Secretion of Sucrase by Leishmania donovani

ABSTRACT. Leishmania donovani promastigotes were collected, washed, resuspended in buffer, and assayed for sucrase activity. No activity was observed in the intact washed cells, but activity was measurable when the cells were permeabilized with Triton X-100. Intracellular sucrase activity was highest in promastigotes grown at pH 7.4, somewhat lower in promastigotes grown at pH 5.5, and significantly lower in "amastigotes" grown at pH 5.5. No trehalase, lactase, or maltase activities were observed. Assay of the medium in which the cells had grown showed that most the sucrase activity was extracellular, i.e. was secreted into the medium during growth.     

Decarboxylation of Substituted Cinnamic Acids by Enterobacteria: the Influence on Beer Flavour

Many species within the Enterobacteriaceae decarboxylate the substituted cinnamic acids p -coumaric acid and ferulic acid. The enzyme responsible is principally associated with the 'free-living' genera, Klebsiella, Enterobacter and Hafnia and is absent from Proteus mirabilis, Escherichia coli, Serratia and Salmonella spp. Some strains of Hafnia protea , a common bacterial contaminant of brewers' yeast display decarboxylase activity towards hydroxycin-namic acids. These H. protea strains (members of taxonomic group 1) produce higher concentrations of steam-volatile phenolic compounds when grown in wort than strains lacking the decarboxylase. The addition of ferulic acid or p -coumaric acid to wort prior to the growth of H. protea group 1 strains increases the concentration of steam-volatile phenolic compounds thus implicating this route as a source of phenolic off-flavours in beer.     

On the Metabolism of Organic Acids by Clostridium acetobutylicum

Racemiase, an enzyme which catalyzed racemization of lactic acids, was isolated from culture filtrate of Clostridium acetobutylicum by salting-out, and its purification was attained to about twenty-fold by treating with calcium phosphate gel. It was shown that racemiase requires for its full activity cofactors, pyridoxamine phosphate and ferrous ions. These substances were detected in the racemiasc preparation. Several other properties of racemiase were also investigated.     

Influence of Exogenous Fatty Acids on Cottonseed Germination

Effects of exogenous free fatty acid application on percentage germination and radicle length were investigated with more chill sensitive (Pima S-4) and less chill sensitive (Pima S-5) cottonseed (Gossypium barbadense L.) at chilling (14°C) and optimal (34°C) temperatures. Of the organic solvents able to solubilize free fatty acids, aqueous solutions as high as 5% dimethyl sulfoxide did not adversely affect germination at 34°C. Palmitic, oleic and linoleic acids (120 μM) were solubilized in 5% DMSO. At 14°C, percent germination of fatty acid treated Pima S-5 significantly increased, while no difference was observed for Pima S-4. Conversely, radicle length of fatty acid treated Pima S-4 significantly increased especially with oleate and linoleate, while no difference was detected for Pima S-5. Fatty acid supplementation influenced neither germination nor radicle length for Pima S-4 and Pima S-5 at 34°C.     

腐植酸对植物生理活动的影响

本文介绍了腐植酸的形成、提取、分类以及活性基团等方面的特征。腐植酸能影响植物的多种生理活动,包括植物的生长、营养元素的吸收、蛋白质和核酸的合长、光合作用、呼吸作用以及有些酶的活性等。腐植酸对植物的这些作用受自身不同成分、浓度、植物种类、外界营养条件等多方面的影响。本文也从细胞或分子水平讨论了腐植酸促进植物生长、影响营养元素吸收促进呼吸作用的机理。     

Influence of the soil on certain dermatophytes and their evolutional trend

Conclusions From our experiments it could be seen that a quite definite relationship exists between various dermatophytes and the soil which is expressed on the one side by antagonistic action of the microflora in the soil inhibiting the growth of dermatophytes and on the other, by ability of some dermatophytes to persist in the soil or to use the soil as habitat in their saprophytic life. This condition appears to be the reflection of the evolutive tendency of dermatophytes to develop from its primary habitat, the soil, to the parasitic life on man and animal. It is persumed that this evolution of dermatophytes is based on mutations of gens as one of the fundamental phenomenons in nature. It is obvious that this evolution of dermatophytes is not completed. Our experiments regardingT. mentagrophytes indicate that this species is at present still to a certain extent in a transitional evolutive stage with retained but limited ability to the life in the soil and with an evident tendency for adaption on small rodents and human beings. In this course of development on a lower level isK. ajelloi andM. gypseum with full ability of saprophytic life in the soil and with slowly but increasing pathogenicity for men and animals. E. I. Grin, Prof. of Dermatology, Med. Faculty, Univ. Sarajevo, Director Institute of Dermatovenerology. L. Oegovi, Prof. of Intern. Dis., Veter. Faculty, Univ. Sarajevo, Chief of Dept. of Mycology Inst. of Dermatovenerology.     

