Biomedical subjects

H Li

Publications and source records attributed to H Li.

At least 811 records · Page 45Linked to original sources

PubMed1999

Production of malignant catarrhal fever virus-free sheep.

The study was designed to better define the variables affecting the success of the establishment of ovine herpesvirus 2 (OHV-2)-free sheep flocks. A total of 38 lambs born to OHV-2-positive ewes was selected and divided into four groups. Three groups of 10 lambs each were separated from the positive ewes at 2, 2.5 and 3 months of age, respectively, and maintained in isolation facilities. One group of eight remained in the positive flock as controls. Peripheral blood samples from each lamb were examined regularly by PCR for OHV-2 DNA. All lambs (100%) that were weaned and maintained in isolation from the ages of 2, 2.5 and 3 months remained negative until the termination of the experiment at 1 year of age. One lamb was discovered to be PCR-positive on the day of isolation at 2.5 months of age, and was promptly removed from the isolation group. In contrast, all lambs (100%) that remained with the flock became PCR-positive by 6 months of age. The data confirmed that, with rare exceptions, separation of lambs from OHV-2 infected animals at around 2 months of age reliably yields OHV-2-free sheep. Appropriate PCR monitoring will enable the rare exceptions to be removed from the group, and is recommended as a safety measure.

Alphaherpesvirinae↗

PubMed1999

Use of RhD fusion protein expressed on K562 cell surface in the study of molecular basis for D antigenic epitopes.

The human D antigens, one of the most clinically important blood groups, are presented by RhD protein with a putative 12 transmembrane topology. To understand the molecular basis for the complex antigenic profile of RhD protein, we expressed a series of RhD fusion proteins using different portions of Duffy protein as a tag in erythroleukemic K562 cells. Because the reactivity of monoclonal anti-RhD antibody, LOR15C9, depends mainly on the sequence coded by exon 7 of RhD, we altered DNA sequence corresponding to the amino acid residues 323-331(A) and 350-354(B) in the exon 7. The mutation in region B resulted in a severe reduction in LOR15C9 binding by flow cytometry analysis, suggesting that region B may play an important role in constituting antigen epitopes recognized by LOR15C9. On the other hand, a slight decrease in the antibody binding was observed for the region A mutant, suggesting that the intracellularly located region A may elicit a long distance effect on the formation of exofacial antigen epitopes. In addition, using various monoclonal antibodies against RhD, we compared the antigenic profile of expressed RhD fusion protein with that of endogenous RhD in K562 cells as well as in erythrocytes.

Amino Acid Sequence↗

PubMed1999

Characterization of genomic regions directing the cell-specific expression of the mouse aldose reductase gene.

Aldose reductase (AR), an enzyme implicated in the pathogenesis of diabetic complications, is highly expressed in such target organs of complications as the lens and peripheral nerve of experimental animals. In mouse, however, a very low level of the transcript was expressed in these tissues. To explore the unique expression pattern of AR in mice, genomic structure and upstream regions regulating the basal expression of the enzyme were determined. In NIH3T3 cells, a -1.1-kb upstream portion demonstrated the highest promoter activity. The ability to drive the luciferase reporter gene was reduced by 56% when the -1.1/-0.86-kb region was deleted. In Chinese hamster ovary (CHO) cells, deletion up to -0.67 kb did not affect basal promoter activity. The activity in CHO cells was reduced by 73% when the -0. 67/-0.24-kb region was deleted. These findings indicate that a genomic region directing the cell-specific transcription of the mouse AR gene exists.

3T3 Cells↗

PubMed1999

Supertetrahedral sulfide crystals with giant cavities and channels

Although aluminosilicates and metal phosphates can form porous open-framework materials such as zeolites, sulfide analogs usually form high-density phases because of the relatively small tetrahedral angle at sulfur atoms. One strategy to overcome this limitation is to use tetrahedral clusters as the building blocks to achieve porous sulfide-based networks. The preparation and crystal structures of two indium sulfide open frameworks (ASU-31 and ASU-32) built of supertetrahedral clusters around organic template and water guests are described. ASU-31, based on the sodalite-tetrahedrite network, contains cavities 25.6 angstroms in diameter, and ASU-32, based on the tetragonal CrB4 network, contains channels with a minimum diameter of 14.7 angstroms. The organic cations can be completely exchanged with sodium ions in aqueous solution at room temperature without degradation of the crystals.

