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Biomedical subjects

C Lu

Publications and source records attributed to C Lu.

At least 271 records · Page 15Linked to original sources
PubMed1990

In vivo expression of rat liver c-erbA beta thyroid hormone receptor in yeast (Saccharomyces cerevisiae).

To study thyroid hormone receptor (TR), we developed an in vivo expression system in yeast by using a copper-responsive yeast metallothionein promoter and ubiquitin-fusion protein technology. The cDNA encoding full-length rat liver TR beta was expressed under the control of copper. The [125I]T3 binding activities to yeast extracts were significantly correlated with the added copper sulfate into the medium. Partially purified TR from the transformed yeast had a high hormone binding affinity (Kd = 0.34) for T3 and could bind thyroid hormone response element in gel retardation analysis.

Animals↗
PubMed1990

Regulation of parathyroid hormone-related peptide gene expression by cycloheximide.

A novel parathyroid hormone-related peptide (PTHRP) has been isolated from tumors associated with the syndrome of humoral hypercalcemia of malignancy. The human PTHRP gene appears to use multiple promoters and contains alternatively spliced 3' exons which give rise to three PTHRP mRNA classes, each bearing multiple copies of an AU motif that has been associated with mRNA instability. We report here that inhibition of protein synthesis leads to the super-induction of PTHRP mRNA expression in a number of human and rat cell lines. This phenomenon was found to reflect both an increase in the rate of PTHRP gene transcription and a stabilization of PTHRP mRNAs. The transcriptional mechanism appears to preferentially involve the activity of a short downstream promoter of the gene, which is presumed to be regulated by a labile repressor protein. Our findings indicate that both transcriptional and posttranscriptional mechanisms may be important control points in the regulation of PTHRP expression in normal and malignant cells.

Actins↗
PubMed1990

Simultaneous measurement of TSH-binding inhibitor immunoglobulin and thyroid stimulating autoantibody activities using cultured FRTL-5 cells in patients with untreated Graves' disease.

A new and practical assay was developed using cultured FRTL-5 cells for simultaneous assessment of TS-ab and TSH-binding inhibitor immunoglobulin, allowing direct comparison of these two activities under the same conditions. Subsequent to the TS-ab assay in which extracellular cAMP concentration in Hanks' medium without NaCl was determined, [125I]b TSH in this medium was added to observe the ability of serum Ig to inhibit the binding of [125I]b TSH to FRTL-5 cells. We found a much higher specific binding of [125I]b TSH to FRTL-5 cells and a much greater inhibition of [125I]bTSH binding to the cells exposed to Graves' Ig in hypotonic NaCl-free than in NaCl containing Hanks' medium, indicating that the binding of both TSH and Graves' Ig to the TSH receptor was salt-sensitive. The inhibitory activity of [125I]bTSH binding to the cells was 0.2 +/- 4.6% (mean +/- SD) in 45 normals. Inter-assay coefficients of variation in two positive controls with the mean values of 18.0 and 65.8% were 15.8 and 16.5%, respectively. Among 46 patients with untreated hyperthyroidism owing to Graves' disease, 45 (97.8%) were positive for TS-ab; 35 (76.1%) and 40 (87.0%) were positive for TSH-binding inhibitor in Ig assays using FRTL-5 cells and solubilized porcine thyroid membranes, respectively. TS-ab activities correlated less closely with TSH-binding inhibitory activities determined using FRTL-5 cells (r = 0.576, p less than 0.001) than with those determined using porcine thyroid membranes (r = 0.745, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Autoantibodies↗
PubMed1990

[Estimation of pulmonary vascular resistance by Doppler echocardiography with simultaneous catheterization].

