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At least 19 recordsLinked to original sources
PubMed1976

Preparation and enzymatic properties of subtilisin Novo chemically attached to soluble DEAE-dextran and insoluble DEAE-sephadex.

Analogous soluble and insoluble derivatives of subtilisin Novo (EC 3.4.21.14) were prepared by coupling the enzyme to CNBr-activated DEAE-dextran and DEAE-Sephadex, respectively. The DEAE-dextran-subtilisin displayed pH optima and Km values for ester hydrolysis similar to subtilisin, whereas the pH versus activity profiles obtained with DEAE-Sephadex-subtilisin were shifter towards the alkaline pH region and the Km values were increased. Compared with subtilisin, DEAE-dextran-subtilisin showed a 40-65% reduction of kcat for hydrolysis of N-acetyl-L-tyrosine ethyl ester, p-tosyl-L-arginine methyl ester and benzyloxycarbonyl-glycyl-L-tyrosinamide and its maximum velocities for digestion of casein and clupein also amounted to 40-60% of the subtilisin values. With Deae-sephadex-subtilisin, in contrast, the maximum velocity of hydrolysis decreased to a greater extent for polypeptide substrates compared to ester substrates. The present results indicate that the chemical nature of a support can effect intrinsic properties of a matrix-bound enzyme in addition to the steric and diffusional effects usually observed with polymer-attached enzymes.

Caseins↗
PubMed1975

Chalone-like effect abrogated by dextran sulphate and heparin polyanion pretreatment of target cells.

Chalone prepared from primary BALB/c mouse embryo fibroblasts caused a 33% reduction in incorporation of tritiated thymidine in the cultures of the second in vitro passage of BALB/c embryo fibroblasts, whereas chalone prepared from thymus, skin and spleen was without effect. Pretreatment of BALB/c secondary fibroblasts with the polyanions dextran sulphate and heparin abrogated the chalone effect. The polycations DEAE-dextran and polybrene were without effect. The effect of incubation with the dextran sulphate polyanion was reversed when followed by incubation with DEAE-dextran polycation.

Animals↗
PubMed1975

Demonstration of infectious DNA in transformed cells. II. Characterization of uptake of SV40-transformed mouse cell DNA by simian cells.

The initial steps in the DNA-transfer, or transfection, method of virus rescue were characterized using primary green monkey (GMK) cells exposed to SV40-transformed mouse (SV-3T3) cell DNA in the presence of 1 mg/ml DEAE-dextran. When large amounts (10-50mug) of high molecular weight DNA (greater than 10(7) daltons) were inoculated onto 10(6) GMK cells, usually less than 1 mug became cell-associated. DNA fragmented to a size of 1-3 X 10(6) daltons was bound more efficiently by the recipient cells, but generally only 5-10 per cent of the inoculum (representing 1-4 mug) was taken up. Approximately 50 per cent of the cell-associated DNA had penetrated to a DNase-resistant state by the end of the 30-minute incubation period. The effect of the size of thr transformed cell DNA molecule on the recovery of SV40 in transfection experiments was investigated. The trend appeared to be that rescue was more efficient with the larger molecular weight samples.

Animals↗
PubMed1975

Are cytotoxicity and interferon inducing activity of poly(I).poly(C) invariably linked in interferon-treated L cells.

Interferon-treated L cells exhibit a specific enhanced susceptibility to the cytotoxic and interferon inducing activities of double-stranded RNAs such as poly(1). poly(C). These activities remained closely linked through widely varying assay conditions, involving, for example, different time anddosage schedules of poly(1). poly (C),suggesting that there is at least one common step in the mechanisms leading to interferon formation and toxicity in interferon-primed cells exposed to poly(1).poly(C). However, some procedures such as addition of metabolic inhibitors (actinomycin D, cycloheximide) and repeated administration of poly(1).poly(C) suppressed the interferon inducing capacity of poly(1).poly(C) without a concomitant decrease of toxicity. Other procedures such as brief treatment of the cells with interferon or DEAE-dextran permitted full expression of the interferon inducing activity of poly(1).poly(C) without any sign of toxicity. The latter results suggest that the mechanisms underlying interferon production and toxicity of poly(1).poly(C) in interferon-treated L cells diverge from a certain point onward.

