Biomedical subjects

K M Nielsen

Publications and source records attributed to K M Nielsen.

At least 19 recordsLinked to original sources

PubMed2006

Comparative DNA analysis of two vanA plasmids from Enterococcus faecium strains isolated from poultry and a poultry farmer in Norway.

The DNA sequences of two plasmids carrying vanA, pVEF1 (39,626 bp) and pVEF2 (39,714 bp), were determined. Forty-three shared coding sequences were identified, and the only nucleotide difference was an 88-bp indel. A postsegregational killing system was identified. This system possibly explains the persistence of the vanA gene cluster in Norwegian poultry farms.

Animals↗

PubMed2006

Medical students' assessments of skill development in rural primary care clinics.

INTRODUCTION: This study assessed the impact of a rural primary care preceptorship on medical students' self-perceived ability to provide acute, chronic, and preventive care, to perform procedures, to communicate with patients, and to understand the community and healthcare system. METHODS: Students were surveyed about their self-assessed skills on 11 major components (97 items) immediately before and after a 16 week preceptorship in a rural primary care clinic. Responses were analyzed for 96 medical students using a paired comparisons t-test and univariate statistics. RESULTS: Students' skills significantly increased on all components and items. The skills most highly assessed post-preceptorship were those skills related to the management of chronic problems, the provision of patient education and health maintenance, and the ability to handle undifferentiated and acute problems. Among the 11 components assessed, students ranked their skills in performing procedures the lowest. The largest cumulative gain in skills was in the areas of understanding health systems and the community. CONCLUSIONS: This study provides a unique opportunity to look at skill development before and after a rural clerkship. From the student's perspective, the 16 week preceptorship appears to be of significant educational benefit. Future studies need to examine other measures of performance and outcomes of training in rural primary care settings.

Adult↗

PubMed2006

Enhanced monsoon precipitation and nitrogen deposition affect leaf traits and photosynthesis differently in spring and summer in the desert shrub Larrea tridentata.

Leaf-level CO2 assimilation (A(area)) can largely be predicted from stomatal conductance (g(s)), leaf morphology (SLA) and nitrogen (N) content (N(area)) in species across biomes and functional groups. The effects of simulated global change scenarios, increased summer monsoon rain (+H2O), N deposition (+N) and the combination (+H2O +N), were hypothesized to affect leaf trait-photosynthesis relationships differently in the short- and long-term for the desert shrub Larrea tridentata. During the spring, +H2O and +H2O +N plants had lower A(area) and g(s), but similar shoot water potential (Psi(shoot)) compared with control and +N plants; differences in A(area) were attributed to lower leaf N(area) and g(s). During the summer, +H2O and +H2O +N plants displayed higher A(area) than control and +N plants, which was attributed to higher Psi(shoot), g(s) and SLA. Throughout the year, A(area) was strongly correlated with g(s) but weakly correlated with leaf N(area) and SLA. We concluded that increased summer monsoon had a stronger effect on the performance of Larrea than increased N deposition. In the short term, the +H2O and +H2O +N treatments were associated with increasing A(area) in summer, but also with low leaf N(area) and lower A(area) in the long term the following spring.

Carbon Dioxide↗

PubMed2006

Danish singles have a twofold risk of acute coronary syndrome: data from a cohort of 138 290 persons.

STUDY OBJECTIVE: Atherosclerosis of the coronary and other arteries is an important health problem in virtually all countries of the world, and thus there is a persisting need for the development of preventive programmes including population risk group identification. The aim of the study was to identify sociodemographic population risk indicators of an initial episode of acute coronary syndrome (ACS), including unstable angina pectoris (UAP), myocardial infarction (MI), and sudden cardiac death (SCD). DESIGN: Cohort study of 138 290 residents of the municipality of Aarhus, Denmark, aged 30-69 years. Information on population members' individual age, sex, social background, and eventual death was obtained from Danish Population Registers. SETTING: University hospital. PATIENTS: The study prospectively identified 646 victims of ACS from 1 April 2000 to 31 March 2002. MAIN RESULTS: Based on multiple logistic regression, age and single living were found to be positively associated with incident ACS in both sexes. Women >60 years living alone and men >50 years living alone were at especially high risk. They constituted only 5.4% and 7.7% of the source population, respectively, but they accounted for 34.3% and 62.4% of ACS patients dying within 30 days. CONCLUSIONS: Single living is associated with an increased risk of ACS. Thus, risk groups identified by use of information on their age and family structure may be targets for future more focused and cost effective preventive strategies. In Western populations, such high risk groups will constitute comparatively limited parts of the population, and in Denmark they are easily identifiable in routine population registers.

