Edge preserving techniques in image noise removal process

The paper describes how to prepare dynamic graphic filters, which main goal is to remove noise from an image and also to preserve information on edges between objects. These types of filters are able to focus on operations inside objects, and at the same time weaken the process at objects borders

Topological characterization of the simian virus 40 transcription complex

We have used sedimentation analysis as well as agarose gel electrophoresis to characterize the topological state of the DNA of the Simian Virus 40 (SV40) transcription complex. We found that the complex DNA contained constrained topological tension, presumably resulting from nucleosome-like structures, but no detectable unconstrained (i.e., relaxable) topological tension. These results contradict previous conclusions that the SV40 transcription complex contains only unconstrained topological tension. Our findings are also the opposite of what has been proposed to be the case for the 5S gene analyzed in Xenopus oocytes. Thus the proposal that expression from the 5S gene is associated with substantial topological tension is not valid for expression from the SV40 late gene.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26833/1/0000393.pd

Differential expression of an α-galactosyl-containing trisaccharide on high- and low-malignant murine sarcoma cells: Identification and regulation

Past studies have shown that carbohydrate residues reactive with the Griffonia simplicifolia isolectin B 4 (GS I-B4) are present on the surface of highly-malignant murine sarcoma cells but are lacking or expressed in much lower amounts on the surface of low-malignant cells isolated from the same parent tumors (Am J Pathol 111: 27; J Nat Cancer Inst 71: 1281). In the present study it is shown that an antibody which recognizes the trisaccharide Galα1-3Galβ1-4GlcNAc- is reactive with the highly-malignant cells but is non-reactive with the low-malignant cells. Further studies show that the high-malignant cells not only bind GS I-B 4 but also bind Evonymus europaea lectin (which like GS I-B 4 recognizes terminal galactose in α1-3 linkage) and Erythina crystagalli lectin (which recognizes sub-terminal galactose in the β1-4 linkage – e.g., Galβ1-4GlcNAc). In contrast, the low malignant cells bind Erythina crystagalli lectin as efficiently as the high malignant cells but do not bind (or bind much smaller amounts of) either GS I-B 4 or Evonymus europaea lectin. The present studies also show that there is no significant difference between high- and low-malignant cells in expression of α-galactosidase activity. In contrast, the high-malignant cells express high levels of α-galactosyl transferase activity while this enzyme is virtually undetectable in low-malignant cells. Taken together, these studies indicate that differential expression of a single monosaccharide residue distinguishes high- and low-malignant murine sarcoma cells. These studies also identify a mechanism to account for surface carbohydrate differences between the high- and low-malignant cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42582/1/10585_2004_Article_380463.pd

Calcium- and tyrosine phosphorylation-dependent mechanisms of amyloid precursor protein processing

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 38-41).by Magdalene A. Petryniak.M.Eng

Lectin binding studies on murine peritoneal cells: Physicochemical characterization of the binding of lectins from Datura stramonium, Evonymus europaea, and Griffonia simplicifolia to murine peritoneal cells

Purified 125I-labeled lectins from Datura stramonium, Evonymus europaea, and Griffonia simplicifolia (I-B4 isolectin) were used to analyze changes in the expression of carbohydrates on the surface of resident (PC) and thioglycollate-stimulated murine (C57B/6J) peritoneal exudate cells (PEC). The lectins from D. stramonium, E. europaea, and G. simplicifolia I-B4 bind specifically to PEC with relatively high affinity (Kd = 5.65 +/- 1.08 x 10-7 m, 1.08 +/- 0.12 x 10-8 m, and 1.33 +/- 0.15 x 10-7 m, respectively). Assuming a single lectin molecule binds to each cell surface saccharide, the number of receptor sites per cell ranged for different cell samples from 22.3 to 50.0 x 106, from 3.8 to 4.8 x 106, and from 2.0 to 16.8 x 106 for D. stramonium, E. europaea, and G. simplicifolia I-B4 lectins, respectively. There were approximately 3- to 7-fold, 16- to 20-fold, and 2-to 20-fold increases in binding capacity for D. stramonium, E. europaea and G. simplicifolia I-B4, respectively, compared to the binding to resident, peritoneal cells. Scatchard plots of the binding of all three lectins to PEC were linear, suggesting that the receptor sites for these lectins are homogeneous and noninteracting. The binding capacity of these lectins to PEC was unchanged after trypsin digestion of cells. The expression of carbohydrates on the surface of PEC was also monitored by an agglutination assay. PEC were agglutinated by all three lectins whereas PC either were not agglutinated or were agglutinated only at high lectin concentrations. On the basis of our knowledge of the carbohydrate binding specificity of the D. stramonium and G. simplicifolia I-B4 lectins, we postulate that, parallel with thioglycolate stimulation, there is an increase in the number of N-acetyllactosamine residues and terminal [alpha]--galactosyl end groups. The blood group B, and H type 1 determinants--Ga1[alpha]1,3[Fuc[alpha]1,2]Ga1[beta]1,3(or 4)GlcNAc and Fuc[alpha]1,2Ga1[beta]1,3G1cNAc, respectively, as well as Ga1[alpha]1,3Ga1[beta]1,3(or 4)GlcNAc--may be considered to be possible receptors for the E. europaea lectin. These glycoconjugates, present on the surface of peritoneal exudate cells, provide new chemical markers for studying the differentiation of resident peritoneal cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26332/1/0000419.pd

