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Molecular modelling of tumour-promoting and non-promoting diterpene esters and molecular co-ordinates of the potent irritant resiniferatoxin.

The lowest energy conformer of seventeen diterpenes, representing five different phorbol and daphnane diterpene nuclei, has been generated. TPA possessed the highest minimum free energy of these compounds; all other compounds possessed a lower minimum free energy. Compounds based on the resiniferonol nucleus possessed the lowest minimum free energy (9.4-16.6% of that of TPA). The molecular co-ordinates of the non-promoting but potent irritant resiniferatoxin (Rx) are also reported. These studies may be important in elucidation of the biochemical mechanisms of action of diterpene esters, including an understanding of the interactions of diterpene esters with the phorbol ester binding domain of the protein kinase C isoform family.

Carcinogens↗

Gastric carcinoma promoted by alkaline reflux gastritis -- with special reference to bile and other surfactants as promoters of postoperative gastric cancer.

For reasons that are not known, the incidence of stomach cancer is declining in most countries. In contrast, cancer of the gastric remnant after partial gastrectomy for peptic ulcer disease seems to be increasing. "Stump cancer" has been claimed to be a separate disease entity and has recently been mentioned as an iatrogenic cancer. Alkaline bile reflux, dietary surfactants and maybe the abuse of tobacco are postulated as promoting or initiating agents, in causing malignant transformation of the operated as well as non-operated stomach. Variations in gastric pH, microflora and emptying rate may be of importance in the carcinogenic process. The decline in cancer incidence in the non-operated stomach has mainly been restricted to the intestinal type of cancer. Thus, it is important to note that stump cancer often is of the diffuse type. Different target cells and/or modes of carcinogen exposure may be of etiological importance in these histologically and clinically separate neoplastic diseases.

Animals↗

Beware of a new carcinogenic risk: promotion of promoters.

Restricting the evaluation of carcinogenic risk to genotoxicity or mutagenicity tests, as recently recommended by some researchers, is a hazardous operation, since the carcinogenic process involves a complex sequence of events in which no simple, necessary and sufficient condition is known for either the occurrence or non-occurrence of a cancer. None of the available tests exhibit a generalizable meaning, while none of the carcinogenic process phases should be neglected in prediction studies. In particular, ignoring promoter action and progression or proliferation, as well as targets specificity and other points, should lead to an underestimation of the actual risk.

Animals↗

The 'assembly-promoting sequence region' of microtubule-associated protein 4 failed to promote microtubule assembly.

In order to study the function of the bovine MAP4 microtubule-binding domain (the assembly-promoting (AP) sequence region), a fragment corresponding to the AP sequence region was prepared using an Escherichia coli expression system. When the fragment was mixed with purified tubulin at 37 degrees C, the fragment caused a time- and dose-dependent turbidity increase, and the fragment bound to tubulin. However, the products were cold-stable, and amorphous aggregates were observed by electron microscopy. Using axonemes as the seeds for microtubule assembly, the microtubule-elongating activity of the fragment was examined. A dose-dependent turbidity increase of the sample was observed, and electron microscopic observation revealed that microtubules were dose-dependently elongated from the axonemes. Consequently, the AP sequence region does not nucleate microtubules, but elongates them.

Adrenal Cortex↗

Initiation and promotion at different ages and doses in 2200 mice. II. Decrease in promotion by TPA with ageing.

Using the data described in Paper I, we compare the effects of the same treatment timings and doses given at different ages. Initiation with DMBA at 68 weeks of age, followed 3 weeks later by TPA, has a significantly (P less than 0.0001) less rapid effect on subsequent tumour incidence than does initiation at 8 or at 48 weeks of age, followed 3 weeks later by TPA. We suggested that this is chiefly due not to changes in the numbers of cells initiated by DMBA, but rather to a decrease in the promotional efficacy of TPA in ageing mice.

9,10-Dimethyl-1,2-benzanthracene↗

An operator at -280 base pairs that is required for repression of araBAD operon promoter: addition of DNA helical turns between the operator and promoter cyclically hinders repression.

A site has been found that is required for repression of the Escherichia coli araBAD operon. This site was detected by the in vivo properties of deletion mutants. In vitro protection studies with DNase I and dimethylsulfate showed that araC protein can specifically bind in this area to nucleotides lying at position -265 to -294 with respect to the araBAD operon promoter (PBAD) transcription start point. The previously known sites of protein binding in the ara operon lie between +20 and -160. Since the properties of deletion strains show that all the sites required for araBAD induction lie between +20 and -110, the new site at -280 exerts its repressive action over an unusually large distance along the DNA. Insertions of -16, -8, 0, 5, 11, 15, 24, and 31 base pairs of DNA between the new site and PBAD were constructed. Repression was impaired in those cases in which half-integral turns of the DNA helix were introduced, but repression was nearly normal for the insertions of 0, +11, and +31 base pairs.

