Isolation and Purification of an alpha-Mannosidase from Coleoptiles of Avena sativa

An alpha-mannosidase has been purified from the coleoptiles of Avena sativa L. var. Segrehavre. The enzyme, which is tightly associated with the cell wall, was solubilized with 3 m LiCl. The purification involves precipitation with (NH(4))(2)SO(4), gel filtration, ion exchange chromatography, and isoelectric focusing. The enzyme appears homogeneous when chromatographed on disc gels and on isoelectric focusing gels. The enzyme runs as a single protein of constant specific activity when chromatographed on Sephadex G-200. The estimated molecular weight of the enzyme is 630,000. The enzyme appears to have no metal ion cofactor requirement and is insensitive to p-chloromercuribenzoate. The pH optimum for the enzyme with p-nitrophenyl-alpha-d-mannoside as the substrate is 4.5 and the K(m) is 3.2 mm. The enzyme may have some carbohydrate associated with it as indicated by a positive periodate-Schiff reaction on disc gels.     

Morphology of the gynoecium and systematic position of the Ochnaceae

The gynoecium is syncarpous in all Ochnaceae. In the Ochnoideae carpels are peltate with a conventional cross-zone bearing one ovule, or, in Lophira , a very broad cross-zone with an horizontal ovular row. In Ochna and Brackenridgea , the style is gynobasic, each carpel develops transmitting tissue on its morphologically dorsal surface, and this tissue lines a canal or originates a solid inner strand in each carpel at style level. The style is tubular, with an inner cuticle, and compound, each component with its own transmitting tissue. In Ouratea the style is solid with a single compound transmitting strand. In Lophira and Elvasia the transmitting tissue seems to be developed by the morphologically ventral carpellary surfaces. Ovules are unitegmic with a bivalent integument.
In the Sauvagesioideae carpels are peltate, but with ovules above the cross-zones, on margins of the symplicate zone. In Euthemis , there is one ovule on each side of, and close to, each cross-zone. The single stylar canal is bounded by the morphologically dorsal carpellary surfaces. In Sauvagesia ovules occur on both sides of the cross-zones but most of them are above on carpel margins, as are all ovules of Cespedesia. The stylar canal of Sauvagesia is bounded by the ventral carpel surfaces, three strips of the outer surface passing inside at the sutures and developing into transmitting tissue. The stylar canal of Cespedesia is bounded by the dorsal carpel surfaces. The gynoecium of Wallacea has two epeltate carpels with a laminar placentation, the carpel margins being displaced on to the topographically ventral carpel surfaces with a row of ovules along each margin. Ovules are bitegmic.
The Ochnoideae, which shows relationships with the Rutaceae, Meliaceae, Simaroubaceae and Hippocastanaceae, is more advanced than the Sauvagesioideae, which clearly belongs in the Violales. The Ochnaceae is to be placed in the Violales.     

Ligand-induced structuring of polyreactive immunoglobulins

The influence of several hydrophobic compounds with different structures on the binding of native and chaotropically modified bovine immunoglobulins to native and denatured nonspecific protein immobilized on the surface is researched. It is shown that the character of binding depends on the amount and mutual location of hydrophobic nuclei in the effectors structure. The authors observed moderate suppression of binding or absence of the expressed effect while using one-nucleus effector. The influence of compounds with two distanced benzene nuclei differs qualitatively from the influence of the compound with two condensate ones, described earlier: it was observed that the stimulation level of the binding depends on structural-functional condition of immunoglobulin and immobilized protein. In case of the effector with three spaced hydrophobic nuclei the stimulating effect is much more expressed (3-4 times higher). The concentration dependence of the ligand-induced effects is demonstrated. It is supposed, that stimulative influence of effectors with spaced hydrophobic nuclei is caused by two different processes. The first one is the formation of highly binding center as the result of ligand-induced structuring of immunoglobulins. The other one is the competition for the center formed between dissolved polynuclear effector and ligand groups of aminoacids hydrophobic residues statistically formed on the surface of immobilized protein.     

Use of snake venom immobilized phosphodiesterase for analysis of the nucleotide composition of oligodesoxyribonucleotides]

A simple one-step technique for the analysis of nucleotide composition of oligodeoxyribonucleotides is described. The method is based on enzymatic hydrolysis and subsequent separation of hydrolysate on a "combined" column with Aminex A 28 anionite, on which top immobilyzed on DEAE cellulose snake venom phosphodiesterase is layed. The method is tested using a number of synthetic di- and tri-deoxyribonucleotides.     

