Young Asian women and relationships: traditional or transitional?

This article investigates social and cultural aspects of "teenage life" among south Asian girls in Britain, particularly their experiences of relationships with boys and the extent to which they become involved in sexual activities. In-depth interviews were carried out with teenage girls and young women from Indian, Pakistani and Bangladeshi backgrounds and a comparative group of white British girls, in four schools and one college in the South and West Health Authority Region. Asian teenage girls conformed to different behavioural norms than their white peers. They were influenced by cultural traditions, religious obligations, family loyalties and community expectations. Few Asian girls became involved in relationships or sexual activities. However, once removed from the parental home, the influence of parents and their Asian community, their social and sexual behaviour changes; they experience an independence which often involves relationships and sexual activities. In contrast, white teenage girls experienced a different set of pressures which came from peers and boyfriends and accepted involvement with boys and sexual activity.     

Facile fabrication of thermo-responsive and reduction-sensitive polymeric micelles for anticancer drug delivery

The development of thermo-responsive and reduction-sensitive polymeric micelles based on an amphiphilic block copolymer poly[(PEG-MEMA)-co-(Boc-Cyst-MMAm)]-block-PEG (denoted PEG-P-SS-HP) for the intracellular delivery of anticancer drugs is reported. PTX, as model drug, was loaded into the PEG-P-SS-HP micelles with an encapsulation efficiency >90%, resulting in a high drug loading content (up to 35?wt%). The PTX-loaded PEG-P-SS-HP micelles show slow drug release in PBS and rapid release after incubation with DTT. The PTX-loaded micelles display a better cytotoxic effect than the free drug, whereas empty micelles are found to be non-toxic. The thermo-responsive and reduction-sensitive polymeric micelles described may serve as promising carriers for cytostatic drugs.     

Identification of formaldehyde-induced modifications in proteins: reactions with insulin

Formaldehyde is frequently used to inactivate, stabilize, or immobilize proteins. The treatment results in a large variety of chemical modifications in proteins, such as the formation of methylol groups, Schiff bases, and methylene bridges. The purpose of the present study was to identify the stable formaldehyde-induced modifications in a small protein. Therefore, insulin was treated with excess formaldehyde (CH2O) or deuterated formaldehyde (CD2O). In a separate experiment, insulin was modified by formaldehyde (CH2O vs CD2O) and glycine. The mixture of CH2O-treated and CD2O-treated insulin was digested by the proteinase Glu-C. The peptide fragments obtained were analyzed by liquid chromatography-mass spectrometry (LC-MS). Seven intramolecular cross-links were identified in formaldehyde-treated insulin. Furthermore, eight out of the sixteen potentially reactive sites of the insulin molecule were modified by incubation with formaldehyde and glycine. Both the location and the chemical nature of the modifications could be assigned based on the mass increase of potential adducts as elucidated in our previous study (B. Metz et al. (2004) J. Biol. Chem. 279, 6235-6243). To confirm the assigned structures, LC-MS measurements with collision-induced dissociation (LC-MS/MS) were performed on insulin fragments. The results of the LC-MS/MS analyses agreed excellently with the assignments. The study showed that arginine, tyrosine, and lysine residues were very reactive. However, eight theoretically reactive residues did not show detectable modifications, probably because of their low intrinsic reactivity, inaccessibility, or both. The asparagine, glutamine, and histidine residues were not converted in insulin. The N-termini of insulin were partly converted to the expected imidazolidinone adducts, indicating that the protein conformation affects the accessibility and reactivity of these residues. In conclusion, this study shows that, based on our current insights in the chemistry of the reactions between proteins and formaldehyde, we are able to elucidate the location and nature of formaldehyde-induced modifications in a small protein. The approach followed in this study may be generally applicable to larger formaldehyde-treated proteins, such as toxoids used in vaccines.     

