Climate impacts on transocean dispersal and habitat in gray whales from the Pleistocene to 2100

Arctic animals face dramatic habitat alteration due to ongoing climate change. Understanding how such species have responded to past glacial cycles can help us forecast their response to today's changing climate. Gray whales are among those marine species likely to be strongly affected by Arctic climate change, but a thorough analysis of past climate impacts on this species has been complicated by lack of information about an extinct population in the Atlantic. While little is known about the history of Atlantic gray whales or their relationship to the extant Pacific population, the extirpation of the Atlantic population during historical times has been attributed to whaling. We used a combination of ancient and modern DNA, radiocarbon dating and predictive habitat modelling to better understand the distribution of gray whales during the Pleistocene and Holocene. Our results reveal that dispersal between the Pacific and Atlantic was climate dependent and occurred both during the Pleistocene prior to the last glacial period and the early Holocene immediately following the opening of the Bering Strait. Genetic diversity in the Atlantic declined over an extended interval that predates the period of intensive commercial whaling, indicating this decline may have been precipitated by Holocene climate or other ecological causes. These first genetic data for Atlantic gray whales, particularly when combined with predictive habitat models for the year 2100, suggest that two recent sightings of gray whales in the Atlantic may represent the beginning of the expansion of this species' habitat beyond its currently realized range.     

Automated Analysis of Single-Molecule Photobleaching Data by Statistical Modeling of Spot Populations

The number of fluorophores within a molecule complex can be revealed by single-molecule photobleaching imaging. A widely applied strategy to analyze intensity traces over time is the quantification of photobleaching step counts. However, several factors can limit and bias the detection of photobleaching steps, including noise, high numbers of fluorophores, and the possibility that several photobleaching events occur almost simultaneously. In this study, we propose a new approach, to our knowledge, to determine the fluorophore number that correlates the intensity decay of a population of molecule complexes with the decay of the number of visible complexes. We validated our approach using single and fourfold Atto-labeled DNA strands. As an example we estimated the subunit stoichiometry of soluble CD95L using GFP fusion proteins. To assess the precision of our method we performed in silico experiments showing that the estimates are not biased for experimentally observed intensity fluctuations and that the relative precision remains constant with increasing number of fluorophores. In case of fractional fluorescent labeling, our simulations predicted that the fluorophore number estimate corresponds to the product of the true fluorophore number with the labeling fraction. Our method, denoted by spot number and intensity correlation (SONIC), is fully automated, robust to noise, and does not require the counting of photobleaching events.     

Changes in Neuronal Dopamine Homeostasis following 1-Methyl-4-phenylpyridinium (MPP+) Exposure

1-Methyl-4-phenylpyridinium (MPP⁺), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, selectively kills dopaminergic neurons in vivo and in vitro via a variety of toxic mechanisms, including mitochondrial dysfunction, generation of peroxynitrite, induction of apoptosis, and oxidative stress due to disruption of vesicular dopamine (DA) storage. To investigate the effects of acute MPP⁺ exposure on neuronal DA homeostasis, we measured stimulation-dependent DA release and non-exocytotic DA efflux from mouse striatal slices and extracellular, intracellular, and cytosolic DA (DA_cyt) levels in cultured mouse ventral midbrain neurons. In acute striatal slices, MPP⁺ exposure gradually decreased stimulation-dependent DA release, followed by massive DA efflux that was dependent on MPP⁺ concentration, temperature, and DA uptake transporter activity. Similarly, in mouse midbrain neuronal cultures, MPP⁺ depleted vesicular DA storage accompanied by an elevation of cytosolic and extracellular DA levels. In neuronal cell bodies, increased DA_cyt was not due to transmitter leakage from synaptic vesicles but rather to competitive MPP⁺-dependent inhibition of monoamine oxidase activity. Accordingly, monoamine oxidase blockers pargyline and l-deprenyl had no effect on DA_cyt levels in MPP⁺-treated cells and produced only a moderate effect on the survival of dopaminergic neurons treated with the toxin. In contrast, depletion of intracellular DA by blocking neurotransmitter synthesis resulted in ∼30% reduction of MPP⁺-mediated toxicity, whereas overexpression of VMAT2 completely rescued dopaminergic neurons. These results demonstrate the utility of comprehensive analysis of DA metabolism using various electrochemical methods and reveal the complexity of the effects of MPP⁺ on neuronal DA homeostasis and neurotoxicity.     

