Diet, foraging, and use of space in wild golden-headed lion tamarins

Lion tamarins (Callitrichidae: Leontopithecus) are small frugi-faunivores that defend large home ranges. We describe results from the first long-term investigation of wild golden-headed lion tamarins (L. chrysomelas; GHLTs). We present data about activity budgets, daily activity cycles, diet, daily path length, home range size, home range overlap, and territorial encounters for three groups of GHLTs that were studied for 1.5-2.5 years in Una Biological Reserve, Bahia State, Brazil, an area characterized by aseasonal rainfall. We compare our results to those from other studies of lion tamarins to identify factors that may influence foraging and ranging patterns in this genus. Ripe fruit, nectar, insects, and small vertebrates were the primary components of the GHLT diet, and gums were rarely eaten. Fruit comprised the majority of plant feeding bouts, and the GHLTs ate at least 79 different species of plants from 32 families. The most common foraging sites for animal prey were epiphytic bromeliads. The GHLTs defended large home ranges averaging 123 ha, but showed strong affinities for core areas, spending 50% of their time in approximately 11% of their home range. Encounters with neighboring groups averaged two encounters every 9 days, and they were always aggressive. Data about time budgets and daily activity cycles reveal that the GHLTs spent most of their time foraging for resources or traveling between foraging sites distributed throughout their home ranges. The GHLTs spent much less time consuming exudates compared to lion tamarins in more seasonal environments. Additionally, the GHLTs had much larger home ranges than golden lion tamarins (L. rosalia), and did not engage in territorial encounters as frequently as L. rosalia. GHLT ranging patterns appear to be strongly influenced by resource acquisition and, to a lesser extent, by resource defense.     

Chronic ethanol feeding impairs endothelin-1-stimulated glucose uptake via decreased G alpha 11 expression in rat adipocytes

Chronic ethanol feeding decreases insulin-stimulated glucose uptake in rat adipocytes. Here, we show that chronic ethanol also decreases endothelin-stimulated glucose uptake. Endothelin-1 increased uptake of 2-deoxyglucose 2.4-fold in adipocytes isolated from pair-fed rats. However, in adipocytes isolated from rats that had consumed a diet containing 35% ethanol for 4 wk, endothelin-1 did not increase glucose uptake. Although endothelin-1 increased GLUT4 quantity at the plasma membrane in adipocytes from pair-fed rats, there was no increase in GLUT4 after chronic ethanol feeding. Loss of endothelin-1-stimulated glucose uptake after ethanol feeding was associated with a specific decrease in the quantity of Galpha11 in plasma membranes, with no change in Galphaq quantity. Activation of proline-rich tyrosine kinase 2 (PYK2), a downstream target of Galphaq/11 that is required for endothelin-1-stimulated GLUT4 translocation in 3T3-L1 adipocytes, was also suppressed after chronic ethanol feeding. In contrast, activation of p38 MAPK by endothelin-1 was not affected by chronic ethanol exposure. These data demonstrate that chronic ethanol feeding suppresses endothelin-1-stimulated glucose uptake and suggest that decreased expression of Galpha11 coupled to impaired endothelin-1-dependent activation of PYK2 contributes to this response.     

An improved competitive inhibition enzymatic immunoassay method for tetrodotoxin quantification

Quantifying tetrodotoxin (TTX) has been a challenge in both ecological and medical research due to the cost, time and training required of most quantification techniques. Here we present a modified Competitive Inhibition Enzymatic Immunoassay for the quantification of TTX, and to aid researchers in the optimization of this technique for widespread use with a high degree of accuracy and repeatability.     

