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Biomedical subjects

E Wist

Publications and source records attributed to E Wist.

86 records · Page 5Linked to original sources
PubMed1979

Partial purification of deoxyuridine triphosphate nucleotidohydrolase and its effect on DNA synthesis in isolated HeLa cell nuclei.

Deoxyuridine triphosphate nucleotidohydrolase (EC 3.6.U.23) has been partially purified from HeLa S3 cells, and found to have an apparent molecular weight of 50--55 000 by gel filtration under non-denaturing conditions. The enzyme is specific for the hydrolysis of dUTP, requires Mg2+ and is inhibited by EDTA. The apparent Km for dUTP is 0.1 microM. Isolated HeLa cell nuclei were treated with dUTPase before pulse-labelling with [3H]dTTP which also had been pretreated with dUTPase. This pretreatment changed neither the total amount nor the size of the primary DNA pieces. A role for dUTP incorporation in their genesis can therefore be excluded and these primary DNA pieces are considered to be true intermediates in discontinuous DNA replication.

Cell Nucleus↗
PubMed1979

The role of DNA polymerases alpha, beta and gamma in nuclear DNA synthesis.

The effects of the inhibitors 2'3' dideoxythymidine triphosphate (ddTTP) and 1-beta-D-arabinofuranosyl cytosine triphosphate (araCTP) on DNA synthesis in isolated S-phase HeLa S3 nuclei have been examined. These effects are compared with the effects of the same inhibitors in partially purified preparations of DNA polymerases alpha and beta. The effect of ddTTP on partially purified DNA polymerase gamma was also tested. DNA polymerases beta and gamma were very sensitive to ddTTP whereas DNA polymerase alpha and DNA synthesis in isolated nuclei were quite resistant. The synthesis and subsequent ligation of primary DNA pieces ('Okazaki fragments') were not affected by the presence of this inhibitor. DNA synthesis in isolated nuclei and DNA polymerase alpha activity were very sensitive to araCTP whereas DNA polymerase beta was almost totally resistant to the inhibitor. The results indicate a major role for DNA polymerase alpha in DNA replication.

Arabinofuranosylcytosine Triphosphate↗
PubMed1979

The effect of aphidicolin on DNA synthesis in isolated HeLa cell nuclei.

The effect of the inhibitor aphidicolin on DNA synthesis in isolated nuclei from HeLa cells and on the activities of partially purified DNA polymerases has been tested. Aphidicolin inhibited DNA synthesis and DNA polymerase alpha very efficiently whereas DNA polymerases beta and gamma were insensitive to the drug. The results indicate that DNA polymerase alpha is the polymerase active during elongation as well as in the gapfilling process of discontinuous DNA synthesis.

Anti-Bacterial Agents↗
PubMed1978

Accumulation of small fragments of DNA in isolated HeLa cell nuclei due to transient incorporation of dUMP.

[3H]dUMP was incorporated into DNA of isolated S-phase HeLa S3 cell nuclei during DNA synthesis. The incorporated radioactivity was made acid soluble during a chase with excess TTP. A partially purified DNA polymerase alpha incorporated [3H]dUMP into activated salmon sperm DNA. The incorporation rate was equal to the incorporation of [3H]TMP, and the radioactivity incorporated was not made acid soluble during a chase. The nuclei thus have the ability to remove misincorporated uracil. From cytosol we have partially purified an enzyme (80 times purification) that splits the N-glycosidic bond between uracil and deoxyribose in dUMP-containing DNA. This uracil-N-glycosidase has a molecular weight of about 50 000. It does not accept dUTP or RNA as substrates. Pulse labelling of isolated nuclei with radioactive deoxyribonucleoside triphosphates in the presence of dUTP lead to a large accumulation of label in small DNA fragments. The size of these fragments was about 80 nucleotides in a 60 s pulse and no increase in size was observed with increasing pulse length. The corresponding value for control experiments with no dUTP, was 200 nucleotides and the fragments increased in size with increasing pulse length. About 90% of the radioactivity was found in the small fragments after a 3 min pulse when the concentration of dUTP in the test mixture was 100 micrometer and no exogenous TTP was present. In control experiments with no dUTP present, only 14% of the radioactivity was found in small DNA pieces. When test mixture containing dUTP was preincubated with cytosol for 60 s before adding the isolated nuclei, the small fragments increased in size to that of DNA fragments found in control incubations; also the relative amount of label bound to the fragments returned to the levels found in the controls. Increasing the TTP concentration from 5 micrometer to 1.88 mM in the absence of exogenous dUTP had no effect on the size of the DNA fragments.

Cell Cycle↗
PubMed1977

DNA replication intermediates in whole HeLa cells and isolated nuclei.

Replicative intermediates have been studied in intact HeLa cells and in nuclei isolated from such cells. In whole cells the smallest DNA (primary DNA pieces) observed after pulse labelling with [3H]thymidine were 90-160 nucleotides long, and the size of the molecules in this class of DNA did not increase with increasing pulse length. Some increase in size was, however, observed when cells were pulse labelled at 25 degrees C instead of 37 degrees C. Chase experiments using nuclei from pulse-labelled cells suggested that the primary DNA pieces could be chased rapidly into DNA of high molecular weight (30-70 S, corresponding to a molecular weight of 0.7 - 10(7)-6.4-10(7)). Longer chases showed that the label eventually accumulated in DNA with s values greater than 150 S. In isolated nuclei the primary DNA pieces after a 1 min pulse at 37 degrees C were approximately 200 nucleotides long. Primary pieces of this size were also rapidly chased into the 30-70 S region. However, during longer pulses in vitro a fraction of the primary DNA pieces grew beyond their normal size to reach a size of up to 2000-3000 nucleotides before being attached to the 30-70 S molecules.

