Photoluminescence studies of spray pyrolytically grown nanostructured tin oxide semiconductor thin films on glass substrates

SnO2 nanocrystalline thin films were deposited on glass substrates by the spray pyrolysis technique in air atmosphere at 375, 400, 425, 450 and 500 ◦C substrate temperatures. The obtained films were characterized by using XRD. The room temperature photoluminescence (PL) spectra of these films have near band edge (NBE) and deep level emission under the excitation of 325 nm radiation. NBE PL peak intensity decreased consistently with temperatures for samples prepared at 400, 450 and 500 ◦C, while a sudden reduction in intensity is observed for the sample prepared at 425 ◦C. A similar effect was observed for the optical transmittance spectra. These effects can be explained on the basis of the change in population of oxygen vacancies as indicated by the change in a values

Optimization of parameters of chemical spray pyrolysis technique to get n and p-type layers of SnS

SnS thin films were prepared using automated chemical spray pyrolysis (CSP) technique. Single-phase, p-type, stoichiometric, SnS films with direct band gap of 1.33 eV and having very high absorption coefficient (N105/cm) were deposited at substrate temperature of 375 °C. The role of substrate temperature in determining the optoelectronic and structural properties of SnS films was established and concentration ratios of anionic and cationic precursor solutions were optimized. n-type SnS samples were also prepared using CSP technique at the same substrate temperature of 375 °C, which facilitates sequential deposition of SnS homojunction. A comprehensive analysis of both types of films was done using x-ray diffraction, energy dispersive x-ray analysis, scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurements. Deposition temperatures required for growth of other binary sulfide phases of tin such as SnS2, Sn2S3 were also determined

Caracterització i revaloració de la fracció plasmàtica de la sang de porc procedent d'escorxadors industrials

