The microcirculation of myocutaneous island flaps in pigs studied with radioactive blood volume tracers and microspheres of different sizes.

In order to further improve the understanding of hemodynamic changes in the immediate postoperative phase after elevation of myocutaneous flaps, regional blood flow and arteriovenous (A-V) shunting were measured in rectus abdominis island flaps in 8 pigs. Radioactive microspheres of two sizes (15 and 50 micron) were used. Approximately half (53.4 +/- 6 percent) of the 15-micron microspheres and one-fourth (24.1 +/- 6 percent) of the 50-micron microspheres entering the flap appeared in the venous outflow. Compared with the control area, A-V shunting was significantly increased in muscle and substantially more pronounced in skin. Nutritional blood flow, total blood flow, and vascular volume were increased in muscle and unchanged in skin and subcutis. The lowest tissue hematocrit of 7 +/- 1 percent was found in skin as compared with a central hematocrit of 35 +/- 2 percent. Tissue hematocrit in flap muscle was decreased to 17 +/- 2 percent when compared with control muscle (22 +/- 3 percent), and the mean transit time for blood was correspondingly decreased. Thus vasodilation provided increased perfusion through muscular capillaries and through A-V shunts. Shunting of 15-micron microspheres appeared to take place not only in skin, but also in subcutis and muscle, which challenges the widespread belief that A-V shunting does not occur in muscle.     

Linking Data Choices and Context Specificity in Life Cycle Assessment of Waste Treatment Technologies: A Landfill Case Study

To generate meaningful results, life cycle assessments (LCAs) require accurate technology data that are consistent with the goal and scope of the analysis. While literature data are available for many products and processes, finding representative data for highly site‐specific technologies, such as waste treatment processes, remains a challenge. This study investigated representative life cycle inventory (LCI) modeling of waste treatment technologies in consideration of variations in technological level and climate. The objectives were to demonstrate the importance of representative LCI modeling as a function of the specificity of the study, and to illustrate the necessity of iteratively refining the goal and scope of the study as data are developed. A landfill case study was performed where 52 discrete landfill data sets were built and grouped to represent different technology options and geographical sites, potential impacts were calculated, and minimum/maximum (min‐max) intervals were generated for each group. The results showed decreasing min‐max intervals with increasing specificity of the scope of study, which indicates that compatibility between the scope of study and LCI model is critical. Hereby, this study quantitatively demonstrates the influence of representative modeling on LCA results. The results indicate that technology variations and site‐specific conditions (e.g., the influence of precipitation and cover permeability on landfill gas generation and collection) should be carefully addressed by a systematic analysis of the key process parameters. Therefore, a thorough understanding of the targeted waste treatment technologies is necessary to ensure that appropriate data choices are made within the boundaries of the defined scope of the study.     

Strong effects of hydrologic environment and weak effects of elevated CO<Subscript>2</Subscript> on the invasive weed <Emphasis Type="Italic">Alternanthera philoxeroides</Emphasis> and the biocontrol beetle <Emphasis Type="Italic">Agasicles hygrophila</Emphasis>

Global change, such as elevated CO₂, may alter interactions between invasive plants and biocontrol agents, impacting biocontrol efficacy. Here, we conducted four experiments in Texas, USA to test how elevated CO₂ influences an invasive plant (Alternanthera philoxeroides) and its interactions with an introduced biocontrol beetle (Agasicles hygrophila) in terrestrial (well-watered) and flooded environments. We grew plants for 9 months in ambient or elevated CO₂ (800 ppm) chambers in continuously flooded or well-watered conditions. In no-choice trials, flooding increased leaf toughness and decreased beetle consumption but beetles only oviposited on ambient CO₂ leaves. In choice trials, beetles preferred to feed and oviposit on terrestrial plants but were also less likely to damage elevated CO₂ leaves. Caged beetle populations were larger in terrestrial conditions than aquatic conditions for a second set of plants grown in the chambers. With a third set of plants grown in the ambient or elevated CO₂ chambers, damage for plants placed in the field (aquatic setting) was higher for plants grown in terrestrial conditions vs. flooded conditions at ambient CO₂. Our results suggest that elevated CO₂ will have minor effects on the efficacy of this biocontrol agent by decreasing oviposition and number of leaves damaged, and hydrologic environment may affect invasive plant performance by altering herbivore oviposition and feeding preferences. A broader understanding of the effects of global change on biocontrol will help prevent and manage future spread of invasive plants.     

Purification, characterization and stability of barley grain peroxidase BP 1, a new type of plant peroxidase

The major peroxidase of barley grain (BP 1) has enzymatic and spectroscopic properties that are very differeant from those of other known plant peroxidases (EC 1.11.1.7) and can therefore contribute to the understanding of the many physiological functions ascribed to these enzymes. To study the structure-function relationships of this unique model peroxidase, large-scale and Jaboratory-scale purifications have been developed. The two batches of pure BP 1 obtained were identical in their enzymatic and spectral properties, and confirmed that BP 1 is different from the prototypical horseradish peroxidase isoenzyme C (HRP C). However, when measuring the specific activity of BP 1 at pH 4.0 in the presence of 1 m M C_aCl₂, the enzyme was as competent as HRP C at neutral pH towards a variety of substrates (m M mg⁻¹ min⁻¹): coniferyl alcohol (930±48), caffeic acid (795±53), ABTS (2,2'-azino-di-[3-ethyl-benzothiazoline-(6)-sulfonic acid]) (840±47), ferulic acid (415±20), p -coumaric acid (325±12), and guaiacol (58±3). The absorption spectrum of BP 1 is blue-shifted compared to that of HRP C with a Soret maximum of 399–402 nm, depending on pH. The prosthetic group was shown to be iron-protoporphyrin IX, which is characteristic of plant peroxidases. BP 1 is stable from pH 3 to 11, indicating that its unusual spectral characteristics do not result from enzyme instability. The thermostability is also normal with a melting temperature of 75°C at pH 6.6, and 67°C at pH 4.0 and 8.3. It is clear that the unusual properties of BP 1 are genuine, and reflect a novel regulation of plant peroxidase function.