Search PubMed⌕ Search

Biomedical subjects

R Ekanger

Publications and source records attributed to R Ekanger.

15 recordsLinked to original sources
PubMed2000

[High dose chemotherapy with autologous stem cell support in cancer patients].

INTRODUCTION: In 1996 it was decided that high-dose chemotherapy with peripheral stem cell support should be offered by all five university hospitals in Norway. MATERIAL AND METHODS: We report on the first 49 patients from the western part of Norway treated with this modality at Haukeland University Hospital in the 1996-98 period. RESULTS: All patients had a total of > 2-10(6) CD34 positive cells/kg collected before high-dose chemotherapy. To achieve this critical stem cell dose, five patients had to have three or more stem cell collections; four of them had to be mobilised several times. Poor stem cell mobilisation was mostly marked in patients with soft tissue sarcoma and testicular cancer, but was also observed in a few heavily pre-treated patients with non-Hodgkins lymphoma. With the exception of one lymphoma patient who developed a rapid bone marrow relapse, all patients had satisfactory sign of bone marrow regeneration after reinfusion of the stem cells. This also applied to the poor mobilisors. No treatment-related deaths have occurred. Four to 38 months after high-dose therapy, 33% of patients with multiple myeloma and 52% of patients with malignant lymphoma were alive and in complete remission. Three of the four patients with soft tissue sarcoma relapsed 3-7 months after high-dose chemotherapy.

Adolescent↗
PubMed1989

Comparison of the two classes of binding sites (A and B) of type I and type II cyclic-AMP-dependent protein kinases by using cyclic nucleotide analogs.

cAMP analogs, all 96 of which were modified in the adenine moiety, were examined quantitatively for their ability to inhibit the binding of [3H]cAMP to each of the two classes (A and B) of cAMP-binding sites of type I (rabbit skeletal muscle) and type II (bovine heart) cAMP-dependent protein kinase. The study showed that analogs can be constructed that have a higher affinity than cAMP for a binding site. N6-phenyl-cAMP had 18-fold increased affinity for site A of RI (AI) and 40-fold increased affinity for site AII. 2-chloro-8-methylamino-cAMP had a 7-fold increased affinity for BI, and 8-(4-chlorophenylthio)-cAMP had 17-fold increased affinity for BII. Analogs could discriminate between the two classes of binding sites by more than two orders of magnitude in binding affinity: 2-chloro-8-methylamino-cAMP had 170-fold higher affinity for BI than for AI, and 2-n-butyl-8-thiobenzyl-cAMP had 700-fold higher affinity for BII than for AII. Analogs could also discriminate between the homologous binding sites of the isozymes: 2-n-butyl-8-bromo-cAMP had 260-fold higher affinity for AI than for AII (22-fold higher for BII than BI), and 8-piperidino-cAMP had 50-fold higher affinity for BII than for BI (and 50-fold higher for AI than for AII). The data suggest the following conclusions. (a) Stacking interactions are important for the binding of cAMP to all the binding sites. (b) Subtle differences exist between the sites as to the optimal electron distribution in the adenine ring since modifications that withdraw electrons at C2 and donate at C8 favour binding to BI, and disfavour binding to AI and AII. (c) There are no hydrogen bonds between the adenine ring of cAMP and any of the binding sites. (d) All sites bind cAMP in the syn conformation. (e) The subsites adjacent to the N6 and C8 positions may have nonpolar neighbouring regions since hydrophobic substituents at N6 could increase the affinity for AI and AII and similar substituents at C8 could increase the affinity for BII. Finally, (f) the sites differed in their ability to accomodate bulky substituents at C2 and C8. For all compounds tested, their potency as activators of protein kinases I and II was found to correlate, in a predictable fashion, to their mean affinity for the two classes of binding sites, rather than to the affinity for only one of the sites.

Animals↗
PubMed1989

The expression of cAMP-dependent protein kinase subunits is differentially regulated during liver regeneration.

