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C Peterson

Publications and source records attributed to C Peterson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Clustering ECG complexes using hermite functions and self-organizing maps.

An integrated method for clustering of QRS complexes is presented which includes basis function representation and self-organizing neural networks (NN's). Each QRS complex is decomposed into Hermite basis functions and the resulting coefficients and width parameter are used to represent the complex. By means of this representation, unsupervised self-organizing NN's are employed to cluster the data into 25 groups. Using the MIT-BIH arrhythmia database, the resulting clusters are found to exhibit a very low degree of misclassification (1.5%). The integrated method outperforms, on the MIT-BIH database, both a published supervised learning method as well as a conventional template cross-correlation clustering method.

Algorithms↗
PubMed2000

Effectiveness of prenatal chromosomal analysis using multicolor fluorescent in situ hybridisation.

OBJECTIVE: To evaluate the clinical effectiveness of multicolour fluorescent in situ hybridisation (FISH) analysis in routine prenatal diagnosis. DESIGN: Prospective study. SAMPLE: 3,203 amniotic fluid samples. METHODS: Unique DNA (chromosomes 13 and 21) and alpha satellite centromeric-specific (chromosomes X, Y and 18) probes were used in two mixes to permit the simultaneous analysis of several chromosomes. The performance of multicolour FISH and conventional cytogenetic analysis was compared. RESULTS: Conventional cytogenetic analysis identified 111 chromosomal abnormalities, of which 94 were potentially detectable by the FISH technique and 97 would be typically associated with neonatal phenotypic abnormalities. Multicolour FISH analysis detected 84% (93/111) of all chromosome abnormalities and 99% (93/94) of abnormalities where there was a specific probe. The sensitivity of multicolour FISH analysis was 95% (92/97) for chromosomal abnormalities likely to result in an abnormal postnatal outcome. Multiple ultrasound abnormalities were detected in all five cases of clinically relevant chromosomal abnormalities missed by multicolour FISH. FISH results were available within 48 hours and the sample failure rate was 0 x 1% (3/3,202). CONCLUSION: Multicolour FISH analysis is a sensitive and reliable technique for the rapid prenatal diagnosis of chromosomal abnormalities. Examining only five chromosomes allowed 95% of clinically relevant chromosomal abnormalities to be diagnosed correctly. As routine antenatal screening is targeted at the major autosomal trisomies and sex chromosome aneuploidies, multicolour FISH analysis may potentially replace conventional cytogenetic analysis in routine prenatal diagnosis.

Chromosome Aberrations↗
PubMed2000

Heterogeneity of isolated mononuclear cells from patients with acute myeloid leukemia affects cellular accumulation and efflux of daunorubicin.

BACKGROUND AND OBJECTIVE: Pharmacologic studies on blasts from patients with leukemia are generally performed on density gradient isolated blood or bone marrow cells. Thereby, cellular drug accumulation and efflux are determined as mean values of the entire cell population. The objective of the present study was to characterize the heterogeneity in the accumulation and efflux of daunorubicin in various subpopulations of mononuclear cells isolated from patients with acute myeloid leukemia (AML). DESIGN AND METHODS: Mononuclear cells from 33 patients with AML were isolated from peripheral blood by density gradient centrifugation on Lymphoprep (1. 077 g/mL). Cellular accumulation of fluorescent daunorubicin was determined by flow cytometry after incubation of the cells at +37C for 1 hour. Thereafter, the cells were washed and reincubated in drug-free medium. Kinetics of drug efflux were determined by frequent determination of cellular fluorescence during 30 min. Daunorubicin accumulation and efflux were compared in the total isolated mononuclear cell population and in the various blast cell populations gated on FSC/SSC according to the results of immunophenotyping. RESULTS: In 8 of these 33 (24%) patient samples, two distinct blast cell populations could be identified. In 7 out of 8 these cases the more immature blasts had a lower drug accumulation and in 6 out of the 8 cases also a higher efflux rate than the differentiating cell population. Cyclosporin A increased daunorubicin accumulation and reduced efflux in the immature blast population. In the differentiating cell population cyclosporin A increased both the accumulation and the efflux. In patients with a single blast cell population, the gated blast cells had a significantly lower drug accumulation but also a lower drug efflux rate than the total cell population. INTERPRETATION AND CONCLUSIONS: The results imply that drug transport studies on cells isolated from patients with AML give somewhat different results depending on the cell population studied. Some, but not all, of these differences in daunorubicin accumulation and efflux as well as in the effect of cyclo-sporin A can be explained by a heterogenous expression of the mdr1-gene. The observed heterogeneity may be of special relevance with regard to drug resistance. The presence of even a small resistant cell clone may jeopardize the effect of the chemotherapy due to expansion resulting in relapse of disease.

