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Biomedical subjects

G A Quash

Publications and source records attributed to G A Quash.

At least 19 recordsLinked to original sources
PubMed1996

Murine cytomegalovirus inactivated by sodium periodate is innocuous and immunogenic in mice and protects them against death and infection.

Sodium periodate (10 mM, 4 degrees C) inactivated murine cytomegalovirus (MCMV) very rapidly (loss of 2 to 3 log of viral infectivity per minute). Periodate-treated MCMV (PI-MCMV) was shown to be innocuous in mice, as determined by the inability of the virus to replicate. PI-MCMV induced a strong humoral immune response, with a high level of neutralizing antibodies. Mice immunized with PI-MCMV were protected against death and infection, when a lethal challenge with the virulent virus was administered 3 weeks after immunization and from death but not infection when virulent virus was administered at 3 months. Finally, no reactivation of potentially latent challenge virus (sublethal dose at 3 weeks) was observed in animals immunosuppressed at 6 months after immunization. Taken together, these results suggest that periodate could serve as an inactivating agent to prepare killed vaccines.

Animals↗
PubMed1990

Aldehyde dehydrogenase activity in xenografted human brain tumor in nude mice. Preliminary results in human glioma biopsies.

ALDH activity measured fluorimetrically using a high concentration of aliphatic aldehyde as substrate was studied in human glioblastomas grafted in nude mice. Compared with normal brain, ALDH activity is significantly increased in malignant glioma tissue, especially in the cytosolic subcellular fraction. Correlatively, in comparison with normal brain tissue, MDA levels were significantly reduced in whole homogenates and in cytosolic fractions of xenografted glioblastoma tissue. Preliminary results concerning human malignant glioma biopsies are in good agreement with our experimental data. In view of previous works, these results suggest a relationship between alterations in ALDH iso-enzymes activities and cytosolic aldehyde concentrations with respect to normal or tumoral cell growth.

Aldehyde Dehydrogenase↗
PubMed1986

Catalytic properties of the A/H3N2 influenza neuraminidases: influence of antigenic variations.

Antigenic variation of the neuraminidase of A/H3N2 influenza viruses may be associated with modifications of the catalytic activity of this enzyme. We observed this phenomenon when studying two prototype strains: A/Hong Kong/1/68 (X31K) and A/Bangkok/2/79. For the neuraminidases of these strains, we determined their substrate specificity, initial velocity, optimum pH, optimum temperature, heat inactivation and Michaelis constants and their inactivation by chemical group-specific reagents. In order to examine the relationship between antigenic variation and enzyme activity of the influenza neuraminidases, three X31K monoclonal variants were selected using anti-neuraminidase monoclonal antibodies. Two of these (X31/NC92 and X31/NC56) were modified at a single neuraminidase epitope, and the third one (X31/NC92/NC56) at two epitopes. The neuraminidase activity of the monoclonal variants was analysed and compared to that of the prototype strains. Compared to A/Hong Kong/1/68, the A/Bangkok/2/79 strain neuraminidase was more susceptible to inactivation by physical (pH, temperature) and chemical agents [urea, dithiothreitol, 1-ethyl-3-(3-dimethylaminopropyl carbodiimide), iodoacetamide, acetic anhydride, 2,3-butanedione] and showed a twofold lower substrate affinity for N-acetylneuraminlactose. The neuraminidase activity of the monoclonal variants of X31K became more susceptible to inactivation by both physical and chemical agents than the original strain and exhibited various substrate affinities. Therefore, we conclude that the enzymic properties of the structurally conserved active sites of the neuraminidase molecule may be influenced by antigenic modifications that affect the variable areas of the neuraminidase and that the degree of this enzymic variation is related to the nature and number of the modified epitope(s). A local conformational change in the neuraminidase molecule reflected as antigenic variation could be involved in modification of enzyme activity.

Antigens, Viral↗
PubMed1984

Cellular myeloperoxidase activity in human monocytes stimulated by hyposialylated immunoglobulins and rheumatoid factors.

