Search PubMed⌕ Search

Biomedical subjects

A Lu

Publications and source records attributed to A Lu.

At least 55 records · Page 3Linked to original sources
PubMed1998

Fullerene pipes

Single-wall fullerene nanotubes were converted from nearly endless, highly tangled ropes into short, open-ended pipes that behave as individual macromolecules. Raw nanotube material was purified in large batches, and the ropes were cut into 100- to 300-nanometer lengths. The resulting pieces formed a stable colloidal suspension in water with the help of surfactants. These suspensions permit a variety of manipulations, such as sorting by length, derivatization, and tethering to gold surfaces.

Journal Article↗
PubMed1998

Differences in immune responses induced by oral and rectal immunizations with Salmonella typhi Ty21a: evidence for compartmentalization within the common mucosal immune system in humans.

Based on the concept of the common mucosal immune system, immunization at various inductive sites can induce an immune response at other, remote mucosal surfaces. The immune responses elicited through rectal and oral routes of antigen delivery were compared with respect to (i) measurement of antibody responses in serum and various external secretions of the vaccinees and (ii) characterization of the nature and homing potentials of circulating antibody-secreting cells (ASC). Specific ASC appeared in the circulation in 4 of 5 volunteers after oral and 9 of 11 volunteers after rectal immunization with Salmonella typhi Ty21a. The kinetics, magnitude, and immunoglobulin isotype distribution of the ASC responses were similar in the two groups. In both groups, almost all ASC (99 or 95% after oral or rectal immunization, respectively) expressed alpha4 beta7, the gut homing receptor (HR), whereas L-selectin, the peripheral lymph node HR, was expressed only on 22 or 38% of ASC, respectively. Oral immunization elicited a more pronounced immune response in saliva and vaginal secretion, while rectal immunization was more potent in inducing a response in nasal secretion, rectum, and tears. No major differences were found in the abilities of the two immunization routes to induce a response in serum or intestinal secretion. Thus, the rectal antigen delivery should be considered as an alternative to the oral immunization route. The different immune response profiles found in various secretions after oral versus rectal antigen administration provide evidence for a compartmentalization within the common mucosal immune system in humans.

Administration, Oral↗
PubMed1998

[Integrating qualitative analysis with quantitative grey relation analysis in the comprehensive evaluation for solving medical problems].

This paper integrates qualitativ analysis with quantitative grey relation analysis in the comprehensive evaluation for solving medical problems, especially diagnostic problems, and good results are obtained. In it, some new medical concepts such as diagnostic value, diagnostic grey degree and information cover rate are defined. The given example demonstrates that when used in clinical diagnosis, this diagnostic model makes a feature of high diagnostic coincidence rate as well as low misdiagnosis rate and it overcomes the common disability of general medical diagnostic model in quantitative analysis.

Clinical Competence↗
PubMed1997

Identification of the antithrombin III heparin binding site.

The heparin binding site of the anticoagulant protein antithrombin III (ATIII) has been defined at high resolution by alanine scanning mutagenesis of 17 basic residues previously thought to interact with the cofactor based on chemical modification experiments, analysis of naturally occurring dysfunctional antithrombins, and proximity to helix D. The baculovirus expression system employed for this study produces antithrombin which is highly similar to plasma ATIII in its inhibition of thrombin and factor Xa and which resembles the naturally occurring beta-ATIII isoform in its interactions with high affinity heparin and pentasaccharide (Ersdal-Badju, E., Lu, A., Peng, X., Picard, V., Zendehrouh, P., Turk, B., Björk, I., Olson, S. T., and Bock, S. C. (1995) Biochem. J. 310, 323-330). Relative heparin affinities of basic-to-Ala substitution mutants were determined by NaCl gradient elution from heparin columns. The data show that only a subset of the previously implicated basic residues are critical for binding to heparin. The key heparin binding residues, Lys-11, Arg-13, Arg-24, Arg-47, Lys-125, Arg-129, and Arg-145, line a 50-A long channel on the surface of ATIII. Comparisons of binding residue positions in the structure of P14-inserted ATIII and models of native antithrombin, derived from the structures of native ovalbumin and native antichymotrypsin, suggest that heparin may activate antithrombin by breaking salt bridges that stabilize its native conformation. Specifically, heparin release of intramolecular helix D-sheet B salt bridges may facilitate s123AhDEF movement and generation of an activated species that is conformationally primed for reactive loop uptake by central beta-sheet A and for inhibitory complex formation. In addition to providing a structural explanation for the conformational change observed upon heparin binding to antithrombin III, differences in the affinities of native, heparin-bound, complexed, and cleaved ATIII molecules for heparin can be explained based on the identified binding site and suggest why heparin functions catalytically and is released from antithrombin upon inhibitory complex formation.

