Biomedical subjects

E Hallberg

Publications and source records attributed to E Hallberg.

At least 37 records · Page 2Linked to original sources

PubMed1998

The influence of intestinal ischemia and reperfusion on bidirectional intestinal barrier permeability, cellular membrane integrity, proteinase inhibitors, and cell death in rats.

Intestinal ischemia and reperfusion injury (I/R) is probably involved in the pathogenesis of intestinal barrier dysfunction, associated with the concomitant translocation of enteric bacteria and toxins and the potential development of multiple organ failure. The intestinal endothelial and epithelial layers play a major role preventing the entry of toxic substances from the gut, but the influence of protease-antiprotease systemic balance on these barrier functions and the relationship between epithelial DNA synthesis, apoptosis, and endothelial and epithelial barrier macromolecule permeability are not fully investigated. Endothelial and epithelial barrier macromolecular permeability, epithelial DNA synthesis, the endothelial and epithelial plasma membrane system, apoptosis and oncosis, plasma levels of proteinase inhibitors, and proenzymes were measured in rats subjected to 20 and 40 min intestinal ischemia and 1, 3, 6, or 12 h reperfusion. Endothelial permeability increased after both 20 and 40 min intestinal ischemia. Epithelial permeability significantly increased during 1-6 h reperfusion after 20 min ischemia and during 1-12 h reperfusion after 40 min ischemia. Epithelial DNA synthesis increased in animals with 20 min ischemia followed by 12 h reperfusion. Plasma levels of prekallikrein, C1-esterase inhibitor, and alpha1-macroglobulin were significantly lower following both 20 and 40 min ischemia from 3 h reperfusion and on. Apoptotic epithelial cells significantly increased in animals subjected to 20 min ischemia followed by 12 h reperfusion. The severity of reperfusion injury in the intestinal endothelial and epithelial barrier seems to correlate with the period of ischemia and the pathway of cell damage and death, together with proteinase-antiproteinase imbalance.

Albumins↗

PubMed1997

Intracellular distribution of an integral nuclear pore membrane protein fused to green fluorescent protein--localization of a targeting domain.

The 121-kDa pore membrane protein (POM121) is a bitopic integral membrane protein specifically located in the pore membrane domain of the nuclear envelope with its short N-terminal tail exposed on the luminal side and its major C-terminal portion adjoining the nuclear pore complex. In order to locate a signal for targeting of POM121 to the nuclear pores, we overexpressed selected regions of POM121 alone or fused to the green fluorescent protein (GFP) in transiently transfected COS-1 cells or in a stably transfected neuroblastoma cell line. Microscopic analysis of the GFP fluorescence or immunostaining was used to determine the intracellular distribution of the overexpressed proteins. The endofluorescent GFP tag had no effect on the distribution of POM121, since the chimerical POM121-GFP fusion protein was correctly targeted to the nuclear pores of both COS-1 cells and neuroblastoma cells. Based on the differentiated intracellular sorting of the POM121 variants, we conclude that the first 128 amino acids of POM121 contains signals for targeting to the continuous endoplasmic reticulum/nuclear envelope membrane system but not specifically to the nuclear pores and that a specific nuclear pore targeting signal is located between amino acids 129 and 618 in the endoplasmically exposed portion of POM121.

Animals↗

PubMed1997

Molecular genetic analysis of Rts1p, a B' regulatory subunit of Saccharomyces cerevisiae protein phosphatase 2A.

The Saccharomyces cerevisiae gene RTS1 encodes a protein homologous to a variable B-type regulatory subunit of the mammalian heterotrimeric serine/threonine protein phosphatase 2A (PP2A). We present evidence showing that Rts1p assembles into similar heterotrimeric complexes in yeast. Strains in which RTS1 has been disrupted are temperature sensitive (ts) for growth, are hypersensitive to ethanol, are unable to grow with glycerol as their only carbon source, and accumulate at nonpermissive temperatures predominantly as large-budded cells with a 2N DNA content and a nondivided nucleus. This cell cycle arrest can be overcome and partial suppression of the ts phenotype of rts1-null cells occurs if the gene CLB2, encoding a Cdc28 kinase-associated B-type cyclin, is expressed on a high-copy-number plasmid. However, CLB2 overexpression has no suppressive effects on other aspects of the rts1-null phenotype. Expression of truncated forms of Rts1p can also partially suppress the ts phenotype and can fully suppress the inability of cells to grow on glycerol and the hypersensitivity of cells to ethanol. By contrast, the truncated forms do not suppress the accumulation of large-budded cells at high temperatures. Coexpression of truncated Rts1p and high levels of Clb2p fully suppresses the ts phenotype, indicating that the inhibition of growth of rts1-null cells at high temperatures is due to both stress-related and cell cycle-related defects. Genetic analyses show that the role played by Rts1p in PP2A regulation is distinctly different from that played by the other known variable B regulatory subunit, Cdc55p, a protein recently implicated in checkpoint control regulation.