The levels of the regulatory (RI and RII) and catalytic (C) components of cAMP-dependent protein kinase and of their messages were studied during the first 36 h of liver regeneration after 70% hepatectomy. Both RI alpha mRNA and RII alpha mRNA started to increase 4 h after the resection, reaching peak levels after 9 h. RI mRNA decreased abruptly 9-12 h after resection, whereas RII mRNA stayed elevated. C alpha mRNA was rather constant during the period of study. In accordance with the mRNA data the level of C was constant while RI and RII increased during the prereplicative phase of liver regeneration. RI increased rapidly when its message became elevated. RII, however, increased noticeably only 6-8 h after its mRNA had become elevated. The increased expression of R led to a disproportion between R and C that was most pronounced 14 h after resection, i.e. coinciding with the prereplicative cAMP burst. The increased R/C ratio at that time of regeneration diminished the concentration of active C subunit during the cAMP burst. In that way the otherwise inhibitory effect of high concentrations of active C on the DNA replication may have been decreased. The fractional saturation of RI and RII by endogenous cAMP fluctuated in parallel as a function of liver cAMP levels, although there was a tendency that RI was more highly saturated than RII at high concentrations of cAMP.

Animals↗
PubMed1988

The amounts of rat liver cyclic AMP-dependent protein kinase I and II are differentially regulated by diet.

1. The fluctuations in rat hepatocyte volume and protein content in response to dietary perturbations (starvation, protein restriction, refeeding) were accompanied by corresponding fluctuations in the amount of the regulatory (R) and catalytic (C) subunits of cyclic AMP-dependent protein kinase. Thus the intracellular concentration of this key enzyme was adjusted to be near constant. 2. The adjustment of cellular R was accomplished almost exclusively by regulating cytosolic RI (R subunit of type I kinase). The preferential down-regulation of cytosolic RI in response to starvation/protein restriction indicates that particulate RI and cytosolic as well as particulate RII are more resistant to breakdown during general catabolism in the hepatocyte. 3. The diet-induced fluctuations of kinase subunits were uniformly distributed in all populations of parenchymatous hepatocytes, regardless of their size and density. It is thus possible to isolate hepatocytes with uniformly altered RI/RII ratio from livers of rats with different feeding regimens. 4. The binding of endogenous cyclic AMP to RI and RII was similar in livers with high RI/RII ratio (fed rats) and low RI/RII ratio (fasted rats) as well as in hepatocytes isolated from fasted rats. Under the conditions of the experiment (short-term stimulation by glucagon), therefore, neither the dietary state nor the RI/RII ratio seemed to affect the apparent affinity of the isoreceptors for cyclic AMP. However, RI appeared to show a slightly higher co-operativity of intracellular cyclic AMP binding than did RII in all states.

Animals↗
PubMed1987

Characterization of the cyclic adenosine 3':5'-monophosphate effector system in hormone-dependent and hormone-independent rat mammary carcinomas.

We have compared the properties of cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinases I and II in hormone-dependent/cAMP-sensitive (DMBA tumor) and hormone-independent/cAMP-resistant (DMBA 1 tumor) rat mammary carcinomas. cAMP-resistance was not due to less total kinase in the hormone-independent tumor, grossly altered distribution between soluble and particulate forms of the kinase (80% soluble in either tumor), alteration in the relative proportion of isozymes I and II of the protein kinase (the soluble and the particulate fraction from both tumors contained about 50% of either isozyme), or a decreased sensitivity towards cAMP (both isozymes had affinities for cAMP and its derivatives that corresponded closely with those of isozymes from normal tissues). Furthermore, the sensitivity of the enzymes towards thermal denaturation was identical for samples from the two tumor types. Subtle differences did, however, exist between the regulatory moieties [regulatory subunit of cAMP-dependent protein kinase II (RII)] of isozyme II from the two tumors: autophosphorylated RII from the hormone-independent tumor migrated as a doublet corresponding to Mrs 54,000 and 52,000 on sodium dodecyl sulfate-polyacrylamide gels, against Mrs 53,000 and 52,000 for RII from the hormone-dependent tumor; RII from the two tumors showed different elution profiles upon DEAE-cellulose chromatography; a considerable proportion of the soluble RII in the hormone-independent tumor formed supramolecular aggregates as judged by size-exclusion chromatography. No such microheterogeneity was noted for isozyme I. This study thus shows that the lack of cAMP-responsiveness of one tumor is related either to a defect distal to the cAMP-dependent protein kinases or to the appearance of the new subtype of RII in the resistant tumor. If the latter explanation is correct, it means that the part of the RII molecule responsible for interaction with other proteins rather than that responsible for cAMP-binding and control of protein kinase activity modulates the growth-inhibiting response to cAMP.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

Relation between induction of ornithine decarboxylase and specific gene expression in rat liver in response to the tumor promoter agent clofibrate.

