A phylogenetic comparison of gene trees constructed from plastid, mitochondrial and genomic DNA of Plasmodium species.

Gene trees of Plasmodium species have been reported for the nuclear encoded genes (e.g. the Small Subunit rRNA) and a mitochondrial encoded gene, cytochrome b. Here, we have analyzed a plastid gene coding for caseinolytic protease ClpC, whose structure, function and evolutionary history have been studied in various organisms. This protein possesses a 220-250 amino acid long AAA domain (ATPases associated with a variety of cellular activities) that belongs to the Walker super family of ATPases and GTPases. We have sequenced the AAA motif of this gene, encoding the protein from nine different species of Plasmodium infecting rodents, birds, monkeys, and humans. The codon usage and GC content of each gene were nearly identical in contrast to the widely varying nucleotide composition of genomic DNAs. Phylogenetic trees derived from both DNA and inferred protein sequences have consistent topologies. We have used the ClpC sequence to analyze the phylogenetic relationship among Plasmodium species and compared it with those derived from mitochondrial and genomic sequences. The results corroborate well with the trees constructed using the mitochondrially encoded cytochrome b. However, an important element distinguishes the trees: the placement of Plasmodium elongatum near the base of the plastid tree, indicating an ancient lineage of parasites in birds that branches from the tree prior to other lineages of avian malaria and the human parasite, P. falciparum.

Synthetic fibronectin peptides suppress arthritis in rats by interrupting leukocyte adhesion and recruitment.

In an experimental model of arthritis, increased leukocyte adhesion is associated with the evolution of acute and chronic synovial inflammation. Whereas peripheral blood mononuclear cells (PBMC) from control animals bind minimally to fibronectin matrices, PBMC from animals receiving arthropathic doses of bacterial cell walls demonstrate increased integrin mRNA expression and enhanced adhesion. To determine whether this augmented adhesion was causal in the development of synovial pathology, peptides synthesized from several fibronectin domains which inhibited leukocyte adhesion in vitro were administered to arthritic animals either as free peptides or coupled to a carrier molecule. Not only were peptides containing either the RGD or CS-1 cell-binding domains inhibitory to chronic synovial pathology (articular index = 10.5 +/- 0.3 for untreated animals compared to 1.25 +/- 0.25 for RGD and 2.5 +/- 0.7 for CS-1), but three peptides synthesized from the carboxy-terminal 33-kD heparin-binding domain of fibronectin were also found to significantly inhibit leukocyte recruitment and the evolution of arthritis. Based on these data, which are the first to explore the therapeutic potential of heparin-binding fibronectin peptides in chronic inflammation, it appears that antagonism of cellular adhesion and recruitment by fibronectin peptides may provide an important mechanism for modulating the multi-step adhesion process and attenuating aberrant inflammatory responses.

Diltiazem and nitrendipine suppress hypoxic contracture in quiescent ventricular myocardium.

Calcium blocking agents may protect the ischaemic heart by reducing ventricular afterload and cardiac contractility, or by augmenting myocardial perfusion. To determine whether protection is mediated in part by mechanisms unrelated to myocardial work and perfusion, we examined effects of diltiazem and nitrendipine on unperfused myocardium subjected to hypoxia. Rabbit right ventricular papillary muscles were mounted in a myograph containing Krebs buffer equilibrated at 37 degrees C with 95% O2-5% CO2. During brief electrical pacing at a frequency of 12 min-1, a preload of 1363 +/- 60 mg produced a maximal isometric force development of 4892 +/- 273 mg (SE; n = 113). After 60 min without pacing, the quiescent muscles were pre-equilibrated randomly for 20 min without drug for control (C = 38), or with 10(-6) diltiazem (n = 38) or 10(-6) mol l-1 nitrendipine (n = 38). Changes in resting force during equilibration did not exceed +/- 12 mg. Subsequent sudden de-oxygenation with 95% N2-5% CO2 evoked in controls an increase in force beginning after 16 +/- 1 min. The onset of hypoxic contracture was significantly (P less than 0.1) delayed in treated muscles and started after 31 +/- 3 min with diltiazem and after 23 +/- 2 min with nifedipine. Peak contracture was significantly (P less than 0.1) inhibited by diltiazem and nitrendipine compared to controls, respectively values averaging 264 +/- 22 mg, 480 +/- 44 mg and 895 +/- 70 mg. Thus, calcium blockers delayed and suppressed hypoxic contracture in quiescent myocardium, demonstrating that the drugs acted directly on cardiac muscle in the absence of rhythmic electrical and mechanical activity.