Improvement of Escherichia coli microaerobic oxygen metabolism by Vitreoscilla hemoglobin: New insights from NAD(P)H fluorescence and culture redox potential

On-line NAD(P)H fluorescence and culture redox potential (CRP) measurements were utilized to investigate the role of Vitreoscilla hemoglobin (VHb) in perturbing oxygen metabolism of microaerobic Escherichia coli Batch cultures of a VHb-synthesizing E. coli strain and the iso-genic control under fully aerated conditions were subject to several high/low oxygen transitions, and the NAD(P)H fluorescence and CRP were monitored during these passages. The presence of VHb decreased the rate of net NAD(P)H generation by 2.4-fold under diminishing oxygen tension. In the absence of aeration, the strain producing VHb maintained a steady NAD(P)H level 1.8-fold less than that of the control, indicating that the presence of VHb keeps E. coli in a more oxidized state under oxygen-limited conditions. Estimated from CRP, the oxygen uptake rates near anoxia were 25% higher for cells with VHb than those without. These results suggest that VHb-expressing cells have a higher microaerobic electron transport chain turnover rate. To examine how NAD(P)H utilization of VHb-expressing cells responds to rapidly changing oxygen tension, which is common in large-scale fermentations, we pulsed air intermittently into a cell suspension and recorded the fluorescence response to the imposed dissolved oxygen (DO) fluctuation. Relative to the control, cells containing VHb had a sluggish fluorescence response to sudden changes of oxygen tension, suggesting that VHb buffers intracellular redox perturbations caused by extracellular DO fluctuations.(c) John Wiley & Sons, Inc.     

The Mouse Spam1 maps to proximal Chromosome 6 and is a candidate for the sperm dysfunction in Rb(6.16)24Lub and Rb(6.15)lAld heterozygotes

We have determined the chromosomal localization of the murine gene encoding the 68-kDa sperm adhesion molecule 1, Spam1 or Ph-20. Using two independent approaches, fluorescence in situ hybridization (FISH) and interspecific backcross analysis, we show that Spam1 maps to proximal mouse Chromosome (Chr) 6. This map position is within the conserved linkage group corresponding to human Chr 7q, where the human homolog, SPAM 1, has been shown to map previously. Genetic mapping shows the gene to be very closely linked to Met, one of the most proximal loci on MMU 6. It thus places the gene near the centromere and the junction of the Rb(6.16)24Lub and Rb(6.15)1Ald translocations. The essential role of the Spam1 sperm antigen in mouse sperm-egg interactions and its gene location provide strong support for its candidacy as the gene involved in the dysfunction of mouse sperm bearing the Rb(6.16)24Lub or Rb(6.15)1Ald translocation. Received: 16 July 1996 / Accepted: 23 September 1996     

Scaling and spatial dynamics in plant-pathogen systems: from individuals to populations

Components of transmission for primary infection from soil-borne inoculum and secondary (plant to plant) infection are estimated from experiments involving single plants. The results from these individual-based experiments are used in a probabilistic spatial contact process (cellular automaton) to predict the progress of an epidemic. The model accounts for spatial correlations between infected and susceptible plants due to inhomogeneous mixing caused by restricted movement of the pathogen in soil. It also integrates nonlinearities in infection, including small stochastic differences in primary infection that become amplified by secondary infection. The model predicts both the mean and the variance of the infection dynamics of R. solani when compared with replicated epidemics in populations of plants grown in microcosms. The broader consequences of the combination of experimental and modelling approaches for scaling-up from individual to population behaviour are discussed. <br>     

Rco-3, a Gene Involved in Glucose Transport and Conidiation in Neurospora Crassa

Macroconidiation in Neurospora crassa is influenced by a number of environmental cues, including the nutritional status of the growing organism. Conidia formation is normally observed when the fungus is exposed to air. However, carbon limitation can induce conidiation in mycelia submerged in an aerated liquid medium. A mutant was previously isolated that could conidiate in submerged culture without imposing nutrient limitation and the gene responsible for this phenotype (rco-3) has now been cloned. RCO3 exhibits sequence similarity to members of the sugar transporter gene superfamily, with greatest similarity to glucose transporters of yeast. Consistent with this structural similarity, we find that glucose transport activity is altered in the mutant. However, growth of the mutant in media containing alternate carbon sources does not suppress conidiation in submerged culture. The properties of the mutant suggest that RCO3 is required for expression of glucose transport activity, glucose regulation of gene expression, and general carbon repression of development.     

