Phylogenomics of the killer whale indicates ecotype divergence in sympatry.

For many highly mobile species, the marine environment presents few obvious barriers to gene flow. Even so, there is considerable diversity within and among species, referred to by some as the 'marine speciation paradox'. The recent and diverse radiation of delphinid cetaceans (dolphins) represents a good example of this. Delphinids are capable of extensive dispersion and yet many show fine-scale genetic differentiation among populations. Proposed mechanisms include the division and isolation of populations based on habitat dependence and resource specializations, and habitat release or changing dispersal corridors during glacial cycles. Here we use a phylogenomic approach to investigate the origin of differentiated sympatric populations of killer whales (Orcinus orca). Killer whales show strong specialization on prey choice in populations of stable matrifocal social groups (ecotypes), associated with genetic and phenotypic differentiation. Our data suggest evolution in sympatry among populations of resource specialists.

Peri/nuclear localization of intact insulin-like growth factor binding protein-2 and a distinct carboxyl-terminal IGFBP-2 fragment in vivo.

Insulin-like growth factor binding protein-2 (IGFBP-2) as one of the most important IGFBPs has never been assessed in the intracellular compartment in vivo. Since there is evidence for novel intracellular functions of distinct IGFBPs, we investigated the presence of IGFBP-2 inside the cell. In peri/nuclear fractions of various tissues isolated from IGFBP-2 transgenic and non-transgenic mice we were able to show the presence of intact IGFBP-2. In addition, we demonstrate the presence of a highly conserved carboxyl-terminal IGFBP-2 fragment in the peri/nuclear fraction by using different peptide-induced antibodies. In pancreatic sections, confocal microscopy revealed the presence of IGFBP-2 on the nuclear surface but not within the nucleus. Our findings suggest novel functions of intact IGFBP-2 and IGFBP-2 fragments within the cell.

Mutation of the RGD sequence does not affect plasma membrane association and growth inhibitory effects of elevated IGFBP-2 in vivo.

Using insulin-like growth factor-binding protein-2 (IGFBP-2) transgenic mice (D mice) as a model of elevated IGFBP-2 expression, which is often found in unphysiological conditions, we found association of IGFBP-2 to purified plasma membranes of many organs. To determine whether the RGD (Arg-Gly-Asp) motif of IGFBP-2 mediates cell surface binding in vivo, we mutated the RGD motif of IGFBP-2 into an RGE (Arg-Gly-Glu) sequence and produced transgenic mice (E mice) which express elevated amounts of mutated IGFBP-2. Our data demonstrate that in vivo IGFBP-2 cell surface association is not dependent on the RGD motif and that mutation of this sequence does not alter growth inhibitory effects of IGFBP-2.

Prolonged total circulatory support using direct mechanical ventricular actuation.

Direct mechanical ventricular actuation (DMVA) is a unique, non blood contacting method for biventricular cardiac assist. Although DMVA has successfully provided cardiac assist for more than 7 days in humans, with long-term survival, its potential for long-term circulatory support has not been adequately investigated. DMVA has not been studied in the large ruminants commonly used to evaluate support devices. To develop a large animal experimental model of prolonged total circulatory support using DMVA, Suffolk sheep (n = 10) underwent sterile instrumentation for hemodynamic and chemistry monitoring. After baseline values were obtained, a left lateral thoracotomy and pericardotomy were performed. Upon electrical ventricular fibrillation (VF), DMVA was begun and the thoracotomy closed. Total circulatory support was continued until mean arterial pressure (MAP) persisted below 50% of the baseline value for more than 1 hr, with a goal of 7 days' support. Mean duration (plus or minus the standard deviation [SD]) of circulatory support was 65.9 +/- 56.8 hr (range, 10-168 hr). Pressors were not used during DMVA support. The subject supported for the maximal time (7 days) was defibrillated into sinus rhythm. No CK-MB fraction was greater than 1%, suggesting that DMVA, even with prolonged application during VF, does not result in myocardial injury. Blood urea nitrogen and creatinine levels indicate renal function was preserved. The model described represents the longest period any animal has been supported in VF using DMVA. This new model will be useful in determining what limitations, if any, exist to the prolonged use of DMVA for circulatory support.

Phospholipid/cholesteryl ester microemulsions containing unesterified cholesterol: model systems for low density lipoproteins.

As models for the effects of unesterified cholesterol (UC) on the lipid organization of low density lipoprotein (LDL), microemulsions containing either egg yolk phosphatidylcholine (EYPC) or dimyristoyl phosphatidylcholine (DMPC) as the surface component, cholesteryl oleate (CO) as the core component, and varying amounts of unesterified cholesterol were prepared by sonication. Gel filtration chromatography showed coelution of each of the lipid components, demonstrating the formation of well-defined microemulsion populations. Unesterified cholesterol incorporation into the microemulsions was proportional to the composition of the original mixture at low unesterified cholesterol compositions, but reached saturation at compositions of approximately 15 and 10 mol% unesterified cholesterol for EYPC/CO and DMPC/CO microemulsions, respectively. The Stokes' radius of the microemulsions was constant and similar to native LDL for initial compositions less than 15 mol% unesterified cholesterol, but increased at compositions above 15 mol%. In both EYPC/CO/UC and DMPC/CO/UC microemulsions, no significant changes were observed for the calorimetric or Van't Hoff enthalpy for the thermal transition of the core cholesteryl ester; however, increases in the transition temperature as a function of increasing unesterified cholesterol composition suggests that unesterified cholesterol has a stabilizing effect on the core transition. In DMPC/CO/UC microemulsions, the effect of unesterified cholesterol on the surface-located DMPC could be clearly observed as a broadening of the thermal transition of the acyl chains. These results demonstrate that unesterified cholesterol is located primarily in the surface of these protein-free lipid model systems for LDL.