Nippostrongylus brasiliensis: feeding activity in the mouse

Nippostrongylus brasiliensis incorporated the fluorescent dye, Rhodamine B, while feeding in vivo. Uptake of dye in both sexes of helminth increased linearly from 30 to 120 min after the hosts were given dye per os. Feeding by female N. brasiliensis significantly exceeded that of the male at 4 and 5 days postinfection. Feeding declined in older helminths of both sexes. The density of helminths had no effect on their incorporation of dye in vivo. Feeding in male- and female-only groups of worms was similar to that seen in populations of mixed sexes. Feeding by helminths decreased during the first 36 h of food deprivation in the host, but increased during subsequent fasting of the host. Both sexes of N. brasiliensis resumed feeding within 15 min after the fasted hosts were fed. Growth of N. brasiliensis increased linearly from 4 to 7 days postinfection, based on dry weight. Seven-day-old and older females were significantly heavier than males.     

Hydrogen peroxide metabolism as an index of water stress tolerance in jute

Two species of jute plants Corchorus capsularis L. (cv. JRC 212) and C. olitorius L. (cv. JRO 632) were subjected to water stress for 2 and 4 days by withholding water. The relative water content (RWC) decreased in both plants under water stress but to a greater extent in C. olitorius . The C. olitorius seedlings also showed greater membrane injury than C. capsularis seedlings under water stress as was evident from injury index data. Water stress increased glycolate oxidase (EC 1.1.3.1.) activity more in C. olitorius than in C. capsularis . The activity of superoxide dismutase (SOD, EC 1.15.1.1.) and catalase (EC 1.11.1.6.) decreased under water stress and their decrease was higher in C. olitorius than in C capsularis . The level of hydrogen peroxide and lipid peroxidation also increased in both plants under water stress and the increase was higher in C. olitorius than in C. capsularis seedlings. Under comparable external water stress, C. capsularis seedlings showed lower membrane damage, lower H₂O₂ accumulation and lower lipid peroxidation than C. olilorius which may be taken as indicative of higher water stress tolerance capacity of the former.     

Effects of saponin extracts from Solanum elaeagnifotium fruits on ion uptake by clover seedlings

Solanum elaeagnifolium Cav. fruits contain high concentrations of steroidal saponins. Treatment of 3-day-old clover seedlings with aqueous fruit extracts modified Ca²⁺ uptake without significantly altering K⁺ and H₂PO₄⁻ uptake. The extracts increased Ca²⁺ uptake in the concentration range of 0.2 to 20 m M Ca²⁺. Uptake curves could be represented by two phases. In the lower phase (0.2-1.0 m M Ca²⁺), this change could be related to an increase in V_max. Pretreatment of seedlings with saponin extracts significantly reduced ATP-dependent Ca²⁺ uptake and Ca²⁺-dependent ATPase activity in a fraction isolated from root homogenates by centrifugation at 1500 g for 15 min. Saponins purified from S. eleagnifolium extracts by thin-layer chromatography modified in vitro the Ca²⁺-ATPase activity of this fraction, indicating that the steroid may act directly on Ca²⁺ transport across membranes.     

Water-soluble glucans from the seed of Coix lacryma-jobi var. ma-yuen

The water-soluble major polysaccharides from the seed of Coix lacryma-jobi var. ma-yuen eluted as a broad peak by gel filtration on Sepharose CL-2B. The mixture (CS-Glucan) was resolved into 7 glucans by HPLC on the column of Asahi-Pak GS-510 + GS-320. Similarities were observed between M, shown in the gel filtration profile and the elution volume in HPLC. Methylation analysis indicated that the ethanol-fractionated CS-glucan contained 4-O- and 4,6-di-O-substituted glucosyl residues. ¹H and ¹³C NMR data accorded with the results of methylation analysis, and the glycosidic linkages were shown to have an α-configuration. Thus, CS-glucan contained (1 → 4) linked α-d-glucans to which are attached glucosyl side chains at O-6 of the main chain in a similar way to amylopectin. Each purified glucan was shown to have different absorption maxima ( > 550 nm or 530 nm) in the iodine reaction. The results of the methylation analysis and of the pullulanase digestion suggest that the 550 nm-glucan has a lower branching frequency and shorter side chains than the 530 nm-glucan. Although CS-glucan was found to have weak anti-complementary activity, HPLC-purified > 550 nm-glucan was found to be more potent than the 530 nm-glucan. Thus CS-glucan is highly heterogeneous, and the glucans which form a tight complex when tested with iodine, generally tend to have considerable anti-complementary activity.     

