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Biomedical subjects

A Hansen

Publications and source records attributed to A Hansen.

At least 91 records · Page 5Linked to original sources
PubMed1999

Labor and delivery characteristics and risks of cranial ultrasonographic abnormalities among very-low-birth-weight infants. The Developmental Epidemiology Network Investigators.

OBJECTIVE: The objective of this study was to evaluate the relationships between 3 labor and delivery characteristics (duration of labor, interval between membrane rupture and delivery, and route of delivery) and 4 neonatal cranial ultrasonographic abnormalities (intraventricular hemorrhage, ventriculomegaly, echodensity of cerebral white matter, and periventricular leukomalacia). STUDY DESIGN: We prospectively gathered data on 1588 very low birth weight infants including neonatal cranial ultrasonographic studies, maternal interview, and maternal and infant chart reviews. We performed univariate and multivariate analyses. RESULTS: In univariate analysis vaginal delivery was associated with an increased risk of all 4 cranial ultrasonographic abnormalities. In multivariate analysis, however, vaginal delivery was no longer associated with periventricular leukomalacia. Moreover, the risks of intraventricular hemorrhage, ventriculomegaly, and echodensity attributable to vaginal delivery were no longer elevated when the sample was limited to infants born within 1 hour after membrane rupture and adjustment was made for fetal vasculitis and for other potential confounders. CONCLUSION: Vaginal delivery was the only obstetric characteristic consistently associated with intracranial hemorrhage and white matter disease in these preterm infants. Because its relationship to brain lesions was markedly reduced when placental inflammation was accounted for, however, vaginal delivery may simply have acted as a marker for antecedent inflammation or infection and not as a direct contributor to brain disorders.

Brain↗
PubMed1999

Competition between correlated buoyancy and uncorrelated capillary effects during drainage.

We study drainage in a horizontally oriented rough fracture joint filled with glass beads. The shape and structure of the drained areas is the result of competition between two effects: (1) variations in the capillary thresholds necessary to be overcome in order to drain the pores and (2) the height variations due to the roughness of the fracture joint. These height variations have long range correlations due to the self-affine nature of the fracture. The capillary thresholds are uncorrelated. We tune the relative strength of these two effects by performing experiments in a centrifuge and thus changing the "strength of gravity." As gravity is increased, the structure of the drained areas change from that of invasion percolation to a structure composed of compact blobs linked together by threadlike links. We study both the geometry and the effect of trapping while changing acceleration of gravity from zero to 6g(0). At high centrifugal acceleration we further observe fragmentation, migration and coalescence of bubbles of fluid inside the drained areas.

Journal Article↗
PubMed1999

Symptom-giving pelvic girdle relaxation in pregnancy. I: Prevalence and risk factors.

BACKGROUND: Previous studies concerning symptom-giving pelvic girdle relaxation in pregnancy have to our knowledge been retrospective. We wanted to 1) determine the incidence during pregnancy and the prevalence two, six, and twelve months post partum, 2) identify possible predisposing factors, and 3) determine the frequency and duration of sicklisting, prospectively. MATERIAL AND METHODS: A cohort of 1600 consecutive pregnant women filled in a questionnaire. At the routine prenatal examinations they were asked about pelvic pain. Those who fulfilled the inclusion criteria were examined by a rheumatologist to confirm the diagnosis. The affected women were seen again two, six, and twelve months post partum. All participants were asked about sicklisting in pregnancy. RESULTS: The incidence during pregnancy was 14%, the prevalence two, six, and twelve months post partum were 5%, 4%, and 2% respectively. Multivariate analysis indicates that the most important predisposing factor is pelvic pain in a previous pregnancy. Other factors were uncomfortable working conditions, lack of exercise, and previous low back pain and low abdominal pain. At least 37% of the women with symptom-giving pelvic girdle relaxation had been sicklisted in pregnancy due to pelvic pain, on average for twelve weeks. CONCLUSION: Symptom-giving pelvic girdle relaxation is a considerable problem both in pregnancy and post partum. The occupational risk can possibly be prevented. The syndrome has a great social impact because of the frequent sicklisting.