To establish a noninvasive prediction of pulmonary vascular resistance (PVR), we combined continuous wave Doppler pressure gradient with pulsed Doppler volumetric flow methods for measuring mean pulmonary arterial pressure (mPAP) and pulmonary flow (QP) respectively and calculated PVR by the Poiseullie equation. Simultaneous invasive and noninvasive measurements were made beat to beat in 28 patients: 18 patients with patent ductus arteriosus (PDA), 10 with other heart diseases complicated with pulmonary regurgitation (PR). In the PR group, the peak of Doppler determined pressure gradient during diastole correlated well with mPAP measured via catheter, r = 0.99. In the PDA group, the Doppler determined mPAP (subtracts mean pressure gradient across PDA measured by the continuous wave Doppler from brachial artery blood pressure) correlated well with catheter, r = 0.98, Doppler determined QP and PVR also correlated well with catheter, r = 0.98 and 0.99. There were high linear correlations between the mPAP, QP, PVR in all patients by Doppler and catheter, r = 0.99, 0.98, 0.98, respectively. The results indicate that combined continuous wave and pulsed Doppler can predict mPAP, QP, and PVR dynamic indices for PDA and other heart diseases complicated with PR quite accurately.

Adult↗
PubMed1990

Selective effect of zinc compared to other divalent metals on L-triiodothyronine binding to rat c-erbA alpha and beta proteins.

The effects of zinc and other divalent metals on the [125I]T3 binding to rat c-erbA alpha and beta recombinant proteins were assessed. The addition of ZnCl2 caused a reversible and dose-dependent inhibition of [125I]T3 binding to rc-erbA beta proteins with half maximum inhibition occurring at 50-100 microM, but no significant effect on [125I]T3 binding to rc-erbA alpha under the same assay conditions. Scatchard analysis revealed a decrease in [125I]T3 binding capacity to beta protein without marked change in Kd values in presence of zinc. Moreover, significant inhibitions of [125I]T3 binding to both alpha and beta proteins were observed in the presence of 100 microM of either MnCl2, CdCl2 or CuCl2, but not MgCl2. Thus, the selective effect of zinc compared to other divalent metals to inhibit T3 binding to rc-erbA beta, but not alpha, proteins was documented and suggest a possible regulatory role for zinc in modulating the intracellular action of thyroid hormone.

Animals↗
PubMed1990

[Effect of wuwei chongji on the mechanical activity of the stomach of SD rats in vivo].

The effect of Wuwei Chongji on the mechanical activity of stomach of SD rats was studied using fixed point method. The experimental results showed that Wuwei Chongji increased the amplitude and frequency of contraction of stomach in rats, and was able to adjust the high and low tension of contraction of stomach. The contraction of the stomach was not influenced by Natrii Chloridi (0.9%) at the same dose.

Animals↗
PubMed1990

[Studies of the determination of selenium by hydride generation atomic absorption spectrometry].

Potassium ferricyanide has a masking effect of Cu2+, Ni2+ and other interferential ions in the determination of selenium by hydride generation atomic absorption spectrometry. Interference was not observed in the determination of 5ng/ml of Se(IV) in the presence of 10micrograms/ml of Cu2+ under recommended conditions. The stability of analyte and potassium borohydride solutions in storage was also studied.

Selenium↗
PubMed1989

Transcriptional regulation of the parathyroid hormone-related peptide gene by glucocorticoids and vitamin D in a human C-cell line.

A parathyroid hormone-related peptide (PTHRP) has been identified in human tumors associated with the syndrome of humoral hypercalcemia of malignancy. The PTHRP and parathyroid hormone (PTH) genes appear to have arisen by duplication and to represent members of a gene family. PTHRP mRNAs have been demonstrated in a number of normal tissues, but little is known concerning the regulation of PTHRP gene expression in any site. We studied PTHRP gene expression in TT cells, a human C-cell line which also produces calcitonin and calcitonin gene-related peptide. We found that both the synthetic glucocorticoid, dexamethasone, and the active vitamin D metabolite, 1,25-dihydroxyvitamin D3, decreased steady-state PTHRP mRNA levels in TT cells in a time- and dose-dependent fashion. The dexamethasone effect was completely blocked by the glucocorticoid antagonist RU-486. 24,25-dihydroxyvitamin D3 was found to be inactive. Neither dexamethasone nor 1,25-dihydroxyvitamin D3 appeared to influence PTHRP mRNA stability in TT cells, and both agents were shown by nuclear transcription run-off assay to decrease PTHRP gene transcription. These findings indicate that the PTHRP gene is under the transcriptional control of glucocorticoids and vitamin D in a cell line with prototypical neuroendocrine features.

