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S Jensen

Publications and source records attributed to S Jensen.

At least 55 records · Page 3Linked to original sources
PubMed1998

Expression of the O antigen gene cluster is regulated by RfaH through the JUMPstart sequence.

O antigen genes are clustered, with a JUMPstart sequence located upstream. JUMPstart is a 39-bp sequence, present upstream of many polysaccharide gene clusters and also upstream of haemolysin and F factor gene clusters. RfaH is known to regulate the expression of E. coli group II capsule, haemolysin, F factor and the outer core of lipopolysaccharide all of which have the JUMPstart sequence, and has been shown to function as a transcriptional antiterminator in some cases. Using lacZ fusions to genes in the O antigen gene cluster of Salmonella enterica serovar Typhimurium, we found that RfaH also regulates the expression of O antigen. We showed that RfaH enhances expression of the 18-kb O antigen gene cluster, with promoter-distal genes affected more dramatically. We also showed that the JUMPstart sequence was required for RfaH function.

Antigens, Bacterial↗
PubMed1998

Hutchinson-Gilford progeria: faithful DNA maintenance, inheritance and allelic transcription of beta(1-4) galactosyltransferase.

Hutchinson-Gilford progeria syndrome (HGPS) is a fatal segmental aging disorder affecting children. There is a paucity of prior data at the nucleotide level on DNA maintenance in HGPS. We have examined the specific nucleotide sequences and production of allelic transcripts from the locus GGTB2 encoding beta(1-4) galactosyltransferase. Quantitative Northern blots of mRNA from HGPS and control fibroblasts indicated identical mature beta(1-4) galactosyltransferase transcript sizes and amounts, regardless of their altered glycosylation status. DNA sequencing of cDNA derived from HGPS beta(1-4) galactosyltransferase mRNA populations confirmed the encoded amino acid sequence was unaffected. Population studies of 41 unrelated individuals provided allelic frequency estimates for a novel FokI polymorphism, which was identified in two of six progeria cell strains. The polymorphism was faithfully inherited in a progeria pedigree in a Mendelian manner. Furthermore, the polymorphism provided direct evidence through sequencing of reverse transcription polymerase chain reaction products that both alleles were transcribed and generated mature mRNA. Any defects in transcripts were below detectable levels over the lengths of coding sequences examined, despite multiple replication events from conception leading to the production and maintenance of patient-derived cells. These results indicate faithful transcription in HGPS.

Alleles↗
PubMed1998

Temporal trends of organochlorines in Northern Europe, 1967-1995. Relation to global fractionation, leakage from sediments and international measures.

The time trend monitoring of organochlorine pollution was carried out in Sweden since the late 1960s. This report presents data on concentrations of DDT, PCB, HCHs and HCB in biota samples collected and analysed annually. All the matrices and compounds studied show a significant decrease over time. The data cover severely polluted Swedish marine and fresh water in southern Sweden as well as locally unpolluted waters in remote northern Arctic regions of Sweden. A total of 13 time series representing different locations and species are presented for the different pollutants. The period studied covers the time when pollution was serious as well as the time of recovery. All monitoring activities were carried out at the same laboratories over the entire study period, which means that comparability over time is good in the sets of data presented. The various time trends show a convincing agreement with trends and annual change over time, although the concentrations differ between the species and locations investigated, the highest concentrations being in the south. Since the annual changes are normally similar regardless of locations and species, spatial variations in concentrations remain over time, although concentrations are lower today. The onset of changes in concentrations over time can be related to international measures or other circumstances that lowered releases into the environment. Similarities in the annual changes, as well as the time when changes began, are discussed with respect to suggested hypotheses on the fate of the investigated organochlorines. It was not possible to verify that the oxygenation of anoxic sediments mobilised old pollution in Baltic sediments. Neither was it possible to conclude that eutrophication has caused a measurable effect on the rate and timing of the decreases. Finally, long-range transport to Arctic regions seems to be due more to a one step transport than to the 'Grass-hopper' effect. The comprehensive database used, clearly shows how important it is to have datasets big enough to describe between-year variation before attempting to evaluate the time trend. In addition, if between-year variation is not known, it is then also difficult to evaluate spatial variation on the basis of single year observations.

Journal Article↗
PubMed1998

Chlorinated contaminants, growth and thyroid function in schoolchildren from the Aral Sea region in Kazakhstan.