Journal Article↗

PubMed1999

Peripheral-type benzodiazepine receptor (PBR) in human breast cancer: correlation of breast cancer cell aggressive phenotype with PBR expression, nuclear localization, and PBR-mediated cell proliferation and nuclear transport of cholesterol.

Aberrant cell proliferation and increased invasive and metastatic behavior are hallmarks of the advancement of breast cancer. Numerous studies implicate a role for cholesterol in the mechanisms underlying cell proliferation and cancer progression. The peripheral-type benzodiazepine receptor (PBR) is an Mr 18,000 protein primarily localized to the mitochondria. PBR mediates cholesterol transport across the mitochondrial membranes in steroidogenic cells. A role for PBR in the regulation of tumor cell proliferation has also been shown. In this study, we examined the expression, characteristics, localization, and function of PBR in a battery of human breast cancer cell lines differing in their invasive and chemotactic potential as well as in several human tissue biopsies. Expression of PBR ligand binding and mRNA was dramatically increased in the highly aggressive cell lines, such as MDA-231, relative to nonaggressive cell lines, such as MCF-7. PBR was also found to be expressed at high levels in aggressive metastatic human breast tumor biopsies compared with normal breast tissues. Subcellular localization with both antibodies and a fluorescent PBR drug ligand revealed that PBR from the MDA-231 cell line as well as from aggressive metastatic human breast tumor biopsies localized primarily in and around the nucleus. This localization is in direct contrast to the largely cytoplasmic localization seen in MCF-7 cells, normal breast tissue, and to the typical mitochondrial localization seen in mouse tumor Leydig cells. Pharmacological characterization of the receptor and partial nucleotide sequencing of PBR cDNA revealed that the MDA-231 PBR is similar, although not identical, to previously described PBR. Addition of high affinity PBR drug ligands to MDA-231 cells increased the incorporation of bromodeoxyuridine into the cells in a dose-dependent manner, suggesting a role for PBR in the regulation of MDA-231 cell proliferation. Cholesterol uptake into isolated MDA-231 nuclei was found to be 30% greater than into MCF-7 nuclei. High-affinity PBR drug ligands regulated the levels of cholesterol present in MDA-231 nuclei but not in MCF-7. In addition, the PBR-dependent MDA-231 cell proliferation was found to highly correlate (r = -0.99) with the PBR-mediated changes in nuclear membrane cholesterol levels. In conclusion, these data suggest that PBR expression, nuclear localization, and PBR-mediated cholesterol transport into the nucleus are involved in human breast cancer cell proliferation and aggressive phenotype expression, thus participating in the advancement of the disease.

Amino Acid Sequence↗

PubMed1999

[Linkage studies of a familial spastic paraplegia pedigree from Tibet].

OBJECTIVE: To study the location of disease-related gene in a hereditary spastic paraplegia family with autosomal dominant inheritance in Tibet. METHODS: The AD-HSP family in Tibet was analyzed by linkage studies using 9 highly polymorphic microsatellite DNA markers at three chromosomal regions. RESULTS: The maxium Lod- Score of D14S264 was 0.5163(theta=0.05); of D14S75, 2. 1072 (theta=0);+D14S69, 0.2840 (theta=0.10); of D14S266, 0.9311 (theta=0);of D14S66, 0.7991(theta=0);OF GABRB3, 0(theta =0.40);of D15S128, 0(theta=0.40); of D2S2255, 0 (theta=0.40);and of D2S2347,0(theta=0.40). CONCLUSION: In this Tibetian family, the disease-related gene is linked to D14S75 locus of SPG3 region.

Female↗

PubMed1999

Mapping RNA-protein interactions in ribonuclease P from Escherichia coli using electron paramagnetic resonance spectroscopy.

Ribonuclease P (RNase P) is a catalytic ribonucleoprotein (RNP) essential for tRNA biosynthesis. In Escherichia coli, this RNP complex is composed of a catalytic RNA subunit, M1 RNA, and a protein cofactor, C5 protein. Using the sulfhydryl-specific reagent (1-oxyl-2,2,5, 5-tetramethyl-Delta3-pyrroline-3-methyl)methanethiosulfonate (MTSL), we have introduced a nitroxide spin label individually at six genetically engineered cysteine residues (i.e., positions 16, 21, 44, 54, 66, and 106) and the native cysteine residue (i.e., position 113) in C5 protein. The spin label covalently attached to any protein is sensitive to structural changes in its microenvironment. Therefore, we expected that if the spin label introduced at a particular position in C5 protein was present at the RNA-protein interface, the electron paramagnetic resonance (EPR) spectrum of the spin label would be altered upon binding of the spin-labeled C5 protein to M1 RNA. The EPR spectra observed with the various MTSL-modified mutant derivatives of C5 protein indicate that the spin label attached to the protein at positions 16, 44, 54, 66, and 113 is immobilized to varying degrees upon addition of M1 RNA but not in the presence of a catalytically inactive, deletion derivative of M1 RNA. In contrast, the spin label attached to position 21 displays an increased mobility upon binding to M1 RNA. The results from this EPR spectroscopy-based approach together with those from earlier studies identify residues in C5 protein which are proximal to M1 RNA in the RNase P holoenzyme complex.

