Search PubMed⌕ Search

Biomedical subjects

O Dahl

Publications and source records attributed to O Dahl.

At least 91 records · Page 5Linked to original sources
PubMed1987

Mechanistic studies on the phosphoramidite coupling reaction in oligonucleotide synthesis. I. Evidence for nucleophilic catalysis by tetrazole and rate variations with the phosphorus substituents.

Tetrazole catalyzed reactions of a series of phosphoramidites, 5'-O-DMTdT-3'-O-P(OR1)NR2(2) (1a-h), with 3'-O-SiButPh2-6-N-benzoyl-dA (2a) in acetonitrile solution have been studied. It is found that the coupling rate depends very much on whether tetrazole is added before or after 2a, and that dialkylammonium tetrazolide salts are inhibitors. These and other facts are evidence that the reactions are subjected to nucleophilic catalysis by tetrazole, in addition to acid catalysis. The rate variations with phosphorus substituents of 1a-h are NEt2 greater than NPri2 greater than N(CH2CH2)O greater than NMePh, and OMe greater than OCH2CH2CN greater than OCHMeCH2CN greater than OCMe2CH2CN much greater than OC6H4Cl. The inhibitor properties of dialkylammonium tetrazolides have practical consequences for the efficiency of DNA syntheses, when in situ prepared phosphoramidites are used; the same would apply for segmented, simultaneous syntheses or syntheses where recycling is performed.

Indicators and Reagents↗
PubMed1987

Acute systemic toxicity of combined cis-diamminedichloroplatinum and hyperthermia in the rat.

To investigate the previously observed increased morbidity and mortality of combined cis-diamminedichloroplatinum (cis-DDP) and hyperthermia, BD IX rats were given 4 mg/kg cis-DDP i.p., waterbath hind leg heating (44 degrees C, 60 min) with resultant whole body hyperthermia, or combined treatment with or without systemic cooling. Cardiac blood and histopathologic sections of kidney, small intestine and liver were examined in rats sacrificed 2, 3 and 5 days after and femur bone marrow 5 days after treatment. In a separate experiment, the effect of systemic hyperthermia on renal function was tested. The most significant finding was a marked increase in cis-DDP induced renal damage by systemic hyperthermia, expressed as elevated creatinine levels and quantitatively enhanced proximal tubular necrosis. As both systemic hyperthermia and cis-DDP can result in primarily altered renal haemodynamics, it is postulated that relative tubular epithelial hypoxia and increased tubular exposure time to cis-DDP due to reduced tubular filtrate flow rate are likely mechanisms for the increased toxicity.

Animals↗
PubMed1987

Statistical analysis of clinicopathological features, radiotherapy, and survival in 170 cases of oligodendroglioma.

The postoperative survival time of 170 nonrandomized patients treated for cerebral oligodendrogliomas in Norway from 1953 to 1977 was studied. Survival times were significantly prolonged if postoperative irradiation was performed in addition to surgery (median survival time 26.5 vs. 38 months, p = 0.039). In the group without postoperative radiotherapy, the 5-year rate of survival was 27% compared with 36% in the irradiated patients. The respective survival rates after 8 years were 14% versus 17%; thus, there was little effect on long-term survival. Irradiation appears not to be of benefit after "total" removal. Patients with partly resected lesions appeared to benefit from postoperative radiotherapy; the median survival period after subtotal tumor resection was 37 months with and 26 months without radiotherapy (p = 0.0089). The findings also indicate that irradiation doses between 40 and 50 Gy were as effective as doses between 50 and 60 Gy in increasing the patients' probability of surviving 5 years after subtotal tumor resection. Since the risk of radiation necrosis is proportional to the dose applied, the lower dose is recommended. These conclusions were also valid when adjustments were made for prognostically significant histological and clinical features.

Brain Neoplasms↗
PubMed1986

Application of 2-cyanoethyl N,N,N',N'-tetraisopropylphosphorodiamidite for in situ preparation of deoxyribonucleoside phosphoramidites and their use in polymer-supported synthesis of oligodeoxyribonucleotides.

Deoxyribonucleoside phosphoramidites are prepared in situ from 5'-O,N-protected deoxyribonucleosides and 2-cyanoethyl N,N,N',N'-tetraisopropylphosphorodiamidite with tetrazole as catalyst, and the solutions applied directly on an automatic solid-phase DNA synthesizer. Using LCAA-CPG support and a cycle time of 12.5 min, oligonucleotides of 16-25 bases are obtained with a DMT-efficiency per cycle of 98.0-99.3%. The crude and fully deblocked products are of a purity comparable to that obtained using purified phosphoramidites. In case of d(G)16 the product was difficult to analyse and a better product was not obtained using doubly protected (O-6 diphenylcarbamoyl) guanine.

Base Sequence↗
PubMed1985

Doxifluridine (5'-dFUrd) in patients with advanced colorectal carcinoma. A phase II study.

Infusion of 5'-dFUrd (2.0-3.0 g/m2 over 1 h on days 1-5 every 3rd week) resulted in one partial response in 21 patients with advanced and progressing colorectal cancer. No patient had received chemotherapy before the 5'-dFUrd trial. Hematological and gastrointestinal toxicity were generally mild. In 4 patients peripheral neurotoxicity was diagnosed during treatment, whereas transient cerebellopathy was observed in one. Cardiac side effects (repeated angina pectoris following 5'-dFUrd infusion) led to discontinuation of treatment after two courses in one patient. It is concluded that 5'-dFUrd at the above doses is not superior to conventional 5-FU treatment in colorectal cancer. Neurological and cardiac side effects are rare but may be a problem in individual patients.

Angina Pectoris↗
PubMed1985

Antibody to hepatitis B surface antigen among employees in the National Hospital, Oslo, Norway: a prevalence study.

During the last decade, several studies of serologic markers of hepatitis B virus infections in hospital personnel have demonstrated an increased prevalence of antibodies to hepatitis B virus (anti-HB) compared with the general population. Norway has a very low incidence rate of hepatitis B as seen on a global scale, and this study was performed to evaluate the infection risk by hospital workers in such environments. The employees, 2,546 (94.7% of the population), in the 800-bed National Hospital in Oslo were tested for antibody to hepatitis B surface antigen (anti-HBs) in serum. Five per cent (128 persons) were anti-HBs-positive; this was only slightly higher than that in the general Norwegian population. Male employees were more often positive than females (7.0% vs. 4.4%). Staff more than 50 years of age or with 16 or more years of employment in the health services had a rate twice as high as the rest of the employees. Staff in the porter services (mostly men) had a higher rate than others, whereas the rates in the different professional groups showed no statistical differences. Contrary to many other studies, significant differences in prevalence according to frequency of patient contact or blood handling were not found.

Adolescent↗