La tesi s'ha estructurat en tres apartats que, en conjunt, han de permetre determinar les possibilitats d'aprofitament dins la mateixa indústria alimentària de la fracció plasmàtica de la sang de porc generada per escorxadors que utilitzen sistemes oberts de recollida higiènica. 1. En la primera part s'analitza la composició de la sang higiènica que s'està recollint actualment i s'estudien les característiques tant físico-químiques com microbiològiques que determinen la seva qualitat. La caracterització s'ha realitzat amb sang recollida en diferents escorxadors industrials de les comarques de Girona i s'ha centrat principalment en l'estudi de la contaminació microbiològica i el nivell d'hemòlisi de la sang. S'ha fet un disseny experimental que ha permès alhora valorar l'efecte d'alguns factors sobre la qualitat de la sang: possibles diferències relacionades amb (1) la climatologia del període de l'any en el qual es fa la recollida, (2) particularitats dels escorxadors (grandària, sistemes de dessagnat, tipus, dosi i sistema de dosificació de l'anticoagulant, condicions de processament, maneig i emmagatzematge després de la recollida, etc.). Els resultats obtinguts ens permeten constatar que, en les condicions actuals, la sang que s'està recollint en els escorxadors estudiats no es pot considerar adequada per a una matèria primera de productes destinats a alimentació humana. La major part de la microbiota contaminant s'adquireix en el propi sagnador. S'ha constatat que el sistema de dessagnat en posició horitzontal podria ser una mesura útil per minimitzar la contaminació d'origen fecal o provinent de la pell de l'animal sacrificat i que la separació immediata de les fraccions en el propi escorxador també pot contribuir a reduir la contaminació. Així doncs, en el benentès que l'efectivitat pot obtenir-se del conjunt de mesures preses, més que de l'aplicació d'una sola d'elles, es suggereix la introducció d'una sèrie d'actuacions que potser permetrien reduir els nivells de contaminació que s'obtenen actualment. El tractament mecànic de la sang, el sistema d'addició d'anticoagulant, el volum i concentració de la solució anticoagulant afegida i el període d'emmagatzematge són els factors responsables de l'hemòlisi; mentre que nivells elevats de contaminació microbiològica i el tipus d'anticoagulant utilitzat deterrminen la velocitat d'increment de l'hemòlisi de sang refrigerada. S'ha constatat que quan la sang no pot ser processada immediatament i s'ha d'emmagatzemar en refrigeració és millor utilitzar citrat sòdic enlloc de polifosfat com a anticoagulant ja que l'increment d'hemòlisi es dóna més lentament. 2. El segon apartat s'ha centrat en la fracció plasmàtica de la sang. S'ha utilitzat la deshidratació per atomització com a tecnologia de conservació del plasma i s'ha fet una caracterització del producte en pols resultant des del punt de vista de composició i qualitat. A més de la contaminació microbiològica, que determina la qualitat higiènico-sanitària del producte, s'ha realitzat un estudi de les propietats funcionals que podrien fer del plasma un producte útil en la formulació d'aliments (capacitat escumant, emulsionant, gelificant). S'ha fet especial incidència en (1) determinar l'efecte del procés tecnològic de deshidratació sobre la funcionalitat del producte i (2) estudiar l'estabilitat del plasma deshidratat durant el període d'emmagatzematge. En les condicions de deshidratació per atomització aplicades no es provoca desnaturalització de la fracció proteica i s'obté un producte suficientment deshidratat, amb una aw<0,4 per permetre suposar una bona estabilitat. Algunes mostres de plasma deshidratat analitzades presenten nivells detectables de determinats residus (sulfonamides i corticosteroides). La qualitat microbiològica del producte en pols reflecteix l'elevada contaminació que contenia la matèria primera utilitzada, tot i que la deshidratació per atomització ha comportat la reducció en una unitat logarítmica de la càrrega contaminant. Els recomptes generals de microorganismes són encara preocupants i més tenint en compte que s'ha evidenciat la presència de toxines estafilocòciques en algunes mostres. L'avaluació de les propietats funcionals del producte deshidratat en relació a les que presentava el plasma líquid ens ha permès comprovar que: (1) El procés de deshidratació no ha afectat la solubilitat de les proteïnes. Això, junt amb el fet que no s'obtinguin diferències significatives en l'anàlisi calorimètrica de mostres líquides o deshidratades, permet concloure que el procés no provoca desnaturalització proteica. (2) No s'observen efectes negatius del procés tecnològic sobre la capacitat escumant ni en l'activitat emulsionant de les proteïnes plasmàtiques, dues propietats funcionals que possibiliten l'aplicació del plasma amb aquestes finalitats en l'elaboració d'alguns aliments. (3) La deshidratació tampoc perjudica de manera important les característiques dels gels que s'obtenen per escalfament, ja que els gels obtinguts a partir del plasma líquid i del plasma deshidratat presenten la mateixa capacitat de retenció d'aigua i no s'observen diferències en la microestructura de la xarxa proteica d'ambdós tipus de gel. Tanmateix, els que s'obtenen a partir del producte en pols mostren una menor resistència a la penetració. L'estudi d'estabilitat ens ha permès comprovar que la mostra de plasma deshidratat per atomització perd algunes de les seves propietats funcionals (facilitat de rehidratació, capacitat de retenció d'aigua i fermesa dels gels) si s'emmagatzema a temperatura ambient, mentre que aquestes característiques es mantenen un mínim de sis mesos quan el producte en pols es conserva a temperatura de refrigeració. 3. En l'última part, tenint en compte les conclusions derivades dels resultats dels apartats anteriors, s'han assajat tres possibles sistemes de reducció de la contaminació aplicables a la fracció plasmàtica com a pas previ a la deshidratació, per tal de millorar les característiques de qualitat microbiològica i les perspectives d'estabilitat del producte durant l'emmagatzematge. S'ha determinat l'eficàcia, i l'efecte sobre les propietats del plasma deshidratat, que poden tenir tractaments d'higienització basats en la centrifugació, la microfiltració tangencial i l'aplicació d'altes pressions. Els tractaments de bactofugació aplicats permeten reduir entre el 96 i el 98% la contaminació microbiana del plasma. Aquesta reducció s'aconsegueix tant amb un sistema discontinu com amb un sistema continu treballant a una velocitat de 12 L/h, fet que permetria adaptar el tractament de bactofugació a un procés de producció industrial. Un sistema combinat de bactofugació en continu i microfiltració tangencial permet incrementar l'eficàcia fins a un 99,9 % de reducció. Cal tenir present, però, que aquest tractament provoca també una disminució de l'extracte sec que afecta negativament les propietats funcionals del plasma líquid. Malgrat suposar una pèrdua pel que fa al rendiment, aquest efecte negatiu sobre la funcionalitat no suposaria cap inconvenient si s'utilitzés la deshidratació com a tecnologia de conservació del plasma, ja que es podria corregir l'extracte sec durant la reconstitució del producte. Caldria avaluar si la millora en la qualitat higiènico-sanitària del producte compensa o no les pèrdues que suposa aquest sistema d'higienització combinat. Amb relació als tractaments d'alta pressió, de totes les condicions de tractament assajades, les pressions de fins 450 MPa permeten obtenir plasma sense modificacions importants que impedeixin la seva deshidratació per atomització. Així doncs, les condicions de procés que s'han aplicat són pressuritzacions a 450 MPa de 15 minuts de durada. La temperatura de tractament que s'ha mostrat més eficaç en la reducció dels recomptes de microorganismes ha estat de 40ºC. Els tractaments a aquesta temperatura permeten assolir reduccions del 99,97% i disminuir en un 80% la capacitat de creixement dels microorganismes supervivents a la pressurització en relació a la que presentava la població contaminant del plasma abans del tractament. L'estudi de l'efecte d'aquest tractament (450 MPa, 15 min i 40ºC) sobre les propietats funcionals del plasma ha permès observar que la pressurització comporta una disminució en la solubilitat del producte però una millora en les propietats de superfície -estabilitat de l'escuma i activitat emulsionant- i un increment de la capacitat de retenció d'aigua i de la duresa dels gels obtinguts per escalfament. Calen més estudis per confirmar i caracteritzar aquesta millora en la funcionalitat, així com per establir si el tractament de pressurització afecta també l'estabilitat del producte durant l'emmagatzematge. De totes les tecnologies d'higienització assajades, l'alta pressió és la que permet obtenir millors resultats en el sentit de poder garantir un producte de bona qualitat microbiològica i segur, des del punt de vista sanitari i tecnològic, per a la seva utilització com a ingredient alimentari.

