Acid Concentration Ratio Research Articles

Changes in the zirconium local surrounding on ligand substitution in solutions

EXAFS and SAXS methods have been used to examine zirconium hydroxide and oxychloride aqueous solutions in the presence of sulfuric acid in a wide range of concentrations, as well as a zirconium sulfate aqueous solution. The structure of the complexes and their transformation regularities were determined. Structures of the given complexes and structures of zirconium hydroxide and zirconium oxychloride and hydroxide complexes in aqueous solutions were compared. Complexes in zirconium hydroxide and oxychloride aqueous solutions have identical structures in the presence of sulfuric acid. When the concentration ratio of sulfuric acid and the initial compound is low (20–30), the complex is an open trimer with zirconium atoms bonded by sulfate groups. Bridge sulfate groups form Zr-O-S-O-Zr bonds. Apart from the bridge sulfate groups, there are three terminal sulfate groups and three terminal hydroxyl groups for each zirconium atom. When the concentration of sulfuric acid is increased (up to a ratio of 40–100), closed trimers are observed in the solution.

A novel wet-etching method using joint proton source in LiNbO/sub 3/

By mixing benzoic and adipic acids as the source of proton exchange, wet etched ridge waveguides are fabricated in Z-cut LiNbO3. Under appropriate adipic-benzoic acid concentration ratios, the joint proton source can suppress the proton diffusion in the lateral directions, and thus, the sidewalls are much more vertical than the usual. The etched depths are also enhanced for more than 30%. And meanwhile, the fabricated ridge waveguides possess smooth surfaces and the scattering losses are lower than that of the conventionally produced samples

Electrospun PLGA nanofiber scaffolds for articular cartilage reconstruction: mechanical stability, degradation and cellular responses under mechanical stimulation in vitro

We investigated the potential of a nanofiber-based poly(DL-lactide-co-glycolide) (PLGA) scaffold to be used for cartilage reconstruction. The mechanical properties of the nanofiber scaffold, degradation of the scaffold and cellular responses to the scaffold under mechanical stimulation were studied. Three different types of scaffold (lactic acid/glycolic acid content ratio = 75 : 25, 50 : 50, or a blend of 75 : 25 and 50 : 50) were tested. The tensile modulus, ultimate tensile stress and corresponding strain of the scaffolds were similar to those of skin and were slightly lower than those of human cartilage. This suggested that the nanofiber scaffold was sufficiently mechanically stable to withstand implantation and to support regenerated cartilage. The 50 : 50 PLGA scaffold was degraded faster than 75 : 25 PLGA, probably due to the higher hydrophilic glycolic acid content in the former. The nanofiber scaffold was degraded faster than a block-type scaffold that had a similar molecular weight. Therefore, degradation of the scaffold depended on the lactic acid/glycolic acid content ratio and might be controlled by mixing ratio of blend PLGA. Cellular responses were evaluated by examining toxicity, cell proliferation and extracellular matrix (ECM) formation using freshly isolated chondrocytes from porcine articular cartilage. The scaffolds were non-toxic, and cell proliferation and ECM formation in nanofiber scaffolds were superior to those in membrane-type scaffolds. Intermittent hydrostatic pressure applied to cell-seeded nanofiber scaffolds increased chondrocyte proliferation and ECM formation. In conclusion, our nanofiber-based PLGA scaffold has the potential to be used for cartilage reconstruction.