Animals↗
PubMed1979

[Comparative antiviral and interferonogenic activity of natural and synthetic interferon inducers in vitro and in vivo].

Biological activities of the RNA replicative form of phage f2, a natural interferon inductor and poly-I -- poly-C, a synthetic polyribonucleotide complex were studied comparatively. Differences in the comparative interferonogenic and antiviral activity of the inductors were as dependent on the type of the cell system. It was shown that DEAE-dextran increased the interferon-inducing activity of RFf2 in the cell culture by 4 to 8 times. The dynamics of the interferonogenic and antiviral activity of RFf2 in the L-929 cell culture was studied. Interferon appeared in the culture fluid in 6--8 hours and reached its maximum titers (128 IU50/ml) by the 24th hour, the maximum protection of the cells being also developed by the 12th--24th hour, reaching on an average 51 g PFU/ml. It was shown in the experiments with green marmosets that administration of RFf2 in the form of aerosol in a dose of 2.3 mg/kg induced interferon production in the blood serum the titers of which amounted to 80--160 IU50/ml 24 hours after the administration.

Animals↗
PubMed1976

The effect of combination of different inducers on the refractory state in interferon production.

A second injection of 100 mug poly (rI) poly (rC) per mouse at 6 and 24 hours after the first injection stimulated additional peaks of interferon production. The dynamics of the process of accumulation and disappearance of interferon was similar to that after a single injection of poly (rI). poly (rC). Injection of the above dose 12 hours after the first injection induced no interferon production as it apparently coincided with the refractory state in interferon production. After pretreatment of poly (rI) poly (rC) with DEAE-dextran, the refractory phase occurred in 6 hours. Inoculation of Venezuelan equine encephalomyelitis virus as a second interferon inducer resulted in a repeated stimulation of interferon production both in animals and in tissue culture; however, interferon titres in this case were low. The use of an inactivated virus as a second interferon inducer stimulated interferon production to higher titres (5120 IU/ml) than a single injection of DEAE-dextran-treated poly (rI). poly (rC). It is possible that a combined use of poly (rI). poly (rC) and noninfectious virus as a second interferon inducer eliminates the development of the refractory state.

Animals↗
PubMed1975

Cellular adsorption function of the sialoglycoprotein of vesicular stomatitis virus and its neuraminic acid.

Exposure of vesicular stomatitis (VS) virions to neuraminidase resulted in loss of their ability to agglutinate goose erythrocytes and to attach to L cells concomitant with hydrolysis of sialic acid. These viral adsorptive functions were also destroyed by tryspsinization. Sialyl transferase resialylation in vitro of neuraminidase-treated VS virions restored their hamagglutinating and adsorptive functions almost to original levels. Erythrocyte and L cell receptors for attachment of VS virions were blocked by fully sialylated fetuin and by VS viral sialoglycopeptides. Smaller VS viral glycopeptides generated by extensive trypsinization were less effective inhibitors of hemagglutination than were larger glycopeptides; neuraminic acid and neuraminosyl lactose had no capacity to inhibit hamagglutination or adsorption of virus to L cells. These data suggest that cellular receptors for viral adsorption recognize sialoglycopeptides of a certain size. Neuraminidase desialylation did not significantly alter the isoelectric point of VS virions. Cells exposed to DEAE-dextran, trypsin, or neuraminidase showed significantly increased capacity to attach fully sialylated but not desialylated VS virions. Neuraminidase desialylation of L cells, Chinese hamster ovary cells, and Madin-Darby bovine kidney cells resulted in enhanced susceptibility to plaque formation by VS virus.

Adsorption↗
PubMed1975

Enhancement of interferon production in vitro: a property of tilorone-poly rL:rC/DEAE-Dextran.

Tilorone and Poly rI:rC, in the presence of DEAE-dextran, were found to exhibit a marked synergism with respect to the induction of interferon in L929 and primary mouse embryo fibroblasts, but not human foreskin fibroblasts, in cell cultures. The degree of synergism was proportional to the concentrations of tilorone and Poly rI:rC and was influenced by the times of addition of the compounds relative to each other.

Animals↗
PubMed1976

Development of an in vitro infectivity assay for the C-type bovine leukemia virus.

