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Biomedical subjects

E Gustafsson

Publications and source records attributed to E Gustafsson.

At least 19 recordsLinked to original sources
PubMed2006

Attosecond pulse trains generated using two color laser fields.

We investigate the spectral and temporal structure of high harmonic emission from argon exposed to an infrared laser field and its second harmonic. For a wide range of generating conditions, trains of attosecond pulses with only one pulse per infrared cycle are generated. The synchronization necessary for producing such trains ensures that they have a stable pulse-to-pulse carrier envelope phase, unlike trains generated from one color fields, which have two pulses per cycle and a pi phase shift between consecutive pulses. Our experiment extends the generation of phase stabilized few cycle pulses to the extreme ultraviolet regime.

Journal Article↗
PubMed2005

Reconstruction of attosecond pulse trains using an adiabatic phase expansion.

We propose a new method to reconstruct the electric field of attosecond pulse trains. The phase of the high-order harmonic emission electric field is Taylor expanded around the maximum of the laser pulse envelope in the time domain and around the central harmonic in the frequency domain. Experimental measurements allow us to determine the coefficients of this expansion and to characterize the radiation with attosecond accuracy over a femtosecond time scale. The method gives access to pulse-to-pulse variations along the train, including the timing, the chirp, and the attosecond carrier envelope phase.

Journal Article↗
PubMed2001

Mice lacking desmocollin 1 show epidermal fragility accompanied by barrier defects and abnormal differentiation.

The desmosomal cadherin desmocollin (Dsc)1 is expressed in upper epidermis where strong adhesion is required. To investigate its role in vivo, we have genetically engineered mice with a targeted disruption in the Dsc1 gene. Soon after birth, null mice exhibit flaky skin and a striking punctate epidermal barrier defect. The epidermis is fragile, and acantholysis in the granular layer generates localized lesions, compromising skin barrier function. Neutrophils accumulate in the lesions and further degrade the tissue, causing sloughing (flaking) of lesional epidermis, but rapid wound healing prevents the formation of overt lesions. Null epidermis is hyperproliferative and overexpresses keratins 6 and 16, indicating abnormal differentiation. From 6 wk, null mice develop ulcerating lesions resembling chronic dermatitis. We speculate that ulceration occurs after acantholysis in the fragile epidermis because environmental insults are more stringent and wound healing is less rapid than in neonatal mice. This dermatitis is accompanied by localized hair loss associated with formation of utriculi and dermal cysts, denoting hair follicle degeneration. Possible resemblance of the lesions to human blistering diseases is discussed. These results show that Dsc1 is required for strong adhesion and barrier maintenance in epidermis and contributes to epidermal differentiation.

Aging↗
PubMed2001

Functional consequences of integrin gene mutations in mice.

Integrins are cell-surface receptors responsible for cell attachment to extracellular matrices and to other cells. The application of mouse genetics has significantly increased our understanding of integrin function in vivo. In this review, we summarize the phenotypes of mice carrying mutant integrin genes and compare them with phenotypes of mice lacking the integrin ligands.

Animals↗
PubMed2001

Early expression of endomucin on endothelium of the mouse embryo and on putative hematopoietic clusters in the dorsal aorta.

Endomucin is a recently identified sialomucin that is specifically expressed on endothelium of the adult mouse. Here, we have analysed the expression of endomucin during development of the vascular system by immunohistochemistry by using three monoclonal antibodies (mAb). We demonstrate that two of the mAb, V.5C7 and V.1A7, recognize epitopes on the nonglycosylated protein, because they recognize the antigen when it is synthesized as a bacterial fusion protein and when it is in vitro translated in a membrane-free reticulocyte lysate. During in vitro differentiation of embryonic stem cells to endothelial cells, endomucin is expressed at day 6 after onset of differentiation, 1 day later than PECAM-1. During differentiation of the mouse embryo, endomucin is first detected at E8.0 in all embryonic blood vessels detectable at this stage but is absent in blood islands of the yolk sac. Analysing the paraaortic-splanchnopleura (P-SP) region and the aorta-gonad-mesonephros (AGM) region as sites of intraembryonic hematopoiesis, we found that endothelium of the dorsal aorta is brightly positive for endomucin at E8.5-9.0 and at E11.5. At later stages and in the adult aorta, endothelial staining is strongly reduced and confined to focal areas. Cell clusters associated with the luminal surface of the endothelium of the dorsal aorta could be stained for endomucin and for CD34. At a later stage (E15.5) single leukocytes in the lumen of large venules were stained for endomucin. We conclude that endomucin is an early endothelial-specific antigen that is also expressed on putative hematopoietic progenitor cells.

