Multiple effects of nordihydroguaiaretic acid on ionic currents in rat isolated type I carotid body cells

1. The effects of the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) on the ionic currents of rat carotid body type I cells were investigated by use of whole-cell and outside-out patch clamp techniques. 2. NDGA (5-50 microM) produced a concentration-dependent inhibition of whole-cell K+ currents at all activating test potentials (holding potential -70 mV). The time-course of the inhibition was also concentration-dependent and the effects of NDGA were only reversible following brief periods of exposure (<2 min). Another lipoxygenase inhibitor, phenidone (5 microM), was without effect on whole-cell K+ currents in carotid body type I cells. 3. NDGA (5-50 microM) also inhibited whole-cell Ca2+ channel currents (recorded with Ba2+ as charge carrier) in a concentration-dependent manner. 4. Isolation of voltage-gated K+ channels by use of high [Mg2+] (6 mM), low [Ca2+] (0.1 mM) solutions revealed a direct inhibition of the voltage-sensitive component of the whole-cell K+ current by NDGA (50 microM). 5. In excised, outside-out patches NDGA (20-50 microM) increased large conductance, Ca2+ activated K+ channel activity approximately 10 fold, an effect which could be reversed by either tetraethylammonium (10 mM) or charybdotoxin (30 nM). 6. It is concluded that NDGA activates maxi-K+ channels in carotid body type I cells and over the same concentration range inhibits voltage-sensitive K+ and Ca2+ channels. The inhibition of whole cell K+ currents seen is most likely due to a combination of direct inhibition of the voltage-sensitive K+ current and indirect inhibition of maxi-K+ channel activity through blockade of Ca2+ channels.     

Radiometric Transfer: Example‐based Radiometric Linearization of Photographs

We present an example‐based approach for radiometrically linearizing photographs that takes as input a radiometrically linear exemplar image and a target regular uncalibrated image of the same scene, possibly from a different viewpoint and/or under different lighting. The output of our method is a radiometrically linearized version of the target image. Modeling the change in appearance of a small image patch seen from a different viewpoint and/or under different lighting as a linear 1D subspace, allows us to recast radiometric transfer in a form similar to classic radiometric calibration from exposure stacks. The resulting radiometric transfer method is lightweight and easy to implement. We demonstrate the accuracy and validity of our method on a variety of scenes.     

Autoxidation of methyl linolenate and methyl linoleate: The effect of α-tocopherol

α-Tocopherol substantially affects the distribution of peroxidic compounds formed during the autoxidation of methyl linolenate and methyl linoleate. In the autoxidation of both these unsaturated fatty acid esters the proportion of monohydroperoxides with conjugated double bonds in the trans, trans configuration is reduced until at high concentrations of α-tocopherol (5%) only cis, trans isomers are formed. In the autoxidation of methyl linolenate the proportion of hydroperoxy-epidioxides is reduced and only monohydroperoxides are formed when 5% α-tocopherol is present. The results are discussed in terms of recent findings concerning the mechanism of the autoxidation of unsaturated lipids.     

Recent observations on the occurrence of fishy flavour in bacon

An examination of reject bacon samples supplied directly from a factory showed that some samples described by a sensory panel as oily and fishy contained significantly higher levels of long chain polyunsaturated fatty acids (PUFA) in their fat than normal samples. When bacon samples obtained from retail outlets were similarly analysed and then subjected to sensory assessment, those found to contain long chain PUFA were given significantly higher scores for oily and fishy flavour. Observations on the fatty acid composition of fishy bacon samples as compared to non-fishy ones and further investigation into the diets of pigs producing suspect carcasses led to the conclusion that too high a content of fish products in the diet was the main cause of the problem. Contrary to what had been believed, fresh non-fishy bacon samples did not develop fishy flavour after storage at ?20°C for 15 weeks. Perceived fishiness was not related to total copper content as determined by atomic absorption spectroscopy.     

Hypoxia enhances [3H]noradrenaline release evoked by nicotinic receptor activation from the human neuroblastoma SH-SY5Y

We have used the human sympathetic neuronal line SH-SY5Y to investigate the effects of hypoxia on noradrenaline (NA) release evoked by either raised [K+]o (100 mM) or the nicotinic acetylcholine receptor (nAChR) agonist dimethylphenylpiperazinium iodide (DMPP). NA release was monitored by loading cells with [3H]NA and collecting effluent fractions from perfused cells kept in a sealed perifusion chamber. Cells were challenged twice with either stimulus and release was expressed as that evoked by the second challenge as a fraction of that evoked by the first. K+-evoked release was unaffected by hypoxia (PO2 approximately 30-38 mm Hg), but release evoked by DMPP was significantly increased. For both stimuli, replacement of Ca2+o with 1 mM EGTA abolished NA release. K+-evoked release was also dramatically reduced in the presence of 200 microM Cd2+ to block voltage-gated Ca2+ channels, but DMPP-evoked release was less affected. In hypoxia, DMPP-evoked Cd2+-resistant NA release was dramatically increased. Our findings indicate that hypoxia increases NA release evoked from SH-SY5Y cells in response to nAChR activation by increasing Ca2+ influx through the nAChR pore, or by activating an unidentified Cd2+-resistant Ca2+-influx pathway. As acetylcholine is the endogenous transmitter at sympathetic ganglia, these findings may have important implications for sympathetic activity under hypoxic conditions.     

