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Biomedical subjects

F Lee

Publications and source records attributed to F Lee.

At least 271 records · Page 15Linked to original sources
PubMed1985

Use of a cDNA expression vector for isolation of mouse interleukin 2 cDNA clones: expression of T-cell growth-factor activity after transfection of monkey cells.

A cDNA sequence coding for mouse interleukin 2 (IL-2) has been cloned from a cDNA library prepared from mRNA derived from a concanavalin A-activated mouse T-cell clone. The library was constructed by using the pcD vector system, which permits the expression of cDNA inserts in mammalian cells. Screening of the library was performed by transfecting COS-7 monkey cells with pools of cDNA clones in order to express the products encoded by full-length cDNA inserts. By assaying the supernatant fluid, IL-2 cDNA clones that express T-cell growth-factor (TCGF) activity were identified. The DNA sequence codes for a polypeptide of 169 amino acid residues including a putative signal peptide. The mouse IL-2 amino acid sequence deduced from the nucleotide sequence of its cDNA shares extensive homology with the human IL-2 amino acid sequence reported previously. These results demonstrate that identification of full-length cDNA clones for many lymphokines may be achieved entirely on the basis of detection of the functional polypeptides in mammalian cells.

Amino Acid Sequence↗
PubMed1985

Isolation of cDNA for a human granulocyte-macrophage colony-stimulating factor by functional expression in mammalian cells.

A cDNA sequence coding for a human granulocyte-macrophage colony-stimulating factor has been isolated from cDNA libraries prepared from mRNA derived from concanavalin A-activated human T-cell clones. The libraries constructed in the pcD vector system were screened by transfecting COS-7 monkey cells with DNA pools to express the products encoded by full-length cDNA inserts. By assaying the cell supernatants, we identified clones encoding a factor that stimulates the formation of granulocyte and macrophage colonies from human progenitor cells. These results demonstrate that identification of full-length cDNAs for many colony-stimulating factors may be achieved entirely on the basis of detecting the functional polypeptide produced in mammalian cells.

Amino Acid Sequence↗
PubMed1985

Structure of the chromosomal gene for murine interleukin 3.

We have isolated the mouse interleukin 3 (IL-3) gene from a mouse sperm DNA library based on homology with the mouse mast-cell growth-factor (MCGF) cDNA sequence. The nucleotide sequence determined for the gene and its flanking regions reveals that the IL-3 gene is composed of four introns and five exons. The nucleotide sequence of the exons agrees with that determined for the MCGF cDNA. A "TATA"-like sequence preceded by a G + C-rich region is found in the 5' flanking region. At the 3' region of the second intron are nine repeats of a closely related 14-base-pair (bp) sequence. These repeated sequences share extensive homology with a 20-bp repeated sequence found in the human genome, which was shown to have enhancer activity. Eight out of nine repeats form a 73-bp duplicated sequence and each 73-bp repeat contains sequences homologous to the core sequence suggested for enhancer elements. These sequences may play a role in the expression of the IL-3 gene in concanavalin A- or antigen-stimulated T lymphocytes. Stable transformants of L cells generated by co-transformation of the IL-3 gene with pSV2neo constitutively express MCGF activity indicating that the isolated gene is functional in vivo.

Animals↗
PubMed1985

Adenovirus ELISA for the evaluation of cerebrospinal fluid in patients with suspected neurosyphilis.

An enzyme-linked immunosorbent assay (ELISA) detecting antibodies against the adenovirus group antigen was used to examine cerebrospinal fluid (CSF) of suspected neurosyphilis patients for serum contamination or blood-brain barrier (BBB) leakage. Adenovirus antibodies are ubiquitous, produce high antibody titers, and rarely cause central nervous system (CNS) infections. Of 52 normal adult sera tested with this ELISA, only one lacked antibodies. CSF from 48 healthy individuals did not present a detectable amount of anti-adenovirus antibodies. CSF from 33 suspected neurosyphilis patients with positive results in the fluorescent treponemal antibody-absorption (FTA-ABS)-CSF test were examined. Eighteen showed anti-adenovirus antibodies indicating contamination of the CSF with peripheral blood or damaged BBB by syphilis or other disease, resulting in questionable CSF treponemal results. The remaining 15 of these patients appeared to be producing their anti-treponemal antibodies in the CNS. This procedure may prove to be of considerable help in excluding false positive FTA-ABS results in CSF samples.

Adenoviridae↗
PubMed1985

Oncogenic osteomalacia: strange tumours in strange places.

Two patients presented with hypophosphataemic osteomalacia and were subsequently found to have small tumours unusual histopathology and location causing the osteomalacia. Each tumour was found after an intensive search for occult masses. Studies of vitamin D metabolism and renal tubular function before and after surgery yielded further insight into the pathophysiology of oncogenic osteomalacia. These cases demonstrate that microscopic quantities of tumour are capable of causing the syndrome and further illustrate the high index of suspicion often necessary to locate causative tumours in patients with hypophosphataemic osteomalacia.