Animals↗
PubMed2001

Identification of proteins from Escherichia coli using two-dimensional semi-preparative electrophoresis and mass spectrometry.

Escherichia coli is a gram-negative bacterium that causes sepsis and infections of the nervous system, and the digestive and urinary tracts. The availability of the complete nucleotide sequence encoding the E. coli K-12 genome has made this organism an excellent model for proteomic studies. Semi-preparative two-dimensional electrophoresis, including liquid phase isoelectric focusing (IEF), one-dimensional sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and gel elution, have for the first time been used in combination with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOFMS), electrospray tandem mass spectrometry and database searching for rapid separation of proteins from a uropathogenic strain of E. coli. The identity of 30 proteins, including the membrane protein nmpC, was obtained using this approach.

Bacterial Proteins↗
PubMed2001

Neonatal ingestion of IgG-containing milk increases the survival of adoptively transferred B-lineage cells in B cell-deficient mice.

This study shows that neonatal ingestion of immunoglobulin-containing milk increases the survival of adoptively transferred B-lineage cells in non-irradiated B cell-deficient (mu-/-) mice. Neonatal mu-/- mice were either transferred to lactating mu+/+ foster dams, allowing them to suckle IgG-containing milk, or were kept with their mu-) dams, without IgG in the milk. After adoptive transfer of spleen cells as adults, serum-IgG levels, numbers of plasma cells, T and B cells in spleen and bone marrow were determined. The results showed that the mice which had received milk-IgG had significantly higher levels of serum-IgG and splenic B cells, as well as a higher number of Ig-secreting cells in spleen and bone marrow. This indicates that the mice might have been tolerised against IgG as neonates, if allowed to ingest Ig-containing milk. There is, however, a possibility that B cells in the milk may also contribute to the observed tolerising effect. In summary, the results suggest that 'cross-fostering' could be a suitable method to facilitate the long-term reconstitution of B- and plasma cell numbers in non-irradiated B cell-deficient mice.

Adoptive Transfer↗
PubMed2001

Tie-1-directed expression of Cre recombinase in endothelial cells of embryoid bodies and transgenic mice.

Tissue-specific gene inactivation using the Cre-loxP system has become an important tool to unravel functions of genes when the conventional null mutation is lethal. We report here the generation of a transgenic mouse line expressing Cre recombinase in endothelial cells. In order to avoid the production and screening of multiple transgenic lines we used embryonic stem cell and embryoid body technology to identify recombinant embryonic stem cell clones with high, endothelial-specific Cre activity. One embryonic stem cell clone that showed high Cre activity in endothelial cells was used to generate germline chimeras. The in vivo efficiency and specificity of the transgenic Cre was analysed by intercrossing the tie-1-Cre line with the ROSA26R reporter mice. At initial stages of vascular formation (E8-9), LacZ staining was detected in almost all cells of the forming vasculature. Between E10 and birth, LacZ activity was detected in most endothelial cells within the embryo and of extra-embryonic tissues such as yolk sac and chorioallantoic placenta. Ectopic expression of Cre was observed in approximately 12-20% of the adult erythroid, myeloid and lymphoid cells and in subregions of the adult brain. These results show that the tie-1-Cre transgenic strain can efficiently direct deletion of floxed genes in endothelial cells in vivo.

Animals↗
PubMed2001

Distinct roles for dystroglycan, beta1 integrin and perlecan in cell surface laminin organization.