Anticoagulants↗
PubMed1997

Autographa californica nuclear polyhedrosis virus p143 gene product is a DNA-binding protein.

We have identified the protein product of the Autographa californica nuclear polyhedrosis virus (AcMNPV) p143 gene by constructing a recombinant baculovirus overexpressing the gene product P143. The overexpressed protein exhibited a relative mobility of approximately 140 kDa and was stable for at least 12 hr after synthesis. Immunoblotting using a monoclonal antibody developed against the overexpressed protein identified a similar polypeptide in AcMNPV-infected cells which was detectable by 4 hr postinfection. P143 was present within infected cell nuclei at relatively constant amounts until at least 72 hr after infection, suggesting that P143 may perform other functions at late times after infection. P143, purified from infected cell nuclei by chromatography over hydroxylapatite and DNA cellulose, bound in a sequence-independent fashion to double-stranded but not to single-stranded DNA to form a ladder of retarded protein-DNA complexes. Together, these data are consistent with the essential role of P143 for viral DNA replication and suggest that P143 may function by direct binding to DNA.

Animals↗
PubMed1997

[Hepatitis C virus infection among long-term hemodialysis patients].

We determined the prevalence and incidence of hepatitis C virus (HCV) infection among hemodialysis patients and evaluate their risk factors. 80 patients on maintenance hemodialysis in Peking Union Medical College Hospital Dialysis Center from December 1994 to June 1995 were studied. 30 medical students were used as health controls. Serum samples were tested for HCV antibodies by a second-generation enzyme-linked immunosorbent assay (ELISA) and for HCV RNA using nested polymerase chain reaction (PCR) and retested for anti-HCV and HCV RNA three months later. 24 (30%) of 80 hemodialysis patients were anti-HCV positive, and 2 (3.6%) of 56 anti-HCV negative cases were found HCV RNA positive. By combined assessment, the HCV infection rate of hemodialysis patient was 32.5% (26/80). Mantel-Haenszel analysis showed that HCV infection was associated with multi-transfusions, dialysis over a long period, renal transplantation, history of operation. Samples of dialysate in 9 serum HCV RNA positive cases were directly detected for HCV RNA, and 3 were found HCV RNA detectable. HCV infection rate in hemodialysis patients is higher than that of general population. The main risk factors for HCV transmission is transfusion of unscreened blood but is not an independent factor, hemodialysis itself plays an important role, the length of time on dialysis, renal transplantation, blood-contaminated material and contaminated dialysis equipment are also the risk factors. Infected hemodialysis patients should be isolated.

Adult↗
PubMed1997

[Photoluminescence and UV-Vis absorption spectra characteristics of metal complexes of 8-hydroxyquinoline].

8-hydroxyquinoline complexes of Na(I), Ca(II), Mg(II), Zn(II), Cu(II), Mn(II), Al(III), In(III) and La(III) were synthesized. Photoluminescence (PL) and UV-Vis absorption spectra characteristics of these complexes and 8-hydroxyquinoline are reported. Except complexes of Cu and Mn, most of these complexes reveal photoluminescence. With the polarization force of metal cations increasing, the PL peak shows red-shift and two broad absorption peak in UV-Vis (300-400nm) absorption spectra distinctly appears apart.

