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W Liu

Publications and source records attributed to W Liu.

At least 739 records · Page 41Linked to original sources
PubMed1996

Biosynthesis and function of all-trans- and 9-cis-retinoic acid in parathyroid cells.

We demonstrate that cultured human and bovine parathyroid cells incubated with all-trans-[11,12-3H]-retinol convert this tracer into all-trans- and 9-cis-retinoic acid. By using RT-PCR, cellular retinol-binding protein type I (CRBP I), cellular retinoic acid binding protein I and II (CRABP I and II), retinoic acid receptors (RARs) alpha, beta and gamma, and 9-cis-retinoic acid receptor (RXR) alpha transcripts were detected in human parathyroid cDNA. CRBP I and CRABP I expression was confirmed by immunohistochemistry. Both 9-cis- and all-trans-RA were found to suppress parathyroid hormone (PTH) secretion from dispersed human adenomatous parathyroid cells, which was augmented by combined treatment with 1mM RA and 100 nM 1,25 (OH)2D3. The present data establish parathyroid gland as a target for retinoids and as a site of synthesis of the hormonal forms of vitamin A (retinol), all-trans- and 9-cis-retinoic acid.

Alitretinoin↗
PubMed1996

Increased expression of cyclin D1 in the adult rat brain following kainic acid treatment.

Recent evidence has implicated aberrant cell cycle regulation as a possible mechanism of apoptosis in non-dividing cells. We previously demonstrated increased expression of the p53 tumor suppressor gene, a prominent cell cycle regulator, in apoptotic neurons. Here we investigated the potential involvement of cyclin D1, a G1 phase cell cycle protein under p53 regulation, in kainic acid-mediated neuronal degeneration. Adult male Sprague-Dawley rats were treated systemically with kainic acid and sacrificed between 1 h and 5 days following seizure onset. Cyclin D1 expression was studied by Western blot analysis and immunohistochemistry using a rabbit polyclonal anti-cyclin D1 antibody. In untreated control rats low levels of cyclin D1 expression were detected in multiple brain regions. Between 8 and 16 h after the onset of kainic acid-induced seizures, increased cyclin D1 immunoreactivity was observed in vulnerable hippocampal pyramidal cells. Five days after seizure onset increased cyclin D1 expression was evident in reactive astrocytes. These results support a role for cyclin D1 in certain neuronal death pathways, and suggest that cyclin D1 has multiple and cell type-specific functions in the central nervous system.

Animals↗
PubMed1996

Isolation of the promoter for Type I hexokinase from rat.

A genomic clone containing sequence identical to the 5' region of the cDNA for rat Type I hexokinase was isolated from a lambda Charon 4A library. A 5.4-kb EcoRI fragment from this clone, containing the matching sequence, was sequenced in its entirety. Rapid amplification of 5' cDNA ends (5' RACE), reverse transcription polymerase chain reaction, and ribonuclease protection experiments were consistent with the existence of multiple transcriptional start sites clustered in three regions approximately 460, 300, and 100 nucleotides upstream from the translational start codon. Together with results of previous work, the 5' untranslated sequence defined in the present study accounts for the 4.3-kb mRNA for Type I hexokinase seen on Northern blots. Fragments from the 5' flanking region were cloned into a reporter vector containing the luciferase coding region. Based on transfection experiments with both PC12 and H9c2 cells, promoter activity was associated with a region lying between nucleotide positions -742 and -516 (with A of the ATG codon at the translational start site defined as +1). The promoter region lacks a TATA sequence and, together with the transcriptional start sites, is located within a GC rich segment (a "CpG island") approximately 1 kb in length. These characteristics have previously been associated with the promoter and transcriptional start sites of genes for "housekeeping enzymes."

Animals↗
PubMed1996

Time trend and age-period-cohort effect on incidence of bladder cancer in Connecticut, 1935-1992.