Dystroglycan (DG) is a cell surface receptor for several extracellular matrix (ECM) molecules including laminins, agrin and perlecan. Recent data indicate that DG function is required for the formation of basement membranes in early development and the organization of laminin on the cell surface. Here we show that DG-mediated laminin clustering on mouse embryonic stem (ES) cells is a dynamic process in which clusters are consolidated over time into increasingly more complex structures. Utilizing various null-mutant ES cell lines, we define roles for other molecules in this process. In beta1 integrin-deficient ES cells, laminin-1 binds to the cell surface, but fails to organize into more morphologically complex structures. This result indicates that beta1 integrin function is required after DG function in the cell surface-mediated laminin assembly process. In perlecan-deficient ES cells, the formation of complex laminin-1 structures is defective, implicating perlecan in the laminin matrix assembly process. Moreover, laminin and perlecan reciprocally modulate the organization of the other on the cell surface. Taken together, the data support a model whereby DG serves as a receptor essential for the initial binding of laminin on the cell surface, whereas beta1 integrins and perlecan are required for laminin matrix assembly processes after it binds to the cell.

Animals↗
PubMed2001

The 'innate' host response protects and damages the infected urinary tract.

Symptoms of infection and tissue pathology are caused by the host response; not by the microbe per se. The same response is also critical for the defence and is needed to clear infection. It is therefore essential to understand how the host response is activated and to identify the critical effector mechanisms of the defence. We have studied these issues in the urinary tract infection (UTI) model. The symptoms of UTI and the host defence both rely on the so-called 'innate' immune system, making this one of the best characterized human disease models of 'innate immunity. We discuss the critical molecular events that determine whether the host response will be activated by P-fimbriated uropathogenic Escherichia coli as well as factors determining whether the patient develops acute pyelonephritis or asymptomatic bacteriuria. We will describe the glycoconjugate receptors used by the P-fimbriated bacteria adhering to host tissues, the recruitment of TLR4 co-receptors and the signalling pathways that allow progression to symptomatic disease, and discuss how these mechanisms are altered in asymptomatic carriers, presenting the possible genetic basis for unresponsiveness. We have shown that neutrophils are the critical effectors of the host defence and that neutrophil dysfunctions lead to acute pyelonephritis and renal scarring. Here we discuss the mechanisms of neutrophil-mediated, chemokine receptor (CXCR1)-dependent clearance, and the defect in interleukin-8 receptor homolog knock-out (IL-8Rh KO) mice and describe the data linking low CXCR1 expression to recurrent pyelonephritis in man, as well as the information on the genetic basis for low CXCR1 expression in affected patients. Finally, the mechanisms of renal scarring in IL8Rh KO mice will be discussed in relation to human disease. Our studies hold the promise to provide a molecular and genetic explanation for disease susceptibility in some patients with UTI and to offer more precise tools for the diagnosis and therapy of these infections.

Animals↗
PubMed2000

Identification of protein vaccine candidates from Helicobacter pylori using a preparative two-dimensional electrophoretic procedure and mass spectrometry.

Helicobacter pylori is an important human gastric pathogen for which the entire genome sequence is known. This microorganism displays a uniquely complex pattern of binding to complex carbohydrates presented on host mucosal surfaces and other tissues, through adhesion molecules (adhesins) on the microbial cell surface. Adhesins and other membrane-associated proteins are important targets for vaccine development. The identification and characterization of cell-surface proteins expressed by H. pylori is a prerequisite for the development of vaccines designed to interfere with bacterial colonization of host tissues. However, identification of membrane proteins is difficult using a traditional proteomics approach employing 2D-PAGE. We have used a novel approach in the identification of microbial proteins that employs a rapid preparative two-dimensional electrophoretic separation followed by mass spectrometry and database searches. No pre-enrichment of bacterial membranes was required. The entire process, from sample preparation to protein identification, can be completed in less than 18 hours, and the presence of proteins can be monitored after both the first- and second-dimensional separations using mass spectrometry. We were able to identify 40 proteins from a detergent-solubilized H. pylori preparation; over one-third of these were membrane or membrane-associated proteins. A functionally characterized low-abundance membrane protein, the Leb-binding adhesin, was found in this group. The use of this rapid 2D electrophoretic separation in proteomic studies of H. pylori is expected to speed up the identification of expressed virulence proteins and vaccine targets in this and other microbial pathogens.

Amino Acid Sequence↗
PubMed2000

Immunoglobulin-secreting cells of maternal origin can be detected in B cell-deficient mice.

