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PubMed2005

Cryopreservation of flounder (Paralichthys olivaceus) embryos by vitrification.

Conventional cryopreservation of complex teleost embryos has been unsuccessful, possibly because their large size (1-7 mm diameter), multi-compartmental structure and low water permeability lead to intracellular ice formation and chilling injury. To overcome these obstacles, we have developed a vitrification procedure for cryopreservation of flounder (Paralichthys olivaceus) embryos. In initial toxicity tests, propylene glycol (PG) and methanol (MeOH) were less toxic to embryos than dimethylformamide (DMF) or dimethyl sulfoxide (Me2SO), whereas ethylene glycol (EG) and glycerol (Gly) were toxic to all tested embryos. Embryos between four-somite and tail bud stages were more tolerant to vitrifying solutions than embryos in other developmental stages. Four vitrifying solutions (FVS1-FVS4) were prepared by combining a basic saline solution (BS2) and cryoprotectants PG and MeOH in different proportions (FVS1: 67, 20 and 13%; FVS2: 60, 24 and 16%; FVS3: 55, 27 and 18%; FVS4: 50, 30 and 20% of BS2, PG and MeOH, respectively). Their impact on flounder embryos was then compared. FVS1 produced the highest survival rate; whereas deformation rate was highest for FVS4. Five-step equilibration of embryos in FVS2 resulted in higher survival rates than equilibration in 4, 3, 2 or 1 steps. Flounder embryos varying from the 14-somite to the pre-hatching stage were cryopreserved in the four vitrifying solutions in liquid nitrogen for 1-7 h. From eight experiments, 20 viable thawed embryos were recovered from 292 cryopreserved embryos. Fourteen larvae with normal morphology hatched successfully from the 20 surviving frozen-thawed embryos from five experiments. Embryos at the tail bud stage exhibited greater tolerance to vitrification than embryos at other stages. These results establish that cryopreservation of flounder embryos by vitrification is possible. The technology has many potential applications in teleost germplasm resource conservation.

Animals↗

PubMed1975

Structural and electronic effects on the polarographic half-wave potentials of copper (II) chelate complexes.

Polarographic measurements in dimethylformamide solution have been performed on 37 bis-chelate Cu(II) complexes containing primarily salicylaldimine, geta-ketoamine, beta-iminoamine, and pyrrole-2-aldimine ligand systems. The complexes were selected in order to reveal the effect of stereochemical and donor atom variations on half-wave potentials. Mono- and binuclear complexes undergo one-and two-electron reductions, respectively, which were established for representative cases by controlled potential coulometry. The response of Cu(II)/Cu(I) potentials to these variations reveals that nonplanar bis-chelate complexes are easier to reduce than their planar analogs, rigid planar tetradentate or related planar bis-chelate complexes, and complexes differing only in donor atoms are more readily reduced in the order N4 less than N2O2 less than N2S2. Binuclear complexes are reduced in one two-electron or two resolvable one-electron steps depending on ligand structure. Potentials of these and other complexes previously examined are considered in relation to the markedly positive potentials of "blue" copper proteins and ligand structural features which might afford Cu(II)/Cu(I) potentials in the protein range are noted.

Binding Sites↗

PubMed2001

A very efficient method to cleave Lipid A and saccharide components in bacterial lipopolysaccharides.

A novel mild procedure for the selective cleavage of ketosidic linkages is developed using ceric ammonium nitrate (CAN) in anhydrous N,N-dimethylformamide. Its application to lipopolysaccharides (LPS) is very significant because in the so far investigated LPS, the connection between the Lipid A region and the oligo(poly)saccharide part is always a keto-sugar. This procedure has been tested on LPS of Escherichia coli which contains Kdo as a linker between Lipid A and OPS and on Acinetobacter haemoliticus which contains D-glycero-D-talo-2-octulopyranosonic acid (Ko) as a linker and it performed efficiently in both cases.

Acinetobacter↗

PubMed2001

Extension of the application range of UV-absorbing organic solvents in capillary electrophoresis by the use of a contactless conductivity detector.

