Alteration of the fatty acid composition of membrane phospholipids in mouse lymphoid cells

A simple method is described for introducing exogenous fatty acids into the membrane phospholipids of the murine leukemia cell EL-4, and into the membrane phospholipids of resting mouse lymphocytes. The method involves culturing of the cells with free or methylated fatty acids at concentrations up to 50 microgram/ml. The presence of serum in the culture medium does not interfere with fatty acid uptake, but does increase the growth rate and viability of the cells. Membrane lipid composition returns to normal after the cells are grown in medium without exogenous fatty acid. Fractionation of the cell membranes confirmed that exogenous fatty acids were incorporated into the phospholipids of the plasma membrane.     

The effects of temperature and growth rate on the proportion of unsaturated fatty acids in bacterial lipids

The effects of temperature and growth rate on the fatty acid composition of the extractable lipids of four mesophilic and three psychotrophic bacteria were examined. Two of the mesophiles (Escherichia coli and Pseudomonas aeruginosa) increased the proportion of unsaturated fatty acids in their lipids with decreasing temperature over their whole growth temperature range. The other mesophiles (Enterobacter aerogenes and Lactobacillus casei) increased the proportion of unsaturated fatty acids with decreasing temperature only over the lower half of their growth temperature ranges. The psychrotrophs Pseudomonas fluorescens and Enterobacter sp. had a constant proportion of unsaturated acids over the lower half of their growth temperature range, while the psychotrophic Lactobacillus sp. showed no consistent change in its unsaturated fatty acid composition with temperature. All species showed some variation of unsaturated fatty acid composition with growth rate at the highest and lowest growth temperatures, although such variations were small in some species (Ent. aerogenes and Lactobacillus sp.).     

Paternal regulation of seed development in wheat hybrids

Summary Diallel crosses among Triticum boeoticum (4 lines from different geographical areas), T.urartu, Aegilops squarrosa and Ae. speltoides exhibited reciprocal differences in hybrid seed morphology, endosperm development, and embryo viability. T. urartu and Ae. squarrosa as females with T. boeotiaum and Ae. speltoides lead to shrivelled inviable seed. T.boeoticum accessions as female with Ae.speltoides also lead to shrivelled seeds. The reciprocal crosses produced plump seeds which either resembled the maternal parent or showed size differences. By altering the endospermic genome ratios, hybrid seeds with 1 (PF)/1 (PM) showed extreme shrivelling whereas those with 4 (PF)/1 (PM) were medium shrivelled to plump. Genetic experiments involving hybrids of T. boeoticum, T. urartu and T. monococcum showed that a factor is present in pollen or male gametes, which shows dosage effect and which, by interacting with the maternal genome, leads to endosperm abortion.     

Contamination of red-meat carcasses by Campylobacter fetus subsp. jejuni.

Campylobacter fetus subsp. jejuni was commonly present in the feces of unweaned calves (2 to 3 weeks old) and from two of four groups of sheep. One new season lamb (12 to 16 weeks old) carried the organism, but the bacteria were not isolated from cattle. With unweaned calves, the fractions of animals infected and carcasses contaminated were similar. Contamination of carcasses usually involved low densities of C. fetus subsp. jejuni (ca. 1 to 10/cm2), which were isolated from flank but not rump areas. The organism was recovered less frequently from chilled carcasses and deboned veal. Small numbers of C. fetus subsp. jejuni could be recovered from equipment during the processing of unweaned calves but not after routine cleaning.     

Microbial spoilage of whole sheep livers.

When liver treated with antibiotics to inhibit microbial growth were held at 10 degrees C, the initial high pH (6.4) declined as lactic acid accumulated throughout the storage period of 10 days. The glycogen content also declined, but the glucose concentration in the tissues remained high. When livers were allowed to spoil at 10 degrees C, distinct but variable floras developed within the tissues, in the drip, and on the upper surface. Deep-tissue floras were composed of anaerobic and facultative organisms (Lactobacillus, Enterobacter, Aeromonas); surface floras were generally dominated by strictly aerobic organisms (Pseudomonas, Acinetobacter); drip floras contained variable proportions of organisms of all three types, but the facultatively anaerobic Enterobacter were usually present as a major component. Spoilage occurred after 4 to 6 days with the development of visible discrete colonies on the upper surface without spoilage odors being evident. Changes in tissue and drip composition due to microbial activity could be detected only when spoilage had reached an advanced stage.     