English Abstract↗
PubMed1996

Very low rates of hip fracture in Beijing, People's Republic of China the Beijing Osteoporosis Project.

One third of the world's hip fractures are said to occur in Asia, mostly in China. However, there have as yet been no validated studies of hip fracture rates in China. The authors estimated the incidence of hip fractures in Beijing, People's Republic of China, and took several steps to validate the estimates. All 76 Beijing hospitals reported all 1988-1992 admissions that had been coded as 820 (hip fracture) or 821 (other femoral fracture) according to the International Classification of Diseases, Ninth Revision. The authors then compared a random sample of the reports with original medical records, and discovered that 70% of intertrochanteric hip fractures had been miscoded as "other femoral fractures." The authors retrained all hospital staffs to provide corrected reports. Revised reports missed only 13% of the hip fracture cases recorded in operating room logs of 11 randomly selected hospitals. To validate hospital-based estimates of hip fracture rates, the authors interviewed a random sample of 2,113 Beijing women aged 50 years or more (97% response rate); all but 4% of past fractures and all seven hip fractures had been treated in hospitals. Finally, the authors surveyed the 27 hospitals in the counties surrounding Beijing. No Beijing residents had been treated for hip fracture outside of the city. Based on the 1990 China census, age-standardized rates of hip fracture (per 100,000) in Beijing-87 for women, 97 for men-were much lower than those seen in Hong Kong in 1985 (353 for women, 181 for men) or in US Caucasians (510-559 for women, 174-207 for men). From 1988 to 1992, the rates in Beijing increased 34% in women and 33% in men. The authors conclude that hip fracture rates in Beijing are among the lowest in the world but may be rising rapidly.

Adult↗
PubMed1996

Sequence, function, and phylogenetic analysis of an ascovirus DNA polymerase gene.

We have sequenced a 5.5-kb region of the DNA genome of the Spodoptera Ascovirus (SAV) containing a DNA polymerase gene. The gene codes for a 1104-amino-acid polypeptide with seven motifs characteristic of DNA polymerases and three additional motifs associated with polymerases possessing 3' to 5' exonuclease activity. The SAV DNA polymerase gene was able to functionally substitute for a baculovirus DNA polymerase gene in a transient assay that relies on origin-specific reporter plasmid DNA replication. Analysis of the predicted DNA polymerase sequence using neighbor-joining and protein parsimony algorithms indicated that this gene was only distantly related to other known viral and cellular DNA polymerases. The SAV DNA polymerase gene is the first ascovirus gene to be identified and sequenced. The molecular phylogenetic analyses of this gene supports the placement of insect ascoviruses in a separate virus family.

Amino Acid Sequence↗
PubMed1996

Regulation of adrenal steroidogenesis during chronic stress.

The mechanism of the altered adrenal responsiveness during chronic stress was studied by analysis of ACTH and Ang II responses and the expression and activity of steroidogenic enzymes in the adrenal cortex of rats subjected to repeated immobilization (2 hr/day for 14 days), or repeated i.p. injection of 1.5 M NaCl. Concomitant with increased pregnenolone production and reduced aldosterone secretion by isolated adrenal glomerulosa cells of chronically stressed rats, P-450scc mRNA were increased and P-450aldo mRNA levels were decreased in adrenal zona glomerulosa. Consistent with elevated plasma corticosterone levels, isolated adrenal fasciculata cells from stressed rats showed higher cAMP, pregnenolone and corticosterone responses to ACTH. Adrenal fasciculata area and levels of P-450scc, but not those of P-450(11s) hydroxylase were significantly increased. The effects of repeated stress on adrenal steroidogenesis were mimicked by repeated ACTH injections. The half life of corticosterone in plasma measured with [3H]corticosterone was increased in stressed rats but not in ACTH injected rats. This study shows that chronic stress leads to a) inhibition of mineralocorticoid secretion due to inhibition of the late biosynthetic pathway, and b) increased circulating glucocorticoids due to increased ACTH receptor activity, expression and activity of the early pathway, and decreased glucocorticoid clearance. Altered adrenal glomerulosa and fasciculata function, but not changes in glucocorticoid clearance, are probably mediated by increased ACTH secretion during chronic stress.

