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S Funderud

Publications and source records attributed to S Funderud.

82 records · Page 5Linked to original sources
PubMed1982

DNA replication in Physarum polycephalum: electron microscopic analysis of patterns of DNA replication in the presence of cycloheximide.

DNA from synchronously replicating nuclei of Physarum polycephalum was studied electron microscopically after 15, 30, 60, and 90 or 120 min of replication in the presence or absence of the protein synthesis inhibitor cycloheximide. The replication-loop size-distribution showed that replication fork progression is severely retarded in the presence of cycloheximide. Analysis of replication-loop frequency showed a similar pattern in control and cyclo-heximide-treated samples, with an increase from 15 to 30 and 60 min. This suggests, surprisingly, that initiations of new replicons either may not be inhibited by cycloheximide or, alternatively, that all initiations have already taken place at the very start of S-phase. The latter conclusion is favored in the light of previous results in our laboratory, discussed here.

Cycloheximide↗
PubMed1981

Inhibitory effect on tumour colony formation of mouse serum associated with tumour resistance in vivo in semi syngeneic mice.

Differences in tumour susceptibility between strains of mice (C57Bl/6 and C57Bl/6 X DBA/2 = B6D2F1) could be demonstrated for several tumours of C57Bl origin, both solid tumours (B16 melanoma and Lewis lung carcinoma) and lymphomas (RBL-5, 136-3 and ALC). Serum from mice with high tumour resistance in vivo (B6D2F1) showed an inhibitory effect on tumour colony formation in a soft agar colony assay. Serum from mice with lower tumour resistance (C57Bl/6) had no effect. When other F1 hybrids of C57Bl/6 parental origin were tested, the same correlation between in vitro inhibition of tumour colony formation and in vivo susceptibility was found. The serum factor was species non-specific, since the activity was expressed against in vitro grown cell lines of human origin. The tumour colony inhibitory activity was heat sensitive (56 degrees C for 30 minutes), precipitable by (NH4)2SO4, and not removed by adsorption on tumour cells. These results demonstrate the existance of a naturally-occurring humoral tumerostatic factor(s) which correlates to in vivo susceptibility to tumour cells. Its relationship to NK cell activity is discussed.

Animals↗
PubMed1981

Growth inhibitory effect of mouse serum on eukaryotic cells in a micro assay.

Inhibition of cell growth by B6D2F1 (C57Bl/6 X DBA/2) mouse serum in tissue culture wells confirming previous findings in the soft agar tumour colony assay is reported. The assay was time saving, more sensitive, and the amount of mouse serum used could in each experiment be reduced by 95%. In addition non-neoplastic cells ordinarily not forming colonies in the soft agar assay could be tested. Such cells were less sensitive to the growth inhibitory effect when compared to neoplastic cells.

Animals↗
PubMed1979

DNA replication in Physarum polycephalum: electron microscopic and autoradiographic analysis of replicating DNA from defined stages of the S-period.

Electron microscopic and autoradiographic analysis of replicating DNA from Physarum showed that replication occurs at a rate of 0.4 micron/min/per replicon and that replicons of size 10--15 mu occur in temporal clusters with an average of about 4 replicons per cluster. These results are compared with previous hydrodynamic measurements and with those obtained in other organisms.

Autoradiography↗
PubMed1978

Size distribution and maturation of newly replicated DNA through the S and G2 phases of Physarum polycephalum.

The size distribution of newly made DNA and the dynamics of size maturation of progeny DNA molecules were studied in the synchronous S and G2 phases of Physarum polycephalum. Pulse labeling of DNA and analysis of the products on alkaline sucrose gradients showed that synthesis of primary replication units (which will also be referred to as "Okazaki" fragments) occurred throughout the S period. Pulse and pulse-chase experiments revealed a distinct pattern of size maturation. An apparently linear increase in molecular weight of progeny DNA molecules during the first hour of the S phase occurred at a rate of approximately 4-5 X 10(5) daltons per min at 26 degrees C, corresponding to the joining of 6-8 Okazaki fragments. The resulting 35-45S (1.1-2.2 X 10(7) daltons) DNA molecules may correspond to the Physarum "replicon." The further size increases of the newly made DNA appear to occur in steps, possibly reflecting a clustering of isochronous replicons along the chromatide. These observations are discussed with regard to mechanisms of DNA replication and size maturation.

