ABLATIVE TECHNIQUES FOR SURGICAL TREATMENT OF PAROXYSMAL TACHYCARDIA

In this report, the collaborative efforts of cardiologists and surgeons to provide optimal treatment of patients with rhythm disturbances are discussed, along with definitive advances in new surgical techniques to relieve supraventricular tachycardia and paroxysmal ventricular tachycardia. Some of the techniques described are destined to find a permanent place in the surgeon's armamentarium.     

Complete genome sequence of Rhizobium leguminosarum bv. trifolii strain WSM1325, an effective microsymbiont of annual Mediterranean clovers

Rhizobium leguminosarum bv trifolii is a soil-inhabiting bacterium that has the capacity to be an effective nitrogen fixing microsymbiont of a diverse range of annual Trifolium (clover) species. Strain WSM1325 is an aerobic, motile, non-spore forming, Gram-negative rod isolated from root nodules collected in 1993 from the Greek Island of Serifos. WSM1325 is produced commercially in Australia as an inoculant for a broad range of annual clovers of Mediterranean origin due to its superior attributes of saprophytic competence, nitrogen fixation and acid-tolerance. Here we describe the basic features of this organism, together with the complete genome sequence, and annotation. This is the first completed genome sequence for a microsymbiont of annual clovers. We reveal that its genome size is 7,418,122 bp encoding 7,232 protein-coding genes and 61 RNA-only encoding genes. This multipartite genome contains 6 distinct replicons; a chromosome of size 4,767,043 bp and 5 plasmids of size 828,924 bp, 660,973 bp, 516,088 bp, 350,312 bp and 294,782 bp.     

A diverse family of inositol 5-phosphatases playing a role in growth and development in Dictyostelium discoideum

Inositol phosphate-containing molecules play an important role in a broad range of cellular processes. Inositol 5-phosphatases participate in the regulation of these signaling molecules. We have identified four inositol 5-phosphatases in Dictyostelium discoideum, Dd5P1-4, showing a high diversity in domain composition. Dd5P1 possesses only a inositol 5-phosphatase catalytic domain. An unique domain composition is present in Dd5P2 containing a RCC1-like domain. RCC1 has a seven-bladed propeller structure and interacts with G-proteins. Dd5P3 and Dd5P4 have a domain composition similar to human Synaptojanin with a SacI domain and OCRL with a RhoGAP domain, respectively. We have expressed the catalytic domains and show that these inositol 5-phosphatases have different substrate preferences. Single and double gene inactivation suggest a functional redundancy for Dd5P1, Dd5P2, and Dd5P3. Inactivation of the gene coding for Dd5P4 leads to defects in growth and development. These defects are restored by the expression of the complete protein but not by the 5-phosphatase catalytic domain.     

Normal conjunctival flora in the North American opossum (Didelphis virginiana) and raccoon (Procyon lotor)

We documented the normal conjunctival bacterial flora from 17 opossums (Didelphis virginiana) and 10 raccoons (Procyon lotor) trapped in Manhattan, Kansas (USA) from November 1999 to January 2000. Both raccoons and opossums were free of apparent ocular disease. The inferior conjunctival sacs of each animal were swabbed for aerobic bacterial and Mycoplasma culture and polymerase chain reaction (PCR) for Mycoplasma and Chlamydia detection. All conjunctival samples were positive for one or more species of aerobic bacteria. The most common isolate from opossums was Staphylococcus spp. Other isolates included Streptococcus spp., Bacillus spp., Corynebacterium spp., and Enterococcus faecalis. The most common isolates in raccoons was Bacillus spp. Other isolates included Streptococcus spp., Staphylococcus spp., non-hemolytic Escherichia coli, and Enterococcus faecalis. Mycoplasma culture was negative in samples from opossums and raccoons. Evidence of Mycoplasma and Chlamydia presence was detected by PCR.     

A Structure-Activity Relationship for the Hydrolysis of Acetylamino Acids by Porcine Aminoacylase

A structure-activity relationship is presented that satisfactorily predicts the rates of hydrolysis of a series of acetylglycine derivatives by porcine aminoacylase. It is apparent that the substrate specificity of aminoacylase is mainly kinetic in origin, the observed correlation with Taft's E(s) parameter supporting the notion that enzymolysis proceeds through a mechanism that is analogous to chemical hydrolysis. It is suggested that the alpha-CH(2)CH group of those substrates that possess this moiety is conformationally immobile upon binding. This lock facilitates rapid hydrolysis and results from steric interactions between the enzyme and substrate. The incorporation of alpha-methyl amino acid derivatives in the structure-activity relationship is consistent with a flexible active site model and it is concluded that the alpha-methyl effect in this system is a binding phenomenon. It is evident that the active center of porcine aminoacylase can comfortably accommodate amino acid derivatives with side chains containing less than six carbon atoms, contrary to previous assertions. It is suggested that the binding of bulkier derivatives necessitates the distortion of the active site. Derivatives possessing beta-hydroxyl groups are found to deviate from expected behavior and a nonproductive binding model is presented. Copyright 2000 Academic Press.     