The Influence of Measurement Parameters on the Specific Rotation of Amino Acids

The effects of solute and hydrochloric acid concentrations on optical rotation were studied using 20 naturally occuring amino acids.

There appeared to be no common factor among the amino acids as far as the inclination of optical rotation was concerned. Lutz-Jirgenson’s rule could be applied to few amino acids in the cationic form. Therefore, in the determination of the optical rotation, the concentration of the solute, nature of solvent and temperature must be rigorously controlled. The optical conditions of measurement and the specific rotation of 20 amino acids were recommended based on this work.     

Pectin-Lipid Self-Assembly: Influence on the Formation of Polyhydroxy Fatty Acids Nanoparticles

Nanoparticles, named cutinsomes, have been prepared from aleuritic (9,10,16-trihidroxipalmitic) acid and tomato fruit cutin monomers (a mixture of mainly 9(10),16-dihydroxypalmitic acid (85%, w/w) and 16-hydroxyhexadecanoic acid (7.5%, w/w)) with pectin in aqueous solution. The process of formation of the nanoparticles of aleuritic acid plus pectin has been monitored by UV-Vis spectrophotometry, while their chemical and morphological characterization was analyzed by ATR-FTIR, TEM, and non-contact AFM. The structure of these nanoparticles can be described as a lipid core with a pectin shell. Pectin facilitated the formation of nanoparticles, by inducing their aggregation in branched chains and favoring the condensation between lipid monomers. Also, pectin determined the self-assembly of cutinsomes on highly ordered pyrolytic graphite (HOPG) surfaces, causing their opening and forming interconnected structures. In the case of cutin monomers, the nanoparticles are fused, and the condensation of the hydroxy fatty acids is strongly affected by the presence of the polysaccharide. The interaction of pectin with polyhydroxylated fatty acids could be related to an initial step in the formation of the plant biopolyester cutin.     

Influence of selenium on the efficiency of fungicide action against certain fungi

Aspergillus funiculosus was isolated from rotted banana fruits, whereas Alternaria tenuis and Fusarium sp. were isolated from rotted tomato fruits. The isolated fungi tolerated relatively high levels of the fungicide, Dithane, up to 2560 ppm on solid medium, but grew well at 40 ppm when supplemented with liquid medium. They are able to tolerate selenite up to 2% (w/v) sodium selenite. A. funiculosus showed no growth in the presence of mixture of 2.5 ppm selenium and 20 ppm Dithane, whereas Fusarium sp. failed to grow at 2.5 ppm selenium and 10 ppm Dithane, or at 10 ppm of each. Nevertheless, Alternaria tenuis is more tolerant; it showed growth in the presence of relatively high levels of selenium and Dithane; up to 10 ppm selenium and 40 ppm Dithane, however, its growth was inhibited by the presence of a mixture of both. The results suggested new form of highly active fungicides. Selenium as an essential nutrient at such very low concentrations, as well as the application of very low concentrations of the fungicide, would certainly reduce the hazardous effect of such pollutant in the environment.     

Inversion of gravitropism by symmetric blue light on the clinostat

Gravitropic stimulation of maize (Zea mays L.) seedlings resulted in a continuous curvature of the coleoptiles in a direction opposing the vector of gravity when the seedlings were rotated on a horizontal clinostat. The orientation of this response, however, was reversed when the gravitropic stimulation was preceeded by symmetric preirradiation with blue light (12.7 mol photons·m^–2). The fluence-response curve of this blue light exhibited a lower threshold at 0.5 mol·m^–2, and could be separated into two parts: fluences exceeding 5 mol·m^–2 reversed the direction of the gravitropic response, whereas for a range between the threshold and 4 mol·m^–2 a split population was obtained. In all cases a very strong curvature resulted either in the direction of gravity or in the opposite orientation. A minor fraction of seedlings, however, curved towards the caryopsis. Furthermore, the capacity of blue light to reverse the direction of the gravitropic response disappeared with the duration of gravitropic stimulation and it depended on the delay time between both stimulations. Thistonic blue-light influence appears to be transient, which is in contrast to the stability observed fortropistic blue-light effects.This work was supported by the Deutsche Forschungsgemeinschaft.     

