Evolution of ant-cultivar specialization and cultivar switching in Apterostigma fungus-growing ants

Almost all of the more than 200 species of fungus-growing ants (Formicidae: Attini) cultivate litter-decomposing fungi in the family Lepiotaceae (Basidiomycota: Agaricales). The single exception to this rule is a subgroup of ant species within the lower attine genus Apterostigma, which cultivate pterulaceous fungi distantly related to the Lepiotaceae. Comparison of cultivar and ant phylogenies suggests that a switch from lepiotaceous to pterulaceous fungiculture occurred only once in the history of the fungus-growing ants. This unique switch occurred after the origin of the genus Apterostigma, such that the basal Apterostigma lineages retained the ancestral attine condition of lepiotaceous fungiculture, and none of the Apterostigma lineages in the monophyletic group of pterulaceous fungiculturists are known to have reverted back to lepiotaceous fungiculture. The origin of pterulaceous fungiculture in attine ants may have involved a unique transition from the ancestral cultivation of litter-decomposing lepiotaceous fungi to the cultivation of wood-decomposing pterulaceous fungi. Phylogenetic analyses further indicate that distantly related Apterostigma ant species sometimes cultivate the same cultivar lineage, indicating evolutionarily frequent, and possibly ongoing, exchanges of fungal cultivars between Apterostigma ant species. The pterulaceous cultivars form two sister clades, and different Apterostigma ant lineages are invariably associated with, and thus specialized on, only one of the two cultivar clades. However, within clades Apterostigma ant species are able to switch between fungi. This pattern of broad specialization by attine ants on defined cultivar clades, coupled with flexible switching between fungi within cultivar clades, is also found in other attine lineages and appears to be a general phenomenon of fungicultural evolution in all fungus-growing ants.     

Phenylalanine requirement in children with classical PKU determined by indicator amino acid oxidation

Dietary restriction of phenylalanine is the main treatment for phenylketonuria (PKU), and current estimates of requirements are based on plasma phenylalanine concentration and growth. The present study aimed to determine more precisely the phenylalanine requirements in patients with the disease by use of indicator amino acid oxidation, with L-[1-13C]lysine as the indicator. Breath 13CO2 production (F 13 CO2) was used as the end point. Finger-prick blood samples were also collected for measurement of phenylalanine to relate phenylalanine intake to blood phenylalanine levels. The mean phenylalanine requirement, estimated using a two-phase linear regression crossover analysis, was 14 mg. kg(-1). day(-1), and the safe population intake (upper 95% confidence interval of the mean) was found to be 19.5 mg. kg(-1). day(-1). A balance between phenylalanine intake and the difference between fed and fasted blood phenylalanine concentration was observed at an intake of 20 mg. kg(-1). day(-1). The similarity between these two values (19.5 and 20 mg. kg(-1). day(-1)) suggests that the maximal phenylalanine intake for children with PKU should be no higher than 20 mg. kg(-1). day(-1).     

High performance liquid chromatography and UV detection for the separation and quantitation of prostaglandins

A fast and reliable method for the separation and quantitation of arachidonic acid metabolites PGF_1α, PGF_2α, PGD₂, PGE₁, PGE₂, PGB₂, PGA₂, 6-keto PGE₁, 6-keto PGF_1α, T×B₂ and 15-keto PGE₂ by high-performance liquid chromatography has been developed. Utilizing a single reverse-phase column and a UV spectrophotometer, sensitivity as little as 30 nanograms of each of these prostaglandins can be separated and subsequently detected. Although this study was performed using standards, it is highly promising for future application to biological fluids.     

Low Level Pro-inflammatory Cytokines Decrease Connexin36 Gap Junction Coupling in Mouse and Human Islets through Nitric Oxide-mediated Protein Kinase Cδ