It is well known that the transfer of immunoglobulins (Igs) from mother to young via milk contributes to the offspring's immune defense. The present study suggests that not only is IgG transmitted to progeny, but that functional maternal Ig-secreting cells (or B cells) can also be transferred to the neonate. We have used B cell-deficient (micro(-/-)) mice and found that a high proportion of them obtain long-lasting, partial reconstitution of their serum Ig levels if born to micro(+/-) mothers. In some of these serum IgG-positive micro(-/-) mice, Ig-secreting cells were detected in spleen and bone marrow. To ensure that cells of maternal origin were present in the progeny, micro(-/-) offspring born to micro(+/-) dams transgenic for green fluorescent protein (GFP) were used. In spleens and bone marrow from some of these micro(-/-)GFP(-/-) offspring, GFP-positive cells were detected, which demonstrated that cells of maternal origin could infiltrate the progeny. In addition, splenic Ig-secreting cells were detected in micro(-/-) mice that were born to micro(-/-) dams and transferred to a lactating micro(+/+) foster dam at birth. This indicates that maternal Ig-secreting cells can be transferred postnatally via milk.

Adoptive Transfer↗
PubMed2000

Mammalian skeletogenesis and extracellular matrix: what can we learn from knockout mice?

Formation of the vertebrate skeleton and the proper functions of bony and cartilaginous elements are determined by extracellular, cell surface and intracellular molecules. Genetic and biochemical analyses of human heritable skeletal disorders as well as the generation of knockout mice provide useful tools to identify the key players of mammalian skeletogenesis. This review summarises our recent work with transgenic animals carrying ablated genes for cartilage extracellular matrix proteins. Some of these mice exhibit a lethal phenotype associated with severe skeletal defects (type II collagen-null, perlecan-null), whereas others show mild (type IX collagen-null) or no skeletal abnormalities (matrilin-1-null, fibromodulin-null, tenascin-C-null). The appropriate human genetic disorders are discussed and contrasted with the knockout mice phenotypes.

Animals↗
PubMed1999

Perlecan maintains the integrity of cartilage and some basement membranes.

Perlecan is a heparan sulfate proteoglycan that is expressed in all basement membranes (BMs), in cartilage, and several other mesenchymal tissues during development. Perlecan binds growth factors and interacts with various extracellular matrix proteins and cell adhesion molecules. Homozygous mice with a null mutation in the perlecan gene exhibit normal formation of BMs. However, BMs deteriorate in regions with increased mechanical stress such as the contracting myocardium and the expanding brain vesicles showing that perlecan is crucial for maintaining BM integrity. As a consequence, small clefts are formed in the cardiac muscle leading to blood leakage into the pericardial cavity and an arrest of heart function. The defects in the BM separating the brain from the adjacent mesenchyme caused invasion of brain tissue into the overlaying ectoderm leading to abnormal expansion of neuroepithelium, neuronal ectopias, and exencephaly. Finally, homozygotes developed a severe defect in cartilage, a tissue that lacks BMs. The chondrodysplasia is characterized by a reduction of the fibrillar collagen network, shortened collagen fibers, and elevated expression of cartilage extracellular matrix genes, suggesting that perlecan protects cartilage extracellular matrix from degradation.

Animals↗
PubMed1999

Human choriocarcinoma-derived JEG-3 cells transfected with murine MHC class II Aq expression vectors present antigen to Aq-restricted murine T-cell hybridoma.

MHC class II molecules are not normally expressed on the cell surface of placental cells. This absence of class II molecules is assumed to be of importance for mammalian reproduction, since such expression is likely to increase the risk of harmful anti-placental immune responses. The present study was aimed to clarify whether post-transcriptional events prohibit proper cell surface expression of MHC class II molecules in cell lines of placental origin. The murine trophoblast cell line SM9-1 as well as the human choriocarcinoma-derived cell line JEG-3 were transiently co-transfected with MHC class II Aq a and b genes under the control of viral promoter systems. The transfected cells were stained for surface expression of MHC class II and assayed for antigen presentation in vitro. Only a small proportion of the transfected murine SM9-1 cells showed detectable class II cell surface expression, which made functional studies of this cell line difficult. The transfected JEG-3 cells, however, showed a high proportion of cells with distinct surface expression of murine class II Aq molecules and the antigen presentation assays revealed T cell activation upon addition of processed antigen, but not with unprocessed antigen. These results show that ectopic MHC class II gene transcription can result in cell surface expression of immunohistochemically detectable MHC class II on cells of placental origin. The fact that murine class II molecules could be expressed in a functional manner on human JEG-3 cells also strongly suggests that proper accessory gene activities are not essential for obtaining surface expression.

