24 results on '"Brønstad G"'
Search Results
2. CONTROL OF CYCLIC AMP FORMATION IN CULTURED RAT HEPATOMA CELLS AND IN SOLID RAT HEPATOMAS GROWING IN VIVO
- Author
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Christoffersen, T., primary, Brønstad, G., additional, Rugstad, H.E., additional, and øye, I., additional
- Published
- 1977
- Full Text
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3. Kartlegging av miljøgifter i sedimenter i Indre Drammensfjorden 1993
- Author
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Konieczny, R., Bruskeland, O., Brønstad, G., Helland, A., Hovde, L.R., and Konieczny, R. - Project manager
- Subjects
marin fjord ,miljøgifter-marin ,organic ,miljøgift ,fjord ,micropollutant ,oljeforurensning ,oil ,environmental ,Matematikk og naturvitenskap: 400 [VDP] ,sediment ,pollution ,heavy metals ,organiske miljøgifter tungmetall - Abstract
Totalt 18 sedimentstasjoner i indre fjordområde og 2 løsmasseprøver fra Holmen i utløpet av Drammenselva ble undersøkt for innholdet av miljøgifter. I tillegg er det foretatt evaluering av en rekke mulige forurensningskilder, samt nærmere karakterisering av ren tjæreprøve fra Gilhusbukta. Hovedresultatene viser at belastningen mht. tungmetaller er liten til moderat i sedimentene og samlet viser metallene maksimalt tilstandsklasse III. Flere ulike kilder til tungmetallforekomstene kan antydes. Av de organiske miljøgiftene er forekomstene av PCB mest markert, og antyder tilstandsklasse III-IV for store deler av fjorden. PAH forekommer i svært høye konsentrasjoner, men har hovedsakelig en begrenset og lokal utbredelse. Både PCB og PAH forekomstene kan stamme fra flere ulike kilder i indre del av fjorden. Av andre klororganiske forbindelser ble kun DDT registrert i forhøyde konsentrasjoner og synes å være knyttet til Lierelva. Oljeforurensningen (THC) var mer moderat og var mest framtredende i elva utenfor Holmen. Referansestasjonen utenfor Sandtangen, synes å ligge i et akkumulasjonsområde for forurensninger i fjorden, da det gjennomgående ble registrert høye konsentrasjoner her for alle miljøgiftene. Løsmasseprøvene fra Holmen var ikke forurenset. Fylkesmannen i Buskerud, Miljøvernavdelingen
- Published
- 1994
4. Phosphoglycerate kinase deficiency in two brothers with McArdle-like clinical symptoms
- Author
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Aasly, J., primary, van Diggelen, O. P., additional, Boer, A. M., additional, and Brønstad, G., additional
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- 2000
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5. The antitumour agent 5-(3,3-dimethyl-1-triazeno) imidazole-4-carboxamide (DTIC) inhibits rat liver cAMP phosphodiesterase and amplifies hormone effects in hepatocytes and hepatoma cells.
- Author
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Larsson, P G, Haffner, F, Brønstad, G O, Christoffersen, T, and Brłnstad, G O
- Published
- 1979
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6. Effect of prostaglandins and hormones on cyclic AMP formation in rat hepatomas and liver tissue.
- Author
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Brønstad, G O, Christoffersen, T, Johansen, E J, and Øye, I
- Published
- 1978
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7. The proliferative response of rat liver parenchymal cells after partial hepatectomy A methodological study comparing flow cytometry of nuclear DNA content and in vivo and in vitro uptake of thymidine
- Author
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Digernes, V., primary, Brønstad, G., additional, Sand, T.‐E., additional, and Christoffersen, T., additional
- Published
- 1982
- Full Text
- View/download PDF
8. Adrenaline Increases Cyclic 3′5′-AMP Formation in Hamster Epidermis
- Author
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BRØNSTAD, G. O., primary, ELGJO, K., additional, and ØYE, I., additional
- Published
- 1971
- Full Text
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9. 945 - CONTROL OF CYCLIC AMP FORMATION IN CULTURED RAT HEPATOMA CELLS AND IN SOLID RAT HEPATOMAS GROWING IN VIVO
- Author
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Christoffersen, T., Brønstad, G., Rugstad, H.E., and øye, I.
