Glutamate Oxidation by Soybean Cotyledon and Leaf Mitochondria

Mitochondria purified from cotyledons of soybean seedlings fiveto ten days old have the capacity to rapidly oxidize glutamate(measured as glutamate dependent oxygen consumption). This capacitywas greatest at ten days after planting but was very low priorto emergence of cotyledons from the vermiculite and during senescence.Solubilized glutamate dehydrogenase activity, on the other hand,was substantial at two days after planting, peaked at sevendays, then declined and rose again during senescence. It issuggested that mitochondrial glutamate oxidation plays a rolein reserve mobilization and amino acid metabolism during seedlinggrowth. Leaf mitochondria and those from senescing cotyledonscould not sustain rapid rates of glutamate oxidation despiteready oxidation of other substrates and high solubilized glutamatedehydrogenase activity, suggesting an alternative role for theenzyme in these tissues. Possible controlling factors are discussed. ² Present address, Garvan Institute, Darlinghurst, N. S. W.,Australia. ³ Permanent address, Department de Biologia Vegetal, Facultatde Biologia, Universitat de Barcelona, Barcelona, Spain. (Received May 6, 1988; Accepted August 3, 1988)     

Onchocerca volvulus. Monoclonal anti-idiotype antibody as antigen signal for the microfilaricidal cytotoxicity of diethylcarbamazine-treated platelets

Over the past 35 yr, diethylcarbamazine (DEC) has been the most widely used agent for the treatment of filarial diseases, particularly in onchocerciasis. The microfilaricidal action of DEC has been recently shown to be mediated by blood platelets with the additional triggering of a filarial excretory Ag (FEA). This FEA could be detected by using mAb in the serum of infected patients. By using one mAb (IA2(23] directed against Onchocerca volvulus and recognizing circulating Ag (Ab1), we purified by affinity chromatography the target molecule of IA2(23) (an O. volvulus glycoprotein recognized by IA2(23) mAb). This compound had a dose-dependent effect on the cytotoxic action of DEC-treated platelets. We subsequently produced an anti-idiotype mAb to Ab1 (Ab2), and considered the possibility of replacing the O. volvulus glycoprotein recognized by IA2(23) mAb by Ab2. Ab2 was selected according to its ability to inhibit the binding of radioiodinated Ab1 to the filarial target Ag. It induced the production of anti-O. volvulus antibodies (Ab3) in rats. At a constant concentration of DEC platelets, the addition of increasing amounts of Ab2 led to a dose-dependent cytotoxic effect against parasite larvae. Experiments performed with Ab2 on detergent solubilized surface proteins of platelets identified four bands of Mr 18, 26, 43.5, and 100 kDa, supporting the idea of the presence of binding sites on the platelets for a FEA required for the microfilaricidal cytotoxicity of DEC-treated platelets.     

Anaerobic biotransformations of pollutant chemicals in aquifers

Summary Anaerobic microbial communities sampled from either a methanogenic or sulfate-reducing aquifer site have been tested for their ability to degrade a variety of groundwater pollutants, including halogenated aromatic compounds, simple alkyl phenols and tetrachloroethylene. The haloaromatic chemicals were biodegraded in methanogenic incubations but not under sulfate-reducing conditions. The primary degradative event was typically the reductive removal of the aryl halides. Complete dehalogenation of the aromatic moiety was required before substrate mineralization was observed. The lack of dehalogenation activity in sulfatereducing incubations was due, at least in part, to the high levels of sulfate rather than a lack of metabolic potential. In contrast, the degradation of cresol isomers occurred in both types of incubations but proved faster under sulfate-reducing conditions. The requisite microorganisms were enriched and the degradation pathway forp-cresol under the latter conditions involved the anaerobic oxidation of the aryl methyl group. Tetrachloroethylene was also degraded by reductive dehalogenation but under both incubation conditions. The initial conversion of this substrate to trichloroethylene was generally faster under methanogenic conditions. However, the transformation pathway slowed when dichloroethylene was produced and only trace concentrations of vinyl chloride were detected. These results illustrate that pollutant compounds can be biodegraded under anoxic conditions and a knowledge of the predominant ecological conditions is essential for accurate predictions of the transport and fate of such materials in aquifers.     