Earlier studies indicated that the incidence rates for bladder cancers rose rapidly in both the United States and Europe. Tobacco smoking is considered to be the major risk factor for urinary bladder cancer, and recent studies from Connecticut show that several smoking-related cancers have started leveling off or decreasing. The time trend for bladder cancer, however, is not clear in Connecticut. The current study examined the long-term trend of bladder cancer in Connecticut. Our results show that urinary bladder cancer has been increasing, with a marked increase among males. The rate of increase, however, has slowed since the early 1980s. Birth-cohort examination shows that the rates have leveled off for those born after about 1935 in both males and females. Age-period-cohort modeling results also show that the birth-cohort patterns of bladder cancer are somewhat similar to those observed for lung cancer in Connecticut, thus supporting the findings from analytical epidemiologic studies which indicate that cigarette smoking is one of the major risk factors for urinary bladder cancer. Our results also suggest that the difference in environmental and occupational exposures between males and females may be responsible for the large difference in the incidence rate of bladder cancer seen between the sexes.

Adult↗
PubMed1996

Regulation of HIV-1 long terminal repeats by interaction of C/EBP(NF-IL6) and NF-kappaB/Rel transcription factors.

We report the characterization of a CAAT enhancer-binding protein (C/EBP) (NF-IL6) element encompassing the region from -174 to -166 of the U3 long terminal repeat (LTR) region of HIV-1. This C/EBP cis sequence was found to bind to C/EBPbeta and C/EBPdelta factors in DNA band shift assay. Transfection of NTera-2 cells with a HIV-1-LTR CAT construct (pC15CAT), together with C/EBPbeta or C/EBPdelta expression plasmids showed that C/EBP proteins strongly activated the HIV-1 promoter. Deletions encompassing the C/EBP-binding site resulted in the enhancement of the LTR activation mediated by C/EBP proteins, suggesting that other sequences located 3' to -170 were indeed the target for C/EBP factors. This possibility was confirmed by using the pCD54E9CAT plasmid, in which the NF-kappaB enhancer was inserted 5' to the HIV-1 LTR TATA box. A NF-kappaB1(p50) expression plasmid was also utilized to test for functional co-operation between NF-kappaB and C/EBP factors. We observed that p50 middle dotC/EBPbeta and p50 middle dotC/EBPdelta complexes were generated in tested cells and strongly activated the HIV-1 LTR by binding to the NF-kappaB sequences. The physical association of NF-kappaB1(p50) with C/EBP factors was assayed by direct interaction of in vitro translated p50 proteins with C/EBPbeta or C/EBPdelta produced as glutathione S-transferase fusion proteins. Moreover, p50 middle dotC/EBPbeta complexes were observed in vivo by using DNA affinity studies with biotinylated NF-kappaB oligonucleotides. By using mutant forms of p50 or C/EBPbeta proteins we found that the transactivation of HIV-1 LTR by p50 middle dotC/EBPbeta complexes required the DNA-binding domain of p50 and the transcription activation domain of C/EBPbeta.

Binding Sites↗
PubMed1996

Regulation of vascular endothelial growth factor expression in human colon carcinoma cells by cell density.

To determine the effect of cell density on vascular endothelial growth factor (VEGF) expression and the mechanism of this effect, four human colon cancer cell lines were grown as sparse or confluent monolayers or as spheroids. VEGF mRNA increased > 2-fold in cells grown as confluent monolayers or spheroids compared with cells grown as sparse monolayers. Semiquantitative reverse transcription-PCR demonstrated a 2-fold increase in the larger VEGF mRNA isoform (189 bp) in confluent cells. Sparse cells grown in conditioned medium from confluent cells demonstrated a > 2-fold increase in VEGF mRNA. These data suggest that VEGF expression may be regulated by an unidentified soluble factor.

Base Sequence↗
PubMed1996

Platelet-derived endothelial cell growth factor in human colon cancer angiogenesis: role of infiltrating cells.

