Extracellular ATP signaling in the rabbit lung: erythrocytes as determinants of vascular resistance

Previously, it was reported that red blood cells (RBCs) are required to demonstrate participation of nitric oxide (NO) in the regulation of rabbit pulmonary vascular resistance (PVR). RBCs do not synthesize NO; hence, we postulated that ATP, present in millimolar amounts in RBCs, was the mediator, which evoked NO synthesis in the vascular endothelium. First, we found that deformation of RBCs, as occurs on passage across the pulmonary circulation with increasing flow rate, evoked increments in ATP release. Here, ATP (300 nM), administered to isolated, salt solution-perfused (PSS) rabbit lungs, decreased total and upstream (arterial) PVR, a response inhibited by NG-nitro-L-arginine methyl ester (L-NAME, 100 microM). In lungs perfused with PSS containing RBCs, L-NAME increased total and upstream PVR. In lungs perfused with PSS containing glibenclamide-treated RBCs, which inhibits ATP release, L-NAME was without effect. Apyrase grade VII (8 U/ml), which degrades ATP to AMP, was without effect on PVR in PSS-perfused lungs. These results are consistent with the hypothesis that ATP, released from RBCs as they traverse the pulmonary circulation, evokes endogenous NO synthesis.     

Bactericidal peptidoglycan recognition protein induces oxidative stress in Escherichia coli through a block in respiratory chain and increase in central carbon catabolism

Mammalian Peptidoglycan Recognition Proteins (PGRPs) kill both Gram‐positive and Gram‐negative bacteria through simultaneous induction of oxidative, thiol and metal stress responses in bacteria. However, metabolic pathways through which PGRPs induce these bactericidal stress responses are unknown. We screened Keio collection of Escherichia coli deletion mutants and revealed that deleting genes for respiratory chain flavoproteins or for tricarboxylic acid (TCA) cycle resulted in increased resistance of E. coli to PGRP killing. PGRP‐induced killing depended on the production of hydrogen peroxide, which required increased supply of NADH for respiratory chain oxidoreductases from central carbon catabolism (glycolysis and TCA cycle), and was controlled by cAMP‐Crp. Bactericidal PGRP induced a rapid decrease in respiration, which suggested that the main source of increased production of hydrogen peroxide was a block in respiratory chain and diversion of electrons from NADH oxidoreductases to oxygen. CpxRA two‐component system was a negative regulator of PGRP‐induced oxidative stress. By contrast, PGRP‐induced thiol stress (depletion of thiols) and metal stress (increase in intracellular free Zn²⁺ through influx of extracellular Zn²⁺) were mostly independent of oxidative stress. Thus, manipulating pathways that induce oxidative, thiol and metal stress in bacteria could be a useful strategy to design new approaches to antibacterial therapy.     

Building a Comprehensive Mill-Level Database for the Industrial Sectors Integrated Solutions (ISIS) Model of the U.S. Pulp and Paper Sector

Air emissions from the U.S. pulp and paper sector have been federally regulated since 1978; however, regulations are periodically reviewed and revised to improve efficiency and effectiveness of existing emission standards. The Industrial Sectors Integrated Solutions (ISIS) model for the pulp and paper sector is currently under development at the U.S. Environmental Protection Agency (EPA), and can be utilized to facilitate multi-pollutant, sector-based analyses that are performed in conjunction with regulatory development. The model utilizes a multi-sector, multi-product dynamic linear modeling framework that evaluates the economic impact of emission reduction strategies for multiple air pollutants. The ISIS model considers facility-level economic, environmental, and technical parameters, as well as sector-level market data, to estimate the impacts of environmental regulations on the pulp and paper industry. Specifically, the model can be used to estimate U.S. and global market impacts of new or more stringent air regulations, such as impacts on product price, exports and imports, market demands, capital investment, and mill closures. One major challenge to developing a representative model is the need for an extensive amount of data. This article discusses the collection and processing of data for use in the model, as well as the methods used for building the ISIS pulp and paper database that facilitates the required analyses to support the air quality management of the pulp and paper sector.     

