Sulphation requirement for GlyCAM-1, an endothelial ligand for L-selectin

L-selectin participates in the initial attachment of leukocytes to the vascular endothelium. On lymphocytes, it mediates binding to high endothelial venules of lymph nodes. As a selectin it functions as a calcium-dependent lectin recognizing carbohydrate-bearing ligands on endothelial cells. Two lymph node ligands for L-selectin have been identified as sulphated glycoproteins of M(r) approximately 50K and approximately 90K, called Sgp50 and Sgp90 (ref. 10). The recently cloned Sgp50 (ref. 12), now designated GlyCAM-1, is a high endothelial venule-associated, mucin-like glycoprotein containing predominantly O-linked carbohydrate chains. Sialylation of GlyCAM-1 is necessary for its ligand activity and a role for fucosylation is suspected. We have used chlorate as a metabolic inhibitor of sulphation, and report here that GlyCAM-1 has an additional requirement for sulphate.     

Improved velocity estimation for low-speed and transient regimes using low-resolution encoders

This paper presents a new estimation method, entitled the asynchronous sampling pulse method (ASPM), for determining velocity in systems with low but variable speeds, and/or with low-resolution encoders. The ASPM forces the estimator procedure to synchronize with the actual encoder pulse input, thus eliminating encoder positioning error independent of target velocity variations. This method is based on using an auxiliary sampling period to measure the time interval between the moment of encoder input and the control sampling instant, and its precision is shown to be dependent only on this auxiliary sampling period. Thus, the ASPM improves over existing methods in which estimator performance is dependent on both target acceleration and encoder resolution. Simulation and experimental results are used to verify the method.     

Distortion product otoacoustic emissions in human newborns and adults. I. Frequency effects

This study varied stimulus frequency and recorded distortion product otoacoustic emissions (DPOAEs) in human newborns and adults. Because of outer and middle ear acoustics, the same auditory input resulted in higher newborn stimulus sound pressure levels across a broad frequency range in the occluded outer ear canal. Noise levels in the canal were 5-15 dB lower for adults at frequencies less than about 3 kHz. The 2 f1-f2 DPOAE was the most reliably recorded DPOAE except at the lowest frequencies assessed. At the lowest frequencies the 2 f2-f1 DPOAE was more frequently recorded than any other DPOAE. There were no striking developmental differences in the kinds of DPOAEs that were recorded. The amplitudes of consecutively recorded 2 f1-f2 DPOAEs were generally within 1.5 dB of each other for all age groups (slightly better reproducibility for adults than newborns). The phases of consecutively recorded 2 f1-f2 DPOAEs were generally within 15 degrees of each other (often less than 10 and 5 degrees for newborns and adults respectively). At the highest frequencies assessed (f2 = 4.2-9.9 kHz) all subjects had similar amplitude 2 f1-f2 DPOAEs. At lower frequencies adult 2 f1-f2 amplitudes were significantly less than those of newborns. At the lowest frequencies reliably assessed (f2 = 1.5-2.1 kHz) term newborns had significantly larger 2 f1-f2 DPOAEs than preterm newborns. Newborn and adult 2 f1-f2 DPOAE amplitude X f2/f1, functions were quite similar although there were reliable differences. Age related differences in the outer and middle ears may explain some of the differences in DPOAEs that were observed.     

Tin Pest: Elusive Threat in Lead-Free Soldering?

Tin pest is the result of an allotropic transformation of tin from its β phase to its α phase at temperatures below 13 °C. This transformation is accompanied by a change in density from 7.31 to 5.77 g/cm³. The resulting expansion usually results in degradation of the affected part, as the α phase material is mechanically weak and over time becomes little more than a gray powder. The tin pest effect is cumulative unless the sample in question is exposed to temperatures above 70 °C or so, where some reversion back to white tin has been observed. However, by this point a tin sample’s physical integrity may have been destroyed by the partial β to α transformation. The transformation to α tin is inhibited strongly by soluble alloying elements such as bismuth and antimony at concentrations of about 0.5%, or lead at concentrations of about 5%. Hence, tin pest is generally observed only in quite pure tin. However, nearly pure tin alloys may become common. For example, the advent of the European Union’s RoHS law, which essentially eliminates lead from solder, has spawned lead-free alloys that can be almost pure tin and may be at risk of tin pest. This risk has caused some concern over the long-term stability of emergent, lead-free solders during low temperature service. This overview article is written in light of this concern.     