- Published
- 1977
- Full Text
- View/download PDF
10. Short-term effects of endotracheal suctioning in post-cardiac arrest patients: A prospective observational cohort study.
- Author
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Eggen IB, Brønstad G, Langeland H, Klepstad P, and Nordseth T
- Abstract
Background: Endotracheal suctioning (ETS) is required in critically ill patients but may lead to adverse physiologic effects. The aim of this study was to investigate risk factors associated with adverse respiratory and circulatory effects of ETS, in post-cardiac arrest patients receiving controlled ventilation., Methods: Patients with return of spontaneous circulation after out-of-hospital cardiac arrest were followed the first five days in the intensive care unit (ICU). For each ETS procedure performed, data were extracted from the electronic ICU records 10 min before and until 30 min after the procedure. Adverse events were defined as heart rate > 120 beats/min, systolic blood pressure > 200 or < 80 mmHg or SpO
2 < 85%. Multivariate logistic regression was applied with SpO2 < 85% and systolic blood pressure < 80 mmHg as primary outcomes., Results: For the 36 patients included in the study, the median number of ETS-procedures per patient was 13 (range 1-33). Oxygen desaturation occurred in 10.3% of procedures and severe hypotension in 6.6% of procedures. In the multivariate analysis, dose of noradrenaline, light sedation and oxygen desaturation prior to suctioning were associated with increased risk of oxygen desaturation. Doses of noradrenaline, suction with manual ventilation, suction in combination with patient repositioning, and first day of treatment in the ICU were significantly associated with severe hypotension., Conclusions: The risk of circulatory and respiratory deterioration during ETS in post-cardiac arrest patients is increased the first day of ICU care, and related to sedation, dose of noradrenaline and pre-procedure hypoxemia., (© 2022 The Author(s).)- Published
- 2022
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11. Characterization and complete genome sequences of L. rhamnosus DSM 14870 and L. gasseri DSM 14869 contained in the EcoVag ® probiotic vaginal capsules.
- Author
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Marcotte H, Krogh Andersen K, Lin Y, Zuo F, Zeng Z, Larsson PG, Brandsborg E, Brønstad G, and Hammarström L
- Subjects
- Anti-Bacterial Agents, Antibiosis, Bacterial Adhesion genetics, Bacterial Proteins genetics, Caco-2 Cells, Chromosomes, Bacterial, DNA Transposable Elements, DNA, Bacterial, Drug Resistance, Bacterial genetics, Female, Fimbriae, Bacterial genetics, Gardnerella vaginalis growth & development, Gene Transfer, Horizontal, Humans, Lactobacillus gasseri cytology, Lactobacillus gasseri growth & development, Lacticaseibacillus rhamnosus cytology, Lacticaseibacillus rhamnosus growth & development, Membrane Proteins genetics, Multigene Family, Capsules therapeutic use, Genes, Bacterial genetics, Lactobacillus gasseri genetics, Lacticaseibacillus rhamnosus genetics, Probiotics therapeutic use, Vagina microbiology, Vaginosis, Bacterial drug therapy, Whole Genome Sequencing
- Abstract
Lactobacillus rhamnosus DSM 14870 and Lactobacillus gasseri DSM 14869 were previously isolated from the vaginal epithelial cells (VEC) of healthy women and selected for the development of the vaginal EcoVag
® probiotic capsules. EcoVag® was subsequently shown to provide long-term cure and reduce relapse of bacterial vaginosis (BV) as an adjunct to antibiotic therapy. To identify genes potentially involved in probiotic activity, we performed genome sequencing and characterization of the two strains. The complete genome analysis of both strains revealed the presence of genes encoding functions related to adhesion, exopolysaccharide (EPS) biosynthesis, antimicrobial activity, and CRISPR adaptive immunity but absence of antibiotic resistance genes. Interesting features of L. rhamnosus DSM 14870 genome include the presence of the spaCBA-srtC gene encoding spaCBA pili and interruption of the gene cluster encoding long galactose-rich EPS by integrases. Unique to L. gasseri DSM 14869 genome was the presence of a gene encoding a putative (1456 amino acid) new adhesin containing two rib/alpha-like repeats. L. rhamnosus DSM 14870 and L. gasseri DSM 14869 showed acidification of the culture medium (to pH 3.8) and a strong adhesion capability to the Caco-2 cell line and VEC. L. gasseri DSM 14869 could produce a thick (40nm) EPS layer and hydrogen peroxide. L. rhamnosus DSM 14870 was shown to produce SpaCBA pili and a 20nm EPS layer, and could inhibit the growth of Gardnerella vaginalis, a bacterium commonly associated with BV. The genome sequences provide a basis for further elucidation of the molecular basis for their probiotic functions., (Copyright © 2017 Elsevier GmbH. All rights reserved.)- Published
- 2017
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12. The guanylate cyclase-C signaling pathway is down-regulated in inflammatory bowel disease.
