PubMed Health⌕ Search

Biomedical subjects

K E Brown

Publications and source records attributed to K E Brown.

At least 19 recordsLinked to original sources
PubMed1995

Goose parvovirus--an autonomous member of the dependovirus genus?

Goose parvovirus is the etiological agent of Derzsy's disease, a fatal hepatitis of young geese. The virus infects geese and Muscovy ducks and can be propagated in the laboratory in primary embryonic goose fibroblasts. To date the virus has only been classified by morphological, biochemical, and culture characteristics as an autonomous parvovirus. We now report the cloning and partial sequencing of 3434 nucleotides of the viral genome. Three overlapping clones were obtained, encoding regions in the nonstructural and capsid coding region. The nucleotide sequence show little homology to other autonomous parvoviruses but 55% homology to the dependovirus AAV2. The homology to AAV2 was also confirmed at the amino acid level (nonstructural protein 55%, capsid coding region 51%). DNA cross hybridization studies indicate an even closer similarity of goose parvovirus to the yet unsequenced human dependoviruses AAV1 and AAV3 than to AAV2. These findings suggest that goose parvovirus may be genetically related to the dependovirus genus rather than to the other autonomous parvoviruses.

Amino Acid Sequence↗
PubMed1995

Cloning and sequencing of the simian parvovirus genome.

We recently reported the identification of a novel simian parvovirus in cynomolgus monkeys with severe anemia. We now describe the cloning and sequencing of 4986 nucleotides of the viral DNA. Like the human parvovirus B19, simian parvovirus encapsidates both positive and negative single-stranded DNA. The positive strand contains two large open reading frames, with the left open reading frame encoding the nonstructural protein(s) and the right reading frame encoding the two capsid proteins. Simian parvovirus has little homology with the autonomous parvoviruses or the dependovirus AAV-2 but 50% overall homology with parvovirus B19 DNA. At the amino acid level there was 70% homology with B19 capsid proteins and 50% homology with B19 nonstructural protein. Based on this genetic similarity and with the known tropism of the virus for cynomolgus erythroid precursors, we suggest that this new virus should be classified as a new member of the Erythrovirus genus of the Parvoviridae.

Amino Acid Sequence↗
PubMed1995

Developmental transformation of dendritic arbors in mouse whisker thalamus.

Neurons in slices though the somatosensory thalamus of postnatal day 6 and adult mice were injected with Lucifer yellow. Dendritic arbors on postnatal day 6 are confined to single barreloids (single whisker representations); in adults they are seven times longer, extending beyond their barreloid to adjacent barreloids. The postnatal transformation of dendritic arbors by total process growth and extension to adjacent barreloids suggests a developmental change in the role of these cells from instructing whisker pattern formation to integrating sensory information from more than one whisker.

Aging↗
PubMed1995

Morphology and antigenicity of recombinant B19 parvovirus capsids expressed in transfected COS-7 cells.

COS-7 cells transfected with parvovirus B19-simian virus 40 (SV40) hybrid vectors have previously been shown to express B19 structural proteins. In this study the morphology and antigenicity of B19 proteins expressed in these cells were investigated. At 84 h after transfection, approximately 10% of the COS-7 cells expressed B19 antigen, and the yield was equivalent to 2 x 10(3) to 2 x 10(5) B19 particles/transfected cell. The B19 proteins self-assembled into capsids that were morphologically and antigenically similar to native B19 virions, and could substitute for native antigen in a B19 IgM assay. Recombinant capsids lacking the recently described 11 kDa protein also resembled native virions.

Animals↗
PubMed1995

Influence of Pseudomonas aeruginosa exoproducts on virulence factor production in Burkholderia cepacia: evidence of interspecies communication.

The effect of concentrated cell-free extracellular material from stationary-phase cultures of Burkholderia cepacia 10661 and Pseudomonas aeruginosa PAO1 on virulence factor production in B. cepacia was assessed. While increasing concentrations of the B. cepacia exoproduct caused a slight increase in siderophore, lipase, and protease production in the producing organism, a significant in productivity was observed for all three virulence factors with the addition of the PAO1 exoproduct. Moreover, the addition of the exoproduct from a strain of P. aeruginosa producing reduced amounts of autoinducer caused only a slightly greater response than that of the control. Both B. cepacia 10661 and P. aeruginosa PAO1, along with two matched clinical isolates of both organisms obtained from a cystic fibrotic patient, were shown to produce variable amounts of three different types of autoinducer. The potential for interspecies signalling in microbial pathogenicity is discussed.

Burkholderia cepacia↗
PubMed1995

Human parvovirus B19 can infect cynomolgus monkey marrow cells in tissue culture.

The human pathogenic parvovirus B19 cannot be grown in standard tissue culture but propagates in human bone marrow, where it is cytotoxic to erythroid progenitor cells. We now show that parvovirus B19 can replicate in cynomolgus bone marrow. Cynomolgus monkeys may be a suitable animal model for pathogenesis studies of parvovirus B19.

Animals↗
PubMed1994

Congenital anaemia after transplacental B19 parvovirus infection.

We report three children with congenital anaemia after intrauterine infection with B19 parvovirus. All the fetuses developed hydrops fetalis that was treated by blood transfusion. After delivery the infants had hypogammaglobulinaemia. In all three, sera lacked B19 but viral DNA was found in bone marrow. All were treated with immunoglobulin. One child died and B19 was found in various tissues. In the other two cases, virus could no longer be detected after therapy but the patients remain persistently anaemic. Persistent B19 infection should be suspected in infants with congenital red-cell aplasia.

Agammaglobulinemia↗
PubMed1994

In situ hybridisation and in situ polymerase chain reaction detection of parvovirus B19 DNA within cells.

