Abscisic Acid induces anaerobiosis tolerance in corn

Flooding is a frequently occurring environmental stress that can severely affect plant growth. This study shows that treatment of corn (Zea mays L.) seedlings with abscisic acid (ABA) increases their tolerance to anoxia 10-fold over untreated seedlings and twofold over seedlings treated with water. Corn seedlings stressed anoxically for 1 day showed only 8% survival when planted in vermiculite. Pretreatment of root tips with 100 micromolar ABA or water for 24 hours before the 1 day anoxic stress increased the anoxic survivability of seedlings to 87% and 47%, respectively. Cycloheximide (5 milligrams per liter), added together with ABA, reduced the seedling survival rate, indicating that the induction of anoxic tolerance in corn by ABA was partly a result of the synthesis of new proteins. ABA treatment induced a threefold increase in alcohol dehydrogenase enzyme activity in corn roots. However, after 24 h of anoxia, alcohol dehydrogenase enzyme activity between the ABA-pretreated and non-pretreated corn roots was not significantly different. The results indicated that ABA played an important role in inducing anoxic tolerance in corn and that the induced tolerance was probably mediated by an increase in alcohol dehydrogenase enzyme activity before the anoxic stress.     

The root-knot nematode resistance gene (Mi) in tomato: construction of a molecular linkage map and identification of dominant cDNA markers in resistant genotypes

A dominant allele at the Mi locus on chromosome 6 of tomato (Lycopersicon esculentum Mill) confers resistance to three species of root-knot nematodes (Meloidogyne). The resistance, which is associated with a localized necrotic response, was originally introduced into tomato from the wild species Lycopersicon peruvianum. As a step towards the molecular cloning of Mi, we have identified closely linked DNA markers from both cDNA and genomic DNA libraries as restriction fragment length polymorphisms (RFLPs). DNA from tomato populations segregating for nematode resistance was analyzed to generate a high-resolution genetic map of this region. Additional information on gene order was obtained by comparing the size of the introgressed L. peruvianum chromosomal segment within a collection of nematode-resistant tomato lines. Among the four cDNA markers that are tightly linked to Mi, three are dominant, i.e. L. peruvianum-specific. One cDNA marker corresponds to a gene family comprising 20-30 members, one of which is diagnostic for all nematode-resistant genotypes tested. The presence of non-homologous sequences around the Mi gene may contribute to the suppression of recombination in this region of the genome in crosses heterozygous for Mi. The potential of 'walking' from closely linked markers to Mi is discussed.     

脂质过氧化对人红细胞膜脂流动性的影响

研究枯稀过氧化氢/高铁血红素体系所产生的烷基过氧自由基对红细胞的损伤。测定了脂质过氧化的产物——丙二脂的生成,并证明阿魏酸钠对脂质过氧化的抑制。荧光偏振的结果指出,膜脂过氧化以后降低了膜脂的流动性。人红细胞用5DSA和16DSA标记并用ESR检测膜脂流动性,结果表明,序参数S几乎没有发生变化,旋转相关时间τ值的增加证明膜脂过氧化以后,疏水尾部的物理状态发生了改变。经脂质过氧化以后,红细胞膜中的不饱和脂防酸的减少,可能是降低膜脂流动性的原因之一。     

Changes of carp myosin subfragment-1 induced by temperature acclimation

Summary Heavy meromyosin subfragment-1 (S1) was prepared by -chymotrypsin from myosin of carp acclimated to either 10°C or 30°C for a minimum of 5 weeks. The objective of these studies was to document thermally-induced changes in the myosin molecule and to extend previous observations. Ca²⁺- and K⁺ (EDTA)-ATPase activities of cold-acclimated carp S1 were 1.1 and 0.8 mol P_i·min^-1·mg^-1, respectively, and these values did not differ significantly from those of warm-acclimated carp. The inactivation rate constant (K_D) of S1 from cold-acclimated carp was 32.1x10^-4· s^-1, compared to 13.2x10^-4·s^-1 for warm-acclimated carp. The maximum initial velocity of acto-S1 Mg²⁺-ATPase activity at pH 7.0 in 0.05 M KCl was 9.3 s^-1 with cold-acclimated carp, about 3.7 times higher than that for warm-acclimated carp. However, no significant difference was observed in the apparent affinity of S1 to actin. Peptides maps of the heavy chain of S1 were different and suggested distinct isoforms for the myosins from warm- and cold-acclimated muscle.Abbreviations ATPase adenosine 5-triphosphatase - DTNB 5,5-dithiobis (2-nitrobenzoic acid) - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycol bis (-aminoethylether)-N,N,N,N-tetraacetic acid - K _D inactivation rate constant - K _m apparent dissociation constant - P _i inorganic -phosphate - PMSF phenylmethane-sulfonyl fluoride - S ₁ heavy meromyosin subfragment-1 - SDS sodium dodecyl sulfate - SDS-PAGE SDS-polyacrylamide gel electrophoresis - TPCK N-tosyl-l-phenylalanyl chloromethyl ketone - V _max maximum initial velocity     