Tumour necrosis factor alpha induces rapid reduction in AMPA receptor-mediated calcium entry in motor neurones by increasing cell surface expression of the GluR2 subunit: relevance to neurodegeneration

The AMPA receptor (AMPAR) subunit GluR2, which regulates excitotoxicity and the inflammatory cytokine tumour necrosis factor alpha (TNF alpha) have both been implicated in motor neurone vulnerability in Amyotrophic Lateral Sclerosis/Motor Neurone Disease. TNF alpha has been reported to increase cell surface expression of AMPAR subunits to increase synaptic strength and enhance excitotoxicity, but whether this mechanism occurs in motor neurones is unknown. We used primary cultures of mouse motor neurones and cortical neurones to examine the interaction between TNF alpha receptor activation, GluR2 availability, AMPAR-mediated calcium entry and susceptibility to excitotoxicity. Short exposure to a physiologically relevant concentration of TNFalpha (10 ng/ml, 15 min) caused a marked redistribution of both GluR1 and GluR2 to the cell surface as determined by cell surface biotinylation and immunofluorescence. Using Fura-2 AM microfluorimetry we showed that exposure to TNFalpha caused a rapid reduction in the peak amplitude of AMPA-mediated calcium entry in a PI3-kinase and p38 kinase-dependent manner, consistent with increased insertion of GluR2-containing AMPAR into the plasma membrane. This resulted in a protection of motor neurones against kainate-induced cell death. Our data therefore, suggests that TNF alpha acts primarily as a physiological regulator of synaptic activity in motor neurones rather than a pathological drive in ALS

Reduction of arsenic uptake by lettuce with ferrous sulfate applied to contaminated soil