Male brood provisioning rates provide evidence for inter‐age competition for mates in female Cooper's Hawks Accipiter cooperii

Life history theory predicts that individuals should maximize lifetime reproductive success (LRS) by breeding as soon as they reach sexual maturity, yet many species delay breeding, either because there are insufficient available mates or breeding sites, or because delayed breeding yields higher LRS. Accipitriform species, such as Cooper's Hawk Accipiter cooperii, exhibit both delayed breeding and delayed plumage maturation. However, in certain circumstances, first‐year females in non‐definitive plumage do breed and apparently compete with older females for high‐quality breeding territories. We predicted that these young females are at a competitive disadvantage compared with older females and that older females would have both higher reproductive success and be able to acquire higher quality nesting territories. We conducted brood counts and measured prey delivery rates by male Cooper's Hawks in an expanding urban population located in Albuquerque, New Mexico (USA), to assess our prediction. We found that older females had higher reproductive success, fledging 1.6 more offspring than younger females, and that they occupied territories where males provisioned at higher rates of 0.37 more prey items per 2‐h period. Our results showed that older females fared better than first‐year females but it is unclear if this is the result of passive or active competition. Older females initiated nesting 14.3 days sooner than first‐year females and thus may have filled vacant, high‐quality territories before first‐year females began seeking mates. Additionally, first‐year females were never observed persistently to confront older females for breeding territories, but they did actively compete against each other. First‐year females may defer to older females who, in a direct competitive interaction, would be most likely to prevail. Thus, delayed plumage maturation in Cooper's Hawks may serve to focus competition for nesting territories within age classes.     

Nuclear Calcium/Calmodulin-dependent Protein Kinase II Signaling Enhances Cardiac Progenitor Cell Survival and Cardiac Lineage Commitment

Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) signaling in the heart regulates cardiomyocyte contractility and growth in response to elevated intracellular Ca²⁺. The δB isoform of CaMKII is the predominant nuclear splice variant in the adult heart and regulates cardiomyocyte hypertrophic gene expression by signaling to the histone deacetylase HDAC4. However, the role of CaMKIIδ in cardiac progenitor cells (CPCs) has not been previously explored. During post-natal growth endogenous CPCs display primarily cytosolic CaMKIIδ, which localizes to the nuclear compartment of CPCs after myocardial infarction injury. CPCs undergoing early differentiation in vitro increase levels of CaMKIIδB in the nuclear compartment where the kinase may contribute to the regulation of CPC commitment. CPCs modified with lentiviral-based constructs to overexpress CaMKIIδB (CPCeδB) have reduced proliferative rate compared with CPCs expressing eGFP alone (CPCe). Additionally, stable expression of CaMKIIδB promotes distinct morphological changes such as increased cell surface area and length of cells compared with CPCe. CPCeδB are resistant to oxidative stress induced by hydrogen peroxide (H₂O₂) relative to CPCe, whereas knockdown of CaMKIIδB resulted in an up-regulation of cell death and cellular senescence markers compared with scrambled treated controls. Dexamethasone (Dex) treatment increased mRNA and protein expression of cardiomyogenic markers cardiac troponin T and α-smooth muscle actin in CPCeδB compared with CPCe, suggesting increased differentiation. Therefore, CaMKIIδB may serve as a novel modulatory protein to enhance CPC survival and commitment into the cardiac and smooth muscle lineages.     

