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P Lund

Publications and source records attributed to P Lund.

At least 19 recordsLinked to original sources
PubMed1992

A plant signal sequence enhances the secretion of bacterial ChiA in transgenic tobacco.

When the secreted bacterial protein ChiA is expressed in transgenic tobacco, a fraction of the protein is glycosylated and secreted from the plant cells; however most of the protein remains inside the cells. We tested whether the efficiency of secretion could be improved by replacing the bacterial signal sequence with a plant signal sequence. We found the signal sequence and the first two amino acids of the PR1b protein attached to the ChiA mature protein directs complete glycosylation and secretion of the ChiA from plant cells. Glycosylation of this protein is not required for its efficient secretion from plant cells.

Amino Acid Sequence↗
PubMed1991

Binding of a chaperonin to the folding intermediates of lactate dehydrogenase.

When Bacillus stearothermophilus LDH dimer is incubated with increasing concentrations of the denaturant guanidinium chloride, three distinct unfolded states of the molecule are observed at equilibrium [Smith, C. J., et al. (1991) Biochemistry 30, 1028-1036]. The kinetics of LDH refolding are consistent with an unbranched progression through these states. The Escherichia coli chaperonin, GroEL, binds with high affinity to the completely denatured form and more weakly to the earliest folding intermediate, thus retarding the refolding process. A later structurally defined folding intermediate, corresponding to a molten globule form, is not bound by GroEL; neither is the inactive monomer. The complex between GroEL and denatured LDH is destabilized by the binding of magnesium/ATP (Mg/ATP) or by the nonhydrolyzable analogue adenylyl imidodiphosphate (AMP-PNP). From our initial kinetic data, we propose that GroEL exists in two interconvertible forms, one of which is stabilized by the binding of Mg/ATP but associates weakly with the unfolded protein. The other is destabilized by Mg/ATP and associates strongly with unfolded LDH. The relevance of these findings to the role of GroEL in vivo is discussed.

Adenine Nucleotides↗
PubMed1991

Expression of antifreeze proteins in transgenic plants.

The quality of frozen fruits and vegetables can be compromised by the damaging effects of ice crystal growth within the frozen tissue. Antifreeze proteins in the blood of some polar fishes have been shown to inhibit ice recrystallization at low concentrations. In order to determine whether expression of genes of this type confers improved freezing properties to plant tissue, we have produced transgenic tobacco and tomato plants which express genes encoding antifreeze proteins. The afa3 antifreeze gene was expressed at high steady-state mRNA levels in leaves from transformed plants, but we did not detect inhibition of ice recrystallization in tissue extracts. However, both mRNA and fusion proteins were detectable in transgenic tomato tissue containing a chimeric gene encoding a fusion protein truncated staphylococcal protein A and antifreeze protein. Furthermore, ice recrystallization inhibition was detected in this transgenic tissue.

Amino Acid Sequence↗
PubMed1991

Ceftriaxone vs. ampicillin + metronidazole as prophylaxis against infections after clean-contaminated abdominal surgery.

In a prospective, controlled, double-blind study, 496 patients undergoing abdominal surgery were given antibiotic prophylaxis with a single dose of either ceftriaxone or ampicillin + metronidazole. No significant intergroup difference was found between the respective overall rates of infectious complications (3.2% and 4.9%). Analysis of the microbiologic findings showed incisional wound infections, mainly caused by gram-negative rods, to be more common in the ampicillin-metronidazole group, whereas deep wound infections were more frequent in the ceftriaxone group. It is concluded that ceftriaxone seems to be more efficient than ampicillin-metronidazole as prophylaxis against incisional wound infection, but should preferably be supplemented with an antianaerobic agent to prevent deep wound infections.

Abdomen↗
PubMed1990

Maintenance of energy-linked functions in rat liver mitochondria.

EGTA and EDTA are compared with respect to their ability to preserve ATP-requiring reactions in rat liver mitochondria. The presence of EGTA sustains the high ATP requirement of citrulline synthesis. EDTA does not, even with excess Mg2+. Carboxylation of pyruvate, which has a lower ATP demand, is not influenced by the type of chelating agent. In mitochondria stored for 24 h at 4 degrees C, EGTA is more effective than EDTA in preventing loss of these energy-linked functions.

Adenine Nucleotides↗
PubMed1990

[Mr. Hilde].

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Afghanistan↗
PubMed1990

Homologous recombination in plant cells after Agrobacterium-mediated transformation.

