Evidence for an accessory role of LFA-1 in lymphocyte-high endothelium interaction during homing

In a variety of lymphocyte interactions, lymphocyte function-associated antigen-1 (LFA-1) plays an important role as an accessory mechanism mediating cell adhesion. We tested the possibility that LFA-1 could also be involved in the specific binding of lymphocytes to high endothelial venules (HEV) during homing. Antibodies against LFA-1 but not against various other cell surface molecules (except the putative gp90 homing receptor defined by the MEL-14 antibody) were found to inhibit in vitro adherence of lymphocytes to HEV in frozen sections of lymph nodes. Binding of T cell lines to HEV was also inhibited by anti-LFA-1 antibody. Using sublines selected for differential expression of the MEL-14 antigen, MEL-14 high cells (which bind well to HEV) were less susceptible to inhibition by anti-LFA-1 than poor binders with low levels of the homing receptor, supporting the model of LFA-1 being an accessory mechanism strengthening weak interactions between cells. Parallel results were found in vivo where anti-LFA-1 antibodies reduced the migration of normal lymphocytes into lymph nodes and Peyer's patches by 40 to 60%. Localization in the lung, especially of activated lymphocytes, was also impaired, although to a lesser extent. These findings suggest that LFA-1 plays an accessory role in cellular interactions relevant for lymphocyte migration.     

The N-Myc oncoprotein is associated in vivo with the phosphoprotein Max(p20/22) in human neuroblastoma cells.

Proteins encoded by the proto-oncogenes c-myc, L-myc, and N-myc contain at their carboxy-terminus a tripartite segment comprising a basic DNA binding region (BR), a helix-loop-helix (HLH) and a leucine zipper motif (Zip), that are believed to be involved in DNA binding and protein-protein interaction. The N-Myc oncoprotein is overexpressed in certain human tumors that share neuroectodermal features due to amplification of the N-myc gene. Using a monoclonal antibody directed against an N-terminal epitope of the N-Myc protein in immunoprecipitations performed with extracts of neuroblastoma cells, two nuclear phosphoprotein, p20/22, forming a hetero-oligomeric complex with N-Myc are identified. Both proteins are phosphorylated by casein kinase II in vitro. By partial proteolytic maps we show that p20 and p22 are structurally related to each other and that p20 is identical with Max, a recently described in vitro binding partner of myc proteins. Time course experiments show the presence of the complex in cellular extracts immunoprecipitated within a 5 min interval after the preparation of the cell extract. While the expression of N-myc is restricted, expression of both Max(p20/22) and the murine homolog Myn(p20/22) was observed in cells of diverse human and murine embryonal lineages as detected by heterologous complex formation. By introduction of expression vectors containing the wild type N-myc gene or N-myc genes with in frame deletions or point mutations into recipient cells and subsequent immunoprecipitation of the resulting N-Myc proteins we show that the HLH-Zip region is essential to the formation of the N-Myc-p20/22 complex.     

A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera

Levels of mitochondrial DNA (mtDNA) sequence divergence between species within each of several avian (Anas, Aythya, Dendroica, Melospiza, and Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were compared. An analysis of digestion profiles generated by 13-18 restriction endonucleases indicates little overlap in magnitude of mtDNA divergence for the avian versus nonavian taxa examined. In 55 interspecific comparisons among the avian congeners, the fraction of identical fragment lengths (F) ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these translate into estimates of nucleotide sequence divergence (p) ranging from 0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater than 0.070. The small mtDNA distances among avian congeners are associated with protein-electrophoretic distances (D values) less than approximately 0.2, while the mtDNA distances among assayed fish and amphibian congeners are associated with D values usually greater than 0.4. Since the conservative pattern of protein differentiation previously reported for many avian versus nonavian taxa now appears to be paralleled by a conservative pattern of mtDNA divergence, it seems increasingly likely that many avian species have shared more recent common ancestors than have their nonavian taxonomic counterparts. However, estimates of avian divergence times derived from mtDNA- and protein-calibrated clocks cannot readily be reconciled with some published dates based on limited fossil remains. If the earlier paleontological interpretations are valid, then protein and mtDNA evolution must be somewhat decelerated in birds. The empirical and conceptual issues raised by these findings are highly analogous to those in the long-standing debate about rates of molecular evolution and times of separation of ancestral hominids from African apes.      