Adult↗
PubMed1999

Symptom-giving pelvic girdle relaxation in pregnancy. II: Symptoms and clinical signs.

BACKGROUND: Pelvic pain in pregnancy appears to be a problem that is increasing. This study was undertaken to describe and analyze the relationship between subjective symptoms, daily disability, and clinical findings in women with symptom-giving pelvic girdle relaxation in pregnancy MATERIALS AND METHODS: Out of 1600 pregnant women 238 had pelvic pain. After a clinical examination 11 women were excluded due to low back pain. The rest, 227 women, was considered having symptom-giving pelvic girdle relaxation during pregnancy. RESULTS: Symptom-giving pelvic girdle relaxation in pregnancy seriously interferes with many activities of daily living such as housekeeping, walking, working, and sexual life. The women's statements of pelvic pain are well correlated to the number of positive clinical tests. CONCLUSION: Symptom-giving pelvic girdle relaxation in pregnancy causes considerable disabilities concerning daily activities.

Activities of Daily Living↗
PubMed1999

Blood management in two-stage revision knee arthroplasty for deep prosthetic infection.

Treatment of infected total knee arthroplasty requires aggressive management to treat the infection and restore joint function. For patients with infected knee arthroplasties, a two-stage procedure is used that involves resection of the joint and placement of an antibiotic impregnated cement spacer followed by implantation of a new prosthetic 6 weeks later. Patients undergoing the two-stage procedure typically endure high allogeneic blood transfusion rates (82% to 88%) and progressive anemia because the two surgeries are spaced closely and because the infection precludes the use of alternatives to allogeneic blood. Records were reviewed of 75 patients who underwent two-stage total knee arthroplasty to characterize perioperative hemoglobin levels and blood transfusion needs in this patient group. Although transfusions were administered only when warranted by clinical symptoms and were not based on predetermined hematologic values, 62 (82%) patients received a mean of 2.3 units of blood at first-stage surgery, and 60 (80%) patients received a mean of 2.1 units of blood at the second stage. Overall, only 12% of patients did not have allogeneic blood transfusion. At the first stage before resection, mean hemoglobin concentration was 11.6 g/dL and reached a mean nadir of 8.6 g/dL 3 days after surgery. At the second stage before reimplantation, hemoglobin concentration averaged 11.1 g/dL and reached a mean nadir of 8.2 g/dL 3 days after surgery. After the first stage, allogeneic blood transfusion failed to improve postoperative hemoglobin levels enough to prevent transfusions associated with the second-stage. Patients undergoing two-stage total knee arthroplasty have anemia, and a substantial proportion of these patients require allogeneic blood transfusion at both stages. Thus, novel blood management practices are required to improve hemoglobin levels and reduce allogeneic transfusion rates in this patient population.

Aged↗
PubMed1999

Influence of catheter position and equipment-related factors on the accuracy of intravascular ultrasound measurements.

BACKGROUND: Intravascular ultrasound (IVUS) is frequently used as an adjunct to coronary angiography to guide revascularization procedures and, more recently, to estimate atherosclerotic plaque volumes. Although accuracy of IVUS imaging and analysis is crucial for these measurements, available data are scarce. The purpose of this in vitro study is to determine the extent to which transducer position and equipment-related factors influence measurement accuracy. METHODS: Cross-sectional views of tubular vessel phantoms (diameter 2-14 mm) were acquired using 3.2 French catheters in coaxially centered, eccentric and oblique positions. Catheters were sequentially connected to two different ultrasound systems (A and B) to estimate equipment-related variability. In system B, two software versions were used to analyze ultrasound images. Longitudinal views of phantom segments were reconstructed to document transducer misplacement. RESULTS: Oblique transducer positioning resulted in a non-linear overestimation of phantom areas that was independent of lumen size and also resulted in dramatic distortions of three-dimensionally reconstructed phantom geometry. Eccentric positioning did not significantly influence measurement accuracy. In coaxial positioning, differences between measured and true areas increased non-linearly from 0.36 to 4.5 mm2 in system B and in a linear fashion from -0.01 to 2.68 mm2 in system A with increasing phantom diameters. Relative differences decreased from 11.4% to 2.9% with increasing reference areas in system B (positive off-set error). When using updated software in system B, the off-set error was negative and relative error diminished from -1.34% to 0.44% with increasing phantom size. CONCLUSION: Transducer position and equipment-related factors influence the accuracy of intravascular ultrasound, which may lead to misinterpretation of vessel size and geometry even in straight vessel segments. Transducer position may be controlled by the reconstruction of longitudinal images. Ultrasound equipment should be calibrated before using it for quantitative measurements.

