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We have constructed an alternating-field (AF) demagnetizer with a magnetic core in a passively air-cooled coil that can routinely operate at fields up to 0.5 T, almost 3 times higher than we could attain before in our commercial instrument. The field is powered by a commercial 1 kW power amplifier and is transverse to the bore, uniform to ±2% over a 25 mm paleomagnetic sample, and compatible with our existing sample handler for automated demagnetization and measurement. Even harmonics are ≤1 ppm of the fundamental and so generate negligible anhysteretic remanence. The much higher peak alternating field, 2 and 5 times that commonly available in air-core solenoidal and Helmhotz coil configurations, respectively, enables successful AF demagnetization of many samples that could not be completely demagnetized with commercially available equipment. This capability is especially useful for high-coercivity sedimentary and igneous rocks and extraterrestrial materials that contain magnetic minerals that alter during thermal demagnetization. In addition to the benefits, this instrument brings to our own research, a much broader potential impact is that it could replace the transverse coils of most automated AF demagnetization systems in use today, whether for discrete or continuous U-channel measurements, which are commonly limited to peak fields of ∼100 mT. Manual and tumbling demagnetizers would benefit as well by the ∼2 times increase in maximum field over those that can be attained by commercial solenoidal coils. Furthermore, we expect that it and similarly designed magnetic-core instruments will be capable of attaining even higher fields, of order 1 T.

Background S. aureus is a major medical pathogen contributing to healthcare-associated costs and mortality. Metastatic S. aureus infection is commonly associated with skin and soft-tissue infections. Macrophages as resident tissue phagocytes are essential for bacterial clearance and effectively phagocytose and kill S. aureus at low inocula. Formation of an intracellular reservoir develops when the capacity for macrophages to eradicate S. aureus is overwhelmed at increased inocula. Phagosomal maturation after bacterial ingestion involves sequential fusion with endosomes and lysosomes, reducing luminal pH, facilitating bacterial degradation. In the context of intracellular S. aureus, incomplete phagosomal maturation is demonstrable with impaired acidification and failure of lysosome fusion. Inhibition of phagosomal maturation is dependent upon bacterial factors as it is reversed in heat-killed bacteria. Intracellular survival of S. aureus is associated with reduced antimicrobial effectivity and increased complications. Within the intracellular environment, persistence of S. aureus is associated with adaptation of gene expression which confers greater resistance to antimicrobial effector mechanisms. Methods An ordered mutant library of S. aureus provides the opportunity to give a comprehensive evaluation of gene function. The Nebraska transposon (Tn) mutant library contains 1952 sequence-defined Tn insertion mutants derivative of USA300 LAC S. aureus, each with a single non-essential gene deletion. The mutants were labeled with a fluorescent stain activated at pH < 6 and challenged against differentiated human monocyte-derived macrophages for 4 hours. A high-content microscopy screen was developed to identify the bacterial genes associated with impairment of phagosomal acidification. Results The results of the high-throughput screen indicate the global regulators agr and saeR, hemolysin A and catalase are associated with the inhibition of phagosomal acidification. Conclusion The burden of S. aureus bacteremia and metastatic disease makes the targeting of intracellular S. aureus essential. Identification of bacterial factors associated with impaired phagosomal acidification and maturation offers targets to limit S. aureus infections. Disclosures All authors: No reported disclosures.

Potato maltodextrin (Paselli Excel; DE < 3) was used at a fixed concentration of 15 wt %. On holding at 5°C after rapid quenching from 45°C the onset of conversion from disordered coils to aggregated double helices was seen as a steep increase in turbidity (monitored by absorbance at 600 nm) after ∼50 min, and gelation was observed (visually) after ∼120 min. Incorporation of increasing concentrations of gum arabic (1, 2, 4 and 8 wt %) caused a large, progressive decrease in the time required for structure formation and gelation to occur. A similar massive increase in rate of self-association of maltodextrin was observed for mixtures with the same concentrations (1, 2, 4 and 8 wt %) of hydroxypropylmethylcellulose (HPMC). Unlike gum arabic, however, HPMC caused very large increases in the values of turbidity recorded immediately after quenching. This cannot be attributed to phase separation, since the mixtures did not resolve into two liquid layers on high-speed centrifugation, or to ordering of maltodextrin, which was seen as a sharp increase in turbidity at longer times. Our interpretation is that segregative interactions with disordered maltodextrin promote hydrophobic association of HPMC at temperatures where it would normally remain un-associated, in the same way as HPMC and gum Arabic promote self-association of maltodextrin. These conclusions accord well with a previous investigation which showed massive precipitation of low-DE potato maltodextrin from single-phase mixtures with disordered gelatin.