Acute Disease↗
PubMed2000

In response

Explore the source record for details and available documents.

Journal Article↗
PubMed1999

Design of sequences with good folding properties in coarse-grained protein models.

BACKGROUND: Designing amino acid sequences that are stable in a given target structure amounts to maximizing a conditional probability. A straightforward approach to accomplishing this is a nested Monte Carlo where the conformation space is explored over and over again for different fixed sequences; this requires excessive computational demand. Several approximate attempts to remedy this situation, based on energy minimization for fixed structure or high-T expansions, have been proposed. These methods are fast but often not accurate, as folding occurs at low T. RESULTS: We have developed a multisequence Monte Carlo procedure where both sequence and conformational space are simultaneously probed with efficient prescriptions for pruning sequence space. The method is explored on hydrophobic/polar models. First we discuss short lattice chains in order to compare with exact data and with other methods. The method is then successfully applied to lattice chains with up to 50 monomers and to off-lattice 20mers. CONCLUSIONS: The multisequence Monte Carlo method offers a new approach to sequence design in coarse-grained models. It is much more efficient than previous Monte Carlo methods, and is, as it stands, applicable to a fairly wide range of two-letter models.

Energy Metabolism↗
PubMed1999

Prior treatment received by patients with bulimia nervosa.

OBJECTIVE: This study examined the frequency with which subjects with bulimia nervosa (BN) presenting for treatment or follow-up studies had previously received either adequate pharmacologic treatment or cognitive-behavioral therapy (CBT). METHOD: Semistructured telephone screening of individuals who called in response to advertisements about research studies was used to establish diagnoses and to clarify prior pharmacologic and psychotherapeutic treatments for BN. RESULTS: Of 581 women responding, 353 (60.8%) had probable BN. Overall, 61.4% of these subjects had received psychotherapy (96.7%) but rarely CBT (6.9%). Over one half (63.7%) had received pharmacologic treatment, most commonly with fluoxetine (72.5%). Of those having received any medication treatment, 46.2% were judged to have received at least one adequate trial. Overall, 35.0% of those previously treated had received at least one prior course of adequate pharmacotherapy or CBT for BN. CONCLUSION: Although efficacious treatments for BN have been established, they have not been received by most individuals presenting for further treatment.

Adolescent↗
PubMed1999

In vitro cytotoxic drug activity and in vivo pharmacokinetics in childhood acute myeloid leukemia.

Since May 1996 all Nordic countries have been participating in a study of childhood acute myeloid leukemia (AML). The aim is to correlate the in vitro sensitivity of leukemic cells and individual plasma concentrations of cytotoxic drugs with clinical effect. Blast cells from bone marrow and/or peripheral blood are tested against a panel of cytotoxic agents using the fluorometric microculture cytotoxicity assay (FMCA). Plasma concentrations of cytotoxic drugs are analysed during induction therapy. Bone marrow samples from the participating centres generally reached the analysing laboratory within 24 hours. 61 out of 71 (86%) samples were successfully analysed, 47 de novo AML and 14 relapses. Relapsing patients tended to have a more resistant test profile than newly diagnosed patients. Steady state plasma levels of doxorubicin, etoposide and 6-thioguanine nucleotide varied about 10-fold between patients. The intra-individual variation was much less, suggesting that dose adjustment based on pharmacokinetic data might be useful in the future.

Amsacrine↗
PubMed1999

Low-dose oral pulse methotrexate as monotherapy in elderly patients with bullous pemphigoid.

