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J Petersen

Publications and source records attributed to J Petersen.

At least 37 records · Page 2Linked to original sources
PubMed2002

Monitoring the content and intake of trace elements from food in Denmark.

The content of cadmium, lead, nickel, mercury and selenium in 83 foods was monitored from 1993 to 1997. In comparison with similar results from 1988 to 1992, a general decrease in lead levels had occurred, whereas the contents of cadmium, nickel, mercury and selenium were stable or declined only slightly. The distribution in dietary intake of the five trace elements was estimated by combining the mean trace element concentrations with food consumption data from 1837 Danes aged 15-80 years. The lead intake for 1993-97 showed a decrease in comparison with similar estimates from the previous monitoring cycles: 1983-87 and 1988-92. The intake of cadmium and mercury decreased to a lesser extent, whereas the intake of selenium and nickel remained unchanged in the same period. The dietary intake of trace elements was compared with the provisional tolerable weekly intake (PTWI). The 95th percentile of the distribution in cadmium intake amounts to 34% of PTWI, which is relatively high, and therefore calls for a more detailed future risk assessment. The intakes of lead and mercury were 11% of PTWI and, like the intake of nickel, did not cause any health concern in the adult population. The Danes ingest close to 100% of the Nordic Nutrition Recommendation for selenium at 50 microg day(-1), and no individuals had an intake less than the lower limit of 20 microg day(-1).

Adolescent↗
PubMed2002

Reaching homeless youths for Chlamydia trachomatis and Neisseria gonorrhoeae screening in Denver, Colorado.

BACKGROUND AND RATIONALE: The availability of urine based testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) provides a unique opportunity to screen for these pathogens outside traditional clinical settings. The researchers investigated the feasibility of street based CT/GC screening in the context of an outreach programme among street/homeless adolescents in Denver. OBJECTIVES: To describe the integration of urine based CT/GC screening into an existing outreach programme among street/homeless youths and the yield of CT/GC testing in this setting. METHODS: The Denver Department of Public Health (DPH) collaborated with outreach staff from Urban Peak (a community based organisation serving street/homeless youths in Denver) to offer urine based CT/GC testing to males and females in street settings. Tests were conducted on the street in areas where street/homeless youths congregate. RESULTS: Urban Peak outreach staff were trained by DPH staff to conduct CT testing, process urine specimens, and provide test results to participating youths. DPH remained responsible for treatment of people with CT or GC infection as well as CT/GC case reporting. CT testing started in January 2000; GC testing was added in July 2000. Throughout April 2002 a total of 414 CT and 302 GC tests were conducted, respectively 11.6% and 2.7% of which were positive. Among first testers, 13.0% were positive for CT and 3.7% for GC. CONCLUSIONS: CT/GC urine testing can be incorporated into existing outreach programmes without considerable extra effort. Overall CT rates were high and suggest the need for ongoing screening in this manner. LEARNING OBJECTIVE: To understand the role of CT/GC screening in the context of services provided to street/homeless youths in outreach settings.

Adolescent↗
PubMed2001

Lassa fever encephalopathy: Lassa virus in cerebrospinal fluid but not in serum.

The pathogenesis of neurologic complications of Lassa fever is poorly understood. A Nigerian patient had fever, disorientation, seizures, and blood-brain barrier dysfunction, and Lassa virus was found in cerebrospinal fluid (CSF) but not in serum. The concentration of Lassa virus RNA in CSF corresponded to 1 x 10(3) pfu/mL, as determined by a quantitative real-time polymerase chain reaction assay. To characterize the Lassa virus in CSF, the 3.5-kb S RNA was sequenced. In the S RNA coding sequences, the CSF strain differed between 20% and 24.6% from all known prototype strains. These data suggest that Lassa virus or specific Lassa virus strains can persist in the central nervous system and thus contribute to neuropathogenesis. Lassa virus infection should be considered in West African patients or in travelers returning from this area who present only with fever and neurologic signs.

Amino Acid Sequence↗
PubMed2001

20-fold increase in risk of lamivudine resistance in hepatitis B virus subtype adw.

We investigated subtype-dependent development of lamivudine resistance in hepatitis B virus (HBV) longitudinally in 26 consecutive patients (13 adw and 13 ayw carriers) during antiviral treatment of chronic hepatitis B. Lamivudine resistance developed in seven adw carriers and one ayw carrier. Risk of lamivudine resistance was significantly higher for adw carriers than for ayw carriers (p=0.03). We believe that the adw subtype of HBV is associated with a high risk of lamivudine resistance, which might be linked to simultaneous changes of the HBsAg that occurs with the emergence of resistance.

