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Biomedical subjects

K Hemminki

Publications and source records attributed to K Hemminki.

At least 361 records · Page 20Linked to original sources
PubMed1988

Detection of DNA adducts by postlabelling with 3H-acetic anhydride.

A method has been developed for detecting 7-alkylguanines which is based on derivatization of hydroxyl and primary amino groups with 3H-acetic anhydride. The derivatization procedure is devised for 7-methylguanine, with examination of reaction kinetics. The method is applied to the detection of the isomeric styrene oxide-guanine adducts; styrene-7,8-oxide is the active metabolite of styrene. The procedure can be used as a postlabelling method for the simultaneous detection of several adducts after selective depurination of 7-alkylguanines from DNA.

Acetic Anhydrides↗
PubMed1988

Determination of cisplatin in blood compartments of cancer patients.

A new approach has been developed to determine the levels of cisplatin in different blood compartments of treated cancer patients. The cisplatin content of plasma, plasma proteins, red blood cells and white blood cell DNA can be measured by atomic absorption spectroscopy (AAS). The approximate levels of cisplatin were 10, 500 and 100 ng Pt/ml blood in plasma, plasma proteins and haemoglobin, respectively; in white blood cell DNA, the level of cisplatin was about 1 pg/microgram DNA. Preliminary data indicate that cancer patients have measurable amounts of cisplatin in their blood compartments. Furthermore, antibodies have been raised against cisplatin-DNA, with which 50% inhibition occurs at 50-100 fmol cisplatin. The detection limit is about 1-10 fmol cisplatin/microgram DNA. Enzyme immunoassay techniques will be used to detect cisplatin-DNA adducts in white blood cell DNA of cancer patients.

Cisplatin↗
PubMed1987

Kinetics of hydrolysis in vitro of nornitrogen mustard, a metabolite of phosphoramide mustard and cyclophosphamide.

A gas chromatographic (GC-ECD) method was developed for the determination of nornitrogen mustard (NOR) and its hydrolysis products. The method was based on derivatization by heptafluorobutyric anhydride. The structures of the derivatives of NOR were established by GC-MS. The method was used to characterize the rate of transformation of NOR and phosphoramide mustard (PAM), important metabolites of cyclophosphamide, into secondary products in vitro at 37 degrees C and pH 7.4. The rate of disappearance of NOR had a half-life of 20 min. The half-life of appearance of N-(2-chloroethyl)-N-(2-hydroxyethyl)amine (NOR-OH) was 19 min. While most NOR appeared to be converted to NOR-OH, the yield of N,N-bis(2-hydroxyethyl)amine (NOR-OH-OH) was a small fraction of the starting material. The disappearance of NOR, when PAM was used as a starting material, had a half-life of 19 min; in these experiments NOR-OH and NOR-OH-OH were relatively much more abundant compared to when NOR was used as the starting material.

Amides↗
PubMed1987

DNA-binding products of nornitrogen mustard, a metabolite of cyclophosphamide.

Nornitrogen mustard was shown to bind to the N-7 position of guanine in DNA and guanosine. The initial binding product was NOR-G. N-(2-chloroethyl)-N-[2-(7-guaninyl)ethyl]amine but it was converted with time to a hydroxylated derivative. NOR-OH-G and to a cross-link, G-NOR-G. The NOR-OH-G adduct was also seen in the reactions of aziridineethanol. The cross-link appeared to depurinate slower than the two other adducts so that it was the main adduct after 72 h of incubation. The rate of reaction was higher at pH 6.0 than at pH 7.4 but even at pH 7.4 adducts were formed. When isolated NOR-G was incubated it was shown to be converted exclusively to NOR-OH-G at pH 5 but at pH 7.4 the main product was a dimer. The half-life of NOR-OH-G formation at pH 7.4 and 37 degrees C was 4 h. The mustard arms of NOR-G and NOR-OH-G had pKa values of about 7.5 and 10, respectively. This was probably related to the somewhat higher rate of imidazole ring-opening of NOR-OH-gua as compared to NOR-gua. The lability of the imidazole ring of the guanosine adducts of nornitrogen mustard is intermediate to those of phosphoramide mustard and nitrogen mustard.

Chemical Phenomena↗
PubMed1987

Mono- and bifunctional binding of cis-diamminedichloroplatinum(II) to dinucleotides.

cis-Diamminedichloroplatinum(II) (cis-Pt) was reacted with four homodinucleotides (GpG, ApA, CpC, and UpU) and six heterodinucleotides (GpC, CpG, GpU, UpG, GpA, and ApG) at pH 6, and the reaction products were purified by HPLC. The most important products were characterized by 1H-NMR spectra. In all the heterodinucleotides except the ones containing uridine the main Pt-adduct was an intramolecular cross-link, but monofunctional adducts and intermolecular cross-links were also detected. Intramolecular cross-links were also formed with GpU and UpG but the amounts of them were about the same as the amounts of intermolecular cross-links. In the case of homodinucleotides GpG gave almost entirely intramolecular cross-links, in which cis-Pt was chelated between the N-7 atoms of two guanines. cis-Pt reacted also with ApA forming both monofunctional and bifunctional Pt-adducts. The main adducts were intramolecular cross-links. cis-Pt reacted equally well with all guanosine-containing dinucleotides, while the reaction with ApA was much slower. With CpC and UpU no reaction products were formed.