We have measured the electrical resistivity of Fe3O4 to pressures of 48 GPa at temperatures between 258 and 300 K in order to evaluate compression-induced changes in electron exchange between divalent and trivalent iron ions. At ambient pressures, inverse spinel-structured magnetite is well known for its electron hopping between divalent and trivalent iron octahedral sites, and our results thus provide constraints on the role of intervalence charge transfer in altering the electrical resistivity of iron-rich phases. The resistivity of Fe3O4 decreases by more than an order of magnitude between 0 and ∼20 GPa, where it reaches a minimum, subsequently increasing by a factor of 2 between ∼20 and 48 GPa. This finding implies that the electronic exchange between Fe2+ and Fe3+ ions is notably enhanced by the initial 7% of volumetric compression but is marginally impeded at higher compressions. We associate this discontinuity in slope with a phase transition from the inverse spinel structure to a monoclinic structure at ∼20 GPa. Both previous Mossbauer work and the small change in magnitude of the resistivity indicate that electron hopping persists as the mechanism of charge transport through the transition. The resistivity at these pressures is within an order of magnitude of characteristic metallic values, but measurements of the temperature dependence of resistivity demonstrate that the high-pressure phase remains semiconducting. However, the resistivity of Fe3O4 is 1–2 orders of magnitude less than that of Fe0.94O at 48 GPa, illustrating the profound effect of intervalence charge transfer (particularly at high pressures) on the electrical properties of iron-rich oxides. By measuring electrical resistivity at pressures between 48 and 12 GPa, at temperatures between 258 and 300 K, we also constrain the pressure dependence of the activation enthalpy for conduction of the high-pressure phase of Fe3O4. We demonstrate that the activation volume of conduction is pressure dependent for the low-pressure (magnetite) phase. Such pressure dependent behavior implies that simulations of mantle resistivity that use a constant activation volume may underestimate the resistivity of the lower mantle. We also evaluate the shifts in the iron-wustite, wustite-magnetite, magnetite-hematite, and wustite-hematite oxygen fugacity buffers with depth in order to assess the oxygen fugacity conditions that could generate mixed valence compounds in the lower mantle.

Islet amyloid polypeptide (IAPP) is the constituent peptide of amyloid deposits found in the islets of non-insulin-dependent diabetic patients. Formation of islet amyloid is associated with a progressive destruction of insulin-producing beta cells. Factors responsible for the conversion of IAPP into insoluble amyloid fibrils are unknown. Both the amino acid sequence of human IAPP (hIAPP) and hypersecretion of hIAPP have been implicated as factors for amyloid fibril formation in man. We have generated transgenic mice using rat insulin promoter-hIAPP or rat IAPP (rIAPP) gene constructs. No fibrillar islet amyloid was detectable in vivo in these normoglycemic mice, although small amorphous perivascular accumulations of IAPP were observed in hIAPP mice only. To determine the effects of glucose on IAPP secretion and fibrillogenesis, pancreatic islets from transgenic and control mice were examined in vitro. Islet IAPP secretion and content were increased in transgenic islets compared with control islets. IAPP-immunoreactive fibrils were formed at both intra- and extracellular sites in isolated hIAPP islets cultured with glucose at 11.1 and 28 mM for only 7 days. At 28 mM glucose, fibrils were present in deep invaginations of beta cells as observed in non-insulin-dependent diabetic patients. No fibrils were present at low glucose concentrations in hIAPP islets or at any glucose concentration in rIAPP or control islets. Thus, glucose-induced expression and secretion of hIAPP in transgenic mouse islets can lead to formation of amyloid fibrils similar to that found in non-insulin-dependent diabetes mellitus.