Pro-inflammatory cytokines contribute to the decline in islet function during the development of diabetes. Cytokines can disrupt insulin secretion and calcium dynamics; however, the mechanisms underlying this are poorly understood. Connexin36 gap junctions coordinate glucose-induced calcium oscillations and pulsatile insulin secretion across the islet. Loss of gap junction coupling disrupts these dynamics, similar to that observed during the development of diabetes. This study investigates the mechanisms by which pro-inflammatory cytokines mediate gap junction coupling. Specifically, as cytokine-induced NO can activate PKCδ, we aimed to understand the role of PKCδ in modulating cytokine-induced changes in gap junction coupling. Isolated mouse and human islets were treated with varying levels of a cytokine mixture containing TNF-α, IL-1β, and IFN-γ. Islet dysfunction was measured by insulin secretion, calcium dynamics, and gap junction coupling. Modulators of PKCδ and NO were applied to determine their respective roles in modulating gap junction coupling. High levels of cytokines caused cell death and decreased insulin secretion. Low levels of cytokine treatment disrupted calcium dynamics and decreased gap junction coupling, in the absence of disruptions to insulin secretion. Decreases in gap junction coupling were dependent on NO-regulated PKCδ, and altered membrane organization of connexin36. This study defines several mechanisms underlying the disruption to gap junction coupling under conditions associated with the development of diabetes. These mechanisms will allow for greater understanding of islet dysfunction and suggest ways to ameliorate this dysfunction during the development of diabetes.     

Unraveling the diversification and systematic puzzle of the highly polymorphic Psammobates tentorius (Bell, 1828) complex (Reptilia: Testudinidae) through phylogenetic analyses and species delimitation approaches

The high level of phenotypic diversity in southern African tent tortoises (Psammobates tentorius complex) has for decades prevented systematists from developing a stable taxonomy for the group. Here, we used a comprehensive DNA sequence dataset (mtDNA: Cytb, ND4, ND4 adjacent tRNA-His, and tRNA-Ser, 12S, 16S; and nDNA: PRLR gene) of 455 specimens, and the latest phylogenetic and species delimitation analytical procedures, to unravel the long-standing P. tentorius complex systematic puzzle. Our results for mtDNA and nDNA were incongruent, with the poorly supported nDNA phylogeny differentiating the three recognized subspecies, and showing potential hybridization in some regions. In contrast, the concatenated mtDNA phylogeny identified seven operational taxonomic units, with strong support. Clades 1, 4, 5, and 7 corresponded to tortoises identified as P. t. tentorius, clade 3 to P. t. trimeni, and clades 2 and 6 to P. t. verroxii. Our analyses showed conflicting topologies for the placement of C6 (P. t. verroxii north of the Orange River), with stronger support for it being sister to C2 + C3 than to the other clades. Clades 1, 2, and 6 had significantly higher genetic diversity than clades 3, 4, 5, and 7, perhaps because these clades inhabit substantially larger areas. The potential for future cladogenic radiations seems high in C1 and C6, particularly in C6 for which the within-clade diversification level was highest. Further research involving microsatellite DNA, phylogeographic evaluations, and morphological variation among clades is crucial for understanding the adaptive radiation of the P. tentorius complex and for modifying their taxonomy.     

Structural and functional analysis of human cytomegalovirus US3 protein

Human cytomegalovirus (HCMV) unique short region 3 (US3) protein, a type I membrane protein, prevents maturation of class I major histocompatibility complex (MHC) molecules by retaining them in the endoplasmic reticulum (ER) and thus helps inhibit antigen presentation to cytotoxic T cells. US3 molecules bind to class I MHC molecules in a transient fashion but retain them very efficiently in the ER nonetheless. The US3 luminal domain is responsible for ER retention of US3 itself, while both the US3 luminal and transmembrane domains are necessary for retaining class I MHC in the ER. We have expressed the luminal domain of US3 molecule in Escherichia coli and analyzed its secondary structure by using nuclear magnetic resonance. We then predicted the US3 tertiary structure by modeling it based on the US2 structure. Unlike the luminal domain of US2, the US3 luminal domain does not obviously interact with class I MHC molecules. The luminal domain of US3 dynamically oligomerizes in vitro and full-length US3 molecules associate with each other in vivo. We present a model depicting how dynamic oligomerization of US3 may enhance its ability to retain class I molecules within the ER.     