A contactless conductivity detection (CCD) system is used for capillary zone electrophoresis (CZE) with non-aqueous solvents of the buffering background electrolyte, which exhibit strong UV absorbance below 230 nm. It is found that the CCD characteristics with such solvents (propylene carbonate, N,N-dimethylformamide and N.N-dimethylacetamide as examples) is the same as with aqueous solutions: the same signal and noise is obtained for a given electric conductance of the background electrolyte, independent of the kind of the solvent. Therefore CCD enables the extension of the application range to solvents with restricted use for common UV detection in CZE due to their unfavourable or even unfitting optical properties. The applicability of CCD is demonstrated by CZE of aliphatic ammonium compounds in these solvents.

Acetamides↗

PubMed1986

Germ cell tumors of the testicle among aircraft repairmen.

A cluster of testicular germ cell tumors occurred among 3 of 153 white men who worked in a shop engaged in repair of exterior surfaces and electrical components of the airframes of F4 Phantom Jet aircraft. Evaluation of an occupationally identical shop at a second F4 rework facility at which there had been no previous reports of excess neoplasms revealed 4 additional men with a history of testicular germ cell tumors (p less than 0.01, Poisson, compared to the expected number of cases based on national incidence rates). Our investigation raises but does not prove a hypothesis of association between subsequent development of testicular germ cell cancer and history of extensive exposure to a mixture containing dimethylformamide, which had been used in F4 repair work at these facilities in the 1960s and 1970s. This represents the first report of 2 corresponding mini-epidemics of testicular tumors among workers in occupationally identical industrial settings.

Aircraft↗

PubMed1998

Steroidal 5-en-3-ones, intermediates of the transformation of steroidal 5-en-3 beta-ols to steroidal 4-en-3,6-diones oxidized by pyridinium dichromate and pyridinium chlorochromate.

Oxidation of cholesterol (1a) or pregnenolone (1b) with pyridinium dichromate (PDC) in dimethylformamide (DMF) or in dichloromethane (DCM) and pyridinium chlorochromate (PCC) in DCM provided cholest-4-en-3,6-dione (2a) or pregn-4-en-3,6,20-trione (2b). TLC monitoration of the reactions implied that cholest-5-en-3-one (3a) or pregn-5-en-3,20-dione (3b) and cholest-4-en-3-one (4a) or pregn-4-en-3,20-dione (4b) might be intermediates. Individual oxidation of 3a or 3b with PDC and PCC could give 2a or 2b, but 4a or 4b remained unchanged. Further investigation indicated that 4a or 4b was an isomerization product of 3a or 3b on silica gel TLC plate rather than really existence in the reaction mixture. These results shown steroidal 5-en-3-ones were intermediates of the transformation of steroidal 5-en-3 beta-ols to steroidal 4-en-3,6-diones oxidized by PDC and PCC.

Cholestenones↗

PubMed1997

A new concept for risk assessment of the hazards of non-genotoxic chemicals--electronmicroscopic studies of the cell surface. Evidence for the action of lipophilic chemicals on the Ca2+ signaling system.

Recently, we presented evidence for the localization of components of the cellular Ca2+ signaling pathway in microvilli. On stimulation of this pathway, microvilli undergo characteristic morphological changes which can be detected by scanning electron microscopy (SEM) of the cell surface. Here we show that both receptor-mediated (vasopressin) and unspecific stimulation of the Ca2+ signaling system by the lipophilic tumor promoters thapsigargin (TG) and phorbolmyristateacetate (PMA) are accompanied by the same type of morphological changes of the cell surface. Since stimulated cell proliferation accelerates tumor development and sustained elevation of the intracellular Ca2+ concentrations is a precondition for stimulated cell proliferation, activated Ca2+ signaling is one possible mechanism of non-genomic tumor promotion. Using isolated rat hepatocytes we show that all tested lipophilic chemicals with known tumor promoter action, caused characteristic microvillar shape changes. On the other hand, lipophilic solvents that were used as differentiating agents in cell cultures such as dimethylsulfoxide (DMSO) and dimethylformamide also, failed to change the microvillar shapes. Instead DMSO stabilized the original appearance of microvilli. The used technique provides a convenient method for the evaluation of non-genomic carcinogenicity of chemicals prior to their industrial application.

