Effects of fructose on human fibroblast metabolism: the application of DNA measurements as a basis for interpretation

Summary A fluorometric procedure for measuring DNA was used to study growth and metabolic responses of eight cell strains of human foreskin fibroblasts. In preliminary studies this procedure gave more precise specific activity changes inN-acetyl-β-d-glucosaminidase (NAG) than did a protein activity basis, when changes in this enzyme's specific activity were investigated as a function of experimental cell manipulation. When fibroblast growth in eight cell strains was compared in 134 mM d-fructose vs. 13.4 mM glucose-supplemented minimum essential media, a significant increase in cellular DNA (50%) and protein (45%) occurred over an 11-d period. No significant differences in media pH change, lactate production, or carbohydrate uptake occurred on a DNA basis when cell metabolism was compared over the last 24 h of culture in the two media. Cells grown in fructose-containing media tended to show a reduction in NAG specific activity when compared with those grown in glucose-containing media.     

Aspects of the mineral nutrition of some native British plants — inter-site variation

Fifteen common native British plants were each sampled at a range of sites in Great Britain and green tissues analysed for several inorganic nutrients. Sampling criteria are discussed. The inter-site variation of each element within a species is assessed as a frequency distribution of raw data. Sample values of parameters including arithmetic mean, variance (coefficient of variation), skewness and kurtosis are presented. Their stability is assessed from nitrogen in sub-samples of Pteridium. This suggested sample sizes were adequate but some distributions had sufficient kurtosis to affect the variance. These parameters showed distinctions between macro- and micro-elements and between species. Some mean values sharply distinguished between species and may help to assess current theories of strategy and adaptation but a wider range of species is needed to clarify trends. Coefficients of variation are discussed and were relatively low for a nation-wide survey after allowing for sampling constraints. Coefficients of skewness and kurtosis showed two-thirds of the sample distributions were non-normal. Ecological aspects of the distributions are discussed and are relevant to studies along environmental gradients. Published hypotheses linking positive skewness to stress in the field are considered and two other postulates discussed. Distribution bounds such as those confining 95% of the values are discussed in relation to possible critical levels of nutrients.Nomenclature follows Clapham et al. (1981), Excursion flora of the British Isles. 3rd ed. University Press, Cambridge, except Chamaenerion.     

Nuclear DNA content in differentiated tissues of sunflower (Helianthus annuus L.)

Summary Scanning cytophotometry following Feulgen-staining was used to determine nuclear DNA content in many differentiated tissues of nine cultivars, hybrids or selfed lines ofHelianthus annuus. Apart from such ephemeral tissues as endosperm and anther tapetum, it was found that tissue differentiation in sunflower occurs in the diploid condition, cells being arrested in the DNA presynthetic phase (G₁). In certain cases, however, the nuclear DNA content of differentiated G₁ cells does not exactly match the 2C DNA content found in meristematic cells, but may be either higher or lower. In endosperm and anther tapetum cells, nuclear DNA content may be as high as 24 C and 32 C, respectively. Cytological and autoradiographic analyses after³H-thymidine incorporation reveal that polyploidy in the tapetal cells is due to chromosome endoreduplication. No detectable difference between male-fertile and male-sterile plants exists as far as occurrence and level of cell polyploidy are concerned. The results are discussed in the context of previous investigations on the nuclear condition of differentiatedHelianthus annuus tissue.     