Acute Disease↗

PubMed2005

Comparative effects of acute or chronic administration of levodopa to 6-hydroxydopamine-lesioned rats on the expression of glutamic acid decarboxylase in the neostriatum and GABAA receptors subunits in the substantia nigra, pars reticulata.

Current evidence suggests that behavioral sensitization to the chronic administration of levodopa (L-DOPA) to dopamine-depleted animals involves a plasticity of GABA-mediated signaling in output regions of the basal ganglia. The purpose of this study was to compare in adult rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion the effects of an acute or chronic (for 3 or 7 days) injection of L-DOPA on mRNA levels encoding for glutamic acid decarboxylase (GAD65 and GAD67) in the striatum and GABA(A) receptor alpha1, beta2 and gamma2 subunits in the substantia nigra, pars reticulata (SNr), by in situ hybridization histochemistry. In addition, immunostaining levels for the alpha1 subunit were examined in the SNr. In agreement with previous studies, we found that L-DOPA administration increased GAD mRNA levels in the striatum of 6-OHDA-lesioned rats. However, the magnitude of this effect increased with the number of injections of L-DOPA. On the other hand, we found that 6-OHDA lesions resulted in increases in alpha1, beta2 and gamma2 mRNA levels in the ipsilateral SNr, which were normalized or decreased compared with the contralateral side by the acute or chronic administration of L-DOPA. In addition, alpha1 immunostaining in the SNr was significantly decreased in rats injected for 7 days but not for 3 days or acutely with L-DOPA. Our results demonstrate that a chronic administration of L-DOPA results in a progressive increase in GAD and decrease in GABA(A) receptor expression in the striatum and SNr, respectively. They provide further evidence that behavioral sensitization and dyskinesia induced by a chronic administration of L-DOPA in an experimental model of Parkinson's disease is paralleled by a plasticity of GABA-mediated signaling in the SNr.

Adrenergic Agents↗

PubMed2004

Normalization of glutamate decarboxylase gene expression in the entopeduncular nucleus of rats with a unilateral 6-hydroxydopamine lesion correlates with increased GABAergic input following intermittent but not continuous levodopa.

The expression of mRNA encoding for the 67 kilodalton isoform of glutamate decarboxylase (GAD67) was examined by in situ hybridization histochemistry in the entopeduncular nucleus (EP) of adult rats with a 6-hydroxydopamine unilaterally lesion of dopamine neurons. Our results provide original evidence that continuous or intermittent levodopa administration is equally effective at reversing the lesion-induced increase in GAD67 mRNA expression in the EP when compared with vehicle controls. To characterize the GABAergic interactions that may mediate levodopa-induced alterations in the EP, double-labeling in situ hybridization was conducted with a combination of GAD67 radioactive and preproenkephalin or preprotachykinin digoxigenin-labeled complementary RNA probes in the striatum. Levels of GAD67 mRNA labeling were significantly increased by intermittent, but not continuous levodopa. Analysis at the cellular level in a dorsal sector of the striatum revealed that GAD67 mRNA levels increased predominantly in preproenkephalin-unlabeled neuronal profiles, presumably striatal/EP neurons (+99.3%). Saturation analyses of (3)H-flunitrazepam binding to GABA(A) receptors in the EP showed that the increase in GAD67 mRNA in preproenkephalin-unlabeled neurons by intermittent levodopa paralleled a significant decrease in number of GABA(A) receptors (Bmax) in the EP ipsilateral to the lesion. Continuous levodopa failed to alter striatal GAD67 mRNA levels, or the number or affinity of GABA(A) receptors when compared with vehicle-treated controls. These results suggest the normalization of GAD gene expression in the EP by intermittent levodopa involves an increase in GABAergic inhibition by striatonigral/EP neurons of the direct pathway. Conversely, the effects of continuous levodopa on GAD mRNA levels in the EP do not appear to be mediated by GABA.

Animals↗

PubMed2004

Genes without frontiers?

For bacteria, the primary genetic barrier against the genetic exchange of DNA that is not self-transmissible is dissimilarity in the bacterial DNA sequences concerned. Genetic exchange by homologous recombination is frequent among close bacterial relatives and recent experiments have shown that it can enable the uptake of closely linked nonhomologous foreign DNA. Artificial vectors are mosaics of mobile DNA elements from free-living bacterial isolates and so bear a residual similarity to their ubiquitous natural progenitors. This homology is tightly linked to the multitude of different DNA sequences that are inserted into synthetic vectors. Can homology between vector and bacterial DNA enable the uptake of these foreign DNA inserts? In this review we investigate pUC18 as an example of an artificial vector and consider whether its homology to broad host-range antibiotic resistance transposons and plasmid origins of replication could enable the uptake of insert DNA in the light of studies of homology-facilitated foreign DNA uptake. We also discuss the disposal of recombinant DNA, its persistence in the environment and whether homologies to pUC18 may exist in naturally competent bacteria. Most DNA that is inserted into the cloning site of artificial vectors would be of little use to a bacterium, but perhaps not all.

