PubMed Health⌕ Search

Biomedical subjects

C Sarraf

Publications and source records attributed to C Sarraf.

At least 19 recordsLinked to original sources
PubMed2000

Branched chain amino acids induce apoptosis in neural cells without mitochondrial membrane depolarization or cytochrome c release: implications for neurological impairment associated with maple syrup urine disease.

Maple syrup urine disease (MSUD) is an inborn error of metabolism caused by a deficiency in branched chain alpha-keto acid dehydrogenase that can result in neurodegenerative sequelae in human infants. In the present study, increased concentrations of MSUD metabolites, in particular alpha-keto isocaproic acid, specifically induced apoptosis in glial and neuronal cells in culture. Apoptosis was associated with a reduction in cell respiration but without impairment of respiratory chain function, without early changes in mitochondrial membrane potential and without cytochrome c release into the cytosol. Significantly, alpha-keto isocaproic acid also triggered neuronal apoptosis in vivo after intracerebral injection into the developing rat brain. These findings suggest that MSUD neurodegeneration may result, at least in part, from an accumulation of branched chain amino acids and their alpha-keto acid derivatives that trigger apoptosis through a cytochrome c-independent pathway.

Amino Acids, Branched-Chain↗
PubMed1999

Targeting an adenoviral gene vector to cytokine-activated vascular endothelium via E-selectin.

We have aimed at selective gene delivery to vascular endothelial cells (EC) at sites of inflammation, by targeting E-selectin, a surface adhesion molecule that is only expressed by activated EC. An anti-E-selectin mAb, 1.2B6, was complexed with the adenovirus vector AdZ.FLAG (expressing the FLAG peptide) by conjugating it to an anti-FLAG mAb. Gene transduction of cultured EC was increased 20-fold compared with AdZ.FLAG complexed with a control bsAb providing EC were activated by cytokines. The anti-E-selectin-complexed vector transduced 29 +/- 9% of intimal EC in segments of pig aorta cultured with cytokines ex vivo, compared with less than 0.1% transduced with the control construct (P < 0.05). This strategy could be developed to target endothelium in inflammation with genes capable of modifying the inflammatory response.

Adenoviridae↗
PubMed1998

Wound healing in the liver with particular reference to stem cells.

The efficiency of liver regeneration in response to the loss of hepatocytes is widely acknowledged, and this is usually accomplished by the triggering of normally proliferatively quiescent hepatocytes into the cell cycle. However, when regeneration is defective, tortuous ductular structures, initially continuous with the biliary tree, proliferate and migrate into the surrounding hepatocyte parenchyma. In humans, these biliary cells have variously been referred to as ductular structures, neoductules and neocholangioles, and have been observed in many forms of chronic liver disease, including cancer. In experimental animals, similar ductal cells are usually called oval cells, and their association with impaired regeneration has led to the conclusion that they are the progeny of facultative stem cells. Oval cells are of considerable biological interest as they may represent a target population for hepatic carcinogens, and they may also be useful vehicles for ex vivo gene therapy for the correction of inborn errors of metabolism. This review proposes that the liver harbours stem cells that are located in the biliary epithelium, that oval cells are the progeny of these stem cells, and that these cells can undergo massive expansion in their numbers before differentiating into hepatocytes. This is a conditional process that only occurs when the regenerative capacity of hepatocytes is overwhelmed, and thus, unlike the intestinal epithelium, the liver is not behaving as a classical, continually renewing, stem cell-fed lineage. We focus on the biliary network, not merely as a conduit for bile, but also as a cell compartment with the ability to proliferate under appropriate conditions and give rise to fully differentiated hepatocytes and other cell types.

Animals↗
PubMed1998

Relation of impaired energy metabolism to apoptosis and necrosis following transient cerebral hypoxia-ischaemia.

This study investigated whether both mild and severe hypoxia-ischaemia (HI) caused significant numbers of cells to die by apoptosis in the developing brain in vivo. Newborn piglets were subjected to transient global HI and the fraction of all cells in the cingulate gyrus that were apoptotic or necrotic counted 48 h after resuscitation. The mean (S.D.) proportion of apoptotic cells was 11.9% (6.7%) (sham operated controls 4.1% (2.7%)), while 11.4% (8.4%) were necrotic (controls 0.7% (1.3%)) (P<0.05). Apoptotic and necrotic cell counts were both linearly related to the severity of impaired cerebral energy metabolism measured by magnetic resonance spectroscopy (P<0.05), as shown by: (1) the decline in the ratio of nucleotide triphosphates to the exchangeable phosphate pool during HI; (2) the fall in the ratio of phosphocreatine to inorganic phosphate 8 - 48 h after HI; and (3) an increased ratio of lactate to total creatine at both these times. Thus both apoptosis and necrosis occurred in the cingulate gyrus after both severe and mild HI in vivo in proportion to the severity of the insult.

