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W R Brown

Publications and source records attributed to W R Brown.

At least 109 records · Page 6Linked to original sources
PubMed1988

A physical map of the human pseudoautosomal region.

A physical map of the human pseudoautosomal region has been constructed using pulsed field gel electrophoresis and the infrequently cutting restriction enzymes BssHIII, EagI, SstII, NotI, MluI and NruI. This map extends 2.3 Mbp from the telomere to sex-chromosome-specific DNA, includes at least seven CpG islands and locates four genetically mapped loci. Five of the CpG islands are organized into two clusters. One cluster is adjacent to the telomere, the other extends into sex-chromosome-specific DNA. There is congruence between the genetic and physical maps which implies that the frequency of recombination is approximately uniform throughout the DNA.

Cell Line↗
PubMed1988

Posttranslational modification of ras proteins: detection of a modification prior to fatty acid acylation and cloning of a gene responsible for the modification.

Products of ras genes are synthesized as precursors in the cytosol and transported to the plasma membrane by a process which involves posttraslational modification by fatty acid. In this paper, we present evidence for the occurrence in the cytosol of an intermediate modification of ras proteins prior to the fatty acid acylation. The modification is detected by a slight shift in the mobility of the protein on SDS polyacrylamide gel. The fatty acid acylation does not contribute to this mobility shift. This modification is affected by the dprl mutation which has recently been shown to affect the processing of yeast RAS proteins. To further characterize the nature of the modification event, we have cloned DPR1 gene from the DNA of Saccharomyces cerevisiae. The gene is actively transcribed in yeast cells producing mRNA of approximately 1.6 kb. Genes related to the DRP1 appear to be present in a distantly related yeast, Schizosaccharomyces pombe as well as in guinea pig and human cells.

Acylation↗
PubMed1988

Expression of cell-surface antigens on rat colonic cancer cells.

Previously, we reported that two glycoproteins, carcinoembryonic antigen and secretory component, are preferentially expressed on the apical or laterobasal surfaces, respectively, of normal human colonic epithelial cells, whereas these antigens may be expressed over the entire cell surface of colonic cancer cells. These observations have prompted us to develop an animal model of aberrantly distributed normal surface antigens in colonic carcinoma. We prepared four monoclonal antibodies, three of which react specifically with antigens located on the microvillus surface and one that reacts specifically with the laterobasal surface of normal rat colonocytes. Three of the four cell-surface antigens were expressed by cells at all levels of the colonic crypt, but one of the microvillar antigens (p66) was expressed only on the mature colonocytes at the luminal surface. We then documented that a microvillus antigen (p66) detected by one of the antibodies and a laterobasal membrane antigen detected by another antibody were expressed over the entire surface of poorly differentiated colonic carcinoma cells induced by dimethylhydrazine. p66 was more often expressed on poorly differentiated colonic cancers than were the other three antigens. These observations indicate that (a) polarity of surface membrane antigens is a characteristic of normal rat colonic epithelial cells, (b) this polarity is not present in some experimental colonic carcinomas, and (c) the malignant phenotype of colonic carcinoma cells does not result merely from a block in normal differentiation of colonocytes.

Adenocarcinoma↗
PubMed1988

Serum antibodies to mycobacterial antigens in active Crohn's disease.

Infection with a species of Mycobacterium has been implicated in the pathogenesis of Crohn's disease. Therefore, we attempted to determine whether a specific serum antibody response to mycobacteria occurs in patients with the disease. We tested sera of patients with active Crohn's disease and several control groups in an enzyme-linked immunosorbent assay for reactivity with two mycobacterial antigens: (a) lipoarabinomannan, a highly immunogenic somatic lipopolysaccharide present in the cell walls of all species of the Mycobacterium genus, and (b) a protoplasmic antigenic preparation from M. sp strain linda, the mycobacterium that has been specifically implicated in Crohn's disease. We found no significant elevation in immunoglobulin A, immunoglobulin G, or immunoglobulin M antibody levels to these two antigen preparations in the Crohn's disease patients. Moreover, no subset of patients (sex, age, Crohn's disease activity index, location of disease, duration of disease, operations, or response to treatment) had elevated antibody levels. As virtually all known chronic infectious diseases have an associated serologic response to the etiologic agent, our findings greatly diminish the likelihood that Crohn's disease is caused by an infection with a mycobacterium.

Adult↗
PubMed1988

Immunologic outcome of enteric administration of ovalbumin to neonatal rats is anatomic-site specific.

