Search PubMed⌕ Search

Biomedical subjects

R Nygaard

Publications and source records attributed to R Nygaard.

At least 19 recordsLinked to original sources
PubMed2001

A rate distortion optimal ECG coding algorithm.

Signal compression is an important problem encountered in many applications. Various techniques have been proposed over the years for addressing the problem. In this paper, we present a time domain algorithm based on the coding of line segments which are used to approximate the signal. These segments are fit in a way that is optimal in the rate distortion sense. Although the approach is applicable to any type of signal, we focus, in this paper, on the compression of electrocardiogram (ECG) signals. ECG signal compression has traditionally been tackled by heuristic approaches. However, it has been demonstrated [1] that exact optimization algorithms outperform these heuristic approaches by a wide margin with respect to reconstruction error. By formulating the compression problem as a graph theory problem, known optimization theory can be applied in order to yield optimal compression. In this paper, we present an algorithm that will guarantee the smallest possible distortion among all methods applying linear interpolation given an upper bound on the available number of bits. Using a varied signal test set, extensive coding experiments are presented. We compare the results from our coding method to traditional time domain ECG compression methods, as well as, to more recently developed frequency domain methods. Evaluation is based both on percentage root-mean-square difference (PRD) performance measure and visual inspection of the reconstructed signals. The results demonstrate that the exact optimization methods have superior performance compared to both traditional ECG compression methods and the frequency domain methods.

Algorithms↗
PubMed2000

Induction of Mx protein by interferon and double-stranded RNA in salmonid cells.

Mx protein is one of several antiviral proteins that are induced by the type I interferons (IFN), IFNalpha and beta, in mammals. In this work induction of a 76 kDa Mx protein by double-stranded RNA (dsRNA) or type I IFN-like activity in Atlantic salmon macrophages, Atlantic salmon fibroblast cells (AS cells) and in Chinook salmon embryo cells (CHSE-214) is reported. Type I IFN-like activity was produced by the stimulation of Atlantic salmon macrophages with the synthetic dsRNA polyinosinic polycytidylic acid (poly I:C). A correlation appeared to exist between Mx protein expression and protection against infectious pancreatic necrosis virus (IPNV) induced by IFN in CHSE-214 cells. Several observations in the present work suggest that, as in mammals, the induction of Mx protein by dsRNA in fish cells primarily occurs via induction of type I IFN. First, type I IFN-like activity but not poly I:C, induced Mx protein expression in CHSE-214 cells. These cells apparently lack the ability to produce IFN in response to poly I:C. Second, the putative IFN induced maximal Mx protein expression 48 h earlier than poly I:C in AS cells. Third, the peak expression of Mx protein in macrophages induced by poly I:C occurred after 48 h whereas peak in IFN-like activity was observed by 24 h after addition of poly I:C. The present work supports the notion of using Mx protein as a molecular marker for the production of putative type I IFN in fish.

Animals↗
PubMed2000

Variability in methotrexate serum and cerebrospinal fluid pharmacokinetics in children with acute lymphocytic leukemia: relation to assay methodology and physiological variables.

Methotrexate (MTX) steady state concentrations were evaluated in 42 children who had received high-dose infusions (6-8 g/m2) for acute lymphocytic leukemia. Concentrations in serum and cerebrospinal fluid (CSF) measured by immunoassay were found to be highly variable. Reanalysis by a reference high-pressure liquid chromatography method ruled out analytical factors as a source of this variability. The correlation coefficient between the analytical methods was 0.77 for the serum data and 0.88 for the CSF data. The variability of serum and CSF concentrations was higher in younger patients (serum; P = 0.05 and CSF; P = 0.18), and the CSF concentration decreased with decreasing age and in later courses. Body surface area, body mass index, weight, and gender were not significantly related to MTX variability. We conclude that the pronounced pharmacokinetic variability seen during MTX infusions remains largely unexplained.

Antimetabolites, Antineoplastic↗
PubMed2000

Improving outcome through two decades in childhood ALL in the Nordic countries: the impact of high-dose methotrexate in the reduction of CNS irradiation. Nordic Society of Pediatric Haematology and Oncology (NOPHO).

