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Biomedical subjects

B Lu

Publications and source records attributed to B Lu.

At least 163 records · Page 9Linked to original sources
PubMed1998

[Three-dimensional reconstruction of electron beam computed tomography angiography for evaluating coronary artery bypass graft patency].

OBJECTIVE: To probe into the value of electron beam computed tomography (EBCT) for evaluating coronary artery bypass graft (CABG) patency follow-up. METHODS: EBCT enhanced single slice mode (SSM) and flow study were performed in 150 patients. The results of 3-D reconstruction of CABG were correlated with bypass operation records and coronary arteriograms in 7 patients. RESULTS: 318 of 399 coronary bypass grafts including IMA in 87/100(87%) and SVG in 228/296(77%) were patent. The overall patent rate was 79.7%. In 7 patients with 12 coronary bypass grafts, EBCT studies showed graft patency in 7 and occlusion in 5, as were confirmed by conventional graft angiography. CONCLUSION: EBCT angiography is a noninvasive method that could replace conventional coronary arteriography for CABG follow-up.

Adult↗
PubMed1998

[Study on Trichosanthin induced apoptosis of leukemia K562 cells].

Trichosanthin (TCS), an eukaryotic ribosome-inactivating protein isolated from the root tuber of Trichosanthes plant, has various biological activities including abortion induction, antitumor, and anti-HIV. In this study, cultured human leukemia K562 cells treated with trichosanthin were examined. Analysis of the cells by single laser flow cytometry showed the sub-G1 peak. DNA extracted from these cells formed a characteristic "ladder" on agarose gel electrophoresis. Under electromicroscope, typical morphological changes of apoptosis were also observed. From all of these findings, we concluded that trichosanthin was able to induce apoptosis in K562 cells.

Antineoplastic Agents, Phytogenic↗
PubMed1998

[A comparison of amino acid composition of proteins from thermophiles and mesophiles].

The thermophilic feature of thermophiles are due to the high thermostability of their proteins. In order to investigate the mechanism of the high thermostability of thermophilic proteins and compare the difference of amino acid composition between thermophilic and mesophilic proteins, 110 pairs of homologous protein sequences from thermophiles and mesophiles respectively are collected and the amino acid composition, percentage of hydrophobic amino acids, hydropathy index, percentage of charged amino acids of the two protein groups are compared. It reveals that the two groups have evidently different composition in several kinds of amino acids, and thermophilic proteins have higher average hydropathy and charged amino acids composition. A comparison of the aliphatic indices between the two protein groups indicates that the reason that thermophilic proteins have higher aliphatic index is that thermophilic proteins have higher leucine composition, and thus sheds doubt on the validity of aliphatic index. It shows that it is possible to disclose some general rules with regard to the mechanism of protein thermostability by comparing a large amount of protein sequence data.

Amino Acids↗
PubMed1997

Cleavage of Chordin by Xolloid metalloprotease suggests a role for proteolytic processing in the regulation of Spemann organizer activity.

The Xolloid secreted metalloprotease, a tolloid-related protein, was found to cleave Chordin and Chordin/BMP-4 complexes at two specific sites in biochemical experiments Xolloid mRNA blocks secondary axes caused by chordin, but not by noggin, follistatin, or dominant-negative BMP receptor, mRNA injection. Xolloid-treated Chordin protein was unable to antagonize BMP activity. Furthermore, Xolloid digestion released biologically active BMPs from Chordin/BMP inactive complexes. Injection of dominant-negative Xolloid mRNA indicated that the in vivo function of Xolloid is to limit the extent of Spemann's organizer field. We propose that Xolloid regulates organizer function by a novel proteolytic mechanism involving a double inhibition pathway required to pattern the dorsoventral axis: [formula in text].

Amino Acid Sequence↗
PubMed1997

Targeted disruption of the beta-chemokine receptor CCR1 protects against pancreatitis-associated lung injury.

beta-Chemokines and their receptors mediate the trafficking and activation of a variety of leukocytes including the lymphocyte and macrophage. An array of no less than eight beta-chemokine receptors has been identified, four of which are capable of recognizing the chemokines MIP1alpha and RANTES. Genetic deletion of one of the MIP1alpha and RANTES receptors, CCR5, is associated with protection from infection with HIV-1 in humans, while deletion of the ligand MIP1alpha protects against Coxsackie virus-associated myocarditis. In this report we show that the deletion of another receptor for MIP1alpha and RANTES, the CCR1 receptor, is associated with protection from pulmonary inflammation secondary to acute pancreatitis in the mouse. The protection from lung injury is associated with decreased levels of TNF-alpha in a temporal sequence indicating that the activation of the CCR1 receptor is an early event in the systemic inflammatory response syndrome.