Bacteria↗

PubMed2001

Recent origin of Plasmodium falciparum from a single progenitor.

Genetic variability of Plasmodium falciparum underlies its transmission success and thwarts efforts to control disease caused by this parasite. Genetic variation in antigenic, drug resistance, and pathogenesis determinants is abundant, consistent with an ancient origin of P. falciparum, whereas DNA variation at silent (synonymous) sites in coding sequences appears virtually absent, consistent with a recent origin of the parasite. To resolve this paradox, we analyzed introns and demonstrated that these are deficient in single-nucleotide polymorphisms, as are synonymous sites in coding regions. These data establish the recent origin of P. falciparum and further provide an explanation for the abundant diversity observed in antigen and other selected genes.

Africa↗

PubMed2000

Natural transformation of Acinetobacter sp. strain BD413 with cell lysates of Acinetobacter sp., Pseudomonas fluorescens, and Burkholderia cepacia in soil microcosms.

To elucidate the biological significance of dead bacterial cells in soil to the intra- and interspecies transfer of gene fragments by natural transformation, we have exposed the kanamycin-sensitive recipient Acinetobacter sp. strain BD413(pFG4) to lysates of the kanamycin-resistant donor bacteria Acinetobacter spp., Pseudomonas fluorescens, and Burkholderia cepacia. Detection of gene transfer was facilitated by the recombinational repair of a partially (317 bp) deleted kanamycin resistance gene in the recipient bacterium. The investigation revealed a significant potential of these DNA sources to transform Acinetobacter spp. residing both in sterile and in nonsterile silt loam soil. Heat-treated (80 degrees C, 15 min) cell lysates were capable of transforming strain BD413 after 4 days of incubation in sterile soil and for up to 8 h in nonsterile soil. Transformation efficiencies obtained in vitro and in situ with the various lysates were similar to or exceeded those obtained with conventionally purified DNA. The presence of cell debris did not inhibit transformation in soil, and the debris may protect DNA from rapid biological inactivation. Natural transformation thus provides Acinetobacter spp. with an efficient mechanism to access genetic information from different bacterial species in soil. The relatively short-term biological activity (e.g., transforming activity) of chromosomal DNA in soil contrasts the earlier reported long-term physical stability of DNA, where fractions have been found to persist for several weeks in soil. Thus, there seems to be a clear difference between the physical and the functional significance of chromosomal DNA in soil.

Acinetobacter↗

PubMed2000

Transformation of Acinetobacter sp. strain BD413(pFG4DeltanptII) with transgenic plant DNA in soil microcosms and effects of kanamycin on selection of transformants.

Here we show that horizontal transfer of DNA, extracted from transgenic sugar beets, to bacteria, based on homologous recombination, can occur in soil. Restoration of a 317-bp-deleted nptII gene in Acinetobacter sp. strain BD413(pFG4) cells incubated in sterile soil microcosms was detected after addition of nutrients and transgenic plant DNA encoding a functional nptII gene conferring bacterial kanamycin resistance. Selective effects of the addition of kanamycin on the population dynamics of Acinetobacter sp. cells in soil were found, and high concentrations of kanamycin reduced the CFU of Acinetobacter sp. cells from 10(9) CFU/g of soil to below detection. In contrast to a chromosomal nptII-encoded kanamycin resistance, the pFG4-generated resistance was found to be unstable over a 31-day incubation period in vitro.

Acinetobacter↗

PubMed1999

[The elderly in general psychiatry].

The Danish National Board of Health recommends that the counties offer psychogeriatric services. The target group for geriatric psychiatry in the County of North Jutland only concerns elderly people with severe dementia. It has been our aim to describe and discuss the geriatric psychiatric supply of services and admission pattern for elderly with psychiatric morbidity in the County of North Jutland. We have made a cross-sectional study of all patients referred to the general and psychogeriatric service in 1997. In psychogeriatric service 40 of 46 referrals were dealt with as out-patient contact. In general psychiatry the 57 referrals resulted in 33 admissions of which 31 were acute. There is a high number of acute admissions in general psychiatry. The County of North Jutland does not have a suitable service for diagnostic work-up and treatment of people with possible to moderate dementia.