Bicarbonates↗
PubMed1986

Reaction products of styrene oxide with deoxynucleosides and DNA in vitro.

The reaction of styrene oxide with deoxynucleosides and DNA were carried out in aqueous conditions at pH 7.4 and in acetic acid, to prepare large quantities of reaction products. The purification of the products were performed by HPLC and characterized by UV spectra in neutral, acid and alkali pH. The main products identified were 7-, N2-, O6-alkyldeoxyguanosine, 1-, N6-alkyldeoxyadenosine, N4-, 3-, and O2-alkyldeoxycytidine. In acetic acid additionally 3-alkyladenine and O4-alkylthymidine were formed. In DNA incubations the dominant product isolated was 7-alkylguanine. N2-guanine was also detected.

Alkylation↗
PubMed1986

Binding of styrene oxide to amino acids, human serum proteins and hemoglobin.

The covalent binding of 3H-styrene oxide to amino acids, and whole human blood was investigated in vitro. After reaction, serum, and red cells were separated, and proteins were digested into amino acids; styrene oxide derivatives were isolated by HPLC. The order of binding to free amino acids was cysteine much greater than histidine greater than lysine greater than serine. In serum proteins and hemoglobin cysteine-derivatives predominated. When styrene oxide was reacted with free cysteine and with proteins two isomers were observed. These were likely to present binding through the alpha and beta carbon of styrene oxide, and their abundance was about 2:1.

Amino Acids↗
PubMed1986

DNA adducts in experimental cancer research.

The role of DNA adducts in the initiation of cancer is scrutinized in this presentation. Work on the activation of oncogenes, particularly on ras, has provided new evidence to link DNA adducts and tumour formation. Polycyclic hydrocarbons and nitroso compounds can cause activation of ras oncogenes through a defined point mutation. The properties of two DNA binding agents, styrene oxide and cisplatin are discussed. Styrene oxide is a versatile electrophile causing numerous adducts; cisplatin has a high specificity towards guanine-N-7 and cross-link formation. Finally, the relation of specific adducts to carcinogenic potency as defined by TD50 values is investigated. For small alkyl groups, O-alkylation of bases correlates with potency but among others, particularly the bulky carcinogens, 7-alkylguanines appear as correlates of potency. Most such potent agents forming 7-alkylguanines induce depurination and imidazole ring-opening.

Alkylation↗
PubMed1986

Properties of 7-substituted deoxyguanosines formed by cis-diamminedichloroplatinum(II).

cis-Diamminedichloroplatinum(II) (cis-Pt) was reacted with deoxyguanosine and guanosine at pH 6 and the reaction products were purified by HPLC. The products were characterized by UV and 1H-NMR spectra and by incubating cis-Pt with 7-methylguanosine, N2-methylguanosine, [8-3H]guanosine and [U-14C]guanosine. The main product was shown to be a cross-link, in which cis-Pt was linked to the N-7 atoms of two guanines. In the other product cis-Pt was bound monofunctionally to the N-7 atom of guanine. The cis-Pt adducts had many unique properties compared to other N-7 alkylated guanosines. When cis-Pt was incubated with [8-3H]guanosine, the products still had their 8-3H-radioactivity. At pH 10 at room temperature the imidazole ring of the monoadduct was not opened in 20 days, while the half-life of imidazole ring-opening for 7-methyldeoxyguanosine was 21.5 min. The half-lives of acid-catalyzed depurination in 0.1 M HCl at 70 degrees C for deoxyguanosine, 7-methyldeoxyguanosine and the monoadduct were 30 s, 48 s and 35 min, respectively.

Chromatography, High Pressure Liquid↗
PubMed1986

Stabilities of 7-alkylguanosines and 7-deoxyguanosines formed by phosphoramide mustard and nitrogen mustard.

7-Alkylguanosine and 7-alkyldeoxyguanosine were prepared from phosphoramide mustard and nitrogen mustard in nonaqueous conditions. The guanosine products were N-(2-chloroethyl)-N-[2-(7-guanosinyl)ethyl] phosphorodiamidic acid, and N-(2-chloroethyl)-N-[2-(7-guanosinyl)ethyl]methylamine, respectively. These were also formed in aqueous reactions but they rapidly underwent secondary reactions. The half-life of the phosphoramide mustard-guanosine adduct was 3.1 h (37 degrees C, pH 7.4) and that of the nitrogen mustard adduct 1 h (25 degrees C, pH 7.4), as determined by HPLC. The half-lives of the respective adducts for imidazole ring-opening were 9.5 h and 0.78 h (37 degrees C, pH 7.4). The respective deoxyguanosine derivatives depurinated with half-lives of 8.5 h and 1.6 h (25 degrees C, pH 4.2). The mustard adducts are notably more labile than simple alkyl substituted guanosines and deoxyguanosines.