Molecular basis of evolutionary loss of the α1,3-galactosyltransferase gene in higher primates

Galactose-α1,3-galactose (αGal) epitopes, the synthesis of which requires the enzyme product of α1,3-galactosyltransferase (α1,3GT), are sugar chains on the cell surface of most mammalian species. Notable exceptions are higher primates including Old World monkeys, apes, and humans. The αGal-negative species as well as mice with deletion of the α1,3GT gene produce abundant anti-αGal antibodies. The evolutionary loss of αGal epitopes has been attributed to point mutations in the coding region of the gene. Because no transcripts could be found in the higher primate species with Northern blot analysis, a potential alternative explanation has been loss of upstream regulation of the gene. Here, we have demonstrated that the rhesus promoter is functional. More importantly, a variety of full-length transcripts were detected with sensitive PCR-based methods in the tissues of rhesus monkeys, orangutans, and humans. Five crucial mutations were delineated in the coding region of the human and rhesus and three in the orangutan, any one of which could be responsible for inactivation of the α1,3GT gene. Two of the mutations were shared by all three higher primates. These findings, which elucidate the molecular basis for the evolutionary loss of αGal expression, may have implications in medical research

Differential expression of glycoproteins containing [alpha]--galactosyl groups on normal human breast epithelial cells and MCF-7 human breast carcinoma cells

Cell surface glycoproteins were isolated from the lysates of 125I-labeled normal human mammary epithelial cells (NHMEC) and from the human breast carcinoma cell line MCF-7, of blood-group O phenotype, by affinity chromatography on Griffonia simplicifolia I lectin-Sepharose. Specific elution of glycoproteins from the column with methyl [alpha]--galactoside suggests the presence of [alpha]--galactosyl groups on these moieties. SDS-PAGE analysis of isolated glycoproteins revealed both quantitative and qualitative differences between glycoproteins from normal and malignant cells. Three major glycoproteins of Mr 180 kDa, 85 kDa and the 44 kDa were obtained from MCF-7 cells. The 180-kDa glycoprotein was absent in NHMEC and the 44-kDa glycoprotein was very weakly expressed in these cells. The only glycoprotein which was found in almost equal amount in the lysate from both normal and malignant cells was the 85-kDa glycoprotein. These results indicate differences between normal human mammary epithelial cells and one kind of malignant human mammary epithelial cells, in the expression of glycoproteins containing [alpha]--galactosyl groups, irrespective of blood-group phenotype; they also demonstrate that [alpha]--galactosyl group are expressed in a very restrictive manner on the surface of this tumor cell line.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29093/1/0000129.pd

Conditional control of selectin ligand expression and global fucosylation events in mice with a targeted mutation at the FX locus

Glycoprotein fucosylation enables fringe-dependent modulation of signal transduction by Notch transmembrane receptors, contributes to selectin-dependent leukocyte trafficking, and is faulty in leukocyte adhesion deficiency (LAD) type II, also known as congenital disorder of glycosylation (CDG)-IIc, a rare human disorder characterized by psychomotor defects, developmental abnormalities, and leukocyte adhesion defects. We report here that mice with an induced null mutation in the FX locus, which encodes an enzyme in the de novo pathway for GDP–fucose synthesis, exhibit a virtually complete deficiency of cellular fucosylation, and variable frequency of intrauterine demise determined by parental FX genotype. Live-born FX(−/−) mice exhibit postnatal failure to thrive that is suppressed with a fucose-supplemented diet. FX(−/−) adults suffer from an extreme neutrophilia, myeloproliferation, and absence of leukocyte selectin ligand expression reminiscent of LAD-II/CDG-IIc. Contingent restoration of leukocyte and endothelial selectin ligand expression, general cellular fucosylation, and normal postnatal physiology is achieved by modulating dietary fucose to supply a salvage pathway for GDP–fucose synthesis. Conditional control of fucosylation in FX(−/−) mice identifies cellular fucosylation events as essential concomitants to fertility, early growth and development, and leukocyte adhesion