Planktonic-cell yield of a pseudomonad biofilm

Biofilm cells differ phenotypically from their free-floating counterparts. Differential growth rates in biofilms are often referred to, particularly in response to limited diffusion of oxygen and nutrients. We observed growth rates of attached Pseudomonas sp. strain CT07 cells that were notably higher than the maximum specific growth rate measured in batch culture. Despite dilution rates in continuous flow cells that exceeded the maximum planktonic specific growth rate by 58 times, sampling of the effluent revealed >10(9) cells ml(-1), suggesting that biofilms function as a source of planktonic cells through high cell yield and detachment. Further investigation demonstrated considerable planktonic cell yield from biofilms as young as 6 h, indicating that detachment is not limited to established biofilms. These biofilm-detached cells were more sensitive to a commercial biocide than associated biofilm- and chemostat-cultivated populations, implying that detached biofilm cells exhibit a character that is distinct from that of attached and planktonic cell populations.     

SphK1 and SphK2, sphingosine kinase isoenzymes with opposing functions in sphingolipid metabolism

The potent sphingolipid metabolite sphingosine 1-phosphate is produced by phosphorylation of sphingosine catalyzed by sphingosine kinase (SphK) types 1 and 2. In contrast to pro-survival SphK1, the putative BH3-only protein SphK2 inhibits cell growth and enhances apoptosis. Here we show that SphK2 catalytic activity also contributes to its ability to induce apoptosis. Overexpressed SphK2 also increased cytosolic free calcium induced by serum starvation. Transfer of calcium to mitochondria was required for SphK2-induced apoptosis, as cell death and cytochrome c release was abrogated by inhibition of the mitochondrial Ca(2+) transporter. Serum starvation increased the proportion of SphK2 in the endoplasmic reticulum and targeting SphK1 to the endoplasmic reticulum converted it from anti-apoptotic to pro-apoptotic. Overexpression of SphK2 increased incorporation of [(3)H]palmitate, a substrate for both serine palmitoyltransferase and ceramide synthase, into C16-ceramide, whereas SphK1 decreased it. Electrospray ionizationmass spectrometry/mass spectrometry also revealed an opposite effect on ceramide mass levels. Importantly, specific down-regulation of SphK2 reduced conversion of sphingosine to ceramide in the recycling pathway and conversely, down-regulation of SphK1 increased it. Our results demonstrate that SphK1 and SphK2 have opposing roles in the regulation of ceramide biosynthesis and suggest that the location of sphingosine 1-phosphate production dictates its functions.     

Coastal swimming patterns of white sharks (<Emphasis Type="Italic">Carcharodon carcharias</Emphasis>) at Mossel Bay,South Africa

Between June and December 2005, active and passive acoustic telemetry was used to examine fine scale movements of 13 white sharks (Carcharodon carcharias) (ten passive, three active) at Mossel Bay. A total of 24 active trackings (ranging from 2 h to 103 h in duration) were conducted. Patterns of rate of movement (ROM), swimming linearity (LI), swimming bearing, and instantaneous swimming speed (ISS) were assessed. A conversion quotient (Q) of 1.21 between ISS and ROM (10 min sample interval) was calculated suggesting ROM is a good indicator of white shark activity. The mean ROM for tracked sharks was 0.52 m·s⁻¹, with a greatest sustained ROM of 1.33 m·s⁻¹ (4.8 km·h⁻¹). Sharks displayed greatest LI and ROM during directional travels between the three persistent aggregation sites. The majority of the shark movement was, however, non-linear as the sharks repeat patrolled at the three aggregation sites. Two of these sites were not associated with pinniped presence, and sharks typically patrolled back and forth parallel to the shore line at a comparatively low ROM which suggested resting. The third aggregation site was adjacent to Seal Island, and despite low LI, sharks displayed a high ROM, indicating high activity levels. We propose that the high ROM is related to maximising search area when patrolling to hunt Cape fur seals (Arctocephalus p. pusillus).     

Vagrant Antarctic fur seals at Gough Island in 2009

The Antarctic fur seal Arctocephalus gazella at Gough Island (40°20′S, 09°54′W) in the South Atlantic Ocean, first seen in October/November 2005, was recorded again in September–October 2009. Up to three different individual Antarctic fur seals were sighted on a single day, on a particular beach. A total of seven different individuals were recorded over a 3-week period, well before the onset of the breeding (pupping) season of the resident population of Subantarctic fur seals A. tropicalis. Positively identified individuals were all male, mostly subadult and lean. Only a fraction (~20%) of the available beaches was searched, and it is unknown if the Antarctic fur seals were still present at Gough Island during the austral summer breeding season of southern fur seals.