Kinetic properties of IAA oxidase from mung bean cotyledons

A crude enzyme preparation from mung bean cotyledons was separated into peroxidative and non-peroxidative IAA oxidase on a DEAE-cellulose column. Both fractions differed in their pH optima, K_m and V_max. The K_m and V_max of non-peroxidative IAA oxidase were higher than those of peroxidative IAA oxidase. Peroxidative IAA oxidase showed a linear increase in absorption at 247 and 254 nm after a short lag of 2–3 min. The addition of catalytic amounts of hydrogen peroxide eliminated the lag period and also enhanced the rate of IAA degradation. The non-peroxidative IAA oxidase fraction, however, did not exhibit any significant increase in absorption at 247 and 254 nm and showed a lag period of 5 min which was not affected by hydrogen peroxide. Instead, addition of the same catalytic amount of hydrogen peroxide inhibited the rate of IAA degradation. The peroxidative IAA oxidase fraction exhibited the reaction kinetics characteristic of peroxidase-catalysed IAA degradation. The rate of IAA oxidation by purified non-peroxidative IAA oxidase was very low. The slow rate of catalysis shown by non-peroxidative IAA oxidase appears to be due to the presence of inhibitor(s).     

Deprenyl Protects Dopamine Neurons from the Neurotoxic Effect of 1-Methyl-4-Phenylpyridinium Ion

1-Methyl-4-phenylpyridinium ion (MPP+) is the product of the metabolic oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidase (MAO). MPP+ is toxic to 3,4-dihydroxyphenylethylamine (dopamine, DA) neurons in explant cultures of rat embryonic midbrain. Addition of 2.5 microM MPP+ to the feeding medium for 6 days results in significant reduction of the DA levels in the cultures (to 19% of control) as well as in the uptake of [3H]DA (to 32% of control). When the cultures are treated with the MAO inhibitor deprenyl (10 microM) 24 h prior to and during exposure to MPP+, the DA neurons are protected from the toxicity of the drug. In the combined deprenyl plus MPP+ treatment, the levels of DA in the cultures remain at the control range and the [3H]DA uptake is reduced to only 73% of control. These results indicate that MAO is involved in the toxicity of MPP+ on DA neurons.     

Dopamine Sulfoconjugation in the Rat Brain: Regulation by Monoamine Oxidase

An increase of free 3,4-dihydroxyphenylethylamine (DA, dopamine) in the rat brain such as is found following 3,4-dihydroxyphenylalanine (L-DOPA) administration or an intraventricular injection of free dopamine did not result in DA sulfate formation, despite the presence of phenolsulfotransferase activity in various regions of the brain and the high affinity of DA for this enzyme. However, when rats were pretreated with pargyline, a monoamine oxidase inhibitor, the same treatment with L-DOPA or free DA led to active synthesis of DA sulfate. The increase in DA sulfate was significantly correlated with the degree of monoamine oxidase inhibition and directly proportional to free DA concentrations in the hypothalamus (r = 0.86), striatum (r = 0.54), and brainstem (r = 0.89). The highest ratio of DA sulfate to free DA was found in the hypothalamus, suggesting that sulfoconjugation is most active in this region. Prior treatment of rats with 6-hydroxydopamine did not decrease DA sulfate concentrations, indicating that sulfoconjugation occurs most likely in extraneuronal tissues not destroyed by the neurotoxin. The results are compatible with the notion that phenolsulfotransferase may be highly compartmentalized and that inhibition of monoamine oxidase allows the newly generated free DA to become accessible to the sulfoconjugating enzyme, resulting in increase in DA sulfation.     

Effect of temperature on ethylene biosynthesis in carnation petals

Carnation petals, at a stage in which they are already producing ethylene, show a sigmoidal dependency of ethylene production on temperature within the range of 0 to 30°C. An Arrhenius plot of these data show a break atca. 22°C in the straight lines connecting the points. The activity of the ethylene-forming enzyme (EFE), measured bothin vitro, using isolated membranes, andin vivo, using petals pretreated with 1-aminocyclopropane-1-carboxylic acid (ACC), shows an exponential dependency on temperature within the same range. Arrhenius plots of EFE activity fail to show any discontinuity.In contrast, ACC synthase activity measuredin vitro shows the same sigmoidal dependency on temperature as that of the intact petals. We suggest, therefore, that ACC synthase activity is the rate-limiting step mediating the influence of temperature on ethylene biosynthesis by carnation petals over the range studied.     

Control of l-amino acid oxidase in Neurospora crassa by different regulatory circuits

l-Amino acid oxidase is synthesized in Neurospora crassa in response to three different physiological stimuli: (i) starvation in phosphate buffer, (ii) mating, and (iii) nitrogen derepression in the presence of amino acids. During starvation in phosphate buffer, or after mating, l-amino acid oxidase synthesis occurred in parallel with that of tyrosinase. Exogenous sulfate repressed the formation of the two enzymes in starved cultures, but not in mated cultures. Sulfate repression was relieved by protein synthesis inhibitors, suggesting that the effect of sulfate required the synthesis of a metabolically unstable protein repressor. With amino acids as the sole nitrogen source only l-amino acid oxidase was produced. Under these conditions enzyme synthesis was repressed by ammonium and was insensitive to sulfate. Biochemical evidence suggested that the l-amino acid oxidase formed under the three different conditions was the same protein. Therefore, the expression of l-amino acid oxidase appeared to be under the control of least two regulatory circuits. One, also controlling tyrosinase, seems to respond to developmental signals related to sexual morphogenesis. The other, controlling other enzymes of the nitrogen catabolic system, is used by the organism to obtain nitrogen from alternative sources such as proteins and amino acids.