Quantitation and structures of oligosaccharide chains in human trachea mucin glycoproteins

Human respiratory mucin glycoproteins from patients with cystic fibrosis were purified and oligosaccharide chains were released by treatment with alkaline borohydride. A neutral oligosaccharide alditol fraction was isolated from mucin obtained from a patient with A blood group determinant by chromatography on DEAF-cellulose and individual oligosaccharide chains were then isolated by gel filtration on BioGel P-6 columns and high performance liquid chromatography with gradient and isocratic solvent systems. The structures of the purified oligosaccharides were determined by methylation analysis, sequential glycosidase digestion and H-NMR spectroscopy. The amount of each chain was determined by compositional analysis. A wide array of discrete branched oligosaccharide structures that contain from 3 to 22 sugar residues were found. Many of the oligosaccharides are related and appear to be precursors of larger chains. The predominant branched oligosaccharides which accumulate contain terminal blood group H (Fuc2Ga14) or blood group A (Fuc2(Ga1NAc3) (Ga14) determinants which stop further branching and chain elongation. The elongation of oligosaccharide chains in respiratory mucins occurs on the 3-linked G1cNAc at branch points, whereas the 6-linked GlcNAc residue ultimately forms short side chains with a Fuc2 (Ga1NAc3) Gal4 G1cNAc6 structure in individuals with A blood group determinant.The results obtained in the current studies further suggest that even higher molecular weight oligosaccharide chains with analogous branched structures are present in some human respiratory mucin glycoproteins. Increasing numbers of the repeating sequence shown in the oligosaccharide below is present in the higher molecular weight chains. {ie75-1} This data in conjunction with our earlier observations on the extensive branching of these oligosaccharide chains helps to define and explain the enormous range of oligosaccharide structures found in human and swine respiratory mucin glycoproteins. Comparison of the relative concentrations of each oligosaccharide chain suggest that these oligosaccharides represent variations of a common branched core structure which may be terminated by the addition of a2-linked fucose to the 3/4 linked galactose residue at each branch point. These chains accumulate and are found in the highest concentrations in these respiratory mucins.     

Oxygen-derived free radicals and hemolysis during open heart surgery

Reperfusion injury occurs during open-heart surgery after prolonged cardioplegic arrest. Cardiopulmonary bypass also is known to cause hemolysis. Since reperfusion of ischemic myocardium is associated with the generation of oxygen free radicals, and since free radicals can attack a protein molecule, it seems reasonable to assume that hemolysis might be the consequence of free radical attack on hemoglobin protein. The results of this study demonstrated that reperfusion following ischemic arrest caused an increase in free hemoglobin and free heme concentrations, simultaneously releasing free iron and generating hydroxyl radicals. In vitro studies using pure hemoglobin indicated that superoxide anion generated by the action of xanthine oxidase on xanthine could release iron from the heme ring and cause deoxygenation of oxyhemoglobin into ferrihemoglobin. This study further demonstrated that before the release of iron from the heme nucleus, oxyhemoglobin underwent deoxygenation to ferrihemoglobin. The released iron can catalyze the Fenton reaction, leading to the formation of cytotoxic hydroxyl radical (OH·). In fact, the formation of OH. in conjunction with hemolysis occurs during cardiac surgery, and when viewed in the light of the in vitro results, it seems likely that oxygen-derived free radicals may cause hemolysis during cardiopulmonary bypass and simultaneously release iron from the heme ring, which can catalyze the formation of OH·.     

The “ON”-bipolar agonist,L-2-amino-4-phosphonobutyrate,blocks light-evoked cone contraction in xenopus eye cups

Rhythmic photoreceptor metabolism in relationship to light-dark cycles is now thought be regulated through a retinal feed-back mechanism with dopamine serving as a principal signal initiating light-evoked events. In order to test the hypothesis that depolarizing ON-bipolar neurons participate in the retinal signalling pathway, we determined the effects of L-2-amino-4-phosphonobutyrate (L-APB) on light-evoked cone contraction in eye cups fromXenopus laevis. L-APB blocked the response stereospecifically when applied over a broad concentration range. The high specificity of L-APB in retina suggests that sign-inverting bipolar neurons which depolarize in light are in the signalling pathway. One possibility is that this pathway conveys signals that regulate dopamine release.Special issue dedicated to Dr. Frederick E. Samson.     

Behavioral response ofGraminella nigrifrons (Homoptera: Cicadellidae) to experimentally manipulated vibrational signals

Mate recognition for the leafhopper Graminella nigrifrons(Forbes) occurs when a male spontaneously emits a multisectional vibrational calling song to which females respond by emitting simple pulses. Significant differences were found among males in the duration, number of chirps, and chirp rate within sections of the song and the total song. Repeatability (proportion of total variation due to differences among males) of call features ranged from very low (0.04 for total chirps in song) to high (0.67 for section 3 chirp rate). However, song modification and playback experiments revealed that the variation in the measured song features was not important in determining whether a female will respond. Rather, female response depended only on the presence of two of the three types of pulses which comprise a chirp. These essential pulses were found within chirps of all call sections that contain chirps. Manipulation of chirp rates from 0.58 to 2.70 times the normal rate did not affect female response, nor did changing the period of silence between the essential pulse types from 0.25 to 1.75 times the normal period. These results suggest that components of the male calling song function in mate recognition but are not used by females to discriminate among conspecific males.     