Adrenal Cortex↗
PubMed1996

Factors regulating baculovirus late and very late gene expression in transient-expression assays.

Eighteen genes of Autographa californica nuclear polyhedrosis virus are necessary and sufficient to transactivate expression from the late vp39 promoter in transient-expression assays in SF-21 cells. These 18 genes, known as late expression factor genes (lefs), are also required to transactivate the very late promoter of the polyhedrin gene, polh, but expression from this promoter is relatively weak compared with expression from the vp39 promoter. To further define the factors required for late and very late promoter expression, we first determined that the eighteen lefs were also required for expression from two other major baculovirus promoters: the late basic 6.9-kDa protein gene, p6.9, and the very late 10-kDa protein gene, p10. We next examined the effect of the very late expression factor 1 gene (vlf-1), a gene previously identified by analysis of a temperature-sensitive mutant, in the transient expression assay and found that vlf-1 specifically transactivated the two very late promoters but not the two late promoters. We then surveyed the Autographa californica nuclear polyhedrosis virus genome for additional genes which might specifically regulate very late gene expression; no additional vlf genes were detected, suggesting that VLF-1 is the primary regulator of very late gene expression. Finally, we found that the relative contribution of the antiapoptosis gene p35, which behaves as a lef in these transient-expression assays, depended on the nature of the other viral genes provided in the cotransfection mixtures, suggesting that other viral genes also contribute to the ability of the virus to block apoptosis.

Animals↗
PubMed1996

Species-specific effects of the hcf-1 gene on baculovirus virulence.

The host cell-specific factor 1 gene (hcf-1) of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) is required for the efficient replication and/or stability of reporter plasmids carrying an AcMNPV-derived origin of DNA replication in a cell-specific manner; hcf-1 is required for reporter plasmid replication or stability in TN-368 cells, a cell line derived from the cabbage looper Trichoplusia ni, but not in IPLB-SF-21 (SF-21) cells, a cell line derived from the fall armyworm Spodoptera frugiperda (A. Lu and L. K. Miller, J. Virol. 69:6265-6272, 1995). To further define the function of hcf-1, recombinant viruses with null mutations in hcf-1 were constructed in SF-21 cells and the phenotype of the mutants was determined in selected cell lines as well as in insect larvae. In S.frugiperda larvae and SF-21 cells, the phenotype of hcf-1 mutants was indistinguishable from that of wild-type AcMNPV. In T. ni larvae as well as T. ni-derived cell lines, hcf-1 mutants exhibited a mutant phenotype. In TN-368 cells, the replication of hcf-1 mutants was extremely impaired; the phenotype included a defect in viral DNA replication, late gene transcription, and virus production as well as a complete cessation of host and viral protein synthesis. In another cell line derived from T. ni, the BTI-TN5B1-4 cell line, the hcf-1 mutants exhibited a less severe phenotype. In T. ni larvae, the infectivity of the budded form of hcf-1 mutants was decreased significantly (50-fold), although no difference in the oral infectivity of the occluded form was observed. T. ni larvae infected with hcf-1 mutants by either oral or hemocoelic routes, however, died 20 to 30% more slowly than those infected with wild-type AcMNPV. These data indicate that there is a host-specific requirement for hcf-1 and that it exerts cell line-specific effects and possibly tissue-specific effects on the rate at which the virus replicates, thereby affecting the virulence of the virus in a species-specific manner.

