Delayed-onset synergism between leukotriene B4 and prostaglandin E2 in human skin

The time-course of cutaneous inflammatory responses to LTB4 and PGE2 both alone and in combination has been studied in 10 healthy volunteers. LTB4 induced a transient wheal and flare response in some subjects, maximal at 15 minutes and succeeded by an erythematous, indurated lesion at 2-4 hours. PGE2 elicited a wheal and erythema response which resolved within 1-2 hours. Combination of LTB4 and PGE2 produced acute wheal and erythema responses which did not differ significantly from the summation of responses to the individual constituents of the mixture or from responses to a two-fold increase in the concentration of either component. Wheal and erythema responses persisted, however, with significant potentiation of responses 4 hours after injection. As both leukotrienes and prostaglandins are generated in acute allergic reactions, the effects of these mediators in combination could contribute to persisting and late-onset responses to allergen, in both the skin and lung. In particular, sustained responses to the combination of LTB4 and PGE2 might be important in the pathogenesis of inflammatory skin diseases such as psoriasis.     

Phenotypic variation in susceptibility of honey bees,Apis mellifera,to infestation by tracheal mites,Acarapis woodi

A laboratory bioassay was used to study phenotypic differences in susceptibility of honey bees,Apis mellifera L., to tracheal mites,Acarapis woodi Rennie. Significantly different infestation frequencies were found in bees from 23 colonies containing queens that were instrumentally inseminated with single drones. Queens and drones originated from a closed population composed of commercial stock from various areas of the United States.Mites were randomly distributed with respect to right and left prothoracic tracheae. Tracheae containing mites were no more or less attractive to migrating mites than non-infested tracheae. The same quantity of progeny per female was produced in tracheae containing 1–3 mites. Female mites apparently do not migrate a second time after egg laying begins.The degree of phenotypic variation suggests that selection of honey bees for tracheal mite resistance is feasible.     

Galactoside-proton symport in a lacYUN mutant of Escherichia coli investigated by analysis of transport progress curves.

The kinetics of galactoside-proton symport catalysed by a wild-type strain and one carrying a mutation, previously reported to cause uncoupling of the symport reaction, have been examined. The mutation does not affect the stoichiometry during the initial period of uptake, when the internal concentration of galactoside is low, but it does result in much greater competition from the galactoside as it is accumulated. Simple methods for the analysis of the uptake progress curves have been developed and used to estimate the initial rate of uptake and affinity for internal galactoside. The maximum rate of uptake is decreased by a factor of 2 at most whereas the affinity for internal galactoside is increased up to 50-fold by the mutation. The pH-dependence of the galactoside efflux reaction is changed in a manner which suggests that the defect is in the interaction between proton-binding and galactoside-binding sites rather than in the structure of either site.     

A 45,X male with Y-specific DNA translocated onto chromosome 15.

A 20-year-old male patient with chromosomal constitution 45,X, testes and normal external genitalia was examined. Neither mosaicism nor a structurally aberrant Y chromosome was observed when routine cytogenetic analysis was performed on both lymphocytes and skin fibroblasts. Y chromosome-specific single-copy and repeated DNA sequences were detected in the patient's genome by means of 11 different recombinant-DNA probes of known regional assignment on the human Y chromosome. Data indicated that the short arm, the centromere, and part of the long-arm euchromatin of the Y chromosome have been retained and that the patient lacks deletion intervals 6 and 7 of Yq. High-resolution analysis of prometaphase chromosomes revealed additional euchromatic material on the short arm of one of the patient's chromosomes 15. After in situ hybridization with the Y chromosome-specific probe pDP105, a significant grain accumulation was observed distal to 15p11.2, suggesting a Y/15 chromosomal translocation. We conclude that some 45,X males originate from Y-chromosome/autosome translocations following a break in the proximal long arm of the Y chromosome.     

Production of poly-β-hydroxybutyrate by Azotobacter vinelandii strain UWD during growth on molasses and other complex carbon sources

Summary Azotobacter vinelandii strain UWD formed >2 mg/ml poly--hydroxybutyrate (pHB) during exponential growth in media containing ammonium acetate and 1% w/v glucose, fructose, sucrose, or maltose, and >1.5 mg/ml with 1% w/v sodium gluconate or glycerol. After acetate exhaustion, pHB formation accompanied carbohydrate utilization and pHB rapidly accounted for 53%–70% of the cell mass. Strain UWD also formed >2 mg/ml pHB when it was grown with 2% w/v corn syrup, cane molasses, beet molasses, or malt extract. Beet molasses had a growth stimulatory effect which promoted higher yields of pHB/ml and a high ratio of pHB/protein. Malt extract also promoted higher yields of pHB/ml. In this case, pHB formation was no longer subject to acetate repression and the cells contained a higher ratio of pHB/protein. This study shows that unrefined carbon sources support pHB formation in strain UWD and that the yields of pHB were comparable to or better than those obtained with refined carbon sources.     

