The interface between an alternating CG motif and a random sequence motif displays altered nuclease activity.

Previously we described the B-Z junctions produced in oligomers containing (5meCG)4 segments in the presence of 5.0 M NaCl or 50 uM Co(NH3)6+3 [Sheardy, R.D. & Winkle, S.A., Biochemistry 28, 720-725 (1989); Winkle, S.A., Aloyo, M.C., Morales, N., Zambrano, T.Y. & Sheardy, R.D., Biochemistry 30, 10601-10606 (1991)]. The circular dichroism spectra of an analogous unmethylated oligomer containing (CG)4, termed BZ-IV, in 5.0 M NaCl and in 50 uM Co(NH3)+3 suggest, however, that this oligomer does not form a B-Z hybrid. BZ-IV possesses Hha I sites (CGCG) in the (CG)4 segment and an Mbo I site (GATC) at the terminus of the (CG)4 segment. BZ-IV is equally digestible in the presence and absence of cobalt hexamine by Hha I, further indicating that the structure of BZ-IV is fully B-like under these conditions. The Mbo I cleavage site at the juncture between the (CG)4 segment and the adjacent random segment displays enhanced cleavage by both Mbo I and its isoschizomer Sau3AI in the presence of cobalt hexamine. In addition, exonuclease III digestion of BZ-IV is inhibited at this juncture. Actinomycin inhibits Mbo I activity in the presence of cobalt hexamine but not in the absence. Together, these results suggest that enzymes recognize the interfaces of (CG)n and adjacent random sequences as altered substrates even in the absence of a B-Z junction formation.     

The multiple-minima problem in small peptides revisited. The Threshold Accepting approach.

A recently reported optimization method, known as Threshold Accepting, was tested for the purpose of locating the structure of several peptide molecules with the lowest conformational energy. A comparison with previous results obtained with the Simulated Annealing technique was made. Our study indicate Threshold Accepting as a better technique in locating such structures.     

Endothelin induces vascular and mucosal lesions, enhances the injury by HCl/ethanol, and the antibody exerts gastroprotection.

Vascular factors play an important role in the pathogenesis and prevention of acute gastric mucosal lesions. Endothelin-3 (ET-3), a potent vasoactive peptide, was infused intra-arterially to induce gastric microvascular and hemorrhagic mucosal lesions, and to enhance the damaging effects of dilute HCl and ethanol. ET-3 antibody was injected intravenously to decrease hemorrhagic mucosal lesions induced by ethanol. Locally infused ET (0.01, 0.1, and 1.0 nmol.100 g-1.min-1 for up to 15 min) was followed in some cases by intragastric dilute ethanol or HCl, which alone caused no or only mild vascular and mucosal lesions. Monastral blue was used to visualize and quantify vascular injury. ET-3 produced dose-dependent vascular lesions that affected the walls of mucosal capillaries and venules and induced mucosal congestion and focal endothelial labeling in vessels of the gastric muscular layers. The highest dose of ET induced hemorrhagic gastric mucosal lesions, mortality, and periods of hyper- and hypotension in the rat. Medium and low doses of ET-3 caused vascular injury, and dose-dependently potentiated the vascular and hemorrhagic mucosal lesions caused by dilute HCl and ethanol. Indomethacin slightly enhanced damage induced by ET and 50% ethanol, suggesting a limited mediatory role of prostaglandins in the ET-induced mucosal lesions. Anti-ET-3 serum dose-dependently decreased but did not abolish the hemorrhagic gastric mucosal lesions induced by 75% ethanol. Thus, ET-3 causes endothelial damage in capillaries and venules of rat stomach and predisposes to mucosal damage even after exposure to dilute ethanol or HCl. ET is more potent than leukotrienes and histamine and thus may play an important role in the mechanisms of acute gastric mucosal injury and protection where the vascular network appears to be a major target.     

Detection of Cryptosporidium circulating antigens in human and calf sera.

Cryptosporidium-specific circulating antigens were detected in sera of experimentally infected calves and AIDS patients by an enzyme-linked immunosorbent assay. Antigenemia was detectable from 2 to a minimum of 22 days post-infection (d.p.i.) in calves whose feces were parasitologically positive from 2-10 d.p.i. Antigenemia was detected in AIDS patients showing no a sero-conversion to immunoglobulin (Ig) M or to IgG. The detection of circulating antigens in humans allows early diagnosis of cryptosporidiosis, even in immunosuppressed patients.     

Light environment within dense algal populations: cell size influences on self-shading

The influence of algal cell size on the light environment withindense phytoplankton populations was analysed in cultures of11 freshwater algae (mostly Chlorophyta) varying widely in cellsize and growing at saturated (220 µM m² s^–1) andlimited (11 µM m^–2 s^–1) irradiances Chlorophyll-a-specificabsorbance coefficients did not bear any obvious relationshipto cell size and, as expected from previous analyses, were stronglyinfluenced by the light intensity at which the algae were grown.However, biomass (fresh weight)-specific absorbance coefficientsdecreased as algal cell volume increased regardless of the incomingirradiance Intracellular chlorophyll a concentration (c₁), whichdecreased as algal cell size increased, explained a substantialfraction of the variance in biomass (fresh weight)-specifjcabsorbance coefficients. Thus, this study supports the notionthat reduced serf-shading allows large algae to support greatermaximal biomass than smaller algae.     