Alkanes↗

PubMed1997

Removal of Thermafil root canal filling material.

The aim of this study was to evaluate if removal of Thermafil plastic carriers and reestablishment of working length were possible in single rooted teeth filled with the Thermafil system. Twenty freshly extracted maxillary central incisors were prepared and filled with #30 Thermafil plastic obturators according to manufacturer's recommendations. Teeth were divided in two groups: Group I: 10 teeth were retreated using dimethylformamide as a solvent. Group II: 10 teeth were retreated using chloroform as a solvent. Removal of filling material was performed manually using K files and H files alternately between carrier and dentinal walls. The average time needed to remove the plastic carrier was 7 min for group I and approximately 6 1/2 min for group II. No deformation of the plastic carrier was observed after removal from the canal. Removal of plastic carriers and measurement of the proper working length were easily performed using manual endodontic instruments. Chloroform greatly enhanced this procedure.

Chloroform↗

PubMed2001

Preparation and mechanical properties of nanocomposites of poly(D,L-lactide) with Ca-deficient hydroxyapatite nanocrystals.

Nanocomposites of high molecular poly(D,L-lactide) (PLA) with Ca-deficient hydroxyapatite nanocrystals (d-HAP) were successfully prepared through solvent-cast technique. Such composites are of great importance to make bone-like substitutes as d-HAP nanocrystals have similar composition, morphology and crystal structure as natural apatite crystals. Of all the PLA solvents studied, N,N-dimethylformamide is the best one to disperse d-HAP nanocrystals. The resultant sol is a blue, stable dispersion that could preserve several days with only slight precipitation. The bright-field TEM micrograph shows that d-HAP nanocrystals form homogeneous dispersion in the PLA matrix at a microscopic level. The tensile modulus for PLA/d-HAP nanocomposites increases with d-HAP loading. Theoretical prediction of the modulus has been made by assuming the nanocomposites as short fiber filled systems. The calculated values based on Halpin-Tsai equations show excellent agreement with the experimental results. The yield stress for the nanocomposites has not been undermined by the presence of the nanocrystals. This preservation of strength for PLA/d-HAP nanocomposites may be due to the homogeneous dispersion of d-HAP nanocrystals in the PLA matrix as well as the good interfacial adhesion.

Biomechanical Phenomena↗

PubMed1980

Electroanalytical investigation on the interaction between 6-mercaptopurine and zinc(II), lead(II), and cadmium(II) ions in nonaqueous solvents.

Different electroanalytical techniques have been employed in the study of the interaction between 6-mercaptopurine and zinc(II), lead(II), and cadmium(II) ions in ethanol, dimethylformamide, and dimethylsulfoxide. The stoichiometry of the formed complexes was determined as well as their instability constants. The kinetic parameters of the electrode processes have been also evaluated.

Cadmium↗

PubMed1999

Non-aqueous capillary electrophoresis of drugs: properties and application of selected solvents.

The electrophoretic mobility of selected acidic and basic test solutes have been determined in non-aqueous media prepared by adding various combinations of ammonium acetate, sodium acetate, methane sulphonic acid and acetic acid to acetonitrile, propylene carbonate, methanol, formamide, N-methylformamide, N,N-dimethylformamide and dimethylsulphoxide, respectively. The apparent pH (pH*) of these non-aqueous media have been measured and it was found that pH* is an important factor for the separations in non-aqueous capillary electrophoresis. However, in some solvents the concentration of sodium acetate has a strong influence on the mobility despite very small changes in pH*. Due to the fact that a change in one parameter influences a number of other parameters it is very difficult to conduct systematic studies in non-aqueous media and to compare the migration of the species at fixed pH* values from one solvent to another. Thus pH* is only of value for comparison when used with a specific solvent or solvent mixture. The viscosity of the above-mentioned solvents were measured at various temperatures and means to adjust the viscosity of the non-aqueous media used for capillary electrophoresis are discussed and the separation of ibuprofen and its major metabolites in urine is used as an example.

