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Biomedical subjects

B Pettersson

Publications and source records attributed to B Pettersson.

At least 73 records · Page 4Linked to original sources
PubMed1995

Simultaneous quantitation of methotrexate and its two main metabolites in biological fluids by a novel solid-phase extraction procedure using high-performance liquid chromatography.

We have developed an assay for the simultaneous determination of methotrexate (MTX) and its main metabolites, 7-hydroxymethotrexate (7-OHMTX) and 2,4-diamino-N10-methylpteroic acid (DAMPA) in plasma, urine and saliva meeting the requirement of rapidity for routine use in high-dose MTX therapy and the requirement of sensitivity for its potential use in therapeutic drug monitoring in low-dose MTX therapy. Sample preparation is based on solid-phase extraction using C8 Isolute cartridges. Chromatographic separation was achieved with a reversed-phase column (C18), and quantitation by subsequent exposure to UV light of 254 nm, which converted MTX and its two metabolites by photolytic oxidation to fluorescent products. The recoveries of MTX, 7-OHMTX and DAMPA from plasma at 100 nmol/l were 85.8, 91.1 and 102.3%, respectively. The limits of detection for MTX, 7-OHMTX and DAMPA in plasma and saliva were 0.1 nmol/l. In urine the limit of detection was 10 nmol/l for all compounds. The limits of quantitation in plasma and saliva were 0.5 nmol/l for all compounds.

Chromatography, High Pressure Liquid↗
PubMed1995

Parity and risk of thyroid cancer: a nested case-control study of a nationwide Swedish cohort.

The association between parity and risk of thyroid cancer was examined in a case-control study nested within a cohort of Swedish women born 1925-60. A total of 1,409 cases of thyroid cancer were compared with 7,019 age-matched controls. Odds ratios (OR) and 95 percent confidence intervals (CI) were calculated as estimates of relative risk. A weak association was found between parity and risk of thyroid cancer (OR for ever-parous women cf nulliparous was 1.1, CI = 1.0-1.3). For the subset of papillary cancers, there was a significantly increased risk (OR for ever-parous cf nulliparous = 1.3, CI = 1.0-1.6), and among women diagnosed at the age of 50 or older, there was a positive linear trend with increasing number of livebirths. Women during the first year after a livebirth had an increased risk of thyroid cancer compared with women who delivered 10 or more years before; this association was most prominent among uniparous women (OR = 2.5, CI = 1.1-5.9). An increased risk was also apparent for age over 20 years at livebirth (among uniparous women) and age over 25 years at last livebirth (among multiparous women). A negligible effect of parity on thyroid cancer risk was seen, but each livebirth may have a short-term and age-dependent promoting effect.

Adenocarcinoma, Follicular↗
PubMed1995

Phylogeny of Serpulina based on sequence analyses of the 16S rRNA gene and comparison with a scheme involving biochemical classification.

Twenty-one putative Serpulina strains, representing six proposed biochemical groups, were selected for phylogenetic studies based on 16S rRNA sequencing. The biochemical groups were distinguished by the degree of beta-haemolysis, indole production, hippurate hydrolysis and alpha-galactosidase-, and beta-glucosidase activity. The 16S rRNA sequences of the U2 to U5 region, including three evolutionarily variable regions, from representatives of each biochemical group were determined by automated solid phase DNA sequencing after in vitro amplification by the polymerase chain reaction (PCR). The sequences generated were 532 nucleotides in length. Sequence alignments showed that all the strains were closely related, with six informative positions in the region sequenced. A dendrogram was constructed from these data and compared with the tentative biochemical classification. The results support the proposed biochemical classification and indicate that at least five genetic variants of the genus Serpulina can be identified.

Animals↗
PubMed1995

Identification of the causative agent of granulocytic ehrlichiosis in Swedish dogs and horses by direct solid phase sequencing of PCR products from the 16S rRNA gene.

Seven Swedish isolates of Ehrlichia species from the blood of four dogs and three horses with clinical granulocytic ehrlichiosis, were identified by direct solid phase DNA sequencing of polymerase chain reaction (PCR) products from the 16S rRNA gene. The amplified DNA fragments were produced with primers complementary to the universal regions, U1, U2, U5 and U8 of the 16S rRNA molecule. Identical sequences were obtained from all seven isolates. This nucleotide sequence was similar to the sequences deposited in GenBank for Ehrlichia phagocytophila and E equi. The sequence of the Swedish ehrlichiae differed in two nucleotide positions from the E phagocytophila sequence and in three positions from the E equi sequence, and it is tentatively proposed that it is a subspecies of one of these two. The alignment of the sequence of the Swedish isolates with a recently deposited sequence from human cases of ehrlichiosis in the USA revealed 100 per cent identity in a segment of about 1400 bp.

