Fish oil supplementation reduces excretion of 2,3-dinor-6-oxo-PGF1α and the 11-dehydrothromboxane B2/2,3-dinor-6-oxo-PGF1α excretion ratio in adult men

Dietary supplementation with a fish oil concentrate (FOC) reduced the endogenous synthesis of prostacyclin (PGI₂), as measured by the excretion of its major urinary catabolite, 2,3-dinor-6-oxo-PGF_1α (PGI₂-M). Thirty-four healthy men (24–57 years old) were given controlled diets and supplements that provided 40% of the energy from fat and a minimum of 22 mg/d of α-tocopherol for two consecutive experimental periods of 10 weeks each. During the experimental periods, the men received capsules containing 15 g/d of a placebo oil (PO) (period 1) or 15 g/d of the FOC (period 2). In addition to the PO or FOC, capsules contained 1 mg of α-tocopherol per g of fat as an antioxidant. The average daily excretion of PGI₂-M during the last week of FOC supplementation (period 2) was 22% less (P = 0.0001) than at the end of the first period. These results are at variance with those reported in comparable human studies conducted by other investigators during the middle and late 1980s. A 20% reduction (P = 0.003) in the 11-dehydrothromboxane B₂ to 2,3-dinor-6-oxo-PGF_1α excretion ratio at the end of period 2 in this study demonstrates that a shift of the n-6 to n-3 polyunsaturated fatty acid ratio from 12.5 to 2.3 brings about a substantial modulation of the eicosanoid system.     

Single-cell investigation by laser scanning confocal microscopy of cytochemical alterations resulting from extracellular oxidant challenge

Confocal laser scanning fluorescence microscopy coupled to image analysis was employed in order to develop and evaluate procedures for the appraisal at the single-cell level of: (1) protein-bound 4-hydroxynonenal, the specific product of membrane peroxidation (by means of immunocytochemistry with biotin-avidin revelation); (2) protein oxidation (by reaction of protein carbonyls with 2,4-dinitrophenyl-hydrazine followed by immunocytochemistry of dinitrophenyl moieties); and (3) cellular protein thiols (by direct alkylation of sulfhydryl groups with thiol-specific fluorescent reagents possessing different cell permeabilities). The procedures proved able to reveal the subcellular distribution of cytochemical parameters useful as indices of oxidative stress conditions, and may allow redox phenotyping of isolated cells, which would provide an efficient tool in selected experimental models.     

Selective colocalization of lipid peroxidation and protein thiol loss in chemically induced hepatic preneoplastic lesions: the role of γ-glutamyltranspeptidase activity

A number of studies indicate that cell proliferation can be modulated by changes in the redox balance of (soluble and protein) cellular thiols. Free radical processes, including lipid peroxidation (LPO), can affect such a balance, and a role for LPO in multistage carcinogenesis has been envisaged. The present study was aimed to assess the relationships between the protein thiol redox status and the LPO process in chemically induced preneoplastic tissue. The Solt-Farber's initiation-promotion model of chemical carcinogenesis in the rat liver was used. In fresh cryostat sections, preneoplastic lesions were identified by the reexpression of γ-glutamyltranspeptidase (GGT) activity. In serial sections, different classes of protein thiols were stained; in additional sections, LPO was elicited by various prooxidant mixtures and determined thereafter by the hydroxynaphthoic hydrazide-Fast Blue B procedure. The incubation of sections in the presence of chelated iron plus substrates for GGT activity leads to the development of LPO in selected section areas closely corresponding to GGT-positive lesions, indicating the ability of GGT activity to initiate LPO. Protein-reactive thiols, as well as total protein sulfur, were decreased by 20–25% in cells belonging to GGT-positive preneoplastic nodules, suggesting the occurrence of oxidative conditions in vivo. The incubation of additional adjacent sections with the prooxidant mixture H₂O₂ plus iron(II), in order to induce the complete oxidation of lipid present in the section, showed a decreased basal concentration of oxidizable lipid substrate in GGT-rich areas. The decreased levels of both protein thiols and lipid-oxidizable substrate in GGT-positive nodules suggest that the observed GGT-dependent path-way of LPO initiation can be chronically operative in vivo during early stages of chemical carcinogenesis, in cells expressing GGT as part of their transformed phenotype.     

