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Biomedical subjects

A Liss

Publications and source records attributed to A Liss.

At least 19 recordsLinked to original sources
PubMed2001

The chicken RelB transcription factor has transactivation sequences and a tissue-specific expression pattern that are distinct from mammalian RelB.

Rel/NF-kappaB proteins are eukaryotic transcription factors that control the expression of genes involved in a large variety of cellular processes. Rel proteins share a highly conserved DNA-binding/dimerization domain called the Rel Homology (RH) domain. We have constructed and characterized a composite cDNA encoding most of the chicken RelB transcription factor. The predicted chicken RelB protein has a high degree of sequence similarity to other vertebrate RelB proteins within the RH domain, but is much less conserved outside this domain. Chicken RelB does not bind DNA as a homodimer, but forms DNA-binding heterodimers with NF-kappaB p50 or p52. Overexpressed chicken RelB localizes to the nucleus in chicken embryo fibroblasts, and the nonconserved C-terminal sequences of chicken RelB contain a transactivation domain that functions in chicken and mouse fibroblasts. Thus, chicken RelB has functional properties similar to other vertebrate RelB proteins. However, Western blotting of diverse chicken tissues indicates that chicken RelB is more widely expressed than mammalian RelB.

Active Transport, Cell Nucleus↗
PubMed2001

One manufacturer's approach to using nucleic acid testing for enhanced plasma-product safety.

Source plasma must contain the lowest possible pathogen bioburden so as to minimize the stress placed on subsequent viral reduction steps. Differences exist between European and US criteria for developing assays used to detect these viral pathogens. The approach used by 1 plasma-product manufacturer is described here. By adding polymerase chain reaction (PCR) detection techniques for various viral pathogens (including human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus) to the plasma screening process, this manufacturer maximizes the use of cutting-edge technology for plasma product safety while satisfying both European and US criteria and requirements for this process. The protocol begins with maxipool testing and eventually identifies any specific donor plasma that might be positive in the contributing minipools. The goal is to identify reactive donors for possible periodic monitoring and to use only nonreactive donations to continue producing a particular plasma product. Controversy surrounding the use of PCR to screen emerging organisms of questionable pathogenicity or known organisms that are of minimal pathogenicity for most of the population is also discussed, and possible solutions to this debate are provided.

DNA, Viral↗
PubMed1999

Primary sensory neuron survival following targeted administration of nerve growth factor to an injured nerve.

Nerve injuries induce neurochemical changes within primary sensory neurons, including expression of neuropeptides, and a loss of a substantial proportion of the neurons may possibly be caused by a lack of neurotrophic support. In the present study the role of nerve growth factor (NGF) in preventing these changes was investigated in monkeys by giving NGF peripherally through a fibronectin (Fn) conduit. A sensory nerve (superficial radial) was transected and a gap of 5 mm was bridged with either autologous sural nerve graft (SNG), Fn, or Fn impregnated with NGF (Fn-NGF). After four months the dorsal root ganglia, that received the cutaneous afferents of the nerve, were removed and analysed by quantitative immunohistochemistry using antibodies to calcitonin gene related polypeptide (CGRP) and substance P. The percentage of immunostained cells was taken as an indication of neuronal survival. The results showed that SNG and Fn-NGF reduced the loss of CGRP positive sensory neurons compared with Fn alone. For substance P-positive neurons the differences were small with only a tendency towards reduction of neuronal death after NGF had been given, suggesting that NGF might act preferentially on a subpopulation of CGRP immunoreactive sensory neurons that do not coexist with substance P.

Animals↗
PubMed1987

Perfluorinated fatty acids alter merocyanine 540 dye binding to plasma membranes.

We have evaluated the effect of the perfluorinated fatty acids pentadecafluoro-n-octanoic acid (PFOA) and nonadecafluoro-n-decanoic acid (NDFDA) on the ability of a human B-lymphoblastoid cell line to bind the lipid-binding, membrane-impermeant, fluorescent dye merocyanine 540 (MC540). Subtoxic concentrations of perfluorinated fatty acids (0.9 mM PFOA; 0.5 mM NDFDA) greatly diminish binding of MC540 by normal plasma membranes, as determined by fluorescence flow cytometry. When perfluorinated fatty acids are added to cells at toxic or lethal concentrations (1.2 mM PFOA; 0.75 mM NDFDA), MC540 binding increases dramatically, with entrance of dye to internal membrane domains. Neither perfluorinated fatty acid molecule reduces the ability of surface immunoglobulin to migrate laterally and cap on cells. Our data suggest that perfluorinated fatty acids either interact directly with lipid binding sites for MC540, and thereby inhibit dye intercalation, or alter membrane lipid architecture and lipid packing to diminish MC540 binding. Both possibilities support a direct, physical, membrane-altering mechanism for perfluorinated fatty acid toxicity on mammalian cells.