Capillary electrophoresis in N,N‐dimethylformamide

N,N-Dimethylformamide (DMF) is a dipolar protophilic solvent with physicochemical properties that makes it suitable as solvent for capillary electrophoresis (CE). It is prerequisite for the proper application of CE to adjust and to change the pH of the background electrolyte (BGE) in a defined manner. This was done in the present work using benzoic acid-benzoate by selecting different concentration ratios of acid and salt, and calculating the theoretical pH from the activity-corrected Henderson-Hasselbalch equation. The mobilities of the analytes (chloro- and nitro-substituted phenolates) were found to follow reasonably well the typical sigmoid mobility versus pH curve as predicted by theory. The actual mobilities and pK(a) values (at 25 degrees C) of the analytes were derived from these curves. pK(a) values were in the range of 11.1-11.7, being thus 3-4.4 units higher than in water. This pK(a) shift is caused by the destabilization of the analyte anion and the better stability (solubility) of the molecular analyte acid in DMF, which overcome the higher basicity of DMF compared to water. Absolute mobilities were calculated from the actual mobilities; they were between 32x10(-9) and 42x10(-9) m(2)/Vxs. Slight deviations of the measured mobilities from the theoretical mobility versus pH curve were discussed on the bases of ion pairing and heteroconjugation and homoconjugation of either buffer components or buffer components and analytes. Heteroconjugation was used as a mechanism for the electrically driven separation of neutral analyte molecules in a BGE where salicylate acted as complex forming ion. Rough estimation of the complexation constants for the phenolic analytes gave values in the range of 100-200 L/mol. Addition of water to the solvent decreased the effect of heteroconjugation, but it was still present up to the surprisingly high concentration of 20% water. Electrophoretically relevant parameters like ionic mobilities and pK(a) values, and conjugation and ion pairing are dependent on the water content of the solvent. The water uptake of DMF was measured when exposed to humidity of ambient air. The resulted behavior of the water uptake was found rather similar to that for acetonitrile and methanol.

Simultaneous Determination of Copper and Bismuth by Anodic Stripping Voltammetry Using H‐Point Standard Addition Method with Simultaneous Addition of Analytes

AbstractSimultaneous determination of bismuth and copper by anodic stripping voltammetry using H‐point standard addition method (HPSAM) with simultaneous addition of analytes is described. The effect of various parameters including acid concentration, accumulation time, accumulation potential and concentration ratio of analytes in the standard solution on the sensitivity and accuracy of method were investigated. The results of applying the H‐point standard addition method showed that Cu2+ and Bi3+ could be determined simultaneously with the concentration ratios of Cu2+ to Bi3+ varying from 1 : 15 to 16 : 1 in the mixed sample. The method was successfully applied to the simultaneous determination of copper and bismuth in some synthetic mixtures.

Altered Brain Penetration of Diclofenac and Mefenamic Acid, but Not Acetaminophen, in Shiga-Like Toxin II-Treated Mice

It is well accepted that bacterial and virus infections elevate the levels of cytokines in serum and cerebrospinal fluids. Such high levels of cytokines might alter the integrity of the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCSFB), subsequently affecting brain penetration of drugs. However, few reports have addressed this issue. Thus, we investigated brain penetration of cyclooxygenase (COX) inhibitors, commonly used as antipyretics, in mice treated with Shiga-like toxin II (SLT-II) derived from E. coli O157:H7, which significantly elevates cytokine levels. As antipyretics, we used diclofenac, mefenamic acid, and acetaminophen. We found that SLT-II significantly increased the brain-to-plasma concentration ratio (Kp) of diclofenac and mefenamic acid, but not of acetaminophen. Moreover, the Kp of diclofenac and mefenamic acid was increased by probenecid, an anionic compound. These results suggest that efflux anion transporters might be involved in the transport of diclofenac and mefenamic acid. Western blot analysis revealed that SLT-II decreased the expression of organic anion transporter-3, an efflux transporter located on the BBB and/or BCSFB. Taken together, these results suggest that SLT-II and/or SLT-II-stimulated cytokines might change brain penetration of drugs and could possibly increase the risk of their side-effects by altering the expression of transporters.

Vesicles in fatty acid salt–fatty acid stabilized o/w emulsion—emulsion structure and rheology