AraC Transcription Factor↗

Inhibition of mouse skin tumor promotion and of promoter-induced epidermal polyamine biosynthesis by methylglyoxal bis(butylamidinohydrazone).

Effects of methylglyoxal bis(butylamidinohydrazone) (MGBB), a reversible inhibitor of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced increases of ODC and AdoMetDC activities, ODC and mRNA level and polyamine contents in mouse skin were investigated in connection with tumor formation. Formation of papillomas by applications of TPA to 7,12-dimethylbenz[a]anthracene (DMBA)-initiated mouse skin was effectively inhibited by simultaneous topical applications of MGBB, MGBB also dose-dependently inhibited the ability of TPA to induce increases of ODC activity, ODC mRNA level and the accumulation of putrescine and spermidine in mouse skin. Induction of AdoMetDC activity was not affected by the drug. These inhibitory effects of MGBB on ODC induction and tumor promotion were more evident in multiple application experiments than with a single application of the drug.

9,10-Dimethyl-1,2-benzanthracene↗

Essential structure of E. coli promoter: effect of spacer length between the two consensus sequences on promoter function.

A promoter with the consensus sequence(TTGACA and TATAAT) at -35 and -10 regions was constructed, and the distance between the two consensus sequences was independently altered at two restriction sites. In an in vitro transcription system, a maximum activity was observed at the spacer length of 17 base-pairs regardless of the sites of space adjustment. Evidence was also provided that the start point of transcription was fixed by the consensus sequence at the -10 region.

Base Composition↗

PTHrP promotes murine secondary trophoblast giant cell differentiation through induction of endocycle, upregulation of giant-cell-promoting transcription factors and suppression of other trophoblast cell types.

The murine trophoblast cell lineage represents an intriguing experimental cell model as it is composed of four trophoblast stem (TS)-derived cell types: trophoblast giant cells (TGCs), spongiotrophoblast, syncytotrophoblast, and glycogen trophoblast cells. To investigate the role of parathyroid hormone-related protein (PTHrP) in TGC differentiation, we analyzed the effect of exogenous PTHrP on secondary TGCs of day 8.5 p.c. ectoplacental cone explant culture. Secondary TGCs expressed PTHrP and PTHR1 receptor in vivo and in vitro. TGCs treated with PTHrP had reduced proliferation and decreased apoptosis starting from day 2 in culture, and enhanced properties of giant cell differentiation: increased DNA synthesis, number of cells with giant nuclei and expression of placental lactogen-II (PL-II). The induction of TGC formation by PTHrP correlated with downregulation of cyclin B1 and mSNA expression, but upregulation of cyclin D1, thus allowing mitotic-endocycle transition. Moreover, PTHrP treatment influenced TGC differentiation by inducing the expression of transcription factors known to stimulate giant cell formation: Stra13 and AP-2gamma, and inhibiting the formation of other trophoblast cell types by suppressing trophoblast progenitors and spongiotrophoblast-promoting factors, Eomes, Mash-2, and mSNA. Taken together with the spatial and temporal patterns of TGC formation and PTHrP synthesis in vivo, these findings indicate an important role for PTHrP in the differentiation of secondary TGCs during placentation.

Animals↗

Dbf4p, an essential S phase-promoting factor, is targeted for degradation by the anaphase-promoting complex.

The Dbf4p/Cdc7p protein kinase is essential for the activation of replication origins during S phase. The catalytic subunit, Cdc7p, is present at constant levels throughout the cell cycle. In contrast, we show here that the levels of the regulatory subunit, Dbf4p, oscillate during the cell cycle. Dbf4p is absent from cells during G(1) and accumulates during the S and G(2) phases. Dbf4p is rapidly degraded at the time of chromosome segregation and remains highly unstable during pre-Start G(1) phase. The rapid degradation of Dbf4p during G(1) requires a functional anaphase-promoting complex (APC). Mutation of a sequence in the N terminus of Dbf4p which resembles the cyclin destruction box eliminates this APC-dependent degradation of Dbf4p. We suggest that the coupling of Dbf4p degradation to chromosome separation may play a redundant role in ensuring that prereplicative complexes, which assemble after chromosome segregation, do not immediately refire.

Anaphase↗

Growth hormone promotes human T cell adhesion and migration to both human and murine matrix proteins in vitro and directly promotes xenogeneic engraftment.