Animals↗
PubMed1997

Comparison of estrogen receptor DNA binding in untreated and acquired antiestrogen-resistant human breast tumors.

Preliminary studies have suggested that measuring the ability of immunoreactive 67-kDa estrogen receptor (ER) to bind DNA and form in vitro complexes with its cognate estrogen response element (ERE) might serve to identify breast tumors most likely to respond to antiestrogens like tamoxifen. Data from two different surveys of untreated primary breast tumors confirmed that only 67% (74 of 111) of ER-positive tumors express a receptor capable of forming ER-ERE complexes by gel-shift assay, with tumors of lower ER content having significantly reduced ER DNA-binding frequency (56%) relative to those of higher ER content (82%; P = 0.007). In contrast to these untreated tumors, a panel of 41 receptor-positive breast tumors excised after acquiring clinical resistance to tamoxifen during either primary (n = 26) or adjuvant therapy (n = 15) showed a significantly greater ER DNA-binding frequency, with nearly 90% capable of forming ER-ERE complexes (P < 0.02). To assess experimentally whether ER DNA-binding function is altered during the development of antiestrogen resistance, nude mouse MCF-7 tumor xenografts were analyzed before and after the acquisition of in vivo resistance to either tamoxifen or a pure steroidal antiestrogen, ICI 182,780. Tamoxifen-resistant MCF-7 tumors retained full expression of 67-kDa DNA-binding ER, and despite a markedly reduced ER content in the ICI 182,780-treated tumors, the expressed ER in these antiestrogen-resistant tumors exhibited full ability to form ER-ERE complexes. These findings indicate that breast tumors with acquired antiestrogen resistance continue to express ER of normal size and DNA-binding ability and suggest that the failure of antiestrogens to arrest tumor growth during emergence of clinical resistance results from an altered gene-regulatory mechanism(s) other than ER-ERE complex formation.

Animals↗
PubMed1997

Impaired inflammatory responses in the reverse arthus reaction through genetic deletion of the C5a receptor.

We recently demonstrated that gene-targeted disruption of the C5a anaphylatoxin receptor prevented lung injury in immune complex-mediated inflammation. In this study, we compare the effect of C5aR deficiency in immune complex-induced inflammation in the peritoneal cavity and skin with the results derived from our immune complex alveolitis model. C5aR- deficient mice exhibit decreased migration of neutrophils and decreased levels of TNF-alpha and interleukin 6 in the peritoneal reverse passive Arthus reaction compared to their wild-type littermates. In the reverse passive Arthus reaction in the skin the C5aR was also required for the full expression of neutrophil influx and edema formation; C5aR-deficient mice showed reduced neutrophil migration and microvascular permeability changes. In contrast to our studies in immune complex-induced lung inflammation, C5aR deficiency does not completely prevent injury in the peritoneal cavity and skin. These data indicate a dominant role for the C5aR and its ligand in the reverse passive Arthus reaction in the lung and a synergistic role together with other inflammatory mediators in immune complex-mediated peritonitis and skin injury.

Animals↗
PubMed1997

Identification of a STAT6 domain required for IL-4-induced activation of transcription.

Tyrosine phosphorylation of STAT6 in response to IL-4 results in the formation of STAT6 homodimers that bind specific DNA elements. Although binding sites for STAT6 have been shown to be important for the function of several IL-4-inducible promoters, the role of STAT6 in this activation has not been defined. To determine whether STAT6 is a transcriptional activator, different portions of the carboxyl terminus of STAT6 were fused to the yeast Gal4 protein DNA binding domain. Analysis of these chimeric Gal4-STAT6 proteins demonstrates that a 140-amino-acid proline-rich region of the carboxyl terminus of STAT6 contains a region that activates transcription. Truncation mutants of STAT6 that lack this domain cannot activate transcription and are capable of repressing transcription stimulated by a wild-type STAT6 protein. Strikingly, the ability of IL-4 to induce transcription from the Ig germline epsilon promoter is suppressed by overexpression of a carboxyl-terminal deletion mutant of STAT6. These studies demonstrate that the carboxyl terminus of STAT6 contains an activating domain required for the induction of genes by IL-4.

Amino Acid Sequence↗
PubMed1997

Activity-dependent expression of NT-3 in muscle cells in culture: implications in the development of neuromuscular junctions.