Slow conformational exchange in DNA minihairpin loops: A conformationalstudy of the circular dumbbell d〈pCGC-TT-GCG-TT〉

In recent years various examples of highly stable two-residue hairpin loops (miniloops) in DNA have been encountered. As the detailed structure and stability of miniloops appear to be determined not only by the nature and sequence of the two bases in the loop, but also by the closing base pair, it is desirable to carry out in-depth studies of especially designed small model DNA compounds. Therefore, a circular DNA dumbbell-like molecule is tailored to consist of a stem of three Watson–Crick base pairs, flanked on each side by a minihairpin loop. The resulting circular DNA decanter 5′-d〈pCGC- TT-GCG- TT〉 -3′ ( I ) is studied in solution by means of nmr spectroscope. At a temperature of 269 K the molecule occurs in a 50/50 mixture of two dumbbell structures (denoted L2L2 and L2L4). L2L2 contains three Watson–Crick C-G base pairs and two two-residue loops (H2-family type) in opposite parts of the molecule. On raising the temperature from 269 to 314 K. The L2L4 conformer becomes increasingly dominant (95% at 314 K). This conformer has a partially disrupted closing G-C base pair in the 5′-GTTC-3′ loop with only one remaining solvent-accessible hydrogen bond between NH_α of the cytosine C(1) and O6 of the guanine G(8), whereas the opposite 5′-CTTG-3′ loop remains stable. The disruption of the C(1)-G(8) base pair in the L2L4 form is correlated with the presence of a syn orientation for the C(1) base at the 5′-3′ loop-stem junction in the 5′-GTTC-3′ loop. The two conformers. L2L2 and L2L4, occur in slow equilibrium (2–20 s^?1). Moderate line broadening of specific ¹H, ¹³C, and ³¹P resonances of residues C(1), G(8), T(9), and T(10) at low temperatures, due to chemical exchange between L2L2 and L2L4, show that the interconversion from an anti to syn conformer in residue C(1) has a small local effect on the structure of the dumbbell. T₁ relaxation measurements, chemical-shift considerations, and complete hand-shape calculations of the exchange process of the G(8) imino proton reveal a possibility for the existence of multiconformational slates in the anti–syn equilibrium. © 1995 John Wiley & Sons, Inc.     

Delayed leaf senescence in ethylene-deficient ACC-oxidase antisense tomato plants: molecular and physiological analysis

To determine the role of ethylene during tomato (Lycopersicon esculentum Mill. cv. Alisa Craig) leaf senescence, transgenic ACC oxidase antisense plants were analysed. Northern analysis of wild-type plants indicated that ACC oxidase mRNA accumulation normally begins in pre-senescent green leaves but was severely reduced in the antisense plants. Although the levels of ethylene evolved by wild-type and transgenic leaves increased during the progression of senescence, levels were extremely low in transgenic leaves. Leaf senescence, as assessed by colour change from green to yellow, was clearly delayed by 10–14 days in the antisense plants when compared with wild-type plants. Northern analysis of the photosynthesis-associated genes, cab and rbcS, indicated that levels of the corresponding mRNAs were higher in transgenic leaves which were not yet senescing compared with senescing wild-type leaves of exactly the same age. Northern analysis using probes for tomato fruit ripening-related genes expressed during leaf senescence indicated that once senescence was initiated the expression pattern of these mRNAs was similar in transgenic and wild-type leaves. In the antisense plants chlorophyll levels, photosynthetic capacity and chlorophyll fluorescence were higher when compared with senescing wild-type plants of the same age. Photosynthetic capacity and the quantum efficiency of photosystem II were maintained for longer in the transformed plants at values close to those observed in wild-type leaves prior to the visible onset of senescence. These results indicate that inhibiting ACC oxidase expression and ethylene synthesis results in delayed leaf senescence, rather than inducing a stay-green phenotype. Once senescence begins, it progresses normally. Onset of senescence is not, therefore, related to a critical level of ethylene. The correlation between higher levels prior to senescence and early onset, however, suggests that ethylene experienced by the plant may be a significant contributing factor in the timing of senescence.     

