ABSTRACT
In Streptomyces coelicolor, the AbsA1-AbsA2 two-component system regulates the expression of multiple antibiotic gene clusters. Here, we show that the response regulator encoded by the absA2 gene is a negative regulator of these antibiotic gene clusters. A genetic analysis shows that the phosphorylated form of the AbsA2 response regulator (phospho-AbsA2), generated by the cognate AbsA1 sensor histidine kinase, is required for normal growth phase regulation of antibiotic synthesis. In the absence of phospho-AbsA2, antibiotics are produced earlier and more abundantly. Overexpression of AbsA1 also deregulates antibiotic synthesis, apparently shifting the AbsA1 protein from a kinase-active to a phospho-AbsA2 phosphatase-active form. The absA1 and absA2 genes, which are adjacent, are located in one of the antibiotic gene clusters that they regulate, the cluster for the calcium-dependent antibiotic (CDA). The absA genes themselves are growth phase regulated, with phospho-AbsA2 responsible for growth phase-related positive autoregulation. We discuss the possible role and mechanism of AbsA-mediated regulation of antibiotic synthesis in the S. coelicolor life cycle.
Subject(s)
Anti-Bacterial Agents/biosynthesis , Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Streptomyces/genetics , Transcription Factors/genetics , Anthraquinones/metabolism , Bacterial Proteins/metabolism , Calcium/metabolism , Gene Deletion , Genes, Bacterial , Ionophores/metabolism , Multigene Family , Mutagenesis, Site-Directed , Peptides , Phosphorylation , Plasmids/genetics , Prodigiosin/analogs & derivatives , Prodigiosin/biosynthesis , Signal Transduction , Single-Strand Specific DNA and RNA Endonucleases/metabolism , Streptomyces/growth & development , Streptomyces/metabolism , Transcription Factors/metabolism , Transcription, GeneticABSTRACT
Dentin specimens from 46 extracted human molar teeth were used in a matched-pair design examining the factors of temperature/humidity on shear bond strength of a dentinal adhesive to dentin. For one tooth-half, all procedures using restorative materials were accomplished in a controlled temperature and humidity chamber (humidity 95.0 +/- 2.0%, temperature 37.0 +/- 0.3 degrees C). For the other matched tooth-half all procedures were performed at ambient room conditions (humidity 52%, temperature 23.3 degrees C/74 degrees F). Oil-free air and water were used in all restorative procedures. Application of Scotchbond Multi-Purpose Adhesive System was followed by placement of Z100 Restorative Resin, and thermocycling 1000 cycles from 5 to 55 degrees C. Each matched specimen was tested 24 hours later in an Instron Testing Machine. A paired t-test was performed for comparison of bond strength set values, since they were obtained from matching halves of the same teeth. Paired t-test comparison showed that the average humidity/temperature chamber mean of 7.14 +/- 3.12 MPa was significantly less than the ambient conditions mean of 14.29 +/- 5.07 (P = 0.0000). Bond strength testing under simulated oral conditions may produce significantly different findings than customary bench-top laboratory experiments.
Subject(s)
Dentin-Bonding Agents/chemistry , Resin Cements/chemistry , Composite Resins , Dental Restoration, Permanent/methods , Humans , Humidity , Matched-Pair Analysis , Materials Testing , Silicon Dioxide , Temperature , Tensile Strength , ZirconiumABSTRACT
The present study investigates the extent to which marital partners are different or similar in their ways of enacting the therapeutic, or supportive, role. Specifically, the article compares husbands and wives categorically as in non-dyadic studies and then as marital partners as in dyadic studies. In addition, this study, by using data from the Aging Couples Study, included only dual-earner couples so as to control for the effects of work life on marital relations. Results showed that studies of individual married men and women understate the differences between marital partners in that some wives "overbenefit" in the exchange of conjugal supports. However, husbands more often "overbenefit." Findings also indicated that the norm of reciprocity does not prevail regarding the extent of support, although it does for the types of support exchanged.
Subject(s)
Aged/psychology , Interpersonal Relations , Marriage/psychology , Social Support , Spouses/psychology , Communication , Employment , Female , Humans , Male , Middle Aged , United StatesABSTRACT
This study compared the shear bond strength to enamel of Scotchbond Multi-Purpose Dental Adhesive System's bonding resin following etching of enamel with 10% maleic, 1.6% oxalic, 10% phosphoric, and 35% phosphoric acids for 15, 30, and 60 seconds. Three hundred and sixty human molar teeth were used to create 12 groups of 30 enamel specimens per group (n = 30). Flattened enamel surfaces were treated with the different etchants for the time periods indicated, the surfaces primed, and adhesive resin applied according to the manufacturer's recommendations. The specimens were completed with Silux Plus resin and subjected to 1000 thermocycles (5-55 degrees C) followed by shear stress in an Instron Testing Machine to failure within a 24-hour period. A two-way ANOVA revealed significant differences for shear bond strength values by type of etchant (10% phosphoric, 35% phosphoric > 10% maleic > 1.6% oxalic acid) (P < 0.005) and by length of application time (P < 0.005). The interaction term for these two treatments was statistically significant (P < 0.005).
Subject(s)
Acid Etching, Dental/methods , Dentin-Bonding Agents , Resin Cements , Analysis of Variance , Dental Bonding , Dental Enamel , Humans , Maleates , Materials Testing , Oxalates , Oxalic Acid , Phosphoric Acids , Time FactorsABSTRACT
The purpose of this study was to investigate the factor structure of social support among older spouses. The sample consisted of 298 older marital dyads who participated in the Aging Couples Study. Confirmatory factor analysis techniques were used to examine conjugal support in a series of nested measurement models at the couple and individual levels. Two research questions were addressed: (a) the viability of conjugal support as a couple's construct, and (b) the dimensionality of social support within the marital dyad. Results showed that conjugal support was a husband/wife, rather than a couple, construct. Findings also showed that conjugal support was a multidimensional construct consisting of three factors: instrumental support, emotional support, and confiding. Moreover, husbands and wives perceived the dimensions of conjugal support differently.
Subject(s)
Aged/psychology , Marriage , Social Support , Female , Humans , MaleABSTRACT
Interview data obtained from 132 women sixty-five and older reveals that the widows and married women have a comparable number of primary friends. Being over age seventy-four influences the size of the friendship network for widows but not married women. The primary friendships of widows and married women parallel each other in terms of endurance and stability. Primary ties with men are the exception rather than the norm, for both widows and married women. Widows do differ from married women in that the former rely on confidant friends to a greater extent. Ties between older women and their confidants are characterized by norms of reciprocity.
