Publications by authors named "Johan Berg"

15 Publications

  • Page 1 of 1

Effect of Delayed Cord Clamping on Neurodevelopment at 3 Years: A Randomized Controlled Trial.

Neonatology 2021 May 7:1-7. Epub 2021 May 7.

Department of Clinical Sciences Lund, Pediatrics, Lund University, Lund, Sweden,

Introduction: Iron deficiency (ID) is associated with poor neurodevelopment. We have previously shown that delayed umbilical cord clamping (CC) improves iron stores at 8 months and neurodevelopment at 1 year in term, healthy infants in Nepal.

Objective: The aim of this study was to assess the effects of delayed CC (≥180 s) compared to early CC (≤60 s) on neurodevelopment using the Ages and Stages Questionnaire (ASQ) at age 3 years.

Methods: In 2014, 540 healthy Nepalese infants born at term were randomized in a 1:1 ratio to delayed or early CC. At 3 years of age, ASQ assessment was performed by phone interviews with parents. A score >1 standard deviation below the mean was defined as "at risk" for developmental impairment.

Results: At 3 years of age, 350 children were followed up, 170 (63.0%) in the early CC group and 180 (66.7%) in the delayed CC group. No significant differences in ASQ scores in any domains between groups were found. However, more girls were "at risk" for affected gross motor development in the early CC group: 14 (18.9%) versus 6 (6.3%), p = 0.02.

Conclusion: There were no significant differences in ASQ scores in any domains between groups. In the subgroup analysis, fewer girls who underwent delayed CC were "at risk" for delayed gross motor development. Due to the pronounced difference in iron stores at 8 months postpartum in this cohort, follow-up studies at an older age are motivated since neurodevelopmental impairment after early ID may be more detectable with increasing age.
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http://dx.doi.org/10.1159/000515838DOI Listing
May 2021

Helicopter Emergency Medical Services Response to a Major Incident.

Air Med J 2020 Nov - Dec;39(6):506-508. Epub 2020 Oct 16.

HALO Aviation, Johannesburg, Gauteng, South Africa.

Major incidents account for a vast number of consequences, whether it be individual morbidity and mortality or economic disruption and expense. Because of the infrequent nature, it poses a variety of unique risks and challenges for individual emergency medical services systems. Air ambulances are usually dispatched based on the clinical presentation of an individual patient who needs emergent critical care intervention. The response to a major incident is unusual and infrequent, but the benefit of tasking air ambulances to such incidents has been described by various authors. Here, such a response is described in a low- to middle-income country that saw the immediate tasking of 2 separate air ambulances to a single, multivehicle collision with multiple injured patients that occurred near a small, rural hospital not capable of treating critically ill patients. The benefits of tasking of the air ambulance in the sense of additional expertise as well as potential other nonclinical benefits are discussed and described here.
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http://dx.doi.org/10.1016/j.amj.2020.09.007DOI Listing
October 2020

Lipid Composition Affects the Efficiency in the Functional Reconstitution of the Cytochrome Oxidase.

Int J Mol Sci 2020 Sep 23;21(19). Epub 2020 Sep 23.

Institute of Chemistry and Biochemistry, Emmy-Noether Group "Bionanointerfaces", Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany.

The transmembrane protein cytochrome oxidase (CO) is the terminal oxidase in the respiratory chain of many aerobic organisms and catalyzes the reduction of dioxygen to water. This process maintains an electrochemical proton gradient across the membrane hosting the oxidase. CO is a well-established model enzyme in bioenergetics to study the proton-coupled electron transfer reactions and protonation dynamics involved in these processes. Its catalytic mechanism is subject to ongoing intense research. Previous research, however, was mainly focused on the turnover of oxygen and electrons in CO, while studies reporting proton turnover rates of CO, that is the rate of proton uptake by the enzyme, are scarce. Here, we reconstitute CO from into liposomes containing a pH sensitive dye and probe changes of the pH value inside single proteoliposomes using fluorescence microscopy. CO proton turnover rates are quantified at the single-enzyme level. In addition, we recorded the distribution of the number of functionally reconstituted COs across the proteoliposome population. Studies are performed using proteoliposomes made of native lipid sources, such as a crude extract of soybean lipids and the polar lipid extract of , as well as purified lipid fractions, such as phosphatidylcholine extracted from soybean lipids. It is shown that these lipid compositions have only minor effects on the CO proton turnover rate, but can have a strong impact on the reconstitution efficiency of functionally active COs. In particular, our experiments indicate that efficient functional reconstitution of CO is strongly promoted by the addition of anionic lipids like phosphatidylglycerol and cardiolipin.
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http://dx.doi.org/10.3390/ijms21196981DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7583929PMC
September 2020

Kinetic advantage of forming respiratory supercomplexes.

