Transgenic overproduction of islet amyloid polypeptide (amylin) is not sufficient for islet amyloid formation

Islet amyloid polypeptide forms islet amyloid deposits in non-insulin-dependent diabetes mellitus. We have generated transgenic mice which express human islet amyloid polypeptide in their pancreatic beta cells yet do not develop islet amyloid deposits despite producing levels of the amyloidogenic human peptide 2 - 3 fold higher than the native (mouse) peptide. To determine whether marked overproduction of islet amyloid polypeptide is a potential cause of islet amyloid formation, we increased expression of this transgene by producing homozygous transgenic animals and by making heterozygous mice experimentally insulin resistant with nicotinic acid. Pancreatic content of islet amyloid polypeptide-like immunoreactivity in homozygous and nicotinic acid-treated mice was 2-fold (25 +/- 7 fmol/microg; n = 6) and 3.5-fold (47 +/- 20 fmol/microg; n = 3) higher, respectively, than that of untreated heterozygous animals (13+/-2 fmol/microg; n = 11; both p < 0.05). Despite this marked increase in production of islet amyloid polypeptide, neither group of mice developed gross islet amyloid deposits even after 16 months of age. We conclude that overproduction of islet amyloid polypeptide, even as produced by extreme insulin resistance, is not in itself sufficient for islet amyloid formation.     

Study of the solubility,antioxidant activity and structure of inclusion complex of vanillin with β-cyclodextrin

In the present study, complexes of vanillin with β-cyclodextrin (β-CD) were prepared by the freeze-drying method. The formation of the inclusion complex was confirmed by differential scanning calorimetry (DSC). DSC thermograms indicated that the endothermic peak of vanillin and the physical mixture of vanillin with β-CD, due to the melting of vanillin crystals, were absent in DSC thermograms obtained for the freeze-dried inclusion complex. Moreover, the DSC studies under oxidation conditions indicate that the complex of vanillin with β-CD is protected towards oxidation since it remains intact at temperatures where the free vanillin is oxidising. The structure of the complex in aqueous solutions was established by nuclear magnetic resonance (NMR) studies and specifically by two-dimensional rotational frame NOE spectra. NMR studies showed inclusion of the entire vanillin molecule in the β-CD in a tilted manner and with the aldehyde group in the primary side. The stoichiometry of the complex was 1:1. A phase solubility study was performed by mixing an excess amount of vanillin with aqueous solutions containing increasing amounts of β-CD. The results indicated that the complex of a vanillin/β-CD inclusion is more soluble in water than vanillin alone.     

Dietary evaluation of Mediterranean fish and molluscs pan‐fried in virgin olive oil

The effect of domestic pan‐frying in virgin olive oil (VOO) on the proximate composition, energy content, cholesterol, squalene and fatty acids in the edible portion of six species of finfish, common squid and mussels just caught from several regions of the Aegean Sea (Mediterranean Sea) was investigated. The species selected are traditionally consumed pan‐fried in VOO by the Greeks. On a fresh weight basis, pan‐frying caused significant water loss and increase of total fat, crude protein and energy content. The amount of VOO absorbed during frying ranged from 4.5 to 14.2% of fresh matter, showing a non‐linear negative correlation with initial fat, fish length and fish weight. Cholesterol content increased from 25 to 106 mg 100 g^?1 fresh weight (fw) to 33–130 mg 100 g^?1 fw after frying. VOO absorbed during frying resulted in a 20–78 times increase of squalene content and in significant alteration of fatty acid composition, the major change being the increase of monounsaturated fatty acids which became predominant in all fried samples. The intakes of fat and major fatty acid classes by consuming the pan‐fried seafood were comparable with the respective average Greek values. Frying in VOO resulted in a two to three times decrease of the atherogenic index and a slightly less decrease of the thrombogenic index. Both indices remained lower than 0.45 in all fried samples. The cholesterol‐saturated fat index and the cholesterol index increased up to twice after frying, ranging between 3.4–9.9 and 2.9–9.3, respectively. From the results obtained it is concluded that fish and shellfish pan‐fried in VOO present a healthy lipid profile in terms of the n‐6/n‐3 ratio, major fatty acid classes and total fat content. Copyright © 2004 Society of Chemical Industry     