Modification of an in situ polymerase chain reaction (ISPCR) technique is described for the detection of B19 parvovirus infection. Specific amplification of B19 DNA inside fixed cells was followed by hybridisation with a digoxigenin-labelled probe and then visualised by immunochemical reaction. The assay had higher sensitivity compared to direct in situ hybridisation and still allowed cellular localisation and characterisation of infected cells. This assay can be used as a confirmatory method for PCR in tissues and will allow further identification of tissues permissive for B19 parvovirus infection.

Base Sequence↗
PubMed1994

Dissecting the centromere of the human Y chromosome with cloned telomeric DNA.

We have used telomeric DNA to break the human Y chromosome within the centromeric array of alphoid satellite DNA and have created two derivative chromosomes; one consists of the short arm and 140 kb of alphoid DNA, the other consists of the long arm and 480 kb of alphoid DNA. Both segregate accurately at mitosis. It is known that there is no large scale sequence duplication around the alphoid DNA and so the simplest interpretation of our results is that the sequence responsible for accurate segregation is the alphoid DNA itself. Although the long arm acrocentric derivative segregates accurately it lags with respect to the other chromosomes in about 10% of anaphase cells and thus additional sequences may be required for orderly segregation. The short arm acrocentric chromosome is probably no larger than 12 Mb in size and thus our results also demonstrate that chromosomes of this size are capable of accurate segregation.

Cells, Cultured↗
PubMed1994

Integrin regulatory switching in development: oscillation of beta 5 integrin mRNA expression during epithelial-mesenchymal interactions in tooth development.

Integrin receptors for extracellular matrix molecules are thought to play important roles in morphogenesis since they mediate aspects of embryonic cell adhesion and migration. Using in situ hybridization, the mRNA expression pattern of the beta 5 integrin receptor subunit was examined during murine tooth development, a classical system for studying morphogenesis. In developing tooth, high-level expression of beta 5 integrin mRNA alternates from epithelium to mesenchyme and back to epithelium. Each switch in localization occurs within one day. These results demonstrate that an integrin mRNA can be precisely and rapidly up- and down-regulated over unexpectedly short time spans, and that expression can oscillate between adjacent, interacting epithelial and mesenchymal tissues during morphogenesis. This rapid modulation of mRNA expression suggests a potential regulatory role for the beta 5 integrin receptor in morphogenesis.

Animals↗
PubMed1992

Expression of the c-myb proto-oncogene in bovine vascular smooth muscle cells.

Previously we have shown that bovine vascular smooth muscle cells (SMCs) express c-myb mRNA (Reilly, C. F., Kindy, M. S., Brown, K. E., Rosenberg, R. D., and Sonenshein, G. E. (1989) J. Biol. Chem. 264, 6990-6995). Here we have characterized changes in the low level of c-myb mRNA expressed in quiescent serum-deprived subconfluent SMCs upon entry into the cell cycle. After serum stimulation, levels of c-myb mRNA increased 3-4-fold during late G1 and remained at this level during S phase. A 1.5-kilobase partial c-myb cDNA clone, isolated from a bovine SMC library, was partially sequenced and found to be 89 and 85% homologous to the human and murine c-myb genes, respectively. Using bovine and murine c-myb clones, no change in the rate of c-myb gene transcription or mRNA stability was detected during the cell cycle. Thus, the regulation of changes in c-myb mRNA levels in SMCs appears distinct from mechanisms seen in hematopoietic or fibroblastic cells. Vectors containing myb binding sites linked to the thymidine kinase promoter and the chloramphenicol acetyltransferase reporter gene were transiently transfected into SMC cultures. KHK-CAT-dAX, which contains nine concatenated myb binding sites, exhibited 7-fold more activity than the parental dAX-TK-CAT vector in exponentially growing SMCs. The levels of chloramphenicol acetyltransferase activity in exponentially growing cells were approximately 2-fold higher than in cells that had been serum deprived for 24 h and were entering quiescence. Thus SMCs produce a functional c-myb protein that can activate transcription from a heterologous promoter. Furthermore, introduction of antisense c-myb oligonucleotides to quiescent serum-deprived SMC cultures severely inhibited entry of cells into S phase upon serum addition. Thus, expression of the c-myb oncogene plays an important role in cell cycle progression of SMCs.

Animals↗
PubMed1992

Haemagglutination by parvovirus B19.

Human parvovirus B19 is a member of the autonomous parvoviridae but in contrast to other members of the genus has not been shown to agglutinate red blood cells. We now report that the virus agglutinates red cells of primate origin, though with plasma-derived virus this activity is masked by the presence of an IgM-like inhibitor. This observation is consistent with the presence on the erythroid precursor target cell of a specific receptor for parvovirus B19.

Animals↗
PubMed1992

Prokaryotic expression of a VP1 polypeptide antigen for diagnosis by a human parvovirus B19 antibody enzyme immunoassay.

To produce parvovirus B19 antigen for diagnostic purposes, partially overlapping segments covering the genes encoding the viral structural proteins VP1 and VP2 were cloned into expression vectors. The constructs were induced in Escherichia coli, resulting in the expression of beta-galactosidase fusion proteins. In immunoblotting experiments with sera from patients with erythema infectiosum, immunoglobulin G (IgG) and IgM antibodies bound to a single polypeptide of 235 amino acids at the N terminus of VP1. The DNA fragment encoding this polypeptide was amplified by the polymerase chain reaction and cloned into an expression vector. The viral capsid antigen expressed in E. coli was purified by preparative agarose gel electrophoresis and used in IgG and IgM solid-phase enzyme immunoassays. Comparison with reference gamma- and mu-capture radioimmunoassays using whole virus antigen showed that these antibody tests are suitable for the serodiagnosis of human infections caused by parvovirus B19.

Antibodies, Viral↗