Effects of alkylating agents on lymphocytes from controls and from patients with Fanconi's anemia

Summary The frequency of sister chromatid exchanges (SCE) and chromosome aberrations and the dynamics of cell division in peripheral blood lymphocytes of four patients with Fanconi's anemia were studied after in vitro exposure to alkylating agents TEPA and mitomycin.SCE frequency was significantly increased even after very low doses of mutagens, while chromosome aberrations were significantly increased only after high doses (0.160 g/ml mitomycin and 10^-5 M TEPA). The responses of Fanconi's anemia cells and control cells did not differ significantly. The increased frequency of both SCE and chromosome aberrations was accompanied by gradual delay of cell division, which was most conspicuous in cells from patients with Fanconi's anemia.     

The cytotoxic and cytocidal effect of colicin E3 on mammalian tissue cells

The plasma membrane of mammalian cells can mediate the cytotoxic and cytocidal effects of colicin E3. As little as 10² lethal units of purified colicin E3 per cell exert a pronounced cytocidal effect on human epithelial HeLa cells and as little as 10⁴ lethal units per cell also on line L mouse fibroblasts in tissue culture. Cells in complete monolayers are rapidly killed, become spherical and shrink, they are detached from the support and finally autolyzed. The percentage of killed cells in both lines is directly proportional to the multiplicity of colicin used. Theld ₅₀ for HeLa cells is about 30 times lower than for L cells. At the multiplicity of 10⁵ l.u., usually 100 % HeLa cells and 90 % L cells are killed in 2–3 days. Purified colicins E2 and D have no demonstrable cytological effect on HeLa cells, although DNA synthesis in L cells appears to be partly inhibited by colicin E2. The profound effect of colicin E3 on mammalian cells could be interpreted in a similar way as in bacteria,viz. as a specific cleavage of rRNA.     

Physiological characteristics of chemostatically grownCitrobacter freundii as a function of the specific growth rate and type of nutrient limitation

Citrobacter freundii was grown aerobically in a chemostat on a mineral medium witn galactose or glucose as carbon and energy sources under limitation by carbon or nitrogen source respectively. At various specific growth rates ranging from 7 to 95% μ_max the culture in steady state was analysed and growth yield, specific metabolic rate of substrate utilization, intracellular concentration of pyruvate, ATP, ADP, AMP and energy charge were determined and plotted as functions of dilution rate. In all four types of experiments the physiological state of cells remained practically independent of dilution rate up toD = 0.6 μ_max, and at a given specific growth rate nearly independent on μ_max and type of limitation. At approximatelyD = 0.6 μ_max, which is close to the maximum output dilution rateD _m, the physiological state of the cells changed: growth yields decreased and intr cellular pyruvate and adenylates concentrations increased. Consequently, in a given medium two dilution rates exist at which growth rate dx/dt is the same but the physiology of the population is quite different.     

Regulation of hypoxanthine transport in Neurospora crassa.

Hypoxanthine uptake and hypoxanthine phosphoribosyltransferase activity (EC 2.4.2.8) were determined in germinated conidia from the adenine auxotrophic strains ad-1 and ad-8 and the double mutant strain ad-1 ad-8. The mutant strain ad-1 appears to lack aminoimidazolecarboximide ribonucleotide formyltransferase (EC 2.1.2.3) or inosine 5'monophosphate cyclohydrolase (EC 3.5.1.10) activities, or both, whereas the ad-8 strain lacks adenylosuccinate synthase activity (EC 6.3.4.4). Normal (or wild-type) hypoxanthine transport capacity was found to the ad-1 conidia, whereas the ad-8 strains failed to take up any hypoxanthine. The double mutant strains showed intermediate transport capacities. Similar results were obtained for hypoxanthine phosphoribosyl-transferase activity assayed in germinated conidia. The ad-1 strain showed greatest activity, the ad-8 strain showed the least activity, and the double mutant strain showed intermediate activity levels. Ion-exchange chromatography of the growth media revealed that in the presence of NH+/4, the ad-8 strain excreted hypoxanthine or inosine, the ad-1 strain did not excrete any purines, and the ad-1 ad-8 double mutant strain excreted uric acid. In the absence of NH+/4, none of the strains excreted any detectable purine compounds.     

Galium procurrens,a new diploid relic species of theG. sylvaticum-group from the Balkan Peninsula

Galium procurrens is described as a new diploid relic species from Montenegro/N. Albania and SW. Bulgaria. It is related to the tetraploidG. laevigatum and other diploid and polyploid taxa of theG. sylvaticum-group inhabiting European deciduous forests.     

Lectinomics I. Relevance of exogenous plant lectins in biomedical diagnostics

This review focuses on utilization of plant lectins as medical diagnostic reagents and tools. The lectin-related diagnostic is aimed at detection of several diseases connected to alteration of the glycosylation profiles of cells and at identification of microbial and viral agents in clinical microbiology. Certain lectins, proposed for or used as diagnostic tools could even recognize those cellular determinants, which are not detected by available antibodies. Broad information is presented on the lectinomics field, illustrating that lectin diagnostics might become practical alternative to antibody-based diagnostic products. In addition, the rising trend of lectin utilization in biomedical diagnostics might initiate a development of innovative methods based on better analytical technologies. Lectin microarray, a rapid and simple methodology, can be viewed as an example for such initiative. This technology could provide simple and efficient screening tools for analysis of glycosylation patterns in biological samples (cellular extracts, tissues and the whole cells), allowing thus personalized detection of changes associated with carbohydrate-related diseases.