Characterization of cellular DGK-θ

In this report we have summarized the data regarding the regulation of DGK-θ by two phospholipids: PtdSer and PtdOH. Our previous data has shown that stimulation of quiescent fibroblasts with a potent mitogen (α-thrombin) leads to an increase in nuclear localized DGK-θ ([Bregoli et al., 2001] and [Bregoli et al., 2002]), as has been seen in neuronal cells ([Tabellini et al., 2003] and [Tabellini et al., 2004]). Furthermore, these previous studies demonstrated that DGK-θ is actually localized to the nuclear matrix ([Bregoli et al., 2002] and [Tabellini et al., 2003]). As we have also previously shown that PtdSer and PtdOH modulate DGK-θ activity ([Tu-Sekine et al., 2006] and [Tu-Sekine et al., 2007]), we examined the phospholipid composition of the nuclear matrix as well as the phospholipid composition of the intact nuclei and non-nuclear membranes. This analysis has revealed that there are phospholipids in the “matrix” of nuclei and the composition of these lipids largely resembles those of the other membranes. The physical form and localization of the matrix-associated lipids has not been established, though the nearly identical percent composition of the non-nuclear membranes and the nuclear matrix lend credence to the hypothesis that at least some of the internal nuclear lipid is derived from invaginations of the cellular membranes through the nuclear interior known as nuclear tubules ([Fricker et al., 1997] and [Lee et al., 2006]).An important finding resulting from this analysis is that the nuclear envelope is enriched in PtdSer relative to the nuclear matrix and to cellular membranes, and that over-expression of DGK-θ reduces both the PtdSer and PtdEth levels of the nuclear envelope. While the mechanism behind these fluctuations is unknown, the data are consistent with a DGK-regulated phosphatidylcholine-dependent phosphatidylserine synthase (PSS-1) (EC 2.7.8.8) activity at the nuclear envelope. PtdSer synthesis in mammalian cells proceeds by headgroup exchange with PtdCho or PtdEth, catalyzed by PSS-1 or PSS-2, respectively. Interestingly, the decrease in both PtdSer and PtdEth at the nuclear membrane mirrors effects observed in the CHO-K1 mutant cell lines M.6.1.1 and PSA-3, which have been shown to be deficient in PSS-1 activity (Vance and Steenbergen, 2005). While there is very little information on the regulation of mammalian PSS enzymes, phosphorylation has been shown to regulate serine exchange activities in rat brain (Kanfer et al., 1988), and we have shown that nuclear DGK-θ regulates the exit of PKC-α from the nucleus (see regulation of PKC-α). To our knowledge, there is currently no reported study of nuclear phosphatidylyserine synthases.One other notable fluctuation in cellular lipids from DGK-θ expression is an increase in plasmalogen-PtdEth in both the NNM and nuclear matrix. While the majority of studies conducted on plasmalogen synthesis agree in that there is an almost complete dependence on the classical CDP-ethanolamine pathway to provide the headgroup for precursor plasmalogen synthesized in the peroxisome, there are several studies utilizing radiolabeled serine that report approximately 20–30% of cellular plasmalogen-PtdEth can be derived from PtdSer in at least some cell models ([Yorek et al., 1985] and [Xu et al., 1991]). Whether nuclear PtdSer-derived PtdEth a precursor for the membrane plasmalogen-PtdEth present in DGK-θ expressing cells is not evident from the data presented here, though one potential mechanism for an increase in flux through this pathway could be an increase in PtdSer-derived PtdEth. At this juncture we can only speculate on the cause of the lipid perturbations, and further work is required to support our hypothesis that DGK-θ impacts PtdSer and plasmalogen metabolism.The physiological role for nuclear DGK-θ has remained a mystery. It has long been recognized that an obvious role for DGKs is to modulate cellular levels of its DAG substrate thereby modulating DAG-sensitive proteins like such as many PKCs (Merida et al., 2008). Our data support this notion as suppression of DGK-θ, either by expression of RhoA or a dominant-negative construct of DGK-θ, leads to a sustained increase in nuclear PKC-α (Fig. 2).In addition to the regulation by PtdSer and PtdOH, we report here that the regulation of nuclear DGK-θ by RhoA is modulated by a Class I PI 3-kinase. Furthermore, we have examined the effect of various inhibitors on the activity of DGK-θ in lysates over-expressing this isoform. This is important as many studies often use pharmacologic inhibitors to determine the role of selected enzymes in signaling pathways. While this approach is useful for comparative analyses, there are no data pertaining to the effect of these inhibitors on DGK-θ. We have found that one well-established PI-PLC inhibitor, U73122, but not its inactive analog U73343, competitively inhibits this isoform with respect to its diacylglycerol (DAG) substrate. These data indicate that studies designed to examine the role of PI-PLC in modulating DGK-θ activity using this inhibitor should be interpreted with caution.     