A single amino-acid change in the acetolactate synthase (ALS) protein of tobacco confers resistance to the herbicide chlorsulfuron. A deleted, nonfunctional fragment from the acetolactate synthase gene, carrying the mutant site specifying chlorsulfuron resistance plus a closely linked novel restriction site marker, was cloned into a binary vector. Tobacco protoplasts transformed with Agrobacterium tumefaciens carrying this vector yielded chlorsulfuron-resistant colonies. DNA gel blot analysis of DNA from these colonies suggested that in three transformants homologous recombination had occurred between the endogenous ALS gene and the deleted ALS gene present in the incoming T-DNA. Plants were regenerated from these chlorsulfuron-resistant colonies, and in two of the transformants, genetic analysis of their progeny showed that the novel gene segregated as a single Mendelian locus. Possible models for the generation of these recombinant plants are discussed.

Acetolactate Synthase↗
PubMed1990

Gastric emptying and subjective symptoms of nausea: lack of effects of a 5-hydroxytryptamine-3 antagonist ondansetron on gastric emptying in patients with gastric stasis syndrome.

Thirty-seven consecutive patients referred to a regional gastroenterology outpatient clinic with complaints of persistent nausea had a double isotopic scintigraphic evaluation of solid and liquid gastric emptying. Gastric emptying of both forms followed an exponential model. Marked day to day variation of gastric emptying was noted with a coefficient of variation of approximately 0.20 for both phases. Only 9 of 37 patients had delayed gastric emptying rate of the solid component (greater than 180 min) and no correlation between gastric stasis syndrome and nausea was established. Among these patients the median time for the stomach to empty 50% of the solid component was 261 min and 50% of the liquid component was 66 min. Treatment of these 9 patients shown to have gastric stasis syndrome and further 3 patients with diabetic gastroparesis with ondansetron, a highly selective antagonist of 5-hydroxytryptamine-3-receptors, resulted in a gastric emptying rate which was not statistically faster than after placebo (p = 0.11).

Adult↗
PubMed1989

Chelating agents and rat liver mitochondria.

The chelating agents (EGTA and EDTA) and inorganic phosphate (Pi) are the most variable components of experiments involving isolated liver mitochondria. In the absence of EGTA or EDTA, swelling induced by Pi leads to rapid loss of endogenous adenine nucleotides to adenosine. Chelating agents prevent swelling and loss of adenine nucleotides. Concentrations below about 0.1 mM are ineffective. The protective effects depend on the continuous presence of the chelating agent; they are lost on washing EGTA-containing suspensions with chelating-agent-free medium. We question the accepted view that chelating agents stabilize mitochondria by binding Ca2+ to prevent activation of phospholipase.

Adenine Nucleotides↗
PubMed1989

Up-promoter mutations in the positively-regulated mer promoter of Tn501.

Transcription from the mer promoter of transposon Tn501 is repressed by MerR (the product of the merR gene) in the absence of Hg2+, and activated by MerR in the presence of Hg2+. In the absence of MerR, the mer promoter has weak constitutive activity. The DNA sequence of the mer promoter shows candidate -35 and -10 sequences at the unusually high spacing of 19 base-pairs. We have selected for spontaneous mutations in the mer promoter that confer an up-promoter phenotype. Four different mutants have been isolated. Three of these are single base-pair deletions between the -10 and -35 sequences. A fourth removes the -10 sequence entirely, and places a second potential -10 sequence 17 base-pairs from the -35 sequence. None of these mutant promoters are induced by MerR in the presence of Hg2+. Two of them are repressed by MerR irrespective of the presence or absence of Hg2+. Models for the mode of action of the MerR protein are discussed in the light of these results. Our data support a mechanism in which the MerR protein in the presence of Hg2+ acts to change the conformation of DNA in the mer promoter.

Bacterial Proteins↗
PubMed1989

High hepatitis B carrier rate among non-Oriental patients with acute salpingitis.

Hepatitis B surface antigen screening was performed on non-Oriental patients with the diagnosis of acute salpingitis. Six of 59 (10.17%) had hepatitis B surface antigenemia. We therefore recommend hepatitis B screening for all patients with salpingitis. The detection of covert hepatitis B helps to protect hospital staff and provides important information for the patient. Further, the administration of hepatitis B vaccine may be appropriate for those patients with acute salpingitis who are found to be hepatitis B surface antigen-negative.

Acute Disease↗