4-Aminobenzoic Acid↗

PubMed1998

Studies on kinetic parameters and stability of aminoacylase in non-conventional media.

Catalytic properties and conformational stability of aminoacylase (N-acylamino acid amidohydrolase, EC 3.5.1.14) were studied in water-N,N-dimethylformamide (DMF) and water-dioxane solvent mixtures. Beside the prompt inhibition the solvents caused further inactivation during incubations. In the presence of 5% DMF content the inactivation proceeds with a well-measurable rate (t1/2 39 min), while in the case of 20% DMF the enzyme practically lost its starting activity during 50 min incubation (t1/2 13 min). The K(m) value of the enzyme increased about three times with increasing DMF concentrations up to about 2.6 M DMF, while the Vmax value decreased practically to zero in the same concentration range.

Amidohydrolases↗

PubMed2002

A new procedure to produce lignocellulosic anion exchangers from agricultural waste materials.

Two lignocellulosic agricultural waste materials (LCM), sugarcane bagasse (BG) and rice hull (RH), were converted into weak-base anion exchanger and evaluated for their exchanger capacity for nitrate. Pure cellulose (PC) and pure alkaline lignin (PL) were also used as reference materials to elucidate possible reactivity in LCM. Epoxy and amino groups were introduced into BG, RH, PC and PL substrates after the reaction with epichlorohydrin and dimethylamine in the presence of pyridine and an organic solvent N,N-dimethylformamide (DMF). Amino group incorporation into cellulose decreased with the presence of water in the reaction mixture and increased with the reaction time and presence of a catalyst (pyridine). The highest maximum nitrate exchange capacity (Qmax) and yields of the prepared exchangers was obtained from PL (1.8 mmol g(-1) and 412.5%), followed by BG (1.41 mmol g(-1) and 300%), PC (1.34 mmol g(-1) and 166%) and RH (1.32 mmol g(-1) and 180%). The proposed synthetic procedure was effective in modifying PL, PC and LCM chemically resulting in a higher yield and nitrate removal capacity.

Agriculture↗

PubMed1998

Synthesis of 1-[11C]methylpiperidin-4-yl propionate ([11C]PMP) for in vivo measurements of acetylcholinesterase activity.

Synthesis of 1-[11C]methylpiperidin-4-yl propionate ([11C]PMP), an in vivo substrate for acetylcholinesterase, is reported. An improved preparation of 4-piperidinyl propionate (PHP), the immediate precursor for radiolabeling, was accomplished in three steps from 4-hydroxypiperidine by (a) protection of the amine as the benzyl carbamate, (b) acylation with propionyl chloride, and (c) deprotection of the carbamate by catalytic hydrogenation. The final product was obtained in an overall 82% yield. Reaction of the free base form of PHP with [11C]methyl trifluoromethanesulfonate at room temperature in N,N-dimethylformamide, followed by high performance liquid chromatography (HPLC) purification, provided [11C]PMP in 57% radiochemical yield, > 99% radiochemical purity, and > 1500 Ci/mmol at the end of synthesis. The total synthesis time from end-of-bombardment was 35 min. [11C]PMP can thus be reliably prepared for routine clinical studies of acetylcholinesterase in human brain using positron emission tomography.

Acetylcholinesterase↗

PubMed2001

Photosensitizing properties of a boronated phthalocyanine: studies at the molecular and cellular level.

A synthetic procedure has been developed for the preparation of a Zn-phthalocyanine peripherally substituted with a dodecaborane. The absorption spectrum of the derivative is typical of the phthalocyanine chromophore. Moreover, the boronated phthalocyanine exhibits a high photosensitizing efficiency against a model biological substrate, such as N-acetyl-L-tryptophanamide, and a singlet oxygen quantum yield of 0.53 in dimethylformamide. Even though the presence of the dodecaborane moiety appears to decrease the affinity of the phthalocyanine for HT-1080 transformed human fibroblasts, the boronated phthalocyanine causes an essentially complete loss of cell viability upon irradiation with 600-700 nm light under mild conditions (1 microM concentration, 5-min irradiation at 10 mW/cm(2)).