BACKGROUND: Prednisone alone or in combination with an immunosuppressive drug is usually effective in controlling bullous pemphigoid. However, corticosteroids often cause potentially hazardous side effects, especially in elderly patients. OBJECTIVE: Our purpose was to evaluate low-dose treatment with methotrexate in elderly patients with generalized bullous pemphigoid. METHODS: Oral methotrexate, at an initial dosage of 5 mg/wk, was given to 11 consecutive patients older than 70 years of age who were not responding to potent topical steroids. If the response was insufficient, the methotrexate dose was increased by 2.5 mg/wk to a maximum of 12.5 mg/wk. RESULTS: All patients responded with a marked and rapid decrease in disease activity. The disease was controlled in the majority of patients (8 of 11) with 5 to 7.5 mg of methotrexate per week. Three patients required a weekly dose of 10 to 12.5 mg. At 24 months of follow-up 7 patients were in complete remission and did not require methotrexate. CONCLUSION: Our study suggests that low-dose oral pulse methotrexate constitutes an effective therapeutic alternative in elderly patients with generalized bullous pemphigoid.

Administration, Oral↗
PubMed1999

Conditions in blood sampling procedures that extend the ex vivo stability of eosinophil activity markers in peripheral blood from allergic patients and healthy controls.

BACKGROUND: Serum-ECP, EG2-epitope on intracellular ECP and surface expression of CD9 and CD11b in peripheral blood eosinophils (PBE) are considered to be markers that mirror clinical parameters in allergic inflammation. OBJECTIVE: The aim was to investigate the impact of the blood sampling procedure on PBE markers and to identify optimal conditions for extended pre-analysis storage. METHODS: Blood, from healthy individuals and patients with allergic rhinitis/asthma, was collected in tubes with EDTA, citrate, or without anti-coagulant. The expression of EG2-epitope, CD9, and CD11b were analyzed in eosinophils and neutrophils after 1, 5, and 24 hours of storage at +4 degrees C, according to the FOG-method and flow cytometry. In vitro stimulation with fMLP/PMA was used for metabolic activity analysis and CD11b mobilization. Following a 1-hour clotting period at +20 to 22 degrees C, samples were stored at +4 degrees C and serum-ECP levels were measured. RESULTS: The EG2-epitope, serum-ECP, and CD9 were stable in samples from both healthy controls and allergic patients at all storage conditions. The EG2-epitope, serum-ECP and PBE count were significantly increased in the patient group, whereas no differences were observed in the expression of CD9 or CD11b. Both granulocytes and monocytes retained their metabolic activity for 24 hours. Neutrophils in citrate-blood increased their ability to respond to fMLP, as compared with EDTA-blood. CONCLUSION: In vitro analysis of selected activity markers and functional tests could be performed on granulocytes from both healthy individuals and allergic patients after 24 hours storage at +4 degrees C. The anticoagulant citrate seems to be preferable to EDTA when monocytes or CD11b expression are analyzed.

Adult↗
PubMed1999

Encouraging narratives in preschoolers: an intervention study.

Twenty economically disadvantaged preschoolers (mean age 3;7) were randomly assigned to an intervention or a control group, and their mothers' styles of eliciting narratives from their children were assessed before and after intervention. Mothers of intervention children were encouraged to spend more time in narrative conversation, ask more open-ended and context-eliciting questions, and encourage longer narratives through back-channel responses. Children's narrative and vocabulary skills were assessed before and after the year-long intervention and 14 children participated in a follow-up assessment a year later. Narrative measures included the number and length of narratives as well as how decontextualized and informative they were. Intervention children showed significant vocabulary improvement immediately after intervention terminated, and a year later they showed overall improvements in narrative skill. In particular, intervention children produced more context-setting descriptions about where and especially when the described events took place. Such decontextualized language has been emphasized as important for literacy acquisition.

Child Behavior↗
PubMed1999

Interviewing preschoolers: comparisons of yes/no and wh- questions.