The non-glyceride saponifiables of shea butter

Triterpene alcohols and sterols were found to be present in a commercial sample of shea butter (the seed fat of Butyrospermum parkii, Sapotaceae) as esters of both cinnamic and fatty acids. These non-glyceride saponifiables represented 6% by weight of the shea butter under study, whereas free triterpene alcohols and sterols accounted for only 1 % by weight. Cinnamic acid was found neither in the free form, nor esterified to glycerol. Saponification of the non-glyceride saponifiables yielded the triterpene alcohols α-amyrin, butyrospermol, lupeol, β-amyrin and germanicol as major components. Other alcohols identified were parked, 24-methylenelanost-9(11)-en-3-ol, dammaradienol, 24-methylenedammarenol and the two sterols α-spinasterol and Δ⁷-stigmastenol. Esterified to these alcohols were cinnamic (trans and cis), palmitic, stearic, oleic, linoleic and arachidic acids. The fatty acid composition of the non-glyceride saponifiables is different from that of the glycerides. No selectivity was observed in the esterification of these fatty acids by triterpene alcohols and sterols. Investigation of the products from acid catalysed transmethylation has led to two new experimental findings: (i) the difference in reaction rate of fatty acid and cinnamic acid esters and (ii) the formation of methoxylated artifacts from alcohols having unsaturation, in the C¹⁷ side chain, between C²⁴ and C²⁵ by the addition of methanol across the double bond. Analysis of the lipids extracted from shea kernels confirmed that the cinnamic acid esters were only present as non-glyceride saponifiables.     

Deterioration of sunflower seed oil under simulated frying conditions and during small-scale frying of potato chips

The changes occurring in sunflower seed oil under simulated frying conditions and during potato chip frying were monitored. The changes monitored were in: (a) fatty acid composition, (b) triglyceride content, (c) octanoate content, (d) titratable acidity, and (e) colour. To simulate frying conditions either argon or air, with or without steam, was bubbled through the hot oil. For the frying of potato chips, two methods of frying were used, viz continuous frying throughout 1 day and intermittent frying over a total of 10 days. It was found that whenever the hot oil was exposed to air, whether during simulated frying or the frying of potato chips, there was evidence of oxidative deterioration. Steam appeared to have an antioxidant effect in the simulated frying experiments. In all experiments the molar yield of acidity was comparable in magnitude with that of the octanoate. The correlation of octanoate production with the losses of linoleate and triglyceride is discussed.     

The Electronic Spectrum of Gaseous CoO in the Visible Region

Laser excitation spectra of gaseous CoO have been recorded using Doppler-limited intracavity spectroscopy and supersonic jet-cooled molecular beam methods. As seen in the molecular beam spectra there are nearly 100 bands arising from the X4Delta7/2 spin component of the ground state in the wavelength region 430-720 nm. All of them are very strongly red-degraded and most of them are perturbed. 59Co hyperfine broadenings or splittings have been observed in many. The bands can be arranged into five electronic transitions, together with a considerable number of "extra" bands induced by perturbations; two of the excited electronic states are 4Phi, while the other three, which lie within 1700 cm-1, are 4Delta. Semi-empirical calculations have been carried out for the 4Delta excited states, using exchange integrals transferred from the TiO and VO spectra; the predicted energies, spin-orbit structures, and relative intensities in absorption are consistent with the assignment of all three 4Delta states to the same electron configuration, (4ssigma)1(3ddelta)3(3dpi)2(3dsigma)1. It seems that there are extensive interactions between the excited 4Delta states, because only one of them gives rise to a recognizable, though irregular, long vibrational progression in absorption. The other two progressions die out abruptly and unexpectedly after three or four members, presumably as a result of interference effects; however, wavelength-resolved fluorescence studies, together with calculations of the Franck-Condon overlap integrals to the various vibrational levels of the ground state, show that the upper state progressions reappear following a region of confused absorption. All of the excited states show highly irregular variations of their vibrational intervals and rotational constants with the vibrational quantum number, v. The wavelength-resolved fluorescence spectra give evidence for new low-lying electronic states of CoO at 3038, 5989, and 9105 cm-1; based on its vibrational frequency the 3038 cm-1 state is possibly the sigmadelta4pi2 B4Sigma- state. Copyright 1997 Academic Press. Copyright 1997Academic Press     

An Adaptive BRDF Fitting Metric

We propose a novel image-driven fitting strategy for isotropic BRDFs. Whereas existing BRDF fitting methods minimize a cost function directly on the error between the fitted analytical BRDF and the measured isotropic BRDF samples, we also take into account the resulting material appearance in visualizations of the BRDF. This change of fitting paradigm improves the appearance reproduction fidelity, especially for analytical BRDF models that lack the expressiveness to reproduce the measured surface reflectance. We formulate BRDF fitting as a two-stage process that first generates a series of candidate BRDF fits based only on the BRDF error with measured BRDF samples. Next, from these candidates, we select the BRDF fit that minimizes the visual error. We demonstrate qualitatively and quantitatively improved fits for the Cook-Torrance and GGX microfacet BRDF models. Furthermore, we present an analysis of the BRDF fitting results, and show that the image-driven isotropic BRDF fits generalize well to other light conditions, and that depending on the measured material, a different weighting of errors with respect to the measured BRDF is necessary.     

Real-time rendering of deformable heterogeneous translucent objects using multiresolution splatting

In this paper, we present a novel real-time rendering algorithm for heterogenous translucent objects with deformable geometry. The proposed method starts by rendering the surface geometry in two separate geometry buffers—the irradiance buffer and the splatting buffer—with corresponding mipmaps from the lighting and viewing directions, respectively. Irradiance samples are selected from the irradiance buffer according to geometric and material properties using a novel and fast selection algorithm. Next, we gather the irradiance per visible surface point by splatting the irradiance samples to the splatting buffer. To compute the appearance of long-distance low-frequency subsurface scattering, as well as short-range detailed scattering, a fast novel multiresolution GPU algorithm is developed that computes everything on the fly and which does not require any precomputations. We illustrate the effectiveness of our method on several deformable geometries with measured heterogeneous translucent materials.