Activated oxygen species and oxidation of food constituents

Activated oxygen species which may be important in initiating oxidative changes in foods include singlet oxygen, hydroxyl radical, ozone, superoxide anion (perhydroxyl radical at low pH), and hydrogen peroxide. Chemical and enzymic reactions known to occur in biological materials can generate singlet oxygen, hydroxyl radical, superoxide anion, and hydrogen peroxide. Ozone is primarily a product of photoreactions in polluted air. Reactions involving singlet oxygen, hydroxyl radical, and ozone with food constituents can ultimately yield peroxides which decompose to initiate oxidative chain reactions. Superoxide anion and hydrogen peroxide are relatively inert toward organic molecules but can decompose to produce the more reactive singlet oxygen and hydroxyl radical. Inhibition of reactions initiated by reactive oxygen species in foods should be very important in preserving the oxidative stability of foods. The generation, detection, measurement, reaction, and inhibition of reactions of active oxygen species are surveyed in this review.

Affinity of phytoestrogens for estradiol-binding proteins and effect of coumestrol on growth of 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors

A number of nonsteroidal estrogens, which are common naturally occurring substances in human foods, were examined for competitive binding to estrogen receptor proteins. These compounds bound competitively to estrogen receptor proteins in rat uterine cytosol, in tissue from 7,12-dimethylbenz[a]anthracene (DMBA)-induced rat mammary tumors, and in human mammary tumor tissue. The relative affinity of these estrogens for rat uterine cytosol receptors paralleled closely the affinities reported for other receptors. Oral administration of coumestrol did not appear to support the growth of DMBA-induced rat mammary tumors, nor did coumestrol act as an antiestrogen when administered orally in combination with 17 beta-estradiol. Coumestrol administered sc might, however, be able to support the growth of these tumors.

Pigmentary dispersion syndrome and pigmentary glaucoma. A prospective study of the natural history

The natural evolution of pigmentary dispersion syndrome and pigmentary glaucoma was studied in 55 patients for six to 43 months (mean, 27 months). Active dispersion of pigment was observed in 45 eyes in 31 patients and was associated with worsening of glaucoma in 32 eyes. Dispersion of pigment was defined as active when there was increase in iris transillumination, increase in corneal pigmentation, or appearance of pigment granules on the surface of the lens in the pupil. There were no differences in the frequency of active dispersion of pigment and worsening of glaucoma comparing patients aged less than 44, 45 to 64, and 65 or more years. This study demonstrates that active dispersion of pigment is clinically detectable, is correlated with elevation of intraocular pressure, and continues to occur in older patients.

Sterol Oxides in Foodstuffs: A Review

The toxicological significance of oxidized cholesterol has been well documented in numerous studies. This review focuses on the analysis of dietary sterol oxides in the foodstuffs examined to date with particular emphasis on isolation and characterization techniques. Eight common oxidation products of cholesterol have been identified in certain cholesterol-rich foods subjected to oxidative stress during food processing and/or storage. These products include 25-hydroxycholesterol, α or β 5,6-epoxycholesterol, α or β 7-hydroxycholesterol, 7-ketocholesterol, cholesta-3,5-dien-7-one and cholestane-3β, 5α, 6β-triol. A limited number of studies on the biological effects of dietary phytosterol oxides indicate these products may also be of nutritional concern. Four common autoxidation products of β-sitosterol have been identified in edible oils; these include α or β 7-hydroxysitosterol, 7-ketositosterol and setosta-3,5-dien-7-one. Few quantitative data are available on the sterol oxide content of foods. Moreover, studies without apparent precautions against the artifactual formation of sterol oxides may be flawed. Additional research is necessary to adequately identify and quantify the sterol oxides which most likely exist in certain foods.