Animals↗
PubMed1997

Lack of detectable major histocompatibility complex class II a beta-chain messenger ribonucleic acid in placentas of interferon-gamma- and 5-azacytidine-treated mice.

Trophoblast cells do not normally express major histocompatibility complex (MHC) class II antigens during placental development in either mice or rats. We have previously observed that in vivo treatment of pregnant mice with interferon-gamma (IFN gamma) induces immunohistochemically detectable class II cell surface expression in many maternal cell types, but not on placental cells or other cells of extra-embryonic origin. Both IFN gamma- and 5-azacytidine-induced placental class II expression have been reported in mice by other scientists, however, which made it important to further clarify this issue. The present study was performed to analyze whether treatment of pregnant mice with recombinant IFN gamma or the drug 5-azacytidine in vivo can induce detectable MHC class II Ab mRNA expression. A strain of transgenic mice carrying a cytomegalovirus-regulated MHC class II Abq transgene, which was strongly expressed in the placenta, was used as a positive control in all in situ hybridizations and ribonuclease protection analyses. All mice were analyzed on gestation Days 12.5 and 17.5. Treatment of pregnant mice with IFN gamma did not induce detectable class II expression in the placental cells, whereas the maternal decidua showed expression both at the mRNA and protein level. Similarly, treatment with 5-azacytidine did not induce class II expression in the placenta, while a slight increase in mRNA expression was detected in the maternal decidual and uterine tissues. These results strengthen the opinion that MHC class II mRNA cannot normally be induced in murine placental cells after IFN gamma or 5-azacytidine treatments.

Animals↗
PubMed1996

Sympatholytic and minimum anesthetic concentration-sparing responses are preserved in rats rendered tolerant to the hypnotic and analgesic action of dexmedetomidine, a selective alpha(2)-adrenergic agonist.

BACKGROUND: The development of tolerance to the sympatholytic and anesthetic-reducing effects of alpha(2) agonists after prolonged administration of dexmedetomidine and how the number of available alpha(2) adrenoceptors affects these dexmedetomidine-induced responses was studied. METHODS: The sympatholytic action of acute and chronic (3 and 10 micrograms.kg-1.h-1 for 7 days) dexmedetomidine, was assessed by the decrease in norepinephrine turnover in the locus coeruleus and hippocampus. The anesthetic-reducing effect of chronic (7 days) dexmedetomidine (5 and 10 micrograms.kg-1.h-1) was studied by determining the minimum alveolar concentration (MAC) for halothane that prevented rats from responding to a supramaximal noxious stimulus of dexmedetomidine (10 or 30 micrograms.kg-1), doses in the steep part of the dose-response curve. The receptor reserve for the norepinephrine turnover and anesthetic-sparing responses to dexmedetomidine was delineated with 0.3-1.0 mg.kg-1 N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline, an irreversible alkylating agent. RESULTS: After chronic administration of dexmedetomidine at both doses, acute dexmedetomidine significantly decreased norepinephrine turnover in the hippocampus and locus coeruleus. The baseline minimum anesthetic concentration (MAC) and the MAC-sparing effect to acutely administered dexmedetomidine were preserved after chronic dexmedetomidine treatment. In the N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline experiments, the dexmedetomidine-induced norepinephrine turnover effect required less than 20% and greater than 4% alpha(2) adrenoceptor availability in the locus coeruleus and the dexmedetomidine induced MAC-sparing effect required less than 40% and greater than 20% alpha(2) adrenoceptor availability in the locus coeruleus. CONCLUSION: Tolerance does not develop for either the sympatholytic or MAC-sparing actions of dexmedetomidine, although it is present for the hypnotic response. The durable quality of the sympatholytic and MAC-sparing responses to dexmedetomidine after chronic treatment is explained by a comparatively larger receptor reserve than is needed for the hypnotic and analgesic responses, which are blunted by the same drug treatment regimen.

Adrenergic alpha-2 Receptor Agonists↗