Although activity-dependent expression of neurotrophins has been studied extensively in the CNS, its physiological role during synapse development is not well established. At the developing neuromuscular junction in culture, exogenous application of the neurotrophin BDNF or NT-3 has been shown to acutely potentiate synaptic transmission and chronically promote synapse maturation. Using the same cell culture model, we have investigated activity-dependent neurotrophin expression in muscle cells and its role in developing neuromuscular synapses. Membrane depolarization, elicited by either depolarizing agents or repetitive electric stimulation, rapidly and specifically increased the levels of NT-3 mRNA in developing Xenopus laevis muscle cells in culture. NT-3 gene expression also was enhanced by acetylcholine (ACh), the neurotransmitter that causes muscle membrane depolarization. The effects of depolarization were mediated by increasing intracellular calcium concentration. Moreover, factor(s) induced by membrane depolarization appeared to enhance synaptic transmission at the developing neuromuscular junction. The frequency of spontaneous synaptic currents (SSCs) recorded from neuromuscular synapses was increased significantly after treatment with conditioned medium from depolarized muscle cultures. The amplitude, rise time, and decay time of SSCs were not affected, indicating a presynaptic action of the conditioned medium. The effects of the conditioned medium were blocked, partially, by the NT-3 scavenger TrkC-IgG, suggesting that the potentiation of synaptic efficacy was attributable, at least in part, to elevated NT-3 as a consequence of muscle depolarization. Thus, activity-dependent expression of muscle NT-3 may contribute to the development of the neuromuscular synapse.

Amino Acid Sequence↗
PubMed1997

Calpain II expression is increased by changes in mechanical loading of muscle in vivo.

In the present investigation, we have tested the hypothesis that calpain expression or activity in skeletal muscle is influenced by changes in mechanical loading in vivo. Muscle unloading for 10 days produced no change in the concentrations of calpain I, or II, and no change in calpain activation, as assessed by measurements of the proportion of calpain I or II isoforms that exhibited autoproteolytic modifications. However, muscle reloading for 2 days produced a 90% increase in calpain II concentration per unit wet weight of muscle relative to ambulatory controls. Although no change in the activation index for calpain I or II was identified for reloaded muscle, this index is an expression of the proportion of the total mass of each calpain isoform that is autoproteolyzed. Thus, there is also approximately a 90% increase in autolyzed calpain II in muscle experiencing increased loading than in controls. Northern analysis shows that the concentration of mRNA for calpain II is increased in reloaded muscle, but no change in calpain II mRNA concentration in unloaded muscle. In situ reverse transcription polymerase chain reaction was used to confirm that nearly all calpain II mRNA in reloaded muscle is located in muscle fibers, with very little detectable calpain II mRNA in non-muscle cells present in the tissue. Together, these findings show that increased muscle loading causes a selective increase in the expression of calpain II isoform, thereby indicating that its regulation is independent from other calpain isoforms.

Animals↗
PubMed1997

Recent progress in studies of neurotrophic factors and their clinical implications.

Neurotrophic factors are endogenous soluble proteins that regulate long-term survival and differentiation of neurons of the peripheral and central nervous systems. These factors play an important role in the structural integrity of the nervous system, and therefore are good candidates as therapeutic agents for neurodegenerative diseases. However, recent studies have revealed some unexpected, novel roles of neurotrophic factors. Of particular significance is the discovery of the new functions of brain-derived neurotrophic factor (BDNF) and glia-derived neurotrophic factor (GDNF). Physiological experiments indicate that BDNF may serve as regulatory factors for synaptic transmission as well as for learning and memory. Gene targeting studies demonstrate that GDNF may be essential for development of the enteric nervous system (ENS) and kidney organogenesis. These results not only provide new insights into our understanding of the function of neurotrophic factors but may also have significant implications in the therapeutic usages of neurotrophic factors.

Animals↗
PubMed1997

The Ca2+ binding protein, frequenin is a nervous system-specific protein in mouse preferentially localized in neurites.

Frequenin is a Ca2+-binding protein that has been implicated in the regulation of neurotransmitter release at the neuromuscular junction [15,16]. However, its cellular and subcellular localization in brain have not been determined. Therefore, we cloned mouse frequenin (Mfreq) and investigated its expression both in vivo and in vitro. The amino acid sequence of Mfreq is homologous to that of frequenins from other species. Northern and Western blot analyses indicated that the Mfreq mRNA is a single species of 4.2 kb, and that the protein has a mass of 24 kDa protein on SDS gel, respectively. Expression of Mfreq is nervous system specific. However, Mfreq mRNA and protein are widely distributed in the brain, spinal cord, and dorsal root ganglia. Mfreq is expressed in early embryonic brain and the levels of Mfreq remain high throughout development. In situ hybridization and immunocytochemistry demonstrated that Mfreq is expressed primarily in neurons and presumptive astrocytes. The Mfreq protein was preferentially localized in neurites (dendrites and axons). Double immunofluorescence microscopy established that Mfreq was co-localized with the dendritic marker, MAP-2 and the synapse marker, SV2 in cultured hippocampal neurons. The distribution and subcellular localization of Mfreq may help understand its cellular function.