The ability of the bovine C-type leukemia virus to induce syncytia formation in monolayer cell cultures has been used to develop a specific and simple infectivity assay for the virus. Using bovine embryonic spleen cells or human diploid embryonic lung cells as indicator cells, the results of the assay can be evaluated in 4 to 6 or 6 to 8 days, respectively. Pretreatment of the indicator cells with DEAE-dextran greatly increases the sensitivity of the assay. The assay is quantitative and can be applied as a direct method for the identification of bovine C-type leukemia virus-infected animals; it also provides a simple, and sensitive procedure for the detection and titration of virus-neutralizing antibodies.

Antibodies, Viral↗
PubMed1977

Effects of carrageenan on immune responses. Studies on the macrophage dependency of various antigens after treatment with carrageenan.

Carrageenan, a sulfated polygalactose having macrophage toxic properties, elicited a marked suppression of IgM response to T cell-dependent antigens such as sheep red blood cells (SRBC), dinitrophenylated bovine serum gamma-globulin (DNP-BGG), and trinitrophenylated concanavalin A (TNP-Con A). In contrast, carrageenan did not inhibit antibody responses to such T cell-independent antigens as trinitrophenylated DEAE-dextran (TNP-DEAE-dextran), trinitrophenylated polyvinyl pyrrolidone(TNP-PVP), and trinitrophenylated Ficoll (TNP-Ficoll). Compared to total spleen cells, spleen cells from which macrophages had been removed by adhesion to plastic Petri dishes had less effect on the production of antibody against T cell-dependent antigens, but no change or a rather stimulated effect was observed in in vitro antibiody synthesis against T cell-independent antigens. These results strongly suggest that macrophages are involved in antibody responses to T cell-dependent antigens but not in those to T cell-independent antigens. However, the antibody response to trinitrophenylated lipopolysaccharide (TNP-LPS), a T cell-independent antigen, was inhibited by carrageenan treatment, suggesting that the response is macrophage dependent. Moreover, antibody response to higher doses of dinitrophenylated phytohemagglutinin (DNP-PHA), a T cell-dependent antigen, was shown to be macrophage independent by carrageenan treatment, although the antibody response to low doses of the antigen was macrophage dependent. Considering all these results, carrageenan treatment seems to be a very useful method to determine whether immune response to various antigens are macrophage dependent or not.

Animals↗
PubMed1976

Further studies of the physical and metabolic properties of foot-and-mouth disease virus temperature-sensitive mutants.

Three temperature-sensitive (ts) mutants of foot-and-mouth disease virus were classified as ribonucleic acid negative and as belonging to the same complementation group when measured by virus yields and [3H] uridine incorporation in paired, mixed infections at the nonpermissive temperature (38.5C). Mutant ts-22, the only mutant able to produce plaques at 38.5 C, was more sensitive to acid than were the parental wild-type or other mutant viruses. Diethylaminoethyl-dextran did not enhance the plaque-forming ability of the mutant viruses at 38.5C. All of the viruses inhibited host cell protein syntehsis at both permissive (33C) and nonpermissive (38.5C) temperatures.

Aphthovirus↗
PubMed1975

Restitution of infectivity to spikeless vesicular stomatitis virus by solubilized viral components.

Noninfectious spikeless particles have been obtained from vesicular stomatitis virus (VSV, Indiana serotype) by bromelain or Pronase treatment. They lack the viral glycoprotein (G) but contain all the other viral components (RNA, lipid, and other structural proteins). Triton-solubilized VSV-Indiana glycoprotein preparations, containing the viral G protein as well as lipids (including phospholipids), have been extracted from whole virus preparations, freed from the majority of the detergent, and used to restore infectivity to spikeless VSV. The infectivity of such particles has been found to be enhanced by poly-L-ornithine but inhibited by Trition or homologous antiserum pretreatment. Heat-denatured glycoprotein preparations were not effective in restoring the infectivity to spikeless VSV. Heterologous glycoprotein preparations from the serologically distinct VSV-New Jersey serotype were equally capable of making infectious entities with VSV-Indiana spikeless particles, and the infectivity of these structures was inhibited by VSV-New Jersey antiserum but not by VSV-Indiana antiserum. Purified, detergent-free glycoprotein selectively solubilized from VSV-Indiana by the dialyzable detergent, octylglucoside, also restored infectivity of spikeless virions of VSV-Indiana and VSV-New Jersey.

Animals↗