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Biomedical subjects

Y Lu

Publications and source records attributed to Y Lu.

At least 595 records · Page 33Linked to original sources
PubMed1997

Effect of leader peptides on the permeability of mitochondria.

Peptides with sequences based on the leader sequence of yeast cytochrome c oxidase subunit IV (pCOX IV-(1-25)) activate the electrophoretic uptake of K+ and other cations such as tetraethylammonium and lysine by rat liver mitochondria with EC50 = 11-15 microM. Uptake of these cations is dependent on respiration and is prevented by uncoupling agents, and the Vmax for K+ is 1.2-1.5 micromol/min/mg. Albeit more slowly, the non-electrolytes mannitol and sucrose are also transported by this pathway. Treatment of the peptides with proteinase K eliminates the stimulatory effect. Since the stimulated rate is not inhibited by ATP or by cyclosporin, we conclude that this pathway is not related to the mitochondrial KATP channel or the Ca2+-dependent permeability transition pore. Transport is stimulated by pCOX IV-(1-23), pCOX IV-(1-22), and pCOX IV-(1-12)Y, but not by a 13-amino acid peptide representing the nuclear location sequence of the SV40 large T antigen, which is responsible for directing that protein to the nucleus. Spermine, which has four positive charges, also has no stimulatory effect, and an amphiphilic 22-residue peptide derived from antithrombin III with seven net charges is only one-twentieth as effective as pCOX IV-(1-22). Thus, these data indicate that the sequence/structure is important for activation of transport. We also demonstrate that mitochondrial uncoupling, previously reported to be induced by these peptides, actually reflects coupled accumulation of salt. In view of our findings, it is also likely that the lytic effects attributed to these peptides are secondary to swelling and are not due to membrane damage per se. Finally, we show that, in non-ionic media, the peptide is an inhibitor of cytochrome c oxidase.

ATP-Binding Cassette Transporters↗
PubMed1997

Binding sites of cytoplasmic effectors TRAF1, 2, and 3 on CD30 and other members of the TNF receptor superfamily.

CD30 is present on the surfaces of malignant cells from patients with Hodgkin's lymphoma, anaplastic large cell lymphoma, and other lymphomas. The yeast two hybrid genetic screen method was used to identify molecular effectors which mediate CD30 signalling events. Clones corresponding to genes coding for TRAF1, TRAF2, and TRAF3 molecules, postulated to be involved in signalling via the TNF and CD40 receptors, were isolated. In this report, we show that the CD30 intracellular tail contains two motifs that bind TRAFs. The more amino terminal motif, 558PHYPEQET565, binds TRAF2 and 3, while the more carboxyl terminal motif, 576MLSVEEEG583, binds TRAF1 and 2. We show that these amino acid motifs are conserved in TNFRp75 and CD40 and that sequences in these receptors homologous to TRAF-binding sequences found in CD30 can selectively bind the TRAFs in a predictable manner.

Amino Acid Sequence↗
PubMed1997

Determinants of mouse hepatitis virus 3C-like proteinase activity.

The coronavirus, mouse hepatitis virus strain A59 (MHV), expresses a chymotrypsin-like cysteine proteinase (3CLpro) within the gene 1 polyprotein. The MHV 3CLpro is similar to the picornavirus 3C proteinases in the relative location of confirmed catalytic histidine and cysteine residues and in the predicted use of Q/(S, A, G) dipeptide cleavage sites. However, less is known concerning the participation of aspartic acid or glutamic acid residues in catalysis by the coronavirus 3C-like proteinases or of the precise coding sequence of 3CLpro within the gene 1 polyprotein. In this study, aspartic acid residues in MHV 3CLpro were mutated and the mutant proteinases were tested for activity in an in vitro trans cleavage assay. MHV 3CLpro was not inactivated by substitutions at Asp3386 (D53) or Asp3398 (D65), demonstrating that they were not catalytic residues. MHV 3CLpro was able to cleave at a glutamine-glycine (QG3607-8) dipeptide within the 3CLpro domain upstream from the predicted carboxy-terminal QS3636-6 cleavage site of 3CLpro. The predicted full-length 3CLpro (S3334 to Q3635) had an apparent mass of 27 kDa, identical to the p27 3CLpro in cells, whereas the truncated proteinase (S3334 to Q3607) had an apparent mass of 24 kDa. This 28-amino-acid carboxy-terminal truncation of 3CLpro rendered it inactive in a trans cleavage assay. Thus, MHV 3CLpro was able to cleave at a site within the putative full-length proteinase, but the entire predicted 3CLpro domain was required for activity. These studies suggest that the coronavirus 3CL-proteinases may have a substantially different structure and catalytic mechanism that other 3C-like proteinases.