Recovery and distribution of natural antioxidants (α-tocopherol,polyphenols and terpenic acids) after pan-frying of Mediterranean finfish in virgin olive oil

Samples of eight finfish representing the most popular fish species in Greece were pan-fried in virgin olive oil according to the Greek traditional culinary practice. Analyses for polyphenols, hydroxy pentacyclic triterpene acids (HPTA) and α-tocopherol were performed in the fresh and fried oils and fish. Polyphenols and HPTA were determined by GC/MS and α-tocopherol by HPLC. Nine polyphenols were determined in the frying oil samples; six of them were also found in fried fish. The terpenic acids oleanolic, maslinic and ursolic were also determined in frying oils and fried fish. No polyphenols and no HPTA were detectable in raw fish, while α-tocopherol was present in all samples. Besides water loss and oil absorption, pan frying caused the partial loss of all the antioxidants studied in the fried oils, as well as their enrichment in the fried fish. The overall retention of α-tocopherol in the fried oil and fish ranged from 30% to 80%, the respective values for polpyphenols and HPTA ranging between 51–87% and 46–88%. The polarity of the antioxidants studied, seems to affect to some extent their partition between the frying oil and the water-containing fish.     

Triacylglycerol Species of Less Common Edible Vegetable Oils

Chromatographic and spectroscopic methods used for the detection and quantification of triacylglycerol (TAG) species present in less common edible vegetable oils (almond, hazelnut, pumpkin seed, safflower, sesame, walnut, and wheatgerm oils) are reviewed. For these oils, as well as for thistle oil and high-oleic sunflower oil, for which no data exist on their TAG composition, both high-performance liquid chromatography (HPLC) and gas chromatography (GC) chromatographic plus spectrometric techniques have also been performed. Triacylglycerol comparison of the data found in the literature is also presented. Five fatty acyl moieties (palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, and linolenoyl-) are found to mainly contribute to the formation of TAG species of the aforementioned edible vegetable oils, whereas six more (palmitoleoyl-, arachidoyl-, gadoleoyl-, heptadecenoyl-, margaroyl-, and erucoyl-) are reported as minors. Only 19 to 33 TAG make up the mass of these oils. These TAG are also found in most common edible oils, thus indicating a “uniformity” in the minor and main TAG composition of edible vegetable oils. Trioleoyl-glycerol predominates in almond (13.3-48.6%), hazelnut (35.3-57.9%), and high oleic sunflower (44.2% and 52.9%) oils, trilinoleoyl-glycerol in safflower (40.1-49.7%), thistle (36.9% and 46.0%), walnut (25.9-38.1%), and wheatgerm (15.7-33.0%) oils. Sesame and pumpkin seed oils are rich in dioleoyl-linoleoyl-glycerol (5.9-17.5%, 9.5% and 18.6%, respectively) and oleoyl-dilinoleoyl-glycerol (8.0-18.7% and 12.8-21.1%, respectively).     

Characterisation of certain major polyphenolic antioxidants in grape (<Emphasis Type="Italic">Vitis vinifera</Emphasis> cv. Roditis) stems by liquid chromatography-mass spectrometry

The stem extract, which was shown to contain high amounts of phenolics and significant antioxidant potency, was further analysed employing liquid chromatography-electrospray ionisation mass spectrometry, in an effort to obtain a deeper insight into its polyphenolic composition. The compounds identified were mainly flavanols (a trimer and a galloylated dimer), flavonols (rutin and quercetin 3-O-glucuronide), stilbenes (trans-resveratrol and a resveratrol dehydrodimer) and a dihydroflavonol glycoside (astilbin).     

Providing rate guarantees for internet application traffic across ATM networks

The TCP⁄IP protocol suite is the standard requirement for all applications that need to communicate over the Internet. As TCP⁄IP applications are unable to specify the QoS parameters needed for most Asynchronous Transfer Mode (ATM) services, they tend to use the unspecified bit rate (UBR) service category when running across ATM networks. The UBR service utilizes any bandwidth that is left unused by the rest of the ATM services. This has led the ATM Forum's Traffic Management Group to define a new service category called guaranteed frame rate (GFR). GFR is intended to provide minimum cell rate guarantees and fair access to excess bandwidth left over from higher-priority services. This article first presents a tutorial overview of GFR and then presents a survey of the research work that has been carried out toward the design and implementation of associated ATM switch mechanisms.     