Soil contamination by arsenic (As) presents a hazard in many countries and there is a need for techniques to minimize As uptake by plants. A proposed in situ remediation method was tested by growing lettuce (Lactuca sativa L. cv. Kermit) in a greenhouse pot experiment on soil that contained 577 mg As kg(-1), taken from a former As smelter site. All combinations of iron (Fe) oxides, at concentrations of 0.00, 0.22, 0.54, and 1.09% (w/w), and lime, at concentrations of 0.00, 0.27, 0.68, and 1.36% (w/w), were tested in a factorial design. To create the treatments, field-moist soil, commercial-grade FeSO4, and ground agricultural lime were mixed and stored for one week, allowing Fe oxides to precipitate. Iron oxides gave highly significant (P < 0.001) reductions in lettuce As concentrations, down to 11% of the lettuce As concentration for untreated soil. For the Fe oxides and lime treatment combinations where soil pH was maintained nearly constant, the lettuce As concentration declined in an exponential relationship with increasing FeSO4 application rate and lettuce yield was almost unchanged. Iron oxides applied at a concentration of 1.09% did not give significantly lower lettuce As concentrations than the 0.54% treatment. Simultaneous addition of lime with FeSO4 was essential. Ferrous sulfate with insufficient lime lowered soil pH and caused mobilization of Al, Ba, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn. At the highest Fe oxide to lime ratios, Mn toxicity caused severe yield loss.

Uneven distribution of nutrients in the root zone affects the incidence of blossom end rot and concentration of calcium and potassium in fruits of tomato

Tomato plants ( Lycopersicon esculentum Mill. var. DRK) were grown hydroponically to determine the effect of an uneven distribution of nutrients in the root zone on blossomend rot (BER) and Ca and K concentrations in the fruits. The plants were grown in rockwool with their root system divided into two portions. Each portion was irrigated with nutrient solutions with either the same or the different electrical conductivity (EC) in the range 0 to 6 dS m(-1). Solutions with high EC supplied to both sides of the root system significantly increased the incidence of BER. However, when only water or a solution of low EC was supplied to one portion, BER was reduced by 80%. Fruit yields were significantly higher ( P < 0.01) for plants that received solutions of the uneven EC treatments (6/0 or 4.5/0 EC treatment). Plants supplied with solutions of uneven EC generally had higher leaf and fruit concentrations of Ca but lower concentrations of K than those supplied with solutions of high EC. There was no difference in Ca concentration at the distal end of young fruits of the uneven EC treatment but it was reduced in the high EC treatments. The concentration of K in the mature fruits of the uneven EC treatments was lower than that of the high EC treatments and higher or similar that of the 3/3 or 2.5/2.5 EC treatments ( controls). A clear relationship was found between the incidence of BER and the exudation rate. High rate of xylem exudation was observed in the uneven EC treatments. Reduction of BER in the uneven EC treatments is most likely to be the effect of high exudation rate on Ca status in the young fruits. It was concluded that high EC of solution had positive effects on Ca concentration and incidence of BER provided that nutrient solution with low EC or water is supplied to the one portion of the root system.

Reduction of arsenic uptake by lettuce with ferrous sulfate applied to contaminated soil

Soil contamination by arsenic (As) presents a hazard in many countries and there is a need for techniques to minimize As uptake by plants. A proposed in situ remediation method was tested by growing lettuce (Lactuca sativa L. cv. Kermit) in a greenhouse pot experiment on soil that contained 577 mg As kg(-1), taken from a former As smelter site. All combinations of iron (Fe) oxides, at concentrations of 0.00, 0.22, 0.54, and 1.09% (w/w), and lime, at concentrations of 0.00, 0.27, 0.68, and 1.36% (w/w), were tested in a factorial design. To create the treatments, field-moist soil, commercial-grade FeSO4, and ground agricultural lime were mixed and stored for one week, allowing Fe oxides to precipitate. Iron oxides gave highly significant (P < 0.001) reductions in lettuce As concentrations, down to 11% of the lettuce As concentration for untreated soil. For the Fe oxides and lime treatment combinations where soil pH was maintained nearly constant, the lettuce As concentration declined in an exponential relationship with increasing FeSO4 application rate and lettuce yield was almost unchanged. Iron oxides applied at a concentration of 1.09% did not give significantly lower lettuce As concentrations than the 0.54% treatment. Simultaneous addition of lime with FeSO4 was essential. Ferrous sulfate with insufficient lime lowered soil pH and caused mobilization of Al, Ba, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn. At the highest Fe oxide to lime ratios, Mn toxicity caused severe yield loss.