- Author
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Brenna Ø, Bruland T, Furnes MW, Granlund Av, Drozdov I, Emgård J, Brønstad G, Kidd M, Sandvik AK, and Gustafsson BI
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- Animals, Biopsy, Needle, Case-Control Studies, Colonoscopy methods, Disease Models, Animal, Female, Humans, Immunohistochemistry, Male, Rats, Reference Values, Signal Transduction genetics, Down-Regulation genetics, Gene Expression Regulation, Guanylate Cyclase genetics, Inflammatory Bowel Diseases genetics, Inflammatory Bowel Diseases pathology
- Abstract
Objective: Activation of membrane receptor guanylate cyclase-C (GC-C) is implicated in gastrointestinal fluid and electrolyte balance, preservation of intestinal barrier integrity, anti-trophic effects and inhibition of pain sensation. To evaluate GC-C signaling, we examined the regulation of GC-C (GUCY2C/Gucy2c) and its endogenous ligands guanylin (GN/GUCA2A/Guca2a) and uroguanylin (UGN/GUCA2B/Guca2b) in colonic Crohn's disease (CD), ulcerative colitis (UC) and in rats with 2,4,6-Trinitrobenzene sulphonic acid (TNBS) colitis. Correlation analyses between expression of GUCA2A and GUCY2C and expression of inflammatory cytokines (IL1A, IL1B, TNFA and IFNG) were conducted. Additionally, expression of transcription factors for GUCA2A and GUCY2C, and the GC-C signaling pathway, were examined., Material and Methods: Biopsies from active UC/CD, un-inflamed UC/CD and healthy controls, and inflamed and healthy rat colon were investigated with gene expression microarray, immunohistochemistry (IHC) and in situ hybridization (ISH)., Results: GUCA2A/Guca2a, GUCA2B, GUCY2C/Gucy2c, transcription factors, as well as several cyclic guanosine-3',5'-monophosphate downstream mediators were all significantly down-regulated in both inflamed colonic inflammatory bowel disease (IBD) mucosa and TNBS colitis. Expression of GUCA2A and GUCY2C negatively correlated to expression of inflammatory cytokines. IHC and ISH confirmed microarray results for GUCA2A/Guca2a and GUCY2C/Gucy2c in inflamed samples. We identified a highly significant positive correlation between the expression of the transcription factor caudal type homeobox 2 (CDX2) and the expression of the downstream target gene GUCY2C., Conclusions: GUCA2A, GUCA2B and GUCY2C as well as several steps of the GC-C signaling pathway are down-regulated in IBD. This may have implications in IBD pathogenesis.
- Published
- 2015
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13. Elevated levels of cerebrospinal fluid α-synuclein oligomers in healthy asymptomatic LRRK2 mutation carriers.
- Author
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Aasly JO, Johansen KK, Brønstad G, Warø BJ, Majbour NK, Varghese S, Alzahmi F, Paleologou KE, Amer DA, Al-Hayani A, and El-Agnaf OM
- Abstract
Mutations in the leucine-rich repeat kinase 2 gene are the most common cause of autosomal dominant Parkinson's disease (PD). To assess the cerebrospinal fluid (CSF) levels of α-synuclein oligomers in symptomatic and asymptomatic leucine-rich repeat kinase 2 mutation carriers, we used enzyme-linked immunosorbent assays (ELISA) to investigate total and oligomeric forms of α-synuclein in CSF samples. The CSF samples were collected from 33 Norwegian individuals with leucine-rich repeat kinase 2 mutations: 13 patients were clinically diagnosed with PD and 20 patients were healthy, asymptomatic leucine-rich repeat kinase 2 mutation carriers. We also included 35 patients with sporadic PD (sPD) and 42 age-matched healthy controls. Levels of CSF α-synuclein oligomers were significantly elevated in healthy asymptomatic individuals carrying leucine-rich repeat kinase 2 mutations (n = 20; P < 0.0079) and in sPD group (n = 35; P < 0.003) relative to healthy controls. Increased α-synuclein oligomers in asymptomatic leucine-rich repeat kinase 2 mutation carriers showed a sensitivity of 63.0% and a specificity of 74.0%, with an area under the curve of 0.66, and a sensitivity of 65.0% and a specificity of 83.0%, with an area under the curve of 0.74 for sPD cases. An inverse correlation between CSF levels of α- synuclein oligomers and disease severity and duration was observed. Our study suggests that quantification of α-synuclein oligomers in CSF has potential value as a tool for PD diagnosis and presymptomatic screening of high-risk individuals.
