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Biomedical subjects

D Nielsen

Publications and source records attributed to D Nielsen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Influx of daunorubicin in multidrug resistant Ehrlich ascites tumour cells: correlation to expression of P-glycoprotein and efflux. Influence of verapamil.

Classic multidrug resistance is characterized by a decrease in the intracellular concentration of drugs in resistant cells as compared to sensitive cells. This is correlated with the presence of P-glycoprotein in the membrane. P-glycoprotein is responsible for an active efflux of drug. In this study we investigated the correlation between P-glycoprotein and influx of daunorubicin. Four Ehrlich ascites tumour cell lines selected in vivo for resistance to daunorubicin were investigated. The sublines EHR2/0.1, EHR2/0.2, passage no. 12 of EHR2/0.8, EHR2/0.4, and passage no. 72 of EHR2/0.8 were 6-, 6-, 5-, 33-, and 35-fold resistant to daunorubicin, respectively. All sublines overexpressed P-glycoprotein as determined with Western blot. Influx was measured over 40 sec. In glucose-enriched medium influx was significantly decreased in all but one of the resistant sublines. A correlation between P-glycoprotein, degrees of resistance, and influx was demonstrated in four sublines. Comparing influx experiments with efflux experiments (Nielsen et al., Biochem Pharmacol 1994, 47, 2125-2135) we found a linear relationship between influx and efflux in the resistant sublines (r = 0.97). Verapamil (5.5 microM, 11.0 microM) increased influx significantly in all resistant sublines, whereas the drug had no effect on sensitive cells. Verapamil (3.3 microM) increased influx in the EHR2/0.8 (passage no. 72) subline to the level of sensitive cells. Comparing this result with efflux experiments, verapamil was found to increase influx preferentially. Depletion of energy (medium without glucose including Na(+)-azide) increased influx in all resistant sublines. In EHR2/0.4 and EHR2/0.8 (passage no. 72) the influx, however, was still significantly decreased after depletion of energy. In these cells further addition of verapamil increased influx to the level of EHR2. These data were consistent with the hypothesis that P-glycoprotein effluxes drug directly from the plasma membrane.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

In vivo transfer of GPI-linked complement restriction factors from erythrocytes to the endothelium.

Many proteins are associated with the outer layer of the cell membrane through a posttranslationally added glycosyl phosphatidylinositol (GPI) anchor. The functional significance of this type of protein linkage is unclear, although it results in increased lateral mobility, sorting to the apical surface of the cell, reinsertion into cell membranes, and possibly cell signaling. Here evidence is presented that GPI-linked proteins can undergo intermembrane transfer in vivo. GPI-linked proteins expressed on the surface of transgenic mouse red blood cells were transferred in a functional form to endothelial cells in vivo. This feature of GPI linkage may be potentially useful for the delivery of therapeutic proteins to vascular endothelium.

Animals↗
PubMed1995

Mapping quantitative trait loci controlling milk production in dairy cattle by exploiting progeny testing.

We have exploited "progeny testing" to map quantitative trait loci (QTL) underlying the genetic variation of milk production in a selected dairy cattle population. A total of 1,518 sires, with progeny tests based on the milking performances of > 150,000 daughters jointly, was genotyped for 159 autosomal microsatellites bracketing 1645 centimorgan or approximately two thirds of the bovine genome. Using a maximum likelihood multilocus linkage analysis accounting for variance heterogeneity of the phenotypes, we identified five chromosomes giving very strong evidence (LOD score > or = 3) for the presence of a QTL controlling milk production: chromosomes 1, 6, 9, 10 and 20. These findings demonstrate that loci with considerable effects on milk production are still segregating in highly selected populations and pave the way toward marker-assisted selection in dairy cattle breeding.

Animals↗
PubMed1994

Clinal variation and selection of MDH allozymes in honey bee populations.

Latitudinal clines of malate dehydrogenase-1 (MDH-1) allozymes occur within honey bee populations on three continents: Europe, North America and South America. The North and South American populations are introduced and demonstrate that Mdh allelic clines were established within the last 150 years. The frequency of the 'medium' electrophoretic allele increases in frequency with increasing latitude while the 'fast' allele decreases with latitude on all the three continents. The clines are best explained by the average daily high temperature for July on all continents. These parallel clines provide evidence for selection on Mdh alleles in honey bees.

Alleles↗
PubMed1994

Kinetics of daunorubicin transport in Ehrlich ascites tumor cells with different expression of P-glycoprotein.

