A comparison of responses to raised extracellular potassium and endothelium-derived hyperpolarizing factor (EDHF) in rat pressurised mesenteric arteries

The present study examined the hypothesis that potassium ions act as an endothelium-derived hyperpolarizing factor (EDHF) released in response to ACh in small mesenteric arteries displaying myogenic tone. Small mesenteric arteries isolated from rats were set up in a pressure myograph at either 60 or 90 mmHg. After developing myogenic tone, responses to raising extracellular potassium were compared to those obtained with ACh (in the presence of nitric oxide synthase and cyclo- oxygenase inhibitors). The effects of barium and ouabain, or capsaicin, on responses to raised extracellular potassium or ACh were also determined. The effects of raised extracellular potassium levels and ACh on membrane potential, were measured using sharp microelectrodes in pressurised arteries. Rat small mesenteric arteries developed myogenic tone when pressurised. On the background of vascular tone set by a physiological stimulus (i.e pressure), ACh fully dilated the small arteries in a concentration-dependent manner. This response was relatively insensitive to the combination of barium and ouabain, and insensitive to capsaicin. Raising extracellular potassium produced a more inconsistent and modest vasodilator response in pressurised small mesenteric arteries. Responses to raising extracellular potassium were sensitive to capsaicin, and the combination of barium and ouabain. ACh caused a substantial hyperpolarisation in pressurized arteries, while raising extracellular potassium did not. These data indicate that K+ is not the EDHF released in response to ACh in myogenically active rat mesenteric small arteries. Since the hyperpolarization produced by ACh was sensitive to carbenoxolone, gap junctions are the likely mediator of EDH responses under physiological conditions

Pooled analysis of WHO Surgical Safety Checklist use and mortality after emergency laparotomy

Background The World Health Organization (WHO) Surgical Safety Checklist has fostered safe practice for 10 years, yet its place in emergency surgery has not been assessed on a global scale. The aim of this study was to evaluate reported checklist use in emergency settings and examine the relationship with perioperative mortality in patients who had emergency laparotomy. Methods In two multinational cohort studies, adults undergoing emergency laparotomy were compared with those having elective gastrointestinal surgery. Relationships between reported checklist use and mortality were determined using multivariable logistic regression and bootstrapped simulation. Results Of 12 296 patients included from 76 countries, 4843 underwent emergency laparotomy. After adjusting for patient and disease factors, checklist use before emergency laparotomy was more common in countries with a high Human Development Index (HDI) (2455 of 2741, 89.6 per cent) compared with that in countries with a middle (753 of 1242, 60.6 per cent; odds ratio (OR) 0.17, 95 per cent c.i. 0.14 to 0.21, P <0001) or low (363 of 860, 422 per cent; OR 008, 007 to 010, P <0.001) HDI. Checklist use was less common in elective surgery than for emergency laparotomy in high-HDI countries (risk difference -94 (95 per cent c.i. -11.9 to -6.9) per cent; P <0001), but the relationship was reversed in low-HDI countries (+121 (+7.0 to +173) per cent; P <0001). In multivariable models, checklist use was associated with a lower 30-day perioperative mortality (OR 0.60, 0.50 to 073; P <0.001). The greatest absolute benefit was seen for emergency surgery in low- and middle-HDI countries. Conclusion Checklist use in emergency laparotomy was associated with a significantly lower perioperative mortality rate. Checklist use in low-HDI countries was half that in high-HDI countries.Peer reviewe

Unexpected high diversity of galling insects in the Amazonian upper canopy: The savanna out there

A relatively large number of studies reassert the strong relationship between galling insect diversity and extreme hydric and thermal status in some habitats, and an overall pattern of a greater number of galling species in the understory of scleromorphic vegetation. We compared galling insect diversity in the forest canopy and its relationship with tree richness among upland terra firme, várzea, and igapó floodplains in Amazonia, Brazil. The soils of these forest types have highly different hydric and nutritional status. Overall, we examined the upper layer of 1,091 tree crowns. Galling species richness and abundance were higher in terra firme forests compared to várzea and igapó forests. GLM-ANCOVA models revealed that the number of tree species sampled in each forest type was determinant in the gall-forming insect diversity. The ratio between galling insect richness and number of tree species sampled (GIR/TSS ratio) was higher in the terra firme forest and in seasonally flooded igapó, while the várzea presented the lowest GIR/TSS ratio. In this study, we recorded unprecedented values of galling species diversity and abundance per sampling point. The GIR/TSS ratio from várzea was approximately 2.5 times higher than the highest value of this ratio ever reported in the literature. Based on this fact, we ascertained that várzea and igapó floodplain forests (with lower GIA and GIR), together with the speciose terra firme galling community emerge as the gall diversity apex landscape among all biogeographic regions already investigated. Contrary to expectation, our results also support the "harsh environment hypothesis", and unveil the Amazonian upper canopy as similar to vegetation habitats, hygrothermically stressed environments with temperature at lethal limits and high levels of leaf sclerophylly. © 2014 Julião et al

