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The effects of cold work on dynamic flow strength is studied through measurements of dislocation density and elastic precursor attenuation in shocked aluminium. High-purity aluminium and Al 6082 alloy samples are subjected to up to three passes of rotary swaging, a severe plastic deformation (SPD) technique, in order to produce large variations in starting material conditions. Detailed material characterisation is performed using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) to determine the initial dislocation density, texture, grain boundary density and misorientation distribution. Variations in dynamic strength are studied through the evolution of the elastic precursor amplitude with propagation distance in specimens with thicknesses between 0.2 and 1 mm, shock loaded to impact stresses of about 4.6 GPa. It is shown that dynamic strength decreases with increasing initial dislocation density in both materials, demonstrating rare, quantified measurements of a reversal in the effect of dislocation density on yield strength at strain rates around 104s-1and above.

Metallic cylinders of rolled homogeneous armour (RHA) steel, Ti6Al4V, and FNC tungsten alloy of four different length lto diameter dratios (dimensions in mm): 8/4, 4/8, 10/8, 8/10) were deformed at high rates of deformation using a direct impact Hopkinson pressure bar. Highspeed photographic sequences of the deformation were taken using a Hadland Imacon 790 imageconverter camera working at either 1 or 2 x 104frames/s. It was found that titanium alloy cylinders of all four aspect ratios shear-banded and fractured, but that cylinders made from RHA steel and FNC tungsten behaved in a ductile manner when l/d< 1 but in a brittle manner when l/d> 1. We conclude that adiabatic shear banding is not just an inherent material property but that in some materials size effects/geometry can trigger this phenomenon.

Objective:: Evaluate the impact of a non-neonatal intensive care unit (NICU)-specific peer counseling (PC) program on the cessation of human milk receipt at and post-NICU discharge. Study Design:: A multivariable logistic regression model used data from 400 mother–infant dyads from a level IV NICU to compare cessation of human milk receipt at NICU discharge by PC program status. Kaplan–Meier distributions and a multivariable Cox proportional hazards model assessed the relationship between participants/non-participants and cessation of human milk post-NICU discharge. Results:: No statistically significant differences between groups in cessation of human milk either by or post-discharge were observed. Identified variables associated with the outcome(s) of interest included maternal and infant age, length of stay, presence of a breastfeeding duration goal and frequency of NICU lactation consultant contact. Conclusion:: Exposure to a non NICU-specific PC program was not associated with human milk receipt either by or post-NICU discharge.

The relationship between ocular toxoplasmosis and levels of toxoplasma specific antibodies was examined in 195 patients. Using clinical information collected by questionnaires, patients were divided into: 97 with ocular toxoplasmosis (group 1) and 98 with ocular lesions not due to toxoplasma (group 2). The geometric mean of dye test titres (±S.D. natural log titre) in group 1 was 53·2 (±0·95) compared with 24·6 (±1·11) in group 2 (P&lt;0·001). Young females tended to have more active lesions compared with young males (P&lt;0·05). There was an age-dependent difference in dye test titres between the groups (P&lt;0·001). Group 1 showed a decline in titre with age compared with an increase in group 2. Ocular toxoplasmosis was diagnosed most frequently among 21–30 year olds. More group 1 patients had dye test titres 65 iu/ml than group 2 (P&lt;0·05). Dye test titres 65 iu/ml support a diagnosis of ocular toxoplasmosis whereas lower titres suggest other causes for eye lesions.

A recent report (Nanba O, Satoh K: Proc. Natl. Acad. Sci. USA 84: 109–112, 1987) described the isolation from spinach of a putative photosystem 2 reaction centre which contained cytochrome b-559 and three other electrophoretically resolvable polypeptide bands, two of which have molecular weights comparable to the D1 and D2 polypeptides. We have used in vivo labelling with radioactive methionine and probed with D1 and D2 monospecific antibodies (raised against synthetically expressed sequences of the psbA and psbD genes) for specific detection of these proteins in a similarly prepared photosystem 2 reaction centre preparation. These techniques identified a 32 000 dalton D1 band, a 30 000 dalton D2 band and a 55 000 dalton D1/D2 aggregate, the latter apparently arising from the detergent treatments employed. Digestions with a lysine-specific protease further confirmed the identification of the lysine-free D1 polypeptide and also confirmed that the D1 molecules in the 55 000 dalton band were in aggregation with other bands and not in self-aggregates. The D1 and D2 polypeptides (including the aggregate) are considerably enriched in the photosystem two reaction centre preparation compared to the other resolved fractions.

A specific antiserum for morphine-6-glucuronide (M6G) has been raised in a rabbit in response to immunization with a novel hapten: Protein conjugate (N-aminobutylnormorphine-6-glucuronide-thyroglobulin). Cross-reactivity with morphine and structurally related compounds was found to be negligible as expected from the nature of this immunogen. Using this antiserum, a simple, rapid and robust radioimmunoassay (RIA) has been developed for determination of M6G in samples of human plasma. The assay has a sensitivity of 0·05 ng/mL using 100 μL sample volumes and affords complete recovery of M6G over the range 2–200 ng/mL. The presence of morphine or morphine-3-glucuronide at concentrations up to 100 times the levels of M6G did not result in any measurable interference. Close agreement was obtained between M6G results obtained using the RIA and a specific high-performance liquid chromatography assay. This RIA offers an attractive alternative to existing methods for the determination of M6G in human plasma and will facilitate further metabolic and pharmacokinetic studies of morphine and M6G in the clinical setting.

