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Biomedical subjects

M A Thompson

Publications and source records attributed to M A Thompson.

At least 19 recordsLinked to original sources
PubMed1992

Conservation of coding and transcriptional control sequences within the snRNP E protein gene.

The snRNP E protein is one of several proteins associated with the U family of small nuclear RNAs that are involved in RNA processing. Isolation and characterization of the snRNP E protein cDNA sequences from mouse and chicken revealed a 100% conservation of the predicted amino acid sequence when compared to that of the human homologue. Further characterization of a genomic clone for the mouse snRNP E protein gene revealed that the 5' untranslated region and the immediate 5' upstream region have also been highly conserved: 72 and 70%, respectively. Conserved 5' regions include multiple copies of the CTTCCG hexamer sequence which are involved in regulating transcription of the human snRNP E protein gene. Mobility shift assays using corresponding DNA fragments from both human and mouse reveal that both fragments can compete for binding of at least one common transcription factor. These studies demonstrate that along with the amino acid sequence conservation between human and mouse, the snRNP E protein gene has also maintained a high DNA sequence conservation within its basal promoter structure.

Animals↗
PubMed1992

Calcium regulation of immediate early gene transcription.

Cellular immediate early genes (IEGs) are a class of genes whose transcription is transiently activated within minutes of exposure of cells to a wide range of extracellular stimuli. In mature neurons IEG expression can be triggered by a variety of neutrotransmitters and neurotrophic factors. The IEGs, many of which encode transcription factors, are believed to control the physiological response of the cells to the initial stimulation event by activating secondary programs of gene expression. The mechanism by which membrane depolarization/Ca2+ influx trigger the activation of one IEG, c-fos, has been characterized in PC12 cells. In these cells, the cAMP response element-binding protein (CREB) functions as a Ca2+ regulated transcription factor. In addition, CREB is an in vitro substrate for several Ca2+ calmodulin-dependent protein kinases (CaM kinases). These results suggest a model whereby activation of voltage sensitive Ca2+ channels stimulates CaM kinase activation leading to CREB phosphorylation and c-fos transcriptional activation.

Animals↗
PubMed1992

Regulation of cyclic AMP response element-binding protein (CREB) phosphorylation by acute and chronic morphine in the rat locus coeruleus.

Previous studies have implicated adaptations in the cyclic AMP system in mechanisms of opiate tolerance, dependence, and withdrawal in the rat locus coeruleus. It has been speculated that such adaptations may occur at the level of gene expression. To understand better the mechanism by which opiates produce these intracellular adaptations, we studied morphine regulation of the state of phosphorylation of cyclic AMP response element-binding protein (CREB), a transcription factor that mediates some of the effects of the cyclic AMP system on gene expression. We show here, by use of a back phosphorylation and immunoprecipitation procedure, that acute morphine decreases the state of phosphorylation of CREB, an effect that becomes completely attenuated after chronic morphine administration. In contrast, acute precipitation of opiate withdrawal, via administration of an opiate receptor antagonist, increases the phosphorylation state of CREB. Such regulation of CREB phosphorylation could be part of the molecular pathway by which opiates produce changes in gene expression that lead to addiction.

Animals↗
PubMed1992

Nerve growth factor-induced derepression of peripherin gene expression is associated with alterations in proteins binding to a negative regulatory element.

The peripherin gene, which encodes a neuronal-specific intermediate filament protein, is transcriptionally induced with a late time course when nerve growth factor (NGF) stimulates PC12 cells to differentiate into neurons. We have studied its transcriptional regulation in order to better understand the neuronal-specific end steps of the signal transduction pathway of NGF. By 5' deletion mapping of the peripherin promoter, we have localized two positive regulatory elements necessary for full induction by NGF: a distal positive element and a proximal constitutive element within 111 bp of the transcriptional start site. In addition, there is a negative regulatory element (NRE; -179 to -111), the deletion of which results in elevated basal expression of the gene. Methylation interference footprinting of the NRE defined a unique sequence, GGCAGGGCGCC, as the binding site for proteins present in nuclear extracts from both undifferentiated and differentiated PC12 cells. However, DNA mobility shift assays using an oligonucleotide probe containing the footprinted sequence demonstrate a prominent retarded complex in extracts from undifferentiated PC12 cells which migrates with slower mobility than do the complexes produced by using differentiated PC12 cell extract. Transfection experiments using peripherin-chloramphenicol acetyltransferase constructs in which the footprinted sequence has been mutated confirm that the NRE has a functional, though not exclusive, role in repressing peripherin expression in undifferentiated and nonneuronal cells. We propose a two-step model of activation of peripherin by NGF in which dissociation of a repressor from the protein complex at the NRE, coupled with a positive signal from the distal positive element, results in depression of the gene.