Biochim Biophys Acta Bioenerg 2020 07 19;1861(7):148193. Epub 2020 Mar 19.

Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden. Electronic address:

Components of respiratory chains in mitochondria and some aerobic bacteria assemble into larger, multiprotein membrane-bound supercomplexes. Here, we address the functional significance of supercomplexes composed of respiratory-chain complexes III and IV. Complex III catalyzes oxidation of quinol and reduction of water-soluble cytochrome c (cyt c), while complex IV catalyzes oxidation of the reduced cyt c and reduction of dioxygen to water. We focus on two questions: (i) under which conditions does diffusion of cyt c become rate limiting for electron transfer between these two complexes? (ii) is there a kinetic advantage of forming a supercomplex composed of complexes III and IV? To answer these questions, we use a theoretical approach and assume that cyt c diffuses in the water phase while complexes III and IV either diffuse independently in the two dimensions of the membrane or form supercomplexes. The analysis shows that the electron flux between complexes III and IV is determined by the equilibration time of cyt c within the volume of the intermembrane space, rather than the cyt c diffusion time constant. Assuming realistic relative concentrations of membrane-bound components and cyt c and that all components diffuse independently, the data indicate that electron transfer between complexes III and IV can become rate limiting. Hence, there is a kinetic advantage of bringing complexes III and IV together in the membrane to form supercomplexes.
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http://dx.doi.org/10.1016/j.bbabio.2020.148193DOI Listing
July 2020

Structural changes at the surface of cytochrome c oxidase alter the proton-pumping stoichiometry.

Biochim Biophys Acta Bioenerg 2020 02 14;1861(2):148116. Epub 2019 Nov 14.

Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden. Electronic address:

Data from earlier studies showed that minor structural changes at the surface of cytochrome c oxidase, in one of the proton-input pathways (the D pathway), result in dramatically decreased activity and a lower proton-pumping stoichiometry. To further investigate how changes around the D pathway orifice influence functionality of the enzyme, here we modified the nearby C-terminal loop of subunit I of the Rhodobacter sphaeroides cytochrome c oxidase. Removal of 16 residues from this flexible surface loop resulted in a decrease in the proton-pumping stoichiometry to <50% of that of the wild-type enzyme. Replacement of the protonatable residue Glu552, part of the same loop, by an Ala, resulted in a similar decrease in the proton-pumping stoichiometry without loss of the O-reduction activity or changes in the proton-uptake kinetics. The data show that minor structural changes at the orifice of the D pathway, at a distance of ~40 Å from the proton gate of cytochrome c oxidase, may alter the proton-pumping stoichiometry of the enzyme.
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http://dx.doi.org/10.1016/j.bbabio.2019.148116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6943178PMC
February 2020

Countertransference in Swedish psychotherapists: testing the factor structure of the Therapist Response Questionnaire.

Res Psychother 2019 Apr 17;22(1):331. Epub 2019 Jan 17.

Department of Behavioural Sciences and Learning, Linkoping University, Sweden.

Questionnaires need testing of reliability and factor structure before clinical use or research in new languages or cultures. The aim of this study was to evaluate the Therapist Response Questionnaire (TRQ) in Sweden compared to corresponding factor analyses in USA and Italy. A national sample of psychotherapists (N=242) registered their countertransference with a single client using TRQ. The data were analyzed with confirmatory factor analysis (CFA) to test factor structures from previous studies, and exploratory factor analysis (EFA). The CFA did not verify the factor structure from the previous studies. The EFA extracted seven factors as the best solution: Helpless/Inadequate, Overwhelmed/Disorganized, Hostile/Angry, Parental/Protective, Disengaged, Special/Overinvolved, Sexualized. Analysis of convergent validity indicated that five of these could be considered equivalent to factors in the previous studies, and the remaining two were conceptually related to corresponding factors. Even though the factor structure was not confirmed by the CFA, the concordance was large, indicating a reliable self-report instrument with promising validity for measurement of complex aspects of countertransference. Common countertransference themes can inform psychotherapy supervision and education, give feedback to the therapist, and lay ground for a taxonomy for therapist reactions and feelings.
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http://dx.doi.org/10.4081/ripppo.2019.331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7453160PMC
April 2019

Trends in tissue engineering for blood vessels.