- Published
- 2014
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14. Changes in matrix metalloprotease activity and progranulin levels may contribute to the pathophysiological function of mutant leucine-rich repeat kinase 2.
- Author
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Caesar M, Felk S, Zach S, Brønstad G, Aasly JO, Gasser T, and Gillardon F
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- Animals, Cells, Cultured, Chemokines metabolism, Female, Fibroblasts physiology, Granulins, Humans, Intercellular Signaling Peptides and Proteins cerebrospinal fluid, Interleukin-1beta metabolism, Leucine-Rich Repeat Serine-Threonine Protein Kinase-2, Leukocytes physiology, Male, Mice, Mice, Transgenic, Microglia physiology, Mutation, Parkinson Disease cerebrospinal fluid, Parkinson Disease physiopathology, Progranulins, Protein Serine-Threonine Kinases genetics, Swiss 3T3 Cells, Intercellular Signaling Peptides and Proteins metabolism, Matrix Metalloproteinases metabolism, Protein Serine-Threonine Kinases metabolism
- Abstract
Increasing evidence suggests that Parkinson's disease (PD)-linked Leucine-rich repeat kinase 2 (LRRK2) has a role in peripheral and brain-resident immune cells. Furthermore, dysregulation of the anti-inflammatory, neurotrophic protein progranulin (PGRN) has been demonstrated in several chronic neurodegenerative diseases. Here we show that PGRN levels are significantly reduced in conditioned medium of LRRK2(R1441G) mutant mouse fibroblasts, leukocytes, and microglia, whereas levels of proinflammatory factors, like interleukin-1β and keratinocyte-derived chemokine, were significantly increased. Decreased PGRN levels were also detected in supernatants of cultured human fibroblasts isolated from presymptomatic LRRK2(G2019S) mutation carriers, while mitochondrial function was unaffected. Furthermore, medium levels of matrix metalloprotease (MMP) 2 increased, whereas MMP 9 decreased in LRRK2(R1441G) mutant microglia. Increased proteolytic cleavage of the MMP substrates ICAM-5 and α-synuclein in synaptoneurosomes from LRRK2(R1441G) mutant mouse brain indicates increased net synaptic MMP activity. PGRN levels were decreased in the cerebrospinal fluid of presymptomatic LRRK2 mutant mice, whereas PGRN levels were increased in aged symptomatic mutant mice. Notably, PGRN levels were also increased in the cerebrospinal fluid of PD patients carrying LRRK2 mutations, but not in idiopathic PD patients and in healthy control donors. Our data suggest that proinflammatory activity of peripheral and brain-resident immune cells may particularly contribute to the early stages of Parkinson's disease caused by LRRK2 mutations., (Copyright © 2014 Wiley Periodicals, Inc.)
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- 2014
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15. Peptides' role in autism with emphasis on exorphins.
- Author
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Reichelt KL, Tveiten D, Knivsberg AM, and Brønstad G
- Abstract
Problem: The nature of the peptides found increased in urine from autism needs verification of their structure, especially those that show opioid activity., Methods: The peptides were separated on reverse phase C-18 HPLC in Trifluoroacetic acid-acetonitril gradients. Peaks eluting where synthetic opioids appear, and peaks that are common to most autistic children were analyzed by mass spectrometry and fragmentation pattern on a quadropole mass-spectrometer., Results: We could demonstrate exorphins in the urine from autistic children, and their length varied from one patient to the next., Conclusion: Exorphins are found in urine of autistic children and may account for their symptoms.
