Selective use of abciximab in coronary stenting: overall outcomes can still be equivalent to those in the EPISTENT treatment group

BACKGROUND: The EPISTENT trial reported improved early outcomes with routine use of abciximab after coronary stenting. Increasing use of stents means that routine abciximab adds significantly to costs of percutaneous coronary intervention (PCI). This paper reports the results of a protocol encouraging restriction of abciximab therapy to high-risk patients only. METHODS: Data were collected prospectively over a 34-month period for patients undergoing PCI with stenting. In addition to those who fulfilled criteria for inclusion in the EPISTENT trial, patients treated in the setting of acute myocardial infarction (AMI) were studied. Demographic data, procedural details and early clinical outcomes were recorded. RESULTS: Of 808 patients studied, 601 fulfilled EPISTENT inclusion criteria and comprised 367 patients (45%) treated for stable angina and 234 (30%) treated for unstable or post-infarct angina. The additional 207 patients (25%) were treated during AMI. The 808 patients received a total of 981 stents. Abciximab was given in only 88 cases (10.9%). Major adverse clinical events occurred in 39 patients (4.8%). CONCLUSION: Selective use of abciximab for patients undergoing coronary stenting can be associated with outcomes equivalent to those reported for routine use, but with significant cost savings.     

A rate-independent technique for analysis of nucleic acid sequences: evolutionary parsimony

The method of evolutionary parsimony--or operator invariants--is a technique of nucleic acid sequence analysis related to parsimony analysis and explicitly designed for determining evolutionary relationships among four distantly related taxa. The method is independent of substitution rates because it is derived from consideration of the group properties of substitution operators rather than from an analysis of the probabilities of substitution in branches of a tree. In both parsimony and evolutionary parsimony, three patterns of nucleotide substitution are associated one-to-one with the three topologically linked trees for four taxa. In evolutionary parsimony, the three quantities are operator invariants. These invariants are the remnants of substitutions that have occurred in the interior branch of the tree and are analogous to the substitutions assigned to the central branch by parsimony. The two invariants associated with the incorrect trees must equal zero (statistically), whereas only the correct tree can have a nonzero invariant. The chi 2-test is used to ascertain the nonzero invariant and the statistically favored tree. Examples, obtained using data calculated with evolutionary rates and branchings designed to camouflage the true tree, show that the method accurately predicts the tree, even when substitution rates differ greatly in neighboring peripheral branches (conditions under which parsimony will consistently fail). As the number of substitutions in peripheral branches becomes fewer, the parsimony and the evolutionary-parsimony solutions converge. The method is robust and easy to use.      

Phylogenetic analysis of the South American electric fishes (order Gymnotiformes) and the evolution of their electrogenic system: a synthesis based on morphology, electrophysiology, and mitochondrial sequence data

The order Gymnotiformes (South American electric fishes) is a fascinating assemblage of freshwater fishes that share the unusual ability to produce and sense electric fields used for electrolocation and social communication. In the last few decades, the electrogenic and electrosensory systems (EES) of these fish have served as an excellent model to study motor and sensory physiology in vertebrates. In an attempt to the evolution of characters associated with the EES in the group, we applied maximum-parsimony (MP), minimum-evolution (ME), and maximum-likelihood (ML) methods to analyze 302 aligned bases of the mitochondrial 12S rRNA and 416 bases of the mitochondrial 16S rRNA of 19 gymnotiform genera representing all six recognized families. Six catfish genera (order Siluriformes) were also sequenced and used as outgroups. The phylogenetic hypothesis resultant from molecular data analysis differs in some respects from previous hypotheses based on morphological studies. Our results were most informative within the family level, as we were unable to elucidate the relationships among deeper branches in this order with sufficient confidence by using molecular data alone. The phylogenetic information of both mitochondrial DNA segments appears to be affected by functional constraints, and the resultant topologies were sensitive to different weighting schemes and the algorithm used. Nonetheless, we found unanimous support for the following phylogenetic relationships: (1) the family Sternopygidae is an unnatural group, and Sternopygus is the sole representative of a unique lineage within the order; (2) the family Hypopomidae is not monophyletic; and (3) the order Gymnotiformes is composed of at least six natural clades: Sternopygus, family Apteronotidae, a new clade consisting of the remaining sternopygids, families Hypopomidae + Rhamphicthyidae, family Electrophoridae, and family Gymnotidae. By combining molecular, morphological, and physiological information, we propose a new hypothesis for the phylogeny of this group and suggest a new family Eigenmanniidae n. (order Gymnotiformes).      

Formation of enlarged mitochondria in a liver cell line in response to a synthetic glucocorticoid

For a number of years it has been recognized that glucocorticoids cause alterations in liver cell morphology (6, 9). Several investigators have shown that in liver in vivo mitochondria can be enlarged to many times their normal volume by treatment with cortisone (13, 15). There is a concomitant decrease in mitochondrial number, and the results of Kimberg and Loeb suggest that this is due to mitochondrial fusion (7). However, the exact mechanism whereby mitochondrial volume is altered and whether in fact cortisone is the direct causal agent are not known due to the complexity of studying these questions in a whole animal system. We have found that dexamethasone sodium phosphate (dex), a synthetic glucocorticoid, causes the formation of enlarged mitochondria in a liver cell line RLC-GAI, which grows in defined medium. In this paper we present our observations on the amount of enlargement that occurs after 5 days of treatment. The formation of enlarged mitochondria is reversible upon removal of the hormone from the medium, and we have attempted to determine whether "mitochondrial" or "nonmitochondrial" inhibitors are more effective in blocking the return of mitochondria to their normal size when the hormone is removed.     