Calculation of half-lives of proteins in vivo. Heterogeneity in the rate of degradation of yeast proteins

Summary A method is given for the calculation of half-lives of proteins in vivo from the measurement of the decrease of radioactivity in pulse-labelled proteins with time. This method could be particularly useful for the study of the degradation of proteins in cells that have a low growth rate.The method applied to growing yeast indicates that there are two major classes of protein. The class with low turnover constitutes the bulk of yeast protein and has a half-life of 160 h in a medium with glucose or galactose and of 50 h in a medium with ethanol. The class of proteins with high turnover (half-life between 0.8 and 2.4 hours) represents from 1% of total protein in yeast growing on glucose to 7% in yeast growing on ethanol.It is shown that some proteins which are derepressed during growth on ethanol or induced during growth on galactose are particularly susceptible to degradation in a medium which contains glucose.It is proposed that protein degradation is regulated by a coarse control at the level of protease activity and a fine control on the susceptibility of individual proteins to proteases.     

On the mechanism of action of alkylguanidines on oxidative phosphorylation in mitochondria.

The effect of octylguanidine and oligomycin on the oxygen uptake of rat liver mitochondria and on the ATPase activity of "sonic" submitochondrial particles has been studied. 1. Octylguanidine inhibits state 3 respiration with glutamate-malate and succinate as substrates, but much lower concentrations are required to inhibit oxygen uptake with the former substrates. State 4 respiration is unaffected by octylguanidine. 2. The titration-curve for the octylguanidine inhibition of glutamate-malate oxidation is hyperbolic and apparently biphasic, half-maximal inhibition is obtained at 30 muM octylguanidine. The octylguanidine-curve for inhibition of succinate oxidation is sigmoid with half-maximal inhibition at about 250 muM. 3. Octylguanidine and oligomycin show additive inhibitory action on state 3 respiration with both glutamate plus malage and succinate as respiratory substrates. 4. Concentrations of oligomycin or octylguanidine, which added separately are ineffective on state 3 respiration, become inhibitory when the two inhibitors are added together. 5. Octylguanidine inhibits the ATPase activity of sonic submitochondrial particles with a hyperbolic titration-curve analogous to that obtained for oligomycin inhibition. The inhibitory actions of octylguanidine and oligomycin on the ATPase activity are additive. 6. It is concluded that octylguanidine acts directly on the ATPase complex and that its binding at the action site is mutually exclusive with the binding of oligomycin. A kinetic explanation is given for the reported higher sensitivity of site I phosphorylation to octylguanidine.     

A Pleiotropic Nonadditive Model of Variation in Quantitative Traits

A model of mutation-selection-drift balance incorporating pleiotropic and dominance effects of new mutations on quantitative traits and fitness is investigated and used to predict the amount and nature of genetic variation maintained in segregating populations. The model is based on recent information on the joint distribution of mutant effects on bristle traits and fitness in Drosophila melanogaster from experiments on the accumulation of spontaneous and P element-induced mutations. These experiments suggest a leptokurtic distribution of effects with an intermediate correlation between effects on the trait and fitness. Mutants of large effect tend to be partially recessive while those with smaller effect are on average additive, but apparently with very variable gene action. The model is parameterized with two different sets of information derived from P element insertion and spontaneous mutation data, though the latter are not fully known. They differ in the number of mutations per generation which is assumed to affect the trait. Predictions of the variance maintained for bristle number assuming parameters derived from effects of P element insertions, in which the proportion of mutations with an effect on the trait is small, fit reasonably well with experimental observations. The equilibrium genetic variance is nearly independent of the degree of dominance of new mutations. Heritabilities of between 0.4 and 0.6 are predicted with population sizes from 10(4) to 10(6), and most of the variance for the metric trait in segregating populations is due to a small proportion of mutations (about 1% of the total number) with neutral or nearly neutral effects on fitness and intermediate effects on the trait (0.1-0.5σ(P)). Much of the genetic variance is contributed by recessive or partially recessive mutants, but only a small proportion (about 10%) of the genetic variance is dominance variance. The amount of apparent selection on the trait itself generated by the model is very small. If a model is assumed in which all mutation events have an effect on the quantitative trait, the majority of the genetic variance is contributed by deleterious mutations with tiny effects on the trait. If such a model is assumed for viability, the heritability is about 0.1, independent of the population size.     