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- 2012
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16. Epidemiological consequences of introducing new biochemical markers for detection of acute myocardial infarction.
- Author
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Graven T, Krüger O, and Brønstad G
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- Adult, Aged, Aged, 80 and over, Angina Pectoris blood, Angina Pectoris complications, Angina Pectoris diagnosis, Creatine Kinase blood, Creatine Kinase, MB Form, Electrocardiography, Humans, Isoenzymes blood, Middle Aged, Myocardial Infarction complications, Myocardial Infarction mortality, Norway epidemiology, Survival Analysis, Troponin I blood, World Health Organization, Biomarkers blood, Myocardial Infarction diagnosis
- Abstract
Objective: To evaluate how the use of different biochemical markers of myocardial injury affects the recorded numbers of cases of diagnosed acute myocardial infarction (AMI) and unstable angina pectoris (UAP) and also the observed in-hospital mortality of AMI., Design: 442 patients admitted with suspected acute coronary syndrome (ACS) were studied. Based on the World Health Organization (WHO) criteria, the patients were classified into five categories: acute Q-wave myocardial infarction (QMI): acute non-Q-wave myocardial infarction (NQMI); UAP; stable angina pectoris; and chest pain of non-cardiac origin., Results: Using total creatine kinase (tCK) as the "gold standard" for diagnosis, we found 172 AMI. 100 UAP and 170 with other diagnoses. If we used CK-MB (>6 microg/L) or cTnl (> 1 microg/L) for diagnosing AMI, the numbers of AMI increased significantly by 50 (29%) and 64 (37%), respectively. Using tCk, CK-MB or cTnl for diagnosing AMI, the observed in-hospital mortality was 14%, 11% and 10%, respectively. The group of patients with elevated cTnl but negative tCK had similar long-term survival as the group of patients with cTnI >30 microg/L, comprising 95% of the patients with the diagnosis AMI based on tCK., Conclusion: The introduction of new biochemical markers for detection of AMI may lead to significant changes in the recorded incidence and in-hospital mortality of AMI. New biochemical markers of myocardial injury must be validated against the traditional markers as they are introduced into clinical practice by the new diagnostic criteria.
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- 2001
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17. Bidirectional concentration-dependent effects of glucagon and dibutyryl cyclic AMP on DNA synthesis in cultured adult rat hepatocytes.
- Author
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Brønstad GO, Sand TE, and Christoffersen T
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- Animals, Cells, Cultured, Dose-Response Relationship, Drug, Kinetics, Liver drug effects, Male, Rats, Rats, Inbred Strains, Bucladesine pharmacology, DNA Replication drug effects, Glucagon pharmacology, Liver metabolism
- Abstract
Glucagon and dibutyryl cyclic AMP exerted both stimulatory and inhibitory effects on hepatocyte DNA synthesis when added to primary monolayer cultures in the presence of serum, dexamethasone, insulin and epidermal growth factor. The stimulation occurred at low concentrations of glucagon (1 pM-1 nM) or dibutyryl cyclic AMP (1 nM-1 microM), while the agents inhibited DNA synthesis at higher concentrations (usually glucagon at over 10 nM or dibutyryl cyclic AMP at over 10 microM). The stimulatory effect was stronger at low cell densities (less than 20 X 10(3) hepatocytes/cm2). When the hepatocytes were cultured at higher densities, stimulatory effects were reduced or absent and the inhibition of (hormone-induced) DNA synthesis by a high concentration of glucagon was much more pronounced than at low cell densities. These results indicate dual, bidirectional, effects of cyclic AMP on hepatocyte DNA synthesis.
- Published
- 1983
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18. Changes in hormone responsiveness and cyclic AMP metabolism in rat hepatocytes during primary culture and effects of supplementing the medium with insulin and dexamethasone.
