Evolution of miniaturization and the phylogenetic position of <Emphasis Type="Italic">Paedocypris</Emphasis>, comprising the world's smallest vertebrate

Background  

Paedocypris, a highly developmentally truncated fish from peat swamp forests in Southeast Asia, comprises the world's smallest vertebrate. Although clearly a cyprinid fish, a hypothesis about its phylogenetic position among the subfamilies of this largest teleost family, with over 2400 species, does not exist. Here we present a phylogenetic analyses of 227 cypriniform taxa, including 213 cyprinids, based upon complete mitochondrial DNA cytochrome b nucleotide sequences in order to determine the phylogenetic position of Paedocypris and to study the evolution of miniaturization among cyprinids.     

Electromechanical Interactions in Cell Walls of Gram-Positive Cocci

Isolated cell walls of Staphylococcus aureus and Micrococcus lysodeikticus were found to expand and contract in response to changes in environmental pH and ionic strength. These volume changes, which could amount to as much as a doubling of wall dextran-impermeable volume, were related to changes in electrostatic interactions among fixed, ionized groups in wall polymers, including peptidoglycans. S. aureus walls were structurally more compact in the hydrated state and had a higher maximum charge density than M. lysodeikticus walls. However, they were less responsive to changes in electrostatic interactions, apparently because of less mechanical compliance. In media of nearly neutral pH, S. aureus walls had a net positive charge whereas M. lysodeikticus walls had a net negative charge. These charge differences were reflected in Donnan distributions of mobile ions between wall phases and bulk medium phases. Cell walls of unfractionated cocci also could be made to swell and contract, and wall tonus in intact cells appeared to be set partly by electrostatic interactions and partly by mechanical tension in the elastic structures due to cell turgor pressure. The experimental results led to the conclusions that bacterial cell walls have many of the properties of polyelectrolyte gels and that peptidoglycans are flexible polymers. A reasonable mechanical model for peptidoglycan structure might be a sort of three-dimensional rope ladder with relatively rigid, polysaccharide rungs and relatively flexible polypeptide ropes. Thus, the peptidoglycan network surrounding cocci appeared to be predominantly an elastic restraining structure rather than a rigid shell.     

Cloning and characterization of Hunk, a novel mammalian SNF1-related protein kinase

We previously identified a novel protein kinase, Hunk, by means of a degenerate PCR screen designed to isolate kinases expressed in the murine mammary gland. We now describe the molecular cloning, chromosomal localization, and activity of this kinase and characterize its spatial and temporal pattern of expression in the mouse. We have isolated a 5.0-kb full-length cDNA clone that contains the 714-amino-acid open reading frame encoding Hunk. Analysis of this cDNA reveals that Hunk is most closely related to the SNF1 family of serine/threonine kinases and contains a newly described SNF1 homology domain. Accordingly, antisera specific for Hunk detect an 80-kDa polypeptide with associated phosphotransferase activity. Hunk is located on distal mouse chromosome 16 in a region of conserved synteny with human chromosome 21q22. During fetal development and in the adult mouse, Hunk mRNA expression is developmentally regulated and tissue-specific. Moreover, in situ hybridization analysis reveals that Hunk expression is restricted to subsets of cells within a variety of organs in the adult mouse. These findings suggest a role for Hunk in murine development.     

Dielectric properties of native and decoated spores of Bacillus megaterium.

A general model for use in interpreting dielectric data obtained with bacterial endospores is developed and applied to past results for Bacillus cereus spores and new results for Bacillus megaterium spores. The latter were also subjected to a decoating treatment to yield dormant cells with damaged outer membranes that could be germinated with lysozyme. For both spore types, core ions appeared to be completely immobilized, and decoating of B. megaterium spores did not affect this extreme state of electrostasis in the core. The cortex of B. megaterium appeared to contain a high level of mobile ions, in the cortex of B. cereus. The outer membrane-coat complex of B. megaterium acted dielectrically as an insulating layer around the cortex, so that native dormant spores showed a Maxwell-Wagner dispersion over the frequency range from about 1 to 20 MHz. The decoating treatment resulted in a shift in the dispersion to frequencies below the range of observation. Increases in cell conductivity in response to increases in environmental ionic strength indicated that the coats. of B. megaterium could be penetrated by environmental ions and that they had an inherent fixed charge concentration of about 10 to 20 milliequivalents per liter. In contrast, the dispersion for B. cereus spores was very sensitive to changes in environmental ion concentration, and it appeared that some 40% of the spore volume could be penetrated by environmental ions and that these ions traversed a dielectrically effective layer, either the exosporium or the outer membrane. It appears that dormancy is associated with extreme electrostasis of core ions but not necessarily of ions in enveloping structures and that the coat-outer membrane complex is dielectrically effective but not required for maintenance of extreme electrostasis in the core.     

Intracellular Leishmania: your iron or mine?

Iron is a co-factor for several essential enzymes and biochemical pathways, including those required for replication of pathogens such as Leishmania in macrophages. Iron acquisition is emerging as a key battleground in which the iron import systems of microbes are pitted against the iron withdrawal and sequestration systems of macrophages, with both competing for iron at the interface of host-pathogen interaction. The recent characterization of a ferrous iron transport system (LIT1) in Leishmania amazonensis that is induced intracellularly and is required for survival in macrophages and for virulence in vivo provides an elegant example of the adaptation of protozoa to the iron-poor phagosomal environment.     