L-DOPA production from tyrosinase immobilized on nylon 6,6

The production of L-DOPA immobilized on chemically modified nylon 6,6 membranes was studied in a batch reactor. Tyrosinase was immobilized on nylon using glutaraldehyde as a crosslinking agent. The effects of membrane pore size and glutaraldehyde concentration upon enzyme uptake and L-DOPA production were investigated. Enzyme uptake was unaffected by glutaraldehyde concentration; approximately 70% uptake was observed when 25% w/v (group 1), 5% (group 2), and 3% (group 3) glutaraldehyde were used, indicating that glutaraldehyde was in excess. Similarly, uptake was the same for membranes with 0.20 and 10 mum pore sizes.Membranes produced using different levels of glutaraldehyde exhibited dramatically different capacities for L-DOPA production, despite the fact that enzyme uptake was equivalent. Membranes from groups 2 and 3 (5% and 3% glutaraldehyde) produced L-DOPA at a rate of 1.70 mg L(-1) h(-1) over 170 h in a 500-mL batch reactor. However, no free L-DOPA was detected when group 1 membranes were used. Experimental evidence suggests that L-DOPA was produced, but remained bound to these membranes via excess glutaraldehyde left over from the immobilization process. Membrane pore size also effected L-DOPA production; less production was observed when 10-mum membranes were used, despite equivalent enzyme uptake. The observed difference in production may be due to differences in the pore density on the two types of membranes which could affect the access of the substrate to the immobilized enzyme.The results of these studies indicate that tyrosinase can be effectively immobilized on nylon 6,6. L-DOPA production was optimal when 0.20-mum-pore-size membranes were activated with 3-5% glutaraldehyde. Stability studies indicated a 20% reduction in activity over 14 days when the immobilized enzyme was used under turnover conditions. (c) 1996 John Wiley & Sons, Inc.     

NAD+ binding to the Escherichia coli K+-uptake protein TrkA and sequence similarity between TrkA and domains of a family of dehydrogenases suggest a role for NAD+ in bacterial transport

The nucleotide sequence of trkA, a gene encoding a surface component of the constitutive K⁺-uptake systems TrkG and TrkH from Escherichia coli, was determined. The structure of the TrkA protein deduced from the nucleotide sequence accords with the view that TrkA is peripherally bound to the inner side of the cytoplasmic membrane. Analysis by a dot matrix revealed that TrkA is composed of similar halves. The M-terminal part of each TrkA half (residues 1–130 and 234–355, respectively) is similar to the complete NAD⁺-binding domain of NAD⁺-dependent dehydrogenases. The C-terminal part of each TrkA half (residues 131–233 and 357–458, respectively) aligns with the first 100 residues of the catalytic domain of glyceraldehyde-3-phosphate dehydrogenase. Strong u.v. illumination at 252 nm led to cross-linking of NAD⁺ or NADH, but not of ATP to the isolated TrkA protein.     

Oxide-Based Solid-State Batteries: A Perspective on Composite Cathode Architecture

The garnet-type phase Li₇La₃Zr₂O₁₂ (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs.     

Vasoconstriction in active skeletal muscles: a potential role for P2X purinergic receptors?

There is evidence that ATP acts as a neurotransmitter in vascular smooth muscle and is coreleased with norepinephrine from sympathetic nerves. We hypothesized that P2X-receptor stimulation with the selective P2X-receptor agonist alpha,beta-methylene ATP would produce vasoconstriction in resting and exercising skeletal muscle. Six mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs and a catheter in one femoral artery. The selective P2X agonist alpha,beta-methylene ATP was infused as a bolus into the femoral artery catheter at rest and during mild, moderate, and heavy exercise. Intra-arterial infusions of alpha,beta-methylene ATP elicited reductions in vascular conductance of 54 +/- 5, 49 +/- 8, 39 +/- 8, and 30 +/- 6% at rest, 3 miles/h, 6 miles/h, and 6 miles/h at a 10% grade, respectively. The agonist infusions did not affect blood flow in the contralateral iliac artery. To examine whether nitric oxide is responsible for the attenuated vasoconstrictor response to P2X stimulation, the infusions were repeated in the presence of NG-nitro-l-arginine methyl ester. After nitric oxide synthase blockade, intra-arterial infusions of alpha,beta-methylene ATP elicited reductions in vascular conductance of 56 +/- 7, 61 +/- 8, 52 +/- 9, and 40 +/- 7% at rest, 3 miles/h, 6 miles/h, and 6 miles/h at a 10% grade, respectively. P2X-receptor responsiveness was attenuated during exercise compared with rest. Blockade of nitric oxide production did not affect the attenuation of P2X-receptor responsiveness during exercise. These data support the hypothesis that P2X purinergic receptors can produce vasoconstriction in exercising skeletal muscle.     

Imagining the Future of the Anthropology of Education if We Take Laura Nader Seriously

The large corpus of scholarship of cultural anthropologist Laura Nader is relevant to the contemporary practice of the anthropology of education. In particular, her work is relevant to contemporary debates about methodology and what constitutes "scientifically based" education research; to the prospect and need for more crossfertilization within the discipline of anthropology; and for the proud assertion of anthropology's distinctive suitability for understanding and responding to many contemporary educational challenges, including how to have anthropologically derived insights more favorably compete in the "marketplace of ideas" against less empirically grounded claims and strategies.