- Author
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Christoffersen T, Refsnes M, Brønstad GO, Ostby E, Huse J, Haffner F, Sand TE, Hunt NH, and Sonne O
- Subjects
- 3',5'-Cyclic-AMP Phosphodiesterases metabolism, Adenylyl Cyclase Inhibitors, Adenylyl Cyclases metabolism, Animals, Cells, Cultured, Epinephrine pharmacology, Glucagon antagonists & inhibitors, Insulin pharmacology, Liver enzymology, Male, Rats, Rats, Inbred Strains, Catecholamines physiology, Cyclic AMP metabolism, Dexamethasone pharmacology, Glucagon physiology, Glucocorticoids physiology, Insulin physiology, Liver metabolism
- Abstract
Primary monolayer cultures of rat hepatocytes were used for studies of long-term and acute effects of hormones on the cyclic AMP system. When hepatocyte lysates were assayed at various times after plating of the cells three major changes in the metabolism of cyclic AMP and its regulation were observed: Glucagon-sensitive adenylate cyclase activity gradually declined in culture. In contrast, catecholamine-sensitive activity, being very low in normal adult male rat liver and freshly isolated hepatocytes, showed a strong and rapid increase after seeding of the cells. Concomitantly, there was an early elevation (peak approximately equal to 6 h) and a subsequent decrease in activity of both high-Km and low-Km cyclic AMP phosphodiesterase. These enzymic changes probably explained the finding that in intact cultured cells the cyclic AMP response to glucagon was diminished for 2-24 h after seeding, followed by an increase in the responsiveness to glucagon as well as to adrenergic agents up to 48 h of culture. Supplementation of the culture media with dexamethasone and/or insulin influenced the formation and breakdown of cyclic AMP in the hepatocytes. Insulin added at the time of plating moderately increased the adenylate cyclase activity assayed at 48 h, while dexamethasone had no significant effect. In the presence of dexamethasone, insulin exerted a stronger, and dose-dependent (1 pM - 1 microM), elevation of the adenylate cyclase activity in the lysates, particularly of the glucagon responsiveness. Thus, insulin plus dexamethasone counteracted the loss of glucagon-sensitive adenylate cyclase activity occurring in vitro. Kinetic plots of the cyclic AMP phosphodiesterase activity showed three affinity regions for the substrate. Of these, the two with high and intermediate substrate affinity (Km approximately equal to 1 and approximately equal to 10 microM) were decreased in the dexamethasone-treated cells. Insulin partly prevented this effect of dexamethasone. Accumulation of cyclic AMP in intact cells in response to glucagon or beta-adrenergic agents was strongly increased in cultures pretreated with dexamethasone. The results suggest that insulin and glucocorticoids modulate the effects of glucagon and epinephrine on hepatocytes by exerting long-term influences on the cyclic AMP system.
- Published
- 1984
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19. The proliferation response of rat liver parenchymal cells after partial hepatectomy. A methodological study comparing flow cytometry of nuclear DNA content and in vivo and in vitro uptake of thymidine.
- Author
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Digernes V, Brønstad G, Sand TE, and Christoffersen T
- Subjects
- Animals, Autoradiography, Cell Division, Cell Nucleus metabolism, Cell Separation, DNA biosynthesis, Flow Cytometry, Hepatectomy, Interphase, Kinetics, Rats, Scintillation Counting, Thymidine metabolism, Liver cytology, Liver Regeneration
- Abstract
DNA synthesis in rat hepatocytes, from livers regenerating after 70% hepatectomy, was assessed by flow cytometric determination of nuclear DNA content and by incorporation of [3H]thymidine. Parenchymal liver cells were isolated by collagenase perfusion and low-speed centrifugation. Nuclei from the isolated cells were prepared for flow cytometry by a treatment with detergent, pepsin and RNase, and stained with ethidium bromide. Parallel samples of cells were incubated with [3H]thymidine and analysed for rate of incorporation of radioactivity into DNA and for labelling index determination. The flow cytometric measure of the replicative response, i.e. the presence of cells with S-phase DNA content within the diploid and tetraploid cell populations, was compared with the incorporation of [3H]thymidine. For each of fourteen animals, including two control rats and twelve partially hepatectomized animals killed either before (at 13 hr after hepatectomy), at the onset (16 and 18 hr) or at the peak (24 hr) of regenerating activity, a fairly good correlation was found between the different methods. Satisfactory resolution of the flow cytometric detection of S-phase cells was indicated by a sorting experiment using an Ortho (system 50-H) cell sorter which demonstrated that after [3H]thymidine injection in vivo 88% of the diploid and 84% of the tetraploid S-phase nuclei were labelled, while labelling in the G1-fractions was only 2 and 7%, respectively.