Effect of cadmium acetate on the conformation of lysozyme: functional implications

Structural variations of lysozyme as a consequence of its interaction with CdAc2, as well as the implications on the protein functionality have been studied. Variations in the conformation of the macromolecule are seen, however these changes are not reflected on the secondary structure. The interaction of the salt with the polypeptide chain is weak and thermodynamically unfavourable. Molecular aggregates (dimer forms) are observed at the highest salt concentrations. This interaction causes an inhibitory effect on lysozyme, the activity loss being 50% at the highest salt concentration studied. The inhibition is of mixed type with an uncompetitive component. Thus cadmium does not bind to the active site of the enzyme which is in accordance with the not very large activity loss observed. The substrate inhibition of lysozyme is favoured in the presence of the salt, so interaction with the macromolecule is at low affinity sites.     

Mechanism of genetic recombination in bacterial conjugation. VIII. The heterogeneity of the progeny of exconjugants]

It is shown on several examples that the heterogeneity of recombinant clones after conjugation is independent on the conditions of primary selection (i.e. on the yield of primary clones). Therefore the prediction of the model of autonomously multiplying donor fragments is not confirmed by experimental data. Two additional characteristics of heterogeneity are introduced. The statistical distribution of merozygotes according to segregation time is measured. It is an exponential curve with a relaxation time approximately coinsident with the third cell division. A liner function is found for the dependence of heterogeneity on the distance between the selective and non-selective markers. The highest value for non-linked markers is about 15%. Alternative models for the explanation of the heterogeneity of exconjugants are discussed.     

The effect of tied rank numbers on the linearity of dominance hierarchies

The occurence of tied rank numbers in dominance hierarchies is discussed, especially its effect on the linearity of the hierarchy. This linearity is measured with Landau's index, that is calculated for several hierarchies with tied ranks on one, two of three levels. Linearity is mostly affected by ties in small groups with many ties. A distinction is made between a hierarchy of individuals and hierarchical levels. The phenomenon of despotism is called an extreme case of tied ranks. It is proposed to regard hierarchies with a linearity in a continuous scale.     

The effect of different concentrations of lead on inversion polymorphism in Drosophila subobscura

Drosophila subobscura is a wild Drosophila species that is spread over almost all of Europe. It possesses an uniquely rich inversion polymorphism on all five long chromosomes. This polymorphism is to a certain degree associated with the variation and dynamics of ecological factors in space and time. We analyzed the changes of inversion polymorphism components of Drosophila subobscura flies maintained on media with different concentrations of lead in laboratory conditions. The effects of lead on inversion polymorphism were observed by cytological analysis of gene arrangements on all of the five acrocentric chromosomes, as well as by cytological analysis of karyotypes on all of the four autosomes. The frequencies of particular gene arrangements on the four autosomes changed significantly in the samples maintained on medium not supplemented with lead. The frequencies of some gene arrangements on all of the five acrocentric chromosomes changed significantly in the flies maintained on media supplemented with lead. The length of exposure to different lead concentrations results in a significant change in the frequency of a few gene arrangements on two autosomes. However, the results show that different concentrations of lead, as well as the length of exposure, do not affect major parameters of inversion polymorphism. The results suggest that some gene arrangements could be linked with adaptive processes in evolving heavy metal resistance.     

The mechanisms of inhibition of Desulfovibrio and Desulfotomaculum species by selenate and molybdate

The effects of two specific inhibitors of sulphate-reducing bacteria, selenate and molybdate, have been studied by measurement of sulphate uptake and by measurement of the effects of these compounds on growth of the bacteria on a variety of media. The results obtained with selenate are consistent with the view that it acts as a competitive inhibitor of sulphate transport. The results obtained with molybdate show that there is more than one site of action and suggest that the primary effect is also on sulphate transport.     

The influence of environmental factors on the dynamics of the size and spatial structure of the chamois (Rupicapra rupicapra caucasica) population on the Caucasian Reserve

The size and structure of the chamois (Rupicapra rupicapra caucasica) population as well as the influence of anthropogenic factors on it were studied on the Caucasian Reserve (Western Caucasus). The negative effect of the snow cover, the thickness of which differed from the usual level, is shown. The effect of winters with thick snow cover is confirmed by the relation between these factors and the proportion of yearlings in the population one year after the winter. An increased death rate of animals in winters with a deep snow cover is observed in the case when their density exceeds the optimal one. Wolf predation does not affect the chamois population on the reserve. The number of wolves increases with an increase in the chamois population density to 15–20 ind./1000 ha. The adverse impact of humans on the chamois population is manifested in the regions with motor roads. The chamois, as compared to the deer, suffers from poachers to a lesser degree because it inhabits inaccessible areas and its trophy value is low.     

