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At least 397 records · Page 22Linked to original sources
PubMed2003

Thyroxine prevents reoxygenation injury in isolated proximal tubule cells.

Ischemia is characterized by cessation of blood flow and oxygen delivery to tissues that results in disruption of cellular structure and organelles. However, restoration of blood flow following ischemia causes reperfusion injury, characterized by further damage in the tissues mediated by reactive oxygen species. In the kidney, reactive oxygen molecules have been implicated in ischemic, toxic and immunological glomerular damage. Thyroxine has been shown to be cytoprotective in toxic and ischemic injury. Thyroxine's cytoprotective effect is postulated to be secondary to stimulation of intracellular ATP synthesis. However, the underlying mechanism of that beneficial effect remains to be investigated. In this study we investigated the effect of thyroxine (T4) on free oxygen radical production in an in vitro model of reperfusion injury. Free oxygen radical (FOR) levels were determined by a chemiluminescence method after freshly isolated rabbit proximal tubule cells were subjected to 15 min of anoxia followed by 45 min of reoxygenation. Reoxygenation injury resulted in a significant increase in FOR levels (P<0.0001). FOR levels were significantly lower in the group treated with thyroxine (P=0.01) and cells treated with thyroxine displayed better preservation of cellular structure. We conclude that thyroxine's cytoprotective effect might be via decreased synthesis of FOR, and thyroxine treatment may confer cytoprotection in renal conditions characterized by FOR-mediated injury.

Animals↗
PubMed1988

Diurnal Growth of Tall Fescue Leaf Blades : II. Dry Matter Partitioning and Carbohydrate Metabolism in the Elongation Zone and Adjacent Expanded Tissue.

The spatial distributions of net deposition rates of water soluble carbohydrate-free dry matter (WSC-free DM) and WSC were evaluated within and above the elongation zone of tall fescue (Festuca arundinacea Schreb.) leaf blades during light and darkness. Imported DM used for WSC-free DM synthesis during darkness (67% of the total in experiment I and 59% in experiment II) was greater than during light (47% in both experiments), suggesting that the 65% higher leaf elongation rate during darkness was accompanied by higher rates of synthesis of cellular structural components. Deposition rates of WSC in the basal and central part of the elongation zone (0-20 mm from the ligule) were similar during light and darkness, but above 20 millimeters WSC deposition occurred during light and WSC loss occurred during darkness. WSC deposition and loss throughout the elongation zone and the recently expanded tissue were mostly due to net synthesis and degradation of fructan. Fructan was predominantly low molecular weight and contributed about 50% of the total osmotic partial pressure of WSC. In the most actively growing region, where fructan synthesis was most rapid, no diurnal change occurred in molecular weight distribution of fructan. WSC solute concentrations were diluted in the most actively growing tissue during darkness because net monosaccharide and fructan deposition were unaltered and sucrose deposition was decreased, but growth-associated water deposition was increased by 77%. Net rates of fructan synthesis and degradation were not related to tissue sucrose concentration, but appeared to respond to the balance between assimilate import and assimilate use in synthesis of cellular structural components (i.e. WSC-free DM) and deposition of monosaccharides. Fructan synthesized in tissue during most active elongation was degraded when the respective tissue reached the distal limit of the elongation zone where assimilate import in darkness was insufficient to maintain synthetic processes associated with further differentiation of cells.

Journal Article↗
PubMed2003

Influence of intraluminal thrombus on structural and cellular composition of abdominal aortic aneurysm wall.

INTRODUCTION: It has been suggested that the intraluminal thrombus of abdominal aortic aneurysm (AAA) affects the underlying vessel wall. Aneurysm enlargement has been associated with growth of thrombus, and rupture has been proposed to occur after bleeding into the thrombus. To examine how thrombus affects the vessel wall, we compared the morphology of aneurysm wall covered with thrombus with wall segments exposed to flowing blood. Material and methods Sixteen patients (14 men, 2 women; age range, 56-79 years) undergoing elective repair of AAA, where computed tomography scans showed thrombus and segments of the aneurysm wall exposed to flowing blood, were included in the study. Specimens from the aneurysm were taken for light and electron microscopy. Masson trichrome staining was performed for wall thickness determination and demonstration of collagen, and Weigert-van Gieson staining for elastin. The cellular composition was analyzed by immunohistochemistry with antibodies against CD3 for T cells, CD4 for T helper cells, CD8 for T cytotoxic cells, CD20 for B cells, CD68 for macrophages, and smooth muscle alpha-actin for smooth muscle cells (SMCs). Caspase-3 staining and TUNEL analysis were performed to evaluate apoptosis. RESULTS: The aneurysm wall covered with thrombus was thinner and contained fewer elastin fibers, and the few that were found were often fragmented. This part of the wall also contained fewer SMCs and more apoptotic nuclei than the wall exposed to flowing blood. Clusters of inflammatory cells were detected in the media of the aneurysm wall and in higher numbers in the parts covered with thrombus. Electron microscopy showed that the aneurysm wall without thrombus contained a dense collagenous matrix with differentiated SMCs. In the segment covered with thrombus, SMCs were more dedifferentiated (synthetic) and apoptotic or necrotic. There were also an increased number of inflammatory cells located in close contact with SMCs in various stages of apoptosis. CONCLUSION: The aneurysm wall covered with thrombus is thinner and shows more frequent signs of inflammation, apoptosis of SMCs, and degraded extracellular matrix. These findings suggest that thrombus formation and accumulation of inflammatory cells may perturb the structural integrity and stability of the vessel wall and thereby increase the risk for aneurysm rupture.

Aged↗
PubMed2005

MS-KIF18A, new kinesin; structure and cellular expression.