In this population-based material from the five Nordic countries (Denmark, Finland, Iceland, Norway and Sweden), 2860 children below 15 years of age were diagnosed with acute lymphoblastic leukemia (ALL) from July 1981 to June 1998. The annual incidence was 3.9/100,000 children and was stable throughout the study period. The development from regional or national protocols to common Nordic treatment protocols for all risk groups was completed in 1992 through a successive intensification with multidrug chemotherapy, including pulses of methotrexate in high doses and avoidance of cranial irradiation in most children. The overall event-free survival (EFS) at 5 years has increased from 56.5 +/- 1.7% in the early 1980s to 77.6 +/- 1.4% during the 1990s. The main improvements were seen in children with non-high risk leukemia. In high-risk patients, progress has been moderate, especially in children with high WBC (> or =100 x 10(9)/l) at diagnosis. During the last time period (January 1992-June 1998), only 10% of the patients have received cranial irradiation in first remission, while 90% of the patients have received pulses of high dose methotrexate (5-8 g/m2) isolated or combined with high-dose cytosine arabinoside (total dose 12 g/m2) plus multiple intrathecal injections of methotrexate as CNS-targeted treatment, not translating into increased cumulative incidence of CNS relapse.

Antimetabolites, Antineoplastic↗
PubMed2000

Agency orientation and chronic musculoskeletal pain: effects of a group learning program based on the personal construct theory.

OBJECTIVE: This study evaluated the effects of a group learning program on patients with chronic musculoskeletal pain and high absenteeism and investigates what characterizes those patients who may benefit from such a program. The learning program was based on personal construct theory. The theory included the following: (1) participation in an educational program is related to a favorable outcome across the outcome measures (pain, pain coping, management of daily life, absenteeism, and use of health care), (2) patients with high agency orientation (i.e., inner-directed) cope with their pain and manage daily life in a better manner than do patients with low agency orientation (i.e., outer-directed), and (3) patients with high personal control, measured in terms of agency orientation, in terms of health locus of control, or in both terms, will benefit more from the educational program than will patients with low personal control. DESIGN: The study was a randomized controlled study. PATIENTS: One hundred and sixteen patients with chronic musculoskeletal pain and high absenteeism answered a questionnaire before and after the intervention program. The intervention group (n = 61) consisted of nine subgroups geographically spread through the eastern part of Norway and met for four hours every 2 weeks from February 1997 to October 1997. A total of 12 meetings were held. RESULTS: The intervention group reported a significantly higher score for the variable "management of everyday life" (p <0.005) and for the variable "health care consumption" (p <0.001) than did the control group. Patients with high agency orientation benefited more from the program with regard to pain reduction and improved pain coping than did those patients with low agency orientation (p <0.05). Patients with high agency orientation also reported less absenteeism than did those patients with low agency orientation (p <0.05).

Absenteeism↗
PubMed1999

[Adults treated as children for acute lymphocytic leukemia--methotrexate, late effects and quality of life].

From 1975 to 1980, 153 Norwegian children were diagnosed with acute lymphocytic leukaemia. In 1995, all 98 survivors were studied and compared to matched family controls. 132 children were treated with the national protocol. Of these, 93 (70.5%) were survivors at the time of the study. The remaining five survivors were treated with different treatment schemes. The national protocol included methotrexate infusions combined with intrathecal methotrexate as prophylactics against neuroleukaemia, instead of the irradiation. Neither doxorubicin nor cyclophosphamide were included. In this study, a questionnaire was used that covered demographic data, quality of life, and medical information the response rates were 96% (94 persons) for survivors and 92% (90 persons) for family controls. Information was also obtained for the remaining four survivors. No significant differences were found between survivors and controls with regard to quality of life and demographics, with one exception, Somatisation on the GHQ-28. Hospital records of all patients were checked for possible late effects. One case of serious sequela (hemiparesis during therapy) was found, probably related to methotrexate therapy. Seven other serious, possible sequelae were recorded, but probably not related to methotrexate. There were no cases of secondary malignant neoplasm.

Adolescent↗
PubMed1997

On the prognostic value of systemic methotrexate clearance in childhood acute lymphocytic leukemia.