Recombinant human growth hormone (rhGH) promotes human T cell engraftment in mice with severe combined immunodeficiency, suggesting that rhGH may have effects on T cell adhesion and migration in vivo. The ability of rhGH to directly affect the adhesion capacity of human T cells to a variety of human or murine adhesion molecules and extracellular matrix proteins was examined. rhGH induced significant human T cell adherence to both human and murine substrates via either beta 1 or beta 2 integrin molecules. rhGH was capable of inducing significant migration of resting and activated human T cells and their subsets. Most of the migratory response to rhGH was chemokinetic rather than chemotactic. In vivo engraftment studies in severe combined immunodeficiency mice receiving human T cells revealed that treatment with rhGH resulted in improved thymic engraftment, whereas treatment with non-human-reactive ovine GH demonstrated no significant effects. These data demonstrate that rhGH directly augments human T cell trafficking to peripheral murine lymphoid tissues. rhGH appears to be capable of directly altering the adhesive and migratory capacity of human T cells to molecules of either murine or human origin. Therefore, GH may, under either isogeneic or xenogeneic conditions, play a role in normal lymphocyte recirculation.

Animals↗

Enhancing effect of absorption promoters on percutaneous absorption of a model dye (6-carboxyfluorescein) as poorly absorbable drugs. II. Study on the absorption promoting effect of azone.

The percutaneous absorption of drugs was investigated in rats by measuring plasma levels, using mainly 6-carboxyfluorescein (CF) as a model of poorly absorbable drugs. Azone (AZ), a new useful promoter for the percutaneous absorption of drugs, was used instead of dimethylsulfoxide. We have examined the effects of the solubilized state and concentration of AZ on the percutaneous absorption of CF. AZ was dissolved with the aid of surface-active agents, beta-cyclodextrin (CD) or dimethyl-beta-cyclodextrin (DMCD). When AZ (2 v/v%) was dissolved completely by a surface-active agent (HCO-60: polyoxyethylene hardened castor oil derivative), plasma CF levels showed the highest value. Plasma CF levels following the administration of CF with AZ which formed a complex with CD or DMCD were scarcely increased as compared to that of CF alone. In the case of fluorescin (FL), which has a higher partition coefficient than CF, the percutaneous absorption of FL was more enhanced by the addition of AZ than in the case of CF.

Adjuvants, Pharmaceutic↗

Promoting protein, a silkworm hemolymph protein promoting in vitro replication of nucleopolyhedrovirus, binds to beta-glucans.

A protein which bound to 125I-labeled peptidoglycan (PGN) was isolated from hemolymph of silkworm larvae. The N-terminal amino acid sequence and the molecular weight of the protein were in accord with those described for Promoting Protein (PP) from the silkworm. The binding of the protein to [125I]PGN was competitively inhibited by various beta-glucans. The binding kinetics of PGN and chitin to the protein were analyzed in a biosensor.

Animals↗

Attempts at analysis of toxicity of pertussis vaccine. III. Effects of endotoxin on leukocytosis in mice due to lymphocytosis-promoting factor and reference preparations for determination of lymphocytosis-promoting factor.

The effect of bacterial endotoxin on the change in peripheral leukocyte population in mice due to the lymphocytosis-promoting factor (LPF) was investigated. Endotoxin affected not only the total leukocyte count but also the leukocyte proportions at any observation time. Both the coefficient and the intercept of regression of the leukocytic response on dose of LPF were modified by endotoxin. Therefore, in a valid biological assay for LPF using the peripheral leukocyte count as a response, a common reference preparation available for any test materials, irrespective of presence or absence of endotoxin, will be impracticable. Two reference preparations were tentatively established, one being a vaccine and the other an LPF preparation containing little endotoxin. A unitage of LP activity was assigned to each reference preparation. The results also showed that an LPF material to be tested for its possible effects on the lymphatic tissues or the reticuloendothelial system should be free from endotoxin.

Animals↗

Peptidoglycans as promoters of slow-wave sleep. I. Structure of the sleep-promoting factor isolated from human urine.

Fast atom bombardment-mass spectrometry (FABMS) has been used to determine the structure of the urinary sleep-promoting factor (FSu), the nature of whose components had been reported earlier. Less than 1 nmol of the underivatized substance sufficed for the FABMS experiments. The major somnogenic constituent of the purified preparation was a peptidoglycan of Mr = 921 with the structure N-acetylglucosaminyl-N -acetylanhydromuramylalanylglutamyldiaminopimelylalanine. The anhydro linkage is between C-1 and C-6 of the muramyl entity. Two additional substances accompanied the above compound. These were the hydrated form (i.e. in which the muramyl entity had a free reducing end, and a free hydroxyl on C-6), and an anhydro analogue lacking the terminal alanine. The Mr values were 939 and 850, respectively. Methyl esters were prepared, and these were also acetylated. The mass spectra of the methyl ester of Mr = 921 displayed an increase in Mr of 42 (i.e. 3 X 14), indicating the presence, originally, of three free carboxyls. Acetylation increased Mr by a further 168 units (i.e. 4 X 42), indicating 4 hydroxyl or amino groups. These data are consistent with the structure cited above for the main entity of FSu. Similar confirmatory results were obtained for the two minor constituents described above. These operations were worked out on natural muramyl peptides of known structure, obtained from other sources, and the data are given for comparison.

Acetylmuramyl-Alanyl-Isoglutamine↗