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Biomedical subjects

B Lu

Publications and source records attributed to B Lu.

At least 181 records · Page 10Linked to original sources
PubMed1997

Dynamic structure of the sarcin/ricin domain in rat 28S ribosomal RNA investigated by hybridization with oligodeoxynucleotide.

In the static state of the ribosome, its S/R domain is not accessible to a probe of 1 4-mer oligodeoxyribonucleotide complementary to the region. However, during the in vitro translation process, the probe can specifically hybridize with the region in ribosome and inhibit translation. It appears that the S/R domain is well-protected when the ribosome is in the static state. This site is partially exposed at some stage(s) of translation. These results indicate that the S/R domain is not a simple single-strand, but a reversibly dynamic structure.

Animals↗
PubMed1997

Validation of the heat treatment step used in the production of diaspirin crosslinked hemoglobin (DCLHb) for viral inactivation--effect of crosslinking.

Two experiments were performed to assess viral inactivation during the crosslinking and heat treatment steps of the DCLHb manufacturing process. Stroma free hemoglobin (SFHb) collected from a large scale manufacturing lot was tested in a 1:680 scaled down system in which the key parameters used in the manufacturing process were replicated. In the first study Porcine Parvovirus (PPV), a non-enveloped virus, was used to assess inactivation, while in the second study Bovine Viral Diarrhea Virus (BVDV), an enveloped virus, was utilized. In both experiments, the SFHb solution was deoxygenated and an aliquot of virus suspension was added. To initiate the crosslinking reaction, a solution of bis (3,5-dibromosalicyl) fumarate (DBBF) in HEPES buffer was added to the test solution. In both experiments the reaction times and the degree of crosslinking were normal. After crosslinking, the reaction mixtures were heated to 74 +/- 1 degrees C over 30 minutes, held at 74 +/- 1 degrees C for 90 minutes, and cooled to less than 10 degrees C over 30 minutes. In each experiment the degree of crosslinking of final product was 100% and yield of hemoglobin recovery was normal. Samples were removed prior to crosslinking, after crosslinking and before, during and after heat treatment for determination of virus titer and evaluation of key process parameters. The results from these experiments were consistent with those obtained from the full scale manufacturing process for the deoxygenation, crosslinking and the heat treatment step during the production of DCLHb. The results of virus assays showed that crosslinking has no effect on viruses and their subsequent inactivation by heat treatment.

Animals↗
PubMed1997

[Establishment of immediate implant animal model in mongrel dog's fresh extraction socket].

The purpose of the study was to establish the animal models which had clinical characteristics in bone defect sizes around immediate implants. The mesial region of dogs' fresh extraction sockets were made with 3 mm x 3 mm x 5 mm size bone defects around implants with a round bur, then observed their osseous changes at 2 weeks, 4 weeks, 8 weeks, 12 weeks with and without demineralized freeze-dried bone allograft (DFDBA) filled. The results showed that the bone defects in DFDBA grafted group were substituted by new bone, but the defects in ungrafted group were only substituted to 3/5. Such animal models had the advantages of simple preparations and similar clinical characteristics, so they were beneficial to investigation of the immediate implantation.

Animals↗
PubMed1997

[The Raman scatting of carbon nanotubes].

Raman scattering measurements of the cathode deposite produced by carbon arc discharge method and graphite was repotred. The results indicate that the inner core of the deposite containing large quantities of carbon nanotubes undergoing crystallization process. Carbon nanotube is one kind of micro-crystal of quasi-graphite.

English Abstract↗
PubMed1997

Finite element analysis of acetabular wear. Validation, and backing and fixation effects.

A two-phase investigation was undertaken to study computational performance aspects of a recently developed finite element formulation that has shown promise in the study of design related influences on total hip arthroplasty wear. In the first phase, computational model predictions were evaluated against directly corresponding physical wear measurements performed in a biaxial rocking hip simulator. The discrepancy between the predictions and the measurements was approximately 4.1%. In the second phase, a bony support bed was introduced to supersede the model's previous simplifying assumption of rigid support at the cup backing. Other factors being equal, computed wear rates differed negligibly for three very different cup backing and fixation modalities studied with the new bony bed support condition, and for two individual cups studied with bony bed support versus the rigid backing support simplification.

Acetabulum↗
PubMed1996

Carboxylate interactions involved in the disassembly of tobacco mosaic tobamovirus.

