Antiapoptotic effect of alpha-tocopherol at micro- and nanomolar concentrations on cells of neuronal line PC12 according to data of flow cytometry

By the method of flow cytometry it has been shown that alpha-tocopherol at micromolar concentrations produces antiapoptotic effect on the PC12 neuronal line cells exposed to the toxic agent hydrogen peroxide at various terms of incubation with it. At the same time, alpha-tocopherol at nanomolar concentrations had protective (antiapoptotic) effect only after the long (18 h) preincubation of the PC12 cells with it prior to exposure to hydrogen peroxide. This seems to indicate that the alpha-tocopherol effect at these concentrations is mediated by a signal transduction system.     

Modulation of CPP32 activity and induction of apoptosis in Human CEM X 174 lymphocytes by heptachlor, a chlorinated hydrocarbon insecticide

Heptachlor is an organochlorine insecticide used worldwide for the control of pests both agriculturally and domestically. Its lipophilic structure allows it to bioaccumulate and pass through the food chain, exposing those who come in contact with it to its tumor promoting and possible carcinogenic effects. As a mechanism of tumor promotion, we explored the possibility of heptachlor suppressing the apoptotic process in human CEM x 174 lymphocytes. In this article, we describe the effect of heptachlor on the activity of the apoptosis protease CPP32. We show that heptachlor by itself was able to stimulate CPP32 activity at relatively high concentrations. When combined with the chemotherapeutic agent doxorubicin, a known CPP32 activator, a dual effect was observed. Low concentrations of heptachlor (5 microM-10 microM) suppressed doxorubicin-induced CPP32 activity, and high concentrations of heptachlor (80 microM-120 microM) augmented it. We also showed that heptachlor alone at relatively high concentrations induced apoptosis-associated changes in CEM x 174 cells including high molecular weight (HMW) DNA cleavage and chromatin condensation. From these results, it appears that heptachlor has tumor promoting-like effects at lower concentrations, and at higher concentrations induces apoptosis as a mechanism of cytotoxicity.     

Gossypol: uncoupling of respiratory chain and oxidative phosphorylation

Gossypol produced adverse effects $\text{in vitro}$ on rat liver mitochondira. It stimulated mitochondrial respiration at low concentrations, inhibited it at high concentrations; abolished ADP/O and respiration control ratios; reversed inhibition caused by oligomycin; stimulated adenosine triphosphatase activity at low concentrations and inhibited it at high concentrations; and its effect on this enzyme was pH dependent. The possibility that gossypol may exert its toxic effect on poultry and animals by uncoupling respiratory chain-linked phosphorylation is discussed.     

Antiapoptotic effect of alpha-tocopherol at micro- and nanomolar concentrations on cells of neuronal line PC12 according to data of flow cytometry

By the method of flow cytometry it has been shown that alpha-tocopherol at micromolar concentrations produces antiapoptotic effect on PC12 neuronal line cells exposed to the toxic agent hydrogen peroxide at various terms of incubation with it. At the same time, α-tocopherol at nanomolar concentrations had protective (antiapoptotic) effect only after the long (18 h) preincubation of the PC12 cells with it prior to exposure to hydrogen peroxide. This seems to indicate that the α-tocopherol effect at these concentrations is mediated by a signal transduction system.     

The denaturation of ribonuclease A by combinations of urea and salt denaturants.

When urea is added to ribonuclease A that has already been denatured by salt (CaCl₂, LiClO₄ or LiCl were used), a second co-operative transition occurs, supporting the previous demonstration that these salts cause only partial denaturation. Also we have studied the effect of the salts on the urea denaturation, and the effect of urea on the salt denaturation. At low concentrations urea makes the salt transitions occur at lower concentrations, but at higher concentrations it changes the transition so that the completely disordered protein found in urea is produced by the salt. At low concentrations the salts actually stabilize the protein against denaturation by urea, but at higher concentrations they destabilize it. The data are presented in “phase diagrams” which are found to be very useful for such three-component systems.     