Cell Cycle↗
PubMed1978

DNA replication in Physarum polycephalum: bidirectional replication of DNA within replicons.

The direction of replication of DNA within replicons of Physarum polycephalum was studied by pulse-labelling with 5-bromouracil-deoxyriboside (BrdUrd) and 3H-adenosine deoxyriboside (dAdo), followed by ultraviolet- (UV) -photolysis and analysis of molecular weights of single strand DNA fragments on alkaline sucrose gradients. Newly made DNA within replicons at all stages of completion is split in two equal halves upon UV irradiation when BrdUrd was given at the time of initiation of DNA synthesis. This shows that replication within replicons of Physarum polycephalum starts at an origin located in the center of each unit, proceeding bidirectionally from this origin.

Bromodeoxyuridine↗
PubMed1978

DNA replication in Physarum polycephalum: UV photolysis of maturing 5-bromo-deoxyuridine substituted DNA.

Combinations of 5-bromodeoxyuridine (BrdUrd) and 3H-deoxyadenosine (3H-DAdo) short pulses were given in the synchronous DNA-replication period of Physarum polycephalum. After a chase period, UV-photolysis products were analyzed on alkaline sucrose gradients. This strategy has allowed the following conclusions. a) at the time of master-initiation of DNA replication, points separated by 1.1-2.2x10(7) daltons of single strand DNA may initiate DNA synthesis. b) among these, only selected groups of replicons actually proceed in DNA replication at this time, while others appear to hold (later temporal sets of replicons). The origins of the ones that proceed in replication are separated from each other by a distance corresponding to 1.1-2.x10(7) daltons. c) regions in actual replication are separated from each other by increasing distances (up to 1.5x10(8) daltons single strand DNA) at later times in S.

Bromodeoxyuridine↗
PubMed1977

DNA replication in Physarum polycephalum: characterization of DNA replication products made in vivo in the presence of cycloheximide in strains sensitive and resistant to cycloheximide.

Synchronous plasmodia of cycloheximide-sensitive and cycloheximide-resistant strains of Physarum polycephalum were labelled with 3[H]-deoxyadenosine in pulse and pulse-chase experiments in presence and absence of cycloheximide. The replication products were studied with alkaline sucrose gradient sedimentation analysis. We show that the action of cycloheximide on DNA replication in Physarum is mediated through the ribosome, since the ribosomally located resistance also makes the plasmodial DNA replication refractile to the action of cycloheximide. Cycloheximide caused inhibition of three stages in DNA replication in the wild type: first, the formation of primary replication units ("Okazaki" size fragments), secondly, the ligation of primary units into secondary ("Replicon" size) units and thirdly, the ligation of secondary units into mature DNA.

Centrifugation, Density Gradient↗
PubMed1975

DNA replication in Physarum polycephalum: characterization of replication products in vivo.

Synchronous plasmodia of Physarum polycephalum in DNA synthesis were pulse-labelled with [oH]- thymidine for time periods of 15 seconds up to 9 minutes, or given a 30 seconds pulse followed by chase periods of 9 minutes up to 6 hours. Sedimentation analysis in alkaline sucrose gradients revealed at least five species of single stranded DNA14 molecules in the pulse experiments. Co-sedimentation of [14C]-labelled phage-DNA gave relative S-values of 5-7, 13-15, 23-25, 30 and 33-35 for these DNA molecules, all of which can be chased into DNA of higher molecular weight.

Cell Nucleus↗