Synaptic junctional glycoconjugates from chick brain

Forebrains from day-old chicks were homogenized and fractionated by differential sedimentation and density gradient centrifugation to yield subcellular fractions. The synaptosomal plasma membrane fraction was further treated with Triton X-100 to yield subsynaptic membrane fractions including synaptic junctions. Glycoproteins from these subsynaptic membrane fractions were identified after separation by SDS-polyacrylamide gel electrophoresis by incubating the gel slabs with radioiodinated concanavalin A. Two lectin-binding proteins were discerned in the synaptic junction fraction while none were observed in the Triton-soluble portion of the synaptic plasma membrane. The carbohydrate content of the glycoproteins from each subcellular fraction was quantitated after methanolysis and derivatization aso-methyl-trifluoroacetyl analogs by gas-liquid chromatography. The lowest concentration of glycoprotein sugars was found in the synaptic junction, mitochondrial, and soluble fractions while the greatest concentration was found in the myelin, light-synaptic plasma membrane, and the Triton-soluble portion of the synaptic plasma membrane. Of the subcellular fractions, the synaptic junction contained the highest porportion of mannose and lowest proportion of sialic acid. Moreover, this fraction's content of galactose andN-acetylglucosamine, relative to mannose was the lowest while its content of fucose was low. The oligosaccharide chains extending into the synaptic cleft therefore are predominantly of the neutral, mannose-rich type and are attached to a limited number of high-molecular-weight glycoproteins.     

Selected factors limiting the microbial degradation of recalcitrant compounds

Summary The focus of this review is to examine some of the reasons biodegradation may not take place in the environment even though its occurrence in the laboratory has been demonstrated. Some approaches for dealing with chemical persistence will be discussed. In addition, the potential of bioremediation as an in situ clean-up technology will be considered.     

Response surface optimization for joint contact model evaluation

When optimization is used to evaluate a joint contact model's ability to reproduce experimental measurements, the high computational cost of repeated contact analysis can be a limiting factor. This paper presents a computationally-efficient response surface optimization methodology to address this limitation. Quadratic response surfaces were fit to contact quantities (contact force, maximum pressure, average pressure, and contact area) predicted by a discrete element contact model of the tibiofemoral joint for various combinations of material modulus and relative bone pose (i.e., position and orientation). The response surfaces were then used as surrogates for costly contact analyses in optimizations that minimized differences between measured and predicted contact quantities. The methodology was evaluated theoretically using six sets of synthetic (i.e., computer-generated) contact data, and practically using one set of experimental contact data. For the synthetic cases, the response surface optimizations recovered all contact quantities to within 3.4% error. For the experimental case, they matched all contact quantities to within 6.3% error except for maximum contact pressure, which was in error by up to 50%. Response surface optimization provides rapid evaluation of joint contact models within a limited range of relative bone poses and can help identify potential weaknesses in contact model formulation and/or experimental data quality.     

Immunochemistry of the HLA class II molecules isolated from a mouse cell transfected with DQ alpha and beta genes from a DR4 haplotype

Cells from a mouse B lymphoma were transfected by DQ alpha and DQ beta genes derived from a DR4 haplotype. Quantitatively, the resulting expression of human class II molecules was similar to that of human B lymphoblastoid cell lines. Qualitatively, the transformant class II molecules differed from normal class II molecules in their carbohydrate moiety. As for their antigenic specificity, they were shown to carry two determinants previously identified on DQ molecules controlled by DR4 haplotypes, i. e., DQw3 and DCHON. The transformant molecules did not carry a third DR4-associated specificity, DC5 (equivalent to TA10), and must possess a structure allelic to DC5. However, no corresponding alloantigenic specificity was detected by a screening of relevant alloantisera.