The outflow tract in pigmentary glaucoma: a light and electron microscopic study

Buttons obtained by trephination from both eyes of a 44-year-old myopic man with pigmentary glaucoma were studied by light and electron microscopy. Although clinically both eyes exhibited heavy pigmentation of the trabecular meshwork in the whole circumference, microscopically the trabecular meshwork of the left eye contained more pigment granules than that of the right eye, which appeared relatively acellular with collapse of the trabecular sheets. In both eyes endothelial cells covering the trabecular sheets were filled with pigment and showed various stages of degeneration. The intertrabecular spaces contained free pigment granules as well as cell debris. These observations suggest that plugging of the trabecular spaces by pigment and cell debris together with fragmentation and collapse of trabecular sheets contribute to the decrease in the facility of outflow that occurs in pigmentary glaucoma.

Developmental responses of amphibians to solar and artificial UVB sources: a comparative study

Many amphibian species, in widely scattered locations, currently show population declines and/or reductions in range, but other amphibian species show no such declines. There is no known single cause for these declines. Differential sensitivity to UVB radiation among species might be one contributing factor. We have focused on amphibian eggs, potentially the most UVB-sensitive stage, and compared their resistance to UVB components of sunlight with their levels of photolyase, typically the most important enzyme for repair of the major UV photoproducts in DNA, cyclobutane pyrimidine dimers. Photolyase varied 100-fold among eggs/oocytes of 10 species. Among three species-Hyla regilla, Rana cascadae, and Bufo boreas-for which resistance of eggs to solar UVB irradiance in their natural locations was measured, hatching success correlated strongly with photolyase. Two additional species, Rana aurora and Ambystoma gracile, now show similar correlations. Among the low-egg-photolyase species, R. cascadae and B. boreas are showing declines, and the status of A. gracile is not known. Of the two high-photolyase species, populations of H. regilla remain robust, but populations of R. aurora are showing declines. To determine whether levels of photolyase or other repair activities are affected by solar exposures during amphibian development, we have initiated an extended study of H. regilla and R. cascadae, and of Xenopus laevis, laboratory-reared specimens of which previously showed very low photolyase levels. Hyla regilla and R. cascadae tadpoles are being reared to maturity in laboratories supplemented with modest levels of UV light or light filtered to remove UVB wavelengths. Young X. laevis females are being reared indoors and outdoors. Initial observations reveal severe effects of both UVA and UVB light on H. regilla and R. cascadae tadpoles and metamorphs, including developmental abnormalities and high mortalities. Assays of photolyase levels in the skins of young animals roughly parallel previous egg/oocyte photolyase measurements for all three species.

Humoral response to oligomeric human immunodeficiency virus type 1 envelope protein

The humoral immune response to human immunodeficiency virus type 1 (HIV-1) is often studied by using monomeric or denatured envelope proteins (Env). However, native HIV-1 Env complexes that maintain quaternary structure elicit immune responses that are qualitatively distinct from those seen with monomeric or denatured Env. To more accurately assess the levels and types of antibodies elicited by HIV-1 infection, we developed an antigen capture enzyme-linked immunosorbent assay using a soluble, oligomeric form of HIV-1IIIB Env (gp140) that contains gp120 and the gp41 ectodomain. The gp140, captured by various monoclonal antibodies (MAbs), retained its native oligomeric structure: it bound CD4 and was recognized by MAbs to conformational epitopes in gp120 and gp41, including oligomer-specific epitopes in gp41. We compared the reactivities of clade B and clade E serum samples to captured Env preparations and found that while both reacted equally well with oligomeric gp140, clade B seras reacted more strongly with monomeric gp120 than did clade E samples. However, these differences were minimized when gp120 was captured by a V3 loop MAb, which may lead to increased exposure of the CD4 binding site. We also measured the ability of serum samples to block binding of MAbs to epitopes in gp120 and gp41. Clade B serum samples consistently blocked binding of oligomer-dependent MAbs to gp41 and, to a slightly lesser extent, MAbs to the CD4 binding site in gp120. Clade E serum samples showed equivalent or greater blocking of oligomer-dependent gp41 antibodies and considerably less blocking of CD4-binding-site MAbs. Finally, we found that < 5% of the antibodies in clade B sera bound to epitopes present only in monomeric gp120, 30% bound to epitopes present in both monomeric gp120 and oligomeric gp140, and 70% bound to epitopes present in oligomeric gp140, which includes gp41. Thus, captured oligomeric Env closely reflects the antigenic characteristics of Env protein on the surface of virions and infected cells, retains highly conserved epitopes that are recognized by antibodies raised against different clades, and makes it possible to detect a much greater fraction of total anti-HIV-1 Env activity in sera than does native monomeric gp120.