Adult↗
PubMed1985

Regulation of IL 3 expression by glucocorticoids in cloned murine T lymphocytes.

We have examined the effects of glucocorticoids on the concanavalin A (Con A)-stimulated production of interleukin 3 (IL 3) by a murine helper T cell clone Cl.Ly-1+2-/9. The addition of Con A to Cl.Ly-1+2-/9 cells leads to the rapid induction of both IL 3 mRNA and activity. A synthetic glucocorticoid, dexamethasone, inhibits the appearance of IL 3 activity in the supernatants of Con A-stimulated cells, as well as the accumulation of IL 3 mRNA in the cells. A similar effect is observed with other Con A-inducible mRNA, such as the mRNA encoding granulocyte-macrophage colony-stimulating factor (GM-CSF), but the hormone effects are not general; the constitutive synthesis of Thy-1 mRNA is not altered by dexamethasone treatment. Several lines of evidence suggest that dexamethasone directly inhibits transcription of the IL 3 gene: the kinetics of dexamethasone action on IL 3 mRNA are rapid; the stability of IL 3 mRNA is not affected by dexamethasone; hormone treatment does not inhibit either mRNA processing or transport from the nucleus. Our findings demonstrate that a set of mitogen-inducible genes in helper T cells can be subject to a second level of regulation mediated by glucocorticoid hormones.

Animals↗
PubMed1984

Functional analysis of the steroid hormone control region of mouse mammary tumor virus.

Gene fusions between the mouse mammary tumor virus long terminal repeat and the E. coli lacZ gene have been shown to exhibit hormone dependent expression of beta-galactosidase activity. These constructions were used in transient expression experiments to assess the effects of specific modifications introduced into the region upstream of the transcription initiation site. 5' deletions demonstrate that sequences sufficient for wild-type promoter function are contained downstream of residue -64 relative to the initiation site. Other deletions define a region of approximately 80 base pairs between -220 and -140 which contains sequences essential for hormonal control. Between this control region and the promoter lie sequences dispensable for both functions.

Animals↗
PubMed1984

Exercise subcostal two-dimensional echocardiography: a new method of segmental wall motion analysis.

This study determines the effectiveness of the subcostal view 2-dimensional (2-D) echocardiogram in providing images of left ventricular wall motion at rest and during symptom-limited upright bicycle exercise, and compares 2-D echocardiographic regional wall motion analysis with first-pass radionuclide angiography. Diagnostic-quality subcostal 2-D echocardiograms at rest were obtained in 95% of unselected persons studied (16 of 17 normal subjects and 23 of 24 patients who had had myocardial infarction [MI] ). All who had adequate studies at rest had diagnostic-quality maximal exercise studies. Segmental wall motion at rest and exercise determined by 2-D echocardiography correlated well with radionuclide angiography in both the normal and post-MI groups. The chi-squared values for the 3 segments analyzed were: anterior 52 (p less than 0.001), apical 56 (p less than 0.001) and inferior 37 (p less than 0.001). It is concluded that subcostal view 2-D echocardiography at rest and at the peak of symptom-limited upright bicycle exercise is a feasible and accurate noninvasive method for the analysis of segmental left ventricular function.

Adult↗
PubMed1984

Isolation and characterization of a mouse cDNA clone that expresses mast-cell growth-factor activity in monkey cells.

A cDNA sequence coding for mouse mast-cell growth-factor (MCGF) has been cloned from a cDNA library prepared from mRNA derived from a concanavalin A-activated mouse T-cell clone. Cloning was achieved using the pcD vector that permits expression of cDNA inserts in mammalian cells. The DNA sequence codes for a polypeptide of 166 amino acid residues including a putative signal peptide. The supernatant fluid obtained after transfection of COS-7 monkey cells with the pcD-MCGF plasmid had mouse MCGF activity. The MCGF amino acid sequence between amino acids 33 and 41, deduced from the nucleotide sequence of its cDNA, is identical to the NH2-terminal sequence of the mouse lymphokine, interleukin 3, suggesting that MCGF is related to interleukin 3.

Amino Acid Sequence↗
PubMed1983

Floor of mouth cancer: patient selection and treatment results.

Retrospective review of 126 primarily treated floor of mouth (FOM) cancers was done to study patient selection and to search for more optimum treatment strategies. Small surface lesions were treated by local excision (LE); small lesions invading FOM without lymph nodes were treated by radiation alone (RA), while larger lesions and those with palpable nodes were treated by preoperative irradiation and surgery (R + S). Ultimate control of the FOM cancer and nodes was achieved for 100% of the LE, 71% of the RA, and 75% of the R + S patients. The majority of primary tumor and nodal recurrences developed by 15 months and 35% of the failures were salvaged by additional treatment. Change in treatment strategies are suggested for surface lesions because of a poor rate of initial tumor control (43%), for patients treated by RA because of a high rate of complications (41%), and for patients without palpable lymph nodes who can be successfully treated by elective neck irradiation.