It has been shown by others that offspring of mothers who had been exposed to dioxins and polychlorinated biphenyls (PCBs) during pregnancy have elevated plasma levels of thyroid-stimulating hormone (TSH) for at least 3 months after birth and reduced plasma levels of free and total thyroxine during the second week after birth. As elevated levels of dioxins and PCB s can thus alter thyroid hormone status, the relation between the levels of some polychlorinated organic compounds in the blood lipids and growth and thyroid hormone status was studied in 12 hospitalized schoolchildren from the Aral Sea region known to have high exposure to such compounds. Their level of PCBs was two to four times higher than in healthy Stockholm children. Their height was found to be lower than in healthy Swedish children of the same age mean (SDS -0.52) and the body mass index (BMI) was inversely correlated to the total concentrations of PCBs and dichlorodiphenyltrichloroethane (DDT) and its metabolite dichlorophenyldichloroethylene (DDE) in the blood lipids. As the levels of insulin-like growth factor- were reduced to the same extent as the BMI it seems likely that PCBs and DDT cause malnutrition as a result of malabsorption. None of the children had any impairment of thyroid function, as revealed by the plasma levels of TSH and thyroxine. Although the concentrations of beta-hexachlorocyclohexane (beta-HCH) and DDE were extremely high in some of the children there was no relation between thyroid hormone status and the blood lipid levels of PCBs, hexachlorocyclohexane and DDT. However, the concentration of dioxins was not analysed.

Adolescent↗
PubMed1998

Methanol improves methane uptake in starved methanotrophic microorganisms.

Methanotrophs in enrichment cultures grew and sustained atmospheric methane oxidation when supplied with methanol. If they were not supplied with methanol or formate, their atmospheric methane oxidation came to a halt, but it was restored within hours in response to methanol or formate. Indigenous forest soil methanotrophs were also dependent on a supply of methanol upon reduced methane access but only when exposed to a methane-free atmosphere. Their immediate response to each methanol addition, however, was to shut down the oxidation of atmospheric methane and to reactivate atmospheric methane oxidation as the methanol was depleted.

Journal Article↗
PubMed1997

Coacervation characteristics of recombinant human tropoelastin.

Coacervation of soluble tropoelastin molecules is characterized by thermodynamically reversible association as temperature is increased under appropriately juxtaposed ionic conditions, protein concentration and pH. Coacervation plays a critical role in the assembly of these elastin precursors in elastic fiber formation. To examine the effect of physiological parameters on the ability of tropoelastin molecules to associate, solutions of recombinant human tropoelastin were monitored spectrophotometrically by light scattering over a broad range of temperatures. Coacervation of recombinant human tropoelastin is strongly influenced by the concentration of protein and NaCl and to a lesser extent on pH. Trends towards maximal association are apparent when each of these parameters is varied. Remarkably, optimal coacervation is found at 37 degrees C, 150 mM NaCl and pH 7-8. Using the data generated by time courses, estimates of thermodynamic parameters were made. These estimates confirm that coacervation is endothermic and is marked by a strong entropic contribution. Circular dichroism of recombinant human tropoelastin revealed that, rather than being random, the structure is compatible with being largely that, of an all-beta protein (with secondary structure estimated to be 3% alpha-helix, 41% beta-sheet, 21% beta-turn and 33% other), exhibiting a spectrum as previously seen for tropoelastin populations and soluble elastin from naturally-derived sources.

Circular Dichroism↗
PubMed1997

Environmental pollution and child health in the Aral Sea region in Kazakhstan.

The deterioration of human health with increasing infant mortality rate, declining life expectancy at birth and increasing prevalence of serious infectious diseases in Russia and other former Soviet Republics is thought to be due to a combination of several factors such as inadequate nutrition, poor sanitation, collapse of the health care system and pollution from Soviet agriculture and industries. In the Aral Sea region in Kazakhstan, the environmental problems are of near catastrophic proportions. As a result of the implementation of a massive irrigation scheme to support the cotton fields in the former desert land, the water flow to the Aral Sea was reduced to less than half. Industrial pollutants such as PCB-compounds and heavy metals, but also the use of large quantities of pesticides to control parasites and weeds have accumulated not only in water, but also in soil and have been deposited over large areas by atmospheric transport to enter the food chain leading to humans. In a study of 15 children and of an additional 12 children referred from the region of the Aral Sea to the National Children's Rehabilitation Center in Almaty with symptoms and signs of 'ecological disease', we have found that the concentration of PCB compounds in the blood lipids is elevated in relation to healthy Swedish children. In addition, the blood lipid concentration of the beta-isomer of the hexachlorocyclohexanes was extremely high and of DDT-compounds was elevated up to 20 times. The concentrations of lead in red blood cells was moderately elevated and that of cadmium slightly elevated compared to the findings in Stockholm children. To study the role of these pollutants in the diseases found in children from the Aral Sea region accurate epidemiological studies have to be performed.