The dawning of a 'Golden era' in lantibiotic bioengineering

There are many examples of highly modified antimicrobial peptides in nature, many of which are non-ribosomally synthesized. However, the bacterial lantibiotics are produced as gene-encoded pre-peptides that are subsequently modified by dedicated enzyme systems to form extraordinarily potent inhibitors. Consequently, they are much more amenable to bioengineering which could lead to the generation of a new arsenal of potent antimicrobials. However, although bioengineering of these compounds has been underway for at least two decades, significant progress has only been reported in recent years. This review charts these recent developments which suggest that we are entering a 'Golden era' of lantibiotic bioengineering.     

Evidence of separate pathways for lactate uptake and release by the perfused rat heart

The simultaneous release and uptake of lactate by the heart has been observed both in vivo and ex vivo; however, the pathways underlying these observations have not been satisfactorily explained. Consequently, the purpose of this study was to test the hypothesis that hearts release lactate from glycolysis while simultaneously taking up exogenous lactate. Therefore, we determined the effects of fatty acids and diabetes on the regulation of lactate uptake and release. Hearts from control and 1-wk diabetic animals were perfused with 5 mM glucose, 0.5 mM [3-(13)C]lactate, and 0, 0.1, 0.32, or 1.0 mM palmitate. Parameters measured include perfusate lactate concentrations, fractional enrichment, and coronary flow rates, which enabled the simultaneous, but independent, measurements of the rates of 1) uptake of exogenous [(13)C]lactate and 2) efflux of unlabeled lactate from metabolism of glucose. Although the rates of lactate uptake and efflux were both similarly inhibited by the addition of palmitate, (i.e., the ratio of lactate uptake to efflux remained constant), the ratio of lactate uptake to efflux was significantly higher in the controls compared with the diabetic group (1.00 +/- 0.14 vs. 0.50 +/- 0.07, P < 0.002). These data, combined with heterogeneous (13)C enrichment of tissue lactate, pyruvate, and alanine, suggest that glycolytically derived lactate production and oxidation of exogenous lactate operate as functionally separate metabolic pathways. These results are consistent with the concept of an intracellular lactate shuttle.     

Use of dermal regeneration template in contracture release procedures: a multicenter evaluation

Integra dermal regeneration template (Integra Life Sciences, Plainsboro, N.J.) is an effective treatment for full-thickness burns. It can also be useful in contracture release procedures; however, the clinical utility of a dermal regeneration template in contracture release procedures has not been adequately characterized. In this multicenter investigation, the outcomes of release procedures incorporating a dermal regeneration template for 89 consecutive patients, who underwent a total of 127 contracture releases, were retrospectively evaluated. The procedures involved the application of Integra, which includes a temporary silicone epidermal substitute and an artificial dermal layer. After formation of a neodermis, the silicone layer is removed and replaced with an epidermal autograft. Data on patient and contracture site history, treatment methods, physician assessments of range of motion or function, patient satisfaction, recurrence, and adverse events were collected with a standardized questionnaire. Release procedures for the study patients involved the neck, axilla, trunk, elbow, knee, hand, and other anatomical sites. The mean postoperative follow-up period was 11.4 months. At 76 percent of the release sites, range of motion or function was rated as good (significant improvement in range of motion or function) or excellent (maximal range of motion or function possible) by physicians. Responding patients expressed satisfaction with the overall results of treatment at 82 percent of the sites. No recurrence of contracture at 75 percent of the sites was observed during follow-up monitoring. Patient age and prior surgical treatment at the site did not significantly affect the results of treatment. However, outcomes were superior at mature sites, i.e., those for which more than 12 months had elapsed since the original injury. Postoperative complications rarely necessitated regrafting. These results indicate that a dermal regeneration template provides a useful alternative technique for contracture release procedures. The study data indicate that this approach leads to favorable functional outcomes and a high rate of patient satisfaction. This modality also seems to be versatile, because a range of anatomical sites are amenable to treatment with a dermal regeneration template, regardless of prior surgical treatment, and both pediatric and adult patients respond well to this form of therapy. Furthermore, Integra confers functional and cosmetic benefits similar to those of full-thickness grafts but without comparable potential for donor-site morbidity.