Animals↗
PubMed1992

Myb expression is higher in malignant human colonic carcinoma and premalignant adenomatous polyps than in normal mucosa.

Expression of the protooncogene c-Myb protein was assessed in normal mucosa and in tumor samples resected from six patients. We found that the tumor samples always expressed higher levels of full length Myb protein than the normal tissue. This contrasts with the situation in c-myb-associated hemopoietic malignancies of the mouse and chicken, in which Myb proteins are generally amino or carboxyl truncated. Tissues from five patients with colonic adenomatous polyps were also examined and found to express levels of Myb that were, in general, intermediate between those found in normal tissues and tumors. Of particular interest is that the more dysplastic polyps displayed higher Myb levels. In one patient with carcinoma and multiple colonic polyps, some polyps had intermediate levels of Myb, whereas one polyp with carcinoma in situ expressed tumor-like levels of Myb. To directly test the hypothesis that Myb expression may be important in determining the rate of colonic cell proliferation, we examined three colonic carcinoma cell lines and one polyp cell line. We found that the cell lines with the most rapid doubling times exhibited the highest Myb levels. In addition, we show that antisense myb oligonucleotides retard the proliferation of one of these colonic cell lines which expresses the highest level of Myb.

Base Sequence↗
PubMed1991

CREB: a Ca(2+)-regulated transcription factor phosphorylated by calmodulin-dependent kinases.

The mechanism by which Ca2+ mediates gene induction in response to membrane depolarization was investigated. The adenosine 3',5'-monophosphate (cAMP) response element-binding protein (CREB) was shown to function as a Ca(2+)-regulated transcription factor and as a substrate for depolarization-activated Ca(2+)-calmodulin-dependent protein kinases (CaM kinases) I and II. CREB residue Ser133 was the major site of phosphorylation by the CaM kinases in vitro and of phosphorylation after membrane depolarization in vivo. Mutation of Ser133 impaired the ability of CREB to respond to Ca2+. These results suggest that CaM kinases may transduce electrical signals to the nucleus and that CREB functions to integrate Ca2+ and cAMP signals.

Animals↗
PubMed1991

The amino-terminal region of a proteochondroitin core protein, secreted by aortic smooth muscle cells, shares sequence homology with the pre-propeptide region of the biglycan core protein from human bone.

Smooth muscle cells, isolated from rat and bovine aortae and grown in vitro, synthesize chondroitin sulfate proteoglycans which are secreted into the growth media. Analysis of metabolically [35S]-labeled macromolecules, employing ion-exchange chromatography, revealed a single peak of radioactivity, upon elution with a linear salt gradient. Treatment of the material with enzymes that specifically degrade chondroitin sulfate demonstrated that chondroitin-4-sulfate was the predominant species isolated from rat smooth muscle cells and that chondroitin-4-sulfate and dermatan sulfate were the predominant species isolated from bovine aortic smooth muscle cells. Treatment of the native proteoglycans with chondroitinase ABC and subsequent SDS-PAGE analysis of the digestion products resulted in the appearance of a band with an apparent molecular weight of 45,000. Electrotransfer of the core protein to Immobilon-P membrane and gas phase sequencing of the amino-terminal region revealed striking homology between the core proteins of the rat and bovine proteochondroitin with the pre-propeptide region of human bone biglycan.

Aggrecans↗
PubMed1991

Structural and functional integrity of ovarian tumor tissue obtained by ultrasonic aspiration.