The tocopherol content of greek olive oils

Four types of Greek olive oil were analysed for α-and γ-tocopherols by high performance liquid chromatography. Certain seed oils widely consumed in Greece were also analysed for comparison with the olive oils. Virgin, pure, residual and refined oils contained an average of 113,81,156 and 37 mg kg^?1 of α-tocopherol, respectively. The α-tocopherol level within each type of olive oil appeared to be influenced by different factors. The content of y-tocopherol averaged 17 and 33 mg kg^?1of virgin and residual oil, respectively. Refined and pure olive oil contained very low levels of y-tocopherol. The α-tocopherol equivalent per gram of polyunsaturated fatty acids was calculated to be 1·48, 0·60, 0·88, 1·07 and 0·58 for edible olive oils, corn, cottonseed, sunflower and partially hydrogenated soya bean oil, respectively.     

Content of trans,trans‐2,4‐decadienal in deep‐fried and pan‐fried potatoes

Trans,trans‐2,4‐decadienal is a by‐product of frying oil that is also transferred to fried food. This aldehyde has been found and quantified both in frying oils and fumes generated during frying. Furthermore, it has been reported that 2,4‐decadienal has cytotoxic and genotoxic effects and promotes LDL oxidation. In the present work trans,trans‐2,4‐decadienal was detected directly in fried potatoes (french‐fries). Moreover, the influence of frying conditions (deep‐frying, pan‐frying), the oil type (olive oil, sunflower oil, cottonseed oil, palm oil and a vegetable shortening) and the degree of thermal deterioration (eight successive frying sessions without replenishment) on the production of 2,4‐decadienal in oil and potatoes was studied. The isolation of the aldehyde was performed by methanol extraction, while the identification and quantification was performed by RP‐HPLC. The quantity of trans,trans‐2,4‐decadienal produced during successive pan‐frying demonstrated a peak at the third and fourth frying session. The highest concentration of trans,trans‐2,4‐decadienal was detected in potatoes fried in sunflower oil, and the lowest in olive oil. The quantity of trans,trans‐2,4‐decadienal in fried potatoes decreased during successive deep‐frying at the seventh frying session or remained stable, except for cottonseed oil. The quantity of trans,trans‐2,4‐decadienal in fried potatoes was considered to be dependent on the oil used, on the frying process and, to a lesser extent, on the oil deterioration. In all cases tested, the highest concentration of trans,trans‐2,4‐decadienal was detected during deep‐frying. The unsaturation degree of the frying oil was considered to promote the formation of trans,trans‐2,4‐decadienal. Considering the quantity of 2,4‐decadienal found in french‐fries and in the respective frying medium, direct quantification of 2,4‐decadienal is required in order to make an estimation of intake from french‐fries.     

A simple and precise method for the routine determination of platelet-activating factor in blood and urine

A simple and precise method is described for the measurement of platelet-activating factor (PAF) in blood and urine. The method involves the isolation of PAF from blood samples by two successive steps. In the first step, blood proteins are precipitated with ethanol and the “free” PAF, i.e. the PAF which is extractable with ethanol, is recovered. In the second step, “bound” PAF, i.e., PAF not extractable with ethanol, is extracted from the protein precipitate with chloroform/methanol/water. The extraction of PAF from urine samples requires only the ethanol extraction step. “Free” and “bound” PAF are then each fractionated by silicic acid column chromatography, and the methanol/water eluent containing PAF is then further fractionated by high-performance liquid chromatography using an isocratic solvent system of acetonitrile/methanol/water. PAF is then quantitated by measuring its ability to induce platelet aggregation in an aggregometer. Application of the method to blood and urine samples from twenty-three healthy volunteers revealed PAF levels in blood of 140–480 pg/mL (630–254.4 pg “free” PAF/mL and 64–225.6 pg “bound” PAF/mL), and of 1.2–4.0 pg PAF/mL in urine. The method overcomes various technical problems and was shown to be very precise. It should prove useful for monitoring PAF levels in various disease conditions.