心房钠泵因子对颈动脉窦压力感受器反射的易化作用

Effects of atriopeptin II (APII) on the carotid sinus baroreflex in anesthetized rats and on the sinus nerve afferent activity in the anesthetized rabbits were investigated. The results were as follows: (1) By perfusing the isolated left carotid sinus with APII (1 microgram/ml) in anesthetized rats (n = 10), the threshold pressure (TP) of the carotid baroreflex did not show any change, while the equilibrium pressure (EP), the saturation pressure (SP) and the operating range (OR) were decreased from 101 +/- 2.8 to 95 +/- 2.0 mmHg (P less than 0.05), 202 +/- 5.2 to 168 +/- 6.1 mmHg (P less than 0.001) and 128 +/- 5.5 to 93 +/- 6.3 mmHg (P less than 0.001), respectively. The function curve of the baroreflex was shifted to the left and downward with a peak slope (PS) increased during perfusing with APII. In contrast, by perfusing the carotid sinus with sodium nitroprusside (NP, 0.5 micrograms/ml), TP and EP remained unchanged, whereas SP and OR were increased from 188 +/- 6.4 to 218 +/- 6.0 mmHg (n = 6, P less than 0.01) and from 107 +/- 6.9 to 132 +/- 7.6 mmHg (P less than 0.05), respectively. The function curve of the baroreflex and its PS were not affected by NP. The sinus nerve afferent activity was quite stable with the perfusion of carotid sinus at constant intrasinus pressure (ISP) in the rabbits (n = 6) and increased during the elevation of ISP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence for age-related changes in pyridine nucleotide content of isolated rat islets

The purpose of this study was to document the effect of age on alpha-glycerophosphate activity and pyridine nucleotide concentration in pancreatic islets isolated from rats. In order to do this, islets were isolated from pancreases of 2 and 12 month-old rats, and measurements made of alpha-glycerophosphate activity and of NAD+ and NADH, determinations were made following incubation at both basal (5.6 mM) and elevated glucose concentrations (28 mM). The results indicated that islet alpha-glycerophosphate dehydrogenase activity was decreased (P less than 0.001) by approximately 50% in the older rats. This was associated with an increase in mean (+/- SEM) basal NADH content (pmol/microgram DNA) in 12 month-old (4.48 +/- 0.31) as compared to 2 month-old rats (2.73 +/- 0.49). Although mean (+/- SEM) basal NAD+ levels (pmol/microgram DNA) were the same in 2 and 12 month-old rats (29.4 +/- 2.5 and 30.8 +/- 2.8, respectively), NAD+ content following incubation at elevated levels of glucose declined (absolutely and relatively) to a significantly greater degree in the younger rats. The incremental rise in islet NADH concentration following incubation at the elevated glucose concentration was similar in the two groups, but the relative increase was only approximately half as great in islets from 12 month-old rats. These data indicate that the age-related decline in the activity of alpha-glycerophosphate dehydrogenase, the enzyme regulating the glycerophosphate shuttle system in 12 month-old rats, is associated with alterations in islet pyridine nucleotide composition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insulin induces activation and translocation of protein kinase FA (a multifunctional protein phosphatase activator) in human platelet

Protein kinase FA (an activator of the ATP.Mg-dependent multifunctional protein phosphatase) has been identified in both cytosol and plasma membrane isolated from human platelets. The FA activity in the cytosol is active whereas the FA activity in the membrane is inactive. Quantitative analysis further indicates that approximately 90% of total FA is present in the membrane whereas only 10% of FA is localized in the cytosol, suggesting that the inactive membrane-associated FA might be regulated. This notion has subsequently been demonstrated that exposure of platelets to physiological concentrations of insulin for only 1 min resulted in an increase in cytosolic FA activity to about 300% of control values in the absence of insulin and in a corresponding decrease in FA activity in the membrane. It is concluded that the molecular basis for insulin action on cellular metabolism may partly be mediated through the activation and translocation of protein kinase FA in the membrane. It is suggested that redistribution of protein kinase FA may represent a transmembrane signal of insulin.