Identification of a novel polyproline recognition site in the cytoskeletal associated protein, proline serine threonine phosphatase interacting protein

Protein-protein interactions are often mediated by the recognition of proline-rich domains by SH3 or WW modules. Previously, we demonstrated that the PEST-type protein-tyrosine phosphatase, PTP HSCF (hematopoietic stem cell fraction), bound to a novel cytoskeletal associated protein, proline serine threonine phosphatase interacting protein (PST PIP), via an interaction between the proline-rich COOH terminus of the PTP and a site within the putative coiled-coil domain of PST PIP. Here we describe a more detailed analysis of this interaction. Earlier data suggested that the NH2 terminus of PST PIP was important for binding to the phosphatase, and deletion of the NH2-terminal 50 amino acids of the PST PIP resulted in an apparently misfolded protein that was incapable of binding PTP HSCF. To examine the region involved with binding to PTP HSCF, alanine-scanning mutants were produced at intervals throughout PST PIP. This analysis demonstrated that a tryptophan at position 232 was essential for binding in vitro. Transfection experiments demonstrated that the Trp232 mutant protein was capable of association with the cortical cytoskeleton but was not bound to PTP HSCF in vivo. Alanine scanning of a peptide derived from the COOH-terminal proline-rich domain of PTP HSCF revealed that a subset of prolines, as well as other residues, was required for efficient binding to PST PIP, and introduction of alanines at some of these positions in the protein resulted in decreased binding to PST PIP in vitro and in vivo. Analysis of in vivo tyrosine phosphorylation of the Trp232 mutant of PST PIP in the presence of v-Src revealed that this protein was phosphorylated more efficiently than the wild-type molecule. Thus, the interaction between PTP HSCF and PST PIP is mediated by a novel site in the cytoskeletal associated protein which interacts with residues within the proline-rich COOH terminus of the phosphatase.     

Chelate mediated transfer of iron from transferrin to desferrioxamine

Desferrioxamine, widely used for the treatment of iron overload in Cooley's anaemia, binds iron so tightly that it should quantitatively remove iron from transferrin. Studies conducted in vivo and in vitro, however, have failed to demonstrate significant depletion of transferrin-bound iron by a stoichiometric excess of desferrioxamine. However, low molecular weight chelating agents, capable of forming ternary complexes with transferrin and ferric iron, can promote a rapid transfer of iron from transferrin to desferrioxamine. A possible mechanism for this facilitated exchange is offered.     

Robust independent joint controller design for industrial robotmanipulators

A novel approach is presented for the design of simple robust independent joint controllers for industrial robot manipulators. In this approach, each joint actuator is treated as a simple inertial system plus a disturbance torque representing all the unmodeled dynamics. By a very simple algorithm, the disturbance is instantly estimated and rejected, thus allowing a simple proportional-derivative (PD) control scheme to be used. The stability of the proposed control law is analyzed. Experimental evaluations of the controller on a microcomputer-controlled PUMA 560 arm were performed. It is shown that the control scheme is simple and practical and that it can be easily implemented on an industrial manipulator presently in use     

Oxidation-induced defect generation in advanced DRAM structures

Structures containing deep-trenched storage capacitors and shallow-trench isolation were examined in patterns suitable for future generation dynamic RAMs (DRAMs). These same effects were also examined in similar structures which included only the shallow isolation trenches. Observed was a strong interaction between the deep and shallow trenches, which makes structures which incorporate both types much more susceptible to oxidation-induced defect generation than those without deep trenches. It was observed that at higher oxidation temperatures, more oxide can be grown before defects are generated. This is interpreted as a combination of more-efficient visco-elastic relaxation in the oxide and a lower differential oxidation rate between the {110} trench sidewalls and the {100} planar surface at higher temperatures. It was also observed that substantial defect immunity can be obtained by incorporating an oxidation barrier in the trench structures. An overall processing strategy to eliminate defect generation in these advanced structures is suggested     

Differential regulation of vitamin D receptors in clonal populations of a chronic myelogenous leukemia cell line

BACKGROUND: Both crystalloid and blood cardioplegia result in cardiac dysfunction associated with myocardial edema. This edema is partially due to the lack of myocardial contraction during cardioplegia, which stops myocardial lymph flow. As an alternative, acceptable surgical conditions have been created in patients undergoing coronary artery bypass operations with esmolol-induced minimal myocardial contraction. We hypothesized that minimal myocardial contraction during circulatory support using either standard cardiopulmonary bypass (CPB) or a biventricular assist device would prevent myocardial edema by maintaining cardiac lymphatic function and thus prevent cardiac dysfunction. METHODS: We placed 6 dogs on CPB and 6 dogs on a biventricular assist device and serially measured myocardial lymph flow rate and myocardial water content in both groups and preload recruitable stroke work only in the CPB dogs. In all dogs we minimized heart rate with esmolol for 1 hour during total circulatory support. RESULTS: Although myocardial lymph flow remained at baseline level during CPB and increased during biventricular assistance, myocardial water accumulation still occurred during circulatory support. However, as edema resolved rapidly after separation from circulatory support, myocardial water content was only slightly increased after CPB and biventricular assistance, and preload recruitable stroke work was normal. CONCLUSIONS: Our data suggest that minimal myocardial contraction during both CPB and biventricular assistance supports myocardial lymphatic function, resulting in minimal myocardial edema formation associated with normal left ventricular performance after circulatory support. The concept of minimal myocardial contraction may be a useful alternative for myocardial protection, especially in high-risk patients with compromised left ventricular function.