Boron Compounds↗

PubMed2001

Sensitized photoxygenation of piroxicam in neat solvents and solvent mixtures.

Detection of O(2)(1Delta(g)) phosphorescence emission, lambda(max)=1270 nm, following laser excitation and steady state methods were employed to determine the total rate constant, k(T), for the reaction between the non-steroidal anti-inflammatory drug piroxicam (PRX) and singlet oxygen in several solvents. Values of k(T) ranged from 0.048+/-0.003 x 10(6) M(-1) s(-1) in chloroform to 71.2+/-2.2 x 10(6) M(-1) s(-1) in N,N-dimethylformamide. The chemical reaction rate constant, k(R), was determined by using thermal decomposition of 1,4-dimethylnaphthalene endoperoxide as the singlet oxygen source. In acetonitrile, the k(R) value is equal to 5.0+/-0.4 x 10(6) M(-1) s(-1), very close to the k(T) value. This result indicates that, in this solvent, the chemical reaction corresponds to the main reaction path. Dependence of total rate constant on the solvent parameters pi* and beta can be explained in terms of a reaction mechanism that involves the formation of a perepoxide intermediate. Rearrangement of the perepoxide to dioxetane followed by ring cleavage and transacylation accounts for the formation of N-methylsaccharine and N-(2-pyridyl)oxamic acid, the main reaction products. Data obtained in dioxane-water (pH 4) mixtures with neutral enolic and zwitterionic tautomers of piroxicam in equilibrium show that the zwitterionic tautomer reacts with singlet oxygen faster than the enolic tautomer.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Single-coordinate-driving method for molecular docking: application to modeling of guest inclusion in cyclodextrin.

An extension of the computer program CICADA has been developed that allows us to use the single-coordinate-driving (SCD) method for flexible molecular docking. The docking procedure is composed of three independent space rotations, three independent translations, and the torsions selected by the user. One of the coordinates is driven; the other coordinates are relaxed. This procedure follows low-energy wells on the potential energy surface of the entire system. The program allows us to dock more than one ligand molecule to the receptor. We ran two test examples, docking N,N-dimethylformamide into alpha-cyclodextrin and R-phenoxypropionic acid into beta-cyclodextrin. The test examples showed that the SCD approach is able to overcome high-energy barriers and to cover the entire box within which the search is performed. The limitations of molecular dynamics docking in comparison with our approach also are discussed. The philosophy of the newly developed approach is not only to find the best dock for the receptor-ligand(s) system, but also to describe all the important binding modes and provide a good starting point for studying the dynamics within the cavity during the docking process.

Carbohydrate Conformation↗

PubMed2002

Effect of organic solvents on stability and activity of two related alcohol dehydrogenases: a comparative study.

A comparative study was performed regarding the catalytic activity and stability of two related enzymes (thermophilic alcohol dehydrogenase from Thermoanaerobacter brockii and its mesophilic counterpart from yeast) in the presence of a number of miscible and immiscible organic solvents. The study was performed in view of the practical usefulness of organic solvents for alcohol dehydrogenases which have been shown to catalyse a variety of industrially-important dehydrogenation reactions. A number of organic solvents of different physicochemical characteristics were used and substantial stabilization was achieved. The non-polar solvents utilized showed the ability to enhance thermal stability of both proteins. Protection against thermal denaturation was especially pronounced by n-dodecane, the solvent with the highest logP used in the present study. Dimethylformamide and dioxane, employed as two miscible organic solvents, showed the ability to cause substrate inhibition and changes in protein conformation as indicated by kinetic and fluorescence studies. A higher resistance of the thermophilic protein to the deleterious effect of pyridine and thermostabilization of the mesophilic enzyme by non-polar solvents are especially emphasized. Combined differences in protein structure and nature of organic solvents are suggested to explain the differences in stability and catalytic activity observed in the present investigation.

Alcohol Dehydrogenase↗