- Published
- 1982
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20. Elevated level of beta-adrenergic receptors in hepatocytes from regenerating rat liver. Time study of [125I]iodocyanopindolol binding following partial hepatectomy and its relationship to catecholamine-sensitive adenylate cyclase.
- Author
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Sandnes D, Sand TE, Sager G, Brønstad GO, Refsnes MR, Gladhaug IP, Jacobsen S, and Christoffersen T
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- Animals, Cyclic AMP physiology, Hepatectomy, Iodocyanopindolol, Isoproterenol pharmacology, Male, Pindolol metabolism, Rats, Rats, Inbred Strains, Receptors, Adrenergic, beta metabolism, Adenylyl Cyclases metabolism, Liver analysis, Liver Regeneration, Pindolol analogs & derivatives, Receptors, Adrenergic, beta analysis
- Abstract
Hepatocytes from regenerating rat liver show an enhanced epinephrine-sensitive adenylate cyclase activity and cAMP response, which may be involved in triggering of the cell proliferation. We have determined adrenergic receptors and adenylate cyclase activity in hepatocytes isolated at various time points after partial hepatectomy. The number of beta-adrenergic receptors, measured by binding of [125I]iodocyanopindolol ([125I]CYP) to a particulate fraction prepared from isolated hepatocytes, increased rapidly after partial hepatectomy as compared with sham-operated or untreated controls. The maximal increase, which was observed at 48 h, was between 5- and 6-fold (from approximately 1 800 to approximately 10 500 sites per cell). Thereafter, the number of beta-adrenergic receptors decreased gradually. Competition experiments indicated beta 2-type receptors. Parallelism was found between the change in the number of beta 2-adrenergic receptors and the isoproterenol-responsive adenylate cyclase activity. The number of alpha 1-adrenergic receptors, determined by binding of [3H]prazosin, was transiently lowered by about 35% at 18-24 h, with no significant change in Kd. Although the results of this study do not exclude the possibility of post-receptor events, they suggest that the increased number of beta 2-adrenergic receptors is a major factor responsible for the enhanced catecholamine-responsive adenylate cyclase activity in regenerating liver.
- Published
- 1986
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21. Quantitative aspects of the effects of insulin, epidermal growth factor and dexamethasone on DNA synthesis in cultured adult rat hepatocytes.
- Author
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Sand TE, Brønstad G, Digernes V, Killi A, Amara W, Refsnes M, and Christoffersen T
- Subjects
- Animals, Autoradiography, Cell Division drug effects, Cells, Cultured, Hydroxyurea pharmacology, Interphase drug effects, Liver cytology, Male, Rats, Rats, Inbred Strains, DNA biosynthesis, Dexamethasone pharmacology, Epidermal Growth Factor pharmacology, Insulin pharmacology, Liver metabolism
- Abstract
Epidermal growth factor (EGF) and insulin in combination have previously been shown to initiate S-phase in primary cultures of adult rat hepatocytes. We here describe the detailed time course and dose-dependency of the effects of EGF and insulin on DNA synthesis in cultured hepatocytes. The DNA synthesis was assessed either biochemically or autoradiographically with a fairly good correlation between the two methods. DNA synthesis started 24-30 h after plating of the cells and peaked at approximately 70 h. Up to 70% of the cells entered DNA synthesis during this period. EGF and insulin acted synergistically on the DNA synthesis. Dexamethasone raised the DNA synthesis slightly, maximal effect occurred at concentrations above 2.5 nM and this agent was routinely used in the experiments with EGF and insulin. In the presence of 0.4 microM insulin from the time of plating, EGF dose-dependently increased the DNA synthesis with maximal effect at 5-15 nM. When added in combination with 1.7 nM EGF, insulin enhanced the DNA synthesis over the concentration range from 0.1 to 3 nM. These studies show that primary cultures of hepatocytes are useful in assessing the quantitative aspects of the interactions between the growth stimulating effects of hormones.
- Published
- 1985
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22. Inhibitory effect of prostaglandins on the stimulation by glucagon and adrenaline of formation of cyclic AMP in rat hepatocytes.