This study investigated the influence of question format on preschool-aged children's errors, their response accuracy, and their tendency to say "I don't know" when given non-misleading questions in a neutral, unbiased context. Children (3 to 5 years old) participated in a craft-making session that included a staged "accident" with two experimenters differing in gender and appearance; the environment also had several distinctive features. One week later children were interviewed about actions, participants, and environment; questions were yes/no format with the veridical response "yes" ("yes" questions), yes/no format with the veridical response "no" ("no" questions), and specific wh- format questions. Question format substantially influenced children's responses: they were most likely to make errors if asked "no" questions, and were unlikely to answer either yes/no question with "I don't know." In contrast, children spontaneously and frequently said "I don't know" to wh- questions about content they did not recall (environment), but not about content that was well recalled (actions). Implications of question format for reliability of eyewitness testimony by preschoolers are discussed.

Child, Preschool↗
PubMed1999

Children's memory for medical emergencies: 2 years later.

Long-term recall of medical emergencies (including both injury and hospital treatment) by 2- to 13-year-olds was assessed 2 years after injury. Event identity was important: Children recalled injury details better than hospital treatment. Ninety-six children were interviewed 3 times prior to the 2-year recall; amount recalled decreased only for hospital treatment details, although accuracy of recall decreased for both injury and treatment. Twenty-one children were interviewed only twice prior to the 2-year interview. An extra interview 1 year after their injury had little effect on how much older children recalled about both injury and treatment or how much younger children recalled about injury details, but it helped younger children recall the less memorable hospital event. The extra interview also helped all children maintain accuracy when recalling hospital details but was unnecessary for the more memorable injury event. Implications for children's testimony are discussed.

Child↗
PubMed1999

Suppression of telomerase reverse transcriptase (hTERT) expression in differentiated HL-60 cells: regulatory mechanisms.

Telomerase activity, associated with cellular immortalization and tumorigenesis, is suppressed during terminal differentiation of HL-60 promyelocytic leukaemic cells. However, it is poorly understood how telomerase activity is regulated in differentiated HL-60 cells. In the present study, we demonstrate that the down-regulation of telomerase reverse transcriptase (hTERT) expression, the catalytic subunit, occurs prior to the suppression of telomerase activity in differentiated HL-60 cells. In contrast, the expression of telomerase RNA template (hTR) and telomerase associated protein (TP1) is not reduced. This down-regulation of hTERT expression is achieved through inhibition of gene transcription, in which process new protein synthesis is required. Moreover, the rapid down-regulation of hTERT expression followed by the inhibition of telomerase activity is a specific component of the differentiation programme and not simply a consequence of cell cycle arrest. Serum-deprivation of HL-60 cells causes cell cycle arrest without differentiation and this does not result in a significant reduction in hTERT mRNA levels within the first 24 h. Our findings suggest that hTERT expression is stringently controlled at transcriptional level in HL-60 cells. The downregulation of hTERT expression in the HL-60 cell differentiation model may represent a general regulatory mechanism through which telomerase becomes repressed during development and differentiation of human somatic cells.

Cell Cycle↗
PubMed1999

High levels of lung resistance related protein mRNA in leukaemic cells from patients with acute myelogenous leukaemia are associated with inferior response to chemotherapy and prior treatment with mitoxantrone.

Expression of the mdr1 (multidrug resistance), mrp (multidrug resistance associated protein), and lrp (lung resistance related protein) genes is associated with transport related MDR (multidrug resistance). We quantified mRNA levels of these genes using competitive reverse transcription polymerase chain reaction (RT-PCR) in 128 samples of leukaemic cells from 92 patients with acute myelogenous leukaemia (AML). There was a wide variation between the samples in mRNA levels of all three genes. The mean mdr1 mRNA level was 1.3 transcripts per cell (range undetectable to 15.8), the mean mrp level was 7.9 (range 0.1-36.2) and mean lrp 3.9 (range 0.1-29). Lrp mRNA levels were higher in samples drawn at diagnosis from the 15 patients with resistant disease than from the 37 with chemosensitive disease (4.9 SD 3.1 v 2.9 SD 2.3, P = 0.016). Neither mdr1 nor mrp mRNA levels were predictive for response to chemotherapy. In samples from patients who had received chemotherapy, those that had received mitoxantrone (n = 24) had higher lrp mRNA levels (mean 4.8, SD 2.5) than those that had not (n = 20, mean 2.8, SD 2.4, P = 0.012). In conclusion, the results indicate that lrp expression is associated with inferior response to chemotherapy in AML and that lrp expression increases after exposure to mitoxantrone.

Adult↗