In vitro degradation behavior of microspheres based on cross-linked dextran

The aim of this study was to investigate the in vitro degradation of hydroxyl ethyl methacrylated dextran (dex-HEMA) microspheres. Dextran microspheres were incubated in phosphate buffer pH 7.4 at 37 degrees C, and the dry mass, mechanical strength, and chemical composition of the microspheres were monitored in time. The amount and nature of the formed degradation products were established for microspheres with different cross-link densities by FT-IR (Fourier transformed infrared spectroscopy), NMR, mass spectrometry, SEC analysis, and XPS (X-ray photoelectron microscopy). The dex-HEMA microspheres DS 12 (degree of HEMA substitution; the number of HEMA groups per 100 glucose units) incubated at pH 7.4 and 37 degrees C showed a continuous mass loss, leaving after 6 months a residue of about 10% (w/w) of water-insoluble products. NMR, mass spectrometry, and SEC showed that the water-soluble degradation products consisted of dextran, low molecular weight pHEMA (M(n) approximately 15 kg/mol), and small amounts of unreacted HEMA and HEMA-DMAP (intermediate reaction product of the Baylis-Hillman reaction of HEMA with DMAP (4-dimethyl aminopyridine)). Microscopy revealed that the water-insoluble residue consisted of particles with shape and size similar to that of nondegraded microspheres. However, these particles had lost their mechanical strength as evidenced from micromanipulation experiments. FT-IR and XPS (X-ray photoelectron microscopy) revealed that these particles consisted of pHEMA, of which a small fraction was soluble in methanol (M(n) ranging between 27 and 82 kg/mol). The insoluble material likely consisted of lightly cross-linked pHEMA. In conclusion, in vitro degradation of dex-HEMA microspheres results in the formation of water-soluble degradation products (mainly dextran), leaving a small water-insoluble residue mainly consisting of pHEMA.     

Holmium-loaded poly(L-lactic acid) microspheres: in vitro degradation study

The clinical application of holmium-loaded poly(L-lactic acid) (PLLA) microspheres for the radionuclide treatment of liver malignancies requires in depth understanding of the degradation characteristics of the microspheres. To this end, an in-vitro degradation study was conducted. PLLA-microspheres with and without HoAcAc loading, and before and after neutron or gamma irradiation, were incubated in a phosphate buffer at 37 degrees C for 12 months. In contrast with the other microsphere formulations, only the neutron-irradiated Ho-PLLA-MS disintegrated. At the end of the experiment (52 weeks) highly crystalline fragments, as evidenced from Differential Scanning Calorimetry, were present. Infrared spectroscopy showed that these fragments consisted of holmium lactate. In conclusion, this study demonstrates that the degradation of neutron-irradiated Ho-PLLA-MS was substantially accelerated by the HoAcAc incorporation and subsequent neutron irradiation. The degradation of these microspheres in aqueous solution resulted in the formation of insoluble holmium lactate microcrystals without release of Ho3+.     

Macroscopic hydrogels by self-assembly of oligolactate-grafted dextran microspheres

A novel approach is presented to create self-assembling hydrogels. Microspheres based on cross-linked dextran were chemically modified with L- or D-oligolactate chains. Successful grafting of the particles was confirmed by Fourier transform infrared (FT-IR) and Raman and X-ray photoelectron spectroscopy (XPS). Rheological analysis of aqueous dispersions of oligolactate-grafted microspheres demonstrated that hydrophobic interactions between oligolactate chains on the surface of various microspheres resulted in the formation of an almost fully elastic gel. A mixture of microspheres substituted with L- or D-oligolactates of opposite chirality resulted in gels with highest strength, likely due to stereocomplexation between the enantiomers. The network properties could be modulated by varying the solid content of the gel, the DS (i.e., number of lactate grafts per 100 glucopyranose units) and the DP (i.e., degree of polymerization) of the oligolactate grafts. Protein loading of the hydrogels could be achieved by simply mixing the microspheres with protein solution. Release experiments showed a continuous release of the entrapped lysozyme, with 50% released after 5 days and full preservation of its enzymatic activity. The biocompatible nature of the material, the protein-friendly self-assembly of the hydrogel and the possibility to tailor the gel properties, makes this hydrogel system an attractive candidate for pharmaceutical and biomedical applications.     

Enzymatic degradation of liposome-grafted poly(hydroxyethyl L-glutamine)

Liposomes coated with poly(hydroxyethyl L-glutamine) (PHEG) show prolonged circulation times and biodistribution patterns comparable to PEG-coated liposomes. While PEG is a nondegradable polymer, PHEG is expected to be hydrolyzed by proteases. In this study the enzymatic degradability of PHEG both in its free form and grafted onto liposomes was investigated, using the proteases papain, pronase E, and cathepsin B. Enzymatic action was monitored with a ninhydrin assay, which quantifies amine groups formed due to hydrolysis of amide bonds, and the degradation products were characterized by MALDI-ToF mass spectrometry. PHEG, both in its free form and when grafted onto liposomes, showed degradation into low molecular weight peptides by the enzymes. Thus, we present a polymer-coated long-circulating liposome with an enzymatically degradable coating polymer, avoiding the risk of cellular accumulation.     

A rapid technique to predict malting quality in barley prior to harvest

Samples of grain from three spring barley cultivars of differing malting quality were collected at regular intervals during four weeks prior to harvest. The samples were dried, then assessed for relative grain hardness using the "Milling Energy" test. Ranking order of the cultivars for this character, which relates strongly to malting quality, was unaltered throughout. In a further experiment, it was demonstrated that selection for milling energy could be successfully practised on oven-dried grain collected six weeks after ear emergence.     

Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded.