Biomedical subjects

C Roos

Publications and source records attributed to C Roos.

At least 19 recordsLinked to original sources

PubMed2006

Comparison of transvaginal sonography in recumbent and standing maternal positions to predict spontaneous preterm birth in singleton and twin pregnancies.

OBJECTIVE: To evaluate whether serial transvaginal sonographic examination of the cervix with the woman in a standing position improves the prediction of spontaneous preterm birth (SPB) compared with the conventional posture. METHODS: For both a recumbent and upright maternal position, the inter- and intraobserver agreement of cervical length (CL) measurement was calculated. In 363 pregnancies at risk for SPB, we determined prospectively CL and funnel width (FW) including differences between the positions and between longitudinal measurements from 15 weeks onwards. Multivariate logistic regression analysis, contingency tables and receiver-operating characteristics (ROC) curves were used. Data were stratified according to singleton or twin pregnancy, maternal position, gestational age at examination and different cut-off values to predict SPB < 36 weeks. RESULTS: The interobserver variability in each position was similar, with an interclass correlation coefficient (95% CI) of 0.952 (0.811-0.984) in the recumbent and 0.942 (0.837-0.978) in the upright maternal position. After exclusion of pregnancies with iatrogenic preterm birth, 15/138 (11%) singletons and 29/153 (19%) twin pairs were born at <36 weeks. The incidence of funneling was greater in an upright compared with a recumbent maternal position by 12.3% in singleton and 13.1% in twin pregnancies before 25 weeks, and by 13.0% and 21.6% between 25 and 30 weeks, respectively. This resulted in an earlier and more accurate prediction of SPB by transvaginal ultrasound in an upright compared with a recumbent maternal position, which could be shown by all applied statistical methods. The influence of posture on the prognostic value of the CL varied depending on the cut-off value. Differences in CL or FW between 15-20 and 25-30 weeks predicted SPB better than did differences between shorter intervals. CONCLUSIONS: Evaluation of the cervix with the woman in the upright position permits earlier detection of funneling. This may enable earlier and more appropriate intervention to avoid SPB.

Adult↗

PubMed2005

Primate phylogeny: molecular evidence from retroposons.

In these postgenomic times where aspects of functional genetics and character evolution form a focal point of human-mouse comparative research, primate phylogenetic research gained a widespread interest in evolutionary biology. Nevertheless, it also remains a controversial subject. Despite the surge in available primate sequences and corresponding phylogenetic interpretations, primate origins as well as several branching events in primate divergence are far from settled. The analysis of SINEs - short interspersed elements - as molecular cladistic markers represents a particularly interesting complement to sequence data. The following summarizes and discusses potential applications of this new approach in molecular phylogeny and outlines main results obtained with SINEs in the context of primate evolutionary research. Another molecular cladistic marker linking the tarsier with the anthropoid primates is also presented. This eliminates any possibility of confounding phylogenetic interpretations through lineage sorting phenomena and makes use of a new point of view in settling the phylogenetic relationships of the primate infraorders.

Animals↗

PubMed2004

Spontaneous emission lifetime of a single trapped Ca(+) ion in a high finesse cavity.

We investigate the spontaneous emission lifetime of a single trapped (40)Ca+ ion placed at different positions in the vacuum standing wave inside a high finesse cavity which is stabilized to the atomic transition. The lifetime is measured by quantum state detection after pi-pulse excitation. The result for the natural lifetime of the D(5/2) metastable state of 1161(22) ms agrees, within 1 standard deviation, with the most precise published value. We observe a reduction of the spontaneous emission lifetime of approximately 15% in the node of the vacuum field.

Journal Article↗

PubMed2004

Predicting psychrometric conditions in biocontaminant microenvironments with a microclimate heat and moisture transfer model -- description and field comparison.

UNLABELLED: A numerical model is described that is designed to model psychrometric conditions in biocontaminant microenvironments, such as in bedding and the base of carpets for dust-mites, and on the surface of linings for molds. The model is very general and can include room air, other room components, other zones including the outdoors, other rooms and any subfloor space. Mechanical plant can be modeled. Good agreement between modeled and field results are reported for the complex case of an occupied bed and for the microclimate in the base of a carpet, before and after its timber floor above a crawl space was retrofitted with insulation. PRACTICAL IMPLICATIONS: Biocontaminants such as dust-mites and molds can pose serious health problems. Understanding microclimates in biocontaminant microhabitats, when coupled with biologic models, will make it possible to predict how the life cycles of these biocontaminants are affected as these conditions change. In turn, this will suggest which interventions that modify indoor climate and microclimate are likely to control these biocontaminants. Furthermore such interventions might include indoor humidity control, changing building insulation and ventilation levels, covering mattresses, use of electric blankets, use of carpet heating, etc. Such models will provide a fast way for screening for interventions that are likely to be effective in the control of biocontaminants.

