Distribution of Feline Blood Types Detected in the Copenhagen Area of Denmark

The purpose of the present study was to make the first survey of the distribution of feline AB blood types in the Copenhagen area of Denmark. A total of 244 cats (139 purebred cats and 105 Domestic Shorthair cats) were tested. 93% of all tested cats had blood type A. Neither an AB nor an O type cat was detected and thus, the frequency of blood type B among all tested cats was 7%. Most type B cats were purebred cats (Birman, British Shorthair and Persian cats). No association between sex and blood type could be demonstrated among British Shorthair and Persian cats. Thus, the present study indicates that cats in Denmark predominantly have blood type A, and that blood type B cats are rare, except for certain breeds such as Birman and British Shorthair cats.     

The X-ray structure analysis of bis-2,2′,N,N′-bipyridyl ketone cobalt(III) nitrate dihydrate

An X-ray structural analysis of bis-2,2′,N,N′-bipyridyl ketone cobalt(III) nitrate dihydrate, CoC₂₂H₂₀N₄O₄⁺· NO₃⁻·2H₂O,M_r=559.38 g/mol, P , a=8.862(2), b=16.195(3), c=8.772(2) Å, α=103.54(2), β=95.74(3), γ=105.07°, V=1164.4(4) ų, Z=2, D_x=1.595 g/cm³, Mo Kα radiation (λ=0.71073 Å), μ=7.8 cm⁻¹ and R=0.079, revealed a Co(III) cation in a slightly distorted octahedral environment. The structure reveals that the ligand di-2-pyridyl ketone (dpk) has undergone a hydration reaction across the ketone double bond and one of the hydrate oxygen atoms coordinated to the metal forming a tridentate chelate. This new Co(dpk-hydrate)₂⁺ complex displays the least distorted geometry yet reported for either 1:1 or 1:2 (metal:ligand) complexes. A geometry optimization using the INDO model Hamiltonian as implemented in the program ZINDO was performed on the title complex with the Co³⁺ modeled as a singlet. The result of the computation corroborates the geometry of the title complex as that expected for Co³⁺.     

Excess capacity of H(+)-ATPase and inverse respiratory control in Escherichia coli.

With succinate as free-energy source, Escherichia coli generating virtually all ATP by oxidative phosphorylation might be expected heavily to tax its ATP generating capacity. To examine this the H(+)-ATPase (ATP synthase) was modulated over a 30-fold range. Decreasing the amount of H(+)-ATPase reduced the growth rate much less than proportionally; the H(+)-ATPase controlled growth rate by < 10%. This lack of control reflected excess capacity: the rate of ATP synthesis per H(+)-ATPase (the turnover number) increased by 60% when the number of enzymes was decreased by 40%. At 15% H(+)-ATPase, the enzyme became limiting and its turnover was increased even further, due to an increased driving force caused by a reduction in the total flux through the enzymes. At smaller reductions of [H(+)-ATPase] the total flux was not reduced, revealing a second cause for increased turnover number through increased membrane potential: respiration was increased, showing that in E.coli, respiration and ATP synthesis are, in part, inversely coupled. Indeed, growth yield per O2 decreased, suggesting significant leakage or slip at the high respiration rates and membrane potential found at low H(+)-ATPase concentrations, and explaining that growth yield may be increased by activating the H(+)-ATPase.     

Clues from a halophilic methanogen about aromatic amino acid biosynthesis in archaebacteria