Basic Helix-Loop-Helix Proteins↗

PubMed1997

Influence of heparin coating on in vitro bacterial adherence to poly(vinyl chloride) segments.

End-point attached, covalently bound heparin has been shown to be effective in preventing activation of the coagulation cascade by biomaterials. Data concerning its possible influence on bacterial attachment and resistance to biomaterial-associated infection are, so far, lacking. In the present work, the in vitro adherence of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli, one isolate of each species, to plain poly(vinyl chloride) (plain PVC) and heparin coated poly(vinyl chloride) (EPA-PVC) segments was compared. Also, the influence of precoating the segments with human normal plasma for 2 h was studied. 35S-Methionine was used to radiolabel bacteria. The segments were exposed to bacterial suspensions of approximately 10(7) colony forming units (CFU) per milliliter at 37 degrees C for 0.5-6 h. Following repeated washing in phosphate buffered saline (PBS), radioactivity associated with the segments was measured. Plain PVC as compared to EPA-PVC bound significantly more cells of all three tested species. Plasma precoating significantly decreased adherence of the tested species to plain PVC but did not affect the binding to EPA-PVC. However, after precoating with human plasma, EPA-PVC compared to plain PVC showed a higher binding of S. aureus which might possibly be due to bridging effects of fibronectin or other plasma proteins, interacting with S. aureus.

Bacterial Adhesion↗

PubMed1997

The influence of circulatory and gut luminal challenges on bidirectional intestinal barrier permeability in rats.

BACKGROUND: The endothelial and epithelial barriers are important for maintenance of intestinal barrier function. The present study evaluated the response of these barriers after various challenges. METHODS: Mucosal endothelial and epithelial barrier integrity was evaluated by the leakage of human serum albumin, labeled with different isotopes, from the circulation to the interstitium and the intestinal lumen, or from the intestinal lumen to the interstitium and the circulation, in rats with endothelial or epithelial challenge. RESULTS: Epithelial barrier dysfunction and alterations in epithelial microvillous ultrastructure showed a pattern dependent on the dose of the intraluminal detergents, whereas only higher doses induced an increase in endothelial barrier permeability. Intravenous challenge with CHAPS or Triton caused a dose-dependent increase in both endothelial and epithelial barrier permeability. The development of endothelial barrier dysfunction was related to a decrease in blood pH values. CONCLUSIONS: The results indicate that capillary endothelial barrier integrity may play an important role in maintaining intestinal barrier function and that endothelial injury may initiate or at least be involved in the development of intestinal barrier failure.

Acetic Acid↗

PubMed1996

Formation of nuclear bodies in cells overexpressing the nuclear pore protein POM121.

POM121 is an integral membrane protein specifically localized in the pore membrane domain of the nuclear envelope. We have investigated the intracellular distribution of rat POM121 heterologously overexpressed in monkey COS cells by immunofluorescence and fluorescence digital imaging microscopy. At low levels of expression overexpressed POM121 was distributed in the nuclear envelope in a punctate fashion, partially overlapping with the distribution of nuclear pores. At high levels of expression, however, the overexpressed protein accumulated in intranuclear bodies. These bodies represent a novel subnuclear structure, displaying a defined cylindrical structure and a distinct localization at or adjacent to the inner nuclear membrane. The C-terminal portion of POM121, which contains a pentapeptide repeat domain common to a subfamily of related nucleoporins, was sufficient to mediate targeting to the nuclear envelope as well as formation of intranuclear bodies.

Animals↗

PubMed1996

A bacteriologic and scanning electron microscope study after implantation of foreign bodies in the biliary tract in rats.