An evaluation of machine-learning methods for predicting pneumonia mortality

This paper describes the application of eight statistical and machine-learning methods to derive computer models for predicting mortality of hospital patients with pneumonia from their findings at initial presentation. The eight models were each constructed based on 9847 patient cases and they were each evaluated on 4352 additional cases. The primary evaluation metric was the error in predicted survival as a function of the fraction of patients predicted to survive. This metric is useful in assessing a model's potential to assist a clinician in deciding whether to treat a given patient in the hospital or at home. We examined the error rates of the models when predicting that a given fraction of patients will survive. We examined survival fractions between 0.1 and 0.6. Over this range, each model's predictive error rate was within 1% of the error rate of every other model. When predicting that approximately 30% of the patients will survive, all the models have an error rate of less than 1.5%. The models are distinguished more by the number of variables and parameters that they contain than by their error rates; these differences suggest which models may be the most amenable to future implementation as paper-based guidelines.

Anomalous behavior of bovine alpha s1- and beta-caseins on gel electrophoresis in sodium dodecyl sulfate buffers

Electrophoresis in the presence of sodium dodecyl sulfate (SDS) provides a relatively simple means of determining molecular weights of proteins. This technique relies on the validity of a correlation between some function of Mr and the mobility of the protein through the gel matrix. However, bovine caseins (especially alpha s1-casein) have lower mobilities than expected on the basis of their known Mr. The binding of SDS to both alpha s1-casein (Mr 23,600) and beta-casein (Mr 24,000) reached a maximum at the slightly low value of 1.3 g SDS/g protein. Gel-filtration chromatography showed, however, that the alpha s1-casein:SDS complex was larger than the beta-casein:SDS complex at pH 6.8 or 7.0, but that they were similar in size at pH 2.9 or 3.0. Circular dichroism spectra indicated that the low helical structure content of both alpha s1- and beta-casein increased with the addition of SDS and/or decreasing the pH to 1.5. 13C NMR results showed that SDS bound to alpha s1- and beta-casein in the same way as it did to bovine serum albumin. Either esterification or dephosphorylation followed by amidation of alpha s1-casein increased its mobility in SDS-gel electrophoresis, but neither modification affected beta-casein mobility. These and other results indicate that the low electrophoretic velocity of alpha s1-casein in SDS-gel electrophoresis results from its unexpectedly large hydrodynamic size. This is caused by localized high negative charges on certain segments of alpha s1-casein, which would induce a considerable amount of inter- and intrasegmental electrostatic repulsion, leading to an expanded or extended structure for portions of the alpha s1-casein molecule in the presence of SDS. It is clear that the conformation, and hence the equivalent radius, of an SDS:protein complex is determined by the sequence of amino acids in the protein and that, a priori, it cannot be anticipated that the electrophoretic mobility of such a complex will bear more than a casual relationship to the Mr of the protein.

