Flash photolysis has become an essential technique for dynamic investigations of living cells and tissues. This approach offers several advantages for instantly changing the concentration of ...bioactive compounds outside and inside living cells with high spatial resolution. Light sources for photolysis need to deliver pulses of high intensity light in the near UV range (300–380
nm), to photoactivate a sufficient amount of molecules in a short time. UV lasers are often required as the light source, making flash photolysis a costly approach. Here we describe the use of a high power 365
nm light emitting diode (UV LED) coupled to an optical fiber to precisely deliver the light to the sample. The ability of the UV LED light source to photoactivate several caged compounds (CMNB-fluorescein, MNI-glutamate, NP-EGTA, DMNPE-ATP) as well as to evoke the associated cellular Ca
2+ responses is demonstrated in both neurons and astrocytes. This report shows that UV LEDs are an efficient light source for flash photolysis and represent an alternative to UV lasers for many applications. A compact, powerful, and low-cost system is described in detail.
Instrumental observations and reconstructions of global and hemispheric temperature evolution reveal a pronounced warming during the past ∼150 years. One expression of this warming is the observed ...increase in the occurrence of heatwaves. Conceptually this increase is understood as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small. Here we show that this framework fails to explain the record-breaking central European summer temperatures in 2003, although it is consistent with observations from previous years. We find that an event like that of summer 2003 is statistically extremely unlikely, even when the observed warming is taken into account. We propose that a regime with an increased variability of temperatures (in addition to increases in mean temperature) may be able to account for summer 2003. To test this proposal, we simulate possible future European climate with a regional climate model in a scenario with increased atmospheric greenhouse-gas concentrations, and find that temperature variability increases by up to 100%, with maximum changes in central and eastern Europe.
Local changes in surface temperature have a powerful influence on the perfusion of human skin. Heating increases local skin blood flow, but the mechanisms and mediators of this response (thermal ...hyperemia response) are incompletely elucidated. In the present study, we examined the possible dependence of the thermal hyperemia response on stimulation of muscarinic cholinergic receptors and on production of vasodilator prostanoids. In 13 male healthy subjects aged 20-30 yr, a temperature-controlled chamber was positioned on the volar face of one forearm and used to raise surface temperature from 34 to 41 degrees C. The time course of the resulting thermal hyperemia response was recorded with a laser-Doppler imager. In one experiment, each of eight subjects received an intravenous bolus of the antimuscarinic agent glycopyrrolate (4 microg/kg) on one visit and saline on the other. The thermal hyperemia response was determined within the hour after the injections. Glycopyrrolate effectively inhibited the skin vasodilation induced by iontophoresis of acetylcholine but did not influence the thermal hyperemia response. In a second experiment, conducted in five other subjects, 1 g of the cyclooxygenase inhibitor aspirin administered orally totally abolished the vasodilation induced in the skin by anodal current but also failed to modify the thermal hyperemia response. The present study excludes the stimulation of muscarinic receptors and the production of vasodilator prostaglandins as essential and nonredundant mechanisms for the vasodilation induced by local heating in human forearm skin.
Food security is important. A rising world population coupled with climate change creates growing pressure on global world food supplies. States alleviate this pressure domestically by attracting ...agri–foreign direct investment (agri-FDI). This is a high-risk strategy for weak states: the state may gain valuable foreign currency, technology and debt-free growth; but equally, investors may fail to deliver on their commitments and exploit weak domestic legal infrastructure to 'grab' large areas of prime agricultural land, leaving only marginal land for domestic production. A net loss to local food security and to the national economy results. This is problematic because the state must continue to guarantee its citizens' right to food and property. Agri-FDI needs close regulation to maximise its benefit. This article maps the multilevel system of governance covering agri-FDI. We show how this system creates asymmetric rights in favour of the investor to the detriment of the host state's food security and how these problems might be alleviated.
Background: In humans, local heating increases skin perfusion by mechanisms dependent on nitric oxide (NO). Because the vascular effects of NO may be subject to desensitization, we examined whether a ...first local thermal stimulus would attenuate the hyperemic response to a second one applied later. Methods: Twelve healthy young men were studied. Skin blood flow (SkBF) was measured on forearm skin with laser Doppler imaging. Local thermal stimuli (temperature step from 34 to 41°C maintained for 30 minutes) were applied with temperature-controlled chambers. We also tested the influence of prior local heating on the vasodilation induced by sodium nitroprusside (SNP), a donor of NO. Results: On reheating the same spot after two hours, the response of SkBF (i.e., plateau SkBF at 30 minutes minus SkBF at 34°C) was lower than during the first stimulation (mean±SD 404±212 perfusion units PU vs. 635±100 PU; P<0.001). There was no such difference when reheating after four hours (654±153 vs. 645±103 PU; P=NS). Two, but not four, hours after local heating, the response of SkBF to SNP was reduced. Conclusion: The NO-dependent hyperemic response induced by local heating in human skin is subject to desensitization. At least one part of the mechanism implicated consists of a desensitization to the effects of NO itself.
GATT Generalized system of preference (GSP) schemes - current voluntary and discretionary schemes - no obligation for developed countries to grant binding preferences - solutions to prevent the ...withdrawal of tariff preferences - binding preferences and qualifications - procedures for notification and negotiation - product and country exclusions - current legality of GSP exclusions.
Rats, like other crepuscular animals, have excellent auditory capacities and they discriminate well between different sounds Heffner HE, Heffner RS, Hearing in two cricetid rodents: wood rats (
...Neotoma floridana) and grasshopper mouse (
Onychomys leucogaster). J Comp Psychol 1985;99(3):275–88. However, most experimental literature concerning spatial orientation almost exclusively emphasizes the use of visual landmarks Cressant A, Muller RU, Poucet B. Failure of centrally placed objects to control the firing fields of hippocampal place cells. J Neurosci 1997;17(7):2531–42; and Goodridge JP, Taube JS. Preferential use of the landmark navigational system by head direction cells in rats. Behav Neurosci 1995;109(1):49–61. To address the important issue of whether rats are able to achieve a place navigation task relative to auditory beacons, we designed a place learning task in the water maze. We controlled cue availability by conducting the experiment in total darkness. Three auditory cues did not allow place navigation whereas three visual cues in the same positions did support place navigation. One auditory beacon directly associated with the goal location did not support taxon navigation (a beacon strategy allowing the animal to find the goal just by swimming toward the cue). Replacing the auditory beacons by one single visual beacon did support taxon navigation. A multimodal configuration of two auditory cues and one visual cue allowed correct place navigation. The deletion of the two auditory or of the one visual cue did disrupt the spatial performance. Thus rats can combine information from different sensory modalities to achieve a place navigation task. In particular, auditory cues support place navigation when associated with a visual one.
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