Incomplete cerebral ischemia in the rat provokes increase of tissue and plasma malondialdehyde

Short-term incomplete cerebral ischemia was induced in the rat by bilaterally clamping for 5 min the common carotid arteries; subsequent reperfusion of 10 min was obtained by removing carotid occlusion. At the end of ischemia or reperfusion, animals were sacrificed by decapitation. A control group was represented by sham-operated rats. Peripheral venous blood samples were withdrawn from the femoral vein from rats subjected to cerebral reperfusion 5 min before ischemia, at the end of ischemia, and 10 min after reperfusion. A highly sensitive HPLC method for the direct determination of malondialdehyde, oxypurines, and nucleosides was used on 200 μL of brain tissue and plasma extracts. Incomplete cerebral ischemia induced the, appearance of a significant amout of tissue malondialdehyde (undetectable in control animals) and a decrease of ascorbic acid. A further 6.6-fold increase of malondialdehyde and a 18.5% decrease of ascorbic acid occurred after 10 min of reperfusion. Plasma malondialdehyde, which was present in minimal amount before ischemia, significantly increased after 5 min of ischemia, being strikingly augmented after 10 min of reperfusion. A similar trend was observed for oxypurines and nucleosides. From these data, it can be affirmed that tissue concentrations of malondialdehyde and ascorbic acid, and plasma levels of malondialdehyde, oxypurines, and nucleosides, reflect both the oxygen radical-mediated tissue injury and the depression of energy metabolism thus representing early biochemical markers of short-term incomplete brain ischemia, and reperfusion in the rat.     

Characterization of a 160 kD Photosystem II reaction center complex isolated from photoinhibited Dunaliella salina thylakoids

Photoinhibition in the green alga Dunaliella salina is accompanied by the formation of inactive Photosystem II reaction centers. In SDS-PAGE analysis, the latter appear as 160 kD complexes. These complexes are structurally stable, enough to withstand re-electrophoresis of excised gel slices from the 160 kD region. Western blot analyses with specific polyclonal antibodies raised against the D1 or D2 reaction center proteins provided evidence for the presence of both of these polypeptides in the re-electrophoresed 160 kD complex. Incubation of excised gel slices from the 160 kD region, under aerobic conditions at 4°C for a prolonged period of time, caused a break-up of the 160 kD complex into a 52 kD D1-containing and 80 and 26 kD D2-containing pieces. Western blot analysis with polyclonal antibodies raised against the apoproteins of CPI (reaction center proteins of PS I) did not show cross-reaction either with the 160 kD complex or with the 52, 80 and 26 kD pieces. The results show the presence of both D1 and D2 in the 160 kD complex and strengthen the notion of a higher molecular weight D1- and D2-containing complex that forms upon disassembly of photodamaged PS II units.Abbreviations Chl chlorophyll - PS II Photosystem II - D1 the 32 kD reaction center protein of PS II, encoded by the chloroplast psbA gene - D2 the 34 kD reaction center protein of PS II, encoded by the chloroplast psbD gene - CPI the 82 and 83 kD reaction center proteins of PS I, encoded by the chloroplast psaA and psaB genes - HL high light - LL low light This publication is dedicated to the memory of the late Professor Daniel Arnon, whom the first author will fondly remember for his many accounts of past scientific discovery and debate.     

Repair mechanisms of UV-induced DNA damage in soybean chloroplasts

In order to better understand the biochemical mechanisms of DNA metabolism in chloroplasts, repair of UV induced plastome damage in vivo was determined by exposure of soybean suspension cells to UV light and subsequent quantitation of the damage remaining in nuclear and chloroplast encoded genes with time by quantitative polymerase chain reaction (QPCR). The kinetics of damage rapir in the nuclear rbcS gene suggest that photoreactivation and dark mechanisms are active, while for the plastome encoded psbA gene only a light-dependent repair process was detected which is considerably slower than would be expected for photolyase-mediated photoreactivation.     