Can Leaf Spectroscopy Predict Leaf and Forest Traits Along a Peruvian Tropical Forest Elevation Gradient?

High-resolution spectroscopy can be used to measure leaf chemical and structural traits. Such leaf traits are often highly correlated to other traits, such as photosynthesis, through the leaf economics spectrum. We measured VNIR (visible-near infrared) leaf reflectance (400–1,075&nbsp;nm) of sunlit and shaded leaves in ~150 dominant species across ten, 1&nbsp;ha plots along a 3,300&nbsp;m elevation gradient in Peru (on 4,284 individual leaves). We used partial least squares (PLS) regression to compare leaf reflectance to chemical traits, such as nitrogen and phosphorus, structural traits, including leaf mass per area (LMA), branch wood density and leaf venation, and “higher-level” traits such as leaf photosynthetic capacity, leaf water repellency, and woody growth rates. Empirical models using leaf reflectance predicted leaf N and LMA (r2&nbsp;&gt;&nbsp;30% and %RMSE&nbsp;&lt;&nbsp;30%), weakly predicted leaf venation, photosynthesis, and branch density (r2 between 10 and 35% and %RMSE between 10% and 65%), and did not predict leaf water repellency or woody growth rates (r2&lt;5%). Prediction of higher-level traits such as photosynthesis and branch density is likely due to these traits correlations with LMA, a trait readily predicted with leaf spectroscopy

The effect of pH, dilution, and temperature on the viscosity of ocular lubricants—shift in rheological parameters and potential clinical significance

&lt;p&gt;Objective: To investigate the effect of temperature, dilution, and pH on the viscosity of ocular lubricants.&lt;/p&gt; &lt;p&gt;Design: Laboratory based investigation of viscosity.&lt;/p&gt; &lt;p&gt;Participants: No human subjects.&lt;/p&gt; &lt;p&gt;Methods: Hypromellose 0.3%, sodium hyaluronate 0.4%, carboxymethylcellulose sodium 0.5%/glycerin 0.9%, and carmellose sodium 0.5% were investigated. Ostwald capillary viscometers were utilised for viscosity measurements. The kinematic viscosity of each lubricant was tested quantitatively from 22 to 40 °C, and over a pH range of 5–8 under isothermal conditions. The kinematic viscosity of each eye drop was also tested under dilution by varying the mass fraction of each eye drop under isothermal conditions.&lt;/p&gt; &lt;p&gt;Main outcome measure: Changes in kinematic viscosity.&lt;/p&gt; &lt;p&gt;Results: Hypromellose 0.3% had an initial pH of 8.34, while the other lubricants had a pH close to neutral. From 22 to 35 °C, the kinematic viscosity of sodium hyaluronate 0.4 fell by 36% from 37.8 to 24.4 mm2/s, carboxymethylcellulose sodium 0.5%/glycerin 0.9% fell by 35% from 16.98 to 11.1 mm2/s, hypromellose fell by 37% from 6.89 to 3.69 mm2/s, and carmellose sodium 0.5% fell by 25% from 2.77 to 1.87 mm2/s. At 32 °C only sodium hyaluronate 0.4%, and carboxymethylcellulose sodium 0.5%/glycerin 0.9% retained sufficient kinematic viscosity to maintain precorneal residence. Kinematic viscosities of all the topical lubricants were unaffected by pH but decreased significantly with dilution.&lt;/p&gt; &lt;p&gt;Conclusions: This study suggests that currently used ocular lubricants have limited bioavailability due to reductions in viscosity by temperature and dilutional changes under physiological conditions. Developing lubricants with stable viscosities may maximise therapeutic efficacy.&lt;/p&gt