1-Methylguanine and 7-methylguanine increase cell agglutinability

Summary 1-Methylguanine and 7-methylguanine, both metabolic products of tRNA degradation, are known to induce transformation of Chinese hamster fibroblasts in culture. The effects of these compounds on the cell membrane have been studied by the method of Concanavalin A-mediated hemadsorption. 1-Methylguanine or 7-methylguanine induced a 50% increase of Con A-mediated hemadsorption within 20 hours of exposure of the cells to the agent at a concentration of 10^-5 M. This alteration was reversed within 13 days when the cells were grown in the control medium. Prolonged treatment with 1-methylguanine or 7-methylguanine resulted in changes which were only slowly reversed during growth of the cells in the control medium. The effect of the methylated purines on the cell membrane could be completely inhibited by simultaneous addition of dibutyryl-cAMP at a concentration of 10^-5 M. The possible mechanism of cell membrane alteration by methylated purines and its relevance to transformation in vitro are discussed.     

A rapid cell membrane permeability test using flourescent dyes and flow cytometry

A reliable and rapid test to detect cytotoxic chemicals which affect cell membranes is described. Fluorescein diacetate freely penetrates intact cells where it is hydrolyzed to its fluorochrome, fluorescein, which is retained in the cell due to its polarity. On the other hand, ethidium bromide is known to be excluded from the intact cell, staining only nucleic acids of membrane-damaged cells. The combination of both fluorochromes results in counter-staining: intact cells fluoresce green (cytoplasm) and membrane-damaged cells fluoresce red (nucleus and RNA). Rat thymocytes freshly isolated without enzyme treatment were incubated simultaneously with test substance and dye solution fluorescein diacetate and ethidium bromide. A two-parameter analysis was performed on a flow cytometer with an on-line computer. Concentration-dependent effects of various detergents and solvents were quantified by measuring the amount of dye retention, i.e., the decrease or increase in fluorescein—fluorescence (peak shift), and the decrease in dye exclusion (increase in ethidium bromide-staining) relative to the untreated control. The assay can be used for rapid monitoring of chemical insults to cell membranes which precede the decrease of the viability measured by pure dye exclusion techniques.Abbreviations DMA dimethyl sulfate - DMSO dimethyl sulfoxide - EB ethidium bromide - F fluorescein - FDA fluorescein diacetate - FS₂₅ concentration of test substance resulting in a F-peak left-shift of 25% from control - PBS phosphate buffered saline - SCT forward light scatter - SDS sodium dodecyl sulfate     

Thymus-independent induction and antigen-dependent recovery of idiotype-specific suppression

BALB/c nude (nu/nu) mice and euthymic (nu/+) littermates were treated as neonates with anti-T15 antibody and challenged at various ages with either a thymus-independent, PC-Brucella abortus (PC-BA), or thymus-dependent, PC-keyhole limpet hemocyanin (PC-KLH), form of phosphorylcholine (PC). Nu/nu mice challenged with PC-KLH received KLH-primed splenic T cells prior to immunization. Neither neonatally anti-idiotype-treated nu/+ nor nu/nu mice responded with the production of T15-positive anti-PC antibodies after challenge with either form of PC antigen. It is concluded that neither induction nor maintenance of a state of T15-specific suppression requires thymus-matured T cells. Recovery of anti-PC responsiveness in suppressed nu/+ or nu/nu mice was similar and was found to be related to the form of antigen used to elicit the response. Immunization with PC-KLH revealed a long-lasting unresponsiveness (up to 16 weeks). In contrast, immunization with PC-BA elicited a full anti-PC response as early as at 6.5 weeks of age.     

Fine structural and enzyme histochemical observations on the dorsal tail tubercle of Mertensiella caucasica (Urodela,Amphibia)

Summary Dorsal tubercle and skin of Mertensiella caucasica have been investigated with the electron microscope and enzyme histochemical methods. The epidermis of the tubercle consists of 8–9 cell layers, that of normal dorsal skin of 5–6. The tubercle is filled with large mucous glands which are surrounded by an almost complete layer of smooth muscle cells (myoepithelial cells). Their glandular cells undergo cyclical changes and are characterized by specific secretory granules, which differ from those of the relatively small mucous glands of the normal dorsal skin.In the connective tissue of the tubercle a relatively rich supply of nerve fibres has been found, which in part contain synaptic and dense core vesicles or accumulations of mitochondria. In the normal dorsal skin nerve fibres occur less frequently.The following enzymes have been demonstrated in the mucous glands of the tubercle: SDH, acid phosphatase, unspecific esterases, E 600 resistant esterase.The tubercle seems to stimulate the female cloaca chemically and mechanically.     

DEGRADATION OF RIBONUCLEIC ACID IN MOUSE FIBROBLASTS TREATED WITH ACTINOMYCIN

The cellular RNA content of mouse fibroblasts incubated with actinomycin decreases at a rate of about 1 to 1.5 per cent per hour, while DNA and protein content remain unchanged. This degradation affects nuclear and cytoplasmic RNA, ribosomal and soluble RNA. The breakdown products appear quantitatively in the acid-soluble fraction of the cells and the medium. Polynucleotides synthesized a short period (120 minutes) prior to exposure to actinomycin are degraded before those synthesized 8 to 12 hours previously.     

Fundamentals of an applied ecosystem research project in the Wadden Sea of Schleswig-Holstein

The aims, content, and organisatory structure of a proposed interdisciplinary ecosystem research project in the Wadden Sea of Schleswig-Holstein (W. Germany) are briefly presented. The project will include research on both fundamental as well as applied aspects of the Wadden Sea ecosystems and their interaction with local human activities. In contrast to most of the other completed or currently running ecosystem research projects on tidal coasts, a considerable part of the scientific work will also deal with aspects of ecosystem management and protection of the various marine and semiterrestrial habitats of the Wadden Sea. Considerable attention is paid to theoretical and methodological aspects of research on ecosystems and landscape units. In particular, the adoption of a hierarchical view of complex biological and environmental systems is recommended. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988)     

Carnivora: the primary structure of the beach marten (Martes foina, Mustelidae) hemoglobin

The primary structures of alpha- and beta-chains from the hemoglobin of the Beach Marten (Martes foina, Carnivora) are presented. The globin chains were separated on CM-cellulose in 8M urea buffer. The amino-acid sequences were established by automatic liquid- and gas-phase Edman degradation of the intact chains and the tryptic peptides from oxidized chains. Comparison of the sequences with human hemoglobin shows 21 exchanges in the alpha- and 12 in the beta-chains. The differences concerning heme and interchain contact sites as well as the substitution alpha 77 (EF6)Pro----Ala are discussed. The latter is observed for the first time in a mammalian hemoglobin. The sequences are compared with those of other Carnivora. The beta-chains of Martes foina and Pteronura brasiliensis (Giant Otter) are found to be identical, but their alpha-chains differ in 7 positions. The surprising small numbers of exchanges between the hemoglobin from Beach marten and that from Lesser and Greater Panda are discussed.     

the frooxidant-induced and spontaneous mitochondrial calcium release: Inhibition by meta-iodo-benzylguanidine (mibg), a substrate for mono (adpribosylation)

The norepinephrine analogue meta-iodo-benzylguanidine (MIBG). a substrate for mono(ADP-ribosylation) and inhibitor of eukaryotic ADP-ribosyltransferases. inhibits the prooxidant-induced and spontaneous calcium release from intact rat liver mitochondria without affecting pyridine nucleotide oxidation and hydrolysis. This finding strongly suggests regulation of calcium release by ADP-ribosylation in mitochondria. and may be relevant for the cellular and pharmacological effects of MIBG