Calcitonin↗
PubMed1989

UmuC mutagenesis protein of Escherichia coli: purification and interaction with UmuD and UmuD'.

The introduction of a replication-inhibiting lesion into the DNA of Escherichia coli produces a marked elevation in mutation rate. The mutation pathway is a component of the induced, multigene SOS response. SOS mutagenesis is a tightly regulated process dependent on two RecA-mediated proteolytic events: cleavage of the LexA repressor to induce the UmuC and UmuD mutagenesis proteins, and cleavage of UmuD to UmuD' to activate the mutation pathway. To investigate the protein-protein interactions responsible for SOS mutagenesis, we have studied the interaction of UmuC, UmuD, and UmuD'. To probe intracellular interaction, we have used immunoprecipitation techniques with antibodies against UmuC or UmuD and UmuD'. We have found that antibody to UmuC precipitates UmuD' from cell extracts, and antibody to UmuD and UmuD' precipitates UmuC. Thus we conclude that UmuC probably associates tightly with UmuD' in cells. For biochemical studies, we have purified the UmuC and UmuD' proteins to use with the previously purified UmuD. UmuC associates strongly with an affinity column of UmuD and UmuD', eluting only under strongly dissociating conditions (2 M urea or 1.5 M KSCN). UmuC also associates efficiently with UmuD or UmuD' in solution, as judged by velocity sedimentation in a glycerol gradient. The likely stoichiometry is one UmuC with a dimeric UmuD or UmuD'. From these experiments and previous work, we infer that SOS mutagenesis depends on the action of the UmuC-UmuD' complex and probably RecA to rescue a stalled DNA polymerase III holoenzyme at the DNA lesion.

Bacterial Proteins↗
PubMed1989

Glucocorticoid regulation of parathyroid hormone-related peptide gene transcription in a human neuroendocrine cell line.

A PTH-related peptide (PTHRP) has been identified and its cDNA cloned from tumors associated with the syndrome of humoral hypercalcemia of malignancy. The PTHRP and PTH genes appear to represent members of a gene family. Whereas the PTH gene is expressed exclusively in the parathyroids, the PTHRP gene appears to be widely expressed, but little is known concerning the regulation of its expression in any site. We studied the regulation of PTHRP gene expression in a human carcinoid cell line (NCI-H727) which has neuroendocrine features and also produces calcitonin, calcitonin gene-related peptide, and chromogranin-A. We found that the synthetic glucocorticoid triamcinolone produced time- and dose-dependent decreases in steady state PTHRP and calcitonin mRNA levels in NCI-H727 cells. This effect was blocked by the competitive glucocorticoid inhibitor RU-486. Messenger RNA stability and transcription run-off experiments revealed that triamcinolone decreased PTHRP and calcitonin expression by repressing the transcription rates of both genes.

Calcitonin↗
PubMed1989

Mechanisms of increased sensitivity for detection of thyroid stimulating antibodies by use of hypotonic medium.

We have attempted to clarify the mechanism whereby the sensitivity to detect thyroid stimulating antibodies by use of cultured thyroid cells is enhanced when sodium chloride is removed from isotonic medium. Preexposure of cultured porcine thyroid cells to 10(-4) mol/l cycloheximide increased the subsequent cAMP response to TSab stimulation in isotonic NaCl medium, but not in hypotonic NaCl-free medium. Crude membrane fractions from porcine thyroid tissues were incubated with 6 Graves' IgGs in NaCl or NaCl-free medium at 37 degrees C for 1 h, centrifuged, washed, added [125I]TSH, and incubated for another hour. The result of the 'residual TBII assay' indicated that all 6 IgGs exhibited greater inhibition of [125I]TSH binding to the membranes when pre-incubated under hypotonic than isotonic conditions. When cultured porcine thyroid cells were incubated with 7 TSab samples in NaCl or NaCl-free medium depleted with 3-isobutyl-1-methylxanthine at 37 degrees C for 1 h, washed, added the NaCl-free medium containing 3-isobutyl-1-methylxanthine, and incubated for another 2 h, the use of NaCl-free medium during the pre-incubation resulted in greater increase in cAMP elicited by all 7 samples. In summary, 1) an inhibitory mechanism upon adenylate cyclase seems to be involved under isotonic conditions and may require new protein synthesis; 2) the binding of TSH receptor antibodies to the TSH receptor increases when NaCl is removed from isotonic medium, and 3) these factors are considered responsible for the enhanced sensitivity under hypotonic conditions.

