Enhancing Nitric Oxide Bioavailability via Exogen Nitric Oxide Synthase and L-Arginine Attenuates Ischemia-Reperfusion-Induced Microcirculatory Alterations.

BACKGROUND: Nitric oxide (NO) is an important cytoprotective agent against ischemia and reperfusion injury (IRI). Enhancing NO bioavailability via exogen NO synthases (NOSs) and L-arginine promotes conversation to NO, circumventing the problem of nonfunctioning NOSs under hypoxic and acidic conditions. In this study, the authors evaluated the therapeutic efficacy of endothelial, inducible and neuronal NOS, and L-arginine on reperfusion-induced microcirculatory alterations and hemodynamic adverse effects in the microvasculature of skeletal muscle. METHODS: Vascular pedicle isolated rat cremaster model was used that underwent 2 hours of warm ischemia followed by 1 hour of reperfusion. At 30 minutes before ischemia, normal saline (control group with/without ischemia), endothelial-, inducible-, and neuronal NOSs (2 IE) and L-arginine (50 mg/kg BW) were administered systemically (IV). Ischemia-reperfusion-induced microcirculatory alterations were measured after 1 hour of reperfusion. Mean arterial blood pressure and heart frequency were measured throughout the experiment to determine hemodynamic adverse effects. RESULTS: The isoforms of NOSs and L-arginine attenuated ischemia-reperfusion-induced vasoconstriction, improved red blood cell velocity, capillary flow, and leukocyte adherence to the endothelium wall. Hemodynamics was stable throughout the experiment. CONCLUSIONS: Enhancing NO bioavailability via exogen application of NOSs and L-arginine significantly attenuated ischemia-reperfusion-induced microcirculatory alterations in the microvasculature of skeletal muscle. Significant hemodynamic adverse effects were not present, thus demonstrating this approach might be useful for therapeutic intervention. This "pharmacologic preconditioning" could be an easy and effective interventional strategy to uphold conversation of L-arginine to NO under ischemic conditions.

Key Edaphic Properties Largely Explain Temporal and Geographic Variation in Soil Microbial Communities across Four Biomes.

Soil microbial communities play a critical role in nutrient transformation and storage in all ecosystems. Quantifying the seasonal and long-term temporal extent of genetic and functional variation of soil microorganisms in response to biotic and abiotic changes within and across ecosystems will inform our understanding of the effect of climate change on these processes. We examined spatial and seasonal variation in microbial communities based on 16S rRNA gene sequencing and phospholipid fatty acid (PLFA) composition across four biomes: a tropical broadleaf forest (Hawaii), taiga (Alaska), semiarid grassland-shrubland (Utah), and a subtropical coniferous forest (Florida). In this study, we used a team-based instructional approach leveraging the iPlant Collaborative to examine publicly available National Ecological Observatory Network (NEON) 16S gene and PLFA measurements that quantify microbial diversity, composition, and growth. Both profiling techniques revealed that microbial communities grouped strongly by ecosystem and were predominately influenced by three edaphic factors: pH, soil water content, and cation exchange capacity. Temporal variability of microbial communities differed by profiling technique; 16S-based community measurements showed significant temporal variability only in the subtropical coniferous forest communities, specifically through changes within subgroups of Acidobacteria. Conversely, PLFA-based community measurements showed seasonal shifts in taiga and tropical broadleaf forest systems. These differences may be due to the premise that 16S-based measurements are predominantly influenced by large shifts in the abiotic soil environment, while PLFA-based analyses reflect the metabolically active fraction of the microbial community, which is more sensitive to local disturbances and biotic interactions. To address the technical issue of the response of soil microbial communities to sample storage temperature, we compared 16S-based community structure in soils stored at -80°C and -20°C and found no significant differences in community composition based on storage temperature. Free, open access datasets and data sharing platforms are powerful tools for integrating research and teaching in undergraduate and graduate student classrooms. They are a valuable resource for fostering interdisciplinary collaborations, testing ecological theory, model development and validation, and generating novel hypotheses. Training in data analysis and interpretation of large datasets in university classrooms through project-based learning improves the learning experience for students and enables their use of these significant resources throughout their careers.

High-dose vitamin C treatment reduces capillary leakage after burn plasma transfer in rats.