BACKGROUND: Development of new blood vessels is essential for tumor growth and metastasis and depends on the production of angiogenic factors by tumor and/or infiltrating cells. We previously showed that vascular endothelial growth factor (VEGF) expression and vessel count correlate with metastasis in human colon cancer. Although most tumors with high vessel counts express high levels of VEGF, some do not. Recently, platelet-derived endothelial cell growth factor (PD-ECGF), another potent angiogenic factor, has been reported to be expressed in colon cancer. PURPOSE: In this study, we examined the role of PD-ECGF in colon cancer angiogenesis and whether PD-ECGF is derived from the tumor or infiltrating cells. METHODS: Immunostaining for PD-ECGF was performed on 96 colon cancer specimens, some of which were previously stained for VEGF and factor VIII, a marker that is specific for endothelial cells. Double staining was done by using antibodies to PD-ECGF and to CD68 (macrophage specific) or CD3 (lymphocyte specific) to confirm which infiltrating cells produce PD-ECGF. Northern blot analysis for PD-ECGF messenger RNA (mRNA) was performed on four colon cancer specimens and corresponding normal colon mucosae (same patients) and four human colon cancer cell lines (KM12SM, SW620, HT29, and NCI-H508) to determine whether colon cancer epithelium expresses PD-ECGF. RESULTS: Immunohistochemical analysis demonstrated that PD-ECGF was expressed in infiltrating cells in most of the colon cancer specimens (80 [83%] of 96) but rarely in tumor epithelium (five [5%] of 96). Double staining demonstrated that infiltrating cells staining positive for both PD-ECGF and CD68 were more predominant than those staining positive for both PD-ECGF and CD3. The intensity of staining for PD-ECGF in infiltrating cells correlated with vessel counts (Spearman's rank correlation coefficient (R) = .29; P = .004), but did not correlate with the intensity of VEGF staining (R = .176, P = .086) or metastasis (Mann-Whitney U test, P = .253). PD-ECGF staining intensity was higher in specimens with a high vessel count (> 50 at high magnification) and low VEGF-staining intensity (< or = 2+) than in specimens with a high vessel count (again, > 50) and high VEGF-staining intensity (3+). Northern blot analysis revealed that colon cancer specimens and normal mucosae expressed relatively high levels of PD-ECGF mRNA, whereas PD-ECGF mRNA transcripts were not detectable in colon cancer cell lines. CONCLUSIONS AND IMPLICATIONS: PD-ECGF expression in human colon cancer specimens is associated with vessel count and may be responsible for tumor vascularity in those tumors with low VEGF expression. Infiltrating cells expressing PD-ECGF may contribute to angiogenesis, thus providing an additional mechanism for tumor neovascularization.

Blotting, Northern↗
PubMed1996

Time trend and age-period-cohort effect on incidence of thyroid cancer in Connecticut, 1935-1992.

Recent studies from Europe suggest a continuing increase in thyroid cancer, but it is unclear whether this trend also applies to the United States. The current study examined the long-term trend of thyroid cancer in Connecticut. Our results show that the overall age-adjusted incidence rate of thyroid cancer has been increasing in Connecticut, from 1.30/100,000 in 1935-1939 to 5.78/100,000 in 1990-1992 in females, and from 0.30/100,000 in 1935-1939 to 2.77/100,000 in 1990-1992 in males. The increase mainly comes from papillary carcinoma of the thyroid. The birth cohort analyses indicate that the increase in thyroid cancer occurred among cohorts born between 1915 and 1945, which experienced an increase of 31.4% every 5 years in males and 17.3% in females over the period 1960-1979. For those born since the 1945 cohort, the incidence has been decreasing, at rates of 9.3% and 8.3% every 5 years over the period 1975-1992 in males and females, respectively. Age-period-cohort modeling results also suggest a strong birth cohort effect on the observed time trend in both sexes, which closely follows the introduction of radiation treatment of benign childhood conditions in the head and neck between 1920 and the 1950s in the United States. Our results are consistent with the suggested radiation hypothesis, indicating that radiation treatment of benign childhood conditions in the head and neck is largely responsible for the observed increase of thyroid cancer in Connecticut.

Adenocarcinoma, Follicular↗
PubMed1996

Noradrenaline induces IPSCs in rat medial septal/diagonal band neurons: involvement of septohippocampal GABAergic neurons.

