Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several antitumor substances that effectively inhibited the growth of ascites and solid tumor cells transplanted in mice were isolated from pine cone NaOH extract by acid- and ethanol-precipitation. These antitumor substances were also potent antiviral agents against human immunodeficiency virus, herpes simplex virus and influenza virus; they induced antimicrobial activity against Staphylococcal aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans, and induced antiparasite activity against Hymenolepis nana in mice. Chemical analysis of these substances by IR, UV, NMR, ESR and partition chromatography on cellulose-TLC plate disclosed that they had lignin-related structures complexed with sugars or polysaccharides. Chlorinated decomposition of the lignin portion significantly reduced their antiviral activity. In agreement with this, the antiviral activity of synthesized lignins prepared by polymerization of phenylpropanoid precursors was comparable to that of the undecomposed counterparts of the pine cone extract. Acid hydrolysis of the polysaccharide portion significantly reduced the ability of the substances to induce antitumor and antimicrobial activities in mice. With an appropriate eliciting agent, intravenous administration of natural lignified substances transiently induced endogenous production of a cytotoxic factor (possibly tumor necrosis factor) in normal mice. Their priming activity was significantly higher than that of their component units or degradation products. These data suggest the importance of conjugating lignins with polysaccharides for in vivo expression of various kinds of immunopotentiating activity. As possible explanations for their induction of a variety of immunopotentiating activities, these natural and synthetic lignins stimulated macrophage NBT-reducing activity, polymorphonuclear cell (PMN) iodination and splenocyte DNA synthesis and inhibited poly (ADP-ribose) glycohydrolase, RNA-dependent DNA polymerase (reverse transcriptase) and RNA-dependent RNA polymerase activities.
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PMID:Antitumor, antiviral and immunopotentiating activities of pine cone extracts: potential medicinal efficacy of natural and synthetic lignin-related materials (review). 164 35

FK-506 (Tacrolimus) has been shown to block T cell proliferation in vitro by inhibiting the generation of several lymphokines, especially interleukin (IL)-2, but little direct evidence is available to support the view that the immunosuppressive effects of FK-506 in vivo are mediated by a similar inhibition of lymphokine cascade. To investigate the mechanisms of FK-506-induced immunosuppression, the effects of FK-506 on cell-mediated immunity to Hymenolepis nana were examined in mice. FK-506 administration into BALB/c mice daily at a dose of 10.0 mg/kg (but not 5.0 mg/kg) for 5 days caused suppression of protective immunity against H. nana challenge infection. During the infection of mice with H. nana, IL-2 and interferon (IFN)-gama were produced by mesenteric lymph node (MLN) cells with a time course corresponding to that of MLN T cell proliferation. These responses were completely suppressed by repeated administration of FK-506 for 5 days at a dose of 10.0 mg/kg/day (but not 5.0 mg/kg/day). In contrast to the effects of FK-506 on IL-2 and IFN-gamma productions in MLN, IL-1 and tumor necrosis factor-alpha in the intestinal wall, which were enhanced by H. nana infection, were not completely decreased as a result of 10.0 mg/kg FK-506 treatment. The reverse transcriptase-PCR revealed complete inhibition of IL-2 and IFN-gamma mRNA expression on mesenteric L3T4+ cells that were induced by H. nana infection, when mice were given 10.0 mg/kg/day FK-506 for 5 days. These results strongly suggest that FK-506 affects cell-mediated immunity in vivo with mechanisms similar to those observed in vitro.
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PMID:Mode of action of FK-506 on protective immunity to Hymenolepis nana in mice. 898 61