Antitumour activities of levans produced by Zymomonas mobilis strains

Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.     

Characteristics of lactococci cultures produced in commercial media

Strains ofLactococcus lactis ssplactis andL. lactis sspcremoris were propagated on milk, three commercial highly buffered media (HB media), and four commercial media designed for external pH control (EC media). With milk and HB media, fermentation was allowed to proceed until a pH of 4.9 was reached. With EC media, pH was maintained at 6.0 with 5 N NH₄OH. The cultures were analyzed for chain length, viable population, specific acidifying activity (SAA) and specific proteolytic activity (SPA). The starters were stored at 4° C for 3 days, and analyses for chain length, viable population and SAA were repeated. It was more difficult to standardize medium composition with the rehydrated commercial blends, as their titratable acidities had greater proportional variations than milk. As a rule, chain length was longer in fresh cultures than in the stored starters, andL. lactis sppcremoris cultures had longer chains thanL. lactis ssplactis. All commercial media produced starters with total populations at least as high as that obtained in milk. With the EC media, populations could be five times greater than with milk; increases were less important in HB media. The increase in population in EC and HB media was more marked withL. lactis ssplactis than forL. lactis sspcremoris strains. Storage at 4° C for 3 days did not significantly reduceL. lactis populations, but mortality (up to 70%) was observed withL. lactis sspcremoris. The overall SAA ofL. lactis ssplactis cultures in EC media was 35% lower than milk- or HB media-grown starters, but the greater populations reached in EC media enabled a significant reduction in inoculation rate. Some statistically significant correlations were obtained between SAA and SPA (positive) as well as with chain length (negative), but the coefficients of determination were generally very low. The drop in pH during storage at 4° C was less with HB media than in milk, and was in relation to their buffering capacity.     

Combined effects of sulfites, temperature, and agitation time on production of glycerol in grape juice by Saccharomyces cerevisiae.

Analysis of variance was used to evaluate the simultaneous effects of strain, incubation temperature (15 to 25 degrees C), agitation time (0 to 24 h), and initial sulfite concentration (100 to 300 ppm) on glycerol production in grape juice by Saccharomyces cerevisiae. Fourteen strains were studied to determine their growth patterns in the presence of sulfites and ethanol. Baker's yeast strains were more sensitive to sulfite than wine strains, and little growth occurred at initial sulfite levels greater than 150 ppm. Sensitivity to sulfite increased with increasing levels of ethanol. Three strains exhibiting the best growth in the presence of sulfites and ethanol were selected for interaction studies. Fermentations were carried out until the solids content had decreased to less than 6 degrees Brix, which was the point that glycerol content became stable. For the three strains used, the greatest level of glycerol production was observed in the presence of 300 ppm of sulfite for most incubation temperatures and agitation times. There was significant interaction between the strain, incubation temperature, and agitation time parameters for glycerol synthesis, and a response surface method was used to predict the optimal conditions for glycerol production. Under static conditions, the highest level of glycerol production was observed at 20 degrees C, while incubation at 25 degrees C gave the best results when the cultures were agitated for 24 h. Response surface equations were used to predict that the optimum conditions for glycerol production by S. cerevisiae Y11 were a temperature of 22 degrees C, an initial sulfite concentration of 300 ppm, and no agitation, which yielded 0.68 g of glycerol per 100 ml.     

Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex

The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S nuclear ribosomal DNA sequence and the intervening 5.8S region were sequenced from three individuals in each of eight taxa of the Mimulus guttatus species complex. Three discrete variants, or "types," of ITS sequences were found, among which 30%-40% of sites differed, compared with 1%-2% within types. Dot plots indicate that these types were not related by conspicuous rearrangements or inversions. More than one ITS type was often found in the same taxon, and two of three ITS types span species boundaries, indicating their presence prior to speciation. These ITS sequences showed essentially no positional homology with the nearest sequenced relative, tomato. In contrast, the 5.8S region was relatively unvaried, with 8 of 162 sites varied in the sample among all eight taxa. The phylogeny inferred by the most common ITS sequence type, rooted by the two other ITS types, agreed with isozymes in showing the distinctness of M. nudatus, M. laciniatus, and M. tilingii from the other five taxa.      