ABSTRACI The quantitative measurement ofdietary fiber does not recognize its diverse actions on nutrient absorption, sterol metabolism, fermentation in the colon, and stool weight. These differences in action are more likely due to differences in physical characteristics along the gastrointestinal tract. This paper explores such physical characteristics and attempts to classify dietary fiber in a more physical manner. This approach recognizes the diverse and variant action of each dietary fiber, which may be modified as a result of processing and cooking without changing in any way the quantitative measurement of dietary fiber. The general principles developed in this paper could also be applied to other polymeric materials passing along the gastrointestinal tract. Am J C/in Nutr 1992;55:436-42.

Serum IgG antibodies to ovalbumin, gliadin and β-lactoglobulin were determined in a group of 18 atopic adults, and compared to the concentrations observed in an age/sex matched group of non-atopic subjects. Anti-ovalbumin IgG concentrations were significantly higher (mean ± s.e.m., 369 ± 93 μg/ml) in the atopic group compared with the non-atopic group (169 ± 31 μg/ml; P < 0.05). Anti-gliadin and anti-β-lactoglobulin IgG concentrations snowed no differences between the atopic and non-atopic subjects. Anti-ovalbumin IgG concentrations in both groups were significantly higher than the concentrations of IgG antibodies to gliadin and pMactoglobulin. The concentrations of the three same specific food antibodies were determined in five atopic and five non-atopic subjects at six week intervals over the period of 12 months. No significant changes in specific antibody titres were noted over this period of time in either atopic or non-atopic subjects.

The effect of NaCl on the formation, melting, and mechanical properties of Na+ gellan gels can be divided into five regions of rheological response. 1. Small additions of salt, up to a total Na+ concentration of about 25 mM, have virtually no effect on the rheological properties of the ordered polymer at low temperature; the solutions remain fluid on cooling, and give mechanical spectra similar to those of entangled polysaccharide coils. 2. Slightly higher concentrations (about 40 mM Na+) induce formation of “weak gels” (i.e. solutions that remain pourable but give gel-like mechanical spectra). Network formation is attributed to Na+ ions promoting helix-helix aggregation by binding to carboxyl groups of the polymer and thus reducing charge density, and by suppressing residual electrostatic repulsion by nonspecific charge screening. 3. Na+ concentrations in the approximate range 100–300 mM give true, self-supporting, gels whose strength and setting point (T o) increase with increasing concentration of salt and which melt in two steps, attributed to dissociation of unassociated helices and cation-mediated aggregates, respectively. 4. To continues to increase with Na+ concentration over the range 300–750 mM, but the gel strength falls, suggesting destabilisation of the network structure by association of helices into a progressively smaller number of progressively larger aggregates. 5. At NaCl concentrations above about 750 mM, T o drops sharply. It is tentatively suggested that this reduction in the stability of the helix structure is of lyotropic origin.

During the Persian Gulf War, soldiers may have inhaled, ingested, and/or experienced wound contamination by depleted uranium (DU), which is used in military projectiles and armor. DU is produced by depleting natural uranium of 234U and 235U during the uranium-enrichment process. Although the long-term effects of significant DU exposures require investigation, many veterans express fears about its impact on health. An assay by which DU exposure can be assessed would not only be a useful research tool, but the information could help mitigate the concerns of exposed individuals. In this study, urine samples from individuals enrolled in the Depleted Uranium Follow-Up Program at the Baltimore Veterans Administration Medical Center were examined for uranium content. Isotopic composition of urine uranium was determined by measuring the 235U/238U ratio, using an inductively coupled plasma mass spectrometer. Using this method, natural and depleted uranium could be readily differentiated. By demonstrating the absence of DU in soldiers who suspect exposure by inhalation or ingestion, the assay should reduce psychological stress in these individuals.