Effect of salinity on stomatal number,size and opening in barley Genotypes

Salinity had a varying effect on stomatal frequency, size and pore in barley (Hordeum vulgare L.). This variation in stomatal frequency, size and pore under salinity offers a scope of selecting cultivars with lesser increase in stomatal number to avoid excessive loss of water due to transpiration without effecting photosynthetic efficiency.     

Ligand-induced internalization and increased cell calcium are mediated via distinct structural elements in the carboxyl terminus of the epidermal growth factor receptor.

Signals that can mediate ligand-induced receptor internalization and calcium regulation are present in a 48-amino acid "calcium-internalization" domain in the C' terminus of the epidermal growth factor (EGF) receptor. The basis of calcium and internalization regulation signalled by this 48-amino acid sequence was analyzed using deletion and substitution mutant receptors. Cells expressing truncated receptors containing either the NH2- or COOH-terminal portion of the 48-residue domain displayed high affinity EGF-dependent endocytosis and receptor down-regulation. These endocytosis-competent EGF receptor mutants that lacked any autophosphorylation site were unable to increase the concentration of intracellular calcium. To investigate the role of self-phosphorylation in EGF-induced calcium mobilization, phenylalanine was substituted for the single autophosphorylated tyrosine residue in this region of an internalization-competent truncated receptor. The receptor-mediated calcium response was abolished, while ligand-dependent receptor internalization was unimpaired. These results demonstrate that EGF-dependent receptor endocytosis and calcium mobilization are separate events. Tyrosine self-phosphorylation is required for increased [Ca2+]i, while structural features distinct from autophosphorylation are required for receptor internalization.     

A dodecamer of globin chains is the principal functional subunit of the extracellular hemoglobin of Lumbricus terrestris

Repeated dissociation of the approximately 3600-kDa hexagonal bilayer extracellular hemoglobin of Lumbricus terrestris in 4 M urea followed by gel filtration at neutral pH produces a subunit that retains the oxygen affinity of the native molecule (approximately 12 torr), but only two-thirds of the cooperativity (nmax = 2.1 +/- 0.2 versus 3.3 +/- 0.3). The mass of this subunit was estimated to be 202 +/- 15 kDa by gel filtration and 202 +/- 26 kDa from mass measurements of unstained freeze-dried specimens by scanning transmission electron microscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this subunit showed that it consists predominantly of the heme-containing subunits M (chain I, 17 kDa) and T (disulfide-bonded chains II-IV, 50 kDa). Mixing of subunits M and T isolated concurrently with the 200-kDa subunit resulted in partial association into particles that had a mass of 191 +/- 13 kDa determined by gel filtration and 200 +/- 38 kDa determined by scanning transmission electron microscopy and whose oxygen affinity and cooperativity were the same as those of the 200-kDa subunit. The results imply that the 200-kDa subunit is a dodecamer of globin chains, consisting of three copies each of subunits M and T (3 x chains (I + II + III + IV], in good agreement with the mass of 209 kDa calculated from the amino acid sequences of the four chains, and represents the largest functional subunit of Lumbricus hemoglobin. Twelve copies of this subunit would account for two-thirds of the total mass of the molecule, as suggested earlier (Vinogradov, S. N., Lugo, S. L., Mainwaring, M. G., Kapp, O. H., and Crewe, A. V. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 8034-8038). The retention of only partial cooperativity by the 200-kDa subunit implies that full cooperativity is dependent on the presence of a complete hexagonal bilayer structure, wherein 12 200-kDa subunits are linked together by approximately 30-kDa heme-deficient chains.