Oxidative stress after burn injuries leads to systemic capillary leakage and leukocyte activation. This study evaluates whether antioxidative treatment with high-dose vitamin C leads to burn edema reduction and prevention of leukocyte activation after burn plasma transfer. Donor rats underwent a burn (n = 7; 100 degrees C water, 12 seconds, 30% body surface area) or sham burn (37 degrees C water; n = 2) procedure and were killed after 4 hours for plasma harvest. This plasma was administered to study rats (continuous infusion). Rats were randomized to four groups (n = 8 each; burn plasma alone [BP]; burn plasma/vitamin C-bolus 66 mg/kg and maintenance dose 33 mg/kg/hr [VC66]; burn plasma/vitamin C-bolus 33 mg/kg and maintenance dose 17.5 mg/kg/hr [VC33]; and sham burn plasma [SB]). Intravital fluorescence microscopy in the mesentery was performed at 0, 60, and 120 minutes for microhemodynamic parameters, leukocyte adherence, and fluorescein isothiocyanate-albumin extravasation. No differences were observed in microhemodynamics at any time. Burn plasma induced capillary leakage, which was significantly higher compared with sham burn controls (P < .001). VC66 treatment reduced microvascular barrier dysfunction to sham burn levels, whereas VC33 had no significant effect. Leukocyte sticking increased after burn plasma infusion, which was not found for sham burn. Vitamin C treatment did not influence leukocyte activation (P > .05). Burn plasma transfer leads to systemic capillary leakage. High-dose vitamin C treatment (bolus 66 mg/kg and maintenance dose 33 mg/kg/hr) reduces endothelial damage to sham burn levels, whereas half the dose is inefficient. Leukocyte activation is not influenced by antioxidative treatment. Therefore, capillary leakage seems to be independent from leukocyte-endothelial interactions after burn plasma transfer. High-dose vitamin C should be considered for parenteral treatment in every burn patient.

Burn plasma transfer induces burn edema in healthy rats.

Thermal injuries greater than 20% body surface area (BSA) result in systemic shock with generalized edema in addition to local tissue destruction. Burn shock is induced by a variety of mediators, mainly immunomodulative cytokines. This experimental study evaluates if burn shock can be induced in healthy rats by transfer of burn plasma (BP) with mediators. Thermal injury was induced by hot water (100 degrees C water, 12 s, 30% BSA) in male syngenic Wistar rats. Donor rats were killed 4 h posttrauma, and BP was harvested. Burn plasma was transferred to healthy animals by continuous intravenous infusion in three types of dilution (100%, 10%, and 1%). Positive controls were directly examined 4 h after thermal injury, and negative control rats had a continuous infusion done with sham burn (SB) plasma (37 degrees C water, 12 s, 30% BSA). Afterwards, intravital fluorescence microscopy was performed in postcapillary mesenteric venules at 0, 60, and 120 min. Edema formation was assessed by relative changes over time in fluorescence intensity of fluorescein isothiocyanate-albumin in the intravascular versus the extravascular space. The interactions of leucocytes and endothelium were evaluated by quantification of leukocyte sticking. Additionally, microhemodynamic (volumetric blood flow, erythrocyte velocity, venular wall shear rate, venular diameters) and macrohemodynamic parameters (blood pressure, heart frequency, temperature) were assessed online (arterial catheter). For statistics, an ANOVA was performed with Bonferroni adjustment procedure. Differences were considered significant when P < 0.05. There are no statistically significant differences in microhemodynamics or macrohemodynamics between study groups. Burn plasma infusion and thermal injury lead to significant increases in fluorescein isothiocyanate-albumin extravasation, whereas SB plasma shows no significant changes. Even BP diluted in 0.9% saline (10% and 1%) results in a similar transvascular flux of plasma proteins as direct thermal injury. Differences between positive controls and BP infusion are not significant, whereas all groups are statistically different from the SB group (P<0.05). Leukocyte sticking is significantly increased in all groups except the SB group, and the number of adherent leukocytes is dose dependent. The present study demonstrates that as early as 4 h after thermal injury, there are sufficient factors (e.g., cytokines) in BP to induce systemic burn shock in healthy rats even in diluted plasma (1%). However, the "key" cytokines are not identified at this point. The burned tissue is no longer required for burn shock induction, and the pathophysiologic process seems to be self-perpetuating as early as 4 h posttrauma. Leukocytes are activated by thermal injury and BP infusion. The role of leukocyte-endothelium interactions for edema formation remains uncertain and requires further investigation.