The prognostic value of systemic methotrexate clearance (ClMTX) during high-dose therapy was evaluated in a cohort of 42 children with acute lymphocytic leukemia (ALL). As part of an extensive chemotherapy protocol, they had received a total of 293 methotrexate (MTX) infusions in the 6-8 g/m2 dose range. At the termination of the study, when they had all been followed up for 3.5 years or more, 26 of these patients were still in continuous complete remission, whereas 16 had suffered relapse. The intrapatient variability in ClMTX during the eight courses was up to six-fold. In 67% of the patients, the maximum level of ClMTX reached at least twice the minimum value. The coefficients of variation for the intra- and interindividual variability in ClMTX were 9-57% and 26-41%, respectively. The cumulative probability of relapse, estimated by the Kaplan-Meier procedure, was increased for patients with a high ClMTX during the initial treatment course, but the difference was not significant on a 5% level. There was no significant relationship between high individual median ClMTX and subsequent relapse of ALL. However, ClMTX during the initial infusion, the time-dependent mean for ClMTX, and the individual patient's median ClMTX, were significant predictors for event-free survival in a Cox proportional hazards regression analysis. The present study demonstrates gross pharmacokinetic variability and unpredictable values of ClMTX in subsequent courses after standardized administration of MTX to paediatric patients with ALL. In spite of the association between ClMTX and prognosis shown by some of the analyses, estimates of ClMTX rates may not necessarily be related to disease outcome in a way that can be exploited to the benefit of the individual patient.

Adolescent↗
PubMed1996

Magnetic resonance imaging and neurological evaluation after treatment with high-dose methotrexate for acute lymphocytic leukaemia in young children.

This study evaluates the occurrence of permanent cerebral white matter changes and neurological abnormalities in children treated at a young age for acute lymphocytic leukaemia. Our pilot treatment protocol did not include central nervous system irradiation, but intrathecal methotrexate and high-dose methotrexate infusions followed by very intensive folinic acid rescue. We examined 12 children in complete remission and off therapy 18 months to 9.5 years after their last methotrexate infusion. They were below 5 years of age at diagnosis and therefore expected to be at special risk of neurotoxic sequelae. Cerebral magnetic resonance imaging in the 11 cases thus evaluated did not reveal white matter abnormalities or other signal changes as signs of permanent treatment-related sequelae. We did not observe any pathological clinical neurological findings likely due to methotrexate.

Age Factors↗
PubMed1991

Reproduction following treatment for childhood leukemia: a population-based prospective cohort study of fertility and offspring.

Of all children diagnosed with leukemia in Denmark, Finland, Iceland, Norway, and Sweden, 981 had discontinued therapy before 1985 and had been followed up annually after cessation of therapy. Progeny was registered and fertility evaluated among survivors who passed age 18 years without a relapse (n = 299). By April 1989, 48 offspring were registered, one of whom had congenital anomalies. This was no more than expected from the incidence of birth defects in the general population. No childhood malignancies or genetic diseases have so far been diagnosed in the progeny. In the study group, none of the 19 female and 8 male survivors of myeloid leukemias had become parents, and only 4 fathers were reported among the 131 male survivors of acute lymphoblastic leukemia (ALL). However, 23 of the 149 females treated for ALL had delivered 41 children. Fertility was measured as cumulative rates of first birth by maternal age. In a Cox regression analysis, cases who had received prophylactic radiation of the central nervous system (CNS) had a lower first birth rate than those without radiation (rate ratio 0.39, 95% CI 0.15-1.00), indicating that doses of 18-24 Gy to the brain may possibly be a risk factor. By using the Norwegian birth cohort of 1966 as a control group, matching the median year of birth for the study subjects, the group of female ALL survivors as a whole was as likely as the general female population to have given birth up to the age of 23. The first generation of females successfully treated for childhood ALL seems to have a nearly normal reproductive pattern during young adulthood, without increased risk of congenital anomalies in the offspring. However, cranial radiation as CNS prophylaxis may possibly impair subsequent reproduction.

Adolescent↗
PubMed1991

Second malignant neoplasms in patients treated for childhood leukemia. A population-based cohort study from the Nordic countries. The Nordic Society of Pediatric Oncology and Hematology (NOPHO).