Adult↗
PubMed2001

The role of Plo1 kinase in mitotic commitment and septation in Schizosaccharomyces pombe.

Plo1-associated casein kinase activity peaked during mitosis before septation. Phosphatase treatment abolished this activity. Mitotic Plo1 activation had a requirement for prior activation of M-phase promoting factor (MPF), suggesting that Plo1 does not act as a mitotic trigger kinase to initiate MPF activation during mitotic commitment. A link between Plo1 and the septum initiating network (SIN) has been suggested by the inability of plo1 Delta cells to septate and the prolific septation following plo1(+) overexpression. Interphase activation of Spg1, the G protein that modulates SIN activity, induced septation but did not stimulate Plo1-associated kinase activity. Conversely, SIN inactivation did not affect the mitotic stimulation of Plo1-associated kinase activity. plo1.ts4 cells formed a misshapen actin ring, but rarely septated at 36 degrees C. Forced activation of Spg1 enabled plo1.ts4 mutant cells, but not cells with defects in the SIN component Sid2, to convert the actin ring to a septum. The ability of plo1(+) overexpression to induce septation was severely compromised by SIN inactivation. We propose that Plo1 acts before the SIN to control septation.

CDC2 Protein Kinase↗
PubMed2001

Correlation of hepatitis B virus load with loss of e antigen and emerging drug-resistant variants during lamivudine therapy.

It remains unclear whether sequential assessment of hepatitis B virus (HBV) load during lamivudine therapy can predict the loss of hepatitis B e antigen or emergence of drug-resistant variants. Therefore, a longitudinal study was carried out in 28 consecutive patients with chronic hepatitis B who started lamivudine therapy for a median of 12 months (range, 6-31). HBV DNA copy numbers were determined at 3-month intervals. From month 6 onward, HBV viral load below the detection limit of the PCR was predictive of the loss of envelope antigen (P = 0.043). Continuously detectable HBV DNA during the first 12 months of treatment indicated emergence of drug-resistant variants (P = 0.034). These data suggest that the goal of lamivudine therapy should be complete suppression of serum HBV DNA.

Administration, Oral↗
PubMed2001

Structural and functional heterogeneity of naturally occurring hepatitis B virus variants.

Most organisms have developed sophisticated machineries to preserve their genomic integrity. On the contrary hepatitis B virus (HBV), like a lot of other viruses can undergo rapid and drastic sequence changes, especially if the virus has to cope with natural or therapy induced antiviral mechanisms in the host. Here, we try to summarize possible implications for the molecular pathogenesis of HBV based on the extensive research on the genetic variants of HBV.

Genes, Viral↗
PubMed2001

Tumour necrosis factor-alpha (TNF), lymphotoxin and TNF receptor levels in serum from patients with Wegener's granulomatosis.

Wegener's granulomatosis (WG) is a systemic inflammatory disease with vasculitis as the key feature. Abnormal expression of tumour necrosis factor alpha (TNFalpha) is considered of prime pathogenic importance in several inflammatory diseases. The effects of TNFa are mediated by TNF receptors (TNF-R), and these receptors are often found in soluble forms (sTNF-R), which can modulate TNFalpha actions. To evaluate the clinical importance of the TNF family of cytokines, the serum levels of TNFalpha, TNFbeta, now termed lymphotoxin (LTalpha), and sTNF-R1 and sTNF-R2 were measured by ELISA in 8 patients with WG during active disease and during immunosuppressive treatment, and in 11 healthy controls in parallel. Serum concentrations of TNFalpha were undetectable in all except two controls (18%) and three patients with WG (37%). After 7 days of therapy, six of the WG patients had measurable TNFalpha levels. Examination of the relative amounts of TNFalpha and sTNF-R indicated that TNFalpha was mostly bound to its soluble receptors. In WG, the serum levels of sTNF-R1 and sTNF-R2 were dramatically increased (p<0.01), with little or no variation during treatment. While the IL-1beta levels did not deviate significantly from controls, the IL-1ra levels were significantly elevated in the WG patients throughout the study period (p<0.01).

Adult↗
PubMed2001

Repopulation of mouse liver with human hepatocytes and in vivo infection with hepatitis B virus.