We analyzed the effect of human chorionic gonadotropin (hCG) on drug concentrations in testicular interstitial fluid and whole testis tissue samples in rats receiving hCG prior to methotrexate (MTX) administration and in animals that did not receive hCG.Adult male Sprague-Dawley rats were injected subcutaneously with 200 i.u. hCG (Goldline Laboratories, Ft. Lauderdale, FL.). Controls were injected subcutaneously with normal saline (0.2 cc). Sixteen hours after injection, each rat was given methotrexate (Methotrexate LPF, Immunex Corp. Seattle WA.) via a carotid artery cannula in a dose of 30 mg./kg. Methotrexate (MTX) levels were collected 60 minutes post infusion time in 27 rats and 90 minutes post infusion in 27 rats. MTX levels were measured in serum, testicular interstitial fluid and testicular tissue. MTX levels were measured using high performance liquid chromatography (HPLC).A significantly higher concentration of MTX was found in testicular interstitial fluid (TIF) in rats injected with hCG when specimens were collected 60 minutes post infusion. MTX levels in TIF had reversed 90 minutes post infusion with higher levels found in control rats. Tissue levels of MTX demonstrated no significant difference at either 60 or 90 minutes in the hCG treated animals or controls.Our results suggest that hCG effects the tissue distribution of MTX within the testis. Human chorionic gonadotropin may have this effect on the testicular microvasculature by 1) selectively increasing capillary permeability, 2) increasing lymphatic flow within the testes or 3) increasing testicular blood flow.

Differentiated cultures of Caco-2 human colonic cells were used to examine the importance of reduction of nonheme ferric iron, Fe(III), for transport across the brush border surface. Cultures accumulated approximately 100 pmol Fe/(h.mg protein) when 10 mumol Fe(III) as the nitrilotriacetic acid complex (1Fe:2NTA) was added to the apical compartment. Ascorbic acid enhanced cellular acquisition of iron in a dose-dependent manner, with a concentration as low as 8 mumol/L ascorbate increasing iron uptake by 50%. Similarly, the rate of iron transport from the apical to the basolateral compartment increased 5.6- and 30-fold when 100 and 1000 mumol/L ascorbic acid, respectively, were present in the apical chamber. Ascorbate-mediated stimulation of iron uptake was temperature dependent and required the reduction of Fe(III) to Fe(II), because it was inhibited by ascorbate oxidase and chelators of Fe(II). Moreover, Caco-2 cells recycled dehydroascorbic acid to ascorbic acid. Ferricyanide and Fe(II) chelators also partially inhibited iron uptake from a medium devoid of ascorbic acid. Intact Caco-2 cells exhibited a ferrireductase activity on the apical surface that accounted for the majority of iron accumulated by cells incubated in the absence of exogenous reductant. These data suggest that reduction of Fe(III) within the lumen or at the cell surface is required for transfer of this essential micronutrient across the intestinal brush border surface.

Polysaccharides, which are the principal constituents of dietary fibre, show a wide spectrum of physical properties, reflecting the nature and extent of intermolecular association. At one extreme, the polymer chains may be packed together into ordered assemblies, such as cellulose fibrils, which are almost totally resistant to hydration and swelling. At the other extreme, polysaccharide chains can exist in solution as fluctuating, disordered coils, interacting with one another only by physical entanglement. Between these extremes lie the hydrated, swollen networks typical of plant tissue and of many manufactured foods.

Dietary supplements of guar gum are known to improve blood glucose control in diabetic patients. The efficacy of guar is probably dependent mainly upon its capacity to hydrate rapidly and thus to increase viscosity in the small intestine post-prandially. Measurement of the rate of hydration in vitro might therefore be a useful index of the effectiveness of guar formulations. A simple method for monitoring the hydration rate of guar gum has been developed, which involves measuring the changes in viscosity at discrete time intervals over a period of 5 h using a Brookfield RVT rotoviscometer. Six different samples of guar gum (four pharmaceutical preparations and two food grades of guar flour) were hydrated in sealed glass jars rotated at 6 rev min-1 in order to prevent particle aggregation. Marked differences in hydration rate and ultimate (maximum) viscosity between the different guar samples were observed. Three of the four pharmaceutical preparations were lower in viscosity than the food grades of guar flour during the first 60 min of hydration. Two of the preparations hydrated so slowly that even after 5 h they attained viscosity levels of only 60% of their ultimate viscosity. These results may explain why some guar gum preparations are clinically ineffective.