The classical multidrug resistance (MDR) phenotype is characterized by a decrease in the intracellular drug concentration in resistant cells as compared to sensitive cells. P-glycoprotein (P-gp) is thought to be responsible for an active efflux of lipophilic drugs. Four Ehrlich ascites tumor cell lines selected in vivo for resistance to daunorubicin (DNR) and their sensitive counterpart were investigated. The resistant sublines EHR2/0.1, EHR2/0.2, EHR2/0.4, and EHR2/0.8 were developed by treatment of tumor bearing mice with DNR 0.1, 0.2, 0.4, and 0.8 mg/kg x 4 weekly, respectively. One passage from EHR2/0.1, EHR2/0.2, and EHR2/0.4 and two passages from EHR2/0.8 were investigated. Western blot analysis showed significantly different amounts of P-gp (a 6-fold variation). Efflux of DNR in a drug free medium was investigated with and without presence of verapamil (VER). Efflux from sensitive and resistant cells was described by mono- and bi-exponential kinetics, respectively. In all cases but one, a correlation between resistance, expression of P-gp, P-gp mediated efflux capacity and effect of VER was established. In passage No. 12 of EHR2/0.8, however, a high expression of P-gp was found in spite of a low degree of resistance and a low efflux capacity. In this subline the effect of VER did not correlate to the expression of P-gp. Active efflux seemed to be saturable and was suggested to constitute the major route of efflux in MDR cells. A dose-response relationship was established for the effect of VER on efflux. In conclusion, the results support that P-gp acts as a drug efflux pump. No simple correlation, however, could be established between P-gp and drug transport in all the investigated cell lines. Other factors which might influence transmembranous transportation of DNR are suggested. The active efflux capacity of the cell lines seemed to determine the degree of resistance and the sensitivity to circumvention by VER.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Chromosomal localization of the callipyge gene in sheep (Ovis aries) using bovine DNA markers.

A mutation causing muscular hypertrophy, with associated leanness and improved feed efficiency, has been recently identified in domestic sheep (Ovis aries). Preliminary results indicate that an autosomal dominant gene may be responsible for this economically advantageous trait. We have exploited the conservation in sequence and chromosomal location of DNA markers across Bovidae to map the corresponding callipyge locus to ovine chromosome 18 using a battery of bovine chromosome 21 markers. Chromosomal localization of the ovine callipyge locus is the first step toward positional cloning of the corresponding gene.

Animals↗
PubMed1994

Serotonin, violent behavior and alcohol.

At the NIAAA intramural research program, in collaboration with investigators at the Department of Psychiatry, University of Helsinki, we have mounted an extensive research program on early onset male alcoholism. A central serotonergic deficit is common among these patients. This finding has led to behavioral, biochemical, physiological and molecular genetic studies on the serotonin system in early onset, antisocial and violent male alcoholics and in appropriate control populations. The results of the studies completed by the fall of 1993 are summarized in this communication.

Age Factors↗
PubMed1993

Microsatellite mapping of the gene causing weaver disease in cattle will allow the study of an associated quantitative trait locus.

A genetic disease in cattle, progressive degenerative myeloencephalopathy (weaver disease), is associated with increased milk production. This association could result from population stratification, from a pleiotropic effect of a single gene, or from linkage disequilibrium between the gene causing weaver disease and a quantitative trait locus (QTL) for milk production. To test these hypotheses, we performed an extensive linkage study in a bovine pedigree segregating for the weaver condition and identified a microsatellite locus (TGLA116) closely linked to the weaver gene (zmax, 8.15; theta, 0.03). TGLA116 and, by extension, the weaver locus were assigned to bovine synteny group 13. This microsatellite can be used to identify weaver carriers, to select against this genetic defect, and to study the effect of the corresponding chromosomal region on milk production in Brown Swiss and other breeds of cattle.

Animals↗
PubMed1993

Microsatellite mapping of a gene affecting horn development in Bos taurus.

The presence or absence of horns in Bos taurus is thought to be under the genetic control of the autosomal polled locus, characterized by two alleles: P dominant over p, and causing the polled or hornless phenotype. We have demonstrated genetic linkage between the polled locus and two microsatellite markers, GMPOLL-1 and GMPOLL-2, and have assigned the corresponding linkage group to bovine chromosome 1. This confirms the existence of the postulated polled locus and the hypothesized inheritance pattern. It will allow marker assisted selection for the polledness trait in breeding programs and is a first step towards positional cloning and molecular study of a gene that has been subjected to both natural and artificial selection.

Alleles↗
PubMed1993

A novel method for monitoring high-risk breast cancer with tumor markers: CA 15.3 compared to CEA and TPA.