Damage Functions for Three Meloidogyne Species on Arachis hypogaea in Texas

The yield response of Florunner peanut to different initial population (Pi) densities of Meloidogyne arenaria, M. javanica, and an undescribed Meloidogyne species (isolate 93-13a) was determined in microplots in 1995 and 1996. Seven Pi''s (0, 0.5, 1, 5, 10, 50, and 100 eggs and J2/500 cm³ soil) were used for each Meloidogyne species in both years. The three species reproduced abundantly on Florunner in both years. In 1995, mean reproduction differed among the three species; mean Rf values were 10,253 for isolate 93-13, 4,256 for M. arenaria, and 513 for M. javanica. In 1996, the reproduction of M. arenaria (mean Rf = 7,820) and isolate 93-13a (mean Rf = 7,506) were similar, and both had greater reproduction on peanut than did M. javanica (mean Rf = 2,325). All three nematode species caused root and pod galling, and a positive relationship was observed between Pi and the percentage of pods galled. Meloidogyne arenaria caused a higher percentage of pod galling than did M. javanica or isolate 93-13a. A negative linear relationship between log₁₀ (Pi + 1) and pod yield was observed for all three nematode species each year. The yield response slopes were similar except for that of M. javanica, which was less negative than that of isolate 93-13a in 1995, and less negative than that of M. arenaria and isolate 93-13a in 1996.     

褐稻虱在武育粳2号上不同生育期危害对水稻产量结构的影响

通过试验测定在武育粳2号上水稻拔节期正处于幼穗形成阶段,受褐稻虱危害实粒数减少,产量下降;孕穗期较耐褐稻虱危害,有明显的补偿作用;孕穗末期至灌浆初期为水稻受害最敏感的时期,危害后使结实率和千粒重均明显下降,水稻显著减产;灌浆后期至乳熟期受褐稻虱危害主要导致干粒重降低,且越接近成熟产量损失越低。     

Melatonin administration prevents lipopolysaccharide-induced oxidative damage in phenobarbital-treated animals

The protective effect of melatonin on lipopolysaccharide (LPS)-induced oxidative damage in phenobarbital-treated rats was measured using the following parameters: changes in total glutathione (tGSH) concentration, levels of oxidized glutathione (GSSG), the activity of the antioxidant enzyme glutathione peroxidase (GSH-PX) in both brain and liver, and the content of cytochrome P450 reductase in liver. Melatonin was injected intraperitoneally (ip, 4mg/kg BW) every hour for 4 h after LPS administration; control animals received 4 injections of diluent. LPS was given (ip, 4 mg/kg) 6 h before the animals were killed. Prior to the LPS injection, animals were pretreated with phenobarbital (PB), a stimulator of cytochrome P450 reductase, at a dose 80 mg/kg BW ip for 3 consecutive days. One group of animals received LPS together with N^w-nitro-L-arginine methyl ester (L-NAME), a blocker of nitric oxide synthase (NOS) (for 4 days given in drinking water at a concentration of 50 mM). In liver, PB, in all groups, increased significantly both the concentration of tGSH and the activity of GSH-PX. When the animals were injected with LPS the levels of tGSH and GSSG were significantly higher compared with other groups while melatonin and L-NAME significantly enhanced tGSH when compared with that in the LPS-treated rats. Melatonin alone reduced GSSG levels and enhanced the activity of GSH-PX in LPS-treated animals. Additionally, LPS diminished the content of cytochrome P450 reductase with this effect being largely prevented by L-NAME administration. Melatonin did not change the content of P450 either in PB- or LPS-treated animals. In brain, melatonin and L-NAME increased both tGSH levels and the activity of GSH-PX in LPS-treated animals. The results suggest that melatonin protects against LPS-induced oxidative toxicity in PB-treated animals in both liver and brain, and the findings are consistent with previously published observations related to the antioxidant activity of the pineal hormone.     

