Hydroxyl radical induced cross-linking between phenylalanine and 2-deoxyribose

Hydroxy radicals induce cross-linking between phenylalanine (Phe) and 2-deoxyribose (dR) via formation of corresponding free radical intermediates. The cross-linked products were separated and identified by capillary gas chromatography-mass spectrometry. When phenylalanine and 2-deoxyribose radicals were generated in a 1:1 ratio, the predominant interaction was between Phe and dR radicals while the Phe-Phe and dR-dR cross-links were less abundant. The newly discovered cross-link between 2-deoxyribose and phenylalanine may serve as a model for radiation or free radical induced cross-linking between DNA and proteins and in general between sugar moieties and amino acids.     

Radiation-induced crosslinks between thymine and phenylalanine

OH radicals generated by ionizing radiation in aqueous solutions of thymine (T) and phenylalanine (Phe) induce crosslinking between thymine and phenylalanine. The crosslinked products were isolated and characterized by capillary gas chromatography-mass spectrometry. They are formed via OH radical adducts to thymine and phenylalanine and the reaction between dissimilar radicals is greatly favoured (T-Phe:Phe-Phe:T-T = 0.46:0.14:0.05). The reaction mechanism presented may serve as a model for radiation or any free radical-induced crosslinks between DNA and proteins.     

Antioxidant Activity of 5-Hydroxytryptophan, 5-Hydroxyindole, and Dopa Against Microsomal Lipid Peroxidation and Its Dependence on Vitamin E

The antioxidant capacity of 5-hydroxy-tryptophan. 5-hydroxy-indole. and DOPA (3,4-dihydroxy-phenyI-alanine) was tested in the Fe-induced lipid peroxidation of liver microsomes of normal- and vitamin E-deficient rats, using ascorbate as a reductant. Lipid peroxidation was monitored as low-level chemilu-minescence, indicative of generation of electronically-excited states arising from the recombination of secondary lipid peroxyl radicals.     

Spike discharges of skeletomotor neurons during random noise modulated transmembrane current stimulation and muscle stretch

 Spike discharges of skeletomotor neurons innervating triceps surae muscles elicited by white noise modulated transmembrane current stimulation and muscle stretch were studied in decerebrated cats. The white noise modulated current intensity ranged from 4.3 to 63.2 nA peak-to-peak, while muscle stretches ranged from 100 μm to 4.26 mm peak-to-peak. The neuronal responses were studied by averaging the muscle length records centered at the skeletomotor action potentials (peri-spike average, PSA) and by Wiener analysis. Skeletomotor spikes appeared after a sharp peak in PSA of the injected current, preceded by a longer-lasting smaller wavelet of either depolarizing or hyperpolarizing direction. The PSA amplitude was not related to the injected current amplitude nor showed any differences related to the motor unit type. The PSA amplitudes were virtually independent of the stretching amplitude σ, after an initial increase with stretching amplitudes in the range of 15–40 μm (S.D.), or 100–270 μm peak-to-peak.Analyses of cross-spectra indicated a small or absent increase in gain with frequency in response to injected current, but about 20 dB/decade in the range 10–100 Hz in response to muscle stretch. The peaks of both Wiener kernels in response to current injection appear to decrease with the amplitude of injected current, but this decrease was not statistically significant. The narrow first-order kernels suggest that the transfer function between the current input and spike discharge is lowpass with a wide passband, i.e. there is very little change in dynamics. The values of the second-order kernels appear to be nonzero only along the main diagonal. This is characteristic of a simple Hammerstein type cascade, i.e. a zero memory nonlinearity followed by a linear system. Small values of second-order kernels away from the origin and narrow first-order kernels suggest that the linear cascade contributes very little to the overall dynamic response.In contrast to Wiener kernels found in response to current injection, the Wiener kernels in response to stretch showed a decreasing trend with stretch amplitude. The size of the second-order kernels decreased to a somewhat larger extent with input amplitude than that of the first-order kernels, indicating an amplitude-dependent nonlinearity. Overall, the transformation between length and spike output was described as an LNNL cascade with second-order nonlinearities. Received: 1 April 1993/Accepted in revised form: 24 March 1994     

Quality Assessment of Bee Pollen-Honey Mixtures Using Thin-Layer Chromatography in Combination with Chemometrics