J Biomed Biotechnol 2012 8;2012:956345. Epub 2012 Nov 8.

Regenerative Medicine Laboratory, Stem Cell Research Center, Department of Biomedical Science and Technology, SMART Institute of Advanced Biomedical Science, Konkuk University, 143-701 Seoul, Republic of Korea.

Over the years, cardiovascular diseases continue to increase and affect not only human health but also the economic stability worldwide. The advancement in tissue engineering is contributing a lot in dealing with this immediate need of alleviating human health. Blood vessel diseases are considered as major cardiovascular health problems. Although blood vessel transplantation is the most convenient treatment, it has been delimited due to scarcity of donors and the patient's conditions. However, tissue-engineered blood vessels are promising alternatives as mode of treatment for blood vessel defects. The purpose of this paper is to show the importance of the advancement on biofabrication technology for treatment of soft tissue defects particularly for vascular tissues. This will also provide an overview and update on the current status of tissue reconstruction especially from autologous stem cells, scaffolds, and scaffold-free cellular transplantable constructs. The discussion of this paper will be focused on the historical view of cardiovascular tissue engineering and stem cell biology. The representative studies featured in this paper are limited within the last decade in order to trace the trend and evolution of techniques for blood vessel tissue engineering.
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http://dx.doi.org/10.1155/2012/956345DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3518873PMC
April 2013

A single-step competitive binding assay for mapping of single DNA molecules.

Biochem Biophys Res Commun 2012 Jan 7;417(1):404-8. Epub 2011 Dec 7.

Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.

Optical mapping of genomic DNA is of relevance for a plethora of applications such as scaffolding for sequencing and detection of structural variations as well as identification of pathogens like bacteria and viruses. For future clinical applications it is desirable to have a fast and robust mapping method based on as few steps as possible. We here demonstrate a single-step method to obtain a DNA barcode that is directly visualized using nanofluidic devices and fluorescence microscopy. Using a mixture of YOYO-1, a bright DNA dye, and netropsin, a natural antibiotic with very high AT specificity, we obtain a DNA map with a fluorescence intensity profile along the DNA that reflects the underlying sequence. The netropsin binds to AT-tetrads and blocks these binding sites from YOYO-1 binding which results in lower fluorescence intensity from AT-rich regions of the DNA. We thus obtain a DNA barcode that is dark in AT-rich regions and bright in GC-rich regions with kilobasepair resolution. We demonstrate the versatility of the method by obtaining a barcode on DNA from the phage T4 that captures its circular permutation and agrees well with its known sequence.
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http://dx.doi.org/10.1016/j.bbrc.2011.11.128DOI Listing
January 2012

Electric field controlled magnetic anisotropy in a single molecule.

Nano Lett 2010 Sep;10(9):3307-11

Kavli Institute of Nanoscience, Delft University of Technology, PO Box 5046, 2600 GA Delft, The Netherlands.

We have measured quantum transport through an individual Fe(4) single-molecule magnet embedded in a three-terminal device geometry. The characteristic zero-field splittings of adjacent charge states and their magnetic field evolution are observed in inelastic tunneling spectroscopy. We demonstrate that the molecule retains its magnetic properties and, moreover, that the magnetic anisotropy is significantly enhanced by reversible electron addition/subtraction controlled with the gate voltage. Single-molecule magnetism can thus be electrically controlled.
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http://dx.doi.org/10.1021/nl1009603DOI Listing
September 2010

Heterologous carotenoid production in Saccharomyces cerevisiae induces the pleiotropic drug resistance stress response.

Yeast 2010 Dec;27(12):983-98

Fungal Genomics, Laboratory of Microbiology, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, The Netherlands.