Animals↗
PubMed1995

Classification of Erysipelothrix strains on the basis of restriction fragment length polymorphisms.

Restriction fragment length polymorphisms of the 16S rRNA genes of Erysipelothrix strains were studied by cleavage of the chromosomal DNA with restriction endonuclease EcoRI, followed by hybridization to a 420-bp internal fragment of the 16S rRNA gene. Thirty-two Erysipelothrix type and reference strains were classified, together with seven field strains. Reference strains of all serotypes and the type strains of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum were included. Nine ribopatterns were observed. Pattern A was represented by 16 strains and included strains of serotypes 1b, 2 to 8, 11 to 13, 15 to 17, 19, and 23. Pattern B was represented by two strains (serotypes 1a and 9). Pattern C was represented by five strains (serotypes 5, 6, and 21). Pattern D was represented by one strain of serotype 4. Pattern E was represented by 11 strains of serotypes 2, 7, 10, 20, 22, 24, and 25. Patterns F, G, H, and I were each represented by a single strain of serotypes 26, 2, 18, and 3, respectively. All the different ribopatterns had some bands in common. Patterns B, C, and D were most similar to pattern A, while patterns F, G, H, and I resembled pattern E. Partial sequencing of the 16S rRNA gene of nine selected strains resulted in three different sequences, i.e., the typical E. rhusiopathiae sequence, the E. tonsillarum sequence, and a third sequence found for two strains. Strains of the same serotype were found to have different ribopatterns as well as different partial 16S rDNA sequences.

Animals↗
PubMed1994

NotI linking clones as a tool for joining physical and genetic maps of the human genome.

To study the connection among NotI linking clones, CpG islands, and genes, the sequence surrounding 143 NotI sites was determined. These NotI linking clones were isolated from human chromosome 3-specific libraries and contain an average C + G content of 65%. These clones represent sequence-tagged sites that can be positioned onto chromosome maps and used for generating a long-range NotI map of the human genome. A majority (about 90%) of these clones contain transcribed sequences, as detected by Northern blot hybridization, providing an efficient link between physical and functional (genetic) maps. The GenBank nucleotide database was searched with sequences from these NotI linking clones. For many clones, homology was found to human and other vertebrate genes. About 20 clones contained various repeats in their sequences and may represent microsatellite loci. Most of these NotI linking clones therefore represent evolutionarily conserved DNA fragments and also can be used for comparative genome mapping of other mammalian species. In addition, approximately 20% of all sequenced human CpG island-containing genes and more than 12% of all well-characterized human genes were found to possess NotI restriction sites. This is at least 2-5 times more than has been previously estimated and suggests that NotI sites have a much stronger association with genes.

Animals↗
PubMed1994

Shot-gun sequencing strategy for long-range genome mapping: a pilot study.

We have recently proposed a strategy for construction of long-range physical maps based on random sequencing of NotI linking and jumping clones. Here, we present results of sequence comparison between 168 NotI linking (100 of them were sequenced from both sides) and 81 chromosome 3-specific jumping clones. We were able to identify 14 NotI jumping clones (17%), each joined with two NotI linking clones. The average size of chromosomal jumps was about 650 kb. The assembled 42 NotI genomic fragments correspond to 12-15% of chromosome 3. These results demonstrate the value of random sequencing of NotI linking and jumping clones for genome mapping. This mapping proposal can be used for connecting physical and genetic maps of the human genome and will be a valuable supplement to YAC and cosmid library based mapping projects.

Animals↗
PubMed1994

Prognostic factors and relapse patterns in early-stage cervical carcinoma after brachytherapy and radical hysterectomy.