Protein Depalmitoylation Is Induced by Wnt5a and Promotes Polarized Cell Behavior

Wnt5a signaling regulates polarized cell behavior, but the downstream signaling events that promote cell polarity are not well understood. Our results show that Wnt5a promotes depalmitoylation of the melanoma cell adhesion molecule (MCAM) at cysteine 590. Mutation of Cys-590 to glycine is sufficient to polarize MCAM localization, similar to what is observed with Wnt5a stimulation. Inhibition of the depalmitoylating enzyme APT1 blocks Wnt5a-induced depalmitoylation, asymmetric MCAM localization, and cell invasion. Directly altering expression of the basal protein palmitoylation machinery is sufficient to promote cell invasion. Additionally, cancer mutations in palmitoyltransferases decrease MCAM palmitoylation and have impaired ability to suppress cell invasion. Our results provide evidence that Wnt5a induces protein depalmitoylation, which promotes polarized protein localization and cell invasion.     

Antiinflammatory Activity of a Novel Folic Acid Targeted Conjugate of the mTOR Inhibitor Everolimus

Folate receptor (FR)-β has been identified as a promising target for antimacrophage and antiinflammatory therapies. In the present study, we investigated EC0565, a folic acid–derivative of everolimus, as a FR-specific inhibitor of the mammalian target of rapamycin (mTOR). Because of its amphiphilic nature, EC0565 was first evaluated for water solubility, critical micelle formation, stability in culture and FR-binding specificity. Using FR-expressing macrophages, the effect of EC0565 on mTOR signaling and cellular proliferation was studied. The pharmacokinetics, metabolism and bioavailability of EC0565 were studied in normal rats. The in vivo activity of EC0565 was assessed in rats with adjuvant arthritis, a “macrophage-rich” model with close resemblance to rheumatoid arthritis. EC0565 forms micellar aggregates in physiological buffers and demonstrates good water solubility as well as strong multivalent FR-binding capacity. EC0565 inhibited mTOR signaling in rat macrophages at nanomolar concentrations and induced G0/G1 cell cycle arrest in serum-starved RAW264.7 cells. Subcutaneously administered EC0565 in rats displayed good bioavailability and a relatively long half-life (~12 h). When given at 250 nmol/kg, EC0565 selectively inhibited proliferating cell nuclear antigen expression in thioglycollate-stimulated rat peritoneal cells. With limited dosing regimens, the antiarthritic activity of EC0565 was found superior to that of etanercept, everolimus and a nontargeted everolimus analog. The in vivo activity of EC0565 was also comparable to that of a folate-targeted aminopterin. Folate-targeted mTOR inhibition may be an effective way of suppressing activated macrophages in sites of inflammation, especially in nutrient-deprived conditions, such as in the arthritic joints. Further investigation and improvement upon the physical and biochemical properties of EC0565 are warranted.     

Chromium is not an essential trace element for mammals: effects of a “low-chromium�?diet

Chromium was proposed to be an essential trace element over 50?years ago and has been accepted as an essential element for over 30?years. However, the studies on which chromium’s status are based are methodologically flawed. Whether chromium is an essential element has been examined for the first time in carefully controlled metal-free conditions using a series of purified diets containing various chromium contents. Male Zucker lean rats were housed in specially designed metal-free cages for 6?months and fed the AIN-93G diet with no added chromium in the mineral mix component of the diet, the standard AIN-93G diet, the standard AIN-93G diet supplemented with 200?μg?Cr/kg, or the standard AIN-93G diet supplemented with 1,000?μg?Cr/kg. The chromium content of the diet had no effect on body mass or food intake. Similarly, the chromium content of the diet had no effect on glucose levels in glucose tolerance or insulin tolerance tests. However, a distinct trend toward lower insulin levels under the curve after a glucose challenge was observed with increasing chromium content in the diet; rats on the supplemented AIN-93G diets had significantly lower areas (P?<?0.05) than rats on the low-chromium diet. The studies reveal that a diet with as little chromium as reasonably possible had no effect on body composition, glucose metabolism, or insulin sensitivity compared with a chromium-“sufficient??diet. Together with the results of other recent studies, these results clearly indicate that chromium can no longer be considered an essential element.