Carbon dioxide induced stomatal closure increases radiative forcing of climate via a rapid reduction in low cloud

We performed an ensemble of twelve five-year experiments using a coupled climate-carbon-cycle model with scenarios of prescribed atmospheric carbon dioxide concentration; CO2 was instantaneously doubled or quadrupled at the start of the experiments. Within these five years, climate feedback is not significantly influenced by the effects of climate change on the carbon system. However, rapid changes take place, within much less than a year, due to the physiological effect of CO2 on plant stomatal conductance, leading to adjustment in the shortwave cloud radiative effect over land, due to a reduction in low cloud cover. This causes a 10% enhancement to the radiative forcing due to CO2, which leads to an increase in the equilibrium warming of 0.4 and 0.7 K for doubling and quadrupling. The implications for calibration of energy-balance models are discussed.

The influence of commercial film-forming polymers on reducing salt spray injury in evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.)

A field trial was undertaken to determine the influence of four commercially available film-forming polymers (Bond [alkyl phenyl hydroxyl polyoxyethylene], Newman Crop Spray 11E™ [paraffinic oil], Nu-Film P [poly-1-p menthene], and Spray Gard [di-1-p menthene]) on reducing salt spray injury on two woody species, evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.). Irrespective of species, the film-forming polymers Nu-Film-P and Spay Gard did not provide any significant degree of protection against salt spray damage irrespective of concentration (1% or 2%) applied as measured by leaf chlorophyll concentrations, photosynthetic efficiency, visual leaf necrosis, foliar sodium and chloride content, and growth (height, leaf area). The film-forming polymer Newman Crop Spray 11E™ provided only 1-week protection against salt spray injury. The film-forming polymer Bond provided a significant (P < 0.05) degree of protection against salt spray injury 3 months after application as manifest by higher leaf chlorophyll content, photosynthetic efficiency, height and leaf area, and lower visual leaf necrosis and foliar Na and Cl content compared with nontreated controls. In conclusion, results indicate that application of a suitable film-forming polymer can provide a significant degree of protection of up to 3 months against salt spray injury in evergreen oak and laurel. Results also indicate that when applied at 1% or 2% solutions, no problems associated with phytotoxicity and rapid degradation on the leaf surface exist.

Anthraquinone catalysis in the glucose-driven reduction of indigo to leuco-indigo

Anthraquinone immobilised onto the surface of indigo microcrystals enhances the reductive dissolution of indigo to leuco-indigo. Indigo reduction is driven by glucose in aqueous NaOH and a vibrating gold disc electrode is employed to monitor the increasing leuco-indigo concentration with time. Anthraquinone introduces a strong catalytic effect which is explained by invoking a molecular "wedge effect'' during co-intercalation of Na+ and anthraquinone into the layered indigo crystal structure. The glucose-driven indigo reduction, which is in effective in 0.1 M NaOH at 65 degrees C, becomes facile and goes to completion in the presence of anthraquinone catalyst. Electron microscopy of indigo crystals before and after reductive dissolution confirms a delamination mechanism initiated at the edges of the plate-like indigo crystals. Catalysis occurs when the anthraquinone-indigo mixture reaches a molar ratio of 1:400 (at 65 degrees C; corresponding to 3 mu M anthraquinone) with excess of anthraquinone having virtually no effect. A strong temperature effect ( with a composite E-A approximate to 120 kJ mol(-1)) is observed for the reductive dissolution in the presence of anthraquinone. The molar ratio and temperature effects are both consistent with the heterogeneous nature of the anthraquinone catalysis in the aqueous reaction mixture.