Alkylation↗
PubMed1986

Characterization of reaction products between styrene oxide and deoxynucleosides and DNA.

Styrene oxide was reacted with deoxynucleosides and DNA in aqueous buffer at pH 7.4. The products were purified by HPLC, characterized by UV spectroscopy and by chemical ionization mass spectrometry. The main products identified were 7-alkyl-, N2-alkyl- and O6-alkyldeoxyguanosine, 1-alkyl-, and N6-alkyldeoxyadenosine, N4-alkyl-, 3-alkyl- and O2-alkyldeoxycytidine and 3-alkylthymidine. The relative yields of alkylated deoxynucleosides were dG greater than dC greater than dA greater than T. In the reactions of styrene oxide with DNA the dominant product isolated was 7-alkylguanine but N2-alkylguanine was also detected.

Animals↗
PubMed1986

Stability of 7-alkyldeoxyguanosines of trichloropropylene oxide, epichlorohydrin and glycidol.

Deoxyguanosine was reacted with trichloropropylene oxide (TCPO), epichlorohydrin and glycidol in aqueous solution and the products were isolated by high pressure liquid chromatography (HPLC). For each compound 7-alkyldeoxyguanosine was the main adduct; TPCO reacted about 3 times faster than epichlorohydrin and about 10 times faster than glycidol. The pKa's of the 7-alkyldeoxyguanosines were 6.7, 6.8 and 6.9 for the TCPO-, epichlorohydrin-, and glycidol-adducts, respectively. The respective half-lives of imidazole ring-opening were 6.3, 15 and 27 hrs (pH 8.5, 28 degrees) and those of depurination 1.9, 3.4 and 4.4 hrs (pH 5.5, 28 degrees).

Alkylation↗
PubMed1986

Spontaneous abortions among women working in the pharmaceutical industry.

A register based study was conducted on the pregnancy outcome of female workers in eight Finnish pharmaceutical factories to determine whether they had a higher risk of spontaneous abortion than the general population or matched controls. Information about all female workers who had been employed in the factories during the years 1973 or 1975 (four factories) to 1980 was obtained from the employers. The workers' pregnancy data were collected from the nation wide hospital discharge register and polyclinic data of hospitals from 1973 to 1981. The total number of 1795 pregnancies included 1179 deliveries, 142 spontaneous abortions, and 474 induced abortions. The spontaneous abortion rate (the number of spontaneous abortions X 100, divided by the number of spontaneous abortions plus the number of births) during employment was 10.9% and before/after employment 10.6%. The rate for all the women in the corresponding central hospital districts was 11.3% [corrected] during the study period. A case-control study was also carried out in which the cases were 44 women who had a spontaneous abortion during employment in the pharmaceutical factory. Three age matched female pharmaceutical factory workers who had given birth to a child were chosen as controls for every case. The information about occupational exposures was collected from questionnaires completed by the occupational physician or nurse at the factory. The response rate was 93%. Exposure to chemicals was more common among the cases than among the controls. For methylene chloride, a solvent commonly used in the pharmaceutical industry, the increase in odds ratio of borderline significance (odds ratio 2.3, p = 0.06). In a logistic regression model (which included oestrogen exposure, solvent exposure frequency of the usage, and heavy lifting) the odds ratio was increased for oestrogens (odds ratio 4.2, p = 0.05) and for continuous heavy lifting (odds ratio 5.7, p = 0.02). The odds ratio for spontaneous abortions was greater among those exposed to four or more solvents (odds ratio 3.5, p=0.05) than among those exposed to one to three solvents (odds ration 0.8, p=0.74).

Abortion, Spontaneous↗
PubMed1986

Reactions of nitrogen mustards with DNA.

This paper summarizes the mechanism of action and the covalent modifications of nucleic acids, nucleotides and nucleosides by nitrogen mustards. Nitrogen mustards react preferentially with guanine N7 in DNA in vitro. A few minor adducts have been characterized. Cross-links of nitrogen mustard and metabolites of cyclophosphamide that have been identified are diguanyl derivatives linked at N7. It is essential that studies of alkylation products in vivo be carried out, since characterization of alkylation products of cytostatic drugs should provide further insight into the mechanisms of cytotoxicity and, consequently, facilitate the development of more efficient anticancer agents. Furthermore, the monitoring of DNA adducts of therapeutic significance in patients may provide new avenues for the individualization of cancer therapy.

Acrolein↗