Radioprotection of euoxic bacteria by phenothiazine drugs

Summary Survival studies on irradiated euoxicE. coli B/r cells in presence of various concentrations of four radioprotecting phenothiazine drugs have been carried out. Maximum radioprotection was obtained at a optimal concentration for each drug and it decreased on either side of it. The DNA strand break studies at the maximum protective and non-protective concentrations of chlorpromazine and promethazine revealed that the number of ssbs in DNA were less at the protective concentration which were efficiently repaired by the type-III repair process. On the other hand, at the non-protective concentrations, inhibition of DNA repair was noticed and a higher number of DNA ssbs were detected. We suggest that the membrane is fluidized to a greater extent at the protective concentrations allowing the chemical restitution of damaged sites by NPSH compounds. At the non-protective high concentrations of the drugs, the membrane may be too grossly disorganised to allow any repair and at the same time high concentrations of the drugs or their radicals may also react with radioprotective intracellular sulphhydryls.     

Concentration-dependent differing actions of the nonsteroidal anti-inflammatory drug,celecoxib, in distearoyl phosphatidylcholine multilamellar vesicles

The interactions of the nonsteroidal anti-inflammatory drug, celecoxib, with 1,2-distearoyl-sn-glycero-3-phosphocholine multilamellar vesicles were studied as a function of temperature and different drug concentrations, using Fourier transform infrared spectroscopy, differential scanning calorimetry, and turbidity technique at 440?nm. Our studies reveal that celecoxib lowers the main phase-transition temperature and decreases the fluidity of the membranes at all concentrations. Celecoxib induced opposing effects on molecular order at different concentrations by increasing the ordering of the system at low concentrations and disordering it at high concentrations. Further, the drug increases the number of hydrogen bonds around the carbonyl groups at low concentrations in both phases, whereas the degree of dehydration increases at high concentrations in the gel phase. An evidence of phase separation has also been clearly observed at high concentrations. Thus, depending on the concentration used, celecoxib induces significant changes in the biophysical properties of membranes that may aid in understanding its mechanism of action.     

Promotion of indoleacetic Acid oxidase isoenzymes in tobacco callus cultures by indoleacetic Acid

Indoleacetic acid oxidase in tobacco callus cultures (Nicotiana tabacum L., cv. White Gold) was composed of at least two groups of isoenzymes, which were distinctly different in electrophoretic mobilities and in responses to growth substances. Indoleacetic acid had dual effects; at low concentrations it promoted the development of two fast-migrating indoleacetic acid oxidase isoenzymes, but at high concentrations it increased the level of other indoleacetic acid oxidase isoenzymes with low and moderate electrophoretic mobilities. However, indoleacetic acid was not unique in such effects; 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid were effective at concentrations lower than that of indoleacetic acid.     

Thermodynamics of the purine nucleotide cycle

Since the standard Gibbs energies of formation are known for all the species in the purine nucleotide cycle at 298.15 K, the functions of pH and ionic strength that yield the standard transformed Gibbs energies of formation of the ten reactants can be calculated. This makes it possible to calculate the standard transformed Gibbs energies of reaction, apparent equilibrium constants, and changes in the binding of hydrogen ions for the three reactions at desired pHs and ionic strengths. These calculations are also made for the net reaction and a reaction that is related to it. The equilibrium concentrations for the cycle are calculated when all the reactants are initially present or only some are present initially. Since the concentrations of GTP, GDP, and P(i) may be in steady states, the equilibrium concentrations are also calculated for the system at specified steady-state concentrations.     

Effect of fluid dispersion on cybernetic control of microbial growth on substitutable substrates

Many fermentation media contain two or more substrates, which a microorganism utilizes for similar purposes. Depending on the conditions prior to and during a fermentation, the substrates may be utilized in succession or simultaneously. Since it is difficult to portray this behavior through mechanistic models, a cybernetic method was proposed earlier. Here the microorganism chooses the mode of substrate utilization that maximizes its own survival, usually expressed by the growth rate. In a fully dispersed bioreactor, simultaneous utilization generates higher growth rates but leads to low biomass concentrations since this utilization pattern is preferred at low concentrations of the substrates. In this study it has been shown that by allowing less than complete dispersion in the broth it is possible to shift from sequential to simultaneous utilization at high concentrations, thereby enabling both high growth rates and large biomass concentrations. This strategy thus allows the natural incomplete dispersion in large bioreactors to be gainfully exploited.     

Maltose transport in Escherichia coli K-12: involvement of the bacteriophage lambda receptor.