Texture and rheology properties of fatty acid salt-fatty acid mixture stabilized oil–water (o/w) emulsions are being explored. While NaOH solution was introduced as aqueous phase, oil phase contained in it dissolved lauric acid. When these oil and water phases are brought in contact, a portion of lauric acid transforms into sodium laurate in situ via acid–base reaction, the combination of which at a certain threshold concentration and above is believed to act as emulsifier in stabilizing the given o/w emulsion system. Light microscopy under cross polarizing conditions suggested that in addition to the formation of surfactant stabilized emulsion droplets, formation of molecular aggregates of vesicle type is imminent in these conditions, both the size and number density of which is found to be a function of emulsifier concentration ratio. The concentration of emulsifier (sodium laurate–lauric acid) is being assessed in this work indirectly as a function of NaOH concentration, due to the problem associated with its quantification. Non or a very small number of vesicles was observed at NaOH concentration below 0.4 M, whilst in the presence of 0.4–0.8 M NaOH the vesicle population increased substantially. While vesicle population density decreased past 0.8 M NaOH, their size increased with NaOH concentration from 0.8 to 1 M. These observations suggested that sodium laurate–lauric acid concentration ratio that corresponds to 0.6–0.8 M NaOH is the optimum NaOH concentration at which maximum vesicle number density is observed. As far as rheology properties are concerned, at any given γ ̇ , in the absence of NaOH, the η of the oil solubilized lauric acid was found to be much lower than the η of corresponding sodium laurate–lauric acid stabilized o/w emulsion. Though η( γ ̇ ) profiles of sodium laurate–lauric acid stabilized o/w emulsion was not a linear function under the given sets of experimental conditions, at all conditions η strongly depended on sodium laurate–lauric acid concentrations (concentration of NaOH in this case). What more is that at any given γ ̇ , the η was observed to be maximum at sodium laurate–lauric acid concentration ratio that corresponded to 0.8 M NaOH, a situation which corresponds to the presence of the maximum vesicle number density. In addition to η, in the presence of 0.8 M NaOH, higher values of σ Y was observed, implying that at this particular NaOH concentration these emulsions possessed greater degree of emulsion structuring compared to other NaOH concentrations. These observations lead to the conclusion that sodium laurate concentration plays a great role in the formation of fatty acid salt vesicles, that under the given set of conditions sodium laurate–lauric acid concentration corresponding to 0.8 M NaOH is the optimum concentration at which maximum number of vesicles are produced, and that rheology property of these emulsions depend not only on emulsion droplets but also on the vesicle number density and size. Test on oscillatory shear mode also suggested that much like o/w emulsions stabilized with other type surfactant, the viscoelastic properties of these sodium laurate–lauric acid stabilized o/w emulsions depended highly on surfactant concentration. The fact that G″ response was dominant over G′ response at all measured frequency and sodium laurate–lauric acid concentration, it is evident that viscous property dominated over elastic property in these emulsion. The good news is that improved elastic property is observed at sodium laurate–lauric acid concentration that corresponded to 0.6–0.8 M NaOH. And not only, in the presence of 0.8 M NaOH, while G″ response of these samples was dominant over G′ response at low ϖ domain, the dynamic moduli crossed-over at around 2 Hz, past which the G′ response became dominant over G″. This implies that, at this particular surfactant concentration, emulsions stabilized with sodium laurate–laurate mixture displays an excellent viscoelastic property pertaining to emulsions used in pharmaceutical and cosmetic products. This further suggests that in the presence of 0.8 M NaOH these o/w emulsion both spread easily and stabilized better as well as possess long storage stability and shelf life. With these dynamic moduli responses it is not surprising that the δ of these sodium laurate–lauric acid stabilized emulsions decreased with NaOH concentration from 0.4 to 0.8 M. The fact that these emulsion showed smallest δ in the presence of 0.8 M NaOH as opposed to other NaOH concentrations, it is evident that solid-like elastic property of these emulsions is enhanced and improved at this NaOH concentration. As far as oil type is concerned mineral oil based systems showed better rheology properties compared to corresponding paraffin oil based systems.

Plasma fatty acid profiles in 37 pairs of maternal and umbilical cord blood samples

In order to study the fatty acid transfer from the mother to fetus, their fatty acid profiles were compared by 37 pairs of maternal and umbilical cord plasma specimens obtained from healthy Japanese women at delivery. The fetal/maternal fatty acid concentration ratios differed among individual fatty acids. The ratios were low for linoleic acid (LN, 0.12±0.04) and linolenic acid (LnN, 0.07±0.05) but high for arachidonic acid (AA, 0.66±0.17) and docosahexaenoic acid (DHA, 0.44±0.13). Significant correlations were observed between the maternal and fetal EPA (r=0.74) and DHA (r=0.40) concentrations. These results suggest that DHA and AA are preferentially transferred to the fetus. Fetal fatty acid profile reflects the maternal intake of EPA and DHA.