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

Electrochemical determination of redox active dye species is demonstrated in indigo samples contaminated with high levels of organic and inorganic impurities. The use of a hydrodynamic electrode system based on a vibrating probe (250 Hz, 200 mu m lateral amplitude) allows time-independent diffusion controlled signals to be enhanced and reliable concentration data to be obtained under steady state conditions at relatively fast scan rates up to 4 V s-1In this work the indigo content of a complex plant-derived indigo sample (dye content typically 30%) is determined after indigo is reduced by addition of glucose in aqueous 0.2 M NaOH. The soluble leuco-indigo is measured by its oxidation response at a vibrating electrode. The vibrating electrode, which consisted of a laterally vibrating 500 mu m diameter gold disc, is calibrated with Fe(CN)(6) 3-/4- in 0.1 M KCl and employed for indigo determination at 55, 65, and 75 C in 0.2 M NaOH. Determinations of the indigo content of 25 different samples of plant-derived indigo are compared with those obtained by conventional spectrophotometry. This comparison suggests a significant improvement by the electrochemical method, which appears to be less sensitive to impurities.

Electrochemical and sonoelectrochemical monitoring of indigo reduction by glucose

The reduction of indigo (dispersed in water) to leuco-indigo (dissolved in water) is an important industrial process and investigated here for the case of glucose as an environmentally benign reducing agent. In order to quantitatively follow the formation of leuco-indigo two approaches based on (i) rotating disk voltammetry and (ii) sonovoltammetry are developed. Leuco-indigo, once formed in alkaline solution, is readily monitored at a glassy carbon electrode in the mass transport limit employing hydrodynamic voltammetry. The presence of power ultrasound further improves the leuco-indigo determination due to additional agitation and homogenization effects. While inactive at room temperature, glucose readily reduces indigo in alkaline media at 65 degrees C. In the presence of excess glucose, a surface dissolution kinetics limited process is proposed following the rate law d eta(leuco-indigo)/dt = k x c(OH-) x S-indigo where eta(leuco-indigo) is the amount of leuco-indigo formed, k = 4.1 x 10(-9) m s(-1) (at 65 degrees C, assuming spherical particles of I gm diameter) is the heterogeneous dissolution rate constant,c(OH-) is the concentration of hydroxide, and Sindigo is the reactive surface area. The activation energy for this process in aqueous 0.2 M NaOH is E-A = 64 U mol(-1) consistent with a considerable temperature effects. The redox mediator 1,8-dihydroxyanthraquinone is shown to significantly enhance the reaction rate by catalysing the electron transfer between glucose and solid indigo particles. (c) 2006 Elsevier Ltd. All fights reserved.

Uneven distribution of nutrients in the root zone affects the incidence of blossom end rot and concentration of calcium and potassium in fruits of tomato

Tomato plants ( Lycopersicon esculentum Mill. var. DRK) were grown hydroponically to determine the effect of an uneven distribution of nutrients in the root zone on blossomend rot (BER) and Ca and K concentrations in the fruits. The plants were grown in rockwool with their root system divided into two portions. Each portion was irrigated with nutrient solutions with either the same or the different electrical conductivity (EC) in the range 0 to 6 dS m(-1). Solutions with high EC supplied to both sides of the root system significantly increased the incidence of BER. However, when only water or a solution of low EC was supplied to one portion, BER was reduced by 80%. Fruit yields were significantly higher ( P < 0.01) for plants that received solutions of the uneven EC treatments (6/0 or 4.5/0 EC treatment). Plants supplied with solutions of uneven EC generally had higher leaf and fruit concentrations of Ca but lower concentrations of K than those supplied with solutions of high EC. There was no difference in Ca concentration at the distal end of young fruits of the uneven EC treatment but it was reduced in the high EC treatments. The concentration of K in the mature fruits of the uneven EC treatments was lower than that of the high EC treatments and higher or similar that of the 3/3 or 2.5/2.5 EC treatments ( controls). A clear relationship was found between the incidence of BER and the exudation rate. High rate of xylem exudation was observed in the uneven EC treatments. Reduction of BER in the uneven EC treatments is most likely to be the effect of high exudation rate on Ca status in the young fruits. It was concluded that high EC of solution had positive effects on Ca concentration and incidence of BER provided that nutrient solution with low EC or water is supplied to the one portion of the root system.