Mice containing livers repopulated with human hepatocytes would provide excellent in vivo models for studies on human liver diseases and hepatotropic viruses, for which no permissive cell lines exist. Here, we report partial repopulation of the liver of immunodeficient urokinase-type plasminogen activator (uPA)/recombinant activation gene-2 (RAG-2) mice with normal human hepatocytes isolated from the adult liver. In the transplanted mice, the production of human albumin was demonstrated, indicating that human hepatocytes remained functional in the mouse liver for at least 2 months after transplantation. Inoculation of transplanted mice with human hepatitis B virus (HBV) led to the establishment of productive HBV infection. According to human-specific genomic DNA analysis and immunostaining of cryostat liver sections, human hepatocytes were estimated to constitute up to 15% of the uPA/RAG-2 mouse liver. This is proof that normal human hepatocytes can integrate into the mouse hepatic parenchyma, undergo multiple cell divisions, and remain permissive for a human hepatotropic virus in a xenogenic liver. This system will provide new opportunities for studies on etiology and therapy of viral and nonviral human liver diseases, as well as on hepatocyte biology and hepatocellular transplantation.

Adult↗
PubMed2001

Woodchuck hepatocytes remain permissive for hepadnavirus infection and mouse liver repopulation after cryopreservation.

Isolated hepatocytes represent a relevant model of the liver and are highly required both for research and therapeutic applications. However, sources of primary liver cells from human beings and from some animal species are limited. Therefore, cryopreservation of hepatocytes could greatly facilitate advances in various research areas. The aim of this study was to evaluate whether cryopreserved primary woodchuck hepatocytes could be used for woodchuck hepatitis B virus (WHV) infection studies, and whether they could maintain their regenerative potential in vivo after thawing. Critical steps for good quality of cryopreserved hepatocytes included the use of University of Wisconsin (UW) solution as a main component of the freezing medium, stepwise reduction of dimethylsulfoxide (DMSO) to avoid osmotic shock, and maintenance of low concentrations of DMSO in the culture medium. After cryopreservation, cell viability was still high (70% to 80%), and 50% to 60% of thawed cells attached to the plates. The appearance of covalently closed circular (ccc)DNA and of WHV-replicative forms a few days after in vitro infection demonstrated that thawed woodchuck hepatocytes were still susceptible to viral infection, thus proving maintenance of a very high hepatocyte-specific differentiation status. Furthermore, transplantation of woodchuck hepatocytes into the liver of urokinase-type plasminogen activator (uPA)/recombination activation gene-2 (RAG-2) mice, a model of liver regeneration, demonstrated that cryopreserved cells retained the ability to divide and to extensively repopulate a xenogenic liver. Notably, in vivo susceptibility to infection with WHV and proliferative capacity of frozen/thawed woodchuck hepatocytes in recipient mice were identical to those observed by transplanting fresh hepatocytes.

Animals↗
PubMed2001

[Current status of cell-based therapies in liver diseases].

Major strides have been made during the past 10 years in the fields of liver cell transplantation and liver-directed gene therapy. Pre-clinical studies in animals have shown that primary hepatocytes transplanted into the liver as well as intravenously transfused bone marrow stem cells can generate new liver tissue. Such cell transplantation studies have contributed to our understanding of organogenesis and hepatocyte biology. Furthermore, transplantation of xenogenic hepatocytes has led to the development of new small animal models for studying viral hepatitis. In the clinical setting, liver cell transplantation offers a wide range of potential therapeutic applications, especially in metabolic diseases. In particular, the case of a patient with Crigler-Najjar Syndrome Type I clearly demonstrated the long-term viability of transplanted hepatocytes with stable metabolic function. Further studies are warranted to assess the full potential of cell- based therapies and their clinical application.

Animals↗
PubMed2001

Mass spectrometric analysis of a UV-cross-linked protein-DNA complex: tryptophans 54 and 88 of E. coli SSB cross-link to DNA.