3C Viral Proteases↗
PubMed1997

A sequential learning scheme for function approximation using minimal radial basis function neural networks.

This article presents a sequential learning algorithm for function approximation and time-series prediction using a minimal radial basis function neural network (RBFNN). The algorithm combines the growth criterion of the resource-allocating network (RAN) of Platt (1991) with a pruning strategy based on the relative contribution of each hidden unit to the overall network output. The resulting network leads toward a minimal topology for the RBFNN. The performance of the algorithm is compared with RAN and the enhanced RAN algorithm of Kadirkamanathan and Niranjan (1993) for the following benchmark problems: (1) hearta from the benchmark problems database PROBEN1, (2) Hermite polynomial, and (3) Mackey-Glass chaotic time series. For these problems, the proposed algorithm is shown to realize RBFNNs with far fewer hidden neurons with better or same accuracy.

Algorithms↗
PubMed1997

Tetrandrine inhibits signal-induced NF-kappa B activation in rat alveolar macrophages.

Tetrandrine is a bisbenzylisoquinoline alkaloid isolated from a natural Chinese herbal medicine. While this alkaloid has been shown to exhibit antifibrotic and anti-inflammatory activities, its mechanism of action is unknown. The present study was designed to investigate the inhibitory effect of tetrandrine on NF-kappa B activation in the alveolar macrophage. Three different provocative stimuli were used to activate NF-kappa B in these cells. The results indicate that tetrandrine can inhibit the activation of NF-kappa B and NF-kappa B-dependent reporter gene expression by LPS, PMA, and silica in a dose-dependent manner. In contrast, at the doses used, tetrandrine did not interfere with Sp-1 DNA binding activity or Sp-1-dependent reporter gene expression in these cells. Western blot analysis suggests that the inhibitory effect of tetrandrine on NF-kappa B activation can be attributed to its ability to suppress signal-induced degradation of I kappa B alpha, a cytoplasmic inhibitor of the NF-kappa B transcription factor.

Alkaloids↗
PubMed1997

Can prostate-specific antigen reverse transcriptase-polymerase chain reaction be used as a prospective test to diagnose prostate cancer?

The present study addressed the question as to whether prostate-specific antigen reverse transcriptase-polymerase chain reaction (PSA RT-PCR) could be used to identify prospectively men who have prostate cancer and to help determine which patients with an initially negative biopsy would benefit from rebiopsy. PSA RT-PCR was performed prospectively on 90 patients who were to have a prostate biopsy because of an elevated PSA level, an abnormal digital rectal examination, or both. PSA RT-PCR was performed, and the sensitivity of the test was enhanced by hybridization of the PCR with a 32P-labeled PSA cDNA probe (exons 3-5). Of the 90 men, 36 (40%) had prostate cancer on biopsy. Of these 36 men, 5 (13.9%) had a positive PSA RT-PCR finding, whereas 31 (84.1%) tested negative. Of 54 men with negative biopsies, 8 (14.8%) had a positive PSA RT-PCR result. The sensitivity of PSA RT-PCR for the detection of biopsy-proven prostate cancer was 13.9% and the specificity was 85.2%. Only 3 of 12 (25%) patients with advanced disease had a positive test result. The sensitivity of PSA RT-PCR for the detection of biopsy-proven prostate adenocarcinoma in men suspected of having prostate cancer is poor. Indeed, men without biopsy-proven prostate cancer are just as likely to have a positive result in the PSA RT-PCR as are men with cancer. Whether these men with negative prostate biopsies and positive PSA RT-PCR findings may eventually develop prostate cancer remains to be determined. At this time, PSA RT-PCR for the prospective detection of prostate cancer should be considered investigational.

Adenocarcinoma↗
PubMed1997

Protein kinase C in IL-2 signal transduction.

Interleukin-2 (IL-2), secreted principally by activated helper T-cells, plays a pivotal role in the generation and regulation of the immune response. The various biologic functions of IL-2 have been the focus of intensive study over the years and have been well worked out. By contrast, an understanding of the intracellular signals coupled to the IL-2 receptor and responsible for mediating IL-2 effects in T-cells is far less developed, and the role that protein kinase C (PKC) may play in the various cellular responses to IL-2 receptor activation is unclear. In this article we will discuss IL-2, its receptors, and IL-2 signal transduction in relation to the physiological roles PKC activation may play in IL-2-mediated activation of T-cells and other hematopoietic cells.