The present study describes the cloning and molecular analysis of a new gene, MS-KIF18A, a member of the kinesin family. MS-KIF18A was cloned from a marrow stromal cells expression library. Transcripts derived from this gene were also detected in testis and trachea, although they differed from the stroma mesenchymal cell transcript in the open reading frame (ORF) as well as in the untranslated regions (UTRs). The existence of various transcripts suggests alternative regulation of gene expression and defines tissue specific function of the new kinesin. The cDNA from the marrow stroma, MS-KIF18A, encodes a predicted protein of 898 amino acids with a molecular weight of 100 kDa. Kinesins are motor proteins that consist of a motor domain with microtubule-binding and ATPase sites, a coiled coil region and a cargo-binding domain. Examination of a three-dimensional model of the MS-KIF18A motor domain suggested that this protein associates with microtubules, which was confirmed by immunofluorescence (IF) experiments in stromal cells.

Amino Acid Sequence↗
PubMed1993

Recognition of non-B DNA structures by cellular proteins.

By utilising a gel retardation assay, cytoplasmic extracts of Hela cells have been shown to contain a number of polypeptides which bind preferentially to non-B forms of DNA. These polypeptides vary in apparent molecular weights and are present as minor components of the total extract. Similar properties were demonstrated by purified preparations of eukaryotic topoisomerase I and by a DNA binding subunit of the transcription factor NFkB. These results suggest that non-B DNA binding proteins may represent families of proteins which recognise more open forms of DNA as a cognate parameter to their cellular functions.

Chromatography, Affinity↗
PubMed1995

Tetrameric structure and cellular location of catechol 2,3-dioxygenase.

Catechol 2,3-dioxygenase from the meta-cleavage pathway encoded on the TOL plasmid of Pseudomonas putida (pWWO) was investigated by electron microscopy. Negatively stained samples of the purified catechol 2,3-dioxygenase revealed that the enzyme consists of four subunits arranged in a tetrahedral conformation. Monoclonal antibodies raised against catechol 2,3-dioxygenase showed highly specific reactions and were used to localize the enzyme in Escherichia coli (pAW31) and P. putida (pWWO), using the protein A-gold technique carried out as a post-embedding immunoelectron microscopy procedure. Our in situ labeling studies revealed a cytoplasmic location of the catechol 2,3-dioxygenase in both cell types.

Antibodies, Monoclonal↗
PubMed1989

Duodenal adenomas in familial adenomatous polyposis: their structure and cellular composition with particular reference to endocrine hyperplasia.

134 duodenal biopsies from 14 patients with familial adenomatous polyposis were evaluated by light microscopy for the presence of adenoma. Staining reactions for endocrine cells were applied. 90 biopsies contained adenoma, almost all of the tubular type (98%) with dysplasia, ranging from mild to moderate. Accompanying hyperplasia of argyrophil and argentaffin endocrine cells was found in 91% and 64% of the adenomas, respectively. Based on histological criteria it is concluded that the risk of carcinoma development in the duodenum could equal that in colon and rectum. The observation of endocrine hyperplasia is new, and further investigations are needed before the significance of this finding can be evaluated.

Adenoma↗
PubMed1984

The relationship between localization of Na+, K+-ATPase and cellular fine structure in the rat parotid gland.

A method for the ultrastructural localization of the Na+-pump enzyme, Na+, K+-ATPase has been applied to the rat parotid gland. A ouabain-sensitive final reaction product, dependent on the presence of K+ and Mg2+, was found to be evenly distributed along the basal and basolateral plasma membranes of acinar and striated duct cells. In both cases, it was localized predominantly in the cytoplasm of the extensive foldings of these membranes. It is concluded that the reaction product meets the criteria for valid localization of this enzyme and that potential Na+-pump sites have been demonstrated. This study supports previous findings in salivary glands and contributes to an increasing body of evidence that contraluminal Na+-pumps are common to both reabsorbing and secreting epithelial cells.

Animals↗
PubMed1977

Further observations on the fine structure of cellular cementum from deciduous teeth of pigs.

Examination of microradiographs from the deciduous teeth of pigs revealed large lacunae or radiolucent zones close to the cemento-dentinal junction. Electron microscopic studies of the ground sections showed areas of irregularly shaped zones devoid of mineral and filled with collagen fibers. In the wide unmineralized zones, spherical clusters of crystallites were noted. Several cementum lacunae bordered by a broad rim of unmineralized collagen fibers were noted and some lacunae also contained zones of a moderately electron dense material. This material did not yield a diffraction pattern, while the mineralized part of the cementum gave the diffraction pattern typical of hydroxyapatite.

Animals↗
PubMed1986

Cryptosporidium: cellular localization, structural analysis of absorptive cell-parasite membrane-membrane interactions in guinea pigs, and suggestion of protozoan transport by M cells.

In ilea of spontaneously infested guinea pigs, we examined the interface between the plasma membranes of cryptosporidia and absorptive cells using thin section and freeze fracture techniques. Initially, cryptosporidia invaginate microvilli, and the resulting redundant folds of membrane envelop the protozoan, thereby internalizing it in a membrane sac of host cell origin. Subsequently, a pentalaminar membrane fusion site develops at the base of the protozoan between the parasite's outer plasma membrane and the internalized host membrane. The membrane domains isolated by this fusion site are then modified: the host membrane disintegrates, and the isolated parasite membrane, which now directly contacts absorptive cell cytoplasm, becomes amplified. While cryptosporidia are restricted to the apex of absorptive cells, they may be found deep within the cytoplasm of M cells overlying Peyer's patches. Moreover, both intact and partially digested cryptosporidial organisms associate with macrophages subjacent to such M cells. These findings define the intracellular localization of cryptosporidia and suggest that cryptosporidial antigens may be sampled by intestinal lymphoid cells at sites underlying M cells.

Animals↗