Molecular assembly of proteins and conjugated polymers: Toward development of biosensors

A molecular assembly in which a conjugated polymer is interfaced with a photodynamic protein is described. The conjugated polymer, functionalized with biotion, is designed such that it can be physisorbed on or chemically grown off a glass surface. The streptavidin-derivatized protein is immobilized on the biotinylated polymer matrix through the strong biotin-streptavidin interactions. The assembly, built on the surface of an optical fiber or on the inside walls of a glass capillary, forms an integral part of a biosensor for the detection of environmental pollutants such as organophosphorus-based insecticides. The Protein in the system can be replaced by any biological macromolecule of interest. We study one specific case, the enzyme alkaline phosphatase. The enzyme catalyzes a reaction producing an intermediate compound that chemiluminesces, and the chemiluminescence singnal is monitored to detect and quantify insecticides such as paraoxon and methyl parathion. Preliminary results indicate ppb level detection with response time less than 1 minute. (c) 1995 John Wiley & Sons, Inc.     

Method of radioautographic study of cell cultures

The method of radioautographic study of cell cultures is suggested. It is based on culture embedding into epoxy resin in situ. After this manipulation the photolayer on the lower surface of the polymerized epoxy unit with the cell culture in it is applied. The advantages of this method are discussed.     

Parameters of turbulent structures at the periphery of the FT-2 tokamak

Results are presented from probe measurements carried out in the scrape-off layer of the FT-2 tokamak in the course of additional lower hybrid heating, during which an L-H transition was observed. The objective of this study was to obtain information on the parameters of blobs-turbulent structures with enhanced plasma density. The measurements were performed not only on the low-field side of the torus, but also on the high-field side, which is still poorly studied. Coherent structures with radial velocities directed both toward the vessel wall and into the plasma column were revealed at the tokamak periphery. Blobs propagating toward the vessel wall were found to prevail both before and after the L-H transition. The average radial velocity of blobs in the L- and H-modes was determined experimentally. The dependence of the radial blob velocity on the transverse size and density of the structure agrees with the ballooning mode model. It is found that the average value of the poloidal blob velocity is four to five times higher than the average radial velocity. The results of measurements carried out on both sides of the torus indicate the presence of internal poloidal polarization of blobs. The average drift velocity of such polarized structures is directed toward the vessel wall. The L-H transition is accompanied by a reduction in the radial velocity. At the same time, the average plasma density inside the structures observed on the low-field side increases appreciably during the transition. The obtained dependences of the radial blob velocity on the plasma density inside the structure generally agree with predictions of the ballooning mode model.     

Citrate and the conversion of carbohydrate in fat. The activities of citrate-cleavage enzyme and acetate thiokinase in livers of starved and re-fed rats

1. The activity of citrate-cleavage enzyme varies in accordance with the nutritional state of the animal. It is suppressed on starvation and restored on re-feeding after starvation. 2. The increase in enzyme activity that occurs on re-feeding starved animals depends on the diet. It is largest on diets high in carbohydrate and low in fat, and smallest on diets high in fat. Intermediate increases are obtained with balanced diets. 3. The ratio of activities of citrate-cleavage enzyme to acetate thiokinase varies from 2·5 for animals maintained on a balanced diet to 20 for animals re-fed with a diet high in carbohydrate. 4. The changes in activity of citrate-cleavage enzyme correlate with changes in the rate of fatty acid synthesis and provide evidence for the involvement of the citrate-cleavage reaction in fatty acid synthesis.     

Hydrodynamic analysis of human swimming based on VOF method

A 3-D numerical model, based on the Navier-Strokes equations and the RNG k-ε turbulence closure, for studying hydrodynamic drag on a swimmer with wave-making resistance taken into account is established. The volume of fluid method is employed to capture the undulation of the free surface. The simulation strategy is evaluated by comparison of the computed results with experimental data. The computed results are in good agreement with data from mannequin towing experiments. The effects of the swimmer’s head position and gliding depth on the drag force at different velocities are then investigated. It is found that keeping the head aligned with the body is the optimal posture in streamlined gliding. Also wave-making resistance is significant within 0.3 m depth from the free surface.