Amino Acid Sequence↗

PubMed1999

Postnatal growth of corticospinal axons in the spinal cord of developing mice.

The corticospinal tract (CST) plays an important role in the control of voluntary movements. Although the development of the CST has been studied extensively in other species, limited information is available on its development in mice. In the present study, the growth of corticospinal axons was characterized in developing mice using Phaseolus vulgaris leucoagglutinin (PHA-L). Our results indicate that the leading CST axons reach the 8th cervical segment at postnatal day (PD) 2, the 7th thoracic segment at PD4, the 13th thoracic segment at PD7, and the 5th lumbar segment at PD9. The arrival of corticospinal axons at the distal lumbar cord at PD9 was further confirmed by retrograde tracing using fast blue (FB). A waiting period of 2-3 days exists after the leading CST axons pass a particular segment before sending collaterals into the gray matter of that segment. The CST continues to increase in size in lower thoracic and lumbar areas up to PD14 when its adult appearance is achieved. In this study, the date of animal's sacrifice was used as the specific postnatal date to demonstrate the growth of the CST. This definition gives a more reliable indication of the exact location of the CST at a specific developmental time point since the CST continues to grow after tracer injections and since the dye is transported much faster than axonal growth. We suggest that these findings can be used as a template for studies on both normal and transgenic mice where some developmental significance is given to the CST.

Amidines↗

PubMed1999

Ibuprofen: new explanation for an old phenomenon.

Nuclear factor-kappaB (NF-kappaB) translocation from the cytoplasm into the nucleus and the subsequent DNA binding is an essential prerequisite in the up-regulation of many pro-inflammatory genes, e.g. tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta). The anti-inflammatory drug ibuprofen, thought to exert its beneficial effects mainly by suppressing the production of eicosanoids, inhibited the up-regulation of the pro-inflammatory cytokines IL-1beta and TNF-alpha. This effect was independent of the described potential of ibuprofen as a cyclooxygenase inhibitor. Ibuprofen inhibited the activation and translocation of the key transcription factor NF-kappaB by blocking the degradation of inhibitor-kappaBalpha, a protein that forms a complex with NF-kappaB, thereby preventing the release and subsequent translocation of NF-kappaB into the nucleus and the expression of inflammatory cytokines. The presented data offer a new explanation for the anti-inflammatory effect of ibuprofen.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1999

Preoperative serum level of inhibin A is an independent prognostic factor for the survival of postmenopausal women with epithelial ovarian carcinoma.

BACKGROUND: The aim of this study was to determine the prognostic significance of preoperative serum inhibin and activin levels in postmenopausal women with epithelial ovarian carcinoma (EOC) by correlating serum levels with disease parameters, including tumor stage and grade and patient age. METHODS: Serum levels of inhibin A, inhibin B, pro-alpha C, activin A, and activin B were quantitated with sensitive and specific two-site enzyme-linked immunosorbent assays (ELISAs) in samples collected from 44 postmenopausal women diagnosed with EOC. Serum was obtained within 14 days prior to primary tumor reductive surgery and stored at -55 degrees C. All patients underwent definitive surgical staging and cytoreduction at Mayo Clinic and were followed for at least 5 years or until death. Postoperative adjuvant therapy was selected based on stage of disease. Demographics included 5 Stage I, 2 Stage II, 33 Stage III, and 4 Stage IV tumors, and the predominant histology was serous subtype and poorly differentiated grade. RESULTS: Inhibin A was detected in 98% of the serum samples (range, 0-12.18 pg/mL). Univariate analysis was used to demonstrate an association between patients with serum inhibin A levels exceeding the median (1.21 pg/mL) and compromised disease free (P = 0.025) and overall (P = 0.006) survival. While the 5 year disease free survival (DFS) for the entire population was 32%, the corresponding DFS rates for patients with inhibin A levels above and below the median were 10% and 43%, respectively. Similarly, the 5-year overall survival (OS) for the entire population was 35%, compared with 16% for patients above and 47% for patients below the median inhibin A level. Stepwise regression analysis that incorporated age, stage, grade, and inhibin A levels identified serum inhibin A levels above the median to be the most cogent predictor of DFS and OS. CONCLUSIONS: Preoperative serum inhibin A levels provided valuable prognostic information independent of age, stage, and grade in a postmenopausal cohort given standardized treatment for EOC.