Aged↗

PubMed1999

A Danish national cohort of 730 infants born after intracytoplasmic sperm injection (ICSI) 1994-1997.

This national cohort study included all clinical pregnancies obtained after intracytoplasmic sperm injection (ICSI) registered in Denmark between January 1994 and July 1997 at five public and eight private fertility clinics. Laboratory and clinical data were obtained from the fertility clinics. The couples answered a questionnaire regarding the pregnancy and the health of the child (response rate 94%). Data validation was carried out through discharge charts. The mean age of the women was 32.1 years. In 84.2% of couples, male factor was the main reason for performing ICSI, and in 4.8% epididymal spermatozoa were used. The mean number of embryos replaced was 2.3 (range 1-3) and in 95% of cases fresh embryos were transferred. Only 183 women (28.5%) underwent prenatal diagnosis, resulting in 209 karyotypes with seven (3.3%) chromosome aberrations. Six major chromosomal abnormalities (2.9%) and one inherited structural chromosome aberration (0.5%) were found, but no sex chromosome aberrations. The frequency of multiple birth, Caesarean section rate, gestational age, preterm birth, and birth weight were comparable with previous studies. The perinatal mortality rate was 13.7 per 1000 children born with a gestational age of 24 weeks or more. In 2.2% (n = 16) of the liveborn infants, and in 2.7% (n = 20) of all infants, major birth defects were reported by the parents. Minor birth defects were found in nine liveborn infants (1.2%). In conclusion, the results of this study on outcome of ICSI pregnancies are in line with earlier reports, except that no sex chromosome abnormalities were found.

Adult↗

PubMed1998

Horizontal gene transfer from transgenic plants to terrestrial bacteria--a rare event?

Today, 12 years after the first field release of a genetically modified plant (GMP), over 15,000 field trials at different locations have been performed. As new and unique characteristics are frequently introduced into GMPs, risk assessment has to be performed to assess their ecological impact. The possibilities of horizontal gene transfer (HGT; no parent-to-offspring transfer of genes) from plants to microorganisms are frequently evaluated in such risk assessments of GMPs before release into the field. In this review we indicate why putative HGT from plants to terrestrial (soil and plant associated) bacteria has raised concern in biosafety evaluations. Further, we discuss possible pathways of HGT from plants to bacteria, outline the barriers to HGT in bacteria, describe the strategies used to investigate HGT from plants to bacteria and summarize the results obtained. Only a few cases of HGT from eukaryotes such as plants to bacteria have been reported to date. These cases have been ascertained after comparison of DNA sequences between plants and bacteria. Although experimental approaches in both field and laboratory studies have not been able to confirm the occurrence of such HGT to naturally occurring bacteria, recently two studies have shown transfer of marker genes from plants to bacteria based on homologous recombination. The few examples of HGT indicated by DNA sequence comparisons suggest that the frequencies of evolutionarily successful HGT from plants to bacteria may be extremely low. However, this inference is based on a small number of experimental studies and indications found in the literature. Transfer frequencies should not be confounded with the likelihood of environmental implications, since the frequency of HGT is probably only marginally important compared with the selective force acting on the outcome. Attention should therefore be focused on enhancing the understanding of selection processes in natural environments. Only an accurate understanding of these selective events will allow the prediction of possible consequences of novel genes following their introduction into open environments.

Bacteria↗

PubMed1998

Barriers to horizontal gene transfer by natural transformation in soil bacteria.

Bacteria can utilize horizontally transferred DNA from other bacterial species to adapt and evolve to their changing environments. Natural transformation is a process that allows bacteria, which are able to express a regulated physiological state of competence, to take up and integrate free DNA from their surroundings. This uptake of DNA does not necessarily depend on DNA sequence, thus, indicating the potential of gene transfer from diverged donor organisms. Barriers active against such interspecies transfer are present at different phases of the transformation process. The functionality of these barriers will be discussed, and seen in relation to mechanisms that may enable bacterial cells to respond to environmental stress by adaptive evolution.

Adaptation, Biological↗

PubMed1997

Induced Natural Transformation of Acinetobacter calcoaceticus in Soil Microcosms.