Animals↗
PubMed1989

Pre- and post-operative hypothalamic-pituitary-thyroidal axis function in patients with prolactinoma, growth hormone tumour and ACTH tumour.

Pre- and postoperative hypothalamic-pituitary-thyroid axis function was studied in 38 patients with pituitary adenomas (PRL, GH and ACTH tumours), of whom 35 were surgically confirmed and three diagnosed by clinical signs, CT scanning and hormone assessments. About ten days after operation, the same study was repeated in 10 patients with prolactinoma and 7 with growth hormone (GH) tumour. The preoperative abnormal serum TSH response to TRH was found in 8/20 patients with prolactinoma, 9/16 with GH tumour, and 2/2 with Cushing's disease due to ACTH microadenoma. The incidence of abnormal TSH response to TRH was not significantly increased in patients with larger adenoma in either PRL or GH tumour group. In 8 cases of prolactinoma, metoclopramide (MCP, 10 mg, P.O.) test was also performed and there was a significant positive correlation between TSH responses to TRH and to MCP. Serum TT3 in the GH tumour group was within normal ranges, but significantly higher than that of the normal and prolactinoma groups. After operation, TT3 was significantly decreased as compared with that before operation and there were marked changes in TSH response to TRH. In conclusion, there were some abnormalities in TSH control in patients with non-TSH pituitary tumour, and in serum TT3 control in patients with GH tumour. The surgical treatment of pituitary adenoma can lead to transient decrease in TSH reserve and serum TT3 level probably resulting from both stress and/or destruction of thyro-trophs by the operation.

Adenoma↗
PubMed1987

RecA protein and SOS. Correlation of mutagenesis phenotype with binding of mutant RecA proteins to duplex DNA and LexA cleavage.

The RecA protein of Escherichia coli is required for SOS-induced mutagenesis in addition to its recombinational and regulatory roles. We have suggested that RecA might participate directly in targeted mutagenesis by binding preferentially to the site of the DNA damage (e.g. pyrimidine dimer) because of its partially unwound nature; DNA polymerase III will then encounter RecA-coated DNA at the lesion and might replicate across the damaged site more often but with reduced fidelity. In support of this proposal, we have found that the phenotype of wild-type and mutant RecA for mutagenesis correlates with capacity to bind to double-stranded DNA. Wild-type RecA binds more efficiently to ultraviolet (u.v.)-irradiated, duplex DNA than to non-irradiated DNA. The RecA441 (Tif) protein that is constitutive for mutagenesis binds extremely well to double-stranded DNA with no lesions, whereas the RecA430 protein that is defective in mutagenesis binds poorly even to u.v.-irradiated DNA. The RecA phenotype also correlates with capacity to use duplex DNA as a cofactor for cleavage of the LexA repressor protein for SOS-controlled operons. Wild-type RecA provides efficient cleavage of LexA only with u.v.-irradiated duplex DNA; RecA441 cleaves well with non-irradiated DNA; RecA430 gives very poor cleavage even with u.v.-irradiated DNA. We conclude that the interaction of RecA with damaged double-stranded DNA is likely to be a critical component of SOS mutagenesis and to define a pathway for the LexA cleavage reaction as well.

Bacterial Proteins↗
PubMed1986

Capacity of RecA protein to bind preferentially to UV lesions and inhibit the editing subunit (epsilon) of DNA polymerase III: a possible mechanism for SOS-induced targeted mutagenesis.