For patients with ovarian epithelial cancer, survival increases when residual disease approaches zero after surgical removal of the tumor. A previous study using the Cavitron Ultrasonic Surgical Aspirator (CUSA) (Cavitron Lasersonic Corp., Stamford, CT) showed the successful removal of ovarian tumors from areas often considered unresectable: the diaphragm, spleen, stomach, and small bowel. However, the CUSA has not yet been approved by the Food and Drug Administration for gynecologic surgery except on an experimental basis. This study was designed to test whether ultrasonic irradiation produced by the CUSA caused alterations in cell structure or physiology of gynecologic tissue in adjacent areas. Paired tumor samples, unirradiated and irradiated, were obtained from ten patients, and portions were sent for pathologic structural evaluation and physiologic tissue culture evaluation. Histologic sections, stained with hematoxylin and eosin, showed that CUSA irradiation produced only minor tissue distortion as observed under the light microscope. A correct diagnosis would have been made in all cases had only tissue fragments obtained from the CUSA specimen trap been stained. For nine of ten patients, initial tumor cell viability was similar in the two specimen types. Flow cytometric DNA analysis confirmed that surgical methods produced matched samples. Cells that survived high-frequency ultrasound appeared functionally intact. For five of eight patients, the cells from the CUSA specimen traps survived and/or divided to a greater extent than those from the knife-dissected tumors. Cells from both surgical routes attained a similar number of passages in culture. It seems reasonable to extrapolate these in vitro observations with pelvic tumor tissues to normal surrounding tissue left in situ. Thus pelvic tissue is believed to be uninjured by CUSA ultrasonic irradiation.

Biopsy, Needle↗
PubMed1991

Neurologic complications of nonneuronopathic Gaucher's disease.

We describe eight patients with type 1 Gaucher's disease who developed neurologic complications that were secondary to systemic features of the illness. Four patients experienced neurologic difficulties because of coagulopathy, and the other four patients had involvement of the nervous system secondary to skeletal disease. Early recognition of these complications in patients with type 1 Gaucher's disease may lead to improved neurologic outcome.

Aged↗
PubMed1991

Lupron retards proliferation of ovarian epithelial tumor cells cultured in serum-free medium.

Some patients with recurrent ovarian epithelial cancer respond favorably to treatment with GnRH agonists. This effect was proposed to be mediated by suppression of pituitary gonadotropin release. The present in vitro study investigated effects of human gonadotropin (Pergonal LH/FSH, 1:1) and Lupron, a GnRH agonist, on proliferation of an ovarian cancer cell line, 2774, which is estrogen receptor negative and grows well in serum-free, defined medium. Pergonal, 10 IU/mL or 30 IU/mL, did not enhance cell proliferation, which argues against stabilization of ovarian tumors in vivo due to decreased serum gonadotropin. Lupron, 1.4 micrograms/mL and 140 micrograms/mL, retarded cell division by day 6-8 of culture, in a dose-dependent manner. Flow cytometric cell cycle phase DNA analysis demonstrated Lupron caused a reversible 5-6% increase in the portion of cells in rest phase, G0/G1, compared to controls during log growth, and a corresponding decrease in the portion of cells in DNA synthesis, S phase. However, long-term culture, 3 weeks, with Lupron failed to arrest cells in G0/G1, and experimental cultures plateaued at cell number similar to control cultures. We conclude Lupron's effect on ovarian cancer cell proliferation is independent of gonadotropin and steroid, involves a cell cycle regulatory event, and duration of benefit observed in vivo for some patients may be related to total tumor volume at the time of treatment.

Antineoplastic Agents↗
PubMed1990

Autocrine regulation of human tumor cell proliferation by insulin-like growth factor II: an in-vitro model.

We have shown that a pleomorphic cell line of abnormal human karyotype derived from a stomach carcinoma (LIM-1839) proliferates in serum-free medium, expresses insulin-like growth factor II (IGF-II) mRNA, and secretes IGF-II (up to 56 ng/ml in serum-free conditioned medium, as measured in a rat liver RRA. No detectable levels of IGF-I can be measured in serum-free conditioned medium by RIA. These cells also secrete IGF-binding proteins, detected by a charcoal adsorption assay. The release of IGF-II and IGF binding proteins into serum-free conditioned medium (1.7 pmol/10(6) cells.24 h and 0.8 pmol binding sites/10(6) cells.24 h for 3 days, respectively) is inhibited 80% by cycloheximide (10 micrograms/ml). The LIM-1839 cells have type I and type II IGF receptors, determined by affinity cross-linking and competition binding studies. These cells proliferated 1.6-fold over 4 days in serum-free medium, with fresh medium changes on days 0 and 2: their growth was inhibited 56% by 40 micrograms/ml Sm 1.2, a monoclonal antibody which recognizes IGF-I and IGF-II. The addition of 20 and 50 ng/ml multiplication stimulating activity (rat IGF-II) caused 1.8- and 1.7-fold increases in cell growth between days 0 and 4 compared to controls, while [Thr59]IGF-I, at 20 and 50 ng/ml, caused 1.6- and 2.0-fold increases. Insulin, at 2 and 10 micrograms/ml, had no significant effect. The stimulatory effects of endogenous and exogenous IGFs on LIM-1839 cell proliferation were inhibited by a monoclonal antibody to the type I IGF receptor, alpha IR-3. These results suggest that the LIM-1839 cells are biologically responsive to endogenously produced IGF-II, and may thereby provide an in vitro model for autocrine regulation of human tumor growth by IGF-II.