Complete assignment of 1H, 13C and 15N chemical shifts for bovine β-lactoglobulin: Secondary structure and topology of the native state is retained in a partially unfolded form

Although -lactoglobulin (-LG) has been studied extensively for more than 50 years, its physical properties in solution are not yet understood fully in terms of its three-dimensional (3D) structure. For example, despite a recent high-resolution crystal structure, it is still not clear why the two common variants of bovine -LG which differ by just two residues have different aggregation properties during milk processing. We have conducted solution-state NMR studies on a recombinant form of the A variant of -LG at low pH conditions where the protein is partially unfolded and exists as a monomer rather than a dimer. Using a¹³ C,¹⁵N-labelled sample, expressed in Pichia pastoris, we have employed the standard combination of 3D heteronuclear NMR techniques to obtain near complete assignments of proton, carbon and nitrogen resonances. Using a novel pulse sequence we were able to obtain additional assignments, in particular those of methyl groups in residues preceding proline within the sequence. From chemical shifts and on the basis of inter-residue NOEs, we have inferred the secondary structure and topology of monomeric -LG A. It includes eight antiparallel -strands arranged in a barrel, flanked by an -helix, which is typical of a member of the lipocalin family. A detailed comparison with the crystal structure of the dimeric form (for a mixture of A and B variants) at pH 6.5 reveals a close resemblance in both secondary structure and overall topology. Both forms have a ninth -strand which, at the higher pH, forms part of the dimer interface. These studies represent the first full NMR assignment of -LG and will form the basis for a complete characterisation of the solution structure and dynamics of this protein and its variants.     

Reversal of Small,Dense LDL Subclass Phenotype by Normalization of Adiposity

Excess adiposity and high‐carbohydrate diets have been associated with an atherogenic lipoprotein phenotype (ALP) characterized by increased concentrations of small, dense low‐density lipoprotein (LDL) particles (pattern B). We tested whether weight loss and normalization of adiposity could reverse ALP in overweight men with pattern B. After consuming a moderate‐carbohydrate, high‐fat diet for 3 weeks, pattern B and nonpattern B (pattern A) men were randomized to a weight loss (n = 60 and n = 36, respectively) or control weight‐stable arm (n = 20 and n = 17, respectively). Men in the weight loss arm consumed ～1,000 fewer calories per day over 9 weeks to induce an average ～9 kg weight loss. In the control group, weight stability was maintained for 4 weeks after randomization. Weight loss led to the conversion of pattern B to pattern A in 58% of baseline pattern B men. Among men who achieved BMIs of <25 kg/m² (62% of pattern B men vs. 83% of pattern A men), 81% of pattern B men converted to pattern A. Weight loss was associated with a significantly greater decrease in small, dense LDL subclass 3b in pattern B relative to pattern A men. The lipoprotein profiles of pattern A men who converted from pattern B were comparable to those of men with pattern A at baseline. Conversion of LDL subclass pattern B to pattern A and reversal of ALP can be achieved in a high proportion of overweight men by normalization of adiposity.     

Pericytes display increased CCN2 expression upon culturing

By providing a source of α-smooth muscle actin (α-SMA)-expressing myofibroblasts, microvascular pericytes contribute to the matrix remodeling that occurs during tissue repair. However, the extent to which pericytes may contribute to the fibroblast phenotype post-repair is unknown. In this report, we test whether pericytes isolated from human placenta can in principle become fibroblast-like. Pericytes were cultured in vitro for 11 passages. The Affymetrix mRNA expression profile of passage 2 and passage 11 pericytes was compared. The expression of type I collagen, thrombospondin and fibronectin mRNAs was induced by passaging pericytes in culture. This induction of a fibroblast phenotype was paralleled by induction of connective tissue growth factor (CTGF/CCN2) and type I collagen protein expression and the fibroblast marker ASO2. These results indicate that, in principle, pericytes have the capacity to become fibroblast-like and that pericytes may contribute to the population of fibroblasts in a healed wound.