Structural studies of tobacco mosaic tobamovirus (TMV) have identified two coat protein (CP) intersubunit carboxyl-carboxylate interactions and one CP carboxylate-RNA phosphate interaction whose electrostatic repulsion is believed to drive virion disassembly. In this study, the involvement of each interaction in the disassembly process was examined. Site-directed mutagenesis was used to replace selected negatively charged CP residues, E or D, with neutral residues, Q or N, respectively. Purified mutant CPs were assayed for their ability to inhibit wild-type TMV disassembly both in vitro and in vivo. Results indicate that the lateral carboxylate interaction made by residue E106 is much more complex than previously thought, involving three residues, E95, E97, and D109, from an adjacent subunit. Mutations at all three residues are required to inhibit disassembly significantly. Different mutant coat proteins inhibited disassembly of the wild-type virus to varying degrees. Mutant E50Q, which modified the axial intersubunit interaction, had the greatest ability to inhibit disassembly followed by mutants E95Q/E97Q/D109N and D116N, which modified the lateral and CP-RNA interactions, respectively. Within each set of interacting carboxylate groups, mutations in the face opposite the disassembling surface of the TMV virion conferred the greatest ability to inhibit disassembly. This observation is consistent with the polar nature of TMV disassembly and confirms that repulsive intersubunit interactions derived from the 5' terminal subunits provide the key controlling mechanisms for virion disassembly.

Capsid↗
PubMed1996

Neurogenic amplification of immune complex inflammation.

The formation of intrapulmonary immune complexes in mice generates a vigorous inflammatory response characterized by microvascular permeability and polymorphonuclear neutrophil influx. Gene-targeted disruption of the substance P receptor (NK-1R) protected the lung from immune complex injury, as did disruption of the C5a anaphylatoxin receptor. Immunoreactive substance P was measurable in fluids lining the lung at time points before neutrophil influx and may thus be involved in an early step in the inflammatory response to immune complexes in the lung.

Animals↗
PubMed1996

The C5a chemoattractant receptor mediates mucosal defence to infection.

A family of G-protein-coupled chemoattractant receptors is known to mediate the transport and activation of neutrophils and macrophages This family includes receptors for chemokines, such as interleukin-8, bacterial formylated peptides, platelet-activating factor, leukotriene B4, and the complement anaphylatoxins. The apparent redundancy of these receptors suggests that they have an important underlying role in host defence. To isolate the contribution of particular molecules, we disrupted a gene that encodes a single chemoattractant receptor. Here we show that mice deficient in the chemoattractant C5a receptor, in comparison to their wild-type littermates, were unable to clear intrapulmonary-instilled Pseudomonas aeruginosa, despite a marked increase in neutrophil influx, and succumbed to pneumonia. These C5a-receptor-deficient mice challenged with sublethal inocula of Pseudomonas become superinfected with secondary bacterial strains. We conclude that the C5a receptor has a non-redundant function, and is required for mucosal host defence in the lung.

Animals↗
PubMed1996

Endoderm induction by the organizer-secreted factors chordin and noggin in Xenopus animal caps.

Spemann's organizer has potent neural inducing and mesoderm dorsalizing activities in the Xenopus gastrula. A third activity, the organizer's ability to induce a secondary gut, has been difficult to analyze experimentally due to the lack of early gene markers. Here we introduce endodermin, a pan-endodermal gene marker, and use it to demonstrate that chordin (Chd), a protein secreted by the organizer region, is able to induce endodermal differentiation in Xenopus. The ability of chd, as well as that of noggin, to induce endoderm in animal cap explants is repressed by the ventralizing factor BMP-4. When FGF signaling is blocked by a dominant-negative FGF receptor in chd-injected animal caps, neural induction is inhibited and most of the explant is induced to become endoderm. The results suggest that proteins secreted by the organizer, acting together with known peptide growth factors, regulate differentiation of the endodermal germ layer.

Amino Acid Sequence↗
PubMed1996

Dorsoventral patterning in Xenopus: inhibition of ventral signals by direct binding of chordin to BMP-4.

Chordin (Chd) is an abundant protein secreted by Spemann organizer tissue during gastrulation. Chd antagonizes signaling by mature bone morphogenetic proteins (BMPs) by blocking binding to their receptors. Recombinant Xenopus Chd binds to BMP-4 with high affinity (KD, 3 x 10(-10) M), binding specifically to BMPs but not to activin or TGF-beta1. Chd protein is able to dorsalize mesoderm and to neuralize ectoderm in Xenopus gastrula explants at 1 nM. We propose that the noncell-autonomous effects of Spemann's organizer on dorsoventral patterning are executed in part by diffusible signals that directly bind to and neutralize ventral BMPs during gastrulation.

Activins↗
PubMed1996

Cerberus is a head-inducing secreted factor expressed in the anterior endoderm of Spemann's organizer.

An abundant cDNA enriched in Spemann's organizer, cerberus, was isolated by differential screening. It encodes a secreted protein that is expressed in the anterior endomesoderm. Microinjection of cerberus mRNA into Xenopus embryos induces ectopic heads, and duplicated hearts and livers. The results suggest a role for a molecule expressed in the anterior endoderm in the induction of head structures in the vertebrate embryo.