Air Pollutants↗

PubMed2001

Molecular phylogeny of the major hylobatid divisions.

We describe DNA sequences for the mitochondrial control region and phenylalanine-tRNA from the four extant gibbon subgenera. In contrast to earlier studies on gibbon phylogeny that used other parts of the mtDNA, the control region depicts the crested gibbons (Nomascus) as the most basal group of the Hylobatidae, followed by Symphalangus, with Bunopithecus and Hylobates as the last to diverge. Our data show that the molecular distances among the four gibbon subgenera are in the same range as those between Homo and Pan, or even higher. As a consequence of these findings, we propose to raise all four gibbon subgenera to genus rank.

Animals↗

PubMed2001

The Drosophila VEGF receptor homolog is expressed in hemocytes.

Several signalling pathways have been defined by studies of genes originally characterised in Drosophila. However, some mammalian signalling systems have so far escaped discovery in the fly. Here, we describe the identification and characterisation of fly homologs for the mammalian vascular endothelial growth factor/platelet derived growth factor (VEGF/PDGF) and the VEGF receptor. The Drosophila factor (DmVEGF-1) gene has two splice variants and is expressed during all stages, the signal distribution during embryogenesis being ubiquitous. The receptor (DmVEGFR) gene has several splice variants; the variations affecting only the extracellular domain. The most prominent form is expressed in cells of the embryonic haematopoietic cell lineage, starting in the mesodermal area of the head around stage 10 of embryogenesis. Expression persists in hemocytes as embryonic development proceeds and the cells migrate posteriorly. In a fly strain carrying a deletion uncovering the DmVEGFR gene, hemocytes are still present, but their migration is hampered and the hemocytes remain mainly in the anterior end close to their origin. These data suggest that the VEGF/PDGF signalling system may regulate the migration of the Drosophila embryonic haemocyte precursor cells.

Alternative Splicing↗

PubMed2001

Cloning and expression of Helicobacter pylori GDP-l-fucose synthesizing enzymes (GMD and GMER) in Saccharomyces cerevisiae.

Helicobacter pylori is a Gram-negative gastric pathogen causing diseases from mild gastric infections to gastric cancer. The difference in clinical outcome has been suggested to be due to strain differences. H. pylori undergoes phase variation by changing its lipopolysaccharide structure according to the environmental conditions. The O-antigen of H. pylori contains fucosylated glycans, similar to Lewis structures found in human gastric epithelium. These Lewis glycans of H. pylori have been suggested to play a role in pathogenesis in the adhesion of the bacterium to gastric epithelium. In the synthesis of fucosylated structures, GDP-l-fucose is needed as a fucose donor. Here, we cloned the two key enzymes of GDP-l-fucose synthesis, H. pylori gmd coding for GDP-d-mannose dehydratase (GMD), and gmer coding for GDP-4-keto-6-deoxy-d-mannose-3,5-epimerase/4-reductase (GMER) and expressed them in an enzymatically active form in Saccharomyces cerevisiae. The end product of these enzymes, GDP-l-fucose was used as a fucose donor in a fucosyltransferase assay converting sialyl-N-acetyllactosamine to sialyl Lewis X.

Base Sequence↗

PubMed2001

Identification and structure of the Rhizobium galegae common nodulation genes: evidence for horizontal gene transfer.