BACKGROUND: Bacterial adherence to the stent surfaces, concomitant colonization, and possible stent blockage are the main complications after the use of biliary stents. The present study was assigned to investigate bacteriologic and morphologic changes in the biliary tract after the implantation of biliary drain materials. METHODS: Rubber and silicone pieces with a surface area of 1 cm2 were implanted into the biliary tract in rats after temporary obstruction of the common bile duct by the use of a mini-occluder. The animals were killed at 4, 8 and 14 weeks, respectively, after implantation, and the implants were retrieved, cultured, and examined by scanning electron microscopy (SEM). Bacterial culture and SEM were also performed on tissue samples obtained from the mucosal surface of the biliary tract. RESULTS: Bacterial colonization and biofilm formation were found on the surfaces of the implanted materials and on the mucosal surface of the biliary tract in animals with implants but not on the biliary tract mucosa in rats without implants. CONCLUSION: Foreign bodies implanted in the biliary tract facilitate bacterial adherence not only to the surface of the implants but also to the mucosal surface in the biliary tract.

Animals↗

PubMed1994

Endothelialization of anastomoses in the aorta and inferior vena cava of the rat.

Denuding endothelial damage at anastomoses may lead to thrombotic complications and failure of microvascular reconstructions. Confluent endothelial healing at anastomoses may reduce thrombotic and other complications. The progress of endothelial coverage of anastomotic structures in the aorta and inferior vena cava (IVC) of the rat was evaluated at 3, 5, 8, 11, and 14 days after completion of the anastomoses, by means of scanning electron microscopy. Arterial anastomotic patency was 100%; venous patency was 84%. It was found that endothelial healing progressed towards thin confluent coverage first, thereafter thickening. Coverage was first achieved at the needle defect, then the anastomotic junction, and lastly the suture. The same stage of endothelial coverage of anastomotic structures was reached 5 to 8 days sooner at the IVC anastomosis than in the aorta.

Anastomosis, Surgical↗

PubMed1994

Reduced susceptibility of polytetrafluoroethylene vascular prostheses to colonization by Staphylococcus aureus following in situ endothelialization.

The impact of endothelialization of polytetrafluoroethylene (PTFE) grafts on susceptibility to experimental colonization by Staphylococcus aureus was studied in a rat model. One hundred and eight grafts (2 mm inner diameter, 5 mm length) were implanted into the infrarenal aorta (54 rats) or the infrarenal caval vein (54 rats). The progress of endothelialization following graft implantation was evaluated by SEM at 1, 3, 7, and 14 days on 6 grafts from each group. We found that the endothelialization was more rapid in caval vein than in aorta: The caval vein grafts were completely endothelialized 2 weeks following implantation compared with endothelialization of approximately 0.5 mm of aorta grafts, measured from each anastomosis. During this time, the resistance to standardized intravenous challenge with 10(8) colony-forming units of S. aureus increased gradually in both groups, and all caval vein grafts tested at 2 weeks were sterile. However, all aorta grafts challenged at 2 weeks were colonized, although to a somewhat lower degree than at earlier challenge. Resistance of PTFE grafts to colonization with S. aureus thus correlated to the degree of endothelialization.

Animals↗

PubMed1994

The large C-terminal region of the integral pore membrane protein, POM121, is facing the nuclear pore complex.

POM121 is an integral membrane protein that has been specifically localized to the "pore membrane" domain of the nuclear envelope. Based on its cDNA-deduced primary structure it was suggested that POM121 contains one or two transmembrane segments and that its major C-terminal portion faces the pore side rather than the cisternal side of the pore membrane. We have investigated the membrane topology of POM121 by studying the accessibility of a C-terminal and an N-terminal epitope of POM121 for epitope-specific antibodies. The accessibility of POM121 in unfixed, semi-intact or permeabilized tissue culture cells was analyzed by indirect immunofluorescence. We found that the C-terminal epitope was accessible for antibodies in both semi-intact and permeabilized cells, whereas the N-terminal epitope was only accessible in the permeabilized cells. The results show that the large C-terminal region of POM121, containing more than 90% of its total mass, is exposed on the pore side of the nuclear membrane and suggest that the N-terminal portion is most likely localized in the perinuclear space. The data also show that at least part of the C-terminal epitopes are localized on the cytoplasmic side of the nuclear envelope. The topology suggests that the C-terminal portion of POM121, which contains a nucleoporin-like domain, interacts with the nuclear pore complex and thus, may play a role in biogenesis of the nuclear envelope and the nuclear pore complex.

Amino Acid Sequence↗

PubMed1993

Acute thrombogenicity and 4 weeks healing properties of a new stretch-ePTFE graft.