An important immunologic response to the oral ingestion of a protein antigen is systemic tolerance to subsequent parenteral encounter with the same antigen. In the newborn intestine, ileal epithelial cells nonspecifically take up macromolecules and degrade them in lysosomal enzyme-containing vacuoles. We speculated that processing of protein antigens by the ileal cells helps mediate systemic immunologic tolerance to the antigens. Therefore, we developed a neonatal rat model in which ovalbumin (OVA) was administered either by gastric gavage or by infusion into surgically constructed loops of jejunum or ileum. We also administered OVA to other groups of animals by injection into the intact jejunum or ileum. Two and 4 weeks later, animals were challenged with OVA measured. Whereas animals that received OVA by gastric gavage were made tolerant to the protein (produced no detectable serum IgG anti-OVA antibodies after parenteral challenge), the animals given OVA into the jejunum or ileum did not show tolerance; indeed, some of those given OVA into the ileum were immunized by the enteric exposure. From these data we postulate that the development of systemic immunologic tolerance to a protein antigen in the newborn requires "upstream" processing of the antigen by gastric or pancreatic secretions and that exposure of the distal intestine to intact protein antigens can result in systemic sensitization to the antigens. The latter response might be causally linked to food allergies or autoimmune diseases.

Animals↗
PubMed1988

Lack of correlation between infection with reovirus 3 and extrahepatic biliary atresia or neonatal hepatitis.

Infection with reovirus 3 (Reo-3) has been suggested as the cause of extrahepatic biliary atresia and idiopathic neonatal hepatitis, but confirmation has been lacking. Therefore we have searched for a specific anti-Reo-3 antibody response in the sera of patients with biliary atresia or neonatal hepatitis and for Reo-3 antigens in their hepatobiliary tissues. Sera from 23 infants with extrahepatic biliary atresia, 12 with neonatal hepatitis, 30 age-matched control patients with other liver diseases, and 55 control patients without liver disease were tested by an enzyme-linked immunosorbent assay for total (IgA, IgG, and IgM) anti-Reo-3 antibodies; sera of infants younger than 6 months of age were tested also for IgM anti-Reo-3 antibodies alone. There was no difference between either total or IgM anti-Reo-3 antibody levels in infants with extrahepatic biliary atresia or neonatal hepatitis and levels in control infants. Reo-3 antigens were not detected in the hepatobiliary tissues of 19 infants (18 with biliary atresia, one with neonatal hepatitis) by an immunoperoxidase method that readily demonstrated Reo-3 in control infected HEp-G2 cells. Our data do not support a relationship between neonatal liver diseases and infection with Reo-3.

Antigens, Viral↗
PubMed1988

Circadian rhythms are suppressed in hyperproliferative mouse epidermis.

We examined the chronically hyperproliferative epidermis of the asebia (ab/ab) mouse for circadian rhythms in cell proliferation and in the rate of DNA synthesis, which is related to S phase duration. The curve for the circadian rhythm in cell proliferation for asebia epidermis was suppressed and distorted in comparison to that for BALB/cJ epidermis and in comparison to a composite curve produced by averaging the results from ten other published studies.

Animals↗
PubMed1987

A model for the separation of large DNA molecules by crossed field gel electrophoresis.

The idea that large DNA molecules adopt a stretched conformation as they pass through gels suggests a simple mechanism for the separation of DNA by crossed field electrophoresis: at each change in field direction a DNA molecule takes off in the new direction of the field by a movement which is led by what was formerly its back end. The effect of this ratcheting motion is to subtract from the DNA molecule's forward movement, at each step, an amount which is proportional to its length. We find that this model explains most of the features of the separation, and we describe experiments, using a novel electrophoresis apparatus, which support the model. The apparatus turns the gel between two preset orientations in a uniform electric field at preset time intervals. This separation method has the practical advantage over some others that the DNA molecules follow straight tracks. A further advantage is that the parameters which determine the separation are readily predicted from the simple theory describing their motion.

DNA↗
PubMed1987

Structure of the major block of alphoid satellite DNA on the human Y chromosome.

Alphoid DNA is a family of tandemly repeated simple sequences found mainly at the centromeres of the chromosomes of many primates. This paper describes the structure of the alphoid DNA at the centromere of the human Y chromosome. We have used pulsedfield gradient gel electrophoresis, cosmid cloning and DNA sequencing to determine the organization of the alphoid DNA on each of the Y chromosomes present in two somatic cell hybrids. In each case there is a single major block of alphoid DNA. This is approximately 470,000 bases (475 kb) long on one chromosome and approximately 575 kb long on the other. Apart from the size difference, the structures of the two blocks and the surrounding sequences are very similar. However, one restriction enzyme, AvaII, detects two clusters of sites within one block but does not cleave the other. The alphoid DNA within each block is organized into tandemly repeating units, most of which are about 5.7 kb long. A few variant units present on one chromosome are about 6.0 kb long. These variants, like the AvaII site variants, are clustered. The 5.7 kb and 6.0 kb units themselves consist of tandemly repeating 170 base-pair subunits. The 6.0 kb unit has two more of these subunits than the 5.7 kb unit. Our results provide a basis for further structural analysis of the human Y chromosome centromeric region, and suggest that long-range structural polymorphisms of tandemly repeated sequence families may be frequent.

Base Sequence↗
PubMed1987

Differential expression carcinoembryonic antigen and secretory component during colonic epithelial cell differentiation and in colonic carcinomas.