HIV-1 escape from the CCR5 antagonist maraviroc associated with an altered and less-efficient mechanism of gp120-CCR5 engagement that attenuates macrophage tropism

Maraviroc (MVC) inhibits the entry of human immunodeficiency virus type 1 (HIV-1) by binding to and modifying the conformation of the CCR5 extracellular loops (ECLs). Resistance to MVC results from alterations in the HIV-1 gp120 envelope glycoproteins (Env) enabling recognition of the drug-bound conformation of CCR5. To better understand the mechanisms underlying MVC resistance, we characterized the virus-cell interactions of gp120 from in vitro-generated MVC-resistant HIV-1 (MVC-Res Env), comparing them with those of gp120 from the sensitive parental virus (MVC-Sens Env). In the absence of the drug, MVC-Res Env maintains a highly efficient interaction with CCR5, similar to that of MVC-Sens Env, and displays a relatively modest increase in dependence on the CCR5 N terminus. However, in the presence of the drug, MVC-Res Env interacts much less efficiently with CCR5 and becomes critically dependent on the CCR5 N terminus and on positively charged elements of the drug-modified CCR5 ECL1 and ECL2 regions (His88 and His181, respectively). Structural analysis suggests that the Val323 resistance mutation in the gp120 V3 loop alters the secondary structure of the V3 loop and the buried surface area of the V3 loop-CCR5 N terminus interface. This altered mechanism of gp120-CCR5 engagement dramatically attenuates the entry of HIV-1 into monocyte-derived macrophages (MDM), cell-cell fusion activity in MDM, and viral replication capacity in MDM. In addition to confirming that HIV-1 escapes MVC by becoming heavily dependent on the CCR5 N terminus, our results reveal novel interactions with the drug-modified ECLs that are critical for the utilization of CCR5 by MVC-Res Env and provide additional insights into virus-cell interactions that modulate macrophage tropism.     

Transgenic Increase in N-3/N-6 Fatty Acid Ratio Reduces Maternal Obesity-Associated Inflammation and Limits Adverse Developmental Programming in Mice

Maternal and pediatric obesity has risen dramatically over recent years, and is a known predictor of adverse long-term metabolic outcomes in offspring. However, which particular aspects of obese pregnancy promote such outcomes is less clear. While maternal obesity increases both maternal and placental inflammation, it is still unknown whether this is a dominant mechanism in fetal metabolic programming. In this study, we utilized the Fat-1 transgenic mouse to test whether increasing the maternal n-3/n-6 tissue fatty acid ratio could reduce the consequences of maternal obesity-associated inflammation and thereby mitigate downstream developmental programming. Eight-week-old WT or hemizygous Fat-1 C57BL/6J female mice were placed on a high-fat diet (HFD) or control diet (CD) for 8 weeks prior to mating with WT chow-fed males. Only WT offspring from Fat-1 mothers were analyzed. WT-HFD mothers demonstrated increased markers of infiltrating adipose tissue macrophages (P<0.02), and a striking increase in 12 serum pro-inflammatory cytokines (P<0.05), while Fat1-HFD mothers remained similar to WT-CD mothers, despite equal weight gain. E18.5 Fetuses from WT-HFD mothers had larger placentas (P<0.02), as well as increased placenta and fetal liver TG deposition (P<0.01 and P<0.02, respectively) and increased placental LPL TG-hydrolase activity (P<0.02), which correlated with degree of maternal insulin resistance (r = 0.59, P<0.02). The placentas and fetal livers from Fat1-HFD mothers were protected from this excess placental growth and fetal-placental lipid deposition. Importantly, maternal protection from excess inflammation corresponded with improved metabolic outcomes in adult WT offspring. While the offspring from WT-HFD mothers weaned onto CD demonstrated increased weight gain (P<0.05), body and liver fat (P<0.05 and P<0.001, respectively), and whole body insulin resistance (P<0.05), these were prevented in WT offspring from Fat1-HFD mothers. Our results suggest that reducing excess maternal inflammation may be a promising target for preventing adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.