Five new filamentous,glucose-fermenting Candida isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Five novel representatives of the yeast genus Candida isolated from advanced stages of wood degradation from fallen trunks of Eucryphia cordifolia Cav., Laurelia sempervirens Weim., Laurelia philippiana Weim., Nothofagus dombeyii (Mirb.) Blume, and Nothofagus obliqua (Mirb.) Blume, in the evergreen rainy Valdivian forest of southern Chile, are described and illustrated. They clearly differ from all accepted Candida species to warrant their establishment as five new species of yeasts: Candida coipomensis sp. nov., Candida ralunensis sp. nov., Candida laureliae sp. nov., Candida osornensis sp. nov., and Candida llanquihuensis sp. nov.     

Four new species of Apiotrichum isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Four unusual Apiotrichum, isolated from decayed wood of Eucryphia cordifolia Cav., Nothofagus obliqua (Mirb.) Blume, and Laurelia sempervirens Wein., one of which was also isolated from the intestinal tract of Scaptomyza multispinosa Malloch (Diptera), are described and illustrated. These species differ from all the accepted Apiotrichum species (1–3) to warrant their establishment as four new species: Apiotrichum eucryphiae, Apiotrichum osvaldii, Apiotrichum futronensis and Apiotrichum nothofagi.     

Two new species and one variety of nitrate-utilizing mycelial Candida isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Two unusual species of Candida and one variety of one of them, isolated from decayed wood (palo podrido) (12) in the ultimate stages of degradation, are described and illustrated. They differ sufficiently from all accepted Candida species to warrant their establishment as two new species and one variety: Candida railenensis, Candida bertae, and Candida bertae var. chiloensis.The DNA base composition of these yeasts was not calculated, since our laboratory is not properly equipped for that purpose.     

The effect of membrane phospholipid acyl-chain composition on the activity of brain-beta-N-acetyl-D-glucosaminidase.

The phospholipid acyl-chain dependence of the membrane-bound lysosomal beta-N-acetyl-D-glucosaminidase has been examined on control membranes from rat brain primary cell cultures and on membrane modified by culturing the cells in media supplemented with polyunsaturated fatty acids. The relationship between beta-N-acetyl-D-glucosaminidase activity and the membrane phospholipid acyl-chain composition has been evaluated. An increase in the unsaturation level of phosphatidyl ethanolamines and phosphatidylcholines, the most abundant phospholipids in this membrane fraction, is related to the rate of the enzymic reaction. The Arrhenius plot of the enzyme activity in modified membranes shows break-temperatures, starting from approximately 15 degrees C. The apparent activation energy below and above the break-temperature is not correlated with phospholipid acyl-chain unsaturation.     

Immune surveillance and neoplasia—1 a minimal mathematical model

A deterministic predator-prey model is presented for describing the dynamics of a solid tumor in the presence of a specifically reactive lymphocyte population which is stimulated by, and antagonistic to, the tumor. The qualitative behavior of the solutions is developed and briefly compared to the results of transplantation experiments. Although the model is primitive, it leads to predictions that are in general agreement with observation and intuitive expectations. In particular, it is found that: (1) very low levels of transplanted tumor will not survive in the recipient. (2) At somewhat higher levels, tumor growth will be uncontrolled in the syngeneic recipient. However, immune intervention if early enough, can lead to control and elimination of the tumor. (3) At still higher levels of transplanted tumor, no amount of immune intervention will be effective in controlling the tumor. (4) If the recipients immune system is suppressed prior to transplantation, or is debilitated for any reason, the chance that the tumor will grow increases. (5) If the recipients immune system is stimulated prior to transplantation, the chance of tumor survival decreases. (6) The survival of the tumor is much more sensitive to changes in tumor parameters (for example, antigenicity) than in lymphocyte parameters. In addition it makes the unintuitive prediction that (7) There areisolated instances under which anincrease in the number of lymphocytes canincrease the chance of tumor survival.