A detailed comparison of the polar-lipid composition of chloroplast thylakoid membranes isolated from triazine-susceptible and triazine-resistant biotypes of Chenopodium album, Senecio vulgaris, Poa annua and Amaranthus retroflexus has been carried out. No major differences in the composition of the bulk lipid matrix were found except for a slightly higher monogalactosyldiacylglycerol to digalactosyldiacylglycerol ratio in resistant compared with susceptible biotypes. There was, however, in the case of resistant plants a higher level of phosphatidylglycerol-containing transhexadecenoic acid in membrane fractions enriched in photosystem two. It is concluded that although the minor differences could contribute to triazine resistance it is more likely that they reflect secondary alterations in membrane organisation associated with changes in relative levels of pigment-protein complexes.

The lipid composition and degree of unsaturation of fatty acids has been measured for membranes isolated from leaves of Pisum sativum grown under either summer or winter conditions. Although the lipid-class composition was not significantly changed for the two growth conditions the degree of unsaturation of the fatty acids was greater for winter than summer plants. The difference in unsaturation was evident with all lipid classes of the non-thylakoid membranes including the galactolipids of the chloroplast envelope. In contrast, both the relative amounts of lipid classes and degree of saturation were not greatly changed for summer and winter thylakoids with the exception that phosphatidylglycerol had a greater linolenic acid (18:3) content for the thylakoids of winter grown leaves. However, a striking difference was found for the total acyl lipid to chlorophyll ratio for thylakoids isolated from summer or winter plants, with the former producing a lower ratio than the latter growth conditions. The above changes in lipid composition of chloroplast membranes are discussed in terms of optimizing their functional activities under the different growth conditions.

Incubation of a membrane preparation enriched in Photosystem Two (PSII) at alkaline pH inhibited the water-splitting reactions in two distinct steps. Up to pH 8.5 the inhibition was reversible, whereas at higher alkalinities it was irreversible. It was shown that the reversible phase correlated with loss and rebinding of the 23 kDa extrinsic polypeptide. However, after mild alkaline treatments a partial recovery was possible without the binding of the 23 kDa polypeptide when the assay was at the optimal pH of 6.5 and in a medium containing excess Cl-. The irreversible phase was found to be closely linked with the removal of the 33 kDa extrinsic protein of PSII. Treatments with pH values above 8.5 not only caused the 33 kDa protein to be displaced from the PSII-enriched membranes, but also resulted in an irreversible modification of the binding sites such that the extrinsic 33 kDa protein could not reassociate with PSII when the pH was lowered to 6.5. The results obtained with these more extreme alkaline pH treatments support the notion that the 23 kDa protein cannot bind to PSII unless the 33 kDa protein is already bound. The differential effect of pH on the removal of the 23 kDa and 33 kDa proteins contrasted with the data of Kuwabara & Murata [(1983) Plant Cell Physiol. 24, 741-747], but this discrepancy was accounted for by the use of glycerol in the incubation media.

To test whether secondary and tertiary structures of marine-algal structural polysaccharides may be altered during adaptive responses to hydrodynamic stresses, juvenile Egregia menziesii (Turn.) Aresch. sporophytes were cultured under three different regimes: (i) low-energy (LE) specimens were subjected to water motion produced by standard bubbling and circulation of tank water; (ii) high-energy (HE) specimens received additional movement in pumped streams of water; and (iii) stretched (STR) specimens were grown under low-energy conditions but also were subjected to constant, longitudinal tension (0.7 N). After 6–10 weeks growth, cell-wall structural polysaccharides from specimen blades were isolated by solubilizing less-ordered matrix polysaccharides. Neutral-sugar and uronic acid contents of these isolates were measured, and samples were analyzed by x-ray diffraction and by Raman and 13C-nuclear magnetic resonance (NMR) spectroscopy. On average, structural polysaccharides formed about 7.2% of dry-weight biomass. The portion of isolated mass accountable to neutral sugars ranged from an average of 85% for STR sporophytes to 94% for both LE and HE specimens. For all specimens, glucose composed an average of 99% of this fraction. Uronic acids could not be detected in isolates from any treatment group. Cellulose dominance in each isolate was indicated clearly in x-ray diffraction patterns and in Raman and 13C-NMR spectra. These data further demonstrated that both the cellulose I allomorph and the disordered form of the polymer were present in each isolate and that the STR isolate contained small quantities of the cellulose II allomorph. In general, the LE and HE samples had very similar crystallinity; lateral order was slightly more developed in LE samples. However, the STR treatment produced cellulose with lowest crystallinity and least lateral order. Results suggest that mechanical stress modified cellulose crystallinity in these kelps by altering levels of disordered cellulose and lateral dimensions of cellulose crystallites and, in one instance, changed the crystallinity qualitatively. Physical disturbances to cell plasma membranes may have instigated these trends. In the STR specimens in particular, such disturbances might have been supplemented by fundamental changes to kelp physiology, affecting both substantial decreases in crystallinity and production of the cellulose II allomorph. Changes in the nature of the cellulose cannot, however, account for changes in the elastic moduli.