Anaerobic Hydrogen Production from Sucrose Using an Acid‐Enriched Sewage Sludge Microflora

AbstractA novel and high‐rate anaerobic sequencing bath reactor (ASBR) process was used to evaluate the hydrogen productivity of an acid‐enriched sewage sludge microflora at a temperature of 35 °C. In this ASBR process a 4 h cycle, including feed, reaction, settle, and decant steps, was repeatedly performed in a 5 L reactor. The sucrose substrate concentration was 20 g COD/L; the hydraulic retention time (HRT) was maintained at 12–120 h at the initial period and thereafter at 4–12 h. The reaction/settle period ratio, which is the most important parameter for ASBR operation was 1.7. The experimental results indicated that the hydrogenic activity of the sludge microflora was HRT‐dependent and that proper pH control was necessary for a stable operation of the bioreactor. The peak hydrogenic activity value was attained at an HRT of 8 h and an organic loading rate of 80 kg COD/m3 × day. Each mole of sucrose in the reactor produced 2.8 mol of hydrogen and each gram of biomass produced 39 mmol of hydrogen per day. An overly‐short HRT might deteriorate the hydrogen productivity. The concentration ratios of butyric acid to’acetic acid, as well as volatile fatty acid and soluble microbial products to alkalinity can be used as monitoring indicators for the hydrogenic bioreactor.

Dye-Sensitized Solar Cell Using a TiO2 Nanocrystalline Film Electrode Modified by an Aluminum Phthalocyanine and Myristic Acid Coadsorption Layer

A dye-sensitized solar cell using a nanocrystalline TiO2 film electrode modified by aluminum phthalocyanine, aluminum 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine hydroxide (AlTPPc), and a myristic acid adsorbed layer was developed. The UV−vis absorption spectrum of the TiO2 film electrode modified by an AlTPPc and myristic acid adsorbed layer shows that the aggregation of AlTPPc molecules was suppressed by myristic acid. For a cell using AlTPPc adsorbed on a nanocrystalline TiO2 film electrode, ISC, VOC, and FF were 0.026 mA cm-2, 186 mV, and 40.4%, respectively. The maximum power output was estimated to be 2.25 μW cm-2. In contrast, ISC, VOC, and FF values were 0.061 mA cm-2, 225 mV, and 40.0%, respectively, and the maximum power output was estimated to be 5.40 μW cm-2 using a TiO2 film electrode modified by an AlTPPc and myristic acid layer. The ISC and VOC values increased with the concentration ratio of myristic acid to AlTPPc until 0.1 and then decreased, and the IPCE value at 700 nm of the solar c...

Effects of iNOS-related NO on Hearts Exposed to Liposoluble Iron

Inducible nitric oxide synthase (iNOS) protects heart against ischemia/reperfusion injury. However, it is unknown whether the beneficial effects of iNOS are mediated by the interaction of NO with radical oxygen species (ROS). To address this issue, we examined the effects of liposoluble iron-induced ROS generation in isolated perfused hearts from rats treated with lipopolysaccharide (LPS). LPS administration (10 mg/kg, i.p., 6 h before heart removal) induced iNOS expression and increased NO production as indicated by a 3-fold elevation of nitrite level in coronary effluents relative to control hearts. An enhanced expression of heme-oxygenase 1 protein was also observed in septic hearts compared to control. Iron-induced perfusion and contractile deficits were ameliorated by LPS with more important coronary than myocardial benefits. In iron-loaded hearts, oxidative stress as measured by the 2,3 dihydroxybenzoic acid/salicylic acid concentration ratio in cardiac tissue was 23% lower in septic than in control heart although the difference did not reach significance. In addition, the presence of the NO synthase inhibitor N-nitro-l-arginine in the perfusion medium totally blocked NO production but did not reverse the protective effects of LPS. The results indicate that LPS protects from iron-induced cardiac dysfunction by mechanisms independent on ex vivo NO production and suggest that NO acts as a trigger rather than a direct mediator of the cardioprotective effects of LPS in heart exposed to iron.