To obtain insight into the genome-wide transcriptional response of heterologous carotenoid production in Saccharomyces cerevisiae, the transcriptome of two different S. cerevisiae strains overexpressing carotenogenic genes from the yeast Xanthophyllomyces dendrorhous grown in carbon-limited chemostat cultures was analysed. The strains exhibited different absolute carotenoid levels as well as different intermediate profiles. These discrepancies were further sustained by the difference of the transcriptional response exhibited by the two strains. Transcriptome analysis of the strain producing high carotenoid levels resulted in specific induction of genes involved in pleiotropic drug resistance (PDR). These genes encode ABC-type and major facilitator transporters which are reported to be involved in secretion of toxic compounds out of cells. β-Carotene was found to be secreted when sunflower oil was added to the medium of S. cerevisiae cells producing high levels of carotenoids, which was not observed when added to X. dendrorhous cells. Deletion of pdr10, one of the induced ABC transporters, decreased the transformation efficiency of a plasmid containing carotenogenic genes. The few transformants that were obtained had decreased growth rates and lower carotenoid production levels compared to a pdr5 deletion and a reference strain transformed with the same genes. Our results suggest that production of high amounts of carotenoids in S. cerevisiae leads to membrane stress, in which Pdr10 might play an important role, and a cellular response to secrete carotenoids out of the cell.
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http://dx.doi.org/10.1002/yea.1807DOI Listing
December 2010

Progressive multifocal leukoencephalopathy after natalizumab monotherapy.

N Engl J Med 2009 Sep;361(11):1081-7

Neurology Unit, Division of Internal Medicine, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden.

We describe progressive multifocal leukoencephalopathy (PML) caused by infection with human polyomavirus JC virus in a patient with multiple sclerosis who was treated with natalizumab. The first PML symptoms appeared after 14 monthly infusions of the drug. Magnetic resonance imaging (MRI) showed a presumed multiple sclerosis lesion, and JC virus DNA was not detected on polymerase-chain-reaction (PCR) assay of cerebrospinal fluid. The patient's symptoms worsened, and the diagnosis of PML was established with a more sensitive quantitative PCR assay after 16 infusions of natalizumab. Plasma exchange was used to accelerate clearance of natalizumab. Approximately 3 weeks after plasma exchange, an immune-reconstitution inflammatory syndrome appeared. JC virus DNA was no longer detectable on quantitative PCR assay, and the patient's symptoms improved.
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http://dx.doi.org/10.1056/NEJMoa0810316DOI Listing
September 2009

Genes involved in carotene synthesis and mating in Blakeslea trispora.

Curr Genet 2008 Sep 2;54(3):143-52. Epub 2008 Aug 2.

Section of Fungal Genomics, Wageningen University, Dreijenlaan 2, 6703 Wageningen, HA, The Netherlands.

Mating of Blakeslea trispora and other molds of the order Mucorales requires the interaction of mycelia of opposite sex, (+) and (-), leading to the development of specialized structures and to an enhanced accumulation of beta-carotene. Industry obtains beta-carotene by co-cultivating appropriate strains of Blakeslea ("mated cultures"). Gene transcription in single and mated cultures was assayed by cDNA-AFLP, a technique to observe the differential expression of subsets of mRNA fragments. Overexpression in mated cultures is about ten times more frequent than underexpression. We obtained and sequenced fragments of 97 candidate genes that appeared to be overexpressed during mating and confirmed four of them by reverse transcription and real-time PCR. Comparisons with gene sequences from other organisms suggest functions in carotene biosynthesis (4 genes), energy metabolism (8), cell wall synthesis (1), transfer of acetyl groups (1), and regulatory processes (10). Sodium acetate inhibited sexual overexpression in about two-thirds of the candidate genes and acted as a signal with broad effects on the metabolism and the morphology of mated cultures. Our work offers new materials for the study of carotene biosynthesis and its regulation and for the improvement of carotene production with Mucorales.
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http://dx.doi.org/10.1007/s00294-008-0206-xDOI Listing
September 2008

High-level production of beta-carotene in Saccharomyces cerevisiae by successive transformation with carotenogenic genes from Xanthophyllomyces dendrorhous.

Appl Environ Microbiol 2007 Jul 11;73(13):4342-50. Epub 2007 May 11.

Fungal Genomics, Laboratory of Microbiology, Wageningen University, Dreijenlaan 2, Wageningen, The Netherlands.