Extensive diversity in features of aromatic amino acid biosynthesis and regulation has become recognized in eubacteria, but almost nothing is known about the extent to which such diversity exists within the archaebacteria. Methanohalophilus mahii, a methylotrophic halophilic methanogen, was found to synthesize l-phenylalanine and l-tyrosine via phenylpyruvate and 4-hydroxyphenylpyruvate, respectively. Enzymes capable of using l-arogenate as substrate were not found. Prephenate dehydrogenase was highly sensitive to feedback inhibition by l-tyrosine and could utilize either NADP⁺ (preferred) or NAD⁺ as cosubstrate. Tyrosine-pathway dehydrogenases having the combination of narrow specificity for a cyclohexadienyl substrate but broad specificity for pyridine nucleotide cofactor have not been described before. The chorismate mutase enzyme found is a member of a class which is insensitive to allosteric control. The most noteworthy character state was prephenate dehydratase which proved to be subject to multimetabolite control by feedback inhibitor (l-phenylalanine) and allosteric activators (l-tyrosine, l-tryptophan, l-leucine, l-methionine and l-isoleucine). This interlock type of prephenate dehydratase, also known to be broadly distributed among the gram-positive lineage of the eubacteria, was previously shown to exist in the extreme halophile, Halobacterium vallismortis. The results are consistent with the conclusion based upon 16S rRNA analyses that Methanomicrobiales and the extreme halophiles cluster together.Abbreviation DAHP 3-deoxy-d-arabino-heptulosonate-7-phosphate     

Cyclitol production in transgenic tobacco

High levels of cyclic sugar alcohols (cyclitols) correlate with tolerance to osmotic stress in a number of plant species. A gene encoding a cyclitol biosynthesis enzyme from a halophyte, Mesembryanthemum crystallinum has been introduced into tobacco. The gene, lmt1 , encodes a myo -inositol O -methyl transferase that, in M. crystallinum , catalyzes the first step in the stress-induced accumulation of the cyclitol pinitol. Tobacco transformed with the lmt1 cDNA under the control of the CaMV 35S promoter appeared phenotypically normal and exhibited IMT1 enzyme activity. Transformants accumulated a carbohydrate product not detectable in non-transformed control plants. This product was identified by HPLC and NMR as ononitol (1- d -4- O -methyl myo -inositol). Ononitol was a major carbohydrate constituent in leaf tissue of plants expressing the lmt1 gene, accumulating to up to 25% the level of sucrose in transformant seedlings. The identification of ononitol as the IMT1 product and the specific accumulation of this compound in transformed tobacco support a role for ononitol as a stable intermediate in pinitol biosynthesis and indicate that an epimerization activity lacking in tobacco is responsible for the conversion of ononitol to pinitol in M. crystallinum . The production of ononitol in tobacco indicates that plant carbohydrate metabolism is flexible and can accommodate the synthesis and accumulation of non-endogenous metabolites. The transgenic system described here will serve as a useful model to test the ability of cyclitols such as ononitol to confer tolerance to environmental stress in a normally glycophytic plant.     

Effect of nitrogen application on growth and photosynthetic nitrogen use efficiency in two ecotypes of wild strawberry, Fragaria chiloensis

The relationships between increasing nitrogen fertilization and growth, maximum CO₂ assimilation and the initial slope of the CO₂ response curve were studied in 2 ecotypes of wild strawberry, Fragaria chiloensis (L.) Duchn. Nitrogen accumulation of CA11, an ecotype from a low-nutrient dune site, was greater at all nitrogen concentrations than that of RCP37, an ecotype from a higher-nutrient strand site. Maximum CO₂ assimilation, total Rubisco activity, dry weight, and initiation of leaves and crowns were higher in CAI1 than RCP37 as nitrogen treatment was increased from 0 to 200 mg ^l-1, whereas these parameters were lower in CAl1 when fertilized at 300 mg T¹, but not in RCP37. The mean leaf area of CA11 was greater than RCP37 when grown with no supplemental nitrogen, but mean leaf area of the 2 lines was similar under nitrogen fertilization. Maximum CO₂ assimilation and carboxylation efficiency increased with increasing leaf nitrogen in both clones. At equivalent concentrations of leaf nitrogen, RCP37 had higher CO₂ assimilation and carboxylation efficiency than CA11 and the difference between the 2 clones increased as ieaf nitrogen increased. Thus, RCP37 had a higher photosynthetic nitrogen use efficiency than CA11. However, at a given applied nitrogen level, CA11 allocated more nitrogen to a unit of leaf area so that photosynthetic rates were higher than RCP37, except at the highest application of 300 mg ^l-1. The high nitrogen accumulation capacity and resource allocation to fruiting structures (crowns) in CA11 leads us to suggest that this clone may possess genes that could increase fruit yield in cultivated strawberry.     