Chloroplast thylakoid lipids have been isolated free of photosynthetic pigments using a combination of high performance liquid and thin layer chromatography. The hydrophobic fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH) has been incorporated into aqueous dispersions of the isolated lipids in order to investigate dynamic and structural properties of the resulting bilayer membranes. Time dependent fluorescence anisotropy decays have been measured and analysed assuming the wobbling-in-cone model (Kinosita et al., Biophys J 20 (1977) 289–305). The DPH fluorescence lifetimes and the static and dynamic fluorescence anisotropy decay parameters for the probe in a total lipid mixture or in pure digalactosyldiacylglycerol (DGDG), changed in a predictable way with increasing temperature (10°–36°C). For a given temperature, it was found that the total lipid mixture was in general less ordered and showed greater dynamic motion as judged from DPH fluorescence anisotropy and compared with the pure DGDG system, although at 36°C differences in dynamic parameters were less evident. Overall the results obtained emphasize the highly fluid nature of thylakoid membrane lipids and give a basis for investigating how intrinsic proteins modify structural and dynamic properties of the in vivo membrane.

The extracellular anionic polysaccharide isolated from cultures of a unicellular red alga, Porphyridium cruentum, contains a small amount of protein after extensive purification. The polysaccharide and protein are recovered in the same fraction after isopycnic CsCl-density-gradient centrifugation in 4M-guanidinium chloride, under conditions designed to separate proteins from polysaccharide. The peptide portion of the protein-polysaccharide is released from the polysaccharide by alkali under conditions for beta-elimination. The released peptide is non-diffusible, but in can be separated from the polysaccharide by precipitation of the polysaccharide as the cetylpyridinium complex. Under conditions for beta-elimination of certain O-glycosidic carbohydrate-protein linkages, selective destruction of serine and threonine occurs. The addition of a reducing agent to the alkali mixture produces a selective increase in alanine and alpha-aminobutyric acid. Addition of a tritiated reducing agent to the alkali mixture produces radioactive alanine and alpha-aminobutyric acid, and xylitol as the only sugar alcohol. Similar results are obtained from glycopeptides isolated from partial acid hydrolysates. A macromolecular structure of the protein-polysaccharide is suggested by a comparison of the intrinsic viscosity of material before and after treatment with alkali and proteolytic enzymes.

1. The incorporation of [2-14C]mevalonic acid by Chloropseudomonas ethylica strain 2K into chlorobactene was studied. 2. Oxidative degradation of chlorobactene of constant specific radioactivity produced labelled benzenecarboxylic acids and indicated that the benzene ring originates from mevalonic acid. 3. Decarboxylation studies demonstrated a stereospecific methyl migration in the formation of the 1,2,5-trimethylphenyl group of chlorobactene. The migrating methyl group was derived from the C-3′ position of mevalonic acid.

The biliprotein allophycocyanin was purified from Phormidium luridum, Anabaena variabilis and Plectonema boryanum. R-phycocyanin was purified from Rhodymenia palmata. The chromophores were cleaved from the denatured protein by methanol hydrolysis. They were purified and crystallized as the dimethyl esters. Chromatographic and absorption-spectral (visible–ultraviolet and infrared) comparisons with reference material have established phycocyanobilin as the chromophore of allophycocyanin. Phycocyanobilin and phycoerythrobilin were shown to be the chromophores of R-phycocyanin.

C‐phycocyanin has been prepared from algae representative of various orders and families in the Cyanophyceae and Rhodophyceae. The chromophore phycocyanobilin has been cleaved, purified and crystallized as the dimethyl ester. Each sample was compared with reference phycocyanobilin dimethyl ester and found to be identical on the basis of absorption spectral (ultraviolet, visible and infrared) and chromatographic properties. The phylogenetic implications of these results are discussed.

Frost-resistant winter cereals actively adapt the fluidity of their membranes to decreasing temperatures. We have attempted to study the membrane lipid changes that are responsible for this adaptation. In the total leaf lipids of winter barley plants (Hordeum vulgare L.) 3 weeks' growth at low temperature (4 °C) decreased the number of double bonds per lipid molecule in all lipid classes extracted from leaves. However, there were only minor changes in the degree of fatty acid unsaturation in the lipids of barley thylakoid membranes during this treatment. In contrast, a significant increase in the lipid/protein ratio was observed in cold-adapted thylakoids when compared with control plants. This cold-induced increase in the lipid/protein ratio seems to act as an adaptive mechanism to maintain fluid membranes despite lower growth temperatures. Cold-hardening also caused a marked increase of the total polar lipids of leaves relative to chlorophyll; this was particularly pronounced for the phospholipids, indicating that the adaptation to low growth temperatures could also be associated with accumulation of extra-chloroplastic material in the cells.