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Biomedical subjects

S Jensen

Publications and source records attributed to S Jensen.

At least 19 recordsLinked to original sources
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

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↗
PubMed1995

Lipopolysaccharide in concentrations above 40 ng/ml stimulates proliferation of the IL-6-dependent B9 cell line.

The B9 assay is known to be a specific and sensitive assay for the estimation of interleukin-6 activity. This assay was found to be compromised by lipopolysaccharide in concentrations > or = 40 ng lipopolysaccharide per ml. The lipopolysaccharide stimulates proliferation of the B9 cell line in a dose-dependent manner both when measuring the proliferation by thymidine incorporation and when using the MTT assay. However the LPS dose-response curve is different compared to the dose-response curve for IL-6. A sample containing 100 ng LPS/ml but no IL-6 would be estimated erroneously to contain 12 pg IL-6. The interference of lipopolysaccharide is totally abolished by the addition of polymyxin B to the samples but the addition has no effect on the IL-6 induced proliferation.

Animals↗
PubMed1995

Automatic needle insertion diminishes pain during growth hormone injection.

Non-compliance in children receiving growth hormone (GH) treatment is often caused by pain on injection and difficulties in administration of GH. It has been suggested that automatic needle insertion diminishes pain perception. We quantitatively measured pain intensity on injection with two prototype pens for GH administration, providing either manual or automatic sc needle insertion, using a combined visual analogue/facial scale and a five-item scale in 18 children. With the automatic pen there was a significantly lower maximum pain score compared with the manual pen (median 28.5 versus 52.0 mm) as well as a lower mean pain score (mean 13.7 versus 23.5 mm). The five-item scale revealed that automatic needle insertion was significantly less painful than manual insertion and 13 patients chose to continue treatment with the automatic pen. In conclusion, pain during GH injection can be significantly diminished by automatic needle insertion, which may improve compliance in long-term GH treatment.

Adolescent↗
PubMed1995

Proliferation-associated nuclear antigen Ki-S1 is identical with topoisomerase II alpha. Delineation of a carboxy-terminal epitope with peptide antibodies.

Proliferation-linked expression of the nuclear Ki-S1 antigen is a significant prognostic indicator in mammary carcinomas. Here, we show staining of a protein of 170 kd by Ki-S1 antibody in immunoblots of Saccharomyces cerevisiae expressing human topoisomerase II alpha but not in the parental strain. In HL-60 cells containing both isoforms of human topoisomerase II, Ki-S1 antibody binds selectively to the 170-kd isoenzyme in a similar fashion as peptide-antibodies directed against amino acid residues 1 to 15 or 1512 to 1530 of human topoisomerase II alpha. Conversely, antibodies directed against carboxyl-terminal sequences of human topoisomerase II beta selectively stain a 180-kd protein. The immunoreactive pattern of V8 endoproteinase restriction digests of human topoisomerase II alpha was identical for Ki-S1-antibody and peptide-antibodies directed against residues 1512 to 1530 but different for peptide-antibodies directed against residues 1 to 15. The Rf values of the smallest fragment commonly recognized by Ki-S1 antibody and the carboxy terminus-specific peptide-antibody place the Ki-S1 epitope within the last 495 carboxyl-terminal amino acid residues of topoisomerase II alpha.

Animals↗
PubMed1995

The crash of the Partnair Convair 340/580 in the Skagerrak: traumatological aspects.

In September 1989 an aircraft carrying 55 people crashed into the sea north of Denmark. There was no warning of the crash. The medico-legal investigation of the accident concentrated on finding clues to the cause of the accident, and identifying the victims, all of whom perished. These were found in two groups--31 were immediately recovered from the surface of the sea and 19 were collected from the sea or shore during the following months. The injuries in the two groups differed, indicating that the aircraft broke up in mid-air. One group probably fell into the sea after a free fall, while the other probably remained in the wreckage until hitting the surface. The victims' injuries showed no evidence of fire or explosion. The technical investigators concluded that the aircraft broke up due to a structural failure in the tail.

Accidents, Aviation↗
PubMed1995

The crash of the Partnair Convair 340/580 in the Skagerrak: identification of the deceased.

In 1989, a Norwegian Convair aircraft crashed into the sea near the northwest coast of Jutland. Apparently, the aircraft had disintegrated in midair. On board were 50 passengers and a crew of 5. There were no survivors. Immediately after the crash 31 bodies were found. During the next 10 days, 11 bodies were recovered from the seabed and within the next 6 months, a further 8 bodies were found. Five bodies were never recovered. All the bodies found were positively identified based on personal effects combined with medical and dental findings. Different models for cooperation between the Primary ID-group, who were responsible for the final identification, and the ID-teams, who performed the examination of the bodies, were tested. It was concluded that the fastest and most reliable results were obtained when the ID-teams responsible for the examination of the bodies also took part in the reconciliation sessions.