Rhizobia are soil bacteria able to fix atmospheric nitrogen in symbiosis with leguminous plants. In response to a signal cascade coded by genes of both symbiotic partners, a specific plant organ, the nodule, is formed. Rhizobial nodulation (nod) genes trigger nodule formation through the synthesis of Nod factors, a family of chitolipooligosaccharides that are specifically recognized by the host plant at the first stages of the nodulation process. Here, we present the organization and sequence of the common nod genes from Rhizobium galegae, a symbiotic member of the RHIZOBIACEAE: This species has an intriguing phylogenetic position, being symbiotic among pathogenic agrobacteria, which induce tumors instead of nodules in plant shoots or roots. This apparent incongruence raises special interest in the origin of the symbiotic apparatus of R. galegae. Our analysis of DNA sequence data indicated that the organization of the common nod gene region of R. galegae was similar to that of Sinorhizobium meliloti and Rhizobium leguminosarum, with nodIJ downstream of nodABC and the regulatory nodD gene closely linked to the common nod operon. Moreover, phylogenetic analyses of the nod gene sequences showed a close relationship especially between the common nodA sequences of R. galegae, S. meliloti, and R. leguminosarum biovars viciae and trifolii. This relationship in structure and sequence contrasts with the phylogeny based on 16S rRNA, which groups R. galegae close to agrobacteria and separate from most other rhizobia. The topology of the nodA tree was similar to that of the corresponding host plant tree. Taken together, these observations indicate that lateral nod gene transfer occurred from fast-growing rhizobia toward agrobacteria, after which the symbiotic apparatus evolved under host plant constraint.

Bacterial Proteins↗

PubMed2000

A polymerase chain reaction-based protocol for the detection of transmission of pig endogenous retroviruses in pig to human xenotransplantation.

BACKGROUND: Xenotransplantation of pig organs and tissues to humans bears the risk of infection of immunosuppressed recipients by porcine endogenous retrovirus (PERV) released from the transplanted tissue. However, when diagnosing potential PERV transmission, it is essential to exclude microchimerism, i.e., persisting pig cells in analyzed bioptic material of xenotransplanted patients, which give rise to false positive PERV signals. Polymerase chain reaction (PCR) is so far the only suitable method to diagnose a cross-species transfer of PERV, but the exclusion of microchimerism might be a serious problem because most of the presently employed primer pairs detect PERV sequences with higher sensitivity than primers used for the detection of contaminating pig sequences. METHODS: We designed and evaluated a novel and improved primer set for detection of pig sequences as well as complementing positive control primers on the basis of mitochondrial cytochrome B, an approved marker for phylogenetic studies. We further established primer pairs derived from the long terminal repeat/leader region of PERV isolated from a Duroc German Landrace cross-bred pig and tested their sensitivity in comparison with known PERV- and pig-specific PCR markers. RESULTS: In standard PCR assays, the new cytochrome B-derived primers are at least 10 times more sensitive than the presently used PERV retroviral polymerase gene and mammalian beta-actin primers. When tested in a tissue culture infection model, PERV transmission to human 293 cells can be unambiguously demonstrated, even in the presence of up to 10% pig cells. One of the primer combinations derived from the PERV DuxDL3791 long terminal repeat/leader region amplifies with even lower sensitivity than primers detecting porcine beta-globin, thus permitting the exclusion of microchimerism also via chromosomal loci. CONCLUSIONS: The availability of the new PCR markers allows the proposal of a rigorous setup for the routine detection of PERV transmission after xenotransplantation.

Actins↗

PubMed2000

DNA of nonhuman primates harbors hepatitis C-virus-specific sequences of its 5'-non-coding region (5'-NCR).

The DNA from PBMCs of both hepatitis C virus (HCV)-positive patients and healthy HCV-negative human individuals tested thus far contains essential parts--up to 272/341 nucleotides--of the HCV 5'-non-coding region (5'-NCR). These findings bring up the question of the possible evolutionary background of these sequences. Therefore, using the same methodology, we looked for the same sequences in animals closely related to man, i.e., in nonhuman primates (two chimpanzees, one orang-utan, one Debrazza monkey, two New World monkey species and a prosimian). The DNA from PBMCs of the studied animals belonging to nonhuman primates contains essential parts--up to 272/341 nucleotides--of the HCV 5'-non-coding region (5'-NCR). A common sequence of 82 nucleotides is contained in the DNA of all the tested animals but only the chimpanzee's DNA harbors the same, longer sequence region of 272/341 nucleotides of the 5'-NCR found in human DNA. The results may provide a clue as to the possible origin of parts of the IRES containing sequence area of the HCV.

Animals↗

PubMed2000

Infection of nonhuman primate cells by pig endogenous retrovirus.

The ongoing shortage of human donor organs for transplantation has catalyzed new interest in the application of pig organs (xenotransplantation). One of the biggest concerns about the transplantation of porcine grafts into humans is the transmission of pig endogenous retroviruses (PERV) to the recipients or even to other members of the community. Although nonhuman primate models are excellently suited to mimic clinical xenotransplantation settings, their value for risk assessment of PERV transmission at xenotransplantation is questionable since all of the primate cell lines tested so far have been found to be nonpermissive for PERV infection. Here we demonstrate that human, gorilla, and Papio hamadryas primary skin fibroblasts and also baboon B-cell lines are permissive for PERV infection. This suggests that a reevaluation of the suitability of the baboon model for risk assessment in xenotransplantation is critical at this point.