Cardiac Catheterization↗
PubMed1998

Odorant receptor gene expression in catfish taste tissue.

Odorant receptor expression has been reported in a variety of non-olfactory cells and tissues in several animal models. We therefore investigated the possible expression of odorant receptor genes in taste tissue of channel catfish. Multiple odorant receptor transcripts were amplified by PCR from barbel. In situ hybridization showed that receptors amplified from taste tissue, as well as receptors amplified from olfactory neurons, hybridized to taste epithelium with similar patterns. These results show that odorant receptor transcripts are expressed in catfish taste tissue. Taken with previous data, these results suggest that some members of the odorant receptor superfamily may mediate various chemoreceptive roles in non-olfactory cells.

Amino Acid Sequence↗
PubMed1998

The arginine taste receptor. Physiology, biochemistry, and immunohistochemistry.

The amino acid, L-arginine (L-Arg), is a potent taste stimulus for the channel catfish, Ictalurus punctatus. Receptor binding studies demonstrated a high-affinity binding of L-Arg to putative taste receptor sites. This binding could be inhibited by preincubation of the tissue in the lectins Phaseolus vulgaris agglutinin (PHA) and Ricinus communis agglutinin I (RCA I). Neurophysiological studies demonstrated that the L-Arg receptor is a stimulus-gated ion channel type receptor whose conductance was stimulated by L-Arg and inhibited by D-arginine (D-Arg). To purify the receptor we subjected CHAPS solubilized partial membrane preparation from barbel epithelium to RCA I lectin affinity chromatography. The bound proteins were eluted with D-galactose. When these proteins were reconstituted into lipid bilayers, L-Arg activated single channel currents with conductances between 45 and 85 pS. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the eluted protein showed a distinct band at approximately 83 kDa. Polyclonal antibodies raised against this 83-kDa band in guinea pigs reacted with numerous small (approximately 1 micron) sites within the taste pore of every taste bud when applied to fixed nonpermeabilized barbels. This observation suggests that the antibodies recognize an externally-facing epitope of the putative Arg receptor. The antibodies also inhibited L-Arg-stimulated currents in reconstitution studies. Sephacryl S-300 HR chromatography of the eluant from the affinity column showed a high molecular weight peak (> 700 kDa) which was recognized by the antibodies. Reconstitution of the protein from this peak into a lipid bilayer resulted in L-Arg-stimulated channels that could be inhibited by D-Arg. This high molecular weight component may be aggregates of the arginine taste receptor.

Animals↗
PubMed1998

[Combination therapy of rheumatoid arthritis].

The prevalence of rheumatoid arthritis (RA) is about 0.5-1%. The disease course is variable, but RA causes substantial morbidity and mortality. The effect of conventional therapy for RA, i.e. nonsteroidal antiinflammatory drugs (NSAID), glucocorticosteroids and Slow Acting Anti-Rheumatic Drugs (SAARD) including methotrexate, gold salts, anti-malarials, d-penicillamine and salazopyrine, is often suboptimal. Since the aim of treatment is a complete remission, combination therapy, i.e. treatment with two or more SAARDs, may be feasible since an additive/synergistic effect may be obtained. In this paper the literature about the effectiveness and toxicity of combination therapy is reviewed. Only a few randomized, clinically controlled trials have been published. None of them have documented that gold salts, d-penicillamine and azathioprine in combination with other SAARDs are better than monotherapy. However, recent trials have indicated that methotrexate in combination with salazopyrine and hydroxychloroquine or in combination with cyclosporine may cause a better therapeutic effect than methotrexate alone, without additional toxicity. Long term studies of the effect of combination therapy are not yet available.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Ultrastructure of the olfactory organ in the clawed frog, Xenopus laevis, during larval development and metamorphosis.