Increased n-6 polyunsaturated fatty acids do not attenuate the effects of long-chain n-3 polyunsaturated fatty acids on insulin sensitivity or triacylglycerol reduction in Indian Asians

Background: Indian Asians in Western countries have a higher rate of coronary artery disease than do the indigenous white populations, and this higher rate may be influenced by a dietary imbalance of n-6 and n-3 polyunsaturated fatty acids (PUFAs). Objective: The objective of the study was to test the hypothesis that a high background dietary intake of n-6 PUFA attenuates the effects of fish-oil supplementation on insulin sensitivity and associated blood lipids of the metabolic syndrome. Design: Twenty-nine Indian Asian men were recruited to participate in a 12-wk dietary intervention trial. Volunteers were randomly assigned to receive either a moderate or a high n-6 PUFA diet featuring modified oils and spreads over a 6-wk period. After this 6-wk period, both groups were supplemented with 4.0 g fish oil/d (2.5 g eicosapentaenoic acid + docosahexaenoic acid) for an additional 6 wk in combination with the dietary treatment. Volunteers participated in a postprandial study and an insulin sensitivity test after the 6-wk dietary intervention and again after the fish-oil supplementation period. Results: There was no significant time X treatment interaction for blood lipids or insulin action after dietary intervention with the moderate or high n-6 PUFA diets in combination with fish oil. After the 6-wk period of fish oil supplementation, fasting and postprandial plasma triacylglycerol concentrations decreased significantly. Conclusion: The background dietary n-6 PUFA concentration did not modulate the effect of fish-oil supplementation on blood lipids or measures of insulin sensitivity in this ethnic group.

Cholesterol reduction using manufactured foods high in monounsaturated fatty acids: a randomized crossover study

In two separate studies, the cholesterol-lowering efficacy of a diet high in monounsaturated fatty acids (MUFA) was evaluated by means of a randomized crossover trial. In both studies subjects were randomized to receive either a high-MUFA diet or the control diet first, which they followed for a period of 8 weeks; following a washout period of 4–6 weeks they were transferred onto the opposing diet for a further period of 8 weeks. In one study subjects were healthy middle-aged men (n 30), and in the other they were young men (n 23) with a family history of CHD recruited from two centres (Guildford and Dublin). The two studies were conducted over the same time period using identical foods and study designs. Subjects consumed 38% energy as fat, with 18% energy as MUFA and 10% as saturated fatty acids (MUFA diet), or 13% energy as MUFA and 16% as saturated fatty acids (control diet). The polyunsaturated fatty acid content of each diet was 7%. The diets were achieved by providing subjects with manufactured foods such as spreads, ‘ready meals’, biscuits, puddings and breads, which, apart from their fatty acid compositions, were identical for both diets. Subjects were blind to which of the diets they were following on both arms of the study. Weight changes on the diets were less than 1 kg. In the groups combined (n 53) mean total and LDL-cholesterol levels were significantly lower at the end of the MUFA diet than the control diet by 0×29 (SD 0×61) mmol/l (P,0×001) and 0×38 (SD 0×64) mmol/l (P, 0×0001) respectively. In middle-aged men these differences were due to a mean reduction in LDL-cholesterol of ¹11 (SD 12) % on the MUFA diet with no change on the control diet (¹1×1 (SD 10) %). In young men the differences were due to an increase in LDL-cholesterol concentration on the control diet of þ6×2 (SD 13) % and a decrease on the MUFA diet of ¹7×8 (SD 20) %. Differences in the responses of middle-aged and young men to the two diets did not appear to be due to differences in their habitual baseline diets which were generally similar, but appeared to reflect the lower baseline cholesterol concentrations in the younger men. There was a moderately strong and statistically significant inverse correlation between the change in LDLcholesterol concentration on each diet and the baseline fasting LDL-cholesterol concentration (r¹0×49; P,0×0005). In conclusion, diets in which saturated fat is partially replaced by MUFA can achieve significant reductions in total and LDL-cholesterol concentrations, even when total fat and energy intakes are maintained. The dietary approach used to alter fatty acid intakes would be appropriate for achieving reductions in saturated fat intakes in whole populations.