Aged↗

PubMed1999

Delineation of a membrane-proximal beta-rich domain in the GABAA receptor by progressive deletions.

The type A gamma-aminobutyric acid (GABAA) receptor plays a major inhibitory role in the central nervous system. Structural elucidation of the GABAA receptor has been impeded by the large size of the receptor. We present here the delineation of a minimal structural domain as the first step of dissecting the receptor structure. This was achieved through prediction-assisted progressive deletions: the prediction of a candidate structural domain rich in beta-strands with no close similarity to known structures was tested by deleting putative secondary structure elements from the ends of the proposed domain, as well as mutations within the terminal secondary structures. Such progressive deletions revealed the limits of an integral domain, spanning Cys180 to Met293 (numbering of human alpha1 subunit). Below these limits the intact domain structure, as indicated by its circular dichroism, collapses. Based on its putative position, this domain is provisionally designated the membrane-proximal beta-rich domain of GABAA receptor. The inclusion of sequences from the first two out of four previously suggested transmembrane segments and one of the two conserved Cys residues in this domain defines important constraints to the receptor structure.

Amino Acid Sequence↗

PubMed1999

Different effects of unilateral and bilateral hippocampal lesions in rats on the performance of radial maze and odor-paired associate tasks.

The hippocampus plays an important role in the declarative or explicit memory in humans and is necessary for allocentric spatial learning and olfactory memory in animals. In primates and rodents, the bilateral hemispheres of the brain (especially the forebrain) symmetrically and asymmetrically contribute to diverse cognitive manipulations. In this study, we investigated the role of the hippocampus in spatial memory and in odor-paired associate memory by unilaterally or bilaterally lesioning this region in rats. The bilateral removal, but not the unilateral removal, of the hippocampus impaired both the acquisition of spatial working memory in the radial maze task and the retrieval of maze performance tested 1 month after the acquisition trials. In contrast, neither bilateral nor unilateral removal impaired the odor-paired associate learning. These findings suggest that the hippocampus is critical to the spatial memory, and that a unilateral hippocampus is sufficient for executing a spatial task. The present results also indicate that the hippocampus plays a minor role in odor-dominated associate learning and that some kinds of memories in rats may be processed independently by the left or right hippocampus.

Animals↗

PubMed1999

N-lobe versus C-lobe complexation of bismuth by human transferrin.

Interactions of recombinant N-lobe of human serum transferrin (hTF/2N) with Bi3+, a metal ion widely used in medicine, have been investigated by both UV and NMR spectroscopy. The bicarbonate-independent stability constant for Bi3+ binding (K*) to hTF/2N was determined to be log K* 18.9+/-0.2 in 5 mM bicarbonate/10 mM Hepes buffer at 310 K, pH7.4. The presence of Fe3+ in the C-lobe of intact hTF perturbed Bi3+ binding to the N-lobe, whereas binding of Bi3+ to the C-lobe was unaffected by the presence of Fe3+ in the N-lobe. Reactions of Bi3+ (as bismuth nitrilotriacetate or ranitidine bismuth citrate) with hTF/2N in solutions containing 10 mM bicarbonate induced specific changes to high-field 1H-NMR peaks. The 1H co-ordination shifts induced by Bi3+ were similar to those induced by Fe3+ and Ga3+, suggesting that Bi3+ binding causes similar structural changes to those induced by hTF/2N. 13C-NMR data showed that carbonate binds to hTF/2N concomitantly with Bi3+.

Binding, Competitive↗

PubMed1999

Retargeting to EGFR enhances adenovirus infection efficiency of squamous cell carcinoma.