Cell Nucleus↗
PubMed1976

Effect of 1-beta-D-arabinofuranosylcytosine triphosphate on DNA synthesis in isolated HeLa cell nuclei.

1-beta-D-Arabinofuranosylcytosine 5'-triphosphate (ara-CTP) was found to be a competitive inhibitor of DNA synthesis in nuclei isolated from synchronized S-phase HeLa S3 cells. The inhibition was reversed by dCTP. The main inhibitory effect was to reduce the rate of elongation of the primary DNA pieces from ara-CTP-treated nuclei after a 60-s pulse was about 115-120 nucleotides vs. 215-220 in control nuclei. A reduction in the frequency of initiation of primary DNA pieces probably also occurred. A slight inhibition of the transfer of labeled material from the primary pieces into high-molecular weight DNA was noted and probably arose from the fact that the reduced rate of growth of the primary pieces caused the critical size for ligation to be reached later. Synchronized HeLa S3 cells in suspension were treated with 1-beta-D-arabinofuranosylcytosine for 2 h in S-phase to give a 99% inhibition of DNA synthesis prior to isolation of nuclei. Neither the rate nor the extent of [3H]TTP incorporation into DNA decreased when such nuclei were incubated in the absence of ara-CTP, but the rate of ligation of primary pieces was reduced.

Cell Division↗
PubMed1975

The Aubert-Fleischl phenomenon: a temporal frequency effect on perceived velocity in afferent motion perception.

Apparent velocities of moving visual stimuli are known to be different depending on whether the subject pursues the stimulus (efferently controlled motion perception) or whether the eye is stationary and the image moves across the retina (afferent motion perception). Afferent motion perception of a periodic pattern or a moving single object causes overestimation of velocity (magnitude estimations) as compared to smooth pursuit. This socalled Aubert-Fleischl phenomenon is shown to depend on local temporal frequency stimulation on the retina caused by the repetitive passage of contrast borders of the moving periodic pattern. This is evidenced by the fact that for a given stimulus speed the amount of overestimation is a function of the spatial frequency of the pattern (or the angular subtend of a single moving object) and that the Aubert-Fleischl phenomenon is not observed if a single edge moves. Background characteristics seem not to influence the apparent velocity during smooth pursuit.

Adult↗
PubMedDate not supplied

Primary retroperitoneal sarcomas. A review of 36 cases.

A retrospective study of 36 patients with primary retroperitoneal sarcomas treated at The Norwegian Radium Hospital is presented. The median age at presentation was 57 years. The most common presenting symptom was abdominal pain. Leiomyosarcoma and liposarcoma were the most common histologic subtypes. The median survival in the whole series was 25 months. Patients with completely resected tumors had a longer median survival (59 months) than patients with incomplete resection (16 months) but the difference was not statistically significant. The malignancy grade seemed to be the most important prognostic factor and patients with low grade tumors had a significantly better outlook than those with high grade tumors.

Abdomen↗
PubMedDate not supplied

Subclassification of Hodgkin's disease, nodular sclerosis type. Prognostic value?

Recently, studies have suggested a subclassification of Hodgkin's disease, nodular sclerosis (HDNS). Between 1985-1994, twenty-four patients with HDNS were treated at the University Hospital of Tromsø, Norway. The cases were subclassified according to the histological criteria from the British National Lymphoma Investigation (BNLI) into NS1 (15 patients) and NS2 (9 patients). The relative frequencies of the two subtypes of HDNS in our region were in agreement with other reports. After a median follow up of 33 months, no significant difference between NS1 and NS2 with regard to complete remission rate (87% versus 100%) or predicted 5-year actuarial survival (93% versus 75%) were observed. Although our data are too small to draw specific conclusions, the discrepancy with some of the previous studies could be due to an improved response of the more aggressive type (NS2) to optimal treatment. We hope this study may initiate a raised interest in this field.

Adolescent↗
PubMedDate not supplied

Patients' opinion and use of non-proven therapies related to their view on cancer aetiology.

BACKGROUND: The aim of the study was to investigate patients' attitudes to and use of nonproven therapies (NPTs) in view of their opinions about causes of cancer. MATERIAL AND METHODS: A comparative questionnaire-based study was given to patients with non-malignant disease (n = 305) seen in general practice and cancer patients (n = 252) seen at the Department of Oncology, University Hospital of Tromsø. RESULTS: Among non-cancer patients significantly more NPT-positive than NPT-negative patients considered the environment to be an important cancer cause (74% versus 52%) and that food and drink may be carcinogenic (57% versus 40%). For cancer patients, there was no such difference. 60% of non-cancer patients and 35% of cancer patients believed that life style changes could alter the natural course of cancer. In both groups of patients, the NPT-positive believed, to a higher degree than the NPT-negative, that the outcome of cancer could be improved by a change in life style (69% and 48% versus 53% and 29%). CONCLUSION: Patients positive to NPTs have firmer beliefs with respect to the importance of environmental factors than non-believers/-users. Moreover, these patients believed more strongly than NPT-negative patients that change of lifestyle may influence the outcome of cancer positively.

Adolescent↗