Physical studies and conformational analysis of human glycophorin A suggest a revised model for its molecular organization, self-association, and interactions with the erythrocyte membrane. Intrinsic viscosity has been used to study, under more physiological conditions, the monomer–dimer equilibrium demonstrated previously by polyacrylamide–SDS gel electrophoresis. The results show that the equilibrium persists in the absence of detergent and support earlier indications that the dimer is probably the physiologically relevant form and that it is promoted by salt, inhibited by conventional denaturants, and abolished by carboxymethylation. Combined application of CD, fitted to the poly-(L-lysine) model spectra of Greenfield and Fasman, and conformational prediction, by the statistical method of Chou and Fasman and the stereochemical approach of Lim, suggests five helical sequences in glycophorin A: Arg-39 to Tyr-52 (A); Gln-63 to Glu-70 (B); Glu-72 to Leu-89 (C); Ile-95 to Lys-101 (D); and Leu-118 to Asn-125 (E). Sequence A occurs only at low pH and may be stabilized by favorable noncovalent interactions of O-linked tetrasaccharide side chains. The other four helices all occur in the dimeric form of glycophorin A at physiological pH and ionic strength. Sequence D is destroyed by trypsin, and is also lost on conversion to the monomeric form of the glycoprotein at low ionic strength. Sequence E is denatured by 6M guanidine hydrochloride/4M urea. Sequences B and C, which are separated by a single proline residue, are stable under all these conditions. Dimerization of the major, hydrophobic helical sequence, (C) may be promoted and directed by an adjacent short sequence of intermolecular parallel β-sheet (Leu-90 to Tyr-93). It is proposed that these two structures span the lipid bilayer in vivo, and that helices B and D lie, respectively, along the outer and inner surfaces of the membrane. Molecular organization in the N- and C-terminal regions of the molecule is discussed in terms of evidence from the present work and from other recent investigations.

Previous differential scanning calorimetry studies of native starch have shown an endotherm at ∼ 100°C on heating, which is attributed to melting of an amylose-lipid complex. In the present work we have shown that this transition is fully reversible (ΔH ≈ 0.4 ± 0.1 cal g−1 on heating and cooling) and displays substantial thermal hysteresis (Tm≈76°C on cooling). On removal of lipid by extraction with methanol the transition is lost, but re-appears on addition of sodium palmitate to de-fatted granules. Closely similar thermal behaviour, including hysteresis, is observed on addition of palmitate to amylose. Further evidence of complex formation between amylose and palmitate is the almost total disappearance of high resolution 1H n.m.r. signal, indicating loss of conformational mobility by the polysaccharide chain. Formation of the complex is also accompanied by a large reduction in optical activity. Using an established correlation between D-line optical rotation and the dihedral angles between adjacent residues we have compared the observed optical rotation with values calculated for specific ordered structures of amylose. The measured optical rotation values indicate adoption in solution of a novel right-handed V-amylose structure (calculated [α] D=104°; found = 100±5°) rather than the expected left-handed form characterized in the solid state (calculated [α] D=157°). Analysis of optical rotatory dispersion curves shows that in each case the changes in optical rotation on complex formation arise predominantly from changes in the intensity of the known polysaccharide backbone transition at 161 nm. Physikalische Charakterisierung von Amylose-Fettsaure-Komplexen in Starkekornern und in Losung. Fruhere Differential-Scanning-Kalorimetrie-Untersuchungen haben bei etwa 100°C einen endothermen Phasenubergang gezeigt, welcher der Umwandlung eines Amylose-Lipid-Komplexes zugeschrieben wird. Bei unserer jetzigen Arbeit fanden wir, das dieser Ubergang voll reversibel ist (ΔH ≈ 0,4 ± 0,1 cal g−1 beim Erhitzen und Kuhlen) und Starke thermische Hysterese (Tm ≈ 77°C beim Kuhlen) aufweist. Durch Methanolextraktion der Lipide verschwindet der Phasenubergang. Er tritt jedoch bei entfetteter Starke nach Zugabe von Natriumpalmitat wieder auf. Ein sehr ahnliches thermisches Verhalten einschlieslich der Hysterese wird bei Zugabe von Palmitat zu Amylose beobachtet. Ein weiterer Beweis fur die Komplexbildung zwischen Amylose und Palmitat ist das fast vollstandige Verschwinden der hohen Auflosung des 1HNMR-Signals, was einen Verlust an Konformations-Beweglichkeit der Polysaccharid-Kette anzeigt. Die Komplexbildung wird auch von einer starken Verminderung der optischen Aktivitat begleitet. Unter Anwendung der bekannten Beziehung zwischen der D-Linie der optischen Drehung und den Dihedral-Winkeln zwischen benachbarten Molekulgruppen wurden die beobachteten Werte mit denen verglichen, die fur die spezifischen Strukturen der Amylose berechnet worden waren. Die gemessenen Werte der optischen Drehung in Losung sprechen eher fur die Annahme einer neuartigen rechtsdrehenden V-Amylose-Struktur (berechnet [α]D=104°C; gefunden [α] D=100±5°) als der in festem Zustand erwarteten linksdrehenden Form (berechnet [α] D=157°). Die Analyse von optischen Rotationsdispersionskurven zeigt, das in jedem Fall die Anderungen der optischen Drehung bei der Komplexbildung hauptsachlich durch Anderungen in der Intensitat des bekannten Polysaccharidketten-Ubergangs bei 161 nm eintreten.