Development of the olfactory epithelia of the African clawed frog, Xenopus laevis, was studied by scanning and transmission electron microscopy. Stages examined ranged from hatching through the end of metamorphosis. The larval olfactory organ consists of two chambers, the principal cavity and the vomeronasal organ (VNO). A third sensory chamber, the middle cavity, arises during metamorphosis. In larvae, the principal cavity is exposed to water-borne odorants, but after metamorphosis it is exposed to airborne odorants. The middle cavity and the VNO are always exposed to waterborne odorants. Electron microscopy reveals that in larvae, principal cavity receptor cells are of two types, ciliated and microvillar. Principal cavity supporting cells are also of two types, ciliated and secretory (with small, electron-lucent granules). After metamorphosis, the principal cavity contains only ciliated receptor cells and secretory supporting cells, and the cilia on the receptor cells are longer than in larvae. Supporting cell secretory granules are now large and electron-dense. In contrast, the middle cavity epithelium contains the same cell types seen in the larval principal cavity. The VNO has microvillar receptor cells and ciliated supporting cells throughout life. The cellular process by which the principal cavity epithelium changes during metamorphosis is not entirely clear. Morphological evidence from this study suggests that both microvillar and ciliated receptor cells die, to be replaced by newly generated cells. In addition, ciliated supporting cells also appear to die, whereas there is evidence that secretory supporting cells transdifferentiate into the adult type. In summary, significant developmental additions and neural plasticity are involved in remodeling the olfactory epithelium in Xenopus at metamorphosis.

Animals↗
PubMed1998

Diphospho-myo-inositol phosphates in Dictyostelium and Polysphondylium: identification of a new bisdiphospho-myo-inositol tetrakisphosphate.

The two major diphospho inositol phosphates from the axenic strain Dictyostelium discoideum AX2 were previously investigated and identified as 6-PP-InsP5 and 5,6-bis-PP-InsP4. In order to examine whether these findings are representative of Dictyostelids in general, five non-axenic wild-type species of Dictyostelium and two of Polysphondylium were studied. It was found that all of the Dictyostelium species exhibit similar patterns of diphospho inositol phosphates. By contrast, both of the Polysphondylium species contain 5-PP-InsP5 as the predominant isomer. Besides 5,6-bis-PP-InsP4, a new bis-PP-InsP4 was detected in Polysphondylium. This compound is either 1,5-bis-PP-InsP4 or its corresponding enantiomer 3,5-bis-PP-InsP5. The structures were elucidated by two-dimensional 1H-1H and 1H-31P NMR analysis. Additionally, they were confirmed using a specific 6-PP-InsP(5)-5-kinase from D. discoideum AX2 as an enantio-specific tool and enantiomerically pure reference standards.

Animals↗
PubMed1998

Modulation of the Escherichia coli tryptophan repressor protein by engineered peptides.

We have used the E. coli tryptophan repressor (TrpR) as a model protein for modulation by engineered peptides both in vivo and in vitro. The tryptophan operator promoter-lacZ reporter system was used to investigate the in vivo ability of several synthetic peptides to modulate TrpR function. GMSA (gel mobility shift analysis) was used to study the in vitro ability of the peptides to modulate binding of the TrpR protein to the operator DNA. Peptides WRW, DRW, DW, RW enhanced TrpR binding to the operator in vivo at 100 microM concentrations. The same peptides enhanced TrpR binding to the operator in vitro at 1 mM concentrations. The peptide RRW reduced TrpR binding to the tryptophan operator both in vivo and in vitro. Thus the peptide RRW acted more as an inducer than corepressor. The peptide WR could neither enhance nor impede binding between TrpR and the operator in vivo or in vitro, suggesting that the presence of a carboxyl tryptophan residue may be necessary for binding to the TrpR protein. Thin layer chromatography was used to ensure that the peptides had not been subject to proteolysis during the in vitro gel mobility shift assays.

Bacterial Proteins↗
PubMed1998

The peripheral olfactory organ of the zebrafish, Danio rerio: an ultrastructural study.