Animals↗

PubMed2000

The Pl(A2) polymorphism of integrin beta(3) enhances outside-in signaling and adhesive functions.

Genetic factors are believed to influence the development of arterial thromboses. Because integrin alpha(IIb)beta(3) plays a crucial role in thrombus formation, we analyzed receptor adhesive properties using Chinese hamster ovary and human kidney embryonal 293 cells overexpressing the Pl(A1) or Pl(A2) polymorphic forms of alpha(IIb)beta(3). Soluble fibrinogen binding was no different between Pl(A1) and Pl(A2) cells, either in a resting state or when alpha(IIb)beta(3) was activated with anti-LIBS6. Pl(A1) and Pl(A2) cells bound equivalently to immobilized fibronectin. In contrast, significantly more Pl(A2) cells bound to immobilized fibrinogen in an alpha(IIb)beta(3)-dependent manner than did Pl(A1) cells. Disruption of the actin cytoskeleton by cytochalasin D abolished the increased binding of Pl(A2) cells. Compared with Pl(A1) cells, Pl(A2) cells exhibited a greater extent of polymerized actin and cell spreading, enhanced tyrosine phosphorylation of pp125(FAK), and greater fibrin clot retraction. These adhesion differences appear to depend on a signaling mechanism sensitive to receptor occupancy. Thus, the Pl(A2) polymorphism altered integrin-mediated functions of adhesion, spreading, actin cytoskeleton rearrangement, and clot retraction.

Actins↗

PubMed1999

Convection and thermodiffusion of colloidal gold tracers by laser light scattering.

In a dynamic light scattering experiment, we have investigated the time intensity correlation function and the profile of the transmitted laser beam for organic dispersions of light absorbing colloidal particles containing tiny gold clusters. The correlation functions have been found to show a superposition of an exponential decay, corresponding to Brownian motion of the tracers, and well-defined oscillations. These oscillations are caused by convection due to local heating of the sample by the incident laser beam, which has been confirmed independently via measurements of the local temperature within the sample. It will be shown how the particle convection velocity, which is the order of 1 mm/s, can be obtained quantitatively from the oscillating correlation functions. The profile of the transmitted beam allowed us to determine the Soret coefficient, which is a measure for the thermal diffusion of the particles. This article shows how tracer diffusion, convection, and thermal diffusion can be determined simultaneously by one single experiment, laser light scattering of light absorbing colloidal particles in dispersion.

Journal Article↗

PubMed1998

Priming of platelet alphaIIbbeta3 by oxidants is associated with tyrosine phosphorylation of beta3.

Reactive oxygen species play an important role at the site of vascular injuries and arterial thromboses. We studied the mechanism mediating platelet aggregation induced by H2O2, a major cellular oxidant. Exposure to H2O2 triggered platelet aggregation, but only when the platelets were stirred. Strong platelet aggregation induced99032416 required the presence of the tyrosine phosphatase inhibitor sodium orthovanadate (NaVO4) and was dependent on the participation of integrin alphaIIbbeta3 (glycoprotein IIb-IIIa). A specific inhibitor of alphaIIbbeta3 blocked platelet aggregation induced by H2O2 and NaVO4, thus confirming that aggregation requires this receptor. In the presence of H2O2 and NaVO4, multiple platelet substrates were phosphorylated on tyrosine. Such tyrosine kinase response was necessary but not sufficient to activate alphaIIbbeta3, as detected by binding of soluble fibrinogen to platelets. Stirring of the platelets exposed to H2O2 and NaVO4 was also needed to allow for binding of fibrinogen to alphaIIbbeta3. The tyrosine kinase inhibitor genistein was able to block platelet aggregation induced by H2O2 and NaVO4, thus confirming that tyrosine kinase activity was needed to trigger alphaIIbbeta3 activation on stirring. N-Acetyl-L-cysteine, a cell-permeant antioxidant, blocked the tyrosine phosphorylation of platelet substrates and also the platelet aggregation induced by H2O2 and NaVO4. We found that beta3 was phosphorylated on tyrosine in platelets exposed to H2O2 and NaVO4, even in the absence of aggregation. Hence, tyrosine phosphorylation of beta3 might contribute to the "priming" of alphaIIbbeta3 induced by H2O2 and NaVO4, whereby the receptor can become activated on stirring of the platelets.