Amino Acid Sequence↗
PubMed1997

Effects of acetonitrile on horseradish peroxidase (HRP)-anti HRP antibody interaction.

The effects of the water-miscible organic solvent acetonitrile on the enzymatic activity of horseradish peroxidase (HRP) and on HRP-anti-HRP binding have been investigated. Results showed that both the catalytic activity of HRP and the binding ability of the antibody were affected on increasing the concentration of the organic solvent. The activity of HRP varied with the organic composition of the solvent, indicating that the conformation of the enzyme was affected. The binding ability of the antibody also decreased significantly with an increase of the organic composition of the solvent, and in absolute acetonitrile, the activity of the antibody is about 500 times lower than that in aqueous medium. Binding reversibility experiments indicated that the antibody was not irreversibly damaged in solutions with acetonitrile composition greater than 80% and below 40%; however, an irreversible decrease in the binding was observed in solutions with an acetonitrile composition between 40 and 80%. The reduction in the binding ability is probably due to the irreversible conformation changes in the antibody.

Acetonitriles↗
PubMed1997

The control of microvascular permeability and blood pressure by neutral endopeptidase.

Plasma extravasation from postcapillary venules is one of the earliest steps of inflammation. Substance P (SP) and bradykinin (BK) mediate extravasation and cause hypotension. The cell-surface enzyme neutral endopeptidase (NEP) inactivates both peptides. Thus, absence of NEP may predispose development of inflammation and hypotension. We examined these possibilities in mice in which the NEP gene was deleted by homologous recombination. There was widespread basal plasma extravasation in postcapillary venular endothelia in NEP-/- mice, which was reversed by recombinant NEP and antagonists of SP (NK1) and BK (B2) receptors. Mean arterial blood pressure was 20% lower in NEP-/- animals, but this was unaffected by reintroduction of recombinant NEP and the kinin receptor antagonists. The hypotension was also independent of nitric oxide (NO), because NEP-/- mice treated with a NO synthase inhibitor remained hypotensive relative to the wild type. Thus, NEP has important roles in regulating basal microvascular permeability by degrading SP and BK, and may regulate blood pressure set point through a mechanism that is independent of SP, BK and NO. The use of NEP antagonists as candidate drugs in cardiovascular disease is suggested by the blood pressure data reported herein.

Animals↗
PubMed1997

Effects of hydrostatic pressure on the activity of rat ribosome and cell-free translation system.

The effects of high hydrostatic pressure on the protein synthesis activity of rat liver ribosome and the reconstructed cell-free translation system were studied. The results indicated that the activity of the ribosome decreased with the increase in applied pressure and the activity was totally lost as pressure went up to 2,400 bar, but there was a plateau approximately from 300 to 1,200 bar where the activity only had a minor change. The activity of the cell-free translation system seems to be more sensitive to pressure. Its activity was entirely lost when the pressure was up to 900 bar. The activity of rat ribosome and the cell-free translation system treated by pressure below 900 bar could be almost completely restored by incubation after releasing the pressure, but could be partially restored at higher pressure.

Animals↗
PubMed1997

Topical application of viral vectors for epidermal gene transfer.

Efficient gene transfer with extended gene expression is essential for successful treatment of skin diseases using gene therapy. Previously we evaluated a physical gene transfer method (gene gun delivery) for its ability to transfect the epidermis in vivo. In this study, we tested two viral vectors for their ability to transduce murine epidermis through topical application. Both an adenoviral vector and a herpes simplex virus (HSV) amplicon vector transduced murine epidermis with high efficiency after topical application. Differences in amount and duration of transgene expression were compared between these two vectors. Quantitative analysis of reporter lacZ gene expression showed that the viral vector-mediated gene transfers were superior to gene-gun delivery of plasmid DNA. Significant necrosis and cytotoxicity, however, were observed in the HSV-treated skin. In addition, we show that murine epidermis developed hyperkeratosis and acanthosis 4 d after an adenoviral vector containing a human TGF-alpha expression unit was applied topically. Finally we demonstrate the feasibility of transduction of fetal skin in utero by intraamniotic injection of an adenovirus vector.

Acanthosis Nigricans↗
PubMed1997

Inducible expression of a Porphyromonas gingivalis W83 membrane-associated protease.

The Tpr protease of Porphyromonas gingivalis W83 is a membrane-associated enzyme capable of hydrolyzing a chromogenic bacterial collagenase substrate. An isogenic mutant lacking a functional tpr gene had a greatly reduced ability to hydrolyze the collagenase substrate. Activity was restored to the tpr mutant by introducing a shuttle plasmid containing the tpr gene. Expression of the gene is induced by nutrient limitation, as shown by enzymatic and Northern analyses.

Collagenases↗