Influence of certain stimulation parameters on the character of the cortical self-sustained after-discharge

The ECoG pattern of self-sustained after-discharges (SSADs) evoked by rhythmic electrical stimulation of the cerebral cortex is far from uniform. In acute experiments on male rats the authors studied the significance of the frequency, intensity and length of stimulation for the character of the resultant SSAD. In the first group (11 rats), a stimulation frequency of 8 Hz was used; the stimulation series, which lasted 10 and 20 s, always led to the formation of a SSAD composed of spike-and-wave rhythm right from the outset. Shortening the time of stimulation markedly reduced its effectiveness. In the second group (10 animals), stimulation with 50 Hz frequency often evoked a complex SSAD starting with desynchronization, which was followed by fast spike activity of increasing amplitude and only later by spike-and-wave rhythm or by polyspike-and-wave rhythm. Towards the end, serrated waves--i.e. graphoelements typical of SSADs evoked by electrical stimulation of limbic structures--often appeared in the SSAD. A higher stimulation intensity increased the incidence of this complex SSAD. In this group a minimum duration of stimulation was also essential (series of less than 2 s were not reliably effective). When this second type of SSAD ended, depression of ECoG activity was followed in 27% of the cases by a spontaneous recurrent seizure (RS). The ECoG character of these RS can be very variable. The two types of seizures evoked by slow and fast stimulation differ from each other not only in respect of their ECoG pattern (where the difference is probably due to more pronounced propagation to subcortical structures after faster stimulation), but also as regards the presumed mechanism of their onset.     

Influence of certain soil factors on chocolate spot of beans

In the summer of 1941 chocolate spot of beans was widespread in the South-Eastern Agricultural Province and caused much damage to the crop. Soil samples were collected from forty-nine affected fields on a variety of soil types, and the relation between the severity of attack by chocolate spot and the texture, pH, available potassium and available phosphorus determined. Severity of attack was classified into three grades: 'slight', in which only spotting of the foliage occurred; 'moderate', in which death of leaves and blossoms on the three or four lowest nodes occurred; and 'severe', in which there was generally a total loss of crop. No significant relation between severity of attack and soil texture, pH or available potassium was found. A highly significant relation was found to exist between the severity of attack and the amount of available phosphorus in the soil as determined by the method of soil analysis used in this Province. Damage by chocolate spot was generally slight on soils containing 'medium to medium high' or higher amounts of available phosphorus, and generally severe on soils containing low amounts of available phosphorus.     

Influence of Medium Buffering Capacity on Inhibition of Saccharomyces cerevisiae Growth by Acetic and Lactic Acids

Acetic acid (167 mM) and lactic acid (548 mM) completely inhibited growth of Saccharomyces cerevisiae both in minimal medium and in media which contained supplements, such as yeast extract, corn steep powder, or a mixture of amino acids. However, the yeast grew when the pH of the medium containing acetic acid or lactic acid was adjusted to 4.5, even though the medium still contained the undissociated form of either acid at a concentration of 102 mM. The results indicated that the buffer pair formed when the pH was adjusted to 4.5 stabilized the pH of the medium by sequestering protons and by lessening the negative impact of the pH drop on yeast growth, and it also decreased the difference between the extracellular and intracellular pH values (ΔpH), the driving force for the intracellular accumulation of acid. Increasing the undissociated acetic acid concentration at pH 4.5 to 163 mM by raising the concentration of the total acid to 267 mM did not increase inhibition. It is suggested that this may be the direct result of decreased acidification of the cytosol because of the intracellular buffering by the buffer pair formed from the acid already accumulated. At a concentration of 102 mM undissociated acetic acid, the yeast grew to higher cell density at pH 3.0 than at pH 4.5, suggesting that it is the total concentration of acetic acid (104 mM at pH 3.0 and 167 mM at pH 4.5) that determines the extent of growth inhibition, not the concentration of undissociated acid alone.