Adolescent↗
PubMed1997

Detection of K-ras point mutation by in situ PCR in cell suspensions: comparison of the indirect and direct methods.

In situ PCR is a new technique for the localization of low copy number sequences. We report here a method for the in situ visualization of a point mutation in K-ras codon 12 by indirect in situ PCR. Twenty-five primers were examined to select mutant-specific primers. Harvested cell lines were fixed and suspended in PCR mixture. Forty cycles of PCR in cell suspension was performed in a thermal cycler using a hot start method. Cells were cytocentrifuged onto slides, and post-fixation was performed. The specimens on the slides were then hybridized with a digoxigenin-labeled probe, followed by color reaction. Both Calu-1 (mutated: TGT) and NCI-H460 (wild type: GGT) cells had strong hybridization signals in the nuclei with general primers. But with mutant-specific primers, only Calu-1 cells had hybridization signals. No signal was observed without primers or Taq DNA polymerase. Southern blotting of the same preparation confirmed desired amplification. We also applied direct in situ PCR, but this method failed to detect the point mutation. We conclude that our indirect in situ PCR method shows the feasibility of in situ identification of single cells carrying point mutations.

Blotting, Southern↗
PubMed1997

Catquest questionnaire for use in cataract surgery care: description, validity, and reliability.

PURPOSE: To describe and evaluate the Catquest self-assessment questionnaire for cataract patients. SETTING: Thirty-five Swedish departments of ophthalmology. METHODS: The Catquest is designed to be used by cataract surgeons for continuous quality control regarding appropriateness and outcome of surgery. It is administered before and after cataract surgery. The questionnaire focuses on visual disabilities in daily life, activity level, cataract symptoms, and degree of independence. The results are interpreted using a benefit matrix that credits not only a decrease in visual disabilities and cataract symptoms but also an improvement or a maintenance of a preoperative activity level. The questionnaire was used by consecutive patients having surgery during March 1995 at the participating surgical units. RESULTS: A full range of responses was given to all questions. A strong relationship was found between patients' responses to questions about visual disabilities in daily life and their general opinion about vision (P < .001). The answers showed a high stability when test-retest reliability was evaluated and a high internal consistency when different questions about visual disabilities were compared (P < .001). The answers from cataract patients before surgery were significantly different from those of a control group that did not have cataract (P < .0001). CONCLUSION: The Catquest had high validity and reliability when used as a disease-specific instrument testing visual disabilities in patients having cataract extraction.

Aged↗
PubMed1997

Molecular cloning and characterization of a transcription factor for the copia retrotransposon with homology to the BTB-containing lola neurogenic factor.

By transfection experiments, we previously identified a 72-bp enhancer sequence within the Drosophila copia retrotransposon which is involved in the control of the transcription level of this mobile element in cells in culture. Gel shift assays with nuclear extracts from Drosophila hydei-derived DH-33 cells further demonstrated specific interactions of at least two nuclear factors with this enhancer sequence. Using this sequence as a probe for the screening of an expression cDNA library that we constructed from DH-33 cells RNA, we have isolated a cDNA clone encoding a 110-kDa protein with features common to those of known transcription factors; these include a two-zinc-finger motif at the C terminus, three glutamine-rich domains in the presumptive activation domain of the protein, and an N-terminal domain which shares homology with the Bric-à-brac, Tramtrack, and Broad-Complex BTB boxes. The precise DNA recognition sequence for this transcription factor has been determined by both gel shift assays and footprinting experiments with a recombinant protein made in bacteria. The functionality of the cloned element was demonstrated upon transcriptional activation of copia reporter genes, as well as of a minimal promoter coupled with the identified target DNA sequence, in cotransfection assays in cells in culture with an expression vector for the cloned factor. Southern blot and nucleotide sequence analyses revealed a related gene in Drosophila melanogaster (the lola gene) previously identified by a genetic approach as involved in axon growth and guidance. Transfection assays in cells in culture with lola gene expression vectors and in situ hybridization experiments with lola gene mutants finally provided evidence that the copia retrotransposon is regulated by this neurogenic gene in D.melanogaster, with a repressor effect in the central nervous systems of the embryos.

