The effect of crosslinking in elastomers investigated by NMR analysis of 13C edited transverse 1H NMR relaxation

The transverse nuclear ¹H magnetization decay in poly(styrene-co-butadiene) (SBR) is investigated by editing ¹³C NMR spectra. This technique allows for the assignment of localized ¹H dynamical information by discriminating the chemical sites based on their chemical shift in the ¹³C dimension. Here, the homo- and heteronuclear dipolar couplings contribute to the ¹H NMR relaxation giving additional information to a homonuclear experiment. In this heteronuclear 2D experiment two prominent peaks are observed in the ¹³C dimension, which correspond to CH and CH₂ groups, respectively. The decay rate in the ¹H dimension is found for both groups to scale with the crosslink density. An additional ultra-fast magnetization decay is reported. The effect of the carbon black filler is investigated for this component. The analysis of the ¹³C NMR edited transverse ¹H magnetization relaxation is a useful tool in combining high resolution NMR spectra with information on molecular dynamics, providing insight into crosslink density and filler effects.     

Dominant negative mutations in the C-propeptide of COL2A1 cause platyspondylic lethal skeletal dysplasia, torrance type, and define a novel subfamily within the type 2 collagenopathies

Platyspondylic lethal skeletal dysplasia (PLSD) Torrance type (PLSD-T) is a rare skeletal dysplasia characterized by platyspondyly, brachydactyly, and metaphyseal changes. Generally a perinatally lethal disease, a few long-term survivors have been reported. Recently, mutations in the carboxy-propeptide of type II collagen have been identified in two patients with PLSD-T, indicating that PLSD-T is a type 2 collagen-associated disorder. We studied eight additional cases of PLSD-T and found that all had mutations in the C-propeptide domain of COL2A1. The mutational spectrum includes missense, stop codon and frameshift mutations. All non-sense mutations were located in the last exon, where they would escape non-sense-mediated RNA-decay. We conclude that PLSD-T is caused by mutations in the C-propeptide domain of COL2A1, which lead to biosynthesis of an altered collagen chain (as opposed to a null allele). Similar mutations have recently been found to be the cause of spondyloperipheral dysplasia, a non-lethal dominant disorder whose clinical and radiographical features overlap those of the rare long-term survivors with PLSD-T. Thus, spondyloperipheral dysplasia and PLSD-T constitute a novel subfamily within the type II collagenopathies, associated with specific mutations in the C-propeptide domain and characterized by distinctive radiological features including metaphyseal changes and brachydactyly that set them apart from other type 2 collagenopathies associated with mutations in the triple-helical domain of COL2A1. The specific phenotype of C-propeptide mutations could result from a combination of diminished collagen fibril formation, toxic effects through the accumulation of unfolded collagen chains inside the chondrocytes, and alteration of a putative signaling function of the carboxy-propeptide of type 2 collagen.     

Detection of perforin and granzyme A mRNA in infiltrating cells during infection of mice with lymphocytic choriomeningitis virus

The analysis of gene expression in cytotoxic T cells by in situ hybridization of serial liver and brain sections from mice infected with lymphocytic choriomeningitis virus (LCMV) and immunostaining with T cell marker- and virus-specific antibodies revealed a close histological association of infiltrating lymphocytes expressing the perforin and granzyme A genes with virally infected cells. Maximal frequency of perforin and granzyme A mRNA-containing cells on liver sections preceded by about 2 days maximal LCMV-specific cytotoxicity of the lymphoid liver infiltrating cells. These results are most consistent with an involvement of perforin and granzyme A in cell-mediated cytotoxicity in vivo.     

Anaphylaxis to wheat beer.

BACKGROUND: Despite its worldwide and abundant consumption, beer has rarely been found to cause anaphylaxis. Barley malt contained in lager beers seems to be an important elicitor. OBJECTIVE: To report the unusual case of severe anaphylaxis following the ingestion of wheat beer. METHODS: A 59-year-old man experienced angioedema, generalized urticaria, and unconsciousness after ingestion of wheat beer. He tolerated lager beer well. For diagnostic evaluation, skin prick tests, oral challenge tests, and identification of specific IgE antibodies were performed. RESULTS: Skin prick test results with standard series of common aeroallergens and food allergens were negative with the exception of a 1 + reaction to wheat flour. The results of skin prick tests with native materials were positive for 2 brands of wheat beer and wheat malt shred but negative for baker's yeast, hops, and a brand of lager beer. Oral challenges with wheat beer or wheat flour elicited urticaria. By CAP-FEIA, specific IgE antibodies to wheat and barley flour but not to hops or baker's yeast were found in serum. Immunoblot analysis revealed that patient's IgE was bound to a protein of approximately 35 kDa in wheat extract. CONCLUSIONS: This is the first report, to our knowledge, on anaphylaxis to beer attributable to wheat allergy.     

Chronic pneumonia despite adaptive immune response to Mycobacterium bovis BCG in MyD88-deficient mice

To assess the role of Toll-like receptor (TLR) signalling in host response to mycobacterial infection, mice deficient in the TLR adaptor molecule myeloid differentiation factor 88 (MyD88) were infected with the vaccine strain Mycobacterium bovis (BCG), and the immune response and bacterial burden were investigated. Macrophages and dendritic cells from MyD88-deficient mice stimulated in vitro with BCG mycobacterial antigens produced very low levels of proinflammatory cytokines, while the expression of costimulatory molecules such as CD40 and CD86 was preserved. Upon systemic infection with BCG (2 x 10(6) CFU i.v.) MyD88-deficient mice developed confluent chronic pneumonia with two log higher CFU than wild-type mice. Interestingly, the infection was controlled in liver and spleen and there was efficient systemic T-cell priming with high IFNgamma production by CD4+ splenic T cells in MyD88-deficient mice. Lung infiltrating cells showed IFNgamma production by pulmonary CD4+ T cells upon specific restimulation, and a reduced capacity to produce nitric oxide and IL-10. In summary, despite the dramatic reduction of the innate immune response, MyD88-deficient mice were able to mount an efficient T-cell response to mycobacterial antigens, which was however insufficient to control infection in the lung, resulting in chronic pneumonia in MyD88-deficient mice.     