Humans↗
PubMed1997

GABAergic disinhibition changes the recovery cycle of bat inferior collicular neurons.

This study examines the contribution of GABAergic inhibition to the discharge pattern and recovery properties of 110 bat inferior collicular neurons by means of bicuculline application to their recording sites. When stimulated with single pulses, 74 (67%) neurons discharged one or two impulses (phasic responders), 19 (17%) discharged three to ten impulses (phasic bursters) and 17 (16%) discharged impulses throughout the entire stimulus duration (tonic responders). Bicuculline application changed phasic responders into phasic bursters or tonic responders, increased the number of impulses by 10-2000% and shortened the response latency of most neurons. When stimulated with pairs of sound pulses, the recovery cycles of these neurons can be described as: (1) long inhibition (n = 49, 45%); (2) short inhibition (n = 41, 37%); and (3) fast recovery (n = 20, 18%) based upon the 50% recovery time that was either longer than 20 ms, between 10 and 20 ms or shorter than 10 ms. Bicuculline application shortened the 50% recovery time of most neurons by 11-2350% allowing them to respond to pairs of sound pulses at very short interpulse intervals. These data demonstrate that GABAergic inhibition contributes significantly to auditory temporal processing.

Animals↗
PubMed1997

Development of an in vitro quantal assay in primary cell cultures for a non-occluded baculo-like virus of penaeid shrimp.

An in vitro quantal assay (TCID50) for a non-occluded baculo-like virus isolate from naturally infected Penaeus japonicus obtained from China and experimentally infected P. stylirostris was developed using primary shrimp lymphoid cell cultures in Primaria 24-well tissue culture plates. The virus caused cytopathogenic effect (CPE) in the cell cultures as early as 2 day post-infection (p.i.). Initially, the cells rounded up and finally detached from the culture vessel as the infection progressed. At the present time, there is no established quantitative in vitro cell culture protocol for the assay of this baculo-like virus which has been reported by our laboratory to be highly pathogenic for P. stylirostris and P. vannamei, the two species of penaeid shrimp commercially cultured in Hawaii and the Western hemisphere. This quantal assay thus provides a simple and convenient method for the detection and assay of infectious virus in cultured penaeid shrimp.

Animals↗
PubMed1997

HIV prevention among Zambian adolescents: developing a value utilization/norm change model.

Peer-led interventions are effective in reducing risk for HIV among adolescents. A pre-intervention study was conducted to determine how to successfully carry out a possible future intervention to reduce HIV risk among adolescents in urban Zambia. Ethnographic and sexual data were collected on 276 males and females both attending and not attending secondary school during a 14-month period in 1992-1993. Additionally, several focus groups were conducted. This paper reviews the cultural background of Zambian adolescents and presents an overview of the study results. Among the findings, it was learned that most of the male and female adolescents (average age of 17) are sexually active, very few routinely use condoms, less than half of sexually active adolescents have ever used a condom, AIDS is omnipresent in Zambia, the threat of HIV infection is a very real concern for most of the adolescents, there is a strong desire to protect themselves from HIV infection during sex (but condoms are often seen as ineffective and other forms of safer sex are not discussed), nearly all of the sexually active females and some of the males have received money or gifts for sex, and some of the out-of-school females are engaging in very risky sex (e.g., unprotected anal intercourse, and anilingus) with adult men. The ethnographic data, including a brief trial risk reduction workshop, suggests that the core values and social norms of the adolescents may shape behavioral change. A value utilization/norm change (VUNC) model is developed, which is intended to provide a conceptual framework for understanding how to utilize selected core values of the adolescents to strengthen or alter norms within the social networks in order to elicit desired HIV risk reduction.

Adolescent↗
PubMed1997

Interleukin-8 is a mediator of the final cervical ripening in humans.

OBJECTIVE: The aim of the present study was to investigate the presence of interleukin-8 (IL-8) in the human cervix and whether the levels of interleukin-8 could be related to the ripening process during pregnancy. STUDY DESIGN: Cervical biopsies were obtained in twelve term pregnant and in eight vaginally delivered women. Seven non-pregnant fertile women served as controls. After homogenisation and centrifugation, IL-8 levels were determined in the supernatant by an enzyme-immunoassay (EIA). RESULTS: In women at term, the concentration of IL-8 increased six-fold from median 330 pg/ml to median 2190 pg/ml (P < 0.001). After the final cervical ripening it increased in additional 11-fold to median 26,100 pg/ml (P < 0.001). These changes are highly significant. CONCLUSION: To our knowledge, this is the first time IL-8 has been identified in human cervix. Our results support the involvement of IL-8 in the connective tissue remodelling during the final cervical ripening just before onset of labour.