Spore heat resistance and specific mineralization

Spores of Bacillus megaterium ATCC 19213, Bacillus subtilis niger and Bacillus stearothermophilus ATCC 7953 were converted to fully demineralized, but viable, H forms by controlled acid titration. H forms were more heat sensitive than were native forms, but z values were greater for killing of H spores than those for native spores. Therefore, the differences in heat sensitivity between native and H forms decreased with increasing killing temperature. The increase in heat sensitivity associated with demineralization did not appear to be due to damage to cortex lytic enzymes of the germination system because it could not be moderated by decoating heated H spores and plating them on medium with added lysozyme. H spores could be remineralized by means of back titration with appropriate base solutions. The remineralized spores, except for the Na form, were then more heat resistant than were H spores. Ca and Mn were more effective in restoring resistance than were Mg and K. Generally, the remineralized forms (except for the Na form) had z values greater than those of the native forms but still less than those of the H forms. At lower killing temperatures, the reinstatement of resistance could be related to the extent of remineralization. However, at higher killing temperatures, only a fraction of the mineral was effective in restoring resistance, and higher levels of remineralization did not result in greater resistance. Mineralization is clearly an important factor in spore heat resistance, but the relationship between resistance and mineralization is complex and dependent on killing temperature.     

Granulocyte colony-stimulating factor therapy for stem cell mobilization following anterior wall myocardial infarction: the CAPITAL STEM MI randomized trial

Background:

Small studies have yielded divergent results for administration of granulocyte colony-stimulating factor (G-CSF) after acute myocardial infarction. Adequately powered studies involving patients with at least moderate left ventricular dysfunction are lacking.

Methods:

Patients with left ventricular ejection fraction less than 45% after anterior-wall myocardial infarction were treated with G-CSF (10 μg/kg daily for 4 days) or placebo. After initial randomization of 86 patients, 41 in the placebo group and 39 in the G-CSF group completed 6-month follow-up and underwent measurement of left ventricular ejection fraction by radionuclide angiography.

Results:

Baseline and 6-week mean ejection fraction was similar for the G-CSF and placebo groups: 34.8% (95% confidence interval [CI] 32.6%–37.0%) v. 36.4% (95% CI 33.5%–39.2%) at baseline and 39.8% (95% CI 36.2%–43.4%) v. 43.1% (95% CI 39.2%–47.0%) at 6 weeks. However, G-CSF therapy was associated with a lower ejection fraction at 6 months relative to placebo (40.8% [95% CI 37.4%–44.2%] v. 46.0% [95% CI 42.7%–44.3%]). Both groups had improved left ventricular function, but change in left ventricular ejection fraction was lower in patients treated with G-CSF than in those who received placebo (5.7 [95% CI 3.4–8.1] percentage points v. 9.2 [95% CI 6.3–12.1] percentage points). One or more of a composite of several major adverse cardiac events occurred in 8 patients (19%) within each group, with similar rates of target-vessel revascularization.

Interpretation:

In patients with moderate left ventricular dysfunction following anterior-wall infarction, G-CSF therapy was associated with a lower 6-month left ventricular ejection fraction but no increased risk of major adverse cardiac events. Future studies of G-CSF in patients with left ventricular dysfunction should be monitored closely for safety. Trial registration: ClinicalTrials.gov, no. {"type":"clinical-trial","attrs":{"text":"NCT00394498","term_id":"NCT00394498"}}NCT00394498Rapid reperfusion therapy has become the standard treatment for ST-segment elevation myocardial infarction (STEMI), with congestive heart failure and left ventricular dysfunction continuing as the strongest predictors of higher long-term risk.¹ To date, no definitive therapies exist to regenerate myocardium following myocardial necrosis, and myocardial preservation is therefore the goal of STEMI care. Contemporary studies have suggested the possibility of myocardial regeneration by endogenous stem and progenitor cell populations, and preliminary clinical studies have hinted at potential benefit.^2,3 Studies investigating whether postinfarction myocardial function can be improved by enhancing stem cell–mediated repair are in progress ({"type":"clinical-trial","attrs":{"text":"NCT00936819","term_id":"NCT00936819"}}NCT00936819 and {"type":"clinical-trial","attrs":{"text":"NCT00984178","term_id":"NCT00984178"}}NCT00984178).Granulocyte colony-stimulating factor (G-CSF), an endogenously produced glycoprotein growth factor, when given in pharmacologic doses, stimulates mobilization of hematopoietic stem cells into the peripheral blood. Therapeutically, recombinant synthetic forms have been used to enhance recovery from neutropenia following chemotherapy and for mobilization of stem cells before hematopoietic stem cell transplant.⁴ Numerous small clinical studies have investigated the potential of G-CSF–induced mobilization of stem cells in the peri-infarction period to enhance left ventricular recovery, but they have yielded discordant results. However, meta-analyses have suggested benefit for left ventricular ejection fraction in subgroups who received G-CSF early after infarction or in patients whose left ventricular dysfunction was mild to moderate.^5,6 Larger trials are necessary because, in addition to mobilizing stem cells, G-CSF modulates intracellular signalling cascades within cardiomyocytes and can activate neutrophils, and several trials have been stopped early as a result of excessive in-stent restenosis and acute coronary syndromes in patients with coronary artery disease.^7–11 Animal data have similarly yielded discordant results, depending on the dose and timing of G-CSF.¹²To clarify the role of G-CSF in promoting left ventricular recovery after acute myocardial infarction, we performed an adequately powered randomized clinical trial in patients with moderate left ventricular dysfunction following anterior-wall STEMI.     

Phylogenetic variation and polymorphism at the Toll-like receptor 4 locus (TLR4)

Background  

Differences in responses to bacterial surface lipopolysaccharides (LPSs) are apparent between and within mammalian species. It has been shown in mice that resistance to LPS is caused by defects in the Toll-like receptor 4 gene (Tlr4), the product of which is thought to bind LPS and mediate LPS signal transduction in immune system cells.