Biomass production in a nitrogen-fertilized,tallgrass prairie ecosystem exposed to ambient and elevated levels of CO2

Increased biomass production in terrestrial ecosystems with elevated atmospheric CO₂ may be constrained by nutrient limitations as a result of increased requirement or reduced availability caused by reduced turnover rates of nutrients. To determine the short-term impact of nitrogen (N) fertilization on plant biomass production under elevated CO₂, we compared the response of N-fertilized tallgrass prairie at ambient and twice-ambient CO₂ levels over a 2-year period. Native tallgrass prairie plots (4.5 m diameter) were exposed continuously (24 h) to ambient and twice-ambient CO₂ from 1 April to 26 October. We compared our results to an unfertilized companion experiment on the same research site. Above- and belowground biomass production and leaf area of fertilized plots were greater with elevated than ambient CO₂ in both years. The increase in biomass at high CO₂ occurred mainly aboveground in 1991, a dry year, and belowground in 1990, a wet year. Nitrogen concentration was lower in plants exposed to elevated CO₂, but total standing crop N was greater at high CO₂. Increased root biomass under elevated CO₂ apparently increased N uptake. The biomass production response to elevated CO₂ was much greater on N-fertilized than unfertilized prairie, particularly in the dry year. We conclude that biomass production response to elevated CO₂ was suppressed by N limitation in years with below-normal precipitation. Reduced N concentration in above- and belowground biomass could slow microbial degradation of soil organic matter and surface litter, thereby exacerbating N limitation in the long term.     

Lipase-catalyzed alcoholysis of triglycerides for the preparation of 2-monoglycerides

Rhizopus arrhizus lipase immobilized on celite was used to prepare isomerically pure 2-monoglycerides by alcoholysis of triglycerides in organic media. Reaction parameters such as choice of solvent, choice of alcohol, and alcohol concentration were studied. When 12.5 mM tripalmitin was used as substrate, methyl-tert-butyl ether was the best solvent for alcoholysis at water activity 0.11. Ethanol gave the highest yield (97%) at an optimal ethanol concentration of 200–300 mM. At higher alcohol concentrations, the enzyme activity was substantially lowered. The enzyme preparation showed high stability in repeated-batch reactions.     

Elucidation of the mechanism of CryIIIA overproduction in a mutagenized strain of Bacillus thuringiensis var. tenebrionis

NB176 is a Bacillus thuringiensis mutant derived by λ-irradiation of NB125 Bacillus thuringiensis var. tenebrionis (Krieg). It exhibits two interesting phenotypes: (i) oligosporogeny and (ii) twofold to threefold overproduction of the CryIIIA protein. Southern profiles of the NB176 strain showed an additional copy(s) of the cryIIIA gene located on a 4 kb HindIII fragment, in addition to the expected cryIIIA gene on a 3 kb HindIII fragment. Each cryIIIA gene-bearing HindIII fragment was cloned from NB176. The restriction map of the 3 kb HindIII fragment was identical to that published by Donovan and coworkers. Sequencing of the 4 kb HindIII fragment showed no alterations in the promoter region of the cryIIIA gene but did show replacement of the region immediately following the cryIIIA open reading frame with a sequence encoding a transposase with 50% amino acid homology to that of Tn 1000. These findings suggest that the overproduction phenotype of NB176 results from extra copies of the cryIIIA gene produced from a transposition event(s) induced or stabilized by γ-irradiation. Integration of additional copies of the cryIIIA gene into the native 90MDa plasmid of the wild-type B. thuringiensis var. tenebrionis strain resulted in strains that made enormous crystals, many possessing greatly enhanced insecticidal activity.     

Receptor interactions of the position 4 side chains of angiotensin II analogues: Importance of aromatic ring quadrupole

A triad of interacting group (TyrOH? His$ \underline\ominus$O₂C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr⁴ residue in [Sar¹]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar¹ Nva(δ-OH)⁴]ANG II, [Sar¹ Nva(δ-OCH₃)⁴]ANG II, [Sar¹ Met⁴]ANG II, [Sar¹ Gln⁴]ANG II, [Sar¹ Glu⁴]ANG II and [Sar¹ DL -Alg⁴]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar¹ Nal⁴]ANG II, [Sar¹ Pal⁴]ANG II, [Sar¹ DL -Phg(4′-F)⁴]ANG II, [Sar¹ Phe(4′-F)⁴]ANG II, [Sar¹ Phe(F₅)⁴]ANG II and [Sar¹ His⁴]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar¹] Phe(4′-F)⁴ ANG II (pA₂ = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA₂) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity.     