Apgar Score↗
PubMed1997

How can we measure bone quality?

Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue. This leads to diminished biomechanical competence of the skeleton and is associated with low-trauma or atraumatic fractures. In the past decade, considerable progress has been made in the development of methods for assessing the skeleton non-invasively, so that osteoporosis can be better managed. While dual X-ray absorptiometry (DXA) is still the preferred methodology, several limitations will be addressed. Another densitometric technique which is widely accepted for diagnosis of spinal osteoporosis is single energy QCT. Measurements of vertebral trabecular bone mineral density (BMD) demonstrate larger percentage decrements between vertebrally-fractured subjects and normal controls, and confer higher relative risks for vertebral fracture than either anteroposterior or lateral DXA measurements. As an emerging alternative to photon absorptiometry techniques, there is a growing interest in the use of quantitative ultrasound (QUS) measurements for the non-invasive assessment of osteoporotic fracture risk in the management of osteoporosis. The attractiveness of QUS lies in the fact that indirect and in vitro experience has suggested that ultrasound may give information not only about BMD but also about architecture and elasticity. Whether or not combining QUS and DXA improve fracture prediction is still unclear and needs further analysis. Due to the growing evidence supporting the use of QUS in osteoporosis and the large number of QUS devices already on the market, a general clinical consensus on the application of QUS is urgently needed. Other techniques that are less widely used for the management of osteoporosis. For example, peripheral quantitative computed tomography, quantitative magnetic resonance (QMR) and magnetic resonance microscopy are promising tools for the evaluation of the skeleton. For example, the ability of QMR and high resolution magnetic resonance imaging has been explored and shows promise as a technique for assessing trabecular bone structure in osteoporosis.

Absorptiometry, Photon↗
PubMed1997

Engineering metal-binding sites in proteins.

Metal-binding sites have been engineered into both de novo designed and naturally occurring proteins. Although the redesign of existing metal-binding sites in naturally occurring proteins still offers the most promise for a successful design, the more challenging goal of engineering metal-binding sites in de novo designed proteins and peptides is being achieved with increasing frequency. Creating new metal-binding sites in naturally occurring proteins combines the strength of both approaches. Currently, all three approaches are being used effectively in elucidating the structure and function of naturally occurring metalloproteins.

Binding Sites↗
PubMed1997

Construction and characterization of a manganese-binding site in cytochrome c peroxidase: towards a novel manganese peroxidase.

BACKGROUND: Manganese-binding sites are found in several heme peroxidases, namely manganese peroxidase (MnP), chloroperoxidase, and the cationic isozyme of peanut peroxidase. The Mn-binding site in MnP is of particular interest. Oxidation of Mn(II) to Mn(III) is a key step in the biodegradation of lignin, a complex phenylpropanoid polymer, as well as many aromatic pollutants. Cytochrome c peroxidase (CcP), which is structurally homologous to MnP despite a poor sequence homology, does not bind manganese. Thus, engineering a Mn-binding site into CcP will allow us to elucidate principles behind designing metal-binding sites in proteins, to understand the structure and function of this class of Mn-binding centers, and to prepare novel enzymes that can degrade both lignin and other xenobiotic compounds. RESULTS: Based on a comparison of the crystal structures of CcP and MnP, a site-directed triple mutant (Gly41-->Glu, Val45-->Glu, His181-->Asp) of residues near the putative Mn-binding site in CcP was prepared and purified to homogeneity. Titrating MnSO4 into freshly prepared mutant CcP resulted in electronic absorption spectral changes similar to those observed in MnP. The calculated apparent dissociation constant and the stoichiometry of Mn-binding of CCP were also similar to MnP. Titration with MnSO4 resulted in the disappearance of specific paramagnetically shifted nuclear magnetic resonance spectroscopy signals assigned to residues close to the putative Mn-binding site in the mutant CcP. None of the spectral features were observed in wild-type CcP. In addition, the triple mutant was capable of oxidizing Mn(II) at least five times more efficiently than the native CcP. CONCLUSIONS: A Mn-binding site has been created in CcP and based on our spectroscopic studies the designed Mn-binding site is similar to the Mn-binding site in MnP. The results provide a basis for understanding the structure and function of the Mn-binding site and its role in different heme peroxidases.

Binding Sites↗
PubMed1997

Volumetric quantitative computed tomography of the proximal femur: precision and relation to bone strength.