Maturational changes in opioidergic control of luteinizing hormone and follicle-stimulating hormone in ram lambs

Stimulation by naloxone, an opioid antagonist, of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion was examined in spring-born crossbred ram lambs raised under natural photoperiod. Vehicle (n = 6) or 1 mg naloxone/kg vehicle (n = 6) was injected (i.m.) 3 times at 2-h intervals at 5, 10 and 15 weeks of age and 4 times at 2-h intervals at 20, 25, 30 and 35 weeks of age. Blood samples were taken every 12 min for 6 h at 5, 10 and 15 weeks of age and for 8 h at 20, 25, 30 and 35 weeks of age. Naloxone had no effect on age at sexual maturity (controls 239 +/- 23 days; naloxone 232 +/- 33 days). The only significant (P less than 0.05) effect of naloxone on FSH was a greater pulse amplitude in 10-week-old treated lambs than in control lambs. Naloxone treatment resulted in greater LH pulse amplitude at 5 and 10 weeks of age (P less than 0.05), lower basal serum concentration of LH at 10 weeks of age (P less than 0.05), greater LH pulse frequency at 25 weeks of age (P less than 0.05), and greater mean serum concentrations of LH, basal LH and LH pulse amplitude at 35 weeks of age (P less than 0.01) than in the controls. In both groups of lambs, mean and basal FSH, and LH and FSH pulse amplitude were highest at 5 weeks of age and fell with age. LH pulse amplitude was lowest at 35 weeks of age (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduction of predation risk under the cover of darkness: Avoidance responses of mayfly larvae to a benthic fish

Summary Mayfly larvae of Paraleptophlebia heteronea (McDunnough) had two antipredator responses to a nocturnal fish predator (Rhinichthys cataractae (Valenciennes)): flight into the drift and retreat into interstitial crevices. Drift rates of Paraleptophlebia abruptly increased by 30 fold when fish were actively foraging in the laboratory streams but, even before fish were removed, drift began returning to control levels because larvae settled to the substrate and moved to areas of low risk beneath stones. This drifting response was used as an immediate escape behavior which likely decreases risk of capture from predators which forage actively at night. Surprisingly, drift most often occurred before contact between predator and prey, and we suggest that in darkness this mayfly may use hydrodynamic pressure waves for predator detection, rather than chemical cues, since fish forage in an upstream direction. Although drifting may represent a cost to mayfly larvae in terms of relocation to a new foraging area with unknown food resources, the immediate mortality risk probably out-weighs the importance of staying within a profitable food patch because larvae can survive starvation for at least 2 d. In addition to drifting, mayflies retreated from upper, exposed substrate surfaces to concealed interstitial crevices immediately after a predator encounter, or subsequent to resettlement on the substrate after predator-induced drift. A latency period was associated with this response and mayflies remained in these concealed locations for at least 3 h after dace foraging ceased. Because this mayfly feeds at night and food levels are significantly lower in field refugia under stones, relative to exposed stone surfaces, predator avoidance activity may limit foraging time and, ultimately, reduce the food intake of this stream mayfly.     

Physiological characterization of opine-utilizing rhizobacteria for traits related to plant growth-promoting activity

Thirty-two strains of opine-utilizing rhizobacteria were evaluated for physiological traits which have been related to plant growth-promoting activity. Tests included antibiosis against two bacterial and eight fungal pathogens of potato (Solanum tuberosum L.), production of hydrogen cyanide and fluorescent pigment production. On average, 71 and 12% of the bacteria inhibited the growth of Erwinia carotovora subsp. carotovora and Agrobacterium tumefaciens, respectively. The growth of Botrytis sp. was inhibited by 62% of the bacteria, and half of these produced an inhibition zone of more than 7 mm in diameter. Fusarium solani, Colletotrichum coccodes, Phoma exigua, Verticillium dahliae, F. oxysporum, V. albo-atrum and F. sambucinum were antagonized by 43, 34, 31, 25, 19, 18, and 12% of the bacteria, respectively. Only four strains produce hydrogen cyanide. The inhibition of a plant pathogen was not correlated to the production of fluorescent pigment. No strain produced a hypersensitive reaction whereas only three strains induced soft-rot and two produced polygalacturonase. Some opine-utilizing rhizobacteria were strong inhibitors of all plant pathogens, while most were active against specific plant pathogens.