Experimental and computational study of the radiation-induced decomposition of formaldehyde. Implications to cometary nuclei

The radiation-induced decomposition of aqueous solutions of formaldehyde was studied at 298 and 77 K in order to obtain an insight into the possible role of ionizing radiation on cometary chemistry. Aqueous solutions of 1.0 mol dm^–3 formaldehyde were exposed to -radiation in the dose range from 0.01 kGy to 1.2 MGy. The radiation chemical yield of decomposition of formaldehyde was determined to be: G(–CH₂(OH)₂)=26.3±1.2 at 298 K and G0.48 at 77 K.Based on previous estimates of the total dose of ionizing radiation that comets have accumulated over 4.6 billion years, we predict a radiation-induced depletion of formaldehyde as a function of depth in comet nuclei: 100% destruction in the outer layers (0–20 m) and 10% destruction in the interior layers.A Portion of this work was presented at the XXVIII COSPAR Plenary Meeting (MF. 7) held at the Hague, The Netherlands on June 25–26, 1990.     

Changes in soil microflora associated with control of Sclerotium Rolfsii by Furfuraldehyde

The efficacy of 2‐furfuraldehyde for control of Sclerotium rolfsii was studied in laboratory and greenhouse experiments. Mycelial growth of the fungus was reduced proportionally with concentrations of 0.1–0.5 ml furfuraldehyde l^‐1 agar medium, and viability of sclerotia diminished on exposure to 2‐furfuraldehyde vapours. Detectable populations of bacteria and fungi, including Trichoderma spp., were reduced significantly (9=0.05) when furfuraldehyde was added to the agar used for soil dilution plates of untreated soil. Repeated treatments of natural soil with the fumigant significantly increased populations of Trichoderma spp. and bacteria, but diminished numbers of actinomycetes. Increasing dosages applied to soil artificially infested with S. rolfsii caused a reduction of disease on lentil, Lens culinaris. Results indicate that the compound, when applied to field soil, changes the composition of soil microflora and has potential for integrated control of S. rolfsii.     

A Comparison of the Efficacy of Nuclear Polyhedrosis and Granulosis Viruses in Spray and Bait Formulations for the Control of Agrotis segetum (Lepidoptera: Noctuidae) in Maize

Agrotis segetum nuclear polyhedrosis virus (AsNPV) and granulosis virus (AsGV), propagated in laboratory cultures of A. segetum in England and A. ipsilon in Spain, respectively, were applied to plots of maize plants at the one‐ to four‐leaf stage of growth. Plots were arranged in a 6 x 6 Latin square design and infested with second‐instar A. segetum larvae (the common cutworm). Each virus was applied in separate treatments by two application methods; as an aqueous spray containing 0.1% Agral as a wetting agent, and as a bran bait. The NPV was applied at a rate of 4 X 10¹² polyhedra/ha, and the GV at 4 X 10¹³ granules/ha. Soil and plants were sampled for larvae on three occasions following virus treatment: 24 h, 4 days and 11 days. The larvae were reared on diet in the laboratory, until death or pupation, to examine the rate and level of viral infection. Infection data showed 87.5% and 91% NPV infection and 12.5% and 55% GV infection in spray and bait treatments, respectively, in larvae sampled 24 h after treatment. In larvae sampled 4 days after treatment, the results were 78% and 100% NPV infection, and 13% and 6% GV infection. A total of only six larvae were retrieved on day 11. In both treatments larvae infected with AsNPV died significantly more rapidly and at an earlier instar than those infected with AsGV, indicating that AsNPV appears to have better potential as a control agent for A. segetum.     

The phylogenic expression of plasmolipin in the vertebrate nervous system

Plasmolipin is a plasma membrane proteolipid is a major myelin membrane component (Cochary et al., 1990). In this study we report the phylogenic expression of plasmolipin in the vertebrate nervous system. Using Western blot analysis with polyclonal antibodies, we have analyzed membrane fractions, including myelin, from elasmobranchs, teleosts, amphibians, reptiles, birds and mammals. On the basis of immune detection, plasmolipin appears to be restricted to the mammalian nervous system. Comparison of the central and peripheral nervous systems of mammals showed only minor differences in the level of plasmolipin in these two regions. Within mammals, little quantitative differences were observed when rat, human and bovine membrane fractions were compared. The late evolutionary expression of plasmolipin which results in its restriction to mammals makes it unique among the (major) myelin proteins. The potential physiologic significance of these data are discussed.Abbreviations EDTA Ethylene diamine N.,NN tetracetic acid - EGTA Ethylene glycol bis-(B-Aminoethyl Ether) N,,NN tetracetic acid - MES ([N-Morpholino] ethane sulfonic acid) DCCD, N, Dicyclohexyl carbodiimide