Animals↗
PubMed1997

Wholesale hepatocytic differentiation in the rat from ductular oval cells, the progeny of biliary stem cells.

BACKGROUND/AIMS: Biliary epithelial cells (ductular oval cells) migrate into the periportal and midzonal parenchyma when hepatocyte regeneration after injury is significantly impeded. The potential of oval cells to differentiate into hepatocytes has been questioned. We have sought to resolve this issue using the modified Solt-Farber procedure in which 2-acetylaminofluorene is used to block hepatocyte regeneration in partially hepatectomized rats. METHODS: Rats received 2-acetylaminofluorene by oral gavage for 6 days before and up to 7 days after a two-thirds hepatectomy. The cellular reaction was visualized by the immunohistochemical localization of intermediate filaments cytokeratins 8 and 19 and vimentin, cytochrome P450 enzymatic proteins and alpha-foetoprotein. Expression of albumin and alpha-foetoprotein mRNA transcripts were observed in situ using antisense riboprobes. RESULTS: During the first 9 days after partial hepatectomy long strings of ductular cells spread outwards from the portal areas. These cells exhibited strong diffuse cytoplasmic staining with the anticytokeratin 8 and 19 antibodies, like authentic bile ducts, but in addition also expressed vimentin and alpha-foetoprotein (protein and mRNA)-collectively termed the "oval cell phenotype". Thereafter, these ducts rapidly vanished to be replaced by basophilic hepatocytes which lacked the oval cell phenotype, but which acquired strong expression of albumin mRNA. At 14 days after partial hepatectomy the oval cell phenotype was restricted to the peripheral margins of the newborn periportal hepatocytes, the distal tips of the oval cell ducts, and these too had disappeared within another 7 days. CONCLUSIONS: Ductular oval cells will differentiate into hepatocytes under appropriate experimental conditions.

Albumins↗
PubMed1997

Differential induction of apoptosis in Swiss 3T3 cells by nitric oxide and the nitrosonium cation.

We have investigated the effect of nitric oxide (NO) on apoptosis in Swiss 3T3 fibroblasts and compared it to the effect of the nitrosonium cation (NO+). Both species induced apoptosis, confirmed by electron microscopy, propidium iodide staining, DNA laddering and activation of caspases. The kinetics of triggering apoptosis were different for the two redox species: NO+ required only a 2 hour exposure, whereas NO required 24 hours. Three sources of NO were used: aqueous solutions of NO and two NO donors, S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine. The time course of apoptosis induced by these two S-nitrosothiols correlated with their rate of decomposition to NO. The apoptotic effect of NO was reduced in the presence of the NO scavenger oxyhaemoglobin, or the antioxidants N-acetylcysteine and ascorbic acid, whereas in the case of NO+ these antioxidants potentiated apoptosis. Glutathione also had a potentiating effect on the cytotoxicity of NO+. This suggests that cellular antioxidants may play a role in protecting the cell from NO-induced apoptosis while NO+ may trigger apoptosis independently of oxidative stress mechanisms.

3T3 Cells↗
PubMed1996

Reactive biliary epithelium: the product of a pluripotential stem cell compartment?

Liver parenchymal cells (hepatocytes) have a low rate of turnover, but can nevertheless mount a rapid and efficient regenerative response. However, in some cases of extreme hepatotoxicity hepatocyte proliferation is restricted or even abolished, and instead biliary epithelial cells, commonly referred to as ductular oval cells, migrate into the periportal and midzonal parenchyma. Initially these cells behave as authentic biliary epithelium with expression of the biliary cytokeratin intermediate filaments, but then show hepatocytic traits such as alpha fetoprotein and albumin synthesis. Thereafter these biliary ducts rapidly vanish to be replaced by either small hepatocytes or intestinal-type cells. The proliferation and differentiation of oval cells is probably strongly influenced by paracrine signalling from liver stellate cells. Oval cells appear to be the progeny of facultative pluripotential stem cells which have the lineage potential of uncommitted gastrointestinal stem cells; these stem cells are likely to be located in the cholangioles and small interlobular bile ducts. Oval cells thus constitute an important reserve compartment for hepatocytes when hepatocyte regeneration is compromised.