Relative bioavailability of two iron fortificants, electrolytic Fe and ferric orthophosphate, was related to that of the reference ferrous sulfate with in vitro and rat model depletion-repletion methods in four laboratories to compare values directly with those obtained in a parallel human study. In vitro testing was performed on Fe compounds with both solubility and dialysis in a simulated in vitro gastrointestinal digestion system. Two depletion-repletion techniques, hemoglobin-regeneration efficiency (HRE) and an official method of the Association of Official Analytical Chemists (AOAC), were examined. AOAC relative biological values (RBV) of electrolytic Fe were 0.66 and 0.78 and of FePO4 were 0.25 and 0.34. HRE values were 0.78 and 0.58 for electrolytic Fe and FePO4, respectively. When compared with FeSO4 in a radiolabeled farina-based meal fed to humans, the RBV of FePO4 was 0.25 and electrolytic Fe 0.75. Results obtained with the AOAC method serve as the most reliable prediction of Fe bioavailability in the human although in vitro dialysis is a promising screening technique.

The reactions of trifluoromethyl radicals with dimethylamine, dimethylamine-d, trimethylamine and ethyleneimine have been studied in the temperature range 27–161°C. Arrhenius parameters (based upon a value of 1013.37 mole–1 cm3 sec–1 for the velocity constant for the combination of trifluoromethyl radicals) have been obtained for the reactions : [graphic omitted] With dimethylamine, radical attack is favoured, on a “per-atom basis,” at the nitrogen atom but the difference in reactivities of the C—H and N—H bonds is much less marked than with methyl radicals. Assuming a zero secondary isotope effect, substitution of D for H in dimethylamine alters the reactivity of the amino group by an amount in accord with zero-point-energy difference.

The reactions of trifluoromethyl radicals with methylamine and trideuteromethylamine have been studied in the temperature range 30–160°C in order to determine the rates at which hydrogen and deuterium atoms are abstracted from the molecules. With methylamine, radical attack is favoured at the alkyl position, and substitution of deuterium for hydrogen alters the positional reactivity by an amount in accord with the zero-point energy difference. The pre-exponential factors for attack at the nitrogen site have been explained in terms of a low steric factor due to repulsion forces between the polar molecule and the radical. Arrhenius parameters (based upon a value of 1013.34 mole–1 cm3 sec–1 for the rate constant of combination of trifluoromethyl radicals ) have been measured for the reactions : CF3+CD3NH2→CF3H+CD3NH 9.94±0.22 4.4±0.4, CF3+CD3NH2→CF3D+CD2NH2 11.03±0.09 6.1±0.2, CF3+CH3NH2→CF3H+(CNH4) 10.79±0.16 4.2±0.3, CF3+CH3NH2→CF3H+CH2NH2 10.72±0.39 4.2±0.6, and have been calculated for NHCH3+CF3H→NH2CH2+CH3 9.9 18.4, (units of A, mole–1 cm3 sec–1; and E, kcal mole–1).

The reaction of trifluoromethyl radicals with ammonia in the gas phase has been studied in the temperature range 30-352°. Product formation is not explicable simply in terms of the reactions: and curvature of the Arrhenius plot at high and low temperatures suggests that there are additional sources of fluoroform.