The peripheral olfactory organ of the adult zebrafish, Danio rerio, was investigated by light as well as scanning and transmission electron microscopy. The olfactory organ consists of several lamellae that insert into a midline raphe, thus forming an oval-shaped rosette. Sensory and nonsensory regions are located separately on each lamella. The olfactory epithelium contains three types of receptor cells: two as described classically for other fishes, bearing either cilia or microvilli, the third being a new sensory cell type--the crypt cell. The crypt cell has no olfactory knob but bears microvilli as well as submerged cilia. Its axon travels together with the axons of the other receptor cells towards the basal lamina. Whereas the classical receptor cells are separated by supporting cells with small protrusions on their apical surfaces, the crypt cell is always surrounded by one or two specialized electron-lucent supporting cells which also bear microvillous-like apices. The nonsensory areas contain the goblet cells, ciliated nonsensory cells and epidermal cells with microridges.

Animals↗
PubMed1998

Phosphorylation of the periplasmic binding protein in two transport systems for arginine incorporation in Escherichia coli K-12 is unrelated to the function of the transport system.

In Escherichia coli K-12, the accumulation of arginine is mediated by two distinct periplasmic binding protein-dependent transport systems, one common to arginine and ornithine (AO system) and one for lysine, arginine, and ornithine (LAO system). Each of these systems includes a specific periplasmic binding protein, the AO-binding protein for the AO system and the LAO-binding protein for the LAO system. The two systems include a common inner membrane transport protein which is able to hydrolyze ATP and also phosphorylate the two periplasmic binding proteins. Previously, a mutant resistant to the toxic effects of canavanine, with low levels of transport activities and reduced levels of phosphorylation of the two periplasmic binding proteins, was isolated and characterized (R. T. F. Celis, J. Biol. Chem. 265:1787-1793, 1990). The gene encoding the transport ATPase enzyme (argK) has been cloned and sequenced. The gene possesses an open reading frame with the capacity to encode 268 amino acids (mass of 29.370 Da). The amino acid sequence of the protein includes two short sequence motifs which constitute a well-defined nucleotide-binding fold (Walker sequences A and B) present in the ATP-binding subunits of many transporters. We report here the isolation of canavanine-sensitive derivatives of the previously characterized mutant. We describe the properties of these suppressor mutations in which the transport of arginine, ornithine, and lysine has been restored. In these mutants, the phosphorylation of the AO- and LAO-binding proteins remains at a low level. This information indicates that whereas hydrolysis of ATP by the transport ATPase is an obligatory requirement for the accumulation of these amino acids in E. coli K-12, the phosphorylation of the periplasmic binding protein is not related to the function of the transport system.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Effective reduction of infarct volume by gap junction blockade in a rodent model of stroke.

Several lines of evidence indicate that the extent of ischemic injury is not defined immediately following arterial occlusion; rather that infarction expands over time. Episodes of spreading depression have been linked to this secondary increase in infarct volume. Tissue bordering the infarct fails to repolarize following spreading depression and is incorporated into the infarction. The result is that ischemic infarcts expand stepwise following each episode of spreading depression. Another line of evidence has demonstrated that gap junction blockers effectively inhibit spreading depression. These observations suggest that the efflux of potentially harmful cytosolic messengers from ischemic cells into surrounding nonischemic cells might cause amplification of injury in focal stroke. It is therefore conceivable that minimizing gap junction permeability might reduce final infarct volume. To test this hypothesis, the authors pretreated rats with the gap junction blocker, octanol, before occluding the middle cerebral artery and compared the sizes of the ischemic lesions to those in rats that received vehicle dimethyl sulfoxide prior to arterial occlusion. Histopathological analysis was performed 24 hours later. The 12 octanol-treated animals showed a significantly decreased mean infarction volume (80 +/- 16 mm3) compared with the nine control rats (148 +/- 9 mm3). In a separate set of experiments, the frequency of experimentally induced waves of spreading depression was evaluated following octanol treatment. Octanol pretreatment resulted in complete inhibition in two of nine animals, transient inhibition in five of nine, and no inhibition in two of nine. The results indicate that gap junction inhibitors, when not limited by toxicity, have significant therapeutic potential in the treatment of acute stroke.

Journal Article↗