Brachytherapy↗
PubMed1983

Treatment of epidermoid and undifferentiated carcinomas from occult primaries presenting in cervical lymph nodes.

We treated 83 patients with epidermoid or undifferentiated carcinoma in cervical neck nodes without an obvious primary at our institution between 1964 and 1979. All patients received radiotherapy and 29 patients had radical neck dissection (RND) or total excisional biopsy (TEB) as well. Actuarial survival was 38% at 5 years for the entire group and 25% at 10 years. Fifty-four patients with neck control had significantly better survival (p = .0001) at 5 and 10 years than those whose neck was uncontrolled. Factors associated with improved neck control were initial size of the neck mass and the addition of surgery (RND or TEB). Analysis of failures showed that 50% of patients failed only in the primary or neck and 50% developed distant metastases. Tumor was the major cause of death. We recommend more aggressive treatment with both XRT and neck dissection in patients with large resectable neck masses to prevent regrowth of tumor in the neck.

Actuarial Analysis↗
PubMed1983

Expressing a human proinsulin cDNA in a mouse ACTH-secreting cell. Intracellular storage, proteolytic processing, and secretion on stimulation.

The AtT-20 cell line, derived from the mouse anterior pituitary, synthesizes an adrenocorticotropic hormone (ACTH) precursor, proteolytically processes it to mature ACTH, stores it in secretory granules, and releases mature ACTH on stimulation with a secretagogue. A cDNA for human proinsulin inserted downstream from the SV40 early promoter in an SV40-pBR322 recombinant vector was introduced into AtT-20 cells. The stably transformed cell line, AtT-20ins4b/1, stores immunoreactive insulin, proteolytically processes proinsulin to smaller fragments, and on stimulation with secretagogues releases insulin-like material, not proinsulin, into the medium. Similarly transformed fibroblast L-cells secrete only proinsulin; they do not store it, and their secretion rate is unaffected by secretagogues. The transport mechanism for precursor ACTH thus appears to recognize other prohormones.

Adrenocorticotropic Hormone↗
PubMed1983

Amplification and hormone-regulated expression of a mouse mammary tumor virus-Eco gpt fusion plasmid in mouse 3T6 cells.

Mouse 3T6 cells were transformed with a chimeric DNA plasmid, pSVMgpt, in which the mouse mammary tumor virus (MMTV) promoter was fused to the Escherichia coli gene encoding xanthine-guanine phosphoribosyl transferase (Eco gpt). The transformants exhibited glucocorticoid-inducible expression of Eco gpt. With limiting xanthine concentrations, conditions were established in which cell growth became hormone dependent. Cells selected for their ability to grow in limiting concentrations of both xanthine and glucocorticoids contained amplified levels of Eco gpt DNA, and expression of Eco gpt remained glucocorticoid inducible in these amplified cells. Thus, amplification of the MMTV promoter region in itself did not abolish hormonal responsiveness of a gene. In addition to increased levels of Eco gpt DNA, some of the selected cells also exhibited increased levels (two- to threefold) of glucocorticoid receptors. Lastly, we found that excessive expression of Eco gpt is toxic to 3T6 cells; by maintaining low hormone levels and, therefore, low levels of expression, we were able to select cells with amplified Eco gpt. Thus, the MMTV promoter may be of general utility in expressing genes whose products may be lethal if they are produced in excessive quantities.

Animals↗
PubMed1983

Expression and regulation of Escherichia coli lacZ gene fusions in mammalian cells.

Gene fusions between the Escherichia coli lacZ gene and DNA segments containing the simian virus 40 early promoter or the mouse mammary tumor virus (MMTV) promoter direct the synthesis of functional beta-galactosidase in Cos 7 monkey cells and mouse Ltk-cells. Enzymatic activity was measured either 72 h after transfection or in stable transformants. The sensitive beta-galactosidase assay was used to measure gene expression and to optimize the efficiency of DNA-mediated transfection. Glucocorticoids stimulated the production of beta-galactosidase when lacZ was fused to the hormonally regulated MMTV promoter.

DNA, Recombinant↗
PubMed1982

Dose-response analysis for nasopharyngeal carcinoma: an historical perspective.

Historical review of 118 patients with nasopharyngeal cancer treated in our institution from 1950--1978 showed a 20% improvement in tumor control for patients irradiated during the most recent period (1974--1978). This improvement was attributed to prescription of higher doses of radiation as well as improvements in technical accuracy and dose delivery to the tumor during that period. Rates of severe and mild complications were comparable and survival was not significantly altered over time despite improved tumor control. Within the range of doses delivered, there was no improvement in tumor control with increasing doses of radiation for small or large nasopharyngeal carcinomas. The dose-response analysis for tumor control was less than ideal because a number of prerequisites were lacking and because the study extended over a 28-year span during which there were significant changes in technology and physician orientation.

Follow-Up Studies↗