable for 2-3 weeks. After treatment with TGFalpha, viability was extended by 10 days, following which islets disintegrated. Langerhans islets transformed with v-H-ras and v-myc became immortal and insulin negative. Single infected beta cells, liberated from a primary islet into the surrounding medium, gave rise to neo islet formation. Moreover, single infected beta cells were able to grow and divide, even without fibroblast support. These results indicate that the myc and ras oncogenes are sufficient for commencement of beta cell transformation and, therefore, could represent 'early events' in the multistep carcinogenesis of insulinomas.

3T3 Cells↗
PubMed1998

Accumulation of very-long-chain fatty acids in membrane glycerolipids is associated with dramatic alterations in plant morphology.

Transgenic Arabidopsis plants overexpressing the Arabidopsis FATTY ACID ELONGATION1 gene under the control of the 35S promoter from cauliflower mosaic virus accumulated very-long-chain fatty acids (VLCFAs) throughout the plant. In some transformants, C20 and C22 VLCFAs accounted for >30% of the total fatty acids, accumulating at the expense of C16 and C18 fatty acids. These C20 and C22 fatty acids were incorporated into all of the major membrane glycerolipid classes. Plants with a high VLCFA content displayed a dramatically altered morphology, which included the failure of flowering shoots to elongate, a modified spatial pattern of siliques, an altered floral phenotype, and a large accumulation of anthocyanins. In addition, these plants also exhibited a unique alteration of the chloroplast membrane structure. We discuss a possible role for VLCFAs in establishing the shape/curvature of the membranes, which in turn may affect the shape of the cell and ultimately that of the whole plant.

Acetyltransferases↗
PubMed1991

Effect of insecticides (Dimiline WP 25, Torak EC 24 and Gamacide 20) on hydra (Hydra vulgaris Pallas).

Investigations showed that the three insecticides used had the most damaging effect upon hydra immediately after treatment. The tentacles and the hypostome are the parts most often damaged. Inse the affected cells, lesions appear in the intracellular membranes, the nucleus shell and the membranes of the mitochondria, Golgi complex and the endoplasmic reticulum, while the cell membrane is preserved. The damaged parts of the body regenerate within three days. Zymogen cells play a significant role in the course of regeneration. They dedifferentiate into gastrodermal interstitial cells and later into other types of cells of the ectoderm and the gastroderm. Apart from their intense participation in regeneration, these totipotent cells also invariably participate in the formation of new hydra buds. It was observed that Dimiline WP 25 and Torak EC 24 in the concentrations used stimulate asexual reproduction of this animal.

Animals↗
PubMed1991

Chromoplasts--the last stages in plastid development.

The results of investigations on the development of chromoplast fine structures in various plants are reviewed. Emphasis is placed on the specific pigment-containing structures and their development during chromoplast formation. There is a large variety of these structures, although four fundamental types can be discerned. These are plastoglobules, membranes, crystals, and tubules. During chromoplast development, various types of structure follow one after the other, or they may even be present simultaneously in the same chromoplast. Depending on the structures present in chromoplasts their pigment content also varies. It is still not clear whether the type of structure defines the pigment content of the chromoplast or vice-versa. Various possible ways of chromoplast development and dedifferentiation are discussed.

Carotenoids↗
PubMed1986

Human polymorphonuclear leukocytes aminopeptidases.

In human polymorphonuclear leukocytes a methionine, leucine, arginine, phenylalanine and alanine aminopeptidase activities were detected, both in cytosol and secondary granules. All activities were EDTA sensitive and their pH optima were in the range of pH 6.5 to 8.6. In the cytosol two enzymes could be distinguished, broad substrate specificity aminopeptidase of pH 4.7-4.9 and a chloride dependent arginine aminopeptidase of pI 5.3-5.5. The granules contain aminopeptidase of pI 4.0-4.6 and of pI 9.8-10.2, different from those in the cytosol. Among them broad specificity aminopeptidases and possibly specific methionine and leucine aminopeptidases could be discerned.

Alanine↗
PubMed1977

Effect of mutation on the peripheral reticulum in Tradescantia albiflora chloroplasts.

In the defective plastids of Tradescantia albiflora cv. aureo-vittata, a C3 plant, the mutation (localized with high probability in the plastom) increases the quantity of the peripheral reticulum (PR). The enhancement of PR may be connected with the mutation of a repressive gene or with some metabolic change caused by the mutation. In the early phase of the plastid destruction, the PR can be distinguished from the thylakoid derivatives on the basis of its DAB-negativity. The positive DAB-reaction in the thylakoid membranes is explained by their PS I activity.

Chloroplasts↗
PubMed1975

Transformation of plastids in the leaves of Acer negundo L. var. odessanum (H. Rothe).

The leaves of Acer negundo L. var. odessanum (H. Rothe), if permanently exposed to strong sunlight, do not green, but remain yellow and finally become bleached. In yellow leaves the plastids contain single thylakoids and no grana. In plastids of bleached leaves, however, only vesicles are present. The concentration of chlorophylls and photosynthetic activity are much lower in those leaves than in the green ones. If the illumination is reduced (e.g. by shading) both the yellow and the bleached leaves become greenish, and even fully green after a few days at a sufficiently low light intensity. The plastids of yellow-green leaves contain small grana. In dark green leaves the thylakoid system of the chloroplasts is normally developed forming true grana, regardless of whether the leaves were originally green, or became green by shading the yellow or bleached ones. Their pigment concentration and photosynthetic activity are also normal. If green leaves are exposed to sunlight they do not yellow or bleach. During a 3-week period the structure of the thylakoid system did not perceivably change, with the exception that large plastoglobules formed in the stroma.

Carotenoids↗