Animals↗
PubMed1995

Extra-nuclear location of histones in activated human peripheral blood lymphocytes and cultured T-cells.

Dextrin-2-sulphate (D2S) is a sulphated polysaccharide which inhibits human immunodeficiency virus type 1 infection of T-cells by binding to the cell surface. During our investigations of the nature of this interaction, a cell membrane fraction was prepared by ultracentrifugation from the T-cell line, HPB-ALL. Separation of membrane proteins by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis and analysis for binding proteins using ligand blotting showed that 3H-D2S bound, in a saturable and displaceable manner, to two regions corresponding to molecular weights of 14,000-18,000 and 28,000-32,000. The N-terminal sequences of two of the major protein components in the 14,000-18,000 region were consistent with those of histones H2B and H3. The presence of histone H2B in the cell membrane preparation was confirmed by immunoblotting and enzyme-linked immunosorbent assay using a specific antibody. Histone standards were used to determine the level of each histone in the cell membrane fraction. In addition, the binding of 3H-D2S to purified histone standards was quantified. These results show that all of the binding of 3H-D2S to proteins in the 14,000-18,000 region of the cell membrane preparation can be attributed to the histones present. In contrast to HPB-ALL cells, a cell membrane fraction from freshly isolated human peripheral blood lymphocytes contained very low levels of histones. However, after culture with phytohaemagglutinin for 3 days the cell membrane fraction contained greatly increased levels of histones. To exclude the possibility of contamination of the cell membrane preparation with histones derived from the nucleus, cell membranes were also prepared using an affinity-based method using polyethyleneimine-cellulose. Immunoblotting of adsorbed plasma membranes showed the presence of histone H2B. SDS-polyacrylamide gels stained for protein also indicated that the preparation contained histones H1, H2A, H3 and H4. In further experiments whole cells were used to avoid contamination from nuclear proteins. Lactoperoxidase mediated 125I labelling, a method specific for radiolabelling cell surface proteins, confirmed the presence of histones H2B, H3 and H4 on the surface of HPB-ALL cells. Also, incubation of HPB-ALL cells or phytohaemagglutinin-activated peripheral blood lymphocytes with D2S caused displacement of histones from the cell surface into the supernatant without altering cell viability. In addition, immunocytochemistry of freshly isolated peripheral blood lymphocytes showed that histone H2B was located predominantly in the nucleus. However, in phytohaemagglutinin-activated peripheral blood lymphocytes immunoreactive material was also prominent in the endoplasmic reticulum and on the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Protein extraction and western blotting from methacarn-fixed tissue.

Polyacrylamide gel electrophoresis (PAGE) of proteins with subsequent western blotting has become a routine technique for the analysis of proteins from both cultured cells and fresh whole tissue. We have developed a method to extract proteins from methacarn-fixed tissue which renders them suitable for SDS-PAGE and western blotting. With a panel of antibodies to specific intermediate filaments, transforming growth factor-alpha (TGF-alpha), and albumin, immunohistochemistry was performed in parallel with western blotting on sections cut from methacarn-fixed samples of normal rat liver and liver from rats treated under a regime which induces oval cell proliferation. Immunohistochemistry enabled the determination of changes in tissue distribution and abundance of the target proteins, which was mirrored by the corresponding western blot data. This technique can be especially effective when used in conjunction with immunohistochemistry. Tissue samples are easy to prepare, avoiding the precautions which need to be taken when handling fresh tissue (Abstract: J Pathol 1994; 173S: No. 41).

Acetates↗
PubMed1994

Increased apoptosis in the cingulate sulcus of newborn piglets following transient hypoxia-ischaemia is related to the degree of high energy phosphate depletion during the insult.

An increase in the number of cells undergoing apoptosis was observed in the cingulate sulcus of newborn piglets 48 h after a global hypoxic-ischaemic insult. Apoptotic death was identified morphologically (by light and electron microscopy) and by DNA fragmentation, detected by in situ end labelling. The number of apoptotic cells was directly related to the degree of high-energy phosphate depletion during hypoxia-ischaemia, measured using continuous 31P magnetic resonance spectroscopy. These results may have implications for the understanding and treatment of perinatal hypoxic-ischaemic brain injury.