When hyposialylated , immunoglobulins become immunogenic and tend to form aggregates. In pursuit of the possibility that hyposialylated immunoglobulins (hs-Ig) can trigger human mononuclear phagocytic cells, we have investigated the effects of such hs-Ig on the myeloperoxidase (MPO) activity of these cells. The incubation of human monocytes with aggregated hs-Ig leads to the decrease of intracellular MPO activity. This decrease is dependent on the incubation time, on the amount of hs-Ig added, and on the degree of aggregation. Incubation with unaggregated hs-Ig has a similar effect, thus providing evidence that the loss of sialic acid residues per se is enough to render these molecules capable of decreasing the MPO content of phagocytic cells. Furthermore, human rheumatoid factors, isolated from the sera of rheumatoid arthritis patients, and previously characterized as hyposailylated Ig, interact in the same way with monocytes in triggering the MPO decrease. These observations imply that hs-Ig may be considered as active stimuli in the induction of inflammatory processes, through the initiation of oxidative reactions.

Female↗
PubMed1983

Asialylated immunoglobulins and rheumatoid factors.

A covalently coupled IgG-latex reagent was instrumental in isolating rheumatoid factors (RF) from normal immunoglobulins in the sera of patients with rheumatoid arthritis. It was found that RF contained hyposialylated immunoglobulins of both IgG and IgM classes. This biochemical alteration might be relevant to understanding the etiopathogenesis of the disease.

Aged↗
PubMed1982

The differential contribution of arginase and transamidinase to ornithine biosynthesis in two achromic human melanoma cell lines.

Cellular ornithine biosynthesis could be expected to play a significant role in putrescine formation and hence in growth. Two enzymes are involved in ornithine biosynthesis: arginase and transamidinase. These enzyme activities were studied in two human melanoma cell lines differing in their Km of diamine oxidase for putrescine and in their tumorigenicity in nude mice. Arginase activity accounts for the majority of ornithine formed in the highly tumorigenic cell line, while the majority of ornithine is derived from transamidinase action in the poorly tumorigenic cell line, with concomitant formation of methyl guanidine, a potent inhibitor of diamine oxidase.

Amidinotransferases↗
PubMed1982

Secretion of immunoglobulins by human lymphocytes after infection with influenza virus.

The biosynthesis of IgM by the Epstein-Barr virus-negative RAMOS lymphoblastoid cell line infected with an influenza A virus, fowl plague virus Dobson strain (FPV-B), was investigated. The results show that FPV infection of RAMOS cells slightly inhibited overall cellular protein synthesis only at 24 h after infection, despite the synthesis of FPV-specific proteins. However, even at this time, the synthesis and secretion of IgM were not affected by virus infection. Secreted IgM contained a reduced amount of sialic acid. The quantity of the asialylated IgM increased proportionally to the amount of enzymically active neuraminidase, suggesting that the asialylation of IgM is due to the action of virus neuraminidase. No such asialylated IgM was observed in RAMOS cells infected with measles virus, which does not possess neuraminidase. These results, together with a previous observation of ours that asialylated immunoglobulins acquire an altered antigenicity, suggest that the modulation of enzyme activities in B lymphocytes in response to an exogenous aggression may lead to disturbances in the structure and in the antigenic properties of immunoglobulins.

Cell Line↗
PubMed1981

The antigenicity of asialylated IgG: its relationship to rheumatoid factor.

Native IgG of human or rabbit origin, from which terminal sialic acid is removed by immobilized neuraminidase, undergoes changes in structure and antigenicity. Such asialylated rabbit IgG's tend to agglutinate, and are immunogenic in autologous hosts. The sialic acid content of rheumatoid factor (RF) isolated from the serum of a rheumatoid patient and identified as IgG and IgM, was also found to be lower than that of normal IgG and IgM. These findings indicate that carbohydrate residues influence the secondary structure of IgG and suggest an enzymic mechanism for the genesis of RF.

Animals↗
PubMed1979

Evidence for natural antibodies (IgG) to polyamines in human sera.

Human sera contain IgGs that react with latex-putrescine spheres. Identification of the IgGs has been achieved by polyacrylamide gel electrophoresis and their reaction with peroxidase-labeled antihuman gamma-chain-specific antibodies. The inhibition of IgG fixation to latex-putrescine spheres by free spermine and putrescine provides evidence that these IgGs are specific for polyamines.

Antibody Specificity↗
PubMed1977

Nephelometric assay of antigens and antibodies with latex particles.

Antigens and antibodies covalently bound to latex particles have been used to detect specifically corresponding antibodies and antigens by nephelometry. A systematic study of factors such as wavelength, angle of observation, concentration of latex particles, and reaction time has permitted us to develop a procedure suitable for routine estimation of antigens and antibodies in the nano and picogramme range.

Antibodies↗