The time course of changes in a number of biochemical parameters in rat liver was studied during 10 days of clofibrate administration. Ornithine decarboxylase (ODC) and putrescine levels began to increase within hours of the first dose and reached maxima at about 36 h (40 and 10 times control levels, respectively) and then returned to normal levels by 48 h. This ODC induction by clofibrate is different from that seen in compensatory liver hyperplasia or diethylnitrosamine administration in that it was not accompanied by elevations in cAMP or increased activation of cytoplasmic cAMP-dependent protein kinases, type I or II. Messenger RNA levels, notably of the species coding for the enzymes of the peroxisomal beta-oxidation pathway, increased in parallel with ODC and putrescine to reach a maximum also at 36 h. The enzymes of the peroxisomal beta-oxidation pathway, on the other hand, increased more gradually over time to reach a plateau at approximately 7 - 10 days. The magnitude of increase in mRNA (about 7-fold) was comparable to that of peroxisomal beta-oxidation as measured by cyanide-insensitive palmitoyl-CoA-dependent NAD+ reductase activity; comparable increases in the specific content of enoyl-CoA hydratase: beta-hydroxyacyl-CoA dehydrogenase and of peroxisomal thiolase were observed, as determined by SDS electrophoresis. A gradual increase in long-chain acyl-CoA (1.5-fold) followed the increase in beta-oxidation, whereas a 2-fold increase in acid-soluble CoA (free CoA and short-chain acyl-CoA) was seen as early as 36 h. This sequence of changes is at variance with proposals that increased levels of long-chain acyl-CoA mediate induction of peroxisomal beta-oxidation.

Acyl Coenzyme A↗
PubMed1985

Activation of protein kinase isozymes by cyclic nucleotide analogs used singly or in combination. Principles for optimizing the isozyme specificity of analog combinations.

104 cAMP analogs, most of them modified in the adenine moiety, were tested as activators of cAMP-dependent protein kinase I (from rabbit or rat skeletal muscle) and kinase II (from bovine heart or rat skeletal muscle). When tested singly, only 2-phenyl-1,N6-etheno-cAMP showed a considerably (sevenfold) higher potency as an activator of kinase II than of kinase I. Analogs containing an 8-amino modification preferentially activated kinase I, some being more than 10-fold more potent as activators of kinase I than kinase II. When two analogs were combined, the concentration of one (complementary) analog required to half-maximally activate each isozyme was determined in the presence of a fixed concentration of another (priming) analog. Analogs tested in combination had been analyzed for their affinity for the intrasubunit binding sites (A, B) of isozyme I and II. The degree to which complementary analogs preferentially activated one isozyme was plotted against the mean site selectivity, i.e. (affinity A/B isozyme I X affinity A/B isozyme II) 1/2. This plot produced a straight line, the slope of which reflected the ability of the priming analog to discriminate homologous sites on the isozymes. This means that the isozyme discriminating power of an analog pair can be quantitatively predicted from the affinity of the analogs for site A and B of the two enzymes. It also means that a systematic analysis of those features of analogs imparting a high mean site selectivity or the ability to discriminate between homologous isozyme sites will facilitate the synthesis of new even more isozyme-selective analogs.

Animals↗
PubMed1985

The separate estimation of cAMP intracellularly bound to the regulatory subunits of protein kinase I and II in glucagon-stimulated rat hepatocytes.

A method is described for the separate determination of cAMP intracellularly bound to the regulatory moieties (RI and RII) of protein kinase I and II. The cAMP endogenously bound to RI or RII in hepatocyte extract was adsorbed to protein A-agarose beads coated with antibodies against RI or RII. The endogenously bound cAMP was eluted from the washed beads with dilute acetic acid before being assayed. By all criteria tested, the present method did not perturb the intracellularly established equilibrium between bound and free cAMP. Stabilization of R X cAMP complexes was achieved by including sulfate in the extraction medium and sulfate/glycerol during the subsequent steps. Hepatocytes were isolated from fed male rats and contained about 0.25 pmol of RI and 0.2 pmol of RII per 10(5) cells. An intracellular titration of the cAMP binding sites of RI and RII was achieved by incubating the cells with various concentrations (1 pM to 10 nM) of glucagon. The fractional saturation of RI and RII was always similar, being 20% in nonstimulated cells. 50% saturation occurred when free cAMP was 0.46 pmol/10(5) cells. A Scatchard plot of the data for the endogenous cAMP binding suggested that cAMP interacted with RI and RII in a slightly positively cooperative manner. About 5% of the intracellularly bound cAMP was sedimentable at 10,000 X g. The apparent affinity of these particulate-associated binding sites was similar to that of soluble RI and RII. Under the conditions used no evidence was obtained for cAMP binding to other proteins than RI and RII.

