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.

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.

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.

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.

Ultrastructural localization of photosynthetic activity in thylakoids during chloroplast development in maize.

The localization of photosynthetic activity in developing maize (Zea mays L.) chloroplasts was studied in situ by two electron-microscopic-cytochemical methods. The activity of photosystem I was detected by photooxidation of 3,3'-diaminobenzidine (DAB) and the activity of the photosystem II by photoreduction of thiocarbamyl nitrotetrazolium blue (TCNBT).

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.

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.

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

The leaves of Acer negundo L. var. odessanum (H.

The effects of inhibitors of protein synthesis on the differentiation of plastids in etiolated bean seedlings.

It has been shown that inhibitors of protein synthesis do not influence the breakdown of the crystal-lattice-like structure of the prolamellar bodies in the plastids when etiolated plants are exposed to light. The formation of grana and the greening of leaves are however considerably inhibited, depending on the concentration of the inhibitor used.

[The effect of pre-illumination on the development of plastids in primary leaves of γ-irradiated etiolated bean seedlings].

It has been shown that a short pre-illumination (1-30 min) of etiolated bean seedlings considerably reduces the delay of grana development in the plastids caused by gamma radiation. As in non-irradiated etiolated material the grana formation is stimulated by an equal pre-illumination, it may be concluded that the observed phenomenon is not a consequence of protection or restoration processes but of a photomorphogenic effect which is independent even of gamma radiation.

[Electron microscope studies on the crystal-like structures in the plastid stroma].

The crystal-like structures in the plastid stroma of primary leaves of Phaseolus vulgaris, recently described by several authors, were studied with the electron microscope after different treatments: 1. The crystal-like structures can be seen after fixation in glutaraldehyde followed by a post-fixation with osmium tetroxide as well as after osmium tetroxide fixation alone. They are not preserved by fixation in permanganate.