The reactions of trifluoromethyl radicals with methanol and trideuteromethanol have been studied in the temperature range 84–162°C in order to determine the rate at which hydrogen and deuterium atom abstraction occurs. Over this temperature range, abstraction from the hydroxyl group is slightly favoured over abstraction from the methyl group. Substitution of deuterium for hydrogen alters the positional reactivity by an amount in accord with the zero-point energy difference. Arrhenius parameters (based upon a value of 1013.34 mole–1 cm3 sec–1 of the rate constant of combination of trifluoromethyl radicals) have been measured for the reactions : [graphics omitted] and have been calculated for [graphic omitted] (units of A mole–1 cm3 sec–1 and E kcal mole–1).

The reactions of trifluoromethyl radicals, generated by the photolysis of hexafluoroacetone, with the aldehydes HCOCF3, HCOC2F5 and HCOC3F7 have been studied and the following Arrhenius parameters determined : [graphic omitted] The rate of hydrogen atom abstraction from the fluoroaldehydes at 164°C is independent of the size of the fluoroalkyl group. Direct photolysis of the aldehydes HCOCF3, HCOC2F5 and HCOC3F7 is complicated by the intramolecular elimination reactions : [graphic omitted] A value of 1.95, which is independent of temperature, has been obtained for the cross-combination of CF3 and C2F5 radicals.

SummaryInjurious effects of high phosphorus diets for the guinea pig, which include poor growth, metastatic calcification, and death, are due in part to the fact that this animal does not tolerate an acid diet. This has been demonstrated by the marked drop in urine pH, a decrease in plasma carbon dioxide capacity and an increase in blood inorganic phosphorus. Addition of various cations produced a more alkaline urine, but a combination of sodium or potassium and magnesium proved most beneficial. The guinea pig is highly sensitive to an acid diet because a negligible amount of ammonia is excreted by way of the kidneys.

The sol-gel transition has been studied for two polysaccharide systems, which form gels by the noncovalent association of chain segments in ordered conformations, but which differ in the geometry of these conformations. For ι-carrageenan they are double helices, the formation and melting of which is monitored by [13C]-n.m.r. and by optical rotation. For alginate, the associations involve the site-binding of Ca2+ ions in an egg-box or sandwich-like geometry, the formation of which is monitored and related to similar structures in solid films using circular dichroism spectroscopy. Despite the low concentration of dispersed polysaccharide (of the order of 1 %), each gel network is a very highly associated structure in which almost all sequences of sugar residues having the appropriate covalent structure to permit the ordered binding, are actually involved in binding to other chains.

Phytate:zinc molar ratio, minerals, and fiber contents of regular, ovo-lacto vegetarian, and soy meat-substitute hospital diets were determined. The phytate:zinc molar ratio, minerals, and fiber contents of the soy meat-substitute diet were significantly higher than those of ovo-lacto vegetarian and regular hospital diets is within acceptable limits established by human and animal studies conducted by the USDA's Vitamin and Mineral Nutrition Laboratory.

Bioavailability factors can greatly modify the absorption of dietary iron consumed in different meals by an individual. A greater percentage is generally absorbed of heme iron from animal tissues than of nonheme iron of either animal or plant food. The amount of meat in a meal is the only bioavailability factor known to influence absorption of heme iron. Absorption of iron from the exchangeable nonheme iron pool of a meal is influenced by both enhancing and inhibiting substances or factors. Ascorbic acid, meat, fish, and poultry enhance absorption of nonheme iron, and meals may be classified according to relative bioavailability depending on the content of meat, fish, poultry, and/or ascorbic acid. Some low-molecular-weight organic acids may also increase the bioavailability of nonheme iron. Synthetic metal-chelating agents added to foods and the beverages tea and coffee will inhibit absorption of nonheme iron in a concentration-dependent manner. Wheat bran, soy products, cow's milk, and egg tend to decrease bioavailability of nonheme iron when included in a meal. However, the effect of compounds thought to be responsible for the inhibition in purified form (phytate, fiber, phosphoproteins) is dependent on chemical form and concentration. In some foods there may be as yet unidentified inhibitors or interaction between compounds to inhibit absorption of nonheme iron. Currently available information permits estimation of relative bioavailable iron in a meal.