Regional assignment of human protooncogenec-myb to 6q21→qter

Using human-mouse somatic cell hybrids containing different parts of chromosome 6 and a DNA probe of the oncogene (V-myb) of avian myeloblastosis virus (AMV), we regionally mapped by Southern blot techniques the human cellular myb (cmyb) protooncogene to 6q21qter.     

Shear‐Induced Crystallization and Shear‐Induced Dissolution of Poly(ethylene oxide) in Mixtures with Tetrahydronaphthalene and Oligo(dimethyl siloxane‐b‐ethylene oxide)

Cloud point temperatures (T_cp) and crystallization temperatures (T_l/s) were measured at different constant shear rates for the ternary system tetrahydronaphthalene/poly(ethylene oxide)/oligo(dimethyl siloxane‐b‐ethylene oxide) using a rheo‐optical device and in the case of T_l/s additionally a viscometer. This system enables for the first time a joint investigation of both transitions with a given mixture. Shear favors the homogeneous liquid state and the formation of crystals. T_cp (liquid/liquid demixing, UCST) shifts to lower and T_l/s (liquid/solid, segregation of PEO) to higher temperatures by several degrees as the shear rate, , is increased up to 500 s^?1. The normalized shift in T_cp fits well into previous results for high molecular weight blends, oligomer mixtures, polymer solutions in single solvents and low molecular weight mixtures. A phase separated near critical blend was examined 1 K below its T_cp by means of a shear cell (Linkam) in the quiescent state and under shear with respect to its morphology. Upon an increase in one observes a transition from the co‐continuous structures existing in the quiescent state via deformed and oriented particles to string like morphologies. Finally, at sufficiently high shear rates the mixture becomes homogeneous and structures can no longer be seen under the microscope. The morphologies developing after the secession of shear are pointing to pronounced influences of the flow history of the system on the final structure of two phase blends.

Equilibrium phase diagram of the system THN/COP/PEO at the indicated temperatures as obtained from turbidimetric titration. The curve for 42 °C indicates the compositions under which the mixtures segregate the first solid PEO particles upon cooling. The curves for the higher temperatures denote the demixing of the homogeneous system into two liquid phases.     

Oxidative stress and sleep apnoea in clinically healthy infants in the first year of life

Summary Question of the study   Respiratory instability as well as tissue damage by free radicals (oxidative stress) have been hypothesized to play a role in cases of sudden and unexpected infant death in the first year of life. The ratio of the oxidized/reduced form of redox compounds in the circulation could be used as a marker of oxidative stress. Therefore, the sleep apnoea rate and redox status of coenzyme Q10 (CoQ10) (percentage of the oxidized form in total CoQ10) were measured in a population of clinically healthy infants in their first year of life in order to study whether a physiological parameter of respiratory instability is related to a biochemical parameter of oxidative stress. Patients and methods   Between May and December 1999, 323 infants in the first year of life were referred to a paediatric sleep laboratory. Sleep apnoea rate, periodic breathing and parameters of oxygenation (SaO₂ and TcPO₂) were calculated based on polysomnographic recordings. The CoQ10 redox status was calculated based on high-pressure liquid chromatographic (HPLC) analysis. Results   Statistical analysis showed an age-dependent decrease in apnoea rate ( r = – 0.38) and CoQ10 redox status ( r = – 0.40). An increased CoQ10 redox status (median: 16.6 %; range: 7.3 – 29.7 %) was found in infants with high apnoea rates above the 90^th percentile of a reference group in comparison with infants with apnoea rates below the 90^th percentile of a reference group (median: 10.4 %; range: 5.1 – 20.4 %; P = 0.031). Conclusions   These findings may indicate that high apnoea rates are accompanied by increased formation of free radicals in clinically healthy infants in the first year of life.     

CD2-mediated signaling in T cells lacking the ζ-chain-specific immune receptor tyrosine-based activation (ITAM) motif

T lymphocytes can be activated via the T cell receptor (TCR) or by triggering through a number of other surface structures, including the CD2 co-receptor molecule. Signaling through the CD2 molecule was shown previously to be dependent on the TCR-associated ζ-chain. Here, we show that CD2-induced activation also functions in T cells which express ζ-chains lacking a functional immune-receptor tyrosine-based activation motif (ITAM). TCR-positive T cells that express only the transmembrane part of the ζ-chain protein and thus lack a functional ζ-derived ITAM readily produce interleukin (IL)-2 when cross-linked with CD2-specific monoclonal antibodies (mAb). TCR-negative T cell hybridomas expressing minimal receptors consisting of an extracellular CD25 and an intracellular ζ-chain-derived segment were effectively stimulated via CD2-specific mAb. For CD2-mediated co-stimulation of TCR-negative cells, two ζ-chain-derived ITAM were sufficient to induce IL-2 when the CD2 molecules were co-cross-linked with the chimeric CD25-ζ molecules. Taken together, our results show that CD2-induced signaling does not necessarily employ the ζ-chain in TCR-positive cells and that CD2-dependent co-stimulation in TCR-negative cells can be mediated via two functional ζ-chain-derived ITAM.