Factors affecting natural transformation of Acinetobacter calcoaceticus BD413 with homologous chromosomal DNA in a silt loam soil microcosm were investigated. Inducible transformation of declining populations of noncompetent A. calcoaceticus cells was detectable for up to 6 days when a simple carbon source, salts, and freshly added DNA were used. In two different experimental setups, the residence time in soil of induced cells could be increased to either 11 or 24 h before DNA addition without reduced transformation frequency; 200-to 1,000-fold fewer transformants were observed following the addition of water. These observations suggest that A. calcoaceticus remains transformable for several hours after its activation by nutrients in soil. Increasing the levels of phosphate salts significantly enhanced the numbers of transformants without increasing the recipient counts correspondingly. Variable levels of ammonium or divalent cations (Mg(sup2+) and Ca(sup2+)) did not have a similar major influence. Soil moisture content significantly affected the transformation frequency of A. calcoaceticus cells, with a general tendency of higher frequencies in drier soil. A minimal frequency was observed at around 35% soil moisture. The data indicate that A. calcoaceticus cells in soil which cannot be detectably transformed are easily induced by nutrients to undergo natural transformation with chromosomal DNA. Access to nutrients seems to be critical for the development and maintenance of competence in soil, which is also affected by abiotic factors like moisture level and phosphate salt concentration.

Journal Article↗

PubMed1997

Natural transformation and availability of transforming DNA to Acinetobacter calcoaceticus in soil microcosms.

A small microcosm, based on optimized in vitro transformation conditions, was used to study the ecological factors affecting the transformation of Acinetobacter calcoaceticus BD413 in soil. The transforming DNA used was A. calcoaceticus homologous chromosomal DNA with an inserted gene cassette containing a kanamycin resistance gene, nptII. The effects of soil type (silt loam or loamy sand), bacterial cell density, time of residence of A. calcoaceticus or of DNA in soil before transformation, transformation period, and nutrient input were investigated. There were clear inhibitory effects of the soil matrix on transformation and DNA availability. A. calcoaceticus cells reached stationary phase and lost the ability to be transformed shortly after introduction into sterile soil. The use of an initially small number of A. calcoaceticus cells and nutrients, resulting in bacterial growth, enhanced transformation frequencies within a limited period. The availability of introduced DNA for transformation of A. calcoaceticus cells disappeared within a few hours in soil. Differences in transformation frequencies between soils were found; A. calcoaceticus cells were transformed at a higher rate and for a longer period in a silt loam than in a loamy sand. Physical separation of DNA and A. calcoaceticus cells had a negative effect on transformation. Transformation was also detected in nonsterile soil microcosms, albeit only in the presence of added nutrients and at a reduced frequency. These results suggest that chromosomal DNA released into soil rapidly becomes unavailable for transformation of A. calcoaceticus. In addition, strain BD413 quickly loses the ability to receive, stabilize, and/or express exogenous DNA after introduction into soil.

Acinetobacter calcoaceticus↗

PubMed1997

Agravitropic behaviour of roots of rapeseed (Brassica napus L.) transformed by Agrobacterium rhizogenes.

Transgenic hairy roots of Brassica napus (cv. Omega) have been developed, using Agrobacterium rhizogenes strain AR 25, for use as a model system in the investigation of physiological and morphological differences between transgenic and normal roots. The basic parameters of growth and normal or altered gravitropical behaviour of hairy roots are for the first time presented in this paper together with an ultrastructural and morphological analysis of the root statocytes. The results obtained also represented the basis for the TRANSF0RM-experiment on the IML-2 mission performed onboard the Space Shuttle Columbia. Typical hairy root traits such as hormone-autonomous growth high growth rate, lateral branching, and changed/absence of gravitropism were detected. The transformed nature of the roots was confirmed by Southern blot analyses. The gravitropical behaviour of apices from hairy root cultures of this clone has been compared with root tips from normal seedlings. While the wild type roots curved progressively with increasing stimulation angles, the transformed roots showed no curvature when stimulated at 45 degrees, 90 degrees or 135 degrees on the ground. The morphology and ultrastructure of the root tip regions were examined by light microscopy and transmission electron microscopy. At the ultrastructural level no major differences could be detected between the roots studied. There was, however, a slight reduction in the starch content of most of the amyloplasts of the transgenic root tips, and the root cap was more V-shaped in the transgenic roots than in the wild type. Preliminary results from the Shuttle experiment TRANSFORM show a random distribution of amyloplasts in the root cells of both transformed and wild type root caps after 14 h on a 1xg centrifuge followed by 37 h in microgravity.

Agrobacterium tumefaciens↗

PubMed1991

[Development of endometrial cancer during tamoxifen therapy].

The cases of two postmenopausal women are presented. Both developed endometrial cancer after continuous treatment with tamoxifen for several years. The possible connection between endometrial cancer and treatment with tamoxifen is discussed.

Adenocarcinoma↗