Procedure for whole mount fluorescence in situ hybridization of interphase nuclei on Arabidopsis thaliana

A procedure for whole mount fluorescence in situ hybridization (FISH) on plant tissue is reported. The technique was demonstrated on seedlings and flowers of Arabidopsis thaliana L. with rDNA as a probe, labelled, both for direct and indirect detection. It was found that fixation in 1% formaldehyde yielded the best results with respect to morphology and hybridization efficiency. The combination of whole mount FISH and confocal scanning laser microscopy allowed the nuclear localization of the rDNA loci in all tissues of both seedlings and flowers. Direct labelling yielded the best signal-to-noise ratio, especially in the apical zones of the seedlings. The technique was further illustrated on seedlings of A. thaliana in double labelling experiments with rDNA and a tandemly repeated, 500 bp sequence of A. thaliana. Although nuclei in all tissues in the seedling exhibited both signals, hybridization efficiency for both signals was reduced in the dense, apical zones as compared with single labelling experiments with rDNA.     

1α,25-dihydroxyvitamin D3 hybrid analogs with structural changes at both the A-ring and the C,D-ring side-chain

Calcitrol analogs 5, designed to combine two remote structural changes each of which separately produces a sharply different biological profile, have biological activities that are a blending of the effects of each structural change.     

Apparent regression of the CGG repeat in FMR1 to an allele of normal size

The fragile X syndrome is the result of amplification of a CGG trinucleotide repeat in the FMR1 gene and anticipation in this disease is caused by an intergenerational expansion of this repeat. Although regression of a CGG repeat in the premutation range is not uncommon, regression from a full premutation (>200 repeats) or premutation range (50–200 repeats) to a repeat of normal size (<50 repeats) has not yet been documented. We present here a family in which the number of repeats apparently regressed from approximately 110 in the mother to 44 in her daughter. Although the CGG repeat of the daughter is in the normal range, she is a carrier of the fragile X mutation based upon the segregation pattern of Xq27 markers flanking FMR1. It is unclear, however, whether this allele of 44 repeats will be stably transmitted, as the daughter has as yet no progeny. Nevertheless, the size range between normal alleles and premutation alleles overlap, a factor that complicates genetic counseling.     

Thermodynamics of ubiquitin unfolding

The energetics of ubiquitin unfolding have been studied using differential scanning microcalorimetry. For the first time it has been shown directly that the enthalpy of protein unfolding is a nonlinear function of temperature. Thermodynamic parameters of ubiquitin unfolding were correlated with the structure of the protein. The enthalpy of hydrogen bonding in ubiquitin was calculated and compared to that obtained for other proteins. It appears that the energy of hydrogen bonding correlates with the average length of the hydrogen bond in a given protein structure. © 1994 John Wiley & Sons, Inc.     

Localization of a New Type of X-Linked Liver Glycogenosis to the Chromosomal Region Xp22 Containing the Liver α-Subunit of Phosphorylase Kinase (PHKA2)

We describe here a new type of X-linked liver glycogen storage disease. The main symptoms include liver enlargement and growth retardation. The clinical and biochemical abnormalities of this glycogenosis are similar to those of classical X-linked liver glycogenosis due to phosphorylase kinase deficiency (XLG). However, in contrast to patients with XLG, the patients described here have no reduced phosphorylase kinase activity in erythrocytes and leukocytes, and no enzyme deficiency could be found. Linkage analysis of four families with this X-linked type of liver glycogenosis assigned the disease gene to Xp22. Lod scores obtained with the markers DXS987, DXS207, and DXS999 were 3.97, 2.71, and 2.40, respectively, all at 0% recombination. Multipoint linkage analysis localized the disease gene between DXS143 and DXS989 with a maximum lod score of 4.70 at θ = 0, relative to DXS987. As both the classical XLG gene and the liver α-subunit of PHK (PHKA2) are also located in Xp22, this variant type of XLG may be allelic to classical XLG, and both diseases may be caused by mutations in PHKA2. Therefore, we propose to classify XLG as XLG type I (the classical type of XLG) and XLG type II (the variant type of XLG).     

The loss of culturability by Escherichia coli cells in seawater depends on availability of phosphate ions and phosphate transport systems

Using strains with or without the PhoE porin or different components of the phosphate regulon, we determined that maintenance of the culturability of Escherichia coli in seawater depended significantly on the presence of structures allowing access of phosphate ions to the periplasm, then to the cytoplasm of cells. Cells totally deprived of the two main phosphate transport systems (Pit, Pst) exhibited the highest loss of culturability. Most of this effect resulted from the loss of the high-affinity Pst system, and more specifically that of the periplasmic phosphate-binding protein PhoS. Survival was enhanced in seawater supplemented with phosphate (0.5 mm), whether or not these structures were present. From an ecological point of view, it is assumed that the presence of phosphate ions, even at low concentrations, can influence the behavior of E. coli cells in seawater. Offprint requests to: M.J. Gauthier