Studies on sorption of copper(II) complexes with IDA and NTA acids on strongly and weakly basic anion exchangers

Aminopolycarboxylic acids are very popular and widely applied in many branches of industry. Due to their activity, they combine with metal ions and form very stable complexes. The aim was to examine the possibility of using the weakly and strongly basic acrylate anion exchangers for removal of those complexes from the systems of different types. The influence of time contact phase, pH, metal concentration, nature of active groups and metal-aminopolycarboxylic acid concentration ratio on the sorption was studied. The percentage of Cu(II) was determined by means of AAS.

Preparation of (Ba xSr 1− x)TiO 3 sols used for ceramic film jet-printing

As one of the ways for solid free-form fabrication, jet-printing technique directly deposits the ceramic sols on a substrate to form ceramic films using a ink-jet printer. In this process, the properties of ceramic sols are the key to determine the printing effect. In this paper, Ba–Ti, Sr–Ti and Ba–Sr–Ti sols used for ceramic film jet-printing were prepared using barium acetate, strontium acetate and tetrabutyl titanate as starting materials. The properties of the sols were determined and adjusted successfully through the variation of processing parameters. Formamide was added into the sols to improve the stability and the viscosity of the sols. For a constant concentration of ethylene glycol, the stability of the sol increases and the viscosity of the sol decreases as the concentration of formamide increases. The concentration ratio of acetic acid to ethylene glycol R ac/eg is crucial to obtain stable sols for jet-printing process. The optimal R ac/eg value is 3:1 for Sr–Ti sols, 3:2 for Ba–Ti and Ba–Sr–Ti sols.

Atmospheric conversion of sulfur dioxide to particulate sulfate and nitrogen dioxide to particulate nitrate and gaseous nitric acid in an urban area.

Sulfur dioxide, nitrogen dioxide, particulate sulfate and nitrate, gaseous nitric acid, ozone and meteorological parameters (temperature and relative humidity) were measured during the winter season (1999-2000) and summer season (2000) in an urban area (Dokki, Giza, Egypt). The average particulate nitrate concentrations were 6.20 and 9.80 microg m(-3), while the average gaseous nitric acid concentrations were 1.14 and 6.70 microg m(-3) in the winter and summer seasons, respectively. The average sulfate concentrations were 15.32 microg m(-3) during the winter and 25.10 microg m(-3) during the summer season. The highest average concentration ratio of gaseous nitric acid to total nitrate was found during the summer season. Particulate sulfate and nitrate and gaseous nitric acid concentrations were relatively higher in the daytime than those in the nighttime. Sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) defined in the text were calculated from the field measurement data. Sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) in the summer were about 2.22 and 2.97 times higher than those in the winter season, respectively. Moreover, sulfur conversion ratio (Fs) and nitrogen conversion ratio (Fn) were higher in the daytime than those in the nighttime during the both seasons. The sulfur conversion ratio (Fs) increases with increasing ozone concentration and relative humidity. This indicates that the droplet phase reactions and gas phase reactions are important for the oxidation of SO2 to sulfate. Moreover, the nitrogen conversion ratio (Fn) increases with increasing ozone concentration, and the gas phase reactions are important and predominant for the oxidation of NO2 to nitrate.

Interference-Based Electrochemical Biosensor for the Measurement of the Concentration and Isomer Ratio of Urocanic Acid

Urocanic acid (UCA) is known to be synthesized as the trans isomer (trans-UCA) in the skin, and trans-UCA is transformed by UV light to the cis isomer (cis-UCA), which may be involved in photoimmunosuppression. An electrochemical method has been developed for the measurement of the concentration and isomer ratio of UCA. A heme peptide-modified electrode (HP electrode) reduces hydrogen peroxide at +150 mV vs Ag/AgCl, and the reduction current is inhibited by UCA. Since cis-UCA is a stronger inhibitor than trans-UCA, irradiation of a sample solution with UV light increases the percent inhibition. The concentration and isomer ratio of UCA in the sample solution can be estimated from the values of percent inhibition before and after the UV irradiation.