Cross-species transferability and mapping of genomic and cDNA SSRs in pines

Two unigene datasets of Pinus taeda and Pinus pinaster were screened to detect di-, tri- and tetranucleotide repeated motifs using the SSRIT script. A total of 419 simple sequence repeats (SSRs) were identified, from which only 12.8% overlapped between the two sets. The position of the SSRs within their coding sequences were predicted using FrameD. Trinucleotides appeared to be the most abundant repeated motif (63 and 51% in P. taeda and P. pinaster, respectively) and tended to be found within translated regions (76% in both species), whereas dinucleotide repeats were preferentially found within the 5'- and 3'-untranslated regions (75 and 65%, respectively). Fifty-three primer pairs amplifying a single PCR fragment in the source species (mainly P. taeda), were tested for amplification in six other pine species. The amplification rate with other pine species was high and corresponded with the phylogenetic distance between species, varying from 64.6% in P. canariensis to 94.2% in P. radiata. Genomic SSRs were found to be less transferable; 58 of the 107 primer pairs (i.e. 54%) derived from P. radiata amplified a single fragment in P. pinaster. Nine cDNA-SSRs were located to their chromosomes in two P. pinaster linkage maps. The level of polymorphism of these cDNA-SSRs was compared to that of previously and newly developed genomic-SSRs. Overall, genomic SSRs tend to perform better in terms of heterozygosity and number of alleles. This study suggests that useful SSR markers can be developed from pine ESTs.

The TETRAD Project: Constraint Based Aids to Causal Model Specification

The statistical community has brought logical rigor and mathematical precision to the problem of using data to make inferences about a model's parameter values. The TETRAD project, and related work in computer science and statistics, aims to apply those standards to the problem of using data and background knowledge to make inferences about a model's specification. We begin by drawing the analogy between parameter estimation and model specification search. We then describe how the specification of a structural equation model entails familiar constraints on the covariance matrix for all admissible values of its parameters; we survey results on the equivalence of structural equation models, and we discuss search strategies for model specification. We end by presenting several algorithms that are implemented in the TETRAD I1 program.

Composition and ultrastructure of calcium phosphate-citrate complexes in bovine milk systems

The present studies show that the colloidal calcium phosphate of cows' milk has a (Ca + Mg)/Pi ratio of 1.67 (+/- 0.10; n = 22) and contains citrate, Mg and Zn at molar ratios to Ca averaging 0.05, 0.03 and 0.003, respectively. The composition of the natural colloidal phosphate of milk is similar to the precipitates formed by neutralization of ultrafiltrates obtained from acidified milks, and to that of the calcium phosphate-enriched fraction produced by extensive enzymic hydrolysis of the casein micelles in milk. Examination by electron microscopy of these artificial preparations of milk calcium phosphate revealed in both a very fine and uniform substructure which consisted of granules having an average, true diameter of approx. 2.5 nm. The size and shape of these tiny granules closely resemble the morphologies reported for the colloidal phosphate particles in native casein micelles, as well as for the subunits of amorphous calcium phosphate observed during calcification in other biological systems such as mitochondria and bone.

The Hypocholesteremic Effect of Milk - A Review

Each Maasai tribesman in Africa ordinarily consumes 4-5 liters of fermented whole milk per day in addition to substantial quantities of meat. In spite of this diet high in saturated fat and cholesterol, the Maasai have low serum cholesterol levels and a very low incidence of clinical coronary heart disease. In studying this paradox, Mann and co-workers serendipitiously discovered that there is apparently a milk factor (MF) in the fermented milk responsible for the low serum cholesterol levels of the Maasai. A hypocholesteremic effect of fermented whole and skim milk was subsequently confirmed on American volunteers, each consuming 2-4 liters per day. Administration of radioactive acetate to human subjects on the fermented milk diet indicated that cholesterol biosynthesis was inhibited by MF. In later studies with human volunteers, English workers demonstrated a hypocholesteremic effect of unfermented whole and skim milk when consumed at a level of about 2 liters per day per caput for 2 weeks. Although the MF apparently exists in unfermented milk, there are suggestions that its concentration is slightly higher in fermented compared to unfermented milks. A hypocholesteremic effect of milk has also been demonstrated in rats by several researchers. Even though the identity of the MF is unknown at this time, it has been suggested that it may be 3-hydroxy-3-methylglutaric acid (HMG) and/or orotic acid. It is not known whether HMG occurs in cow's milk, but HMG is known to inhibit the rate limiting enzyme in cholesterol biosynthesis, HMG-CoA-reductase. Orotic acid does occur in cow's milk (73-122 mg/liter), and it has marked effects on lipid metabolism in rats. The hypolipemic action of orotic acid in rats is accompanied by induction of a fatty liver.