This review has approached zinc requirements, bioavailabilities and recommended dietary allowances from a historical view. For example, a requirement for zinc was first demonstrated for the microorganism Aspergillus niger more than a century ago, although zinc has been recognized as a dietary nutrient for humans only within the last decade. Dietary requirement was defined as that quantity of zinc which must be provided daily in order to meet the metabolic requirement. The degree of bioavailability determines the total dietary zinc which must be consumed by humans to remain in metabolic equilibrium. In regard to recommended dietary allowances (RDA), they are recommended average daily intakes of nutrients that population groups should consume. RDA are not synonymous with requirements. Metabolic requirements (the quantity that must be provided to the circulating blood daily) have been determined previously using radio-isotope studies and have indicated a calculated need of approximately 6 mg for an adult per day. More recently a similar amount (4-6 mg) has been found to be required daily (intravenously) in order to maintain plasma zinc concentrations and daily urinary zinc excretion within normal range in hospitalized subjects. Average zinc intakes of large segments of the U.S. population are receiving levels approaching one-half or less the RDA with no apparent deleterious effects. These subjects include pregnant and lactating women. In addition, the zinc content of breast milk is lower than previous studies indicated. Thus, it appears that the majority of breast-fed infants are receiving no more than 70% of the recommended intake, with a recent study indicating less than 50%. Factors reported to affect bioavailability of zinc from foods are discussed. These include fiber and phytate. It was concluded that no definite conclusion can be reached regarding the overall effect of food fiber on zinc balance. Many of the studies were of short duration, with the longest being 32 days. It is probable that different sources of food fiber may have different effects on zinc balance. The apparent discrepancy in the literature regarding the effect of soy protein on zinc requirement was cited. Lastly, the phytate:zinc molar ratio concept was designed to test it as a predictor of zinc bioavailability to humans. The concept must be expanded to recognize the relevance of the total daily dietary zinc intake. Specifically, impairment of absorption of zinc by phytate would be more critical if the total dietary intake was low since the metabolic requirements might not be met.(ABSTRACT TRUNCATED AT 400 WORDS)

The literature indicates that phytate:zinc and phytate X calcium:zinc millimolar ratios of a diet may provide useful indexes of the bioavailability of dietary zinc. However, there is little information on the phytate:zinc and phytate X calcium:zinc millimolar ratios for total human diets. We have therefore determined the phytate:zinc and phytate X calcium:zinc millimolar ratios of self-selected diets of 29 American omnivores, 23 American vegetarians, 30 Asian Indian immigrant vegetarians, and 26 Nepalese lactating vegetarians. Criteria for selection of subjects were: good health, no extreme dietary habits, and no intake of nutrient supplements. According to the limited literature, the suggested critical values for phytate:zinc and phytate X calcium:zinc millimolar ratios in animal diets and retrospective calculations from human diets are greater than 10 and greater than 200, respectively. The mean phytate:zinc and phytate X calcium:zinc millimolar ratios of American omnivorous diets in the present study were less than 10 and 200, respectively. Confirmation of the critical molar ratios as indexes of the bioavailability of zinc in human diets has not been established by experimentation. However, if the data from animal studies are applicable to human diets, the present study suggests that phytate has little influence on zinc bioavailability of most American diets. In contrast, the mean phytate:zinc and phytate X calcium:zinc millimolar ratios of all vegetarian diets were above the proposed critical levels. Those data, therefore, suggest that phytate might increase the risk of impaired zinc bioavailability for vegetarians consuming a relatively high level of calcium.

We conducted a medical records survey of 270 randomly selected patients 20 years of age or older seen by family practice residents in a university-based training program. This study concerned residents' compliance with certain preventive recommendations made by four expert groups: the American Cancer Society, the Canadian Task Force on the Periodic Health Examination, the Immunization Practices Advisory Committee, and the National Institutes of Health Consensus Development Conference on treating elevated cholesterol. The interventions studied were breast examination, mammography, pelvic examination, Pap testing, digital rectal examination, stool guaiac slide testing, serum cholesterol screening, and pneumococcal and influenza vaccinations. We calculated the percentage of eligible patients receiving each of these interventions. The highest rates of resident compliance with health screening recommendations were for Pap testing in women 20-34 and 35-59 years of age (31.7% and 22.6%, respectively), breast examination in women 20-39 years of age (27.3%), and influenza vaccination (23.0%). There were no other rates of compliance that exceeded 20%. Our data thus indicate that residents in this program did not comply well with health maintenance recommendations.