Recently a new expanded polytetrafluoroethylene (ePTFE) graft with length compliant characteristics has been developed. The present study compared the acute thrombogenicity and 4 weeks healing characteristics of the stretch ePTFE graft to standard ePTFE grafts in vivo. Grafts of 6 cm length and 8 mm internal diameter were inserted end-to-side into the iliac arteries in pigs. Platelet adhesion was assessed by infusing indium-111-oxine (20 MBq) labelled autologous platelets and dynamically imaging the grafts. Explanted grafts (n = 14) were opened longitudinally and the thrombus-free surface (TFS) and segmental accumulation of platelets were determined. Stretch ePTFE grafts had significantly less platelet deposition when compared to standard ePTFE graft (p < 0.01). The dynamic increase of activity from 10 min after start of measurement was also significantly reduced (p < 0.05) for 170 min as compared to standard ePTFE grafts. TFS was 68 +/- 5% for stretch ePTFE and 37 +/- 5% for standard ePTFE grafts (p < 0.01). After explanation and fixation the grafts were investigated by light microscopy, scanning and transmission electron microscopy. At 1 week after surgery, both kind of grafts were covered by a fibrinous layer containing platelets and leukocytes. After 2 weeks a pseudoendothelial layer was found in the perianastomotic regions. After 4 weeks, two out of four standard ePTFE grafts were occluded due to intimal hyperplasia and subsequent thrombosis in the midportion of the grafts. All stretch ePTFE grafts were patent and covered by a smooth pseudointima. This study thus demonstrates a lower acute thrombogenicity in stretch ePTFE grafts compared to the standard graphs.

Anastomosis, Surgical↗

PubMed1993

An integral membrane protein of the pore membrane domain of the nuclear envelope contains a nucleoporin-like region.

We have identified an integral membrane protein of 145 kD (estimated by SDS-PAGE) of rat liver nuclear envelopes that binds to WGA. We obtained peptide sequence from purified p145 and cloned and sequenced several cDNA clones and one genomic clone. The relative molecular mass of p145 calculated from its complete, cDNA deduced primary structure is 120.7 kD. Antibodies raised against a synthetic peptide represented in p145 reacted monospecifically with p145. In indirect immunofluorescence these antibodies gave punctate staining of the nuclear envelope. Immunogold EM showed specific decoration of the nuclear pores. Thus p145 is an integral membrane protein located specifically in the "pore membrane" domain of the nuclear envelope. To indicate this specific location, and based on its calculated relative molecular mass, the protein is termed POM 121 (pore membrane protein of 121 kD). The 1,199-residue-long primary structure shows a hydrophobic region (residues 29-72) that is likely to form one (or two adjacent) transmembrane segment(s). The bulk of the protein (residues 73-1199) is predicted to be exposed not on the cisternal side but on the pore side of the pore membrane. It contains 36 consensus sites for various kinases. However, its most striking feature is a repetitive pentapeptide motif XFXFG that has also been shown to occur in several nucleoporins. This nucleoporin-like domain of POM 121 is proposed to function in anchoring components of the nuclear pore complex to the pore membrane.

Amino Acid Sequence↗

PubMed1993

Surface structure of the temporomandibular joint in normal and steroid-treated rats: a scanning electron microscopic study.

The aim was to study the ultrastructure of the surface of the temporomandibular joint (TMJ) in mature rats. The TMJs from control rats and rats given corticosteroids for 10 days or 38 days were examined. In three joints from the control rats the disk was detached from the condyle before preparation and analysis. Scanning electron microscopy was performed on the condyle, the disk, and the temporal component. Generally, the surface of the three components was predominantly smooth, although the condyle exhibited a more even surface than the disk and the temporal component. In the fossa a pitted or ridged appearance was observed in some areas. There was a striking difference between the surface structure of disks attached to, and that of disks detached from, the condyle during preparation. A prominent undulation of surface was evident in disks detached from the condyle. Below the surface layer of the articular cartilage, a network of collagen fibers and fibrils running in all directions could be observed in all three components. In limited areas there was fibrillation and shallow defects of the surface layer. These changes were seen in all rats given corticosteroids for 38 days but also in some rats given corticosteroids for 10 days and in a few control rats.

Animals↗

PubMed1992

The aesthetasc concept: structural variations of putative olfactory receptor cell complexes in Crustacea.