Animals↗
PubMed1996

Nucleotide sequence, insertional mutagenesis, and transcriptional mapping of a conserved region of the baculovirus Autographa californica nuclear polyhedrosis virus (map unit 64.8-66.9).

The nucleotide sequence of a 2773-bp region of the Autographa californica nuclear polyhedrosis virus HR3 variant (AcMNPV) (map unit 64.4-68.2) has been determined. This region lies between the previously analyzed p6.9 and p80 genes. Three open reading frames were contained within this region, potentially coding for proteins of 45, 40, and 12 kDa. The 5' ends of transcripts capable of coding for the 45- and 12-kDa proteins map to consensus baculovirus late transcription start sites (ATAAG), while the major 5' end of the transcript coding for the 40-kDa protein maps 16 nucleotides downstream from another late transcription start site sequence, GTAAG. Attempts to prepare recombinant viruses containing insertions within these three genes were negative, suggesting that they are all essential for virus replication in cell culture. The size and organization of transcripts expressed from this region of AcMNPV were very similar to those of the previously described homologous region of Orgyia pseudotsugata nuclear polyhedrosis virus (OpMNPV). The three AcMNPV protein sequences (p45, p40, and p12) showed amino acid sequence homology with the proteins p48, p45, and p12 of OpMNPV, suggesting this region is highly conserved in baculoviruses.

Amino Acid Sequence↗
PubMed1996

[Transgenic Brassica napus resistant to turnip mosaic virus].

A system for obtaining regenerated plantlets of "double low" Brassica napus by using cotyledonary petioles as material was established. The turnip mosaic virus coat protein (TuMV-CP) gene inserted in the binary vector pBTu in the Agrobacterium tumefaciens LBA 4404 was integrated into Brassica napus through co-culture of cotyledonary petioles with LBA4404, and the material in co-culture was selected under the stress of Kanamycin. Regenerated plantlets were obtained, and the specific TuMV-CP gene was proved to be integrated into the genomic DNA of the regenerated plants by the specific PCR amplification, dot hybridization and Southern blot. All these transgenic plants were proved to be resistant to virulent TuMV by virus challenge in different degree.

Brassica↗
PubMed1995

Elimination of glycosylation heterogeneity affecting heparin affinity of recombinant human antithrombin III by expression of a beta-like variant in baculovirus-infected insect cells.

In order to promote homogeneity of recombinant antithrombin III interactions with heparin, an asparagine-135 to alanine substitution mutant was expressed in baculovirus-infected insect cells. The N135A variant does not bear an N-linked oligosaccharide on residue 135 and is therefore similar to the beta isoform of plasma antithrombin. Purified bv.hat3.N135A is homogeneous with respect to molecular mass, charge and elution from immobilized heparin. Second-order rate constants for thrombin and factor Xa inhibition determined in the absence and presence of heparin are in good agreement with values established for plasma antithrombin and these enzymes. Based on far- and near-UV CD, bv.hat3.N135A has a high degree of conformational similarity to plasma antithrombin. Near-UV CD, absorption difference and fluorescence spectroscopy studies indicate that it also undergoes an identical or very similar conformational change upon heparin binding. The Kds of bv.hat3.N135A for high-affinity heparin and pentasaccharide were determined and are in good agreement with those of the plasma beta-antithrombin isoform. The demonstrated similarity of bv.hat3.N135A and plasma antithrombin interactions with target proteinases and heparins suggest that it will be a useful base molecule for investigating the structural basis of antithrombin III heparin cofactor activity.

Animals↗
PubMed1995

Inhibition of kainic acid binding to glutamate receptors by extracts of Gastrodia.

S-(4-hydroxybenzyl)glutathione was isolated as the major principle responsible for the inhibition of the in vitro binding of kainic acid to brain glutamate receptors by water extracts of the plant Gastrodia elata. The affinity (IC50 value) of the compound is slightly lower compared to glutamate and glutathione.

Drugs, Chinese Herbal↗