Protein-nucleic acid complexes are commonly studied by photochemical cross-linking. UV-induced cross-linking of protein to nucleic acid may be followed by structural analysis of the conjugated protein to localize the cross-linked amino acids and thereby identify the nucleic acid binding site. Mass spectrometry is becoming increasingly popular for characterization of purified peptide-nucleic acid heteroconjugates derived from UV cross-linked protein-nucleic acid complexes. The efficiency of mass spectrometry-based methods is, however, hampered by the contrasting physico-chemical properties of nucleic acid and peptide entities present in such heteroconjugates. Sample preparation of the peptide-nucleic acid heteroconjugates is, therefore, a crucial step in any mass spectrometry-based analytical procedure. This study demonstrates the performance of four different MS-based strategies to characterize E. coli single-stranded DNA binding protein (SSB) that was UV-cross-linked to a 5-iodouracil containing DNA oligomer. Two methods were optimized to circumvent the need for standard liquid chromatography and gel electrophoresis, thereby dramatically increasing the overall sensitivity of the analysis. Enzymatic degradation of protein and oligonucleotide was combined with miniaturized sample preparation methods for enrichment and desalting of cross-linked peptide-nucleic acid heteroconjugates from complex mixtures prior to mass spectrometric analysis. Detailed characterization of the peptidic component of two different peptide-DNA heteroconjugates was accomplished by matrix-assisted laser desorption/ionization mass spectrometry and allowed assignment of tryptophan-54 and tryptophan-88 as candidate cross-linked residues. Sequencing of those peptide-DNA heteroconjugates by nanoelectrospray quadrupole time-of-flight tandem mass spectrometry identified tryptophan-54 and tryptophan-88 as the sites of cross-linking. Although the UV-cross-linking yield of the protein-DNA complex did not exceed 15%, less than 100 pmole of SSB protein was required for detailed structural analysis by mass spectrometry.

Amino Acids↗
PubMed2001

Optimization of hepatocyte spheroid formation for hepatic tissue engineering on three-dimensional biodegradable polymer within a flow bioreactor prior to implantation.

We hypothesize that in vitro conditioning of hepatocytes within biodegradable poly-L-lactic acid (PLLA) polymer matrices prior to implantation may increase hepatocyte survival and function after transplantation. The purpose of this study was to optimize the culture conditions of hepatocytes in a pulsatile flow bioreactor. PLLA discs were seeded with rat hepatocytes in a concentration of 2.5, 5, 10, 20 and 40 x 10(6) cells/ml. Seeded discs were exposed to recirculated perpendicular flow of 0, 7, 15, 24, 32, 52 ml/min of supplemented Williams' Medium E and harvested after 6 days in flow culture. Only under flow conditions the hepatocytes formed spheroidal aggregates (SphA) of 50-260 microm in diameter with a liver-like morphology and active metabolic function. The number of SphA was examined by phase contrast microscopy and the reductive enzyme function of the hepatocytes was tested using MTT. Hematoxylin and eosin histology showed vital hepatocytes within the SphA less than 200 microm in diameter but central necrosis in the SphA exceeding this size. Immunohistochemical staining confirmed albumin production of hepatocytes within the SphA. The optimal cell seeding concentration was 10 x 10(6) cells/ml with a flow speed of 24 ml/min. SphA of hepatocytes cultured with this flow bioreactor method may prove useful as a functional unit for tissue engineering of an in vivo liver substitute.

Albumins↗
PubMed2001

Hepatic tissue engineering on 3-dimensional biodegradable polymers within a pulsatile flow bioreactor.

BACKGROUND: An optimal method for hepatocyte transplantation is not yet determined. With the principles of tissue engineering in vitro conditioning of hepatocytes on biodegradable polymer in a flow bioreactor before implantation forming spheroids may achieve increased cell mass and function to replace lost organ function in vivo. METHODS: Biodegradable poly-L-lactic (PLLA) polymer discs were seeded with rat hepatocytes in a concentration of 10 x 10(6) cells per ml and exposed to a medium flow of 24 ml/min for 1, 2, 4 and 6 days. The number and diameter of spheroidal aggregates was measured by phase-contrast microscopy. H&E histology was performed. Albumin production as hepatocyte specific function was determined by ELISA. RESULTS: Spheroids of viable hepatocytes of 50-200 microm in diameter were formed. Both the number and diameter of the spheroids increased during the first 2 days and then remained constant until day 6. Albumin production was maintained throughout the culture period. CONCLUSION: Short (2- 3 days) pre-transplant conditioning of hepatocytes in a flow bioreactor on biodegradable PLLA resulted in formation of spheroids with a liver-like morphology and preserved specific metabolic function. Tissue engineered hepatocyte spheroids on polymer may represent a functionally active and easy transplantable neotissue and may serve as an in vivo substitute for lost liver function.