1. The physiological and pharmacological actions of noradrenaline (NA) on neurons of the medial septum and diagonal band of Broca (MSDB) were examined using extracellular, intracellular and whole-cell patch-clamp recordings in an in vitro rat brain slice preparation. 2. In current- and voltage-clamp recordings with KCl- or potassium gluconate-containing electrodes, bath-applied NA increased the number of tetrodoxin- and bicuculline-sensitive synaptic events in > 80% of cholinergic- and GABA-type neurons tested. The NA-induced synaptic activity originated from GABAergic neurons located within the MSDB itself, as a similar effect occurred in brain slices in which the MSDB had been surgically isolated from neighbouring structures. 3. In antidromic studies, NA dose-dependently increased firing in a subpopulation of septohippocampal neurons with fast conducting fibres (mean conduction velocity, 1.78 +/- 0.10 m s-1; presumably GABAergic). The NA excitation was mimicked by the alpha 1-agonist phenylephrine (PE) and blocked by the alpha 1-antagonists prazosin and WB-4101, suggesting the presence of alpha 1-receptors on septohippocampal GABAergic neurons. 4. Similarly, in whole-cell recordings in both cholinergic- and non-cholinergic-type MSDB neurons, prazosin blocked the effects of NA and PE mimicked the effects of NA by inducing IPSCs with a similar amplitude distribution. 5. Consistent with the above findings, GABA-type neurons that responded directly to NA and PE with a prazosin-sensitive inward current were found within the MSDB. 6. In conclusion, NA, via alpha 1-adrenoceptors, excites MSDB septohippocampal GABAergic neurons and influences both septal and septohippocampal circuitry.

Animals↗
PubMed1996

Immunochemical analysis of the human erythrocyte Rh polypeptides.

We have used rabbit polyclonal antisera raised against synthetic peptides complementary to different domains of the Rh polypeptides and Rh glycoprotein to examine the topography and organization of these proteins in the human erythrocyte membrane. Previously unrecognized exofacial protease sites have been identified on Rh CcEe, D proteins, and Rh glycoprotein. The Rh D protein has two specific bromelain cleavage sites located within the first and sixth predicted external domains, with the site of cleavage localized in the sixth domain to lie between residues 353 and 354. All Rh polypeptide species were found to be susceptible to cleavage with trypsin and subtilisin within the first external domain of these proteins. The Rh glycoprotein has two bromelain cleavage sites within the first external domain. These flank the single N-glycosylation site (Asn37), with the cleavage site toward the C-terminal side of this residue being between residues 39 and 40. Bromelain treatment was found to deglycosylate the Rh glycoprotein. Immunoprecipitation experiments have revealed that anti-C, -c,E, -e, and -D immune complexes are reactive with antisera raised against the fourth predicted external loop of the Rh proteins and the C-terminal domain. These data indicate that the hypothesis that suggests Rh C/c antigens are expressed on truncated Rh polypeptides by a mechanism of alternate splicing is incorrect and support the hypothesis that Rh Cc and Ee antigens are expressed on a single polypeptide chain.

Amino Acid Sequence↗
PubMed1996

A "double adaptor" method for improved shotgun library construction.

The efficiency of shotgun DNA sequencing depends to a great extent on the quality of the random-subclone libraries used. We here describe a novel "double adaptor" strategy for efficient construction of high-quality shotgun libraries. In this method, randomly sheared and end-repaired fragments are ligated to oligonucleotide adaptors creating 12-base overhangs. Nonphosphorylated oligonucleotides are used, which prevents formation of adaptor dimers and ensures efficient ligation of insert to adaptor. The vector is prepared from a modified M13 vector, by KpnI/PstI digestion followed by ligation to oligonucleotides with ends complementary to the overhangs created in the digest. These adaptors create 5'-overhangs complementary to those on the inserts. Following annealing of insert to vector, the DNA is directly used for transformation without a ligation step. This protocol is robust and shows three- to fivefold higher yield of clones compared to previous protocols. No chimeric clones can be detected and the background of clones without an insert is <1%. The procedure is rapid and shows potential for automation.

Base Sequence↗
PubMed1996

NGF, BDNF and NT-3 play unique roles in the in vitro development and patterning of innervation of the mammalian inner ear.