Amino Acid Sequence↗
PubMed1996

Human DNA topoisomerases II alpha and II beta can functionally substitute for yeast TOP2 in chromosome segregation and recombination.

The ability of the human DNA topoisomerase II alpha and II beta isozymes to complement functional defects conferred by conditional top2 mutations in Saccharomyces cerevisiae has been investigated. At the restrictive temperature, top2 strains show multiple abnormalities, including an inability to complete mitotic and meiotic division owing to a defect in chromosome segregation, and hyper-recombination within the repetitive rDNA gene cluster. We show that the human topoisomerases II alpha and II beta can each support both vegetative growth and the production of viable spores in a top2-4 mutant at the restrictive temperature. Similarly, both human isozymes can rescue a strain carrying a top2 gene disruption, and suppress hyper-recombination within the rDNA gene cluster. We conclude that the human topoisomerase II alpha and II beta isozymes are functionally interchangeable with yeast topoisomerase II and suggest that any isozyme-specific roles in human cells are likely to be dependent upon factors other than inherent differences in catalytic ability between the alpha and beta isozymes.

Antigens, Neoplasm↗
PubMed1996

Active heterodimers are formed from human DNA topoisomerase II alpha and II beta isoforms.

DNA topoisomerase II is a nuclear enzyme essential for chromosome dynamics and DNA metabolism. In mammalian cells, two genetically and biochemically distinct topoisomerase II forms exist, which are designated topoisomerase II alpha and topoisomerase II beta. In our studies of human topoisomerase II, we have found that a substantial fraction of the enzyme exists as alpha/beta heterodimers in HeLa cells. The ability to form heterodimers was verified when human topoisomerases II alpha and II beta were coexpressed in yeast and investigated in a dimerization assay. Analysis of purified heterodimers shows that these enzymes maintain topoisomerase II specific catalytic activities. The natural existence of an active heterodimeric subclass of topoisomerase II merits attention whenever topoisomerases II alpha and II beta function, localization, and cell cycle regulation are investigated.

Amino Acid Sequence↗
PubMed1996

Determination of chlorinated pesticides and PCB in pine needles - improved method for the monitoring of airborne organochlorine pollutants.

A method to determine organochlorine pollutants in pine needles is described. Fresh, whole needles have been extracted for 48 h in dichloromethane to obtain the epicuticular wax fraction. The remainder has been cut into small pieces and again extracted with dichloromethane to obtain the internal lipids. Prior to gas chromatography, both the wax and the internal lipid extracts have been fractionated on two columns: first a silica gel/silica gel : sulphuric acid 2 : 1 column with dichloromethane as eluent and then a nitrophenyl silica column with hexane as eluent. Three fractions have been collected, fraction 1 containing hexachlorobenzene (HCB), fraction 2 containing polychlorinated biphenyls (PCB) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (DDE), and fraction 3 containing the remaining, more polar, organochlorine pesticides. For some pine species, the nitrophenyl silica column has been combined with a short aminopropyl silica column to obtain chromatograms of the PCB fraction free from negative peaks. The precision is in the range of 4-12% relative standard deviation, and the overall recovery is around 65-90%.

Journal Article↗
PubMed1996

Analysis of functional domain organization in DNA topoisomerase II from humans and Saccharomyces cerevisiae.

The functional domain structure of human DNA topoisomerase IIalpha and Saccharomyces cerevisiae DNA topoisomerase II was studied by investigating the abilities of insertion and deletion mutant enzymes to support mitotic growth and catalyze transitions in DNA topology in vitro. Alignment of the human topoisomerase IIalpha and S. cerevisiae topoisomerase II sequences defined 13 conserved regions separated by less conserved or differently spaced sequences. The spatial tolerance of the spacer regions was addressed by insertion of linkers. The importance of the conserved regions was assessed through deletion of individual domains. We found that the exact spacing between most of the conserved domains is noncritical, as insertions in the spacer regions were tolerated with no influence on complementation ability. All conserved domains, however, are essential for sustained mitotic growth of S. cerevisiae and for enzymatic activity in vitro. A series of topoisomerase II carboxy-terminal truncations were investigated with respect to the ability to support viability, cellular localization, and enzymatic properties. The analysis showed that the divergent carboxy-terminal region of human topoisomerase IIalpha is dispensable for catalytic activity but contains elements that specifically locate the protein to the nucleus.