Pathways of Transformation in Ustilago Maydis Determined by DNA Conformation

Ustilago maydis was transformed by plasmids bearing a cloned, selectable gene but lacking an autonomously replicating sequence. Transformation was primarily through integration at nonhomologous loci when the plasmid DNA was circular. When the DNA was made linear by cleavage within the cloned gene, the spectrum of integration events shifted from random to targeted recombination at the resident chromosomal allele. In a large fraction of the transformants obtained using linear DNA, the plasmid DNA was not integrated but was maintained in an extrachromosomal state composed of a concatameric array of plasmid units joined end-to-end. The results suggest the operation of several pathways for transformation in U. maydis, and that DNA conformation at the time of transformation governs choice of pathways.     

Novel mutations in the pheA gene of Escherichia coli K-12 which result in highly feedback inhibition-resistant variants of chorismate mutase/prephenate dehydratase.

The bifunctional enzyme chorismate mutase/prephenate dehydratase (EC 5.4.99.5/4.2.1.51), which is encoded by the pheA gene of Escherichia coli K-12, is subject to strong feedback inhibition by L-phenylalanine. Inhibition of the prephenate dehydratase activity is almost complete at concentrations of L-phenylalanine greater than 1 mM. The pheA gene was cloned, and the promoter region was modified to enable constitutive expression of the gene on plasmid pJN302. As a preliminary to sequence analysis, a small DNA insertion at codon 338 of the pheA gene unexpectedly resulted in a partial loss of prephenate dehydratase feedback inhibition. Four other mutations in the pheA gene were identified following nitrous acid treatment of pJN302 and selection of E. coli transformants that were resistant to the toxic phenylalanine analog beta-2-thienylalanine. Each of the four mutations was located within codons 304 to 310 of the pheA gene and generated either a substitution or an in-frame deletion. The mutations led to activation of both enzymatic activities at low phenylalanine concentrations, and three of the resulting enzyme variants displayed almost complete resistance to feedback inhibition of prephenate dehydratase by phenylalanine concentrations up to 200 mM. In all four cases the mutations mapped in a region of the enzyme that has not been implicated previously in feedback inhibition sensitivity of the enzyme.     

Does progressive nuclear staining with hemalum (alum hematoxylin) involve DNA,and what is the nature of the dye-chromatin complex?

Previous investigators have disagreed about whether hemalum stains DNA or its associated nucleoproteins. I review here the literature and describe new experiments in an attempt to resolve the controversy. Hemalum solutions, which contain aluminum ions and hematein, are routinely used to stain nuclei. A solution containing 16 Al³⁺ ions for each hematein molecule, at pH 2.0–2.5, provides selective progressive staining of chromatin without cytoplasmic or extracellular “background color.” Such solutions contain a red cationic dye-metal complex and an excess of Al³⁺ ions. The red complex is converted to an insoluble blue compound, assumed to be polymeric, but of undetermined composition, when stained sections are blued in water at pH 5.5–8.5. Staining experiments with DNA, histone and DNA + histone mixtures support the theory that DNA, not histone, is progressively colored by hemalum. Extraction of nucleic acids, by either a strong acid or nucleases at near neutral pH, prevented chromatin staining by a simple cationic dye, thionine, pH 4, and by hemalum, with pH adjustments in the range, 2.0–3.5. Staining by hemalum at pH 2.0–3.5 was not inhibited by methylation, which completely prevented staining by thionine at pH 4. Staining by hemalum and other dye-metal complexes at pH ≤ 2 may be due to the high acidity of DNA-phosphodiester (pK_a ~ 1). This argument does not explain the requirement for a much higher pH to stain DNA with those dyes and fluorochromes not used as dye-metal complexes. Sequential treatment of sections with Al₂(SO₄)₃ followed by hematein provides nuclear staining that is weaker than that attainable with hemalum. Stronger staining is seen if the pH is raised to 3.0–3.5, but there is also coloration of cytoplasm and other materials. These observations do not support the theory that Al³⁺ forms bridges between chromatin and hematein. When staining with hematein is followed by an Al₂(SO₄)₃ solution, there is no significant staining. Taken together, the results of my study indicate that the red hemalum cation is electrostatically attracted to the phosphate anion of DNA. The bulky complex cation is too large to intercalate between base pairs of DNA and is unlikely to fit into the minor groove. The short range van der Waals forces that bind planar dye cations to DNA probably do not contribute to the stability of progressive hemalum staining. The red cation is precipitated in situ as a blue compound, insoluble in water, ethanol and water-ethanol mixtures, when a stained preparation is blued at pH > 5.5.