Search

Managers of most low-volume roads (LVR) face a deteriorating bridge population, and replacement is frequently the most cost-effective solution. With more structures needing replacement than available funds to do so, low-cost alternatives that are constructible in-house are a desirable option. The modified beam-in-slab bridge (MBISB) is one such alternative that has been developed specifically for LVRs. The MBISB system consists of longitudinal steel stringers that support a transverse concrete arched deck. Composite action is obtained by using an alternative shear connector (ASC) rather than shear studs. Other than nominal transverse reinforcement, which is part of ASC, MBISB requires minimal additional reinforcement—approximately 70% of that required in conventional decks. Two demonstration bridges—MBISB 1, 50 ft (15.24 m) long and 31 ft (9.45 m) wide, and MBISB 2, 70 ft (21.34 m) long and 32 ft (9.75 m) wide-saved the bridge owner slightly more than 20% of the cost of conventional bridge systems. Field testing of both demonstration bridges determined the behavior of the bridges under service loading. Strains and deflections were measured at critical locations; the resulting data were used to confirm composite action and to determine the load distribution characteristics for use in the design methodology that was developed. On the basis of analyses and the field data, the demonstration MBISBs exceed AASHTO design requirements. Supporting documentation describes the construction and structural behavior of the MBISBs.

Funding for the repair and replacement of structurally deficient and functionally obsolete bridges is a nationwide problem. This problem is magnified for the managers of low-volume-road (LVR) systems who have limited budgets; thus, innovative replacement alternatives are always being sought. The beam-in-slab bridge (BISB) is an alternative replacement bridge developed in Iowa. The bridge consists of W-beam sections spaced 24 in. (610 mm) on center, with concrete filling the void space between them. Spans up to 50 ft (15.24 m) can be constructed with this low-cost alternative. Field and laboratory testing confirmed that the system is capable of handling legal loads. Modifications to the BISB have been investigated to improve its structural efficiency to make it possible to use the system in longer spans. An alternative shear connector (ASC) has been developed to provide composite action in the BISB. The ASC consists of holes, either torched or drilled, through the web of the girder for the formation of concrete dowels that provide for composite action. Ongoing research promises more structural efficiency with the development of an arched formwork system, which will make possible wider girder spacings and reduced self-weight. Combining the ASC with the arched formwork should result in an essentially steel-free system that is relatively easy to construct. From initial results, it should be possible to construct spans up to 75 ft (22.86 m) to carry legal loads in Iowa with these modifications.

Funding for the repair and replacement of structurally deficient and functionally obsolete bridges is a nationwide problem. This problem is magnified for the managers of low-volume-road (LVR) systems who have limited budgets; thus, innovative replacement alternatives are always being sought. The beam-in-slab bridge (BISB) is an alternative replacement bridge developed in Iowa. The bridge consists of W-beam sections spaced 24 in. (610 mm) on center, with concrete filling the void space between them. Spans up to 50 ft (15.24 m) can be constructed with this low-cost alternative. Field and laboratory testing confirmed that the system is capable of handling legal loads. Modifications to the BISB have been investigated to improve its structural efficiency to make it possible to use the system in longer spans. An alternative shear connector (ASC) has been developed to provide composite action in the BISB. The ASC consists of holes, either torched or drilled, through the web of the girder for the formation of concrete dowels that provide for composite action. Ongoing research promises more structural efficiency with the development of an arched formwork system, which will make possible wider girder spacings and reduced self-weight. Combining the ASC with the arched formwork should result in an essentially steel-free system that is relatively easy to construct. From initial results, it should be possible to construct spans up to 75 ft (22.86 m) to carry legal loads in Iowa with these modifications.

The internalization of the N-terminal catalytic domain of Bordetella pertussis adenylate cyclase toxin (ACT) across the cytoplasmic membrane has been considered to occur independently from protein-protein interactions which can lead to oligomerization required for hemolytic activity by its C-terminal hemolysin domain. Here we report that when added in excess, this hemolysin domain stimulates the internalization, suggesting the involvement of protein-protein interactions in cell-invasive activity of ACT, as well as its hemolytic activity.

The effect of Bordetella pertussis adenylate cyclase toxin (ACT) on platelet aggregation was investigated. This cell-invasive adenylate cyclase completely suppressed ADP (10 microM)-induced aggregation of rabbit platelets at 3 micrograms/ml and strongly suppressed thrombin (0. 2 U/ml)-induced aggregation at 10 micrograms/ml. The suppression was accompanied by marked increase in platelet intracellular cyclic AMP (cAMP) content and was diminished by the anti-ACT monoclonal antibody B7E11. A catalytically inactive point mutant of ACT did not show the suppressive effect. Since an increase of cAMP content is a known cause of platelet dysfunction, these results indicate that the observed platelet inactivation was due to the catalytic activity of ACT through increase of intracellular cAMP.