Nutrient and plankton dynamics in the Oyashio region of the western subarctic Pacific Ocean

Abstract Nutrients and plankton dynamics were investigated in the Oyashio region of the western subarctic Pacific. Observations were carried out between 1990 and 1998 along A-line, which crosses the Oyashio, a cold western boundary current of the North Pacific. Nutrient concentrations were highest in March and decreased with the spring phytoplankton bloom, which was observed in April and/or May. Nitrate and silicic acid concentrations at the sea surface declined to near-depletion by August. Compared with the eastern subarctic Pacific, the Oyashio region is characterized by large seasonal variability in nutrients and plankton biomass. The magnitudes of seasonal changes in nitrate and silicic acid in the Oyashio region were 2.6 and 2.8 times those of Station P in the eastern subarctic Pacific, respectively. Phytoplankton and zooplankton were 53 and 7.9 times higher in the Oyashio than at Station P, respectively. These differences were suggested to be a result of higher new production and higher ecological efficiency of the Oyashio ecosystem than in the eastern subarctic Pacific. The spring bloom ended by June–July when both nitrate and silicic acid were still replete at half of the stations. Thus, high-nutrient low-chlorophyll water occurred in the Oyashio region during late spring to summer. This result indicated that factors other than macronutrient depletion were important in terminating the spring bloom. The concentration ratio of silicic acid to nitrate (Rsw) at the sea surface was 1.65 before the spring bloom. Rsw was almost constant at the early-bloom period. During the mid- to late-bloom period, the ratio first increased, then decreased. The net consumption ratio of silicic acid to nitrate (ΔSi(OH)4:ΔNO3) at the sea surface was 1.28 during March and April, and ΔSi(OH)4:ΔNO3 increased to 2.59 during April and May. The preferential uptake of silicic acid suggests diatoms were stressed during mid- to late-bloom period and the stress influenced nutrient and plankton dynamics in the Oyashio region. In order to understand the controlling factors of nutrient and plankton dynamics during the spring bloom, mathematical simulations with a silicon–nitrogen cycle model were carried out. The model showed that light and silicic acid limitation depressed phytoplankton growth, and cell sinking and zooplankton grazing decreased phytoplankton biomass. Changes in silicic acid and nitrate uptake by diatoms during the spring bloom was essential in reproducing the temporal change in nutrient dynamics in the Oyashio region. Although zooplankton grazing did not prevent the initiation of the spring bloom, grazing pressure was an important factor controlling the magnitude and the duration of the spring bloom. The observed large fluctuations in the biomass and timing of zooplankton recruitment suggested that zooplankton play an important role in determining the interannual variations of the spring bloom in the Oyashio region.

LiNbO/sub 3/ optical waveguides formed in a new proton source

Proton-exchanged planar waveguides have been fabricated on Z-cut and X-cut lithium niobate crystals by using a new proton source formed by a mixture of benzoic and adipic acids. Waveguide index profiles and optical characteristics have been obtained at different values of the adipic-benzoic acid concentration ratio. The samples have been structurally characterized by Raman and infrared (IR) absorption spectroscopy and double-crystal X-ray diffraction. Good quality samples have been fabricated by using 30 mol% ratio dilution, showing very low scattering levels (<0.1 dB/cm), relatively high electrooptic coefficient (r/sub 33/=0.88 pm/V), and low relative percentage of interstitial protons (26%). The main factor limiting the waveguide optical properties is the substitutional-interstitial proton ratio, which can be easily controlled to produce good quality waveguides. A demonstration of the repeatability of the exchange process in the acid mixture is also provided.