Selected functionality changes of beta-lactoglobulin upon esterification of side-chain carboxyl groups

Free carboxyl groups of bovine beta-lactoglobulin were esterified with methanol, ethanol, and n-butanol. The modified proteins showed increased positive charge as the number of ionizable carboxyl groups was reduced. The methyl, ethyl, and butyl esters of beta-lactoglobulin showed enhanced surface activity, determined with surface and interfacial tension measurements at an air/water and oil/water interface, respectively. The methyl ester showed the largest enhancement in surface activity relative to the native protein. The ethyl and butyl esters were less effective in lowering the surface and interfacial tension but were more surface active than the native protein. The hydrophobic probe, 1,8-anilinonaphthalene sulfonate, showed enhanced fluorescence in the presence of native and modified beta-lactoglobulin. The largest enhancement in fluorescence of the hydrophobic probe was noted in the presence of the methyl ester of beta-lactoglobulin. The ethyl ester also effectively enhanced the fluorescence of the probe. The slopes of the curves of the fluorescent response for the native and modified proteins were graphically related to the interfacial tension at an oil/water interface for the corresponding protein. A large positive correlation was noted between the effectiveness of the proteins in reducing the interfacial tension and the enhancement in fluorescence of ANS with hydrophobic binding by the proteins. A general method to quantify carboxyl groups of proteins, employing the formation of a colored hydroxamate-ferric ion chelate, was also developed. Modification of the reaction for proteins in general, and carboxyl-modified proteins in particular, appears to have potential. Use of the hydroxamic acid reaction made it possible to estimate the apparent extent of carboxyl modification of beta-lactoglobulin through esterification with methanol, ethanol, and n-butanol.

Phagocytosis by trabecular meshwork cells: sequence of events in cats and monkeys

Trabecular meshwork cells have well-established phagocytic properties. However, the sequential stages of this process have not been studied in detail. Zymosan particles, yeast cell walls 3 micron in diameter, were either injected or perfused into the anterior chambers (AC) of cats and monkeys. Glutaraldehyde (3%) was then infused into the AC at 1-, 6-, 17-, 30- and 60 min and the fate of the particles observed by transmission electron microscopy. After contact with zymosan particles, trabecular meshwork cells demonstrated short cytoplasmic extensions at contact sites and an increased number of cytoplasmic organelles. Internalization of the particles occurred by 6 min in the cat and by 17 min in the monkey. In both species similar events occurred following internalization of zymosan: trabecular cells, laden with particles, rounded up, detached from their underlying collagenous beams and migrated towards Schlemm's canal or the aqueous plexus. By 1 hr the individual trabecular cells completed the entire sequence of phagocytic events although some cells were always observed in earlier stages of the process. These data document for the first time the timing of the cellular events that take place during zymosan particle phagocytosis by trabecular meshwork cells.

Antioxidant activity of skim milk: effect of sonication

The antioxidant activity of skim milk was evaluated in a linoleate emulsion system with hemoglobin as a pro-oxidant. Sonication greatly increased the antioxidant activity of skim milk. The antioxidant activity of the casein fraction of milk was increased most by sonication, and this increase was nearly as great as that for skim milk, suggesting that casein was almost totally responsible for the antioxidant effect of sonication. Total sulfhydryl groups of skim milk decreased upon prolonged sonication, probably the result of the heat evolved in the process. Reactive sulfhydryl content was unchanged by sonication. Sonication had no effect on antioxidant activity of beta-lactoglobulin, reduced urease, or reduced ribonuclease, proteins with free sulfhydryl groups. Apparently sulfhydryl groups were not involved in the increased antioxidant activity of sonicated skim milk. Homogenization at 281.5 kg/cm2 did not increase the antioxidant effect of skim milk. Sonication probably disrupted casein micelles, increasing the effective concentration of casein, which could account for the increased antioxidant activity in the system.