We previously suggested that insulin increases diacylglycerol (DAG) in BC3H-1 myocytes, both by increases in synthesis de novo of phosphatidic acid (PA) and by hydrolysis of non-inositol-containing phospholipids, such as phosphatidylcholine (PC) and phosphatidylethanolamine (PE). We have now evaluated these insulin effects more thoroughly, and several potential mechanisms for their induction. In studies of the effect on PA synthesis de novo, insulin stimulated [2-3H]glycerol incorporation into PA, DAG, PC/PE and total glycerolipids of BC3H-1 myocytes, regardless of whether insulin was added simultaneously with, or after 2 h or 3 or 10 days of prelabelling with, [2-3H]glycerol. In prelabelled cells, time-related changes in [2-3H]glycerol labelling of DAG correlated well with increases in DAG content: both were maximal in 30-60 s and persisted for 20-30 min. [2-3H]Glycerol labelling of glycerol 3-phosphate, on the other hand, was decreased by insulin, presumably reflecting increased utilization for PA synthesis. Glycerol 3-phosphate concentrations were 0.36 and 0.38 mM before and 1 min after insulin treatment, and insulin effects could not be explained by increases in glycerol 3-phosphate specific radioactivity. In addition to that of [2-3H]glycerol, insulin increased [U-14C]glucose and [1,2,3-3H]glycerol incorporation into DAG and other glycerolipids. Effects of insulin on [2-3H]glycerol incorporation into DAG and other glycerolipids were half-maximal and maximal at 2 nM- and 20 nM-insulin respectively, and were not dependent on glucose concentration in the medium, extracellular Ca2+ or protein synthesis. Despite good correlation between [3H]DAG and DAG content, calculated increases in DAG content from glycerol 3-phosphate specific radioactivity (i.e. via the pathway of PA synthesis de novo) could account for only 15-30% of the observed increases in DAG content. In addition to increases in [3H]glycerol labelling of PC/PE, insulin rapidly (within 30 s) increased PC/PE labelling by [3H]arachidonic acid, [3H]myristic acid, and [14C]choline. Phenylephrine, ionophore A23187 and phorbol esters did not increase [2-3H]glycerol incorporation into DAG or other glycerolipids in 2-h-prelabelling experiments; thus activation of the phospholipase C which hydrolyses phosphatidylinositol, its mono- and bis-phosphate, Ca2+ mobilization, and protein kinase C activation, appear to be ruled out as mechanisms to explain the insulin effect on synthesis de novo of PA, DAG and PC.(ABSTRACT TRUNCATED AT 400 WORDS)

We examined the major pathogenic substances of Bordetella pertussis for the ability to induce nitric oxide, and important biological function of macrophages, via gamma interferon in spleen cells. B. pertussis, which produces a variety of pathogenic substances, including pertussis toxin and filamentous hemagglutinin, causes a severe respiratory disease. Nitric oxide was detected in the culture fluid of spleen cells stimulated with pertussis toxin or its B oligomer but not in the culture fluid of spleen cells stimulated with the A protomer of pertussis toxin or with filamentous hemagglutinin. Incubation of the peritoneal exudate macrophages with pertussis toxin, B oligomer, A protomer, or filamentous hemagglutinin induced little nitric oxide, whereas incubation with gamma interferon induced a significant amount of nitric oxide. The induction of nitric oxide in spleen cells stimulated with pertussis toxin was completely inhibited by anti-gamma interferon antibody. The treatment of spleen cells with anti-Thy-1.2 antibody plus complement followed by stimulation with pertussis toxin decreased the secretion of gamma interferon and nitric oxide. These results suggest that gamma interferon from T lymphocytes stimulated with pertussis toxin induces nitric oxide.

BC3H-1 myocytes were cultured in the presence of [3H]inositol or [3H]glucosamine during their entire growth cycle to ensure that all lipids containing inositol and glucosamine were labelled to isotopic equilibrium or maximal specific radioactivity. After such labelling, a lipid (or group of lipids), which was labelled with both inositol and glucosamine, was observed to migrate between phosphatidylinositol 4-phosphate and phosphatidylinositol (PI) in two different t.l.c. systems. Insulin provoked rapid, sizeable, increases in the inositol-labelling of this lipid (presumably a PI-glycan), and these increases were similar to those observed in PI and PI phosphates. Our results indicate that insulin provokes co-ordinated increases in the net synthesis de novo of PI and its derivatives, PI phosphates and the PI-glycan, in BC3H-1 myocytes. This increase in synthesis of PI may serve as the mechanism for replenishing the PI-glycan during stimulation of its hydrolysis by insulin. Moreover, increases in the content of the PI-glycan may contribute to increases in the generation of head-group ‘mediators’ during insulin action.

We examined the major pathogenic substances of Bordetella pertussis for the ability to induce nitric oxide, and important biological function of macrophages, via gamma interferon in spleen cells. B. pertussis, which produces a variety of pathogenic substances, including pertussis toxin and filamentous hemagglutinin, causes a severe respiratory disease. Nitric oxide was detected in the culture fluid of spleen cells stimulated with pertussis toxin or its B oligomer but not in the culture fluid of spleen cells stimulated with the A protomer of pertussis toxin or with filamentous hemagglutinin. Incubation of the peritoneal exudate macrophages with pertussis toxin, B oligomer, A protomer, or filamentous hemagglutinin induced little nitric oxide, whereas incubation with gamma interferon induced a significant amount of nitric oxide. The induction of nitric oxide in spleen cells stimulated with pertussis toxin was completely inhibited by anti-gamma interferon antibody. The treatment of spleen cells with anti-Thy-1.2 antibody plus complement followed by stimulation with pertussis toxin decreased the secretion of gamma interferon and nitric oxide. These results suggest that gamma interferon from T lymphocytes stimulated with pertussis toxin induces nitric oxide.