Blood Physiological Phenomena↗
PubMed1987

Enzymological features of aromatic amino acid biosynthesis reflect the phylogeny of mycoplasmas.

Acholeplasma laidlawii possesses a biochemical pathway for tyrosine and phenylalanine biosynthesis, while Mycoplasma iowae and Mycoplasma gallinarum do not. The detection of 7-phospho-2-dehydro-3-deoxy-D-arabino-heptonate (DAHP) synthase (EC 4.1.2.15), dehydro-shikimate reductase (EC 1.1.1.25) and 3-enol-pyruvoylshikimate-5-phosphate synthase (EC 2.5.1.19) activities in cell-free extracts established the presence in A. laidlawii of a functional shikimate pathway. L-Phenylalanine synthesis occurs solely through the phenylpyruvate route via prephenate dehydratase (EC 4.2.1.51), no arogenate dehydratase activity being found. Although arogenate dehydrogenase was detected, L-tyrosine synthesis appears to occur mainly through the 4-hydroxyphenylpyruvate route, via prephenate dehydrogenase (EC 1.3.1.12), which utilized NAD+ as a preferred coenzyme substrate. L-Tyrosine was found to be the key regulatory molecule governing aromatic biosynthesis. DAHP synthase was feedback inhibited by L-tyrosine, but not by L-phenylalanine or L-tryptophan; L-tyrosine was a potent feedback inhibitor of prephenate dehydrogenase and an allosteric activator of prephenate dehydratase. Chorismate mutase (EC 5.4.99.5) was sensitive to product inhibition by prephenate. Prephenate dehydratase was feedback inhibited by L-phenylalanine. It was also activated by hydrophobic amino acids (L-valine, L-isoleucine and L-methionine), similar to results previously found in a number of other genera that share the Gram-positive line of phylogenetic descent. Aromatic-pathway-encoded cistrons present in saprophytic large-genome mycoplasmas may have been eliminated in the parasitic small-genome mycoplasmas.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMed1987

Cytotoxic and cytolytic activity of nonadecafluoro-n-decanoic acid on Acholeplasma laidlawii.

We studied the interactions between the perfluorinated fatty acid nonadecafluoro-n-decanoic acid (NDFDA) and the cell wall-less procaryote Acholeplasma laidlawii, which were cultured in an identical medium base but with different serum supplements. When grown in mycoplasma media supplemented with PPLO serum fraction (Difco Laboratories, Detroit, Mich.), A. laidlawii was rapidly killed by low concentrations of toxicant (less than 1.0 mM). At higher concentrations (greater than 10 mM), NDFDA treatment appeared to lyse cells. A. laidlawii cells grown in horse serum-supplemented mycoplasma media were both killed and lysed at the same NDFDA concentration (greater than 10 mM). These data suggest that this perfluorinated fatty acid can be cytotoxic and cytolytic to mycoplasmas. Changes in active concentrations occurred in parallel with changes in growth medium serum supplementation, which is known to alter mycoplasma membrane composition. We propose that NDFDA interacts with the membranes of A. laidlawii cells, resulting in cell death or cell lysis or both.

Acholeplasma laidlawii↗
PubMed1987

Isolation of a virus from Mycoplasma pulmonis.

A virus designated mycoplasma virus P1 has been isolated from Mycoplasma pulmonis. The virus infects M. pulmonis strain UAB 6510, and a plaque-forming unit assay has been developed. P1 has a tailed, polyhedral morphology with a head diameter of about 28 nm. Nucleic acid isolated from crude preparations of P1 virus contains double-stranded RNA, suggesting that P1 may be the first example of an RNA-containing mycoplasma virus.

Bacteriophages↗
PubMed1986

Toxicity of perfluorinated fatty acids for human and murine B cell lines.