To determine whether Saccharomyces cerevisiae can serve as a host for efficient carotenoid and especially beta-carotene production, carotenogenic genes from the carotenoid-producing yeast Xanthophyllomyces dendrorhous were introduced and overexpressed in S. cerevisiae. Because overexpression of these genes from an episomal expression vector resulted in unstable strains, the genes were integrated into genomic DNA to yield stable, carotenoid-producing S. cerevisiae cells. Furthermore, carotenoid production levels were higher in strains containing integrated carotenogenic genes. Overexpression of crtYB (which encodes a bifunctional phytoene synthase and lycopene cyclase) and crtI (phytoene desaturase) from X. dendrorhous was sufficient to enable carotenoid production. Carotenoid production levels were increased by additional overexpression of a homologous geranylgeranyl diphosphate (GGPP) synthase from S. cerevisiae that is encoded by BTS1. Combined overexpression of crtE (heterologous GGPP synthase) from X. dendrorhous with crtYB and crtI and introduction of an additional copy of a truncated 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene (tHMG1) into carotenoid-producing cells resulted in a successive increase in carotenoid production levels. The strains mentioned produced high levels of intermediates of the carotenogenic pathway and comparable low levels of the preferred end product beta-carotene, as determined by high-performance liquid chromatography. We finally succeeded in constructing an S. cerevisiae strain capable of producing high levels of beta-carotene, up to 5.9 mg/g (dry weight), which was accomplished by the introduction of an additional copy of crtI and tHMG1 into carotenoid-producing yeast cells. This transformant is promising for further development toward the biotechnological production of beta-carotene by S. cerevisiae.
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http://dx.doi.org/10.1128/AEM.02759-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1932764PMC
July 2007

A new group of exo-acting family 28 glycoside hydrolases of Aspergillus niger that are involved in pectin degradation.

Biochem J 2006 Nov;400(1):43-52

Section Fungal Genomics, Laboratory of Microbiology, Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands.

The fungus Aspergillus niger is an industrial producer of pectin-degrading enzymes. The recent solving of the genomic sequence of A. niger allowed an inventory of the entire genome of the fungus for potential carbohydrate-degrading enzymes. By applying bioinformatics tools, 12 new genes, putatively encoding family 28 glycoside hydrolases, were identified. Seven of the newly discovered genes form a new gene group, which we show to encode exoacting pectinolytic glycoside hydrolases. This group includes four exo-polygalacturonan hydrolases (PGAX, PGXA, PGXB and PGXC) and three putative exo-rhamnogalacturonan hydrolases (RGXA, RGXB and RGXC). Biochemical identification using polygalacturonic acid and xylogalacturonan as substrates demonstrated that indeed PGXB and PGXC act as exo-polygalacturonases, whereas PGXA acts as an exo-xylogalacturonan hydrolase. The expression levels of all 21 genes were assessed by microarray analysis. The results from the present study demonstrate that exo-acting glycoside hydrolases play a prominent role in pectin degradation.
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http://dx.doi.org/10.1042/BJ20060703DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635439PMC
November 2006

Cloning of the astaxanthin synthase gene from Xanthophyllomyces dendrorhous (Phaffia rhodozyma) and its assignment as a beta-carotene 3-hydroxylase/4-ketolase.

Mol Genet Genomics 2006 Feb 17;275(2):148-58. Epub 2006 Jan 17.

Department of Applied Microbiology, Nippon Roche Research Center, Kamakura, Kanagawa, Japan.

A gene has been cloned from Xanthophyllomyces dendrorhous by complementation of astaxanthin formation in a beta-carotene accumulating mutant. It consists of 3,166 bp and contains 17 introns. For the beta-carotene mutant ATCC 96815, a single point mutation in the splicing sequence of intron 8 was found. The resulting improper splicing of the mRNA results in an inactive protein. The cDNA of this beta-carotene oxygenase encodes a cytochrome P450 monooxygenase belonging to the 3A subfamily. P450-specific domains were identified including a cytochrome P450 and an oxygen binding motif. Electrons are provided by a cytochrome P450 reductase. Functional characterization of the enzyme by genetic modification of X. dendrorhous demonstrated that this P450 monooxygenase is multifunctional catalyzing all steps from beta-carotene to astaxanthin formation by oxygenation of carbon 3 and 4. The reaction sequence is first 4-ketolation of beta-carotene followed by 3-hydroxylation. A hydroxylation mechanism at allylic carbon atoms has been proposed for the generation of 4-keto and 3-hydroxy groups at both beta-ionone ends.
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http://dx.doi.org/10.1007/s00438-005-0072-xDOI Listing
February 2006