Amino Acid Sequence↗
PubMed1995

[The effect of ranitidine on postoperative monocyte and neutrophil granulocyte function].

The histamine H-2-receptor antagonist ranitidine hydrochloride has been shown to alleviate trauma-, blood transfusion- and sepsis-induced immunosuppression. We evaluated the effect of ranitidine on the postoperative impairment of monocyte and neutrophil function in 24 patients undergoing major elective abdominal surgery. The patients were randomized to receive postoperative adjuvant treatment with ranitidine hydrochloride (100 mg) administered intravenously twice daily for four days, followed by oral ranitidine hydrochloride (150 mg) administered twice daily for five days (n = 11), or no adjuvant treatment (n = 13). Blood monocyte and neutrophil chemotaxis and chemiluminescence were analyzed before the operation and on post-operative days one, three and nine. Monocyte chemotaxis to C5a in the 13 control patients was significantly decreased on day one compared to day 0. Chemotaxis in the 11 ranitidine-treated patients increased significantly from day 0 to day one (p < .01 between groups). Neutrophil chemiluminescence to zymosan and N-f-methionyl-leucylphenylalanine was significantly increased in control patients on day one compared to day 0 (p < .05), while ranitidine reduced chemiluminescence to zymosan insignificantly on day one (p < .07 between groups). Five of the 13 control patients developed postoperative infectious complications, which were related to decreased monocyte chemotaxis to C5a and increased neutrophil chemiluminescence to zymosan when compared to noninfected patients. A significant difference (P < .05) in chemiluminescence to zymosan between infected and noninfected control patients was observed on day three, before clinical signs of infectious disease could be detected. There were no infectious complications in ranitidine-treated patients. These results support previous studies on the effect of ranitidine in reducing postoperative immunosuppression.

Administration, Oral↗
PubMed1995

Defective I elements introduced into Drosophila as transgenes can regulate reactivity and prevent I-R hybrid dysgenesis.

The I-R hybrid dysgenesis syndrome is characterized by a high level of sterility and I element transposition, occurring in the female offspring of crosses between males of inducer (I) strains, which contain full-length transposable I elements, and females of reactive (R) strains, devoid of functional I elements. The intensity of the syndrome in the dysgenic cross is essentially dependent on the reactivity level of the R females, which is ultimately controlled by still unresolved polygenic chromosomal determinants. In the work reported here, we have introduced a transposition-defective I element with a 2.6 kb deletion within its second open reading frame into a highly reactive R strain, by P-mediated transgenesis. We demonstrate that this defective I element gradually alters the level of reactivity in the three independent transgenic lines that were obtained, over several generations. After > 15 generations, the transgenic Drosophila show strongly reduced reactivity, and finally become refractory to hybrid dysgenesis, without, however, acquiring the inducer phenotype. Induction of a low reactivity level is reversible--reactivity again increases upon transgene removal--and is maternally inherited, as observed for the control of reactivity in natural R strains. These results demonstrate that defective I elements introduced as single-copy transgenes can act as regulators of reactivity, and suggest that some of the ancestral defective pericentromeric I elements that can be found in all reactive strains could be the molecular determinants of reactivity.

Animals↗
PubMed1995

Molecular analysis at the NF1 locus in astrocytic brain tumors.

BACKGROUND: Patients with neurofibromatosis type 1 (NF1) are at increased risk for developing malignant neural crest tumors and juvenile myeloid leukemia. Although the normal allele of the NF1 tumor-suppressor gene is frequently deleted in some of the malignant tumors that arise in patients with NF1, the role of NF1 alterations in the sporadic forms of these cancers is unclear. METHODS: A series of intragenic sequence polymorphisms was used to investigate lymphocyte and tumor DNA samples from 22 adults with high grade malignant gliomas for loss of heterozygosity (LOH) at NF1. In addition, an assay based on the polymerase chain reaction was used to screen these tumors for point mutations at codon 1423. RESULTS: One recurrent anaplastic astrocytoma showed LOH within NF1 but not with a flanking marker located near the gene. Of 21 informative tumors, none showed point mutations affecting codon 1423 of NF1. CONCLUSION: These data suggest that LOH at NF1 is uncommon in sporadic high grade astrocytoma, and codon 1423 is not a "hot spot" for activating point mutations in these tumors.

Adult↗