The cellular and ultrastructural distribution of carcinoembryonic antigen and secretory component during differentiation of normal colonic epithelium and in colonic carcinomas was evaluated by peroxidase-labeled antibody immunocytochemistry. Carcinoembryonic antigen and secretory component were found to be markers of distinctly different stages of normal colonocyte differentiation. Whereas secretory component was expressed principally by proliferating absorptive cells in the midcrypt, carcinoembryonic antigen expression was diminished in this crypt zone and was associated principally with mature columnar cells at the luminal surface and with undifferentiated cells at the crypt base. Carcinoembryonic antigen was preferentially expressed on the microvillar plasma membrane and secretory component on the basolateral plasma membrane in the normal colon. In 13 colon cancers studied, carcinoembryonic antigen was expressed on the entire surface of all the colon cancers except one anaplastic tumor, whereas secretory component was only expressed on five well or moderately differentiated cancers. These observations suggest that differentiation of colon cancers as assessed by morphology and phenotypic markers is not totally analogous to that found in the normal colon.

Carcinoembryonic Antigen↗
PubMed1987

Search for a specific marker of mucosal dysplasia in chronic ulcerative colitis.

We have tried to identify a histochemical or immunohistochemical marker that would reliably detect mucosal dysplasia in chronic ulcerative colitis. Colonic biopsy specimens were taken from patients with long-standing ulcerative colitis undergoing surveillance colonoscopy. Control tissue was obtained from the margins of colonic resections performed for neoplastic or nonneoplastic diseases. Sections of the specimens were examined by periodic acid-Schiff staining, high iron diamine Alcian blue staining for sialomucins and sulfomucins, and binding of the lectins peanut agglutinin, Ulex europeus agglutinin I, and Ricinis communis I agglutinin. Sections were reacted also with anticarcinoembryonic antigen antibodies to determine whether a nonpolar surface distribution of the antigen was a feature of dysplasia. We found that changes in colonic mucin, characterized by periodic acid-Schiff-positive mucin outside of goblet cells, an increase in binding of peanut agglutinin, and an increase in the relative amount of sialylated mucin, were associated with morphologic dysplasia. However, identical alterations were observed, albeit less commonly, in colitis without dysplasia, particularly in the presence of active inflammation. No abnormality in the surface distribution of carcinoembryonic antigen or Ricinis communis I agglutinin was observed. Thus, we did not identify a reliable corollary test to the histologic diagnosis of mucosal dysplasia in ulcerative colitis. With regard to these histochemical markers, the colonic mucosa appears to respond similarly to inflammation and neoplasia.

Carcinoembryonic Antigen↗
PubMed1987

Serial observations of colonic carcinogenesis in the rat. Premalignant mucosa binds Ulex europeus agglutinin.

We evaluated certain histochemical tests for their ability to detect premalignant mucosa in the dimethylhydrazine model of colonic carcinogenesis. Biweekly colonoscopic biopsies of the descending colon were performed for 29 wk in control and dimethylhydrazine-treated rats. Biopsy specimens of the splenic flexure, rectum, and any visualized tumors were taken. The specimens were stained with periodic acid-Schiff to detect neutral mucins, high-iron diamine alcian blue to detect sialylated and sulfated mucins, fluoresceinated peanut agglutinin, and fluoresceinated Ulex europeus agglutinin. None of the first three tests consistently detected premalignant mucosa. However, Ulex europeus agglutinin, which bound to only 3% of control biopsy specimens throughout the course of the study, bound to increasing numbers of biopsy specimens in the dimethylhydrazine-treated animals, reaching a maximum of 90% positivity by 13-16 wk. Moreover, Ulex europeus agglutinin bound strongly to all biopsy specimens from tissues adjacent to tumors and to 93% of tumors. Mucosal atrophy and focal dysplasia were present more frequently in specimens taken from the rectum (but not the splenic flexure) of dimethylhydrazine-treated animals than of control animals, but there was no correlation between the histochemical markers and either atrophy or dysplasia. We conclude that Ulex europeus agglutinin binding is a consistent feature of premalignant colonic mucosa in dimethylhydrazine-treated rats.

Animals↗
PubMed1987

Monoclonal antibodies identifying antigens on distinct domains of rat hepatocytes.

To aid in evaluating the functional significance of various domains of the hepatocyte plasma membrane, we have developed monoclonal antibodies that react with three different antigens on the surface of rat hepatocytes. One antigen is present on the sinusoidal-lateral plasma membrane but is absent from the bile canalicular membrane. On the basis of apparent molecular weight and ability to bind a desialylated glycoprotein, this antigen may be the asialoglycoprotein receptor. It was also identified immunocytochemically on the sinusoidal-lateral plasma membrane of human hepatocytes. The second antigen is present only on the bile canalicular membrane, whereas the third is present on the entire cell surface of rat hepatocytes. Our monoclonal antibodies may be useful in investigations of the sorting mechanisms of hepatocyte membrane proteins and the pathogenesis of certain liver diseases.

Animals↗