The energy-conserving nitric-oxide-reductase system in Paracoccus denitrificans. Distinction from the nitrite reductase that catalyses synthesis of nitric oxide and evidence from trapping experiments for nitric oxide as a free intermediate during denitrification

1. A Clark-type electrode that responds to nitric oxide has been used to show that cytoplasmic membrane vesicles of Paracoccus denitrificans have a nitric-oxide reductase activity. Nitrous oxide is the reaction product. NADH, succinate or isoascorbate plus 2,3,5,6-tetramethyl-1,4-phenylene diamine can act as reductants. The NADH-dependent activity is resistant to freezing of the vesicles and thus the NADH:nitric-oxide oxidoreductase activity of stored frozen vesicles provides a method for calibrating the electrode by titration of dissolved nitric oxide with NADH. The periplasmic nitrite reductase and nitrous-oxide reductase enzymes are absent from the vesicles which indicates that nitric-oxide reductase is a discrete enzyme associated with the denitrification process. This conclusion was supported by the finding that nitric-oxide reductase activity was absent from both membranes prepared from aerobically grown P. denitrificans and bovine heart submitochondrial particles. 2. The NADH: nitric-oxide oxidoreductase activity was inhibited by concentrations of antimycin or myxothiazol that were just sufficient to inhibit the cytochrome bc1 complex of the ubiquinol--cytochrome-c oxidoreductase. The activity was deduced to be proton translocating by the observations of: (a) up to 3.5-fold stimulation upon addition of an uncoupler; and (b) ATP synthesis with a P:2e ratio of 0.75. 3. Nitrite reductase of cytochrome cd1 type was highly purified from P. denitrificans in a new, high-yield, rapid two- or three-step procedure. This enzyme catalysed stoichiometric synthesis of nitric oxide. This observation, taken together with the finding that the maximum rate of NADH:nitric-oxide oxidoreductase activity catalysed by the vesicles was comparable with that of NADH:nitrate-oxidoreductase, is consistent with a role for nitric-oxide reductase in the physiological conversion of nitrate or nitrite to dinitrogen gas. 4. Intact cells of P. denitrificans also reduced nitric oxide in an antimycin- or myxothiazol-sensitive manner. However, nitric oxide was not detected by the electrode during the reduction of nitrate. Nitric-oxide synthesis from nitrate could be detected with cells in the presence of very low concentrations of Triton X-100 which selectively inhibits nitric-oxide reductase activity. 5. Nitric oxide was detected as an intermediate in denitrification by including haemoglobin with an anaerobic suspension of cells that was reducing nitrate. The characteristic spectrum of the nitric oxide derivative of haemoglobin was observed.(ABSTRACT TRUNCATED AT 400 WORDS)     

Catechol Formation and Melanization by Na+ -Dependent Azotobacter chroococcum: a Protective Mechanism for Aeroadaptation?

Aeroadaptive microaerophilic Azotobacter chroococcum 184 produced a cell-associated black pigment when grown at high aeration rates under nitrogen-fixing conditions. This pigment was shown to be a catechol melanin. Polyphenol oxidase activity was detected in cell extracts of cells grown for 72 h. Melanin formation was optimal in the later stages of growth, and there was no correlation between nitrogenase activity and melanization. Nitrogenase activity in strain 184 was optimal at 10% O₂, and melanin formation was suppressed by O₂ limitation. In the presence of charcoal, an adsorbent of toxic oxygen intermediates, and benzoic acid, a scavenger of hydroxyl radicals, melanization was inhibited. However, in the presence of copper, the intensity of pigment color increased and melanization was accelerated. Copper also eliminated catalase and peroxidase activities of the organism but still permitted aerobic growth. In the presence of low levels of iron, melanization was accelerated under high aeration rates, and under low rates of aeration, melanization was observed only at higher levels of iron. Hydroxamate-siderophore production was detectable in the presence of soluble iron under high rates of aeration but was repressed by the same levels of iron under low aeration rates. Unlike melanization and hydroxamate formation, catechol formation was observed under both low and high rates of aeration under nitrogen-fixing conditions. Catechol formation and melanization were repressed by 14 mM NH₄⁺, at which level nitrogenase activity was also repressed. Copper reversed the repressive effect of NH₄⁺. A role for catechol formation and melanization in aeroadaptation is proposed.