Humans↗

PubMed1997

The introns of the canine rod opsin gene show higher sequence homology to the human than to the rodent introns.

Using genomic DNA from late-onset retinal degenerate and wild type Labrador Retrievers as templates and canine exon-specific oligonucleotides as primers in polymerase chain reaction, all four introns of opsin were cloned and sequenced. Dot-matrix comparisons were made for human, murine and canine introns. Selected sequences containing either intronic or coding sequences were aligned and used for phylogenetic relationship analysis. The opsin gene introns are conserved between the human, the mouse and the dog with regards to number and length. In addition there is an astonishingly high degree of sequence homology between the second and fourth introns. Introns 2(1277 bp in dog) and 4 (863 bp in dog) are 72% and 71% homologous to the human introns, and 57% and 52% homologous to the mouse introns, respectively. The coding sequence (CDS) of the dog shows 93% homology to human CDS and 88% homology to mouse CDS. A phylogenetic analysis of the intronic sequences 2 and 4 confirms the higher relatedness between dog and human than between mouse and human opsin genes. As there are good reasons to believe that the primate and rodent lineages are closer to each other than to the Canis familiaris, there must be some functional constraints on the evolution of human and dog opsins.

Animals↗

PubMed1996

5-HT1A receptors are not involved in clozapine's lack of cataleptogenic potential.

Clozapine and 8-OH-DPAT antagonized haloperidol-induced catalepsy in rats (ED50 10 and 0.1 mg/kg s.c., respectively). Whereas the selective 5-HT1A receptor antagonist WAY 100635 (0.1 mg/kg s.c.) completely antagonized the inhibitory effect of 8-OH-DPAT, clozapine's effect was not affected. On the other hand, clozapine and 8-OH-DPAT inhibited ultrasonic vocalization in rats (ED50 0.7 and 0.03 mg/kg s.c., respectively), which effects were antagonized by WAY 100635. The lack of catalepsy of clozapine, therefore, cannot be addressed primarily to clozapine's agonistic activity at 5-HT1A receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1995

Polytene chromosomes show normal gene activity but some mRNAs are abnormally accumulated in the pseudonurse cell nuclei of Drosophila melanogaster otu mutants.

Certain mutant alleles of the ovarian tumor (otu) locus give rise to polytene chromosomes in the pseudonurse cells (PNCs). We have previously shown that the banding pattern of these germ line-derived chromosomes is similar to that in the larval salivary gland chromosomes. In this study, we have examined the gene activity of these chromosomes. General gene expression from these chromosomes was studied by uridine autoradiography. The expression of specific genes was monitored by in situ hybridisation to mRNA and also by combining enhancer trap lines with otu mutants. We found that most of the genes studied were expressed in the PNCs as they were in the wild-type nurse cells. Four out of the 12 mRNAs studied accumulated in the nuclei instead of migrating to the cytoplasm. The intensity of accumulation directly correlated with the extent of polytenisation in the PNC nuclei. We suggest that the otu mRNA remains partly attached to the polytene chromosome template after transcription and discuss the effects of this phenomenon on polytenisation of the PNC chromosomes.

Animals↗

PubMed1995

Two otu transcripts are selectively localised in Drosophila oogenesis by a mechanism that requires a function of the otu protein.

The ovarian tumour gene (otu) is required for several processes during Drosophila oogenesis. The locus encodes two protein isoforms that have been proposed to act during different stages of oogenesis. Here we show that the corresponding otu mRNAs display a dynamic pattern of expression during oogenesis. The 4.1 kb mRNA encoding the 104 kDa isoform is expressed throughout adult oogenesis, but is mainly restricted to nurse cells. The 3.2 kb mRNA encoding the 98 kDa protein isoform is selectively localised in the oocyte up to stage 9. Both mRNAs are expressed abundantly in nurse cells at stages 10-11. We propose that the oocyte-specific function of otu is realised by the 98 kDa isoform. We show that the export of the 3.2 kb mRNA from the nurse cell nuclei requires a functional otu protein. The otu protein is also required for the correct distribution of the pumilio and oskar mRNAs, while the Bic-D, K10 and staufen mRNAs are localised in wild type fashion in otu mutants. Furthermore, we have observed a region of homology between the carboxy-terminal part of the otu protein and the mammalian microtubule associated proteins. The more severe the mutation in this region of homology, the more disturbed mRNA distribution is observed in otu mutants.

Amino Acid Sequence↗