Amino Acid Sequence↗
PubMed1996

Regulation of synaptic responses to high-frequency stimulation and LTP by neurotrophins in the hippocampus.

Neurotrophins promote neuronal survival and differentiation, but the fact that their expression is modified by neuronal activity, suggests a role in regulating synapse development and plasticity. In developing hippocampus, the expression of brain derived neurotrophic factor (BDNF) and its receptor TrkB increases in parallel with the ability to undergo long-term potentiation (LTP). Here we report a mechanism by which BDNF modulates hippocampal LTP. Exogenous BDNF promoted the induction of LTP by tetanic stimulation in young (postnatal day 12-13) hippocampal slices, which in the absence of BDNF show only short-term potentiation (STP). This effect was due to an enhanced ability of hippocampal synapses to respond to tetanic stimulation, rather than to a direct modulation of the LTP-triggering mechanism. A TrkB-IgG fusion protein, which scavenges endogenous BDNF, reduced the synaptic responses to tetanus as well as the magnitude of LTP in adult hippocampus. Our results suggest that BDNF may regulate LTP in developing and adult hippocampus by enhancing synaptic responses to tetanic stimulation.

Animals↗
PubMed1996

Fully edited and partially edited nad9 transcripts differ in size and both are associated with polysomes in potato mitochondria.

Two classes of nad9 transcripts are present at different abundances in the steady-state RNA pool of potato mitochondria. The 5'- and 3' termini of the transcripts were determined by primer extension and S1 nuclease protection analyses respectively. Using two primer pairs that will either specifically amplify the larger transcript or amplify both the larger and the smaller transcripts in RT-PCR analyses it was found that the larger nad9 transcripts are partially edited, while the smaller transcripts are fully edited. Both the larger and the smaller transcripts were found to be associated with mitochondrial polysomes. The polysome association was found to be sensitive to EDTA and puromycin treatment. Therefore, both fully and partially edited nad9 transcripts appear to be engaged in translation.

Base Sequence↗
PubMed1996

Neutral endopeptidase modulates septic shock.

Neutral endopeptidase (NEP; EC 3.4.24.11) is a type-2 cell-surface metalloproteinase known by a variety of eponyms, including enkephalinase, common acute lymphoblastic leukemia antigen (CALLA), and CD10. Identified substrates are largely neural or humoral oligopeptide agonists, and the enzyme functions to terminate signaling by degrading the ligand, analogous to the acetylcholine/acetylcholinesterase system. Targeted disruption of the NEP locus in mice results in enhanced lethality to endotoxin shock with a pronounced gene-dosage effect. The site(s) of action appears downstream from release of TNF and IL-1, as NEP-deficient animals demonstrate increased sensitivity to these mediators as well. This unexpected finding indicates an important protective role for NEP in septic shock.

Amino Acid Sequence↗
PubMed1996

Indirect UV detection of carbohydrates in capillary zone electrophoresis by using tryptophan as a marker.

A rapid and sensitive method for the analysis of sugars was developed by capillary zone electrophoresis (CZE) with indirect UV detection. A mixture of nine mono- and oligosaccharides was separated in about 20 minutes on a fused silica capillary in a highly alkaline (pH > 12) background electrolyte (BGE). With tryptophan as the marker detected at 280 nm the femtomole level detection of sugars was possible. The system was optimized by studies on the buffer pH, the marker concentration, as well as the inner diameter of the capillary. The indirect detection of sugars was also performed with a cationic marker, N-benzylcinchonidium chloride (BCDC). However, the detection sensitivity was much lower in comparison to the tryptophan marker system.

Buffers↗
PubMed1996

Effect of loading and fracture motions on diaphyseal tibial fractures.

A computerized motion sensor was used to record the three-dimensional components of interfragmentary motion during healing in three patients with closed, low-energy fractures of the tibial diaphysis treated with functional braces. At the first measurement session 2 weeks after fracture, the patients applied approximately 15 kg to the injured limb. Although this produced 1-4 mm of translation of the fragments, this was recovered when the load was removed. The maximum rotational and angulatory displacements often occurred as the patients rose from the chair with no weight applied to the limb and frequently were reduced as the 15 kg of load was applied. Under load, the maximum axial rotation was 3 degrees and the maximum angular displacement was 1 degree. As with the translations, the initial rotational and angulatory positions of the fragments were recovered when the load was removed and the patient returned to the seated position. At 8 weeks, the patient applied full body weight, producing a maximum interfragmentary translation of 0.5 mm and maximum axial rotation or angulation of 0.5 degrees. Abundant peripheral callus formed in all three fractures, and they healed by 15 weeks through typical gradual consolidation and mineralization of the callus, accompanied by a corresponding reduction in interfragmentary motions.

Adult↗