The RecA protein of Escherichia coli is required for SOS-induced mutagenesis in addition to its recombinational and regulatory roles. Most SOS-induced mutations probably occur during replication across a DNA lesion (targeted mutagenesis). We have suggested previously that RecA might participate in targeted mutagenesis by binding preferentially to the site of the DNA damage (e.g., pyrimidine dimer) because of its partially unwound character; DNA polymerase III (polIII) will then encounter RecA-coated DNA at the lesion and might replicate across the damaged site with reduced fidelity. In this report, we analyze at a biochemical level two major predictions of this model. With respect to lesion recognition, we show that purified RecA protein binds more efficiently to UV-irradiated double-stranded DNA than to nonirradiated DNA, as judged by filter-binding and gel electrophoresis assays. With respect to replication fidelity, Fersht and Knill-Jones [Fersht, A. R. & Knill-Jones, J. W. (1983) J. Mol. Biol. 165, 669-682] have found that RecA inhibits the 3'----5' exonuclease (editing function) of polIII holoenzyme. We extend this observation by demonstrating that RecA inhibits the exonuclease of the purified editing subunit of polIII, epsilon protein. Thus, we suggest that the activities of RecA required for targeted mutagenesis are lesion-recognition, followed by localized inhibition of the editing capacity of the epsilon subunit of polIII holoenzme. In this proposed mechanism, one activation signal for RecA for mutagenesis is the lesion itself. Because UV-irradiated, double-stranded DNA efficiently activates RecA for cleavage of the LexA repressor, the lesion itself may also often serve as an activation signal for induction of SOS-controlled genes.

Antibody Diversity↗
PubMed1984

The role of computed tomography of the chest in the management of small-cell lung cancer.

Despite the wide application of computed tomography (CT) in the diagnosis and management of lung cancer, the role of this diagnostic modality in the management of small-cell lung cancer (SCC) has not yet been defined. We therefore compared information gained from routine chest radiography (CXR) and CT scans performed on 32 patients with SCC who were treated on an intensive chemotherapy-radiotherapy protocol. Seventy-nine pairs of CXRs and CT scans were retrospectively reviewed. We found that although CT delineates a greater extent of intrathoracic disease in each of nine anatomic areas evaluated than does CXR, agreement between CT and CXR was significant for all areas except the pericardium. Pericardial thickening was seen only on CT scan and is more frequent in SCC patients than has previously been appreciated, but both its etiology and prognostic significance are unclear at this time. CT also allowed interpretation of disease status in cases where radiation-induced fibrosis made interpretation of the CXR impossible. We do not recommend routine use of chest CT at time of diagnosis of SCC, but we recommend that its use be reserved for evaluation of new symptoms or suspected relapse, or when radiation fibrosis on CXR is severe.

Carcinoma, Small Cell↗
PubMed1984

Preliminary results of high-dose busulfan and cyclophosphamide with syngeneic or autologous bone marrow rescue.

The toxic effects of high-dose busulfan (16 mg/kg) and cyclophosphamide (200 mg/kg) with autologous or syngeneic bone marrow rescue were evaluated in 19 patients (11 with acute myelocytic leukemia, one with acute lymphocytic leukemia, one with acute myelofibrosis, two with chronic myelocytic leukemia, one with Hodgkin's disease, and three with non-Hodgkin's lymphoma). Their mean age was 26 years (range, 6-50); nine patients had syngeneic and ten had autologous bone marrow rescue (six of whom had in vitro bone marrow incubation with 4-hydroperoxycyclophosphamide). Severe myelosuppression was expected and was seen in all patients; leukocyte and platelet count recovery occurred at a median of 19 days (range, 11-59) and 30 days (range, 20-89), respectively. Nausea, vomiting, and diarrhea were frequent but readily managed with vigorous medical therapy. Stomatitis was severe in 14 patients. Skin, renal, cardiac, pulmonary, and CNS complications directly attributable to drug-related toxic effects were transient and non-life-threatening. Hepatic function abnormalities were common but tended to be transient. Most patients tolerated high-dose busulfan and cyclophosphamide with manageable side effects. Hepatic veno-occlusive disease was fatal in two patients, while diffuse interstitial pneumonitis with disseminated herpes virus infection was fatal in three patients with lymphoma. All patients treated in relapse or without previous therapy had a complete tumor response. Further studies with this regimen should be pursued.

Acute Disease↗