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At least 289 records · Page 16Linked to original sources
PubMed1985

Trypanosoma brucei: five commonly used trypanocides assayed in vitro with a mammalian feeder layer system for cultivation of bloodstream forms.

The in vitro activity of five commonly used trypanocides on bloodstream forms of Trypanosoma brucei brucei TC 221 was examined in 24-well culture plates in the presence of bovine fibroblast feeder layer cells. The minimum effective concentrations determined were as follows: Berenil 1.0 microgram/ml; Samorin 10.0 micrograms/ml; Antrycide dimethylsulfate 0.1 microgram/ml; Arsobal 0.01 microgram/ml; Naganol 1.0 microgram/ml. Contrary to values obtained with other in vitro assays, minimum effective concentrations obtained here were within the range of drug levels reached in blood, plasma, or serum of humans and animals after treatment with curative doses. The trypanocidal activity of Naganol in this assay was of particular interest, since Naganol has been hitherto considered to be inactive in vitro.

Animals↗
PubMed1990

Application of 13C(omega 1)-half-filtered [1H,1H]-NOESY for studies of a complex formed between DNA and a 13C-labeled minor-groove-binding drug.

The complex formed between the anticancer drug 4-[p-[p-(4-quinolylamino)benzamido]anilino]pyridine (SN 6999) and the decadeoxyribonucleoside nonaphosphate d-(GCATTAATGC)2 was investigated using two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) with a 13C(omega 1)-half-filter. The two quaternary methyl groups in SN 6999 had been labeled with 13C for these experiments. The simplified subspectra of [1H,1H]-NOESY obtained with this procedure greatly facilitate the identification and assignment of intermolecular NOEs. Quite generally, the combined use of isotope labeling and heteronuclear filters in [1H,1H]-NOESY provides an improved experimental basis for structural studies of drug/DNA complexes.

Base Sequence↗
PubMed1992

Effect of modulation of protein kinase C on the cAMP-dependent chloride conductance in T84 cells.

The regulation of chloride conductance was investigated in the T84 human colon carcinoma cell line by the quenching of the fluorescent probe 6-methoxy-N-(3-sulfopropyl)quinolinium. The permeable cAMP analog 8-Br-cAMP (100 microM) and the calcium ionophore ionomycin (1 microM) activate a chloride conductance. A prolonged (4 h) preincubation of cells with phorbol 12-myristate 13-acetate (100 nM) or with the diacylglycerol analog 1-oleoyl-2-acetyl-glycerol (100 microM): (i) down-modulates to almost zero the protein kinase C activity in the membranes; (ii) inhibits the activation of the chloride conductance mediated by 8-Br-cAMP but not by calcium; (iii) reduces the mRNA without changing the expression of the protein product of the cystic fibrosis gene. The data suggest that PKC is essential for the activation of the cAMP-dependent chloride conductance in T84 cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Engineering resistance to 'aging' of phosphylated human acetylcholinesterase. Role of hydrogen bond network in the active center.

Recombinant human acetylcholinesterase (HuAChE) and selected mutants (E202Q, Y337A, E450A) were studied with respect to catalytic activity towards charged and noncharged substrates, phosphylation with organophosphorus (OP) inhibitors and subsequent aging of the OP-conjugates. Amino acid E450, unlike residues E202 and Y337, is not within interaction distance from the active center. Yet, the bimolecular rates of catalysis and phosphylation are 30-100 fold lower for both E450A and E202Q compared to Y337A or the wild type and in both mutants the resulting OP-conjugates show striking resistance to aging. It is proposed that a hydrogen bond network, that maintains the functional architecture of the active center, involving water molecules and residues E202 and E450, is responsible for the observed behaviour.

Acetylcholinesterase↗
PubMed1990

Hypoxia causes ischemic bowel necrosis in rats: the role of platelet-activating factor (PAF-acether).

We have previously shown that injection of platelet-activating factor causes necrotizing enterocolitis in the rat and that platelet-activating factor is an endogenous mediator in lipopolysaccharide-induced bowel necrosis. Because hypoxia is a known predisposing factor for neonatal necrotizing enterocolitis, we investigated the effect of hypoxia on platelet-activating factor formation and intestinal necrosis. Young male Sprague-Dawley rats were made severely hypoxic by placing them in a 100% N2 chamber for 2 minutes; moderate hypoxia was accomplished using 10% O2 for 15 or 30 minutes. To evaluate the role of platelet-activating factor on intestinal perfusion and injury, two platelet-activating factor antagonists, SRI 63-441 and WEB 2086, were injected 10 minutes before the hypoxic exposure. We found that plasma platelet-activating factor levels were significantly elevated after 2 minutes of severe hypoxia (13.8 +/- 2.9 ng/mL vs. control 2.1 +/- 0.8 ng/mL) and after 30 minutes of moderate hypoxia (41.1 +/- 11.7 ng/mL). This increase in platelet-activating factor level was not caused by decreased degradation, because neither plasma nor intestinal platelet-activating factor acetylhydrolase was decreased in the hypoxic rats. (Intestinal acetylhydrolase activity was actually increased). Intestinal perfusion was markedly decreased at 30 minutes in hypoxic animals. In contrast, all platelet-activating factor antagonist-treated animals had normal intestinal perfusion. Histological examination of affected bowel from hypoxic animals showed early intestinal necrosis which was completely prevented by pretreatment with SRI 63-441 and WEB 2086. Because 30 minutes of hypoxia also resulted in metabolic acidosis, we further investigated if acidosis alone could induce platelet-activating factor release and bowel injury. We found that acidosis alone resulted in moderate increase of plasma platelet-activating factor but did not produce bowel injury. We conclude that platelet-activating factor plays a central role in mediating hypoxia-induced intestinal necrosis. Acidosis may enhance the effect of hypoxia on platelet-activating factor production.