Mutants affected in lamB, the structural gene for phage lambda receptor, are unable to utilize maltose when it is present at low concentrations (less than or equal 10 muM). During growth in a chemostat at limiting maltose concentrations, the lamB mutants tested were selected against in the presence of the wild-type strain. Transport studies demonstrate that most lamB mutants have deficient maltose transport capacities at low maltose concentrations. When antibodies against purified phage lambda receptor are added to a wild-type strain, transport of maltose at low concentrations is significantly reduced. These results strongly suggest that the phage lambda receptor molecule is involved in maltose transport.     

Brassinolide influences the regeneration of adventitious shoots from cultured leaf discs of tobacco

When several concentrations of brassinolide (BL) were added to a shoot induction medium (SIM) that contained only BA, redifferentiation of adventitious shoots from tobacco leaf discs was unaffected at low BL levels (10^-10~10^-8 M), but was inhibited at higher concentrations. In comparison, when BL was applied without BA, only cell expansion occurred and no shoots formed. The determination time for shoot formation was shortened at low BL concentrations, but their formation was postponed (i.e., time was lengthened) at higher concentrations. Elongation of shoots incubated for 30 d was unaffected at low BL concentrations, but was inhibited as that amount increased.NTH1, a tobacco homeobox gene that is expressed in the central zone of the tobacco shoot apex, showed greater expression levels in the SIM over time, and its expression was stronger in media treated with low concentrations of BL compared with the SIM control at the same time point. Expression ofNTH1 was postponed at higher BL concentrations. In conclusion, at low concentrations, brassinolide has no effect on shoot formation. However, it inhibits their formation at high concentrations when cytokinin is included in the media.     

Low fat contents in female silver eels: indications of insufficient energetic stores for migration and gonadal development

The main energetic stores at the silver eel stage were studied by analysing muscle fat concentrations and hepatosomatic indices in female silver eels from various habitats in Sweden. Muscle fat concentrations varied both within and between localities and lean eels with muscle fat concentrations <20% occurred at all study sites. Furthermore, no correlation could be found between muscle fat content and internal or external maturation indices, neither was the relative liver size related to the maturation process, as the correlation between the hepatosomatic and gonadosomatic indices was very weak. Consequently, it was concluded that silvering and the spawning migration may begin also at low muscle fat concentrations. However, most of the energy reserve is stored as muscle fat in eel, and it is highly unlikely that female silver eels with such low fat contents, as were observed occasionally in this study, will ever recruit to the next generation. Therefore, it is suggested that the maturation process in eel is more flexible than previously recognized, and that this process might be temporarily arrested and feeding resumed during the first part of the migratory phase.     

Reexamination of respiration-impairing effect of bikaverin on isolated mitochondria

Summary  Kovac et al (1) have shown that bikaverin uncouples oxidative phosphorylation of mitochondria at 20μg/ml (52 nmol/ml) in the reaction system without magnesium (Mg²⁺). In the present study, the effects of bikaverin on mitochondrial reactions were reexamined in detail at various concentrations both in the reaction systems with and without magnesium, using isolated rat liver mitochondria and submitochondrial particles (SMP) to characterize its mode of actions to mitochondrial respiration at low concentrations (<30nmol/mg mitochondrial protein). It was concluded that bikaverin showed no uncoupling effect (no decrease in P/O ratio) at low concentrations and did it at high concentrations in consequence of disturbing the ion permeability in the mitochondrial inner membranes. At low concentrations, bikaverin repressed both NAD- and succinate-linked respirations, but did not interfere with electron transport and energy transfer systems of mitochondria.     

PolyADP ribosylation and Friend erythroleukemic-cell differentiation: Action of poly(ADP-ribose) polymerase inhibitors

Previous studies have shown that benzamide and nicotinamide, two inhibitors of poly(ADP-ribose) polymerase, induce erythroid differentiation in Friend erythroleukemic cells. In contrast, we observed that two other commonly used inhibitors, i.e., 3-aminobenzamide and 3-methoxybenzamide, not merely failed to induce differentiation but actually inhibited it. Furthermore, we observed that benzamide at high concentrations induced differentiation, whereas at low concentrations, it inhibited differentiation. We propose that the induction occurring at high concentrations is due to the polar-planar properties of the molecule, while the inhibition at low concentrations might be due to the inhibition of poly(ADP-ribose) polymerase. Cells that were first exposed to an inducer (hexamethylene bisacetamide) and an inhibitor (3-aminobenzamide) and were subsequently incubated in medium lacking these substances did not differentiate. However, re-exposure to the inducer resulted in a very rapid increase in commitment to terminal differentiation. Therefore, 3-aminobenzamide appears to block differentiation prior to the commitment stage. We infer from these findings that polyADP-ribosylation is required for the terminal differentiation of Friend erythroleukemia cells.     