Patients with cervical carcinoma FIGO stage IB and IIA (n = 167) treated with brachytherapy, radical hysterectomy, and pelvic lymphadenectomy at the University Hospital of Uppsala were evaluated, and a multivariate analysis was performed to reveal clinical and histopathological variables of predictive value of recurrence. The 5-year survival rate was 90%. Nineteen patients developed recurrent disease (11%), 15 of whom died. Patient age, clinical stage, type, and histologic grade of tumor did not indicate an increased risk of recurrence. However, multiparity (3 children or more; relative risk, RR = 4.6), lymph node metastases (RR = 6.4), tumor size (RR = 5.1), and residual carcinoma in the hysterectomy specimen (RR = 3.4) were important predictive indicators of recurrence. The median interval from initial treatment to the diagnosis of recurrence was 15 months. The majority of recurrences occurred during the first 2 years after treatment (74%) and most of them had symptoms (84%). Only three patients with recurrence were diagnosed within our surveillance program. The data suggest that surveillance for recurrence can be made more cost efficient with a more individualized follow-up during the first 2 years after treatment, concentrating on the patients with high-risk factors such as large tumors, residual carcinoma after irradiation therapy, and/or lymph node metastases.

Adult↗
PubMed1994

Analysis of 2-chloro-2'-deoxyadenosine in human blood plasma and urine by high-performance liquid chromatography using solid-phase extraction.

A reversed-phase high-performance liquid chromatographic (HPLC) method for the simultaneous determination of a new and promising anticancer drug, 2-chloro-2'-deoxyadenosine (CdA), and its metabolite, 2-chloroadenine (CAde), in plasma and urine was developed. A solid-phase extraction procedure with guaneran as internal standard (IS) was used. Plasma (1 ml) or diluted urine (1/100) mixed with 1 ml of phosphate buffer (10 mM, pH 6.5) was applied on a C8 isolute cartridge, which was prewashed with acetonitrile and phosphate buffer. The cartridge was further washed with 2.5 ml of 1% acetonitrile/phosphate buffer and 2.5 ml of hexane/dichloromethane (50/50). The compounds were eluted from the cartridge with 2.5 ml 5% MeOH in ethyl acetate. Chromatographic separation was achieved on C18 column eluted isocratically with phosphate buffer (10 mM, pH 3.0) containing 11% MeOH and 7% acetonitrile, and ultraviolet (UV) detection at 265 nm. Recoveries of CdA and CAde at 100 nmol/L were 90.6 +/- 4.9 and 98.7 +/- 7.8%, respectively. Recovery of IS was 96.1 +/- 6.1% at 250 nmol/l. The inter- and intraday coefficients of variation (CV) were < 10% at different concentrations within the range 1-500 nmol/L for both substances. In plasma, limits of detection of CdA and CAde were 1 and 2 nmol/L, respectively. In urine, the limit of detection was 100 nmol/L for both compounds. Standard curves were linear up to 50 and 500 nmol/L for urine and plasma, respectively. The present method will be a useful tool for further investigations of the pharmacokinetics of CdA in patients treated with different routes of administration.

Chromatography, High Pressure Liquid↗
PubMed1994

Sequence analysis of 16S rRNA from mycoplasmas by direct solid-phase DNA sequencing.

Automated solid-phase DNA sequencing was used for determination of partial 16S ribosomal DNA sequences of mycoplasmas. The sequence information was used to establish phylogenetic relationships of 11 different mycoplasmas whose 16S rRNA sequences had not been determined earlier. A biotinylated fragment corresponding to positions 344 to 939 in the Escherichia coli sequence was generated by PCR. The PCR product was immobilized onto streptavidin-coated paramagnetic beads, and direct sequencing was performed in both directions. One previously unclassified avian mycoplasma was found to belong to the Mycoplasma lipophilum cluster of the hominis group. Microheterogeneities were discovered in the rRNA operons of Mycoplasma mycoides subsp. mycoides (SC type), confirming the existence of two different rRNA operons. The 16S rRNA sequence of M. mycoides subsp. capri was identical to that of M. mycoides subsp. mycoides (type SC), except that no microheterogeneities were revealed. Furthermore, automated solid-phase DNA sequencing was used to identify a mycoplasmal contamination of a cell culture as Mycoplasma hyorhinis, which proved to be very difficult by conventional methods. The results suggest that the direct solid-phase DNA sequencing procedure is a powerful tool for identification of mycoplasmas and is also useful in taxonomic studies.

Base Sequence↗
PubMed1994

The use of ethanol-tagged mannitol in transurethral resection of the prostate does not alter the bleeding time in patients who absorb irrigation fluid.