The structure of the aesthetascs has been investigated in the prawn Macrobrachium rosenbergii (larvae and juveniles), the opossum shrimp Neomysis integer, the euphausid Meganyctiphanes, and in the water-fleas Daphnia magna and D. longispina. The aesthetascs, that are thought to represent olfactory receptors, exhibit a considerable structural variation, ranging from the well known aesthetascs of higher crustaceans (lobster, crab, crayfish) to the corresponding sensilla found in the water-fleas and the males of opossum shrimps. The two following morphological characteristics of the aesthetascs are thought to indicate an olfactory function: the shape of the cuticular hair that is long and essentially hose-shaped, and the thin, loosely arranged cuticle of at least the outer part of the cuticular hair. The presence of other structural elements such as sensory cells, cilia, and enveloping cells are vital for the olfactory function, but the development is variable, which makes their use in the morphological definition of aesthetascs problematic.

Animals↗

PubMed1992

Functional specialization of olfactory glomeruli in a moth.

The specific function of the glomerular structures present in the antennal lobes or olfactory bulbs of organisms ranging from insects to humans has been obscure because of limitations in neuronal marking methods. By tracing individual neurons in the moth Agrotis segetum, it was determined that physiologically distinct types of pheromone receptor neurons project axons to different regions of the macroglomerular complex (MGC). Each glomerulus making up the MGC has a specific functional identity, initially processing information about one specific pheromone component. This indicates that, at least through the first stage of synapses, olfactory information moves through labeled lines.

Animals↗

PubMed1992

Postembryonic development of leucokinin I-immunoreactive neurons innervating a neurohemal organ in the turnip moth Agrotis segetum.

In the abdominal ganglia of the turnip moth Agrotis segetum, an antibody against the cockroach neuropeptide leucokinin I recognizes neurons with varicose fibers and terminals innervating the perisympathetic neurohemal organs. In the larva, the abdominal perisympathetic organs consist of a segmental series of discrete neurohemal swellings on the dorsal unpaired nerve and the transverse nerves originating at its bifurcation. These neurohemal structures are innervated by varicose terminals of leucokinin I-immunoreactive (LKIR) fibers originating from neuronal cell bodies located in the preceding segment. In the adult, the abdominal segmental neurohemal units are more or less fused into a plexus that extends over almost the whole abdominal nerve cord. The adult plexus consists of peripheral nerve branches and superficial nerve fibers beneath the basal lamina of the neural sheath of the nerve cord. During metamorphosis, the LKIR fibers closely follow the restructuration of the perisympathetic organs. In both larvae and adults the LKIR fibers in the neurohemal structures originate from the same cell bodies, which are distributed as ventrolateral bilateral pairs in all abdominal ganglia. The transformation of the series of separated and relatively simple larval neurohemal organs into the larger, continuous and more complex adult neurohemal areas occurs during the first of the two weeks of pupal life. The efferent abdominal LKIR neurons of the moth Agrotis segetum thus belong to the class of larval neurons which persist into adult life with substantial peripheral reorganization occurring during metamorphosis.

Animals↗

PubMed1992

Regenerative response to membranous and enchondral lyophilized allogeneic bone in rabbit skull defects.

The regenerative responses of inlays of lyophilized allogeneic bone of membranous (skull) and enchondral (tibia) origin were studied in an experimental cranioplasty model in rabbits. The lyophilized bone particles were also bioassayed for inductive bone production in an orthotopic critical size defect rat model. Three trephined calvarial defects were evaluated in each of 14 adult rabbits. The experimental materials were implanted into two of the defects and the third was left empty for control purposes. The implants disclosed no major structural divergences as assessed by scanning electron microscopy. Healing was evaluated by light microscopy and contact radiography after periods of four and 15 weeks. The lyophilized bone allografts of both embryonic origins displayed a similar fashion of bone regeneration, bone marrow reappearance, and volumetric density of trabecular bone substance and displayed no obvious differences between experimental groups or intervals. The two materials exhibited low osteoinductive potential.

Animals↗

PubMed1992

The effect of antimicrobial impregnation on vascular graft healing. An experimental porcine study.

This study evaluates the impregnation of a phenol derivative (Y105) to polymerized Dacron grafts. Y-105 has broad spectrum anti-microbial characteristics. The grafts were inserted end to side in the iliac artery of pigs. Reexploration and graft removal was performed after 7, 14 and 30 days. After pressure fixation with glutaraldehyde the grafts were evaluated for gross morphology and by scanning electron microscopy. A gradual development of pseudo-intima was observed without sign of graft occlusion. The addition of the antimicrobial impregnation did not interfere with healing.

Animals↗