COMPETITION BETWEEN STAURASTRUM LUETKEMUELLERII (CHLOROPHYCEAE) AND MICROCYSTIS AERUGINOSA(CYANOPHYCEAE) UNDER VARYING MODES OF PHOSPHATE SUPPLY1

The desmid Staurastrum luetkemuellerii Donat et Ruttner and the cyanobacterium Microcystis aeruginosa Kütz. were grown in mixed cultures with various phosphate (P_i) additions. One pulse of P_i each day (semi-continuous cultures) favored M. aeruginosa whereas S. luetkemuellerii was favored when the same quantity of P_i was supplied continuously (chemostats). Both species coexisted under P limitation provided that the nutrient was supplied in an appropriate mode. The ability of each species to compete for P depended on their P_i uptake characteristics and their capability to retain the accumulated P_i. High affinity in uptake at low P_i concentrations contributed considerably to the growth eficiency of S. luetkemuellerii under continuous supply of P_iM. aeruginosa was, however, consistently superior to S. luetkemuellerii in accuniulatiug the newly added P, but had a high rate of P_i release. In both -types of cultures, a net high of P went from M. aeruginosa to S. luetkemuellerii. The kinetic characteristics of the two species were used to simulate the outcome of competition experiments. Simulations agreed with the experimental data f both uptake and P_i release were considered in the model. The zlariable P*(the concentration of P_i at which the net uptake is equal to μ·Q_P is a function of uptake and release of P_i but could not explain the chemostat results. S. luetkemuellerii was the winner in many experiments even if its P*was higher thou that of M. aeruginosa. Thus, in the present case P_c (the concentration at which the net uptake is zero) was a better predictor of the ability to compete for P_i under steady state as well as transient conditions in the P_i supply.     

Listeria monocytogenes in poultry and poultry products: epidemiological investigations in seven Danish abattoirs

Listeria monocytogenes was isolated from 11/236 (4·7%) caecal samples from parent flocks, providing broilers to the abattoirs investigated. Caecal samples from 2078 broilers representing 90 randomly selected broiler flocks were negative for L. monocytogenes. A total of 3080 samples from seven abattoirs including poultry processing line samples, and final products were also examined for L. monocytogenes. Listeria monocytogenes was isolated in 0·3% to 18·7% of the samples collected in the different abattoirs. Epidemiological typing of 247 L. monocytogenes isolates, including serotyping, phage typing, pulsed-field gel electrophoresis and ribotyping revealed 62 different clones. Based upon typability and discriminatory power, DNA typing methods used were found equally suitable as epidemiological markers. Serotyping and phage typing were not found useful as epidemiological markers for poultry isolates of L. monocytogenes since only 120/247 (48·6%) isolates were typable by phage typing and 230/247 (93·1%) L. monocytogenes belonged to serotype 01 while 6/247 (2·4%) belonged to 04. The discovery of a few dominating clones in each abattoir might indicate an endemic occurrence of L. monocytogenes. It is concluded that L. monocytogenes in the broiler production is primarily localized to the abattoirs. The incidence of L. monocytogenes may be reduced by improving the hygiene.     

Purification and characterization of recombinantStreptomyces clavuligerus isopenicillin N synthase produced inEscherichia coli

Recombinant isopenicillin N synthase fromStreptomyces clavuligerus was produced in the form of inactive inclusion bodies inEscherichia coli. These inclusion bodies were solubilized by treatment with 5 M urea under reducing conditions. Optimization of refolding conditions to recover active isopenicillin N synthase indicated that a dialysis procedure carried out at a protein concentration of about 1.0 mg ml^–1 gave maximal recovery of active isopenicillin N synthase. Solubilized isopenicillin N synthase of more than 95% purity was obtained by passing this material through a DEAE-Trisacryl ion exchange column. Expression studies conducted at different temperatures indicated that isopenicillin N synthase was produced predominantly in a soluble, active form when expression was conducted at 20°C, and accounted for about 20% of the total soluble protein. This high-level production facilitated the purification of soluble isopenicillin N synthase to near homogeneity in four steps. Characterization of the purified soluble and solubilized isopenicillin N synthase revealed that they are very similar.