Palaeoecological and phytosociological reconstruction of precultural vegetation in the Bílý Kříž area,the Moravskoslezské Beskydy Mts,Slovak Republic

A combined palynological and phytosociological methodological approach was used in the reconstruction of precultural forest vegetation in a small model area of Bílý Kí-Janík in the Moravskoslezské Beskydy mountains (northwest Slovakia). Two pollen diagrams show the predominance of Fagus sylvatica, Abies alba and Picea abies in past natural mixed forests. The present-day occurrence and distribution of forest herbs allow the differentiation of five past vegetation types with above mentioned forest climax trees covering the area before the beginning of human interference. A map of reconstructed natural vegetation is presented which can be used for revitalization of present secondary spruce plantations, heavily affected by air pollution.     

The rate assay of alpha-toxin assembly in membrane

Abstract A rapid and easy method to determine the 'rate' of the assembly of α-toxin from Staphylococus aureus in erythrocyte membrane was described. Upon addition of a small amount of α-toxins into erythrocyte suspension, absorbance at 700 nm decreased linearly after a short period of lag time. From the linear portion of the record the rate of the assembly of α-toxin was calculated. An optimum temperature and an optimum pH for the assembly of the toxin on erythrocyte membranes were found to be 25–30°C and pH 5.     

Membrane damage by a toxin from the sea anemone Stoichactis helianthus. I. Formation of transmembrane channels in lipid bilayers

The addition of nanomolar amounts of a toxin preparation derived from the sea anemone Stoichactis helianthus to black lipid membranes increases their electrical conductance by one million-fold. In addition, the membranes become permeable predominantly to monovalent cations. The elevated bilayer conductance is voltage-dependent, and the current-voltage curves of these bilayers display rectification as well as a region of negative resistance. The membrane activity of the toxin is proportional to the third power of its concentration, and at very low concentrations the membrane conductance increases in discrete uniform steps. These observations indicate that the mechanism of toxin action involves the formation of transmembrane channels constructed by the aggregation of protein molecules which are inserted in the bilayer. The voltage-dependent membrane conductance arises from two distinct channel characteristics: (1) the unit conductance of individual channels is dependent on the polarity of applied voltage; (2) the number of ion-conducting channels is influenced by the polarity as well as the magnitude of applied potential. It is believed that these effects are due to the influence of an electric field on the insertion of toxin molecules into the bilayer or on their subsequent association with each other to produce channels. Partial chemical characterization of the toxin material has shown that the membrane active factor is a basic protein with a molecular weight of 17 500.     

Effect of neutralization and addition of urea,sucrose, and various glycols on phosphorus absorption and leaf damage from foliar-applied phosphate

Summary Inclusion of sucrose in the solution applied to soybean (Glycine max L. merr.) leaves much reduced the severity of the damage to the leaves from application of urea and, to a lesser extent, from application of phosphorus (P) as orthophosphoric acid. Sucrose had no evident effect on P absorption. Damage to the leaves from joint application of orthophosphoric acid and urea exceeded the sum of the damage caused by the substances individually. Urea did not seem to influence P absorption, but the effect, if any, was not readily determined because nearly all values for P absorption exceeded 90%.Neutralization of orthophosphoric acid with nitrogen-containing organic bases, including choline, guanidine, and guanyl urea, did not prove useful as a technique for increasing the quantity of orthophosphate that could be applied without damage to the leaves.Absorption and translocation of orthophosphate by corn (Zea mays L.) and soybean leaves were not influenced by the pH of the solution within the range from 2 to 10. Absorption of tripolyphosphate by corn leaves decreased with an increase in pH of the solution applied, but translocation of the absorbed P was not influenced by pH. With soybeans, absorption of tripolyphosphate decreased with an increase in pH of the solution. Translocation of P applied to soybean leaves as tripolyphosphate was less than 5% of the amount absorbed within the first 24 hr and decreased with an increase in pH after 10 days.