BACKGROUND: An early and reliable diagnosis of metastatic spread has increased interest in serum tumor markers. This study investigated the ability of CA 15.3, CEA, and TPA to identify, predict, and exclude metastases in bone/viscera during adjuvant treatment and follow-up of high-risk breast cancer. METHODS: Ninety females with high-risk breast cancer were included in the study. Response evaluation was based upon clinical examination, x-rays or histology and elaborated marker criteria. RESULTS: During the marker monitoring period, metastases in four patients were confined to skin or lymph nodes, 21 developed metastases to bone/viscera, and 65 females had no evidence of metastases. CA 15.3, CEA, and TPA correctly classified 48%, 10%, and 19% of the patients with metastases in bone/viscera, and 100%, 94%, and 98% without. Following CA 15.3, CEA, and TPA recurrence, 100%, 33%, and 60% of the patients developed metastases in bone/viscera. Metastases in bone/viscera were excluded in 86%, 76%, and 79% of patients without CA 15.3, CEA, and TPA recurrence. CONCLUSION: Only CA 15.3 gave reliable information about recurrence. Metastases in bone/viscera were identified in 10 of the 21 patients with CA 15.3. There was no false-positive CA 15.3 information on the 65 patients without clinical recurrence. The PVneg (86%) indicated that when CA 15.3 did not signal recurrence, metastases to bone/viscera were not likely.

Adult↗
PubMed1993

Prognostic value of serum tetranectin in patients with metastatic breast cancer.

To evaluate serum tetranectin as a prognostic marker before first-line chemotherapy, serum levels were studied in 67 patients with metastatic breast cancer. In the Cox analyses, the relative risk (RR) for death of cancer varied with the cut-off level of serum tetranectin. A maximal RR of 5.0 was found for patients with serum tetranectin < or = 5.4 mg/l. The maximal RR of death for the other prognostic variables were multiple metastases 2.8, and for a poor performance status 2.0. Testing for the outcome, progressive disease, a maximal RR of 3.8 was found for patients with serum tetranectin < or = 5.3 mg/l, a maximal RR of 3.7 for multiple metastases and a maximal RR of 1.8 for a poor performance status. Significantly lower serum tetranectin values were found in patients with a poor treatment response compared to well responding patients. Serum tetranectrin seems to be useful as an additional prognostic factor in metastatic breast cancer.

Adult↗
PubMed1993

Therapy-related myelodysplasia and acute myeloid leukemia. Cytogenetic characteristics of 115 consecutive cases and risk in seven cohorts of patients treated intensively for malignant diseases in the Copenhagen series.

Therapy-related acute myeloid leukemia (t-AML), often presenting as myelodysplasia (t-MDS), has become the most serious long-term complication of cancer therapy and offers a unique opportunity to study chemical leukemogenesis. Seven cohorts of patients treated for six different types of primary tumor have been followed closely for leukemic complications, and 115 consecutive patients with t-MDS or t-AML, including 45 cases from the cohorts, have been investigated cytogenetically at our institutions during the past 16 years. In patients primarily treated with alkylating agents, the risk of t-MDS and t-AML increased by approximately 1% per year from 2 to at least 8 years after start of treatment. In most cases, the disease presented as t-MDS with loss of a whole chromosome 5 or 7, or various parts of their long arms, and the leukemias were of FAB-subtypes M1, M2, or M4. In patients treated with drugs targeting at DNA-topoisomerase II, such as etoposide, doxorubicin, 4-epidoxorubicin, or mitoxantrone combined with drugs reacting directly with DNA, such as cisplatin or alkylating agents, the risk of leukemia increased much more steeply from only one year after start of therapy. These early onset cases often presented as overt leukemia of FAB-subtypes M4 or M5 with balanced translocations to chromosome bands 11q23 and 21q22, whereas later onset cases often shared characteristics with cases observed after therapy with alkylating agents alone. Both alkylation of DNA and poisoning of DNA-topoisomerase II may result in development of t-AML with different clinical and cytogenetic characteristics. There may be a synergistic leukemogenic effect between the two types of drug, and in patients with germ cell tumors treated with etoposide, cisplatin and bleomycin, reassessment suggested the risk of leukemia to increase exponentially with increasing doses of cisplatin and etoposide.

Adult↗
PubMed1993

Interpretation of results for tumor markers on the basis of analytical imprecision and biological variation.