The aim of this study is to develop a rapid, effect-directed screening method for quality assessment of bee pollen-honey mixtures. The comparative antioxidant potential and phenolic content of honey, bee pollen, and the bee pollen-honey mixtures, was performed using spectrophotometry. The total phenolic content and antioxidative activity of bee pollen-honey mixtures with 20 % bee pollen share were in the range 3.03–3.11 mg GAE/g, and 6.02–6.96 mmol TE/kg, respectively, while mixtures with 30 % bee pollen share contained 3.92–4.18 mg GAE/g, and 9.69–10.11 mmol TE/kg. Chromatographic fingerprint of bee pollen-honey mixtures was performed by high-performance thin-layer chromatography with conditions developed by authors and reported for the first time. Fingerprint analysis hyphenated with chemometrics enabled authenticity assessments of honey in mixtures. Results indicate that bee pollen-honey mixtures represent a food with highly, both, nutritious characteristics and health-promoting effect.     

Genetic transformation of alfalfa somatic embryos and their clonal propagation through repetitive somatic embryogenesis

Genetically transformed alfalfa (Medicago sativa L., cv. Zajearska 83) plantlets were obtained by inoculating somatic embryos with Agrobacterium tumefaciens strains A281/pGA472 and LBA4404/pBI121. Single somatic embryos, 5–7 mm long, were released from a repetitively embryogenic culture, wounded, and cocultivated with the bacteria. The agar-solidified culture medium contained mineral salts, vitamins, 40 g l^–1 sucrose, 1 g l^–1 yeast extract and 0.05 mg l^–1 BA. Five clones, transformed with A281/pGA472, and 4 clones transformed with LBA4404/pBI121, were selected for proliferation by repetitive somatic embryogenesis, on media containing 100 mg l^–1 of kanamycin. The transformation of kanamycin-resistant clones was confirmed by assaying the activity of neomycin phosphotransferase II and/or -glucuronidase enzymes, and by the Southern blot analysis. It is suggested that the transformation/regeneration system based on somatic embryogenesis may be suitable for establishing transgenic alfalfa lines. The relatively low frequency of embryo transformation is compensated for by abundant proliferation in secondary somatic embryogenesis.Abbreviations BA 6-benzyladenine - GUS -glucuronidase - Km kanamycin - NPTII neomycin phosphotransferase II - X-gluc 5-bromo-4-chloro-3-indolyl--glucuronic acid - BM basal medium     

Influence of maternal adrenalectomy on the ultrastructure of the adrenal gland in neonatal rats

Maternal adrenalectomy at 7 or 14 days of gestation produced increased cell necrosis within zona reticularis cells on the day of birth and at 24 or 48 h after birth. Small remnants or large portions of adrenocortical cells were present within macrophages. In otherwise normal adrenocortical cells, lipid droplets were incorporated within some mitochondria. Autophagocytosis of single mitochondria was observed within adrenocortical cells. Undoubtedly ultrastructural changes represent stimulation of adrenocortical cells in neonatal rats in response to maternal adrenalectomy.     

Urinary biomarkers and the rate of DNA damage in carcinogenesis and anticarcinogenesis.

Endogenous oxidative processes are shown to generate hydrogen peroxide and .OH radicals, which react in vivo to form a variety of products. Thymidine glycol (Tg) and 8-hydroxydeoxyguanosine (8-dRG-OH) are such products. They result from the excision repair of DNA and are excreted in urine. Both products can be used as biomarkers in the dosimetry of oxidative damage to DNA. Since oxidative processes and accumulation of their effects contribute to carcinogenesis, the proposed rate-of-damage hypothesis provides a rationale for using these biomarkers in early diagnostics and in the assessment of carcinogenic and anticarcinogenic properties of diets, foods, and food components, as well as certain exogenous toxicants and agents. Approaches for measurement of urinary biomarkers of DNA damage are reviewed.     

Isolation of Streptomyces rimosus Mutants with Reduced Actinophage Susceptibility

The infection of Streptomyces rimosus by the virulent actinophage RP1 was partially characterized. RP1 infection of the host cells results in a dramatic decrease in viable cell count, followed by reduced antibiotic production. Phage-resistant mutants were isolated after mutagenic treatment and RP1 selective pressure. Characterization of the isolated mutants has revealed that RP1 infection had no influence on their growth and antibiotic production. However, multiplication of the phage particles in the lawns of resistant mutants was detected. Since these strains differ from the wild type in RP1 relative efficiency of plating, plaque morphology, and the time necessary for plaque appearance, they are considered to be semiresistant mutants. The propagation of RP1 on semiresistant strains is characterized by lower adsorption of phage particles and longer latent and rise periods. As a consequence, the multiplication of the phage is slower than that of their host, which consequently reduces the ratio of phage to its host, thus diluting out the phage.