Carbohydrate and the cytokine response to 2.5h of running

Nehlsen-Cannarella, S. L., O. R. Fagoaga, D. C. Nieman, D. A. Henson, D. E. Butterworth, R. L. Schmitt, E. M. Bailey, B. J. Warren, A. Utter, and J. M. Davis. Carbohydrate and the cytokineresponse to 2.5 h of running. J. Appl.Physiol. 82(5): 1662-1667, 1997.This randomized,double-blind, placebo-controlled study was designed to determine theinfluence of 6% carbohydrate (C) vs. placebo (P) beverage ingestion oncytokine responses (5 total samples over 9 h) to 2.5 h ofhigh-intensity running (76.7 ± 0.4% maximalO₂ uptake) by 30 experiencedmarathon runners. For interleukin-6 (IL-6), a difference in the patternof change between groups was found, highlighted by a greater increasein P vs. C immediately postrun (753 vs. 421%) and 1.5 h postrun (193 vs. 86%) [F(4,112) = 3.77, P = 0.006]. Forinterleukin-1-receptor antagonist (IL-1ra), a difference in the patternof change between groups was found, highlighted by a greater increasein P vs. C 1.5 h postrun (231 vs. 72%)[F(2,50) = 6.38, P = 0.003]. No significant interaction effects were seen for bioactive IL-6 or IL-1. The immediate postrun plasma glucose concentrations correlated negatively with those of plasma cortisol (r = 0.67, P < 0.001); postrun plasma cortisol (r = 0.70, P < 0.001) and IL-6 levels(r = 0.54, P = 0.003) correlated positively withlevels of IL-1ra. Taken together, the data indicate that carbohydrateingestion attenuates cytokine levels in the inflammatory cascade inresponse to heavy exertion.

     

Cultured hepatoma cells for the study of enzyme regulation: Induction of ornithine decarboxylase by insulin and asparagine

Summary The induction and decay of ornithine decarboxylase (ODC) by insulin and asparagine in cultures of H4-II-EC3 (H35) hepatoma cells was studied in a modified Waymouth medium in the presence of fetal bovine serum (FBS) and in serum-free media. The insulin response was enhanced by the presence of asparagine although the effect of asparagine was not so much on the initial increase as it was on a slowing of the decline after the maximum was reached at 6 to 8 h after the supplements were added together with fresh medium. In all cases the initial ODC activity was zero at zero time for addition of media and supplements, and, after reaching the maximum, activity declined to near zero by 24 h. Fetal bovine serum gave induction that followed a similar time course but was inferior to the combintion, of insulin plus asparagine and, in fact, FBS inhibited the latter response. Putrescine (the product formed from ornithine by ODC), at 10⁻⁵ M, markedly inhibited the induction of ODC by insulin or FBS, but the inhibition was less when asparagine was present. This work was supported in part by Grants CA-07175, CA-22484, and CA-17334 from the National Cancer Institute. D. P. G. is a Predoctoral Fellow at the Food Research Institute, supported by a fellowship from the Monsanto Fund and by NIH Grant R01-AI 15693 to Prof. Michael W. Pariza, Food Research Institute, University of Wisconsin, Madison.     

In vitro induction of lymphocyte responsiveness by a Strongylus vulgaris-derived mitogen

Proliferation in vitro of peripheral blood lymphocytes both from horses infected with Strongylus vulgaris and from helminth-free ponies was observed in the presence of extracts of the fourth and fifth stage larvae and adults of S. vulgaris. In addition, S. vulgaris extracts induced transformation in cultures of peripheral blood lymphocytes from sheep and dogs and in mouse spleen cell cultures. Nylon wool non-adherent, T cell enriched fractions of lymphocytes from both mice and horses were stimulated by the S. vulgaris larval mitogen while no proliferation was observed in cultures containing nylon wool adherent, B cell enriched fractions. Macrophage co-operation appeared not to be necessary for S. vulgaris mitogen-induced transformation of spleen cells. The S. vulgaris mitogen stimulated a subpopulation of mouse spleen cells different from those responsive to PHA, Con A and LPS. These cells might be T helper cells since B cells were stimulated to proliferate in the presence of both T cells and S. vulgaris larval mitogen. In addition, the supernatant of in vitro cultured larvae of S. vulgaris induced slight, but significant transformation of equine peripheral blood lymphocytes. Therefore, it is possible that the S. vulgaris mitogen released by both viable parasites and degenerating larvae might induce T cell dependent production of immunoglobulin in vivo and account for the beta-globulinaemia, of which IgG(T) is a major component, in S vulgaris infected horses.     

Discrimination by male ring-tailed Lemurs (Lemur catta) between the scent marks of male and those of female conspecifics

Olfaction plays an important role in the social communication of all prosimians. (The experiment reported in this paper forms part of an intensive chemobehavioral study of olfaction in Lemur catta (ring-tailed lemur) being carried out in this laboratory.) Five male Lemur cattawere tested on their behavioral responses to paired scent stimuli. Responses measured were (1) total investigation time, (2) arm-marking, (3) ABO/BO rubbing, and (4) flehmen. Males showed a strong discrimination between the scent stimuli,giving higher levels of response to female scent on measures 1, 3, and 4. This response suggests an olfactory-related preference by males for female scent under controlled conditions. This preference may be a consequence of the females’ dominance over males and the brevity of estrus in L. catta,both of which would favor such choice behavior.     

A mathematical model for lambda dv plasmid replication: analysis of copy number mutants

A mathematical model based on the molecular control mechanisms for lambda dv plasmid replication in a single Escherichia coli cell has been applied to simulate replication of mutant lambda dv plasmids. Model simulations of changes in repressor level and copy number resulting from mutations in the promoter-operator PROR region are consistent with experimental data. Calculated effects on lambda dv plasmid copy number of oligomer formation and of alternations in termination efficiency at tR1 also agree with experiment. The model has been employed to simulate the influence of cro mutants and of cro and tR1 double mutants on copy number and stable maintenance of lambda dv plasmid copy number. The genetic structure included in formulation of the replicon model provides a framework for relating changes in specific genetic loci on the plasmid with resulting alterations in host-plasmid system function.