BACKGROUND: Adenovirus-mediated gene therapy has been used for squamous cell carcinoma of the head and neck (SCCHN), but the in vivo efficacy has been limited by a lack of tissue specificity and low infection efficiency. We are interested in improving cancer gene therapy strategies using targeted adenovirus vectors. OBJECTIVE: To determine if the infection efficiency of adenovirus-mediated gene transfer to SCCHN cells could be enhanced by retargeting to the epidermal growth factor receptor (EGFR), which is known to be overexpressed in these tumors. DESIGN: Epidermal growth factor receptor retargeting in SCCHN cells was accomplished with a bispecific antibody that recognized the knob domain of adenovirus as well as EGFR. Using this retargeting schema, we compared the infection efficiency and specificity of unmodified and EGFR-retargeted adenovirus. RESULTS: Squamous cell carcinoma of the head and neck cell lines were shown to be infected by adenovirus with low efficiency, which is likely because of the low level of adenovirus receptor expressed in the SCCHN cells. Epidermal growth factor receptor retargeting markedly enhanced transduction in both SCCHN cell lines and primary tumor tissue, as indicated by the elevated levels of reporter gene expression. Furthermore, retargeting enhanced infection of tumor tissue compared with normal tissue from the same patient. CONCLUSIONS: Epidermal growth factor receptor retargeting enhanced adenovirus infection of SCCHN cells and, in doing so, augments the potency of the vector. This modification makes the vector potentially more valuable in the clinical setting.

Adenoviridae↗

PubMed1999

Prenatal prediction of spinal muscular atrophy in Chinese.

We used linkage analysis, non-isotope SSCP (single-strand conformation polymorphism) and PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) for prenatal diagnosis of spinal muscular atrophy (SMA). A total of 26 cases from 20 SMA families (16, type 1 and 4) were evaluated. 5 out of 26 fetuses were affected and, following genetic counselling, the parents decided to terminate the pregnancies. Aborted fetal tissues were examined and the diagnosis was confirmed in each case. The 21 unaffected cases were either normals (12 cases) or carriers (9 cases). These children have been followed for six months to two and a half years. No false-negative or false-positive results on prenatal testing were found. We conclude that prenatal diagnosis of SMA is reliable and accurate.

Deoxyribonucleases, Type II Site-Specific↗

PubMed1999

Chromosome arm 6q loss is the most common recurrent autosomal alteration detected in primary pediatric ependymoma.

We analyzed 23 samples of primary pediatric ependymoma for significant gains or losses of genomic DNA, using comparative genomic hybridization (CGH) and a rigorous statistical approach. Nine of the tumors in this series (39%) appeared normal by CGH. The remainder had a limited number of regions of genomic imbalance, most often involving losses of chromosome arms 6q and 22q and the X chromosome, or gains of either 1q or 9. Recurrent and exclusive losses of 6q or 22q suggest that these regions harbor tumor suppressor genes that may contribute independently to the pathogenesis of childhood ependymoma.

Adolescent↗

PubMed1999

Loss of markers linked to BRCA1 precedes loss at important cell cycle regulatory genes in epithelial ovarian cancer.

Advanced-stage epithelial ovarian cancers (EOC) from 114 patients were assessed for loss of heterozygosity (LOH or allelic imbalance) at several tumor suppressor gene loci as an initial step in identifying gene alterations important to the development of these tumors. The highest frequency of loss, 84% (86 of 102 cases), was observed for markers mapping near or within BRCA1; other significant frequencies of LOH were observed for loci mapping near or within CDKN2A/CDKN2B (56%), BRCA2 (61%), RB1 (67%), or TP53 (73%). No instance of TP53 LOH was observed without simultaneous allelic imbalance at the BRCA1 region (P = 0.0005). LOH of CDKN2 without loss near the BRCA1 region was seen in only 2 of 75 cases (P < 0.0001), and RB1 LOH without BRCA1 loss occurred in only 1 of 35 tumors (P = 0.0703). These data suggest that LOH of BRCA1, or a closely linked locus, precedes the loss of CDKN2, TP53, and RB1, and imply that inactivation of a tumor suppressor gene in this region is an important early step in the development of these tumors.

Adult↗

PubMed1999

Studies on in vitro metabolism of shikonin.

Shikonin is one of the active components isolated from the root of Arnebia euchrona (Royle) Johnst. It has been shown to possess significant antibacterial, antiinflammatory and antitumour activities and has been used clinically. In this paper, rat liver microsomes were incubated in vitro to study the metabolism of shikonin and a reverse-phase high performance liquid chromatography/photodiode array detector (DAD) method was used to separate and detect the metabolites. The effects of several factors on the metabolism were investigated and the metabolic system was optimized. The main metabolites were purified by RP-HPLC and their structures were determined by UV, 1H-NMR and MS. S-1 was dihydroxylated shikonin, S-2 was 2-OH shikonin and S-3 was 6-OH or 7-OH shikonin.

Animals↗