- Author
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Brønstad GO and Christoffersen T
- Subjects
- 3',5'-Cyclic-AMP Phosphodiesterases metabolism, Adenylyl Cyclases metabolism, Animals, Drug Interactions, Glucagon metabolism, Male, Rats, Cyclic AMP metabolism, Epinephrine pharmacology, Glucagon pharmacology, Liver drug effects, Liver metabolism, Prostaglandins E pharmacology
- Abstract
Several prostaglandins were found to inhibit hormone-induced cyclic AMP accumulation in suspensions of intact rat hepatocytes. Prostaglandin E1 in concentrations of 0.05--25 micrometers inhibited the cyclic AMP response to glucagon. Maximal inhibition was about 50%. The effect was rapid, being evident within 30 s. Prostaglandins E2, F1 alpha, F2 alpha, A1 and A2 also inhibited the glucagon effect on cyclic AMP in hepatocytes. In cells made highly responsive to adrenaline, by pretreatment of the animals with the carcinogen 2-acetylaminofluorene, and inhibitory effect of prostaglandin E1 was seen also on adrenaline-induced cyclic AMP accumulation. The mechanism of the inhibitory effect of prostaglandins on hormone-stimulated cyclic AMP accumulation was not clarified. Prostaglandin E1 did not inhibit glucagon binding to intact hepatocytes, and so far we have not been able to demonstrate any effect of the prostaglandins on the adenylate cyclase or phosphodiesterase in broken cell preparations. It is concluded that while several previous studies have shown that stimulatory effects of prostaglandins on cyclic AMP are only marginal or lacking in parenchymal liver cells the present data indicate that several prostaglandins exert strong inhibitory interference with hormone-induced cyclic AMP accumulation.
- Published
- 1981
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23. Increased effect of adrenaline on cyclic AMP formation and positive beta-adrenergic modulation of DNA-synthesis in regenerating hepatocytes.
- Author
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Brønstad G and Christoffersen T
- Subjects
- Animals, Cells, Cultured, Glucagon pharmacology, Guanylyl Imidodiphosphate pharmacology, Kinetics, Male, Prostaglandins E pharmacology, Rats, Sodium Fluoride pharmacology, Adenylyl Cyclases metabolism, Cyclic AMP metabolism, DNA biosynthesis, DNA Replication drug effects, Epinephrine pharmacology, Isoproterenol pharmacology, Liver metabolism, Liver Regeneration drug effects
- Published
- 1980
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24. The regulation of cyclic AMP levels in cultured MH1C1 rat hepatoma cells and in solid tumours derived from MH1C1 cell inoculates.
- Author
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Brønstad GO, Gladhaug IP, Haffner F, Rugstad HE, and Christoffersen T
- Subjects
- 3',5'-Cyclic-AMP Phosphodiesterases metabolism, Animals, Cells, Cultured, Epinephrine pharmacology, Fibroblasts metabolism, Glucagon pharmacology, Isoproterenol pharmacology, Liver metabolism, Prostaglandins E pharmacology, Rats, Cyclic AMP metabolism, Liver Neoplasms, Experimental metabolism
- Abstract
Several studies have found high cAMP content in hepatomas in vivo, while hepatoma cells in vitro have very low levels. To explore this discrepancy and the regulation of cAMP in hepatomas, we have examined the cell line MH1C1 from Morris hepatoma 7795. These cells in culture contained low intracellular cAMP concentrations (approximately 0.5 pmol/mg protein at confluency), and were unresponsive to glucagon and prostaglandins (PG) E1 and E2. In contrast, solid hepatomas in rats developed from inoculates of MH1C1 had a 40-fold higher basal cAMP concentration and were stimulated by PGE1 and PGE2. Fibroblasts cultured from these tumours also contained high cAMP levels and responded strongly to PGE1. This may suggest that the difference in cAMP regulation between hepatomas in vivo and hepatoma cells in vitro results from the presence of other cells in the solid tumour rather than from selection of low-cAMP cells during the cloning procedure. Low-Km and intermediate-Km cAMP phosphodiesterase activity was high in MH1C1, compared to normal hepatocytes. This might contribute to the low cAMP level. The ability of MH1C1 to form cAMP was not defective, as the level could be increased more than 200-fold by beta-adrenergic activation in the presence of the phosphodiesterase inhibitor methylisobutylxanthine.
- Published
- 1987
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