Antibodies, Monoclonal↗
PubMed1989

Structure of the gene encoding peripherin, an NGF-regulated neuronal-specific type III intermediate filament protein.

We have cloned the rat gene encoding peripherin, a neuronal-specific intermediate filament protein that is NGF-regulated. Determination of the complete sequence, including 821 nucleotides of the 5'-flanking region, allows us to make conclusions about the evolutionary origin of the peripherin gene, its homology with other intermediate filament proteins, and possible mechanisms of regulation of peripherin expression in neurons. The positions of the eight peripherin gene introns correspond to the intron patterns of desmin, vimentin, and GFAP, with one example of intron sliding. Together with protein sequence homologies, this conclusively demonstrates that peripherin is a type III intermediate filament protein. The peripherin promoter contains sequences homologous to regions of other NGF-regulated promoters, which may function in peripherin induction by NGF.

Amino Acid Sequence↗
PubMed1986

Influence of ketanserin pretreatment on the haemodynamic responses to sternotomy.

The effect of intravenous ketanserin on the pressor response to sternotomy was studied in 36 patients undergoing coronary artery surgery. Two doses of the drug (10 mg and 20 mg) were compared with a placebo injection of saline. After induction of anaesthesia, haemodynamic variables were measured until the institution of cardiopulmonary bypass. Plasma and platelet 5-hydroxyindoles and 5-hydroxytryptamine were measured in a subset of 13 patients. Ketanserin induced a dose-dependent amelioration of the pressor response to sternotomy. Plasma 5-hydroxyindoles and platelet 5-hydroxytryptamine levels did not correlate with clinical response. The increased effectiveness of the higher dose of ketanserin may be due to an effect other than serotonin antagonism.

Drug Evaluation↗
PubMed1979

Arterial pressure and pulse interval responses to repetitive carotid baroreceptor stimuli in man.

1. Carotid baroreceptors of eight healthy young men were stimulated with brief (0.6 sec), moderate (30 mmHg), single or repetitive (2, 3 or 5), R wave coupled neck suction during held expiration, and brachial arterial pressure and pulse interval changes were measured for 10 sec. 2. Mean systolic arterial pressure declined significantly from control levels after single or multiple baroreceptor stimuli. The reduction of systolic pressure was significant within the first sec after the onset of trains of baroreceptor stimuli; its duration was proportional to the number of stimuli. 3. The sinus node response to a single baroreceptor stimulus was biphasic: inhibition was followed by less intense, but more prolonged facilitation (cardio-acceleration). A single baroreflex stimulus modulated sinus node function for about 7 sec. The integral of sinus node inhibition was linearly related to the number of baroreceptor stimuli. Inhibition with five repetitive stimuli peaked at about 1.5 sec after the onset of stimulation and delcined to a new steady-state level during the period of baroreceptor stimulation. 4. Human baroreflex adjustments of arterial pressure and sinus node function occur very early after a step increase of phasic baroreceptor afferent activity. The perturbation of sinus node function is complex and probably reflects changing temporal relationships between the arterial pulse and sinus node activity, and interactions between oscillating levels of acetylcholine and sinus node responsiveness to acetylcholine.

Adult↗
PubMed1979

False-positive reactions in the rapid plasma reagin-card, fluorescent treponemal antibody-absorbed, and hemagglutination treponemal syphilis serology tests.

Sera from 628 nonsyphilitic individuals were tested with the Rapid Plasma Reagin-Card, Fluorescent Treponemal Antibody-Absorbed, and Hemagglutination Treponemal Test for Syphilis tests to ascertain the comparative specificity of these tests. Many sera were also tested with the quantitative Venereal Disease Research Laboratory test. Sera included in the study were from both normal individuals and patients with a variety of illnesses and conditions. The Hemagglutination Treponemal Test for Syphilis gave the lowest overall percentage of false-positive reactions (1.6%), followed by the Fluorescent Treponemal Antibody-Absorbed test (3.3%) and the Rapid Plasma Reagin-Card test (10.8%).

Adult↗