Animals↗
PubMed1995

Systematic study of field and concentration effects in capillary electrophoresis of DNA in polymer solutions.

A systematic study of the separation of double-stranded DNA in hydroxypropylcellulose (HPC) with a molecular mass of 10(6) was undertaken, using a variety of concentrations (from 0.1 to 1%) and different electric fields (from 6 to 540 V/cm). The data show that at high polymer concentrations ( > or = 0.4%) and low fields, the separation mechanism is similar to that occurring in gels. The results are in good agreement with theoretical models, and in particular with a recently proposed theory for gels with a pore size smaller than the persistence length of DNA. For more dilute solutions and high fields, however, the separation pattern cannot be explained by existing theories. The existence of an original mechanism was confirmed by the direct observation of the conformation of double-stranded DNA molecules in the polymer solution by fluorescence videomicroscopy. Practical conclusions for the capillary electrophoretic separation of duplex DNA are drawn.

Benzoxazoles↗
PubMed1995

YOPRO-1 permits cytofluorometric analysis of programmed cell death (apoptosis) without interfering with cell viability.

In the absence of cell permeabilization, the impermeant nuclear dye YOPRO-1 permits accurate analysis of apoptosis using cytofluorometry or fluorescent microscopy. Several immune cell populations were studied including dexamethasone-treated thymocytes, irradiated peripheral blood mononuclear cells and a growth factor-depleted tumor B cell line. Excellent correlation values were found with acridine orange using cytofluorometry and with eosin-hematoxylin using optical microscopy. Under fluorescent microscopy, YOPRO-1-fluorescent cells demonstrate the morphological features of cells undergoing apoptosis such as nuclear shrinkage and fragmentation. An important characteristic of the dye that differs from all other nuclear dyes previously used for the detection of apoptosis is that it does not label living cells. Cell sorting after flow cytofluorometry analysis confirmed that only the apoptotic cell population was labelled with YOPRO-1. Further studies showed that while incubation of living cells with Hoechst 33342 almost completely abrogated the capacity of T cells to proliferate in response to several stimuli, YOPRO-1 had no inhibitory effect. This new simple, rapid and reproducible use of the YOPRO-1 dye should prove useful in the analysis of apoptotic cells as well as for investigations of the functional properties of living cells in a culture containing apoptotic cells.

Acridine Orange↗
PubMed1978

New chemotherapeutic agent for root canal treatment. A preliminary electron microscopic study on an in vivo and in vitro endodontically treated tooth.

A preliminary in vivo and in vitro electron microscopic study of root canals treated endodontically with EDTA-C and Salvizol proved the latter to be superior as a chemomechanical and irrigation solution, especially in the apical third of the roots. A further virtue of Salvizol, as has been demonstrated, is its capability to dissolve the organic matrix of dentin, thus exposing the mineralizing front and the patent tubules even in the apical third of the canal. The combined properties of Salvizol which introduce it as a chemotherapeutic agent for endodontics are: (1) broad spectrum of bactericidal activity, (2) ability to dissolve calcium, (3) neutral pH, (4) cleansing potency, and (5) biologic compatibility.

Dental Pulp Cavity↗
PubMed1980

Chelation in root canal therapy.

The effectiveness of three chelating agents (EDTA, Rc-Prep, and Salvisol) in achieving cleanliness of prepared and unprepared root canal surfaces was evaluated by means of the scanning electron microscope. In unprepared root surfaces Salvisol (solution) has the best chelating effect. In the instrumented group, EDTA was the most effective agent.

Animals↗
PubMed1983

Quantitative evaluation of the influence of dequalinium acetate and sodium hypochlorite on human dentition.

The effect of 5 percent DA, 2.5 percent and 5.5 percent sodium hypochlorite, and saline on the solubility of organic matrix of the dentin was studied on extracted human teeth. The results showed that sodium hypochlorite dissolved collagen from the canal walls, while DA did not dissolve any collagen into the media. It is concluded that the root-canal-cleansing effect of DA is achieved by another mechanism, most likely by surface activity.

Chemical Phenomena↗
PubMed1984

The influence of bis-dequalinium acetate on bone regeneration induced by grafts of combined inorganic heterologous bone and autologous marrow.

The present study was undertaken in order to determine the influence of BDA on bone regeneration and remodeling. Pieces of Kiel bone soaked with autologous bone marrow were implanted in the axial area of rats. The implantation sites were injected with 0.3 cc of 0.005% BDA 3 to 14 days after grafting; the control group was injected with Hartmann solution. Results indicated that BDA does not interfere with the bone-remodeling process. It does, however, have an inhibitory effect on the early stage of mesenchymal cell proliferation, that is, the development of osteoblasts from bone marrow stromal cells. Extrapolation of these findings to earlier evidence regarding the mode of action of this material is currently being investigated.

Animals↗
PubMed1992

In vivo assays for drug resistance in Babesia divergens using the Mongolian gerbil, Meriones unguiculatus.

Two in vivo drug resistance assays were developed using gerbils. Cross resistance, involving related babesicides as well as the chemically unrelated antibiotic, oxytetracycline, was demonstrated, but the suggestion that imidocarb may select for pathogenic strains of parasites was not supported. Limited tests of field strains did not detect resistance. It is suggested that an in vitro assay would be more appropriate for surveys through in vivo assays would be essential for confirmatory studies.

Animals↗