To increase patient safety ethanol tagging of irrigation fluid is practised at several hospitals in Sweden to detect absorption of irrigation fluid during transurethral prostatic resection. Using this method it is found that almost half of the patients undergoing transurethral prostatic resections absorb irrigation fluid to some extent. Patients absorbing irrigation fluid bleed more than others. The phenomenon has been blamed on the open veins and sinusoides. Further, these patients are older, have larger prostates and longer operating times. To exclude an effect of ethanol-tagged irrigation fluid on the skin bleeding time this was measured before and after the operation in 57 patients. In 18 (32%) 160-1760 ml of irrigation fluid was absorbed, and in 9 patients over 480 ml. No difference in skin bleeding time emerged between absorbers and non-absorbers, and absorbers showed no differences in bleeding time between preoperative and postoperative values. There was a slight but insignificant decrease in the skin bleeding time after the operation in both absorbers and non-absorbers.

Absorption↗
PubMed1993

Solid phase DNA minisequencing by an enzymatic luminometric inorganic pyrophosphate detection assay.

A solid phase DNA sequencing method for non-radioactive detection of single base changes without the need for electrophoresis is presented. The concept relies on the detection of DNA polymerase activity by an enzymatic luminometric inorganic pyrophosphate detection assay (P. Nyrén, 1987, Anal. Biochem. 167, 235-238). Immobilized DNA fragments amplified with the polymerase chain reaction are used as template. A detection primer is annealed in front of the mutation and four aliquots of this mixture are incubated with DNA polymerase and one of the four different dideoxynucleotides. The presence or absence of an incorporated dideoxynucleotide is thereafter monitored by the release of inorganic pyrophosphate during the following primer extension step. We show that the concept can be used for sequencing of single bases as well as stepwise analysis of several subsequent bases.

Base Sequence↗
PubMed1993

On the interaction between cytosine arabinoside and etoposide in vivo and in vitro.

Cytosine arabinoside (ara-C) and etoposide are often used in combination in the treatment of acute myelocytic leukemia (AML). The intracellular phosphorylation of ara-C to its 5'-triphosphate (ara-CTP) is a prerequisite for its cytotoxic effects. It has been shown in vitro that etoposide can impair the formation of ara-CTP in leukemia cells. The present study was undertaken in order to elucidate whether this interaction may be of clinical importance. Leukemia cells were isolated from 3 patients with acute myelocytic leukemia and incubated in medium (RPMI-1640) with or without 10% fetal calf serum or in human plasma. When the cells were incubated in RPMI-1640 with ara-C (10 mumol/l) and etoposide during 2 h, the formation of ara-CTP was decreased to 71 +/- 18 (mean +/- S.D.) and 30 +/- 15% of control at 1 and 10 micrograms/ml etoposide, respectively. When the cells were incubated in human plasma, the formation of ara-CTP was not influenced by the presence of etoposide (101 +/- 6 and 103 +/- 20% at 1 and 10 micrograms/ml etoposide). When incubated in RPMI supplemented with 10% fetal calf serum, the corresponding figures were 81 +/- 8 and 70 +/- 20%. Six patients with AML were therefore treated with ara-C 0.5 or 1.0 g/m2 as a 2-h infusion every 12 h and, during 1 h before the second ara-C infusion, 100 or 200 mg/m2 etoposide was administered. The median change in the AUC of cellular ara-CTP between the first and second ara-C dose was 0% (-37 to +21%). The corresponding median change in rate of accumulation of ara-CTP in leukemia cells was 12% (-26 to +110%). The concentration of etoposide in plasma during the ara-C infusion was 18.7 +/- 5.1 micrograms/ml while the non-protein bound etoposide was 0.73 +/- 0.34 micrograms/ml. Thus, despite exposure to higher etoposide concentrations in vivo than in vitro, no impairment of ara-CTP formation was seen in the patients. This corresponds to the results obtained when leukemic cells were incubated in plasma. It is concluded that the inhibition of ara-CTP formation by etoposide seen in vitro is offset by the high protein binding of etoposide in plasma (96%) and that etoposide does not impair the formation of ara-CTP in leukemia cells in vivo during treatment with standard-dose etoposide.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

In vivo accumulation of etoposide in peripheral leukemic cells in patients treated for acute myeloblastic leukemia; relation to plasma concentrations and protein binding.