Animals↗
PubMed1994

Cell behavior in the acetylaminofluorene-treated regenerating rat liver. Light and electron microscopic observations.

When hepatocyte regeneration is impaired, facultative stem cells and their descendants, also called oval cells, become activated and produce cell progeny that eventually differentiate. We have observed these cells in the rat liver after partial hepatectomy when the animals have been fed 2-acetylaminofluorene. Oval cells emerge from the portal areas and stain strongly with monoclonal antibodies raised against cytokeratins 8 and 19 and vimentin, the intermediate filament traditionally associated with mesenchymal cells. The majority of oval cells appeared to be part of a bile ductular reaction, manifest by their cytokeratin expression, and the bile duct injection of pigmented gelatin confirmed that these oval cells were essentially tortuous, arborizing duct-like structures (cholangioles) branched from and continuous with preexisting bile ducts. In situ hybridization studies showed that hepatocyte growth factor mRNA-expressing sinusoid lining cells were most numerous in the periportal areas during the period of ductular proliferation. At 1 week after partial hepatectomy, we observed morphological evidence of areas of in situ focal differentiation in the ductular structures, either to a columnar intestinal-type epithelia or to a hepatocyte phenotype, with abundant large mitochondria and membranous cytokeratin 8 immunoreactivity contrasting with the diffuse staining of the ductular cells. By following the fate of oval cells the authors conclude that in this model proliferated bile ductules represent the oval cell compartment capable of producing pluripotential progenitor cells.

2-Acetylaminofluorene↗
PubMed1993

Trefoil peptide gene expression in gastrointestinal epithelial cells in inflammatory bowel disease.

BACKGROUND: This work expands on recent observations that the trefoil peptides pS2 and human spasmolytic polypeptide (hSP) are expressed in the ulceration-associated cell lineage (UACL) glands developing in chronic ulcerative conditions. METHODS: Trefoil peptide expression in small intestinal Crohn's disease was examined by in situ hybridization to reveal sites of expression of the messenger RNAs encoding pS2 and hSP and by immunohistochemistry and immunoelectron microscopy to localize the peptides in the UACL and adjacent goblet and neuroendocrine cells. RESULTS: Goblet cells near the UACL expressed pS2 messenger RNA and peptide; ultrastructural immunolocalization revealed pS2 copackaged within mucous cell granules. Neuroendocrine cell hyperplasia was marked in crypts near the UACL; pS2 was copackaged with the neuroendocrine granules. CONCLUSIONS: Copackaging of a secretory protein, pS2, in both mucous and neuroendocrine granules, which have different functions, is unusual and indicates an important role for pS2 in the secretory process itself or as a ligand delivered to its receptors via different routes. It is concluded that trefoil peptides are of considerable potential functional importance in inflammatory bowel disease.

Cell Line↗
PubMed1993

Trefoil peptide gene expression in small intestinal Crohn's disease and dietary adaptation.

We examined the patterns of trefoil peptide gene expression in the ulcer-associated cell lineage (UACL) and mucosa adjacent to Crohn's disease in humans and during gastrointestinal adaptation to enteral feeding in rats. In the UACL, human spasmolytic polypeptide (hSP) mRNA and peptide are present in the acinar and proximal duct cells, whereas pS2 mRNA and peptide are found in the distal duct cells and in the surface cells. In mucosa adjacent to UACL, pS2 mRNA and peptide are expressed ectopically by goblet cells and neuroendocrine cells. Intestinal crypts associated with the UACL showed marked neuroendocrine cell hyperplasia. Ultrastructural immunolocalization showed pS2 to be copackaged in the mucous cell and neuroendocrine granules. The copackaging of a secretory protein in both mucous and neuroendocrine granules, which have different functions, is unusual and indicates an important role for pS2 in the secretory process itself or as a ligand delivered to its receptor via multiple routes. We also cloned the newest trefoil peptide, intestinal trefoil factor (ITF), from human and rat intestinal mucosa. Using in situ hybridization we demonstrated its synthesis by normal rat intestinal goblet cells. RNAse protection analysis revealed that the level of mRNA for rat ITF in small and large intestine was affected by the process of enteral feeding. We conclude that trefoil peptides are widely distributed in the intestine in human inflammatory bowel disease and are of considerable potential functional importance.

Animals↗
PubMed1992

Glomerular mesangial cells and inflammatory macrophages ingest neutrophils undergoing apoptosis.