Developing cochleovestibular ganglion (CVG) neurons depend upon interaction with the otocyst, their peripheral target tissue, for both trophic support and tropic guidance. RT-PCR of E11 through E14 otocyst-CVG RNA extracts have shown that NGF as well as BDNF and NT-3 are expressed in the developing inner ear (in situ RT-PCR on tissue sections of E12 otocysts localized all three neurotrophins to the otocyst). To evaluate the functional significance of NGF, BDNF and NT-3 expression, E10.5 otocyst-CVG explants were treated with antisense oligonucleotides and compared to sense treated and control cultures. Confocal microscopic analysis revealed that treatment with BDNF antisense resulted in extensive neuronal cell death, downregulation of NGF caused an inhibition of neuritogenesis and a decrease in the neuronal population of the CVG, whereas treatment with NT-3 antisense resulted in a loss of target directed CVG neuritic ingrowth in this in vitro model. The effect of NGF or BDNF antisense treatment could be prevented by the simultaneous addition of the respective growth factor. These findings demonstrate that each of the three neurotrophins have important roles during the onset of neuritic ingrowth of the CVG neurons to the otocyst.

Animals↗
PubMed1996

Internal architecture of the thoracic pedicle. An anatomic study.

STUDY DESIGN: In this study, data are presented that provide the surgeon with additional information about the internal structure of the thoracic pedicle, which is especially useful for pedicle screw fixation in the thoracic spine. OBJECTIVES: To quantify the internal structure of the pedicle in the thoracic spine. SUMMARY OF BACKGROUND DATA: There are many studies describing the external dimensions of the thoracic pedicle (i.e., pedicle height, pedicle width, and pedicle axis in the transverse and sagittal planes). However, there is little reliable information concerning the internal structure of the pedicle. METHODS: Eighteen thoracic vertebrae were attached to a thin-sectioning machine and both pedicles were cut in six 1.0-mm thin slices. Slides of contact radiographs were rear-projected to a digitizer and the internal and external borders of the pedicle were digitized. Using special computer software, two external dimensions (i.e., pedicle height and pedicle width) and four internal dimensions (i.e., cortical thicknesses of the superior, inferior, medial, and lateral walls) were calculated. RESULTS: The cancellous core was more than twice as large as the cortical shell, with a range from 65.6% to 78.6% with respect to the pedicle height, and 61.3% to 71.6% with respect to the pedicle width. The medial wall was between two and three times thicker than the lateral wall throughout all the pedicle slices and thoracic levels. These differences were highly significant (P < 0.001). CONCLUSIONS: The thoracic pedicle is a complex three-dimensional structure that is mostly filled with cancellous bone. The medial wall is significantly thicker than the lateral wall, which could explain the fact that most of the pedicle fractures related to pedicle screw insertion occur laterally.

Adult↗
PubMed1996

Defective HSV-1 vector expressing BDNF in auditory ganglia elicits neurite outgrowth: model for treatment of neuron loss following cochlear degeneration.

The neurotrophins are a family of growth factors that play an important role in the development and maintenance of the nervous system. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family that appears to participate in the maturation and function of mammalian auditory neurons. Forms of deafness due to varied injurious stimuli that are amenable to treatment with implantable prosthetic devices require the survival of these BDNF-responsive auditory neurons for effective outcome. To evaluate the feasibility of developing a gene therapy for deafness that may be used in conjunction with a prosthetic device, we constructed replication-defective herpes simplex virus (HSV) amplicon vectors that carry the human BDNF cDNA. Using these vectors, HSVbdnf and HSVbdnflac (expresses BDNF and Escherichia coli beta-galactosidase), we evaluated the expression and biological activity in established cell lines and explant cultures prepared from spiral ganglia of the murine ear. Gene transfer with HSVbdnf resulted in the efficient expression of human BDNF mRNA in murine fibroblasts. Using two BDNF-responsive cell lines, PC12trkB and MG87trkB, we demonstrate efficient secretion of biologically active BDNF. Finally, transduction of explanted spiral ganglia with HSVbdnflac elicited robust neuritic process outgrowth comparable to exogenously added BDNF. Overall, these data demonstrate that HSV vectors can efficiently transfer and express the BDNF gene in many cell types, including auditory neurons. Moreover, they suggest that similar vectors may be used to express the neurotrophin in auditory neurons in vivo and perhaps as adjunctive gene therapy for deafness.

Animals↗