The Germicidal Properties of Ozone—Olefin Mixtures

S ummary : The use of the reaction products between ozone and olefins as a germicidal agent for the maintenance of sterility in rooms during the treatment of patients is discussed. The product is effective against vegetative bacteria and viruses but does not attack bacterial spores at low concentrations. It is most active at high humidities and possesses low power of penetration into cloth. It rapidly disappears from a system once generation ceases, without leaving unpleasant residues. Its high efficiency at low concentrations on finely dispersed bacterial aerosols renders it attractive in special situations. The possibility that it may prove carcinogenic after long human exposures in the presence of influenza virus, the difficulties involved in monitoring the concentrations generated and greatly reduced efficiency in dealing with organisms contained in large particles combine to render it unattractive for hospital use.     

盐胁迫下木麻黄幼苗抗氧化酶活性的变化及Ca2+对它的调控

在单纯NaCl处理下,随着NaCl浓度的加大,木麻黄幼苗的蛋白质含量逐渐升高,超氧化物歧化酶(SOD)活性下降,过氧化物酶(POD)活性则逐渐增加,过氧化氢酶(CAT)活性在低盐下下降,高盐下明显升高.加入适量Ca2 后,SOD活性上升,POD活性和蛋白质含量下降.CAT活性低时加Ca2 ,CAT活性增加;CAT活性高时加Ca2 ,CAT活性则降低.     

Yield-determining factors in high-solids enzymatic hydrolysis of lignocellulose

Background  

Working at high solids (substrate) concentrations is advantageous in enzymatic conversion of lignocellulosic biomass as it increases product concentrations and plant productivity while lowering energy and water input. However, for a number of lignocellulosic substrates it has been shown that at increasing substrate concentration, the corresponding yield decreases in a fashion which can not be explained by current models and knowledge of enzyme-substrate interactions. This decrease in yield is undesirable as it offsets the advantages of working at high solids levels. The cause of the 'solids effect' has so far remained unknown.     

Effect of protein concentration on the molecular weight of delta5-3-ketosteroid isomerase.

The molecular weight of delta-5-3-ketosteroid isomerase from Pseudomonas testosteroni was determined by means of sedimentation equilibrium and exclusion chromatography over a wide range of enzyme concentrations in 0.2 M potassium phosphate buffer, pH 7.0. In addition, the sedimentation constant of the enzyme was determinded over an extended range of concentrations. The enzyme was found to have a molecular weight of 26,000 plus or equal to 1,000, suggesting that it is a dimer of identical or similar 13,400 molecular weight polypeptide chains. In the ultracentrifuge this dimeric species was found to undergo aggregation at enzyme concentrations above 2 mg per ml and dissociation at enzyme concentrations below 0.05 mg per ml. Exclusion chromatography studies indicate that under the conditions of chromatography the oligomeric enzyme is partially dissociated at enzyme concentrations in the range 0.2 to 0.002 mug per ml. These results suggest that under conditions of enzyme assay in 0.2 M potassium phosphate buffer, pH 7.0, isomerase is in a monomeric state of aggregation.     

Oligomycin inhibition of Na,K,ATPase

It is shown that the incomplete, uncompetitive inhibition pattern exhibited by oligomycin toward Na,K,ATPase cannot be explained by a single-cycle enzyme model. In contrast, the experimental data are easily explained in terms of a dimeric enzyme, only one subunit of which can bind oligomycin at a time, and that subunit is then rendered inactive. In a brief analysis of the model thus obtained by way of numerical examples it is shown that it may show activation at small concentrations of moderator, which disappears at higher concentrations, a property observed for the hydrolysis ofp-nitro-phenylphosphate, which is also catalyzed by Na,K,ATPase.