Since etoposide interacts with the nuclear enzyme topoisomerase II, the drug concentrations in the malignant cells during chemotherapy may have clinical correlates. Plasma protein binding of etoposide is extensive (94%) and alterations of the non-proteinbound fraction affect pharmacokinetic behavior of the drug. The pharmacokinetics of etoposide was therefore studied in plasma, total and non-proteinbound concentrations, and in leukemic cells isolated from peripheral blood samples from 22 patients after the first dose of the induction treatment for acute myelocytic leukemia. Fourteen patients received 100 mg/m2 and eight patients 200 mg/m2 as a 1 h infusion. The mean area under the concentration versus time curve AUC(0-infinity) in plasma was at the lower dose level 78.4 +/- 29.1 (mean +/- S.D.) micrograms/ml x h and 201.0 +/- 56.5 micrograms/ml x h at the higher dose level. The fraction of non-proteinbound etoposide in plasma was 5.2 +/- 3.4 and 5.4 +/- 2.1% in the two treatment groups. AUC(0-16h) in leukemic cells was 8.4 +/- 8.7 and 22.4 +/- 12.1 micrograms/ml x h at the two dose levels, respectively. The cellular etoposide concentration was 12.1 +/- 7.9 and 14.7 +/- 5.1% of the plasma concentration at the end of the infusion. The interpatient variability in cellular drug levels was considerable and exceeded the variability in plasma concentrations. Cellular accumulation of etoposide could be important for treatment outcome.

Adult↗
PubMed1992

On the biochemical modulation of 6-mercaptopurine by methotrexate in murine WEHI-3b leukemia cells in vitro.

The chemicals 6-mercaptopurine (6-MP) and methotrexate (MTX) are the cornerstones in the maintenance treatment of acute lymphoblastic leukemia. The intracellular metabolism of 6-MP to 6-thioguanosine nucleotides (TGN) via 6-thioinosine 5'-monophosphate (TIMP) is crucial for its cytotoxic effect. MTX inhibits purine de novo synthesis and thereby increases the intracellular PRPP being a substrate for the phosphoribosylation of 6-MP to TIMP. Hypoxanthine has been shown to inhibit the uptake of 6-MP over the cell membrane and the phosphoribosylation of 6-MP to TIMP. We have previously shown that the conversion of TIMP to TGN decreases at 6-MP concentrations above 5 microM in vitro. The aim of the present study was therefore to investigate the effect of MTX increasing the PRPP and TIMP concentrations and of hypoxanthine decreasing the TIMP concentration on the formation of TGN from TIMP. Murine myelomonocytic leukemia cells (WEHI-3b) were treated with 6-MP in vitro. The drug concentration was kept constant by continuous addition of 6-MP during the experiment. With this technique, the concentration of TGN begins to decrease already at 6-MP concentrations above 2 microM. The addition of 0.2 microM MTX 6 h before 6-MP strongly inhibited the purine de novo synthesis, decreased the ATP, and increased the PRPP concentration 4-fold. The intracellular concentrations of TIMP and to a lesser extent TXMP also increased. The concentrations of the TGN were, however, basically unaffected by the preincubation with MTX. Simultaneous addition of 20-50 microM hypoxanthine and 6-MP decreased the accumulation of all cellular 6-MP metabolites. It is concluded that the synergistic cytotoxic effect of the combination of 6-MP and MTX is not based on biochemical modulation of the 6-MP metabolism by MTX.

Animals↗
PubMed1992

Reduced risk of hip fracture in women with endometrial cancer.

The effect of excessive endogenous oestrogens on the risk of hip fracture was investigated in a population-based cohort of 2111 women with endometrial carcinoma who were followed up from age 50 years regarding the occurrence of a first hip fracture. Overall, 77 cases of hip fracture were observed, as against 120.8 expected, which meant a significantly reduced relative risk, standardized incidence ratio (SIR) = 0.6, 95% confidence interval (CI): 0.5-0.8. This possible protective effect was significant for cervical fractures, SIR = 0.6 (95% CI: 0.4-0.8), but not for trochanteric, SIR = 0.8 (95% CI: 0.5-1.1). Age at endometrial cancer diagnosis was not a determinant of the risk of hip fracture. A lowered relative risk was present regardless of age at diagnosis and persisted during the entire follow-up period and into advanced ages. A case-control analysis within the cohort, and based on medical record data, indicated that a higher weight might be associated with a greater protective effect, as compared with a lower weight. Exposure to exogenous oestrogens was infrequent and could not have explained the present results. We conclude that persistent influence of oestrogens, notably of endogenous origin, can reduce the risk of hip fractures, and that this protective effect may be long-lasting and extend to advanced ages.

Adult↗