Albumins↗
PubMed2001

The S. pombe aurora-related kinase Ark1 associates with mitotic structures in a stage dependent manner and is required for chromosome segregation.

Metazoans contain three aurora-related kinases. Aurora A is required for spindle formation while aurora B is required for chromosome condensation and cytokinesis. Less is known about the function of aurora C. S. pombe contains a single aurora-related kinase, Ark1. Although Ark1 protein levels remained constant as cells progressed through the mitotic cell cycle, its distribution altered during mitosis and meiosis. Throughout G2 Ark1 was concentrated in one to three nuclear foci that were not associated with the spindle pole body/centromere complex. Following commitment to mitosis Ark1 associated with chromatin and was particularly concentrated at several sites including kinetochores/centromeres. Kinetochore/centromere association diminished during anaphase A, after which it was distributed along the spindle. The protein became restricted to a small central zone that transiently enlarged as the spindle extended. As in many other systems mitotic fission yeast cells exhibit a much greater degree of phosphorylation of serine 10 of histone H3 than interphase cells. A number of studies have linked this modification with chromosome condensation. Ark1 immuno-precipitates phosphorylated serine 10 of histone H3 in vitro. This activity was highest in mitotic extracts. The absence of the histone H3 phospho-serine 10 epitope from mitotic cells in which the ark1(+) gene had been deleted (ark1.Delta1); the inability of these cells to resolve their chromosomes during anaphase and the co-localisation of this phospho-epitope with Ark1 early in mitosis, all suggest that Ark1 phosphorylates serine 10 of histone H3 in vivo. ark1.Delta1 cells also exhibited a reduction in kinetochore activity and a minor defect in spindle formation. Thus the enzyme activity, localisation and phenotype arising from our manipulations of this single fission yeast aurora kinase family member suggest that this single kinase is executing functions that are separately implemented by distinct aurora A and aurora B kinases in higher systems.

Anaphase↗
PubMed2001

MTOC formation during mitotic exit in fission yeast.

Microtubules polymerise from nucleation templates containing gamma tubulin. These templates are generally concentrated in discrete structures called microtubule organising centres (MTOCs). In Schizosaccharomyces pombe, an equatorial MTOC (EMTOC) forms mid-way through anaphase B and then disassembles during the final stages of cell separation. We show that the EMTOC was generated by recruiting gamma tubulin to the equatorial F-actin ring before it constricted to cleave the cell in two during cytokinesis. The EMTOC was not a continuous ring. It had a variable structure ranging from a horseshoe to a number of short bars. EMTOC integrity depended upon the integrity of the F-actin but not the microtubule cytoskeleton. EMTOC assembly required the activity of both the septation-inducing network (SIN) that regulates the onset of cytokinesis and the anaphase-promoting complex. Activation of the SIN in interphase cells induced F-actin ring formation and contraction and the synthesis of the primary septum but did not promote EMTOC assembly. In contrast, overproduction of the polo-like kinase, Plo1, which also induced multiple rounds of septation in interphase cells, induced EMTOC formation. Thus, the network governing EMTOC formation shared many of the regulatory elements that control cytokinesis but was more complex and revealed an additional function for Plo1 during mitotic exit.

Actins↗
PubMed2001

Origin and conservation genetics of the threatened Ute ladies'-tresses, Spiranthes diluvialis (Orchidaceae).

The Ute ladies'-tresses, Spiranthes diluvialis, is listed as a threatened orchid in west-central United States by the Federal government. Information on its origin and patterns of genetic variation is needed to develop effective conservation strategies for this species. DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to evaluate genetic variation and structure of 23 populations of S. diluvialis. In addition, four congeneric species were analyzed to determine possible origins of the putative allotetraploid S. diluvialis. DNA sequencing and PCR-RFLP analysis of the nuclear ribosomal internal transcribed spacer (ITS) and mitochondrial and chloroplast DNA noncoding regions revealed no genetic variation within or among populations of S. diluvialis. DNA sequencing revealed that S. diluvialis has rDNA of both S. magnicamporum and S. romanzoffiana, supporting the proposed origin of the allotetraploid. Parsimony and maximum likelihood analyses of cpDNA and mtDNA sequences revealed that these S. diluvialis organellar sequences were most closely related to those of S. romanzoffiana, providing evidence that the latter species is the maternal parent of S. diluvialis. The lack of genetic diversity is significant for the development of a long-term conservation strategy for S. diluvialis.

Journal Article↗