Accidents, Aviation↗
PubMed1994

Identification of a strong transcriptional activator for the copia retrotransposon responsible for its differential expression in Drosophila hydei and melanogaster cell lines.

We have characterized the regulatory properties of a 72bp sequence located in the 5' untranslated domain of the Drosophila copia retrotransposon, 3' to the left LTR, by transient transfection assays with cell lines derived from either Drosophila hydei (DH33 cells) or Drosophila melanogaster (Schneider II and Kc cells). Reporter plasmids were constructed which contained the lacZ gene under the control of either the entire copia LTR with 5' untranslated domain, or a minimal heterologous promoter flanked with the identified copia regulatory sequences. Upon transfection into the copia-free DH33 cells, the presence of the 72bp sequence resulted for all reporter plasmids in a 100-700 fold increase in expression level -as well as in reporter gene RNA levels- whereas this sequence had no enhancing effect upon transfection of the same plasmids into the copia-containing Schneider II or Kc cells. Moreover, mobility shift assays with the 72bp enhancer sequence disclosed two specific bands of retarded mobility with whole-cell extracts from DH33 cells, whereas no retarded band could be detected, under identical conditions, with extracts from Schneider II cells. UV crosslinking experiments between the enhancer sequence and DH33 extracts revealed a single protein species -of app. mol. wt. 50kD- for both retarded bands, thus strongly suggesting that they simply correspond to the sequential binding of two identical factor molecules to the enhancer sequence. These data demonstrate that the copia-free D. hydei cells express a strong transcriptional activator for the copia element and possible interpretations for the absence of this factor in the copia-containing D. melanogaster cells are discussed in terms of a possible "adaptation" of the "host" (D. melanogaster) to an otherwise highly mutagenic "parasite" (copia with its transcription factor).

Animals↗
PubMed1994

Retrotransposition of the Drosophila LINE I element can induce deletion in the target DNA: a simple model also accounting for the variability of the normally observed target site duplications.

Retrotransposition of the Drosophila melanogaster LINE I element normally generates target site duplications of variable length, as classically observed for most LINE elements. Using an I element "marked" with an indicator gene for in vivo detection of transposition that we previously developed, we show that deletion in the target DNA can also take place, as a direct consequence of I element transposition. We propose a simple model accounting for the generation of both target site duplications of variable length and target DNA deletions, which relies upon template switching of the LINE-encoded reverse transcriptase between single-strand DNA at the target site and the LINE template.

Animals↗
PubMed1994

[Midazolam and lorazepam as premedication. A randomized double-blind study].

Oral administration of midazolam and lorazepam as premedication was compared in a double-blind randomized clinical trial. Eighty patients scheduled for minor gynaecological surgery in general anaesthesia and 80 patients scheduled for hip arthroplasty in spinal anaesthesia were included. Assessments were: 1. patients subjective evaluation of the premedication, 2. sedation scale, 3. recovery of cognitive function assessed by Simple Paper-and-Pencil test and Postbox test, 4. amnesic effects. In the general anaesthesia group midazolam caused less postoperative sedation, less postoperative amnesia and cognitive function returned more rapidly. In the spinal anaesthesia group cognitive function returned more rapidly after midazolam. Midazolam should be preferred for premedication if rapid recovery is desired.

Administration, Oral↗
PubMed1994

Retrotransposition of a marked Drosophila line-like I element in cells in culture.

We have marked a Drosophila transposable element--the LINE-like I element--with an intron-containing indicator gene inserted in place of a large deletion in the I element second ORF encompassing the reverse transcriptase domain, and this marked element was placed downstream to a potent actin promoter. An expression vector for the I element ORFs was also constructed, under the same heterologous promoter. The indicator gene contains a lacZ reporter gene the expression of which is conditioned by retrotransposition of the marked element, thus allowing detection of transposition events by testing for either beta-galactosidase expression or occurrence of spliced DNA molecules. The marked I element was introduced into Drosophila melanogaster cells in culture by transfection. Spliced DNA copies of the marked element and specifically stained beta-galactosidase-expressing cells were detected only upon co-transfection with the I expression vector, thus indicating that an ORF2-deleted element can be complemented in trans for transposition. This simple assay for retrotransposition in Drosophila cells in culture provides a tool for the rapid analysis of the mechanism of I transposition in its cis and trans sequence requirements.

Animals↗