Among a cohort of 981 children who were followed up 4.3-26.5 years after cessation of antileukemic therapy, eight patients in remission of acute lymphoblastic leukemia (ALL) developed a distinctively new malignant disease. The second malignant neoplasms (SMN) included brain tumors, basal cell carcinomas, thyroid cancer, leiomyosarcoma and finally rhabdomyosarcoma in a patient who also had suffered from Hodgkin's disease while still on antileukemic treatment. Cranial radiation had been given to 58.4% of the patients in the study group, which consisted of 895 ALL patients who had completed various chemotherapy protocols. With one exception, the SMN appeared after 7.5-16.5 years at a location previously exposed to radiotherapy (RT). The estimated cumulative risk of SMN appearing within 20 years after diagnosis was 2.9%, and the corresponding risk for cases with RT was 8.1% compared to 0.3% for those without (p = 0.05). In a Cox regression analysis, the incidence rate ratio of SMN between patients with and without RT was 6.7 (95% CI = 0.8, 57.7). Based on age-, year- and sex-specific cancer incidence figures for Norway, the overall standardized incidence rate ratio (SIR) of SMN after treatment for ALL was 5.9 (95% CI = 2.2, 12.9). The number of brain tumors among patients who had received cranial radiation was nearly 27 times greater than expected, whereas no such tumors were seen after chemotherapy. Individuals treated for childhood ALL are at increased risk of a new malignancy, and this seems mainly to be associated with previous irradiation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

[Treatment considerations for children during terminal care].

There should be a special obligation to shield children with a terminal illness from pain and from the psychological suffering when death is approaching. In spite of this, the child has the right to be informed about the prognosis and decisions taken concerning treatment. We discuss the difficult question of informed consent in pediatrics. Who can make an informed consent on behalf of a minor? At which age should a child make its own decisions concerning medical treatment? In pediatrics there are certain circumstances where withdrawal of intensive medical care is justified. Examples are given from oncological and neuromuscular diseases, as well as from the neonatal period. We discuss how termination of intensive care could take place. The medical team should make the decision alone, but should never go against the parents' will. It is underlined that termination of intensive care in the above-mentioned circumstances is completely different from active euthanasia, which we strongly oppose.

Adolescent↗
PubMed1990

Discrimination of relative spatial position.

Subjects can accurately discriminate small changes in the relative position of features within a pattern. Simple patterns (intersected line segments) can undergo magnification and a variety of transformations without significantly affecting the discrimination thresholds. Features to be localized and compared need not be similar. We suggest that such relative position discriminations could support complex object identification.

Discrimination, Psychological↗
PubMed1989

Late relapses after treatment for acute lymphoblastic leukemia in childhood: a population-based study from the Nordic countries.

Seven late relapses of acute lymphoblastic leukemia occurring 5.5 to 12.3 years after cessation of therapy are reported in 986 patients who had discontinued treatment for leukemia acquired before the age of 15. The study covers patients from the five Nordic countries. Of the 434 patients with ALL who had passed 5 years of follow-up without recurrence, seven have subsequently relapsed so far; an estimated cumulative proportion of 6.9% within the 10 years. In addition, we report a girl 15.9 years old at diagnosis who relapsed 7.3 years after cessation of therapy. These findings confirm that "cure" of acute lymphoblastic leukemia treated in the 1970s cannot be considered definite, even 5 years after discontinuation of therapy.

Adolescent↗
PubMed1989

Structural chromosome aberrations in lymphocytes from children previously treated for Wilms' tumor or Hodgkin's disease.

Nineteen children treated for Wilms' tumor (thirteen cases) or Hodgkin's disease (six cases) with cytostatic agents and/or radiotherapy were studied cytogenetically on lymphocytes cultivated from blood samples drawn after at least 1 year of complete remission after end of therapy. A reference group of children was matched for age, sex, and residence. The frequencies of sister chromatid exchange (5.4 versus 5.6 SCE/cell), and chromosome damage type gaps (6.6 versus 7.1%) and breaks (1.9 versus 1.9%) were not different in the two groups, but exchange type aberrations were more frequent in the patients (0.9 versus 0.06%). Fifty karyotypes were analyzed in all but two cases of Hodgkin's disease. The overall frequency of stable (3.1 versus 3.8%) and unstable (1.7 versus 1.4%) structural chromosome changes such as translocations, deletions, chromatid exchanges, and dicentrics were not different in the patient and the control groups. If the chromosome data reflect a general cancer risk, this risk cannot be considerably higher among the cancer-treated children.

Adolescent↗
PubMed1988

Thyroid function in children after cytostatic treatment for acute leukemia.

Sixty-one children were examined for thyroid dysfunction as an adverse late effect after cessation of antileukemic treatment. The aim of the study was to contribute to clarifying which types of therapy can cause this endocrine disorder. Our treatment protocols do not include cranial irradiation as CNS prophylaxis, but we give relatively intensive intrathecal methotrexate treatment. The results indicate that this cytostatic regimen alone does not cause thyroid dysfunction as an adverse late effect.

Adolescent↗