Comparison of fatty acid content and DNA homology of the filamentous gliding bacteriaVitreoscilla,Flexibacter, Filibacter

DNA hybridization experiments showed that there was a high degree of homology amongVitreoscilla strains but not with DNA fromFilibacter limicola. Flexibacter spp were much more heterogeneous indicating a low genetic similarity. These results were also reflected in the membrane fatty acids of the bacteria. TheVitreoscilla strains were very similar with the 16:17c fatty acid being dominant. The membrane fatty acids ofF. limicola were dominated by a15:0 and a17:0 components which provided additional support for its relatedness to the genusBacillus. There was much greater diversity in the fatty acid patterns of theFlexibacter spp.F. aurantiacus, F. ruber andF. elegans shared the common dominant fatty acids 16:17c with theVitreoscilla strains, but this was replaced by the 16:16c acid inF. flexilis. F. ruber was distinguished by the absence of branched odd-chain monounsaturated fatty acids andF. elegans by the dominance of the -OH i15:0 acid. Precise determination of fatty acid double bond positions and geometry are essential for correct interpretation of increasingly complex ecological and taxonomic data sets.     

Isolation and characterization of a human interleukin 2 gene

An interleukin 2 (IL-2) gene was isolated from a Charon 4A human gene library. Electron microscopic examination of 15 heteroduplexes formed between the genomic DNAs and the IL-2 cDNAs demonstrated that the size of the IL-2 gene is about 5.1 +/- 0.5 kb and that there are at least two introns in this gene. Nucleotide sequence of the 5' flanking region of the IL-2 gene showed a homology with that of the corresponding region of the human immune interferon gene.     

Light-driven proton transport of bacteriorhodopsin incorporated into long-term stable liposomes of a polymerizable sulfolipid

The chromoprotein bacteriorhodopsin from Halobacterium halobium has been incorporated into liposomes made of a fully synthetic, polymerizable lipid. Bacteriorhodopsin is found to be active in these polymer liposomes. The advantage in the use of such polymer systems concerning long-term stability in comparison with liposomes made of natural lipid is demonstrated.     

The Identity of Hexokinase Activities from Mitochondrial and Cytoplasmic Fractions of Rat Brain Homogenates

Cytoplasmic hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) was purified from the soluble fraction of a rat brain homogenate by a procedure that included a unique affinity elution of the enzyme from Blue Dextran-Sepharose. The purified enzyme was examined with respect to properties in which the impure cytoplasmic enzyme has been reported to differ from the solubilized mitochondrial enzyme. These included the ability to bind to mitochondria, inhibition by quercetin, effect of pH on activity, and kinetics. In all regards the purified mitochondrial and cytoplasmic enzymes appeared identical. In addition, comparative peptide maps after partial proteolysis showed no detectable differences. These results do not support the view that there exist distinct mitochondrial and cytoplasmic forms of hexokinase, the latter being permanently relegated to a cytoplasmic location and unable to participate in a dynamic equilibrium with the mitochondrially-bound enzyme. Alternatives are proposed to explain previous results that had been interpreted as indirect evidence for the existence of a distinct cytoplasmic hexokinase.     

Different structure of polytene chromosomes ofPhaseolus coccineus suspensors during early embryogenesis

Summary The pattern of DNA and RNA puffs in pair VII of polytene chromosomes has been investigated in the suspensor ofPhaseolus coccineus during early embryo development. The pattern of³H-TdR and³H-U incorporation has been also detected. Collected data indicate that: 1. both heterochromatic regions, p₁₁ and q_(111+112), of chromosome pair VII, organize large DNA puffs; 2. DNA puffs of both regions are specific of different embryo differentiation steps; 3. a seasonal influence on the DNA puffing seems also to be present, as demonstrated by the comparison of the results collected in two different crops; 4. the incorporation experiment by³H-TdR evidences that not all DNA puffs show clustered labeling; 5. the RNA puffing of the two regions seems also to be specific of determined embryo stages.     

Electrophoretic elution of nucleic acids from acrylamide and agarose gels

A simple method for electrophoretic elution of nucleic acids from gel slices is described. The procedure utilizes a standard tube gel system and can be completed in as little as one hour. Nucleic acids are recovered in a small volume with almost 100% efficiency. The procedure is applicable equally to acrylamide and agarose gels, and small as well as large RNA and DNA molecules. The eluted nucleic acids are essentially undegraded and are suitable for a variety of structural and biological analyses.