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Biomedical subjects

I Sela

Publications and source records attributed to I Sela.

At least 37 records · Page 2Linked to original sources
PubMed1985

Plant oligoadenylates: enzymatic synthesis, isolation, and biological activities.

An enzyme that converts [3H, 32P]ATP, with a 3H:32P ratio of 1:1, to oligoadenylates with the same 3H:32P ratio was increased in plants following treatment with human leukocyte interferon or plant antiviral factor or inoculation with tobacco mosaic virus. The enzyme was extracted from tobacco leaves, callus tissue cultures, or cell suspension cultures. The enzyme, a putative plant oligoadenylate synthetase, was immobilized on poly(rI) . poly(rC)-agarose columns and converted ATP into plant oligoadenylates. These oligoadenylates were displaced from DEAE-cellulose columns with 350 mM KCl buffer, dialyzed, and further purified by high-performance liquid chromatography (HPLC) and DEAE-cellulose gradient chromatography. In all steps of purification, the ratio of 3H:32P in the oligoadenylates remained 1:1. The plant oligoadenylates isolated by displacement with 350 mM KCl had a molecular weight greater than 1000. The plant oligoadenylates had charges of 5- and 6-. HPLC resolved five peaks, three of which inhibited protein synthesis in reticulocyte and wheat germ systems. Partial structural elucidation of the plant oligoadenylates has been determined by enzymatic and chemical treatments. An adenylate with a 3',5'-phosphodiester and/or a pyrophosphoryl linkage with either 3'- or 5'-terminal phosphates is postulated on the basis of treatment of the oligoadenylates with T2 RNase, snake venom phosphodiesterase, and bacterial alkaline phosphatase and acid and alkaline hydrolyses. The plant oligoadenylates at 8 X 10(-7) M inhibit protein synthesis by 75% in lysates from rabbit reticulocytes and 45% in wheat germ cell-free systems.(ABSTRACT TRUNCATED AT 250 WORDS)

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Antiviral activity of natural and recombinant human leukocyte interferons in tobacco protoplasts.

Several purified species of human leukocyte interferon, including recombinant interferons, inhibit the multiplication of tobacco mosaic virus (TMV) in tobacco protoplasts derived from various cultivars. Viral RNA accumulation was determined by dot-blot hybridization to specific cDNA probes, and virus antigen was determined serologically. Interferon apparently inhibited both TMV-RNA replication and its expression into coat protein. However, these effects were of limited duration. Maximum effect was obtained when interferon was applied to the cells either prior to inoculation or within the first hour after inoculation. Antibodies to interferon abolished its antiviral activity in protoplasts. Tobacco protoplasts were about 1000 times more responsive to interferon than the reference animal viral-cell system and showed an "antiviral state" at a ratio of 1 molecule of interferon per cell.

DNA Replication↗
PubMed1984

5'-dephosphorylated 2',5'-adenylate trimer and its analogs. Inhibition of tobacco mosaic virus replication in tobacco mosaic virus-infected leaf discs, protoplasts, and intact tobacco plants.

The effect of the 5'-dephosphorylated 2',5'-adenylate trimer and its 2',5'-trimer core analogs on the inhibition of tobacco mosaic virus (TMV) replication was determined in tobacco leaf discs, protoplasts, and whole tobacco plants, using infectivity tests and enzyme-linked immunosorbent assays. A structure-activity-metabolic stability-toxicity analysis of the 2',5'-adenylate trimer core molecule in TMV-infected Nicotiana glutinosa was determined. Modification at either the 6-amino position of the adenylate residues (i.e. inosinate trimer core) or at the 2' terminus (i.e. A-A-ara-A or A-A-Tu) inhibited replication of TMV. Modification of the 3'-hydroxyl group of the adenylate residues to 3-deoxyribose (i.e. the 2',5'-cordycepin trimer core) inhibited TMV replication better than the 2',5'-adenylate trimer core molecule. With enzyme-linked immunosorbent assays, there was complete inhibition of TMV replication by 200 nM 2',5'-adenylate trimer core for 60 h and by 200 nM 2',5'-cordycepin trimer core for 96 h. The amount of 2',5'-oligonucleotides associated with the leaves was determined using 2',5'-[3H]cordycepin trimer core; 1 X 10(-12) mol/cm2 of plant leaves inhibited TMV replication by 99%. No 2',5'-phosphodiesterase activity was detected in TMV-infected and noninfected leaf extracts. Therefore, the 2',5'-trimer cores were potent inhibitors of TMV replication at nanomolar concentrations, i.e. at 1000-fold lower concentration than that required in mammalian systems.

Adenosine↗
PubMed1982

Multiplication of tobacco mosaic virus in tobacco leaf disks is inhibited by (2'-5) oligoadenylate.

The oligonucleotide (2'-5') oligoadenylate that is induced in interferon-treated animal cells protects plant tissue from infection by the tobacco mosaic virus. This inhibition of virus multiplication was obtained at concentrations comparable to those affecting protein synthesis and antiviral activities in animal cells. After treatment with (2'-5') oligoadenylate, the multiplicability of tobacco mosaic virus was reduced by 80 to 90 percent as measured by enzyme-linked immunosorbent assay. These results, along with the observation that human interferon protects tobacco tissue from infection by tobacco mosaic virus, indicate that plants and animals may have a common pathway for virus resistance.

Adenine Nucleotides↗
PubMed1982

Human interferons protect plants from virus infection.

Unfractionated human leukocyte interferon, as well as highly purified subspecies of this interferon, and a purified recombinant of human leukocyte interferon produced in bacteria are active in suppressing multiplicability of tobacco mosaic virus in tobacco leaf discs. Human fibroblast interferon exhibits diverse levels of antiviral activity against tobacco mosaic virus but becomes as active as human leukocyte interferon upon incubation with glycosidases. The effect of interferon is reversible; normal multiplication of tobacco mosaic virus resumes upon removal of interferon.

Enzyme-Linked Immunosorbent Assay↗
PubMed1980

Ultrastructural studies of partially solubilized polyhedral inclusion bodies of a baculovirus infecting Spodoptera littoralis (Boisduval).

Polyhedra were solubilized under mild alkaline conditions and their structure during solubilization was studied by transmission and scanning electron microscopy. Some new structural features such as the extent of virion-packing in a polyhedral body and the cavities remaining in polyhedral bodies following the release of the occluded particles are demonstrated. Some other, previously reported features, such as the presence of polyhedral "membrane" and the crystalline array of the soluble polyhedral protein are accentuated at the various stages of solubilization.

Animals↗
PubMed1977

Further studies on the biology of an antiviral factor (AVF) from virus-infected plants and its association with the N-gene of Nicotiana species.

The antiviral factor (AVF) from virus-infected plants, purified on polyacrylamide gels, could be labelled with radioactive phosphorus and its activity could be eluted from the gels. The radioactivity and the antiviral activity were co-purified and thus co-electrophoresed; hence, the previously reported radioactive zone (Antignus, Sela & Harpaz, 1975) can be regarded as AVF. The production of AVF requires both the presence of the N-gene in the plant as well as virus infection. AVF production is inhibited by actinomycin D, but its activity is not affected by this drug. AVF production is correlated in time with the development of virus resistance in a local-lesion host. AVF inhibits TMV multiplication in infected leaves and suppresses virus synthesis almost totally in a local-lesion host. Some AVF is also produced when Nicotiana glutinosa L. is infected with a non-localized virus, but to a much lesser extent and at a later stage of infection. The production of AVF in N. glutinosa is not blocked at 30 degrees C. even though TMV is no longer localized at this temperature.

Dactinomycin↗