Apoptosis or programmed cell death of senescent neutrophils leading to their uptake by phagocytes is a general mechanism by which neutrophils may be removed from inflamed sites in vivo, promoting resolution rather than persistence of inflammation. We now report morphological evidence of neutrophil apoptosis leading to uptake by glomerular cells in rats with experimental glomerulonephritis. In addition to confirming that inflammatory macrophages take up apoptotic neutrophils, these studies indicated that glomerular mesangial cells can also participate in this mode of neutrophil clearance. Furthermore, human neutrophils which had been "aged" in vitro so as to undergo apoptosis were ingested by 31.5 +/- 1.3% (mean +/- SE) of cultured human mesangial cells, but there was minimal recognition of freshly isolated neutrophils (2.2 +/- 0.1%). Centrifugal elutriation of aged neutrophil populations yielded fractions with varying degrees of apoptosis (from 11.1 to 79.4%). Uptake of these fractions (by 8.2% to 59.8% of mesangial cells) was closely correlated with apoptosis (r = 0.96, P less than 0.0001). This demonstrated that recognition was dependent upon apoptosis, as in previous reports of macrophage recognition of aged neutrophils. However, by contrast, a partial requirement for serum was observed. These data indicate a hitherto unexpected function for the mesangial cell in clearance of senescent neutrophils from the glomerulus which may supplement inflammatory macrophage uptake of leucocytes undergoing apoptosis.

Animals↗
PubMed1992

Trefoil peptide expression in intestinal adaptation and renewal.

There are many avenues where molecular biology is important in studying the gut, and here we explore methods for defining expression of a new gene family in the gut. We have defined the pattern of trefoil peptide gene expression in the ulceration-associated cell lineage (UACL) and in the nearby mucosa in Crohn's disease. In the UACL, human spasmolytic polypeptide mRNA and peptide are expressed in the acinar and proximal duct cells, whereas pS2 mRNA and peptide are found in the distal duct cells and in the surface cells. In adjacent mucosa, pS2 mRNA and protein are expressed ectopically by goblet cells. Ultrastructural immunolocalisation showed the pS2 to be co-packaged in the mucous cell granules. pS2 peptide was demonstrated in local neuroendocrine cells and was also co-packaged with the neuroendocrine granules. The crypts associated with the UACL also showed marked neuroendocrine cell hyperplasia. We have also cloned the newest trefoil peptide intestinal trefoil factor from human and rat intestinal mucosa and shown its co-expression with mucus by normal intestinal goblet cells. The co-packaging of the same secretory protein in both mucous and neuroendocrine granules, which have different functions, is unusual and indicates an important role for pS2 in the secretory process itself or as a ligand delivered to its receptor via multiple routes. We conclude that the trefoil peptides are widely distributed in the intestine in inflammatory bowel disease and are of considerable potential functional importance.

Amino Acid Sequence↗
PubMed1992

Trefoil peptide gene expression in gastrointestinal epithelial cells in inflammatory bowel disease.

Trefoil peptides are a growing group of proteins with interesting structural and functional properties. We have defined the pattern of trefoil peptide gene expression in the ulceration-associated cell lineage (UACL) and in the nearby mucosa in Crohn's disease. In the UACL, human spasmolytic polypeptide (hSP) mRNA is expressed in the acinar and proximal duct cells, while pS2 mRNA and peptide are found in the distal duct cells and in the surface cells. In adjacent mucosa, pS2 mRNA and protein are expressed by goblet cells, with the pS2 peptide concentrated in the area of the Golgi and also in the theca. Ultrastructural immunolocalisation showed the pS2 to be co-packaged in the mucous cell granules before being secreted into the intestinal lumen. In addition, pS2 peptide was demonstrated in local neuroendocrine cells and was also co-packaged with the neuroendocrine granules. The crypts associated with the UACL also showed marked neuroendocrine cell hyperplasia. We conclude that pS2 peptide is secreted locally into the viscoelastic coat covering the intestinal mucosa which surrounds Crohn's disease ulcers. In addition, it is clear that intestinal goblet cells, in addition to producing mucins, are a rich source of regulatory peptides. Moreover, pS2 is clearly co-packaged with neurosecretory granules, which are released through basal and lateral membranes so that the contained peptides can act in a paracrine manner. These findings are interpreted in terms of the epidermal growth factor/urogastrone released by the UACL, stimulating pS2 gene expression in surrounding cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Crohn Disease↗