We have developed a three-dimensional computed tomography (CT) scanning and image analysis method for measurement of trabecular and integral bone mineral density (BMD) and geometry in automatically determined femoral-neck and trochanteric subregions of the proximal femur. We measured the correlation of the density and geometry variables to femoral strength assessed in vitro under loading simulating a single-limb condition and a fall to the side. While BMD alone accounted for 48%-77% of the variability in strength for the stance loading configuration, femoral neck cross-sectional area (minCSA) and femoral neck axis length (FNAL) also contributed independently to femoral strength, and a combination of BMD and geometry variables explained 87%-93% of the variance in the data. For the fall loading configuration, trochanteric trabecular BMD alone explained 87% of the variability of strength. The reproducibility in vivo of the technique was assessed in a group of seven postmenopausal women, who underwent repeat scans with repositioning. For trabecular BMD, the precision was 1.1% and 0.6% for the femoral neck and trochanteric subregions, respectively, compared to 3.3% and 1.6% for the corresponding integral envelopes. Thus, trabecular BMD measurements were reproducible and highly correlated to biomechanical strength measurements. These results support further exploration of quantitative CT for assessment of osteoporosis at the proximal femur.

Accidental Falls↗
PubMed1997

IFN-gamma inducibility of class II transactivator is specifically lacking in human tumour lines: relevance to retinoblastoma protein rescue of IFN-gamma inducibility of the HLA class II genes.

We have previously reported that HLA class II induction by IFN-gamma is rescuable by reconstitution of functional retinoblastoma protein (RB) in two RB-defective tumour lines: the breast carcinoma line, MDA-468-S4 (S4) and the non-small cell lung carcinoma line, H2009. To determine the range of tumours and tumour types in which RB rescues HLA class II inducibility, we examined another RB-defective tumour line, the retinoblastoma line, WERI-Rb1. As in the case of S4 and H2009, HLA-DRA and -DRB were non-inducible by IFN-gamma in WERI-Rb1. However, neither inducibility of DRA nor DRB mRNA was resulted in an RB-positive stable transformant of WERI-Rb1, WLRB-8. While guanylate-binding protein (GBP) inducibility indicated that the basic IFN-gamma signal transduction pathway remained intact in WERI-Rb1, mRNA for class II transactivator (CIITA), a mediator of the IFN-gamma activation of the HLA class II genes and several other genes related to immune function, was not detectable in IFN-gamma-treated WERI-Rb1, indicating that the lack of CIITA expression was responsible, at least in part, for the inability of RB to rescue HLA class II-inducibility. The HLA class II-associated invariant chain (Ii), the expression of which is also up-regulated by CIITA, was non-inducible in WERI-Rb1, consistent with non-inducible CIITA. Also, IFN-gamma failed to activate the DRA, DRB and Ii promoters in WERI-Rb1. However, exogenous CIITA expression in WERI-Rb1 activated the DRA, DRB and Ii promoter-chloramphinocol acetyltransferase constructs, confirming that CIITA was not induced in WERI-Rb1 and indicating that other proteins required for activation of the class II and Ii promoters were functional in this cell line. Examination of additional cell lines for GBP and CIITA induction revealed that a specific lack of the CIITA IFN-gamma response is common in human tumour lines. The possible role of CIITA defects in tumorigenesis is discussed.

Chloramphenicol O-Acetyltransferase↗
PubMed1997

Differential antinociceptive effects of spinal opioids on foot withdrawal responses evoked by C fibre or A delta nociceptor activation.

1. Intrathecal application of mu, delta, and kappa opioids attenuate responses on several tests of animal nociception. However, the potency of these opioids differ depending on which tests were used. One factor contributing to these discrepancies is that different types of noxious stimuli activate different sets of nociceptor types, which may be differentially sensitive to opiate inhibition. To examine this hypothesis, we used a recently developed behavioural test which allows for differential assessment of nociception evoked by the activation of myelinated (A delta) and unmyelinated C thermonociceptors. 2. Administration of a kappa-selective agonist was ineffective on either type of response. Delta1 drugs were slightly more potent on C fibre-mediated responses than on A delta-mediated responses. 3. Intrathecal mu and delta2 drugs were antinociceptive on both A delta and C nociceptor-mediated responses. However, unlike the delta1 effects, the dose-response curves for mu and delta2 drugs were significantly more steep for A delta than for C fibre-mediated responses, potentially indicating differences in the mechanisms by which the drugs act on these 2 response types.

Analgesics↗