Production of concentrated freeze-dried cultures of Bifidobacterium longumin k-carrageenan-locust bean gum gel

Bifidobacterium longum was immobilized in k-carrageenan/locust bean gum gel beads, and cultured in a medium containing Lactobacillus MRS broth and whey-permeate. The same beads were incubated for 5 successive batch fermentations and freeze-dried following mixing with a protective solution. Viable population in the beads increased from 8 3 10 7 to 4.7 3 10 10 cfu/g after three batch fermentations, but no further increase in viable cell population could be achieved in the last two fermentations. The freeze-dried culture contained 3 3 10 10 cfu/g with a survival rate of approximately 10%. Survival to freeze-drying of immobilized cells was as good as that of classical free-cell cultures. Stability of freeze-dried cultures during storage at minus 17, 4 and 20°C was not influenced by immobilization.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Complete cDNA sequences of mouse rod photoreceptor cGMP phosphodiesterase alpha- and beta-subunits, and identification of beta'-, a putative beta-subunit isozyme produced by alternative splicing of the beta-subunit gene.

We have characterized overlapping cDNA clones encoding cGMP phosphodiesterase (PDE) alpha- and beta-subunits of mouse retinal rod photoreceptors. The open reading frames predict an alpha-subunit of 100 kDa (856 residues), and a beta-subunit of 99 kDa (853 residues). Sequence analysis of two of twelve beta-subunit clones predicts the presence in the retina of an additional PDE, termed beta', which is generated by alternative splicing of the beta-subunit gene. beta' differs from beta only at the C-terminus being 55 residues shorter and lacking the Caax motif found at the C-termini of both the alpha- and beta-subunits. A 300 residue segment thought to contain the active site is present in the C-terminal half of alpha, beta and beta'.     

Effect of medium on growth and subsequent survival,after freeze-drying,ofLactobacillus delbrueckii subsp.bulgaricus

Summary Growth ofLactobacillus delbrueckii subsp.bulgaricus, grown at a constant pH (5.7) in papain-or pepsin-treated whey was superior to that in whey or whey permeate, but inferior to growth in milk; it was not significantly different from that found in a 1:1 whey: milk medium. When 2% sodium citrate was added to the fermented medium, the cell recovery levels (59–75%) upon centrifugation were not significantly different in papain-treated media compared to untreated substrates. Cultures obtained from papain-treated milk or whey showed similar mortality levels following freeze-drying (99%) to those grown on untreated milk or whey. Addition of Tween 80 to the growth medium improved survival rate by a factor of ten.     

Preparative steps necessary for the accurate measurement of malondialdehyde by high-performance liquid chromatography.

The need for a more specific, reliable, and reproducible technique for the measurement of malondialdehyde (MDA) has prompted modifications of currently available methods based on the formation and recovery of the complex between MDA and thiobarbituric acid (TBA). To 500 microliters of plasma or to 300 mg of liver homogenate, 2 ml of H2O and 500 microliters of 0.5% butylated hydroxytoluene in methanol were added to prevent further formation of MDA. Precipitation of proteins carried out with 200 microliters of 0.66 N H2SO4 and 150 microliters of 10% Na2WO4 (w/v) led to complete recovery of the MDA standard. Maximum formation of the MDA-TBA complex was obtained by adjusting the pH between 2.5 and 4.5 and heating the MDA-TBA mixture at 100 degrees C for 60 min. Extraction of the MDA-TBA complex was a critical step and proved complete with n-butanol at pH less than 0.75. It was then evaporated at 37 degrees C under nitrogen. The MDA-TBA complex solubilized in H2O was shown to be stable for at least 7 days. These preparative steps led to the detection of a single peak that on spectral analysis was identified as pure MDA-TBA. This procedure offers several advantages in terms of specificity, recovery, and reproducibility.     

Particular structural role of H1 in complexes with DNA and comparison with H2A- and H4-DNA complexes investigated by IR linear dichroism.

The particular role of H1 in the structure of histone–DNA associations is shown by means of ir linear dichroism. H1–, H2A–, and H4–DNA complexes are studied for different histone: DNA input ratios and various relative humidities (r.h.). The measurement of the dichroic ratios allows one to determine the secondary structure of DNA in the complexes. It is shown that the progressive addition of histone H2A or H4 to DNA inhibits the structural B → A transition and DNA remains in a B-type form at low r.h. It is found that the B → A transition is inhibited for 19 or 26 base pairs of DNA per molecule of H2A or H4. The stabilization of DNA in a B-conformation by H2A and H4 has been also observed by H2B and H3 but with a different efficiency. In contrast, histone H1, which does not belong to the core of the nucleosomes in chromatin, leaves the DNA in H1–DNA complexes free to adopt an A conformation at low r.h. for H1/DNA ratios below 0.6/1. Thus a major difference in the structural role between histone H1 and histones belonging to the nucleosomal core with respect to the conformational flexibility of DNA in the histone–DNA complexes is demonstrated.