Comparison of LDL fatty acid and carotenoid concentrations and oxidative resistance of LDL in volunteers from countries with different rates of cardiovascular disease

Within Europe there are differences in cardiovascular disease (CVD) risk between countries and this might be related to dietary habits. Oxidative modification of LDL is suggested to increase the risk of CVD and both the fatty acid and antioxidant content of LDL can affect its oxidation. In the present study, concentration of LDL fatty acid and antioxidant micronutrients (tocopherols and carotenoids) and ex vivo oxidative resistance of LDL (lag phase) was compared in volunteers from five countries with different fruit and vegetable intakes and reported rates of CVD. Eighty volunteers (forty males, forty females per centre), age range 25-45 years, were recruited from France, Northern Ireland, UK, Republic of Ireland, The Netherlands, and Spain, and their LDL composition and lag phase were measured. There were some differences in LDL carotenoid and alpha-tocopherol concentrations between countries. alpha-Tocopherol was low and beta- + gamma-tocopherol were high (P<0.001) in the Dutch subjects. Beta-Carotene concentrations were significantly different between the French and Spanish volunteers, with French showing the highest and Spanish the lowest concentration. LDL lycopene was not different between centres in contrast to lutein, which was highest in French (twofold that in the Dutch and Spanish and threefold that in Northern Ireland and the Republic of Ireland, P<0.001). However absolute LDL saturated, monounsaturated, polyunsaturated and total unsaturated fatty acid concentrations were different between countries (P<0.001, total unsaturated highest in Northern Ireland) there was little difference in unsaturated:saturated fatty acid concentration ratios and no difference in polyunsaturated:saturated fatty acid concentration ratios. LDL from the Republic of Ireland (a region with a high rate of CVD) had greater resistance to Cu-stimulated oxidation than samples obtained from volunteers in other countries. In conclusion, LDL composition did not predict resistance to Cu-stimulated oxidation, nor is there evidence that LDL from volunteers in countries with lower rates of CVD have greater resistance to oxidation.

Intraspinal Pressure Influences CSF Disposition of Tryptophan and 5-HIAA

Cerebrospinal fluid (CSF) concentrations of monoamine compounds are influenced by factors such as age, gender, height, body weight, tapping time, and atmospheric pressure. We have now examined the role of intraspinal pressure. Thirteen male volunteers underwent lumbar puncture in the right decubitus position without preceding strict bed rest. The intraspinal pressure was recorded, and monoamine precursors, transmitters, and metabolites were analyzed in two consecutively collected CSF fractions. Tryptophan in 12 ml of CSF and the 5-hydroxyindoleacetic acid concentration ratio [fraction II (7–12 ml CSF)/fraction I (0–6 ml CSF)] correlated with the intraspinal pressure. Hypothetically, the intraspinal pressure may be a confounding factor for a correct interpretation of CSF tryptophan and 5-hydroxyindoleacetic acid concentrations, and this is an issue that has to be addressed in future CSF studies.

Dietary Manipulation and Increase in Plasma Unsaturated Fatty Acids in Sheep

Forty three 7-month old, Barbados Black Belly × Malin crossbred sheep were used for the trial. They were allotted into three treatment groups fed varying levels of oil palm (Elaeis guineensis) frond pellets and commercial sheep pellets. Treatment diets were 80% commercial pellet+20 % (% w/w) oil palm frond pellet (CON group, n=15), 50% commercial pellet+50% oil palm frond pellet (% w/w) (HAF group, n=14) and 80% oil palm frond pellet+20% (% w/w) commercial pellet (OPF group, n=14). The plasma fatty acid profiles from these animals were compared before and after 14 weeks of feeding. Results showed that total unsaturated fatty acid content in the CON group had increased by 10% (p<0.01) from the pre-treatment values. All three treatment groups had significantly different plasma n-6 and n-3 polyunsaturated fatty acid contents at the end of the trial. In fact, the CON group had significantly (p<0.01) more n-6 polyunsaturated fatty acid content compared to its own initial values, and also the values from the HAF and OPF groups. However there was a significant (p<0.01) decline in plasma n-3 polyunsaturated fatty acids in all groups. The final total unsaturated to saturated fatty acid content ratio was significantly (p<0.01) highest in the CON group, demonstrating the high plasma unsaturated fatty acid content in these animals. This study shows the plasma unsaturated fatty acids in sheep can be increased by dietary manipulation.