Interpretation of results for CA 15.3, carcinoembryonic antigen (CEA), and tissue polypeptide antigen (TPA) during breast cancer monitoring requires data on intra- (CVP) and inter- (CVG) individual biological variation, analytical imprecision (CVA), and indices of individuality. The average CVP and CVG obtained from 22 healthy women were, respectively, 6.2% and 62.9% (CA 15.3), 9.3% and 86.8% (CEA), and 28.3% and 133% (TPA). The indices of individuality were all < 0.6: 0.2 (CA 15.3), 0.15 (CEA), and 0.2 (TPA). CVA depended on the concentration of the analytes. CVP and CVA determine what constitutes a significant difference between sequential results. Assuming a CVA of 11.2% (CA 15.3), 9.5% (CEA), or 11.9% (TPA), results must differ by 30%, 31%, or 72%, respectively, for P < or = 0.05. We found that CVP and CVA contribute considerably to the variation during breast cancer monitoring. Consequently, both CVP and CVA should be considered in criteria for marker evaluation. Because of low indices of individuality, conventional cutoff limits are inappropriate both for initial identification and for follow-up of breast cancer.

Adult↗
PubMed1992

P-glycoprotein as multidrug transporter: a critical review of current multidrug resistant cell lines.

MDR has been studied extensively in mammalian cell lines. According to usual practice, the MDR phenotype is characterized by the following features: cross resistance to multiple chemotherapeutic agents (lipophilic cations), defective intracellular drug accumulation and retention, overexpression of P-gp (often accompanied by gene amplification), and reversal of the phenotype by addition of calcium channel blockers. An hypothesis for the function of P-gp has been proposed in which P-gp acts as a carrier protein that actively extrudes MDR compounds out of the cells. However, basic questions, such as what defines the specificity of the pump and how is energy for active efflux transduced, remain to be answered. Furthermore, assuming that P-gp acts as a drug transporter, one will expect a relationship between P-gp expression and accumulation defects in MDR cell lines. A review of papers reporting 97 cell lines selected for resistance to the classical MDR compounds has revealed that a connection exists in most of the reported cell lines. However, several exceptions can be pointed out. Furthermore, only a limited number of well characterized series of sublines with different degrees of resistance to a single agent have been reported. In many of these, a correlation between P-gp expression and transport properties can not be established. Co-amplification of genes adjacent to the mdr1 gene, mutations [122], splicing of mdr1 RNA [123], modulation of P-gp by phosphorylation [124] or glycosylation [127], or experimental conditions [26,78] could account for some of the complexity of the phenotype and the absence of correlation in some of the cell lines. However, both cell lines with overexpression of P-gp without increased efflux [i.e., 67,75] and cell lines without P-gp expression and accumulation defects/increased efflux [i.e., 25,107] have been reported. Thus, current results from MDR cell lines contradict--but do not exclude--that P-gp acts as multidrug transporter. Other models for the mechanism of resistance have been proposed: (1) An energy-dependent permeability barrier working with greater efficacy in resistant cells. This hypothesis is supported by studies of influx which, although few, all except one demonstrate decreased influx in resistant cells; (2) Resistant cells have a greater endosomal volume, and a greater exocytotic activity accounts for the efflux.(ABSTRACT TRUNCATED AT 400 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Carbohydrate antigen 549 in metastatic breast cancer during cytostatic treatment and follow-up.

This study was designed to investigate whether the serum tumour marker CA 549 gave early and reliable information about disease activity among metastatic breast cancer patients during cytostatic treatment and follow-up. 50 females with metastatic breast cancer were monitored clinically and with the tumour marker CA 549. Response evaluation was based upon clinical (World Health Organization) and elaborated CA 549 criteria, respectively. In 113 blindly and matched evaluations, concordance appeared in 73/113 and discordance in 40/113 evaluations. In 27, discordance concerned degree of response, in 2 clinical progression followed marker progression after the end of the study, and in 11 progressive disease was established by clinical investigation alone. CA 549 response excluded clinical progression in bone or viscera and reversed. Clinical progression within 2 months in viscera and bone was predicted among 91% by marker progression. Clinical progression was excluded among 93% without marker progression. In conclusion, monitoring of metastatic breast cancer patients could include CA 549 if standardised criteria for marker evaluation are used.

Adult↗
PubMed1992

Teniposide in advanced breast cancer. A phase II trial in patients with no prior chemotherapy.

The objective response rates were determined using teniposide as first-line chemotherapy for patients with recurrent breast cancer. Twenty-seven evaluable patients with advanced disease received teniposide 70 mg/m2 i.v. days 1-5 every 3 weeks. A total of 211 courses were given. Responses included one complete (4%) and 9 partial responses (33%) with a median duration of response of 9 months (range 2-31 months). The main toxicity was myelosuppression. The results show that teniposide has at least modest activity in patients with advanced breast cancer treated previously with endocrine therapy.

Aged↗