The toxicity of two perfluorinated fatty acids, penta decafluoro-n-octanoic acid (PFOA) and nonadecafluoro-n-decanoic acid (NDFDA), on three mammalian B cell lines was evaluated. Cells were exposed to the perfluorinated molecules for either 24 or 48 hr under a variety of culture conditions. Immunoglobulin secretion and surface membrane expression were unaffected by both PFOA and NDFDA at sublethal concentrations. Lethal effects of PFOA and NDFDA are diminished by either lowering culture temperature (37 to 20 degrees C) or including fetal bovine serum or human serum albumin in media. At lethal concentrations, both PFOA and NDFDA possess detergent activity since they can release IgM in soluble form from a cell line that does not secrete immunoglobulins, and brief exposure (15 min) to 1-2 mM of both perfluorinated fatty acids results in solubilization of F4 cells equivalent to the anionic detergent deoxycholic acid. Our data suggest that at subtoxic concentrations, neither PFOA nor NDFDA alters expression or secretion of a differentiated gene product (IgM). At lethal levels, both chemicals cause increased solubilization of proteins from lymphoblastoid cell lines.

Animals↗
PubMed1985

Acholeplasma laidlawii cells acutely and chronically infected with group 1 acholeplasmavirus.

Interactions between group 1 acholeplasmaviruses and their host cells were studied. Acutely infected, chronically infected and uninfected cultures of Acholeplasma laidlawii strain JA1 were compared by their growth in broth and on agar, by the sensitivities of the uninfected and chronically infected cells to representatives of each of the three groups of acholeplasmaviruses, and by their SDS-PAGE polypeptide profiles. Acutely infected cells resembled uninfected cells by these criteria, except for the fact that progeny virus was being released. Two types of chronically infected cells were found:rapid growers (the same doubling time as uninfected cells) and slow growers. The latter resembled uninfected cells, except for their slower growth and low-level release of virus, and the former was resistant to group 1 viruses and had a unique polypeptide profile. These biological characterizations help to establish the non-lytic, non-cytocidal cycle of the group 1 acholeplasmaviruses.

Acholeplasma laidlawii↗
PubMed1983

Characterization of the enveloped plasmavirus MVL2 after propagation on three Acholeplasma laidlawii hosts.

Plasmavirus MVL2 was propagated on three Acholeplasma laidlawii strains, JA1, S2, or BC1-13. Previously reported host-controlled modification (HCM) of MVL2, as reflected by changes in plating efficiency, was observed. Adsorption rates and one-step growth curves varied according to host used. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the three MVL2 populations revealed differences in polypeptide profiles.

Acholeplasma laidlawii↗
PubMed1983

Colonial opacity variation in Mycoplasma pulmonis.

Colonial size and opacity variation were observed in four independently isolated strains of the murine pathogen Mycoplasma pulmonis. Selecting colonial opacity variants of similar size, we identified opaque and transparent stable variants. Opaque colony-derived broth cultures shed transparent colonies at a rate of about 1.2 X 10(-8) per CFU per generation. The reverse conversion was about two orders of magnitude less frequent. Appearance of opacity and plating efficiency of each pure culture were altered by changing the serum source used to supplement the growth medium. Horse or sheep serum was most efficient at accentuating visualization of opacity differences. Fetal bovine serum was least efficient. In two M. pulmonis strains, each opacity variant showed a distinctive polypeptide profile, as displayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the same strains, distinctive intrastrain differences were found by agarose gel electrophoresis to display the DNA fragments produced after digestion by several endonucleases. Each pure culture variant retained these differences in DNA even when grown in a medium supplemented with a serum which did not accentuate visualization of the opacity phenotype. Characterization of variants in 30 other M. pulmonis strains is in progress.

DNA Restriction Enzymes↗
PubMed1980

Membrane composition and virus susceptibility of Acholeplasma laidlawii.

The membrane composition of 11 strains of Acholeplasma laidlawii, including three strains persistently infected with mycoplasmaviruses MVL51, MVL2, and MVL3, was studied and correlated with mycoplasmavirus sensitivity. Membranes of the strains had similiar sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, and all strains were inhibited by an antiserum produced against membranes from one of the strains. The amounts of integral membrane proteins solubilized by the nonionic detergent Tween 20 differed considerably. Therefore, characteristic crossed immunoelectrophoresis patterns were obtained for each strain. Strains persistently infected with MVL2 and MVL3 were notably different from the noninfected host. The ability to propagate any of the viruses was not correlated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis or crossed immunoelectrophoresis patterns. The persistently infected strains had a characteristic lipid composition. MVL51-resistant strains, including a resistant clone selected from a sensitive strain, were characterized by a large monoglucosyldiglyceride/diglucosyldiglyceride ratio and trace amounts of diphosphatidylglyceol (as opposed to the sensitive strains). Differences in lipid composition in A. laidlawii seem to affect the relationship between cells and viruses.

Acholeplasma laidlawii↗