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G A Peters

Publications and source records attributed to G A Peters.

At least 37 records · Page 2Linked to original sources
PubMed1978

Near-fatal and fatal anaphylactic reactions to insect sting.

Two patients experienced anaphylactic reaction to insect stings, with residual encephalopathy. One patient had anaphylaxis despite hyposensitization with whole-body extracts, thus supporting recent reports that reliable protection cannot be achieved unless pure venom is used. The other patient had pathologic confirmation of anoxic encephalopathy, thus supporting the concept that encephalopathy with anaphylaxis is secondary to associated circulatory collapse rather than a primary allergic response of brain disease.

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PubMed1977

Azolla-Anabaena azollae Relationship: V. N(2) Fixation, Acetylene Reduction, and H(2) Production.

In order to characterize the reactions catalyzed by nitrogenase in the Azolla-Anabaena association, (15)N(2) fixation, C(2)H(2) reduction, and ATP-dependent H(2) production were measured in both the Azolla-Anabaena complex and in the alga isolated from the complex.The rate of reduction of substrates and of ATP-dependent H(2) evolution was determined at various partial pressures of C(2)H(2) and N(2). A pC(2)H(2) of 0.1 atm was nearly optimal for C(2)H(4) production and inhibited H(2) production by 95%. The ratio of C(2)H(2) reduced to N(2) fixed was determined as a function of constant pC(2)H(2) (0.1 atm) and variable pN(2). This ratio decreased with increasing pN(2) and the decrease was correlated with less H(2) production. Ratios obtained at N(2) partial pressures of approximately 0.3, 0.6, and 0.8 atm, respectively, were 3.2, 2.0, and 1.7 for the association and 4.4, 3.0, and 2.5 for the isolated symbiont. Rates obtained for C(2)H(2) reduction, N(2) fixation, and H(2) production were used to obtain an expression of the electron balance in vivo.

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PubMed1976

Azolla-Anabaena azollae Relationship: IV. Photosynthetically Driven, Nitrogenase-catalyzed H(2) Production.

The water fern, Azolla caroliniana Willd., containing the symbiotic, heterocystous blue-green alga, Anabaena azollae, has been studied under various growth conditions to characterize its light-dependent production of H(2). The response of H(2) production to N(2) and C(2)H(2) and the absence of a differential effect of m-chlorocarbonyl cyanide phenylhydrazone on H(2) production and C(2)H(2) reduction, coupled with the parallel inhibition of both processes by DCMU imply that the production of H(2) is nitrogenase-catalyzed and ATP-dependent.H(2) was produced by fronds grown under air-CO(2) in the presence or absence of combined nitrogen. When cultured under argon-O(2)-CO(2), only those fronds provided with combined nitrogen remained viable and produced H(2). Fronds grown on nitrate under air plus 2% CO also produced H(2). In comparison to fronds grown on N(2) alone, fronds grown on nitrate had an increased rate of H(2) production relative to C(2)H(2) reduction, and the inhibition of H(2) production by air was less.CO in argon +/- CO(2) resulted in a partial inhibition of H(2) production, whereas CO in argon-CO(2)-C(2)H(2) enhanced H(2) production in fronds grown without combined nitrogen. Our studies strongly indicate that H(2) production is nitrogenase-catalyzed but the possibility that the symbiont contains a hydrogenase cannot be totally excluded.

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PubMed1974

The Azolla, Anabaena azollae Relationship: I. Initial Characterization of the Association.

Cultures of Azolla caroliniana Willd. free of the symbiotic blue-green alga, Anabaena azollae, were obtained by treatment of Azolla fronds with a regimen of antibiotics. These symbiontfree plants can be maintained only on medium containing a combined nitrogen source.Morphological aspects of the symbiotic association show the confinement of the Anabaena azollae within the leaf cavity of the Azolla. Procedures were established for the isolation of pure preparations of Anabaena azollae and Azolla chloroplasts. It has not yet been possible to grow the isolated alga in independent culture.Photochemical activities of the isolated alga and fern chloroplasts were measured by spectrophotometric assays for photosystems I and II as well as by P700-content (photosystem I) and delayed light emission (photosystem II). In the algal fraction, both photosystems were repressed when compared to freeliving Anabaena cylindrica, but the relative ratio of photosystem I to photosystem II may be appreciably greater in Anabaena azollae. Azolla chloroplasts were generally comparable to spinach chloroplasts.A comparison of the chlorophyll a and b content of Azolla fronds with and without the symbiotic alga resulted in an estimate that in the symbiotic association, the Anabaena azollae accounts for from 7.5 to 15% of the total chlorophyll.

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PubMed1974

The Azolla, Anabaena azollae Relationship: II. Localization of Nitrogenase Activity as Assayed by Acetylene Reduction.

Anaerobic (microaerophilic) acetylene reduction by Azolla caroliniana Willd. was dependent on light and saturated at approximately 450 foot candles. Maximum rates of acetylene reduction were 60 nmoles/mg chlorophyll minute. However, rates of 25 to 30 nmoles/mg chlorophyll minute were more common.The growth of Azolla for 35 days with nitrate or urea as a nitrogen source decreased the rate of acetylene reduction approximately 30% compared to controls grown on nitrogen. Prolonged growth on nitrate or urea (6-7 months) resulted in a 90% decrease in the rate of acetylene reduction.The inhibition of acetylene reduction by 3 (3,4-dichlorophenol) 1,1-dimethylurea (12 muM) was not pronounced until the Azolla became depleted of the reserves formed during photosynthesis. The interval required for this depletion was dependent upon pretreatment and varied from 2 to more than 12 hours. Oxygen evolution was inhibited 75% in 10 minutes by the same concentration of 3 (3,4-dichlorophenol) 1,1-dimethylurea.The addition of oxygen, 20% volume per volume, resulted in a 30 to 40% decrease in the rate of acetylene reduction and the onsetof 3(3,4-dichlorophenol) 1,1-dimethylurea inhibition was more rapid then under microaerophilic conditions. The aerobic dark reduction of acetylene was from 10 to 30% of the rate of aerobic reduction in the light.Acetylene reduction activity was absent in fronds freed ofthe symbiotic algae and present in isolated Anabaena azollae. This study shows that the alga is the agent of acetylene reduction and suggests that there is considerable transport of metabolites between the fern and the blue-green alga.

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