Animals↗
PubMed1985

Characterization of cyclic adenosine 3':5'-monophosphate-dependent protein kinase isozymes in normal and neoplastic fetal rat brain cells.

Fetal brain cells from rats given a transplacental pulse of N-ethyl-N-nitrosourea progressively acquire malignant characteristics and dedifferentiate when grown in vitro. One aspect of this dedifferentiation is a decreased morphological response to cyclic adenosine 3':5'-monophosphate (cAMP). In the present study, we have characterized and compared the isozymes (I, II) of cAMP-dependent protein kinase in fetal brain cells and in the neoplastically transformed, dedifferentiated BT5C glioma cell line. This is a first approach to find the mechanism behind the subresponsiveness of such cells towards cAMP. It is also part of a broader investigation of the cAMP effector system in cells showing various rates of normal and malignant growth. We found the regulatory and catalytic subunits of cAMP-dependent protein kinase to be expressed to a similar degree in both cell types. Sixty % of the enzyme was located in the 30,000 X g supernatant. The glioma cell line had a significantly higher ratio (1.2) between protein kinase I and II than did the normal fetal cells (0.5). This difference in isozyme distribution was not apparent using conventional methods for enzyme separation and detection, the use of specific antibodies being essential for that purpose. Of the chromatographically separated forms (a, b) of protein kinase II, Form IIa was selectively decreased in the glioma cell line. The alterations of the protein kinases in the glioma cell line described above may be of importance for some of the neoplastic properties of these cells. However, the subdued response of such cells towards cAMP is not explained since the concentrations of cAMP or its analogues required for activation of the kinases were similar for the enzymes from normal and neoplastically transformed cells.

Animals↗
PubMed1983

Relationship of cyclic AMP binding capacity and estrogen receptor to hormone sensitivity in human breast cancer.

Estrogen receptor (ER) and total binding capacity for cyclic AMP (cAR) were measured in cytosols from human mammary tumors. Patients with advanced, evaluable breast cancer were biopsied before the start of endocrine treatment, and ER and cAR measurements were performed. All patients included in this study were ER positive. Sixteen of 30 patients (53%) had an objective response to endocrine treatment. When ER and cAR were expressed as a ratio and this ratio was related to treatment response, it was found that all objective responders had ratio values above 2.5 X 10(-3). Nine of 14 nonresponders had ER/cAR ratios below this value. In our limited series of patients a threshold limit of 2.5 X 10(-3) would have correctly predicted the response to endocrine treatment in 25 of 30 patients (83%). In patients with ER values below 100 fmol/mg protein and PgR negative or unknown, cAR might strengthen the predictive value of steroid receptor measurements.

Adult↗
PubMed1978

Performance, mood, and clinical symptoms in men exposed to prolonged, severe physical work and sleep deprivation.

There were 44 young men who participated in strenuous combat courses of 4 d (course I) or 5 d (course II), almost without sleep. They were tested and examined clinically each morning. Groups 1 and 2 had no organized sleep, whereas groups 3 and 4 got 3 and 6 h, respectively, in the middle of each course. Substantial impairment was observed in all tests, as well as clinical symptoms toward the end of the courses for groups 1 and 2. In the vigilance test, the reaction time task, the code test, and the profile of mood-state, significant impairment was observed even after 24 h. Complaints of symptoms came first. Disturbance of senses and behaviour appeared later. Group 4 had significantly better results than groups 1 and 2 in clinical symptoms and all tests, except the positive score in mood-state. Group 3 occupied an intermediate position. Corresponding results were obtained in the two separate courses. In the morning following the course, recovery after 4 h of sleep was less extensive for courses II than course I participants.

Achievement↗